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Sample records for alters meiotic crossover

  1. A Link between Meiotic Prophase Progression and CrossoverControl

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    Carlton, Peter M.; Farruggio, Alfonso P.; Dernburg, Abby F.

    2005-07-06

    During meiosis, most organisms ensure that homologous chromosomes undergo at least one exchange of DNA, or crossover, to link chromosomes together and accomplish proper segregation. How each chromosome receives a minimum of one crossover is unknown. During early meiosis in Caenorhabditis elegans and many other species, chromosomes adopt a polarized organization within the nucleus, which normally disappears upon completion of homolog synapsis. Mutations that impair synapsis even between a single pair of chromosomes in C. elegans delay this nuclear reorganization. We quantified this delay by developing a classification scheme for discrete stages of meiosis. Immunofluorescence localization of RAD-51 protein revealed that delayed meiotic cells also contained persistent recombination intermediates. Through genetic analysis, we found that this cytological delay in meiotic progression requires double-strand breaks and the function of the crossover-promoting heteroduplex HIM-14 (Msh4) and MSH-5. Failure of X chromosome synapsis also resulted in impaired crossover control on autosomes, which may result from greater numbers and persistence of recombination intermediates in the delayed nuclei. We conclude that maturation of recombination events on chromosomes promotes meiotic progression, and is coupled to the regulation of crossover number and placement. Our results have broad implications for the interpretation of meiotic mutants, as we have shown that asynapsis of a single chromosome pair can exert global effects on meiotic progression and recombination frequency.

  2. Contrasted patterns of crossover and non-crossover at Arabidopsis thaliana meiotic recombination hotspots.

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    Jan Drouaud

    2013-11-01

    Full Text Available The vast majority of meiotic recombination events (crossovers (COs and non-crossovers (NCOs cluster in narrow hotspots surrounded by large regions devoid of recombinational activity. Here, using a new molecular approach in plants, called "pollen-typing", we detected and characterized hundreds of CO and NCO molecules in two different hotspot regions in Arabidopsis thaliana. This analysis revealed that COs are concentrated in regions of a few kilobases where their rates reach up to 50 times the genome average. The hotspots themselves tend to cluster in regions less than 8 kilobases in size with overlapping CO distribution. Non-crossover (NCO events also occurred in the two hotspots but at very different levels (local CO/NCO ratios of 1/1 and 30/1 and their track lengths were quite small (a few hundred base pairs. We also showed that the ZMM protein MSH4 plays a role in CO formation and somewhat unexpectedly we also found that it is involved in the generation of NCOs but with a different level of effect. Finally, factors acting in cis and in trans appear to shape the rate and distribution of COs at meiotic recombination hotspots.

  3. REC-1 and HIM-5 distribute meiotic crossovers and function redundantly in meiotic double-strand break formation in Caenorhabditis elegans.

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    Chung, George; Rose, Ann M; Petalcorin, Mark I R; Martin, Julie S; Kessler, Zebulin; Sanchez-Pulido, Luis; Ponting, Chris P; Yanowitz, Judith L; Boulton, Simon J

    2015-09-15

    The Caenorhabditis elegans gene rec-1 was the first genetic locus identified in metazoa to affect the distribution of meiotic crossovers along the chromosome. We report that rec-1 encodes a distant paralog of HIM-5, which was discovered by whole-genome sequencing and confirmed by multiple genome-edited alleles. REC-1 is phosphorylated by cyclin-dependent kinase (CDK) in vitro, and mutation of the CDK consensus sites in REC-1 compromises meiotic crossover distribution in vivo. Unexpectedly, rec-1; him-5 double mutants are synthetic-lethal due to a defect in meiotic double-strand break formation. Thus, we uncovered an unexpected robustness to meiotic DSB formation and crossover positioning that is executed by HIM-5 and REC-1 and regulated by phosphorylation. © 2015 Chung et al.; Published by Cold Spring Harbor Laboratory Press.

  4. AAA-ATPase FIDGETIN-LIKE 1 and Helicase FANCM Antagonize Meiotic Crossovers by Distinct Mechanisms.

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    Chloe Girard

    2015-07-01

    Full Text Available Meiotic crossovers (COs generate genetic diversity and are critical for the correct completion of meiosis in most species. Their occurrence is tightly constrained but the mechanisms underlying this limitation remain poorly understood. Here we identified the conserved AAA-ATPase FIDGETIN-LIKE-1 (FIGL1 as a negative regulator of meiotic CO formation. We show that Arabidopsis FIGL1 limits CO formation genome-wide, that FIGL1 controls dynamics of the two conserved recombinases DMC1 and RAD51 and that FIGL1 hinders the interaction between homologous chromosomes, suggesting that FIGL1 counteracts DMC1/RAD51-mediated inter-homologue strand invasion to limit CO formation. Further, depleting both FIGL1 and the previously identified anti-CO helicase FANCM synergistically increases crossover frequency. Additionally, we showed that the effect of mutating FANCM on recombination is much lower in F1 hybrids contrasting from the phenotype of inbred lines, while figl1 mutation equally increases crossovers in both contexts. This shows that the modes of action of FIGL1 and FANCM are differently affected by genomic contexts. We propose that FIGL1 and FANCM represent two successive barriers to CO formation, one limiting strand invasion, the other disassembling D-loops to promote SDSA, which when both lifted, leads to a large increase of crossovers, without impairing meiotic progression.

  5. mlh3 mutations in baker's yeast alter meiotic recombination outcomes by increasing noncrossover events genome-wide.

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    Najla Al-Sweel

    2017-08-01

    Full Text Available Mlh1-Mlh3 is an endonuclease hypothesized to act in meiosis to resolve double Holliday junctions into crossovers. It also plays a minor role in eukaryotic DNA mismatch repair (MMR. To understand how Mlh1-Mlh3 functions in both meiosis and MMR, we analyzed in baker's yeast 60 new mlh3 alleles. Five alleles specifically disrupted MMR, whereas one (mlh3-32 specifically disrupted meiotic crossing over. Mlh1-mlh3 representatives for each class were purified and characterized. Both Mlh1-mlh3-32 (MMR+, crossover- and Mlh1-mlh3-45 (MMR-, crossover+ displayed wild-type endonuclease activities in vitro. Msh2-Msh3, an MSH complex that acts with Mlh1-Mlh3 in MMR, stimulated the endonuclease activity of Mlh1-mlh3-32 but not Mlh1-mlh3-45, suggesting that Mlh1-mlh3-45 is defective in MSH interactions. Whole genome recombination maps were constructed for wild-type and MMR+ crossover-, MMR- crossover+, endonuclease defective and null mlh3 mutants in an S288c/YJM789 hybrid background. Compared to wild-type, all of the mlh3 mutants showed increases in the number of noncrossover events, consistent with recombination intermediates being resolved through alternative recombination pathways. Our observations provide a structure-function map for Mlh3 that reveals the importance of protein-protein interactions in regulating Mlh1-Mlh3's enzymatic activity. They also illustrate how defective meiotic components can alter the fate of meiotic recombination intermediates, providing new insights for how meiotic recombination pathways are regulated.

  6. Local and sex-specific biases in crossover vs. noncrossover outcomes at meiotic recombination hot spots in mice

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    de Boer, Esther; Jasin, Maria; Keeney, Scott

    2015-01-01

    Meiotic recombination initiated by programmed double-strand breaks (DSBs) yields two types of interhomolog recombination products, crossovers and noncrossovers, but what determines whether a DSB will yield a crossover or noncrossover is not understood. In this study, we analyzed the influence of sex and chromosomal location on mammalian recombination outcomes by constructing fine-scale recombination maps in both males and females at two mouse hot spots located in different regions of the same chromosome. These include the most comprehensive maps of recombination hot spots in oocytes to date. One hot spot, located centrally on chromosome 1, behaved similarly in male and female meiosis: Crossovers and noncrossovers formed at comparable levels and ratios in both sexes. In contrast, at a distal hot spot, crossovers were recovered only in males even though noncrossovers were obtained at similar frequencies in both sexes. These findings reveal an example of extreme sex-specific bias in recombination outcome. We further found that estimates of relative DSB levels are surprisingly poor predictors of relative crossover frequencies between hot spots in males. Our results demonstrate that the outcome of mammalian meiotic recombination can be biased, that this bias can vary depending on location and cellular context, and that DSB frequency is not the only determinant of crossover frequency. PMID:26251527

  7. The spatial regulation of meiotic recombination hotspots: are all DSB hotspots crossover hotspots?

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    Serrentino, Maria-Elisabetta; Borde, Valérie

    2012-07-15

    A key step for the success of meiosis is programmed homologous recombination, during which crossovers, or exchange of chromosome arms, take place. Crossovers increase genetic diversity but their main function is to ensure accurate chromosome segregation. Defects in crossover number and position produce aneuploidies that represent the main cause of miscarriages and chromosomal abnormalities such as Down's syndrome. Recombination is initiated by the formation of programmed double strand breaks (DSBs), which occur preferentially at places called DSB hotspots. Among all DSBs generated, only a small fraction is repaired by crossover, the other being repaired by other homologous recombination pathways. Crossover maps have been generated in a number of organisms, defining crossover hotspots. With the availability of genome-wide maps of DSBs as well as the ability to measure genetically the repair outcome at several hotspots, it is becoming more and more clear that not all DSB hotspots behave the same for crossover formation, suggesting that chromosomal features distinguish different types of hotspots. Copyright © 2012. Published by Elsevier Inc.

  8. Genesis by meiotic unequal crossover of a de novo deletion that contributes to steroid 21-hydroxylase deficiency

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    Sinnott, P.; Collier, S.; Dyer, P.A.; Harris, R.; Strachan, T.; Costigan, C.

    1990-01-01

    The HLA-linked human steroid 21-hydroxylase gene CYP21B and its closely homologous pseudogene CYP21A are each normally located centromeric to a fourth component of complement (C4) gene, C4B and C4A, respectively, in an organization suggesting tandem duplication of a ca. 30-kilobase DNA unit containing a CYP21 gene and a C4 gene. Such an organization has been considered to facilitate gene deletion and addition events by unequal crossover between the tandem repeats. The authors have identified a steroid 21-hydroxylase deficiency patient who has a maternally inherited disease haplotype that carries a de novo deletion of a ca. 30-kilobase repeat unit including the CYP21B gene and associated C4B gene. This disease haplotype appears to have been generated as a result of meiotic unequal crossover between maternal homologous chromosomes. One of the maternal haplotypes is the frequently occurring HLA-DR3,B8,A1 haplotype that normally carries a deletion of a ca. 30-kilobase unit including the CYP21A gene and C4A gene. Haplotypes of this type may possible act as premutations, increasing the susceptibility of developing a 21-hydroxylase deficiency mutation by facilitating unequal chromosome pairing

  9. Mlh1-Mlh3, a Meiotic Crossover and DNA Mismatch Repair Factor, Is a Msh2-Msh3-stimulated Endonuclease*

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    Rogacheva, Maria V.; Manhart, Carol M.; Chen, Cheng; Guarne, Alba; Surtees, Jennifer; Alani, Eric

    2014-01-01

    Crossing over between homologous chromosomes is initiated in meiotic prophase in most sexually reproducing organisms by the appearance of programmed double strand breaks throughout the genome. In Saccharomyces cerevisiae the double-strand breaks are resected to form three prime single-strand tails that primarily invade complementary sequences in unbroken homologs. These invasion intermediates are converted into double Holliday junctions and then resolved into crossovers that facilitate homolog segregation during Meiosis I. Work in yeast suggests that Msh4-Msh5 stabilizes invasion intermediates and double Holliday junctions, which are resolved into crossovers in steps requiring Sgs1 helicase, Exo1, and a putative endonuclease activity encoded by the DNA mismatch repair factor Mlh1-Mlh3. We purified Mlh1-Mlh3 and showed that it is a metal-dependent and Msh2-Msh3-stimulated endonuclease that makes single-strand breaks in supercoiled DNA. These observations support a direct role for an Mlh1-Mlh3 endonuclease activity in resolving recombination intermediates and in DNA mismatch repair. PMID:24403070

  10. Arabidopsis PCH2 Mediates Meiotic Chromosome Remodeling and Maturation of Crossovers.

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    Christophe Lambing

    2015-07-01

    Full Text Available Meiotic chromosomes are organized into linear looped chromatin arrays by a protein axis localized along the loop-bases. Programmed remodelling of the axis occurs during prophase I of meiosis. Structured illumination microscopy (SIM has revealed dynamic changes in the chromosome axis in Arabidopsis thaliana and Brassica oleracea. We show that the axis associated protein ASY1 is depleted during zygotene concomitant with synaptonemal complex (SC formation. Study of an Atpch2 mutant demonstrates this requires the conserved AAA+ ATPase, PCH2, which localizes to the sites of axis remodelling. Loss of PCH2 leads to a failure to deplete ASY1 from the axes and compromizes SC polymerisation. Immunolocalization of recombination proteins in Atpch2 indicates that recombination initiation and CO designation during early prophase I occur normally. Evidence suggests that CO interference is initially functional in the mutant but there is a defect in CO maturation following designation. This leads to a reduction in COs and a failure to form COs between some homologous chromosome pairs leading to univalent chromosomes at metaphase I. Genetic analysis reveals that CO distribution is also affected in some chromosome regions. Together these data indicate that the axis remodelling defect in Atpch2 disrupts normal patterned formation of COs.

  11. Controlling meiotic recombinational repair - specifying the roles of ZMMs, Sgs1 and Mus81/Mms4 in crossover formation.

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    Ashwini Oke

    2014-10-01

    Full Text Available Crossovers (COs play a critical role in ensuring proper alignment and segregation of homologous chromosomes during meiosis. How the cell balances recombination between CO vs. noncrossover (NCO outcomes is not completely understood. Further lacking is what constrains the extent of DNA repair such that multiple events do not arise from a single double-strand break (DSB. Here, by interpreting signatures that result from recombination genome-wide, we find that synaptonemal complex proteins promote crossing over in distinct ways. Our results suggest that Zip3 (RNF212 promotes biased cutting of the double Holliday-junction (dHJ intermediate whereas surprisingly Msh4 does not. Moreover, detailed examination of conversion tracts in sgs1 and mms4-md mutants reveal distinct aberrant recombination events involving multiple chromatid invasions. In sgs1 mutants, these multiple invasions are generally multichromatid involving 3-4 chromatids; in mms4-md mutants the multiple invasions preferentially resolve into one or two chromatids. Our analysis suggests that Mus81/Mms4 (Eme1, rather than just being a minor resolvase for COs is crucial for both COs and NCOs in preventing chromosome entanglements by removing 3'- flaps to promote second-end capture. Together our results force a reevaluation of how key recombination enzymes collaborate to specify the outcome of meiotic DNA repair.

  12. The C. elegans DSB-2 protein reveals a regulatory network that controls competence for meiotic DSB formation and promotes crossover assurance.

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    Simona Rosu

    Full Text Available For most organisms, chromosome segregation during meiosis relies on deliberate induction of DNA double-strand breaks (DSBs and repair of a subset of these DSBs as inter-homolog crossovers (COs. However, timing and levels of DSB formation must be tightly controlled to avoid jeopardizing genome integrity. Here we identify the DSB-2 protein, which is required for efficient DSB formation during C. elegans meiosis but is dispensable for later steps of meiotic recombination. DSB-2 localizes to chromatin during the time of DSB formation, and its disappearance coincides with a decline in RAD-51 foci marking early recombination intermediates and precedes appearance of COSA-1 foci marking CO-designated sites. These and other data suggest that DSB-2 and its paralog DSB-1 promote competence for DSB formation. Further, immunofluorescence analyses of wild-type gonads and various meiotic mutants reveal that association of DSB-2 with chromatin is coordinated with multiple distinct aspects of the meiotic program, including the phosphorylation state of nuclear envelope protein SUN-1 and dependence on RAD-50 to load the RAD-51 recombinase at DSB sites. Moreover, association of DSB-2 with chromatin is prolonged in mutants impaired for either DSB formation or formation of downstream CO intermediates. These and other data suggest that association of DSB-2 with chromatin is an indicator of competence for DSB formation, and that cells respond to a deficit of CO-competent recombination intermediates by prolonging the DSB-competent state. In the context of this model, we propose that formation of sufficient CO-competent intermediates engages a negative feedback response that leads to cessation of DSB formation as part of a major coordinated transition in meiotic prophase progression. The proposed negative feedback regulation of DSB formation simultaneously (1 ensures that sufficient DSBs are made to guarantee CO formation and (2 prevents excessive DSB levels that could

  13. Topoisomerase 3alpha and RMI1 suppress somatic crossovers and are essential for resolution of meiotic recombination intermediates in Arabidopsis thaliana.

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    Frank Hartung

    2008-12-01

    Full Text Available Topoisomerases are enzymes with crucial functions in DNA metabolism. They are ubiquitously present in prokaryotes and eukaryotes and modify the steady-state level of DNA supercoiling. Biochemical analyses indicate that Topoisomerase 3alpha (TOP3alpha functions together with a RecQ DNA helicase and a third partner, RMI1/BLAP75, in the resolution step of homologous recombination in a process called Holliday Junction dissolution in eukaryotes. Apart from that, little is known about the role of TOP3alpha in higher eukaryotes, as knockout mutants show early lethality or strong developmental defects. Using a hypomorphic insertion mutant of Arabidopsis thaliana (top3alpha-2, which is viable but completely sterile, we were able to define three different functions of the protein in mitosis and meiosis. The top3alpha-2 line exhibits fragmented chromosomes during mitosis and sensitivity to camptothecin, suggesting an important role in chromosome segregation partly overlapping with that of type IB topoisomerases. Furthermore, AtTOP3alpha, together with AtRECQ4A and AtRMI1, is involved in the suppression of crossover recombination in somatic cells as well as DNA repair in both mammals and A. thaliana. Surprisingly, AtTOP3alpha is also essential for meiosis. The phenotype of chromosome fragmentation, bridges, and telophase I arrest can be suppressed by AtSPO11 and AtRAD51 mutations, indicating that the protein is required for the resolution of recombination intermediates. As Atrmi1 mutants have a similar meiotic phenotype to Attop3alpha mutants, both proteins seem to be involved in a mechanism safeguarding the entangling of homologous chromosomes during meiosis. The requirement of AtTOP3alpha and AtRMI1 in a late step of meiotic recombination strongly hints at the possibility that the dissolution of double Holliday Junctions via a hemicatenane intermediate is indeed an indispensable step of meiotic recombination.

  14. Cold stress alters transcription in meiotic anthers of cold tolerant chickpea (Cicer arietinum L.).

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    Sharma, Kamal Dev; Nayyar, Harsh

    2014-10-11

    Cold stress at reproductive phase in susceptible chickpea (Cicer arietinum L.) leads to pollen sterility induced flower abortion. The tolerant genotypes, on the other hand, produce viable pollen and set seed under cold stress. Genomic information on pollen development in cold-tolerant chickpea under cold stress is currently unavailable. DDRT-PCR analysis was carried out to identify anther genes involved in cold tolerance in chickpea genotype ICC16349 (cold-tolerant). A total of 9205 EST bands were analyzed. Cold stress altered expression of 127 ESTs (90 up-regulated, 37 down-regulated) in anthers, more than two third (92) of which were novel with unknown protein identity and function. Remaining about one third (35) belonged to several functional categories such as pollen development, signal transduction, ion transport, transcription, carbohydrate metabolism, translation, energy and cell division. The categories with more number of transcripts were carbohydrate/triacylglycerol metabolism, signal transduction, pollen development and transport. All but two transcripts in these categories were up-regulated under cold stress. To identify time of regulation after stress and organ specificity, expression levels of 25 differentially regulated transcripts were also studied in anthers at six time points and in four organs (anthers, gynoecium, leaves and roots) at four time points. Limited number of genes were involved in regulating cold tolerance in chickpea anthers. Moreover, the cold tolerance was manifested by up-regulation of majority of the differentially expressed transcripts. The anthers appeared to employ dual cold tolerance mechanism based on their protection from cold by enhancing triacylglycerol and carbohydrate metabolism; and maintenance of normal pollen development by regulating pollen development genes. Functional characterization of about two third of the novel genes is needed to have precise understanding of the cold tolerance mechanisms in chickpea anthers.

  15. Regulation of Meiotic Recombination

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    Gregory p. Copenhaver

    2011-11-09

    Meiotic recombination results in the heritable rearrangement of DNA, primarily through reciprocal exchange between homologous chromosome or gene conversion. In plants these events are critical for ensuring proper chromosome segregation, facilitating DNA repair and providing a basis for genetic diversity. Understanding this fundamental biological mechanism will directly facilitate trait mapping, conventional plant breeding, and development of genetic engineering techniques that will help support the responsible production and conversion of renewable resources for fuels, chemicals, and the conservation of energy (1-3). Substantial progress has been made in understanding the basal recombination machinery, much of which is conserved in organisms as diverse as yeast, plants and mammals (4, 5). Significantly less is known about the factors that regulate how often and where that basal machinery acts on higher eukaryotic chromosomes. One important mechanism for regulating the frequency and distribution of meiotic recombination is crossover interference - or the ability of one recombination event to influence nearby events. The MUS81 gene is thought to play an important role in regulating the influence of interference on crossing over. The immediate goals of this project are to use reverse genetics to identify mutants in two putative MUS81 homologs in the model plant Arabidopsis thaliana, characterize those mutants and initiate a novel forward genetic screen for additional regulators of meiotic recombination. The long-term goal of the project is to understand how meiotic recombination is regulated in higher eukaryotes with an emphasis on the molecular basis of crossover interference. The ability to monitor recombination in all four meiotic products (tetrad analysis) has been a powerful tool in the arsenal of yeast geneticists. Previously, the qrt mutant of Arabidopsis, which causes the four pollen products of male meiosis to remain attached, was developed as a facile system

  16. Meiotic recombination in human oocytes.

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    Edith Y Cheng

    2009-09-01

    Full Text Available Studies of human trisomies indicate a remarkable relationship between abnormal meiotic recombination and subsequent nondisjunction at maternal meiosis I or II. Specifically, failure to recombine or recombination events located either too near to or too far from the centromere have been linked to the origin of human trisomies. It should be possible to identify these abnormal crossover configurations by using immunofluorescence methodology to directly examine the meiotic recombination process in the human female. Accordingly, we initiated studies of crossover-associated proteins (e.g., MLH1 in human fetal oocytes to analyze their number and distribution on nondisjunction-prone human chromosomes and, more generally, to characterize genome-wide levels of recombination in the human female. Our analyses indicate that the number of MLH1 foci is lower than predicted from genetic linkage analysis, but its localization pattern conforms to that expected for a crossover-associated protein. In studies of individual chromosomes, our observations provide evidence for the presence of "vulnerable" crossover configurations in the fetal oocyte, consistent with the idea that these are subsequently translated into nondisjunctional events in the adult oocyte.

  17. Meiotic recombination hotspots - a comparative view.

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    Choi, Kyuha; Henderson, Ian R

    2015-07-01

    During meiosis homologous chromosomes pair and undergo reciprocal genetic exchange, termed crossover. Meiotic recombination has a profound effect on patterns of genetic variation and is an important tool during crop breeding. Crossovers initiate from programmed DNA double-stranded breaks that are processed to form single-stranded DNA, which can invade a homologous chromosome. Strand invasion events mature into double Holliday junctions that can be resolved as crossovers. Extensive variation in the frequency of meiotic recombination occurs along chromosomes and is typically focused in narrow hotspots, observed both at the level of DNA breaks and final crossovers. We review methodologies to profile hotspots at different steps of the meiotic recombination pathway that have been used in different eukaryote species. We then discuss what these studies have revealed concerning specification of hotspot locations and activity and the contributions of both genetic and epigenetic factors. Understanding hotspots is important for interpreting patterns of genetic variation in populations and how eukaryotic genomes evolve. In addition, manipulation of hotspots will allow us to accelerate crop breeding, where meiotic recombination distributions can be limiting. © 2015 The Authors The Plant Journal © 2015 John Wiley & Sons Ltd.

  18. Nicotine-induced Disturbances of Meiotic Maturation in Cultured Mouse Oocytes: Alterations of Spindle Integrity and Chromosome Alignment

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    Zenzes Maria

    2004-09-01

    Full Text Available Abstract We investigated whether nicotine exposure in vitro of mouse oocytes affects spindle and chromosome function during meiotic maturation (M-I and M-II. Oocytes in germinal vesicle (GV stage were cultured in nicotine for 8 h or for 16 h, to assess effects in M-I and in metaphase II (M-II. The latter culture setting used the three protocols: 8 h nicotine then 8 h medium (8N + 8M; 16 h nicotine (16N; 8 h medium then 8 h nicotine (8M + 8N. Non-toxic concentrations of nicotine at 1.0, 2.5, 5.0 and 10.0 mmol/L were used. Spindle-chromosome configurations were analyzed with wide-field optical sectioning microscopy. In 8 h cultures, nicotine exposure resulted in dose-related increased proportions of M-I oocytes with defective spindle-chromosome configurations. A dose-related delayed entry into anaphase I was also detected. In 16 h cultures, nicotine exposure for the first 8 h (8N + 8M, or for 16 h (16N, resulted in dose- and time-related increased proportions of oocytes arrested in M-I (10 mmol/L; 8 h: 53.2%, controls 9.6%; 16 h: 87.6%, controls 8.5%. Defects in M-I spindles and chromosomes caused M-I arrest leading to dose-related decreased proportions of oocytes that reached metaphase-II (10 mmol/L 8 h: 46.8%, controls 90.4%;16 h: 12.4%, controls 91.5%. A delayed anaphase-I affected the normal timing of M-II, leading to abnormal oocytes with dispersed chromosomes, or with double spindles and no polar body. Nicotine exposure during the second 8 h (8M + 8N resulted in dose-related, increased proportions of M-II oocytes with defective spindles and chromosomes (10 mmol/L: 42.9%, controls 2.0%. Nicotine has no adverse effects on GV break down, but induces spindle and chromosome defects compromising oocyte meiotic maturation and development.

  19. The mismatch repair protein MLH1 marks a subset of strongly interfering crossovers in tomato

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    Lhuissier, F.G.P.; Offenberg, H.H.; Wittich, P.E.; Vischer, N.O.E.; Heyting, C.

    2007-01-01

    In most eukaryotes, the prospective chromosomal positions of meiotic crossovers are marked during meiotic prophase by protein complexes called late recombination nodules (LNs). In tomato (Solanum lycopersicum), a cytological recombination map has been constructed based on LN positions. We

  20. Initiation of Meiotic Recombination in Mammals

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    Rajeev Kumar

    2010-12-01

    Full Text Available Meiotic recombination is initiated by the induction of programmed DNA double strand breaks (DSBs. DSB repair promotes homologous interactions and pairing and leads to the formation of crossovers (COs, which are required for the proper reductional segregation at the first meiotic division. In mammals, several hundred DSBs are generated at the beginning of meiotic prophase by the catalytic activity of SPO11. Currently it is not well understood how the frequency and timing of DSB formation and their localization are regulated. Several approaches in humans and mice have provided an extensive description of the localization of initiation events based on CO mapping, leading to the identification and characterization of preferred sites (hotspots of initiation. This review presents the current knowledge about the proteins known to be involved in this process, the sites where initiation takes place, and the factors that control hotspot localization.

  1. The joy of six: how to control your crossovers.

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    Globus, Samuel T; Keeney, Scott

    2012-03-30

    Meiotic cells tightly regulate the number and distribution of crossovers to promote accurate chromosome segregation. Yokoo and colleagues uncover a metazoan-specific, cyclin-like protein that is crucial for crossover formation. They utilize this protein's unique properties to explore a remarkable example of biological numerology, whereby nearly every meiotic cell in C. elegans makes precisely six crossovers, one for each of its six chromosome pairs. Copyright © 2012 Elsevier Inc. All rights reserved.

  2. Managing meiotic recombination in plant breeding

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    Wijnker, T.G.; Jong, de J.H.S.G.M.

    2008-01-01

    Crossover recombination is a crucial process in plant breeding because it allows plant breeders to create novel allele combnations on chromosomes that can be used for breeding superior F1 hybrids. Gaining control over this process, in terms of increasing crossover incidence, altering crossover

  3. SLX-1 is required for maintaining genomic integrity and promoting meiotic noncrossovers in the Caenorhabditis elegans germline.

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    Takamune T Saito

    2012-08-01

    Full Text Available Although the SLX4 complex, which includes structure-specific nucleases such as XPF, MUS81, and SLX1, plays important roles in the repair of several kinds of DNA damage, the function of SLX1 in the germline remains unknown. Here we characterized the endonuclease activities of the Caenorhabditis elegans SLX-1-HIM-18/SLX-4 complex co-purified from human 293T cells and determined SLX-1 germline function via analysis of slx-1(tm2644 mutants. SLX-1 shows a HIM-18/SLX-4-dependent endonuclease activity toward replication forks, 5'-flaps, and Holliday junctions. slx-1 mutants exhibit hypersensitivity to UV, nitrogen mustard, and camptothecin, but not gamma irradiation. Consistent with a role in DNA repair, recombination intermediates accumulate in both mitotic and meiotic germ cells in slx-1 mutants. Importantly, meiotic crossover distribution, but not crossover frequency, is altered on chromosomes in slx-1 mutants compared to wild type. This alteration is not due to changes in either the levels or distribution of double-strand breaks (DSBs along chromosomes. We propose that SLX-1 is required for repair at stalled or collapsed replication forks, interstrand crosslink repair, and nucleotide excision repair during mitosis. Moreover, we hypothesize that SLX-1 regulates the crossover landscape during meiosis by acting as a noncrossover-promoting factor in a subset of DSBs.

  4. Polyploidization increases meiotic recombination frequency in Arabidopsis

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    Rehmsmeier Marc

    2011-04-01

    Full Text Available Abstract Background Polyploidization is the multiplication of the whole chromosome complement and has occurred frequently in vascular plants. Maintenance of stable polyploid state over generations requires special mechanisms to control pairing and distribution of more than two homologous chromosomes during meiosis. Since a minimal number of crossover events is essential for correct chromosome segregation, we investigated whether polyploidy has an influence on the frequency of meiotic recombination. Results Using two genetically linked transgenes providing seed-specific fluorescence, we compared a high number of progeny from diploid and tetraploid Arabidopsis plants. We show that rates of meiotic recombination in reciprocal crosses of genetically identical diploid and autotetraploid Arabidopsis plants were significantly higher in tetraploids compared to diploids. Although male and female gametogenesis differ substantially in meiotic recombination frequency, both rates were equally increased in tetraploids. To investigate whether multivalent formation in autotetraploids was responsible for the increased recombination rates, we also performed corresponding experiments with allotetraploid plants showing strict bivalent pairing. We found similarly increased rates in auto- and allotetraploids, suggesting that the ploidy effect is independent of chromosome pairing configurations. Conclusions The evolutionary success of polyploid plants in nature and under domestication has been attributed to buffering of mutations and sub- and neo-functionalization of duplicated genes. Should the data described here be representative for polyploid plants, enhanced meiotic recombination, and the resulting rapid creation of genetic diversity, could have also contributed to their prevalence.

  5. Mek1/Mre4 is a master regulator of meiotic recombination in budding yeast

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    Nancy M. Hollingsworth

    2016-02-01

    Full Text Available Sexually reproducing organisms create gametes with half the somatic cell chromosome number so that fusion of gametes at fertilization does not change the ploidy of the cell. This reduction in chromosome number occurs by the specialized cell division of meiosis in which two rounds of chromosome segregation follow a single round of chromosome duplication. Meiotic crossovers formed between the non-sister chromatids of homologous chromosomes, combined with sister chromatid cohesion, physically connect homologs, thereby allowing proper segregation at the first meiotic division. Meiotic recombination is initiated by programmed double strand breaks (DSBs whose repair is highly regulated such that (1 there is a bias for recombination with homologs rather than sister chromatids, (2 crossovers are distributed throughout the genome by a process called interference, (3 crossover homeostasis regulates the balance between crossover and non-crossover repair to maintain a critical number of crossovers and (4 each pair of homologs receives at least one crossover. It was previously known that the imposition of interhomolog bias in budding yeast requires meiosis-specific modifications to the DNA damage response and the local activation of the meiosis-specific Mek1/Mre4 (hereafter Mek1 kinase at DSBs. However, because inactivation of Mek1 results in intersister, rather than interhomolog DSB repair, whether Mek1 had a role in interhomolog pathway choice was unknown. A recent study by Chen et al. (2015 reveals that Mek1 indirectly regulates the crossover/non-crossover decision between homologs as well as genetic interference. It does this by enabling phosphorylation of Zip1, the meiosis-specific transverse filament protein of the synaptonemal complex (SC, by the conserved cell cycle kinase, Cdc7-Dbf4 (DDK. These results suggest that Mek1 is a “master regulator” of meiotic recombination in budding yeast.

  6. ATM promotes the obligate XY crossover and both crossover control and chromosome axis integrity on autosomes.

    Directory of Open Access Journals (Sweden)

    Marco Barchi

    2008-05-01

    Full Text Available During meiosis in most sexually reproducing organisms, recombination forms crossovers between homologous maternal and paternal chromosomes and thereby promotes proper chromosome segregation at the first meiotic division. The number and distribution of crossovers are tightly controlled, but the factors that contribute to this control are poorly understood in most organisms, including mammals. Here we provide evidence that the ATM kinase or protein is essential for proper crossover formation in mouse spermatocytes. ATM deficiency causes multiple phenotypes in humans and mice, including gonadal atrophy. Mouse Atm-/- spermatocytes undergo apoptosis at mid-prophase of meiosis I, but Atm(-/- meiotic phenotypes are partially rescued by Spo11 heterozygosity, such that ATM-deficient spermatocytes progress to meiotic metaphase I. Strikingly, Spo11+/-Atm-/- spermatocytes are defective in forming the obligate crossover on the sex chromosomes, even though the XY pair is usually incorporated in a sex body and is transcriptionally inactivated as in normal spermatocytes. The XY crossover defect correlates with the appearance of lagging chromosomes at metaphase I, which may trigger the extensive metaphase apoptosis that is observed in these cells. In addition, control of the number and distribution of crossovers on autosomes appears to be defective in the absence of ATM because there is an increase in the total number of MLH1 foci, which mark the sites of eventual crossover formation, and because interference between MLH1 foci is perturbed. The axes of autosomes exhibit structural defects that correlate with the positions of ongoing recombination. Together, these findings indicate that ATM plays a role in both crossover control and chromosome axis integrity and further suggests that ATM is important for coordinating these features of meiotic chromosome dynamics.

  7. Bloom syndrome helicase in meiosis: Pro-crossover functions of an anti-crossover protein.

    Science.gov (United States)

    Hatkevich, Talia; Sekelsky, Jeff

    2017-09-01

    The functions of the Bloom syndrome helicase (BLM) and its orthologs are well characterized in mitotic DNA damage repair, but their roles within the context of meiotic recombination are less clear. In meiotic recombination, multiple repair pathways are used to repair meiotic DSBs, and current studies suggest that BLM may regulate the use of these pathways. Based on literature from Saccharomyces cerevisiae, Arabidopsis thaliana, Mus musculus, Drosophila melanogaster, and Caenorhabditis elegans, we present a unified model for a critical meiotic role of BLM and its orthologs. In this model, BLM and its orthologs utilize helicase activity to regulate the use of various pathways in meiotic recombination by continuously disassembling recombination intermediates. This unwinding activity provides the meiotic program with a steady pool of early recombination substrates, increasing the probability for a DSB to be processed by the appropriate pathway. As a result of BLM activity, crossovers are properly placed throughout the genome, promoting proper chromosomal disjunction at the end of meiosis. This unified model can be used to further refine the complex role of BLM and its orthologs in meiotic recombination. © 2017 WILEY Periodicals, Inc.

  8. Variation and Evolution of the Meiotic Requirement for Crossing Over in Mammals.

    Science.gov (United States)

    Dumont, Beth L

    2017-01-01

    The segregation of homologous chromosomes at the first meiotic division is dependent on the presence of at least one well-positioned crossover per chromosome. In some mammalian species, however, the genomic distribution of crossovers is consistent with a more stringent baseline requirement of one crossover per chromosome arm. Given that the meiotic requirement for crossing over defines the minimum frequency of recombination necessary for the production of viable gametes, determining the chromosomal scale of this constraint is essential for defining crossover profiles predisposed to aneuploidy and understanding the parameters that shape patterns of recombination rate evolution across species. Here, I use cytogenetic methods for in situ imaging of crossovers in karyotypically diverse house mice (Mus musculus domesticus) and voles (genus Microtus) to test how chromosome number and configuration constrain the distribution of crossovers in a genome. I show that the global distribution of crossovers in house mice is thresholded by a minimum of one crossover per chromosome arm, whereas the crossover landscape in voles is defined by a more relaxed requirement of one crossover per chromosome. I extend these findings in an evolutionary metaanalysis of published recombination and karyotype data for 112 mammalian species and demonstrate that the physical scale of the genomic crossover distribution has undergone multiple independent shifts from one crossover per chromosome arm to one per chromosome during mammalian evolution. Together, these results indicate that the chromosomal scale constraint on crossover rates is itself a trait that evolves among species, a finding that casts light on an important source of crossover rate variation in mammals. Copyright © 2017 by the Genetics Society of America.

  9. Hybrid Sterility Locus on Chromosome X Controls Meiotic Recombination Rate in Mouse.

    Directory of Open Access Journals (Sweden)

    Maria Balcova

    2016-04-01

    Full Text Available Meiotic recombination safeguards proper segregation of homologous chromosomes into gametes, affects genetic variation within species, and contributes to meiotic chromosome recognition, pairing and synapsis. The Prdm9 gene has a dual role, it controls meiotic recombination by determining the genomic position of crossover hotspots and, in infertile hybrids of house mouse subspecies Mus m. musculus (Mmm and Mus m. domesticus (Mmd, it further functions as the major hybrid sterility gene. In the latter role Prdm9 interacts with the hybrid sterility X 2 (Hstx2 genomic locus on Chromosome X (Chr X by a still unknown mechanism. Here we investigated the meiotic recombination rate at the genome-wide level and its possible relation to hybrid sterility. Using immunofluorescence microscopy we quantified the foci of MLH1 DNA mismatch repair protein, the cytological counterparts of reciprocal crossovers, in a panel of inter-subspecific chromosome substitution strains. Two autosomes, Chr 7 and Chr 11, significantly modified the meiotic recombination rate, yet the strongest modifier, designated meiotic recombination 1, Meir1, emerged in the 4.7 Mb Hstx2 genomic locus on Chr X. The male-limited transgressive effect of Meir1 on recombination rate parallels the male-limited transgressive role of Hstx2 in hybrid male sterility. Thus, both genetic factors, the Prdm9 gene and the Hstx2/Meir1 genomic locus, indicate a link between meiotic recombination and hybrid sterility. A strong female-specific modifier of meiotic recombination rate with the effect opposite to Meir1 was localized on Chr X, distally to Meir1. Mapping Meir1 to a narrow candidate interval on Chr X is an important first step towards positional cloning of the respective gene(s responsible for variation in the global recombination rate between closely related mouse subspecies.

  10. Hybrid Sterility Locus on Chromosome X Controls Meiotic Recombination Rate in Mouse.

    Science.gov (United States)

    Balcova, Maria; Faltusova, Barbora; Gergelits, Vaclav; Bhattacharyya, Tanmoy; Mihola, Ondrej; Trachtulec, Zdenek; Knopf, Corinna; Fotopulosova, Vladana; Chvatalova, Irena; Gregorova, Sona; Forejt, Jiri

    2016-04-01

    Meiotic recombination safeguards proper segregation of homologous chromosomes into gametes, affects genetic variation within species, and contributes to meiotic chromosome recognition, pairing and synapsis. The Prdm9 gene has a dual role, it controls meiotic recombination by determining the genomic position of crossover hotspots and, in infertile hybrids of house mouse subspecies Mus m. musculus (Mmm) and Mus m. domesticus (Mmd), it further functions as the major hybrid sterility gene. In the latter role Prdm9 interacts with the hybrid sterility X 2 (Hstx2) genomic locus on Chromosome X (Chr X) by a still unknown mechanism. Here we investigated the meiotic recombination rate at the genome-wide level and its possible relation to hybrid sterility. Using immunofluorescence microscopy we quantified the foci of MLH1 DNA mismatch repair protein, the cytological counterparts of reciprocal crossovers, in a panel of inter-subspecific chromosome substitution strains. Two autosomes, Chr 7 and Chr 11, significantly modified the meiotic recombination rate, yet the strongest modifier, designated meiotic recombination 1, Meir1, emerged in the 4.7 Mb Hstx2 genomic locus on Chr X. The male-limited transgressive effect of Meir1 on recombination rate parallels the male-limited transgressive role of Hstx2 in hybrid male sterility. Thus, both genetic factors, the Prdm9 gene and the Hstx2/Meir1 genomic locus, indicate a link between meiotic recombination and hybrid sterility. A strong female-specific modifier of meiotic recombination rate with the effect opposite to Meir1 was localized on Chr X, distally to Meir1. Mapping Meir1 to a narrow candidate interval on Chr X is an important first step towards positional cloning of the respective gene(s) responsible for variation in the global recombination rate between closely related mouse subspecies.

  11. ZIP4H (TEX11 deficiency in the mouse impairs meiotic double strand break repair and the regulation of crossing over.

    Directory of Open Access Journals (Sweden)

    Carrie A Adelman

    2008-03-01

    Full Text Available We have recently shown that hypomorphic Mre11 complex mouse mutants exhibit defects in the repair of meiotic double strand breaks (DSBs. This is associated with perturbation of synaptonemal complex morphogenesis, repair and regulation of crossover formation. To further assess the Mre11 complex's role in meiotic progression, we identified testis-specific NBS1-interacting proteins via two-hybrid screening in yeast. In this screen, Zip4h (Tex11, a male germ cell specific X-linked gene was isolated. Based on sequence and predicted structural similarity to the S. cerevisiae and A. thaliana Zip4 orthologs, ZIP4H appears to be the mammalian ortholog. In S. cerevisiae and A. thaliana, Zip4 is a meiosis-specific protein that regulates the level of meiotic crossovers, thus influencing homologous chromosome segregation in these organisms. As is true for hypomorphic Nbs1 (Nbs1(DeltaB/DeltaB mice, Zip4h(-/Y mutant mice were fertile. Analysis of spermatocytes revealed a delay in meiotic double strand break repair and decreased crossover formation as inferred from DMC1 and MLH1 staining patterns, respectively. Achiasmate chromosomes at the first meiotic division were also observed in Zip4h(-/Y mutants, consistent with the observed reduction in MLH1 focus formation. These results indicate that meiotic functions of Zip4 family members are conserved and support the view that the Mre11 complex and ZIP4H interact functionally during the execution of the meiotic program in mammals.

  12. Site-specific mouth rinsing can improve oral odor by altering bacterial counts. Blind crossover clinical study.

    Science.gov (United States)

    Alqumber, Mohammed A; Arafa, Khaled A

    2014-11-01

    To determine whether site-specific mouth rinsing with oral disinfectants can improve oral odor beyond the traditional panoral mouth disinfection with mouth rinses by targeting specifically oral malodor implicated anaerobic bacteria. Twenty healthy fasting subjects volunteered for a blinded prospective, descriptive correlational crossover cross-section clinical trial conducted during the month of Ramadan between July and August 2013 in Albaha province in Saudi Arabia involving the application of Listerine Cool Mint mouth rinse by either the traditional panoral rinsing method, or a site-specific disinfection method targeting the subgingival and supragingival plaque and the posterior third of the tongue dorsum, while avoiding the remaining locations within the oral cavity. The viable anaerobic and aerobic bacterial counts, volatile sulfur compounds (VSCs) levels, organoleptic assessment of oral odor, and the tongue-coating index were compared at baseline, one, 5, and 9 hours after the treatment. The site-specific disinfection method reduced the VSCs and anaerobic bacterial loads while keeping the aerobic bacterial numbers higher than the traditional panoral rinsing method. Site-specific disinfection can more effectively maintain a healthy oral cavity by predominantly disinfecting the niches of anaerobic bacteria within the oral cavity.

  13. Electric crossover

    International Nuclear Information System (INIS)

    Schuster, R.M.; Luria, N.G.

    1977-01-01

    This invention concerns an electric crossover that makes a steam and pressure-tight seal for a conductor crossing two separate walls of a nuclear reactor vessel that seismic tremors or thermal expansion of the walls and conductor subject to relative displacements. The conductors, that have to cross the vessels, are fixed to the walls of the vessel in crossover systems fitted in crossover channels made in the walls of the vessel on their initial manufacture. The separate walls of the vessel move independently when they undergo an earth tremor or a temperature change between the walls or between the conductor. This shift can damage the conductor or the crossover system and this could give rise to cause steam or other materials to leak in the reactor should leaks occur in the primary system. Furthermore, in the case of medium or high power conductors, which are relatively rigid, the non-alignment of the crossover channels can bring about awkward stresses in the conductors or their protective sheathing. The aims of this invention are fulfilled by designing an electric crossover to pass at least one conductor through the two separate walls of a vessels, that includes an initial sub-assembly crossover, secured in a leak-tight manner to the first wall and a second sub-sessembly crossover in sliding or rolling contact with the second wall, whilst forming a leak-tight seal with it [fr

  14. Protein Determinants of Meiotic DNA Break Hotspots

    Science.gov (United States)

    Fowler, Kyle R.; Gutiérrez-Velasco, Susana

    2013-01-01

    SUMMARY Meiotic recombination, crucial for proper chromosome segregation and genome evolution, is initiated by programmed DNA double-strand breaks (DSBs) in yeasts and likely all sexually reproducing species. In fission yeast, DSBs occur up to hundreds of times more frequently at special sites, called hotspots, than in other regions of the genome. What distinguishes hotspots from cold regions is an unsolved problem, although transcription factors determine some hotspots. We report the discovery that three coiled-coil proteins – Rec25, Rec27, and Mug20 – bind essentially all hotspots with unprecedented specificity even without DSB formation. These small proteins are components of linear elements, are related to synaptonemal complex proteins, and are essential for nearly all DSBs at most hotspots. Our results indicate these hotspot determinants activate or stabilize the DSB-forming protein Rec12 (Spo11 homolog) rather than promote its binding to hotspots. We propose a new paradigm for hotspot determination and crossover control by linear element proteins. PMID:23395004

  15. Origin of meiotic nondisjunction in Drosophila females

    International Nuclear Information System (INIS)

    Grell, R.F.

    1978-01-01

    Meiotic nondisjunction can be induced by external agents, such as heat, radiation, and chemicals, and by internal genotypic alterations, namely, point mutations and chromosomal rearrangements. In many cases nondisjunction arises from a reduction or elimination of crossing-over, leading to the production of homologous univalents which fail to co-orient on the metaphase plate and to disjoin properly. In some organisms, e.g., Drosophila and perhaps man, distributive pairing [i.e., a post-exchange, size-dependent pairing] ensures the regular segregation of such homologous univalents. When a nonhomologous univalent is present, which falls within a size range permitting nonhomologous recognition and pairing, distributive nondisjunction of the homologues may follow. Examples of nondisjunction induced by inversion heterozygosity, translocation heterozygosity, chromosome fragments, radiation, heat, and recombination-defective mutants are presented

  16. Haplotype mapping of a diploid non-meiotic organism using existing and induced aneuploidies.

    Directory of Open Access Journals (Sweden)

    Melanie Legrand

    2008-01-01

    Full Text Available Haplotype maps (HapMaps reveal underlying sequence variation and facilitate the study of recombination and genetic diversity. In general, HapMaps are produced by analysis of Single-Nucleotide Polymorphism (SNP segregation in large numbers of meiotic progeny. Candida albicans, the most common human fungal pathogen, is an obligate diploid that does not appear to undergo meiosis. Thus, standard methods for haplotype mapping cannot be used. We exploited naturally occurring aneuploid strains to determine the haplotypes of the eight chromosome pairs in the C. albicans laboratory strain SC5314 and in a clinical isolate. Comparison of the maps revealed that the clinical strain had undergone a significant amount of genome rearrangement, consisting primarily of crossover or gene conversion recombination events. SNP map haplotyping revealed that insertion and activation of the UAU1 cassette in essential and non-essential genes can result in whole chromosome aneuploidy. UAU1 is often used to construct homozygous deletions of targeted genes in C. albicans; the exact mechanism (trisomy followed by chromosome loss versus gene conversion has not been determined. UAU1 insertion into the essential ORC1 gene resulted in a large proportion of trisomic strains, while gene conversion events predominated when UAU1 was inserted into the non-essential LRO1 gene. Therefore, induced aneuploidies can be used to generate HapMaps, which are essential for analyzing genome alterations and mitotic recombination events in this clonal organism.

  17. Unisexual reproduction drives meiotic recombination and phenotypic and karyotypic plasticity in Cryptococcus neoformans.

    Directory of Open Access Journals (Sweden)

    Sheng Sun

    2014-12-01

    Full Text Available In fungi, unisexual reproduction, where sexual development is initiated without the presence of two compatible mating type alleles, has been observed in several species that can also undergo traditional bisexual reproduction, including the important human fungal pathogens Cryptococcus neoformans and Candida albicans. While unisexual reproduction has been well characterized qualitatively, detailed quantifications are still lacking for aspects of this process, such as the frequency of recombination during unisexual reproduction, and how this compares with bisexual reproduction. Here, we analyzed meiotic recombination during α-α unisexual and a-α bisexual reproduction of C. neoformans. We found that meiotic recombination operates in a similar fashion during both modes of sexual reproduction. Specifically, we observed that in α-α unisexual reproduction, the numbers of crossovers along the chromosomes during meiosis, recombination frequencies at specific chromosomal regions, as well as meiotic recombination hot and cold spots, are all similar to those observed during a-α bisexual reproduction. The similarity in meiosis is also reflected by the fact that phenotypic segregation among progeny collected from the two modes of sexual reproduction is also similar, with transgressive segregation being observed in both. Additionally, we found diploid meiotic progeny were also produced at similar frequencies in the two modes of sexual reproduction, and transient chromosomal loss and duplication likely occurs frequently and results in aneuploidy and loss of heterozygosity that can span entire chromosomes. Furthermore, in both α-α unisexual and a-α bisexual reproduction, we observed biased allele inheritance in regions on chromosome 4, suggesting the presence of fragile chromosomal regions that might be vulnerable to mitotic recombination. Interestingly, we also observed a crossover event that occurred within the MAT locus during α-α unisexual

  18. Unisexual Reproduction Drives Meiotic Recombination and Phenotypic and Karyotypic Plasticity in Cryptococcus neoformans

    Science.gov (United States)

    Sun, Sheng; Billmyre, R. Blake; Mieczkowski, Piotr A.; Heitman, Joseph

    2014-01-01

    In fungi, unisexual reproduction, where sexual development is initiated without the presence of two compatible mating type alleles, has been observed in several species that can also undergo traditional bisexual reproduction, including the important human fungal pathogens Cryptococcus neoformans and Candida albicans. While unisexual reproduction has been well characterized qualitatively, detailed quantifications are still lacking for aspects of this process, such as the frequency of recombination during unisexual reproduction, and how this compares with bisexual reproduction. Here, we analyzed meiotic recombination during α-α unisexual and a-α bisexual reproduction of C. neoformans. We found that meiotic recombination operates in a similar fashion during both modes of sexual reproduction. Specifically, we observed that in α-α unisexual reproduction, the numbers of crossovers along the chromosomes during meiosis, recombination frequencies at specific chromosomal regions, as well as meiotic recombination hot and cold spots, are all similar to those observed during a-α bisexual reproduction. The similarity in meiosis is also reflected by the fact that phenotypic segregation among progeny collected from the two modes of sexual reproduction is also similar, with transgressive segregation being observed in both. Additionally, we found diploid meiotic progeny were also produced at similar frequencies in the two modes of sexual reproduction, and transient chromosomal loss and duplication likely occurs frequently and results in aneuploidy and loss of heterozygosity that can span entire chromosomes. Furthermore, in both α-α unisexual and a-α bisexual reproduction, we observed biased allele inheritance in regions on chromosome 4, suggesting the presence of fragile chromosomal regions that might be vulnerable to mitotic recombination. Interestingly, we also observed a crossover event that occurred within the MAT locus during α-α unisexual reproduction. Our results

  19. Functional Roles of Acetylated Histone Marks at Mouse Meiotic Recombination Hot Spots

    Science.gov (United States)

    Wu, Zhen; Fallahi, Mohammad; Ouizem, Souad; Liu, Qin; Li, Weimin; Costi, Roberta; Roush, William R.; Bois, Philippe R. J.

    2016-01-01

    ABSTRACT Meiotic recombination initiates following the formation of DNA double-strand breaks (DSBs) by the Spo11 endonuclease early in prophase I, at discrete regions in the genome coined “hot spots.” In mammals, meiotic DSB site selection is directed in part by sequence-specific binding of PRDM9, a polymorphic histone H3 (H3K4Me3) methyltransferase. However, other chromatin features needed for meiotic hot spot specification are largely unknown. Here we show that the recombinogenic cores of active hot spots in mice harbor several histone H3 and H4 acetylation and methylation marks that are typical of open, active chromatin. Further, deposition of these open chromatin-associated histone marks is dynamic and is manifest at spermatogonia and/or pre-leptotene-stage cells, which facilitates PRDM9 binding and access for Spo11 to direct the formation of DSBs, which are initiated at the leptotene stage. Importantly, manipulating histone acetylase and deacetylase activities established that histone acetylation marks are necessary for both hot spot activity and crossover resolution. We conclude that there are functional roles for histone acetylation marks at mammalian meiotic recombination hot spots. PMID:27821479

  20. Regulation of meiotic gene expression in plants

    Directory of Open Access Journals (Sweden)

    Adele eZhou

    2014-08-01

    Full Text Available With the recent advances in genomics and sequencing technologies, databases of transcriptomes representing many cellular processes have been built. Meiotic transcriptomes in plants have been studied in Arabidopsis thaliana, rice (Oryza sativa, wheat (Triticum aestivum, petunia (Petunia hybrida, sunflower (Helianthus annuus, and maize (Zea mays. Studies in all organisms, but particularly in plants, indicate that a very large number of genes are expressed during meiosis, though relatively few of them seem to be required for the completion of meiosis. In this review, we focus on gene expression at the RNA level and analyze the meiotic transcriptome datasets and explore expression patterns of known meiotic genes to elucidate how gene expression could be regulated during meiosis. We also discuss mechanisms, such as chromatin organization and non-coding RNAs, that might be involved in the regulation of meiotic transcription patterns.

  1. Genomic features shaping the landscape of meiotic double-strand-break hotspots in maize.

    Science.gov (United States)

    He, Yan; Wang, Minghui; Dukowic-Schulze, Stefanie; Zhou, Adele; Tiang, Choon-Lin; Shilo, Shay; Sidhu, Gaganpreet K; Eichten, Steven; Bradbury, Peter; Springer, Nathan M; Buckler, Edward S; Levy, Avraham A; Sun, Qi; Pillardy, Jaroslaw; Kianian, Penny M A; Kianian, Shahryar F; Chen, Changbin; Pawlowski, Wojciech P

    2017-11-14

    Meiotic recombination is the most important source of genetic variation in higher eukaryotes. It is initiated by formation of double-strand breaks (DSBs) in chromosomal DNA in early meiotic prophase. The DSBs are subsequently repaired, resulting in crossovers (COs) and noncrossovers (NCOs). Recombination events are not distributed evenly along chromosomes but cluster at recombination hotspots. How specific sites become hotspots is poorly understood. Studies in yeast and mammals linked initiation of meiotic recombination to active chromatin features present upstream from genes, such as absence of nucleosomes and presence of trimethylation of lysine 4 in histone H3 (H3K4me3). Core recombination components are conserved among eukaryotes, but it is unclear whether this conservation results in universal characteristics of recombination landscapes shared by a wide range of species. To address this question, we mapped meiotic DSBs in maize, a higher eukaryote with a large genome that is rich in repetitive DNA. We found DSBs in maize to be frequent in all chromosome regions, including sites lacking COs, such as centromeres and pericentromeric regions. Furthermore, most DSBs are formed in repetitive DNA, predominantly Gypsy retrotransposons, and only one-quarter of DSB hotspots are near genes. Genic and nongenic hotspots differ in several characteristics, and only genic DSBs contribute to crossover formation. Maize hotspots overlap regions of low nucleosome occupancy but show only limited association with H3K4me3 sites. Overall, maize DSB hotspots exhibit distribution patterns and characteristics not reported previously in other species. Understanding recombination patterns in maize will shed light on mechanisms affecting dynamics of the plant genome.

  2. Spermatogenesis-specific features of the meiotic program in Caenorhabditis elegans.

    Directory of Open Access Journals (Sweden)

    Diane C Shakes

    2009-08-01

    Full Text Available In most sexually reproducing organisms, the fundamental process of meiosis is implemented concurrently with two differentiation programs that occur at different rates and generate distinct cell types, sperm and oocytes. However, little is known about how the meiotic program is influenced by such contrasting developmental programs. Here we present a detailed timeline of late meiotic prophase during spermatogenesis in Caenorhabditis elegans using cytological and molecular landmarks to interrelate changes in chromosome dynamics with germ cell cellularization, spindle formation, and cell cycle transitions. This analysis expands our understanding C. elegans spermatogenesis, as it identifies multiple spermatogenesis-specific features of the meiotic program and provides a framework for comparative studies. Post-pachytene chromatin of spermatocytes is distinct from that of oocytes in both composition and morphology. Strikingly, C. elegans spermatogenesis includes a previously undescribed karyosome stage, a common but poorly understood feature of meiosis in many organisms. We find that karyosome formation, in which chromosomes form a constricted mass within an intact nuclear envelope, follows desynapsis, involves a global down-regulation of transcription, and may support the sequential activation of multiple kinases that prepare spermatocytes for meiotic divisions. In spermatocytes, the presence of centrioles alters both the relative timing of meiotic spindle assembly and its ultimate structure. These microtubule differences are accompanied by differences in kinetochores, which connect microtubules to chromosomes. The sperm-specific features of meiosis revealed here illuminate how the underlying molecular machinery required for meiosis is differentially regulated in each sex.

  3. Error-prone meiotic division and subfertility in mice with oocyte-conditional knockdown of pericentrin.

    Science.gov (United States)

    Baumann, Claudia; Wang, Xiaotian; Yang, Luhan; Viveiros, Maria M

    2017-04-01

    Mouse oocytes lack canonical centrosomes and instead contain unique acentriolar microtubule-organizing centers (aMTOCs). To test the function of these distinct aMTOCs in meiotic spindle formation, pericentrin (Pcnt), an essential centrosome/MTOC protein, was knocked down exclusively in oocytes by using a transgenic RNAi approach. Here, we provide evidence that disruption of aMTOC function in oocytes promotes spindle instability and severe meiotic errors that lead to pronounced female subfertility. Pcnt-depleted oocytes from transgenic (Tg) mice were ovulated at the metaphase-II stage, but show significant chromosome misalignment, aneuploidy and premature sister chromatid separation. These defects were associated with loss of key Pcnt-interacting proteins (γ-tubulin, Nedd1 and Cep215) from meiotic spindle poles, altered spindle structure and chromosome-microtubule attachment errors. Live-cell imaging revealed disruptions in the dynamics of spindle assembly and organization, together with chromosome attachment and congression defects. Notably, spindle formation was dependent on Ran GTPase activity in Pcnt-deficient oocytes. Our findings establish that meiotic division is highly error-prone in the absence of Pcnt and disrupted aMTOCs, similar to what reportedly occurs in human oocytes. Moreover, these data underscore crucial differences between MTOC-dependent and -independent meiotic spindle assembly. © 2017. Published by The Company of Biologists Ltd.

  4. Female meiotic sex chromosome inactivation in chicken.

    Directory of Open Access Journals (Sweden)

    Sam Schoenmakers

    2009-05-01

    Full Text Available During meiotic prophase in male mammals, the heterologous X and Y chromosomes remain largely unsynapsed, and meiotic sex chromosome inactivation (MSCI leads to formation of the transcriptionally silenced XY body. In birds, the heterogametic sex is female, carrying Z and W chromosomes (ZW, whereas males have the homogametic ZZ constitution. During chicken oogenesis, the heterologous ZW pair reaches a state of complete heterologous synapsis, and this might enable maintenance of transcription of Z- and W chromosomal genes during meiotic prophase. Herein, we show that the ZW pair is transiently silenced, from early pachytene to early diplotene using immunocytochemistry and gene expression analyses. We propose that ZW inactivation is most likely achieved via spreading of heterochromatin from the W on the Z chromosome. Also, persistent meiotic DNA double-strand breaks (DSBs may contribute to silencing of Z. Surprisingly, gammaH2AX, a marker of DSBs, and also the earliest histone modification that is associated with XY body formation in mammalian and marsupial spermatocytes, does not cover the ZW during the synapsed stage. However, when the ZW pair starts to desynapse, a second wave of gammaH2AX accumulates on the unsynapsed regions of Z, which also show a reappearance of the DSB repair protein RAD51. This indicates that repair of meiotic DSBs on the heterologous part of Z is postponed until late pachytene/diplotene, possibly to avoid recombination with regions on the heterologously synapsed W chromosome. Two days after entering diplotene, the Z looses gammaH2AX and shows reactivation. This is the first report of meiotic sex chromosome inactivation in a species with female heterogamety, providing evidence that this mechanism is not specific to spermatogenesis. It also indicates the presence of an evolutionary force that drives meiotic sex chromosome inactivation independent of the final achievement of synapsis.

  5. Meiotic behaviour of tetraploid wheats (Triticum turgidum L.) and ...

    Indian Academy of Sciences (India)

    cause for the meiotic instability (Oettler 2005). Meiotic in- stability in triticale seems to have another molecular cause. Rye chromosomes generally .... economic yield is the product of sexual reproduction (Saini. 1997). Global warming is now ...

  6. Meiotic behaviour of tetraploid wheats (Triticum turgidum L.)

    Indian Academy of Sciences (India)

    Meiotic behaviour of plant chromosomes is influenced by both genetic and environmental factors. In this study, the meiotic behaviour of cereal crops was investigated, which includes tetraploid wheat genotypes (with and without the meiotic restitution trait) and their derivates (synthetic hexaploid wheats and a doubled ...

  7. Separable Crossover-Promoting and Crossover-Constraining Aspects of Zip1 Activity during Budding Yeast Meiosis.

    Directory of Open Access Journals (Sweden)

    Karen Voelkel-Meiman

    2015-06-01

    Full Text Available Accurate chromosome segregation during meiosis relies on the presence of crossover events distributed among all chromosomes. MutSγ and MutLγ homologs (Msh4/5 and Mlh1/3 facilitate the formation of a prominent group of meiotic crossovers that mature within the context of an elaborate chromosomal structure called the synaptonemal complex (SC. SC proteins are required for intermediate steps in the formation of MutSγ-MutLγ crossovers, but whether the assembled SC structure per se is required for MutSγ-MutLγ-dependent crossover recombination events is unknown. Here we describe an interspecies complementation experiment that reveals that the mature SC is dispensable for the formation of Mlh3-dependent crossovers in budding yeast. Zip1 forms a major structural component of the budding yeast SC, and is also required for MutSγ and MutLγ-dependent crossover formation. Kluyveromyces lactis ZIP1 expressed in place of Saccharomyces cerevisiae ZIP1 in S. cerevisiae cells fails to support SC assembly (synapsis but promotes wild-type crossover levels in those nuclei that progress to form spores. While stable, full-length SC does not assemble in S. cerevisiae cells expressing K. lactis ZIP1, aggregates of K. lactis Zip1 displayed by S. cerevisiae meiotic nuclei are decorated with SC-associated proteins, and K. lactis Zip1 promotes the SUMOylation of the SC central element protein Ecm11, suggesting that K. lactis Zip1 functionally interfaces with components of the S. cerevisiae synapsis machinery. Moreover, K. lactis Zip1-mediated crossovers rely on S. cerevisiae synapsis initiation proteins Zip3, Zip4, Spo16, as well as the Mlh3 protein, as do the crossovers mediated by S. cerevisiae Zip1. Surprisingly, however, K. lactis Zip1-mediated crossovers are largely Msh4/Msh5 (MutSγ-independent. This separation-of-function version of Zip1 thus reveals that neither assembled SC nor MutSγ is required for Mlh3-dependent crossover formation per se in budding yeast

  8. Translocations of chromosome end-segments and facultative heterochromatin promote meiotic ring formation in evening primroses.

    Science.gov (United States)

    Golczyk, Hieronim; Massouh, Amid; Greiner, Stephan

    2014-03-01

    Due to reciprocal chromosomal translocations, many species of Oenothera (evening primrose) form permanent multichromosomal meiotic rings. However, regular bivalent pairing is also observed. Chiasmata are restricted to chromosomal ends, which makes homologous recombination virtually undetectable. Genetic diversity is achieved by changing linkage relations of chromosomes in rings and bivalents via hybridization and reciprocal translocations. Although the structural prerequisite for this system is enigmatic, whole-arm translocations are widely assumed to be the mechanistic driving force. We demonstrate that this prerequisite is genome compartmentation into two epigenetically defined chromatin fractions. The first one facultatively condenses in cycling cells into chromocenters negative both for histone H3 dimethylated at lysine 4 and for C-banding, and forms huge condensed middle chromosome regions on prophase chromosomes. Remarkably, it decondenses in differentiating cells. The second fraction is euchromatin confined to distal chromosome segments, positive for histone H3 lysine 4 dimethylation and for histone H3 lysine 27 trimethylation. The end-segments are deprived of canonical telomeres but capped with constitutive heterochromatin. This genomic organization promotes translocation breakpoints between the two chromatin fractions, thus facilitating exchanges of end-segments. We challenge the whole-arm translocation hypothesis by demonstrating why reciprocal translocations of chromosomal end-segments should strongly promote meiotic rings and evolution toward permanent translocation heterozygosity. Reshuffled end-segments, each possessing a major crossover hot spot, can furthermore explain meiotic compatibility between genomes with different translocation histories.

  9. The RTR complex as caretaker of genome stability and its unique meiotic function in plants

    Directory of Open Access Journals (Sweden)

    Alexander eKnoll

    2014-02-01

    Full Text Available The RTR complex consisting of a RecQ helicase, a type IA topoisomerase and the structural protein RMI1 is involved in the processing of DNA recombination intermediates in all eukaryotes. In Arabidopsis thaliana the complex partners RECQ4A, topoisomerase 3α and RMI1 have been shown to be involved in DNA repair and in the suppression of homologous recombination (HR in somatic cells. Interestingly, mutants of AtTOP3A and AtRMI1 are also sterile due to extensive chromosome breakage in meiosis I, a phenotype that seems to be specific for plants. Although both proteins are essential for meiotic recombination it is still elusive on what kind of intermediates they are acting on. Recent data indicate that the pattern of non-crossover (NCO-associated meiotic gene conversion (GC differs between plants and other eukaryotes, as less NCOs in comparison to crossovers (CO could be detected in Arabidopsis. This indicates that NCOs happen either more rarely in plants or that the conversion tract length is significantly shorter than in other organisms. As the TOP3α/RMI1-mediated dissolution of recombination intermediates results exclusively in NCOs, we suggest that the peculiar GC pattern found in plants is connected to the unique role, members of the RTR complex play in plant meiosis.

  10. The SMC-5/6 Complex and the HIM-6 (BLM Helicase Synergistically Promote Meiotic Recombination Intermediate Processing and Chromosome Maturation during Caenorhabditis elegans Meiosis.

    Directory of Open Access Journals (Sweden)

    Ye Hong

    2016-03-01

    Full Text Available Meiotic recombination is essential for the repair of programmed double strand breaks (DSBs to generate crossovers (COs during meiosis. The efficient processing of meiotic recombination intermediates not only needs various resolvases but also requires proper meiotic chromosome structure. The Smc5/6 complex belongs to the structural maintenance of chromosome (SMC family and is closely related to cohesin and condensin. Although the Smc5/6 complex has been implicated in the processing of recombination intermediates during meiosis, it is not known how Smc5/6 controls meiotic DSB repair. Here, using Caenorhabditis elegans we show that the SMC-5/6 complex acts synergistically with HIM-6, an ortholog of the human Bloom syndrome helicase (BLM during meiotic recombination. The concerted action of the SMC-5/6 complex and HIM-6 is important for processing recombination intermediates, CO regulation and bivalent maturation. Careful examination of meiotic chromosomal morphology reveals an accumulation of inter-chromosomal bridges in smc-5; him-6 double mutants, leading to compromised chromosome segregation during meiotic cell divisions. Interestingly, we found that the lethality of smc-5; him-6 can be rescued by loss of the conserved BRCA1 ortholog BRC-1. Furthermore, the combined deletion of smc-5 and him-6 leads to an irregular distribution of condensin and to chromosome decondensation defects reminiscent of condensin depletion. Lethality conferred by condensin depletion can also be rescued by BRC-1 depletion. Our results suggest that SMC-5/6 and HIM-6 can synergistically regulate recombination intermediate metabolism and suppress ectopic recombination by controlling chromosome architecture during meiosis.

  11. The SMC-5/6 Complex and the HIM-6 (BLM) Helicase Synergistically Promote Meiotic Recombination Intermediate Processing and Chromosome Maturation during Caenorhabditis elegans Meiosis.

    Science.gov (United States)

    Hong, Ye; Sonneville, Remi; Agostinho, Ana; Meier, Bettina; Wang, Bin; Blow, J Julian; Gartner, Anton

    2016-03-01

    Meiotic recombination is essential for the repair of programmed double strand breaks (DSBs) to generate crossovers (COs) during meiosis. The efficient processing of meiotic recombination intermediates not only needs various resolvases but also requires proper meiotic chromosome structure. The Smc5/6 complex belongs to the structural maintenance of chromosome (SMC) family and is closely related to cohesin and condensin. Although the Smc5/6 complex has been implicated in the processing of recombination intermediates during meiosis, it is not known how Smc5/6 controls meiotic DSB repair. Here, using Caenorhabditis elegans we show that the SMC-5/6 complex acts synergistically with HIM-6, an ortholog of the human Bloom syndrome helicase (BLM) during meiotic recombination. The concerted action of the SMC-5/6 complex and HIM-6 is important for processing recombination intermediates, CO regulation and bivalent maturation. Careful examination of meiotic chromosomal morphology reveals an accumulation of inter-chromosomal bridges in smc-5; him-6 double mutants, leading to compromised chromosome segregation during meiotic cell divisions. Interestingly, we found that the lethality of smc-5; him-6 can be rescued by loss of the conserved BRCA1 ortholog BRC-1. Furthermore, the combined deletion of smc-5 and him-6 leads to an irregular distribution of condensin and to chromosome decondensation defects reminiscent of condensin depletion. Lethality conferred by condensin depletion can also be rescued by BRC-1 depletion. Our results suggest that SMC-5/6 and HIM-6 can synergistically regulate recombination intermediate metabolism and suppress ectopic recombination by controlling chromosome architecture during meiosis.

  12. Many functions of the meiotic cohesin.

    Science.gov (United States)

    Bardhan, Amit

    2010-12-01

    Sister chromatids are held together from the time of their formation in S phase until they segregate in anaphase by the cohesin complex. In meiosis of most organisms, the mitotic Mcd1/Scc1/Rad21 subunit of the cohesin complex is largely replaced by its paralog named Rec8. This article reviews the specialized functions of Rec8 that are crucial for diverse aspects of chromosome dynamics in meiosis, and presents some speculations relating to meiotic chromosome organization.

  13. Meiotic recombination analyses of individual chromosomes in male domestic pigs (Sus scrofa domestica.

    Directory of Open Access Journals (Sweden)

    Nicolas Mary

    Full Text Available For the first time in the domestic pig, meiotic recombination along the 18 porcine autosomes was directly studied by immunolocalization of MLH1 protein. In total, 7,848 synaptonemal complexes from 436 spermatocytes were analyzed, and 13,969 recombination sites were mapped. Individual chromosomes for 113 of the 436 cells (representing 2,034 synaptonemal complexes were identified by immunostaining and fluorescence in situ hybridization (FISH. The average total length of autosomal synaptonemal complexes per cell was 190.3 µm, with 32.0 recombination sites (crossovers, on average, per cell. The number of crossovers and the lengths of the autosomal synaptonemal complexes showed significant intra- (i.e. between cells and inter-individual variations. The distributions of recombination sites within each chromosomal category were similar: crossovers in metacentric and submetacentric chromosomes were concentrated in the telomeric regions of the p- and q-arms, whereas two hotspots were located near the centromere and in the telomeric region of acrocentrics. Lack of MLH1 foci was mainly observed in the smaller chromosomes, particularly chromosome 18 (SSC18 and the sex chromosomes. All autosomes displayed positive interference, with a large variability between the chromosomes.

  14. Meiotic behaviour in three interspecific three-way hybrids between ...

    Indian Academy of Sciences (India)

    In H17, abnormalities were more frequent from anaphase II, when many laggard chromosomes appeared, suggesting that each genome presented a different genetic control for meiotic phase timing. Despite the phylogenetic proximity among these two species, these three hybrids presented a high frequency of meiotic ...

  15. Meiotic chromosome behaviour and sexual sterility in two Nigerian ...

    African Journals Online (AJOL)

    The behaviour of meiotic chromosomes and the subsequent behaviour of the meiotic products were investigated in two Nigerian species of Aloe, namely Aloe keayi and Aloe macrocarpa var major with a view to uncovering the cause of their inability to reproduce sexually. The two plant materials used in this study were ...

  16. VDE-initiated intein homing in Saccharomyces cerevisiae proceeds in a meiotic recombination-like manner.

    Science.gov (United States)

    Fukuda, Tomoyuki; Nogami, Satoru; Ohya, Yoshikazu

    2003-07-01

    Inteins and group I introns found in prokaryotic and eukaryotic organisms occasionally behave as mobile genetic elements. During meiosis of the yeast Saccharomyces cerevisiae, the site-specific endonuclease encoded by VMA1 intein, VDE, triggers a single double-strand break (DSB) at an inteinless allele, leading to VMA1 intein homing. Besides the accumulating information on the in vitro activity of VDE, very little has been known about the molecular mechanism of intein homing in yeast nucleus. We developed an assay to detect the product of VMA1 intein homing in yeast genome. We analysed mutant phenotypes of RecA homologs, Rad51p and Dmc1p, and their interacting proteins, Rad54p and Tid1p, and found that they all play critical roles in intein inheritance. The absence of DSB end processing proteins, Sae2p and those in the Mre11-Rad50-Xrs2 complex, also causes partial reduction in homing efficiency. As with meiotic recombination, crossover events are frequently observed during intein homing. We also observed that the absence of premeiotic DNA replication caused by hydroxyurea (HU) or clb5delta clb6delta mutation reduces VDE-mediated DSBs. The repairing system working in intein homing shares molecular machinery with meiotic recombination induced by Spo11p. Moreover, like Spo11p-induced DNA cleavage, premeiotic DNA replication is a prerequisite for a VDE-induced DSB. VMA1 intein thus utilizes several host factors involved in meiotic and recombinational processes to spread its genetic information and guarantee its progeny through establishment of a parasitic relationship with the organism.

