New technologies for the study of carnivore reproduction

Routine analysis of urinary metabolites of estrogen and progesterone provided substantial information about the estrous cycle of bears. However, these data alone were not adequate to determine the precise timing of ovulation needed to maximize AI success rates, or to distinguish between pregnancy and pseudopregnancy. Therefore, there is a critical need to develop technologies that will enhance understanding of the reproductive mechanisms of ursids. Using the domestic dog as a model, three techniques were investigated for potential application to the propagation of captive endangered bears. In a modification of standard staining of bitch vaginal cells, trichrome staining of giant panda cells revealed two consistent chromic shifts 9 and 2 days prior to the periovulatory decrease in urinary estrone sulfate, enhancing the ability to predict ovarian events preceding ovulation. To further define the relationship between the decrease in estrogen and ovulation, the utility of a rapid immunochromatographic LH assay was investigated for giant pandas using a commercial LH kit canine serum. Serum collected during estrus exhibited positive test results, indicating the cross-reactivity of giant panda LH with canine LH antibodies, and preliminary data supported further development of the LH kit for the detection of LH in bear urine. Due to the limitations of hormone analysis for distinguishing pregnancy from pseudopregnancy in canids and ursids, forward-looking infrared thermography was evaluated as a method to visualize proliferating placental tissue, fetuses, or both. While further investigation is needed to confirm the utility of thermal imaging for pregnancy diagnosis in the domestic bitch, pregnancy and pseudopregnancy were successfully detected in two giant pandas.     

Parturition prediction and timing of canine pregnancy

An accurate method of predicting the date of parturition in the bitch is clinically useful to minimize or prevent reproductive losses by timely intervention. Similarly, an accurate method of timing canine ovulation and gestation is critical for development of assisted reproductive technologies, e.g. estrous synchronization and embryo transfer. This review discusses present methods for accurately timing canine gestational age and outlines their use in clinical management of high-risk pregnancies and embryo transfer research.     

Accuracy of canine parturition date prediction using fetal measurements obtained by ultrasonography

The length of canine gestation is 65 days from the luteinizing hormone (LH) surge. Early and accurate determination of canine gestational age is useful for predicting and managing parturition. We performed a retrospective study on fetal measurements obtained by transabdominal ultrasonographic examination of 83 bitches (32 breeds) to estimate gestational age. Gestational age was estimated using two published tables correlating either (1). embryonic vesicle diameter (EVD), crown-rump length (CRL), body diameter (BD), and biparietal diameter (HD) to the LH surge in mid-gestational beagles or (2). BD and HD to parturition in late-gestation retrievers. Parturition date was predicted by obtaining the difference between the gestational age estimate and 65 days. Bitches were divided into four body weight (BW) groups based on nonpregnant body weight: small (9-20 kg), large (>20-40 kg), and giant (>40 kg). Mean+/-S.D. litter size (LS) was calculated for each BW group. The BW groups were then divided into small, average, or large LS groups. The accuracy of the prediction was not affected by LS but was affected by maternal body weight for small and giant BW groups only. When adjusted for weight, the accuracy of prediction within +/-1 day and +/-2 day intervals was 75 and 87%, respectively. Using stepwise logisitic regression, the most accurate prediction of parturition date was obtained when fetuses were measured at 30 days after the LH surge, regardless of body weight or LS. Parturition date predictions made after 39 days of gestation using only biparietal and BD fetal measurements were <50% accurate within +/-2 days.     

Ultrasonographic characteristics of early pregnancy failure in bitches

Resorption of conceptuses was identified in 6 of 20 bitches examined daily from 15 to 35 d after the estimated pre-ovulatory LH surge. One or more conceptuses were resorbed in each bitch but there was continuation of the remaining pregnancy to term. This paper details the ultrasonographic embryological features of normal and resorbing conceptuses. Impending resorption may be predicted by detecting a delay in the time of development of a specific embryological feature or measuring a slow growth rate. Interestingly, there were greater number of conceptuses initially identified in bitches that subsequently resorbed than in those which did not.     

