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Sibling mating in prairie deer mice (Peromyscus maniculatus bairdi) results in poor reproductive performance. Siblings experimentally paired before puberty exhibit delayed reproduction when adult. A behavioral mechanism is involved in this reproductive delay, since prepubertal familiarity also delays reproduction in nonsibling pairs. Such a reproductive delay may act to reduce inbreeding depression and regulate population growth.
The bacterium Photorhabdus luminescens is a symbiont of the entomopathogenic nematode Heterorhabditis bacteriophora. The nematode requires the bacterium for infection of insect larvae and as a substrate for growth and reproduction. The nematodes do not grow and reproduce in insect hosts or on artificial media in the absence of viable P. luminescens cells. In an effort to identify bacterial factors that are required for nematode growth and reproduction, transposon-induced mutants of P. luminescens were screened for the loss of the ability to support growth and reproduction of H. bacteriophora nematodes. One mutant, NGR209, consistently failed to support nematode growth and reproduction. This mutant was also defective in the production of siderophore and antibiotic activities. The transposon was inserted into an open reading frame homologous to Escherichia coli EntD, a 4'-phosphopantetheinyl (Ppant) transferase, which is required for the biosynthesis of the catechol siderophore enterobactin. Ppant transferases catalyze the transfer of the Ppant moiety from coenzyme A to a holo-acyl, -aryl, or -peptidyl carrier protein(s) required for the biosynthesis of fatty acids, polyketides, or nonribosomal peptides. Possible roles of a Ppant transferase in the ability of P. luminescens to support nematode growth and reproduction are discussed.
BACKGROUND: Although more epidemiological studies of reproductive health have been published recently, important scientific achievements remain few. Among the reasons for this are existing methodological constraints. Fertility is low in most parts of the industralized world, making the observation time short. Pregnancy itself is under extremely close medical surveillance with intensive health care interventions such as prenatal screening, induced abortions, induced labour, and prescribed changes in environmental exposures, but the epidemiologists are generally left with cause-effect experiences which escaped medical attention or study of diseases for which there is no cure. The main problem in non-experimental research of reproductive failure, however, is the most pregnancies are planned and past pregnancy experience is used in the planning. Self selection into different exposure categories according to past pregnancy experience should therefore be considered when studies are designed and analysed. STUDY OBJECTIVE: To consider how to deal with past pregnancy experience as an indicator "background" risk of reproductive failure. The present standard is to take parity or gravidity into consideration but this may be of little value and could even be very misleading. MAIN RESULTS: No simple and universal analytic strategy is available in reproductive epidemiology. On some occasions studies should be restricted to the first pregnancy only, in other situations the past reproductive experience may be used to form groups that are comparable in terms of pre-exposure risk.
Seasonal breeding of rodents is often associated with changes in adrenal function; altered adrenal function could account, in part, for seasonal changes in immune function and, ultimately, influence seasonal fluctuations in survival. Animals commonly monitor the annual change in photoperiod to ascertain the time of year and to make appropriate seasonal adjustments in physiology and behavior. Several extrinsic factors affect reproductive responsiveness to photoperiod. The interaction between population density and reproductive and adrenal responsiveness to photoperiod was assessed in the present experiment. Adult male prairie voles (Microtus ochrogaster) were maintained individually for 10 wk in long [light:dark (LD) 16:8] or short (LD 8:16) photoperiods in rooms with either high (10.96 animals/m3) or low (0.18 animals/m3) population densities. Regardless of population density, short-day voles regressed the size of their reproductive organs; reproductive organ masses were higher in long-day voles housed in high-density compared with low-density rooms. Paired adrenal masses were reduced in short-day voles, but were unaffected by population density; serum corticosterone concentrations were significantly elevated in short-day compared with long-day animals. In both photoperiods, basal blood corticosterone levels were higher in voles from low-density compared with high-density rooms. Splenic masses were unaffected by day length, but were elevated among high-density animals. Similarly, serum immunoglobulin (IgG) levels were elevated among high-density animals. These results suggest that population density per se, in the absence of behavioral interactions, can affect reproductive size, and possibly function, in long-day conditions, and that prairie voles, which are highly social, exhibit higher corticosterone and lower IgG levels in low compared with high densities. These results may be important in understanding arvicoline population fluctuations, as well as improving animal husbandry practices in the lab.