  17. Variation in genome-wide levels of meiotic recombination is established at the onset of prophase in mammalian males.

    Directory of Open Access Journals (Sweden)

    Brian Baier

    2014-01-01

    Full Text Available Segregation of chromosomes during the first meiotic division relies on crossovers established during prophase. Although crossovers are strictly regulated so that at least one occurs per chromosome, individual variation in crossover levels is not uncommon. In an analysis of different inbred strains of male mice, we identified among-strain variation in the number of foci for the crossover-associated protein MLH1. We report studies of strains with "low" (CAST/EiJ, "medium" (C3H/HeJ, and "high" (C57BL/6J genome-wide MLH1 values to define factors responsible for this variation. We utilized immunofluorescence to analyze the number and distribution of proteins that function at different stages in the recombination pathway: RAD51 and DMC1, strand invasion proteins acting shortly after double-strand break (DSB formation, MSH4, part of the complex stabilizing double Holliday junctions, and the Bloom helicase BLM, thought to have anti-crossover activity. For each protein, we identified strain-specific differences that mirrored the results for MLH1; i.e., CAST/EiJ mice had the lowest values, C3H/HeJ mice intermediate values, and C57BL/6J mice the highest values. This indicates that differences in the numbers of DSBs (as identified by RAD51 and DMC1 are translated into differences in the number of crossovers, suggesting that variation in crossover levels is established by the time of DSB formation. However, DSBs per se are unlikely to be the primary determinant, since allelic variation for the DSB-inducing locus Spo11 resulted in differences in the numbers of DSBs but not the number of MLH1 foci. Instead, chromatin conformation appears to be a more important contributor, since analysis of synaptonemal complex length and DNA loop size also identified consistent strain-specific differences; i.e., crossover frequency increased with synaptonemal complex length and was inversely related to chromatin loop size. This indicates a relationship between recombination

  18. Translocations of Chromosome End-Segments and Facultative Heterochromatin Promote Meiotic Ring Formation in Evening Primroses[W][OPEN

    Science.gov (United States)

    Golczyk, Hieronim; Massouh, Amid; Greiner, Stephan

    2014-01-01

    Due to reciprocal chromosomal translocations, many species of Oenothera (evening primrose) form permanent multichromosomal meiotic rings. However, regular bivalent pairing is also observed. Chiasmata are restricted to chromosomal ends, which makes homologous recombination virtually undetectable. Genetic diversity is achieved by changing linkage relations of chromosomes in rings and bivalents via hybridization and reciprocal translocations. Although the structural prerequisite for this system is enigmatic, whole-arm translocations are widely assumed to be the mechanistic driving force. We demonstrate that this prerequisite is genome compartmentation into two epigenetically defined chromatin fractions. The first one facultatively condenses in cycling cells into chromocenters negative both for histone H3 dimethylated at lysine 4 and for C-banding, and forms huge condensed middle chromosome regions on prophase chromosomes. Remarkably, it decondenses in differentiating cells. The second fraction is euchromatin confined to distal chromosome segments, positive for histone H3 lysine 4 dimethylation and for histone H3 lysine 27 trimethylation. The end-segments are deprived of canonical telomeres but capped with constitutive heterochromatin. This genomic organization promotes translocation breakpoints between the two chromatin fractions, thus facilitating exchanges of end-segments. We challenge the whole-arm translocation hypothesis by demonstrating why reciprocal translocations of chromosomal end-segments should strongly promote meiotic rings and evolution toward permanent translocation heterozygosity. Reshuffled end-segments, each possessing a major crossover hot spot, can furthermore explain meiotic compatibility between genomes with different translocation histories. PMID:24681616

  19. Fine-scale variation in meiotic recombination in Mimulus inferred from population shotgun sequencing

    Energy Technology Data Exchange (ETDEWEB)

    Hellsten, Uffe [USDOE Joint Genome Inst., Walnut Creek, CA (United States); Wright, Kevin M. [Harvard Univ., Cambridge, MA (United States); Jenkins, Jerry [USDOE Joint Genome Inst., Walnut Creek, CA (United States); HudsonAlpha Inst. of Biotechnology, Huntsville, AL (United States); Shu, Shengqiang [USDOE Joint Genome Inst., Walnut Creek, CA (United States); Yuan, Yao-Wu [Univ. of Connecticut, Storrs, CT (United States); Wessler, Susan R. [Univ. of California, Riverside, CA (United States); Schmutz, Jeremy [USDOE Joint Genome Inst., Walnut Creek, CA (United States); HudsonAlpha Inst. of Biotechnology, Huntsville, AL (United States); Willis, John H. [Duke Univ., Durham, NC (United States); Rokhsar, Daniel S. [USDOE Joint Genome Inst., Walnut Creek, CA (United States); Univ. of California, Berkeley, CA (United States)

    2013-11-13

    Meiotic recombination rates can vary widely across genomes, with hotspots of intense activity interspersed among cold regions. In yeast, hotspots tend to occur in promoter regions of genes, whereas in humans and mice hotspots are largely defined by binding sites of the PRDM9 protein. To investigate the detailed recombination pattern in a flowering plant we use shotgun resequencing of a wild population of the monkeyflower Mimulus guttatus to precisely locate over 400,000 boundaries of historic crossovers or gene conversion tracts. Their distribution defines some 13,000 hotspots of varying strengths, interspersed with cold regions of undetectably low recombination. Average recombination rates peak near starts of genes and fall off sharply, exhibiting polarity. Within genes, recombination tracts are more likely to terminate in exons than in introns. The general pattern is similar to that observed in yeast, as well as in PRDM9-knockout mice, suggesting that recombination initiation described here in Mimulus may reflect ancient and conserved eukaryotic mechanisms

  20. Contributions of classical and molecular cytogenetic in meiotic analysis and pollen viability for plant breeding.

    Science.gov (United States)

    Lavinscky, M P; Souza, M M; Silva, G S; Melo, C A F

    2017-09-27

    The analysis of meiotic behavior has been widely used in the study of plants as they provide relevant information about the viability of a species. Meiosis boasts a host of highly conserved events and changes in genes that control these events will give rise to irregularities that can alter the normal course of meiosis and may lead to complete sterility of the plant. The recombination of genes that occur in meiosis is an important event to generate variability and has been important in studies for genetic improvement and to create viable hybrids. The use of fluorescence in situ hybridization and genomic in situ hybridization (GISH) in meiosis allows the localization of specific regions, enables to differentiate genomes in a hybrid, permits to observe the pairing of homoeologous chromosomes, and if there was a recombination between the genomes of progenitor species. Furthermore, the GISH allows us to observe the close relationship between the species involved. This article aims to report over meiosis studies on plants and hybrids, the use and importance of molecular cytogenetic in meiotic analysis and contributions of meiotic analysis in breeding programs.

  1. Transient and Partial Nuclear Lamina Disruption Promotes Chromosome Movement in Early Meiotic Prophase.

    Science.gov (United States)

    Link, Jana; Paouneskou, Dimitra; Velkova, Maria; Daryabeigi, Anahita; Laos, Triin; Labella, Sara; Barroso, Consuelo; Pacheco Piñol, Sarai; Montoya, Alex; Kramer, Holger; Woglar, Alexander; Baudrimont, Antoine; Markert, Sebastian Mathias; Stigloher, Christian; Martinez-Perez, Enrique; Dammermann, Alexander; Alsheimer, Manfred; Zetka, Monique; Jantsch, Verena

    2018-04-23

    Meiotic chromosome movement is important for the pairwise alignment of homologous chromosomes, which is required for correct chromosome segregation. Movement is driven by cytoplasmic forces, transmitted to chromosome ends by nuclear membrane-spanning proteins. In animal cells, lamins form a prominent scaffold at the nuclear periphery, yet the role lamins play in meiotic chromosome movement is unclear. We show that chromosome movement correlates with reduced lamin association with the nuclear rim, which requires lamin phosphorylation at sites analogous to those that open lamina network crosslinks in mitosis. Failure to remodel the lamina results in delayed meiotic entry, altered chromatin organization, unpaired or interlocked chromosomes, and slowed chromosome movement. The remodeling kinases are delivered to lamins via chromosome ends coupled to the nuclear envelope, potentially enabling crosstalk between the lamina and chromosomal events. Thus, opening the lamina network plays a role in modulating contacts between chromosomes and the nuclear periphery during meiosis. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

  2. Meiotic recombination, synapsis, meiotic inactivation and sperm aneuploidy in a chromosome 1 inversion carrier.

    Science.gov (United States)

    Kirkpatrick, Gordon; Chow, Victor; Ma, Sai

    2012-01-01

    Disrupted meiotic behaviour of inversion carriers may be responsible for suboptimal sperm parameters in these carriers. This study investigated meiotic recombination, synapsis, transcriptional silencing and chromosome segregation effects in a pericentric inv(1) carrier. Recombination (MLH1), synapsis (SYCP1, SYCP3) and transcriptional inactivation (γH2AX, BRCA1) were examined by fluorescence immunostaining. Chromosome specific rates of recombination were determined by fluorescence in-situ hybridization. Furthermore, testicular sperm was examined for aneuploidy and segregation of the inv(1). Our findings showed that global recombination rates were similar to controls. Recombination on the inv(1) and the sex chromosomes were reduced. The inv(1) associated with the XY body in 43.4% of cells, in which XY recombination was disproportionately absent, and 94.3% of cells displayed asynapsed regions which displayed meiotic silencing regardless of their association with the XY body. Furthermore, a low frequency of chromosomal imbalance was observed in spermatozoa (3.4%). Our results suggest that certain inversion carriers may display unimpaired global recombination and impaired recombination on the involved and the sex chromosomes during meiosis. Asynapsis or inversion-loop formation in the inverted region may be responsible for impaired spermatogenesis and may prevent sperm-chromosome imbalance. Copyright © 2011 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  3. Combinatorial regulation of meiotic holliday junction resolution in C. elegans by HIM-6 (BLM) helicase, SLX-4, and the SLX-1, MUS-81 and XPF-1 nucleases.

    Science.gov (United States)

    Agostinho, Ana; Meier, Bettina; Sonneville, Remi; Jagut, Marlène; Woglar, Alexander; Blow, Julian; Jantsch, Verena; Gartner, Anton

    2013-01-01

    Holliday junctions (HJs) are cruciform DNA structures that are created during recombination events. It is a matter of considerable importance to determine the resolvase(s) that promote resolution of these structures. We previously reported that C. elegans GEN-1 is a symmetrically cleaving HJ resolving enzyme required for recombinational repair, but we could not find an overt role in meiotic recombination. Here we identify C. elegans proteins involved in resolving meiotic HJs. We found no evidence for a redundant meiotic function of GEN-1. In contrast, we discovered two redundant HJ resolution pathways likely coordinated by the SLX-4 scaffold protein and also involving the HIM-6/BLM helicase. SLX-4 associates with the SLX-1, MUS-81 and XPF-1 nucleases and has been implicated in meiotic recombination in C. elegans. We found that C. elegans [mus-81; xpf-1], [slx-1; xpf-1], [mus-81; him-6] and [slx-1; him-6] double mutants showed a similar reduction in survival rates as slx-4. Analysis of meiotic diakinesis chromosomes revealed a distinct phenotype in these double mutants. Instead of wild-type bivalent chromosomes, pairs of "univalents" linked by chromatin bridges occur. These linkages depend on the conserved meiosis-specific transesterase SPO-11 and can be restored by ionizing radiation, suggesting that they represent unresolved meiotic HJs. This suggests the existence of two major resolvase activities, one provided by XPF-1 and HIM-6, the other by SLX-1 and MUS-81. In all double mutants crossover (CO) recombination is reduced but not abolished, indicative of further redundancy in meiotic HJ resolution. Real time imaging revealed extensive chromatin bridges during the first meiotic division that appear to be eventually resolved in meiosis II, suggesting back-up resolution activities acting at or after anaphase I. We also show that in HJ resolution mutants, the restructuring of chromosome arms distal and proximal to the CO still occurs, suggesting that CO initiation

  4. RNAi and heterochromatin repress centromeric meiotic recombination

    DEFF Research Database (Denmark)

    Ellermeier, Chad; Higuchi, Emily C; Phadnis, Naina

    2010-01-01

    During meiosis, the formation of viable haploid gametes from diploid precursors requires that each homologous chromosome pair be properly segregated to produce an exact haploid set of chromosomes. Genetic recombination, which provides a physical connection between homologous chromosomes, is essen......During meiosis, the formation of viable haploid gametes from diploid precursors requires that each homologous chromosome pair be properly segregated to produce an exact haploid set of chromosomes. Genetic recombination, which provides a physical connection between homologous chromosomes....... Surprisingly, one mutant derepressed for recombination in the heterochromatic mating-type region during meiosis and several mutants derepressed for centromeric gene expression during mitotic growth are not derepressed for centromeric recombination during meiosis. These results reveal a complex relation between...... types of repression by heterochromatin. Our results also reveal a previously undemonstrated role for RNAi and heterochromatin in the repression of meiotic centromeric recombination and, potentially, in the prevention of birth defects by maintenance of proper chromosome segregation during meiosis....

  5. The Fanconi anemia ortholog FANCM ensures ordered homologous recombination in both somatic and meiotic cells in Arabidopsis.

    Science.gov (United States)

    Knoll, Alexander; Higgins, James D; Seeliger, Katharina; Reha, Sarah J; Dangel, Natalie J; Bauknecht, Markus; Schröpfer, Susan; Franklin, F Christopher H; Puchta, Holger

    2012-04-01

    The human hereditary disease Fanconi anemia leads to severe symptoms, including developmental defects and breakdown of the hematopoietic system. It is caused by single mutations in the FANC genes, one of which encodes the DNA translocase FANCM (for Fanconi anemia complementation group M), which is required for the repair of DNA interstrand cross-links to ensure replication progression. We identified a homolog of FANCM in Arabidopsis thaliana that is not directly involved in the repair of DNA lesions but suppresses spontaneous somatic homologous recombination via a RecQ helicase (At-RECQ4A)-independent pathway. In addition, it is required for double-strand break-induced homologous recombination. The fertility of At-fancm mutant plants is compromised. Evidence suggests that during meiosis At-FANCM acts as antirecombinase to suppress ectopic recombination-dependent chromosome interactions, but this activity is antagonized by the ZMM pathway to enable the formation of interference-sensitive crossovers and chromosome synapsis. Surprisingly, mutation of At-FANCM overcomes the sterility phenotype of an At-MutS homolog4 mutant by apparently rescuing a proportion of crossover-designated recombination intermediates via a route that is likely At-MMS and UV sensitive81 dependent. However, this is insufficient to ensure the formation of an obligate crossover. Thus, At-FANCM is not only a safeguard for genome stability in somatic cells but is an important factor in the control of meiotic crossover formation.

  6. Measuring Meiotic Crossovers via Multi-Locus Genotyping of Single Pollen Grains in Barley

    Czech Academy of Sciences Publication Activity Database

    Dreissig, S.; Fuchs, J.; Cápal, Petr; Kettles, N.; Byrne, E.; Houben, A.

    2015-01-01

    Roč. 10, č. 9 (2015), e0137677 E-ISSN 1932-6203 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : RECOMBINATION LANDSCAPE * ARABIDOPSIS * PLANTS Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.057, year: 2015

  7. Chromosome numbers and meiotic behavior of some Paspalum accessions

    Directory of Open Access Journals (Sweden)

    Eleniza de Victor Adamowski

    2005-12-01

    Full Text Available Chromosome number and meiotic behavior were evaluated in 36 Brazilian accessions of the grass Paspalum (which had never previously been analyzed to determinate which accessions might be useful in interspecific hybridizations. The analysis showed that one accession of Paspalum coryphaeum was diploid (2n = 2x = 20 and one accession of Paspalum conspersum hexaploid (2n = 6x = 60, the remaining 34 accessions being tetraploid (2n = 4x = 40. The pairing configuration was typical for the ploidy level i.e. in the diploid, chromosomes paired as 10 bivalents, in tetraploids as bi-, tri- and quadrivalents, and in hexaploid as 30 bivalents. A low frequency of meiotic abnormalities (less than 10% was observed in the diploid, hexaploid and some tetraploid accessions, although the majority of tetraploid accessions showed a high frequency of meiotic irregularities. The use of accessions with a low frequency of meiotic abnormalities in breeding programs is discussed.

  8. Magic with moulds: Meiotic and mitotic crossing over in Neurospora ...

    Indian Academy of Sciences (India)

    2006-02-16

    Feb 16, 2006 ... Home; Journals; Journal of Biosciences; Volume 31; Issue 1. Commentary: Magic with moulds: Meiotic and mitotic crossing over in Neurospora inversions and duplications. Durgadas P Kasbekar. Volume 31 Issue 1 March 2006 pp 3-4 ...

  9. wtf genes are prolific dual poison-antidote meiotic drivers.

    Science.gov (United States)

    Nuckolls, Nicole L; Bravo Núñez, María Angélica; Eickbush, Michael T; Young, Janet M; Lange, Jeffrey J; Yu, Jonathan S; Smith, Gerald R; Jaspersen, Sue L; Malik, Harmit S; Zanders, Sarah E

    2017-06-20

    Meiotic drivers are selfish genes that bias their transmission into gametes, defying Mendelian inheritance. Despite the significant impact of these genomic parasites on evolution and infertility, few meiotic drive loci have been identified or mechanistically characterized. Here, we demonstrate a complex landscape of meiotic drive genes on chromosome 3 of the fission yeasts Schizosaccharomyces kambucha and S. pombe . We identify S. kambucha wtf4 as one of these genes that acts to kill gametes (known as spores in yeast) that do not inherit the gene from heterozygotes. wtf4 utilizes dual, overlapping transcripts to encode both a gamete-killing poison and an antidote to the poison. To enact drive, all gametes are poisoned, whereas only those that inherit wtf4 are rescued by the antidote. Our work suggests that the wtf multigene family proliferated due to meiotic drive and highlights the power of selfish genes to shape genomes, even while imposing tremendous costs to fertility.

  10. Meiotic behaviour in three interspecific three-way hybrids between ...

    Indian Academy of Sciences (India)

    The meiotic behaviour of three three-way interspecific promising hybrids (H17, H27, and H34) was evaluated. ... Arrangement of parental genomes in distinct ... vanna due to its physiological tolerance to low fertility acid ... nomic evaluations.

  11. Cytological techniques to study human female meiotic prophase.

    Science.gov (United States)

    Roig, Ignasi; Garcia-Caldés, Montserrat

    2009-01-01

    Most of the human aneuploidies have a maternal origin. This feature makes the study of human female meiosis a fundamental topic to understand the reasons leading to this important social problem. Unfortunately, due to sample collection difficulties, not many studies have been performed on human female meiotic prophase. In this chapter we present a comprehensive collection of protocols that allows the study of human female meiotic prophase through different technical approaches using both spread and structurally preserved oocytes.

  12. Sordaria, a model system to uncover links between meiotic pairing and recombination.

    Science.gov (United States)

    Zickler, Denise; Espagne, Eric

    2016-06-01

    The mycelial fungus Sordaria macrospora was first used as experimental system for meiotic recombination. This review shows that it provides also a powerful cytological system for dissecting chromosome dynamics in wild-type and mutant meioses. Fundamental cytogenetic findings include: (1) the identification of presynaptic alignment as a key step in pairing of homologous chromosomes. (2) The discovery that biochemical complexes that mediate recombination at the DNA level concomitantly mediate pairing of homologs. (3) This pairing process involves not only resolution but also avoidance of chromosomal entanglements and the resolution system includes dissolution of constraining DNA recombination interactions, achieved by a unique role of Mlh1. (4) Discovery that the central components of the synaptonemal complex directly mediate the re-localization of the recombination proteins from on-axis to in-between homologue axis positions. (5) Identification of putative STUbL protein Hei10 as a structure-based signal transduction molecule that coordinates progression and differentiation of recombinational interactions at multiple stages. (6) Discovery that a single interference process mediates both nucleation of the SC and designation of crossover sites, thereby ensuring even spacing of both features. (7) Discovery of local modulation of sister-chromatid cohesion at sites of crossover recombination. Copyright © 2016 Elsevier Ltd. All rights reserved.

  13. Depletion of Key Meiotic Genes and Transcriptome-Wide Abiotic Stress Reprogramming Mark Early Preparatory Events Ahead of Apomeiotic Transition

    Directory of Open Access Journals (Sweden)

    Jubin N Shah

    2016-10-01

    Full Text Available Molecular dissection of apomixis - an asexual reproductive mode - is anticipated to solve the enigma of loss of meiotic sex, and to help fixing elite agronomic traits. The Brassicaceae genus Boechera comprises of both sexual and apomictic species, permitting comparative analyses of meiotic circumvention (apomeiosis and parthenogenesis. Whereas previous studies reported local transcriptome changes during these events, it remained unclear whether global changes associated with hybridization, polyploidy and environmental adaptation that arose during evolution of Boechera might hint as (epigenetic regulators of early development prior apomictic initiation. To identify these signatures during vegetative stages, we compared seedling RNA-seq transcriptomes of an obligate triploid apomict and a diploid sexual, both isolated from a drought-prone habitat. Uncovered were several genes differentially expressed between sexual and apomictic seedlings, including homologues of meiotic genes ASYNAPTIC 1 (ASY1 and MULTIPOLAR SPINDLE 1 (MPS1 that were down-regulated in apomicts. An intriguing class of apomict-specific deregulated genes included several NAC transcription factors, homologues of which are known to be transcriptionally reprogrammed during abiotic stress in other plants. Deregulation of both meiotic and stress-response genes during seedling stages might possibly be important in preparation for meiotic circumvention, as similar transcriptional alteration was discernible in apomeiotic floral buds too. Furthermore, we noted that the apomict showed better tolerance to osmotic stress in vitro than the sexual, in conjunction with significant upregulation of a subset of NAC genes. In support of the current model that DNA methylation epigenetically regulates stress, ploidy, hybridization and apomixis, we noted that ASY1, MPS1 and NAC019 homologues were deregulated in Boechera seedlings upon DNA demethylation, and ASY1 in particular seems to be repressed by

  14. Dimensional crossover in fragmentation

    Science.gov (United States)

    Sotolongo-Costa, Oscar; Rodriguez, Arezky H.; Rodgers, G. J.

    2000-11-01

    Experiments in which thick clay plates and glass rods are fractured have revealed different behavior of fragment mass distribution function in the small and large fragment regions. In this paper we explain this behavior using non-extensive Tsallis statistics and show how the crossover between the two regions is caused by the change in the fragments’ dimensionality during the fracture process. We obtain a physical criterion for the position of this crossover and an expression for the change in the power-law exponent between the small and large fragment regions. These predictions are in good agreement with the experiments on thick clay plates.

  15. Meiotic transmission of Drosophila pseudoobscura chromosomal arrangements.

    Directory of Open Access Journals (Sweden)

    Richard P Meisel

    Full Text Available Drosophila pseudoobscura harbors a rich gene arrangement polymorphism on the third chromosome generated by a series of overlapping paracentric inversions. The arrangements suppress recombination in heterokaryotypic individuals, which allows for the selective maintenance of coadapted gene complexes. Previous mapping experiments used to determine the degree to which recombination is suppressed in gene arrangement heterozygotes produced non-recombinant progeny in non-Mendelian ratios. The deviations from Mendelian expectations could be the result of viability differences between wild and mutant chromosomes, meiotic drive because of achiasmate pairing of homologues in heterokaryotypic females during meiosis, or a combination of both mechanisms. The possibility that the frequencies of the chromosomal arrangements in natural populations are affected by mechanisms other than adaptive selection led us to consider these hypotheses. We performed reciprocal crosses involving both heterozygous males and females to determine if the frequency of the non-recombinant progeny deviates significantly from Mendelian expectations and if the frequencies deviate between reciprocal crosses. We failed to observe non-Mendelian ratios in multiple crosses, and the frequency of the non-recombinant classes differed in only one of five pairs of reciprocal crosses despite sufficient power to detect these differences in all crosses. Our results indicate that deviations from Mendelian expectations in recombination experiments involving the D. pseudoobscura inversion system are most likely due to fitness differences of gene arrangement karyotypes in different environments.

  16. Phosphorylation of the Synaptonemal Complex Protein Zip1 Regulates the Crossover/Noncrossover Decision during Yeast Meiosis.

    Directory of Open Access Journals (Sweden)

    Xiangyu Chen

    2015-12-01

    Full Text Available Interhomolog crossovers promote proper chromosome segregation during meiosis and are formed by the regulated repair of programmed double-strand breaks. This regulation requires components of the synaptonemal complex (SC, a proteinaceous structure formed between homologous chromosomes. In yeast, SC formation requires the "ZMM" genes, which encode a functionally diverse set of proteins, including the transverse filament protein, Zip1. In wild-type meiosis, Zmm proteins promote the biased resolution of recombination intermediates into crossovers that are distributed throughout the genome by interference. In contrast, noncrossovers are formed primarily through synthesis-dependent strand annealing mediated by the Sgs1 helicase. This work identifies a conserved region on the C terminus of Zip1 (called Zip1 4S, whose phosphorylation is required for the ZMM pathway of crossover formation. Zip1 4S phosphorylation is promoted both by double-strand breaks (DSBs and the meiosis-specific kinase, MEK1/MRE4, demonstrating a role for MEK1 in the regulation of interhomolog crossover formation, as well as interhomolog bias. Failure to phosphorylate Zip1 4S results in meiotic prophase arrest, specifically in the absence of SGS1. This gain of function meiotic arrest phenotype is suppressed by spo11Δ, suggesting that it is due to unrepaired breaks triggering the meiotic recombination checkpoint. Epistasis experiments combining deletions of individual ZMM genes with sgs1-md zip1-4A indicate that Zip1 4S phosphorylation functions prior to the other ZMMs. These results suggest that phosphorylation of Zip1 at DSBs commits those breaks to repair via the ZMM pathway and provides a mechanism by which the crossover/noncrossover decision can be dynamically regulated during yeast meiosis.

  17. Temporal analysis of meiotic DNA double-strand break formation and repair in Drosophila females.

    Science.gov (United States)

    Mehrotra, S; McKim, K S

    2006-11-24

    Using an antibody against the phosphorylated form of His2Av (gamma-His2Av), we have described the time course for the series of events leading from the formation of a double-strand break (DSB) to a crossover in Drosophila female meiotic prophase. MEI-P22 is required for DSB formation and localizes to chromosomes prior to gamma-His2Av foci. Drosophila females, however, are among the group of organisms where synaptonemal complex (SC) formation is not dependent on DSBs. In the absence of two SC proteins, C(3)G and C(2)M, the number of DSBs in oocytes is significantly reduced. This is consistent with the appearance of SC protein staining prior to gamma-His2Av foci. However, SC formation is incomplete or absent in the neighboring nurse cells, and gamma-His2Av foci appear with the same kinetics as in oocytes and do not depend on SC proteins. Thus, competence for DSB formation in nurse cells occurs with a specific timing that is independent of the SC, whereas in the oocytes, some SC proteins may have a regulatory role to counteract the effects of a negative regulator of DSB formation. The SC is not sufficient for DSB formation, however, since DSBs were absent from the heterochromatin even though SC formation occurs in these regions. All gamma-His2Av foci disappear before the end of prophase, presumably as repair is completed and crossovers are formed. However, oocytes in early prophase exhibit a slower response to X-ray-induced DSBs compared to those in the late pachytene stage. Assuming all DSBs appear as gamma-His2Av foci, there is at least a 3:1 ratio of noncrossover to crossover products. From a comparison of the frequency of gamma-His2Av foci and crossovers, it appears that Drosophila females have only a weak mechanism to ensure a crossover in the presence of a low number of DSBs.

  18. Ex-vivo assessment of chronic toxicity of low levels of cadmium on testicular meiotic cells

    Energy Technology Data Exchange (ETDEWEB)

    Geoffroy-Siraudin, Cendrine [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Laboratoire de Biologie de la Reproduction, AP-HM, Hôpital de la Conception, 147, Boulevard Baille, 13385 Marseille cedex 5 (France); Perrard, Marie-Hélène [Institut de Génomique Fonctionnelle de Lyon, UMR 5242 CNRS INRA Ecole Normale Supérieure de Lyon 1, 46 allée d' Italie, F-69364 Lyon Cedex 07 (France); Ghalamoun-Slaimi, Rahma [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Laboratoire de Biologie de la Reproduction, AP-HM, Hôpital de la Conception, 147, Boulevard Baille, 13385 Marseille cedex 5 (France); Ali, Sazan [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Chaspoul, Florence [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Unité de Chimie-Physique, Faculté de Pharmacie 13005, Marseille (France); Lanteaume, André [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Achard, Vincent [Laboratoire de Biologie de la Reproduction, AP-HM, Hôpital de la Conception, 147, Boulevard Baille, 13385 Marseille cedex 5 (France); Gallice, Philippe [Aix-Marseille Univ, UMR CNRS IMBE 7263, FR 3098 ECCOREV, 13005, Marseille (France); Unité de Chimie-Physique, Faculté de Pharmacie 13005, Marseille (France); Durand, Philippe [Institut de Génomique Fonctionnelle de Lyon, UMR 5242 CNRS INRA Ecole Normale Supérieure de Lyon 1, 46 allée d' Italie, F-69364 Lyon Cedex 07 (France); and others

    2012-08-01

    Using a validated model of culture of rat seminiferous tubules, we assessed the effects of 0.1, 1 and 10 μg/L cadmium (Cd) on spermatogenic cells over a 2‐week culture period. With concentrations of 1 and 10 μg/L in the culture medium, the Cd concentration in the cells, determined by ICP-MS, increased with concentration in the medium and the day of culture. Flow cytometric analysis enabled us to evaluate changes in the number of Sertoli cells and germ cells during the culture period. The number of Sertoli cells did not appear to be affected by Cd. By contrast, spermatogonia and meiotic cells were decreased by 1 and 10 μg/L Cd in a time and dose dependent manner. Stage distribution of the meiotic prophase I and qualitative study of the synaptonemal complexes (SC) at the pachytene stage were performed by immunocytochemistry with an anti SCP3 antibody. Cd caused a time-and-dose-dependent increase of total abnormalities, of fragmented SC and of asynapsis from concentration of 0.1 μg/L. Additionally, we observed a new SC abnormality, the “motheaten” SC. This abnormality is frequently associated with asynapsis and SC widening which increased with both the Cd concentration and the duration of exposure. This abnormality suggests that Cd disrupts the structure and function of proteins involved in pairing and/or meiotic recombination. These results show that Cd induces dose-and-time-dependent alterations of the meiotic process of spermatogenesis ex-vivo, and that the lowest metal concentration, which induces an adverse effect, may vary with the cell parameter studied. -- Highlights: ► Cadmium induces ex-vivo severe time- and dose-dependent germ cell abnormalities. ► Cadmium at very low concentration (0.1 µg/l) induces synaptonemal complex abnormalities. ► The lowest concentration inducing adverse effect varied with the cell parameter studied. ► Cadmium alters proteins involved in pairing and recombination. ► Cadmium leads to achiasmate univalents and

  19. Comparison of meiotic abnormalities induced by gamma-rays between a diploid and a tetraploid species of physalis

    International Nuclear Information System (INIS)

    Gupta, S.K.; Roy, S.K.

    1985-01-01

    Radiosensitivity of a diploid (P. ixocarpa) and a tetraploid (P. peruviana) species of Physalis has been studied. Meiotic abnormalities induced by γ-rays were compared in both species and found that it was always greater in tetraploid than in diploid species at each corresponding dose. The tetraploid plant due to greater chromosomal volume is more vulnerable to radiation hits and its immediate consequences are expected to contribute to the formation of sterile pollen, but this defect could be overcome by the buffering action of the unaltered genes over the altered ones at multiple loci, which normalizes the induced plant sterility. The diploid P. ixocarpa exhibited higher radiosensitivity than the tetraploid P. peruviana. Comparison between the frequencies of meiotic anomalies of M 2 and M 1 indicated that the latter has exaggerated values on these at all exposure levels. The lowered values of M 2 indicated their elimination through diplontic selection or intrasomatic or competitive elimination during the course of time lapse. (author)

  20. Asy2/Mer2: an evolutionarily conserved mediator of meiotic recombination, pairing, and global chromosome compaction.

    Science.gov (United States)

    Tessé, Sophie; Bourbon, Henri-Marc; Debuchy, Robert; Budin, Karine; Dubois, Emeline; Liangran, Zhang; Antoine, Romain; Piolot, Tristan; Kleckner, Nancy; Zickler, Denise; Espagne, Eric

    2017-09-15

    Meiosis is the cellular program by which a diploid cell gives rise to haploid gametes for sexual reproduction. Meiotic progression depends on tight physical and functional coupling of recombination steps at the DNA level with specific organizational features of meiotic-prophase chromosomes. The present study reveals that every step of this coupling is mediated by a single molecule: Asy2/Mer2. We show that Mer2, identified so far only in budding and fission yeasts, is in fact evolutionarily conserved from fungi (Mer2/Rec15/Asy2/Bad42) to plants (PRD3/PAIR1) and mammals (IHO1). In yeasts, Mer2 mediates assembly of recombination-initiation complexes and double-strand breaks (DSBs). This role is conserved in the fungus Sordaria However, functional analysis of 13 mer2 mutants and successive localization of Mer2 to axis, synaptonemal complex (SC), and chromatin revealed, in addition, three further important functions. First, after DSB formation, Mer2 is required for pairing by mediating homolog spatial juxtaposition, with implications for crossover (CO) patterning/interference. Second, Mer2 participates in the transfer/maintenance and release of recombination complexes to/from the SC central region. Third, after completion of recombination, potentially dependent on SUMOylation, Mer2 mediates global chromosome compaction and post-recombination chiasma development. Thus, beyond its role as a recombinosome-axis/SC linker molecule, Mer2 has important functions in relation to basic chromosome structure. © 2017 Tessé et al.; Published by Cold Spring Harbor Laboratory Press.

  1. Meiotic recombination breakpoints are associated with open chromatin and enriched with repetitive DNA elements in potato

    Science.gov (United States)

    Meiotic recombination provides the framework for the genetic variation in natural and artificial populations of eukaryotes through the creation of novel haplotypes. Thus, determining the molecular characteristics of meiotic recombination remains essential for future plant breeding efforts, which hea...

  2. Gamma radiations induced meiotic abnormalities in cape gosseberry (Physalis peruviana Linn.)

    International Nuclear Information System (INIS)

    Gupta, S.K.

    1987-01-01

    The cytological alterations were systematically scored in Physalis peruviana after treatment with 5 to 60 Krads of gamma radiation. In control plant diplotenediakinesis revealed 24 bivalents and cytokinesis produced normal tetrads, whereas PMCs of differently treated plants showed various anomalies viz., altered configuration of chromosomes, clumping/sickness, fragments, bridges, laggards, unequal segregation and non-orientation of chromosomes and unequal groupings of chromosomes. Abnormal karyokinesis and/or cytokinesis led to the formation of abnormal sporads which later on causes pollen and plant sterility. While every type of anomaly is dose-dependent and tend to increase with advancing dose showing a fair degree of correlation with the dose of radiation. The persistence of meiotic abnormalities with reduce d frequency in M 2 generation also bears correlation with administered dose. (author). 10 refs

  3. Meiotic analysis in induced tetraploids of Brachiaria decumbens Stapf

    Directory of Open Access Journals (Sweden)

    Carine Simioni

    2011-01-01

    Full Text Available The meiotic behavior of three tetraploid plants (2n=4x=36 originated from somatic chromosome duplication ofsexually reproducing diploid plants of Brachiaria decumbens was evaluated. All the analyzed plants presented abnormalities relatedto polyploidy, such as irregular chromosome segregation, leading to precocious chromosome migration to the poles and micronucleiduring both meiotic divisions. However, the abnormalities observed did not compromise the meiotic products which were characterizedby regular tetrads and satisfactory pollen fertility varying from 61.36 to 64.86%. Chromosomes paired mostly as bivalents indiakinesis but univalents to tetravalents were also observed. These studies contributed to the choice of compatible fertile sexualgenitors to be crossed to natural tetraploid apomicts in the B. decumbens by identifying abnormalities and verifying pollen fertility.Intraespecific crosses should reduce sterility in the hybrids produced in the breeding program of Brachiaria, a problem observedwith the interspecific hybrids produced so far.

  4. The role of meiotic drive in hybrid male sterility.

    Science.gov (United States)

    McDermott, Shannon R; Noor, Mohamed A F

    2010-04-27

    Meiotic drive causes the distortion of allelic segregation away from Mendelian expected ratios, often also reducing fecundity and favouring the evolution of drive suppressors. If different species evolve distinct drive-suppressor systems, then hybrid progeny may be sterile as a result of negative interactions of these systems' components. Although the hypothesis that meiotic drive may contribute to hybrid sterility, and thus species formation, fell out of favour early in the 1990s, recent results showing an association between drive and sterility have resurrected this previously controversial idea. Here, we review the different forms of meiotic drive and their possible roles in speciation. We discuss the recent empirical evidence for a link between drive and hybrid male sterility, also suggesting a possible mechanistic explanation for this link in the context of chromatin remodelling. Finally, we revisit the population genetics of drive that allow it to contribute to speciation.

  5. Chromosome numbers and meiotic analysis in the pre-breeding of ...

    Indian Academy of Sciences (India)

    Among the diploid accessions, the rate of meiotic abnormalities was low, ranging from 0.82% to 7.93%. In the 27 tetraploid accessions, the rate of meiotic abnormalities ranged from 18.41% to 65.83%. The most common meiotic abnormalities were related to irregular chromosome segregation, but chromosome stickiness ...

  6. ATR acts stage specifically to regulate multiple aspects of mammalian meiotic silencing

    NARCIS (Netherlands)

    Royo, Hélène; Prosser, Haydn; Ruzankina, Yaroslava; Mahadevaiah, Shantha K.; Cloutier, Jeffrey M.; Baumann, Marek; Fukuda, Tomoyuki; Höög, Christer; Tóth, Attila; de Rooij, Dirk G.; Bradley, Allan; Brown, Eric J.; Turner, James M. A.

    2013-01-01

    In mammals, homologs that fail to synapse during meiosis are transcriptionally inactivated. This process, meiotic silencing, drives inactivation of the heterologous XY bivalent in male germ cells (meiotic sex chromosome inactivation [MSCI]) and is thought to act as a meiotic surveillance mechanism.

  7. [Identification of the meiotic events in grasshopper spermatogenesis].

    Science.gov (United States)

    Liu, Meng-Hao; Zhao, Kai-Qiang; Wang, Ya-Dong; Yang, Meng-Ping; Zhao, Ning-Ning; Yang, Da-Xiang

    2012-12-01

    The grasshoppers are ideal materials to study various meiotic stages of spermatogenesis due to their easy availability, fairly large chromosomes, and fewer numbers of chromosomes. It is easy to make temporary squash preparation of grasshopper testes; however, it is usually difficult for the beginners to differentiate between stages of meiosis. In view of this, we demonstrated the method of identification of meiotic stages by chromosome number and chromosome conformation, taking spermatogonial meiosis of Locusta migratoria manilensis as an example. We described briefly the mitosis of spermatogonia and the spermatogenesis of this species as well.

  8. Positive Feedback of NDT80 Expression Ensures Irreversible Meiotic Commitment in Budding Yeast

    Science.gov (United States)

    Tsuchiya, Dai; Yang, Yang; Lacefield, Soni

    2014-01-01

    In budding yeast, meiotic commitment is the irreversible continuation of the developmental path of meiosis. After reaching meiotic commitment, cells finish meiosis and gametogenesis, even in the absence of the meiosis-inducing signal. In contrast, if the meiosis-inducing signal is removed and the mitosis-inducing signal is provided prior to reaching meiotic commitment, cells exit meiosis and return to mitosis. Previous work has shown that cells commit to meiosis after prophase I but before entering the meiotic divisions. Since the Ndt80 transcription factor induces expression of middle meiosis genes necessary for the meiotic divisions, we examined the role of the NDT80 transcriptional network in meiotic commitment. Using a microfluidic approach to analyze single cells, we found that cells commit to meiosis in prometaphase I, after the induction of the Ndt80-dependent genes. Our results showed that high-level expression of NDT80 is important for the timing and irreversibility of meiotic commitment. A modest reduction in NDT80 levels delayed meiotic commitment based on meiotic stages, although the timing of each meiotic stage was similar to that of wildtype cells. A further reduction of NDT80 resulted in the surprising finding of inappropriately uncommitted cells: withdrawal of the meiosis-inducing signal and addition of the mitosis-inducing signal to cells at stages beyond metaphase I caused return to mitosis, leading to multi-nucleate cells. Since Ndt80 enhances its own transcription through positive feedback, we tested whether positive feedback ensured the irreversibility of meiotic commitment. Ablating positive feedback in NDT80 expression resulted in a complete loss of meiotic commitment. These findings suggest that irreversibility of meiotic commitment is a consequence of the NDT80 transcriptional positive feedback loop, which provides the high-level of Ndt80 required for the developmental switch of meiotic commitment. These results also illustrate the

  9. Senataxin plays an essential role with DNA damage response proteins in meiotic recombination and gene silencing.

    Directory of Open Access Journals (Sweden)

    Olivier J Becherel

    2013-04-01

    Full Text Available Senataxin, mutated in the human genetic disorder ataxia with oculomotor apraxia type 2 (AOA2, plays an important role in maintaining genome integrity by coordination of transcription, DNA replication, and the DNA damage response. We demonstrate that senataxin is essential for spermatogenesis and that it functions at two stages in meiosis during crossing-over in homologous recombination and in meiotic sex chromosome inactivation (MSCI. Disruption of the Setx gene caused persistence of DNA double-strand breaks, a defect in disassembly of Rad51 filaments, accumulation of DNA:RNA hybrids (R-loops, and ultimately a failure of crossing-over. Senataxin localised to the XY body in a Brca1-dependent manner, and in its absence there was incomplete localisation of DNA damage response proteins to the XY chromosomes and ATR was retained on the axial elements of these chromosomes, failing to diffuse out into chromatin. Furthermore persistence of RNA polymerase II activity, altered ubH2A distribution, and abnormal XY-linked gene expression in Setx⁻/⁻ revealed an essential role for senataxin in MSCI. These data support key roles for senataxin in coordinating meiotic crossing-over with transcription and in gene silencing to protect the integrity of the genome.

  10. Meiotic double-strand breaks at the interface of chromosome movement, chromosome remodeling, and reductional division

    Science.gov (United States)

    Storlazzi, Aurora; Tessé, Sophie; Gargano, Silvana; James, Françoise; Kleckner, Nancy; Zickler, Denise

    2003-01-01

    Chromosomal processes related to formation and function of meiotic chiasmata have been analyzed in Sordaria macrospora. Double-strand breaks (DSBs), programmed or γ-rays-induced, are found to promote four major events beyond recombination and accompanying synaptonemal complex formation: (1) juxtaposition of homologs from long-distance interactions to close presynaptic coalignment at midleptotene; (2) structural destabilization of chromosomes at leptotene/zygotene, including sister axis separation and fracturing, as revealed in a mutant altered in the conserved, axis-associated cohesin-related protein Spo76/Pds5p; (3) exit from the bouquet stage, with accompanying global chromosome movements, at zygotene/pachytene (bouquet stage exit is further found to be a cell-wide regulatory transition and DSB transesterase Spo11p is suggested to have a new noncatalytic role in this transition); (4) normal occurrence of both meiotic divisions, including normal sister separation. Functional interactions between DSBs and the spo76-1 mutation suggest that Spo76/Pds5p opposes local destabilization of axes at developing chiasma sites and raise the possibility of a regulatory mechanism that directly monitors the presence of chiasmata at metaphase I. Local chromosome remodeling at DSB sites appears to trigger an entire cascade of chromosome movements, morphogenetic changes, and regulatory effects that are superimposed upon a foundation of DSB-independent processes. PMID:14563680

  11. DNA Sequence-Mediated, Evolutionarily Rapid Redistribution of Meiotic Recombination Hotspots

    Science.gov (United States)

    Wahls, Wayne P.; Davidson, Mari K.

    2011-01-01

    Hotspots regulate the position and frequency of Spo11 (Rec12)-initiated meiotic recombination, but paradoxically they are suicidal and are somehow resurrected elsewhere in the genome. After the DNA sequence-dependent activation of hotspots was discovered in fission yeast, nearly two decades elapsed before the key realizations that (A) DNA site-dependent regulation is broadly conserved and (B) individual eukaryotes have multiple different DNA sequence motifs that activate hotspots. From our perspective, such findings provide a conceptually straightforward solution to the hotspot paradox and can explain other, seemingly complex features of meiotic recombination. We describe how a small number of single-base-pair substitutions can generate hotspots de novo and dramatically alter their distribution in the genome. This model also shows how equilibrium rate kinetics could maintain the presence of hotspots over evolutionary timescales, without strong selective pressures invoked previously, and explains why hotspots localize preferentially to intergenic regions and introns. The model is robust enough to account for all hotspots of humans and chimpanzees repositioned since their divergence from the latest common ancestor. PMID:22084420

  12. BRIT1/MCPH1 is essential for mitotic and meiotic recombination DNA repair and maintaining genomic stability in mice.

    Directory of Open Access Journals (Sweden)

    Yulong Liang

    2010-01-01

    Full Text Available BRIT1 protein (also known as MCPH1 contains 3 BRCT domains which are conserved in BRCA1, BRCA2, and other important molecules involved in DNA damage signaling, DNA repair, and tumor suppression. BRIT1 mutations or aberrant expression are found in primary microcephaly patients as well as in cancer patients. Recent in vitro studies suggest that BRIT1/MCPH1 functions as a novel key regulator in the DNA damage response pathways. To investigate its physiological role and dissect the underlying mechanisms, we generated BRIT1(-/- mice and identified its essential roles in mitotic and meiotic recombination DNA repair and in maintaining genomic stability. Both BRIT1(-/- mice and mouse embryonic fibroblasts (MEFs were hypersensitive to gamma-irradiation. BRIT1(-/- MEFs and T lymphocytes exhibited severe chromatid breaks and reduced RAD51 foci formation after irradiation. Notably, BRIT1(-/- mice were infertile and meiotic homologous recombination was impaired. BRIT1-deficient spermatocytes exhibited a failure of chromosomal synapsis, and meiosis was arrested at late zygotene of prophase I accompanied by apoptosis. In mutant spermatocytes, DNA double-strand breaks (DSBs were formed, but localization of RAD51 or BRCA2 to meiotic chromosomes was severely impaired. In addition, we found that BRIT1 could bind to RAD51/BRCA2 complexes and that, in the absence of BRIT1, recruitment of RAD51 and BRCA2 to chromatin was reduced while their protein levels were not altered, indicating that BRIT1 is involved in mediating recruitment of RAD51/BRCA2 to the damage site. Collectively, our BRIT1-null mouse model demonstrates that BRIT1 is essential for maintaining genomic stability in vivo to protect the hosts from both programmed and irradiation-induced DNA damages, and its depletion causes a failure in both mitotic and meiotic recombination DNA repair via impairing RAD51/BRCA2's function and as a result leads to infertility and genomic instability in mice.

  13. RPA homologs and ssDNA processing during meiotic recombination.

    Science.gov (United States)

    Ribeiro, Jonathan; Abby, Emilie; Livera, Gabriel; Martini, Emmanuelle

    2016-06-01

    Meiotic homologous recombination is a specialized process that involves homologous chromosome pairing and strand exchange to guarantee proper chromosome segregation and genetic diversity. The formation and repair of DNA double-strand breaks (DSBs) during meiotic recombination differs from those during mitotic recombination in that the homologous chromosome rather than the sister chromatid is the preferred repair template. The processing of single-stranded DNA (ssDNA) formed on intermediate recombination structures is central to driving the specific outcomes of DSB repair during meiosis. Replication protein A (RPA) is the main ssDNA-binding protein complex involved in DNA metabolism. However, the existence of RPA orthologs in plants and the recent discovery of meiosis specific with OB domains (MEIOB), a widely conserved meiosis-specific RPA1 paralog, strongly suggest that multiple RPA complexes evolved and specialized to subdivide their roles during DNA metabolism. Here we review ssDNA formation and maturation during mitotic and meiotic recombination underlying the meiotic specific features. We describe and discuss the existence and properties of MEIOB and multiple RPA subunits in plants and highlight how they can provide meiosis-specific fates to ssDNA processing during homologous recombination. Understanding the functions of these RPA homologs and how they interact with the canonical RPA subunits is of major interest in the fields of meiosis and DNA repair.

  14. Meiotic faults as a major cause of offspring inviability

    DEFF Research Database (Denmark)

    Levitis, Daniel; Zimmerman, Kolea; Pringle, Anne

    2014-01-01

    , this result demonstrates that failures associated with meiosis are a major cause of offspring inviability not only for meiotic parthenogenesis, but for sexual reproducers such as humans. Meiosis is necessary for genetic recombination in eukaryotes, but is vestigial, and costly, in parthenogens. The question...... range of organisms....

  15. INDUCTION OF ARTIFICIAL MEIOTIC GY~OGENESIS WITH ...

    African Journals Online (AJOL)

    BSN

    INDUCTION OF ARTIFICIAL MEIOTIC GY~OGENESIS WITH. ULTRAVIOLET RAYS IN THE AFRICA:" CATFISH, CI.ARIAS. ANGUILLARIS. ABSTRACT. P.O. ALUKO. National Institute for Freshwater Fisheries. Research, P.M.B. 6006, New Bussa. Artificial gynogenesis was induced in Clarias a11gw aris ) fenilizing the eggs ...

  16. Highlights of meiotic genes in Arabidopsis thaliana | Consiglio ...

    African Journals Online (AJOL)

    Meiosis is a fascinating and complex phenomenon and, despite its central role in sexual plant reproduction, little is known on the molecular mechanisms involved in this process. We review the progress made in recent years using Arabidopsis thaliana mutants for isolating meiotic genes. In particular, emphasis is given on ...

  17. Meiotic Consequences of Genetic Divergence Across the Murine Pseudoautosomal Region.

    Science.gov (United States)

    Dumont, Beth L

    2017-03-01

    The production of haploid gametes during meiosis is dependent on the homology-driven processes of pairing, synapsis, and recombination. On the mammalian heterogametic sex chromosomes, these key meiotic activities are confined to the pseudoautosomal region (PAR), a short region of near-perfect sequence homology between the X and Y chromosomes. Despite its established importance for meiosis, the PAR is rapidly evolving, raising the question of how proper X / Y segregation is buffered against the accumulation of homology-disrupting mutations. Here, I investigate the interplay of PAR evolution and function in two interfertile house mouse subspecies characterized by structurally divergent PARs, Mus musculus domesticus and M. m. castaneus Using cytogenetic methods to visualize the sex chromosomes at meiosis, I show that intersubspecific F 1 hybrids harbor an increased frequency of pachytene spermatocytes with unsynapsed sex chromosomes. This high rate of asynapsis is due, in part, to the premature release of synaptic associations prior to completion of prophase I. Further, I show that when sex chromosomes do synapse in intersubspecific hybrids, recombination is reduced across the paired region. Together, these meiotic defects afflict ∼50% of spermatocytes from F 1 hybrids and lead to increased apoptosis in meiotically dividing cells. Despite flagrant disruption of the meiotic program, a subset of spermatocytes complete meiosis and intersubspecific F 1 males remain fertile. These findings cast light on the meiotic constraints that shape sex chromosome evolution and offer initial clues to resolve the paradox raised by the rapid evolution of this functionally significant locus. Copyright © 2017 by the Genetics Society of America.

  18. Disruption of CHTF18 causes defective meiotic recombination in male mice.

    Directory of Open Access Journals (Sweden)

    Karen M Berkowitz

    Full Text Available CHTF18 (chromosome transmission fidelity factor 18 is an evolutionarily conserved subunit of the Replication Factor C-like complex, CTF18-RLC. CHTF18 is necessary for the faithful passage of chromosomes from one daughter cell to the next during mitosis in yeast, and it is crucial for germline development in the fruitfly. Previously, we showed that mouse Chtf18 is expressed throughout the germline, suggesting a role for CHTF18 in mammalian gametogenesis. To determine the role of CHTF18 in mammalian germ cell development, we derived mice carrying null and conditional mutations in the Chtf18 gene. Chtf18-null males exhibit 5-fold decreased sperm concentrations compared to wild-type controls, resulting in subfertility. Loss of Chtf18 results in impaired spermatogenesis; spermatogenic cells display abnormal morphology, and the stereotypical arrangement of cells within seminiferous tubules is perturbed. Meiotic recombination is defective and homologous chromosomes separate prematurely during prophase I. Repair of DNA double-strand breaks is delayed and incomplete; both RAD51 and γH2AX persist in prophase I. In addition, MLH1 foci are decreased in pachynema. These findings demonstrate essential roles for CHTF18 in mammalian spermatogenesis and meiosis, and suggest that CHTF18 may function during the double-strand break repair pathway to promote the formation of crossovers.

  19. Repression of meiotic genes by antisense transcription and by Fkh2 transcription factor in Schizosaccharomyces pombe.

    Science.gov (United States)

    Chen, Huei-Mei; Rosebrock, Adam P; Khan, Sohail R; Futcher, Bruce; Leatherwood, Janet K

    2012-01-01

    In S. pombe, about 5% of genes are meiosis-specific and accumulate little or no mRNA during vegetative growth. Here we use Affymetrix tiling arrays to characterize transcripts in vegetative and meiotic cells. In vegetative cells, many meiotic genes, especially those induced in mid-meiosis, have abundant antisense transcripts. Disruption of the antisense transcription of three of these mid-meiotic genes allowed vegetative sense transcription. These results suggest that antisense transcription represses sense transcription of meiotic genes in vegetative cells. Although the mechanism(s) of antisense mediated transcription repression need to be further explored, our data indicates that RNAi machinery is not required for repression. Previously, we and others used non-strand specific methods to study splicing regulation of meiotic genes and concluded that 28 mid-meiotic genes are spliced only in meiosis. We now demonstrate that the "unspliced" signal in vegetative cells comes from the antisense RNA, not from unspliced sense RNA, and we argue against the idea that splicing regulates these mid-meiotic genes. Most of these mid-meiotic genes are induced in mid-meiosis by the forkhead transcription factor Mei4. Interestingly, deletion of a different forkhead transcription factor, Fkh2, allows low levels of sense expression of some mid-meiotic genes in vegetative cells. We propose that vegetative expression of mid-meiotic genes is repressed at least two independent ways: antisense transcription and Fkh2 repression.

  20. Repression of Meiotic Genes by Antisense Transcription and by Fkh2 Transcription Factor in Schizosaccharomyces pombe

    Science.gov (United States)

    Chen, Huei-Mei; Rosebrock, Adam P.; Khan, Sohail R.; Futcher, Bruce; Leatherwood, Janet K.

    2012-01-01

    In S. pombe, about 5% of genes are meiosis-specific and accumulate little or no mRNA during vegetative growth. Here we use Affymetrix tiling arrays to characterize transcripts in vegetative and meiotic cells. In vegetative cells, many meiotic genes, especially those induced in mid-meiosis, have abundant antisense transcripts. Disruption of the antisense transcription of three of these mid-meiotic genes allowed vegetative sense transcription. These results suggest that antisense transcription represses sense transcription of meiotic genes in vegetative cells. Although the mechanism(s) of antisense mediated transcription repression need to be further explored, our data indicates that RNAi machinery is not required for repression. Previously, we and others used non-strand specific methods to study splicing regulation of meiotic genes and concluded that 28 mid-meiotic genes are spliced only in meiosis. We now demonstrate that the “unspliced” signal in vegetative cells comes from the antisense RNA, not from unspliced sense RNA, and we argue against the idea that splicing regulates these mid-meiotic genes. Most of these mid-meiotic genes are induced in mid-meiosis by the forkhead transcription factor Mei4. Interestingly, deletion of a different forkhead transcription factor, Fkh2, allows low levels of sense expression of some mid-meiotic genes in vegetative cells. We propose that vegetative expression of mid-meiotic genes is repressed at least two independent ways: antisense transcription and Fkh2 repression. PMID:22238674

  1. Repression of meiotic genes by antisense transcription and by Fkh2 transcription factor in Schizosaccharomyces pombe.

    Directory of Open Access Journals (Sweden)

    Huei-Mei Chen

    Full Text Available In S. pombe, about 5% of genes are meiosis-specific and accumulate little or no mRNA during vegetative growth. Here we use Affymetrix tiling arrays to characterize transcripts in vegetative and meiotic cells. In vegetative cells, many meiotic genes, especially those induced in mid-meiosis, have abundant antisense transcripts. Disruption of the antisense transcription of three of these mid-meiotic genes allowed vegetative sense transcription. These results suggest that antisense transcription represses sense transcription of meiotic genes in vegetative cells. Although the mechanism(s of antisense mediated transcription repression need to be further explored, our data indicates that RNAi machinery is not required for repression. Previously, we and others used non-strand specific methods to study splicing regulation of meiotic genes and concluded that 28 mid-meiotic genes are spliced only in meiosis. We now demonstrate that the "unspliced" signal in vegetative cells comes from the antisense RNA, not from unspliced sense RNA, and we argue against the idea that splicing regulates these mid-meiotic genes. Most of these mid-meiotic genes are induced in mid-meiosis by the forkhead transcription factor Mei4. Interestingly, deletion of a different forkhead transcription factor, Fkh2, allows low levels of sense expression of some mid-meiotic genes in vegetative cells. We propose that vegetative expression of mid-meiotic genes is repressed at least two independent ways: antisense transcription and Fkh2 repression.

  2. The kinesin AtPSS1 promotes synapsis and is required for proper crossover distribution in meiosis.

    Directory of Open Access Journals (Sweden)

    Yann Duroc

    2014-10-01

    Full Text Available Meiotic crossovers (COs shape genetic diversity by mixing homologous chromosomes at each generation. CO distribution is a highly regulated process. CO assurance forces the occurrence of at least one obligatory CO per chromosome pair, CO homeostasis smoothes out the number of COs when faced with variation in precursor number and CO interference keeps multiple COs away from each other along a chromosome. In several organisms, it has been shown that cytoskeleton forces are transduced to the meiotic nucleus via KASH- and SUN-domain proteins, to promote chromosome synapsis and recombination. Here we show that the Arabidopsis kinesin AtPSS1 plays a major role in chromosome synapsis and regulation of CO distribution. In Atpss1 meiotic cells, chromosome axes and DNA double strand breaks (DSBs appear to form normally but only a variable portion of the genome synapses and is competent for CO formation. Some chromosomes fail to form the obligatory CO, while there is an increased CO density in competent regions. However, the total number of COs per cell is unaffected. We further show that the kinesin motor domain of AtPSS1 is required for its meiotic function, and that AtPSS1 interacts directly with WIP1 and WIP2, two KASH-domain proteins. Finally, meiocytes missing AtPSS1 and/or SUN proteins show similar meiotic defects suggesting that AtPSS1 and SUNs act in the same pathway. This suggests that forces produced by the AtPSS1 kinesin and transduced by WIPs/SUNs, are required to authorize complete synapsis and regulate maturation of recombination intermediates into COs. We suggest that a form of homeostasis applies, which maintains the total number of COs per cell even if only a part of the genome is competent for CO formation.

  3. Meiosis gene inventory of four ciliates reveals the prevalence of a synaptonemal complex-independent crossover pathway.

    Science.gov (United States)

    Chi, Jingyun; Mahé, Frédéric; Loidl, Josef; Logsdon, John; Dunthorn, Micah

    2014-03-01

    To establish which meiosis genes are present in ciliates, and to look for clues as to which recombination pathways may be treaded by them, four genomes were inventoried for 11 meiosis-specific and 40 meiosis-related genes. We found that the set of meiosis genes shared by Tetrahymena thermophila, Paramecium tetraurelia, Ichthyophthirius multifiliis, and Oxytricha trifallax is consistent with the prevalence of a Mus81-dependent class II crossover pathway that is considered secondary in most model eukaryotes. There is little evidence for a canonical class I crossover pathway that requires the formation of a synaptonemal complex (SC). This gene inventory suggests that meiotic processes in ciliates largely depend on mitotic repair proteins for executing meiotic recombination. We propose that class I crossovers and SCs were reduced sometime during the evolution of ciliates. Consistent with this reduction, we provide microscopic evidence for the presence only of degenerate SCs in Stylonychia mytilus. In addition, lower nonsynonymous to synonymous mutation rates of some of the meiosis genes suggest that, in contrast to most other nuclear genes analyzed so far, meiosis genes in ciliates are largely evolving at a slower rate than those genes in fungi and animals.

  4. Meiotic Consequences of Genetic Divergence Across the Murine Pseudoautosomal Region

    OpenAIRE

    Dumont, Beth L.

    2017-01-01

    The production of haploid gametes during meiosis is dependent on the homology-driven processes of pairing, synapsis, and recombination. On the mammalian heterogametic sex chromosomes, these key meiotic activities are confined to the pseudoautosomal region (PAR), a short region of near-perfect sequence homology between the X and Y chromosomes. Despite its established importance for meiosis, the PAR is rapidly evolving, raising the question of how proper X/Y segregation is buffered against the ...

  5. Meiotic delay of translocation carrying spermatocytes responsible for reduced transmission

    International Nuclear Information System (INIS)

    Buul, P.P.W. van

    1991-01-01

    Using in vivo pulse labelling of spermatocytes from mice irradiated with different doses of X-rays (6 and 7 Gy). The authors demonstrated that cells having translocations derived from irradiated stem cells tend to spend longer time at the meiotic prophase than normal cells. At the 2 Gy level this effect is much less pronounced. The recorded delay forms a good explanation for the reduced transmission of translocations to the next generation observed by others. (author)

  6. Distinct DNA-binding surfaces in the ATPase and linker domains of MutLγ determine its substrate specificities and exert separable functions in meiotic recombination and mismatch repair.

    Directory of Open Access Journals (Sweden)

    Corentin Claeys Bouuaert

    2017-05-01

    Full Text Available Mlh1-Mlh3 (MutLγ is a mismatch repair factor with a central role in formation of meiotic crossovers, presumably through resolution of double Holliday junctions. MutLγ has DNA-binding, nuclease, and ATPase activities, but how these relate to one another and to in vivo functions are unclear. Here, we combine biochemical and genetic analyses to characterize Saccharomyces cerevisiae MutLγ. Limited proteolysis and atomic force microscopy showed that purified recombinant MutLγ undergoes ATP-driven conformational changes. In vitro, MutLγ displayed separable DNA-binding activities toward Holliday junctions (HJ and, surprisingly, single-stranded DNA (ssDNA, which was not predicted from current models. MutLγ bound DNA cooperatively, could bind multiple substrates simultaneously, and formed higher-order complexes. FeBABE hydroxyl radical footprinting indicated that the DNA-binding interfaces of MutLγ for ssDNA and HJ substrates only partially overlap. Most contacts with HJ substrates were located in the linker regions of MutLγ, whereas ssDNA contacts mapped within linker regions as well as the N-terminal ATPase domains. Using yeast genetic assays for mismatch repair and meiotic recombination, we found that mutations within different DNA-binding surfaces exert separable effects in vivo. For example, mutations within the Mlh1 linker conferred little or no meiotic phenotype but led to mismatch repair deficiency. Interestingly, mutations in the N-terminal domain of Mlh1 caused a stronger meiotic defect than mlh1Δ, suggesting that the mutant proteins retain an activity that interferes with alternative recombination pathways. Furthermore, mlh3Δ caused more chromosome missegregation than mlh1Δ, whereas mlh1Δ but not mlh3Δ partially alleviated meiotic defects of msh5Δ mutants. These findings illustrate functional differences between Mlh1 and Mlh3 during meiosis and suggest that their absence impinges on chromosome segregation not only via reduced

  7. Repression of Meiotic Genes by Antisense Transcription and by Fkh2 Transcription Factor in Schizosaccharomyces pombe

    OpenAIRE

    Chen, Huei-Mei; Rosebrock, Adam P.; Khan, Sohail R.; Futcher, Bruce; Leatherwood, Janet K.

    2012-01-01

    In S. pombe, about 5% of genes are meiosis-specific and accumulate little or no mRNA during vegetative growth. Here we use Affymetrix tiling arrays to characterize transcripts in vegetative and meiotic cells. In vegetative cells, many meiotic genes, especially those induced in mid-meiosis, have abundant antisense transcripts. Disruption of the antisense transcription of three of these mid-meiotic genes allowed vegetative sense transcription. These results suggest that antisense transcription ...

  8. Meiotic and post-meiotic studies in the male mouse exposed to X-rays and their human implications

    International Nuclear Information System (INIS)

    Szemere, G.

    1977-01-01

    Cytological studies were carried out on the meiotic process of control and irradiated male mice in order to provide direct means of estimating the non-disjunction rate for autosomes and sex chromosomes. Analysis of second meiotic divisions showed that while spontaneous rates of anaphase I non-disjunctions were extremely low, they could be enhanced by X-ray treatment of prophase spermatocytes. Irradiation at pre-leptotene resulted in a higher rate of anaphase I non-disjunction than did irradiation at pachytene, while early spermatogonia were relatively insensitive. In the present experiments, a relatively high proportion of chromosomally abnormal fetuses (including triploidy, X monosomy, autosomal trisomy and several mosaicisms) have been found amoung the progeny of males irradiated at pre-leptotene. The human implications of these findings with respect to the radiation hazards are discussed

  9. Hands-Off Time for Endotracheal Intubation during CPR Is Not Altered by the Use of the C-MAC Video-Laryngoscope Compared to Conventional Direct Laryngoscopy. A Randomized Crossover Manikin Study.

    Directory of Open Access Journals (Sweden)

    Philipp Schuerner

    Full Text Available Sufficient ventilation and oxygenation through proper airway management is essential in patients undergoing cardio-pulmonary resuscitation (CPR. Although widely discussed, securing the airway using an endotracheal tube is considered the standard of care. Endotracheal intubation may be challenging and causes prolonged interruption of chest compressions. Videolaryngoscopes have been introduced to better visualize the vocal cords and accelerate intubation, which makes endotracheal intubation much safer and may contribute to intubation success. Therefore, we aimed to compare hands-off time and intubation success of direct laryngoscopy with videolaryngoscopy (C-MAC, Karl Storz, Tuttlingen, Germany in a randomized, cross-over manikin study.Twenty-six anesthesia residents and twelve anesthesia consultants of the University Hospital Zurich were recruited through a voluntary enrolment. All participants performed endotracheal intubation using direct laryngoscopy and C-MAC in a random order during ongoing chest compressions. Participants were strictly advised to stop chest compression only if necessary.The median hands-off time was 1.9 seconds in direct laryngoscopy, compared to 3 seconds in the C-MAC group. In direct laryngoscopy 39 intubation attempts were recorded, resulting in an overall first intubation attempt success rate of 97%, compared to 38 intubation attempts and 100% overall first intubation attempt success rate in the C-MAC group.As a conclusion, the results of our manikin-study demonstrate that video laryngoscopes might not be beneficial compared to conventional, direct laryngoscopy in easily accessible airways under CPR conditions and in experienced hands. The benefits of video laryngoscopes are of course more distinct in overcoming difficult airways, as it converts a potential "blind intubation" into an intubation under visual control.

  10. Hands-Off Time for Endotracheal Intubation during CPR Is Not Altered by the Use of the C-MAC Video-Laryngoscope Compared to Conventional Direct Laryngoscopy. A Randomized Crossover Manikin Study.

    Science.gov (United States)

    Schuerner, Philipp; Grande, Bastian; Piegeler, Tobias; Schlaepfer, Martin; Saager, Leif; Hutcherson, Matthew T; Spahn, Donat R; Ruetzler, Kurt

    2016-01-01

    Sufficient ventilation and oxygenation through proper airway management is essential in patients undergoing cardio-pulmonary resuscitation (CPR). Although widely discussed, securing the airway using an endotracheal tube is considered the standard of care. Endotracheal intubation may be challenging and causes prolonged interruption of chest compressions. Videolaryngoscopes have been introduced to better visualize the vocal cords and accelerate intubation, which makes endotracheal intubation much safer and may contribute to intubation success. Therefore, we aimed to compare hands-off time and intubation success of direct laryngoscopy with videolaryngoscopy (C-MAC, Karl Storz, Tuttlingen, Germany) in a randomized, cross-over manikin study. Twenty-six anesthesia residents and twelve anesthesia consultants of the University Hospital Zurich were recruited through a voluntary enrolment. All participants performed endotracheal intubation using direct laryngoscopy and C-MAC in a random order during ongoing chest compressions. Participants were strictly advised to stop chest compression only if necessary. The median hands-off time was 1.9 seconds in direct laryngoscopy, compared to 3 seconds in the C-MAC group. In direct laryngoscopy 39 intubation attempts were recorded, resulting in an overall first intubation attempt success rate of 97%, compared to 38 intubation attempts and 100% overall first intubation attempt success rate in the C-MAC group. As a conclusion, the results of our manikin-study demonstrate that video laryngoscopes might not be beneficial compared to conventional, direct laryngoscopy in easily accessible airways under CPR conditions and in experienced hands. The benefits of video laryngoscopes are of course more distinct in overcoming difficult airways, as it converts a potential "blind intubation" into an intubation under visual control.

  11. Dicer1 depletion in male germ cells leads to infertility due to cumulative meiotic and spermiogenic defects.

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    Yannick Romero

    Full Text Available BACKGROUND: Spermatogenesis is a complex biological process that requires a highly specialized control of gene expression. In the past decade, small non-coding RNAs have emerged as critical regulators of gene expression both at the transcriptional and post-transcriptional level. DICER1, an RNAse III endonuclease, is essential for the biogenesis of several classes of small RNAs, including microRNAs (miRNAs and endogenous small interfering RNAs (endo-siRNAs, but is also critical for the degradation of toxic transposable elements. In this study, we investigated to which extent DICER1 is required for germ cell development and the progress of spermatogenesis in mice. PRINCIPAL FINDINGS: We show that the selective ablation of Dicer1 at the early onset of male germ cell development leads to infertility, due to multiple cumulative defects at the meiotic and post-meiotic stages culminating with the absence of functional spermatozoa. Alterations were observed in the first spermatogenic wave and include delayed progression of spermatocytes to prophase I and increased apoptosis, resulting in a reduced number of round spermatids. The transition from round to mature spermatozoa was also severely affected, since the few spermatozoa formed in mutant animals were immobile and misshapen, exhibiting morphological defects of the head and flagellum. We also found evidence that the expression of transposable elements of the SINE family is up-regulated in Dicer1-depleted spermatocytes. CONCLUSIONS/SIGNIFICANCE: Our findings indicate that DICER1 is dispensable for spermatogonial stem cell renewal and mitotic proliferation, but is required for germ cell differentiation through the meiotic and haploid phases of spermatogenesis.

  12. A new seed-based assay for meiotic recombination in Arabidopsis thaliana.

    NARCIS (Netherlands)

    Melamed-Bessudo, C.; Yehuda, E.; Stuitje, A.R.; Levy, A.A.

    2005-01-01

    Meiotic recombination is a fundamental biological process that plays a central role in the evolution and breeding of plants. We have developed a new seed-based assay for meiotic recombination in Arabidopsis. The assay is based on the transformation of green and red fluorescent markers expressed

  13. Meiotic behavior and pollen fertility of five species in the genus ...

    African Journals Online (AJOL)

    Meiotic behavior and pollen fertility were analysed in five Epimedium species: Epimedium chlorandrum, Epimedium acuminatum, Epimedium davidii, Epimedium ecalcaratum and Epimedium pubescens. Chromosome numbers for five species were 2n = 2x = 12. All examined species displayed stable meiotic process and ...

  14. Genetically enhanced asynapsis of autosomal chromatin promotes transcriptional dysregulation and meiotic failure

    Czech Academy of Sciences Publication Activity Database

    Homolka, David; Jansa, Petr; Forejt, Jiří

    2012-01-01

    Roč. 121, č. 1 (2012), s. 91-104 ISSN 0009-5915 R&D Projects: GA MŠk(CZ) LD11079 Institutional research plan: CEZ:AV0Z50520514 Keywords : meiotic silencing of unsynapsed chromatin * meiotic sex chromosome inactivation * autosomal translocation Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.340, year: 2012

  15. Excess single-stranded DNA inhibits meiotic double-strand break repair.

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    Rebecca Johnson

    2007-11-01

    Full Text Available During meiosis, self-inflicted DNA double-strand breaks (DSBs are created by the protein Spo11 and repaired by homologous recombination leading to gene conversions and crossovers. Crossover formation is vital for the segregation of homologous chromosomes during the first meiotic division and requires the RecA orthologue, Dmc1. We analyzed repair during meiosis of site-specific DSBs created by another nuclease, VMA1-derived endonuclease (VDE, in cells lacking Dmc1 strand-exchange protein. Turnover and resection of the VDE-DSBs was assessed in two different reporter cassettes that can repair using flanking direct repeat sequences, thereby obviating the need for a Dmc1-dependent DNA strand invasion step. Access of the single-strand binding complex replication protein A, which is normally used in all modes of DSB repair, was checked in chromatin immunoprecipitation experiments, using antibody against Rfa1. Repair of the VDE-DSBs was severely inhibited in dmc1Delta cells, a defect that was associated with a reduction in the long tract resection required to initiate single-strand annealing between the flanking repeat sequences. Mutants that either reduce Spo11-DSB formation or abolish resection at Spo11-DSBs rescued the repair block. We also found that a replication protein A component, Rfa1, does not accumulate to expected levels at unrepaired single-stranded DNA (ssDNA in dmc1Delta cells. The requirement of Dmc1 for VDE-DSB repair using flanking repeats appears to be caused by the accumulation of large quantities of ssDNA that accumulate at Spo11-DSBs when Dmc1 is absent. We propose that these resected DSBs sequester both resection machinery and ssDNA binding proteins, which in wild-type cells would normally be recycled as Spo11-DSBs repair. The implication is that repair proteins are in limited supply, and this could reflect an underlying mechanism for regulating DSB repair in wild-type cells, providing protection from potentially harmful effects

  16. Meiotic Clade AAA ATPases: Protein Polymer Disassembly Machines.

    Science.gov (United States)

    Monroe, Nicole; Hill, Christopher P

    2016-05-08

    Meiotic clade AAA ATPases (ATPases associated with diverse cellular activities), which were initially grouped on the basis of phylogenetic classification of their AAA ATPase cassette, include four relatively well characterized family members, Vps4, spastin, katanin and fidgetin. These enzymes all function to disassemble specific polymeric protein structures, with Vps4 disassembling the ESCRT-III polymers that are central to the many membrane-remodeling activities of the ESCRT (endosomal sorting complexes required for transport) pathway and spastin, katanin p60 and fidgetin affecting multiple aspects of cellular dynamics by severing microtubules. They share a common domain architecture that features an N-terminal MIT (microtubule interacting and trafficking) domain followed by a single AAA ATPase cassette. Meiotic clade AAA ATPases function as hexamers that can cycle between the active assembly and inactive monomers/dimers in a regulated process, and they appear to disassemble their polymeric substrates by translocating subunits through the central pore of their hexameric ring. Recent studies with Vps4 have shown that nucleotide-induced asymmetry is a requirement for substrate binding to the pore loops and that recruitment to the protein lattice via MIT domains also relieves autoinhibition and primes the AAA ATPase cassettes for substrate binding. The most striking, unifying feature of meiotic clade AAA ATPases may be their MIT domain, which is a module that is found in a wide variety of proteins that localize to ESCRT-III polymers. Spastin also displays an adjacent microtubule binding sequence, and the presence of both ESCRT-III and microtubule binding elements may underlie the recent findings that the ESCRT-III disassembly function of Vps4 and the microtubule-severing function of spastin, as well as potentially katanin and fidgetin, are highly coordinated. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Prevention of DNA Rereplication Through a Meiotic Recombination Checkpoint Response

    Directory of Open Access Journals (Sweden)

    Nicole A. Najor

    2016-12-01

    Full Text Available In the budding yeast Saccharomyces cerevisiae, unnatural stabilization of the cyclin-dependent kinase inhibitor Sic1 during meiosis can trigger extra rounds of DNA replication. When programmed DNA double-strand breaks (DSBs are generated but not repaired due to absence of DMC1, a pathway involving the checkpoint gene RAD17 prevents this DNA rereplication. Further genetic analysis has now revealed that prevention of DNA rereplication also requires MEC1, which encodes a protein kinase that serves as a central checkpoint regulator in several pathways including the meiotic recombination checkpoint response. Downstream of MEC1, MEK1 is required through its function to inhibit repair between sister chromatids. By contrast, meiotic recombination checkpoint effectors that regulate gene expression and cyclin-dependent kinase activity are not necessary. Phosphorylation of histone H2A, which is catalyzed by Mec1 and the related Tel1 protein kinase in response to DSBs, and can help coordinate activation of the Rad53 checkpoint protein kinase in the mitotic cell cycle, is required for the full checkpoint response. Phosphorylation sites that are targeted by Rad53 in a mitotic S phase checkpoint response are also involved, based on the behavior of cells containing mutations in the DBF4 and SLD3 DNA replication genes. However, RAD53 does not appear to be required, nor does RAD9, which encodes a mediator of Rad53, consistent with their lack of function in the recombination checkpoint pathway that prevents meiotic progression. While this response is similar to a checkpoint mechanism that inhibits initiation of DNA replication in the mitotic cell cycle, the evidence points to a new variation on DNA replication control.

  18. Chromosomal rearrangement interferes with meiotic X chromosome inactivation

    Czech Academy of Sciences Publication Activity Database

    Homolka, David; Ivánek, Robert; Čapková, Jana; Jansa, Petr; Forejt, Jiří

    2007-01-01

    Roč. 17, č. 10 (2007), s. 1431-1437 ISSN 1088-9051 R&D Projects: GA MŠk(CZ) 1M0520; GA ČR GA301/06/1334; GA ČR GA301/07/1383 Grant - others:Howard Hughes Medical Institute(US) HHMI 55000306 Institutional research plan: CEZ:AV0Z50520514 Keywords : chromosomal translocations * meiotic X chromosome inactivation * spermatogenesis Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 11.224, year: 2007

  19. Meiotic behavior of wild Caricaceae species potentially suitable for papaya improvement

    Directory of Open Access Journals (Sweden)

    Emanuelli Narducci da Silva

    2012-01-01

    Full Text Available The purpose of this study was to evaluate the meiotic behavior and determine the meiotic index and pollen viability of representative plants of the wild species V. goudotiana, V. quercifolia and J. spinosa. Meiotic analysis confirmed that the species are diploid and have 18 chromosomes. Meiosis was partially normal, since some abnormalities, e.g, sticky and lagging chromosomes, precocious segregation, lack of synchrony, and disturbances in the spindle fibers were observed. These abnormalities resulted in post-meiotic products (monads, dyads, triads, and polyads that probably contributed to the meiotic index of 85.7 % (V. goudotiana to 95.9 % (J. spinosa; significant variation was observed in the species V. goudotiana. The pollen viability of 68.0% (V. goudotiana to 96.0 % (J. spinosa was reasonably good in these wild species. Crossings in breeding programs involving V. goudotiana should therefore be carefully planned, since part of the gametes of this species is unviable.

  20. The BCS-BEC Crossover

    Science.gov (United States)

    Parish, Meera M.

