Pre-implantation embryos of Chinese hamster. I. Incidence of karyotype anomalies in 226 control embryos

The detection of viable heritable translocations by chromosome banding procedures

Ethyl methanesulfonate was tested for its ability to induce viable heritable translocations in progeny of male rats given a single IP injection prior to breeding. Reproductively competent Wistar rats were used as the test animals. Males were treated with either 75 or 150 mg/kg EMS or vehicle control. Neonates were used for primary tissue culture; the fibroblasts were harvested for cytogenetic analysis of chromosomes banded by Giemsa banding procedures. Since the cells examined were somatic cells, it was necessary to karyotype only two to three per neonate to ascertain inherited translocations. A reduction in fertility was observed in males treated with EMS. A statistically significant (p less than 0.05) dose-related increase in heritable translocations was observed in the F1 generation of treated animals.

Evaluation of chemically induced cytogenetic lesions in rabbit oocytes. I. The test system and the effects of streptonigrin

An appropriate method for evaluating transmissible genetic damage in female germ cells is presented. Analysis of karyotype preparations from preimplantation (6- day) rabbit embryos for consistent structural chromosome abnormalities is described as a sensitive way in which these determinations can be made. A table prepared from summarized research reports shows that less than 1 in 2000 rabbit blastocysts karyotyped thus far has a consistent structural chromosome abnormality. In the new data presented in this study, none of the 90 control blastocysts karyotyped had consistent structural chromosome abnormalities while 13 of 278 from female rabbits treated with streptonigrin (NSC-45383) before conception did. These findings demonstrate that karyotype analysis for consistent chromosome lesions in preimplantation rabbit embryos from females exposed to chemical clastogens can serve as a sensitive and quantitative means of estimating effects on oocytes. The results of the study also show that the consistent structural chromosome lesions in the blastocyst karyotypes are what would be predicted from the mode of action of streptonigrin and the segregation of chromosomes during meiosis. The relative efficiency of this system based on the rabbit as compared to another recently described system bases on the hamster is also discussed.

Expression of TEM-induced damage to postmeiotic stages of spermatogenesis of the mouse during early embryogenesis. II. Cytological investigations

After treatment of postmeiotic stages of spermatogenesis of the mouse with TEM (0.2 or 0.4 mg/kg), dose- and stage-of-spermatogenesis-dependent frequencies of cytogenetic aberrations can be observed in early embryos. The frequencies of first-cleavage metaphases exhibiting structural aberrations (all of the chromosome type), the frequencies of 2 cell embryos and of 4--8 cell embryos containing nuclei accompanied by micronuclei or nuclei connected by bridges show a close correlation to frequencies of preimplantation loss of embryos recorded in a dominant lethal test. The frequencies of morulae/blastulae exhibiting blastomeres with micronuclei show a close correlation to the frequencies of total (pre- and post-implantation) loss of embryos. This indicates delayed expression of TEM-induced chromosomal damage which could persist undetected in very early stages of embryogenesis.

Pre-implantation embryos of Chinese hamster. II incidence and type of karyotype anomalies after treatment of the paternal post-meiotic germ cells with an alkylating mutagen

Ninety-two male Chinese hamsters were treated with a single, sub-lethal dose of the alkylating cytostatic drug Trenimon. After 3--23 days they were mated with untreated females. The great majority of the male germ cells had been exposed to the mutagen while they were in the highly sensitive post-meiotic spermatid stage. The karyotypes of the resulting embryos were studied in the 4--8-cell stage. Out of 221 analysable embryos, 24.4% had aberrant karyotypes. Ploidy and genome mutations were, at 0.9% each, within control limits. Structural aberrations, involving one or several chromosomes, were present in 23.6% of the embryos (control 1.8%). 51% had a single aberrant centric element. The most frequent aberration types were deletions (54%), dicentrics (16%), translocations inversions and complex rearrangements with 22% and rings with 7%. About one-third of the cells, in addition, contained acentric fragments.