Increased UV-induced sister-chromatid exchange in cultured fibroblasts of first-degree relatives of melanoma patients

International Nuclear Information System (INIS)

Knees-Matzen, S.; Roser, M.; Reimers, U.; Ehlert, U.; Weichenthal, M.; Breitbart, E.W.; Ruediger, H.W.

1991-01-01

Cultured fibroblasts of 17 first-degree relatives of familial melanoma patients and six first-degree relatives of cutaneous melanoma (CMM) patients with multiple CMM primaries were tested for in vitro sensitivity to UV light. Fibroblasts of nine familial CMM patients with a known UV-sensitivity and 19 healthy probands served as a control. Sister chromatid exchange (SCE) was used as a parameter to detect UV-induced genotoxic damage. The authors found significantly (p less than 0.001) increased UV-induced SCE levels in familial melanoma patients, as well as in first-degree relatives of familial melanoma patients (p less than 0.001) after UV-A,B irradiation (375 J/m2), compared to the healthy probands without a family history of CMM. A significant (p less than 0.001) increase of UV-induced SCE was also observed in the relatives of CMM patients with multiple CMM primaries. In addition, the spontaneous SCE were significantly increased (p less than 0.05) in familial CMM patients. This study shows that increased UV sensitivity is a familial phenomenon. It is consistent with the concept of a genetic predisposition to CMM, which is based on increased UV sensitivity and may help to define groups with an elevated risk of developing cutaneous malignant melanoma

Sister chromatid exchanges induced in CHO cells by X-rays or 5.5 MeV neutrons

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Bocian, E.; Rosiek, O.; Sablinski, J.; Ziemba-Zoltowska, B.

1986-01-01

The induction of sister chromatid exchanges (SCEs) by X-rays (1-9 Gy) and 5.5 MeV neutrons (0.5-4 Gy) was studied in CHO cells. A dose-dependent increase of the frequency of SCE was found for both radiations when cells with BrdUrd substituted DNA were irradiated. The similar doubling dose, approx. 4 Gy, was found for X-rays and neutrons. The increase of the SCE frequency was not clearly dependent on the dose when cells with BrdUrd unsubstituted DNA were irradiated. In this case a dose of 4 Gy enhanced the SCE frequency only by the factor of 1.3. (author)

Modelling and testing the molecular mechanism of radiation-induced chromatid breaks

International Nuclear Information System (INIS)

Bryant, P. E.

2001-01-01

Chromatid breaks induced by ionizing radiation in the G2 phase of the cell cycle are considered as markers of individual human radiosensitivity and may indicate the presence of low-penetrance genes regulating susceptibility to breast and other cancers). Together with our own study of Scottish (Tayside) breast cancer patients and a group of normal controls these studies show an overall 10-fold variation in chromatid break frequency (the parameter defining individual chromosomal 'radiosensitivity'). Thus, an understanding of the mechanisms and genes involved in determining these widely different responses should help to clarify the reasons for individual radiosensitivity and may lead us to identify key genes involved in cancer susceptibility. The presence of colour-switches at around 16% of chromatid break points (detected in harlequin-stained chromosomes) indicates that this type of chromatid break is formed by a chromatin rearrangement involving one or more large chromatin domains of the order of 3 - 5 Mbp, possibly representing transcription 'factories'. The signal model of chromatid breaks assumes that all chromatid breaks are the result of chromatin rearrangements, and that the initiating DNA double-strand break (dsb) is itself not involved in the rearrangement but signals its presence (possibly via ATM protein or DNAPK) leading to the initiation of the chromatin rearrangement. Experimental evidence from radiosensitive cell lines (e.g. human AT and hamster irs2) and with the nucleoside analogue araA (9-β-D-arabinofuranosyladenine) demonstrates the lack of correspondence between the rejoining kinetics of dsb and that of disappearance of chromatid breaks, thus supporting the signal model. Coupled with the linear induction of chromatid breaks with dose in both human and rodent cell lines of various types, and the production of chromatid breaks by single dsb in genetically engineered cell lines the classical 'breakage-first' model of chromatid breaks is no longer

Evaluation of the persistence in the induction of Sister Chromatid Exchanges (SCE) by alkylating agents

International Nuclear Information System (INIS)

Rodriguez R, R.; Huerta V, C.; MOrales R, P.R.

2006-01-01

The persistence in the induction of sister chromatid exchanges (SCE) by the alkylating agents methyl and ethyl-methanesulfonates (MMS and EMS) was evaluated. For it, to groups of mice its were administered a dose of these agents and later its were analyzed the induced SCE's in two periods: early and late. Both agents caused high increments of SCE in the early period and small in the late one; however, the caused lately by EMS was significantly bigger. This late induction of SCE by EMS possibly is associated with an epigenetic change or with the presence of etiladucts in the phosphodiester bonds of the DNA. (Author)

Acute wood or coal exposure with carbon monoxide intoxication induces sister chromatid exchange

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Ozturk, S.; Vatansever, S.; Cefle, K.; Palanduz, S.; Guler, K.; Erten, N.; Erk, O.; Karan, M.A.; Tascioglu, C. [University of Istanbul, Istanbul (Turkey). Istanbul Faculty of Medicine

2002-07-01

The object of this study was to investigate the genotoxic effect of acute overexposure to combustion products originating from coal or wood stoves in patients presenting with acute carbon monoxide intoxication. The authors analyzed the frequency of sister chromatid exchange and the carboxyhemoglobin concentration in 20 consecutive patients without a history of smoking or drug use who had been treated in the Emergency Care Unit of Istanbul Medical Faculty due to acute carbon monoxide intoxication. All of these cases were domestic accidents due to dysfunctioning coal or wood stoves. The results were compared with a control group of 20 nonsmoking, nondrug-using healthy individuals matched for age, sex, and absence of other chemical exposure. It was concluded that acute exposure to combustion products of wood or coal is genotoxic to DNA. Potential causes of genotoxicity include known mutagenic compounds present in coal or wood smoke and ash, oxygen radicals formed during combustion, as well as hypoxic and reperfusion injury mechanisms initiated by carbon monoxide intoxication.

Frequency of sister chromatid exchanges in lymphocyte cultures of human peripheral blood after the combined effect of γ-radiation and caffeine

International Nuclear Information System (INIS)

Nugis, V.Yu.; Pyatkin, E.K.

1986-01-01

Keeping of human peripheral blood lymphocytes, irradiated in vitro with 60 Co-γ-quanta at a dose of 3 Gy at G 0 phase, with caffeine of 16 and 160 μg/ml during cultivation with PHA had no appreciable influence on the fraquency of sister chromatid exchanges. A minor increase in the number of sister chromatid exchanges was only noted when nonirradiated and irradiated lymphocytes were cultured with 160 μg/ml caffeine

Effect of chlorophyllin on frequency radiation-induced of sister chromatid exchanges (SCE) and other cytogenetic events in mice bone marrow cells In Vivo

International Nuclear Information System (INIS)

Garcia Rodriguez, M.C.

1992-01-01

The effect of chlorophyllin on gamma radiation induced Sister chromatid exchanges (SCE) and on the mitotic index (IM) and average generation time was determined. Groups of mice were treated in one of the following regimens: (1) untreated, (2) treated with chlorophyllin only, (3) irradiated and (4) treated with chlorophyllin and irradiated intraperitoneal administration of chlorophyllin preceding gamma radiation exposure protected again SCE induction and diminution of IM. However, radioprotection was not reflected in the average generation time for the chlorophyllin per se acceleration the average generation time. The results suggest that, under the experimental conditions of the study the SCE and IM are caused by free radicals produced by radiation and wat the action mechanics of chlorophyllin is scavenger free radicals. (Author)

Sister chromatid exchanges in the bone marrow cells of in vivo rats induced by gamma radiation and chemical mutagens

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Rodriguez R, R.G.

1981-01-01

Sister chromatid exchanges (SCE) in the bone marrow of in vivo rats induced by gamma radiation doses and by the chemical mutagens, mitomycin C (MMC), cyclophosphamide (CP), and sulphonate-methylmethane (SMM), were studied. The purpose was to evaluate the sensitivity and reproducibility of a simplified SCE in vivo detecting system developed in our laboratory and to compare the results obtained with those reported elsewhere. Simplification consisted in administering the amounts of 5-bromo-2'-deoxyuridine (BrdU) necessary to observe the SCE, after first adsorbing the BrdU in activated carbon and then injecting it interperitoneally, into the rats. The results were a longer time in vivo ADN incorporation without convulsions in the rats, and a reduction in the time course as compared to other methods. We observed a basal rate of 3.6+-0.37 SCE/cell and that: 0.44 Gy of gamma radiation induced 7.7+-0.73 SCE/cell; 1.6 μg/g of MMC induced 8.1+-1.20 SCE/cell; 5 μg/g of CP induced 8.25+-1.5 SCE/cell, 40 μg/g of SMM induced 22.0+-5 SCE/cell and 380 μg/g of sulphonate-ethylmethane induced 8.6+-1.2 SCE/cell. This showed that all the agents were capable of inducing SCE in the bone marrow cells of rats in vivo under our conditions. We noted a greater induced efficiency for gamma radiation than the obtained by other investigators and a relatively similar efficiency in the case of chemical mutagens as reported in other studies. (author)

Induction of sister chromatid exchange in the presence of gadolinium-DTPA and its reduction by dimethyl sulfoxide

International Nuclear Information System (INIS)

Yamazaki, Etsuo; Fukuda, Hozumi; Shibuya, Hitoshi; Matsubara, Sho

1996-01-01

The authors investigate the frequency of sister chromatid exchange (SCE) after the addition of gadolinium (Gd)-DTPA to venous blood samples. Venous blood was obtained from nonsmokers. Samples were incubated with Gd-DTPA alone or in combination with mitomycin C, cytarabine, and dimethyl sulfoxide (DMSO), and then evaluated for SCEs. The frequency of SCE increased with the concentration of Gd-DTPA and as each chemotherapeutic agent was added. Sister chromatid exchange frequencies were lower when the blood was treated with a combination of Gd-DTPA and DMSO compared with Gd-DTPA alone. The increase in frequency of SCE seen after the addition of Gd-DTPA was decreased by the addition of DMSO, indicating the production of hydroxyl radicals. The effect likely is dissociation-related. 14 refs., 6 tabs

A comparative investigation of DNA strand breaks, sister chromatid exchanges and K-ras gene mutations induced by cadmium salts in cultured human cells

International Nuclear Information System (INIS)

Mouron, Silvana Andrea; Grillo, Claudia Alejandra; Dulout, Fernando Noel; Golijow, Carlos Daniel

2004-01-01

Cadmium (Cd) is a toxic heavy metal of continuing occupational and environmental concern with a wide variety of adverse effects. Several studies have shown that cadmium produces DNA strand breaks, DNA-protein cross-links, oxidative DNA damage, chromosomal aberrations, dysregulation of gene expression resulting in enhanced proliferation, depressed apoptosis and/or altered DNA repair. This study was undertaken to investigate the ability of cadmium chloride (CdCl 2 ) and cadmium sulphate (CdSO 4 ) to induce point mutations in codon 12 of the K-ras protooncogene assessed by polymerase chain reaction-single strand conformation polymorphisms (PCR-SSCP) and RFLP-enriched PCR methods. Also their genotoxic effects were analyzed by the comet assay and sister chromatid exchanges test. The human lung fibroblast cell line MRC-5 was used for the experiments. Sister chromatid exchanges assay (SCEs) frequencies were significantly increased in cells exposed to cadmium salts in relation to controls (p < 0.001). Despite the slow increment observed in the three comet parameters considered when cells were treated with cadmium chloride, significant differences between groups were only found in the variable comet moment (CM) (p < 0.005). On the other hand, when cells were exposed to cadmium sulphate, the Kruskal-Wallis test showed highly significant differences between groups for migration, tail moment and comet moment parameters (p < 0.001). Nevertheless, a null or weak point mutation induction in K-ras protooncogene was detected using polymerase chain reaction-low ionic strength-single strand conformation polymorphisms (PCR-LIS-SSCP) and RFLP-enriched PCR methods when cells were treated with cadmium salts. Thus, inorganic cadmium produces genotoxicity in human lung fibroblast MRC-5 cells, in the absence of significant point mutation of the K-ras gene

Chromatid interchanges at intrachromosomal telomeric DNA sequences

International Nuclear Information System (INIS)

Fernandez, J.L.; Vazquez-Gundin, F.; Bilbao, A.; Gosalvez, J.; Goyanes, V.

1997-01-01

Chinese hamster Don cells were exposed to X-rays, mitomycin C and teniposide (VM-26) to induce chromatid exchanges (quadriradials and triradials). After fluorescence in situ hybridization (FISH) of telomere sequences it was found that interstitial telomere-like DNA sequence arrays presented around five times more breakage-rearrangements than the genome overall. This high recombinogenic capacity was independent of the clastogen, suggesting that this susceptibility is not related to the initial mechanisms of DNA damage. (author)

A proposal of a standardised nomenclature for terminal minute sister chromatid exchanges

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Máximo E. Drets

2006-01-01

Full Text Available We described spontaneous minute sister chromatid exchanges (SCE in telomeric regions of human and Chinese hamster ovary (CHO chromosomes more than 10 years ago. These structures, which we called t-SCE, were detected by means of highly precise quantitative microphotometrical scanning and computer graphic image analysis. Recently, several authors using the CO-FISH method also found small SCEs in telomeric regions and called them T-SCE. The use of different terms for designating the same phenomenon should be avoided. We propose ter SCE as a uniform nomenclature for minute telomeric SCEs.

Protection of halogenated DNA from strand breakage and sister-chromatid exchange induced by the topoisomerase I inhibitor camptothecin

International Nuclear Information System (INIS)

Orta, Manuel Luis; Mateos, Santiago; Cantero, Gloria; Wolff, Lisa J.; Cortes, Felipe

2008-01-01

The fundamental nuclear enzyme DNA topoisomerase I (topo I), cleaves the double-stranded DNA molecule at preferred sequences within its recognition/binding sites. We have recently reported that when cells incorporate halogenated nucleosides analogues of thymidine into DNA, it interferes with normal chromosome segregation, as shown by an extraordinarily high yield of endoreduplication, and results in a protection against DNA breakage induced by the topo II poison m-AMSA [F. Cortes, N. Pastor, S. Mateos, I. Dominguez, The nature of DNA plays a role in chromosome segregation: endoreduplication in halogen-substituted chromosomes, DNA Repair 2 (2003) 719-726; G. Cantero, S. Mateos, N. Pastor; F. Cortes, Halogen substitution of DNA protects from poisoning of topoisomerase II that results in DNA double-strand breaks (DSBs), DNA Repair 5 (2006) 667-674]. In the present investigation, we have assessed whether the presence of halogenated nucleosides in DNA diminishes the frequency of interaction of topo I with DNA and thus the frequency with which the stabilisation of cleavage complexes by the topo I poison camptothecin (CPT) takes place, in such a way that it protects from chromosome breakage and sister-chromatid exchange. This protective effect is shown to parallel a loss in halogen-substituted cells of the otherwise CPT-increased catalytic activity bound to DNA

A comparison of G2 phase radiation-induced chromatid break kinetics using calyculin-PCC with those obtained using colcemid block.

Science.gov (United States)

Bryant, Peter E; Mozdarani, Hossein

2007-09-01

To study the possible influence of cell-cycle delay on cells reaching mitosis during conventional radiation-induced chromatid break experiments using colcemid as a blocking agent, we have compared the chromatid break kinetics following a single dose of gamma rays (0.75 Gy) in metaphase CHO cells using calyculin-induced premature chromosome condensation (PCC), with those using colcemid block. Calyculin-induced PCC causes very rapid condensation of G2 cell chromosomes without the need for a cell to progress to mitosis, hence eliminating any effect of cell-cycle checkpoint on chromatid break frequency. We found that the kinetics of the exponential first-order decrease in chromatid breaks with time after irradiation was similar (not significantly different) between the two methods of chromosome condensation. However, use of the calyculin-PCC technique resulted in a slightly increased rate of disappearance of chromatid breaks and thus higher frequencies of breaks at 1.5 and 2.5 h following irradiation. We also report on the effect of the nucleoside analogue ara A on chromatid break kinetics using the two chromosome condensation techniques. Ara A treatment of cells abrogated the decrease in chromatid breaks with time, both using the calyculin-PCC and colcemid methods. We conclude that cell-cycle delay may be a factor determining the absolute frequency of chromatid breaks at various times following irradiation of cells in G2 phase but that the first-order disappearance of chromatid breaks with time and its abrogation by ara A are not significantly influenced by the G2 checkpoint.

Possible mechanisms of chromosomal aberrations: VII. Comparative dynamics of sister chromatid disjunction and realization of radiation-induced chromosomal aberrations during mitosis

International Nuclear Information System (INIS)

Lebedeva, L.I.; Akhmamet'eva, E.M.

1994-01-01

An increase in radiation-induced chromosomal aberrations during c-metaphase sister chromatid disjunction was demonstrated in murine bone marrow cells exposed to a total γ-irradiation at 0.5 Gy. Caffeine (Cf) treatment during mitosis partially suppressed the chromatid disjunction rate and increased the number of radiation-induced aberrations in this mitosis. Nalidixic acid (NA) treatment of c-metaphase cells completely suppressed chromatid disjunction and the realization of induced aberrations. Topoisomerase 2 was assumed to be involved during mitosis in both processes

Characterization of the enhancing effect of caffeine on sister-chromatid exchanges induced by ultraviolet radiation in excision-proficient xeroderma pigmentosum lymphoblastoid cells

International Nuclear Information System (INIS)

Thoda, Hiroko; Oikawa, Atsushi

1988-01-01

Cells of some excision-proficient xeroderma pigmentosum (XP) cell lines are highly sensitive to post-UV caffeine treatment in terms of sister-chromatid exchange (SCE) induction as well as cell lethality. In the present study, the authors conducted a detailed investigation of the enhancing effect of caffeine on SCE frequency induced by UV in excision-proficient XP cells, and obtained the following results. (1). Continuous post-UV treatment with 1mM caffeine markedly enhances UV-induced SCEs and such enhanced SCEs occur with similar frequency during either the 1st or the 2nd cell cycle in the presence of caffeine and 5-bromodeoxyuridine (BrdUrd). (2) The high sensitivity of the cells to post-UV caffeine treatment persists for at least 2 days after UV when irradiated cells are held in either the proliferating of the nonproliferating state prior to the addition of BrdUrd. (3) Caffeine exerts its effect on cells in S phase. The most likely explanation for our findings is as follows. In excision-proficient XP cells, the cause of SCE formation such as UV-induced lesions or resulting perturbations of DNA replication persists untill the 2nd round or more of post-UV DNA replication. If caffeine is given as post-UV treatment, such abnormalities may be amplified, resulting in a synergistic increase in SCE frequency. (author). 21 refs.; 4 figs.; 4 tabs

Effects of a tumor promoter and an anti-promoter on spontaneous and UV-induced 6-thioguanine-resistant mutations and sister-chromatid exchanges in V79 Chinese hamster cells

International Nuclear Information System (INIS)

Fujiwara, Y.; Kano, Y.; Tatsumi, M.; Paul, P.

1980-01-01

The effects of a tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) and/or an anti-promoter antipain (protease inhibitor) on spontaneous and ultraviolet-induced sister-chromatid exchanges (SCEs) and 6-thioguanine-resistant (6TGsup(r)) recessive mutations were examined in V79 Chinese hamster cells in culture. TPA and/or antipain neither significantly altered base-line and UV-induced immediate SCE frequencies, nor decreased the level of delayed SCEs which persisted 6-7 days after irradiation. TPA and/or antipain appeared to enhance the recovery of UV-induced 6TGsup(r) colonies at the plateau expression phase despite non-mutagenicity by themselves and unaltered metabolic cooperation. Thus, the results conceivably imply that the 6TGsup(r)-recessive mutation expression, but not fixation, can be modulated at the cell level by TPA and/or antipain. Our results, together with the recent results of Loveday and Latt, may argue against the notion that TPA enhances the antipain-suppressible SCEs as an index of mitotic recombination in relevance with a tumor-promotion mechanism. (orig.)

Non-random intrachromosomal distribution of radiation-induced chromatid aberrations in Vicia faba. [Aberration clustering

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Schubert, I; Rieger, R [Akademie der Wissenschaften der DDR, Gatersleben. Zentralinst. fuer Genetik und Kulturpflanzenforschung

1976-04-01

A reconstructed karyotype of Vicia faba, with all chromosomes individually distinguishable, was treated with X-rays, fast neutrons, (/sup 3/H) uridine (/sup 3/HU). The distribution within metaphase chromosomes of induced chromatid aberrations was non-random for all agents used. Aberration clustering, in part agent specific, occurred in chromosome segments containing heterochromatin as defined by the presence of G bands. The pattern of aberration clustering found after treatment with /sup 3/HU did not allow the recognition of chromosome regions active in transcription during treatment. Furthermore, it was impossible to obtain unambiguous indications of the presence of AT- and GC-base clusters from the patterns of /sup 3/HT- and /sup 3/HC-induced chromatid aberrations, respectively. Possible reasons underlying these observations are discussed.

Sister chromatid exchange in children of Seventh-Day Adventists and matched controls.

Science.gov (United States)

Hermansen, R; Waksvik, H; Fønnebø, V

1991-03-01

The low risk of cancer in Seventh-Day Adventists (SDAs) has been suggested to be due to genetic selection. To investigate this claim we examined the sister chromatid exchange (SCE) frequency in peripheral blood lymphocytes in 16 SDA children in Tromsø, all aged 0.5-8 years and 16 controls matched for sex and age. In 12 of 16 pairs, the SDA children had a lower SCE frequency than the controls. The mean difference was 4.06 (95% confidence interval -17.02-8.89, P = 0.51). There was no sex difference, and no correlation between age and SCE frequency. The genetic starting point with regard to SCE frequency seems to be the same for SDA children and controls.

Alkaline DNA fragmentation, DNA disentanglement evaluated viscosimetrically and sister chromatid exchanges, after treatment in vivo with nitrofurantoin.

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Parodi, S; Pala, M; Russo, P; Balbi, C; Abelmoschi, M L; Taningher, M; Zunino, A; Ottaggio, L; de Ferrari, M; Carbone, A; Santi, L

1983-07-01

Nitrofurantoin was not positive as a carcinogen in long term assays. In vitro it was positive in some short term tests and negative in others. We have examined Nitrofurantoin for its capability of inducing DNA damage in vivo. With the alkaline elution technique, Nitrofurantoin appeared clearly positive in all the tissues examined (liver, kidney, lung, spleen and bone marrow). In the liver we also observed some cross-linking effect. In bone marrow cells Nitrofurantoin was also clearly positive in terms of sister chromatid exchanges (SCEs) induction. DNA damage in vivo was also examined with a viscosimetric method, more sensitive than alkaline elution. With this method the results were essentially negative, suggesting that the two methods detect different types of damage. In view of its positivity in many organs and in two short term tests in vivo, the carcinogenic potential of Nitrofurantoin should be reconsidered.

Elevated sister chromatid exchange frequencies in New Zealand Vietnam War veterans.

Science.gov (United States)

Rowland, R E; Edwards, L A; Podd, J V

2007-01-01

From July 1965 until November 1971, New Zealand Defence Force Personnel fought in the Vietnam War. During this time more than 76,500,000 litres of phenoxylic herbicides were sprayed over parts of Southern Vietnam and Laos, the most common being known as 'Agent Orange'. The current study aimed to ascertain whether or not New Zealand Vietnam War veterans show evidence of genetic disturbance arising as a consequence of their now confirmed exposure to these defoliants. A sample group of 24 New Zealand Vietnam War veterans and 23 control volunteers were compared using an SCE (sister chromatid exchange) analysis. The results from the SCE study show a highly significant difference (P Vietnam War veterans studied here were exposed to a clastogenic substance(s) which continues to exert an observable genetic effect today, and suggest that this is attributable to their service in Vietnam. Copyright 2007 S. Karger AG, Basel.

Similar kinetics of chromatid aberrations in X-irradiated xrs 5 and wild-type Chinese hamster ovary cells

International Nuclear Information System (INIS)

MacLeod, R.A.F.; Bryant, P.E.

1990-01-01

We have studied the kinetics of chromatid aberrations in cells of the Chinese hamster ovary (CHO-K1) derived, X-ray sensitive cell line xrs 5 irradiated in the G 2 phase at 37 0 C, as well as during a cell cycle extended by transient hypothermia at 33 0 C. While a given X-ray dose was estimated to produce about 4 times as many chromatid break and twice the frequency of exchanges in xrs 5 cells as in the parent line, there was no difference between the lines in the rates of disappearance of chromatid breaks during G 2 at either temperature; and similar patterns of chromatid exchange kinetics were observed in the two lines. Both the frequencies and distributions of chromatid breaks at different times after irradiation are consistent with the view that the disappearance of these during incubation represents a repair process. These results imply that the G 2 chromosomal radiosensitivity of the xrs 5 mutant resides at the level of initial chromatid damage. (author)

Evidence that cyclophosphamide can to induce exchanges in the sister chromatids (ICH) through secondary injuries

International Nuclear Information System (INIS)

Morales R, P.; Rodriguez R, R.

1997-01-01

By means of the use of destination protocol of ICH inductive injuries (DLI-ICH), it was studied if interchanges in the sister chromatids (ICH) induced by cyclophosphamide (CP), in the second post-treatment division (ICH-2) are produced by secondary injuries or by fresh injuries. For discard between these possibilities it was administered CP at different periods before of the first post-treatment division, taking as reference the administered time for high dose of bromodeoxyuridine (BrdU ) which was approximately at the beginning of this division. The ICH frequencies that occur in the first, the second and the third synthesis stages (S) were determined. It was observed that when the administered CP was four hours before BrdU , the ICH frequencies of the second and the third S were reduced. The frequency of the first ICH increased lightly in relation to those of the normal protocol (0.5 h before BrdU ) and that the supplying of CP six hours before caused almost a total reduction of ICH of second and third S and an important increment of ICH of first S.This was interpreted as evidence that the ICH-2 are product of secondary injuries. (Author)

In vivo study on the replicative model validity of sister chromatid exchanges production

International Nuclear Information System (INIS)

Cruz V, V.L.

1996-01-01

The sister chromatid exchanges (SCE) frequency determination has been used as index of damage to DNA, however the biological meaning of this event is still ignored. Different models in order to explain the mechanism of their formation have been proposed and they could be contained in two categories: a) those that consider that the SCE is produced by means of discreet lesions to the DNA and that they occur in the place of the lesion, and b) those that propose that the SCE is caused by a group of lesions and that therefore the place in which they occur could not be associated with a lesion in particular. The model of Painter (1980) belongs to this last group. It suggests that the region of the DNA where the clusters are united, is the only place in which the exchange of double chain could happen during the synthesis of the DNA and makes the prediction that since the x rays retard the beginning of the duplication, the pretreatment with ionizing radiation would reduce the frequency of SCE induced by agents capable to block the lengthening of the chain of DNA, that are the most efficient SCE inducers. The objective of the present work was to establish the validity of this replicative model for the SCE formation, based in its prediction. The effect of the unilateral preexposition of mouse to gamma radiation was determined on the SCE induction by Mitomycin C (MMC), in cells of the femoral bone marrow In vivo. This strategy allows to determine the effect of the pretreatment in the same organism, minimizing the variability of the response between individuals. There was not a significant variability between the frequencies of SCE, basal and induced by gamma radiation or MMC in the same organism. The animals that received the gamma radiation pretreatment, showed a reduction of approximately the 30 % in the frequency of SCE, assuming an additive effect of the radiation with the MMC. These results coincide with the prediction of the model of Painter, however it is not

In vitro and occupational induction of sister-chromatid exchanges in human lymphocytes with furfuryl alcohol and furfural

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Gomez-Arroyo, S.; Souza, V.

1985-06-01

Sister-chromatid exchanges (SCEs) in human lymphocytes were studied using the FPG technique in order to determine the cytogenetic effect of furfural and furfuryl alcohol. The induction of SCEs was also investigated in workers occupationally exposed to these solvents that are commonly used in the manufacture of furoic resins. The results obtained from the in vitro treatments show that furfural increased the number of SCEs, while furfuryl alcohol did not. In exposed workers, neither of these solvents increased the spontaneous frequency of SCEs per metaphase.

Sister chromatid exchanges in X-ray irradiated blood lymphocytes from patients with hereditary diseases with radioresistant DNA synthesis

International Nuclear Information System (INIS)

Pleskach, N.M.; Andriadze, M.I.; Mikhel'son, V.M.; Zhestyanikov, V.D.

1988-01-01

X-ray irradiation induced sister chromatid exchanges (SCE) in blood lymphocytes from patient with Down's syndrome and adult progeria (in both the cases radioresistant DNA synthesis takes place). In normal lymphocytes (in which ionizing radiation inhibits the replicative synthesis of DNA) the rate of SCE rises with the rise of radiation dose. Thus, the rate of SCE in X-ray irradiated lymphocytes is in reverse dependence with radioresistance of replicative synthesis of DNA. The data obtained are explained in accordance with the replicative hypothesis of the SCE nature (Painter, 1980a): in cells of patients with Down's syndrome, xeroderma pigmentosum from 2 and progeria of adults the time of existence of partly replicated clusters of replicons is decreased due to radioresistant replicative synthesis of DNA, but the presence of partly replicated clusters of replicons in necessary for SCE formation. Therefore the rate of SCF in X-irradiated cells of these patients decreases

Use of a ring chromosome and pulsed-field gels to study interhomolog recombination, double-strand DNA breaks and sister-chromatid exchange in yeast

International Nuclear Information System (INIS)

Game, J.C.; Sitney, K.C.; Cook, V.E.; Mortimer, R.K.

1989-01-01

The authors describe a system that uses pulsed-field gels for the physical detection of recombinant DNA molecules, double-strand DNA breaks (DSB) and sister-chromatid exchange in the yeast Saccharomyces cerevisiae. The system makes use of a circular variant of chromosome II (Chr. III). Meiotic recombination between this ring chromosome and a linear homolog produces new molecules of sizes distinguishable on gels from either parental molecule. They demonstrate that these recombinant molecules are not present either in strains with two linear Chr. III molecules or in rad50 mutants, which are defective in meiotic recombination. In conjunction with the molecular endpoints. They present data on the timing of commitment to meiotic recombination scored genetically. They have used x-rays to linearize circular Chr. III, both to develop a sensitive method for measuring frequency of DSB and as a means of detecting double-size circles originating in part from sister-chromatid exchange, which they find to be frequent during meiosis

Effect of chlorophyllin on induction of exchanges in sister chromatids by gamma irradiation in mice spermatogonia in vivo

International Nuclear Information System (INIS)

Mendiola C, M.T.

1994-01-01

Mouse were exposed to different doses of gamma radiation and the effect on Sister Chromatid Exchange (SCE) frequency in spermatogonias was evaluated. The effect was analyzed before and after Bromodeoxyuridine (BrdU) incorporation to determine the interference of such agent with the cellular response induced by radiation. The capacity of chlorophyllin (sodium and Copper salt derivative from chlorophyll) to reduce SCE induction by radiation in normal and BrdU radio sensitized spermatogonia was also determined. The results indicate that there was a significant increase in SCE frequency by gamma radiation exposure in these cells, such effect was higher irradiating after BrdU incorporation than before. This fact confirms previous observations that BrdU sensitizes some cells to SCE induction. With regard to the chlorophyllin effect, it was determined that this salt acts as a radioprotector reducing gamma-rays induced SCE before or after BrdU incorporation Total protection was obtained with 200 μg of chlorophyllin per g of body weight in both protocols. Under the experimental conditions this study there was no evidence of genotoxicity induced by chlorophyllin itself. The results suggest that this agent may act as a radioprotector by scavenging free radicals produced by gamma-radiation which cause DNA lesions that are involved in SCE formation. (Author)

Sister chromatid exchanges and micronuclei analysis in lymphocytes of men exposed to simazine through drinking water.

Science.gov (United States)

Suárez, Susanna; Rubio, Arantxa; Sueiro, Rosa Ana; Garrido, Joaquín

2003-06-06

In some cities of the autonomous community of Extremadura (south-west of Spain), levels of simazine from 10 to 30 ppm were detected in tap water. To analyse the possible effect of this herbicide, two biomarkers, sister chromatid exchanges (SCE) and micronuclei (MN), were used in peripheral blood lymphocytes from males exposed to simazine through drinking water. SCE and MN analysis failed to detect any statistically significant increase in the people exposed to simazine when compared with the controls. With respect to high frequency cells (HFC), a statistically significant difference was detected between exposed and control groups.

G2-chromatid breaks and rejoining in HO8910 cells induced by γ-rays

International Nuclear Information System (INIS)

Wang Zhuanzi; Liu Bing; Duan Xin

2006-01-01

The premature chromosome condensation technique was used to estimate the dosage effect on the G2-chromosome breaks in HO8910 after exposure to γ-rays, and to investigate the time effect on the rejoining of the G2-chromosome breaks. The results show that the number of G2 chromatid-type breaks linearly increased with doses and the number of G2 iso-chromatid breaks increased with dose in a linear-square manner. With the prolongation of culture time, G2 chromatid-type breaks obviously got repaired, and almost 65% chromatid-type breaks got repaired in the early 24 hour post-irradiation, whereas only about 20% iso-chromatid breaks got repaired during the same time. Furthermore, the rejoining of the two types of chromatid breaks occurred mostly in 2 hours after irradiation and from 12 to 24 hours after irradiation, the number of chromatid breaks was found to get stabilized basically, which indicates that the repairing process is over in the early 24 hours of post-irradiation. (authors)

Genome-wide mapping of sister chromatid exchange events in single yeast cells using Strand-seq

NARCIS (Netherlands)

Claussin, Clemence; Porubsky, David; Spierings, Diana C. J.; Halsema, Nancy; Rentas, Stefan; Guryev, Victor; Lansdorp, Peter M.; Chang, Michael

2017-01-01

Homologous recombination involving sister chromatids is the most accurate, and thus most frequently used, form of recombination-mediated DNA repair. Despite its importance, sister chromatid recombination is not easily studied because it does not result in a change in DNA sequence, making

Sister chromatid exchange analysis and chromosoma aberration studies in interventional cardiology laboratory workers. One year follow up study

International Nuclear Information System (INIS)

Erol, M.K.; Oztas, S.; Bozkurt, E.; Karakelleoglu, S.

2002-01-01

Invasive cardiology laboratory workers are occupationally exposed to chronic ionizing radiation. It is known that ionizing radiation has a damaging effect on chromosomes. In present study, we investigated the frequency of sister chromatid exchange (SCE) and chromosomal aberrations in 11 invasive cardiology laboratory workers and 11 healthy controls. After a vacation period, we took blood samples for chromosome analysis in months 0, 4, 8 and 12 (last two month period was the nonradiation time). The SCE frequencies did not change significantly after exposure to ionizing radiation in any worker. Our study has revealed that non-specific structural chromosome aberrations such as gaps, isogaps, acentric chromosomes, chromatids and chromosome breakage could be in the 4th and 8th months after ionizing radiation exposure in the metaphase plaques. All abnormal chromosomal effects had disappeared by the end of the two month non-exposure period in each worker. In conclusion, the results suggest that SCE frequencies are not significantly affected in invasive cardiology laboratory workers who are exposed occupationally to ionizing radiation, although some degree of reversible chromosomal aberrations did appear. (author)

Cell elongation is an adaptive response for clearing long chromatid arms from the cleavage plane

Science.gov (United States)

Kotadia, Shaila; Montembault, Emilie; Sullivan, William

2012-01-01

Chromosome segregation must be coordinated with cell cleavage to ensure correct transmission of the genome to daughter cells. Here we identify a novel mechanism by which Drosophila melanogaster neuronal stem cells coordinate sister chromatid segregation with cleavage furrow ingression. Cells adapted to a dramatic increase in chromatid arm length by transiently elongating during anaphase/telophase. The degree of cell elongation correlated with the length of the trailing chromatid arms and was concomitant with a slight increase in spindle length and an enlargement of the zone of cortical myosin distribution. Rho guanine-nucleotide exchange factor (Pebble)–depleted cells failed to elongate during segregation of long chromatids. As a result, Pebble-depleted adult flies exhibited morphological defects likely caused by cell death during development. These studies reveal a novel pathway linking trailing chromatid arms and cortical myosin that ensures the clearance of chromatids from the cleavage plane at the appropriate time during cytokinesis, thus preserving genome integrity. PMID:23185030

X-ray sensitization of chromatids with unifilarly and bifilarly substituted DNA

International Nuclear Information System (INIS)

Wolff, S.

1981-01-01

When cells are grown for two rounds of DNA replication in the presence of the thymidine analogue 5-bromodeoxyuridine, chromosomes containing one chromatid with unifilarly substituted DNA and one with bifilarly substituted DNA are found. These can be distinguished by harlequin staining techniques that stain one chromatid dark and one light. When the degree of substitution is 60% or greater, 3 times as many X-ray-induced chromatid breaks are produced as in unsubstituted chromatids. This represents maximal sensitization. The unifilarly substituted (dark) chromatid is as sensitive as its bifilarly substituted (light) sister chromatid. If cells are grown in low concentrations of 5-bromodeoxyuridine (BrdUrd), then the amount of substitution is less and the bifilarly substituted chromatic is more sensitive than the unifilarly substituted one. When large numbers of cells are grown in very low concentrations of BrdUrd, the analogue is almost completely depleted during the first round of replication leading to harlequin chromosomes containing one unsubstituted (dark) and one unifilarly substituted (light) chromatid. Under these conditions a maximal sensitization between light-staining and dark-staining chromatids can occur. This can be confused with the differential sensitivity between unifilarly and bifilarly substituted chromatids. The apparent discrepant results obtained by different investigators are most likely caused by the use of very low levels of BrdUrd in some of the experiments. (orig.)

Frequencies of chromosomal aberrations and sister chromatid exchanges in the benthic worm Neanthes arenaceodentata exposed to ionizing radiation

International Nuclear Information System (INIS)

Harrison, F.L.; Rice, D.W. Jr.; Moore, D.H.

1984-07-01

Traditional bioassays are unsuitable for assessing sublethal effects from ocean disposal of low-level radioactive waste because mortality and phenotypic responses are not anticipated. We compared the usefulness of chromosomal aberration and sister chromatid exchange (SCE) induction as measures of low-level radiation effects in a sediment-dwelling marine worm, Neanthes arenaceodentata. The SCEs, in contrast to chromosomal aberrations, do not alter the overall chromosome morphology and in mammalian cells appear to be a more sensitive indicator of DNA alterations caused by environmental mutagens. Newly hatched larvae were exposed to two radiation-exposure regimes of either x rays at a high dose rate of 0.7 Gy (70 rad)/min for as long as 5.5 min or to 60 Co gamma rays at a low dose rate of from 4.8 x 10 -5 to 1.2 x 10 -1 Gy (0.0048 to 12 rad)/h for 24 h. After irradiation, the larvae were exposed to 3 x 10 -5 M bromodeoxyuridine (BrdUrd) for 28 h (x-ray-irradiated larvae) or for 54 h ( 60 Co-irradiated larvae). Larval cells were examined for the proportion of cells in first, second, and third or greater division. Frequencies of chromosomal aberrations and SCEs were determined in first and second division cells, respectively. Results from x-ray irradiation indicated that dose-related increases occur in chromosome and chromatid deletions, but a dose of equal or greater 2 Gy (equal to or greater than 200 rad) was required to observe a significant increase. Worm larvae receiving 60 Co irradiation showed elevated SCE frequencies with a significant increase of 0.6 Gy (60 rad). We suggest that both SCEs and chromosomal aberrations may be useful for measuring effects on genetic material induced by radiation. 56 references, 7 figures, 9 tables

Can consumption of raw vegetables decrease the count of sister chromatid exchange? Results from a cross-sectional study in Krakow, Poland

OpenAIRE

Galas, Aleksander; Cebulska-Wasilewska, Antonina

2014-01-01

Background Sister chromatid exchange (SCE) is a widely used sensitive cytogenetic biomarker of exposure to genotoxic and cancerogenic agents. Results of human monitoring studies and cytogenetic damage have revealed that biological effects of genotoxic exposures are influenced by confounding factors related to life-style. Vegetable and fruit consumption may play a role, but available results are not consistent. The purpose of the study was to investigate the effect of consumption of raw and co...

Amount of sister chromatid exchanges and survival of Chinese hamster V79-4 cells after irradiation with 0,7 MeV neutrons

International Nuclear Information System (INIS)

Lapidus, I.L.; Nasonova, E.A.

1987-01-01

The dependence of the survival and induction of sister chromatid exchanges (SCEs) in Chinese hamster V79-4 cells on the dose of γ-rays and neutrons with average energy 0.7 MeV has been analysed. The value of RBE for neutrons was 5.5. It has been shown that the number of SCE increased with the dose of γ-irradiation and no induction could be detected after neutron irradiation

Cell-stage-specific enhancement by caffeine of the frequency of chromatid aberrations induced by X-rays in neutral ganglia of Drosophila melanogaster

International Nuclear Information System (INIS)

De Marco, A.; Polani, S.

1981-01-01

Caffeine (10 -2 M) induced a high level of chromatid aberrations in neural ganglia of third-instar larvae of Drosophila melanogaster only when it was added to cells in late G 2 and mitotic prophase. No aberrations were observed after treatment in late S-middle G 2 or C-mitosis. We observed that, in these stages, caffeine strongly increased X-ray-induced damage (500 R). This potentiation was quantitatively similar. But it involved all types of aberration after treatment in C-mitosis, and essentially isochromatid deletions and chromatid exhanges after treatment in S-G 2 . Some hypotheses are put forth to explain the possible mechanism of action of caffeine in the potentiation of X-ray-induced damage. (orig.)

Health assessment of gasoline and fuel oxygenate vapors: micronucleus and sister chromatid exchange evaluations.

Science.gov (United States)

Schreiner, Ceinwen A; Hoffman, Gary M; Gudi, Ramadevi; Clark, Charles R

2014-11-01

Micronucleus and sister chromatid exchange (SCE) tests were performed for vapor condensate of baseline gasoline (BGVC), or gasoline with oxygenates, methyl tert-butyl ether (G/MTBE), ethyl tert butyl ether (G/ETBE), t-amyl methyl ether (G/TAME), diisopropyl ether (G/DIPE), t-butyl alcohol (TBA), or ethanol (G/EtOH). Sprague Dawley rats (the same 5/sex/group for both endpoints) were exposed to 0, 2000, 10,000, or 20,000mg/m(3) of each condensate, 6h/day, 5days/week over 4weeks. Positive controls (5/sex/test) were given cyclophosphamide IP, 24h prior to sacrifice at 5mg/kg (SCE test) and 40mg/kg (micronucleus test). Blood was collected from the abdominal aorta for the SCE test and femurs removed for the micronucleus test. Blood cell cultures were treated with 5μg/ml bromodeoxyuridine (BrdU) for SCE evaluation. No significant increases in micronucleated immature erythrocytes were observed for any test material. Statistically significant increases in SCE were observed in rats given BGVC alone or in female rats given G/MTBE. G/TAME induced increased SCE in both sexes at the highest dose only. Although DNA perturbation was observed for several samples, DNA damage was not expressed as increased micronuclei in bone marrow cells. Inclusion of oxygenates in gasoline did not increase the effects of gasoline alone or produce a cytogenetic hazard. Copyright © 2014 Elsevier Inc. All rights reserved.

Trex2 enables spontaneous sister chromatid exchanges without facilitating DNA double-strand break repair.

Science.gov (United States)

Dumitrache, Lavinia C; Hu, Lingchuan; Son, Mi Young; Li, Han; Wesevich, Austin; Scully, Ralph; Stark, Jeremy; Hasty, Paul

2011-08-01

Trex2 is a 3' → 5' exonuclease that removes 3'-mismatched sequences in a biochemical assay; however, its biological function remains unclear. To address biology we previously generated trex2(null) mouse embryonic stem (ES) cells and expressed in these cells wild-type human TREX2 cDNA (Trex2(hTX2)) or cDNA with a single-amino-acid change in the catalytic domain (Trex2(H188A)) or in the DNA-binding domain (Trex2(R167A)). We found the trex2(null) and Trex2(H188A) cells exhibited spontaneous broken chromosomes and trex2(null) cells exhibited spontaneous chromosomal rearrangements. We also found ectopically expressed human TREX2 was active at the 3' ends of I-SceI-induced chromosomal double-strand breaks (DSBs). Therefore, we hypothesized Trex2 participates in DNA DSB repair by modifying 3' ends. This may be especially important for ends with damaged nucleotides. Here we present data that are unexpected and prompt a new model. We found Trex2-altered cells (null, H188A, and R167A) were not hypersensitive to camptothecin, a type-1 topoisomerase inhibitor that induces DSBs at replication forks. In addition, Trex2-altered cells were not hypersensitive to γ-radiation, an agent that causes DSBs throughout the cell cycle. This observation held true even in cells compromised for one of the two major DSB repair pathways: homology-directed repair (HDR) or nonhomologous end joining (NHEJ). Trex2 deletion also enhanced repair of an I-SceI-induced DSB by both HDR and NHEJ without affecting pathway choice. Interestingly, however, trex2(null) cells exhibited reduced spontaneous sister chromatid exchanges (SCEs) but this was not due to a defect in HDR-mediated crossing over. Therefore, reduced spontaneous SCE could be a manifestation of the same defect that caused spontaneous broken chromosomes and spontaneous chromosomal rearrangements. These unexpected data suggest Trex2 does not enable DSB repair and prompt a new model that posits Trex2 suppresses the formation of broken

Persistence of sister chromatid exchanges and in vitro morphological transformation of Syrian hamster fetal cells by chemical and physical carcinogens

International Nuclear Information System (INIS)

Popescu, N.C.; Amsbaugh, S.C.; DiPaolo, J.A.

1985-01-01

The induction of neoplastic cell transformation is closely associated with DNA alterations which occur shortly after carcinogen exposure. Sister chromatid exchange (SCE) formation is a sensitive indicator of carcinogen-DNA interaction and correlates with the induction of morphological cell transformation. The persistence of lesions generating SCE produced by chemical and physical carcinogens and its relevance to the induction of morphologic transformation was evaluated in coordinated experiments with cultured Syrian hamster fetal cells (HFC). Exponentially growing HFC were exposed for 1 h to benzo[a]pyrene (BP), methyl-methanesulfonate (MMS), cis-platinum (II) diaminedichloride (cis Pt II), N-methyl-N'-nitrosourea (MNU), mitomycin C (MMC), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), N-acetoxy-2-fluorenyl-acetamide (AcAAF) or u.v. light irradiated. SCE analysis demonstrates that for a period of 48 h after carcinogen exposure, during which time the cells undergo at least four replicative cycles, DNA damage generating SCE induced by all chemical carcinogens either persisted or was partially removed, whereas u.v.-induced lesions were completely removed. An elevated SCE frequency persisted after two additional cell cycles after treatment with BP, AcAAF or MMC without increased cell lethality as compared to other carcinogens whose lesions were completely eliminated during the same period

Induction and disappearance of G2 chromatid breaks in lymphocytes after low doses of low LET γ - rays and high LET fast neutrons

International Nuclear Information System (INIS)

Vral, Anne; Thierens, Hubert; Baeyens, Ans; De Ridder, Leo

2001-01-01

In view of the potential importance of the G2 assay for detecting chromosomal radiosensitivity and possible predisposition to cancer the need to elucidate the mechanism underlying the formation of chromatid breaks, observed with the G2 assay after low dose irradiation, has been recognised. In this study we irradiated blood samples of 4 healthy donors with low LET γ-rays and high LET neutrons, which initially produce the same number of dsb but of a different quality. By means of the G2 assay, we determined the number of chromatid breaks induced by γ-rays and neutrons and compared the kinetics of chromatid break rejoining for radiations of different quality. In a first set of experiments a dose-response curve for the formation of chromatid breaks was carried out for γ-rays and neutrons with doses ranging between 0.1 and 0.5 Gy. In a second set of experiments the kinetics of chromatid break formation and disappearance was investigated after a dose of 0.5 Gy using post-irradiation times ranging between 0.5 h and 3.5 h. For the highest dose of 0.5 Gy the number of isochromatid breaks were also scored. No significant differences in the number of chromatid breaks were observed between low LET γ-rays and high LET neutrons for the 4 donors at any of the doses given. The dose response curves for the formation of chromatid breaks are linear for both radiation qualities and RBE values equal to one were obtained. Scoring of isochromatid breaks at the highest dose of 0.5 Gy revealed that high LET neutrons are however more effective at inducing isochromatid breaks (RBE of 6.2). The rejoining experiments further showed that the kinetics of disappearance of chromatid breaks following irradiation with low LET γ-rays or high-LET neutrons are not significantly different. T 1/2 0.92 h for γ-rays and t 1/2 = 0.84 h for neutrons were obtained. In conclusion, our results show that at low doses of radiation the induction as well as the disappearance of G2 chromatid breaks is LET

Enhanced stimulation of chromosomal translocations and sister chromatid exchanges by either HO-induced double-strand breaks or ionizing radiation in Saccharomyces cerevisiae yku70 mutants

International Nuclear Information System (INIS)

Fasullo, Michael; St Amour, Courtney; Zeng Li

2005-01-01

DNA double-strand break (DSB) repair occurs by homologous recombination (HR) or non-homologous endjoining (NHEJ). In Saccharomyces cerevisiae, expression of both MAT a and MATα inhibits NHEJ and facilitates DSB-initiated HR. We previously observed that DSB-initiated recombination between two his3 fragments, his3-Δ5' and his3-Δ3'::HOcs is enhanced in haploids and diploids expressing both MAT a and MATα genes, regardless of the position or orientation of the his3 fragments. Herein, we measured frequencies of DNA damage-associated translocations and sister chromatid exchanges (SCEs) in yku70 haploid mutants, defective in NHEJ. Translocation and SCE frequencies were measured in strains containing the same his3 fragments after DSBs were made directly at trp1::his3-Δ3'::HOcs. Wild type and yku70 cells were also exposed to ionizing radiation and radiomimetic agents methyl methanesulfonate (MMS), phleomycin, and 4-nitroquinolone-1-oxide (4-NQO). Frequencies of X-ray-associated and DSB-initiated translocations were five-fold higher in yku70 mutants compared to wild type; however, frequencies of phleomycin-associated translocations were lower in the yku70 haploid mutant. Frequencies of DSB-initiated SCEs were 1.8-fold higher in the yku70 mutant, compared to wild type. Thus, DSB-initiated HR between repeated sequences on non-homologous chromosomes and sister chromatids occurs at higher frequencies in yku70 haploid mutants; however, higher frequencies of DNA damage-associated HR in yku70 mutants depend on the DNA damaging agent

Excision and crosslink repair of DNA and sister chromatid exchanges in cultured human fibroblasts with different repair capacities

Energy Technology Data Exchange (ETDEWEB)

Fujiwara, Y; Kano, Y; Paul, P; Goto, K; Yamamoto, K [Kobe Univ. (Japan). School of Medicine

1981-01-01

Xeroderma pigmentosum (XP) groups A to G lacked the initial stage of ultraviolet (UV) excision repair in the order of A = G > C > D > E asymptotically equals F, while the XP variant was weakly defective in the later repair steps. Killing sensitivities were in the orders of A >= G > D > C > E asymptotically equals F asymptotically equals variant > normal to UV, A = G > D > F > C = E > variant > normal to 4-nitroquinoline-1-oxide (4NQO), and A > C > D = E = F = variant > G = normal to decarbamoyl mitomycin-C(DCMC). The induced sister chromatid exchange (SCE) frequency was unrelated to the extent of repair deficiency. The SCE induction rate was consistently 3 - 6 fold higher by these UV-like mutagens in XP group A cells than in normal cells. However, repair-proficient Cockayne's syndrome (CS) cells showed a higher SCE induction by UV, which was normalized by NAD/sup +/, suggesting that chromatin lesions as well as DNA damage contribute to SCE. Two-step crosslink repair involves a first rapid half-excision and a second slow nucleotide-excision repair. Fanconi's anemia (FA) cells had an impaired first half-excision and were supersensitive to MC, but not to UV and DCMC. The SCE frequency induced by MC (1 hr) was higher in FA cells than in normal cells despite their normal response to DCMC, and vice versa in XP cells. FA cells lacked the first rapid decline and showed higher remaining SCEs. Thus, part of the crosslink seems to lead to SCE formation. Caffeine synergistically elevated UV-induced SCEs, but not UV induced mutations in V79 cells, implying that SCE may not necessarily involve mutation.

Excision and crosslink repair of DNA and sister chromatid exchanges in cultured human fibroblasts with different repair capacities

International Nuclear Information System (INIS)

Fujiwara, Yoshisada; Kano, Yoshio; Paul, P.; Goto, Kaoru; Yamamoto, Kazuo

1981-01-01

Xeroderma pigmentosum (XP) groups A to G lacked the initial stage of ultraviolet (UV) excision repair in the order of A = G > C > D > E asymptotically equals F, while the XP variant was weakly defective in the later repair steps. Killing sensitivities were in the orders of A >= G > D > C > E asymptotically equals F asymptotically equals variant > normal to UV, A = G > D > F > C = E > variant > normal to 4-nitroquinoline-1-oxide (4NQO), and A > C > D = E = F = variant > G = normal to decarbamoyl mitomycin-C(DCMC). The induced sister chromatid exchange (SCE) frequency was unrelated to the extent of repair deficiency. The SCE induction rate was consistently 3 - 6 fold higher by these UV-like mutagens in XP group A cells than in normal cells. However, repair-proficient Cockayne's syndrome (CS) cells showed a higher SCE induction by UV, which was normalized by NAD + , suggesting that chromatin lesions as well as DNA damage contribute to SCE. Two-step crosslink repair involves a first rapid half-excision and a second slow nucleotide-excision repair. Fanconi's anemia (FA) cells had an impaired first half-excision and were supersensitive to MC, but not to UV and DCMC. The SCE frequency induced by MC (1 hr) was higher in FA cells than in normal cells despite their normal response to DCMC, and vice versa in XP cells. FA cells lacked the first rapid decline and showed higher remaining SCEs. Thus, part of the crosslink seems to lead to SCE formation. Caffeine synergistically elevated UV-induced SCEs, but not UV induced mutations in V79 cells, implying that SCE may not necessarily involve mutation. (J.P.N.)

Excision and crosslink repair of DNA and sister chromatid exchanges in cultured human fibroblasts with different repair capacities

Energy Technology Data Exchange (ETDEWEB)

Fujiwara, Y.; Kano, Y.; Paul, P.; Goto, K.; Yamamoto, K. (Kobe Univ. (Japan). School of Medicine)

1981-01-01

Xeroderma pigmentosum (XP) groups A to G lacked the initial stage of ultraviolet (UV) excision repair in the order of A = G > C > D > E asymptotically equals F, while the XP variant was weakly defective in the later repair steps. Killing sensitivities were in the orders of A >= G > D > C > E asymptotically equals F asymptotically equals variant > normal to UV, A = G > D > F > C = E > variant > normal to 4-nitroquinoline-1-oxide (4NQO), and A > C > D = E = F = variant > G = normal to decarbamoyl mitomycin-C(DCMC). The induced sister chromatid exchange (SCE) frequency was unrelated to the extent of repair deficiency. The SCE induction rate was consistently 3 - 6 fold higher by these UV-like mutagens in XP group A cells than in normal cells. However, repair-proficient Cockayne's syndrome (CS) cells showed a higher SCE induction by UV, which was normalized by NAD/sup +/, suggesting that chromatin lesions as well as DNA damage contribute to SCE. Two-step crosslink repair involves a first rapid half-excision and a second slow nucleotide-excision repair. Fanconi's anemia (FA) cells had an impaired first half-excision and were supersensitive to MC, but not to UV and DCMC. The SCE frequency induced by MC (1 hr) was higher in FA cells than in normal cells despite their normal response to DCMC, and vice versa in XP cells. FA cells lacked the first rapid decline and showed higher remaining SCEs. Thus, part of the crosslink seems to lead to SCE formation. Caffeine synergistically elevated UV-induced SCEs, but not UV induced mutations in V79 cells, implying that SCE may not necessarily involve mutation.

Very low sister-chromatid exchange rate in Seventh-Day Adventists.

Science.gov (United States)

Wulf, H C; Iversen, A S; Husum, B; Niebuhr, E

1986-08-01

42 Seventh-Day Adventists (SDAs) and 42 controls matched for sex, age and occupation had their sister-chromatid exchange (SCE) examined in peripheral blood lymphocytes. This was done to examine if the SCE frequency was lower in this group of people, who are known to have a decreased cancer risk compared to the general population. The average SCE/cell in 30 cells from each person was 5.54 +/- 0.07 (mean +/- standard error of the mean) for the SDAs and 8.00 +/- 0.15 for the controls, the difference being statistically significant (p less than 0.00001). No difference in SCE frequency was found between SDAs eating only an ovo-lacto-vegetarian diet and those eating some fish or meat. The mitotic index (MI) was significantly higher and the replication index (RI) was significantly lower in SDAs than in controls. No correlation was found between gamma (a statistical transformation of SCEs/cell) and MI or RI within the groups of SDAs or controls. In the pooled data there was a negative correlation of gamma and MI and a positive correlation of gamma and RI. Of the interpersonal variation in gamma 8% and 14% could be explained by MI and RI. The finding of a lower SCE frequency in a group of SDAs who have a low risk of cancer might indirectly indicate a relation between SCE and cancer and encourages further studies of SCE and diet.

Evaluation of the persistence in the induction of Sister Chromatid Exchanges (SCE) by alkylating agents; Evaluacion de la persistencia en la induccion de Intercambio en las Cromatidas Hermanas (ICH) por agentes alquilantes

Energy Technology Data Exchange (ETDEWEB)

Rodriguez R, R.; Huerta V, C.; MOrales R, P.R. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

2006-07-01

The persistence in the induction of sister chromatid exchanges (SCE) by the alkylating agents methyl and ethyl-methanesulfonates (MMS and EMS) was evaluated. For it, to groups of mice its were administered a dose of these agents and later its were analyzed the induced SCE's in two periods: early and late. Both agents caused high increments of SCE in the early period and small in the late one; however, the caused lately by EMS was significantly bigger. This late induction of SCE by EMS possibly is associated with an epigenetic change or with the presence of etiladucts in the phosphodiester bonds of the DNA. (Author)

Evaluation of the persistence in the induction of Sister Chromatid Exchanges (SCE) by alkylating agents; Evaluacion de la persistencia en la induccion de Intercambio en las Cromatidas Hermanas (ICH) por agentes alquilantes

Energy Technology Data Exchange (ETDEWEB)

Rodriguez R, R; Huerta V, C; MOrales R, P R [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

2006-07-01

The persistence in the induction of sister chromatid exchanges (SCE) by the alkylating agents methyl and ethyl-methanesulfonates (MMS and EMS) was evaluated. For it, to groups of mice its were administered a dose of these agents and later its were analyzed the induced SCE's in two periods: early and late. Both agents caused high increments of SCE in the early period and small in the late one; however, the caused lately by EMS was significantly bigger. This late induction of SCE by EMS possibly is associated with an epigenetic change or with the presence of etiladucts in the phosphodiester bonds of the DNA. (Author)

Effects of radiation on frequency of chromosomal aberrations and sister chromatid exchange in the benthic worm Neanthes arenaceodentata

International Nuclear Information System (INIS)

Harrison, F.L.; Rice, D.W. Jr.; Moore, D.H.; Varela, M.

1983-04-01

Traditional bioassays are unsuitable for assessing sublethal effects of low levels of radioactivity because mortality and phenotypic responses are not anticipated. We compared the usefulness of chromosomal aberration (CA) and sister chromatid exchange (SCE) induction as measures of low-level radiation effects in a sediment-dwelling marine worm, Neanthes arenaceodentata. Newly hatched larvae were exposed to two radiation exposure regimes. Groups of 100 larvae were exposed to either x rays delivered at high dose rates (0.7 Gy min -1 ) or to 60 Co gamma rays delivered at low dose rates (4.8 X 10 -5 to 1.2 X 10 -1 Gy h -1 ). After irradiation, the larvae were exposed to 3 X 10 -5 M bromodeoxyuridine (BrdUrd) for 28 h (x-ray-irradiated larvae) or for 54 h ( 60 Co-irradiated larvae). Slides of larval cells were prepared for observation of CAs and SCEs. Frequencies of CAs were determined in first division cells; frequencies of SCEs were determined in second division cells. Results from x-ray irradiation indicated that dose-related increases occur in chromosome and chromatid deletions, but an x-ray dose greater than or equal to 2 Gy was required to observe a significant increase. Worm larvae receiving 60 Co irradiation showed elevated SCE frequencies; a significant increase in SCE frequency was observed at 0.6 Gy. 49 references, 2 figures

Kinetics of chromatid aberrations in G2 ataxia-telangiectasia cells exposed to X-rays and ara A

International Nuclear Information System (INIS)

Mozdarani, Hossein; Bryant, P.E.

1989-01-01

The cytogenetic effects of X-rays alone or in combination with 9-β-D-arabinofuranosyladenine (ara A) were studied in an immortalized fibroblastic line of ataxia-telangiectasia (A-T) cells. It is postulated that the kinetics of disappearance (rejoining) of chromatid deletions with postirradiation incubation time reflects the underlying repair of dsb, and is inhibited by ara A. The rejoining kinetics for deletions in A-T was similar to that found in a previous study of normal human fibroblasts (Mozdarani and Bryant 1987). The number of deletions in X-irradiated A-T cells at 1.5 h before fixation was found to be higher by a factor of approximately 2 than that found previously in normals, indicating that in A-T a higher rate of conversion of dsb into chromatid deletions occurs. The frequency of exchanges induced in G2 A-T cells was similarly enhanced but, unlike the situation in normal cells, ara A was found to cause only a slight increase in this frequency. (author)

As to the clastogenic-, sister-chromatid exchange inducing-and cytotoxic activity of inosine triphosphate in cultures of human peripheral lymphocytes.

Science.gov (United States)

Vormittag, W; Brannath, W

2001-05-09

The influence of commercial inosine triphosphate (ITP) on the chromosome aberration rate, the mitotic rate, sister-chromatid exchange (SCE) frequency, and the proportion of first (X1), second (X2) and third (X3) division metaphases was investigated in 72h cultures of human peripheral lymphocytes. The blood donors had mild inactive arthrosis and a normal health check-up. All cultures of each volunteer were set-up simultaneously. In contrast to a previous report [Arch. Biochem. Biophys. 278 (1990) 238-244], it was demonstrated in two preliminary studies (number of subjects, n=5 each) that ITP at a final concentration of 100 microM does not induce chromosomal aberrations and, furthermore, that not ITP concentrations higher than 100 microM but ITP doses higher than 3.8mM prohibit culture growth. Based on these results, cultures with a final ITP concentration of 3.6mM (max.) and 1.8mM (max./2) were compared with control cultures (number of subjects n=10; three males and seven females, mean age x=57.6 years). Whereas no increase in the chromosomal breakage rate was observed in cultures with an ITP concentration of 1.8mM and only a marginally significant one (P=0.048) for 3.6mM ITP cultures, a highly significant induction of SCEs, not only at an ITP concentration of 3.6mM (Prate from 0 to 1.8mM as well as from 1.8 to 3.6mM in the aberration studies (all P values are equal to smallest possible one for a sample size of 10, namely, 0.002), and in the SCE studies there is a significant decrease in the X3 frequency when ITP is increased (0-1.8mM: P=0.0061 and 1.8-3.6mM: Pchanges significantly only at the second dose step (0-1.8mM ITP: P=0.22 and 1.8-3.6mM ITP: P<0.0001). The results are discussed.

Role of oxygen free radicals in the induction of sister chromatid exchanges by cigarette smoke

International Nuclear Information System (INIS)

Lee, C.K.; Brown, B.G.; Rice, W.Y. Jr.; Doolittle, D.J.

1989-01-01

Cigarette smoke has been reported to contain free radicals and free radical generators in both the gas and particulate phases. Studies in our laboratory have shown that both cigarette smoke condensate (CSC) and smoke bubbled through phosphate buffered saline solution (smoke-PBS) increased sister chromatid exchanges (SCE) in Chinese hamster ovary cells in a dose-dependent manner. Since oxygen free radicals have been shown to cause SCEs and other chromosomal damage, we investigated the role of these radicals in the induction of SCEs by CSC and smoke-PBS. Addition of the antioxidant enzymes catalase and superoxide dismutase or the oxygen-radical scavenger ascorbic acid failed to reduce the SCE frequency in the presence of either CSC or smoke-PBS. Additional studies indicated that the quantity of hydrogen peroxide produced in CSC or smoke-PBS is too small to account for the observed SCE induction. It appears, therefore, that SCE induction by CSC or smoke-PBS does not involve the participation of oxygen free radicals

Comparison of 6-thioguanine-resistant mutation and sister chromatid exchanges in Chinese hamster V79 cells with forty chemical and physical agents

International Nuclear Information System (INIS)

Nishi, Y.; Hasegawa, M.M.; Taketomi, M.; Ohkawa, Y.; Inui, N.

1984-01-01

The induction of sister chromatid exchanges (SCE) and mutation at the hypoxanthine-guanine phosphoribosyl transferase locus and toxicities of 40 different chemical and physical agents were examined on Chinese hamster V79 cells. These agents included mono-, di-, tri-, and polyfunctional alkylating agents, intercalators, gamma-rays, and UV light irradiation. Mutation was measured as resistance to 6-thioguanine and toxicity as loss of cell-plating efficiency. SCE were examined 29 hr after treatment. With the agents examined, a highly positive correlation existed between SCE-inducing and mutagenic potencies, when expressed as increase in the number per a unit dose over the control values. But the great difference of the ratios of mutagenic potencies versus SCE-inducing potencies among agents was observed, the maximal difference in the ratios being about 200-fold. The agents that showed the higher values of the ratio (agents producing more mutations than SCE) were bleomycin, cobalt-60 gamma-rays, all ethylating agents (N-ethyl-N-nitrosourea, N-ethyl-N'-nitro-N-nitrosoguanidine, ethyl methanesulfonate, and diethylsulfate), N-propyl-N-nitrosourea, N-butyl-N-nitrosourea, isopropyl methanesulfonate, intercalating acridine compounds (2-methoxy-6-chloro-9-[3-(ethyl-2-chloroethyl)aminopropylamino]-acridine X 2HCl and 2-methoxy-6-chloro-9-[3-(chloroethyl)-aminopropylamino]acridine 2HCl) and UV light at 254 nm

Repairability during G 1 phase of inducting lesions of sister chromatid exchange produced by mitomycin C in salivary gland cells of mice In Vivo

International Nuclear Information System (INIS)

Cruz Vallejo, V.L.

1991-01-01

The repairability of the injuries that lead to the formation of sister chromatid exchange (SCE) produced by mitomycin C (MMC) with a dose of 2.1 mg/g in vivo, during the G 1 phase in the first cycle of cellular division (before the incorporation of BrdU [5-bromo-2 deoxyurine] to the DNA), as well as during the G 1 phase of the second cycle of cellular division (after the incorporation of BrdU) were analyzed. A 35.1% decrease in the frequency of SCE produced by Mitomycin C was observed, in the early G 1 phase of the first division, with respect to the frequency of SCE induced in the later G 1 phase. When Mitomycin C is given to cells whose DNA is substituted with BrdU in only one of the chain's filaments such decrease is not observed. The results suggest that the injuries caused by MMC, which give place to the SCE, in cells of the salivary glands of the mouse in vivo, are partially repaired only when induced in DNA which has not been substituted with BrdU. (Author)

Variation in sister chromatid exchange frequencies between human and pig whole blood, plasma leukocyte, and mononuclear leukocyte cultures

International Nuclear Information System (INIS)

Larramendy, M.L.; Reigosa, M.A.

