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PubMed1994

Some bounds on estimates for reproductive ratios derived from the age-specific force of infection.

In this paper we shall look at estimation of reproductive ratios for common childhood infections such as chickenpox, measles, mumps, and hepatitis A with and without a vaccination program. The paper starts with a survey of previous work in this area. We suppose that we are given data in the form of an age-related serological profile with a given vaccination program. This is used to estimate the reproductive ratio and evaluate vaccination campaigns. The effect of different mixing patterns, such as homogeneous mixing, assortative mixing, proportional mixing, and symmetric mixing are discussed. R phi denotes the reproductive ratio when a steady-state vaccination campaign phi is used. Assortative mixing maximizes the reproductive ratio R phi. A mixing pattern which minimizes R phi and a lower bound for R phi for the important symmetric mixing case are found. The most usual situation is that we are given the age-serological profile with no vaccination so that we have bounds for the basic reproductive ratio R0. These results are illustrated with an application to vaccination against hepatitis A in Bulgaria. Numerical evaluations of the effect of different elimination vaccination strategies are examined.

Adult↗

PubMed1993

Correlation between reproductive photoresponsiveness and photoregulated locomotor activity in meadow voles.

Some rodent populations contain individuals that undergo complete gonadal regression under short day lengths, other individuals whose gonads are little affected by such treatment, and still others that are intermediate in their response. Meadow voles exhibiting this variation were used to explore the relationship between reproductive photoresponsiveness and photoregulated locomotor activity. The activity patterns of the two extreme phenotypes--reproductively photoresponsive vs. nonresponsive--were compared, first under short day lengths and then under long day lengths. The primary component of the daily running wheel activity pattern for both phenotypes under both conditions was ultradian. Within that framework, reproductively photoresponsive voles were predominantly nocturnal in their locomotor activity under both day lengths. In contrast, the nonresponsive individuals showed no significant circadian variation in their activity under either day length. These results suggest that reproductively photoresponsive and nonresponsive individuals may have fundamentally different patterns of activity throughout the year in the wild. Furthermore, the data suggest that the inability of some voles to respond reproductively to variations in photoperiod may be caused by a decoupling of the circadian system from the entraining effects of day length.

Animals↗

PubMed1988

The effect of the reproductive system on mutation load.

J. B. S. Haldane (Amer. Nat. 71, 337-349, 1937) argued that, in equilibrium populations, the effect of deleterious mutation on average fitness depends primarily on the mutation rate and is independent of the severity of the mutations. Specifically, the equilibrium population fitness is e-microH, where microH is the haploid genomic mutation rate. Here we extend Haldane's result to a variety of reproductive systems. Using an analysis based on the frequency of classes of individuals with a specified number of mutations, we show that Haldane's principle holds exactly for haploid sex, haploid apomixis, and facultative haploid sex. In the cases of diploid automixis with terminal fusion, diploid automixis with central fusion, and diploid selfing, Haldane's principle holds exactly for recessive mutations and approximately for mutations with some heterozygous effect. In the cases of K-ploid apomixis, diploid endomitosis, and haplodiploidy, we show that Haldane's principle holds exactly for recessive lethal mutations. In addition we extend Haldane's result to various mixtures of the above-mentioned reproductive systems. In the case of diploid out-crossing sexuals, we do not obtain an exact analytic result, but present arguments and computer simulations which show that Haldane's result extends to this case as well in the limit as the number of loci becomes large. Although diverse reproductive systems are equally fit at equilibrium, different reproductive systems harbor vastly different numbers of recessive genes at equilibrium and we provide estimates of these numbers. These different numbers of mutations may create transient selective pressures on individuals with reproductive systems different from that of the equilibrium population.

Animals↗

PubMed1987

Reproductive activity in Finnish Landrace x Rambouillet ewes exposed to various daylength cycles applied over periods of six months.