Association between the preovulatory luteinizing hormone surge and the early ultrasonographic detection of pregnancy and fetal heartbeats in beagle dogs

The size of the gestational sac and embryonic mass as well as the embryonic heartbeat were examined ultrasonographically from Day 16 to 25 of pregnancy in 15 beagle bitches, using a 7.5 MHz transducer. Results were more consistent when gestational age was based on the day of the preovulatory luteinizing hormone (LH) surge than on the day of first breeding. The gestational sac was first detected at 17 to 20 d after the LH surge, when it was 1 to 2 mm in diameter and 1 to 4 mm in length. The diameter and length of the gestational sac increased exponentially. At Day 25, the mean diameter was 8.2 +/- 0.3 mm (7 to 9 mm) and mean length was 20.3 +/- 1.1 mm (14 to 24 mm). Embryonic mass and heartbeat were first detected at 23 to 25 d after the LH surge. The embryonic heartbeat was detected on the day of or the day after detection of the embryonic mass, at which time the embryonic mass was 1 to 4 mm in length and was located at the periphery of the gestational sac.     

Impact of maternal undernutrition during the periconceptional period, fetal number, and fetal sex on the development of the hypothalamo-pituitary adrenal axis in sheep during late gestation

Evidence from epidemiologic, clinical, and experimental studies has shown that a suboptimal intrauterine environment during early pregnancy can alter fetal growth and gestation length and is associated with an increased prevalence of adult hypertension and cardiovascular disease. It has been postulated that maternal nutrient restriction may act to reprogram the development of the pituitary-adrenal axis, resulting in excess glucocorticoid exposure and adverse health outcomes in later life. It is unknown, however, whether maternal nutrient restriction during the periconceptional period alters the development of the fetal pituitary-adrenal axis or whether the effects of periconceptional undernutrition can be reversed by the provision of an adequate level of maternal nutrition throughout the remainder of pregnancy. We have investigated the effect of restricted periconceptional nutrition (70% of control feed allowance) from 60 days before until 7 days after mating and the effect of restricted gestational nutrition from Day 8 to 147 of gestation on the development of the fetal hypothalamo-pituitary adrenal (HPA) axis in the sheep. In these studies, we have also investigated the effects of fetal number and sex on the pituitary-adrenal responses to periconceptional and gestational undernutrition. In ewes maintained on a control diet throughout the periconceptional and gestational periods, fetal plasma ACTH concentrations were higher and the prepartum surge in cortisol occurred earlier in singletons compared with twins. Plasma ACTH concentrations were also significantly higher in male compared with female singletons, and in twin fetuses, the prepartum surge in cortisol concentrations occurred earlier in males than in females. Periconceptional undernutrition resulted in higher fetal plasma concentrations of ACTH between 110 and 145 days of gestation and a significantly greater cortisol response to a bolus dose of corticotropin-releasing hormone in twin, but not singleton, fetuses in late gestation. We have therefore demonstrated that fetal number and sex each has an impact on the timing of the prepartum activation of the HPA axis in the sheep. Restriction of the level of maternal nutrition before and in the first week of a twin pregnancy results in stimulation of the fetal pituitary-adrenal axis in late gestation, and this effect is not reversed by the provision of a maintenance control diet from the second week of pregnancy.     

Evidence against a role of prolactin in the timing of ovulation in the turkey

Two separate experiments in which blood was sampled at 2-h intervals from turkeys hens failed to show a significant change in plasma prolactin (Prl) concentrations in relation to the preovulatory surge of luteinizing hormone (LH) for the first (C1) ovulation of a sequence. Intravenous injection of 125 IU of ovine Prl (NIH-P-S10) or of 1 or 2 ml of antiserum to turkey Prl at varying intervals before C1 ovulation had no effect on the timing or incidence of C1 ovulation. However, injection of Prl before C1 ovulation tended to inhibit ovulation of the second (C2) egg of the sequence, while injection of antiserum to Prl before C1 ovulation tended to either advance or inhibit C2 ovulation. Possibly, the effects of Prl and Prl antiserum on C2 ovulation reflect interference with maturation of the C2 ovarian follicle rather than interference with neuroendocrine processes that regulate the timing of the preovulatory surge of LH. The data for C1 ovulation argue against a change in circulating levels of Prl as a factor in the timing of the preovulatory surge of LH.     

