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PubMed1979

The birth and survival of wildebeest calves.

This paper describes social organization, parturition, post partum behavior of wildebeest mothers and offspring, and calf predation during the annual birth peak in Ngorongoro Crater, Tanzania. The wildebeest's "follower-calf" system, unique among the Bovidae, is remarkably effective in protecting neonates. Even during hte one-month peak, the major predator on calves, the spotted hyena, is unable to feed to satiation. Calf survival is consistently high, despite large fluctuations in the numbers of wildebeest, with consequent effects on the size of the yearly calf crop.

Adaptation, Physiological↗
PubMed2005

Effect of nutrition on plasma progesterone levels, metabolic parameters and small follicles development in unstimulated goats reared under constant photoperiod regimen.

Sixteen local adult goats were submitted for 9 weeks to 2.09 (high group) and 0.54 (low group) x dietary maintenance respectively. During the experimental period, goats were weighed, oestrus was detected and plasma insulin, urea, non-esterified fatty acids and progesterone concentrations were assessed. At the end of the experiment, ovarian small follicles population was studied by histological analysis. Final weight loss in low group was 18.37 +/- 2.02%, whereas weight gain of high group was 13.84 +/- 2.70%. Insulin and urea were lower in low group, while non-esterified fatty acids were significantly higher. A lower number of fasted goats was in oestrus or ovulated and an extended length of oestrus (p < 0.05) and a higher frequency of short or long cycles (p < 0.05) were also observed. Fed animals showed heavier ovaries (p < 0.01) and a lower number of primordial follicles (p < 0.05). In restricted goats a significant qualitative alteration of follicle classes involved in the initiation process of primordial pool was found. In this phase, granulosa thickness and oocyte size were the most affected (p < 0.01). However in small follicles beyond the primary stage no differences were found between the groups in either number or qualitative characteristics (p > 0.05). Collectively, these results indicate that opposite dietary intakes for a medium period induce a composite reproductive response in goats and can regulate the early onset of follicle growth.

Animal Nutritional Physiological Phenomena↗
PubMed2004

Ethnicity and birth outcome: New Zealand trends 1980-2001: Part 2. Pregnancy outcomes for Maori women.

BACKGROUND: While traditionally Maori perinatal mortality has been similar to that of other ethnic groups, rates of preterm birth, small for gestational age (SGA) and teenage pregnancy have remained high. AIMS: To review current trends in preterm birth, SGA and teenage pregnancy for Maori during 1980-2001 and to highlight the major factors that have influenced Maori reproductive outcomes during this period. METHODS: De-identified birth registration data from 1 189 120 singleton live births and 5775 stillbirths were analysed for 1980-2001. Outcomes of interest included preterm birth, SGA and late fetal death while explanatory variables included maternal ethnicity, age and NZ Deprivation Index decile. Trend analysis was undertaken for 1980-1994 and multivariate logistic regression was used to explore risk factors for 1996-2001. RESULTS: During 1980-1994, Maori women had the highest preterm birth rates of any ethnic group in New Zealand, but in relative terms, inequalities declined as a consequence of a non-significant 7% fall in rates being offset by a statistically significant 30% increase for the European/other ethnic group. Rates of SGA were also higher amongst Maori women but declined by 25% during the 1980-1994 period. In addition, Maori women experienced significant socioeconomic gradients in SGA, with risk for Maori women in the most deprived NZDep areas being double that of Maori living affluent areas. Paradoxically, while Maori women had high rates of teenage pregnancy, this did not confer additional risk for preterm birth or SGA during the 1996-2001 period. CONCLUSIONS: While high rates of teenage pregnancy amongst Maori women appear not to confer additional risk for preterm birth or SGA, the social consequences of early childbearing may well be significant. The persistence of elevated rates of preterm birth and large socioeconomic gradients in SGA amongst Maori suggest that broader social and policy interventions are necessary if Maori are to achieve optimal birth outcomes in the coming decades.

Adolescent↗
PubMed1970

Porifera: sudden sperm release by tropical Demonspongiae.

Three tropical marine demosponges inhabiting the deep coral reefs of Jamaica expel immense clouds of milky fluid from exhalant apertures. Analysis of samples shows this fluid to contain mature male gametes. The behavior is an individual or a population event in different species.

Animals↗
PubMed1991

Prolactin short-loop feedback and prolactin inhibition of luteinizing hormone secretion during the breeding season and seasonal anoestrus in the ewe.

