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PubMed2004

Which reproductive technologies are most relevant to studying, managing and conserving wildlife?

The advent of in vitro fertilisation (IVF) and embryo transfer in the 1970s led to speculation about the potential value of these and other 'reproductive technologies' to conserving endangered species. So far, and for the most part, assisted breeding techniques that are routine in domesticated species are not easily adapted to wildlife. Species differences in reproductive form (anatomy/morphology) and function (mechanisms regulating reproductive success) limit the practical applicability for offspring production. Thus, the limiting factor is the lack of basic knowledge about thousands of unstudied species, the foundation that is essential to allowing reproduction to be enhanced and/or controlled. There now is excellent evidence that reproductive technologies are most useful as tools for studying how different species reproduce, especially defining novel and unique mechanisms. The present paper reviews the status and relevance of various reproductive technologies that are useful or have potential for wildlife. Modern examples of progress are provided indicating how these tools are being used to understand ways that wildlife species reproduce and, in some cases, how such knowledge has been used for successful assisted breeding, improved management and conservation.

Animals↗

PubMed2004

Tug-of-war over reproduction in a social bee.

One of the main transitions in evolution is the shift from solitary organisms to societies with reproductive division of labour. Understanding social evolution requires us to determine how ecological, social and genetic factors jointly influence group stability and partitioning of reproduction between group members. Here we test the role of the three key factors predicted to influence social evolution by experimentally manipulating them in a social allodapine bee. We show that increased relatedness between nestmates results in more even reproduction among group members and a greater productivity per individual. By contrast, the degree of reproductive skew is not influenced by the opportunity for solitary breeding or by the potential benefits of cooperation. Relatedness also has a positive effect on group stability and overall productivity. These findings are in line with predictions of the tug-of-war models, in which the degree of reproductive division of labour is determined primarily by selfish competition between group members. The alternative view, where the degree of reproductive skew is the outcome of a social contract between potential breeders, was not supported by the data.

Animals↗

PubMed2002

Reproductive success in reindeer males in a herd with varying sex ratio.

In polygynous species, male reproductive success is often correlated with dominance status of individual males and sex ratio in the population. Reindeer, Rangifer tarandus, is a polygynous species, and here we compared the variation in male reproductive success and dominance status during two successive years in a herd with a male:female sex ratio of 1:7 and 1:3. Copulations were recorded, together with data on male dominance hierarchy and size of mating groups. Male reproductive success was estimated by paternity analysis of calves using microsatellite DNA markers. The distribution of reproductive success among the males was highly skewed for both years with the most dominant male also being the most successful. The largest mating group was established in the herd with the least skew in sex ratio. In this herd some of the adult males present were less reproductively successful than some of the more subordinate younger males. Estimates of the mating group size of males, correcting for dominance status when more than one male is present in the groups, gave good prediction of individual males' reproductive success.

Animals↗

PubMed2002

Surface alterations in the bovine pelvic peritoneum following rectal examination of reproductive organs: a scanning electron microscopy study.

The aim of the present study was to evaluate possible injury provoked by an intensive reproductive programme based on rectal palpation in the cow. Alterations to the mesothelial surface of the peritoneum and to the oviductal mucosa were explored by scanning electron microscopy (SEM). Nine multiparous Friesian cows were selected from each of two commercial dairy herds. Cows in herd 1 were maintained on a weekly reproductive health programme, while those in herd 2 were not subjected to gynaecological exploration. Surface features of the mesothelial cells of the reproductive tract and adjacent ligaments, and the oviductal mucosa were explored by SEM observation of tissue specimens from each animal. Six cows in the intensive reproductive programme showed microscopic alterations of the peritoneal surface. Strands were observed in the oviducts and adjacent ligaments in five of these cows. These strands, composed of filaments covered with mesothelial cells, were probably adhesions. Cells with abundant vacuoles on their surface were detected in the mesothelium corresponding to three animals, two of which also showed microscopic strands. No peritoneal surface alterations were observed in the cows from herd 2. No oviductal mucosal modifications were detected in either group. These findings suggest that intensive reproductive programmes based on rectal palpation may increase the risk of peritoneal surface alterations in the cow, but effects on reproductive physiology are unlikely.

Animals↗

PubMed1999

Effects of growth hormone overexpression and growth hormone resistance on neuroendocrine and reproductive functions in transgenic and knock-out mice.

