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PubMed2002

Determinants of the annual pattern of reproduction in mature male Merino and Suffolk sheep: modification of responses to photoperiod by an annual cycle in food supply.

Rams of a 'Mediterranean breed' (Merino) and a 'temperate breed' (Suffolk) were compared to determine how much of the differences between their reproductive seasons is owing to variation in their responses to photoperiodic and nutritional cues. In a previous study, both nutritional and photoperiodic inputs were held constant, and it was found that the two breeds show similar endogenous rhythms and, when the animals are challenged with a Mediterranean photoperiodic cycle, these endogenous rhythms are similarly modified. The present study tested whether an annual cycle in the supply of forage might modify the patterns that are generated by the interaction between photoperiod and endogenous rhythms. Both breeds were subjected to a simulated 'Mediterranean' annual cycle in photoperiod (10L:14D to 14D:10L) and provided with either constant food supply or a simulated 'Mediterranean' annual cycle in food supply. In Merino rams, testicular growth responded to photoperiod, but nutrition dominated those responses. In Suffolk rams, changes in testicular size can be completely out of phase with changes in body mass because they are driven primarily by photoperiod, with only subtle responses to changes in diet. The cycle of testicular growth in the Suffolk was driven by changes in the secretion of gonadotrophins (follicle-stimulating hormone concentrations and luteinizing hormone pulse frequency). By contrast, in the Merino, the nutritionally driven seasonal cycle of testicular growth was associated primarily with changes in body mass and this relationship could not always be explained by changes in gonadotrophin secretion. Melatonin secretion was not affected by food supply. Thus, the 'Mediterranean' and 'temperate' genotypes have similar endogenous rhythms that are similarly modified by photoperiod but, with respect to seasonal changes in nutrition, they differ in both the nature of their reproductive response and the physiological mechanisms that mediate those responses.

Animals↗
PubMed1996

Reproductive control in wild baboons measured by fecal steroids.

Measurements of reproductive hormones (progestins and estrogens) excreted in feces were used to discriminate between 25 conceptive and 76 nonconceptive (including undetected early abortion) cycles of free-ranging yellow baboons at Mikumi National Park, Tanzania. Conceptive cycles had significantly higher luteal-phase progestin and estrogen concentrations than nonconceptive cycles as early as Day 4 postovulation. However, mean early luteal-phase progestin concentrations in conceptive cycles were lower when conception occurred during ecologically optimal vs. suboptimal times, and among females of high compared to low dominance rank. Mean estrogen concentrations in conceptive cycles showed the opposite dominance rank pattern: mean luteal-phase estrogen concentrations were higher in conceptive cycles of high-compared to low-ranking females. None of these relations existed for nonconceptive cycles. These data suggest that successful implantation is facilitated by relatively high early luteal-phase progestin and estrogen concentrations. However, long-term environmental cues predicting the probability of offspring survival appear to influence the amount of progesterone required for successful implantation; progesterone concentrations necessary to facilitate successful implantation are higher during suboptimal seasons or among females of low dominance rank-cues that also suggest that offspring survival conditions are relatively poor. This may act as a reproductive filter, restricting conception to females whose immediate condition (e.g., low social stress and good physical health) enables them to compensate physiologically and behaviorally for effects associated with these relatively harsh offspring survival conditions.

Animals↗
PubMed2004

An epidemiological study of the incidence of abnormal pregnancy in areas heavily contaminated with methylmercury.

To determine the relationship between abnormal pregnancy in humans and methylmercury contamination, a retrospective study was conducted on women in two heavily contaminated areas, Modo (area M) and Akasaki (area A). Abnormal pregnancy was defined as fetal death, i.e., stillbirth and spontaneous abortion. In area M, prior to 1956, the incidence of abnormal pregnancy among the respondents was 7.0%. The incidence increased to 18.1% in the period between 1956 and 1968, when the pollution become serious. In area A, the incidence increased from 5.4% before 1956 to 14.2% between 1956 and 1968. In each area, the difference in the incidence between two periods, i.e., before and during the severe contamination, was statistically significant (area M, p<0.01; area A, p<0.001). Women living in Ikitsuki Island (area I) were selected as the control group. The incidence of the abnormal pregnancy in the three areas was compared by the birth years of mothers. Among women born between 1931 and 1940, the incidences were 26%, 15.1% and 13.5% in areas M, A and I, respectively. These women reached their reproductive age during the period of severe contamination in the two areas. The differences in the incidence between areas M and A and between areas M and I were statistically significant (areas M and A, p<0.05; areas M and I, p<0.01). These suggest that there is a relationship between methylmercury contamination and the increase in abnormal pregnancy in humans.