1986-01-01

Sister chromatid exchange (SCE) induction by ultraviolet (UV) light was studied in both human and pig whole blood cultures (WBC) and plasma leukocyte cultures (PLC). No variation in SCE frequency was observed between pig WBC and PLC in control as well as in treated cells. Conversely, SCE frequencies of human PLC were consistently higher than those of WBC in control and UV-exposed cells. Thus, red blood cells (RBCs) do not influence the sensitivity of lymphocytes to UV LIGHT exposure, and there must be some different culture condition(s) in the inducation of SCEs between human WBC and PLC but not in swine lymphocyte cultures. Since the BrdUrd/lymphocyte ratio of WBC was halved in PLC, the effect of BrdUrd concentration in inducing the SCE baseline frequency of PLC may be ruled out. Neither the cell separation technique nor polymorphonuclear leukocytes had a significant role in the elevated SCE frequency of human PLC or MLC. Experiments where human RBCs were titrated into human PLC showed that the induction of an elevated SCE frequency of PLC was suppressed in a dose-dependent manner by the presence of RBCs in the culture medium. Since the incorporation of pig or human RBCs into human PLC as well as into MLC reduced the SCE frequency to that of WBC, a common component and/or function existing in these cells is suggested. Analysis of different RBC components showed that RBCs, specifically RBC ghosts, release a diffusible but not dialyzable corrective factor into culture medium that is able to reduce the SCE frequencies of PLC

Mechanics of Sister Chromatids studied with a Polymer Model

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Yang eZhang

2013-10-01

Full Text Available Sister chromatid cohesion denotes the phenomenon that sister chromatids are initially attached to each other in mitosis to guarantee the error-free distribution into the daughter cells. Cohesion is mediated by binding proteins and only resolved after mitotic chromosome condensation is completed. However, the amount of attachement points required to maintain sister chromatid cohesion while still allowing proper chromosome condensation is not known yet. Additionally the impact of cohesion on the mechanical properties of chromosomes also poses an interesting problem. In this work we study the conformational and mechanical properties of sister chromatids by means of computer simulations. We model both protein-mediated cohesion between sister chromatids and chromosome condensation with a dynamic binding mechanisms. We show in a phase diagram that only specific link concentrations lead to connected and fully condensed chromatids that do not intermingle with each other nor separate due to entropic forces. Furthermore we show that dynamic bonding between chromatids decrease the Young's modulus compared to non-bonded chromatids.

Very low dose and dose-rate X-ray induced adaptive response in human lymphocytes at various cell cycle stages against bleomycin induced chromatid aberrations

International Nuclear Information System (INIS)

Hossein Mozdarani; Moghadam, R.N.

2007-01-01

Complete text of publication follows. Objective: To study the adaptive response induced by very low doses of X-rays at very low dose rate in human lymphocytes at different cell cycle stages followed by a challenge dose of bleomycin sulphate at G2 phase. Materials and Methods: Human peripheral blood lymphocytes before (G0) and after PHA stimulation (G1 and G2) were exposed to 1 and 5 cGy X-rays generated by a fluoroscopy unit with a dose rate of 5.56 mGy/min and challenged with 5 μg/ml bleomycin sulphate (BLM) 48 hours after culture initiation. Mitotic cells were arrested at metaphase by addition of colcemid in cultures 1.5 h before harvesting. Harvesting and slide preparation was performed using standard method. 100 well spread metaphases were analyzed for the presence of chromatid type aberrations for each sample. Results: Results obtained indicate that there is a linear relationship between the dose of BLM and chromatid aberrations below 5 μg/ml (R=0.93, p<0.0001). The results also show that pretreatment of lymphocytes with low dose X-rays at G0, G1 and G2 phases of the cell cycle significantly reduced the sensitivity of lymphocytes to the clastogenic effects of BLM in G2. Much lower frequencies of chromatid aberrations were observed in X-ray irradiated lymphocytes following BLM treatment (p<0.05). The magnitudes of adaptation induced at different phases of the cell cycle were not significantly different. Furthermore, there was no a significant difference in the magnitude of adaptive response induced by either 1 or 5 cGy X-rays. Conclusion: These observations might indicate that resistance of pre-exposure of lymphocytes to very low doses of X-rays protects them from clastogenic effects of BLM. This effect might be due to initial DNA damage induced in these cells leading to provocation of an active DNA repair mechanism independent of cell cycle stage.

Sister chromatid exchanges and structural chromosome aberrations in lymphocytes in operating room personnel

Energy Technology Data Exchange (ETDEWEB)

Husum, B; Niebuhr, E; Wulf, H C; Norgaard, I

1983-06-01

Information on possible chromosomal damage in humans after long-term exposure to trace concentrations of waste anaesthetic gases is scarce. We examined peripheral lymphocytes in operating room personnel for both chromosome aberrations and sister chromatid exchanges (SCE). Following a standardized procedure of cultivation and staining, 30 cells from each person were scored for SCE and 100 cells from each person were examined for chromosome aberrations. A total of 45 persons were examined, representing anaesthetists (n . 15), operating room nurses assisting the surgeon (n . 10), nurses circulating in the operating room (n . 8) and healthy, unexposed controls (n . 12). The median duration of working in the operating room was 102 months, respectively. Time-weighted concentration levels of 2.5-4.3 p.p.m. of halothane and 25-400 p.p.m. of nitrous oxide were measured in the breathing zones of the anaesthetists during mask anaesthesia. Examination of SCE and chromosome aberrations yielded corresponding qualitative results. With both tests, no statistically significant difference was observed between the four groups of persons. It was concluded that by examination of both SCE and chromosome aberrations in peripheral lymphocytes in operating room personnel, no indication was found of a mutagenic effect of long-term exposure to trace concentrations of waste anaesthetic gases.

Mechanisms of sister chromatid recombination

International Nuclear Information System (INIS)

Nakai, Sayaka; Machida, Isamu; Tsuji, Satsuki

1985-01-01

Studies using T948 as a model system have been carried out aimed at elucidating the mechanism of sister chromatid recombination (SCR). Characterization of U.V. light- and x-ray-induced SCR, the relationiship between SCR induction and DNA repair using rad mutations, and the relationship between SCR induction and the time of cell division using cdc mutations are presented. It has been supposed that SCR is induced at the phase of S-G 2 following DNA replication, that postreplication break of DNA strands is strongly involved in the induction of SCR, and that induction type of SCR, i.e., conversion type or recombination type, is dependent upon the type of molecular damage of DNA. (Namekawa, K.)

Cytotoxicity and genotoxicity of UVA irradiation in Chinese hamster ovary cells measured by specific locus mutations, sister chromatid exchanges and chromosome aberrations

International Nuclear Information System (INIS)

Lundgren, Karsten; Wulf, H.C.

1988-01-01

The increasing use of artificial UVA (320-400 nm) suntanning devices has brought attention to possible hazardous effects of UVA. In contrast with earlier studies, several groups recently have described that UVA possibly is mutagenic. We evaluate the genotoxic properties of broad band UVA using CHO cells and three different assays: specific locus (HGPRT) mutations, chromosome aberrations, and sister chromatid exchanges (SCEs). The UVA-source was an UVASUN 2000 S (Mutzhas), emitting UVA above 340 nm. The survival curve of the cells exhibited a shoulder up to 200 kJ/m 2 , that was followed by exponential killing at higher fluences. Mutations were induced linearly in the fluence range of 0-200 kJ/m 2 to a level seven fold higher than the spontaneous, followed by a decrease at fluences above 300 kJ/m 2 . Over the total range of tested fluences (0-300 kJ/m 2 ) a linear dose-response relationship was observed for UVA-induced SCEs. A significantly higher percentage of the cells showed chromosomes with aberrations at the higher levels of exposure (200, 300 and 400 kJ/m 2 ), but no dose response was demonstrated. Our results confirm recent findings showing that UVA is mutagenic in mammalian cells and suggest that UVA exposure may contribute to the total burden of genetic damage caused by exposure to ultraviolet light. (author)

Defects in the Fanconi Anemia Pathway and Chromatid Cohesion in Head and Neck Cancer.

Science.gov (United States)

Stoepker, Chantal; Ameziane, Najim; van der Lelij, Petra; Kooi, Irsan E; Oostra, Anneke B; Rooimans, Martin A; van Mil, Saskia E; Brink, Arjen; Dietrich, Ralf; Balk, Jesper A; Ylstra, Bauke; Joenje, Hans; Feller, Stephan M; Brakenhoff, Ruud H

2015-09-01

Failure to repair DNA damage or defective sister chromatid cohesion, a process essential for correct chromosome segregation, can be causative of chromosomal instability (CIN), which is a hallmark of many types of cancers. We investigated how frequent this occurs in head and neck squamous cell carcinoma (HNSCC) and whether specific mechanisms or genes could be linked to these phenotypes. The genomic instability syndrome Fanconi anemia is caused by mutations in any of at least 16 genes regulating DNA interstrand crosslink (ICL) repair. Since patients with Fanconi anemia have a high risk to develop HNSCC, we investigated whether and to which extent Fanconi anemia pathway inactivation underlies CIN in HNSCC of non-Fanconi anemia individuals. We observed ICL-induced chromosomal breakage in 9 of 17 (53%) HNSCC cell lines derived from patients without Fanconi anemia. In addition, defective sister chromatid cohesion was observed in five HNSCC cell lines. Inactivation of FANCM was responsible for chromosomal breakage in one cell line, whereas in two other cell lines, somatic mutations in PDS5A or STAG2 resulted in inadequate sister chromatid cohesion. In addition, FANCF methylation was found in one cell line by screening an additional panel of 39 HNSCC cell lines. Our data demonstrate that CIN in terms of ICL-induced chromosomal breakage and defective chromatid cohesion is frequently observed in HNSCC. Inactivation of known Fanconi anemia and chromatid cohesion genes does explain CIN in the minority of cases. These findings point to phenotypes that may be highly relevant in treatment response of HNSCC. ©2015 American Association for Cancer Research.

Increased sister chromatid cohesion and DNA damage response factor localization at an enzyme-induced DNA double-strand break in vertebrate cells.

LENUS (Irish Health Repository)

Dodson, Helen

2009-10-01

The response to DNA damage in vertebrate cells involves successive recruitment of DNA signalling and repair factors. We used light microscopy to monitor the genetic dependencies of such localization to a single, induced DNA double strand break (DSB) in vertebrate cells. We used an inducible version of the rare-cutting I-SceI endonuclease to cut a chromosomally integrated I-SceI site beside a Tet operator array that was visualized by binding a Tet repressor-GFP fusion. Formation of gamma-H2AX foci at a single DSB was independent of ATM or Ku70. ATM-deficient cells showed normal kinetics of 53Bp1 recruitment to DSBs, but Rad51 localization was retarded. 53Bp1 and Rad51 foci formation at a single DSB was greatly reduced in H2AX-null DT40 cells. We also observed decreased inter-sister chromatid distances after DSB induction, suggesting that cohesin loading at DSBs causes elevated sister chromatid cohesion. Loss of ATM reduced DSB-induced cohesion, consistent with cohesin being an ATM target in the DSB response. These data show that the same genetic pathways control how cells respond to single DSBs and to multiple lesions induced by whole-cell DNA damage.

Investigations into the molecular mechanism of chromatid breakage in the G2-phase of mammalian cells

International Nuclear Information System (INIS)

Bryant, P.E.; Armstrong, G.N.; Gray, L.; Frankenberg, D.; Mozdarani, H.

2003-01-01

Chromatid breakage following irradiation of cells in the G2-phase of the cell cycle results from the induction of DNA double-strand breaks (dsb). The conversion of dsb into chromatid breaks (cb) has a genetic basis, seemingly different from that of dsb rejoining. The variation in extent of this conversion is exemplified by the stiking variation in frequency of cb in irradiated cycling T-lymphocytes between different normal individuals. Elevated cb frequency in lymphocytes of around 40% of breast cancer patients and their first-degree relatives suggests the presence of mutations in low penetrance cancer predisposing genes that also affect conversion of dsb to cb. Investigation of the mechanism of chromatid radiosensitivity using genetically engineered rodent cell lines containing unique dsb break sites indicate that a single isolated dsb is sufficient to cause a cb. The single-event nature of chromatid breakage is confirmed by the fact that cb are induced as a linear function of radiation dose. Moreover, we have recently shown that ultrasoft carbon-K X-rays also induce chromatid breakage. In this case the energy of the secondary electrons produced by carbon-K X-rays is too low to span more than one DNA double helix, thus further supporting our conclusion that a single dsb is responsible for the formation of a cb. Chromatid breakage is thought to involve a rearrangement between DNA strands at the crossover points of chromatin loop(s) triggered by the presence of a dsb within the loop structure. The occasional observation of 'looped-out' sections of chromatin at cb sites supports this hypothesis. The occurrence of 'colour-switches' between FPG stained chromatids at a proportion of break sites (e.g. about 16% in CHO cells) shows that a significant proportion of cb definitely result from chromatin rearrangements. Measurements of altered colour-switch ratio (csr) in mutant rodent and human cells (irs1 and AT cells respectively) also indicate a genetic basis for the

Terminalia catappa , an anticlastogenic agent against MMS induced ...

African Journals Online (AJOL)

Subjects: Anticarcinogenic potential of methanolic extract of T. catappa has been tested against the carcinogenicity induced by methyl methanesulfonate in the in vitro and in vivo models. Methods: The parameters for evaluation included chromosomal aberrations (CA), sister chromatid exchanges (SCEs) and replication ...

Chromosomal aberration

International Nuclear Information System (INIS)

Ishii, Yutaka

1988-01-01

Chromosomal aberrations are classified into two types, chromosome-type and chromatid-type. Chromosom-type aberrations include terminal deletion, dicentric, ring and interstitial deletion, and chromatid-type aberrations include achromatic lesion, chromatid deletion, isochromatid deletion and chromatid exchange. Clastogens which induce chromosomal aberration are divided into ''S-dependent'' agents and ''S-independent''. It might mean whether they can induce double strand breaks independent of the S phase or not. Double strand breaks may be the ultimate lesions to induce chromosomal aberrations. Caffeine added even in the G 2 phase appeared to modify the frequency of chromatid aberrations induced by X-rays and mitomycin C. Those might suggest that the G 2 phase involves in the chromatid aberration formation. The double strand breaks might be repaired by ''G 2 repair system'', the error of which might yield breakage types of chromatid aberrations and the by-pass of which might yield chromatid exchanges. Chromosome-type aberrations might be formed in the G 1 phase. (author)

Sister chromatid segregation in meiosis II

Science.gov (United States)

Wassmann, Katja

2013-01-01

Meiotic divisions (meiosis I and II) are specialized cell divisions to generate haploid gametes. The first meiotic division with the separation of chromosomes is named reductional division. The second division, which takes place immediately after meiosis I without intervening S-phase, is equational, with the separation of sister chromatids, similar to mitosis. This meiotic segregation pattern requires the two-step removal of the cohesin complex holding sister chromatids together: cohesin is removed from chromosome arms that have been subjected to homologous recombination in meiosis I and from the centromere region in meiosis II. Cohesin in the centromere region is protected from removal in meiosis I, but this protection has to be removed—deprotected”—for sister chromatid segregation in meiosis II. Whereas the mechanisms of cohesin protection are quite well understood, the mechanisms of deprotection have been largely unknown until recently. In this review I summarize our current knowledge on cohesin deprotection. PMID:23574717

Relationship of the demethylation of the DNA with the induction of the sister chromatid exchanges (SCE) In vivo

International Nuclear Information System (INIS)

Toribio E, E.

2005-01-01

The methylation of the DNA is an epigenetic modification that has an important paper in the regulation of the functionality of the genome of the organisms. It can be altered by demethylation processes, either natural or experimentally induced. The 5-azacytidine (Aza) is a compound that causes the demethylation of the DNA (dm-DNA), inducing with it, expression genic and increase in the frequency of the Sister Chromatid Exchange (SCE). The SCE is a genotoxicity indicator, caused by diverse mutagens and carcinogen. Since the biological meaning and the formation mechanism of this phenomenon has not been totally illustrious, the exploration of the relation between the dm-DNA and the induction of SCE, it could offer new knowledge to explain those queries. The purpose of this work was to study in cells of the mouse bone marrow In vivo, the effect of the Aza on the induction of SCE, based on two aspects: 1) dose answer and 2) the effectiveness of multiple exhibition. To six groups of three to five animals, they are administered Aza to dose of 5, 10, 15 or 20 mg/Kg of weight; in sharp or multiple form, previously to the bromodeoxyuridine supply and 24 h was sacrificed after this; 2 h after an injection with colchicine. Preparations of those metaphases were made, those which were dyed by means of a technique of fluorescence more Giemsa. It was observed that to sharp low dose, the Aza produced an increment in the frequency of SCE that although small it was proportional and statistically significant. To sharp and multiple high doses, the Aza doesn't cause additional increments of SCE, but if toxicity at cellular level and of individuals. It is concluded that a relationship exists between the dm-DNA and the induction of SCE. It is suggested that the total demethylation of the DNA causes 2 SCE/Cell in cells of the mouse bone marrow, or that the cytotoxicity prevents to evidence a bigger induction. (Author)

Colchicine promotes a change in chromosome structure without loss of sister chromatid cohesion in prometaphase I-arrested bivalents.

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Rodríguez, E M; Parra, M T; Rufas, J S; Suja, J A

2001-12-01

In somatic cells colchicine promotes the arrest of cell division at prometaphase, and chromosomes show a sequential loss of sister chromatid arm and centromere cohesion. In this study we used colchicine to analyse possible changes in chromosome structure and sister chromatid cohesion in prometaphase I-arrested bivalents of the katydid Pycnogaster cucullata. After silver staining we observed that in colchicine-arrested prometaphase I bivalents, and in contrast to what was found in control bivalents, sister kinetochores appeared individualised and sister chromatid axes were completely separated all along their length. However, this change in chromosome structure occurred without loss of sister chromatid arm cohesion. We also employed the MPM-2 monoclonal antibody against mitotic phosphoproteins on control and colchicine-treated spermatocytes. In control metaphase I bivalents this antibody labelled the tightly associated sister kinetochores and the interchromatid domain. By contrast, in colchicine-treated prometaphase I bivalents individualised sister kinetochores appeared labelled, but the interchromatid domain did not show labelling. These results support the notion that MPM-2 phosphoproteins, probably DNA topoisomerase IIalpha, located in the interchromatid domain act as "chromosomal staples" associating sister chromatid axes in metaphase I bivalents. The disappearance of these chromosomal staples would induce a change in chromosome structure, as reflected by the separation of sister kinetochores and sister axes, but without a concomitant loss of sister chromatid cohesion.

Assessment of DNA Damage in Peripheral Blood Lymphocytes of Radiation Workers at Al-Tuwaitha Site by Using the Sister Chromatid Exchange and the Comet Assay

International Nuclear Information System (INIS)

Ali, A.K.; Muttar, A.J.; Khayon, S.K.; Haider, Y.L.; Ali, H.F.; Abdullah, A.K.

2015-01-01

The sister chromatid exchange was performed on peripheral blood lymphocytes obtained from 40 individuals of workers occupationally exposed to low ionizing radiation doses in Al-Tuwaitha site due to decommissioning to radioactive contamination then compared with 40 control individuals living in Baghdad. SCEs were scored in metaphase chromosomes were identified by fluorescent plus Giemsa staining (Figure 2).The mean frequencies of SCEs per cell differed significantly (p≺0 0.05) between individuals of radiation workers and control, being 7.78 0.45 SCE/cells and 6.28 0.22 SCE/cells , respectively. However SCE frequency was statistically significant (P≺0 0.05) among radiation workers as compared to control individuals.

Stage specificity and dose-response relationships for chromosome aberrations induced in mouse primary spermatocytes following X-irradiation

Energy Technology Data Exchange (ETDEWEB)

Matsuda, Y.; Tobari, I.; Utsugi, T.

1986-05-01

In this study, dose-response relationships were examined for chromosome aberrations observed at diakinesis-metaphase I of spermatocytes with X-irradiation at various stages of meiosis (diplotene, mid-pachytene, zygotene and leptotene). The frequencies of cells with X-ray-induced chromosome aberrations increased with dose at all stages in the applied range of 0.5-3.0 Gy and tended to increase as the irradiated stages descended after leptotene stage. In three stages, the frequencies increased exponentially with dose, but the rates of induction of chromosome breaks were markedly different depending on the stages at which spermatocytes were irradiated with X-rays. The rate of induction was the highest at diplotene and the lowest at leptotene, suggesting that diplotene spermatocytes had the highest radiosensitivity to the induction of chromosome breaks, followed by pachytene, zygotene and leptotene spermatocytes in that order. The dose-response relationships fitted well to linear equations for deletion-type aberrations at each stage, and to linear-quadratic equations for exchange-type aberrations at all stages except for leptotene. At leptotene, the chromatid exchanges were hardly observed, the aberrations being mainly consisted of iso-chromatid fragments. On the contrary, chromatid exchanges and iso-chromatide deletions were mainly observed at later stages (zygotene-diplotene).

Cell killing and chromosomal aberration induced by heavy-ion beams in cultured human tumor cells

International Nuclear Information System (INIS)

Takakura, K.; Funada, A.; Mohri, M.; Lee, R.; Aoki, M.; Furusawa, Y.; Gotoh, E.

2003-01-01

Full text: To clarify the relation between cell death and chromosomal aberration in cultured human tumor cells irradaited with heavy-ion beams. The analyses were carried out on the basis of the linear energy transfer (LET) values of heavy ion beams as radiation source. Exponentially growing human tumor cells, Human Salivary Gland Tumor cells (HSG cells), were irradiated with various high energy heavy ions, such as 13 keV/micrometer carbon (C) ions as low LET charged particle radiation source, 120 keV/ micrometer carbon (C) ions and 440 keV/micrometer iron (Fe) ions as high LET charged particle radiation sources.The cell death was analysed by the colony formation method, and the chromosomal aberration and its repairing kinetics was analysed by prematurely chromosome condensation method (PCC method) using calyculin A. Chromatid-type breaks, isochromatid breaks and exchanges were scored for the samples from the cells keeping with various incubation time after irradiation. The LET dependence of the cell death was similar to that of the chromosome exchange formation after 12 hours incubation. A maximum peak was around 120 keV/micrometer. However it was not similar to the LET dependence of isochromatid breaks or chromatid breaks after 12 hours incubation. These results suggest that the exchanges formed in chromosome after irradiation should be one of essential causes to lead the cell death. The different quality of induced chromosome damage between high-LET and low-LET radiation was also shown. About 89 % and 88 % chromatid breaks induced by X rays and 13 keV/micrometer C ions were rejoined within 12 hours of post-irradiation, though only 71% and 58 % of chromatid breaks induced by 120 keV/micrometer C ions and 440 keV/micrometer Fe ions were rejoined within 12 hours of post-irradiation

Repairability during G1 of the inductor leisure of exchanges in the sister chromatid induced by alkylating agents in DNA substituted and no substituted with BUDR, in cells of the salivary gland of mouse In vivo

International Nuclear Information System (INIS)

Gonzalez B, F.

2004-01-01

In this work you determines the repair of the lesions inductoras of Sister chromatid exchange (ICHs) generated in the cells of the salivary gland of mouse, for the treatment with the N-Methyl-N-Nitrosourea (MNU), the N-Ethyl-N-Nitrosourea (ENU), the Methyl methanesulfonate (MMS) and the Ethyl methanesulfonate (EMS) in early and slow G1 of the first one and the second cellular division, that is to say before and after the cells incorporate 5-bromine-2 -Desoxyuridine (BrdU) in the DNA. Groups witness non treaties were included with mutagen. The cells of the salivary gland repaired the generated lesions partially by the MNU, the MMS and the EMS in the 1st division, and only the lesions induced by the ENU and MMS were repaired partially in the 2nd division. The ENU generates injure that they were not repaired in the 1st division and those taken place by the EMS were little repaired in the 2nd division. The methylating agents generated but ICHs that the ethylating. One observes that the BrdU makes to the molecule of the DNA but susceptible to the damage generated by the alkylating agents that induce the formation of the ICHs. This susceptibility was incremented around 150% for the treatment with the MNU, the ENU and the MMS, on the other hand for the EMS it was 3 times minor. It is proposed that the one electronegative atom of this analog of the timine would to work as a nucleophyllic center with which the electrophyllic compounds react. (Author)

Splitting the chromosome: cutting the ties that bind sister chromatids.

Science.gov (United States)

Nasmyth, K; Peters, J M; Uhlmann, F

2001-01-01

In eukaryotic cells, replicated DNA molecules remain physically connected from their synthesis in S phase until they are separated during anaphase. This phenomenon, called sister chromatid cohesion, is essential for the temporal separation of DNA replication and mitosis and for the equal separation of the duplicated genome. Recent work has identified a number of chromosomal proteins required for cohesion. In this review we discuss how these proteins may connect sister chromatids and how they are removed from chromosomes to allow sister chromatid separation at the onset of anaphase.

Cleavage of cohesin rings coordinates the separation of centrioles and chromatids.

Science.gov (United States)

Schöckel, Laura; Möckel, Martin; Mayer, Bernd; Boos, Dominik; Stemmann, Olaf

2011-07-10

Cohesin pairs sister chromatids by forming a tripartite Scc1-Smc1-Smc3 ring around them. In mitosis, cohesin is removed from chromosome arms by the phosphorylation-dependent prophase pathway. Centromeric cohesin is protected by shugoshin 1 and protein phosphatase 2A (Sgo1-PP2A) and opened only in anaphase by separase-dependent cleavage of Scc1 (refs 4-6). Following chromosome segregation, centrioles loosen their tight orthogonal arrangement, which licenses later centrosome duplication in S phase. Although a role of separase in centriole disengagement has been reported, the molecular details of this process remain enigmatic. Here, we identify cohesin as a centriole-engagement factor. Both premature sister-chromatid separation and centriole disengagement are induced by ectopic activation of separase or depletion of Sgo1. These unscheduled events are suppressed by expression of non-cleavable Scc1 or inhibition of the prophase pathway. When endogenous Scc1 is replaced by artificially cleavable Scc1, the corresponding site-specific protease triggers centriole disengagement. Separation of centrioles can alternatively be induced by ectopic cleavage of an engineered Smc3. Thus, the chromosome and centrosome cycles exhibit extensive parallels and are coordinated with each other by dual use of the cohesin ring complex.

Epigenetic differences between sister chromatids?

NARCIS (Netherlands)

Lansdorp, Peter M.; Falconer, Ester; Tao, Jiang; Brind'Amour, Julie; Naumann, Ulrike; Kanz, L; Fibbe, WE; Lengerke, C; Dick, JE

2012-01-01

Semi-conservative replication ensures that the DNA sequence of sister chromatids is identical except for replication errors and variation in the length of telomere repeats resulting from replicative losses and variable end processing. What happens with the various epigenetic marks during DNA

Role of oxidative stress and intracellular calcium in nickel carbonate hydroxide-induced sister-chromatid exchange, and alterations in replication index and mitotic index in cultured human peripheral blood lymphocytes

Energy Technology Data Exchange (ETDEWEB)

M' Bemba-Meka, Prosper [Universite de Montreal, Human Toxicology Research Group (TOXHUM), Department of Environmental and Occupational Health, Main Station, P.O. Box 6128, Montreal, QC (Canada); University of Louisville, Department of Pharmacology and Toxicology, Center for Genetics and Molecular Medicine, Louisville, KY (United States); Lemieux, Nicole [Universite de Montreal, Department of Pathology and Cellular Biology, Faculty of Medicine, Main Station, P.O. Box 6128, Montreal, QC (Canada); Chakrabarti, Saroj K. [Universite de Montreal, Human Toxicology Research Group (TOXHUM), Department of Environmental and Occupational Health, Main Station, P.O. Box 6128, Montreal, QC (Canada)

2007-02-15

Human peripheral lymphocytes from whole blood cultures were exposed to either soluble form of nickel carbonate hydroxide (NiCH) (0-60 {mu}M), or of nickel subsulfide (Ni{sub 3}S{sub 2}) (0-120 {mu}M), or of nickel oxide (NiO) (0-120 {mu}M), or nickel sulfate (NiSO{sub 4}) (0-120 {mu}M) for a short duration of 2 h. The treatments occurred 46 h after the beginning of the cultures. The cultures were harvested after a total incubation of 72 h, and sister-chromatid exchange (SCE), replication index (RI), and mitotic index (MI) were measured for each nickel compound. The soluble form of NiCH at 30 {mu}M but those of Ni{sub 3}S{sub 2} and NiO at 120 {mu}M produced significant increase in the SCE per cell compared to the control value, whereas NiSO{sub 4} failed to produce any such significant increase. Except NiSO{sub 4}, the soluble forms of NiCH, Ni{sub 3}S{sub 2}, and NiO produced significant cell-cycle delay (as measured by the inhibition of RI) as well as significant inhibition of the MI at respective similar concentrations as mentioned above. Pretreatment of human blood lymphocytes with catalase (H{sub 2}O{sub 2} scavenger), or superoxide dismutase (superoxide anion scavenger), or dimethylthiourea (hydroxyl radical scavenger), or deferoxamine (iron chelator), or N-acetylcysteine (general antioxidant) inhibited NiCH-induced SCE, and changes in RI and MI. This suggests the participation of oxidative stress involving H{sub 2}O{sub 2}, the superoxide anion radical, the hydroxyl radical, and iron in the NiCH-induced genotoxic responses. Cotreatment of NiCH with either verapamil (inhibitor of intracellular calcium ion ([Ca{sup 2+}]{sub i}) movement through plasma membranes), or dantrolene (inhibitor of [Ca{sup 2+}]{sub i} release from sarcoplasmic reticulum), or BAPTA (Ca{sup 2+} chelator) also inhibited the NiCH-induced responses. These results suggest that [Ca{sup 2+}]{sub i} is also implicated in the genotoxicity of NiCH. Overall these data indicate that various types

Effects of hyperthermia and x irradiation on sister chromatid exchange (SCE) frequency in Chinese hamster ovary (CHO) cells

International Nuclear Information System (INIS)

Livingston, G.K.; Dethlefsen, L.A.

1979-01-01

The BrdUrd labeling method was used to evaluate the effects of hyperthermia, x irradiation, and the combined treatment on the incidence of sister chromatid exchange (SCE) in Chinese hamster ovary (CHO) cells. Cells cultured in McCoy's 5A media containing 10 μM 5-bromodeoxyuridine were synchronized after one cell cycle by mitotic shake-off. Early-G 1 cells were heated by submerging culture flasks in a 44 +- 0.05 0 C water bath for periods of 20, 40, and 60 min. By the same method, other cultures were x irradiated at doses of 100, 200, 400, and 600 rad. A third protocol involved combined treatment of 20 min at 44 0 C followed immediately by one of the above radiation doses. A fourth protocol reversed the sequence of the combined treatment applying x irradiation (200 or 400 rad) followed immediately by hyperthermia. The data showed that hyperthermia and x irradiation both elevated the frequency of SCEs significantly whether applied separately or together. The combined treatment (heat: 20 min at 44 0 C plus varying x-radiation doses) produced results suggestive of a synergistic interaction. The sequence of the heat and x irradiation did not appear to have a significant effect on the production of SCE

The Relationship between Dioxin Congeners in the Breast Milk of Vietnamese Women and Sister Chromatid Exchange

Directory of Open Access Journals (Sweden)

Hiroyuki Suzuki

2014-04-01

Full Text Available The aim of this study was to clarify the relationship between dioxin concentrations in breast milk and the sister chromatid exchange (SCE frequency in women from herbicide-sprayed and non sprayed areas. Blood samples were taken from 21 women with high TCDD (tetrachlorodibenzo-p-dioxin levels from sprayed areas, 23 women with moderate TCDD levels from sprayed areas, and 19 women from non sprayed areas to determine their SCE frequency. The SCE frequencies for the high and moderate TCDD groups from the sprayed area and for the non sprayed area group were 2.40, 2.19, and 1.48 per cell, respectively. Multiple regression analysis showed that the standardized β values for 1,2,3,6,7,8-hexaCDD (β = 0.60, 1,2,3,4,6,7,8-heptaCDD (β = 0.64, and octaCDD (β = 0.65 were higher than those for TCDD (β = 0.34 and 1,2,3,7,8-pentaCDD (β = 0.42. The adjusted R2 value for polyCDDs (R2 = 0.38 was higher than that for polyCDD toxic equivalents (TEQ (toxic equivalents; R2 = 0.23. This study therefore shows that levels of hexa-, hepta-, and octaCDD, which were previously regarded as being less toxic than TCDD, are closely related to SCE frequency and that the level of dioxin (pg/g lipid is potentially more useful as an indicator than TEQ value for explaining SCE frequency.

Radiation-cytogenetic study of the mechanism of formation of chromosome aberations in Crepis capillaris cells

International Nuclear Information System (INIS)

Belyaev, I.Ya.; Semakin, A.B.; Grigorova, N.V.; Akif'ev, A.P.; AN SSSR, Moscow. Inst. Khimicheskoj Fiziki)

1986-01-01

Incomplete chromatid exchanges induced by γ-quanta at G 2 stage of Crepis capillaris meristem cells are transformed into complete chromosome exchanges during the second nuclear cycle. After the combined effect of γ-quanta and DNA synthesis inhibitor 5-fluoro-2-deoxyridine, the exchange aberrations disappear. During the second nuclear cycle, the chromatid exchanges, which were not realized in the presence of 5-fluro-2-deoxyuridne and regarded as potential ones, are transformed into chromosome exchanges. The breaks induced by 5-fluoro-2-deoxyuridine at G 2 stage are repaired after one nuclear cycle

In vivo study on the replicative model validity of sister chromatid exchanges production; Estudio In vivo sobre la validez del modelo replicativo de produccion de intercambios en las cromatidas hermanas

Energy Technology Data Exchange (ETDEWEB)

Cruz V, V L

1997-12-31

The sister chromatid exchanges (SCE) frequency determination has been used as index of damage to DNA, however the biological meaning of this event is still ignored. Different models in order to explain the mechanism of their formation have been proposed and they could be contained in two categories: (a) those that consider that the SCE is produced by means of discrete lesions to the DNA and that they occur in the place of the lesion, and (b) those that propose that the SCE is caused by a group of lesions and that therefore the place in which they occur could not be associated with a lesion in particular. The model of Painter (1980) belongs to this last group. It suggests that the region of the DNA where the clusters are united, is the only place in which the exchange of double chain could happen during the synthesis of the DNA and makes the prediction that since the x rays retard the beginning of the duplication, the pretreatment with ionizing radiation would reduce the frequency of SCE induced by agents capable to block the lengthening of the chain of DNA, that are the most efficient SCE inducers. The objective of the present work was to establish the validity of this replicative model for the SCE formation, based in its prediction. The effect of the unilateral preexposition of mouse to gamma radiation was determined on the SCE induction by Mitomycin C (MMC), in cells of the femoral bone marrow In vivo. This strategy allows to determine the effect of the pretreatment in the same organism, minimizing the variability of the response between individuals. There was not a significant variability between the frequencies of SCE, basal and induced by gamma radiation or MMC in the same organism. The animals that received the gamma radiation pretreatment, showed a reduction of approximately the 30 % in the frequency of SCE, assuming an additive effect of the radiation with the MMC. These results coincide with the prediction of the model of Painter. (Abstract Truncated)

Micronuclear and sister chromatid exchange analyses in peripheral lymphocytes of patients with oral lichen planus--a pilot study.

Science.gov (United States)

Ergun, S; Warnakulasuriya, S; Duman, N; Saruhanoğlu, A; Sevinç, B; Oztürk, S; Ozel, S; Cefle, K; Palanduz, S; Tanyeri, H

2009-10-01

The purpose of this study was to determine the genetic instability of peripheral blood lymphocytes from patients diagnosed with oral lichen planus (OLP) by investigation of frequencies of micronuclei (MN) and sister chromatid exchange (SCE). A total of 22 newly diagnosed and untreated patients with OLP of same severity scores and twenty healthy controls participated in this study. They were all non-smokers with no previous history or family history of cancer. The periodontal status, flow rate and buffering capacity of whole mouth saliva were recorded. SCE and MN analyses were performed on peripheral blood lymphocytes of OLP patients and healthy controls. The frequencies of MN (50.00 +/- 22.36) and SCE (6.89 +/- 1.48) in OLP patients were found to be significantly elevated compared with that in normal individuals (25.20 +/- 9.52 and 5.93 +/- 1.31; z = 3.946, P = 0.0001; z = 2.346, P = 0.019). There were no significant differences in the MN frequency and SCE between the two subgroups with reticular or erosive types of OLP. These pilot data indicate an increased genomic instability in peripheral blood lymphocytes of a cohort of Turkish patients diagnosed with oral lichen planus as compared with that of healthy individuals. As patients with OLP may have an increased or potential risk for oral malignancy, these assays could be used in translational research to monitor beneficial effects of interventions and long-term prognosis.

Effect of low 60Co dose rates on sister chromatid exchange incidence in the benthic worm. Neanthes arenaceodentata

International Nuclear Information System (INIS)

Harrison, F.L.; Rice, D.W. Jr.

1981-01-01

The usefulness of sister chromatid exchange (SCE) induction as a measure of low-level radiation effect was examined in a benthic marine worm, Neanthes arenaceodentata. Larvae were exposed to 60 Co radiation for 12 to 24 h at total doses ranging from 0.5 to 309 R and at dose rates from 0.04 to 13 R/h. Animals exposed at intermediate dose rates (0.5, 0.6, 1.25, 2.0, and 2.5 R/h) had SCE frequencies per chromosome about twice that of those receiving no radiation (controls), whereas those exposed at the higher dose rates (7.0 and 13 R/h) had SCE frequencies lower than the controls. Animals exposed at the lower dose rates (0.04 and 0.1 R/h) had lower SCE frequencies than those exposed at intermediate dose rates (and higher SCE frequencies than controls). The length of chromosome pair number one differed among metaphase spreads and was used as an index of chromosome condensation in a given metaphase. Because there is a possibility that chromosome morphology may affect the ability to resolve SCEs, morphology will be monitored in future studies. A preliminary experiment was performed to assess the effects of 2.2 and 11.5 R/h for 24 h on growth and development. Larvae observed at 6 and 17 d after irradiation did not have significantly different numbers of abnormal larvae or survival rates

Differences in sensitivity of murine spermatogonia and somatic cells in vivo to sister-chromatid exchange induction by nitrosoureas.

Science.gov (United States)

Morales-Ramírez, P; Cruz-Vallejo, V; Rodríguez-Reyes, R

2001-07-01

Previously published data indicate that spermatogonia (SPG) are less sensitive to a sister-chromatid exchange (SCE) induction for different mutagens. In an earlier study, we have observed that bromodeoxyuridine (BrdU) substituted murine SPG are less sensitive to SCE induction by gamma ray in cells, than bone marrow (BM) and salivary gland (SG) cells in vivo. This was interpreted to mean that SPG are more efficient in DNA repair or are less prone to SCE induction. That the lower induction of SCE could be due to a reduced accessibility of mutagens to the SPG by virtue of a physiological barrier, was discarded by using gamma radiation. The aim of the present study was to establish whether or not there are differences in SCE induction by nitrosoureas among SPG, SG and BM cells with BrdU substituted or unsubstituted DNA. It was observed that SCE induction by methylnitrosourea (MNU) or by ethylnitrosourea (ENU) in SPG was, respectively, five and two times lower than in SG, and ten and three times lower than in BM. In SPG after BrdU incorporation, there was no increase in efficiency of SCE induction; in fact, there was even a slight decrease by exposure to MNU or ENU. BM and SG cells showed an increased efficiency in SCE induction after BrdU incorporation. This implies that SPG are also less sensitive to SCE induction by nitrosoureas, which cause a different kind of damage from previously assayed mutagens.

Effect of chlorophyllin on induction of exchanges in sister chromatids by gamma irradiation in mice spermatogonia in vivo; Efecto de la clorofilina sobre la induccion de intercambios en las cromatidas hermanas (ICH) por radiacion gamma en espermatogonias de raton In vivo

Energy Technology Data Exchange (ETDEWEB)

Mendiola C, M T

1994-12-31

Mouse were exposed to different doses of gamma radiation and the effect on Sister Chromatid Exchange (SCE) frequency in spermatogonias was evaluated. The effect was analyzed before and after Bromodeoxyuridine (BrdU) incorporation to determine the interference of such agent with the cellular response induced by radiation. The capacity of chlorophyllin (sodium and Copper salt derivative from chlorophyll) to reduce SCE induction by radiation in normal and BrdU radio sensitized spermatogonia was also determined. The results indicate that there was a significant increase in SCE frequency by gamma radiation exposure in these cells, such effect was higher irradiating after BrdU incorporation than before. This fact confirms previous observations that BrdU sensitizes some cells to SCE induction. With regard to the chlorophyllin effect, it was determined that this salt acts as a radioprotector reducing gamma-rays induced SCE before or after BrdU incorporation Total protection was obtained with 200 {mu}g of chlorophyllin per g of body weight in both protocols. Under the experimental conditions this study there was no evidence of genotoxicity induced by chlorophyllin itself. The results suggest that this agent may act as a radioprotector by scavenging free radicals produced by gamma-radiation which cause DNA lesions that are involved in SCE formation. (Author).

Can consumption of raw vegetables decrease the count of sister chromatid exchange? Results from a cross-sectional study in Krakow, Poland.

Science.gov (United States)

Galas, Aleksander; Cebulska-Wasilewska, Antonina

2015-03-01

Sister chromatid exchange (SCE) is a widely used sensitive cytogenetic biomarker of exposure to genotoxic and cancerogenic agents. Results of human monitoring studies and cytogenetic damage have revealed that biological effects of genotoxic exposures are influenced by confounding factors related to life-style. Vegetable and fruit consumption may play a role, but available results are not consistent. The purpose of the study was to investigate the effect of consumption of raw and cooked vegetables and fruits on SCE frequency. A total of 62 participants included colorectal cancer (CRC) patients, hospital-based controls and healthy laboratory workers. SCE frequency was assessed in blood lymphocytes. Frequency of vegetable and fruit consumption was gathered by structured semi-quantitative food frequency questionnaire. SCE frequency was lowest among hospital-based controls (4.4 ± 1.1), a bit higher in CRC patients (4.5 ± 1.0) and highest among laboratory workers (7.4 ± 1.2) (p consumption, but not so for intake of cooked vegetables and fruits. The results of the study have shown the beneficial effect of consumption of raw vegetables on disrupted replication of DNA measured by SCE frequency, implying protection against genotoxic agents. Further effort is required to verify the role of cooked vegetables and fruits.

The yield of fission neutron-induced chromatid aberrations in G[sub 2]-stage human lymphocytes: effect of caffeine, hydroxyurea and cytosine arabinoside post-irradiation

Energy Technology Data Exchange (ETDEWEB)

Antoccia, A.; Tanzarella, C. (La Sapienza Univ., Rome (Italy)); Palitti, F. (Tuscia Univ., Viterbo (Italy) La Sapienza Univ., Rome (Italy)); Raggi, T. (Tuscia Univ., Viterbo (Italy)); Catena, C. (ENEA, Casaccia (Italy). Centro Ricerche Energia)

1992-11-01

To evaluate the influence of inhibitors of DNA synthesis/repair on the yield of chromosomal aberrations in the G[sub 2] phase of the cell cycle, whole-blood cultures of human lymphocytes were exposed to various doses of fission neutrons or X-rays and treated post-irradiation during the last 2.45 h before harvesting, with 5mM hydroxyurea (HU) and 0.05 mM cytosine arabinoside (ara-C). The presence of caffeine and HU strongly potentiated the yield of chromatid-type aberrations induced by both neutrons and X-rays. No potentiating effect, except at the highest dose of neutrons, was observed when irradiated cells were subsequently treated with ara-C. In addition, neutron-induced mitotic delay was shortened by treatment with caffeine, mainly within the first 2 h after irradiation. (Author).

In vitro studies on chemoprotective effect of Purnark against benzo(a)pyrene-induced chromosomal damage in human lymphocytes.

Science.gov (United States)

Ghaisas, S D; Bhide, S V

1994-01-01

Human lymphocytes were used as an assay system to test chemopreventive activity of natural products. Purnark, a mixture of extracts of turmeric, betel leaf and catechu, was tested for its chemoprotective activity against BP induced DNA damage. Sister chromatid exchange and micronuclei were used as markers to assess the protective activity of Purnark. Purnark gave 50-60% protection against BP induced SCEs and micronuclei. Purnark at 100 micrograms dose did not show any genotoxicity.

In Vivo Cytogenetic Studies on Aspartame

Directory of Open Access Journals (Sweden)

Entissar S. AlSuhaibani

2010-01-01

Full Text Available Aspartame (a-Laspartyl-L-phenylalanine 1-methylester is a dipeptide low-calorie artificial sweetener that is widely used as a nonnutritive sweetener in foods and drinks. The safety of aspartame and its metabolic breakdown products (phenylalanine, aspartic acid and methanol was investigated in vivo using chromosomal aberration (CA test and sister chromatid exchange (SCE test in the bone marrow cells of mice. Swiss Albino male mice were exposed to aspartame (3.5, 35, 350 mg/kg body weight. Bone marrow cells isolated from femora were analyzed for chromosome aberrations and sister chromatid exchanges. Treatment with aspartame induced dose dependently chromosome aberrations at all concentrations while it did not induce sister chromatid exchanges. On the other hand, aspartame did not decrease the mitotic index (MI. However, statistical analysis of the results show that aspartame is not significantly genotoxic at low concentration.

The chromosome damage induced by x-ray radiation doses. Comparison between dicentric chromosomes, micronuclei and Sister Chromatid Exchanges analyses. Valoracion de dao cromosomico originado por una dosis de rayos X. Comparacion de los analisis de cromosomas dicentricos, micronucleos e intercambios entre cromatidas hermanas

Energy Technology Data Exchange (ETDEWEB)

Fernandez, J.L.; Losada, C.; Losada, G.; Veiras, C. (Centro Oncologico de Galicia. La Corua (Spain)); Goyanes, V.J. (Hospital ' ' Teresa Herrera' ' . La Corua (Spain))

1993-01-01

Exposure to ionizing radiations is a well-known source of chromosome damage. Here we present a comparison among three different methodologies employed to recognize cytogenetic damage, after an acute exposure of human lymphocytes to 3 Gy of X-rays (100kVp). Scoring of dicentric chromosomes, present in first mitosis ''in vitro'', was the method of preference as dicentrics increased 937.5 times with respect to background. Micronucleus scoring in binucleated-cytokinesis blocked cells showed an increase of 32.5 times, while it was only of 1.46 times when Sister Chromatid Exchanges (SCEs) were analyzed. The estimated probability of an acentric fragment becoming a micronucleus was around 0.25. Intercellular distribution of dicentrics agree with Poisson, while micronucleus were overdispersed. When analyzed at second cycle after damage induction, the dicentrics yield as well as the level of cells with unstable cromosome aberrations, decreased around a half. Finally, SCEs level was similar in cells with or without unstable structural chromosome aberrations. (Author)

Evidence that cyclophosphamide can to induce exchanges in the sister chromatids (ICH) through secondary injuries; Evidencia de que la ciclofosfamida puede inducir intercambios en las cromatidas hermanas (ICH) a traves de lesiones secundarias

Energy Technology Data Exchange (ETDEWEB)

Morales R, P.; Rodriguez R, R. [Instituto Nacional de Investigaciones nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico)

1997-07-01

By means of the use of destination protocol of ICH inductive injuries (DLI-ICH), it was studied if interchanges in the sister chromatids (ICH) induced by cyclophosphamide (CP), in the second post-treatment division (ICH-2) are produced by secondary injuries or by fresh injuries. For discard between these possibilities it was administered CP at different periods before of the first post-treatment division, taking as reference the administered time for high dose of bromodeoxyuridine (BrdU ) which was approximately at the beginning of this division. The ICH frequencies that occur in the first, the second and the third synthesis stages (S) were determined. It was observed that when the administered CP was four hours before BrdU , the ICH frequencies of the second and the third S were reduced. The frequency of the first ICH increased lightly in relation to those of the normal protocol (0.5 h before BrdU ) and that the supplying of CP six hours before caused almost a total reduction of ICH of second and third S and an important increment of ICH of first S.This was interpreted as evidence that the ICH-2 are product of secondary injuries. (Author)

Post-irradiation treatment of human lymphocytes with spermidine reduced frequency of chromatid breaks

International Nuclear Information System (INIS)

Bocian, E.; Rosiek, O.; Ziemba-Zoltowska, B.

1978-01-01

Human lymphocyte cultures were X-irradiated with a single dose of 100 or 200 rad 46 h after phytohemagglutinin stimulation. In dose-fractionation experiments, 2h later the second dose was applied. All the cultures were harvested at 54 h after their initiation. In lymphocytes irradiated with a single dose of 200 rad, 2h post-irradiation contact with 10 -5 M exogeneous spermidine resulted in reduction of chromatid breaks by 34 %. Introduction of spermidine into culture medium for fractionation interval between the 2 doses of 100 rad reduced the frequency of chromatid breaks by 42 %. (author)

Abnormal centromere-chromatid apposition (ACCA) and Peters' anomaly.

Science.gov (United States)

Wertelecki, W; Dev, V G; Superneau, D W

1985-08-01

Abnormal centromere-chromatid apposition (ACCA) was noted in a patient with Peters' anomaly. Previous reports of ACCA emphasized its association with tetraphocomelia and other congenital malformations (Roberts, SC Phocomelia, Pseudothalidomide Syndromes). This report expands the array of congenital malformations associated with ACCA and emphasizes the diagnostic importance of ocular defects for the ascertainment of additional cases of ACCA and its possible relationship with abnormal cell division.

Meiotic sister chromatid cohesion and recombination in two filamentous fungi

NARCIS (Netherlands)

Heemst, van D.

2000-01-01

Homologous recombination and sister chromatid cohesion play important roles in the maintenance of genome integrity and the fidelity of chromosome segregation in mitosis and meiosis. Within the living cell, the integrity of the DNA is threatened by various factors that cause DNA-lesions, of

Effect of pretreatment with venom of Apis mellifera bees on the yield of gamma-ray induced chromosome aberrations in human blood lymphocytes

International Nuclear Information System (INIS)

Varanda, E.A.; Takahashi, C.S.

1993-01-01

Venom of the honey bee Apis mellifera induced a protective effect against the induction of dicentric chromosomes by gamma radiation (2.0 Gy) in human peripheral blood lymphocytes when the cultures were treated with 0.00015 μl venom/1 ml medium 6 h before irradiation. In cultures to which the venom was added immediately before irradiation with 0.25, 1.0 and 2.0 Gy, no significant differences in number of dicentric chromosomes induced was observed when compared to cultures submitted to irradiation only. The venom did not induce clastogenic effects nor did it increase the frequency of sister chromatid exchanges. (author)

Phospho-H1 Decorates the Inter-chromatid Axis and Is Evicted along with Shugoshin by SET during Mitosis.

Science.gov (United States)

Krishnan, Swathi; Smits, Arne H; Vermeulen, Michiel; Reinberg, Danny

2017-08-17

Precise control of sister chromatid separation during mitosis is pivotal to maintaining genomic integrity. Yet, the regulatory mechanisms involved are not well understood. Remarkably, we discovered that linker histone H1 phosphorylated at S/T18 decorated the inter-chromatid axial DNA on mitotic chromosomes. Sister chromatid resolution during mitosis required the eviction of such H1S/T18ph by the chaperone SET, with this process being independent of and most likely downstream of arm-cohesin dissociation. SET also directed the disassembly of Shugoshins in a polo-like kinase 1-augmented manner, aiding centromere resolution. SET ablation compromised mitotic fidelity as evidenced by unresolved sister chromatids with marked accumulation of H1S/T18ph and centromeric Shugoshin. Thus, chaperone-assisted eviction of linker histones and Shugoshins is a fundamental step in mammalian mitotic progression. Our findings also elucidate the functional implications of the decades-old observation of mitotic linker histone phosphorylation, serving as a paradigm to explore the role of linker histones in bio-signaling processes. Copyright © 2017 Elsevier Inc. All rights reserved.

Variation in the human lymphocyte sister chromatid exchange frequency as a function of time: results of daily and twice-weekly sampling

Energy Technology Data Exchange (ETDEWEB)

Tucker, J.D.; Christensen, M.L.; Strout, C.L.; McGee, K.A.; Carrano, A.V.

1987-01-01

The variation in lymphocyte sister chromatid exchange (SCE) frequency was investigated in healthy nonsmokers who were not taking any medication. Two separate studies were undertaken. In the first, blood was drawn from four women twice a week for 8 weeks. These donors recorded the onset and termination of menstruation and times of illness. In the second study, blood was obtained from two women and two men for 5 consecutive days on two separate occasions initiated 14 days apart. Analysis of the mean SCE frequencies in each study indicated that significant temporal variation occurred in each donor, and that more variation occurred in the longer study. Some of the variation was found to be associated with the menstrual cycle. In the daily study, most of the variation appeared to be random, but occasional day-to-day changes occurred that were greater than those expected by chance. To determine how well a single SCE sample estimated the pooled mean for each donor in each study, the authors calculated the number of samples that encompassed that donor's pooled mean within 1 or more standard errors. For both studies, about 75% of the samples encompassed the pooled mean within 2 standard errors. An analysis of high-frequency cells (HFCs) was also undertaken. The results for each study indicate that the proportion of HFCs, compared with the use of Fisher's Exact test, is significantly more constant than the means, which were compared by using the t-test. These results coupled with our previous work suggest that HFC analysis may be the method of choice when analyzing data from human population studies.

Effect of interleukin-2 on cell proliferation, sister-chromatid exchange induction, and nuclear stress protein phosphorylation in PHA-stimulated Fischer 344 rat spleen lymphocytes: Modulation by 2-mercaptoethanol

Energy Technology Data Exchange (ETDEWEB)

Morris, S.M.; Aidoo, A.; Domon, O.E.; McGarrity, L.J.; Kodell, R.L.; Schol, H.M.; Hinson, W.G.; Pipkin, J.L.; Casciano, D.A. (National Center for Toxicological Research, Jefferson, AR (USA))

1990-01-01

The effect of interleukin-2 (IL-2) on cell proliferation, sister-chromatid exchange (SCE) frequency, and the phosphorylation of nuclear stress proteins was evaluated in phytohemagglutinin (PHA)-stimulated spleen lymphocytes isolated from Fischer 344 rats. In addition, the ability of 2-mercaptoethanol (2-ME) to modulate the induction of these biological responses was characterized. Cell proliferation, as measured by the mitotic index, increased significantly. The average generation time (AGT) did not respond to IL-2 in a concentration-dependent manner and decreased significantly. The number of SCE increased significantly from control frequencies, to frequencies of 18.5 to 21.5 SCE per cell as the concentration of IL-2 in the culture medium increased to 50 half-maximal units per ml. A reduction in SCE frequency was observed when cells were cultured with 20 {mu}M 2-ME and IL-2 compared to IL-2 alone. Three nuclear proteins, with relative molecular masses of approximately 13,000-18,000, 20,000, and 80,000, were phosphorylated in IL-2-exposed G{sub 1}-phase nuclei. Elicitation of these nuclear proteins in IL-2-exposed cells was not affected by exposure to 2-ME.

Chromosomal aberrations induced by caffeine, 3H-thymidine and by X-rays in two L5178Y sublines of different radiosensitivity. Part 1. Chromosomal aberrations in cells treated with 2mM caffeine and tritiated thymidine

International Nuclear Information System (INIS)

Bocian, E.; Bouzyk, E.; Rosiek, O.; Ziemba-Zoltowska, B.

1982-01-01

Chromosomal aberrations were studied in two sublines of L5178Y cells with different sensitivity to X-rays. Cells were treated with 2 mM caffeine for 12 h. Then they were examined at various time intervals from 5 to 24 h. Caffeine caused over three times more aberrations, mainly chromatid breaks and gaps, in radiation-sensitive L5178Y-S than in radiation-resistant L5178Y-R cells. The maximum frequency of chromatid breaks in both sublines was found at 8 h and that of chromatid exchanges and isochromatid breaks at 12 h after treatment. A dramatic decrease of the frequency of all types of aberrations at 24 h was observed. In the pulse labelled experiments caffeine enhanced the frequency of aberrations that were induced by 3 H-thymidine at a concentration of 1 μCi/ml. This effect of caffeine was greater in L5178Y-R than in L5178Y-S cells. (author)

DNA damage and chromosome aberration induced by heavy-ion beams

International Nuclear Information System (INIS)

Takakura, Kahoru; Funada, Aya; Aoki, Mizuho; Furusawa, Yoshiya

2003-01-01

The aim of this study is to clarify the relation between cell death and chromosomal aberration in cultured human cells (human salivary gland (HSG) tumor cells and GM05389 human normal fibroblasts) irradiated with heavy ion beams on the basis of linear energy transfer (LET) values. The LET dependences of cell death were observed for the both cells by the method of colony assay. The LET dependences of the chromosomal aberrations, breaks and gaps, isochromatid breaks and exchanges were also observed for the both cells using the premature chromosome condensation (PCC) method. From these results it is suggested that exchange formation is essential for the cell death caused by heavy ion beam irradiation. It is suspected that the densely ionizing track structure of hight LET heavy ions inhibits the effective repair in the chromatid breaks and isochromatid breaks and finally induce much exchange in the cells, which should be essential cause of cell death. (author)

Differential features of sister-chromatid exchange responses to ultraviolet radiation and caffeine in xeroderma pigmentosum lymphoblastoid cell lines

International Nuclear Information System (INIS)

Tohda, H.; Oikawa, A.

1983-01-01

Sister-chromatic exchange (SCE) induced by ultraviolet (UV) irradiation and viability after UV irradiation were studied in lymphoblastoid cell lines derived from 7 patients with xeroderma pigmentosum (XP) and 6 normal donors. UV irradiation caused significant increases of SCEs in both XP and normal cells. In 3 XP cell lines, which were deficient in unscheduled DNA synthesis (UDS) and sensitive to the killing effect of UV, very high SCE frequencies were observed after UV irradiation. Cells from a patient with the De Sanctis-Cacchione syndrome were the most sensitive to UV in terms of both SCE induction and cell killing. In 2 of 4 UDS-proficient XP cell lines tested, the incidences of UV-induced SCEs were similar to those in normal cell lines, but in 2 other UDS-proficient lines from 2 XP patients with skin cancer, the frequencies of UV-induced SCEs were significantly higher than in normal cells. (orig./AJ)

Influence of GSTM1 and GSTT1 genotypes and confounding factors on the frequency of sister chromatid exchange and micronucleus among road construction workers.

Science.gov (United States)

Kumar, Anil; Yadav, Anita; Giri, Shiv Kumar; Dev, Kapil; Gautam, Sanjeev Kumar; Gupta, Ranjan; Aggarwal, Neeraj

2011-07-01

In the present study, we have investigated the influence of polymorphism of GSTM1 and GSTT1 genes and confounding factors such as age, sex, exposure duration and consumption habits on cytogenetic biomarkers. Frequency of sister chromatid exchanges (SCEs), high frequency cell (HFC) and cytokinesis blocked micronuclei (CBMN) were evaluated in peripheral blood lymphocytes of 115 occupationally exposed road construction workers and 105 unexposed individuals. The distribution of null and positive genotypes of glutathione-S transferase gene was evaluated by multiplex PCR among control and exposed subjects. An increased frequency of CBMN (7.03±2.08); SCE (6.95±1.76) and HFC (6.28±1.69) were found in exposed subjects when compared to referent (CBMN - 3.35±1.10; SCE - 4.13±1.30 and HFC - 3.98±1.56). These results were found statistically significant at p<0.05. When the effect of confounding factors on the frequency of studied biomarkers was evaluated, a strong positive interaction was found. The individuals having GSTM1 and GSTT1 null genotypes had higher frequency of CBMN, SCE and HFC. The association between GSTM1 and GSTT1 genotypes and studied biomarkers was found statistically significant at p<0.05. Our findings suggest that individuals having null type of GST are more susceptible to cytogenetic damage by occupational exposure regardless of confounding factors. There is a significant effect of polymorphism of these genes on cytogenetic biomarkers which are considered as early effects of genotoxic carcinogens. Copyright © 2011 Elsevier Ltd. All rights reserved.

Implications of S-phase exchanges for the mechanisms of radiosensitivity in trisomy 21

International Nuclear Information System (INIS)

Athanasiou, K.; Bartsocas, C.S.

1982-01-01

Human lymphocytes obtained from four patients with Down syndrome and from two normal individuals were irradiated with X-rays during their S phase and examined for chromatid type aberrations. It is suggested that the significantly increased frequency of asymmetrical chromatid interchanges found in trisomic cells is related to an altered DNA repair system. This altered repair system is probably responsible for the increased frequency of chromosome aberrations that can be induced in these cells by x-rays and the increased tendency for leukemia observed in Down syndrome as well

Roles of the sister chromatid cohesion apparatus in gene expression, development, and human syndromes

Science.gov (United States)

Dorsett, Dale

2006-01-01

The sister chromatid cohesion apparatus mediates physical pairing of duplicated chromosomes. This pairing is essential for appropriate distribution of chromosomes into the daughter cells upon cell division. Recent evidence shows that the cohesion apparatus, which is a significant structural component of chromosomes during interphase, also affects gene expression and development. The Cornelia de Lange (CdLS) and Roberts/SC phocomelia (RBS/SC) genetic syndromes in humans are caused by mutations affecting components of the cohesion apparatus. Studies in Drosophila suggest that effects on gene expression are most likely responsible for developmental alterations in CdLS. Effects on chromatid cohesion are apparent in RBS/SC syndrome, but data from yeast and Drosophila point to the likelihood that changes in expression of genes located in heterochromatin could contribute to the developmental deficits. PMID:16819604

Assessment of drug induced genotoxicity in gastric cancer patients ...

African Journals Online (AJOL)

Cytogenetic studies were carried out in peripheral blood lymphocytes of study population by adopting standard cytogenetic protocols such as (a) chromosomal aberrations (CA) and (b) sister chromatid exchanges (SCE). Student t- test was adopted to analyze the statistical significance. An increased pattern in the frequency ...

INDUCTION OF DNA STRAND BREAKS BY TRIHALOMETHANES IN PRIMARY HUMAN LUNG EPITHELIAL CELLS

Science.gov (United States)

Abstract Trihalomethanes (TEMs) are disinfection by-products and suspected human carcinogens present in chlorinated drinking water. Previous studies have shown that many THMs induce sister chromatid exchanges and DNA strand breaks in human peripheral blood lymphocyte...

Biomonitoring of genotoxic risk in radar facility workers: comparison of the comet assay with micronucleus assay and chromatid breakage assay

International Nuclear Information System (INIS)

Garaj-Vrhovac, V.; Kopjar, N.

2003-01-01

Genotoxic risks of occupational exposure in a radar facility were evaluated by using alkaline comet assay, micronucleus assay and chromatid breakage assay on peripheral blood leukocytes in exposed subjects and corresponding controls. Results show that occupational exposure to microwave radiation correlates with an increase of genome damage in somatic cells. The levels of DNA damage in exposed subjects determined by using alkaline comet assay were increased compared to control and showed interindividual variations. Incidence of micronuclei was also significantly increased compared to baseline control values. After short exposure of cultured lymphocytes to bleomycin, cells of occupationally exposed subjects responded with high numbers of chromatid breaks. Although the level of chromosome damage generated by bleomycin varied greatly between individuals, in exposed subjects a significantly elevated number of chromatid breaks was observed. Our results support data reported in literature indicating that microwave radiation represents a potential DNA-damaging hazard. Alkaline comet assay is confirmed as a sensitive and highly reproducible technique for detection of primary DNA damage inflicted in somatic cells. Micronucleus assay was confirmed as reliable bio-markers of effect and chromatid breakage assay as sensitive bio-marker of individual cancer susceptibility. The results obtained also confirm the necessity to improve measures and to perform accurate health surveillance of individuals occupationally exposed to microwave radiation

A CO-FISH assay to assess sister chromatid segregation patterns in mitosis of mouse embryonic stem cells.

Science.gov (United States)

Sauer, Stephan; Burkett, Sandra S; Lewandoski, Mark; Klar, Amar J S

2013-05-01

Sister chromatids contain identical DNA sequence but are chiral with respect to both their helical handedness and their replication history. Emerging evidence from various model organisms suggests that certain stem cells segregate sister chromatids nonrandomly to either maintain genome integrity or to bias cellular differentiation in asymmetric cell divisions. Conventional methods for tracing of old vs. newly synthesized DNA strands generally lack resolution for individual chromosomes and employ halogenated thymidine analogs with profound cytotoxic effects on rapidly dividing cells. Here, we present a modified chromosome orientation fluorescence in situ hybridization (CO-FISH) assay, where identification of individual chromosomes and their replication history is achieved in subsequent hybridization steps with chromosome-specific DNA probes and PNA telomere probes. Importantly, we tackle the issue of BrdU cytotoxicity and show that our method is compatible with normal mouse ES cell biology, unlike a recently published related protocol. Results from our CO-FISH assay show that mitotic segregation of mouse chromosome 7 is random in ES cells, which contrasts previously published results from our laboratory and settles a controversy. Our straightforward protocol represents a useful resource for future studies on chromatid segregation patterns of in vitro-cultured cells from distinct model organisms.

Relationship of the demethylation of the DNA with the induction of the sister chromatid exchanges (SCE) In vivo; Relacion de la desmetilacion del ADN con la induccion de intercambios en las cromatidas hermanas (ICH) In vivo

Energy Technology Data Exchange (ETDEWEB)

Toribio E, E

2005-07-01

The methylation of the DNA is an epigenetic modification that has an important paper in the regulation of the functionality of the genome of the organisms. It can be altered by demethylation processes, either natural or experimentally induced. The 5-azacytidine (Aza) is a compound that causes the demethylation of the DNA (dm-DNA), inducing with it, expression genic and increase in the frequency of the Sister Chromatid Exchange (SCE). The SCE is a genotoxicity indicator, caused by diverse mutagens and carcinogen. Since the biological meaning and the formation mechanism of this phenomenon has not been totally illustrious, the exploration of the relation between the dm-DNA and the induction of SCE, it could offer new knowledge to explain those queries. The purpose of this work was to study in cells of the mouse bone marrow In vivo, the effect of the Aza on the induction of SCE, based on two aspects: 1) dose answer and 2) the effectiveness of multiple exhibition. To six groups of three to five animals, they are administered Aza to dose of 5, 10, 15 or 20 mg/Kg of weight; in sharp or multiple form, previously to the bromodeoxyuridine supply and 24 h was sacrificed after this; 2 h after an injection with colchicine. Preparations of those metaphases were made, those which were dyed by means of a technique of fluorescence more Giemsa. It was observed that to sharp low dose, the Aza produced an increment in the frequency of SCE that although small it was proportional and statistically significant. To sharp and multiple high doses, the Aza doesn't cause additional increments of SCE, but if toxicity at cellular level and of individuals. It is concluded that a relationship exists between the dm-DNA and the induction of SCE. It is suggested that the total demethylation of the DNA causes 2 SCE/Cell in cells of the mouse bone marrow, or that the cytotoxicity prevents to evidence a bigger induction. (Author)

Relationship of the demethylation of the DNA with the induction of the sister chromatid exchanges (SCE) In vivo; Relacion de la desmetilacion del ADN con la induccion de intercambios en las cromatidas hermanas (ICH) In vivo

Energy Technology Data Exchange (ETDEWEB)

Toribio E, E

2005-07-01

The methylation of the DNA is an epigenetic modification that has an important paper in the regulation of the functionality of the genome of the organisms. It can be altered by demethylation processes, either natural or experimentally induced. The 5-azacytidine (Aza) is a compound that causes the demethylation of the DNA (dm-DNA), inducing with it, expression genic and increase in the frequency of the Sister Chromatid Exchange (SCE). The SCE is a genotoxicity indicator, caused by diverse mutagens and carcinogen. Since the biological meaning and the formation mechanism of this phenomenon has not been totally illustrious, the exploration of the relation between the dm-DNA and the induction of SCE, it could offer new knowledge to explain those queries. The purpose of this work was to study in cells of the mouse bone marrow In vivo, the effect of the Aza on the induction of SCE, based on two aspects: 1) dose answer and 2) the effectiveness of multiple exhibition. To six groups of three to five animals, they are administered Aza to dose of 5, 10, 15 or 20 mg/Kg of weight; in sharp or multiple form, previously to the bromodeoxyuridine supply and 24 h was sacrificed after this; 2 h after an injection with colchicine. Preparations of those metaphases were made, those which were dyed by means of a technique of fluorescence more Giemsa. It was observed that to sharp low dose, the Aza produced an increment in the frequency of SCE that although small it was proportional and statistically significant. To sharp and multiple high doses, the Aza doesn't cause additional increments of SCE, but if toxicity at cellular level and of individuals. It is concluded that a relationship exists between the dm-DNA and the induction of SCE. It is suggested that the total demethylation of the DNA causes 2 SCE/Cell in cells of the mouse bone marrow, or that the cytotoxicity prevents to evidence a bigger induction. (Author)

Metazoan Scc4 homologs link sister chromatid cohesion to cell and axon migration guidance

NARCIS (Netherlands)

V.C. Seitan (Vlad); P.A. Banks (Peter); S. Laval (Steve); N.A. Majid (Nazia); D. Dorsett (Dale); A. Rana (Amer); J. Smith (Jeremy); A. Bateman (Alex); S. Krpic (Sanja); A. Hostert (Arnd); S.M. Rollins; H. Erdjument-Bromage (Hediye); P. Tempst (Paul); C.Y. Benard (Claire); S. Hekimi (Siegfried); S.F. Newbury (Sarah); T. Strachan (Tom)

2006-01-01

textabstractSaccharomyces cerevisiae Scc2 binds Scc4 to form an essential complex that loads cohesin onto chromosomes. The prevalence of Scc2 orthologs in eukaryotes emphasizes a conserved role in regulating sister chromatid cohesion, but homologs of Scc4 have not hitherto been identified outside

The time-dependence of exchange-induced relaxation during modulated radio frequency pulses.