    2015-09-01

    This chapter presents the crossover from the Bardeen-Cooper-Schrieffer (BCS) state of weakly correlated pairs of fermions to the Bose-Einstein condensation (BEC) of diatomic molecules in the atomic Fermi gas. Our aim is to provide a pedagogical review of the BCS-BEC crossover, with an emphasis on the basic concepts, particularly those that are not generally known or are difficult to find in the literature. We shall not attempt to give an exhaustive survey of current research in the limited space here; where possible, we will direct the reader to more extensive reviews.

  1. Mre11 and Exo1 contribute to the initiation and processivity of resection at meiotic double-strand breaks made independently of Spo11.

    Science.gov (United States)

    Hodgson, Adam; Terentyev, Yaroslav; Johnson, Rebecca A; Bishop-Bailey, Anna; Angevin, Thibaut; Croucher, Adam; Goldman, Alastair S H

    2011-02-07

    During meiosis DNA double-strand breaks (DSBs) are induced and repaired by homologous recombination to create gene conversion and crossover products. Mostly these DSBs are made by Spo11, which covalently binds to the DSB ends. More rarely in Saccharomyces cerevisiae, other meiotic DSBs are formed by self-homing endonucleases such as VDE, which is site specific and does not covalently bind to the DSB ends. We have used experimentally located VDE-DSB sites to analyse an intermediate step in homologous recombination, resection of the single-strand ending 5' at the DSB site. Analysis of strains with different mutant alleles of MRE11 (mre11-58S and mre11-H125N) and deleted for EXO1 indicated that these two nucleases make significant contributions to repair of VDE-DSBs. Physical analysis of single-stranded repair intermediates indicates that efficient initiation and processivity of resection at VDE-DSBs require both Mre11 and Exo1, with loss of function for either protein causing severe delay in resection. We propose that these experiments model what happens at Spo11-DSBs after removal of the covalently bound protein, and that Mre11 and Exo1 are the major nucleases involved in creating resection tracts of widely varying lengths typical of meiotic recombination. Copyright © 2010 Elsevier B.V. All rights reserved.

  2. Crossover distribution and frequency are regulated by him-5 in Caenorhabditis elegans.

    Science.gov (United States)

    Meneely, Philip M; McGovern, Olivia L; Heinis, Frazer I; Yanowitz, Judith L

    2012-04-01

    Mutations in the him-5 gene in Caenorhabditis elegans strongly reduce the frequency of crossovers on the X chromosome, with lesser effects on the autosomes. him-5 mutants also show a change in crossover distribution on both the X and autosomes. These phenotypes are accompanied by a delayed entry into pachytene and premature desynapsis of the X chromosome. The nondisjunction, progression defects and desynapsis can be rescued by an exogenous source of double strand breaks (DSBs), indicating that the role of HIM-5 is to promote the formation of meiotic DSBs. Molecular cloning of the gene shows that the inferred HIM-5 product is a highly basic protein of 252 amino acids with no clear orthologs in other species, including other Caenorhabditis species. Although him-5 mutants are defective in segregation of the X chromosome, HIM-5 protein localizes preferentially to the autosomes. The mutant phenotypes and localization of him-5 are similar but not identical to the results seen with xnd-1, although unlike xnd-1, him-5 has no apparent effect on the acetylation of histone H2A on lysine 5 (H2AacK5). The localization of HIM-5 to the autosomes depends on the activities of both xnd-1 and him-17 allowing us to begin to establish pathways for the control of crossover distribution and frequency.

  3. Genome-Wide Analysis of Heteroduplex DNA in Mismatch Repair–Deficient Yeast Cells Reveals Novel Properties of Meiotic Recombination Pathways

    Science.gov (United States)

    Martini, Emmanuelle; Borde, Valérie; Legendre, Matthieu; Audic, Stéphane; Regnault, Béatrice; Soubigou, Guillaume; Dujon, Bernard; Llorente, Bertrand

    2011-01-01

    Meiotic DNA double-strand breaks (DSBs) initiate crossover (CO) recombination, which is necessary for accurate chromosome segregation, but DSBs may also repair as non-crossovers (NCOs). Multiple recombination pathways with specific intermediates are expected to lead to COs and NCOs. We revisited the mechanisms of meiotic DSB repair and the regulation of CO formation, by conducting a genome-wide analysis of strand-transfer intermediates associated with recombination events. We performed this analysis in a SK1 × S288C Saccharomyces cerevisiae hybrid lacking the mismatch repair (MMR) protein Msh2, to allow efficient detection of heteroduplex DNAs (hDNAs). First, we observed that the anti-recombinogenic activity of MMR is responsible for a 20% drop in CO number, suggesting that in MMR–proficient cells some DSBs are repaired using the sister chromatid as a template when polymorphisms are present. Second, we observed that a large fraction of NCOs were associated with trans–hDNA tracts constrained to a single chromatid. This unexpected finding is compatible with dissolution of double Holliday junctions (dHJs) during repair, and it suggests the existence of a novel control point for CO formation at the level of the dHJ intermediate, in addition to the previously described control point before the dHJ formation step. Finally, we observed that COs are associated with complex hDNA patterns, confirming that the canonical double-strand break repair model is not sufficient to explain the formation of most COs. We propose that multiple factors contribute to the complexity of recombination intermediates. These factors include repair of nicks and double-stranded gaps, template switches between non-sister and sister chromatids, and HJ branch migration. Finally, the good correlation between the strand transfer properties observed in the absence of and in the presence of Msh2 suggests that the intermediates detected in the absence of Msh2 reflect normal intermediates. PMID

  4. Genome-wide analysis of heteroduplex DNA in mismatch repair-deficient yeast cells reveals novel properties of meiotic recombination pathways.

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    Emmanuelle Martini

    2011-09-01

    Full Text Available Meiotic DNA double-strand breaks (DSBs initiate crossover (CO recombination, which is necessary for accurate chromosome segregation, but DSBs may also repair as non-crossovers (NCOs. Multiple recombination pathways with specific intermediates are expected to lead to COs and NCOs. We revisited the mechanisms of meiotic DSB repair and the regulation of CO formation, by conducting a genome-wide analysis of strand-transfer intermediates associated with recombination events. We performed this analysis in a SK1 × S288C Saccharomyces cerevisiae hybrid lacking the mismatch repair (MMR protein Msh2, to allow efficient detection of heteroduplex DNAs (hDNAs. First, we observed that the anti-recombinogenic activity of MMR is responsible for a 20% drop in CO number, suggesting that in MMR-proficient cells some DSBs are repaired using the sister chromatid as a template when polymorphisms are present. Second, we observed that a large fraction of NCOs were associated with trans-hDNA tracts constrained to a single chromatid. This unexpected finding is compatible with dissolution of double Holliday junctions (dHJs during repair, and it suggests the existence of a novel control point for CO formation at the level of the dHJ intermediate, in addition to the previously described control point before the dHJ formation step. Finally, we observed that COs are associated with complex hDNA patterns, confirming that the canonical double-strand break repair model is not sufficient to explain the formation of most COs. We propose that multiple factors contribute to the complexity of recombination intermediates. These factors include repair of nicks and double-stranded gaps, template switches between non-sister and sister chromatids, and HJ branch migration. Finally, the good correlation between the strand transfer properties observed in the absence of and in the presence of Msh2 suggests that the intermediates detected in the absence of Msh2 reflect normal intermediates.

  5. Genetic analysis of variation in human meiotic recombination.

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    Reshmi Chowdhury

    2009-09-01

    Full Text Available The number of recombination events per meiosis varies extensively among individuals. This recombination phenotype differs between female and male, and also among individuals of each gender. In this study, we used high-density SNP genotypes of over 2,300 individuals and their offspring in two datasets to characterize recombination landscape and to map the genetic variants that contribute to variation in recombination phenotypes. We found six genetic loci that are associated with recombination phenotypes. Two of these (RNF212 and an inversion on chromosome 17q21.31 were previously reported in the Icelandic population, and this is the first replication in any other population. Of the four newly identified loci (KIAA1462, PDZK1, UGCG, NUB1, results from expression studies provide support for their roles in meiosis. Each of the variants that we identified explains only a small fraction of the individual variation in recombination. Notably, we found different sequence variants associated with female and male recombination phenotypes, suggesting that they are regulated by different genes. Characterization of genetic variants that influence natural variation in meiotic recombination will lead to a better understanding of normal meiotic events as well as of non-disjunction, the primary cause of pregnancy loss.

  6. Meiotically stable natural epialleles of Sadhu, a novel Arabidopsis retroposon.

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    Sanjida H Rangwala

    2006-03-01

    Full Text Available Epigenetic variation is a potential source of genomic and phenotypic variation among different individuals in a population, and among different varieties within a species. We used a two-tiered approach to identify naturally occurring epigenetic alleles in the flowering plant Arabidopsis: a primary screen for transcript level polymorphisms among three strains (Col, Cvi, Ler, followed by a secondary screen for epigenetic alleles. Here, we describe the identification of stable, meiotically transmissible epigenetic alleles that correspond to one member of a previously uncharacterized non-LTR retroposon family, which we have designated Sadhu. The pericentromeric At2g10410 element is highly expressed in strain Col, but silenced in Ler and 18 other strains surveyed. Transcription of this locus is inversely correlated with cytosine methylation and both the expression and DNA methylation states map in a Mendelian manner to stable cis-acting variation. The silent Ler allele can be converted by the epigenetic modifier mutation ddm1 to a meiotically stable expressing allele with an identical primary nucleotide sequence, demonstrating that the variation responsible for transcript level polymorphism among Arabidopsis strains is epigenetic. We extended our characterization of the Sadhu family members and show that different elements are subject to both genetic and epigenetic variation in natural populations. These findings support the view that an important component of natural variation in retroelements is epigenetic.

  7. X-ray induction of mitotic and meiotic chromosome aberrations

    International Nuclear Information System (INIS)

    Yao, K.T.S.

    1980-01-01

    In 1964 six pairs of rat kangaroo (Potorous tridactylis) were obtained from Australia. The tissues of these animals were used to initiate cell lines. Since this species has a low chromosome number of six pairs, each pair with its own distinctive morphology, it is particularly favorable for cytogenetic research. In cell cultures derived from the corneal endothelial tissues of one animal there emerged a number of haploid cells. The number of haploid cells in the cultures reached as high as 20% of the total mitotic configurations. The in vitro diploid and haploid mixture cell cultures could be a resemblance or a coincidence to the mixture existence of the diploid primary spermatocytes and the haploid secondary spermatocytes (gametes) in the in vivo testicular tissues of the male animals. It would be interesting to compare reactions of the haploid and diploid cell mixture, either in the cultures or in the testes, to x-ray exposure. Two other studies involving x-ray effects on Chinese hamster oocyte maturation and meiotic chromosomes and the x-ray induction of Chinese hamster spermatocyte meiotic chromosome aberrations have been done in this laboratory. A review of these three studies involving diploid and haploid chromosomes may lead to further research in the x-ray induction of chromosome aberrations

  8. Cross-Over Clinical Trials?

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    Latif Gachkar

    2017-01-01

    Full Text Available Abstract Cross-Over Clinical Trials in comparison with Parallel groups clinical trials have some advantages such as control of confounding variables, small sample size, and short time to implement the research project. But this type of research has few essential limitations that discusses in this monogram.

  9. Meiotic interference among MLH1 foci requires neither an intact axial element structure nor full synapsis

    NARCIS (Netherlands)

    Boer, den E.; Dietrich, A.J.J.; Höög, C.; Stam, P.; Heyting, C.

    2007-01-01

    During meiosis, homologous chromosomes (homologs) perform reciprocal exchanges (crossovers) at a high frequency. Crossovers display interference, i.e. their spacing is more even than would be expected if they were placed randomly along the chromosomes. Concomitantly with crossover formation,

  10. A high incidence of meiotic silencing of unsynapsed chromatin is not associated with substantial pachytene loss in heterozygous male mice carrying multiple simple robertsonian translocations.

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    Marcia Manterola

    2009-08-01

    Full Text Available Meiosis is a complex type of cell division that involves homologous chromosome pairing, synapsis, recombination, and segregation. When any of these processes is altered, cellular checkpoints arrest meiosis progression and induce cell elimination. Meiotic impairment is particularly frequent in organisms bearing chromosomal translocations. When chromosomal translocations appear in heterozygosis, the chromosomes involved may not correctly complete synapsis, recombination, and/or segregation, thus promoting the activation of checkpoints that lead to the death of the meiocytes. In mammals and other organisms, the unsynapsed chromosomal regions are subject to a process called meiotic silencing of unsynapsed chromatin (MSUC. Different degrees of asynapsis could contribute to disturb the normal loading of MSUC proteins, interfering with autosome and sex chromosome gene expression and triggering a massive pachytene cell death. We report that in mice that are heterozygous for eight multiple simple Robertsonian translocations, most pachytene spermatocytes bear trivalents with unsynapsed regions that incorporate, in a stage-dependent manner, proteins involved in MSUC (e.g., gammaH2AX, ATR, ubiquitinated-H2A, SUMO-1, and XMR. These spermatocytes have a correct MSUC response and are not eliminated during pachytene and most of them proceed into diplotene. However, we found a high incidence of apoptotic spermatocytes at the metaphase stage. These results suggest that in Robertsonian heterozygous mice synapsis defects on most pachytene cells do not trigger a prophase-I checkpoint. Instead, meiotic impairment seems to mainly rely on the action of a checkpoint acting at the metaphase stage. We propose that a low stringency of the pachytene checkpoint could help to increase the chances that spermatocytes with synaptic defects will complete meiotic divisions and differentiate into viable gametes. This scenario, despite a reduction of fertility, allows the spreading

  11. Meiotic Recombination Analyses in Pigs Carrying Different Balanced Structural Chromosomal Rearrangements.

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    Nicolas Mary

    Full Text Available Correct pairing, synapsis and recombination between homologous chromosomes are essential for normal meiosis. All these events are strongly regulated, and our knowledge of the mechanisms involved in this regulation is increasing rapidly. Chromosomal rearrangements are known to disturb these processes. In the present paper, synapsis and recombination (number and distribution of MLH1 foci were studied in three boars (Sus scrofa domestica carrying different chromosomal rearrangements. One (T34he was heterozygote for the t(3;4(p1.3;q1.5 reciprocal translocation, one (T34ho was homozygote for that translocation, while the third (T34Inv was heterozygote for both the translocation and a pericentric inversion inv(4(p1.4;q2.3. All three boars were normal for synapsis and sperm production. This particular situation allowed us to rigorously study the impact of rearrangements on recombination. Overall, the rearrangements induced only minor modifications of the number of MLH1 foci (per spermatocyte or per chromosome and of the length of synaptonemal complexes for chromosomes 3 and 4. The distribution of MLH1 foci in T34he was comparable to that of the controls. Conversely, the distributions of MLH1 foci on chromosome 4 were strongly modified in boar T34Inv (lack of crossover in the heterosynaptic region of the quadrivalent, and crossover displaced to the chromosome extremities, and also in boar T34ho (two recombination peaks on the q-arms compared with one of higher magnitude in the controls. Analyses of boars T34he and T34Inv showed that the interference was propagated through the breakpoints. A different result was obtained for boar T34ho, in which the breakpoints (transition between SSC3 and SSC4 chromatin on the bivalents seemed to alter the transmission of the interference signal. Our results suggest that the number of crossovers and crossover interference could be regulated by partially different mechanisms.

  12. Crossover patterning by the beam-film model: analysis and implications.

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    Liangran Zhang

    2014-01-01

    Full Text Available Crossing-over is a central feature of meiosis. Meiotic crossover (CO sites are spatially patterned along chromosomes. CO-designation at one position disfavors subsequent CO-designation(s nearby, as described by the classical phenomenon of CO interference. If multiple designations occur, COs tend to be evenly spaced. We have previously proposed a mechanical model by which CO patterning could occur. The central feature of a mechanical mechanism is that communication along the chromosomes, as required for CO interference, can occur by redistribution of mechanical stress. Here we further explore the nature of the beam-film model, its ability to quantitatively explain CO patterns in detail in several organisms, and its implications for three important patterning-related phenomena: CO homeostasis, the fact that the level of zero-CO bivalents can be low (the "obligatory CO", and the occurrence of non-interfering COs. Relationships to other models are discussed.

  13. A simple model for the influence of meiotic conversion tracts on GC content.

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    Marie-Claude Marsolier-Kergoat

    Full Text Available A strong correlation between GC content and recombination rate is observed in many eukaryotes, which is thought to be due to conversion events linked to the repair of meiotic double-strand breaks. In several organisms, the length of conversion tracts has been shown to decrease exponentially with increasing distance from the sites of meiotic double-strand breaks. I show here that this behavior leads to a simple analytical model for the evolution and the equilibrium state of the GC content of sequences devoid of meiotic double-strand break sites. In the yeast Saccharomyces cerevisiae, meiotic double-strand breaks are practically excluded from protein-coding sequences. A good fit was observed between the predictions of the model and the variations of the average GC content of the third codon position (GC3 of S. cerevisiae genes. Moreover, recombination parameters that can be extracted by fitting the data to the model coincide with experimentally determined values. These results thus indicate that meiotic recombination plays an important part in determining the fluctuations of GC content in yeast coding sequences. The model also accounted for the different patterns of GC variations observed in the genes of Candida species that exhibit a variety of sexual lifestyles, and hence a wide range of meiotic recombination rates. Finally, the variations of the average GC3 content of human and chicken coding sequences could also be fitted by the model. These results suggest the existence of a widespread pattern of GC variation in eukaryotic genes due to meiotic recombination, which would imply the generality of two features of meiotic recombination: its association with GC-biased gene conversion and the quasi-exclusion of meiotic double-strand breaks from coding sequences. Moreover, the model points out to specific constraints on protein fragments encoded by exon terminal sequences, which are the most affected by the GC bias.

  14. Homeostatic regulation of meiotic DSB formation by ATM/ATR

    International Nuclear Information System (INIS)

    Cooper, Tim J.; Wardell, Kayleigh; Garcia, Valerie; Neale, Matthew J.

    2014-01-01

    Ataxia–telangiectasia mutated (ATM) and RAD3-related (ATR) are widely known as being central players in the mitotic DNA damage response (DDR), mounting responses to DNA double-strand breaks (DSBs) and single-stranded DNA (ssDNA) respectively. The DDR signalling cascade couples cell cycle control to damage-sensing and repair processes in order to prevent untimely cell cycle progression while damage still persists [1]. Both ATM/ATR are, however, also emerging as essential factors in the process of meiosis; a specialised cell cycle programme responsible for the formation of haploid gametes via two sequential nuclear divisions. Central to achieving accurate meiotic chromosome segregation is the introduction of numerous DSBs spread across the genome by the evolutionarily conserved enzyme, Spo11. This review seeks to explore and address how cells utilise ATM/ATR pathways to regulate Spo11-DSB formation, establish DSB homeostasis and ensure meiosis is completed unperturbed

  15. Homeostatic regulation of meiotic DSB formation by ATM/ATR

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, Tim J.; Wardell, Kayleigh; Garcia, Valerie; Neale, Matthew J., E-mail: m.neale@sussex.ac.uk

    2014-11-15

    Ataxia–telangiectasia mutated (ATM) and RAD3-related (ATR) are widely known as being central players in the mitotic DNA damage response (DDR), mounting responses to DNA double-strand breaks (DSBs) and single-stranded DNA (ssDNA) respectively. The DDR signalling cascade couples cell cycle control to damage-sensing and repair processes in order to prevent untimely cell cycle progression while damage still persists [1]. Both ATM/ATR are, however, also emerging as essential factors in the process of meiosis; a specialised cell cycle programme responsible for the formation of haploid gametes via two sequential nuclear divisions. Central to achieving accurate meiotic chromosome segregation is the introduction of numerous DSBs spread across the genome by the evolutionarily conserved enzyme, Spo11. This review seeks to explore and address how cells utilise ATM/ATR pathways to regulate Spo11-DSB formation, establish DSB homeostasis and ensure meiosis is completed unperturbed.

  16. Using Micromanipulation to Analyze Control of Vertebrate Meiotic Spindle Size

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    Jun Takagi

    2013-10-01

    Full Text Available The polymerization/depolymerization dynamics of microtubules (MTs have been reported to contribute to control of the size and shape of spindles, but quantitative analysis of how the size and shape correlate with the amount and density of MTs in the spindle remains incomplete. Here, we measured these parameters using 3D microscopy of meiotic spindles that self-organized in Xenopus egg extracts and presented a simple equation describing the relationship among these parameters. To examine the validity of the equation, we cut the spindle into two fragments along the pole-to-pole axis by micromanipulation techniques that rapidly decrease the amount of MTs. The spheroidal shape spontaneously recovered within 5 min, but the size of each fragment remained small. The equation we obtained quantitatively describes how the spindle size correlates with the amount of MTs while maintaining the shape and the MT density.

  17. Dimensional crossover in directed percolation

    International Nuclear Information System (INIS)

    Chame, A.M.N.; Queiroz, S.L.A. de; Santos, Raimundo R. dos.

    1984-04-01

    We study the dimensional crossover in directed percolation in three dimensions. Bonds are allowed to have different concentrations along the three cartesian axes of the lattice. Through a Position Space Renormalization Group we obtain the phase-diagrama where non-percolating, 1-D, 2-D and 3-D percolating phases are present. We find that the isotropic fixed points are unstable with respect to anisotropy, thus driving the system into a different universality class. (author) [pt

  18. Aberrant meiotic behavior in Agave tequilana Weber var. azul.

    Science.gov (United States)

    Ruvalcaba-Ruiz, Domingo; Rodríguez-Garay, Benjamin

    2002-10-23

    Agave tequilana Weber var. azul, is the only one variety permitted by federal law in México to be used for tequila production which is the most popular contemporary alcoholic beverage made from agave and recognized worldwide. Despite the economic, genetic, and ornamental value of the plant, it has not been subjected to detailed cytogenetic research, which could lead to a better understanding of its reproduction for future genetic improvement. The objective of this work was to study the meiotic behavior in pollen mother cells and its implications on the pollen viability in Agave tequilana Weber var. azul. The analysis of Pollen Mother Cells in anaphase I (A-I) showed 82.56% of cells with a normal anaphase and, 17.44% with an irregular anaphase. In which 5.28% corresponded to cells with side arm bridges (SAB); 3.68% cells with one bridge and one fragment; 2.58% of irregular anaphase showed cells with one or two lagging chromosomes and 2.95% showed one acentric fragment; cells with two bridges and cells with two bridges and one acentric fragment were observed in frequencies of 1.60% and 1.35% respectively. In anaphase II some cells showed bridges and fragments too. Aberrant A-I cells had many shrunken or empty pollen grains (42.00%) and 58.00 % viable pollen. The observed meiotic irregularities suggest that structural chromosome aberrations have occurred, such as heterozygous inversions, sister chromatid exchanges, deletions and duplications which in turn are reflected in a low pollen viability.

  19. Aberrant meiotic behavior in Agave tequilana Weber var. azul

    Directory of Open Access Journals (Sweden)

    Rodríguez-Garay Benjamin

    2002-10-01

    Full Text Available Abstract Background Agave tequilana Weber var. azul, is the only one variety permitted by federal law in México to be used for tequila production which is the most popular contemporary alcoholic beverage made from agave and recognized worldwide. Despite the economic, genetic, and ornamental value of the plant, it has not been subjected to detailed cytogenetic research, which could lead to a better understanding of its reproduction for future genetic improvement. The objective of this work was to study the meiotic behavior in pollen mother cells and its implications on the pollen viability in Agave tequilana Weber var. azul. Results The analysis of Pollen Mother Cells in anaphase I (A-I showed 82.56% of cells with a normal anaphase and, 17.44% with an irregular anaphase. In which 5.28% corresponded to cells with side arm bridges (SAB; 3.68% cells with one bridge and one fragment; 2.58% of irregular anaphase showed cells with one or two lagging chromosomes and 2.95% showed one acentric fragment; cells with two bridges and cells with two bridges and one acentric fragment were observed in frequencies of 1.60% and 1.35% respectively. In anaphase II some cells showed bridges and fragments too. Aberrant A-I cells had many shrunken or empty pollen grains (42.00% and 58.00 % viable pollen. Conclusion The observed meiotic irregularities suggest that structural chromosome aberrations have occurred, such as heterozygous inversions, sister chromatid exchanges, deletions and duplications which in turn are reflected in a low pollen viability.

  20. Polaron crossover in molecular solids

    International Nuclear Information System (INIS)

    Zoli, Marco; Das, A N

    2004-01-01

    An analytical variational method is applied to the molecular Holstein Hamiltonian in which the dispersive features of the dimension dependent phonon spectrum are taken into account by a force constant approach. The crossover between a large and a small size polaron is monitored, in one, two and three dimensions and for different values of the adiabatic parameter, through the behaviour of the effective mass as a function of the electron-phonon coupling. By increasing the strength of the intermolecular forces the crossover becomes smoother and occurs at higher e-ph couplings. These effects are more evident in three dimensions. We show that our modified Lang-Firsov method starts to capture the occurrence of a polaron self-trapping transition when the electron energies become of order of the phonon energies. The self-trapping event persists in the fully adiabatic regime. At the crossover we estimate polaron effective masses of order ∼ 5-40 times the bare band mass according to the dimensionality and the value of the adiabatic parameter. Modified Lang-Firsov polaron masses are substantially reduced in two and three dimensions. There is no self-trapping in the antiadiabatic regime

  1. Meiotic genes and sexual reproduction in the green algal class Trebouxiophyceae (Chlorophyta)

    KAUST Repository

    Fučí ková , Karolina; Pažoutová , Marie; Rindi, Fabio

    2015-01-01

    being the only partial exceptions (only four genes present). The evidence of sex provided by the meiotic genes is phylogenetically widespread in the class and indicates that sexual reproduction is not associated with any particular morphological

  2. The temporal response of recombination events to gamma radiation of meiotic cells in Sordaria brevicollis.

    Science.gov (United States)

    Lewis, L A

    1982-01-01

    The temporal frequencies of different stages of prophase I were determined cytologically in Sordaria brevicollis (Olive and Fantini) as the basis for ascertaining the degree of synchrony in meiosis in this ascomycete. Croziers, karyogamy-zygotene and pachytene asci were shown to be in significant majorities at three distinct periods of the meiotic cycle. The response of recombination frequency to ionizing radiation was examined for the entire meiotic cycle. Three radiosensitive periods were determined. This response, which correlated temporally with each of the three peaks in ascal frequency, is interpreted as showing that the meiotic cycle of this organism is divided into periods of recombination commitment (radiation reduced frequencies) during the pre-meiotic S phase and recombination consummation (radiation induced frequencies) during zygotene and pachytene. The results are discussed in the context of the time at which recombination is consummated in eukaryotes such as yeast and Drosophila.

  3. Meiotic behavior of Adesmia DC. (Leguminosae-Faboideae species native to Rio Grande do Sul, Brazil

    Directory of Open Access Journals (Sweden)

    Coelho Liliana Gressler May

    1998-01-01

    Full Text Available Meiotic behavior in Adesmia DC. is described for the first time. The study encompassed twelve populations of seven Adesmia DC. species native to Rio Grande do Sul, Brazil. Populations with 2n = 2x = 20 are A. securigerifolia 9615, A. riograndensis 9590 (subnudae, A. latifolia 1568, 1775, 15025, A. bicolor JB-UFSM, A. incana var. incana 9636, 10288, A. punctata var. hilariana 6885, 10812, and A. tristis 10757. A. incana var. incana 9637 is a tetraploid with 2n = 4x = 40. The material was stained with 1% acetic orcein. The meiotic behavior of the populations studied was considered normal. The meiotic index (MI and the estimates of pollen grain viability were above 95%, except for A. latifolia 1568 (MI = 89%. The present data indicate that these plants are meiotically stable and potentially fertile, apparently with no problems for use in programs of selection, crossing and viable seed production.

  4. The fission yeast MTREC and EJC orthologs ensure the maturation of meiotic transcripts during meiosis.

    Science.gov (United States)

    Marayati, Bahjat Fadi; Hoskins, Victoria; Boger, Robert W; Tucker, James F; Fishman, Emily S; Bray, Andrew S; Zhang, Ke

    2016-09-01

    Meiosis is a highly regulated process by which genetic information is transmitted through sexual reproduction. It encompasses unique mechanisms that do not occur in vegetative cells, producing a distinct, well-regulated meiotic transcriptome. During vegetative growth, many meiotic genes are constitutively transcribed, but most of the resulting mRNAs are rapidly eliminated by the Mmi1-MTREC (Mtl1-Red1 core) complex. While Mmi1-MTREC targets premature meiotic RNAs for degradation by the nuclear 3'-5' exoribonuclease exosome during mitotic growth, its role in meiotic gene expression during meiosis is not known. Here, we report that Red5, an essential MTREC component, interacts with pFal1, an ortholog of eukaryotic translation initiation factor eIF4aIII in the fission yeast Schizosaccharomyces pombe In mammals, together with MAGO (Mnh1), Rnps1, and Y14, elF4AIII (pFal1) forms the core of the exon junction complex (EJC), which is essential for transcriptional surveillance and localization of mature mRNAs. In fission yeast, two EJC orthologs, pFal1 and Mnh1, are functionally connected with MTREC, specifically in the process of meiotic gene expression during meiosis. Although pFal1 interacts with Mnh1, Y14, and Rnps1, its association with Mnh1 is not disrupted upon loss of Y14 or Rnps1. Mutations of Red1, Red5, pFal1, or Mnh1 produce severe meiotic defects; the abundance of meiotic transcripts during meiosis decreases; and mRNA maturation processes such as splicing are impaired. Since studying meiosis in mammalian germline cells is difficult, our findings in fission yeast may help to define the general mechanisms involved in accurate meiotic gene expression in higher eukaryotes. © 2016 Marayati et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.

  5. Radiation-induced mitotic and meiotic aneuploidy in the yeast Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Parry, J.M.; Sharp, D.; Tippins, R.S.; Parry, E.M.

    1979-01-01

    A number of genetic systems are described which in yeast may be used to monitor the induction of chromosome aneuploidy during both mitotic and meiotic cell division. Using these systems the authors have been able to demonstrate the induction of both monosomic and trisomic cells in mitotically dividing cells and disomic spores in meiotically dividing cells after both UV light and X-ray exposure. (Auth.)

  6. Meiotic behaviour and spermatogenesis in male mice heterozygous for translocation types also occurring in man

    International Nuclear Information System (INIS)

    Nijhoff, J.H.

    1981-01-01

    In this thesis a start was made with meiotic observations of mouse translocation types - a Robertsonian translocation and a translocation between a metacentric and an acrocentric chromosome - which also occur in man. As an exogeneous factor of possible influence, the meiotic effects of two types of radiation (fission neutrons and X-rays) administered at relatively low doses 2 and 3 hours before prometaphase-metaphase II (probably during metaphase-anaphase I), were determined in Rb4Bnr/+-males. (Auth.)

  7. Colocalization of somatic and meiotic double strand breaks near the Myc oncogene on mouse chromosome 15.

    Science.gov (United States)

    Ng, Siemon H; Maas, Sarah A; Petkov, Petko M; Mills, Kevin D; Paigen, Kenneth

    2009-10-01

    Both somatic and meiotic recombinations involve the repair of DNA double strand breaks (DSBs) that occur at preferred locations in the genome. Improper repair of DSBs during either mitosis or meiosis can lead to mutations, chromosomal aberration such as translocations, cancer, and/or cell death. Currently, no model exists that explains the locations of either spontaneous somatic DSBs or programmed meiotic DSBs or relates them to each other. One common class of tumorigenic translocations arising from DSBs is chromosomal rearrangements near the Myc oncogene. Myc translocations have been associated with Burkitt lymphoma in humans, plasmacytoma in mice, and immunocytoma in rats. Comparing the locations of somatic and meiotic DSBs near the mouse Myc oncogene, we demonstrated that the placement of these DSBs is not random and that both events clustered in the same short discrete region of the genome. Our work shows that both somatic and meiotic DSBs tend to occur in proximity to each other within the Myc region, suggesting that they share common originating features. It is likely that some regions of the genome are more susceptible to both somatic and meiotic DSBs, and the locations of meiotic hotspots may be an indicator of genomic regions more susceptible to DNA damage. (c) 2009 Wiley-Liss, Inc.

  8. Conditional genomic rearrangement by designed meiotic recombination using VDE (PI-SceI) in yeast.

    Science.gov (United States)

    Fukuda, Tomoyuki; Ohya, Yoshikazu; Ohta, Kunihiro

    2007-10-01

    Meiotic recombination plays critical roles in the acquisition of genetic diversity and has been utilized for conventional breeding of livestock and crops. The frequency of meiotic recombination is normally low, and is extremely low in regions called "recombination cold domains". Here, we describe a new and highly efficient method to modulate yeast meiotic gene rearrangements using VDE (PI-SceI), an intein-encoded endonuclease that causes an efficient unidirectional meiotic gene conversion at its recognition sequence (VRS). We designed universal targeting vectors, by use of which the strain that inserts the VRS at a desired site is acquired. Meiotic induction of the strains provided unidirectional gene conversions and frequent genetic rearrangements of flanking genes with little impact on cell viability. This system thus opens the way for the designed modulation of meiotic gene rearrangements, regardless of recombinational activity of chromosomal domains. Finally, the VDE-VRS system enabled us to conduct meiosis-specific conditional knockout of genes where VDE-initiated gene conversion disrupts the target gene during meiosis, serving as a novel approach to examine the functions of genes during germination of resultant spores.

  9. Selective Regulation of Oocyte Meiotic Events Enhances Progress in Fertility Preservation Methods

    Directory of Open Access Journals (Sweden)

    Onder Celik

    2015-01-01

    Full Text Available Following early embryonic germ cell migration, oocytes are surrounded by somatic cells and remain arrested at diplotene stage until luteinizing hormone (LH surge. Strict regulation of both meiotic arrest and meiotic resumption during dormant stage are critical for future fertility. Intercellular signaling system between the somatic compartment and oocyte regulates these meiotic events and determines the follicle quality. As well as the collected number of eggs, their qualities are also important for in vitro fertilization (IVF outcome. In spontaneous and IVF cycles, germinal vesicle (GV–stage oocytes, premature GV breakdown, and persistence of first meiotic arrest limit the reproductive performance. Likewise, both women with premature ovarian aging and young cancer women are undergoing chemoradiotherapy under the risk of follicle loss because of unregulated meiotic events. Understanding of oocyte meiotic events is therefore critical for the prevention of functional ovarian reserve. High levels of cyclic guanosine monophophate (cGMP, cyclic adenosine monophophate (cAMP and low phosphodiesterase (PDE 3A enzyme activity inside the oocyte are responsible for maintaining of meiotic arrest before the LH surge. cGMP is produced in the somatic compartment, and natriuretic peptide precursor C (Nppc and natriuretic peptide receptor 2 (Npr2 regulate its production. cGMP diffuses into the oocyte and reduces the PDE3A activity, which inhibits the conversion of cAMP to the 5′AMP, and cAMP levels are enhanced. In addition, oocyte itself has the ability to produce cAMP. Taken together, accumulation of cAMP inside the oocyte induces protein kinase activity, which leads to the inhibition of maturation-promoting factor and meiotic arrest also continues. By stimulating the expression of epidermal growth factor, LH inhibits the Nppc/Npr2 system, blocks cGMP synthesis, and initiates meiotic resumption. Oocytes lacking the functional of this pathway may lead to

  10. The mismatch repair and meiotic recombination endonuclease Mlh1-Mlh3 is activated by polymer formation and can cleave DNA substrates in trans.

    Science.gov (United States)

    Manhart, Carol M; Ni, Xiaodan; White, Martin A; Ortega, Joaquin; Surtees, Jennifer A; Alani, Eric

    2017-04-01

    Crossing over between homologs is initiated in meiotic prophase by the formation of DNA double-strand breaks that occur throughout the genome. In the major interference-responsive crossover pathway in baker's yeast, these breaks are resected to form 3' single-strand tails that participate in a homology search, ultimately forming double Holliday junctions (dHJs) that primarily include both homologs. These dHJs are resolved by endonuclease activity to form exclusively crossovers, which are critical for proper homolog segregation in Meiosis I. Recent genetic, biochemical, and molecular studies in yeast are consistent with the hypothesis of Mlh1-Mlh3 DNA mismatch repair complex acting as the major endonuclease activity that resolves dHJs into crossovers. However, the mechanism by which the Mlh1-Mlh3 endonuclease is activated is unknown. Here, we provide evidence that Mlh1-Mlh3 does not behave like a structure-specific endonuclease but forms polymers required to generate nicks in DNA. This conclusion is supported by DNA binding studies performed with different-sized substrates that contain or lack polymerization barriers and endonuclease assays performed with varying ratios of endonuclease-deficient and endonuclease-proficient Mlh1-Mlh3. In addition, Mlh1-Mlh3 can generate religatable double-strand breaks and form an active nucleoprotein complex that can nick DNA substrates in trans. Together these observations argue that Mlh1-Mlh3 may not act like a canonical, RuvC-like Holliday junction resolvase and support a novel model in which Mlh1-Mlh3 is loaded onto DNA to form an activated polymer that cleaves DNA.

  11. Induction of congenital malformations in the offspring of male mice treated with X-rays at pre-meiotic and post-meiotic stages

    International Nuclear Information System (INIS)

    Kirk, K.M.; Lyon, M.F.

    1984-01-01

    The induction of congenital malformations among the offspring of male mice treated with X-rays at pre-meiotic and post-meiotic stages has been studied in two experiments. Firstly, animals were exposed to varying doses of X-rays and mated at various time intervals, so as to sample spermatozoa, spermatids and spermatogonial stem cells. In the second experiment, only treated spermatogonial stem cells were sampled. One group of males was given a single dose, a second group a fractionated dose and a third group was left unexposed. In the first experiment, induced post-implantation dominant lethality increased with dose, and was highest in week 3, in line with the known greater radiosensitivity of the early spermatid stage. Preimplantation loss also increased with dose and was highest in week 3. There was no clear induction of either pre-implantation or post-implantation loss at spermatogonial stem cell stages. There was a clear induction of congenital malformations at post-meiotic stages. At the two highest doses the early spermatids (15-21 days) appeared more sensitive than spermatozoa, and at this stage the incidence of malformations increased with dose. Expt. 2 showed a statistically significant induction of malformations at both dose levels. The relative sensitivities of male stem cells, post-meiotic stages and mature oocytes to the induction of congenital malformations were reasonably similar to their sensitivities for specific-locus mutations, except that the expected enhancing effect of the fractionation regime used was not seen. (Auth.)

  12. Induction of congenital malformations in the offspring of male mice treated with X-rays at pre-meiotic and post-meiotic stages

    Energy Technology Data Exchange (ETDEWEB)

    Kirk, K.M.; Lyon, M.F. (Medical Research Council, Harwell (UK). Radiobiological Research Unit)

    1984-01-01

    The induction of congenital malformations among the offspring of male mice treated with X-rays at pre-meiotic and post-meiotic stages has been studied in two experiments. Firstly, animals were exposed to varying doses of X-rays and mated at various time intervals, so as to sample spermatozoa, spermatids and spermatogonial stem cells. In the second experiment, only treated spermatogonial stem cells were sampled. One group of males was given a single dose, a second group a fractionated dose and a third group was left unexposed. In the first experiment, induced post-implantation dominant lethality increased with dose, and was highest in week 3, in line with the known greater radiosensitivity of the early spermatid stage. Preimplantation loss also increased with dose and was highest in week 3. There was no clear induction of either pre-implantation or post-implantation loss at spermatogonial stem cell stages. There was a clear induction of congenital malformations at post-meiotic stages. At the two highest doses the early spermatids (15-21 days) appeared more sensitive than spermatozoa, and at this stage the incidence of malformations increased with dose. Expt. 2 showed a statistically significant induction of malformations at both dose levels. The relative sensitivities of male stem cells, post-meiotic stages and mature oocytes to the induction of congenital malformations were reasonably similar to their sensitivities for specific-locus mutations, except that the expected enhancing effect of the fractionation regime used was not seen.

  13. Preimplantation genetic diagnosis outcomes and meiotic segregation analysis of robertsonian translocation carriers.

    Science.gov (United States)

    Ko, Duck Sung; Cho, Jae Won; Lee, Hyoung-Song; Kim, Jin Yeong; Kang, Inn Soo; Yang, Kwang Moon; Lim, Chun Kyu

    2013-04-01

    To investigate the meiotic segregation patterns of cleavage-stage embryos from robertsonian translocation carriers and aneuploidy of chromosome 18 according to meiotic segregation patterns. Retrospective study. Infertility center and laboratory of reproductive biology and infertility. Sixty-two couples with robertsonian translocation carriers. One blastomere was biopsied from embryos and diagnosed with the use of fluorescence in situ hybridization (FISH). Translocation chromosomes were analyzed with the use of locus-specific and subtelomeric FISH probes. Aneuploidy of chromosome 18 was assessed simultaneously with translocation chromosomes. Preimplantation genetic diagnosis (PGD) outcomes, meiotic segregation patterns of robertsonian translocation, and aneuploidy of chromosome 18 depending on meiotic segregation patterns. Two hundred seventy embryos of 332 transferrable embryos were transferred in 113 cycles, and 27 healthy babies were born. The alternate segregation was significantly higher in male carriers than in female carriers (43.9% vs. 29.9%, respectively), and adjacent segregation was higher in female carriers than in male carriers (44.7% vs. 38.7%, respectively). Aneuploidy of chromosome 18 was significantly increased in 3:0-segregated or chaotic embryos. Forty-seven alternate embryos were excluded from embryo replacement owing to aneuploidy of chromosome 18. In carriers of robertsonian translocation, meiotic segregation showed differences between men and women. Frequent meiotic errors caused by premature predivision or nondisjunction and less stringent checkpoint in women might cause such differences between sexes. Aneuploidy of chromosome 18 might be influenced by meiotic segregation of translocation chromosomes. Factors that cause malsegregation, such as 3:0 or chaotic segregation, seem to play a role in aneuploidy of chromosome 18. Copyright © 2013 American Society for Reproductive Medicine. Published by Elsevier Inc. All rights reserved.

  14. Meiotic consequences of induced chromosomal anomalies in Triticum aestivum L

    International Nuclear Information System (INIS)

    Larik, A.S.; Hafiz, H.M.I.; Ansari, N.N.

    1981-01-01

    Investigations on the mechanism of chromosome breakages, types of aberrations and their genetic consequences form an integral part of the most of the studies on radiation genetics (BROCK 1977; KONZAK et al. 1977; LARIK 1975; SEARS 1977; SHARMA & FORSBEGR 1977), covering a wide range of plants belonging to both wild and cultivated species. Mutations due to deficiency of genes with a dominant or epistatic effect occur in very high frequency (MAC KEY 1968) because the well buffered genomes of polyploids can tolerate losses of large chromosome segments and even of entire chromosomes (LARIK 1978a; LARIK & THOMAS 1979; LARIK et al. 1980a). Extensive investigations on the effect of physical and chemical mutagens on the cytological behaviour of wheat and other plants have already been reported (GAUL 1977). However, cytological studies on the M 2 and M 3 populations are very limited (LARIK et al. 1980a). An attempt has been made in the present work to extend these studies. This paper presents an analysis of meiotic anomalies in M 3 populations of bread wheat and discusses their significance with reference to genetics and plant breeding

  15. Recombination Proteins Mediate Meiotic Spatial Chromosome Organization and Pairing

    Science.gov (United States)

    Storlazzi, Aurora; Gargano, Silvana; Ruprich-Robert, Gwenael; Falque, Matthieu; David, Michelle; Kleckner, Nancy; Zickler, Denise

    2010-01-01

    SUMMARY Meiotic chromosome pairing involves not only recognition of homology but also juxtaposition of entire chromosomes in a topologically regular way. Analysis of filamentous fungus Sordaria macrospora reveals that recombination proteins Mer3, Msh4 and Mlh1 play direct roles in all of these aspects, in advance of their known roles in recombination. Absence of Mer3 helicase results in interwoven chromosomes, thereby revealing the existence of features that specifically ensure “entanglement avoidance”. Entanglements that remain at zygotene, i.e. “interlockings”, require Mlh1 for resolution, likely to eliminate constraining recombinational connections. Patterns of Mer3 and Msh4 foci along aligned chromosomes show that the double-strand breaks mediating homologous alignment have spatially separated ends, one localized to each partner axis, and that pairing involves interference among developing interhomolog interactions. We propose that Mer3, Msh4 and Mlh1 execute all of these roles during pairing by modulating the state of nascent double-strand break/partner DNA contacts within axis-associated recombination complexes. PMID:20371348

  16. On the origin of sex chromosomes from meiotic drive

    Science.gov (United States)

    Úbeda, Francisco; Patten, Manus M.; Wild, Geoff

    2015-01-01

    Most animals and many plants make use of specialized chromosomes (sex chromosomes) to determine an individual's sex. Best known are the XY and ZW sex-determination systems. Despite having evolved numerous times, sex chromosomes present something of an evolutionary puzzle. At their origin, alleles that dictate development as one sex or the other (primitive sex chromosomes) face a selective penalty, as they will be found more often in the more abundant sex. How is it possible that primitive sex chromosomes overcome this disadvantage? Any theory for the origin of sex chromosomes must identify the benefit that outweighs this cost and enables a sex-determining mutation to establish in the population. Here we show that a new sex-determining allele succeeds when linked to a sex-specific meiotic driver. The new sex-determining allele benefits from confining the driving allele to the sex in which it gains the benefit of drive. Our model requires few special assumptions and is sufficiently general to apply to the evolution of sex chromosomes in outbreeding cosexual or dioecious species. We highlight predictions of the model that can discriminate between this and previous theories of sex-chromosome origins. PMID:25392470

  17. Meiotic Chromosome Analysis of the Giant Water Bug, Lethocerus indicus

    Science.gov (United States)

    Wisoram, Wijit; Saengthong, Pradit; Ngernsiri, Lertluk

    2013-01-01

    The giant water bug, Lethocerus indicus (Lepeletier and Serville) (Heteroptera: Belostomatidae), a native species of Southeast Asia, is one of the largest insects belonging to suborder Heteroptera. In this study, the meiotic chromosome of L. indicus was studied in insect samples collected from Thailand, Myanmar, Loas, and Cambodia. Testicular cells stained with lacto-acetic orcein, Giemsa, DAPI, and silver nitrate were analyzed. The results revealed that the chromosome complement of L. indicus was 2n = 22A + neo-XY + 2m, which differed from that of previous reports. Each individual male contained testicular cells with three univalent patterns. The frequency of cells containing neo-XY chromosome univalent (∼5%) was a bit higher than that of cells with autosomal univalents (∼3%). Some cells (∼0.5%) had both sex chromosome univalents and a pair of autosomal univalents. None of the m-chromosome univalents were observed during prophase I. In addition, this report presents clear evidence about the existence of m-chromosomes in Belostomatidae. PMID:23895100

  18. Prdm9, a major determinant of meiotic recombination hotspots, is not functional in dogs and their wild relatives, wolves and coyotes.

    Directory of Open Access Journals (Sweden)

    Violeta Muñoz-Fuentes

    Full Text Available Meiotic recombination is a fundamental process needed for the correct segregation of chromosomes during meiosis in sexually reproducing organisms. In humans, 80% of crossovers are estimated to occur at specific areas of the genome called recombination hotspots. Recently, a protein called PRDM9 was identified as a major player in determining the location of genome-wide meiotic recombination hotspots in humans and mice. The origin of this protein seems to be ancient in evolutionary time, as reflected by its fairly conserved structure in lineages that diverged over 700 million years ago. Despite its important role, there are many animal groups in which Prdm9 is absent (e.g. birds, reptiles, amphibians, diptera and it has been suggested to have disruptive mutations and thus to be a pseudogene in dogs. Because of the dog's history through domestication and artificial selection, we wanted to confirm the presence of a disrupted Prdm9 gene in dogs and determine whether this was exclusive of this species or whether it also occurred in its wild ancestor, the wolf, and in a close relative, the coyote. We sequenced the region in the dog genome that aligned to the last exon of the human Prdm9, containing the entire zinc finger domain, in 4 dogs, 17 wolves and 2 coyotes. Our results show that the three canid species possess mutations that likely make this gene non functional. Because these mutations are shared across the three species, they must have appeared prior to the split of the wolf and the coyote, millions of years ago, and are not related to domestication. In addition, our results suggest that in these three canid species recombination does not occur at hotspots or hotspot location is controlled through a mechanism yet to be determined.

  19. DNA helicase HIM-6/BLM both promotes MutSγ-dependent crossovers and antagonizes MutSγ-independent interhomolog associations during caenorhabditis elegans meiosis.

    Science.gov (United States)

    Schvarzstein, Mara; Pattabiraman, Divya; Libuda, Diana E; Ramadugu, Ajit; Tam, Angela; Martinez-Perez, Enrique; Roelens, Baptiste; Zawadzki, Karl A; Yokoo, Rayka; Rosu, Simona; Severson, Aaron F; Meyer, Barbara J; Nabeshima, Kentaro; Villeneuve, Anne M

    2014-09-01

    Meiotic recombination is initiated by the programmed induction of double-strand DNA breaks (DSBs), lesions that pose a potential threat to the genome. A subset of the DSBs induced during meiotic prophase become designated to be repaired by a pathway that specifically yields interhomolog crossovers (COs), which mature into chiasmata that temporarily connect the homologs to ensure their proper segregation at meiosis I. The remaining DSBs must be repaired by other mechanisms to restore genomic integrity prior to the meiotic divisions. Here we show that HIM-6, the Caenorhabditis elegans ortholog of the RecQ family DNA helicase BLM, functions in both of these processes. We show that him-6 mutants are competent to load the MutSγ complex at multiple potential CO sites, to generate intermediates that fulfill the requirements of monitoring mechanisms that enable meiotic progression, and to accomplish and robustly regulate CO designation. However, recombination events at a subset of CO-designated sites fail to mature into COs and chiasmata, indicating a pro-CO role for HIM-6/BLM that manifests itself late in the CO pathway. Moreover, we find that in addition to promoting COs, HIM-6 plays a role in eliminating and/or preventing the formation of persistent MutSγ-independent associations between homologous chromosomes. We propose that HIM-6/BLM enforces biased outcomes of recombination events to ensure that both (a) CO-designated recombination intermediates are reliably resolved as COs and (b) other recombination intermediates reliably mature into noncrossovers in a timely manner. Copyright © 2014 by the Genetics Society of America.

  20. Utilization during mitotic cell division of loci controlling meiotic recombination and disjunction in Drosophila melanogaster

    International Nuclear Information System (INIS)

    Baker, B.S.; Carpenter, A.T.C.; Ripoll, P.

    1978-01-01

    To inquire whether the loci identified by recombination-defective and disjunction-defective meiotic mutants in Drosophila are also utilized during mitotic cell division, the effects of 18 meiotic mutants (representing 13 loci) on mitotic chromosome stability have been examined genetically. To do this, meiotic-mutant-bearing flies heterozygous for recessive somatic cell markers were examined for the frequencies and types of spontaneous clones expressing the cell markers. In such flies, marked clones can arise via mitotic recombination, mutation, chromosome breakage, nondisjunction or chromosome loss, and clones from these different origins can be distinguished. In addition, meiotic mutants at nine loci have been examined for their effects on sensitivity to killing by uv and x rays. Mutants at six of the seven recombination-defective loci examined (mei-9, mei-41, c(3)G, mei-W68, mei-S282, mei-352, mei-218) cause mitotic chromosome instability in both sexes, whereas mutants at one locus (mei-218) do not affect mitotic chromosome stability. Thus many of the loci utilized during meiotic recombination also function in the chromosomal economy of mitotic cells

  1. MEIOB targets single-strand DNA and is necessary for meiotic recombination.

    Directory of Open Access Journals (Sweden)

    Benoit Souquet

    Full Text Available Meiotic recombination is a mandatory process for sexual reproduction. We identified a protein specifically implicated in meiotic homologous recombination that we named: meiosis specific with OB domain (MEIOB. This protein is conserved among metazoan species and contains single-strand DNA binding sites similar to those of RPA1. Our studies in vitro revealed that both recombinant and endogenous MEIOB can be retained on single-strand DNA. Those in vivo demonstrated the specific expression of Meiob in early meiotic germ cells and the co-localization of MEIOB protein with RPA on chromosome axes. MEIOB localization in Dmc1 (-/- spermatocytes indicated that it accumulates on resected DNA. Homologous Meiob deletion in mice caused infertility in both sexes, due to a meiotic arrest at a zygotene/pachytene-like stage. DNA double strand break repair and homologous chromosome synapsis were impaired in Meiob (-/- meiocytes. Interestingly MEIOB appeared to be dispensable for the initial loading of recombinases but was required to maintain a proper number of RAD51 and DMC1 foci beyond the zygotene stage. In light of these findings, we propose that RPA and this new single-strand DNA binding protein MEIOB, are essential to ensure the proper stabilization of recombinases which is required for successful homology search and meiotic recombination.

  2. Correlation of Meiotic DSB Formation and Transcription Initiation Around Fission Yeast Recombination Hotspots.

    Science.gov (United States)

    Yamada, Shintaro; Okamura, Mika; Oda, Arisa; Murakami, Hiroshi; Ohta, Kunihiro; Yamada, Takatomi

    2017-06-01

    Meiotic homologous recombination, a critical event for ensuring faithful chromosome segregation and creating genetic diversity, is initiated by programmed DNA double-strand breaks (DSBs) formed at recombination hotspots. Meiotic DSB formation is likely to be influenced by other DNA-templated processes including transcription, but how DSB formation and transcription interact with each other has not been understood well. In this study, we used fission yeast to investigate a possible interplay of these two events. A group of hotspots in fission yeast are associated with sequences similar to the cyclic AMP response element and activated by the ATF/CREB family transcription factor dimer Atf1-Pcr1. We first focused on one of those hotspots, ade6-3049 , and Atf1. Our results showed that multiple transcripts, shorter than the ade6 full-length messenger RNA, emanate from a region surrounding the ade6-3049 hotspot. Interestingly, we found that the previously known recombination-activation region of Atf1 is also a transactivation domain, whose deletion affected DSB formation and short transcript production at ade6-3049 These results point to a possibility that the two events may be related to each other at ade6-3049 In fact, comparison of published maps of meiotic transcripts and hotspots suggested that hotspots are very often located close to meiotically transcribed regions. These observations therefore propose that meiotic DSB formation in fission yeast may be connected to transcription of surrounding regions. Copyright © 2017 by the Genetics Society of America.

  3. Structural and functional adaptations of the mammalian nuclear envelope to meet the meiotic requirements.

    Science.gov (United States)

    Link, Jana; Jahn, Daniel; Alsheimer, Manfred

    2015-01-01

    Numerous studies in the past years provided definite evidence that the nuclear envelope is much more than just a simple barrier. It rather constitutes a multifunctional platform combining structural and dynamic features to fulfill many fundamental functions such as chromatin organization, regulation of transcription, signaling, but also structural duties like maintaining general nuclear architecture and shape. One additional and, without doubt, highly impressive aspect is the recently identified key function of selected nuclear envelope components in driving meiotic chromosome dynamics, which in turn is essential for accurate recombination and segregation of the homologous chromosomes. Here, we summarize the recent work identifying new key players in meiotic telomere attachment and movement and discuss the latest advances in our understanding of the actual function of the meiotic nuclear envelope.

  4. Meiotic events in Oenothera - a non-standard pattern of chromosome behaviour.

    Science.gov (United States)

    Golczyk, Hieronim; Musiał, Krystyna; Rauwolf, Uwe; Meurer, Jörg; Herrmann, Reinhold G; Greiner, Stephan

    2008-11-01

    The genus Oenothera shows an intriguing extent of permanent translocation heterozygosity. Reciprocal translocations of chromosome arms in species or populations result in various kinds of chromosome multivalents in diakinesis. Early meiotic events conditioning such chromosome behaviour are poorly understood. We found a surprising uniformity of the leptotene-diplotene period, regardless of the chromosome configuration at diakinesis (ring of 14, 7 bivalents, mixture of bivalents and multivalents). It appears that the earliest chromosome interactions at Oenothera meiosis are untypical, since they involve pericentromeric regions. During early leptotene, proximal chromosome parts cluster and form a highly polarized Rabl configuration. Telomeres associated in pairs were seen at zygotene. The high degree of polarization of meiotic nuclei continues for an exceptionally long period, i.e., during zygotene-pachytene into the diplotene contraction stage. The Rabl-polarized meiotic architecture and clustering of pericentromeres suggest a high complexity of karyotypes, not only in structural heterozygotes but also in bivalent-forming homozygous species.

  5. HIM-8 binds to the X chromosome pairing center and mediates chromosome-specific meiotic synapsis.

    Science.gov (United States)

    Phillips, Carolyn M; Wong, Chihunt; Bhalla, Needhi; Carlton, Peter M; Weiser, Pinky; Meneely, Philip M; Dernburg, Abby F

    2005-12-16

    The him-8 gene is essential for proper meiotic segregation of the X chromosomes in C. elegans. Here we show that loss of him-8 function causes profound X chromosome-specific defects in homolog pairing and synapsis. him-8 encodes a C2H2 zinc-finger protein that is expressed during meiosis and concentrates at a site on the X chromosome known as the meiotic pairing center (PC). A role for HIM-8 in PC function is supported by genetic interactions between PC lesions and him-8 mutations. HIM-8 bound chromosome sites associate with the nuclear envelope (NE) throughout meiotic prophase. Surprisingly, a point mutation in him-8 that retains both chromosome binding and NE localization fails to stabilize pairing or promote synapsis. These observations indicate that stabilization of homolog pairing is an active process in which the tethering of chromosome sites to the NE may be necessary but is not sufficient.

  6. A meiotic linkage map of the silver fox, aligned and compared to the canine genome.

    Science.gov (United States)

    Kukekova, Anna V; Trut, Lyudmila N; Oskina, Irina N; Johnson, Jennifer L; Temnykh, Svetlana V; Kharlamova, Anastasiya V; Shepeleva, Darya V; Gulievich, Rimma G; Shikhevich, Svetlana G; Graphodatsky, Alexander S; Aguirre, Gustavo D; Acland, Gregory M

    2007-03-01

    A meiotic linkage map is essential for mapping traits of interest and is often the first step toward understanding a cryptic genome. Specific strains of silver fox (a variant of the red fox, Vulpes vulpes), which segregate behavioral and morphological phenotypes, create a need for such a map. One such strain, selected for docility, exhibits friendly dog-like responses to humans, in contrast to another strain selected for aggression. Development of a fox map is facilitated by the known cytogenetic homologies between the dog and fox, and by the availability of high resolution canine genome maps and sequence data. Furthermore, the high genomic sequence identity between dog and fox allows adaptation of canine microsatellites for genotyping and meiotic mapping in foxes. Using 320 such markers, we have constructed the first meiotic linkage map of the fox genome. The resulting sex-averaged map covers 16 fox autosomes and the X chromosome with an average inter-marker distance of 7.5 cM. The total map length corresponds to 1480.2 cM. From comparison of sex-averaged meiotic linkage maps of the fox and dog genomes, suppression of recombination in pericentromeric regions of the metacentric fox chromosomes was apparent, relative to the corresponding segments of acrocentric dog chromosomes. Alignment of the fox meiotic map against the 7.6x canine genome sequence revealed high conservation of marker order between homologous regions of the two species. The fox meiotic map provides a critical tool for genetic studies in foxes and identification of genetic loci and genes implicated in fox domestication.

  7. The fission yeast RNA binding protein Mmi1 regulates meiotic genes by controlling intron specific splicing and polyadenylation coupled RNA turnover.

    Directory of Open Access Journals (Sweden)

    Huei-Mei Chen

    Full Text Available The polyA tails of mRNAs are monitored by the exosome as a quality control mechanism. We find that fission yeast, Schizosaccharomyces pombe, adopts this RNA quality control mechanism to regulate a group of 30 or more meiotic genes at the level of both splicing and RNA turnover. In vegetative cells the RNA binding protein Mmi1 binds to the primary transcripts of these genes. We find the novel motif U(U/C/GAAAC highly over-represented in targets of Mmi1. Mmi1 can specifically regulate the splicing of particular introns in a transcript: it inhibits the splicing of introns that are in the vicinity of putative Mmi1 binding sites, while allowing the splicing of other introns that are far from such sites. In addition, binding of Mmi1, particularly near the 3' end, alters 3' processing to promote extremely long polyA tails of up to a kilobase. The hyperadenylated transcripts are then targeted for degradation by the nuclear exonuclease Rrp6. The nuclear polyA binding protein Pab2 assists this hyperadenylation-mediated RNA decay. Rrp6 also targets other hyperadenylated transcripts, which become hyperadenylated in an unknown, but Mmi1-independent way. Thus, hyperadenylation may be a general signal for RNA degradation. In addition, binding of Mmi1 can affect the efficiency of 3' cleavage. Inactivation of Mmi1 in meiosis allows meiotic expression, through splicing and RNA stabilization, of at least 29 target genes, which are apparently constitutively transcribed.

  8. 24 CFR 3285.701 - Electrical crossovers.

    Science.gov (United States)

    2010-04-01

    ... URBAN DEVELOPMENT MODEL MANUFACTURED HOME INSTALLATION STANDARDS Electrical Systems and Equipment § 3285.701 Electrical crossovers. Multi-section homes with electrical wiring in more than one section require... installation instructions. ...

  9. Localization and roles of Ski8p protein in Sordaria meiosis and delineation of three mechanistically distinct steps of meiotic homolog juxtaposition.

    Science.gov (United States)

    Tessé, Sophie; Storlazzi, Aurora; Kleckner, Nancy; Gargano, Silvana; Zickler, Denise

    2003-10-28

    Ski8p is implicated in degradation of non-poly(A) and double-stranded RNA, and in meiotic DNA recombination. We have identified the Sordaria macrospora SKI8 gene. Ski8p is cytoplasmically localized in all vegetative and sexual cycle cells, and is nuclear localized, specifically in early-mid-meiotic prophase, in temporal correlation with Spo11p, the meiotic double-strand break (DSB) transesterase. Localizations of Ski8p and Spo11p are mutually interdependent. ski8 mutants exhibit defects in vegetative growth, entry into the sexual program, and sporulation. Diverse meiotic defects, also seen in spo11 mutants, are diagnostic of DSB absence, and they are restored by exogenous DSBs. These results suggest that Ski8p promotes meiotic DSB formation by acting directly within meiotic prophase chromosomes. Mutant phenotypes also divide meiotic homolog juxtaposition into three successive, mechanistically distinct steps; recognition, presynaptic alignment, and synapsis, which are distinguished by their differential dependence on DSBs.

  10. Meiotic behavior and pollen fertility of five species in the genus ...

    African Journals Online (AJOL)

    fe

    2011-11-16

    Nov 16, 2011 ... Meiotic behavior and pollen fertility were analysed in five Epimedium species: Epimedium chlorandrum,. Epimedium acuminatum, Epimedium davidii, Epimedium ecalcaratum and Epimedium pubescens. Chromosome numbers for five species were 2n = 2x = 12. All examined species displayed stable ...

  11. Insulin alone can lead to a withdrawal of meiotic arrest in the carp

    Indian Academy of Sciences (India)

    Meiotic arrest of oocyte in an Indian carp, Labeo rohita Ham. has been found for the first time to be withdrawn by insulin only. Addition of insulin to oocytes in vitro caused germinal vesicle breakdown (GVBD), one of the first visual markers to determine initiation of the final maturational process. Under the influence of insulin ...

  12. Segregation distortion in chicken and the evolutionary consequences of female meiotic drive in birds

    DEFF Research Database (Denmark)

    Axelsson, Erik Gunnar; Albrechtsen, Anders; Van, A. P.

    2010-01-01

    As all four meiotic products give rise to sperm in males, female meiosis result in a single egg in most eukaryotes. Any genetic element with the potential to influence chromosome segregation, so that it is preferentially included in the egg, should therefore gain a transmission advantage; a process...

  13. Meiotic recombination breakpoints are associated with open chromatin and enriched with Stowaway transposons in potato

    Science.gov (United States)

    Meiotic recombination is the foundation for genetic variation in natural and artificial populations of eukaryotes. Although genetic recombination maps have been developed in numerous plant species since late the 1980s, very few of these maps have provided the necessary resolution needed to investiga...

  14. SOLO: a meiotic protein required for centromere cohesion, coorientation, and SMC1 localization in Drosophila melanogaster.

    Science.gov (United States)

    Yan, Rihui; Thomas, Sharon E; Tsai, Jui-He; Yamada, Yukihiro; McKee, Bruce D

    2010-02-08

    Sister chromatid cohesion is essential to maintain stable connections between homologues and sister chromatids during meiosis and to establish correct centromere orientation patterns on the meiosis I and II spindles. However, the meiotic cohesion apparatus in Drosophila melanogaster remains largely uncharacterized. We describe a novel protein, sisters on the loose (SOLO), which is essential for meiotic cohesion in Drosophila. In solo mutants, sister centromeres separate before prometaphase I, disrupting meiosis I centromere orientation and causing nondisjunction of both homologous and sister chromatids. Centromeric foci of the cohesin protein SMC1 are absent in solo mutants at all meiotic stages. SOLO and SMC1 colocalize to meiotic centromeres from early prophase I until anaphase II in wild-type males, but both proteins disappear prematurely at anaphase I in mutants for mei-S332, which encodes the Drosophila homologue of the cohesin protector protein shugoshin. The solo mutant phenotypes and the localization patterns of SOLO and SMC1 indicate that they function together to maintain sister chromatid cohesion in Drosophila meiosis.

  15. Nested Inversion Polymorphisms Predispose Chromosome 22q11.2 to Meiotic Rearrangements

    NARCIS (Netherlands)

    Demaerel, Wolfram; Hestand, Matthew S.; Vergaelen, Elfi; Swillen, Ann; López-Sánchez, Marcos; Pérez-Jurado, Luis A.; McDonald-Mcginn, Donna M.; Zackai, Elaine; Emanuel, Beverly S.; Morrow, Bernice E.; Breckpot, Jeroen; Devriendt, Koenraad; Vermeesch, Joris R.; Antshel, Kevin M.; Arango, Celso; Armando, Marco; Bassett, Anne S.; Bearden, Carrie E.; Boot, Erik; Bravo-Sanchez, Marta; Breetvelt, Elemi; Busa, Tiffany; Butcher, Nancy J.; Campbell, Linda E.; Carmel, Miri; Chow, Eva W C; Crowley, T. Blaine; Cubells, Joseph; Cutler, David; Demaerel, Wolfram; Digilio, Maria Cristina; Duijff, Sasja; Eliez, Stephan; Emanuel, Beverly S.; Epstein, Michael P.; Evers, Rens; Fernandez Garcia-Moya, Luis; Fiksinski, Ania; Fraguas, David; Fremont, Wanda; Fritsch, Rosemarie; Garcia-Minaur, Sixto; Golden, Aaron; Gothelf, Doron; Guo, Tingwei; Gur, Ruben C.; Gur, Raquel E.; Heine-Suner, Damian; Hestand, Matthew; Hooper, Stephen R.; Kates, Wendy R.; Kushan, Leila; Laorden-Nieto, Alejandra; Maeder, Johanna; Marino, Bruno; Marshall, Christian R.; McCabe, Kathryn; McDonald-Mcginn, Donna M.; Michaelovosky, Elena; Morrow, Bernice E.; Moss, Edward; Mulle, Jennifer; Murphy, Declan; Murphy, Kieran C.; Murphy, Clodagh M.; Niarchou, Maria; Ornstein, Claudia; Owen, Michael J; Philip, Nicole; Repetto, Gabriela M.; Schneider, Maude; Shashi, Vandana; Simon, Tony J.; Swillen, Ann; Tassone, Flora; Unolt, Marta; Van Amelsvoort, Therese; van den Bree, Marianne B M; Van Duin, Esther; Vergaelen, Elfi; Vermeesch, Joris R.; Vicari, Stefano; Vingerhoets, Claudia; Vorstman, Jacob; Warren, Steve; Weinberger, Ronnie; Weisman, Omri; Weizman, Abraham; Zackai, Elaine; Zhang, Zhengdong; Zwick, Michael

    2017-01-01

    Inversion polymorphisms between low-copy repeats (LCRs) might predispose chromosomes to meiotic non-allelic homologous recombination (NAHR) events and thus lead to genomic disorders. However, for the 22q11.2 deletion syndrome (22q11.2DS), the most common genomic disorder, no such inversions have

  16. Meiotic anomalies induced by X-rays in Capsicum annuum L

    Energy Technology Data Exchange (ETDEWEB)

    Subhash, K; Nizam, J [Department of Botany, Kakatiya University, Vidyaranyapuri, Warangal (A.P.) (India)

    1977-01-01

    Various types of meiotic anomalies in the M/sub 1/ generation such as multivalents, fragments, bridges, micronuclei, polyads and in particular multispindle formation, were observed after seed X-ray irradiation in Capsicum annuum L. With increasing dose the number of aberrations gradually increased.

  17. A meiotic study of two translocations and a tertiary trisomic in the mouse (Mus musculus)

    NARCIS (Netherlands)

    Boer, de P.

    1975-01-01

    In this section, the order of the articles has not been closely followed. Each point ends with the number(s) of the article(s) (as given in the contents), where the conclusion is based on.

    1) Cytological meiotic studies of T(2;8)26H and T(1;13)70H heterozygotes and Ts(1

  18. Expression analysis of genes implicated in meiotic resumption in vivo and developmental competence

    NARCIS (Netherlands)

    Algriany, O.A.

    2007-01-01

    This thesis investigated the gene expression in bovine oocytes during meiotic resumption, at 6 h post LH surge, coinciding with germinal vesicle breakdown, which was supposed to give a picture of the major cell cycle regulation changes, cytoskeleton rearrangement and chromosome alignment.

  19. Scrambling Eggs: Meiotic Drive and the Evolution of Female Recombination Rates

    Science.gov (United States)

    Brandvain, Yaniv; Coop, Graham

    2012-01-01

    Theories to explain the prevalence of sex and recombination have long been a central theme of evolutionary biology. Yet despite decades of attention dedicated to the evolution of sex and recombination, the widespread pattern of sex differences in the recombination rate is not well understood and has received relatively little theoretical attention. Here, we argue that female meiotic drivers—alleles that increase in frequency by exploiting the asymmetric cell division of oogenesis—present a potent selective pressure favoring the modification of the female recombination rate. Because recombination plays a central role in shaping patterns of variation within and among dyads, modifiers of the female recombination rate can function as potent suppressors or enhancers of female meiotic drive. We show that when female recombination modifiers are unlinked to female drivers, recombination modifiers that suppress harmful female drive can spread. By contrast, a recombination modifier tightly linked to a driver can increase in frequency by enhancing female drive. Our results predict that rapidly evolving female recombination rates, particularly around centromeres, should be a common outcome of meiotic drive. We discuss how selection to modify the efficacy of meiotic drive may contribute to commonly observed patterns of sex differences in recombination. PMID:22143919

  20. Meiotic homoeologous recombination-based alien gene introgression in the genomics era of wheat

    Science.gov (United States)

    Wheat (Triticum spp.) has a narrow genetic basis due to its allopolyploid origin. However, wheat has numerous wild relatives usable for expanding genetic variability of its genome through meiotic homoeologous recombination. Traditionally, laborious cytological analyses have been employed to detect h...

  1. Meiotic anomalies induced by X-rays in Capsicum annuum L

    International Nuclear Information System (INIS)

    Subhash, K.; Nizam, J.

    1977-01-01

    Various types of meiotic anomalies in the M 1 generation such as multivalents, fragments, bridges, micronuclei, polyads and in particular multispindle formation, were observed after seed X-ray irradiation in Capsicum annuum L. With increasing dose the number of aberrations gradually increased. (author)

  2. Meiotic genes and sexual reproduction in the green algal class Trebouxiophyceae (Chlorophyta)

    Czech Academy of Sciences Publication Activity Database

    Fučíková, K.; Pažoutová, Marie; Rindi, F.

    2015-01-01

    Roč. 51, č. 3 (2015), s. 419-430 ISSN 0022-3646 Institutional support: RVO:60077344 Keywords : algal genomes * Chlorophyta * green algae * meiotic genes * sexual reproduction * Trebouxiophyceae Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.536, year: 2015

  3. Meiotic chromosome behaviours in M1 generation of bread wheat irradiated by gamma-rays

    International Nuclear Information System (INIS)

    Watanabe, Y.; Takato, S.

    1982-01-01

    Growing plants of bread wheat (Triticum aestivum L. 2 n=6x=42, AABBDD) were subjected to acute or chronic irradiation by gamma-rays from 60Co and meiotic chromosome behaviours of PMCS in M 1 generation were cytologically compared. Both acute and chronic irradiations produced different types of chromosomal aberrations at the meiotic stages. Among them, translocation type was the most frequent, followed by univalent type. A mixed type, i. e. translocation accompanying one or more univalents was often detected. Even normal type which lacked translocation and univalent included laggards and briclges without exception. Other meiotic abnormalities such as deletion, iso-chromosome and micronuclei were observed frequently in both treatments. Dose dependency of translocation frequency was not recognized in this experiment. In chronic irradiation, different chromosome numbers and meiotic behaviours were found not only among florets of a spike but also among anthers of a floret. A number of plants with aneuploid-like grass types occurred at a high frequency in M 1 , especially with low exposure

  4. Meiotic behaviour and spermatogenesis in male mice heterozygous for translocation types also occurring in man

    NARCIS (Netherlands)

    Nijhoff, J.H.

    1981-01-01

    In this thesis a start was made with meiotic observations of mouse translocation types - a Robertsonian translocation and a translocation between a metacentric and an acrocentric chromosome - which also occur in man. It is generally accepted that, when no chromosomal rearrangements are involved, man

  5. Mutations in Caenorhabditis elegans him-19 show meiotic defects that worsen with age.

    Science.gov (United States)

    Tang, Lois; Machacek, Thomas; Mamnun, Yasmine M; Penkner, Alexandra; Gloggnitzer, Jiradet; Wegrostek, Christina; Konrat, Robert; Jantsch, Michael F; Loidl, Josef; Jantsch, Verena

    2010-03-15

    From a screen for meiotic Caenorhabditis elegans mutants based on high incidence of males, we identified a novel gene, him-19, with multiple functions in prophase of meiosis I. Mutant him-19(jf6) animals show a reduction in pairing of homologous chromosomes and subsequent bivalent formation. Consistently, synaptonemal complex formation is spatially restricted and possibly involves nonhomologous chromosomes. Also, foci of the recombination protein RAD-51 occur delayed or cease altogether. Ultimately, mutation of him-19 leads to chromosome missegregation and reduced offspring viability. The observed defects suggest that HIM-19 is important for both homology recognition and formation of meiotic DNA double-strand breaks. It therefore seems to be engaged in an early meiotic event, resembling in this respect the regulator kinase CHK-2. Most astonishingly, him-19(jf6) hermaphrodites display worsening of phenotypes with increasing age, whereas defects are more severe in female than in male meiosis. This finding is consistent with depletion of a him-19-dependent factor during the production of oocytes. Further characterization of him-19 could contribute to our understanding of age-dependent meiotic defects in humans.

  6. DNMT3L is a regulator of X chromosome compaction and post-meiotic gene transcription.

    Directory of Open Access Journals (Sweden)

    Natasha M Zamudio

    Full Text Available Previous studies on the epigenetic regulator DNA methyltransferase 3-Like (DNMT3L, have demonstrated it is an essential regulator of paternal imprinting and early male meiosis. Dnmt3L is also a paternal effect gene, i.e., wild type offspring of heterozygous mutant sires display abnormal phenotypes suggesting the inheritance of aberrant epigenetic marks on the paternal chromosomes. In order to reveal the mechanisms underlying these paternal effects, we have assessed X chromosome meiotic compaction, XY chromosome aneuploidy rates and global transcription in meiotic and haploid germ cells from male mice heterozygous for Dnmt3L. XY bodies from Dnmt3L heterozygous males were significantly longer than those from wild types, and were associated with a three-fold increase in XY bearing sperm. Loss of a Dnmt3L allele resulted in deregulated expression of a large number of both X-linked and autosomal genes within meiotic cells, but more prominently in haploid germ cells. Data demonstrate that similar to embryonic stem cells, DNMT3L is involved in an auto-regulatory loop in germ cells wherein the loss of a Dnmt3L allele resulted in increased transcription from the remaining wild type allele. In contrast, however, within round spermatids, this auto-regulatory loop incorporated the alternative non-coding alternative transcripts. Consistent with the mRNA data, we have localized DNMT3L within spermatids and sperm and shown that the loss of a Dnmt3L allele results in a decreased DNMT3L content within sperm. These data demonstrate previously unrecognised roles for DNMT3L in late meiosis and in the transcriptional regulation of meiotic and post-meiotic germ cells. These data provide a potential mechanism for some cases of human Klinefelter's and Turner's syndromes.

