Pathogenic mechanisms of Acute Graft versus Host Disease

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Ferrara James L.M.

2002-01-01

Full Text Available Graft-versus-host-disease (GVHD is the major complication of allogeneic Bone Marrow Transplant (BMT. Older BMT recipients are a greater risk for acute GVHD after allogeneic BMT, but the causes of this association are poorly understood. Using well-characterized murine BMT models we have explored the mechanisms of increased GVHD in older mice. GVHD mortality and morbidity, and pathologic and biochemical indices were all worse in old recipients. Donor T cell responses were significantly increased in old recipients both in vivo and in vitro when stimulated by antigen-presenting cells (APCs from old mice. In a haploidential GVHD model, CD4+ donor T cells mediated more severe GVHD in old mice. We confirmed the role of aged APCs in GVHD using bone marrow chimera recipient created with either old or young bone marrow. APCs from these mice also stimulated greater responses from allogeneic cells in vitro. In a separate set of experiments we evaluated whether alloantigen expression on host target epithelium is essential for tissue damage induced by GVHD. Using bone marrow chimeras recipients in which either MHC II or MHC I alloantigen was expressed only on APCs, we found that acute GVHD does not require alloantigen expression on host target epithelium and that neutralization of tumor necrosis factor-alpha and interleukin-1 prevents acute GVHD. These results pertain to CD4-mediated GVHD and to a lesser extent in CD8-mediated GVHD, and confirm the central role of most APCs as well as inflammatory cytokines.

Anti-pathogen protection versus survival costs mediated by an ectosymbiont in an ant host.

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Konrad, Matthias; Grasse, Anna V; Tragust, Simon; Cremer, Sylvia

2015-01-22

The fitness effects of symbionts on their hosts can be context-dependent, with usually benign symbionts causing detrimental effects when their hosts are stressed, or typically parasitic symbionts providing protection towards their hosts (e.g. against pathogen infection). Here, we studied the novel association between the invasive garden ant Lasius neglectus and its fungal ectosymbiont Laboulbenia formicarum for potential costs and benefits. We tested ants with different Laboulbenia levels for their survival and immunity under resource limitation and exposure to the obligate killing entomopathogen Metarhizium brunneum. While survival of L. neglectus workers under starvation was significantly decreased with increasing Laboulbenia levels, host survival under Metarhizium exposure increased with higher levels of the ectosymbiont, suggesting a symbiont-mediated anti-pathogen protection, which seems to be driven mechanistically by both improved sanitary behaviours and an upregulated immune system. Ants with high Laboulbenia levels showed significantly longer self-grooming and elevated expression of immune genes relevant for wound repair and antifungal responses (β-1,3-glucan binding protein, Prophenoloxidase), compared with ants carrying low Laboulbenia levels. This suggests that the ectosymbiont Laboulbenia formicarum weakens its ant host by either direct resource exploitation or the costs of an upregulated behavioural and immunological response, which, however, provides a prophylactic protection upon later exposure to pathogens. © 2014 The Author(s) Published by the Royal Society. All rights reserved.

Mycobacterial nonhomologous end joining mediates mutagenic repair of chromosomal double-strand DNA breaks.

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Stephanou, Nicolas C; Gao, Feng; Bongiorno, Paola; Ehrt, Sabine; Schnappinger, Dirk; Shuman, Stewart; Glickman, Michael S

2007-07-01

Bacterial nonhomologous end joining (NHEJ) is a recently described DNA repair pathway best characterized in mycobacteria. Bacterial NHEJ proteins LigD and Ku have been analyzed biochemically, and their roles in linear plasmid repair in vivo have been verified genetically; yet the contributions of NHEJ to repair of chromosomal DNA damage are unknown. Here we use an extensive set of NHEJ- and homologous recombination (HR)-deficient Mycobacterium smegmatis strains to probe the importance of HR and NHEJ in repairing diverse types of chromosomal DNA damage. An M. smegmatis Delta recA Delta ku double mutant has no apparent growth defect in vitro. Loss of the NHEJ components Ku and LigD had no effect on sensitivity to UV radiation, methyl methanesulfonate, or quinolone antibiotics. NHEJ deficiency had no effect on sensitivity to ionizing radiation in logarithmic- or early-stationary-phase cells but was required for ionizing radiation resistance in late stationary phase in 7H9 but not LB medium. In addition, NHEJ components were required for repair of I-SceI mediated chromosomal double-strand breaks (DSBs), and in the absence of HR, the NHEJ pathway rapidly mutates the chromosomal break site. The molecular outcomes of NHEJ-mediated chromosomal DSB repair involve predominantly single-nucleotide insertions at the break site, similar to previous findings using plasmid substrates. These findings demonstrate that prokaryotic NHEJ is specifically required for DSB repair in late stationary phase and can mediate mutagenic repair of homing endonuclease-generated chromosomal DSBs.

Acetylation-Mediated Proteasomal Degradation of Core Histones during DNA Repair and Spermatogenesis

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Qian, Min-Xian; Pang, Ye; Liu, Cui Hua; Haratake, Kousuke; Du, Bo-Yu; Ji, Dan-Yang; Wang, Guang-Fei; Zhu, Qian-Qian; Song, Wei; Yu, Yadong; Zhang, Xiao-Xu; Huang, Hai-Tao; Miao, Shiying; Chen, Lian-Bin; Zhang, Zi-Hui; Liang, Ya-Nan; Liu, Shan; Cha, Hwangho; Yang, Dong; Zhai, Yonggong; Komatsu, Takuo; Tsuruta, Fuminori; Li, Haitao; Cao, Cheng; Li, Wei; Li, Guo-Hong; Cheng, Yifan; Chiba, Tomoki; Wang, Linfang; Goldberg, Alfred L.; Shen, Yan; Qiu, Xiao-Bo

2013-01-01

SUMMARY Histone acetylation plays critical roles in chromatin remodeling, DNA repair, and epigenetic regulation of gene expression, but the underlying mechanisms are unclear. Proteasomes usually catalyze ATP- and polyubiquitin-dependent proteolysis. Here we show that the proteasomes containing the activator PA200 catalyze the polyubiquitin-independent degradation of histones. Most proteasomes in mammalian testes (“spermatoproteasomes”) contain a spermatid/sperm-specific α-subunit α4s/PSMA8 and/or the catalytic β-subunits of immunoproteasomes in addition to PA200. Deletion of PA200 in mice abolishes acetylation-dependent degradation of somatic core histones during DNA double-strand breaks, and delays core histone disappearance in elongated spermatids. Purified PA200 greatly promotes ATP-independent proteasomal degradation of the acetylated core histones, but not polyubiquitinated proteins. Furthermore, acetylation on histones is required for their binding to the bromodomain-like regions in PA200 and its yeast ortholog, Blm10. Thus, PA200/Blm10 specifically targets the core histones for acetylation-mediated degradation by proteasomes, providing mechanisms by which acetylation regulates histone degradation, DNA repair, and spermatogenesis. PMID:23706739

Repair of oxidative DNA base damage in the host genome influences the HIV integration site sequence preference.

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Geoffrey R Bennett

Full Text Available Host base excision repair (BER proteins that repair oxidative damage enhance HIV infection. These proteins include the oxidative DNA damage glycosylases 8-oxo-guanine DNA glycosylase (OGG1 and mutY homolog (MYH as well as DNA polymerase beta (Polβ. While deletion of oxidative BER genes leads to decreased HIV infection and integration efficiency, the mechanism remains unknown. One hypothesis is that BER proteins repair the DNA gapped integration intermediate. An alternative hypothesis considers that the most common oxidative DNA base damages occur on guanines. The subtle consensus sequence preference at HIV integration sites includes multiple G:C base pairs surrounding the points of joining. These observations suggest a role for oxidative BER during integration targeting at the nucleotide level. We examined the hypothesis that BER repairs a gapped integration intermediate by measuring HIV infection efficiency in Polβ null cell lines complemented with active site point mutants of Polβ. A DNA synthesis defective mutant, but not a 5'dRP lyase mutant, rescued HIV infection efficiency to wild type levels; this suggested Polβ DNA synthesis activity is not necessary while 5'dRP lyase activity is required for efficient HIV infection. An alternate hypothesis that BER events in the host genome influence HIV integration site selection was examined by sequencing integration sites in OGG1 and MYH null cells. In the absence of these 8-oxo-guanine specific glycosylases the chromatin elements of HIV integration site selection remain the same as in wild type cells. However, the HIV integration site sequence preference at G:C base pairs is altered at several positions in OGG1 and MYH null cells. Inefficient HIV infection in the absence of oxidative BER proteins does not appear related to repair of the gapped integration intermediate; instead oxidative damage repair may participate in HIV integration site preference at the sequence level.

The Mechanism of Nucleotide Excision Repair-Mediated UV-Induced Mutagenesis in Nonproliferating Cells

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Kozmin, Stanislav G.; Jinks-Robertson, Sue

2013-01-01

Following the irradiation of nondividing yeast cells with ultraviolet (UV) light, most induced mutations are inherited by both daughter cells, indicating that complementary changes are introduced into both strands of duplex DNA prior to replication. Early analyses demonstrated that such two-strand mutations depend on functional nucleotide excision repair (NER), but the molecular mechanism of this unique type of mutagenesis has not been further explored. In the experiments reported here, an ade2 adeX colony-color system was used to examine the genetic control of UV-induced mutagenesis in nondividing cultures of Saccharomyces cerevisiae. We confirmed a strong suppression of two-strand mutagenesis in NER-deficient backgrounds and demonstrated that neither mismatch repair nor interstrand crosslink repair affects the production of these mutations. By contrast, proteins involved in the error-prone bypass of DNA damage (Rev3, Rev1, PCNA, Rad18, Pol32, and Rad5) and in the early steps of the DNA-damage checkpoint response (Rad17, Mec3, Ddc1, Mec1, and Rad9) were required for the production of two-strand mutations. There was no involvement, however, for the Pol η translesion synthesis DNA polymerase, the Mms2-Ubc13 postreplication repair complex, downstream DNA-damage checkpoint factors (Rad53, Chk1, and Dun1), or the Exo1 exonuclease. Our data support models in which UV-induced mutagenesis in nondividing cells occurs during the Pol ζ-dependent filling of lesion-containing, NER-generated gaps. The requirement for specific DNA-damage checkpoint proteins suggests roles in recruiting and/or activating factors required to fill such gaps. PMID:23307894

Mechanisms of Coronavirus Cell Entry Mediated by the Viral Spike Protein

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Gary R. Whittaker

2012-06-01

Full Text Available Coronaviruses are enveloped positive-stranded RNA viruses that replicate in the cytoplasm. To deliver their nucleocapsid into the host cell, they rely on the fusion of their envelope with the host cell membrane. The spike glycoprotein (S mediates virus entry and is a primary determinant of cell tropism and pathogenesis. It is classified as a class I fusion protein, and is responsible for binding to the receptor on the host cell as well as mediating the fusion of host and viral membranes—A process driven by major conformational changes of the S protein. This review discusses coronavirus entry mechanisms focusing on the different triggers used by coronaviruses to initiate the conformational change of the S protein: receptor binding, low pH exposure and proteolytic activation. We also highlight commonalities between coronavirus S proteins and other class I viral fusion proteins, as well as distinctive features that confer distinct tropism, pathogenicity and host interspecies transmission characteristics to coronaviruses.

Host plant quality mediates competition between arbuscular mycorrhizal fungi

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Knegt, B.; Jansa, J.; Franken, O.; Engelmoer, D.J.P.; Werner, G.D.A.; Bücking, H.; Kiers, E.T.

2016-01-01

Arbuscular mycorrhizal fungi exchange soil nutrients for carbon from plant hosts. Empirical works suggests that hosts may selectively provide resources to different fungal species, ultimately affecting fungal competition. However, fungal competition may also be mediated by colonization strategies of

USP22 Induces Cisplatin Resistance in Lung Adenocarcinoma by Regulating γH2AX-Mediated DNA Damage Repair and Ku70/Bax-Mediated Apoptosis

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Aman Wang

2017-05-01

Full Text Available Resistance to platinum-based chemotherapy is one of the most important reasons for treatment failure in advanced non-small cell lung cancer, but the underlying mechanism is extremely complex and unclear. The present study aimed to investigate the correlation of ubiquitin-specific peptidase 22 (USP22 with acquired resistance to cisplatin in lung adenocarcinoma. In this study, we found that overexpression of USP22 could lead to cisplatin resistance in A549 cells. USP22 and its downstream proteins γH2AX and Sirt1 levels are upregulated in the cisplatin- resistant A549/CDDP cell line. USP22 enhances DNA damage repair and induce cisplatin resistance by promoting the phosphorylation of histone H2AX via deubiquitinating histone H2A. In addition, USP22 decreases the acetylation of Ku70 by stabilizing Sirt1, thus inhibiting Bax-mediated apoptosis and inducing cisplatin resistance. The cisplatin sensitivity in cisplatin-resistant A549/CDDP cells was restored by USP22 inhibition in vivo and vitro. In summary, our findings reveal the dual mechanism of USP22 involvement in cisplatin resistance that USP22 can regulate γH2AX-mediated DNA damage repair and Ku70/Bax-mediated apoptosis. USP22 is a potential target in cisplatin-resistant lung adenocarcinoma and should be considered in future therapeutic practice.

Electron Transfer Mechanisms of DNA Repair by Photolyase

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Zhong, Dongping

2015-04-01

Photolyase is a flavin photoenzyme that repairs two DNA base damage products induced by ultraviolet (UV) light: cyclobutane pyrimidine dimers and 6-4 photoproducts. With femtosecond spectroscopy and site-directed mutagenesis, investigators have recently made significant advances in our understanding of UV-damaged DNA repair, and the entire enzymatic dynamics can now be mapped out in real time. For dimer repair, six elementary steps have been characterized, including three electron transfer reactions and two bond-breaking processes, and their reaction times have been determined. A unique electron-tunneling pathway was identified, and the critical residues in modulating the repair function at the active site were determined. The dynamic synergy between the elementary reactions for maintaining high repair efficiency was elucidated, and the biological nature of the flavin active state was uncovered. For 6-4 photoproduct repair, a proton-coupled electron transfer repair mechanism has been revealed. The elucidation of electron transfer mechanisms and two repair photocycles is significant and provides a molecular basis for future practical applications, such as in rational drug design for curing skin cancer.

Bartonella entry mechanisms into mammalian host cells.

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Eicher, Simone C; Dehio, Christoph

2012-08-01

The Gram-negative genus Bartonella comprises arthropod-borne pathogens that typically infect mammals in a host-specific manner. Bartonella bacilliformis and Bartonella quintana are human-specific pathogens, while several zoonotic bartonellae specific for diverse animal hosts infect humans as an incidental host. Clinical manifestations of Bartonella infections range from mild symptoms to life-threatening disease. Following transmission by blood-sucking arthropods or traumatic contact with infected animals, bartonellae display sequential tropisms towards endothelial and possibly other nucleated cells and erythrocytes, the latter in a host-specific manner. Attachment to the extracellular matrix (ECM) and to nucleated cells is mediated by surface-exposed bacterial adhesins, in particular trimeric autotransporter adhesins (TAAs). The subsequent engulfment of the pathogen into a vacuolar structure follows a unique series of events whereby the pathogen avoids the endolysosomal compartments. For Bartonella henselae and assumingly most other species, the infection process is aided at different steps by Bartonella effector proteins (Beps). They are injected into host cells through the type IV secretion system (T4SS) VirB/D4 and subvert host cellular functions to favour pathogen uptake. Bacterial binding to erythrocytes is mediated by Trw, another T4SS, in a strictly host-specific manner, followed by pathogen-forced uptake involving the IalB invasin and subsequent replication and persistence within a membrane-bound intra-erythrocytic compartment. © 2012 Blackwell Publishing Ltd.

Repair-defective mutants of Alteromonas espejiana, the host for bacteriophage PM2

International Nuclear Information System (INIS)

Zerler, B.R.; Wallace, S.S.

1984-01-01

The in vivo repair processes of Alteromonas espejiana, the host for bacteriophage PM2, were characterized, and UV- and methyl methanesulfonate (MMS)-sensitive mutants were isolated. Wild-type A. espejiana cells were capable of photoreactivation, excision, recombination, and inducible repair. There was no detecttable pyrimidine dimer-DNA N-glycosylase activity, and pyrimidine dimer removal appeared to occur by a pathway analogous to the Escherichia coli Uvr pathway. The UV- and MMS-sensitive mutants of A. espejiana included three groups, each containing at least one mutation involved with excision, recombination, or inducible repair. One group that was UV sensitive but not sensitive to MMS or X rays showed a decreased ability to excise pyrimidine dimers. Mutants in this group were also sensitive to psoralen plus near-UV light and were phenotypically analogous to the E. coli uvr mutants. A second group was UV and MMS sensitive but not sensitive to X rays and appeared to contain mutations in a gene(s) involved in recombination repair. These recombination-deficient mutants differed from the E. coli rec mutants, which are MMS and X-ray sensitive. The third group of A. espejiana mutants was sensitive to UV, MMS, and X rays. These mutants were recombination deficient, lacked inducible repair, and were phenotypically similar to E. coli recA mutants

The extracellular adherence protein (Eap) of Staphylococcus aureus inhibits wound healing by interfering with host defense and repair mechanisms.

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Athanasopoulos, Athanasios N; Economopoulou, Matina; Orlova, Valeria V; Sobke, Astrid; Schneider, Darius; Weber, Holger; Augustin, Hellmut G; Eming, Sabine A; Schubert, Uwe; Linn, Thomas; Nawroth, Peter P; Hussain, Muzaffar; Hammes, Hans-Peter; Herrmann, Mathias; Preissner, Klaus T; Chavakis, Triantafyllos

2006-04-01

Staphylococcus aureus is a major human pathogen interfering with host-cell functions. Impaired wound healing is often observed in S aureus-infected wounds, yet, the underlying mechanisms are poorly defined. Here, we identify the extracellular adherence protein (Eap) of S aureus to be responsible for impaired wound healing. In a mouse wound-healing model wound closure was inhibited in the presence of wild-type S aureus and this effect was reversible when the wounds were incubated with an isogenic Eap-deficient strain. Isolated Eap also delayed wound closure. In the presence of Eap, recruitment of inflammatory cells to the wound site as well as neovascularization of the wound were prevented. In vitro, Eap significantly reduced intercellular adhesion molecule 1 (ICAM-1)-dependent leukocyte-endothelial interactions and diminished the consequent activation of the proinflammatory transcription factor nuclear factor kappaB (NFkappaB) in leukocytes associated with a decrease in expression of tissue factor. Moreover, Eap blocked alphav-integrin-mediated endothelial-cell migration and capillary tube formation, and neovascularization in matrigels in vivo. Collectively, the potent anti-inflammatory and antiangiogenic properties of Eap provide an underlying mechanism that may explain the impaired wound healing in S aureus-infected wounds. Eap may also serve as a lead compound for new anti-inflammatory and antiangiogenic therapies in several pathologies.

Selenium-Mediated Dehalogenation of Halogenated Nucleosides and its Relevance to the DNA Repair Pathway.

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Mondal, Santanu; Manna, Debasish; Mugesh, Govindasamy

2015-08-03

Halogenated nucleosides can be incorporated into the newly synthesized DNA of replicating cells and therefore are commonly used in the detection of proliferating cells in living tissues. Dehalogenation of these modified nucleosides is one of the key pathways involved in DNA repair mediated by the uracil-DNA glycosylase. Herein, we report the first example of a selenium-mediated dehalogenation of halogenated nucleosides. We also show that the mechanism for the debromination is remarkably different from that of deiodination and that the presence of a ribose or deoxyribose moiety in the nucleosides facilitates the deiodination. The results described herein should help in understanding the metabolism of halogenated nucleosides in DNA and RNA. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Signaling factors in stem cell-mediated repair of infarcted myocardium

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Vandervelde, S; van Luyn, MJA; Tio, RA; Harmsen, MC

Myocardial infarction leads to scar formation and subsequent reduced cardiac performance. The ultimate therapy after myocardial infarction would pursue stem cell-based regeneration. The aim of stem cell-mediated cardiac repair embodies restoration of cardiac function by regeneration of healthy

The Trw type IV secretion system of Bartonella mediates host-specific adhesion to erythrocytes.

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Muriel Vayssier-Taussat

2010-06-01

Full Text Available Bacterial pathogens typically infect only a limited range of hosts; however, the genetic mechanisms governing host-specificity are poorly understood. The alpha-proteobacterial genus Bartonella comprises 21 species that cause host-specific intraerythrocytic bacteremia as hallmark of infection in their respective mammalian reservoirs, including the human-specific pathogens Bartonella quintana and Bartonella bacilliformis that cause trench fever and Oroya fever, respectively. Here, we have identified bacterial factors that mediate host-specific erythrocyte colonization in the mammalian reservoirs. Using mouse-specific Bartonella birtlesii, human-specific Bartonella quintana, cat-specific Bartonella henselae and rat-specific Bartonella tribocorum, we established in vitro adhesion and invasion assays with isolated erythrocytes that fully reproduce the host-specificity of erythrocyte infection as observed in vivo. By signature-tagged mutagenesis of B. birtlesii and mutant selection in a mouse infection model we identified mutants impaired in establishing intraerythrocytic bacteremia. Among 45 abacteremic mutants, five failed to adhere to and invade mouse erythrocytes in vitro. The corresponding genes encode components of the type IV secretion system (T4SS Trw, demonstrating that this virulence factor laterally acquired by the Bartonella lineage is directly involved in adherence to erythrocytes. Strikingly, ectopic expression of Trw of rat-specific B. tribocorum in cat-specific B. henselae or human-specific B. quintana expanded their host range for erythrocyte infection to rat, demonstrating that Trw mediates host-specific erythrocyte infection. A molecular evolutionary analysis of the trw locus further indicated that the variable, surface-located TrwL and TrwJ might represent the T4SS components that determine host-specificity of erythrocyte parasitism. In conclusion, we show that the laterally acquired Trw T4SS diversified in the Bartonella lineage

Wound repair and regeneration: Mechanisms, signaling, and translation

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Eming, Sabine A.; Martin, Paul; Tomic-Canic, Marjana

2015-01-01

The cellular and molecular mechanisms underpinning tissue repair and its failure to heal are still poorly understood, and current therapies are limited. Poor wound healing after trauma, surgery, acute illness, or chronic disease conditions affects millions of people worldwide each year and is the consequence of poorly regulated elements of the healthy tissue repair response, including inflammation, angiogenesis, matrix deposition, and cell recruitment. Failure of one or several of these cellular processes is generally linked to an underlying clinical condition, such as vascular disease, diabetes, or aging, which are all frequently associated with healing pathologies. The search for clinical strategies that might improve the body’s natural repair mechanisms will need to be based on a thorough understanding of the basic biology of repair and regeneration. In this review, we highlight emerging concepts in tissue regeneration and repair, and provide some perspectives on how to translate current knowledge into viable clinical approaches for treating patients with wound-healing pathologies. PMID:25473038

Tension (re)builds: Biophysical mechanisms of embryonic wound repair.

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Zulueta-Coarasa, Teresa; Fernandez-Gonzalez, Rodrigo

2017-04-01

Embryonic tissues display an outstanding ability to rapidly repair wounds. Epithelia, in particular, serve as protective layers that line internal organs and form the skin. Thus, maintenance of epithelial integrity is of utmost importance for animal survival, particularly at embryonic stages, when an immune system has not yet fully developed. Rapid embryonic repair of epithelial tissues is conserved across species, and involves the collective migration of the cells around the wound. The migratory cell behaviours associated with wound repair require the generation and transmission of mechanical forces, not only for the cells to move, but also to coordinate their movements. Here, we review the forces involved in embryonic wound repair. We discuss how different force-generating structures are assembled at the molecular level, and the mechanisms that maintain the balance between force-generating structures as wounds close. Finally, we describe the mechanisms that cells use to coordinate the generation of mechanical forces around the wound. Collective cell movements and their misregulation have been associated with defective tissue repair, developmental abnormalities and cancer metastasis. Thus, we propose that understanding the role of mechanical forces during embryonic wound closure will be crucial to develop therapeutic interventions that promote or prevent collective cell movements under pathological conditions. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Recent Advances in Type-2-Cell-Mediated Immunity: Insights from Helminth Infection.

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Harris, Nicola L; Loke, P'ng

2017-12-19

Type-2-cell-mediated immune responses play a critical role in mediating both host-resistance and disease-tolerance mechanisms during helminth infections. Recently, type 2 cell responses have emerged as major regulators of tissue repair and metabolic homeostasis even under steady-state conditions. In this review, we consider how studies of helminth infection have contributed toward our expanding cellular and molecular understanding of type-2-cell-mediated immunity, as well as new areas such as the microbiome. By studying how these successful parasites form chronic infections without overt pathology, we are gaining additional insights into allergic and inflammatory diseases, as well as normal physiology. Copyright © 2017 Elsevier Inc. All rights reserved.

Molecular mechanisms of DNA repair inhibition by caffeine

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Selby, C.P.; Sancar, A. (Univ. of North Carolina School of Medicine, Chapel Hill (USA))

1990-05-01

Caffeine potentiates the mutagenic and lethal effects of genotoxic agents. It is thought that this is due, at least in some organisms, to inhibition of DNA repair. However, direct evidence for inhibition of repair enzymes has been lacking. Using purified Escherichia coli DNA photolyase and (A)BC excinuclease, we show that the drug inhibits photoreactivation and nucleotide excision repair by two different mechanisms. Caffeine inhibits photoreactivation by interfering with the specific binding of photolyase to damaged DNA, and it inhibits nucleotide excision repair by promoting nonspecific binding of the damage-recognition subunit, UvrA, of (A)BC excinuclease. A number of other intercalators, including acriflavin and ethidium bromide, appear to inhibit the excinuclease by a similar mechanism--that is, by trapping the UvrA subunit in nonproductive complexes on undamaged DNA.

A modified fluorimetric host cell reactivation assay to determine the repair capacity of primary keratinocytes, melanocytes and fibroblasts

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Gebhard Daniel

2010-06-01

Full Text Available Abstract Background The Host Cell Reactivation Assay (HCRA is widely used to identify circumstances and substances affecting the repair capacity of cells, however, it is restricted by the transfection procedure used and the sensitivity of the detection method. Primary skin cells are particularly difficult to transfect, and therefore sensitive methods are needed to detect any variations due to the cell-type or inter-individual differences or changes induced by diverse substances. A sensitive and repeatable method to detect the repair capacity of skin cells would be useful in two different aspects: On the one hand, to identify substances influencing the repair capacity in a positive manner (these substances could be promising ingredients for cosmetic products and on the other hand, to exclude the negative effects of substances on the repair capacity (this could serve as one step further towards replacing or at least reducing animal testing. Results In this paper, we present a rapid and sensitive assay to determine the repair capacity of primary keratinocytes, melanocytes and fibroblasts based on two wave-length Green Fluorescent Protein (GFP and DsRed reporter technology in order to test different substances and their potential to influence the DNA repair capacity. For the detection of plasmid restoration, we used FACS technology, which, in comparison to luminometer technology, is highly sensitive and allows single cell based analysis. The usefulness of this assay and studying the repair capacity is demonstrated by the evidence that DNA repair is repressed by Cyclosporin A in fibroblasts. Conclusions The methodology described in this paper determines the DNA repair capacity in different types of human skin cells. The described transfection protocol is suitable for the transfection of melanocytes, keratinocytes and fibroblasts, reaching efficacies suitable for the detection of the restored plasmids by FACS technology. Therefore the repair capacity

Host and Viral Factors in HIV-Mediated Bystander Apoptosis

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Garg, Himanshu; Joshi, Anjali

2017-01-01

Human immunodeficiency virus (HIV) infections lead to a progressive loss of CD4 T cells primarily via the process of apoptosis. With a limited number of infected cells and vastly disproportionate apoptosis in HIV infected patients, it is believed that apoptosis of uninfected bystander cells plays a significant role in this process. Disease progression in HIV infected individuals is highly variable suggesting that both host and viral factors may influence HIV mediated apoptosis. Amongst the viral factors, the role of Envelope (Env) glycoprotein in bystander apoptosis is well documented. Recent evidence on the variability in apoptosis induction by primary patient derived Envs underscores the role of Env glycoprotein in HIV disease. Amongst the host factors, the role of C-C Chemokine Receptor type 5 (CCR5), a coreceptor for HIV Env, is also becoming increasingly evident. Polymorphisms in the CCR5 gene and promoter affect CCR5 cell surface expression and correlate with both apoptosis and CD4 loss. Finally, chronic immune activation in HIV infections induces multiple defects in the immune system and has recently been shown to accelerate HIV Env mediated CD4 apoptosis. Consequently, those factors that affect CCR5 expression and/or immune activation in turn indirectly regulate HIV mediated apoptosis making this phenomenon both complex and multifactorial. This review explores the complex role of various host and viral factors in determining HIV mediated bystander apoptosis. PMID:28829402

General Mechanical Repair. Minor Automotive Maintenance, Small Engine [Repair, and] Welding: Student Manual.

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Hamlin, Larry

This document is a student manual for a general mechanical repair course. Following a list of common essential elements of trade and industrial education, the manual is divided into three sections. The first section, on minor automotive maintenance, contains 13 units: automotive shop safety; engine principles; fuel system operation and repair;…

The BER necessities: the repair of DNA damage in human-adapted bacterial pathogens.

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van der Veen, Stijn; Tang, Christoph M

2015-02-01

During colonization and disease, bacterial pathogens must survive the onslaught of the host immune system. A key component of the innate immune response is the generation of reactive oxygen and nitrogen species by phagocytic cells, which target and disrupt pathogen molecules, particularly DNA, and the base excision repair (BER) pathway is the most important mechanism for the repair of such oxidative DNA damage. In this Review, we discuss how the human-specific pathogens Mycobacterium tuberculosis, Helicobacter pylori and Neisseria meningitidis have evolved specialized mechanisms of DNA repair, particularly their BER pathways, compared with model organisms such as Escherichia coli. This specialization in DNA repair is likely to reflect the distinct niches occupied by these important human pathogens in the host.

High LET radiation and mechanism of DNA damage repair

International Nuclear Information System (INIS)

Furusawa, Yoshiya

2004-01-01

Clarifying the mechanism of repair from radiation damage gives most important information on radiation effects on cells. Approximately 10% of biological experiments groups in Heavy Ion Medical Accelerator in Chiba (HIMAC) cooperative research group has performed the subject. They gave a lot of new findings on the mechanism, and solved some open questions. The reason to show the peak of relative biological effectiveness RBE at around 100-200 keV/μm causes miss-repair of DNA damage. Sub-lethal damage generated by high linear energy transfer (LET) radiation can be repaired fully. Potentially lethal damages by high-LET radiation also repaired, but the efficiency decreased with the LET, and so on. (author)

Midgut microbiota and host immunocompetence underlie Bacillus thuringiensis killing mechanism

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Caccia, Silvia; Di Lelio, Ilaria; La Storia, Antonietta; Marinelli, Adriana; Varricchio, Paola; Franzetti, Eleonora; Banyuls, Núria; Tettamanti, Gianluca; Casartelli, Morena; Giordana, Barbara; Ferré, Juan; Gigliotti, Silvia; Pennacchio, Francesco

2016-01-01

Bacillus thuringiensis is a widely used bacterial entomopathogen producing insecticidal toxins, some of which are expressed in insect-resistant transgenic crops. Surprisingly, the killing mechanism of B. thuringiensis remains controversial. In particular, the importance of the septicemia induced by the host midgut microbiota is still debated as a result of the lack of experimental evidence obtained without drastic manipulation of the midgut and its content. Here this key issue is addressed by RNAi-mediated silencing of an immune gene in a lepidopteran host Spodoptera littoralis, leaving the midgut microbiota unaltered. The resulting cellular immunosuppression was characterized by a reduced nodulation response, which was associated with a significant enhancement of host larvae mortality triggered by B. thuringiensis and a Cry toxin. This was determined by an uncontrolled proliferation of midgut bacteria, after entering the body cavity through toxin-induced epithelial lesions. Consequently, the hemolymphatic microbiota dramatically changed upon treatment with Cry1Ca toxin, showing a remarkable predominance of Serratia and Clostridium species, which switched from asymptomatic gut symbionts to hemocoelic pathogens. These experimental results demonstrate the important contribution of host enteric flora in B. thuringiensis-killing activity and provide a sound foundation for developing new insect control strategies aimed at enhancing the impact of biocontrol agents by reducing the immunocompetence of the host. PMID:27506800

Neuroinflammatory contributions to pain after SCI: roles for central glial mechanisms and nociceptor-mediated host defense.

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Walters, Edgar T

2014-08-01

Neuropathic pain after spinal cord injury (SCI) is common, often intractable, and can be severely debilitating. A number of mechanisms have been proposed for this pain, which are discussed briefly, along with methods for revealing SCI pain in animal models, such as the recently applied conditioned place preference test. During the last decade, studies of animal models have shown that both central neuroinflammation and behavioral hypersensitivity (indirect reflex measures of pain) persist chronically after SCI. Interventions that reduce neuroinflammation have been found to ameliorate pain-related behavior, such as treatment with agents that inhibit the activation states of microglia and/or astroglia (including IL-10, minocycline, etanercept, propentofylline, ibudilast, licofelone, SP600125, carbenoxolone). Reversal of pain-related behavior has also been shown with disruption by an inhibitor (CR8) and/or genetic deletion of cell cycle-related proteins, deletion of a truncated receptor (trkB.T1) for brain-derived neurotrophic factor (BDNF), or reduction by antisense knockdown or an inhibitor (AMG9810) of the activity of channels (TRPV1 or Nav1.8) important for electrical activity in primary nociceptors. Nociceptor activity is known to drive central neuroinflammation in peripheral injury models, and nociceptors appear to be an integral component of host defense. Thus, emerging results suggest that spinal and systemic effects of SCI can activate nociceptor-mediated host defense responses that interact via neuroinflammatory signaling with complex central consequences of SCI to drive chronic pain. This broader view of SCI-induced neuroinflammation suggests new targets, and additional complications, for efforts to develop effective treatments for neuropathic SCI pain. Copyright © 2014 Elsevier Inc. All rights reserved.

Host epithelial cell invasion by Campylobacter jejuni: trigger or zipper mechanism?

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Tadhg eÓ Cróinín

2012-03-01

Full Text Available Campylobacter jejuni, a spiral-shaped Gram-negative pathogen, is a highly frequent cause of gastrointestinal foodborne illness in humans worldwide. Clinical outcome of C. jejuni infections ranges from mild to severe diarrheal disease, and some other complications including reactive arthritis and Guillain–Barré syndrome. This review article highlights various C. jejuni pathogenicity factors, host cell determinants and proposed signaling mechanisms involved in human host cell invasion and their potential role in the development of C. jejuni-mediated disease. A model is presented which outlines the various important interactions of C. jejuni with the intestinal epithelium, and we discuss the pro’s and con’s for the zipper over the trigger mechanism of invasion. Future work should clarify the contradictory role of some previously identified factors, and should identify and characterize novel virulence determinants, which are crucial to provide fresh insights into the diversity of strategies employed by this pathogen to cause disease.

Host-Mediated Mechanisms of Resistance to Antitumor Therapies

NARCIS (Netherlands)

Daenen, L.G.M.

2013-01-01

In addition to their direct effects on tumor cells, certain anticancer therapies elicit a prosurvival response in benign tissues in the tumor microenvironment. This host response can be seen as an attempt of the body to diminish chemotherapy-induced damage in tissues crucial for functioning.

Meniscal repair following meniscectomy: Mechanism and protective effect

International Nuclear Information System (INIS)

Berjon, J.J.; Munuera, L.; Calvo, M.

1990-01-01

Meniscal repair was studied to evaluate the mechanism and its potential protective effects on the articular cartilage in an experimental model consisting of 68 knees of adult dogs on which five different types of medial meniscectomy were performed. The results were assessed by macroscopic, microangiographic, and histological methods, after a sequential follow-up period of 10-450 days. Two different mechanisms of meniscal repair were observed, depending on whether meniscal section had been performed in vascular (total meniscectomy) or avascular (subtotal or partial meniscectomy) zones. It was also observed that the repaired meniscal tissue does not prevent articular cartilage degeneration. This is more closely related to the size of the meniscal fragment preserved at meniscetomy. Due to the biomechanical importance of the meniscus and the lack of functional relevance of the repaired meniscal tissue, the most conservative approach possible to meniscectomy is recommended. (orig.)

Deficiency of Double-Strand DNA Break Repair Does Not Impair Mycobacterium tuberculosis Virulence in Multiple Animal Models of Infection

OpenAIRE

Heaton, Brook E.; Barkan, Daniel; Bongiorno, Paola; Karakousis, Petros C.; Glickman, Michael S.

2014-01-01

Mycobacterium tuberculosis persistence within its human host requires mechanisms to resist the effector molecules of host immunity, which exert their bactericidal effects through damaging pathogen proteins, membranes, and DNA. Substantial evidence indicates that bacterial pathogens, including M. tuberculosis, require DNA repair systems to repair the DNA damage inflicted by the host during infection, but the role of double-strand DNA break (DSB) repair systems is unclear. Double-strand DNA bre...

DNA polymerase I-mediated ultraviolet repair synthesis in toluene-treated Escherichia coli

International Nuclear Information System (INIS)

Dorson, J.W.; Moses, R.E.

1978-01-01

DNA synthesis after ultraviolet irradiation is low in wild type toluene-treated cells. The level of repair incorporation is greater in strains deficient in DNA polymerase I. The low level of repair synthesis is attributable to the concerted action of DNA polymerase I and polynucleotide ligase. Repair synthesis is stimulated by blocking ligase activity with the addition of nicotinamide mononucleotide (NMN) or the use of a ligase temperature-sensitive mutant. NMN stimulation is specific for DNA polymerase I-mediated repair synthesis, as it is absent in isogenic strains deficient in the polymerase function or the 5' yields 3' exonuclease function associated with DNA polymerase I. DNA synthesis that is stimulated by NMN is proportional to the ultraviolet exposure at low doses, nonconservative in nature, and is dependent on the uvrA gene product but is independent of the recA gene product. These criteria place this synthesis in the excision repair pathway. The NMN-stimulated repair synthesis requires ATP and is N-ethylmaleimide-resistant. The use of NMN provides a direct means for evaluating the involvement of DNA polymerase I in excision repair

A role for host cell exocytosis in InlB-mediated internalisation of Listeria monocytogenes.

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Van Ngo, Hoan; Bhalla, Manmeet; Chen, Da-Yuan; Ireton, Keith

2017-11-01

The bacterial surface protein InlB mediates internalisation of Listeria monocytogenes into human cells through interaction with the host receptor tyrosine kinase, Met. InlB-mediated entry requires localised polymerisation of the host actin cytoskeleton. Apart from actin polymerisation, roles for other host processes in Listeria entry are unknown. Here, we demonstrate that exocytosis in the human cell promotes InlB-dependent internalisation. Using a probe consisting of VAMP3 with an exofacial green fluorescent protein tag, focal exocytosis was detected during InlB-mediated entry. Exocytosis was dependent on Met tyrosine kinase activity and the GTPase RalA. Depletion of SNARE proteins by small interfering RNA demonstrated an important role for exocytosis in Listeria internalisation. Depletion of SNARE proteins failed to affect actin filaments during internalisation, suggesting that actin polymerisation and exocytosis are separable host responses. SNARE proteins were required for delivery of the human GTPase Dynamin 2, which promotes InlB-mediated entry. Our results identify exocytosis as a novel host process exploited by Listeria for infection. © 2017 John Wiley & Sons Ltd.

Salmonella Disrupts Host Endocytic Trafficking by SopD2-Mediated Inhibition of Rab7

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Vanessa M. D’Costa

2015-09-01

Full Text Available Intracellular bacterial pathogens of a diverse nature share the ability to evade host immunity by impairing trafficking of endocytic cargo to lysosomes for degradation, a process that is poorly understood. Here, we show that the Salmonella enterica type 3 secreted effector SopD2 mediates this process by binding the host regulatory GTPase Rab7 and inhibiting its nucleotide exchange. Consequently, this limits Rab7 interaction with its dynein- and kinesin-binding effectors RILP and FYCO1 and thereby disrupts host-driven regulation of microtubule motors. Our study identifies a bacterial effector capable of directly binding and thereby modulating Rab7 activity and a mechanism of endocytic trafficking disruption that may provide insight into the pathogenesis of other bacteria. Additionally, we provide a powerful tool for the study of Rab7 function, and a potential therapeutic target.

Endothelial microparticle-mediated transfer of MicroRNA-126 promotes vascular endothelial cell repair via SPRED1 and is abrogated in glucose-damaged endothelial microparticles.

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Jansen, Felix; Yang, Xiaoyan; Hoelscher, Marion; Cattelan, Arianna; Schmitz, Theresa; Proebsting, Sebastian; Wenzel, Daniela; Vosen, Sarah; Franklin, Bernardo S; Fleischmann, Bernd K; Nickenig, Georg; Werner, Nikos

2013-10-29

Repair of the endothelium after vascular injury is crucial for preserving endothelial integrity and preventing the development of vascular disease. The underlying mechanisms of endothelial cell repair are largely unknown. We sought to investigate whether endothelial microparticles (EMPs), released from apoptotic endothelial cells (ECs), influence EC repair. Systemic treatment of mice with EMPs after electric denudation of the endothelium accelerated reendothelialization in vivo. In vitro experiments revealed that EMP uptake in ECs promotes EC migration and proliferation, both critical steps in endothelial repair. To dissect the underlying mechanisms, Taqman microRNA array was performed, and microRNA (miR)-126 was identified as the predominantly expressed miR in EMPs. The following experiments demonstrated that miR-126 was transported into recipient human coronary artery endothelial cells by EMPs and functionally regulated the target protein sprouty-related, EVH1 domain-containing protein 1 (SPRED1). Knockdown of miR-126 in EMPs abrogated EMP-mediated effects on human coronary artery endothelial cell migration and proliferation in vitro and reendothelialization in vivo. Interestingly, after simulating diabetic conditions, EMPs derived from glucose-treated ECs contained significantly lower amounts of miR-126 and showed reduced endothelial repair capacity in vitro and in vivo. Finally, expression analysis of miR-126 in circulating microparticles from 176 patients with stable coronary artery disease with and without diabetes mellitus revealed a significantly reduced miR-126 expression in circulating microparticles from diabetic patients. Endothelial microparticles promote vascular endothelial repair by delivering functional miR-126 into recipient cells. In pathological hyperglycemic conditions, EMP-mediated miR-126-induced EC repair is altered.

DNA Repair Mechanisms and the Bypass of DNA Damage in Saccharomyces cerevisiae

Science.gov (United States)

Boiteux, Serge; Jinks-Robertson, Sue

2013-01-01

DNA repair mechanisms are critical for maintaining the integrity of genomic DNA, and their loss is associated with cancer predisposition syndromes. Studies in Saccharomyces cerevisiae have played a central role in elucidating the highly conserved mechanisms that promote eukaryotic genome stability. This review will focus on repair mechanisms that involve excision of a single strand from duplex DNA with the intact, complementary strand serving as a template to fill the resulting gap. These mechanisms are of two general types: those that remove damage from DNA and those that repair errors made during DNA synthesis. The major DNA-damage repair pathways are base excision repair and nucleotide excision repair, which, in the most simple terms, are distinguished by the extent of single-strand DNA removed together with the lesion. Mistakes made by DNA polymerases are corrected by the mismatch repair pathway, which also corrects mismatches generated when single strands of non-identical duplexes are exchanged during homologous recombination. In addition to the true repair pathways, the postreplication repair pathway allows lesions or structural aberrations that block replicative DNA polymerases to be tolerated. There are two bypass mechanisms: an error-free mechanism that involves a switch to an undamaged template for synthesis past the lesion and an error-prone mechanism that utilizes specialized translesion synthesis DNA polymerases to directly synthesize DNA across the lesion. A high level of functional redundancy exists among the pathways that deal with lesions, which minimizes the detrimental effects of endogenous and exogenous DNA damage. PMID:23547164

Dose- and time-dependence of the host-mediated response to paclitaxel therapy: a mathematical modeling approach.

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Benguigui, Madeleine; Alishekevitz, Dror; Timaner, Michael; Shechter, Dvir; Raviv, Ziv; Benzekry, Sebastien; Shaked, Yuval

2018-01-05

It has recently been suggested that pro-tumorigenic host-mediated processes induced in response to chemotherapy counteract the anti-tumor activity of therapy, and thereby decrease net therapeutic outcome. Here we use experimental data to formulate a mathematical model describing the host response to different doses of paclitaxel (PTX) chemotherapy as well as the duration of the response. Three previously described host-mediated effects are used as readouts for the host response to therapy. These include the levels of circulating endothelial progenitor cells in peripheral blood and the effect of plasma derived from PTX-treated mice on migratory and invasive properties of tumor cells in vitro . A first set of mathematical models, based on basic principles of pharmacokinetics/pharmacodynamics, did not appropriately describe the dose-dependence and duration of the host response regarding the effects on invasion. We therefore provide an alternative mathematical model with a dose-dependent threshold, instead of a concentration-dependent one, that describes better the data. This model is integrated into a global model defining all three host-mediated effects. It not only precisely describes the data, but also correctly predicts host-mediated effects at different doses as well as the duration of the host response. This mathematical model may serve as a tool to predict the host response to chemotherapy in cancer patients, and therefore may be used to design chemotherapy regimens with improved therapeutic outcome by minimizing host mediated effects.

PCAF/GCN5-Mediated Acetylation of RPA1 Promotes Nucleotide Excision Repair

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Meimei Zhao

2017-08-01

Full Text Available The RPA complex can integrate multiple stress signals into diverse responses by activating distinct DNA repair pathways. However, it remains unclear how RPA1 elects to activate a specific repair pathway during different types of DNA damage. Here, we report that PCAF/GCN5-mediated K163 acetylation of RPA1 is crucial for nucleotide excision repair (NER but is dispensable for other DNA repair pathways. Mechanistically, we demonstrate that the acetylation of RPA1 is critical for the steady accumulation of XPA at damaged DNA sites and preferentially activates the NER pathway. DNA-PK phosphorylates and activates PCAF upon UV damage and consequently promotes the acetylation of RPA1. Moreover, the acetylation of RPA1 is tightly regulated by HDAC6 and SIRT1. Together, our results demonstrate that the K163 acetylation of RPA1 plays a key role in the repair of UV-induced DNA damage and reveal how the specific RPA1 modification modulates the choice of distinct DNA repair pathways.

Multiple repair pathways mediate cellular tolerance to resveratrol-induced DNA damage.

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Liu, Ying; Wu, Xiaohua; Hu, Xiaoqing; Chen, Ziyuan; Liu, Hao; Takeda, Shunichi; Qing, Yong

2017-08-01

Resveratrol (RSV) has been reported to exert health benefits for the prevention and treatment of many diseases, including cancer. The anticancer mechanisms of RSV seem to be complex and may be associated with genotoxic potential. To better understand the genotoxic mechanisms, we used wild-type (WT) and a panel of isogenic DNA-repair deficient DT40 cell lines to identify the DNA damage effects and molecular mechanisms of cellular tolerance to RSV. Our results showed that RSV induced significant formation of γ-H2AX foci and chromosome aberrations (CAs) in WT cells, suggesting direct DNA damage effects. Comparing the survival of WT with isogenic DNA-repair deficient DT40 cell lines demonstrated that single strand break repair (SSBR) deficient cell lines of Parp1 -/- , base excision repair (BER) deficient cell lines of Polβ -/- , homologous recombination (HR) mutants of Brca1 -/- and Brca2 -/- and translesion DNA synthesis (TLS) mutants of Rev3 -/- and Rad18 -/- were more sensitive to RSV. The sensitivities of cells were associated with enhanced DNA damage comparing the accumulation of γ-H2AX foci and number of CAs of isogenic DNA-repair deficient DT40 cell lines with WT cells. These results clearly demonstrated that RSV-induced DNA damage in DT40 cells, and multiple repair pathways including BER, SSBR, HR and TLS, play critical roles in response to RSV- induced genotoxicity. Copyright © 2017. Published by Elsevier Ltd.

Molecular mechanisms of induced mutagenesis. Replication in vivo of bacteriophage phiX174 single-stranded, ultraviolet light-irradiated DNA in intact and irradiated host cells

Energy Technology Data Exchange (ETDEWEB)

Caillet-Fauquet, P; Defais, M; Radman, M [Brussels Univ. (Belgium)

1977-11-25

Genetic analysis has revealed that radiation and many chemical mutagens induce in bacteria an error-prone DNA repair process which is responsible for their mutagenic effect. The biochemical mechanism of this inducible error-prone repair has been studied by analysis of the first round of DNA synthesis on ultraviolet light-irradiated phiX174 DNA in both intact and ultraviolet light-irradiated host cells. Intracellular phiX174 DNA was extracted, subjected to isopycnic CsCl density-gradient analysis, hydroxylapatite chromatography and digestion by single-strand-specific endonuclease S/sub 1/. Ultraviolet light-induced photolesions in viral DNA cause a permanent blockage of DNA synthesis in intact Escherichia coli cells. However, when host cells were irradiated and incubated to induce fully the error-prone repair system, a significant fraction of irradiated phiX174 DNA molecules can be fully replicated. Thus, inducible error-prone repair in E.coli is manifested by an increased capacity for DNA synthesis on damaged phiX174 DNA. Chloramphenicol (100 ..mu.. g/ml), which is an inhibitor of the inducible error-prone DNA repair, is also an inhibitor of this particular inducible DNA synthesis.

DNA repair mechanism in radioresistant bacteria

International Nuclear Information System (INIS)

Kitayama, Shigeru

1992-01-01

Many radiation resistant bacteria have been isolated from various sources which are not in high background field. Since Deinococcus radiodurans had been isolated first in 1956, studies on the mechanism for radioresistance were carried out mostly using this bacterium. DNA in this bacterium isn't protected against injury induced by not only ionizing radiation but also ultraviolet light. Therefore, DNA damages induced by various treatments are efficiently and accurately repaired in this cells. Damages in base and/or sugar in DNA are removed by endonucleases which, if not all, are synthesized during postirradiation incubation. Following the endonucleolytic cleavage the strand scissions in DNA are seemed to be rejoined by a process common for the repair of strand scissions induced by such as ionizing radiations. Induce protein(s) is also involved in this rejoining process of strand scissions. DNA repair genes were classified into three phenotypic groups. (1)Genes which are responsible for the endonucleolytic activities. (2) Genes involved in the rejoining of DNA strand scissions. (3) Genes which participate in genetic recombination and repair. Three genes belong to (1) and (2) were cloned onto approximately 1 kbp DNA fragments which base sequences have been determined. (author)

DNA repair mechanism in radioresistant bacteria

International Nuclear Information System (INIS)

Kitayama, Shigeru

1992-01-01

Many radiation resistant bacteria have been isolated from various sources which are not in high background field. Since Deinococcus radiodurans had been isolated first in 1956, the studies on the mechanism of radioresistance were mostly carried out using this bacterium. DNA in this bacterium isn't protected against injury induced by not only ionizing radiation but also ultraviolet light. Therefore, DNA damages induced by various treatments are efficiently and accurately repaired in this cells. Damages in base and/or sugar in DNA are removed by endonucleases which, if not all, are synthesized during postirradiation incubation. Following the endonucleolytic cleavage the strand scissions in DNA are seemed to be rejoined by a process common for the repair of strand scissions induced by such as ionizing radiations. Induce protein(s) is also involved in this rejoining process of strand scissions. DNA repair genes were classified into three phenotypic groups. (1) Genes which are responsible for the endonucleolytic activities. (2) Genes involved in the rejoining of DNA strand scissions. (3) Genes which participate in genetic recombination and repair. Three genes belong to (1) and (2) were cloned onto approximately 1 kbp DNA fragments which base sequences have been determined. (author)

My journey to DNA repair.

Science.gov (United States)

Lindahl, Tomas

2013-02-01

I completed my medical studies at the Karolinska Institute in Stockholm but have always been devoted to basic research. My longstanding interest is to understand fundamental DNA repair mechanisms in the fields of cancer therapy, inherited human genetic disorders and ancient DNA. I initially measured DNA decay, including rates of base loss and cytosine deamination. I have discovered several important DNA repair proteins and determined their mechanisms of action. The discovery of uracil-DNA glycosylase defined a new category of repair enzymes with each specialized for different types of DNA damage. The base excision repair pathway was first reconstituted with human proteins in my group. Cell-free analysis for mammalian nucleotide excision repair of DNA was also developed in my laboratory. I found multiple distinct DNA ligases in mammalian cells, and led the first genetic and biochemical work on DNA ligases I, III and IV. I discovered the mammalian exonucleases DNase III (TREX1) and IV (FEN1). Interestingly, expression of TREX1 was altered in some human autoimmune diseases. I also showed that the mutagenic DNA adduct O(6)-methylguanine (O(6)mG) is repaired without removing the guanine from DNA, identifying a surprising mechanism by which the methyl group is transferred to a residue in the repair protein itself. A further novel process of DNA repair discovered by my research group is the action of AlkB as an iron-dependent enzyme carrying out oxidative demethylation. Copyright © 2013. Production and hosting by Elsevier Ltd.

FGF2 mediates DNA repair in epidermoid carcinoma cells exposed to ionizing radiation

International Nuclear Information System (INIS)

Marie, Melanie; Hafner, Sophie; Moratille, Sandra; Vaigot, Pierre; Rigaud, Odile; Martin, Michele T.; Mine, Solene

2012-01-01

Fibroblast growth factor 2 (FGF2) is a well-known survival factor. However, its role in DNA repair is poorly documented. The present study was designed to investigate in epidermoid carcinoma cells the potential role of FGF2 in DNA repair. The side population (SP) with cancer stem cell-like properties and the main population (MP) were isolated from human A431 squamous carcinoma cells. Radiation-induced DNA damage and repair were assessed using the alkaline comet assay. FGF2 expression was quantified by enzyme linked immunosorbent assay (ELISA). SP cells exhibited rapid repair of radiation induced DNA damage and a high constitutive level of nuclear FGF2. Blocking FGF2 signaling abrogated the rapid DNA repair. In contrast, in MP cells, a slower repair of damage was associated with low basal expression of FGF2. Moreover, the addition of exogenous FGF2 accelerated DNA repair in MP cells. When irradiated, SP cells secreted FGF2, whereas MP cells did not. FGF2 was found to mediate DNA repair in epidermoid carcinoma cells. We postulate that carcinoma stem cells would be intrinsically primed to rapidly repair DNA damage by a high constitutive level of nuclear FGF2. In contrast, the main population with a low FGF2 content exhibits a lower repair rate which can be increased by exogenous FGF2. (authors)

Repair process and a repaired component

Energy Technology Data Exchange (ETDEWEB)

Roberts, III, Herbert Chidsey; Simpson, Stanley F.

2018-02-20

Matrix composite component repair processes are disclosed. The matrix composite repair process includes applying a repair material to a matrix composite component, securing the repair material to the matrix composite component with an external securing mechanism and curing the repair material to bond the repair material to the matrix composite component during the securing by the external securing mechanism. The matrix composite component is selected from the group consisting of a ceramic matrix composite, a polymer matrix composite, and a metal matrix composite. In another embodiment, the repair process includes applying a partially-cured repair material to a matrix composite component, and curing the repair material to bond the repair material to the matrix composite component, an external securing mechanism securing the repair material throughout a curing period, In another embodiment, the external securing mechanism is consumed or decomposed during the repair process.

Genomic survey and expression analysis of DNA repair genes in the genus Leptospira.

Science.gov (United States)

Martins-Pinheiro, Marinalva; Schons-Fonseca, Luciane; da Silva, Josefa B; Domingos, Renan H; Momo, Leonardo Hiroyuki Santos; Simões, Ana Carolina Quirino; Ho, Paulo Lee; da Costa, Renata M A

2016-04-01

Leptospirosis is an emerging zoonosis with important economic and public health consequences and is caused by pathogenic leptospires. The genus Leptospira belongs to the order Spirochaetales and comprises saprophytic (L. biflexa), pathogenic (L. interrogans) and host-dependent (L. borgpetersenii) members. Here, we present an in silico search for DNA repair pathways in Leptospira spp. The relevance of such DNA repair pathways was assessed through the identification of mRNA levels of some genes during infection in animal model and after exposition to spleen cells. The search was performed by comparison of available Leptospira spp. genomes in public databases with known DNA repair-related genes. Leptospires exhibit some distinct and unexpected characteristics, for instance the existence of a redundant mechanism for repairing a chemically diverse spectrum of alkylated nucleobases, a new mutS-like gene and a new shorter version of uvrD. Leptospira spp. shares some characteristics from Gram-positive, as the presence of PcrA, two RecQ paralogs and two SSB proteins; the latter is considered a feature shared by naturally competent bacteria. We did not find a significant reduction in the number of DNA repair-related genes in both pathogenic and host-dependent species. Pathogenic leptospires were enriched for genes dedicated to base excision repair and non-homologous end joining. Their evolutionary history reveals a remarkable importance of lateral gene transfer events for the evolution of the genus. Up-regulation of specific DNA repair genes, including components of SOS regulon, during infection in animal model validates the critical role of DNA repair mechanisms for the complex interplay between host/pathogen.

The Design of Intelligent Repair Welding Mechanism and Relative Control System of Big Gear

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Hong-Yu LIU

2014-10-01

Full Text Available Effective repair of worn big gear has large influence on ensuring safety production and enhancing economic benefits. A kind of intelligent repair welding method was put forward mainly aimed at the big gear restriction conditions of high production cost, long production cycle and high- intensity artificial repair welding work. Big gear repair welding mechanism was designed in this paper. The work principle and part selection of big gear repair welding mechanism was introduced. The three dimensional mode of big gear repair welding mechanism was constructed by Pro/E three dimensional design software. Three dimensional motions can be realized by motor controlling ball screw. According to involute gear feature, the complicated curve motion on curved gear surface can be transformed to linear motion by orientation. By this way, the repair welding on worn gear area can be realized. In the design of big gear repair welding mechanism control system, Siemens S7-200 series hardware was chosen. Siemens STEP7 programming software was chosen as system design tool. The entire repair welding process was simulated by experiment simulation. It provides a kind of practical and feasible method for the intelligent repair welding of big worn gear.

Regulation of stem-cell mediated host immunity by the sphingolipid ...

International Development Research Centre (IDRC) Digital Library (Canada)

Regulation of stem-cell mediated host immunity by the sphingolipid pathway ... in the generation of mature immune cells and the functioning of the surrounding ... methods with human cells and genetically engineered mice to examine how the ...

Numt-mediated double-strand break repair mitigates deletions during primate genome evolution.

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Einat Hazkani-Covo

2008-10-01

Full Text Available Non-homologous end joining (NHEJ is the major mechanism of double-strand break repair (DSBR in mammalian cells. NHEJ has traditionally been inferred from experimental systems involving induced double strand breaks (DSBs. Whether or not the spectrum of repair events observed in experimental NHEJ reflects the repair of natural breaks by NHEJ during chromosomal evolution is an unresolved issue. In primate phylogeny, nuclear DNA sequences of mitochondrial origin, numts, are inserted into naturally occurring chromosomal breaks via NHEJ. Thus, numt integration sites harbor evidence for the mechanisms that act on the genome over evolutionary timescales. We have identified 35 and 55 lineage-specific numts in the human and chimpanzee genomes, respectively, using the rhesus monkey genome as an outgroup. One hundred and fifty two numt-chromosome fusion points were classified based on their repair patterns. Repair involving microhomology and repair leading to nucleotide additions were detected. These repair patterns are within the experimentally determined spectrum of classical NHEJ, suggesting that information from experimental systems is representative of broader genetic loci and end configurations. However, in incompatible DSBR events, small deletions always occur, whereas in 54% of numt integration events examined, no deletions were detected. Numts show a statistically significant reduction in deletion frequency, even in comparison to DSBR involving filler DNA. Therefore, numts show a unique mechanism of integration via NHEJ. Since the deletion frequency during numt insertion is low, native overhangs of chromosome breaks are preserved, allowing us to determine that 24% of the analyzed breaks are cohesive with overhangs of up to 11 bases. These data represent, to the best of our knowledge, the most comprehensive description of the structure of naturally occurring DSBs. We suggest a model in which the sealing of DSBs by numts, and probably by other filler

Mechanical properties of hyaline and repair cartilage studied by nanoindentation.

Science.gov (United States)

Franke, O; Durst, K; Maier, V; Göken, M; Birkholz, T; Schneider, H; Hennig, F; Gelse, K

2007-11-01

Articular cartilage is a highly organized tissue that is well adapted to the functional demands in joints but difficult to replicate via tissue engineering or regeneration. Its viscoelastic properties allow cartilage to adapt to both slow and rapid mechanical loading. Several cartilage repair strategies that aim to restore tissue and protect it from further degeneration have been introduced. The key to their success is the quality of the newly formed tissue. In this study, periosteal cells loaded on a scaffold were used to repair large partial-thickness cartilage defects in the knee joint of miniature pigs. The repair cartilage was analyzed 26 weeks after surgery and compared both morphologically and mechanically with healthy hyaline cartilage. Contact stiffness, reduced modulus and hardness as key mechanical properties were examined in vitro by nanoindentation in phosphate-buffered saline at room temperature. In addition, the influence of tissue fixation with paraformaldehyde on the biomechanical properties was investigated. Although the repair process resulted in the formation of a stable fibrocartilaginous tissue, its contact stiffness was lower than that of hyaline cartilage by a factor of 10. Fixation with paraformaldehyde significantly increased the stiffness of cartilaginous tissue by one order of magnitude, and therefore, should not be used when studying biomechanical properties of cartilage. Our study suggests a sensitive method for measuring the contact stiffness of articular cartilage and demonstrates the importance of mechanical analysis for proper evaluation of the success of cartilage repair strategies.

Kinetic theory approach to modeling of cellular repair mechanisms under genome stress.

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Jinpeng Qi

Full Text Available Under acute perturbations from outer environment, a normal cell can trigger cellular self-defense mechanism in response to genome stress. To investigate the kinetics of cellular self-repair process at single cell level further, a model of DNA damage generating and repair is proposed under acute Ion Radiation (IR by using mathematical framework of kinetic theory of active particles (KTAP. Firstly, we focus on illustrating the profile of Cellular Repair System (CRS instituted by two sub-populations, each of which is made up of the active particles with different discrete states. Then, we implement the mathematical framework of cellular self-repair mechanism, and illustrate the dynamic processes of Double Strand Breaks (DSBs and Repair Protein (RP generating, DSB-protein complexes (DSBCs synthesizing, and toxins accumulating. Finally, we roughly analyze the capability of cellular self-repair mechanism, cellular activity of transferring DNA damage, and genome stability, especially the different fates of a certain cell before and after the time thresholds of IR perturbations that a cell can tolerate maximally under different IR perturbation circumstances.