Abortion, Spontaneous↗
PubMed2006

The hypothalamic-pituitary-adrenal and the hypothalamic- pituitary-gonadal axes interplay.

Vertebrates respond to stress with activation of the hypothalamic-pituitary-adrenal (HPA) axis, the adrenergic and the autonomic nervous systems. The principal central nervous system regulators of the HPA axis are corticotropin releasing hormone (CRH) and antidiuretic hormone (AVP). Apart from in the central nervous system, CRH has been found in the adrenal medulla, ovaries, myometrium, endometrium, placenta, testis and elsewhere. The activation of the HPA axis during stress affects all body systems. The reproductive axis is inhibited by the HPA axis for the sake of saving energy. The changes to the hypothalamic-pituitary-gonadal (HPG) axis during stress are species-specific, and depend on the type and duration of the stimulus. Several conditions may be associated with altered regulation of the HPA axis. Polycystic ovary syndrome, anorexia nervosa and pregnancy in the third trimester are all characterized by HPA axis activation. In contrast, during the postpartum period, HPA axis suppression is implicated in the "postpartum blues". The actions of CRH are also essential in fetal development and neonatal survival.

Adolescent↗
PubMed2005

Internalization of seasonal time.

Orientation of physiology and behavior in time is a major adaptation common to many organisms and represents a significant challenge. In the face of predictable seasonal changes in climatic factors, and as a result of natural selection, many mammals now restrict their reproductive efforts to the fraction of the year when conditions of temperature, food, and water are most favorable for successful weaning of offspring. Changes in day length figure prominently in the synchronization of mammalian seasonal reproductive cycles. In summer breeders (e.g., several hamster, vole, and mouse species), decreasing summer day lengths induce reproductive involution. During this interval, neuroendocrine mechanisms analogous to a simple reference memory permit discrimination of stimulatory from inhibitory photoperiods. The non-reproductive phenotype is sustained for several months thereafter by the inhibitory short days of late summer, autumn, and early winter. Mid-winter reactivation of the reproductive system is triggered after 20-25 weeks of exposure to decreasing or short days by an interval timer that renders the reproductive neuroendocrine system refractory to short days. Recent work that has explored formal and physiological properties of this photorefractoriness interval timer has identified sex differences, neural substrates, and changes in hypothalamic gene expression that may participate in the measurement of seasonal time.

Animals↗
PubMed1989

Maternal transfer of photoperiodic information in Siberian hamsters. II. The nature of the maternal signal, time of signal transfer, and the effect of the maternal signal on peripubertal reproductive development in the absence of photoperiodic input.

Peripubertal reproductive development of Siberian hamsters is controlled by maternally derived photoperiodic information and the ambient photoperiod present after weaning. Previous experiments suggested that the maternally derived information is transferred during gestation, not during lactation. Development was examined in several photoperiods following manipulation of gestational and lactational photoperiods; development was influenced by the gestational, but not lactational, photoperiod. Second, effects of the gestational photoperiod were observed in young reared in constant light (LL) from Day 15. Depriving the young of ambient photoperiodic information after Day 15 allows a more direct assessment of the signal received from their dams. Finally, melatonin injections to long-day dams, at certain times of day, caused transmission of a short-day signal to young, as evidenced by their development in LL and light-dark cycles. Thus, a maternally derived signal that is dependent on melatonin influences reproductive development of the young during gestation; the maternally directed pattern of development can subsequently be modified by the youngs' own response to ambient photoperiods after weaning.

Aging↗
PubMed1986

[Reproduction studies of VP 16-213 (II)--Oral administration to rats during the period of fetal organogenesis].

VP 16-213 (etoposide, abbr. to VP), an oncostatic drug, was administered orally to pregnant Crj: CD (Sprague-Dawley) rats from day 7 through 17 of gestation at dose levels of 1, 3 and 10 mg/kg/day. The summarized results obtained are as follows: VP 10 mg/kg suppressed the maternal body weight increase from day 12 through 20 of gestation. VP 10 mg/kg brought the inhibition of fetal growth accompanied by the lowered values in body weight and body length. Furthermore, the elevated incidences of skeletal anomalies and unossified 5th and 6th sternums, as well as retarded ossification of thoracic vertebrae were also noted in this dose level. VP 10 mg/kg induced anophthalmia, microphthalmia and dilated lateral ventricles in fetuses (F1), as well as unilateral anophthalmia in offspring (F1). VP 10 mg/kg increased the days required for opening of eyelids and descending of testes in offspring (F1), but failed to affect their learning ability, motility, motor activity or emotional development. VP 10 mg/kg suppressed the growth of genital organs in F1 rats of both sexes, but failed to affect their reproductive ability or gestation period. As for F2 newborns derived from F1 rats whose dams had ever received VP 10 mg/kg during the period of fetal organogenesis, the number of implantations and survivors as well as birth indexes lowered due to changes in these items restricted to a few litters. Based on these results, the no-effect dose level of VP under the present experimental condition was estimated to be 3 mg/kg/day against dams and their offspring.

