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Biomedical subjects

J W Allen

Publications and source records attributed to J W Allen.

At least 145 records · Page 8Linked to original sources
PubMed1988

A cytogenetic comparison of the responses of mouse and human peripheral blood lymphocytes to 60Co gamma radiation.

Experiments were conducted to compare the chromosome damaging effects of 60Co gamma radiation on mouse and human peripheral blood lymphocytes (PBLs). Either whole blood or isolated and pelleted mononuclear leucocytes (MNLs) were irradiated with a 60Co unit to yield exposures of 1, 2, 3, or 4 Gy. In addition, mice were whole-body irradiated in vivo with the same doses so that an in vitro-in vivo comparison could be made. The results indicate that mouse PBLs irradiated in whole blood, whether in vivo or in vitro, respond similarly to 60Co gamma rays as measured by dicentric chromosome formation. In addition, mouse and human PBLs showed a similar radiosensitivity, but because the mouse PBL data were best fitted to an exponential function and the human PBL data to a quadratic function, direct comparisons were difficult to make. Pelleted MNLs from mice were much less sensitive to the clastogenic effects of gamma radiation than whole blood. This is believed to be due to hypoxic conditions that developed during irradiation and transport. Human PBLs did not show a marked difference whether irradiated in whole blood or as pelleted MNLs in tissue culture medium.

Adult↗
PubMed1987

Relationships between benzo(a)pyrene-DNA adduct levels and genotoxic effects in mammalian cells.

The effectiveness of benzo(a)pyrene [B(a)P]-DNA binding as an internal dosimeter was evaluated. Data were obtained from concurrent studies, measuring B(a)P induced genotoxic effects and DNA adducts in several short-term bioassay systems: cytotoxicity, gene mutation, and sister chromatid exchange in Chinese hamster V79 cells; cytotoxicity, gene mutation, and chromosome aberrations in mouse lymphoma L5178Y TK+/-; cytotoxicity and enhanced virus transformation in Syrian hamster embryo cells; and cytotoxicity and morphological transformation in C3H10T1/2CL8 mouse embryo fibroblasts. Both total B(a)P-DNA binding and specific B(a)P-DNA adducts were measured. N2-(10 beta-[7 beta,8 alpha,9 alpha-trihydroxy-7,8,9,10-tetrahydrobenzo(a)pyrene]yl)deoxyguanosine [BPDE I-dGuo] was one of the major adducts identified in all bioassay systems. DNA binding and genotoxic responses varied significantly between bioassays. Each genetic end point was induced with a differing efficiency on a per adduct basis. However, the relationships between frequency of genetic effect or morphological transformation and B(a)P-DNA binding or BPDE I-dGuo were linear within a given assay. In order to compare biological end points of diverse frequencies in diverse biological systems, a doubling adduct level, expressed as the number of BPDE I-dGuo adducts per unit of DNA required to double the induced frequency of biological response, was applied to the data.

Animals↗
PubMed1987

Sister chromatid exchange analysis in lung and peripheral blood lymphocytes of mice exposed to methyl isocyanate by inhalation.

Mice were exposed to 1, 3, or 6 ppm methyl isocyanate (MIC) for 6 hr/day for four consecutive days. Lung cells and peripheral blood lymphocytes (PBLs) were removed and cultured for analysis of sister chromatid exchange (SCE) and cell cycle kinetics. MIC caused a small but significant increase in SCE frequency of cultured lung cells from mice exposed to 1, 3, or 6 ppm MIC. MIC did not significantly increase SCE levels in PBLs of mice exposed to concentrations as high as 6 ppm. In cultured PBLs, MIC had a stimulatory effect on cell cycling rates as measured by the replicative index, and it caused a significant reduction in mononuclear leucocyte counts and the mitotic indices.

Administration, Inhalation↗
PubMed1987

Diaziquone-induced micronuclei in cytochalasin B-blocked mouse peripheral blood lymphocytes.