Kinetic theory approach to modeling of cellular repair mechanisms under genome stress.

Science.gov (United States)

Qi, Jinpeng; Ding, Yongsheng; Zhu, Ying; Wu, Yizhi

2011-01-01

Under acute perturbations from outer environment, a normal cell can trigger cellular self-defense mechanism in response to genome stress. To investigate the kinetics of cellular self-repair process at single cell level further, a model of DNA damage generating and repair is proposed under acute Ion Radiation (IR) by using mathematical framework of kinetic theory of active particles (KTAP). Firstly, we focus on illustrating the profile of Cellular Repair System (CRS) instituted by two sub-populations, each of which is made up of the active particles with different discrete states. Then, we implement the mathematical framework of cellular self-repair mechanism, and illustrate the dynamic processes of Double Strand Breaks (DSBs) and Repair Protein (RP) generating, DSB-protein complexes (DSBCs) synthesizing, and toxins accumulating. Finally, we roughly analyze the capability of cellular self-repair mechanism, cellular activity of transferring DNA damage, and genome stability, especially the different fates of a certain cell before and after the time thresholds of IR perturbations that a cell can tolerate maximally under different IR perturbation circumstances.

General Mechanical Repair. Minor Automotive Maintenance, Small Engine [Repair, and] Welding: Curriculum Guide and Lesson Plans.

Science.gov (United States)

Hamlin, Larry

This document contains a curriculum guide and lesson plans for a general mechanical repair course with three sections: minor automotive maintenance, small engine repair, and welding. The curriculum guide begins with a matrix that relates the lesson plans to essential elements of math, science, language arts, and social studies and to Texas…

Ku-mediated coupling of DNA cleavage and repair during programmed genome rearrangements in the ciliate Paramecium tetraurelia.

Directory of Open Access Journals (Sweden)

Antoine Marmignon

2014-08-01

Full Text Available During somatic differentiation, physiological DNA double-strand breaks (DSB can drive programmed genome rearrangements (PGR, during which DSB repair pathways are mobilized to safeguard genome integrity. Because of their unique nuclear dimorphism, ciliates are powerful unicellular eukaryotic models to study the mechanisms involved in PGR. At each sexual cycle, the germline nucleus is transmitted to the progeny, but the somatic nucleus, essential for gene expression, is destroyed and a new somatic nucleus differentiates from a copy of the germline nucleus. In Paramecium tetraurelia, the development of the somatic nucleus involves massive PGR, including the precise elimination of at least 45,000 germline sequences (Internal Eliminated Sequences, IES. IES excision proceeds through a cut-and-close mechanism: a domesticated transposase, PiggyMac, is essential for DNA cleavage, and DSB repair at excision sites involves the Ligase IV, a specific component of the non-homologous end-joining (NHEJ pathway. At the genome-wide level, a huge number of programmed DSBs must be repaired during this process to allow the assembly of functional somatic chromosomes. To understand how DNA cleavage and DSB repair are coordinated during PGR, we have focused on Ku, the earliest actor of NHEJ-mediated repair. Two Ku70 and three Ku80 paralogs are encoded in the genome of P. tetraurelia: Ku70a and Ku80c are produced during sexual processes and localize specifically in the developing new somatic nucleus. Using RNA interference, we show that the development-specific Ku70/Ku80c heterodimer is essential for the recovery of a functional somatic nucleus. Strikingly, at the molecular level, PiggyMac-dependent DNA cleavage is abolished at IES boundaries in cells depleted for Ku80c, resulting in IES retention in the somatic genome. PiggyMac and Ku70a/Ku80c co-purify as a complex when overproduced in a heterologous system. We conclude that Ku has been integrated in the Paramecium

Arterial Injury and Endothelial Repair: Rapid Recovery of Function after Mechanical Injury in Healthy Volunteers

Directory of Open Access Journals (Sweden)

Lindsey Tilling

2014-01-01

Full Text Available Objective. Previous studies suggest a protracted course of recovery after mechanical endothelial injury; confounders may include degree of injury and concomitant endothelial dysfunction. We sought to define the time course of endothelial function recovery using flow-mediated dilation (FMD, after ischaemia-reperfusion (IR and mechanical injury in patients and healthy volunteers. The contribution of circulating CD133+/CD34+/VEGFR2+ “endothelial progenitor” (EPC or repair cells to endothelial repair was also examined. Methods. 28 healthy volunteers aged 18–35 years underwent transient forearm ischaemia induced by cuff inflation around the proximal biceps and radial artery mechanical injury induced by inserting a wire through a cannula. A more severe mechanical injury was induced using an arterial sheath and catheter inserted into the radial artery of 18 patients undergoing angiography. Results. IR and mechanical injury produced immediate impairment of FMD (from 6.5 ± 1.2% to 2.9 ± 2.2% and from 7.4 ± 2.3% to 1.5 ± 1.6% for IR and injury, resp., each P<0.001 but recovered within 6 hours and 2 days, respectively. FMD took up to 4 months to recover in patients. Circulating EPC did not change significantly during the injury/recovery period in all subjects. Conclusions. Recovery of endothelial function after IR and mechanical injury is rapid and not associated with a change in circulating EPC.

General Mechanical Repair. Minor Automotive Maintenance, Small Engine [Repair, and] Welding: Competency Test Package.

Science.gov (United States)

Hamlin, Larry

This document contains the competency test package for three sections of a general mechanical repair course: minor automotive maintenance, small engine mechanics, and welding. Following a list of the common essential elements for trade and industrial education, competency tests for the three sections are provided. Each test includes unit name,…

Host-Plant Specialization Mediates the Influence of Plant Abundance on Host Use by Flower Head-Feeding Insects.

Science.gov (United States)

Nobre, Paola A F; Bergamini, Leonardo L; Lewinsohn, Thomas M; Jorge, Leonardo R; Almeida-Neto, Mário

2016-02-01

Among-population variation in host use is a common phenomenon in herbivorous insects. The simplest and most trivial explanation for such variation in host use is the among-site variation in plant species composition. Another aspect that can influence spatial variation in host use is the relative abundance of each host-plant species compared to all available hosts. Here, we used endophagous insects that develop in flower heads of Asteraceae species as a study system to investigate how plant abundance influences the pattern of host-plant use by herbivorous insects with distinct levels of host-range specialization. Only herbivores recorded on three or more host species were included in this study. In particular, we tested two related hypotheses: 1) plant abundance has a positive effect on the host-plant preference of herbivorous insects, and 2) the relative importance of plant abundance to host-plant preference is greater for herbivorous species that use a wider range of host-plant species. We analyzed 11 herbivore species in 20 remnants of Cerrado in Southeastern Brazil. For 8 out of 11 herbivore species, plant abundance had a positive influence on host use. In contrast to our expectation, both the most specialized and the most generalist herbivores showed a stronger positive effect of plant species abundance in host use. Thus, we found evidence that although the abundance of plant species is a major factor determining the preferential use of host plants, its relative importance is mediated by the host-range specialization of herbivores.

Light emission mechanism of mixed host organic light-emitting diodes

Science.gov (United States)

Song, Wook; Lee, Jun Yeob

2015-03-01

Light emission mechanism of organic light-emitting diodes with a mixed host emitting layer was studied using an exciplex type mixed host and an exciplex free mixed host. Monitoring of the current density and luminance of the two type mixed host devices revealed that the light emission process of the exciplex type mixed host was dominated by energy transfer, while the light emission of the exciplex free mixed host was controlled by charge trapping. Mixed host composition was also critical to the light emission mechanism, and the contribution of the energy transfer process was maximized at 50:50 mixed host composition. Therefore, it was possible to manage the light emission process of the mixed host devices by managing the mixed host composition.

In wound repair vimentin mediates the transition of mesenchymal leader cells to a myofibroblast phenotype.

Science.gov (United States)

Walker, J L; Bleaken, B M; Romisher, A R; Alnwibit, A A; Menko, A S

2018-05-02

Following injury, mesenchymal repair cells are activated to function as leader cells that modulate wound healing. These cells have the potential to differentiate to myofibroblasts, resulting in fibrosis and scarring. The signals underlying these differing pathways are complex and incompletely understood. The ex vivo mock cataract surgery cultures are an attractive model with which to address this question. With this model we study, concurrently, the mechanisms that control mesenchymal leader cell function in injury repair within their native microenvironment, and the signals that induce this same cell population to acquire a myofibroblast phenotype when these cells encounter the environment of the adjacent tissue culture platform. Here, we show that upon injury, the cytoskeletal protein vimentin is released into the extracellular space, binds to the cell surface of the mesenchymal leader cells located at the wound edge in the native matrix environment, and supports wound closure. In pro-fibrotic environments, the extracellular vimentin pool also links specifically to the mesenchymal leader cells, and has an essential role in signaling their fate change to a myofibroblast. These findings suggest a novel role for extracellular, cell-surface-associated vimentin in mediating repair-cell function in wound repair and in transitioning these cells to a myofibroblast phenotype. Movie S1 Movie S1 Collective movement of mesenchymal leader and epithelial follower cells across the tissue culture substrate (ECZ) in response to injury was followed by time-lapse imaging from D0-D3. The mesenchymal cells at the leading edge were easily distinguished morphologically from the lens epithelial follower cells.

Apical External Root Resorption and Repair in Orthodontic Tooth Movement: Biological Events.

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Feller, Liviu; Khammissa, Razia A G; Thomadakis, George; Fourie, Jeanine; Lemmer, Johan

2016-01-01

Some degree of external root resorption is a frequent, unpredictable, and unavoidable consequence of orthodontic tooth movement mediated by odontoclasts/cementoclasts originating from circulating precursor cells in the periodontal ligament. Its pathogenesis involves mechanical forces initiating complex interactions between signalling pathways activated by various biological agents. Resorption of cementum is regulated by mechanisms similar to those controlling osteoclastogenesis and bone resorption. Following root resorption there is repair by cellular cementum, but factors mediating the transition from resorption to repair are not clear. In this paper we review some of the biological events associated with orthodontically induced external root resorption.

Apical External Root Resorption and Repair in Orthodontic Tooth Movement: Biological Events

Directory of Open Access Journals (Sweden)

Liviu Feller

2016-01-01

Full Text Available Some degree of external root resorption is a frequent, unpredictable, and unavoidable consequence of orthodontic tooth movement mediated by odontoclasts/cementoclasts originating from circulating precursor cells in the periodontal ligament. Its pathogenesis involves mechanical forces initiating complex interactions between signalling pathways activated by various biological agents. Resorption of cementum is regulated by mechanisms similar to those controlling osteoclastogenesis and bone resorption. Following root resorption there is repair by cellular cementum, but factors mediating the transition from resorption to repair are not clear. In this paper we review some of the biological events associated with orthodontically induced external root resorption.

Plasmids which make their host bacteria mutable as well as resistant to ultraviolet irradiation

International Nuclear Information System (INIS)

Arai, Toshihiko; Ando, Takao

1980-01-01

Some of the naturally occurring Iα, I zeta, M, N, O and T group plasmids increase both the mutability and UV resistance of their host bacteria, while group H and S plasmids only increase mutability. This suggests that these two plasmid-mediated repair functions are separable. The two functions have no direct relation to their restriction-modification systems and nitrofuran resistant functions. In addition, the close linking between the restriction-modification genes and these repair function genes was suggested in group N plasmids. (author)

CD4 T cell-mediated protection from lethal influenza: perforin and antibody-mediated mechanisms give a one-two punch.

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Brown, Deborah M; Dilzer, Allison M; Meents, Dana L; Swain, Susan L

2006-09-01

The mechanisms whereby CD4 T cells contribute to the protective response against lethal influenza infection remain poorly characterized. To define the role of CD4 cells in protection against a highly pathogenic strain of influenza, virus-specific TCR transgenic CD4 effectors were generated in vitro and transferred into mice given lethal influenza infection. Primed CD4 effectors conferred protection against lethal infection over a broad range of viral dose. The protection mediated by CD4 effectors did not require IFN-gamma or host T cells, but did result in increased anti-influenza Ab titers compared with untreated controls. Further studies indicated that CD4-mediated protection at high doses of influenza required B cells, and that passive transfer of anti-influenza immune serum was therapeutic in B cell-deficient mice, but only when CD4 effectors were present. Primed CD4 cells also acquired perforin (Pfn)-mediated cytolytic activity during effector generation, suggesting a second mechanism used by CD4 cells to confer protection. Pfn-deficient CD4 effectors were less able to promote survival in intact BALB/c mice and were unable to provide protection in B cell-deficient mice, indicating that Ab-independent protection by CD4 effectors requires Pfn. Therefore, CD4 effectors mediate protection to lethal influenza through at least two mechanisms: Pfn-mediated cytotoxicity early in the response promoted survival independently of Ab production, whereas CD4-driven B cell responses resulted in high titer Abs that neutralized remaining virus.

Histones as mediators of host defense, inflammation and thrombosis.

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Hoeksema, Marloes; van Eijk, Martin; Haagsman, Henk P; Hartshorn, Kevan L

2016-01-01

Histones are known for their ability to bind to and regulate expression of DNA. However, histones are also present in cytoplasm and extracellular fluids where they serve host defense functions and promote inflammatory responses. Histones are a major component of neutrophil extracellular traps that contribute to bacterial killing but also to inflammatory injury. Histones can act as antimicrobial peptides and directly kill bacteria, fungi, parasites and viruses, in vitro and in a variety of animal hosts. In addition, histones can trigger inflammatory responses in some cases acting through Toll-like receptors or inflammasome pathways. Extracellular histones mediate organ injury (lung, liver), sepsis physiology, thrombocytopenia and thrombin generation and some proteins can bind histones and reduce these potentially harmful effects.

DNA repair in ultraviolet-irradiated spores of Bacillus subtilis

International Nuclear Information System (INIS)

Wang, T.C.V.

1976-01-01

It has been shown previously by others that at least two independent repair mechanisms are present in Bacillus subtilis for removing ''spore photoproduct'' from DNA of ultraviolet (254 nm)-irradiated spores after germination. One of these, designated as ''spore repair,'' is shown in this study to restore ''spore photoproduct'' to two thymine residues, leaving the DNA backbone intact at the end of the process in vivo. The circumstances under which this repair can occur and some characteristics of its energy requirements have been clarified. The second repair process is identified as excision repair, which can excise both ''spore photoproduct'' from DNA of irradiated spores and cyclobutane-type pyrimidine dimers from DNA of irradiated vegetative cells. In this study it is shown that the gene hcr 1 affects an enzyme activity for the incision step initiating this repair, while the gene hcr 42 affects a step subsequent to incision in the mechanism. In addition a third, independent repair system, termed ''germinative excision repair,'' is discovered and shown to be specific for excising only cyclobutane-type pyrimidine dimers but not ''spore photoproduct.'' This repair system is responsible for the observed high ultraviolet-resistance and temporary capacity for host cell reactivation on recently germinated spores of Bacillus subtilis HCR - strains

Gene repair of an Usher syndrome causing mutation by zinc-finger nuclease mediated homologous recombination.

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Overlack, Nora; Goldmann, Tobias; Wolfrum, Uwe; Nagel-Wolfrum, Kerstin

2012-06-26

Human Usher syndrome (USH) is the most frequent cause of inherited deaf-blindness. It is clinically and genetically heterogeneous, assigned to three clinical types of which the most severe type is USH1. No effective treatment for the ophthalmic component of USH exists. Gene augmentation is an attractive strategy for hereditary retinal diseases. However, several USH genes, like USH1C, are expressed in various isoforms, hampering gene augmentation. As an alternative treatment strategy, we applied the zinc-finger nuclease (ZFN) technology for targeted gene repair of an USH1C, causing mutation by homologous recombination. We designed ZFNs customized for the p.R31X nonsense mutation in Ush1c. We evaluated ZFNs for DNA cleavage capability and analyzed ZFNs biocompatibilities by XTT assays. We demonstrated ZFNs mediated gene repair on genomic level by digestion assays and DNA sequencing, and on protein level by indirect immunofluorescence and Western blot analyses. The specifically designed ZFNs did not show cytotoxic effects in a p.R31X cell line. We demonstrated that ZFN induced cleavage of their target sequence. We showed that simultaneous application of ZFN and rescue DNA induced gene repair of the disease-causing mutation on the genomic level, resulting in recovery of protein expression. In our present study, we analyzed for the first time ZFN-activated gene repair of an USH gene. The data highlight the ability of ZFNs to induce targeted homologous recombination and mediate gene repair in USH. We provide further evidence that the ZFN technology holds great potential to recover disease-causing mutations in inherited retinal disorders.

Resident enhanced repair: novel repair process action on plasmid DNA transformed into Escherichia coli K-12

International Nuclear Information System (INIS)

Strike, P.; Roberts, R.J.

1982-01-01

The survival of UV-irradiated DNA of plasmid NTP16 was monitored after its transformation into recipient cells containing an essentially homologous undamaged plasmid, pLV9. The presence of pLV9 resulted in a substantial increase in the fraction of damaged NTP16 molecules which survived in the recipient cells. This enhanced survival requires the host uvrA + and uvrB + gene products, but not the host recA + gene product. The requirement for both homologous DNA and the uvrA + gene products suggests that a novel repair process may act on plasmid DNA. Possible mechanisms for this process are considered

Radiation-Induced Upregulation of Gene Expression From Adenoviral Vectors Mediated by DNA Damage Repair and Regulation

International Nuclear Information System (INIS)

Nokisalmi, Petri; Rajecki, Maria; Pesonen, Sari; Escutenaire, Sophie; Soliymani, Rabah; Tenhunen, Mikko; Ahtiainen, Laura; Hemminki, Akseli

2012-01-01

Purpose: In the present study, we evaluated the combination of replication-deficient adenoviruses and radiotherapy in vitro. The purpose of the present study was to analyze the mechanism of radiation-mediated upregulation of adenoviral transgene expression. Methods and Materials: Adenoviral transgene expression (luciferase or green fluorescent protein) was studied with and without radiation in three cell lines: breast cancer M4A4-LM3, prostate cancer PC-3MM2, and lung cancer LNM35/enhanced green fluorescent protein. The effect of the radiation dose, modification of the viral capsid, and five different transgene promoters were studied. The cellular responses were studied using mass spectrometry and immunofluorescence analysis. Double strand break repair was modulated by inhibitors of heat shock protein 90, topoisomerase-I, and DNA protein kinase, and transgene expression was measured. Results: We found that a wide range of radiation doses increased adenoviral transgene expression regardless of the cell line, transgene, promoter, or viral capsid modification. Treatment with adenovirus, radiation, and double strand break repair inhibitors resulted in persistence of double strand breaks and subsequent increases in adenovirus transgene expression. Conclusions: Radiation-induced enhancement of adenoviral transgene expression is linked to DNA damage recognition and repair. Radiation induces a global cellular response that results in increased production of RNA and proteins, including adenoviral transgene products. This study provides a mechanistic rationale for combining radiation with adenoviral gene delivery.

SPOC1-mediated antiviral host cell response is antagonized early in human adenovirus type 5 infection

DEFF Research Database (Denmark)

Schreiner, Sabrina; Kinkley, Sarah; Bürck, Carolin

2013-01-01

, and playing a role in DNA damage response. SPOC1 co-localized with viral replication centers in the host cell nucleus, interacted with Ad DNA, and repressed viral gene expression at the transcriptional level. We discovered that this SPOC1-mediated restriction imposed upon Ad growth is relieved by its...... viruses (HSV-1, HSV-2, HIV-1, and HCV) also depleted SPOC1 in infected cells. Our findings provide a general model for how pathogenic human viruses antagonize intrinsic SPOC1-mediated antiviral responses in their host cells. A better understanding of viral entry and early restrictive functions in host...

Srs2 mediates PCNA-SUMO-dependent inhibition of DNA repair synthesis

International Nuclear Information System (INIS)

Burkovics, Peter; Sebesta, Marek; Kolesar, Peter; Sisakova, Alexandra; Marini, Victoria; Plault, Nicolas; Szukacsov, Valeria; Pinter, Lajos; Haracska, Lajos; Robert, Thomas; Kolesar, Peter; Gangloff, Serge; Krejci, Lumir

2013-01-01

Completion of DNA replication needs to be ensured even when challenged with fork progression problems or DNA damage. PCNA and its modifications constitute a molecular switch to control distinct repair pathways. In yeast, SUMOylated PCNA (S-PCNA) recruits Srs2 to sites of replication where Srs2 can disrupt Rad51 filaments and prevent homologous recombination (HR). We report here an unexpected additional mechanism by which S-PCNA and Srs2 block the synthesis-dependent extension of a recombination intermediate, thus limiting its potentially hazardous resolution in association with a cross-over. This new Srs2 activity requires the SUMO interaction motif at its C-terminus, but neither its translocase activity nor its interaction with Rad51. Srs2 binding to S-PCNA dissociates Polδ and Polη from the repair synthesis machinery, thus revealing a novel regulatory mechanism controlling spontaneous genome rearrangements. Our results suggest that cycling cells use the Siz1-dependent SUMOylation of PCNA to limit the extension of repair synthesis during template switch or HR and attenuate reciprocal DNA strand exchanges to maintain genome stability. (authors)

Host-cell reactivation of uv-irradiated and chemically treated Herpes simplex virus type 1 strain MP in normal and xeroderma pigmentosum skin fibroblasts

International Nuclear Information System (INIS)

Selsky, C.A.

1976-01-01

The host-cell reactivation of UV-irradiated and N-acetoxy-2-acetylaminofluorene-treated herpes simplex virus type 1 strain mp was studied in normal human skin fibroblasts and xeroderma pigmentosum skin fibroblasts from XP genetic complementation groups A-D and in an XP variant. The increasing relative order for the host-cell reactivation of both types of damaged virus in the different complementation groups is A = D < B < C; XP variant = normal controls. XP complementation group D cells, which manifest the most severe inhibition of her ability for both UV-irradiated and N-acetoxy-2-acetylaminofluorene-treated virus, can reactivate nitrogen mustard treated HSV-1 mp to the same extent as normal cells. Together, these results indicate that (1) Excision repair of UV and N-acetoxy-2-acetylaminofluorene DNA damaged viruses share a common rate limiting enzymatic step and (2) The repair defect in xeroderma pigmentosum cells plays little or no role in the recovery of nitrogen mustard treated virus. The results of studies on the effect of caffeine on the survival of both UV- and N-acetoxy-2-acetylaminofluorene-treated virus in normal and XP cells imply that the reactivation of HSV-1 mp is mediated by an excision repair process with little if any recovery contributed by post-replication repair mechanisms. The host-cell reactivation of N-acetoxy-2-acetylaminofluorene-treated HSV-1 mp was also correlated with the defective UV-induced unscheduled DNA synthesis in two skin fibroblast strains established from a skin biopsy obtained from each of two juvenile females who had been clinically diagnosed as xeroderma pigmentosum. These findings are discussed in relation to the further characterization of the xeroderma pigmentosum phenotype and their possible utilization for the selection and isolation of new mammalian cell DNA repair mutants

Coral bleaching under thermal stress: putative involvement of host/symbiont recognition mechanisms.

Science.gov (United States)

Vidal-Dupiol, Jeremie; Adjeroud, Mehdi; Roger, Emmanuel; Foure, Laurent; Duval, David; Mone, Yves; Ferrier-Pages, Christine; Tambutte, Eric; Tambutte, Sylvie; Zoccola, Didier; Allemand, Denis; Mitta, Guillaume

2009-08-04

Coral bleaching can be defined as the loss of symbiotic zooxanthellae and/or their photosynthetic pigments from their cnidarian host. This major disturbance of reef ecosystems is principally induced by increases in water temperature. Since the beginning of the 1980s and the onset of global climate change, this phenomenon has been occurring at increasing rates and scales, and with increasing severity. Several studies have been undertaken in the last few years to better understand the cellular and molecular mechanisms of coral bleaching but the jigsaw puzzle is far from being complete, especially concerning the early events leading to symbiosis breakdown. The aim of the present study was to find molecular actors involved early in the mechanism leading to symbiosis collapse. In our experimental procedure, one set of Pocillopora damicornis nubbins was subjected to a gradual increase of water temperature from 28 degrees C to 32 degrees C over 15 days. A second control set kept at constant temperature (28 degrees C). The differentially expressed mRNA between the stressed states (sampled just before the onset of bleaching) and the non stressed states (control) were isolated by Suppression Subtractive Hybridization. Transcription rates of the most interesting genes (considering their putative function) were quantified by Q-RT-PCR, which revealed a significant decrease in transcription of two candidates six days before bleaching. RACE-PCR experiments showed that one of them (PdC-Lectin) contained a C-Type-Lectin domain specific for mannose. Immunolocalisation demonstrated that this host gene mediates molecular interactions between the host and the symbionts suggesting a putative role in zooxanthellae acquisition and/or sequestration. The second gene corresponds to a gene putatively involved in calcification processes (Pdcyst-rich). Its down-regulation could reflect a trade-off mechanism leading to the arrest of the mineralization process under stress. Under thermal stress

Lung-Derived Mediators Induce Cytokine Production in Downstream Organs via an NF-κB-Dependent Mechanism

Directory of Open Access Journals (Sweden)

E. K. Patterson

2013-01-01

Full Text Available In the setting of acute lung injury, levels of circulating inflammatory mediators have been correlated with adverse outcomes. Previous studies have demonstrated that injured, mechanically ventilated lungs represent the origin of the host inflammatory response; however, mechanisms which perpetuate systemic inflammation remain uncharacterized. We hypothesized that lung-derived mediators generated by mechanical ventilation (MV are amplified by peripheral organs in a “feed forward” mechanism of systemic inflammation. Herein, lung-derived mediators were collected from 129X1/SVJ mice after 2 hours of MV while connected to the isolated perfused mouse lung model setup. Exposure of liver endothelial cells to lung-derived mediators resulted in a significant increase in G-CSF, IL-6, CXCL-1, CXCL-2, and MCP-1 production compared to noncirculated control perfusate media (P<0.05. Furthermore, inhibition of the NF-κB pathway significantly mitigated this response. Changes in gene transcription were confirmed using qPCR for IL-6, CXCL-1, and CXCL-2. Additionally, liver tissue obtained from mice subjected to 2 hours of in vivo MV demonstrated significant increases in hepatic gene transcription of IL-6, CXCL-1, and CXCL-2 compared to nonventilated controls. Collectively, this data demonstrates that lung-derived mediators, generated in the setting of MV, are amplified by downstream organs in a feed forward mechanism of systemic inflammation.

Role of Host Type IA Phosphoinositide 3-Kinase Pathway Components in Invasin-Mediated Internalization of Yersinia enterocolitica.

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Dowd, Georgina C; Bhalla, Manmeet; Kean, Bernard; Thomas, Rowan; Ireton, Keith

2016-06-01

Many bacterial pathogens subvert mammalian type IA phosphoinositide 3-kinase (PI3K) in order to induce their internalization into host cells. How PI3K promotes internalization is not well understood. Also unclear is whether type IA PI3K affects different pathogens through similar or distinct mechanisms. Here, we performed an RNA interference (RNAi)-based screen to identify components of the type IA PI3K pathway involved in invasin-mediated entry of Yersinia enterocolitica, an enteropathogen that causes enteritis and lymphadenitis. The 69 genes targeted encode known upstream regulators or downstream effectors of PI3K. A similar RNAi screen was previously performed with the food-borne bacterium Listeria monocytogenes The results of the screen with Y. enterocolitica indicate that at least nine members of the PI3K pathway are needed for invasin-mediated entry. Several of these proteins, including centaurin-α1, Dock180, focal adhesion kinase (FAK), Grp1, LL5α, LL5β, and PLD2 (phospholipase D2), were recruited to sites of entry. In addition, centaurin-α1, FAK, PLD2, and mTOR were required for remodeling of the actin cytoskeleton during entry. Six of the human proteins affecting invasin-dependent internalization also promote InlB-mediated entry of L. monocytogenes Our results identify several host proteins that mediate invasin-induced effects on the actin cytoskeleton and indicate that a subset of PI3K pathway components promote internalization of both Y. enterocolitica and L. monocytogenes. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

How Human Papillomavirus Replication and Immune Evasion Strategies Take Advantage of the Host DNA Damage Repair Machinery.

Science.gov (United States)

Bordignon, Valentina; Di Domenico, Enea Gino; Trento, Elisabetta; D'Agosto, Giovanna; Cavallo, Ilaria; Pontone, Martina; Pimpinelli, Fulvia; Mariani, Luciano; Ensoli, Fabrizio

2017-12-19

The DNA damage response (DDR) is a complex signalling network activated when DNA is altered by intrinsic or extrinsic agents. DDR plays important roles in genome stability and cell cycle regulation, as well as in tumour transformation. Viruses have evolved successful life cycle strategies in order to ensure a chronic persistence in the host, virtually avoiding systemic sequelae and death. This process promotes the periodic shedding of large amounts of infectious particles to maintain a virus reservoir in individual hosts, while allowing virus spreading within the community. To achieve such a successful lifestyle, the human papilloma virus (HPV) needs to escape the host defence systems. The key to understanding how this is achieved is in the virus replication process that provides by itself an evasion mechanism by inhibiting and delaying the host immune response against the viral infection. Numerous studies have demonstrated that HPV exploits both the ataxia-telangiectasia mutated (ATM) and ataxia-telangiectasia and rad3-related (ATR) DDR pathways to replicate its genome and maintain a persistent infection by downregulating the innate and cell-mediated immunity. This review outlines how HPV interacts with the ATM- and ATR-dependent DDR machinery during the viral life cycle to create an environment favourable to viral replication, and how the interaction with the signal transducers and activators of transcription (STAT) protein family and the deregulation of the Janus kinase (JAK)-STAT pathways may impact the expression of interferon-inducible genes and the innate immune responses.

Bacterial radiosensitivity to gamma and ultraviolet. Compositional dependence and repair mechanisms

International Nuclear Information System (INIS)

Saez Angulo, R. M.; Davila, C. A.

1974-01-01

The gamma and ultraviolet radiosensitivity of several species of bacteria has been determined its dependence on DNAs composition and repair processes has been studied. Base composition are evaluated by chromatography, DNA melting temperature and isopycnic sedimentation on CsCl gradient. Repair capacity of gamma -and UV- lesions has been studied in two bacterial strains with same DMA base composition. It is concluded that the postulated correlation between radiosensitivity and base composition can not be generalized, the enzymatic repair mechanisms being of determining on radiosensitivity. (Author) 248 refs

Complex DNA repair pathways as possible therapeutic targets to overcome temozolomide resistance in glioblastoma

International Nuclear Information System (INIS)

Yoshimoto, Koji; Mizoguchi, Masahiro; Hata, Nobuhiro; Murata, Hideki; Hatae, Ryusuke; Amano, Toshiyuki; Nakamizo, Akira; Sasaki, Tomio

2012-01-01

Many conventional chemotherapeutic drugs exert their cytotoxic function by inducing DNA damage in the tumor cell. Therefore, a cell-inherent DNA repair pathway, which reverses the DNA-damaging effect of the cytotoxic drugs, can mediate therapeutic resistance to chemotherapy. The monofunctional DNA-alkylating agent temozolomide (TMZ) is a commonly used chemotherapeutic drug and the gold standard treatment for glioblastoma (GBM). Although the activity of DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) has been described as the main modulator to determine the sensitivity of GBM to TMZ, a subset of GBM does not respond despite MGMT inactivation, suggesting that another DNA repair mechanism may also modulate the tolerance to TMZ. Considerable interest has focused on MGMT, mismatch repair (MMR), and the base excision repair (BER) pathway in the mechanism of mediating TMZ resistance, but emerging roles for the DNA strand-break repair pathway have been demonstrated. In the first part of this review article, we briefly review the significant role of MGMT, MMR, and the BER pathway in the tolerance to TMZ; in the last part, we review the recent publications that demonstrate possible roles of DNA strand-break repair pathways, such as single-strand break repair and double-strand break repair, as well as the Fanconi anemia pathway in the repair process after alkylating agent-based therapy. It is possible that all of these repair pathways have a potential to modulate the sensitivity to TMZ and aid in overcoming the therapeutic resistance in the clinic.

Complex DNA repair pathways as possible therapeutic targets to overcome temozolomide resistance in glioblastoma

Energy Technology Data Exchange (ETDEWEB)

Yoshimoto, Koji; Mizoguchi, Masahiro; Hata, Nobuhiro; Murata, Hideki; Hatae, Ryusuke; Amano, Toshiyuki; Nakamizo, Akira; Sasaki, Tomio, E-mail: kyoshimo@ns.med.kyushu-u.ac.jp [Department of Neurosurgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka (Japan)

2012-12-05

Many conventional chemotherapeutic drugs exert their cytotoxic function by inducing DNA damage in the tumor cell. Therefore, a cell-inherent DNA repair pathway, which reverses the DNA-damaging effect of the cytotoxic drugs, can mediate therapeutic resistance to chemotherapy. The monofunctional DNA-alkylating agent temozolomide (TMZ) is a commonly used chemotherapeutic drug and the gold standard treatment for glioblastoma (GBM). Although the activity of DNA repair protein O6-methylguanine-DNA methyltransferase (MGMT) has been described as the main modulator to determine the sensitivity of GBM to TMZ, a subset of GBM does not respond despite MGMT inactivation, suggesting that another DNA repair mechanism may also modulate the tolerance to TMZ. Considerable interest has focused on MGMT, mismatch repair (MMR), and the base excision repair (BER) pathway in the mechanism of mediating TMZ resistance, but emerging roles for the DNA strand-break repair pathway have been demonstrated. In the first part of this review article, we briefly review the significant role of MGMT, MMR, and the BER pathway in the tolerance to TMZ; in the last part, we review the recent publications that demonstrate possible roles of DNA strand-break repair pathways, such as single-strand break repair and double-strand break repair, as well as the Fanconi anemia pathway in the repair process after alkylating agent-based therapy. It is possible that all of these repair pathways have a potential to modulate the sensitivity to TMZ and aid in overcoming the therapeutic resistance in the clinic.

Type 2 immunity and wound healing: evolutionary refinement of adaptive immunity by helminths

Science.gov (United States)

Gause, William C.; Wynn, Thomas A.; Allen, Judith E.

2013-01-01

Helminth-induced type 2 immune responses, which are characterized by the T helper 2 cell-associated cytokines interleukin-4 (IL-4) and IL-13, mediate host protection through enhanced tissue repair, the control of inflammation and worm expulsion. In this Opinion article, we consider type 2 immunity in the context of helminth-mediated tissue damage. We examine the relationship between the control of helminth infection and the mechanisms of wound repair, and we provide a new understanding of the adaptive type 2 immune response and its contribution to both host tolerance and resistance. PMID:23827958

Neocarzinostatin-mediated DNA damage and repair in wild-type and repair-deficient Chinese hamster ovary cells

International Nuclear Information System (INIS)

Kuo, W.L.; Meyn, R.E.; Haidle, C.W.

1984-01-01

The formation and repair of neocarzinostatin (NCS)-mediated DNA damage were examined in two strains of Chinese hamster ovary cells. The response in strain EM9, a mutant line selected for its sensitivity to ethyl methanesulfonate and shown to have a defect in the repair of X-ray-induced DNA breaks, was compared with that observed in the parental strain (AA8). The DNA strand breaks and their subsequent rejoining were measured using the method of elution of DNA from filters under either alkaline (for single-strand breaks), or nondenaturing conditions (for double-strand breaks). Colony survival assays showed that the mutant was more sensitive to the action of NCS than was the parental strain by a factor of approximately 1.5. Elution analyses showed that the DNA from both strains was damaged by NCS; the mutant displayed more damage than the parent under the same treatment conditions. Single-strand breaks were produced with a frequency of about 10 to 15 times the frequency of double-strand breaks. Both strains were able to rejoin both single-strand breaks and double-strand breaks induced by NCS treatment. The strand break data suggest that the difference in NCS-mediated cytotoxicity between EM9 and AA8 cells may be directly related to the enhanced production of DNA strand breaks in EM9. However, the fact that much higher doses of NCS were required in the DNA studies compared to the colony survival assays implies that either a small number of DNA breaks occur in a critical region of the genome, or that lesions other than DNA strand breaks are partly responsible for the observed cytotoxicity

Interplay of DNA repair with transcription: from structures to mechanisms.

Science.gov (United States)

Deaconescu, Alexandra M; Artsimovitch, Irina; Grigorieff, Nikolaus

2012-12-01

Many DNA transactions are crucial for maintaining genomic integrity and faithful transfer of genetic information but remain poorly understood. An example is the interplay between nucleotide excision repair (NER) and transcription, also known as transcription-coupled DNA repair (TCR). Discovered decades ago, the mechanisms for TCR have remained elusive, not in small part due to the scarcity of structural studies of key players. Here we summarize recent structural information on NER/TCR factors, focusing on bacterial systems, and integrate it with existing genetic, biochemical, and biophysical data to delineate the mechanisms at play. We also review emerging, alternative modalities for recruitment of NER proteins to DNA lesions. Copyright © 2012 Elsevier Ltd. All rights reserved.

General Mechanical Repair 2. Minor Automotive Maintenance, Small Engine [Repair, and] Welding. Curriculum Guide.

Science.gov (United States)

Hamlin, Larry

This curriculum guide provides materials for teachers to use in developing a 1-year course in general mechanical repair as part of the trade and industrial education curriculum. The guide contains the following: (1) essential elements common to all trade and industrial courses; (2) an instructional delivery outline (teaching sequence) for the…

Repair of potentially lethal and sublethal radiation damage in x-irradiated ascites tumor cells

International Nuclear Information System (INIS)

Tsuboi, Atsushi; Okamoto, Mieko; Tsuchiya, Takehiko.

1985-01-01

The ability of cells to repair cellular radiation damage during the growth of TMT-3 ascites tumor and the effect of host reaction on the repair ability were examined by using an in vitro assay of cell clonogenicity after in situ irradiation of tumor cells. In single-dose experiments, the repair of potentially lethal radiation damage (PLD) was observed in stationary phase cells (12-day tumor) of the unirradiated host, but not in exponential phase cells (3-day tumor) of the unirradiated host animals. However, if previously irradiated host animals were used, even the exponentially growing tumor cells showed repair of PLD. In two-dose experiments, the ability to repair sublethal radiation damage (SLD) in exponential phase tumor cells was less than that of stationary phase cells in the unirradiated host. In the pre-irradiated host, the extent of the repair in exponential phase cells was somewhat enhanced. These results suggest that irradiation of host animals might suppress a factor that inhibits repair, resulting in enhancement of the repair capability of tumor cells. (author)

X-ray repair cross complementing protein 1 in base excision repair

DEFF Research Database (Denmark)

Hanssen-Bauer, Audun; Solvang-Garten, Karin; Akbari, Mansour

2012-01-01

X-ray Repair Cross Complementing protein 1 (XRCC1) acts as a scaffolding protein in the converging base excision repair (BER) and single strand break repair (SSBR) pathways. XRCC1 also interacts with itself and rapidly accumulates at sites of DNA damage. XRCC1 can thus mediate the assembly of large...

Repair mechanisms inducible to the DNA in I.M.M.S. biological systems

International Nuclear Information System (INIS)

Guzman, J.; Arceo, C.; Cortinas, C.; Rosa, M.E. De la; Olvera, O.; Cruces, M.; Pimentel, E.

1990-03-01

Given the characteristics of the MMS and the relative antecedents to the repair mechanisms in eucariontes are sought to determine the effect of the MMS on the genetic material and their repair in Drosophila melanogaster. (Author)

Effect of multiple repairs in girth welds of pipelines on the mechanical properties

International Nuclear Information System (INIS)

Vega, O.E.; Hallen, J.M.; Villagomez, A.; Contreras, A.

2008-01-01

This work presents the results of multiple weld repairs in the same area in seamless API X-52 microalloyed steel pipe. Four conditions of shielded metal arc welding repairs and one as-welded specimen of the girth weld were characterized to determine changes in the microstructure, grain size in the heat affected zone, and to evaluate their effect on the mechanical properties of the weld joints. The mechanical properties by means of tension tests, Charpy-V impact resistance and Vickers hardness of the welds were analyzed. The results indicate that significant changes are not generated in the microstructural constituents of the heat affected zone. Grain growth in the heat affected zone at the specimen mid-thickness with the number of repairs was observed. Tensile strength of the weld joints meets the requirement of the API 1104 standard even after the fourth weld repair. Significant reduction in Charpy-V impact resistance with the number of weld repairs was found when the notch location was in the intersection of the fusion line with the specimen mid-thickness. A significant increase in the Vickers hardness of the heat affected zone occurred after the first repair and a gradual decrease in the Vickers hardness occurred as the number of repairs increases

Guardians of the mycobacterial genome: A review on DNA repair systems in Mycobacterium tuberculosis.

Science.gov (United States)

Singh, Amandeep

2017-12-01

The genomic integrity of Mycobacterium tuberculosis is continuously threatened by the harsh survival conditions inside host macrophages, due to immune and antibiotic stresses. Faithful genome maintenance and repair must be accomplished under stress for the bacillus to survive in the host, necessitating a robust DNA repair system. The importance of DNA repair systems in pathogenesis is well established. Previous examination of the M. tuberculosis genome revealed homologues of almost all the major DNA repair systems, i.e. nucleotide excision repair (NER), base excision repair (BER), homologous recombination (HR) and non-homologous end joining (NHEJ). However, recent developments in the field have pointed to the presence of novel proteins and pathways in mycobacteria. Homologues of archeal mismatch repair proteins were recently reported in mycobacteria, a pathway previously thought to be absent. RecBCD, the major nuclease-helicase enzymes involved in HR in E. coli, were implicated in the single-strand annealing (SSA) pathway. Novel roles of archeo-eukaryotic primase (AEP) polymerases, previously thought to be exclusive to NHEJ, have been reported in BER. Many new proteins with a probable role in DNA repair have also been discovered. It is now realized that the DNA repair systems in M. tuberculosis are highly evolved and have redundant backup mechanisms to mend the damage. This review is an attempt to summarize our current understanding of the DNA repair systems in M. tuberculosis.

Coral bleaching under thermal stress: putative involvement of host/symbiont recognition mechanisms

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Tambutte Sylvie

2009-08-01

Full Text Available Abstract Background Coral bleaching can be defined as the loss of symbiotic zooxanthellae and/or their photosynthetic pigments from their cnidarian host. This major disturbance of reef ecosystems is principally induced by increases in water temperature. Since the beginning of the 1980s and the onset of global climate change, this phenomenon has been occurring at increasing rates and scales, and with increasing severity. Several studies have been undertaken in the last few years to better understand the cellular and molecular mechanisms of coral bleaching but the jigsaw puzzle is far from being complete, especially concerning the early events leading to symbiosis breakdown. The aim of the present study was to find molecular actors involved early in the mechanism leading to symbiosis collapse. Results In our experimental procedure, one set of Pocillopora damicornis nubbins was subjected to a gradual increase of water temperature from 28°C to 32°C over 15 days. A second control set kept at constant temperature (28°C. The differentially expressed mRNA between the stressed states (sampled just before the onset of bleaching and the non stressed states (control were isolated by Suppression Subtractive Hybridization. Transcription rates of the most interesting genes (considering their putative function were quantified by Q-RT-PCR, which revealed a significant decrease in transcription of two candidates six days before bleaching. RACE-PCR experiments showed that one of them (PdC-Lectin contained a C-Type-Lectin domain specific for mannose. Immunolocalisation demonstrated that this host gene mediates molecular interactions between the host and the symbionts suggesting a putative role in zooxanthellae acquisition and/or sequestration. The second gene corresponds to a gene putatively involved in calcification processes (Pdcyst-rich. Its down-regulation could reflect a trade-off mechanism leading to the arrest of the mineralization process under stress

Crystal Structures of DNA-Whirly Complexes and Their Role in Arabidopsis Organelle Genome Repair

Energy Technology Data Exchange (ETDEWEB)

Cappadocia, Laurent; Maréchal, Alexandre; Parent, Jean-Sébastien; Lepage, Étienne; Sygusch, Jurgen; Brisson, Normand (Montreal)

2010-09-07

DNA double-strand breaks are highly detrimental to all organisms and need to be quickly and accurately repaired. Although several proteins are known to maintain plastid and mitochondrial genome stability in plants, little is known about the mechanisms of DNA repair in these organelles and the roles of specific proteins. Here, using ciprofloxacin as a DNA damaging agent specific to the organelles, we show that plastids and mitochondria can repair DNA double-strand breaks through an error-prone pathway similar to the microhomology-mediated break-induced replication observed in humans, yeast, and bacteria. This pathway is negatively regulated by the single-stranded DNA (ssDNA) binding proteins from the Whirly family, thus indicating that these proteins could contribute to the accurate repair of plant organelle genomes. To understand the role of Whirly proteins in this process, we solved the crystal structures of several Whirly-DNA complexes. These reveal a nonsequence-specific ssDNA binding mechanism in which DNA is stabilized between domains of adjacent subunits and rendered unavailable for duplex formation and/or protein interactions. Our results suggest a model in which the binding of Whirly proteins to ssDNA would favor accurate repair of DNA double-strand breaks over an error-prone microhomology-mediated break-induced replication repair pathway.

Sutureless liver repair and hemorrhage control using laser-mediated fusion of human albumin as a solder.

Science.gov (United States)

Wadia, Y; Xie, H; Kajitani, M

2001-07-01

Major liver trauma has a high mortality because of immediate exsanguination and a delayed morbidity from septicemia, peritonitis, biliary fistulae, and delayed secondary hemorrhage. We evaluated laser soldering using liquid albumin for welding liver injuries. Fourteen lacerations (6 x 2 cm) and 13 nonanatomic resection injuries (raw surface, 8 x 2 cm) were repaired. An 805-nm laser was used to weld 53% liquid albumin-indocyanine green solder to the liver surface, reinforcing it by welding a free autologous omental scaffold. The animals were heparinized and hepatic inflow occlusion was used for vascular control. For both laceration and resection injuries, 16 soldering repairs were evaluated acutely at 3 hours. Eleven animals were evaluated chronically, two at 2 weeks and nine at 4 weeks. All 27 laser mediated-liver repairs had minimal blood loss compared with the suture controls. No dehiscence, hemorrhage, or bile leakage was seen in any of the laser repairs after 3 hours. All 11 chronic repairs healed without complication. This modality effectively seals the liver surface, joins lacerations with minimal thermal injury, and works independently of the patient's coagulation status.

The long-term behavior of lightweight and heavyweight meshes used to repair abdominal wall defects is determined by the host tissue repair process provoked by the mesh.

Science.gov (United States)

Pascual, Gemma; Hernández-Gascón, Belén; Rodríguez, Marta; Sotomayor, Sandra; Peña, Estefania; Calvo, Begoña; Bellón, Juan M

2012-11-01

Although heavyweight (HW) or lightweight (LW) polypropylene (PP) meshes are widely used for hernia repair, other alternatives have recently appeared. They have the same large-pore structure yet are composed of polytetrafluoroethylene (PTFE). This study compares the long-term (3 and 6 months) behavior of meshes of different pore size (HW compared with LW) and composition (PP compared with PTFE). Partial defects were created in the lateral wall of the abdomen in New Zealand White rabbits and then repaired by the use of a HW or LW PP mesh or a new monofilament, large-pore PTFE mesh (Infinit). At 90 and 180 days after implantation, tissue incorporation, gene and protein expression of neocollagens (reverse transcription-polymerase chain reaction/immunofluorescence), macrophage response (immunohistochemistry), and biomechanical strength were determined. Shrinkage was measured at 90 days. All three meshes induced good host tissue ingrowth, yet the macrophage response was significantly greater in the PTFE implants (P .05). Host collagen deposition is mesh pore size dependent whereas the macrophage response induced is composition dependent with a greater response shown by PTFE. In the long term, macroporous meshes show comparable biomechanical behavior regardless of their pore size or composition. Copyright © 2012 Mosby, Inc. All rights reserved.

Regulatory mechanisms of RNA function: emerging roles of DNA repair enzymes.

Science.gov (United States)

Jobert, Laure; Nilsen, Hilde

2014-07-01

The acquisition of an appropriate set of chemical modifications is required in order to establish correct structure of RNA molecules, and essential for their function. Modification of RNA bases affects RNA maturation, RNA processing, RNA quality control, and protein translation. Some RNA modifications are directly involved in the regulation of these processes. RNA epigenetics is emerging as a mechanism to achieve dynamic regulation of RNA function. Other modifications may prevent or be a signal for degradation. All types of RNA species are subject to processing or degradation, and numerous cellular mechanisms are involved. Unexpectedly, several studies during the last decade have established a connection between DNA and RNA surveillance mechanisms in eukaryotes. Several proteins that respond to DNA damage, either to process or to signal the presence of damaged DNA, have been shown to participate in RNA quality control, turnover or processing. Some enzymes that repair DNA damage may also process modified RNA substrates. In this review, we give an overview of the DNA repair proteins that function in RNA metabolism. We also discuss the roles of two base excision repair enzymes, SMUG1 and APE1, in RNA quality control.

The Impact of Hedgehog Signaling Pathway on DNA Repair Mechanisms in Human Cancer

International Nuclear Information System (INIS)

Meng, Erhong; Hanna, Ann; Samant, Rajeev S.; Shevde, Lalita A.

2015-01-01

Defined cellular mechanisms have evolved that recognize and repair DNA to protect the integrity of its structure and sequence when encountering assaults from endogenous and exogenous sources. There are five major DNA repair pathways: mismatch repair, nucleotide excision repair, direct repair, base excision repair and DNA double strand break repair (including non-homologous end joining and homologous recombination repair). Aberrant activation of the Hedgehog (Hh) signaling pathway is a feature of many cancer types. The Hh pathway has been documented to be indispensable for epithelial-mesenchymal transition, invasion and metastasis, cancer stemness, and chemoresistance. The functional transcription activators of the Hh pathway include the GLI proteins. Inhibition of the activity of GLI can interfere with almost all DNA repair types in human cancer, indicating that Hh/GLI functions may play an important role in enabling tumor cells to survive lethal types of DNA damage induced by chemotherapy and radiotherapy. Thus, Hh signaling presents an important therapeutic target to overcome DNA repair-enabled multi-drug resistance and consequently increase chemotherapeutic response in the treatment of cancer

The Impact of Hedgehog Signaling Pathway on DNA Repair Mechanisms in Human Cancer

Energy Technology Data Exchange (ETDEWEB)

Meng, Erhong; Hanna, Ann; Samant, Rajeev S.; Shevde, Lalita A., E-mail: lsamant@uab.edu [Department of Pathology, Comprehensive Cancer Center, University of Alabama at Birmingham, WTI320D, 1824 6th Avenue South, Birmingham, AL 35233 (United States)

2015-07-21

Defined cellular mechanisms have evolved that recognize and repair DNA to protect the integrity of its structure and sequence when encountering assaults from endogenous and exogenous sources. There are five major DNA repair pathways: mismatch repair, nucleotide excision repair, direct repair, base excision repair and DNA double strand break repair (including non-homologous end joining and homologous recombination repair). Aberrant activation of the Hedgehog (Hh) signaling pathway is a feature of many cancer types. The Hh pathway has been documented to be indispensable for epithelial-mesenchymal transition, invasion and metastasis, cancer stemness, and chemoresistance. The functional transcription activators of the Hh pathway include the GLI proteins. Inhibition of the activity of GLI can interfere with almost all DNA repair types in human cancer, indicating that Hh/GLI functions may play an important role in enabling tumor cells to survive lethal types of DNA damage induced by chemotherapy and radiotherapy. Thus, Hh signaling presents an important therapeutic target to overcome DNA repair-enabled multi-drug resistance and consequently increase chemotherapeutic response in the treatment of cancer.

Mechanisms of DNA damage repair in adult stem cells and implications for cancer formation.

Science.gov (United States)

Weeden, Clare E; Asselin-Labat, Marie-Liesse

2018-01-01

Maintenance of genomic integrity in tissue-specific stem cells is critical for tissue homeostasis and the prevention of deleterious diseases such as cancer. Stem cells are subject to DNA damage induced by endogenous replication mishaps or exposure to exogenous agents. The type of DNA lesion and the cell cycle stage will invoke different DNA repair mechanisms depending on the intrinsic DNA repair machinery of a cell. Inappropriate DNA repair in stem cells can lead to cell death, or to the formation and accumulation of genetic alterations that can be transmitted to daughter cells and so is linked to cancer formation. DNA mutational signatures that are associated with DNA repair deficiencies or exposure to carcinogenic agents have been described in cancer. Here we review the most recent findings on DNA repair pathways activated in epithelial tissue stem and progenitor cells and their implications for cancer mutational signatures. We discuss how deep knowledge of early molecular events leading to carcinogenesis provides insights into DNA repair mechanisms operating in tumours and how these could be exploited therapeutically. Copyright © 2017 Elsevier B.V. All rights reserved.

Mechanism of host substrate acetylation by a YopJ family effector.

Science.gov (United States)

Zhang, Zhi-Min; Ma, Ka-Wai; Gao, Linfeng; Hu, Zhenquan; Schwizer, Simon; Ma, Wenbo; Song, Jikui

2017-07-24

The Yersinia outer protein J (YopJ) family of bacterial effectors depends on a novel acetyltransferase domain to acetylate signalling proteins from plant and animal hosts. However, the underlying mechanism is unclear. Here, we report the crystal structures of PopP2, a YopJ effector produced by the plant pathogen Ralstonia solanacearum, in complex with inositol hexaphosphate (InsP 6 ), acetyl-coenzyme A (AcCoA) and/or substrate Resistance to Ralstonia solanacearum 1 (RRS1-R) WRKY . PopP2 recognizes the WRKYGQK motif of RRS1-R WRKY to position a targeted lysine in the active site for acetylation. Importantly, the PopP2-RRS1-R WRKY association is allosterically regulated by InsP 6 binding, suggesting a previously unidentified role of the eukaryote-specific cofactor in substrate interaction. Furthermore, we provide evidence for the reaction intermediate of PopP2-mediated acetylation, an acetyl-cysteine covalent adduct, lending direct support to the 'ping-pong'-like catalytic mechanism proposed for YopJ effectors. Our study provides critical mechanistic insights into the virulence activity of YopJ class of acetyltransferases.

Deficiency of double-strand DNA break repair does not impair Mycobacterium tuberculosis virulence in multiple animal models of infection.

Science.gov (United States)

Heaton, Brook E; Barkan, Daniel; Bongiorno, Paola; Karakousis, Petros C; Glickman, Michael S

2014-08-01

Mycobacterium tuberculosis persistence within its human host requires mechanisms to resist the effector molecules of host immunity, which exert their bactericidal effects through damaging pathogen proteins, membranes, and DNA. Substantial evidence indicates that bacterial pathogens, including M. tuberculosis, require DNA repair systems to repair the DNA damage inflicted by the host during infection, but the role of double-strand DNA break (DSB) repair systems is unclear. Double-strand DNA breaks are the most cytotoxic form of DNA damage and must be repaired for chromosome replication to proceed. M. tuberculosis elaborates three genetically distinct DSB repair systems: homologous recombination (HR), nonhomologous end joining (NHEJ), and single-strand annealing (SSA). NHEJ, which repairs DSBs in quiescent cells, may be particularly relevant to M. tuberculosis latency. However, very little information is available about the phenotype of DSB repair-deficient M. tuberculosis in animal models of infection. Here we tested M. tuberculosis strains lacking NHEJ (a Δku ΔligD strain), HR (a ΔrecA strain), or both (a ΔrecA Δku strain) in C57BL/6J mice, C3HeB/FeJ mice, guinea pigs, and a mouse hollow-fiber model of infection. We found no difference in bacterial load, histopathology, or host mortality between wild-type and DSB repair mutant strains in any model of infection. These results suggest that the animal models tested do not inflict DSBs on the mycobacterial chromosome, that other repair pathways can compensate for the loss of NHEJ and HR, or that DSB repair is not required for M. tuberculosis pathogenesis. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

DREMECELS: A Curated Database for Base Excision and Mismatch Repair Mechanisms Associated Human Malignancies.

Directory of Open Access Journals (Sweden)

Ankita Shukla

Full Text Available DNA repair mechanisms act as a warrior combating various damaging processes that ensue critical malignancies. DREMECELS was designed considering the malignancies with frequent alterations in DNA repair pathways, that is, colorectal and endometrial cancers, associated with Lynch syndrome (also known as HNPCC. Since lynch syndrome carries high risk (~40-60% for both cancers, therefore we decided to cover all three diseases in this portal. Although a large population is presently affected by these malignancies, many resources are available for various cancer types but no database archives information on the genes specifically for only these cancers and disorders. The database contains 156 genes and two repair mechanisms, base excision repair (BER and mismatch repair (MMR. Other parameters include some of the regulatory processes that have roles in these disease progressions due to incompetent repair mechanisms, specifically BER and MMR. However, our unique database mainly provides qualitative and quantitative information on these cancer types along with methylation, drug sensitivity, miRNAs, copy number variation (CNV and somatic mutations data. This database would serve the scientific community by providing integrated information on these disease types, thus sustaining diagnostic and therapeutic processes. This repository would serve as an excellent accompaniment for researchers and biomedical professionals and facilitate in understanding such critical diseases. DREMECELS is publicly available at http://www.bioinfoindia.org/dremecels.

Differential role of base excision repair proteins in mediating cisplatin cytotoxicity.

Science.gov (United States)

Sawant, Akshada; Floyd, Ashley M; Dangeti, Mohan; Lei, Wen; Sobol, Robert W; Patrick, Steve M

2017-03-01

Interstrand crosslinks (ICLs) are covalent lesions formed by cisplatin. The mechanism for the processing and removal of ICLs by DNA repair proteins involves nucleotide excision repair (NER), homologous recombination (HR) and fanconi anemia (FA) pathways. In this report, we monitored the processing of a flanking uracil adjacent to a cisplatin ICL by the proteins involved in the base excision repair (BER) pathway. Using a combination of extracts, purified proteins, inhibitors, functional assays and cell culture studies, we determined the specific BER proteins required for processing a DNA substrate with a uracil adjacent to a cisplatin ICL. Uracil DNA glycosylase (UNG) is the primary glycosylase responsible for the removal of uracils adjacent to cisplatin ICLs, whereas other uracil glycosylases can process uracils in the context of undamaged DNA. Repair of the uracil adjacent to cisplatin ICLs proceeds through the classical BER pathway, highlighting the importance of specific proteins in this redundant pathway. Removal of uracil is followed by the generation of an abasic site and subsequent cleavage by AP endonuclease 1 (APE1). Inhibition of either the repair or redox domain of APE1 gives rise to cisplatin resistance. Inhibition of the lyase domain of Polymerase β (Polβ) does not influence cisplatin cytotoxicity. In addition, lack of XRCC1 leads to increased DNA damage and results in increased cisplatin cytotoxicity. Our results indicate that BER activation at cisplatin ICLs influences crosslink repair and modulates cisplatin cytotoxicity via specific UNG, APE1 and Polβ polymerase functions. Copyright © 2017 Elsevier B.V. All rights reserved.

Insulin-like growth factor-1 sustains stem cell mediated renal repair.

NARCIS (Netherlands)

Imberti, B.; Morigi, M.; Tomasoni, S.; Rota, C.; Corna, D.; Longaretti, L.; Rottoli, D.; Valsecchi, F.; Benigni, A.; Wang, J.; Abbate, M.; Zoja, C.; Remuzzi, G.

2007-01-01

In mice with cisplatin-induced acute kidney injury, administration of bone marrow-derived mesenchymal stem cells (MSC) restores renal tubular structure and improves renal function, but the underlying mechanism is unclear. Here, we examined the process of kidney cell repair in co-culture experiments

The Mannose Receptor in Regulation of Helminth-Mediated Host Immunity

Directory of Open Access Journals (Sweden)

Irma van Die

2017-11-01

Full Text Available Infection with parasitic helminths affects humanity and animal welfare. Parasitic helminths have the capacity to modulate host immune responses to promote their survival in infected hosts, often for a long time leading to chronic infections. In contrast to many infectious microbes, however, the helminths are able to induce immune responses that show positive bystander effects such as the protection to several immune disorders, including multiple sclerosis, inflammatory bowel disease, and allergies. They generally promote the generation of a tolerogenic immune microenvironment including the induction of type 2 (Th2 responses and a sub-population of alternatively activated macrophages. It is proposed that this anti-inflammatory response enables helminths to survive in their hosts and protects the host from excessive pathology arising from infection with these large pathogens. In any case, there is an urgent need to enhance understanding of how helminths beneficially modulate inflammatory reactions, to identify the molecules involved and to promote approaches to exploit this knowledge for future therapeutic interventions. Evidence is increasing that C-type lectins play an important role in driving helminth-mediated immune responses. C-type lectins belong to a large family of calcium-dependent receptors with broad glycan specificity. They are abundantly present on immune cells, such as dendritic cells and macrophages, which are essential in shaping host immune responses. Here, we will focus on the role of the C-type lectin macrophage mannose receptor (MR in helminth–host interactions, which is a critically understudied area in the field of helminth immunobiology. We give an overview of the structural aspects of the MR including its glycan specificity, and the functional implications of the MR in helminth–host interactions focusing on a few selected helminth species.

Mechanical interaction between historical brick and repair mortar: experimental and numerical tests

International Nuclear Information System (INIS)

Bocca, P; Grazzini, A; Masera, D; Alberto, A; Valente, S

2011-01-01

An innovative laboratory procedure, developed at the Non Destructive Testing Laboratory of the Politecnico di Torino, as a preliminary design stage for the pre-qualification of repair mortars applied to historical masonry buildings is described. Tested repair mortars are suitable for new dehumidified plaster in order to stop the rising damp effects by capillary action on historical masonry walls. Long-term plaster delamination occurs frequently as a consequence of not compatible mechanical characteristics of mortar. Preventing this phenomenon is the main way to increase the durability of repair work. In this direction, it is useful to analyse, through the cohesive crack model, the evolutionary phenomenon of plaster delamination. The parameters used in the numerical simulation of experimental tests are able to characterize the mechanical behaviour of the interface. It is therefore possible to predict delamination in problems with different boundary conditions.

