bluuebunny/crossref_metadata_2025_split huggingface dataset:
DNA‐damaging effect of cyclophosphamide on human blood cells in vivo and in vitro studied with the single‐cell gel test (comet assay)
Authors: Hartmann Andreas , Herkommer Kathleen , Glück Michael , Speit Günter 
Published: February 2007

AbstractThe single‐cell gel (SCG) test was used to study the induction and persistence of DNA damage by cy‐clophosphamide (CP) in human blood cells after treatment in vitro and in vivo. S9‐mix‐activated CP (from 0.1 mM upward) induced DNA effects in a concentration‐dependent manner in the in‐vitro SCG test. Blood cells from various donors showed considerable intra‐ and interindividual variability. Incubation of CP‐treated blood samples at 37°C caused a rapid decrease in DNA effects, but DNA migration was still significantly increased 1 hr after the end of the CP treatment. Comparative studies with the in vitro sister chromatid exchange (SCE) test were performed that demonstrated that much lower CP concentrations (about 100 times) were required for a significant induction of SCEs. A group of 11 patients who suffered from vasculitis/collagen disease and were treated with low CP doses (50–200 mg/day) exhibited an elevated level of DNA damage in the SCG test with peripheral blood cells, compared with a group of 11 control persons or 5 patients without chemotherapy. Increases in DNA damage were variable and not clearly related to the CP dose. SCE tests could successfully be performed with 5 out of the 11 CP‐treated patients; all showed significantly increased SCE frequencies. For six patients no result could be obtained with the SCE test due to a failure of lymphocyte proliferation. Three multiple sclerosis patients who received high doses of CP were investigated with the SCG test before, during, and after the treatment. The results indicate that CP‐induced DNA effects that are detectable with the SCG test persist in vivo for a period of several days, but for less than 2 weeks. The results of our study provide information with regard to the use of the SCG test in human monitoring. The advantages and limitations of the test are discussed. © 1995 Wiley‐Liss, Inc.
Sodium arsenite induces chromosome endoreduplication and inhibits protein phosphatase activity in human fibroblasts
Authors: Huang Rong‐Nan , Ho I‐Ching , Yih Ling‐Hui , Lee Te‐Chang 
Published: February 2007

AbstractArsenic, strongly associated with increased risks of human cancers, is a potent clastogen in a variety of mammalian cell systems. The effect of sodium arsenite (a trivalent arsenic compound) on chromatid separation was studied in human skin fibroblasts (HFW). Human fibroblasts were arrested in S phase by the aid of serum starvation and aphidicolin blocking and then these cells were allowed to synchronously progress into G2 phase. Treatment of the G2‐enriched HFW cells with sodium arsenite (0–200 μM) resulted in arrest of cells in the G2 phase, interference with mitotic division, inhibition of spindle assembly, and induction of chromosome endoreduplication in their second mitosis. Sodium arsenite treatment also inhibited the activities of serine/threonine protein phosphatases and enhanced phosphorylation levels of a small heat shock protein (HSP27). These results suggest that sodium arsenite may mimic okadaic acid to induce chromosome endoreduplication through its inhibitory effect on protein phosphatase activity. © 1995 Wiley‐Liss, Inc.
Overview of mutation assays in transgenic mice for routine testing
Authors: Gorelick N. J. 
Published: February 2007

AbstractThere is scientific and regulatory interest in using mutation assays in transgenic mice in safety assessments for new chemicals and drugs. Currently these assays are in the process of being validated, and protocols for routine testing are being defined. Some of the issues and results to date with regard to assay validation include reproducibility of the assay results (they are qualitatively reproducible), relevance of the test system (the transgene closely approximates an endogenous mammalian gene as a mutational target for the limited number of compounds tested), and the predictivity of the assay for heritable effects (unknown at this time) or carcinogenicity (the assays show good positive predictivity for carcinogenicity; the negative predictivity of the assay requires further investigation). Definition of appropriate study protocols for routine testing requires that applicable statistical methods are available and that the experimental parameters that affect the detection of mutations are known. Progress made in identifying these parameters is discussed. A proposal is made for the custom design of routine safety studies, which is based on the anticipated use of each individual test agent. A working group has been formed to conduct some of the studies still required for validation of these assays. © 1995 Wiley‐Liss, Inc.
Comparison of results from mouse bone marrow chromosome aberration and micronucleus tests
Authors: Shelby M. D. , Witt K. L. 
Published: February 2007

