Cytogenetic analysis of mouse oocytes after experimental induction of follicular overripening

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Abstract
Graafian follicle overripening was induced in adult mice by inhibiting the ovulatory discharge of gonadotrophins with antibodies to LHRH and immature mice by injection of PMSG [pregnant mare''s serum gonadotropin] to promote follicular maturation before the neuroendocrine system was competent to produce an ovulatory stimulus. The numbers of follicles capable of meiotic maturation after exogenous LH [luteinizing hormone] were sharply reduced during the period of overripening and there was a corresponding increase in the proportion of cystically enlarged follicles, many of which were undergoing atresia. Freshly ovulated ova were collected after delaying ovulation for 2 days and prepared for cytogenetic study of metaphase chromosomes. The incidence of non-disjunction and other errors was indistinguishable from that of ova collected after spontaneous ovulation during 4- or 5-day cycles.