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Biomedical subjects

C J Dominic

Publications and source records attributed to C J Dominic.

At least 19 recordsLinked to original sources
PubMed1997

Duration of the luteotrophic memory of the stud male odors formed in the female mouse.

Presence of the stud male prevents the novel male-induced block to early pregnancy in mice, while reexposure to the stud male after the pregnancy block induces pseudopregnancy in the females. These two phenomena involve luteotrophy in the female, and a (luteotrophic) memory of the stud male characteristics formed in her is necessary for such a luteotrophic response. Two experiments were conducted to evaluate the effective duration of the "luteotrophic memory" of the stud male odors formed in the female mouse. The first experiment investigated whether exposure to excreta of the stud male at different intervals will induce pseudopregnancy in pregnancy-blocked females; some females mated with a second male and experienced a second consecutive pregnancy failure before the exposure to the excreta of the first stud male. The females, mated once or twice, failed to exhibit pseudopregnancy when exposure to the excreta of the first stud male was begun 8 or 9 days after the first mating. In the second experiment, each pregnancy-blocked female was mated with the (alien) male that induced failure of the first pregnancy and then housed with simultaneous access to the excreta of another alien male and that of the first stud male. Excreta of the first stud male did not prevent failure of the second pregnancy. The results indicate that the (luteotrophic) memory of the stud male-originating olfactory cues formed in the female or its effectiveness in reactivating the luteotrophic system (when the female is reexposed to the odors of the first stud male) lasts only up to about day 7 postcoitum. The present results also show that exposure to only the excreta of the stud male can prevent the pheromonal block to pregnancy or induce pseudopregnancy after pregnancy block in the female mouse.

Animals↗
PubMed1996

Rat-induced disruption of early pregnancy in mice and its prevention by the stud male.

Recently inseminated mice exhibited a high rate of pregnancy failure following exposure to male rats irrespective of whether they were housed in direct physical contact with the rat or not. Pregnancy disruption was also seen in mice which were housed on male rat-soiled bedding. By contrast, inseminated mice housed with female rats or on bedding soiled by female rats showed a significantly lower rate of pregnancy failure. The presence of the stud male prevented the pregnancy failure in mice induced by exposure to male rats or male rat-soiled bedding. This protective effect of the stud male on pregnancy in rat-exposed mice is analogous to the protective effect of the stud male on pregnancy in conspecific novel male-exposed mice and in mice subjected to nutritional stress. Hence the possibility that the protective effect of the stud male on pregnancy in male rat-exposed mice is due to the stimulation of luteotrophic activity by the stud male-originating olfactory cues cannot be ruled out. However, it is not clear whether the pregnancy failure in newly inseminated mice induced by exposure to rats is the result of a general stress or is mediated through rat-originating chemosignals acting interspecifically.

Animals↗
PubMed1995

Nutritional stress-induced implantation failure in laboratory mice: inhibition by continuous illumination.

The implantation failure in newly inseminated mice induced by food deprivation for 48 hr, beginning at 0900 hrs on day 4 post coitum, was prevented by simultaneous exposure to light continuously for 48 or 36 hr. Food-deprived females that were exposed to continuous light for 36 hr showed a significant increase in fetal resorption as compared with food-deprived females exposed to continuous light for 48 hr. Since failure of hypophysial prolactin release appears to be the primary endocrine cause of the inanition-induced implantation failure, the results suggest that exposure to continuous light protects implantation in food-deprived females by stimulating luteotrophic activity.

Animals↗
PubMed1994

Failure of conspecific males to prevent the water deprivation-induced disruption of oestrous cycle in laboratory mice.

Chronic water deprivation induced severe disruption of the oestrous cycle in regularly cycling laboratory mice. Most of the water-deprived females became anoestrous from the beginning of water deprivation or after one complete cycle in the initial stages. The presence of a conspecific male was ineffective in preventing the cycle disruption in water-deprived females. The inability of conspecific males to prevent the water deprivation-induced disruption of oestrous cycle in females contrasts with the ability of conspecific males to prevent the diet restriction-induced irregularities in the oestrous cycle in females. It is suggested that as compared with diet restriction, water deprivation induces a greater suppressive effect on the hypothalamo-hypophysial-gonadal axis in females which cannot be removed by the male-originating olfactory cues.

Animals↗
PubMed1993

Male-induced implantation failure (the Bruce effect) in mice: protective effect of familiar males on implantation.

