ISSN:0893-6692    

DOI:10.1002/em.2850220302

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

年代:1993

数据来源: WILEY

ISSN:0893-6692    

DOI:10.1002/em.2850220303

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

年代:1993

数据来源: WILEY

摘要:

AbstractChange in chromosome number, numerical aneuploidy, has been consistently linked with cancer development. Since 90% of cancers arise in epithelial tissues, techniques that measure aneuploidy in these tissues would be very useful. Here we describe methods of optimization and suggest use of fluorescent in situ hybridization (FISH) to detect aneuploidy in exfoliated epithelial cells collected from the mouth and bladder. A total of 10,383 urothelial cells and 4,691 buccal cells were scored in order to determine a baseline frequency of aneuploidy in human volunteers using a classical satellite probe for chromosome 9. Protein digestion with pepsin was found to be more efficient at removing the keratinized cell membrane and optimizing probe penetration than acid washes, detergent washes, or hypotonic treatments. A 20 min cellular digestion with 200 μg/ml and a 30 min digestion with 300 μg/ml of pepsin in 0.01 M HCI optimized probe penetration in urothelial and buccal cells, respectively. Average frequencies for 0, 1, 2, 3, and 4 hybridization regions were 10.3, 10.1, 78.4, 1.0, and 0.3% for urothelial cells and 8.8, 9.8, 79.4, 1.3, and 0.3% for buccal cells, respectively. These results are very similar to those previously described in lymphocytes. The urothelial cells of males had a lower frequency of diploid cells and a higher frequency of cells without hybridization regions than females (P<0.02). No statistically significant variability was found between individuals or sex groups in buccal cells. Our data show that FISH is a useful tool to detect changes in frequency of aneuploidy in exfoliated epithelial cells and has good potential for monitoring human populations exposed to genotoxic agents. © 1993 Wiley‐Liss,

ISSN:0893-6692    

DOI:10.1002/em.2850220304

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe occurrence of deletions, coding sequence alterations, and intronic changes leading to aberrant splicing has been characterized among 33 spontaneous HPRT−mutants in TK6 human lymphoblasts. Deletions detectable by multiplex PCR amplification accounted for 45% (15/33) of the mutant collection. Base substitutions represented 30% (10/33) of the total, and were predominated by changes at G:C base pairs. The remaining mutants were distributed among frameshifts (9%, 3/33), small deletions (6%, 2/33), and compound alterations (9%, 3/33). Five mutants (15%) demonstrated aberrant splicing of thehprttranscript. A cluster of 4 deletion/insertion events was identified inhprtexon 6. A nearly perfect 13 bp duplication differed from the original sequence only by an A:T to G:C transition, which was observed as a unique alteration in another HPRT−mutant. A model involving correction of a mismatch in a secondary structure formed by the duplicated sequence may account for these results. © 1993 Wiley‐Lis

ISSN:0893-6692    

DOI:10.1002/em.2850220305

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe investigated the effects of dose rate on the frequency of sister chromatid exchange (SCE) in bone marrow and spleen cells of rats exposed to ethylene oxide (EtO). Four groups (18/group) of male Fischer 344 rats were exposed to EtO by inhalation. The exposures consisted of 100 ppm for 6 hr/day, 300 ppm for 2 hr/day, 600 ppm for 1 hr/day, and clean air control. All EtO treated rats were given a total exposure dose of 600 ppm‐hr daily, 5 days/week for 3, 6, or 9 months. Six rats per group were sacrificed at each time point, and SCEs were measured in cultured spleen and bone marrow cells. A statistically significant increase was found in SCEs in both bone marrow and spleen cells for all treated groups and at each time point when compared to the control, except at the 3‐month exposure for the middle and high dose‐rate groups in bone marrow cells. In the spleen, the increases in SCEs were similar among the three experimental groups. In bone marrow, the lowest dose rate (100 ppm) resulted in higher SCE frequencies than the medium and high dose‐rate group after 3 and 6 month exposures. The overall frequencies of SCEs in the spleen cells were higher than in the bone marrow cells. The increase in SCE frequencies and decrease in the replicative index in spleen cells were also dependent on the duration of exposure. These results indicate that (1) EtO, by inhalation, can cause SCEs both in spleen and bone marrow cells of Fischer 344 rats, (2) spleen cells are more sensitive to EtO than bone marrow cells, and (3) in bone marrow cells the lowest dose‐rate (longest) exposure causes more SCEs than the highest dose‐rate (shortest) exposures. © 1993 Wil

