摘要:

AbstractWe have developed a computer database containing information on over 1,000 human hypoxanthine guanine phosphoribosyl transferase (HPRT) mutants. Both published and unpublished data are present. The database itself is maintained in a dBASE format (.DBF) and we provide a set of programs to examine and extract information from the database. A program to input information into the database is also supplied. The database and programs are available directly from us or via remote FTP (file transfer protocol) using BITNET/INTERNET. All programs require an IBM‐compatible computer, the MS‐DOS operating system (version 3.3 or greater), and a hard disk with about 5 megabytes of free disk space.The purpose of the database is 1) to allow investigators to contribute their HPRT mutants directly to the database in a standardized fashion, and 2) to allow access to the entire database with a set of programs that allows manipulation and extraction of data. For example, using our programs it is possible to i) order the database by base pair position, ii) examine only information regarding mutagenesis by a particular agent, iii) search for a particular author, iv) create a report which contains selected portions of the database, the report can be printed or saved as a file.The database will be updated every several months and distributed. © 1992 Wiley‐Lis

ISSN:0893-6692    

DOI:10.1002/em.2850200202

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA mutation spectrum was constructed from a series of randomly isolated spontaneous His+revertants of the frameshift mutanthis4–38inSaccharomyces cerevisiae.For each true revertant, a 438 bp region encompassinghis4–38on chromosome III was recovered into a shuttle vector by double‐strand gap repair. Of the 45 independent His+revertants sequenced, 44 were −1 base deletions and one revertant was a +2 base insertion. The −1 deletions exhibited a bimodal distribution. Of the bases encompassing thehis4–38region from +153–181, 45% were not involved in a reversion event, although a −1 frameshift within this region will result in a viable His+revertant. Approximately 49% of −1 events occurred within runs of 3 repeated bases. At these sites the strand‐slippage model for frameshift mutation is supported. However, the −1 events occurring at sites of 2 repeated bases and the low frequency (2%) of +2 base insertions suggest that the transiently misaligned template model is a significant mechanism in reversion ofhis4–38.When the distribution of −1 events at repeated bases was discounted, a hotspot involving a ‐T at position +163 was resol

ISSN:0893-6692    

DOI:10.1002/em.2850200203

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractTen intron mutations and one exon mutation giving rise to defective splicing in the human gene for hypoxanthine phosporibosyl transferase (hprt) in T‐lymphocytes have been characterized. the splicing mutants were detected by PCR amplification of hprt cDNA and direct sequencing. Nine of the mutants showed skipping of whole exons or parts of exons in the cDNA, one mutant had an inclusion of an intron sequence into the cDNA, and one mutant showed both inclusion of an intron sequence and skipping of exons as well as a normal cDNA. Genomic PCR and direct sequencing of the splice sites involved showed one deletion of three base pairs and 10 different single base alterations to be responsible for these splice alterations. One mutation in the last base pair of exon 6 causing skipping of the entire exon 6 was found, whereas an identical mutation in the last base pair of exon 2 caused no aberrant splicing. It was also found that a deletion mutation in the pyrimidine rich stretch of the acceptor site of intron 7 caused skipping of the entire exon 8, whereas a base substitution in the last base of intron 7 caused exclusion of only the first 21 base pairs of exon 8 as a result of the activation of a cryptic acceptor site in exon 8. The results show that many different types of mutations at several different sites can cause splicing errors in the hprt gene and that the sequence differences between the splice sites influence the possible spectrum of mutations in each site. © 1992 Wiley‐Liss,

ISSN:0893-6692    

DOI:10.1002/em.2850200204

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe study ofhprtmutations in cynomolgus monkey T‐lymphocytes is part of our effort to understand the mechanisms of mutagenesis in vivo. This primate model allows us to study mutations and their kinetics at the molecular level under well‐controlled conditions using recently developed techniques for selection of mutant T‐cells and polymerase chain reaction (PCR) amplification ofhprtcDNA, which is directly sequenced. This is the first report of the sequence of the coding region of the cynomolgus monkeyhprtgene and PCR/DNA sequence analysis of seven spontaneous mutant T‐cell clones, as well as 23 mutant clones isolated 63 and 601 days after treatment with ethylnitrosourea (ENU, 77 mg/ kg, intraperitoneal). cDNA was reverse transcribed fromhprtmRNA directly from a lysate of about 2–4 × 103cells, and a 700 bp fragment including the coding region was amplified by PCR and sequenced. Of the seven spontaneous mutants, only one point mutation (GC↠ transition) was detected, and the other six failed to amplify by PCR, possibly due to functional deletions. Of the 14 mutant clones isolated 63 days after ENU treatment, nine base substitutions were detected in ten clones: four transitions (three AT↠GC and one GC↠AT) and five transversions (four AT↠TA and one AT↠CG). Of the nine mutants isolated 601 days after ENU treatment, six single base substitutions were detected in six clones (five AT↠TA and one AT↠CG transversions), and one mutant had a large deletion or insertion. No changes were detected in three clones (one Day 63 and two Day 601 clones). In summary, only one of 15 single base substitutions isolated after ENU treatment was a GC↠AT transition mutation and the rest were transitions and transversions at AT sit

