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PubMed1998

The effect of bovine virus diarrhoea virus on reproduction in recently infected Norwegian dairy herds.

A group of 32 dairy herds, recently infected with bovine virus diarrhoea virus (BVDV), was compared with a control group consisting of 75 BVDV free herds during a 3-year-period. Variables related to reproduction were registered. Results of multiple antibody examinations in bulk milk as well as samples of milk and blood from younger animals were used to select the herds. The incidence of abortions was statistically significantly different in the 2 groups, while the number of stillbirths, weak born calves, and congenital anomalies was not. Other variables such as percentage of non return, average number of inseminations per cow and calving interval showed during the study a trend to improve in the BVDV group, while they remained stable in the control group.

Abortion, Veterinary↗
PubMed1987

The plasma sex steroid profiles in the freshwater, sex-reversing teleost fish, Monopterus albus (Zuiew).

The plasma levels of both the free and conjugated forms of six sex steroids (androstenedione, testosterone, 11-oxotestosterone, 11 beta-hydroxytestosterone, estrone, and 17 beta-estradiol) were determined by radioimmunoassay combined with Celite chromatography in different sexual phases of the protogynous Monopterus albus throughout the reproductive cycle. The amounts of 11-oxotestosterone and 11 beta-hydroxytestosterone were found to be very low and variable in all the specimens investigated. No conjugated 17 beta-estradiol or free estrone was detected. Female individuals showed a prespawning rise of androstenedione which subsequently dropped to a low level in the spawning period. The estrogen levels in the female phase were found to be higher than those in all other sexual phases during the spawning period, but the testosterone level remained constant throughout the reproductive cycle in the female phase. The level of androstenedione was highest in the early intersexual and mid-intersexual phases during the postspawning/inactive period. Compared with the female specimens in the same reproductive period, the early intersexual individuals showed a higher level of 17 beta-estradiol, while the mid-intersexual animals showed a higher level of testosterone in the postspawned/inactive period. In the mid-intersexual phase, the levels of androstenedione, testosterone, 17 beta-estradiol, and estrone dropped progressively in relation to the seasonal reproductive cycle. The male fish had a constant level of androstenedione, estrone, and 17 beta-estradiol. However, the level of testosterone increased as the spawning period approached. The hormonal profile in the late intersexual phase was essentially similar to that in the male phase. The changes in the plasma levels of sex steroids in M. albus apparently were related to the maturation of the female and male sex tissues and to their seasonal reproductive cycle.

Androstenedione↗
PubMed1995

Histopathology of postpartum placental sites in mink (Mustela vison) exposed to polychlorinated biphenyls or fractions thereof.

Polychlorinated biphenyls (PCB) cause reproductive failure in mink. Ovulation and nidation occur, but the fetuses die during gestation. The toxicity of different chlorinated biphenyl (CB) congeners differs markedly. Dioxin-like congeners with no (0-ortho CBs) chlorine in the ortho position to the biphenyl bond are considered to be highly toxic. Altogether, 13 groups of 10 female mink (Mustela vison) were exposed to PCB or CB fractions thereof during the reproductive season of 1988 and 1989. In 1988, one group of mink received 2 mg/day of Clophen A50 and five groups received single fractions thereof or synthetic 0-ortho CB in their diet. In 1989, one group received 1.64 mg/day of Aroclor 1254 and six groups received combinations of fractions thereof. The daily amounts of the fractions administered per animal were equivalent to those present in 2 mg of Clophen A50 or 1.64 mg of Aroclor 1254. After administration for 3 months in both experiments, the animals were killed 5 days after parturition. Histological examination focused on the placental sites. The most involuted placental sites were those of early fetal death in primiparous, non-whelping animals in the 1989 experiment. The least involuted placental sites, displaying a hyperplastic and pleomorphic uterine luminal epithelium, in which proliferating cell nuclear antigen (PCNA) was present, were those of late fetal death in biparous, non-whelping animals in the 1988 experiment. The survival of the fetoplacental unit was related to PCB exposure. The histology of the placental sites seemed only to be related to the survival time of the fetuses and to the number of former reproductive seasons.

