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E Zeiger

Publications and source records attributed to E Zeiger.

At least 73 records · Page 4Linked to original sources
PubMed1992

Ozone is mutagenic in Salmonella.

Ozone is a highly reactive gas that has been tested for genotoxicity in a number of systems. Induced genetic damage resulting from ozone treatment may not be readily observed because of the high toxicity of the chemical and difficulties in generating and administering controlled concentrations. The mutagenicity of ozone was investigated in Salmonella typhimurium using a plate test protocol designed for reactive vapours and gases. Ozone, at two to three consecutive doses, induced weak, albeit statistically significant, mutagenic responses in tester strain TA102 with and without Aroclor-induced rat liver S9 (lowest effective mean concentration of 0.019 ppm; 35 min total exposure). However, dose-related responses were not always obtained. No mutagenicity was detected in strains TA98, TA100, or TA1535, with or without S9. In strain TA104, ozone induced a weak response only at a single dose with S9; this response was not reproducible. Mutagenicity was dependent on the ozone flow rate and total exposure time, with variations in the optimum dose-time regimen leading to toxicity or complete inactivity. The data show that ozone is a very weak bacterial mutagen and only when tested under narrowly prescribed, subtoxic dosing conditions.

Animals↗
PubMed1992

Salmonella mutagenicity tests: V. Results from the testing of 311 chemicals.

311 chemicals were tested under code, for mutagenicity, in Salmonella typhimurium; 35 of the chemicals were tested more than once in the same or different laboratories. The tests were conducted using a preincubation protocol in the absence of exogenous metabolic activation, and in the presence of liver S-9 from Aroclor-induced male Sprague-Dawley rats and Syrian hamsters. Some of the volatile chemicals were also tested in desiccators. A total of 120 chemicals were mutagenic or weakly mutagenic, 3 were judged questionable, and 172 were non-mutagenic. The remaining 16 chemicals produced different responses in the two or three laboratories in which they were tested. The results and data from these tests are presented.

Animals↗
PubMed1992

The role of glutathione in the bacterial mutagenicity of vapour phase dichloromethane.

Dichloromethane (DCM) vapour by inhalation is carcinogenic to rodents and is an in vivo rodent cell clastogen and a bacterial mutagen. It has been suggested that the bacterial mutagenicity of DCM is mediated by glutathione (GSH) conjugation. The involvement of endogenous and exogenous GSH in the conversion of DCM to a bacterial mutagen has been studied in a vapour phase protocol using wild-type and GSH-deficient (NG54; gsh) Salmonella typhimurium TA100 strains in the presence and absence of various rat liver fractions. The effect of the duration of exposure was also investigated in these Salmonella strains and in E. coli WP2 uvrA pKM101. Dose- and time-related increases in revertants occurred with all metabolic activation systems used (without exogenous metabolic activation; with Aroclor-induced rat liver S9, microsomes, or cytosol fractions), with minor quantitative differences among the 3 strains. Mutagenicity was marginally highest in the presence of cytosol at the highest DCM concentrations. Strain NG54 gsh, which contains approximately 25% of the TA100 level of GSH/microgram protein, was slightly less responsive to DCM-induced mutagenicity than TA100. Addition of 0.33 mumoles/plate of GSH had little effect on the mutagenic responses of TA100 or NG54 in the presence or absence of S9. In these 2 strains, exogenous S9 produced small increases in mutagenicity at the highest concentrations of DCM (2 and 4% v/v). These results suggest that if an interaction between DCM and GSH is required for the activation of DCM to a bacterial mutagen, it occurs at low levels of endogenous GSH and is not significantly affected by GSH supplementation.

Animals↗
PubMed1992

Fast Fluorescence Quenching from Isolated Guard Cell Chloroplasts of Vicia faba Is Induced by Blue Light and Not by Red Light.

Chlorophyll a fluorescence transients from isolated Vicia faba guard cell chloroplasts were used to probe the response of these organelles to light quality. Guard cell chloroplasts were isolated from protoplasts by passing them through a 10-mum nylon net. Intact chloroplasts were purified on a Percoll gradient. Chlorophyll a fluorescence transients induced by actinic red or blue light were measured with a fluorometer equipped with a measuring beam. Actinic red light induced a monophasic quenching, and transients induced by blue light showed biphasic kinetics having a slow and a fast component. The difference between the red and blue light-induced transients could be observed over a range of fluence rates tested (200-800 mumol m(-2) s(-1)). The threshold fluence rate of blue light for the induction of the fast component of quenching was 200 mumol m(-2) s(-1), but in the presence of saturating red light, fluence rates as low as 25 mumol m(-2) s(-1) induced the fast quenching. These results indicate that guard cell chloroplasts have a specific response to blue light.