Administration, Oral↗
PubMed2000

Circulating LH levels and the response to exogenous GnRH in the common mole-rat: implications for reproductive regulation in this social, seasonal breeding species.

The effects of breeding season and reproductive status on male and female reproduction were investigated in the common mole-rat, Cryptomys hottentotus hottentotus, a cooperatively breeding rodent which exhibits a unique combination of seasonal breeding and a reproductive division of labor. Pituitary function was examined by measuring the luteinizing hormone (LH) responses to single doses of 2 microg exogenous gonadotrophin-releasing hormone (GnRH) and physiological saline in 69 males and 58 females from 35 wild caught colonies. Neither males nor females exhibited any apparent manifestation of season on basal LH concentrations or on pituitary sensitivity to stimulation by exogenous GnRH. The continuance of reproductive function during the nonbreeding period is essential in common mole-rat males and females, as this period coincides with the period of maximal dispersal opportunity in the winter rainfall area they inhabit. Normal circulating levels of reproductive hormones in dispersing animals may aid intersexual recognition, assist pairbond formation, and thus prime animals for independent reproduction. Circulating basal concentrations of LH as well as LH levels measured in response to a single exogenous GnRH challenge were not significantly different between the reproductive and non-reproductive groups of either sex, suggest the absence of a physiologically well-defined suppression of reproduction in subordinate common mole-rats.

Animals↗
PubMed1995

[Comparative study of 4 combined hormonal contraceptive preparations with reduced hormonal levels].

The authors do clinic-laboratory investigation of the affect of four hormonal contraceptive preparations: Minisston, Gravistat 125, Rigevidon, Anteovin, on 179 patients in reproductive age for the period of 895 menstrual cycles. The investigation is specified with respect of investigation of 10 clinic indexes, which are considered as side effects in the reception of hormonal contraception, as well as with respect to reconstruction of ovary function after reception breaking in first, second and third month. The received results demonstrate high effectiveness of the experimented preparations with respect to pregnancy prevention, good acceptance - the appearance of side effects is under the accidentally error limit, as well as good reproductive ability of ovaries after tablet reception breaking. Especially to Anteovin preparation the authors accept that it is with minimum side effects. They considered that this is due to increasing dose of gestagen during the second phase of the menstrual cycle, which appears stabilizing factor with respect to the good acceptance of the preparation without difference in age and fertile realization of the investigated patients.

Adolescent↗
PubMed1978

Primate infant's effects on mother's future reproduction.

Female savanna baboons (Papio cynocephalus) had a longer postpartum amenorrhea and thereafter cycled longer before conceiving if their previous infant survived than if that infant died. Among mothers of surviving infants, differences in maternal care produced differences in age of weaning and age of independence but did not result in differences in interbirth intervals.

Amenorrhea↗
PubMed1980

Relationship between early postpartum blood composition and reproductive performance in dairy cattle.

Blood samples were collected over 1 year from 115 postpartum Holstein cows to determine the relationship between blood composition and reproductive performance. Blood samples were collected from each cow at 14 to 21 days (sample 1) and 38 to 45 days (sample 2) postpartum. These samples were analyzed for packed cell volume, hemoglobin, total protein, calcium, phosphorus, magnesium, copper, zinc, and selenium. Blood composition varied little with lactation number and season, and relationships were not consistent for the two collection periods. Hemoglobin, packed cell volume, total protein and zinc were associated negatively and calcium and magnesium associated positively with at least one measure of milk yield. None of the blood components examined at the two collection periods had a consistent relationship to reproductive performance. The most important relationship was the positive relationship of selenium concentration at first collection period with services per conception and days open.

Animals↗
PubMed1995

Collaborative assessment of optimal administration period and parameters to detect effects on male fertility in the rat: effects of cyclophosphamide on the male reproductive system.

As part of a collaborative project to determine optimal administration period and parameters to detect compound effects on male fertility in the rat, adult male rats were administered cyclophosphamide daily at 5, 10, 20 and 40 mg/kg for 2 weeks, or at 2.5, 5 and 10 mg/kg for 4 or 9 weeks. After the pre-pairing administration period, each male was paired with an untreated female. After mating, testes and epididymides were removed and examined for organ weights, sperm head counts, sperm morphology and histopathology. Mated females were caesarean-sectioned on Day 13 of gestation. Although atrophy of epithelia in the cauda epididymides and decreases of spermatogenic cells in the testes were observed in the higher dose groups in the 2w study, no other effects on the male reproductive system were noted in any of the studies. There were clear effects on pregnancy outcome; implantation efficiency was decreased in the highest dosage groups and postimplantation losses increased in all the dosage groups in all studies. These results suggest that a fertility study with females is needed particularly in the case of mutagenic agents, together with a detailed histopathological evaluation for reliable detection of toxicity on the male reproductive system.

