The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform
C. David Rollo - One of the best experts on this subject based on the ideXlab platform.
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Trojan Genes and Transparent Genomes: Sexual Selection, Regulatory Evolution and the Real Hopeful Monsters
Evolutionary Biology, 2014Co-Authors: C. David RolloAbstract:Potential impacts of genetically modified (GM) animals in natural environments are explored in a framework of regulatory evolution. Transgenic growth hormone animals express remarkable alterations and plasticity in development, physiology and behavior in response to environmental factors (nutrition, temperature, photoperiod), suggesting that standard laboratory assessments are likely to underestimate their evolutionary potential. Sexual selection is examined in the context of female self-referent appraisal of male fitness that reflects performance in the species-specific niche. Wild-type females may recognize and discriminate against GM males (the Transparent Genome Hypothesis) but if accepted as mates, pleiotropic disruption associated with GMs may reduce fitness of the natural population (the Trojan Gene Hypothesis). Alternatively, facilitation of regulatory evolution by sexual reproduction (recombination and segregation) may derive modifier selection, masking, integration, or niche shifts. Other aspects explored include mutation theory, purging, pleiotropy, epigenetics and plasticity, behavior and the Bruce Effect, and mismatch of genetic or epigenetic background between GM stock and natural populations.
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Trojan Genes or Transparent Genomes? Sexual Selection and Potential Impacts of Genetically Modified Animals in Natural Ecosystems
Evolutionary Biology, 2014Co-Authors: C. David Rollo, Aarti Kumar, Richard Smith, Jiaxi Wang, Vadim Aksenov, Parul KhannaAbstract:Introgression of genetically engineered modifications (GMs) into natural populations represents a new realm for mutation theory. GMs, like mutations, have direct and pleiotropic impacts that can disrupt evolved adaptive suites. If GM males are more competitive or attractive mates, the “Trojan Gene Hypothesis” predicts potentially drastic impacts. We examined sexual selection in transgenic growth hormone (Tg) mice that are strong Trojan candidates given their exceptional size and extensive pleiotropic deficits. We hypothesized that the sophisticated olfactory abilities of females would recognize dysregulation of Tg males (the Transparent Genome Hypothesis). Females expressed interest in Tg males and their volatile scent, but when allowed nasal contact with urine (critical to mate choice) they preferred normal males. Tg male urine had reduced major urinary proteins (important in social signaling) and contained albumin and transferrin indicative of pathology. Novel Tg males failed to elicit pregnancy block in recently inseminated females (the “Bruce Effect”) whereas normal males were highly Effective. Normal males expressed high aggression but Tg males were placid, non-aggressive and were largely ignored by normal males. Female mice also strongly preferred normal males over p53^± knockout males in response to volatiles, contact with urine and male presence. This study suggests that conspecific discrimination of fitness may be more powerful than generally appreciated. This has great implications for introductions of GM animals and sexual selection generally.
Jerry O Wolff - One of the best experts on this subject based on the ideXlab platform.
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Laboratory Studies with Rodents: Facts or Artifacts?
BioScience, 2003Co-Authors: Jerry O WolffAbstract:Abstract Rodents have been studied extensively in the laboratory as model species to address and, in some cases, develop paradigms in mammalian behavioral biology. However, the laboratory environment presents obvious limitations that can compromise results, inferences, and application to evolutionary theory and the species’ natural history. Here I revisit several research areas that have been developed in the laboratory that either have never been tested in the field or, when they were tested, did not support laboratory results. Some of these studies include the Bruce Effect, scent marking, mate choice, artificial selection, predator-induced reproductive suppression, and other behavioral anomalies. Whether laboratory results for these and other studies have produced facts or artifacts is equivocal, but they warrant critical evaluation. Rodents are excellent model systems for testing hypotheses in behavioral ecology. However, to improve our confidence in results from laboratory studies, the behavior being ...