Journal Article↗
PubMed1992

Vanadate inhibits blue light-stimulated swelling of vicia guard cell protoplasts.

When supplied under low chloride concentrations, vanadate inhibits the blue light-stimulated swelling of Vicia faba L. guard cell protoplasts in a dose-dependent fashion. The volume of guard cell protoplasts incubated in 10 mm K-imino-diacetic acid, 0.4 m mannitol, and 1 mm CaCl(2) remained essentially constant under 1000 mumol m(-2) s(-1) red light, but increased an average of 27% after 8 min of the addition of 50 mumol m(-2) s(-1) blue light to the background red light. At 500 mum, vanadate completely inhibits the response to blue light. Vanadate also inhibits the swelling of guard cell protoplasts stimulated by the H(+)-ATPase agonist fusicoccin. The vanadate sensitivity of the blue light-stimulated swelling implicates a proton-pumping ATPase as a component of the sensory transduction of blue light in guard cells.

Journal Article↗
PubMed1991

Blue light-modulation of chlorophyll a fluorescence transients in guard cell chloroplasts.

Chlorophyll a fluorescence transients from mesophyll and single guard cell pairs of Vicia faba were measured by microspectrofluorometry. In both chloroplast types, fluorescence induction (O to P) was similar under actinic blue and green light. In slow transients from mesophyll cell chloroplasts, blue and green light induced identical, typical rapid quenching from P to S, and the M peak. In contrast, the P to S transient from guard cell (GC) chloroplasts irradiated with blue light showed a much slower quenching rate, and the P to T transition showed no M peak. Actinic green light induced mesophyll-like transients in GC chloroplasts, including rapid quenching from P to S and the M peak. Detection of these transients in single pairs of GC and isolated protoplasts ruled out mesophyll contamination as a signal source. Green light induced a rapid quenching and the M peak in GC chloroplasts from several species. The effect of CO(2) concentration on the fluorescence transients was investigated in the presence of HCO(3) (-) at pH 6.8 and 10.0. In transients induced by green light in both chloroplast types, a pH increase concomitant with a reduction in CO(2) concentration caused an increase in the initial rate of quenching and the elimination of the M peak. Actinic blue light induced mesophyll-like transients from GC chloroplasts in the presence of 10 micromolar KCN, a concentration at which the blue light-induced stomatal opening is inhibited. Addition of 100 to 200 micromolar phosphate also caused large increases in fluorescence quenching rates and a M peak. These results indicate that blue light modulates photosynthetic activity in GC chloroplasts. This blue light effect is not observed in the absence of transduction events connected with the blue light response and in the presence of high phosphate concentrations.

Journal Article↗
PubMed1991

Enhanced Photosynthesis and Stomatal Conductance of Pima Cotton (Gossypium barbadense L.) Bred for Increased Yield.

Yield of Pima cotton (Gossypium barbadense L.) has tripled over the last 40 years with the development of new cultivars. Six genetic lines representing successive stages in the breeding process (one primitive noncultivated accession, four cultivars with release dates from 1949 to 1983, and one unreleased breeding line) were grown in a greenhouse, and their gas exchange properties were compared. Among the cultivated types, genetic advances were closely associated with increasing single-leaf photosynthetic rate (A) and stomatal conductance (g(s)), especially in the morning. The A and g(s) of the primitive line approached those of the cultivated types early in the morning, but were much lower for the rest of the day. In both morning and afternoon, A was correlated with g(s) across genotypes but was not correlated with leaf thickness, concentrations of chlorophyll or starch, or intercellular CO(2) concentration (c(i)). In the oldest cultivar, the relationship of A to c(i) did not change between morning and afternoon. In the two most recent lines, the slopes of the A:c(i) curves at limiting c(i) exceeded that of the oldest cultivar by 25 to 50% in the morning, but the differences were much smaller in the afternoon. The maximum A of the newer lines at high c(i) exceeded that of the oldest cultivar only in the morning. Breeding for increasing yield has enhanced the photosynthetic capacity and stomatal conductance of Pima cotton and altered the diurnal regulation of photosynthesis.

Journal Article↗
PubMed1990

Cytogenetic analyses of mice exposed to dichloromethane.