Low-Intensity Ultrasound-Induced Anti-inflammatory Effects Are Mediated by Several New Mechanisms Including Gene Induction, Immunosuppressor Cell Promotion, and Enhancement of Exosome Biogenesis and Docking

Directory of Open Access Journals (Sweden)

Qian Yang

2017-10-01

Full Text Available Background: Low-intensity ultrasound (LIUS was shown to be beneficial in mitigating inflammation and facilitating tissue repair in various pathologies. Determination of the molecular mechanisms underlying the anti-inflammatory effects of LIUS allows to optimize this technique as a therapy for the treatment of malignancies and aseptic inflammatory disorders.Methods: We conducted cutting-edge database mining approaches to determine the anti-inflammatory mechanisms exerted by LIUS.Results: Our data revealed following interesting findings: (1 LIUS anti-inflammatory effects are mediated by upregulating anti-inflammatory gene expression; (2 LIUS induces the upregulation of the markers and master regulators of immunosuppressor cells including MDSCs (myeloid-derived suppressor cells, MSCs (mesenchymal stem cells, B1-B cells and Treg (regulatory T cells; (3 LIUS not only can be used as a therapeutic approach to deliver drugs packed in various structures such as nanobeads, nanospheres, polymer microspheres, and lipidosomes, but also can make use of natural membrane vesicles as small as exosomes derived from immunosuppressor cells as a novel mechanism to fulfill its anti-inflammatory effects; (4 LIUS upregulates the expression of extracellular vesicle/exosome biogenesis mediators and docking mediators; (5 Exosome-carried anti-inflammatory cytokines and anti-inflammatory microRNAs inhibit inflammation of target cells via multiple shared and specific pathways, suggesting exosome-mediated anti-inflammatory effect of LIUS feasible; and (6 LIUS-mediated physical effects on tissues may activate specific cellular sensors that activate downstream transcription factors and signaling pathways.Conclusions: Our results have provided novel insights into the mechanisms underlying anti-inflammatory effects of LIUS, and have provided guidance for the development of future novel therapeutic LIUS for cancers, inflammatory disorders, tissue regeneration and tissue repair.

Divergent impact of Toll-like receptor 2 deficiency on repair mechanisms in healthy muscle versus Duchenne muscular dystrophy.

Science.gov (United States)

Mojumdar, Kamalika; Giordano, Christian; Lemaire, Christian; Liang, Feng; Divangahi, Maziar; Qureshi, Salman T; Petrof, Basil J

2016-05-01

Injury to skeletal muscle, whether acute or chronic, triggers macrophage-mediated innate immunity in a manner which can be either beneficial or harmful for subsequent repair. Endogenous ligands for Toll-like receptor 2 (TLR2) are released by damaged tissues and might play an important role in activating the innate immune system following muscle injury. To test this hypothesis, we compared macrophage behaviour and muscle repair mechanisms in mice lacking TLR2 under conditions of either acute (cardiotoxin-induced) or chronic (mdx mouse genetic model of Duchenne muscular dystrophy; DMD) muscle damage. In previously healthy muscle subjected to acute damage, TLR2 deficiency reduced macrophage numbers in the muscle post-injury but did not alter the expression pattern of the prototypical macrophage polarization markers iNOS and CD206. In addition, there was abnormal persistence of necrotic fibres and impaired regeneration in TLR2-/- muscles after acute injury. In contrast, TLR2 ablation in chronically diseased muscles of mdx mice not only resulted in significantly reduced macrophage numbers but additionally modified their phenotype by shifting from inflammatory (iNOS(pos) CD206(neg) ) to more anti-inflammatory (iNOS(neg) CD206(pos) ) characteristics. This decrease in macrophage-mediated inflammation was associated with ameliorated muscle histopathology and improved force-generating capacity of the dystrophic muscle. Our results suggest that the role of TLR2 in macrophage function and skeletal muscle repair depends greatly upon the muscle injury context, and raise the possibility that inhibition of TLR2 could serve as a useful therapeutic measure in DMD. Copyright © 2016 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Double Strand Break Repair, one mechanism can hide another: Alternative non-homologous end joining

International Nuclear Information System (INIS)

Rass, E.; Grabarz, A.; Bertrand, P.; Lopez, B.S.

2012-01-01

DNA double strand breaks are major cytotoxic lesions encountered by the cells. They can be induced by ionizing radiation or endogenous stress and can lead to genetic instability. Two mechanisms compete for the repair of DNA double strand breaks: homologous recombination and non-homologous end joining (NHEJ). Homologous recombination requires DNA sequences homology and is initiated by single strand resection. Recently, advances have been made concerning the major steps and proteins involved in resection. NHEJ, in contrast, does not require sequence homology. The existence of a DNA double strand break repair mechanism, independent of KU and ligase IV, the key proteins of the canonical non homologous end joining pathway, has been revealed lately and named alternative non homologous end joining. The hallmarks of this highly mutagenic pathway are deletions at repair junctions and frequent use of distal micro-homologies. This mechanism is also initiated by a single strand resection of the break. The aim of this review is firstly to present recent data on single strand resection, and secondly the alternative NHEJ pathway, including a discussion on the fidelity of NHEJ. Based on current knowledge, canonical NHEJ does not appear as an intrinsically mutagenic mechanism, but in contrast, as a conservative one. The structure of broken DNA ends actually dictates the quality repair of the alternative NHEJ and seems the actual responsible for the mutagenesis attributed beforehand to the canonical NHEJ. The existence of this novel DNA double strand breaks repair mechanism needs to be taken into account in the development of radiosensitizing strategies in order to optimise the efficiency of radiotherapy. (authors)

ATR- and ATM-Mediated DNA Damage Response Is Dependent on Excision Repair Assembly during G1 but Not in S Phase of Cell Cycle.

Science.gov (United States)

Ray, Alo; Blevins, Chessica; Wani, Gulzar; Wani, Altaf A

2016-01-01

Cell cycle checkpoint is mediated by ATR and ATM kinases, as a prompt early response to a variety of DNA insults, and culminates in a highly orchestrated signal transduction cascade. Previously, we defined the regulatory role of nucleotide excision repair (NER) factors, DDB2 and XPC, in checkpoint and ATR/ATM-dependent repair pathway via ATR and ATM phosphorylation and recruitment to ultraviolet radiation (UVR)-induced damage sites. Here, we have dissected the molecular mechanisms of DDB2- and XPC- mediated regulation of ATR and ATM recruitment and activation upon UVR exposures. We show that the ATR and ATM activation and accumulation to UVR-induced damage not only depends on DDB2 and XPC, but also on the NER protein XPA, suggesting that the assembly of an active NER complex is essential for ATR and ATM recruitment. ATR and ATM localization and H2AX phosphorylation at the lesion sites occur as early as ten minutes in asynchronous as well as G1 arrested cells, showing that repair and checkpoint-mediated by ATR and ATM starts early upon UV irradiation. Moreover, our results demonstrated that ATR and ATM recruitment and H2AX phosphorylation are dependent on NER proteins in G1 phase, but not in S phase. We reasoned that in G1 the UVR-induced ssDNA gaps or processed ssDNA, and the bound NER complex promote ATR and ATM recruitment. In S phase, when the UV lesions result in stalled replication forks with long single-stranded DNA, ATR and ATM recruitment to these sites is regulated by different sets of proteins. Taken together, these results provide evidence that UVR-induced ATR and ATM recruitment and activation differ in G1 and S phases due to the existence of distinct types of DNA lesions, which promote assembly of different proteins involved in the process of DNA repair and checkpoint activation.

Understanding regulation of the host-mediated gut symbiont population and the symbiont-mediated host immunity in the Riptortus-Burkholderia symbiosis system.

Science.gov (United States)

Kim, Jiyeun Kate; Lee, Jun Beom; Jang, Ho Am; Han, Yeon Soo; Fukatsu, Takema; Lee, Bok Luel

2016-11-01

Valuable insect models have tremendously contributed to our understanding of innate immunity and symbiosis. Bean bug, Riptortus pedestris, is a useful insect symbiosis model due to harboring cultivable monospecific gut symbiont, genus Burkholderia. Bean bug is a hemimetabolous insect whose immunity is not well-understood. However, we recently identified three major antimicrobial peptides of Riptortus and examined the relationship between gut symbiosis and host immunity. We found that the presence of Burkholderia gut symbiont positively affects Riptortus immunity. From studying host regulation mechanisms of symbiont population, we revealed that the symbiotic Burkholderia cells are much more susceptible to Riptortus immune responses than the cultured cells. We further elucidated that the immune-susceptibility of the Burkholderia gut symbionts is due to the drastic change of bacterial cell envelope. Finally, we show that the immune-susceptible Burkholderia symbionts are able to prosper in host owing to the suppression of immune responses of the symbiotic midgut. Copyright © 2016 Elsevier Ltd. All rights reserved.

Manipulating or superseding host recombination functions: a dilemma that shapes phage evolvability.

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Louis-Marie Bobay

Full Text Available Phages, like many parasites, tend to have small genomes and may encode autonomous functions or manipulate those of their hosts'. Recombination functions are essential for phage replication and diversification. They are also nearly ubiquitous in bacteria. The E. coli genome encodes many copies of an octamer (Chi motif that upon recognition by RecBCD favors repair of double strand breaks by homologous recombination. This might allow self from non-self discrimination because RecBCD degrades DNA lacking Chi. Bacteriophage Lambda, an E. coli parasite, lacks Chi motifs, but escapes degradation by inhibiting RecBCD and encoding its own autonomous recombination machinery. We found that only half of 275 lambdoid genomes encode recombinases, the remaining relying on the host's machinery. Unexpectedly, we found that some lambdoid phages contain extremely high numbers of Chi motifs concentrated between the phage origin of replication and the packaging site. This suggests a tight association between replication, packaging and RecBCD-mediated recombination in these phages. Indeed, phages lacking recombinases strongly over-represent Chi motifs. Conversely, phages encoding recombinases and inhibiting host recombination machinery select for the absence of Chi motifs. Host and phage recombinases use different mechanisms and the latter are more tolerant to sequence divergence. Accordingly, we show that phages encoding their own recombination machinery have more mosaic genomes resulting from recent recombination events and have more diverse gene repertoires, i.e. larger pan genomes. We discuss the costs and benefits of superseding or manipulating host recombination functions and how this decision shapes phage genome structure and evolvability.

Adhesion to the host cell surface is sufficient to mediate Listeria monocytogenes entry into epithelial cells

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Ortega, Fabian E.; Rengarajan, Michelle; Chavez, Natalie; Radhakrishnan, Prathima; Gloerich, Martijn; Bianchini, Julie; Siemers, Kathleen; Luckett, William S.; Lauer, Peter; Nelson, W. James; Theriot, Julie A.

2017-01-01

The intestinal epithelium is the first physiological barrier breached by the Gram-positive facultative pathogen Listeria monocytogenes during an in vivo infection. Listeria monocytogenes binds to the epithelial host cell receptor E-cadherin, which mediates a physical link between the bacterium and filamentous actin (F-actin). However, the importance of anchoring the bacterium to F-actin through E-cadherin for bacterial invasion has not been tested directly in epithelial cells. Here we demonstrate that depleting αE-catenin, which indirectly links E-cadherin to F-actin, did not decrease L. monocytogenes invasion of epithelial cells in tissue culture. Instead, invasion increased due to increased bacterial adhesion to epithelial monolayers with compromised cell–cell junctions. Furthermore, expression of a mutant E-cadherin lacking the intracellular domain was sufficient for efficient L. monocytogenes invasion of epithelial cells. Importantly, direct biotin-mediated binding of bacteria to surface lipids in the plasma membrane of host epithelial cells was sufficient for uptake. Our results indicate that the only requirement for L. monocytogenes invasion of epithelial cells is adhesion to the host cell surface, and that E-cadherin–mediated coupling of the bacterium to F-actin is not required. PMID:28877987

The 2015 Nobel Prize in Chemistry The Discovery of Essential Mechanisms that Repair DNA Damage.

Science.gov (United States)

Lindahl, Tomas; Modrich, Paul; Sancar, Aziz

2016-01-01

The Royal Swedish Academy awarded the Nobel Prize in Chemistry for 2015 to Tomas Lindahl, Paul Modrich and Aziz Sancar for their discoveries in fundamental mechanisms of DNA repair. This pioneering research described three different essential pathways that correct DNA damage, safeguard the integrity of the genetic code to ensure its accurate replication through generations, and allow proper cell division. Working independently of each other, Tomas Lindahl, Paul Modrich and Aziz Sancar delineated the mechanisms of base excision repair, mismatch repair and nucleotide excision repair, respectively. These breakthroughs challenged and dismissed the early view that the DNA molecule was very stable, paving the way for the discovery of human hereditary diseases associated with distinct DNA repair deficiencies and a susceptibility to cancer. It also brought a deeper understanding of cancer as well as neurodegenerative or neurological diseases, and let to novel strategies to treat cancer.

Double strand break repair: two mechanisms in competition but tightly linked to cell cycle

International Nuclear Information System (INIS)

Delacote, F.

2002-11-01

DNA double strand breaks (DSB) are highly toxic damage although they can be induced to create genetic diversity. Two distinct pathways can repair DSB: Homologous Recombination (HR) and Non Homologous End Joining (NHEJ). If un- or mis-repaired, this damage can lead to cancer. Thus, it is essential to investigate how these two pathways are regulated for DSB repair. NHEJ inhibition leads to HR DSB repair stimulation. However, this channeling to HR is tightly linked to cell cycle since NHEJ and HR are active in G1/early S and late S/G2, respectively. Our results suggest that G1-unrepaired DSB go through S phase to be repaired by HR in G2. Those results allow a better understanding of DSB repair mechanisms regulation. (author)

Regulation of Rad51-Mediated Homologous Recombination by BRCA2, DSS1 and RAD52

DEFF Research Database (Denmark)

Rants, Louise Olthaver Juhl

Homologous recombination (HR) provides a mechanism to restore integrity and maintain stability of the genetic material. HR is a major pathway for repair of DNA double-strand breaks (DSB), recovery of broken replication forks and generation of meiotic crossovers. The defining step in HR is homolog......Homologous recombination (HR) provides a mechanism to restore integrity and maintain stability of the genetic material. HR is a major pathway for repair of DNA double-strand breaks (DSB), recovery of broken replication forks and generation of meiotic crossovers. The defining step in HR...... is homologous strand exchange directed by the RecA-related recombinase Rad51. BRCA2 participates in HR by mediating Rad51 homology-directed repair. Both BRCA2 and Rad51 are essential for HR, DNA repair, and the maintenance of genome stability. In the present study, we seek to understand the mechanism of BRCA2...... with RAD52-mediated repair at sites of CPT-induced DNA damage. The synthetic lethality approach using RAD52 small molecule inhibitors in brca-deficient cancers is a promising therapeutic strategy for cancer treatment....

Interleukin-12 induces sustained activation of multiple host inflammatory mediator systems in chimpanzees

NARCIS (Netherlands)

Lauw, F. N.; Dekkers, P. E.; te Velde, A. A.; Speelman, P.; Levi, M. [=Marcel M.; Kurimoto, M.; Hack, C. E.; van Deventer, S. J.; van der Poll, T.

1999-01-01

To determine in vivo effects of interleukin (IL)-12 on host inflammatory mediator systems, 4 healthy chimpanzees received recombinant human IL-12 (1 microg/kg) by intravenous injection. IL-12 induced increases in plasma concentrations of IL-15, IL-18, and interferon-gamma (IFN-gamma), plus a marked

Efficient Generation of Orthologous Point Mutations in Pigs via CRISPR-assisted ssODN-mediated Homology-directed Repair

Directory of Open Access Journals (Sweden)

Kankan Wang

2016-01-01

Full Text Available Precise genome editing in livestock is of great value for the fundamental investigation of disease modeling. However, genetically modified pigs carrying subtle point mutations were still seldom reported despite the rapid development of programmable endonucleases. Here, we attempt to investigate single-stranded oligonucleotides (ssODN mediated knockin by introducing two orthologous pathogenic mutations, p.E693G for Alzheimer's disease and p.G2019S for Parkinson's disease, into porcine APP and LRRK2 loci, respectively. Desirable homology-directed repair (HDR efficiency was achieved in porcine fetal fibroblasts (PFFs by optimizing the dosage and length of ssODN templates. Interestingly, incomplete HDR alleles harboring partial point mutations were observed in single-cell colonies, which indicate the complex mechanism of ssODN-mediated HDR. The effect of mutation-to-cut distance on incorporation rate was further analyzed by deep sequencing. We demonstrated that a mutation-to-cut distance of 11 bp resulted in a remarkable difference in HDR efficiency between two point mutations. Finally, we successfully obtained one cloned piglet harboring the orthologous p.C313Y mutation at the MSTN locus via somatic cell nuclear transfer (SCNT. Our proof-of-concept study demonstrated efficient ssODN-mediated incorporation of pathogenic point mutations in porcine somatic cells, thus facilitating further development of disease modeling and genetic breeding in pigs.

Regulation of DNA repair mechanism in human glioma xenograft cells both in vitro and in vivo in nude mice.

Science.gov (United States)

Ponnala, Shivani; Veeravalli, Krishna Kumar; Chetty, Chandramu; Dinh, Dzung H; Rao, Jasti S

2011-01-01

Glioblastoma Multiforme (GBM) is the most lethal form of brain tumor. Efficient DNA repair and anti-apoptotic mechanisms are making glioma treatment difficult. Proteases such as MMP9, cathepsin B and urokinase plasminogen activator receptor (uPAR) are over expressed in gliomas and contribute to enhanced cancer cell proliferation. Non-homologous end joining (NHEJ) repair mechanism plays a major role in double strand break (DSB) repair in mammalian cells. Here we show that silencing MMP9 in combination with uPAR/cathepsin B effects NHEJ repair machinery. Expression of DNA PKcs and Ku70/80 at both mRNA and protein levels in MMP9-uPAR (pMU) and MMP9-cathepsin B (pMC) shRNA-treated glioma xenograft cells were reduced. FACS analysis showed an increase in apoptotic peak and proliferation assays revealed a significant reduction in the cell population in pMU- and pMC-treated cells compared to untreated cells. We hypothesized that reduced NHEJ repair led to DSBs accumulation in pMU- and pMC-treated cells, thereby initiating cell death. This hypothesis was confirmed by reduced Ku70/Ku80 protein binding to DSB, increased comet tail length and elevated γH2AX expression in treated cells compared to control. Immunoprecipitation analysis showed that EGFR-mediated lowered DNA PK activity in treated cells compared to controls. Treatment with pMU and pMC shRNA reduced the expression of DNA PKcs and ATM, and elevated γH2AX levels in xenograft implanted nude mice. Glioma cells exposed to hypoxia and irradiation showed DSB accumulation and apoptosis after pMU and pMC treatments compared to respective controls. Our results suggest that pMU and pMC shRNA reduce glioma proliferation by DSB accumulation and increase apoptosis under normoxia, hypoxia and in combination with irradiation. Considering the radio- and chemo-resistant cancers favored by hypoxia, our study provides important therapeutic potential of MMP9, uPAR and cathepsin B shRNA in the treatment of glioma from clinical stand

Regulation of DNA repair mechanism in human glioma xenograft cells both in vitro and in vivo in nude mice.

Directory of Open Access Journals (Sweden)

Shivani Ponnala

Full Text Available Glioblastoma Multiforme (GBM is the most lethal form of brain tumor. Efficient DNA repair and anti-apoptotic mechanisms are making glioma treatment difficult. Proteases such as MMP9, cathepsin B and urokinase plasminogen activator receptor (uPAR are over expressed in gliomas and contribute to enhanced cancer cell proliferation. Non-homologous end joining (NHEJ repair mechanism plays a major role in double strand break (DSB repair in mammalian cells.Here we show that silencing MMP9 in combination with uPAR/cathepsin B effects NHEJ repair machinery. Expression of DNA PKcs and Ku70/80 at both mRNA and protein levels in MMP9-uPAR (pMU and MMP9-cathepsin B (pMC shRNA-treated glioma xenograft cells were reduced. FACS analysis showed an increase in apoptotic peak and proliferation assays revealed a significant reduction in the cell population in pMU- and pMC-treated cells compared to untreated cells. We hypothesized that reduced NHEJ repair led to DSBs accumulation in pMU- and pMC-treated cells, thereby initiating cell death. This hypothesis was confirmed by reduced Ku70/Ku80 protein binding to DSB, increased comet tail length and elevated γH2AX expression in treated cells compared to control. Immunoprecipitation analysis showed that EGFR-mediated lowered DNA PK activity in treated cells compared to controls. Treatment with pMU and pMC shRNA reduced the expression of DNA PKcs and ATM, and elevated γH2AX levels in xenograft implanted nude mice. Glioma cells exposed to hypoxia and irradiation showed DSB accumulation and apoptosis after pMU and pMC treatments compared to respective controls.Our results suggest that pMU and pMC shRNA reduce glioma proliferation by DSB accumulation and increase apoptosis under normoxia, hypoxia and in combination with irradiation. Considering the radio- and chemo-resistant cancers favored by hypoxia, our study provides important therapeutic potential of MMP9, uPAR and cathepsin B shRNA in the treatment of glioma from

Long-term anisotropic mechanical response of surgical meshes used to repair abdominal wall defects.

Science.gov (United States)

Hernández-Gascón, B; Peña, E; Pascual, G; Rodríguez, M; Bellón, J M; Calvo, B

2012-01-01

Routine hernia repair surgery involves the implant of synthetic mesh. However, this type of procedure may give rise to pain and bowel incarceration and strangulation, causing considerable patient disability. The purpose of this study was to compare the long-term behaviour of three commercial meshes used to repair the partially herniated abdomen in New Zealand White rabbits: the heavyweight (HW) mesh, Surgipro(®) and lightweight (LW) mesh, Optilene(®), both made of polypropylene (PP), and a mediumweight (MW) mesh, Infinit(®), made of polytetrafluoroethylene (PTFE). The implanted meshes were mechanical and histological assessed at 14, 90 and 180 days post-implant. This behaviour was compared to the anisotropic mechanical behaviour of the unrepaired abdominal wall in control non-operated rabbits. Both uniaxial mechanical tests conducted in craneo-caudal and perpendicular directions and histological findings revealed substantial collagen growth over the repaired hernial defects causing stiffness in the repair zone, and thus a change in the original properties of the meshes. The mechanical behaviour of the healthy tissue in the craneo-caudal direction was not reproduced by any of the implanted meshes after 14 days or 90 days of implant, whereas in the perpendicular direction, SUR and OPT achieved similar behaviour. From a mechanical standpoint, the anisotropic PP-lightweight meshes may be considered a good choice in the long run, which correlates with the structure of the regenerated tissue. Copyright © 2011 Elsevier Ltd. All rights reserved.

Detection of abnormalities in the superficial zone of cartilage repaired using a tissue engineered construct derived from synovial stem cells

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W Ando

2012-09-01

Full Text Available The present study investigated the surface structure and mechanical properties of repair cartilage generated from a tissue engineered construct (TEC derived from synovial mesenchymal stem cells at six months post-implantation compared to those of uninjured cartilage. TEC-mediated repair tissue was cartilaginous with Safranin O staining, and had comparable macro-scale compressive properties with uninjured cartilage. However, morphological assessments revealed that the superficial zone of TEC-mediated tissue was more fibrocartilage-like, in contrast to the middle or deep zones that were more hyaline cartilage-like with Safranin O staining. Histological scoring of the TEC-mediated tissue was significantly lower in the superficial zone than in the middle and deep zones. Scanning electron microscopy showed a thick tangential bundle of collagen fibres at the most superficial layer of uninjured cartilage, while no corresponding structure was detected at the surface of TEC-mediated tissue. Immunohistochemical analysis revealed that PRG4 was localised in the superficial area of uninjured cartilage, as well as the TEC-mediated tissue. Friction testing showed that the lubrication properties of the two tissues was similar, however, micro-indentation analysis revealed that the surface stiffness of the TEC-repair tissue was significantly lower than that of uninjured cartilage. Permeability testing indicated that the TEC-mediated tissue exhibited lower water retaining capacity than did uninjured cartilage, specifically at the superficial zone. Thus, TEC-mediated tissue exhibited compromised mechanical properties at the superficial zone, properties which need improvement in the future for maintenance of long term repair cartilage integrity.

Detection of abnormalities in the superficial zone of cartilage repaired using a tissue engineered construct derived from synovial stem cells.

Science.gov (United States)

Ando, Wataru; Fujie, Hiromichi; Moriguchi, Yu; Nansai, Ryosuke; Shimomura, Kazunori; Hart, David A; Yoshikawa, Hideki; Nakamura, Norimasa

2012-09-28

The present study investigated the surface structure and mechanical properties of repair cartilage generated from a tissue engineered construct (TEC) derived from synovial mesenchymal stem cells at six months post-implantation compared to those of uninjured cartilage. TEC-mediated repair tissue was cartilaginous with Safranin O staining, and had comparable macro-scale compressive properties with uninjured cartilage. However, morphological assessments revealed that the superficial zone of TEC-mediated tissue was more fibrocartilage-like, in contrast to the middle or deep zones that were more hyaline cartilage-like with Safranin O staining. Histological scoring of the TEC-mediated tissue was significantly lower in the superficial zone than in the middle and deep zones. Scanning electron microscopy showed a thick tangential bundle of collagen fibres at the most superficial layer of uninjured cartilage, while no corresponding structure was detected at the surface of TEC-mediated tissue. Immunohistochemical analysis revealed that PRG4 was localised in the superficial area of uninjured cartilage, as well as the TEC-mediated tissue. Friction testing showed that the lubrication properties of the two tissues was similar, however, micro-indentation analysis revealed that the surface stiffness of the TEC-repair tissue was significantly lower than that of uninjured cartilage. Permeability testing indicated that the TEC-mediated tissue exhibited lower water retaining capacity than did uninjured cartilage, specifically at the superficial zone. Thus, TEC-mediated tissue exhibited compromised mechanical properties at the superficial zone, properties which need improvement in the future for maintenance of long term repair cartilage integrity.

Host cell virus entry mediated by Australian bat lyssavirus G envelope glycoprotein occurs through a clathrin-mediated endocytic pathway that requires actin and Rab5.

Science.gov (United States)

Weir, Dawn L; Laing, Eric D; Smith, Ina L; Wang, Lin-Fa; Broder, Christopher C

2014-02-27

Australian bat lyssavirus (ABLV), a rhabdovirus of the genus Lyssavirus which circulates in both pteropid fruit bats and insectivorous bats in mainland Australia, has caused three fatal human infections, the most recent in February 2013, manifested as acute neurological disease indistinguishable from clinical rabies. Rhabdoviruses infect host cells through receptor-mediated endocytosis and subsequent pH-dependent fusion mediated by their single envelope glycoprotein (G), but the specific host factors and pathways involved in ABLV entry have not been determined. ABLV internalization into HEK293T cells was examined using maxGFP-encoding recombinant vesicular stomatitis viruses (rVSV) that express ABLV G glycoproteins. A combination of chemical and molecular approaches was used to investigate the contribution of different endocytic pathways to ABLV entry. Dominant negative Rab GTPases were used to identify the endosomal compartment utilized by ABLV to gain entry into the host cell cytosol. Here we show that ABLV G-mediated entry into HEK293T cells was significantly inhibited by the dynamin-specific inhibitor dynasore, chlorpromazine, a drug that blocks clathrin-mediated endocytosis, and the actin depolymerizing drug latrunculin B. Over expression of dominant negative mutants of Eps15 and Rab5 also significantly reduced ABLV G-mediated entry into HEK293T cells. Chemical inhibitors of caveolae-dependent endocytosis and macropinocytosis and dominant negative mutants of Rab7 and Rab11 had no effect on ABLV entry. The predominant pathway utilized by ABLV for internalization into HEK293T cells is clathrin-and actin-dependent. The requirement of Rab5 for productive infection indicates that ABLV G-mediated fusion occurs within the early endosome compartment.

Impact of occupational mechanical exposures on risk of lateral and medial inguinal hernia requiring surgical repair

DEFF Research Database (Denmark)

Vad, Marie Vestergaard; Frost, Poul; Bay-Nielsen, Morten

2012-01-01

We undertook a register-based cohort study to evaluate exposure-response relations between cumulative occupational mechanical exposures, and risk of lateral and medial inguinal hernia repair.......We undertook a register-based cohort study to evaluate exposure-response relations between cumulative occupational mechanical exposures, and risk of lateral and medial inguinal hernia repair....

The role of DNA repair in herpesvirus pathogenesis.

Science.gov (United States)

Brown, Jay C

2014-10-01

In cells latently infected with a herpesvirus, the viral DNA is present in the cell nucleus, but it is not extensively replicated or transcribed. In this suppressed state the virus DNA is vulnerable to mutagenic events that affect the host cell and have the potential to destroy the virus' genetic integrity. Despite the potential for genetic damage, however, herpesvirus sequences are well conserved after reactivation from latency. To account for this apparent paradox, I have tested the idea that host cell-encoded mechanisms of DNA repair are able to control genetic damage to latent herpesviruses. Studies were focused on homologous recombination-dependent DNA repair (HR). Methods of DNA sequence analysis were employed to scan herpesvirus genomes for DNA features able to activate HR. Analyses were carried out with a total of 39 herpesvirus DNA sequences, a group that included viruses from the alpha-, beta- and gamma-subfamilies. The results showed that all 39 genome sequences were enriched in two or more of the eight recombination-initiating features examined. The results were interpreted to indicate that HR can stabilize latent herpesvirus genomes. The results also showed, unexpectedly, that repair-initiating DNA features differed in alpha- compared to gamma-herpesviruses. Whereas inverted and tandem repeats predominated in alpha-herpesviruses, gamma-herpesviruses were enriched in short, GC-rich initiation sequences such as CCCAG and depleted in repeats. In alpha-herpesviruses, repair-initiating repeat sequences were found to be concentrated in a specific region (the S segment) of the genome while repair-initiating short sequences were distributed more uniformly in gamma-herpesviruses. The results suggest that repair pathways are activated differently in alpha- compared to gamma-herpesviruses. Copyright © 2014. Published by Elsevier Inc.

Repair of endogenous and ionizing radiation-induced DNA damages: mechanisms and biological functions

International Nuclear Information System (INIS)

Boiteux, S.

2002-01-01

The cellular DNA is continuously exposed to endogenous and exogenous stress. Oxidative stress due to cellular metabolism is the major cause of endogenous DNA damage. On the other hand, ionizing radiation (IR) is an important exogenous stress. Both induce similar DNA damages: damaged bases, abasic sites and strand breakage. Most of these lesions are lethal and/or mutagenic. The survival of the cell is managed by efficient and accurate DNA repair mechanisms that remove lesions before their replication or transcription. DNA repair pathways involved in the removal of IR-induced lesions are briefly described. Base excision repair (BER) is mostly involved in the removal of base damage, abasic sites and single strand breaks. In contrast, DNA double strand breaks are mostly repaired by non-homologous end joining (NHEJ) or homologous recombination (HR). How DNA repair pathways prevent cancer process is also discussed. (author)

Mutagenicity of irradiated food in the host mediated assay system

International Nuclear Information System (INIS)

Johnston-Arthur, T.; Turanitz, K.; Hruby, R.; Stehlik, G.; Brena-Valle, M.

1975-01-01

Groups of Swiss albino mice (SPF) fed with normal and gamma-irradiated food at doses of 0.75, 1.5 and 3.0 Mrad, were injected intraperitoneally with SALMONELLA TYPHIMURIUM TA 1530 for the host mediated assay test of mutagenesis. The mutation frequency was calculated in terms of the number of mutant colonies per unit number of surviving cells. The results indicate that there is a significant increase in mutation frequency induced by the 3 Mrad sterilized food. No difference was observed in the 0.75 Mrad dose when compared with the control

FANCD2 Maintains Fork Stability in BRCA1/2-Deficient Tumors and Promotes Alternative End-Joining DNA Repair

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Zeina Kais

2016-06-01

Full Text Available BRCA1/2 proteins function in homologous recombination (HR-mediated DNA repair and cooperate with Fanconi anemia (FA proteins to maintain genomic integrity through replication fork stabilization. Loss of BRCA1/2 proteins results in DNA repair deficiency and replicative stress, leading to genomic instability and enhanced sensitivity to DNA-damaging agents. Recent studies have shown that BRCA1/2-deficient tumors upregulate Polθ-mediated alternative end-joining (alt-EJ repair as a survival mechanism. Whether other mechanisms maintain genomic integrity upon loss of BRCA1/2 proteins is currently unknown. Here we show that BRCA1/2-deficient tumors also upregulate FANCD2 activity. FANCD2 is required for fork protection and fork restart in BRCA1/2-deficient tumors. Moreover, FANCD2 promotes Polθ recruitment at sites of damage and alt-EJ repair. Finally, loss of FANCD2 in BRCA1/2-deficient tumors enhances cell death. These results reveal a synthetic lethal relationship between FANCD2 and BRCA1/2, and they identify FANCD2 as a central player orchestrating DNA repair pathway choice at the replication fork.

Faulty DNA-polymerase δ/ε-mediated excision-repair in response to gamma-radiation or ultraviolet-light in P53-deficient fibroblast strains from affected members of a cancer-prone family with Li-Fraumeni syndrome

International Nuclear Information System (INIS)

Mirzayans, R.; Enns, L.; Dietrich, K.; Barley, R.D.C.; Paterson, M.C.; Alberta Univ., Edmonton, AB; Alberta Univ., Edmonton, AB

1996-01-01

Dermal fibroblast strains cultured from affected members of a cancer-prone family with Li-Fraumeni syndrome (LFS) harbor a point mutation in one allele of the p53 tumor suppressor gene, resulting in loss of normal p53-deficient strains to carry out the long-patch mode of excision repair, mediated by DNA polymerases delta and epsilon, after exposure to Co-60 gamma radiation or far ultraviolet (UV) (chiefly 254 mm) light. Repair was monitored by incubation of the irradiated cultures in the presence of aphidicolin (ape) or 1-beta-D-arabinofuranosylcytosine (araC), each a specific inhibitor of long-patch repair, followed by measurement of drug-induced DNA strand breaks (reflecting non-ligated strand incision events) by alkaline surcrose velocity sedimentation. The LFS strains displayed deficient repair capacity in response to both gamma rays and UV light. The repair anomaly in UV-irradiated LFS cultures was manifested not only in the overall genome, but also in the transcriptionally active, preferentially repaired c-myc gene. Using autoradiography we also assessed unscheduled DNA synthesis (UDS) after UV irradiation and found this conventional measure of repair replication to be deficient in LFS strains. Moreover, both ape and araC decreased the level of UV-induced UDS by similar to 75% in normal cells, but each had only a marginal effect on LFS cells. We further demonstrated that the LFS strains are impaired in the recovery of both RNA and replicative DNA syntheses after UV treatment, two molecular anomalies of the DNA repair deficiency disorders xeroderma pigmentosum and Cockayne's syndrome. Together these results imply a critical role for wild-type p53 protein in DNA polymerase delta/epsilon-mediated excision repair, both the mechanism operating on the entire genome and that acting on expressed genes. (Author)

DNA repair , cell repair and radiosensitivity

International Nuclear Information System (INIS)

Zhestyanikov, V.D.

1983-01-01

Data obtained in laboratory of radiation cytology and literature data testifying to a considerable role of DNA repair in cell sensitivity to radiation and chemical DNA-tropic agents have been considered. Data pointing to the probability of contribution of inducible repair of DNA into plant cells sensitivity to X-rays are obtained. Certain violations of DNA repair do not result in the increase of radiosensitivity. It is assumed that in the cases unknown mechanisms of DNA repair operate

Pro-Resolving Mediators in Regulating and Conferring Macrophage Function

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Jesmond Dalli

2017-11-01

Full Text Available Macrophages are central in coordinating the host response to both sterile and infective insults. Clearance of apoptotic cells and cellular debris is a key biological action preformed by macrophages that paves the way to the resolution of local inflammation, repair and regeneration of damaged tissues, and re-establishment of function. The essential fatty acid-derived autacoids termed specialized pro-resolving mediators (SPM play central roles in promoting these processes. In the present article, we will review the role of microvesicles in controlling macrophage efferocytosis and SPM production. We will also discuss the role of both apoptotic cells and microvesicles in providing substrate for transcellular biosynthesis of several SPM families during efferocyotsis. In addition, this article will discuss the biological actions of the recently uncovered macrophage-derived SPM termed maresins. These mediators are produced via 14-lipoxygenation of docosahexaenoic acid that is either enzymatically converted to mediators carrying two hydroxyl groups or to autacoids that are peptide-lipid conjugates, coined maresin conjugates in tissue regeneration. The formation of these mediators is temporally regulated during acute self-limited infectious-inflammation where they promote the uptake and clearance of apoptotic cells, regulate several aspects of the tissue repair and regeneration, and display potent anti-nociceptive actions.

Mechanical Complication with Broviac Repair Kit in a 4-Year-Old Boy with MEN 2a.

Science.gov (United States)

Sesia, Sergio B; Haecker, Frank-Martin; Mayr, Johannes

2009-01-01

Background. Mechanical complications in the use of indwelling central venous catheters (CVCs) such as the Broviac catheter (BC) include kinking, occlusion, dislocation or leaking. We report on a mechanical complication after using a repair kit for the BC. Method. A 4-year old boy, suffering from multiple endocrine neoplasia type 2a (MEN 2a), intestinal aganglionosis (Hirschsprung's disease), and short bowel syndrome, required a BC for home parenteral nutrition. Result. Due to recurrent leakage of the BC, 5 subsequent repairs were necessary within seven months. During one repair a metallic tube belonging to the repair kit was found to have migrated proximally to the skin entrance level within the BC and requiring surgical removal. Conclusion. To our knowledge, this is the first report focusing on such a serious complication using a BC and its repair kit. The proximal migration of this metallic tube constitutes a distinct theoretical risk of endothoracic foreign body embolization.

DNA repair

International Nuclear Information System (INIS)

Setlow, R.

1978-01-01

Some topics discussed are as follows: difficulty in extrapolating data from E. coli to mammalian systems; mutations caused by UV-induced changes in DNA; mutants deficient in excision repair; other postreplication mechanisms; kinds of excision repair systems; detection of repair by biochemical or biophysical means; human mutants deficient in repair; mutagenic effects of UV on XP cells; and detection of UV-repair defects among XP individuals

Alkaline gel electrophoresis assay to detect DNA strand breaks and repair mechanisms in Escherichia coli

International Nuclear Information System (INIS)

Mattos, Jose Carlos Pelielo de; Motta, Ellen Serri da; Oliveira, Marcia Betania Nunes de; Dantas, Flavio Jose da Silva; Araujo, Adriano Caldeira de

2008-01-01

Reactive oxygen species (ROS) can induce lesions in different cellular targets, including DNA. Stannous chloride (SnCl 2 ) is a ROS generator, leading to lethality in Escherichia coli (E. coli), with the base excision repair (BER) mechanism playing a role in this process. Many techniques have been developed to detect genotoxicity, as comet assay, in eukaryotic cells, and plasmid DNA agarose gel electrophoresis. In this study, an adaptation of the alkaline gel electrophoresis method was carried out to ascertain the induction of strand breaks by SnCl 2 in bacterial DNA, from E. coli BER mutants, and its repair pathway. Results obtained show that SnCl 2 was able to induce DNA strand breaks in all strains tested. Moreover, endonuclease IV and exonuclease III play a role in DNA repair. On the whole, data has shown that the alkaline gel electrophoresis assay could be used both for studying DNA strand breaks induction and for associated repair mechanisms. (author)

Alkaline gel electrophoresis assay to detect DNA strand breaks and repair mechanisms in Escherichia coli

Energy Technology Data Exchange (ETDEWEB)

Mattos, Jose Carlos Pelielo de; Motta, Ellen Serri da; Oliveira, Marcia Betania Nunes de; Dantas, Flavio Jose da Silva; Araujo, Adriano Caldeira de [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil). Dept. de Biofisica e Biometria. Lab. de Radio e Fotobiologia]. E-mail: jcmattos@uerj.br

2008-12-15

Reactive oxygen species (ROS) can induce lesions in different cellular targets, including DNA. Stannous chloride (SnCl{sub 2}) is a ROS generator, leading to lethality in Escherichia coli (E. coli), with the base excision repair (BER) mechanism playing a role in this process. Many techniques have been developed to detect genotoxicity, as comet assay, in eukaryotic cells, and plasmid DNA agarose gel electrophoresis. In this study, an adaptation of the alkaline gel electrophoresis method was carried out to ascertain the induction of strand breaks by SnCl{sub 2} in bacterial DNA, from E. coli BER mutants, and its repair pathway. Results obtained show that SnCl{sub 2} was able to induce DNA strand breaks in all strains tested. Moreover, endonuclease IV and exonuclease III play a role in DNA repair. On the whole, data has shown that the alkaline gel electrophoresis assay could be used both for studying DNA strand breaks induction and for associated repair mechanisms. (author)

IFN-gamma-inducible Irga6 mediates host resistance against Chlamydia trachomatis via autophagy.

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Munir A Al-Zeer

Full Text Available Chlamydial infection of the host cell induces Gamma interferon (IFNgamma, a central immunoprotector for humans and mice. The primary defense against Chlamydia infection in the mouse involves the IFNgamma-inducible family of IRG proteins; however, the precise mechanisms mediating the pathogen's elimination are unknown. In this study, we identify Irga6 as an important resistance factor against C. trachomatis, but not C. muridarum, infection in IFNgamma-stimulated mouse embryonic fibroblasts (MEFs. We show that Irga6, Irgd, Irgm2 and Irgm3 accumulate at bacterial inclusions in MEFs upon stimulation with IFNgamma, whereas Irgb6 colocalized in the presence or absence of the cytokine. This accumulation triggers a rerouting of bacterial inclusions to autophagosomes that subsequently fuse to lysosomes for elimination. Autophagy-deficient Atg5-/- MEFs and lysosomal acidification impaired cells surrender to infection. Irgm2, Irgm3 and Irgd still localize to inclusions in IFNgamma-induced Atg5-/- cells, but Irga6 localization is disrupted indicating its pivotal role in pathogen resistance. Irga6-deficient (Irga6-/- MEFs, in which chlamydial growth is enhanced, do not respond to IFNgamma even though Irgb6, Irgd, Irgm2 and Irgm3 still localize to inclusions. Taken together, we identify Irga6 as a necessary factor in conferring host resistance by remodelling a classically nonfusogenic intracellular pathogen to stimulate fusion with autophagosomes, thereby rerouting the intruder to the lysosomal compartment for destruction.

Gut microbiome remodeling induces depressive-like behaviors through a pathway mediated by the host's metabolism.

Science.gov (United States)

Zheng, P; Zeng, B; Zhou, C; Liu, M; Fang, Z; Xu, X; Zeng, L; Chen, J; Fan, S; Du, X; Zhang, X; Yang, D; Yang, Y; Meng, H; Li, W; Melgiri, N D; Licinio, J; Wei, H; Xie, P

2016-06-01

Major depressive disorder (MDD) is the result of complex gene-environment interactions. According to the World Health Organization, MDD is the leading cause of disability worldwide, and it is a major contributor to the overall global burden of disease. However, the definitive environmental mechanisms underlying the pathophysiology of MDD remain elusive. The gut microbiome is an increasingly recognized environmental factor that can shape the brain through the microbiota-gut-brain axis. We show here that the absence of gut microbiota in germ-free (GF) mice resulted in decreased immobility time in the forced swimming test relative to conventionally raised healthy control mice. Moreover, from clinical sampling, the gut microbiotic compositions of MDD patients and healthy controls were significantly different with MDD patients characterized by significant changes in the relative abundance of Firmicutes, Actinobacteria and Bacteroidetes. Fecal microbiota transplantation of GF mice with 'depression microbiota' derived from MDD patients resulted in depression-like behaviors compared with colonization with 'healthy microbiota' derived from healthy control individuals. Mice harboring 'depression microbiota' primarily exhibited disturbances of microbial genes and host metabolites involved in carbohydrate and amino acid metabolism. This study demonstrates that dysbiosis of the gut microbiome may have a causal role in the development of depressive-like behaviors, in a pathway that is mediated through the host's metabolism.

Occupational Contact Dermatitis in Mechanics and Repairers Referred for Patch Testing: Retrospective Analysis From the North American Contact Dermatitis Group 1998-2014.

Science.gov (United States)

Warshaw, Erin M; Hagen, Solveig L; Sasseville, Denis; Maibach, Howard I; DeKoven, Joel G; Belsito, Donald V; Fowler, Joseph F; Zug, Kathryn A; Taylor, James S; Mathias, C G Toby; Fransway, Anthony F; DeLeo, Vincent A; Marks, James G; Pratt, Melanie D; Zirwas, Matthew J; Storrs, Frances J

Contact dermatoses are common in mechanic and repair occupations. This study aimed to (1) estimate the prevalence of occupationally related contact dermatitis among mechanics/repairers patch tested from 1998 to 2014 by the North American Contact Dermatitis Group, (2) characterize responsible allergens and irritants, and their sources, and (3) compare results among 3 occupational subgroups (mechanics, electrical/electronic, and other). A cross-sectional analysis of patients patch tested by the North American Contact Dermatitis Group between 1998 and 2014. Of 38,784 patients patch tested, 691 (1.8%) were mechanics/repairers. Male sex (93.5%) and hand involvement (59.5%) were common overall. Occupationally related skin disease was more prevalent among vehicle and mobile equipment mechanics/repairers (52.7%) and other mechanics/repairers (41.4%) than electrical/electronic equipment mechanics/repairers (21.3%). Overall, carba mix, thiuram mix, and methylchloroisothiazolone/methylisothiazolone were the most common occupation-related clinically relevant allergens. Gloves, automotive vehicles, solvents, oils, lubricants, and fuels were the most common sources of responsible allergens. Common occupationally related allergens included rubber accelerators and the preservative methylchloroisothiazolone/methylisothiazolone.

Endogenous DNA Damage and Repair Enzymes: -A short summary of the scientific achievements of Tomas Lindahl, Nobel Laureate in Chemistry 2015.

Science.gov (United States)

Klungland, Arne; Yang, Yun-Gui

2016-06-01

Tomas Lindahl completed his medical studies at Karolinska Institute in 1970. Yet, his work has always been dedicated to unraveling fundamental mechanisms of DNA decay and DNA repair. His research is characterized with groundbreaking discoveries on the instability of our genome, the identification of novel DNA repair activities, the characterization of DNA repair pathways, and the association to diseases, throughout his 40 years of scientific career. Copyright © 2015 The Authors. Production and hosting by Elsevier Ltd.. All rights reserved.

USING THE OUTSOURCING MECHANISM TO INCREASE THE EFFICIENCY OF REPAIR AND MAINTENANCE IN METALLURGICAL ENTERPRISES

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Elena I. Kozlova

2017-01-01

Full Text Available Abstract. Objectives The aim of the work is to study the outsourcing mechanism from the point of view of increasing the efficiency of repair and maintenance at a metallurgical enterprise. Method Analysis of the experience of using outsourcing of repair services at domestic and foreign metallurgical enterprises was carried out. Analysis of the experience of the withdrawal from enterprise repair services into a separate outsourcing company has shown that the main advantages of this method of organising repair activities are an increase in the transparency of the costs of repairs and maintenance, and hence their reduction, as well as a reduction in the amount of equipment downtime. The main characteristics of outsourcing were revealed, substantiating its expediency. The restructuring of the repair system provides a step-by-step transition from decentralised to centralised structures of technical, mechanical, power and electrical repair services of enterprises, from the principle of "self-service" to the principle of "proprietary service" by isolating the subdivisions of the repair system from the structure of enterprises and creating competing members of the repair services market. Put another way, this is typified by moving away from the status of auxiliary production to a selfdependent activity. The stages of outsourcing the repair services of the enterprise are considered and possible problems that may arise in the course of the work of a working group are established to determine the suitability of outsourcing and to resolve the numerous issues arising from the transfer of repair functions. Results The findings of the research include approaches developed for overcoming risky situations: providing guarantees from the customer and the contractor and indicating them in the contract, increasing the motivation of the outsourcing company through a key performance indicator that should increase the interest of the performer in providing quality

Hijacking of the Host Ubiquitin Network by Legionella pneumophila

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Jiazhang Qiu

2017-12-01

Full Text Available Protein ubiquitination is critical for regulation of numerous eukaryotic cellular processes such as protein homeostasis, cell cycle progression, immune response, DNA repair, and vesicular trafficking. Ubiquitination often leads to the alteration of protein stability, subcellular localization, or interaction with other proteins. Given the importance of ubiquitination in the regulation of host immunity, it is not surprising that many infectious agents have evolved strategies to interfere with the ubiquitination network with sophisticated mechanisms such as functional mimicry. The facultative intracellular pathogen Legionella pneumophila is the causative agent of Legionnaires' disease. L. pneumophila is phagocytosed by macrophages and is able to replicate within a niche called Legionella-containing vacuole (LCV. The biogenesis of LCV is dependent upon the Dot/Icm type IV secretion system which delivers more than 330 effector proteins into host cytosol. The optimal intracellular replication of L. pneumophila requires the host ubiquitin-proteasome system. Furthermore, membranes of the bacterial phagosome are enriched with ubiquitinated proteins in a way that requires its Dot/Icm type IV secretion system, suggesting the involvement of effectors in the manipulation of the host ubiquitination machinery. Here we summarize recent advances in our understanding of mechanisms exploited by L. pneumophila effector proteins to hijack the host ubiquitination pathway.

Repair mechanism of retinal pigment epithelial tears in age-related macular degeneration.

Science.gov (United States)

Mukai, Ryo; Sato, Taku; Kishi, Shoji

2015-03-01

To investigate repair mechanisms of retinal pigment epithelial (RPE) tears in age-related macular degeneration. The authors retrospectively studied 10 eyes with age-related macular degeneration that developed RPE tears during follow-up or after treatment with an anti-vascular endothelial growth factor drug or photodynamic therapy combined with ranibizumab. After development of the RPE tears, all follow-ups exceeded 13 months. Spectral domain or swept-source optical coherence tomography have been used to examine consecutive retinal changes where the RPE tears developed and attempted to determine the repair mechanisms. Retinal pigment epithelial tears developed during the natural course (n = 4) after ranibizumab treatment (n = 2) and after photodynamic therapy and ranibizumab (n = 4). Subretinal fluid persisted for more than 6 months after the RPE tears developed (n = 4), with the area where the RPE was lost found to be covered with thickened proliferative tissue. In 6 eyes where the subretinal fluid was absorbed within 2 months, optical coherence tomography showed the outer retina appeared to be directly attached to Bruch membrane, and there was attenuation of the normal hyperreflective band attributable to normal RPE during follow-up. Results suggest that two repair processes may be present in the area where RPE tears developed. Persistent subretinal fluid may lead to repair with thick proliferative tissue, while the outer retina appears to attach to Bruch membrane when there is early subretinal fluid resolution after RPE tear development.

Adaptive immunity alters distinct host feeding pathways during nematode induced inflammation, a novel mechanism in parasite expulsion.

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John J Worthington

2013-01-01

Full Text Available Gastrointestinal infection is often associated with hypophagia and weight loss; however, the precise mechanisms governing these responses remain poorly defined. Furthermore, the possibility that alterations in feeding during infection may be beneficial to the host requires further study. We used the nematode Trichinella spiralis, which transiently inhabits the small intestine before migrating to skeletal muscle, as a biphasic model of infection to determine the cellular and molecular pathways controlling feeding during enteric and peripheral inflammation. Through the infection of genetically modified mice lacking cholecystokinin, Tumor necrosis factor α receptors and T and B-cells, we observed a biphasic hypophagic response to infection resulting from two separate immune-driven mechanisms. The enteroendocrine I-cell derived hormone cholecystokinin is an essential mediator of initial hypophagia and is induced by CD4+ T-cells during enteritis. In contrast, the second hypophagic response is extra-intestinal and due to the anorectic effects of TNFα during peripheral infection of the muscle. Moreover, via maintaining naive levels of the adipose secreted hormone leptin throughout infection we demonstrate a novel feedback loop in the immunoendocrine axis. Immune driven I-cell hyperplasia and resultant weight loss leads to a reduction in the inflammatory adipokine leptin, which in turn heightens protective immunity during infection. These results characterize specific immune mediated mechanisms which reduce feeding during intestinal or peripheral inflammation. Importantly, the molecular mediators of each phase are entirely separate. The data also introduce the first evidence that I-cell hyperplasia is an adaptively driven immune response that directly impinges on the outcome to infection.

Defective DNA repair mechanisms in prostate cancer: impact of olaparib

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De Felice F

2017-03-01

Full Text Available Francesca De Felice,1 Vincenzo Tombolini,1 Francesco Marampon,2 Angela Musella,3 Claudia Marchetti3 1Department of Radiotherapy, Policlinico Umberto I, “Sapienza” University of Rome, Rome, 2Department of Biotechnological and Applied Clinical Sciences, Laboratory of Radiobiology, University of L’Aquila, L’Aquila, 3Department of Gynecological and Obstetrical Sciences and Urological Sciences, “Sapienza” University of Rome, Rome, Italy Abstract: The field of prostate oncology has continued to change dramatically. It has truly become a field that is intensely linked to molecular genetic alterations, especially DNA-repair defects. Germline breast cancer 1 gene (BRCA1 and breast cancer 2 gene (BRCA2 mutations are implicated in the highest risk of prostate cancer (PC predisposition and aggressiveness. Poly adenosine diphosphate ribose polymerase (PARP proteins play a key role in DNA repair mechanisms and represent a valid target for new therapies. Olaparib is an oral PARP inhibitor that blocks DNA repair pathway and coupled with BRCA mutated-disease results in tumor cell death. In phase II clinical trials, including patients with advanced castration-resistant PC, olaparib seems to be efficacious and well tolerated. Waiting for randomized phase III trials, olaparib should be considered as a promising treatment option for PC. Keywords: prostate cancer, metastatic disease, castration resistant, BRCA, DNA-repair, PARP, olaparib

Cell Therapy in Parkinson's Disease: Host Brain Repair Machinery Gets a Boost From Stem Cell Grafts.

Science.gov (United States)

Napoli, Eleonora; Borlongan, Cesar V

2017-06-01

This commentary highlights the major findings and future research directions arising from the recent publication by Zuo and colleagues in Stem Cells 2017 (in press). Here, we discuss the novel observations that transplanted human neural stem cells can induce endogenous brain repair by specifically stimulating a host of regenerative processes in the neurogenic niche (i.e., subventricular zone [SVZ]) in an animal model of Parkinson's disease. That the identified therapeutic proteomes, neurotrophic factors, and anti-inflammatory cytokines in the SVZ may facilitate brain regeneration and behavioral recovery open a new venue of research for our understanding of the pathology and treatment of Parkinson's disease. Stem Cells 2017;35:1443-1445. © 2017 AlphaMed Press.

DNA Repair and Photoprotection: Mechanisms of Overcoming Environmental Ultraviolet Radiation Exposure in Halophilic Archaea.

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Jones, Daniel L; Baxter, Bonnie K

2017-01-01

Halophilic archaea push the limits of life at several extremes. In particular, they are noted for their biochemical strategies in dealing with osmotic stress, low water activity and cycles of desiccation in their hypersaline environments. Another feature common to their habitats is intense ultraviolet (UV) radiation, which is a challenge that microorganisms must overcome. The consequences of high UV exposure include DNA lesions arising directly from bond rearrangement of adjacent bipyrimidines, or indirectly from oxidative damage, which may ultimately result in mutation and cell death. As such, these microorganisms have evolved a number of strategies to navigate the threat of DNA damage, which we differentiate into two categories: DNA repair and photoprotection. Photoprotection encompasses damage avoidance strategies that serve as a "first line of defense," and in halophilic archaea include pigmentation by carotenoids, mechanisms of oxidative damage avoidance, polyploidy, and genomic signatures that make DNA less susceptible to photodamage. Photolesions that do arise are addressed by a number of DNA repair mechanisms that halophilic archaea efficiently utilize, which include photoreactivation, nucleotide excision repair, base excision repair, and homologous recombination. This review seeks to place DNA damage, repair, and photoprotection in the context of halophilic archaea and the solar radiation of their hypersaline environments. We also provide new insight into the breadth of strategies and how they may work together to produce remarkable UV-resistance for these microorganisms.

Host-microbiota interplay in mediating immune disorders.

Science.gov (United States)

Felix, Krysta M; Tahsin, Shekha; Wu, Hsin-Jung Joyce

2018-04-01

To maintain health, the immune system must maintain a delicate balance between eliminating invading pathogens and avoiding immune disorders such as autoimmunity and allergies. The gut microbiota provide essential health benefits to the host, particularly by regulating immune homeostasis. Dysbiosis, an alteration and imbalance of the gut microbiota, is associated with the development of several autoimmune diseases in both mice and humans. In this review, we discuss recent advances in understanding how certain factors, such as age and gender, affect the gut microbiota, which in turn can influence the development of autoimmune diseases. The age factor in microbiota-dependent immune disorders indicates a window of opportunity for future diagnostic and therapeutic approaches. We also discuss unique commensal bacteria with strong immunomodulatory activity. Finally, we provide an overview of the potential molecular mechanisms whereby gut microbiota induce autoimmunity, as well as the evidence that gut microbiota trigger extraintestinal diseases by inducing the migration of gut-derived immune cells. Elucidating the interaction of gut microbiota and the host immune system will help us understand the pathogenesis of immune disorders, and provide us with new foundations to develop novel immuno- or microbe-targeted therapies. © 2017 New York Academy of Sciences.

Molecular mechanism of VDE-initiated intein homing in yeast nuclear genome.

Science.gov (United States)

Fukuda, Tomoyuki; Nagai, Yuri; Ohya, Yoshikazu

2004-01-01

In Saccharomyces cerevisiae, VMA1 intein encodes a homing endonuclease termed VDE which is produced by an autocatalytic protein splicing reaction. VDE introduces a DSB at its recognition sequence on intein-minus allele, resulting in the lateral transfer of VMA1 intein. In this review, we summarize a decade of in vitro study on VDE and describe our recent study on the in vivo behavior of both VDE and host proteins involved in intein mobility. Meiotic DSBs caused by VDE are repaired in the similar pathway to that working in meiotic recombination induced by Spo11p-mediated DSBs. Meiosis-specific DNA cleavage and homing is shown to be guaranteed by the two distinct mechanisms, the subcellular localization of VDE and a requirement of premeiotic DNA replication. Based on these lines of evidence, we present the whole picture of molecular mechanism of VDE-initiated homing in yeast cells.

Differential recruitment of DNA Ligase I and III to DNA repair sites

Science.gov (United States)

Mortusewicz, Oliver; Rothbauer, Ulrich; Cardoso, M. Cristina; Leonhardt, Heinrich

2006-01-01

DNA ligation is an essential step in DNA replication, repair and recombination. Mammalian cells contain three DNA Ligases that are not interchangeable although they use the same catalytic reaction mechanism. To compare the recruitment of the three eukaryotic DNA Ligases to repair sites in vivo we introduced DNA lesions in human cells by laser microirradiation. Time lapse microscopy of fluorescently tagged proteins showed that DNA Ligase III accumulated at microirradiated sites before DNA Ligase I, whereas we could detect only a faint accumulation of DNA Ligase IV. Recruitment of DNA Ligase I and III to repair sites was cell cycle independent. Mutational analysis and binding studies revealed that DNA Ligase I was recruited to DNA repair sites by interaction with PCNA while DNA Ligase III was recruited via its BRCT domain mediated interaction with XRCC1. Selective recruitment of specialized DNA Ligases may have evolved to accommodate the particular requirements of different repair pathways and may thus enhance efficiency of DNA repair. PMID:16855289

Rapid assessment of repair of ultraviolet DNA damage with a modified host-cell reactivation assay using a luciferase reporter gene and correlation with polymorphisms of DNA repair genes in normal human lymphocytes

Energy Technology Data Exchange (ETDEWEB)

Qiao Yawei; Spitz, Margaret R.; Guo Zhaozheng; Hadeyati, Mohammad; Grossman, Lawrence; Kraemer, Kenneth H.; Wei Qingyi

2002-11-30

As DNA repair plays an important role in genetic susceptibility to cancer, assessment of the DNA repair phenotype is critical for molecular epidemiological studies of cancer. In this report, we compared use of the luciferase (luc) reporter gene in a host-cell reactivation (HCR) (LUC) assay of repair of ultraviolet (UV) damage to DNA to use of the chloramphenicol (cat) gene-based HCR (CAT) assay we used previously for case-control studies. We performed both the assays on cryopreserved lymphocytes from 102 healthy non-Hispanic white subjects. There was a close correlation between DNA repair capacity (DRC) as measured by the LUC and CAT assays. Although these two assays had similar variation, the LUC assay was faster and more sensitive. We also analyzed the relationship between DRC and the subjects' previously determined genotypes for four polymorphisms of two nucleotide-excision repair (NER) genes (in intron 9 of xeroderma pigmentosum (XP) C and exons 6, 10 and 23 of XPD) and one polymorphism of a base-excision repair gene in exon 10 of X-ray complementing group 1 (XRCC1). The DRC was significantly lower in subjects homozygous for one or more polymorphisms of the two NER genes than in subjects with other genotypes (P=0.010). In contrast, the polymorphic XRCC1 allele had no significant effect on DRC. These results suggest that the post-UV LUC assay measures NER phenotype and that polymorphisms of XPC and XPD genes modulate DRC. For population studies of the DNA repair phenotype, many samples need to be evaluated, and so the LUC assay has several advantages over the CAT assay: the LUC assay was more sensitive, had less variation, was not radioactive, was easier to perform, and required fewer cryopreserved cells. These features make the LUC-based HCR assay suitable for molecular epidemiological studies.

Stem Cells for Cartilage Repair: Preclinical Studies and Insights in Translational Animal Models and Outcome Measures

OpenAIRE

Lo Monaco, Melissa; Merckx, Greet; Ratajczak, Jessica; Gervois, Pascal; Hilkens, Petra; Clegg, Peter; Bronckaers, Annelies; Vandeweerd, Jean-Michel; Lambrichts, Ivo

2018-01-01

Due to the restricted intrinsic capacity of resident chondrocytes to regenerate the lost cartilage postinjury, stem cell-based therapies have been proposed as a novel therapeutic approach for cartilage repair. Moreover, stem cell-based therapies using mesenchymal stem cells (MSCs) or induced pluripotent stem cells (iPSCs) have been used successfully in preclinical and clinical settings. Despite these promising reports, the exact mechanisms underlying stem cell-mediated cartilage repair remain...

