Involvement of contact stimuli in the male-induced implantation block (the Bruce effect) in mice

Confinement of newly inseminated female mice exposed to confined alien males significantly decreased the male-induced implantation failure (the Bruce effect). By contrast, free (unconfined) females exposed to confined alien males showed a high rate of implantation failure. The results suggest that the pheromone of male origin involved in the Bruce effect is non-volatile and acts on the female through contact. The vomeronasal organ appears to be involved in the perception of this pheromone.     

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.     

Differential response to the odor of familiar intruder mice in male mice (Mus musculus)

Responses to the odor of familiar intruder male mice according to their dominance were investigated. Responses were classified into 2 aspects: the investigation of the odor and the decision-making regarding avoiding it or not. The results varied according to the dominance of the respondents and the odor donor, and also according to the context of previous encounter situations. The dominants that had attacked an intruder dominant mouse responded randomly to its odor, whereas the dominants that had fought with it tended to avoid the odor. The subordinates that had observed an intruder dominant mouse being attacked by its dominant cagemate preferred the passage with the intruder's odor. The odor of a subordinate mouse was neither avoided nor preferred by either the dominants or subordinates. It was suggested that mice distinguished the dominance of the odor donor regardless of the context of the previous encounter situation, but they responded differently according to it and also according to their own dominance status.     

Failure of platelet-activating factor (PAF-acether) to induce decidualization in mice and failure of antagonists of PAF to inhibit implantation

The possible role of platelet-activating factor (PAF) in the uterine responses associated with implantation was investigated. Attempts to trigger a decidual cell response in the uteri of hormonally sensitized, ovariectomized mice by instilling PAF-acether (1-1000 ng) intraluminally were unsuccessful. The effect of PAF antagonists on implantation was investigated in females ovariectomized on Day 3 of pregnancy and treated with progesterone. Implantation was induced in these females by injection of 10 ng oestradiol-17 beta on Day 8. Hourly intraperitoneal injections of three PAF antagonists (WEB 2086, CV 3988 and BN 52021 at doses of 1.2-1.4 mg/kg) given over a 24-h period starting 1 h before the injection of oestradiol-17 beta had no significant effect on the occurrence of implantation sites. Intraluminal injection of WEB 2086 (15 micrograms) or BN 52021 (5 micrograms) either 3 h before or 6 h after the nidatory oestradiol also had no significant inhibitory effect on implantation. SRI 63-441 given once daily over the first 4 days of pregnancy at a dose of 40 micrograms/30 g body weight had no inhibitory effect on the establishment of pregnancy. These results are not consistent with a critical role for PAF in implantation in mice.     

Failure to confirm abnormal copper utilization in crinkler (cr) mice

A number of aspects of copper utilization have been studied in crinkled mice, the symptoms of which have been claimed to result from copper deficiency. In none of these aspects has any evidence been found to support this contention.1. Copper concentrations in liver, kidney, and brain, and serum ceruloplasmin oxidase activity were normal incr/cr mice.2. Copper concentrations in cultured lung fibroblasts and kidney epithelial cells derived fromcr/cr mice were normal.3. The elution profile of bound copper by gel-filtration chromatography of liver homogenates was the same in +/? andcr/cr mice.4. Neither maternal nor direct copper supplementation resulted in any reduction in mortality ofcr/cr mice.5. No increase in the concentration of hair sulfhydryl groups was apparent incr/cr mice.6. Histological studies revealed that the thin skin incr/cr mice owed to a reduction of the cutis; the epidermal and dermal layers were of normal thickness.7. Lysyl oxidase activity was normal in extracts of skin from 6-day-oldcr/cr mice, and in the culture medium ofcr/cr lung fibroblasts.8. Chemical analysis of brain myelin from 21- and 60-day-oldcr/cr mice showed no differences from +/? mice.     

Investigations on the Olfactory Discrimination Exhibited by the Females in the Male-induced Implantation Failure (the Bruce Effect) in Laboratory Mice

Direct contact with the alien male pheromone for 7 days before mating significantly decreased the rate of male-induced implantation failure (the Bruce effect) in newly inseminated female mice. By contrast, females housed with alien males for 7 days before mating so that physical contact with the latter was prevented exhibited a high rate of implantation failure following exposure to alien males after mating. Exposure to an air-borne pheromone produced by alien males induced oestrus (the Whitten effect) in a significant number of grouped females. The results do not support the suggestion that the inability of the stud male to block implantation is due to his original induction of oestrus. The results also do not support the view that the key factor in the induction of the Bruce effect is the ability of the female to identify the stud as an individual which prevents her from responding to him but allows her to react to a new male with hormonal changes leading to implantation failure and return to oestrus. It is suggested that the olfactory discrimination exhibited by the female in the Bruce effect is influenced by her overall olfactory experience before and after mating. The results are consistent with the view that the male-originating pheromone involved in the Bruce effect is distinct from the one involved in the Whitten effect.