OBJECTIVES: Most studies on the costs of assisted reproductive technologies (ART) identify the total cost of the procedure with the direct cost, without considering important items such as overhead or intermediate costs. The objective of this study was to determine the cost per ART procedure in a public hospital in 2003 and to compare the results with those in the same hospital in 1998. METHODS: Data from the Human Reproduction Unit of the Virgen de las Nieves University Hospital in Granada (Spain) from 1998 and 2003 were analyzed. Since the total costs of the unit were known, the cost of the distinct ART procedures performed in the hospital was calculated by means of a methodology for cost distribution. RESULTS: Between 1998 and 2003, the activity and costs of the Human Reproduction Unit analyzed evolved differently. Analysis of activity showed that some techniques, such as intracytoplasmic sperm injection, were consolidated while others, such as stimulation without assisted reproduction or intracervical insemination were abandoned. In all procedures, unit costs per cycle and per delivery decreased in the period analyzed. CONCLUSIONS: Important changes took place in the structure of costs of ART in the Human Reproduction Unit of the Virgen de las Nieves University Hospital between 1998 and 2003. Some techniques were discontinued, while others gained importance. Technological advances and structural innovations, together with a "learning effect," modified the structure of ART-related costs.
Field observations on reproductive activity in the Panamanian tamarin (Saguinus oedipus geoffroyi) were made in conjunction with the examination of 131 reproductive tracts collected at regular intervals over one year. Reproductive tract characteristics were compared over seasons. Embryonic and fetal development were also assessed. A distinct birth peak was observed from April to early June. Pregnancies in April and May point to a potential, but unrealized, birth peak in August and September. Despite the tendency toward birth peaks, reproductive activity occurred throughout the year. Reproduction was limited to a single female per social group. The average number of infants born per female was two. Groups inhabiting lowland areas appeared to be more successful in raising young than groups inhabiting upland areas.
The purpose of this study was to obtain data for facilitating the planning, monitoring and evaluation of reproductive health services in Mongolia. The survey was carried out in 17 randomly selected health facilities where health professionals were graded on their reproductive health knowledge and also in 64 adjacent households where 162 women of childbearing age were interviewed for their comments on reproductive health services and to obtain their reproductive health knowledge/behaviour. We rated the reproductive healthcare delivery system, using the methodology of Kielmann et al. The results from the women's interviews are encouraging and show a high acceptance of and satisfaction with family planning services.
A method to evaluate developmental and reproductive toxicity for a wide variety of chemicals has been developed. The assessment includes all effects on male and female reproductive function as well as effects in the developing embryo or fetus. Effects are evaluated using primary literature. Studies are classified as adequate, supportive or inadequate. Only adequate studies are used in further assessment. Reproductive and developmental toxicity of each chemical is assessed using both qualitative and quantitative information. Three elements are used to describe developmental toxicity of chemicals: Lowest Observed Effect Level (LOEL), weight-of-evidence classification and a Risk Ratio (RR). For reproductive toxicity only two elements are used, LOEL and weight-of-evidence. LOEL is defined as the lowest dose at which statistically significant effects are found. A risk ratio is calculated using the levels of the chemical producing acute maternal lethality (LD50 or LC50) to the levels producing developmental toxicity in the same animal species and route of administration. The risk ratio is used to indicate the extent to which the developing embryo or fetus is more susceptible than the dam to the toxic effects of a chemical. A toxicity score (A through E) is assigned to each chemical from a two- or three-dimensional matrix based on the elements of assessment. The score reflects the degree of hazard associated with each chemical. To date, 110 chemicals have been evaluated using this system. From the selected databases, 188 articles were reviewed. Of these, 103 (55%) were judged to be adequate, 23 (12%) provide supportive information, and 62 (33%) were inadequate and excluded from the assessment methodology. Scores for 47 chemical with some adequate data available show that high hazard substances (28 A and B) outnumber those associated with lower hazards (a total of 19 C, D and E). This may reflect a selection process for testing which favors substances suspected of causing adverse reproductive and developmental effects.
