Delayed meiotic development and correlated death of spermatocytes in male mice with chromosome abnormalities

The kinetics of germ-cell development were examined in random-bred adult Swiss mice by means of tritium autoradiography. Comparisons were made between males with normal (+/+) and abnormal karyotypes: Rb(11.13)4Bnr/+ and T(1;13)70H/+ heterozygotes, T70H tertiary trisomics, and T70H translocation trisomics. The time taken for the first wave of labelled cells to progress from premeiotic S-phase to diplotene and then on to the second meiotic metaphase was estimated in each stock, and rates of increase of labelled meiotic figures were measured. The S-phase to diplotene interval did not differ significantly among the different genotypes, taking from 10 days, 16 h to 10 days, 19 h. In Rb4Bnr/+, T70H translocation trisomic, and T70H tertiary trisomic males, however, labelled meiotic figures accumulated at a lower rate, particularly in the tertiary trisomics. A cell delay for some meiocytes was thus indicated during meiotic prophase. A correlation was seen between the degree of meiotic delay and severity of reduction in sperm count. The period from late diplotene to metaphase II was also found to be longer in T70H tertiary trisomics than in controls (+/+) or other chromosomally abnormal males.