ISSN:0893-6692    

DOI:10.1002/em.2850220306

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

年代:1993

数据来源: WILEY

摘要:

AbstractWe investigated whether the polymerase chain reaction (PCR) could be used to determine the mechanism of mutation in lymphocyte clones mutated at the HLA‐A locus. Three polymorphisms, at Factor XIIIA, D6S109, and intron 3 of the HLA‐A gene, were used to study a series of clones previously characterised by Southern blotting (SB) at multiple loci on chromosome 6. For detection of loss of heterozygosity, the results of PCR and SB were concordant in 140 of 141 clones when polymorphism in the Factor XIIIA region was studied and in 144 of 145 clones when polymorphism in the HLA‐A gene was studied. For classification of the mechanism of mutation, PCR and SB gave the same result in 88 of 92 clones (96%) when a combination of the HLA‐A and Factor XIIIA polymorphisms was used and in 46 of 47 clones (98%) when a combination of the HLA‐A and D6S109 polymorphisms was used. The results indicate that PCR provides a simple and reliable method for categorising mutations at the HLA‐A locus as arising from mitotic recombination, deletion, or from presumptive minor changes within the gene. Rare events such as gene conversion, nondisjunction, or large deletions extending to the telomere will be misclassified. However, such events are rare for mutations at this locus. © 1993 Wil

ISSN:0893-6692    

DOI:10.1002/em.2850220307

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe SOS chromotest is a simple colorimetric genotoxicity assay that monitors DNA repair by measuring the induction of the genesfiAinEscherichia coliK‐12.E. coliPQ300, a diagnostic SOS tester strain for the detection of oxidative genotoxins, carries a mutation in a key gene for antioxidative defense,oxyR.This mutation renders PQ300 more sensitive to oxidative genotoxins, particularly to H2O2. We found that induction of the SOS response by H2O2inE. coliPQ300 is dependent on the composition of the incubation medium; a substantially reduced response was obtained in minimal phosphate buffered saline (PBS) as opposed to complex Luria broth (LB) medium. Supplementation of PBS with histidine or cysteine stimulated H2O2‐induced SOS induction to levels exceeding those found in LB medium. Low concentrations of glutathione (20–70 μM) also enhanced the H2O2‐induced SOS response inE. coliPQ300, whereas higher concentrations (>150 μM) were protective. Preincubation of tester cells with the chelators o‐phenanthroline, 2,2‐dipyridyl, and ethylenediaminetetraacetic acid (EDTA) protected cells from the effects of H2O2, although EDTA was only partially effective. Pretreatment of PQ300 with the antioxidant ascorbic acid or the hydroxyl radical scavenger dimethyl sulfoxide also diminished the SOS response, whereas mannitol and glucose were ineffective. The results show that the net effect of H2O2‐induced DNA damage is influenced by the balance of oxidative and antioxidative factors and, furthermore, can be modulated by constituents of the extracellular milieu. © 1993

ISSN:0893-6692    

DOI:10.1002/em.2850220308

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

年代:1993

数据来源: WILEY

摘要:

AbstractChlorophyllin (CHL) is a water‐soluble salt of chlorophyll that exhibits antimutagenic activity in short‐term genotoxicity assays and inhibits carcinogen‐DNA binding in vivo. The antimutagenic potency of CHL was studied against several structurally related heterocyclic amines using the Salmonella assay. The mutagens included 2‐amino‐3‐methylimidazo[4,5,‐f]‐quinoline (IQ) and seven related IQ‐type compounds, and 3‐amino‐1‐methyl‐5H‐pyrido[4,3‐b]indole (Trp‐P‐2) and three additional non‐IQ‐type compounds. No relationship was observed between mutagenic potency (revertants/ng mutagen) and antimutagenic potency when expressed in terms of the CHL dose/plateinhibiting mutagenicity by 50 percent (l50). However, a correlation was observed between mutagenic potency and the mole ratio of CHL to mutagen giving 50% inhibition (MR50), with most mutagens requiring several hundredfold to several thousandfold molar excess of CHL for inhibition. In spectrophotometric studies, CHL formed noncovalent molecular complexes with the heterocyclic amines, with binding constants in the range 3–13 x 103M−1. Binding constants were inversely correlated with l50and MR50values, i.e., with increasing strength of complex formation less CHL/plate and a lower mole ratio of CHL to mutagen was required to inhibit mutagenicity. The results support an inhibitory mechanism in which chlorophylls operate as “interceptor molecules,” interacting with carcinogens and mutagens directly and limiting

ISSN:0893-6692    

DOI:10.1002/em.2850220309

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

年代:1993

数据来源: WILEY

摘要:

AbstractHuman lymphocytes (HL) as well as lymphocytes (RL), hepatocytes (RH), and gastric mucosa cells (GM) of Sprague‐Dawley rats were treated in vitro for 1 h with methylmercury chloride (MMC, 0.5–4 μg/ml) and dimethylmercury (DMM, 5–40 μg/ml). The cytotoxicity of the two organic mercury compounds was assessed by dye exclusion, and the extent of induced DNA fragmentation was measured with a single‐cell microgel electrophoresis assay. Both MMC and DMM induced DNA damage and cytotoxicity in a dose‐related manner in HL, RL, and GM. MMC was more effective in causing a significant increase in median DNA migration than DMM at doses yielding approximately the same degree of cytotoxicity. In rat hepatocytes the MMC‐induced DNA damage was, however, lower than in the other cells. An analysis of repair kinetics following exposure to 2 μg/ml MMC was carried out in human lymphocytes obtained from an adult male donor. The bulk of DNA repair occurred 90 min after in vitro exposure, and it was about complete by 120 min following cessation of exposure. Finally, in order to have a basis for extrapolating to the human situation, in vivo studies were performed with Sprague‐Dawley rats, also assessing the DNA damage and cytotoxicity in the lymphocytes and gastric mucosa cells. These in vivo results after oral exposure may be directly compared to the in vitro data obtained in the same cells. © 199

ISSN:0893-6692    

DOI:10.1002/em.2850220310

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

年代:1993

数据来源: WILEY

摘要:

AbstractA difference in biological response to enantiomers is not an uncommon observation and is, therefore, to be expected in various manifestations of genotoxicity. The bacterial mutagen mucochloric acid (2,3‐dichloro‐5‐hydroxy‐2(5H)‐furanone) has one chiral center, at C‐5, but this mutagen exists in racemic form because of the facile stereoisomerization occurring by the mechanism of ring‐chain tautomerism. Two readily synthesized enantiomeric analogs of mucochloric acid, as well as the racemic form of the two, were prepared from mucochloric acid and (R)‐(+)‐, (S)‐(‐)‐, and (R,S)‐(+/‐)‐cysteine. UsingSalmonella typhimurium(TA100), the enantiomeric compounds were assayed together in four dose/response assays along with mucochloric acid, the reference mutagen. In three of the same four assays, the racemic form was also assayed. Neither statistically significant differences in mutagenicity, as determined in slope responses, nor distinctions from the plotted curves were observed among the two enantiomers and their racemic form. Therefore, no enantiospecific interaction between enantiomers and chiral DNA or enzymes involved in repair or replication could be conc

ISSN:0893-6692    

DOI:10.1002/em.2850220311

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

年代:1993

数据来源: WILEY