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PubMed2005

Juvenile hormone, reproduction, and worker behavior in the neotropical social wasp Polistes canadensis.

Previous studies of the division of labor in colonies of eusocial Hymenoptera (wasps and bees) have led to two hypotheses regarding the evolution of juvenile hormone (JH) involvement. The novel- or single-function hypothesis proposes that the role of JH has changed from an exclusively reproductive function in primitively eusocial species (those lacking morphologically distinct queen and worker castes), to an exclusively behavioral function in highly eusocial societies (those containing morphologically distinct castes). In contrast, the split-function hypothesis proposes that JH originally functioned in the regulation of both reproduction and behavior in ancestral solitary species. Then, when reproductive and brood-care tasks came to be divided between queens and workers, the effects of JH were divided as well, with JH involved in regulation of reproductive maturation of egg-laying queens, and behavioral maturation, manifested as age-correlated changes in worker tasks, of workers. We report experiments designed to test these hypotheses. After documenting age-correlated changes in worker behavior (age polyethism) in the neotropical primitively eusocial wasp Polistes canadensis, we demonstrate that experimental application of the JH analog methoprene accelerates the onset of guarding behavior, an age-correlated task, and increases the number of foraging females; and we demonstrate that JH titers correlate with both ovarian development of queens and task differentiation in workers, as predicted by the split-function hypothesis. These findings support a view of social insect evolution that sees the contrasting worker and queen phenotypes as derived via decoupling of reproductive and brood-care components of the ancestral solitary reproductive physiology.

Aging↗

PubMed2005

Genetic diversity and reproductive success in mandrills (Mandrillus sphinx).

Recent studies of wild animal populations have shown that estimators of neutral genetic diversity, such as mean heterozygosity, are often correlated with various fitness traits, such as survival, disease susceptibility, or reproductive success. We used two estimators of genetic diversity to explore the relationship between heterozygosity and reproductive success in male and female mandrills (Mandrillus sphinx) living in a semifree ranging setting in Gabon. Because social rank is known to influence reproductive success in both sexes, we also examined the correlation between genetic diversity and social rank in females, and acquisition of alpha status in males, as well as length of alpha male tenure. We found that heterozygous individuals showed greater reproductive success, with both females and males producing more offspring. However, heterozygosity influenced reproductive success only in dominant males, not in subordinates. Neither the acquisition of alpha status in males, nor social rank in females, was significantly correlated with heterozygosity, although more heterozygous alpha males showed longer tenure than homozygous ones. We also tested whether the benefits of greater genetic diversity were due mainly to a genome-wide effect of inbreeding depression or to heterosis at one or a few loci. Multilocus effects best explained the correlation between heterozygosity and reproductive success and tenure, indicating the occurrence of inbreeding depression in this mandrill colony.

Animals↗

PubMed2006

Ecological divergence exhibits consistently positive associations with reproductive isolation across disparate taxa.

To what degree is the divergent adaptation responsible for life's phenotypic variety also responsible for generating the millions of species that manifest this variation? Theory predicts that ecological divergence among populations should promote reproductive isolation, and recent empirical studies provide support for this hypothesis in a limited number of specific taxa. However, the essential question of whether ecology plays a truly general role in speciation has yet to be systematically evaluated. Here we address this integral issue using an approach that adds an ecological dimension to comparative studies investigating the relationship between reproductive isolation and divergence time. Specifically, we quantify ecological divergence for >500 species pairs from eight plant, invertebrate, and vertebrate taxa and statistically isolate its association with reproductive isolation. This approach demonstrates a highly consistent and significant positive association between ecological divergence and reproductive isolation across taxa. This relationship was also observed across different aspects of ecological divergence and components of reproductive isolation. These findings are highly consistent with the hypothesis that ecological adaptation plays a fundamental and taxonomically general role in promoting reproductive isolation and speciation.

Animals↗

PubMed2006

A Caenorhabditis elegans tissue model of radiation-induced reproductive cell death.

We have developed a tissue model of radiation-induced reproductive cell death in the nematode Caenorhabditis elegans. Reproductive cell death is the primary mode of death in tissue multipotential precursor cells, or "clonogens," the targets of cytotoxic therapy, whose elimination results in normal tissue damage as well as solid-tumor eradication. Through extensive morphologic and genetic analysis, we have confirmed that cell death in this model represents reproductive cell death in isolation from apoptotic cell death, affording the opportunity to define the genetic pathways required for protection from reproductive cell death. We have additionally found that the DNA damage response pathway is necessary for protection from reproductive cell death, supporting the long-held tenet that DNA damage is the cause of reproductive cell death and further validating this model. This genetic tissue model provides a valuable tool for oncology-based research and affords a platform to broaden our insight into responses to cytotoxic therapy in tissues.