Housing newly inseminated female mice in contact with a familiar male (a male that had cohabited with the female for 24 h during the pericopulatory period, but not the coital partner) depressed the implantation failure (the Bruce effect) induced by exposure to alien males. This is comparable to the protective effect of stud males on implantation in alien male-exposed females. The findings imply that exposure to a male (stud or any other) during the pericopulatory period enables the female to memorize the male-originating olfactory cues, and that this memory formation is not contingent upon mating. Reexposure to the male-originating olfactory cues induces a luteotrophic effect in the newly inseminated female, which accounts for the protective effect of the stud/familiar male on implantation in the alien male-exposed female. The male-originating olfactory cues that provide the protective effect on implantation act through contact. The findings also lend support to the view that the female mouse is capable of identifying a male as an individual through olfactory cues perceived during the pericopulatory period.

Animals↗
PubMed1993

Protective influence of spayed and androgen-treated females on oestrous cycle in food-restricted mice.

Diet restriction induced disruption of oestrous cycle in regularly cycling female mice. The irregularities in the oestrous cycle in females were directly related to the degree of diet restriction. The presence of spayed and androgen-treated females prevented these irregularities and helped to maintain regular oestrous cycles in underfed females. The ability of androgen-treated females to prevent the irregularities in the oestrous cycle in underfed females was inversely related to the degree of diet restriction. The results suggest that the production of the male-originating pheromone that helps to prevent the underfeeding-induced disruption of oestrous cycles in females is androgen-dependent.

Androgens↗
PubMed1993

The male-induced implantation failure (the Bruce effect) in mice: effect of exogenous progesterone on maintenance of pregnancy in male-exposed females.

The effect of exogenous progesterone given early during pregnancy in maintaining pregnancy in alien male-exposed mice was investigated. Administration of progesterone, 1 mg/female/day, on days 1 to 5 post coitum was fully effective and on day 2 to 6 post coitum was partially effective in maintaining pregnancy in females. However, progesterone injection on days 3 to 7 post coitum was totally ineffective in maintaining pregnancy in females. The results suggest that only when administration of progesterone is begun early during male exposure, luteal failure in newly inseminated females is prevented. The results also suggest that failure of corpus luteum function or some other irreversible changes leading to luteolysis occur in females early during exposure to alien males before the external manifestation of implantation failure (vaginal cornification). It is suggested that exogenous progesterone given early during alien male exposure prevents luteal failure and maintains pregnancy in females through its facilitatory effect on hypophysial prolactin secretion.

Animals↗
PubMed1992

Bromocriptine-induced implantation failure in mice: failure of the stud male to protect pregnancy.

The presence of the stud male failed to prevent implantation failure in newly inseminated females induced by administration of bromocriptine. This is in contrast with the ability of the stud male to prevent implantation failure in females induced by alien male exposure, and nutritional stress. Since bromocriptine is a potent inhibitor of hypophysial prolactin release by virtue of its stimulatory effect on hypothalamic dopaminergic activity, the results suggest that the stud male-originating luteotrophic stimulus is incapable of overriding the dopaminergic activity in bromocriptine-treated females.

Animals↗
PubMed1991

Protective effect of ectopic pituitary graft on nutritional stress-induced implantation failure in mice.

Implantation failure in newly inseminated mice induced by food deprivation was prevented by the presence of an ectopic pituitary graft. Since a pituitary graft in an ectopic site is known to secrete prolactin continuously, it is suggested that suppression of implantation failure in pituitary-grafted females is due to the luteotrophic support provided by the graft. The results provide supportive evidence for the view that depression of hypophysial prolactin is the primary endocrine cause of the nutritional stress-induced implantation failure in mice.

Animals↗
PubMed1991

Oestrous cycle disruption in group-housed mice: evaluation of the involvement of tactile and pheromonal stimuli.

The role of tactile stimuli and pheromonal stimuli in the induction of oestrous cycle irregularities in mice was evaluated. In contrast to an adult regularly cycling female (the test female) housed in contact with 6 adult females, a test female housed in contact with 6 impuberal females failed to show disruption of oestrous cycle. Likewise, a test female housed in contact with bedding soiled by 6 group-housed adult females failed to exhibit disruption of oestrous cycle. By contrast, a test female housed in contact with 6 impuberal females on bedding soiled by 6 adult group-housed females exhibited a significant increase in the incidence of prolonged cycles. However, a test female housed with 6 impuberal females without direct contact with the bedding soiled by adult group-housed females exhibited a significant decrease in the incidence of prolonged cycles. The results suggest that tactile stimuli and pheromonal stimuli (probably present in the excrete of adult females) act synergistically in inducing cycle disruption. The findings further indicate that the female-originating pheromone involved in oestrous cycle disruption is non-volatile (not air-borne) and that it acts through contact.

Animal Husbandry↗
PubMed1990

Stud male protection of implantation in food-deprived mice: evaluation of the involvement of olfactory-vomeronasal systems.