In seasonally breeding mammals, plasma prolactin (PRL) concentrations vary on an annual basis with levels high in summer and low in winter. In this study of the ewe, we determined, first, whether PRL secretion is regulated by short-loop feedback and, second, whether the high summer levels of PRL are due to a change in sensitivity or loss of this feedback loop. Because the high summer levels of PRL coincide with the period of seasonal anoestrus in the ewe and could therefore be involved in the seasonal suppression of gonadotrophins, the effects of intracerebroventricular PRL on pulsatile LH secretion were also determined. Ovary intact ewes received intracerebroventricular injections of ovine PRL (oPRL; 50 micrograms) or anti-PRL serum. From 3 to 13 h after central administration of oPRL, plasma PRL concentrations were significantly reduced compared with the vehicle-treated controls. In contrast, following injection of anti-PRL serum, plasma PRL levels increased significantly. To determine whether there was a seasonal change in sensitivity to PRL feedback, a series of experiments were conducted in July and November when PRL concentrations are high and low, respectively. At each time of year, ovariectomized oestradiol-implanted ewes were injected intracerebroventricularly with 10 and 50 micrograms oPRL with control animals receiving the vehicle. At both times of year there was clear evidence of PRL short-loop feedback with no indication that sensitivity was reduced in the July trial. Luteinizing hormone (LH) pulse frequency, pulse amplitude and mean LH were not affected by intracerebroventricular oPRL at either time of year.(ABSTRACT TRUNCATED AT 250 WORDS)

Anestrus↗
PubMed2002

Developing a laboratory animal model for perinatal endocrine disruption: the hamster chronicles.

At the biomedical, regulatory, and public level, considerable concern surrounds the concept that inappropriate exposure to endocrine-disrupting chemicals, especially during the prenatal and/or neonatal period, may disrupt normal reproductive tract development and adult function. The intent of this review was to 1. Describe some unique advantages of the hamster for perinatal endocrine disruptor (ED) studies, 2. Summarize the morphological and molecular consequences of exposure to the established perinatal ED, diethylstilbestrol, in the female and male hamster, 3. Present some new, histomorphological insight into the process of neonatal diethylstilbestrol-induced disruption in the hamster uterus, and 4. Introduce recent efforts and future plans to evaluate the potency and mechanism of action of other putative EDs in the hamster experimental system. Taken together, the findings indicate that the hamster represents a unique and sensitive in vivo system to probe the phenomenon of endocrine disruption. The spectrum of candidate endpoints includes developmental toxicity, neoplasia, and more subtle endpoints of reproductive dysfunction.

Animals↗
PubMed2002

Cytoplasmic and nuclear Fos protein forms regulate resumption of spermatogenesis in the frog, Rana esculenta.

The role of Fos proteins in the regulation of germ cell progression during spermatogenesis has been studied in the frog, Rana esculenta. A peculiarity of this animal model is the finding of Fos in cytoplasmic compartment of primary spermatogonia during the resting period of the annual reproductive cycle. Interestingly, Fos is localized in the nuclear compartment when spermatogenesis resumes. Using Western blot analysis, we show that a 52-kDa Fos protein occurs in testicular cytosolic preparations, whereas two different Fos signals of 43 and 68 kDa are typical of the nuclear compartment. The 68-kDa Fos immunoreactive protein increases in nuclear extracts in concomitance with spermatogonia (SPG) proliferation either during the annual sexual cycle or in experimental animal groups where SPG proliferation was induced by thermal stimulus (24 C). Indeed, an increase in proliferating cell nuclear antigen was detectable after thermal induction of mitotic activity. A decrease in the 52-kDa signal and a concomitant increase in the 68-kDa signal is observed in testes of 24 C treated groups. The use of alkaline phosphatase and alkaline phosphatase inhibitors indicates that the 68-kDa protein is a phosphorylated form. Estrogens, which are able to induce SPG proliferation, are responsible for the appearance of the 43-kDa Fos form in nuclear testicular extracts. In conclusion, our results show, for the first time in a vertebrate species, that storage in the cytoplasm, on the one hand, and appearance as well as phosphorylation of Fos proteins in the nucleus of germ cells, on the other hand, regulate spermatogenesis progression during the seasonal breeding. Moreover, the phosphorylated 68-kDa Fos form may be involved in mechanisms underlying SPG proliferation.

Animals↗
PubMed1988

Oestrus and the vaginal smear cycle of the river otter, Lutra canadensis.

Vaginal smears of river otters contained specific cellular associations which can be used to monitor their reproductive cycle. The anoestrous period was identified by the presence of large intermediate epithelial cells while the onset of pro-oestrus was gradual and the duration difficult to determine. Oestrus was indicated by an influx of nucleated and non-nucleated cornified cells which continue after mating. The metoestrous smear was characterized by large quantities of leucocytes and mucus.

Animals↗
PubMed1989

Time of the sidereal year affects responsiveness to the phase-resetting effects of photoperiod in the ewe.