Science.gov (United States)

Sorce, Dennis J; Michaeli, Shalom; Garwood, Michael

2006-03-01

The problem of the relaxation of identical spins 1/2 induced by chemical exchange between spins with different chemical shifts in the presence of time-dependent RF irradiation (in the first rotating frame) is considered for the fast exchange regime. The solution for the time evolution under the chemical exchange Hamiltonian in the tilted doubly rotating frame (TDRF) is presented. Detailed derivation is specified to the case of a two-site chemical exchange system with complete randomization between jumps of the exchanging spins. The derived theory can be applied to describe the modulation of the chemical exchange relaxation rate constants when using a train of adiabatic pulses, such as the hyperbolic secant pulse. Theory presented is valid for quantification of the exchange-induced time-dependent rotating frame longitudinal T1rho,ex and transverse T2rho,ex relaxations in the fast chemical exchange regime.

Adaptive response induced by low concentrations of MMC in human peripheral lymphocytes

International Nuclear Information System (INIS)

Sun Shuqing; Wang Bin; Jiang Jie

1998-01-01

Samples of cultured human peripheral lymphocytes were pre-treated with mitomycin C (MMC) in concentrations of 0.01∼0.1 μg/mL at 34 h of incubation and then exposed to 1.5 Gy of X-rays. Chromosome aberrations, sister chromatid exchanges and micronuclei for these lymphocytes were observed. The results show that the chromosome aberration rates for lymphocytes pre-treated with MMC in concentrations of 0.5 and 0.075 μg/mL and the frequencies of sister chromatid exchanges for lymphocytes pre-treated with MMC in concentrations of 0.01 μg/mL were significantly lower than their own expected values but the rates of micronuclei for lymphocytes pre-treated with MMC in concentrations of 0.05, 0.075 and 0.1 μg/mL were significantly higher than the expected values. Such results suggest that for studying the cross resistance of lymphocytes to chemicals and ionizing radiation, inconsistent conclusions may be obtained if different endpoints are based on

Dipole-induced exchange bias.

Science.gov (United States)

Torres, Felipe; Morales, Rafael; Schuller, Ivan K; Kiwi, Miguel

2017-11-09

The discovery of dipole-induced exchange bias (EB), switching from negative to positive sign, is reported in systems where the antiferromagnet and the ferromagnet are separated by a paramagnetic spacer (AFM-PM-FM). The magnitude and sign of the EB is determined by the cooling field strength and the PM thickness. The same cooling field yields negative EB for thin spacers, and positive EB for thicker ones. The EB decay profile as a function of the spacer thickness, and the change of sign, are attributed to long-ranged dipole coupling. Our model, which accounts quantitatively for the experimental results, ignores the short range interfacial exchange interactions of the usual EB theories. Instead, it retains solely the long range dipole field that allows for the coupling of the FM and AFM across the PM spacer. The experiments allow for novel switching capabilities of long range EB systems, while the theory allows description of the structures where the FM and AFM are not in atomic contact. The results provide a new approach to design novel interacting heterostructures.

UDS and SCE in lymphocytes of persons occupationally exposed to low levels of ionizing radiation

International Nuclear Information System (INIS)

Tuschl, H.; Kovac, R.; Altmann, H.

1983-03-01

Unscheduled DNA synthesis induced by 'in vitro' UV-irradiation was investigated in lymphocytes of persons occupationally exposed to low doses of ionizing radiation (maximum registered radiation dose: 98 mrad/month). For radiation exposures >14 mrad/month, above background level, increased rates of UDS after in vitro UV-irradiation of lymphocytes were found. The bromodeoxyuridine differential chromatid labeling technique was applied to the examination of spontaneous and mytomycin C induced sister chromatid exchanges in the same population. No statistically significant difference could be determined in spontaneously occurring SCEs, while MMC induced SCEs were significantly reduced in persons exposed to radiation doses >14 mrad/month, thus indicating increased repair capability for DNA lesions inflicted by a second insult after protracted low dose irradiation. (Author) [de

The frequency of chromatide aberrations as a function of radiation dose estimated by the number of dicentrics found by the cytogenetic analysis of lymphocytes in subjects affected by the Chernobyl accident

International Nuclear Information System (INIS)

Nugis, V.Yu.; Chirkov, A.A.

1990-01-01

A study was made of the frequency of chromatide aberrations in lymphocyte culture of subjects affected by the Chernobyl accident as a function of dose estimated by the incidence of dicentrics. The average number of chromatide aberrations was nearly the same within the dose range from 0 to 5 Gy exhibiting a tendency towards growth with dose. A high individual variability of the chromatide aberration frequency was observed

Chromatin Structure and Radiation-Induced Intrachromosome Exchange

Science.gov (United States)

Mangala; Zhang, Ye; Hada, Megumi; Cucinotta, Francis A.; Wu, Honglu

2011-01-01

We have recently investigated the location of breaks involved in intrachromosomal type exchange events, using the multicolor banding in situ hybridization (mBAND) technique for human chromosome 3. In human epithelial cells exposed to both low- and high-LET radiations in vitro, intrachromosome exchanges were found to occur preferentially between a break in the 3p21 and one in the 3q11. Exchanges were also observed between a break in 3p21 and one in 3q26, but few exchanges were observed between breaks in 3q11 and 3q26, even though the two regions were on the same arm of the chromosome. To explore the relationships between intrachromosome exchanges and chromatin structure, we used probes that hybridize the three regions of 3p21, 3q11 and 3q26, and measured the distance between two of the three regions in interphase cells. We further analyzed fragile sites on the chromosome that have been identified in various types of cancers. Our results demonstrated that the distribution of breaks involved in radiation-induced intrachromosome aberrations depends upon both the location of fragile sites and the folding of chromatins

Biochemical evidence for deficient DNA repair leading to enhanced G2 chromatid radiosensitivity and susceptibility to cancer

International Nuclear Information System (INIS)

Gantt, R.; Parshad, R.; Price, F.M.; Sanford, K.K.

1986-01-01

Human tumor cells and cells from cancer-prone individuals, compared with those from normal individuals, show a significantly higher incidence of chromatid breaks and gaps seen in metaphase cells immediately after G2 X irradiation. Previous studies with DNA repair-deficient mutants and DNA repair inhibitors strongly indicate that the enhancement results from a G2 deficiency(ies) in DNA repair. We report here biochemical evidence for a DNA repair deficiency that correlates with the cytogenetic studies. In the alkaline elution technique, after a pulse label with radioactive thymidine in the presence of 3-acetylaminobenzamide (a G2-phase blocker) and X irradiation, DNA from tumor or cancer-prone cells elutes more rapidly during the postirradiation period than that from normal cells. These results indicate that the DNA of tumor and cancer-prone cells either repairs more slowly or acquires more breaks than that of normal cells; breaks can accumulate during incomplete or deficient repair processes. The kinetic difference between normal and tumor or cancer-prone cells in DNA strand-break repair reaches a maximum within 2 h, and this maximum corresponds to the kinetic difference in chromatid aberration incidence following X irradiation reported previously. These findings support the concept that cells showing enhanced G2 chromatid radiosensitivity are deficient in DNA repair. The findings could also lead to a biochemical assay for cancer susceptibility

Development of Design Criteria for Fluid Induced Structural Vibrations in Steam Generators and Heat Exchangers

International Nuclear Information System (INIS)

Uvan Catton; Dhir, Vijay K.; Deepanjan Mitra; Omar Alquaddoomi; Pierangelo Adinolfi

2004-01-01

Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers

Adaptive response induced by occupational exposures to ionizing radiation

International Nuclear Information System (INIS)

Barquinero, J.F.; Caballin, M.R.; Barrios, L.; Murtra, P.; Egozcue, J.; Miro, R.; Ribas, M.

1997-01-01

We have found a significant decreased sensitivity to the cytogenetic effects of ionizing radiation (IR) and bleomycin (BLM) in lymphocytes from individuals occupationally exposed to IR when compared with a control population. These results suggest that occupational exposures to IR can induce adaptive response that can be detected by a subsequent treatment by IR or by BLM. However, no correlation between the results obtained with both treatments was observed. A great heterogeneity in the frequencies of chromatid aberrations induced by BLM was observed. The study of the influence of different harvesting times showed that there was no correlation with the frequencies of chromatid breaks. Our results indicate that the use of BLM to detect adaptive response has several difficulties at the individual level. (author)

Repair of chromosome damage induced by X-irradiation during G2 phase in a line of normal human fibroblasts and its malignant derivative

International Nuclear Information System (INIS)

Parshad, R.; Gantt, R.; Sanford, K.K.; Jones, G.M.; Tarone, R.E.

1982-01-01

A line of normal human skin fibroblasts (KD) differed from its malignant derivative (HUT-14) in the extent of cytogenetic damage induced by X-irradiation during G2 phase. Malignant cells had significantly more chromatid breaks and gaps after exposure to 25, 50, or 100 rad. The gaps may represent single-strand breaks. Results from alkaline elution of cellular DNA immediately after irradiation showed that the normal and malignant cells in asynchronous population were equally sensitive to DNA single-strand breakage by X-irradiation. Caffeine or beta-cytosine arabinoside (ara-C), inhibitors of DNA repair, when added directly following G2 phase exposure, significantly increased the incidence of radiation-induced chromatid damage in the normal cells. In contrast, similar treatment of the malignant cells had little influence. Ara-C differed from caffeine in its effects; whereas both agents increased the frequency of chromatid breaks and gaps, only ara-C increased the frequency of gaps to the level observed in the irradiated malignant cells. Addition of catalase, a scavenger of the derivative free hydroxyl radical (.OH), to the cultures of malignant cells before, during, and following irradiation significantly reduced the chromatid damage; and catalase prevented formation of chromatid gaps. The DNA damage induced by X-ray during G2 phase in the normal KD cells was apparently repaired by a caffeine- and ara-C-sensitive mechanism(s) that was deficient or absent in their malignant derivatives

Repair of chromosome damage induced by X-irradiation during G2 phase in a line of normal human fibroblasts and its malignant derivative

International Nuclear Information System (INIS)

Parshad, R.; Gantt, R.; Sanford, K.K.; Jones, G.M.; Tarone, R.E.

1982-01-01

A line of normal human skin fibroblasts (KD) differed from its malignant derivative (HUT-14) in the extent of cytogenetic damage induced by X-irradiation during G 2 phase. Malignant cells had significantly more chromatid breaks and gaps after exposure to 25, 50, or 100 rad. Results from alkaline elution of cellular DNA immediately after irradiation showed that the normal and malignant cells in asynchronous population were equally sensitive to DNA single-strand breakage by X-irradiation. Caffeine or #betta#-cytosine arabinoside (ara-C), inhibitors of DNA repair, when added directly following G 2 phase exposure, significantly increased the incidence of radiation-induced chromatid damage in the normal cells. In contrast, similar treatment of the malignant cells had little influence. Ara-C differed from caffeine in its effects; whereas both agents increased the frequency of chromatid breaks and gaps, only ara-C increased the frequency of gaps to the level observed in the irradiated malignant cells. Addition of catalase, which destroys H 2 O 2 , or mannitol, a scavenger of the derivative free hydroxyl radical (.OH), to the cultures of malignant cells before, during, and following irradiation significantly reduced the chromatid damage; and catalase prevented formation of chromatid gaps. The DNA damage induced by X-ray during G 2 phase in the normal KD cells was apparently repaired by a caffeine- and ara-C-sensitive mechanism(s) that was deficient or absent in their malignant derivatives

Flow-induced vibration analysis of heat exchanger and steam generator designs

International Nuclear Information System (INIS)

Pettigrew, M.J.; Sylvestre, Y.; Campagna, A.O.

1977-08-01

Tube and shell heat exchange components such as steam generators, heat exchangers and condensers are essential parts of CANDU nuclear power stations. Excessive flow-induced vibration may cause tube failures by fatigue or more likely by fretting-wear. Such failures may lead to station shutdowns that are very undesirable in terms of lost production. Hence good performance and reliability dictate a thorough flow-induced vibration analysis at the design stage. This paper presents our approach and techniques in this respect. (author)

Studies on chromosome aberrations induced in human lymphocytes by very low-dose exposure to tritium

International Nuclear Information System (INIS)

Hori, T.; Moriya, Junko; Nakai, Sayaka

1978-01-01

Assessment of potential hazard from environmental tritium to man becomes very important with increasing the development of nuclear-power industry. However, little data are available as to the determination on the genetic effect of tritium especially at the low levels. The object of the present study is to obtain quantitative data for chromosome aberrations in human lymphocytes, as an indicator for genetic risk estimation, induced by tritium at very low dose levels. Leukocyte cultures of human peripheral blood were chronically exposed for 48h to tritiated water and 3 H-thymidine using a wide range of tritium doses, and aberrations in lymphocyte chromosomes at the first metaphases were examined. In the experimental conditions, the types of aberrations induced by radiation emitted from both tritiated water and 3 H-thymidine were mostly chromatid types, such as chromatid gaps and deletions. The dose-response relations for chromatid breaks per cell exhibited unusual dose-dependency in both cases. It was demonstrated that at higher dose range the yields of chromatid breaks increased linearly with dose, while those at lower dose range were significantly higher than would be expected by a downward extraporation from the linear relation. Partial-hit or partial-target kinetics events appeared at very low dose exposure. (author)

UBL5 is essential for pre-mRNA splicing and sister chromatid cohesion in human cells

DEFF Research Database (Denmark)

Oka, Yasuyoshi; Varmark, Hanne; Vitting-Seerup, Kristoffer

2014-01-01

UBL5 is an atypical ubiquitin-like protein, whose function in metazoans remains largely unexplored. We show that UBL5 is required for sister chromatid cohesion maintenance in human cells. UBL5 primarily associates with spliceosomal proteins, and UBL5 depletion decreases pre-mRNA splicing efficien...

Influence of ion bombardment induced patterning of exchange bias in pinned artificial ferrimagnets on the interlayer exchange coupling

Energy Technology Data Exchange (ETDEWEB)

Schmalhorst, Jan; Reiss, Guenter; Hoenik, V. [Thin Films and Nanostructures, Department of Physics, Univ. Bielefeld (Germany); Weis, Tanja; Engel, Dieter; Ehresmann, Arno [Institute of Physics and Center for Interdisciplinary Nanostructure Science and Technology, Kassel Univ. (Germany)

2007-07-01

Artificial ferrimagnets (AFi) have many applications as, e.g., pinned reference electrodes in magnetic tunnel junctions. It is known that the application of ion bombardment induced magnetic patterning with He ions on a single layer reference electrode of magnetic tunnel junctions is possible. For some applications a combination of ion bombardment induced magnetic patterning and artificial ferrimagnets as a reference electrode is desirable. The effect of ion bombardment induced magnetic patterning on pinned artificial ferrimagnets with a Ru interlayer which is frequently used in magnetic tunnel junctions as well as pinned AFis with a Cu interlayer has been tested. Special attention has been given to the question whether the antiferromagnetic interlayer exchange coupling can withstand the ion dose necessary to turn the exchange bias.

Andrographia paniculata a Miracle Herbs for cancer treatment: In ...

African Journals Online (AJOL)

It is extensively used as home remedy for various diseases in Indian traditional system ... Aim: In our present work, extracts of these ayurvedic plants were tested for their ... and anticarcinogenic properties against Aflatoxin B1 induced toxicity. ... (CA), sister chromatid exchanges (SCEs) and cell growth kinetics (RI) both in the ...

Repairability during G1 of the inductor leisure of exchanges in the sister chromatid induced by alkylating agents in DNA substituted and no substituted with BUDR, in cells of the salivary gland of mouse In vivo; Reparabilidad durante G1 de las lesiones inductoras de intercambios en las cromatidas hermanas inducidos por agentes alquilantes en ADN sustituido y no sustituido con BrdU, en celulas de la glandula salival de raton In vivo

Energy Technology Data Exchange (ETDEWEB)

Gonzalez B, F

2004-07-01

In this work you determines the repair of the lesions inductoras of Sister chromatid exchange (ICHs) generated in the cells of the salivary gland of mouse, for the treatment with the N-Methyl-N-Nitrosourea (MNU), the N-Ethyl-N-Nitrosourea (ENU), the Methyl methanesulfonate (MMS) and the Ethyl methanesulfonate (EMS) in early and slow G1 of the first one and the second cellular division, that is to say before and after the cells incorporate 5-bromine-2 -Desoxyuridine (BrdU) in the DNA. Groups witness non treaties were included with mutagen. The cells of the salivary gland repaired the generated lesions partially by the MNU, the MMS and the EMS in the 1st division, and only the lesions induced by the ENU and MMS were repaired partially in the 2nd division. The ENU generates injure that they were not repaired in the 1st division and those taken place by the EMS were little repaired in the 2nd division. The methylating agents generated but ICHs that the ethylating. One observes that the BrdU makes to the molecule of the DNA but susceptible to the damage generated by the alkylating agents that induce the formation of the ICHs. This susceptibility was incremented around 150% for the treatment with the MNU, the ENU and the MMS, on the other hand for the EMS it was 3 times minor. It is proposed that the one electronegative atom of this analog of the timine would to work as a nucleophyllic center with which the electrophyllic compounds react. (Author)

Sister chromatid exchanges and high-frequency cells in men environmentally and occupationally exposed to ambient air pollutants. An intergroup comparison with respect to seasonal changes and smoking habit

Energy Technology Data Exchange (ETDEWEB)

Pendzich, Joanna; Motykiewicz, Grazyna; Michalska, Jadwiga; Kostowska, Alina; Chorazy, Mieczyslaw [Department of Tumor Biology, Institute of Oncology, Gliwice (Poland); Wang, Li You [Graduate Institute of Epidemiology, College of Public Health, National Taiwan University, Taipei (Taiwan, Province of China)

1997-11-28

Sister chromatid exchanges (SCE) and high-frequency cells (HFC) were measured in peripheral blood lymphocytes from men environmentally and occupationally exposed to a mixture of ambient air pollutants. The environmentally exposed individuals were inhabitants of the industrial region of Upper Silesia; those occupationally exposed were Silesian cokery or steel plant workers, while the control group consisted of rural region residents. A total of 147 males were enrolled in the study. Blood samples were collected in winter (February) and summer (September) seasons. Three major areas were investigated during the study: exposure-based dose dependency, seasonal changes, and influence of smoking habits on the SCE frequencies. The latter is frequently reported as a confounding factor in SCE analyses. In both winter and summer samples, statistically significant increases of SCE were observed in the environmentally and occupationally exposed groups compared to the controls (p<0.001). The difference between both exposed groups was also significant (p<0.001). An intergroup comparison was based on ANOVA after adjustment for smoking status. In all three groups of interest, a seasonal variation was found with higher levels in winter. However, in a part of the study in which each donor served as his own control, statistical differences were only found within the exposed groups. Control region inhabitants did not have significantly higher frequencies of SCE in winter, compared to summer samples. The impact of two major confounders, age of the donor and smoking habit, was investigated by multiple regression analysis. Smoking was a major factor influencing the level of SCE. Nevertheless, the effect was seen in winter samples only, which suggests an additive response and adds new information to this known effect

Analysis of flow induced vibration in heat exchangers

International Nuclear Information System (INIS)

Beek, A.W. van

1977-01-01

A description will be given of three different types of heat exchangers developed by the Dutch Nuclear Industry Group ''Neratoom'' in cooperation with TNO for the sodium-cooled fast breeder reactor SNR-300 at Kalkar. Moreover, the research related with flow induced vibrations carried out by TNO (Organization for Applied Scientific Research) will be presented. The flow induced forces on the tubes of the straight-tube steam generators were measured at the inlet and outlet section where partial crossflow occurs. With the measured flow induced forces the response of a tube was calculated as a function of the tube-to-supportbush clearances taking into account the non-linear damping effects from the sodium. The theoretical results showed that for this particular design no tube impact damage is to be expected which was confirmed later by a full scale experiment. Special attention will be devoted to the steam generator with helical-coil tube-bundles, where the sodium flows in a counter cross-flow over the tube-bundle. Extensive measurements of the power spectra of the flow induced forces were carried out since no information could be found in the literature. The vibration analysis will be presented and vibration modes of the entire bundle will be compared with experimentally obtained results. Finally a description of the vibration tests to be carried out on the intermediate heat exchanger (IHX) will be presented. (author)

Analysis of flow induced vibration in heat exchangers

Energy Technology Data Exchange (ETDEWEB)

Beek, A.W. van [Institute for Mechanical Constructions TNO, Delft (Netherlands)

1977-12-01

A description will be given of three different types of heat exchangers developed by the Dutch Nuclear Industry Group ''Neratoom'' in cooperation with TNO for the sodium-cooled fast breeder reactor SNR-300 at Kalkar. Moreover, the research related with flow induced vibrations carried out by TNO (Organization for Applied Scientific Research) will be presented. The flow induced forces on the tubes of the straight-tube steam generators were measured at the inlet and outlet section where partial crossflow occurs. With the measured flow induced forces the response of a tube was calculated as a function of the tube-to-supportbush clearances taking into account the non-linear damping effects from the sodium. The theoretical results showed that for this particular design no tube impact damage is to be expected which was confirmed later by a full scale experiment. Special attention will be devoted to the steam generator with helical-coil tube-bundles, where the sodium flows in a counter cross-flow over the tube-bundle. Extensive measurements of the power spectra of the flow induced forces were carried out since no information could be found in the literature. The vibration analysis will be presented and vibration modes of the entire bundle will be compared with experimentally obtained results. Finally a description of the vibration tests to be carried out on the intermediate heat exchanger (IHX) will be presented. (author)

Sister chromatid cohesion defects are associated with chromosome instability in Hodgkin lymphoma cells

International Nuclear Information System (INIS)

Sajesh, Babu V; Lichtensztejn, Zelda; McManus, Kirk J

2013-01-01

Chromosome instability manifests as an abnormal chromosome complement and is a pathogenic event in cancer. Although a correlation between abnormal chromosome numbers and cancer exist, the underlying mechanisms that cause chromosome instability are poorly understood. Recent data suggests that aberrant sister chromatid cohesion causes chromosome instability and thus contributes to the development of cancer. Cohesion normally functions by tethering nascently synthesized chromatids together to prevent premature segregation and thus chromosome instability. Although the prevalence of aberrant cohesion has been reported for some solid tumors, its prevalence within liquid tumors is unknown. Consequently, the current study was undertaken to evaluate aberrant cohesion within Hodgkin lymphoma, a lymphoid malignancy that frequently exhibits chromosome instability. Using established cytogenetic techniques, the prevalence of chromosome instability and aberrant cohesion was examined within mitotic spreads generated from five commonly employed Hodgkin lymphoma cell lines (L-1236, KM-H2, L-428, L-540 and HDLM-2) and a lymphocyte control. Indirect immunofluorescence and Western blot analyses were performed to evaluate the localization and expression of six critical proteins involved in the regulation of sister chromatid cohesion. We first confirmed that all five Hodgkin lymphoma cell lines exhibited chromosome instability relative to the lymphocyte control. We then determined that each Hodgkin lymphoma cell line exhibited cohesion defects that were subsequently classified into mild, moderate or severe categories. Surprisingly, ~50% of the mitotic spreads generated from L-540 and HDLM-2 harbored cohesion defects. To gain mechanistic insight into the underlying cause of the aberrant cohesion we examined the localization and expression of six critical proteins involved in cohesion. Although all proteins produced the expected nuclear localization pattern, striking differences in RAD21

Phonic and induced level of mutations and mutagenicity in bioorganisms habitating in the environs of Ignalina APP

International Nuclear Information System (INIS)

Lekevichius, R.; Morkunas, V.; Knabikas, A.

1992-01-01

The investigation of the extracts from the water, mud and hydrobionts of the lake Drukshiai before the construction of the Ignalina atomic power plant (1982-1984) and after its construction enabled to detect the moment of the build-up of mutagens in the hydrobionts (in 1986), when the extracts began to induce spot mutations in Salmonella typhimurium and exchanges of sister chromatids in human leukocytes in vitro. The mutagenicity of rain water, sewerage water and water from the cooler of the atomic power plant to drosophila and Salmonella typhimurium has been detected. The increments of mutations in the populations of Larus ridibundus and Microtus arvalis inhabiting the surroundings of the atomic power plant has not been noticed. (author). 4 figs., 4 refs

RPA Mediates Recruitment of MRX to Forks and Double-Strand Breaks to Hold Sister Chromatids Together.

Science.gov (United States)

Seeber, Andrew; Hegnauer, Anna Maria; Hustedt, Nicole; Deshpande, Ishan; Poli, Jérôme; Eglinger, Jan; Pasero, Philippe; Gut, Heinz; Shinohara, Miki; Hopfner, Karl-Peter; Shimada, Kenji; Gasser, Susan M

2016-12-01

The Mre11-Rad50-Xrs2 (MRX) complex is related to SMC complexes that form rings capable of holding two distinct DNA strands together. MRX functions at stalled replication forks and double-strand breaks (DSBs). A mutation in the N-terminal OB fold of the 70 kDa subunit of yeast replication protein A, rfa1-t11, abrogates MRX recruitment to both types of DNA damage. The rfa1 mutation is functionally epistatic with loss of any of the MRX subunits for survival of replication fork stress or DSB recovery, although it does not compromise end-resection. High-resolution imaging shows that either the rfa1-t11 or the rad50Δ mutation lets stalled replication forks collapse and allows the separation not only of opposing ends but of sister chromatids at breaks. Given that cohesin loss does not provoke visible sister separation as long as the RPA-MRX contacts are intact, we conclude that MRX also serves as a structural linchpin holding sister chromatids together at breaks. Copyright © 2016 Elsevier Inc. All rights reserved.

Development of Design Criteria for Fluid Induced Structural Vibrations in Steam Generators and Heat Exchangers

International Nuclear Information System (INIS)

Catton, Ivan; Dhir, Vijay K.; Alquaddoomi, O.S.; Mitra, Deepanjan; Adinolfi, Pierangelo

2004-01-01

OAK-B135 Flow-induced vibration in heat exchangers has been a major cause of concern in the nuclear industry for several decades. Many incidents of failure of heat exchangers due to apparent flow-induced vibration have been reported through the USNRC incident reporting system. Almost all heat exchangers have to deal with this problem during their operation. The phenomenon has been studied since the 1970s and the database of experimental studies on flow-induced vibration is constantly updated with new findings and improved design criteria for heat exchangers. In the nuclear industry, steam generators are often affected by this problem. However, flow-induced vibration is not limited to nuclear power plants, but to any type of heat exchanger used in many industrial applications such as chemical processing, refrigeration and air conditioning. Specifically, shell and tube type heat exchangers experience flow-induced vibration due to the high velocity flow over the tube banks. Flow-induced vibration in these heat exchangers leads to equipment breakdown and hence expensive repair and process shutdown. The goal of this research is to provide accurate measurements that can help modelers to validate their models using the measured experimental parameters and thereby develop better design criteria for avoiding fluid-elastic instability in heat exchangers. The research is divided between two primary experimental efforts, the first conducted using water alone (single phase) and the second using a mixture of air or steam and water as the working fluid (two phase). The outline of this report is as follows: After the introduction to fluid-elastic instability, the experimental apparatus constructed to conduct the experiments is described in Chapter 2 along with the measurement procedures. Chapter 3 presents results obtained on the tube array and the flow loop, as well as techniques used in data processing. The project performance is described and evaluated in Chapter 4 followed by

Chiasmata promote monopolar attachment of sister chromatids and their co-segregation toward the proper pole during meiosis I.

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Yukinobu Hirose

2011-03-01

Full Text Available The chiasma is a structure that forms between a pair of homologous chromosomes by crossover recombination and physically links the homologous chromosomes during meiosis. Chiasmata are essential for the attachment of the homologous chromosomes to opposite spindle poles (bipolar attachment and their subsequent segregation to the opposite poles during meiosis I. However, the overall function of chiasmata during meiosis is not fully understood. Here, we show that chiasmata also play a crucial role in the attachment of sister chromatids to the same spindle pole and in their co-segregation during meiosis I in fission yeast. Analysis of cells lacking chiasmata and the cohesin protector Sgo1 showed that loss of chiasmata causes frequent bipolar attachment of sister chromatids during anaphase. Furthermore, high time-resolution analysis of centromere dynamics in various types of chiasmate and achiasmate cells, including those lacking the DNA replication checkpoint factor Mrc1 or the meiotic centromere protein Moa1, showed the following three outcomes: (i during the pre-anaphase stage, the bipolar attachment of sister chromatids occurs irrespective of chiasma formation; (ii the chiasma contributes to the elimination of the pre-anaphase bipolar attachment; and (iii when the bipolar attachment remains during anaphase, the chiasmata generate a bias toward the proper pole during poleward chromosome pulling that results in appropriate chromosome segregation. Based on these results, we propose that chiasmata play a pivotal role in the selection of proper attachments and provide a backup mechanism that promotes correct chromosome segregation when improper attachments remain during anaphase I.

Variations in dysfunction of sister chromatid cohesion in esco2 mutant zebrafish reflect the phenotypic diversity of Roberts syndrome

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Stefanie M. Percival

2015-08-01

Full Text Available Mutations in ESCO2, one of two establishment of cohesion factors necessary for proper sister chromatid cohesion (SCC, cause a spectrum of developmental defects in the autosomal-recessive disorder Roberts syndrome (RBS, warranting in vivo analysis of the consequence of cohesion dysfunction. Through a genetic screen in zebrafish targeting embryonic-lethal mutants that have increased genomic instability, we have identified an esco2 mutant zebrafish. Utilizing the natural transparency of zebrafish embryos, we have developed a novel technique to observe chromosome dynamics within a single cell during mitosis in a live vertebrate embryo. Within esco2 mutant embryos, we observed premature chromatid separation, a unique chromosome scattering, prolonged mitotic delay, and genomic instability in the form of anaphase bridges and micronuclei formation. Cytogenetic studies indicated complete chromatid separation and high levels of aneuploidy within mutant embryos. Amongst aneuploid spreads, we predominantly observed decreases in chromosome number, suggesting that either cells with micronuclei or micronuclei themselves are eliminated. We also demonstrated that the genomic instability leads to p53-dependent neural tube apoptosis. Surprisingly, although many cells required Esco2 to establish cohesion, 10-20% of cells had only weakened cohesion in the absence of Esco2, suggesting that compensatory cohesion mechanisms exist in these cells that undergo a normal mitotic division. These studies provide a unique in vivo vertebrate view of the mitotic defects and consequences of cohesion establishment loss, and they provide a compensation-based model to explain the RBS phenotypes.

Evaluation of cytogenetic effects of very short laser pulsed radiations

International Nuclear Information System (INIS)

Guedeney, G.; Courant, D.; Malarbet, J.-L.; Dolloy, M.-T.; Court, L.

1992-01-01

The aim of this study is to evaluate the capacity of a laser, delivering very short pulses in the near infrared spectrum with a high pulse ratio frequency, to induce genetic modification on biological tissues. Chromatid exchanges and chromosomal aberrations studies are used to test potential effect on human lymphocytes. The laser irradiation induces a significant increase of acentric fragments but the absence of dicentric suggests that a repetitive very short pulses irradiation has a relatively low capacity to induce genetic abnormalities. (author)

The MCM-binding protein ETG1 aids sister chromatid cohesion required for postreplicative homologous recombination repair.

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Naoki Takahashi

2010-01-01

Full Text Available The DNA replication process represents a source of DNA stress that causes potentially spontaneous genome damage. This effect might be strengthened by mutations in crucial replication factors, requiring the activation of DNA damage checkpoints to enable DNA repair before anaphase onset. Here, we demonstrate that depletion of the evolutionarily conserved minichromosome maintenance helicase-binding protein ETG1 of Arabidopsis thaliana resulted in a stringent late G2 cell cycle arrest. This arrest correlated with a partial loss of sister chromatid cohesion. The lack-of-cohesion phenotype was intensified in plants without functional CTF18, a replication fork factor needed for cohesion establishment. The synergistic effect of the etg1 and ctf18 mutants on sister chromatid cohesion strengthened the impact on plant growth of the replication stress caused by ETG1 deficiency because of inefficient DNA repair. We conclude that the ETG1 replication factor is required for efficient cohesion and that cohesion establishment is essential for proper development of plants suffering from endogenous DNA stress. Cohesion defects observed upon knockdown of its human counterpart suggest an equally important developmental role for the orthologous mammalian ETG1 protein.

Effect of 60-Hz magnetic fields on ultraviolet light-induced mutation and mitotic recombination in Saccharomyces cerevisiae.

Science.gov (United States)

Ager, D D; Radul, J A

1992-12-01

The purpose of this study was to examine the effect of extremely low frequency (ELF) magnetic fields on the induction of genetic damage. In general, mutational studies involving ELF magnetic fields have proven negative. However, studies examining sister-chromatid exchange and chromosome aberrations have yielded conflicting results. In this study, we have examined whether 60-Hz magnetic fields are capable of inducing mutation or mitotic recombination in the yeast Saccharomyces cerevisiae. In addition we determined whether magnetic fields were capable of altering the genetic response of S. cerevisiae to UV (254 nm). We measured the frequencies of induced mutation, gene conversion and reciprocal mitotic crossing-over for exposures to magnetic fields alone (1 mT) or in combination with various UV exposures (2-50 J/m2). These experiments were performed using a repair-proficient strain (RAD+), as well as a strain of yeast (rad3) which is incapable of excising UV-induced thymine dimers. Magnetic field exposures did not induce mutation, gene conversion or reciprocal mitotic crossing-over in either of these strains, nor did the fields influence the frequencies of UV-induced genetic events.

Characterization of muntjac DNA

International Nuclear Information System (INIS)

Davis, R.C.

1981-01-01

Sister chromatid exchange (SCE) in muntjac chromosomes is generally proportional to the chromosomal DNA content, but the SCE frequency is reduced in the heterochromatic neck region of the X chromosome. The physical properties of muntjac DNA and the kinetics of repair of UV damage in muntjac heterochromatin and euchromatin were examined and compared with the distribution of sister chromatid exchange

Characterization of muntjac DNA

Energy Technology Data Exchange (ETDEWEB)

Davis, R.C.

1981-05-27

Sister chromatid exchange (SCE) in muntjac chromosomes is generally proportional to the chromosomal DNA content, but the SCE frequency is reduced in the heterochromatic neck region of the X chromosome. The physical properties of muntjac DNA and the kinetics of repair of UV damage in muntjac heterochromatin and euchromatin were examined and compared with the distribution of sister chromatid exchange.

Study on radiogenotoxicological effect induced by retention of fission product 147Pm

International Nuclear Information System (INIS)

Zhu Shoupeng; Zheng Siying; Luo Zhongyu; Wang Liuyi; Zhao Xiuying

1988-01-01

Internal contamination of 147 Pm can be induced 4 chromatid breakage in one cell. This phenomenon might be due in part to nonuniform irradiation of bone marrow cells with local deposition of 147 Pm. In addition, among the types of aberrations induced by 147 Pm were predominantly of chromatid type, accompanied with a few chromosome breakage and translocation. A statistically significant elevation of SCEs was observed after 147 Pm injection. The number of SECs per cell in bone marrow cells were always higher in mice when the animals were maintained on the radioactive dose of 0.001 μCi/g level of 147 Pm. The results showed that obvious increase of mincronucleus rates could be induced by 147 Pm with low dose as 0.005 μCi/g. While the peak value appeared at 1.34% after injecting 5 μCu/g of 147 Pm for 24hr. In general, the induction of chromosomal alterations by 147 Pm to induce chromosome aberration was only 0.001 μGi/g. This value was lower than ALI of 147 Pm, as reported by ICRP publication

Antigenotoxic Effect of Curcumin and Carvacrol against Parathion Induced DNA Damage in Cultured Human Peripheral Blood Lymphocytes and Its Relation to GSTM1 and GSTT1 Polymorphism

Directory of Open Access Journals (Sweden)

Neeraj Kumar

2014-01-01

Full Text Available In recent years, the use of organophosphorus pesticides has been extensively increased and these compounds signify a major class of agricultural pesticides today. We studied antigenotoxic potential of curcumin and carvacrol against the parathion induced DNA damage in cultured peripheral blood lymphocytes using sister chromatid exchanges as a biomarker of genotoxicity. Heparinised fresh blood from healthy individuals was treated with 2.5 μg/mL concentration of parathion in presence of curcumin and carvacrol in order to observe the antigenotoxic potential of both curcumin and carvacrol. Significant reduction (P0.05 of GSTT1 and GSTM1 polymorphism on genotoxicity of parathion and antigenotoxic potential of curcumin and carvacrol.

Baseline frequency of chromosomal aberrations and sister chromatid exchanges in peripheral blood lymphocytes of healthy individuals living in Turin (North-Western Italy): assessment of the effects of age, sex and GSTs gene polymorphisms on the levels of genomic damage.

Science.gov (United States)

Santovito, Alfredo; Cervella, Piero; Delpero, Massimiliano

2016-05-01

The increased exposure to environmental pollutants has led to the awareness of the necessity for constant monitoring of human populations, especially those living in urban areas. This study evaluated the background levels of genomic damage in a sample of healthy subjects living in the urban area of Turin (Italy). The association between DNA damage with age, sex and GSTs polymorphisms was assessed. One hundred and one individuals were randomly sampled. Sister Chromatid Exchanges (SCEs) and Chromosomal Aberrations (CAs) assays, as well as genotyping of GSTT1 and GSTM1 genes, were performed. Mean values of SCEs and CAs were 5.137 ± 0.166 and 0.018 ± 0.002, respectively. Results showed age and gender associated with higher frequencies of these two cytogenetic markers. The eldest subjects (51-65 years) showed significantly higher levels of genomic damage than younger individuals. GSTs polymorphisms did not appear to significantly influence the frequencies of either markers. The CAs background frequency observed in this study is one of the highest reported among European populations. Turin is one of the most polluted cities in Europe in terms of air fine PM10 and ozone and the clastogenic potential of these pollutants may explain the high frequencies of chromosomal rearrangements reported here.

In vitro studies on chemoprotective effect of borax against aflatoxin B1-induced genetic damage in human lymphocytes.

Science.gov (United States)

Turkez, Hasan; Geyikoğlu, Fatime; Dirican, Ebubekir; Tatar, Abdulgani

2012-12-01

A common dietary contaminant, aflatoxin B1 (AFB1), has been shown to be a potent mutagen and carcinogen in humans and many animal species. Since the eradication of AFB1 contamination in agricultural products has been rare, the use of natural or synthetic free radical scavengers could be a potential chemopreventive strategy. Boron compounds like borax (BX) and boric acid are the major components of industry and their antioxidant role has recently been reported. In the present report, we evaluated the capability of BX to inhibit the rate of micronucleus (MN) and sister chromatid exchange (SCE) formations induced by AFB1. There were significant increases (P Borax gave 30-50 % protection against AFB1 induced SCEs and MNs. In conclusion, the support of borax was especially useful in aflatoxin-toxicated blood tissue. Thus, the risk on target tissues of AFB1 could be reduced and ensured early recovery from its toxicity.

The Scc2/Scc4 complex acts in sister chromatid cohesion and transcriptional regulation by maintaining nucleosome-free regions

Science.gov (United States)

Lopez-Serra, Lidia; Kelly, Gavin; Patel, Harshil; Stewart, Aengus; Uhlmann, Frank

2014-01-01

The cohesin complex is at the heart of many chromosomal activities, including sister chromatid cohesion and transcriptional regulation1-3. Cohesin loading onto chromosomes depends on the Scc2/Scc4 cohesin loader complex4-6, but the chromatin features that form cohesin loading sites remain poorly understood. Here, we show that the RSC chromatin remodeling complex recruits budding yeast Scc2/Scc4 to broad nucleosome-free regions, that the cohesin loader itself helps to maintain. Consequently, inactivation of the cohesin loader or RSC complex have similar effects on nucleosome positioning, gene expression and sister chromatid cohesion. These results reveal an intimate link between local chromatin structure and higher order chromosome architecture. Our findings pertain to the similarities between two severe human disorders, Cornelia de Lange syndrome, caused by mutations in the human cohesin loader, and Coffin-Siris syndrome, resulting from mutations in human RSC complex components7-9. Both could arise from gene misregulation due to related changes in the nucleosome landscape. PMID:25173104

Desalination by electrodialysis with the ion-exchange membrane prepared by radiation-induced graft polymerization

Energy Technology Data Exchange (ETDEWEB)

Choi, Seong-Ho; Han Jeong, Young; Jeong Ryoo, Jae; Lee, Kwang-Pill E-mail: kplee@kyungpook.ac.kr

2001-07-01

Ion-exchange membranes modified with the triethylamine [-N(CH{sub 2}CH{sub 3}){sub 3}] and phosphoric acid (-PO{sub 3} H) groups were prepared by radiation-induced grafting of glycidyl methacrylate (GMA) onto the polyolefin nonwavon fabric (PNF) and subsequent chemical modification of poly(GMA) graft chains. The physical and chemical properties of the GMA-grafted PNF and the PNF modified with ion-exchange groups were investigated by SEM, XPS, TGA, and DSC. Furthermore, electrochemical properties such as specific electric resistance, transport number of K{sup +}, and desalination were examined. The grafting yield increased with increasing reaction time and reaction temperature. The maximum grafting yield was obtained with 40% (vol.%) monomer concentration in dioxane at 60 deg. C. The content of the cation- and anion-exchange group increased with increasing grafting yield. Electrical resistance of the PNF modified with TEA and -PO{sub 3} H group decreased, while the water uptake (%) increased with increasing ion-exchange group capacities. Transport number of the PNF modified with ion-exchange group were the range of ca. 0.82-0.92. The graft-type ion-exchange membranes prepared by radiation-induced graft copolymerization were successfully applied as separators for electrodialysis. (author)

Adaptive response to ionizing radiation induced by low doses of gamma rays in human cell lines

International Nuclear Information System (INIS)

Seong, Jinsil; Chang, Ok Suh; Gwi, Eon Kim

1995-01-01

Purpose: The aim of this study was to investigate whether the adaptive response could be induced in human lymphoblastoid cell lines and human tumor cell lines. The time necessary for the expression of the adaptive response was also investigated. Materials and Methods: Three lymphoblastoid cell lines from ataxia telangiectasia (AT) homozygote (GM 1526), AT heterozygote (GM 3382), and normal individual (3402p) and two hepatoma cell lines, Hep G2 and Hep 3B, were used in this study. Experiments were carried out by delivering 0.01 Gy followed by 0.5 Gy of gamma radiation to the exponentially growing cells. The time necessary for the expression of the adaptive response was determined by varying the time interval between the two doses from 1 to 72 h. In some experiments, 3-aminobenzamide, a potent inhibitor of poly (ADP-ribose) polymerase, was added immediately after the 0.5 Gy exposure. The cultures were fixed 30 min (for the G 2 chromatid) and 6 h (for the S chromatid) after the 0.5 Gy exposure. Metaphase chromosome assay was carried out to score chromatid breaks as an end point. Results: A prior exposure to 0.01 Gy of gamma rays significantly reduced the number of chromatid breaks induced by subsequent higher doses (0.5 Gy) in all the tested cell lines. The magnitude of the adaptive response was similar among the cell lines despite their different radiosensitivities. In the G 2 chromatids, the adaptive response was observed both at short-time intervals, as early as 1 h, and at long-time intervals. In the S chromatids, however, the adaptive response was shown only at long-time intervals. When 3-aminobenzamide was added after the 0.5 Gy, the adaptive responses were abolished in all the experimental groups. Conclusion: The adaptive response was observed in human lymphoblastoid cell lines and hepatoma cell lines. The magnitude of the adaptive response did not seem to be related to the radiosensitivity of the cells. The elimination of the adaptive response with 3

Modulation of mutagen-induced biological effects by inhibitors of DNA repair

International Nuclear Information System (INIS)

Natarajan, A.T.; Mullenders, L.F.H.; Zwanenburg, T.S.B.

1986-01-01

When lesions are induced in the DNA by mutagenic agents, they are subjected to cellular repair. Unrepaired and misrepaired lesions lead to biological effects, such as cell killing, point mutations and chromosomal alterations (aberrations and sister chromatid exchanges - SCEs). It is very difficult to directly correlate any particular type of lesion to a specific biological effect. However, in specific cases, this has been done. For example, short wave UV induced biological effects (cell killing, chromosomal alterations) result predominantly from induced cyclobutane dimers and by photoreactivation experiments, one can demonstrate that with the removal of dimers all types biological effects are diminished. In cases where many types of lesions are considered responsible for the observed biological effects other strategies have been employed to identify the possible lesion. The frequencies of induced chromosomal alterations and point mutations increase with the dose of the mutagen employed and an inhibition of DNA repair following treatment with the mutagen. Prevention of the cells from dividing following mutagen treatment allows them to repair premutational damage, thus reducing the biological effects induced. By comprehensive studies involving quantification of primary DNA lesions, their repair and biological effects will enable us to understand to some extent the complex processes involved in the manifestation of specific biological effects that follow the treatment of cells with mutagenic carcinogens

Microcystin-LR and Cylindrospermopsin Induced Alterations in Chromatin Organization of Plant Cells

Science.gov (United States)

Máthé, Csaba; M-Hamvas, Márta; Vasas, Gábor

2013-01-01

Cyanobacteria produce metabolites with diverse bioactivities, structures and pharmacological properties. The effects of microcystins (MCYs), a family of peptide type protein-phosphatase inhibitors and cylindrospermopsin (CYN), an alkaloid type of protein synthesis blocker will be discussed in this review. We are focusing mainly on cyanotoxin-induced changes of chromatin organization and their possible cellular mechanisms. The particularities of plant cells explain the importance of such studies. Preprophase bands (PPBs) are premitotic cytoskeletal structures important in the determination of plant cell division plane. Phragmoplasts are cytoskeletal structures involved in plant cytokinesis. Both cyanotoxins induce the formation of multipolar spindles and disrupted phragmoplasts, leading to abnormal sister chromatid segregation during mitosis. Thus, MCY and CYN are probably inducing alterations of chromosome number. MCY induces programmed cell death: chromatin condensation, nucleus fragmentation, necrosis, alterations of nuclease and protease enzyme activities and patterns. The above effects may be related to elevated reactive oxygen species (ROS) and/or disfunctioning of microtubule associated proteins. Specific effects: MCY-LR induces histone H3 hyperphosphorylation leading to incomplete chromatid segregation and the formation of micronuclei. CYN induces the formation of split or double PPB directly related to protein synthesis inhibition. Cyanotoxins are powerful tools in the study of plant cell organization. PMID:24084787

Microcystin-LR and Cylindrospermopsin Induced Alterations in Chromatin Organization of Plant Cells

Directory of Open Access Journals (Sweden)

Gábor Vasas

2013-09-01

Full Text Available Cyanobacteria produce metabolites with diverse bioactivities, structures and pharmacological properties. The effects of microcystins (MCYs, a family of peptide type protein-phosphatase inhibitors and cylindrospermopsin (CYN, an alkaloid type of protein synthesis blocker will be discussed in this review. We are focusing mainly on cyanotoxin-induced changes of chromatin organization and their possible cellular mechanisms. The particularities of plant cells explain the importance of such studies. Preprophase bands (PPBs are premitotic cytoskeletal structures important in the determination of plant cell division plane. Phragmoplasts are cytoskeletal structures involved in plant cytokinesis. Both cyanotoxins induce the formation of multipolar spindles and disrupted phragmoplasts, leading to abnormal sister chromatid segregation during mitosis. Thus, MCY and CYN are probably inducing alterations of chromosome number. MCY induces programmed cell death: chromatin condensation, nucleus fragmentation, necrosis, alterations of nuclease and protease enzyme activities and patterns. The above effects may be related to elevated reactive oxygen species (ROS and/or disfunctioning of microtubule associated proteins. Specific effects: MCY-LR induces histone H3 hyperphosphorylation leading to incomplete chromatid segregation and the formation of micronuclei. CYN induces the formation of split or double PPB directly related to protein synthesis inhibition. Cyanotoxins are powerful tools in the study of plant cell organization.

Desalination by electrodialysis with ion-exchange membrane prepared by radiation-induced graft polymerization

Energy Technology Data Exchange (ETDEWEB)

Choi, Seong-Ho; Jeong, Young Han; Ryoo, Jae Jeong; Lee, Kwang-Pill [Department of Chemistry Graduate School, Kyungpook National University, Taegu (Korea)

2000-07-01

Ion-exchange membranes modified with triethylamine [-N(CH{sub 2}CH{sub 3}){sub 3}] and phosphoric acid (-PO{sub 3}H) groups were prepared by radiation-induced grafting of glycidyl methacrylate (GMA) onto polyolefin nonwavon fabric (PNF) and subsequent chemical modification of poly (GMA) graft chains. The physical and chemical properties of the GMA-grafted PNF and the PNF modified with ion-exchange groups were investigated by SEM and XPS. The ion-exchange capacities of the cation- and anion-exchange membrane were 0.20 and 1.24mmol/g, respectively. The content of cation- and anion exchange group increased with increasing grafting yield (d.g.=100%). Electrical resistance of PNF modified with TEA and -PO{sub 3}H group decreased with increasing ion-exchange group capacities. Application of the graft-type ion-exchange membranes as separators for electrodialysis enabled use to reduce the time required to achieve 85.5% desalination of the 0.5M NaCl solution. (author)

Radiation induced graft copolymerization for preparation of cation exchange membranes: a review

International Nuclear Information System (INIS)

Mohamed Mahmoud Nasef; Hamdani Saidi; Hussin Mohd Nor

1999-01-01

Cation exchange membranes are regarded as the ideal solid polymer electrolyte materials for the development of various electrochemical energy conversion applications where significant improvements in the current density are required. Such membranes require special polymers and preparation techniques to maintain high chemical , mechanical and thermal stability in addition to high ionic conductivity and low resistance. A lot of different techniques have been proposed in the past to prepare such membranes. Radiation-induced graft copolymerization provides an attractive ft method for modification of chemical and physical properties of polymeric materials and is of particular interest in achieving specially desired cation exchange membranes as well as excellent membrane properties. This is due to the ability to control the membrane compositions as well as properties by proper selection of grafting conditions. Therefore numerous parameters have to be investigated to properly select the right polymeric materials, radiation grafting technique and the grafting conditions to be employed. In this paper a state-of-the-art of radiation-induced graft copolymerization for preparation of cation exchange membranes and their applications are briefly reviewed. (Author)

Analysis of chromosomal aberrations, sister-chromatid exchanges and micronuclei in peripheral lymphocytes of pharmacists before and after working with cytostatic drugs.

Science.gov (United States)

Roth, S; Norppa, H; Järventaus, H; Kyyrönen, P; Ahonen, M; Lehtomäki, J; Sainio, H; Sorsa, M

1994-12-01

The frequencies of chromosome aberrations, SCEs and micronuclei (cytokinesis-block method) in blood lymphocytes were compared among six nonsmoking female pharmacists before and after 1 year of working with cytostatic drugs. All possible precautions were taken to avoid exposure to cytostatics, including proper protective clothing and a monitored, negative-pressured working environment with vertical laminar flow cabinet. As referents, an age-matched group of six nonsmoking female hospital workers not dealing with cytostatics was simultaneously sampled twice with the same time interval. The pharmacists showed a marginally higher mean frequency of SCEs/cell (6.3; P = 0.049) after the working period than 1 year earlier (5.8). On the other hand, the referents, with no obvious exposure, had a higher mean number of cells with chromatid-type aberrations, gaps excluded, in the second sampling (2.0%; P = 0.048) than in the first one (0.5%). In addition, a slight (P = 0.055) trend towards a higher frequency of micronucleated binucleate cells was observed in the second sampling for both the exposed and control subjects. As such findings suggest technical variation in the cytogenetic parameters, the small difference observed in SCEs for the pharmacists between the two samplings was probably not related to the cytostatics exposure. No statistically significant differences were observed for any of the cytogenetic parameters in comparisons between the pharmacists and the referents. The findings suggest that caution should be exercised in comparing results obtained from two different samplings in prospective cytogenetic studies.

Genes on chromosomes 1 and 4 in the mouse are associated with repair of radiation-induced chromatin damage.

Science.gov (United States)

Potter, M; Sanford, K K; Parshad, R; Tarone, R E; Price, F M; Mock, B; Huppi, K

1988-04-01

Early-passage skin fibroblasts from different inbred and congenic strains of mice were X-irradiated (1 Gy), and the number of chromatid breaks was determined at 2.0 h after irradiation. The cells from DBA/2N, C3H/HeN, STS/A, C57BL/6N, BALB/cJ, and AKR/N had 25 to 42 chromatid breaks per 100 metaphase cells (efficient repair phenotype). NZB/NJ had greater than 78 and BALB/cAn had 87 to 110 chromatid breaks per 100 cells (inefficient repair phenotype). Differences between BALB/cAn and BALB/c. DBA/2 congenic strains which carry less than 1% of the DBA/2 genome indicate that two genes, one on chromosome 1 linked to bcl-2-Pep-3 and the other on chromosome 4 closely linked to Fv-1, affect the efficiency with which the cells repair radiation-induced chromatin damage.

Anisotropic exchange interaction induced by a single photon in semiconductor microcavities

Science.gov (United States)

Chiappe, G.; Fernández-Rossier, J.; Louis, E.; Anda, E. V.

2005-12-01

We investigate coupling of localized spins in a semiconductor quantum dot embedded in a microcavity. The lowest cavity mode and the quantum dot exciton are coupled and close in energy, forming a polariton. The fermions forming the exciton interact with localized spins via exchange. Exact diagonalization of a Hamiltonian in which photons, spins, and excitons are treated quantum mechanically shows that a single polariton induces a sizable indirect anisotropic exchange interaction between spins. At sufficiently low temperatures strong ferromagnetic correlations show up without an appreciable increase in exciton population. In the case of a (Cd,Mn)Te quantum dot, Mn-Mn ferromagnetic coupling is still significant at 1 K : spin-spin correlation around 3 for exciton occupation smaller than 0.3. We find that the interaction mediated by photon-polaritons is 10 times stronger than the one induced by a classical field for equal Rabi splitting.

High local carcinogenic activity of 1,3-dimethyl-3-phenyl-1-nitrosourea and its inactivation by intravenous application in rats: comparison of in vivo findings with the in vitro direct and a combined in vivo/in vitro sister chromatid exchange assay in V79-E cells.

Science.gov (United States)

Thust, R; Martin, J; Mendel, J; Schreiber, D

1987-02-01

1,3-Dimethyl-3-phenyl-1-nitrosourea (DMPNU) is a very potent local carcinogen in rats and induces a 100% frequency of forestomach carcinomas when applied i.g. in two different dosages (10 applications of 0.3 or 0.03 mmol/kg body wt, respectively, at 14-day intervals), but it is inactive upon i.v. administration (10 applications of 0.03 mmol/kg body wt at 14-day intervals). By means of the direct sister chromatid exchange (SCE) assay in V79-E cells in the presence of rat blood, serum or plasma, respectively, as well as by a 'host-mediated' SCE assay (in which the agent was given i.v. to rats, and blood taken from the animal was checked for the recovery of genotoxic activity in cell cultures), we tried to elucidate the unexpected lack of carcinogenic activity of i.v. DMPNU. The direct SCE assay revealed a drastic reduction of DMPNU genotoxicity by rat blood, serum or plasma, respectively, which is abolished by the esterase inhibitor diisopropylfluorophosphate. In the 'host-mediated' SCE assay a genotoxic activity of DMPNU was only recoverable after a very high i.v. dose and when the blood added to the cell cultures had been taken from the rat heart within 1 min after DMPNU administration in vivo. 1-Methyl-1-nitrosourea (MNU) and 1-methyl-3-phenyl-1-nitrosourea (MPNU) were used as positive controls in these experiments and also gave a lower response than theoretically expected, but the relative loss of activity with the latter compounds was much lower than with DMPNU. It is assumed that an esterase in rat blood effectively decomposes this trisubstituted nitrosourea. Problems of the novel 'host-mediated' SCE assay are discussed.

Frequent and efficient use of the sister chromatid for DNA double-strand break repair during budding yeast meiosis.

Directory of Open Access Journals (Sweden)

Tamara Goldfarb

2010-10-01

Full Text Available Recombination between homologous chromosomes of different parental origin (homologs is necessary for their accurate segregation during meiosis. It has been suggested that meiotic inter-homolog recombination is promoted by a barrier to inter-sister-chromatid recombination, imposed by meiosis-specific components of the chromosome axis. Consistent with this, measures of Holliday junction-containing recombination intermediates (joint molecules [JMs] show a strong bias towards inter-homolog and against inter-sister JMs. However, recombination between sister chromatids also has an important role in meiosis. The genomes of diploid organisms in natural populations are highly polymorphic for insertions and deletions, and meiotic double-strand breaks (DSBs that form within such polymorphic regions must be repaired by inter-sister recombination. Efforts to study inter-sister recombination during meiosis, in particular to determine recombination frequencies and mechanisms, have been constrained by the inability to monitor the products of inter-sister recombination. We present here molecular-level studies of inter-sister recombination during budding yeast meiosis. We examined events initiated by DSBs in regions that lack corresponding sequences on the homolog, and show that these DSBs are efficiently repaired by inter-sister recombination. This occurs with the same timing as inter-homolog recombination, but with reduced (2- to 3-fold yields of JMs. Loss of the meiotic-chromosome-axis-associated kinase Mek1 accelerates inter-sister DSB repair and markedly increases inter-sister JM frequencies. Furthermore, inter-sister JMs formed in mek1Δ mutants are preferentially lost, while inter-homolog JMs are maintained. These findings indicate that inter-sister recombination occurs frequently during budding yeast meiosis, with the possibility that up to one-third of all recombination events occur between sister chromatids. We suggest that a Mek1-dependent reduction in

Higher incidence of spontaneous sister-chromatid exchanges (SCEs) and X-ray-induced chromosome aberrations in peripheral blood lymphocytes during pregnancy

International Nuclear Information System (INIS)

Sharma, T.; Das, B.C.

1986-01-01

In vitro cultures of peripheral blood lymphocytes from human and muntjac (barking deer) females who were at an advanced stage of pregnancy (32-37 weeks pregnant women and 20-24 weeks pregnant muntjacs) showed an enhanced frequency of SCEs and X-ray-induced chromosome aberrations when compared with those of nonpregnant females. Lymphocyte cultures of nonpregnant females to which sex hormones progesterone, oestrogen and human chorionic gonadotropin (HCG) were added together exogenously also showed higher frequency of SCEs. The plausible reason(s) for such high incidence of SCEs during pregnancy is discussed. (orig.)

Left-right symmetry breaking in mice by left-right dynein may occur via a biased chromatid segregation mechanism, without directly involving the Nodal gene

Energy Technology Data Exchange (ETDEWEB)

Sauer, Stephan; Klar, Amar J. S., E-mail: sauers@mail.nih.gov, E-mail: klara@mail.nih.gov [Gene Regulation and Chromosome Biology Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD (United States)

2012-11-16

Ever since cloning the classic iv (inversedviscerum) mutation identified the “left-right dynein” (lrd) gene in mice, most research on body laterality determination has focused on its function in motile cilia at the node embryonic organizer. This model is attractive, as it links chirality of cilia architecture to asymmetry development. However, lrd is also expressed in blastocysts and embryonic stem cells, where it was shown to bias the segregation of recombined sister chromatids away from each other in mitosis. These data suggested that lrd is part of a cellular mechanism that recognizes and selectively segregates sister chromatids based on their replication history: old “Watson” versus old “Crick” strands. We previously proposed that the mouse left-right axis is established via an asymmetric cell division prior to/or during gastrulation. In this model, left-right dynein selectively segregates epigenetically differentiated sister chromatids harboring a hypothetical “left-right axis development 1” (“lra1”) gene during the left-right axis establishing cell division. Here, asymmetry development would be ultimately governed by the chirality of the cytoskeleton and the DNA molecule. Our model predicts that randomization of chromatid segregation in lrd mutants should produce embryos with 25% situs solitus, 25% situs inversus, and 50% embryonic death due to heterotaxia and isomerism. Here we confirmed this prediction by using two distinct lrd mutant alleles. Other than lrd, thus far Nodal gene is the most upstream function implicated in visceral organs laterality determination. We next tested whether the Nodal gene constitutes the lra1 gene hypothesized in the model by testing mutant’s effect on 50% embryonic lethality observed in lrd mutants. Since Nodal mutation did not suppress lethality, we conclude that Nodal is not equivalent to the lra1 gene. In summary, we describe the origin of 50% lethality in lrd mutant mice not yet explained by any other

Left-right symmetry breaking in mice by left-right dynein may occur via a biased chromatid segregation mechanism, without directly involving the Nodal gene

International Nuclear Information System (INIS)

Sauer, Stephan; Klar, Amar J. S.

2012-01-01

Ever since cloning the classic iv (inversedviscerum) mutation identified the “left-right dynein” (lrd) gene in mice, most research on body laterality determination has focused on its function in motile cilia at the node embryonic organizer. This model is attractive, as it links chirality of cilia architecture to asymmetry development. However, lrd is also expressed in blastocysts and embryonic stem cells, where it was shown to bias the segregation of recombined sister chromatids away from each other in mitosis. These data suggested that lrd is part of a cellular mechanism that recognizes and selectively segregates sister chromatids based on their replication history: old “Watson” versus old “Crick” strands. We previously proposed that the mouse left-right axis is established via an asymmetric cell division prior to/or during gastrulation. In this model, left-right dynein selectively segregates epigenetically differentiated sister chromatids harboring a hypothetical “left-right axis development 1” (“lra1”) gene during the left-right axis establishing cell division. Here, asymmetry development would be ultimately governed by the chirality of the cytoskeleton and the DNA molecule. Our model predicts that randomization of chromatid segregation in lrd mutants should produce embryos with 25% situs solitus, 25% situs inversus, and 50% embryonic death due to heterotaxia and isomerism. Here we confirmed this prediction by using two distinct lrd mutant alleles. Other than lrd, thus far Nodal gene is the most upstream function implicated in visceral organs laterality determination. We next tested whether the Nodal gene constitutes the lra1 gene hypothesized in the model by testing mutant’s effect on 50% embryonic lethality observed in lrd mutants. Since Nodal mutation did not suppress lethality, we conclude that Nodal is not equivalent to the lra1 gene. In summary, we describe the origin of 50% lethality in lrd mutant mice not yet explained by any other

Left-right symmetry breaking in mice by left-right dynein may occur via a biased chromatid segregation mechanism, without directly involving the Nodal gene

Directory of Open Access Journals (Sweden)

Stephan eSauer

2012-11-01

Full Text Available Ever since cloning the classic iv mutation identified the ‘left-right dynein’ (lrd gene in mice, most research on body laterality determination has focused on its function in motile cilia at the node embryonic organizer. This model is attractive, as it links chirality of cilia architecture to asymmetry development. However, lrd is also expressed in blastocysts and embryonic stem cells, where it was shown to bias the segregation of recombined sister chromatids away from each other in mitosis. These data suggested that lrd is part of a cellular mechanism that recognizes and selectively segregates sister chromatids based on their replication history: old ‘Watson’ vs. old ‘Crick’ strands. We previously proposed that the mouse left-right axis is established via an asymmetric cell division prior to/or during gastrulation. In this model, left-right dynein selectively segregates epigenetically differentiated sister chromatids harboring a hypothetical ‘left-right axis development 1’ (‘lra1’ gene during the left-right axis establishing cell division. Here, asymmetry development would be ultimately governed by the chirality of the cytoskeleton and the DNA molecule. Our model predicts that randomization of chromatid segregation in lrd mutants should produce embryos with 25% situs solitus, 25% situs inversus, and 50% embryonic death due to heterotaxia and isomerism. Here we confirmed this prediction by using two distinct lrd mutant alleles. Other than lrd, thus far Nodal gene is the most upstream function implicated in visceral organs laterality determination. We next tested whether the Nodal gene constitutes the lra1 gene hypothesized in the model by testing mutant’s effect on 50% embryonic lethality observed in lrd mutants. Since Nodal mutation did not suppress lethality, we conclude that Nodal is not equivalent to the lra1 gene. In summary, we describe the origin of 50% lethality in lrd mutant mice not yet explained by any other

Effects of cellular non-protein sulfhydryl depletion in radiation induced oncogenic transformation and genotoxicity in mouse C3H 10T1/2 cells

International Nuclear Information System (INIS)

Hei, T.K.; Geard, C.R.; Hall, E.J.

1984-01-01

A study was made of the effects of cellular non-protein sulfhydryl (NPSH) depletion on cytotoxicity, cell cycle kinetics, oncogenic transformation and sister chromatid exchange (SCE) in C 3 H 10T1/2 cells. Using DL-Buthionine S-R-Sulfoximine (BSO) to deplete thiols, it was found spectrophotometrically that less than 5% of control NPSH level remained in the cells after 24-hour treatment under aerated conditions. Such NPSH depleted cells, when subject to a 3 Gy γ-ray treatment, were found to have no radiosensitizing response either in terms of cell survival or oncogenic transformation. In addition, decreased levels of NPSH had no effect on spontaneous or radiation-induced SCE nor were cell cycle kinetics additionally altered. Therefore, the inability of NPSH depletion to alter γ-ray induced cellular transformation was unrelated to any possible effect of BSO on the cell cycle. These results suggest that such depletion may result in little or no additional oncogenic or genotoxic effects on aerated normal tissues

Biomarkers of exposure, effect, and susceptibility of arsenic-induced health hazards in Taiwan

International Nuclear Information System (INIS)

Chen, C.-J.; Hsu, L.-I; Wang, C.-H.

2005-01-01

Long-term exposure to inorganic arsenic from drinking water has been documented to induce cancers and vascular diseases in a dose-response relationship. A series of molecular environmental epidemiological studies have been carried out to elucidate biomarkers of exposure, effect, and susceptibility for arsenic-related health hazards in Taiwan. Arsenic levels in urine, hair, and nail are biomarkers for short-term (<1 year) internal dose, skin hyperpigmentation and palmoplantar hyperkeratosis are for long-term (many years) internal dose, and percentage of monomethylarsonic acid in total metabolites of inorganic arsenic in urine may be considered as an exposure marker for biologically effective dose. The biomarkers of early biological effects of ingested inorganic arsenic included blood levels of reactive oxidants and anti-oxidant capacity, genetic expression of inflammatory molecules, as well as cytogenetic changes including sister chromatid exchange, micronuclei, and chromosome aberrations of peripheral lymphocytes. Both mutation type and hot spots of p53 gene were significantly different in arsenic-induced and non-arsenic-induced TCCs. The frequency of chromosomal imbalances analyzed by comparative genomic hybridization and the frequency of loss of heterozygosity were significantly higher in arsenic-induced TCC than non-arsenic-induced TCC at specific sites. Biomarkers of susceptibility to arsenic-induced health hazards included genetic polymorphisms of enzymes involved in xenobiotic metabolism, DNA repair, and oxidative stress, as well as serum level of carotenoids. Gene-gene and gene-environment interactions are involved in arsenic-induced health hazards through toxicological mechanisms including genomic instability and oxidative stress

Flow induced vibration in shell and tube heat exchangers

International Nuclear Information System (INIS)

Soper, B.M.H.