Animals↗
PubMed2004

Expression of the arylhydrocarbon receptor in the peri-implantation period of the mouse uterus and the impact of dioxin on mouse implantation.

The arylhydrocarbon receptor (AhR) is a nuclear transcription factor mediating toxic effects of chemicals such as dioxins. The 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a member of polyhalogenated aromatic hydrocarbons family, exerts a wide-variety of toxic effects in a tissue- and species-specific manner including the reproduction process. Recently, AhR-mediated direct effects of TCDD on a cell-specific interaction with ovarian steroids have been shown. However, information regarding the effects of TCDD on the mouse implantation is limited. We therefore examined the expression and localization of AhR in the pregnant mouse uterus from 4 to 10 days of gestation (day 4 to day 10) using immunohistochemistry to investigate the effect of TCDD on uterine tissue during the peri-implantation period. Intense AhR expression was detected in the uterine vasculature throughout the periods examined. We also found that implanted blastocysts and their surrounding luminal epithelia and decidualized stroma expressed AhR on day 5. On days 6 and 7, persistent AhR expression was found in the transitional zone between the invading embryonic tissue and decidual tissue. On days 9 to 10, placental vasculature and spongiotrophoblasts displayed AhR immunoreactivity. The administration of TCDD on day 4 decreased the number of surviving implanted embryos on day 7 in a dose-dependent manner. This effect of TCDD was inhibited by the simultaneous administration of an AhR antagonist, alpha-naphthoflavone (alpha-NF). The spatio-temporal expression of AhR during the peri-implantation phase of the mouse uterus may indicate functional roles of this orphan receptor in fetomaternal interactions as well as substantiate the risk of exposure to chemicals such as dioxins during the reproductive period.

Animals↗
PubMed2001

Adult survival, maturation, and reproduction of the desert locust Schistocerca gregaria infected with the fungus Metarhizium anisopliae var acridum.

Studies were conducted with two different doses of Metarhizium anisopliae var acridum to examine the effects on survival and reproductive potential of adult Schistocerca gregaria under conditions that either limited thermoregulation or enabled optimal thermoregulation. Adult S. gregaria infected with the fungal pathogen showed either a rapid and high mortality at relatively constant temperatures or a much reduced mortality and lengthened survival time when allowed to thermoregulate. Mortality rate varied from >90% after 10 days under constant temperature conditions to 66% after 70 days under optimal thermoregulatory conditions. Effects of infection on maturation and reproduction depended on the age of the adults at the time of inoculation, the nighttime temperature regime, the fungal dose, and the length of time of the monitoring period. No difference in reproductive behaviors in treated and control insects were found in one experiment that utilized older adults and was conducted over 25 days. In a second experiment with newly fledged locusts, differences in maturation rates and total reproductive output were observed due to infection. The results from these experiments are discussed in terms of the potential of M. anisopliae var acridum to alter the balance of insect endocrine systems and the importance of the assessment of behavioral changes and their impact on microbial control agents in the long term.

Aging↗
PubMed1998

Gonadotropin pulsations across development.

Initiation and maintenance of the reproductive axis in the human is contingent upon the pulsatile secretion of gonadotropin-releasing hormone (GnRH) from the hypothalamus. In man, tracking endogenous GnRH secretion relies on frequent peripheral sampling of three glycoprotein products of the gonadotrope, luteinizing hormone (LH), follicle-stimulating hormone (FSH) and free alpha-subunit (FAS). FAS is superior to LH as a surrogate marker of GnRH secretory dynamics in those circumstances where GnRH secretion is rapid or where the pituitary LH response is low. The pattern of GnRH secretion is constantly changing across development; from high levels during the neonatal period, through a period of quiescence in mid-childhood, followed by sleep-entrained reactivation of the reproductive axis at the onset of puberty, ultimately culminating in the adult pattern of pulsatile secretion which in the male is approximately every 2 h and in the female varies with the stage of the menstrual cycle. This episodic mode of secretion allows differential impact of feedback mechanisms on the GnRH neurons and facilitates the maintenance of the reproductive axis during periods of stress by allowing frequency and amplitude modulations.