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a field test of the Bruce Effect in the monogamous prairie vole microtus ochrogaster
Behavioral Ecology and Sociobiology, 2002Co-Authors: Scott J Mahady, Jerry O WolffAbstract:The Bruce Effect is a widely studied reproductive phenomenon in rodents in which exposure of pregnant females to unknown males causes termination of the current pregnancy. The Bruce Effect has been reported from numerous studies in the laboratory, and one field study with the promiscuous gray-tailed vole, Microtus canicaudus, failed to support it. We conducted a field study with the monogamous prairie vole, M. ochrogaster, to determine if complete replacement of the male population every 10–14 days affected pregnancy and juvenile recruitment. The mean days to first parturition for control and treatment females were 36.8 and 44.4 days. Fifty-five percent of control females and 33% of treatment females conceived within the first 14 days of the study. All control females and 79% of treatment females successfully delivered at least one litter. These differences between treatment and control populations provide minimal support for the Bruce Effect when compared with results from laboratory studies. Nulliparous females may have experienced some pregnancy disruption, but not parous females. Removal of mates, rather than exposure to strange males, may have contributed more to the lower reproductive success of treatment females than exposure to strange males. Treatment females, however, had lower juvenile recruitment than controls, which may have been due to infanticide from strange males. Our results are more similar to those of the field study of the gray-tailed vole than predicted, based on laboratory studies of prairie voles.
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Exposure to strange adults does not cause pregnancy disruption or infanticide in the gray-tailed vole
Behavioral Ecology and Sociobiology, 1999Co-Authors: Helen M. De La Maza, Jerry O Wolff, Amber LindseyAbstract:A widely accepted paradigm in mammalian behavioral biology is that exposure to unfamiliar males causes pregnancy disruption in female rodents (commonly known as the Bruce Effect). This behavioral phenomenon has been demonstrated in the laboratory with at least 12 species of rodents, primarily within the genus Microtus , and is supposedly an adaptation that provides male perpetrators with reproductive access to females, and functions, for females, as a counterstrategy to infanticide. However, neither the Bruce Effect nor its adaptive significance have been tested experimentally in the field. In a controlled field study, we exposed reproducing female gray-tailed voles ( Microtus canicaudus ) to treatments in which males were removed and replaced by either unfamiliar males or females, and found no significant differences in intervals between parturitions, number of pregnancies, and juvenile recruitment among the treatment and control animals. Thus, we conclude that neither the Bruce Effect nor infanticide occurred differentially as a consequence of the treatments in gray-tailed voles. Multimale mating to confuse paternity, and postpartum estrus resulting in simultaneous pregnancy and lactation may deter infanticide and functionally negate any benefits of pregnancy disruption in gray-tailed voles and perhaps other murid rodents with similar mating systems. In light of our results, we recommend field verification for other species of murid rodents that exhibit the Bruce Effect in the laboratory before the results are applied to evolutionary theory.
Denys Decatanzaro - One of the best experts on this subject based on the ideXlab platform.
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Sex steroids as pheromones in mammals: the exceptional role of estradiol.
Hormones and behavior, 2014Co-Authors: Denys DecatanzaroAbstract:This article is part of a Special Issue (Chemosignals and Reproduction). Whether from endogenous or exogenous sources, 17β-estradiol (E2) has very powerful influences over mammalian female reproductive physiology and behavior. Given its highly lipophilic nature and low molecular mass, E2 readily enters excretions and can be absorbed from exogenous sources via nasal, cutaneous, and other modes of exposure. Indeed, systemic injection of tritiated estradiol ((3)H-E2) into a male mouse or bat has been shown to produce significant levels of radioactivity in the reproductive tissues and brain of cohabiting female conspecifics. Bioactive E2 and other steroids are naturally found in male mouse urine and other excretions, and males actively direct their urine at proximate females. Very low doses of E2 can mimic the Bruce Effect (disruption of peri-implantation pregnancy by novel males), the Vandenbergh Effect (early reproductive maturation induced by novel males), and male-induced estrus and ovulation. Males' capacities to induce the Bruce and Vandenbergh Effects can both be diminished by manipulations that reduce their urinary E2. Uterine dynamics during the Bruce and Vandenbergh Effects are consistent with the actions of E2. Collectively, these data demonstrate a critical role of male-sourced E2 in these major mammalian pheromonal Effects.