AbstractTests for the induction of chromosomal aberrations (ABS) and micronuclei (MN) in bone marrow cells of mice have been conducted on 65 chemicals. Although these tests were not conducted with the purpose of comparing the outcomes of these two in vivo genetic toxicity end‐points, the availability of these test results permits such a comparison. Based on studies to date, results from the 2 tests agree for more than 80% of the chemicals; 17 gave positive results in both tests, and 36 gave negative results in both. Seven chemicals were positive only for ABS and 5 were positive only for MN. Three chemicals that were originally concluded to be positive for ABS but not for MN were found to induce MN when the MN protocol was modified to more closely reflect the ABS protocol. Among the 12 chemicals for which there are discrepant results, there are only 2 for which the difference is convincing. One of these, selenium sulfide (MN negative, ABS positive) remains an enigma; further studies are being conducted. The second, isoprene (MN positive, ABS negative) will be difficult to pursue because the studies reported here were done by inhalation exposure. Based on the outcomes of these comparisons, protocol factors, rather than endpoint specificity, appear to be the major source of discrepant test results. Thus, these results do not support a recommendation that both tests be conducted in a primary testing scheme for genetic toxicity. © 1995 Wiley‐Liss, IncThis article is a US Government work and, as such, i s in the public domain in the United States of America.
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Sources of variability in the human lymphocyte micronucleus assay: A population‐based study
Authors: Radack Kenneth L. , Pinney Susan M. , Livingston Gordon K. 
Published: February 2007

AbstractThe cytokinesis block method was used to examine the intraclass correlation coefficient of the human lymphocyte micronucleus assay, sources of variability, and practical issues regarding the number of samples per subject. Twenty samples of 100 binucleate cells from a single phlebotomy per subject were analyzed (n = 112), using methods to evaluate variance components. The results showed marked intraindividual (sampling error) variation greater than interindividual variation, and no between‐group contribution to the total variance. The intraclass correlation was 41.6%, indicating that slightly greater than half of the total variation in micronucleus outcomes was due to error variance (i.e., 58.4%). After adjusting for age, the intraclass correlation coefficient decreased trivially from 41.6% to 39.8%. There was a strong differential gender effect, favoring a greater micronuclei frequency in women. In conclusion, the data suggest that most of the variability in our data set for the micronucleus assay was due to sampling error; a strong differential gender effect favoring females was also verified. Equally important, in terms of practical applications, our analysis of the appropriate number of samples per subject revealed that scoring greater than 1,000 cells (10 determinations per subject) yielded no substantial improvement in statistical sensitivity, compared to the traditional 20 determinations. We suggest that more attention should be directed toward improving the assay's utility, while reducing sampling error. © 1995 Wiley‐Liss, Inc.
Micronucleus frequency in spleen lymphocytes from severely malnourished rats during lactation
Authors: Ortiz Rocío , Cortés Edith , González Cristina , Pérez Lourdes , Betancourt Miguel 
Published: February 2007

AbstractThe purpose of this ex vivo study was to determine if severe malnutrition increases the frequency of micronuclei in spleen lymphocytes of experimentally malnourished rats during lactation. Micronucleus frequencies were analyzed in binucleate cells produced by the cytokinesis block method. The overall micronucleus frequency was significantly higher in binucleate cells from malnourished rats (21.3%‰) as compared to that observed in control rats (11.5%‰). The number of binucleate cells with more than one micronucleus was also higher in malnourished rats than in controls (3.1%‰ vs. 1.2%‰). These results indicate that severe malnutrition produces cellular damage in vivo, as was evidenced by the increased micronucleus frequency in rat spleen lymphocytes in vitro. This damage may produce negative effects for the further development of the organism, since the spleen is an important lymphopoietic organ in rodents. © 1995 Wiley‐Liss, Inc.
Streptozotocin‐induced toxicity in CHO‐9 and V79 cells
Authors: Capucci M. S. , Hoffmann M. E. , De Groot A. , Natarajan A. T. 
Published: February 2007