In laboratory-bred rodent populations, intraspecific variation in circadian system organization is a known cause of individual variation in reproductive photoresponsiveness. The authors sought to determine whether circadian system variation accounted for individual variation in reproductive photoresponsiveness in a single, highly genetically variable population of Peromyscus leucopus recently derived from the wild. Running-wheel activity patterns of male and female mice, aged 70 to 90 days, from artificially selected lines of reproductively photoresponsive (R) and nonresponsive (NR) lines were monitored under short-day photoperiod (8 h light, 16 h dark), long-day photoperiod (16 h light, 8 h dark), and constant darkness (DD). NR mice displayed a significantly longer mean free-running period (24.08 h) in DD compared with R mice (23.75 h), due in large part to a difference between NR and R females (24.25 h vs. 23.74 h, respectively). All other entrainment characteristics (alpha, phase angle of activity) under short days, long days, and DD were similar between R and NR mice. Variation in free-running period and entrainment characteristics has been shown to affect photoresponsiveness in other rodent species by altering the manner in which the circadian system interprets short days. To determine whether variation in photoresponsiveness in P. leucopus is due to differences in free-running period instead of variation downstream from the central circadian clock in the pathway controlling photoresponsiveness, the authors exposed young R and NR mice to DD and measured the effect on reproductive organ development. If variation in free-running period affected how the circadian system of mice interpreted short days, then both R and NR mice exposed to DD should have exhibited a delay in gonadal development. Only R mice exhibited pubertal delay in DD. NR mice exhibited large paired testes, paired seminal vesicles, paired ovaries, and uterine weight typical of mice nonresponsive to short days, whereas R mice exhibited reproductive organ weight typical of mice responsive to short days. These data suggest that despite significant differences in free-running period between R and NR mice, individual variation in photoresponsiveness is not due to differences in how the circadian systems of R and NR mice interpret the LD cycle.
Understanding the physiological basis of environmental regulation of reproduction at the cellular level has been difficult or unfeasible in vertebrate species because of the highly complex and diffuse nature of vertebrate neuroendocrine systems. This is not the case with the simple nervous system of mollusks in which reproductive neuroendocrine cells are often readily identifiable in living tissue. Given that there are mollusks that are seasonal breeders, that the neuroendocrine cells controlling reproduction have been identified in several molluskan species, that these neurons are conducive to cell physiological analysis, and that basic features of cell biology have been highly conserved between mammals and mollusks, it seems that the mollusk would provide an excellent model system to investigate cell-physiological events that mediate effects of environmental signals on reproduction. The purpose of this review is to explore this idea in three species in which the topic of the neural basis of seasonal reproduction has been studied: the giant garden slug Limax maximus, the freshwater pond snail Lymnaea stagnalis, and the marine snail Aplysia californica.
An adaptive decline in average clutch size with progressive date of laying is characteristic of most bird species with a single clutch of variable size per year. The effect of photoperiod on timing of laying, clutch size, and subsequent molt was investigated in kestrel pairs breeding and raising their young in captivity. In natural daylight (nLD), clutch size, under ad libitum feeding, showed the same decline with date as in nature. Birds breeding later also started molt later and molted faster (more feathers simultaneously), so that all birds completed molt more or less at the same time. Constant long days (LD 17.5:6.5 and LD 13:11) from December 1 onward advanced both reproduction and molt. The LD 17.5:6.5 group developed the reproductive system faster, had a shorter courtship period, and laid eggs earlier than the LD 13:11 group. In both photoperiods there was a decrease in clutch size with progressive laying date, similar to that in nLD. Molt started in both groups at about the end of the laying period and slowed down in the longer photoperiod, especially in males. Plasma luteinizing hormone (LH) changes in the two photoperiods were different for males and females. Males showed the expected slower LH response in the shorter photoperiod, but the initial LH response by females was the same in both photoperiods. Data on LH, reproductive behavior, and body mass suggest that females have a wider annual reproductive window than males. Data on time of laying and number of eggs suggest that clutch size in the kestrel is determined by laying date itself, following an endogenous rhythm that is phase-locked to the reproductive cycle.