Chromosome damage was studied in female B6C3F1 mice exposed to dichloromethane (DCM) by subcutaneous or inhalation treatments. No increase in the frequency of either sister chromatid exchanges (SCEs) or chromosome aberrations (CAs) in bone marrow cells was observed after a single subcutaneous injection of 2,500 or 5,000 mg/kg DCM. Inhalation exposure to DCM for 10 days at concentrations of 4,000 or 8,000 ppm resulted in significant increases in frequencies of SCEs in lung cells and peripheral blood lymphocytes, CAs in lung and bone marrow cells, and micronuclei (MN) in peripheral blood erythrocytes. Lung cell CAs and blood erythrocyte MN reached frequencies of approximately two times control levels. Following a 3-month inhalation exposure to 2,000 ppm DCM, mice showed small but significant increases in lung cell SCEs and peripheral blood erythrocyte MN. These findings suggest that genotoxicity may play a role in the carcinogenicity of DCM in the lungs of B6C3F1 female mice.

Administration, Inhalation↗
PubMed1990

Chromosome aberration and sister chromatid exchange tests in Chinese hamster ovary cells in vitro. V: Results with 46 chemicals.

Forty-six coded chemicals were tested for their ability to induce sister chromatid exchanges (SCEs) and chromosomal aberrations (ABs) in cultured Chinese hamster ovary (CHO) cells using a standard protocol with and without exogenous metabolic activation. Sixteen chemicals were negative and 15 were positive in both assays; 15 were positive for SCEs only (one chemical that was positive for SCEs was equivocal for ABs), and no chemicals induced ABs only. The effect of cell harvest time on the ability to detect the induction of ABs was examined for 18 chemicals. Seven chemicals produced a positive response using both standard and extended harvest times, five were positive only using an extended harvest time, and six were negative using both harvest times. The relationship between cell cycle delay and SCE induction was also examined, and the two appear to be unrelated.

Animals↗
PubMed1990

Evaluation of four in vitro genetic toxicity tests for predicting rodent carcinogenicity: confirmation of earlier results with 41 additional chemicals.

The effectiveness of four in vitro short-term tests (STT) for genetic toxicity, induction of mutations in Salmonella (SAL) and mouse lymphoma L5178Y cells (MLA), and induction of sister chromatid exchanges (SCE) and chromosome aberrations (ABS) in Chinese hamster ovary cells that are used for predicting rodent carcinogenicity were examined. The in vitro results were compared with the results from 41 rodent carcinogenicity studies performed by the National Toxicology Program. The predictive values of, and interrelationships among, the STT for these 41 chemicals were similar to those previously reported for 73 chemicals and confirm those earlier results [Tennant RW, Margolin BH, Shelby MD, Zeiger E, Haseman JK, Spalding J, Caspary W, Resnick M, Stasiewicz S, Anderson B, Minor R (1987): Science 236:933-941]. Because of this similarity among the two datasets, the chemicals were combined into a single dataset of 114. The results with 114 chemicals show that SAL had the lowest sensitivity (.48) and the highest specificity (.91), whereas MLA had the highest sensitivity (.72) and the lowest specificity (.40). The concordances of the test results with rodent carcinogenicity were .66, .61, .59, and .59, for SAL, ABS, SCE, and MLA, respectively. Salmonella was the most predictive for carcinogenicity; 89% of the chemicals mutagenic in SAL were carcinogenic in rodents, however a negative result in any or all of the STT was not indicative of noncarcinogenicity. The STT results reported here show good agreement with the potential electrophilicity of the chemicals, and the majority of carcinogens that are undetected by the STT do not have an electrophilic structure. There was no complementarity among the tests and no combination of the four tests was more effective than any single test for predicting carcinogenicity.

Animals↗
PubMed1990

Mutagenicity of 42 chemicals in Salmonella.

The mutagenicity results and data for 42 chemicals are reported. All chemicals were tested using the Salmonella/microsome assay preincubation protocol, and four were also tested using vapor phase exposure in a desiccator. These comprise the chemicals studied in the update of the National Toxicology Program's evaluation of the efficacy of in vitro short-term tests for detecting carcinogens and noncarcinogens.

Molecular Structure↗
PubMed1990

Chromosome aberration and sister chromatid exchange test results with 42 chemicals.

