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C. J. DOMINIC

Summary.

Grafting of a single anterior pituitary gland from another female to the renal capsule of an intact mouse causes irregularity in the oestrous cycles. The commonest external manifestation of this modification is the recurrence of pseudopregnancy-like cycles. This is due to the continued secretion of prolactin by the transplanted pituitary, which prolongs the life-span of the corpora lutea. Controls bearing a similar graft of cerebellum remain unaffected. The luteotrophic activity of the hypophysial graft is shown by positive deciduoma response of the uterus and by the histological appearance of the graft. On removal of the graft, the female promptly returns to the 4- to 5-day cycles.

Evidence is presented that the ectopic pituitary graft in the intact female mouse remains functional for long periods, in these experiments at least for more than 12 months. In spite of the continued secretion of prolactin by the pituitary graft, there is cyclic recurrence of oestrus at intervals of 2 or 3 weeks during which periods ovulation occurs and fertile mating takes place, if the female has access to a male.

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C. J. DOMINIC

Summary.

Ovo-implantation is blocked in over 80% of newly mated female mice by exposing the females to fresh urine of alien (CBA) males. The same effect is also produced by topical application of male urine to the females three times a day. Pseudopregnancy induced by sterile mating is also blocked by exposure of the females to the fresh urine of alien males. Urine of alien males collected in a mixture of antibiotics and an antioxidant and stored for 1 to 7 days retains the pregnancy-blocking capacity to a large extent.

The percentage of pregnancy failures in untreated controls is close to the percentage of spontaneous failure of pregnancy in undisturbed females. Hence it is concluded that urine is the immediate source of the pheromones produced by male mice which cause the failure of ovo-implantation in newly mated females.

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C. J. DOMINIC

Summary.

The neuro-endocrine mechanisms involved in the olfactory block to ovo-implantation in mice were studied by investigating methods of preventing the block from taking place. Daily administration of 50 i.u. of prolactin to females on Days 1 to 5 is fully effective in preventing the block to pregnancy. Pregnancy block can also be inhibited in normal females by the presence of a functioning ectopic pituitary homograft, which serves as an additional source of prolactin. Reserpine is also effective in inhibiting the block to pregnancy, thus providing a direct proof of hypothalamic intervention in the reaction. The inhibition of the pregnancy block by exogenous progesterone and the histological appearance of the corpora lutea give further support to the view that implantation failure is due to failed luteal function. The results reported in this study provide additional evidence in favour of the view that olfactory stimulation from males causes the failure of prolactin secretion and initiates the secretion of fsh and lh by stimulating the hypothalamus. This, in turn, causes the failure of corpus luteum development and the return of the female to oestrus in the ordinary way.

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C.J. DOMINIC

Summary.

In contrast to normal and spayed cba females, spayed and androgenized cba females are as effective as normal cba males in blocking ovo-implantation in newly mated P mice. Hence it is concluded that the pheromones involved in producing the block to ovo-implantation are associated with androgens either directly, or indirectly through some androgen-dependent gland.

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SITARAMAIAH MOKKAPATI and C. J. DOMINIC

Summary.

The main source of citric acid in the accessory sex glands of the musk shrew (Suncus murinus) was the prostate and fructose was abundantly produced by the ampullary glands.

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A. Krishna and C. J. Dominic

Summary. Spermatozoa were observed in all parts of the genital tract in females killed in January, February, March and April although copulation occurs only until early February. The spermatozoa were arranged linearly with their heads orientated towards the epithelial lining.

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G. Rajendren and C. J. Dominic

Summary. Even though castration abolished the ability of alien males to induce implantation failure (the Bruce effect) in newly inseminated females, treatment of intact alien males with the steroidal antiandrogen, cyproterone acetate, for 14 days (short term) did not significantly depress their ability to induce the Bruce effect. However, prolonged treatment (42 days) with cyproterone acetate suppressed the pregnancy-blocking ability of alien males to some extent, possibly due to the antigonadotrophic properties of the drug. Ovariectomized alien females treated with implants of testosterone (androgenized females) exhibited the ability to block implantation in newly inseminated females, but concurrent treatment of androgenized females with cyproterone acetate did not depress this ability. The results strongly suggest that the pheromone involved in the male-induced implantation failure is not the product of an androgen-dependent tissue, but is likely to be a product of androgen metabolism.

Keywords: androgen metabolite; cyproterone acetate; implantation; mouse; pheromone