Animals↗
PubMed1997

The effects of nerve growth factor and anti-nerve growth factor antibody on the neuroendocrine reproductive system in the European starling Sturnus vulgaris.

Thyroidectomy of starlings causes them to remain in breeding condition indefinitely; deactivation of gonadotrophin-releasing hormone neurons that is characteristic of photorefractoriness does not occur. We hypothesise that a neurotrophin, whose presence or ability to function is dependent upon thyroid hormones, is somehow involved in this termination of gonadotrophin-releasing hormone release. Nerve growth factor is one such candidate. Mouse 7S-nerve growth factor dissolved in artificial cerebro-spinal fluid was therefore infused into the lateral ventricle of thyroidectomised male starlings held on long days four times daily for 21 days and 31 days, in separate experiments, to see if photorefractoriness would occur. The result was significant gonadal regression in the treatment groups during the infusion period, with no change in testicular volume in the control groups. Testicular recrudescence occurred after the end of the treatment period. To see if this was a non-specific effect, or progression towards photorefractoriness per se, we used castrated, photorefractory starlings held on long days. Anti-nerve growth factor antibody was infused into the lateral ventricle at increasing concentrations and frequency. There was a significant rise in circulating luteinising hormone levels in the treatment groups as compared to controls, increasing with antibody dosage.

Animals↗
PubMed1984

Spinocerebellar ataxia in a large kindred: age at onset, reproduction, and genetic linkage studies.

We studied a large kindred with autosomal dominant spinocerebellar ataxia (SCA) to assess reproductive performance, the impact of genetic counseling, and linkage relationships of the SCA locus. Reproduction was not lower in those with SCA than in unaffected sibs or first cousins. Genetic counseling reduced reproduction during the risk period for development of SCA. Given autosomal dominant transmission of a single gene, we found strong evidence that the locus for SCA in this kindred is linked to the HLA loci.

Adolescent↗
PubMed1998

Reproductive seasonality and maturation throughout the complete life-cycle in the mouflon ram (Ovis musimon).

To document the process of physical and reproductive maturation in a long-lived mammal, the long-term changes in endocrine (follicle stimulating hormone-FSH, prolactin and testosterone) and morphological parameters (body weight, testis diameter, neck girth, sex skin colour, horn growth, wool growth, moult and pelage characteristics) were measured throughout the full life-span in a group of captive mouflon rams, Ovis musimon (n=4, 12-year study). Live body weight increased to a maximum at 7 years of age and declined in old age, while horn size (length and volume) increased throughout the full life-span. Every year there was a marked and consistent cycle in the blood plasma concentrations of FSH and testosterone, and growth of the testes, with peak reproductive function in September and October associated with the rut. The annual maximum in plasma FSH and testosterone concentrations, and the size of the testes increased progressively from 1-6 years of age (or later into the life-cycle for testosterone). There was also a marked annual cycle in plasma prolactin concentrations (peak in May and June), and growth of the horns and pelage. The annual maximum in prolactin concentrations increased throughout the life-cycle, while the rate of horn growth (annual increments) decreased. The overall conclusion is that neuroendocrine mechanisms regulate both the annual and the age-related changes in the reproductive axis, and reproductive maturation proceeds gradually through the life-cycle. Because the acquisition of adult characteristics (large body size, large horns, conspicuous male secondary sexual characteristics) greatly affects male competitiveness, sexual maturity is closely linked to physical maturity, and this occurs long after the initial onset of fertility at puberty.

Aging↗
PubMed1981

Postpartum distribution of costs and disorders of health.

More than 17,000 events from 1,305 lactations of 551 cows in two herds were analyzed to quantify the distribution of costs and disorders of health during a lactation. Categories were mammary, reproduction, locomotion, digestion, respiration, other, insemination, and total. The largest costs and most disorders were associated with initiation of lactation rather than period of peak daily milk yield. Mammary and reproductive costs were 71% of total health cost in the first 30 days postpartum. Mammary and reproductive costs were 55% of the total health cost in an average 30-day interval. Insemination cost was 50% of the total health cost between 60 to 89 days postpartum. Parturition and extended days open were periods of large reproductive cost. Postpartum distributions of health cost and health disorders were similar implying that the prices assigned for severity added little information to counting disorders.

Animals↗