  7. Genome Dynamics of Hybrid Saccharomyces cerevisiae During Vegetative and Meiotic Divisions

    Directory of Open Access Journals (Sweden)

    Abhishek Dutta

    2017-11-01

    Full Text Available Mutation and recombination are the major sources of genetic diversity in all organisms. In the baker’s yeast, all mutation rate estimates are in homozygous background. We determined the extent of genetic change through mutation and loss of heterozygosity (LOH in a heterozygous Saccharomyces cerevisiae genome during successive vegetative and meiotic divisions. We measured genome-wide LOH and base mutation rates during vegetative and meiotic divisions in a hybrid (S288c/YJM789 S. cerevisiae strain. The S288c/YJM789 hybrid showed nearly complete reduction in heterozygosity within 31 generations of meioses and improved spore viability. LOH in the meiotic lines was driven primarily by the mating of spores within the tetrad. The S288c/YJM789 hybrid lines propagated vegetatively for the same duration as the meiotic lines, showed variable LOH (from 2 to 3% and up to 35%. Two of the vegetative lines with extensive LOH showed frequent and large internal LOH tracts that suggest a high frequency of recombination repair. These results suggest significant LOH can occur in the S288c/YJM789 hybrid during vegetative propagation presumably due to return to growth events. The average base substitution rates for the vegetative lines (1.82 × 10−10 per base per division and the meiotic lines (1.22 × 10−10 per base per division are the first genome-wide mutation rate estimates for a hybrid yeast. This study therefore provides a novel context for the analysis of mutation rates (especially in the context of detecting LOH during vegetative divisions, compared to previous mutation accumulation studies in yeast that used homozygous backgrounds.

  8. Apoptosis in mouse fetal and neonatal oocytes during meiotic prophase one

    Directory of Open Access Journals (Sweden)

    Hartshorne Geraldine M

    2007-07-01

    Full Text Available Abstract Background The vast majority of oocytes formed in the fetal ovary do not survive beyond birth. Possible reasons for their loss include the elimination of non-viable genetic constitutions arising through meiosis, however, the precise relationship between meiotic stages and prenatal apoptosis of oocytes remains elusive. We studied oocytes in mouse fetal and neonatal ovaries, 14.5–21 days post coitum, to examine the relationship between oocyte development and programmed cell death during meiotic prophase I. Results Microspreads of fetal and neonatal ovarian cells underwent immunocytochemistry for meiosis- and apoptosis-related markers. COR-1 (meiosis-specific highlighted axial elements of the synaptonemal complex and allowed definitive identification of the stages of meiotic prophase I. Labelling for cleaved poly-(ADP-ribose polymerase (PARP-1, an inactivated DNA repair protein, indicated apoptosis. The same oocytes were then labelled for DNA double strand breaks (DSBs using TUNEL. 1960 oocytes produced analysable results. Oocytes at all stages of meiotic prophase I stained for cleaved PARP-1 and/or TUNEL, or neither. Oocytes with fragmented (19.8% or compressed (21.2% axial elements showed slight but significant differences in staining for cleaved PARP-1 and TUNEL to those with intact elements. However, fragmentation of axial elements alone was not a good indicator of cell demise. Cleaved PARP-1 and TUNEL staining were not necessarily coincident, showing that TUNEL is not a reliable marker of apoptosis in oocytes. Conclusion Our data indicate that apoptosis can occur throughout meiotic prophase I in mouse fetal and early postnatal oocytes, with greatest incidence at the diplotene stage. Careful selection of appropriate markers for oocyte apoptosis is essential.

  9. Meiotic sex ratio variation in natural populations of Ceratodon purpureus (Ditrichaceae).

    Science.gov (United States)

    Norrell, Tatum E; Jones, Kelly S; Payton, Adam C; McDaniel, Stuart F

    2014-09-01

    • Sex ratio variation is a common but often unexplained phenomenon in species across the tree of life. Here we evaluate the hypothesis that meiotic sex ratio variation can contribute to the biased sex ratios found in natural populations of the moss Ceratodon purpureus.• We obtained sporophytes from several populations of C. purpureus from eastern North America. From each sporophyte, we estimated the mean spore viability by germinating replicate samples on agar plates. We estimated the meiotic sex ratio of each sporophyte by inferring the sex of a random sample of germinated spores (mean = 77) using a PCR-RFLP test. We tested for among-sporophyte variation in viability using an ANOVA and for deviations from 1:1 sex ratio using a χ(2)-test and evaluated the relationship between these quantities using a linear regression.• We found among-sporophyte variation in spore viability and meiotic sex ratio, suggesting that genetic variants that contribute to variation in both of these traits segregate within populations of this species. However, we found no relationship between these quantities, suggesting that factors other than sex ratio distorters contribute to variation in spore viability within populations.• These results demonstrate that sex ratio distortion may partially explain the population sex ratio variation seen in C. purpureus, but more generally that genetic conflict over meiotic segregation may contribute to fitness variation in this species. Overall, this study lays the groundwork for future studies on the genetic basis of meiotic sex ratio variation. © 2014 Botanical Society of America, Inc.

  10. Variations in survival and ''petite'' mutagenesis induced by ultraviolet light during the meiotic cycle of Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Hottinguer-de Margerie, Helene; Moustacchi, Ethel

    1975-01-01

    Cyclic variations in sensitivity to killing and cytoplasmic ''petite'' rho induction by ultraviolet light occur during the meiosis of Saccharomyces cerevisiae. Maximal sensitivity to killing coincides with the period of meiotic nuclear DNA synthesis. Cyclic fluctuations in ''petite'' induction could not be correlated with known meiotic events and the pattern could vary temporarily from batch to batch. A dark liquid holding of irradiated cells aided the repair of lethal lesions but on the other hand an enhancement of ''petite'' induction was observed at all meiotic stages [fr

  11. Single nucleotide polymorphisms in the SEPTIN12 gene may be associated with azoospermia by meiotic arrest in Japanese men.

    Science.gov (United States)

    Miyamoto, Toshinobu; Tsujimura, Akira; Miyagawa, Yasushi; Koh, Eitetsu; Namiki, Mikio; Horikawa, Michiharu; Saijo, Yasuaki; Sengoku, Kazuo

    2012-01-01

    To investigate the association between SEPTIN12 gene variants and the risk of azoospermia caused by meiotic arrest. Mutational analysis of the SEPTIN12 gene was performed using DNA from 30 Japanese patients with azoospermia by meiotic arrest and 140 fertile male controls. The frequencies of the c.204G>C (Gln38His) allele and the CC genotype were significantly higher in patients than in fertile controls (p C (Gln38His) variant in the SEPTIN12 gene was associated with increased susceptibility to azoospermia caused by meiotic arrest.

  12. A role for Caenorhabditis elegans chromatin-associated protein HIM-17 in the proliferation vs. meiotic entry decision.

    Science.gov (United States)

    Bessler, Jessica B; Reddy, Kirthi C; Hayashi, Michiko; Hodgkin, Jonathan; Villeneuve, Anne M

    2007-04-01

    Chromatin-associated protein HIM-17 was previously shown to function in the chromosomal events of meiotic prophase. Here we report an additional role for HIM-17 in regulating the balance between germ cell proliferation and meiotic development. A cryptic function for HIM-17 in promoting meiotic entry and/or inhibiting proliferation was revealed by defects in germline organization in him-17 mutants grown at high temperature (25 degrees) and by a synthetic tumorous germline phenotype in glp-1(ar202); him-17 mutants at 15 degrees.

  13. Crossover transition in the fluctuation of Internet

    Science.gov (United States)

    Qian, Jiang-Hai

    2018-06-01

    The inconsistent fluctuation behavior of Internet predicted by preferential attachment(PA) and Gibrat's law requires empirical investigations on the actual system. By using the interval-tunable Gibrat's law statistics, we find the actual fluctuation, characterized by the conditional standard deviation of the degree growth rate, changes with the interval length and displays a crossover transition from PA type to Gibrat's law type, which has not yet been captured by any previous models. We characterize the transition dynamics quantitatively and determine the applicative range of PA and Gibrat's law. The correlation analysis indicates the crossover transition may be attributed to the accumulative correlation between the internal links.

  14. Analysis of self-fertilization and meiotic behavior of eleven Brazilian triticale cultivars at two sowing dates

    Directory of Open Access Journals (Sweden)

    Divanilde Guerra

    2011-01-01

    Full Text Available Eleven Brazilian hexaploid triticale cultivars (2n = 6x = 42, from three breeding programs, were evaluated for theirability of self-fertilization in 2006 and for meiotic behavior, meiotic index and pollen viability at two sowing dates in 2007. Highpotential of self-fertilization was observed, with values up to 89.52 %. Many irregularities were found in the meiotic analysis, suchas the presence of univalents, laggard chromosomes and micronuclei in tetrads, which compromised both meiotic behavior andmeiotic index. At the first sowing date, more suitable for normal plant development, overall mean values of 52.68 % for normal cellsand 64.95 % for meiotic index were observed. At the second sowing date, less appropriate for the crop, overall means of 52.23 %for normal cells and 58.24 % for meiotic index were obtained. Despite all the irregularities, considerable pollen viability wasobserved, reaching overall means of 92.08 % and 91.07 % for the first and second sowing dates, respectively.

  15. Meiotic aneuploidy: its origins and induction following chemical treatment in Sordaria brevicollis.

    Science.gov (United States)

    Bond, D J; McMillan, L

    1979-08-01

    A system suitable for the detection of meiotic aneuploidy is described in which various different origins of the aneuploidy can be distinguished. Aneuploid meiotic products are detected as black disomic spores held in asci containing all the products of a single meiosis. Aneuploidy may result from nondisjunction or from a meiosis in which an extra replica of one of the chromosomes has been generated in some other way, e.g., extra replication. By using this system it has been shown that pFPA treatment increase aneuploidy, primarily through an effect on nondisjunction. Preliminary results with trifluralin have indicated that this compound, too, may increase aneuploidy. There is a good possibility that the system can be further developed to permit a more rapid screening using a random plating method; this will allow a more efficient two-part analysis of the effects of compounds under test.

  16. Meiotic behavior of two polyploid species of genus Pleurodema (Anura: Leiuperidae from central Argentina

    Directory of Open Access Journals (Sweden)

    Nancy E. Salas

    2014-06-01

    Full Text Available Polyploidy is an important evolutionary force but rare in vertebrates. However, in anurans, the genus Pleurodema has polyploid species, two of them tetraploid and one octoploid. The manner in which the chromosomes join in diakinesis can vary among species and, crucially, if they differ in their ploidy levels. In this work, we describe the meiotic configurations in two cryptic species from central Argentina, with different ploidy levels, Pleurodema kriegi (tetraploid and P. cordobae (octoploid. A total of 306 diakineses from 19 individuals were analyzed. In meiosis, P. kriegi form 22 bivalents, whereas P. cordobae exhibits variation in meiotic figures. We discuss the possible allo- and autopolyploid origin of these species, and we consider that the autopolyploid origin of P. cordobae from P. kriegi might be the most feasible.

  17. Meiotic drive on aberrant chromosome 1 in the mouse is determined by a linked distorter.

    Science.gov (United States)

    Agulnik, S I; Sabantsev, I D; Orlova, G V; Ruvinsky, A O

    1993-04-01

    An aberrant chromosome 1 carrying an inverted fragment with two amplified DNA regions was isolated from wild populations of Mus musculus. Meiotic drive favouring the aberrant chromosome was demonstrated for heterozygous females. Its cause was preferential passage of aberrant chromosome 1 to the oocyte. Genetic analysis allowed us to identify a two-component system conditioning deviation from equal segregation of the homologues. The system consists of a postulated distorter and responder. The distorter is located on chromosome 1 distally to the responder, between the ln and Pep-3 genes, and it acts on the responder when in trans position. Polymorphism of the distorters was manifested as variation in their effect on meiotic drive level in the laboratory strain and mice from wild populations.

  18. DAF-2 and ERK Couple Nutrient Availability to Meiotic Progression during Caenorhabditis elegans Oogenesis

    Science.gov (United States)

    Lopez, Andrew L.; Chen, Jessica; Joo, Hyoe-Jin; Drake, Melanie; Shidate, Miri; Kseib, Cedric; Arur, Swathi

    2013-01-01

    Coupling the production of mature gametes and fertilized zygotes to favorable nutritional conditions improves reproductive success. In invertebrates, the proliferation of female germ line stem cells is regulated by nutritional status. But, in mammals the number of female germ line stem cells is set early in development, with oocytes progressing through meiosis later in life. Mechanisms that couple later steps of oogenesis to environmental conditions remain largely undefined. We show that in the presence of food, the DAF-2 insulin-like receptor signals through the RAS-ERK pathway to drive meiotic prophase I progression and oogenesis; in the absence of food, the resultant inactivation of insulin-like signaling leads to downregulation of RAS-ERK pathway, and oogenesis is stalled. Thus, the insulin-like signaling pathway couples nutrient sensing to meiotic I progression and oocyte production in C. elegans, ensuring that oocytes are only produced under conditions favorable for the survival of the resulting zygotes. PMID:24120884

  19. HIM-8 binds to the X chromosome pairing center and mediates chromosome-specific meiotic synapsis

    International Nuclear Information System (INIS)

    Phillips, Carolyn M.; Wong, Chihunt; Bhalla, Needhi; Carlton, Peter M.; Weiser, Pinky; Meneely, Philip M.; Dernburg, Abby F.

    2005-01-01

    The him-8 gene is essential for proper meiotic segregation of the X chromosomes in C. elegans. Here we show that loss of him-8 function causes profound X-chromosome-specific defects in homolog pairing and synapsis.him-8 encodes a C2H2 zinc finger protein that is expressed during meiosis and concentrates at a site on the X chromosome known as themeiotic Pairing Center (PC). A role for HIM-8 in PC function is supported by genetic interactions between PC lesions and him-8 mutations. HIM-8-bound chromosome sites associate with the nuclear envelope (NE)throughout meiotic prophase. Surprisingly, a point mutation in him-8 that retains both chromosome binding and NE localization fails to stabilize pairing or promote synapsis. These observations indicate that stabilization of homolog pairing is an active process in which the tethering of chromosome sites to the NE may be necessary but is not sufficient

  20. Recent advances of spin crossover research

    NARCIS (Netherlands)

    Gutlich, P; van Koningsbruggen, PJ; Renz, F; Schonherr, T

    2004-01-01

    Thermal spin transition (spin crossover), one of the most fascinating dynamic electronic structure phenomena occurring in coordination compounds of third row transition metal ions, mostly of iron(II), iron(III) and cobalt(II) with critical ligand field strengths competing with the spin pairing

  1. Optimal design of work zone median crossovers.

    Science.gov (United States)

    2010-09-01

    The use of temporary median crossovers in work zones allows for the closure of one side of a multi-lane roadway while : maintaining two-way traffic on the opposite side. This process provides the ability for construction and maintenance crews : to co...

  2. Expression of arf tumor suppressor in spermatogonia facilitates meiotic progression in male germ cells.

    Directory of Open Access Journals (Sweden)

    Michelle L Churchman

    2011-07-01

    Full Text Available The mammalian Cdkn2a (Ink4a-Arf locus encodes two tumor suppressor proteins (p16(Ink4a and p19(Arf that respectively enforce the anti-proliferative functions of the retinoblastoma protein (Rb and the p53 transcription factor in response to oncogenic stress. Although p19(Arf is not normally detected in tissues of young adult mice, a notable exception occurs in the male germ line, where Arf is expressed in spermatogonia, but not in meiotic spermatocytes arising from them. Unlike other contexts in which the induction of Arf potently inhibits cell proliferation, expression of p19(Arf in spermatogonia does not interfere with mitotic cell division. Instead, inactivation of Arf triggers germ cell-autonomous, p53-dependent apoptosis of primary spermatocytes in late meiotic prophase, resulting in reduced sperm production. Arf deficiency also causes premature, elevated, and persistent accumulation of the phosphorylated histone variant H2AX, reduces numbers of chromosome-associated complexes of Rad51 and Dmc1 recombinases during meiotic prophase, and yields incompletely synapsed autosomes during pachynema. Inactivation of Ink4a increases the fraction of spermatogonia in S-phase and restores sperm numbers in Ink4a-Arf doubly deficient mice but does not abrogate γ-H2AX accumulation in spermatocytes or p53-dependent apoptosis resulting from Arf inactivation. Thus, as opposed to its canonical role as a tumor suppressor in inducing p53-dependent senescence or apoptosis, Arf expression in spermatogonia instead initiates a salutary feed-forward program that prevents p53-dependent apoptosis, contributing to the survival of meiotic male germ cells.

  3. [Meiotic abnormalities of oocytes from patients with endometriosis submitted to ovarian stimulation].

    Science.gov (United States)

    Barcelos, Ionara Diniz Evangelista Santos; Vieira, Rodolpho Cruz; Ferreira, Elisa Melo; Araújo, Maria Cristina Picinato Medeiros de; Martins, Wellington de Paula; Ferriani, Rui Alberto; Navarro, Paula Andrea de Albuquerque Salles

    2008-08-01

    to evaluate the meiotic spindle and the chromosome distribution of in vitro mature oocytes from stimulated cycles of infertile women with endometriosis, and with male and/or tubal infertility factors (Control Group), comparing the rates of in vitro maturation (IVM) between the two groups evaluated. fourteen patients with endometriosis and eight with male and/or tubal infertility factors, submitted to ovarian stimulation for intracytoplasmatic sperm injection have been prospectively and consecutively selected, and formed a Study and Control Group, respectively. Immature oocytes (46 and 22, respectively, from the Endometriosis and Control Groups) were submitted to IVM. Oocytes presenting extrusion of the first polar corpuscle were fixed and stained for microtubules and chromatin evaluation through immunofluorescence technique. Statistical analysis has been done by the Fisher's exact test, with statistical significance at pControl Groups, respectively). The chromosome and meiotic spindle organization was observed in 18 and 11 oocytes from the Endometriosis and Control Groups, respectively. In the Endometriosis Group, eight oocytes (44.4%) presented themselves as normal metaphase II (MII), three (16.7%) as abnormal MII, five (27.8%) were in telophase stage I and two (11.1%) underwent parthenogenetic activation. In the Control Group, five oocytes (45.4%) presented themselves as normal MII, three (27.3%) as abnormal MII, one (9.1%) was in telophase stage I and two (18.2%) underwent parthenogenetic activation. There was no significant difference in meiotic anomaly rate between the oocytes in MII from both groups. the present study data did not show significant differences in the IVM or in the meiotic anomalies rate between the IVM oocytes from stimulated cycles of patients with endometriosis, as compared with controls. Nevertheless, they have suggested a delay in the outcome of oocyte meiosis I from patients with endometriosis, shown by the higher proportion of oocytes in

  4. A meiotic linkage map of the silver fox, aligned and compared to the canine genome

    OpenAIRE

    Kukekova, Anna V.; Trut, Lyudmila N.; Oskina, Irina N.; Johnson, Jennifer L.; Temnykh, Svetlana V.; Kharlamova, Anastasiya V.; Shepeleva, Darya V.; Gulievich, Rimma G.; Shikhevich, Svetlana G.; Graphodatsky, Alexander S.; Aguirre, Gustavo D.; Acland, Gregory M.

    2007-01-01

    A meiotic linkage map is essential for mapping traits of interest and is often the first step toward understanding a cryptic genome. Specific strains of silver fox (a variant of the red fox, Vulpes vulpes), which segregate behavioral and morphological phenotypes, create a need for such a map. One such strain, selected for docility, exhibits friendly dog-like responses to humans, in contrast to another strain selected for aggression. Development of a fox map is facilitated by the known cytogen...

  5. Meiotic genes and sexual reproduction in the green algal class Trebouxiophyceae (Chlorophyta)

    KAUST Repository

    Fučíková, Karolina

    2015-04-06

    © 2015 Phycological Society of America. Sexual reproduction is widespread in eukaryotes and is well documented in chlorophytan green algae. In this lineage, however, the Trebouxiophyceae represent a striking exception: in contrast to its relatives Chlorophyceae and Ulvophyceae this group appears to be mostly asexual, as fertilization has been rarely observed. Assessments of sexual reproduction in the Trebouxiophyceae have been based on microscopic observation of gametes fusing. New genomic data offer now the opportunity to check for the presence of meiotic genes, which represent an indirect evidence of a sexual life cycle. Using genomic and transcriptomic data for 12 taxa spanning the phylogenetic breadth of the class, we tried to clarify whether genuine asexuality or cryptic sexuality is the most likely case for the numerous putatively asexual trebouxiophytes. On the basis of these data and a bibliographic review, we conclude that the view of trebouxiophytes as primarily asexual is incorrect. In contrast to the limited number of reports of fertilization, meiotic genes were found in all genomes and transcriptomes examined, even in species presumed asexual. In the taxa examined the totality or majority of the genes were present, Helicosporidium and Auxenochlorella being the only partial exceptions (only four genes present). The evidence of sex provided by the meiotic genes is phylogenetically widespread in the class and indicates that sexual reproduction is not associated with any particular morphological or ecological trait. On the basis of the results, we expect that the existence of the meiotic genes will be documented in all trebouxiophycean genomes that will become available in the future.

  6. The inhibition of polo kinase by matrimony maintains G2 arrest in the meiotic cell cycle.

    Directory of Open Access Journals (Sweden)

    Youbin Xiang

    2007-12-01

    Full Text Available Many meiotic systems in female animals include a lengthy arrest in G2 that separates the end of pachytene from nuclear envelope breakdown (NEB. However, the mechanisms by which a meiotic cell can arrest for long periods of time (decades in human females have remained a mystery. The Drosophila Matrimony (Mtrm protein is expressed from the end of pachytene until the completion of meiosis I. Loss-of-function mtrm mutants result in precocious NEB. Coimmunoprecipitation experiments reveal that Mtrm physically interacts with Polo kinase (Polo in vivo, and multidimensional protein identification technology mass spectrometry analysis reveals that Mtrm binds to Polo with an approximate stoichiometry of 1:1. Mutation of a Polo-Box Domain (PBD binding site in Mtrm ablates the function of Mtrm and the physical interaction of Mtrm with Polo. The meiotic defects observed in mtrm/+ heterozygotes are fully suppressed by reducing the dose of polo+, demonstrating that Mtrm acts as an inhibitor of Polo. Mtrm acts as a negative regulator of Polo during the later stages of G2 arrest. Indeed, both the repression of Polo expression until stage 11 and the inactivation of newly synthesized Polo by Mtrm until stage 13 play critical roles in maintaining and properly terminating G2 arrest. Our data suggest a model in which the eventual activation of Cdc25 by an excess of Polo at stage 13 triggers NEB and entry into prometaphase.

  7. Production and characterization of radiation-sensitive meiotic mutants of Coprinus cinereus

    International Nuclear Information System (INIS)

    Zolan, M.E.; Tremel, C.J.; Pukkila, P.J.

    1988-01-01

    We have isolated four gamma-sensitive mutants of the basidiomycete Coprinus cinereus. When homozygous, two of these (rad 3-1 and rad 9-1) produce fruiting bodies with very few viable basidiospores, the products of meiosis in this organism. A less radiation-sensitive allele of RAD 3, rad 3-2, causes no apparent meiotic defect in homozygous strains. Quantitative measurements of oidial survival of rad 3-1;rad 9-1 double mutants compared to the single mutants indicated that rad 3-1 and rad 9-1 mutants are defective in the same DNA repair pathway. In the pew viable basidiospores that are produced by these two strains, essentially normal levels of meiotic recombination can be detected. None of the mutants exhibits increased sensitivity to UV radiation. Cytological examination of meiotic chromosomes from mutant and wild-type fruiting bodies showed that rad 3-1 homozygous strains fail to condense and pair homologous chromosomes during prophase I. Although rad 9-1 strains are successful at chromosome pairing, meiosis is usually not completed in these mutants

  8. From genes to games: cooperation and cyclic dominance in meiotic drive.

    Science.gov (United States)

    Traulsen, Arne; Reed, Floyd A

    2012-04-21

    Evolutionary change can be described on a genotypic level or a phenotypic level. Evolutionary game theory is typically thought of as a phenotypic approach, although it is frequently argued that it can also be used to describe population genetic evolution. Interpreting the interaction between alleles in a diploid genome as a two player game leads to interesting alternative perspectives on genetic evolution. Here we focus on the case of meiotic drive and illustrate how meiotic drive can be directly and precisely interpreted as a social dilemma, such as the prisoners dilemma or the snowdrift game, in which the drive allele takes more than its fair share. Resistance to meiotic drive can lead to the well understood cyclic dominance found in the rock-paper-scissors game. This perspective is well established for the replicator dynamics, but there is still considerable ground for mutual inspiration between the two fields. For example, evolutionary game theorists can benefit from considering the stochastic evolutionary dynamics arising from finite population size. Population geneticists can benefit from game theoretic tools and perspectives on genetic evolution. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Eccentric localization of catalase to protect chromosomes from oxidative damages during meiotic maturation in mouse oocytes.

    Science.gov (United States)

    Park, Yong Seok; You, Seung Yeop; Cho, Sungrae; Jeon, Hyuk-Joon; Lee, Sukchan; Cho, Dong-Hyung; Kim, Jae-Sung; Oh, Jeong Su

    2016-09-01

    The maintenance of genomic integrity and stability is essential for the survival of every organism. Unfortunately, DNA is vulnerable to attack by a variety of damaging agents. Oxidative stress is a major cause of DNA damage because reactive oxygen species (ROS) are produced as by-products of normal cellular metabolism. Cells have developed eloquent antioxidant defense systems to protect themselves from oxidative damage along with aerobic metabolism. Here, we show that catalase (CAT) is present in mouse oocytes to protect the genome from oxidative damage during meiotic maturation. CAT was expressed in the nucleus to form unique vesicular structures. However, after nuclear envelope breakdown, CAT was redistributed in the cytoplasm with particular focus at the chromosomes. Inhibition of CAT activity increased endogenous ROS levels, but did not perturb meiotic maturation. In addition, CAT inhibition produced chromosomal defects, including chromosome misalignment and DNA damage. Therefore, our data suggest that CAT is required not only to scavenge ROS, but also to protect DNA from oxidative damage during meiotic maturation in mouse oocytes.

  10. Modulation of Prdm9-controlled meiotic chromosome asynapsis overrides hybrid sterility in mice.

    Science.gov (United States)

    Gregorova, Sona; Gergelits, Vaclav; Chvatalova, Irena; Bhattacharyya, Tanmoy; Valiskova, Barbora; Fotopulosova, Vladana; Jansa, Petr; Wiatrowska, Diana; Forejt, Jiri

    2018-03-14

    Hybrid sterility is one of the reproductive isolation mechanisms leading to speciation. Prdm9 , the only known vertebrate hybrid-sterility gene, causes failure of meiotic chromosome synapsis and infertility in male hybrids that are the offspring of two mouse subspecies. Within species, Prdm9 determines the sites of programmed DNA double-strand breaks (DSBs) and meiotic recombination hotspots. To investigate the relation between Prdm9 -controlled meiotic arrest and asynapsis, we inserted random stretches of consubspecific homology on several autosomal pairs in sterile hybrids, and analyzed their ability to form synaptonemal complexes and to rescue male fertility. Twenty-seven or more megabases of consubspecific (belonging to the same subspecies) homology fully restored synapsis in a given autosomal pair, and we predicted that two or more DSBs within symmetric hotspots per chromosome are necessary for successful meiosis. We hypothesize that impaired recombination between evolutionarily diverged chromosomes could function as one of the mechanisms of hybrid sterility occurring in various sexually reproducing species. © 2018, Gregorova et al.

  11. Association of poly-purine/poly-pyrimidine sequences with meiotic recombination hot spots

    Directory of Open Access Journals (Sweden)

    Pitt Joel PW

    2006-07-01

    Full Text Available Abstract Background Meiotic recombination events have been found to concentrate in 1–2.5 kilo base regions, but these recombination hot spots do not share a consensus sequence and why they occur at specific sites is not fully understood. Some previous evidence suggests that poly-purine/poly-pyrimidine (poly-pu/py tracts (PPTs, a class of sequence with distinctive biochemical properties, could be involved in recombination, but no general association of PPTs with meiotic recombination hot spots has previously been reported. Results We used computational methods to investigate in detail the relationship between PPTs and hot spots. We show statistical associations of PPT frequency with hot spots of meiotic recombination initiating lesions, double-strand breaks, in the genome of the yeast S. cerevisiae and with experimentally well characterized human meiotic recombination hot spots. Supporting a possible role of poly-pu/py-rich sequences in hot spot recombination, we also found that all three single nucleotide polymorphisms previously shown to be associated with human hot spot activity changes occur within sequence contexts of 14 bp or longer that are 85% or more poly-pu/py and at least 70% G/C. These polymorphisms are all close to the hot spot mid points. Comparing the sequences of experimentally characterized human hot spots with the orthologous regions of the chimpanzee genome previously shown not to contain hot spots, we found that in all five cases in which comparisons for the hot spot central regions are possible with publicly available sequence data, there are differences near the human hot spot mid points within sequences 14 bp or longer consisting of more than 80% poly-pu/py and at least 50% G/C. Conclusion Our results, along with previous evidence for the unique biochemical properties and recombination-stimulating potential of poly-pu/py-rich sequences, suggest that the possible functional involvement of this type of sequence in meiotic

  12. Mlh1 is required for female fertility in Drosophila melanogaster: An outcome of effects on meiotic crossing over, ovarian follicles and egg activation.

    Science.gov (United States)

    Vimal, Divya; Kumar, Saurabh; Pandey, Ashutosh; Sharma, Divya; Saini, Sanjay; Gupta, Snigdha; Ravi Ram, Kristipati; Chowdhuri, Debapratim Kar

    2018-03-01

    Mismatch repair (MMR) system, a conserved DNA repair pathway, plays crucial role in DNA recombination and is involved in gametogenesis. The impact of alterations in MMR family of proteins (bacterial MutS and MutL homologues) on mammalian fertility is well documented. However, an insight to the role of MMR in reproduction of non-mammalian organisms is limited. Hence, in the present study, we analysed the impact of mlh1 (a MutL homologue) on meiotic crossing over/recombination and fertility in a genetically tractable model, Drosophila melanogaster. Using mlh1 e00130 hypomorphic allele, we report female specific adverse reproductive outcome for reduced mlh1 in Drosophila: mlh1 e00130 homozygous females had severely reduced fertility while males were fertile. Further, mlh1 e00130 females contained small ovaries with large number of early stages as well as significantly reduced mature oocytes, and laid fewer eggs, indicating discrepancies in egg production and ovulation. These observations contrast the sex independent and/or male specific sterility and normal follicular development as well as ovulation reported so far for MMR family proteins in mammals. However, analogous to the role(s) of mlh1 in meiotic crossing over and DNA repair processes underlying mammalian fertility, ovarian follicles from mlh1 e00130 females contained significantly increased DNA double strand breaks (DSBs) and reduced synaptonemal complex foci. In addition, large proportion of fertilized eggs display discrepancies in egg activation and fail to proceed beyond stage 5 of embryogenesis. Hence, reduction of the Mlh1 protein level leads to defective oocytes that fail to complete embryogenesis after fertilization thereby reducing female fertility. Copyright © 2017 Elsevier GmbH. All rights reserved.

  13. Dimensional crossover in fluids under nanometer-scale confinement.

    Science.gov (United States)

    Das, Amit; Chakrabarti, J

    2012-05-01

    Several earlier studies have shown signatures of crossover in various static and dynamics properties of a confined fluid when the confining dimension decreases to about a nanometer. The density fluctuations govern the majority of such properties of a fluid. Here, we illustrate the crossover in density fluctuation in a confined fluid, to provide a generic understanding of confinement-induced crossover of fluid properties, using computer simulations. The crossover can be understood as a manifestation of changes in the long-wavelength behavior of fluctuation in density due to geometrical constraints. We further show that the confining potential significantly affects the crossover behavior.

  14. Chiral crossover transition in a finite volume

    Science.gov (United States)

    Shi, Chao; Jia, Wenbao; Sun, An; Zhang, Liping; Zong, Hongshi

    2018-02-01

    Finite volume effects on the chiral crossover transition of strong interactions at finite temperature are studied by solving the quark gap equation within a cubic volume of finite size L. With the anti-periodic boundary condition, our calculation shows the chiral quark condensate, which characterizes the strength of dynamical chiral symmetry breaking, decreases as L decreases below 2.5 fm. We further study the finite volume effects on the pseudo-transition temperature {T}{{c}} of the crossover, showing a significant decrease in {T}{{c}} as L decreases below 3 fm. Supported by National Natural Science Foundation of China (11475085, 11535005, 11690030, 51405027), the Fundamental Research Funds for the Central Universities (020414380074), China Postdoctoral Science Foundation (2016M591808) and Open Research Foundation of State Key Lab. of Digital Manufacturing Equipment & Technology in Huazhong University of Science & Technology (DMETKF2015015)

  15. Onset and progress of meiotic prophase in the oocytes in the B6.YTIR sex-reversed mouse ovary.

    Science.gov (United States)

    Park, E-H; Taketo, T

    2003-12-01

    When the Y chromosome of a Mus musculus domesticus male mouse (caught in Tirano, Italy) is placed on a C57BL/6J genetic background, approximately half of the XY (B6.YTIR) progeny develop into normal-appearing but infertile females. We have previously reported that the primary cause of infertility can be attributed to their oocytes. To identify the primary defect in the XY oocyte, we examined the onset and progress of meiotic prophase in the B6.YTIR fetal ovary. Using bromo-deoxyuridine incorporation and culture, we determined that the germ cells began to enter meiosis at the developmental ages and in numbers comparable to those in the control XX ovary. Furthermore, the meiotic prophase appeared to progress normally until the late zygotene stage. However, the oocytes that entered meiosis early in the XY ovary failed to complete the meiotic prophase. On the other hand, a considerable number of oocytes entered meiosis at late developmental stages and completed the meiotic prophase in the XY ovary. We propose that the timing of entry into meiosis and the XY chromosomal composition influence the survival of oocytes during meiotic prophase in the fetal ovary.

  16. Sexual antagonism and meiotic drive cause stable linkage disequilibrium and favour reduced recombination on the X chromosome.

    Science.gov (United States)

    Rydzewski, W T; Carioscia, S A; Liévano, G; Lynch, V D; Patten, M M

    2016-06-01

    Sexual antagonism and meiotic drive are sex-specific evolutionary forces with the potential to shape genomic architecture. Previous theory has found that pairing two sexually antagonistic loci or combining sexual antagonism with meiotic drive at linked autosomal loci augments genetic variation, produces stable linkage disequilibrium (LD) and favours reduced recombination. However, the influence of these two forces has not been examined on the X chromosome, which is thought to be enriched for sexual antagonism and meiotic drive. We investigate the evolution of the X chromosome under both sexual antagonism and meiotic drive with two models: in one, both loci experience sexual antagonism; in the other, we pair a meiotic drive locus with a sexually antagonistic locus. We find that LD arises between the two loci in both models, even when the two loci freely recombine in females and that driving haplotypes will be enriched for male-beneficial alleles, further skewing sex ratios in these populations. We introduce a new measure of LD, Dz', which accounts for population allele frequencies and is appropriate for instances where these are sex specific. Both models demonstrate that natural selection favours modifiers that reduce the recombination rate. These results inform observed patterns of congealment found on driving X chromosomes and have implications for patterns of natural variation and the evolution of recombination rates on the X chromosome. © 2016 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2016 European Society For Evolutionary Biology.

  17. The Pch2 AAA+ ATPase promotes phosphorylation of the Hop1 meiotic checkpoint adaptor in response to synaptonemal complex defects.

    Science.gov (United States)

    Herruzo, Esther; Ontoso, David; González-Arranz, Sara; Cavero, Santiago; Lechuga, Ana; San-Segundo, Pedro A

    2016-09-19

    Meiotic cells possess surveillance mechanisms that monitor critical events such as recombination and chromosome synapsis. Meiotic defects resulting from the absence of the synaptonemal complex component Zip1 activate a meiosis-specific checkpoint network resulting in delayed or arrested meiotic progression. Pch2 is an evolutionarily conserved AAA+ ATPase required for the checkpoint-induced meiotic block in the zip1 mutant, where Pch2 is only detectable at the ribosomal DNA array (nucleolus). We describe here that high levels of the Hop1 protein, a checkpoint adaptor that localizes to chromosome axes, suppress the checkpoint defect of a zip1 pch2 mutant restoring Mek1 activity and meiotic cell cycle delay. We demonstrate that the critical role of Pch2 in this synapsis checkpoint is to sustain Mec1-dependent phosphorylation of Hop1 at threonine 318. We also show that the ATPase activity of Pch2 is essential for its checkpoint function and that ATP binding to Pch2 is required for its localization. Previous work has shown that Pch2 negatively regulates Hop1 chromosome abundance during unchallenged meiosis. Based on our results, we propose that, under checkpoint-inducing conditions, Pch2 also possesses a positive action on Hop1 promoting its phosphorylation and its proper distribution on unsynapsed chromosome axes. © The Author(s) 2016. Published by Oxford University Press on behalf of Nucleic Acids Research.

  18. Regulation of spatial selectivity by crossover inhibition.

    Science.gov (United States)

    Cafaro, Jon; Rieke, Fred

    2013-04-10

    Signals throughout the nervous system diverge into parallel excitatory and inhibitory pathways that later converge on downstream neurons to control their spike output. Converging excitatory and inhibitory synaptic inputs can exhibit a variety of temporal relationships. A common motif is feedforward inhibition, in which an increase (decrease) in excitatory input precedes a corresponding increase (decrease) in inhibitory input. The delay of inhibitory input relative to excitatory input originates from an extra synapse in the circuit shaping inhibitory input. Another common motif is push-pull or "crossover" inhibition, in which increases (decreases) in excitatory input occur together with decreases (increases) in inhibitory input. Primate On midget ganglion cells receive primarily feedforward inhibition and On parasol cells receive primarily crossover inhibition; this difference provides an opportunity to study how each motif shapes the light responses of cell types that play a key role in visual perception. For full-field stimuli, feedforward inhibition abbreviated and attenuated responses of On midget cells, while crossover inhibition, though plentiful, had surprisingly little impact on the responses of On parasol cells. Spatially structured stimuli, however, could cause excitatory and inhibitory inputs to On parasol cells to increase together, adopting a temporal relation very much like that for feedforward inhibition. In this case, inhibitory inputs substantially abbreviated a cell's spike output. Thus inhibitory input shapes the temporal stimulus selectivity of both midget and parasol ganglion cells, but its impact on responses of parasol cells depends strongly on the spatial structure of the light inputs.

  19. Single-crossover recombination in discrete time.

    Science.gov (United States)

    von Wangenheim, Ute; Baake, Ellen; Baake, Michael

    2010-05-01

    Modelling the process of recombination leads to a large coupled nonlinear dynamical system. Here, we consider a particular case of recombination in discrete time, allowing only for single crossovers. While the analogous dynamics in continuous time admits a closed solution (Baake and Baake in Can J Math 55:3-41, 2003), this no longer works for discrete time. A more general model (i.e. without the restriction to single crossovers) has been studied before (Bennett in Ann Hum Genet 18:311-317, 1954; Dawson in Theor Popul Biol 58:1-20, 2000; Linear Algebra Appl 348:115-137, 2002) and was solved algorithmically by means of Haldane linearisation. Using the special formalism introduced by Baake and Baake (Can J Math 55:3-41, 2003), we obtain further insight into the single-crossover dynamics and the particular difficulties that arise in discrete time. We then transform the equations to a solvable system in a two-step procedure: linearisation followed by diagonalisation. Still, the coefficients of the second step must be determined in a recursive manner, but once this is done for a given system, they allow for an explicit solution valid for all times.

  20. Crossover of coherent Rabi oscillations in graphene

    International Nuclear Information System (INIS)

    Enamullah; Kumar, Vipin; Setlur, Girish S.

    2012-01-01

    We study the phenomenon of crossover of Rabi oscillations in graphene as a function of detuning - the difference between the frequency of the incident wave and interband energy (2v F |k|). It is shown by comparison with an exactly solved model with bands having linear dispersion but lacking pseudospin that this crossover is unique to graphene, attributable to the pseudospin character of the graphene hamiltonian. A group theoretic argument for why this model is solvable is given. We compute the nonlinear current using our formalism, the main prediction being the threshold behavior (with exponent equal to 1/2) of the slowly varying part of the current in frequency domain with threshold frequency being 2ω R 2 /ω (‘anomalous’ Rabi frequency) where ω R is the Rabi frequency for zero detuning. The novelty of our approach is the introduction of an alternative to the rotating wave approximation (RWA) (called asymptotic RWA here) which is argued to be important in demonstrating this crossover. We provide an interpolation method between these two regimes, that shows novel phenomena attributable to harmonic generation. A fully numerical solution to the Bloch equations verifies the analytical results and the various approximation schemes.

  1. Absence of SUN-domain protein Slp1 blocks karyogamy and switches meiotic recombination and synapsis from homologs to sister chromatids

    Science.gov (United States)

    Vasnier, Christelle; de Muyt, Arnaud; Zhang, Liangran; Tessé, Sophie; Kleckner, Nancy E.; Zickler, Denise; Espagne, Eric

    2014-01-01

    Karyogamy, the process of nuclear fusion is required for two haploid gamete nuclei to form a zygote. Also, in haplobiontic organisms, karyogamy is required to produce the diploid nucleus/cell that then enters meiosis. We identify sun like protein 1 (Slp1), member of the mid–Sad1p, UNC-84–domain ubiquitous family, as essential for karyogamy in the filamentous fungus Sordaria macrospora, thus uncovering a new function for this protein family. Slp1 is required at the last step, nuclear fusion, not for earlier events including nuclear movements, recognition, and juxtaposition. Correspondingly, like other family members, Slp1 localizes to the endoplasmic reticulum and also to its extensions comprising the nuclear envelope. Remarkably, despite the absence of nuclear fusion in the slp1 null mutant, meiosis proceeds efficiently in the two haploid “twin” nuclei, by the same program and timing as in diploid nuclei with a single dramatic exception: the normal prophase program of recombination and synapsis between homologous chromosomes, including loading of recombination and synaptonemal complex proteins, occurs instead between sister chromatids. Moreover, the numbers of recombination-initiating double-strand breaks (DSBs) and ensuing recombinational interactions, including foci of the essential crossover factor Homo sapiens enhancer of invasion 10 (Hei10), occur at half the diploid level in each haploid nucleus, implying per-chromosome specification of DSB formation. Further, the distribution of Hei10 foci shows interference like in diploid meiosis. Centromere and spindle dynamics, however, still occur in the diploid mode during the two meiotic divisions. These observations imply that the prophase program senses absence of karyogamy and/or absence of a homolog partner and adjusts the interchromosomal interaction program accordingly. PMID:25210014

  2. RESULTS OF IN VITRO MATURATION OF MEIOTICALLY IMMATURE HUMAN OOCYTES IN A SIMPLE MEDIUM

    Directory of Open Access Journals (Sweden)

    Borut Kovačič

    2002-12-01

    Full Text Available Background. Among oocytes obtained during aspiration of preovulatory ovarian follicles in hormonally stimulated cycles, we ascertained the percentage of immature oocytes with the nucleus in the metaphase (M I oocytes or even in the prophase (GV oocytes of the first meiotic division and their capacity to mature in vitro in a simple medium without hormonal supplements.Methods. In 818 women, stimulated by gonadotropin releasing hormone agonist (GnRHa and gonadotropins, aspiration of preovulatory size follicles yielded 4972 oocytes. From these we denuded cells of cumulus oophorus and corona, meiotic maturity was evaluated under a microscope. Cells in the metaphase of the second meiotic division (M II oocytes and those maturing after 5 hours were used clinically in the intracytoplasmic sperm injection (ICSI procedure. Immature cells were left in the simple medium. The degree of their nuclear maturity was evaluated after one and after two days of culture. In vitro maturation was clinically used also in 14 cycles with no mature oocytes.Results. Among 4731 oocytes with denuded corona and cumulus, 4199 (88.8% were mature M II oocytes, 295 (6.2% immature M I oocytes and 237 (5% immature GV oocytes. Under in vitro conditions, 68.7% (90/131 GV oocytes attained maturity. Among M I oocytes, 63.6% (136/214 cells matured already after 5 hours and 26.6% (57/214 until the next day. In all 14 women with only immature oocytes, the embryos for embryotransfer were obtained after in vitro maturation and ICSI procedure. The result was four pregnancies and two deliveries.Conclusions. Immature oocytes, obtained in hormonally stimulated cycles, may become clinically applicable if left to mature in vitro in a simple medium without supplementation of growth factors and hormones.

  3. The roles of the Saccharomyces cerevisiae RecQ helicase SGS1 in meiotic genome surveillance.

    Directory of Open Access Journals (Sweden)

    Amit Dipak Amin

    2010-11-01

    Full Text Available The Saccharomyces cerevisiae RecQ helicase Sgs1 is essential for mitotic and meiotic genome stability. The stage at which Sgs1 acts during meiosis is subject to debate. Cytological experiments showed that a deletion of SGS1 leads to an increase in synapsis initiation complexes and axial associations leading to the proposal that it has an early role in unwinding surplus strand invasion events. Physical studies of recombination intermediates implicate it in the dissolution of double Holliday junctions between sister chromatids.In this work, we observed an increase in meiotic recombination between diverged sequences (homeologous recombination and an increase in unequal sister chromatid events when SGS1 is deleted. The first of these observations is most consistent with an early role of Sgs1 in unwinding inappropriate strand invasion events while the second is consistent with unwinding or dissolution of recombination intermediates in an Mlh1- and Top3-dependent manner. We also provide data that suggest that Sgs1 is involved in the rejection of 'second strand capture' when sequence divergence is present. Finally, we have identified a novel class of tetrads where non-sister spores (pairs of spores where each contains a centromere marker from a different parent are inviable. We propose a model for this unusual pattern of viability based on the inability of sgs1 mutants to untangle intertwined chromosomes. Our data suggest that this role of Sgs1 is not dependent on its interaction with Top3. We propose that in the absence of SGS1 chromosomes may sometimes remain entangled at the end of pre-meiotic replication. This, combined with reciprocal crossing over, could lead to physical destruction of the recombined and entangled chromosomes. We hypothesise that Sgs1, acting in concert with the topoisomerase Top2, resolves these structures.This work provides evidence that Sgs1 interacts with various partner proteins to maintain genome stability throughout

  4. Viable calves produced by somatic cell nuclear transfer using meiotic-blocked oocytes.

    Science.gov (United States)

    De Bem, Tiago H C; Chiaratti, Marcos R; Rochetti, Raquel; Bressan, Fabiana F; Sangalli, Juliano R; Miranda, Moysés S; Pires, Pedro R L; Schwartz, Kátia R L; Sampaio, Rafael V; Fantinato-Neto, Paulo; Pimentel, José R V; Perecin, Felipe; Smith, Lawrence C; Meirelles, Flávio V; Adona, Paulo R; Leal, Cláudia L V

    2011-10-01

    Somatic cell nuclear transfer (SCNT) has had an enormous impact on our understanding of biology and remains a unique tool for multiplying valuable laboratory and domestic animals. However, the complexity of the procedure and its poor efficiency are factors that limit a wider application of SCNT. In this context, oocyte meiotic arrest is an important option to make SCNT more flexible and increase the number of cloned embryos produced. Herein, we show that the use of butyrolactone I in association with brain-derived neurotrophic factor (BDNF) to arrest the meiotic division for 24 h prior to in vitro maturation provides bovine (Bos indicus) oocytes capable of supporting development of blastocysts and full-term cloned calves at least as efficiently as nonarrested oocytes. Furthermore, the procedure resulted in cloned blastocysts with an 1.5- and twofold increase of POU5F1 and IFNT2 expression, respectively, which are well-known markers of embryonic viability. Mitochondrial DNA (mtDNA) copy number was diminished by prematuration in immature oocytes (718,585±34,775 vs. 595,579±31,922, respectively, control and treated groups) but was unchanged in mature oocytes (522,179±45,617 vs. 498,771±33,231) and blastocysts (816,627±40,235 vs. 765,332±51,104). To our knowledge, this is the first report of cloned offspring born to prematured oocytes, indicating that meiotic arrest could have significant implications for laboratories working with SCNT and in vitro embryo production.

  5. Radiation-induced mitotic and meiotic aneuploidy in the yeast Saccharomyces cerevisiae.

    Science.gov (United States)

    Parry, J M; Sharp, D; Tippins, R S; Parry, E M

    1979-06-01

    A number of genetic systems are described which in yeast may be used to monitor the induction of chromosome aneuploidy during both mitotic and meiotic cell division. Using these systems we have been able to demonstrate the induction of both monosomic and trisomic cells in mitotically dividing cells and disomic spores in meiotically dividing cells after both UV light and X-ray exposure. The frequency of UV-light-induced monosomic colonies were reduced by post-treatment with photoreactivity light and both UV-light- and X-ray-induced monosomic colonies were reduced by liquid holding post-treatment under non-nutrient conditions. Both responses indicate an involvement of DNA-repair mechanisms in the removal of lesions which may lead to monosomy in yeast. This was further confirmed by the response of an excision-defective yeast strain which showed considerably increased sensitivity to the induction of monosomic colonies by UV-light treatment at low doses. Yeast cultures irradiated at different stages of growth showed variation in their responses to both UV-light and X-rays, cells at the exponential phase of growth show maximum sensitivity to the induction of monosomic colonies at low doses whereas stationary phase cultures showed maximum induction of monosomic colonies at high does. The frequencies of X-ray-induced chromosome aneuploidy during meiosis leading to the production of disomic spores was shown to be dependent upon the stage of meiosis at which the yeast cells were exposed to radiation. Cells which had proceeded beyond the DNA synthetic stage of meiosis were shown to produce disomic spores at considerably lower radiation doses than those cells which had only recently been inoculated into sporulation medium. The results obtained suggest that the yeast sustem may be suitable for the study of sensitivities of the various stages of meiotic cell division to the induction of chromosome aneuploidy after radiation exposure.

  6. X chromosome control of meiotic chromosome synapsis in mouse inter-subspecific hybrids

    Czech Academy of Sciences Publication Activity Database

    Bhattacharyya, Tanmoy; Reifová, R.; Gregorová, Soňa; Šimeček, Petr; Gergelits, Václav; Mistrik, M.; Martincová, Iva; Piálek, Jaroslav; Forejt, Jiří

    2014-01-01

    Roč. 10, č. 2 (2014), e1004088 ISSN 1553-7404 R&D Projects: GA AV ČR Premium Academiae of the Academy of Sciences of the Czech Republic; GA MŠk(CZ) LD11079; GA ČR GA206/08/0640; GA MŠk ED1.1.00/02.0109 Institutional support: RVO:68081766 ; RVO:68378050 Keywords : hybrid sterility * meiotic asynapsis * chromosome substitution strains Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 8.167, year: 2013

  7. Mitotic and meiotic chromosomes of a southern Brazilian population of Boophilus microplus (Acari, Ixodidae

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    Rosane Nunes Garcia

    Full Text Available Using conventional staining with acetic orcein and C-banding techniques it was investigated constitutive heterochromatin chromosomal polymorphisms and the mitotic and the meiotic behavior of male and female chromosomes of Boophilus microplus (Canestrini, 1887. Some differences were detected in the population of southern Brazil as compared to the data of other authors for populations in other latitudes. The differences being mainly concerned with the distribution of constitutive centromeric heterochromatin and variation in the length of heterochromatic blocks in the pericentromeric regions of some chromosome pairs.

  8. Direct and indirect control of the initiation of meiotic recombination by DNA damage checkpoint mechanisms in budding yeast.

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    Bilge Argunhan

    Full Text Available Meiotic recombination plays an essential role in the proper segregation of chromosomes at meiosis I in many sexually reproducing organisms. Meiotic recombination is initiated by the scheduled formation of genome-wide DNA double-strand breaks (DSBs. The timing of DSB formation is strictly controlled because unscheduled DSB formation is detrimental to genome integrity. Here, we investigated the role of DNA damage checkpoint mechanisms in the control of meiotic DSB formation using budding yeast. By using recombination defective mutants in which meiotic DSBs are not repaired, the effect of DNA damage checkpoint mutations on DSB formation was evaluated. The Tel1 (ATM pathway mainly responds to unresected DSB ends, thus the sae2 mutant background in which DSB ends remain intact was employed. On the other hand, the Mec1 (ATR pathway is primarily used when DSB ends are resected, thus the rad51 dmc1 double mutant background was employed in which highly resected DSBs accumulate. In order to separate the effect caused by unscheduled cell cycle progression, which is often associated with DNA damage checkpoint defects, we also employed the ndt80 mutation which permanently arrests the meiotic cell cycle at prophase I. In the absence of Tel1, DSB formation was reduced in larger chromosomes (IV, VII, II and XI whereas no significant reduction was found in smaller chromosomes (III and VI. On the other hand, the absence of Rad17 (a critical component of the ATR pathway lead to an increase in DSB formation (chromosomes VII and II were tested. We propose that, within prophase I, the Tel1 pathway facilitates DSB formation, especially in bigger chromosomes, while the Mec1 pathway negatively regulates DSB formation. We also identified prophase I exit, which is under the control of the DNA damage checkpoint machinery, to be a critical event associated with down-regulating meiotic DSB formation.

  9. Amplifying recombination genome-wide and reshaping crossover landscapes in Brassicas

    Science.gov (United States)

    Falque, Matthieu; Trotoux, Gwenn; Eber, Frédérique; Nègre, Sylvie; Gilet, Marie; Huteau, Virginie; Lodé, Maryse; Jousseaume, Thibaut; Dechaumet, Sylvain; Morice, Jérôme; Coriton, Olivier; Rousseau-Gueutin, Mathieu

    2017-01-01

    Meiotic recombination by crossovers (COs) is tightly regulated, limiting its key role in producing genetic diversity. However, while COs are usually restricted in number and not homogenously distributed along chromosomes, we show here how to disrupt these rules in Brassica species by using allotriploid hybrids (AAC, 2n = 3x = 29), resulting from the cross between the allotetraploid rapeseed (B. napus, AACC, 2n = 4x = 38) and one of its diploid progenitors (B. rapa, AA, 2n = 2x = 20). We produced mapping populations from different genotypes of both diploid AA and triploid AAC hybrids, used as female and/or as male. Each population revealed nearly 3,000 COs that we studied with SNP markers well distributed along the A genome (on average 1 SNP per 1.25 Mbp). Compared to the case of diploids, allotriploid hybrids showed 1.7 to 3.4 times more overall COs depending on the sex of meiosis and the genetic background. Most surprisingly, we found that such a rise was always associated with (i) dramatic changes in the shape of recombination landscapes and (ii) a strong decrease of CO interference. Hybrids carrying an additional C genome exhibited COs all along the A chromosomes, even in the vicinity of centromeres that are deprived of COs in diploids as well as in most studied species. Moreover, in male allotriploid hybrids we found that Class I COs are mostly responsible for the changes of CO rates, landscapes and interference. These results offer the opportunity for geneticists and plant breeders to dramatically enhance the generation of diversity in Brassica species by disrupting the linkage drag coming from limits on number and distribution of COs. PMID:28493942

  10. Xenopus laevis Kif18A is a highly processive kinesin required for meiotic spindle integrity

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    Martin M. Möckel

    2017-04-01

    Full Text Available The assembly and functionality of the mitotic spindle depends on the coordinated activities of microtubule-associated motor proteins of the dynein and kinesin superfamily. Our current understanding of the function of motor proteins is significantly shaped by studies using Xenopus laevis egg extract as its open structure allows complex experimental manipulations hardly feasible in other model systems. Yet, the Kinesin-8 orthologue of human Kif18A has not been described in Xenopus laevis so far. Here, we report the cloning and characterization of Xenopus laevis (Xl Kif18A. Xenopus Kif18A is expressed during oocyte maturation and its depletion from meiotic egg extract results in severe spindle defects. These defects can be rescued by wild-type Kif18A, but not Kif18A lacking motor activity or the C-terminus. Single-molecule microscopy assays revealed that Xl_Kif18A possesses high processivity, which depends on an additional C-terminal microtubule-binding site. Human tissue culture cells depleted of endogenous Kif18A display mitotic defects, which can be rescued by wild-type, but not tail-less Xl_Kif18A. Thus, Xl_Kif18A is the functional orthologue of human Kif18A whose activity is essential for the correct function of meiotic spindles in Xenopus oocytes.

  11. The Phosphatase Dusp7 Drives Meiotic Resumption and Chromosome Alignment in Mouse Oocytes

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    Thomas Tischer

    2016-10-01

    Full Text Available Mammalian oocytes are stored in the ovary, where they are arrested in prophase for prolonged periods. The mechanisms that abrogate the prophase arrest in mammalian oocytes and reinitiate meiosis are not well understood. Here, we identify and characterize an essential pathway for the resumption of meiosis that relies on the protein phosphatase DUSP7. DUSP7-depleted oocytes either fail to resume meiosis or resume meiosis with a significant delay. In the absence of DUSP7, Cdk1/CycB activity drops below the critical level required to reinitiate meiosis, precluding or delaying nuclear envelope breakdown. Our data suggest that DUSP7 drives meiotic resumption by dephosphorylating and thereby inactivating cPKC isoforms. In addition to controlling meiotic resumption, DUSP7 has a second function in chromosome segregation: DUSP7-depleted oocytes that enter meiosis show severe chromosome alignment defects and progress into anaphase prematurely. Altogether, these findings establish the phosphatase DUSP7 as an essential regulator of multiple steps in oocyte meiosis.

  12. Correlation between pairing initiation sites, recombination nodules and meiotic recombination in Sordaria macrospora.

    Science.gov (United States)

    Zickler, D; Moreau, P J; Huynh, A D; Slezec, A M

    1992-09-01

    The decrease of meiotic exchanges (crossing over and conversion) in two mutants of Sordaria macrospora correlated strongly with a reduction of chiasmata and of both types of "recombination nodules." Serial section reconstruction electron microscopy was used to compare the synapsis pattern of meiotic prophase I in wild type and mutants. First, synapsis occurred but the number of synaptonemal complex initiation sites was reduced in both mutants. Second, this reduction was accompanied by, or resulted in, modifications of the pattern of synapsis. Genetic and synaptonemal complex maps were compared in three regions along one chromosome arm divided into well marked intervals. Reciprocal exchange frequencies and number of recombination nodules correlated in wild type in the three analyzed intervals, but disparity was found between the location of recombination nodules and exchanges in the mutants. Despite the twofold exchange decrease, sections of the genome such as the short arm of chromosome 2 and telomere regions were sheltered from nodule decrease and from pairing modifications. This indicated a certain amount of diversity in the control of these features and suggested that exchange frequency was dependent not only on the amount of effective pairing but also on the localization of the pairing sites, as revealed by the synaptonemal complex progression in the mutants.

  13. The Nuclear Cap-Binding Complex Mediates Meiotic Silencing by Unpaired DNA

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    Logan M. Decker

    2017-04-01

    Full Text Available In the filamentous fungus Neurospora crassa, cross walls between individual cells are normally incomplete, making the entire fungal network vulnerable to attack by viruses and selfish DNAs. Accordingly, several genome surveillance mechanisms are maintained to help the fungus combat these repetitive elements. One of these defense mechanisms is called meiotic silencing by unpaired DNA (MSUD, which identifies and silences unpaired genes during meiosis. Utilizing common RNA interference (RNAi proteins, such as Dicer and Argonaute, MSUD targets mRNAs homologous to the unpaired sequence to achieve silencing. In this study, we have identified an additional silencing component, namely the cap-binding complex (CBC. Made up of cap-binding proteins CBP20 and CBP80, CBC associates with the 5′ cap of mRNA transcripts in eukaryotes. The loss of CBC leads to a deficiency in MSUD activity, suggesting its role in mediating silencing. As confirmed in this study, CBC is predominantly nuclear, although it is known to travel in and out of the nucleus to facilitate RNA transport. As seen in animals but not in plants, CBP20’s robust nuclear import depends on CBP80 in Neurospora. CBC interacts with a component (Argonaute of the perinuclear meiotic silencing complex (MSC, directly linking the two cellular factors.

  14. Meiotic UV-sensitive mutant that causes deletion of duplications in neurospora

    International Nuclear Information System (INIS)

    Newmeyer, D.; Galeazzi, D.R.

    1978-01-01

    The meiotic-3 (mei-3) mutant of Neurospora crassa has several effects: (1) when homozygous, it almost completely blocks meiosis and ascospore formation, (2) it is sensitive to uv, (3) its growth is inhibited by histidine, and (4) it increases the instability of nontandem duplications. This was shown for duplications produced by five different rearrangements and was demonstrated by two different criteria. The effects on meiosis and duplication instability are expressed strongly at 25 0 ; the effects on sensitivity to uv and to histidine are expressed strongly at 38.5 0 but only slightly at 25 0 . Nevertheless, all four effects were shown to be due to a single gene. Mei-3 is not allelic with previously reported uv-sensitive mutants. Two other results were obtained that are not necessarily due to mei-3: (1) a cross involving mei-3 produced a new unlinked meiotic mutant, mei-4, which is not sensitive to uv or histidine, and (2) a burst of several new mutants occurred in a different mei-3 stock, including a partial revertant to mei-3. Mei-3 has previously been shown to cause frequent complete loss of a terminal duplicate segment, beginning exactly at the original rearrangement breakpoint. Possible mechanisms are discussed by which a uv-sensitive mutant could cause such precise deletions

  15. Identification of new genes required for meiotic recombination in Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Ajimura, M.; Lee, S.H.; Ogawa, H.

    1993-01-01

    Mutants defective in meiotic recombination were isolated from a disomic haploid strain of Saccharomyces cerevisiae by examining recombination within the leu2 and his4 heteroalleles located on chromosome III. The mutants were classified into two new complementation groups (MRE2 and MRE11) and eight previously identified groups, which include SPO11, HOP1, REC114, MRE4/MEK1 and genes in the RAD52 epistasis group. All of the mutants, in which the mutations in the new complementation groups are homozygous and diploid, can undergo premeiotic DNA synthesis and produce spores. The spores are, however, not viable. The mre2 and mre11 mutants produce viable spores in a spo13 background, in which meiosis I is bypassed, suggesting that these mutants are blocked at an early step in meiotic recombination. The mre2 mutant does not exhibit any unusual phenotype during mitosis and it is, thus, considered to have a mutation in a meiosis-specific gene. By contrast, the mre11 mutant is sensitive to damage to DNA by methyl methanesulfonate and exhibits a hyperrecombination phenotype in mitosis. Among six alleles of HOP1 that were isolated, an unusual pattern of intragenic complementation was observed

  16. Competition between meiotic and apomictic pathways during ovule and seed development results in clonality.

    Science.gov (United States)

    Hojsgaard, Diego H; Martínez, Eric J; Quarin, Camilo L

    2013-01-01

    Meiotic and apomictic reproductive pathways develop simultaneously in facultative aposporous species, and compete to form a seed as a final goal. This developmental competition was evaluated in tetraploid genotypes of Paspalum malacophyllum in order to understand the low level of sexuality in facultative apomictic populations. Cyto-embryology on ovules, flow cytometry on seeds and progeny tests by DNA fingerprinting were used to measure the relative incidence of each meiotic or apomictic pathway along four different stages of the plant's life cycle, namely the beginning and end of gametogenesis, seed formation and adult offspring. A high variation in the frequencies of sexual and apomictic pathways occurred at the first two stages. A trend of radical decline in realized sexuality was then observed. Sexual and apomictic seeds were produced, but the efficiency of the sexual pathway dropped drastically, and exclusively clonal offspring remained. Both reproductive pathways are unstable at the beginning of development, and only the apomictic one remains functional. Key factors reducing sexuality are the faster growth and parthenogenetic development in the aposporous pathway, and an (epi)genetically negative background related to the extensive gene de-regulation pattern responsible for apomixis. The effects of inbreeding depression during post-fertilization development may further decrease the frequency of effective sexuality. No claim to original US government works. New Phytologist © 2012 New Phytologist Trust.

  17. Biochanin a and Daidzein Influence Meiotic Maturation of Pig Oocytes in a Different Manner

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    Hošková K.

    2014-09-01

    Full Text Available The aim of the study was to determine the influence of different concentrations of phytoestrogens biochanin A (BIO A; 20, 40, 50μg ml-1 and daidzein (DAI; 10, 20, 40, 50μg ml-1 on the course of meiotic maturation of pig oocytes. After a 24-hour cultivation, a stage of nuclear maturation was achieved and the areas of cumulus-oocyte complexes (COCs, as an indicator of cumulus expansion, were evaluated. The effects of both contaminants on oocytes were mani - fested from the lowest concentration used. Nuclear maturation was inhibited in a dose-dependent manner in the case of BIO A. Effects of DAI reached a plateau at a concentration of 20μg ml-1.Possible relationship to limited solubility of DAI was excluded because limits of DAI solubility in culture medium were confirmed at 50 μg ml-1.The cumulus expansion was also influenced in a different manner - reduction of the COC’s area by BIO A was dose-dependent, whereas DAI had the strongest effect on CCs in the lowest and highest concentrations used. Both phytoestrogens negatively influence the meiotic maturation of porcine oocytes but there are significant differences in their concrete effects which could relate to the diverse mechanisms of their acting on target cells.

  18. Pattern of callose deposition during the course of meiotic diplospory in Chondrilla juncea (Asteraceae, Cichorioideae).

    Science.gov (United States)

    Musiał, Krystyna; Kościńska-Pająk, Maria

    2017-07-01

    Total absence of callose in the ovules of diplosporous species has been previously suggested. This paper is the first description of callose events in the ovules of Chondrilla juncea, which exhibits meiotic diplospory of the Taraxacum type. We found the presence of callose in the megasporocyte wall and stated that the pattern of callose deposition is dynamically changing during megasporogenesis. At the premeiotic stage, no callose was observed in the ovules. Callose appeared at the micropylar pole of the cell entering prophase of the first meioticdivision restitution but did not surround the megasporocyte. After the formation of a restitution nucleus, a conspicuous callose micropylar cap and dispersed deposits of callose were detected in the megasporocyte wall. During the formation of a diplodyad, the micropylar callose cap decreased and the walls of a newly formed megaspores showed scattered distribution of callose. Within the older diplodyad, callose was mainly accumulated in the wall between megaspores, as well as in the wall of the micropylar cell; however, a dotted fluorescence of callose was also visible in the wall of the chalazal megaspore. Gradual degradation of callose in the wall of the chalazal cell and intense callose accumulation in the wall of the micropylar cell were related to the selection of the functional megaspore. Thus, our findings may suggest that callose fulfills a similar role both during megasporogenesis in sexual angiosperms and in the course of meiotic diplospory in apomicts and seems to form a regulatory interface between reproductive and somatic cells.

  19. Nested Inversion Polymorphisms Predispose Chromosome 22q11.2 to Meiotic Rearrangements.

    Science.gov (United States)

    Demaerel, Wolfram; Hestand, Matthew S; Vergaelen, Elfi; Swillen, Ann; López-Sánchez, Marcos; Pérez-Jurado, Luis A; McDonald-McGinn, Donna M; Zackai, Elaine; Emanuel, Beverly S; Morrow, Bernice E; Breckpot, Jeroen; Devriendt, Koenraad; Vermeesch, Joris R

    2017-10-05

    Inversion polymorphisms between low-copy repeats (LCRs) might predispose chromosomes to meiotic non-allelic homologous recombination (NAHR) events and thus lead to genomic disorders. However, for the 22q11.2 deletion syndrome (22q11.2DS), the most common genomic disorder, no such inversions have been uncovered as of yet. Using fiber-FISH, we demonstrate that parents transmitting the de novo 3 Mb LCR22A-D 22q11.2 deletion, the reciprocal duplication, and the smaller 1.5 Mb LCR22A-B 22q11.2 deletion carry inversions of LCR22B-D or LCR22C-D. Hence, the inversions predispose chromosome 22q11.2 to meiotic rearrangements and increase the individual risk for transmitting rearrangements. Interestingly, the inversions are nested or flanking rather than coinciding with the deletion or duplication sizes. This finding raises the possibility that inversions are a prerequisite not only for 22q11.2 rearrangements but also for all NAHR-mediated genomic disorders. Copyright © 2017. Published by Elsevier Inc.

  20. Temperature dependence of intracellular Ca2+ homeostasis in rat meiotic and postmeiotic spermatogenic cells.

    Science.gov (United States)

    Herrera, E; Salas, K; Lagos, N; Benos, D J; Reyes, J G

    2001-10-01

    The hypothesis that intracellular [Ca2+] is a cell parameter responsive to extreme temperatures in rat meiotic and postmeiotic spermatogenic cells was tested using intracellular fluorescent probes for Ca2+ and pH. In agreement with this hypothesis, extreme temperatures induced a rapid increase of cytosolic [Ca2+] in rat pachytene spermatocytes and round spermatids. Oscillatory changes in temperature can induce oscillations in cytosolic [Ca2+] in these cells. Intracellular [Ca2+] homeostasis in round spermatids was more sensitive to high temperatures compared with pachytene spermatocytes. The calculated activation energies for SERCA ATPase-mediated fluxes in pachytene spermatocytes and round spermatids were 62 and 75 kJ mol(-1), respectively. The activation energies for leak fluxes from intracellular Ca2+ stores were 55 and 68 kJ mol(-1) for pachytene spermatocytes and round spermatids, respectively. Together with changes in cytosolic [Ca2+], round spermatids undergo a decrease in pH(i) at high temperatures. This temperature-induced decrease in pH(i) appears to be partially responsible for the increase in cytosolic [Ca2+] of round spermatids induced by high temperatures. This characteristic of rat meiotic and postmeiotic spermatogenic cells to undergo an increment in cytosolic Ca2+ at temperatures > 33 degrees C can be related to the induction of programmed cell death by high temperatures in these cells.

  1. Male and female meiotic behaviour of an intrachromosomal insertion determined by preimplantation genetic diagnosis

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    Doshi Alpesh

    2010-02-01

    Full Text Available Abstract Background Two related family members, a female and a male balanced carrier of an intrachromosomal insertion on chromosome 7 were referred to our centre for preimplantation genetic diagnosis. This presented a rare opportunity to investigate the behaviour of the insertion chromosome during meiosis in two related carriers. The aim of this study was to carry out a detailed genetic analysis of the preimplantation embryos that were generated from the three treatment cycles for the male and two for the female carrier. Patients underwent in vitro fertilization and on day 3, 22 embryos from the female carrier and 19 embryos from the male carrier were biopsied and cells analysed by fluorescent in situ hybridization. Follow up analysis of 29 untransferred embryos was also performed for confirmation of the diagnosis and to obtain information on meiotic and mitotic outcome. Results In this study, the female carrier produced more than twice as many chromosomally balanced embryos as the male (76.5% vs. 36%, and two pregnancies were achieved for her. Follow up analysis showed that the male carrier had produced more highly abnormal embryos than the female (25% and 15% respectively and no pregnancies occurred for the male carrier and his partner. Conclusion This study compares how an intrachromosomal insertion has behaved in the meiotic and preimplantation stages of development in sibling male and female carriers. It confirms that PGD is an appropriate treatment in such cases. Reasons for the differing outcome for the two carriers are discussed.

  2. B microchromosomes in the family Curimatidae (Characiformes): mitotic and meiotic behavior.

    Science.gov (United States)

    Sampaio, Tatiane Ramos; Gravena, Waleska; Gouveia, Juceli Gonzalez; Giuliano-Caetano, Lucia; Dias, Ana Lúcia

    2011-01-01

    Cyphocharax voga (Hensel, 1870), Cyphocharax spilotus (Vari, 1987), Cyphocharax saladensis (Meinken, 1933), Cyphocharax modestus (Fernández-Yépez, 1948), Steindachnerina biornata (Braga & Azpelicueta, 1987) and Steindachnerina insculpta (Fernández-Yépez, 1948) collected from two hydrographic basins. All samples presented 2n=54 meta-submetacentric (m-sm) chromosomes and FN equal to 108, and 1 or 2 B microchromosomes in the mitotic and meiotic cells of the six sampled populations showing inter-and intraindividual variation. The analysis of the meiotic cells in Cyphocharax saladensis, Cyphocharax spilotus, and Cyphocharax voga showed a modal number of 54 chromosomes in the spermatogonial metaphases and 27 bivalents in the pachytene, diplotene, diakinesis and in metaphase I stages, and 27 chromosomes in metaphase II; in Cyphocharax modestus, Steindachnerina biornata, and Steindachnerina insculpta, spermatogonial metaphases with 54 chromosomes and pachytene and metaphase I with 27 bivalents were observed. The B microchromosome was observed as univalent in the spermatogonial metaphase of Cyphocharax spilotus, in the pachytene stage in the other species, with the exception of Cyphocharax saladensis, and Steindachnerina biornata in metaphase I. New occurrences of the B microchromosome in Cyphocharax voga, Cyphocharax saladensis and Steindachnerina biornata were observed, confirming that the presence of this type of chromosome is a striking characteristic of this group of fish.

  3. Histone H2AFX Links Meiotic Chromosome Asynapsis to Prophase I Oocyte Loss in Mammals.

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    Jeffrey M Cloutier

    2015-10-01

    Full Text Available Chromosome abnormalities are common in the human population, causing germ cell loss at meiotic prophase I and infertility. The mechanisms driving this loss are unknown, but persistent meiotic DNA damage and asynapsis may be triggers. Here we investigate the contribution of these lesions to oocyte elimination in mice with chromosome abnormalities, e.g. Turner syndrome (XO and translocations. We show that asynapsed chromosomes trigger oocyte elimination at diplonema, which is linked to the presence of phosphorylated H2AFX (γH2AFX. We find that DNA double-strand break (DSB foci disappear on asynapsed chromosomes during pachynema, excluding persistent DNA damage as a likely cause, and demonstrating the existence in mammalian oocytes of a repair pathway for asynapsis-associated DNA DSBs. Importantly, deletion or point mutation of H2afx restores oocyte numbers in XO females to wild type (XX levels. Unexpectedly, we find that asynapsed supernumerary chromosomes do not elicit prophase I loss, despite being enriched for γH2AFX and other checkpoint proteins. These results suggest that oocyte loss cannot be explained simply by asynapsis checkpoint models, but is related to the gene content of asynapsed chromosomes. A similar mechanistic basis for oocyte loss may operate in humans with chromosome abnormalities.

  4. Location of RAD51-like protein during meiotic prophase in Eimeria tenella.

    Science.gov (United States)

    Del Cacho, Emilio; Gallego, Margarita; Pagés, Marc; Barbero, José Luís; Monteagudo, Luís; Sánchez-Acedo, Caridad

    2011-05-31

    This study focuses on reporting events in Eimeria tenella oocysts from early to late prophase I in terms of RAD51 protein in association with the synaptonemal complex formed between homologous chromosomes. The aim of the study was the sequential localization of RAD51 protein, which is involved in the repair of double-strand breaks (DSBs) on the eimerian chromosomes as they synapse and desynapse. Structural Maintenance of Chromosome protein SMC3, which plays a role in synaptonemal complex formation, was labeled to identify initiation and progress of chromosome synapsis and desynapsis in parallel with the appearance and disappearance of RAD51 foci. Antibodies directed against RAD51 and cohesin subunit SMC3 proteins were labeled with either fluorescence or colloidal gold to visualize RAD51 protein foci and synaptonemal complexes. RAD51 protein localization during prophase I was studied on meiotic chromosomes spreads obtained from oocysts at different points in time after the start of sporulation. The present findings showed that foci detected with the antibody directed against RAD51 protein first appeared at the pre-leptotene stage before homologous chromosomes began pairing. Subsequently, the foci were detected in association with the lateral elements at the precise sites where synapsis were in progress. These findings lead us to suggest that in E. tenella, homologous chromosome pairing was a DSB-dependent mechanism and reinforced the participation of RAD51 protein in meiotic homology search, alignment and pairing of chromosomes. Copyright © 2010 Elsevier B.V. All rights reserved.

  5. Histone H2AFX Links Meiotic Chromosome Asynapsis to Prophase I Oocyte Loss in Mammals

    Science.gov (United States)

    Cloutier, Jeffrey M.; Mahadevaiah, Shantha K.; ElInati, Elias; Nussenzweig, André; Tóth, Attila; Turner, James M. A.

    2015-01-01

    Chromosome abnormalities are common in the human population, causing germ cell loss at meiotic prophase I and infertility. The mechanisms driving this loss are unknown, but persistent meiotic DNA damage and asynapsis may be triggers. Here we investigate the contribution of these lesions to oocyte elimination in mice with chromosome abnormalities, e.g. Turner syndrome (XO) and translocations. We show that asynapsed chromosomes trigger oocyte elimination at diplonema, which is linked to the presence of phosphorylated H2AFX (γH2AFX). We find that DNA double-strand break (DSB) foci disappear on asynapsed chromosomes during pachynema, excluding persistent DNA damage as a likely cause, and demonstrating the existence in mammalian oocytes of a repair pathway for asynapsis-associated DNA DSBs. Importantly, deletion or point mutation of H2afx restores oocyte numbers in XO females to wild type (XX) levels. Unexpectedly, we find that asynapsed supernumerary chromosomes do not elicit prophase I loss, despite being enriched for γH2AFX and other checkpoint proteins. These results suggest that oocyte loss cannot be explained simply by asynapsis checkpoint models, but is related to the gene content of asynapsed chromosomes. A similar mechanistic basis for oocyte loss may operate in humans with chromosome abnormalities. PMID:26509888

  6. Molecular Basis for Enhancement of the Meiotic DMCI Recombinase by RAD51AP1

    Energy Technology Data Exchange (ETDEWEB)

    Dray, Eloise; Dunlop, Myun Hwa; Kauppi, Liisa; San Filippo, Joseph San; Wiese, Claudia; Tsai, Miaw-Sheue; Begovic, Sead; Schild, David; Jasin, Maria; Keeney, Scott; Sung, Patrick

    2010-11-05

    Homologous recombination is needed for meiotic chromosome segregation, genome maintenance, and tumor suppression. RAD51AP1 (RAD51 Associated Protein 1) has been shown to interact with and enhance the recombinase activity of RAD51. Accordingly, genetic ablation of RAD51AP1 leads to enhanced sensitivity to and also chromosome aberrations upon DNA damage, demonstrating a role for RAD51AP1 in mitotic homologous recombination. Here we show physical association of RAD51AP1 with the meiosis-specific recombinase DMC1 and a stimulatory effect of RAD51AP1 on the DMC1-mediated D-loop reaction. Mechanistic studies have revealed that RAD51AP1 enhances the ability of the DMC1 presynaptic filament to capture the duplex DNA partner and to assemble the synaptic complex, in which the recombining DNA strands are homologously aligned. We also provide evidence that functional co-operation is dependent on complex formation between DMC1 and RAD51AP1, and that distinct epitopes in RAD51AP1 mediate interactions with RAD51 and DMC1. Finally, we show that RAD51AP1 is expressed in mouse testes, and that RAD51AP1 foci co-localize with a subset of DMC1 foci in spermatocytes. These results suggest that RAD51AP1 also serves an important role in meiotic homologous recombination.