Twenty-six Finnish LandracexRambouillet ewes were exposed to a series of artificial daylength cycles over periods of 6 mo. The cycles in general consisted of 3 mo. of long or increasing daylength, followed by 3 mo. of short or decreasing daylength. Increasing daylength to 22 hr.; 17.5 hr. or 15.75 hr. but not 14 hr. resulted in the onset of anestrus in all ewes. Only four of eight ewes in the 14 hr. cycle became anestrus. Abrupt decreases in daylength resulted in a more rapid return to reproductive cyclicity than a gradual decline. In addition, there appeared to be an inverse relationship between the length of the longest day of a treatment cycle and the time taken for ewes to return to reproductive cyclicity, following a subsequent abrupt decrease in daylength. Reducing daylength form 22 hr. to 17.5 hr. did not induce reproductive cyclicity. Reducing daylength from 17.5 hr. to 15 hr.; 12.75 hr. or 7.5 hr. did result in the onset of reproductive cyclicity. Finally, extending the period of long day exposure in a daylength cycle decreased the response time to a subsequent reduction in daylength. It was concluded that reproductive seasonality may be initiated by the interaction of darkness with a daily photosensitive phase in the ewe.

Journal Article↗

PubMed1987

Research in animal reproduction: An analysis of the contribution made by Latin America.

In an analysis carried out on the proceedings of the last two international congresses on animal reproduction and artificial insemination (1980 and 1984), a total of 944 papers presented were classified according to sex and species of the experimental animal, reproductive event studied, and country of origin. Latin America was found to be responsible for almost 10% of presentations, with Venezuela and Mexico making up half that total. The bovine species was the most studied both by Latin American countries (51.1%) and in general (42.7%). Approximately 15% of the Latin American contribution was concerned with goat studies versus 3.4% in general. Overall, the female was studied twice as much as the male. Fertility and estrous cycle were the reproductive events most studied both in general (36.3% and 31.6%, respectively) and by Latin American authors (27.2% and 33.3%, respectively). Latin American research concentrated on two main aspects: the effect of environment on reproduction and reproductive efficiency (25.8% and 13.7% of the total, respectively).

Journal Article↗

PubMed1988

Use of plasma progesterone profiles for the assessment of reproductive functions in indigenous Nigerian Zebu cattle.

The reproductive performance of Zebu cattle is generally low. However, blood concentrations of progesterone may be of practical value in assessing the reproductive status of the Zebu female. This paper reviews recent findings regarding plasma progesterone profiles during different phases of the reproductive cycle of some Nigerian Zebu cattle. The reproductive phases examined include the estrous cycle, early pregnancy and the postpartum periods. Our findings describe variations in plasma progesterone profiles observed under field conditions. The practical implications of these findings in assessing reproductive functions in indigenous Nigerian Zebu cattle are examined.

Journal Article↗

PubMed1994

Reproductive disorders caused by animal trypanosomiases: a review.

Pathogenic animal trypanosomes are causative agents of the most common livestock diseases which have an important economic impact on many African countries. These diseases usually cause debilitating symptoms manifested by anemia and cachexia which may result in death. Recent studies show that they cause a wide range of reproductive disorders in animals, including degeneration of the hypothalamus, pituitary glands and gonads with consequent disruptions in the secretions and plasma concentrations of the hormones necessary for normal reproductive processes in both sexes. Reproductive disorders caused in male animals include delayed puberty, loss of libido, severe degenerative changes of the genitalia manifested by the production of very poor quality semen or the cessation of semen production. In female animals trypanosomiases cause severe genital lesions, temporary or permanent anestrus, and abnormal estrous cycles. Additionally, trypanosomal-induced death during pregnancy, abnormal pregnancy, dystocia, abortion, premature birth, low birth weight, stillbirth, transplacental fetal infection, neonatal death and other pathogenic effects on fetuses and offspring have been reported. Early treatment with trypanocides may prevent some of the trypanosomal-induced reproductive disorders and the resolution of mild genital lesions. Trypanosomal-induced reproductive disorders in animals are of significant economic importance, especially in sub-Saharan Africa, where tsetse transmitted trypanosomiases are endemic.

Journal Article↗

PubMed1985

Neuroendocrine regulation of seasonal reproductive activity in the male golden hamster.