Temporal relations between plasma concentrations of luteinizing hormone, follicle-stimulating hormone, estradiol-17beta, progesterone, prolactin, and alpha-melanocyte-stimulating hormone during the follicular, ovulatory, and early luteal phase in the bitch

Compared with other domestic animals, relatively little is known about the changes in, and temporal relations between, reproductive hormones around the time of ovulation in the domestic bitch. Therefore, plasma concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), estradiol-17beta, progesterone, prolactin (PRL), and alpha-melanocyte-stimulating hormone (alpha-MSH) were determined one to six times daily from the start of the follicular phase until 5 days after the estimated day of ovulation in six Beagle bitches. In all bitches, the pre-ovulatory LH surge was accompanied by a pre-ovulatory FSH surge. A pre-ovulatory PRL or alpha-MSH surge was not observed. The pre-ovulatory FSH and LH surges started concomitantly in four bitches, but in two bitches the FSH surge started 12 h earlier than the LH surge. The FSH surge (110+/-8 h) lasted significantly longer than the LH surge (36+/-5 h). In contrast with the pre-ovulatory FSH surge, the pre-ovulatory LH surge was bifurcated in four of six bitches. The mean plasma LH concentrations before (1.9+/-0.4 microg/L) and after (1.9+/-0.3 microg/L) the LH surge were similar, but the mean plasma FSH concentration before the FSH surge (1.6+/-0.3 U/L) was significantly lower than that after the FSH surge (3.1+/-0.2 U/L). In most bitches the highest plasma estradiol-17beta concentration coincided with or followed the start of the pre-ovulatory LH surge. In five of the six bitches the plasma progesterone concentration started to rise just before or concurrently with the start of the LH surge. In conclusion, the results of this study provide evidence for the differential regulation of the secretion of LH and FSH in the bitch. In addition, the interrelationship of the plasma profiles of estradiol-17beta and LH suggests a positive feedback effect of estradiol-17beta on LH surge release. The start of the pre-ovulatory LH surge is associated with an increase in the plasma progesterone concentration in this species.     

Synchronization of estrus and ovulation and associated endocrine changes in Bos indicus cows

The effects of 4 estrus synchronization treatments on intervals to and synchrony of estrus and ovulation, on timing of the preovulatory LH surge and associated changes in plasma progesterone, LH, FSH, and 17beta-estradiol (E(2)) were investigated in 48 Bos indicus cows. Treatment 1 consisted of 2 injections of PGF(2alpha) 14 d apart (n = 12); Treatment 2 of a subcutaneous 3-mg norgestomet implant and an intramuscular injection of 3 mg of norgestomet and 5 mg estradiol valerate, with the implant removed 10 d later (n = 12; norgestomet-estradiol); Treatment 3 of norgestomet-estradiol, with a subcutaneous injection of PMSG given at time of implant removal (Day 10; n = 12); and Treatment 4 of norgestomet implant (as for Treatments 2 and 3) inserted for 10 d, with an intramuscular injection of PGF(2alpha) given at the time of implant removal (n = 12). The experiment was conducted in 2 replicates (24 cows/replicate, 6 cows/group). Estrus, ovulation and timing of the preovulatory surge of LH varied less in cows treated with norgestomet-estradiol and PMSG than in cows in Treatments 1 and 4 (P < 0.008). Treatment with PMSG reduced variation in ovulation times and timing of the LH surge in cows treated with norgestomet-estradiol (P < 0.02). Concentrations of E(2) were higher in cows in Treatments 2 and 3 on the final day of treatment and at about 6 h post ovulation compared with cows in Treatments 1 and 4 (P < 0.05). Different methods for synchronizing estrus did not alter sequential endocrine and behavioral changes in relation to the timing of the LH peak, and the results were consistent with current recommendations for insemination times in Bos taurus cattle.     