  7. Biogeography-Based Optimization with Orthogonal Crossover

    Directory of Open Access Journals (Sweden)

    Quanxi Feng

    2013-01-01

    Full Text Available Biogeography-based optimization (BBO is a new biogeography inspired, population-based algorithm, which mainly uses migration operator to share information among solutions. Similar to crossover operator in genetic algorithm, migration operator is a probabilistic operator and only generates the vertex of a hyperrectangle defined by the emigration and immigration vectors. Therefore, the exploration ability of BBO may be limited. Orthogonal crossover operator with quantization technique (QOX is based on orthogonal design and can generate representative solution in solution space. In this paper, a BBO variant is presented through embedding the QOX operator in BBO algorithm. Additionally, a modified migration equation is used to improve the population diversity. Several experiments are conducted on 23 benchmark functions. Experimental results show that the proposed algorithm is capable of locating the optimal or closed-to-optimal solution. Comparisons with other variants of BBO algorithms and state-of-the-art orthogonal-based evolutionary algorithms demonstrate that our proposed algorithm possesses faster global convergence rate, high-precision solution, and stronger robustness. Finally, the analysis result of the performance of QOX indicates that QOX plays a key role in the proposed algorithm.

  8. Linear combinations come alive in crossover designs.

    Science.gov (United States)

    Shuster, Jonathan J

    2017-10-30

    Before learning anything about statistical inference in beginning service courses in biostatistics, students learn how to calculate the mean and variance of linear combinations of random variables. Practical precalculus examples of the importance of these exercises can be helpful for instructors, the target audience of this paper. We shall present applications to the "1-sample" and "2-sample" methods for randomized short-term 2-treatment crossover studies, where patients experience both treatments in random order with a "washout" between the active treatment periods. First, we show that the 2-sample method is preferred as it eliminates "conditional bias" when sample sizes by order differ and produces a smaller variance. We also demonstrate that it is usually advisable to use the differences in posttests (ignoring baseline and post washout values) rather than the differences between the changes in treatment from the start of the period to the end of the period ("delta of delta"). Although the intent is not to provide a definitive discussion of crossover designs, we provide a section and references to excellent alternative methods, where instructors can provide motivation to students to explore the topic in greater detail in future readings or courses. Copyright © 2017 John Wiley & Sons, Ltd.

  9. Amplified fragment length polymorphism analysis to assess crossover interference and homozygosity in gynogenetic diploid Pacific abalone (Haliotis discus hannai).

    Science.gov (United States)

    Nie, H-T; Li, Q; Kong, L-F

    2014-06-01

    Recombination analysis in gynogenetic diploids is a powerful tool for assessing the degree of inbreeding, investigating crossover events and understanding chiasma interference during meiosis. To estimate the marker-centromere recombination rate, the inheritance pattern of 654 amplified fragment length polymorphism (AFLP) markers was examined in the 72-h veliger larvae of two meiogynogenetic diploid families in the Pacific abalone (Haliotis discus hannai). The second-division segregation frequency (y) of the AFLP loci ranged from 0.00 to 0.96, with 23.9% of loci showing y-values higher than 0.67, evidencing the existence of interference. The average recombination frequency across the 654 AFLP loci was 0.45, allowing estimation of the fixation index of 0.55, indicating that meiotic gynogenesis could provide an effective means of rapid inbreeding in the Pacific abalone. The AFLP loci have a small proportion (4.4%) of y-values greater than 0.90, suggesting that a relatively low or intermediate degree of chiasma interference occurred in the abalone chromosomes. The information obtained in this study will enhance our understanding of the abalone genome and will be useful for genetic studies in the species. © 2014 Stichting International Foundation for Animal Genetics.

  10. The Chromatin Protein DUET/MMD1 Controls Expression of the Meiotic Gene TDM1 during Male Meiosis in Arabidopsis.

    Science.gov (United States)

    Andreuzza, Sébastien; Nishal, Bindu; Singh, Aparna; Siddiqi, Imran

    2015-09-01

    Meiosis produces haploid cells essential for sexual reproduction. In yeast, entry into meiosis activates transcription factors which trigger a transcriptional cascade that results in sequential co-expression of early, middle and late meiotic genes. However, these factors are not conserved, and the factors and regulatory mechanisms that ensure proper meiotic gene expression in multicellular eukaryotes are poorly understood. Here, we report that DUET/MMD1, a PHD finger protein essential for Arabidopsis male meiosis, functions as a transcriptional regulator in plant meiosis. We find that DUET-PHD binds H3K4me2 in vitro, and show that this interaction is critical for function during meiosis. We also show that DUET is required for proper microtubule organization during meiosis II, independently of its function in meiosis I. Remarkably, DUET protein shows stage-specific expression, confined to diplotene. We identify two genes TDM1 and JAS with critical functions in cell cycle transitions and spindle organization in male meiosis, as DUET targets, with TDM1 being a direct target. Thus, DUET is required to regulate microtubule organization and cell cycle transitions during male meiosis, and functions as a direct transcription activator of the meiotic gene TDM1. Expression profiling showed reduced expression of a subset comprising about 12% of a known set of meiosis preferred genes in the duet mutant. Our results reveal the action of DUET as a transcriptional regulator during male meiosis in plants, and suggest that transcription of meiotic genes is under stagewise control in plants as in yeast.

  11. Comparative Meiotic Studies in Triatoma sordida (Stål and T. guasayana Wygodzinsky & Abalos (Reduviidae, Heteroptera

    Directory of Open Access Journals (Sweden)

    P Rebagliati

    1998-05-01

    Full Text Available Triatoma sordida and T. guasayana are competent Trypanosoma cruzi vectors, with overlapping distribution areas in Argentina. Both species are morphologically similar, and their immature stages are hard to discriminate. Cytogenetic studies in the genus Triatoma reveal scarce karyotypic variations, being 2n= 20 + XY the most frequent diploid number in males. In the present work the meiotic behaviour of different Argentinian populations of T. sordida and T. guasayana has been analyzed; the meiotic karyotype of both species has also been compared. The species differ in total chromosome area and in the relative area of the sex chromosomes. These meiotic karyotypic differences constitute an additional tool for the taxonomic characterization of T. sordida and T. guasayana. The analysis of an interpopulation hybrid of T. sordida (Brazil x Argentina reveals a regular meiotic behaviour, despite the presence of heteromorphic bivalents. Our observations support the hypothesis that karyotype variations through the gain or loss of heterochromatin can not be considered as a primary mechanism of reproductive isolation in Triatoma.

  12. The Saccharomyces cerevisiae MUM2 gene interacts with the DNA replication machinery and is required for meiotic levels of double strand breaks.

    Science.gov (United States)

    Davis, L; Barbera, M; McDonnell, A; McIntyre, K; Sternglanz, R; Jin , Q; Loidl, J; Engebrecht, J

    2001-01-01

    The Saccharomyces cerevisiae MUM2 gene is essential for meiotic, but not mitotic, DNA replication and thus sporulation. Genetic interactions between MUM2 and a component of the origin recognition complex and polymerase alpha-primase suggest that MUM2 influences the function of the DNA replication machinery. Early meiotic gene expression is induced to a much greater extent in mum2 cells than in meiotic cells treated with the DNA synthesis inhibitor hydroxyurea. This result indicates that the mum2 meiotic arrest is downstream of the arrest induced by hydroxyurea and suggests that DNA synthesis is initiated in the mutant. Genetic analyses indicate that the recombination that occurs in mum2 mutants is dependent on the normal recombination machinery and on synaptonemal complex components and therefore is not a consequence of lesions created by incompletely replicated DNA. Both meiotic ectopic and allelic recombination are similarly reduced in the mum2 mutant, and the levels are consistent with the levels of meiosis-specific DSBs that are generated. Cytological analyses of mum2 mutants show that chromosome pairing and synapsis occur, although at reduced levels compared to wild type. Given the near-wild-type levels of meiotic gene expression, pairing, and synapsis, we suggest that the reduction in DNA replication is directly responsible for the reduced level of DSBs and meiotic recombination. PMID:11238403

  13. Crossover ensembles of random matrices and skew-orthogonal polynomials

    International Nuclear Information System (INIS)

    Kumar, Santosh; Pandey, Akhilesh

    2011-01-01

    Highlights: → We study crossover ensembles of Jacobi family of random matrices. → We consider correlations for orthogonal-unitary and symplectic-unitary crossovers. → We use the method of skew-orthogonal polynomials and quaternion determinants. → We prove universality of spectral correlations in crossover ensembles. → We discuss applications to quantum conductance and communication theory problems. - Abstract: In a recent paper (S. Kumar, A. Pandey, Phys. Rev. E, 79, 2009, p. 026211) we considered Jacobi family (including Laguerre and Gaussian cases) of random matrix ensembles and reported exact solutions of crossover problems involving time-reversal symmetry breaking. In the present paper we give details of the work. We start with Dyson's Brownian motion description of random matrix ensembles and obtain universal hierarchic relations among the unfolded correlation functions. For arbitrary dimensions we derive the joint probability density (jpd) of eigenvalues for all transitions leading to unitary ensembles as equilibrium ensembles. We focus on the orthogonal-unitary and symplectic-unitary crossovers and give generic expressions for jpd of eigenvalues, two-point kernels and n-level correlation functions. This involves generalization of the theory of skew-orthogonal polynomials to crossover ensembles. We also consider crossovers in the circular ensembles to show the generality of our method. In the large dimensionality limit, correlations in spectra with arbitrary initial density are shown to be universal when expressed in terms of a rescaled symmetry breaking parameter. Applications of our crossover results to communication theory and quantum conductance problems are also briefly discussed.

  14. Crossover of burnout and engagement in work teams

    NARCIS (Netherlands)

    Bakker, A.B.; Van Emmerik, IJ.H.; Euwema, M.C.

    2005-01-01

    This study investigates the crossover of burnout and work engagement among 2,229 Royal Dutch constabulary officers, working in one of 85 teams. The authors hypothesized that both states may transfer from teams to individual team members. The results of multilevel analyses confirm this crossover

  15. Study of active crossover network | Tyona | Nigerian Journal of Physics

    African Journals Online (AJOL)

    An active crossover network system has been realized using an active component LF356 with a JFET input. The net work has two drives, the low frequency drive (Bass) and the high frequency drive (Treble). It employs high level crossover technique. The circuit performance was adequately verified and the frequency ...

  16. Regulatory complexity revealed by integrated cytological and RNA-seq analyses of meiotic substages in mouse spermatocytes.

    Science.gov (United States)

    Ball, Robyn L; Fujiwara, Yasuhiro; Sun, Fengyun; Hu, Jianjun; Hibbs, Matthew A; Handel, Mary Ann; Carter, Gregory W

    2016-08-12

    The continuous and non-synchronous nature of postnatal male germ-cell development has impeded stage-specific resolution of molecular events of mammalian meiotic prophase in the testis. Here the juvenile onset of spermatogenesis in mice is analyzed by combining cytological and transcriptomic data in a novel computational analysis that allows decomposition of the transcriptional programs of spermatogonia and meiotic prophase substages. Germ cells from testes of individual mice were obtained at two-day intervals from 8 to 18 days post-partum (dpp), prepared as surface-spread chromatin and immunolabeled for meiotic stage-specific protein markers (STRA8, SYCP3, phosphorylated H2AFX, and HISTH1T). Eight stages were discriminated cytologically by combinatorial antibody labeling, and RNA-seq was performed on the same samples. Independent principal component analyses of cytological and transcriptomic data yielded similar patterns for both data types, providing strong evidence for substage-specific gene expression signatures. A novel permutation-based maximum covariance analysis (PMCA) was developed to map co-expressed transcripts to one or more of the eight meiotic prophase substages, thereby linking distinct molecular programs to cytologically defined cell states. Expression of meiosis-specific genes is not substage-limited, suggesting regulation of substage transitions at other levels. This integrated analysis provides a general method for resolving complex cell populations. Here it revealed not only features of meiotic substage-specific gene expression, but also a network of substage-specific transcription factors and relationships to potential target genes.

  17. Extended precedence preservative crossover for job shop scheduling problems

    Science.gov (United States)

    Ong, Chung Sin; Moin, Noor Hasnah; Omar, Mohd

    2013-04-01

    Job shop scheduling problems (JSSP) is one of difficult combinatorial scheduling problems. A wide range of genetic algorithms based on the two parents crossover have been applied to solve the problem but multi parents (more than two parents) crossover in solving the JSSP is still lacking. This paper proposes the extended precedence preservative crossover (EPPX) which uses multi parents for recombination in the genetic algorithms. EPPX is a variation of the precedence preservative crossover (PPX) which is one of the crossovers that perform well to find the solutions for the JSSP. EPPX is based on a vector to determine the gene selected in recombination for the next generation. Legalization of children (offspring) can be eliminated due to the JSSP representation encoded by using permutation with repetition that guarantees the feasibility of chromosomes. The simulations are performed on a set of benchmarks from the literatures and the results are compared to ensure the sustainability of multi parents recombination in solving the JSSP.

  18. Alteration of gene conversion patterns in Sordaria fimicola by supplementation with DNA bases.

    Science.gov (United States)

    Kitani, Y; Olive, L S

    1970-08-01

    Supplementation with DNA bases in crosses of Sordaria fimicola heterozygous for spore color markers (g(1), h(2)) within the gray-spore (g) locus has been found to cause significant alterations in patterns of gene conversion at the two mutant sites. Each base had its own characteristic effect in altering the conversion pattern, and responses of the two mutant sites to the four bases were different in several ways. Also, the responses of the two involved chromatids of the meiotic bivalent were different.

  19. Whole grain-rich diet reduces body weight and systemic low-grade inflammation without inducing major changes of the gut microbiome: a randomised cross-over trial

    DEFF Research Database (Denmark)

    Roager, Henrik Munch; Vogt, Josef Korbinian; Kristensen, Mette

    2017-01-01

    Objective To investigate whether a whole grain diet alters the gut microbiome and insulin sensitivity, as well as biomarkers of metabolic health and gut functionality. Design 60 Danish adults at risk of developing metabolic syndrome were included in a randomised cross-over trial with two 8-week d...

  20. Estimation of pre-meiotic DNA synthesis period in the dog spermatozoa

    International Nuclear Information System (INIS)

    Ghosal, S.K.; Bandyopadhyay, T.; De, S.; Beauregard, L.J.

    1976-01-01

    About 10 μCi of 3 H-thymidine was injected into each of 4 arbitarary sites in each testis of 6 dogs. Biopsies were taken at 4-hour intervals coverning a period from 20.0 to 22.2 days post-injection. Kinetics of labelled spermatocytes was followed employing Kodak NTB-3 emulsion to conventionally prepared air-dried slides. The technique for calculating pre-meiosis DNA synthesis duration is same as that for estimating S period in mitotic cells. Current investigation suggests that the mean duration of pre-meiotic S period of Canine spermatocytes is 20.4 hrs as compared to 29 and 40 hrs in spermatocytes of mouse and golden hamster respectively. (author)

  1. Ascospores of large-spored Metschnikowia species are genuine meiotic products of these yeasts

    DEFF Research Database (Denmark)

    Marinoni, G.; Piskur, Jure; Lachance, M.A.

    2003-01-01

    continentalis var. continentalis, and M. continentalis var. borealis. Asci were dissected and the segregation patterns for various phenotypes analyzed. In all cases (n = 47) both mating types (h(+) and h(-)) were recovered in pairs of sister spores, casting further uncertainty as to whether normal meiosis takes...... place. However, the segregation patterns for cycloheximide resistance and several auxotrophic markers were random, suggesting that normal meiosis indeed occurs. To explain the lack of second-division segregation of mating types, we concluded that crossing-over does not occur between the mating......-type locus and the centromere, and that meiosis I is tied to spore formation, which explains why the number of spores is limited to two. The latter assumption was also supported by fluorescence microscopy. The second meiotic division takes place inside the spores and is followed by the resorption of two...

  2. Mapping genes by meiotic and UV-induced mitotic recombination in Coprinus cinereus

    International Nuclear Information System (INIS)

    Amirkhanian, J.D.; Cowan, J.W.

    1985-01-01

    Three morphological mutants in Coprinus cinereus—one spontaneous (den-2) and two chemically induced (zigand sta)—were assigned to linkage groups and utilized in meiotic and mitotic mapping. Mutants den-2 and zig belong to linkage group III, den-2 being close to the centromere and about 20 map units (mu) from zig. The mutant sta in linkage group ‘G’ is at a distance of about 37 mu from ade-3. Mitotic mapping confirmed the gene order in linkage group III and provided evidence that trp-2 in linkage group ‘G’ was between the centromere and ade-3. These morphological mutants are compact in colony growth and therefore suited to high-density plating. The rarity of spontaneously occurring mitotic segregants suggests that diploids of Coprinus cinereus, heterozygous for morphoiogical markers in repuision, could serve as useful test systems for rapid screening of chemical mutagen/carcinogens via mitotic recombination studies

  3. Meiotic transmission of an in vitro-assembled autonomous maize minichromosome.

    Directory of Open Access Journals (Sweden)

    Shawn R Carlson

    2007-10-01

    Full Text Available Autonomous chromosomes are generated in yeast (yeast artificial chromosomes and human fibrosarcoma cells (human artificial chromosomes by introducing purified DNA fragments that nucleate a kinetochore, replicate, and segregate to daughter cells. These autonomous minichromosomes are convenient for manipulating and delivering DNA segments containing multiple genes. In contrast, commercial production of transgenic crops relies on methods that integrate one or a few genes into host chromosomes; extensive screening to identify insertions with the desired expression level, copy number, structure, and genomic location; and long breeding programs to produce varieties that carry multiple transgenes. As a step toward improving transgenic crop production, we report the development of autonomous maize minichromosomes (MMCs. We constructed circular MMCs by combining DsRed and nptII marker genes with 7-190 kb of genomic maize DNA fragments containing satellites, retroelements, and/or other repeats commonly found in centromeres and using particle bombardment to deliver these constructs into embryogenic maize tissue. We selected transformed cells, regenerated plants, and propagated their progeny for multiple generations in the absence of selection. Fluorescent in situ hybridization and segregation analysis demonstrated that autonomous MMCs can be mitotically and meiotically maintained. The MMC described here showed meiotic segregation ratios approaching Mendelian inheritance: 93% transmission as a disome (100% expected, 39% transmission as a monosome crossed to wild type (50% expected, and 59% transmission in self crosses (75% expected. The fluorescent DsRed reporter gene on the MMC was expressed through four generations, and Southern blot analysis indicated the encoded genes were intact. This novel approach for plant transformation can facilitate crop biotechnology by (i combining several trait genes on a single DNA fragment, (ii arranging genes in a defined

  4. ARG-walker: inference of individual specific strengths of meiotic recombination hotspots by population genomics analysis.

    Science.gov (United States)

    Chen, Hao; Yang, Peng; Guo, Jing; Kwoh, Chee Keong; Przytycka, Teresa M; Zheng, Jie

    2015-01-01

    Meiotic recombination hotspots play important roles in various aspects of genomics, but the underlying mechanisms for regulating the locations and strengths of recombination hotspots are not yet fully revealed. Most existing algorithms for estimating recombination rates from sequence polymorphism data can only output average recombination rates of a population, although there is evidence for the heterogeneity in recombination rates among individuals. For genome-wide association studies (GWAS) of recombination hotspots, an efficient algorithm that estimates the individualized strengths of recombination hotspots is highly desirable. In this work, we propose a novel graph mining algorithm named ARG-walker, based on random walks on ancestral recombination graphs (ARG), to estimate individual-specific recombination hotspot strengths. Extensive simulations demonstrate that ARG-walker is able to distinguish the hot allele of a recombination hotspot from the cold allele. Integrated with output of ARG-walker, we performed GWAS on the phased haplotype data of the 22 autosome chromosomes of the HapMap Asian population samples of Chinese and Japanese (JPT+CHB). Significant cis-regulatory signals have been detected, which is corroborated by the enrichment of the well-known 13-mer motif CCNCCNTNNCCNC of PRDM9 protein. Moreover, two new DNA motifs have been identified in the flanking regions of the significantly associated SNPs (single nucleotide polymorphisms), which are likely to be new cis-regulatory elements of meiotic recombination hotspots of the human genome. Our results on both simulated and real data suggest that ARG-walker is a promising new method for estimating the individual recombination variations. In the future, it could be used to uncover the mechanisms of recombination regulation and human diseases related with recombination hotspots.

  5. Computer-aided meiotic maturation assay (CAMMA) of zebrafish (danio rerio) oocytes in vitro.

    Science.gov (United States)

    Lessman, Charles A; Nathani, Ravikanth; Uddin, Rafique; Walker, Jamie; Liu, Jianxiong

    2007-01-01

    We have developed a new technique called Computer-Aided Meiotic Maturation Assay (CAMMA) for imaging large arrays of zebrafish oocytes and automatically collecting image files at regular intervals during meiotic maturation. This novel method uses a transparency scanner interfaced to a computer with macro programming that automatically scans and archives the image files. Images are stacked and analyzed with ImageJ to quantify changes in optical density characteristic of zebrafish oocyte maturation. Major advantages of CAMMA include (1) ability to image very large arrays of oocytes and follow individual cells over time, (2) simultaneously image many treatment groups, (3) digitized images may be stacked, animated, and analyzed in programs such as ImageJ, NIH-Image, or ScionImage, and (4) CAMMA system is inexpensive, costing less than most microscopes used in traditional assays. We have used CAMMA to determine the dose response and time course of oocyte maturation induced by 17alpha-hydroxyprogesterone (HP). Maximal decrease in optical density occurs around 5 hr after 0.1 micro g/ml HP (28.5 degrees C), approximately 3 hr after germinal vesicle migration (GVM) and dissolution (GVD). In addition to changes in optical density, GVD is accompanied by streaming of ooplasm to the animal pole to form a blastodisc. These dynamic changes are readily visualized by animating image stacks from CAMMA; thus, CAMMA provides a valuable source of time-lapse movies for those studying zebrafish oocyte maturation. The oocyte clearing documented by CAMMA is correlated to changes in size distribution of major yolk proteins upon SDS-PAGE, and, this in turn, is related to increased cyclin B(1) protein.

  6. Timing of food intake impacts daily rhythms of human salivary microbiota: a randomized, crossover study.

    Science.gov (United States)

    Collado, María Carmen; Engen, Phillip A; Bandín, Cristina; Cabrera-Rubio, Raúl; Voigt, Robin M; Green, Stefan J; Naqib, Ankur; Keshavarzian, Ali; Scheer, Frank A J L; Garaulet, Marta

    2018-04-01

    The composition of the diet (what we eat) has been widely related to the microbiota profile. However, whether the timing of food consumption (when we eat) influences microbiota in humans is unknown. A randomized, crossover study was performed in 10 healthy normal-weight young women to test the effect of the timing of food intake on the human microbiota in the saliva and fecal samples. More specifically, to determine whether eating late alters daily rhythms of human salivary microbiota, we interrogated salivary microbiota in samples obtained at 4 specific time points over 24 h, to achieve a better understanding of the relationship between food timing and metabolic alterations in humans. Results revealed significant diurnal rhythms in salivary diversity and bacterial relative abundance ( i.e., TM7 and Fusobacteria) across both early and late eating conditions. More importantly, meal timing affected diurnal rhythms in diversity of salivary microbiota toward an inverted rhythm between the eating conditions, and eating late increased the number of putative proinflammatory taxa, showing a diurnal rhythm in the saliva. In a randomized, crossover study, we showed for the first time the impact of the timing of food intake on human salivary microbiota. Eating the main meal late inverts the daily rhythm of salivary microbiota diversity which may have a deleterious effect on the metabolism of the host.-Collado, M. C., Engen, P. A., Bandín, C., Cabrera-Rubio, R., Voigt, R. M., Green, S. J., Naqib, A., Keshavarzian, A., Scheer, F. A. J. L., Garaulet, M. Timing of food intake impacts daily rhythms of human salivary microbiota: a randomized, crossover study.

  7. The effect of high intensity exercise and anticipation on trunk and lower limb biomechanics during a crossover cutting manoeuvre.

    Science.gov (United States)

    Whyte, Enda F; Richter, Chris; O'connor, Siobhan; Moran, Kieran A

    2018-04-01

    We investigated the effects of high intensity, intermittent exercise (HIIP) and anticipation on trunk, pelvic and lower limb biomechanics during a crossover cutting manoeuvre. Twenty-eight male, varsity athletes performed crossover cutting manoeuvres in anticipated and unanticipated conditions pre- and post-HIIP. Kinematic and kinetic variables were captured using a motion analysis system. Statistical parametric mapping (repeated-measures ANOVA) was used to identify differences in biomechanical patterns. Results demonstrated that both unanticipation and fatigue (HIIP) altered the biomechanics of the crossover cutting manoeuvre, whereas no interactions effects were observed. Unanticipation resulted in less trunk and pelvic side flexion in the direction of cut (d = 0.70 - 0.79). This led to increased hip abductor and external rotator moments and increased knee extensor and valgus moments with small effects (d = 0.24-0.42), potentially increasing ACL strain. The HIIP resulted in trivial to small effects only with a decrease in internal knee rotator and extensor moment and decreased knee power absorption (d = 0.35), reducing potential ACL strain. The effect of trunk and hip control exercises in unanticipated conditions on the crossover cutting manoeuvre should be investigated with a view to refining ACL injury prevention programmes.

  8. Pressure and Temperature Sensors Using Two Spin Crossover Materials.

    Science.gov (United States)

    Jureschi, Catalin-Maricel; Linares, Jorge; Boulmaali, Ayoub; Dahoo, Pierre Richard; Rotaru, Aurelian; Garcia, Yann

    2016-02-02

    The possibility of a new design concept for dual spin crossover based sensors for concomitant detection of both temperature and pressure is presented. It is conjectured from numerical results obtained by mean field approximation applied to a Ising-like model that using two different spin crossover compounds containing switching molecules with weak elastic interactions it is possible to simultaneously measure P and T. When the interaction parameters are optimized, the spin transition is gradual and for each spin crossover compounds, both temperature and pressure values being identified from their optical densities. This concept offers great perspectives for smart sensing devices.

  9. Ground-state fidelity in the BCS-BEC crossover

    International Nuclear Information System (INIS)

    Khan, Ayan; Pieri, Pierbiagio

    2009-01-01

    The ground-state fidelity has been introduced recently as a tool to investigate quantum phase transitions. Here, we apply this concept in the context of a crossover problem. Specifically, we calculate the fidelity susceptibility for the BCS ground-state wave function, when the intensity of the fermionic attraction is varied from weak to strong in an interacting Fermi system, through the BCS-Bose-Einstein Condensation crossover. Results are presented for contact and finite-range attractive potentials and for both continuum and lattice models. We conclude that the fidelity susceptibility can be useful also in the context of crossover problems.

  10. Analysis of multi-step transitions in spin crossover nanochains

    Energy Technology Data Exchange (ETDEWEB)

    Chiruta, Daniel [GEMaC, Université de Versailles Saint-Quentin-en-Yvelines, CNRS-UVSQ (UMR 8635), 78035 Versailles Cedex (France); LISV, Université de Versailles Saint-Quentin-en-Yvelines, 78140 Velizy (France); Faculty of Electrical Engineering and Computer Science, Stefan cel Mare University, Suceava 720229 (Romania); Linares, Jorge, E-mail: jorge.linares@uvsq.fr [GEMaC, Université de Versailles Saint-Quentin-en-Yvelines, CNRS-UVSQ (UMR 8635), 78035 Versailles Cedex (France); Garcia, Yann, E-mail: yann.garcia@uclouvain.be [Institute of Condensed Matter and Nanosciences, Université Catholique de Louvain, Molecules, Solids and Reactivity (IMCN/MOST), Place Louis Pasteur, 1, 1348 Louvain-la-Neuve (Belgium); Dimian, Mihai [Faculty of Electrical Engineering and Computer Science, Stefan cel Mare University, Suceava 720229 (Romania); Dahoo, Pierre Richard [LATMOS, Université de Versailles-Saint-Quentin-en-Yvelines, CNRS-UPMC-UVSQ (UMR 8190), 78280 Guyancourt (France)

    2014-02-01

    The temperature driven phase transition occurring in spin crossover nanochains has been studied by an Ising-like model considering both short-range and long-range interactions. Various types of spin crossover profiles have been described in this framework, including a novel three-step transition identified in a nanosystem with eight molecules, which is modeled for the first time. A special interest has been also given to stepwise transitions accompanied by two hysteresis loops. The edge and size effects on spin crossover behavior have been investigated in order to get a deeper insight of the underlying mechanisms involved in these unusual spin transitions.

  11. Pressure and Temperature Sensors Using Two Spin Crossover Materials

    Science.gov (United States)

    Jureschi, Catalin-Maricel; Linares, Jorge; Boulmaali, Ayoub; Dahoo, Pierre Richard; Rotaru, Aurelian; Garcia, Yann

    2016-01-01

    The possibility of a new design concept for dual spin crossover based sensors for concomitant detection of both temperature and pressure is presented. It is conjectured from numerical results obtained by mean field approximation applied to a Ising-like model that using two different spin crossover compounds containing switching molecules with weak elastic interactions it is possible to simultaneously measure P and T. When the interaction parameters are optimized, the spin transition is gradual and for each spin crossover compounds, both temperature and pressure values being identified from their optical densities. This concept offers great perspectives for smart sensing devices. PMID:26848663

  12. Pressure and Temperature Sensors Using Two Spin Crossover Materials

    Directory of Open Access Journals (Sweden)

    Catalin-Maricel Jureschi

    2016-02-01

    Full Text Available The possibility of a new design concept for dual spin crossover based sensors for concomitant detection of both temperature and pressure is presented. It is conjectured from numerical results obtained by mean field approximation applied to a Ising-like model that using two different spin crossover compounds containing switching molecules with weak elastic interactions it is possible to simultaneously measure P and T. When the interaction parameters are optimized, the spin transition is gradual and for each spin crossover compounds, both temperature and pressure values being identified from their optical densities. This concept offers great perspectives for smart sensing devices.

  13. A microscopic model of ballistic-diffusive crossover

    International Nuclear Information System (INIS)

    Bagchi, Debarshee; Mohanty, P K

    2014-01-01

    Several low-dimensional systems show a crossover from diffusive to ballistic heat transport when system size is decreased. Although there is some phenomenological understanding of this crossover phenomenon at the coarse-grained level, a microscopic picture that consistently describes both the ballistic and the diffusive transport regimes has been lacking. In this work we derive a scaling form for the thermal current in a class of one dimensional systems attached to heat baths at boundaries and rigorously show that the crossover occurs when the characteristic length scale of the system competes with the system size. (paper)

  14. Microelectromechanical systems integrating molecular spin crossover actuators

    Energy Technology Data Exchange (ETDEWEB)

    Manrique-Juarez, Maria D. [LCC, CNRS and Université de Toulouse, UPS, INP, F-31077 Toulouse (France); LAAS, CNRS and Université de Toulouse, INSA, UPS, F-31077 Toulouse (France); Rat, Sylvain; Salmon, Lionel; Molnár, Gábor; Bousseksou, Azzedine, E-mail: liviu.nicu@laas.fr, E-mail: azzedine.bousseksou@lcc-toulouse.fr [LCC, CNRS and Université de Toulouse, UPS, INP, F-31077 Toulouse (France); Mathieu, Fabrice; Saya, Daisuke; Séguy, Isabelle; Leïchlé, Thierry; Nicu, Liviu, E-mail: liviu.nicu@laas.fr, E-mail: azzedine.bousseksou@lcc-toulouse.fr [LAAS, CNRS and Université de Toulouse, INSA, UPS, F-31077 Toulouse (France)

    2016-08-08

    Silicon MEMS cantilevers coated with a 200 nm thin layer of the molecular spin crossover complex [Fe(H{sub 2}B(pz){sub 2}){sub 2}(phen)] (H{sub 2}B(pz){sub 2} = dihydrobis(pyrazolyl)borate and phen = 1,10-phenantroline) were actuated using an external magnetic field and their resonance frequency was tracked by means of integrated piezoresistive detection. The light-induced spin-state switching of the molecules from the ground low spin to the metastable high spin state at 10 K led to a well-reproducible shift of the cantilever's resonance frequency (Δf{sub r} = −0.52 Hz). Control experiments at different temperatures using coated as well as uncoated devices along with simple calculations support the assignment of this effect to the spin transition. This latter translates into changes in mechanical behavior of the cantilever due to the strong spin-state/lattice coupling. A guideline for the optimization of device parameters is proposed so as to efficiently harness molecular scale movements for large-scale mechanical work, thus paving the road for nanoelectromechanical systems (NEMS) actuators based on molecular materials.

  15. Laser frequency stabilization using bichromatic crossover spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jeong, Taek; Seb Moon, Han, E-mail: hsmoon@pusan.ac.kr [Department of Physics, Pusan National University, Busan 609-735 (Korea, Republic of)

    2015-03-07

    We propose a Doppler-free spectroscopic method named bichromatic crossover spectroscopy (BCS), which we then use for the frequency stabilization of an off-resonant frequency that does not correspond to an atomic transition. The observed BCS in the 5S{sub 1/2} → 5P{sub 1/2} transition of {sup 87}Rb is related to the hyperfine structure of the conventional saturated absorption spectrum of this transition. Furthermore, the Doppler-free BCS is numerically calculated by considering all of the degenerate magnetic sublevels of the 5S{sub 1/2} → 5P{sub 1/2} transition in an atomic vapor cell, and is found to be in good agreement with the experimental results. Finally, we successfully achieve modulation-free off-resonant locking at the center frequency between the two 5S{sub 1/2}(F = 1 and 2) → 5P{sub 1/2}(F′ = 1) transitions using a polarization rotation of the BCS. The laser frequency stability was estimated to be the Allan variance of 2.1 × 10{sup −10} at 1 s.

  16. SAD-3, a Putative Helicase Required for Meiotic Silencing by Unpaired DNA, Interacts with Other Components of the Silencing Machinery

    Science.gov (United States)

    Hammond, Thomas M.; Xiao, Hua; Boone, Erin C.; Perdue, Tony D.; Pukkila, Patricia J.; Shiu, Patrick K. T.

    2011-01-01

    In Neurospora crassa, genes lacking a pairing partner during meiosis are suppressed by a process known as meiotic silencing by unpaired DNA (MSUD). To identify novel MSUD components, we have developed a high-throughput reverse-genetic screen for use with the N. crassa knockout library. Here we describe the screening method and the characterization of a gene (sad-3) subsequently discovered. SAD-3 is a putative helicase required for MSUD and sexual spore production. It exists in a complex with other known MSUD proteins in the perinuclear region, a center for meiotic silencing activity. Orthologs of SAD-3 include Schizosaccharomyces pombe Hrr1, a helicase required for RNAi-induced heterochromatin formation. Both SAD-3 and Hrr1 interact with an RNA-directed RNA polymerase and an Argonaute, suggesting that certain aspects of silencing complex formation may be conserved between the two fungal species. PMID:22384347

  17. Hysteretic behavior of spin-crossover noise driven system

    Energy Technology Data Exchange (ETDEWEB)

    Gudyma, Iurii [Department of General Physics, Chernivtsi National University, Chernivtsi 58012 (Ukraine); Maksymov, Artur, E-mail: maxyartur@gmail.com [Department of General Physics, Chernivtsi National University, Chernivtsi 58012 (Ukraine); Advanced Materials Research Institute, University of New Orleans, LA 70148 (United States); Dimian, Mihai [Department of Electrical and Computer Engineering, Howard University, Washington DC, 20059 (United States); Faculty of Electrical Engineering and Computer Science, Stefan cel Mare University, Suceava 720229 (Romania)

    2016-04-01

    The influence of white Gaussian noise on hysteretic behavior of spin-crossover system is analyzed in the framework of stochastic Langevin dynamics. Various stochastic simulations are performed and several important properties of spin-transition in spin-crossover system driven by noise are reproduced. The numerical results are tested against the stationary probability function and the associated dynamic potential obtained from Fokker–Planck equation corresponding to spin-crossover Langevin dynamics. The dependence of light-induced optical hysteresis width and non-hysteretic transition curve slope on the noise intensity is illustrated. The role of low-spin and high-spin phase stabilities in the hysteretic behavior of noise-driven spin-crossover system is discussed.

  18. Comparative Analysis of Genetic Crossover Operators in Knapsack ...

    African Journals Online (AJOL)

    ADOWIE PERE

    Knapsack problem via GA (Genetic Algorithm) is presented. We compared ... Keywords: Genetic Algorithm, Crossover, Heuristic, Arithmetic, Intermediate, Evolutionary Algorithm. The knapsack .... application to 0/1 Knapsack problem, Applied.

  19. DMC1 functions in a Saccharomyces cerevisiae meiotic pathway that is largely independent of the RAD51 pathway

    International Nuclear Information System (INIS)

    Dresser, M.E.; Ewing, D.J.; Conrad, M.N.; Dominguez, A.M.; Barstead, R.; Jiang, H.; Kodadek, T.

    1997-01-01

    Meiotic recombination in the yeast Saccharomyces cerevisiae requires two similar recA-like proteins, Dmc1p and Rad51p. A screen for dominant meiotic mutants provided DMC1-G126D, a dominant allele mutated in the conserved ATP-binding site (specifically, the A-loop motif) that confers a null phenotype. A recessive null allele, dmc1-K69E, was isolated as an intragenic suppressor of DMC1-G126D. Dmc1-K69Ep, unlike Dmc1p, does not interact homotypically in a two-hybrid assay, although it does interact with other fusion proteins identified by two-hybrid screen with Dmc1p. Dmc1p, unlike Rad51p, does not interact in the two-hybrid assay with Rad52p or Rad54p. However, Dmc1p does interact with Tid1p, a Rad54p homologue, with Tid4p, a Rad16p homologue, and with other fusion proteins that do not interact with Rad51p, suggesting that Dmc1p and Rad51p function in separate, though possibly overlapping, recombinational repair complexes. Epistasis analysis suggests that DMC1 and RAD51 function in separate pathways responsible for meiotic recombination. Taken together, our results are consistent with a requirement for DMC1 for meiosis-specific entry of DNA double-strand break ends into chromatin. Interestingly, the pattern on CHEF gels of chromosome fragments that result from meiotic DNA double-strand break formation is different in DMC1 mutant strains from that seen in rad50S strains. (author)

  20. The role of meiotic cohesin REC8 in chromosome segregation in {gamma} irradiation-induced endopolyploid tumour cells

    Energy Technology Data Exchange (ETDEWEB)

    Erenpreisa, Jekaterina [Latvian Biomedicine Research and Study Centre, Riga, LV-1067 (Latvia); Cragg, Mark S. [Tenovus Laboratory, Cancer Sciences Division, Southampton University School of Medicine, General Hospital, Southampton SO16 6YD (United Kingdom); Salmina, Kristine [Latvian Biomedicine Research and Study Centre, Riga, LV-1067 (Latvia); Hausmann, Michael [Kirchhoff Inst. fuer Physik, Univ. of Heidelberg, D-69120 Heidelberg (Germany); Scherthan, Harry, E-mail: scherth@web.de [Inst. fuer Radiobiologie der Bundeswehr in Verbindung mit der Univ. Ulm, D-80937 Munich (Germany); MPI for Molec. Genetics, 14195 Berlin (Germany)

    2009-09-10

    Escape from mitotic catastrophe and generation of endopolyploid tumour cells (ETCs) represents a potential survival strategy of tumour cells in response to genotoxic treatments. ETCs that resume the mitotic cell cycle have reduced ploidy and are often resistant to these treatments. In search for a mechanism for genome reduction, we previously observed that ETCs express meiotic proteins among which REC8 (a meiotic cohesin component) is of particular interest, since it favours reductional cell division in meiosis. In the present investigation, we induced endopolyploidy in p53-dysfunctional human tumour cell lines (Namalwa, WI-L2-NS, HeLa) by gamma irradiation, and analysed the sub-cellular localisation of REC8 in the resulting ETCs. We observed by RT-PCR and Western blot that REC8 is constitutively expressed in these tumour cells, along with SGOL1 and SGOL2, and that REC8 becomes modified after irradiation. REC8 localised to paired sister centromeres in ETCs, the former co-segregating to opposite poles. Furthermore, REC8 localised to the centrosome of interphase ETCs and to the astral poles in anaphase cells where it colocalised with the microtubule-associated protein NuMA. Altogether, our observations indicate that radiation-induced ETCs express features of meiotic cell divisions and that these may facilitate chromosome segregation and genome reduction.

  1. Reticulate Evolution of the Rock Lizards: Meiotic Chromosome Dynamics and Spermatogenesis in Diploid and Triploid Males of the Genus Darevskia.

    Science.gov (United States)

    Spangenberg, Victor; Arakelyan, Marine; Galoyan, Eduard; Matveevsky, Sergey; Petrosyan, Ruzanna; Bogdanov, Yuri; Danielyan, Felix; Kolomiets, Oxana

    2017-05-24

    Knowing whether triploid hybrids resulting from natural hybridization of parthenogenetic and bisexual species are fertile is crucial for understanding the mechanisms of reticulate evolution in rock lizards. Here, using males of the bisexual diploid rock lizard species Darevskia raddei nairensis and Darevskia valentini and a triploid hybrid male Darevskia unisexualis × Darevskia valentini , we performed karyotyping and comparative immunocytochemistry of chromosome synapsis and investigated the distribution of RAD51 and MLH1 foci in spread spermatocyte nuclei in meiotic prophase I. Three chromosome sets were found to occur in cell nuclei in the D. unisexualis × D. valentini hybrid, two originating from a parthenogenetic D. unisexualis female and one from the D. valentini male. Despite this distorted chromosome synapsis and incomplete double-strand breaks repair in meiotic prophase I, the number of mismatch repair foci in the triploid hybrid was enough to pass through both meiotic divisions. The defects in synapsis and repair did not arrest meiosis or spermatogenesis. Numerous abnormal mature spermatids were observed in the testes of the studied hybrid.

  2. The role of meiotic cohesin REC8 in chromosome segregation in γ irradiation-induced endopolyploid tumour cells

    International Nuclear Information System (INIS)

    Erenpreisa, Jekaterina; Cragg, Mark S.; Salmina, Kristine; Hausmann, Michael; Scherthan, Harry

    2009-01-01

    Escape from mitotic catastrophe and generation of endopolyploid tumour cells (ETCs) represents a potential survival strategy of tumour cells in response to genotoxic treatments. ETCs that resume the mitotic cell cycle have reduced ploidy and are often resistant to these treatments. In search for a mechanism for genome reduction, we previously observed that ETCs express meiotic proteins among which REC8 (a meiotic cohesin component) is of particular interest, since it favours reductional cell division in meiosis. In the present investigation, we induced endopolyploidy in p53-dysfunctional human tumour cell lines (Namalwa, WI-L2-NS, HeLa) by gamma irradiation, and analysed the sub-cellular localisation of REC8 in the resulting ETCs. We observed by RT-PCR and Western blot that REC8 is constitutively expressed in these tumour cells, along with SGOL1 and SGOL2, and that REC8 becomes modified after irradiation. REC8 localised to paired sister centromeres in ETCs, the former co-segregating to opposite poles. Furthermore, REC8 localised to the centrosome of interphase ETCs and to the astral poles in anaphase cells where it colocalised with the microtubule-associated protein NuMA. Altogether, our observations indicate that radiation-induced ETCs express features of meiotic cell divisions and that these may facilitate chromosome segregation and genome reduction.

  3. The role of meiotic cohesin REC8 in chromosome segregation in gamma irradiation-induced endopolyploid tumour cells.

    Science.gov (United States)

    Erenpreisa, Jekaterina; Cragg, Mark S; Salmina, Kristine; Hausmann, Michael; Scherthan, Harry

    2009-09-10

    Escape from mitotic catastrophe and generation of endopolyploid tumour cells (ETCs) represents a potential survival strategy of tumour cells in response to genotoxic treatments. ETCs that resume the mitotic cell cycle have reduced ploidy and are often resistant to these treatments. In search for a mechanism for genome reduction, we previously observed that ETCs express meiotic proteins among which REC8 (a meiotic cohesin component) is of particular interest, since it favours reductional cell division in meiosis. In the present investigation, we induced endopolyploidy in p53-dysfunctional human tumour cell lines (Namalwa, WI-L2-NS, HeLa) by gamma irradiation, and analysed the sub-cellular localisation of REC8 in the resulting ETCs. We observed by RT-PCR and Western blot that REC8 is constitutively expressed in these tumour cells, along with SGOL1 and SGOL2, and that REC8 becomes modified after irradiation. REC8 localised to paired sister centromeres in ETCs, the former co-segregating to opposite poles. Furthermore, REC8 localised to the centrosome of interphase ETCs and to the astral poles in anaphase cells where it colocalised with the microtubule-associated protein NuMA. Altogether, our observations indicate that radiation-induced ETCs express features of meiotic cell divisions and that these may facilitate chromosome segregation and genome reduction.

  4. Meiotic behaviour and its implication on species inter-relationship in the genus Curcuma (Linnaeus, 1753 (Zingiberaceae

    Directory of Open Access Journals (Sweden)

    Judith Mary Lamo

    2017-10-01

    Full Text Available In this paper, detailed meiotic analysis was investigated in seven species of Curcuma (Linnaeus, 1753 which can contribute significantly to our understanding about species inter-relationship, speciation and evolution. The species were divided into two groups viz., Group I having 2n = 42 (C. comosa Roxburgh, 1810, C. haritha Mangaly & M.Sabu, 1993, C. mangga Valeton & Zijp, 1917, and C. motana Roxburgh, 1800 and Group II with 2n = 63 (C. caesia Roxburgh, 1810, C. longa Linnaeus, 1753 and C. sylvatica Valeton, 1918. Both groups display varying degree of chromosome associations. Group I species showed the prevalence of bivalents, however occasional quadrivalents besides univalents were also encountered. About 48% of the PMCs analyzed in C. mangga showed 21 bivalents (II meiotic configurations, 32% in C. comosa and 16% in C. haritha. Group II species as expected showed the presence of trivalents besides bivalents, univalents and quadrivalents. About 32% of the PMCs analyzed at MI in C. sylvatica showed 21 trivalents (III meiotic configurations, 24% in C. longa and 8% in C. caesia. Overall, low frequency of multivalent associations as compared to bivalents indicates that Curcuma is an allopolyploid complex. Moreover, x = 21 is too high a basic number, therefore, we suggest that the genus Curcuma has evolved by hybridization of species with different chromosome numbers of 2n = 24 and 18, resulting in a dibasic amphidiploid species.

  5. The fidelity of synaptonemal complex assembly is regulated by a signaling mechanism that controls early meiotic progression.

    Science.gov (United States)

    Silva, Nicola; Ferrandiz, Nuria; Barroso, Consuelo; Tognetti, Silvia; Lightfoot, James; Telecan, Oana; Encheva, Vesela; Faull, Peter; Hanni, Simon; Furger, Andre; Snijders, Ambrosius P; Speck, Christian; Martinez-Perez, Enrique

    2014-11-24

    Proper chromosome segregation during meiosis requires the assembly of the synaptonemal complex (SC) between homologous chromosomes. However, the SC structure itself is indifferent to homology, and poorly understood mechanisms that depend on conserved HORMA-domain proteins prevent ectopic SC assembly. Although HORMA-domain proteins are thought to regulate SC assembly as intrinsic components of meiotic chromosomes, here we uncover a key role for nuclear soluble HORMA-domain protein HTP-1 in the quality control of SC assembly. We show that a mutant form of HTP-1 impaired in chromosome loading provides functionality of an HTP-1-dependent checkpoint that delays exit from homology search-competent stages until all homolog pairs are linked by the SC. Bypassing of this regulatory mechanism results in premature meiotic progression and licensing of homology-independent SC assembly. These findings identify nuclear soluble HTP-1 as a regulator of early meiotic progression, suggesting parallels with the mode of action of Mad2 in the spindle assembly checkpoint. Copyright © 2014 Elsevier Inc. All rights reserved.

  6. A quantitative study of the second meiotic metaphase in male mice (Mus musculus).

    Science.gov (United States)

    Beatty, R A; Lim, M C; Coulter, V J

    1975-01-01

    Over 11,000 second meiotic metaphase spreads stained for the pericentromeric region have been studied quantitatively in male mice of 14 strains. The sex-chromosome constitution of a cell could be judged objectively if X and Y chromosomes and ploidy were all scored. A bias arose if only Y chromosomes and ploidy were scored but could be corrected statistically. There was no sign of other forms of bias. The original contiguity of X and Y second metaphases in vivo was very occasionally evident in the preparations. Most of the subhaploid aneuploid counts were assumed to be artifactual. The incidence of truly aneuploid second metaphases in 13 strains was estimated as 0.38+/-0.12%. The estimated average rate per chromosome was 0.019+/-0.006%, with a comparable order of magnitude for the sex chromosomes alone. Simultaneous aneuploidy of two or more chromosomes of the haploid set was estimated to be very rare. Of the spreads from 13 strains, 9.6% were polyploid (2N, 3N, 4N) and showed most of the possible combinations of sex chromosomes. Nearly all the polyploid spreads were considered to arise by artifactual cell fusion at the time of second metaphase during the preparative technique, especially of the X and Y daughter-cell products of the first meiotic division. Other modes of origin (true polyploidy, accidental superposition of cells during preparation) were unlikely. The data could be accommodated by a statistical model with only four parameters. It allowed for artifactual fusion mainly between daughter cells but also between non-daughter cells, bias in one scoring method, and bias in the numbers of cells with given ploidy successfully mounted. Current techniques of chromosome preparation were thought to be wholly unsuitable for the recognition of true polyploidy. The artifactual origin of polyploid spreads was borne out by an absence of polyploid spermatozoa in 14 strains. There appeared to be a virtually constant transmission rate of paternal X and Y chromosomes from

  7. Meiotic Studies on Combinations of Chromosomes With Different Sized Centromeres in Maize

    Directory of Open Access Journals (Sweden)

    Fangpu Han

    2018-06-01

    Full Text Available Multiple centromere misdivision derivatives of a translocation between the supernumerary B chromosome and the short arm of chromosome 9 (TB-9Sb permit investigation of how centromeres of different sizes behave in meiosis in opposition or in competition with each other. In the first analysis, heterozygotes were produced between the normal TB-9Sb and derivatives of it that resulted from centromere misdivision that reduced the amounts of centromeric DNA. These heterozygotes could test whether these drastic differences would result in meiotic drive of the larger chromosome in female meiosis. Cytological determinations of the segregation of large and small centromeres among thousands of progeny of four combinations were made. The recovery of the larger centromere was at a few percent higher frequency in two of four combinations. However, examination of phosphorylated histone H2A-Thr133, a characteristic of active centromeres, showed a lack of correlation with the size of the centromeric DNA, suggesting an expansion of the basal protein features of the kinetochore in two of the three cases despite the reduction in the size of the underlying DNA. In the second analysis, plants containing different sizes of the B chromosome centromere were crossed to plants with TB-9Sb with a foldback duplication of 9S (TB-9Sb-Dp9. In the progeny, plants containing large and small versions of the B chromosome centromere were selected by FISH. A meiotic “tug of war” occurred in hybrid combinations by recombination between the normal 9S and the foldback duplication in those cases in which pairing occurred. Such pairing and recombination produce anaphase I bridges but in some cases the large and small centromeres progressed to the same pole. In one combination, new dicentric chromosomes were found in the progeny. Collectively, the results indicate that the size of the underlying DNA of a centromere does not dramatically affect its segregation properties or its ability

  8. The dynamical crossover in attractive colloidal systems

    Energy Technology Data Exchange (ETDEWEB)

    Mallamace, Francesco [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Corsaro, Carmelo [Dipartimento di Fisica e Scienze della Terra, Università di Messina and CNISM, I-98168 Messina (Italy); Stanley, H. Eugene [Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215 (United States); Mallamace, Domenico [Dipartimento di Scienze dell’Ambiente, della Sicurezza, del Territorio, degli Alimenti e della Salute, Università di Messina, I-98166 Messina (Italy); Chen, Sow-Hsin [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2013-12-07

    We study the dynamical arrest in an adhesive hard-sphere colloidal system. We examine a micellar suspension of the Pluronic-L64 surfactant in the temperature (T) and volume fraction (ϕ) phase diagram. According to mode-coupling theory (MCT), this system is characterized by a cusp-like singularity and two glassy phases: an attractive glass (AG) phase and a repulsive glass (RG) phase. The T − ϕ phase diagram of this system as confirmed by a previous series of scattering data also exhibits a Percolation Threshold (PT) line, a reentrant behavior (AG-liquid-RG), and a glass-to-glass transition. The AG phase can be generated out of the liquid phase by using T and ϕ as control parameters. We utilize viscosity and nuclear magnetic resonance (NMR) techniques. NMR data confirm all the characteristic properties of the colloidal system phase diagram and give evidence of the onset of a fractal-like percolating structure at a precise threshold. The MCT scaling laws used to study the shear viscosity as a function of ϕ and T show in both cases a fragile-to-strong liquid glass-forming dynamic crossover (FSC) located near the percolation threshold where the clustering process is fully developed. These results suggest a larger thermodynamic generality for this phenomenon, which is usually studied only as a function of the temperature. We also find that the critical values of the control parameters, coincident with the PT line, define the locus of the FSC. In the region between the FSC and the glass transition lines the system dynamics are dominated by clustering effects. We thus demonstrate that it is possible, using the conceptual framework provided by extended mode-coupling theory, to describe the way a system approaches dynamic arrest, taking into account both cage and hopping effects.

  9. LDsplit: screening for cis-regulatory motifs stimulating meiotic recombination hotspots by analysis of DNA sequence polymorphisms.

    Science.gov (United States)

    Yang, Peng; Wu, Min; Guo, Jing; Kwoh, Chee Keong; Przytycka, Teresa M; Zheng, Jie

    2014-02-17

    As a fundamental genomic element, meiotic recombination hotspot plays important roles in life sciences. Thus uncovering its regulatory mechanisms has broad impact on biomedical research. Despite the recent identification of the zinc finger protein PRDM9 and its 13-mer binding motif as major regulators for meiotic recombination hotspots, other regulators remain to be discovered. Existing methods for finding DNA sequence motifs of recombination hotspots often rely on the enrichment of co-localizations between hotspots and short DNA patterns, which ignore the cross-individual variation of recombination rates and sequence polymorphisms in the population. Our objective in this paper is to capture signals encoded in genetic variations for the discovery of recombination-associated DNA motifs. Recently, an algorithm called "LDsplit" has been designed to detect the association between single nucleotide polymorphisms (SNPs) and proximal meiotic recombination hotspots. The association is measured by the difference of population recombination rates at a hotspot between two alleles of a candidate SNP. Here we present an open source software tool of LDsplit, with integrative data visualization for recombination hotspots and their proximal SNPs. Applying LDsplit on SNPs inside an established 7-mer motif bound by PRDM9 we observed that SNP alleles preserving the original motif tend to have higher recombination rates than the opposite alleles that disrupt the motif. Running on SNP windows around hotspots each containing an occurrence of the 7-mer motif, LDsplit is able to guide the established motif finding algorithm of MEME to recover the 7-mer motif. In contrast, without LDsplit the 7-mer motif could not be identified. LDsplit is a software tool for the discovery of cis-regulatory DNA sequence motifs stimulating meiotic recombination hotspots by screening and narrowing down to hotspot associated SNPs. It is the first computational method that utilizes the genetic variation of

  10. High-Resolution Patterns of Meiotic Recombination across the Human Major Histocompatibility Complex

    Science.gov (United States)

    Cullen, Michael; Perfetto, Stephen P.; Klitz, William; Nelson, George; Carrington, Mary

    2002-01-01

    Definitive characteristics of meiotic recombination events over large (i.e., >1 Mb) segments of the human genome remain obscure, yet they are essential for establishing the haplotypic structure of the genome and for efficient mapping of complex traits. We present a high-resolution map of recombination at the kilobase level across a 3.3-Mb interval encompassing the major histocompatibility complex (MHC). Genotyping of 20,031 single sperm from 12 individuals resulted in the identification and fine mapping of 325 recombinant chromosomes within genomic intervals as small as 7 kb. Several principal characteristics of recombination in this region were observed: (1) rates of recombination can differ significantly between individuals; (2) intense hot spots of recombination occur at least every 0.8 Mb but are not necessarily evenly spaced; (3) distribution in the location of recombination events can differ significantly among individuals; (4) between hot spots, low levels of recombination occur fairly evenly across 100-kb segments, suggesting the presence of warm spots of recombination; and (5) specific sequence motifs associate significantly with recombination distribution. These data provide a plausible model for recombination patterns of the human genome overall. PMID:12297984

  11. Ultrastructural characterization of the meiotic prophase. A tool in the assessment of radiation damage in man

    Energy Technology Data Exchange (ETDEWEB)

    Holm, P.B.; Rasmussen, S.W.; von Wettstein, D. (Carlsberg Lab., Copenhagen (Denmark). Dept. of Physiology)

    1982-01-01

    The three-dimensional reconstruction of meiotic nuclei from serial sections micrographed in the electron microscope has provided information about man and several other organisms that is not obtainable by light microscopy or biochemical analysis. At zygotene, the previously unpaired chromosomes align and form synaptonemal complexes between homologous chromosome segments either by progressive initiation from the telomeres or by interstitial recognition. Chromosome and bivalent interlocking at zygotene is a regular phenomenon and occurs at a frequency of 0.7-4.0 per nucleus in samples of meiocytes analyzed from different organisms. This frequency is reduced to 0.1 per nucleus at pachytene. The interlockings are resolved by breakage and precise rejoining of the broken ends. This breakage and rejoining can also occur in the absence of the DNA nicking and repair involved in crossing-over. The synaptonemal complexes combining homologous chromosome segments are stabilized by recombination nodules, after which a second round of synaptonemal complex formation between as yet unpaired or unstably paired chromosome segments occurs, apparently for optimization of bivalent formation. Nonhomologous pairing with the synaptonemal complex can take place in this phase of pachytene.

  12. Autophagy is required for efficient meiosis progression and proper meiotic chromosome segregation in fission yeast.

    Science.gov (United States)

    Matsuhara, Hirotada; Yamamoto, Ayumu

    2016-01-01

    Autophagy is a conserved intracellular degradation system, which contributes to development and differentiation of various organisms. Yeast cells undergo meiosis under nitrogen-starved conditions and require autophagy for meiosis initiation. However, the precise roles of autophagy in meiosis remain unclear. Here, we show that autophagy is required for efficient meiosis progression and proper meiotic chromosome segregation in fission yeast. Autophagy-defective strains bearing a mutation in the autophagy core factor gene atg1, atg7, or atg14 exhibit deformed nuclear structures during meiosis. These mutant cells require an extracellular nitrogen supply for meiosis progression following their entry into meiosis and show delayed meiosis progression even with a nitrogen supply. In addition, they show frequent chromosome dissociation from the spindle together with spindle overextension, forming extra nuclei. Furthermore, Aurora kinase, which regulates chromosome segregation and spindle elongation, is significantly increased at the centromere and spindle in the mutant cells. Aurora kinase down-regulation eliminated delayed initiation of meiosis I and II, chromosome dissociation, and spindle overextension, indicating that increased Aurora kinase activity may cause these aberrances in the mutant cells. Our findings show a hitherto unrecognized relationship of autophagy with the nuclear structure, regulation of cell cycle progression, and chromosome segregation in meiosis. © 2015 The Molecular Biology Society of Japan and Wiley Publishing Asia Pty Ltd.

  13. Meiotic inheritance of a fungal supernumerary chromosome and its effect on sexual fertility in Nectria haematococca.

    Science.gov (United States)

    Garmaroodi, Hamid S; Taga, Masatoki

    2015-10-01

    PDA1-conditionally dispensable chromosome (CDC) of Nectria haematococca MP VI has long served as a model of supernumerary chromosomes in plant pathogenic fungi because of pathogenicity-related genes located on it. In our previous study, we showed the dosage effects of PDA1-CDC on pathogenicity and homoserine utilization by exploiting tagged PDA1-CDC with a marker gene. CDC content of mating partners and progenies analyzed by PCR, PFGE combined with Southern analysis and chromosome painting via FISH. In this study, we analyzed mode of meiotic inheritance of PDA1-CDC in several mating patterns with regard to CDC content and found a correlation between CDC content of parental strains with fertility of crosses. The results showed non-Mendelian inheritance of this chromosome followed by duplication or loss of the CDC in haploid genome through meiosis that probably were due to premature centromere division, not by nondisjunction as reported for the supernumerary chromosomes in other species. Correlation of CDC with fertility is the first time to be examined in fungi in this study. Copyright © 2015 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.

  14. Meiotic changes in Vicia faba L. subsequent to treatments of hydrazine hydrate and maleic hydrazide

    Directory of Open Access Journals (Sweden)

    Shaheen Husain

    2013-01-01

    Full Text Available Assessing the impact of mutagens for creating variations in crops like faba bean (Vicia faba L. is an important criterion in the contemporary world where food insecurity and malnutrition is alarming at the doors of various nations. Impact of two chemical mutagens viz. hydrazine hydrate (HZ and maleic hydrazide (MH on the two varieties (NDF-1 and HB-405 of Vicia faba were analysed in terms of meiotic behavior and pollen sterility. Since there are not enough data about the effect of these mutagens on the chromosomal behaviors of Vicia faba, this study presents the role of hydrazine hydrate and maleic hydrazide as well as various types of chromosomal aberrations in crop improvement. The lower concentration of mutagens showed less pollen sterility compared to the higher concentrations. Manipulation of plant structural component to induce desirable alternations provides valuable material for the breeders and could be used favorably for increasing mutation rate and obtaining a desirable spectrum of mutation in faba beans based on preliminary studies of cell division.

  15. The sea lamprey meiotic map improves resolution of ancient vertebrate genome duplications.

    Science.gov (United States)

    Smith, Jeramiah J; Keinath, Melissa C

    2015-08-01

    It is generally accepted that many genes present in vertebrate genomes owe their origin to two whole-genome duplications that occurred deep in the ancestry of the vertebrate lineage. However, details regarding the timing and outcome of these duplications are not well resolved. We present high-density meiotic and comparative genomic maps for the sea lamprey (Petromyzon marinus), a representative of an ancient lineage that diverged from all other vertebrates ∼550 million years ago. Linkage analyses yielded a total of 95 linkage groups, similar to the estimated number of germline chromosomes (1n ∼ 99), spanning a total of 5570.25 cM. Comparative mapping data yield strong support for the hypothesis that a single whole-genome duplication occurred in the basal vertebrate lineage, but do not strongly support a hypothetical second event. Rather, these comparative maps reveal several evolutionarily independent segmental duplications occurring over the last 600+ million years of chordate evolution. This refined history of vertebrate genome duplication should permit more precise investigations of vertebrate evolution. © 2015 Smith and Keinath; Published by Cold Spring Harbor Laboratory Press.

  16. Reduced polymorphism associated with X chromosome meiotic drive in the stalk-eyed fly Teleopsis dalmanni.

    Directory of Open Access Journals (Sweden)

    Sarah J Christianson

    Full Text Available Sex chromosome meiotic drive has been suggested as a cause of several evolutionary genetic phenomena, including genomic conflicts that give rise to reproductive isolation between new species. In this paper we present a population genetic analysis of X chromosome drive in the stalk-eyed fly, Teleopsis dalmanni, to determine how this natural polymorphism influences genetic diversity. We analyzed patterns of DNA sequence variation at two X-linked regions (comprising 1325 bp approximately 50 cM apart and one autosomal region (comprising 921 bp for 50 males, half of which were collected in the field from one of two allopatric locations and the other half were derived from lab-reared individuals with known brood sex ratios. These two populations are recently diverged but exhibit partial postzygotic reproductive isolation, i.e. crosses produce sterile hybrid males and fertile females. We find no nucleotide or microsatellite variation on the drive X chromosome, whereas the same individuals show levels of variation at autosomal regions that are similar to field-collected flies. Furthermore, one field-caught individual collected 10 years previously had a nearly identical X haplotype to the drive X, and is over 2% divergent from other haplotypes sampled from the field. These results are consistent with a selective sweep that has removed genetic variation from much of the drive X chromosome. We discuss how this finding may relate to the rapid evolution of postzygotic reproductive isolation that has been documented for these flies.

  17. A specific family of interspersed repeats (SINEs facilitates meiotic synapsis in mammals

    Directory of Open Access Journals (Sweden)

    Johnson Matthew E

    2013-01-01

    Full Text Available Abstract Background Errors during meiosis that affect synapsis and recombination between homologous chromosomes contribute to aneuploidy and infertility in humans. Despite the clinical relevance of these defects, we know very little about the mechanisms by which homologous chromosomes interact with one another during mammalian meiotic prophase. Further, we remain ignorant of the way in which chromosomal DNA complexes with the meiosis-specific structure that tethers homologs, the synaptonemal complex (SC, and whether specific DNA elements are necessary for this interaction. Results In the present study we utilized chromatin immunoprecipitation (ChIP and DNA sequencing to demonstrate that the axial elements of the mammalian SC are markedly enriched for a specific family of interspersed repeats, short interspersed elements (SINEs. Further, we refine the role of the repeats to specific sub-families of SINEs, B1 in mouse and AluY in old world monkey (Macaca mulatta. Conclusions Because B1 and AluY elements are the most actively retrotransposing SINEs in mice and rhesus monkeys, respectively, our observations imply that they may serve a dual function in axial element binding; i.e., as the anchoring point for the SC but possibly also as a suppressor/regulator of retrotransposition.

  18. Meiotic drive influences the outcome of sexually antagonistic selection at a linked locus.

    Science.gov (United States)

    Patten, M M

    2014-11-01

    Most meiotic drivers, such as the t-haplotype in Mus and the segregation distorter (SD) in Drosophila, act in a sex-specific manner, gaining a transmission advantage through one sex although suffering only the fitness costs associated with the driver in the other. Their inheritance is thus more likely through one of the two sexes, a property they share with sexually antagonistic alleles. Previous theory has shown that pairs of linked loci segregating for sexually antagonistic alleles are more likely to remain polymorphic and that linkage disequilibrium accrues between them. I probe this similarity between drive and sexual antagonism and examine the evolution of chromosomes experiencing these selection pressures simultaneously. Reminiscent of previous theory, I find that: the opportunity for polymorphism increases for a sexually antagonistic locus that is physically linked to a driving locus; the opportunity for polymorphism at a driving locus also increases when linked to a sexually antagonistic locus; and stable linkage disequilibrium accompanies any polymorphic equilibrium. Additionally, I find that drive at a linked locus favours the fixation of sexually antagonistic alleles that benefit the sex in which drive occurs. Further, I show that under certain conditions reduced recombination between these two loci is selectively favoured. These theoretical results provide clear, testable predictions about the nature of sexually antagonistic variation on driving chromosomes and have implications for the evolution of genomic architecture. © 2014 European Society For Evolutionary Biology. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

  19. Random and non-random mating populations: Evolutionary dynamics in meiotic drive.

    Science.gov (United States)

    Sarkar, Bijan

    2016-01-01

    Game theoretic tools are utilized to analyze a one-locus continuous selection model of sex-specific meiotic drive by considering nonequivalence of the viabilities of reciprocal heterozygotes that might be noticed at an imprinted locus. The model draws attention to the role of viability selections of different types to examine the stable nature of polymorphic equilibrium. A bridge between population genetics and evolutionary game theory has been built up by applying the concept of the Fundamental Theorem of Natural Selection. In addition to pointing out the influences of male and female segregation ratios on selection, configuration structure reveals some noted results, e.g., Hardy-Weinberg frequencies hold in replicator dynamics, occurrence of faster evolution at the maximized variance fitness, existence of mixed Evolutionarily Stable Strategy (ESS) in asymmetric games, the tending evolution to follow not only a 1:1 sex ratio but also a 1:1 different alleles ratio at particular gene locus. Through construction of replicator dynamics in the group selection framework, our selection model introduces a redefining bases of game theory to incorporate non-random mating where a mating parameter associated with population structure is dependent on the social structure. Also, the model exposes the fact that the number of polymorphic equilibria will depend on the algebraic expression of population structure. Copyright © 2015 Elsevier Inc. All rights reserved.

  20. Effects of Mild and Severe Vitamin B Deficiencies on the Meiotic Maturation of Mice Oocytes

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    Ai Tsuji

    2017-03-01

    Full Text Available We investigated the effects of vitamin B 1 deficiency on the meiosis maturation of oocytes. Female Crl:CD1 (ICR mice were fed a 20% casein diet (control group or a vitamin B 1 –free diet (test group. The vitamin B 1 concentration in ovary was approximately 30% lower in the test group than in the control group. Oocyte meiosis was not affected by vitamin B 1 deficiency when the deficiency was not accompanied by body weight loss. On the contrary, frequency of abnormal oocyte was increased by vitamin B 1 deficiency when deficiency was accompanied by body weight loss (referred to as severe vitamin B 1 deficiency; frequency of abnormal oocyte, 13.8% vs 43.7%, P  = .0071. The frequency of abnormal oocytes was decreased by refeeding of a vitamin B 1 –containing diet (13.9% vs 22.9%, P  = .503. These results suggest that severe vitamin B 1 deficiency inhibited meiotic maturation of oocytes but did not damage immature oocytes.

  1. Influence of Meiotic Stages on Developmental Competence of Goat’ Oocyte After Vitrification

    Science.gov (United States)

    Wahyuningsih, S.; Ihsan, M. N.

    2018-02-01

    This objective of this research was to investigate effect of goat oocyte meiotic stages on developmental competence after cryopreservation. Ovaries were collected from slaugterhouse and oocytes was aspirated from2-6 mm of follicles. Oocyte with compacted cumulus cells and evenly granulated ooplasm were selected for this experiment. The lenght of in vitro maturation before vitrification was 8 or 22 h in IVM media TCM 199 + FCS 10 % + PMSG 10 IU + hCG 10 IU at 38.5 °C in a humidified atmosphere of 5 % CO2 in air and were vitrified. After vitrification process, GVBD and MII oocyte were matured for 18 or 4 h to fullfill 26 h maturation requirement and then oocytes were subjected to IVF and culture. Cleavage and blastocyst formation rate were to asses their developmental competence. Cleavage rates were obtained for both GVBD ( 56.78 %) and MII (69.64 % ) oocytes (PGoat oocytes in different maturation stages response to vitrification differently and MII stages have better developmental competence than GVBD.

  2. Double trouble: combined action of meiotic drive and Wolbachia feminization in Eurema butterflies.

    Science.gov (United States)

    Kern, Peter; Cook, James M; Kageyama, Daisuke; Riegler, Markus

    2015-05-01

    Arthropod sex ratios can be manipulated by a diverse range of selfish genetic elements, including maternally inherited Wolbachia bacteria. Feminization by Wolbachia is rare but has been described for Eurema mandarina butterflies. In this species, some phenotypic and functional females, thought to be ZZ genetic males, are infected with a feminizing Wolbachia strain, wFem. Meanwhile, heterogametic WZ females are not infected with wFem. Here, we establish a quantitative PCR assay allowing reliable sexing in three Eurema species. Against expectation, all E. mandarina females, including wFem females, had only one Z chromosome that was paternally inherited. Observation of somatic interphase nuclei confirmed that W chromatin was absent in wFem females, but present in females without wFem. We conclude that the sex bias in wFem lines is due to meiotic drive (MD) that excludes the maternal Z and thus prevents formation of ZZ males. Furthermore, wFem lines may have lost the W chromosome or harbour a dysfunctional version, yet rely on wFem for female development; removal of wFem results in all-male offspring. This is the first study that demonstrates an interaction between MD and Wolbachia feminization, and it highlights endosymbionts as potentially confounding factors in MD of sex chromosomes. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  3. Meiotic and mitotic analyses of a reciprocal translocation in pisum sativum

    International Nuclear Information System (INIS)

    Muller, D.

    1974-01-01

    After X-irradiation of air-dried seeds of Pisum sativum, mutant 210 A was selected on the basis of the characteristic 'low number of seeds per pod', that segregates during following generations. Studies of pollen show a reduced fertility of 49.4% in about 50% of the plants. In meiotic metaphase I association of 4 chromosomes were observed in about 90% PMC in which more than half showed co-orientation of centromeres. A 3:1 segregation of the 4 linking chromosomes appeared in about 24% of all cases. Laggards, bridges and fragments reached a frequency of 11% in anaphase II. Seed production per pod in 2 vegetative periods varied from 63-67%; seed setting per plant fluctuated in the same year, between 55% and 43%. The analysis of karyotype proved the presumption of a simple reciprocal translocation. The exchange occurred between the long arms of the chromosomes 3 and 5. The break position is believed to be situated near the centromers of chromosome 3 and the lower half of the long arm of chromosome 5. (author)

  4. PRDM9 variation strongly influences recombination hot-spot activity and meiotic instability in humans.

    Science.gov (United States)

    Berg, Ingrid L; Neumann, Rita; Lam, Kwan-Wood G; Sarbajna, Shriparna; Odenthal-Hesse, Linda; May, Celia A; Jeffreys, Alec J

    2010-10-01

    PRDM9 has recently been identified as a likely trans regulator of meiotic recombination hot spots in humans and mice. PRDM9 contains a zinc finger array that, in humans, can recognize a short sequence motif associated with hot spots, with binding to this motif possibly triggering hot-spot activity via chromatin remodeling. We now report that human genetic variation at the PRDM9 locus has a strong effect on sperm hot-spot activity, even at hot spots lacking the sequence motif. Subtle changes within the zinc finger array can create hot-spot nonactivating or enhancing variants and can even trigger the appearance of a new hot spot, suggesting that PRDM9 is a major global regulator of hot spots in humans. Variation at the PRDM9 locus also influences aspects of genome instability-specifically, a megabase-scale rearrangement underlying two genomic disorders as well as minisatellite instability-implicating PRDM9 as a risk factor for some pathological genome rearrangements.

  5. Downregulation of surface sodium pumps by endocytosis during meiotic maturation of Xenopus laevis oocytes

    International Nuclear Information System (INIS)

    Schmalzing, G.; Eckard, P.; Kroener, S.P.; Passow, H.

    1990-01-01

    During meiotic maturation, plasma membranes of Xenopus laevis oocytes completely lose the capacity to transport Na and K and to bind ouabain. To explore whether the downregulation might be due to an internalization of the sodium pump molecules, the intracellular binding of ouabain was determined. Selective permeabilization of the plasma membrane of mature oocytes (eggs) by digitonin almost failed to disclose ouabain binding sites. However, when the eggs were additionally treated with 0.02% sodium dodecyl sulfate (SDS) to permeabilize inner membranes, all sodium pumps present before maturation were recovered. Phosphorylation by [gamma-32P]ATP combined with SDS-polyacrylamide gel electrophoresis (PAGE) and autoradiography showed that sodium pumps were greatly reduced in isolated plasma membranes of eggs. According to sucrose gradient fractionation, maturation induced a shift of sodium pumps from the plasma membrane fraction to membranes of lower buoyant density with a protein composition different from that of the plasma membrane. Endocytosed sodium pumps identified on the sucrose gradient from [3H]ouabain bound to the cell surface before maturation could be phosphorylated with inorganic [32P]phosphate. The findings suggest that downregulation of sodium pumps during maturation is brought about by translocation of surface sodium pumps to an intracellular compartment, presumably endosomes. This contrasts the mechanism of downregulation of Na-dependent cotransport systems, the activities of which are reduced as a consequence of a maturation-induced depolarization of the membrane without a removal of the corresponding transporter from the plasma membrane

  6. Smectite alteration

    International Nuclear Information System (INIS)

    Anderson, D.M.

    1984-11-01

    This report contains the proceedings of a second workshop in Washington DC December 8-9, 1983 on the alteration of smectites intended for use as buffer materials in the long-term containment of nuclear wastes. It includes extended summaries of all presentations and a transcript of the detailed scientific discussion. The discussions centered on three main questions: What is the prerequisite for and what is the precise mechanism by which smectite clays may be altered to illite. What are likly sources of potassium with respect to the KBS project. Is it likely that the conversion of smectite to illite will be of importance in the 10 5 to the 10 6 year time frame. The workshop was convened to review considerations and conclusions in connection to these questions and also to broaden the discussion to consider the use of smectite clays as buffer materials for similar applications in different geographical and geological settings. SKBF/KBS technical report 83-03 contains the proceedings from the first workshop on these matters that was held at the State University of New York, Buffalo May 26-27, 1982. (Author)

  7. Interference-mediated synaptonemal complex formation with embedded crossover designation

    Science.gov (United States)

    Zhang, Liangran; Espagne, Eric; de Muyt, Arnaud; Zickler, Denise; Kleckner, Nancy E.