Winter is often stressful. Increased energetic demands in winter and concurrent reductions in energy availability can lead to an energetic imbalance and compromise survival. To increase the odds of surviving winter, individuals of some nontropical rodent species have evolved mechanisms to enhance immune function in advance of harsh winter conditions. Short day lengths provide a proximate cue for enhancement of immune function, an adaptive functional response to counter environmental stress-induced reduction in immune function. In the present study, photoperiod, ambient temperature, and food availability were manipulated and reproductive function and cell-mediated immunity were assessed in adult male deer mice (Peromyscus maniculatus). Mice maintained in short days regressed their reproductive systems and displayed enhanced immune function compared to long-day animals. Reduced food availability elevated corticosterone concentrations and suppressed reproductive and immune function, whereas ambient temperature alone had no effect on cell-mediated immunity. The suppressive effect of food restriction on reproductive and immune function was overcome by maintaining animals in short days. However, short-day, food-restricted mice maintained at low ambient temperatures displayed reduced reproductive and immune function compared to animals maintained at mild temperatures. Taken together, these results suggest that short-day enhancement of immune function can counteract some, but not all, of the immunosuppressive effects of winter stressors. These data are consistent with the hypothesis that immune function is enhanced in short days to counteract stress-mediated immune suppression occurring during winter.
PURPOSE: This study evaluated reproductive intentions, fertility-related knowledge, prior fertility counseling, and factors associated with reproductive intentions among transgender and nonbinary individuals receiving care at a Brazilian public reference center. METHODS: This cross-sectional study with a qualitative component was conducted between July and November 2025 in a specialized gender-affirming care clinic in Brazil. Quantitative data included sociodemographic characteristics, reproductive history, gender-affirming hormone therapy (GAHT), and fertility-related variables. Logistic regression was used to assess factors associated with desire for future parenthood. Responses to a single open-ended question regarding perceived effects of GAHT on fertility were analyzed using thematic content analysis. RESULTS: Eighty-two participants were included (mean age 27.5 ± 7.4 years). Most identified as transgender men (65.9%), followed by transgender women (26.8%) and nonbinary individuals (7.3%); 79.3% were receiving GAHT. Although 63.4% expressed a desire for future parenthood, only 7.3% had children. Current interest in fertility preservation was reported by 20.8% (15/72). Having children (adjusted odds ratio [aOR] = 0.03; 95% confidence interval [CI]: 0.001-0.62; p = 0.023) and each additional year of GAHT duration (aOR = 0.83; 95% CI: 0.70-0.99; p = 0.038) were associated with lower odds of desiring future parenthood. Sex assigned at birth was not independently associated with reproductive intentions. Qualitative analysis revealed misconceptions, uncertainty, and conditional beliefs regarding fertility. CONCLUSIONS: Desire for future parenthood was common among transgender and nonbinary individuals, whereas engagement with fertility preservation remained limited. These findings highlight the need for longitudinal, patient-centered reproductive counseling integrated into gender-affirming care.
BACKGROUND: Differences among species and among years in reproductive seasonality (the tendency for clusters of events to fall at approximately the same point in each year) and synchrony (amount of clustering of events within a year) have been intensively studied in bats, but are difficult to assess. Here, we use randomization methods with circular statistics to test for synchrony and seasonality of reproduction in three species of nectarivorous megachiropteran bats on Negros Island in the central Philippines. RESULTS: In Rousettus amplexicaudatus, estimated dates of birth were both highly synchronous and highly seasonal. In Macroglossus minimus, estimated births were seasonal and significantly clustered within years, but within each year births occurred over a broad period, indicating a low level of synchrony. In Eonycteris spelaea, estimated births were also seasonal and had statistically significant synchrony, with birth periods within years intermediate in synchrony between R. amplexicaudatus and M. minimus. All three species had a similar seasonal pattern, with two birth periods in each year, centered on March or April and August or September. In one species, R. amplexicaudatus, primigravid females (in their first pregnancy) produced their young in June and July, a birth period significantly different in timing from the two birth periods of older adult females. This more conservative pattern of young females may allow higher survival of parents and offspring at cost of a lost reproductive opportunity. There was weak evidence that in some years primigravid females of M. minimus might differ in timing from older adults. There were few significant differences in reproductive timing among different years, and those differences were generally less than two weeks, even during a severe drought in the severe el Niño of 1983. CONCLUSION: The results suggest that these species follow an obligately seasonal pattern of reproductive timing with very little phenotypic plasticity. The resampling methods were sensitive to differences in timing of under two weeks, in some cases, suggesting that these are useful methods for analyses of seasonality in wild populations of bats.