Animals↗
PubMed1983

Latitude of origin influences photoperiodic control of reproduction of deer mice (Peromyscus maniculatus).

Three subspecies of Peromyscus maniculatus originating from different latitudes were maintained from birth in light dark cycles that provided between 10 and 18 h of light per day. At 50 days of age, Chihuahua, Mexico mice (latitude of origin 27 degrees N) and South Dakota, U.S.A. mice (44 degrees N) kept in the 10L:14D photoperiod had reduced gonadal and seminal vesicle weights and a lower spermatogenic index than corresponding mice kept in a 14L:10D photoperiod. Some Chihuahua and South Dakota mice, apparently constituting nonphotoperiodic subpopulations, developed their gonads while kept in the short-day photoperiod. The critical day length for stimulation of sexual maturation was greater for mice from Manitoba, Canada (55 degrees N) than for mice from the lower latitudes. At 70 days of age, testes and seminal vesicle weights, and the spermatogenic index of Manitoba mice in the 14L:10D photoperiod, were lower than those of animals maintained in 16L:8D and 18L:6D photoperiods. Responsiveness to short day lengths was greater among adult South Dakota than adult Chihuahau mice and melatonin treatment significantly reduced testes weights of South Dakota but not of Chihuahua adult mice. Photoperiodic regulation of the reproductive system varies with latitude of origin. Differences in the critical day length necessary for stimulating development of functional reproductive activity and variations in the percent of photoperiodic animals within each subspecies, appear to contribute to latitudinal gradients in reproduction.

Animals↗
PubMed1979

[Modification of the ovarian cycle, ovulation and reproduction in rat by administration of p-chlorophenylalanine in the pre and post ovulation period (author's transl)].

The effect of p-Chlorophenylalanine (PCPA) administered in pre and post-ovulation phases on ovulation reproduction and ovarian cycle was studied in rats. Vaginal smears, number of ovules, mature follicles and ovaric histologic features were evaluated. PCPA administered in the periods after follicular rupture prolongs the diestrus phase from 2 to 10 consecutive days and totally inhibits the reproductive conduct. When administered in the periods just prior to follicular rupture, PCPA prolongs the estrus phase from 2 to 4 consecutive days and does not totally inhibit reproduction. A progressive increase in reproduction took place as treatment time approached ovulation, to such an extent that the number of inseminated and fertilized rats when treated at the ninth hour of the proestrus phase, was superior to the control group. PCPA administered in periods after and before follicular rupture totally inhibits ovulation in all cases. Ovaries present many mature follicles, as many as in the controls sacrificed at the 18 hour of the proestrus, just before ovulation.

Animals↗
PubMed2004

Monogamy in marine fishes.

The formation of long-term pair bonds in marine fish has elicited much empirical study. However, the evolutionary mechanisms involved remain contested and previous theoretical frameworks developed to explain monogamy in birds and mammals are not applicable to many cases of monogamy in marine fish. In this review, we summarise all reported occurrences of social monogamy in marine fish, which has so far been observed in 18 fish families. We test quantitatively the role of ecological and behavioural traits previously suggested to be important for the evolution of monogamy and show that monogamous species occur primarily in the tropics and are associated with coral reef environments in which territory defence and site attachment is facilitated. However, there is little evidence that obligately monogamous species are smaller in body size than species that can adopt a polygynous mating system. We review the evidence pertaining to six hypotheses suggested for the evolution of monogamous pair bonds: (1) biparental care, (2) habitat limitation, (3) low population density/low mate availability/low mobility, (4) increased reproductive efficiency, (5) territory defence, and (6) net benefit of single mate sequestration. We outline predictions and associated empirical tests that can distinguish between these hypotheses, and assess how generally each hypothesis explains monogamy within and between breeding periods for species with different types of territories (i.e. feeding only or feeding and breeding). Hypotheses (1) and (2) have limited applicability to marine fishes, while hypotheses (3)-(5) have little empirical support beyond the species for which they were designed. However, the role of paternal care in promoting monogamous pair bonds is not explicit in these hypotheses, yet paternal care has been reported in more than 70 monogamous marine fish. We show that paternal care may act to increase the likelihood of monogamy in combination with each of the proposed hypotheses through decreased benefits to males from searching for additional mates or increased advantages to females from sequestering a single high-quality mate. Among species defending breeding and feeding territories, the benefits, both within and between reproductive periods, of sequestering a single high-quality mate (hypothesis 6) appear to be the best explanation for socially monogamous pairs. For species without parental care (i.e. holding only feeding territories), territory defence (hypothesis 5) in combination with the benefits of guarding a large mate (hypothesis 6) could potentially explain most instances of monogamy. Empirical studies of marine fishes over the past two decades are therefore slowly changing the view of monogamy from a mating system imposed upon species by environmental constraints to one with direct benefits to both sexes.