1981-01-01

Assessing heat exchanger designs, from the standpoint of flow induced vibration, is becoming increasingly important as shell side flow velocities are increased in a quest for better thermal performance. This paper reviews the state of the art concerning the main sources of vibration excitation, i.e. vortex shedding resonance, turbulent buffeting, fluidelastic instability and acoustic resonance, as well as the structural dynamics of the tubes. It is concluded that there are many areas which require further investigation but there are sufficient data available at present to design, with reasonable confidence, units that will be free from flow induced vibration. Topics which are considered to be key areas for further work are listed

Action of the poison of Apis mellifera bee and gamma radiation on bone marrow cells of Wistar rats and on lymphocytes of human peripheral blood

International Nuclear Information System (INIS)

Varanda, E.A.

1987-01-01

''In vivo'' and ''in vitro'' experiments are performed to determine the radioprotective action of the poison of Apis mellifera bees. The frequency of chromosome aberrations, induced by gamma radiation, is studied in two assays: ''in vivo'' in bone marrow cells from Wistar rats and ''in vitro'' in human peripheral blood lymphocyte cultures. The sister chromatid exchanges (SCE) are studied in the ''in vitro'' assays. (M.A.C.) [pt

The enhancement by caffeine of the frequency of lethal dominant mutation induced by gamma radiation in oocytes of Musca domestica

International Nuclear Information System (INIS)

Targa, H.J.; Rogatko, A.

1982-01-01

The results obtained, when a new technique for feeding insects is employed, on the effects of caffeine of the radiation - induced breaks of oocyte chromatids of Musca domestica are presented. (M.A.) [pt

A modified wake oscillator model for predicting vortex induced vibration of heat exchanger tube

International Nuclear Information System (INIS)

Feng Zhipeng; Zang Fenggang; Zhang Yixiong; Ye Xianhui

2014-01-01

Base on the classical wake oscillator model, a new modified wake oscillator model is proposed, for predicting vortex induced vibration of heat exchanger tube in uniform current. The comparison between the new wake oscillator model and experimental show that the present model can simulate the characteristics of vortex induced vibration of tube. Firstly, the research shows that the coupled fluid-structure dynamical system should be modeled by combined displacement and acceleration mode. Secondly, the empirical parameter in wake oscillator model depends on the material properties of the structure, instead of being a universal constant. Lastly, the results are compared between modified wake oscillator model and fluid-structure interaction numerical model. It shows the present, predicted results are compared to the fluid-structure interaction numerical data. The new modified wake oscillator model can predict the vortex induced heat exchanger tube vibration feasibly. (authors)

Probing the mechanism of sister chromatid exchange formation with the fluorescent plus Giemsa technique

International Nuclear Information System (INIS)

Yu, L.C.

1976-01-01

The effects of x rays and light flashes on the SCE formation in BrdUrd-substituted Chinese hamster ovary (CHO) cells are examined using the fluorescent plus Giemsa (FPG) technique, which allows SCE's to be visualized with greater precision than 3 H autoradiography does. Near-diploid cells are selected and scoring SCE from every chromosome of near-diploid cells or from chromosome no. 1 is found to give a more accurate measure of the SCE induction. Double synchronous cells are used for the x ray study and asynchronous cells are used for the light flash study. The results indicate that x rays can induce SCE's throughout the cell cycle with S the most sensitive stage and G 2 the least sensitive stage. Light flashes can induce an appreciable amount of SCE's while no appreciable amount of chromosomal aberrations can be detected under conditions used in this study. For x-ray-induced chromosomal aberrations, G 2 is the most sensitive stage with G 1 being slightly more sensitive than S, which is consistent with other observations. Additionally, aberration induction is shown to be a more sensitive indicator of x-ray-induced cell damage than SCE induction, but SCE induction is a potentially good indicator of mutation induction. This study also suggests that symmetrically reunited isochromatid breaks can not be the sole source of SCE's and SCE induction is a different but not independent radiobiological effect from chromosomal aberration induction. SCE formation is proposed to be a consequence of specific type(s) of single strand breaks in DNA

Rec8p, a meiotic recombination and sister chromatid cohesion phosphoprotein of the Rad21p family conserved from fision yeast to humans.

NARCIS (Netherlands)

S. Parisi; M.J. McKay (Michael); M. Molnar; M.A. Thompson (Anne); P.J. van der Spek (Peter); E. van Drunen-Schoenmaker; R. Kanaar (Roland); E. Lehmann; J.H.J. Hoeijmakers (Jan); J. Kohli

1999-01-01

textabstractOur work and that of others defined mitosis-specific (Rad21 subfamily) and meiosis-specific (Rec8 subfamily) proteins involved in sister chromatid cohesion in several eukaryotes, including humans. Mutation of the fission yeast Schizosaccharomyces pombe rec8 gene was previously shown to

Assessment of flow induced vibration in a sodium-sodium heat exchanger

Energy Technology Data Exchange (ETDEWEB)

Prakash, V. [Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu (India)], E-mail: prakash@igcar.gov.in; Thirumalai, M.; Prabhakar, R.; Vaidyanathan, G. [Fast Reactor Technology Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu (India)

2009-01-15

The 500 MWe Prototype Fast Breeder Reactor (PFBR) is under construction at Kalpakkam. It is a liquid metal sodium cooled pool type fast reactor with all primary components located inside a sodium pool. The heat produced due to fission in the core is transported by primary sodium to the secondary sodium in a sodium to sodium Intermediate Heat Exchanger (IHX), which in turn is transferred to water in the steam generator. PFBR IHX is a shell and tube type heat exchanger with primary sodium on shell side and secondary sodium in the tube side. Since IHX is one of the critical components placed inside the radioactive primary sodium, trouble-free operation of the IHX is very much essential for power plant availability. To validate the design and the adequacy of the support system provided for the IHX, flow induced vibration (FIV) experiments were carried out in a water test loop on a 60 deg. sector model. This paper discusses the flow induced vibration measurements carried out in 60 deg. sector model of IHX, the modeling criteria, the results and conclusion.

Repair of O6-(2-chloroethyl)guanine mediates the biological effects of chloroethylnitrosoureas.

OpenAIRE

Bodell, W J; Aida, T; Berger, M S; Rosenblum, M L

1985-01-01

Chloroethylnitrosoureas (CENUs) are alkylating and crosslinking agents used for the treatment of human cancer; they are both mutagenic and carcinogenic. We compared the levels of induction of sister chromatid exchanges (SCEs) and the cytotoxicity of nitrosoureas that alkylate only with CENUs. CENUs are 200-fold more cytotoxic and induce SCEs with 45-fold greater efficiency than agents that do not crosslink; therefore, crosslinking is probably the most important molecular event that leads to c...

Synthesis and SAR studies of 5-(pyridin-4-yl)-1,3,4-thiadiazol-2-amine derivatives as potent inhibitors of Bloom helicase

DEFF Research Database (Denmark)

Rosenthal, Andrew S; Dexheimer, Thomas S; Gileadi, Opher

2013-01-01

complementary strands of duplex DNA as well as atypical DNA structures such as Holliday junctions. Mutations of the BLM gene can result in Bloom syndrome, an autosomal recessive disorder associated with cancer predisposition. BLM-deficient cells exhibit increased sensitivity to DNA damaging agents indicating...... and related analogs, which possess potent BLM inhibition and exhibit selectivity over related helicases. Moreover, these compounds demonstrated cellular activity by inducing sister chromatid exchanges, a hallmark of Bloom syndrome....

Induced magnetic structure in exchange-coupled ferro-/antiferromagnet thin films

Science.gov (United States)

Morales, Rafael

2007-03-01

The most prominent feature observed in exchange-coupled ferromagnetic/ antiferromagnetic (FM/AF) bilayers is the so-called exchange bias field (HEB), i.e. the shift of the hysteresis loop along the magnetic field axis. However the exchange bias phenomenon can induce other interesting effects on the FM. In this talk we show two methods to establish a bi-domain state in the FM, due to the coexistence of domains with opposite sign of HEB [1-3]. Magneto-optical, polarized neutron and soft X-ray measurements show that this lateral structure becomes more complex for low magnetocrystalline anisotropy materials where a spin depth profile is created in the FM due to the exchange coupling with the AF [4-6]. The internal magnetic structure in the AF and its role on exchange bias has also been investigated using FM/AF/FM trilayers. These studies demonstrate that the bulk spin configuration in the AF plays a crucial role in the pinning of uncompensated spins at the interface thus determining the HEB . Supported by the US-DOE, European Marie-Curie-OIF and the Alfred P. Sloan Foundation. [1] O. Petracic et al. Appl. Phys. Lett. 87, 222509 (2005) [2] I. V. Roshchin et al. Europhys. Lett. 71, 297 (2005) [3] J. Olamit et al. Phys. Rev. B 72, 012408 (2005) [4] R. Morales et al. Appl. Phys. Lett. 89, 072504 (2006) [5] S. Roy et al. Phys. Rev. Lett. 95, 047201 (2005) [6] Z-P. Li et al. Phys. Rev. Lett. 96, 217205 (2006)

Abnormally banded chromosomal regions in doxorubicin-resistant B16-BL6 murine melanoma cells.

Science.gov (United States)

Slovak, M L; Hoeltge, G A; Ganapathi, R

1986-08-01

B16-BL6 murine melanoma cells were selected for cytogenetic evaluation during the stepwise development of increasing resistance in vitro to the antitumor antibiotic, doxorubicin (DOX). Karyotypic studies demonstrated extensive heteroploidy with both numerical and structural abnormalities which were not present in the parental DOX-sensitive B16-BL6 cells. Trypsin-Giemsa banding revealed the presence of several marker chromosomes containing abnormally banding regions (ABRs) in the 44-fold B16-BL6 DOX-resistant subline. These ABRs appeared to be more homogeneously staining at the higher DOX concentrations. Length measurements (ABR index) in seven banded metaphases indicated a direct correlation with increasing DOX concentration. When the DOX-resistant cells were grown in drug-free medium for 1 yr, the drug-resistant phenotype gradually declined in parallel with the level of resistance and the ABR index. DOX-induced cytogenetic damage examined by sister chromatid exchange methodology in parental B16-BL6 cells indicated a linear sister chromatid exchange:DOX dose-response relationship. However, after continuous treatment of parental B16-BL6 cells with DOX (0.01 microgram/ml) for 30 days, sister chromatid exchange scores were found to return to base-line values. The B16-BL6 resistant cells demonstrated a cross-resistant phenotype with N-trifluoroacetyladriamycin-14-valerate, actinomycin D, and the Vinca alkaloids but not with 1-beta-D-arabinofuranosylcytosine. The results suggest that ABR-containing chromosomes in DOX-resistant sublines may represent cytogenetic alterations of specific amplified genes involved in the expression of DOX resistance. Further studies are required to identify and define the possible gene products and to correlate their relationship to the cytotoxic action of doxorubicin.

Differential response of biochemical parameters to EMS and MMS treatments and their dose effect relationship on chromosomes in induced diabetic mouse

Directory of Open Access Journals (Sweden)

B.B.D. Khalandar

2015-10-01

Conclusion: (1 Even though alkylating agents induce chromosomal aberrations in diabetic mice, MMS, a methylating agent is a more potent inducer of chromatid type of aberrations than EMS, an ethylating agent. (2 Diabetic mouse is more resistant than the non diabetic to alkylating agents and (3 the tested agents altered the analyzed biochemical parameters.

Immediate and repair induced DNA double strand breaks in mammalian cells

International Nuclear Information System (INIS)

Bryant, P.E.

1986-01-01

It seems logical to postulate that double strand breaks (dsb) arising both at the time of irradiation and via repair processes are potentially equally damaging for a cell in terms of the potential to induce chromosomal aberrations. However, in some cell systems the repair of double es or es-ssb sites may run concurrently with the incision so that these lesions do not remain open for long: hence the lack of accumulation of dsb during repair. The rate of incision will thus determine both the accumulation and the probability of exchanges leading to chromosomal aberrations between these and other frank dsb. Rapid incision leading to a large additional pool of dsb appears to be the case in Chinese hamster V79 cells. Some evidence also exists for the conversion of base damage, via dsb, into deletion type chromatid aberrations which accumulate in irradiated G2 human cells treated with ara C. A small fraction of dsb, probably arising both at the time of irradiation as well as enzymatically during repair of base or sugar damage, appears to be either left unrepaired, yielding deletion type chromosomal aberrations, or is misrepaired, yielding exchange aberrations. The induction of these aberrations appears to be of central importance in the biological effects of ionizing radiation such as mutations, oncogenic transformation, and cell death. 52 refs., 5 figs

Seasonal trends in reduced leaf gas exchange and ozone-induced foliar injury in three ozone sensitive woody plant species

International Nuclear Information System (INIS)

Novak, K.; Schaub, M.; Fuhrer, J.; Skelly, J.M.; Hug, C.; Landolt, W.; Bleuler, P.; Kraeuchi, N.

2005-01-01

Seasonal trends in leaf gas exchange and ozone-induced visible foliar injury were investigated for three ozone sensitive woody plant species. Seedlings of Populus nigra L., Viburnum lantana L., and Fraxinus excelsior L. were grown in charcoal-filtered chambers, non-filtered chambers and open plots. Injury assessments and leaf gas exchange measurements were conducted from June to October during 2002. All species developed typical ozone-induced foliar injury. For plants exposed to non-filtered air as compared to the charcoal-filtered air, mean net photosynthesis was reduced by 25%, 21%, and 18% and mean stomatal conductance was reduced by 25%, 16%, and 8% for P. nigra, V. lantana, and F. excelsior, respectively. The timing and severity of the reductions in leaf gas exchange were species specific and corresponded to the onset of visible foliar injury. - Reductions in leaf gas exchange corresponded to the onset of ozone-induced visible foliar injury for seedlings exposed to ambient ozone exposures

Seasonal trends in reduced leaf gas exchange and ozone-induced foliar injury in three ozone sensitive woody plant species

Energy Technology Data Exchange (ETDEWEB)

Novak, K. [Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903 Birmensdorf (Switzerland)]. E-mail: kristopher.novak@wsl.ch; Schaub, M. [Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903 Birmensdorf (Switzerland); Fuhrer, J. [Swiss Federal Research Station for Agroecology and Agriculture FAL, 8046 Zurich (Switzerland); Skelly, J.M. [Department of Plant Pathology, The Pennsylvania State University, University Park, PA 16802 (United States); Hug, C. [Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903 Birmensdorf (Switzerland); Landolt, W. [Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903 Birmensdorf (Switzerland); Bleuler, P. [Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903 Birmensdorf (Switzerland); Kraeuchi, N. [Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zuercherstrasse 111, 8903 Birmensdorf (Switzerland)

2005-07-15

Seasonal trends in leaf gas exchange and ozone-induced visible foliar injury were investigated for three ozone sensitive woody plant species. Seedlings of Populus nigra L., Viburnum lantana L., and Fraxinus excelsior L. were grown in charcoal-filtered chambers, non-filtered chambers and open plots. Injury assessments and leaf gas exchange measurements were conducted from June to October during 2002. All species developed typical ozone-induced foliar injury. For plants exposed to non-filtered air as compared to the charcoal-filtered air, mean net photosynthesis was reduced by 25%, 21%, and 18% and mean stomatal conductance was reduced by 25%, 16%, and 8% for P. nigra, V. lantana, and F. excelsior, respectively. The timing and severity of the reductions in leaf gas exchange were species specific and corresponded to the onset of visible foliar injury. - Reductions in leaf gas exchange corresponded to the onset of ozone-induced visible foliar injury for seedlings exposed to ambient ozone exposures.

Genome-wide high-resolution mapping of UV-induced mitotic recombination events in Saccharomyces cerevisiae.

Directory of Open Access Journals (Sweden)

Yi Yin

2013-10-01

Full Text Available In the yeast Saccharomyces cerevisiae and most other eukaryotes, mitotic recombination is important for the repair of double-stranded DNA breaks (DSBs. Mitotic recombination between homologous chromosomes can result in loss of heterozygosity (LOH. In this study, LOH events induced by ultraviolet (UV light are mapped throughout the genome to a resolution of about 1 kb using single-nucleotide polymorphism (SNP microarrays. UV doses that have little effect on the viability of diploid cells stimulate crossovers more than 1000-fold in wild-type cells. In addition, UV stimulates recombination in G1-synchronized cells about 10-fold more efficiently than in G2-synchronized cells. Importantly, at high doses of UV, most conversion events reflect the repair of two sister chromatids that are broken at approximately the same position whereas at low doses, most conversion events reflect the repair of a single broken chromatid. Genome-wide mapping of about 380 unselected crossovers, break-induced replication (BIR events, and gene conversions shows that UV-induced recombination events occur throughout the genome without pronounced hotspots, although the ribosomal RNA gene cluster has a significantly lower frequency of crossovers.

Indirect intergenic suppression of a radiosensitive mutant of Sordaria macrospora defective in sister-chromatid cohesiveness.

Science.gov (United States)

Huynh, A D; Leblon, G; Zickler, D

1986-01-01

Six ultra violet (UV) mutageneses were performed on the spo76 UV-sensitive mutant of Sordaria macrospora. Spo76 shows an early centromere cleavage associated with an arrest at the first meiotic division and therefore does not form ascospores. Moreover, it exhibits altered pairing structure (synaptonemal complex), revealing a defect in the sister-chromatid cohesiveness. From 37 revertants which partially restored sporulation, 34 extragenic suppressors of spo76 were isolated. All suppressors are altered in chromosomal pairing but, unlike spo76, show a wild type centromere cleavage. The 34 suppressors were assigned to six different genes and mapped. Only one of the suppressor genes is involved in repair functions.

Regulation of Centromere Localization of the Drosophila Shugoshin MEI-S332 and Sister-Chromatid Cohesion in Meiosis

Science.gov (United States)

Nogueira, Cristina; Kashevsky, Helena; Pinto, Belinda; Clarke, Astrid; Orr-Weaver, Terry L.

2014-01-01

The Shugoshin (Sgo) protein family helps to ensure proper chromosome segregation by protecting cohesion at the centromere by preventing cleavage of the cohesin complex. Some Sgo proteins also influence other aspects of kinetochore-microtubule attachments. Although many Sgo members require Aurora B kinase to localize to the centromere, factors controlling delocalization are poorly understood and diverse. Moreover, it is not clear how Sgo function is inactivated and whether this is distinct from delocalization. We investigated these questions in Drosophila melanogaster, an organism with superb chromosome cytology to monitor Sgo localization and quantitative assays to test its function in sister-chromatid segregation in meiosis. Previous research showed that in mitosis in cell culture, phosphorylation of the Drosophila Sgo, MEI-S332, by Aurora B promotes centromere localization, whereas Polo phosphorylation promotes delocalization. These studies also suggested that MEI-S332 can be inactivated independently of delocalization, a conclusion supported here by localization and function studies in meiosis. Phosphoresistant and phosphomimetic mutants for the Aurora B and Polo phosphorylation sites were examined for effects on MEI-S332 localization and chromosome segregation in meiosis. Strikingly, MEI-S332 with a phosphomimetic mutation in the Aurora B phosphorylation site prematurely dissociates from the centromeres in meiosis I. Despite the absence of MEI-S332 on meiosis II centromeres in male meiosis, sister chromatids segregate normally, demonstrating that detectable levels of this Sgo are not essential for chromosome congression, kinetochore biorientation, or spindle assembly. PMID:25081981

Exchange bias induced at a Co2FeAl0.5Si0.5/Cr interface

International Nuclear Information System (INIS)

Yu, C N T; Vick, A J; Inami, N; Ono, K; Frost, W; Hirohata, A

2017-01-01

In order to engineer the strength of an exchange bias in a cubic Heusler alloy layer, crystalline strain has been induced at a ferromagnet/antiferromagnet interface by their lattice mismatch in addition to the conventional interfacial exchange coupling between them. Such interfaces have been formed in (Co 2 FeAl 0.5 Si 0.5 (CFAS)/Cr) 3 structures grown by ultrahigh vacuum molecular beam epitaxy. The magnetic and structural properties have been characterised to investigate the exchange interactions at the CFAS/Cr interfaces. Due to the interfacial lattice mismatch of 1.4%, the maximum offset of 18 Oe in a magnetisation curve has been measured for the case of a CFAS (2 nm)/Cr (0.9 nm) interface at 193 K. The half-metallic property of CFAS has been observed to remain unchanged, which agrees with the theoretical prediction by Culbert et al (2008 J. Appl. Phys . 103 07D707). Such a strain-induced exchange bias may provide insight of the interfacial interactions and may offer a wide flexibility in spintronic device design. (paper)

Chromatid repulsion associated with Roberts/SC phocomelia syndrome is reduced in malignant cells and not expressed in interspecies somatic-cell hybrids.

Science.gov (United States)

Krassikoff, N E; Cowan, J M; Parry, D M; Francke, U

1986-01-01

Different cell types from a female patient with Roberts/SC phocomelia syndrome were evaluated quantitatively for the presence of repulsion of heterochromatin and satellite regions of mitotic chromosomes. Whereas EBV-transformed lymphoblasts from an established cell line revealed these phenomena at frequencies equal to those in PHA-stimulated lymphocytes and cultured skin fibroblasts, aneuploid cells from a metastatic melanoma displayed them at 50% lower frequency. Cocultivation of the patient's fibroblasts with either an immortal Chinese hamster cell line or with a human male fibroblast strain carrying a t(4;6)(p14;q21) translocation showed that the phenomenon was not corrected or induced by a diffusible factor or by cell-to-cell contact. In each experiment, only the patient's metaphase spreads revealed chromatid repulsion. In fusion hybrids between the patient's fibroblasts and an established Chinese hamster cell line, the human chromosomes behaved perfectly normally, suggesting that the gene product which is missing or mutant in Roberts/SC phocomelia syndrome is supplied by the Chinese hamster genome. Images Fig. 1 Fig. 2 Fig. 3 PMID:3788975

Steroid sulfatase gene in XX males.

OpenAIRE

Mohandas, T K; Stern, H J; Meeker, C A; Passage, M B; Müller, U; Page, D C; Yen, P H; Shapiro, L J

1990-01-01

The human X and Y chromosomes pair and recombine at their distal short arms during male meiosis. Recent studies indicate that the majority of XX males arise as a result of an aberrant exchange between X and Y chromosomes such that the testis-determining factor gene (TDF) is transferred from a Y chromatid to an X chromatid. It has been shown that X-specific loci such as that coding for the red cell surface antigen, Xg, are sometimes lost from the X chromosome in this aberrant exchange. The ste...

Radiation-induced decomposition of anion exchange resins

International Nuclear Information System (INIS)

Baidak, Aliaksandr; LaVerne, Jay A.

2010-01-01

Radiation-induced degradation of the strongly basic anion exchange resin Amberlite TM IRA400 in NO 3 - , Cl - and OH - forms has been studied. The research focused on the formation of molecular hydrogen in the gamma-radiolysis of water slurries of these quaternary ammonium resins with varying water content. Extended studies with various electron scavengers (NO 3 - , N 2 O and O 2 ) prove an important role of e solv - in the formation of H 2 from these resins. An excess production of H 2 in these systems at about 85% water weight fraction was found to be due to trimethylamine, dimethylamine and other compounds that leach from the resin to the aqueous phase. Irradiations with 5 MeV 4 He ions were performed to simulate the effects of α-particles.

High frequencies of chromatid aberrations produced during G/sub 2/ in human lymphocytes by very low doses (0. 025-0. 4 Gy) of X-rays in combination with inhibitors of DNA synthesis

Energy Technology Data Exchange (ETDEWEB)

Andersson, H.C.; Kihlman, B.A. (Uppsala Univ. (Sweden). Dept. of Genetics)

1984-09-01

Whole-blood cultures of human lymphocytes were exposed in the G/sub 2/-phase (3.5 h before harvesting) to various doses of X-rays and post-treated for 3 h with inhibitors of DNA synthesis. The inhibitors used were 2'-deoxyadenosine (dAdo), hydroxyurea (HU) and 1-..beta..-D-arabinofuranosylcytosine (ara-C). To prevent deamination of dAdo by adenosine deaminase (ADA), the dAdo treatments were carried out in the presence of the ADA inhibitor coformycin. HU and ara-C were used either alone or in combination. After the 3-h inhibitor treatments, the cultures were harvested and slides prepared and analyzed for chromatid aberrations in metaphase. When the inhibitors were used at concentrations high enough to cause marked chromosome damage by themselves, very low doses of X-rays (0.025-0.2 Gy) were sufficient to produce a dramatic increase in the frequency of chromatid aberrations. High frequencies of chromatid aberrations were also obtained when cultures that had received moderate doses of X-rays (0.4-0.8 Gy) were post-treated with low inhibitor concentrations that produce no or only a few aberrations by themselves.

Induction and prevention of micronuclei and chromosomal aberrations in cultured human lymphocytes exposed to the light of halogen tungsten lamps.

Science.gov (United States)

D'Agostini, F; Caimo, A; De Filippi, S; De Flora, S

1999-07-01

Previous studies have shown that the light emitted by halogen tungsten lamps contains UV radiation in the UV-A, UV-B and UV-C regions, induces mutations and irreparable DNA damage in bacteria, enhances the frequency of micronuclei in cultured human lymphocytes and is potently carcinogenic to the skin of hairless mice. The present study showed that the light emitted by an uncovered, traditional halogen lamp induces a significant, dose-related and time-related increase not only in micronuclei but also in chromosome-type aberrations, such as breaks, and even more in chromatid-type aberrations, such as isochromatid breaks, exchanges and isochromatid/chromatid interchanges, all including gaps or not, in cultured human lymphocytes. All these genotoxic effects were completely prevented by shielding the same lamp with a silica glass cover, blocking UV radiation. A new model of halogen lamp, having the quartz bulb treated in order to reduce the output of UV radiation, was considerably less genotoxic than the uncovered halogen lamp, yet induction of chromosomal alterations was observed at high illuminance levels.

Inhomogeneity induced and appropriately parameterized semilocal exchange and correlation energy functionals in two-dimensions

Science.gov (United States)

Patra, Abhilash; Jana, Subrata; Samal, Prasanjit

2018-04-01

The construction of meta generalized gradient approximations based on the density matrix expansion (DME) is considered as one of the most accurate techniques to design semilocal exchange energy functionals in two-dimensional density functional formalism. The exchange holes modeled using DME possess unique features that make it a superior entity. Parameterized semilocal exchange energy functionals based on the DME are proposed. The use of different forms of the momentum and flexible parameters is to subsume the non-uniform effects of the density in the newly constructed semilocal functionals. In addition to the exchange functionals, a suitable correlation functional is also constructed by working upon the local correlation functional developed for 2D homogeneous electron gas. The non-local effects are induced into the correlation functional by a parametric form of one of the newly constructed exchange energy functionals. The proposed functionals are applied to the parabolic quantum dots with a varying number of confined electrons and the confinement strength. The results obtained with the aforementioned functionals are quite satisfactory, which indicates why these are suitable for two-dimensional quantum systems.

Damage of chromosomes in mouse bone marrow cells after combined treatment with gamma radiation and cyclophosphamide

International Nuclear Information System (INIS)

Rupova, Ivanka

2008-01-01

Full text: Current approaches to successful management of malignancy include combined modalities of treatment with ionizing radiation and anticancer drugs. Together with tumor cells normal tissues and cells are also submitted to the damaging effect of these agents, creating thus a probability for development of secondary neoplastic processes. The aim of the present study was to investigate the rate of chromosome damage at different modalities of combined exposures to gamma irradiation and cyclophosphamide(CY) of mice. Chromosomal aberration frequency in metaphase bone marrow cells was used as a measure to evaluate the effect. Combination treatments with 3 Gy gamma irradiation and 20 mg/kg cyclophosphamide were given at different intervals - simultaneously or at 12 hr interval, in order to establish the conditions and factors influencing the rate of chromosome damage. The distribution of different types of chromosome aberrations, such as chromatid fragments, chromatid exchanges, chromosome fragments and chromosome exchanges was analyzed. The results showed a high synergistic effect at simultaneous treatment with both agents if assessed by the index of aberrations per cell (%). An attempt has been made to suggest a possible explanation of the effects at different combined treatments related to the type of induced chromosomal aberrations. (author)

An investigation of the genetic toxicology of irradiated foodstuffs using short-term test systems

International Nuclear Information System (INIS)

Phillips, B.J.; Kranz, E.; Elias, P.S.

1980-01-01

As part of a programme of short-term tests used to detect possible genetic toxicity in irradiated foodstuffs, cultured Chinese hamster ovary cells were exposed to extracts and digests of irradiated and unirradiated dates, fish and chicken and subjected to tests for cytotoxicity, sister chromatid exchange induction and mutation to thioguanine resistance. The results showed no evidence of genetic toxicity induced in food by irradiation. The general applicability of cell culture tests to the detection of mutagens in food is discussed. (author)

Selective accumulation of 147Pm in organism on induction of PCE's micronucleus and SCE of bone marrow cells as well as the chromosome aberrations on fetal liver and spleen

International Nuclear Information System (INIS)

Zhu Shoupeng; Zheng Siying; Wang Liuyi; Lu Zhongyan; Yang Shuqin

1989-01-01

Study of accumulation peculiarity of 147 Pm showed that I.V. different doses of 147 Pm were the same selectively localized in skeleton and liver. Retention of 147 Pm in skeleton and liver was elevated when the radioactive doses of 147 Pm were increased. At the same time absorption does of 147 Pm radiation was heightened. The ability of 147 Pm to induce sister chromatid exchanges (SCEs) has been investigated by IdU labelling methods. A statistically significant elevation of SCEs was observed after 147 Pm intake.In mice the number of SCEs per cell in bone marrow cells was always higher when the animals were maintained on the doses of 37 Bq/g. The injurious effects of 147 Pm, using PCE's micronucleus rates in bone marrow cells were observed. 147 Pm was dominantly deposited on maternal liver. Deposition of 147 Pm in maternal spleen was about quandrantal of the maternal liver. Studies indicated that maternal contamination of 147 Pm could induced chromosome aberrations in fetal liver and spleen cells. Among the type of aberrations induced by 147 Pm, chromatid breakage were predominant. The incidence of chromosome aberrations on fetal liver cells induced by 147 Pm was higher on fetal spleen cells

Effect of cysteamine on sister chromatid exchange (SCE) induction by gamma rays

International Nuclear Information System (INIS)

Mendiola Cruz, M.T.

1987-01-01

The effect of different doses of cysteamine (3, 15 and 150 μg/g bw) on gamma ray-induced SCE was evaluated and compared with the responses obtained with regard to frequency of chromosomal aberrations, frequency of proliferating cells and the rate of cellular proliferating kinetics in mouse bone marrow cells in vivo. Groups of mice were either irradiated, treated with cysteamine and irradiated, only treated with cysteamine or left without treatment for determination of these parameters. The intraperitoneal administration of cysteamine preceding 1 Gy of gamma ray exposure, produces a dose dependent radioprotection on SCE-induction obtaining the greatest effect with 150 μg/g bw. However, this effect was not observed in the mitotic index nor in the average generation time. Chromosomic aberrations in animals irradiated after treatment with cysteamine were also detected. It was not observed any citotoxic or genotoxic effect produced by cysteamine per se. The results suggest that, under the experimental conditions of this study, the SCE are caused by free radicals produced by gamma radiation; not so, the additional damage indexes measured. (author)

Carnosine attenuates cyclophosphamide-induced bone marrow suppression by reducing oxidative DNA damage

Directory of Open Access Journals (Sweden)

Jie Deng

2018-04-01

Full Text Available Oxidative DNA damage in bone marrow cells is the main side effect of chemotherapy drugs including cyclophosphamide (CTX. However, not all antioxidants are effective in inhibiting oxidative DNA damage. In this study, we report the beneficial effect of carnosine (β-alanyl-l-histidine, a special antioxidant with acrolein-sequestering ability, on CTX-induced bone marrow cell suppression. Our results show that carnosine treatment (100 and 200 mg/kg, i.p. significantly inhibited the generation of reactive oxygen species (ROS and 8-hydroxy-2′-deoxyguanosine (8-oxo-dG, and decreased chromosomal abnormalities in the bone marrow cells of mice treated with CTX (20 mg/kg, i.v., 24 h. Furthermore, carnosine evidently mitigated CTX-induced G2/M arrest in murine bone marrow cells, accompanied by reduced ratios of p-Chk1/Chk1 and p-p53/p53 as well as decreased p21 expression. In addition, cell apoptosis caused by CTX was also suppressed by carnosine treatment, as assessed by decreased TUNEL-positive cell counts, down-regulated expressions of Bax and Cyt c, and reduced ratios of cleaved Caspase-3/Caspase-3. These results together suggest that carnosine can protect murine bone marrow cells from CTX-induced DNA damage via its antioxidant activity. Keywords: Carnosine, Cyclophosphamide, Oxidative DNA damage, Sister chromatid exchange, Apoptosis, Cell cycle arrest

Intermediate heat exchanger tube vibration induced by cross and parallel mixed flow

International Nuclear Information System (INIS)

Kawamura, Koji

1986-01-01

The characteristics of pool type LMFBR intermediate heat exchanger (IHX) tube vibrations induced by cross and parallel mixed flow were basically investigated. Secondary coolant in IHX tube bundle is mixed flow of parallel jit flow along the tube axis through flow holes in baffle plates and cross flow. By changing these two flow rate, flow distributions vary in the tube bundle. Mixed flow also induces vibrations which cause fretting wear and fatigue of tube. It is therefore very important to evaluate the tube vibration characteristics for estimating the tube integrity. The results show that the relationships between tube vibrations and flow distributions in the tube bundle were cleared, and mixed flow induced tube vibration could be evaluated on the base of the characteristics of both parallel and cross flow induced vibration. From these investigations it could be concluded that the characteristics of tube vibration for various flow distributions can be systematically evaluated. (author)

Freeze-thaw cycles induce content exchange between cell-sized lipid vesicles

Science.gov (United States)

Litschel, Thomas; Ganzinger, Kristina A.; Movinkel, Torgeir; Heymann, Michael; Robinson, Tom; Mutschler, Hannes; Schwille, Petra

2018-05-01

Early protocells are commonly assumed to consist of an amphiphilic membrane enclosing an RNA-based self-replicating genetic system and a primitive metabolism without protein enzymes. Thus, protocell evolution must have relied on simple physicochemical self-organization processes within and across such vesicular structures. We investigate freeze-thaw (FT) cycling as a potential environmental driver for the necessary content exchange between vesicles. To this end, we developed a conceptually simple yet statistically powerful high-throughput procedure based on nucleic acid-containing giant unilamellar vesicles (GUVs) as model protocells. GUVs are formed by emulsion transfer in glass bottom microtiter plates and hence can be manipulated and monitored by fluorescence microscopy without additional pipetting and sample handling steps. This new protocol greatly minimizes artefacts, such as unintended GUV rupture or fusion by shear forces. Using DNA-encapsulating phospholipid GUVs fabricated by this method, we quantified the extent of content mixing between GUVs under different FT conditions. We found evidence of nucleic acid exchange in all detected vesicles if fast freezing of GUVs at ‑80 °C is followed by slow thawing at room temperature. In contrast, slow freezing and fast thawing both adversely affected content mixing. Surprisingly, and in contrast to previous reports for FT-induced content mixing, we found that the content is not exchanged through vesicle fusion and fission, but that vesicles largely maintain their membrane identity and even large molecules are exchanged via diffusion across the membranes. Our approach supports efficient screening of prebiotically plausible molecules and environmental conditions, to yield universal mechanistic insights into how cellular life may have emerged.

The Vibration Analysis of Tube Bundles Induced by Fluid Elastic Excitation in Shell Side of Heat Exchanger

Science.gov (United States)

Bao, Minle; Wang, Lu; Li, Wenyao; Gao, Tianze

2017-09-01

Fluid elastic excitation in shell side of heat exchanger was deduced theoretically in this paper. Model foundation was completed by using Pro / Engineer software. The finite element model was constructed and imported into the FLUENT module. The flow field simulation adopted the dynamic mesh model, RNG k-ε model and no-slip boundary conditions. Analysing different positions vibration of tube bundles by selecting three regions in shell side of heat exchanger. The results show that heat exchanger tube bundles at the inlet of the shell side are more likely to be failure due to fluid induced vibration.

Chromosome aberrations in workers of beach sand mineral industries

International Nuclear Information System (INIS)

Meenakshi, C.; Mohankumar, Mary N.

2013-01-01

Beach Sand Mining (BSM) is a profitable industry earning a sizable income for the country by way of foreign exchange. The Indian coast is rich in rare earths such as ilmenite, rutile, leucoxene, zircon, garnet and sillimanite, and is invariably associated with radioactive monazite. Due to the nature of the separation processes involved and the manual handling, workers in these factories are continuously being exposed to suspended particles containing naturally occurring radioactive materials. An attempt was made to estimate DNA damage using a chromosome aberration assay to monitor radiation effects in workers of BSM industries in India. The study group comprised 27 BSM workers and 20 controls. Percentage yields of dicentrics, acentric fragments and chromatid breaks observed in the control group were 0.058 ± 0.017, 0.073 ± 0.03 and 0.22 ± 0.112, respectively. Percentage yields of dicentrics + centric rings, acentric fragments and chromatid breaks observed in the BSM group were 0.029 ± 0.01 (P value 0.19), 0.24 ± 0.06 (P value 0.006) and 0.455 ± 0.06 (P value 0.0004), respectively. Elevated levels of fragments and chromatid aberrations are suggestive of low-dose radiation effects and also chemically-induced DNA damage. (authors)

Suppression of topoisomerase IIα expression and function in human cells decreases chromosomal radiosensitivity

International Nuclear Information System (INIS)

Terry, Samantha Y.A.; Riches, Andrew C.; Bryant, Peter E.

2009-01-01

The mechanism behind chromatid break formation is as yet unclear, although it is known that DNA double-strand breaks (DSBs) are the initiating lesions. Chromatid breaks formed in cells in the G2-phase of the cell-cycle disappear ('rejoin') as a function of time between radiation exposure and cell fixation. However, the kinetics of disappearance of chromatid breaks does not correspond to those of DSB rejoining, leading us to seek alternative models. We have proposed that chromatid breaks could be formed indirectly from DSB and that the mechanism involves topoisomerase IIα. In support of this hypothesis we have recently shown that frequencies of radiation-induced chromatid breaks are lower in two variant human promyelocytic leukaemic cell lines with reduced topoisomerase IIα expression. Here we report that suppression of topoisomerase IIα in human hTERT-RPE1 cells, either by its abrogation using specific siRNA or by inhibition of its catalytic activity with the inhibitor ICRF-193, causes a reduction in frequency of chromatid breaks in radiation-exposed cells. The findings support our hypothesis for the involvement of topoisomerase IIα in the formation of radiation-induced chromatid breaks, and could help explain inter-individual variation in human chromosomal radiosensitivity; elevation of which has been linked with cancer susceptibility.

Rifampicin Induces Bicarbonate-Rich Choleresis in Rats: Involvement of Anion Exchanger 2.

Science.gov (United States)

Wang, Wei; Ren, Xiaofei; Cai, Yi; Chen, Lihong; Zhang, Weiping; Xu, Jianming

2016-01-01

Previous studies have shown that rifampicin induced choleresis, the mechanisms of which have not been described. The aim of this study was to investigate the mechanisms underlying in vivo rifampicin-induced choleresis. In one experimental set, rats were treated chronically with rifampicin on days 1, 3 and 7. Serum and biliary parameters were assayed, and mRNA and protein levels, as well as the locations of the hepatic export transporters were analyzed by real-time PCR, western blot and immunofluorescence. Ductular mass was evaluated immunohistochemically. In another experimental set, rats received an acute infusion of rifampicin. The amount of rifampicin in bile was detected using HPLC. Biliary parameters were monitored following intrabiliary retrograde fluxes of the Cl(-)/HCO3 (-) exchange inhibitor 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) or 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB) in the infused rats. Biliary bicarbonate output increased in parallel to the augmented bile flow in response to rifampicin, and this effect was abolished with intrabiliary administration of DIDS, but not NPPB. The biliary secretion of rifampicin with increases in bile flow and biliary rifampicin in response to different infused doses of the antibiotic show no significant correlations. After rifampicin treatment, the expression level of anion exchanger 2 (AE2) increased, while the location of hepatic transporters did not change. However, RIF treatment did not increase ductular mass significantly. These results indicate that the increase in bile flow induced by rifampicin is mainly due to increased HCO3 (-) excretion mediated by increased AE2 protein expression and activity.

Kinetics of the radiation-induced exchange reactions of H2, D2, and T2: a review

International Nuclear Information System (INIS)

Pyper, J.W.; Briggs, C.K.

1978-01-01

Mixtures of H 2 --T 2 or D 2 --T 2 will exchange to produce HT or DT due to catalysis by the tritium β particle. The kinetics of the reaction D 2 + T 2 = 2DT may play an important role in designing liquid or solid targets of D 2 --DT--T 2 for implosion fusion, and distillation schemes for tritium cleanup systems in fusion reactors. Accordingly, we have critically reviewed the literature for information on the kinetics and mechanism of radiation-induced self-exchange reactions among the hydrogens. We found data for the reaction H 2 + T 2 = 2HT in the gas phase and developed a scheme based on these data to predict the halftime to equilibrium for any gaseous H 2 + T 2 mixture at ambient temperature with an accuracy of +-10 percent. The overall order of the H 2 + T 2 = 2HT reaction is 1.6 based on an initial rate treatment of the data. The most probable mechanism for radiation-induced self-exchange reaction is an ion-molecule chain mechanism

A correlation between ultraviolet-induced sister chromatid exchanges and ultraviolet-indced mutagenesis in ''Muntiacus muntjak'' (Indian Muntjac) skin fibroblasts in culture

International Nuclear Information System (INIS)

Lugo, M.H.

1983-01-01

The purpose of this thesis was to develop the capability of simultaneously assaying SCEs and mutations in Indian muntjac cells to determine (1) the relationship between the ultraviolet radiation (UVR) induction of SCEs and the UVR induction of mutations at the (UVR) HGPRT locus in Indian muntjac cells and (2) the possible role of DNA repair in the UVR induction of these two events. Indian muntjac skin fibroblasts were chosen for this study because of a unique karyotype consisting of a diploid chromosome number of 6 in females and 7 in males. An HGPRT mutation assay in Indian muntjac cells was developed by this author since at the time this study was undertaken no mutational assay system utilizing Indian muntjac cells existed. It is concluded from this study that a linear correlation exists betwen the UVR-induction of SCEs and of mutations to 6TG resistance in Indian muntjac cells. As more time is allowed between the UVR-induced DNA damage and onset of DNA replication, more of the lesions leading to both mutations and SCE formation are repaired. The fact that SCE and mutation frequencies are reduced at different rates may indicate that the lesions responsible for SCEs and for mutations are repaired differently

Heat exchanger vibration

International Nuclear Information System (INIS)

Richards, D.J.W.

1977-01-01

The heat exchangers of various types are common items of plant in the generation and transmission of electricity. The amount of attention given to the flow-induced vibrations of heat exchangers by designers is usually related to the operational history of similar items of plant. Consequently, if a particular design procedure yields items of plant which behave in a satisfactory manner during their operational life, there is little incentive to improve or refine the design procedure. On the other hand, failures of heat exchangers clearly indicate deficiencies in the design procedures or in the data available to the designer. When such failures are attributable to flow-induced vibrations, the identification of the mechanisms involved is a prime importance. Ideally, basic research work provides the background understanding and the techniques necessary to be able to identify the important mechanisms. In practice, the investigation of a flow-induced vibration problem may identify the presence of mechanisms but may not be able to quantify their effects adequately. In these circumstances the need for additional work is established and the objectives of the research programme emerge. The purpose of this paper is to outline the background to the current research programme at C.E.R.L. on heat exchanger vibration

Heat exchanger vibration

Energy Technology Data Exchange (ETDEWEB)

Richards, D J.W. [CERL, CEGB, Leatherhead, Surrey (United Kingdom)

1977-12-01

The heat exchangers of various types are common items of plant in the generation and transmission of electricity. The amount of attention given to the flow-induced vibrations of heat exchangers by designers is usually related to the operational history of similar items of plant. Consequently, if a particular design procedure yields items of plant which behave in a satisfactory manner during their operational life, there is little incentive to improve or refine the design procedure. On the other hand, failures of heat exchangers clearly indicate deficiencies in the design procedures or in the data available to the designer. When such failures are attributable to flow-induced vibrations, the identification of the mechanisms involved is a prime importance. Ideally, basic research work provides the background understanding and the techniques necessary to be able to identify the important mechanisms. In practice, the investigation of a flow-induced vibration problem may identify the presence of mechanisms but may not be able to quantify their effects adequately. In these circumstances the need for additional work is established and the objectives of the research programme emerge. The purpose of this paper is to outline the background to the current research programme at C.E.R.L. on heat exchanger vibration.

Drosophila TDP-43 RNA-Binding Protein Facilitates Association of Sister Chromatid Cohesion Proteins with Genes, Enhancers and Polycomb Response Elements.

Directory of Open Access Journals (Sweden)

Amanda Swain

2016-09-01

Full Text Available The cohesin protein complex mediates sister chromatid cohesion and participates in transcriptional control of genes that regulate growth and development. Substantial reduction of cohesin activity alters transcription of many genes without disrupting chromosome segregation. Drosophila Nipped-B protein loads cohesin onto chromosomes, and together Nipped-B and cohesin occupy essentially all active transcriptional enhancers and a large fraction of active genes. It is unknown why some active genes bind high levels of cohesin and some do not. Here we show that the TBPH and Lark RNA-binding proteins influence association of Nipped-B and cohesin with genes and gene regulatory sequences. In vitro, TBPH and Lark proteins specifically bind RNAs produced by genes occupied by Nipped-B and cohesin. By genomic chromatin immunoprecipitation these RNA-binding proteins also bind to chromosomes at cohesin-binding genes, enhancers, and Polycomb response elements (PREs. RNAi depletion reveals that TBPH facilitates association of Nipped-B and cohesin with genes and regulatory sequences. Lark reduces binding of Nipped-B and cohesin at many promoters and aids their association with several large enhancers. Conversely, Nipped-B facilitates TBPH and Lark association with genes and regulatory sequences, and interacts with TBPH and Lark in affinity chromatography and immunoprecipitation experiments. Blocking transcription does not ablate binding of Nipped-B and the RNA-binding proteins to chromosomes, indicating transcription is not required to maintain binding once established. These findings demonstrate that RNA-binding proteins help govern association of sister chromatid cohesion proteins with genes and enhancers.

Ion-Exchange-Induced Selective Etching for the Synthesis of Amino-Functionalized Hollow Mesoporous Silica for Elevated-High-Temperature Fuel Cells.

Science.gov (United States)

Zhang, Jin; Liu, Jian; Lu, Shanfu; Zhu, Haijin; Aili, David; De Marco, Roland; Xiang, Yan; Forsyth, Maria; Li, Qingfeng; Jiang, San Ping

2017-09-20

As differentiated from conventional synthetic processes, amino-functionalized hollow mesoporous silica (NH 2 -HMS) has been synthesized using a new and facile strategy of ion-exchange-induced selective etching of amino-functionalized mesoporous silica (NH 2 -meso-silica) by an alkaline solution. Nuclear magnetic resonance (NMR) spectroscopy and in situ time-resolved small-angle X-ray scattering (SAXS) reveal that ion-exchange-induced selective etching arises from the gradient distribution of OH - in the NH 2 -meso-silica nanospheres. Moreover, the ion-exchange-induced selective etching mechanism is verified through a successful synthesis of hollow mesoporous silica. After infiltration with phosphotungstic acid (PWA), PWA-NH 2 -HMS nanoparticles are dispersed in the poly(ether sulfone)-polyvinylpyrrolidone (PES-PVP) matrix, forming a hybrid PWA-NH 2 -HMS/PES-PVP nanocomposite membrane. The resultant nanocomposite membrane with an optimum loading of 10 wt % of PWA-NH 2 -HMS showed an enhanced proton conductivity of 0.175 S cm -1 and peak power density of 420 mW cm -2 at 180 °C under anhydrous conditions. Excellent durability of the hybrid composite membrane fuel cell has been demonstrated at 200 °C. The results of this study demonstrated the potential of the facile synthetic strategy in the fabrication of NH 2 -HMS with controlled mesoporous structure for application in nanocomposite membranes as a technology platform for elevated-temperature proton exchange membrane fuel cells.

Sister chromatid exchanges (SCEs) in lymphocytes of inhabitants in high background radiation area

International Nuclear Information System (INIS)

Li Jinsheng; Zheng Qiaoling

1985-01-01

Blood samples were taken from 126 students of 15-16 years old, living in the high background radiation area, and from 124 controls of the same age range, living in the normal background radiation area. All students were interviewed for evaluation of their health status. Whole blood cultures were done with RPMI 1640 medium supplemented with 20% fetal calf serum and antibiotics, The culture were incubated for 54-56 h in the presence of BrdU (10 μg/ml). Metaphases were stained for SCE using a modified techniqu of perry and Wolff. From each person 20 second division metaphases were analysed for SCEs. The average frequencies of SCEs observed in the high background group and the control group are presented. More SCEs were observed in the high background group than in the control with a statistically signigicant difference. In regard to the sex factor, it was found that the SCE frequencies in both sexes of the high background group were slightly higher than those in the control group. These findings suggest that continuous low-level irradiation by the high background radiation may induce increased frequency of SCEs

Influence of the soil-atmosphere exchange on the hydric profile induced in soil-structure system

Directory of Open Access Journals (Sweden)

A. Al Qadad

2012-06-01

Full Text Available Soil-atmosphere exchange leads to a moisture change in the soil. This can cause major damage to engineering structures due to the soil expansion and shrinkage. The soil-atmosphere exchange is related to several parameters, in particular the soil characteristics and climate conditions. The presence of an engineering structure causes a variation of the hydraulic profile in the soil, which can lead to heterogeneous soil movement and consequently to structural damage. This paper presents a coupled numerical model based on the consideration of both water flow in unsaturated soils and soil-atmosphere exchange. After the validation of the model, the paper presents its use for the analysis of the influence of the presence of structures on moisture change induced under climatic conditions recorded in a semi-arid region. Analysis shows that the presence of the structure leads to important change in the moisture distribution, in particular in the vicinity of the structure.

Dominant-lethal mutations and heritable translocations in mice

Energy Technology Data Exchange (ETDEWEB)

Generoso, W.M.

1983-01-01

Chromosome aberrations are a major component of radiation or chemically induced genetic damage in mammalian germ cells. The types of aberration produced are dependent upon the mutagen used and the germ-cell stage treated. For example, in male meiotic and postmeiotic germ cells certain alkylating chemicals induce both dominant-lethal mutations and heritable translocations while others induce primarily dominant-lethal mutations. Production of these two endpoints appears to be determined by the stability of alkylation products with the chromosomes. If the reaction products are intact in the male chromosomes at the time of sperm entry, they may be repaired in fertilized eggs. If repair is not effected and the alkylation products persist to the time of pronuclear chromosome replication, they lead to chromatid-type aberrations and eventually to dominant-lethality. The production of heritable translocations, on the other hand, requires a transformation of unstable alkylation products into suitable intermediate lesions. The process by which these lesions are converted into chromosome exchange within the male genome takes place after sperm enters the egg but prior to the time of pronuclear chromosome replication (i.e., chromosome-type). Thus, dominant-lethal mutations result from both chromatid- and chromosome-type aberrations while heritable translocations result primarily from the latter type. DNA target sites associated with the production of these two endpoints are discussed.

Dominant-lethal mutations and heritable translocations in mice

International Nuclear Information System (INIS)

Generoso, W.M.

1983-01-01

Chromosome aberrations are a major component of radiation or chemically induced genetic damage in mammalian germ cells. The types of aberration produced are dependent upon the mutagen used and the germ-cell stage treated. For example, in male meiotic and postmeiotic germ cells certain alkylating chemicals induce both dominant-lethal mutations and heritable translocations while others induce primarily dominant-lethal mutations. Production of these two endpoints appears to be determined by the stability of alkylation products with the chromosomes. If the reaction products are intact in the male chromosomes at the time of sperm entry, they may be repaired in fertilized eggs. If repair is not effected and the alkylation products persist to the time of pronuclear chromosome replication, they lead to chromatid-type aberrations and eventually to dominant-lethality. The production of heritable translocations, on the other hand, requires a transformation of unstable alkylation products into suitable intermediate lesions. The process by which these lesions are converted into chromosome exchange within the male genome takes place after sperm enters the egg but prior to the time of pronuclear chromosome replication (i.e., chromosome-type). Thus, dominant-lethal mutations result from both chromatid- and chromosome-type aberrations while heritable translocations result primarily from the latter type. DNA target sites associated with the production of these two endpoints are discussed

Cytological and cytochemical effects of sodium benzoate and gamma irradiation on human peripheral lymphocytes

International Nuclear Information System (INIS)

Mohamed, N.A.F.

1981-01-01

In vitro studies of human peripheral lymphocytes were conducted to elucidate and compare the effects of a suspected chemical clastogen, sodium benzoate, widely used in the food industry as an antimicrobial food additive, to that of a well-known physical mutagen, gamma rays. Blood from ten normal donors, five males and five females, was collected and treated with various doses of the two agents independently and in combination during G 0 or G 1 phase. Induction of structural chromosomal aberrations, sister chromatid exchanges (SCEs) and unscheduled DNA synthesis were used as parameters to monitor the effects of the two agents. Sodium benzoate at the same concentrations used in the food industry (0.05% and 0.10%) caused inhibition of mitosis and induced chromatid-type aberrations (gaps and breaks). The frequency of aberrations increased as the concentration of sodium benzoate increased. No increase in SCEs over the control level was observed as either concentration tested. The relative amount of DNA damage inflicted in the treated lymphocytes estimated as 3 H-tritiated thymidine incorporation (unscheduled DNA synthesis) was highly significant. In contrast, blood irradiated with 300, 600, or 900 rad 60 Co gamma rays produced chromatid and chromosome aberrations in cultured lymphocytes, dicentrics being the most frequent exchange event. The aberration yield was found to be dose-dependent and to fit the quadratic model. Unscheduled DNA synthesis as measured by lymphocyte 3 H-TdR incorporation following gamma irradiation was highly significantly increased with the largest uptake occurring during the first hour of incubation. The combined treatment of gamma irradiation plus 0.05% sodium benzoate did not increase the aberration frequencies over the independent irradiation treatments and had no effect on SCEs frequencies

Kinetics of hydrogen isotope exchange reactions

International Nuclear Information System (INIS)

Gold, V.; McAdam, M.E.

1975-01-01

Under the influence of tritium β-radiation, 1,4-dioxan undergoes hydrogen exchange with the solvent water. The inhibition of the reaction by known electron scavengers (Ag + , Cu 2+ , Ni 2+ , Co 2+ , Zn 2+ , H 3 + O) and also by species with high reactivity towards hydroxyl radicals but negligible reactivity towards solvated electrons (N 3 - , Br - , SCN - ) has been examined in detail. γ-irradiation similarly induces hydrogen exchange. The action of scavengers is interpreted as requiring the involvement of two separately scavengeable primary radiolysis products in the sequence of reactions leading to exchange. The presence of electron scavengers, even at high concentration, does not totally inhibit the exchange, and a secondary exchange route, involving a low vacancy state of inhibitor cations, is considered responsible for the 'unscavengeable' portion of the reaction, by providing an alternative exchange route. Analogies are drawn between the exchange reaction and other radiation-induced reactions that are thought to involve spur processes. Some implication of radiation-chemical studies in water-alcohol mixtures are indicated. (author)

The Correlation of Interphase Chromatin Structure with the Radiation-Induced Inter- and Intrachromosome Exchange Hotspots

Science.gov (United States)

Zhang, Ye; Mangala, Lingegowda S.; Purgason, Ashley M.; Hada, Megumi; Cucinotta, Francis A.; Wu, Honglu

2011-01-01

To investigate the relationship between chromosome aberrations induced by radiation and chromatin folding, we reconstructed three dimensional structure of chromosome 3 and measured the physical distances between different regions of the chromosome. Previously, we have investigated the location of breaks involved in inter- and intrachromosomal type exchange events in human chromosome 3, using the multicolor banding in situ hybridization (mBAND) technique. In human epithelial cells exposed to both low- and high-LET radiations in vitro, we reported that intra-chromosome exchanges occurred preferentially between a break in the 3p21 and one in the 3q11 regions, and the breaks involving in inter-chromosome exchanges occurred in two regions towards the telomeres of the chromosome. Exchanges were also observed between a break in 3p21 and one in 3q26, but few exchanges were observed between breaks in 3q11 and 3q26, even though the two regions are located on the same arm of the chromosome. In this study, human epithelial cells were fixed at G1 phase and the interphase cells were hybridized using the XCyte3 mBAND kit from MetaSystems. The z-section images of chromosome 3 were captured with a Leica and an LSM 510 Meta laser scanning confocal microscopes. A total of 100 chromosomes were analyzed. The reconstruction of three dimensional structure of interphase chromosome 3 with six different colored regions was achieved using the Imaris software. The relative distance between different regions was measured as well. We further analyzed fragile sites on the chromosome that have been identified in various types of cancers. The data showed that, in majority of the cells, the regions containing 3p21 and 3q11 are colocalized in the center of the chromosome, whereas, the regions towards the telomeres of the chromosome are either physically wrapping outside the chromosome center or with arms sticking out. Our results demonstrated that the distribution of breaks involved in radiation-induced

Interfacial Exchange Coupling Induced Anomalous Anisotropic Magnetoresistance in Epitaxial γ′-Fe 4 N/CoN Bilayers

KAUST Repository

Li, Zirun; Mi, Wenbo; Wang, Xiaocha; Zhang, Xixiang

2015-01-01

Anisotropic magnetoresistance (AMR) of the facing-target reactively sputtered epitaxial γ′-Fe4N/CoN bilayers is investigated. The phase shift and rectangular-like AMR appears at low temperatures, which can be ascribed to the interfacial exchange coupling. The phase shift comes from the exchange bias (EB) that makes the magnetization lag behind a small field. When the γ′-Fe4N thickness increases, the rectangular-like AMR appears. The rectangular-like AMR should be from the combined contributions including the EB-induced unidirectional anisotropy, intrinsic AMR of γ′-Fe4N layer and interfacial spin scattering.

Interfacial Exchange Coupling Induced Anomalous Anisotropic Magnetoresistance in Epitaxial γ′-Fe 4 N/CoN Bilayers

KAUST Repository

Li, Zirun

2015-02-02

Anisotropic magnetoresistance (AMR) of the facing-target reactively sputtered epitaxial γ′-Fe4N/CoN bilayers is investigated. The phase shift and rectangular-like AMR appears at low temperatures, which can be ascribed to the interfacial exchange coupling. The phase shift comes from the exchange bias (EB) that makes the magnetization lag behind a small field. When the γ′-Fe4N thickness increases, the rectangular-like AMR appears. The rectangular-like AMR should be from the combined contributions including the EB-induced unidirectional anisotropy, intrinsic AMR of γ′-Fe4N layer and interfacial spin scattering.

A simple and reliable in vitro test system for the analysis of induced aneuploidy as well as other cytogenetic end-points using Chinese hamster cells

International Nuclear Information System (INIS)

Dulout, F.N.; Natarajan, A.T.

1987-01-01

Although aneuploidy is a serious human health problem, the experimental methodology devised until now to study the mechanisms involved in the induction of aneuploidy and for the screening of aneuploidy-inducing agents has not been so much employed to have the necessary validation. A procedure using primary cell cultures of Chinese hamster embryo cells grown on cover glasses is described. To avoid the excessive scattering and subsequent loss of chromosomes, a hypotonic treatment with a 0.17% sodium chloride solution, at room temperature, followed by in situ fixation has been standardized. This procedure improves the method through the reduction of the spontaneous frequency of aneuploid cells. Experiments carried out with cells treated with X-rays, X-rays plus caffeine, and the synthetic estrogen diethylstilbestrol (DES) demonstrated the accuracy of the system since the average chromosome number remained constant in spite of the induction of high frequencies of aneuploid cells. Moreover, the method allows for the analysis of other cytogenetic endpoints such as anaphase-telophase alterations, structural chromosome aberrations or sister chromatid exchanges. (author)

Genetic Damage Induced by Accidental Environmental Pollutants

Directory of Open Access Journals (Sweden)

Beatriz Pérez-Cadahía

2006-01-01

Full Text Available Petroleum is one of the main energy sources worldwide. Its transport is performed by big tankers following some established marine routes. In the last 50 years a total amount of 37 oil tankers have given rise to great spills in different parts of the world, Prestige being the last one. After the accident, a big human mobilisation took place in order to clean beaches, rocks and fauna, trying to reduce the environmental consequences of this serious catastrophe. These people were exposed to the complex mixture of compounds contained in the oil. This study aimed at determine the level of environmental exposure to volatile organic compounds (VOC, and the possible damage induced on the population involved in the different cleaning tasks by applying the genotoxicity tests sister chromatid exchanges (SCE, micronucleus (MN test, and comet assay. Four groups of individuals were included: volunteers (V, hired manual workers (MW, hired high-pressure cleaner workers (HPW and controls. The higher VOC levels were associated with V environment, followed by MW and lastly by HPW, probably due to the use of high-pressure cleaners. Oil exposure during the cleaning tasks has caused an increase in the genotoxic damage in individuals, the comet assay being the most sensitive biomarker to detect it. Sex, age and tobacco consumption have shown to influence the level of genetic damage, while the effect of using protective devices was less noticeable than expected, perhaps because the kind used was not the most adequate.

Adaptive response induced by occupational exposures to ionizing radiation

International Nuclear Information System (INIS)

Barquinero, J.F.; Caballin, M.R.; Barrios, L.; Egozcue, J.; Miro, R.; Ribas, M.

1997-01-01

We have found a significant decreased sensitivity to the cytogenetic effects of both ionizing radiation (IR) (2 Gy of γ rays) and bleomycin (BLM, 0,03 U/ml), in lymphocytes from individuals occupationally exposed to IR when compared with controls. These results suggest that occupational exposures to IR can induce adaptive response that can be detected by a subsequent treatment either by IR or by BLM. When a comparison is made between the cytogenetic effects of both treatments, no correlation was observed at the individual level. On the other hand, the individual frequencies of chromosome aberrations induced by a challenge dose of IR were negatively correlated with the occupationally received doses during the last three years. This correlation was not observed after the challenge treatment of BLM. Moreover, the individual frequencies of chromosome aberrations induced by IR treatment were homogeneous. This is not the case of the individual frequencies of chromatid aberrations induced by BLM, where a great heterogeneity was observed. (authors)

Reversible brain inactivation induces discontinuous gas exchange in cockroaches.

Science.gov (United States)

Matthews, Philip G D; White, Craig R

2013-06-01

Many insects at rest breathe discontinuously, alternating between brief bouts of gas exchange and extended periods of breath-holding. The association between discontinuous gas exchange cycles (DGCs) and inactivity has long been recognised, leading to speculation that DGCs lie at one end of a continuum of gas exchange patterns, from continuous to discontinuous, linked to metabolic rate (MR). However, the neural hypothesis posits that it is the downregulation of brain activity and a change in the neural control of gas exchange, rather than low MR per se, which is responsible for the emergence of DGCs during inactivity. To test this, Nauphoeta cinerea cockroaches had their brains inactivated by applying a Peltier-chilled cold probe to the head. Once brain temperature fell to 8°C, cockroaches switched from a continuous to a discontinuous breathing pattern. Re-warming the brain abolished the DGC and re-established a continuous breathing pattern. Chilling the brain did not significantly reduce the cockroaches' MR and there was no association between the gas exchange pattern displayed by the insect and its MR. This demonstrates that DGCs can arise due to a decrease in brain activity and a change in the underlying regulation of gas exchange, and are not necessarily a simple consequence of low respiratory demand.

Large exchange bias induced by polycrystalline Mn3Ga antiferromagnetic films with controlled layer thickness

Science.gov (United States)

Wu, Haokaifeng; Sudoh, Iori; Xu, Ruihan; Si, Wenshuo; Vaz, C. A. F.; Kim, Jun-young; Vallejo-Fernandez, Gonzalo; Hirohata, Atsufumi

2018-05-01

Polycrystalline Mn3Ga layers with thickness in the range from 6–20 nm were deposited at room temperature by a high target utilisation sputtering. To investigate the onset of exchange-bias, a ferromagnetic Co0.6Fe0.4 layer (3.3–9 nm thick) capped with 5 nm Ta, were subsequently deposited. X-ray diffraction measurements confirm the presence of Mn3Ga (0 0 0 2) and (0 0 0 4) peaks characteristic of the D019 antiferromagnetic structure. The 6 nm thick Mn3Ga film shows the largest exchange bias of 430 Oe at 120 K with a blocking temperature of 225 K. The blocking temperature is found to decrease with increasing Mn3Ga thickness. These results in combination with x-ray reflectivity measurements confirm that the quality of the Mn3Ga/Co0.6Fe0.4 interface controls the exchange bias, with the sharp interface with the 6-nm-thick Mn3Ga inducing the largest exchange bias. The magneto-crystalline anisotropy for 6 nm thick Mn3Ga thin film sample is calculated to be . Such a binary antiferromagnetic Heusler alloy is compatible with the current memory fabrication process and hence has a great potential for antiferromagnetic spintronics.

Biomonitoring of genotoxic exposure among stainless steel welders

DEFF Research Database (Denmark)

Knudsen, Lisbeth E.; Boisen, T; Christensen, J M

1992-01-01

A biosurvey in the Danish metal industry measured the genotoxic exposure from stainless steel welding. The study comprised measurements of chromosomal aberrations (CA), sister-chromatid exchanges (SCE), unscheduled DNA synthesis (UDS) in peripheral lymphocytes and serum immunoglobulin G. Environm......A biosurvey in the Danish metal industry measured the genotoxic exposure from stainless steel welding. The study comprised measurements of chromosomal aberrations (CA), sister-chromatid exchanges (SCE), unscheduled DNA synthesis (UDS) in peripheral lymphocytes and serum immunoglobulin G....... A higher frequency of chromosomal aberrations, classified as translocations, double minutes, exchanges and rings, was observed in stainless steel welders than in non-welders. SCE was lower in welders working with both MMA and TIG welding than in reference persons. N-Acetoxy-N-acetylaminofluorene (NA...... lymphocytes in exposed persons compared with non-exposed are suggested. MMA welding gave the highest exposure to chromium, an increased number of chromosomal aberrations and a decrease in SCE when compared with TIG welding. Consequently improvements in the occupational practice of stainless steel welding...

Foreign Exchange Markets in Russia: Understanding the Reforms

OpenAIRE

Linda S. Goldberg

1993-01-01

This paper analyzes and interprets the changes that took place in Russia's exchange rate system during 1992. The multiple exchange rate regime that existed in Russia prior to July 3, 1992, created strong incentives for exporters to refrain from repatriating foreign exchange earnings, induced both importers and exporters to participate in unofficial markets for foreign exchange, and encouraged international barter transactions. Efforts to manage the exchange rate through heavy foreign exchange...