AbstractThe cytotoxicity of streptozotocin (STZ) was investigated in Chinese hamster fibroblast lines (CHO‐9 and V79) in comparison to two other alkylating agents, methylnitrosourea (MNU) and ethylnitro‐sourea (ENU), using cell survival as the endpoint. It was found that V79 cells were far more resistant to methylation induced by STZ and MNU than CHO‐9 cells (20 and four times, respectively) but equally sensitive to the ethylating agent ENU. The extent of STZ‐induced DNA methylation was estimated by analyzing the extent of O6‐metG and N7‐metG adducts in the DNA of treated cells through high‐performance liquid chromatography (HPLC) with electrochemical detection. The number of adducts as well the efficiencies of their removal from the DNA were similar in both cell lines. The response of these cells to the presence of DNA damage was evaluated by analysis of STZ effects on DNA replication and cell cycle progression. Measurement of [3H]‐thymidine incorporation showed a similar pattern of response at the level of inhibition of DNA synthesis in both cell lines. However, analysis of meta‐phase cells 36 hr after STZ exposure showed an accumulation of cells in the second cycle in the CHO‐9 line, indicating induction of a cell cycle arrest. Only a slight effect was observed on cell cycle progression in V79 cells, indicating that the methylation resistance of these cells could be related to their ability to progress through the cell cycle despite the presence of DNA lesions. © 1995 Wiley‐Liss, Inc.
Structure‐mutagenicity relationships of four amino‐imidazonaphthyridines and imidazoquinolines
Authors: Vikse R. , Hatch F. T. , Winter N. W. , Knize M. G. , Grivas S. , Felton J. S. 
Published: February 2007

AbstractWe tested four isomeric imidazonaphthyridines and one imidazoquinoline compound for mutagenic activity in the Ames/Salmonella mutagenicity assay, using strain TA98 and strain YG1024, an analogue of strain TA98 with elevated O‐acetyl‐transferase levels. Their potency was related to calculated electronic parameters. Five compounds with a linear arrangement of 3 rings showed a positive response in strain YG1024. Compound 2 (1‐methyl‐imidazo[4,5‐b][1,7]naphthyridin‐2‐amine) is the most mutagenic in both strains, giving specific activities of about 200 and 30 revertants per microgram in strains YG1024 and TA98, respectively. Three of the compounds were weak mutagens, giving a positive dose‐response only in strain YG1024, with 3–5 revertants per microgram. A higher response of all five compounds in strain YG1024 as opposed to TA98 indicates that they require O‐acetyltransferase activity for their metabolism. Mutagenic potencies in strain YG1024 were positively correlated to the energy of the LUMO (lowest unoccupied molecular orbital) of the nitrenium ion. © 1995 Wiley‐Liss, Inc.
Molecular nature of spontaneous mutations at the hypoxanthine‐guanine phosphoribosyltransferase (hprt) locus in chinese hamster ovary cells
Authors: Xu Zhidong , Yu Yongjia , Schwartz Jeffrey L. , Meltz Martin L. , Hsie Abraham W. 
Published: February 2007

AbstractThe hypoxanthine‐guanine phosphoribosyltransferase (hprt) locus has been widely used as a selectable genetic marker for studies of mammalian cell mutagenesis. We report here the spontaneous mutation spectrum at the hprt locus in 64 independently isolated mutants of Chinese hamster ovary (CHO) cells. All nine hprt exons were simultaneously analyzed via multiplex polymerase chain reaction (PCR) for rapid detection of gene deletions or insertions. Structural point mutations were identified by direct sequence analysis of the PCR amplified cDNA. The molecular nature of RNA splicing errors and insertions was analyzed by solid‐phase direct exon sequencing. Single base substitutions were found in 24 mutants (38%), of which 21 were missense and 3 were nonsense mutations. Transversions were about twice as frequent as transitions. Fifteen mutants (23%) had deletions involving either intragenic small fragments (2), single exons (9), or multiple exons (4). The majority of deletion breakpoints (71%) were located in regions surrounding exons 4, 5, and 6. RNA splicing mutations were observed in 15 mutants (23%) and affected exons 3–8; most (6/15) resulted in the loss of exon 7. Two insertion mutants, one with a 209 bp insert in exon 4 and the other with a 88 bp insert accompanied by a 24 bp deletion in exon 6, represent novel mutations reported for the first time in spontaneous mutants of the mammalian hprt gene. © 1995 Wiley‐Liss, Inc.
Analysis of mutations induced by replication of UV‐damaged plasmid DNA in hela cell extracts
Authors: Carty Michael P. , El‐Saleh Saleh , Zernik‐Kobak Maria , Dixon Kathleen 
Published: February 2007