Transgenic mice overexpressing growth hormone (GH) exhibit alterations in the function of the hypothalamic-pituitary-gonadal (HPG) axis and the H-P-adrenal axis. Alterations in the turnover of hypothalamic neurotransmitters, in plasma hormone levels, and in regulation of their release are associated with reproductive deficits, particularly in females. Results reported after publication of our minireview on this subject provided evidence that GH-transgenic mice have increased binding of GH to GH binding proteins in plasma, are hyperinsulinemic and insulin resistant, and have major alterations in energy budgets with increased allocation to growth. Reduced life span and fertility of these animals may be related to insufficient allocation of energy to reproduction and maintenance. Growth hormone resistance induced by transgenic expression of an antagonistic bGH analog or by targeted disruption (knock-out, KO) of the GH receptor (GH-R) gene leads to dramatic suppression of plasma levels of insulin-like growth factor-1 (IGF-1), and dwarf phenotype due to reduced growth and increased adiposity. In both models of GH resistance, there are marked reproductive deficits in females, decline of breeding performance of males, and alterations in the function of the HPG axis. In GH-R-KO females, puberty is delayed, and litter size is reduced. Fetal weights are reduced whereas placental weights are increased, and the weight of newborn pups is reduced despite an increase in the length of gestation. In GH-R-KO males, copulatory behavior and fertility are reduced, plasma PRL is elevated, and responses to luteinizing hormone releasing hormone (LHRH) in vivo and to LH in vitro are suppressed. However, reproductive deficits in GH-R-KO mice are very mild when compared to those described previously in IGF-KO animals. Apparently, the amounts of IGF-1 that may be produced locally in the absence of GH stimulation are sufficient for sexual maturation and fertility in both sexes, whereas quantitative deficits in reproductive function reflect absence of GH-dependent IGF-1 production and other consequences of eliminating GH signaling. The reproduction phenotype of the GH-R-KO mice is also mild when compared to dwarf mice that lack GH, prolactin (PRL), and thyroid stimulating hormone (TSH). This is presumably related to the presence of redundant mechanisms in the stimulatory control of the gonads by the pituitary and the ability of animals capable of producing PRL and TSH to compensate partially for the absence of GH signaling.

Animals↗

PubMed1999

Intergenerational concepts of adolescent sexuality: implications for community-based reproductive health care with Haitian immigrants.

Intergenerational conflict occurs when immigrant parents hold different values from those of their more rapidly acculturating offspring. These conflicts frequently involve disparate views related to sex roles and reproduction. A community-based study of 19 immigrant Haitian parent-adolescent pairs in South Florida compared their attitudes and values about sexuality and reproduction. Data were obtained through focused, open-ended interviews. Content analysis procedures at the level of words and phrases facilitated the categorization of responses. Data revealed considerable differences between parents and adolescents about the sources and types of information learned about reproduction and contraception, when such information is learned, and expectations regarding premarital sexual intercourse. Both parents and adolescents lacked accurate biomedical information about contraception, placed responsibility for contraceptive use primarily on the female partner, considered reproduction a natural rather than a medical event, and believed parents have the major responsibility for educating children about reproduction and contraception. Implications for culturally-appropriate health care center on increasing the role of the public health nurse in health education, minimizing intergenerational and intercultural conflict, and engaging the Haitian immigrant community in the promotion of reproductive health.

Adolescent↗

PubMed2003

[Reproductive disorders in Glossina palpalis palpalis (Diptera: Glossinidae) in forested areas of Ivory Coast].

Study of reproductive disorders were carried out through the dissection of 11,012 tsetse flies caught over a period of one year in forested different habitats of Glossina palpalis palpalis of Daloa in Ivory Coast. The proportion of females with reproductive disorders was very low and estimated at 0.79%. Out of 87 tsetse files with reproductive disorders, 93.10% were abortions, 5.77% were ovular blockage and 1.13% was uterine pupaison. Reproductive disorders were recorded from all age groups: 0.78% in young parous (out of 6,398 tsetse flies examined) and 0.80% in old parous (out of 4,614 tsetse flies dissequed). Our results show that reproductive disorders occur at any stage of the female pregnancy cycle. Amplifying these reproductive disorders using chemical compounds is proposed as a way of improving the efficacy of insecticide-impregnated targets (pour-on, traps and screens) of tsetse control in rain-forest areas.