A mouse peripheral blood lymphocyte (PBL) micronucleus (MN) test was developed using a modification of the technique for assessing MN in human PBLs described by Fenech and Morley (1985). Male C57Bl/6 mice (5/dose) were injected i.p. with either 0, 2.5, 5.0, 7.5, or 10.0 mg diaziquone (AZQ)/kg. After 24 h the mice were bled by cardiac puncture, PBLs were isolated on a Ficoll-density gradient and then cultured in RPMI 1640 medium using 8 micrograms phytohemagglutinin/ml. In some cultures cytochalasin B (CYB) was added at 21 h during the medium change to block cytokinesis. In other cultures, CYB was omitted to compare the sensitivity of analyzing MN in binucleate versus unblocked mononucleate cells. All doses of AZQ yielded significant increases in MN-containing binucleated PBLs. The use of CYB in the mouse PBL MN test increased the sensitivity approximately 3-fold. The MN test in mouse PBLs should be useful in comparative cytogenetic studies of mice and humans.

Animals↗
PubMed1987

Synaptonemal complex damage as a measure of chemical mutagen effects on mammalian germ cells.

As heritable chromosome anomalies are implicated in a variety of human disabilities, their induction in germ cells by environmental chemicals is viewed as a threat to health (National Research Council, 1982; Hook, 1983). Synaptonemal complex (SC) analysis is a novel approach for the detection of germ-line chromosomal damage. This sensitive cytological procedure reveals induced structural damage and pairing abnormalities in SCs of meiotic prophase chromosomes, together with other germ-line toxic effects, in the testes of rodents treated with mitomycin C and cyclophosphamide. Our results demonstrate the effectiveness of SC analysis as a rapid and practical in vivo germ-line mutagen assay that lacks many of the short-comings of existing tests.

Animals↗
PubMed1987

Results of in vitro and in vivo genetic toxicity tests on methyl isocyanate.

Methyl isocyanate (MIC) was tested for genetic toxicity in a variety of in vitro and in vivo assays. Negative results were obtained in the Salmonella/mammalian microsome assay using five bacterial strains in a preincubation protocol. The Drosophila sex-linked recessive lethal test also gave negative results in studies that involved three routes of administration: inhalation, feeding, and injection. Positive results were obtained for three endpoints in cultured mammalian cells. Reproducible, dose-related increases in trifluorothymidine-resistant clones were induced in L5178Y mouse lymphoma cells, and the frequencies of both SCE and chromosomal aberrations increased in Chinese hamster ovary cells. These effects were independent of exogenous metabolism. In mice exposed to methyl isocyanate by inhalation, cytogenetic analyses were carried out on bone marrow, blood, and lung cells. A single, 2-hr exposure to concentrations of 0, 3, 10, and 30 ppm MIC produced no evidence of chromosomal effects in the bone marrow, although significant cell cycle delay was observed. In four experiments involving exposures on 4 consecutive days to 0, 1, 3, or 6 ppm, delays in bone marrow cell cycle were again observed. Increases in SCE and chromosomal aberrations were observed in bone marrow cells, and a dose-related increase in SCE occurred in lung cells but not in peripheral blood lymphocytes. A significant increase in micronucleated polychromatic erythrocytes in the peripheral blood was observed in male mice in one experiment. From these results, it appears that methyl isocyanate has the capacity to affect chromosome structure but not to induce gene mutations.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Sister chromatid exchange and chromosome aberration analyses in mice after in vivo exposure to acrylonitrile, styrene, or butadiene monoxide.

The use of polymers in plastic and rubber products has generated concern that monomers potentially active in biological systems may be eluted from these substances. We have evaluated two such monomers, acrylonitrile and styrene, for the induction of chromosome damage in mice. Butadiene monoxide, a presumed metabolite of a third important monomer, 1,3-butadiene, was also tested. These chemicals were administered as a single intraperitoneal injection; sister chromatid exchanges and chromosome aberrations were analyzed in bone marrow cells. Acrylonitrile and styrene were largely negative for these endpoints when tested at doses ranging to 60 mg/kg and 1,000 mg/kg, respectively. Butadiene monoxide, which previously has not been tested in a mammalian system, was determined to be a very effective inducer of sister chromatid exchanges and chromosome aberrations. Both endpoints showed a clear dose response and a greater than ten-fold increase over control levels at high doses. These studies represent an initial step in our efforts to evaluate genetic risk associated with exposure to common polymeric chemicals.

Acrylonitrile↗
PubMed1986

Sister chromatid exchange analysis in cultured primary lung, liver, and kidney cells of mice following in vivo exposure to vinyl carbamate.