    2014-01-01

    Biological systems exhibit complex patterns at length scales ranging from the molecular to the organismic. Along chromosomes, events often occur stochastically at different positions in different nuclei but nonetheless tend to be relatively evenly spaced. Examples include replication origin firings, formation of chromatin loops along chromosome axes and, during meiosis, localization of crossover recombination sites (“crossover interference”). We present evidence in the fungus Sordaria macrospora that crossover interference is part of a broader pattern that includes synaptonemal complex (SC) nucleation. This pattern comprises relatively evenly spaced SC nucleation sites, among which a subset are crossover sites that show a classical interference distribution. This pattern ensures that SC forms regularly along the entire length of the chromosome as required for the maintenance of homolog pairing while concomitantly having crossover interactions locally embedded within the SC structure as required for both DNA recombination and structural events of chiasma formation. This pattern can be explained by a threshold-based designation and spreading interference process. This model can be generalized to give diverse types of related and/or partially overlapping patterns, in two or more dimensions, for any type of object. PMID:25380597

  8. The occurrence of double strand DNA breaks is not the sole condition for meiotic crossing over in Drosophila melanogaster.

    Science.gov (United States)

    Portin, P; Rantanen, M

    2000-01-01

    Analysis of the interchromosomal effects of In(2L + 2R)Cy, In(3L + 3R)LVM and their joint effect on the frequencies of single and double crossovers in the cv-v-f region of the X chromosome as well as interference showed that both inversions, occurring separately, increased the frequency of single as well as double crossovers and the coefficient of coincidence. However, when the inversions occurred together the frequencies of single crossovers no longer increased, but the frequency of double crossovers, as well as the coefficient of coincidence did increase. These results indicate firstly that the interchromosomal effects influence some precondition of exchange, but that this precondition is not an occurrence of double strand DNA breaks. Thus, the occurrence of double strand DNA breaks is not the sole condition for crossing over in Drosophila melanogaster.

  9. Modelling of the PROTO-II crossover network

    International Nuclear Information System (INIS)

    Proulx, G.A.; Lackner, H.; Spence, P.; Wright, T.P.

    1985-01-01

    In order to drive a double ring, symmetrically fed bremsstrahlung diode, the PROTO II accelerator was redesigned. The radially converging triplate water line was reconfigured to drive two radial converging triplate lines in parallel. The four output lines were connected to the two input lines via an electrically enclosed tubular crossover network. Low-voltage Time Domain Reflectrometry (TDR) experiments were conducted on a full scale water immersed model of one section of the crossover network as an aid in this design. A lumped element analysis of the power flow through the network was inadequate in explaining the observed wave transmission and reflection characteristics. A more detailed analysis was performed with a circuit code in which we considered both localized lump-element and transmission line features of the crossover network. Experimental results of the model tests are given and compared with the circuit simulations. 7 figs

  10. Modular invariance, universality and crossover in the quantum Hall effect

    International Nuclear Information System (INIS)

    Dolan, Brian P.

    1999-01-01

    An analytic form for the conductivity tensor in crossover between two quantum Hall plateaux is derived, which appears to be in good agreement with existing experimental data. The derivation relies on an assumed symmetry between quantum Hall states, a generalisation of the law of corresponding states from rational filling factors to complex conductivity, which has a mathematical expression in terms of an action of the modular group on the upper-half complex conductivity plane. This symmetry implies universality in quantum Hall crossovers. The assumption that the β-function for the complex conductivity is a complex analytic function, together with some experimental constraints, results in an analytic expression for the crossover, as a function of the external magnetic field

  11. Crossover from equilibration to aging: Nonequilibrium theory versus simulations.

    Science.gov (United States)

    Mendoza-Méndez, P; Lázaro-Lázaro, E; Sánchez-Díaz, L E; Ramírez-González, P E; Pérez-Ángel, G; Medina-Noyola, M

    2017-08-01

    Understanding glasses and the glass transition requires comprehending the nature of the crossover from the ergodic (or equilibrium) regime, in which the stationary properties of the system have no history dependence, to the mysterious glass transition region, where the measured properties are nonstationary and depend on the protocol of preparation. In this work we use nonequilibrium molecular dynamics simulations to test the main features of the crossover predicted by the molecular version of the recently developed multicomponent nonequilibrium self-consistent generalized Langevin equation theory. According to this theory, the glass transition involves the abrupt passage from the ordinary pattern of full equilibration to the aging scenario characteristic of glass-forming liquids. The same theory explains that this abrupt transition will always be observed as a blurred crossover due to the unavoidable finiteness of the time window of any experimental observation. We find that within their finite waiting-time window, the simulations confirm the general trends predicted by the theory.

  12. Relativistic BCS-BEC Crossover at Quark Level

    Directory of Open Access Journals (Sweden)

    Zhuang P.

    2010-10-01

    Full Text Available The non-relativistic G0G formalism of BCS-BEC crossover at finite temperature is extended to relativistic fermion systems. The theory recovers the BCS mean field approximation at zero temperature and the non-relativistic results in a proper limit. For massive fermions, when the coupling strength increases, there exist two crossovers from the weak coupling BCS superfluid to the non-relativistic BEC state and then to the relativistic BEC state. For color superconductivity at moderate baryon density, the matter is in the BCS-BEC crossover region, and the behavior of the pseudogap is quite similar to that found in high temperature superconductors.

  13. Pressure effect on hysteresis in spin-crossover solid materials

    Energy Technology Data Exchange (ETDEWEB)

    Gudyma, Iurii, E-mail: yugudyma@gmail.com [Department of General Physics, Chernivtsi National University, Chernivtsi 58012 (Ukraine); Ivashko, Victor [Department of General Physics, Chernivtsi National University, Chernivtsi 58012 (Ukraine); Dimian, Mihai [Department of Electrical and Computer Engineering, Howard University, Washington DC 20059 (United States); Faculty of Electrical Engineering and Computer Science & Integrated Center for Research, Development and Innovation in Advanced Materials, Nanotechnologies, and Distributed Systems for fabrication and control, Stefan cel Mare University, Suceava 720229 (Romania)

    2016-04-01

    A generalized microscopic Ising-like model is proposed to describe behavior of compressible spin-crossover solids with two states: low-spin and high-spin. The model was solved in mean-field approximation and shows hysteretic behavior at low energy difference between the states. We study the thermal transition between states under external hydrostatic pressure taking into account the changes in the volume of spin-crossover molecules in different states. Depending on the applied pressure, a spin-crossover system can have three types of behavior of molecular fraction in the high-spin state: hysteretic, second-order phase transition and no-phase transition. For the hysteretic regime, it is shown that the transition temperature under pressure is increased while the width of the hysteresis reduced.

  14. Spin-crossover behavior of polymeric iron(III) complexes

    International Nuclear Information System (INIS)

    Maeda, Yonezo; Miyamoto, Makoto; Takashima, Yoshimasa; Oshio, Hiroaki

    1989-01-01

    Polymeric spin-crossover iron(III) complexes possessing poly(4-vinylpyridine), poly(N-vinylimidazole) or poly(octylmethacrylate-co-4-vinylpyridine) as ligand are prepared. In this experience enriched 57 Fe was used to get strong Moessbauer absorption. The enriched behavior of the complexes were examined by magnetic susceptibilities measurement, and Moessbauer and esr spectroscopies. Some of them show spin-state behavior over a wide range of temperature. Some of them show rapid spin-state interexchange compared to the Moessbauer time scale and others not. Spin-crossover behavior of polymeric complexes is characterized of wide spin-state transition temperature range

  15. Probing Spin Crossover in a Solution by Paramagnetic NMR Spectroscopy.

    Science.gov (United States)

    Pavlov, Alexander A; Denisov, Gleb L; Kiskin, Mikhail A; Nelyubina, Yulia V; Novikov, Valentin V

    2017-12-18

    Spin transitions in spin-crossover compounds are now routinely studied in the solid state by magnetometry; however, only a few methods exist for studies in solution. The currently used Evans method, which relies on NMR spectroscopy to measure the magnetic susceptibility, requires the availability of a very pure sample of the paramagnetic compound and its exact concentration. To overcome these limitations, we propose an alternative NMR-based technique for evaluating spin-state populations by only using the chemical shifts of a spin-crossover compound; those can be routinely obtained for a solution that contains unknown impurities and paramagnetic admixtures or is contaminated otherwise.

  16. X chromosome control of meiotic chromosome synapsis in mouse inter-subspecific hybrids.

    Directory of Open Access Journals (Sweden)

    Tanmoy Bhattacharyya

    2014-02-01

    Full Text Available Hybrid sterility (HS belongs to reproductive isolation barriers that safeguard the integrity of species in statu nascendi. Although hybrid sterility occurs almost universally among animal and plant species, most of our current knowledge comes from the classical genetic studies on Drosophila interspecific crosses or introgressions. With the house mouse subspecies Mus m. musculus and Mus m. domesticus as a model, new research tools have become available for studies of the molecular mechanisms and genetic networks underlying HS. Here we used QTL analysis and intersubspecific chromosome substitution strains to identify a 4.7 Mb critical region on Chromosome X (Chr X harboring the Hstx2 HS locus, which causes asymmetrical spermatogenic arrest in reciprocal intersubspecific F1 hybrids. Subsequently, we mapped autosomal loci on Chrs 3, 9 and 13 that can abolish this asymmetry. Combination of immunofluorescent visualization of the proteins of synaptonemal complexes with whole-chromosome DNA FISH on pachytene spreads revealed that heterosubspecific, unlike consubspecific, homologous chromosomes are predisposed to asynapsis in F1 hybrid male and female meiosis. The asynapsis is under the trans- control of Hstx2 and Hst1/Prdm9 hybrid sterility genes in pachynemas of male but not female hybrids. The finding concurred with the fertility of intersubpecific F1 hybrid females homozygous for the Hstx2(Mmm allele and resolved the apparent conflict with the dominance theory of Haldane's rule. We propose that meiotic asynapsis in intersubspecific hybrids is a consequence of cis-acting mismatch between homologous chromosomes modulated by the trans-acting Hstx2 and Prdm9 hybrid male sterility genes.

  17. Meiotic gene-conversion rate and tract length variation in the human genome.

    Science.gov (United States)

    Padhukasahasram, Badri; Rannala, Bruce

    2013-02-27

    Meiotic recombination occurs in the form of two different mechanisms called crossing-over and gene-conversion and both processes have an important role in shaping genetic variation in populations. Although variation in crossing-over rates has been studied extensively using sperm-typing experiments, pedigree studies and population genetic approaches, our knowledge of variation in gene-conversion parameters (ie, rates and mean tract lengths) remains far from complete. To explore variability in population gene-conversion rates and its relationship to crossing-over rate variation patterns, we have developed and validated using coalescent simulations a comprehensive Bayesian full-likelihood method that can jointly infer crossing-over and gene-conversion rates as well as tract lengths from population genomic data under general variable rate models with recombination hotspots. Here, we apply this new method to SNP data from multiple human populations and attempt to characterize for the first time the fine-scale variation in gene-conversion parameters along the human genome. We find that the estimated ratio of gene-conversion to crossing-over rates varies considerably across genomic regions as well as between populations. However, there is a great degree of uncertainty associated with such estimates. We also find substantial evidence for variation in the mean conversion tract length. The estimated tract lengths did not show any negative relationship with the local heterozygosity levels in our analysis.European Journal of Human Genetics advance online publication, 27 February 2013; doi:10.1038/ejhg.2013.30.

  18. Mitotic and meiotic irregularities in somatic hybrids of Lycopersicon esculentum and Solanum tuberosum.

    Science.gov (United States)

    Wolters, A M; Schoenmakers, H C; Kamstra, S; Eden, J; Koornneef, M; Jong, J H

    1994-10-01

    Chromosome numbers were determined in metaphase complements of root-tip meristems of 107 tomato (+) potato somatic hybrids, obtained from five different combinations of parental genotypes. Of these hybrids 79% were aneuploid, lacking one or two chromosomes in most cases. All four hybrids that were studied at mitotic anaphase of root tips showed laggards and bridges, the three aneuploids in a higher frequency than the single euploid. Hybrid K2H2-1C, which showed the highest percentage of aberrant anaphases, possessed 46 chromosomes. Fluorescence in situ hybridization with total genomic DNA showed that this hybrid contained 23 tomato, 22 potato, and 1 recombinant chromosome consisting of a tomato chromosome arm and a potato chromosome arm. The potato parent of K2H2-1C was aneusomatic in its root tips with a high frequency of monosomic and trisomic cells and a relatively high frequency of cells with one fragment or telosome. Meiotic analyses of three tomato (+) potato somatic hybrids revealed laggards, which occurred most frequently in the triploid hybrids, and bridges, which were frequently present in pollen mother cells (PMCs) at anaphase I of hypotetraploid K2H2-1C. We observed putative trivalents in PMCs at diakinesis and metaphase I of eutriploid A7-82A and quadrivalents in part of the PMCs of hypotetraploid K2H2-1C, suggesting that homoeologous recombination between tomato and potato chromosomes occurred in these hybrids. All three hybrids showed a high percentage of first division restitution, giving rise to unreduced gametes. However, shortly after the tetrad stage all microspores completely degenerated, resulting in exclusively sterile pollen.

  19. Reproductive isolation in hybrid mice due to spermatogenesis defects at three meiotic stages.

    Science.gov (United States)

    Oka, Ayako; Mita, Akihiko; Takada, Yuki; Koseki, Haruhiko; Shiroishi, Toshihiko

    2010-09-01

    Early in the process of speciation, reproductive failures occur in hybrid animals between genetically diverged populations. The sterile hybrid animals are often males in mammals and they exhibit spermatogenic disruptions, resulting in decreased number and/or malformation of mature sperms. Despite the generality of this phenomenon, comparative study of phenotypes in hybrid males from various crosses has not been done, and therefore the comprehensive genetic basis of the disruption is still elusive. In this study, we characterized the spermatogenic phenotype especially during meiosis in four different cases of reproductive isolation: B6-ChrX(MSM), PGN-ChrX(MSM), (B6 × Mus musculus musculus-NJL/Ms) F(1), and (B6 × Mus spretus) F(1). The first two are consomic strains, both bearing the X chromosome of M. m. molossinus; in B6-ChrX(MSM), the genetic background is the laboratory strain C57BL/6J (predominantly M. m. domesticus), while in PGN-ChrX(MSM) the background is the PGN2/Ms strain purely derived from wild M. m. domesticus. The last two cases are F(1) hybrids between mouse subspecies or species. Each of the hybrid males exhibited cell-cycle arrest and/or apoptosis at either one or two of three distinct meiotic stages: premeiotic stage, zygotene-to-pachytene stage of prophase I, and metaphase I. This study shows that the sterility in hybrid males is caused by spermatogenic disruptions at multiple stages, suggesting that the responsible genes function in different cellular processes. Furthermore, the stages with disruptions are not correlated with the genetic distance between the respective parental strains.

  20. X chromosome control of meiotic chromosome synapsis in mouse inter-subspecific hybrids.

    Science.gov (United States)

    Bhattacharyya, Tanmoy; Reifova, Radka; Gregorova, Sona; Simecek, Petr; Gergelits, Vaclav; Mistrik, Martin; Martincova, Iva; Pialek, Jaroslav; Forejt, Jiri

    2014-02-01

    Hybrid sterility (HS) belongs to reproductive isolation barriers that safeguard the integrity of species in statu nascendi. Although hybrid sterility occurs almost universally among animal and plant species, most of our current knowledge comes from the classical genetic studies on Drosophila interspecific crosses or introgressions. With the house mouse subspecies Mus m. musculus and Mus m. domesticus as a model, new research tools have become available for studies of the molecular mechanisms and genetic networks underlying HS. Here we used QTL analysis and intersubspecific chromosome substitution strains to identify a 4.7 Mb critical region on Chromosome X (Chr X) harboring the Hstx2 HS locus, which causes asymmetrical spermatogenic arrest in reciprocal intersubspecific F1 hybrids. Subsequently, we mapped autosomal loci on Chrs 3, 9 and 13 that can abolish this asymmetry. Combination of immunofluorescent visualization of the proteins of synaptonemal complexes with whole-chromosome DNA FISH on pachytene spreads revealed that heterosubspecific, unlike consubspecific, homologous chromosomes are predisposed to asynapsis in F1 hybrid male and female meiosis. The asynapsis is under the trans- control of Hstx2 and Hst1/Prdm9 hybrid sterility genes in pachynemas of male but not female hybrids. The finding concurred with the fertility of intersubpecific F1 hybrid females homozygous for the Hstx2(Mmm) allele and resolved the apparent conflict with the dominance theory of Haldane's rule. We propose that meiotic asynapsis in intersubspecific hybrids is a consequence of cis-acting mismatch between homologous chromosomes modulated by the trans-acting Hstx2 and Prdm9 hybrid male sterility genes.

  1. Meiotic sex chromosome inactivation is disrupted in sterile hybrid male house mice.

    Science.gov (United States)

    Campbell, Polly; Good, Jeffrey M; Nachman, Michael W

    2013-03-01

    In male mammals, the X and Y chromosomes are transcriptionally silenced in primary spermatocytes by meiotic sex chromosome inactivation (MSCI) and remain repressed for the duration of spermatogenesis. Here, we test the longstanding hypothesis that disrupted MSCI might contribute to the preferential sterility of heterogametic hybrid males. We studied a cross between wild-derived inbred strains of Mus musculus musculus and M. m. domesticus in which sterility is asymmetric: F1 males with a M. m. musculus mother are sterile or nearly so while F1 males with a M. m. domesticus mother are normal. In previous work, we discovered widespread overexpression of X-linked genes in the testes of sterile but not fertile F1 males. Here, we ask whether this overexpression is specifically a result of disrupted MSCI. To do this, we isolated cells from different stages of spermatogenesis and measured the expression of several genes using quantitative PCR. We found that X overexpression in sterile F1 primary spermatocytes is coincident with the onset of MSCI and persists in postmeiotic spermatids. Using a series of recombinant X genotypes, we then asked whether X overexpression in hybrids is controlled by cis-acting loci across the X chromosome. We found that it is not. Instead, one large interval in the proximal portion of the M. m. musculus X chromosome is associated with both overexpression and the severity of sterility phenotypes in hybrids. These results demonstrate a strong association between X-linked hybrid male sterility and disruption of MSCI and suggest that trans-acting loci on the X are important for the transcriptional regulation of the X chromosome during spermatogenesis.

  2. X Chromosome Control of Meiotic Chromosome Synapsis in Mouse Inter-Subspecific Hybrids

    Science.gov (United States)

    Bhattacharyya, Tanmoy; Reifova, Radka; Gregorova, Sona; Simecek, Petr; Gergelits, Vaclav; Mistrik, Martin; Martincova, Iva; Pialek, Jaroslav; Forejt, Jiri

    2014-01-01

    Hybrid sterility (HS) belongs to reproductive isolation barriers that safeguard the integrity of species in statu nascendi. Although hybrid sterility occurs almost universally among animal and plant species, most of our current knowledge comes from the classical genetic studies on Drosophila interspecific crosses or introgressions. With the house mouse subspecies Mus m. musculus and Mus m. domesticus as a model, new research tools have become available for studies of the molecular mechanisms and genetic networks underlying HS. Here we used QTL analysis and intersubspecific chromosome substitution strains to identify a 4.7 Mb critical region on Chromosome X (Chr X) harboring the Hstx2 HS locus, which causes asymmetrical spermatogenic arrest in reciprocal intersubspecific F1 hybrids. Subsequently, we mapped autosomal loci on Chrs 3, 9 and 13 that can abolish this asymmetry. Combination of immunofluorescent visualization of the proteins of synaptonemal complexes with whole-chromosome DNA FISH on pachytene spreads revealed that heterosubspecific, unlike consubspecific, homologous chromosomes are predisposed to asynapsis in F1 hybrid male and female meiosis. The asynapsis is under the trans- control of Hstx2 and Hst1/Prdm9 hybrid sterility genes in pachynemas of male but not female hybrids. The finding concurred with the fertility of intersubpecific F1 hybrid females homozygous for the Hstx2Mmm allele and resolved the apparent conflict with the dominance theory of Haldane's rule. We propose that meiotic asynapsis in intersubspecific hybrids is a consequence of cis-acting mismatch between homologous chromosomes modulated by the trans-acting Hstx2 and Prdm9 hybrid male sterility genes. PMID:24516397

  3. LDSplitDB: a database for studies of meiotic recombination hotspots in MHC using human genomic data.

    Science.gov (United States)

    Guo, Jing; Chen, Hao; Yang, Peng; Lee, Yew Ti; Wu, Min; Przytycka, Teresa M; Kwoh, Chee Keong; Zheng, Jie

    2018-04-20

    Meiotic recombination happens during the process of meiosis when chromosomes inherited from two parents exchange genetic materials to generate chromosomes in the gamete cells. The recombination events tend to occur in narrow genomic regions called recombination hotspots. Its dysregulation could lead to serious human diseases such as birth defects. Although the regulatory mechanism of recombination events is still unclear, DNA sequence polymorphisms have been found to play crucial roles in the regulation of recombination hotspots. To facilitate the studies of the underlying mechanism, we developed a database named LDSplitDB which provides an integrative and interactive data mining and visualization platform for the genome-wide association studies of recombination hotspots. It contains the pre-computed association maps of the major histocompatibility complex (MHC) region in the 1000 Genomes Project and the HapMap Phase III datasets, and a genome-scale study of the European population from the HapMap Phase II dataset. Besides the recombination profiles, related data of genes, SNPs and different types of epigenetic modifications, which could be associated with meiotic recombination, are provided for comprehensive analysis. To meet the computational requirement of the rapidly increasing population genomics data, we prepared a lookup table of 400 haplotypes for recombination rate estimation using the well-known LDhat algorithm which includes all possible two-locus haplotype configurations. To the best of our knowledge, LDSplitDB is the first large-scale database for the association analysis of human recombination hotspots with DNA sequence polymorphisms. It provides valuable resources for the discovery of the mechanism of meiotic recombination hotspots. The information about MHC in this database could help understand the roles of recombination in human immune system. DATABASE URL: http://histone.scse.ntu.edu.sg/LDSplitDB.

  4. Casein kinase 1 alpha regulates chromosome congression and separation during mouse oocyte meiotic maturation and early embryo development.

    Directory of Open Access Journals (Sweden)

    Lu Wang

    Full Text Available Casein kinase I alpha (CK1α is a member of serine/threonine protein kinase, generally present in all eukaryotes. In mammals, CK1α regulates the transition from interphase to metaphase in mitosis. However, little is known about its role in meiosis. Here we examined Ck1α mRNA and protein expression, as well as its subcellular localization in mouse oocytes from germinal vesicle to the late 1-cell stage. Our results showed that the expression level of CK1α was increased in metaphase. Immunostaining results showed that CK1α colocalized with condensed chromosomes during oocyte meiotic maturation and early embryo development. We used the loss-of-function approach by employing CK1α specific morpholino injection to block the function of CK1α. This functional blocking leads to failure of polar body 1 (PB1 extrusion, chromosome misalignment and MII plate incrassation. We further found that D4476, a specific and efficient CK1 inhibitor, decreased the rate of PB1 extrusion. Moreover, D4476 resulted in giant polar body extrusion, oocyte pro-MI arrest, chromosome congression failure and impairment of embryo developmental potential. In addition, we employed pyrvinium pamoate (PP, an allosteric activator of CK1α, to enhance CK1α activity in oocytes. Supplementation of PP induced oocyte meiotic maturation failure, severe congression abnormalities and misalignment of chromosomes. Taken together, our study for the first time demonstrates that CK1α is required for chromosome alignment and segregation during oocyte meiotic maturation and early embryo development.

  5. Comportamiento meiótico de diferentes especies de lulo, Solanum sp Meiotic behavior of lulo species, Solanum sp

    Directory of Open Access Journals (Sweden)

    Nancy Maricela Pareja Ordóñez

    2010-10-01

    Full Text Available Se realizó un análisis del comportamiento meiótico de las especies de lulo S. hirtum, S. quitoense y S. sessiliflorum, siguiendo la metodología convencional para los estudios de microsporogénesis. Se tomaron botones florales en diferentes estados de desarrollo, fijándolos por 24 horas en una solución de tres partes de etanol por una parte de ácido acético, saturada con trazas de cristales de cloruro férrico. Para la preparación de las placas se siguió la técnica de aplastamiento, se liberaron las células madres del grano de polen y finalmente se hicieron las observaciones bajo microscopía de luz. El análisis mostró que la meiosis se presenta en longitudes de antera que van desde los 2,79 mm hasta los 4,45 mm. La normalidad meiótica fue del 100%, tanto para meiosis I, como para la meiosis II. El índice meiótico en las tres especies fue del 99,98% lo cual indica que son buenos parentales y que pueden utilizarse en programas de cruzamiento. Las tres especies evaluadas tienen igual número de cromosomas (2n=2X=24. La frecuencia de anormalidades durante el proceso meiótico fue baja para S. hirtum, y alta para S. quitoense; sin embargo, la viabilidad polínica fue de gran magnitud (91,2-97,3%.An analysis of meiotic behavior of lulo species S. hirtum, S. quitoense and S. sessiliflorum, following the conventional methodology for studies of microsporogenesis was realized. Flower buds were taken at different stages of development, fixing them for 24 hours in a solution of three parts of ethanol per one part of acetic acid, saturated with traces of ferric chloride crystals. For the preparation of the slides following the technique of squash, releasing pollen mother cells and finally made the observations under light microscopy. The analysis showed that meiosis occurs in anther ranging from 2.79 to 4.45 mm. Meiotic normality was 100% for both meiosis I and II. The meiotic index in all three species was 99,98% indicating that they are

  6. OSD1 promotes meiotic progression via APC/C inhibition and forms a regulatory network with TDM and CYCA1;2/TAM.

    Science.gov (United States)

    Cromer, Laurence; Heyman, Jefri; Touati, Sandra; Harashima, Hirofumi; Araou, Emilie; Girard, Chloe; Horlow, Christine; Wassmann, Katja; Schnittger, Arp; De Veylder, Lieven; Mercier, Raphael

    2012-01-01

    Cell cycle control is modified at meiosis compared to mitosis, because two divisions follow a single DNA replication event. Cyclin-dependent kinases (CDKs) promote progression through both meiosis and mitosis, and a central regulator of their activity is the APC/C (Anaphase Promoting Complex/Cyclosome) that is especially required for exit from mitosis. We have shown previously that OSD1 is involved in entry into both meiosis I and meiosis II in Arabidopsis thaliana; however, the molecular mechanism by which OSD1 controls these transitions has remained unclear. Here we show that OSD1 promotes meiotic progression through APC/C inhibition. Next, we explored the functional relationships between OSD1 and the genes known to control meiotic cell cycle transitions in Arabidopsis. Like osd1, cyca1;2/tam mutation leads to a premature exit from meiosis after the first division, while tdm mutants perform an aberrant third meiotic division after normal meiosis I and II. Remarkably, while tdm is epistatic to tam, osd1 is epistatic to tdm. We further show that the expression of a non-destructible CYCA1;2/TAM provokes, like tdm, the entry into a third meiotic division. Finally, we show that CYCA1;2/TAM forms an active complex with CDKA;1 that can phosphorylate OSD1 in vitro. We thus propose that a functional network composed of OSD1, CYCA1;2/TAM, and TDM controls three key steps of meiotic progression, in which OSD1 is a meiotic APC/C inhibitor.

  7. 49 CFR 236.203 - Hand operated crossover between main tracks; protection.

    Science.gov (United States)

    2010-10-01

    ...) Electric locking of the switches of the crossover. Signals governing movements over either switch shall... crossover is occupied by a train, locomotive or car in such a manner as to foul the main track. It shall not... electric locking releases. ...

  8. Crossover Improvement for the Genetic Algorithm in Information Retrieval.

    Science.gov (United States)

    Vrajitoru, Dana

    1998-01-01

    In information retrieval (IR), the aim of genetic algorithms (GA) is to help a system to find, in a huge documents collection, a good reply to a query expressed by the user. Analysis of phenomena seen during the implementation of a GA for IR has led to a new crossover operation, which is introduced and compared to other learning methods.…

  9. Bloodcurdling movies and measures of coagulation: Fear Factor crossover trial

    NARCIS (Netherlands)

    Nemeth, Banne; Scheres, Luuk J. J.; Lijfering, Willem M.; Rosendaal, Frits R.

    2015-01-01

    To assess whether, as has been hypothesised since medieval times, acute fear can curdle blood. Crossover trial. Main meeting room of Leiden University's Department of Clinical Epidemiology, the Netherlands, converted to a makeshift cinema. 24 healthy volunteers aged ≤30 years recruited among

  10. Theoretical Study of Spin Crossover in 30 Iron Complexes

    DEFF Research Database (Denmark)

    Kepp, Kasper Planeta

    2016-01-01

    Spin crossover was studied in 30 iron complexes using density functional theory to quantify the direction and magnitude of dispersion, relativistic effects, zero-point energies, and vibrational entropy. Remarkably consistent entropy−enthalpy compensation was identified. Zero-point energies favor...

  11. Crossover to entangled dynamics in polymer solutions and melts

    International Nuclear Information System (INIS)

    Schweizer, K.S.; Szamel, G.

    1995-01-01

    A statistical dynamical theory of the crossover from unentangled Rouse dynamics to entangled behavior is constructed for chain polymer solutions and melts. Both time and spatial crossovers in long chain fluids, and the degree of polymerization crossover for short polymers, are treated. The analysis is based on a microscopic theory of the perturbative dynamical corrections to Rouse theory arising from chain connectivity and intermolecular excluded volume forces. The dependence of crossover properties such as the plateau shear modulus and entanglement time and length scale on solution density, solvent quality, and chain statistical segment length are derived by combining the dynamical theory with equilibrium liquid state integral equation methods. Scaling relations are obtained which appear to be in general accord with most experiments on both solutions and melts. The physical origin of the predicted scaling behaviors is the fractional power law temporal decay of the entanglement friction memory function on intermediate time scales, and power law reduced density dependence of the equilibrium force correlations. The theory is also applied to compute the dependence of the chain normal mode relaxation times on polymer density and chain length. Favorable qualitative comparisons with recent neutron spin echo experiments are made. copyright 1995 American Institute of Physics

  12. Activation of coagulation system during air travel: a crossover study

    NARCIS (Netherlands)

    Schreijer, A. J. M.; Cannegieter, S. C.; Meijers, J. C. M.; Middeldorp, S.; Büller, H. R.; Rosendaal, F. R.

    2006-01-01

    BACKGROUND: There is an increased risk of venous thrombosis after air travel, but the underlying mechanism is unclear. Our aim was to ascertain whether flying leads to a hypercoagulable state. METHODS: We did a crossover study in 71 healthy volunteers (15 men, 56 women), in whom we measured markers

  13. Catalytic Activity Control via Crossover between Two Different Microstructures

    KAUST Repository

    Zhou, Yuheng; Zhu, Yihan; Wang, Zhi-Qiang; Zou, Shihui; Ma, Guicen; Xia, Ming; Kong, Xueqian; Xiao, Liping; Gong, Xue-Qing; Fan, Jie

    2017-01-01

    microstructural control through the crossover between multiply-twinned nanoparticle (MTP) and single crystal (SC) can be readily achieved by solvent post-treatment on gold nanoparticles (AuNPs). Polar solvents (e.g. water, methanol) direct the transformation from

  14. Heme: From quantum spin crossover to oxygen manager of life

    DEFF Research Database (Denmark)

    Kepp, Kasper Planeta

    2016-01-01

    The review discusses how the electronic structure of heme explains its central importance to oxygen-based life on Earth. Emphasis is on the chemical bonding of heme, its spin crossover, reversible O2 binding, and O-O bond activation, put in relation to its physiological functions. The review disc...

  15. Influence of crossover methods used by genetic algorithm-based ...

    Indian Academy of Sciences (India)

    numerical methods like Newton–Raphson, sequential homotopy calculation, Walsh ... But the paper does not touch upon the elements of crossover operators. ... if SHE problems are solved with optimization tools like GA (Schutten ..... Goldberg D E 1989 Genetic algorithms in search, optimization and machine learning.

  16. Caenorhabditis elegans histone methyltransferase MET-2 shields the male X chromosome from checkpoint machinery and mediates meiotic sex chromosome inactivation.

    Directory of Open Access Journals (Sweden)

    Paula M Checchi

    2011-09-01

    Full Text Available Meiosis is a specialized form of cellular division that results in the precise halving of the genome to produce gametes for sexual reproduction. Checkpoints function during meiosis to detect errors and subsequently to activate a signaling cascade that prevents the formation of aneuploid gametes. Indeed, asynapsis of a homologous chromosome pair elicits a checkpoint response that can in turn trigger germline apoptosis. In a heterogametic germ line, however, sex chromosomes proceed through meiosis with unsynapsed regions and are not recognized by checkpoint machinery. We conducted a directed RNAi screen in Caenorhabditis elegans to identify regulatory factors that prevent recognition of heteromorphic sex chromosomes as unpaired and uncovered a role for the SET domain histone H3 lysine 9 histone methyltransferase (HMTase MET-2 and two additional HMTases in shielding the male X from checkpoint machinery. We found that MET-2 also mediates the transcriptional silencing program of meiotic sex chromosome inactivation (MSCI but not meiotic silencing of unsynapsed chromatin (MSUC, suggesting that these processes are distinct. Further, MSCI and checkpoint shielding can be uncoupled, as double-strand breaks targeted to an unpaired, transcriptionally silenced extra-chromosomal array induce checkpoint activation in germ lines depleted for met-2. In summary, our data uncover a mechanism by which repressive chromatin architecture enables checkpoint proteins to distinguish between the partnerless male X chromosome and asynapsed chromosomes thereby shielding the lone X from inappropriate activation of an apoptotic program.

  17. Cytoplasmic and Genomic Effects on Meiotic Pairing in Brassica Hybrids and Allotetraploids from Pair Crosses of Three Cultivated Diploids

    Science.gov (United States)

    Cui, Cheng; Ge, Xianhong; Gautam, Mayank; Kang, Lei; Li, Zaiyun

    2012-01-01

    Interspecific hybridization and allopolyploidization contribute to the origin of many important crops. Synthetic Brassica is a widely used model for the study of genetic recombination and “fixed heterosis” in allopolyploids. To investigate the effects of the cytoplasm and genome combinations on meiotic recombination, we produced digenomic diploid and triploid hybrids and trigenomic triploid hybrids from the reciprocal crosses of three Brassica diploids (B. rapa, AA; B. nigra, BB; B. oleracea, CC). The chromosomes in the resultant hybrids were doubled to obtain three allotetraploids (B. juncea, AA.BB; B. napus, AA.CC; B. carinata, BB.CC). Intra- and intergenomic chromosome pairings in these hybrids were quantified using genomic in situ hybridization and BAC-FISH. The level of intra- and intergenomic pairings varied significantly, depending on the genome combinations and the cytoplasmic background and/or their interaction. The extent of intragenomic pairing was less than that of intergenomic pairing within each genome. The extent of pairing variations within the B genome was less than that within the A and C genomes, each of which had a similar extent of pairing. Synthetic allotetraploids exhibited nondiploidized meiotic behavior, and their chromosomal instabilities were correlated with the relationship of the genomes and cytoplasmic background. Our results highlight the specific roles of the cytoplasm and genome to the chromosomal behaviors of hybrids and allopolyploids. PMID:22505621

  18. Maize histone H2B-mCherry: a new fluorescent chromatin marker for somatic and meiotic chromosome research.

    Science.gov (United States)

    Howe, Elizabeth S; Clemente, Thomas E; Bass, Hank W

    2012-06-01

    Cytological studies of fluorescent proteins are rapidly yielding insights into chromatin structure and dynamics. Here we describe the production and cytological characterization of new transgenic maize lines expressing a fluorescent histone fusion protein, H2B-mCherry. The transgene is expressed under the control of the maize ubiquitin1 promoter, including its first exon and intron. Polymerase chain reaction-based genotyping and root-tip microscopy showed that most of the lines carrying the transgene also expressed it, producing bright uniform staining of nuclei. Further, plants showing expression in root tips at the seedling stage also showed expression during meiosis, late in the life cycle. Detailed high-resolution three-dimensional imaging of cells and nuclei from various somatic and meiotic cell types showed that H2B-mCherry produced remarkably clear images of chromatin and chromosome fiber morphology, as seen in somatic, male meiotic prophase, and early microgametophyte cells. H2B-mCherry also yielded distinct nucleolus staining and was shown to be compatible with fluorescence in situ hybridization. We found several instances where H2B-mCherry was superior to DAPI as a generalized chromatin stain. Our study establishes these histone H2B-mCherry lines as new biological reagents for visualizing chromatin structure, chromosome morphology, and nuclear dynamics in fixed and living cells in a model plant genetic system.

  19. PRDM9 drives evolutionary erosion of hotspots in Mus musculus through haplotype-specific initiation of meiotic recombination.

    Science.gov (United States)

    Baker, Christopher L; Kajita, Shimpei; Walker, Michael; Saxl, Ruth L; Raghupathy, Narayanan; Choi, Kwangbom; Petkov, Petko M; Paigen, Kenneth

    2015-01-01

    Meiotic recombination generates new genetic variation and assures the proper segregation of chromosomes in gametes. PRDM9, a zinc finger protein with histone methyltransferase activity, initiates meiotic recombination by binding DNA at recombination hotspots and directing the position of DNA double-strand breaks (DSB). The DSB repair mechanism suggests that hotspots should eventually self-destruct, yet genome-wide recombination levels remain constant, a conundrum known as the hotspot paradox. To test if PRDM9 drives this evolutionary erosion, we measured activity of the Prdm9Cst allele in two Mus musculus subspecies, M.m. castaneus, in which Prdm9Cst arose, and M.m. domesticus, into which Prdm9Cst was introduced experimentally. Comparing these two strains, we find that haplotype differences at hotspots lead to qualitative and quantitative changes in PRDM9 binding and activity. Using Mus spretus as an outlier, we found most variants affecting PRDM9Cst binding arose and were fixed in M.m. castaneus, suppressing hotspot activity. Furthermore, M.m. castaneus×M.m. domesticus F1 hybrids exhibit novel hotspots, with large haplotype biases in both PRDM9 binding and chromatin modification. These novel hotspots represent sites of historic evolutionary erosion that become activated in hybrids due to crosstalk between one parent's Prdm9 allele and the opposite parent's chromosome. Together these data support a model where haplotype-specific PRDM9 binding directs biased gene conversion at hotspots, ultimately leading to hotspot erosion.

  20. CENTRAL REGION COMPONENT1, a Novel Synaptonemal Complex Component, Is Essential for Meiotic Recombination Initiation in Rice[C][W

    Science.gov (United States)

    Miao, Chunbo; Tang, Ding; Zhang, Honggen; Wang, Mo; Li, Yafei; Tang, Shuzhu; Yu, Hengxiu; Gu, Minghong; Cheng, Zhukuan

    2013-01-01

    In meiosis, homologous recombination entails programmed DNA double-strand break (DSB) formation and synaptonemal complex (SC) assembly coupled with the DSB repair. Although SCs display extensive structural conservation among species, their components identified are poorly conserved at the sequence level. Here, we identified a novel SC component, designated CENTRAL REGION COMPONENT1 (CRC1), in rice (Oryza sativa). CRC1 colocalizes with ZEP1, the rice SC transverse filament protein, to the central region of SCs in a mutually dependent fashion. Consistent with this colocalization, CRC1 interacts with ZEP1 in yeast two-hybrid assays. CRC1 is orthologous to Saccharomyces cerevisiae pachytene checkpoint2 (Pch2) and Mus musculus THYROID RECEPTOR-INTERACTING PROTEIN13 (TRIP13) and may be a conserved SC component. Additionally, we provide evidence that CRC1 is essential for meiotic DSB formation. CRC1 interacts with HOMOLOGOUS PAIRING ABERRATION IN RICE MEIOSIS1 (PAIR1) in vitro, suggesting that these proteins act as a complex to promote DSB formation. PAIR2, the rice ortholog of budding yeast homolog pairing1, is required for homologous chromosome pairing. We found that CRC1 is also essential for the recruitment of PAIR2 onto meiotic chromosomes. The roles of CRC1 identified here have not been reported for Pch2 or TRIP13. PMID:23943860

  1. Central region component1, a novel synaptonemal complex component, is essential for meiotic recombination initiation in rice.

    Science.gov (United States)

    Miao, Chunbo; Tang, Ding; Zhang, Honggen; Wang, Mo; Li, Yafei; Tang, Shuzhu; Yu, Hengxiu; Gu, Minghong; Cheng, Zhukuan

    2013-08-01

    In meiosis, homologous recombination entails programmed DNA double-strand break (DSB) formation and synaptonemal complex (SC) assembly coupled with the DSB repair. Although SCs display extensive structural conservation among species, their components identified are poorly conserved at the sequence level. Here, we identified a novel SC component, designated central region component1 (CRC1), in rice (Oryza sativa). CRC1 colocalizes with ZEP1, the rice SC transverse filament protein, to the central region of SCs in a mutually dependent fashion. Consistent with this colocalization, CRC1 interacts with ZEP1 in yeast two-hybrid assays. CRC1 is orthologous to Saccharomyces cerevisiae pachytene checkpoint2 (Pch2) and Mus musculus THYROID receptor-interacting protein13 (TRIP13) and may be a conserved SC component. Additionally, we provide evidence that CRC1 is essential for meiotic DSB formation. CRC1 interacts with homologous pairing aberration in rice meiosis1 (PAIR1) in vitro, suggesting that these proteins act as a complex to promote DSB formation. PAIR2, the rice ortholog of budding yeast homolog pairing1, is required for homologous chromosome pairing. We found that CRC1 is also essential for the recruitment of PAIR2 onto meiotic chromosomes. The roles of CRC1 identified here have not been reported for Pch2 or TRIP13.

  2. Stage sensitivity and dose response of meiotic chromosomes of pollen mother cells of Tradescantia to X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Ma, T H; Kontos, Jr, G J; Anderson, V A [Western Illinois Univ., Macomb (USA). Dept. of Biological Sciences

    1980-05-01

    Chromosome damage induced by physical and chemical mutagens can be quantitated by the frequencies of micronuclei (MCN) produced in tetrads of the meiotic pollen mother cells of Tradescantia, i.e. the 'MCN-in-Tetrad' test. The stage sensitivity and dose response of these meiocytes to low exposures of X-rays was studied to improve the efficiency and reliability of this test. Stage sensitivity was determined by observing, at 3 hr intervals, the frequencies of X-ray (35 rads)-induced MCN in tetrads from a series of 16 fixations of tetrad-containing inflorescences. Late stages of meiosis (3-9 hr post-irradiation fixation groups) were insensitive (5-14 MCN/100 tetrads). Relatively high sensitivity was exhibited in the early stages of meiosis. The first and second sensitive peaks (62 and 61 MCN/100 tetrads) centered around the 21 and 39 hr post-irradiation fixation groups respectively. Control groups yielded around 3-4 MCN/100 tetrads. A dose-response relation for MCN was determined by treating early stages of meiotic pollen mother cells with X-ray exposures ranging from 9.5 to 57.5 rads. A linear regression line was established with about 20 MCN/100 tetrads per 10 rad increment.

  3. Stage sensitivity and dose response of meiotic chromosomes of pollen mother cells of Tradescantia to X-rays

    International Nuclear Information System (INIS)

    Ma, T.-H.; Kontos, G.J. Jr.; Anderson, V.A.

    1980-01-01

    Chromosome damage induced by physical and chemical mutagens can be quantitated by the frequencies of micronuclei (MCN) produced in tetrads of the meiotic pollen mother cells of Tradescantia, i.e. the 'MCN-in-Tetrad' test. The stage sensitivity and dose response of these meiocytes to low exposures of X-rays was studied to improve the efficiency and reliability of this test. Stage sensitivity was determined by observing, at 3 hr intervals, the frequencies of X-ray (35 rads)-induced MCN in tetrads from a series of 16 fixations of tetrad-containing inflorescences. Late stages of meiosis (3-9 hr post-irradiation fixation groups) were insensitive (5-14 MCN/100 tetrads). Relatively high sensitivity was exhibited in the early stages of meiosis. The first and second sensitive peaks (62 and 61 MCN/100 tetrads) centered around the 21 and 39 hr post-irradiation fixation groups respectively. Control groups yielded around 3-4 MCN/100 tetrads. A dose-response relation for MCN was determined by treating early stages of meiotic pollen mother cells with X-ray exposures ranging from 9.5 to 57.5 rads. A linear regression line was established with about 20 MCN/100 tetrads per 10 rad increment. (author)

  4. Slow Freezing or Vitrification of Oocytes: Their Effects on Survival and Meiotic Spindles, and the Time Schedule for Clinical Practice

    Directory of Open Access Journals (Sweden)

    Shee-Uan Chen

    2009-03-01

    Full Text Available Both the slow-freezing method with increased sucrose concentration and new vitrification techniques significantly improve the results of cryopreservation of human oocytes. The recent perfection for vitrification includes the concepts of increase of cooling and warming rates using minimum volume methods, and decrease of toxicity by reducing the concentration of cryoprotectants. In the recent literature, the survival of cryopreserved oocytes ranged from 74% to 90% using the slow-freezing method and from 84% to 99% by vitrification. Overall, the survival rate of oocytes from vitrification (95%, 899/948 appeared higher than that of the slow-freezing method (75%, 1,275/1,683. The microtubules of meiotic spindles are vulnerable to the thermal changes and will depolymerize. After incubation, the microtubules repolymerize. Spindle recovery is faster after vitrification than slow freezing. Even so, after 3 hours of incubation, spindle recuperation is similar between vitrification and slow freezing. Considering both aspects of spindle recovery and oocyte aging, the time schedule for oocyte cryopreservation program makes fertilization in the optimal time. Intracytoplasmic sperm injection is performed for oocytes at 3 hours of post-thaw incubation from the slow-freezing method and 2 hours from vitrification, with restoration of meiotic spindles. The pregnancy potential of cryopreserved oocytes is comparable to that of fresh oocytes or frozen embryos. Cryopreservation of oocytes would importantly contribute to oocyte donation and preservation of fertility for cancer patients.

  5. Sex chromosome-specific regulation in the Drosophila male germline but little evidence for chromosomal dosage compensation or meiotic inactivation.

    Directory of Open Access Journals (Sweden)

    Colin D Meiklejohn

    2011-08-01

    Full Text Available The evolution of heteromorphic sex chromosomes (e.g., XY in males or ZW in females has repeatedly elicited the evolution of two kinds of chromosome-specific regulation: dosage compensation--the equalization of X chromosome gene expression in males and females--and meiotic sex chromosome inactivation (MSCI--the transcriptional silencing and heterochromatinization of the X during meiosis in the male (or Z in the female germline. How the X chromosome is regulated in the Drosophila melanogaster male germline is unclear. Here we report three new findings concerning gene expression from the X in Drosophila testes. First, X chromosome-wide dosage compensation appears to be absent from most of the Drosophila male germline. Second, microarray analysis provides no evidence for X chromosome-specific inactivation during meiosis. Third, we confirm the previous discovery that the expression of transgene reporters driven by autosomal spermatogenesis-specific promoters is strongly reduced when inserted on the X chromosome versus the autosomes; but we show that this chromosomal difference in expression is established in premeiotic cells and persists in meiotic cells. The magnitude of the X-autosome difference in transgene expression cannot be explained by the absence of dosage compensation, suggesting that a previously unrecognized mechanism limits expression from the X during spermatogenesis in Drosophila. These findings help to resolve several previously conflicting reports and have implications for patterns of genome evolution and speciation in Drosophila.

  6. What's Mine Is Yours: The Crossover of Day-Specific Self-Esteem

    Science.gov (United States)

    Neff, Angela; Sonnentag, Sabine; Niessen, Cornelia; Unger, Dana

    2012-01-01

    This diary study examines the daily crossover of self-esteem within working couples. By integrating self-esteem research into the crossover framework, we hypothesized that the day-specific self-esteem experienced by one partner after work crosses over to the other partner. Furthermore, we proposed that this daily crossover process is moderated by…

  7. Retinoic Acid signalling and the control of meiotic entry in the human fetal gonad.

    Directory of Open Access Journals (Sweden)

    Andrew J Childs

    Full Text Available The development of mammalian fetal germ cells along oogenic or spermatogenic fate trajectories is dictated by signals from the surrounding gonadal environment. Germ cells in the fetal testis enter mitotic arrest, whilst those in the fetal ovary undergo sex-specific entry into meiosis, the initiation of which is thought to be mediated by selective exposure of fetal ovarian germ cells to mesonephros-derived retinoic acid (RA. Aspects of this model are hard to reconcile with the spatiotemporal pattern of germ cell differentiation in the human fetal ovary, however. We have therefore examined the expression of components of the RA synthesis, metabolism and signalling pathways, and their downstream effectors and inhibitors in germ cells around the time of the initiation of meiosis in the human fetal gonad. Expression of the three RA-synthesising enzymes, ALDH1A1, 2 and 3 in the fetal ovary and testis was equal to or greater than that in the mesonephros at 8-9 weeks gestation, indicating an intrinsic capacity within the gonad to synthesise RA. Using immunohistochemistry to detect RA receptors RARα, β and RXRα, we find germ cells to be the predominant target of RA signalling in the fetal human ovary, but also reveal widespread receptor nuclear localization indicative of signalling in the testis, suggesting that human fetal testicular germ cells are not efficiently shielded from RA by the action of the RA-metabolising enzyme CYP26B1. Consistent with this, expression of CYP26B1 was greater in the human fetal ovary than testis, although the sexually-dimorphic expression patterns of the germ cell-intrinsic regulators of meiotic initiation, STRA8 and NANOS2, appear conserved. Finally, we demonstrate that RA induces a two-fold increase in STRA8 expression in cultures of human fetal testis, but is not sufficient to cause widespread meiosis-associated gene expression. Together, these data indicate that while local production of RA within the fetal ovary may

  8. Retinoic Acid Signalling and the Control of Meiotic Entry in the Human Fetal Gonad

    Science.gov (United States)

    Kinnell, Hazel L.; Anderson, Richard A.; Saunders, Philippa T. K.

    2011-01-01

    The development of mammalian fetal germ cells along oogenic or spermatogenic fate trajectories is dictated by signals from the surrounding gonadal environment. Germ cells in the fetal testis enter mitotic arrest, whilst those in the fetal ovary undergo sex-specific entry into meiosis, the initiation of which is thought to be mediated by selective exposure of fetal ovarian germ cells to mesonephros-derived retinoic acid (RA). Aspects of this model are hard to reconcile with the spatiotemporal pattern of germ cell differentiation in the human fetal ovary, however. We have therefore examined the expression of components of the RA synthesis, metabolism and signalling pathways, and their downstream effectors and inhibitors in germ cells around the time of the initiation of meiosis in the human fetal gonad. Expression of the three RA-synthesising enzymes, ALDH1A1, 2 and 3 in the fetal ovary and testis was equal to or greater than that in the mesonephros at 8–9 weeks gestation, indicating an intrinsic capacity within the gonad to synthesise RA. Using immunohistochemistry to detect RA receptors RARα, β and RXRα, we find germ cells to be the predominant target of RA signalling in the fetal human ovary, but also reveal widespread receptor nuclear localization indicative of signalling in the testis, suggesting that human fetal testicular germ cells are not efficiently shielded from RA by the action of the RA-metabolising enzyme CYP26B1. Consistent with this, expression of CYP26B1 was greater in the human fetal ovary than testis, although the sexually-dimorphic expression patterns of the germ cell-intrinsic regulators of meiotic initiation, STRA8 and NANOS2, appear conserved. Finally, we demonstrate that RA induces a two-fold increase in STRA8 expression in cultures of human fetal testis, but is not sufficient to cause widespread meiosis-associated gene expression. Together, these data indicate that while local production of RA within the fetal ovary may be important in

  9. Origin of triploid Arachis pintoi (Leguminosae) by autopolyploidy evidenced by FISH and meiotic behaviour

    Science.gov (United States)

    Lavia, Graciela Inés; Ortiz, Alejandra Marcela; Robledo, Germán; Fernández, Aveliano; Seijo, Guillermo

    2011-01-01

    Background and Aims Polyploidy is a dominant feature of flowering-plant genomes, including those of many important crop species. Arachis is a largely diploid genus with just four polyploid species. Two of them are economically important: the cultivated peanut and A. glabrata, a tropical forage crop. Even though it is usually accepted that polyploids within papilionoid legumes have arisen via hybridization and further chromosome doubling, it has been recently suggested that peanut arose through bilateral sexual polyploidization. In this paper, the polyploid nature of the recent, spontaneously originated triploid cytotype of the tropical lucerne, A. pintoi, was analysed, and thereby the mechanism by which polyploids may arise in the genus. Methods Chromosome morphology of 2x and 3x A. pintoi was determined by the Feulgeńs technique and the rDNA sites were mapped by FISH. To investigate whether polyploidization occurred by means of unreduced gametes, a detailed analysis of the microsporogenesis and pollen grains was made. Key Results The 2x and 3x plants presented 9m + 1sm and a satellited chromosome type 2 in each haploid genome. Physical mapping revealed a cluster of 18S–26S rDNA, proximally located on chromosome 6, and two 5S rDNA loci on chromosomes 3 and 5. Diploid plants presented 10II in meiosis while trivalents were observed in all triploids, with a maximum of 10III by cell. Diploid A. pintoi produced normal tetrads, but also triads, dyads and monads. Two types of pollen grains were detected: (1) normal-sized with a prolate shape and (2) large ones with a tetrahedral morphology. Conclusions Karyotype and meiotic analysis demonstrate that the 3x clone of A. pintoi arose by autopolyploidy. The occurrence of unreduced gametes strongly supports unilateral sexual polyploidization as the most probable mechanism that could have led to the origin of the triploid cytotype. This mechanism of polyploidization would probably be one of the most important mechanisms

  10. Origin of triploid Arachis pintoi (Leguminosae) by autopolyploidy evidenced by FISH and meiotic behaviour.

    Science.gov (United States)

    Lavia, Graciela Inés; Ortiz, Alejandra Marcela; Robledo, Germán; Fernández, Aveliano; Seijo, Guillermo

    2011-07-01

    Polyploidy is a dominant feature of flowering-plant genomes, including those of many important crop species. Arachis is a largely diploid genus with just four polyploid species. Two of them are economically important: the cultivated peanut and A. glabrata, a tropical forage crop. Even though it is usually accepted that polyploids within papilionoid legumes have arisen via hybridization and further chromosome doubling, it has been recently suggested that peanut arose through bilateral sexual polyploidization. In this paper, the polyploid nature of the recent, spontaneously originated triploid cytotype of the tropical lucerne, A. pintoi, was analysed, and thereby the mechanism by which polyploids may arise in the genus. Chromosome morphology of 2x and 3x A. pintoi was determined by the Feulgeńs technique and the rDNA sites were mapped by FISH. To investigate whether polyploidization occurred by means of unreduced gametes, a detailed analysis of the microsporogenesis and pollen grains was made. The 2x and 3x plants presented 9m + 1sm and a satellited chromosome type 2 in each haploid genome. Physical mapping revealed a cluster of 18S-26S rDNA, proximally located on chromosome 6, and two 5S rDNA loci on chromosomes 3 and 5. Diploid plants presented 10II in meiosis while trivalents were observed in all triploids, with a maximum of 10III by cell. Diploid A. pintoi produced normal tetrads, but also triads, dyads and monads. Two types of pollen grains were detected: (1) normal-sized with a prolate shape and (2) large ones with a tetrahedral morphology. Karyotype and meiotic analysis demonstrate that the 3x clone of A. pintoi arose by autopolyploidy. The occurrence of unreduced gametes strongly supports unilateral sexual polyploidization as the most probable mechanism that could have led to the origin of the triploid cytotype. This mechanism of polyploidization would probably be one of the most important mechanisms involved in the origin of economically important species

  11. Skating crossovers on a motorized flywheel: a preliminary experimental design to test effect on speed and on crossovers.

    Science.gov (United States)

    Smith, Aynsley M; Krause, David A; Stuart, Michael J; Montelpare, William J; Sorenson, Matthew C; Link, Andrew A; Gaz, Daniel V; Twardowski, Casey P; Larson, Dirk R; Stuart, Michael B

    2013-12-01

    Ice hockey requires frequent skater crossovers to execute turns. Our investigation aimed to determine the effectiveness of training crossovers on a motorized, polyethylene high-resistance flywheel. We hypothesized that high school hockey players training on the flywheel would perform as well as their peers training on ice. Participants were 23 male high-school hockey players (age 15-19 years). The study used an experimental prospective design to compare players who trained for 9 sessions on the 22-foot flywheel with players who trained for 9 sessions on a similarly sized on-ice circle. Both groups were compared with control subjects who were randomly selected from the same participant pool as those training on ice. All players were tested before and after their 3-week training regimens, and control subjects were asked to not practice crossovers between testing. Group 1 trained in a hockey training facility housing the flywheel, and group 2 trained in the ice hockey arena where testing occurred. Primary outcome measures tested in both directions were: (a) speed (time in seconds) required to skate crossovers for 3 laps of a marked face-off circle, (b) cadence of skating crossovers on the similarly sized circles, and (c) a repeat interval speed test, which measures anaerobic power. No significant changes were found between groups in on-ice testing before and after training. Among the group 1 players, 7 of 8 believed they benefited from flywheel training. Group 2 players, who trained on ice, did not improve performance significantly over group 1 players. Despite the fact that no significant on-ice changes in performance were observed in objective measures, players who trained on the flywheel subjectively reported that the flywheel is an effective cost-effective alternative to training on ice. This is a relevant finding when placed in context with limited availability of on-ice training.

  12. Alteration of fasting heat production during fescue toxicosis in Holstein steers

    Science.gov (United States)

    This study was designed to examine alteration of fasting heat production (FHP) during fescue toxicosis. Six ruminally cannulated Holstein steers (BW=348 ±13 kg) were weight-matched into pairs and utilized in a two period crossover design experiment. Each period consisted of two temperature segments,...

  13. Release from Xenopus oocyte prophase I meiotic arrest is independent of a decrease in cAMP levels or PKA activity.

    Science.gov (United States)

    Nader, Nancy; Courjaret, Raphael; Dib, Maya; Kulkarni, Rashmi P; Machaca, Khaled

    2016-06-01

    Vertebrate oocytes arrest at prophase of meiosis I as a result of high levels of cyclic adenosine monophosphate (cAMP) and protein kinase A (PKA) activity. In Xenopus, progesterone is believed to release meiotic arrest by inhibiting adenylate cyclase, lowering cAMP levels and repressing PKA. However, the exact timing and extent of the cAMP decrease is unclear, with conflicting reports in the literature. Using various in vivo reporters for cAMP and PKA at the single-cell level in real time, we fail to detect any significant changes in cAMP or PKA in response to progesterone. More interestingly, there was no correlation between the levels of PKA inhibition and the release of meiotic arrest. Furthermore, we devised conditions whereby meiotic arrest could be released in the presence of sustained high levels of cAMP. Consistently, lowering endogenous cAMP levels by >65% for prolonged time periods failed to induce spontaneous maturation. These results argue that the release of oocyte meiotic arrest in Xenopus is independent of a reduction in either cAMP levels or PKA activity, but rather proceeds through a parallel cAMP/PKA-independent pathway. © 2016. Published by The Company of Biologists Ltd.

  14. Specific deletion of Cdc42 does not affect meiotic spindle organization/migration and homologous chromosome segregation but disrupts polarity establishment and cytokinesis in mouse oocytes

    DEFF Research Database (Denmark)

    Wang, Zhen-Bo; Jiang, Zong-Zhe; Zhang, Qing-Hua

    2013-01-01

    Mammalian oocyte maturation is distinguished by highly asymmetric meiotic divisions during which a haploid female gamete is produced and almost all the cytoplasm is maintained in the egg for embryo development. Actin-dependent meiosis I spindle positioning to the cortex induces the formation...

  15. Inducible protective processes in animal systems XV: Hyperthermia enhances the Ethyl methanesulfonate induced adaptive response in meiotic cells of grasshopper Poecilocerus pictus

    Directory of Open Access Journals (Sweden)

    R. Venu

    2016-04-01

    Conclusion: There is a protection against EMS induced anomalies by hyperthermia in in vivo P. pictus. As far as our knowledge is concerned, this is the first report to demonstrate that hyperthermia enhances the EMS induced adaptive response in in vivo meiotic cells.

  16. Analysis of meiosis in SUN1 deficient mice reveals a distinct role of SUN2 in mammalian meiotic LINC complex formation and function.

    Directory of Open Access Journals (Sweden)

    Jana Link

    2014-02-01

    Full Text Available LINC complexes are evolutionarily conserved nuclear envelope bridges, composed of SUN (Sad-1/UNC-84 and KASH (Klarsicht/ANC-1/Syne/homology domain proteins. They are crucial for nuclear positioning and nuclear shape determination, and also mediate nuclear envelope (NE attachment of meiotic telomeres, essential for driving homolog synapsis and recombination. In mice, SUN1 and SUN2 are the only SUN domain proteins expressed during meiosis, sharing their localization with meiosis-specific KASH5. Recent studies have shown that loss of SUN1 severely interferes with meiotic processes. Absence of SUN1 provokes defective telomere attachment and causes infertility. Here, we report that meiotic telomere attachment is not entirely lost in mice deficient for SUN1, but numerous telomeres are still attached to the NE through SUN2/KASH5-LINC complexes. In Sun1(-/- meiocytes attached telomeres retained the capacity to form bouquet-like clusters. Furthermore, we could detect significant numbers of late meiotic recombination events in Sun1(-/- mice. Together, this indicates that even in the absence of SUN1 telomere attachment and their movement within the nuclear envelope per se can be functional.

  17. Individual and crossover effects of stress on adjustment in medical student marriages.

    Science.gov (United States)

    Katz, J; Monnier, J; Libet, J; Shaw, D; Beach, S R

    2000-07-01

    High-stress individuals may benefit from social support, although their support providers may be adversely affected via stress crossover effects. Individual and crossover effects of perceived stress within medical student marriages (n = 30) were investigated. Perceived spousal support was positively associated with individuals' own marital and emotional adjustment, attenuating stress effects. With regard to crossover effects, medical students' perceived stress was significantly associated with their spouses' emotional adjustment. Further, medical students' own emotional adjustment fully mediated this crossover effect. Results suggest that the contagion of negative affect may serve as a key mechanism through which stress crossover effects operate in marriage.

  18. DMFC performance and methanol cross-over: Experimental analysis and model validation

    Energy Technology Data Exchange (ETDEWEB)

    Casalegno, A.; Marchesi, R. [Dipartimento di Energia, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano (Italy)

    2008-10-15

    A combined experimental and modelling approach is proposed to analyze methanol cross-over and its effect on DMFC performance. The experimental analysis is performed in order to allow an accurate investigation of methanol cross-over influence on DMFC performance, hence measurements were characterized in terms of uncertainty and reproducibility. The findings suggest that methanol cross-over is mainly determined by diffusion transport and affects cell performance partly via methanol electro-oxidation at the cathode. The modelling analysis is carried out to further investigate methanol cross-over phenomenon. A simple model evaluates the effectiveness of two proposed interpretations regarding methanol cross-over and its effects. The model is validated using the experimental data gathered. Both the experimental analysis and the proposed and validated model allow a substantial step forward in the understanding of the main phenomena associated with methanol cross-over. The findings confirm the possibility to reduce methanol cross-over by optimizing anode feeding. (author)

  19. Investigation of iron spin crossover pressure in Fe-bearing MgO using hybrid functional

    Science.gov (United States)

    Cheng, Ya; Wang, Xianlong; Zhang, Jie; Yang, Kaishuai; Zhang, Chuanguo; Zeng, Zhi; Lin, Haiqin

    2018-04-01

    Pressure-induced spin crossover behaviors of Fe-bearing MgO were widely investigated by using an LDA  +  U functional for describing the strongly correlated Fe–O bonding. Moreover, the simulated spin crossover pressures depend on the applied U values, which are sensitive to environments and parameters. In this work, the spin crossover pressures of (Mg1‑x ,Fe x )O are investigated by using the hybrid functional with a uniform parameter. Our results indicate that the spin crossover pressures increase with increasing iron concentration. For example, the spin crossover pressure of (Mg0.03125,Fe0.96875)O and FeO was 56 GPa and 127 GPa, respectively. The calculated crossover pressures agreed well with the experimental observations. Therefore, the hybrid functional should be an effective method for describing the pressure-induced spin crossover behaviors in transition metal oxides.

  20. Persistent User Bias in Case-Crossover Studies in Pharmacoepidemiology

    DEFF Research Database (Denmark)

    Hallas, Jesper; Pottegård, Anton; Wang, Shirley

    2016-01-01

    Studying the effect of chronic medication exposure by means of a case-crossover design may result in an upward-biased odds ratio. In this study, our aim was to assess the occurrence of this bias and to evaluate whether it is remedied by including a control group (the case-time-control design...... for the retinal detachment controls were similar, leading to near-null case-time-control estimates for all 3 medication classes. For wrist fracture and stroke, the odds ratios were higher for cases than for controls, and case-time-control odds ratios were consistently above unity, thus implying significant...... residual bias. In case-crossover studies of medications, contamination by persistent users confers a moderate bias upward, which is partly remedied by using a control group. The optimal strategy for dealing with this problem is currently unknown....

  1. Assessing fluctuating evolutionary pressure in yeast and mammal evolutionary rate covariation using bioinformatics of meiotic protein genetic sequences

    Science.gov (United States)

    Dehipawala, Sunil; Nguyen, A.; Tremberger, G.; Cheung, E.; Holden, T.; Lieberman, D.; Cheung, T.

    2013-09-01

    The evolutionary rate co-variation in meiotic proteins has been reported for yeast and mammal using phylogenic branch lengths which assess retention, duplication and mutation. The bioinformatics of the corresponding DNA sequences could be classified as a diagram of fractal dimension and Shannon entropy. Results from biomedical gene research provide examples on the diagram methodology. The identification of adaptive selection using entropy marker and functional-structural diversity using fractal dimension would support a regression analysis where the coefficient of determination would serve as evolutionary pathway marker for DNA sequences and be an important component in the astrobiology community. Comparisons between biomedical genes such as EEF2 (elongation factor 2 human, mouse, etc), WDR85 in epigenetics, HAR1 in human specificity, clinical trial targeted cancer gene CD47, SIRT6 in spermatogenesis, and HLA-C in mosquito bite immunology demonstrate the diagram classification methodology. Comparisons to the SEPT4-XIAP pair in stem cell apoptosis, testesexpressed taste genes TAS1R3-GNAT3 pair, and amyloid beta APLP1-APLP2 pair with the yeast-mammal DNA sequences for meiotic proteins RAD50-MRE11 pair and NCAPD2-ICK pair have accounted for the observed fluctuating evolutionary pressure systematically. Regression with high R-sq values or a triangular-like cluster pattern for concordant pairs in co-variation among the studied species could serve as evidences for the possible location of common ancestors in the entropy-fractal dimension diagram, consistent with an example of the human-chimp common ancestor study using the FOXP2 regulated genes reported in human fetal brain study. The Deinococcus radiodurans R1 Rad-A could be viewed as an outlier in the RAD50 diagram and also in the free energy versus fractal dimension regression Cook's distance, consistent with a non-Earth source for this radiation resistant bacterium. Convergent and divergent fluctuating evolutionary

  2. Hyperon puzzle, hadron-quark crossover and massive neutron stars

    International Nuclear Information System (INIS)

    Masuda, Kota; Hatsuda, Tetsuo; Takatsuka, Tatsuyuki

    2016-01-01

    Bulk properties of cold and hot neutron stars are studied on the basis of the hadron-quark crossover picture where a smooth transition from the hadronic phase to the quark phase takes place at finite baryon density. By using a phenomenological equation of state (EOS) ''CRover'', which interpolates the two phases at around 3 times the nuclear matter density (ρ 0 ), it is found that the cold NSs with the gravitational mass larger than 2M CircleDot can be sustained. This is in sharp contrast to the case of the first-order hadron-quark transition. The radii of the cold NSs with the CRover EOS are in the narrow range (12.5 ± 0.5) km which is insensitive to the NS masses. Due to the stiffening of the EOS induced by the hadron-quark crossover, the central density of the NSs is at most 4 ρ 0 and the hyperon-mixing barely occurs inside the NS core. This constitutes a solution of the long-standing hyperon puzzle. The effect of color superconductivity (CSC) on the NS structures is also examined with the hadron-quark crossover. For the typical strength of the diquark attraction, a slight softening of the EOS due to two-flavor CSC (2SC) takes place and the maximum mass is reduced by about 0.2M CircleDot . The CRover EOS is generalized to the supernova matter at finite temperature to describe the hot NSs at birth. The hadron-quark crossover is found to decrease the central temperature of the hot NSs under isentropic condition. The gravitational energy release and the spin-up rate during the contraction from the hot NS to the cold NS are also estimated. (orig.)

  3. Hyperon puzzle, hadron-quark crossover and massive neutron stars

    Energy Technology Data Exchange (ETDEWEB)

    Masuda, Kota [The University of Tokyo, Department of Physics, Tokyo (Japan); Nishina Center, RIKEN, Theoretical Research Division, Wako (Japan); Hatsuda, Tetsuo [Nishina Center, RIKEN, Theoretical Research Division, Wako (Japan); The University of Tokyo, Kavli IPMU (WPI), Chiba (Japan); Takatsuka, Tatsuyuki [Nishina Center, RIKEN, Theoretical Research Division, Wako (Japan)

    2016-03-15

    Bulk properties of cold and hot neutron stars are studied on the basis of the hadron-quark crossover picture where a smooth transition from the hadronic phase to the quark phase takes place at finite baryon density. By using a phenomenological equation of state (EOS) ''CRover'', which interpolates the two phases at around 3 times the nuclear matter density (ρ{sub 0}), it is found that the cold NSs with the gravitational mass larger than 2M {sub CircleDot} can be sustained. This is in sharp contrast to the case of the first-order hadron-quark transition. The radii of the cold NSs with the CRover EOS are in the narrow range (12.5 ± 0.5) km which is insensitive to the NS masses. Due to the stiffening of the EOS induced by the hadron-quark crossover, the central density of the NSs is at most 4 ρ{sub 0} and the hyperon-mixing barely occurs inside the NS core. This constitutes a solution of the long-standing hyperon puzzle. The effect of color superconductivity (CSC) on the NS structures is also examined with the hadron-quark crossover. For the typical strength of the diquark attraction, a slight softening of the EOS due to two-flavor CSC (2SC) takes place and the maximum mass is reduced by about 0.2M {sub CircleDot}. The CRover EOS is generalized to the supernova matter at finite temperature to describe the hot NSs at birth. The hadron-quark crossover is found to decrease the central temperature of the hot NSs under isentropic condition. The gravitational energy release and the spin-up rate during the contraction from the hot NS to the cold NS are also estimated. (orig.)

  4. Vortex profiles and vortex interactions at the electroweak crossover

    OpenAIRE

    Chernodub, M. N.; Ilgenfritz, E. -M.; Schiller, A.

    1999-01-01

    Local correlations of Z-vortex operators with gauge and Higgs fields (lattice quantum vortex profiles) as well as vortex two-point functions are studied in the crossover region near a Higgs mass of 100 GeV within the 3D SU(2) Higgs model. The vortex profiles resemble certain features of the classical vortex solutions in the continuum. The vortex-vortex interactions are analogous to the interactions of Abrikosov vortices in a type-I superconductor.

  5. Crossover from Nonequilibrium Fractal Growth to Equilibrium Compact Growth

    DEFF Research Database (Denmark)

    Sørensen, Erik Schwartz; Fogedby, Hans C.; Mouritsen, Ole G.

    1988-01-01

    Solidification controlled by vacancy diffusion is studied by Monte Carlo simulations of a two-dimensional Ising model defined by a Hamiltonian which models a thermally driven fluid-solid phase transition. The nonequilibrium morphology of the growing solid is studied as a function of time as the s...... as the system relaxes into equilibrium described by a temperature. At low temperatures the model exhibits fractal growth at early times and crossover to compact solidification as equilibrium is approached....

  6. Elastic scattering crossovers from 50 to 175 GeV

    International Nuclear Information System (INIS)

    Anderson, R.L.; Ayres, D.S.; Barton, D.S.; Brenner, A.E.; Butler, J.; Cutts, D.; DeMarzo, C.; Diebold, R.; Elias, J.E.; Fines, J.; Friedman, J.I.; Gittelman, B.; Gottschalk, B.; Guerriero, L.; Gustavson, D.; Kendall, H.W.; Lanou, R.E.; Lavopa, P.; Levinson, L.J.; Litt, J.; Loh, E.; Maclay, G.J.; Maggi, G.; Massimo, J.T.; Meunier, R.; Mikenberg, G.; Nelson, B.; Posa, F.; Rich, K.; Ritson, D.M.; Rosenson, L.; Selvaggi, G.; Sogard, M.; Spinelli, P.; Verdier, R.; Waldner, F.; Weitsch, G.A.

    1976-01-01

    A comparison of K/sup plus-or-minus/p and p/sup plus-or-minus/p elastic scattering is made for incident energy 50 to 175 GeV. Average values of 0.19 +- 0.04 and 0.11 +- 0.02 GeV 2 were found for the invariant-momentum-transfer values of the Kp and pp crossover points, respectively

  7. Pressure and Temperature Spin Crossover Sensors with Optical Detection

    Science.gov (United States)

    Linares, Jorge; Codjovi, Epiphane; Garcia, Yann

    2012-01-01

    Iron(II) spin crossover molecular materials are made of coordination centres switchable between two states by temperature, pressure or a visible light irradiation. The relevant macroscopic parameter which monitors the magnetic state of a given solid is the high-spin (HS) fraction denoted nHS, i.e., the relative population of HS molecules. Each spin crossover material is distinguished by a transition temperature T1/2 where 50% of active molecules have switched to the low-spin (LS) state. In strongly interacting systems, the thermal spin switching occurs abruptly at T1/2. Applying pressure induces a shift from HS to LS states, which is the direct consequence of the lower volume for the LS molecule. Each material has thus a well defined pressure value P1/2. In both cases the spin state change is easily detectable by optical means thanks to a thermo/piezochromic effect that is often encountered in these materials. In this contribution, we discuss potential use of spin crossover molecular materials as temperature and pressure sensors with optical detection. The ones presenting smooth transitions behaviour, which have not been seriously considered for any application, are spotlighted as potential sensors which should stimulate a large interest on this well investigated class of materials. PMID:22666041

  8. Crossover phenomena in the critical range near magnetic ordering transition

    Science.gov (United States)

    Köbler, U.

    2018-05-01

    Among the most important issues of Renormalization Group (RG) theory are crossover events and relevant (or non-relevant) interactions. These terms are unknown to atomistic theories but they will be decisive for future field theories of magnetism. In this experimental study the importance of these terms for the critical dynamics above and below magnetic ordering transition is demonstrated on account of new analyses of published data. When crossover events are overlooked and critical data are fitted by a single power function of temperature over a temperature range including a crossover event, imprecise critical exponents result. The rather unsystematic and floating critical exponents reported in literature seem largely to be due to this problem. It is shown that for appropriate data analyses critical exponents are obtained that are to a good approximation rational numbers. In fact, rational critical exponents can be expected when spin dynamics is controlled by the bosons of the continuous magnetic medium (Goldstone bosons). The bosons are essentially magnetic dipole radiation generated by the precessing spins. As a result of the here performed data analyses, critical exponents for the magnetic order parameter of β = 1/2, 1/3, 1/4 and 1/6 are obtained. For the critical paramagnetic susceptibility the exponents are γ = 1 and γ = 4/3.

  9. Crossover integral equation theory for the liquid structure study

    International Nuclear Information System (INIS)

    Lai, S.K.; Chen, H.C.

    1994-08-01

    The main purpose of this work is to report on a calculation that describes the role of the long-range bridge function [H. Iyetomi and S. Ichimaru, Phys. Rev. A 25, 2434 (1982)] as applied to the study of structure of simple liquid metals. It was found here that this bridge function accounts pretty well for the major part of long-range interactions but is physically inadequate for describing the short-range part of liquid structure. To improve on the theory we have drawn attention to the crossover integral equation method which, in essence, amounts to adding to the above bridge function a short-range correction of bridge diagrams. The suggested crossover procedure has been tested for the case of liquid metal Cs. Remarkably good agreement with experiment was obtained confirming our conjecture that the crossover integral equation approach as stressed in this work is potentially an appropriate theory for an accurate study of liquid structure possibly for the supercooled liquid regime. (author). 21 refs, 3 figs

  10. Surface-environment effects in spin crossover solids

    Energy Technology Data Exchange (ETDEWEB)

    Gudyma, Iu., E-mail: yugudyma@gmail.com; Maksymov, A.