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Oestradiol treatment restores the capacity of castrated males to induce both the Vandenbergh and the Bruce Effects in mice (Mus musculus)
Reproduction (Cambridge England), 2011Co-Authors: Joelle B. Thorpe, Denys DecatanzaroAbstract:Androgen-dependent urinary constituents from males hasten reproductive maturation (the Vandenbergh Effect) and disrupt peri-implantation pregnancy (the Bruce Effect) in nearby females. Each of these Effects can be mimicked in socially isolated females by direct administration of exogenous oestrogens. The current experiments were designed to determine the role of males' urinary 17β-oestradiol (E(2)) in their capacities to induce these Effects. A preliminary experiment showed that both males on a phyto-oestrogen-rich soy-based diet and those on a phyto-oestrogen-free diet could induce both Effects. For subsequent experiments, males were castrated and treated with either oil vehicle or E(2). Enzyme immunoassay was conducted on non-invasively collected urine samples from these males. Concentrations of urinary testosterone were subnormal in both conditions, but urinary E(2) was restored to the normal range for intact males in castrates given E(2). Urinary creatinine was also quantified as a measure of hydration and was significantly reduced in males treated with E(2). Castration diminished the capacity of males to promote growth of the immature uterus and also their capacity to disrupt blastocyst implantation in inseminated females. Injections of E(2) to castrated males restored both capacities. These data converge with other studies indicating that E(2) is the main constituent of male urine responsible for induction of both the Vandenbergh and the Bruce Effects.
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Blastocyst implantation is vulnerable to stress-induced rises in endogenous estrogens and also to excretions of estrogens by proximate males
Journal of reproductive immunology, 2011Co-Authors: Denys DecatanzaroAbstract:Abstract Although estrogens help to prepare the uterus for blastocyst implantation, small elevations above optimal levels can prevent implantation. In diverse mammals, stressors including extreme temperatures, physical restraint, environment changes, and predator exposure can impede implantation. This can be mimicked by treating inseminated females with exogenous estrogens. Peri-implantation stressors can elevate estradiol levels, while exogenous estrogen antibodies can mitigate the influences of stress on implantation. Another stimulus that disrupts implantation is exposure to novel males (the "Bruce Effect"). This Effect, best known in mice, is mediated by chemical factors in male urine. Although a longstanding hypothesis relates the Bruce Effect to the female's olfactory memory trace of the sire and reaction to odors of novel males, evidence increasingly supports an alternative hypothesis that implicates males' excreted estrogens. Male urine contains substantial amounts of unconjugated estradiol, and males actively deliver urine toward females which impinges on their nasal region. The Bruce Effect can be diminished by drug treatment of males that reduces urinary estradiol, and by treatment of females with estrogen antibodies. Tritiated estradiol ( 3 H-E 2 ) systemically delivered to male mice was evident in their urine. When 3 H-E 2 was given intra-nasally to inseminate females, it was found in their circulation and in diverse tissues, with greatest radioactivity in the uterus. Accordingly, evidence indicates that males' excreted estradiol can arrive at the female reproductive tract, where it can disrupt implantation through known mechanisms.