Animals↗

PubMed2002

Hypothalamic gene expression in reproductively photoresponsive and photorefractory Siberian hamsters.

An interval timing mechanism in the brain governs reproduction in seasonally breeding mammals by triggering refractoriness to inhibitory short photoperiods during midwinter. The neural mechanisms responsible for the timing and induction of photorefractoriness by this seasonal clock are unknown. Using cDNA microarrays and RT-PCR, we identified a class of genes encoding thyroxine (T4)-binding proteins (transthyretin, T4-binding globulin, albumin) whose expression is associated with reproductive refractoriness to short day lengths. Down-regulation of these genes was associated with reduced hypothalamic T4 uptake, which was reversed by long-day photoperiod treatments that restored responsiveness to short days. Circulating T4 concentrations did not vary with states of photoresponsiveness in euthyroid hamsters, but blockade of thyroid function accelerated the onset of photorefractoriness to short days. These data link changes in gene expression in the hypothalamus to the functional output of a seasonal clock. Reproductive inhibition in short days depends on T4 only late in the nonbreeding season. Down-regulation of genes encoding T4-binding proteins in the hypothalamus during this interval may restrict access of a static T4 signal to hypothalamic target tissues that regulate reproduction, thereby timing annual transitions in reproductive function. Hypothalamic autoregulation of T4 influx may constitute a critical cellular process involved in the generation and expression of seasonal reproductive rhythms and suggests a previously undescribed mechanism by which neural targets gain access to peripheral hormones.

Albumins↗

PubMed2000

The coevolution of cell senescence and diploid sexual reproduction in unicellular organisms.

In this paper, we investigate the coevolution of diploid sexual reproduction and cell senescence (i.e., cell aging). We use probability analysis, computer simulation, and exact numerical computation to analyze the impacts of deleterious recessive mutations on sexual and asexual reproduction. The main conclusion is that, without cell senescence, the evolutionary advantages of sexual reproduction cannot be realized in unicellular organisms that reproduce both sexually and asexually. Also, cell senescence is found to be useful in the maintenance of sexual reproduction. This result suggests that diploid sexual reproduction was unlikely to establish itself as a widespread reproduction mechanism without the complementary process of cell senescence.

Biological Evolution↗

PubMedDate not supplied

A nova vida: the commoditization of reproduction in Central Mozambique.

In Central Mozambique economic austerity and shifts in domestic organization have transformed kinship and gender relations in ways that reinforce reproductive demands on women. Against this backdrop of economic and social restructuring, commodification of long-standing reproductive practices has intensified. This paper examines the influence of commodification and female economic marginalization on virginity reviews, seduction fees, bride wealth payments, and childbirth assistance. Constructions of reproductive risk as human or spirit-induced threats of witchcraft, sorcery, or spirit possession resonate in this atmosphere of competition and instability. Rather than disappearing, occult practices may be increasing in response to the new inequalities associated with "modernity." This pressure contributes to women's reproductive vulnerability and informs new strategies to manage risk during pregnancy. Life history and pregnancy case study data reveal how women facing growing inequality and increasing danger to reproductive health mobilize cultural resources in ways that, paradoxically, both reinforce and contest dominant relations of reproduction.

Adolescent↗

PubMed2006

A category approach for reproductive effects of phthalates.

In regulatory toxicology, the experimental assessment of reproductive toxicity is one of the most costly endpoints to perform. Categorizing chemicals is an approach that can be used to reduce animal tests in risk assessments of chemicals, for example, via REACH (Registration, Evaluation, and Authorization of Chemicals). The category approach was tested for reproductive toxicity with a group of 10 ortho-phthalate esters, with different side chain lengths. Three ortho-phthalates were used for testing the category. Phthalates with side-chain lengths C4 to C6 that are commonly known to cause reproductive effects were included, as well as the recently discovered mechanism that indicates antiandrogenic effects. The differences in physicochemical properties, absorption rates, and metabolism between the phthalates investigated could not fully explain the difference in reproductive toxicity. It was concluded that phthalates with the alkyl side-chain length from C4 to C6 produce similar severe reproductive effects in experimental animals. It is expected that phthalates included in the tight boundaries of the proposed category would all show severe reproductive effects, especially the antiandrogenic effects. Further testing might not be needed for phthalates within these boundaries. If necessary, limited testing could focus on the critical endpoints. Detailed mechanistic information is needed on phthalates to apply the categories for regulatory toxicology.