Departure mechanisms for host search on high-density patches by the Meteorus pulchricornis.

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Sheng, Sheng; Feng, Sufang; Meng, Ling; Li, Baoping

2014-01-01

Less attention has been paid to the parasitoid-host system in which the host occurs in considerably high density with a hierarchical patch structure in studies on time allocation strategies of parasitoids. This study used the parasitoid Meteorus pulchricornis (Wesmael) (Hymenoptera: Braconidae) and the Oriental leafworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) as the parasitoids-host model system to investigate patch-leaving mechanisms as affected by the high-host density, hierarchical patch structure, and foraging behaviors on both former and current patches. The results showed that three out of eight covariates tested had significant effects on the patch-leaving tendency, including the host density, ovipositor insertion, and host rejection on the current patch. The parasitoid paid more visits to the patch with high-density hosts. While the patch with higher host densities decreased the leaving tendency, the spatial distribution of hosts examined had no effect on the leaving tendency. Both oviposition and host rejection decreased the patch-leaving tendency. The variables associated with the former patch, such as the host density and number of ovipositor insertions, however, did not have an effect on the leaving tendency. Our study suggested that M. pulchricornis females may use an incremental mechanism to exploit high-density patches to the fullest. © The Author 2014. Published by Oxford University Press on behalf of the Entomological Society of America.

DMPD: The interferon regulatory factor family in host defense: mechanism of action. [Dynamic Macrophage Pathway CSML Database

Lifescience Database Archive (English)

Full Text Available 17502370 The interferon regulatory factor family in host defense: mechanism of acti....html) (.csml) Show The interferon regulatory factor family in host defense: mechanism of action. PubmedID 1...7502370 Title The interferon regulatory factor family in host defense: mechanism

Host-Induced Gene Silencing of Rice Blast Fungus Magnaporthe oryzae Pathogenicity Genes Mediated by the Brome Mosaic Virus.

Science.gov (United States)

Zhu, Lin; Zhu, Jian; Liu, Zhixue; Wang, Zhengyi; Zhou, Cheng; Wang, Hong

2017-09-26

Magnaporthe oryzae is a devastating plant pathogen, which has a detrimental impact on rice production worldwide. Despite its agronomical importance, some newly-emerging pathotypes often overcome race-specific disease resistance rapidly. It is thus desirable to develop a novel strategy for the long-lasting resistance of rice plants to ever-changing fungal pathogens. Brome mosaic virus (BMV)-induced RNA interference (RNAi) has emerged as a useful tool to study host-resistance genes for rice blast protection. Planta-generated silencing of targeted genes inside biotrophic pathogens can be achieved by expression of M. oryzae -derived gene fragments in the BMV-mediated gene silencing system, a technique termed host-induced gene silencing (HIGS). In this study, the effectiveness of BMV-mediated HIGS in M. oryzae was examined by targeting three predicted pathogenicity genes, MoABC1, MoMAC1 and MoPMK1 . Systemic generation of fungal gene-specific small interfering RNA (siRNA) molecules induced by inoculation of BMV viral vectors inhibited disease development and reduced the transcription of targeted fungal genes after subsequent M. oryzae inoculation. Combined introduction of fungal gene sequences in sense and antisense orientation mediated by the BMV silencing vectors significantly enhanced the efficiency of this host-generated trans-specific RNAi, implying that these fungal genes played crucial roles in pathogenicity. Collectively, our results indicated that BMV-HIGS system was a great strategy for protecting host plants against the invasion of pathogenic fungi.

The potential for host switching via ecological fitting in the emerald ash borer-host plant system.

Science.gov (United States)

Cipollini, Don; Peterson, Donnie L

2018-02-27

The traits used by phytophagous insects to find and utilize their ancestral hosts can lead to host range expansions, generally to closely related hosts that share visual and chemical features with ancestral hosts. Host range expansions often result from ecological fitting, which is the process whereby organisms colonize and persist in novel environments, use novel resources, or form novel associations with other species because of the suites of traits that they carry at the time they encounter the novel environment. Our objective in this review is to discuss the potential and constraints on host switching via ecological fitting in emerald ash borer, Agrilus planipennis, an ecologically and economically important invasive wood boring beetle. Once thought of as an ash (Fraxinus spp.) tree specialist, recent studies have revealed a broader potential host range than was expected for this insect. We discuss the demonstrated host-use capabilities of this beetle, as well as the potential for and barriers to the adoption of additional hosts by this beetle. We place our observations in the context of biochemical mechanisms that mediate the interaction of these beetles with their host plants and discuss whether evolutionary host shifts are a possible outcome of the interaction of this insect with novel hosts.

Biomaterial-mediated strategies targeting vascularization for bone repair.

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García, José R; García, Andrés J

2016-04-01

Repair of non-healing bone defects through tissue engineering strategies remains a challenging feat in the clinic due to the aversive microenvironment surrounding the injured tissue. The vascular damage that occurs following a bone injury causes extreme ischemia and a loss of circulating cells that contribute to regeneration. Tissue-engineered constructs aimed at regenerating the injured bone suffer from complications based on the slow progression of endogenous vascular repair and often fail at bridging the bone defect. To that end, various strategies have been explored to increase blood vessel regeneration within defects to facilitate both tissue-engineered and natural repair processes. Developments that induce robust vascularization will need to consolidate various parameters including optimization of embedded therapeutics, scaffold characteristics, and successful integration between the construct and the biological tissue. This review provides an overview of current strategies as well as new developments in engineering biomaterials to induce reparation of a functional vascular supply in the context of bone repair.

Combined effects of scaffold stiffening and mechanical preconditioning cycles on construct biomechanics, gene expression, and tendon repair biomechanics.

Science.gov (United States)

Nirmalanandhan, Victor Sanjit; Juncosa-Melvin, Natalia; Shearn, Jason T; Boivin, Gregory P; Galloway, Marc T; Gooch, Cynthia; Bradica, Gino; Butler, David L

2009-08-01

Our group has previously reported that in vitro mechanical stimulation of tissue-engineered tendon constructs significantly increases both construct stiffness and the biomechanical properties of the repair tissue after surgery. When optimized using response surface methodology, our results indicate that a mechanical stimulus with three components (2.4% strain, 3000 cycles/day, and one cycle repetition) produced the highest in vitro linear stiffness. Such positive correlations between construct and repair stiffness after surgery suggest that enhancing structural stiffness before surgery could not only accelerate repair stiffness but also prevent premature failures in culture due to poor mechanical integrity. In this study, we examined the combined effects of scaffold crosslinking and subsequent mechanical stimulation on construct mechanics and biology. Autologous tissue-engineered constructs were created by seeding mesenchymal stem cells (MSCs) from 15 New Zealand white rabbits on type I collagen sponges that had undergone additional dehydrothermal crosslinking (termed ADHT in this manuscript). Both constructs from each rabbit were mechanically stimulated for 8h/day for 12 consecutive days with half receiving 100 cycles/day and the other half receiving 3000 cycles/day. These paired MSC-collagen autologous constructs were then implanted in bilateral full-thickness, full-length defects in the central third of rabbit patellar tendons. Increasing the number of in vitro cycles/day delivered to the ADHT constructs in culture produced no differences in stiffness or gene expression and no changes in biomechanical properties or histology 12 weeks after surgery. Compared to MSC-based repairs from a previous study that received no additional treatment in culture, ADHT crosslinking of the scaffolds actually lowered the 12-week repair stiffness. Thus, while ADHT crosslinking may initially stiffen a construct in culture, this specific treatment also appears to mask any benefits

The Bcl-2 Family in Host-Virus Interactions.

Science.gov (United States)

Kvansakul, Marc; Caria, Sofia; Hinds, Mark G

2017-10-06

Members of the B cell lymphoma-2 (Bcl-2) family are pivotal arbiters of mitochondrially mediated apoptosis, a process of fundamental importance during tissue development, homeostasis, and disease. At the structural and mechanistic level, the mammalian members of the Bcl-2 family are increasingly well understood, with their interplay ultimately deciding the fate of a cell. Dysregulation of Bcl-2-mediated apoptosis underlies a plethora of diseases, and numerous viruses have acquired homologs of Bcl-2 to subvert host cell apoptosis and autophagy to prevent premature death of an infected cell. Here we review the structural biology, interactions, and mechanisms of action of virus-encoded Bcl-2 proteins, and how they impact on host-virus interactions to ultimately enable successful establishment and propagation of viral infections.

Evidence for a second 'Prereplicative G2' repair mechanism, specific for γ-induced damage, in wild-type schizosaccharomyces pombe

International Nuclear Information System (INIS)

Gentner, N.E.; Atomic Energy of Canada Ltd., Chalk River, Ontario. Chalk River Nuclear Labs.)

1977-01-01

The major part of the substantial γ-resistance of wild-type Schizosaccharomyces pombe appears to be due to prereplicative recombinational repair mechanisms. The existence of a second 'prereplicative G2' repair pathway, specific for γ-induced damage, has now been deduced from studies of the effect of the repair inhibitor caffeine on γ-irradiated G1 phase and G2 phase cells. Only G2 cells are additionally inactivated on exposure to caffeine after γ-irradiation. This shows that both known caffeine-sensitive γ-repair processes (Genter and Werner, Molec. gen. Genet. 145, 1-5 [1976]) are dependent on the presence of a duplicated genome (2c) at the time of radiation exposure. Pathway I is the known 'prereplicative G2' repair process (Fabre, Radiation Res. 56, 528-539 [1973]) which is involved in both UV- and γ-repair, and which requires post-irradiation protein synthesis for activity. Pathway II represents a second distinct 'prereplicative G2' repair mechanism; it differs from the first in that it is specific for repair of γ-induced damage and appears to be constitutive. (orig.) [de

Midgut microbiota and host immunocompetence underlie Bacillus thuringiensis killing mechanism

OpenAIRE

Caccia, Silvia; Di Lelio, Ilaria; La Storia, Antonietta; Marinelli, Adriana; Varricchio, Paola; Franzetti, Eleonora; Banyuls, Núria; Tettamanti, Gianluca; Casartelli, Morena; Giordana, Barbara; Ferré, Juan; Gigliotti, Silvia; Ercolini, Danilo; Pennacchio, Francesco

2016-01-01

Bacillus thuringiensis and its toxins are widely used for insect control. Notwithstanding the remarkable importance of this insect pathogen, its killing mechanism has yet to be fully elucidated. Here we show that the microbiota resident in the host midgut triggers a lethal septicemia. The infection process is enhanced by reducing the host immune response and its control on replication of midgut bacteria invading the body cavity through toxin-induced epithelial lesions. The experimental approa...

Host-detrimental role of Esx-1-mediated inflammasome activation in mycobacterial infection.

Directory of Open Access Journals (Sweden)

Fredric Carlsson

2010-05-01

Full Text Available The Esx-1 (type VII secretion system is a major virulence determinant of pathogenic mycobacteria, including Mycobacterium marinum. However, the molecular events and host-pathogen interactions underlying Esx-1-mediated virulence in vivo remain unclear. Here we address this problem in a non-lethal mouse model of M. marinum infection that allows detailed quantitative analysis of disease progression. M. marinum established local infection in mouse tails, with Esx-1-dependent formation of caseating granulomas similar to those formed in human tuberculosis, and bone deterioration reminiscent of skeletal tuberculosis. Analysis of tails infected with wild type or Esx-1-deficient bacteria showed that Esx-1 enhanced generation of proinflammatory cytokines, including the secreted form of IL-1beta, suggesting that Esx-1 promotes inflammasome activation in vivo. In vitro experiments indicated that Esx-1-dependent inflammasome activation required the host NLRP3 and ASC proteins. Infection of wild type and ASC-deficient mice demonstrated that Esx-1-dependent inflammasome activation exacerbated disease without restricting bacterial growth, indicating a host-detrimental role of this inflammatory pathway in mycobacterial infection. These findings define an immunoregulatory role for Esx-1 in a specific host-pathogen interaction in vivo, and indicate that the Esx-1 secretion system promotes disease and inflammation through its ability to activate the inflammasome.

Host-mediated antitumor effect of DMG, a degraded D-manno-D-glucan from Microellobosporia grisea culture fluid.

Science.gov (United States)

Nakajima, H; Hashimoto, S; Nagao, S; Kita, Y; Khono, M; Ogawa, H; Abe, S; Mizuno, D

1984-03-01

DMG, a new polysaccharide with a well-characterized structure, isolated from the culture filtrate of an actinomycetes and then degraded by acid treatment, was tested for antitumor activity on allogeneic and syngeneic tumors in mice. In the allogeneic Ehrlich solid tumor system, DMG showed antitumor activity over a wide dose range, its optimal dose being 10-100 mg/kg. The optimal time of DMG administration was 1-2 weeks after tumor inoculation, but DMG was also effective when given before tumor inoculation. DMG was effective when given ip, sc, it (intratumorally) or iv. DMG also had antitumor effects on syngeneic tumors. It rapidly inhibited the growth of MM46 mammary carcinoma, MH134 hepatoma, and Meth A fibrosarcoma, and also inhibited spontaneous pulmonary metastases of B16-BL6 melanoma. However, it had no direct cytocidal action on tumor cells in vitro. Its antitumor activity was much less in athymic nude mice and in mice immunosuppressed by whole-body X-irradiation than in normal hosts.Thus, DMG was shown to exert antitumor activity via host-mediated mechanisms. Its antitumor activity is discussed in comparison with those of other antitumor polysaccharides.

Deoxyribonucleic Acid Damage and Repair: Capitalizing on Our Understanding of the Mechanisms of Maintaining Genomic Integrity for Therapeutic Purposes

Directory of Open Access Journals (Sweden)

Jolene Michelle Helena

2018-04-01

Full Text Available Deoxyribonucleic acid (DNA is the self-replicating hereditary material that provides a blueprint which, in collaboration with environmental influences, produces a structural and functional phenotype. As DNA coordinates and directs differentiation, growth, survival, and reproduction, it is responsible for life and the continuation of our species. Genome integrity requires the maintenance of DNA stability for the correct preservation of genetic information. This is facilitated by accurate DNA replication and precise DNA repair. DNA damage may arise from a wide range of both endogenous and exogenous sources but may be repaired through highly specific mechanisms. The most common mechanisms include mismatch, base excision, nucleotide excision, and double-strand DNA (dsDNA break repair. Concurrent with regulation of the cell cycle, these mechanisms are precisely executed to ensure full restoration of damaged DNA. Failure or inaccuracy in DNA repair contributes to genome instability and loss of genetic information which may lead to mutations resulting in disease or loss of life. A detailed understanding of the mechanisms of DNA damage and its repair provides insight into disease pathogeneses and may facilitate diagnosis and the development of targeted therapies.

DNA Repair and Photoprotection: Mechanisms of Overcoming Environmental Ultraviolet Radiation Exposure in Halophilic Archaea

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Daniel L. Jones

2017-09-01

Full Text Available Halophilic archaea push the limits of life at several extremes. In particular, they are noted for their biochemical strategies in dealing with osmotic stress, low water activity and cycles of desiccation in their hypersaline environments. Another feature common to their habitats is intense ultraviolet (UV radiation, which is a challenge that microorganisms must overcome. The consequences of high UV exposure include DNA lesions arising directly from bond rearrangement of adjacent bipyrimidines, or indirectly from oxidative damage, which may ultimately result in mutation and cell death. As such, these microorganisms have evolved a number of strategies to navigate the threat of DNA damage, which we differentiate into two categories: DNA repair and photoprotection. Photoprotection encompasses damage avoidance strategies that serve as a “first line of defense,” and in halophilic archaea include pigmentation by carotenoids, mechanisms of oxidative damage avoidance, polyploidy, and genomic signatures that make DNA less susceptible to photodamage. Photolesions that do arise are addressed by a number of DNA repair mechanisms that halophilic archaea efficiently utilize, which include photoreactivation, nucleotide excision repair, base excision repair, and homologous recombination. This review seeks to place DNA damage, repair, and photoprotection in the context of halophilic archaea and the solar radiation of their hypersaline environments. We also provide new insight into the breadth of strategies and how they may work together to produce remarkable UV-resistance for these microorganisms.

Abundant genetic overlap between blood lipids and immune-mediated diseases indicates shared molecular genetic mechanisms.

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Ole A Andreassen

Full Text Available Epidemiological studies suggest a relationship between blood lipids and immune-mediated diseases, but the nature of these associations is not well understood. We used genome-wide association studies (GWAS to investigate shared single nucleotide polymorphisms (SNPs between blood lipids and immune-mediated diseases. We analyzed data from GWAS (n~200,000 individuals, applying new False Discovery Rate (FDR methods, to investigate genetic overlap between blood lipid levels [triglycerides (TG, low density lipoproteins (LDL, high density lipoproteins (HDL] and a selection of archetypal immune-mediated diseases (Crohn's disease, ulcerative colitis, rheumatoid arthritis, type 1 diabetes, celiac disease, psoriasis and sarcoidosis. We found significant polygenic pleiotropy between the blood lipids and all the investigated immune-mediated diseases. We discovered several shared risk loci between the immune-mediated diseases and TG (n = 88, LDL (n = 87 and HDL (n = 52. Three-way analyses differentiated the pattern of pleiotropy among the immune-mediated diseases. The new pleiotropic loci increased the number of functional gene network nodes representing blood lipid loci by 40%. Pathway analyses implicated several novel shared mechanisms for immune pathogenesis and lipid biology, including glycosphingolipid synthesis (e.g. FUT2 and intestinal host-microbe interactions (e.g. ATG16L1. We demonstrate a shared genetic basis for blood lipids and immune-mediated diseases independent of environmental factors. Our findings provide novel mechanistic insights into dyslipidemia and immune-mediated diseases and may have implications for therapeutic trials involving lipid-lowering and anti-inflammatory agents.

Experimental Observation of the Skeletal Adaptive Repair Mechanism and Bionic Topology Optimization Method

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Kaysar Rahman

2014-01-01

Full Text Available Bone adaptive repair theory considers that the external load is the direct source of bone remodeling; bone achieves its maintenance by remodeling some microscopic damages due to external load during the process. This paper firstly observes CT data from the whole self-repairing process in bone defects in rabbit femur. Experimental result shows that during self-repairing process there exists an interaction relationship between spongy bone and enamel bone volume changes of bone defect, that is when volume of spongy bone increases, enamel bone decreases, and when volume of spongy bone decreases, enamel bone increases. Secondly according to this feature a bone remodeling model based on cross-type reaction-diffusion system influenced by mechanical stress is proposed. Finally, this model coupled with finite element method by using the element adding and removing process is used to simulate the self-repairing process and engineering optimization problems by considering the idea of bionic topology optimization.

Evasion of Human Neutrophil-Mediated Host Defense during Toxoplasma gondii Infection.

Science.gov (United States)

Lima, Tatiane S; Gov, Lanny; Lodoen, Melissa B

2018-02-13

Neutrophils are a major player in host immunity to infection; however, the mechanisms by which human neutrophils respond to the intracellular protozoan parasite Toxoplasma gondii are still poorly understood. In the current study, we found that, whereas primary human monocytes produced interleukin-1beta (IL-1β) in response to T. gondii infection, human neutrophils from the same blood donors did not. Moreover, T. gondii inhibited lipopolysaccharide (LPS)-induced IL-1β synthesis in human peripheral blood neutrophils. IL-1β suppression required active parasite invasion, since heat-killed or mycalolide B-treated parasites did not inhibit IL-1β release. By investigating the mechanisms involved in this process, we found that T. gondii infection of neutrophils treated with LPS resulted in reduced transcript levels of IL-1β and NLRP3 and reduced protein levels of pro-IL-1β, mature IL-1β, and the inflammasome sensor NLRP3. In T. gondii -infected neutrophils stimulated with LPS, the levels of MyD88, TRAF6, IKKα, IKKβ, and phosphorylated IKKα/β were not affected. However, LPS-induced IκBα degradation and p65 phosphorylation were reduced in T. gondii- infected neutrophils, and degradation of IκBα was reversed by treatment with the proteasome inhibitor MG-132. Finally, we observed that T. gondii inhibited the cleavage and activity of caspase-1 in human neutrophils. These results indicate that T. gondii suppression of IL-1β involves a two-pronged strategy whereby T. gondii inhibits both NF-κB signaling and activation of the NLRP3 inflammasome. These findings represent a novel mechanism of T. gondii evasion of human neutrophil-mediated host defense by targeting the production of IL-1β. IMPORTANCE Toxoplasma gondii is an obligate intracellular parasite that infects approximately one-third of humans worldwide and can invade virtually any nucleated cell in the human body. Although it is well documented that neutrophils infiltrate the site of acute T

Combinations of resting RSA and RSA reactivity impact maladaptive mood repair and depression symptoms.

Science.gov (United States)

Yaroslavsky, Ilya; Bylsma, Lauren M; Rottenberg, Jonathan; Kovacs, Maria

2013-10-01

We examined whether the combined indices of respiratory sinus arrhythmia at rest (resting RSA) and in response to a sad film (RSA reactivity) predict effective and ineffective responses to reduce sadness (adaptive vs. maladaptive mood repair) in women with histories of juvenile-onset depression (n=74) and no history of major mental disorders (n=75). Structural equation models were used to estimate latent resting RSA, depression, and adaptive and maladaptive mood repair and to test the study hypotheses. Results indicated that combinations of resting RSA+RSA reactivity (RSA patterns) predicted maladaptive mood repair, which in turn, mediated the effects of RSA pattern on depression. Further, RSA patterns moderated the depressogenic effects of maladaptive mood repair. RSA patterns were unrelated to adaptive mood repair. Our findings suggest that mood repair is one mechanism through which physiological vulnerabilities adversely affect mental health. Copyright © 2013 Elsevier B.V. All rights reserved.

Hierarchical mechanisms for transcription factor-mediated reprogramming of fibroblasts to neurons

Science.gov (United States)

Wapinski, Orly L.; Vierbuchen, Thomas; Qu, Kun; Lee, Qian Yi; Chanda, Soham; Fuentes, Daniel R.; Giresi, Paul G.; Ng, Yi Han; Marro, Samuele; Neff, Norma F.; Drechsel, Daniela; Martynoga, Ben; Castro, Diogo S.; Webb, Ashley E.; Brunet, Anne; Guillemot, Francois; Chang, Howard Y.; Wernig, Marius

2013-01-01

SUMMARY Direct lineage reprogramming is a promising approach for human disease modeling and regenerative medicine with poorly understood mechanisms. Here we reveal a hierarchical mechanism in the direct conversion of fibroblasts into induced neuronal (iN) cells mediated by the transcription factors Ascl1, Brn2, and Myt1l. Ascl1 acts as an “on target” pioneer factor by immediately occupying most cognate genomic sites in fibroblasts. In contrast, Brn2 and Myt1l do not access fibroblast chromatin productively on their own; instead Ascl1 recruits Brn2 to Ascl1 sites genome-wide. A unique trivalent chromatin signature in the host cells predicts the permissiveness for Ascl1 pioneering activity among different cell types. Finally, we identified Zfp238 as a key Ascl1 target gene that can partially substitute for Ascl1 during iN cell reprogramming. Thus, precise match between pioneer factor and the chromatin context at key target genes is determinative for trans-differentiation to neurons and likely other cell types. PMID:24243019

RPA-Mediated Recruitment of the E3 Ligase RFWD3 Is Vital for Interstrand Crosslink Repair and Human Health.

Science.gov (United States)

Feeney, Laura; Muñoz, Ivan M; Lachaud, Christophe; Toth, Rachel; Appleton, Paul L; Schindler, Detlev; Rouse, John

2017-06-01

Defects in the repair of DNA interstrand crosslinks (ICLs) are associated with the genome instability syndrome Fanconi anemia (FA). Here we report that cells with mutations in RFWD3, an E3 ubiquitin ligase that interacts with and ubiquitylates replication protein A (RPA), show profound defects in ICL repair. An amino acid substitution in the WD40 repeats of RFWD3 (I639K) found in a new FA subtype abolishes interaction of RFWD3 with RPA, thereby preventing RFWD3 recruitment to sites of ICL-induced replication fork stalling. Moreover, single point mutations in the RPA32 subunit of RPA that abolish interaction with RFWD3 also inhibit ICL repair, demonstrating that RPA-mediated RFWD3 recruitment to stalled replication forks is important for ICL repair. We also report that unloading of RPA from sites of ICL induction is perturbed in RFWD3-deficient cells. These data reveal important roles for RFWD3 localization in protecting genome stability and preserving human health. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

Fragile DNA Repair Mechanism Reduces Ageing in Multicellular Model

DEFF Research Database (Denmark)

Bendtsen, Kristian Moss; Juul, Jeppe Søgaard; Trusina, Ala

2012-01-01

increases the amount of unrepaired DNA damage. Despite this vicious circle, we ask, can cells maintain a high DNA repair capacity for some time or is repair capacity bound to continuously decline with age? We here present a simple mathematical model for ageing in multicellular systems where cells subjected...... to DNA damage can undergo full repair, go apoptotic, or accumulate mutations thus reducing DNA repair capacity. Our model predicts that at the tissue level repair rate does not continuously decline with age, but instead has a characteristic extended period of high and non-declining DNA repair capacity......DNA damages, as well as mutations, increase with age. It is believed that these result from increased genotoxic stress and decreased capacity for DNA repair. The two causes are not independent, DNA damage can, for example, through mutations, compromise the capacity for DNA repair, which in turn...

Non-host Plant Resistance against Phytophthora capsici Is Mediated in Part by Members of the I2 R Gene Family in Nicotiana spp.

Science.gov (United States)

Vega-Arreguín, Julio C; Shimada-Beltrán, Harumi; Sevillano-Serrano, Jacobo; Moffett, Peter

2017-01-01

The identification of host genes associated with resistance to Phytophthora capsici is crucial to developing strategies of control against this oomycete pathogen. Since there are few sources of resistance to P. capsici in crop plants, non-host plants represent a promising source of resistance genes as well as excellent models to study P. capsici - plant interactions. We have previously shown that non-host resistance to P. capsici in Nicotiana spp. is mediated by the recognition of a specific P. capsici effector protein, PcAvr3a1 in a manner that suggests the involvement of a cognate disease resistance (R) genes. Here, we have used virus-induced gene silencing (VIGS) and transgenic tobacco plants expressing dsRNA in Nicotiana spp. to identify candidate R genes that mediate non-host resistance to P. capsici . Silencing of members of the I2 multigene family in the partially resistant plant N. edwardsonii and in the resistant N. tabacum resulted in compromised resistance to P. capsici . VIGS of two other components required for R gene-mediated resistance, EDS1 and SGT1 , also enhanced susceptibility to P. capsici in N. edwardsonii , as well as in the susceptible plants N. benthamiana and N. clevelandii . The silencing of I2 family members in N. tabacum also compromised the recognition of PcAvr3a1. These results indicate that in this case, non-host resistance is mediated by the same components normally associated with race-specific resistance.

Is the Dresden technique a mechanical design of choice suitable for the repair of middle third Achilles tendon ruptures? A biomechanical study.

Science.gov (United States)

de la Fuente, C; Carreño-Zillmann, G; Marambio, H; Henríquez, H

2016-01-01

To compare the mechanical failure of the Dresden technique for Achilles tendon repair with the double modified Kessler technique controlled repair technique. The maximum resistance of the two repair techniques are also compared. A total of 30 Achilles tendon ruptures in bovine specimens were repaired with an Ethibond(®) suture to 4.5cm from the calcaneal insertion. Each rupture was randomly distributed into one of two surgical groups. After repair, each specimen was subjected to a maximum traction test. The mechanical failure (tendon, suture, or knot) rates (proportions) were compared using the exact Fisher test (α=.05), and the maximum resistances using the Student t test (α=.05). There was a difference in the proportions of mechanical failures, with the most frequent being a tendon tear in the Dresden technique, and a rupture of the suture in the Kessler technique. The repair using the Dresden technique performed in the open mode, compared to the Kessler technique, has a more suitable mechanical design for the repair of middle third Achilles tendon ruptures on developing a higher tensile resistance in 58.7%. However, its most common mechanical failure was a tendon tear, which due to inappropriate loads could lead to lengthening of the Achilles tendon. Copyright © 2016 SECOT. Publicado por Elsevier España, S.L.U. All rights reserved.

Cellular heredity in haploid cultures of somatic cells. Progress report, August 1977--August 1978. [Role of DNA repair mechanisms in uv mutagenesis in cultured frog and fish cells

Energy Technology Data Exchange (ETDEWEB)

Freed, J.J.

1978-09-01

Studies in progress on cultured frog and fish cells, exploring the relation between the frequency of mutation after ultraviolet irradiation and the pathway through which DNA repair takes place are reported. The rationale is that the mutation frequency induced by a uv exposure is determined not only by the dose delivered but by the fidelity of the DNA repair process. Since frog cells express photoreversal enzyme, whether repair takes place by error-free photoreversal or by other, error-prone, mechanisms can be determined experimentally. An important question is whether an inducible, error-prone mutagenic form of repair is demonstrable. During the past year, methods necessary to determine uv survival and mutation frequency over a range of uv exposures were worked out. Using these methods, we have tested for alteration of the uv survival curve by previous conditioning exposures in frog cells was studied and uv survival and photoreversal capacity in fish cells were determined. The relation between uv survival and induction of ouabain resistance by an alkylating agent (MNNG) was examined as a background for further studies with uv. A procedure intended to accomplish DNA-mediated transfer of frog DNA photolyase enzyme to Chinese hamster cells is described.

Modulation of Host Learning in Aedes aegypti Mosquitoes.

Science.gov (United States)

Vinauger, Clément; Lahondère, Chloé; Wolff, Gabriella H; Locke, Lauren T; Liaw, Jessica E; Parrish, Jay Z; Akbari, Omar S; Dickinson, Michael H; Riffell, Jeffrey A

2018-02-05

How mosquitoes determine which individuals to bite has important epidemiological consequences. This choice is not random; most mosquitoes specialize in one or a few vertebrate host species, and some individuals in a host population are preferred over others. Mosquitoes will also blood feed from other hosts when their preferred is no longer abundant, but the mechanisms mediating these shifts between hosts, and preferences for certain individuals within a host species, remain unclear. Here, we show that olfactory learning may contribute to Aedes aegypti mosquito biting preferences and host shifts. Training and testing to scents of humans and other host species showed that mosquitoes can aversively learn the scent of specific humans and single odorants and learn to avoid the scent of rats (but not chickens). Using pharmacological interventions, RNAi, and CRISPR gene editing, we found that modification of the dopamine-1 receptor suppressed their learning abilities. We further show through combined electrophysiological and behavioral recordings from tethered flying mosquitoes that these odors evoke changes in both behavior and antennal lobe (AL) neuronal responses and that dopamine strongly modulates odor-evoked responses in AL neurons. Not only do these results provide direct experimental evidence that olfactory learning in mosquitoes can play an epidemiological role, but collectively, they also provide neuroanatomical and functional demonstration of the role of dopamine in mediating this learning-induced plasticity, for the first time in a disease vector insect. Copyright © 2017 Elsevier Ltd. All rights reserved.

Use of Suture-Mediated Closure Device in Percutaneous Direct Carotid Puncture During Chimney-Thoracic Endovascular Aortic Repair

International Nuclear Information System (INIS)

Chan, Gabriel; Quek, Lawrence Hwee Han; Tan, Glenn Leong Wei; Pua, Uei

2016-01-01

BackgroundInsertion of a carotid chimney graft during thoracic endovascular aortic repair (Ch-TEVAR) is a recognized technique to extend the proximal landing zone into the aortic arch in the treatment of thoracic aortic disease. Conventional technique requires surgical exposure of the carotid artery for insertion of the carotid chimney graft.MethodologyWe describe our experience in the use of a suture-mediated closure device in percutaneous Ch-TEVAR in four patients.ResultsSuccessful hemostasis was achieved in all four patients. No complications related to the carotid puncture were recorded.ConclusionWe conclude that using suture-mediated closure device for carotid closure appears feasible and deserves further studies as a potential alternative to conventional surgical approach.

Use of Suture-Mediated Closure Device in Percutaneous Direct Carotid Puncture During Chimney-Thoracic Endovascular Aortic Repair

Energy Technology Data Exchange (ETDEWEB)

Chan, Gabriel, E-mail: dr.changabriel@gmail.com; Quek, Lawrence Hwee Han, E-mail: lawrence-quek@ttsh.com.sg [Tan Tock Seng Hospital, Department of Diagnostic Radiology (Singapore); Tan, Glenn Leong Wei, E-mail: glenn-tan@ttsh.com.sg [Tan Tock Seng Hospital, Department of General Surgery (Singapore); Pua, Uei, E-mail: druei@yahoo.com [Tan Tock Seng Hospital, Department of Diagnostic Radiology (Singapore)

2016-07-15

BackgroundInsertion of a carotid chimney graft during thoracic endovascular aortic repair (Ch-TEVAR) is a recognized technique to extend the proximal landing zone into the aortic arch in the treatment of thoracic aortic disease. Conventional technique requires surgical exposure of the carotid artery for insertion of the carotid chimney graft.MethodologyWe describe our experience in the use of a suture-mediated closure device in percutaneous Ch-TEVAR in four patients.ResultsSuccessful hemostasis was achieved in all four patients. No complications related to the carotid puncture were recorded.ConclusionWe conclude that using suture-mediated closure device for carotid closure appears feasible and deserves further studies as a potential alternative to conventional surgical approach.

Perturbation of host-cell membrane is a primary mechanism of HIV cytopathology.

Science.gov (United States)

Cloyd, M W; Lynn, W S

1991-04-01

Cytopathic viruses injure cells by a number of different mechanisms. The mechanism by which HIV-1 injures T cells was studied by temporally examining host-cell macromolecular syntheses, stages of the cell cycle, and membrane permeability following acute infection. T cells cytopathically infected at an m.o.i. of 1-5 grew normally for 24-72 hr, depending on the cell line, followed by the first manifestation of cell injury, slowing of cell division. At that time significant amounts of unintegrated HIV DNA and p24 core protein became detectable, and acridine orange flow cytometric cell cycle studies demonstrated the presence of fewer cells in the G2/M stage of the cell cycle. There was no change in the frequency of cells in the S-stage, and metabolic pulsing with radioactive precursors demonstrated that host-cell DNA, RNA, and protein syntheses were normal at that time and normal up to the time cells started to die (approximately 24 hr later), when all three decreased. Cellular lipid synthesis, however, was perturbed when cell multiplication slowed, with phospholipid synthesis reduced and neutral lipid synthesis enhanced. Permeability of the host-cell membrane to small molecules, such as Ca2+ and sucrose, was slightly enhanced early postinfection, and by the time of slowing of cell division, host membrane permeability was greatly increased to both Ca2+ and sucrose (Stokes radius 5.2 A) but not to inulin (Stokes radium 20 A). These changes in host-cell membrane permeability and phospholipid synthesis were not observed in acutely infected H9 cells, which are not susceptible to HIV cytopathology. Thus, HIV-1 appeared to predominantly injure T cells by perturbing host-cell membrane permeability and lipid synthesis, which is similar to the cytopathic mechanisms of paramyxoviruses.

VirHostNet 2.0: surfing on the web of virus/host molecular interactions data.

Science.gov (United States)

Guirimand, Thibaut; Delmotte, Stéphane; Navratil, Vincent

2015-01-01

VirHostNet release 2.0 (http://virhostnet.prabi.fr) is a knowledgebase dedicated to the network-based exploration of virus-host protein-protein interactions. Since the previous VirhostNet release (2009), a second run of manual curation was performed to annotate the new torrent of high-throughput protein-protein interactions data from the literature. This resource is shared publicly, in PSI-MI TAB 2.5 format, using a PSICQUIC web service. The new interface of VirHostNet 2.0 is based on Cytoscape web library and provides a user-friendly access to the most complete and accurate resource of virus-virus and virus-host protein-protein interactions as well as their projection onto their corresponding host cell protein interaction networks. We hope that the VirHostNet 2.0 system will facilitate systems biology and gene-centered analysis of infectious diseases and will help to identify new molecular targets for antiviral drugs design. This resource will also continue to help worldwide scientists to improve our knowledge on molecular mechanisms involved in the antiviral response mediated by the cell and in the viral strategies selected by viruses to hijack the host immune system. © The Author(s) 2014. Published by Oxford University Press on behalf of Nucleic Acids Research.

Failure mechanism dependence and reliability evaluation of non-repairable system

International Nuclear Information System (INIS)

Chen, Ying; Yang, Liu; Ye, Cui; Kang, Rui

2015-01-01

Reliability study of electronic system with the physics-of-failure method has been promoted due to the increase knowledge of electronic failure mechanisms. System failure initiates from independent failure mechanisms, have effect on or affect by other failure mechanisms and finally result in system failure. Failure mechanisms in a non-repairable system have many kinds of correlation. One failure mechanism developing to a certain degree will trigger, accelerate or inhibit another or many other failure mechanisms, some kind of failure mechanisms may have the same effect on the failure site, component or system. The destructive effect will be accumulated and result in early failure. This paper presents a reliability evaluation method considering correlativity among failure mechanisms, which includes trigger, acceleration, inhibition, accumulation, and competition. Based on fundamental rule of physics of failure, decoupling methods of these correlations are discussed. With a case, reliability of electronic system is evaluated considering failure mechanism dependence. - Highlights: • Five types of failure mechanism correlations are described. • Decoupling methods of these correlations are discussed. • A reliability evaluation method considering mechanism dependence is proposed. • Results are quite different to results under failure independence assumption

Chromosome End Repair and Genome Stability in Plasmodium falciparum.

Science.gov (United States)

Calhoun, Susannah F; Reed, Jake; Alexander, Noah; Mason, Christopher E; Deitsch, Kirk W; Kirkman, Laura A

2017-08-08

The human malaria parasite Plasmodium falciparum replicates within circulating red blood cells, where it is subjected to conditions that frequently cause DNA damage. The repair of DNA double-stranded breaks (DSBs) is thought to rely almost exclusively on homologous recombination (HR), due to a lack of efficient nonhomologous end joining. However, given that the parasite is haploid during this stage of its life cycle, the mechanisms involved in maintaining genome stability are poorly understood. Of particular interest are the subtelomeric regions of the chromosomes, which contain the majority of the multicopy variant antigen-encoding genes responsible for virulence and disease severity. Here, we show that parasites utilize a competitive balance between de novo telomere addition, also called "telomere healing," and HR to stabilize chromosome ends. Products of both repair pathways were observed in response to DSBs that occurred spontaneously during routine in vitro culture or resulted from experimentally induced DSBs, demonstrating that both pathways are active in repairing DSBs within subtelomeric regions and that the pathway utilized was determined by the DNA sequences immediately surrounding the break. In combination, these two repair pathways enable parasites to efficiently maintain chromosome stability while also contributing to the generation of genetic diversity. IMPORTANCE Malaria is a major global health threat, causing approximately 430,000 deaths annually. This mosquito-transmitted disease is caused by Plasmodium parasites, with infection with the species Plasmodium falciparum being the most lethal. Mechanisms underlying DNA repair and maintenance of genome integrity in P. falciparum are not well understood and represent a gap in our understanding of how parasites survive the hostile environment of their vertebrate and insect hosts. Our work examines DNA repair in real time by using single-molecule real-time (SMRT) sequencing focused on the subtelomeric

Host defense peptides of thrombin modulate inflammation and coagulation in endotoxin-mediated shock and Pseudomonas aeruginosa sepsis.

Science.gov (United States)

Kalle, Martina; Papareddy, Praveen; Kasetty, Gopinath; Mörgelin, Matthias; van der Plas, Mariena J A; Rydengård, Victoria; Malmsten, Martin; Albiger, Barbara; Schmidtchen, Artur

2012-01-01

Gram-negative sepsis is accompanied by a disproportionate innate immune response and excessive coagulation mainly induced by endotoxins released from bacteria. Due to rising antibiotic resistance and current lack of other effective treatments there is an urgent need for new therapies. We here present a new treatment concept for sepsis and endotoxin-mediated shock, based on host defense peptides from the C-terminal part of human thrombin, found to have a broad and inhibitory effect on multiple sepsis pathologies. Thus, the peptides abrogate pro-inflammatory cytokine responses to endotoxin in vitro and in vivo. Furthermore, they interfere with coagulation by modulating contact activation and tissue factor-mediated clotting in vitro, leading to normalization of coagulation responses in vivo, a previously unknown function of host defense peptides. In a mouse model of Pseudomonas aeruginosa sepsis, the peptide GKY25, while mediating a modest antimicrobial effect, significantly inhibited the pro-inflammatory response, decreased fibrin deposition and leakage in the lungs, as well as reduced mortality. Taken together, the capacity of such thrombin-derived peptides to simultaneously modulate bacterial levels, pro-inflammatory responses, and coagulation, renders them attractive therapeutic candidates for the treatment of invasive infections and sepsis.

Host defense peptides of thrombin modulate inflammation and coagulation in endotoxin-mediated shock and Pseudomonas aeruginosa sepsis.

Directory of Open Access Journals (Sweden)

Martina Kalle

Full Text Available Gram-negative sepsis is accompanied by a disproportionate innate immune response and excessive coagulation mainly induced by endotoxins released from bacteria. Due to rising antibiotic resistance and current lack of other effective treatments there is an urgent need for new therapies. We here present a new treatment concept for sepsis and endotoxin-mediated shock, based on host defense peptides from the C-terminal part of human thrombin, found to have a broad and inhibitory effect on multiple sepsis pathologies. Thus, the peptides abrogate pro-inflammatory cytokine responses to endotoxin in vitro and in vivo. Furthermore, they interfere with coagulation by modulating contact activation and tissue factor-mediated clotting in vitro, leading to normalization of coagulation responses in vivo, a previously unknown function of host defense peptides. In a mouse model of Pseudomonas aeruginosa sepsis, the peptide GKY25, while mediating a modest antimicrobial effect, significantly inhibited the pro-inflammatory response, decreased fibrin deposition and leakage in the lungs, as well as reduced mortality. Taken together, the capacity of such thrombin-derived peptides to simultaneously modulate bacterial levels, pro-inflammatory responses, and coagulation, renders them attractive therapeutic candidates for the treatment of invasive infections and sepsis.

Predators and patterns of within-host growth can mediate both among-host competition and evolution of transmission potential of parasites.

Science.gov (United States)

Auld, Stuart K J R; Hall, Spencer R; Housley Ochs, Jessica; Sebastian, Mathew; Duffy, Meghan A

2014-08-01

Parasite prevalence shows tremendous spatiotemporal variation. Theory indicates that this variation might stem from life-history characteristics of parasites and key ecological factors. Here, we illustrate how the interaction of an important predator and the schedule of transmission potential of two parasites can explain parasite abundance. A field survey showed that a noncastrating fungus (Metschnikowia bicuspidata) commonly infected a dominant zooplankton host (Daphnia dentifera), while a castrating bacterial parasite (Pasteuria ramosa) was rare. This result seemed surprising given that the bacterium produces many more infectious propagules (spores) than the fungus upon host death. The fungus's dominance can be explained by the schedule of within-host growth of parasites (i.e., how transmission potential changes over the course of infection) and the release of spores from "sloppy" predators (Chaoborus spp., who consume Daphnia prey whole and then later regurgitate the carapace and parasite spores). In essence, sloppy predators create a niche that the faster-schedule fungus currently occupies. However, a selection experiment showed that the slower-schedule bacterium can evolve into this faster-schedule, predator-mediated niche (but pays a cost in maximal spore yield to do so). Hence, our study shows how parasite life history can interact with predation to strongly influence the ecology, epidemiology, and evolution of infectious disease.

Test of mutagenicity of an irradiated standard diet for laboratory animals in the host-mediated assay with salmonella typhimurium TA 1530

International Nuclear Information System (INIS)

Muenzner, R.; Renner, H.W.

1976-01-01

Feed irradiated at a dose of 3 Mrad was tested for mutagenic activity in the host-mediated assay with the mouse as host and Salmonella typhimurium TA 1530 as indicator organism. In the in vivo and in the in vitro comparative test the irradiated feed showed no mutagenic effect. (orig.) [de

Reversible Guest Exchange Mechanisms in Supramolecular Host-GuestAssemblies

Energy Technology Data Exchange (ETDEWEB)

Pluth, Michael D.; Raymond, Kenneth N.

2006-09-01

Synthetic chemists have provided a wide array of supramolecular assemblies able to encapsulate guest molecules. The scope of this tutorial review focuses on supramolecular host molecules capable of reversibly encapsulating polyatomic guests. Much work has been done to determine the mechanism of guest encapsulation and guest release. This review covers common methods of monitoring and characterizing guest exchange such as NMR, UV-VIS, mass spectroscopy, electrochemistry, and calorimetry and also presents representative examples of guest exchange mechanisms. The guest exchange mechanisms of hemicarcerands, cucurbiturils, hydrogen-bonded assemblies, and metal-ligand assemblies are discussed. Special attention is given to systems which exhibit constrictive binding, a motif common in supramolecular guest exchange systems.

Mechanism of Enzyme Repair by the AAA+ Chaperone Rubisco Activase.

Science.gov (United States)

Bhat, Javaid Y; Miličić, Goran; Thieulin-Pardo, Gabriel; Bracher, Andreas; Maxwell, Andrew; Ciniawsky, Susanne; Mueller-Cajar, Oliver; Engen, John R; Hartl, F Ulrich; Wendler, Petra; Hayer-Hartl, Manajit

2017-09-07

How AAA+ chaperones conformationally remodel specific target proteins in an ATP-dependent manner is not well understood. Here, we investigated the mechanism of the AAA+ protein Rubisco activase (Rca) in metabolic repair of the photosynthetic enzyme Rubisco, a complex of eight large (RbcL) and eight small (RbcS) subunits containing eight catalytic sites. Rubisco is prone to inhibition by tight-binding sugar phosphates, whose removal is catalyzed by Rca. We engineered a stable Rca hexamer ring and analyzed its functional interaction with Rubisco. Hydrogen/deuterium exchange and chemical crosslinking showed that Rca structurally destabilizes elements of the Rubisco active site with remarkable selectivity. Cryo-electron microscopy revealed that Rca docks onto Rubisco over one active site at a time, positioning the C-terminal strand of RbcL, which stabilizes the catalytic center, for access to the Rca hexamer pore. The pulling force of Rca is fine-tuned to avoid global destabilization and allow for precise enzyme repair. Copyright © 2017 Elsevier Inc. All rights reserved.

Inducible error-prone repair in B. subtilis. Progress report, September 1, 1981-April 30, 1985

Energy Technology Data Exchange (ETDEWEB)

Yasbin, R.E.

1984-12-01

The objective was to investigate and elucidate the molecular mechanisms responsible for (i) inducible DNA repair system(s) and for (ii) error-prone repair in the gram positive bacterium Bacillus subtilis. The SOS-like system of Bacillus subtilis consists of several coordinately induced phenomena (e.g., cellular filamentation, prophage induction, and Weigle reactivation of uv-damaged bacteriophage) which are expressed after cellular insult such as DNA damage or inhibition of DNA replication. Mutagenesis of the bacterial chromosome and the development or maintenance of competence also appear to be involved in the SOS-like response in this bacterium. The genetic characterization of the SOS-like system has involved an analysis of (i) the effects of various DNA repair mutations on the expression of inducible phenomena and (ii) the tsi-23 mutation, which renders host strains thermally inducible for each of the SOS-like functions. Bacterial filamentation was unaffected by any of the DNA repair mutations studied. In contrast, the induction of prophage after thermal or uv pretreatment was abolished in strains carrying the recE4, recA1, recB2, or recG13 mutation. Weigle reactivation was also inhibited by the recE4, recA1, recB2, or recG13 mutation, whereas levels of W-reactivation were lower in strains which carried the uvrA42, polA5, or rec-961 mutation than in the DNA repair-proficient strain. Strains which carried the recE4 allele were incapable of chromosomal DNA-mediated transformation, and the frequency of this event was decreased in strains carrying the recA1, recB2, or tsi-23 mutation. Plasmid DNA transformation efficiency was decreased only in strains carrying the tsi-23 mutation in addition to the recE4, recA1, recB2, mutation. The results indicate that the SOS-like or SOB system of B. subtilis is regulated at different levels by two or more gene products.

Host age modulates within-host parasite competition.

Science.gov (United States)

Izhar, Rony; Routtu, Jarkko; Ben-Ami, Frida

2015-05-01

In many host populations, one of the most striking differences among hosts is their age. While parasite prevalence differences in relation to host age are well known, little is known on how host age impacts ecological and evolutionary dynamics of diseases. Using two clones of the water flea Daphnia magna and two clones of its bacterial parasite Pasteuria ramosa, we examined how host age at exposure influences within-host parasite competition and virulence. We found that multiply-exposed hosts were more susceptible to infection and suffered higher mortality than singly-exposed hosts. Hosts oldest at exposure were least often infected and vice versa. Furthermore, we found that in young multiply-exposed hosts competition was weak, allowing coexistence and transmission of both parasite clones, whereas in older multiply-exposed hosts competitive exclusion was observed. Thus, age-dependent parasite exposure and host demography (age structure) could together play an important role in mediating parasite evolution. At the individual level, our results demonstrate a previously unnoticed interaction of the host's immune system with host age, suggesting that the specificity of immune function changes as hosts mature. Therefore, evolutionary models of parasite virulence might benefit from incorporating age-dependent epidemiological parameters. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Mechanisms involved in the evasion of the host defence by Pseudomonas aeruginosa

DEFF Research Database (Denmark)

Kharazmi, A

1991-01-01

Pseudomonas aeruginosa, an extracellular opportunistic pathogen, utilizes two major mechanisms to evade the host defence system. One of these mechanisms is the production of a large number of extracellular products, such as proteases, toxins, and lipases. The two proteases, alkaline protease and ...

Phytochemicals radiosensitize cancer cells by inhibiting DNA repair

International Nuclear Information System (INIS)

Singh, Rana P.

2017-01-01

Solid tumors are mostly treated with radiotherapy. Radiotherapy is toxic to normal tissues and also promote the invasiveness and radioresistance in cancer cells. The resistance against radiotherapy and adverse effects to normal cells reduce the overall therapeutic effects of the treatment. Radiosensitizing agents usually show limited success during clinical trials. Therefore, the search and development of new radiosensitizers showing selective response to only cancer cells is desirable. We analyzed the radiosensitizing effects including cell death effect of silibinin, a phytochemical on prostate cancer cells. Silibinin enhanced gamma radiation (2.5-10 Gy) induced inhibition in colony formation selectively in prostate cancer cells. In cell cycle progression, G2/M phase is the most sensitive phase for radiation-induced damage which was delayed by the compound treatment in radiation exposed cells. The lower concentrations of silibinin substantially enhanced radiation-induced apoptosis. A prolonged reactive oxygen species production was also observed in these treatments EGFR signaling pathway can contribute to radiation-induced pro-survival mechanisms and to the therapeutic resistance. Agent treatment reduced the IR-induced EGFR phosphorylation and consequently reversed the resistance mediating mechanisms within the cancer cell. Thus, inhibiting DNA repair in cancer cells would enhance therapeutic response of radiation in cancer cells. Silibinin affected the localization of EGFR and DNA-dependent protein kinase, the DNA-PK is known to be an important mediator of DSB repair in human cells, and showed increased number of pH2AX (ser139) foci, and thus indicating lower DNA repair in these cancer cells. This was also confirmed in the tumor xenograft study. Our findings suggest that a combination of silibinin with radiation could be an effective treatment of radioresistant human prostate cancer and warrants further investigation. (author)

Wolbachia mediate variation of host immunocompetence.

Directory of Open Access Journals (Sweden)

Christine Braquart-Varnier

Full Text Available BACKGROUND: After decades during which endosymbionts were considered as silent in their hosts, in particular concerning the immune system, recent studies have revealed the contrary. In the present paper, we addressed the effect of Wolbachia, the most prevalent endosymbiont in arthropods, on host immunocompetence. To this end, we chose the A. vulgare-Wolbachia symbiosis as a model system because it leads to compare consequences of two Wolbachia strains (wVulC and wVulM on hosts from the same population. Moreover, A. vulgare is the only host-species in which Wolbachia have been directly observed within haemocytes which are responsible for both humoral and cellular immune responses. METHODOLOGY/PRINCIPAL FINDINGS: We sampled gravid females from the same population that were either asymbiotic, infected with wVulC, or infected with wVulM. The offspring from these females were tested and it was revealed that individuals harbouring wVulC exhibited: (i lower haemocyte densities, (ii more intense septicaemia in their haemolymph and (iii a reduced lifespan as compared to individuals habouring wVulM or asymbiotic ones. Therefore, individuals in this population of A. vulgare appeared to suffer more from wVulC than from wVulM. Symbiotic titer and location in the haemocytes did not differ for the two Wolbachia strains showing that these two parameters were not responsible for differences observed in their extended phenotypes in A. vulgare. CONCLUSION/SIGNIFICANCE: The two Wolbachia strains infecting A. vulgare in the same population induced variation in immunocompetence and survival of their hosts. Such variation should highly influence the dynamics of this host-symbiont system. We propose in accordance with previous population genetic works, that wVulM is a local strain that has attenuated its virulence through a long term adaptation process towards local A. vulgare genotypes whereas wVulC, which is a widespread and invasive strain, is not locally adapted.

Mechanical characterization of composite repairs for fiberglass wind turbine blades

Science.gov (United States)

Chawla, Tanveer Singh

While in service, wind turbine blades experience various modes of loading. An example is impact loading in the form of hail or bird strikes, which might lead to localized damage or formation of cracks a few plies deep on the blade surface. One of the methods to conduct repairs on wind turbine blades that are damaged while in service is hand lay-up of the repair part after grinding out the damaged portion and some of its surrounding area. The resin used for such repairs usually differs from the parent plate resin in composition and properties such as gel time, viscosity, etc. As a result the properties of the repaired parts are not the same as that of the undamaged blades. Subsequent repetitive loading can be detrimental to weak repairs to such an extent so as to cause delamination at the parent-repair bondline causing the repairs to eventually fall off the blade. Thus the strength and toughness of the repair are of critical importance. Initial part of this work consists of an effort to increase repair strength by identifying an optimum hand layup repair resin for fiberglass wind turbine blades currently being manufactured by a global company. As delamination of the repair from the parent blade is a major concern and unidirectional glass fibers along with a polymer resin are used to manufacture blades under consideration, testing method detailed in ASTM D 5528 (Test Method for Mode I Interlaminar Fracture Toughness of Unidirectional Fiber-Reinforced Polymer Matrix Composites) was followed to determine propagation fracture toughness values of the prospective vinyl ester repair resin candidates. These values were compared to those for a base polyester repair resin used by the company. Experimental procedure and results obtained from the above mentioned testing using double cantilever beam (DCB) specimens are detailed. Three new repair resins were shortlisted through mode I testing. It was also found that variation in the depth of the ground top ply of the parent part

Magnetic Resonance Mediated Radio Frequency Coagulation for Vascular Repair

Science.gov (United States)

Zhao, Ming

Purpose. Magnetic Resonance Mediated Radiofrequency Coagulation employs the RF heating effect of MRI scanning to coagulate biomaterials for repair of vascular defects. Coagulation of a protein biomaterial by MR-induced RF heating is a novel means to effect repair of defects such as aneurysms or arteriovenous malformations. Our novel method is to coagulate a thermosetting material (such as egg white, which can be used for investigating heat coagulation behavior and MR relaxation properties) delivered endovascularly by catheter and coagulated by RF-induced heating of an intracatheter resonant wire antenna in the scanner. Methods. Experiments were performed on a Siemens 1.5 T MRI scanner and a Bruker 14T NMR spectrometer. Egg white was brought to equilibrium at seven temperatures (20, 30, 40, 50, 60, 70 and 37 °C) in sequence. Measurement of the water spin-lattice relaxation time Ti, spin-spin relaxation time T2, spin-lattice relaxation time in the rotating frame T1p, or full width at half maximum of the MT spectrum were performed at each temperature. Relaxation parameters of raw egg white and egg white after coagulation at 70 °C were measured in the scanner at 20 °C to determine optimum inversion time, echo time and offset frequency for good image contrast between coagulated and uncoagulated protein. Finally, coagulation of egg white within a glass aneurysm phantom by RF heating in the scanner was performed to demonstrate the MR coagulation methodology and the ability to achieve image contrast between coagulated and uncoagulated biomaterial. Results. Water T2, T1p and MT gave the most definitive indication of the change from uncoagulated at low temperature to fully coagulated at 60 °C, while water T1 showed only the expected gradual increase with temperature, and no response to coagulation. MT weighted imaging is expected to be the optimum method to establish the coagulation condition of the biomaterial.

Mycobacteria exploit three genetically distinct DNA double-strand break repair pathways.

Science.gov (United States)

Gupta, Richa; Barkan, Daniel; Redelman-Sidi, Gil; Shuman, Stewart; Glickman, Michael S

2011-01-01

Bacterial pathogens rely on their DNA repair pathways to resist genomic damage inflicted by the host. DNA double-strand breaks (DSBs) are especially threatening to bacterial viability. DSB repair by homologous recombination (HR) requires nucleases that resect DSB ends and a strand exchange protein that facilitates homology search. RecBCD and RecA perform these functions in Escherichia coli and constitute the major pathway of error-free DSB repair. Mycobacteria, including the human pathogen M. tuberculosis, elaborate an additional error-prone pathway of DSB repair via non-homologous end-joining (NHEJ) catalysed by Ku and DNA ligase D (LigD). Little is known about the relative contributions of HR and NHEJ to mycobacterial chromosome repair, the factors that dictate pathway choice, or the existence of additional DSB repair pathways. Here we demonstrate that Mycobacterium smegmatis has three DSB repair pathway options: HR, NHEJ and a novel mechanism of single-strand annealing (SSA). Inactivation of NHEJ or SSA is compensated by elevated HR. We find that mycobacterial RecBCD does not participate in HR or confer resistance to ionizing radiation (IR), but is required for the RecA-independent SSA pathway. In contrast, the mycobacterial helicase-nuclease AdnAB participates in the RecA-dependent HR pathway, and is a major determinant of resistance to IR and oxidative DNA damage. These findings reveal distinctive features of mycobacterial DSB repair, most notably the dedication of the RecBCD and AdnAB helicase-nuclease machines to distinct repair pathways. © 2010 Blackwell Publishing Ltd.

The GraS Sensor in Staphylococcus aureus Mediates Resistance to Host Defense Peptides Differing in Mechanisms of Action.

Science.gov (United States)

Chaili, Siyang; Cheung, Ambrose L; Bayer, Arnold S; Xiong, Yan Q; Waring, Alan J; Memmi, Guido; Donegan, Niles; Yang, Soo-Jin; Yeaman, Michael R

2016-02-01

Staphylococcus aureus uses the two-component regulatory system GraRS to sense and respond to host defense peptides (HDPs). However, the mechanistic impact of GraS or its extracellular sensing loop (EL) on HDP resistance is essentially unexplored. Strains with null mutations in the GraS holoprotein (ΔgraS) or its EL (ΔEL) were compared for mechanisms of resistance to HDPs of relevant immune sources: neutrophil α-defensin (human neutrophil peptide 1 [hNP-1]), cutaneous β-defensin (human β-defensin 2 [hBD-2]), or the platelet kinocidin congener RP-1. Actions studied by flow cytometry included energetics (ENR); membrane permeabilization (PRM); annexin V binding (ANX), and cell death protease activation (CDP). Assay conditions simulated bloodstream (pH 7.5) or phagolysosomal (pH 5.5) pH contexts. S. aureus strains were more susceptible to HDPs at pH 7.5 than at pH 5.5, and each HDP exerted a distinct effect signature. The impacts of ΔgraS and ΔΕL on HDP resistance were peptide and pH dependent. Both mutants exhibited defects in ANX response to hNP-1 or hBD-2 at pH 7.5, but only hNP-1 did so at pH 5.5. Both mutants exhibited hyper-PRM, -ANX, and -CDP responses to RP-1 at both pHs and hypo-ENR at pH 5.5. The actions correlated with ΔgraS or ΔΕL hypersusceptibility to hNP-1 or RP-1 (but not hBD-2) at pH 7.5 and to all study HDPs at pH 5.5. An exogenous EL mimic protected mutant strains from hNP-1 and hBD-2 but not RP-1, indicating that GraS and its EL play nonredundant roles in S. aureus survival responses to specific HDPs. These findings suggest that GraS mediates specific resistance countermeasures to HDPs in immune contexts that are highly relevant to S. aureus pathogenesis in humans. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

SCAI promotes DNA double-strand break repair in distinct chromosomal contexts

DEFF Research Database (Denmark)

Hansen, Rebecca Kring; Mund, Andreas; Poulsen, Sara Lund

2016-01-01

cell invasion) as a 53BP1-interacting chromatin-associated protein that promotes the functionality of several DSB repair pathways in mammalian cells. SCAI undergoes prominent enrichment at DSB sites through dual mechanisms involving 53BP1-dependent recruitment to DSB-surrounding chromatin and 53BP1...... in repressive chromatin environments. Moreover, we establish an important role of SCAI in meiotic recombination, as SCAI deficiency in mice leads to germ cell loss and subfertility associated with impaired retention of the DMC1 recombinase on meiotic chromosomes. Collectively, our findings uncover SCAI...... as a physiologically important component of both NHEJ- and HR-mediated pathways that potentiates DSB repair efficiency in specific chromatin contexts....