WRNIP1 functions upstream of DNA polymerase η in the UV-induced DNA damage response

Energy Technology Data Exchange (ETDEWEB)

Yoshimura, Akari, E-mail: akari_yo@stu.musashino-u.ac.jp [Molecular Cell Biology Laboratory, Research Institute of Pharmaceutical Sciences, Faculty of Pharmacy, Musashino University, 1-1-20 Shinmachi, Nishitokyo-shi, Tokyo 202-8585 (Japan); Kobayashi, Yume [Molecular Cell Biology Laboratory, Research Institute of Pharmaceutical Sciences, Faculty of Pharmacy, Musashino University, 1-1-20 Shinmachi, Nishitokyo-shi, Tokyo 202-8585 (Japan); Tada, Shusuke [Department of Medical Biochemistry, Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi-shi, Chiba 274-8510 (Japan); Seki, Masayuki [Department of Biochemistry, Tohoku Pharmaceutical University, 4-4-1 Komatsushima, Aoba-ku, Sendai-shi, Miyagi 981-8558 (Japan); Enomoto, Takemi [Molecular Cell Biology Laboratory, Research Institute of Pharmaceutical Sciences, Faculty of Pharmacy, Musashino University, 1-1-20 Shinmachi, Nishitokyo-shi, Tokyo 202-8585 (Japan)

2014-09-12

Highlights: • The UV sensitivity of POLH{sup −/−} cells was suppressed by disruption of WRNIP1. • In WRNIP1{sup −/−/−}/POLH{sup −/−} cells, mutation frequencies and SCE after irradiation reduced. • WRNIP1 defect recovered rate of fork progression after irradiation in POLH{sup −/−} cells. • WRNIP1 functions upstream of Polη in the translesion DNA synthesis pathway. - Abstract: WRNIP1 (WRN-interacting protein 1) was first identified as a factor that interacts with WRN, the protein that is defective in Werner syndrome (WS). WRNIP1 associates with DNA polymerase η (Polη), but the biological significance of this interaction remains unknown. In this study, we analyzed the functional interaction between WRNIP1 and Polη by generating knockouts of both genes in DT40 chicken cells. Disruption of WRNIP1 in Polη-disrupted (POLH{sup −/−}) cells suppressed the phenotypes associated with the loss of Polη: sensitivity to ultraviolet light (UV), delayed repair of cyclobutane pyrimidine dimers (CPD), elevated frequency of mutation, elevated levels of UV-induced sister chromatid exchange (SCE), and reduced rate of fork progression after UV irradiation. These results suggest that WRNIP1 functions upstream of Polη in the response to UV irradiation.

Essential roles of BCCIP in mouse embryonic development and structural stability of chromosomes.

Directory of Open Access Journals (Sweden)

Huimei Lu

2011-09-01

Full Text Available BCCIP is a BRCA2- and CDKN1A(p21-interacting protein that has been implicated in the maintenance of genomic integrity. To understand the in vivo functions of BCCIP, we generated a conditional BCCIP knockdown transgenic mouse model using Cre-LoxP mediated RNA interference. The BCCIP knockdown embryos displayed impaired cellular proliferation and apoptosis at day E7.5. Consistent with these results, the in vitro proliferation of blastocysts and mouse embryonic fibroblasts (MEFs of BCCIP knockdown mice were impaired considerably. The BCCIP deficient mouse embryos die before E11.5 day. Deletion of the p53 gene could not rescue the embryonic lethality due to BCCIP deficiency, but partially rescues the growth delay of mouse embryonic fibroblasts in vitro. To further understand the cause of development and proliferation defects in BCCIP-deficient mice, MEFs were subjected to chromosome stability analysis. The BCCIP-deficient MEFs displayed significant spontaneous chromosome structural alterations associated with replication stress, including a 3.5-fold induction of chromatid breaks. Remarkably, the BCCIP-deficient MEFs had a ∼20-fold increase in sister chromatid union (SCU, yet the induction of sister chromatid exchanges (SCE was modestly at 1.5 fold. SCU is a unique type of chromatid aberration that may give rise to chromatin bridges between daughter nuclei in anaphase. In addition, the BCCIP-deficient MEFs have reduced repair of irradiation-induced DNA damage and reductions of Rad51 protein and nuclear foci. Our data suggest a unique function of BCCIP, not only in repair of DNA damage, but also in resolving stalled replication forks and prevention of replication stress. In addition, BCCIP deficiency causes excessive spontaneous chromatin bridges via the formation of SCU, which can subsequently impair chromosome segregations in mitosis and cell division.

Mechanisms of aluminium-induced crystallization and layer exchange upon low-temperature annealing of amorphous Si/polycrystalline Al bilayers.

Science.gov (United States)

Wang, J Y; Wang, Z M; Jeurgens, L P H; Mittemeijer, E J

2009-06-01

Aluminium-induced crystallization (ALIC) of amorphous Si and subsequent layer exchange (ALILE) occur in amorphous-Si/polycrystalline-Al bilayers (a-Si/c-Al) upon annealing at temperatures as low as 165 degrees C and were studied by X-ray diffraction and Auger electron spectroscopic depth profiling. It follows that: (i) nucleation of Si crystallization is initiated at Al grain boundaries and not at the a-Si/c-Al interface; (ii) low-temperature annealing results in a large Si grain size in the continuous c-Si layer produced by ALILE. Thermodynamic model calculations show that: (i) Si can "wet" the Al grain boundaries due to the favourable a-Si/c-Al interface energy (as compared to the Al grain-boundary energy); (ii) the wetting-induced a-Si layer at the Al grain boundary can maintain its amorphous state only up to a critical thickness, beyond which nucleation of Si crystallization takes place; and (iii) a tiny driving force controls the kinetics of the layer exchange.

Radiation induced grafting of tetrafluoroethylene on Nafion Films for ion exchange membrane application

International Nuclear Information System (INIS)

Geraldes, Adriana Napoleao; Silva, Dionisio Furtunato da; Ferreto, Helio Fernando Rodrigues; Souza, Camila Pinheiro; Parra, Duclerc Fernandes; Lugao, Ademar Benevolo

2011-01-01

Grafting of TFE nanocomposites onto Nafion was studied for synthesis of ion exchange membranes. Radiation-induced grafting of TFE gas onto Nafion films was investigated after simultaneous irradiation using a 60 Co source. The thermal degradation of polytetrafluoroethylene (PTFE) waste has been used for production of TFE. Nafion films were irradiated at 15 kGy dose at room temperature and chemical changes were monitored after contact with TFE gas for grafting. The modified films were evaluated by differential scanning calorimetry analysis (DSC), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Characterization by XRD suggests crystallinity changes after TFE grafting. The ion exchange capacity (IEC) of membranes was determined by acid-base titration and the values for modified films were achieved similar to Nafion pristine films. DSC measurements revealed a displacement in the endothermic peaks and it was probably associated with the TFE graft. The graft forces the Nafion polymer chains to re-organize themselves and form a more cross-linked structure within the clusters. (author)

Radiation induced grafting of tetrafluoroethylene on Nafion Films for ion exchange membrane application

Energy Technology Data Exchange (ETDEWEB)

Geraldes, Adriana Napoleao; Silva, Dionisio Furtunato da; Ferreto, Helio Fernando Rodrigues; Souza, Camila Pinheiro; Parra, Duclerc Fernandes; Lugao, Ademar Benevolo [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2011-07-01

Grafting of TFE nanocomposites onto Nafion was studied for synthesis of ion exchange membranes. Radiation-induced grafting of TFE gas onto Nafion films was investigated after simultaneous irradiation using a {sup 60}Co source. The thermal degradation of polytetrafluoroethylene (PTFE) waste has been used for production of TFE. Nafion films were irradiated at 15 kGy dose at room temperature and chemical changes were monitored after contact with TFE gas for grafting. The modified films were evaluated by differential scanning calorimetry analysis (DSC), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and X-ray diffraction (XRD). Characterization by XRD suggests crystallinity changes after TFE grafting. The ion exchange capacity (IEC) of membranes was determined by acid-base titration and the values for modified films were achieved similar to Nafion pristine films. DSC measurements revealed a displacement in the endothermic peaks and it was probably associated with the TFE graft. The graft forces the Nafion polymer chains to re-organize themselves and form a more cross-linked structure within the clusters. (author)

Ultrastructural analysis of radiation induced chromosome breaks and rearrangements

International Nuclear Information System (INIS)

Fernandez, J.L.; Goyanes, V.J.; Campos, A.; Cajigal, D.

1990-01-01

Chinese Hamster chromosomes R-banded in vitro were gamma-irradiated and chromatid breaks and rearrangements examined by electron microscopy employing whole-mounting technique. Breaks were preferentially located at the point of transition between G- and R-bands where the chromosome showed an average diameter 71.65 % of the wide condensed R-bands. This result was similar to the average diameter of narrow G-bands. Three chromosomes which were thin sectioned presented their broken terminal end organized as a coil constituted by two 23 nm wide chromatin fibers coiling together. Coils diameter was 43.70 % of the mean chromatid diameter. The border of damage-breakage was analyzed in whole-mounted chromosomes where breaks were photoinduced in BrdU-substituted DNA. Measurements of the angle of the sharp border of damage with respect to the chromatid axis showed a tendency to be more perpendicular as condensation progressed. These results clearly correlate with the several levels of chromatin fiber organization of the metaphase chromosome. (author)

DNA asymmetry in stem cells - immortal or mortal?

Science.gov (United States)

Yadlapalli, Swathi; Yamashita, Yukiko M

2013-09-15

The immortal strand hypothesis proposes that stem cells retain a template copy of genomic DNA (i.e. an 'immortal strand') to avoid replication-induced mutations. An alternative hypothesis suggests that certain cells segregate sister chromatids non-randomly to transmit distinct epigenetic information. However, this area of research has been highly controversial, with conflicting data even from the same cell types. Moreover, historically, the same term of 'non-random sister chromatid segregation' or 'biased sister chromatid segregation' has been used to indicate distinct biological processes, generating a confusion in the biological significance and potential mechanism of each phenomenon. Here, we discuss the models of non-random sister chromatid segregation, and we explore the strengths and limitations of the various techniques and experimental model systems used to study this question. We also describe our recent study on Drosophila male germline stem cells, where sister chromatids of X and Y chromosomes are segregated non-randomly during cell division. We aim to integrate the existing evidence to speculate on the underlying mechanisms and biological relevance of this long-standing observation on non-random sister chromatid segregation.

Development of novel ion-exchange membranes for electrodialysis of seawater by electron-beam-induced graft polymerization (4). Polymeric structures of cation-exchange membranes based on nylon-6 film

International Nuclear Information System (INIS)

Miyazawa, Tadashi; Asari, Yuki; Miyoshi, Kazuyoshi; Umeno, Daisuke; Saito, Kyoichi; Nagatani, Takeshi; Yoshikawa, Naohito; Motokawa, Ryuhei; Koizumi, Satoshi

2010-01-01

Cation-exchange membranes containing a sulfonic acid group were prepared by electron-beam-induced graft polymerization of sodium styrene sulfonate (SSS) onto a nylon-6 film with a thickness of 25 μm. The lamella sizes and lamella-to-lamella intervals of the resultant cation-exchange membranes (SSS membranes) were evaluated by X-ray diffraction (XRD) analysis and small-angle neutron scattering (SANS), respectively. With increasing degrees of grafting, the lamella size decreased, whereas the lamella-to-lamella interval increased. This can be explained by that the poly-SSS chain grafted to the periphery of the lamella of nylon 6 partially destroys the lamella and invades the amorphous domain among the lamella. The SSS membrane with a degree of grafting of 150% exhibited a similar performance in the electrodialysis of 0.5 M sodium chloride as a current cation-exchange membrane and possessed the lamella sizes and lamella-to-lamella intervals of 7.6 and 13 nm, respectively. (author)

Thrombopoietin-induced Polyploidization of Bone Marrow Megakaryocytes Is Due to a Unique Regulatory Mechanism in Late Mitosis

Science.gov (United States)

Nagata, Yuka; Muro, Yoshinao; Todokoro, Kazuo

1997-01-01

Megakaryocytes undergo a unique differentiation program, becoming polyploid through repeated cycles of DNA synthesis without concomitant cell division. However, the mechanism underlying this polyploidization remains totally unknown. It has been postulated that polyploidization is due to a skipping of mitosis after each round of DNA replication. We carried out immunohistochemical studies on mouse bone marrow megakaryocytes during thrombopoietin- induced polyploidization and found that during this process megakaryocytes indeed enter mitosis and progress through normal prophase, prometaphase, metaphase, and up to anaphase A, but not to anaphase B, telophase, or cytokinesis. It was clearly observed that multiple spindle poles were formed as the polyploid megakaryocytes entered mitosis; the nuclear membrane broke down during prophase; the sister chromatids were aligned on a multifaced plate, and the centrosomes were symmetrically located on either side of each face of the plate at metaphase; and a set of sister chromatids moved into the multiple centrosomes during anaphase A. We further noted that the pair of spindle poles in anaphase were located in close proximity to each other, probably because of the lack of outward movement of spindle poles during anaphase B. Thus, the reassembling nuclear envelope may enclose all the sister chromatids in a single nucleus at anaphase and then skip telophase and cytokinesis. These observations clearly indicate that polyploidization of megakaryocytes is not simply due to a skipping of mitosis, and that the megakaryocytes must have a unique regulatory mechanism in anaphase, e.g., factors regulating anaphase such as microtubule motor proteins might be involved in this polyploidization process. PMID:9334347

Sister Chromatid Exchanges (=SCEs) in Lymphocytes of persons working at Shlobin (USSR), 150km north of Chernobyl

International Nuclear Information System (INIS)

Tuschl, H.; Kovac, R.

1988-08-01

SCEs are considered to be a sensitive indicator for the DNA damaging effects of mutagenic and carcinogenic agents. In 1986, during the Chernobyl accident, employees of an Austrian company worked at Shlobin, 150km north of Chernobyl. At their return to Austria blood as taken and spontaneously occurring and MMC induced SCEs were studied. Spontaneously occurring SCEs in lymphocytes of 'exposed' and 'unexposed' persons were only insignificantly different when results were summarized for all test persons. A significant influence of smoking could be established. When results were correlated with the time interval between the Chernobyl accident and the date of blood sampling, the increased rate of spontaneous SCEs observed soon after the accident decreased to the normal range during the following months. Irrespective of the molecular mechanism that might be the rationale for the observed decreased induction of SCEs in lymphocytes of exposed persons, the estimation of MMC induced SCEs proved to be the most sensitive test to demonstrate population exposure to low doses of ionizing radiation. 7 refs., 1 fig., 5 tabs. (Author)

The phenotype of FancB-mutant mouse embryonic stem cells

International Nuclear Information System (INIS)

Kim, Tae Moon; Ko, Jun Ho; Choi, Yong Jun; Hu Lingchuan; Hasty, Paul

2011-01-01

Fanconi anemia (FA) is a rare autosomal recessive disease characterized by bone marrow failure, developmental defects and cancer. There are multiple FA genes that enable the repair of interstrand crosslinks (ICLs) in coordination with a variety of other DNA repair pathways in a way that is poorly understood. Here we present the phenotype of mouse embryonic stem (ES) cells mutated for FancB. We found FancB-mutant cells exhibited reduced cellular proliferation, hypersensitivity to the crosslinking agent mitomycin C (MMC), increased spontaneous and MMC-induced chromosomal abnormalities, reduced spontaneous sister chromatid exchanges (SCEs), reduced gene targeting, reduced MMC-induced Rad51 foci and absent MMC-induced FancD2 foci. Since FancB is on the X chromosome and since ES cells are typically XY, FancB is an excellent target for an epistatic analysis to elucidate FA's role in ICL repair.

Study of the influence of Nb buffer layer on the exchange coupling induced at the Co/IrMn interface

Energy Technology Data Exchange (ETDEWEB)

Merino, I.L.C., E-mail: isabel5cas@gmail.com [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil); Figueiredo, L.C. [Instituto de Física, Universidade de Brasília, Brasília 70910-900 (Brazil); Passamani, E.C.; Nascimento, V.P. [Departamento de Física, Universidade Federal do Espírito Santo, Vitória 29075-910 (Brazil); Pelegrini, F. [Instituto de Física, Universidade Federal de Goiás, Goiânia 74560-900 (Brazil); Baggio Saitovitch, E. [Centro Brasileiro de Pesquisas Físicas, Rio de Janeiro 22290-180 (Brazil)

2017-06-15

Highlights: • Nb buffer layer favors smooth/rough Co/IrMn interfaces, depending on its thickness. • Double and single-like hysteresis loop features depend on the Nb thickness. • Co uniaxial anisotropy induced exchange-bias in as-deposited sample. • Uniaxial and exchange-bias anisotropy directions depend on the Nb thickness. • Thicker Nb favors non-collinear anisotropies, while thinner Nb favors collinear. - Abstract: Hybrid Nb(t{sub Nb})/Co(10 nm)/IrMn(15 nm)/Nb(10 nm) heterostructured materials were prepared by DC Magnetron Sputtering and systematically studied by X-ray, magnetization and ferromagnetic resonance techniques. For thinner Nb buffer layer (≤10 nm), it was found that there is an inter-diffusion at Co/IrMn interface, which favors double-like hysteresis loop. For thicker Nb layers, however, a gradual transition from double to single-like hysteresis loops is observed and it is associated with the reduction of the Nb roughness, which also enhances the exchange coupling at the Co/IrMn interface. Nb grown on IrMn layer induces the formation of an NbIrMn alloy layer, while no evidence of inter-diffusion at the Co/Nb interface is observed. For rougher Nb buffer layers (t{sub Nb} < 50 nm), exchange bias and Co uniaxial anisotropies are pointing at the same direction (β∼zero), but for smoother Nb buffer layer (t{sub Nb} = 50 nm) a β angle of 150{sup o} is found. Exchange bias effect was measured in as-prepared and in field-cooled samples; being its presence, in as-prepared sample, attributed to the unidirectional anisotropy of the Co layer (its intensity is modified in case of sample with a CoIrMn alloy layer). Considering that the Si/Nb/Co/IrMn interfaces have different β values (t{sub Nb} = 35 and 50 nm), a study of the influence of magnetization direction, governed by exchange-biased layers, on superconducting properties of Nb films can be successfully done in this hybrid system.

Medium from X-rayed cultures induces DNA strand-breaks in non-irradiated HeLa cells

International Nuclear Information System (INIS)

Ikushima, T.; Okuyama, K.; Tanizaki, Y.

2002-01-01

There is growing evidence to indicate that several types of responses are induced by ionizing radiation in non-irradiated cells. Such bystander effects include the killing of non-irradiated cells, the induction of sister chromatid exchanges and chromosomal aberrations, and the induction of gene mutations and chromosomal instability and enhanced cell growth. In the present study, we assessed whether the medium from irradiated cultures can induce DNA strand-breaks in non-irradiated cells, using single-cell gel electrophoresis assay (comet assay). HeLa cells in culture were irradiated with 0.5 to 8 Gy of 140 kVp X-rays and one hour later, the medium was taken from the irradiated culture, passed through a filter and transferred to the parallel culture of non-irradiated HeLa cells as non-target cells. After incubation for 30 min, the comet assay was performed under alkaline and neutral conditions. Such treatments resulted in a dose-dependent increase in tail moment under either alkaline or neutral condition, indicating the induction of DNA single- or double-strand breaks, respectively. It was also shown that the clonogenic survival was reduced in the cells cultured in the medium from irradiated cultures. Such a change was not detected at all when medium alone was irradiated. These results provided disputed evidence that irradiated cells released certain genotoxic factor(s) into the culture medium that can induce DNA strand breaks leading to cell death. Our results suggest that physical contact between irradiated and non-irradiated cells may not be necessary for the bystander effects observed in this study. It appears that bystander responses may be mediated by multiple mechanisms

The mitosis-regulating and protein-protein interaction activities of astrin are controlled by aurora-A-induced phosphorylation.

Science.gov (United States)

Chiu, Shao-Chih; Chen, Jo-Mei Maureen; Wei, Tong-You Wade; Cheng, Tai-Shan; Wang, Ya-Hui Candice; Ku, Chia-Feng; Lian, Chiao-Hsuan; Liu, Chun-Chih Jared; Kuo, Yi-Chun; Yu, Chang-Tze Ricky

2014-09-01

Cells display dramatic morphological changes in mitosis, where numerous factors form regulatory networks to orchestrate the complicated process, resulting in extreme fidelity of the segregation of duplicated chromosomes into two daughter cells. Astrin regulates several aspects of mitosis, such as maintaining the cohesion of sister chromatids by inactivating Separase and stabilizing spindle, aligning and segregating chromosomes, and silencing spindle assembly checkpoint by interacting with Src kinase-associated phosphoprotein (SKAP) and cytoplasmic linker-associated protein-1α (CLASP-1α). To understand how Astrin is regulated in mitosis, we report here that Astrin acts as a mitotic phosphoprotein, and Aurora-A phosphorylates Astrin at Ser(115). The phosphorylation-deficient mutant Astrin S115A abnormally activates spindle assembly checkpoint and delays mitosis progression, decreases spindle stability, and induces chromosome misalignment. Mechanistic analyses reveal that Astrin phosphorylation mimicking mutant S115D, instead of S115A, binds and induces ubiquitination and degradation of securin, which sequentially activates Separase, an enzyme required for the separation of sister chromatids. Moreover, S115A fails to bind mitosis regulators, including SKAP and CLASP-1α, which results in the mitotic defects observed in Astrin S115A-transfected cells. In conclusion, Aurora-A phosphorylates Astrin and guides the binding of Astrin to its cellular partners, which ensures proper progression of mitosis. Copyright © 2014 the American Physiological Society.

Chromosome fragility in Freemartin cattle

Directory of Open Access Journals (Sweden)

V. Barbieri

2010-04-01

Full Text Available The aim of the present study was to verify chromosome fragility in freemartin cattle using chromosome aberration (CA and sister chromatid exchange (SCE tests. A total of eighteen co-twins were investigated. Fourteen animals were identified as cytogenetically chimeric (2n=60, XX/XY while 4 were classified as normal. Freemartin cattle showed a higher percentage of aneuploid cells (18.64% and highly significant statistical differences (P < 0.001 in mean values of gaps (4.53 ± 2.05, chromatid breaks (0.26 ± 0.51, and significant statistical differences (P < 0.005 in mean values of chromosome breaks (0.12 ± 0.43 when compared to 10 control animals from single births (aneuploid cells, 11.20%; gaps, 2.01 ± 1.42; chromatid breaks, 0.05 ± 0.22; chromosome breaks, 0.02 ± 0.14.

Cytogenetic effects of near ultraviolet radiation in normal and systemic lupus erythematosus lymphocytes

Energy Technology Data Exchange (ETDEWEB)

Caporossi, D.; Sebastiani, G.; Nicoletti, B. (Rome 2 University (Italy). Department of Public Health and Cellular Biology); Masala, C. (' La Sapienza' University, rome (Italy). Institute of Infectious and Tropical Diseases)

1990-03-01

The authors conducted a study on the spontaneous and UV-A induced frequency of chromosomal breaks and sister-chromatid exchanges (SCE) in purified lymphocytes from normal donors and from systemic lupus erythematosus (SLE) patients who were in clinical remission at the time of the study. Our results show that although SLE lymphocytes exhibit a higher frequency of spontaneous SCEs than controls, the rate of chromosomal breakage is comparable in the 2-groups. In both controls and patients, irradiation with UV-A (320-400 nm) increases the SCE values but does not significantly affect the frequency of chromosomal aberrations. (author). 14 refs.; 1 fig.; 3 tabs.

Cytogenetic effects of near ultraviolet radiation in normal and systemic lupus erythematosus lymphocytes

International Nuclear Information System (INIS)

Caporossi, D.; Sebastiani, G.; Nicoletti, B.; Masala, C.

1990-01-01

The authors conducted a study on the spontaneous and UV-A induced frequency of chromosomal breaks and sister-chromatid exchanges (SCE) in purified lymphocytes from normal donors and from systemic lupus erythematosus (SLE) patients who were in clinical remission at the time of the study. Our results show that although SLE lymphocytes exhibit a higher frequency of spontaneous SCEs than controls, the rate of chromosomal breakage is comparable in the 2-groups. In both controls and patients, irradiation with UV-A (320-400 nm) increases the SCE values but does not significantly affect the frequency of chromosomal aberrations. (author). 14 refs.; 1 fig.; 3 tabs

The C-terminal domain of the Bloom syndrome DNA helicase is essential for genomic stability

Directory of Open Access Journals (Sweden)

Noonan James P

2001-07-01

Full Text Available Abstract Background Bloom syndrome is a rare cancer-prone disorder in which the cells of affected persons have a high frequency of somatic mutation and genomic instability. Bloom syndrome cells have a distinctive high frequency of sister chromatid exchange and quadriradial formation. BLM, the protein altered in BS, is a member of the RecQ DNA helicase family, whose members share an average of 40% identity in the helicase domain and have divergent N-terminal and C-terminal flanking regions of variable lengths. The BLM DNA helicase has been shown to localize to the ND10 (nuclear domain 10 or PML (promyelocytic leukemia nuclear bodies, where it associates with TOPIIIα, and to the nucleolus. Results This report demonstrates that the N-terminal domain of BLM is responsible for localization of the protein to the nuclear bodies, while the C-terminal domain directs the protein to the nucleolus. Deletions of the N-terminal domain of BLM have little effect on sister chromatid exchange frequency and chromosome stability as compared to helicase and C-terminal mutations which can increase SCE frequency and chromosome abnormalities. Conclusion The helicase activity and the C-terminal domain of BLM are critical for maintaining genomic stability as measured by the sister chromatid exchange assay. The localization of BLM into the nucleolus by the C-terminal domain appears to be more important to genomic stability than localization in the nuclear bodies.

Heat transfer in tube bundles of heat exchangers with flow baffles induced forced mixing

International Nuclear Information System (INIS)

AbuRomia, M.M.; Chu, A.W.; Cho, S.M.

1976-01-01

Thermal analysis of shell-and-tube heat exchangers is being investigated through geometric modeling of the unit configuration in addition to considering the heat transfer processes taking place within the tube bundle. The governing equations that characterize the heat transfer from the shell side fluid to the tube side fluid across the heat transfer tubewalls are indicated. The equations account for the heat transfer due to molecular conduction, turbulent thermal diffusion, and forced fluid mixing among various shell side fluid channels. The analysis, though general in principle, is being applied to the Clinch River Breeder Reactor Plant-Intermediate Heat Exchanger, which utilizes flow baffles appropriately designed for induced forced fluid mixing in the tube bundle. The results of the analysis are presented in terms of the fluid and tube wall temperature distributions of a non-baffled and baffled tube bundle geometry. The former case yields axial flow in the main bundle region while the latter is associated with axial/cross flow in the bundle. The radial components of the axial/cross flow yield the necessary fluid mixing that results in reducing the thermal unbalance among the heat transfer to the allowable limits. The effect of flow maldistribution, present on the tube or shell sides of the heat exchangers, in altering the temperature field of tube bundles is also noted

Single-cell template strand sequencing by Strand-seq enables the characterization of individual homologs

NARCIS (Netherlands)

Sanders, Ashley D; Falconer, Ester; Hills, Mark; Spierings, Diana C J; Lansdorp, Peter M.

The ability to distinguish between genome sequences of homologous chromosomes in single cells is important for studies of copy-neutral genomic rearrangements (such as inversions and translocations), building chromosome-length haplotypes, refining genome assemblies, mapping sister chromatid exchange

Variability in benthic exchange rate, depth, and residence time beneath a shallow coastal estuary

Science.gov (United States)

Russoniello, C. J.; Michael, H. A.; Heiss, J.

2017-12-01

Hydrodynamically-driven exchange of water between the water column and shallow seabed aquifer, benthic exchange, is a significant and dynamic component of coastal and estuarine fluid budgets, but wave-induced benthic exchange has not been measured in the field. Mixing between surface water and groundwater solutes promotes ecologically important chemical reactions, so quantifying benthic exchange rates, depths, and residence times, constrains estimates of coastal chemical cycling. In this study, we present the first field-based direct measurements of wave-induced exchange and compare it to exchange induced by the other primary drivers of exchange - tides, and currents. We deployed instruments in a shallow estuary to measure benthic exchange and temporal variability over an 11-day period. Differential pressure sensors recorded pressure gradients across the seabed, and up-and down-looking ADCPs recorded currents and pressures from which wave parameters, surface-water currents, and water depth were determined. Wave-induced exchange was calculated directly from 1) differential pressure measurements, and indirectly with an analytical solution based on wave parameters from 2) ADCP and 3) weather station data. Groundwater flow models were used to assess the effects of aquifer properties on benthic exchange depth and residence time. Benthic exchange driven by tidal pumping or current-bedform interaction was calculated from tidal stage variation and from ADCP-measured currents at the bed, respectively. Waves were the primary benthic exchange driver (average = 20.0 cm/d, maximum = 92.3 cm/d) during the measurement period. Benthic exchange due to tides (average = 3.7 cm/d) and current-bedform interaction (average = 6.5x10-2 cm/d) was much lower. Wave-induced exchange calculated from pressure measurements and ADCP-measured wave parameters matched well, but wind-based rates underestimated wave energy and exchange. Groundwater models showed that residence time and depth increased

Structural analysis of radiation-induced chromosome aberrations by atomic force microscope (AFM) before and after Giemsa staining

International Nuclear Information System (INIS)

Murakami, M.; Kanda, R.; Minamihisamatsu, M.; Hayata, I.

2003-01-01

Full text: We have studied structures of chromosome aberration induced by ionizing radiation by an atomic force microscope (AFM). The AFM could visualize the fine structure of chromosomes on Giemsa stained or unstained samples, although it was difficult to visualize unstained chromosomes by light microscope. The height data of chromosomes obtained by AFM provided useful information to describe detailed structure of chromatid gaps induced by heavy ion irradiation. A fibrous structure was observed on the unstained chromosome and these structures were considered to be the 30nm fibers on the chromosome. These types of structures were observed in the gaps as well as on surface of the chromosome. Further more, other types of chromosome aberration induced by ionizing radiation visualized by AFM will be presented

Neutrons and X-rays, comparative studies with Drosophila melanogaster. Pt. 2

International Nuclear Information System (INIS)

Leigh, B.; Veerkamp-van Baarle, A.M.A.; Sobels, F.H.; Broese, J.J.

1981-01-01

Losses and duplications of Bsup(S)Y γ + -chromosome markers werde induced by irradiation of spermatozoa with either 0.5-MeV neutrons or 100-kV X-rays. These 2 types of radiation are known to induce significantly different ratios of double:single strand breaks in DNA. Exceptional progeny were grouped into 3 categories; no Y marker, one Y marker, and Y marker duplications + mosaics. The last combination consisted of exceptions derived from only chromatid-type rearrangements. All other classes of exceptions may be derived from either chromatid- or chromosome-type rearrangements. Doses of 15 Gy neutrons and 27 Gy X-rays induced identical frequencies of exceptional progeny, giving an RBE of 1.8. The ratios of the 3 classes of exceptions were similar for both types of radiation. This observation can be interpreted as indicating that, under the conditions used here, chromosome and chromatid rearrangements are not derived directly from double and single DNA strand breaks, respectively. (orig.)

Electric-field-induced modification of the magnon energy, exchange interaction, and curie temperature of transition-metal thin films.

Science.gov (United States)

Oba, M; Nakamura, K; Akiyama, T; Ito, T; Weinert, M; Freeman, A J

2015-03-13

The electric-field-induced modification in the Curie temperature of prototypical transition-metal thin films with the perpendicular magnetic easy axis, a freestanding Fe(001) monolayer and a Co monolayer on Pt(111), is investigated by first-principles calculations of spin-spiral structures in an external electric field (E field). An applied E field is found to modify the magnon (spin-spiral formation) energy; the change arises from the E-field-induced screening charge density in the spin-spiral states due to p-d hybridizations. The Heisenberg exchange parameters obtained from the magnon energy suggest an E-field-induced modification of the Curie temperature, which is demonstrated via Monte Carlo simulations that take the magnetocrystalline anisotropy into account.

Design specifications to ensure flow-induced vibration and fretting-wear performance in CANDU steam generators and heat exchangers

International Nuclear Information System (INIS)

Janzen, V.P.; Han, Y.; Pettigrew, M.J.

2009-01-01

Preventing flow-induced vibration and fretting-wear problems in steam generators and heat exchangers requires design specifications that bring together specific guidelines, analysis methods, requirements and appropriate performance criteria. This paper outlines the steps required to generate and support such design specifications for CANDU nuclear steam generators and heat exchangers, and relates them to typical steam-generator design features and computer modeling capabilities. It also describes current issues that are driving changes to flow-induced vibration and fretting-wear specifications that can be applied to the design process for component refurbishment, replacement or new designs. These issues include recent experimental or field evidence for new excitation mechanisms, e.g., the possibility of in-plane fluidelastic instability of U-tubes, the demand for longer reactor and component lifetimes, the need for better predictions of dynamic properties and vibration response, e.g., two-phase random-turbulence excitation, and requirements to consider system 'excursions' or abnormal scenarios, e.g., a main steam line break in the case of steam generators. The paper describes steps being taken to resolve these issues. (author)

Mapping temperature-induced conformational changes in the Escherichia coli heat shock transcription factor sigma 32 by amide hydrogen exchange

DEFF Research Database (Denmark)

Rist, Wolfgang; Jørgensen, Thomas J D; Roepstorff, Peter

2003-01-01

Stress conditions such as heat shock alter the transcriptional profile in all organisms. In Escherichia coli the heat shock transcription factor, sigma 32, out-competes upon temperature up-shift the housekeeping sigma-factor, sigma 70, for binding to core RNA polymerase and initiates heat shock...... gene transcription. To investigate possible heat-induced conformational changes in sigma 32 we performed amide hydrogen (H/D) exchange experiments under optimal growth and heat shock conditions combined with mass spectrometry. We found a rapid exchange of around 220 of the 294 amide hydrogens at 37...... degrees C, indicating that sigma 32 adopts a highly flexible structure. At 42 degrees C we observed a slow correlated exchange of 30 additional amide hydrogens and localized it to a helix-loop-helix motif within domain sigma 2 that is responsible for the recognition of the -10 region in heat shock...

Inhibition of repair activity induced by γ-radiation, UV-rays and radiomimetics in the in vitro cultured cells of patients wiyh schizophrenia

International Nuclear Information System (INIS)

Zasukhina, G.D.; Zharikov, N.M.; L'vova, G.N.; Vasil'eva, I.M.; Chekova, V.V.; Alekhina, N.I.; Ivanova, T.N.

1986-01-01

A study was made of the processes of repair, virus reactivation, and formation of sister chromatid exchages (SCE) in blood cells of patients with schizophrenia after the effect of γ-radiation and 4-nitroquinoline-1-oxide. These processes were estimated by 12 criteria. The mutagen-induced disturbances in the processes of repair and SCE formation were found in cells of patients with schizophrenia and were absent in the control cells of healthy donors

Positive pressure ventilation with the open lung concept optimizes gas exchange and reduces ventilator-induced lung injury in newborn piglets

NARCIS (Netherlands)

van Kaam, Anton H.; de Jaegere, Anne; Haitsma, Jack J.; van Aalderen, Wim M.; Kok, Joke H.; Lachmann, Burkhard

2003-01-01

Previous studies demonstrated that high-frequency oscillatory ventilation using the open lung concept (OLC resulted in superior gas exchange and a reduction in ventilator-induced lung injury (VILI). We hypothesized that these beneficial effects could also be achieved by applying the OLC during

Possible role of protein damages in the origin of UV-induced isochromatid breaks

International Nuclear Information System (INIS)

Lebedeva, L.I.; Ostrovskaya, R.M.; Tsimmerman, V.G.

1978-01-01

Formation of aberrations was studied in the first and second mitosis following UV irradiation with the aim to elucidate the nature of the sensitive target responsible for aberrations formed during the G 2 period. The primary embryonic fibroblast culture from BALB mice was used; UV irradiation was at 254, 265, 280 and 302 nm and 40 and 80 erg/mm 2 doses. The cycle stages and exact times, when fixation was done, were determined from labelled mitosis curves. The frequency of chromosome aberrations after irradiation of cells at the G 2 stage was approximately the same at the wave lengths of 254, 265 and 280 nm, suggesting that DNA and protein are the targets responsible for aberrations.For chromatid aberrations the efficiency spectrum corresponded to the thymine absorption spectrum. Isochromatid break efficiency spectrum was similar to the protein absorption spectra. Caffeine, when applied during S period of the second mitosis, increased the frequency of chromatid breaks and did not affect other aberrations. It is supposed that the formation of chromatid aberrations and isochromatid breaks is underlied by different mechanisms. Chromatid aberrations are initiated by the formation of DNA-DNA cross linkages resulting from thymine dimers. For isochromatid breaks, the presence of a protein chromophore is important

Comparison of radiosensitivity between human hematopoietic cell lines derived from patients with Down's syndrome and from normal persons

International Nuclear Information System (INIS)

Huang, C.C.; Banerjee, A.; Tan, J.C.; Hou, Y.

1977-01-01

Seven hematopoietic cell lines, four derived from the peripheral blood of patients with Down's syndrome (DS) and three from normal persons, were irradiated with 100, 150, 300, and 500 rads from a 60 Co source and harvested for cell count and chromosome aberration studies every 12 hours for 72 hours post irradiation. Cell growth inhibition and an increase in chromosome aberration were observed in all the cell lines at each dose level and time interval. No significant difference was observed in the effects between DS and normal cell lines. The most common types of aberrations in the 12-hour samples were chromosome and/or chromatid breaks. In the later samples, chromatid exchanges were predominant. The results of the variance analyses on the induced chromosome aberrations in six lines (three DS and three normal lines) showed radiation dosage to be the largest component of total variance, following postirradiation duration and cell lines. The samples harvested 24 and 36 hours post irradiation generally showed greater effects than the samples of other harvest durations. The cell line variance could only be attributed to the differences among and between individual cell lines rather than the difference between DS and normal cell lines

New trends and techniques in chromosome aberration analysis

International Nuclear Information System (INIS)

Bender, M.A.

1978-01-01

The following topics are discussed: automation of chromosome analysis; storage of fixed cells from cultures of lymphocytes obtained routinely during periodic employee medical examinations; analysis of banded chromosomes; identification of first division metaphases; sister chromatid exchange; and patterns of aberration induction

BLM helicase suppresses recombination at G-quadruplex motifs in transcribed genes

NARCIS (Netherlands)

van Wietmarschen, Niek; Merzouk, Sarra; Halsema, Nancy; Spierings, Diana C J; Guryev, Victor; Lansdorp, Peter M

2018-01-01

Bloom syndrome is a cancer predisposition disorder caused by mutations in the BLM helicase gene. Cells from persons with Bloom syndrome exhibit striking genomic instability characterized by excessive sister chromatid exchange events (SCEs). We applied single-cell DNA template strand sequencing

Preparation of the proton exchange membranes for fuel cell under pre-irradiation induced grafting method

International Nuclear Information System (INIS)

Li Jingye; Muto, F.; Matsuura, A.; Kakiji, T.; Miura, T.; Oshima, A.; Washio, M.; Katsumura, Y.

2006-01-01

Proton exchange membranes (PEMs) were prepared via pre-irradiation induced grafting of styrene or styrene/divinylbenzene (S/DVB) into the crosslinked polytetrafluoroethylene (RX-PTFE) films with thickness around 10 m and then sulfonated by chlorosulfonic acid. The membrane electrode assembles (MEAs) based on these PEMs with ion exchange capacity (IEC) values around 2meq/g were prepared by hot-press with Nafion dispersion coated on the surfaces of the membranes and electrodes. And the MEA based on the Nafion 112 membrane was also prepared under same procedure as a comparison. The performances of the MEAs in single fuel cell were tested under different working temperatures and humidification conditions. The performance of the synthesized PEMs showed better results than that of Nafion 112 membrane under low humidification at 80 degree C. The electrochemical impedance spectra (EIS) were taken with the direct current density of 0.5A/cm 2 and the resulted curves in Nyqvist representation obeyed the half circle pattern. (authors)

Merotelic kinetochore attachment in oocyte meiosis II causes sister chromatids segregation errors in aged mice.

Science.gov (United States)

Cheng, Jin-Mei; Li, Jian; Tang, Ji-Xin; Hao, Xiao-Xia; Wang, Zhi-Peng; Sun, Tie-Cheng; Wang, Xiu-Xia; Zhang, Yan; Chen, Su-Ren; Liu, Yi-Xun

2017-08-03

Mammalian oocyte chromosomes undergo 2 meiotic divisions to generate haploid gametes. The frequency of chromosome segregation errors during meiosis I increase with age. However, little attention has been paid to the question of how aging affects sister chromatid segregation during oocyte meiosis II. More importantly, how aneuploid metaphase II (MII) oocytes from aged mice evade the spindle assembly checkpoint (SAC) mechanism to complete later meiosis II to form aneuploid embryos remains unknown. Here, we report that MII oocytes from naturally aged mice exhibited substantial errors in chromosome arrangement and configuration compared with young MII oocytes. Interestingly, these errors in aged oocytes had no impact on anaphase II onset and completion as well as 2-cell formation after parthenogenetic activation. Further study found that merotelic kinetochore attachment occurred more frequently and could stabilize the kinetochore-microtubule interaction to ensure SAC inactivation and anaphase II onset in aged MII oocytes. This orientation could persist largely during anaphase II in aged oocytes, leading to severe chromosome lagging and trailing as well as delay of anaphase II completion. Therefore, merotelic kinetochore attachment in oocyte meiosis II exacerbates age-related genetic instability and is a key source of age-dependent embryo aneuploidy and dysplasia.

Solvent exchange-induced in situ forming gel comprising ethyl cellulose-antimicrobial drugs.

Science.gov (United States)

Phaechamud, Thawatchai; Mahadlek, Jongjan

2015-10-15

Solvent-exchanged in situ forming gel is a drug delivery system which is in sol form before administration. When it contacts with the body fluid, then the water miscible organic solvent dissipates and water penetrates into the system, leading the polymer precipitation as in situ gel at the site of injection. The aim of this research was to study the parameters affecting the gel properties, drug release and antimicrobial activities of the in situ forming gels prepared from ethyl cellulose (EC) dissolved in N-methyl pyrrolidone (NMP) to deliver the antimicrobial agents (doxycycline hyclate, metronidazole and benzyl peroxide) for periodontitis treatment. The gel appearance, pH, viscosity, rheology, syringeability, gel formation, rate of water diffusion into the gels, in vitro degradation, drug release behavior and antimicrobial activities against Staphylococcus aureus, Escherichia coli, Candida albicans, Streptococcus mutans and Porphyrommonas gingivalis were determined. Increasing the amount of EC increased the viscosity of system while still exhibiting Newtonian flow and increased the work of syringeability whereas decreased the releasing of drug. The system transformed into the rigid gel formation after being injected into the simulated gingival crevicular fluid. The developed systems containing 5% w/w antimicrobial agent showed the antimicrobial activities against all test bacteria. Thus the developed solvent exchange-induced in situ forming gels comprising EC-antimicrobial drugs exhibited potential use for periodontitis treatment. Copyright © 2015 Elsevier B.V. All rights reserved.

Sensitivity to ultraviolet radiation in a dominantly inherited form of xeroderma pigmentosum

International Nuclear Information System (INIS)

Imray, F.P.; Relf, W.; Ramsay, R.G.; Kidson, C.; Hockey, A.

1986-01-01

An Australian family is described in which a mild form of xeroderma pigmentosum (XP) is inherited as an autosomal dominant trait. Studies of lymphoblastoid cells and fibroblasts from affected person demonstrated sensitivity to ultraviolet (UV) light as judged by diminished clonogenicity and higher frequencies of UV induced chromosome aberrations compared to normal controls. After UV irradiation of dominant XP cells, replicative DNA synthesis was depressed to a greater extent than normal and the level of UV induced DNA repair synthesis was lower than that in normal cells. The level of sister chromatid exchanges and the numbers of 6-thioguanine resistant mutants induced by UV irradiation were equal to those found in normal controls. Although two subjects in the family had skin cancers, this dominant form of XP is not apparently associated with high risk, or large numbers of skin cancers in affected persons. (author)

The phenotype of FancB-mutant mouse embryonic stem cells

Energy Technology Data Exchange (ETDEWEB)

Kim, Tae Moon; Ko, Jun Ho; Choi, Yong Jun; Hu Lingchuan [Department of Molecular Medicine and Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 15355 Lambda Drive, San Antonio, TX 78245 (United States); Hasty, Paul, E-mail: hastye@uthscsa.edu [Department of Molecular Medicine and Institute of Biotechnology, University of Texas Health Science Center at San Antonio, 15355 Lambda Drive, San Antonio, TX 78245 (United States)

2011-07-01

Fanconi anemia (FA) is a rare autosomal recessive disease characterized by bone marrow failure, developmental defects and cancer. There are multiple FA genes that enable the repair of interstrand crosslinks (ICLs) in coordination with a variety of other DNA repair pathways in a way that is poorly understood. Here we present the phenotype of mouse embryonic stem (ES) cells mutated for FancB. We found FancB-mutant cells exhibited reduced cellular proliferation, hypersensitivity to the crosslinking agent mitomycin C (MMC), increased spontaneous and MMC-induced chromosomal abnormalities, reduced spontaneous sister chromatid exchanges (SCEs), reduced gene targeting, reduced MMC-induced Rad51 foci and absent MMC-induced FancD2 foci. Since FancB is on the X chromosome and since ES cells are typically XY, FancB is an excellent target for an epistatic analysis to elucidate FA's role in ICL repair.

Certain tryptophan photoproducts are inhibitors of cytochrome P450-dependent mutagenicity

International Nuclear Information System (INIS)

Rannug, U.; Agurell, E.; Cederberg, H.; Rannug, A.

1992-01-01

Two photoproducts, derived from UV-irradiation of the amino acid L-tryptophan and with high Ah (TCDD) receptor binding affinity, were tested for genotoxic and antimutagenic effects. The two indolo[3,2-b]carbazole derivatives, with the molecular weights of 284 and 312, respectively, were tested in Saccharomyces cerevisiae strain D7 for mitotic gene conversion and reverse mutation and in strain RS112 for sister chromatid conversion and gene conversion. No significant (P > 0.05) genotoxic effects were found in strain D7, while strain RS112 showed a small but significant increase in the frequency of sister chromatid conversions. In Chinese hamster ovary (CHO) cells the two compounds induced a statistically significant but less than twofold increase in the frequency of sister chromatid exchanges (SCE). No mutations were detected when the compounds were tested in Salmonella tphimurium strains TA98 and TA100. However, both 284 and 312 acted as antimutagens on strain TA100+S9 in the presence of benzo(a)pyrene. The decrease in mutagenicity by the most potent compound 284 was 20 revertants/nmol. This effect could be explained by an inhibitory effect on the cytochrome P450-dependent ethoxyresorufin O-deethylase (EROD) activity as seen in rat hepatocytes. The two compounds were also tested with hamster cells expressing rat cytochrome P-4501A1. The results support the conclusion that this cytochrome P-450 isozyme is inhibited by the tryptophan photoproducts. Similar results were also seen with two other high affinity Ah receptor ligands the quinazolinocarboline alkaloids rutaecapine and dehydrorutaecarpine. 20 refs., 3 figs., 4 tabs

DNA template strand sequencing of single-cells maps genomic rearrangements at high resolution

NARCIS (Netherlands)

Falconer, Ester; Hills, Mark; Naumann, Ulrike; Poon, Steven S. S.; Chavez, Elizabeth A.; Sanders, Ashley D.; Zhao, Yongjun; Hirst, Martin; Lansdorp, Peter M.

DNA rearrangements such as sister chromatid exchanges (SCEs) are sensitive indicators of genomic stress and instability, but they are typically masked by single-cell sequencing techniques. We developed Strand-seq to independently sequence parental DNA template strands from single cells, making it

Flow-Induced New Channels of Energy Exchange in Multi-Scale Plasma Dynamics - Revisiting Perturbative Hybrid Kinetic-MHD Theory.

Science.gov (United States)

Shiraishi, Junya; Miyato, Naoaki; Matsunaga, Go

2016-05-10

It is found that new channels of energy exchange between macro- and microscopic dynamics exist in plasmas. They are induced by macroscopic plasma flow. This finding is based on the kinetic-magnetohydrodynamic (MHD) theory, which analyses interaction between macroscopic (MHD-scale) motion and microscopic (particle-scale) dynamics. The kinetic-MHD theory is extended to include effects of macroscopic plasma flow self-consistently. The extension is realised by generalising an energy exchange term due to wave-particle resonance, denoted by δ WK. The first extension is generalisation of the particle's Lagrangian, and the second one stems from modification to the particle distribution function due to flow. These extensions lead to a generalised expression of δ WK, which affects the MHD stability of plasmas.

The sodium-calcium exchanger is a mechanosensitive transporter.

Science.gov (United States)

Reeves, John P; Abdellatif, Maha; Condrescu, Madalina

2008-03-15

This report describes the influence of fluid flow and osmotically induced volume changes on Na(+)-Ca(2+) exchange (NCX) activity in transfected CHO cells. Exchange activity was measured as Na(+)-dependent Ca(2+) or Ba(2+) fluxes using the fluorescent probe fura-2. When exchange activity was initiated by superfusing Ba(2+)-containing solutions over the cells for a 20 s interval, a high rate of Ba(2+) uptake was observed while the solution was being applied but the rate of Ba(2+) uptake declined > 10-fold when the solution flow ceased. Ba(2+) efflux in exchange for extracellular Na(+) or Ca(2+) (Ba(2+)-Ca(2+) exchange) was similarly biphasic. During NCX-mediated Ca(2+) uptake, a rapid increase in cytosolic [Ca(2+)] to a peak value occurred, followed by a decline in [Ca(2+)](i) to a lower steady-state value after solution flow ceased. When NCX activity was initiated by an alternate procedure that minimized the duration of solution flow, the rapid phase of Ba(2+) influx was greatly reduced in magnitude and Ca(2+) uptake became nearly monophasic. Solution superfusion did not produce any obvious changes in cell shape or volume. NCX-mediated Ba(2+) and Ca(2+) influx were also sensitive to osmotically induced changes in cell volume. NCX activity was stimulated in hypotonic media and inhibited in hypertonic media; the osmotically induced changes in activity occurred within seconds and were rapidly reversible. We conclude that NCX activity is modulated by both solution flow and osmotically induced volume changes.

DNA repair in Bloom's syndrome skin fibroblasts after ultraviolet light irradiation

International Nuclear Information System (INIS)

Kurihara, Takayuki; Inoue, Masao; Kawashima, Hiroko; Yagi, Takashi; Takebe, Hiraku.

1981-01-01

Skin fibroblasts from a patient with Bloom's syndrome (86NoKi) were assayed for various DNA repair activities after ultraviolet light (UV) irradiation. Cultured fibroblasts as well as lymphocytes obtained from this patient showed a high frequency of spontaneous sister chromatid exchanges (SCEs). There was no significant difference between 86NoKi fibroblasts and skin fibroblasts from normal donors in the sensitivity to UV as measured by inactivation of colony forming activity, the capacity of host-cell reactivation (HCR) of UV-irradiated virus, and the amount of unscheduled DNA synthesis (UDS) after UV irradiation. However, the yield of UV-induced SCEs in 86NoKi cells was significantly higher than that in normal cells. (author)

Regulation of the Drosophila Enhancer of split and invected-engrailed gene complexes by sister chromatid cohesion proteins.

Directory of Open Access Journals (Sweden)

Cheri A Schaaf

2009-07-01

Full Text Available The cohesin protein complex was first recognized for holding sister chromatids together and ensuring proper chromosome segregation. Cohesin also regulates gene expression, but the mechanisms are unknown. Cohesin associates preferentially with active genes, and is generally absent from regions in which histone H3 is methylated by the Enhancer of zeste [E(z] Polycomb group silencing protein. Here we show that transcription is hypersensitive to cohesin levels in two exceptional cases where cohesin and the E(z-mediated histone methylation simultaneously coat the entire Enhancer of split and invected-engrailed gene complexes in cells derived from Drosophila central nervous system. These gene complexes are modestly transcribed, and produce seven of the twelve transcripts that increase the most with cohesin knockdown genome-wide. Cohesin mutations alter eye development in the same manner as increased Enhancer of split activity, suggesting that similar regulation occurs in vivo. We propose that cohesin helps restrain transcription of these gene complexes, and that deregulation of similarly cohesin-hypersensitive genes may underlie developmental deficits in Cornelia de Lange syndrome.

Xanthium strumarium L. extracts produce DNA damage mediated by cytotoxicity in in vitro assays but does not induce micronucleus in mice.

Science.gov (United States)

Piloto Ferrer, Janet; Cozzi, Renata; Cornetta, Tommaso; Stano, Pasquale; Fiore, Mario; Degrassi, Francesca; De Salvia, Rosella; Remigio, Antonia; Francisco, Marbelis; Quiñones, Olga; Valdivia, Dayana; González, Maria L; Pérez, Carlos; Sánchez-Lamar, Angel

2014-01-01

Xanthium strumarium L. is a member of the Asteraceae commonly used in Cuba, mainly as diuretic. Some toxic properties of this plant have also been reported and, to date, very little is known about its genotoxic properties. The present work aims was to evaluate the potential cytotoxic and genotoxic risk of whole extract from Xanthium strumarium L. whole extract of aerial parts. No positive response was observed in a battery of four Salmonella typhimurium strains, when exposed to concentrations up to 5 mg/plate, with and without mammalian metabolic activation (liver microsomal S9 fraction from Wistar rats). In CHO cells, high concentrations (25-100 μg/mL) revealed significant reduction in cell viability. Results from sister chromatid exchanges, chromosome aberrations, and comet assay showed that X. strumarium extract is genotoxic at the highest concentration used, when clear cytotoxic effects were also observed. On the contrary, no increase in micronuclei frequency in bone marrow cells was observed when the extract was orally administered to mice (100, 500, and 2000 mg/Kg doses). The data presented here constitute the most complete study on the genotoxic potential of X. strumarium L. and show that the extract can induce in vitro DNA damage at cytotoxic concentrations.

Xanthium strumarium L. Extracts Produce DNA Damage Mediated by Cytotoxicity in In Vitro Assays but Does Not Induce Micronucleus in Mice

Directory of Open Access Journals (Sweden)

Janet Piloto Ferrer

2014-01-01

Full Text Available Xanthium strumarium L. is a member of the Asteraceae commonly used in Cuba, mainly as diuretic. Some toxic properties of this plant have also been reported and, to date, very little is known about its genotoxic properties. The present work aims was to evaluate the potential cytotoxic and genotoxic risk of whole extract from Xanthium strumarium L. whole extract of aerial parts. No positive response was observed in a battery of four Salmonella typhimurium strains, when exposed to concentrations up to 5 mg/plate, with and without mammalian metabolic activation (liver microsomal S9 fraction from Wistar rats. In CHO cells, high concentrations (25–100 μg/mL revealed significant reduction in cell viability. Results from sister chromatid exchanges, chromosome aberrations, and comet assay showed that X. strumarium extract is genotoxic at the highest concentration used, when clear cytotoxic effects were also observed. On the contrary, no increase in micronuclei frequency in bone marrow cells was observed when the extract was orally administered to mice (100, 500, and 2000 mg/Kg doses. The data presented here constitute the most complete study on the genotoxic potential of X. strumarium L. and show that the extract can induce in vitro DNA damage at cytotoxic concentrations.

Nonadiabatic exchange dynamics during adiabatic frequency sweeps.

Science.gov (United States)

Barbara, Thomas M

2016-04-01

A Bloch equation analysis that includes relaxation and exchange effects during an adiabatic frequency swept pulse is presented. For a large class of sweeps, relaxation can be incorporated using simple first order perturbation theory. For anisochronous exchange, new expressions are derived for exchange augmented rotating frame relaxation. For isochronous exchange between sites with distinct relaxation rate constants outside the extreme narrowing limit, simple criteria for adiabatic exchange are derived and demonstrate that frequency sweeps commonly in use may not be adiabatic with regard to exchange unless the exchange rates are much larger than the relaxation rates. Otherwise, accurate assessment of the sensitivity to exchange dynamics will require numerical integration of the rate equations. Examples of this situation are given for experimentally relevant parameters believed to hold for in-vivo tissue. These results are of significance in the study of exchange induced contrast in magnetic resonance imaging. Copyright © 2016 Elsevier Inc. All rights reserved.

Perturbation of Incenp function impedes anaphase chromatid movements and chromosomal passenger protein flux at centromeres.

Science.gov (United States)

Ahonen, Leena J; Kukkonen, Anu M; Pouwels, Jeroen; Bolton, Margaret A; Jingle, Christopher D; Stukenberg, P Todd; Kallio, Marko J

2009-02-01

Incenp is an essential mitotic protein that, together with Aurora B, Survivin, and Borealin, forms the core of the chromosomal passenger protein complex (CPC). The CPC regulates various mitotic processes and functions to maintain genomic stability. The proper subcellular localization of the CPC and its full catalytic activity require the presence of each core subunit in the complex. We have investigated the mitotic tasks of the CPC using a function blocking antibody against Incenp microinjected into cells at different mitotic phases. This method allowed temporal analysis of CPC functions without perturbation of complex assembly or activity prior to injection. We have also studied the dynamic properties of Incenp and Aurora B using fusion protein photobleaching. We found that in early mitotic cells, Incenp and Aurora B exhibit dynamic turnover at centromeres, which is prevented by the anti-Incenp antibody. In these cells, the loss of centromeric CPC turnover is accompanied by forced mitotic exit without the execution of cytokinesis. Introduction of anti-Incenp antibody into early anaphase cells causes abnormalities in sister chromatid separation through defects in anaphase spindle functions. In summary, our data uncovers new mitotic roles for the CPC in anaphase and proposes that CPC turnover at centromeres modulates spindle assembly checkpoint signaling.

Exchangers man the pumps

Science.gov (United States)

Barkla, Bronwyn J; Hirschi, Kendal D

2008-01-01

Tonoplast-localised proton-coupled Ca2+ transporters encoded by cation/H+ exchanger (CAX) genes play a critical role in sequestering Ca2+ into the vacuole. These transporters may function in coordination with Ca2+ release channels, to shape stimulus-induced cytosolic Ca2+ elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a role in mediating the plant's stress response. A common feature of these mutants was the perturbation of H+-ATPase activity at both the tonoplast and the plasma membrane, suggesting a tight interplay between the Ca2+/H+ exchangers and H+ pumps. We speculate that indirect regulation of proton flux by the exchangers may be as important as the direct regulation of Ca2+ flux. These results suggest cautious interpretation of mutant Ca2+/H+ exchanger phenotypes that may be due to either perturbed Ca2+ or H+ transport. PMID:19841670

Terminalia arjuna, a herbal remedy against environmental ...

African Journals Online (AJOL)

... 429 due to AFB1 to 141 due to 5th concentration of Terminalia extracts at 32 h of exposure. Conclusion: The ameliorating potential of Terminalia extracts was dose and time dependant. Keywords: Ayurvedic medicine; Carcinogen; Chromosomal aberration; Sister chromatid exchange; Replication index; Terminalia arjuna ...

Variability in Benthic Exchange Rate, Depth, and Residence Time Beneath a Shallow Coastal Estuary

Science.gov (United States)

Russoniello, Christopher J.; Heiss, James W.; Michael, Holly A.

2018-03-01

Hydrodynamically driven benthic exchange of water between the water column and shallow seabed aquifer is a significant and dynamic component of coastal and estuarine fluid budgets. Associated exchange of solutes promotes ecologically important chemical reactions, so quantifying benthic exchange rates, depths, and residence times constrains coastal chemical cycling estimates. We present the first combined field, numerical, and analytical modeling investigation of wave-induced exchange. Temporal variability of exchange was calculated with data collected by instruments deployed in a shallow estuary for 11 days. Differential pressure sensors recorded pressure gradients across the seabed, and up- and down-looking ADCPs recorded currents and pressures to determine wave parameters, surface-water currents, and water depth. Wave-induced exchange was calculated (1) directly from differential pressure measurements, and indirectly with an analytical model based on wave parameters from (2) ADCP and (3) wind data. Wave-induced exchange from pressure measurements and ADCP-measured wave parameters matched well, but both exceeded wind-based values. Exchange induced by tidal pumping and current-bed form interaction—the other primary drivers in shallow coastal waters were calculated from tidal stage variation and ADCP-measured currents. Exchange from waves (mean = 20.0 cm/d; range = 1.75-92.3 cm/d) greatly exceeded exchange due to tides (mean = 3.7 cm/d) and current-bed form interaction (mean = 6.5 × 10-2 cm/d). Groundwater flow models showed aquifer properties affect wave-driven benthic exchange: residence time and depth increased and exchange rates decreased with increasing hydraulic diffusivity (ratio of aquifer permeability to compressibility). This new understanding of benthic exchange will help managers assess its control over chemical fluxes to marine systems.

A comparative study of the potentiating effect of caffeine and poly-D-lysine on chromosome damage induced by X-rays in plant cells

Energy Technology Data Exchange (ETDEWEB)

Mateos, S.; Panneerselvam, N.; Cortes, F. (Sevilla University, Faculty of Biology (Spain). Department of Cell Biology); Mateos, J.C. (Centro Regional de Oncologia ' Duque del Infantado' , Sevilla (Spain))

1992-04-01

X-ray-induced chromosomal aberrations (CA) were potentiated by post-treatments in G{sub 2} with either caffeine (caff) or poly-D-lysine (PDL) in root-tip cells of Allium cepa. The enhancement of the yield of CA was concomittant with an increase in the frequency of mitosis. The results seem to support the idea of a direct relationship between radiation-induced G{sub 2} delay and repair of chromosome damage. Similarities between caff and PDL are reported in both decreasing G{sub 2} delay and enhancing chromatid aberration yield. The possible molecular mechanism(s) of action responsible for the cytogenetic effects observed are discussed. (author). 20 refs.; 2 tabs.

Parallel increases in sister chromatid exchanges at base level and with UV treatment in human opiate users

International Nuclear Information System (INIS)

Shafer, D.A.; Falek, A.; Madden, J.J.; Tadayon, F.; Pline, M.; Kuehnle, J.C.; Mendelson, J.

1983-01-01

The SCE base level frequency and SCE levels induced by far-UV (254 nm) treatment of cells in early G 1 and early S phases of the cell cycle were significantly higher in leukocytes from heroin addicts as compared to controls. The increased SCE levels in addicts was greatest at base level and smallest after UV irradiation of cells in S phase. These results corrobate and extend our previous findings of increased chromosome damage and reduced DNA-repair synthesis in heroin users. Since opiates do not directly damage DNA, the elevated cytogenetic effects associated with opiate use probably arise from secondary promotional effects related to opiate-mediated alterations in leukocyte metabolism. (orig.)

40 CFR 79.65 - In vivo sister chromatid exchange assay.

Science.gov (United States)

2010-07-01

... PROGRAMS (CONTINUED) REGISTRATION OF FUELS AND FUEL ADDITIVES Testing Requirements for Registration § 79.65... appropriate concentration level, a pilot or trial study may be advisable. Initially, one concentration of the...., “Cytogenetic Studies of Mice Exposed to Styrene by Inhalation.”, Mutation Research, 280:35-43, 1992. (7) Wolff...

Collision-induced absorption with exchange effects and anisotropic interactions: theory and application to H2 - H2.

Science.gov (United States)

Karman, Tijs; van der Avoird, Ad; Groenenboom, Gerrit C

2015-02-28

We discuss three quantum mechanical formalisms for calculating collision-induced absorption spectra. First, we revisit the established theory of collision-induced absorption, assuming distinguishable molecules which interact isotropically. Then, the theory is rederived incorporating exchange effects between indistinguishable molecules. It is shown that the spectrum can no longer be written as an incoherent sum of the contributions of the different spherical components of the dipole moment. Finally, we derive an efficient method to include the effects of anisotropic interactions in the computation of the absorption spectrum. This method calculates the dipole coupling on-the-fly, which allows for the uncoupled treatment of the initial and final states without the explicit reconstruction of the many-component wave functions. The three formalisms are applied to the collision-induced rotation-translation spectra of hydrogen molecules in the far-infrared. Good agreement with experimental data is obtained. Significant effects of anisotropic interactions are observed in the far wing.

Lanthanide shift reagents, binding, shift mechanisms and exchange

International Nuclear Information System (INIS)

Boer, J.W.M. de

1977-01-01

Paramagnetic lanthanide shift reagents, when added to a solution of a substrate, induce shifts in the nuclear magnetic resonance (NMR) spectrum of the substrate molecules. The induced shifts contain information about the structure of the shift reagent substrate complex. The structural information, however, may be difficult to extract because of the following effects: (1) different complexes between shift reagent and substrate may be present in solution, e.g. 1:1 and 1:2 complexes, and the shift observed is a weighed average of the shifts of the substrate nuclei in the different complexes; (2) the Fermi contact interaction, arising from the spin density at the nucleus, contributes to the induced shift; (3) chemical exchange effects may complicate the NMR spectrum. In this thesis, the results of an investigation into the influence of these effects on the NMR spectra of solutions containing a substrate and LSR are presented. The equations describing the pseudo contact and the Fermi contact shift are derived. In addition, it is shown how the modified Bloch equations describing the effect of the chemical exchange processes occurring in the systems studied can be reduced to the familiar equations for a two-site exchange case. The binding of mono- and bifunctional ethers to the shift reagent are reported. An analysis of the induced shifts is given. Finally, the results of the experiments performed to study the exchange behavior of dimethoxyethane and heptafluorodimethyloctanedionato ligands are presented

The cohesion protein SOLO associates with SMC1 and is required for synapsis, recombination, homolog bias and cohesion and pairing of centromeres in Drosophila Meiosis.

Science.gov (United States)

Yan, Rihui; McKee, Bruce D

2013-01-01

Cohesion between sister chromatids is mediated by cohesin and is essential for proper meiotic segregation of both sister chromatids and homologs. solo encodes a Drosophila meiosis-specific cohesion protein with no apparent sequence homology to cohesins that is required in male meiosis for centromere cohesion, proper orientation of sister centromeres and centromere enrichment of the cohesin subunit SMC1. In this study, we show that solo is involved in multiple aspects of meiosis in female Drosophila. Null mutations in solo caused the following phenotypes: 1) high frequencies of homolog and sister chromatid nondisjunction (NDJ) and sharply reduced frequencies of homolog exchange; 2) reduced transmission of a ring-X chromosome, an indicator of elevated frequencies of sister chromatid exchange (SCE); 3) premature loss of centromere pairing and cohesion during prophase I, as indicated by elevated foci counts of the centromere protein CID; 4) instability of the lateral elements (LE)s and central regions of synaptonemal complexes (SCs), as indicated by fragmented and spotty staining of the chromosome core/LE component SMC1 and the transverse filament protein C(3)G, respectively, at all stages of pachytene. SOLO and SMC1 are both enriched on centromeres throughout prophase I, co-align along the lateral elements of SCs and reciprocally co-immunoprecipitate from ovarian protein extracts. Our studies demonstrate that SOLO is closely associated with meiotic cohesin and required both for enrichment of cohesin on centromeres and stable assembly of cohesin into chromosome cores. These events underlie and are required for stable cohesion of centromeres, synapsis of homologous chromosomes, and a recombination mechanism that suppresses SCE to preferentially generate homolog crossovers (homolog bias). We propose that SOLO is a subunit of a specialized meiotic cohesin complex that mediates both centromeric and axial arm cohesion and promotes homolog bias as a component of chromosome

Chromosomal Integrity after UV Irradiation Requires FANCD2-Mediated Repair of Double Strand Breaks.