Forty-two chemicals were tested for their ability to induce cytogenetic change in Chinese hamster ovary cells using assays for chromosome aberrations (ABS) and sister chromatid exchanges (SCE). These chemicals were included in the National Toxicology Program's evaluation of the ability of four in vitro short-term genetic toxicity assays to distinguish between rodent carcinogens and noncarcinogens. The conclusions of this comparison are presented in Zeiger et al. [Zeiger E, Haseman JK, Shelby MD, Margolin BH, Tennant RW (1990): [Environ Molec Mutagen 16(Suppl 18): 1-14]. The in vitro cytogenetic testing was conducted at four laboratories, each using a standard protocol to evaluate coded chemicals with and without exogenous metabolic activation. Most chemicals were tested in a single laboratory; however, two chemicals, tribromomethane and p-chloroaniline, were tested at two laboratories as part of an interlaboratory comparison. Four chemicals (C.I. basic red 9 HCl, 2-mercaptobenzothiazole, oxytetracycline HCl, and rotenone) were tested for SCE in one laboratory and in a different laboratory for ABS. Tetrakis(hydroxymethyl)phosphonium sulfate was tested at one laboratory and the chloride form was tested at a different laboratory. Twenty-five of the 42 chemicals tested induced SCE. Sixteen of these also induced ABS; all chemicals that induced ABS also induced SCE. There was approximately 79% reproducibility of results in repeat tests, thus, we conclude that this protocol is effective and reproducible in detecting ABS and SCE.

Animals↗
PubMed1990

Autoxidation and mutagenicity of sodium bisulfite.

An inverse correlation exists between the autoxidation of bisulfite and its mutagenicity in Salmonella. Temperature, pH, and the addition of mannitol, ethanol, or Oxoid broth affect both autoxidation and mutagenicity. A decrease in autoxidation resulted in an increase in the half-life of the parent compound, bisulfite, and its availability for uptake by the cells, leading to increased mutagenesis. The autoxidation of bisulfite is known to produce both sulfur- and oxygen-centered free radicals. The lack of mutagenicity of ammonium persulfate and peroxymonosulfate, which generate the radicals SO4- and SO5-, respectively, argues against the involvement of these oxygen-centered radicals in bisulfite mutagenesis. Inhibition of mutagenesis by the radical spin-trapping agent, DMPO, is consistent with the hypothesis that the sulfur-centered radical, SO3-, plays an important role in bisulfite mutagenesis. The mechanism of bisulfite mutagenesis suggested in this study may have relevance to other known effects attributed to bisulfite, i.e., co-carcinogenesis and immune hypersensitivity.

Ammonium Sulfate↗
PubMed1990

A comparison of chromosome aberration induction by 25 compounds tested by two Chinese hamster cell (CHL and CHO) systems in culture.

Twenty-five chemicals were tested for the induction of chromosomal aberrations in 2 cultured mammalian cell systems, Chinese hamster lung cells (CHL) and Chinese hamster ovary cells (CHO). This study was carried out to provide a data set that would permit an assessment of the extent to which the 2 systems agree in the results produced. Results presented for the 2 systems in this paper are not based on the same criteria but rather on the criteria standardly used in each of the systems. In tests conducted in the absence of S9 mix, 7 chemicals gave positive results in both systems and 12 were negative in both. In tests with S9 mix, 5 were positive in both systems and 9 were negative in both. When the overall results including tests both with and without S9 mix were considered, the 2 systems agreed on 15 results, 11 positives and 4 negatives. A review of the test conditions and data suggests that disagreements in test results were more often due to differences in the protocols used in these 2 systems than to a difference in the sensitivities of the 2 cell lines.

Animals↗
PubMed1990

Effects of Salmonella genotypes and testing protocols on H2O2-induced mutation.

Hydrogen peroxide (H2O2) was shown to be mutagenic in a number of strains of Salmonella typhimurium. Strain SB1106p (hisC3108, hisO1242, pKM101), a newly-constructed strain carrying the histidine mutation at a UGA chain-terminating codon, was more responsive to H2O2 than TA104 or TA102, the two hisG428 strains originally developed for detecting oxidative mutagens. The largest proportional increase in revertants of strain TA104 was in the fraction of intragenic deletions. Three other strains (TA97, SB1111 and SB1106) gave unequivocal positive responses to H2O2 in both the liquid pre-incubation procedure and standard plate incorporation procedure. The response of TA100 varied among experiments, ranging from negative to a weak positive. Variations in the catalase content among the tester strains did not correlate with the relative responses obtained in the mutagenicity assays.

Codon↗