Host response mechanisms in periodontal diseases

Directory of Open Access Journals (Sweden)

Nora SILVA

2015-06-01

Full Text Available Periodontal diseases usually refer to common inflammatory disorders known as gingivitis and periodontitis, which are caused by a pathogenic microbiota in the subgingival biofilm, including Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia and Treponema denticola that trigger innate, inflammatory, and adaptive immune responses. These processes result in the destruction of the tissues surrounding and supporting the teeth, and eventually in tissue, bone and finally, tooth loss. The innate immune response constitutes a homeostatic system, which is the first line of defense, and is able to recognize invading microorganisms as non-self, triggering immune responses to eliminate them. In addition to the innate immunity, adaptive immunity cells and characteristic cytokines have been described as important players in the periodontal disease pathogenesis scenario, with a special attention to CD4+ T-cells (T-helper cells. Interestingly, the T cell-mediated adaptive immunity development is highly dependent on innate immunity-associated antigen presenting cells, which after antigen capture undergo into a maturation process and migrate towards the lymph nodes, where they produce distinct patterns of cytokines that will contribute to the subsequent polarization and activation of specific T CD4+ lymphocytes. Skeletal homeostasis depends on a dynamic balance between the activities of the bone-forming osteoblasts (OBLs and bone-resorbing osteoclasts (OCLs. This balance is tightly controlled by various regulatory systems, such as the endocrine system, and is influenced by the immune system, an osteoimmunological regulation depending on lymphocyte- and macrophage-derived cytokines. All these cytokines and inflammatory mediators are capable of acting alone or in concert, to stimulate periodontal breakdown and collagen destruction via tissue-derived matrix metalloproteinases, a characterization of the progression of periodontitis as

Host response mechanisms in periodontal diseases

Science.gov (United States)

SILVA, Nora; ABUSLEME, Loreto; BRAVO, Denisse; DUTZAN, Nicolás; GARCIA-SESNICH, Jocelyn; VERNAL, Rolando; HERNÁNDEZ, Marcela; GAMONAL, Jorge

2015-01-01

Periodontal diseases usually refer to common inflammatory disorders known as gingivitis and periodontitis, which are caused by a pathogenic microbiota in the subgingival biofilm, including Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Tannerella forsythia and Treponema denticola that trigger innate, inflammatory, and adaptive immune responses. These processes result in the destruction of the tissues surrounding and supporting the teeth, and eventually in tissue, bone and finally, tooth loss. The innate immune response constitutes a homeostatic system, which is the first line of defense, and is able to recognize invading microorganisms as non-self, triggering immune responses to eliminate them. In addition to the innate immunity, adaptive immunity cells and characteristic cytokines have been described as important players in the periodontal disease pathogenesis scenario, with a special attention to CD4+ T-cells (T-helper cells). Interestingly, the T cell-mediated adaptive immunity development is highly dependent on innate immunity-associated antigen presenting cells, which after antigen capture undergo into a maturation process and migrate towards the lymph nodes, where they produce distinct patterns of cytokines that will contribute to the subsequent polarization and activation of specific T CD4+ lymphocytes. Skeletal homeostasis depends on a dynamic balance between the activities of the bone-forming osteoblasts (OBLs) and bone-resorbing osteoclasts (OCLs). This balance is tightly controlled by various regulatory systems, such as the endocrine system, and is influenced by the immune system, an osteoimmunological regulation depending on lymphocyte- and macrophage-derived cytokines. All these cytokines and inflammatory mediators are capable of acting alone or in concert, to stimulate periodontal breakdown and collagen destruction via tissue-derived matrix metalloproteinases, a characterization of the progression of periodontitis as a stage that

DNA Damage: Quantum Mechanics/Molecular Mechanics Study on the Oxygen Binding and Substrate Hydroxylation Step in AlkB Repair Enzymes

Science.gov (United States)

Quesne, Matthew G; Latifi, Reza; Gonzalez-Ovalle, Luis E; Kumar, Devesh; de Visser, Sam P

2014-01-01

AlkB repair enzymes are important nonheme iron enzymes that catalyse the demethylation of alkylated DNA bases in humans, which is a vital reaction in the body that heals externally damaged DNA bases. Its mechanism is currently controversial and in order to resolve the catalytic mechanism of these enzymes, a quantum mechanics/molecular mechanics (QM/MM) study was performed on the demethylation of the N1-methyladenine fragment by AlkB repair enzymes. Firstly, the initial modelling identified the oxygen binding site of the enzyme. Secondly, the oxygen activation mechanism was investigated and a novel pathway was found, whereby the catalytically active iron(IV)–oxo intermediate in the catalytic cycle undergoes an initial isomerisation assisted by an Arg residue in the substrate binding pocket, which then brings the oxo group in close contact with the methyl group of the alkylated DNA base. This enables a subsequent rate-determining hydrogen-atom abstraction on competitive σ-and π-pathways on a quintet spin-state surface. These findings give evidence of different locations of the oxygen and substrate binding channels in the enzyme and the origin of the separation of the oxygen-bound intermediates in the catalytic cycle from substrate. Our studies are compared with small model complexes and the effect of protein and environment on the kinetics and mechanism is explained. PMID:24339041

Characterizing the macro and micro mechanical properties of scaffolds for rotator cuff repair.

Science.gov (United States)

Smith, Richard D J; Zargar, Nasim; Brown, Cameron P; Nagra, Navraj S; Dakin, Stephanie G; Snelling, Sarah J B; Hakimi, Osnat; Carr, Andrew

2017-11-01

Retearing after rotator cuff surgery is a major clinical problem. Numerous scaffolds are being used to try to reduce retear rates. However, few have demonstrated clinical efficacy. We hypothesize that this lack of efficacy is due to insufficient mechanical properties. Therefore, we compared the macro and nano/micro mechanical properties of 7 commercially available scaffolds to those of the human supraspinatus tendons, whose function they seek to restore. The clinically approved scaffolds tested were X-Repair, LARS ligament, Poly-Tape, BioFiber, GraftJacket, Permacol, and Conexa. Fresh frozen cadaveric human supraspinatus tendon samples were used. Macro mechanical properties were determined through tensile testing and rheometry. Scanning probe microscopy and scanning electron microscopy were performed to assess properties of materials at the nano/microscale (morphology, Young modulus, loss tangent). None of the scaffolds tested adequately approximated both the macro and micro mechanical properties of human supraspinatus tendon. Macroscale mechanical properties were insufficient to restore load-bearing function. The best-performing scaffolds on the macroscale (X-Repair, LARS ligament) had poor nano/microscale properties. Scaffolds approximating tendon properties on the nano/microscale (BioFiber, biologic scaffolds) had poor macroscale properties. Existing scaffolds failed to adequately approximate the mechanical properties of human supraspinatus tendons. Combining the macroscopic mechanical properties of a synthetic scaffold with the micro mechanical properties of biologic scaffold could better achieve this goal. Future work should focus on advancing techniques to create new scaffolds with more desirable mechanical properties. This may help improve outcomes for rotator cuff surgery patients. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

Germline Chromothripsis Driven by L1-Mediated Retrotransposition and Alu/Alu Homologous Recombination

DEFF Research Database (Denmark)

Nazaryan-Petersen, Lusine; Bertelsen, Birgitte; Bak, Mads

2016-01-01

Chromothripsis (CTH) is a phenomenon where multiple localized double-stranded DNA breaks result in complex genomic rearrangements. Although the DNA-repair mechanisms involved in CTH have been described, the mechanisms driving the localized "shattering" process remain unclear. High-throughput sequ......Chromothripsis (CTH) is a phenomenon where multiple localized double-stranded DNA breaks result in complex genomic rearrangements. Although the DNA-repair mechanisms involved in CTH have been described, the mechanisms driving the localized "shattering" process remain unclear. High......-throughput sequence analysis of a familial germline CTH revealed an inserted SVAE retrotransposon associated with a 110-kb deletion displaying hallmarks of L1-mediated retrotransposition. Our analysis suggests that the SVAE insertion did not occur prior to or after, but concurrent with the CTH event. We also observed...... L1-endonuclease potential target sites in other breakpoints. In addition, we found four Alu elements flanking the 110-kb deletion and associated with an inversion. We suggest that chromatin looping mediated by homologous Alu elements may have brought distal DNA regions into close proximity...

Investigation of DNA damage and repair mechanism using deinococcus radiodurans

International Nuclear Information System (INIS)

Lau How Mooi; Kikuchi, M.; Kobayashi, Y.; Narumi, I.; Watanabe, H.

1997-01-01

Deninococcus Radiodurans, formerly known as Micrococcus Radiodurans, is a popular bacterium because of its high resistance to damage by carcinogens such as ionizing radiation (Dean et. al. 1966; Kitayama and Matsuyama 1968) and UV radiation (Gasvon et. al., 1995; Arrange et. al. 1993). In this report, we investigated the high resistance to ionizing radiation by this bacterium. The bacteria had been exposed from I to 5 kGy of gamma radiation and then incubated in TGY medium to study their ability to repair the broken DNA. The repair time was measured by Pulse Field Gel Electrophoresis (PFGE) method. The repair time for each dose was determined. Also in order to ensure that the repair was perfect, the bacterium was subjected to a second exposure of ionizing radiation after it has fully repaired. It was found that the 'second' repair characteristic was similar to the first repair. This confirmed that the repair after the exposure to the ionizing radiation was perfect

Facile fabrication of a superhydrophobic fabric with mechanical stability and easy-repairability.

Science.gov (United States)

Zhu, Xiaotao; Zhang, Zhaozhu; Yang, Jin; Xu, Xianghui; Men, Xuehu; Zhou, Xiaoyan

2012-08-15

The poor mechanical stability of superhydrophobic fabrics severely hindered their use in practical applications. Herein, to address this problem, we fabricated a superhydrophobic fabric with both mechanical stability and easy-repairability by a simple method. The mechanical durability of the obtained superhydrophobic fabric was evaluated by finger touching and abrasion with sandpaper. The results show that rough surface textures of the fabric were retained, and the fabric surface still exhibited superhydrophobicity after tests. More importantly, when the fabric lost its superhydrophobicity after a long-time abrasion, it can be easily rendered with superhydrophobicity once more by a regeneration process. Copyright © 2012 Elsevier Inc. All rights reserved.

Modulation of Wound Healing and Scar Formation by MG53 Protein-mediated Cell Membrane Repair*

Science.gov (United States)

Li, Haichang; Duann, Pu; Lin, Pei-Hui; Zhao, Li; Fan, Zhaobo; Tan, Tao; Zhou, Xinyu; Sun, Mingzhai; Fu, Minghuan; Orange, Matthew; Sermersheim, Matthew; Ma, Hanley; He, Duofen; Steinberg, Steven M.; Higgins, Robert; Zhu, Hua; John, Elizabeth; Zeng, Chunyu; Guan, Jianjun; Ma, Jianjie

2015-01-01

Cell membrane repair is an important aspect of physiology, and disruption of this process can result in pathophysiology in a number of different tissues, including wound healing, chronic ulcer and scarring. We have previously identified a novel tripartite motif family protein, MG53, as an essential component of the cell membrane repair machinery. Here we report the functional role of MG53 in the modulation of wound healing and scarring. Although MG53 is absent from keratinocytes and fibroblasts, remarkable defects in skin architecture and collagen overproduction are observed in mg53−/− mice, and these animals display delayed wound healing and abnormal scarring. Recombinant human MG53 (rhMG53) protein, encapsulated in a hydrogel formulation, facilitates wound healing and prevents scarring in rodent models of dermal injuries. An in vitro study shows that rhMG53 protects against acute injury to keratinocytes and facilitates the migration of fibroblasts in response to scratch wounding. During fibrotic remodeling, rhMG53 interferes with TGF-β-dependent activation of myofibroblast differentiation. The resulting down-regulation of α smooth muscle actin and extracellular matrix proteins contributes to reduced scarring. Overall, these studies establish a trifunctional role for MG53 as a facilitator of rapid injury repair, a mediator of cell migration, and a modulator of myofibroblast differentiation during wound healing. Targeting the functional interaction between MG53 and TGF-β signaling may present a potentially effective means for promoting scarless wound healing. PMID:26306047

Mechanisms of symbiont-conferred protection against natural enemies: an ecological and evolutionary framework.

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Gerardo, Nicole M; Parker, Benjamin J

2014-10-01

Many vertically-transmitted microbial symbionts protect their insect hosts from natural enemies, including host-targeted pathogens and parasites, and those vectored by insects to other hosts. Protection is often achieved through production of inhibiting toxins, which is not surprising given that toxin production mediates competition in many environments. Classical models of macroecological interactions, however, demonstrate that interspecific competition can be less direct, and recent research indicates that symbiont-protection can be mediated through exploitation of limiting resources, and through activation of host immune mechanisms that then suppress natural enemies. Available data, though limited, suggest that effects of symbionts on vectored pathogens and parasites, as compared to those that are host-targeted, are more likely to result from symbiont activation of the host immune system. We discuss these different mechanisms in light of their potential impact on the evolution of host physiological processes. Copyright © 2014 Elsevier Inc. All rights reserved.

Bacteriophage T4 gene 32 participates in excision repair as well as recombinational repair of UV damages

International Nuclear Information System (INIS)

Mosig, G.

1985-01-01

Gene 32 of phage T4 has been shown previously to be involved in recombinational repair of UV damages but, based on a mutant study, was thought not to be required for excision repair. However, a comparison of UV-inactivation curves of several gene 32 mutants grown under conditions permissive for progeny production in wild-type or polA- hosts demonstrates that gene 32 participates in both kinds of repair. Different gene 32 mutations differentially inactivate these repair functions. Under conditions permissive for DNA replication and progeny production, all gene 32 mutants investigated here are partially defective in recombinational repair, whereas only two of them, P7 and P401, are also defective in excision repair. P401 is the only mutant whose final slope of the inactivation curve is significantly steeper than that of wild-type T4. These results are discussed in terms of interactions of gp32, a single-stranded DNA-binding protein, with DNA and with other proteins

Proton Mediated Chemistry and Catalysis in a Self-Assembled Supramolecular Host

Energy Technology Data Exchange (ETDEWEB)

Pluth, Michael; Bergman, Robert; Raymond, Kenneth

2009-04-10

Synthetic supramolecular host assemblies can impart unique reactivity to encapsulated guest molecules. Synthetic host molecules have been developed to carry out complex reactions within their cavities, despite the fact that they lack the type of specifically tailored functional groups normally located in the analogous active sites of enzymes. Over the past decade, the Raymond group has developed a series of self-assembled supramolecules and the Bergman group has developed and studied a number of catalytic transformations. In this Account, we detail recent collaborative work between these two groups, focusing on chemical catalysis stemming from the encapsulation of protonated guests and expanding to acid catalysis in basic solution. We initially investigated the ability of a water-soluble, self-assembled supramolecular host molecule to encapsulate protonated guests in its hydrophobic core. Our study of encapsulated protonated amines revealed rich host-guest chemistry. We established that self-exchange (that is, in-out guest movement) rates of protonated amines were dependent on the steric bulk of the amine rather than its basicity. The host molecule has purely rotational tetrahedral (T) symmetry, so guests with geminal N-methyl groups (and their attendant mirror plane) were effectively desymmetrized; this allowed for the observation and quantification of the barriers for nitrogen inversion followed by bond rotation. Furthermore, small nitrogen heterocycles, such as N-alkylaziridines, N-alkylazetidines, and N-alkylpyrrolidines, were found to be encapsulated as proton-bound homodimers or homotrimers. We further investigated the thermodynamic stabilization of protonated amines, showing that encapsulation makes the amines more basic in the cavity. Encapsulation raises the effective basicity of protonated amines by up to 4.5 pK{sub a} units, a difference almost as large as that between the moderate and strong bases carbonate and hydroxide. The thermodynamic stabilization

Proton-Mediated Chemistry and Catalysis in a Self-Assembled Supramolecular Host

International Nuclear Information System (INIS)

Pluth, Michael; Bergman, Robert; Raymond, Kenneth

2009-01-01

Synthetic supramolecular host assemblies can impart unique reactivity to encapsulated guest molecules. Synthetic host molecules have been developed to carry out complex reactions within their cavities, despite the fact that they lack the type of specifically tailored functional groups normally located in the analogous active sites of enzymes. Over the past decade, the Raymond group has developed a series of self-assembled supramolecules and the Bergman group has developed and studied a number of catalytic transformations. In this Account, we detail recent collaborative work between these two groups, focusing on chemical catalysis stemming from the encapsulation of protonated guests and expanding to acid catalysis in basic solution. We initially investigated the ability of a water-soluble, self-assembled supramolecular host molecule to encapsulate protonated guests in its hydrophobic core. Our study of encapsulated protonated amines revealed rich host-guest chemistry. We established that self-exchange (that is, in-out guest movement) rates of protonated amines were dependent on the steric bulk of the amine rather than its basicity. The host molecule has purely rotational tetrahedral (T) symmetry, so guests with geminal N-methyl groups (and their attendant mirror plane) were effectively desymmetrized; this allowed for the observation and quantification of the barriers for nitrogen inversion followed by bond rotation. Furthermore, small nitrogen heterocycles, such as N-alkylaziridines, N-alkylazetidines, and N-alkylpyrrolidines, were found to be encapsulated as proton-bound homodimers or homotrimers. We further investigated the thermodynamic stabilization of protonated amines, showing that encapsulation makes the amines more basic in the cavity. Encapsulation raises the effective basicity of protonated amines by up to 4.5 pK a units, a difference almost as large as that between the moderate and strong bases carbonate and hydroxide. The thermodynamic stabilization of

The age factor in axonal repair after spinal cord injury: A focus on neuron-intrinsic mechanisms.

Science.gov (United States)

Geoffroy, Cédric G; Meves, Jessica M; Zheng, Binhai

2017-06-23

Age is an important consideration for recovery and repair after spinal cord injury. Spinal cord injury is increasingly affecting the middle-aged and aging populations. Despite rapid progress in research to promote axonal regeneration and repair, our understanding of how age can modulate this repair is rather limited. In this review, we discuss the literature supporting the notion of an age-dependent decline in axonal growth after central nervous system (CNS) injury. While both neuron-intrinsic and extrinsic factors are involved in the control of axon growth after injury, here we focus on possible intrinsic mechanisms for this age-dependent decline. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

Relationship among the repair mechanisms and the genetic recombination

International Nuclear Information System (INIS)

Alcantara D, D.

1987-12-01

In accordance with the previous reports of the Project BZ87 of the Department of Radiobiology, a dependent stimulation of the system exists in E.coli SOS, of the recombination of the bacteriophage Lambda whose genetic material has not been damaged. This stimulation is not due to the increase of the cellular concentration of the protein RecA and the mechanism but probable for which we find that it is carried out, it is through a cooperation among the product of the gene rec N of E. coli and the system Net of recombination of Lambda. The gene recN belongs to the group of genes SOS and its expression is induced when damaging the bacterial DNA where it intervenes in the repair of breaks of the double helix of the molecule (Picksley et, 1984). If the repair of breaks of this type is a factor that limits the speed with which it happens the recombination among viral chromosomes, then the biggest readiness in the protein RecN, due to the induction of the functions SOS, would facilitate the repair of such ruptures. In this new project it is to enlarge the knowledge about this phenomenon, it was, on one hand of corroborating in a way but he/she specifies the relationship between the recombinogenic response of Lambda and the System SOS of E. coli and for the other one to determine the effect that has the inhibition of the duplication of the DNA on the stimulation of the viral recombination. Everything it with the idea of making it but evident and to be able to use it as a system of genotoxic agents detection in E. coli. (Author)

Low Dose Radiation-Induced Genome and Epigenome Instability Symposium and Epigenetic Mechanisms, DNA Repair, and Chromatin Symposium at the EMS 2008 Annual Meeting - October 2008

Energy Technology Data Exchange (ETDEWEB)

Morgan, William F; Kovalchuk, Olga; Dolinoy, Dana C; Dubrova, Yuri E; Coleman, Matthew A; Schär, Primo; Pogribny, Igor; Hendzel, Michael

2010-02-19

The Low Dose Radiation Symposium thoughtfully addressed ionizing radiation non-mutational but transmissable alterations in surviving cells. Deregulation of epigenetic processes has been strongly implicated in carcinogenesis, and there is increasing realization that a significant fraction of non-targeted and adaptive mechanisms in response to ionizing radiation are likely to be epigenetic in nature. Much remains to be learned about how chromatin and epigenetic regulators affect responses to low doses of radiation, and how low dose radiation impacts other epigenetic processes. The Epigenetic Mechanisms Symposium focused on on epigenetic mechanisms and their interplay with DNA repair and chromatin changes. Addressing the fact that the most well understood mediators of epigenetic regulation are histone modifications and DNA methylation. Low levels of radiation can lead to changes in the methylation status of certain gene promoters and the expression of DNA methyltransferases, However, epigenetic regulation can also involve changes in higher order chromosome structure.

The relative contribution of paracine effect versus direct differentiation on adipose-derived stem cell transplantation mediated cardiac repair.

Directory of Open Access Journals (Sweden)

Dezhong Yang

Full Text Available BACKGROUND: Recent studies have demonstrated that transplantation of adipose-derived stem cell (ADSC can improve cardiac function in animal models of myocardial infarction (MI. However, the mechanisms underlying the beneficial effect are not fully understood. In this study, we characterized the paracrine effect of transplanted ADSC and investigated its relative importance versus direct differentiation in ADSC transplantation mediated cardiac repair. METHODOLOGY/PRINCIPAL FINDINGS: MI was experimentally induced in mice by ligation of the left anterior descending coronary artery. Either human ADSC, conditioned medium (CM collected from the same amount of ADSC or control medium was injected into the peri-infarct region immediately after MI. Compared with the control group, both ADSC and ADSC-CM significantly reduced myocardial infarct size and improved cardiac function. The therapeutic efficacy of ADSC was moderately superior to ADSC-CM. ADSC-CM significantly reduced cardiomyocyte apoptosis in the infarct border zone, to a similar degree with ADSC treatment. ADSC enhanced angiogenesis in the infarct border zone, but to a stronger degree than that seen in the ADSC-CM treatment. ADSC was able to differentiate to endothelial cell and smooth muscle cell in post-MI heart; these ADSC-derived vascular cells amount to about 9% of the enhanced angiogenesis. No cardiomyocyte differentiated from ADSC was found. CONCLUSIONS: ADSC-CM is sufficient to improve cardiac function of infarcted hearts. The therapeutic function of ADSC transplantation is mainly induced by paracrine-mediated cardioprotection and angiogenesis, while ADSC differentiation contributes a minor benefit by being involved in angiogenesis. Highlights 1 ADSC-CM is sufficient to exert a therapeutic potential. 2. ADSC was able to differentiate to vascular cells but not cardiomyocyte. 3. ADSC derived vascular cells amount to about 9% of the enhanced angiogenesis. 4. Paracrine effect is the major

MECHANISMS OF MICROBE-HOST-INTERACTION IN CROHN'S DISEASE: DYSBIOSIS VS. PATHOBIONT SELECTION

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Ludovica F. Buttó

2015-11-01

Full Text Available Crohn’s disease (CD is a systemic chronic inflammatory condition mainly characterized by discontinuous transmural pathology of the gastrointestinal tract and frequent extra-intestinal manifestations with intermittent episodes of remission and relapse. Genome-wide association studies identified a number of risk loci that, catalyzed by environmental triggers, result in the loss of tolerance towards commensal bacteria based on dysregulated innate effector functions and anti-microbial defense, leading to exacerbated adaptive immune responses responsible for chronic immune-mediated tissue damage. In this review, we discuss the interrelated role of changes in the intestinal microbiota, epithelial barrier integrity and immune cell functions on the pathogenesis of CD, describing the current approaches available to investigate the molecular mechanisms underlying the disease. Substantial effort has been dedicated to define disease-associated changes in the intestinal microbiota (dysbiosis and to link pathobionts to the aetiology of IBD. A cogent definition of dysbiosis is lacking, as well as an agreement of whether pathobionts or complex shifts in the microbiota trigger inflammation in the host. Among the rarely available animal models, SAMP/Yit and TNFdeltaARE mice are the best known displaying a transmural CD-like phenotype. New hypothesis-driven mouse models e.g. epithelial-specific Caspase8-/-, ATG16L1-/- and XBP-1-/- mice validate pathway-focused function of specific CD-associated risk genes highlighting the role of Paneth cells in antimicrobial defense. To study the causal role of bacteria in initiating inflammation in the host, the use of germfree mouse models is indispensable. Unraveling the interactions of genes, immune cells and microbes constitute a criterion for the development of safe, reliable and effective treatment options for CD.

Genipin crosslinker releasing sutures for improving the mechanical/repair strength of damaged connective tissue.

Science.gov (United States)

Sundararaj, Sharath; Slusarewicz, Paul; Brown, Matt; Hedman, Thomas

2017-11-01

The most common mode of surgical repair of ruptured tendons and ligaments involves the use of sutures for reattachment. However, there is a high incidence of rerupture and repair failure due to pulling out of the suture material from the damaged connective tissue. The main goal of this research was to achieve a localized delivery of crosslinking agent genipin (GP) from rapid-release biodegradable coatings on sutures, for strengthening the repair of ruptured connective tissue. Our hypothesis is that GP released from the suture coating will lead to exogenous crosslinking of native connective tissue resulting in beneficial effects on clinically relevant mechanical parameters such as tear resistance, tissue strength, and energy required to rupture the tissue (toughness). Sutures were successfully coated with a biodegradable polymer layer loaded with the crosslinking agent genipin, without compromising the mechanical properties of the suture. The rapid-release of genipin was achieved under both in vitro and ex vivo conditions. Exogenous crosslinking using these genipin releasing sutures was demonstrated using equine tendons. The tendons treated with genipin releasing sutures showed significant improvement in failure load, energy required for pull-out failure, and stiffness. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 2199-2205, 2017. © 2016 Wiley Periodicals, Inc.

Evidence for repair of ultraviolet light-damaged herpes virus in human fibroblasts by a recombination mechanism

International Nuclear Information System (INIS)

Hall, J.D.; Featherston, J.D.; Almy, R.E.

1980-01-01

Human cells were either singly or multiply infected with herpes simplex virus (HSV-1) damaged by ultraviolet (uv) light, and the fraction of cells able to produce infectious virus was measured. The fraction of virus-producing cells was considerably greater for multiply infected cells than for singly infected cells at each uv dose examined. These high survival levels of uv-irradiated virus in multiply infected cells demonstrated that multiplicity-dependent repair, possibly due to genetic exchanges between damaged HSV-1 genomes, was occurring in these cells. To test whether uv light is recombinogenic for HSV-1, the effect of uv irradiation on the yield of temperature-resistant viral recombinants in cells infected with pairs of temperature-sensitive mutants was also investigated. The results of these experiments showed that the defective functions in these mutant host cells are not required for multiplicity-dependent repair or uv-stimulated viral recombination in herpes-infected cells

Cytokines in the host response to Candida vaginitis: Identifying a role for non-classical immune mediators, S100 alarmins

Science.gov (United States)

Yano, Junko; Noverr, Mairi C.; Fidel, Paul L.

2011-01-01

Vulvovaginal candidiasis (VVC), caused by Candida albicans, affects a significant number of women during their reproductive years. More than two decades of research have been focused on the mechanisms associated with susceptibility or resistance to symptomatic infection. Adaptive immunity by Th1-type CD4+ T cells and downstream cytokine responses are considered the predominant host defense mechanisms against mucosal Candida infections. However, numerous clinical and animal studies have indicated no or limited protective role of cells and cytokines of the Th1 or Th2 lineage against vaginal infection. The role for Th17 is only now begun to be investigated in-depth for VVC with results already showing significant controversy. On the other hand, a clinical live-challenge study and an established animal model have shown that a symptomatic condition is intimately associated with the vaginal infiltration of polymorphonuclear leukocytes (PMNs) but with no effect on vaginal fungal burden. Subsequent studies identified S100A8 and S100A9 Alarmins as key chemotactic mediators of the acute PMN response. These chemotactic danger signals appear to be secreted by vaginal epithelial cells upon interaction and early adherence of Candida. Thus, instead of a putative immunodeficiency against Candida involving classical immune cells and cytokines of the adaptive response, the pathological inflammation in VVC is now considered a consequence of a non-productive innate response initiated by non-classical immune mediators. PMID:22182685

Malaria-induced changes in host odors enhance mosquito attraction.

Science.gov (United States)

De Moraes, Consuelo M; Stanczyk, Nina M; Betz, Heike S; Pulido, Hannier; Sim, Derek G; Read, Andrew F; Mescher, Mark C

2014-07-29

Vector-borne pathogens may alter traits of their primary hosts in ways that influence the frequency and nature of interactions between hosts and vectors. Previous work has reported enhanced mosquito attraction to host organisms infected with malaria parasites but did not address the mechanisms underlying such effects. Here we document malaria-induced changes in the odor profiles of infected mice (relative to healthy individuals) over the course of infection, as well as effects on the attractiveness of infected hosts to mosquito vectors. We observed enhanced mosquito attraction to infected mice during a key period after the subsidence of acute malaria symptoms, but during which mice remained highly infectious. This attraction corresponded to an overall elevation in the volatile emissions of infected mice observed during this period. Furthermore, data analyses--using discriminant analysis of principal components and random forest approaches--revealed clear differences in the composition of the volatile blends of infected and healthy individuals. Experimental manipulation of individual compounds that exhibited altered emission levels during the period when differential vector attraction was observed also elicited enhanced mosquito attraction, indicating that compounds being influenced by malaria infection status also mediate vector host-seeking behavior. These findings provide important insights into the cues that mediate vector attraction to hosts infected with transmissible stages of malaria parasites, as well as documenting characteristic changes in the odors of infected individuals that may have potential value as diagnostic biomarkers of infection.

Repair of ultraviolet-light damaged ColE1 factor carrying Escherichia coli genes for guanine synthesis

International Nuclear Information System (INIS)

Kibe, A.; Shimada, K.; Tagaki, Y.

1979-01-01

Hybrid ColE1 plasmids called ColE1-cos lambda-guaA or ColE1-cos lambda-gal can be efficiently transduced into various E.coli K-12 cells through packaging into lambda phage particles. Using these plasmids, repair of ultraviolet-light (UV) damaged ColE1 DNAs was studied in various UV sensitive E.coli K-12 mutants. The host mutations uvrA and uvrB markedly reduced host-cell reactivation of UV-irradiated ColE1-cos lambda-guaA. Pre-existing hybrid ColE1 plasmids had no effect on the frequency of lambda phage-mediated transduction of another differentially marked hybrid ColE1 DNAs. ColE1-cos lambda-guaA and ColE1-cos lambda-gal DNAs could temporarily but not stably co-exist in E.coli K-12 recA cells. The presence of ColE1-cos lambda-gal in uvrB cells promoted the repair of super-infected UV-irradiated ColE1-cos lambda-guaA about 7-fold. The same ColE1-cos lambda-gal plasmid in a uvrB recA double mutant did not have this promoting effect. These results indicate that the effect of resident hybrid ColE1 plasmids is manifested by the host recA + gene function(s) and suggest that ColE1 plasmit itself provides no recA + -like functions. (orig.) [de

Repair of ultraviolet-light damaged ColE1 factor carrying Escherichia coli genes for guanine synthesis

Energy Technology Data Exchange (ETDEWEB)

Kibe, A; Shimada, K; Tagaki, Y [Kyushu Univ., Fukuoka (Japan). Dept. of Biochemistry

1979-01-01

Hybrid ColE1 plasmids called ColE1-cos lambda-guaA or ColE1-cos lambda-gal can be efficiently transduced into various E.coli K-12 cells through packaging into lambda phage particles. Using these plasmids, repair of ultraviolet-light (UV) damaged ColE1 DNAs was studied in various UV sensitive E.coli K-12 mutants. The host mutations uvrA and uvrB markedly reduced host-cell reactivation of UV-irradiated ColE1-cos lambda-guaA. Pre-existing hybrid ColE1 plasmids had no effect on the frequency of lambda phage-mediated transduction of another differentially marked hybrid ColE1 DNAs. ColE1-cos lambda-guaA and ColE1-cos lambda-gal DNAs could temporarily but not stably co-exist in E.coli K-12 recA cells. The presence of ColE1-cos lambda-gal in uvrB cells promoted the repair of super-infected UV-irradiated ColE1-cos lambda-guaA about 7-fold. The same ColE1-cos lambda-gal plasmid in a uvrB recA double mutant did not have this promoting effect. These results indicate that the effect of resident hybrid ColE1 plasmids is manifested by the host recA/sup +/ gene function(s) and suggest that ColE1 plasmit itself provides no recA/sup +/-like functions.

DNA repair

International Nuclear Information System (INIS)

Van Zeeland, A.A.

1984-01-01

In this chapter a series of DNA repair pathways are discussed which are available to the cell to cope with the problem of DNA damaged by chemical or physical agents. In the case of microorganisms our knowledge about the precise mechanism of each DNA repair pathway and the regulation of it has been improved considerably when mutants deficient in these repair mechanisms became available. In the case of mammalian cells in culture, until recently there were very little repair deficient mutants available, because in almost all mammalian cells in culture at least the diploid number of chromosomes is present. Therefore the frequency of repair deficient mutants in such populations is very low. Nevertheless because replica plating techniques are improving some mutants from Chinese hamsters ovary cells and L5178Y mouse lymphoma cells are now available. In the case of human cells, cultures obtained from patients with certain genetic diseases are available. A number of cells appear to be sensitive to some chemical or physical mutagens. These include cells from patients suffering from xeroderma pigmentosum, Ataxia telangiectasia, Fanconi's anemia, Cockayne's syndrome. However, only in the case of xeroderma pigmentosum cells, has the sensitivity to ultraviolet light been clearly correlated with a deficiency in excision repair of pyrimidine dimers. Furthermore the work with strains obtained from biopsies from man is difficult because these cells generally have low cloning efficiencies and also have a limited lifespan in vitro. It is therefore very important that more repair deficient mutants will become available from established cell lines from human or animal origin

DNA repair mechanisms in cancer development and therapy.

Science.gov (United States)

Torgovnick, Alessandro; Schumacher, Björn

2015-01-01

DNA damage has been long recognized as causal factor for cancer development. When erroneous DNA repair leads to mutations or chromosomal aberrations affecting oncogenes and tumor suppressor genes, cells undergo malignant transformation resulting in cancerous growth. Genetic defects can predispose to cancer: mutations in distinct DNA repair systems elevate the susceptibility to various cancer types. However, DNA damage not only comprises a root cause for cancer development but also continues to provide an important avenue for chemo- and radiotherapy. Since the beginning of cancer therapy, genotoxic agents that trigger DNA damage checkpoints have been applied to halt the growth and trigger the apoptotic demise of cancer cells. We provide an overview about the involvement of DNA repair systems in cancer prevention and the classes of genotoxins that are commonly used for the treatment of cancer. A better understanding of the roles and interactions of the highly complex DNA repair machineries will lead to important improvements in cancer therapy.

DNA Repair Mechanisms in Cancer Development and Therapy

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Alessandro eTorgovnick

2015-04-01

Full Text Available DNA damage has been long recognized as causal factor for cancer development. When erroneous DNA repair leads to mutations or chromosomal aberrations affecting oncogenes and tumor suppressor genes, cells undergo malignant transformation resulting in cancerous growth. Genetic defects can predispose to cancer: Mutations in distinct DNA repair systems elevate the susceptibility to various cancer types. However, DNA damage not only comprises a root cause for cancer development but also continues to provide an important avenue for chemo- and radiotherapy. Since the beginning of cancer therapy, genotoxic agents have been applied that trigger DNA damage checkpoints that halt the growth and trigger the apoptotic demise of cancer cells. We provide an overview about the involvement of DNA repair systems in cancer prevention and the classes of genotoxins that are commonly used for the treatment of cancer. A better understanding of the roles and interactions of the highly complex DNA repair machineries will lead to important improvements in cancer therapy.

Co-transcriptomic Analysis by RNA Sequencing to Simultaneously Measure Regulated Gene Expression in Host and Bacterial Pathogen

KAUST Repository

Ravasi, Timothy; Mavromatis, Charalampos Harris; Bokil, Nilesh J.; Schembri, Mark A.; Sweet, Matthew J.

2016-01-01

Intramacrophage pathogens subvert antimicrobial defence pathways using various mechanisms, including the targeting of host TLR-mediated transcriptional responses. Conversely, TLR-inducible host defence mechanisms subject intramacrophage pathogens to stress, thus altering pathogen gene expression programs. Important biological insights can thus be gained through the analysis of gene expression changes in both the host and the pathogen during an infection. Traditionally, research methods have involved the use of qPCR, microarrays and/or RNA sequencing to identify transcriptional changes in either the host or the pathogen. Here we describe the application of RNA sequencing using samples obtained from in vitro infection assays to simultaneously quantify both host and bacterial pathogen gene expression changes, as well as general approaches that can be undertaken to interpret the RNA sequencing data that is generated. These methods can be used to provide insights into host TLR-regulated transcriptional responses to microbial challenge, as well as pathogen subversion mechanisms against such responses.

Co-transcriptomic Analysis by RNA Sequencing to Simultaneously Measure Regulated Gene Expression in Host and Bacterial Pathogen

KAUST Repository

Ravasi, Timothy

2016-01-24

Intramacrophage pathogens subvert antimicrobial defence pathways using various mechanisms, including the targeting of host TLR-mediated transcriptional responses. Conversely, TLR-inducible host defence mechanisms subject intramacrophage pathogens to stress, thus altering pathogen gene expression programs. Important biological insights can thus be gained through the analysis of gene expression changes in both the host and the pathogen during an infection. Traditionally, research methods have involved the use of qPCR, microarrays and/or RNA sequencing to identify transcriptional changes in either the host or the pathogen. Here we describe the application of RNA sequencing using samples obtained from in vitro infection assays to simultaneously quantify both host and bacterial pathogen gene expression changes, as well as general approaches that can be undertaken to interpret the RNA sequencing data that is generated. These methods can be used to provide insights into host TLR-regulated transcriptional responses to microbial challenge, as well as pathogen subversion mechanisms against such responses.

Mechanisms and mediators of hypertension induced by erythropoietin and related molecules.

Science.gov (United States)

Agarwal, Rajiv

2017-12-08

Hypertension is a common but frequently overlooked adverse effect of erythropoietin (EPO) therapy. Underreporting of hypertension with EPO is likely due to either more aggressively managing hypertension through the prescription of antihypertensive drugs or closer attention to dry weight. The purpose and focus of this review is to critically evaluate the mechanisms of EPO-induced hypertension. Preclinical data are considered first, followed by clinical data where available. Mediated by a variety of molecules, there is an imbalance in the vascular tone favoring net vasoconstriction that mediates EPO-induced hypertension. Animal studies show the primary importance of chronic kidney disease in the genesis of EPO-induced hypertension. Preclinical studies show deranged regulation of the nitric oxide, endothelins and porstanoids and the sympathoadrenal and renin-angiotensin pathways as causes of EPO-induced hypertension. Human studies suggest that EPO administration is also associated with increased responsiveness to catecholamines and angiotensin II on vascular tissue; in addition, hypoxia-induced vasodilation may be impaired in those with EPO-induced hypertension. There is little evidence for EPO as a direct vasoconstrictor or its effect on blood viscosity as a mechanism of EPO-induced hypertension. EPO-induced hypertension, at least in part, appears to be independent of an increase in hemoglobin, because experiments show that hemoglobin may be increased by EPO without an increase in blood pressure (BP) by simply treating the animals with EPO-binding protein and that treatment with EPO in the setting of iron deficiency may not increase hemoglobin but may still increase BP. However, experimental data are not consistent across studies and better mechanistic designs are needed, especially in patients with chronic kidney disease, to dissect the precise mechanism of EPO-induced hypertension. Animal studies suggest that hypoxia-inducible factor stablizers may induce

ASPECTS REGARDING THE METHOD OF REALIZING THE TECHNICAL EXPERTISE FOR REPAIRING THE TRANSLATION MECHANISM OF A M4A COAL-MINING MACHINE

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Marius Liviu CÎRȚÎNĂ

2018-05-01

Full Text Available This paper presents the technical state of the mechanism of translation of the coalmining machine after the technical expertise. The rehabilitation to which the translation mechanism will be subjected will be carried out by performing the intervention works that will bring back into the normal operating parameters both the structural part and the functional part. The paper presents: the proposed solutions for repair after verification of the translation mechanism and the way of repairing the mechanism.

Dental Pulp Defence and Repair Mechanisms in Dental Caries.

Science.gov (United States)

Farges, Jean-Christophe; Alliot-Licht, Brigitte; Renard, Emmanuelle; Ducret, Maxime; Gaudin, Alexis; Smith, Anthony J; Cooper, Paul R

2015-01-01

Dental caries is a chronic infectious disease resulting from the penetration of oral bacteria into the enamel and dentin. Microorganisms subsequently trigger inflammatory responses in the dental pulp. These events can lead to pulp healing if the infection is not too severe following the removal of diseased enamel and dentin tissues and clinical restoration of the tooth. However, chronic inflammation often persists in the pulp despite treatment, inducing permanent loss of normal tissue and reducing innate repair capacities. For complete tooth healing the formation of a reactionary/reparative dentin barrier to distance and protect the pulp from infectious agents and restorative materials is required. Clinical and in vitro experimental data clearly indicate that dentin barrier formation only occurs when pulp inflammation and infection are minimised, thus enabling reestablishment of tissue homeostasis and health. Therefore, promoting the resolution of pulp inflammation may provide a valuable therapeutic opportunity to ensure the sustainability of dental treatments. This paper focusses on key cellular and molecular mechanisms involved in pulp responses to bacteria and in the pulpal transition between caries-induced inflammation and dentinogenic-based repair. We report, using selected examples, different strategies potentially used by odontoblasts and specialized immune cells to combat dentin-invading bacteria in vivo.

Dental Pulp Defence and Repair Mechanisms in Dental Caries

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Jean-Christophe Farges

2015-01-01

Full Text Available Dental caries is a chronic infectious disease resulting from the penetration of oral bacteria into the enamel and dentin. Microorganisms subsequently trigger inflammatory responses in the dental pulp. These events can lead to pulp healing if the infection is not too severe following the removal of diseased enamel and dentin tissues and clinical restoration of the tooth. However, chronic inflammation often persists in the pulp despite treatment, inducing permanent loss of normal tissue and reducing innate repair capacities. For complete tooth healing the formation of a reactionary/reparative dentin barrier to distance and protect the pulp from infectious agents and restorative materials is required. Clinical and in vitro experimental data clearly indicate that dentin barrier formation only occurs when pulp inflammation and infection are minimised, thus enabling reestablishment of tissue homeostasis and health. Therefore, promoting the resolution of pulp inflammation may provide a valuable therapeutic opportunity to ensure the sustainability of dental treatments. This paper focusses on key cellular and molecular mechanisms involved in pulp responses to bacteria and in the pulpal transition between caries-induced inflammation and dentinogenic-based repair. We report, using selected examples, different strategies potentially used by odontoblasts and specialized immune cells to combat dentin-invading bacteria in vivo.

Genome-wide maps of alkylation damage, repair, and mutagenesis in yeast reveal mechanisms of mutational heterogeneity.

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Mao, Peng; Brown, Alexander J; Malc, Ewa P; Mieczkowski, Piotr A; Smerdon, Michael J; Roberts, Steven A; Wyrick, John J

2017-10-01

DNA base damage is an important contributor to genome instability, but how the formation and repair of these lesions is affected by the genomic landscape and contributes to mutagenesis is unknown. Here, we describe genome-wide maps of DNA base damage, repair, and mutagenesis at single nucleotide resolution in yeast treated with the alkylating agent methyl methanesulfonate (MMS). Analysis of these maps revealed that base excision repair (BER) of alkylation damage is significantly modulated by chromatin, with faster repair in nucleosome-depleted regions, and slower repair and higher mutation density within strongly positioned nucleosomes. Both the translational and rotational settings of lesions within nucleosomes significantly influence BER efficiency; moreover, this effect is asymmetric relative to the nucleosome dyad axis and is regulated by histone modifications. Our data also indicate that MMS-induced mutations at adenine nucleotides are significantly enriched on the nontranscribed strand (NTS) of yeast genes, particularly in BER-deficient strains, due to higher damage formation on the NTS and transcription-coupled repair of the transcribed strand (TS). These findings reveal the influence of chromatin on repair and mutagenesis of base lesions on a genome-wide scale and suggest a novel mechanism for transcription-associated mutation asymmetry, which is frequently observed in human cancers. © 2017 Mao et al.; Published by Cold Spring Harbor Laboratory Press.

Pathogen- and Host-Directed Antileishmanial Effects Mediated by Polyhexanide (PHMB.

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Rebuma Firdessa

Full Text Available Cutaneous leishmaniasis (CL is a neglected tropical disease caused by protozoan parasites of the genus Leishmania. CL causes enormous suffering in many countries worldwide. There is no licensed vaccine against CL, and the chemotherapy options show limited efficacy and high toxicity. Localization of the parasites inside host cells is a barrier to most standard chemo- and immune-based interventions. Hence, novel drugs, which are safe, effective and readily accessible to third-world countries and/or drug delivery technologies for effective CL treatments are desperately needed.Here we evaluated the antileishmanial properties and delivery potential of polyhexamethylene biguanide (PHMB; polyhexanide, a widely used antimicrobial and wound antiseptic, in the Leishmania model. PHMB showed an inherent antileishmanial activity at submicromolar concentrations. Our data revealed that PHMB kills Leishmania major (L. major via a dual mechanism involving disruption of membrane integrity and selective chromosome condensation and damage. PHMB's DNA binding and host cell entry properties were further exploited to improve the delivery and immunomodulatory activities of unmethylated cytosine-phosphate-guanine oligodeoxynucleotides (CpG ODN. PHMB spontaneously bound CpG ODN, forming stable nanopolyplexes that enhanced uptake of CpG ODN, potentiated antimicrobial killing and reduced host cell toxicity of PHMB.Given its low cost and long history of safe topical use, PHMB holds promise as a drug for CL therapy and delivery vehicle for nucleic acid immunomodulators.

Microbial endocrinology: Host-microbiota neuroendocrine interactions influencing brain and behavior.

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Lyte, Mark

2014-01-01

The ability of microorganisms, whether present as commensals within the microbiota or introduced as part of a therapeutic regimen, to influence behavior has been demonstrated by numerous laboratories over the last few years. Our understanding of the mechanisms that are responsible for microbiota-gut-brain interactions is, however, lacking. The complexity of the microbiota is, of course, a contributing factor. Nonetheless, while microbiologists approaching the issue of microbiota-gut-brain interactions in the behavior well recognize such complexity, what is often overlooked is the equal complexity of the host neurophysiological system, especially within the gut which is differentially innervated by the enteric nervous system. As such, in the search for common mechanisms by which the microbiota may influence behavior one may look for mechanisms which are shared by both host and microbiota. Such interkingdom signaling can be found in the shared production of neurochemical mediators that are found in both eukaryotes and prokaryotes. The study of the production and recognition of neurochemicals that are exactly the same in structure to those produced in the vertebrate organisms is known as microbial endocrinology. The examination of the microbiota from the vantage point of host-microbiota neuroendocrine interactions cannot only identify new microbial endocrinology-based mechanisms by which the microbiota can influence host behavior, but also lead to the design of interventions in which the composition of the microbiota may be modulated in order to achieve a specific microbial endocrinology-based profile beneficial to overall host behavior.

Biaxial analysis of synthetic scaffolds for hernia repair demonstrates variability in mechanical anisotropy, non-linearity and hysteresis.

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Deeken, Corey R; Thompson, Dominic M; Castile, Ryan M; Lake, Spencer P

2014-10-01

Over the past 60 years, the soft tissue repair market has grown to include over 50 types of hernia repair materials. Surgeons typically implant these materials in the orientation that provides maximum overlap of the mesh over the defect, with little regard for mechanical properties of the mesh material. If the characteristics of the meshes were better understood, an appropriate material could be identified for each patient, and meshes could be placed to optimize integration with neighboring tissue and avoid the mechanical mis-match that can lead to impaired graft fixation. The purpose of this study was to fully characterize and compare the mechanical properties of thirteen types of hernia repair materials via planar biaxial tensile testing. Equibiaxial (i.e., equal simultaneous loading in both directions) and strip biaxial (i.e., loading in one direction with the other direction held fixed) tests were utilized as physiologically relevant loading regimes. After applying a 0.1N pre-load on each arm, samples were subjected to equibiaxial cyclic loading using a triangular waveform to 2.5mm displacement on each arm at 0.1Hz for 10 cycles. Samples were then subjected to two strip biaxial tests (using the same cyclic loading protocol), where extension was applied along a single axis with the other axis held fixed. The thirteen evaluated mesh types exhibited a wide range of mechanical properties. Some were nearly isotropic (C-QUR™, DUALMESH(®), PHYSIOMESH™, and PROCEED(®)), while others were highly anisotropic (Ventralight™ ST, Bard™ Mesh, and Bard™ Soft Mesh). Some displayed nearly linear behavior (Bard™ Mesh), while others were non-linear with a long toe region followed by a sharp rise in tension (INFINIT(®)). These materials are currently utilized in clinical settings as if they are uniform and interchangeable, and clearly this is not the case. The mechanical properties most advantageous for successful hernia repairs are currently only vaguely described

Modulation of wound healing and scar formation by MG53 protein-mediated cell membrane repair.

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Li, Haichang; Duann, Pu; Lin, Pei-Hui; Zhao, Li; Fan, Zhaobo; Tan, Tao; Zhou, Xinyu; Sun, Mingzhai; Fu, Minghuan; Orange, Matthew; Sermersheim, Matthew; Ma, Hanley; He, Duofen; Steinberg, Steven M; Higgins, Robert; Zhu, Hua; John, Elizabeth; Zeng, Chunyu; Guan, Jianjun; Ma, Jianjie

2015-10-02

Cell membrane repair is an important aspect of physiology, and disruption of this process can result in pathophysiology in a number of different tissues, including wound healing, chronic ulcer and scarring. We have previously identified a novel tripartite motif family protein, MG53, as an essential component of the cell membrane repair machinery. Here we report the functional role of MG53 in the modulation of wound healing and scarring. Although MG53 is absent from keratinocytes and fibroblasts, remarkable defects in skin architecture and collagen overproduction are observed in mg53(-/-) mice, and these animals display delayed wound healing and abnormal scarring. Recombinant human MG53 (rhMG53) protein, encapsulated in a hydrogel formulation, facilitates wound healing and prevents scarring in rodent models of dermal injuries. An in vitro study shows that rhMG53 protects against acute injury to keratinocytes and facilitates the migration of fibroblasts in response to scratch wounding. During fibrotic remodeling, rhMG53 interferes with TGF-β-dependent activation of myofibroblast differentiation. The resulting down-regulation of α smooth muscle actin and extracellular matrix proteins contributes to reduced scarring. Overall, these studies establish a trifunctional role for MG53 as a facilitator of rapid injury repair, a mediator of cell migration, and a modulator of myofibroblast differentiation during wound healing. Targeting the functional interaction between MG53 and TGF-β signaling may present a potentially effective means for promoting scarless wound healing. © 2015 by The American Society for Biochemistry and Molecular Biology, Inc.

Mechanisms of Host-Pathogen Protein Complex Formation and Bacterial Immune Evasion of Streptococcus suis Protein Fhb.

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Li, Xueqin; Liu, Peng; Gan, Shuzhen; Zhang, Chunmao; Zheng, Yuling; Jiang, Yongqiang; Yuan, Yuan

2016-08-12

Streptococcus suis serotype 2 (S. suis 2)-induced sepsis and meningitis are often accompanied by bacteremia. The evasion of polymorphonuclear leukocyte-mediated phagocytic clearance is central to the establishment of bacteremia caused by S. suis 2 and is facilitated by the ability of factor H (FH)-binding protein (Fhb) to bind FH on the bacterial surface, thereby impeding alternative pathway complement activation and phagocytic clearance. Here, C3b/C3d was found to bind to Fhb, along with FH, forming a large immune complex. The formation of this immune complex was mediated by domain II of Fhb via electrostatic and hydrophobic interactions, which, to our knowledge, is a new type of interaction. Interestingly, Fhb was found to be associated with the cell envelope and also present in the culture supernatant, where secreted Fhb inhibited complement activation via interactions with domain II, thereby enhancing antiphagocytic clearance by polymorphonuclear leukocytes. Thus, Fhb is a multifunctional bacterial protein, which binds host complement component C3 as well as FH and interferes with innate immune recognition in a secret protein manner. S. suis 2 therefore appears to have developed a new strategy to combat host innate immunity and enhance survival in host blood. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Mechanisms of Host-Pathogen Protein Complex Formation and Bacterial Immune Evasion of Streptococcus suis Protein Fhb*

Science.gov (United States)

Li, Xueqin; Liu, Peng; Gan, Shuzhen; Zhang, Chunmao; Zheng, Yuling; Jiang, Yongqiang; Yuan, Yuan

2016-01-01

Streptococcus suis serotype 2 (S. suis 2)-induced sepsis and meningitis are often accompanied by bacteremia. The evasion of polymorphonuclear leukocyte-mediated phagocytic clearance is central to the establishment of bacteremia caused by S. suis 2 and is facilitated by the ability of factor H (FH)-binding protein (Fhb) to bind FH on the bacterial surface, thereby impeding alternative pathway complement activation and phagocytic clearance. Here, C3b/C3d was found to bind to Fhb, along with FH, forming a large immune complex. The formation of this immune complex was mediated by domain II of Fhb via electrostatic and hydrophobic interactions, which, to our knowledge, is a new type of interaction. Interestingly, Fhb was found to be associated with the cell envelope and also present in the culture supernatant, where secreted Fhb inhibited complement activation via interactions with domain II, thereby enhancing antiphagocytic clearance by polymorphonuclear leukocytes. Thus, Fhb is a multifunctional bacterial protein, which binds host complement component C3 as well as FH and interferes with innate immune recognition in a secret protein manner. S. suis 2 therefore appears to have developed a new strategy to combat host innate immunity and enhance survival in host blood. PMID:27342778

Formamidopyrimidines in DNA: mechanisms of formation, repair, and biological effects.

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Dizdaroglu, Miral; Kirkali, Güldal; Jaruga, Pawel

2008-12-15

Oxidatively induced damage to DNA results in a plethora of lesions comprising modified bases and sugars, DNA-protein cross-links, tandem lesions, strand breaks, and clustered lesions. Formamidopyrimidines, 4,6-diamino-5-formamidopyrimidine (FapyAde) and 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua), are among the major lesions generated in DNA by hydroxyl radical attack, UV radiation, or photosensitization under numerous in vitro and in vivo conditions. They are formed by one-electron reduction of C8-OH-adduct radicals of purines and thus have a common precursor with 8-hydroxypurines generated upon one-electron oxidation. Methodologies using mass spectrometry exist to accurately measure FapyAde and FapyGua in vitro and in vivo. Formamidopyrimidines are repaired by base excision repair. Numerous prokaryotic and eukaryotic DNA glycosylases are highly specific for removal of these lesions from DNA in the first step of this repair pathway, indicating their biological importance. FapyAde and FapyGua are bypassed by DNA polymerases with the insertion of the wrong intact base opposite them, leading to mutagenesis. In mammalian cells, the mutagenicity of FapyGua exceeds that of 8-hydroxyguanine, which is thought to be the most mutagenic of the oxidatively induced lesions in DNA. The background and formation levels of the former in vitro and in vivo equal or exceed those of the latter under various conditions. FapyAde and FapyGua exist in living cells at significant background levels and are abundantly generated upon exposure to oxidative stress. Mice lacking the genes that encode specific DNA glycosylases accumulate these lesions in different organs and, in some cases, exhibit a series of pathological conditions including metabolic syndrome and cancer. Animals exposed to environmental toxins accumulate formamidopyrimidines in their organs. Here, we extensively review the mechanisms of formation, measurement, repair, and biological effects of formamidopyrimidines

DNA repair genes RAD52 and SRS2, a cell wall synthesis regulator gene SMI1, and the membrane sterol synthesis scaffold gene ERG28 are important in efficient Agrobacterium-mediated yeast transformation with chromosomal T-DNA.

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Ohmine, Yuta; Satoh, Yukari; Kiyokawa, Kazuya; Yamamoto, Shinji; Moriguchi, Kazuki; Suzuki, Katsunori

2016-04-02

Plant pathogenic Agrobacterium strains can transfer T-DNA regions of their Ti plasmids to a broad range of eukaryotic hosts, including fungi, in vitro. In the recent decade, the yeast Saccharomyces cerevisiae is used as a model host to reveal important host proteins for the Agrobacterium-mediated transformation (AMT). Further investigation is required to understand the fundamental mechanism of AMT, including interaction at the cell surface, to expand the host range, and to develop new tools. In this study, we screened a yeast mutant library for low AMT mutant strains by advantage of a chromosome type T-DNA, which transfer is efficient and independent on integration into host chromosome. By the mutant screening, we identified four mutant strains (srs2Δ, rad52Δ, smi1Δ and erg28Δ), which showed considerably low AMT efficiency. Structural analysis of T-DNA product replicons in AMT colonies of mutants lacking each of the two DNA repair genes, SRS2 and RAD52, suggested that the genes act soon after T-DNA entry for modification of the chromosomal T-DNA to stably maintain them as linear replicons and to circularize certain T-DNA simultaneously. The cell wall synthesis regulator SMI1 might have a role in the cell surface interaction between the donor and recipient cells, but the smi1Δ mutant exhibited pleiotropic effect, i.e. low effector protein transport as well as low AMT for the chromosomal T-DNA, but relatively high AMT for integrative T-DNAs. The ergosterol synthesis regulator/enzyme-scaffold gene ERG28 probably contributes by sensing a congested environment, because growth of erg28Δ strain was unaffected by the presence of donor bacterial cells, while the growth of the wild-type and other mutant yeast strains was suppressed by their presence. RAD52 and the DNA helicase/anti-recombinase gene SRS2 are necessary to form and maintain artificial chromosomes through the AMT of chromosomal T-DNA. A sterol synthesis scaffold gene ERG28 is important in the high

DNA repair in human fibroblasts, as reflected by host-cell reactivation of a transfected UV-irradiated luciferase gene, is not related to donor age

International Nuclear Information System (INIS)

Merkle, Thomas J.; O'Brien, Katherine; Brooks, Philip J.; Tarone, Robert E.; Robbins, Jay H.

2004-01-01

The effect of donor age on the ability of mammalian cells to repair ultraviolet (UV)-induced DNA damage has been studied using several approaches, most recently via assays that measure the host-cell reactivation (HCR) of UV-irradiated reporter gene-containing plasmid vectors following their transfection into cells. Plasmid HCR assays indirectly quantify a cell line's ability to perform nucleotide excision repair (NER) by measuring the enzyme activity of the repaired reporter gene, e.g., chloramphenical acetyltransferase (cat) or luciferase (luc), and are useful in studies investigating whether increasing age may be a risk factor for the deficient repair of potentially cancer-causing, sunlight-induced, DNA lesions in skin cells. In our study, we quantified the DNA repair ability of cultured, nontransformed, human skin fibroblast lines through their HCR of a transfected UV-C-irradiated plasmid containing luc. HCR was measured at various times after transfection in five lines from normal donors of ages 21-96 years, and from one donor who had xeroderma pigmentosum (XP). The normal lines displayed increasing HCR at successive post-transfection time points and showed no significant correlation between HCR and donor age. The XP-A line, known to be markedly deficient in NER of UV-induced DNA damage, showed minimal evidence of HCR compared to the normal lines. To further assess potential variation in HCR with donor age, fibroblast lines from five old donors, ages 84-94 years, were compared with lines from five young donors, ages 17-26 years. While significant differences in HCR were found between some lines, no significant difference was found between the young and old age groups (P=0.44). Our study provides no indication that the higher incidence of skin cancer observed with increasing age is due to an age-related decrease in the ability to repair UV-induced DNA damage

DNA repair in human fibroblasts, as reflected by host-cell reactivation of a transfected UV-irradiated luciferase gene, is not related to donor age

Energy Technology Data Exchange (ETDEWEB)

Merkle, Thomas J.; O' Brien, Katherine; Brooks, Philip J.; Tarone, Robert E.; Robbins, Jay H

2004-10-04

The effect of donor age on the ability of mammalian cells to repair ultraviolet (UV)-induced DNA damage has been studied using several approaches, most recently via assays that measure the host-cell reactivation (HCR) of UV-irradiated reporter gene-containing plasmid vectors following their transfection into cells. Plasmid HCR assays indirectly quantify a cell line's ability to perform nucleotide excision repair (NER) by measuring the enzyme activity of the repaired reporter gene, e.g., chloramphenical acetyltransferase (cat) or luciferase (luc), and are useful in studies investigating whether increasing age may be a risk factor for the deficient repair of potentially cancer-causing, sunlight-induced, DNA lesions in skin cells. In our study, we quantified the DNA repair ability of cultured, nontransformed, human skin fibroblast lines through their HCR of a transfected UV-C-irradiated plasmid containing luc. HCR was measured at various times after transfection in five lines from normal donors of ages 21-96 years, and from one donor who had xeroderma pigmentosum (XP). The normal lines displayed increasing HCR at successive post-transfection time points and showed no significant correlation between HCR and donor age. The XP-A line, known to be markedly deficient in NER of UV-induced DNA damage, showed minimal evidence of HCR compared to the normal lines. To further assess potential variation in HCR with donor age, fibroblast lines from five old donors, ages 84-94 years, were compared with lines from five young donors, ages 17-26 years. While significant differences in HCR were found between some lines, no significant difference was found between the young and old age groups (P=0.44). Our study provides no indication that the higher incidence of skin cancer observed with increasing age is due to an age-related decrease in the ability to repair UV-induced DNA damage.

Role of mobile passenger lymphocytes in the rejection of renal and cardiac allografts in the rat. A passenger lymphocyte-mediated graft-versus-host reaction amplifies the host response

International Nuclear Information System (INIS)

van Vrieshilfgaarde, R.; Hermans, P.; Terpstra, J.L.; van Breda Viresman, P.J.

1980-01-01

It is demonstrated that passenger lymphocytes migrate out of rat renal allografts into host spleens in a radioresistant fashion. These mobile passenger lymphocytes within BN kidney and heart transplants are immunocompetent, since they elicit a graft-versus-host (GVH) reaction in the spleens of (LEW x BN)F2 hybrid hosts. The greater GVH reaction in (LEW x BN)F1 recipients of BN kidneys reflects the greater number of mobile passenger lymphocytes in the kidney when compared to the heart. The mobile passenger lymphocytes within BN renal allografts also cause a proliferative response in the spleens of the LEW hosts as well as an accelerated rejection of BN renal allografts when compared to BN cardiac allografts, for the differences between BN kidney and heart, both in terms of splenomegaly elicited in LEW as well as tempo of rejection, are abolished by total body x-irradiation of the donor with 900 rad. Results indicate that a mobile passenger lymphocyte mediated GVH reaction in the central lymphoid organs of the host augments the host response to allogenic kidneys and contributes materially to first-set renal allograft rejection; this GVH reaction on the other hand is not conspicuously present in LEW recipients of BN cardiac allografts and has therefore little effect on first-set cardiac allograft rejection

Molecular mechanism of short-patch repair of radiation-damaged DNA by in vitro reconstituted systems

International Nuclear Information System (INIS)

Matsumoto, Y.; Kim, K.; Biade, S.