Golden (Syrian) hamsters are seasonal breeders. Under natural photoperiodic conditions, their reproductive systems are functional during spring and summer and atrophic during the fall and winter. This reproductive cycle can be duplicated in the laboratory by exposing the animals to artificially-created photoperiods. The endocrine correlates of photoperiod-induced changes in reproductive activity of the male hamster are fairly well characterized, but the neural control of seasonal reproductive activity has not been as extensively studied. Recent studies indicate that short day (less than 12.5 hr light/day) exposure leads to complex changes in central neurotransmitter metabolism, as well as neurotransmitter and hormonal receptor content, which, in turn, are reversed by exposure to long days or during the period of spontaneous testicular recrudescence. Many of these endocrine and neuroendocrine changes are dependent on the presence of the pineal gland, but photoperiod-induced changes in neurotransmitter metabolism have also been described in pinealectomized hamsters. Further studies of the neuroendocrine transduction of photoperiodic signals will not only provide a better understanding of seasonal reproductive and metabolic activities, but will increase our basic understanding of the neural control of the endocrine system.

Animals↗

PubMed1991

Effects of food and mates on time budget in Aplysia fasciata: integration of feeding, reproduction, and locomotion.

This study examines the time budgeted to different behaviors in Aplysia fasciata under three conditions: (1) animals have constant access to food and mates: (2) there is access to food, but not to mates; (3) neither food nor mates are present. The data suggest a number of rules underlying behavioral integration: (1) Feeding, reproductive behaviors, and activity seem to be natural categories for behavioral choice. Feeding and reproductive behaviors are controlled in tandem by a common arousal mechanism, while time left over after animals feed and reproduce is distributed in a fixed ratio between locomotion (crawling and swimming) and inactivity (immobility and movement in place). (2) Relative distribution between different forms of locomotion and inactivity is modified by changes in motivational state. More time is spent swimming than crawling when feeding and/or mating is prevented, while more time is spent moving in place than immobile when the arousal level is increased. (3) Feedback control of feeding and reproduction is asymmetric. Satiation of feeding inhibits the common arousal. In the absence of food, time spent on reproductive behaviors increases due to disinhibition of the common arousal. By contrast, positive feedback arising from sexual behavior excites the common arousal. When mating is prevented by removing potential mates, time spent feeding decreases. (4) Generally, animals choose between performing the three main categories of behavior. Although Aplysia simultaneously can feed and mate, or locomote and mate, they do so infrequently. By contrast, different types of reproductive behaviors (male mating, female mating, egg-laying) are commonly performed simultaneously.

Animals↗

PubMed1992

A method for quantitative assessment of reproductive risks to the human male.

There is a need for quantitative assessment of reproductive risks following human exposure to toxic agents. Current methods only estimate exposure levels that are unlikely to produce appreciable risk; they do not address the magnitude of risk. The quantitative reproductive risk estimation (QRRE) approach presented here enables calculation of the increased incidence of infertility in a human population resulting from exposure of males to a toxic agent. The four steps involve (A) obtaining a dose-response curve in experimental animals for the effect of a toxicant on a measure of reproductive function; (B) applying an interspecies extrapolation factor (IEF) derived for a similar toxicant to relate doses in animals and humans that produce equivalent reproductive toxicity; (C) using human exposure and uptake levels, along with the IEF and the dose-response curve, to calculate impairment of the measure in humans; and (D) computing the increase in human infertility caused by that impairment. The QRRE method is used to compute reproductive risks from dibromochloropropane exposure.

Animals↗

PubMedDate not supplied

A hypothesis to integrate partial seizures of temporal lobe origin and reproductive endocrine disorders.

Recent demonstrations of an association between reproductive endocrine disorders and partial seizures of temporal lobe origin (TLE) have led to the following hypothesis: (1) TLE may promote the development of reproductive endocrine disorders, (2) reproductive endocrine disorders may promote the development of epileptic discharges, and (3) TLE and associated reproductive endocrine disorders may represent the parallel effects of prenatal factors which are common to the development of both the brain and the reproductive system. This article focuses on clinical and animal investigative data that form the basis of this hypothesis.