Animal Testing Alternatives↗

PubMedDate not supplied

Two-generation reproduction study and immunotoxicity screen in rats dosed with phenol via the drinking water.

This study evaluated the potential reproductive toxicity of phenol in a rat two-generation reproduction study, which included additional study endpoints, such as sperm count and motility, developmental landmarks, histological evaluation of suspect target organs (liver, kidneys, spleen, and thymus), weanling reproductive organ weights, and an immunotoxicity screening plaque assay. Phenol was administered to 30 Sprague-Dawley rats/sex/group in the drinking water at concentrations of 0, 200, 1000, or 5000 ppm. Parental (P1) animals were treated for 10 weeks prior to mating, during mating, gestation, lactation, and until sacrifice. The F1 generation (P1 offspring) was treated using a similar regimen, while the F2 generation was not treated. After mating, 10 P1 males/group were evaluated using standard clinical pathology parameters and an immunotoxicity screening plaque assay. Significant reductions in water and food consumption were observed in the 5000-ppm group in both generations; corollary reductions in body weight/body weight gain were also observed. Mating performance and fertility in both generations were similar to controls, and no adverse effects on vaginal cytology or male reproductive function were observed. Vaginal opening and preputial separation were delayed in the 5000-ppm group, and were considered to be secondary to the reduction in F1 body weight. Litter survival of both generations was reduced in the 5000-ppm group. Absolute uterus and prostate weights were decreased in the F1 generation at all dose levels; however, no underlying pathology was observed and there was no functional deficit in reproductive performance. Therefore, these findings were not considered to be adverse. No evidence of immunotoxicity was noted in the 5000-ppm group. The effects noted at the high concentration were presumed to be associated with flavor aversion to phenol in the drinking water. Based on a comprehensive examination of all parameters, the no-observable-adverse-effect level (NOAEL) for reproductive toxicity of phenol administered in drinking water to rats is 1000 ppm. The corresponding daily intake of phenol for an adult rat at the NOAEL of 1000 ppm is equivalent to about 70 mg/kg/day for males and 93 mg/kg/day for females.

Administration, Oral↗

PubMed2005

Studies of the toxicological potential of tripeptides (L-valyl-L-prolyl-L-proline and L-isoleucyl-L-prolyl-L-proline): VI. Effects of Lactobacillus helveticus-fermented milk powder on fertility and reproductive performance of rats.

The objective of these studies was to assess the effects of the tripeptides, L-valyl-L-prolyl-L-proline (VPP) and L-isoleucyl-L-prolyl-L-proline (IPP), on reproductive capabilities of male and female rats. The specific goals of the experiments were (1) to determine the effects of orally administered tripeptides on (a) fertility and reproductive behavior in both sexes of rats, (b) embryo-fetal development in pregnant rats, and (c) pre- and postnatal development of rats exposed to tripeptides in utero and during lactation; and (2) to estimate the no-observable-adverse-effect doses of tripeptides in maternal and fetal rats. During the conduct of these classical segment I, II, and III studies, the test material was powdered Lactobacillus helveticus-fermented milk (FM), which contains the tripeptides, VPP and IPP. FM (0, 500, 1000 or 2000 mg/kg body weight [BW]/day--equivalent to 0, 0.8, 1.6, or 3.3 mg/kg BW/day of VPP plus IPP) was administered to males by oral gavage from 4 weeks prior to mating until sacrifice, and to females from 2 weeks prior to mating through day 20 of lactation. Evaluative parameters included monitoring grossly observable clinical signs; food consumption and body weight gains; mating behavior and fertility indices of both sexes; implantation and maintenance of embryos; sex ratio of live pups; fetal viability; incidences of external, visceral or skeletal variations; growth and behavioral development; as well as reproductive capabilities of F1 offspring exposed to FM during gestation and lactation. All animals were subjected to macroscopic examination at termination of their segment of the studies. Clinical signs, body weights, and food consumption were unaffected by administration of FM. During segment I, the test agent had no effect on estrus cycle, mating behavior, fertility index, or reproductive competence of either males or females. The results of segment II experiments revealed no effects of FM on postimplantation survival-loss, sex ratio or birth weights of live fetuses, and there was no evidence of treatment-associated developmental or teratological effects. During segment III, FM was without effect on pup viability, behavioral and sexual maturation, and reproductive capability of the F1 generation. Under the conditions of these experiments, the no-observable-adverse-effect level (NOAEL) of FM on reproductive performance in male and female rats is greater than 2000 mg/kg BW/day, the equivalent of 3.3 mg/kg BW/day of VPP plus IPP.

Animals↗

PubMed2003

History of regulation of assisted reproductive technology (ART) in the USA: a work in progress.