Animals↗

PubMed1994

Transgenic animals in male reproduction research.

Although transgenic mouse technology has already been widely used for the study of gene function and regulation in many areas of biomedicine, it has been applied only sporadically to the investigation of testicular function. Nevertheless, the contribution of this experimental approach to the understanding of male reproduction is considerable, not least because of the frequency of infertility in transgenic mice. Transgenic mice can be produced by microinjection of DNA constructs in the male pronucleus of fertilized eggs that are then retransferred into the oviducts of pseudopregnant females and allowed to develop to term. A proportion of the offspring have the foreign DNA sequences permamently integrated into the genome and thus become transgenic. In this way it is possible to obtain either the over-expression of genes, which can be targeted to the testis using testis-specific promoters, or to effect interruption of the functional integrity of genes by insertional mutagenesis. The regulation of gene expression in vivo can be studied by producing transgenic mice where the transgene is composed of the regulatory sequences of a gene of interest driving the expression of a reporter gene. Specific genes can be "knocked out" by homologous recombination. This article reviews the contribution of the transgenic approach to the following areas of male reproduction: the identification of factors involved in sex determination and development of the reproductive tract; the study of the function and expression of genes important for spermatogenesis and male reproduction; the identification of genes involved in spermatogenesis and of genomic sequences directing the expression of a transgene in the testis; the study of the function of specific reproductive tissues or cells in vivo; oncogenesis in reproductive tissues; the creation of cell lines suitable for in vitro studies; gene therapy.

Animals↗

PubMed2000

The role of HOX genes in the development and function of the female reproductive tract.

HOX genes are a family of regulatory genes that encode transcription factors and are essential during embryonic development. These genes are highly conserved between species such that all metazoans possess a common genetic system for embryonic patterning. This system is conserved in the reproductive tract, where HOX genes are involved in the development of the müllerian system. The reproductive tract is unusual in that HOX genes continue to be expressed in the adult. HOX genes are essential both for appropriate reproductive tract development and for adult function. This article reviews the role of HOX genes in the development of the reproductive tract and the effect of HOX gene mutations on the development of the reproductive tract in both mice and humans. It then reviews the role and regulation of HOX genes in the adult function of the reproductive tract, specifically evidence that HOX genes are important for human endometrial development and receptivity.

Animals↗

PubMed2002

Interactions of stress and reproduction - a personal view.

In the first part of this article, the authors discuss the effect of stress upon reproduction. The paper begins with a discussion of the various stressful factors that influence the functions of reproductive organs under various circumstances, including menarche, gestation and lactation. In general, physical and emotional stress has a negative impact upon reproductive function. Chronic stress may delay pubescence and, during the reproductive years, may impair oogenesis and spermatogenesis. This process may result in transitory infertility in women and permanent sterility in men. If associated with pregnancy, stress may be conducive to spontaneous abortion or premature birth. The second part of the article deals with stressful stimuli attributable to the reproductive process, the problem of infertility, techniques of assisted reproduction, and the management of unwanted gestations including induced abortion, fetal reduction, spontaneous miscarriage as well as in utero fetal death. The stress generating effects of singleton and multiple pregnancies and births are also outlined in some detail. In the third part of this article discuss effect of stress upon the fetus directly or through the maternal organism.

Female↗

PubMed2006

Costs of reproduction as related to the timing of phenological phases in the dioecious Shrub Pistacia lentiscus L.

Females of woody dioecious species usually devote more resources to reproduction than males. This may lead to a decrease in female survival and growth. The costs of reproduction, however, can be lightened through a number of mechanisms, as for example avoiding the temporal coincidence of reproduction and vegetative growth. The aim of this study was to evaluate whether males and females of P. lentiscus differ in the timing of their vegetative growth, and to assess whether the sequencing of vegetative growth and reproduction reduces reproductive costs. We monitored phenology in males and females. We also compared male and female allocation of nutrients and biomass in the branch, and the developmental stability of the growing shoots. We did this both prior to and at the end of the fruiting period. Males and females showed similar vegetative and flowering phenologies. Males invested more biomass in flowering, but the sexes showed equal vegetative biomass and nutrient content prior to the fruiting period. In female branches, no trade-off was found between fruit load and current-year vegetative growth. In P. lentiscus, avoiding the overlap of flowering, vegetative growth and fruiting probably contributes to reduce the immediate costs of reproductive efforts, both in males and females.

