Ovulation rate and embryo survival in Damline ewes after treatment with bovine follicular fluid in the luteal phase of the oestrous cycle

Treatment of Damline ewes with twice daily i.v. injections of bovine follicular fluid during the luteal phase for 10, 6 or 2 days before prostaglandin-induced luteolysis resulted in an increase in ovulation rate. This was associated with a large rebound increase in plasma concentrations of FSH after the last injection of bovine follicular fluid. While conception rate was not affected by bovine follicular fluid treatment, a higher percentage embryonic loss was observed between Days 3 and 34 of pregnancy in the 10-day treatment group only compared to controls. This reflected the increase in ovulation rate above the optimum for embryonic survival in this breed. The present results suggest that the increase in ovulation rate induced by bovine follicular fluid treatment in the luteal phase of the cycle before mating would result in a significant increase in the number of lambs born.     

Prolactin in hypertensive pregnancy.

Plasma prolactin levels were measured in 68 pregnant women with hypertension at 32 weeks gestation. They were raised in pregnancies with pre-eclamptic features, most significantly in women with a rising plasma urate level. No correlation was found between the level of the untreated blood pressure and prolactin. Proteinuria did not influence prolactin levels independently of changes in the plasma urate. The differences in prolactin levels could not be ascribed to the drugs administered.     

The Escherichia coli O157:H7 EhaB autotransporter protein binds to laminin and collagen I and induces a serum IgA response in O157:H7 challenged cattle

Enterohaemorrhagic Escherichia coli (EHEC) are a subgroup of Shiga toxin-producing E. coli that cause gastrointestinal disease with the potential for life-threatening sequelae. Cattle serve as the natural reservoir for EHEC and outbreaks occur sporadically as a result of contaminated beef and other farming products. While certain EHEC virulence mechanisms have been extensively studied, the factors that mediate host colonization are poorly defined. Previously, we identified four proteins (EhaA,B,C,D) from the prototypic EHEC strain EDL933 that belong to the autotransporter (AT) family. Here we characterize the EhaB AT protein. EhaB was shown to be located at the cell surface and overexpression in E. coli K-12 resulted in significant biofilm formation under continuous flow conditions. Overexpression of EhaB in E. coli K12 and EDL933 backgrounds also promoted adhesion to the extracellular matrix proteins collagen I and laminin. An EhaB-specific antibody revealed that EhaB is expressed in E. coli EDL933 following in vitro growth. EhaB also cross-reacted with serum IgA from cattle challenged with E. coli O157:H7, indicating that EhaB is expressed in vivo and elicits a host IgA immune response.     

Elevated prolactin levels immediately precede decisions to babysit by male meerkat helpers

Recent studies suggest that decisions to care for the offspring of others in societies of cooperative vertebrates may have a hormonal basis. The crucial question of whether changes in hormone levels immediately precede or merely follow bouts of offspring care, however, remains largely unanswered. Here, we show that in wild groups of cooperatively breeding meerkats, male helpers that decided to babysit for the day had significantly higher levels of prolactin, coupled with lower levels of cortisol, before initiating a babysitting session compared with similarly aged individuals that decided to forage. In addition, these hormonal differences disappeared over the course of the day, suggesting that hormone levels changed in a fundamentally different way in meerkats that babysat versus those that foraged. In contrast, long-term contributions to babysitting were not significantly associated with plasma levels of prolactin, cortisol, or testosterone in individual male helpers. Our results show, for the first time, that elevated levels of prolactin may immediately precede bouts of helping behavior but differ from recent findings on the same study population in which plasma levels of cortisol, but not prolactin, were significantly and positively associated with rates of pup feeding by male helpers. Together, these results lend significant weight to the idea that decisions to help in cooperative vertebrates have a hormonal basis, although different hormones appear to be associated with different types of care.     

Maternally derived anti-helminth antibodies predict offspring survival in a wild mammal

The transfer of antibodies from mother to offspring provides crucial protection against infection to offspring during early life in humans and domestic and laboratory animals. However, few studies have tested the consequences of variation in maternal antibody transfer for offspring fitness in the wild. Further, separating the immunoprotective effects of antibodies from their association with nutritional resources provided by mothers is difficult. Here, we measured plasma levels of total and parasite-specific antibodies in neonatal (less than 10 days old) wild Soay sheep over 25 years to quantify variation in maternal antibody transfer and test its association with offspring survival. Maternal antibody transfer was predicted by maternal age and previous antibody responses, and was consistent within mothers across years. Neonatal total IgG antibody levels were positively related to early growth, suggesting they reflected nutritional transfer. Neonatal parasite-specific IgG levels positively predicted first-year survival, independent of lamb weight, total IgG levels and subsequent lamb parasite-specific antibody levels. This relationship was partly mediated via an indirect negative association with parasite burden. We show that among-female variation in maternal antibody transfer can have long-term effects on offspring growth, parasite burden and fitness in the wild, and is likely to impact naturally occurring host–parasite dynamics.     