Science.gov (United States)

Federico, María Belén; Vallerga, María Belén; Radl, Analía; Paviolo, Natalia Soledad; Bocco, José Luis; Di Giorgio, Marina; Soria, Gastón; Gottifredi, Vanesa

2016-01-01

Fanconi Anemia (FA) is a rare autosomal recessive disorder characterized by hypersensitivity to inter-strand crosslinks (ICLs). FANCD2, a central factor of the FA pathway, is essential for the repair of double strand breaks (DSBs) generated during fork collapse at ICLs. While lesions different from ICLs can also trigger fork collapse, the contribution of FANCD2 to the resolution of replication-coupled DSBs generated independently from ICLs is unknown. Intriguingly, FANCD2 is readily activated after UV irradiation, a DNA-damaging agent that generates predominantly intra-strand crosslinks but not ICLs. Hence, UV irradiation is an ideal tool to explore the contribution of FANCD2 to the DNA damage response triggered by DNA lesions other than ICL repair. Here we show that, in contrast to ICL-causing agents, UV radiation compromises cell survival independently from FANCD2. In agreement, FANCD2 depletion does not increase the amount of DSBs generated during the replication of UV-damaged DNA and is dispensable for UV-induced checkpoint activation. Remarkably however, FANCD2 protects UV-dependent, replication-coupled DSBs from aberrant processing by non-homologous end joining, preventing the accumulation of micronuclei and chromatid aberrations including non-homologous chromatid exchanges. Hence, while dispensable for cell survival, FANCD2 selectively safeguards chromosomal stability after UV-triggered replication stress.

IL-17A induces Pendrin expression and chloride-bicarbonate exchange in human bronchial epithelial cells.

Directory of Open Access Journals (Sweden)

Kelly M Adams

Full Text Available The epithelium plays an active role in the response to inhaled pathogens in part by responding to signals from the immune system. Epithelial responses may include changes in chemokine expression, increased mucin production and antimicrobial peptide secretion, and changes in ion transport. We previously demonstrated that interleukin-17A (IL-17A, which is critical for lung host defense against extracellular bacteria, significantly raised airway surface pH in vitro, a finding that is common to a number of inflammatory diseases. Using microarray analysis of normal human bronchial epithelial (HBE cells treated with IL-17A, we identified the electroneutral chloride-bicarbonate exchanger Pendrin (SLC26A4 as a potential mediator of this effect. These data were verified by real-time, quantitative PCR that demonstrated a time-dependent increase in Pendrin mRNA expression in HBE cells treated with IL-17A up to 48 h. Using immunoblotting and immunofluorescence, we confirmed that Pendrin protein expression is increased in IL-17 treated HBE cells and that it is primarily localized to the mucosal surface of the cells. Functional studies using live-cell fluorescence to measure intracellular pH demonstrated that IL-17A induced chloride-bicarbonate exchange in HBE cells that was not present in the absence of IL-17A. Furthermore, HBE cells treated with short interfering RNA against Pendrin showed substantially reduced chloride-bicarbonate exchange. These data suggest that Pendrin is part of IL-17A-dependent epithelial changes and that Pendrin may therefore be a therapeutic target in IL-17A-dependent lung disease.

Experimental evaluation of vibrations in heat exchangers

International Nuclear Information System (INIS)

Martin Ghiselli, A.

1997-01-01

Flow induced vibrations may produce damage of heat exchangers, condensers and steam generators tubes. To evaluate this problem a set of tests were developed to know the real support state of the tubes, which have great influence on the vibration response. This paper include a description of the tests and the results obtained applying them on a heat exchanger equipment. (author) [es

Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca exchangers.

Science.gov (United States)

Barkla, Bronwyn J; Hirschi, Kendal D; Pittman, Jon K

2008-05-01

Tonoplast-localised proton-coupled Ca(2+) transporters encoded by cation/H(+)exchanger (CAX) genes play a critical role in sequestering Ca(2+) into the vacuole. These transporters may function in coordination with Ca(2+) release channels, to shape stimulus-induced cytosolic Ca(2+) elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a role in mediating the plant's stress response. A common feature of these mutants was the perturbation of H(+)-ATPase activity at both the tonoplast and the plasma membrane, suggesting a tight interplay between the Ca(2+)/H(+) exchangers and H(+) pumps. We speculate that indirect regulation of proton flux by the exchangers may be as important as the direct regulation of Ca(2+) flux. These results suggest cautious interpretation of mutant Ca(2+)/H(+) exchanger phenotypes that may be due to either perturbed Ca(2+) or H(+) transport.

Oxygen isotope exchange on palladium catalysts

International Nuclear Information System (INIS)

Kravchuk, L.S.; Beschetvertnaya, T.I.; Novorodskij, V.G.; Novikova, M.G.; Zaretskij, M.V.; Valieva, S.V.

1983-01-01

Oxygen heteromolecular isotope exchange on unreduced palladium catalysts, distingushing by metal content is studied. Content of 18 O in gaseous phase is eoual to 46%. Calculations of heteroexchange rates are conducted with decrease of the 18 O in the gaseous phase over solid sample. Method of oxygen thermodesorption has been used to establish that palladium, deposited on γ-Al 2 O 3 during exchange process is in oxidized state; in this case strength of Pd-O bond is determined by content dispersity) of the metal. It is shown that significant increase of exchange rate on the samples with Pd >> 0.5 mass.% content can be induced as by side decomposition reaction of its oxide and corresponding dilution of gaseous mixture by ''light'' oxygen so by possibility of exchange with oxygen of PdO phase

Exchange currents for hypernuclear magnetic moments

International Nuclear Information System (INIS)

Saito, K.; Oka, M.; Suzuki, T.

1997-01-01

The meson (K and π) exchange currents for the hypernuclear magnetic moments are calculated using the effective Lagrangian method. The seagull diagram, the mesonic diagram and the Σ 0 -excitation diagram are considered. The Λ-N exchange magnetic moments for 5 Λ He and A=6 hypernuclei are calculated employing the harmonic oscillator shell model. It is found that the two-body correction is about -9% of the single particle value for 5 Λ He. The π exchange current, induced only in the Σ 0 -excitation diagram, is found to give dominant contribution for the isovector magnetic moments of hypernuclei with A=6. (orig.)

DNA damage responses in human induced pluripotent stem cells and embryonic stem cells.

Directory of Open Access Journals (Sweden)

Olga Momcilovic

2010-10-01

Full Text Available Induced pluripotent stem (iPS cells have the capability to undergo self-renewal and differentiation into all somatic cell types. Since they can be produced through somatic cell reprogramming, which uses a defined set of transcription factors, iPS cells represent important sources of patient-specific cells for clinical applications. However, before these cells can be used in therapeutic designs, it is essential to understand their genetic stability.Here, we describe DNA damage responses in human iPS cells. We observe hypersensitivity to DNA damaging agents resulting in rapid induction of apoptosis after γ-irradiation. Expression of pluripotency factors does not appear to be diminished after irradiation in iPS cells. Following irradiation, iPS cells activate checkpoint signaling, evidenced by phosphorylation of ATM, NBS1, CHEK2, and TP53, localization of ATM to the double strand breaks (DSB, and localization of TP53 to the nucleus of NANOG-positive cells. We demonstrate that iPS cells temporary arrest cell cycle progression in the G(2 phase of the cell cycle, displaying a lack of the G(1/S cell cycle arrest similar to human embryonic stem (ES cells. Furthermore, both cell types remove DSB within six hours of γ-irradiation, form RAD51 foci and exhibit sister chromatid exchanges suggesting homologous recombination repair. Finally, we report elevated expression of genes involved in DNA damage signaling, checkpoint function, and repair of various types of DNA lesions in ES and iPS cells relative to their differentiated counterparts.High degrees of similarity in DNA damage responses between ES and iPS cells were found. Even though reprogramming did not alter checkpoint signaling following DNA damage, dramatic changes in cell cycle structure, including a high percentage of cells in the S phase, increased radiosensitivity and loss of DNA damage-induced G(1/S cell cycle arrest, were observed in stem cells generated by induced pluripotency.

Experimental verification for in vitro technique confirmation of bystander effect induced by gamma radiation in CHO-K1 cell line

International Nuclear Information System (INIS)

Viana, P.H.L.; Goes, A.M.; Gomes, D.A.

2013-01-01

The bystander effect refers to biological responses detected in cells not directly irradiated but influenced, somehow, by signals transmitted from neighboring irradiated cells. These biological responses include sister chromatid exchange, mutations, micronucleus formation, chromosomal aberrations, carcinogenesis, apoptosis and necrosis. Although its existence is unquestionable, the mechanisms involved on triggering the bystander effect are not yet completely elucidated. Previous studies have shown that the bystander effect depends on a large variety of parameters including the radiation dose, the dose rate, the type of radiation and type of cells or tissue. This study aims to confirm the technique previously used in the literature in human cell lines for the bystander effect verification. The results suggest that the working conditions adopted by the group show technical efficiency and enables the reproduction of the bystander effect. (author)

Effects of aphidicolin on repair replication and induced chromosomal aberrations in mammalian cells

International Nuclear Information System (INIS)

Zeeland, A.A. van; Filon, A.R.; Natarajan, A.T.; Bussmann, C.J.M.; Degrassi, F.; Kesteren-van Leeuwen, A.C. van; Palitti, F.; Rome Univ.

1982-01-01

The influence of aphidicolin, an inhibitor of polymerase α, on UV-induced repair replication in human skin fibroblasts, as well as in HeLa cells, was determined. In growing fibroblasts and in HeLa cells, aphidicolin had a potentiating effect on UV-induced repair replication, whereas in fibroblasts grown to confluency, aphidicolin had an inhibitory effect. This inhibitory effect was stronger when measured in the presence of hydroxyurea. In HeLa cells the presence of both aphidicolin and hydroxyurea also had an inhibitory effect, but in the presence of hydroxyurea alone, UV-induced repair replication was enhanced. The results of these studies can be explained on the basis of differences in deoxyribonucleotide triphosphate pool sizes in growing and confluent cells. Post-treatment of X-irradiated human lymphocytes in the G 0 and G 1 stages with aphidicolin increased the frequencies of X-ray-induced chromosomal aberrations. Such an increase was not observed in G 1 cells of CHO after similar treatment with X-rays and aphidicolin. However, treatment with aphidicolin, in the G 2 stage, increased the frequencies of induced chromatid breaks. The significance of these results is discussed. (orig.)

Exchange magnon induced resistance asymmetry in permalloy spin-Hall oscillators

Energy Technology Data Exchange (ETDEWEB)

Langenfeld, S. [Microelectronics Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE (United Kingdom); Walter Schottky Institut and Physik-Department, Technische Universität München, 85748 Garching (Germany); Tshitoyan, V.; Fang, Z.; Ferguson, A. J., E-mail: ajf1006@cam.ac.uk [Microelectronics Group, Cavendish Laboratory, University of Cambridge, Cambridge, CB3 0HE (United Kingdom); Wells, A.; Moore, T. A. [School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT (United Kingdom)

2016-05-09

We investigate magnetization dynamics in a spin-Hall oscillator using a direct current measurement as well as conventional microwave spectrum analysis. When the current applies an anti-damping spin-transfer torque, we observe a change in resistance which we ascribe mainly to the excitation of incoherent exchange magnons. A simple model is developed based on the reduction of the effective saturation magnetization, quantitatively explaining the data. The observed phenomena highlight the importance of exchange magnons on the operation of spin-Hall oscillators.

4. National Congress on Genetics. Memoirs

International Nuclear Information System (INIS)

1993-01-01

According to INIS coverage were analyzed four free works on Life and Environmental Sciences presented during the Congress which are treating over the effects of external irradiation on animals. Between the main aspects are the sister chromatid exchange, spermatogonia, somatic cells, genotoxicity, DNA, chlorophyll, gamma radiation, bone marrow cells and radiation injuries

Andrographia paniculata a Miracle Herbs for cancer treatment: In vivo and in vitro studies against Aflatoxin B1 Toxicity

Directory of Open Access Journals (Sweden)

Md. Sultan Ahmad

2014-04-01

Conclusion: In conclusion A. paniculata extracts significantly reduced the number of aberrant cells and frequencies of aberration per cell at each concentration and duration of exposure in vivo; similarly it reduced chromosomal aberrations and sister chromatid exchanges and replication index was enhanced in vitro that was statistically significant at <0.05 level.

Ion exchange resins as high-dose radiation dosimeters

International Nuclear Information System (INIS)

Alian, A.; Dessouki, A.; El-Assay, N.B.

1984-01-01

This paper reports on the possibility of using various types of ion exchange resins as high-dose radiation dosimeters, by analysis of the decrease in exchange capacity with absorbed dose. The resins studied are Sojuzchim-export-Moscow Cation Exchanger KU-2 and Anion Exchanger AV-17 and Merck Cation Exchanger I, and Merck Anion Exchangers II and III. Over the dose range 1 to 100 kGy, the systems show linearity between log absorbed dose and decrease in resin ion exchange capacity. The slope of this response function differs for the different resins, depending on their ionic form and degree of cross-linking. The radiation sensitivity increases in the order KU-2; Exchanger I; AV-17; Exchanger II; Exchanger III. Merck resins with moisture content of 21% showed considerably higher radiation sensitivity than those with 2 to 3% moisture content. The mechanism of radiation-induced denaturing of the ion exchanger resins involves cleavage and decomposition of functional substituents, with crosslinking playing a stabilizing role, with water and its radiolytic products serving to inhibit radical recombination and interfering with the protection cage effect of crosslinking. (author)

Distributions of Low- and High-LET Radiation-Induced Breaks in Chromosomes are Associated with Inter- and Intrachromosome Exchanges

Science.gov (United States)

Hada, Megumi; Zhang, Ye; Feiveson, Alan; Cucinotta, Francis A.; Wu, Honglu

2010-01-01

To study the breakpoint along the length of the chromosome induced by low- and high-LET radiations, we exposed human epithelial cells in vitro to Cs-137 rays at both low and high dose rates, secondary neutrons at a low dose rate, and 600 MeV/u Fe ions at a high dose rate. The location of the breaks was identified using the multicolor banding in situ hybridization (mBAND) that paints Chromosome 3 in 23 different colored bands. The breakpoint distributions were found to be similar between rays of low and high dose rates and between the two high-LET radiation types. Detailed analysis of the chromosome break ends involved in inter- and intrachromosome exchanges revealed that only the break ends participating in interchromosome exchanges contributed to the hot spots found for low-LET. For break ends participating in intrachromosome exchanges, the distributions for all four radiation scenarios were similar with clusters of breaks found in three regions. Analysis of the locations of the two break ends in Chromosome 3 that joined to form an intrachromosome exchange demonstrated that two breaks with a greater genomic separation may be more likely to rejoin than two closer breaks, indicating that chromatin folding can play an important role in the rejoining of chromosome breaks. Our study demonstrated that the gene-rich regions do not necessarily contain more breaks. The breakpoint distribution depends more on the likelihood that a break will join with another break in the same chromosome or in a different chromosome.

Studies on sister chromatid exchange (SCE) induction by γ-irradiation and protective effect of L-cysteine in HeLa cells

International Nuclear Information System (INIS)

Shah, V.C.; Mittal, S.C.

1987-01-01

Effect of different doses of γ-irradiation on SCE induction in unifiliarly 5-bromo 2-deoxyuridine substituted DNA was studied in various phases of cell cycle. Changes in γ-irradiation induced SCE frequency was measured by post-irradiation treatment with antimutagen L-cysteine. Perturbation in cellular proliferation kinetics due to γ-irradiation and γ-irradiation plus L-cysteine was also studied. It was observed that γ-irradiation is an efficient inducer of SCE and is most effective in S phase. L-cysteine also causes SCE induction which is slightly higher than the spontaneous level of SCEs found in HeLa cells. However, post-irradiation addition of L-cysteine reduces SCE frequency in γ-irradiated cultures and this reduction is maximum in G 1 phase irradiated cells. γ-irradiation delayed the mitosis considerably and this delay continued to increase with increasing doses. L-cysteine reduced the delay in cell cycle caused by γ-irradiation. (orig.) [de

Non-homologous end joining is the responsible pathway for the repair of fludarabine-induced DNA double strand breaks in mammalian cells

International Nuclear Information System (INIS)

Campos-Nebel, Marcelo de; Larripa, Irene; Gonzalez-Cid, Marcela

2008-01-01

Fludarabine (FLU), an analogue of adenosine, interferes with DNA synthesis and inhibits the chain elongation leading to replication arrest and DNA double strand break (DSB) formation. Mammalian cells use two main pathways of DSB repair to maintain genomic stability: homologous recombination (HR) and non-homologous end joining (NHEJ). The aim of the present work was to evaluate the repair pathways employed in the restoration of DSB formed following replication arrest induced by FLU in mammalian cells. Replication inhibition was induced in human lymphocytes and fibroblasts by FLU. DSB occurred in a dose-dependent manner on early/middle S-phase cells, as detected by γH2AX foci formation. To test whether conservative HR participates in FLU-induced DSB repair, we measured the kinetics of Rad51 nuclear foci formation in human fibroblasts. There was no significant induction of Rad51 foci after FLU treatment. To further confirm these results, we analyzed the frequency of sister chromatid exchanges (SCE) in both human cells. We did not find increased frequencies of SCE after FLU treatment. To assess the participation of NHEJ pathway in the repair of FLU-induced damage, we used two chemical inhibitors of the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), vanillin and wortmannin. Human fibroblasts pretreated with DNA-PKcs inhibitors showed increased levels of chromosome breakages and became more sensitive to cell death. An active role of NHEJ pathway was also suggested from the analysis of Chinese hamster cell lines. XR-C1 (DNA-PKcs-deficient) and XR-V15B (Ku80-deficient) cells showed hypersensitivity to FLU as evidenced by the increased frequency of chromosome aberrations, decreased mitotic index and impaired survival rates. In contrast, CL-V4B (Rad51C-deficient) and V-C8 (Brca2-deficient) cell lines displayed a FLU-resistant phenotype. Together, our results suggest a major role for NHEJ repair in the preservation of genome integrity against FLU-induced DSB

Non-homologous end joining is the responsible pathway for the repair of fludarabine-induced DNA double strand breaks in mammalian cells

Energy Technology Data Exchange (ETDEWEB)

Campos-Nebel, Marcelo de [Departamento de Genetica, Instituto de Investigaciones Hematologicas Mariano R. Castex, Academia Nacional de Medicina, Buenos Aires (Argentina)], E-mail: mnebel@hematologia.anm.edu.ar; Larripa, Irene; Gonzalez-Cid, Marcela [Departamento de Genetica, Instituto de Investigaciones Hematologicas Mariano R. Castex, Academia Nacional de Medicina, Buenos Aires (Argentina)

2008-11-10

Fludarabine (FLU), an analogue of adenosine, interferes with DNA synthesis and inhibits the chain elongation leading to replication arrest and DNA double strand break (DSB) formation. Mammalian cells use two main pathways of DSB repair to maintain genomic stability: homologous recombination (HR) and non-homologous end joining (NHEJ). The aim of the present work was to evaluate the repair pathways employed in the restoration of DSB formed following replication arrest induced by FLU in mammalian cells. Replication inhibition was induced in human lymphocytes and fibroblasts by FLU. DSB occurred in a dose-dependent manner on early/middle S-phase cells, as detected by {gamma}H2AX foci formation. To test whether conservative HR participates in FLU-induced DSB repair, we measured the kinetics of Rad51 nuclear foci formation in human fibroblasts. There was no significant induction of Rad51 foci after FLU treatment. To further confirm these results, we analyzed the frequency of sister chromatid exchanges (SCE) in both human cells. We did not find increased frequencies of SCE after FLU treatment. To assess the participation of NHEJ pathway in the repair of FLU-induced damage, we used two chemical inhibitors of the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs), vanillin and wortmannin. Human fibroblasts pretreated with DNA-PKcs inhibitors showed increased levels of chromosome breakages and became more sensitive to cell death. An active role of NHEJ pathway was also suggested from the analysis of Chinese hamster cell lines. XR-C1 (DNA-PKcs-deficient) and XR-V15B (Ku80-deficient) cells showed hypersensitivity to FLU as evidenced by the increased frequency of chromosome aberrations, decreased mitotic index and impaired survival rates. In contrast, CL-V4B (Rad51C-deficient) and V-C8 (Brca2-deficient) cell lines displayed a FLU-resistant phenotype. Together, our results suggest a major role for NHEJ repair in the preservation of genome integrity against FLU-induced

Chromatin dynamics during cell cycle mediate conversion of DNA damage into chromatid breaks and affect formation of chromosomal aberrations: Biological and clinical significance

International Nuclear Information System (INIS)

Terzoudi, Georgia I.; Hatzi, Vasiliki I.; Donta-Bakoyianni, Catherine; Pantelias, Gabriel E.

2011-01-01

The formation of diverse chromosomal aberrations following irradiation and the variability in radiosensitivity at different cell-cycle stages remain a long standing controversy, probably because most of the studies have focused on elucidating the enzymatic mechanisms involved using simple DNA substrates. Yet, recognition, processing and repair of DNA damage occur within the nucleoprotein complex of chromatin which is dynamic in nature, capable of rapid unfolding, disassembling, assembling and refolding. The present work reviews experimental work designed to investigate the impact of chromatin dynamics and chromosome conformation changes during cell-cycle in the formation of chromosomal aberrations. Using conventional cytogenetics and premature chromosome condensation to visualize interphase chromatin, the data presented support the hypothesis that chromatin dynamic changes during cell-cycle are important determinants in the conversion of sub-microscopic DNA lesions into chromatid breaks. Consequently, the type and yield of radiation-induced chromosomal aberrations at a given cell-cycle-stage depends on the combined effect of DNA repair processes and chromatin dynamics, which is cell-cycle-regulated and subject to up- or down-regulation following radiation exposure or genetic alterations. This new hypothesis is used to explain the variability in radiosensitivity observed at various cell-cycle-stages, among mutant cells and cells of different origin, or among different individuals, and to revisit unresolved issues and unanswered questions. In addition, it is used to better understand hypersensitivity of AT cells and to provide an improved predictive G2-assay for evaluating radiosensitivity at individual level. Finally, experimental data at single cell level obtained using hybrid cells suggest that the proposed hypothesis applies only to the irradiated component of the hybrid.

Reducing employees’ turnover intention through Hr-induced organizational citizenship behaviour: Leader-member exchange as the mediator

Directory of Open Access Journals (Sweden)

YU GHEE WEE

2013-07-01

Full Text Available This study examines the possibility of inducing organizational citizenship behavior (OCB through human resource (HR philosophy and high involvement HR practices administered at the workplace. Leader-member exchange (LMX, a basis of relational infrastructure, is posited to be a potential mediator. Data was collected from hotel frontline employees, tested and analyzed through structural equation modeling. Findings show that HR philosophy drives the formulation of the bundles of high involvement human resource practices and such philosophy contribute to employees’ willingness in exhibiting organizational citizenship behavior (OCB directed at individuals (OCBI as well as organizations (OCBO as a whole. High involvement HR practices, however, do not elicit OCB but these practices are significantly related to LMX, a new theoretical insight which should invite future research. Although exchanges between supervisors and subordinates are shown to have influences on employees’ willingness in performing OCB, LMX does not, however, mediate the relationship between high involvement HR practices and OCB. Overall, hotel frontline employees participated in this study exhibit more OCBO, rather than OCBI; and such behavior reduce their intention to leave. Both theoretical and practical implications as well as avenues for future research are discussed.

Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca(2+) exchangers

Science.gov (United States)

Tonoplast-localised proton-coupled Ca(2+) transporters encoded by cation/H(+) exchanger (CAX) genes play a critical role in sequestering Ca(2+) into the vacuole. These transporters may function in coordination with Ca(2+) release channels, to shape stimulus-induced cytosolic Ca(2+) elevations. Recen...

Chromosomal changes in maize induced by hydrogen fluoride gas

Energy Technology Data Exchange (ETDEWEB)

Mohamed, A H

1970-01-01

Maize seedlings were fumigated in growth chambers with hydrogen fluoride at a concentration of about 3 ..mu..g/m/sup 3/. The experiment was run for 10 days, with the first group of treated plants removed from the chambers after 4 days and then at intervals of 2 days. Microsporocyte smears from the treated plants revealed chromosomal aberrations that included asynaptic regions, translocations, inversions, and bridges plus fragments or fragments by themselves. It is believed that these abnormalities were due to the physiological effect of HF causing the chromosomes to become sticky and/or to the occurrence of chromatid breakage followed by reunion to sticky and/or to the occurrence of chromatid breakage followed by reunion to form structural changes. These findings indicate that HF is a mutagenic agent.

Metal-ion exchange induced structural transformation as a way of forming novel Ni(II)− and Cu(II)−salicylaldimine structures

Energy Technology Data Exchange (ETDEWEB)

Wu, Jing-Yun, E-mail: jyunwu@ncnu.edu.tw; Tsai, Chi-Jou; Chang, Ching-Yun; Wu, Yung-Yuan

2017-02-15

A Zn(II)−salicylaldimine complex [Zn(L{sup salpyca})(H{sub 2}O)]{sub n} (1, where H{sub 2}L{sup salpyca}=4-hydroxy-3-(((pyridin-2-yl)methylimino)methyl)benzoic acid), with a one-dimensional (1D) chain structure, has been successfully converted to a discrete Ni(II)−salicylaldimine complex [Ni(L{sup salpyca})(H{sub 2}O){sub 3}] (2) and an infinite Cu(II)−salicylaldimine complex ([Cu(L{sup salpyca})]·3H{sub 2}O){sub n} (3) through a metal-ion exchange induced structural transformation process. However, such processes do not worked by Mn(II) and Co(II) ions. Solid-state structure analyses reveal that complexes 1–3 form comparable coordinative or supramolecular zigzag chains running along the crystallographic [201] direction. In addition, replacing Zn(II) ion by Ni(II) and Cu(II) ions caused changes in coordination environment and sphere of metal centers, from a 5-coordinate intermediate geometry of square pyramidal and trigonal bipyramidal in 1 to a 6-coordinate octahedral geometry in 2, and to a 4-coordiante square planar geometry in 3. This study shows that metal-ion exchange serves as a very efficient way of forming new coordination complexes that may not be obtained through direct synthesis. - Graphical abstract: A Zn(II)−salicylaldimine zigzag chain has been successfully converted to a Ni(II)−salicylaldimine supramolecular zigzag chain and a Cu(II)−salicylaldimine coordinative zigzag chain through metal-ion exchange induced structural transformations, which is not achieved by Mn(II) and Co(II) ions.

Guanidinium chloride induction of partial unfolding in amide proton exchange in RNase A.

Science.gov (United States)

Mayo, S L; Baldwin, R L

1993-11-05

Amide (NH) proton exchange rates were measured in 0.0 to 0.7 M guanidinium chloride (GdmCl) for 23 slowly exchanging peptide NH protons of ribonuclease A (RNase A) at pH* 5.5 (uncorrected pH measured in D2O), 34 degrees C. The purpose was to find out whether GdmCl induces exchange through binding to exchange intermediates that are partly or wholly unfolded. It was predicted that, when the logarithm of the exchange rate is plotted as a function of the molarity of GdmCl, the slope should be a measure of the amount of buried surface area exposed to GdmCl in the exchange intermediate. The results indicate that these concentrations of GdmCl do induce exchange by means of a partial unfolding mechanism for all 23 protons; this implies that exchange reactions can be used to study the unfolding and stability of local regions. Of the 23 protons, nine also show a second mechanism of exchange at lower concentrations of GdmCl, a mechanism that is nearly independent of GdmCl concentration and is termed "limited structural fluctuation."

Cytotoxic, genotoxic and cell-cycle disruptive effects of thio-dimethylarsinate in cultured human cells and the role of glutathione

Energy Technology Data Exchange (ETDEWEB)

Ochi, Takafumi [Laboratory of Toxicology, Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa 229-0195 (Japan); Kita, Kayoko; Suzuki, Toshihide [Laboratory of Toxicology, Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa 229-0195 (Japan); Rumpler, Alice; Goessler, Walter; Francesconi, Kevin A [Karl-Franzens University Graz, Institute of Chemistry-Analytical Chemistry, Universitaetsplatz 1, 8010 Graz (Austria)

2008-04-01

Thio-dimethylarsinate (thio-DMA), a recently discovered urine metabolite in humans, was investigated for its cytotoxic, genotoxic and cell-cycle disruptive effects in the cultured human hepatocarcinoma cell line, HepG2, and Syrian hamster embryo cells. In addition, the role of glutathione (GSH) on the cytotoxic effects of thio-DMA was investigated in terms of the effects of GSH depletion and the effects of exogenously added GSH. LC{sub 50} values of arsenicals for cells incubated for 48 h were 0.026 mM for thio-DMA, 0.343 mM for DMA and 3.66 mM for dithio-DMA. Depletion of cell GSH reduced the cytotoxic effects of thio-DMA. The cytotoxic effects of 0.02 mM and 0.05 mM thio-DMA were enhanced markedly when used in combination with 1 to 3 mM GSH, but decreased again when combined with 5 mM GSH. These results suggested that cytotoxic intermediates were generated by the interaction of thio-DMA with GSH, while an excessive amount of GSH suppressed the generation of these intermediates. Flow-cytometry showed that thio-DMA was an inducer of cells with 4N DNA and hypo 2N DNA. The results also demonstrated that cells arrested in the mitotic phase had abnormalities in their spindle organization and centrosome integrity. In addition, cells arrested in mitosis by thio-DMA had chromosome structural aberrations, such as chromatid gaps, chromatid breaks and chromatid exchanges. Moreover, the cytotoxic effects of thio-DMA may in part be associated with an apoptotic mode of cell death that was evaluated by the appearance of nucleosome level DNA fragmentations and an 85-kDa cleavage fragment of poly (ADP-ribose) polymerase. These findings suggest that the presence of thio-DMA in human urine has implications for human health in terms of arsenic metabolism and toxicity.

Na+/Ca2+ exchange inhibitor, KB-R7943, attenuates contrast-induced acute 
kidney injury.

Science.gov (United States)

Yang, Dingwei; Yang, Dingping; Jia, Ruhan; Tan, Jin

2013-01-01

Intracellular Ca2+ overload is considered to be a key factor in contrast-induced acute kidney injury (CI-AKI). The Na+/Ca2+ exchanger (NCX) system is one of the main pathways of intracellular Ca2+ overload. We investigated the effects of KB-R7943, an inhibitor of the reverse mode of NCX, on CI-AKI in a rat model. Rats were divided into control group, CI-AKI group and pretreatment groups (with KB-R7943 dose of 5 or 10 mg/kg). CI-AKI was induced by diatrizoate administration in rats with cholesterol-supplemented diet for 8 weeks. Renal function and renal hemodynamics were determined 1 day following contrast medium administration. Renal histopathology was observed by light microscope. Renal tubular apoptosis was examined by TUNEL. Renal endothelin-1 (ET-1) was measured by radioimmunoassay. Renal malondialdehyde (MDA) and catalase (CAT) were measured as oxidative markers. Levels of serum creatinine (Scr), renal ET-1, MDA and CAT, and resistance index (RI) of renal blood vessels increased significantly in CI-AKI rats. The 
increases in Scr and RI of renal blood vessels induced by diatrizoate were suppressed significantly and 
dose-dependently by pretreatment with KB-R7943. Histopathological and TUNEL results showed that 
the contrast medium-induced severe renal tubular 
necrosis and apoptosis were significantly and dose-dependently attenuated by KB-R7943. KB-R7943 significantly suppressed the increment of renal ET-1 content and MDA and CAT level induced by contrast medium administration. Activation of the reverse mode of NCX, followed by ET-1 overproduction and increased oxidative stress, seems to play an important role in the pathogenesis of CI-AKI. The inhibitor of the reverse mode of NCX, KB-R7943, has renoprotective effects on CI-AKI.

Exercise attenuates intermittent hypoxia-induced cardiac fibrosis associated with sodium-hydrogen exchanger-1 in rats

Directory of Open Access Journals (Sweden)

Tsung-I Chen

2016-10-01

Full Text Available Purpose: To investigate the role of sodium–hydrogen exchanger-1 (NHE-1 and exercise training on intermittent hypoxia-induced cardiac fibrosis in obstructive sleep apnea (OSA, using an animal model mimicking the intermittent hypoxia of OSA. Methods: Eight-week-old male Sprague–Dawley rats were randomly assigned to control (CON, intermittent hypoxia (IH, exercise (EXE or IH combined with exercise (IHEXE groups. These groups were randomly assigned to subgroups receiving either a vehicle or the NHE-1 inhibitor cariporide. The EXE and IHEXE rats underwent exercise training on an animal treadmill for 10 weeks (5 days/week, 60 minutes/day, 24–30 m/minute, 2–10% grade. The IH and IHEXE rats were exposed to 14 days of IH (30 seconds of hypoxia - nadir of 2-6% O2 - followed by 45 seconds of normoxia for 8 hours/day. At the end of 10 weeks, rats were sacrificed and then hearts were removed to determine the myocardial levels of fibrosis index, oxidative stress, antioxidant capacity and NHE-1 activation. Results: Compared to the CON rats, IH induced higher cardiac fibrosis, lower myocardial catalase and superoxidative dismutase activities, higher myocardial lipid and protein peroxidation and higher NHE-1 activation (p < 0.05 for each, which were all abolished by cariporide. Compared to the IH rats, lower cardiac fibrosis, higher myocardial antioxidant capacity, lower myocardial lipid and protein peroxidation and lower NHE-1 activation were found in the IHEXE rats (p < 0.05 for each. Conclusion: IH-induced cardiac fibrosis was associated with NHE-1 hyperactivity. However, exercise training and cariporide exerted an inhibitory effect to prevent myocardial NHE-1 hyperactivity, which contributed to reduced IH-induced cardiac fibrosis. Therefore, NHE-1 plays a critical role in the effect of exercise on IH-induced increased cardiac fibrosis.

Phosphorylation- and nucleotide-binding-induced changes to the stability and hydrogen exchange patterns of JNK1ß1 provide insight into its mechanisms of activation

CSIR Research Space (South Africa)

Owen, GR

2014-10-01

Full Text Available –deuterium exchange (HX) mass spectrometry were used to investigate the changes to the stability and conformation/conformational dynamics of JNK1ß1 induced by phosphorylative activation. Equivalent studies were also employed to determine the effects of nucleotide...

Unlocking Chain Exchange in Highly Amphiphilic Block Polymer Micellar Systems: Influence of Agitation.

Science.gov (United States)

Murphy, Ryan P; Kelley, Elizabeth G; Rogers, Simon A; Sullivan, Millicent O; Epps, Thomas H

2014-11-18

Chain exchange between block polymer micelles in highly selective solvents, such as water, is well-known to be arrested under quiescent conditions, yet this work demonstrates that simple agitation methods can induce rapid chain exchange in these solvents. Aqueous solutions containing either pure poly(butadiene- b -ethylene oxide) or pure poly(butadiene- b -ethylene oxide- d 4 ) micelles were combined and then subjected to agitation by vortex mixing, concentric cylinder Couette flow, or nitrogen gas sparging. Subsequently, the extent of chain exchange between micelles was quantified using small angle neutron scattering. Rapid vortex mixing induced chain exchange within minutes, as evidenced by a monotonic decrease in scattered intensity, whereas Couette flow and sparging did not lead to measurable chain exchange over the examined time scale of hours. The linear kinetics with respect to agitation time suggested a surface-limited exchange process at the air-water interface. These findings demonstrate the strong influence of processing conditions on block polymer solution assemblies.

Further environmental factors causing variations of SCE frequencies

International Nuclear Information System (INIS)

Tuschl, H.; Kovac, R.; Wottawa, A.

1986-12-01

The frequencies of spontaneously occurring sister chromatid exchanges (=SCE) were determined in control persons, persons exposed to very low doses of ionizing radiation and employees of a rubber factory. Besides smoking habits and the usage of oral contraceptives, background ultraviolet (=UV) radiation seems to exert the most pronounced effect on SCE levels in control persons. (Author)

Cancer predictive value of cytogenetic markers used in occupational health surveillance programs

DEFF Research Database (Denmark)

Hagmar, L; Bonassi, S; Strömberg, U

1998-01-01

It has not previously been clear whether cytogenetic biomarkers in healthy subjects will predict cancer. Earlier analyses of a Nordic and an Italian cohort indicated predictivity for chromosomal aberrations (CAS) but not for sister chromatid exchanges (SCES). A pooled analysis of the updated......, occupational exposures and smoking, will be assessed in a case-referent study within the study base....

Cytogenetic investigation of subjects professionally exposed to radiofrequency radiation.

Science.gov (United States)

Maes, Annemarie; Van Gorp, Urbain; Verschaeve, Luc

2006-03-01

Nowadays, virtually everybody is exposed to radiofrequency radiation (RFR) from mobile phone base station antennas or other sources. At least according to some scientists, this exposure can have detrimental health effects. We investigated cytogenetic effects in peripheral blood lymphocytes from subjects who were professionally exposed to mobile phone electromagnetic fields in an attempt to demonstrate possible RFR-induced genetic effects. These subjects can be considered well suited for this purpose as their RFR exposure is 'normal' though rather high, and definitely higher than that of the 'general population'. The alkaline comet assay, sister chromatid exchange (SCE) and chromosome aberration tests revealed no evidence of RFR-induced genetic effects. Blood cells were also exposed to the well known chemical mutagen mitomycin C in order to investigate possible combined effects of RFR and the chemical. No cooperative action was found between the electromagnetic field exposure and the mutagen using either the comet assay or SCE test.

Radio-adaptive response

International Nuclear Information System (INIS)

Ikushima, Takaji

1991-01-01

An adaptive response to radiation stress was found in cultured Chinese hamster V79 cells, as a suppressed induction of micronuclei (MNs) and sister chromatid exchanges (SCEs) in the cells conditioned by very low doses. The important characteristics of the novel chromosomal response, called radio-adaptive response (RAR), that have newly emerged in this study are: 1) Low doses of beta-rays from tritiated water (HTO) as well as tritiated thymidine can cause the RAR. 2) Thermal neutrons, a high LET radiation, can not act as tritium beta-rays or gamma-rays. 3) The RAR expression is suppressed by an inhibition of protein synthesis. 4) Several proteins are newly synthesized concurrently with the RAR expression after adapting doses, viewed by two-dimensional electrophoresis of cellular proteins. These results suggest that the RAR is an adaptive chromosomal DNA repair induced by very low doses of low LET radiations under restricted conditions, accompanying the inducible specific gene expression. (author)

Avoiding vibration-induced tube failures in shell and tube heat exchangers

International Nuclear Information System (INIS)

Franklin, R.E.; Soper, B.M.H.; Whittle, R.H.

1979-01-01

The past few years has seen a very significant increase of activity in heat exchangers tube vibration research, both analytical and experimental. Some of the results of this work are examined and discussed in the context of how best they may be applied in the assessment of heat exchangers at the design stage. Special attention is focussed on the overall picture and on the simplifications which can be made in many instances. (author)

Physiological gas exchange mapping of hyperpolarized 129 Xe using spiral-IDEAL and MOXE in a model of regional radiation-induced lung injury.

Science.gov (United States)

Zanette, Brandon; Stirrat, Elaine; Jelveh, Salomeh; Hope, Andrew; Santyr, Giles

2018-02-01

To map physiological gas exchange parameters using dissolved hyperpolarized (HP) 129 Xe in a rat model of regional radiation-induced lung injury (RILI) with spiral-IDEAL and the model of xenon exchange (MOXE). Results are compared to quantitative histology of pulmonary tissue and red blood cell (RBC) distribution. Two cohorts (n = 6 each) of age-matched rats were used. One was irradiated in the right-medial lung, producing regional injury. Gas exchange was mapped 4 weeks postirradiation by imaging dissolved-phase HP 129 Xe using spiral-IDEAL at five gas exchange timepoints using a clinical 1.5 T scanner. Physiological lung parameters were extracted regionally on a voxel-wise basis using MOXE. Mean gas exchange parameters, specifically air-capillary barrier thickness (δ) and hematocrit (HCT) in the right-medial lung were compared to the contralateral lung as well as nonirradiated control animals. Whole-lung spectroscopic analysis of gas exchange was also performed. δ was significantly increased (1.43 ± 0.12 μm from 1.07 ± 0.09 μm) and HCT was significantly decreased (17.2 ± 1.2% from 23.6 ± 1.9%) in the right-medial lung (i.e., irradiated region) compared to the contralateral lung of the irradiated rats. These changes were not observed in healthy controls. δ and HCT correlated with histologically measured increases in pulmonary tissue heterogeneity (r = 0.77) and decreases in RBC distribution (r = 0.91), respectively. No changes were observed using whole-lung analysis. This work demonstrates the feasibility of mapping gas exchange using HP 129 Xe in an animal model of RILI 4 weeks postirradiation. Spatially resolved gas exchange mapping is sensitive to regional injury between cohorts that was undetected with whole-lung gas exchange analysis, in agreement with histology. Gas exchange mapping holds promise for assessing regional lung function in RILI and other pulmonary diseases. © 2017 The Authors. Medical Physics published by Wiley

Sevoflurane improves gaseous exchange and exerts protective ...

African Journals Online (AJOL)

Sevoflurane improves gaseous exchange and exerts protective effects in ... Lung water content and cell count were estimated by standard protocols. ... It reversed LPS-induced oxidative stress, as demonstrated by increase in total antioxidant ...

Repair-induced DNA double strand breaks after ultraviolet-light and either aphidocolin or 1-β-D-arabinofuranosylcytosine/hydroxyurea

International Nuclear Information System (INIS)

Bradley, M.O.; Taylor, V.I.

1983-01-01

A study was performed to determine whether 'repair-induced double strand breaks' (RDSBs) occur in IMR-90 cells at low u.v. doses and whether the RDSBs are themselves repairable by holding open the excision-repair induced gaps by inhibiting nucleotide polymerization after u.v. light with hydroxyurea/ara C or aphidocolin. The results show as little as 2.5 J.m -2 of u.v. light induces RDSBs during repair incubation when repair inhibitors are present. This suggests that 'hot spots' of high lesion frequency occur and the overlapping excision in these areas will produce RDSBs. Removing aphidocolin showed that RDSBs are only partially repairable with between 15 and 40% of the breaks unrepaired at 24 h. Because the lesions are partially repairable they should not always cause toxicity and may be involved in processes such as mutation, transformation, and chromosome or chromatid type aberrations of the sort associated with human tumors. (author)

A cytogenetic study of personnel of the Kozloduy NPP with a view to the hazards of late effects

Energy Technology Data Exchange (ETDEWEB)

Bulanova, M; Benova, D; Georgieva, I; Georgieva, V; Yagova, A; Rupova, I; Kusheva, R; Khadzhidekova, V; Topalova, S; Nikolova, T [National Centre of Radiobiology and Radiation Protection, Sofia (Bulgaria)

1996-12-31

Chromosomal analysis of 40 Kozloduy NPP workers has been carried out. Three cytogenetic end-points have been considered: chromosomal aberrations (CA), sister-chromatid exchanges and micro nuclear assays in peripheral blood lymphocytes. A higher incidence of CA has been detected in the investigated group in comparison with a control group. This is attributed to the radiation factor taking into consideration that the highest occurrence is that of dicentric chromosomes induced by radiation exposure. 95% of the workers have been employed for more than 5 years and 60% have received a dose of more than 30 cSv. However no direct relation of CA incidence to the accumulated dose has been observed. Tobacco smoking potentiates additionally the damage of the chromosome structures caused by ionizing radiation. 15 refs., 3 tabs.

Radio-adaptive response

International Nuclear Information System (INIS)

Ikushima, T.

1992-01-01

Knowledge about cellular events in mammalian cells exposed to low doses of ionizing radiation is meager. Recent works showed that human lymphocytes become resistant to radiation-induced chromosomal damage after exposure to low doses of ionizing radiation. Experimental evidence for radio-adaptive response (RAR) in cultured mammalian cells was obtained. Exposure to very low doses of gamma-rays or tritium beta-rays make cells less susceptible to the induction of micronuclei and sister chromatid exchanges by subsequent higher doses. Many important characteristics of the novel response suggest that RAR is a stress response resulting in the enhanced repair of chromosomal DNA damage in cell under restricted conditions. Experiments are still in progress in order to elucidate the molecular basis for RAR processes. (author). 13 refs.; 2 figs., 1 tab

Meiosis in radiation induced triploid and tetraploid plants of pearl millet

International Nuclear Information System (INIS)

Singh, R.B.; Singh, B.D.; Singh, R.M.; Laxmi, V.

1977-01-01

A triploid and a tetraploid plant were isolated from mutagen treated populations of HB3 (Tif23AxJ104) and HBI (Tif23AxBi13B) hybrid pearl millet, respectively. The triploid plant regularly showed univalents (1 to 9 per cell) and trivalents (1 to 6 per cell) at MI. In the case of the tetraploid, only bivalents were observed which showed loose or tight secondary associations at MI; at AI bivalents separated as units (instead of chromosomes) while at AII chromosomes (instead of chromatids) moved to the opposite poles. Although the chromosome behaviour was quite regular, the plant was highly sterile (98%). It is suggested that gamma-rays had induced mutations in a number of genes, including those affecting pairing, concomitant to the induction of tetraploidy. (auth.)

Chromosomal Integrity after UV Irradiation Requires FANCD2-Mediated Repair of Double Strand Breaks.

Directory of Open Access Journals (Sweden)

María Belén Federico

2016-01-01

Full Text Available Fanconi Anemia (FA is a rare autosomal recessive disorder characterized by hypersensitivity to inter-strand crosslinks (ICLs. FANCD2, a central factor of the FA pathway, is essential for the repair of double strand breaks (DSBs generated during fork collapse at ICLs. While lesions different from ICLs can also trigger fork collapse, the contribution of FANCD2 to the resolution of replication-coupled DSBs generated independently from ICLs is unknown. Intriguingly, FANCD2 is readily activated after UV irradiation, a DNA-damaging agent that generates predominantly intra-strand crosslinks but not ICLs. Hence, UV irradiation is an ideal tool to explore the contribution of FANCD2 to the DNA damage response triggered by DNA lesions other than ICL repair. Here we show that, in contrast to ICL-causing agents, UV radiation compromises cell survival independently from FANCD2. In agreement, FANCD2 depletion does not increase the amount of DSBs generated during the replication of UV-damaged DNA and is dispensable for UV-induced checkpoint activation. Remarkably however, FANCD2 protects UV-dependent, replication-coupled DSBs from aberrant processing by non-homologous end joining, preventing the accumulation of micronuclei and chromatid aberrations including non-homologous chromatid exchanges. Hence, while dispensable for cell survival, FANCD2 selectively safeguards chromosomal stability after UV-triggered replication stress.

Heat exchanger vibrations - a case study (Paper No. 5.12)

International Nuclear Information System (INIS)

Khilnaney, V.K.

1992-01-01

The satisfactory performance of heat exchangers is crucial to the reliability of the plant. Thorough vibration analysis is essential at design stage to avoid failures at the time of operation. Detailed vibration analysis techniques were not available at the time of designing these exchangers and the exchangers were designed as per general guidelines and prevalent good engineering practices. The designs were not checked especially from the point of view of their proneness to excessive flow induced vibration. The present paper gives a study of revamping of cooling water heat exchanger at Heavy Water Plant, Kota. (author)

Explaining employment relationships with social exchange and job embeddedness.

Science.gov (United States)

Hom, Peter W; Tsui, Anne S; Wu, Joshua B; Lee, Thomas W; Zhang, Ann Yan; Fu, Ping Ping; Li, Lan

2009-03-01

The research reported in this article clarifies how employee-organization relationships (EORs) work. Specifically, the authors tested whether social exchange and job embeddedness mediate how mutual-investment (whereby employers offer high inducements to employees for their high contributions) and over-investment (high inducements without corresponding high expected contributions) EOR approaches, which are based on Tsui, Pearce, Porter, and Tripoli's (1997) framework, affect quit propensity and organizational commitment. Two studies evaluated these intervening mechanisms. Study 1 surveyed 953 Chinese managers attending part-time master of business administration (MBA) programs in China, whereas Study 2 collected cross-sectional and longitudinal data from 526 Chinese middle managers in 41 firms. Standard and multilevel causal modeling techniques affirmed that social exchange and job embeddedness translate EOR influence. A second multilevel test using lagged outcome measures further established that job embeddedness mediates long-term EOR effects over 18 months. These findings corroborate prevailing views that social exchange explains how mutual- and over-investment EORs motivate greater workforce commitment and loyalty. This study enriches EOR perspectives by identifying job embeddedness as another mediator that is more enduring than social exchange. (c) 2009 APA, all rights reserved.

Exchange rate regimes and inflation: Evidence from India.

OpenAIRE

Mohanty, Biswajit; Bhanumurthy, N.R.

2014-01-01

Exchange rate stability is crucial for inflation management as a stable rate is expected to reduce domestic inflation pressures through a `policy discipline effect'- restricting money supply growth, and a `credibility effect'- inducing higher money demand and reduced velocity of money. Alternatively, the impossibility trillema predicts that in the presence of an open capital account, a stable exchange rate may lead to lack of control on monetary policy and, hence, higher inflation. Using a mo...

Radiation Induced G2 Chromatic Break and Repairs Kinetics in Human Lymphoblastoid Cells

International Nuclear Information System (INIS)

Seong, Jin Sil

1993-01-01

In understanding radiosensitivity a new concept of inherent radiosensitivity based on individuality and heterogeneity within a population has recently beer explored. There has been some discussion of possible mechanism underlying differences in radiosensitivity between cells. Ataxia telangiectasia(AT), a rare autosomal recessive genetic disorder, is characterized by hypersensitivity to lonizing radiation and other DNA damaging agents at the cellular level. There have been a lot of efforts to describe the cause of this hypersensitivity to radiation. At the cellular level, chromosome repair kinetics study would be an appropriate approach. The purpose of this study was to better understand radiosensitivity in an approach to investigate kinetics of induction and repair of G2 chromatic breaks using normal, AT heterozygous(ATH), and AT homozygous lymphoblastoid cell lines. In an attempt to estimate initial damage, 9-β-D-arabinosyl-2-fluoroadenine, an inhibitor of DNA synthesis and repair, was used in this study. It was found from this study that radiation induces higher chromatid breaks in AT than in normal and ATH cells. There was no significant differences of initial chromatid breaks between normal and ATH cells. Repair kinetics was the same for all. So the higher level of breaks in AT G2 cells is thought to be a reflection of the increased initial damage. The amount of initial damage correlated well with survival fraction at 2 Gy of cell survival curve following radiation. Therefore, the difference of radiosensitivity in terms of G2 chromosomal sensitivity is thought to result from the difference of initial damage

Telomere length maintenance--an ALTernative mechanism.

Science.gov (United States)

Royle, N J; Foxon, J; Jeyapalan, J N; Mendez-Bermudez, A; Novo, C L; Williams, J; Cotton, V E

2008-01-01

The Alternative Lengthening of Telomeres (ALT) mechanism is utilised by approximately 10% of human tumours and a higher proportion of some types of sarcomas. ALT+ cell lines and tumours show heterogeneous telomere length, extra-chromosomal circular and linear telomeric DNA, ALT associated promyelocytic bodies (APBs), a high frequency of post-replication exchanges in telomeres (designated as telomere-sister chromatid exchanges, T-SCE) and high instability at a GC-rich minisatellite, MS32 (D1S8). It is clear that there is a link between the minisatellite instability and the mechanism that underpins ALT, however currently the nature of this relationship is uncertain. Single molecule analysis of telomeric DNA from ALT+ cell lines and tumours has revealed complex telomere mutations that have not been seen in cell lines or tumours that express telomerase. These complex telomere mutations cannot be explained by T-SCE but must arise by another inter-molecular process. The break-induced replication (BIR) model that may explain the observed high frequency of T-SCE and the presence of complex telomere mutations is reviewed. Copyright 2008 S. Karger AG, Basel.

Direct in situ transmission electron microscopy observation of Al push up during early stages of the Al-induced layer exchange

International Nuclear Information System (INIS)

Birajdar, B.I.; Antesberger, T.; Butz, B.; Stutzmann, M.; Spiecker, E.

2012-01-01

The mechanism of Al transport during Al-induced layer exchange and crystallization of amorphous Si (a-Si) has been investigated by in situ and analytical transmission electron microscopy. Significant grain boundary realignment and coarsening of Al grains close to the Si crystallization growth front as well as push up of excess Al into the a-Si layer at distances even a few micrometers away from the crystallization front were observed. Stress-mediated diffusion of Al is postulated to explain the experimental observations.

Mitochondrial ADP/ATP exchange inhibition: a novel off-target mechanism underlying ibipinabant-induced myotoxicity.

Science.gov (United States)

Schirris, Tom J J; Ritschel, Tina; Herma Renkema, G; Willems, Peter H G M; Smeitink, Jan A M; Russel, Frans G M

2015-09-29

Cannabinoid receptor 1 (CB1R) antagonists appear to be promising drugs for the treatment of obesity, however, serious side effects have hampered their clinical application. Rimonabant, the first in class CB1R antagonist, was withdrawn from the market because of psychiatric side effects. This has led to the search for more peripherally restricted CB1R antagonists, one of which is ibipinabant. However, this 3,4-diarylpyrazoline derivative showed muscle toxicity in a pre-clinical dog study with mitochondrial dysfunction. Here, we studied the molecular mechanism by which ibipinabant induces mitochondrial toxicity. We observed a strong cytotoxic potency of ibipinabant in C2C12 myoblasts. Functional characterization of mitochondria revealed increased cellular reactive oxygen species generation and a decreased ATP production capacity, without effects on the catalytic activities of mitochondrial enzyme complexes I-V or the complex specific-driven oxygen consumption. Using in silico off-target prediction modelling, combined with in vitro validation in isolated mitochondria and mitoplasts, we identified adenine nucleotide translocase (ANT)-dependent mitochondrial ADP/ATP exchange as a novel molecular mechanism underlying ibipinabant-induced toxicity. Minor structural modification of ibipinabant could abolish ANT inhibition leading to a decreased cytotoxic potency, as observed with the ibipinabant derivative CB23. Our results will be instrumental in the development of new types of safer CB1R antagonists.

Total Plasma Exchange in Hypertriglyceridemia-Induced Pancreatitis: Case Report and Literature Review

Directory of Open Access Journals (Sweden)

Harleen Dehal

2018-01-01

Full Text Available Objective. To emphasize the role of apheresis in management of pancreatitis. Methods. The clinical course of a patient admitted for hypertriglyceridemia-induced pancreatitis (HTGP complicated by multiorgan dysfunction is described, who demonstrated dramatic improvement in his clinical status after total plasma exchange (TPE. In addition, the current guidelines for TPE and the alternative treatment options for HTGP are also presented. Results. A patient presenting with pancreatitis associated with severe systemic inflammatory response was admitted to our hospital with an initial triglyceride level of 1181 mg/dL. Given the patient’s worsening clinical condition, he was started on TPE with a rapid fall in his serum TG levels, in turn leading to early clinical recovery. Conclusion. Though various therapeutic options for the treatment of HTGP are described in literature, there are no set guidelines available to tackle this difficult clinical situation. TPE, albeit not very well known in this context, is one of the many therapies available. Though it leads to a rapid, precipitous fall in the TG levels and early symptom resolution, the data about the long-term morbidity as well as the effectiveness of this therapy is still lacking.

Cytogenetic studies of blood, experiment M111

Science.gov (United States)

Lockhart, L. H.

1977-01-01

Analysis of the chromosome patterns of Skylab crewmen preflight and postflight recorded two types of defects: minor structural defects including chromatid breaks, chromosome breaks, deletions, and fragments were not significantly increased; structural rearrangements including dicentrics, exchange figures, inversions, and translocations occured more frequently. Data indicate that the flight itself in Skylab missions was not a contributing factor to these abberrations.

Thermal hydraulic simulation of moderator heat exchanger

International Nuclear Information System (INIS)

Anil Lal, S.; Rajakumar, A.; Vaidyanathan, G.; Srinivasan, R.; Chetal, S.C.

1993-01-01

Pressurized heavy water reactors form the majority in the first stage of India's nuclear power programme. Heavy water is both moderator and primary coolant. The heat generated in the moderator due to neutron moderation and capture has to be removed in moderator heat exchangers. It has been desired to improve the performance characteristics of moderator heat exchangers, whereby moderator would enter the calandria vessel at a low temperature and would enable higher power of operation for the same limiting temperature of moderator in the calandria. Results of studies carried out using a three dimensional computer code for various operating options are given. Using these velocities the heat exchangers have been analysed for flow induced vibrations. 7 refs., 6 figs., 6 tabs

Anion-Exchange Membrane Fuel Cells with Improved CO2 Tolerance: Impact of Chemically Induced Bicarbonate Ion Consumption.

Science.gov (United States)

Katayama, Yu; Yamauchi, Kosuke; Hayashi, Kohei; Okanishi, Takeou; Muroyama, Hiroki; Matsui, Toshiaki; Kikkawa, Yuuki; Negishi, Takayuki; Watanabe, Shin; Isomura, Takenori; Eguchi, Koichi

2017-08-30

Over the last few decades, because of the significant development of anion exchange membranes, increasing efforts have been devoted the realization of anion exchange membrane fuel cells (AEMFCs) that operate with the supply of hydrogen generated on-site. In this paper, ammonia was selected as a hydrogen source, following which the effect of conceivable impurities, unreacted NH 3 and atmospheric CO 2 , on the performance of AEMFCs was established. As expected, we show that these impurities worsen the performance of AEMFCs significantly. Furthermore, with the help of in situ attenuated total reflection infrared (ATR-IR) spectroscopy, it was revealed that the degradation of the cell performance was primarily due to the inhibition of the hydrogen oxidation reaction (HOR). This is attributed to the active site occupation by CO-related adspecies derived from (bi)carbonate adspecies. Interestingly, this degradation in the HOR activity is suppressed in the presence of both NH 3 and HCO 3 - because of the bicarbonate ion consumption reaction induced by the existence of NH 3 . Further analysis using in situ ATR-IR and electrochemical methods revealed that the poisonous CO-related adspecies were completely removed under NH 3 -HCO 3 - conditions, accompanied by the improvement in HOR activity. Finally, a fuel cell test was conducted by using the practical AEMFC with the supply of NH 3 -contained H 2 gas to the anode and ambient air to the cathode. The result confirmed the validity of this positive effect of NH 3 -HCO 3 - coexistence on CO 2 -tolerence of AEMFCs. The cell performance achieved nearly 95% of that without any impurity in the fuels. These results clearly show the impact of the chemically induced bicarbonate ion consumption reaction on the realization of highly CO 2 -tolerent AEMFCs.

Damping of multispan heat exchanger tubes. Pt. 1: in gases

International Nuclear Information System (INIS)

Pettigrew, M.J.; Goyder, H.G.D.; Qiao, Z.L.; Axisa, F.

1986-07-01

Flow-induced vibration analyses of heat exchanger tubes require the knowledge of damping. This paper treats the question of damping on multispan heat exchanger tubes in air and gases. The different energy dissipation mechanisms that contribute to tube damping are discussed. The available experimental data are reviewed and analysed. We find that the main damping mechanism in gases is friction between tube and tube-supports. Damping is strongly related to tube-support thickness. Damping values are recommended for design purposes. This study is interesting in the nuclear industry for it often uses heat exchangers

Competing exchange bias and field-induced ferromagnetism in La-doped BaFe O3

Science.gov (United States)

Fita, I.; Wisniewski, A.; Puzniak, R.; Iwanowski, P.; Markovich, V.; Kolesnik, S.; Dabrowski, B.

2017-04-01

An exchange bias (EB) effect was observed in mixed valent L axB a1 -xFe O3 (x =0.125 , 0.25, 0.33) perovskites exhibiting the antiferromagnetic (AFM) helical order among F e4 + ions coexisting with the ferromagnetic (FM) cluster phase in the ground state. The L a3 + ions for B a2 + site substitution, associated with increase in number of the AFM coupled F e3 + - F e4 + pairs as well as some F e3 + - F e3 + pairs, leads to strengthening of the AFM phase and consequently to the alteration of the EB characteristics, which depend on level of the La doping x . At low doping x ≤0.25 , an abnormal dependence of the EB field, HEB, on the cooling field, Hcool, was found. The HEB increases rapidly with increasing cooling field at low Hcool, but it falls suddenly at cooling fields higher than 20 kOe, reducing by an order of magnitude at 90 kOe. The suppression of EB is caused by the field-induced increased volume of the FM phase, due to the transformation of the AFM helical spin structure into the FM one. Thus, low-doped L axB a1 -xFe O3 demonstrates a competition of two alternate cooling-field-induced effects, one of which leads to the EB anisotropy and another one to the enhanced ferromagnetism. In contrast, the x =0.33 sample, having a strong AFM constituent, shows no field-induced FM and no drop in the EB field. Accordingly, the HEB vs Hcool dependence was found to be well explained in the framework of a model describing phase-separated AFM-FM systems, namely, the model assuming isolated FM clusters of size ˜4 nm embedded in the AFM matrix.

Thermally induced A'-A site exchange in novel layered perovskites Ag2[Ca1.5M3O10] (M = Nb, Ta).

Science.gov (United States)

Bhuvanesh, Nattamai S P; Woodward, Patrick M

2002-12-04

We have synthesized and characterized new layered perovskites Ag2[A1.5M3O10] (A = Ca, M = Nb, Ta), from their lithium analogues, by soft-chemical ion exchange. These oxides show topotactic irreversible thermally induced A'-A site exchange, resulting in Ag1.1Ca0.9[Ca0.6Ag0.9M3O10], conferred from our high-temperature X-ray and ionic conductivity studies. The latter phases are the first compounds where Ag+ ions reside in both A' and A sites in layered perovskites. The absence of similar phase transition for A = Sr suggests that these transitions strongly depend on the size, charge, and the coordination preference of A' and A cations. This result provides a new synthetic tool for modifying the occupation of the 12-coordinate A site of layered perovskites using soft chemical routes.

Niacin deficiency delays DNA excision repair and increases spontaneous and nitrosourea-induced chromosomal instability in rat bone marrow.

Science.gov (United States)

Kostecki, Lisa M; Thomas, Megan; Linford, Geordie; Lizotte, Matthew; Toxopeus, Lori; Bartleman, Anne-Pascale; Kirkland, James B

2007-12-01

We have shown that niacin deficiency impairs poly(ADP-ribose) formation and enhances sister chromatid exchanges and micronuclei formation in rat bone marrow. We designed the current study to investigate the effects of niacin deficiency on the kinetics of DNA repair following ethylation, and the accumulation of double strand breaks, micronuclei (MN) and chromosomal aberrations (CA). Weanling male Long-Evans rats were fed niacin deficient (ND), or pair fed (PF) control diets for 3 weeks. We examined repair kinetics by comet assay in the 36h following a single dose of ethylnitrosourea (ENU) (30mg/kg bw). There was no effect of ND on mean tail moment (MTM) before ENU treatment, or on the development of strand breaks between 0 and 8h after ENU. Repair kinetics between 12 and 30h were significantly delayed by ND, with a doubling of area under the MTM curve during this period. O(6)-ethylation of guanine peaked by 1.5h, was largely repaired by 15h, and was also delayed in bone marrow cells from ND rats. ND significantly enhanced double strand break accumulation at 24h after ENU. ND alone increased chromosome and chromatid breaks (four- and two-fold). ND alone caused a large increase in MN, and this was amplified by ENU treatment. While repair kinetics suggest that ND may be acting by creating catalytically inactive PARP molecules with a dominant-negative effect on repair processes, the effect of ND alone on O(6)-ethylation, MN and CA, in the absence of altered comet results, suggests additional mechanisms are also leading to chromosomal instability. These data support the idea that the bone marrow cells of niacin deficient cancer patients may be more sensitive to the side effects of genotoxic chemotherapy, resulting in acute bone marrow suppression and chronic development of secondary leukemias.

In vivo mutagenicity studies in rats mice and Chinese hamsters fed irradiated foodstuffs - chicken, fish, dates, pulses, mangoes and cocoa beans

International Nuclear Information System (INIS)

Renner, H.W.

1982-01-01

Three in vivo genetic toxicity tests were performed in rats, mice and Chinese hamsters to detect possible mutagenic effects of irradiated chicken, dried dates, fish, cocoa beans, pulses and mangoes. The tests employed were the micronucleus test and sister-chromatid exchange (SCE) test for irradiated and unirradiated samples of all foodstuffs listed, and the spermatogonia test, (including SCE technique) in mice for irradiated and unirradiated chicken, fish and dates only. In the case of cocoa beans, the mutagenicity tests were performed on an additional test group fed beans fumigated with ethylene oxide. The different mammalian species used for the various experiments are given below. None of the tests provided any evidence of mutagenicity induced by irradiation in any of the foodstuffs studied. Moreover, these tests are currently considered to be the most sensitive in vivo mutagenicity tests in mammals. (orig.)

Exchange anisotropy and micromagnetic properties of PtMn/NiFe bilayers

International Nuclear Information System (INIS)

Pokhil, Taras; Linville, Eric; Mao, Sining

2001-01-01

Magnetic microstructure, exchange induced uniaxial and unidirectional anisotropy and structural transformation have been studied in PtMn/NiFe bilayer films and small elements as a function of annealing time. The relationship between the fcc-fct ordering phase transformation in PtMn and the development of exchange induced magnetic properties in PtMn/NiFe bilayers is complicated by the fact that the transformation occurs throughout the entire volume of the PtMn film, while the exchange between the layers is predominantly an interface effect. Consequently, the development of the exchange anisotropy should depend primarily on the character of the structural transformation at the interface between PtMn and NiFe. The purpose of this article is to correlate the volume phase transformation in PtMn to the development of exchange anisotropy and micromagnetic behavior in PtMn/NiFe bilayers. The interface structure can be inferred from the anisotropy and micromagnetic measurements, leading to a model that explains the relationship between the volume and interface transformation structures in PtMn, and magnetic properties of the bilayers. The structure and magnetic properties were characterized by x-ray diffraction, vibrating sample magnetometry, and magnetic force microscopy. [copyright] 2001 American Institute of Physics

Domain walls and exchange-interaction in Permalloy/Gd films

International Nuclear Information System (INIS)

Ranchal, R; Aroca, C; Lopez, E

2008-01-01

In this work we study the exchange coupling in Permalloy (Py)/gadolinium (Gd) bilayers. The exchange-coupled Py/Gd system is very temperature dependent and moreover the magnetization process in the Py layer is mainly due to domain wall (DW) displacements which are strongly controlled by pinning effects. We propose that this pinning could be caused by magnetostatic and exchange interactions between Py DWs and the magnetostrictive Gd layer. These effects mask the antiferromagnetic coupling between layers and, depending on temperature and Py thicknesses, apparent ferromagnetic coupling occurs. The study has been performed in the 80-300 K temperature range for different Py layer thicknesses and different Py induced anisotropies

Differential radiosensitivity phenotypes of DNA-PKcs mutations affecting NHEJ and HRR systems following irradiation with gamma-rays or very low fluences of alpha particles.

Science.gov (United States)

Lin, Yu-Fen; Nagasawa, Hatsumi; Little, John B; Kato, Takamitsu A; Shih, Hung-Ying; Xie, Xian-Jin; Wilson, Paul F; Brogan, John R; Kurimasa, Akihiro; Chen, David J; Bedford, Joel S; Chen, Benjamin P C

2014-01-01

We have examined cell-cycle dependence of chromosomal aberration induction and cell killing after high or low dose-rate γ irradiation in cells bearing DNA-PKcs mutations in the S2056 cluster, the T2609 cluster, or the kinase domain. We also compared sister chromatid exchanges (SCE) production by very low fluences of α-particles in DNA-PKcs mutant cells, and in homologous recombination repair (HRR) mutant cells including Rad51C, Rad51D, and Fancg/xrcc9. Generally, chromosomal aberrations and cell killing by γ-rays were similarly affected by mutations in DNA-PKcs, and these mutant cells were more sensitive in G1 than in S/G2 phase. In G1-irradiated DNA-PKcs mutant cells, both chromosome- and chromatid-type breaks and exchanges were in excess than wild-type cells. For cells irradiated in late S/G2 phase, mutant cells showed very high yields of chromatid breaks compared to wild-type cells. Few exchanges were seen in DNA-PKcs-null, Ku80-null, or DNA-PKcs kinase dead mutants, but exchanges in excess were detected in the S2506 or T2609 cluster mutants. SCE induction by very low doses of α-particles is resulted from bystander effects in cells not traversed by α-particles. SCE seen in wild-type cells was completely abolished in Rad51C- or Rad51D-deficient cells, but near normal in Fancg/xrcc9 cells. In marked contrast, very high levels of SCEs were observed in DNA-PKcs-null, DNA-PKcs kinase-dead and Ku80-null mutants. SCE induction was also abolished in T2609 cluster mutant cells, but was only slightly reduced in the S2056 cluster mutant cells. Since both non-homologous end-joining (NHEJ) and HRR systems utilize initial DNA lesions as a substrate, these results suggest the possibility of a competitive interference phenomenon operating between NHEJ and at least the Rad51C/D components of HRR; the level of interaction between damaged DNA and a particular DNA-PK component may determine the level of interaction of such DNA with a relevant HRR component.