ISSN:0893-6692    

DOI:10.1002/em.2850200205

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractAssessment of the in vivo aneuploidy/micronucleus Assay in bone marrow cells with 16 chemicals is described. This assay is based on the detection of kinetochores (KC) in micronuclei (MN) by antikinetochore‐specific (CREST) antibodies. Among sixteen chemicals tested, six were known clastogens, three were known aneuploidy‐inducers, and the other seven were suspected spindle poisons. These chemicals were tested for their ability to induce micronuclei with kinetochore(s) in bone marrow cells of CD‐1 mice. The majority of MN formed in bone marrow cells treated with aneuploidy‐inducing agents contained kinetochore(s) which are considered to be formed from whole chromosomes or centric fragments, while in clastogen treated bone marrow cells, majority of them contained no kinetochore(s) which are considered to be formed from acentric chromosomal fragments. Classification of chemicals into either aneuploidy inducing agents or clastogens is based on the relative frequency of MN with and without KC, respectively. These results suggest that the in vivo aneuploidy/micronucleus assay has a great potential to identify aneuploidy‐inducing agents. © 1992 Wiley

ISSN:0893-6692    

DOI:10.1002/em.2850200206

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractMicroncuclei kinetics and persistence in mononucleated and binucleated human peripheral lymphocytes following short‐term (4 hr) and continuous (until harvest) in vitro exposure to vincristine sulfate (VS) and ethlylene dibrode (EDB) were studied. Lymphocytes were exposed to chemicals for various doses and harvested at different culture times. Micronucleus frequenvies were scored in both mononucleated and biucleated cells on the same slide. VS‐treated cells showed a significantly higher incidence of micronucleus in both ononucleated and binucleated cells than controls (p<0.01). The cells treated continuously with VS produced comparatively higher frequencies of micronucleated cells than those treated for 4 hr. Highest micronuclei frequencies were observed 24 hr after chemical treatment in both mononucleated and binucleated cells and decreased later with time. However, the micronucleus frequencies remained significantly higher than the controls even in the cells harvested at 144 hr. VS induced a large number of micronucleated cells with multiple micronuclei. VS also caused a severe decrease in nuclear division due to cytotoxic effect. Lymphoctes treated with EDB for 4 hr and continuously showed a statistically higher incidence of micronuclei in binucleated cells compared to the controls (p<0.05), whereas in mononucleated cells higher micronucleus frequencies were observed only in cultures treated continuously. Continuous presence of EDB induced both dose‐and time‐dependent increase of micronuclei in both mono‐ and binucleated cells(p<0.05). EDB induced relatively few multiple micronucleated cells in comparison with VS. EDB did not affect nuclear divisions even with continuous treatment. HIgh micronucleus frequencies observed at 144 hr harvest following 4 hr treatment of both EDB and VS suggest the persistence of DNA damage in cells. These studies suggest that micronuclei kinetics in human periphearl lymphocytes depends on the genotoxic potentially and cytotoxicity of a geno toxicant. © 1992 Wiley

ISSN:0893-6692    

DOI:10.1002/em.2850200207

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractThe fungicide Captan has been examined for its effects on DNA and DNA processing in order to better understand the genotoxicity associated with this agent. Captan treatment resulted in production of DNA single strand breaks and DNA‐protein cross‐links and elicited an excision repair response in human diploid fibroblasts. Captan was also shown to inhibit cellular DNA synthesis and to form stable adducts in herring sperm and human cellular DNA. Misincorporation of nucleotides into Captan‐treated synthetic DNA templates was significantly elevated in an in vitro assay usingE. coliDNA polymerase I, suggesting that DNA adduct formation by Captan could have mutagenic consequences. In sum, these studies demonstrate that Captan is capable of interacting with DNA at a number of levels and that these interactions could provide the basis for Captan's genotoxicity. The extreme cytotoxicity of this fungicide, however, could be due to other cellular effects since at the IC50for cell killing, approximately 0.8 μM, none of the above genotoxic events could be detected by the methods employed. © 1992 Wiley‐

ISSN:0893-6692    

DOI:10.1002/em.2850200208

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractWhile the liver consists of both parenchymal cells (PC) and nonparenchymal cells (NPC), virtually all studies on promutagen activation have been performed using PC. To evaluate the comparative roles of PC and NPC in promutagen activation, we cocultivated a cell line generally considered to have an insignificant level of xenobiotic metabolism, Chinese hamster ovary (CHO) cells, with either PC, NPC, or a combination of both. The mixed culture was treated with two promutagens: dimethylnitrosamine (DMN) and 3‐methylcholanthrene (3‐MC). The induction of 6‐thioguanine resistant mutants was evaluated using the well‐established CHO/hypoxanthine‐guanine phosphoribosyl transferase (HGPRT) assay. Activation of promutagens, as indicated by an increase in mutant frequency in CHO cells, was observed only when the PC were present with the CHO cells during the treatment period. No activation was observed with NPC. Coculturing of PC and NPC yielded essentially the same results as PC alone. P‐450 mixed function monooxygenase activity measured by the 7‐ethoxycoumarin‐O‐deethylase assay further substantiates that PC had a significantly higher xenobiotic metabolism activity than NPC. Our study therefore indicates that PC, not NPC, are the major cell population in the liver responsible for the activation of promutagens. © 19

ISSN:0893-6692    

DOI:10.1002/em.2850200209

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

摘要:

AbstractA quantitative structure‐activity relationship (QSAR) has been formulated for 15 polycyclic aromatic nitro compounds acting onE. coliPQ37. Upon damage of DNA by these substances β‐galactosidase is induced and can be easily assayed colorimetrically, hence, this is a short‐term test for mutagenicity. The QSAR (log SOSIP = 1.07 log P ‐ 1.57 ± ‐ 6.41) is strikingly similar to that found earlier with nitroaromatics acting in the Ames test (TA100) and differs significantly for that found using TA98 organisms. The QSAR brings out in a unique manner the underlying similarity in the two test systems. © 1992 Wil

ISSN:0893-6692    

DOI:10.1002/em.2850200210

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY

ISSN:0893-6692    

DOI:10.1002/em.2850200201

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1992

数据来源: WILEY