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Excretion and Binding of Tritium-Labelled Oestradiol in Mice (Mus musculus): Implications for the Bruce Effect
Reproduction (Cambridge England), 2010Co-Authors: Adam C Guzzo, Robert G. Berger, Denys DecatanzaroAbstract:Male mouse urine contains 17beta-oestradiol (E(2)) and other steroids. Given that males actively direct urine at proximate females and intrauterine implantation of blastocysts is vulnerable to minute amounts of exogenous oestrogens, males' capacity to disrupt early pregnancy could be mediated by steroids in their urine. When male mice were implanted with osmotic pumps containing tritium-labelled E(2) ((3)H-E(2)) or injected i.p. with (3)H-E(2), radioactivity was reliably detected in their urine. Following intranasal administration of (3)H-E(2) to inseminated females, radioactivity was detected in diverse tissue samples, with there being significantly more in reproductive tissues than in brain tissues. When urine was taken from males injected with (3)H-E(2), and then intranasally administered to inseminated females, radioactivity was detected in the uterus, olfactory bulbs, and mesencephalon and diencephalon (MC+DC). When inseminated and ovariectomised females were perfused at the point of killing to remove blood from tissues, more radioactivity was detected in the uterus than in muscle, olfactory bulbs, MC+DC and cerebral cortex. Pre-treatment with unlabelled E(2) significantly reduced the uptake of (3)H-E(2) in the uterus. Taken with evidence that males deliver their urine to the nasal area of females, these results indicate that male urinary E(2) arrives in tissues, including the uterus, where it could lead to the disruption of blastocyst implantation.
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Inseminated female mice (Mus musculus) investigate rather than avoid novel males that disrupt pregnancy, but sires protect pregnancy.
Journal of comparative psychology (Washington D.C. : 1983), 2004Co-Authors: Denys Decatanzaro, Tasleem MurjiAbstract:Experiment 1 replicated the Bruce Effect, showing pregnancy termination in CF1 strain female mice (Mus musculus) housed underneath novel heterogeneous strain (HS) males. In a 4-arm maze in Experiment 2, inseminated CF1 females approached novel HS males more often than CF1 sires or unfamiliar CF1 males. In Experiment 3, inseminated females showed random nesting sites when housed continuously underneath 4 compartments containing the sire, a novel CF1 male, a novel HS male, and no stimulus. In Experiment 4, when inseminated females were housed with or without the sire below novel HS males, the sire's presence decreased female interaction with novel males and mitigated the Bruce Effect. Inseminated females do not reliably avoid males that disturb pregnancy unless the sire is immediately present.
Thomas Rülicke - One of the best experts on this subject based on the ideXlab platform.
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The Bruce Effect in Norway Rats
Biology of reproduction, 2012Co-Authors: Vera Marashi, Thomas RülickeAbstract:ABSTRACT Intrauterine implantation of fertilized ova can be blocked by exposing recently inseminated females with an unfamiliar male. This selective pregnancy failure, designated as the Bruce Effect (Bruce, Nature 1959; 184:105), is well studied in laboratory mice and has been confirmed in several other rodent species. However, no clear information exists concerning this phenomenon in the laboratory rat. The present study was conducted to investigate whether or not the Bruce Effect exists in the rat. Females of two F1 hybrid strains (ntotal = 354) with different MHC genotypes (F344BNF1, RT1lv1/n, and LEWPVGF1, RT1l/c) were mated with males of their own strain and subsequently exposed during the first 4 days postcoitus either to a male of the other hybrid strain or to an unfamiliar male of the same strain as the stud. The litter rate of each treatment group was determined. As a control, mated females of both strains were reexposed to the stud male to determine baseline litter rates. Female rats of both F1 ...