STOCK EXCHANGE LISTING INDUCES SOPHISTICATION OF CAPITAL BUDGETING

Directory of Open Access Journals (Sweden)

Wesley Mendes-da-Silva

2014-08-01

Full Text Available This article compares capital budgeting techniques employed in listed and unlisted companies in Brazil. We surveyed the Chief Financial Officers (CFOs of 398 listed companies and 300 large unlisted companies, and based on 91 respondents, the results suggest that the CFOs of listed companies tend to use less simplistic methods more often, for example: NPV and CAPM, and that CFOs of unlisted companies are less likely to estimate the cost of equity, despite being large companies. These findings indicate that stock exchange listing may require greater sophistication of the capital budgeting process.

Giant spin torque in systems with anisotropic exchange interaction

OpenAIRE

Korenev, Vladimir L.

2012-01-01

Control of magnetic domain wall movement by the spin-polarized current looks promising for creation of a new generation of magnetic memory devices. A necessary condition for this is the domain wall shift by a low-density current. Here I show that a strongly anisotropic exchange interaction between mobile heavy holes and localized magnetic moments enormously increases the current-induced torque on the domain wall as compared to systems with isotropic exchange. This enables one to control the d...

Probing peptide fragment ion structures by combining sustained off-resonance collision-induced dissociation and gas-phase H/D exchange (SORI-HDX) in Fourier transform ion-cyclotron resonance (FT-ICR) instruments.

Science.gov (United States)

Somogyi, Arpád

2008-12-01

The usefulness of gas-phase H/D exchange is demonstrated to probe heterogeneous fragment and parent ion populations. Singly and multiply protonated peptides/proteins were fragmented by using sustained off-resonance irradiation collision-induced dissociation (SORI-CID). The fragments and the surviving precursor ions then all undergo H/D exchange in the gas-phase with either D(2)O or CD(3)OD under the same experimental conditions. Usually, 10 to 60 s of reaction time is adequate to monitor characteristic differences in the H/D exchange kinetic rates. These differences are then correlated to isomeric ion structures. The SORI-HDX method can be used to rapidly test fragment ion structures and provides useful insights into peptide fragmentation mechanisms.

Treating Coulomb exchange contributions in relativistic mean field calculations: why and how

International Nuclear Information System (INIS)

Giai, Nguyen Van; Liang, Haozhao; Gu, Huai-Qiang; Long, Wenhui; Meng, Jie

2014-01-01

The energy density functional (EDF) method is very widely used in nuclear physics, and among the various existing functionals those based on the relativistic Hartree (RH) approximation are very popular because the exchange contributions (Fock terms) are numerically rather onerous to calculate. Although it is possible to somehow ‘mock up’ the effects of meson-induced exchange terms by adjusting the meson–nucleon couplings, the lack of Coulomb exchange contributions hampers the accuracy of predictions. In this work, we show that the Coulomb exchange effects can be easily included with good accuracy in a perturbative approach. Therefore, it would be desirable for future relativistic EDF models to incorporate Coulomb exchange effects, at least to some order of perturbation

Impact of Oil Price Shocks and Exchange Rate Volatility on Stock Market Behavior in Nigeria

Directory of Open Access Journals (Sweden)

Adedoyin I. Lawal

2016-09-01

Full Text Available The impact of exchange rate and oil prices fluctuation on the stock market has been a subject of hot debate among researchers. This study examined the impact of both the exchange rate volatility and oil price volatility on stock market volatility in Nigeria, so as to guide policy formulation based on the fact that the nation’s economy was foreign induced and mono-cultured with heavy dependence on oil. EGARCH estimation techniques were employed to examine if either the volatility in exchange rate, oil price volatility or both experts on stock market volatility in Nigeria. The result shows that share price volatility is induced by both the exchange rate volatility and oil price volatility. Thus, it is recommended that policymakers should pursue policies that tend to stabilize the exchange rate regime on the one hand, and guarantee the net oil exporting position for the economy, that market practitioners should formulate portfolio strategies in such a way that volatility in both exchange rates and oil price will be factored in time when investment decisions are being made.

Lactose Binding Induces Opposing Dynamics Changes in Human Galectins Revealed by NMR-Based Hydrogen-Deuterium Exchange.

Science.gov (United States)

Chien, Chih-Ta Henry; Ho, Meng-Ru; Lin, Chung-Hung; Hsu, Shang-Te Danny

2017-08-16

Galectins are β-galactoside-binding proteins implicated in a myriad of biological functions. Despite their highly conserved carbohydrate binding motifs with essentially identical structures, their affinities for lactose, a common galectin inhibitor, vary significantly. Here, we aimed to examine the molecular basis of differential lactose affinities amongst galectins using solution-based techniques. Consistent dissociation constants of lactose binding were derived from nuclear magnetic resonance (NMR) spectroscopy, intrinsic tryptophan fluorescence, isothermal titration calorimetry and bio-layer interferometry for human galectin-1 (hGal1), galectin-7 (hGal7), and the N-terminal and C-terminal domains of galectin-8 (hGal8 NTD and hGal8 CTD , respectively). Furthermore, the dissociation rates of lactose binding were extracted from NMR lineshape analyses. Structural mapping of chemical shift perturbations revealed long-range perturbations upon lactose binding for hGal1 and hGal8 NTD . We further demonstrated using the NMR-based hydrogen-deuterium exchange (HDX) that lactose binding increases the exchange rates of residues located on the opposite side of the ligand-binding pocket for hGal1 and hGal8 NTD , indicative of allostery. Additionally, lactose binding induces significant stabilisation of hGal8 CTD across the entire domain. Our results suggested that lactose binding reduced the internal dynamics of hGal8 CTD on a very slow timescale (minutes and slower) at the expense of reduced binding affinity due to the unfavourable loss of conformational entropy.

Reversible Size Control of Silver Nanoclusters via Ligand-exchange

KAUST Repository

Bootharaju, Megalamane Siddaramappa

2015-05-21

The properties of atomically monodisperse noble metal nanoclusters (NCs) are intricately intertwined with their precise molecular formula. The vast majority of size-specific NC syntheses start from the reduction of the metal salt and thiol ligand mixture. Only in gold was it recently shown that ligand-exchange could induce the growth of NCs from one atomically precise species to another; a process of yet unknown reversibility. Here, we present a process for the ligand-exchange-induced growth of atomically precise silver NCs, in a biphasic liquid-liquid system, which is particularly of interest because of its complete reversibility and ability to occur at room temperature. We explore this phenomenon in-depth using Ag35(SG)18 [SG= glutathionate] and Ag44(4-FTP)30 [4-FTP= 4-fluorothiophenol] as model systems. We show that the ligand-exchange conversion of Ag35(SG)18 into Ag44(4-FTP)30 is rapid (< 5 min) and direct, while the reverse process proceeds slowly through intermediate cluster sizes. We adapt a recently developed theory of reverse Ostwald ripening to model the NCs’ interconvertibility. The model’s predictions are in good agreement with the experimental observations, and they highlight the importance of small changes in the ligand-metal binding energy in determining the final equilibrium NC size. Based on the insight provided by this model, we demonstrated experimentally that by varying the choice of ligands, ligand-exchange can be used to obtain different sized NCs. The findings in this work establish ligand-exchange as a versatile tool for tuning cluster sizes.

Reversible Size Control of Silver Nanoclusters via Ligand-exchange

KAUST Repository

Bootharaju, Megalamane Siddaramappa; Burlakov, Victor M.; Besong, Tabot M.D.; Joshi, Chakra Prasad; AbdulHalim, L; Black, David; Whetten, Robert; Goriely, Alain; Bakr, Osman

2015-01-01

The properties of atomically monodisperse noble metal nanoclusters (NCs) are intricately intertwined with their precise molecular formula. The vast majority of size-specific NC syntheses start from the reduction of the metal salt and thiol ligand mixture. Only in gold was it recently shown that ligand-exchange could induce the growth of NCs from one atomically precise species to another; a process of yet unknown reversibility. Here, we present a process for the ligand-exchange-induced growth of atomically precise silver NCs, in a biphasic liquid-liquid system, which is particularly of interest because of its complete reversibility and ability to occur at room temperature. We explore this phenomenon in-depth using Ag35(SG)18 [SG= glutathionate] and Ag44(4-FTP)30 [4-FTP= 4-fluorothiophenol] as model systems. We show that the ligand-exchange conversion of Ag35(SG)18 into Ag44(4-FTP)30 is rapid (< 5 min) and direct, while the reverse process proceeds slowly through intermediate cluster sizes. We adapt a recently developed theory of reverse Ostwald ripening to model the NCs’ interconvertibility. The model’s predictions are in good agreement with the experimental observations, and they highlight the importance of small changes in the ligand-metal binding energy in determining the final equilibrium NC size. Based on the insight provided by this model, we demonstrated experimentally that by varying the choice of ligands, ligand-exchange can be used to obtain different sized NCs. The findings in this work establish ligand-exchange as a versatile tool for tuning cluster sizes.

Chromosomal aberrations induced by caffeine, 3H-thymidine and by X-rays in two L5178Y sublines of different radiosensitivity. Part 2. Effect of 2 mM caffeine on the frequency of chromosomal aberrations induced by X-radiation

International Nuclear Information System (INIS)

Bocian, E.; Bouzyk, E.; Rosiek, O.; Ziemba-Zoltowska, B.

1982-01-01

The effect of 2 mM caffeine on the frequency of X-ray induced chromatid aberrations in two sublines of L5178Y cells with different sensitivity to X-rays was examined. Cells were irradiated with 1 Gy of X-rays and treated with caffeine for 12 h after irradiation. The frequency of aberrations was estimated at time intervals from 5 to 48 h after irradiation. Caffeine increased the frequency of cells with numerous aberrations produced by X radiation in both sublines. Its potentiating effect was greater in the radiation-resistant subline L5178Y-R than in the radiation-sensitive one L5178Y-S. In caffeine-treated L5178Y-S cells chromosomal aberrations were revealed earlier than in the untreated cells. (author)

Modeling and calculation of RKKY exchange coupling to explain Ti-vacancy-induced ferromagnetism in Ta-doped TiO2

Science.gov (United States)

Majidi, Muhammad Aziz; Bupu, Annamaria; Fauzi, Angga Dito

2017-12-01

We present a theoretical study on Ti-vacancy-induced ferromagnetism in anatase TiO2. A recent experimental study has revealed room temperature ferromagnetism in Ta-doped anatase TiO2thin films (Rusydi et al., 2012) [7]. Ta doping assists the formation of Ti vacancies which then induce the formation of localized magnetic moments around the Ti vacancies. As neighboring Ti vacancies are a few unit cells apart, the ferromagnetic order is suspected to be mediated by itinerant electrons. We propose that such an electron-mediated ferromagnetism is driven by Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange interaction. To examine our hypothesis, we construct a tight-binding based model Hamiltonian for the anatase TiO2 system. We calculate the RKKY exchange coupling constant of TiO2 as a function of distance between local magnetic moments at various temperatures. We model the system by taking only the layer containing a unit of TiO2, at which the Ti vacancy is believed to form, as our effective two-dimensional unit cell. Our model incorporates the Hubbard repulsive interactions between electrons occupying Ti d orbitals treated within mean-field approximation. The density of states profile resulting from the model captures the relevant electronic properties of TiO2, such as the energy gap of 3.4 eV and the n-type character, which may be a measure of the adequacy of the model. The calculated RKKY coupling constant shows that the ferromagnetic coupling extends up to 3-4 unit cells and enhances slightly as temperature is increased from 0 to 400 K. These results support our hypothesis that the ferromagnetism of this system is driven by RKKY mechanism.

The Na+/H+ exchanger controls deoxycholic acid-induced apoptosis by a H+-activated, Na+-dependent ionic shift in esophageal cells.

Directory of Open Access Journals (Sweden)

Aaron Goldman

Full Text Available Apoptosis resistance is a hallmark of cancer cells. Typically, bile acids induce apoptosis. However during gastrointestinal (GI tumorigenesis the cancer cells develop resistance to bile acid-induced cell death. To understand how bile acids induce apoptosis resistance we first need to identify the molecular pathways that initiate apoptosis in response to bile acid exposure. In this study we examined the mechanism of deoxycholic acid (DCA-induced apoptosis, specifically the role of Na(+/H(+ exchanger (NHE and Na(+ influx in esophageal cells. In vitro studies revealed that the exposure of esophageal cells (JH-EsoAd1, CP-A to DCA (0.2 mM-0.5 mM caused lysosomal membrane perturbation and transient cytoplasmic acidification. Fluorescence microscopy in conjunction with atomic absorption spectrophotometry demonstrated that this effect on lysosomes correlated with influx of Na(+, subsequent loss of intracellular K(+, an increase of Ca(2+ and apoptosis. However, ethylisopropyl-amiloride (EIPA, a selective inhibitor of NHE, prevented Na(+, K(+ and Ca(2+ changes and caspase 3/7 activation induced by DCA. Ouabain and amphotericin B, two drugs that increase intracellular Na(+ levels, induced similar changes as DCA (ion imbalance, caspase3/7 activation. On the contrary, DCA-induced cell death was inhibited by medium with low a Na(+ concentrations. In the same experiments, we exposed rat ileum ex-vivo to DCA with or without EIPA. Severe tissue damage and caspase-3 activation was observed after DCA treatment, but EIPA almost fully prevented this response. In summary, NHE-mediated Na(+ influx is a critical step leading to DCA-induced apoptosis. Cells tolerate acidification but evade DCA-induced apoptosis if NHE is inhibited. Our data suggests that suppression of NHE by endogenous or exogenous inhibitors may lead to apoptosis resistance during GI tumorigenesis.

Separation and identification of structural isomers by quadrupole collision-induced dissociation-hydrogen/deuterium exchange-infrared multiphoton dissociation (QCID-HDX-IRMPD).

Science.gov (United States)

Gucinski, Ashley C; Somogyi, Arpád; Chamot-Rooke, Julia; Wysocki, Vicki H

2010-08-01

A new approach that uses a hybrid Q-FTICR instrument and combines quadrupole collision-induced dissociation, hydrogen-deuterium exchange, and infrared multiphoton dissociation (QCID-HDX-IRMPD) has been shown to effectively separate and differentiate isomeric fragment ion structures present at the same m/z. This method was used to study protonated YAGFL-OH (free acid), YAGFL-NH(2) (amide), cyclic YAGFL, and YAGFL-OCH(3) (methyl ester). QCID-HDX of m/z 552.28 (C(29)H(38)N(5)O(6)) from YAGFL-OH reveals at least two distributions of ions corresponding to the b(5) ion and a non-C-terminal water loss ion structure. Subsequent IRMPD fragmentation of each population shows distinct fragmentation patterns, reflecting the different structures from which they arise. This contrasts with data for YAGFL-NH(2) and YAGFL-OCH(3), which do not show two distinct H/D exchange populations for the C(29)H(38)N(5)O(6) structure formed by NH(3) and HOCH(3) loss, respectively. Relative extents of exchange for C(29)H(38)N(5)O(6) ions from six sequence isomers (YAGFL, AGFLY, GFLYA, FLYAG, LYAGF, and LFGAY) show a sequence dependence of relative isomer abundance. Supporting action IRMPD spectroscopy data are also presented herein and also show that multiple structures are present for the C(29)H(38)N(5)O(6) species from YAGFL-OH. Copyright 2010. Published by Elsevier Inc.

Proton exchange in acid–base complexes induced by reaction coordinates with heavy atom motions

International Nuclear Information System (INIS)

Alavi, Saman; Taghikhani, Mahdi

2012-01-01

Highlights: ► Proton exchange in acid–base complexes is studied. ► The structures, binding energies, and normal mode vibrations are calculated. ► Transition state structures of proton exchange mechanism are determined. ► In the complexes studied, the reaction coordinate involves heavy atom rocking. ► The reaction coordinate is not simply localized in the proton movements. - Abstract: We extend previous work on nitric acid–ammonia and nitric acid–alkylamine complexes to illustrate that proton exchange reaction coordinates involve the rocking motion of the base moiety in many double hydrogen-bonded gas phase strong acid–strong base complexes. The complexes studied involve the biologically and atmospherically relevant glycine, formic, acetic, propionic, and sulfuric acids with ammonia/alkylamine bases. In these complexes, the magnitude of the imaginary frequencies associated with the proton exchange transition states are −1 . This contrasts with widely studied proton exchange reactions between symmetric carboxylic acid dimers or asymmetric DNA base pair and their analogs where the reaction coordinate is localized in proton motions and the magnitude of the imaginary frequencies for the transition states are >1100 cm −1 . Calculations on complexes of these acids with water are performed for comparison. Variations of normal vibration modes along the reaction coordinate in the complexes are described.

Creation and Annihilation of Skyrmions in the Frustrated Magnets with Competing Exchange Interactions.

Science.gov (United States)

Hu, Yong; Chi, Xiaodan; Li, Xuesi; Liu, Yan; Du, An

2017-11-22

In triangular-lattice magnets, the coexistence of third-neighbor antiferromagnetic and nearest-neighbor ferromagnetic exchange interactions can induce rich magnetic phases including noncoplanar skyrmion crystals. Based on Monte Carlo simulation, we studied the dependence of magnetic phase transition on exchange interaction strength. Under the consideration of uniaxial anisotropy and magnetic field both perpendicular to the film plane, a large antiferromagnetic exchange interaction induces a high frustration. When the value of antiferromagnetic exchange interaction is one and a half times larger than the ferromagnetic one, a magnetic phase composed of canting spin stripes, never observed in the chiral magnets, forms. Interestingly, different canting spin stripes along three 120 degree propagation directions may coexist randomly in a magnetic phase, attesting that the canting spin stripes are three-fold degenerate states akin to helices and the multiple state of canting spin stripes is a circular configuration with zero skyrmion charge number. Moreover, skyrmions and antiskyrmions can be observed simultaneously in the configuration at the low temperature nearly close to 0 K, and their configuration and diameter properties are discussed. Finally, the mechanisms of skyrmion creation and annihilation are properly interpreted by comparing exchange and Zeeman energy terms.

Acute and long-term cytogenetic effects of treatment in childhood cancer

International Nuclear Information System (INIS)

Aronson, M.M.; Miller, R.C.; Hill, R.B.; Nichols, W.W.; Meadows, A.T.

1982-01-01

The incidence of chromosomal aberrations in banded karyotypes and of sister-chromatid exchanges (SCEs) was determined in the lymphocytes of survivors of childhood cancer as 2 parameters which are pertinent in assessing the genetic damage induced by chemotherapy. The proportion of cells with chromosome breakage or structural rearrangement-type aberration was 1 cell in 67 in a control group of 8 untreated cancer patients and 2 parents of cancer patients, 1 cell in 8 in 12 patients currently on therapy, and 1 cell in 50 in 17 patients sampled 6 months to 35 years post-treatment. The range of mean SCE levels per cell was 4.5-6.5 in the untreated cancer patients, 4.0-9.6 in non-cancer controls, 3.3-33.7 in patients on therapy, and 4.6-9.7 in post-therapy survivors. Considerable variability was observed between individuals with both SCE and breakage assays but therapy-induced increases in SCEs were not necessarily correlated with increased levels of aberrations arising from chromosomal breakage. (orig.)

Delayed repair of DNA single-strand breaks does not increase cytogenetic damage

International Nuclear Information System (INIS)

Morgan, W.F.; Djordjevic, M.C.; Jostes, R.F.; Pantelias, G.E.

1985-01-01

DNA damage and cytogenetic effects of ionizing radiation were investigated in Chinese hamster ovary (CHO) cells and unstimulated human peripheral blood lymphocytes. DNA damage and repair were analysed by alkaline elution under conditions that predominantly measured DNA single-strand breaks (ssb). X-radiation (2.5 Gy) induced ssb in both CHO cells and unstimulated lymphocytes, and the breaks were repaired within 30 and 90 min, respectively. This rapid repair was delayed by the poly(ADP-ribose) polymerase inhibitor, 3-aminobenzamide (3AB). The cytogenetic effects of the 3AB-induced delay in DNA repair were examined by analysing sister chromatid exchange (SCE) frequency in CHO cells and fragmentation of prematurely condensed chromosomes (PCC) in unstimulated human lymphocytes after 2.5 Gy of X-rays. Although 3AB delayed the rejoining of DNA ssb, this delay did not result in increased cytogenetic damage manifested as either SCE or fragmentation of PCC. These results indicate that the rapidly rejoining DNA ssb are not important in the production of chromosome damage. (author)

Evaluation of antigenotoxic effects of carotenoids from green algae Chlorococcum humicola using human lymphocytes

Science.gov (United States)

Bhagavathy, S; Sumathi, P

2012-01-01

Objective To identify the available phytochemicals and carotenoids in the selected green algae and evaluate the potential genotoxic/antigenotoxic effect using lymphocytes. Methods Organic solvent extracts of Chlorococcum humicola (C. humicola) were used for the phytochemical analysis. The available carotenoids were assessed by HPLC, and LC-MS analysis. The genotoxicity was induced by the benzo(a)pyrene in the lymphocyte culture, the genotoxic and antigenotoxic effects of algal carotenoids with and without genotoxic inducer were evaluated by chromosomal aberration (CA), sister chromatid exchange (SCE) and micronucleus assay (MN). Results The results of the analysis showed that the algae were rich in carotenoids and fatty acids. In the total carotenoids lutein, β-carotene and α-carotene were found to be present in higher concentration. The frequency of CA and SCE increased by benzo(a)pyrene were significantly decreased by the carotenoids (Pcarotenoids when compared with the positive controls (Pcarotenoids which effectively fight against environmental genotoxic agents, the carotenoids itself is not a genotoxic substance and should be further considered for its beneficial effects. PMID:23569879

Genotoxicity of dill (Anethum graveolens L.), peppermint (Menthaxpiperita L.) and pine (Pinus sylvestris L.) essential oils in human lymphocytes and Drosophila melanogaster.

Science.gov (United States)

Lazutka, J R; Mierauskiene, J; Slapsyte, G; Dedonyte, V

2001-05-01

Genotoxic properties of the essential oils extracted from dill (Anethum graveolens L.) herb and seeds, peppermint (Menthaxpiperita L.) herb and pine (Pinus sylvestris L.) needles were studied using chromosome aberration (CA) and sister chromatid exchange (SCE) tests in human lymphocytes in vitro, and Drosophila melanogaster somatic mutation and recombination test (SMART) in vivo. In the CA test, the most active essential oil was from dill seeds, then followed essential oils from dill herb, peppermint herb and pine needles, respectively. In the SCE test, the most active essential oils were from dill herb and seeds followed by essential oils from pine needles and peppermint herb. Essential oils from dill herb and seeds and pine needles induced CA and SCE in a clear dose-dependent manner, while peppermint essential oil induced SCE in a dose-independent manner. All essential oils were cytotoxic for human lymphocytes. In the SMART test, a dose-dependent increase in mutation frequency was observed for essential oils from pine and dill herb. Peppermint essential oil induced mutations in a dose-independent manner. Essential oil from dill seeds was almost inactive in the SMART test.

Reduction in fluoride-induced genotoxicity in mouse bone marrow cells after substituting high fluoride-containing water with safe drinking water.

Science.gov (United States)

Podder, Santosh; Chattopadhyay, Ansuman; Bhattacharya, Shelley

2011-10-01

Treatment of mice with 15 mg l(-1) sodium fluoride (NaF) for 30 days increased the number of cell death, chromosomal aberrations (CAs) and 'cells with chromatid breaks' (aberrant cells) compared with control. The present study was intended to determine whether the fluoride (F)-induced genotoxicity could be reduced by substituting high F-containing water after 30 days with safe drinking water, containing 0.1 mg F ions l(-1). A significant fall in percentage of CAs and aberrant cells after withdrawal of F-treatment following 30 days of safe water treatment in mice was observed which was highest after 90 days, although their levels still remained significantly high compared with the control group. This observation suggests that F-induced genotoxicity could be reduced by substituting high F-containing water with safe drinking water. Further study is warranted with different doses and extended treatment of safe water to determine whether the induced damages could be completely reduced or not. Copyright © 2011 John Wiley & Sons, Ltd.

Exchange rate policy when the labour market exhibits hysteresis

OpenAIRE

Barry, Frank

1994-01-01

This paper analyzes the effects of exchange rate shocks in a small open economy whose labor market exhibits hysteresis. The model is used to highlight deficiencies in the response of the Irish authorities to exchange rate crisis of 1992/93. A secondary purpose of the paper, though, is to induce those who accept that the Irish labour market is characterised by hysteresis but who reject the argument made here that a more aggressive devaluation should have been pursued, to spell out the labour-m...

Isolation and characterization of a radiosensitive Chinese hamster ovary cell line

International Nuclear Information System (INIS)

Fuller, L.F.

1987-01-01

A x-ray sensitive Chinese hamster ovary cell line was isolated using a semi-automated procedure in which mutagenized CHO cells were allowed to form colonies on top of agar, x-irradiated, then photographed at two later times. Comparison of the photographs allowed the identification of colonies which displayed significant growth arrest. One of the colonies identified in this manner produced a stable, radiosensitive line. This cell line is normal in x-ray induced inhibition of DNA synthesis, and single- and double-strand break repair, and is moderately sensitive to ethyl methane sulfonate and UV light. The sensitive line performs only half as much x-ray-induced repair replication as the parental line and this deficiency is believed to be the primary cause of its radiosensitivity. The sensitive line produces significantly higher numbers of x-ray-induced chromosome and chromatid aberrations including chromatid aberrations following exposure during the G 1 phase of the cell cycle. The line is hypomutable compared to the parental line with x-ray exposure inducing only one-third as many 6-thioguanine resistant colonies

Exchange anisotropy pinning of a standing spin-wave mode

Science.gov (United States)

Magaraggia, R.; Kennewell, K.; Kostylev, M.; Stamps, R. L.; Ali, M.; Greig, D.; Hickey, B. J.; Marrows, C. H.

2011-02-01

Standing spin waves in a thin film are used as sensitive probes of interface pinning induced by an antiferromagnet through exchange anisotropy. Using coplanar waveguide ferromagnetic resonance, pinning of the lowest energy spin-wave thickness mode in Ni80Fe20/Ir25Mn75 exchange-biased bilayers was studied for a range of Ir25Mn75 thicknesses. We show that pinning of the standing mode can be used to amplify, relative to the fundamental resonance, frequency shifts associated with exchange bias. The shifts provide a unique “fingerprint” of the exchange bias and can be interpreted in terms of an effective ferromagnetic film thickness and ferromagnet-antiferromagnet interface anisotropy. Thermal effects are studied for ultrathin antiferromagnetic Ir25Mn75 thicknesses, and the onset of bias is correlated with changes in the pinning fields. The pinning strength magnitude is found to grow with cooling of the sample, while the effective ferromagnetic film thickness simultaneously decreases. These results suggest that exchange bias involves some deformation of magnetic order in the interface region.

Exchange bias coupling in NiO/Ni bilayer tubular nanostructures synthetized by electrodeposition and thermal oxidation

Energy Technology Data Exchange (ETDEWEB)

Yu, T., E-mail: work_tian@scu.edu.cn [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Zhang, Z.W.; Xu, Y.H. [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Liu, Y. [Analytical & Testing Center, Sichuan University, Chengdu 610064 (China); Li, W.J. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, University of Chinese Academy of Sciences, Chinese Academy of Sciences, Beijing 100190 (China); Nie, Y.; Zhang, X. [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China); Xiang, G., E-mail: gxiang@scu.edu.cn [College of Physical Science and Technology, Sichuan University, Chengdu 610064 (China)

2017-05-01

In this paper, we reported the synthesis of NiO/Ni bilayer nanotubes by electrodeposition and thermal oxidation using anodic aluminum oxide templates. The morphology, structure, chemical composition and magnetic properties, especially magnetic exchange bias induced by subsequent magnetic field cooling, in this one-dimensional antiferromagnetic/ferromagnetic hybrid system were investigated. It was found that the effect of the annealing temperature, which mainly dominated the thickness of the NiO layer, and the annealing time, which mainly dominated the grain size of the NiO, on the exchange bias field showed competitive relationship. The optimized exchange bias field was achieved by the combination of the shorter annealing time and higher annealing temperature. - Highlights: • NiO-Ni bilayer tubular nanotubes were fabricated by electrodeposition and thermal oxidation. • The exchange bias effect in NiO-Ni nanotubes was induced by magnetic field cooling. • The competitive effect of annealing temperature and annealing time on the exchange bias coupling was analyzed.

Exchangers man the pumps: Functional interplay between proton pumps and proton-coupled Ca2+ exchangers

OpenAIRE

Barkla, Bronwyn J; Hirschi, Kendal D; Pittman, Jon K

2008-01-01

Tonoplast-localised proton-coupled Ca2+ transporters encoded by cation/H+ exchanger (CAX) genes play a critical role in sequestering Ca2+ into the vacuole. These transporters may function in coordination with Ca2+ release channels, to shape stimulus-induced cytosolic Ca2+ elevations. Recent analysis of Arabidopsis CAX knockout mutants, particularly cax1 and cax3, identified a variety of phenotypes including sensitivity to abiotic stresses, which indicated that these transporters might play a ...

Electric field-controlled magnetization in exchange biased IrMn/Co/PZT multilayers

International Nuclear Information System (INIS)

Huong Giang, D T; Duc, N H; Agnus, G; Maroutian, T; Lecoeur, P

2013-01-01

Electric-field modulating exchange bias and near 180° deterministic magnetization switching at room temperature are demonstrated in simple antiferromagnetic/ferromagnetic/ferroelectric (AFM/FM/FE) exchange-coupled multiferroic multilayers of IrMn/Co/PZT. A rather large exchange bias field shift up to ΔH ex /H ex = 500% was obtained. This change governs mainly the electric-field strength rather than the applied current. It is explained as being realized through the competition between the electric-field induced uniaxial and unidirectional anisotropies. These results show good prospects for low-power spintronic devices. (paper)

Familial melanoma associated with dominant ultraviolet radiation sensitivity

International Nuclear Information System (INIS)

Ramsay, R.G.; Chen, P.; Imray, F.P.; Kidson, C.; Lavin, M.F.; Hockey, A.

1982-01-01

Sensitivity to ultraviolet radiation was studied in lymphoblastoid cell lines derived from 32 members of two families with histories of multiple primary melanomas in several generations. As assayed by colony formation in agar or by trypan blue exclusion following irradiation, cellular sensitivity showed a bimodal distribution. All persons with melanoma or multiple moles were in the sensitive group, while some family members exhibited responses similar to those of controls. Cells from four cases of sporadic melanoma showed normal levels of sensitivity. The data are consistent with a dominantly inherited ultraviolet light sensitivity associated with these examples of familial melanoma. Spontaneous and ultraviolet light-induced sister chromatid exchange frequencies were similar to those in control cell lines. No defect in excision repair was detected in any of the above cell lines, but the sensitive group showed postirradiation inhibition of DNA replication intermediate between controls and an excision-deficient xeroderma pigmentosum cell line

The effect of partner-directed emotion in social exchange decision-making.

Science.gov (United States)

Eimontaite, Iveta; Nicolle, Antoinette; Schindler, Igor; Goel, Vinod

2013-01-01

Despite the prevalence of studies examining economic decision-making as a purely rational phenomenon, common sense suggests that emotions affect our decision-making particularly in a social context. To explore the influence of emotions on economic decision-making, we manipulated opponent-directed emotions prior to engaging participants in two social exchange decision-making games (the Trust Game and the Prisoner's Dilemma). Participants played both games with three different (fictional) partners and their tendency to defect was measured. Prior to playing each game, participants exchanged handwritten "essays" with their partners, and subsequently exchanged evaluations of each essay. The essays and evaluations, read by the participant, were designed to induce either anger, sympathy, or a neutral emotional response toward the confederate with whom they would then play the social exchange games. Galvanic skin conductance level (SCL) showed enhanced physiological arousal during anger induction compared to both the neutral and sympathy conditions. In both social exchange games, participants were most likely to defect against their partner after anger induction and least likely to defect after sympathy induction, with the neutral condition eliciting intermediate defection rates. This pattern was found to be strongest in participants exhibiting low cognitive control (as measured by a Go/no-Go task). The findings indicate that emotions felt toward another individual alter how one chooses to interact with them, and that this influence depends both on the specific emotion induced and the cognitive control of the individual.

The effect of partner-directed emotion in social exchange decision-making

Directory of Open Access Journals (Sweden)

Iveta eEimontaite

2013-07-01

Full Text Available Despite the prevalence of studies examining economic decision-making as a purely rational phenomenon, common sense suggests that emotions affect our decision-making particularly in a social context. To address the influence of emotions on economic decision-making, we manipulated opponent-directed emotions prior to engaging participants in two social exchange decision-making games (the Trust Game and the Prisoner’s Dilemma. Participants played both games with three different (fictional partners and their tendency to defect was measured. Prior to playing each game, participants exchanged handwritten essays with their partners, and subsequently exchanged evaluations of each essay. The essays and evaluations, read by the participant, were designed to induce either anger, sympathy or a neutral emotional response towards the confederate with whom they would then play the social exchange games. Galvanic skin conductance level showed enhanced physiological arousal during anger induction compared to both neutral and sympathy conditions. In both social exchange games, participants were most likely to defect against their partner after anger induction and least likely to defect after sympathy induction, with the neutral condition eliciting intermediate defection rates. This pattern was found to be strongest in participants exhibiting low cognitive control (as measured by a Go/no-Go task. The findings indicate that emotions felt towards another individual alter how one chooses to interact with them, and that this influence depends both on the specific emotion induced and the cognitive control of the individual.

The effect of partner-directed emotion in social exchange decision-making

Science.gov (United States)

Eimontaite, Iveta; Nicolle, Antoinette; Schindler, Igor; Goel, Vinod

2013-01-01

Despite the prevalence of studies examining economic decision-making as a purely rational phenomenon, common sense suggests that emotions affect our decision-making particularly in a social context. To explore the influence of emotions on economic decision-making, we manipulated opponent-directed emotions prior to engaging participants in two social exchange decision-making games (the Trust Game and the Prisoner's Dilemma). Participants played both games with three different (fictional) partners and their tendency to defect was measured. Prior to playing each game, participants exchanged handwritten “essays” with their partners, and subsequently exchanged evaluations of each essay. The essays and evaluations, read by the participant, were designed to induce either anger, sympathy, or a neutral emotional response toward the confederate with whom they would then play the social exchange games. Galvanic skin conductance level (SCL) showed enhanced physiological arousal during anger induction compared to both the neutral and sympathy conditions. In both social exchange games, participants were most likely to defect against their partner after anger induction and least likely to defect after sympathy induction, with the neutral condition eliciting intermediate defection rates. This pattern was found to be strongest in participants exhibiting low cognitive control (as measured by a Go/no-Go task). The findings indicate that emotions felt toward another individual alter how one chooses to interact with them, and that this influence depends both on the specific emotion induced and the cognitive control of the individual. PMID:23898313

Recoil chemistry and solid state exchange in cobalt complexes : a new model

International Nuclear Information System (INIS)

Ramshesh, V.

1981-01-01

During the last thirty years considerable work has been done on various aspects of recoil chemistry and solid state exchange in cobalt complexes. Several interesting features such as 'oxygen effect', 'water of hydration effect', 'dilution with isomorphous materials', etc., have been observed. These data led workers to reject the older hypothesis based on 'fragmentation' and 'recombination' and suggest models based on exciton or electron induced exchange. However some recent data show that perhaps both the processes viz., thermal annealing in n-irradiated systems and solid state exchange are not bulk processes. This has led the author to propose a new model. In this model greater emphasis is placed on dissociation reactions followed by recombination and/or exchange reactions. (author)

Legacy of human-induced C erosion and burial on soil-atmosphere C exchange.

Science.gov (United States)

Van Oost, Kristof; Verstraeten, Gert; Doetterl, Sebastian; Notebaert, Bastiaan; Wiaux, François; Broothaerts, Nils; Six, Johan

2012-11-20

Carbon exchange associated with accelerated erosion following land cover change is an important component of the global C cycle. In current assessments, however, this component is not accounted for. Here, we integrate the effects of accelerated C erosion across point, hillslope, and catchment scale for the 780-km(2) Dijle River catchment over the period 4000 B.C. to A.D. 2000 to demonstrate that accelerated erosion results in a net C sink. We found this long-term C sink to be equivalent to 43% of the eroded C and to have offset 39% (17-66%) of the C emissions due to anthropogenic land cover change since the advent of agriculture. Nevertheless, the erosion-induced C sink strength is limited by a significant loss of buried C in terrestrial depositional stores, which lagged the burial. The time lag between burial and subsequent loss at this study site implies that the C buried in eroded terrestrial deposits during the agricultural expansion of the last 150 y cannot be assumed to be inert to further destabilization, and indeed might become a significant C source. Our analysis exemplifies that accounting for the non-steady-state C dynamics in geomorphic active systems is pertinent to understanding both past and future anthropogenic global change.

Legacy of human-induced C erosion and burial on soil–atmosphere C exchange

Science.gov (United States)

Van Oost, Kristof; Verstraeten, Gert; Doetterl, Sebastian; Notebaert, Bastiaan; Wiaux, François; Broothaerts, Nils; Six, Johan

2012-01-01

Carbon exchange associated with accelerated erosion following land cover change is an important component of the global C cycle. In current assessments, however, this component is not accounted for. Here, we integrate the effects of accelerated C erosion across point, hillslope, and catchment scale for the 780-km2 Dijle River catchment over the period 4000 B.C. to A.D. 2000 to demonstrate that accelerated erosion results in a net C sink. We found this long-term C sink to be equivalent to 43% of the eroded C and to have offset 39% (17–66%) of the C emissions due to anthropogenic land cover change since the advent of agriculture. Nevertheless, the erosion-induced C sink strength is limited by a significant loss of buried C in terrestrial depositional stores, which lagged the burial. The time lag between burial and subsequent loss at this study site implies that the C buried in eroded terrestrial deposits during the agricultural expansion of the last 150 y cannot be assumed to be inert to further destabilization, and indeed might become a significant C source. Our analysis exemplifies that accounting for the non–steady-state C dynamics in geomorphic active systems is pertinent to understanding both past and future anthropogenic global change. PMID:23134723

Analysis of flow-induced vibration of heat exchanger and steam generator tube bundles using the AECL computer code PIPEAU-2

International Nuclear Information System (INIS)

Gorman, D.J.

1983-12-01

PIPEAU-2 is a computer code developed at the Chalk River Nuclear Laboratories for the flow-induced vibration analysis of heat exchanger and steam generator tube bundles. It can perform this analysis for straight and 'U' tubes. All the theoretical work underlying the code is analytical rather than numerical in nature. Highly accurate evaluation of the free vibration frequencies and mode shapes is therefore obtained. Using the latest experimentally determined parameters available, the free vibration analysis is followed by a forced vibration analysis. Tube response due to fluid turbulence and vortex shedding is determined, as well as critical fluid velocity associated with fluid-elastic instability

Using a Spectral Method to Evaluate Hyporheic Exchange and its Effect on Reach Scale Nitrate Removal.

Science.gov (United States)

Moren, I.; Worman, A. L. E.; Riml, J.

2017-12-01

Previous studies have shown that hyporheic exchange processes can be of great importance for the transport, retention and mass removal of nutrients in streams. Specifically, the flow of surface water through the hyporheic zone enhances redox-sensitive reactions such as coupled nitrification-denitrification. This self-cleaning capacity of streams can be utilized in stream restoration projects aiming to improve water quality by reconstructing the geomorphology of the streams. To optimize the effect of restoration actions we need quantitative understanding of the linkage between stream geomorphology, hyporheic exchange processes and the desired water quality targets. Here we propose an analytical, spectral methodology to evaluate how different stream geomorphologies induce hyporheic exchange on a wide range of spatial and temporal scales. Measurements of streambed topographies and surface water profiles from agricultural streams were used to calculate the average hyporheic exchange velocity and residence times and the result was compared with in-stream tracer test. Furthermore, the hyporheic exchange induced by steps in the surface water profile was derived as a comparison of the theoretical capacity of the system. Based on differences in hyporheic exchange, the mass removal of nitrate could be derived for the different geomorphologies. The maximum nitrate mass removal was found to be related to a specific Damkhöler number, which reflects that the mass removal can be either reaction or transport controlled. Therefore, although hyporheic exchange induced by steps in the surface water profile was generally larger than the hyporheic exchange in the observed natural reaches, this would not necessarily lead a larger nitrate mass removal provided that the hyporheic residence times are not long enough to facilitate denitrification processes. The study illustrates the importance to investigate a stream thoroughly before any remediation actions are implemented, specifically

Management of sulcus-fixated single-piece intraocular lens-induced pigmentary glaucoma with 3-piece IOL exchange.

Science.gov (United States)

Rabie, Hossein Mohammad; Esfandiari, Hamed; Rikhtegar, Mohammad Hassan; Hekmat, Vahid

2018-02-01

To describe our experience with exchanging sulcus-fixated single-piece intraocular lens (IOL) with 3-piece IOLs for management of pigmentary glaucoma. In this retrospective study, records of patients who underwent sulcus-fixated single-piece IOL exchanged with 3-piece IOLs were retrieved, and demographic and baseline data of patients, type of IOL, pre- and post-IOL exchange BCVA, IOP, number of anti-glaucoma medications, and optic nerve head examination were documented. Baseline and final examinations were analyzed and compared. Mean age of the patients was 59 ± 10 years, and 5 (41.6%) were female. Mean interval between primary cataract extraction operation and IOL exchange was 17 ± 5 months. Nine patients received in sulcus implantation of Alcon SA60AT, and three patients had SN60WF model at the end of primary surgery. BCVA changed insignificantly from 0.06 ± 0.06 logMAR to 0.06 ± 0.06 after IOL exchange. (P = 0.22) IOP was controlled in 8 cases (66.6%), but four cases (33.3%) needed glaucoma surgery to further control glaucoma condition. IOP decreased significantly from preoperative 17 ± 3 to 14 ± 1 mmHg postoperatively. Patients with advanced age and higher baseline IOP were more likely to undergo glaucoma surgery after IOL exchange. (P = 0.07 and 0.00, respectively). single-piece IOL exchange with 3-piece IOL dramatically decreases pigment release and reduces IOP. Those with advanced age and higher IOP are less likely to respond to IOL exchange and may need glaucoma surgery to control high intraocular pressure.

Sodium-hydrogen exchange in erythrocytes of patients with acute deep venous thromboses.

Science.gov (United States)

Polykarpov, S A; Orlov, S N

1992-05-15

The rate of delta microH(+)-induced Na/H-exchange in erythrocytes of patients with occlusive and with floating types of acute deep venous thromboses, and in control volunteers, was estimated. In patients with occlusive thrombi Na/H-exchange was revealed to be fourfold higher in comparison with patients with floating thrombi and with controls, while no difference was observed between the two latter groups.

New Trends in Magnetic Exchange Bias

Science.gov (United States)

Mougin, Alexandra; Mangin, Stéphane; Bobo, Jean-Francois; Loidl, Alois

2005-05-01

The study of layered magnetic structures is one of the hottest topics in magnetism due to the growing attraction of applications in magnetic sensors and magnetic storage media, such as random access memory. For almost half a century, new discoveries have driven researchers to re-investigate magnetism in thin film structures. Phenomena such as giant magnetoresistance, tunneling magnetoresistance, exchange bias and interlayer exchange coupling led to new ideas to construct devices, based not only on semiconductors but on a variety of magnetic materials Upon cooling fine cobalt particles in a magnetic field through the Néel temperature of their outer antiferromagnetic oxide layer, Meiklejohn and Bean discovered exchange bias in 1956. The exchange bias effect through which an antiferromagnetic AF layer can cause an adjacent ferromagnetic F layer to develop a preferred direction of magnetization, is widely used in magnetoelectronics technology to pin the magnetization of a device reference layer in a desired direction. However, the origin and effects due to exchange interaction across the interface between antiferromagneic and ferromagnetic layers are still debated after about fifty years of research, due to the extreme difficulty associated with the determination of the magnetic interfacial structure in F/AF bilayers. Indeed, in an AF/F bilayer system, the AF layer acts as “the invisible man” during conventional magnetic measurements and the presence of the exchange coupling is evidenced indirectly through the unusual behavior of the adjacent F layer. Basically, the coercive field of the F layer increases in contact with the AF and, in some cases, its hysteresis loop is shifted by an amount called exchange bias field. Thus, AF/F exchange coupling generates a new source of anisotropy in the F layer. This induced anisotropy strongly depends on basic features such as the magnetocrystalline anisotropy, crystallographic and spin structures, defects, domain patterns etc

Na+/H+ exchange activity in the plasma membrane of Arabidopsis.

Science.gov (United States)

Qiu, Quan-Sheng; Barkla, Bronwyn J; Vera-Estrella, Rosario; Zhu, Jian-Kang; Schumaker, Karen S

2003-06-01

In plants, Na+/H+ exchangers in the plasma membrane are critical for growth in high levels of salt, removing toxic Na+ from the cytoplasm by transport out of the cell. The molecular identity of a plasma membrane Na+/H+ exchanger in Arabidopsis (SOS1) has recently been determined. In this study, immunological analysis provided evidence that SOS1 localizes to the plasma membrane of leaves and roots. To characterize the transport activity of this protein, purified plasma membrane vesicles were isolated from leaves of Arabidopsis. Na+/H+ exchange activity, monitored as the ability of Na to dissipate an established pH gradient, was absent in plants grown without salt. However, exchange activity was induced when plants were grown in 250 mm NaCl and increased with prolonged salt exposure up to 8 d. H+-coupled exchange was specific for Na, because chloride salts of other monovalent cations did not dissipate the pH gradient. Na+/H+ exchange activity was dependent on Na (substrate) concentration, and kinetic analysis indicated that the affinity (apparent Km) of the transporter for Na+ is 22.8 mm. Data from two experimental approaches supports electroneutral exchange (one Na+ exchanged for one proton): (a) no change in membrane potential was measured during the exchange reaction, and (b) Na+/H+ exchange was unaffected by the presence or absence of a membrane potential. Results from this research provide a framework for future studies into the regulation of the plant plasma membrane Na+/H+ exchanger and its relative contribution to the maintenance of cellular Na+ homeostasis during plant growth in salt.

Effects of Simultaneous Radiofrequency Radiation and Chemical Exposure of Mammalian Cells. Volume 2

Science.gov (United States)

1988-07-01

chromosome - - - - - - -I aberrations and sister chromatid exchanges (SCE). Yao (1982) exposed rat kangaroo RH5 and RH1l6 cells to 2.45 GHz radiation, and...control was reported in chromosome aberrations. Yac (1982) investigated the cytogenetic consequences of chronic microwave exposure on rat kangaroo RH5...was said to be 280C. The cells were exposed both as conidia, which are "rather inactive metabolically ," and also after DNA replication had been

DNA template strand sequencing of single-cells maps genomic rearrangements at high resolution

OpenAIRE

Falconer, Ester; Hills, Mark; Naumann, Ulrike; Poon, Steven S. S.; Chavez, Elizabeth A.; Sanders, Ashley D.; Zhao, Yongjun; Hirst, Martin; Lansdorp, Peter M.

2012-01-01

DNA rearrangements such as sister chromatid exchanges (SCEs) are sensitive indicators of genomic stress and instability, but they are typically masked by single-cell sequencing techniques. We developed Strand-seq to independently sequence parental DNA template strands from single cells, making it possible to map SCEs at orders-of-magnitude greater resolution than was previously possible. On average, murine embryonic stem (mES) cells exhibit eight SCEs, which are detected at a resolution of up...

Experimental evidence for anisotropic double exchange interaction driven anisotropic transport in manganite heterostructures

NARCIS (Netherlands)

Liao, Zhaoliang; Koster, Gertjan; Huijben, Mark; Rijnders, A.J.H.M.

2017-01-01

An anisotropic double exchange interaction driven giant transport anisotropy is demonstrated in a canonic double exchange system of La2/3Sr1/3MnO3 ultrathin films epitaxially grown on NdGaO3 (110) substrates. The oxygen octahedral coupling at the La2/3Sr1/3MnO3/NdGaO3 interface induces a planar

Segmented heat exchanger

Science.gov (United States)

Baldwin, Darryl Dean; Willi, Martin Leo; Fiveland, Scott Byron; Timmons, Kristine Ann

2010-12-14

A segmented heat exchanger system for transferring heat energy from an exhaust fluid to a working fluid. The heat exchanger system may include a first heat exchanger for receiving incoming working fluid and the exhaust fluid. The working fluid and exhaust fluid may travel through at least a portion of the first heat exchanger in a parallel flow configuration. In addition, the heat exchanger system may include a second heat exchanger for receiving working fluid from the first heat exchanger and exhaust fluid from a third heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the second heat exchanger in a counter flow configuration. Furthermore, the heat exchanger system may include a third heat exchanger for receiving working fluid from the second heat exchanger and exhaust fluid from the first heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the third heat exchanger in a parallel flow configuration.

Nuclear structure and the single charge exchange

International Nuclear Information System (INIS)

Oset, E.; Strottman, D.

1979-01-01

The influence of nuclear structure on meson-induced single-charge-exchange reactions on light nuclei is discussed within the context of the Glauber approximation. Selection rules which are expected to be approximately obeyed in elastic and inelastic pion and kaon scattering are proposed. Theoretical predictions are presented for (π + ,π 0 ) and (K + ,K 0 ) reactions on 13 C. 14 figures

Exchange rate rebounds after foreign exchange market interventions

Science.gov (United States)

Hoshikawa, Takeshi

2017-03-01

This study examined the rebounds in the exchange rate after foreign exchange intervention. When intervention is strongly effective, the exchange rate rebounds at next day. The effect of intervention is reduced slightly by the rebound after the intervention. The exchange rate might have been 67.12-77.47 yen to a US dollar without yen-selling/dollar-purchasing intervention of 74,691,100 million yen implemented by the Japanese government since 1991, in comparison to the actual exchange rate was 103.19 yen to the US dollar at the end of March 2014.

β -carotene effect the induction of the sister chromatid exchanges (ICH) by gamma radiation in mouse radiosensibilized osseous marrow cells In vivo

International Nuclear Information System (INIS)

Morales R, P.; Cruz V, V.L.

1997-01-01

The effect of β- carotene over the ICH radioinduction in radiosensibilized with BrdU osseous marrow cells of mouse was determined In vivo. The treatment with 50 μg β carotene per se induces a significant increment in the ICH frequency and the pre or post-treatment with the same dose causes an additive effect in the ICH frequency produced by 0.62 Gy of gamma radiation. This implies that β- carotene does not have radioprotective activity, under conditions which was developed this experiment. (Author)

The dielectric environment dependent exchange self-energy of the energy structure in graphene

International Nuclear Information System (INIS)

Yang, C.H.; Xu, W.

2010-01-01

We theoretically calculate the energy dispersion in the presence of the screened exchange self-energy in extrinsic monolayer graphene. It is found that the exchange self-energy enhances the renormalized Fermi velocity. With decreasing the dielectric constant, the screening effect and the electron correlation effect increase which induces the Fermi velocity increasing. The screened exchange energy has an energy shift at the Dirac points. The self-energy from the valance band carriers gives the main contribution to the effective energy. We also discuss the electron density dependence of the self-energy.

The dielectric environment dependent exchange self-energy of the energy structure in graphene

Energy Technology Data Exchange (ETDEWEB)

Yang, C.H., E-mail: chyang@nuist.edu.c [Faculty of Maths and Physics, Nanjing University of Information Science and Technology, Nanjing 210044 (China); Xu, W. [Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031 (China)

2010-10-01

We theoretically calculate the energy dispersion in the presence of the screened exchange self-energy in extrinsic monolayer graphene. It is found that the exchange self-energy enhances the renormalized Fermi velocity. With decreasing the dielectric constant, the screening effect and the electron correlation effect increase which induces the Fermi velocity increasing. The screened exchange energy has an energy shift at the Dirac points. The self-energy from the valance band carriers gives the main contribution to the effective energy. We also discuss the electron density dependence of the self-energy.

Experimental verification for in vitro technique confirmation of bystander effect induced by gamma radiation in CHO-K1 cell line; Verificacao experimental para confirmacao da tecnica in vitro do efeito bystander induzido por radiacao gama na linhagem celular CHO-K1

Energy Technology Data Exchange (ETDEWEB)

Viana, P.H.L.; Goes, A.M.; Gomes, D.A., E-mail: pedroleroybio@hotmail.com [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento Bioquimica e Imunologia. Lab. de Imunologia Celular e Molecular; Grynberg, S.E., E-mail: seg@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

2013-08-15

The bystander effect refers to biological responses detected in cells not directly irradiated but influenced, somehow, by signals transmitted from neighboring irradiated cells. These biological responses include sister chromatid exchange, mutations, micronucleus formation, chromosomal aberrations, carcinogenesis, apoptosis and necrosis. Although its existence is unquestionable, the mechanisms involved on triggering the bystander effect are not yet completely elucidated. Previous studies have shown that the bystander effect depends on a large variety of parameters including the radiation dose, the dose rate, the type of radiation and type of cells or tissue. This study aims to confirm the technique previously used in the literature in human cell lines for the bystander effect verification. The results suggest that the working conditions adopted by the group show technical efficiency and enables the reproduction of the bystander effect. (author)

Light-induced cation exchange for copper sulfide based CO2 reduction.

Science.gov (United States)

Manzi, Aurora; Simon, Thomas; Sonnleitner, Clemens; Döblinger, Markus; Wyrwich, Regina; Stern, Omar; Stolarczyk, Jacek K; Feldmann, Jochen

2015-11-11

Copper(I)-based catalysts, such as Cu2S, are considered to be very promising materials for photocatalytic CO2 reduction. A common synthesis route for Cu2S via cation exchange from CdS nanocrystals requires Cu(I) precursors, organic solvents, and neutral atmosphere, but these conditions are not compatible with in situ applications in photocatalysis. Here we propose a novel cation exchange reaction that takes advantage of the reducing potential of photoexcited electrons in the conduction band of CdS and proceeds with Cu(II) precursors in an aqueous environment and under aerobic conditions. We show that the synthesized Cu2S photocatalyst can be efficiently used for the reduction of CO2 to carbon monoxide and methane, achieving formation rates of 3.02 and 0.13 μmol h(-1) g(-1), respectively, and suppressing competing water reduction. The process opens new pathways for the preparation of new efficient photocatalysts from readily available nanostructured templates.

Tensor exchange amplitudes in K +- N charge exchange reactions

International Nuclear Information System (INIS)

Svec, M.

1979-01-01

Tensor (A 2 ) exchange amplitudes in K +- N charge exchange (CEX) are constructed from the K +- N CEX data supplemented by information on the vector (rho) exchange amplitudes from πN sca tering. We observed new features in the t-structure of A 2 exchange amplitudes which contradict the t-de pendence anticipated by most of the Regge models. The results also provide evidence for violation of weak exchange degeneracy

Effects of the spaces available for cations in strongly acidic cation-exchange resins on the exchange equilibria by quaternary ammonium ions and on the hydration states of metal ions.

Science.gov (United States)

Watanabe, Yuuya; Ohnaka, Kenji; Fujita, Saki; Kishi, Midori; Yuchi, Akio

2011-10-01

The spaces (voids) available for cations in the five exchange resins with varying exchange capacities and cross-linking degrees were estimated, on the basis of the additivity of molar volumes of the constituents. Tetraalkylammonium ions (NR(4)(+); R: Me, Et, Pr) may completely exchange potassium ion on the resin having a larger void radius. In contrast, the ratio of saturated adsorption capacity to exchange capacity of the resin having a smaller void radius decreased with an increase in size of NR(4)(+) ions, due to the interionic contacts. Alkali metal ions could be exchanged quantitatively. While the hydration numbers of K(+), Rb(+), and Cs(+) were independent of the void radius, those of Li(+) and Na(+), especially Na(+), decreased with a decrease in void radius. Interionic contacts between the hydrated ions enhance the dehydration. Multivalent metal ions have the hydration numbers, comparable to or rather greater than those in water. A greater void volume available due to exchange stoichiometry released the interionic contacts and occasionally promoted the involvement of water molecules other than directly bound molecules. The close proximity between ions in the conventional ion-exchange resins having higher exchange capacities may induce varying interactions.

Resolving RAD51C function in late stages of homologous recombination

Directory of Open Access Journals (Sweden)

Kuznetsov Sergey G

2007-06-01

Full Text Available Abstract DNA double strand breaks are efficiently repaired by homologous recombination. One of the last steps of this process is resolution of Holliday junctions that are formed at the sites of genetic exchange between homologous DNA. Although various resolvases with Holliday junctions processing activity have been identified in bacteriophages, bacteria and archaebacteria, eukaryotic resolvases have been elusive. Recent biochemical evidence has revealed that RAD51C and XRCC3, members of the RAD51-like protein family, are involved in Holliday junction resolution in mammalian cells. However, purified recombinant RAD51C and XRCC3 proteins have not shown any Holliday junction resolution activity. In addition, these proteins did not reveal the presence of a nuclease domain, which raises doubts about their ability to function as a resolvase. Furthermore, oocytes from infertile Rad51C mutant mice exhibit precocious separation of sister chromatids at metaphase II, a phenotype that reflects a defect in sister chromatid cohesion, not a lack of Holliday junction resolution. Here we discuss a model to explain how a Holliday junction resolution defect can lead to sister chromatid separation in mouse oocytes. We also describe other recent in vitro and in vivo evidence supporting a late role for RAD51C in homologous recombination in mammalian cells, which is likely to be resolution of the Holliday junction.

Strong interfacial exchange field in the graphene/EuS heterostructure

NARCIS (Netherlands)

Wei, Peng; Lee, Sunwoo; Lemaitre, Florian; Pinel, Lucas; Cutaia, Davide; Cha, Wujoon; Katmis, Ferhat; Zhu, Yu; Heiman, Donald; Hone, James; Moodera, Jagadeesh S.; Chen, Ching Tzu

2016-01-01

Exploiting 2D materials for spintronic applications can potentially realize next-generation devices featuring low power consumption and quantum operation capability. The magnetic exchange field (MEF) induced by an adjacent magnetic insulator enables efficient control of local spin generation and

Genetic damages in radiation workers of radiology centers in Bushehr port

Directory of Open Access Journals (Sweden)

Gholamreza Khamisipour

2004-09-01

Full Text Available Unstable genetic aberrations might provide a good marker for assessing genetic damage in populations exposed to low levels of ionizing radiation.The frequency of these aberrations was estimated in peripheral lymphocytes from hospital workers in Bushehr Port, occupationally exposed to low levels of ionizing radiation (54 subjects and age and sex matched controls. A total of 34 (23 males & 11 females subjects had unstable genetic aberrations (50 chromosomal-type & 31 chromatid type but only 7 subjects in control group had unstable genetic aberrations. When compared with controls, exposed workers showed a significant increase in structural chromosomal-type aberrations (p<0.001 OR=11 chromosomal exchange being the most frequent alteration. Chromatid deletion (18 cases and ring chromosome (4 cases were seen only in exposed group. There was no association between smoking status, sex, age, level of education or working years. The increased frequencies of chromosomal damage in radiation workers, indicate conducting cytogenetic analysis in parallel to physical dosimetry in the working place.

Relative biological efficiency of intermediate energy neutrons and 60Co rays for induction of chromosomal aberrations in Chinese hamster fibroblasts

International Nuclear Information System (INIS)

Sturelid, S.; Bergman, R.

1976-01-01

Intermediate energy neutrons are unique in that a considerable fraction of critical interactions and of dose absorbed is not associated with ionization but with atomic collision. It is still unknown to what extent the qualitative difference in primary damage after atomic collision compared to that of ionization and excitation becomes expressed at biological levels. Chromosomal aberrations were studied in Chinese hamster fibroblasts exposed for 5-8 hours at 22 degree C to intermediate energy neutrons, mean energy 8.5 keV, or to 60 Co-gamma rays. RBE at the 10 per cent aberration frequency level in S-phase were 2.2+-0.6 for total aberrations, 2.1+-0.6 for chromatid breaks and 1.8+-0.5 for exchanges. For each chromatid aberration observed after recovery, about 200 bondbreaking atomic collisions besides 3000 primary iniozations should have occured in DNA. However, the extent to which the aberration response is due to atomic collisions is not clear. (author)

Transition density of charge-exchange processes

International Nuclear Information System (INIS)

Lovas, R.G.

1983-01-01

The transition density between parent and analogue states is studied with special reference to its role in charge-exchange nuclear reactions. The structure of the target nucleus is described in a perturbative approach, in which the Coulomb and asymmetry potentials mix the eigenstates of a charge-independent single-particle Hamiltonian. In this model formulae are derived for the transition density, the Coulomb displacement energy and the neutron-proton density difference, and their relationship is used to estimate the transition density. This estimate shows that: the largest contribution comes from the density of the excess neutrons; the weight of the Coulomb-mixing effect is small up to excess neutron number 10, and grows rapidly beyond; the weight of the core polarization term induced by the excess neutrons is modest and is the same for all nuclei. It is indicated that the Coulomb effect may explain the departure from the Lane model of nucleon charge-exchange scattering found for heavy nuclei, whereas the core polarization may account for the observed anomalous dependence of the deg 0 pion charge-exchange cross section on the number of excess neutrons. (author)

UV-sensitivity of bromodeoxyuridine (BUdR)-substituted chromosomes in Chinese hamster cells

International Nuclear Information System (INIS)

Antoshchina, M.M.; Luchnik, N.V.

1990-01-01

Chinese hamster cells with chromosomes differently substituted for BUdR (TT-TT, TT-TB, TB-TB, TB-BB, where T is thymidine containing chromatid and B is BUdR substituted chromatid) were exposed to UV-light in phase G 2 and chromosome aberrations (mainly chromatid breaks) were analysed. Breaks frequency per chromosome was proportional to BUdR content. No breaks were found in TT-TT chromosomes. The frequency of breaks per TB chromatid was similar with TT-TB and TB-BB chromosomes. In TB-BB chromosomes, however, virtually no breaks occured in TB chromatids whereas in BB chromatids, their frequency was much higher than was expected

Dysfunctional telomeres in human BRCA2 mutated breast tumors and cell lines

International Nuclear Information System (INIS)

Bodvarsdottir, Sigridur K.; Steinarsdottir, Margret; Bjarnason, Hordur; Eyfjord, Jorunn E.

2012-01-01

In the present study the possible involvement of telomeres in chromosomal instability of breast tumors and cell lines from BRCA2 mutation carriers was examined. Breast tumors from BRCA2 mutation carriers showed significantly higher frequency of chromosome end-to-end fusions (CEFs) than tumors from non-carriers despite normal telomere DNA content. Frequent CEFs were also found in four different BRCA2 heterozygous breast epithelial cell lines, occasionally with telomere signal at the fusion point, indicating telomere capping defects. Extrachromosomal telomeric repeat (ECTR) DNA was frequently found scattered around metaphase chromosomes and interstitial telomere sequences (ITSs) were also common. Telomere sister chromatid exchanges (T-SCEs), characteristic of cells using alternative lengthening of telomeres (ALT), were frequently detected in all heterozygous BRCA2 cell lines as well as the two ALT positive cell lines tested. Even though T-SCE frequency was similar in BRCA2 heterozygous and ALT positive cell lines they differed in single telomere signal loss and ITSs. Chromatid type alterations were more prominent in the BRCA2 heterozygous cell lines that may have propensity for telomere based chromosome healing. Telomere dysfunction-induced foci (TIFs) formation, identified by co-localization of telomeres and γ-H2AX, supported telomere associated DNA damage response in BRCA2 heterozygous cell lines. TIFs were found in interphase nuclei, at chromosome ends, ITSs and ECTR DNA. In conclusion, our results suggest that BRCA2 has an important role in telomere stabilization by repressing CEFs through telomere capping and the prevention of telomere loss by replication stabilization.

Dysfunctional telomeres in human BRCA2 mutated breast tumors and cell lines

Energy Technology Data Exchange (ETDEWEB)

Bodvarsdottir, Sigridur K., E-mail: skb@hi.is [Cancer Research Laboratory, BioMedical Centre, Faculty of Medicine, University of Iceland, Vatnsmyrarvegi 16, 101 Reykjavik (Iceland); Steinarsdottir, Margret [Chromosome Laboratory, Department of Genetics and Molecular Medicine, Landspitali University Hospital, Reykjavik (Iceland); Bjarnason, Hordur; Eyfjord, Jorunn E. [Cancer Research Laboratory, BioMedical Centre, Faculty of Medicine, University of Iceland, Vatnsmyrarvegi 16, 101 Reykjavik (Iceland)

2012-01-03

In the present study the possible involvement of telomeres in chromosomal instability of breast tumors and cell lines from BRCA2 mutation carriers was examined. Breast tumors from BRCA2 mutation carriers showed significantly higher frequency of chromosome end-to-end fusions (CEFs) than tumors from non-carriers despite normal telomere DNA content. Frequent CEFs were also found in four different BRCA2 heterozygous breast epithelial cell lines, occasionally with telomere signal at the fusion point, indicating telomere capping defects. Extrachromosomal telomeric repeat (ECTR) DNA was frequently found scattered around metaphase chromosomes and interstitial telomere sequences (ITSs) were also common. Telomere sister chromatid exchanges (T-SCEs), characteristic of cells using alternative lengthening of telomeres (ALT), were frequently detected in all heterozygous BRCA2 cell lines as well as the two ALT positive cell lines tested. Even though T-SCE frequency was similar in BRCA2 heterozygous and ALT positive cell lines they differed in single telomere signal loss and ITSs. Chromatid type alterations were more prominent in the BRCA2 heterozygous cell lines that may have propensity for telomere based chromosome healing. Telomere dysfunction-induced foci (TIFs) formation, identified by co-localization of telomeres and {gamma}-H2AX, supported telomere associated DNA damage response in BRCA2 heterozygous cell lines. TIFs were found in interphase nuclei, at chromosome ends, ITSs and ECTR DNA. In conclusion, our results suggest that BRCA2 has an important role in telomere stabilization by repressing CEFs through telomere capping and the prevention of telomere loss by replication stabilization.

Exchange functional by a range-separated exchange hole

International Nuclear Information System (INIS)

Toyoda, Masayuki; Ozaki, Taisuke

2011-01-01

An approximation to the exchange-hole density is proposed for the evaluation of the exact exchange energy in electronic structure calculations within the density-functional theory and the Kohn-Sham scheme. Based on the localized nature of density matrix, the exchange hole is divided into the short-range (SR) and long-range (LR) parts by using an adequate filter function, where the LR part is deduced by matching of moments with the exactly calculated SR counterpart, ensuring the correct asymptotic -1/r behavior of the exchange potential. With this division, the time-consuming integration is truncated at a certain interaction range, largely reducing the computation cost. The total energies, exchange energies, exchange potentials, and eigenvalues of the highest-occupied orbitals are calculated for the noble-gas atoms. The close agreement of the results with the exact values suggests the validity of the approximation.

Theory and design of heat exchanger : shell and tube condenser and reboiler

International Nuclear Information System (INIS)

Min, Ui Dong

1996-02-01

This book gives descriptions of shell and tube heat exchanger including from, sorts, structure like shell and shell side, channel, and sliding bar, basic design of heat exchanger, flow-induced vibration, shell side condenser, tube side condenser and design of basic structure of condenser by types, selection of reboiler type, kettle type reboiler, internal reboiler, pump through reboiler, design of reboiler like kettle and internal reboiler, and horizontal and vertical thermosyphon reboiler.

The Effect of VPA on Increasing Radiosensitivity in Osteosarcoma Cells and Primary-Culture Cells from Chemical Carcinogen-Induced Breast Cancer in Rats.