Epilepsy, Temporal Lobe↗

PubMed2006

An optimised experimental test procedure for measuring chemical effects on reproduction in the fathead minnow, Pimephales promelas.

The production of viable offspring is fundamental to the survival of any population. Tests that quantify effects on reproduction can, therefore, inform on the potential for long-term health effects of exposure to endocrine active chemicals. Surprisingly little is known, however, about the reproductive capacity of laboratory fish species used for chemical testing. As an example, the fathead minnow, Pimephales promelas, is widely used in chronic assessments of reproductive toxicology, and is readily induced to reproduce in captivity, yet there is little agreement on the reproductive capacity (egg number) of this species. For this species, the notable variation in reported estimates of egg number might relate to differences in the methods of egg collection adopted by many laboratories. To investigate this hypothesis, reproduction was assessed in a total of 200 pair-breeding fathead minnow, using egg collection methods that included the addition of trays placed beneath an inverted U-shaped PVC tile that is conventionally used alone for egg collection. The results demonstrated that the placement of a mesh-screened egg collection tray, beneath the spawning tile, increased estimates of the egg number by 25-67%. In addition, adopting the mesh-screened tray reduced variation in egg number between pairs, within an experiment, from >50% to <30% and variation between experiments was reduced from 53% to 7%. Adoption of the revised system for egg collection shows that egg number in the fathead minnow is considerably more consistent than frequently reported and is a highly robust endpoint against which chemical effects can be challenged effectively.

Animals↗

PubMed2006

Relationships between the abnormalities of the male reproductive organs and the accumulation of phenol compounds in the striped field mouse, Apodemus agrarius, inhabiting Korea.

The relationships between the abnormalities of the male reproductive organs in striped field mice and the accumulation of endocrine-disrupting chemicals were assessed. Most mice collected at three areas were contaminated with phenol or organotin compounds. Fourteen to 42% of the mice at each area had abnormally shrunken reproductive organs, and some of them were contaminated with high levels of phenol compounds. Moreover, all the shrunken reproductive organs were damaged in the histological structure. The damage was observed also from several mice accumulating a high level of phenol compounds even though they had normally developed reproductive organs, although no damage was found in the mice accumulating a high level of organotin compounds. Collectively, the abnormalities of the reproductive organs in the mice seemed to be related to the accumulation of phenol compounds rather than of organotin compounds.

Animals↗

PubMed2006

A two generation reproductive toxicity study with curcumin, turmeric yellow, in Wistar rats.

The reproductive toxicity of curcumin, turmeric yellow, in Wistar rats was studied in order to generate additional relevant toxicity information for the use of curcumin in humans by oral administration. The two generation reproduction study was designed and conducted in accordance with OECD Guideline No. 416 [OECD, 1983. Guidelines for Testing of Chemicals, Guideline No. 416. Two Generation Reproduction Toxicity Study, adopted on 26th May 1983] and in compliance with Good Laboratory Practices (OECD, 1997 Principles of Good Laboratory Practice for the Testing of Chemicals. OECD, C(97)186/Final). The curcumin, mixed in the experimental diet at the concentrations of 1500, 3000 and 10,000 ppm was fed to three groups of rats, i.e., low, mid and high dose groups, and studied for two successive generations. A concurrent control group received experimental diet without the curcumin mixture. There were no treatment related adverse toxicological effects in the parental animals. No gross or microscopic changes were observed in any of the organs. None of the reproductive parameters were affected and there were no effects on the offspring other than a small reduction in pre-weaning body weight gain of the F2 pups at the highest dose level. It was concluded that the no observed adverse effect level (NOAEL) for reproductive toxicity of curcumin, fed in the diet for two successive generations to rats in this study was 10,000 ppm, which is equivalent to 847 and 959 mg/kg bodyweight (bw) per day for male rats and 1043 and 1076 for females for F0 and F1 generations, respectively. This study was the final toxicology study on curcumin reviewed by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) at the 61st Meeting, 2003. The JECFA group considered that the small body weight reduction in the F2 pups of the highest dose group prevented this from being regarded as a no adverse effect level, and so allocated an ADI for curcumin of 0-3 mg/kg bw based on the intake of 250-320 mg/kg bw in the mid-dose group as the NOEL.