The advent of human assisted reproductive technology (ART) has engendered much legal and ethical debate. This article examines the evolution of regulation in ART in the USA and discusses the impetus for, and repercussions of, the Human Fertilisation and Embryology Authority in the UK. Key differences in government legislation between the UK and USA have driven the evolution of a distinct regulatory body that oversees ART in the USA. The National Advisory Board on Ethics in Reproduction (NABER) serves as an unofficial advisory body that addresses ethical issues in reproduction. The Society for Assisted Reproductive Technology (SART) maintains a registry that collects, reports and verifies data for individual ART clinics. Clinic-specific success rates are readily available through annual reports published through a collaboration of SART, the American Society of Reproductive Medicine (ASRM), the Center for Disease Control (CDC), and the National Infertility Association (RESOLVE). The ASRM has assumed a strong advisory role in addressing ethical issues and practice guidelines in assisted reproduction. Thus, although there is no central body to regulate ART in the USA, basic legislation, standards and guidelines that drive the provision of these services do exist in the USA.

Female↗

PubMed1999

The Demographic Cost of Reproduction and Its Consequences in Balsam Fir (Abies balsamea).

It is an axiom of life-history theory that reproduction involves age-specific costs in terms of survival or future reproduction. The measurement of costs of reproduction in plants is difficult, and few field studies have measured these costs in terms of fitness or demographic components, thus creating a hiatus between theory and data. In this article, we describe methods for overcoming the problem, illustrated by a field study of balsam fir. We used serial correlation and a permutation test to detect growth costs of reproduction and show how these translate into demographic costs when relative tree size (and therefore growth) is critical to survival. Using chronosequences, we reconstructed the age- and size-specific dynamics of a subalpine population of Abies balsamea. A matrix model describing these dynamics was then used to estimate age- and size-specific probabilities of future survival to maturity ([Formula: see text]). By using a regression model of the relationship between tree size, age, and [Formula: see text], we were able to estimate the maximum age-specific demographic cost of reproduction for trees of all ages. The shape of the age-specific cost curve for A. balsamea may explain why, contrary to a previously published hypothesis, age at first reproduction in A. balsamea does not vary between wave-regenerating and normal populations.

Abies balsamea↗

PubMedDate not supplied

Bilateral enucleation and captivity influence the reproductive cycle of male Viscacha (Lagostomus maximus maximus).

The viscacha (Lagostomus maximus maximus) is a seasonal rodent living in the Southern Hemisphere. The adult males exhibit an annual reproductive cycle characterized by a gonadal regression period during winter. In this study, we investigated the effects of bilateral enucleation and captivity on their annual reproductive cycle. Testicular volume relative to body weight was recorded monthly in intact and bilaterally enucleated animals placed under natural photoperiod, water, and food ad lib. and constant temperature. Testes and accessory organs were evaluated by qualitative and quantitative light microscopic studies. The intact animals showed an annual reproductive cycle with complete gonadal atrophy in the first year. In the second year, testicular regression was observed but attenuated in regard to that recorded in the first winter period, indicating that adaptive changes might be involved. Bilateral enucleation in the viscacha dampened and extended the period of its annual reproductive cycle. The results suggest that both conditions, constant captivity and enucleation, produced stimulatory effects on the reproductive system of this rodent. Furthermore, local control mechanisms might be responsible for the morphological differences observed in testes, epididymis, and seminal vesicles from both groups, which exhibited similar levels of serum testosterone. Finally, an intact retinohypothalamic-pineal axis and/or photoperiodic input would be necessary to maintain the reproductive cycle amplitude and timing in viscacha.

Animals↗

PubMed2007

Divergent host plant adaptation and reproductive isolation between ecotypes of Timema cristinae walking sticks.

Theoretical and empirical studies have demonstrated that divergent natural selection can promote the evolution of reproductive isolation. Three unresolved questions concern the types of reproductive barriers involved, the role of geography, and the factors determining the extent of progress toward complete speciation. Here I synthesize studies of Timema cristinae host plant ecotypes to address these issues. The approach is to compare the magnitude of multiple reproductive barriers among different ecological and geographic scenarios, where pairs of populations within each scenario are the unit of replication. Application of this approach to T. cristinae revealed that divergent host adaptation can promote the evolution of diverse reproductive barriers, including those that are not inherently ecological. Gene flow in parapatry tended to constrain divergence, with the notable exception of the reinforcement of sexual isolation. Thus, geography affected progress toward speciation but did not influence all reproductive barriers in the same way. Studies of any single pair of taxa often capture only certain stages of the speciation process. For example, reproductive isolation between T. cristinae ecotypes is incomplete, and so only the stages before the completion of speciation have been examined. Studies of more divergent taxa within the genus are required to determine the factors that complete speciation.

