Biomedical subjects

C J Sheu

Publications and source records attributed to C J Sheu.

8 recordsLinked to original sources

PubMed1991

The use of uninduced rat liver S-9 to supplement BALB/3T3 cells in the in vitro transformation assay.

Because of limited inherent capacity to metabolize chemicals to their reactive form, the BALB/3T3 transformation assay using clone A31-1-1 cells requires metabolic supplementation with rodent liver homogenate preparations (S-9). Activation by S-9 is limited, however, by its cytotoxicity to the cells, thus necessitating a reduction in treatment time from the usual 24-72 to 1-4 hr. With cyclophosphamide (CP) as a test chemical, we were able to increase the treatment time to 24 hr by using lower concentrations of cofactors and S-9 prepared from the livers of untreated rats. Statistically significant increases in transformed foci were induced in cultures treated with 50 or 100 micrograms CP/ml in the presence of 100 or 200 micrograms of uninduced rat liver S-9/ml and 76 or 380 micrograms each of NADH, NADP, NADPH, and glucose-6-phosphate per ml of incubation medium.

Animals↗

PubMed1987

A guide for mutagenicity testing using the dominant lethal assay.

The dominant lethal assay has been used and continues to be used to provide information about the effects of chemicals on the gonadal cells of male animals. Guidelines for conducting this test are useful but as with any guideline scientists should avoid interpreting them as protocols. Thus this document is a general approach to dominant lethal testing and should be used in conjunction with other available protocols and procedures.

Animals↗

PubMed1985

Current status of bioassays in genetic toxicology--the dominant lethal assay. A report of the U.S. Environmental Protection Agency Gene-Tox Program.

The term dominant lethal may be defined as death of the heterozygote arising through multiple chromosomal breaks. The assay is generally conducted by treating male animals, usually mice or rats, acutely (1 dose), subacutely (5 doses), or over the entire period of spermatogenesis. Animals treated acutely or subacutely are mated at weekly intervals to females for a sufficient number of weeks to cover the period of spermatogenesis. Those treated for the entire spermatogenic cycle are mated for 1 or 2 successive weeks at the termination of treatment. Females usually are killed at 14 days of pregnancy and examined for the number of total implantations in the uterus, the number of implantations classified as early deaths, and, in some cases, the number of corpora lutea. The category of early death is the most significant index of dominant lethality. A total of 249 papers were reviewed and 140 chemicals were evaluated. Of the 140 chemicals, 65 were positive by the criteria used by the Work Group in evaluating each publication. The category of "positive" includes those responses of a borderline nature. 99 chemicals were declared negative. There is considerable overlap of chemicals in both categories, which accounts for the incongruity in the total number of chemicals tested and the number considered positive and negative. A total of 44 animal carcinogens have been tested in the dominant lethal assay, 26 of which were positive and 18 negative for a correlation of 59%. The role of the assay should be that of confirming positive results from lower tier chromosomal aberration-detecting systems (confirming in the sense of indicating the ability of the chemical to penetrate gonadal tissue and to produce cytogenetic damage). The dominant lethal assay should not be used as a risk assessment method.

Animals↗

PubMed1983

A comparison of fertility assessment and cytogenetic analysis for the detection of translocation heterozygotes in CD-1 mice.

A comparison of the fertility and cytogenetic analyses and the combination of both techniques as generally used in the heritable translocation assay was conducted with triethylenemelamine (TEM). CD-1 mice were used as the F0 generation and were divided into two groups that received i.p. either distilled water (control) or TEM at 0.15-0.20 mg/kg. A total of 226 F1 males were generated (125 control, 101 TEM group) and were subjected to both sequential fertility assessment and direct cytogenetic analysis. A litter size of 10 was used for the fertility assessment method and 25 cells per animal were scored for the direct cytogenetic analysis; 20 animals were initially identified as translocation carriers based on the fertility analysis and 16 animals were identified by cytogenetic analysis. When these data were compared and the discrepancies resolved, each method separately identified 16 translocation carriers (15 animals common to both methods). With the combination of data for both techniques, as is done in the heritable translocation assay, a total of 17 translocation heterozygotes were identified. Use of either the fertility method alone or the cytogenetic method as routinely used would have resulted in the separate identification of 16 translocation carriers per procedure, with each method failing to identify one carrier.

Animals↗

PubMed1983

Detection of dominant lethal mutation in mice after repeated low-dose administration of 6-mercaptopurine.

