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SUMMARY The stages of the maturation divisions, ovulation, fertilization and the first cleavage in the eggs of two strains of adult mice have been timed following superovulation treatment. Superovulation was induced by a priming injection of pregnant mares' serum followed after a 40 hr interval by human chorionic gonadotrophin (HCG). The oocytes were in the dictyate (germinal vesicle) stage until 2 hr after the injection of HCG. They then completed the prophase of the first maturation division, and the first metaphase plates were found 30 min later. From approx. 4½ to 8 hr all oocytes were in metaphase. The first maturation division and extrusion of the first polar body were then rapidly completed just before ovulation. Ovulation began, as judged by the presence of eggs with adherent cumulus in the uterine tubes, 11 hr after the injection of HCG and was virtually complete by 14 hr. One strain of mice ovulated slightly later than another strain. The time at which ovulation occurred was very similar in mated and unmated females. Fertilization and the first cleavage were studied in females which mated before ovulation began, and the mean intervals between various stages were as follows. Spermatozoa penetrated through the cumulus and zona pellucida in approx. 1 hr, and remained in the perivitelline space for 50 min. Pronuclei were formed 4¼ hr later, and the first cleavage division occurred at approx. 25 hr after penetration of spermatozoa into the eggs. These estimates are similar to those reported by other workers. The formation of oocytes in the adult mammalian ovary, the timing of early stages in the prophase of the first maturation division, and the relation between natural and induced ovulation are discussed.

An autosomal recessive mutation, characterized by an absence of sebaceous glands, and by hyperkeratosis, alopecia, and single (rather than the usual multiple) hair-follicle units, has occurred spontaneously in the BALB/c strain of mouse. Studies in which reciprocal transplantations of skin were made between normal and mutant mice suggest that some diffusible substance(s) synthesized by normal skin can stimulate hair growth and alleviate the hyperkeratosis characteristic of the skin syndrome.

Ains-To investigate the incidence of functional hyposplenism in a group of patients who had undergone allogeneic bone marrow transplantation (BMT). Methods-Splenic function was assessed by counting the number of gluteraldehyde fixed red blood cells containing pits or indentations as examined by interference phase microscopy. Normal values are <2% whereas splenectomy patients have values of 25 to 40%. Results-Twenty eight BMT recipients (17 men, 11 women) were studied at varying periods post-transplant and the results compared with 20 healthy volunteers and 10 patients who had undergone splenectomy or had splenic atrophy because of haematological conditions. Ofthe 28 BMT recipients, one had undergone a prior splenectomy; ofthe remaining 27 patients, four (15%) had evidence of functional hyposplenism with between 5 0 and 34 0% pitted cells. Of these four patients, one had active extensive chronic graft versus host disease (GvHD) which has been previously reported to be associated with functional hyposplenism following transplantation. Only one of the four patients had peripheral blood red cell changes typical of hyposplenism. Conclusion-These results confirm that extensive chronic GvHD is associated with hyposplenism. Intermediate degrees of functional hyposplenism may also occur following BMT in the absence of chronic GvHD and in the absence of haematological features of hyposplenism on routine blood films. This may be of significance in mediating the susceptibility to infection with encapsulating bacteria seen following allogeneic BMT. (J Clin Pathol 1995;48:257-259)

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