Ontogeny of the insulin response to glucose in fetal and adult sheep

The purpose of the present experiments was to examine in sheep whether the fetal insulin response to glucose was present by day 110 (d110) of pregnancy and whether the magnitude of the fetal insulin response changed between d110 and d145 (term). We also compared the responses observed in fetuses to those of adult nonpregnant sheep. Basal concentrations of glucose measured in plasma collected from the fetal femoral artery rose progressively between d110 and d145 of gestation, but did not attain the plasma glucose concentrations measured in adult sheep. Peak glucose concentrations in fetuses were achieved 10 min following the bolus injection of glucose (0.8 g/kg estimated fetal body weight) into the fetal femoral vein, and peak values increased with gestational age. Significantly higher peak glucose concentrations were achieved in adult sheep. The concentration of insulin rose rapidly in fetuses at d110, and a similar time course of insulin release in plasma was seen at all gestational ages. The peak plasma insulin concentrations were achieved at 20 min and were significantly greater in older (d140-145) than younger (d125-130) fetuses (p less than 0.05). Peak insulin values in fetuses were much less than in adult sheep. In adult sheep glucose and insulin concentrations remained elevated at 120 min following the injection of glucose, whereas in the fetus the concentration of insulin had returned to preinjection values by 60 min. The insulin/glucose ratio did not change in fetal lambs over the last one third of gestation and was not different from the adult sheep.(ABSTRACT TRUNCATED AT 250 WORDS)     

Prospective study of human parvovirus (B19) infection in pregnancy. Public Health Laboratory Service Working Party on Fifth Disease.

OBJECTIVE--To determine the fetal infection rate and outcome of pregnancy among women who acquire infection with human parvovirus (B19) in the antenatal period. DESIGN--Prospective study of infected pregnancies till time of delivery or abortion with virological investigation of fetuses, neonates, and 1 year old infants. SETTING--England and Wales during 1985-8. PATIENTS--190 Pregnant women with serologically confirmed B19 infection in pregnancy, their fetuses, neonates, and 1 year old infants. RESULTS--Of 186 mothers who elected to go to term, 156 (84%) delivered a normal baby. Follow up of 114 of these infants to the age of 1 year disclosed no appreciable abnormalities, although 27 had serological evidence of intrauterine infection. The overall fetal loss rate (30 cases; 16%) was similar to that in an uninfected antenatal sample (unmatched), but there was a pronounced excess of fetal loss in the second trimester in the B19 infected mothers (11.8%; 95% confidence interval 6.8% to 17.8%). Based on virological findings in the aborted fetuses the risk of fetal death due to B19 in an infected pregnancy was estimated to be 9%. The transplacental transmission rate was estimated to be 33%. CONCLUSIONS--Most women with B19 infection in pregnancy had a satisfactory outcome, but there was nevertheless a substantial risk of fetal loss in the second trimester. In view of the absence to date of any evidence of damage to babies who survive maternal infection therapeutic termination of pregnancy is not indicated.     

Fertile estrus induced in bitches by bromocryptine, a dopamine agonist: a clinical trial

The dopamine agonist bromocryptine, probably through amplifying gonadotroph (mainly FSH) secretion, was found to be suitable for provoking fertile estrus during the anestrous phase in bitches without functional cycles and/or ovarian activity. We studied estrus induction in 48 bitches after treatment with semisynthetic ergot alkaloid bromocryptine. For habituation a fractional dose of 0.3 mg/bitch was administered for three days followed by larger doses within the range of 0.6 to 2.5 mg/bitch by selecting dose rates on the basis of individual responsiveness and body weight. The long-term daily bromocryptine dose did not exceed 0.6 mg/bitch and 2.5 mg/bitch in small and large sized bitches, respectively. Gradual habituation and individual dose rates have almost completely eliminated the unwanted side effect of emesis. The period between treatment and onset of estrus varied but the average was 19 days. After the onset of estrus bromocryptine administration was usually continued for another 3 to 6 days. Occurrences of estrus, ovulation and pregnancy were monitored by cytological evaluation of vaginal epithelium, rapid ELISA for plasma progesterone and ultrasonography, respectively. Samples for progesterone were taken on Days 7, 9, 12 and 15 and sonograms of ovarian follicles and of fetuses were taken on Days 0, 22 and 35. The bitches involved in the study either regular or irregular cycles. Bromocryptine treatment induced estrus in all of the bitches including 40 of 48 (83%) with ovulation within a regular estrus and 6 of 48 (12.5%) that showed estrus but did not ovulate. Mating or artificial insemination of bitches in their fertile periods twice at two day intervals resulted in an 83% pregnancy rate (40 cases) and 39 (97.5%) of them gave birth to puppies. However, the average litter size was small with 4.8 +/- 1.6 pups.     