Two groups of ovary-intact ewes were placed in separate photochambers on the day of the vernal equinox (VE). One group was exposed to a 16 h light:8 h dark (16L:8D) photoperiod and the other to 8L:16D. On the day of the summer solstice (SS) and at 90-91-day intervals thereafter [autumnal equinox (AE), winter solstice (WS), VE and SS], each group was changed to the opposite photoperiod. The latent period between each change and either onset or cessation of cycles, as determined by measuring blood progesterone concentrations, was recorded. The latent period between change to 8L:16D and onset of cycles was shortest after the exposure at AE and longest after exposure at WS (P less than 0.001). The latent period after AE was shorter (P less than 0.001) than after VE. The correlations were small between ambient temperature and interval to onset of cycles. The latent period to cessation of cycles in response to 16L:8D was shorter after SS exposure than after WS exposure (P less than 0.01), but other differences were not significant. There was a strong (r = -0.94, P less than 0.05) negative correlation between interval to cessation of cycles and ambient temperature. Cessation of cycles in response to 16L:8D occurred more rapidly (P less than 0.001) than onset in response to 8L:16D. These results show that responsiveness to the inductive effects of photoperiod varies significantly with time of the sidereal year.

Animals↗
PubMed1996

Angiogenesis in the ovary.

In adult tissues, capillary growth (angiogenesis) occurs normally during tissue repair, such as in the healing of wounds and fractures. Inappropriate capillary growth is associated with various pathological conditions, including tumour growth, retinopathies, haemangiomas, fibroses and rheumatoid arthritis in the case of rampant capillary growth, and nonhealing wounds and fractures in the case of inadequate capillary growth. The female reproductive organs exhibit marked, periodic growth and regression, accompanied by equally striking changes in their rates of blood flow. It is not surprising, therefore, that they are some of the few adult tissues in which angiogenesis occurs as a normal process. Ovarian follicles and corpora lutea have been shown to contain and produce angiogenic factors. These angiogenic factors appear to be heparin-binding and to belong to the fibroblast growth factor (FGF) and vascular endothelial growth factor (VEGF) families of proteins. In addition, factors regulating gap junctional communication may play a critical role in coordinating the interactions between luteal vascular and nonvascular tissues. Further elucidation of the specific physiological roles of these factors in follicular and luteal growth, development and function will ultimately lead to improved methods for regulating fertility in mammals.

Adult↗
PubMed1998

Annual changes in serum calcium and inorganic phosphate levels and correlation with gonadal status of a freshwater murrel, Channa punctatus (Bloch).

Adult Channa punctatus murrels of both sexes (60-80 g) were collected locally from Ramgarh Lake during the second week of every month (10 individuals of each sex/month) throughout the year. Blood samples were collected and analyzed for serum calcium and phosphate levels by the methods of Trinder (1960) and Fiske and Subbarow (1925), respectively. Gonads were fixed to judge the state of maturation of the fish. Males exhibited no change in serum calcium levels throughout the year in correlation with testicular maturation. However, serum phosphate levels exhibited a rise in correlation with the increased gonadosomatic index. Females showed marked seasonal changes in serum calcium and phosphate levels which were associated with ovarian maturation (vitellogenesis).

Animals↗
PubMedDate not supplied

The proacrosin binding protein, sp32, is tyrosine phosphorylated during capacitation of pig sperm.

Mammalian sperm must undergo capacitation, a preparation period in the female reproductive tract or in vitro, in order to fertilize. We have previously described a Mr 32 000 tyrosine phosphorylated protein, "p32," that appears in pig sperm during capacitation. The identity of p32 remains unknown; if and how it is involved during capacitation is not understood. The objective of the present study was to identify p32 by proteomic techniques. Western blotting of proteins separated successively under nonreducing and then reducing conditions showed the appearance of the tyrosine phosphorylated p32 only when sperm were incubated in capacitating conditions. The spot was sequenced by mass spectrometry/mass spectrometry and identified as "sp32," a protein implicated in proacrosin maturation. The same membranes probed with anti-sp32 antibody demonstrated that sp32 is present in both noncapacitating and capacitating conditions and revealed exactly the same spot as p32. Immunoprecipitation with either anti-phosphotyrosine or anti-sp32 antibody corroborated these results. Indirect immunofluorescence with anti-phosphotyrosine antibody or anti-sp32 antibody show similar labeling of capacitated sperm, supporting the hypothesis that p32 is a tyrosine phosphorylated form of sp32. After ionophore treatment to induce the acrosome reaction, anti-sp32 and anti-phosphotyrosine labeling on the acrosome disappeared. These results demonstrate that sp32, a (pro)acrosin binding protein, is the p32, a tyrosine phosphorylated protein related to capacitation. We will now focus on the significance of tyrosine phosphorylation on sp32 function during fertilization-related events.

Acrosin↗