1995-01-01

-strand breaks generated by γ-irradiation. Approximately 50% of the UV-irradiated IdU was also repaired by the PCNA-dependent pathway. Conclusion: The PCNA-dependent short-patch repair pathway serves not only as a back-up mechanism for the pol β-dependent pathway but also for the repair of the damage which cannot be a substrate for the pol β-dependent pathway. We are now investigating the characters of such lesions that are generated by ionizing radiation and are able to be repaired only by the PCNA-dependent pathway

Effects of off-specification procedures on the mechanical properties of half-bead weld repairs

International Nuclear Information System (INIS)

Hobson, D.O.; Nanstad, R.K.

1983-07-01

We examined the effects of off-specification procedures on the mechanical properties of half-bead weld repairs. The name half-bead is derived from the specification that half the thickness of the initial weld layer be ground off before the second layer is deposited. In this study the heat-affected zones of a weldment made with both all and none of the first layer removed were tested for toughness, hardness, and microstructural differences, and the results were compared with the properties of a protypical half-bead repair made under ASME Boiler and Pressure Vessel Code, Sect. XI, guidelines. The results of this limited study showed no apparent justification for the requirement to grind off half the first layer in this type of weld repair. The graded electrode sizes used to make the welds probably had more to do with the weld properties than did the range of first-layer thicknesses used in this study

Transfer of Chinese hamster DNA repair gene(s) into repair-deficient human cells (Xeroderma pigmentosum)

International Nuclear Information System (INIS)

Karentz, D.; Cleaver, J.E.

1985-01-01

Transfer of repair genes by DNA transfection into repair-deficient Xeroderma pigmentosum (XP) cells has thus far been unsuccessful, presenting an obstacle to cloning XP genes. The authors chose an indirect route to transfer repair genes in chromosome fragments. DNA repair-competent (UV resistant) hybrid cell lines were established by PEG-mediated fusions of DNA repair-deficient (UV sensitive) human fibroblasts (XP12RO) with wild type Chinese hamster (CHO) cells (AA8). CHO cells were exposed to 5 Krad X-rays prior to fusions, predisposing hybrid cells to lose CHO chromosome fragments preferentially. Repair-competent hybrids were selected by periodic exposures to UV light. Secondary and tertiary hybrid cell lines were developed by fusion of X-irradiated hybrids to XP12RO. The hybrid cell lines exhibit resistance to UV that is comparable to that of CHO cells and they are proficient at repair replication after UV exposure. Whole cell DNA-DNA hybridizations indicate that the hybrids have greater homology to CHO DNA than is evident between XP12RO and CHO. These observations indicate that CHO DNA sequences which can function in repair of UV-damaged DNA in human cells have been transferred into the genome of the repair-deficient XP12RO cells

A downy mildew effector attenuates salicylic acid-triggered immunity in Arabidopsis by interacting with the host mediator complex.

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Marie-Cécile Caillaud

2013-12-01

Full Text Available Plants are continually exposed to pathogen attack but usually remain healthy because they can activate defences upon perception of microbes. However, pathogens have evolved to overcome plant immunity by delivering effectors into the plant cell to attenuate defence, resulting in disease. Recent studies suggest that some effectors may manipulate host transcription, but the specific mechanisms by which such effectors promote susceptibility remain unclear. We study the oomycete downy mildew pathogen of Arabidopsis, Hyaloperonospora arabidopsidis (Hpa, and show here that the nuclear-localized effector HaRxL44 interacts with Mediator subunit 19a (MED19a, resulting in the degradation of MED19a in a proteasome-dependent manner. The Mediator complex of ∼25 proteins is broadly conserved in eukaryotes and mediates the interaction between transcriptional regulators and RNA polymerase II. We found MED19a to be a positive regulator of immunity against Hpa. Expression profiling experiments reveal transcriptional changes resembling jasmonic acid/ethylene (JA/ET signalling in the presence of HaRxL44, and also 3 d after infection with Hpa. Elevated JA/ET signalling is associated with a decrease in salicylic acid (SA-triggered immunity (SATI in Arabidopsis plants expressing HaRxL44 and in med19a loss-of-function mutants, whereas SATI is elevated in plants overexpressing MED19a. Using a PR1::GUS reporter, we discovered that Hpa suppresses PR1 expression specifically in cells containing haustoria, into which RxLR effectors are delivered, but not in nonhaustoriated adjacent cells, which show high PR1::GUS expression levels. Thus, HaRxL44 interferes with Mediator function by degrading MED19, shifting the balance of defence transcription from SA-responsive defence to JA/ET-signalling, and enhancing susceptibility to biotrophs by attenuating SA-dependent gene expression.

Important role of the nucleotide excision repair pathway in Mycobacterium smegmatis in conferring protection against commonly encountered DNA-damaging agents.

Science.gov (United States)

Kurthkoti, Krishna; Kumar, Pradeep; Jain, Ruchi; Varshney, Umesh

2008-09-01

Mycobacteria are an important group of human pathogens. Although the DNA repair mechanisms in mycobacteria are not well understood, these are vital for the pathogen's persistence in the host macrophages. In this study, we generated a null mutation in the uvrB gene of Mycobacterium smegmatis to allow us to compare the significance of the nucleotide excision repair (NER) pathway with two important base excision repair pathways, initiated by uracil DNA glycosylase (Ung) and formamidopyrimidine DNA glycosylase (Fpg or MutM), in an isogenic strain background. The strain deficient in NER was the most sensitive to commonly encountered DNA-damaging agents such as UV, low pH, reactive oxygen species, hypoxia, and was also sensitive to acidified nitrite. Taken together with previous observations on NER-deficient M. tuberculosis, these results suggest that NER is an important DNA repair pathway in mycobacteria.

Conceptualizing knowledge transfer between expatriates and host country nationals: The mediating effect of social capital

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Maimunah Ismail

2015-12-01

Full Text Available This paper aims to propose a conceptual model of knowledge transfer by relating two specific personal factors of expatriate and host country national (HCN dyads as antecedents of knowledge transfer, and mediated by social capital factors. An intensive literature review method was employed to identify and analyse relevant literatures. The paper used a dyadic bi-directional approach in theorizing knowledge transfer by integrating the social capital theory, and the anxiety and uncertainty management theory. The paper considers two personal factors (cultural intelligence and knowledge-seeking behaviour and two social capital variables (trust and shared vision as mediators of knowledge transfer. Upon model validation, the paper could offer practical interventions for human resource practitioners and managers to assist multinational corporations towards managing knowledge transfer involving expatriates and HCNs.

Studies on the molecular mechanism of nucleotide excision repair in human cells

International Nuclear Information System (INIS)

Friedberg, E.C.

1987-01-01

Studies in this laboratory have focused on attempts to define the mechanism of nucleotide excision repair of DNA in human cells, with a view to understanding the molecular pathogenesis of the disease XP. With the advent of recombinant DNA technology, they directed their efforts to the molecular cloning of human genes defective in XP, with a view to using the cloned genes to overexpress proteins of interest for biochemical investigations. Initial studies exploited the selectable phenotype of marked sensitivity to killing of XP group A cells by UV radiation and by other DNA damaging agents. However, except for a single report in 1982 there has been no reproducible demonstration of complementation of the UV sensitivity of XP cells by DNA-mediated transfection. The apparent difficulties associated with transfection of XP cells have been the subject of several recent studies. In view of the multiple problems associated with stable transfection of XP cells using total genomic DNA, they have embarked on an alternative strategy designed to facilitate the cloning of human XP genes. This strategy involves the transfer of single human chromosomes into XP cells and screening for this relatively high frequency event. The idea is to identify chromosomes on which particular XP genes reside and then to isolate non-complementing derivatives of these chromosomes so that highly enriched DNA pools containing genes of interest can be generated by employing one or more subtractive strategies

Seminal Fluid-Mediated Inflammation in Physiology and Pathology of the Female Reproductive Tract

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Anthonio O. Adefuye

2016-01-01

Full Text Available Inflammation is a multifaceted process involving a host of resident and recruited immune cells that eliminate the insult or injury and initiate tissue repair. In the female reproductive tract (FMRT, inflammation-mediated alterations in epithelial, vascular, and immune functions are important components of complex physiological processes and many local and systemic pathologies. It is well established that intracoital and postcoital function of seminal fluid (SF goes beyond nutritive support for the spermatozoa cells. SF, in particular, the inflammatory bioactive lipids, and prostaglandins present in vast quantities in SF, have a role in localized immune modulation and regulation of pathways that can exacerbate inflammation in the FMRT. In sexually active women SF-mediated inflammation has been implicated in physiologic processes such as ovulation, implantation, and parturition while also enhancing tumorigenesis and susceptibility to infection. This review highlights the molecular mechanism by which SF regulates inflammatory pathways in the FMRT and how alterations in these pathways contribute to physiology and pathology of the female reproductive function. In addition, based on findings from TaqMan® 96-Well Plate Arrays, on neoplastic cervical cells treated with SF, we discuss new findings on the role of SF as a potent driver of inflammatory and tumorigenic pathways in the cervix.

Fungal invasion of normally non-phagocytic host cells.

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Scott G Filler

2006-12-01

Full Text Available Many fungi that cause invasive disease invade host epithelial cells during mucosal and respiratory infection, and subsequently invade endothelial cells during hematogenous infection. Most fungi invade these normally non-phagocytic host cells by inducing their own uptake. Candida albicans hyphae interact with endothelial cells in vitro by binding to N-cadherin on the endothelial cell surface. This binding induces rearrangement of endothelial cell microfilaments, which results in the endocytosis of the organism. The capsule of Cryptococcus neoformans is composed of glucuronoxylomannan, which binds specifically to brain endothelial cells, and appears to mediate both adherence and induction of endocytosis. The mechanisms by which other fungal pathogens induce their own uptake are largely unknown. Some angioinvasive fungi, such as Aspergillus species and the Zygomycetes, invade endothelial cells from the abluminal surface during the initiation of invasive disease, and subsequently invade the luminal surface of endothelial cells during hematogenous dissemination. Invasion of normally non-phagocytic host cells has different consequences, depending on the type of invading fungus. Aspergillus fumigatus blocks apoptosis of pulmonary epithelial cells, whereas Paracoccidioides brasiliensis induces apoptosis of epithelial cells. This review summarizes the mechanisms by which diverse fungal pathogens invade normally non-phagocytic host cells and discusses gaps in our knowledge that provide opportunities for future research.

Alcohol consumption negates estrogen-mediated myocardial repair in ovariectomized mice by inhibiting endothelial progenitor cell mobilization and function.

Science.gov (United States)

Mackie, Alexander R; Krishnamurthy, Prasanna; Verma, Suresh K; Thorne, Tina; Ramirez, Veronica; Qin, Gangjian; Abramova, Tatiana; Hamada, Hiromichi; Losordo, Douglas W; Kishore, Raj

2013-06-21

We have shown previously that estrogen (estradiol, E2) supplementation enhances voluntary alcohol consumption in ovariectomized female rodents and that increased alcohol consumption impairs ischemic hind limb vascular repair. However, the effect of E2-induced alcohol consumption on post-infarct myocardial repair and on the phenotypic/functional properties of endothelial progenitor cells (EPCs) is not known. Additionally, the molecular signaling of alcohol-estrogen interactions remains to be elucidated. This study examined the effect of E2-induced increases in ethanol consumption on post-infarct myocardial function/repair. Ovariectomized female mice, implanted with 17β-E2 or placebo pellets were given access to alcohol for 6 weeks and subjected to acute myocardial infarction. Left ventricular functions were consistently depressed in mice consuming ethanol compared with those receiving only E2. Alcohol-consuming mice also displayed significantly increased infarct size and reduced capillary density. Ethanol consumption also reduced E2-induced mobilization and homing of EPCs to injured myocardium compared with the E2-alone group. In vitro, exposure of EPCs to ethanol suppressed E2-induced proliferation, survival, and migration and markedly altered E2-induced estrogen receptor-dependent cell survival signaling and gene expression. Furthermore, ethanol-mediated suppression of EPC biology was endothelial nitric oxide synthase-dependent because endothelial nitric oxide synthase-null mice displayed an exaggerated response to post-acute myocardial infarction left ventricular functions. These data suggest that E2 modulation of alcohol consumption, and the ensuing EPC dysfunction, may negatively compete with the beneficial effects of estrogen on post-infarct myocardial repair.

The time course of repair of ultraviolet-induced DNA damage; implications for the structural organization of repair

International Nuclear Information System (INIS)

Collins, A.; Squires, S.

1986-01-01

Alternative molecular mechanisms can be envisaged for the cellular repair of UV-damaged DNA. In the 'random collision' model, DNA damage distributed throughout the genome is recognised and repaired by a process of random collision between DNA damage and repair enzymes. The other model assumes a 'processive' mechanism, whereby DNA is scanned for damage by a repair complex moving steadily along its length. Random collision should result in a declining rate of repair with time as the concentration of lesions in the DNA falls; but the processive model predicts a constant rate until scanning is complete. The authors have examined the time course of DNA repair in human fibroblasts given low doses of UV light. Using 3 distinct assays, the authors find no sign of a constant repair rate after 4 J/m 2 or less, even when the first few hours after irradiation are examined. Thus DNA repair is likely to depend on random collision. (Auth.)

Theoretical and experimental insights into the ·OH-mediated mineralization mechanism of flutriafol

International Nuclear Information System (INIS)

Liu, Siqi; Zhou, Xiezhen; Han, Weiqing; Li, Jiansheng; Sun, Xiuyun; Shen, Jinyou; Wang, Lianjun

2017-01-01

Highlights: • A complete ·OH-mediated degradation pathway of flutriafol is proposed. • Computational approach is effective to reveal the favorable transformation process. • The electrochemical experiments well verify the theoretical results. - Abstract: Flutriafol is one of the widely used triazole fungicides in global pesticides market, and its degradation mechanisms are important to develop powerful technologies to remove it. Insight into the kinetics and mechanisms of ·OH-mediated mineralization of flutriafol have been obtained using quantum chemical calculation and electrochemical experiment methods. The complete ·OH-mediated degradation pathway of flutriafol was proposed by density functional theory (DFT) simulation and the potential energy surface was mapped out for possible reactions. On the basis of DFT calculations, the optimal ·OH-mediated mineralization mechanism of flutriafol was revealed, and a series of intermediates were observed accumulated in the degradation process, most significance among which were (2-fluorophenyl) (4-fluorophenyl)-Methanone, phenol, dihydroxybenzenes, benzoquinones, muconic acids, maleic acids, oxalic acids and formic acid. To give deeper insight into the ·OH-mediated reaction mechanism, the electrostatic potential (ESP) and average local ionization energy (ALIE) analysis were conducted for o-benzoquinone and p-benzoquinone. The proposed mechanism was further validated by electrochemical experiments at TiO_2-NTs/SnO_2-Sb/PbO_2 anode. The main intermediates were identified and quantified by experimental method, indicating that the proposed ·OH-mediated degradation mechanism derived from DFT calculations was feasible. These detailed findings could be instrumental for a comprehensive understanding of the ·OH-mediated mineralization mechanism of flutriafol and the similar contaminants.

Improvement of adhesion performance of mortar-repair interface with inducing crack path into repair

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A. Satoh

2015-10-01

Full Text Available The most important performance for repair materials is adhesion to the substrate. The authors experimentally find out that high modulus fine aggregates in repair material enhance strength of it as well as the strength of the interface repaired with it, compared to the ordinary repair without fine aggregates. This paper elaborates the mechanisms for that with fractographic observation and FEM analysis based on the results of experiment. Also the authors discuss the ways for enhancing the strength and ductility of the repaired mortar

Lectin-based food poisoning: a new mechanism of protein toxicity.

Science.gov (United States)

Miyake, Katsuya; Tanaka, Toru; McNeil, Paul L

2007-08-01

Ingestion of the lectins present in certain improperly cooked vegetables can result in acute GI tract distress, but the mechanism of toxicity is unknown. In vivo, gut epithelial cells are constantly exposed to mechanical and other stresses and consequently individual cells frequently experience plasma membrane disruptions. Repair of these cell surface disruptions allows the wounded cell to survive: failure results in necrotic cell death. Plasma membrane repair is mediated, in part, by an exocytotic event that adds a patch of internal membrane to the defect site. Lectins are known to inhibit exocytosis. We therefore tested the novel hypothesis that lectin toxicity is due to an inhibitory effect on plasma membrane repair. Repair of plasma membrane disruptions and exocytosis of mucus was assessed after treatment of cultured cell models and excised segments of the GI tract with lectins. Plasma membrane disruptions were produced by focal irradiation of individual cells, using a microscope-based laser, or by mechanical abrasion of multiple cells, using a syringe needle. Repair was then assessed by monitoring the cytosolic penetration of dyes incapable of crossing the intact plasma membrane. We found that cell surface-bound lectins potently inhibited plasma membrane repair, and the exocytosis of mucus that normally accompanies the repair response. Lectins potently inhibit plasma membrane repair, and hence are toxic to wounded cells. This represents a novel form of protein-based toxicity, one that, we propose, is the basis of plant lectin food poisoning.

Lectin-based food poisoning: a new mechanism of protein toxicity.

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Katsuya Miyake

Full Text Available BACKGROUND: Ingestion of the lectins present in certain improperly cooked vegetables can result in acute GI tract distress, but the mechanism of toxicity is unknown. In vivo, gut epithelial cells are constantly exposed to mechanical and other stresses and consequently individual cells frequently experience plasma membrane disruptions. Repair of these cell surface disruptions allows the wounded cell to survive: failure results in necrotic cell death. Plasma membrane repair is mediated, in part, by an exocytotic event that adds a patch of internal membrane to the defect site. Lectins are known to inhibit exocytosis. We therefore tested the novel hypothesis that lectin toxicity is due to an inhibitory effect on plasma membrane repair. METHODS AND FINDINGS: Repair of plasma membrane disruptions and exocytosis of mucus was assessed after treatment of cultured cell models and excised segments of the GI tract with lectins. Plasma membrane disruptions were produced by focal irradiation of individual cells, using a microscope-based laser, or by mechanical abrasion of multiple cells, using a syringe needle. Repair was then assessed by monitoring the cytosolic penetration of dyes incapable of crossing the intact plasma membrane. We found that cell surface-bound lectins potently inhibited plasma membrane repair, and the exocytosis of mucus that normally accompanies the repair response. CONCLUSIONS: Lectins potently inhibit plasma membrane repair, and hence are toxic to wounded cells. This represents a novel form of protein-based toxicity, one that, we propose, is the basis of plant lectin food poisoning.

Kinetics and mechanism of DNA repair

International Nuclear Information System (INIS)

Meldrum, R.A.; Wharton, C.W.; Shall, S.

1990-01-01

Experiments are described in which the feasibility of using caged dideoxy and other nucleoside triphosphate analogues for trapping breaks induced by u.v. radiation damage to mammalian cell DNA is evaluated. These nucleotide analogues that have a photolabile 1-(2-nitrophenyl)ethyl-protecting group attached to the γ-phosphate are placed in situ by permeabilizing cells by exposure to hypo-osmotic medium. The nucleoside triphosphate is released by a 351 nm u.v. laser pulse whence it may incorporate in the growing chain of DNA induced by the excision-repair process and terminate chain elongation. If the photoreleased dideoxynucleoside trisphosphate is isotopically labelled in the α-phosphate position the break is trapped and labelled. Incorporation of radioactivity into trichloroacetic acid insoluble material in these experiments confirms their potential for use in studies of the kinetics of mammalian cell DNA repair. (author)

AKAP12 mediates barrier functions of fibrotic scars during CNS repair.

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Jong-Ho Cha

Full Text Available The repair process after CNS injury shows a well-organized cascade of three distinct stages: inflammation, new tissue formation, and remodeling. In the new tissue formation stage, various cells migrate and form the fibrotic scar surrounding the lesion site. The fibrotic scar is known as an obstacle for axonal regeneration in the remodeling stage. However, the role of the fibrotic scar in the new tissue formation stage remains largely unknown. We found that the number of A-kinase anchoring protein 12 (AKAP12-positive cells in the fibrotic scar was increased over time, and the cells formed a structure which traps various immune cells. Furthermore, the AKAP12-positive cells strongly express junction proteins which enable the structure to function as a physical barrier. In in vivo validation, AKAP12 knock-out (KO mice showed leakage from a lesion, resulting from an impaired structure with the loss of the junction complex. Consistently, focal brain injury in the AKAP12 KO mice led to extended inflammation and more severe tissue damage compared to the wild type (WT mice. Accordingly, our results suggest that AKAP12-positive cells in the fibrotic scar may restrict excessive inflammation, demonstrating certain mechanisms that could underlie the beneficial actions of the fibrotic scar in the new tissue formation stage during the CNS repair process.

A Bacterial Parasite Effector Mediates Insect Vector Attraction in Host Plants Independently of Developmental Changes

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Orlovskis, Zigmunds; Hogenhout, Saskia A.

2016-01-01

Parasites can take over their hosts and trigger dramatic changes in host appearance and behavior that are typically interpreted as extended phenotypes that promote parasite survival and fitness. For example, Toxoplasma gondii is thought to manipulate the behaviors of infected rodents to aid transmission to cats and parasitic trematodes of the genus Ribeiroia alter limb development in their amphibian hosts to facilitate predation of the latter by birds. Plant parasites and pathogens also reprogram host development and morphology. However, whereas some parasite-induced morphological alterations may have a direct benefit to the fitness of the parasite and may therefore be adaptive, other host alterations may be side effects of parasite infections having no adaptive effects on parasite fitness. Phytoplasma parasites of plants often induce the development of leaf-like flowers (phyllody) in their host plants, and we previously found that the phytoplasma effector SAP54 generates these leaf-like flowers via the degradation of plant MADS-box transcription factors (MTFs), which regulate all major aspects of development in plants. Leafhoppers prefer to reproduce on phytoplasma-infected and SAP54-trangenic plants leading to the hypothesis that leafhopper vectors are attracted to plants with leaf-like flowers. Surprisingly, here we show that leafhopper attraction occurs independently of the presence of leaf-like flowers. First, the leafhoppers were also attracted to SAP54 transgenic plants without leaf-like flowers and to single leaves of these plants. Moreover, leafhoppers were not attracted to leaf-like flowers of MTF-mutant plants without the presence of SAP54. Thus, the primary role of SAP54 is to attract leafhopper vectors, which spread the phytoplasmas, and the generation of leaf-like flowers may be secondary or a side effect of the SAP54-mediated degradation of MTFs. PMID:27446117

Biomaterial strategies for engineering implants for enhanced osseointegration and bone repair

Science.gov (United States)

Agarwal, Rachit; García, Andrés J.

2015-01-01

Bone tissue has a remarkable ability to regenerate and heal itself. However, large bone defects and complex fractures still present a significant challenge to the medical community. Current treatments center on metal implants for structural and mechanical support and auto- or allo-grafts to substitute long bone defects. Metal implants are associated with several complications such as implant loosening and infections. Bone grafts suffer from donor site morbidity, reduced bioactivity, and risk of pathogen transmission. Surgical implants can be modified to provide vital biological cues, growth factors and cells in order to improve osseointegration and repair of bone defects. Here we review strategies and technologies to engineer metal surfaces to promote osseointegration with the host tissue. We also discuss strategies for modifying implants for cell adhesion and bone growth via integrin signaling and growth factor and cytokine delivery for bone defect repair. PMID:25861724

Molecular mechanism of radioadaptive response: A cross-adaptive response for enhanced repair of DNA damage in adapted cells

International Nuclear Information System (INIS)

Takaji Ikushima

1997-01-01

The radioadaptive response (RAR) has been attributed to the induction of a repair mechanism by low doses of ionizing radiation, but the molecular nature of the mechanism is not yet elucidated. We have characterized RAR in a series of experiments in cultured Chinese hamster V79 cells. A 4-h interval is required for the full expression of RAR, which decays with the progression of cell proliferation. Treatments with inhibitors of poly(ADP-ribose) polymerase, protein- or RNA synthesis, and protein kinase C suppress the RAR expression. The RAR cross-reacts on clastogenic lesions induced by other physical and chemical DNA-damaging agents. The presence of newly synthesised proteins has been detected during the expression period. Experiments performed using single-cell gel electrophoresis provided more direct evidence for a faster and enhaced DNA repair rate in adapted cells. Here, using single-cell gel electrophoresis, a cross-adaptive response has been demonstrated for enhanced repair of DNA damage induced by neocarzinostatin in radio-adapted cells. (author)

Spread and Control of Mobile Benign Worm Based on Two-Stage Repairing Mechanism

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Meng Wang

2014-01-01

Full Text Available Both in traditional social network and in mobile network environment, the worm is a serious threat, and this threat is growing all the time. Mobile smartphones generally promote the development of mobile network. The traditional antivirus technologies have become powerless when facing mobile networks. The development of benign worms, especially active benign worms and passive benign worms, has become a new network security measure. In this paper, we focused on the spread of worm in mobile environment and proposed the benign worm control and repair mechanism. The control process of mobile benign worms is divided into two stages: the first stage is rapid repair control, which uses active benign worm to deal with malicious worm in the mobile network; when the network is relatively stable, it enters the second stage of postrepair and uses passive mode to optimize the environment for the purpose of controlling the mobile network. Considering whether the existence of benign worm, we simplified the model and analyzed the four situations. Finally, we use simulation to verify the model. This control mechanism for benign worm propagation is of guiding significance to control the network security.

Cd1b-Mediated T Cell Recognition of a Glycolipid Antigen Generated from Mycobacterial Lipid and Host Carbohydrate during Infection

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Moody, D. Branch; Guy, Mark R.; Grant, Ethan; Cheng, Tan-Yun; Brenner, Michael B.; Besra, Gurdyal S.; Porcelli, Steven A.

2000-01-01

T cells recognize microbial glycolipids presented by CD1 proteins, but there is no information regarding the generation of natural glycolipid antigens within infected tissues. Therefore, we determined the molecular basis of CD1b-restricted T cell recognition of mycobacterial glycosylated mycolates, including those produced during tissue infection in vivo. Transfection of the T cell receptor (TCR) α and β chains from a glucose monomycolate (GMM)-specific T cell line reconstituted GMM recognition in TCR-deficient T lymphoblastoma cells. This TCR-mediated response was highly specific for natural mycobacterial glucose-6-O-(2R, 3R) monomycolate, including the precise structure of the glucose moiety, the stereochemistry of the mycolate lipid, and the linkage between the carbohydrate and the lipid. Mycobacterial production of antigenic GMM absolutely required a nonmycobacterial source of glucose that could be supplied by adding glucose to media at concentrations found in mammalian tissues or by infecting tissue in vivo. These results indicate that mycobacteria synthesized antigenic GMM by coupling mycobacterial mycolates to host-derived glucose. Specific T cell recognition of an epitope formed by interaction of host and pathogen biosynthetic pathways provides a mechanism for immune response to those pathogenic mycobacteria that have productively infected tissues, as distinguished from ubiquitous, but innocuous, environmental mycobacteria. PMID:11015438

DNA repair in Mycobacterium tuberculosis revisited.

Science.gov (United States)

Dos Vultos, Tiago; Mestre, Olga; Tonjum, Tone; Gicquel, Brigitte

2009-05-01

Our understanding of Mycobacterium tuberculosis DNA repair mechanisms is still poor compared with that of other bacterial organisms. However, the publication of the first complete M. tuberculosis genome sequence 10 years ago boosted the study of DNA repair systems in this organism. A first step in the elucidation of M. tuberculosis DNA repair mechanisms was taken by Mizrahi and Andersen, who identified homologs of genes involved in the reversal or repair of DNA damage in Escherichia coli and related organisms. Genes required for nucleotide excision repair, base excision repair, recombination, and SOS repair and mutagenesis were identified. Notably, no homologs of genes involved in mismatch repair were identified. Novel characteristics of the M. tuberculosis DNA repair machinery have been found over the last decade, such as nonhomologous end joining, the presence of Mpg, ERCC3 and Hlr - proteins previously presumed to be produced exclusively in mammalian cells - and the recently discovered bifunctional dCTP deaminase:dUTPase. The study of these systems is important to develop therapeutic agents that can counteract M. tuberculosis evolutionary changes and to prevent adaptive events resulting in antibiotic resistance. This review summarizes our current understanding of the M. tuberculosis DNA repair system.

Analysis of mutagenic DNA repair in a thermoconditional mutant of Saccharomyces cerevisiae. IV. Influence of DNA replication and excision repair on REV2 dependent UV-mutagenesis and repair

Energy Technology Data Exchange (ETDEWEB)

Siede, W.; Eckardt, F.

1986-01-01

A double mutant being thermoconditionally defective in mutation induction as well as in repair of pre-lethal UV-induced DNA damage (rev2ts) and deficient in excision repair (rad3-2) was studied in temperature-shift experiments. The influence of inhibitors of DNA replication (hydroxyurea, aphidicolin) was determined. Additionally, an analysis of the dose-response pattern of mutation induction (mutation kinetics) at several ochre alleles was carried out. It was concluded that the UV-inducible REV2 dependent mutagenic repair process is not induced in excision-deficient cells. In excision-deficient cells, REV2 dependent mutation fixation is slow and mostly post-replicative though not dependent on DNA replication. The REV2 mediated mutagenic process could be separated from the repair function.

Lithophysal Rock Mass Mechanical Properties of the Repository Host Horizon

International Nuclear Information System (INIS)

D. Rigby

2004-01-01

The purpose of this calculation is to develop estimates of key mechanical properties for the lithophysal rock masses of the Topopah Spring Tuff (Tpt) within the repository host horizon, including their uncertainties and spatial variability. The mechanical properties to be characterized include an elastic parameter, Young's modulus, and a strength parameter, uniaxial compressive strength. Since lithophysal porosity is used as a surrogate property to develop the distributions of the mechanical properties, an estimate of the distribution of lithophysal porosity is also developed. The resulting characterizations of rock parameters are important for supporting the subsurface design, developing the preclosure safety analysis, and assessing the postclosure performance of the repository (e.g., drift degradation and modeling of rockfall impacts on engineered barrier system components)

Assay for Human Rad51-Mediated DNA Displacement Loop Formation

OpenAIRE

sprotocols

2014-01-01

Authors: Steven Raynard and Patrick Sung Corresponding author ([]()) ### INTRODUCTION Homologous recombination is an important mechanism for the repair of damaged chromosomes, for preventing the demise of damaged replication forks, and for several other aspects of chromosome metabolism and maintenance. The homologous recombination reaction is mediated by the Rad51 recombinase. In the presence of ATP, Rad51 polymerizes on single-stranded D...

DNA repair pathways underlie a common genetic mechanism modulating onset in polyglutamine diseases.

Science.gov (United States)

Bettencourt, Conceição; Hensman-Moss, Davina; Flower, Michael; Wiethoff, Sarah; Brice, Alexis; Goizet, Cyril; Stevanin, Giovanni; Koutsis, Georgios; Karadima, Georgia; Panas, Marios; Yescas-Gómez, Petra; García-Velázquez, Lizbeth Esmeralda; Alonso-Vilatela, María Elisa; Lima, Manuela; Raposo, Mafalda; Traynor, Bryan; Sweeney, Mary; Wood, Nicholas; Giunti, Paola; Durr, Alexandra; Holmans, Peter; Houlden, Henry; Tabrizi, Sarah J; Jones, Lesley

2016-06-01

The polyglutamine diseases, including Huntington's disease (HD) and multiple spinocerebellar ataxias (SCAs), are among the commonest hereditary neurodegenerative diseases. They are caused by expanded CAG tracts, encoding glutamine, in different genes. Longer CAG repeat tracts are associated with earlier ages at onset, but this does not account for all of the difference, and the existence of additional genetic modifying factors has been suggested in these diseases. A recent genome-wide association study (GWAS) in HD found association between age at onset and genetic variants in DNA repair pathways, and we therefore tested whether the modifying effects of variants in DNA repair genes have wider effects in the polyglutamine diseases. We assembled an independent cohort of 1,462 subjects with HD and polyglutamine SCAs, and genotyped single-nucleotide polymorphisms (SNPs) selected from the most significant hits in the HD study. In the analysis of DNA repair genes as a group, we found the most significant association with age at onset when grouping all polyglutamine diseases (HD+SCAs; p = 1.43 × 10(-5) ). In individual SNP analysis, we found significant associations for rs3512 in FAN1 with HD+SCAs (p = 1.52 × 10(-5) ) and all SCAs (p = 2.22 × 10(-4) ) and rs1805323 in PMS2 with HD+SCAs (p = 3.14 × 10(-5) ), all in the same direction as in the HD GWAS. We show that DNA repair genes significantly modify age at onset in HD and SCAs, suggesting a common pathogenic mechanism, which could operate through the observed somatic expansion of repeats that can be modulated by genetic manipulation of DNA repair in disease models. This offers novel therapeutic opportunities in multiple diseases. Ann Neurol 2016;79:983-990. © 2016 The Authors. Annals of Neurology published by Wiley Periodicals, Inc. on behalf of American Neurological Association.

The Role of Lipid Competition for Endosymbiont-Mediated Protection against Parasitoid Wasps in Drosophila

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Juan C. Paredes

2016-07-01

Full Text Available Insects commonly harbor facultative bacterial endosymbionts, such as Wolbachia and Spiroplasma species, that are vertically transmitted from mothers to their offspring. These endosymbiontic bacteria increase their propagation by manipulating host reproduction or by protecting their hosts against natural enemies. While an increasing number of studies have reported endosymbiont-mediated protection, little is known about the mechanisms underlying this protection. Here, we analyze the mechanisms underlying protection from parasitoid wasps in Drosophila melanogaster mediated by its facultative endosymbiont Spiroplasma poulsonii. Our results indicate that S. poulsonii exerts protection against two distantly related wasp species, Leptopilina boulardi and Asobara tabida. S. poulsonii-mediated protection against parasitoid wasps takes place at the pupal stage and is not associated with an increased cellular immune response. In this work, we provide three important observations that support the notion that S. poulsonii bacteria and wasp larvae compete for host lipids and that this competition underlies symbiont-mediated protection. First, lipid quantification shows that both S. poulsonii and parasitoid wasps deplete D. melanogaster hemolymph lipids. Second, the depletion of hemolymphatic lipids using the Lpp RNA interference (Lpp RNAi construct reduces wasp success in larvae that are not infected with S. poulsonii and blocks S. poulsonii growth. Third, we show that the growth of S. poulsonii bacteria is not affected by the presence of the wasps, indicating that when S. poulsonii is present, larval wasps will develop in a lipid-depleted environment. We propose that competition for host lipids may be relevant to endosymbiont-mediated protection in other systems and could explain the broad spectrum of protection provided.

Mechanisms of host seeking by parasitic nematodes.

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Gang, Spencer S; Hallem, Elissa A

2016-07-01

The phylum Nematoda comprises a diverse group of roundworms that includes parasites of vertebrates, invertebrates, and plants. Human-parasitic nematodes infect more than one billion people worldwide and cause some of the most common neglected tropical diseases, particularly in low-resource countries [1]. Parasitic nematodes of livestock and crops result in billions of dollars in losses each year [1]. Many nematode infections are treatable with low-cost anthelmintic drugs, but repeated infections are common in endemic areas and drug resistance is a growing concern with increasing therapeutic and agricultural administration [1]. Many parasitic nematodes have an environmental infective larval stage that engages in host seeking, a process whereby the infective larvae use sensory cues to search for hosts. Host seeking is a complex behavior that involves multiple sensory modalities, including olfaction, gustation, thermosensation, and humidity sensation. As the initial step of the parasite-host interaction, host seeking could be a powerful target for preventative intervention. However, host-seeking behavior remains poorly understood. Here we review what is currently known about the host-seeking behaviors of different parasitic nematodes, including insect-parasitic nematodes, mammalian-parasitic nematodes, and plant-parasitic nematodes. We also discuss the neural bases of these behaviors. Copyright © 2016 Elsevier B.V. All rights reserved.

Base excision repair mechanisms and relevance to cancer susceptibility

International Nuclear Information System (INIS)

Dogliotti, E.; Wilson, S.H.

2009-01-01

The base excision repair (BER) pathway is considered the predominant DNA repair system in mammalian cells for eliminating small DNA lesions generated at DNA bases either exogenously by environmental agents or endogenously by normal cellular metabolic processes (e.g. production of oxyradical species, alkylating agents, etc). The main goal of this project is the understanding of the involvement of BER in genome stability and in particular in sporadic cancer development associated with inflammation such as gastric cancer (GC). A major risk factor of GC is the infection by Helicobacter pylori, which causes oxidative stress. Oxidative DNA damage is mainly repaired by BER

Radiobiological significance of DNA repair

International Nuclear Information System (INIS)

Kuzin, A.M.

1978-01-01

A short outline is given on the history of the problem relating to the repair of radiation injuries, specifically its molecular mechanisms. The most urgent problems which currently confront the researchers are noted. This is a further study on the role of DNA repair in post-radiation recovery, search for ways to activate and suppress DNA repair, investigations into the activity balance of various repair enzymes as well as the problem of errors in the structure of repairing DNA. An important role is attached to the investigations of DNA repair in solving a number of practical problems

Host-to-host variation of ecological interactions in polymicrobial infections

Science.gov (United States)

Mukherjee, Sayak; Weimer, Kristin E.; Seok, Sang-Cheol; Ray, Will C.; Jayaprakash, C.; Vieland, Veronica J.; Swords, W. Edward; Das, Jayajit

2015-02-01

Host-to-host variability with respect to interactions between microorganisms and multicellular hosts are commonly observed in infection and in homeostasis. However, the majority of mechanistic models used to analyze host-microorganism relationships, as well as most of the ecological theories proposed to explain coevolution of hosts and microbes, are based on averages across a host population. By assuming that observed variations are random and independent, these models overlook the role of differences between hosts. Here, we analyze mechanisms underlying host-to-host variations of bacterial infection kinetics, using the well characterized experimental infection model of polymicrobial otitis media (OM) in chinchillas, in combination with population dynamic models and a maximum entropy (MaxEnt) based inference scheme. We find that the nature of the interactions between bacterial species critically regulates host-to-host variations in these interactions. Surprisingly, seemingly unrelated phenomena, such as the efficiency of individual bacterial species in utilizing nutrients for growth, and the microbe-specific host immune response, can become interdependent in a host population. The latter finding suggests a potential mechanism that could lead to selection of specific strains of bacterial species during the coevolution of the host immune response and the bacterial species.

Host-to-host variation of ecological interactions in polymicrobial infections.

Science.gov (United States)

Mukherjee, Sayak; Weimer, Kristin E; Seok, Sang-Cheol; Ray, Will C; Jayaprakash, C; Vieland, Veronica J; Swords, W Edward; Das, Jayajit

2014-12-04

Host-to-host variability with respect to interactions between microorganisms and multicellular hosts are commonly observed in infection and in homeostasis. However, the majority of mechanistic models used to analyze host-microorganism relationships, as well as most of the ecological theories proposed to explain coevolution of hosts and microbes, are based on averages across a host population. By assuming that observed variations are random and independent, these models overlook the role of differences between hosts. Here, we analyze mechanisms underlying host-to-host variations of bacterial infection kinetics, using the well characterized experimental infection model of polymicrobial otitis media (OM) in chinchillas, in combination with population dynamic models and a maximum entropy (MaxEnt) based inference scheme. We find that the nature of the interactions between bacterial species critically regulates host-to-host variations in these interactions. Surprisingly, seemingly unrelated phenomena, such as the efficiency of individual bacterial species in utilizing nutrients for growth, and the microbe-specific host immune response, can become interdependent in a host population. The latter finding suggests a potential mechanism that could lead to selection of specific strains of bacterial species during the coevolution of the host immune response and the bacterial species.

Mechanisms involved in repairing the lesions induced in pBR 322 by PUVA treatment (8-Methoxypsoralen + ultraviolet A light)

International Nuclear Information System (INIS)

Bauluz, C.

1988-01-01

This work deals with the genotoxic effects derived from damaging pBR322 DNA through PUVA treatment (8-Methoxypsoralen plusUVA light), both with respect to the lethality and mutagenicity of the lesions produced by the treatment. The mechanisms involved in the repair of the plasmid lesions have been investigated by transforming several strains of E. coli differing in their DNA-repair capacities. The frequency, distribution and type of mutations occurring in a restriction fragment of the damaged plasmid were determined in order to establish the mutagenic features of the PUVA treatment. Damages produced bY PUVA habe a strong lethal effect on plasmid survival; however, partial recovery is possible through some of the bacterial DNA repair pathways, namely Excision repair, SOS-repair and a third mechanism which appears to be independent from the analised genes and is detected at high density of lesions per plasmid molecule. PUVA treatment produces a high increase in plasmid mutagenesis; however, the contribution of such an increase to the whole plasmid survival is negligible. Only punctual mutations were detected and consisted mainly in base-pair substitutions. Some mutation-prone regions were sound inside the investigated DNA fragment, a though their existence is more likely to be related with the structure acquired by the damaged DNA than with the type of damaging agent. (Author)

Open Abdomen Therapy with Vacuum and Mesh Mediated Fascial Traction After Aortic Repair: an International Multicentre Study.

Science.gov (United States)

Acosta, Stefan; Seternes, Arne; Venermo, Maarit; Vikatmaa, Leena; Sörelius, Karl; Wanhainen, Anders; Svensson, Mats; Djavani, Khatereh; Björck, Martin

2017-12-01

Open abdomen therapy may be necessary to prevent or treat abdominal compartment syndrome (ACS). The aim of the study was to analyse the primary delayed fascial closure (PDFC) rate and complications after open abdomen therapy with vacuum and mesh mediated fascial traction (VACM) after aortic repair and to compare outcomes between those treated with open abdomen after primary versus secondary operation. This was a retrospective cohort, multicentre study in Sweden, Finland, and Norway, including consecutive patients treated with open abdomen and VACM after aortic repair at six vascular centres in 2006-2015. The primary endpoint was PDFC rate. Among 191 patients, 155 were men. The median age was 71 years (IQR 66-76). Ruptured abdominal aortic aneurysm (RAAA) occurred in 69.1%. Endovascular/hybrid and open repairs were performed in 49 and 142 patients, respectively. The indications for open abdomen were inability to close the abdomen (62%) at primary operation and ACS (80%) at secondary operation. Duration of open abdomen was 11 days (IQR 7-16) in 157 patients alive at open abdomen termination. The PDFC rate was 91.8%. Open abdomen initiated at primary (N=103), compared with secondary operation (N=88), was associated with less severe initial open abdomen status (p=.006), less intestinal ischaemia (p=.002), shorter duration of open abdomen (p=.007), and less renal replacement therapy (RRT, popen abdomen initiated at primary versus secondary operation. VACM was associated with a high PDFC rate after prolonged open abdomen therapy following aortic repair. Patient outcomes seemed better when open abdomen was initiated at primary, compared with secondary operation but a selection effect is possible. Copyright © 2017 European Society for Vascular Surgery. Published by Elsevier Ltd. All rights reserved.

Nickel induces transcriptional down-regulation of DNA repair pathways in tumorigenic and non-tumorigenic lung cells.

Science.gov (United States)

Scanlon, Susan E; Scanlon, Christine D; Hegan, Denise C; Sulkowski, Parker L; Glazer, Peter M

2017-06-01

The heavy metal nickel is a known carcinogen, and occupational exposure to nickel compounds has been implicated in human lung and nasal cancers. Unlike many other environmental carcinogens, however, nickel does not directly induce DNA mutagenesis, and the mechanism of nickel-related carcinogenesis remains incompletely understood. Cellular nickel exposure leads to signaling pathway activation, transcriptional changes and epigenetic remodeling, processes also impacted by hypoxia, which itself promotes tumor growth without causing direct DNA damage. One of the mechanisms by which hypoxia contributes to tumor growth is the generation of genomic instability via down-regulation of high-fidelity DNA repair pathways. Here, we find that nickel exposure similarly leads to down-regulation of DNA repair proteins involved in homology-dependent DNA double-strand break repair (HDR) and mismatch repair (MMR) in tumorigenic and non-tumorigenic human lung cells. Functionally, nickel induces a defect in HDR capacity, as determined by plasmid-based host cell reactivation assays, persistence of ionizing radiation-induced DNA double-strand breaks and cellular hypersensitivity to ionizing radiation. Mechanistically, we find that nickel, in contrast to the metalloid arsenic, acutely induces transcriptional repression of HDR and MMR genes as part of a global transcriptional pattern similar to that seen with hypoxia. Finally, we find that exposure to low-dose nickel reduces the activity of the MLH1 promoter, but only arsenic leads to long-term MLH1 promoter silencing. Together, our data elucidate novel mechanisms of heavy metal carcinogenesis and contribute to our understanding of the influence of the microenvironment on the regulation of DNA repair pathways. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Modulation of the DNA repair system and ATR-p53 mediated apoptosis is relevant for tributyltin-induced genotoxic effects in human hepatoma G2 cells.

Science.gov (United States)

Li, Bowen; Sun, Lingbin; Cai, Jiali; Wang, Chonggang; Wang, Mengmeng; Qiu, Huiling; Zuo, Zhenghong

2015-01-01

The toxic effects of tributyltin (TBT) have been extensively documented in several types of cells, but the molecular mechanisms related to the genotoxic effects of TBT have still not been fully elucidated. Our study showed that exposure of human hepatoma G2 cells to 1-4 μmol/L TBT for 3 hr caused severe DNA damage in a concentration-dependent manner. Moreover, the expression levels of key DNA damage sensor genes such as the replication factor C, proliferating cell nuclear antigen and poly (ADP-ribose) polymerase-1 were inhabited in a concentration-dependent manner. We further demonstrated that TBT induced cell apoptosis via the p53-mediated pathway, which was most likely activated by the ataxia telangiectasia mutated and rad-3 related (ATR) protein kinase. The results also showed that cytochrome c, caspase-3, caspase-8, caspase-9, and the B-cell lymphoma 2 were involved in this process. Taken together, we demonstrated for the first time that the inhibition of the DNA repair system might be more responsible for TBT-induced genotoxic effects in cells. Then the generated DNA damage induced by TBT initiated ATR-p53-mediated apoptosis. Copyright © 2014. Published by Elsevier B.V.

Motorcycle Repair.

Science.gov (United States)

Hein, Jim; Bundy, Mike

This motorcycle repair curriculum guide contains the following ten areas of study: brake systems, clutches, constant mesh transmissions, final drives, suspension, mechanical starting mechanisms, electrical systems, fuel systems, lubrication systems, and overhead camshafts. Each area consists of one or more units of instruction. Each instructional…

A Systems Biology Approach to the Coordination of Defensive and Offensive Molecular Mechanisms in the Innate and Adaptive Host-Pathogen Interaction Networks.

Science.gov (United States)

Wu, Chia-Chou; Chen, Bor-Sen

2016-01-01

Infected zebrafish coordinates defensive and offensive molecular mechanisms in response to Candida albicans infections, and invasive C. albicans coordinates corresponding molecular mechanisms to interact with the host. However, knowledge of the ensuing infection-activated signaling networks in both host and pathogen and their interspecific crosstalk during the innate and adaptive phases of the infection processes remains incomplete. In the present study, dynamic network modeling, protein interaction databases, and dual transcriptome data from zebrafish and C. albicans during infection were used to infer infection-activated host-pathogen dynamic interaction networks. The consideration of host-pathogen dynamic interaction systems as innate and adaptive loops and subsequent comparisons of inferred innate and adaptive networks indicated previously unrecognized crosstalk between known pathways and suggested roles of immunological memory in the coordination of host defensive and offensive molecular mechanisms to achieve specific and powerful defense against pathogens. Moreover, pathogens enhance intraspecific crosstalk and abrogate host apoptosis to accommodate enhanced host defense mechanisms during the adaptive phase. Accordingly, links between physiological phenomena and changes in the coordination of defensive and offensive molecular mechanisms highlight the importance of host-pathogen molecular interaction networks, and consequent inferences of the host-pathogen relationship could be translated into biomedical applications.

Mechanism of cluster DNA damage repair in response to high-atomic number and energy particles radiation

Energy Technology Data Exchange (ETDEWEB)

Asaithamby, Aroumougame, E-mail: Aroumougame.Asaithamy@UTsouthwestern.edu [Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390 (United States); Chen, David J., E-mail: David.Chen@UTsouthwestern.edu [Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390 (United States)

2011-06-03

Low-linear energy transfer (LET) radiation (i.e., {gamma}- and X-rays) induces DNA double-strand breaks (DSBs) that are rapidly repaired (rejoined). In contrast, DNA damage induced by the dense ionizing track of high-atomic number and energy (HZE) particles is slowly repaired or is irreparable. These unrepaired and/or misrepaired DNA lesions may contribute to the observed higher relative biological effectiveness for cell killing, chromosomal aberrations, mutagenesis, and carcinogenesis in HZE particle irradiated cells compared to those treated with low-LET radiation. The types of DNA lesions induced by HZE particles have been characterized in vitro and usually consist of two or more closely spaced strand breaks, abasic sites, or oxidized bases on opposing strands. It is unclear why these lesions are difficult to repair. In this review, we highlight the potential of a new technology allowing direct visualization of different types of DNA lesions in human cells and document the emerging significance of live-cell imaging for elucidation of the spatio-temporal characterization of complex DNA damage. We focus on the recent insights into the molecular pathways that participate in the repair of HZE particle-induced DSBs. We also discuss recent advances in our understanding of how different end-processing nucleases aid in repair of DSBs with complicated ends generated by HZE particles. Understanding the mechanism underlying the repair of DNA damage induced by HZE particles will have important implications for estimating the risks to human health associated with HZE particle exposure.

Mechanism of cluster DNA damage repair in response to high-atomic number and energy particles radiation

International Nuclear Information System (INIS)

Asaithamby, Aroumougame; Chen, David J.

2011-01-01

Low-linear energy transfer (LET) radiation (i.e., γ- and X-rays) induces DNA double-strand breaks (DSBs) that are rapidly repaired (rejoined). In contrast, DNA damage induced by the dense ionizing track of high-atomic number and energy (HZE) particles is slowly repaired or is irreparable. These unrepaired and/or misrepaired DNA lesions may contribute to the observed higher relative biological effectiveness for cell killing, chromosomal aberrations, mutagenesis, and carcinogenesis in HZE particle irradiated cells compared to those treated with low-LET radiation. The types of DNA lesions induced by HZE particles have been characterized in vitro and usually consist of two or more closely spaced strand breaks, abasic sites, or oxidized bases on opposing strands. It is unclear why these lesions are difficult to repair. In this review, we highlight the potential of a new technology allowing direct visualization of different types of DNA lesions in human cells and document the emerging significance of live-cell imaging for elucidation of the spatio-temporal characterization of complex DNA damage. We focus on the recent insights into the molecular pathways that participate in the repair of HZE particle-induced DSBs. We also discuss recent advances in our understanding of how different end-processing nucleases aid in repair of DSBs with complicated ends generated by HZE particles. Understanding the mechanism underlying the repair of DNA damage induced by HZE particles will have important implications for estimating the risks to human health associated with HZE particle exposure.

Feeding guild of non-host community members affects host-foraging efficiency of a parasitic wasp

NARCIS (Netherlands)

Rijk, de Marjolein; Yang, Daowei; Engel, Bastiaan; Dicke, Marcel; Poelman, Erik H.

2016-01-01

Interactions between predator and prey, or parasitoid and host, are shaped by trait-and density-mediated processes involving other community members. Parasitoids that lay their eggs in herbivorous insects locate their hosts through infochemicals such as herbivore-induced plant volatiles (HIPVs)

Host-to-host variation of ecological interactions in polymicrobial infections

International Nuclear Information System (INIS)

Mukherjee, Sayak; Seok, Sang-Cheol; Ray, Will C; Jayaprakash, C; Vieland, Veronica J; Das, Jayajit; Weimer, Kristin E; Swords, W Edward

2015-01-01

Host-to-host variability with respect to interactions between microorganisms and multicellular hosts are commonly observed in infection and in homeostasis. However, the majority of mechanistic models used to analyze host–microorganism relationships, as well as most of the ecological theories proposed to explain coevolution of hosts and microbes, are based on averages across a host population. By assuming that observed variations are random and independent, these models overlook the role of differences between hosts. Here, we analyze mechanisms underlying host-to-host variations of bacterial infection kinetics, using the well characterized experimental infection model of polymicrobial otitis media (OM) in chinchillas, in combination with population dynamic models and a maximum entropy (MaxEnt) based inference scheme. We find that the nature of the interactions between bacterial species critically regulates host-to-host variations in these interactions. Surprisingly, seemingly unrelated phenomena, such as the efficiency of individual bacterial species in utilizing nutrients for growth, and the microbe-specific host immune response, can become interdependent in a host population. The latter finding suggests a potential mechanism that could lead to selection of specific strains of bacterial species during the coevolution of the host immune response and the bacterial species. (paper)

Plasmid (pKM101)-mediated enhancement of repair and mutagenesis: dependence on chromosomal genes in 'Escherichia coli' K-12

International Nuclear Information System (INIS)

Walker, G.C.

1977-01-01

The drug resistance plasmid pKM101 plays a major role in the Ames Salmonella/microsome carcinogen detecting system by enhancing chemical mutagenesis. It is shown that in Escherichia coli K-12 the plasmid pKM101 enhances both spontaneous and methyl methanesulfonate-caused reversion of an ochre mutation, bacterial survival after ultaviolet irradiation, and reactivation of ultraviolet-irradiated lambda in unirradiated cells. All these effects are shown to be dependent on the recA + lexA + genotype but not on the recB + recC + or recF + genotypes. The recA lexA-dependence of the plasmid-mediated repair and mutagenesis suggests an interaction with the cell's inducible error-prone repair system. The presence of pKM101 is shown to cause an additional increase in methyl methanesulfonate mutagenesis in a tif mutant beyond that caused by growth at 42 0 . The presence of the plasmid raises the level of the Weigle-reactivation curve for the reactivation of ultraviolet-irradiated lambda in E. coli and causes a shift of the maximum to a higher UV fluence. These observations suggest that pKM101 does not exert its effects by altering the regulation of the cell's error-prone repair system but rather by supplying a mechanistic component or components. (orig.) [de

A Legionella Effector Disrupts Host Cytoskeletal Structure by Cleaving Actin.

Directory of Open Access Journals (Sweden)

Yao Liu

2017-01-01

Full Text Available Legionella pneumophila, the etiological agent of Legionnaires' disease, replicates intracellularly in protozoan and human hosts. Successful colonization and replication of this pathogen in host cells requires the Dot/Icm type IVB secretion system, which translocates approximately 300 effector proteins into the host cell to modulate various cellular processes. In this study, we identified RavK as a Dot/Icm substrate that targets the host cytoskeleton and reduces actin filament abundance in mammalian cells upon ectopic expression. RavK harbors an H95EXXH99 motif associated with diverse metalloproteases, which is essential for the inhibition of yeast growth and for the induction of cell rounding in HEK293T cells. We demonstrate that the actin protein itself is the cellular target of RavK and that this effector cleaves actin at a site between residues Thr351 and Phe352. Importantly, RavK-mediated actin cleavage also occurs during L. pneumophila infection. Cleavage by RavK abolishes the ability of actin to form polymers. Furthermore, an F352A mutation renders actin resistant to RavK-mediated cleavage; expression of the mutant in mammalian cells suppresses the cell rounding phenotype caused by RavK, further establishing that actin is the physiological substrate of RavK. Thus, L. pneumophila exploits components of the host cytoskeleton by multiple effectors with distinct mechanisms, highlighting the importance of modulating cellular processes governed by the actin cytoskeleton in the intracellular life cycle of this pathogen.

ATM is required for the repair of Topotecan-induced replication-associated double-strand breaks

International Nuclear Information System (INIS)

Köcher, Sabrina; Spies-Naumann, Anja; Kriegs, Malte; Dahm-Daphi, Jochen; Dornreiter, Irena

2013-01-01

Purpose: DNA replication is a promising target for anti-cancer therapies. Therefore, the understanding of replication-associated DNA repair mechanisms is of great interest. One key factor of DNA double-strand break (DSB) repair is the PIK kinase Ataxia-Telangiectasia Mutated (ATM) but it is still unclear whether ATM is involved in the repair of replication-associated DSBs. Here, we focused on the involvement of ATM in homology-directed repair (HDR) of indirect DSBs associated with replication. Material and methods: Experiments were performed using ATM-deficient and -proficient human cells. Replication-associated DSBs were induced with Topotecan (TPT) and compared with γ-irradiation (IR). Cell survival was measured by clonogenic assay. Overall DSB repair and HDR were evaluated by detecting residual γH2AX/53BP1 and Rad51 foci, respectively. Cell cycle distribution was analysed by flow cytometry and protein expression by Western blot. Results: ATM-deficiency leads to enhanced numbers of residual DSBs, resulting in a pronounced S/G2-block and decreased survival upon TPT-treatment. In common with IR, persisting Rad51 foci were detected following TPT-treatment. Conclusions: These results demonstrate that ATM is essentially required for the completion of HR-mediated repair of TPT-induced DSBs formed indirectly at replication forks

Mnn10 Maintains Pathogenicity in Candida albicans by Extending α-1,6-Mannose Backbone to Evade Host Dectin-1 Mediated Antifungal Immunity.

Directory of Open Access Journals (Sweden)

Shi Qun Zhang

2016-05-01

Full Text Available The cell wall is a dynamic structure that is important for the pathogenicity of Candida albicans. Mannan, which is located in the outermost layer of the cell wall, has been shown to contribute to the pathogenesis of C. albicans, however, the molecular mechanism by which this occurs remains unclear. Here we identified a novel α-1,6-mannosyltransferase encoded by MNN10 in C. albicans. We found that Mnn10 is required for cell wall α-1,6-mannose backbone biosynthesis and polysaccharides organization. Deletion of MNN10 resulted in significant attenuation of the pathogenesis of C. albicans in a murine systemic candidiasis model. Inhibition of α-1,6-mannose backbone extension did not, however, impact the invasive ability of C. albicans in vitro. Notably, mnn10 mutant restored the invasive capacity in athymic nude mice, which further supports the notion of an enhanced host antifungal defense related to this backbone change. Mnn10 mutant induced enhanced Th1 and Th17 cell mediated antifungal immunity, and resulted in enhanced recruitment of neutrophils and monocytes for pathogen clearance in vivo. We also demonstrated that MNN10 could unmask the surface β-(1,3-glucan, a crucial pathogen-associated molecular pattern (PAMP of C. albicans recognized by host Dectin-1. Our results demonstrate that mnn10 mutant could stimulate an enhanced Dectin-1 dependent immune response of macrophages in vitro, including the activation of nuclear factor-κB, mitogen-activated protein kinase pathways, and secretion of specific cytokines such as TNF-α, IL-6, IL-1β and IL-12p40. In summary, our study indicated that α-1,6-mannose backbone is critical for the pathogenesis of C. albicans via shielding β-glucan from recognition by host Dectin-1 mediated immune recognition. Moreover, our work suggests that inhibition of α-1,6-mannose extension by Mnn10 may represent a novel modality to reduce the pathogenicity of C. albicans.

Plasma membrane wounding and repair in pulmonary diseases.

Science.gov (United States)

Cong, Xiaofei; Hubmayr, Rolf D; Li, Changgong; Zhao, Xiaoli

2017-03-01

Various pathophysiological conditions such as surfactant dysfunction, mechanical ventilation, inflammation, pathogen products, environmental exposures, and gastric acid aspiration stress lung cells, and the compromise of plasma membranes occurs as a result. The mechanisms necessary for cells to repair plasma membrane defects have been extensively investigated in the last two decades, and some of these key repair mechanisms are also shown to occur following lung cell injury. Because it was theorized that lung wounding and repair are involved in the pathogenesis of acute respiratory distress syndrome (ARDS) and idiopathic pulmonary fibrosis (IPF), in this review, we summarized the experimental evidence of lung cell injury in these two devastating syndromes and discuss relevant genetic, physical, and biological injury mechanisms, as well as mechanisms used by lung cells for cell survival and membrane repair. Finally, we discuss relevant signaling pathways that may be activated by chronic or repeated lung cell injury as an extension of our cell injury and repair focus in this review. We hope that a holistic view of injurious stimuli relevant for ARDS and IPF could lead to updated experimental models. In addition, parallel discussion of membrane repair mechanisms in lung cells and injury-activated signaling pathways would encourage research to bridge gaps in current knowledge. Indeed, deep understanding of lung cell wounding and repair, and discovery of relevant repair moieties for lung cells, should inspire the development of new therapies that are likely preventive and broadly effective for targeting injurious pulmonary diseases. Copyright © 2017 the American Physiological Society.

DNA repair protocols

DEFF Research Database (Denmark)

Bjergbæk, Lotte

In its 3rd edition, this Methods in Molecular Biology(TM) book covers the eukaryotic response to genomic insult including advanced protocols and standard techniques in the field of DNA repair. Offers expert guidance for DNA repair, recombination, and replication. Current knowledge of the mechanisms...... that regulate DNA repair has grown significantly over the past years with technology advances such as RNA interference, advanced proteomics and microscopy as well as high throughput screens. The third edition of DNA Repair Protocols covers various aspects of the eukaryotic response to genomic insult including...... recent advanced protocols as well as standard techniques used in the field of DNA repair. Both mammalian and non-mammalian model organisms are covered in the book, and many of the techniques can be applied with only minor modifications to other systems than the one described. Written in the highly...

Evidence for miRNA-mediated modulation of the host transcriptome in cnidarian-dinoflagellate symbiosis

KAUST Repository

Baumgarten, Sebastian

2017-12-08

Reef-building corals and other cnidarians living in symbiotic relationships with intracellular, photosynthetic dinoflagellates in the genus Symbiodinium undergo transcriptomic changes during infection with the algae and maintenance of the endosymbiont population. However, the precise regulatory mechanisms modulating the host transcriptome are unknown. Here we report apparent post-transcriptional gene regulation by miRNAs in the sea anemone Aiptasia, a model system for cnidarian-dinoflagellate endosymbiosis. Aiptasia encodes mainly species-specific miRNAs, and there appears to have been recent differentiation within the Aiptasia genome of miRNAs that are commonly conserved among anthozoan cnidarians. Analysis of miRNA expression showed that both conserved and species-specific miRNAs are differentially expressed in response to endosymbiont infection. Using cross-linking immunoprecipitation of Argonaute, the central protein of the miRNA-induced silencing complex, we identified miRNA binding sites on a transcriptome-wide scale and found that the targets of the miRNAs regulated in response to symbiosis include genes previously implicated in biological processes related to Symbiodinium infection. Our study shows that cnidarian miRNAs recognize their mRNA targets via high-complementarity target binding and suggests that miRNA-mediated modulations of genes and pathways are important during the onset and maintenance of cnidarian-dinoflagellate endosymbiosis. This article is protected by copyright. All rights reserved.