Methods are described for the short-term culture (48 to 56 h) of lung, liver, and kidney cells from C57B1/6 mice. With these techniques, mice can be exposed in vivo to test compounds and the cells grown on cover glasses in the presence of 5-bromo-2'-deoxyuridine (BrdUrd) (5 microM) for analysis of sister chromatid exchange (SCE) and cell cycle kinetics. Mice exposed to vinyl carbamate (VC) ((10 to 60 mg/kg) by i.p. injection were used in the initial examination of this system. Cultured lung and kidney cells from exposed animals (60 mg/kg) exhibited significant increases in SCE frequencies (approximately 3 to 5 times baseline); however, liver cells were much less responsive and showed less than a twofold increase over baseline SCE levels. Lung cultures initiated as long as 320 h after VC exposure (60 mg/kg) revealed a persistence of lesions leading to the formation of SCEs in vitro. This methodology permits analysis of cytogenetic damage in organs with very low mitotic activity after in vivo exposure to known or suspected genotoxicants.

Animals↗
PubMed1986

Rat and hamster hepatocyte-mediated induction of SCEs and mutation in V79 cells and mutation of salmonella by aminofluorene and dimethylnitrosamine.

Aminofluorene (AF) and dimethylnitrosamine (DMN) were examined for their ability to induce multiple genetic endpoints after rat and hamster hepatocyte metabolic activation. The endpoints measured included mutations at the Na+/K+-ATPase (ouabain resistance) and hypoxanthine-guanine-phosphoribosyltransferase (6-thioguanine resistance) loci, and sister-chromatid exchanges (SCEs) in Chinese hamster V79 cells, and mutation of Salmonella typhimurium strains TA98 and TA100. AF, with rat and hamster hepatocyte activation, induced only low levels of mutations at either loci in V79 cells but did induce SCEs. Mutation of Salmonella by AF after hepatocyte activation also occurred and was a sensitive endpoint for detecting this aromatic amine. DMN induced high levels of mutations at both loci in V79 cells in addition to SCEs in the presence of hepatocytes from both species. DMN was also mutagenic to Salmonella, but only with hamster hepatocytes. Salmonella did not respond as strongly to DMN as the V70 cells. Hamster hepatocytes were more active than rat hepatocytes in activating both carcinogens. The results indicate the variable sensitivity of the genetic endpoints and species differences in activation for two potent chemical carcinogens.

Animals↗
PubMed1986

Genotoxicity studies of benz[l]aceanthrylene.

The genotoxicity of the cyclopenta-fused polycyclic aromatic hydrocarbon, benz[l]aceanthrylene (B[l]A), was evaluated in vitro using the L5178Y/TK+/- mouse lymphoma assay and in vivo using the mouse peripheral blood lymphocyte (PBL) culture system. The mutagenicity and sister chromatid exchange (SCE) inducing potential of B[l]A was then compared to that of benzo[a]pyrene (B[a]P). B[l]A appeared to be slightly less mutagenic than B[a]P at the TK locus, and each compound produced both small and large colony mutants indicating that they are clastogenic as well as mutagenic. Gross chromosome aberration analysis of treated L5178Y/TK+/- mouse lymphoma cells confirmed the clastogenicity of B[l]A in vitro. In the mouse PBL system, after administration by gavage, B[l]A was more cytotoxic and produced a sharper elevation in SCE frequency than B[a]P.

Animals↗
PubMed1986

Tumorigenesis and genotoxicity of ethyl carbamate and vinyl carbamate in rodent cells.

Vinyl carbamate (VC) is a suspect metabolic intermediate in ethyl carbamate (EC) carcinogenesis. In the present studies, EC and VC were evaluated for their relative abilities to induce adenomas and sister chromatid exchanges (SCEs) in lung cells of A/J, C3HeB/FeJ, and C57BL/6J strain mice. For both end points, animals were administered a single i.p. injection of the test chemical. Percentage of mice with adenomas and number of adenomas per mouse were compared among the three strains 24 weeks following exposure to EC or VC. Although the relative order of strain sensitivity was the same for both chemicals: A/J greater than C57BL/6J greater than C3HeB/FeJ, VC was much more potent than EC. For SCE analysis of primary lung cells cultured from treated animals, EC and VC showed potency differences similar to those observed for tumorigenesis. All three mouse strains revealed significant dose-dependent increases in SCE frequency. However, there was no strain specificity for this effect. SCE persistence over time was also compared in treated A/J and C57BL/6J mice. Although EC- and VC-induced SCE frequencies declined over a 2-week observation period, again, there was no strain specificity for this effect. VC was also tested for enhancement of SA7 virus transformation of Syrian hamster embryo cells. Significant concentration-dependent increases in cell transformation frequency were observed.