Science.gov (United States)

Liu, Guochao; Wang, Hui; Zhang, Fengmei; Tian, Youjia; Tian, Zhujun; Cai, Zuchao; Lim, David; Feng, Zhihui

2017-05-10

This study explored whether valproic acid (VPA, a histone deacetylase inhibitor) could radiosensitize osteosarcoma and primary-culture tumor cells, and determined the mechanism of VPA-induced radiosensitization. The working system included osteosarcoma cells (U2OS) and primary-culture cells from chemical carcinogen (DMBA)-induced breast cancer in rats; and clonogenic survival, immunofluorescence, fluorescent in situ hybridization (FISH) for chromosome aberrations, and comet assays were used in this study. It was found that VPA at the safe or critical safe concentration of 0.5 or 1.0 mM VPA could result in the accumulation of more ionizing radiation (IR)-induced DNA double strand breaks, and increase the cell radiosensitivity. VPA-induced radiosensitivity was associated with the inhibition of DNA repair activity in the working systems. In addition, the chromosome aberrations including chromosome breaks, chromatid breaks, and radial structures significantly increased after the combination treatment of VPA and IR. Importantly, the results obtained by primary-culture cells from the tissue of chemical carcinogen-induced breast cancer in rats further confirmed our findings. The data in this study demonstrated that VPA at a safe dose was a radiosensitizer for osteosarcoma and primary-culture tumor cells through suppressing DNA-double strand breaks repair function.

Na+/H+ Exchange Activity in the Plasma Membrane of Arabidopsis1

Science.gov (United States)

Qiu, Quan-Sheng; Barkla, Bronwyn J.; Vera-Estrella, Rosario; Zhu, Jian-Kang; Schumaker, Karen S.

2003-01-01

In plants, Na+/H+ exchangers in the plasma membrane are critical for growth in high levels of salt, removing toxic Na+ from the cytoplasm by transport out of the cell. The molecular identity of a plasma membrane Na+/H+ exchanger in Arabidopsis (SOS1) has recently been determined. In this study, immunological analysis provided evidence that SOS1 localizes to the plasma membrane of leaves and roots. To characterize the transport activity of this protein, purified plasma membrane vesicles were isolated from leaves of Arabidopsis. Na+/H+ exchange activity, monitored as the ability of Na to dissipate an established pH gradient, was absent in plants grown without salt. However, exchange activity was induced when plants were grown in 250 mm NaCl and increased with prolonged salt exposure up to 8 d. H+-coupled exchange was specific for Na, because chloride salts of other monovalent cations did not dissipate the pH gradient. Na+/H+ exchange activity was dependent on Na (substrate) concentration, and kinetic analysis indicated that the affinity (apparent Km) of the transporter for Na+ is 22.8 mm. Data from two experimental approaches supports electroneutral exchange (one Na+ exchanged for one proton): (a) no change in membrane potential was measured during the exchange reaction, and (b) Na+/H+ exchange was unaffected by the presence or absence of a membrane potential. Results from this research provide a framework for future studies into the regulation of the plant plasma membrane Na+/H+ exchanger and its relative contribution to the maintenance of cellular Na+ homeostasis during plant growth in salt. PMID:12805632

Do Exchange Rates Really Help Forecasting Commodity Prices?

DEFF Research Database (Denmark)

Bork, Lasse; Kaltwasser, Pablo Rovira; Sercu, Piet

Chen et al. (2010) report that for ‘commodity currencies’, the exchange rate predicts the country’s commodity index but not vice versa. The commodity currency hypothesis is consistent with the Engle and West (2005) exchange rate model if the fundamental is chosen to be the country’s key export...... expectations, one should mostly observe contemporaneous correlations, not one-directional cross-predictability from one variable toward the other. Using three different data sets and various econometric techniques, we do find the contemporaneous correlations as predicted by the financial asset view......-averaged prices in the commodity index data that they use (price averaging induces spurious autocorrelation and predictability) and to features in their test procedures....

In Vivo Cytogenetic Studies on Aspartame

OpenAIRE

AlSuhaibani, Entissar S.

2010-01-01

Aspartame (a-Laspartyl-L-phenylalanine 1-methylester) is a dipeptide low-calorie artificial sweetener that is widely used as a nonnutritive sweetener in foods and drinks. The safety of aspartame and its metabolic breakdown products (phenylalanine, aspartic acid and methanol) was investigated in vivo using chromosomal aberration (CA) test and sister chromatid exchange (SCE) test in the bone marrow cells of mice. Swiss Albino male mice were exposed to aspartame (3.5, 35, 350 mg/kg body weight)....

Automated exchange transfusion and exchange rate.

Science.gov (United States)

Funato, M; Shimada, S; Tamai, H; Taki, H; Yoshioka, Y

1989-10-01

An automated blood exchange transfusion (BET) with a two-site technique has been devised by Goldmann et al and by us, using an infusion pump. With this method, we successfully performed exchange transfusions 189 times in the past four years on 110 infants with birth weights ranging from 530 g to 4,000 g. The exchange rate by the automated method was compared with the rate by Diamond's method. Serum bilirubin (SB) levels before and after BET and the maximal SB rebound within 24 hours after BET were: 21.6 +/- 2.4, 11.5 +/- 2.2, and 15.0 +/- 1.5 mg/dl in the automated method, and 22.0 +/- 2.9, 11.2 +/- 2.5, and 17.7 +/- 3.2 mg/dl in Diamond's method, respectively. The result showed that the maximal rebound of the SB level within 24 hours after BET was significantly lower in the automated method than in Diamond's method (p less than 0.01), though SB levels before and after BET were not significantly different between the two methods. The exchange rate was also measured by means of staining the fetal red cells (F cells) both in the automated method and in Diamond's method, and comparing them. The exchange rate of F cells in Diamond's method went down along the theoretical exchange curve proposed by Diamond, while the rate in the automated method was significantly better than in Diamond's, especially in the early stage of BET (p less than 0.01). We believe that the use of this automated method may give better results than Diamond's method in the rate of exchange, because this method is performed with a two-site technique using a peripheral artery and vein.

Mouse RAD54 affects DNA double-strand break repair and sister chromatid exchange

NARCIS (Netherlands)

H.B. Beverloo (Berna); R.D. Johnson (Roger); M. Jasin (Maria); R. Kanaar (Roland); J.H.J. Hoeijmakers (Jan); M.L.G. Dronkert (Mies)

2000-01-01

textabstractCells can achieve error-free repair of DNA double-strand breaks (DSBs) by homologous recombination through gene conversion with or without crossover. In contrast, an alternative homology-dependent DSB repair pathway, single-strand annealing (SSA), results in deletions. In this study, we

TopBP1 associates with NBS1 and is involved in homologous recombination repair

International Nuclear Information System (INIS)

Morishima, Ken-ichi; Sakamoto, Shuichi; Kobayashi, Junya; Izumi, Hideki; Suda, Tetsuji; Matsumoto, Yoshiyuki; Tauchi, Hiroshi; Ide, Hiroshi; Komatsu, Kenshi; Matsuura, Shinya

2007-01-01

TopBP1 is involved in DNA replication and DNA damage checkpoint. Recent studies have demonstrated that TopBP1 is a direct positive effecter of ATR. However, it is not known how TopBP1 recognizes damaged DNA. Here, we show that TopBP1 formed nuclear foci after exposure to ionizing radiation, but such TopBP1 foci were abolished in Nijmegen breakage syndrome cells. We also show that TopBP1 physically associated with NBS1 in vivo. These results suggested that NBS1 might regulate TopBP1 recruitment to the sites of DNA damage. TopBP1-depleted cells showed hypersensitivity to Mitomycin C and ionizing radiation, an increased frequency of sister-chromatid exchange level, and a reduced frequency of DNA double-strand break induced homologous recombination repair. Together, these results suggested that TopBP1 might be a mediator of DNA damage signaling from NBS1 to ATR and promote homologous recombination repair

Genetic effects of the flavonols quercetin, kaempferol, and galangin on Chinese hamster ovary cells in vitro

Energy Technology Data Exchange (ETDEWEB)

Carver, J.H. (Lawrence Livermore National Lab., Livermore, CA); Carrano, A.V.; MacGregor, J.T.

1983-01-01

The genotoxicity of selected flavonols was evaluated by multiple endpoints in Chinese hamster ovary (CHO) cells. Chromosomal aberrations, sister-chromatid exchange (SCE), and forward mutation at 4 gene loci were measured in a single population of cells exposed to quercetin, kaempferol, or galangin for 15 h with and without metabolic activation. The incidence of chromosomal aberrations was significantly increased by quercetin in the absence of activation and by kaempferol and galangin with and without activation. Flavanol treatment affected SCE and mutation at the hgprt, aprt, or Na/sup +//K/sup +/-ATPase loci only marginally, but significantly increased mutation frequencies at the tk locus. The response at the tk locus suggests that the CHO cells may behave similarly to L5178Y cells, in which the tk locus is thought to reflect chromosomal lesions in addition to point mutation. These results indicate that, at least under the conditions examined, flavonols induce chromosomal aberrations in CHO cells, but have little effect on point mutation or SCE.

In vitro effect of the antimalarial drug proguanil hydrochloride on viability and DNA damage in human peripheral blood lymphocytes.

Science.gov (United States)

Gajski, Goran; Dinter, Domagoj; Garaj-Vrhovac, Vera

2010-11-01

This study aimed to evaluate the effect of proguanil, a chemical substance used for treatment and prevention of malaria on viability and DNA integrity in human lymphocytes in vitro. Two different concentrations of proguanil obtained from the plasma concentrations were used: 130ng/ml used for prophylactic treatment and 520ng/ml used in treatment of malaria. Testing was done with and without metabolic activation. Viability of lymphocytes decreased in time and dose dependent manner. Comet assay parameters showed similar effects, indicating that some damage to DNA molecule can occur. Frequency of sister chromatid exchanges did not show significant deviation from the control samples. As for the proliferation kinetics no significant changes were noticed. Since majority of DNA damaging effect is induced after metabolic activation it is to be concluded that activity of proguanil is dependent upon the active metabolite cycloguanil and that monitoring should be conducted especially among frequent travellers. Copyright © 2010 Elsevier B.V. All rights reserved.

Heat exchanger

International Nuclear Information System (INIS)

Dostatni, A.W.; Dostatni, Michel.

1976-01-01

In the main patent, a description was given of a heat exchanger with an exchange surface in preformed sheet metal designed for the high pressure and temperature service particularly encountered in nuclear pressurized water reactors and which is characterised by the fact that it is composed of at least one exchanger bundle sealed in a containment, the said bundle or bundles being composed of numerous juxtaposed individual compartments whose exchange faces are built of preformed sheet metal. The present addendun certificate concerns shapes of bundles and their positioning methods in the exchanger containment enabling its compactness to be increased [fr

EXFOR Basics. A short guide to the neutron reaction data exchange format

International Nuclear Information System (INIS)

McLane, V.; NUCLEAR DATA CENTER NETWORK

2000-01-01

This manual is intended as a guide to users of nuclear reaction data compiled in the EXFOR format, and is not intended as a complete guide to the EXFOR System. EXFOR is the exchange format designed to allow transmission of nuclear reaction data between the Nuclear Reaction Data Centers. In addition to storing the data and its' bibliographic information, experimental information is also compiled. The status (e.g., the source of the data) and history (e.g., date of last update) of the data set is also included. EXFOR is designed for flexibility in order to meet the diverse needs of the nuclear reaction data centers. It was originally conceived for the exchange of neutron data and was developed through discussions among personnel from centers situated in Saclay, Vienna, Livermore and Brookhaven. It was accepted as the official exchange format of the neutron data centers at Saclay, Vienna, Brookhaven and Obninsk, at a meeting held in November 1969.3 As a result of two meetings held in 1975 and 1976 and attended by several charged-particle data centers, the format was further developed and adapted to cover all nuclear reaction data. The exchange format should not be confused with a center-to-user format. Although users may obtain data from the centers in the EXFOR format, other center-to-user formats have been developed to meet the needs of the users within each center's own sphere of responsibility. The EXFOR format, as outlined, allows a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in a format: l that is machine-readable (for checking and indicating possible errors); l that can be read by personnel (for passing judgment on and correcting errors). The data presently included in the EXFOR exchange file include: a complete compilation of experimental neutron-induced reaction data, a selected compilation of charged-particle-induced reaction data, a selected compilation of photon-induced reaction data

Kinetics of the exchange between fibrous manganese dioxide and Mn2+ ions in solution

International Nuclear Information System (INIS)

Rophael, M.W.

1983-01-01

The rate of exchange between fibrous manganese dioxide epsilon-MnO 2 and a 0.1 M MnSO 4 solution at 25 0 C and pH 2.0 was higher than the corresponding rate at pH 5.4. When the solid was washed with dilute acid (pH 2.0) before the exchange at pH 2.0, the results of the exchange at the two pH values were similar. When epsilon-MnO 2 was partially reduced with N 2 H 4 .H 2 O solution before the exchange, the rate of exchange was appreciably higher than that obtained for the unreduced solid. The exchange, at nearly pH 2.0, between epsilon-MnO 2 and various concentrations of Mn(NO 3 ) 2 solutions was increased to a small extent as the concentration increased tenfold. The exchange was followed by using 56 Mn-labelled MnO 2 and by measuring the β activity acquired by the Mn 2+ ion solution. The activity induced in the solid MnO 2 was produced by irradiation with thermal neutrons from a 241 Am- 9 Be laboratory neutron source. The neutron activation of manganese oxides has the following advantages: (i) a relatively high level of activity can be induced in the 55 Mn of the irradiated oxide because of its 100% abundance and its high neutron activation cross section, whereas the oxygen is unaffected; (ii) the half-life of the product 56 Mn is 9274 s which is convenient for kinetic studies; (iii) the activity produced almost decays in 24 h. (Auth.)

Hydrogen exchange mass spectrometry of bacteriorhodopsin reveals light-induced changes in the structural dynamics of a biomolecular machine.

Science.gov (United States)

Pan, Yan; Brown, Leonid; Konermann, Lars

2011-12-21

Many proteins act as molecular machines that are fuelled by a nonthermal energy source. Examples include transmembrane pumps and stator-rotor complexes. These systems undergo cyclic motions (CMs) that are being driven along a well-defined conformational trajectory. Superimposed on these CMs are thermal fluctuations (TFs) that are coupled to stochastic motions of the solvent. Here we explore whether the TFs of a molecular machine are affected by the occurrence of CMs. Bacteriorhodopsin (BR) is a light-driven proton pump that serves as a model system in this study. The function of BR is based on a photocycle that involves trans/cis isomerization of a retinal chromophore, as well as motions of transmembrane helices. Hydrogen/deuterium exchange (HDX) mass spectrometry was used to monitor the TFs of BR, focusing on the monomeric form of the protein. Comparative HDX studies were conducted under illumination and in the dark. The HDX kinetics of BR are dramatically accelerated in the presence of light. The isotope exchange rates and the number of backbone amides involved in EX2 opening transitions increase roughly 2-fold upon illumination. In contrast, light/dark control experiments on retinal-free protein produced no discernible differences. It can be concluded that the extent of TFs in BR strongly depends on photon-driven CMs. The light-induced differences in HDX behavior are ascribed to protein destabilization. Specifically, the thermodynamic stability of the dark-adapted protein is estimated to be 5.5 kJ mol(-1) under the conditions of our work. This value represents the free energy difference between the folded state F and a significantly unfolded conformer U. Illumination reduces the stability of F by 2.2 kJ mol(-1). Mechanical agitation caused by isomerization of the chromophore is transferred to the surrounding protein scaffold, and subsequently, the energy dissipates into the solvent. Light-induced retinal motions therefore act analogously to an internal heat

Evaluation of cytogenetic and DNA damage in human lymphocytes treated with adrenaline in vitro.

Science.gov (United States)

Djelić, Ninoslav; Radaković, Milena; Spremo-Potparević, Biljana; Zivković, Lada; Bajić, Vladan; Stevanović, Jevrosima; Stanimirović, Zoran

2015-02-01

Catechol groups can be involved in redox cycling accompanied by generation of reactive oxygen species (ROS) which may lead to oxidative damage of cellular macromolecules including DNA. The objective of this investigation was to evaluate possible genotoxic effects of a natural catecholamine adrenaline in cultured human lymphocytes using cytogenetic (sister chromatid exchange and micronuclei) and the single cell gel electrophoresis (Comet) assay. In cytogenetic tests, six experimental concentrations of adrenaline were used in a range from 0.01-500 μM. There were no indications of genotoxic effects of adrenaline in sister chromatid exchange and micronucleus tests. However, at four highest concentrations of adrenaline (5 μM, 50 μM, 150 μM and 300 μM) we observed a decreased mitotic index and cell-cycle delay. In addition, in the Comet assay we used adrenaline in a range from 0.0005-500 μM, at two treatment times: 15 min or 60 min. In contrast to cytogenetic analysis, there was a dose-dependent increase of DNA damage detected in the Comet assay. These effects were significantly reduced by concomitant treatment with quercetin or catalase. Therefore, the obtained results indicate that adrenaline may exhibit genotoxic effects in cultured human lymphocytes, most likely due to production of reactive oxygen species. Copyright © 2014 Elsevier Ltd. All rights reserved.

Contributions of chemical and diffusive exchange to T1ρ dispersion.

Science.gov (United States)

Cobb, Jared Guthrie; Xie, Jingping; Gore, John C

2013-05-01

Variations in local magnetic susceptibility may induce magnetic field gradients that affect the signals acquired for MR imaging. Under appropriate diffusion conditions, such fields produce effects similar to slow chemical exchange. These effects may also be found in combination with other chemical exchange processes at multiple time scales. We investigate these effects with simulations and measurements to determine their contributions to rotating frame (R1ρ ) relaxation in model systems. Simulations of diffusive and chemical exchange effects on R1ρ dispersion were performed using the Bloch equations. Additionally, R1ρ dispersion was measured in suspensions of Sephadex and latex beads with varying spin locking fields at 9.4 T. A novel analysis method was used to iteratively fit for apparent chemical and diffusive exchange rates with a model by Chopra et al. Single- and double-inflection points in R1ρ dispersion profiles were observed, respectively, in simulations of slow diffusive exchange alone and when combined with rapid chemical exchange. These simulations were consistent with measurements of R1ρ in latex bead suspensions and small-diameter Sephadex beads that showed single- and double-inflection points, respectively. These observations, along with measurements following changes in temperature and pH, are consistent with the combined effects of slow diffusion and rapid -OH exchange processes. Copyright © 2012 Wiley Periodicals, Inc.

Ion exchange equilibrium constants

CERN Document Server

Marcus, Y

2013-01-01

Ion Exchange Equilibrium Constants focuses on the test-compilation of equilibrium constants for ion exchange reactions. The book first underscores the scope of the compilation, equilibrium constants, symbols used, and arrangement of the table. The manuscript then presents the table of equilibrium constants, including polystyrene sulfonate cation exchanger, polyacrylate cation exchanger, polymethacrylate cation exchanger, polysterene phosphate cation exchanger, and zirconium phosphate cation exchanger. The text highlights zirconium oxide anion exchanger, zeolite type 13Y cation exchanger, and

Electrical properties of pseudo-single-crystalline Ge films grown by Au-induced layer exchange crystallization at 250 °C

Science.gov (United States)

Higashi, H.; Kudo, K.; Yamamoto, K.; Yamada, S.; Kanashima, T.; Tsunoda, I.; Nakashima, H.; Hamaya, K.

2018-06-01

We study the electrical properties of pseudo-single-crystalline Ge (PSC-Ge) films grown by a Au-induced layer exchange crystallization method at 250 °C. By inserting the SiNx layer between PSC-Ge and SiO2, we initiatively suppress the influence of the Ge/SiO2 interfacial defective layers, which have been reported in our previous works, on the electrical properties of the PSC-Ge layers. As a result, we can detect the influence of the ionized Au+ donors on the temperature-dependent hole concentration and Hall mobility. To further examine their electrical properties in detail, we also fabricate p-thin-film transistors (TFTs) with the PSC-Ge layer. Although the off-state leakage currents are suppressed by inserting the SiNx layer, the value of on/off ratio remains poor (leakage current although a nominal field effect mobility is enhanced up to ˜25 cm2/V s. Considering these features, we conclude that the Au contaminations into the PSC-Ge layer can affect the electrical properties and device performances despite a low-growth temperature of 250 °C. To achieve further high-performance p-TFTs, we have to suppress the Au contaminations into PSC-Ge during the Au-induced crystallization growth.

Adaptive Response to ionizing Radiation Induced by Low Doses of Gamma Rays in Human Lymphoblastoid Cell Lines

International Nuclear Information System (INIS)

Seong, Jin Sil; Suh, Chang Ok; Kim, Gwi Eon

1994-01-01

When cells are exposed to low doses of a mutagenic or clastogenic agents, they often become less sensitive to the effects of a higher does administered subsequently. Such adaptive responses were first described in Escherichia coli and mammalian cells to low doses of an alkylating agent. Since most of the studies have been carried out with human lymphocytes, it is urgently necessary to study this effect in different cellular systems. Its relation with inherent cellular radiosensitivity and underlying mechanism also remain to be answered. In this study, adaptive response by 1 cGy of gamma rays was investigated in three human lymphoblastoid cell lines which were derived from ataxia telangiectasia homozygote, ataxia telangiectasia heterozygote, and normal individual. Experiments were carried out by delivering 1 cGy followed by 50 cGy of gamma radiation and chromatid breaks were scored as an endpoint. The results indicate that prior exposure to 1 cGy of gamma rays reduces the number of chromatid breaks induced by subsequent higher does (50 cGy). The expression of this adaptive response was similar among three cell lines despite of their different radiosensitivity. When 3-aminobenzamide, an inhibitor of poly (ADP-ribose) polymerase, was added after 50 cGy, adaptive responses were abolished in all the tested cell lines. Therefore it is suggested that the adaptive response can be observed in human lymphoblastoid cell lines. Which was first documented through this study. The expression of adaptive response was similar among the cell lines regardless of their radiosensitivity. The elimination of the adaptive response by 3-aminobenzamide is consistent with the proposal that this adaptive response is the result of the induction of a certain chromosomal repair mechanism

Induced dipole-dipole coupling between two atoms at a migration resonance

Science.gov (United States)

Kaur, Maninder; Mian, Mahmood

2018-05-01

Results of numerical simulations for the resonant energy exchange phenomenon called Migration reaction between two cold Rydberg atoms are presented. The effect of spatial interatomic distance on the onset of peculiar coherent mechanism is investigated. Observation of Rabi-like population inversion oscillation at the resonance provides a clear signature of dipole induced exchange of electronic excitations between the atoms. Further we present the results for the dependence of expectation value of the interaction hamiltonian on the interatomic distance, which is responsible for energy exchange process. The results of this observation endorse the range of inter atomic distance within which the excitation exchange process occurs completely or partially. Migration process enhance the Rydberg-Rydberg interaction in the absence of an external field, under the condition of the zero permanent dipole moments. Our next observation sheds light on the fundamental mechanism of induced electric fields initiated by the oscillating dipoles in such energy exchange processes. We explore the dependence of induced electric field on the interatomic distance and angle between the dipoles highlighting the inverse power law dependence and anisotropic property of the field. We put forward an idea to utilise the coherent energy exchange process to build efficient and fast energy transfer channels by incorporating more atoms organised at successive distances with decreasing distance gradient.

In vitro and in vivo genotoxicity of 1,3-butadiene and metabolites.

OpenAIRE

Arce, G T; Vincent, D R; Cunningham, M J; Choy, W N; Sarrif, A M

1990-01-01

1,3-Butadiene and two major genotoxic metabolites 3,4-epoxybutene (EB) and 1,2:3,4-diepoxybutane (DEB) were used as model compounds to determine if genetic toxicity findings in animal and human cells can aid in extrapolating animal toxicity data to man. Sister chromatid exchange (SCE) and micronucleus induction results indicated 1,3-butadiene was genotoxic in the bone marrow of the mouse but not the rat. This paralleled the chronic bioassays which showed mice to be more susceptible than rats ...

Targeting Germinal Matrix Hemorrhage-Induced Overexpression of Sodium-Coupled Bicarbonate Exchanger Reduces Posthemorrhagic Hydrocephalus Formation in Neonatal Rats.

Science.gov (United States)

Li, Qian; Ding, Yan; Krafft, Paul; Wan, Weifeng; Yan, Feng; Wu, Guangyong; Zhang, Yixin; Zhan, Qunling; Zhang, John H

2018-01-31

Germinal matrix hemorrhage (GMH) is a leading cause of mortality and lifelong morbidity in preterm infants. Posthemorrhagic hydrocephalus (PHH) is a common complication of GMH. A sodium-coupled bicarbonate exchanger (NCBE) encoded by solute carrier family 4 member 10 gene is expressed on the choroid plexus basolateral membrane and may play a role in cerebrospinal fluid production and the development of PHH. Following GMH, iron degraded from hemoglobin has been linked to PHH. Choroid plexus epithelial cells also contain iron-responsive element-binding proteins (IRPs), IRP1, and IRP2 that bind to mRNA iron-responsive elements. The present study aims to resolve the following issues: (1) whether the expression of NCBE is regulated by IRPs; (2) whether NCBE regulates the formation of GMH-induced hydrocephalus; and (3) whether inhibition of NCBE reduces PHH development. GMH model was established in P7 rat pups by injecting bacterial collagenase into the right ganglionic eminence. Another group received iron trichloride injections instead of collagenase. Deferoxamine was administered intraperitoneally for 3 consecutive days after GMH/iron trichloride. Solute carrier family 4 member 10 small interfering RNA or scrambled small interfering RNA was administered by intracerebroventricular injection 24 hours before GMH and followed with an injection every 7 days over 21 days. NCBE expression increased while IRP2 expression decreased after GMH/iron trichloride. Deferoxamine ameliorated both the GMH-induced and iron trichloride-induced decrease of IRP2 and decreased NCBE expressions. Deferoxamine and solute carrier family 4 member 10 small interfering RNA improved cognitive and motor functions at 21 to 28 days post GMH and reduced cerebrospinal fluid production as well as the degree of hydrocephalus at 28 days after GMH. Targeting iron-induced overexpression of NCBE may be a translatable therapeutic strategy for the treatment of PHH following GMH. © 2018 The Authors

Exchange rate policy

Directory of Open Access Journals (Sweden)

Plačkov Slađana

2013-01-01

Full Text Available Small oscillations of exchange rate certainly affect the loss of confidence in the currency (Serbian dinar, CSD and because of the shallow market even the smallest change in the supply and demand leads to a shift in exchange rate and brings uncertainty. Some economists suggest that the course should be linked to inflation and thus ensure predictable and stable exchange rates. Real exchange rate or slightly depressed exchange rate will encourage the competitiveness of exporters and perhaps ensure the development of new production lines which, in terms of overvalued exchange rate, had no economic justification. Fixed exchange rate will bring lower interest rates, lower risk and lower business uncertainty (uncertainty avoidance, but Serbia will also reduce foreign exchange reserves by following this trend. On the other hand, a completely free exchange rate, would lead to a (real fall of Serbian currency, which in a certain period would lead to a significant increase in exports, but the consequences for businessmen and citizens with loans pegged to the euro exchange rate, would be disastrous. We will pay special attention to the depreciation of the exchange rate, as it is generally favorable to the export competitiveness of Serbia and, on the other hand, it leads to an increase in debt servicing costs of the government as well as of the private sector. Oscillations of the dinar exchange rate, appreciation and depreciation, sometimes have disastrous consequences on the economy, investors, imports and exports. In subsequent work, we will observe the movement of the dinar exchange rate in Serbia, in the time interval 2009-2012, in order to strike a balance and maintain economic equilibrium. A movement of foreign currencies against the local currency is controlled in the foreign exchange market, so in case economic interests require, The National Bank of Serbia (NBS, on the basis of arbitrary criteria, can intervene in the market.

Controlling exchange bias in Co-CoOx nanoparticles by oxygen content

International Nuclear Information System (INIS)

Kovylina, Miroslavna; Muro, Montserrat GarcIa del; Konstantinovic, Zorica; Iglesias, Oscar; Labarta, AmIlcar; Batlle, Xavier; Varela, Manuel

2009-01-01

We report on the occurrence of exchange bias on laser-ablated granular thin films composed of Co nanoparticles embedded in an amorphous zirconia matrix. The deposition method allows one to control the degree of oxidation of the Co particles by tuning the oxygen pressure at the vacuum chamber (from 2 x 10 -5 to 10 -1 mbar). The nature of the nanoparticles embedded in the nonmagnetic matrix is monitored from metallic, ferromagnetic (FM) Co to antiferromagnetic (AFM) CoO x , with a FM/AFM intermediate regime for which the percentage of the AFM phase can be increased at the expense of the FM phase, leading to the occurrence of exchange bias in particles of about 2 nm in size. For an oxygen pressure of about 10 -3 mbar the ratio between the FM and AFM phases is optimum with an exchange bias field of about 900 Oe at 1.8 K. The mutual exchange coupling between the AFM and FM is also at the origin of the induced exchange anisotropy on the FM leading to high irreversible hysteresis loops, and the blocking of the AFM clusters due to proximity to the FM phase.

Exchange market pressure

NARCIS (Netherlands)

Jager, H.; Klaassen, F.; Durlauf, S.N.; Blume, L.E.

2010-01-01

Currencies can be under severe pressure in the foreign exchange market, but in a fixed (or managed) exchange rate regime that is not fully visible via the change in the exchange rate. Exchange market pressure (EMP) is a concept developed to nevertheless measure the pressure in such cases. This

The gecko visual pigment: the chromophore dark exchange reaction.

Science.gov (United States)

Crescitelli, F

1988-02-01

This study confirms the occurrence of a dark-exchange reaction in the extracted 521-pigment of the Tokay gecko (G. gekko). The present study involved the exchange, in the dark, of the natural 11-cis-chromophore by the 9-cis-10-F-retinal analog. This analog is able to combine with the 521-opsin to regenerate a photopigment at 492 nm. In addition to this shift in absorbance from 521 to 492 nm, the analog photopigment has a photosensitivity some 2.4% that of the native 521-system in the chloride-sufficient state. These two properties of the regenerated analog pigment have simplified the demonstration of a dark exchange of chromophores. At 15 degrees C the 9-cis-10-F-analog replaces the 11-cis-chromophore by at least 30% (density-wise) in about 15 hr. This exchange occurs with the system in the chloride-deficient state. The presence of chloride during the period in the dark significantly reduces the magnitude of the exchange. Apparently, the protein has a more open structure at the chromophoric binding site, allowing this interchange of chromophores. The addition of chloride induces a conformational change at this site, 'burying' the Schiff base and reducing the exchange reaction. The biological implication of this mobile property of the gecko opsin is that it is similar to the behavior of the cone pigment iodopsin but is unlike that of rhodopsins. This supports the idea that the gecko visual cells, despite their appearance as rods, are phylogenetically related to ancestral photopic receptors.

Review of the experience obtained in the evaluation of vibrations and their effects on the structural integrity of heat exchangers

International Nuclear Information System (INIS)

Ghiselli, Alberto M.; Pastorini, Alberto; Kulichevsky Raul

2000-01-01

Flow induced vibrations may produce damage of shell-tube type heat exchangers, condensers and steam generators tubes. These vibrations could be produce by changes in the equipment operational condition or by a wrong evaluation during the design procedure. The typical results are tube damage by impact or fretting wear. This paper include a review of the flow-induced vibration mechanisms that affect shell-tube heat exchangers and some practical examples that show the results obtained evaluating this equipment. (author)

EXTERNALITIES IN EXCHANGE NETWORKS AN ADAPTATION OF EXISTING THEORIES OF EXCHANGE NETWORKS

NARCIS (Netherlands)

Dijkstra, Jacob

2009-01-01

The present paper extends the focus of network exchange research to externalities in exchange networks. Externalities of exchange are defined as direct effects on an actor's utility, of an exchange in which this actor is not involved. Existing theories in the field of network exchange do not inform

Charge exchange and ionization of atoms in collisions with multicharged ions

International Nuclear Information System (INIS)

Presnyakov, L.P.; Uskov, D.B.

1987-01-01

Single-electron transition in continuous and discrete spectra, induced by A atom and B +2 multicharged ion collision with the charge Z>3 are investigated. A theory of quantum transitions in multilevel systems with ion-atom collisions is considered. Main results on charge exchange in slow (v 0 Z 1/2 ) collisions are presented. For analysis of charge exchange analytical method, being generalization of decay model and of approximation of nonadiabatic coupling of two states, that are included into a developed approach as limiting cases, is developed. The calculation results are compared with the available experimental data

Contrasting response of European forest and grassland energy exchange to heatwaves

DEFF Research Database (Denmark)

Teuling, A.J.; Seneviratne, S.I.; Stöckli, R.

2010-01-01

on the exchange of water and energy and the interaction of this exchange with the soil water balance during heatwaves is largely unknown. Here we analyse observations from an extensive network of flux towers in Europe that reveal a difference between the temporal responses of forest and grassland ecosystems...... and induces a critical shift in the regional climate system that leads to increased heating. We propose that this mechanism may explain the extreme temperatures in August 2003. We conclude that the conservative water use of forest contributes to increased temperatures in the short term, but mitigates...

Cytogenetic adaptive response of mouse bone marrow cells to low level HTO

International Nuclear Information System (INIS)

Chen Deqing; Zhang Zhaoyang; Zhou Xiangyan

1993-01-01

Mice were abdominally injected with a adaptive dose of 3.7 x 10 2 -3.7 x 10 5 Bq/gbw HTO, and then exposed to a challenge dose of 1.5 Gy of 6 '0Co γ-rays. In bone marrow cells that received both the adaptive and challenge doses, the chromatid breaks are lower than expected on the basis of additivity of the effects of the individual treatment. The adaptive response induced with 3.7 x 10 3 Bq/gbw HTO is the most remarkable, but at 3.7 x 10 5 Bq/gbw the adaptive response seems to disappear. The adaptive response can be observed by exposing to 1.5 Gy γ-rays from 1 to 5 days after injection of 3.7 x 10 3 Bq/gbw HTO, which is the most obvious one to reduce chromatid breaks to 50% of expected at the 5th day, but at the 7th day to equate to expected. The frequency of chromatid breaks is gradually reduced with time after challenge dose, the maximum index number of adaptive response is 0.50 and appears at 24 hr after challenge dose

Heat exchanger

International Nuclear Information System (INIS)

Leigh, D.G.

1976-01-01

The arrangement described relates particularly to heat exchangers for use in fast reactor power plants, in which heat is extracted from the reactor core by primary liquid metal coolant and is then transferred to secondary liquid metal coolant by means of intermediate heat exchangers. One of the main requirements of such a system, if used in a pool type fast reactor, is that the pressure drop on the primary coolant side must be kept to a minimum consistent with the maintenance of a limited dynamic head in the pool vessel. The intermediate heat exchanger must also be compact enough to be accommodated in the reactor vessel, and the heat exchanger tubes must be available for inspection and the detection and plugging of leaks. If, however, the heat exchanger is located outside the reactor vessel, as in the case of a loop system reactor, a higher pressure drop on the primary coolant side is acceptable, and space restriction is less severe. An object of the arrangement described is to provide a method of heat exchange and a heat exchanger to meet these problems. A further object is to provide a method that ensures that excessive temperature variations are not imposed on welded tube joints by sudden changes in the primary coolant flow path. Full constructional details are given. (U.K.)

Characterization of polyethyleneterephthalate (PET) based proton exchange membranes prepared by UV-radiation-induced graft copolymerization of styrene

Energy Technology Data Exchange (ETDEWEB)

Ahmed, Mostak; Khan, Mohammad B.; Alam, S. Shamsul; Khan, M. Anwar H. [Department of Chemistry, Shahjalal University of Science and Technology, Sylhet 3114 (Bangladesh); Khan, Mubarak A. [Radiation and Polymer Chemistry Laboratory, Institute of Nuclear Science and Technology, Bangladesh Atomic Energy Commission, P.O. Box 3787, Dhaka (Bangladesh); Halim, Md. Abdul [Department of Chemistry, Jahangirnagar University, savar, Dhaka (Bangladesh)

2011-01-15

Polymer electrolyte membranes (PEMs) were successfully prepared by simultaneous ultraviolet (UV) radiation-induced graft copolymerization of styrene (35 vol.% concentration) onto poly(ethyleneterephthalate) (PET) film, followed by sulfonation on the styrene monomer units in the grafting chain using 0.05 M chlorosulfonic acid (ClSO{sub 3}H). The radiation grafting and the sulfonation have been confirmed by titrimetric and gravimetric analyses as well as Fourier Transform Infrared (FTIR) spectroscopy. The maximum ion-exchange capacity (IEC) of the PEM was measured to be 0.04385 mmol g{sup -1} at its highest level of grafting and sulfonation. They exhibited high thermal and mechanical properties as well as oxidative stability. They are highly stable in H{sub 2}SO{sub 4} solutions and can be used in the acidic fuel cells. The membranes showed low water uptake as well as low proton conductivity than Nafion. In this study, the preparation of PEMs from commodity-type polymers is found to be very inexpensive and is a suitable candidate for applications in fuel cells. (author)

Magnetization switching behavior with competing anisotropies in epitaxial Co3FeN /MnN exchange-coupled bilayers

Science.gov (United States)

Hajiri, T.; Yoshida, T.; Jaiswal, S.; Filianina, M.; Borie, B.; Ando, H.; Asano, H.; Zabel, H.; Kläui, M.

2016-11-01

We report unusual magnetization switching processes and angular-dependent exchange bias effects in fully epitaxial Co3FeN /MnN bilayers, where magnetocrystalline anisotropy and exchange coupling compete, probed by longitudinal and transverse magneto-optic Kerr effect (MOKE) magnetometry. The MOKE loops show multistep jumps corresponding to the nucleation and propagation of 90∘ domain walls in as-grown bilayers. By inducing exchange coupling, we confirm changes of the magnetization switching process due to the unidirectional anisotropy field of the exchange coupling. Taking into account the experimentally obtained values of the fourfold magnetocrystalline anisotropy, the unidirectional anisotropy field, the exchange-coupling constant, and the uniaxial anisotropy including its direction, the calculated angular-dependent exchange bias reproduces the experimental results. These results demonstrate the essential role of the competition between magnetocrystalline anisotropy and exchange coupling for understanding and tailoring exchange-coupling phenomena usable for engineering switching in fully epitaxial bilayers made of tailored materials.

Determination of the Optimal Exchange Rate Via Control of the Domestic Interest Rate in Nigeria

Directory of Open Access Journals (Sweden)

Virtue U. Ekhosuehi

2014-01-01

Full Text Available An economic scenario has been considered where the government seeks to achieve a favourable balance-of-payments over a fixed planning horizon through exchange rate policy and control of the domestic interest rate. The dynamics of such an economy was considered in terms of a bounded optimal control problem where the exchange rate is the state variable and the domestic interest rate is the control variable. The idea of balance-of-payments was used as a theoretical underpinning to specify the objective function. By assuming that, changes in exchange rates were induced by two effects: the impact of the domestic interest rate on the exchange rate and the exchange rate system adopted by the government. Instances for both fixed and flexible optimal exchange rate regimes have been determined. The use of the approach has been illustrated employing data obtained from the Central Bank of Nigeria (CBN statistical bulletin. (original abstract

Damping in heat exchanger tube bundles. A review

International Nuclear Information System (INIS)

Iqbal, Qamar; Khushnood, Shahab; Ghalban, Ali Roheim El; Sheikh, Nadeem Ahmed; Malik, Muhammad Afzaal; Arastu, Asif

2007-01-01

Damping is a major concern in the design and operation of tube bundles with loosely supported tubes in baffles for process shell and tube heat exchangers and steam generators which are used in nuclear, process and power generation industries. System damping has a strong influence on the amplitude of vibration. Damping depends upon the mechanical properties of the tube material, geometry of intermediate supports and the physical properties of shell-side fluid. Type of tube motion, number of supports, tube frequency, vibration amplitude, tube mass or diameter, side loads, support thickness, higher modes, shell-side temperature etc., affect damping in tube bundles. The importance of damping is further highlighted due to current trend of larger exchangers with increased shell-side velocities in modern units. Various damping mechanisms have been identified (Friction damping, Viscous damping, Squeeze film damping, Support damping. Two-Phase damping, and very recent-Thermal damping), which affect the performance of process exchangers and steam generators with respect to flow induced vibration design, including standard design guidelines. Damping in two-phase flow is very complex and highly void fraction, and flow-regime dependent. The current paper focuses on the various known damping mechanisms subjected to both single and two-phase cross-flow in process heat exchangers and steam generators and formulates the design guidelines for safer design. (author)

Estimating Exchange Market Pressure and the Degree of Exchange Market Intervention for Finland during the Floating Exchange Rate Regime

OpenAIRE

Pösö, Mika; Spolander, Mikko

1997-01-01

In this paper, we use a fairly simple monetary macro model to calculate the quarterly measures of exchange market pressure and the degree of the Bank of Finland's intervention during the time the markka was floated. Exchange market pressure measures the size of the exchange rate change that would have occurred if the central bank had unexpectedly refrained from intervening in the foreign exchange market. Intervention activity of the central bank is measured as the proportion of exchange marke...

Coupled acoustic-gravity field for dynamic evaluation of ion exchange with a single resin bead.

Science.gov (United States)

Kanazaki, Takahiro; Hirawa, Shungo; Harada, Makoto; Okada, Tetsuo

2010-06-01

A coupled acoustic-gravity field is efficient for entrapping a particle at the position determined by its acoustic properties rather than its size. This field has been applied to the dynamic observation of ion-exchange reactions occurring in a single resin bead. The replacement of counterions in an ion-exchange resin induces changes in its acoustic properties, such as density and compressibility. Therefore, we can visually trace the advancement of an ion-exchange reaction as a time change in the levitation position of a resin bead entrapped in the field. Cation-exchange reactions occurring in resin beads with diameters of 40-120 microm are typically completed within 100-200 s. Ion-exchange equilibrium or kinetics is often evaluated with off-line chemical analyses, which require a batch amount of ion exchangers. Measurements with a single resin particle allow us to evaluate ion-exchange dynamics and kinetics of ions including those that are difficult to measure by usual off-line analyses. The diffusion properties of ions in resins have been successfully evaluated from the time change in the levitation positions of resin beads.

Biotic Control of Surface pH and Evidence of Light-Induced H+ Pumping and Ca2+-H+ Exchange in a Tropical Crustose Coralline Alga.

Directory of Open Access Journals (Sweden)

Laurie C Hofmann

Full Text Available Presently, an incomplete mechanistic understanding of tropical reef macroalgae photosynthesis and calcification restricts predictions of how these important autotrophs will respond to global change. Therefore, we investigated the mechanistic link between inorganic carbon uptake pathways, photosynthesis and calcification in a tropical crustose coralline alga (CCA using microsensors. We measured pH, oxygen (O2, and calcium (Ca2+ dynamics and fluxes at the thallus surface under ambient (8.1 and low (7.8 seawater pH (pHSW and across a range of irradiances. Acetazolamide (AZ was used to inhibit extracellular carbonic anhydrase (CAext, which mediates hydrolysis of HCO3-, and 4,4' diisothiocyanatostilbene-2,2'-disulphonate (DIDS that blocks direct HCO3- uptake by anion exchange transport. Both inhibited photosynthesis, suggesting both diffusive uptake of CO2 via HCO3- hydrolysis to CO2 and direct HCO3- ion transport are important in this CCA. Surface pH was raised approximately 0.3 units at saturating irradiance, but less when CAext was inhibited. Surface pH was lower at pHSW 7.8 than pHSW 8.1 in the dark, but not in the light. The Ca2+ fluxes were large, complex and temporally variable, but revealed net Ca2+ uptake under all conditions. The temporal variability in Ca2+ dynamics was potentially related to localized dissolution during epithallial cell sloughing, a strategy of CCA to remove epiphytes. Simultaneous Ca2+ and pH dynamics suggest the presence of Ca2+/H+ exchange. Rapid light-induced H+ surface dynamics that continued after inhibition of photosynthesis revealed the presence of a light-mediated, but photosynthesis-independent, proton pump. Thus, the study indicates metabolic control of surface pH can occur in CCA through photosynthesis and light-inducible H+ pumps. Our results suggest that complex light-induced ion pumps play an important role in biological processes related to inorganic carbon uptake and calcification in CCA.

Biotic Control of Surface pH and Evidence of Light-Induced H+ Pumping and Ca2+-H+ Exchange in a Tropical Crustose Coralline Alga.

Science.gov (United States)

Hofmann, Laurie C; Koch, Marguerite; de Beer, Dirk

2016-01-01

Presently, an incomplete mechanistic understanding of tropical reef macroalgae photosynthesis and calcification restricts predictions of how these important autotrophs will respond to global change. Therefore, we investigated the mechanistic link between inorganic carbon uptake pathways, photosynthesis and calcification in a tropical crustose coralline alga (CCA) using microsensors. We measured pH, oxygen (O2), and calcium (Ca2+) dynamics and fluxes at the thallus surface under ambient (8.1) and low (7.8) seawater pH (pHSW) and across a range of irradiances. Acetazolamide (AZ) was used to inhibit extracellular carbonic anhydrase (CAext), which mediates hydrolysis of HCO3-, and 4,4' diisothiocyanatostilbene-2,2'-disulphonate (DIDS) that blocks direct HCO3- uptake by anion exchange transport. Both inhibited photosynthesis, suggesting both diffusive uptake of CO2 via HCO3- hydrolysis to CO2 and direct HCO3- ion transport are important in this CCA. Surface pH was raised approximately 0.3 units at saturating irradiance, but less when CAext was inhibited. Surface pH was lower at pHSW 7.8 than pHSW 8.1 in the dark, but not in the light. The Ca2+ fluxes were large, complex and temporally variable, but revealed net Ca2+ uptake under all conditions. The temporal variability in Ca2+ dynamics was potentially related to localized dissolution during epithallial cell sloughing, a strategy of CCA to remove epiphytes. Simultaneous Ca2+ and pH dynamics suggest the presence of Ca2+/H+ exchange. Rapid light-induced H+ surface dynamics that continued after inhibition of photosynthesis revealed the presence of a light-mediated, but photosynthesis-independent, proton pump. Thus, the study indicates metabolic control of surface pH can occur in CCA through photosynthesis and light-inducible H+ pumps. Our results suggest that complex light-induced ion pumps play an important role in biological processes related to inorganic carbon uptake and calcification in CCA.

A continuous exchange factor method for radiative exchange in enclosures with participating media

International Nuclear Information System (INIS)

Naraghi, M.H.N.; Chung, B.T.F.; Litkouhi, B.

1987-01-01

A continuous exchange factor method for analysis of radiative exchange in enclosures is developed. In this method two types of exchange functions are defined, direct exchange function and total exchange function. Certain integral equations relating total exchange functions to direct exchange functions are developed. These integral equations are solved using Gaussian quadrature integration method. The results obtained based on the present approach are found to be more accurate than those of the zonal method

Inhibitor of neuronal nitric oxide synthase improves gas exchange in ventilator-induced lung injury after pneumonectomy

Directory of Open Access Journals (Sweden)

Suborov Evgeny V

2012-06-01

Full Text Available Abstract Background Mechanical ventilation with high tidal volumes may cause ventilator-induced lung injury (VILI and enhanced generation of nitric oxide (NO. We demonstrated in sheep that pneumonectomy followed by injurious ventilation promotes pulmonary edema. We wished both to test the hypothesis that neuronal NOS (nNOS, which is distributed in airway epithelial and neuronal tissues, could be involved in the pathogenesis of VILI and we also aimed at investigating the influence of an inhibitor of nNOS on the course of VILI after pneumonectomy. Methods Anesthetized sheep underwent right pneumonectomy, mechanical ventilation with tidal volumes (VT of 6 mL/kg and FiO2 0.5, and were subsequently randomized to a protectively ventilated group (PROTV; n = 8 keeping VT and FiO2 unchanged, respiratory rate (RR 25 inflations/min and PEEP 4 cm H2O for the following 8 hrs; an injuriously ventilated group with VT of 12 mL/kg, zero end-expiratory pressure, and FiO2 and RR unchanged (INJV; n = 8 and a group, which additionally received the inhibitor of nNOS, 7-nitroindazole (NI 1.0 mg/kg/h intravenously from 2 hours after the commencement of injurious ventilation (INJV + NI; n = 8. We assessed respiratory, hemodynamic and volumetric variables, including both the extravascular lung water index (EVLWI and the pulmonary vascular permeability index (PVPI. We measured plasma nitrite/nitrate (NOx levels and examined lung biopsies for lung injury score (LIS. Results Both the injuriously ventilated groups demonstrated a 2–3-fold rise in EVLWI and PVPI, with no significant effects of NI. In the INJV group, gas exchange deteriorated in parallel with emerging respiratory acidosis, but administration of NI antagonized the derangement of oxygenation and the respiratory acidosis significantly. NOx displayed no significant changes and NI exerted no significant effect on LIS in the INJV group. Conclusion Inhibition of nNOS improved gas exchange

Inhibitor of neuronal nitric oxide synthase improves gas exchange in ventilator-induced lung injury after pneumonectomy.

Science.gov (United States)

Suborov, Evgeny V; Smetkin, Alexey A; Kondratiev, Timofey V; Valkov, Andrey Y; Kuzkov, Vsevolod V; Kirov, Mikhail Y; Bjertnaes, Lars J

2012-06-21

Mechanical ventilation with high tidal volumes may cause ventilator-induced lung injury (VILI) and enhanced generation of nitric oxide (NO). We demonstrated in sheep that pneumonectomy followed by injurious ventilation promotes pulmonary edema. We wished both to test the hypothesis that neuronal NOS (nNOS), which is distributed in airway epithelial and neuronal tissues, could be involved in the pathogenesis of VILI and we also aimed at investigating the influence of an inhibitor of nNOS on the course of VILI after pneumonectomy. Anesthetized sheep underwent right pneumonectomy, mechanical ventilation with tidal volumes (VT) of 6 mL/kg and FiO2 0.5, and were subsequently randomized to a protectively ventilated group (PROTV; n = 8) keeping VT and FiO2 unchanged, respiratory rate (RR) 25 inflations/min and PEEP 4 cm H2O for the following 8 hrs; an injuriously ventilated group with VT of 12 mL/kg, zero end-expiratory pressure, and FiO2 and RR unchanged (INJV; n = 8) and a group, which additionally received the inhibitor of nNOS, 7-nitroindazole (NI) 1.0 mg/kg/h intravenously from 2 hours after the commencement of injurious ventilation (INJV + NI; n = 8). We assessed respiratory, hemodynamic and volumetric variables, including both the extravascular lung water index (EVLWI) and the pulmonary vascular permeability index (PVPI). We measured plasma nitrite/nitrate (NOx) levels and examined lung biopsies for lung injury score (LIS). Both the injuriously ventilated groups demonstrated a 2-3-fold rise in EVLWI and PVPI, with no significant effects of NI. In the INJV group, gas exchange deteriorated in parallel with emerging respiratory acidosis, but administration of NI antagonized the derangement of oxygenation and the respiratory acidosis significantly. NOx displayed no significant changes and NI exerted no significant effect on LIS in the INJV group. Inhibition of nNOS improved gas exchange, but did not reduce lung water extravasation following

Evaluation of radionuclide induced damage in marine invertebrates

International Nuclear Information System (INIS)

Hagger, Josephine Anne

2002-01-01

Limited studies have been carried out to assess the potential effects of ionising radiation on marine organisms. Therefore the general aims of this thesis were, (a) to assess the cytotoxic, genotoxic and developmental effects of ionising radiation on the embryo-larvae of two ecologically relevant marine invertebrates Mytilus edulis and Platynereis dumerilii, (2) to assess the effects of an environmentally relevant cocktail of radionuclides (3) to monitor the potential impact of radiation in the natural environment and finally (4) attempt to predict the potential effects of radiation at a population level. Following validation of developmental stages and mammalian based cytotoxic and genotoxic assays, chromosomal aberrations (Cabs), sister chromatid exchanges (SCEs) and proliferation rate index (PRI), on the embryo-larvae of M. edulis and P. dumerilii, the embryo-larvae stages were exposed to a reference radionuclide, tritium, (0.37,3.7,37 and 370 kBq/ml). Low doses of radiation delivered by tritium were shown to be detrimental to the development of embryo-larvae with an increase in abnormality for P. dumerilii and an increase in mortality for M. edulis. Tritium increased the induction of chromosomal aberrations and sister chromatid exchanges, in exposed embryo-larvae, indicating that tritium is potentially genotoxic. Cytotoxic effects (reduction in the cell proliferation rate) were also observed following exposure of embryo-larvae to tritium. In collaboration with the Royal Devonport Dockyard (DML) investigations on the cytotoxic, genotoxic and developmental effects of a cocktail of radionuclides (radioactive liquid waste diluted to 1.8,3.2, 5.6, 18%) were carried out. All embryo-larvae exposed to 18% radioactive waste were dead within 24h. Both species exhibited increased abnormality, SCEs and Cabs and a reduction in PRI in dilutions 1.8-5.6%. In general M. edulis appeared to be more sensitive to ionising radiation than P. dumerilii embryo-larvae. Following

Enhanced capacity and stability for the separation of cesium in electrically switched ion exchange

International Nuclear Information System (INIS)

Tawfic, A.F.; Dickson, S.E.; Kim, Y.; Mekky, W.

2015-01-01

Electrically switched ion exchange (ESIX) can be used to separate ionic contaminants from industrial wastewater, including that generated by the nuclear industry. The ESIX method involves sequential application of reduction and oxidation potentials to an ion exchange film to induce the respective loading and unloading of cesium. This technology is superior to conventional methods (e.g electrodialysis reversal or reverse osmosis) as it requires very little energy for ionic separation. In previous studies, ESIX films have demonstrated relatively low ion exchange capacities and limited film stabilities over repeated potential applications. In this study, the methodology for the deposition of electro-active films (nickel hexacyanoferrate) on nickel electrodes was modified to improve the ion exchange capacity for cesium removal using ESIX. Cyclic voltammetry was used to investigate the ion exchange capacity and stability. Scanning electron microscopy (SEM) was used to characterize the modified film surfaces. Additionally, the films were examined for the separation of cesium ions. This modified film preparation technique enhanced the ion exchange capacity and improves the film stability compared to previous methods for the deposition of ESIX films. (authors)

Enhanced capacity and stability for the separation of cesium in electrically switched ion exchange

Energy Technology Data Exchange (ETDEWEB)

Tawfic, A.F.; Dickson, S.E.; Kim, Y. [McMaster University, Hamilton, ON (Canada); Mekky, W. [AMEC NSS, Power and Process America, Toronto (Canada)

2015-03-15

Electrically switched ion exchange (ESIX) can be used to separate ionic contaminants from industrial wastewater, including that generated by the nuclear industry. The ESIX method involves sequential application of reduction and oxidation potentials to an ion exchange film to induce the respective loading and unloading of cesium. This technology is superior to conventional methods (e.g electrodialysis reversal or reverse osmosis) as it requires very little energy for ionic separation. In previous studies, ESIX films have demonstrated relatively low ion exchange capacities and limited film stabilities over repeated potential applications. In this study, the methodology for the deposition of electro-active films (nickel hexacyanoferrate) on nickel electrodes was modified to improve the ion exchange capacity for cesium removal using ESIX. Cyclic voltammetry was used to investigate the ion exchange capacity and stability. Scanning electron microscopy (SEM) was used to characterize the modified film surfaces. Additionally, the films were examined for the separation of cesium ions. This modified film preparation technique enhanced the ion exchange capacity and improves the film stability compared to previous methods for the deposition of ESIX films. (authors)

Electron exchange reaction in anion exchangers as observed in uranium isotope separation

International Nuclear Information System (INIS)

Obanawa, Heiichiro; Takeda, Kunihiko; Seko, Maomi

1991-01-01

The mechanism of electron exchange in an ion exchanger, as occurring between U 4+ and UO 2 2+ in uranium isotope separation, was investigated. The height of the separation unit (H q ) in the presence of metal ion catalysts, as obtained from the separation experiments, was found to be almost coincident with the theoretical value of H q as calculated on the basis of the intrasolution acceleration mechanism of the metal ion, suggesting that the electron exchange mechanism in the ion-exchanger is essentially the same as that in the solution when metal ion catalysts are present. Separation experiments with no metal ion catalyst, on the other hand, showed the electron exchange reaction in the ion exchanger to be substantially higher than that in the solution, suggesting an acceleration of the electron exchange reaction by the ion-exchanger which is due to the close existence of higher order Cl - complexes of UO 2 2+ and U 4+ in the vicinity of the ion-exchange group. (author)

Investigation of Chemical Exchange at Intermediate Exchange Rates using a Combination of Chemical Exchange Saturation Transfer (CEST) and Spin-Locking methods (CESTrho)

Science.gov (United States)

Kogan, Feliks; Singh, Anup; Cai, Keija; Haris, Mohammad; Hariharan, Hari; Reddy, Ravinder

2011-01-01

Proton exchange imaging is important as it allows for visualization and quantification of the distribution of specific metabolites with conventional MRI. Current exchange mediated MRI methods suffer from poor contrast as well as confounding factors that influence exchange rates. In this study we developed a new method to measure proton exchange which combines chemical exchange saturation transfer (CEST) and T1ρ magnetization preparation methods (CESTrho). We demonstrated that this new CESTrho sequence can detect proton exchange in the slow to intermediate exchange regimes. It has a linear dependence on proton concentration which allows it to be used to quantitatively measure changes in metabolite concentration. Additionally, the magnetization scheme of this new method can be customized to make it insensitive to changes in exchange rate while retaining its dependency on solute concentration. Finally, we showed the feasibility of using CESTrho in vivo. This sequence is able to detect proton exchange at intermediate exchange rates and is unaffected by the confounding factors that influence proton exchange rates thus making it ideal for the measurement of metabolites with exchangeable protons in this exchange regime. PMID:22009759

Investigation of chemical exchange at intermediate exchange rates using a combination of chemical exchange saturation transfer (CEST) and spin-locking methods (CESTrho).

Science.gov (United States)

Kogan, Feliks; Singh, Anup; Cai, Keija; Haris, Mohammad; Hariharan, Hari; Reddy, Ravinder

2012-07-01

Proton exchange imaging is important as it allows for visualization and quantification of the distribution of specific metabolites with conventional MRI. Current exchange mediated MRI methods suffer from poor contrast as well as confounding factors that influence exchange rates. In this study we developed a new method to measure proton exchange which combines chemical exchange saturation transfer and T(1)(ρ) magnetization preparation methods (CESTrho). We demonstrated that this new CESTrho sequence can detect proton exchange in the slow to intermediate exchange regimes. It has a linear dependence on proton concentration which allows it to be used to quantitatively measure changes in metabolite concentration. Additionally, the magnetization scheme of this new method can be customized to make it insensitive to changes in exchange rate while retaining its dependency on solute concentration. Finally, we showed the feasibility of using CESTrho in vivo. This sequence is able to detect proton exchange at intermediate exchange rates and is unaffected by the confounding factors that influence proton exchange rates thus making it ideal for the measurement of metabolites with exchangeable protons in this exchange regime. Copyright © 2011 Wiley Periodicals, Inc.

On one pion exchange potential with quark exchange in the resonating group method

International Nuclear Information System (INIS)

Braeuer, K.; Faessler, A.; Fernandez, F.; Shimizu, K.

1985-01-01

The effect of quark exchange between different nucleons on the one pion exchange potential is studied in the framework of the resonating group method. The calculated phase shifts including the one pion exchange potential with quark exchange in addition to the one gluon plus sigma meson exchange are shown to be consistent with experiments. Especially the p-wave phase shifts are improved by taking into account the quark exchange on the one pion exchange potential. (orig.)

Analysis and resolution of service water system heat exchanger tube failures at Clinton Power Station

International Nuclear Information System (INIS)

Bhayana, G.K.

1992-01-01

Microbiologically Influenced (or Induced) Corrosion (MIC) is generally prominent in a hospitable open loop environment with warmer temperatures and low flow or stagnant flow conditions. It is further enhanced by lack of chemical treatment of the cooling medium. Microbiologically induced corrosion is initiated by a metabolic process of the mocroorganisms. The influenced corrosion occurs when the growth of microorganisms create an environment for corrosion to exist by forming an oxygen-barrier or by producing metabolic by-products that attack metal surfaces. heat exchanger tubes, constructed of 90-10 Copper Nickel, located in two emergency Diesel Generators had to be replaced twice in less than two years. lack of effective chemical treatment was determined to be a contributing factor in both of the failures. The first failure was attributed to microbiologically induced corrosion and the second failure to a combination of microbiologically induced and influenced corrosion. This paper discusses the CPS heat exchanger tube failure analysis, the development and implementation of the MIC mitigation plan, various observations and the conclusions rendered

Measuring and slowing decoherence in Electromagnetically induced transparency medium

International Nuclear Information System (INIS)

Shuker, M.; Firstenberg, O.; Sagi, Y.; Ben-Kish, A.; Fisher, A.; Ron, A.; Davidson, N.

2005-01-01

Full Text:Electromagnetically induced transparency is a unique light-matter interaction that exhibits extremely narrow-band spectroscopic features along with low absorption. Recent interest in this phenomenon is driven by its possible applications in quantum information (slow light, storage of light), atomic clocks and precise magnetometers. The Electromagnetically induced transparency phenomenon takes place when an atomic ensemble is driven to a coherent superposition of its ground state sub-levels by two phase-coherent radiation fields. A key parameter of the Electromagnetically induced transparency medium, that limits its applicability, is the coherence lifetime of this superposition (decoherence rate). We have developed a simple technique to measure decay rates within the ground state of an atomic ensemble, and specifically the decoherence rate of the Electromagnetically induced transparency coherent superposition. Detailed measurements were performed in a Rubidium vapor cell at 60 - 80 with 30 Torr of Neon buffer gas. We have found that the Electromagnetically induced transparency decoherence is dominated by spin-exchange collisions between Rubidium atoms. We discuss the sensitivity of various quantum states of the atomic ensemble to spin exchange decoherence, and find a set of quantum states that minimize this effect. Finally, we demonstrate a unique quantum state which is both insensitive to spin exchange decoherence and constitutes an Electromagnetically induced transparency state of the medium

Capital accumulation, structural change and real exchange rate in a Keynesian-Structuralist growth model

Directory of Open Access Journals (Sweden)

Oreiro José Luis

2015-01-01

Full Text Available The aim of this paper is to show at theoretical level that maintaining a competitive real exchange rate positively affects the economic growth of developing countries by means of a Keynesian-Structuralist model that combines elements of Kaleckian growth models with the balance of payments constrained growth models pioneered developed by Thirlwall. In this setting, the level of real exchange rate is capable, due to its effect over capital accumulation, to induce a structural change in the economy, making endogenous income elasticities of exports and imports. For reasonable parameter values it is shown that in steady-state growth there is two long-run equilibrium values for real exchange rate, one that corresponds to an under-valued currency and another that corresponds to an over-valued currency. If monetary authorities run exchange rate policy in order to target a competitive level for real exchange rate, than under-valued equilibrium is stable and the economy will show a high growth rate in the long-run.

Differential response of biochemical parameters to EMS and MMS ...

African Journals Online (AJOL)

(1964) and biochemical estimations from the liver was done by the method of Sinha (1972) for catalase, Van der Vies (1954) for glycogen and Uchiyama and Mihara (1978) for MDA. Results: The study has revealed that EMS and MMS induced a dose dependent increase in chromosomal aberrations of chromatid type in the ...

EXFOR basics: A short guide to the nuclear reaction data exchange format

International Nuclear Information System (INIS)

McLane, V.

1996-07-01

This manual is intended as a guide to users of nuclear reaction data compiled in the EXFOR format, and is not intended as a complete guide to the EXFOR System. EXFOR is the exchange format designed to allow transmission of nuclear data between the Nuclear Reaction Data Centers. In addition to storing the data and its' bibliographic information, experimental information, including source of uncertainties, is also compiled. The status and history of the data set is also included, e.g., the source of the data, any updates which have been made, and correlations to other data sets. EXFOR is designed for flexibility in order to meet the diverse needs of the nuclear data compilation centers. This format should not be confused with a center-to-user format. Although users may obtain data from the centers in the EXFOR format, other center-to-user formats have been developed to meet the needs of the users within each center's own sphere of responsibility. The exchange format, as outlined, allows a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in an easily machine-readable format (for checking and indicating possible errors) and a format that can be read by personnel (for passing judgment on and correcting any errors indicated by the machine). The data presently included in the EXFOR exchange include: a complete compilation of experimental neutron-induced reaction data, a selected compilation of charged-particle induced reaction data, a selected compilation of photon-induced reaction data

Ion exchanger material based on Titanium phosphate for liquid radioactive waste treatment

Energy Technology Data Exchange (ETDEWEB)

Maslova, M.; Gerasimova, L. [Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Resources, Kola Scientific Center, Russian Academy of Sciences, Apatity (Russian Federation)

2013-07-01

A comparative study of the physicochemical and service properties of samples of Ti(OH) 1.36(HPO4) 1.32 * 2.3H2O sorbent in the finely dispersed and granulated forms, mastered for commercial production, was made. The sorption of Cs and Sr cations from solutions of various, compositions was studied in batch experiments, and the diffusion coefficients of the exchanging ions were determined. The hydrolytic stability of the. sorbents was examined with the aim to determine the optimal operation conditions. Experiments showed that the cation exchangers based on titanium phosphate are the most efficient in removal from liquid radioactive waste of induced radioactive isotopes of corrosion products, which is due to formation of weakly dissociating compounds of nonferrous metal ions with functional groups of the ion exchangers in the sorbent phase. (author)

IgG4 autoantibodies against muscle-specific kinase undergo Fab-arm exchange in myasthenia gravis patients.

Science.gov (United States)

Koneczny, Inga; Stevens, Jo A A; De Rosa, Anna; Huda, Saif; Huijbers, Maartje G; Saxena, Abhishek; Maestri, Michelangelo; Lazaridis, Konstantinos; Zisimopoulou, Paraskevi; Tzartos, Socrates; Verschuuren, Jan; van der Maarel, Silvère M; van Damme, Philip; De Baets, Marc H; Molenaar, Peter C; Vincent, Angela; Ricciardi, Roberta; Martinez-Martinez, Pilar; Losen, Mario

2017-02-01

Autoimmunity mediated by IgG4 subclass autoantibodies is an expanding field of research. Due to their structural characteristics a key feature of IgG4 antibodies is the ability to exchange Fab-arms with other, unrelated, IgG4 molecules, making the IgG4 molecule potentially monovalent for the specific antigen. However, whether those disease-associated antigen-specific IgG4 are mono- or divalent for their antigens is unknown. Myasthenia gravis (MG) with antibodies to muscle specific kinase (MuSK-MG) is a well-recognized disease in which the predominant pathogenic IgG4 antibody binds to extracellular epitopes on MuSK at the neuromuscular junction; this inhibits a pathway that clusters the acetylcholine (neurotransmitter) receptors and leads to failure of neuromuscular transmission. In vitro Fab-arm exchange-inducing conditions were applied to MuSK antibodies in sera, purified IgG4 and IgG1-3 sub-fractions. Solid-phase cross-linking assays were established to determine the extent of pre-existing and inducible Fab-arm exchange. Functional effects of the resulting populations of IgG4 antibodies were determined by measuring inhibition of agrin-induced AChR clustering in C2C12 cells. To confirm the results, κ/κ, λ/λ and hybrid κ/λ IgG4s were isolated and tested for MuSK antibodies. At least fifty percent of patients had IgG4, but not IgG1-3, MuSK antibodies that could undergo Fab-arm exchange in vitro under reducing conditions. Also MuSK antibodies were found in vivo that were divalent (monospecific for MuSK). Fab-arm exchange with normal human IgG4 did not prevent the inhibitory effect of serum derived MuSK antibodies on AChR clustering in C2C12 mouse myotubes. The results suggest that a considerable proportion of MuSK IgG4 could already be Fab-arm exchanged in vivo. This was confirmed by isolating endogenous IgG4 MuSK antibodies containing both κ and λ light chains, i.e. hybrid IgG4 molecules. These new findings demonstrate that Fab-arm exchanged antibodies