Detection of dominant lethality after repeated low-dose administration was investigated, using the base analog 6-mercaptopurine (6-MP). The compound was administered to groups of 30 outbred CD-1 male mice by i.p. injection at dosage levels of 12.5, 25.0, or 50.0 mg/kg/day 5 days a week for 8 weeks. At the end of treatment, each male was cohoused for 1 week with two untreated females of different strains: one CD-1 and one (C3H x C57BL/10)F1. Negative (solvent) and positive (triethylenemelamine, TEM) control groups were included. Implant data were analyzed statistically. Exposure of male mice to 6-MP at 50 mg/kg/day resulted in 93% mortality and severe weight loss of the survivors. Body weights were also reduced in the group given 25 mg/kg/day. At the lowest dose level of 12.5 mg/kg/day, 6-MP had no noticeable toxic effect on the treated males. Dominant lethal analysis of the implant data showed that a statistically significant increase in dead implantations was induced in CD-1 but not in (C3H x C57BL/10)F1 females. The dominant lethal effect of TEM, the positive control, was detected in both strains of females tested.

Animals↗

PubMed1980

Heritable translocation test in mice.

The status of the heritable-translocation test in mice with respect to its usefulness in practical testing was evaluated by using information available in the open literature. A total of 47 reports were evaluated; 29 were judged to contain adequate information to classify whether or not a given chemical induced heritable translocations. Heritable-translocation data were available for 32 compounds; data were not adequate for 15 compounds. Of the remaining 17 compounds, clear-cut determination of positive or negative effects was made for 14 compounds, while data for 3 compounds were only suggestive of either negative or positive effects. 10 chemicals have been shown to induce heritable translocations. These chemicals are either direct or indirect alkylating agents. The heritable-translocation test needs to be improved before it can be used in wide-scale practical testing. The most important question is whether or not historical controls can be used in tests for significance; the cost of concurrent controls is prohibitive. There is a need to standardize methods used in testing laboratories with respect to the size of error involved in classifying translocation heterozygotes and the power of the test. There is also a need to study in the effectiveness of non-alkylating clastogens in inducing heritable translocations in mice.

Animals↗

PubMed1979

Dominant lethal assay of some hair-dye components in random-bred male rats.

Male rats were exposed to maximally tolerated doses of 5 hair-dye components in a dominant lethal test. Each component was tested at 3 dosage levels with 15 random-bred male rats per level. The highest dose, selected on the basis of subacute toxicity testing, generally reduced weight gains without being lethal. Freshly prepared solutions were injected i.p. at 1 ml/kg 3 times a week for 10 weeks. Rats injected with dimethylsulfoxide and triethylenemelamine served as solvent and positive controls, respectively. A majority of rats survived the treatment at the levels tested and were mated to two virgin females each per week for 2 weeks. The females were sacrificed at midterm of pregnancy and examined for live and dead implants. Dominant lethality was evaluated on the basis of 4 criteria: dead implants per pregnant female, dead implants per total implants, proportion of females with one or more dead implants, and proportion of females with two or more dead implants. 2-Nitro-p-phenylenediamine, 2,4-diaminoanisole sulfate and 2,5-diaminoanisole sulfate produced negative responses, whereas m-phenylenediamine and 4-nitro-o-phenylenediamine induced weak dominant lethality in the first trial. On retesting these weakly positive components, both m-phenylenediamine and 4-nitro-o-phenylenediamine produced negative responses.

Animals↗

PubMed1979

Collaborative studies on cytogenetic and dominant lethal assays.

Two in vivo cytogenetic studies and one dominant lethal study were jointly conducted by members of government, academic, industrial, and independent commercial laboratories between 1970 and 1975 to determine the validity and reproducibility of the techniques. The cytogenetic studies consisted of preparations and analyses of bone marrow cells from male rats for chromosome abnormalities. In the first study, participants from 4 laboratories jointly prepared slides at a Food and Drug Administration (FDA) laboratory according to a prescribed procedure and independently analyzed the slides in their own laboratories. In the second study involving 6 laboratories, a workshop was held at Dow Chemical Co. to reduce scoring differences and to develop a joint protocol. All participants then independently performed the exact procedure in their own laboratories, using animals from a common source. In the dominant lethal study involving 6 laboratories, a workshop was held at the FDA to discuss protocol and to practice the technique. All participants then independently conducted the study in their own laboratories using rats and test chemicals from common sources. In all 3 studies, significant interlaboratory variability existed, and the differences varied with the parameters analyzed.

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