Biomass↗

PubMed2002

Susceptibility of reproduction in female pigs to impairment by stress and the role of the hypothalamo-pituitary-adrenal axis.

Although it is generally considered that stress can impair reproduction, we suggest that the impact of acute or repeated acute stress or acute or repeated acute elevations of cortisol are of little consequence in female pigs, even if these occur during the series of endocrine events that induce oestrus and ovulation. It is important to understand the impact of acute stress on reproduction because, in the intensive production of livestock, animals are often subjected to short-term challenges. There seems little doubt that reproduction in a proportion of female pigs is susceptible to impairment by severe and prolonged stress or the sustained elevation of cortisol but only when this continues for a substantial period. In female pigs, where reproduction is susceptible to impairment by severe prolonged stress, it is possible that the mediators of this suppression are cortisol, corticotrophin-releasing factor and vasopressin but, in pigs, there is evidence to suggest that adrenocorticotrophic hormone is not involved. Other substances secreted during stress may be involved but these are not considered in this review. It is possible that the mediators of stress act at any level of the hypothalamo-pituitary-ovarian axis. Although a variety of experimental manipulations have provided potential mediators and mechanisms for the stress-induced suppression of reproduction, these experimental manipulations rarely represented physiological circumstances so it is not clear if such mechanisms would be important in a physiological context. The precise mediators and mechanisms by which hormones released during stress may inhibit reproductive processes during severe prolonged stress are yet to be determined.

Adrenal Glands↗

PubMed2005

Effects of supplementary food on the winter inhibition of reproduction in male and female four-striped field mice (Rhabdomys pumilio).

The effects of winter food supplementation on reproduction in the seasonally breeding four-striped field mouse Rhabdomys pumilio were investigated at Mountain Zebra National Park in the Eastern Cape Province of South Africa. On both control and supplemented grids, reproductive activity in females was inhibited; no pregnant females were collected and juveniles were only present in the first winter month. The provision of additional food resulted in an increase in body mass and mass of the male and female reproductive organs. However, all males, from both grids, were spermatogenically active. Ovarian activity was not stimulated by the provision of additional food, but the development of the uterus was and the endometrium was thicker and more vascularised in mice from the supplemented grid than from the control grid. We conclude that seasonal reproduction in R. pumilio is controlled by the females, in which reproductive activity is inhibited in winter. However, the provision of supplementary food was not sufficient to override the reproductive inhibition.

Animals↗

PubMed2005

Deficit in reproduction in polygynously mated females of the monogamous mound-building mouse Mus spicilegus.

In monogamous mound-building mice Mus spicilegus, facultative polygyny was observed in April, at the beginning of the reproductive season. In order to evaluate the cost of polygyny, we compared, under laboratory conditions, the reproductive success of trios and pairs composed of sister females mated with unrelated brother males. Females in trios were able to tolerate each other during the reproductive period and to reproduce with the same male under spatial constraints. Nevertheless, polygyny had a strong negative effect on the reproductive success of the females. The average number of young per litter was smaller in trio females than in paired females, whereas the interval between two successive litters was higher. As a result, the number of litters and the number of young per time unit were smaller in each of the trio females compared with paired females. Agonistic behaviour being absent in trios, our results strongly suggest that living in trios led to pheromonal production that affected the female physiological state and reproduction. Males of trios did not obtain a better reproductive success than males in pairs.

Animals↗

PubMed1999

Carboxylesterase overexpression in the male reproductive tract: a universal safeguarding mechanism?

Data on expression patterns of carboxylesterases in the male reproductive tract of different animal groups (i.e. bivalve mollusks, fruitflies and rodents) are summarized to highlight some particularly interesting questions in the context of sperm differentiation, maturation and function. The male reproductive system, in spite of extreme variation in the anatomical/morphological organization in different species, is characterized by similar patterns of male-dependent carboxylesterase overexpression. The phenomenon of conserved carboxylesterase overexpression indicates similar male sex-associated functions of the enzymes. There is possible evidence of carboxylesterase recruitment by male reproductive-tract tissues indicating that it could be adaptive for spermatogenesis, sperm maturation and sperm use. Moreover, this idea can be extended to include a sperm cell lineage protection. This issue is discussed in the light of recent data on environmental reproductive xenobiotics that can provide a basis for a hypothetical explanation of carboxylesterase overexpression in the male reproductive tract. Based on a well-known role of carboxylesterases in detoxification of environmental chemicals such as organophosphate pesticides, it is proposed that various male genital tract carboxylesterases may be characterized by a similar physiological function to protect the male reproductive system against xenobiotic influences that could provoke its dysfunction, thus altering sperm differentiation and maturation.

