Mouse dominant lethal and bone marrow micronucleus studies on methyl vinyl sulfone and divinyl sulfone

Germ cell mutagenicity of gamma-ethyl-gamma-phenyl-butyrolactone (EPBL) detected in the CF1 mouse-dominant lethal study

Female and male CFI mice weighing 25-30 g were given 0, 50, 100 or 200 mg/kg of gamma-ethyl-gamma-phenyl-butyrolactone (EPBL) for 5 days intraperitoneally. In the male-dominant lethal phase, males treated with EPBL were mated with untreated females following a 7-day mating schedule with three consecutive mating events. In the female-dominant lethal phase, females treated with EPBL were caged with untreated males. The above dosages and schedule treatments were used. The incidence of pregnancy of females mated on days 1-7 and 8-14 after males were given 200 mg/kg of EPBL and of females given 200 mg/kg when mated to untreated males was decreased. Upon examining surgically exposed uteri and ovaries of pregnant females during the first phase, on gestation days 13-15, an increased incidence of pre-implantation losses with 200 mg/kg of EPBL and an increased incidence of post-implantation losses with 100 and 200 mg/kg was observed. In addition, an increased frequency of pre- and post-implantation losses was seen in females treated with 200 mg/kg. These results support the conclusion that EPBL is a germ cell mutagen and its effects are more pronounced during the post-meiotic stage.

Dominant lethal mutations, heritable translocations, and unscheduled DNA synthesis induced in male mouse germ cells by glycidamide, a metabolite of acrylamide

The hypothesis that acrylamide induces dominant lethal mutations and heritable translocations in male mice, not through direct adduction, but by conversion to the reactive epoxide, glycidamide, was investigated. Three studies, namely, induction of dominant lethal mutations, heritable translocations, and unscheduled DNA synthesis in spermatids, which were conducted earlier in this laboratory for acrylamide, were also performed for glycidamide to determine its mutagenic properties and to compare responses. Results of these studies are consistent with the proposal that in vivo conversion to glycidamide is responsible for the mutagenicity of acrylamide in male mice.

The rodent dominant lethal assay: a proposed format for data presentation that alerts to pseudo-dominant lethal effects

The rodent dominant lethal (DL) germ cell mutagenicity assay is the primary test for possible human germ cell mutagens. As such, it occupies a critical regulatory position. DL assay data are often difficult to assess because of the quantity of data involved, and because several related assay parameters require to be considered simultaneously. To reduce this difficulty a schematic method of data presentation is proposed and illustrated. This method enables the most pertinent assay data and parameters to be viewed and considered simultaneously. Using this format of data presentation, existing DL studies on cyclophosphamide, methylnitrosourea, diethylhexylphthalate, divinyl sulphone, methyl methanesulphonate, 6-mercaptopurine and ethylenethiourea are re-analysed.

Cytogenetic damage in marrow cells of mice after injections of yttrium-90-labeled monoclonal antibody

Chromosome aberrations, micronuclei and sister-chromatid exchanges were quantified in marrow cells of athymic nude and B6C3F1 mice at various times up to 14 days after injection of 90Y-labeled monoclonal antibody CO17-1A. Aberrations, predominantly of the chromatid type, were sharply elevated at 24 h post-injection then declined in a curvilinear fashion over the 14 days. Micronucleus numbers among polychromatic erythrocytes peaked 3-4 days after treatment, then declined exponentially but remained at higher than expected levels. Sister-chromatid exchanges were roughly double the control rate with no apparent relation to post-treatment time.

Bone marrow micronucleus assay: a review of the mouse stocks used and their published mean spontaneous micronucleus frequencies

We have examined published negative control data from 581 papers on micronucleated bone marrow polychromatic erythrocytes (mnPCE) for differences in mean frequency and the frequency distribution profile among the mouse stocks used with the bone marrow micronucleus assay. For the 55 mouse stocks with published micronucleus assay data, the overall mean frequency is 1.95 mnPCE/1,000 PCE (1.95 mnPCE/1,000); for the 13 stocks most commonly used in the assay, it is 1.88 mnPCE/1,000. During the last 5 years, the mnPCE rate for these 13 major stocks has been 1.74 mnPCE/1,000. This current mean frequency is a substantial decrease from the mean of 3.07 mnPCE/1,000 observed for these 13 stocks for data published prior to 1981. Of the major stocks, the highest mean mnPCE negative control frequencies were observed for MS/Ae > BALB/c > C57Bl/6, and the lowest for CD-1 < Swiss Webster. We note that hybrid mouse stocks appear to have lower and less variable negative control frequencies than either of their parent strains and that the negative control frequency for some progeny stocks have diverged significantly from that of the parent stocks. Overall mean negative control frequencies appear to be correlated with breadth of the frequency distribution profile of published mean negative control values. Furthermore, a possible correlation between negative control frequency in the micronucleus assay and sensitivity to clastogens of different mouse strains may be indicated. The databases generated here allow us to define a range of norms for both the historical mean frequency and individual experimental mean frequencies for most stocks, but in particular, for the more commonly used mouse stocks. Our analysis, for the most part, bears out the recommendation of the first Gene-Tox Report on the micronucleus assay that the historical negative control frequency for a mouse stock should fall between 1 and 3 mnPCE/1,000. Eighty-six percent of the most commonly used mouse stocks have historical mean frequencies within this range. Though individual experimental mean values would not necessarily be expected to fall within the 1-3.00 mnPCE/1,000 range, 65.3% of the 2,327 published negative control values do, and 83.5% are < 3 mnPCE/1,000. The frequency with which an individual experimental mean value lies outside the 1.00 to 3.00 mnPCE/1,000 range differs among stocks and appears related to the mouse mean frequency. We suggest that the recommended range for historical mean frequency be extended slightly, to approximately 3.4 mnPCE/1,000, to accommodate some commonly used strains with overall mean negative control frequencies just above 3.00 mnPCE/1,000.(ABSTRACT TRUNCATED AT 400 WORDS)

Fertility, reproduction, and genetic disease: studies on the mutagenic effects of environmental agents on mammalian germ cells

Because genetically based diseases have a major impact on human health, the National Institute of Environmental Health Sciences (NIEHS) has conducted a research and testing program for more than a decade to address chemical induction of heritable genetic damage in the germ cells of mammals. Although most genetic disease results from preexisting mutations, a portion is due to the occurrence of new mutations. The supposition that exposure to mutagenic chemicals contributes to the occurrence of new mutations in the human population is strongly supported by the results from animal models. Such studies clearly demonstrate the potential of environmental chemicals to induce mutations in both somatic and reproductive cells of mammals. This NIEHS program has become a leader in the identification of genetic hazards in the environment and in the acquisition of animal model data used by regulatory agencies in assessing genetic risks to human health.