Controlled oxidation, such as disulfide bond formation in sperm nuclei and during ovulation, plays a fundamental role in mammalian reproduction. Excess oxidation, however, causes oxidative stress, resulting in the dysfunction of the reproductive process. Antioxidation reactions that reduce the levels of reactive oxygen species are of prime importance in reproductive systems in maintaining the quality of gametes and support reproduction. While anti-oxidative enzymes, such as superoxide dismutase and peroxidase, play a central role in eliminating oxidative stress, reduction-oxidation (redox) systems, comprised of mainly glutathione and thioredoxin, function to reduce the levels of oxidized molecules. Aldo-keto reductase, using NADPH as an electron donor, detoxifies carbonyl compounds resulting from the oxidation of lipids and proteins. Thus, many antioxidative and redox enzyme genes are expressed and aggressively protect gametes and embryos in reproductive systems.
Adolescence is a period in life marked by change, encompassing physiological changes associated with pubertal development, changes in social status and the social stresses that an individual faces, and changes in behavioral affect regulation. The interactions between activity in the reproductive axis, the neural systems that regulate stress, hormones produced in response to stress, and neural systems governing behavioral affect regulation are complex and multifaceted. Although our understanding of these interactions remains rudimentary, we do know that stress can suppress activity of the reproductive axis, that reproductive hormones can modulate the activity of neural systems that govern the body's responses to stress, that both reproductive function and stress responsiveness can be altered in depressed individuals, and that the function of some of the key neural systems regulating behavioral affect (i.e., serotonergic, noradrenergic, dopaminergic systems) are modulated by both gonadal steroid hormones and adrenal steroid hormones. This summary reviews the central interactions discussed in this session on the interrelationships between hormones, behavior, and affect during adolescence and identifies key topics that require further investigation in order to understand the role that pubertal changes in reproductive function, interacting with increased exposure to life stresses, play in modulating behavioral affect regulation during the adolescent period.
In many teleosts, dopamine (DA) exerts direct inhibitory control on gonadotropes, counteracting the stimulatory effect of gonadotropin-releasing hormone (GnRH) on gonadotropin release. This dual control by GnRH and DA has been demonstrated in various adult teleosts and has major implications for aquaculture. Because of its unique life cycle, the European eel has provided a powerful model for demonstrating the key role of DA in the control of puberty. Data from tetrapods suggest that the inhibitory role of DA on reproduction is not restricted to the teleosts. Thus, DA inhibitory control could represent an ancient evolutionary component in the neuroendocrine regulation of reproduction that may have been differentially maintained throughout vertebrate evolution. The intensity of DA inhibition, its main site of action, and its involvement in the control of puberty, seasonal reproduction, ovulation, spermiation, or even sex change may differ among classes of vertebrates, as well as within smaller phylogenetic units such as teleosts or mammals. An inhibitory role for DA has been reported also in some invertebrates, indicating that neuronal DA pathways may have been recruited in various groups of metazoa to participate in the control of reproduction. In addition to the incontestable GnRH neurons, the recruitment of DA neurons for the neuroendocrine control of reproduction provides an additional brain pathway for the integration of various species-specific, internal, and environmental cues. In teleosts, the plasticity of the DA neuroendocrine role may have contributed to their large diversity of biological cycles and to their successful adaptation to various environments.
Estrogen or hormone (estrogen + progestin) replacement is typically prescribed to women for relief from vasomotor symptoms at menopause. Observational studies have shown that such replacement also decreases the risk for Alzheimer's disease. Experimental data from a variety of animal models also suggest that estrogen replacement given to ovariectomized animals is largely neuroprotective. However, the recent intervention trial (Women's Health Initiative Memory Study; WHIMS) concluded that estrogen replacement and hormone replacement prescribed to postmenopausal women increased the risk for global cognitive impairment and dementia, respectively. This paper will examine evidence that the disparity in the human and animal data can be reconciled by consideration of the "reproductive" age of the individual receiving estrogen or hormone replacement. Our recent studies comparing the effects of estrogen replacement on young adult animals with those of estrogen replacement to reproductive senescent animals suggest that the estrogen replacement is beneficial when given to "surgically menopausal" (ovariectomized) animals. However, estrogen replacement appears to be deleterious to acyclic reproductive senescent animals, where target organs such as the brain have been in a prolonged estrogen-deficient state. The paper will also review aging and reproductive age-related changes in the estrogen receptor (ER) systems, specifically ER-alpha, as a potential mechanism for estrogen's deleterious effects in the reproductive senescent animal.