Meiotic behavior of alloxan-treated diabetic and nondiabetic T(;13)70H/+ mice.

The influence of diabetes on first meiotic segregation behavior in female and male T(1;13)70H/+ mice was studied. By treatment with alloxan 60 mg/kg bodyweight both diabetic and non-diabetic control mice were obtained. All female mice were treated with gonadotropins to obtain reasonable numbers of secondary oocytes per female. As a result of this treatment the number of oocytes ovulated and the percentage that could be analyzed were not different in diabetics and controls, indicating that no severe selection occurred as a result of the diabetic state. Male mice were not treated with gonadotropins, and here the low quality of the air-dried preparations and the scarcity of secondary spermatocytes in diabetics suggest that degeneration occurs. In primary spermatocytes we found higher chiasma frequencies in the translocation multivalent in diabetic males than in controls, probably as a result of reduced chiasma terminalization. The analysis of metaphase-II cells in the females revealed less 3:1 segregation and more adjacent-II segregation in the diabetics. In the males no 3:1 segregation was found in either group, but here adjacent-II segregation was lower in diabetics than in controls. No significant differences were found in nondisjunction frequencies of non-translocation-involved bivalents. We conclude that diabetes influences the meiotic segregation behavior of chromosomes and that chromosomes showing higher incidences of unbalanced segregation behavior (i.e., multivalent involved chromosomes) are more susceptible to this influence than other chromosomes. In the diabetic males this influence is undone by the severe selection, affecting primarily the cells, that would give rise to unbalanced metaphase II cells, resulting in even lower frequencies of adjacent-II segregation than in controls.