Animals↗
PubMed1998

[Morphofunctional characteristics of interstitial endocrine cells (Leydig cells) from testis and prostate of Orenburg goats in ontogenesis and under conditions of seasonal changes in their reproductive activity].

Dynamics of structural reorganizations of goat testicular Leydig cells and prostate was monitored in different periods of ontogenesis using light and electron microscopy. Morphological equivalents of endocrinocyte functional activity elevations were noted within the period from d 60 to 70 of embryogenesis, at puberty and in mature animals before the onset of mating period in mature animals. Endocrinocyte foetal population destruction occurs by the 1st postnatal month. Leydig cell maximum activity peak precedes structural and functional differentiation in prostate both at stages of ontogenesis and in periods of seasonal oscillations of reproductive activity.

Animals↗
PubMed1996

Seasonal variation of LH, sex steroids, body mass, molt, display, and laying in two subspecies of Houbara bustard, Chlamydotis undulata macqueenii and Chlamydotis undulata undulata, housed in outdoor cages under natural conditions.

Subspecies of the Houbara bustard are resident in North Africa (Chlamydotis undulata undulata) or are partial latitudinal migrants in Asia (Chlamydotis undulata macqueenii). Houbara breed in arid or semiarid zones, and the reproductive biology of wild Houbara is largely unknown. Body mass, molt, courtship display, laying, and plasma concentrations of LH, testosterone, and progesterone were measured in captive-bred birds of both subspecies, housed in outdoor cages under natural conditions, over a period of 1 year and 6 months, at Taif, Saudi Arabia (21 degrees 15' N). Captive Houbara bustards show a seasonal breeding pattern with a laying period from January to July. Males began displaying well in advance of any eggs laid and display long after the termination of laying. In females, gonadal activity and molt were mutually exclusive; however, in males, slight overlap between sexual display and molt was observed. In females, seasonal variation of LH and progesterone was synchronous with laying activity. In males both testosterone and LH plasma concentrations were highest in January (testosterone approximately 8 ng/ml; LH approximately 3 ng/ml) at the beginning display period. This could correspond, in the wild, to the establishment of territories. Levels dropped significantly before the females started laying but stayed at an intermediate level throughout the breeding season (testosterone approximately 3 ng/ml; LH approximately 1.5 ng/ml). In the middle of August, during molt, and following heavy rainfall, LH and testosterone peaked (testosterone approximately 2.3 ng/ml; LH approximately 1.8 ng/ml), suggesting a possible impact of rainfall on Houbara gonadal activity. Houbara stopped laying before the maximum ambient temperature reached 32 degrees, indicating that high temperature could be a factor terminating laying activity. No major differences were found between the two subspecies in the timing or duration of the reproductive period; only the annual variation of the body mass varied slightly between the subspecies.

Animals↗
PubMed1987

Control theory predictions of reproductive allocation in female dusky salamanders.

A model of the reproductive ecology of female dusky salamanders was used to investigate the allocation scheme that a female might use to maximize her reproductive success. Analysis of the model with techniques of optimal control theory suggests that fecundity is maximized either by allocating food resources to reproduction for the entire time period prior to egg laying, or by growing first, then switching to reproduction later in the year. The analysis also indicates that egg mortality will be minimized if the female provides maternal care at the maximum level throughout egg brooding. These results are not specific to dusky salamanders, but can be extended to other organisms with similar reproductive characteristics.

Animals↗