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Early maternal investment in mice: no evidence for compatible‐genes sexual selection despite hybrid vigor
Journal of evolutionary biology, 2006Co-Authors: Thomas Rülicke, N. Guncz, Claus WedekindAbstract:Confronting a recently mated female with a strange male can induce a pregnancy block ('Bruce Effect'). The physiology of this Effect is well studied, but its functional significance is still not fully understood. The 'anticipated infanticide hypothesis' suggests that the pregnancy block serves to avoid the cost of embryogenesis and giving birth to offspring that are likely to be killed by a new territory holder. Some 'compatible-genes sexual selection hypotheses' suggest that the likelihood of a pregnancy block is also dependent on the female's perception of the stud's and the stimulus male's genetic quality. We used two inbred strains of mice (C57BL/6 and BALB/c) to test all possible combinations of female strain, stud strain, and stimulus strain under experimental conditions (N(total) = 241 mated females). As predicted from previous studies, we found increased rates of pregnancy blocks if stud and stimulus strains differed, and we found evidence for hybrid vigour in offspring of between-strain mating. Despite the observed heterosis, pregnancies of within-strain matings were not more likely to be blocked than pregnancies of between-strain matings. A power analysis revealed that if we missed an existing Effect (type-II error), the Effect must be very small. If a female gave birth, the number and weight of newborns were not significantly influenced by the stimulus males. In conclusion, we found no support for the 'compatible-genes sexual selection hypotheses'.
Ralph Catalano - One of the best experts on this subject based on the ideXlab platform.
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Separating the Bruce and Trivers-Willard Effects in theory and in human data.
American journal of human biology : the official journal of the Human Biology Council, 2017Co-Authors: Ralph Catalano, Alison Gemmill, Joan A. Casey, Deborah Karasek, Holly C. Stewart, Katherine SaxtonAbstract:OBJECTIVES Theories of reproductive suppression predict that natural selection would conserve mechanisms that abort the gestation of offspring otherwise unlikely to thrive in prevailing environments. Research reports evidence among humans of at least two such mechanisms-the Trivers-Willard and Bruce Effects. No literature, however, compares the mechanisms nor estimates their relative contribution to observed characteristics of human birth cohorts. We describe similarities and differences between the Trivers-Willard and Bruce Effects and explore high quality historical data from Sweden to determine which mechanism better describes temporal variation in the ratio of males to females in birth cohorts. METHODS We measure Trivers-Willard exposures with the death rate among women of reproductive age. We measure Bruce exposures with the death rate among children. We use time-series regression methods to estimate the relative contribution of the Trivers-Willard and Bruce Effects to temporal variation in historical Swedish secondary sex ratio data. RESULTS We find that the Bruce Effect appears to be a better predictor of the secondary sex ratio than does the Trivers-Willard Effect. CONCLUSIONS Attempts to identify mechanisms by which reproductive suppression affects fetal loss and characteristics of human birth cohorts should consider the Bruce Effect as an alternative to the Trivers-Willard Effect.
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Reproductive suppression follows threats to child survival.
Journal of evolutionary biology, 2017Co-Authors: Katherine Saxton, Alison Gemmill, Ralph CatalanoAbstract:Natural selection presumably conserved mechanisms that allow females to block or terminate gestation when environmental circumstances threaten the survival of offspring. One example of this adaptive reproductive suppression, the Bruce Effect, has been identified in several species, both in the laboratory and in the wild. Although descriptive epidemiology reports low fertility among women experiencing stressful circumstances, attempts to detect a Bruce Effect in humans have been rare and limited. We contribute to this limited work by examining the relationship between the odds of child death and the sex ratio at birth in Sweden for the years 1751-1840. We find evidence of a generalized Bruce Effect in humans in that unexpected changes in child mortality predict opposite unexpected changes in the secondary sex ratio in the following year, even after adjusting for period life expectancy. Our analysis broadens the scope of the Bruce Effect literature to include humans, suggesting that women, through noncognitive decisional biology, adjust reproductive strategies and investments in response to changing environmental conditions.
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twinning in norway following the oslo massacre evidence of a Bruce Effect in humans
Twin Research and Human Genetics, 2016Co-Authors: Ralph Catalano, Katherine Saxton, Alison Gemmill, Terry HartigAbstract:Emerging theory and empirical work suggest that the Bruce Effect', or the increase in spontaneous abortion observed in non-human species when environments become threatening to offspring survival, ...