AbstractWe have used an SV40‐based shuttle vector, pZ189, to investigate the capacity of HeLa cell extracts to reproduce the in vivo process of mutation fixation. We showed previously that when UV‐irradiated pZ189 is replicated in these extracts, bypass of UV photoproducts occurs, resulting in base substitution mutations in the supF gene of the vector. Here we report the DNA sequence characterization of a collection of 60 of these UV‐induced mutants. Most of the mutations observed are single or tandem double base substitutions at dipyrimidine sites; of these, approximately 90% are G:C→A:T transitions. Mutations are observed predominantly at a few sites, in particular at positions 155 and 156 in the supF sequence. No dramatic differences in the mutation spectrum were observed when the orientation of the supF gene was reversed with respect to the SV40 origin of replication, suggesting that mutation fixation occurs similarly on both the leading and the lagging strands for DNA replication. Generally, the mutational hot spots observed in vitro are at the same sites as those observed when UV‐irradiated pZ189 was passaged in human or monkey cells in culture. Thus, it appears that the replication and mutagenesis of UV‐damaged templates in HeLa cell extracts accurately reflects these processes in the intact cell. © 1995 Wiley‐Liss, Inc.
Analysis of point mutations in the hprt gene of cancer patients treated with radioimmunoglobulin therapy
Authors: Skandalis A. , Curry J. , O'Neill J. P. , Nicklas J. A. , Albertini R. J. , Glickman B. W. 
Published: February 2007

AbstractThe mutagenic impact of various environmental and therapeutic agents can now be directly assayed in humans by the T‐lymphocyte cloning assay. We have previously reported that following radioimmu‐noglobulin therapy, cancer patients exhibited increased mutant frequency at the hprt locus and an increased yield of large intergenic deletions compared to unexposed controls. Here we report the results of the analysis of 26 independent hprt mutations in nine cancer patients who underwent radioimmunoglobulin therapy. The majority of mutations (52%) had lost exon sequences from the mRNA. The remaining mutations were 20% small deletions and frameshifts and 28% base substitutions. The type of mutations observed were similar to those seen in unexposed controls. The site distribution of the mutations, however, indicates that some sequence contexts may be more sensitive to radiation mutagenesis than others. © 1995 Wiley‐Liss, Inc.
Taurine and ellagic acid: Two differently‐acting natural antioxidants
Authors: Cozzi R. , Ricordy R. , Bartolini F. , Ramadori L. , Perticone P. , De Salvia R. 
Published: February 2007

AbstractNaturally occurring antimutagenic compounds are extensively analyzed for their capacity to protect cells from induced damage. We selected two agents, taurine and ellagic acid, treated in the literature as antioxidants, but whose activity is insufficiently known. This paper reports on the ability of these agents to act against damage induced by mitomycin‐C and hydrogen peroxide in Chinese hamster ovary cells cultivated in vitro. Cytogenetic and cytofluorimetric analyses were performed. Ellagic acid proved to have more than one mechanism of action, probably as a scavenger of oxygen species produced by H2O2 treatment, and as a protector of the DNA double helix from alkylating agent injury. In our experimental conditions, taurine seems able to scavenge oxygen species. © 1995 Wiley‐Liss, Inc.
An examination of the potential “genotoxic” carcinogenicity of a biopesticide derived from the neem tree
Authors: Rosenkranz Herbert S. , Klopman Gilles 
Published: February 2007

AbstractStructural analyses of azadirachtin, a promising biopesticide recently introduced into the United States, indicates that this natural product has the potential for acting as a “genotoxic” carcinogen. In view of the fact that genotoxic carcinogens are regarded as presenting a potential carcinogenic risk to humans, the present finding suggests that the possible metabolism of azadirachtin to DNA‐reactive products be evaluated experimentally. © 1995 Wiley‐Liss, Inc.
Methylglyoxal induces hprt mutation and DNA adducts in human T‐lymphocytes in vitro
Authors: Hou Sai‐Mei , Nori Peri , Fang Jia‐Long , Vaca Carlos E. 
Published: February 2007