The protection of implantation in food-deprived females provided by exposure to the stud males was not abolished following surgical ablation of the vomeronasal organ (VNO) from females. By contrast, stud males failed to protect implantation in food-deprived females made peripherally anosmic by intranasal irrigation with ZnSO4. The results suggest that the main olfactory system, and not the accessory olfactory system, is involved in the perception of the stud male-originating olfactory cue that protects implantation in nutritionally-stressed females. The findings also provide circumstantial evidence that the study male-originating olfactory cue involved in the protective effect is volatile (air-borne).

Animals↗
PubMed1990

Stud male-induced protection of implantation in food-deprived mice: masking effect of an artificial scent on pheromonal odour.

In contrast to unscented stud males, stud males anointed with a commercial perfume failed to protect implantation in food-deprived females. It is suggested that the failure of perfumed stud males to protect pregnancy in their coital partners is due to the masking effect of the perfume on the stud male-originating olfactory cue which stimulates luteotrophic activity in females. The results are also consistent with the view that the newly inseminated female mouse identifies the stud male as an individual through a pheromonal cue and this is involved in the protective effect on implantation in the food-deprived female.

Animals↗
PubMed1989

Nutritional stress-induced implantation failure in newly inseminated mice: effect of the presence of stud males.

Implantation failure was induced in a large proportion of newly inseminated female mice by food deprivation for 48 hrs beginning at 10.00 hr on day 4 post coitum. The presence of the stud male prevented implantation failure in food-deprived females. The protective effect on implantation in food-deprived females was not provided by the presence of a conspecific strange male. It is suggested that the newly inseminated female retains the olfactory "memory" of the stud male over a period of time after mating and this memory induces a luteotrophic effect in food-deprived females leading to the protection of implantation. The results also lend strong support to the view that the newly inseminated female mouse identifies her coital partner as an individual through olfactory cues.

Animal Nutritional Physiological Phenomena↗
PubMed1989

Failure of familiar males to prevent alien male-induced implantation block (the Bruce effect) in laboratory mice.

Implantation failure in newly inseminated females induced by exposure to alien males (the Bruce effect) was significantly reduced when the females were housed with the stud male. By contrast, newly inseminated females housed with a familiar male during exposure to alien males exhibited a high rate of implantation failure. The results suggest that the protective effect of the stud male on implantation is not because of the familiarity of the female with his odour cues. The results are consistent with the view that the newly inseminated female mouse identifies her coital partner as an individual because she becomes 'imprinted' with his odour during the pericopulatory period.

Animals↗
PubMed1988

The male-induced implantation failure (the Bruce effect) in laboratory mice: investigations on luteal failure in pregnancy-blocked females.

The luteal function in newly inseminated female mice following exposure to alien males was investigated. The corpora lutea (CL) of newly inseminated females exhibited high delta 5 3 beta hydroxysteroid dehydrogenase (delta 5 3 beta HSD) activity at 24 hr or 48 hr (pro-oestrus) after the beginning of alien male exposure. By contrast, the enzyme activity in the CL at 72 hr (oestrus) after the beginning of alien male exposure was markedly less as compared with that in the CL of unexposed controls. This suggests that the CL of newly inseminated female mice can synthesise progesterone from its substrate at least up to 48 hr after the beginning of alien male exposure. Administration of prolactin to newly inseminated females beginning at 0 hr of alien male exposure prevented implantation failure; the majority of females showed implanted embryos. Prolactin administration starting at 24 hr after the beginning of alien male exposure was only partially effective, and that starting at 48 hr was totally ineffective in preventing implantation failure in newly inseminated females. The results indicate that the CL of newly inseminated females cease to respond to prolactin within 24 hr of alien male exposure, even though they exhibit the capacity to synthesise progesterone (as evidenced by the presence of delta 5 3 beta HSD activity) for a longer period.

3-Hydroxysteroid Dehydrogenases↗
PubMed1988

Effect of cyproterone acetate on the pregnancy-blocking ability of male mice and the possible chemical nature of the pheromone.

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.

Animals↗
PubMed1987

Induction of pseudopregnancy in pregnancy-blocked mice by re-exposure to stud males.

Re-exposure to stud males beginning on day 4 post coitum induced pseudopregnancy in a large proportion of female mice whose pregnancies were terminated by a single injection of 0.5 mg of bromocriptine on day 1 post coitum. By contrast, exposure to alien or strange males was ineffective in inducing pseudopregnancy in pregnancy-blocked females. The results suggest that the newly inseminated female retains the memory of the stud male for some days after mating. Activation of the 'memory' by pheromones of the stud males exerts a luteotrophic effect in pregnancy-blocked females resulting in the incidence of pseudopregnancy. This may account for the inability of the stud male to block pregnancy in his coital partner and also for the inability of alien males to block implantation in newly inseminated females housed with stud males.

Animals↗