Animals↗

PubMed2025

Mendelian randomization reveals causal relationships between cytokines and male reproductive diseases.

This study aims to explore the causal links between cytokines and four male reproductive disorders, namely abnormal spermatozoa (AS), male infertility, erectile dysfunction (ED), and hyperplasia of prostate (HP), employing a two-sample Mendelian randomization (MR) approach. Genetic associations with male reproductive diseases were derived from the IEU OpenGWAS project, with cytokine data from two GWASs focused on the human proteome and cytokines. Estimations were derived using inverse variance weighting, MR-Egger regression, weighted median, weighted model, and simple mode. Furthermore, the robustness of the findings was evaluated through Cochran's Q-test, MR-Egger regression, and leave-one-out sensitivity analysis. Fifteen unique cytokines were identified as having causal relationships with the risk of four male reproductive disorders. Specifically, for AS, interleukin-22 (IL-22), IL-12, and macrophage migration inhibitory factor were negatively correlated with AS, while tumor necrosis factor β levels were positively correlated with AS. In the context of male infertility, IL-2 receptor antagonist levels, IL-34, and granulocyte-colony stimulating factor levels were positively linked to male infertility, whereas IL-21 showed a negative relationship. Regarding ED, IL-19, IL-1β, and eotaxin levels were negatively associated with ED risk, while macrophage inflammatory protein 1β (MIP-1β) levels and interferon gamma-induced protein 10 levels were positively associated. As for HP, stromal-cell-derived factor 1α levels and MIP-1α levels revealed negative associations with HP. In conclusion, this MR analysis revealed that several cytokines were causally associated with male reproductive diseases and could be valuable in offering new insights for further mechanistic and clinical investigations of cytokines-associated male reproductive diseases.

Male↗

PubMed2005

Estrogen's effects on central and circulating immune cells vary with reproductive age.

Previous work from this lab has shown that estrogen attenuates inflammatory cytokine production following brain lesions in young adult female rats, but not in older, reproductive senescent females. The present study was designed to elucidate whether these effects result from estrogen's actions on brain-resident immune cells (microglia) or on circulating immune cells recruited to the brain from blood. Microglia, harvested from the olfactory bulbs of ovariectomized young adult and reproductive senescent animals, were pretreated with 17beta-estradiol and subsequently with the bacterial endotoxin LPS. LPS treatment significantly increased the pro-inflammatory cytokine IL-1beta in microglial cultures harvested from young and senescent females, but estrogen treatment had no effect on cytokine expression in either group. In young adult-derived microglia, LPS treatment also increased nitric oxide (NO), which was attenuated by estrogen, and MMP-9, which was not affected by estrogen. Reproductive senescent-derived microglia cultures had higher basal expression of NO and MMP-9 activity as compared to those from young adult microglial cultures, although LPS did not further stimulate these inflammatory markers. In blood cultures, LPS stimulated a dose-dependent increase in the inflammatory cytokine TNF-alpha expression in both young adult and reproductive senescent animals. Estrogen replacement significantly attenuated TNF-alpha induction by LPS in blood cultures derived from young adult females. Paradoxically, estrogen replacement increased LPS-induced TNF-alpha expression in blood cultures derived from reproductive senescent animals as compared to age-matched controls. The age and estrogen dependent effects on circulating immune cells found in whole blood cultures closely mimic the effects of estrogen on cytokine expression in the young and senescent animals that we reported in vivo, supporting the hypothesis that the immunosuppressive actions of estrogen replacement on neural injury may result from hormone-action on circulating immune cells.

Aging↗

PubMed2004

NTP-CERHR expert panel report on the reproductive and developmental toxicity of methanol.