Evidence for miRNA-mediated modulation of the host transcriptome in cnidarian-dinoflagellate symbiosis

KAUST Repository

Baumgarten, Sebastian; Cziesielski, Maha J.; Thomas, Ludivine; Michell, Craig; Esherick, Lisl Y.; Pringle, John R.; Aranda, Manuel; Voolstra, Christian R.

2017-01-01

Reef-building corals and other cnidarians living in symbiotic relationships with intracellular, photosynthetic dinoflagellates in the genus Symbiodinium undergo transcriptomic changes during infection with the algae and maintenance of the endosymbiont population. However, the precise regulatory mechanisms modulating the host transcriptome are unknown. Here we report apparent post-transcriptional gene regulation by miRNAs in the sea anemone Aiptasia, a model system for cnidarian-dinoflagellate endosymbiosis. Aiptasia encodes mainly species-specific miRNAs, and there appears to have been recent differentiation within the Aiptasia genome of miRNAs that are commonly conserved among anthozoan cnidarians. Analysis of miRNA expression showed that both conserved and species-specific miRNAs are differentially expressed in response to endosymbiont infection. Using cross-linking immunoprecipitation of Argonaute, the central protein of the miRNA-induced silencing complex, we identified miRNA binding sites on a transcriptome-wide scale and found that the targets of the miRNAs regulated in response to symbiosis include genes previously implicated in biological processes related to Symbiodinium infection. Our study shows that cnidarian miRNAs recognize their mRNA targets via high-complementarity target binding and suggests that miRNA-mediated modulations of genes and pathways are important during the onset and maintenance of cnidarian-dinoflagellate endosymbiosis. This article is protected by copyright. All rights reserved.

Replicative bypass repair of ultraviolet damage to DNA of mammalian cells: caffeine sensitive and caffeine resistant mechanism

International Nuclear Information System (INIS)

Fujiwara, Y.; Tatsumi, M.

1976-01-01

Replicative bypass repair of UV damage to DNA was studied in a wide variaty of human, mouse and hamster cells in culture. Survival curve analysis revealed that in established cell lines (mouse L, Chinese hamster V79, HeLa S3 and SV40-transformed xeroderma pigmentosum (XP), post-UV caffeine treatment potentiated cell killing by reducing the extrapolation number and mean lethal UV fluence (Do). In the Do reduction as the result of random inactivation by caffeine of sensitive repair there were marked clonal differences among such cell lines, V79 being most sensitive to caffeine potentiation. However, other diploid cell lines (normal human, excision-defective XP and Syrian hamster) exhibited no obvious reduction in Do by caffeine. In parallel, alkaline sucrose sedimentation results showed that the conversion of initially smaller segments of DNA synthesized after irradiation with 10 J/m 2 to high-molecular-weight DNA was inhibited by caffeine in transformed XP cells, but not in the diploid human cell lines. Exceptionally, diploid XP variants had a retarded ability of bypass repair which was drastically prevented by caffeine, so that caffeine enhanced the lethal effect of UV. Neutral CsCl study on the bypass repair mechanism by use of bromodeoxyuridine for DNA synthesis on damaged template suggests that the pyrimodine dimer acts as a block to replication and subsequently it is circumvented presumably by a new process involving replicative bypassing following strand displacement, rather than by gap-filling de novo. This mechanism worked similarly in normal and XP cells, whether or not caffeine was present, indicating that excision of dimer is not always necessary. However, replicative bypassing became defective in XP variant and transformed XP cells when caffeine was present. It appears, therefore, that the replicative bypass repair process is either caffeine resistant or sensitive, depending on the cell type used, but not necessarily on the excision repair capability

Explaining the differential distribution of Clean Development Mechanism projects across host countries

International Nuclear Information System (INIS)

Winkelman, Andrew G.; Moore, Michael R.

2011-01-01

The Clean Development Mechanism (CDM) of the Kyoto Protocol represents an opportunity to involve all developing countries in the effort to reduce greenhouse gas emissions while also promoting sustainable development. To date, however, the majority of CDM projects have gone to emerging markets such as China, India, Brazil, and Mexico, while very few least developed countries have hosted projects. This paper investigates the differential distribution of CDM activities across countries. We develop a conceptual model for project profitability, which helps to identify potential country-level determinants of CDM activity. These potential determinants are employed as explanatory variables in regression analysis to explain the actual distribution of projects. Human capital and greenhouse gas emission levels influenced which countries have hosted projects and the amount of certified emission reductions (CER) created. Countries that offered growing markets for CDM co-products, such as electricity, were more likely to be CDM hosts, while economies with higher carbon intensity levels had greater CER production. These findings work against the least developed countries and help to explain their lack of CDM activity. - Research Highlights: → Regression models are used to explain the inter-country distribution of CDM projects. → Emissions and human capital are significant for hosting projects and CER creation. → An economy's emissions intensity is significant in determining CERs created. → Capacity building and electricity sector growth are significant in hosting projects. → The experience level for host countries in the CDM is significant for CER creation.

Damage-associated responses of the host contribute to defence against cyst nematodes but not root-knot nematodes

NARCIS (Netherlands)

Shah, Syed Jehangir; Anjam, Muhammad Shahzad; Mendy, Badou; Anwer, Muhammad Arslan; Habash, Samer S.; Lozano-Torres, Jose L.; Grundler, Florian M.W.; Siddique, Shahid

2017-01-01

When nematodes invade and subsequently migrate within plant roots, they generate cell wall fragments (in the form of oligogalacturonides; OGs) that can act as damage-associated molecular patterns and activate host defence responses. However, the molecular mechanisms mediating damage responses in

Prolonged exposure to particulate chromate inhibits RAD51 nuclear import mediator proteins.

Science.gov (United States)

Browning, Cynthia L; Wise, John Pierce

2017-09-15

Particulate hexavalent chromium (Cr(VI)) is a human lung carcinogen and a human health concern. The induction of structural chromosome instability is considered to be a driving mechanism of Cr(VI)-induced carcinogenesis. Homologous recombination repair protects against Cr(VI)-induced chromosome damage, due to its highly accurate repair of Cr(VI)-induced DNA double strand breaks. However, recent studies demonstrate Cr(VI) inhibits homologous recombination repair through the misregulation of RAD51. RAD51 is an essential protein in HR repair that facilitates the search for a homologous sequence. Recent studies show prolonged Cr(VI) exposure prevents proper RAD51 subcellular localization, causing it to accumulate in the cytoplasm. Since nuclear import of RAD51 is crucial to its function, this study investigated the effect of Cr(VI) on the RAD51 nuclear import mediators, RAD51C and BRCA2. We show acute (24h) Cr(VI) exposure induces the proper localization of RAD51C and BRCA2. In contrast, prolonged (120h) exposure increased the cytoplasmic localization of both proteins, although RAD51C localization was more severely impaired. These results correlate temporally with the previously reported Cr(VI)-induced RAD51 cytoplasmic accumulation. In addition, we found Cr(VI) does not inhibit interaction between RAD51 and its nuclear import mediators. Altogether, our results suggest prolonged Cr(VI) exposure inhibits the nuclear import of RAD51C, and to a lesser extent, BRCA2, which results in the cytoplasmic accumulation of RAD51. Cr(VI)-induced inhibition of nuclear import may play a key role in its carcinogenic mechanism since the nuclear import of many tumor suppressor proteins and DNA repair proteins is crucial to their function. Copyright © 2017 Elsevier Inc. All rights reserved.

DNA repair genes

International Nuclear Information System (INIS)

Morimyo, Mitsuoki

1995-01-01

Fission yeast S. pombe is assumed to be a good model for cloning of human DNA repair genes, because human gene is normally expressed in S. pombe and has a very similar protein sequence to yeast protein. We have tried to elucidate the DNA repair mechanisms of S. pombe as a model system for those of mammals. (J.P.N.)

Radiation damage and its repair in non-sporulating bacteria

International Nuclear Information System (INIS)

Moseley, B.E.B.

1984-01-01

A review is given of radiation damage and its repair in non-sporulating bacteria. The identification and measurement of radiation damage in the DNA of the bacteria after exposure to ultraviolet radiation and ionizing radiation is described. Measuring the extent of DNA repair and ways of isolating repair mutants are also described. The DNA repair mechanisms for UV-induced damage are discussed including photoreactivation repair, excision repair, post-replication recombination repair and induced error-prone repair. The DNA repair mechanisms for ionizing radiation damage are also discussed including the repair of both single and double-strand breaks. Other aspects discussed include the effects of growth, irradiation medium and recovery medium on survival, DNA repair in humans, the commercial use of UV and ionizing radiations and the future of ionizing irradiation as a food treatment process. (U.K.)

Host lysozyme-mediated lysis of Lactococcus lactis facilitates delivery of colitis-attenuating superoxide dismutase to inflamed colons

Science.gov (United States)

Ballal, Sonia A.; Veiga, Patrick; Fenn, Kathrin; Michaud, Monia; Kim, Jason H.; Gallini, Carey Ann; Glickman, Jonathan N.; Quéré, Gaëlle; Garault, Peggy; Béal, Chloé; Derrien, Muriel; Courtin, Pascal; Kulakauskas, Saulius; Chapot-Chartier, Marie-Pierre; van Hylckama Vlieg, Johan; Garrett, Wendy S.

2015-01-01

Beneficial microbes that target molecules and pathways, such as oxidative stress, which can negatively affect both host and microbiota, may hold promise as an inflammatory bowel disease therapy. Prior work showed that a five-strain fermented milk product (FMP) improved colitis in T-bet−/− Rag2−/− mice. By varying the number of strains used in the FMP, we found that Lactococcus lactis I-1631 was sufficient to ameliorate colitis. Using comparative genomic analyses, we identified genes unique to L. lactis I-1631 involved in oxygen respiration. Respiration of oxygen results in reactive oxygen species (ROS) generation. Also, ROS are produced at high levels during intestinal inflammation and cause tissue damage. L. lactis I-1631 possesses genes encoding enzymes that detoxify ROS, such as superoxide dismutase (SodA). Thus, we hypothesized that lactococcal SodA played a role in attenuating colitis. Inactivation of the sodA gene abolished L. lactis I-1631’s beneficial effect in the T-bet−/− Rag2−/− model. Similar effects were obtained in two additional colonic inflammation models, Il10−/− mice and dextran sulfate sodium-treated mice. Efforts to understand how a lipophobic superoxide anion (O2−) can be detoxified by cytoplasmic lactoccocal SodA led to the finding that host antimicrobial-mediated lysis is a prerequisite for SodA release and SodA’s extracytoplasmic O2− scavenging. L. lactis I-1631 may represent a promising vehicle to deliver antioxidant, colitis-attenuating SodA to the inflamed intestinal mucosa, and host antimicrobials may play a critical role in mediating SodA’s bioaccessibility. PMID:26056274

NF-κB regulates DNA double-strand break repair in conjunction with BRCA1-CtIP complexes.

Science.gov (United States)

Volcic, Meta; Karl, Sabine; Baumann, Bernd; Salles, Daniela; Daniel, Peter; Fulda, Simone; Wiesmüller, Lisa

2012-01-01

NF-κB is involved in immune responses, inflammation, oncogenesis, cell proliferation and apoptosis. Even though NF-κB can be activated by DNA damage via Ataxia telangiectasia-mutated (ATM) signalling, little was known about an involvement in DNA repair. In this work, we dissected distinct DNA double-strand break (DSB) repair mechanisms revealing a stimulatory role of NF-κB in homologous recombination (HR). This effect was independent of chromatin context, cell cycle distribution or cross-talk with p53. It was not mediated by the transcriptional NF-κB targets Bcl2, BAX or Ku70, known for their dual roles in apoptosis and DSB repair. A contribution by Bcl-xL was abrogated when caspases were inhibited. Notably, HR induction by NF-κB required the targets ATM and BRCA2. Additionally, we provide evidence that NF-κB interacts with CtIP-BRCA1 complexes and promotes BRCA1 stabilization, and thereby contributes to HR induction. Immunofluorescence analysis revealed accelerated formation of replication protein A (RPA) and Rad51 foci upon NF-κB activation indicating HR stimulation through DSB resection by the interacting CtIP-BRCA1 complex and Rad51 filament formation. Taken together, these results define multiple NF-κB-dependent mechanisms regulating HR induction, and thereby providing a novel intriguing explanation for both NF-κB-mediated resistance to chemo- and radiotherapies as well as for the sensitization by pharmaceutical intervention of NF-κB activation.

Mining Host-Pathogen Protein Interactions to Characterize Burkholderia mallei Infectivity Mechanisms

Science.gov (United States)

2015-03-04

the cytoskeleton, in lysosomes , and in the nuclear lumen. These results were consistent with the experimentally observed pathogen interference with...RESEARCH ARTICLE Mining Host- Pathogen Protein Interactions to Characterize Burkholderia mallei Infectivity Mechanisms Vesna Memišević1, Nela...Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases , Fort Detrick, Maryland, United States of America * jaques.reifman.civ

New paradigms in the repair of oxidative damage in human genome: mechanisms ensuring repair of mutagenic base lesions during replication and involvement of accessory proteins.

Science.gov (United States)

Dutta, Arijit; Yang, Chunying; Sengupta, Shiladitya; Mitra, Sankar; Hegde, Muralidhar L

2015-05-01

Oxidized bases in the mammalian genome, which are invariably mutagenic due to their mispairing property, are continuously induced by endogenous reactive oxygen species and more abundantly after oxidative stress. Unlike bulky base adducts induced by UV and other environmental mutagens in the genome that block replicative DNA polymerases, oxidatively damaged bases such as 5-hydroxyuracil, produced by oxidative deamination of cytosine in the template strand, do not block replicative polymerases and thus need to be repaired prior to replication to prevent mutation. Following up our earlier studies, which showed that the Nei endonuclease VIII like 1 (NEIL1) DNA glycosylase, one of the five base excision repair (BER)-initiating enzymes in mammalian cells, has enhanced expression during the S-phase and higher affinity for replication fork-mimicking single-stranded (ss) DNA substrates, we recently provided direct experimental evidence for NEIL1's role in replicating template strand repair. The key requirement for this event, which we named as the 'cow-catcher' mechanism of pre-replicative BER, is NEIL1's non-productive binding (substrate binding without product formation) to the lesion base in ss DNA template to stall DNA synthesis, causing fork regression. Repair of the lesion in reannealed duplex is then carried out by NEIL1 in association with the DNA replication proteins. NEIL1 (and other BER-initiating enzymes) also interact with several accessory and non-canonical proteins including the heterogeneous nuclear ribonucleoprotein U and Y-box-binding protein 1 as well as high mobility group box 1 protein, whose precise roles in BER are still obscure. In this review, we have discussed the recent advances in our understanding of oxidative genome damage repair pathways with particular focus on the pre-replicative template strand repair and the role of scaffold factors like X-ray repairs cross-complementing protein 1 and poly (ADP-ribose) polymerase 1 and other accessory

Human inherited diseases with altered mechanisms for DNA repair and mutagenesis

Energy Technology Data Exchange (ETDEWEB)

Cleaver, J.E.

1977-01-01

A variety of human diseases involving clinical symptoms of increased cancer risk, and disorders of the central nervous system, and of hematopoietic, immunological, ocular, and cutaneous tissues and embryological development have defects in biochemical pathways for excision repair of damaged DNA. Excision repair has multiple branches by which damaged nucleotides, bases, and cross-links are excised and requires cofactors that control the access of repair enzymes to damage in DNA in chromatin. Diseases in which repair defects are a consistent feature of their biochemistry include xeroderma pigmentosum, ataxia telangiectasia and Fanconi's anemia.

Host Preference and Performance of the Yellow Peach Moth (Conogethes punctiferalis on Chestnut Cultivars.

Directory of Open Access Journals (Sweden)

Yanli Du

Full Text Available Suitability of plant tissues as food for insects varies from plant to plant. In lepidopteran insects, fitness is largely dependent on the host-finding ability of the females. Existing studies have suggested that polyphagous lepidopterans preferentially select certain host plant species for oviposition. However, the mechanisms for host recognition and selection have not been fully elucidated. For the polyphagous yellow peach moth Conogethes punctiferalis, we explored the effect of chestnut cultivar on the performance and fitness and addressed the mechanisms of plant-volatile-mediated host recognition. By carrying out laboratory experiments and field investigation on four chestnut Castanea mollissima cultivars (Huaihuang, Huaijiu, Yanhong, and Shisheng, we found that C. punctiferalis females preferentially select Huaijiu for oviposition and infestation, and caterpillars fed on Huaijiu achieved slightly greater fitness than those fed on the other three chestnut cultivars, indicating that Huaijiu was a better suitable host for C. punctiferalis. Plant volatiles played important roles in host recognition by C. punctiferalis. All seven chestnut volatile compounds, α-pinene, camphene, β-thujene, β-pinene, eucalyptol, 3-carene, and nonanal, could trigger EAG responses in C. punctiferalis. The ubiquitous plant terpenoids, α-pinene, camphene and β-pinene, and their specific combination at concentrations and proportions similar to the emissions from the four chestnut cultivars, was sufficient to elicit host recognition behavior of female C. punctiferalis. Nonanal and a mixture containing nonanal, that mimicked the emission of C. punctiferalis infested chestnut fruits, caused avoidance response. The outcome demonstrates the effects of chestnut cultivars on the performance of C. punctiferalis and reveals the preference-performance relationship between C. punctiferalis adults and their offspring. The observed olfactory plasticity in the plant-volatile-mediated

Ontology-based representation and analysis of host-Brucella interactions.

Science.gov (United States)

Lin, Yu; Xiang, Zuoshuang; He, Yongqun

2015-01-01

Biomedical ontologies are representations of classes of entities in the biomedical domain and how these classes are related in computer- and human-interpretable formats. Ontologies support data standardization and exchange and provide a basis for computer-assisted automated reasoning. IDOBRU is an ontology in the domain of Brucella and brucellosis. Brucella is a Gram-negative intracellular bacterium that causes brucellosis, the most common zoonotic disease in the world. In this study, IDOBRU is used as a platform to model and analyze how the hosts, especially host macrophages, interact with virulent Brucella strains or live attenuated Brucella vaccine strains. Such a study allows us to better integrate and understand intricate Brucella pathogenesis and host immunity mechanisms. Different levels of host-Brucella interactions based on different host cell types and Brucella strains were first defined ontologically. Three important processes of virulent Brucella interacting with host macrophages were represented: Brucella entry into macrophage, intracellular trafficking, and intracellular replication. Two Brucella pathogenesis mechanisms were ontologically represented: Brucella Type IV secretion system that supports intracellular trafficking and replication, and Brucella erythritol metabolism that participates in Brucella intracellular survival and pathogenesis. The host cell death pathway is critical to the outcome of host-Brucella interactions. For better survival and replication, virulent Brucella prevents macrophage cell death. However, live attenuated B. abortus vaccine strain RB51 induces caspase-2-mediated proinflammatory cell death. Brucella-associated cell death processes are represented in IDOBRU. The gene and protein information of 432 manually annotated Brucella virulence factors were represented using the Ontology of Genes and Genomes (OGG) and Protein Ontology (PRO), respectively. Seven inference rules were defined to capture the knowledge of host

Riboflavin Provisioning Underlies Wolbachia's Fitness Contribution to Its Insect Host.

Science.gov (United States)

Moriyama, Minoru; Nikoh, Naruo; Hosokawa, Takahiro; Fukatsu, Takema

2015-11-10

selfish manner, which tends to affect a host's fitness negatively. Meanwhile, some theories predict that, at the same time, Wolbachia can directly affect the host's fitness positively, which may potentially reconcile the negative effect and facilitate spread and stability of the symbiotic association. Here we demonstrate, by using comparative genomic and experimental approaches, that among synthetic pathways for B vitamins, the synthetic pathway for riboflavin (vitamin B2) is exceptionally conserved among diverse insect-associated Wolbachia strains, and Wolbachia's riboflavin provisioning certainly contributes to growth, survival, and reproduction in an insect. These findings uncover a nutritional mechanism of a Wolbachia-mediated fitness benefit, which provides empirical evidence highlighting a "Jekyll and Hyde" aspect of Wolbachia infection. Copyright © 2015 Moriyama et al.

Mitophagy confers resistance to siderophore-mediated killing by Pseudomonas aeruginosa.

Science.gov (United States)

Kirienko, Natalia V; Ausubel, Frederick M; Ruvkun, Gary

2015-02-10

In the arms race of bacterial pathogenesis, bacteria produce an array of toxins and virulence factors that disrupt core host processes. Hosts mitigate the ensuing damage by responding with immune countermeasures. The iron-binding siderophore pyoverdin is a key virulence mediator of the human pathogen Pseudomonas aeruginosa, but its pathogenic mechanism has not been established. Here we demonstrate that pyoverdin enters Caenorhabditis elegans and that it is sufficient to mediate host killing. Moreover, we show that iron chelation disrupts mitochondrial homeostasis and triggers mitophagy both in C. elegans and mammalian cells. Finally, we show that mitophagy provides protection both against the extracellular pathogen P. aeruginosa and to treatment with a xenobiotic chelator, phenanthroline, in C. elegans. Although autophagic machinery has been shown to target intracellular bacteria for degradation (a process known as xenophagy), our report establishes a role for authentic mitochondrial autophagy in the innate immune defense against P. aeruginosa.

Virus-mediated suppression of host non-self recognition facilitates horizontal transmission of heterologous viruses.

Directory of Open Access Journals (Sweden)

Songsong Wu

2017-03-01

Full Text Available Non-self recognition is a common phenomenon among organisms; it often leads to innate immunity to prevent the invasion of parasites and maintain the genetic polymorphism of organisms. Fungal vegetative incompatibility is a type of non-self recognition which often induces programmed cell death (PCD and restricts the spread of molecular parasites. It is not clearly known whether virus infection could attenuate non-self recognition among host individuals to facilitate its spread. Here, we report that a hypovirulence-associated mycoreovirus, named Sclerotinia sclerotiorum mycoreovirus 4 (SsMYRV4, could suppress host non-self recognition and facilitate horizontal transmission of heterologous viruses. We found that cell death in intermingled colony regions between SsMYRV4-infected Sclerotinia sclerotiorum strain and other tested vegetatively incompatible strains was markedly reduced and inhibition barrage lines were not clearly observed. Vegetative incompatibility, which involves Heterotrimeric guanine nucleotide-binding proteins (G proteins signaling pathway, is controlled by specific loci termed het (heterokaryon incompatibility loci. Reactive oxygen species (ROS plays a key role in vegetative incompatibility-mediated PCD. The expression of G protein subunit genes, het genes, and ROS-related genes were significantly down-regulated, and cellular production of ROS was suppressed in the presence of SsMYRV4. Furthermore, SsMYRV4-infected strain could easily accept other viruses through hyphal contact and these viruses could be efficiently transmitted from SsMYRV4-infected strain to other vegetatively incompatible individuals. Thus, we concluded that SsMYRV4 is capable of suppressing host non-self recognition and facilitating heterologous viruses transmission among host individuals. These findings may enhance our understanding of virus ecology, and provide a potential strategy to utilize hypovirulence-associated mycoviruses to control fungal diseases.

Statistical grand rounds: understanding the mechanism: mediation analysis in randomized and nonrandomized studies.

Science.gov (United States)

Mascha, Edward J; Dalton, Jarrod E; Kurz, Andrea; Saager, Leif

2013-10-01

In comparative clinical studies, a common goal is to assess whether an exposure, or intervention, affects the outcome of interest. However, just as important is to understand the mechanism(s) for how the intervention affects outcome. For example, if preoperative anemia was shown to increase the risk of postoperative complications by 15%, it would be important to quantify how much of that effect was due to patients receiving intraoperative transfusions. Mediation analysis attempts to quantify how much, if any, of the effect of an intervention on outcome goes though prespecified mediator, or "mechanism" variable(s), that is, variables sitting on the causal pathway between exposure and outcome. Effects of an exposure on outcome can thus be divided into direct and indirect, or mediated, effects. Mediation is claimed when 2 conditions are true: the exposure affects the mediator and the mediator (adjusting for the exposure) affects the outcome. Understanding how an intervention affects outcome can validate or invalidate one's original hypothesis and also facilitate further research to modify the responsible factors, and thus improve patient outcome. We discuss the proper design and analysis of studies investigating mediation, including the importance of distinguishing mediator variables from confounding variables, the challenge of identifying potential mediators when the exposure is chronic versus acute, and the requirements for claiming mediation. Simple designs are considered, as well as those containing multiple mediators, multiple outcomes, and mixed data types. Methods are illustrated with data collected by the National Surgical Quality Improvement Project (NSQIP) and utilized in a companion paper which assessed the effects of preoperative anemic status on postoperative outcomes.

Placental Growth Factor Promotes Cardiac Muscle Repair via Enhanced Neovascularization

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Jianfeng Zhang

2015-06-01

Full Text Available Background/Aims: Transplantation of mesenchymal stem cells (MSCs improves post-injury cardiac muscle repair using ill-defined mechanisms. Recently, we have shown that production and secretion of placental growth factor (PLGF by MSCs play a critical role in the MSCs-mediated post-injury cardiac muscle repair. In this study, we addressed the underlying molecular mechanisms, focusing specifically on the interactions between MSCs, macrophages and endothelial cells. Methods: We isolated macrophages (BM-MΦ from mouse bone-marrow derived cells based on F4/80 expression by flow cytometry. BM-MΦ were treated with different doses of PLGF. Cell number was analyzed by a MTT assay. Macrophage polarization was examined based on CD206 expression by flow cytometry. PLGF levels in macrophage subpopulations were analyzed by RT-qPCR and ELISA. Effects of macrophages on vascularization were evaluated by a collagen gel assay using Human umbilical vein endothelial cells (HUVECs co-cultured with PLGF-treated macrophages. Results: PLGF did not increase macrophage number, but dose-dependently polarized macrophages into a M2 subpopulation. M2 macrophages expressed high levels of PLGF. PLGF-polarized M2 macrophages significantly increased tubular structures in the collagen gel assay. Conclusion: Our data suggest that MSCs-derived PLGF may induce macrophage polarization into a M2 subpopulation, which in turn releases more PLGF to promote local neovascularization for augmenting post-injury cardiac muscle repair. This study thus sheds novel light on the role of PLGF in cardiac muscle regeneration.

Emerging connection between centrosome and DNA repair machinery

International Nuclear Information System (INIS)

Shimada, Mikio; Komatsu, Kenshi

2009-01-01

Centrosomes function in proper cell division in animal cells. The centrosome consists of a pair of centrioles and the surrounding pericentriolar matrix (PCM). After cytokinesis, daughter cells each acquire one centrosome, which subsequently duplicates at the G1/S phase in a manner that is dependent upon CDK2/cyclin-E activity. Defects in the regulation of centrosome duplication lead to tumorigenesis through abnormal cell division and resulting inappropriate chromosome segregation. Therefore, maintenance of accurate centrosome number is important for cell fate. Excess number of centrosomes can be induced by several factors including ionizing radiation (IR). Recent studies have shown that several DNA repair proteins localize to the centrosome and are involved in the regulation of centrosome number possibly through cell cycle checkpoints or direct modification of centrosome proteins. Furthermore, it has been reported that the development of microcephaly is likely caused by defective expression of centrosome proteins, such as ASPM, which are also involved in the response to IR. The present review highlights centrosome duplication in association with genotoxic stresses and the regulatory mechanism mediated by DNA repair proteins. (author)

Dss1 interaction with Brh2 as a regulatory mechanism for recombinational repair

DEFF Research Database (Denmark)

Zhou, Qingwen; Kojic, Milorad; Cao, Zhimin

2007-01-01

Brh2, the BRCA2 ortholog in Ustilago maydis, enables recombinational repair of DNA by controlling Rad51 and is in turn regulated by Dss1. Interplay with Rad51 is conducted via the BRC element located in the N-terminal region of the protein and through an unrelated domain, CRE, at the C terminus....... Mutation in either BRC or CRE severely reduces functional activity, but repair deficiency of the brh2 mutant can be complemented by expressing BRC and CRE on different molecules. This intermolecular complementation is dependent upon the presence of Dss1. Brh2 molecules associate through the region...... overlapping with the Dss1-interacting domain to form at least dimer-sized complexes, which in turn, can be dissociated by Dss1 to monomer. We propose that cooperation between BRC and CRE domains and the Dss1-provoked dissociation of Brh2 complexes are requisite features of Brh2's molecular mechanism...

Metabolite damage and repair in metabolic engineering design

Energy Technology Data Exchange (ETDEWEB)

Sun, Jiayi; Jeffryes, James G.; Henry, Christopher S.; Bruner, Steven D.; Hanson, Andrew D.

2017-11-01

The necessarily sharp focus of metabolic engineering and metabolic synthetic biology on pathways and their fluxes has tended to divert attention from the damaging enzymatic and chemical side-reactions that pathway metabolites can undergo. Although historically overlooked and underappreciated, such metabolite damage reactions are now known to occur throughout metabolism and to generate (formerly enigmatic) peaks detected in metabolomics datasets. It is also now known that metabolite damage is often countered by dedicated repair enzymes that undo or prevent it. Metabolite damage and repair are highly relevant to engineered pathway design: metabolite damage reactions can reduce flux rates and product yields, and repair enzymes can provide robust, host-independent solutions. Herein, after introducing the core principles of metabolite damage and repair, we use case histories to document how damage and repair processes affect efficient operation of engineered pathways - particularly those that are heterologous, non-natural, or cell-free. We then review how metabolite damage reactions can be predicted, how repair reactions can be prospected, and how metabolite damage and repair can be built into genome-scale metabolic models. Lastly, we propose a versatile 'plug and play' set of well-characterized metabolite repair enzymes to solve metabolite damage problems known or likely to occur in metabolic engineering and synthetic biology projects.

Composition of Dietary Fat Source Shapes Gut Microbiota Architecture and Alters Host Inflammatory Mediators in Mouse Adipose Tissue

Science.gov (United States)

Huang, Edmond; Leone, Vanessa; Devkota, Suzanne; Wang, Yunwei; Brady, Matthew; Chang, Eugene

2013-01-01

Background Growing evidence shows that dietary factors can dramatically alter the gut microbiome in ways that contribute to metabolic disturbance and progression of obesity. In this regard, mesenteric adipose tissue has been implicated in mediating these processes through the elaboration of pro-inflammatory adipokines. In this study, we examined the relationship of these events by determining the effects of dietary fat content and source on gut microbiota, as well as the effects on adipokine profiles of mesenteric and peripheral adipocytes. Methods Adult male C57Bl/6 mice were fed milk fat-, lard-(SFA sources), or safflower oil (PUFA)- based high fat diets for four weeks. Body mass and food consumption were measured. Stool 16S rRNA was isolated and analyzed via T-RFLP as well as variable V3-4 sequence tags via next gen sequencing. Mesenteric and gonadal adipose samples were analyzed for both lipogenic and inflammatory mediators via qRT-PCR. Results High-fat feedings caused more weight gain with concomitant increases in caloric consumption relative to low-fat diets. Additionally, each of the high fat diets induced dramatic and specific 16S rRNA phylogenic profiles that were associated with different inflammatory and lipogenic mediator profile of mesenteric and gonadal fat depots. Conclusions Our findings support the notion that dietary fat composition can both reshape the gut microbiota as well as alter host adipose tissue inflammatory/lipogenic profiles. They also demonstrate the interdependency of dietary fat source, commensal gut microbiota, and inflammatory profile of mesenteric fat that can collectively impact the host metabolic state. PMID:23639897

Helicobacter pylori infection affects mitochondrial function and DNA repair, thus, mediating genetic instability in gastric cells

DEFF Research Database (Denmark)

Machado, Ana Manuel Dantas; Desler, Claus; Boggild, Sisse

2013-01-01

Helicobacter pylori infection is an important factor for the development of atrophic gastritis and gastric carcinogenesis. However, the mechanisms explaining the effects of H. pylori infection are not fully elucidated. H. pylori infection is known to induce genetic instability in both nuclear and....... pylori infection, furthermore, the results demonstrate that multiple DNA repair activities are involved in protecting mtDNA during infection. (C) 2013 Elsevier Ireland Ltd. All rights reserved....

Mechanisms of tolerance in murine radiation bone marrow chimeras. II. Absence of nonspecific suppression in mature chimeras

International Nuclear Information System (INIS)

Auchincloss, H. Jr.; Sachs, D.H.

1983-01-01

Spleen cells from a series of allogeneic bone marrow chimeras were sensitized in vitro with stimulator cells from major histocompatibility complex recombinant strains of mice. The combinations were chosen such that both tolerated (host or donor) and nontolerated (third-party) antigens were present on the same stimulator cells in order to determine whether the tolerated host antigens might elicit nonspecific suppressor mechanisms affecting the cell-mediated lympholysis (CML) response to the nontolerated antigens. No evidence for such nonspecific suppression was obtained in several types of assays. Therefore, if suppressor mechanisms exist that mediate such tolerance in mature allogeneic chimeras then these mechanisms must be highly antigen-specific

Polymer nanocomposites for high-temperature composite repair

Energy Technology Data Exchange (ETDEWEB)

Sheng, Xia [Iowa State Univ., Ames, IA (United States)

2008-01-01

A novel repair agent for resin-injection repair of advanced high temperature composites was developed and characterized. The repair agent was based on bisphenol E cyanate ester (BECy) and reinforced with alumina nanoparticles. To ensure good dispersion and compatibility with the BECy matrix in nanocomposites, the alumina nanoparticles were functionalized with silanes. The BECy nanocomposites, containing bare and functionalized alumina nanoparticles, were prepared and evaluated for their thermal, mechanical, rheological, and viscoelastic properties. The monomer of BECy has an extremely low viscosity at ambient temperature, which is good for processability. The cured BECy polymer is a highly cross-linked network with excellent thermal mechanical properties, with a high glass transition temperature (T_g) of 270 C and decomposition temperature above 350 C. The incorporation of alumina nanoparticles enhances the mechanical and rheological properties of the BECy nanocomposites. Additionally, the alumina nanoparticles are shown to catalyze the cure of BECy. Characterization of the nanocomposites included dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, rheological and rheokinetic evaluation, and transmission electron microscopy. The experimental results show that the BECy nanocomposite is a good candidate as repair agent for resin-injection repair applications.

Stem Cells for Cartilage Repair: Preclinical Studies and Insights in Translational Animal Models and Outcome Measures

Directory of Open Access Journals (Sweden)

Melissa Lo Monaco

2018-01-01

Full Text Available Due to the restricted intrinsic capacity of resident chondrocytes to regenerate the lost cartilage postinjury, stem cell-based therapies have been proposed as a novel therapeutic approach for cartilage repair. Moreover, stem cell-based therapies using mesenchymal stem cells (MSCs or induced pluripotent stem cells (iPSCs have been used successfully in preclinical and clinical settings. Despite these promising reports, the exact mechanisms underlying stem cell-mediated cartilage repair remain uncertain. Stem cells can contribute to cartilage repair via chondrogenic differentiation, via immunomodulation, or by the production of paracrine factors and extracellular vesicles. But before novel cell-based therapies for cartilage repair can be introduced into the clinic, rigorous testing in preclinical animal models is required. Preclinical models used in regenerative cartilage studies include murine, lapine, caprine, ovine, porcine, canine, and equine models, each associated with its specific advantages and limitations. This review presents a summary of recent in vitro data and from in vivo preclinical studies justifying the use of MSCs and iPSCs in cartilage tissue engineering. Moreover, the advantages and disadvantages of utilizing small and large animals will be discussed, while also describing suitable outcome measures for evaluating cartilage repair.

Stem Cells for Cartilage Repair: Preclinical Studies and Insights in Translational Animal Models and Outcome Measures.

Science.gov (United States)

Lo Monaco, Melissa; Merckx, Greet; Ratajczak, Jessica; Gervois, Pascal; Hilkens, Petra; Clegg, Peter; Bronckaers, Annelies; Vandeweerd, Jean-Michel; Lambrichts, Ivo

2018-01-01

Due to the restricted intrinsic capacity of resident chondrocytes to regenerate the lost cartilage postinjury, stem cell-based therapies have been proposed as a novel therapeutic approach for cartilage repair. Moreover, stem cell-based therapies using mesenchymal stem cells (MSCs) or induced pluripotent stem cells (iPSCs) have been used successfully in preclinical and clinical settings. Despite these promising reports, the exact mechanisms underlying stem cell-mediated cartilage repair remain uncertain. Stem cells can contribute to cartilage repair via chondrogenic differentiation, via immunomodulation, or by the production of paracrine factors and extracellular vesicles. But before novel cell-based therapies for cartilage repair can be introduced into the clinic, rigorous testing in preclinical animal models is required. Preclinical models used in regenerative cartilage studies include murine, lapine, caprine, ovine, porcine, canine, and equine models, each associated with its specific advantages and limitations. This review presents a summary of recent in vitro data and from in vivo preclinical studies justifying the use of MSCs and iPSCs in cartilage tissue engineering. Moreover, the advantages and disadvantages of utilizing small and large animals will be discussed, while also describing suitable outcome measures for evaluating cartilage repair.

Repair systems with exchangeable items and the longest queue mechanism

NARCIS (Netherlands)

Ravid, R.; Boxma, O.J.; Perry, D.

2013-01-01

We consider a repair facility consisting of one repairman and two arrival streams of failed items, from bases 1 and 2. The arrival processes are independent Poisson processes, and the repair times are independent and identically exponentially distributed. The item types are exchangeable, and a

Repair systems with exchangeable items and the longest queue mechanism

NARCIS (Netherlands)

Ravid, R.; Boxma, O.J.; Perry, D.

2011-01-01

We consider a repair facility consisting of one repairman and two arrival streams of failed items, from bases 1 and 2. The arrival processes are independent Poisson processes, and the repair times are independent and identically exponentially distributed. The item types are exchangeable, and a

Aspergillus fumigatus Copper Export Machinery and Reactive Oxygen Intermediate Defense Counter Host Copper-Mediated Oxidative Antimicrobial Offense

Directory of Open Access Journals (Sweden)

Philipp Wiemann

2017-05-01

Full Text Available The Fenton-chemistry-generating properties of copper ions are considered a potent phagolysosome defense against pathogenic microbes, yet our understanding of underlying host/microbe dynamics remains unclear. We address this issue in invasive aspergillosis and demonstrate that host and fungal responses inextricably connect copper and reactive oxygen intermediate (ROI mechanisms. Loss of the copper-binding transcription factor AceA yields an Aspergillus fumigatus strain displaying increased sensitivity to copper and ROI in vitro, increased intracellular copper concentrations, decreased survival in challenge with murine alveolar macrophages (AMΦs, and reduced virulence in a non-neutropenic murine model. ΔaceA survival is remediated by dampening of host ROI (chemically or genetically or enhancement of copper-exporting activity (CrpA in A. fumigatus. Our study exposes a complex host/microbe multifactorial interplay that highlights the importance of host immune status and reveals key targetable A. fumigatus counter-defenses.

Regulation of the Host Antiviral State by Intercellular Communications

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Sonia Assil

2015-08-01

Full Text Available Viruses usually induce a profound remodeling of host cells, including the usurpation of host machinery to support their replication and production of virions to invade new cells. Nonetheless, recognition of viruses by the host often triggers innate immune signaling, preventing viral spread and modulating the function of immune cells. It conventionally occurs through production of antiviral factors and cytokines by infected cells. Virtually all viruses have evolved mechanisms to blunt such responses. Importantly, it is becoming increasingly recognized that infected cells also transmit signals to regulate innate immunity in uninfected neighboring cells. These alternative pathways are notably mediated by vesicular secretion of various virus- and host-derived products (miRNAs, RNAs, and proteins and non-infectious viral particles. In this review, we focus on these newly-described modes of cell-to-cell communications and their impact on neighboring cell functions. The reception of these signals can have anti- and pro-viral impacts, as well as more complex effects in the host such as oncogenesis and inflammation. Therefore, these “broadcasting” functions, which might be tuned by an arms race involving selective evolution driven by either the host or the virus, constitute novel and original regulations of viral infection, either highly localized or systemic.

Exonuclease 1 is a critical mediator of survival during DNA double strand break repair in nonquiescent hematopoietic stem and progenitor cells.

Science.gov (United States)

Desai, Amar; Qing, Yulan; Gerson, Stanton L

2014-02-01

Hematopoietic stem cell (HSC) populations require DNA repair pathways to maintain their long-term survival and reconstitution capabilities, but mediators of these processes are still being elucidated. Exonuclease 1 (Exo1) participates in homologous recombination (HR) and Exo1 loss results in impaired 5' HR end resection. We use cultured Exo1(mut) fibroblasts and bone marrow to demonstrate that loss of Exo1 function results in defective HR in cycling cells. Conversely, in Exo1(mut) mice HR is not required for maintenance of quiescent HSCs at steady state, confirming the steady state HSC reliance on nonhomologous end joining (NHEJ). Exo1(mut) mice sustained serial repopulation, displayed no defect in competitive repopulation or niche occupancy, and exhibited no increased sensitivity to whole body ionizing radiation. However, when Exo1(mut) HSCs were pushed into cell cycle in vivo with 5-fluorouracil or poly IC, the hematopoietic population became hypersensitive to IR, resulting in HSC defects and animal death. We propose Exo1-mediated HR is dispensable for stem cell function in quiescent HSC, whereas it is essential to HSC response to DNA damage processing after cell cycle entry, and its loss is not compensated by intact NHEJ. In HSCs, the maintenance of stem cell function after DNA damage is dependent on the DNA repair capacity, segregated by active versus quiescent points in cell cycle. © AlphaMed Press.

Meniscal repair devices.

Science.gov (United States)

Barber, F A; Herbert, M A

2000-09-01

Meniscal repair devices not requiring accessory incisions are attractive. Many factors contribute to their clinical effectiveness including their biomechanical characteristics. This study compared several new meniscal repair devices with standard meniscal suture techniques. Using a porcine model, axis-of-insertion loads were applied to various meniscal sutures and repair devices. A single device or stitch was placed in a created meniscal tear and a load applied. Both loads and modes of failure were recorded. The load-to-failure data show stratification into 4 distinct statistical groups. Group A, 113 N for a double vertical stitch; group B, 80 N for a single vertical stitch; group C, 57 N for the BioStinger, 56 N for a horizontal mattress stitch, and 50 N for the T-Fix stitch; and group D, 33 N for the Meniscus Arrow (inserted by hand or gun), 32 N for the Clearfix screw, 31 N for the SDsorb staple, 30 N for the Mitek meniscal repair system, and 27 N for the Biomet staple. The failure mechanism varied. Sutures broke away from the knot. The Meniscus Arrow and BioStinger pulled through the inner rim with the crossbar intact. The Clearfix screw failed by multiple mechanisms, whereas 1 leg of the SDsorb staple always pulled out of the outer rim. The Mitek device usually failed by pullout from the inner rim. The Biomet staple always broke at the crosshead or just below it. Although the surgeon should be aware of the material properties of the repair technique chosen for a meniscal repair, this information is only an indication of device performance and may not correlate with clinical healing results.

Chromatin associated mechanisms in base excision repair - nucleosome remodeling and DNA transcription, two key players.

Science.gov (United States)

Menoni, Hervé; Di Mascio, Paolo; Cadet, Jean; Dimitrov, Stefan; Angelov, Dimitar

2017-06-01

Genomic DNA is prone to a large number of insults by a myriad of endogenous and exogenous agents. The base excision repair (BER) is the major mechanism used by cells for the removal of various DNA lesions spontaneously or environmentally induced and the maintenance of genome integrity. The presence of persistent DNA damage is not compatible with life, since abrogation of BER leads to early embryonic lethality in mice. There are several lines of evidences showing existence of a link between deficient BER, cancer proneness and ageing, thus illustrating the importance of this DNA repair pathway in human health. Although the enzymology of BER mechanisms has been largely elucidated using chemically defined DNA damage substrates and purified proteins, the complex interplay of BER with another vital process like transcription or when DNA is in its natural state (i.e. wrapped in nucleosome and assembled in chromatin fiber is largely unexplored. Cells use chromatin remodeling factors to overcome the general repression associated with the nucleosomal organization. It is broadly accepted that energy-dependent nucleosome remodeling factors disrupt histones-DNA interactions at the expense of ATP hydrolysis to favor transcription as well as DNA repair. Importantly, unlike transcription, BER is not part of a regulated developmental process but represents a maintenance system that should be efficient anytime and anywhere in the genome. In this review we will discuss how BER can deal with chromatin organization to maintain genetic information. Emphasis will be placed on the following challenging question: how BER is initiated within chromatin? Copyright © 2017 Elsevier Inc. All rights reserved.

Studies on maternal repair in Drosophila melanogaster

International Nuclear Information System (INIS)

Mendelson, D.

1976-01-01

The work reported in this thesis is mainly concerned with studies on the nature of the repair mechanism(s) operating in Drosophila oocytes, and which act on chromosome damage induced by X-irradiation of post-meiotic male germ-cells. Caffeine treatment of the females has been used as an analytical tool to gain an insight into the nature of this repair mechanism and its genetic basis

Identification and Sensitivity Analysis for Average Causal Mediation Effects with Time-Varying Treatments and Mediators: Investigating the Underlying Mechanisms of Kindergarten Retention Policy.

Science.gov (United States)

Park, Soojin; Steiner, Peter M; Kaplan, David

2018-06-01

Considering that causal mechanisms unfold over time, it is important to investigate the mechanisms over time, taking into account the time-varying features of treatments and mediators. However, identification of the average causal mediation effect in the presence of time-varying treatments and mediators is often complicated by time-varying confounding. This article aims to provide a novel approach to uncovering causal mechanisms in time-varying treatments and mediators in the presence of time-varying confounding. We provide different strategies for identification and sensitivity analysis under homogeneous and heterogeneous effects. Homogeneous effects are those in which each individual experiences the same effect, and heterogeneous effects are those in which the effects vary over individuals. Most importantly, we provide an alternative definition of average causal mediation effects that evaluates a partial mediation effect; the effect that is mediated by paths other than through an intermediate confounding variable. We argue that this alternative definition allows us to better assess at least a part of the mediated effect and provides meaningful and unique interpretations. A case study using ECLS-K data that evaluates kindergarten retention policy is offered to illustrate our proposed approach.

Major Roles for Pyrimidine Dimers, Nucleotide Excision Repair, and ATR in the Alternative Splicing Response to UV Irradiation

Directory of Open Access Journals (Sweden)

Manuel J. Muñoz

2017-03-01

Full Text Available We have previously found that UV irradiation promotes RNA polymerase II (RNAPII hyperphosphorylation and subsequent changes in alternative splicing (AS. We show now that UV-induced DNA damage is not only necessary but sufficient to trigger the AS response and that photolyase-mediated removal of the most abundant class of pyrimidine dimers (PDs abrogates the global response to UV. We demonstrate that, in keratinocytes, RNAPII is the target, but not a sensor, of the signaling cascade initiated by PDs. The UV effect is enhanced by inhibition of gap-filling DNA synthesis, the last step in the nucleotide excision repair pathway (NER, and reduced by the absence of XPE, the main NER sensor of PDs. The mechanism involves activation of the protein kinase ATR that mediates the UV-induced RNAPII hyperphosphorylation. Our results define the sequence UV-PDs-NER-ATR-RNAPII-AS as a pathway linking DNA damage repair to the control of both RNAPII phosphorylation and AS regulation.

Oxidative Mechanisms of Monocyte-Mediated Cytotoxicity

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Weiss, Stephen J.; Lobuglio, Albert F.; Kessler, Howard B.

1980-01-01

Human monocytes stimulated with phorbol myristate acetate were able to rapidly destroy autologous erythrocyte targets. Monocyte-mediated cytotoxicity was related to phorbol myristate acetate concentration and monocyte number. Purified preparations of lymphocytes were incapable of mediating erythrocyte lysis in this system. The ability of phorbol myristate acetate-stimulated monocytes to lyse erythrocyte targets was markedly impaired by catalase or superoxide dismutase but not by heat-inactivated enzymes or albumin. Despite a simultaneous requirement for superoxide anion and hydrogen peroxide in the cytotoxic event, a variety of hydroxyl radical and singlet oxygen scavengers did not effect cytolysis. However, tryptophan significantly inhibited cytotoxicity. The myeloperoxidase inhibitor cyanide enhanced erythrocyte destruction, whereas azide reduced it modestly. The inability of cyanide to reduce cytotoxicity coupled with the protective effect of superoxide dismutase suggests that cytotoxicity is independent of the classic myeloperoxidase system. We conclude that monocytes, stimulated with phorbol myristate acetate, generate superoxide anion and hydrogen peroxide, which together play an integral role in this cytotoxic mechanism.

Repair of ultraviolet light-induced DNA damage in cholera bacteriophages

International Nuclear Information System (INIS)

Palit, B.N.; Das, G.; Das, J.

1983-01-01

DNA repair-proficient and -deficient strains of Vibrio cholerae were used to examine host cell reactivation, Weigle reactivation and photoreactivation of u.v.-irradiated cholera bacteriophages. U.v. light-induced DNA damage in phages of different morphological and serological groups could be efficiently photoreactivated. Host cell reactivation of irradiated phages of different groups was different on the same indicator host. Phage phi149 was the most sensitive, and phi138 the most resistant to u.v. irradiation. While phi138 showed appreciable host cell reactivation, this was minimal for phi149. Attempts to demonstrate Weigle reactivation of u.v.-irradiated cholera phages were not successful, although u.v.-induced filamentation of host cells was observed. (author)

Rheological and mechanical properties of polyamide 6 modified by electron-beam initiated mediation process

International Nuclear Information System (INIS)

Shin, Boo Young; Kim, Jae Hong

2015-01-01

Polyamide (PA6) has been modified by electron-beam initiated mediator process to improve drawbacks of PA6. Glycidyl methacrylate (GMA) was chosen as a reactive mediator for modification process of PA6. The mixture of the PA6 and GMA was prepared by using a twin-screw extruder, and then the mixture was exposed to electron-beam irradiation at various doses at room temperature. The modified PA6 were characterized by observing rheological and mechanical properties and compared virgin PA6. Thermal properties, water absorption, and gel fraction were also investigated. Tight gel was not found even when PA6 was irradiated at 200 kGy. Complex viscosity and storage modulus of PA6 were remarkably increased by electron-beam irradiation with medium of GMA. Maximum increase in complex viscosity was 75 times higher than virgin PA6 at 0.1 rad/s when it was irradiated at 200 kGy with the GMA. Mechanical properties were also improved without scarifying of processability. The reaction mechanisms for the mediation process with the reactive mediator of GMA were estimated to elucidate the cause of significantly enhanced rheological and mechanical properties without loss of thermoplasticity. - Highlights: • PA6 was modified by the electron-beam initiated mediation process. • Maximum increase in complex viscosity of modified PA6 was 75 times higher than virgin PA6 at 0.1 rad/s. • Mechanical properties were improved without scarifying of processability. • The GMA as a mediator played a key role in the electron-beam initiated mediation process

Mechanisms of recurrent aortic regurgitation after aortic valve repair: predictive value of intraoperative transesophageal echocardiography.

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le Polain de Waroux, Jean-Benoît; Pouleur, Anne-Catherine; Robert, Annie; Pasquet, Agnès; Gerber, Bernhard L; Noirhomme, Philippe; El Khoury, Gébrine; Vanoverschelde, Jean-Louis J

2009-08-01

The aim of the present study was to examine the intraoperative echocardiographic features associated with recurrent severe aortic regurgitation (AR) after an aortic valve repair surgery. Surgical valve repair for AR has significant advantages over valve replacement, but little is known about the predictors and mechanisms of its failure. We blindly reviewed all clinical, pre-operative, intraoperative, and follow-up transesophageal echocardiographic data of 186 consecutive patients who underwent valve repair for AR during a 10-year period and in whom intraoperative and follow-up echo data were available. After a median follow-up duration of 18 months, 41 patients had recurrent 3+ AR, 23 patients presented with residual 1+ to 2+ AR, and 122 had no or trivial AR. In patients with recurrent 3+ AR, the cause of recurrent AR was the rupture of a pericardial patch in 3 patients, a residual cusp prolapse in 26 patients, a restrictive cusp motion in 9 patients, an aortic dissection in 2 patients, and an infective endocarditis in 1 patient. Pre-operatively, all 3 groups were similar for aortic root dimensions and prevalence of bicuspid valve (overall 37%). Patients with recurrent AR were more likely to display Marfan syndrome or type 3 dysfunction pre-operatively. At the opposite end, patients with continent AR repair at follow-up were more likely to have type 2 dysfunction pre-operatively. After cardiopulmonary bypass, a shorter coaptation length, the degree of cusp billowing, a lower level of coaptation (relative to the annulus), a larger diameter of the aortic annulus and the sino-tubular junction, the presence of a residual AR, and the width of its vena contracta were associated with the presence of AR at follow-up. Multivariate Cox analysis identified a shorter coaptation length (odds ratio [OR]: 0.8, p = 0.05), a coaptation occurring below the level of the aortic annulus (OR: 7.9, p < 0.01), a larger aortic annulus (OR: 1.2, p = 0.01), and residual aortic regurgitation

Mouse embryonic stem cells, but not somatic cells, predominantly use homologous recombination to repair double-strand DNA breaks.

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Tichy, Elisia D; Pillai, Resmi; Deng, Li; Liang, Li; Tischfield, Jay; Schwemberger, Sandy J; Babcock, George F; Stambrook, Peter J

2010-11-01

Embryonic stem (ES) cells give rise to all cell types of an organism. Since mutations at this embryonic stage would affect all cells and be detrimental to the overall health of an organism, robust mechanisms must exist to ensure that genomic integrity is maintained. To test this proposition, we compared the capacity of murine ES cells to repair DNA double-strand breaks with that of differentiated cells. Of the 2 major pathways that repair double-strand breaks, error-prone nonhomologous end joining (NHEJ) predominated in mouse embryonic fibroblasts, whereas the high fidelity homologous recombinational repair (HRR) predominated in ES cells. Microhomology-mediated end joining, an emerging repair pathway, persisted at low levels in all cell types examined. The levels of proteins involved in HRR and microhomology-mediated end joining were highly elevated in ES cells compared with mouse embryonic fibroblasts, whereas those for NHEJ were quite variable, with DNA Ligase IV expression low in ES cells. The half-life of DNA Ligase IV protein was also low in ES cells. Attempts to increase the abundance of DNA Ligase IV protein by overexpression or inhibition of its degradation, and thereby elevate NHEJ in ES cells, were unsuccessful. When ES cells were induced to differentiate, however, the level of DNA Ligase IV protein increased, as did the capacity to repair by NHEJ. The data suggest that preferential use of HRR rather than NHEJ may lend ES cells an additional layer of genomic protection and that the limited levels of DNA Ligase IV may account for the low level of NHEJ activity.

Microstructure and mechanical properties of hot wire laser clad layers for repairing precipitation hardening martensitic stainless steel

Science.gov (United States)

Wen, Peng; Cai, Zhipeng; Feng, Zhenhua; Wang, Gang

2015-12-01

Precipitation hardening martensitic stainless steel (PH-MSS) is widely used as load-bearing parts because of its excellent overall properties. It is economical and flexible to repair the failure parts instead of changing new ones. However, it is difficult to keep properties of repaired part as good as those of the substrate. With preheating wire by resistance heat, hot wire laser cladding owns both merits of low heat input and high deposition efficiency, thus is regarded as an advantaged repairing technology for damaged parts of high value. Multi-pass layers were cladded on the surface of FV520B by hot wire laser cladding. The microstructure and mechanical properties were compared and analyzed for the substrate and the clad layer. For the as-cladded layer, microstructure was found non-uniform and divided into quenched and tempered regions. Tensile strength was almost equivalent to that of the substrate, while ductility and impact toughness deteriorated much. With using laser scanning layer by layer during laser cladding, microstructure of the clad layers was tempered to fine martensite uniformly. The ductility and toughness of the clad layer were improved to be equivalent to those of the substrate, while the tensile strength was a little lower than that of the substrate. By adding TiC nanoparticles as well as laser scanning, the precipitation strengthening effect was improved and the structure was refined in the clad layer. The strength, ductility and toughness were all improved further. Finally, high quality clad layers were obtained with equivalent or even superior mechanical properties to the substrate, offering a valuable technique to repair PH-MSS.

On the lack of host-cell reactivation of UV-irradiated phage T5

International Nuclear Information System (INIS)

Chiang, T.; Harm, W.

1976-01-01

Previously reported experiments have shown that host-cell reactivation (HCR) of UV-irradiated phage T1 in excision-repair proficient Escherichia coli cells is inhibited by superinfection with phage T5. Theoretical considerations have led to predictions concerning the dependence of repair inhibition on the multiplicity of superinfecting T5 phage and on the UV fluence to which they were exposed. These predictions have been supported by experimental results described in this paper. The fluence dependence permitted calculation of the relative UV sensitivity of the gene function responsible for repair inhibition; it was found to be about 2.3% that of the plaque-forming ability of phage T5. The T5-inhibitable step in excision repair occurs early in the infective cycle of T1. Furthermore, experiments involving the presence of 400 μg/ml chloramphenicol showed that HCR inhibition of T1 is caused by a protein produced after the FST segment of T5 (i.e. the first 8% of the T5 genome) has entered the host cell. A previously described minor T1 recovery process, occuring in both excision-repair-proficient and -deficient host-cells, is inhibited by T5 infection due to a different substance, which is most likely associated with the 'second-step-transfer' region of T5 DNA (involving the remainder of the genome). Superinfection with T4v 1 phage resulted in HCR inhibition of T1, resembling that observed after T5 superinfection. The discussion of these results suggests that inhibition of the bacterial excision repair system by T5 or T4 infection occurs at the level of UV-endonucleolytic incision, and that lack of HCR both in T-even phages and in T5 can be explained in the same manner

Present status of DNA repair mechanisms in uv irradiated yeast taken as a model eukaryotic system

International Nuclear Information System (INIS)

Moustacchi, E.; Waters, R.; Heude, M.; Chanet, R.

1975-01-01

The repair mechanisms of altered DNA are generally less well understood for eukaryotes than they are for prokaryotes and bacteriophages. For mammalian cell lines cultured in vitro the specific labelling of DNA has allowed the biochemical analysis of some of the steps of the repair processes whereas the determination of their genetic controls is, with a few exceptions, obviously difficult. On the other hand, with fungi and more specifically with yeast taken as a model unicellular eukaryotic system, the genetic approach has been extensively explored: radiosensitive mutants are readily detected and genetically analyzed, double and multiple mutants can be constructed and from their responses to irradiation the number of repair pathways involved can be suggested. The lack of thymidine kinase in these organisms has hampered for a certain time the biochemical analysis of repair. However, the recent isolation of yeast strains capable of taking up and incorporating thymidine 5'-monophosphate into their DNA opens new possibilities for the future. In spite of this difficulty, attempts to measure the induction and removal of uv-induced pyrimidine dimers were performed by several groups during the last three years. The two main repair pathways described for E. coli, i.e., the excision-resynthesis and post-replicative recombinational repair pathways, do exist in yeast. The existence of the former pathway is supported not only by indirect evidence but also by biochemical analysis. The rad 1 and rad 2 mutants for instance have been shown to be blocked in the excision of uv-induced pyrimidine dimers. Other loci are epistatic to rad 1 and rad 2 (rad 3 , rad 4 ) and are likely to act on this excision pathway. The genetic control of the mitochondrial response to a uv treatment involves nuclear genes and mitochondrial determinants

DNA repair in human cells

International Nuclear Information System (INIS)

Regan, J.D.; Carrier, W.L.; Kusano, I.; Furuno-Fukushi, I.; Dunn, W.C. Jr.; Francis, A.A.; Lee, W.H.

1982-01-01

Our primary objective is to elucidate the molecular events in human cells when cellular macromolecules such as DNA are damaged by radiation or chemical agents. We study and characterize (i) the sequence of DNA repair events, (ii) the various modalities of repair, (iii) the genetic inhibition of repair due to mutation, (iv) the physiological inhibition of repair due to mutation, (v) the physiological inhibition of repair due to biochemical inhibitors, and (vi) the genetic basis of repair. Our ultimate goals are to (i) isolate and analyze the repair component of the mutagenic and/or carcinogenic event in human cells, and (ii) elucidate the magnitude and significance of this repair component as it impinges on the practical problems of human irradiation or exposure to actual or potential chemical mutagens and carcinogens. The significance of these studies lies in (i) the ubiquitousness of repair (most organisms, including man, have several complex repair systems), (ii) the belief that mutagenic and carcinogenic events may arise only from residual (nonrepaired) lesions or that error-prone repair systems may be the major induction mechanisms of the mutagenic or carcinogenic event, and (iii) the clear association of repair defects and highly carcinogenic disease states in man [xeroderma pigmentosum (XP)

Models of microbiome evolution incorporating host and microbial selection.

Science.gov (United States)

Zeng, Qinglong; Wu, Steven; Sukumaran, Jeet; Rodrigo, Allen

2017-09-25

Numerous empirical studies suggest that hosts and microbes exert reciprocal selective effects on their ecological partners. Nonetheless, we still lack an explicit framework to model the dynamics of both hosts and microbes under selection. In a previous study, we developed an agent-based forward-time computational framework to simulate the neutral evolution of host-associated microbial communities in a constant-sized, unstructured population of hosts. These neutral models allowed offspring to sample microbes randomly from parents and/or from the environment. Additionally, the environmental pool of available microbes was constituted by fixed and persistent microbial OTUs and by contributions from host individuals in the preceding generation. In this paper, we extend our neutral models to allow selection to operate on both hosts and microbes. We do this by constructing a phenome for each microbial OTU consisting of a sample of traits that influence host and microbial fitnesses independently. Microbial traits can influence the fitness of hosts ("host selection") and the fitness of microbes ("trait-mediated microbial selection"). Additionally, the fitness effects of traits on microbes can be modified by their hosts ("host-mediated microbial selection"). We simulate the effects of these three types of selection, individually or in combination, on microbiome diversities and the fitnesses of hosts and microbes over several thousand generations of hosts. We show that microbiome diversity is strongly influenced by selection acting on microbes. Selection acting on hosts only influences microbiome diversity when there is near-complete direct or indirect parental contribution to the microbiomes of offspring. Unsurprisingly, microbial fitness increases under microbial selection. Interestingly, when host selection operates, host fitness only increases under two conditions: (1) when there is a strong parental contribution to microbial communities or (2) in the absence of a strong

miR-24-mediated down-regulation of H2AX suppresses DNA repair in terminally differentiated blood cells

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Lal, Ashish; Pan, Yunfeng; Navarro, Francisco; Dykxhoorn, Derek M.; Moreau, Lisa; Meire, Eti; Bentwich, Zvi; Lieberman, Judy; Chowdhury, Dipanjan

2010-01-01

Terminally differentiated cells have reduced capacity to repair double strand breaks (DSB), but the molecular mechanism behind this down-regulation is unclear. Here we find that miR-24 is consistently up-regulated during post-mitotic differentiation of hematopoietic cell lines and regulates the histone variant H2AX, a key DSB repair protein that activates cell cycle checkpoint proteins and retains DSB repair factors at DSB foci. The H2AX 3’UTR contains conserved miR-24 binding sites regulated by miR-24. Both H2AX mRNA and protein are substantially reduced during hematopoietic cell terminal differentiation by miR-24 up-regulation both in in vitro differentiated cells and primary human blood cells. miR-24 suppression of H2AX renders cells hypersensitive to γ-irradiation and genotoxic drugs. Antagonizing miR-24 in differentiating cells protects them from DNA damage-induced cell death, while transfecting miR-24 mimics in dividing cells increases chromosomal breaks and unrepaired DNA damage and reduces viability in response to DNA damage. This DNA repair phenotype can be fully rescued by over-expressing miR-24-insensitive H2AX. Therefore, miR-24 up-regulation in post-replicative cells reduces H2AX and thereby renders them highly vulnerable to DNA damage. PMID:19377482

Metabolite damage and repair in metabolic engineering design.