    2017-06-15

    Highlights: • The spin-crossover nanocrystals were described by modified Ising-like model. • The ligand field on the surface is a function of external fluctuations. • The thermal hysteresis with surface and bulk interactions of the lattice was studied. • The system behavior with fluctuating ligand field on the surface was examined. • The fluctuations enlarge the hysteresis, but smaller surface interaction narrows it. - Abstract: The impact of surface effects on thermal induced spin crossover phenomenon is a subject of a broad and current interest. Using the modified Ising-like model of spin crossover solids with the ligand field as function of the molecule’ positions and random component on surface by means of Metropolis Monte Carlo algorithm the thermal spin transition curves were calculated. The analysis of spin configuration during transition gives a general idea about contribution of molecules from the surface and inside the lattice into resulting magnetization of the systems. The behavior of hysteresis loop for various surface coupling and fluctuations strength has been described.

  11. Solving a meiotic LEGO puzzle: transverse filaments and the assembly of the synaptonemal complex in Caenorhabditis elegans.

    Science.gov (United States)

    Hawley, R Scott

    2011-10-01

    The structure of the meiosis-specific synaptonemal complex, which is perhaps the central visible characteristic of meiotic prophase, has been a matter of intense interest for decades. Although a general picture of the interactions between the transverse filament proteins that create this structure has emerged from studies in a variety of organisms, a recent analysis of synaptonemal complex structure in Caenorhabditis elegans by Schild-Prüfert et al. (2011) has provided the clearest picture of the structure of the architecture of a synaptonemal complex to date. Although the transverse filaments of the worm synaptonemal complex are assembled differently then those observed in yeast, mammalian, and Drosophila synaptonemal complexes, a comparison of the four assemblies shows that achieving the overall basic structure of the synaptonemal complex is far more crucial than conserving the structures of the individual transverse filaments.

  12. Molecular Basis of Meiotic Maturation and Apoptosis of Oocytes, Sperm-Oocyte Interactions and Early Cleavage of Embryos in Mice, Role of Phosphatidylinositol 3-Kinase, Mos, Fas-Fas Ligand, Integrinα6 and MAP Kinase

    OpenAIRE

    Yumi Hoshino; Ken-ichi Yamanaka; Ikuo Tomioka; Noritaka Fukunaga; Mehdi Abbasi; Eimei Sato

    2005-01-01

    The interaction between molecular biology and embryology made an extensive progress in the research on gametogenesis, fertilization and early embryogenesis in mice. In this article, molecules involving in meiotic maturation and apoptosis of oocytes, sperm-oocyte interactions and early cleavage of fertilized embryos in mice are described including our recent following experiments. 1) Phosphatidylinositol 3-kinase and Akt participate in the follicle stimulating hormone-induced meiotic maturatio...

  13. Quantification and Sequencing of Crossover Recombinant Molecules from Arabidopsis Pollen DNA.

    Science.gov (United States)

    Choi, Kyuha; Yelina, Nataliya E; Serra, Heïdi; Henderson, Ian R

    2017-01-01

    During meiosis, homologous chromosomes undergo recombination, which can result in formation of reciprocal crossover molecules. Crossover frequency is highly variable across the genome, typically occurring in narrow hotspots, which has a significant effect on patterns of genetic diversity. Here we describe methods to measure crossover frequency in plants at the hotspot scale (bp-kb), using allele-specific PCR amplification from genomic DNA extracted from the pollen of F 1 heterozygous plants. We describe (1) titration methods that allow amplification, quantification and sequencing of single crossover molecules, (2) quantitative PCR methods to more rapidly measure crossover frequency, and (3) application of high-throughput sequencing for study of crossover distributions within hotspots. We provide detailed descriptions of key steps including pollen DNA extraction, prior identification of hotspot locations, allele-specific oligonucleotide design, and sequence analysis approaches. Together, these methods allow the rate and recombination topology of plant hotspots to be robustly measured and compared between varied genetic backgrounds and environmental conditions.

  14. Critical crossover phenomena in compatible polymer blends studied with SANS

    DEFF Research Database (Denmark)

    Schwahn, D.; Janssen, S.; Willner, L.

    1995-01-01

    Polymer blends show a much larger 3d-Ising regime, e.g. a much larger Ginzburg number Gi than predicted by the Ginzburg criterion. This discrepancy is supposed to be explained by the compressibility or the free volume of the blend. In this paper we present and discuss the Gi number of polymer...... on monomeric microstructure and on pressure. This clearly shows that Gi is not a universal function. The observed strong decrease of Gi with pressure is a clear experimental proof that the critical crossover behaviour in polymer blends is indeed strongly influenced by the compressibility or free volume...

  15. BCS-BEC crossover in spatially modulated fermionic condensates

    International Nuclear Information System (INIS)

    Sedrakian, Armen

    2011-01-01

    Several novel multi-component fermionic condensates show universal behavior under imbalance in the number of fermionic species. Here I discuss their phase structure, thermodynamics, and the transition from the weak (BCS) to strong (BEC) coupling regime. The inhomogeneous superconducting phases are illustrated on the example of the Fulde-Ferrell phase which appears in the weak coupling regime, at low temperatures and large asymmetries. The inhomogeneous phases persist through the crossover up to (and possibly beyond) the transition to the strong coupling regime.

  16. BCS-BEC crossover in spatially modulated fermionic condensates

    Energy Technology Data Exchange (ETDEWEB)

    Sedrakian, Armen, E-mail: sedrakian@th.physik.uni-frankfurt.de [Institute for Theoretical Physics, J. W. Goethe-University, Max-von-Laue-Str. 1, 60438 Frankfurt am Main (Germany)

    2011-09-16

    Several novel multi-component fermionic condensates show universal behavior under imbalance in the number of fermionic species. Here I discuss their phase structure, thermodynamics, and the transition from the weak (BCS) to strong (BEC) coupling regime. The inhomogeneous superconducting phases are illustrated on the example of the Fulde-Ferrell phase which appears in the weak coupling regime, at low temperatures and large asymmetries. The inhomogeneous phases persist through the crossover up to (and possibly beyond) the transition to the strong coupling regime.

  17. Crossover in tunneling hops in systems of strongly localized electrons

    International Nuclear Information System (INIS)

    Lien Nguyen, V.; Gamietea, A.D.

    1995-11-01

    Accurate Monte-Carlo simulation data show a consistent crossover in different characters of tunneling hops in two-dimensional systems of strongly localized electrons in the presence of scattering and quantum interference of hopping paths. The results also suggest a negative answer to the question whether there is a two-dimensional sign phase transition. The fractal behaviour observed in the direction perpendicular to the hopping direction is found to be similar to that for eigenstates in one-dimensional localized systems. (author). 16 refs, 6 figs

  18. Goldstone and Higgs Hydrodynamics in the BCS–BEC Crossover

    Directory of Open Access Journals (Sweden)

    Luca Salasnich

    2017-06-01

    Full Text Available We discuss the derivation of a low-energy effective field theory of phase (Goldstone and amplitude (Higgs modes of the pairing field from a microscopic theory of attractive fermions. The coupled equations for Goldstone and Higgs fields are critically analyzed in the Bardeen–Cooper–Schrieffer (BCS-to-Bose–Einstein condensate (BEC crossover—both in three spatial dimensions and in two spatial dimensions. The crucial role of pair fluctuations is investigated, and the beyond-mean-field Gaussian theory of the BCS–BEC crossover is compared with available experimental data of the two-dimensional ultracold Fermi superfluid.

  19. The meiotic consequences of chromosomal aberrations induced by separate and simultaneous applications of gamma rays and NMU in lentil (Lens culinaris Med.)

    International Nuclear Information System (INIS)

    Dixit, Pratibha; Dubey, D.K.

    1983-01-01

    Certain meiotic abnormalities were induced by the application of 5, 10 or 15 Kr of gamma rays and/or 0.02 percent of NMU on seeds of lentil (Lens culinaris Med.) var. T36. Univalents, quadrivalents or higher multivalent associations were induced by gamma rays individually or in combination with NMU, while no such associations were recorded in plants treated with NMU alone. But nucleolar fragmentation, chromatin bridges and non-orientation of chromosome fragments were induced by both the mutagens. The percentage of cells showing meiotic abnormalities in the gamma ray treatments increased with an increase in the irradiation dose, however, the combined treatments of the two mutagens did not show a synergestic influence of the two mutagens in inducing such abnormalities. (author)

  20. Effects of selected endocrine disruptors on meiotic maturation, cumulus expansion, syntesis of hyaluronan and progesterone by porcine oocyte-cumulus complexes

    Czech Academy of Sciences Publication Activity Database

    Mlynarčíková, A.; Nagyová, Eva; Ficková, M.; Scsuková, S.

    2009-01-01

    Roč. 23, - (2009), s. 371-377 ISSN 0887-2333 R&D Projects: GA ČR GA305/05/0960 Grant - others:VEGA(SK) 2/6171/26; EU(XE) QLK4-CT-2002-02637 Institutional research plan: CEZ:AV0Z50450515 Keywords : oocyte-cumulus complex * meiotic maturation * cumulus expansion Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.060, year: 2009

  1. Cows are not mice: the role of cyclic AMP, phosphodiesterases, and adenosine monophosphate-activated protein kinase in the maintenance of meiotic arrest in bovine oocytes.

    Science.gov (United States)

    Bilodeau-Goeseels, Sylvie

    2011-01-01

    Meiotic maturation in mammalian oocytes is initiated during fetal development, and is then arrested at the dictyate stage - possibly for several years. Oocyte meiosis resumes in preovulatory follicles in response to the lutenizing hormone (LH) surge or spontaneously when competent oocytes are removed from follicles and cultured. The mechanisms involved in meiotic arrest and resumption in bovine oocytes are not fully understood, and several studies point to important differences between oocytes from rodent and livestock species. This paper reviews earlier and contemporary studies on the effects of cAMP-elevating agents and phosphodiesterase (PDE) enzyme inhibitors on the maintenance of meiotic arrest in bovine oocytes in vitro. Contrary to results obtained with mouse oocytes, bovine oocyte meiosis is inhibited by activators of the energy sensor adenosine monophosphate-activated protein kinase (AMPK, mammalian gene PRKA), which is activated by AMP, the degradation product of cAMP. It is not clear whether or not the effects were due to AMPK activation, and they may depend on culture conditions. Evidence suggests that other signaling pathways (for example, the cGMP/nitric oxide pathway) are involved in bovine oocyte meiotic arrest, but further studies are needed to understand the interactions between the signaling pathways that lead to maturation promoting factor (MPF) being inactive or active. An improved understanding of the mechanisms involved in the control of bovine oocyte meiosis will facilitate better control of the process in vitro, resulting in increased developmental competence and increased efficiency of in vitro embryo production procedures. Copyright © 2011 Wiley Periodicals, Inc.

  2. Budding yeast ATM/ATR control meiotic double-strand break (DSB levels by down-regulating Rec114, an essential component of the DSB-machinery.

    Directory of Open Access Journals (Sweden)

    Jesús A Carballo

    2013-06-01

    Full Text Available An essential feature of meiosis is Spo11 catalysis of programmed DNA double strand breaks (DSBs. Evidence suggests that the number of DSBs generated per meiosis is genetically determined and that this ability to maintain a pre-determined DSB level, or "DSB homeostasis", might be a property of the meiotic program. Here, we present direct evidence that Rec114, an evolutionarily conserved essential component of the meiotic DSB-machinery, interacts with DSB hotspot DNA, and that Tel1 and Mec1, the budding yeast ATM and ATR, respectively, down-regulate Rec114 upon meiotic DSB formation through phosphorylation. Mimicking constitutive phosphorylation reduces the interaction between Rec114 and DSB hotspot DNA, resulting in a reduction and/or delay in DSB formation. Conversely, a non-phosphorylatable rec114 allele confers a genome-wide increase in both DSB levels and in the interaction between Rec114 and the DSB hotspot DNA. These observations strongly suggest that Tel1 and/or Mec1 phosphorylation of Rec114 following Spo11 catalysis down-regulates DSB formation by limiting the interaction between Rec114 and DSB hotspots. We also present evidence that Ndt80, a meiosis specific transcription factor, contributes to Rec114 degradation, consistent with its requirement for complete cessation of DSB formation. Loss of Rec114 foci from chromatin is associated with homolog synapsis but independent of Ndt80 or Tel1/Mec1 phosphorylation. Taken together, we present evidence for three independent ways of regulating Rec114 activity, which likely contribute to meiotic DSBs-homeostasis in maintaining genetically determined levels of breaks.

  3. Budding Yeast ATM/ATR Control Meiotic Double-Strand Break (DSB) Levels by Down-Regulating Rec114, an Essential Component of the DSB-machinery

    Science.gov (United States)

    Carballo, Jesús A.; Panizza, Silvia; Serrentino, Maria Elisabetta; Johnson, Anthony L.; Geymonat, Marco; Borde, Valérie; Klein, Franz; Cha, Rita S.

    2013-01-01

    An essential feature of meiosis is Spo11 catalysis of programmed DNA double strand breaks (DSBs). Evidence suggests that the number of DSBs generated per meiosis is genetically determined and that this ability to maintain a pre-determined DSB level, or “DSB homeostasis”, might be a property of the meiotic program. Here, we present direct evidence that Rec114, an evolutionarily conserved essential component of the meiotic DSB-machinery, interacts with DSB hotspot DNA, and that Tel1 and Mec1, the budding yeast ATM and ATR, respectively, down-regulate Rec114 upon meiotic DSB formation through phosphorylation. Mimicking constitutive phosphorylation reduces the interaction between Rec114 and DSB hotspot DNA, resulting in a reduction and/or delay in DSB formation. Conversely, a non-phosphorylatable rec114 allele confers a genome-wide increase in both DSB levels and in the interaction between Rec114 and the DSB hotspot DNA. These observations strongly suggest that Tel1 and/or Mec1 phosphorylation of Rec114 following Spo11 catalysis down-regulates DSB formation by limiting the interaction between Rec114 and DSB hotspots. We also present evidence that Ndt80, a meiosis specific transcription factor, contributes to Rec114 degradation, consistent with its requirement for complete cessation of DSB formation. Loss of Rec114 foci from chromatin is associated with homolog synapsis but independent of Ndt80 or Tel1/Mec1 phosphorylation. Taken together, we present evidence for three independent ways of regulating Rec114 activity, which likely contribute to meiotic DSBs-homeostasis in maintaining genetically determined levels of breaks. PMID:23825959

  4. Spectropolarimetry of magnetic stars. IV. The crossover effect.

    Science.gov (United States)

    Mathys, G.

    1995-01-01

    This paper is devoted to the study of the crossover effect in magnetic Ap stars. It is shown that this effect can be measured by the second order moment about their centre of the profiles of spectral lines recorded in the Stokes parameter V. The interpretation of these measurements in terms of magnetic field is developed. It is shown that one can derive from them a quantity called the mean asymmetry of the longitudinal magnetic field, which is the first moment of the component of the magnetic field along the line of sight, about the plane defined by the line of sight and the stellar rotation axis. The consistency of the determination of this quantity with that of the mean longitudinal magnetic field from measurements of wavelength shifts of lines between right and left circular polarization is demonstrated. This technique of analysis is applied to observations of a sample of 29 stars, among which 10 have a detectable crossover effect. For 8 of them, the available observational data allow the study of the variations of the asymmetry of the longitudinal field with rotation phase. In most cases, this variation is sinusoidal and essentially symmetric about 0, and it occurs in quadrature with the variation of the mean longitudinal field. A more complex behaviour is definitely observed in HD 147010 and HD 175362, where the variation of the asymmetry of the longitudinal field is better represented by the superposition of two sinusoids, one with the rotation frequency of the star, and the other with twice that frequency.

  5. Dimensional BCS-BEC crossover in ultracold Fermi gases

    Energy Technology Data Exchange (ETDEWEB)

    Boettcher, Igor

    2014-12-10

    We investigate thermodynamics and phase structure of ultracold Fermi gases, which can be realized and measured in the laboratory with modern trapping techniques. We approach the subject from a both theoretical and experimental perspective. Central to the analysis is the systematic comparison of the BCS-BEC crossover of two-component fermions in both three and two dimensions. A dimensional reduction can be achieved in experiments by means of highly anisotropic traps. The Functional Renormalization Group (FRG) allows for a description of both cases in a unified theoretical framework. In three dimensions we discuss with the FRG the influence of high momentum particles onto the density, extend previous approaches to the Unitary Fermi Gas to reach quantitative precision, and study the breakdown of superfluidity due to an asymmetry in the population of the two fermion components. In this context we also investigate the stability of the Sarma phase. For the two-dimensional system scattering theory in reduced dimension plays an important role. We present both the theoretically as well as experimentally relevant aspects thereof. After a qualitative analysis of the phase diagram and the equation of state in two dimensions with the FRG we describe the experimental determination of the phase diagram of the two-dimensional BCS-BEC crossover in collaboration with the group of S. Jochim at PI Heidelberg.

  6. Meiotic gene conversion mutants in Saccharomyces cerevisiae. I. Isolation and characterization of PMS1-1 and PMS1-2

    International Nuclear Information System (INIS)

    Williamson, M.S.; Game, J.C.; Fogel, S.

    1985-01-01

    The PMS1 mutants, isolated on the basis of sharply elevated meiotic prototroph frequencies for two closely linked HIS4 alleles, display pleiotropic phenotypes in meiotic and mitotic cells. Two isolates carrying recessive mutations in PMS1 were characterized. They identify a function required to maintain low postmeiotic segregation (PMS) frequencies at many heterozygous sites. In addition, they are mitotic mutators. In mutant diploids, spore viability is reduced, and among survivors, gene conversion and postmeiotic segregation frequencies are increased, but reciprocal exchange frequencies are not affected. The conversion event pattern is also dramatically changed in multiply marked regions in PMS1 homozygotes. The PMS1 locus maps near MET4 on chromosome XIV. The PMS1 gene may identify an excision-resynthesis long patch mismatch correction function or a function that facilitates correction tract elongation. The PMS1 gene product may also play an important role in spontaneous mitotic mutation avoidance and correction of mismatches in heteroduplex DNA formed during spontaneous and UV-induced mitotic recombination. Based on meiotic recombination models emphasizing mismatch correction in heteroduplex DNA intermediates, this interpretation is favored, but alternative interpretations involving longer recombination intermediates in the mutants are also considered

  7. A single-item inventory model for expected inventory order crossovers

    NARCIS (Netherlands)

    Riezebos, J.; Gaalman, G.J.C.

    2009-01-01

    Expected inventory order crossovers Occur if at the moment of ordering it is expected that orders will not arrive in the sequence they are ordered. Recent research has shown that (it) expected inventory order crossovers will be encountered more frequently in future, and that (b) use of a myopic

  8. The crossover of work engagement between working couples : a closer look at the role of empathy

    NARCIS (Netherlands)

    Bakker, A.B.; Demerouti, E.

    2009-01-01

    Purpose – The purpose of this paper is to examine the role of empathy (empathic concern and perspective taking) in the crossover process. Specifically, it aims to test whether empathy moderates the crossover effect of women's work engagement to their men's work engagement. Additionally, it seeks to

  9. 50 CFR 660.320 - Open access fishery-crossover provisions.

    Science.gov (United States)

    2010-10-01

    ... 50 Wildlife and Fisheries 9 2010-10-01 2010-10-01 false Open access fishery-crossover provisions... West Coast Groundfish-Open Access Fisheries § 660.320 Open access fishery—crossover provisions. (a) Operating in both limited entry and open access fisheries. See provisions at § 660.60, subpart C. (b...

  10. Fluoropolymer-coated dacron versus PTFE grafts for femorofemoral crossover bypass: randomised trial

    DEFF Research Database (Denmark)

    Eiberg, JP; Røder, Ole Christian; Stahl-Madsen, M

    2006-01-01

    To investigate whether patency of a thin walled 8 mm fluoropassivated Dacron graft was similar to that of a standard 8mm PTFE graft for femorofemoral crossover bypass surgery.......To investigate whether patency of a thin walled 8 mm fluoropassivated Dacron graft was similar to that of a standard 8mm PTFE graft for femorofemoral crossover bypass surgery....

  11. Solution Theory of Ginzburg-Landau Theory on BCS-BEC Crossover

    Directory of Open Access Journals (Sweden)

    Shuhong Chen

    2014-01-01

    Full Text Available We establish strong solution theory of time-dependent Ginzburg-Landau (TDGL systems on BCS-BEC crossover. By the properties of Besov, Sobolev spaces, and Fourier functions and the method of bootstrapping argument, we deduce that the global existence of strong solutions to time-dependent Ginzburg-Landau systems on BCS-BEC crossover in various spatial dimensions.

  12. Probing the crossover in CO desorption from single crystal to nanoparticulate Ru model catalysts

    DEFF Research Database (Denmark)

    Murphy, Shane; Strebel, Christian Ejersbo; Vendelbo, Søren Bastholm

    2011-01-01

    Crossover in CO desorption behavior and nanoscale structure probed with STM from ruthenium single crystals to PVD and mass-selected nanoparticles.......Crossover in CO desorption behavior and nanoscale structure probed with STM from ruthenium single crystals to PVD and mass-selected nanoparticles....

  13. Differential Effects of Red Meat/Refined Grain Diet and Dairy/Chicken/Nuts/Whole Grain Diet on Glucose, Insulin and Triglyceride in a Randomized Crossover Study

    OpenAIRE

    Kim, Yoona; Keogh, Jennifer B.; Clifton, Peter M.

    2016-01-01

    Epidemiological studies suggest that a diet high in processed meat, with a high glycemic index is associated with an increased risk of type 2 diabetes. It is not clear if this is due to altered insulin sensitivity or an enhanced postprandial glucose. We aimed to compare the acute metabolic response of two different types of meals after ingestion of the matching diet for four weeks. The study was a randomized, crossover acute meal study. Volunteers consumed either a red meat/refined grain meal...

  14. Meiotic restitution mechanisms involved in the formation of 2n pollen in Agave tequilana Weber and Agave angustifolia Haw.

    Science.gov (United States)

    Gómez-Rodríguez, Víctor Manuel; Rodríguez-Garay, Benjamín; Barba-Gonzalez, Rodrigo

    2012-01-01

    A cytological analysis of the microsporogenesis was carried out in the Agave tequilana and A. angustifolia species. Several abnormalities such as chromosomal bridges, lagging chromosomes, micronuclei, monads, dyads and triads were found. The morphological analysis of the pollen, together with the above-mentioned 2n microspores, allowed us to confirm the presence of 2n pollen as well as its frequency. In both A. tequilana and A. angustifolia two different mechanisms were observed: the first mechanism, a failure in the cytokinesis in meiosis II caused the formation of dyads with two 2n cells and triads containing two n cells and one 2n cell; the second mechanism, involves an abnormal spindle, which caused the formation of triads with two n cells and one 2n cell. Likewise, the presence of monads was detected in both species, these, might be caused by a failure of the cytokinesis in both meiotic divisions. This is the first report about the presence of a Second Division Restitution mechanism (SDR) which causes the formation of 2n pollen in the genus Agave. The genetic implications of the presence of 2n pollen in the genus Agave are discussed.

  15. Improving ethanol fermentation performance of Saccharomyces cerevisiae in very high-gravity fermentation through chemical mutagenesis and meiotic recombination

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jing-Jing; Ding, Wen-Tao; Zhang, Guo-Chang; Wang, Jing-Yu [Tianjin Univ. (China). Dept. of Biochemical Engineering

    2011-08-15

    Genome shuffling is an efficient way to improve complex phenotypes under the control of multiple genes. For the improvement of strain's performance in very high-gravity (VHG) fermentation, we developed a new method of genome shuffling. A diploid ste2/ste2 strain was subjected to EMS (ethyl methanesulfonate) mutagenesis followed by meiotic recombination-mediated genome shuffling. The resulting haploid progenies were intrapopulation sterile and therefore haploid recombinant cells with improved phenotypes were directly selected under selection condition. In VHG fermentation, strain WS1D and WS5D obtained by this approach exhibited remarkably enhanced tolerance to ethanol and osmolarity, increased metabolic rate, and 15.12% and 15.59% increased ethanol yield compared to the starting strain W303D, respectively. These results verified the feasibility of the strain improvement strategy and suggested that it is a powerful and high throughput method for development of Saccharomyces cerevisiae strains with desired phenotypes that is complex and cannot be addressed with rational approaches. (orig.)

  16. Dynamic maintenance of asymmetric meiotic spindle position through Arp2/3 complex-driven cytoplasmic streaming in mouse oocytes

    Science.gov (United States)

    Yi, Kexi; Unruh, Jay R.; Deng, Manqi; Slaughter, Brian D.; Rubinstein, Boris; Li, Rong

    2012-01-01

    Mature mammalian oocytes are poised for the completion of second polar body extrusion upon fertilization by positioning the metaphase spindle in close proximity to an actomyosin-rich cortical cap. Loss of this spindle position asymmetry is often associated with poor oocyte quality and infertility 1–3. Here, we report a novel role for the Arp2/3 actin nucleation complex in the maintenance of asymmetric spindle position in mature mouse oocytes. The Arp2/3 complex localizes to the cortical cap in a Ran GTPase-dependent manner and accounts for the nucleation of the majority of actin filaments in both the cortical cap and a cytoplasmic actin network. Inhibition of Arp2/3 complex activity or localization leads to rapid dissociation of the spindle from the cortex. High resolution live imaging and spatiotemporal image correlation spectroscopy (STICS) analysis reveal that in normal oocytes actin filaments flow continuously away from the Arp2/3-rich cortex, generating a cytoplamic streaming that results in a net pushing force on the spindle toward the actomyosin cap. Arp2/3 inhibition not only diminishes this actin flow and cytoplamic streaming but also enables a reverse streaming driven by myosin-II-based cortical contraction, leading to spindle movement away from the cortex. We conclude that the Arp2/3 complex maintains asymmetric meiotic spindle position by generating an actin polymerization-driven cytoplamic streaming and by suppressing a counteracting force from myosin-II-based contractility. PMID:21874009

  17. Molecular signature of epistatic selection: interrogating genetic interactions in the sex-ratio meiotic drive of Drosophila simulans.

    Science.gov (United States)

    Chevin, Luis-Miguel; Bastide, Héloïse; Montchamp-Moreau, Catherine; Hospital, Frédéric

    2009-06-01

    Fine scale analyses of signatures of selection allow assessing quantitative aspects of a species' evolutionary genetic history, such as the strength of selection on genes. When several selected loci lie in the same genomic region, their epistatic interactions may also be investigated. Here, we study how the neutral polymorphism pattern was shaped by two close recombining loci that cause 'sex-ratio' meiotic drive in Drosophila simulans, as an example of strong selection with potentially strong epistasis. We compare the polymorphism data observed in a natural population with the results of forward stochastic simulations under several contexts of epistasis between the candidate loci for the drive. We compute the likelihood of different possible scenarios, in order to determine which configuration is most consistent with the data. Our results highlight that fine scale analyses of well-chosen candidate genomic regions provide information-rich data that can be used to investigate the genotype-phenotype-fitness map, which can hardly be studied in genome-wide analyses. We also emphasize that initial conditions and time of observation (here, time after the interruption of a partial selective sweep) are crucial parameters in the interpretation of real data, while these are often overlooked in theoretical studies.

  18. Hybrid Genetic Algorithm with Multiparents Crossover for Job Shop Scheduling Problems

    Directory of Open Access Journals (Sweden)

    Noor Hasnah Moin

    2015-01-01

    Full Text Available The job shop scheduling problem (JSSP is one of the well-known hard combinatorial scheduling problems. This paper proposes a hybrid genetic algorithm with multiparents crossover for JSSP. The multiparents crossover operator known as extended precedence preservative crossover (EPPX is able to recombine more than two parents to generate a single new offspring distinguished from common crossover operators that recombine only two parents. This algorithm also embeds a schedule generation procedure to generate full-active schedule that satisfies precedence constraints in order to reduce the search space. Once a schedule is obtained, a neighborhood search is applied to exploit the search space for better solutions and to enhance the GA. This hybrid genetic algorithm is simulated on a set of benchmarks from the literatures and the results are compared with other approaches to ensure the sustainability of this algorithm in solving JSSP. The results suggest that the implementation of multiparents crossover produces competitive results.

  19. Crossover Phenomena in Detrended Fluctuation Analysis Used in Financial Markets

    International Nuclear Information System (INIS)

    Ma Shihao

    2009-01-01

    A systematic analysis of Shanghai and Japan stock indices for the period of Jan. 1984 to Dec. 2005 is performed. After stationarity is verified by ADF (Augmented Dickey-Fuller) test, the power spectrum of the data exhibits a power law decay as a whole characterized by 1/f β processes with possible long range correlations. Subsequently, by using the method of detrended fluctuation analysis (DFA) of the general volatility in the stock markets, we find that the long-range correlations are occurred among the return series and the crossover phenomena exhibit in the results obviously. Further, Shanghai stock market shows long-range correlations in short time scale and shows short-range correlations in long time scale. Whereas, for Japan stock market, the data behaves oppositely absolutely. Last, we compare the varying of scale exponent in large volatility between two stock markets. All results obtained may indicate the possibility of characteristic of multifractal scaling behavior of the financial markets.

  20. A crossover in anisotropic nanomechanochemistry of van der Waals crystals

    International Nuclear Information System (INIS)

    Shimamura, Kohei; Misawa, Masaaki; Li, Ying; Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya; Shimojo, Fuyuki

    2015-01-01

    In nanoscale mechanochemistry, mechanical forces selectively break covalent bonds to essentially control chemical reactions. An archetype is anisotropic detonation of layered energetic molecular crystals bonded by van der Waals (vdW) interactions. Here, quantum molecular dynamics simulations reveal a crossover of anisotropic nanomechanochemistry of vdW crystal. Within 10 −13 s from the passage of shock front, lateral collision produces NO 2 via twisting and bending of nitro-groups and the resulting inverse Jahn-Teller effect, which is mediated by strong intra-layer hydrogen bonds. Subsequently, as we transition from heterogeneous to homogeneous mechanochemical regimes around 10 −12 s, shock normal to multilayers becomes more reactive, producing H 2 O assisted by inter-layer N-N bond formation. These time-resolved results provide much needed atomistic understanding of nanomechanochemistry that underlies a wider range of technologies

  1. Crossover between spin swapping and Hall effect in disordered systems

    KAUST Repository

    Saidaoui, Hamed Ben Mohamed

    2015-07-16

    We theoretically study the crossover between spin Hall effect and spin swapping, a recently predicted phenomenon that consists of the interchange between the current flow and its spin polarization directions [M. B. Lifshits and M. I. Dyakonov, Phys. Rev. Lett. 103, 186601 (2009)]. Using a tight-binding model with spin-orbit coupled disorder, spin Hall effect, spin relaxation, and spin swapping are treated on equal footing. We demonstrate that spin swapping and spin Hall effect present very different dependencies as a function of the spin-orbit coupling and disorder strengths and confirm that the former exceeds the latter in the parameter range considered. Three setups are proposed for the experimental observation of the spin swapping effect.

  2. BCS-BEC crossover in a system of microcavity polaritons

    International Nuclear Information System (INIS)

    Keeling, Jonathan; Eastham, P.R.; Szymanska, M.H.; Littlewood, P.B.

    2005-01-01

    We investigate the thermodynamics and signatures of a polariton condensate over a range of densities, using a model of microcavity polaritons with internal structure. We determine a phase diagram for this system including fluctuation corrections to the mean-field theory. At low densities the condensation temperature T c behaves like that for point bosons. At higher densities, when T c approaches the Rabi splitting, T c deviates from the form for point bosons, and instead approaches the result of a BCS-like mean-field theory. This crossover occurs at densities much less than the Mott density. We show that current experiments are in a density range where the phase boundary is described by the BCS-like mean-field boundary. We investigate the influence of inhomogeneous broadening and detuning of excitons on the phase diagram

  3. Conjugate schema and basis representation of crossover and mutation operators.

    Science.gov (United States)

    Kazadi, S T

    1998-01-01

    In genetic search algorithms and optimization routines, the representation of the mutation and crossover operators are typically defaulted to the canonical basis. We show that this can be influential in the usefulness of the search algorithm. We then pose the question of how to find a basis for which the search algorithm is most useful. The conjugate schema is introduced as a general mathematical construct and is shown to separate a function into smaller dimensional functions whose sum is the original function. It is shown that conjugate schema, when used on a test suite of functions, improves the performance of the search algorithm on 10 out of 12 of these functions. Finally, a rigorous but abbreviated mathematical derivation is given in the appendices.

  4. Critical behavior and dimension crossover of pion superfluidity

    Science.gov (United States)

    Wang, Ziyue; Zhuang, Pengfei

    2016-09-01

    We investigate the critical behavior of pion superfluidity in the framework of the functional renormalization group (FRG). By solving the flow equations in the SU(2) linear sigma model at finite temperature and isospin density, and making comparison with the fixed point analysis of a general O (N ) system with continuous dimension, we find that the pion superfluidity is a second order phase transition subject to an O (2 ) universality class with a dimension crossover from dc=4 to dc=3 . This phenomenon provides a concrete example of dimension reduction in thermal field theory. The large-N expansion gives a temperature independent critical exponent β and agrees with the FRG result only at zero temperature.

  5. Modeling the quantum to classical crossover in topologically disordered networks

    International Nuclear Information System (INIS)

    Schijven, P; Kohlberger, J; Blumen, A; Mülken, O

    2012-01-01

    We model transport in topologically disordered networks that are subjected to an environment that induces classical diffusion. The dynamics is phenomenologically described within the framework of the recently introduced quantum stochastic walk, allowing study of the crossover between coherent transport and purely classical diffusion. To study the transport efficiency, we connect our system with a source and a drain and provide a detailed analysis of their effects. We find that the coupling to the environment removes all effects of localization and quickly leads to classical transport. Furthermore, we find that on the level of the transport efficiency, the system can be well described by reducing it to a two-node network (a dimer). (paper)

  6. A crossover in anisotropic nanomechanochemistry of van der Waals crystals

    Energy Technology Data Exchange (ETDEWEB)

    Shimamura, Kohei [Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan); Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Graduate School of System Informatics, Kobe University, Kobe 657-8501 (Japan); Misawa, Masaaki [Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan); Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Li, Ying [Argonne Leadership Computing Facility, Argonne National Laboratory, Argonne, Illinois 60439 (United States); Kalia, Rajiv K.; Nakano, Aiichiro; Vashishta, Priya [Collaboratory for Advanced Computing and Simulations, Department of Physics and Astronomy, Department of Computer Science, Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089-0242 (United States); Shimojo, Fuyuki [Department of Physics, Kumamoto University, Kumamoto 860-8555 (Japan)

    2015-12-07

    In nanoscale mechanochemistry, mechanical forces selectively break covalent bonds to essentially control chemical reactions. An archetype is anisotropic detonation of layered energetic molecular crystals bonded by van der Waals (vdW) interactions. Here, quantum molecular dynamics simulations reveal a crossover of anisotropic nanomechanochemistry of vdW crystal. Within 10{sup −13} s from the passage of shock front, lateral collision produces NO{sub 2} via twisting and bending of nitro-groups and the resulting inverse Jahn-Teller effect, which is mediated by strong intra-layer hydrogen bonds. Subsequently, as we transition from heterogeneous to homogeneous mechanochemical regimes around 10{sup −12} s, shock normal to multilayers becomes more reactive, producing H{sub 2}O assisted by inter-layer N-N bond formation. These time-resolved results provide much needed atomistic understanding of nanomechanochemistry that underlies a wider range of technologies.

  7. Crossover between spin swapping and Hall effect in disordered systems

    KAUST Repository

    Saidaoui, Hamed Ben Mohamed; Otani, Y.; Manchon, Aurelien

    2015-01-01

    We theoretically study the crossover between spin Hall effect and spin swapping, a recently predicted phenomenon that consists of the interchange between the current flow and its spin polarization directions [M. B. Lifshits and M. I. Dyakonov, Phys. Rev. Lett. 103, 186601 (2009)]. Using a tight-binding model with spin-orbit coupled disorder, spin Hall effect, spin relaxation, and spin swapping are treated on equal footing. We demonstrate that spin swapping and spin Hall effect present very different dependencies as a function of the spin-orbit coupling and disorder strengths and confirm that the former exceeds the latter in the parameter range considered. Three setups are proposed for the experimental observation of the spin swapping effect.

  8. Workaholism and relationship quality: a spillover-crossover perspective.

    Science.gov (United States)

    Bakker, Arnold B; Demerouti, Evangelia; Burke, Ronald

    2009-01-01

    This study of 168 dual-earner couples examined the relationship between workaholism and relationship satisfaction. More specifically, on the basis of the literature, it was hypothesized that workaholism is positively related to work-family conflict. In addition, the authors predicted that workaholism is related to reduced support provided to the partner, through work-family conflict, and that individuals who receive considerable support from their partners are more satisfied with their relationship. Finally, the authors hypothesized direct crossover of relationship satisfaction between partners. The results of structural equation modeling analyses using the matched responses of both partners supported these hypotheses. Moreover, in line with predictions, the authors found that gender did not affect the strength of the relationships in the proposed model. The authors discuss workplace interventions as possible ways to help workaholics and their partners.

  9. Design and numerical characterization of a crossover EBIS

    Energy Technology Data Exchange (ETDEWEB)

    Geyer, Sabrina, E-mail: geyer@iap.uni-frankfurt.de; Langbein, A., E-mail: geyer@iap.uni-frankfurt.de; Meusel, Oliver, E-mail: geyer@iap.uni-frankfurt.de [Institute of Applied Physics, Goethe University Frankfurt, Frankfurt am Main, HE (Germany); Kester, Oliver [Institute of Applied Physics, Goethe University Frankfurt, Frankfurt am Main, HE, Germany and GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, HE (Germany)

    2015-01-09

    For the investigation of highly charged ions, a crossover EBIS (XEBIS) was developed at the University of Frankfurt. In contrast to conventional EBIS/T devices the compression of the electron beam is achieved by electrostatic focusing to a crossover point in the interaction region. This concept allows a compact and simple design. Simulations performed with EGUN show a perveance of 2.1×10{sup −7} A/V{sup 3/2} for the realized gun system. In the interaction region the electron beam has a density of around 10 A/cm{sup 2} and a minimum radius of 0.15 mm. The XEBIS has a total length of 112 mm with a trap length of 26 mm. It is designed for electron beam energies of up to 6 keV/q. The storage capacity of the trap region is in the order of 1×10{sup 8} charges. Charge state breeding studies with CBSIM indicate for the noble gases as maximal achievable charge state Ar{sup 16+}, Kr{sup 30+} and Xe{sup 35+}. Thus ion beam currents of around 2.04 nA assuming 50 Hz repetition rate can be expected. The emittance of the extracted beam is approximated to 8 mm mrad. After completion of the construction phase, the XEBIS will be installed for first performance investigations at a dedicated test bench, equipped with a fast Faraday Cup (FC), a retarding field spectrometer, a luminescence screen and optical diagnostics. Subsequently the XEBIS will serve as source for highly charged ions at different experimental setups.

  10. Design and numerical characterization of a crossover EBIS

    International Nuclear Information System (INIS)

    Geyer, Sabrina; Langbein, A.; Meusel, Oliver; Kester, Oliver

    2015-01-01

    For the investigation of highly charged ions, a crossover EBIS (XEBIS) was developed at the University of Frankfurt. In contrast to conventional EBIS/T devices the compression of the electron beam is achieved by electrostatic focusing to a crossover point in the interaction region. This concept allows a compact and simple design. Simulations performed with EGUN show a perveance of 2.1×10 −7 A/V 3/2 for the realized gun system. In the interaction region the electron beam has a density of around 10 A/cm 2 and a minimum radius of 0.15 mm. The XEBIS has a total length of 112 mm with a trap length of 26 mm. It is designed for electron beam energies of up to 6 keV/q. The storage capacity of the trap region is in the order of 1×10 8 charges. Charge state breeding studies with CBSIM indicate for the noble gases as maximal achievable charge state Ar 16+ , Kr 30+ and Xe 35+ . Thus ion beam currents of around 2.04 nA assuming 50 Hz repetition rate can be expected. The emittance of the extracted beam is approximated to 8 mm mrad. After completion of the construction phase, the XEBIS will be installed for first performance investigations at a dedicated test bench, equipped with a fast Faraday Cup (FC), a retarding field spectrometer, a luminescence screen and optical diagnostics. Subsequently the XEBIS will serve as source for highly charged ions at different experimental setups

  11. Design and numerical characterization of a crossover EBIS

    Science.gov (United States)

    Geyer, Sabrina; Langbein, A.; Meusel, Oliver; Kester, Oliver

    2015-01-01

    For the investigation of highly charged ions, a crossover EBIS (XEBIS) was developed at the University of Frankfurt. In contrast to conventional EBIS/T devices the compression of the electron beam is achieved by electrostatic focusing to a crossover point in the interaction region. This concept allows a compact and simple design. Simulations performed with EGUN show a perveance of 2.1×10-7 A/V3/2 for the realized gun system. In the interaction region the electron beam has a density of around 10 A/cm2 and a minimum radius of 0.15 mm. The XEBIS has a total length of 112 mm with a trap length of 26 mm. It is designed for electron beam energies of up to 6 keV/q. The storage capacity of the trap region is in the order of 1×108 charges. Charge state breeding studies with CBSIM indicate for the noble gases as maximal achievable charge state Ar16+, Kr30+ and Xe35+. Thus ion beam currents of around 2.04 nA assuming 50 Hz repetition rate can be expected. The emittance of the extracted beam is approximated to 8 mm mrad. After completion of the construction phase, the XEBIS will be installed for first performance investigations at a dedicated test bench, equipped with a fast Faraday Cup (FC), a retarding field spectrometer, a luminescence screen and optical diagnostics. Subsequently the XEBIS will serve as source for highly charged ions at different experimental setups.

  12. Proteomic strategy for the identification of critical actors in reorganization of the post-meiotic male genome.

    Science.gov (United States)

    Govin, Jerome; Gaucher, Jonathan; Ferro, Myriam; Debernardi, Alexandra; Garin, Jerome; Khochbin, Saadi; Rousseaux, Sophie

    2012-01-01

    After meiosis, during the final stages of spermatogenesis, the haploid male genome undergoes major structural changes, resulting in a shift from a nucleosome-based genome organization to the sperm-specific, highly compacted nucleoprotamine structure. Recent data support the idea that region-specific programming of the haploid male genome is of high importance for the post-fertilization events and for successful embryo development. Although these events constitute a unique and essential step in reproduction, the mechanisms by which they occur have remained completely obscure and the factors involved have mostly remained uncharacterized. Here, we sought a strategy to significantly increase our understanding of proteins controlling the haploid male genome reprogramming, based on the identification of proteins in two specific pools: those with the potential to bind nucleic acids (basic proteins) and proteins capable of binding basic proteins (acidic proteins). For the identification of acidic proteins, we developed an approach involving a transition-protein (TP)-based chromatography, which has the advantage of retaining not only acidic proteins due to the charge interactions, but also potential TP-interacting factors. A second strategy, based on an in-depth bioinformatic analysis of the identified proteins, was then applied to pinpoint within the lists obtained, male germ cells expressed factors relevant to the post-meiotic genome organization. This approach reveals a functional network of DNA-packaging proteins and their putative chaperones and sheds a new light on the way the critical transitions in genome organizations could take place. This work also points to a new area of research in male infertility and sperm quality assessments.

  13. Cytoplasmic movement profiles of mouse surrounding nucleolus and not-surrounding nucleolus antral oocytes during meiotic resumption.

    Science.gov (United States)

    Bui, Thi Thu Hien; Belli, Martina; Fassina, Lorenzo; Vigone, Giulia; Merico, Valeria; Garagna, Silvia; Zuccotti, Maurizio

    2017-05-01

    Full-grown mouse antral oocytes are classified as surrounding nucleolus (SN) or not-surrounding nucleolus (NSN), depending on the respective presence or absence of a ring of Hoechst-positive chromatin surrounding the nucleolus. In culture, both types of oocytes resume meiosis and reach the metaphase II (MII) stage, but following insemination, NSN oocytes arrest at the two-cell stage whereas SN oocytes may develop to term. By coupling time-lapse bright-field microscopy with image analysis based on particle image velocimetry, we provide the first systematic measure of the changes to the cytoplasmic movement velocity (CMV) occurring during the germinal vesicle-to-MII (GV-to-MII) transition of these two types of oocytes. Compared to SN oocytes, NSN oocytes display a delayed GV-to-MII transition, which can be mostly explained by retarded germinal vesicle break down and first polar body extrusion. SN and NSN oocytes also exhibit significantly different CMV profiles at four main time-lapse intervals, although this difference was not predictive of SN or NSN oocyte origin because of the high variability in CMV. When CMV profile was analyzed through a trained artificial neural network, however, each single SN or NSN oocyte was blindly identified with a probability of 92.2% and 88.7%, respectively. Thus, the CMV profile recorded during meiotic resumption may be exploited as a cytological signature for the non-invasive assessment of the oocyte developmental potential, and could be informative for the analysis of the GV-to-MII transition of oocytes of other species. © 2017 Wiley Periodicals, Inc.

  14. Boule gene expression underpins the meiotic arrest in spermatogenesis in male rainbow trout (Oncorhynchus mykiss) exposed to DEHP and butachlor.

    Science.gov (United States)

    Ahmadivand, Sohrab; Farahmand, Hamid; Teimoori-Toolabi, Ladan; Mirvaghefi, Alireza; Eagderi, Soheil; Geerinckx, Tom; Shokrpoor, Sara; Rahmati-Holasoo, Hooman

    2016-01-01

    Boule, the ancestor of the DAZ (Deleted in AZoospermia) gene family, in most organisms is mainly involved in male meiosis. The present study investigates the effects of the plasticizer DEHP (50mg/kg body weight) and herbicide butachlor (0.39mg/L) on male rainbow trout (Oncorhynchus mykiss) for a 10-day period in two independent experiments. The results showed that plasma testosterone (T) concentrations were significantly lower in fish exposed to either DEHP or butachlor compared to the control fish (P0.05). In addition, no significant differences were found in the gonadosomatic index (GSI) in both DEHP and butachlor treatments (P>0.05). Histologically, testes of male trout in the control groups were well differentiated and filled with large numbers of cystic structures containing spermatozoa. In contrast, the testes of male trout contained mostly spermatocytes with few spermatozoa in both treated group, suggesting that DEHP and butachlor may inhibit the progression of meiosis. Also, boule gene expression was significantly lower in the testes of male trout affected by DEHP and butachlor in comparison with their control groups (Ptrout. Based on the results, the present study demonstrated that DEHP and butachlor can inhibit the progression of spermatogenesis in male trout, potentially by causing an arrest of meiosis, maybe due to down-regulation of boule gene expression through T and/or IGF1 via ERK1/2 signaling in T-independent pathways. In addition, these results confirmed that boule can be considered as a predictive marker to assess meiotic efficiency. Copyright © 2015 Elsevier Inc. All rights reserved.

  15. Relativistic BCS-BEC crossover at finite temperature and its application to color superconductivity

    International Nuclear Information System (INIS)

    He Lianyi; Zhuang Pengfei

    2007-01-01

    The nonrelativistic G 0 G formalism of BCS-BEC crossover at finite temperature is extended to relativistic fermion systems. The uncondensed pairs contribute a pseudogap to the fermion excitations. The theory recovers the BCS mean field approximation at zero temperature and the nonrelativistic results in a proper limit. For massive fermions, when the coupling strength increases, there exist two crossovers from the weak coupling BCS superfluid to the nonrelativistic BEC state and then to the relativistic BEC state. For color superconductivity at moderate baryon density, the matter is in the BCS-BEC crossover region, and the behavior of the pseudogap is quite similar to that found in high temperature superconductors

  16. Differences in meiotic recombination rates in childhood acute lymphoblastic leukemia at an MHC class II hotspot close to disease associated haplotypes.

    Directory of Open Access Journals (Sweden)

    Pamela Thompson

    Full Text Available Childhood Acute Lymphoblastic Leukemia (ALL is a malignant lymphoid disease of which B-cell precursor- (BCP and T-cell- (T ALL are subtypes. The role of alleles encoded by major histocompatibility loci (MHC have been examined in a number of previous studies and results indicating weak, multi-allele associations between the HLA-DPB1 locus and BCP-ALL suggested a role for immunosusceptibility and possibly infection. Two independent SNP association studies of ALL identified loci approximately 37 kb from one another and flanking a strong meiotic recombination hotspot (DNA3, adjacent to HLA-DOA and centromeric of HLA-DPB1. To determine the relationship between this observation and HLA-DPB1 associations, we constructed high density SNP haplotypes of the 316 kb region from HLA-DMB to COL11A2 in childhood ALL and controls using a UK GWAS data subset and the software PHASE. Of four haplotype blocks identified, predicted haplotypes in Block 1 (centromeric of DNA3 differed significantly between BCP-ALL and controls (P = 0.002 and in Block 4 (including HLA-DPB1 between T-ALL and controls (P = 0.049. Of specific common (>5% haplotypes in Block 1, two were less frequent in BCP-ALL, and in Block 4 a single haplotype was more frequent in T-ALL, compared to controls. Unexpectedly, we also observed apparent differences in ancestral meiotic recombination rates at DNA3, with BCP-ALL showing increased and T-ALL decreased levels compared to controls. In silico analysis using LDsplit sotware indicated that recombination rates at DNA3 are influenced by flanking loci, including SNPs identified in childhood ALL association studies. The observed differences in rates of meiotic recombination at this hotspot, and potentially others, may be a characteristic of childhood leukemia and contribute to disease susceptibility, alternatively they may reflect interactions between ALL-associated haplotypes in this region.

  17. RAD51AP2, a novel vertebrate- and meiotic-specific protein, sharesa conserved RAD51-interacting C-terminal domain with RAD51AP1/PIR51

    Energy Technology Data Exchange (ETDEWEB)

    Kovalenko, Oleg V.; Wiese, Claudia; Schild, David

    2006-07-25

    Many interacting proteins regulate and/or assist the activities of RAD51, a recombinase which plays a critical role in both DNA repair and meiotic recombination. Yeast two-hybrid screening of a human testis cDNA library revealed a new protein, RAD51AP2 (RAD51 Associated Protein 2), that interacts strongly with RAD51. A full-length cDNA clone predicts a novel vertebrate specific protein of 1159 residues, and the RAD51AP2 transcript was observed only in meiotic tissue (i.e. adult testis and fetal ovary), suggesting a meiotic-specific function for RAD51AP2. In HEK293 cells the interaction of RAD51 with an ectopically-expressed recombinant large fragment of RAD51AP2 requires the C-terminal 57 residues of RAD51AP2. This RAD51-binding region shows 81% homology to the C-terminus of RAD51AP1/PIR51, an otherwise totally unrelated RAD51-binding partner that is ubiquitously expressed. Analyses using truncations and point mutations in both RAD51AP1 and RAD51AP2 demonstrate that these proteins use the same structural motif for RAD51 binding. RAD54 shares some homology with this RAD51-binding motif, but this homologous region plays only an accessory role to the adjacent main RAD51-interacting region, which has been narrowed here to 40 amino acids. A novel protein, RAD51AP2, has been discovered that interacts with RAD51 through a C-terminal motif also present in RAD51AP1.

  18. Changes in homologous and heterologous gap junction contacts during maturation-inducing hormone-dependent meiotic resumption in ovarian follicles of Atlantic croaker

    Science.gov (United States)

    Bolamba, D.; Patino, R.; Yoshizaki, G.; Thomas, P.

    2003-01-01

    Homologous (granulosa cell-granulosa cell) gap junction (GJ) contacts increase in ovarian follicles of Atlantic croaker (Micropogonias undulatus) during the early (first) stage of maturation, but their profile during the second stage [i.e., during maturation-inducing hormone (MIH)-mediated meiotic resumption] is unknown. The profile of homologous GJ contacts during the second stage of maturation in croaker follicles was examined in this study and compared to that of heterologous (granulosa cell-oocyte) GJ, for which changes have been previously documented. Follicles were incubated with human chorionic gonadotropin to induce maturational competence (first stage), and then with MIH to induce meiotic resumption. The follicles were collected for examination immediately before and after different durations of MIH exposure until the oocyte had reached the stage of germinal vesicle breakdown (GVBD; index of meiotic resumption). Ultrathin sections were observed by transmission electron microscopy, and homologous and heterologous GJ contacts were quantified along a 100-??m segment of granulosa cell-zona radiata complex per follicle (three follicles/time/fish, n=3 fish). Relatively high numbers of both types of GJ were observed before and after the first few hours of MIH exposure (up to the stage of oil droplet coalescence). GJ numbers declined during partial yolk globule coalescence (at or near GVBD) and were just under 50% of starting values after the completion of GVBD (P<0.05). These results confirm earlier observations that GVBD temporally correlates with declining heterologous GJ contacts, and for the first time in teleosts show that there is a parallel decline in homologous GJ. The significance of the changes in homologous and heterologous GJ is uncertain and deserves further study. ?? 2003 Elsevier Science (USA). All rights reserved.

  19. Abnormal meiotic behavior in three species of Crotalaria Comportamento meiótico anormal em três espécies de Crotalaria

    Directory of Open Access Journals (Sweden)

    Kátia Ferreira

    2009-12-01

    Full Text Available The objective of this work was to compare the meiotic behavior and pollen grain viability of three species of Crotalaria. Slides for meiotic analysis were prepared by the air-drying technique. Pollen grain viability was measured by three staining procedures (Alexander's solution, tetrazolium chloride and fluorescein diacetate and in vitro germination in a sucrose solution. Eight bivalents were observed, confirming previous reports on populations from other regions of Brazil, as well as from other countries. All species showed abnormal meiotic behavior as follows: in Crotalaria micans, cytomixis and abnormal chromosome pairing in diakinesis; in C. spectabilis, abnormal chromosome pairing in diplotene; in C. zanzibarica, shrunk nuclei in leptotene and zygotene. Pollen grains of all three species show low viability, which may be associated with the irregularities of the meiotic behavior.O objetivo deste trabalho foi comparar o comportamento meiótico e a viabilidade dos grãos de pólen de três espécies de Crotalaria. A análise meiótica foi realizada por meio da técnica de secagem ao ar. A viabilidade dos grãos de pólen foi avaliada por testes de coloração (corante de Alexander, cloreto de tetrazólio e diacetato de fluoresceína e por teste de germinação em solução de sacarose. Foram observados oito bivalentes, confirmando relatos prévios em populações de outras regiões do Brasil e de outros países. As três espécies apresentaram comportamento meiótico irregular: em Crotalaria micans, citomixia e pareamento irregular na diacinese; em C. spectabilis, pareamento irregular no diplóteno; e em C. zanzibarica, núcleo fortemente condensado nas fases de leptóteno e zigóteno. A viabilidade dos grãos de pólen das três espécies é baixa, o que pode estar associado às irregularidades do comportamento meiótico.

  20. Mouse Y-linked Zfy1 and Zfy2 are expressed during the male-specific interphase between meiosis I and meiosis II and promote the 2nd meiotic division.

    Science.gov (United States)

    Vernet, Nadège; Mahadevaiah, Shantha K; Yamauchi, Yasuhiro; Decarpentrie, Fanny; Mitchell, Michael J; Ward, Monika A; Burgoyne, Paul S

    2014-06-01

    Mouse Zfy1 and Zfy2 encode zinc finger transcription factors that map to the short arm of the Y chromosome (Yp). They have previously been shown to promote meiotic quality control during pachytene (Zfy1 and Zfy2) and at the first meiotic metaphase (Zfy2). However, from these previous studies additional roles for genes encoded on Yp during meiotic progression were inferred. In order to identify these genes and investigate their function in later stages of meiosis, we created three models with diminishing Yp and Zfy gene complements (but lacking the Y-long-arm). Since the Y-long-arm mediates pairing and exchange with the X via their pseudoautosomal regions (PARs) we added a minute PAR-bearing X chromosome derivative to enable formation of a sex bivalent, thus avoiding Zfy2-mediated meiotic metaphase I (MI) checkpoint responses to the unpaired (univalent) X chromosome. Using these models we obtained definitive evidence that genetic information on Yp promotes meiosis II, and by transgene addition identified Zfy1 and Zfy2 as the genes responsible. Zfy2 was substantially more effective and proved to have a much more potent transactivation domain than Zfy1. We previously established that only Zfy2 is required for the robust apoptotic elimination of MI spermatocytes in response to a univalent X; the finding that both genes potentiate meiosis II led us to ask whether there was de novo Zfy1 and Zfy2 transcription in the interphase between meiosis I and meiosis II, and this proved to be the case. X-encoded Zfx was also expressed at this stage and Zfx over-expression also potentiated meiosis II. An interphase between the meiotic divisions is male-specific and we previously hypothesised that this allows meiosis II critical X and Y gene reactivation following sex chromosome silencing in meiotic prophase. The interphase transcription and meiosis II function of Zfx, Zfy1 and Zfy2 validate this hypothesis.

  1. Whole grain-rich diet reduces body weight and systemic low-grade inflammation without inducing major changes of the gut microbiome: a randomised cross-over trial

    DEFF Research Database (Denmark)

    Roager, Henrik Munch; Vogt, Josef Korbinian; Kristensen, Mette

    2017-01-01

    Objective To investigate whether a whole grain diet alters the gut microbiome and insulin sensitivity, as well as biomarkers of metabolic health and gut functionality. Design 60 Danish adults at risk of developing metabolic syndrome were included in a randomised cross-over trial with two 8-week...... dietary intervention periods comprising whole grain diet and refined grain diet, separated by a washout period of ≥6 weeks. The response to the interventions on the gut microbiome composition and insulin sensitivity as well on measures of glucose and lipid metabolism, gut functionality, inflammatory...... of whole grain consumed, in particular with intake of rye. Conclusion Compared with refined grain diet, whole grain diet did not alter insulin sensitivity and gut microbiome but reduced body weight and systemic low-grade inflammation....

  2. Treatment of hypothyroidism with levothyroxine plus liothyronine: a randomized, double-blind, crossover study.

    Science.gov (United States)

    Kaminski, Juliana; Miasaki, Fabíola Yukiko; Paz-Filho, Gilberto; Graf, Hans; Carvalho, Gisah Amaral de

    2016-01-01

    To compare the effects of a unique fixed combination levothyroxine/liothyronine (LT4/LT3) therapy in patients with primary hypothyroidism. This is a randomized, double-blind, crossover study. Adults with primary hypothyroidism (n = 32, age 42.6 ± 13.3, 30 females) on stable doses of LT4 for ≥ 6 months (125 or 150 μg/day) were randomized to continue LT4 treatment (G1) or to start LT4/LT3 therapy (75/15 μg/day; G2). After 8 weeks, participants switched treatments for 8 more weeks. Thyroid function, lipid profile, plasma glucose, body weight, electrocardiogram, vital signs, and quality of life (QoL) were evaluated at weeks 0, 8 and 16. Free T4 levels were significantly lower while on LT4/LT3 (G1: 1.07 ± 0.29 vs. 1.65 ± 0.46; G2: 0.97 ± 0.26 vs. 1.63 ± 0.43 ng/dL; P < 0.001). TSH and T3 levels were not affected by type of therapy. More patients on LT4/LT3 had T3 levels above the upper limit (15% vs. 3%). The combination therapy led to an increase in heart rate, with no significant changes in electrocardiogram or arterial blood pressure. Lipid profile, body weight and QoL remained unchanged. The combination therapy yielded significantly lower free T4 levels, with no changes in TSH or T3 levels. More patients on LT4/T3 had elevated T3 levels, with no significant alterations in the evaluated outcomes. No clear clinical benefit of the studied formulation could be observed. Future trials need to evaluate different formulations and the impact of the combined therapy in select populations with genetic polymorphisms.

  3. Randomized Crossover Comparison of Personalized MPC and PID Control Algorithms for the Artificial Pancreas.

    Science.gov (United States)

    Pinsker, Jordan E; Lee, Joon Bok; Dassau, Eyal; Seborg, Dale E; Bradley, Paige K; Gondhalekar, Ravi; Bevier, Wendy C; Huyett, Lauren; Zisser, Howard C; Doyle, Francis J

    2016-07-01

    To evaluate two widely used control algorithms for an artificial pancreas (AP) under nonideal but comparable clinical conditions. After a pilot safety and feasibility study (n = 10), closed-loop control (CLC) was evaluated in a randomized, crossover trial of 20 additional adults with type 1 diabetes. Personalized model predictive control (MPC) and proportional integral derivative (PID) algorithms were compared in supervised 27.5-h CLC sessions. Challenges included overnight control after a 65-g dinner, response to a 50-g breakfast, and response to an unannounced 65-g lunch. Boluses of announced dinner and breakfast meals were given at mealtime. The primary outcome was time in glucose range 70-180 mg/dL. Mean time in range 70-180 mg/dL was greater for MPC than for PID (74.4 vs. 63.7%, P = 0.020). Mean glucose was also lower for MPC than PID during the entire trial duration (138 vs. 160 mg/dL, P = 0.012) and 5 h after the unannounced 65-g meal (181 vs. 220 mg/dL, P = 0.019). There was no significant difference in time with glucose PID control for the AP indicates that MPC performed particularly well, achieving nearly 75% time in the target range, including the unannounced meal. Although both forms of CLC provided safe and effective glucose management, MPC performed as well or better than PID in all metrics. © 2016 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

  4. Hysteresis, nucleation and growth phenomena in spin-crossover solids

    Science.gov (United States)

    Ridier, Karl; Molnár, Gábor; Salmon, Lionel; Nicolazzi, William; Bousseksou, Azzedine

    2017-12-01

    The observation and the study of first-order phase transitions in cooperative spin-crossover (SCO) solids exhibiting hysteresis behaviours are of particular interest and currently constitute a burgeoning area in the field of bistable molecular materials. The understanding and the control of the transition mechanisms (nucleation and growth processes) and their dynamics within the hysteresis region appear to be a general and appealing problem from a fundamental point of view and for technological applications as well. This review reports on the recent progresses and most important findings made on the spatiotemporal dynamics of the spin transition in SCO solids, particularly through the universal nucleation and growth process. Both thermally induced and light-induced spin transitions are discussed. We open up this review to the central question of the evolution of the transition mechanisms and dynamics in SCO nano-objects, which constitute promising systems to reach ultra-fast switching, and the experimental issues inherent to such studies at the micro- and nanometric scale.

  5. Crossover from bound to free states in plasmas

    International Nuclear Information System (INIS)

    Lankin, Alexander V; Norman, Genri E

    2009-01-01

    A self-consistent joint description of free and weakly bound electron states in strongly coupled plasmas is presented. The existence of two problems is emphasized. The first one is a well-known restriction of the number of atomic excited states. Another one is a description of the smooth crossover from bound pair electron-ion excited states to collective excitations of free electrons. The fluctuation approach is developed to study the spectrum domain intermediate between low-lying excited atoms and free electron continuous energy levels. The molecular dynamics method is applied to study the plasma model since the method is able to distinguish all kinds of fluctuations. The electron-ion interaction is described by the temperature-independent cut-off Coulomb potential. The diagnostics of pair electron-ion fluctuations is developed. The concept of pair fluctuations elucidates the smooth vanishing of atomic states near the ionization limit. The approach suggested removes the artificial break of the electron state density at the ionization limit: atomic state density divergent at the negative energy side and free electron state density starting from zero density at the positive energy side

  6. Universality of quadratic to linear magnetoresistance crossover in disordered conductors

    Science.gov (United States)

    Lara, Silvia; Ramakrishnan, Navneeth; Lai, Ying Tong; Adam, Shaffique

    Many experiments measuring Magnetoresistance (MR) showed unsaturating linear behavior at high magnetic fields and quadratic behavior at low fields. In the literature, two very different theoretical models have been used to explain this classical MR as a consequence of sample disorder. The phenomenological Random Resistor Network (RRN) model constructs a grid of four-terminal resistors each with a varying random resistance. The Effective Medium Theory (EMT) model imagines a smoothly varying disorder potential that causes a continuous variation of the local conductivity. In this theoretical work, we demonstrate numerically that both the RRN and EMT models belong to the same universality class, and that a single parameter (the ratio of the fluctuations in the carrier density to the average carrier density) completely determines both the magnitude of the MR and the B-field scale for the crossover from quadratic to linear MR. By considering several experimental data sets in the literature, ranging from thin films of InSb to graphene to Weyl semimetals like Na3Bi, we show that this disorder-induced mechanism for MR is in good agreement with the experiments, and that this comparison of MR with theory reveals information about the spatial carrier density inhomogeneity. This work was supported by the National Research Foundation of Singapore (NRF-NRFF2012-01).

  7. Scaling and crossover in a fermion-boson mixture

    International Nuclear Information System (INIS)

    Singh, K.K.

    1987-01-01

    Thermodynamic behaviour of a mixture of weakly interacting fermions and bosons is investigated in (4 - ε) dimensions by the renormalization group method with a view to study scaling and crossover properties of the system in the tricritical region. Conventional tricritical scaling, first found to breakdown for a classical infinite-component model, is seen to do so more spectacularly in the case of the mixture. Whereas in the infinite-component model, conventional scaling holds in the ordered and disordered phases separately (i.e. with different tricritical exponents), no such thing is possible in either of the phases of the mixture. The breakdown of scaling in the mixture is associated with the dimensionless strength v 6 of the 6-point interaction in the effective Hamiltonian which causes the parameters of the renormalized Hamiltonian to depend on two combinations of scaling fields rather than one. The strength v 6 is a quantum mechanical parameter being proportional in 3 dimensions to (b 3 /λ T 4 K F ) where λ T , K F and b denote, respectively, the boson thermal wavelength, the Fermi momentum of the fermion component and the scattering length associated with the fermion-boson interaction. The square root of this quantity agrees with the non-universality parameter which was found to characterize tricritical amplitude ratios in 3 dimensions in an earlier work. (author). 19 refs, 8 figs

  8. Catalytic Activity Control via Crossover between Two Different Microstructures

    KAUST Repository

    Zhou, Yuheng

    2017-09-08

    Metal nanocatalysts hold great promise for a wide range of heterogeneous catalytic reactions, while the optimization strategy of catalytic activity is largely restricted by particle size or shape control. Here, we demonstrate that a reversible microstructural control through the crossover between multiply-twinned nanoparticle (MTP) and single crystal (SC) can be readily achieved by solvent post-treatment on gold nanoparticles (AuNPs). Polar solvents (e.g. water, methanol) direct the transformation from MTP to SC accompanied by the disappearance of twinning and stacking faults. A reverse transformation from SC to MTP is achieved in non-polar solvent (e.g. toluene) mixed with thiol ligands. The transformation between two different microstructures is directly observed by in-situ TEM and leads to a drastic modulation of catalytic activity towards the gas-phase selective oxidation of alcohols. There is a quasi-linear relationship between TOFs and MTP concentrations. Based on the combined experimental and theoretical investigations of alcohol chemisorption on these nanocatalysts, we propose that the exposure of {211}-like microfacets associated with twin boundaries and stack faults accounts for the strong chemisorption of alcohol molecules on MTP AuNPs and thus the exceptionally high catalytic activity.

  9. At grade optical crossover for monolithic optial circuits

    Science.gov (United States)

    Jamieson, Robert S. (Inventor)

    1983-01-01

    Planar optical circuits may be made to cross through each other, (thus eliminating extra steps required to fabricate elevated, nonintersecting crossovers) by control of the dimensions of the crossing light conductors (10, 12) to be significantly greater than d=0.89.lambda. and the angle of crossing as nearly 90.degree. as conveniently possible. A light trap may be provided just ahead of the intersection to trap any light being reflected in the source conductor at angles greater than about 45.degree.. The light trap may take the form of triangular shaped portions (16a, 16b) on each side of the source conductor with the far side of the triangular portion receiving incident light at an angle so that incident light will be reflected to the other side, or it may take the form of windows (18a, 18b) in place of the triangular portions. Planar optical circuit boards (21-23) may be fabricated and stacked to form a keyboard (20) with intersecting conductors (26-29) and keyholes (0-9) where conductors merge at the broad side of the circuit boards. These keyholes may be prearranged to form an array or matrix of keyholes.

  10. Speech perception with mono- and quadrupolar electrode configurations: a crossover study.

    NARCIS (Netherlands)

    Mens, L.H.M.; Berenstein, C.K.

    2005-01-01

    OBJECTIVE: To study the effect of two multipolar electrode configurations on speech perception, pitch perception, and the intracochlear electrical field. STUDY DESIGN: Crossover design; within subject. SETTING: Tertiary referral center. PATIENTS: Eight experienced adult cochlear implant users.

  11. First step towards a Devil´s staircase in spin-crossover materials

    Czech Academy of Sciences Publication Activity Database

    Trzop, E.; Zhang, D.; Pineiro-Lopez, L.; Valverde-Munoz, F.J.; Munoz, M.C.; Palatinus, Lukáš; Guerin, L.; Cailleau, H.; Real, J.A.; Collet, E.

    2016-01-01

    Roč. 55, č. 30 (2016), s. 8675-8679 ISSN 0044-8249 Institutional support: RVO:68378271 Keywords : aperiodicity * coordination polymers * Devil’s staircase * phase transitions * spin-crossover Subject RIV: BM - Solid Matter Physics ; Magnetism

  12. Bio-Inspired Genetic Algorithms with Formalized Crossover Operators for Robotic Applications.

    Science.gov (United States)

    Zhang, Jie; Kang, Man; Li, Xiaojuan; Liu, Geng-Yang

    2017-01-01

    Genetic algorithms are widely adopted to solve optimization problems in robotic applications. In such safety-critical systems, it is vitally important to formally prove the correctness when genetic algorithms are applied. This paper focuses on formal modeling of crossover operations that are one of most important operations in genetic algorithms. Specially, we for the first time formalize crossover operations with higher-order logic based on HOL4 that is easy to be deployed with its user-friendly programing environment. With correctness-guaranteed formalized crossover operations, we can safely apply them in robotic applications. We implement our technique to solve a path planning problem using a genetic algorithm with our formalized crossover operations, and the results show the effectiveness of our technique.

  13. Studies on Methanol Crossover in Liquid-Feed Direct Methanol Pem Fuel Cells

    Science.gov (United States)

    Narayanan, S. R.

    1995-01-01

    The performance of liquid feed direct methanol fuel cells using various types of Nafion membranes as the solid polymer electrolyte have been studied. The rate of fuel crossover and electrical performance has been measured for cells with Nafion membranes of various thicknesses and equivalent weights. The crossover rate is found to decrease with increasing thickness and applied current. The dependence of crossover rate on current density can be understood in terms of a simple linear diffusion model which suggests that the crossover rate can be influenced by the electrode structure in addition to the membrane. The studies suggest that Nafion EW 1500 is a very promising alternate to Nafion EW 1100 for direct methanol fuel cells.

  14. Genetic Algorithm for Traveling Salesman Problem with Modified Cycle Crossover Operator

    Directory of Open Access Journals (Sweden)

    Abid Hussain

    2017-01-01

    Full Text Available Genetic algorithms are evolutionary techniques used for optimization purposes according to survival of the fittest idea. These methods do not ensure optimal solutions; however, they give good approximation usually in time. The genetic algorithms are useful for NP-hard problems, especially the traveling salesman problem. The genetic algorithm depends on selection criteria, crossover, and mutation operators. To tackle the traveling salesman problem using genetic algorithms, there are various representations such as binary, path, adjacency, ordinal, and matrix representations. In this article, we propose a new crossover operator for traveling salesman problem to minimize the total distance. This approach has been linked with path representation, which is the most natural way to represent a legal tour. Computational results are also reported with some traditional path representation methods like partially mapped and order crossovers along with new cycle crossover operator for some benchmark TSPLIB instances and found improvements.

  15. Efficacy and hypnotic effects of melatonin in shift-work nurses: double-blind, placebo-controlled crossover trial

    Directory of Open Access Journals (Sweden)

    Pouryaghoub Gholamreza

    2008-10-01

    Full Text Available Abstract Background Night work is associated with disturbed sleep and wakefulness, particularly in relation to the night shift. Circadian rhythm sleep disorders are characterized by complaints of insomnia and excessive daytime sleepiness that are primarily due to alterations in the internal circadian timing system or a misalignment between the timing of sleep and the 24-h social and physical environment. Methods We evaluated the effect of oral intake of 5 mg melatonin taken 30 minutes before night time sleep on insomnia parameters as well as subjective sleep onset latency, number of awakenings, and duration of sleep. A double-blind, randomized, placebo-controlled crossover study with periods of 1 night and washouts of 4 days comparing melatonin with placebo tablets was conducted. We tried to improve night-time sleep during recovery from night work. Participants were 86 shift-worker nurses aged 24 to 46 years. Each participant completed a questionnaire immediately after awakening. Results Sleep onset latency was significantly reduced while subjects were taking melatonin as compared with both placebo and baseline. There was no evidence that melatonin altered total sleep time (as compared with baseline total sleep time. No adverse effects of melatonin were noted during the treatment period. Conclusion Melatonin may be an effective treatment for shift workers with difficulty falling asleep.

  16. High-pressure water electrolysis: Electrochemical mitigation of product gas crossover

    International Nuclear Information System (INIS)

    Schalenbach, Maximilian; Stolten, Detlef

    2015-01-01

    Highlights: • New technique to reduce gas crossover during water electrolysis • Increase of the efficiency of pressurized water electrolysis • Prevention of safety hazards due to explosive gas mixtures caused by crossover • Experimental realization for a polymer electrolyte membrane electrolyzer • Discussion of electrochemical crossover mitigation for alkaline water electrolysis - Abstract: Hydrogen produced by water electrolysis can be used as an energy carrier storing electricity generated from renewables. During water electrolysis hydrogen can be evolved under pressure at isothermal conditions, enabling highly efficient compression. However, the permeation of hydrogen through the electrolyte increases with operating pressure and leads to efficiency loss and safety hazards. In this study, we report on an innovative concept, where the hydrogen crossover is electrochemically mitigated by an additional electrode between the anode and the cathode of the electrolysis cell. Experimentally, the technique was applied to a proton exchange membrane water electrolyzer operated at a hydrogen pressure that was fifty times larger than the oxygen pressure. Therewith, the hydrogen crossover was reduced and the current efficiency during partial load operation was increased. The concept is also discussed for water electrolysis that is operated at balanced pressures, where the crossover of hydrogen and oxygen is mitigated using two additional electrodes

  17. Experimental analysis of methanol cross-over in a direct methanol fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Casalegno, Andrea [Dipartimento di Energetica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy)]. E-mail: andrea.casalegno@polimi.it; Grassini, Paolo [Dipartimento di Energetica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy)]. E-mail: PGrassini@seal.it; Marchesi, Renzo [Dipartimento di Energetica, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milan (Italy)]. E-mail: renzo.marchesi@polimi.it

    2007-03-15

    Methanol cross-over through the polymeric membrane is one of the main causes limiting direct methanol fuel cell performances. It causes fuel wasting and enhances cathode overpotential. A repeatable and reproducible measurement system, that assures the traceability of the measurement to international reference standards, is necessary to compare different fuel cell construction materials. In this work a method to evaluate methanol cross-over rate and operating condition influence is presented and qualified in term of measurement uncertainty. In the investigated range, the methanol cross-over rate results mainly due to diffusion through the membrane, in fact it is strongly affected by temperature. Moreover the cross-over influence on fuel utilization and fuel cell efficiency is investigated. The methanol cross-over rate appears linearly proportional to electrochemical fuel utilization and values, obtained by measurements at different anode flow rate but constant electrochemical fuel utilization, are roughly equal; methanol wasting, due to cross-over, is considerable and can still be higher than electrochemical utilization. The fuel recirculation effect on energy efficiency has been investigated and it was found that fuel recirculation gives more advantage at low temperature, but fuel cell energy efficiency results are in any event higher at high temperature.

  18. Automated process flowsheet synthesis for membrane processes using genetic algorithm: role of crossover operators

    KAUST Repository

    Shafiee, Alireza

    2016-06-25

    In optimization-based process flowsheet synthesis, optimization methods, including genetic algorithms (GA), are used as advantageous tools to select a high performance flowsheet by ‘screening’ large numbers of possible flowsheets. In this study, we expand the role of GA to include flowsheet generation through proposing a modified Greedysub tour crossover operator. Performance of the proposed crossover operator is compared with four other commonly used operators. The proposed GA optimizationbased process synthesis method is applied to generate the optimum process flowsheet for a multicomponent membrane-based CO2 capture process. Within defined constraints and using the random-point crossover, CO2 purity of 0.827 (equivalent to 0.986 on dry basis) is achieved which results in improvement (3.4%) over the simplest crossover operator applied. In addition, the least variability in the converged flowsheet and CO2 purity is observed for random-point crossover operator, which approximately implies closeness of the solution to the global optimum, and hence the consistency of the algorithm. The proposed crossover operator is found to improve the convergence speed of the algorithm by 77.6%.