Ultrastructure of canine oocytes during in vivo maturation

The aim of the present study was to describe the canine oocyte ultrastructural modifications during in vivo maturation, with precise reference to the timing of the LH surge and of ovulation. Twenty-five bitches were ovariectomized at specific stages between the onset of proestrus and the fifth day post-ovulation: 65 oocytes were observed by transmission electron microscopy (TEM), either before the LH surge (n = 10), between the LH surge and ovulation (n = 12) or after ovulation (n = 43). Prior to the LH surge, the oocyte nucleus had already begun its displacement to the vicinity of the oolemma and reticulated nucleoli were infrequent. The cytoplasm showed signs of immaturity (few organelles preferentially located in the cortical zone, "mitochondrial cloud", scarce cortical granules). The LH surge was immediately followed by cumulus expansion but the ovulation occurred 2 days later. Retraction of the transzonal projections and the meiotic resumption occurred after another 3 days (5 days after the LH peak). The ovulation was then followed by gradual cytoplasmic modifications. Nucleoli re-assumed a reticulated aspect around 24 hr post-ovulation. From 48 hr post-ovulation mitochondria and SER were very numerous and evenly distributed. In conclusion canine oocyte maturation began prior to the LH surge and no cytoplasmic or nuclear modifications followed immediately the LH surge and ovulation. This study suggests that two distinct signals are needed for the final in vivo maturation: one prior to the LH surge (to induce maturation) and another one, around 3 days post-ovulation (to induce meiotic resumption).     

The effect of decrease in body temperature with Nembutal on meiosis and ovulation after induction by gonadotrophin-releasing hormone and luteinizing hormone in adult rats.

Sodium pentobarbital (Nembutal) is often used to block the pro-oestrous luteinizing hormone (LH) surge in rats. Nembutal is also known to lower body temperature. This study was designed to investigate whether Nembutal affected the time course of meiosis and timing of ovulation induced by exogenous hormones, and whether the possible effects of Nembutal on these processes were related to temperature. Gonadotrophin-releasing hormone (GnRH), the GnRH-analogue Ovalyse, or rat luteinizing hormone (LH) were administered to trigger resumption of meiosis and ovulation; Nembutal (35 mg kg-1 body weight) or saline was given 10 or 60 min later. Plasma profiles of LH were measured and Graafian follicles were studied histologically for meiotic progress and ovulation. Nembutal suppressed the spontaneous surge of LH at pro-oestrus and caused a long-lasting decrease in body temperature. If 1000 ng GnRH was given 2 h before the pro-oestrous LH surge, most of the oocytes had extruded a polar body 10 h later and most follicles had ovulated 14 h later. Nembutal given 1 h after GnRH delayed extrusion of the polar body and ovulation by about 2 h. Nembutal caused a similar delay in ovulation when it was administered after 100 ng of Ovalyse, and it also delayed meiosis when given after 1000 ng of LH. This effect of Nembutal was prevented if body temperature was maintained at 37 degrees C. The delaying effect of Nembutal on meiosis and ovulation induced by exogenous GnRH or LH is related to a long-lasting decrease in body temperature.     

Influence of GnRH administration on timing of the LH surge and ovulation in dwarf goats