Science.gov (United States)

Sun, Jiayi; Jeffryes, James G; Henry, Christopher S; Bruner, Steven D; Hanson, Andrew D

2017-11-01

The necessarily sharp focus of metabolic engineering and metabolic synthetic biology on pathways and their fluxes has tended to divert attention from the damaging enzymatic and chemical side-reactions that pathway metabolites can undergo. Although historically overlooked and underappreciated, such metabolite damage reactions are now known to occur throughout metabolism and to generate (formerly enigmatic) peaks detected in metabolomics datasets. It is also now known that metabolite damage is often countered by dedicated repair enzymes that undo or prevent it. Metabolite damage and repair are highly relevant to engineered pathway design: metabolite damage reactions can reduce flux rates and product yields, and repair enzymes can provide robust, host-independent solutions. Herein, after introducing the core principles of metabolite damage and repair, we use case histories to document how damage and repair processes affect efficient operation of engineered pathways - particularly those that are heterologous, non-natural, or cell-free. We then review how metabolite damage reactions can be predicted, how repair reactions can be prospected, and how metabolite damage and repair can be built into genome-scale metabolic models. Lastly, we propose a versatile 'plug and play' set of well-characterized metabolite repair enzymes to solve metabolite damage problems known or likely to occur in metabolic engineering and synthetic biology projects. Copyright © 2017 International Metabolic Engineering Society. All rights reserved.

Lipid exchange between Borrelia burgdorferi and host cells.

Directory of Open Access Journals (Sweden)

Jameson T Crowley

2013-01-01

Full Text Available Borrelia burgdorferi, the agent of Lyme disease, has cholesterol and cholesterol-glycolipids that are essential for bacterial fitness, are antigenic, and could be important in mediating interactions with cells of the eukaryotic host. We show that the spirochetes can acquire cholesterol from plasma membranes of epithelial cells. In addition, through fluorescent and confocal microscopy combined with biochemical approaches, we demonstrated that B. burgdorferi labeled with the fluorescent cholesterol analog BODIPY-cholesterol or (3H-labeled cholesterol transfer both cholesterol and cholesterol-glycolipids to HeLa cells. The transfer occurs through two different mechanisms, by direct contact between the bacteria and eukaryotic cell and/or through release of outer membrane vesicles. Thus, two-way lipid exchange between spirochetes and host cells can occur. This lipid exchange could be an important process that contributes to the pathogenesis of Lyme disease.

Dumbbell DNA-templated CuNPs as a nano-fluorescent probe for detection of enzymes involved in ligase-mediated DNA repair.

Science.gov (United States)

Qing, Taiping; He, Xiaoxiao; He, Dinggeng; Ye, Xiaosheng; Shangguan, Jingfang; Liu, Jinquan; Yuan, Baoyin; Wang, Kemin

2017-08-15

DNA repair processes are responsible for maintaining genome stability. Ligase and polynucleotide kinase (PNK) have important roles in ligase-mediated DNA repair. The development of analytical methods to monitor these enzymes involved in DNA repair pathways is of great interest in biochemistry and biotechnology. In this work, we reported a new strategy for label-free monitoring PNK and ligase activity by using dumbbell-shaped DNA templated copper nanoparticles (CuNPs). In the presence of PNK and ligase, the dumbbell-shaped DNA probe (DP) was locked and could resist the digestion of exonucleases and then served as an efficient template for synthesizing fluorescent CuNPs. However, in the absence of ligase or PNK, the nicked DP could be digested by exonucleases and failed to template fluorescent CuNPs. Therefore, the fluorescence changes of CuNPs could be used to evaluate these enzymes activity. Under the optimal conditions, highly sensitive detection of ligase activity of about 1U/mL and PNK activity down to 0.05U/mL is achieved. To challenge the practical application capability of this strategy, the detection of analyte in dilute cells extracts was also investigated and showed similar linear relationships. In addition to ligase and PNK, this sensing strategy was also extended to the detection of phosphatase, which illustrates the versatility of this strategy. Copyright © 2017 Elsevier B.V. All rights reserved.

Nucleotide excision repair in yeast

NARCIS (Netherlands)

Eijk, Patrick van

2012-01-01

Nucleotide Excision Repair (NER) is a conserved DNA repair pathway capable of removing a broad spectrum of DNA damage. In human cells a defect in NER leads to the disorder Xeroderma pigmentosum (XP). The yeast Saccharomyces cerevisiae is an excellent model organism to study the mechanism of NER. The

Relative roles of uvrA and recA genes in the recovery of Escherichia coli and phage lambda after ultraviolet irradiation

International Nuclear Information System (INIS)

Salaj-Smic, E.; Petranovic, D.; Petranovic, M.; Trgovcevic, Z.

1980-01-01

The action of the host-cell repair system on recovery from uv damage to bacterial and phage DNA was studied. lambda cI857 ind red lysogens were used. These lysogens, although noninducible by uv light, can be induced by raising the temperature from 30 to 42 0 C. Sensitivity of the phage in relation to its host was analyzed in various bacterial backgrounds. Relative sensitivity of the phage and its host is the same if the uv survival curve for colonies is 80 times steeper than for plaques. This same relative sensitivity is observed if the host cell does not possess any mechanism for DNA repair (uvrA recA background). In the uvrA recA + background, the plaque survival is not significantly increased above the level observed in the uvrA recA double mutant. recA-dependent recombinational postreplication repair does not operate on the phage DNA in the cytoplasm; relative sensitivity of the phage is therefore much higher than that of the host. If the lysogenic induction is delayed, a marked increase in the plaque count is seen so the phage shows the same relative sensitivity as the bacterial cell. Short-patch excision repair operates on both phage and bacterial DNA but less efficiently on phage DNA. In the wild-type (uvrA + recA + ) host, the highest survival of plaques and colonies is obtained. Relative sensitivity of the phage is nevertheless 50 times higher then that of the bacterial cell. This may mean the recA gene product is involved in copy-choice excision and/or long-patch excision and/or incision-promoted recombination repair of the phage DNA but it remains unable to mediate its recombinational postreplication repair

Celecoxib Induced Tumor Cell Radiosensitization by Inhibiting Radiation Induced Nuclear EGFR Transport and DNA-Repair: A COX-2 Independent Mechanism

International Nuclear Information System (INIS)

Dittmann, Klaus H.; Mayer, Claus; Ohneseit, Petra A.; Raju, Uma; Andratschke, Nickolaus H.; Milas, Luka; Rodemann, H. Peter

2008-01-01

Purpose: The purpose of the study was to elucidate the molecular mechanisms mediating radiosensitization of human tumor cells by the selective cyclooxygenase (COX)-2 inhibitor celecoxib. Methods and Materials: Experiments were performed using bronchial carcinoma cells A549, transformed fibroblasts HH4dd, the FaDu head-and-neck tumor cells, the colon carcinoma cells HCT116, and normal fibroblasts HSF7. Effects of celecoxib treatment were assessed by clonogenic cell survival, Western analysis, and quantification of residual DNA damage by γH 2 AX foci assay. Results: Celecoxib treatment resulted in a pronounced radiosensitization of A549, HCT116, and HSF7 cells, whereas FaDu and HH4dd cells were not radiosensitized. The observed radiosensitization could neither be correlated with basal COX-2 expression pattern nor with basal production of prostaglandin E2, but was depended on the ability of celecoxib to inhibit basal and radiation-induced nuclear transport of epidermal growth factor receptor (EGFR). The nuclear EGFR transport was strongly inhibited in A549-, HSF7-, and COX-2-deficient HCT116 cells, which were radiosensitized, but not in FaDu and HH4dd cells, which resisted celecoxib-induced radiosensitization. Celecoxib inhibited radiation-induced DNA-PK activation in A549, HSF7, and HCT116 cells, but not in FaDu and HH4dd cells. Consequentially, celecoxib increased residual γH2AX foci after irradiation, demonstrating that inhibition of DNA repair has occurred in responsive A549, HCT116, and HSF7 cells only. Conclusions: Celecoxib enhanced radiosensitivity by inhibition of EGFR-mediated mechanisms of radioresistance, a signaling that was independent of COX-2 activity. This novel observation may have therapeutic implications such that COX-2 inhibitors may improve therapeutic efficacy of radiation even in patients whose tumor radioresistance is not dependent on COX-2

DNA Damage and Repair in Plants under Ultraviolet and Ionizing Radiations

Science.gov (United States)

Gill, Sarvajeet S.; Gill, Ritu; Jha, Manoranjan; Tuteja, Narendra

2015-01-01

Being sessile, plants are continuously exposed to DNA-damaging agents present in the environment such as ultraviolet (UV) and ionizing radiations (IR). Sunlight acts as an energy source for photosynthetic plants; hence, avoidance of UV radiations (namely, UV-A, 315–400 nm; UV-B, 280–315 nm; and UV-C, important target for UV-B induced damage. On the other hand, IR causes water radiolysis, which generates highly reactive hydroxyl radicals (OH•) and causes radiogenic damage to important cellular components. However, to maintain genomic integrity under UV/IR exposure, plants make use of several DNA repair mechanisms. In the light of recent breakthrough, the current minireview (a) introduces UV/IR and overviews UV/IR-mediated DNA damage products and (b) critically discusses the biochemistry and genetics of major pathways responsible for the repair of UV/IR-accrued DNA damage. The outcome of the discussion may be helpful in devising future research in the current context. PMID:25729769

Nuclear translocation contributes to regulation of DNA excision repair activities

DEFF Research Database (Denmark)

Knudsen, Nina Østergaard; Andersen, Sofie Dabros; Lützen, Anne

2009-01-01

for regulation of nuclear import that is necessary for proper localization of the repair proteins. This review summarizes the current knowledge on nuclear import mechanisms of DNA excision repair proteins and provides a model that categorizes the import by different mechanisms, including classical nuclear import......DNA mutations are circumvented by dedicated specialized excision repair systems, such as the base excision repair (BER), nucleotide excision repair (NER), and mismatch repair (MMR) pathways. Although the individual repair pathways have distinct roles in suppressing changes in the nuclear DNA......, it is evident that proteins from the different DNA repair pathways interact [Y. Wang, D. Cortez, P. Yazdi, N. Neff, S.J. Elledge, J. Qin, BASC, a super complex of BRCA1-associated proteins involved in the recognition and repair of aberrant DNA structures, Genes Dev. 14 (2000) 927-939; M. Christmann, M...

Molecular Mechanisms of Foot-and-Mouth Disease Virus Targeting the Host Antiviral Response.

Science.gov (United States)

Rodríguez Pulido, Miguel; Sáiz, Margarita

2017-01-01

Foot-and-mouth disease virus (FMDV) is the causative agent of an acute vesicular disease affecting pigs, cattle and other domestic, and wild animals worldwide. The aim of the host interferon (IFN) response is to limit viral replication and spread. Detection of the viral genome and products by specialized cellular sensors initiates a signaling cascade that leads to a rapid antiviral response involving the secretion of type I- and type III-IFNs and other antiviral cytokines with antiproliferative and immunomodulatory functions. During co-evolution with their hosts, viruses have acquired strategies to actively counteract host antiviral responses and the balance between innate response and viral antagonism may determine the outcome of disease and pathogenesis. FMDV proteases Lpro and 3C have been found to antagonize the host IFN response by a repertoire of mechanisms. Moreover, the putative role of other viral proteins in IFN antagonism is being recently unveiled, uncovering sophisticated immune evasion strategies different to those reported to date for other members of the Picornaviridae family. Here, we review the interplay between antiviral responses induced by FMDV infection and viral countermeasures to block them. Research on strategies used by viruses to modulate immunity will provide insights into the function of host pathways involved in defense against pathogens and will also lead to development of new therapeutic strategies to fight virus infections.

Localization of sclerotic-type chronic graft-vs-host disease to sites of skin injury: potential insight into the mechanism of isomorphic and isotopic responses.

Science.gov (United States)

Martires, Kathryn J; Baird, Kristin; Citrin, Deborah E; Hakim, Fran T; Pavletic, Steven Z; Cowen, Edward W

2011-09-01

The mechanisms responsible for the variable manifestations of chronic cutaneous graft-vs-host disease (cGVHD) are poorly understood. Localization of sclerotic-type chronic graft-vs-host disease to sites of skin injury (isomorphic and isotopic responses), a recognized phenomenon in morphea, suggests a potential common pathway between cGVHD and other sclerotic skin conditions. Four cases of sclerotic-type cGVHD developed at the site of disparate skin injuries (ionizing radiotherapy, repeated needle sticks, central catheter site, and varicella-zoster virus infection). We review the spectrum of previously reported cases of sclerotic and nonsclerotic cGVHD relating to external forces on the skin. Localization of sclerotic-type cGVHD may occur after many types of skin injury, including UV and ionizing radiotherapy, needle sticks, viral infection, and pressure or friction. Recognition of this phenomenon may be helpful for the early diagnosis of sclerotic disease. Recent insights into the immunological consequences of minor skin injury may provide important clues to the underlying pathogenesis of cGVHD-mediated skin disease.

DNA repair in DNA-polymerase-deficient mutants of Escherichia coli

International Nuclear Information System (INIS)

Smith, D.W.; Tait, R.C.; Harris, A.L.

1975-01-01

Escherichia coli mutants deficient in DNA polymerase I, in DNA polymerases I and II, or in DNA polymerase III can efficiently and completely execute excision-repair and postreplication repair of the uv-damaged DNA at 30 0 C and 43 0 C when assayed by alkaline sucrose gradients. Repair by Pol I - and Pol I - , Pol II - cells is inhibited by 1-β-D-arabinofuranosylcytosine (araC) at 43 0 C but not at 30 0 C, whereas that by Pol III - cells is insensitive to araC at any temperature. Thus, either Pol I or Pol III is required for complete and efficient repair, and in their absence Pol II mediates a limited, incomplete dark repair of uv-damaged DNA

Turbine repair process, repaired coating, and repaired turbine component

Science.gov (United States)

Das, Rupak; Delvaux, John McConnell; Garcia-Crespo, Andres Jose

2015-11-03

A turbine repair process, a repaired coating, and a repaired turbine component are disclosed. The turbine repair process includes providing a turbine component having a higher-pressure region and a lower-pressure region, introducing particles into the higher-pressure region, and at least partially repairing an opening between the higher-pressure region and the lower-pressure region with at least one of the particles to form a repaired turbine component. The repaired coating includes a silicon material, a ceramic matrix composite material, and a repaired region having the silicon material deposited on and surrounded by the ceramic matrix composite material. The repaired turbine component a ceramic matrix composite layer and a repaired region having silicon material deposited on and surrounded by the ceramic matrix composite material.

Fcγ receptor-mediated inflammation inhibits axon regeneration.

Directory of Open Access Journals (Sweden)

Gang Zhang

Full Text Available Anti-glycan/ganglioside antibodies are the most common immune effectors found in patients with Guillain-Barré Syndrome, which is a peripheral autoimmune neuropathy. We previously reported that disease-relevant anti-glycan autoantibodies inhibited axon regeneration, which echo the clinical association of these antibodies and poor recovery in Guillain-Barré Syndrome. However, the specific molecular and cellular elements involved in this antibody-mediated inhibition of axon regeneration are not previously defined. This study examined the role of Fcγ receptors and macrophages in the antibody-mediated inhibition of axon regeneration. A well characterized antibody passive transfer sciatic nerve crush and transplant models were used to study the anti-ganglioside antibody-mediated inhibition of axon regeneration in wild type and various mutant and transgenic mice with altered expression of specific Fcγ receptors and macrophage/microglia populations. Outcome measures included behavior, electrophysiology, morphometry, immunocytochemistry, quantitative real-time PCR, and western blotting. We demonstrate that the presence of autoantibodies, directed against neuronal/axonal cell surface gangliosides, in the injured mammalian peripheral nerves switch the proregenerative inflammatory environment to growth inhibitory milieu by engaging specific activating Fcγ receptors on recruited monocyte-derived macrophages to cause severe inhibition of axon regeneration. Our data demonstrate that the antibody orchestrated Fcγ receptor-mediated switch in inflammation is one mechanism underlying inhibition of axon regeneration. These findings have clinical implications for nerve repair and recovery in antibody-mediated immune neuropathies. Our results add to the complexity of axon regeneration in injured peripheral and central nervous systems as adverse effects of B cells and autoantibodies on neural injury and repair are increasingly recognized.

Reaction mechanisms of ruthenium tetroxide mediated oxidations of organic compounds

Energy Technology Data Exchange (ETDEWEB)

Froehaug, Astrid Elisabeth

1995-12-31

This thesis reports a study of the mechanism of ruthenium tetroxide mediated oxidations of saturated hydrocarbons, ethers, alkenes and alcohols. Several methods were used. The RuO{sub 4}-mediated oxidations of adamantane and cis-decalin were studied in CCl{sub 4}-CH{sub 3}CN-H{sub 2}O and in acetone-water. The rate of reaction was found to be moderately influenced by the polarity of the solvent. Solvent properties other than the polarity were also found to influence the reaction rates. From the oxidations of adamantane and adamantane-1,3,5,7-d{sub 4} two primary kinetic deuterium isotope effects were found. These were comparable with the deuterium isotope effects found for the analogous oxidations of cis-decalin and cis-decalin-d{sub 18}. The results seem to exclude both a one step hydride abstraction reaction mechanism and a one step concerted mechanism, as well as a scheme where two such mechanisms compete. The observations may be explained by a two step reaction mechanism consisting of a pre-equilibrium with formation of a substrate-RuO{sub 4} complex followed by a concerted rate determining reaction. The RuO{sub 4}-mediated oxidation of ethers was of kinetic second order with a small enthalpy of activation and a large negative entropy of activation. Oxidation of cyclopropylmethyl methyl ether gave methyl cyclopropanecarboxylate, no rearranged products were observed. On RuO{sub 4} oxidations in CCl{sub 4} with NaIO{sub 4} as stoichiometric oxidant, no chlorinated products were observed. Several observations not in agreement with a hydride or a hydrogen abstraction mechanism may be explained by assuming that the reaction proceeds by either a concerted reaction or by a reversible oxidative addition of the ether to RuO{sub 4} followed by a slow concerted step. 228 refs., 9 figs., 27 tabs.

Protecting DNA from errors and damage: an overview of DNA repair mechanisms in plants compared to mammals.

Science.gov (United States)

Spampinato, Claudia P

2017-05-01

The genome integrity of all organisms is constantly threatened by replication errors and DNA damage arising from endogenous and exogenous sources. Such base pair anomalies must be accurately repaired to prevent mutagenesis and/or lethality. Thus, it is not surprising that cells have evolved multiple and partially overlapping DNA repair pathways to correct specific types of DNA errors and lesions. Great progress in unraveling these repair mechanisms at the molecular level has been made by several talented researchers, among them Tomas Lindahl, Aziz Sancar, and Paul Modrich, all three Nobel laureates in Chemistry for 2015. Much of this knowledge comes from studies performed in bacteria, yeast, and mammals and has impacted research in plant systems. Two plant features should be mentioned. Plants differ from higher eukaryotes in that they lack a reserve germline and cannot avoid environmental stresses. Therefore, plants have evolved different strategies to sustain genome fidelity through generations and continuous exposure to genotoxic stresses. These strategies include the presence of unique or multiple paralogous genes with partially overlapping DNA repair activities. Yet, in spite (or because) of these differences, plants, especially Arabidopsis thaliana, can be used as a model organism for functional studies. Some advantages of this model system are worth mentioning: short life cycle, availability of both homozygous and heterozygous lines for many genes, plant transformation techniques, tissue culture methods and reporter systems for gene expression and function studies. Here, I provide a current understanding of DNA repair genes in plants, with a special focus on A. thaliana. It is expected that this review will be a valuable resource for future functional studies in the DNA repair field, both in plants and animals.

Enrichment of G2/M cell cycle phase in human pluripotent stem cells enhances HDR-mediated gene repair with customizable endonucleases.

Science.gov (United States)

Yang, Diane; Scavuzzo, Marissa A; Chmielowiec, Jolanta; Sharp, Robert; Bajic, Aleksandar; Borowiak, Malgorzata

2016-02-18

Efficient gene editing is essential to fully utilize human pluripotent stem cells (hPSCs) in regenerative medicine. Custom endonuclease-based gene targeting involves two mechanisms of DNA repair: homology directed repair (HDR) and non-homologous end joining (NHEJ). HDR is the preferred mechanism for common applications such knock-in, knock-out or precise mutagenesis, but remains inefficient in hPSCs. Here, we demonstrate that synchronizing synchronizing hPSCs in G2/M with ABT phase increases on-target gene editing, defined as correct targeting cassette integration, 3 to 6 fold. We observed improved efficiency using ZFNs, TALENs, two CRISPR/Cas9, and CRISPR/Cas9 nickase to target five genes in three hPSC lines: three human embryonic stem cell lines, neural progenitors and diabetic iPSCs. neural progenitors and diabetic iPSCs. Reversible synchronization has no effect on pluripotency or differentiation. The increase in on-target gene editing is locus-independent and specific to the cell cycle phase as G2/M phase enriched cells show a 6-fold increase in targeting efficiency compared to cells in G1 phase. Concurrently inhibiting NHEJ with SCR7 does not increase HDR or improve gene targeting efficiency further, indicating that HR is the major DNA repair mechanism after G2/M phase arrest. The approach outlined here makes gene editing in hPSCs a more viable tool for disease modeling, regenerative medicine and cell-based therapies.

Examination of Mechanisms Responsible for Organic Dust-related Diseases: Mediator Release induced by Microorgansims. A review

DEFF Research Database (Denmark)

Norn, Svend; Clementsen, Paul; Kristensen, K.S.

1994-01-01

Farmakologi, org. dust-related diseases, bacteria, pathogenic mechanisms, mediator release, entoxins - fungal spores......Farmakologi, org. dust-related diseases, bacteria, pathogenic mechanisms, mediator release, entoxins - fungal spores...

A model system for DNA repair studies

International Nuclear Information System (INIS)

Lange, C.S.; Perlmutter, E.

1984-01-01

The search for the ''lethal lesion:'' which would yield a molecular explanation of biological survival curves led to attempts to correlate unrepaired DNA lesions with loss of reproductive integrity. Such studies have shown the crucial importance of DNA repair systems. The unrepaired DSB has been sought for such correlation, but in such study the DNA was too large, polydisperse, and/or structurally complex to permit precise measurement of break induction and repair. Therefore, an analog of higher order systems but with a genome of readily measurable size, is needed. Bacteriophage T4 is such an analog. Both its biological (PFU) and molecular (DNA) survival curves are exponentials. Its aerobic /sub PFU/D/sub 37///sub DNA/D/sub 37/ ratio, (410 +- 4.5Gy/540 +- 25 Gy) indicates that 76 +- 4% of lethality at low multiplicity infection (moi 1) the survival is greater than can be explained if the assumption of no parental DSB repair were valid. Both T4 and its host have DSB repair systems which can be studied by the infectious center method. Results of such studies are discussed

Silymarin protects epidermal keratinocytes from ultraviolet radiation-induced apoptosis and DNA damage by nucleotide excision repair mechanism.

Directory of Open Access Journals (Sweden)

Santosh K Katiyar

Full Text Available Solar ultraviolet (UV radiation is a well recognized epidemiologic risk factor for melanoma and non-melanoma skin cancers. This observation has been linked to the accumulation of UVB radiation-induced DNA lesions in cells, and that finally lead to the development of skin cancers. Earlier, we have shown that topical treatment of skin with silymarin, a plant flavanoid from milk thistle (Silybum marianum, inhibits photocarcinogenesis in mice; however it is less understood whether chemopreventive effect of silymarin is mediated through the repair of DNA lesions in skin cells and that protect the cells from apoptosis. Here, we show that treatment of normal human epidermal keratinocytes (NHEK with silymarin blocks UVB-induced apoptosis of NHEK in vitro. Silymarin reduces the amount of UVB radiation-induced DNA damage as demonstrated by reduced amounts of cyclobutane pyrimidine dimers (CPDs and as measured by comet assay, and that ultimately may lead to reduced apoptosis of NHEK. The reduction of UV radiation-induced DNA damage by silymarin appears to be related with induction of nucleotide excision repair (NER genes, because UV radiation-induced apoptosis was not blocked by silymarin in NER-deficient human fibroblasts. Cytostaining and dot-blot analysis revealed that silymarin repaired UV-induced CPDs in NER-proficient fibroblasts from a healthy individual but did not repair UV-induced CPD-positive cells in NER-deficient fibroblasts from patients suffering from xeroderma pigmentosum complementation-A disease. Similarly, immunohistochemical analysis revealed that silymarin did not reduce the number of UVB-induced sunburn/apoptotic cells in the skin of NER-deficient mice, but reduced the number of sunburn cells in their wild-type counterparts. Together, these results suggest that silymarin exert the capacity to reduce UV radiation-induced DNA damage and, thus, prevent the harmful effects of UV radiation on the genomic stability of epidermal cells.

Aspects of DNA repair and nucleotide pool imbalance

Energy Technology Data Exchange (ETDEWEB)

Holliday, R.

1985-01-01

Evidence that optimum repair depends on adequate pools of deoxynucleotide triphosphates (dNTPs) comes from the study of pyrimidine auxotrophs of Ustilago maydis. These strains are sensitive to UV light and X-rays, and for pyr1-1 it has been shown that the intracellular concentration of dTTP is reduced about 7-fold. The survival curve of pyr1-1 after UV-treatment, and split dose experiments with wild-type cells, provide evidence for an inducible repair mechanism, which probably depends on genetic recombination. Although inducible repair saves cellular resources, it has the disadvantage of becoming ineffective at doses which are high enough to inactivate the repressed structural gene(s) for repair enzymes. It is clear that a wide variety of repair mechanisms have evolved to remove lesions which arise either spontaneously or as a result of damage from external agents. Nevertheless, it would be incorrect to assume that all species require all possible pathways of repair. It is now well established that the accuracy of DNA and protein synthesis depends on proof-reading or editing mechanisms. Optimum accuracy levels will evolve from the balance between error avoidance in macromolecular synthesis and physiological efficiency in growth and propagation.

Multiple repair pathways mediate tolerance to chemotherapeutic cross-linking agents in vertebrate cells.

Science.gov (United States)

Nojima, Kuniharu; Hochegger, Helfrid; Saberi, Alihossein; Fukushima, Toru; Kikuchi, Koji; Yoshimura, Michio; Orelli, Brian J; Bishop, Douglas K; Hirano, Seiki; Ohzeki, Mioko; Ishiai, Masamichi; Yamamoto, Kazuhiko; Takata, Minoru; Arakawa, Hiroshi; Buerstedde, Jean-Marie; Yamazoe, Mitsuyoshi; Kawamoto, Takuo; Araki, Kasumi; Takahashi, Jun A; Hashimoto, Nobuo; Takeda, Shunichi; Sonoda, Eiichiro

2005-12-15

Cross-linking agents that induce DNA interstrand cross-links (ICL) are widely used in anticancer chemotherapy. Yeast genetic studies show that nucleotide excision repair (NER), Rad6/Rad18-dependent postreplication repair, homologous recombination, and cell cycle checkpoint pathway are involved in ICL repair. To study the contribution of DNA damage response pathways in tolerance to cross-linking agents in vertebrates, we made a panel of gene-disrupted clones from chicken DT40 cells, each defective in a particular DNA repair or checkpoint pathway, and measured the sensitivities to cross-linking agents, including cis-diamminedichloroplatinum (II) (cisplatin), mitomycin C, and melphalan. We found that cells harboring defects in translesion DNA synthesis (TLS), Fanconi anemia complementation groups (FANC), or homologous recombination displayed marked hypersensitivity to all the cross-linking agents, whereas NER seemed to play only a minor role. This effect of replication-dependent repair pathways is distinctively different from the situation in yeast, where NER seems to play a major role in dealing with ICL. Cells deficient in Rev3, the catalytic subunit of TLS polymerase Polzeta, showed the highest sensitivity to cisplatin followed by fanc-c. Furthermore, epistasis analysis revealed that these two mutants work in the same pathway. Our genetic comprehensive study reveals a critical role for DNA repair pathways that release DNA replication block at ICLs in cellular tolerance to cross-linking agents and could be directly exploited in designing an effective chemotherapy.

Estrogen enhances mismatch repair by induction of MLH1 expression via estrogen receptor-β.

Science.gov (United States)

Lu, Jun-Yu; Jin, Peng; Gao, Wei; Wang, De-Zhi; Sheng, Jian-Qiu

2017-06-13

Epidemiological data demonstrated that hormone replace treatment has protective effect against colorectal cancer (CRC). Our previous studies showed that this effect may be associated with DNA mismatch repair. This study aims to investigate the mechanism of estrogen induction of MLH1, and whether colorectal tumor proliferation can be inhibited through induction of MLH1 by estrogen signal pathway. Human CRC cell lines were used to examine the regulation of MLH1 expression by over-expression and depletion of estrogen receptor-α (ERα) and estrogen receptor-β (ERβ), under the treatment with 17β-estradiol or β-Estradiol 6-(O-carboxy-methyl)oxime:BSA, followed by a real-time Q-PCR and Western blotting analysis. Luciferase reporter and chromatin immunoprecipitation assays were used to identify the estrogen response elements in the proximal promoter of MLH1 gene. Then, the influence of estrogen-induced MLH1 on CRC tumor growth were determined in vitro and in vivo. We found that mismatch repair ability and microsatellite stability of cells were enhanced by estrogen via induction of MLH1 expression, which was mediated by ERβ, through a transcriptional activation process. Furthermore, we identified that ERβ exerted an inhibitory effect on CRC tumor proliferation in vitro and in vivo, combined with 5-FU, through up-regulation of MLH1 expression. Finally, we concluded that estrogen enhances mismatch repair ability and tumor inhibition effect in vitro and in vivo, via induction of MLH1 expression mediated by ERβ.

Competitive repair by naturally dispersed repetitive DNA during non-allelic homologous recombination

Energy Technology Data Exchange (ETDEWEB)

Hoang, Margaret L.; Tan, Frederick J.; Lai, David C.; Celniker, Sue E.; Hoskins, Roger A.; Dunham, Maitreya J.; Zheng, Yixian; Koshland, Douglas

2010-08-27

Genome rearrangements often result from non-allelic homologous recombination (NAHR) between repetitive DNA elements dispersed throughout the genome. Here we systematically analyze NAHR between Ty retrotransposons using a genome-wide approach that exploits unique features of Saccharomyces cerevisiae purebred and Saccharomyces cerevisiae/Saccharomyces bayanus hybrid diploids. We find that DNA double-strand breaks (DSBs) induce NAHR-dependent rearrangements using Ty elements located 12 to 48 kilobases distal to the break site. This break-distal recombination (BDR) occurs frequently, even when allelic recombination can repair the break using the homolog. Robust BDR-dependent NAHR demonstrates that sequences very distal to DSBs can effectively compete with proximal sequences for repair of the break. In addition, our analysis of NAHR partner choice between Ty repeats shows that intrachromosomal Ty partners are preferred despite the abundance of potential interchromosomal Ty partners that share higher sequence identity. This competitive advantage of intrachromosomal Tys results from the relative efficiencies of different NAHR repair pathways. Finally, NAHR generates deleterious rearrangements more frequently when DSBs occur outside rather than within a Ty repeat. These findings yield insights into mechanisms of repeat-mediated genome rearrangements associated with evolution and cancer.

Competitive repair by naturally dispersed repetitive DNA during non-allelic homologous recombination.

Directory of Open Access Journals (Sweden)

Margaret L Hoang

2010-12-01

Full Text Available Genome rearrangements often result from non-allelic homologous recombination (NAHR between repetitive DNA elements dispersed throughout the genome. Here we systematically analyze NAHR between Ty retrotransposons using a genome-wide approach that exploits unique features of Saccharomyces cerevisiae purebred and Saccharomyces cerevisiae/Saccharomyces bayanus hybrid diploids. We find that DNA double-strand breaks (DSBs induce NAHR-dependent rearrangements using Ty elements located 12 to 48 kilobases distal to the break site. This break-distal recombination (BDR occurs frequently, even when allelic recombination can repair the break using the homolog. Robust BDR-dependent NAHR demonstrates that sequences very distal to DSBs can effectively compete with proximal sequences for repair of the break. In addition, our analysis of NAHR partner choice between Ty repeats shows that intrachromosomal Ty partners are preferred despite the abundance of potential interchromosomal Ty partners that share higher sequence identity. This competitive advantage of intrachromosomal Tys results from the relative efficiencies of different NAHR repair pathways. Finally, NAHR generates deleterious rearrangements more frequently when DSBs occur outside rather than within a Ty repeat. These findings yield insights into mechanisms of repeat-mediated genome rearrangements associated with evolution and cancer.

Flexible Plug Repair for Shuttle Wing Leading Edge

Science.gov (United States)

Camarda, Charles J.; Sikora, Joseph; Smith, Russel; Rivers, H.; Scotti, Stephen J.; Fuller, Alan M.; Klacka, Robert; Reinders, Martin; Schwind, Francis; Sullivan, Brian;

Repair of damage induced by ultraviolet radiation in mutator T-1 Escherichia coli transductants

International Nuclear Information System (INIS)

Sideropoulos, A.S.; Greenberg, J.; Warren, G.

1975-01-01

To ascertain whether a relationship commonly exists between azide resistance, ultraviolet (uv) resistance, and the mutator property (mut T-1), we performed uv survival and mutation frequency determinations with and without caffeine (2.571 mM) in nonmutator azide resistant (azi/sup r/) and phage mediated mut T-1 transductants of Escherichia coli K-12, B/r, B/r T-, Bs-1, and Bs-8. The strains constructed were assumed to be ''co-isogenic'' except for the mutator factor. The frequency of mutation to streptomycin resistance (str/sup r/) was relatively constant and approximated 2 x 10- 7 . Transductants carrying the azide marker with or without the mut T-1 gene had the same level of uv survival as the parent with the same mutator phenotype. Dark repair of the prelethal uv lesion is equally caffeine sensitive in the nonmutator and mutator HCR+ strains. Our results indicated that the mut T-1 strains possess an efficient dark repair system for uv damage and that the mechanism of mut T-1 action is independent of uv dark repair processes. (auth)

Molecular and cellular mechanisms of cadmium carcinogenesis

International Nuclear Information System (INIS)

Waisberg, Michael; Joseph, Pius; Hale, Beverley; Beyersmann, Detmar

2003-01-01

Cadmium is a heavy metal, which is widely used in industry, affecting human health through occupational and environmental exposure. In mammals, it exerts multiple toxic effects and has been classified as a human carcinogen by the International Agency for Research on Cancer. Cadmium affects cell proliferation, differentiation, apoptosis and other cellular activities. Cd 2+ does not catalyze Fenton-type reactions because it does not accept or donate electrons under physiological conditions, and it is only weakly genotoxic. Hence, indirect mechanisms are implicated in the carcinogenicity of cadmium. In this review multiple mechanisms are discussed, such as modulation of gene expression and signal transduction, interference with enzymes of the cellular antioxidant system and generation of reactive oxygen species (ROS), inhibition of DNA repair and DNA methylation, role in apoptosis and disruption of E-cadherin-mediated cell-cell adhesion. Cadmium affects both gene transcription and translation. The major mechanisms of gene induction by cadmium known so far are modulation of cellular signal transduction pathways by enhancement of protein phosphorylation and activation of transcription and translation factors. Cadmium interferes with antioxidant defense mechanisms and stimulates the production of reactive oxygen species, which may act as signaling molecules in the induction of gene expression and apoptosis. The inhibition of DNA repair processes by cadmium represents a mechanism by which cadmium enhances the genotoxicity of other agents and may contribute to the tumor initiation by this metal. The disruption of E-cadherin-mediated cell-cell adhesion by cadmium probably further stimulates the development of tumors. It becomes clear that there exist multiple mechanisms which contribute to the carcinogenicity of cadmium, although the relative weights of these contributions are difficult to estimate

Host defense peptides of thrombin modulate inflammation and coagulation in endotoxin-mediated shock and Pseudomonas aeruginosa sepsis

DEFF Research Database (Denmark)

Kalle, Martina; Papareddy, Praveen; Kasetty, Gopinath

2012-01-01

Gram-negative sepsis is accompanied by a disproportionate innate immune response and excessive coagulation mainly induced by endotoxins released from bacteria. Due to rising antibiotic resistance and current lack of other effective treatments there is an urgent need for new therapies. We here...... present a new treatment concept for sepsis and endotoxin-mediated shock, based on host defense peptides from the C-terminal part of human thrombin, found to have a broad and inhibitory effect on multiple sepsis pathologies. Thus, the peptides abrogate pro-inflammatory cytokine responses to endotoxin...

Recent advances in DNA repair and recombination.

Science.gov (United States)

Iwanejko, L A; Jones, N J

1998-09-11

The subjects of the talks at this 1-day DNA Repair Network meeting, held at City University, London on December 15, 1997, encompassed a range of topics and reflected some of the current areas of research in the United Kingdom. Topics included DNA double-strand break repair, V(D)J recombination, DNA ligases, the RecQ family of helicases and Bloom's syndrome, UVB and immunosuppression, the repair of oxidative damage and mismatch repair mechanisms.

Alkylation damage in DNA and RNA--repair mechanisms and medical significance

DEFF Research Database (Denmark)

Drabløs, Finn; Feyzi, Emadoldin; Aas, Per Arne

2004-01-01

Alkylation lesions in DNA and RNA result from endogenous compounds, environmental agents and alkylating drugs. Simple methylating agents, e.g. methylnitrosourea, tobacco-specific nitrosamines and drugs like temozolomide or streptozotocin, form adducts at N- and O-atoms in DNA bases. These lesions...... are mainly repaired by direct base repair, base excision repair, and to some extent by nucleotide excision repair (NER). The identified carcinogenicity of O(6)-methylguanine (O(6)-meG) is largely caused by its miscoding properties. Mutations from this lesion are prevented by O(6)-alkylG-DNA alkyltransferase......, inactivation of the MMR system in an AGT-defective background causes resistance to the killing effects of O(6)-alkylating agents, but not to the mutagenic effect. Bifunctional alkylating agents, such as chlorambucil or carmustine (BCNU), are commonly used anti-cancer drugs. DNA lesions caused by these agents...

Mechanical measurement of hydrogen bonded host-guest systems under non-equilibrium, near-physiological conditions.

Science.gov (United States)

Naranjo, Teresa; Cerrón, Fernando; Nieto-Ortega, Belén; Latorre, Alfonso; Somoza, Álvaro; Ibarra, Borja; Pérez, Emilio M

2017-09-01

Decades after the birth of supramolecular chemistry, there are many techniques to measure noncovalent interactions, such as hydrogen bonding, under equilibrium conditions. As ensembles of molecules rapidly lose coherence, we cannot extrapolate bulk data to single-molecule events under non-equilibrium conditions, more relevant to the dynamics of biological systems. We present a new method that exploits the high force resolution of optical tweezers to measure at the single molecule level the mechanical strength of a hydrogen bonded host-guest pair out of equilibrium and under near-physiological conditions. We utilize a DNA reporter to unambiguously isolate single binding events. The Hamilton receptor-cyanuric acid host-guest system is used as a test bed. The force required to dissociate the host-guest system is ∼17 pN and increases with the pulling rate as expected for a system under non-equilibrium conditions. Blocking one of the hydrogen bonding sites results in a significant decrease of the force-to-break by 1-2 pN, pointing out the ability of the method to resolve subtle changes in the mechanical strength of the binding due to the individual H-bonding components. We believe the method will prove to be a versatile tool to address important questions in supramolecular chemistry.

Recombinational DNA repair and human disease

Energy Technology Data Exchange (ETDEWEB)

Thompson, Larry H.; Schild, David

2002-11-30

We review the genes and proteins related to the homologous recombinational repair (HRR) pathway that are implicated in cancer through either genetic disorders that predispose to cancer through chromosome instability or the occurrence of somatic mutations that contribute to carcinogenesis. Ataxia telangiectasia (AT), Nijmegen breakage syndrome (NBS), and an ataxia-like disorder (ATLD), are chromosome instability disorders that are defective in the ataxia telangiectasia mutated (ATM), NBS, and Mre11 genes, respectively. These genes are critical in maintaining cellular resistance to ionizing radiation (IR), which kills largely by the production of double-strand breaks (DSBs). Bloom syndrome involves a defect in the BLM helicase, which seems to play a role in restarting DNA replication forks that are blocked at lesions, thereby promoting chromosome stability. The Werner syndrome gene (WRN) helicase, another member of the RecQ family like BLM, has very recently been found to help mediate homologous recombination. Fanconi anemia (FA) is a genetically complex chromosomal instability disorder involving seven or more genes, one of which is BRCA2. FA may be at least partially caused by the aberrant production of reactive oxidative species. The breast cancer-associated BRCA1 and BRCA2 proteins are strongly implicated in HRR; BRCA2 associates with Rad51 and appears to regulate its activity. We discuss in detail the phenotypes of the various mutant cell lines and the signaling pathways mediated by the ATM kinase. ATM's phosphorylation targets can be grouped into oxidative stress-mediated transcriptional changes, cell cycle checkpoints, and recombinational repair. We present the DNA damage response pathways by using the DSB as the prototype lesion, whose incorrect repair can initiate and augment karyotypic abnormalities.

Recombinational DNA repair and human disease

International Nuclear Information System (INIS)

Thompson, Larry H.; Schild, David

2002-01-01

We review the genes and proteins related to the homologous recombinational repair (HRR) pathway that are implicated in cancer through either genetic disorders that predispose to cancer through chromosome instability or the occurrence of somatic mutations that contribute to carcinogenesis. Ataxia telangiectasia (AT), Nijmegen breakage syndrome (NBS), and an ataxia-like disorder (ATLD), are chromosome instability disorders that are defective in the ataxia telangiectasia mutated (ATM), NBS, and Mre11 genes, respectively. These genes are critical in maintaining cellular resistance to ionizing radiation (IR), which kills largely by the production of double-strand breaks (DSBs). Bloom syndrome involves a defect in the BLM helicase, which seems to play a role in restarting DNA replication forks that are blocked at lesions, thereby promoting chromosome stability. The Werner syndrome gene (WRN) helicase, another member of the RecQ family like BLM, has very recently been found to help mediate homologous recombination. Fanconi anemia (FA) is a genetically complex chromosomal instability disorder involving seven or more genes, one of which is BRCA2. FA may be at least partially caused by the aberrant production of reactive oxidative species. The breast cancer-associated BRCA1 and BRCA2 proteins are strongly implicated in HRR; BRCA2 associates with Rad51 and appears to regulate its activity. We discuss in detail the phenotypes of the various mutant cell lines and the signaling pathways mediated by the ATM kinase. ATM's phosphorylation targets can be grouped into oxidative stress-mediated transcriptional changes, cell cycle checkpoints, and recombinational repair. We present the DNA damage response pathways by using the DSB as the prototype lesion, whose incorrect repair can initiate and augment karyotypic abnormalities

Repair mechanisms inducible to the DNA in I.M.M.S. biological systems; Mecanismos de reparacion inducible del ADN en sistemas biologicos I.M.M.S

Energy Technology Data Exchange (ETDEWEB)

Guzman, J; Arceo, C; Cortinas, C; Rosa, M.E. De la; Olvera, O; Cruces, M; Pimentel, E

1990-03-15

Given the characteristics of the MMS and the relative antecedents to the repair mechanisms in eucariontes are sought to determine the effect of the MMS on the genetic material and their repair in Drosophila melanogaster. (Author)

DNA damage and repair in plants

International Nuclear Information System (INIS)

Britt, A.B.

1996-01-01

The biological impact of any DNA damaging agent is a combined function of the chemical nature of the induced lesions and the efficiency and accuracy of their repair. Although much has been learned frommicrobes and mammals about both the repair of DNA damage and the biological effects of the persistence of these lesions, much remains to be learned about the mechanism and tissue-specificity of repair in plants. This review focuses on recent work on the induction and repair of DNA damage in higher plants, with special emphasis on UV-induced DNA damage products. (author)

Combined Effects of Scaffold Stiffening and Mechanical Preconditioning Cycles on Construct Biomechanics, Gene Expression, and Tendon Repair Biomechanics

OpenAIRE

Nirmalanandhan, Victor Sanjit; Juncosa-Melvin, Natalia; Shearn, Jason T.; Boivin, Gregory P.; Galloway, Marc T.; Gooch, Cynthia; Bradica, Gino; Butler, David L.

2009-01-01

Our group has previously reported that in vitro mechanical stimulation of tissue-engineered tendon constructs significantly increases both construct stiffness and the biomechanical properties of the repair tissue after surgery. When optimized using response surface methodology, our results indicate that a mechanical stimulus with three components (2.4% strain, 3000 cycles/day, and one cycle repetition) produced the highest in vitro linear stiffness. Such positive correlations between construc...

Endogenous DNA Damage and Repair Enzymes

Directory of Open Access Journals (Sweden)

Arne Klungland

2016-06-01

Full Text Available Tomas Lindahl completed his medical studies at Karolinska Institute in 1970. Yet, his work has always been dedicated to unraveling fundamental mechanisms of DNA decay and DNA repair. His research is characterized with groundbreaking discoveries on the instability of our genome, the identification of novel DNA repair activities, the characterization of DNA repair pathways, and the association to diseases, throughout his 40 years of scientific career.

Effect of endocytosis inhibitors on Coxiella burnetii interaction with host cells

International Nuclear Information System (INIS)

Tujulin, E.; Macellaro, A.; Norlander, L.; Liliehoeoek, B.

1998-01-01

The obligate intracellular rickettsia Coxiella burnetii has previously been reported to reach the intra-vacuolar compartment of host cells by phagocytosis. With the aim to further examine the mechanisms of C. burnetii internalisation, macrophage monolayers were treated with well characterised inhibitors of endocytosis. The treatment with two general inhibitors, colchicine and methylamine, resulted in a pronounced dose-dependent decrease of radiolabelled phase II rickettsiae retained from the intracellular fraction. A third inhibitor used, amiloride, has been reported to reduce effectively clathrin-independent pinocytic pathways. The internalisation of C. burnetii was shown to be substantially reduced also by amiloride and the effect was dependent on its concentration. The passive role of C. burnetii in the internalisation was verified by using heat-killed C. burnetii. Host cells treated with either of the three inhibitors (amiloride, colchicine and methylamine) showed a similar reduction of intracellular C. burnetii after exposure to killed as weal as live organisms. The data presented indicate that different endocytic mechanisms, pinocytosis as well as phagocytosis, may mediate the uptake of C. burnetii by a host cell. Key words: Coxiella burnetii; internalisation; endocytosis (authors)

The transcription fidelity factor GreA impedes DNA break repair.

Science.gov (United States)

Sivaramakrishnan, Priya; Sepúlveda, Leonardo A; Halliday, Jennifer A; Liu, Jingjing; Núñez, María Angélica Bravo; Golding, Ido; Rosenberg, Susan M; Herman, Christophe

2017-10-12

Homologous recombination repairs DNA double-strand breaks and must function even on actively transcribed DNA. Because break repair prevents chromosome loss, the completion of repair is expected to outweigh the transcription of broken templates. However, the interplay between DNA break repair and transcription processivity is unclear. Here we show that the transcription factor GreA inhibits break repair in Escherichia coli. GreA restarts backtracked RNA polymerase and hence promotes transcription fidelity. We report that removal of GreA results in markedly enhanced break repair via the classic RecBCD-RecA pathway. Using a deep-sequencing method to measure chromosomal exonucleolytic degradation, we demonstrate that the absence of GreA limits RecBCD-mediated resection. Our findings suggest that increased RNA polymerase backtracking promotes break repair by instigating RecA loading by RecBCD, without the influence of canonical Chi signals. The idea that backtracked RNA polymerase can stimulate recombination presents a DNA transaction conundrum: a transcription fidelity factor that compromises genomic integrity.

Repair of model compounds of photoinduced lesions in DNA. Electrochemical approaches

International Nuclear Information System (INIS)

Boussicault, F.

2006-09-01

The goal of this work is to better understand the repair mechanism of photoinduced lesions in DNA (cyclobutane dimers and pyrimidine (6-4) pyrimidone adducts) by photolyase redox enzymes, using tools and concepts of molecular electrochemistry. Thanks to the study of model compounds of cyclobutane lesions by cyclic voltametry, we have been able to mimic the key step of the enzymatic repair (dissociative electron transfer) and to monitor the repair of model compounds by Escherichia coli DNA photolyase. From these results, we have discussed the repair mechanism, especially the stepwise or concerted character of the process. Repair mechanism of (6-4) adducts is not known now, but a possible pathway implies an electron transfer coupled to the cleavage of two bonds in the closed form of the lesions (oxetanes). Voltammetric study of reduction and oxidation of model oxetanes and their repair by E. coli DNA photolyase gave some experimental evidence confirming the proposed mechanism and allowing a better understanding of it. (author)

Mirror-smooth surfaces and repair of defects in superconducting RF cavities by mechanical polishing

Energy Technology Data Exchange (ETDEWEB)

Cooper, C. A. [Fermilab; Cooley, L. D. [Fermilab

2012-11-22

Mechanical techniques for polishing the inside surface of niobium superconducting radio-frequency (SRF) cavities have been systematically explored. By extending known techniques to fine polishing, mirror-like finishes were produced, with <15 nm RMS (root mean square) roughness over 1 mm2 scan area. This is an order of magnitude less than the typical roughness produced by the electropolishing of niobium cavities. The extended mechanical polishing (XMP) process was applied to several SRF cavities which exhibited equator defects that caused quench at <20 MV m-1 and were not improved by further electropolishing. Cavity optical inspection equipment verified the complete removal of these defects, and minor acid processing, which dulled the mirror finish, restored performance of the defective cells to the high gradients and quality factors measured for adjacent cells when tested with other harmonics. This innate repair feature of XMP could be used to increase manufacturing yield. Excellent superconducting properties resulted after initial process optimization, with quality factor Q of 3 × 1010 and accelerating gradient of 43 MV m-1 being attained for a single-cell TESLA cavity, which are both close to practical limits. Several repaired nine-cell cavities also attained Q > 8 × 109 at 35 MV m-1, which is the specification for the International Linear Collider. Future optimization of the process and pathways for eliminating requirements for acid processing are also discussed.

Acetylation regulates WRN catalytic activities and affects base excision DNA repair

DEFF Research Database (Denmark)

Muftuoglu, Meltem; Kusumoto, Rika; Speina, Elzbieta

2008-01-01

The Werner protein (WRN), defective in the premature aging disorder Werner syndrome, participates in a number of DNA metabolic processes, and we have been interested in the possible regulation of its function in DNA repair by post-translational modifications. Acetylation mediated by histone...... acetyltransferases is of key interest because of its potential importance in aging, DNA repair and transcription....

Enhanced capacity of DNA repair in human cytomegalovirus-infected cells

International Nuclear Information System (INIS)

Nishiyama, Y.; Rapp, F.

1981-01-01

Plaque formation in Vero cells by UV-irradiated herpes simplex virus was enhanced by infection with human cytomegalovirus (HCMV), UV irradiation, or treatment with methylmethanesulfonate. Preinfection of Vero cells with HCMV enhanced reactivation of UV-irradiated herpes simplex virus more significantly than did treatment with UV or methylmethanesulfonate alone. A similar enhancement by HCMV was observed in human embryonic fibroblasts, but not in xeroderma pigmentosum (XP12BE) cells. It was also found that HCMV infection enhanced hydroxyurea-resistant DNA synthesis induced by UV light or methylmethanesulfonate. Alkaline sucrose gradient sedimentation analysis revealed an enhanced rate of synthesis of all size classes of DNA in UV-irradiated HCMV-infected Vero cells. However, HCMV infection did not induce repairable lesions in cellular DNA and did not significantly inhibit host cell DNA synthesis, unlike UV or methylmethanesulfonate. These results indicate that HCMV enhanced DNA repair capacity in the host cells without producing detectable lesions in cellular DNA and without inhibiting DNA synthesis. This repair appeared to be error proof for UV-damaged herpes simplex virus DNA when tested with herpes simplex virus thymidine kinase-negative mutants

Mediating mechanisms of a military Web-based alcohol intervention.

Science.gov (United States)

Williams, Jason; Herman-Stahl, Mindy; Calvin, Sara L; Pemberton, Michael; Bradshaw, Michael

2009-03-01

This study explored the mediating mechanisms of two Web-based alcohol interventions in a sample of active duty United States military personnel. Personnel were recruited from eight bases and received the Drinker's Check-Up (N=1483), Alcohol Savvy (N=688), or served as controls (N=919). The interventions drew on motivational interviewing and social learning theory and targeted multiple mediators including social norms, perceived risks and benefits, readiness to change, and coping strategies. Baseline data were collected prior to the intervention and follow-up data on alcohol consumption were gathered 1 month and 6 months after program completion. Two mediation models were examined: (1) a longitudinal two-wave model with outcomes and mediators assessed concurrently at the 1-month follow-up; and (2) a three-wave model in which the causal chain was fully lagged. Results indicated strong support for the role of perceived descriptive norms in transmitting the effects of the Drinker's Check-Up, with consistent mediation across the majority of alcohol outcome measures for both the concurrent and fully lagged mediation models. These results suggest that web-based interventions that are effective in lowering perceived norms about the frequency and quantity of drinking may be a viable strategy for reducing alcohol consumption in military populations. The results did not support program mediation by the other targeted variables, indicating the need for future research on the effective components of alcohol interventions. The mediation models also suggest reasons why program effects were not found for some outcomes or were different across programs.

Cloning human DNA repair genes

International Nuclear Information System (INIS)

Jeggo, P.A.; Carr, A.M.; Lehmann, A.R.

1994-01-01

Many human genes involved in the repair of UV damage have been cloned using different procedures and they have been of great value in assisting the understanding of the mechanism of nucleotide excision-repair. Genes involved in repair of ionizing radiation damage have proved more difficult to isolate. Positional cloning has localized the XRCC5 gene to a small region of chromosome 2q33-35, and a series of yeast artificial chromosomes covering this region have been isolated. Very recent work has shown that the XRCC5 gene encodes the 80 kDa subunit of the Ku DNA-binding protein. The Ku80 gene also maps to this region. Studies with fission yeast have shown that radiation sensitivity can result not only from defective DNA repair but also from abnormal cell cycle control following DNA damage. Several genes involved in this 'check-point' control in fission yeast have been isolated and characterized in detail. It is likely that a similar checkpoint control mechanism exists in human cells. (author)

Mussel-inspired tough hydrogels with self-repairing and tissue adhesion

Science.gov (United States)

Gao, Zijian; Duan, Lijie; Yang, Yongqi; Hu, Wei; Gao, Guanghui

2018-01-01

The mussel-inspired polymeric hydrogels have been attractively explored owing to their self-repairing or adhesive property when the catechol groups of dopamine could chelate metal ions. However, it was a challenge for self-repairing hydrogels owning high mechanical properties. Herein, a synergistic strategy was proposed by combining catechol-Fe3+ complexes and hydrophobic association. The resulting hydrogels exhibited seamless self-repairing behavior, tissue adhesion and high mechanical property. Moreover, the pH-dependent stoichiometry of catechol-Fe3+ and temperature-sensitive hydrophobic association endue hydrogels with pH/thermo responsive characteristics. Subsequently, the self-repairing rate and mechanical property of hydrogels were investigated at different pH and temperature. This bio-inspired strategy would build an avenue for designing and constructing a new generation of self-repairing, tissue-adhesive and tough hydrogel.

Influence of the field humiture environment on the mechanical properties of 316L stainless steel repaired with Fe314

Science.gov (United States)

Zhang, Lianzhong; Li, Dichen; Yan, Shenping; Xie, Ruidong; Qu, Hongliang

2018-04-01

The mechanical properties of 316L stainless steel repaired with Fe314 under different temperatures and humidities without inert gas protection were studied. Results indicated favorable compatibility between Fe314 and 316L stainless steel. The average yield strength, tensile strength, and sectional contraction percentage were higher in repaired samples than in 316L stainless steel, whereas the elongation rate was slightly lower. The different conditions of humiture environment on the repair sample exerted minimal influence on tensile and yield strengths. The Fe314 cladding layer was mainly composed of equiaxed grains and mixed with randomly oriented columnar crystal and tiny pores or impurities in the tissue. Results indicated that the hardness value of Fe314 cladding layer under different humiture environments ranged within 419-451.1 HV0.2. The field humiture environment also showed minimal impact on the average hardness of Fe314 cladding layers. Furthermore, 316L stainless steel can be repaired through laser cladding by using Fe314 powder without inert gas protection under different temperatures and humidity environments.

Volatile chemical cues guide host location and host selection by parasitic plants

Science.gov (United States)

Justin B. Runyon; Mark C. Mescher; Consuelo M. De Moraes

2006-01-01

The importance of plant volatiles in mediating interactions between plant species is much debated. Here, we demonstrate that the parasitic plant Cuscuta pentagona (dodder) uses volatile cues for host location. Cuscuta pentagona seedlings exhibit directed growth toward nearby tomato plants (Lycopersicon esculentum...

Human diseases with genetically altered DNA repair processes

International Nuclear Information System (INIS)

Cleaver, J.E.; Bootsma, D.; Friedberg, E.

1975-01-01

DNA repair of single-strand breaks (produced by ionizing radiation) and of base damage (produced by ultraviolet (uv) light) are two repair mechanisms that most mammalian cells possess. Genetic defects in these repair mechanisms are exemplified by cells from the human premature-aging disease, progeria, which fail to rejoin single-strand breaks, and the skin disease, xeroderma pigmentosum (XP), which exhibits high actinic carcinogenesis and involves failure to repair base damage. In terms of the response of XP cells, many chemical carcinogens can be classified as either x-ray-like (i.e., they cause damage that XP cells can repair) or uv-like (i.e., they cause damage that XP cells cannot repair). The first group contains some of the more strongly carcinogenic chemicals (e.g., alkylating agents). XP occurs in at least two clinical forms, and somatic cell hybridization indicates at least three complementation groups. In order to identify cell lines from various different laboratories unambiguously, a modified nomenclature of XP lines is proposed. (U.S.)

Human diseases with genetically altered DNA repair processes

International Nuclear Information System (INIS)

Cleaver, J.E.; Bootsma, D.; Friedberg, E.

1975-01-01

DNA repair of single-strand breaks (produced by ionizing radiation) and of base damage (produced by ultraviolet (UV) light) are two repair mechanisms that most mammalian cells possess. Genetic defects in these repair mechanisms are exemplified by cells from the human premature-aging disease, progeria, which fail to rejoin single-strand breaks, and the skin disease, xeroderma pigmentosum (XP), which exhibits high actinic carcinogenesis and involves failure to repair base damage. In terms of the response of XP cells, many chemical carcinogens can be classified as either X-ray-like (i.e., they cause damage that XP cells can repair) or UV-like (i.e., they cause damage that XP cells cannot repair). The first group contains some of the more strongly carcinogenic chemicals (e.g., alkylating agents). XP occurs in at least two clinical forms, and somatic cell hybridization indicates at least three complementation groups. In order to identify cell lines from various different laboratories unambiguously, a modified nomenclature of XP lines is proposed

Alkaline gel electrophoresis assay to detect DNA strand breaks and repair mechanisms in Escherichia coli

Directory of Open Access Journals (Sweden)

José Carlos Pelielo de Mattos

2008-12-01

Full Text Available Reactive oxygen species (ROS can induce lesions in different cellular targets, including DNA. Stannous chloride (SnCl2 is a ROS generator, leading to lethality in Escherichia coli (E. coli, with the base excision repair (BER mechanism playing a role in this process. Many techniques have been developed to detect genotoxicity, as comet assay, in eukaryotic cells, and plasmid DNA agarose gel electrophoresis. In this study, an adaptation of the alkaline gel electrophoresis method was carried out to ascertain the induction of strand breaks by SnCl2 in bacterial DNA, from E. coli BER mutants, and its repair pathway. Results obtained show that SnCl2 was able to induce DNA strand breaks in all strains tested. Moreover, endonuclease IV and exonuclease III play a role in DNA repair. On the whole, data has shown that the alkaline gel electrophoresis assay could be used both for studying DNA strand breaks induction and for associated repair mechanisms.Espécies reativas de oxigênio (ERO podem induzir lesões em diferentes alvos celulares, incluindo o DNA. O cloreto estanoso (SnCl2 é um gerador de ERO que induz letalidade em E. coli, sendo o reparo por excisão de bases (BER um mecanismo importante neste processo. Técnicas como o ensaio cometa (em eucariotos e a eletroforese de DNA plasmidial em gel de agarose têm sido utilizadas para detectar genotoxicidade. No presente estudo, uma adaptação do método de eletroforese em gel alcalino de agarose foi usada para verificar a indução de quebras, pelo SnCl2, no DNA de E. coli, bem como a participação de enzimas do BER na restauração das lesões. Os resultados mostraram que o SnCl2 induziu quebras no DNA de todas as cepas testadas. Além disso, endonuclease IV e exonuclease III estão envolvidas na reparação dos danos. Em resumo, os dados obtidos indicam que a metodologia de eletroforese em gel alcalino de agarose pode ser empregada tanto para o estudo de quebras no DNA, quanto para avaliação dos