Adaptation, Physiological↗

PubMed2004

HIV/AIDS, sexual and reproductive health: intersections and implications for national programmes.

HIV and AIDS have a myriad of effects on sexual and reproductive health and rights, and sexual and reproductive health services are critical for women and men with HIV and AIDS. Yet there has been a dearth of visible, in-depth mainstream attention to the links between sexual and reproductive health and prevention and treatment of HIV/AIDS since the early 1990s among major stakeholders internationally. This paper argues that access to essential sexual and reproductive health care should be provided in HIV/AIDS prevention, care and treatment programmes, and appropriate forms of prevention and treatment of HIV/AIDS should be included in all sexual and reproductive health services as a public health priority, particularly in sex education, family planning and abortion services, pregnancy-related care, sexually transmitted infection (STI) services and services addressing sexual violence. The paper analyzes existing barriers to linking and integrating these services, e.g. at country level due to the traditional training of health workers to implement vertical programmes, separate sources of funding for National AIDS Control Programmes and sexual and reproductive health services, and in international donor programme and UN agency structures. This paper calls for leadership to be exercised by donors, all the UN agencies working together, governments, health service managers and providers, NGOs and advocates in both fields to develop and implement these linkages at country level. Finally, it is crucial that UNAIDS, WHO, UNFPA, UNICEF, the Global Fund to Fight AIDS, TB and Malaria and those working to reach the targets set by the Millennium Development Goals come on board in these efforts.

Cooperative Behavior↗

PubMed2002

The European study of assisted reproduction families: the transition to adolescence.

BACKGROUND: Findings are presented of the second phase of a European longitudinal study of families created by assisted reproduction. The present investigation reports on data obtained during the child's transition to adolescence. METHODS: A total of 102 IVF families, 94 donor insemination (DI) families, 102 adoptive families, and 102 families with a naturally conceived child were compared on standardized interview and questionnaire measures of parenting and children's psychological well-being. RESULTS: The assisted reproduction families were similar to the adoptive and natural conception families for many of the measures of the quality of parent-child relationships. To the extent that differences were found between the assisted reproduction families and the other family types, these reflected mainly more positive functioning among the assisted reproduction families, with the possible exception of the overinvolvement with their children of a small proportion of assisted reproduction mothers and fathers. The assisted reproduction children were functioning well and did not differ from the adoptive or naturally conceived children on any of the measures of psychological adjustment. However, only 8.6% had been told about their genetic origins. CONCLUSIONS: IVF and DI families with an early adolescent child appear to be functioning well.

Adaptation, Psychological↗

PubMed2006

Reproductive freedom and risk.

It is widely recognized that one person's freedom may be limited to prevent harm to another (non-consenting) person. It is curious, therefore, that where a right to reproductive freedom is recognized, there is considerable reticence to limit or override it in cases where reproduction harms those people who are brought into existence. I argue that this is inappropriate. If there should be no right to inflict a harm in non-reproductive contexts then there should be no right to inflict an equivalent harm in reproductive contexts. Because of the long history of bias and arbitrary discrimination in curtailments of reproductive freedom, I suggest how bias might be avoided in deciding how severe a harm must be to defeat a right to reproductive freedom.

Behavior↗

PubMedDate not supplied

Human reproductive failure II: immunogenetic and interacting factors.

Studies in humans suggest that reproductive failure may be influenced by immunological factors or by genes encoding immunological factors and regulatory mechanisms controlling immunological expression. Using molecular methods, immunological factors can be clearly studied in an immunogenetic context. One example, the major histocompatibility complex (MHC), known as the human leukocyte antigens (HLA) in humans and MHC in other mammals, affects many different stages of reproduction. Studies in some outbred, and in closely related, human populations indicate that HLA, or HLA-linked, genes and HLA regulatory factors affect gamete development, embryo cleavage, blastocyst and trophoblast formation, implantation, fetal development and survival. Studies in non-human mammals indicate that MHC, or MHC-linked, genes such as the grc complex, Ped/Qa-2, t haplotypes and MHC regulatory factors, have similar reproductive effects. Human reproductive failure may also be a consequence of disruption of interacting factors, including interactions between HLA antigens, cytokines and natural killer (NK) cells. In this review, we highlight the importance of immunogenetic and interacting factors in human reproductive failure. We argue that studies in closely related human populations and animal models may contribute to a better understanding of the ways in which immunogenetic and interacting factors are involved in human reproduction.

Abortion, Spontaneous↗