Amino Acid Sequence↗

PubMed2002

Loss of circadian clock function decreases reproductive fitness in males of Drosophila melanogaster.

Circadian coordination of life functions is believed to contribute to an organism's fitness; however, such contributions have not been convincingly demonstrated in any animal. The most significant measure of fitness is the reproductive output of the individual and species. Here we examined the consequences of loss of clock function on reproductive fitness in Drosophila melanogaster with mutated period (per(0)), timeless (tim(0)), cycle (cyc(0)), and Clock (Clk(Jrk)) genes. Single mating among couples with clock-deficient phenotypes resulted in approximately 40% fewer progeny compared with wild-type flies, because of a decreased number of eggs laid and a greater rate of unfertilized eggs. Male contribution to this phenotype was demonstrated by a decrease in reproductive capacity among per(0) and tim(0) males mated with wild-type females. The important role of clock genes for reproductive fitness was confirmed by reversal of the low-fertility phenotype in flies with rescued per or tim function. Males lacking a functional clock showed a significant decline in the quantity of sperm released from the testes to seminal vesicles, and these tissues displayed rhythmic and autonomous expression of clock genes. By combining molecular and physiological approaches, we identified a circadian clock in the reproductive system and defined its role in the sperm release that promotes reproductive fitness in D. melanogaster.

Animals↗

PubMed2004

Previous-year reproduction reduces photosynthetic capacity and slows lifetime growth in females of a neotropical tree.

Females of dioecious plant species typically invest more in reproduction than males because they produce seeds, fruits, and associated structures in addition to flowers. If females are unable to compensate by up-regulating rates of photosynthesis or by reproducing less frequently than males, their greater reproductive investment may result in reduced growth or higher mortality. Here we provide evidence of the cost of reproduction in Ocotea tenera (Lauraceae), a dioecious neotropical tree common in lower montane forests of Monteverde, Costa Rica. Over periods of 12-21 years, females grew more slowly than males in a natural population and in two experimental plots where we were able to control for genotype, age, habitat, and reproductive history. Simultaneous measurements of 10 matched pairs of sibling trees of the opposite sex but same age demonstrated that the photosynthetic capacities of females were 13% lower than those of males. Among females, photosynthetic capacity was negatively correlated with fruit production during the most recent reproductive season but not with lifetime fruit production. Sexual size dimorphism in adult O. tenera trees appears to be a nonadaptive consequence of trading off recent reproduction against maintenance of the photosynthetic apparatus, with long-term negative effects on growth.

Costa Rica↗

PubMed2004

A prolactin family paralog regulates reproductive adaptations to a physiological stressor.

Successful species develop strategies to optimize their reproductive performance. This optimization likely includes the evolution of genes that specifically permit reproduction in physiologically challenging conditions. The prolactin (PRL) family gene cluster is one of 25 mouse-specific gene clusters, the majority of which are associated with reproduction. A prevailing theme characterizing the PRL family is its connection with pregnancy and mechanisms controlling viviparity. PRL-like protein A (PLP-A) is one of 26 genes located within the PRL family locus. It is a nonclassical member of the PRL family (e.g., PLP-A does not use the PRL receptor) produced by trophoblast cells of the chorioallantoic placenta and acts on uterine natural killer cells. In this report, the biology of PLP-A has been investigated by generating mice with a PLP-A null mutation. Under standardized animal husbandry conditions, PLP-A possesses modest effects on reproductive performance. However, this same gene is critical for reproduction when mice are exposed to a physiological stressor. Wild-type mice exposed to hypobaric hypoxia during gestation readily adapt and maintain their pregnancies, whereas PLP-A null mutant mice fail to adapt, resulting in pregnancy failure. PLP-A contributes to hypoxia-induced adaptations critical to hemochorial placentation and thus nutrient flow to extraembryonic and embryonic tissues. The findings provide insights into species-specific reproductive adaptations.

Adaptation, Physiological↗