The National Toxicology Program (NTP) and the National Institute of Environmental Health Sciences (NIEHS) established the NTP Center for the Evaluation of Risks to Human Reproduction (CERHR) in June 1998. The purpose of the Center is to provide timely, unbiased, scientifically sound evaluations of human and experimental evidence for adverse effects on reproduction, including development, caused by agents to which humans may be exposed. Methanol was selected for evaluation by the CERHR based on high production volume, extent of human exposure, and published evidence of reproductive or developmental toxicity. Methanol is used in chemical syntheses and as an industrial solvent. It is a natural component of the human diet and is found in consumer products such as paints, antifreeze, cleaning solutions, and adhesives. It is used in race car fuels and there is potential for expanded use as an automobile fuel. This evaluation is the result of a 10-month effort by a 12-member panel of government and non-government scientists that culminated in a public Expert Panel meeting. This report has been reviewed by CERHR staff scientists, and by members of the Methanol Expert Panel. Copies have been provided to the CERHR Core Committee, which is made up of representatives of NTP-participating agencies. This report is a product of the Expert Panel and is intended to (1). interpret the strength of scientific evidence that a given exposure or exposure circumstance may pose a hazard to reproduction and the health and welfare of children; (2). provide objective and scientifically thorough assessments of the scientific evidence that adverse reproductive/development health effects are associated with exposure to specific chemicals or classes of chemicals, including descriptions of any uncertainties that would diminish confidence in assessment of risks; and (3). identify knowledge gaps to help establish research and testing priorities. The expert panel report becomes a central part of the subsequent NTP-CERHR Monograph. Each monograph includes the NTP Brief on the chemical under evaluation, the expert panel report, and all public comments on the expert panel report. The NTP Brief contains the NTP's conclusions on the potential for exposure to result in adverse effects on human development and reproduction. It is based on the expert panel report, public comments on the report, and relevant data published after the expert panel report was completed. NTP-CERHR Monographs are publicly available and are transmitted to appropriate health and regulatory agencies.

Adult↗

PubMed2004

Diabetes (db/db) mutation-induced female reproductive tract hypercytolipidemia: estrogenic restoration of utero-ovarian indices.

The diabetes (db/db) mutation (leptin-receptor defect) induces a hyperglycemic-hyperinsulinemic endometabolic environment that promotes hypercytolipidemic, utero-ovarian involution in C57BL/KsJ mice, resulting in reproductive sterility and eventual organoatrophy. The effectiveness of low-dose, 17-B-estradiol therapy (E2-HRx), initiated prior to the genetic expression of the overt diabetes-obesity syndrome (DOS) on preventing female reproductive tract involution was evaluated by analysis of cytochemical, endocrine and tissue lipo-metabolic indices relative to oil (O)-vehicle treated (HRx) control (+/?) and (db/db) groups. All HRx treatments started at 4 weeks of age (i.e., pre-overt DOS stage) and continued through 16 weeks of age (i.e., chronic DOS expression) when tissue parameters were evaluated. The DOS promoted a dramatic increase in phenotypic obesity, hyperglycemia and hyperinsulinemia in (db/db) groups, relative to (+/?) indices, throughout the experimental period. In contrast, utero-ovarian weights were dramatically reduced in (db/db) groups relative to (+/?). Chronic low-dose E2-HRx moderated these DOS-induced trends in (db/db) groups, maintaining lowered body weights and normoglycemic parameters while stimulating utero-ovarian weight indices. In addition, E2-HRx prevented the dramatic hypercytolipidemic condition which promotes utero-ovarian involution in (db/db) mice as evidenced by the maintenance of normal reproductive cytoarchitecture. The concurrent moderation of tissue lipase activity and stimulated glucose uptake rates by (db/db) utero-ovarian compartments, under persistent hyperinsulinemic influences, indicated that E2-HRx effectively reduced both the structural and endometabolic consequences of the DOS from promoting (db/db)-associated reproductive organoatrophy. These results indicate that the pathophysiological alterations induced by the (db/db) mutation may be ameliorated through low-dose steroidal therapy, the efficacy of which is suspected to occur via membrane metabolic cascade induction mechanisms or by direct nuclear transcription modulation in reproductive target cells. The subsequent re-establishment of insulin-coupled glucose utilization and suppressed caloric shunting towards lipogenesis promotes the normalization of utero-ovarian structural and metabolic homeostasis in C57BL/KsJ-db/db mutants.

Animals↗