Über den Einfluß von Trenimon und Endoxan auf die Meiose der männlichen Maus

Abstract

Mutagenic activity of alkylating agents has previously been studied in our group by the dominant lethal method (Röhrborn et al.). These investigations have now been supplemented by cytogenetic studies on the influence of trenimon and cytoxan in the same dosages as used by Röhrborn applied in single i.p. injektions. The stages of spermatogenesis treated were estimated using the time table established by Oakberg. The cytogenetic procedures used have been described in the preceeding paper (Schleiermacher, 1966). Relative frequency of meiosis was calculated from the number of meiotic prophases counted in relation to number of interphase nuclei.

Relative frequency of meiotic prophases varied considerably following treatment. After maturation depletion of the tubules marked diminution but never complete disappearence of meiotic prophases occured. This observation corresponds in a certain manner to the sterile period known after X-irradiation. In breeding experiments, however, no definite decrease of fertility has been noted (Röhrborn). As soon as the spermatids disappear as result of lacking regeneration, the relative frequency of meiotic prophases must increase. Other factors also could account for this phenomenon. Change in frequency of meiosis indicates that regeneration of germ cells is slowed down after treatment with trenimon and cytoxan, which is at variance with the results reported of irradiation experiments. The sensible stages, in which retardation of regeneration occurs, are detectable by histological analysis only. This will be attempted in subsequent experiments. Differences in results of experiments with trenimon and cytoxan could be due to dosage effects.

In all phases of spermatogenesis treatment results in increased frequency of univalents. The highest incidence of univalents has been found after treatment of preleptotene with trenimon. This could presumably be caused by invisible structural changes in chromosomes, most likely inversions. The expected occurrence of aneuploid second metaphases could not be demonstrated. Our results indicate that univalents do not play a role in causation of dominant lethals.

Chromosome aberrations in diakinesis, mainly chromosome breaks and translocations, occured after treatment of all phases. In second metaphases breaks, dicentric chromosomes and translocation chromosomes have been seen very rarely. Less chromosome aberrations have been found in either M I or M II than have been expected from the results of irradiation experiments (Ashwood-Smith et al.). Chromosome aberrations even occured in stages of spermatogenesis in which no dominant lethals have been detected by Röhrborn. Whether in our experiments the chromosome aberrations may have been masked by loss of damaged cells cannot yet be decided.