Animals↗
PubMed1985

Investigation of possible age effects on meiotic chromosomal recombination and segregation in Armenian hamster spermatocytes.

Male Armenian hamsters were evaluated for age effects upon meiotic recombination and aneuploidy incidence. Primary spermatocytes from young and old animals revealed similar chiasma frequencies. The incidence of terminal-type chiasmata in sex bivalents was also measured and found to be unaffected by age. Percentages of univalents and of hyperploid metaphase II cells were evaluated by chromosome groups based upon individual chromosome morphologies. Regardless of age, the larger dichiasmate chromosomes were seldom observed as univalents, or as extra chromosomes in hyperploid cells. The monochiasmate small autosomes and sex chromosomes revealed univalent frequencies approximating to 5.5-6.5% in animals from both age groups. However, only the small autosomes appeared to be significantly implicated in hyperploidy. Although still a rare event, metaphase II hyperploidy was significantly increased in older animals (0.9% incidence in young and 2.4% in old hamsters). The events leading to higher aneuploidy levels in older male Armenian hamsters are not clear. A role for reduced meiotic recombination as a function of age cannot be ruled out in the present study. However, there was no support for this hypothesis, and consideration of other possible mechanisms of age effects to increase aneuploidy levels is indicated.

Aging↗
PubMed1984

Sister chromatid exchanges in mammalian meiotic chromosomes.

Meiotic cells have been, and remain, a relatively difficult tissue in which to study SCEs. Experimental evaluations have had to contend with various problems unique to germ cells, i.e., poor in vitro growth, unusual cytotoxicities (from BrdUrd), trying chromosome morphologies, and confusion between chromosome label patterns generated by SCEs, COs, and replication kinetics. Nevertheless, BrdUrd differential staining techniques in insects and rodents have progressed to the point where SCE frequencies can be reliably determined. In the described Armenian hamster system, SCEs may be directly resolved in selected primary spermatocyte bivalents and indirectly assessed in secondary spermatocyte cells. SCE frequencies determined from spermatogonial, primary spermatocyte, and secondary spermatocyte cells are in good agreement. The system should be applicable for studies of possible mechanistic similarities between SCE and CO exchange, and for evaluating genotoxic effects. Experimental evidence in Drosophila (33) argues against a very close molecular relationship between these forms of breakage and recombination. However, it is likely that new information can be gained from cells in which normal SCE and CO frequencies and distributions can be characterized, and from studies of the consequences to these events after various mutagenic perturbations to premeiotic and meiotic DNA.

Animals↗
PubMed1984

Rodent species and strain specificities for sister-chromatid exchange induction and gene mutagenesis effects from ethyl carbamate, ethyl N-hydroxycarbamate, and vinyl carbamate.

Ethyl carbamate (EC) and two related carcinogens, ethyl N-hydroxycarbamate (ENHC) and vinyl carbamate (VC), caused species-specific increases in sister-chromatid exchange (SCE) formation in the bone marrow cells of rodents. Mice exposed to 400 mg/kg of EC had SCE increases of 6-times-baseline, while rats, Chinese hamsters, and golden hamsters showed 3- to 4-times-baseline increases in response to this dose. Lesser, but still significant, differences were found for ENHC and VC; the severest effects consistently occurred in mice. Control bone marrow cell-cycle kinetics among the rodent species were similar. Mouse strains A and C57BL/6, which have high and low susceptibilities to EC induction of lung adenomas, respectively, showed nearly identical levels of SCE induction after in vivo exposure to these carbamates. However, testing of VC, a possible metabolite of EC, in vitro revealed strain-dependent liver enzyme (Aroclor-induced S-9 fraction) capabilities to convert VC to genotoxic products. SCE induction, gene mutation for 6-thioguanine and ouabain resistance, and cytotoxicity in Chinese hamster V79 cells were significantly greater when A strain S-9 enzymes were used as compared with C57BL/6 strain S-9 enzyme preparations. No effect on SCE of reseeding, compared with no reseeding, of VC-treated V79 cells was observed. At a concentration of 25 micrograms/ml, VC caused 6-times-baseline induction of SCE in the presence of A strain S-9 mix and 4-times-baseline induction in the presence of C57BL/6 strain S-9 mix. These in vitro strain-dependent patterns of response are relevant to the current theory that VC may be a proximate carcinogenic metabolite of EC.

Animals↗