Circulating oestrogen concentrations during pregnancy in the African elephant (Loxodonta africana)

Oestrone, oestradiol-17 beta and oestriol were measured in plasma samples from non-pregnant and pregnant African elephants shot in the wild. Enzymic hydrolysis of plasma showed that approximately 90 and 96% of the total (i.e. conjugated plus unconjugated) concentrations of oestrone and oestradiol-17 beta, respectively were represented by conjugated hormones. Unconjugated oestrogens remained low (less than 50 pg ml) in all samples, with no distinction between non-pregnant and pregnant animals. Levels of total oestrone during pregnancy varied between 160 and 594 pg/ml but were not significantly different from non-pregnant values. Total oestradiol-17 beta concentrations were significantly elevated during pregnancy (P less than 0 X 01) and, despite considerable individual variation (193-1428 pg/ml), were consistently higher than non-pregnant values after 6 months of gestation. The elevated levels of oestradiol-17 beta resulted in a reversal of the total oestradiol-17 beta: oestrone concentration ratio at about 6 months of pregnancy. Concentrations of total oestriol did not exceed 103 pg/ml. An indirect method of measurement indicated that oestradiol-17 beta sulphate was probably the most abundant circulating oestrogen during pregnancy in the African elephant.     

Blood concentrations of gonadotrophins, prolactin and gonadal steroids in males and in non-pregnant and pregnant female African elephants (Loxodonta africana)

No seasonal variation in any of the hormones measured was apparent in males or females. Testosterone levels in males increased around puberty (10-11 years) and remained significantly higher in adult than prepubertal males. This was not accompanied by any significant change in levels of LH, FSH or prolactin. In non-pregnant females there was no apparent difference in levels of LH, FSH or prolactin with age. There was a significant increase in progesterone around puberty (12 years) but there was considerable overlap in values between prepubertal and adult females. During pregnancy, progesterone levels were significantly higher than in non-pregnant females with maximum levels occurring at mid-pregnancy (9-12 months). However, there was considerable overlap in values between non-pregnancy and pregnancy. Concentrations of LH and FSH decreased significantly during mid-pregnancy while prolactin levels increased dramatically during pregnancy; after 7 months of gestation until term levels were always at least 8 ng/ml greater than in any non-pregnant female. It is suggested that this consistent increase in plasma/serum levels of prolactin can be used to diagnose pregnancy in the elephant.     

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.     

Alterations in pituitary gland sensitivity in ram lambs to physiological doses of gonadotrophin-releasing hormone (GnRH), after divergent selection based on the luteinizing hormone response to a pharmacological GnRH challenge.

Divergent selection in 10-week-old Finn-Dorset ram lambs was based on the luteinizing hormone (LH) response to a pharmacological dose of GnRH (5 micrograms). After eight generations of selection, the LH responses of the two lines (low and high) to GnRH differed by a factor of five. This study investigates the pituitary sensitivity of the two lines to exogenous GnRH. Initially, two pilot studies were performed: one to determine the range of doses of GnRH which would stimulate LH pulses of similar amplitude to those seen endogenously, and the other to confirm that sodium pentobarbitone prevents pulsatile LH secretion in prepubertal ram lambs. The results indicated that barbiturate anaesthesia suppressed pulsatile LH secretion in castrated and intact ram lambs. A model system was therefore constructed in 18 10-week-old intact ram lambs (high n = 7, low n = 11), whereby endogenous pulsatile LH secretion was prevented by sodium pentobarbitone anaesthesia and the amplitudes of LH pulses produced in response to different doses of exogenous GnRH could be measured. The GnRH dose-response curves demonstrated that there was a five-fold difference in the sensitivity of the pituitary glands of the two lines to stimulation with GnRH. The projected minimum concentration of GnRH required to produce a measurable pulse of LH was 4.75 ng for the high-line animals and 26.6 ng for the low-line animals. The results indicated that the low-line animals required five times more GnRH than the high-line lambs to stimulate LH pulses of similar amplitude (high line 43.67 ng; low line 206.55 ng). These results demonstrate that selection has produced two lines of sheep which differ in the control of LH secretion at the level of the hypothalamus-pituitary gland.     

Isolated Pituitary Gonadotrophin Deficiency: Gonadotrophin Secretion after Synthetic Luteinizing Hormone and Follicle Stimulating Hormone-releasing Hormone

The responses of serum immunoreactive luteinizing hormone (LH) and follicle stimulating hormone (FSH) after intravenous injection of 100 μg of synthetic LH/FSH-RH have been studied in 14 patients with the syndrome of isolated pituitary gonadotrophin deficiency. Nine of the patients showed a rise of both hormones, two a small rise of FSH only, and three were unresponsive. In two of the unresponsive patients injection of a 500-μg dose produced a small rise of LH only. Of the patients who responded, four had LH and FSH responses within the normal adult range, while in the others the responses were smaller and delayed. It is suggested that this syndrome is due to a lack of the hypothalamic-releasing hormone itself, rather than to a pituitary deficiency. However, repeat assessment after prolonged administration of the releasing hormone will be necessary before a pituitary disorder can be excluded in all patients. The synthetic LH/FSH-RH, preferably as a depot preparation, may provide a means of treating these patients to induce the development of puberty and subsequent fertility.