This study was conducted to determine whether or not exogenous gonadotropin releasing hormone (GnRH) alters the timing or improves the synchrony of estrus, the LH surge, and ovulation following estrous synchronization in dwarf goats, and to assess the effects of season on these parameters. In January and June, estrus was synchronized in 12 Pygmy and Nigerian Dwarf goats with a 10-day progestagen sponge, 125 microg cloprostenol i.m. 48 h before sponge removal, and 300 IU equine chorionic gonadotrophin (eCG) i.m. at sponge removal. Six of the 12 goats were given 50 microg GnRH i.m. 24h after sponge removal. Onset of estrus was monitored using two males. Samples for plasma LH were collected at 2 h intervals beginning 22 h after sponge removal and ending at 48 h in January and at 58 h in June. Time of ovulation time was confirmed by laparoscopy at 36, 50, 60, and 74 h in January and at 50, 60, and 74 h in June. Administration of GnRH had no significant effect on the onset of estrus; however, it reduced the interval from sponge removal to the LH surge and improved the synchrony of the LH surge (P<0.05). Treatment with GnRH also reduced the interval from sponge removal to ovulation and improved the synchrony of ovulation (P<0.05). Season had a significant effect on the timing and the synchrony of estrus with and without GnRH treatment (P<0.05). A seasonal shift was also observed in the timing of the LH surge in the absence of GnRH treatment (P<0.05). Further research is required to determine the optimum time for GnRH administration and the minimum effective dose in dwarf goats.     

Induction of precocious puberty in ewe lambs by pulsatile administration of GnRH

Circhoral administration (250 ng/h, i.v.) of GnRH induced a preovulatory-like surge of LH and subsequent luteal function in 4 of 4 ewe lambs 1 month before expected date of puberty. Within 12h of the start of pulsatile delivery of GnRH, mean concentrations of immunoactive and bioactive LH increased significantly (P less than 0.05) and the LH surge occurred by 1.8 +/- 0.6 days of treatment. Mean concentrations of serum progesterone were elevated significantly (P less than 0.001) 3 days after the surge. The biopotency of LH (bioactive LH/immunoactive LH) before the GnRH-induced surge of LH did not differ from LH biopotency in ewe lambs receiving circhoral delivery of saline (0.41 +/- 0.05 and 0.46 +/- 0.04, respectively). Biopotency of LH declined markedly at the GnRH-induced LH surge (0.25 +/- 0.04), but biopotency of serum LH was significantly augmented (P less than 0.05) during the period of luteal activity (0.70 +/- 0.07). Regular oestrous cycles were observed in 3 of 4 ewe lambs after the 10-day GnRH treatment period. These results indicate that pulsatile delivery of GnRH is effective in inducing precocious puberty in ewe lambs. Increase in LH biopotency does not appear to be required in the pubertal transition to reproductive cyclicity in this species. Augmented LH biopotency may be important in support of luteal function after first ovulation.     

Inhibitory effects of a luteinizing-hormone-releasing hormone agonist implant on ovine fetal gonadotrophin secretion and pituitary sensitivity to luteinizing-hormone-releasing hormone.

Sheep fetuses at day 70 of gestation (term = 145 days) were implanted subcutaneously with a biodegradable implant containing a luteinizing-hormone-releasing hormone (LHRH) agonist (buserelin) to investigate whether treatment with LHRH agonist would induce a state of desensitization of the fetal gonadotrophs and thus influence fetal gonadal development. Treatment with the LHRH agonist for 35-40 days caused a significant reduction in mean fetal plasma concentrations of LH and follicle-stimulating hormone (FSH) compared with control fetuses. LH pulses were evident in control fetuses but were completely abolished by buserelin treatment. Furthermore, the pituitary content of LH and FSH was significantly depleted in fetuses implanted with LHRH agonist. A bolus intravenous injection of 500 ng LHRH given to control fetuses caused a rapid and significant increase in plasma LH and FSH concentrations which was sustained for at least 60 min after injection. Pretreatment with buserelin completely abolished the LH and FSH responses to a bolus injection of LHRH. There were no differences between the sexes in fetal gonadotrophin concentrations or pituitary sensitivity to LHRH in control or agonist-treated fetuses. Furthermore, buserelin treatment for 35-40 days had no effect on the morphological appearance of the fetal gonads when compared with control fetuses, at least to day 110 of pregnancy. These results provide evidence for the induction of a state of desensitization of the LHRH receptors of the fetal pituitary gonadotrophs following long-term treatment with an LHRH agonist, but provide no evidence for a role for gonadotrophin secretion in gonadal development at this stage in fetal life.     