AbstractMethylglyoxal (MG) is a mutagen present in several foodstuffs, including coffee. We have used the 32P‐postlabelling method to measure MG‐deoxyguanosine adduct levels, and the T‐cell cloning technique, to study the frequency of hprt (hypoxanthine‐guanine phosphoribosyl transferase) mutant cells after treatment of human lymphocytes with MG in vitro. The mutant induction by single (18 hr) high‐dose (1.0–1.5 mM) treatment was comparable to that induced by repeated (3 × 48 hr) low‐dose (0.1–0.4 mM) treatment. The latter also correlated with the adduct levels measured in the same experiment. The relative cell survival measured by direct cloning after the final treatment agreed well with the growth curves monitored during the expression phase. Our results show that MG is capable of inducing hprt mutations as well as DNA adducts in human lymphocytes at doses with low cytotoxicity. However, significant adduct formation (two‐ to threefold) could be obtained only after the first exposure in cells subjected to a repeated treatment protocol, and the induced mutant frequency was low (two‐to fourfold over background). Thus, MG seems to be a comparatively weak mutagen in this system. © 1995 Wiley‐Liss, Inc.
Sister chromatid exchange in human lymphocytes induced by propoxur following plant activation by Vicia faba
Authors: Gómez‐Arroyo Sandra , Elena Calderón‐Segura M. , Villalobos‐Pietrini Rafael 
Published: February 2007

AbstractBecause the carbamate insecticide propoxur induced sister chromatid exchanges (SCE) in Vicia faba but was ineffective in producing SCE in lymphocytes in culture, it was hardly suspected that plant metabolism was involved. Experiments were conducted in which metabolic activation was afforded by Vicia faba roots, and SCE in human lymphocytes in vitro was used to assess cytogenetic damage. Several concentrations of propoxur (250, 500, 1, 000, 1, 500, and 2, 000 ppm) were applied for 4 hr to the roots of Vicia faba. Extracts prepared from these treatments were added to the lymphocyte cultures and a significant increase of SCE frequencies with a concentration‐response relationship could be detected. The lymphocyte proliferation kinetics and the proliferation rate index (PRI) were not affected (except in the highest concentration, of 2, 000 ppm). This general behavior was in agreement with the presence of an enzymatic system (SI0 fraction) in Vicia roots capable of metabolizing or activating the propoxur. With 2, 000 ppm, cell necrosis was produced in Vicia; therefore, this extract did not induce SCE in lymphocytes. However, lymphocyte proliferation kinetics were delayed and PRI was significantly decreased. Ethanol, a promutagen activated by this plant, was applied directly to the lymphocyte cultures as a positive control, and the response was negative. On the other hand, the extracts of roots treated with ethanol increased the SCE to more than twice that of the negative control, but the lymphocyte proliferation kinetics and PRI were not affected. © 1995 Wiley‐Liss, Inc.
Membrane fouling behavior during filtration of sludge supernatant
Authors: Yang Fenglin , Shi Baoqiang , Meng Fangang , Zhang and Hanmin 
Published: February 2007

AbstractColloidal particles and soluble matter in sludge supernatant are major membrane foulants during the operation of membrane bioreactors in wastewater treatment. The article discusses membrane fouling mechanisms during membrane filtration of sludge supernatant liquor. The influence of supernatant turbidity, transmembrane pressure, and crossflow velocity on membrane fouling was systematically investigated. The membrane fouling was characterized by Fourier transform infrared spectroscopy technique. The results showed that the high supernatant turbidity could result in severe membrane fouling because of the accumulation of colloidal particles and soluble matter on the membrane surfaces. High transmembrane pressure could lead to a high flux decline rate because of the formation of a dense cake layer. The crossflow velocity just had a slight influence on membrane fouling, as it was not larger than 0.12 m/s, However the membrane fouling decreased significantly as crossflow velocity increased to 0.24 m/s. The membrane fouling mechanisms of these operational conditions, including supernatant turbidity, transmembrane pressure, and crossflow velocity, were different from each other. Membrane fouling resistance can be predicted using a simple model based on supernatant turbidity, transmembrane pressure, and crossflow velocity. The major components of the foulants were proteins and polysaccharide materials. © 2007 American Institute of Chemical Engineers Environ Prog 26:86–93, 2007