  19. Experimental analysis of methanol cross-over in a direct methanol fuel cell

    International Nuclear Information System (INIS)

    Casalegno, Andrea; Grassini, Paolo; Marchesi, Renzo

    2007-01-01

    Methanol cross-over through the polymeric membrane is one of the main causes limiting direct methanol fuel cell performances. It causes fuel wasting and enhances cathode overpotential. A repeatable and reproducible measurement system, that assures the traceability of the measurement to international reference standards, is necessary to compare different fuel cell construction materials. In this work a method to evaluate methanol cross-over rate and operating condition influence is presented and qualified in term of measurement uncertainty. In the investigated range, the methanol cross-over rate results mainly due to diffusion through the membrane, in fact it is strongly affected by temperature. Moreover the cross-over influence on fuel utilization and fuel cell efficiency is investigated. The methanol cross-over rate appears linearly proportional to electrochemical fuel utilization and values, obtained by measurements at different anode flow rate but constant electrochemical fuel utilization, are roughly equal; methanol wasting, due to cross-over, is considerable and can still be higher than electrochemical utilization. The fuel recirculation effect on energy efficiency has been investigated and it was found that fuel recirculation gives more advantage at low temperature, but fuel cell energy efficiency results are in any event higher at high temperature

  20. An essential role for trimethylguanosine RNA caps in Saccharomyces cerevisiae meiosis and their requirement for splicing of SAE3 and PCH2 meiotic pre-mRNAs.

    Science.gov (United States)

    Qiu, Zhicheng R; Shuman, Stewart; Schwer, Beate

    2011-07-01

    Tgs1 is the enzyme that converts m(7)G RNA caps to the 2,2,7-trimethylguanosine (TMG) caps characteristic of spliceosomal snRNAs. Fungi grow vegetatively without TMG caps, thereby raising the question of what cellular transactions, if any, are TMG cap-dependent. Here, we report that Saccharomyces cerevisiae Tgs1 methyltransferase activity is essential for meiosis. tgs1Δ cells are specifically defective in splicing PCH2 and SAE3 meiotic pre-mRNAs. The TMG requirement for SAE3 splicing is alleviated by two intron mutations: a UAUUAAC to UACUAAC change that restores a consensus branchpoint and disruption of a stem-loop encompassing the branchpoint. The TMG requirement for PCH2 splicing is alleviated by a CACUAAC to UACUAAC change restoring a consensus branchpoint and by shortening the PCH2 5' exon. Placing the SAE3 and PCH2 introns within a HIS3 reporter confers Tgs1-dependent histidine prototrophy, signifying that the respective introns are portable determinants of TMG-dependent gene expression. Analysis of in vitro splicing in extracts of TGS1 versus tgs1Δ cells showed that SAE3 intron removal was enfeebled without TMG caps, whereas splicing of ACT1 was unaffected. Our findings illuminate a new mode of tunable splicing, a reliance on TMG caps for an essential developmental RNA transaction, and three genetically distinct meiotic splicing regulons in budding yeast.

  1. In vitro growth and maturation of isolated caprine preantral follicles: Influence of insulin and FSH concentration, culture dish, coculture, and oocyte size on meiotic resumption.

    Science.gov (United States)

    Silva, G M; Brito, I R; Sales, A D; Aguiar, F L N; Duarte, A B G; Araújo, V R; Vieira, L A; Magalhães-Padilha, D M; Lima, L F; Alves, B G; Silveira, L B R; Lo Turco, E G; Rodrigues, A P; Campello, C C; Wheeler, M B; Figueiredo, J R

    2017-03-01

    The aims of this study were: (1) to evaluate the effect of different insulin concentrations, alone or in combination with either a fixed FSH concentration or increasing FSH concentrations on the in vitro culture of isolated caprine preantral follicles and (2) to analyze the efficiency of two IVM media and maturation culture systems (with or without coculture with in vivo grown oocytes) on the meiosis resumption. Secondary follicles were cultured for 18 days in a basic medium supplemented with low- or high-insulin concentration alone or with a fixed FSH concentration or with increasing FSH concentrations. Oocytes grown in vivo or in vitro were matured alone or cocultured. The high-insulin concentration associated with fixed FSH treatment had higher meiotic resumption rate (P media. In conclusion, a basic medium supplemented with 10-μg/mL insulin and 100-μg/mL FSH throughout the culture period improved meiotic resumption rate and produced MII oocytes from caprine preantral follicles cultured in vitro. The MII rate was similar between in vivo and in vitro grown oocytes ≥110 μm. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. CHEMERIN (RARRES2) decreases in vitro granulosa cell steroidogenesis and blocks oocyte meiotic progression in bovine species.

    Science.gov (United States)

    Reverchon, Maxime; Bertoldo, Michael J; Ramé, Christelle; Froment, Pascal; Dupont, Joëlle

    2014-05-01

    CHEMERIN, or RARRES2, is a new adipokine that is involved in the regulation of adipogenesis, energy metabolism, and inflammation. Recent data suggest that it also plays a role in reproductive function in rats and humans. Here we studied the expression of CHEMERIN and its three receptors (CMKLR1, GPR1, and CCRL2) in the bovine ovary and investigated the in vitro effects of this hormone on granulosa cell steroidogenesis and oocyte maturation. By RT-PCR, immunoblotting, and immunohistochemistry, we found CHEMERIN, CMKLR1, GPR1, and CCRL2 in various ovarian cells, including granulosa and theca cells, corpus luteum, and oocytes. In cultured bovine granulosa cells, INSULIN, IGF1, and two insulin sensitizers-metformin and rosiglitazone-increased rarres2 mRNA expression whereas they decreased cmklr1, gpr1, and cclr2 mRNA expression. Furthermore, TNF alpha and ADIPONECTIN significantly increased rarres2 and cmklr1 expression, respectively. In cultured bovine granulosa cells, human recombinant CHEMERIN (hRec, 200 ng/ml) reduced production of both progesterone and estradiol, cholesterol content, STAR abundance, CYP19A1 and HMGCR proteins, and the phosphorylation levels of MAPK3/MAPK1 in the presence or absence of FSH (10(-8) M) and IGF1 (10(-8) M). All of these effects were abolished by using an anti-CMKLR1 antibody. In bovine cumulus-oocyte complexes, the addition of hRec (200 ng/ml) in the maturation medium arrested most oocytes at the germinal vesicle stage, and this was associated with a decrease in MAPK3/1 phosphorylation in both oocytes and cumulus cells. Thus, in cultured bovine granulosa cells, hRec decreases steroidogenesis, cholesterol synthesis, and MAPK3/1 phosphorylation, probably through CMKLR1. Moreover, in cumulus-oocyte complexes, it blocked meiotic progression at the germinal vesicle stage and inhibited MAPK3/1 phosphorylation in both the oocytes and cumulus cells during in vitro maturation. © 2014 by the Society for the Study of Reproduction, Inc.

  3. Bloodcurdling movies and measures of coagulation: Fear Factor crossover trial.

    Science.gov (United States)

    Nemeth, Banne; Scheres, Luuk J J; Lijfering, Willem M; Rosendaal, Frits R

    2015-12-16

    To assess whether, as has been hypothesised since medieval times, acute fear can curdle blood. Crossover trial. Main meeting room of Leiden University's Department of Clinical Epidemiology, the Netherlands, converted to a makeshift cinema. 24 healthy volunteers aged ≤30 years recruited among students, alumni, and employees of the Leiden University Medical Center: 14 were assigned to watch a frightening (horror) movie followed by a non-threatening (educational) movie and 10 to watch the movies in reverse order. The movies were viewed more than a week apart at the same time of day and both lasted approximately 90 minutes. The primary outcome measures were markers, or "fear factors" of coagulation activity: blood coagulant factor VIII, D-dimer, thrombin-antithrombin complexes, and prothrombin fragments 1+2. The secondary outcome was participant reported fear experienced during each movie using a visual analogue fear scale. All participants completed the study. The horror movie was perceived to be more frightening than the educational movie on a visual analogue fear scale (mean difference 5.4, 95% confidence interval 4.7 to 6.1). The difference in factor VIII levels before and after watching the movies was higher for the horror movie than for the educational movie (mean difference of differences 11.1 IU/dL (111 IU/L), 95% confidence interval 1.2 to 21.0 IU/dL). The effect of either movie on levels of thrombin-antithrombin complexes, D-dimer, and prothrombin fragments 1+2 did not differ. Frightening (in this case, horror) movies are associated with an increase of blood coagulant factor VIII without actual thrombin formation in young and healthy adults. Trial registration ClinicalTrials.gov NCT02601053. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  4. Eating marshmallows reduces ileostomy output: a randomized crossover trial.

    Science.gov (United States)

    Clarebrough, E; Guest, G; Stupart, D

    2015-12-01

    Anecdotally, many ostomates believe that eating marshmallows can reduce ileostomy effluent. There is a plausible mechanism for this, as the gelatine contained in marshmallows may thicken small bowel fluid, but there is currently no evidence that this is effective. This was a randomized crossover trial. Adult patients with well-established ileostomies were included. Ileostomy output was measured for 1 week during which three marshmallows were consumed three times daily, and for one control week where marshmallows were not eaten. There was a 2-day washout period. Patients were randomly allocated to whether the control or intervention week occurred first. In addition, a questionnaire was administered regarding patient's subjective experience of their ileostomy function. Thirty-one participants were recruited; 28 completed the study. There was a median reduction in ileostomy output volume of 75 ml per day during the study period (P = 0.0054, 95% confidence interval 23.4-678.3) compared with the control week. Twenty of 28 subjects (71%) experienced a reduction in their ileostomy output, two had no change and six reported an increase. During the study period, participants reported fewer ileostomy bag changes (median five per day vs six in the control period, P = 0.0255). Twenty of 28 (71%) reported that the ileostomy effluent was thicker during the study week (P = 0.023). Overall 19 (68%) participants stated they would use marshmallows in the future if they wanted to reduce or thicken their ileostomy output. Eating marshmallows leads to a small but statistically significant reduction in ileostomy output. Colorectal Disease © 2015 The Association of Coloproctology of Great Britain and Ireland.

  5. Triggers for Preeclampsia Onset: a Case-Crossover Study.

    Science.gov (United States)

    Ford, Jane B; Schemann, Kathrin; Patterson, Jillian A; Morris, Jonathan; Herbert, Robert D; Roberts, Christine L

    2016-11-01

    Risk factors for preeclampsia are well established, whereas, the triggers associated with timing of preeclampsia onset are not. The aim of this study was to establish whether recent infection or other triggers were associated with timing of preeclampsia onset. We used a case-crossover design with preeclampsia cases serving as their own controls. Women with singleton pregnancies of ≥20 weeks gestation presenting at three hospitals were eligible for inclusion. Exposures to potential triggers were identified via guided questionnaire. Infective episodes included symptoms lasting >24 h. Preeclampsia was defined as hypertension (BP ≥140 mmHg and/or ≥90 mmHg) and proteinuria (protein/creatinine ratio ≥30 mg/mmol). Conditional logistic regression was used to compare the odds of exposure to potential triggers in the case windows (1-7 days preceding diagnosis of preeclampsia) and control windows (8-14 days prior to diagnosis); unadjusted odds ratios (ORs) are reported. Among 286 recruited women, 25 (8.7%) reported a new infection in the 7 days prior to preeclampsia onset and 21 (7.3%) in the 8-14 days prior. There was no significant association between onset of infection in the 7 days prior and preeclampsia diagnosis (OR 1.24, 95% CI 0.65, 2.34). Consumption of caffeine (OR 0.51, 95% CI 0.33, 0.77), spicy food (OR 0.49, 95% CI 0.30, 0.81), and alcohol (OR 0.26, 95% CI 0.10, 0.71) were strongly inversely associated with preeclampsia onset. Recent infection does not appear to trigger preeclampsia. Decreased consumption of caffeine, spicy food, and alcohol may be prodromal markers. Such behaviours may be early markers of imminent preeclampsia. © 2016 John Wiley & Sons Ltd.

  6. Berezinskii-Kosterlitz-Thouless crossover in a trapped atomic gas.

    Science.gov (United States)

    Hadzibabic, Zoran; Krüger, Peter; Cheneau, Marc; Battelier, Baptiste; Dalibard, Jean

    2006-06-29

    Any state of matter is classified according to its order, and the type of order that a physical system can possess is profoundly affected by its dimensionality. Conventional long-range order, as in a ferromagnet or a crystal, is common in three-dimensional systems at low temperature. However, in two-dimensional systems with a continuous symmetry, true long-range order is destroyed by thermal fluctuations at any finite temperature. Consequently, for the case of identical bosons, a uniform two-dimensional fluid cannot undergo Bose-Einstein condensation, in contrast to the three-dimensional case. However, the two-dimensional system can form a 'quasi-condensate' and become superfluid below a finite critical temperature. The Berezinskii-Kosterlitz-Thouless (BKT) theory associates this phase transition with the emergence of a topological order, resulting from the pairing of vortices with opposite circulation. Above the critical temperature, proliferation of unbound vortices is expected. Here we report the observation of a BKT-type crossover in a trapped quantum degenerate gas of rubidium atoms. Using a matter wave heterodyning technique, we observe both the long-wavelength fluctuations of the quasi-condensate phase and the free vortices. At low temperatures, the gas is quasi-coherent on the length scale set by the system size. As the temperature is increased, the loss of long-range coherence coincides with the onset of proliferation of free vortices. Our results provide direct experimental evidence for the microscopic mechanism underlying the BKT theory, and raise new questions regarding coherence and superfluidity in mesoscopic systems.

  7. Radiation protection philosophy alters

    International Nuclear Information System (INIS)

    Firmin, G.

    1977-01-01

    Two significant events that have taken place this year in the field of radiation protection are reported. New SI units have been proposed (and effectively adopted), and the ICRP has revised its recommendations. Changes of emphasis in the latest recommendations (ICRP Publication 26) imply an altered radiation protection philosophy, in particular the relation of dose limits to estimates of average risk, an altered view of the critical organ approach and a new attitude to genetic dose to the population. (author)

  8. Effects of lipid emulsion particle size on satiety and energy intake: a randomised cross-over trial.

    Science.gov (United States)

    Poppitt, Sally D; Budgett, Stephanie C; MacGibbon, Alastair K; Quek, Siew-Young; Kindleysides, Sophie; Wiessing, Katy R

    2018-03-01

    Emulsified lipids, with central lipid core surrounded by polar lipid 'protective coat', have been proposed to stimulate the ileal brake, alter appetite, food intake and aid weight control. In addition to lipid composition, emulsion particle size may contribute to efficacy with small droplets providing a larger surface area for gastrointestinal (GI) lipase action and larger droplets prolonging and delaying digestion in the GI tract. Tube feeding studies delivering emulsions directly into the small intestine show clear effects of smaller particle size on appetite and food intake, but evidence from oral feeding studies is sparse. The objective of this study was to determine the effects of lipid emulsion particle size on appetite response and food intake. In a three-arm randomised cross-over, high-phospholipid (PL) dairy lipid emulsions or matched control were consumed at breakfast within a yoghurt smoothie: (i) large-particle size emulsion, LPE (diameter 0.759 µm, 10 g lipid emulsion, 190 g yoghurt), (ii) small-particle size emulsion, SPE (diameter 0.290 µm, 10 g lipid emulsion, 190 g yoghurt), (iii) control non-emulsion, NE (10 g non-emulsion lipid, 190 g yoghurt). Twenty male participants completed the study, where postprandial appetite response was rated using visual analogue scales (VAS) and ad libitum energy intake at a lunch meal measured 3 h later. There was a trend for LPE to suppress hunger (P = 0.08) and enhance fullness (P = 0.24) relative to both SPE and NE but not statistically significant, and no significant effect of either emulsion on food intake at the lunch meal (P > 0.05). Altering particle size of a high-PL emulsion did not enhance satiety or alter eating behaviour in a group of lean men.

  9. Meiotic non-disjunction induced by fission neutrons relative to X-rays observed in mouse secondary spermatocytes. Pt. 1. The response of different cell stages to a single radiation dose

    Energy Technology Data Exchange (ETDEWEB)

    Russo, A.; Pacchierotti, F.; Metalli, P. (Nuclear Energy Agency, Rome (Italy). Div. of Physics and Biomedical Sciences)

    1983-03-01

    (C57BL/CnexC3H/Cne)F/sub 1/ male mice were irradiated with 2 Gy of 250-kV X-rays or 0.56 Gy of attenuated fission spectrum neutrons, and killed at various times after treatment. Second meiotic metaphases of spermatogenetic cells irradiated in various meiotic and premeiotic stages were observed. These stages were first meiotic metaphase, diplotene, late pachytene, mid-pachytene, zygotene, pre-leptotene and spermatogonia. Cells were classified by chromosome counting, and those with 18 <=n<=22 were recorded. An index of induction of non-disjunction events was obtained by the frequency of hyper-haploid spermatocytes relative to the sum of hyper-haploid and normal haploid spreads. The frequency of hyper-haploid spermatocytes was 0.7+-0.4 in control mice. It was higher after treatment with both types of radiation at all meiotic stages tested, with a peak of induction at and shortly before metaphase I-diakinesis (16-19%). Irradiated gonial cells also yielded values higher than did controls. The difference was statistically significant after irradiation with neutrons, showing that radiation can induce non-disjunction events in stem cells.

  10. Randomized, Double-Blind, Crossover Trial of Amitriptyline for Analgesia in Painful HIV-Associated Sensory Neuropathy.

    Directory of Open Access Journals (Sweden)

    Natalya Dinat

    Full Text Available We conducted a randomized, double-blind, placebo-controlled, crossover study at a single center in South Africa, to ascertain whether amitriptyline is an effective analgesic for painful HIV-associated sensory neuropathy of moderate to severe intensity in: i antiretroviral drug naive individuals, and ii antiretroviral drug users. 124 HIV-infected participants (antiretroviral drug naive = 62, antiretroviral drug users = 62 who met the study criteria for painful HIV-associated sensory neuropathy were randomized to once-daily oral amitriptyline (titrated to a median: interquartile range of 50: 25-50 mg or placebo for six weeks, followed by a three-week washout period and subsequent treatment crossover. The primary outcome measure was change from baseline in worst pain intensity of the feet (measured by participant self-report using an 11-point numerical pain rating scale after six weeks of treatment. 122 of 124 participants completed all study visits and were included in the analysis of the primary outcome. In the antiretroviral drug-naive group (n = 61 there was no significant difference in the mean change in pain score from baseline after six weeks of treatment with placebo or amitriptyline [amitriptyline: 2.8 (SD 3.3 vs. placebo: 2.8 (3.4]. Similarly, there was no significant difference in the change in pain score after six weeks of treatment with placebo or amitriptyline in the antiretroviral drug-user group (n = 61 [amitriptyline: 2.7 (3.3 vs. placebo: 2.1 (2.8]. Controlling for period effects and treatment order effects did not alter the outcome of the analyses. Nor did analyzing the intention-to-treat cohort (missing data interpolated using baseline observation carried forward alter the outcome of the analyses. In summary, amitriptyline, at the doses used here, was no more effective than an inactive placebo at reducing pain intensity in individuals with painful HIV-associated sensory neuropathy of moderate to severe intensity, irrespective of

  11. Theoretical Study of Spin Crossover in 30 Iron Complexes.

    Science.gov (United States)

    Kepp, Kasper P

    2016-03-21

    Iron complexes are important spin crossover (SCO) systems with vital roles in oxidative metabolism and promising technological potential. The SCO tendency depends on the free energy balance of high- and low-spin states, which again depends on physical effects such as dispersion, relativistic effects, and vibrational entropy. This work studied 30 different iron SCO systems with experimentally known thermochemical data, using 12 different density functionals. Remarkably general entropy-enthalpy compensation across SCO systems was identified (R = 0.82, p = 0.002) that should be considered in rational SCO design. Iron(II) complexes displayed higher ΔH and ΔS values than iron(III) complexes and also less steep compensation effects. First-coordination sphere ΔS values computed from numerical frequencies reproduce most of the experimental entropy and should thus be included when modeling spin-state changes in inorganic chemistry (R = 0.52, p = 3.4 × 10(-3); standard error in TΔS ≈ 4.4 kJ/mol at 298 K vs 16 kJ/mol of total TΔS on average). Zero-point energies favored high-spin states by 9 kJ/mol on average. Interestingly, dispersion effects are surprisingly large for the SCO process (average: 9 kJ/mol, but up to 33 kJ/mol) and favor the more compact low-spin state. Relativistic effects favor low-spin by ∼9 kJ/mol on average, but up to 24 kJ/mol. B3LYP*, TPSSh, B2PLYP, and PW6B95 performed best for the typical calculation scheme that includes ZPE. However, if relativistic and dispersion effects are included, only B3LYP* remained accurate. On average, high-spin was favored by LYP by 11-15 kJ/mol relative to other correlation functionals, and by 4.2 kJ/mol per 1% HF exchange in hybrids. 13% HF exchange was optimal without dispersion, and 15% was optimal with all effects included for these systems.

  12. Music and Alterity Processes

    Directory of Open Access Journals (Sweden)

    Josep Martí

    2014-10-01

    Full Text Available The concept of alterity constitutes an important issue in anthropological research and, therefore, in the study of musical practices, as well. Without it, we could hardly understand other kinds of music situated in different spaces and time from the observer. In order to effectively approach these musical practices, we have to develop strategies to help us reduce as much as possible that which distorts the vision of the other. However, beyond the strictly epistemological and methodological issues, the study of music cannot ignore the ethical question related to the manner in which Western thought has understood and treated the other: through a hierarchical and stereotypical type of thinking based on the condition of otherness. Throughout the article, different alterity procedures are presented and discussed, such as synecdochization, exoticization, undervaluation, overvaluation, misunderstanding and exclusion. Taking these different alterity strategies into account may help us to better understand how the musical other is constructed, used and ultimately instrumentalized.

  13. Social Justice for Crossover Youth: The Intersection of the Child Welfare and Juvenile Justice Systems.

    Science.gov (United States)

    Kolivoski, Karen M; Goodkind, Sara; Shook, Jeffrey J

    2017-10-01

    Social workers are critical to promoting racial and social justice. "Crossover youth," a term used to describe youths who have contact with both the child welfare and juvenile justice systems, are an especially vulnerable but often overlooked population with whom social workers engage. A disproportionate number of crossover youth are African American. Empirical research on crossover youth is growing, but such scholarship rarely engages with a human rights and social justice perspective. African American children and youths have a distinct place within the history and current context of the child welfare and juvenile justice systems. These systems have historically excluded them or treated them differently; now, African American youths are overrepresented in each of them, and evidence suggests they are more likely to cross over. The purpose of this article is to describe the historical and current context of crossover youth, with a particular focus on African American youths, to provide the foundation for a discussion of what social workers can do to promote racial and social justice for crossover youth, including specific implications for practice and policy, as well as broader implications for human and civil rights. © 2017 National Association of Social Workers.

  14. Process of 3D wireless decentralized sensor deployment using parsing crossover scheme

    Directory of Open Access Journals (Sweden)

    Albert H.R. Ko

    2015-07-01

    Full Text Available A Wireless Sensor Networks (WSN usually consists of numerous wireless devices deployed in a region of interest, each able to collect and process environmental information and communicate with neighboring devices. It can thus be regarded as a Multi-Agent System for territorial security, where individual agents cooperate with each other to avoid duplication of effort and to exploit other agent’s capacities. The problem of sensor deployment becomes non-trivial when we consider environmental factors, such as terrain elevations. Due to the fact that all sensors are homogeneous, the chromosomes that encode sensor positions are actually interchangeable, and conventional crossover schemes such as uniform crossover would cause some redundancy as well as over-concentration in certain specific geographical area. We propose a Parsing Crossover Scheme that intends to reduce redundancy and ease geographical concentration pattern in an effort to facilitate the search. The proposed parsing crossover method demonstrates better performances than those of uniform crossover under different terrain irregularities.

  15. On the Crossover of Boundary Currents in an Idealized Model of the Red Sea

    KAUST Repository

    Zhai, Ping

    2015-05-01

    © 2015 American Meteorological Society. The west-to-east crossover of boundary currents has been seen in mean circulation schemes from several past models of the Red Sea. This study investigates the mechanisms that produce and control the crossover in an idealized, eddy-resolving numerical model of the Red Sea. The authors also review the observational evidence and derive an analytical estimate for the crossover latitude. The surface buoyancy loss increases northward in the idealized model, and the resultant mean circulation consists of an anticyclonic gyre in the south and a cyclonic gyre in the north. In the midbasin, the northward surface flow crosses from the western boundary to the eastern boundary. Numerical experiments with different parameters indicate that the crossover latitude of the boundary currents changes with f0, β, and the meridional gradient of surface buoyancy forcing. In the analytical estimate, which is based on quasigeostrophic, β-plane dynamics, the crossover is predicted to lie at the latitude where the net potential vorticity advection (including an eddy component) is zero. Various terms in the potential vorticity budget can be estimated using a buoyancy budget, a thermal wind balance, and a parameterization of baroclinic instability.

  16. Comparison of application of various crossovers in solving inhomogeneous minimax problem modified by Goldberg model

    Science.gov (United States)

    Kobak, B. V.; Zhukovskiy, A. G.; Kuzin, A. P.

    2018-05-01

    This paper considers one of the classical NP complete problems - an inhomogeneous minimax problem. When solving such large-scale problem, there appear difficulties in obtaining an exact solution. Therefore, let us propose getting an optimum solution in an acceptable time. Among a wide range of genetic algorithm models, let us choose the modified Goldberg model, which earlier was successfully used by authors in solving NP complete problems. The classical Goldberg model uses a single-point crossover and a singlepoint mutation, which somewhat decreases the accuracy of the obtained results. In the article, let us propose using a full two-point crossover with various mutations previously researched. In addition, the work studied the necessary probability to apply it to the crossover in order to obtain results that are more accurate. Results of the computation experiment showed that the higher the probability of a crossover, the higher the quality of both the average results and the best solutions. In addition, it was found out that the higher the values of the number of individuals and the number of repetitions, the closer both the average results and the best solutions to the optimum. The paper shows how the use of a full two-point crossover increases the accuracy of solving an inhomogeneous minimax problem, while the time for getting the solution increases, but remains polynomial.

  17. Dimensional analysis and prediction of dielectrophoretic crossover frequency of spherical particles

    Directory of Open Access Journals (Sweden)

    Che-Kai Yeh

    2017-06-01

    Full Text Available The manipulation of biological cells and micrometer-scale particles using dielectrophoresis (DEP is an indispensable technique for lab-on-a-chip systems for many biological and colloidal science applications. However, existing models, including the dipole model and numerical simulations based on Maxwell stress tensor (MST, cannot achieve high accuracy and high computation efficiency at the same time. The dipole model is widely used and provides adequate predictions on the crossover frequency of submicron particles, but cannot predict the crossover frequency for larger particles accurately; on the other hand, the MST method offers high accuracy for a wide variety of particle sizes and shapes, but is time-consuming and may lack predictive understanding of the interplay between key parameters. Here we present a mathematical model, using dimensional analysis and the Buckingham pi theorem, that permits high accuracy and efficiency in predicting the crossover frequency of spherical particles. The curve fitting and calculation are performed using commercial packages OriginLab and MATLAB, respectively. In addition, through this model we also can predict the conditions in which no crossover frequency exists. Also, we propose a pair of dimensionless parameters, forming a functional relation, that provide physical insights into the dependency of the crossover frequency on five key parameters. The model is verified under several scenarios using comprehensive MST simulations by COMSOL Multiphysics software (COMSOL, Inc. and some published experimental data.

  18. Crossover between the Gaussian orthogonal ensemble, the Gaussian unitary ensemble, and Poissonian statistics.

    Science.gov (United States)

    Schweiner, Frank; Laturner, Jeanine; Main, Jörg; Wunner, Günter

    2017-11-01

    Until now only for specific crossovers between Poissonian statistics (P), the statistics of a Gaussian orthogonal ensemble (GOE), or the statistics of a Gaussian unitary ensemble (GUE) have analytical formulas for the level spacing distribution function been derived within random matrix theory. We investigate arbitrary crossovers in the triangle between all three statistics. To this aim we propose an according formula for the level spacing distribution function depending on two parameters. Comparing the behavior of our formula for the special cases of P→GUE, P→GOE, and GOE→GUE with the results from random matrix theory, we prove that these crossovers are described reasonably. Recent investigations by F. Schweiner et al. [Phys. Rev. E 95, 062205 (2017)2470-004510.1103/PhysRevE.95.062205] have shown that the Hamiltonian of magnetoexcitons in cubic semiconductors can exhibit all three statistics in dependence on the system parameters. Evaluating the numerical results for magnetoexcitons in dependence on the excitation energy and on a parameter connected with the cubic valence band structure and comparing the results with the formula proposed allows us to distinguish between regular and chaotic behavior as well as between existent or broken antiunitary symmetries. Increasing one of the two parameters, transitions between different crossovers, e.g., from the P→GOE to the P→GUE crossover, are observed and discussed.

  19. Predictive Factors for Patients Undergoing ASD Device Occlusion Who "Crossover" to Surgery.

    Science.gov (United States)

    Mulukutla, Venkatachalam; Qureshi, Athar M; Pignatelli, Ricardo; Ing, Frank F

    2018-03-01

    The aim of this study was to define characteristics of those patients who are referred for device closure of an Atrial septal defect (ASD), but identified to "crossover" surgery. All patients who underwent surgical and device (Amplatzer or Helex occluder) closures of secundum ASDs from 2001 to 2010 were reviewed and organized into three groups: surgical closure, device closure, and "crossover" group. 369 patients underwent ASD closure (265 device, 104 surgical). 42 of the 265 patients referred for device closure "crossed over" to the surgical group at various stages of the catheterization procedure. The device group had defect size measuring 14.2 mm (mean) and an ASD index (Defect Size (mm)/BSA) of 14.0 compared to the corresponding values in the surgical group (20.1 mm, ASD index 25.9) (P ASD index) (P ASD index of 14.7 compared with the crossover group ASD index of 23.8 (P ASD index greater than 23.7 had a 90% specificity in "crossing over" to surgery. The crossover and surgical groups had statistically larger ASD defect size indexes compared with the device group. Deficient rim in the posterior/inferior rim is associated with a large ASD size index which is a predictive factor for crossing over to surgery. Catheterization did not negatively impact surgical results in the "crossover" group.

  20. Two measures of bilingualism in the memories of immigrants and indigenous minorities: crossover memories and codeswitching.

    Science.gov (United States)

    Altman, Carmit

    2015-04-01

    Two indices of bilingualism, crossover memories and codeswitching (CS), were explored in five groups of immigrant (English-Hebrew, Georgian-Hebrew Russian-Hebrew) and indigenous bilinguals (Arabic-Hebrew, Hebrew-English). Participants recalled memories in response to cue words and then were asked to report the language of retrieval and provide a more elaborate narrative. More memories were 'same language' memories, recalled in the language of the experimental session/cue word, but as many as 48 % of the memories were crossovers, i.e. memories reported in a language other than the language of the session/cue word. In an effort to examine the ecological validity of the self-reported language of the memories, the frequency of CS in the elaborated narratives was investigated. For the entire sample, more CS was found for self-reported crossover memories in L2 sessions. In a further analysis of CS in crossover memories, collapsed across L1 and L2 sessions, significant differences emerged between immigrants and indigenous bilinguals. Differences between immigrant and non-immigrant bilinguals are discussed in terms of the role of activation in crossover memories.

  1. Influence of solvents on species crossover and capacity decay in non-aqueous vanadium redox flow batteries: Characterization of acetonitrile and 1, 3 dioxolane solvent mixture

    Science.gov (United States)

    Bamgbopa, Musbaudeen O.; Almheiri, Saif

    2017-02-01

    The importance of the choice of solvent in a non-aqueous redox flow battery (NARFB) cannot be overemphasized. Several studies demonstrated the influence of the solvent on electrolyte performance in terms of reaction rates, energy/power densities, and efficiencies. In this work, we investigate capacity decay as a direct consequence of varying reactant crossover rates through membranes in different solvent environments. Specifically, we demonstrate the superiority of an 84/16 vol% acetonitrile/1,3 dioxolane solvent mixture over pure acetonitrile in terms of energy efficiency (up to 89%) and capacity retention for vanadium NARFBs - while incorporating a Nafion 115 membrane. The permeability of Nafion to the vanadium acetylacetonate active species is an order of magnitude lower when pure acetonitrile is replaced by the solvent mixture. A method to estimate relative membrane permeability is formulated from numerical analysis of self-discharge experimental data. Furthermore, tests on a modified Nafion/SiO2 membrane, which generally offered low species permeability, also show that different solvents alter membrane permeability. Elemental and morphological analyses of cycled Nafion and NafionSi membranes in different solvent environments indicate that different crossover rates induced by the choice of solvent during cycling are due to changes in the membrane microstructure, intrinsic permeability, swelling rates, and chemical stability.

  2. Sodium bicarbonate ingestion improves Yo-Yo intermittent recovery test 1 performance: a randomized crossover trial

    Directory of Open Access Journals (Sweden)

    Dixon H

    2017-04-01

    Full Text Available Helen Dixon,1 Catherine E Baker,2 Julien S Baker,3 Susan Dewhurst,4 Lawrence D Hayes4 1School of Human Sciences, London Metropolitan University, London, 2English Institute of Sport, Bisham Abbey National Sports Center, Buckinghamshire, 3Institute of Clinical Exercise and Health Science, University of the West of Scotland, Hamilton, 4Department of Medical and Sport Sciences, University of Cumbria, Lancaster, UK Abstract: This study investigated the effect of sodium bicarbonate (NaHCO3– ingestion on the Yo-Yo intermittent recovery test 1 (IR1. We tested the hypothesis that acute ingestion of NaHCO3– would increase blood lactate concentrations [BLa], enhance performance, and reduce rating of perceived exertion (RPE in the Yo-Yo IR1. Eight recreationally active males (N=8, age: 26±4 yr, height: 178±6 cm, body mass: 82±10 kg participated in the Yo-Yo IR1 on two separate occasions, separated by 1 wk, in a randomized crossover design. Following familiarization, during seated rest, participants’ pretest [BLa] was taken, and participants then consumed either a placebo of 0.3 g·kg–1 body weight sodium chloride or 0.3 g·kg–1 body weight NaHCO3–. Sixty minutes postingestion, a standardized warm-up preceded the Yo-Yo IR1. Upon completion, postexercise [BLa] (mmol·L–1, RPE (arbitrary units and Yo-Yo IR1 time to fatigue (s were recorded. Paired t-test revealed a small but significant improvement in Yo-Yo IR1 performance under the NaHCO3– condition (610±267 sec, compared to the placebo condition (556±259 sec; p=0.01; Cohen’s d=0.20. [BLa] increased more under the NaHCO3– condition (1.6±0.7 to 17.5±5.2 mmol·L–1; p<0.001; Cohen’s d=4.29, compared to the placebo condition (2.0±0.7 to 11.5±5.0 mmol·L–1; p=0.001; Cohen’s d=2.66. Postexercise RPE was not significantly different between conditions. The results of this study suggest that acute NaHCO3– ingestion improves Yo-Yo IR1 performance without altering RPE, likely

  3. Popov approximation for composite bosons in the BCS-BEC crossover

    International Nuclear Information System (INIS)

    Pieri, P.; Strinati, G.C.

    2005-01-01

    Theoretical treatments of the BCS-BEC crossover need to provide as accurate as possible descriptions of the two regimes where the diluteness condition applies, either in terms of the constituent fermions (BCS limit) or of the composite bosons which form as bound-fermion pairs (BEC limit). This has to occur via a single fermionic theory that bridges across these two limiting representations. In this paper, we set up successive improvements of the fermionic theory, that result into composite bosons described at the level of either the Bogoliubov or the Popov approximations for pointlike bosons. This work bears on the recent experimental advances on the BCS-BEC crossover with trapped Fermi atoms, which show the need for accurate theoretical descriptions of the BEC side of the crossover

  4. The Crossover between Life Expectancies at Birth and at Age One

    DEFF Research Database (Denmark)

    Canudas-Romo, Vladimir; Becker, S

    2011-01-01

    one are referred to here as imbalanced. This crossover occurs when infant mortality is equal to the inverse of life expectancy at age one. This simple relation between mortality at age zero and mortality after age one divides the world into countries that have achieved the crossover in life......The single most used demographic measure to describe population health is life expectancy at birth, but life expectancies at ages other than zero are also used in the study of human longevity. Our intuition tells us that the longest life expectancy is that of a newborn. However, historically......, the expectation of life at age one (e1) has exceeded the expectation of life at birth (e0). The crossover between e0 and e1 only occurred in the developed world in the second half of the twentieth century. Life tables for populations that have not achieved this crossing between life expectancy at birth and at age...

  5. Phase transformations of under-cooled austenite of new bainitic materials for scissors crossovers

    Directory of Open Access Journals (Sweden)

    J. Pacyna

    2008-07-01

    Full Text Available The paper contains CCT diagrams presenting a transformation kinetics of under-cooled austenite from two new bainitic cast steels which the scissors crossovers for heavy-duty railway tracks (min. 230kN/axle at the speed up to 200 km/h are made of. The cooling ranges of UIC60 type railway tracks plot on the CCT diagrams indicate that there is a 100% bainitic structure in the scissors crossovers made of these cast steels as well, but mainly it would be a favourable for cracking resistance lower bainite. The achievable hardness of scissors crossovers made of new materials make it possible to use high–temperature tempering resulting in obtaining of good crack resistance. However one should provide a good quality of castings made.

  6. Are Emotions Transmitted From Work to Family? A Crossover Model of Psychological Contract Breach.

    Science.gov (United States)

    Liang, Huai-Liang

    2018-01-01

    Based on affective events theory and the crossover model, this study examines the effect of psychological contract breach on employee dysfunctional behavior and partner family undermining and explores the crossover effect of employee dysfunctional behavior on partner family undermining in work-family issues. This study collected 370 employee-partner dyads (277 male employees, 93 female employees, M age = 43.59 years) from a large manufacturing organization. The results of this study support the conception that employees' psychological contract breach results in frustration in the workplace. In addition, mediation analysis results reveal that psychological contract breach relates to employee dysfunctional behavior in the workplace. The findings show that partners' psychological strain mediates the relationship between employee dysfunctional behavior and partner family undermining. Furthermore, these findings provide investigations for the crossover model to display the value of psychological contract breach in family issues.

  7. STAR POLYMERS IN GOOD SOLVENTS FROM DILUTE TO CONCENTRATED REGIMES: CROSSOVER APPROACH

    Directory of Open Access Journals (Sweden)

    S.B.Kiselev

    2002-01-01

    Full Text Available An introduction is given to the crossover theory of the conformational and thermodynamic properties of star polymers in good solvents. The crossover theory is tested against Monte Carlo simulation data for the structure and thermodynamics of model star polymers. In good solvent conditions, star polymers approach a "universal" limit as N → ∞, however, there are two types of approach towards this limit. In the dilute regime, a critical degree of polymerization N* is found to play a similar role as the Ginzburg number in the crossover theory for critical phenomena in simple fluids. A rescaled penetration function is found to control the free energy of star polymer solutions in the dilute and semidilute regions. This equation of state captures the scaling behaviour of polymer solutions in the dilute/semidilute regimes and also performs well in the concentrated regimes, where the details of the monomer-monomer interactions become important.

  8. Crossover replantation after bilateral traumatic lower limb amputations: a case report

    Directory of Open Access Journals (Sweden)

    Fang Jun

    2012-07-01

    Full Text Available Abstract Introduction Replantation of a limb to the contralateral stump after bilateral traumatic amputations is rare. To the best of our knowledge, there are only a few reports of crossover lower limb replantation in the literature. Case presentation We treated a 37-year-old Chinese woman with bilateral lower limb crush injuries sustained in a traffic accident. Her lower limb injuries were at different anatomic levels. We performed emergency bilateral amputations followed by crossover replantation. Five years later, the woman had recovered well, and had perfect movement and stability in her replanted leg. After reviewing the literature, we thought that presentation of our patient’s case might provide useful information for clinicians. Conclusions Crossover replantation should be considered when evaluating a patient with bilateral lower limb injuries, thus allowing the patient to touch the ground and stand using their own foot.

  9. Transient Activation of Apomixis in Sexual Neotriploids May Retain Genomically Altered States and Enhance Polyploid Establishment

    Directory of Open Access Journals (Sweden)

    Diego Hojsgaard

    2018-02-01

    Full Text Available Polyploid genomes evolve and follow a series of dynamic transfigurations along with adaptation and speciation. The initial formation of a new polyploid individual within a diploid population usually involves a triploid bridge, a two-step mechanism of cell fusions between ubiquitous (reduced and rare (unreduced gametes. The primary fusion event creates an intermediate triploid individual with unbalanced genome sets, a situation of genomic-shock characterized by gene expression dysregulation, high dosage sensitivity, disturbed cell divisions, and physiological and reproductive attributes drastically altered. This near-sterile neotriploid must produce (even eupolyploids through secondary fusion events to restore genome steadiness, meiotic balance, and fertility required for the demographic establishment of a nascent lineage. Natural conditions locate several difficulties to polyploid establishment, including the production of highly unbalanced and rarely unreduced (euploid gametes, frequency-dependent disadvantages (minority cytotype exclusion, severe fitness loss, and ecological competition with diploid parents. Persistence and adaptation of neopolyploids depend upon genetic and phenotypic novelty coupled to joint selective forces that preserve shock-induced genomic changes (subgenome homeolog partitioning and drive meiotic (reproductive stabilization and ecological diversification. Thus, polyploid establishment through the triploid bridge is a feasible but not ubiquitous process that requires a number of low-probability events and singular circumstances. Yet, frequencies of polyploids suggest that polyploid establishment is a pervasive process. To explain this disparity, and supported in experimental evidence, I propose that situations like hybridization and ploidy-state transitions associated to genomic shock and substantial developmental alterations can transiently activate apomixis as a mechanism to halt genomic instability and cancel factors

  10. Plasma membrane events associated with the meiotic divisions in the amphibian oocyte: insights into the evolution of insulin transduction systems and cell signaling

    Directory of Open Access Journals (Sweden)

    Morrill Gene A

    2013-01-01

    Full Text Available Abstract Background Insulin and its plasma membrane receptor constitute an ancient response system critical to cell growth and differentiation. Studies using intact Rana pipiens oocytes have shown that insulin can act at receptors on the oocyte surface to initiate resumption of the first meiotic division. We have reexamined the insulin-induced cascade of electrical and ion transport-related plasma membrane events using both oocytes and intact plasma membranes in order to characterize the insulin receptor-steroid response system associated with the meiotic divisions. Results [125I]Insulin binding (Kd = 54 ± 6 nM at the oocyte plasma membrane activates membrane serine protease(s, followed by the loss of low affinity ouabain binding sites, with a concomitant 3–4 fold increase in high affinity ouabain binding sites. The changes in protease activity and ouabain binding are associated with increased Na+/Ca2+ exchange, increased endocytosis, decreased Na+ conductance resulting in membrane hyperpolarization, increased 2-deoxy-D-glucose uptake and a sustained elevation of intracellular pH (pHi. Hyperpolarization is largely due to Na+-channel inactivation and is the main driving force for glucose uptake by the oocyte via Na+/glucose cotransport. The Na+ sym- and antiporter systems are driven by the Na+ free energy gradient generated by Na+/K+-ATPase. Shifts in α and/or β Na+-pump subunits to caveolar (lipid raft membrane regions may activate Na/K-ATPase and contribute to the Na+ free energy gradient and the increase in both Na+/glucose co-transport and pHi. Conclusions Under physiological conditions, resumption of meiosis results from the concerted action of insulin and progesterone at the cell membrane. Insulin inactivates Na+ channels and mobilizes fully functional Na+-pumps, generating a Na+ free energy gradient which serves as the energy source for several membrane anti- and symporter systems.

  11. Short periods of high temperature during meiosis prevent normal meiotic progression and reduce grain number in hexaploid wheat (Triticum aestivum L.).

    Science.gov (United States)

    Draeger, Tracie; Moore, Graham

    2017-09-01

    Exposure of wheat to high temperatures during male meiosis prevents normal meiotic progression and reduces grain number. We define a temperature-sensitive period and link heat tolerance to chromosome 5D. This study assesses the effects of heat on meiotic progression and grain number in hexaploid wheat (Triticum aestivum L. var. Chinese Spring), defines a heat-sensitive stage and evaluates the role of chromosome 5D in heat tolerance. Plants were exposed to high temperatures (30 or 35 °C) in a controlled environment room for 20-h periods during meiosis and the premeiotic interphase just prior to meiosis. Examination of pollen mother cells (PMCs) from immature anthers immediately before and after heat treatment enabled precise identification of the developmental phases being exposed to heat. A temperature-sensitive period was defined, lasting from premeiotic interphase to late leptotene, during which heat can prevent PMCs from progressing through meiosis. PMCs exposed to 35 °C were less likely to progress than those exposed to 30 °C. Grain number per spike was reduced at 30 °C, and reduced even further at 35 °C. Chinese Spring nullisomic 5D-tetrasomic 5B (N5DT5B) plants, which lack chromosome 5D, were more susceptible to heat during premeiosis-leptotene than Chinese Spring plants with the normal (euploid) chromosome complement. The proportion of plants with PMCs progressing through meiosis after heat treatment was lower for N5DT5B plants than for euploids, but the difference was not significant. However, following exposure to 30 °C, in euploid plants grain number was reduced (though not significantly), whereas in N5DT5B plants the reduction was highly significant. After exposure to 35 °C, the reduction in grain number was highly significant for both genotypes. Implications of these findings for the breeding of thermotolerant wheat are discussed.

  12. Evidence that meiotic pairing starts at the telomeres: Molecular analysis of recombination in a family with a pericentric X chromosome inversion

    Energy Technology Data Exchange (ETDEWEB)

    Shashi, V.; Allinson, P.S.; Golden, W.L.; Kelly, T.E. [Univ. of Virginia, Charlottesville, VA (United States)

    1994-09-01

    Recent studies in yeast have shown that telomeres rather than centromeres lead in chromosome movement just prior to meiosis and may have a role in recombination. Cytological studies of meiosis in Drosophila and mice have shown that in pericentric inversion heterozygotes there is lack of loop formation, with recobmination seen only outside the inversion. In a family with Duchenne muscular dystrophy (DMD) we recognized that only affected males and carrier females had a pericentric X chromosome inversion (inv X(p11.4;q26)). Since the short arm inversion breakpoint was proximal to the DMD locus, it could not be implicated in the mutational event causing DMD. There was no history of infertility, recurrent miscarriages or liveborn unbalanced females to suggest there was recombination within the inversion. We studied 22 members over three generations to understand the pattern of meiotic recombination between the normal and the inverted X chromosome. In total, 17 meioses involving the inverted X chromosome in females were studied by cytogenetic analysis and 16 CA repeat polymorphisms along the length of the X chromosome. Results: (a) There was complete concordance between the segregation of the DMD mutation and the inverted X chromosome. (b) On DNA analysis, there was complete absence of recombination within the inverted segment. We also found no recombination at the DMD locus. Recombination was seen only at Xp22 and Xq27-28. (c) Recombination was seen in the same individual at both Xp22 and Xq27-28 without recombination otherwise. Conclusions: (1) Pericentric X inversions reduce the genetic map length of the chromosome, with the physical map length being normal. (2) Meiotic X chromosome pairing in this family is initiated at the telomeres. (3) Following telomeric pairing in pericentric X chromosome inversions, there is inhibition of recombination within the inversion and adjacent regions.

  13. Effects of exercise on the desire to smoke and physiological responses to temporary smoking abstinence: a crossover trial.

    Science.gov (United States)

    Roberts, Vaughan; Gant, Nicholas; Sollers, John J; Bullen, Chris; Jiang, Yannan; Maddison, Ralph

    2015-03-01

    Exercise has been shown to attenuate cigarette cravings during temporary smoking abstinence; however, the mechanisms of action are not clearly understood. The objectives of the study were to compare the effects of three exercise intensities on desire to smoke and explore potential neurobiological mediators of desire to smoke. Following overnight abstinence, 40 participants (25 males, 18-59 years) completed three 15 min sessions of light-, moderate-, or vigorous-intensity exercise on a cycle ergometer in a randomized crossover design. Ratings of desire to smoke were self-reported pre- and post-exercise and heart rate variability was measured throughout. Saliva and blood were analyzed for cortisol and noradrenaline in a sub-sample. Exercise influenced desire to smoke (F [2, 91] = 7.94, p exercise. There were also significant time x exercise intensity interaction effects for heart rate variability and plasma noradrenaline (F [8, 72] = 2.23, p = 0.03), with a bias in noradrenaline occurring between light and vigorous conditions (adjusted mean difference [SE] = 2850 ng/ml [592], p exercise. There was no interaction of time x exercise intensity for plasma and salivary cortisol levels. These findings support the use of vigorous exercise to reduce cigarette cravings, showing potential alterations in a noradrenergic marker.

  14. β-Glucan and Dark Chocolate: A Randomized Crossover Study on Short-Term Satiety and Energy Intake

    Directory of Open Access Journals (Sweden)

    Asli Akyol

    2014-09-01

    Full Text Available Aim: The aims of this study were to adapt a traditional recipe into a healthier form by adding 3 g of oat β-glucan, substituting milk chocolate to dark chocolate with 70% cocoa, and to examine the effect of these alterations on short-term satiety and energy intake. Materials and Methods: Study subjects (n = 25 were tested in a randomized, crossover design with four products closely matched for energy content. Four different versions of a traditional recipe including milk chocolate-control (CON, oat β-glucan (B-GLU, dark chocolate (DARK or oat β-glucan and dark chocolate (B-GLU + DARK were given to subjects on different test days. After subjects were asked to report visual analog scale (VAS scores on sensory outcomes and related satiety for four hours ad libitum, lunch was served and energy intake of individuals was measured. Results: VAS scores indicated that none of the test foods exerted an improved effect on satiety feelings. However, energy intake of individuals during ad libitum lunch was significantly lower in dark chocolate groups (CON: 849.46 ± 47.45 kcal versus DARK: 677.69 ± 48.45 kcal and B-GLU + DARK: 691.08 ± 47.45 kcal, p = 0.014. Conclusion: The study demonstrated that substituting dark chocolate for milk chocolate is more effective in inducing satiety during subsequent food intake in healthy subjects.

  15. Dark chocolate and vascular function in patients with peripheral artery disease: a randomized, controlled cross-over trial.

    Science.gov (United States)

    Hammer, Alexandra; Koppensteiner, Renate; Steiner, Sabine; Niessner, Alexander; Goliasch, Georg; Gschwandtner, Michael; Hoke, Matthias

    2015-01-01

    Flavonoid-rich dark chocolate has positive effects on vascular function in healthy subjects and in patients at risk of atherosclerosis. The impact of dark chocolate on endothelial and microvascular function in patients with symptomatic peripheral artery disease (PAD) has not been investigated so far. In an investigator blinded, randomized, controlled, cross-over trial we assessed the effect of flavonoid-rich dark chocolate and cocoa-free control chocolate on flow-mediated dilatation (FMD) of the brachial artery and on microvascular function (assessed by Laser Doppler fluxmetry) in 21 patients with symptomatic (Fontaine stage II) PAD. Measurements were done in each patient on 2 single days, with an interval of 7 days, at baseline and at 2 hours after ingestion of 50 g dark chocolate or 50 g white chocolate, respectively. FMD remained unchanged after intake of dark chocolate (baseline and 2 hours after ingestion, %: 5.1 [IQR 4.4 to 7.3] and 5.5 [IQR 3.9 to 10.4]; p = 0.57, and after intake of white chocolate (baseline and 2 hours after ingestion, %: 6.4 [IQR 4.5 to 11.4] and 4.4 [IQR 2.6 to 8.7]; p = 0.14. Similarly, microcirculatory parameters were not significantly altered after intake of any chocolate compared with the respective baseline values. In conclusion, a single consumption of 50 g dark chocolate has no effect on endothelial and microvascular function in patients with symptomatic PAD.

  16. β-Glucan and dark chocolate: a randomized crossover study on short-term satiety and energy intake.

    Science.gov (United States)

    Akyol, Asli; Dasgin, Halil; Ayaz, Aylin; Buyuktuncer, Zehra; Besler, H Tanju

    2014-09-23

    The aims of this study were to adapt a traditional recipe into a healthier form by adding 3 g of oat β-glucan, substituting milk chocolate to dark chocolate with 70% cocoa, and to examine the effect of these alterations on short-term satiety and energy intake. Study subjects (n = 25) were tested in a randomized, crossover design with four products closely matched for energy content. Four different versions of a traditional recipe including milk chocolate-control (CON), oat β-glucan (B-GLU), dark chocolate (DARK) or oat β-glucan and dark chocolate (B-GLU + DARK) were given to subjects on different test days. After subjects were asked to report visual analog scale (VAS) scores on sensory outcomes and related satiety for four hours ad libitum, lunch was served and energy intake of individuals was measured. VAS scores indicated that none of the test foods exerted an improved effect on satiety feelings. However, energy intake of individuals during ad libitum lunch was significantly lower in dark chocolate groups (CON: 849.46 ± 47.45 kcal versus DARK: 677.69 ± 48.45 kcal and B-GLU + DARK: 691.08 ± 47.45 kcal, p = 0.014). The study demonstrated that substituting dark chocolate for milk chocolate is more effective in inducing satiety during subsequent food intake in healthy subjects.

  17. Effects of density imbalance on the BCS-BEC crossover in semiconductor electron-hole bilayers

    International Nuclear Information System (INIS)

    Pieri, P.; Strinati, G. C.; Neilson, D.

    2007-01-01

    We study the occurrence of excitonic superfluidity in electron-hole bilayers at zero temperature. We not only identify the crossover in the phase diagram from the BCS limit of overlapping pairs to the BEC limit of nonoverlapping tightly bound pairs but also, by varying the electron and hole densities independently, we can analyze a number of phases that occur mainly in the crossover region. With different electron and hole effective masses, the phase diagram is asymmetric with respect to excess electron or hole densities. We propose, as the criterion for the onset of superfluidity, the jump of the electron and hole chemical potentials when their densities cross

  18. Manipulating charge transfer excited state relaxation and spin crossover in iron coordination complexes with ligand substitution

    DEFF Research Database (Denmark)

    Zhang, Wenkai; Kjær, Kasper Skov; Alonso-Mori, Roberto

    2017-01-01

    iron complexes with four cyanide (CN-;) ligands and one 2,2′-bipyridine (bpy) ligand. This enables MLCT excited state and metal-centered excited state energies to be manipulated with partial independence and provides a path to suppressing spin crossover. We have combined X-ray Free-Electron Laser (XFEL...... state lifetime of iron based complexes due to spin crossover-the extremely fast intersystem crossing and internal conversion to high spin metal-centered excited states. We revitalize a 30 year old synthetic strategy for extending the MLCT excited state lifetimes of iron complexes by making mixed ligand...

  19. Crossover of two power laws in the anomalous diffusion of a two lipid membrane

    Energy Technology Data Exchange (ETDEWEB)

    Bakalis, Evangelos, E-mail: ebakalis@gmail.com, E-mail: francesco.zerbetto@unibo.it; Höfinger, Siegfried; Zerbetto, Francesco, E-mail: ebakalis@gmail.com, E-mail: francesco.zerbetto@unibo.it [Dipartimento di Chimica “G. Ciamician”, Universita’ di Bologna, Via F. Selmi 2, 40126 Bologna (Italy); Venturini, Alessandro [Institute for the Organic Synthesis and Photoreactivity, National Research Council of Italy, Via Gobetti 101, 40129 Bologna (Italy)

    2015-06-07

    Molecular dynamics simulations of a bi-layer membrane made by the same number of 1-palmitoyl-2-oleoyl-glycero-3-phospho-ethanolamine and palmitoyl-oleoyl phosphatidylserine lipids reveal sub-diffusional motion, which presents a crossover between two different power laws. Fractional Brownian motion is the stochastic mechanism that governs the motion in both regimes. The location of the crossover point is justified with simple geometrical arguments and is due to the activation of the mechanism of circumrotation of lipids about each other.

  20. Radius crossover sign: an indication of malreduced radius shaft greenstick fractures.

    Science.gov (United States)

    Wright, Patrick B; Crepeau, Allison E; Herrera-Soto, José A; Price, Charles T

    2012-06-01

    Radius shaft greenstick fractures in children can be a challenging injury to treat because angulation and rotational alignment are difficult to assess. In this report, we describe a simple method for analyzing the deformity and identifying rotational and angular malalignment. This technique involves analyzing the forearm radiographs as 2 segments, proximal and distal, and assuring that the rotational position of each matches the other. We present 3 cases of proximal radius greenstick fractures in malalignment to demonstrate the radius crossover sign. Identifying the radius crossover sign, and proceeding with further closed reduction may prevent deformity that could otherwise result in a significant loss of forearm motion. Level V.

  1. Effects of the electric field on ion crossover in vanadium redox flow batteries

    International Nuclear Information System (INIS)

    Yang, Xiao-Guang; Ye, Qiang; Cheng, Ping; Zhao, Tim S.

    2015-01-01

    Highlights: • Effects of the electric field on ion crossover and capacity decay in VRFB are studied. • The model enables the Donnan-potential jumps to be captured at electrode/membrane interfaces. • Electric field arises and affects ion crossover even at the open-circuit condition. • Enhancing electric-field-driven crossover can mitigate the capacity decay rate. - Abstract: A thorough understanding of the mechanisms of ion crossover through the membranes in vanadium redox flow batteries (VRFBs) is critically important in making improvements to the battery’s efficiency and cycling performance. In this work, we develop a 2-D VRFB model to investigate the mechanisms of ion crossover and the associated impacts it has on the battery’s performance. Unlike previously described models in the literature that simulated a single cell by dividing it into the positive electrode, membrane, and negative electrode regions, the present model incorporates all possible ion crossover mechanisms in the entire cell without a need to specify any interfacial boundary conditions at the membrane/electrode interfaces, and hence accurately captures the Donnan-potential jumps and steep gradient of species concentrations at the membrane/electrode interfaces. With our model, a particular emphasis is given to investigation of the effect of the electric field on vanadium ion crossover. One of the significant findings is that an electric field exists in the membrane even under the open-circuit condition, primarily due to the presence of the H + concentration gradient across the membrane. This finding suggests that vanadium ions can permeate through the membrane from H + -diluted to H + -concentrated sides via migration and convection. More importantly, it is found that the rate of vanadium ion crossover and capacity decay during charge and discharge vary with the magnitude of the electric field, which is influenced by the membrane properties and operating conditions. The simulations

  2. Crossover of two power laws in the anomalous diffusion of a two lipid membrane.

    Science.gov (United States)

    Bakalis, Evangelos; Höfinger, Siegfried; Venturini, Alessandro; Zerbetto, Francesco

    2015-06-07

    Molecular dynamics simulations of a bi-layer membrane made by the same number of 1-palmitoyl-2-oleoyl-glycero-3-phospho-ethanolamine and palmitoyl-oleoyl phosphatidylserine lipids reveal sub-diffusional motion, which presents a crossover between two different power laws. Fractional Brownian motion is the stochastic mechanism that governs the motion in both regimes. The location of the crossover point is justified with simple geometrical arguments and is due to the activation of the mechanism of circumrotation of lipids about each other.

  3. Crossover driven by time-reversal symmetry breaking in quantum chaos

    International Nuclear Information System (INIS)

    Taniguchi, N.; Hashimoto, A.; Simons, B.D.; Altshuler, B.L.

    1994-01-01

    Parametric correlations of the energy spectra of quantum chaotic systems are presented in the presence of time-reversal symmetry-breaking perturbations. The spectra disperse as a function of two external perturbations, one of which preserves time-reversal symmetry, while the other violates it. Exact analytical expressions for the parametric two-point autocorrelation function of the density of states are derived in the crossover region by means of the supermatrix method. For the orthogonal-unitary crossover, the velocity distribution is determined and shown to deviate from Gaussian. (orig.)

  4. Recent Studies on Methanol Crossover in Liquid-Feed Direct Methanol Fuel Cells

    Science.gov (United States)

    Valdez, T. I.; Narayanan, S. R.

    2000-01-01

    In this work, the effects of methanol crossover and airflow rates on the cathode potential of an operating direct methanol fuel cell are explored. Techniques for quantifying methanol crossover in a fuel cell and for separating the electrical performance of each electrode in a fuel cell are discussed. The effect of methanol concentration on cathode potential has been determined to be significant. The cathode is found to be mass transfer limited when operating on low flow rate air and high concentrations of methanol. Improvements in cathode structure and operation at low methanol concentration have been shown to result in improved cell performance.

  5. Holographic entanglement entropy close to crossover/phase transition in strongly coupled systems

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Shao-Jun, E-mail: sjzhang84@hotmail.com

    2017-03-15

    We investigate the behavior of entanglement entropy in the holographic QCD model proposed by Gubser et al. By choosing suitable parameters of the scalar self-interaction potential, this model can exhibit various types of phase structures: crossover, first order and second order phase transitions. We use entanglement entropy to probe the crossover/phase transition, and find that it drops quickly/suddenly when the temperature approaches the critical point which can be seen as a signal of confinement. Moreover, the critical behavior of the entanglement entropy suggests that we may use it to characterize the corresponding phase structures.

  6. Crossover And MTF Characteristics Of A Tabular-Grain X-Ray Film

    Science.gov (United States)

    Huff, K. E.; Wagner, P. W.

    1984-08-01

    An orthochromatic x-ray film made with tabular silver halide grains has a significantly higher MTF when exposed with green-emitting intensifying screens than do conventional films with similar sensitometric properties. The primary reason for the improved MTF is a decrease in the amount of crossover exposure, i.e., exposure by light that has crossed the support one or more times. Two well-established sensitometric procedures for measuring crossover have been compared. One produces results accurate enough for calculations of MTF relationships. Calculated MTF relationships for tabulargrain and conventional films are compared with measured values.

  7. Effects of 24 h working on-call on psychoneuroendocrine and oculomotor function: a randomized cross-over trial.

    Science.gov (United States)

    Ernst, Florian; Rauchenzauner, Markus; Zoller, Heinz; Griesmacher, Andrea; Hammerer-Lercher, Angelika; Carpenter, Roger; Schuessler, Gerhard; Joannidis, Michael

    2014-09-01

    On-call duty (OCD) is frequently associated with health and safety risks for both physicians and patients. The lack of studies conducted in clinical care environments and the ongoing public dialogue concerning OCD led to a detailed investigation of a working schedule including sleep fragmentation and extended work hours. Within-person randomized cross-over trial. Comparison of a 24h on-call shift (OCD) compared to a routine working-day (non on call, NOC) in hospital. 30 residents and senior physicians of the Department of Internal Medicine, Neurology and Otorhinolaryngology at the University Hospital Innsbruck. Sleep variables, cognitive performance (Concentration-Endurance d2 test), emotional status (Eigenschaftswoerterliste 60S), serum-cortisol, urinary cortisol and noradrenaline, heart-rate variability, and saccadic eye movements were determined before and after OCD and NOC respectively. Concentration-endurance performance was significantly reduced after OCD as compared to NOC by 16.4% (preduced after OCD (p<0.05) compared to NOC. 24 h OCD alters both, the sympathetic-adrenomedullary system as well as the hypothalamic pituitary-adrenocortical axis. Moreover, physicians' emotional state, cognitive and oculomotor performance seems to be influenced independently from sleep interruptions. The discrepancy between subjective feeling and objective cognitive impairments pose a risk for performing complex manual and cognitive tasks. Hence, our findings argue against an oversimplified interpretation of alterations in the physicians' psychoneuroendocrine structure in terms of impaired mood and neurocognitive deterioration combined with up-/dysregulated stress axes associated with OCD as a consequence of sleep deprivation. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Immunization alters body odor.

    Science.gov (United States)

    Kimball, Bruce A; Opiekun, Maryanne; Yamazaki, Kunio; Beauchamp, Gary K

    2014-04-10

    Infections have been shown to alter body odor. Because immune activation accompanies both infection and immunization, we tested the hypothesis that classical immunization might similarly result in the alteration of body odors detectable by trained biosensor mice. Using a Y-maze, we trained biosensor mice to distinguish between urine odors from rabies-vaccinated (RV) and unvaccinated control mice. RV-trained mice generalized this training to mice immunized with the equine West Nile virus (WNV) vaccine compared with urine of corresponding controls. These results suggest that there are similarities between body odors of mice immunized with these two vaccines. This conclusion was reinforced when mice could not be trained to directly discriminate between urine odors of RV- versus WNV-treated mice. Next, we trained biosensor mice to discriminate the urine odors of mice treated with lipopolysaccharide (LPS; a general elicitor of innate immunological responses) from the urine of control mice. These LPS-trained biosensors could distinguish between the odors of LPS-treated mouse urine and RV-treated mouse urine. Finally, biosensor mice trained to distinguish between the odors of RV-treated mouse urine and control mouse urine did not generalize this training to discriminate between the odors of LPS-treated mouse urine and control mouse urine. From these experiments, we conclude that: (1) immunization alters urine odor in similar ways for RV and WNV immunizations; and (2) immune activation with LPS also alters urine odor but in ways different from those of RV and WNV. Published by Elsevier Inc.

  9. Safety of a new compact catheter for men with neurogenic bladder dysfunction: a randomised, crossover and open-labelled study

    DEFF Research Database (Denmark)

    Chartier-Kastler, E; Lauge, I; Ruffion, A

    2011-01-01

    Self-catheterising males aged ≥18 years with spinal cord lesion and normal/impaired urethral sensation were enrolled in this comparative, randomised, crossover and open-labelled multicentre trial.......Self-catheterising males aged ≥18 years with spinal cord lesion and normal/impaired urethral sensation were enrolled in this comparative, randomised, crossover and open-labelled multicentre trial....

  10. Safety of a new compact catheter for men with neurogenic bladder dysfunction: a randomised, crossover and open-labelled study

    DEFF Research Database (Denmark)

    Chartier-Kastler, E; Lauge, I; Ruffion, A

    2011-01-01

    Self-catheterising males aged =18 years with spinal cord lesion and normal/impaired urethral sensation were enrolled in this comparative, randomised, crossover and open-labelled multicentre trial.......Self-catheterising males aged =18 years with spinal cord lesion and normal/impaired urethral sensation were enrolled in this comparative, randomised, crossover and open-labelled multicentre trial....

  11. Rhombic-Shaped Nanostructures and Mechanical Properties of 2D DNA Origami Constructed with Different Crossover/Nick Designs.

    Science.gov (United States)

    Ma, Zhipeng; Huang, Yunfei; Park, Seongsu; Kawai, Kentaro; Kim, Do-Nyun; Hirai, Yoshikazu; Tsuchiya, Toshiyuki; Yamada, Hirofumi; Tabata, Osamu

    2018-01-01

    DNA origami methods enable the fabrication of various nanostructures and nanodevices, but their effective use depends on an understanding of their structural and mechanical properties and the effects of basic structural features. Frequency-modulation atomic force microscopy is introduced to directly characterize, in aqueous solution, the crossover regions of sets of 2D DNA origami based on different crossover/nick designs. Rhombic-shaped nanostructures formed under the influence of flexible crossovers placed between DNA helices are observed in DNA origami incorporating crossovers every 3, 4, or 6 DNA turns. The bending rigidity of crossovers is determined to be only one-third of that of the DNA helix, based on interhelical electrostatic forces reported elsewhere, and the measured pitches of the 3-turn crossover design rhombic-shaped nanostructures undergoing negligible bending. To evaluate the robustness of their structural integrity, they are intentionally and simultaneously stressed using force-controlled atomic force microscopy. DNA crossovers are verified to have a stabilizing effect on the structural robustness, while the nicks have an opposite effect. The structural and mechanical properties of DNA origami and the effects of crossovers and nicks revealed in this paper can provide information essential for the design of versatile DNA origami structures that exhibit specified and desirable properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Natural type 3/type 2 intertypic vaccine-related poliovirus recombinants with the first crossover sites within the VP1 capsid coding region.

    Science.gov (United States)

    Zhang, Yong; Zhu, Shuangli; Yan, Dongmei; Liu, Guiyan; Bai, Ruyin; Wang, Dongyan; Chen, Li; Zhu, Hui; An, Hongqiu; Kew, Olen; Xu, Wenbo

    2010-12-21

    Ten uncommon natural type 3/type 2 intertypic poliovirus recombinants were isolated from stool specimens from nine acute flaccid paralysis case patients and one healthy vaccinee in China from 2001 to 2008. Complete genomic sequences revealed their vaccine-related genomic features and showed that their first crossover sites were randomly distributed in the 3' end of the VP1 coding region. The length of donor Sabin 2 sequences ranged from 55 to 136 nucleotides, which is the longest donor sequence reported in the literature for this type of poliovirus recombination. The recombination resulted in the introduction of Sabin 2 neutralizing antigenic site 3a (NAg3a) into a Sabin 3 genomic background in the VP1 coding region, which may have been altered by some of the type 3-specific antigenic properties, but had not acquired any type 2-specific characterizations. NAg3a of the Sabin 3 strain seems atypical; other wild-type poliovirus isolates that have circulated in recent years have sequences of NAg3a more like the Sabin 2 strain. 10 natural type 3/type 2 intertypic VP1 capsid-recombinant polioviruses, in which the first crossover sites were found to be in the VP1 coding region, were isolated and characterized. In spite of the complete replacement of NAg3a by type 2-specific amino acids, the serotypes of the recombinants were not altered, and they were totally neutralized by polyclonal type 3 antisera but not at all by type 2 antisera. It is possible that recent type 3 wild poliovirus isolates may be a recombinant having NAg3a sequences derived from another strain during between 1967 and 1980, and the type 3/type 2 recombination events in the 3' end of the VP1 coding region may result in a higher fitness.

  13. Natural type 3/type 2 intertypic vaccine-related poliovirus recombinants with the first crossover sites within the VP1 capsid coding region.

    Directory of Open Access Journals (Sweden)

    Yong Zhang

    Full Text Available BACKGROUND: Ten uncommon natural type 3/type 2 intertypic poliovirus recombinants were isolated from stool specimens from nine acute flaccid paralysis case patients and one healthy vaccinee in China from 2001 to 2008. PRINCIPAL FINDINGS: Complete genomic sequences revealed their vaccine-related genomic features and showed that their first crossover sites were randomly distributed in the 3' end of the VP1 coding region. The length of donor Sabin 2 sequences ranged from 55 to 136 nucleotides, which is the longest donor sequence reported in the literature for this type of poliovirus recombination. The recombination resulted in the introduction of Sabin 2 neutralizing antigenic site 3a (NAg3a into a Sabin 3 genomic background in the VP1 coding region, which may have been altered by some of the type 3-specific antigenic properties, but had not acquired any type 2-specific characterizations. NAg3a of the Sabin 3 strain seems atypical; other wild-type poliovirus isolates that have circulated in recent years have sequences of NAg3a more like the Sabin 2 strain. CONCLUSIONS: 10 natural type 3/type 2 intertypic VP1 capsid-recombinant polioviruses, in which the first crossover sites were found to be in the VP1 coding region, were isolated and characterized. In spite of the complete replacement of NAg3a by type 2-specific amino acids, the serotypes of the recombinants were not altered, and they were totally neutralized by polyclonal type 3 antisera but not at all by type 2 antisera. It is possible that recent type 3 wild poliovirus isolates may be a recombinant having NAg3a sequences derived from another strain during between 1967 and 1980, and the type 3/type 2 recombination events in the 3' end of the VP1 coding region may result in a higher fitness.

  14. Effect of almond consumption on vascular function in patients with coronary artery disease: a randomized, controlled, cross-over trial.

    Science.gov (United States)

    Chen, C-Y Oliver; Holbrook, Monika; Duess, Mai-Ann; Dohadwala, Mustali M; Hamburg, Naomi M; Asztalos, Bela F; Milbury, Paul E; Blumberg, Jeffrey B; Vita, Joseph A

    2015-06-17

    Almonds reduce cardiovascular disease risk via cholesterol reduction, anti-inflammation, glucoregulation, and antioxidation. The objective of this randomized, controlled, cross-over trial was to determine whether the addition of 85 g almonds daily to a National Cholesterol Education Program (NCEP) Step 1 diet (ALM) for 6 weeks would improve vascular function and inflammation in patients with coronary artery disease (CAD). A randomized, controlled, crossover trial was conducted in Boston, MA to test whether as compared to a control NCEP Step 1 diet absent nuts (CON), incorporation of almonds (85 g/day) into the CON diet (ALM) would improve vascular function and inflammation. The study duration was 22 weeks including a 6-weeks run-in period, two 6-weeks intervention phases, and a 4-weeks washout period between the intervention phases. A total of 45 CAD patients (27 F/18 M, 45-77 y, BMI = 20-41 kg/m(2)) completed the study. Drug therapies used by patients were stable throughout the duration of the trial. The addition of almonds to the CON diet increased plasma α-tocopherol status by a mean of 5.8%, reflecting patient compliance (P ≤0.05). However, the ALM diet did not alter vascular function assessed by measures of flow-mediated dilation, peripheral arterial tonometry, and pulse wave velocity. Further, the ALM diet did not significantly modify the serum lipid profile, blood pressure, C-reactive protein, tumor necrosis factor-α or E-selectin. The ALM diet tended to decrease vascular cell adhesion molecule-1 by 5.3% (P = 0.064) and increase urinary nitric oxide by 17.5% (P = 0.112). The ALM intervention improved the overall quality of the diet by increasing calcium, magnesium, choline, and fiber intakes above the Estimated Average Requirement (EAR) or Recommended Dietary Allowance (RDA). Thus, the addition of almonds to a NECP Step 1 diet did not significantly impact vascular function, lipid profile or systematic inflammation in CAD patients receiving

  15. Effect of Short-Term Fasting on Systemic Cytochrome P450-Mediated Drug Metabolism in Healthy Subjects: A Randomized, Controlled, Crossover Study Using a Cocktail Approach.

    Science.gov (United States)

    Lammers, Laureen A; Achterbergh, Roos; van Schaik, Ron H N; Romijn, Johannes A; Mathôt, Ron A A

    2017-10-01

    Short-term fasting can alter drug exposure but it is unknown whether this is an effect of altered oral bioavailability and/or systemic clearance. Therefore, the aim of our study was to assess the effect of short-term fasting on oral bioavailability and systemic clearance of different drugs. In a randomized, controlled, crossover trial, 12 healthy subjects received a single administration of a cytochrome P450 (CYP) probe cocktail, consisting of caffeine (CYP1A2), metoprolol (CYP2D6), midazolam (CYP3A4), omeprazole (CYP2C19) and warfarin (CYP2C9), on four occasions: an oral (1) and intravenous (2) administration after an overnight fast (control) and an oral (3) and intravenous (4) administration after 36 h of fasting. Pharmacokinetic parameters of the probe drugs were analyzed using the nonlinear mixed-effects modeling software NONMEM. Short-term fasting increased systemic caffeine clearance by 17% (p = 0.04) and metoprolol clearance by 13% (p < 0.01), whereas S-warfarin clearance decreased by 19% (p < 0.01). Fasting did not affect bioavailability. The study demonstrates that short-term fasting alters CYP-mediated drug metabolism in a non-uniform pattern without affecting oral bioavailability.

  16. Application of mapping crossover genetic algorithm in nuclear power equipment optimization design

    International Nuclear Information System (INIS)

    Li Guijiang; Yan Changqi; Wang Jianjun; Liu Chengyang

    2013-01-01

    Genetic algorithm (GA) has been widely applied in nuclear engineering. An improved method, named the mapping crossover genetic algorithm (MCGA), was developed aiming at improving the shortcomings of traditional genetic algorithm (TGA). The optimal results of benchmark problems show that MCGA has better optimizing performance than TGA. MCGA was applied to the reactor coolant pump optimization design. (authors)

  17. Comparison between a diagrammatic theory for the BCS-BEC crossover and quantum Monte Carlo results

    International Nuclear Information System (INIS)

    Pieri, P.; Pisani, L.; Strinati, G.C.

    2005-01-01

    Predictions for the chemical potential and the excitation gap recently obtained by our diagrammatic theory for the Bardeen-Cooper-Schreiffer-Bose-Einstein Condensation crossover in the superfluid phase are compared with quantum Monte Carlo results at zero temperature now available in the literature. A remarkable agreement is found between the results obtained by the two approaches

  18. A Randomized Crossover Study of Web-Based Media Literacy to Prevent Smoking

    Science.gov (United States)

    Shensa, Ariel; Phelps-Tschang, Jane; Miller, Elizabeth; Primack, Brian A.

    2016-01-01

    Feasibly implemented Web-based smoking media literacy (SML) programs have been associated with improving SML skills among adolescents. However, prior evaluations have generally had weak experimental designs. We aimed to examine program efficacy using a more rigorous crossover design. Seventy-two ninth grade students completed a Web-based SML…

  19. The impact of anode design on fuel crossover of direct ethanol fuel cell

    Indian Academy of Sciences (India)

    than methanol due to the higher molecular weight of ethanol compared with methanol .... converted in the cathode side, hydrogen ions were then sent from the cathode to .... retard the ethanol crossover and possibly improve the dura- bility. ... [4] Wan C-H and Chen C-L 2009 Int. J. Hydrogen Energy 34. 9515. [5] Pethaiah ...

  20. A randomized crossover study of bee sting therapy for multiple sclerosis

    NARCIS (Netherlands)

    Wesselius, T; Heersema, DJ; Mostert, JP; Heerings, M; Admiraal-Behloul, F; Talebian, A; van Buchem, MA; De Keyser, J

    2005-01-01

    Background: Bee sting therapy is increasingly used to treat patients with multiple sclerosis (MS) in the belief that it can stabilize or ameliorate the disease. However, there are no clinical studies to justify its use. Methods: In a randomized, crossover study, we assigned 26 patients with