Quantification and classification of pregnancy wastage in 5-day cyclic young through middle-aged rats

Fecundity was quantified in 4 to 11-month old rats with regular 5-day cycles. On the day following mating, less than 5% luteinized unruptured follicles occurred in either 4-month old or 11-month old rats; ovulation rate and also fertilization rate were similar in these young and middle-aged rats. At day 19 of pregnancy embryonic and fetal mortalities were quantified. Pregnancy wastage increased gradually with age; it was already significant in 7-month old rats. In rats of 9 months old it was about 30% and in 11-month old rats it was greater than 65%. Pregnancy wastage was mainly due to preimplantation and early-postimplantation mortality. Pregnancy wastage did not decrease when the pre-ovulatory surge of luteinizing hormone (LH) was reinforced and timed, by injection of the LH-releasing hormone analogue Ovalyse at noon on the day of prooestrus. The results corroborate the idea that pregnancy wastage in middle-aged rats with regular cycles is caused by an age-related reduction of the viability of ovulating eggs.     

The timing of male reproductive effort relative to female ovulation in a capital breeder

1. In large herbivores, the timing of breeding is important for females to hit peak plant protein levels. For males, the timing of reproductive effort is important to maximize the number of females they can mate during autumn rut in competition with other males. The latter depends on when most females are ovulating, but also on how other males with a different competitive ability are timing use of their capital (fat); it may pay younger males to invest more heavily later when prime aged males are exhausted. 2. Based on estimates of body mass loss, we quantify how much timing (start, peak and end dates) of male reproductive effort during rutting varies depending on male age, density and climate as well as timing of female ovulation. 3. Ovulation in adult females was delayed by 5 days from low to high density, and ovulation was also more synchronous at high density. The starting date of decline in male body mass was only later in yearlings than among other age groups. However, at low density, peak and end dates of rut became increasingly earlier and close to peak female ovulation with increasing age up to 7 years of age. Prime-aged males matched peak effort closely with peak rate of prime-aged female ovulation, while younger males were delayed. This is consistent with the view that younger males have a better chance when the prime-aged males are becoming exhausted. 4. Apart from yearlings, male age groups were synchronized in both the starting, peak and end dates of mass decline at high density. Thus, this partly follows change in female ovulation patterns, but also suggests that competition among males decreased with increasing density due probably to lower intensity of sexual selection. The lowered sexual selection may be due not only to more synchronous female ovulation, but also increasingly female-biased sex ratios and a younger male age structure with increasing density. 5. The onset of rutting is somewhat independent of male age (apart from the youngest males), but the peak and end of rutting effort is dependent strongly upon age, density and peak female ovulation. Male rutting phenology is thus best interpreted as a compromise between hitting peak female ovulation and intensity of sexual selection.     

Corticotropin releasing hormone concentrations in umbilical cord blood of preterm fetuses.

Corticotrophin releasing hormone (CRH), dehydroepiandrosterone sulfate (DHEAS) and cortisol were measured in umbilical cord plasma obtained from 90 preterm and 98 term fetuses. Maternal plasma was obtained from 23 women who delivered preterm and from 23 women matched for gestational age who ultimately delivered term infants. Mean umbilical cord plasma CRH concentration was significantly higher in the preterm fetuses (n = 69, 538 +/- 63 pg/ml) compared to the term fetuses (n = 98, 280 +/- 22 pg/ml, P < 0.01). Mean DHEAS level in the preterm fetuses was 208 +/- 22 mg/dl (n = 56), cortisol level was 7 +/- 1 mg/dl (n = 58). Umbilical plasma CRH concentrations (808 +/- 170 pg/ml) were significantly higher at 24-27 weeks than at 28-31 or 31-34 weeks gestation. Cortisol levels (12 +/- 3 micrograms/dl) were highest at 24-27 weeks. Mode of delivery and the presence of labor did not affect fetal CRH levels. The highest fetal CRH levels were measured in the pregnancies complicated by hypertension as well as prematurity; however, fetal CRH levels remained higher in the preterm group compared to the term group when hypertensive pregnancies were excluded. Maternal plasma CRH levels were significantly higher in the group that delivered preterm compared to women who delivered at term matched for gestational age (1058 +/- 184 pg/ml compared to 456 +/- 71 pg/ml, P < 0.00).(ABSTRACT TRUNCATED AT 250 WORDS)