The domestic cat is along with the dog recently the most common and popular pet. Unlike the dog the cat kept her appearance and nature without major changes despite long years of domestication. She has been highly adaptive to extremely variable conditions. Beeing a prolific species she breeds succesfully in wide range of enviromental conditions and in a large spectrum of climatic conditions from subarctic to tropical regions. She reproduces successfully in urban colonies in high density of thousands of cats per square kilometre as well as in arctic regions with the population density equal to one cat per square kilometre. Mating strategy varies from promiscuous behaviour, through polygyny/polyandry system, to monogamy. The infanticide in felinae is a common reproductive strategy. Male kills dependent offspring sired by another male in order to hasten the female oestrus and to reproduce with her himself. In domestic cats the infanticide attracts long-lasting discussion. However, in reality reports on the incidence of infanticide has been scarce. One of the possible female counter-strategies is pregnancy block, known as a Bruce effect. The mated female blocks the blastocyte implantation when facing the treath of possible infanticide to avoid waste of energy by delivering offspring with poor chance for survival. Based on the questionnaire survey we have estimated the possibility of reproduction failure in a situation of potential male infanticide. From data which we have obtained we could not yet check the advanced hypothesis due to lack of variation and very few recorded cases of reproduction failure. On the other hand, we have accumulated extended information of the cat reproduction. In the future we are planning to collect more data in order to be able to test properly the hypothesis.

Mammalian reproduction is vulnerable to psychological and physiological stress. This research focuses on the psychophysiological mechanisms that lead to the disruption of pregnancy by the failure of implantation of fertilized ova into the uterine walls. The underlying hormonal mechanisms of implantation failure are not well understood. It is known that many environmental events have a substantial impact on hormonal dynamics in mammals. These environmentally induced hormonal changes can disrupt implantation. This thesis focuses on the hormonal dynamics of female mice that lose their pregnancy when exposed to a novel male during the implantation period (the Bruce effect). In Study 1, a repeatable and reliable Bruce effect was established by indirectly exposing inseminated females during the implantation period to novel males housed above them separated by a wire grid floor. Separating the animals allowed for the independent study of the chemical transmission from male to female, and the physiological transduction within the female. The findings from this study suggest that females must come in direct contact with the excretions of the stimulus novel males. The more excretions the females encounter, the greater the chance is of pregnancy disruption. The Bruce effect is known to be dependent on androgens in the stimulus males, since castration eliminates their capacity to disrupt pregnancy. Study 2 showed that surgically removing the androgen-dependent preputial glands from the stimulus males does not diminish their capacity to disrupt pregnancy. Study 3 showed that administering 17β-estradiol to castrated males can restore their capacity to disrupt pregnancy. This suggests that 17β-estradiol as well as testosterone is involved in the chemical transmission of the Bruce effect. It has been hypothesized that 17β-estradiol is elevated in females that fail to implant in the presence of a novel male. Administering an antibody specific to 17β-estradiol to females during their implantation period can lower the hypothesized increase in 17β-estradiol and implantation takes place despite the exposure to novel males. Finally, in Study 4 testosterone, 17β-estradiol and its major metabolites the estrone conjugates were quantified in females' urine and feces while exposed to novel males during implantation. It was found that testosterone and 17β-estradiol were significantly elevated in females that failed to implant while exposed to novel males. In conclusion, this line of research reveals a potential role of steroids in novel male induced pregnancy disruptions in mice. Elevated testosterone and 17β-estradiol are shown to be related to the prevention of implantation in mice. These hormonal dynamics may be partially responsible for the physiological transduction of the Bruce effect. / Thesis / Doctor of Philosophy (PhD)

<p>Adhesion of the blastocyst to the uterine wall is a highly sensitive phenomenon referred to as implantation. Novel-males are capable of disrupting the success of this process (the Bruce effect). A leading hypothesis invokes the transfer of estradiol from the male to the female via urine. This estradiol has direct effect on the uterus which may include morphology and molecular dynamics. Estradiol has been related to closure of the uterus around the blastocyst during implantation, which may assist in bringing the blastocyst close to the uterine wall for strong adhesion. E-cadherin, a cellular adhesion molecule, is found on both blastocyst and uterine surfaces and has been suggested to be involved in their interaction during implantation. Estradiol has been observed to reduce e-cadherin expression in hormonally sensitive tissues like the mammary glands, ovaries and uteri. Here, male-induced disruption of implantation was examined across days 2-8 of gestation. Luminal area was quantified in isolated and male-exposed females as a measure of extent of luminal closure. This area was larger in male-exposed animals. E-cadherin was found to have reduced expression on luminal epithelial cells. I suggest that the reduction in e-cadherin may lead to weaker attachment of the blastocyst to the uterine wall as well as reduced adhesion between opposing uterine walls leading to the “opening” of the uterus observed in male exposed animals. Together, these data may in part explain the blastocyst implantation failure observed in male-exposed animals during the Bruce effect.</p> / Master of Science (MSc)

Female mammals are known to exhibit pregnancy failure when exposed to various stimuli during the implantation phase of pregnancy. When newly inseminated female mice are exposed to novel males in the absence of the sire, implantation is disrupted. This phenomenon is known as the Bruce effect. When females are exposed to novel males in the presence of the sire, pregnancy failure does not occur. This latter effect has been referred to as the sire protection effect. In these studies we examine the nature of female and sire behaviour in the context of novel males. Female interactions with novel males significantly decrease in the presence of the sire. This reduction in female-novel male interaction in seen irrespective of whether sires are free or confined within the female's cage. Novel-male exposed females exhibit pregnancy failure and this pregnancy block is removed when either free of corral-confined sires remain present in the cage. Finally, sires are highly motivated to engage in aggressive conflicts with novel males both in the presence and absence of the pregnant female. Sires were observed to behave aggressively towards novel males through a wire-mesh grid and in this context were able to inflict severe wounding upon novel males through the wire-mesh partition. In a direct exposure paradigm, sires were also witnessed to exhibit this aggression and were found to initiate and win all conflicts with novel males. The sire protection affect is likely to involve a complex of both pheromonal and behavioural cues. Sire aggression towards novel males, pheromonal communication and limited behavioural interaction between the sire and the female, and reduced femalenovel male interaction are all likely components of the effect. / Thesis / Master of Science (MSc)