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W. A. Chamley

Summary. The prolactin secretion response to TRF was similar at all stages of pregnancy (Days 40, 66,102 and term).

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W. A. Chamley

Summary. When ovariectomized ewes were treated with LH-RH, all 3 receiving prolactin infusion and 4 out of 5 receiving an infusion of NaCl solution responded.

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D. Matsumoto and W. A. Chamley

Summary. Relaxin was measured by radioimmunoassay in follicular fluid from sows which were of different reproductive states. In non-pregnant animals, follicular fluid relaxin values ranged from 0·23 to 666 ng/ml. For pregnant animals the range was 172·6–32 707 ng/ml and for sows with polycystic ovaries this range was 5·0–2800 ng/ml. For polycystic ovaries only there was a correlation (r = 0·74) between the diameter of the follicle and relaxin concentration in the respective fluid. Gel filtration of follicular fluid from a pregnant sow or one with polycystic ovaries revealed 3 species of relaxin, of molecular weights 27 500, 19 000 and 6000. Relaxin was extracted from 1 kg of ovaries collected from prepubertal pigs and gel filtration studies indicated the presence of large molecular weight species in addition to a molecule of approximately 6000. These experiments suggest that the corpus luteum is not the sole source of relaxin in the pig.

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Gillian D. Bryant and W. A. Chamley

Relaxin is clasically a hormone of pregnancy and is considered to be responsible for the relaxation of the interpubic ligament during pregnancy in small mammals (Hall, 1960). In pigs, the relaxin bioactivity in corpora lutea and blood from pregnant and post-partum animals has been measured (Anderson, Ford, Melampy & Cox, 1973), and a radioimmunoassay for porcine relaxin has been used for measurement of relaxin during pregnancy and parturition (Sherwood, Chang, Bevier & Dziuk, 1975): relaxin levels rose from 3 days before parturition and reached a peak 14 hr before birth. However, the ovaries are required throughout gestation in this species (Belt, Anderson, Cavazos & Melampy, 1971). The pregnant sheep, like women, is not dependent upon a functional corpus luteum for the whole of gestation, but no measurements of relaxin (either bioactivity or immunoactivity) have yet been reported in these species.

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Gillian D. Bryant and W. A. Chamley

Department of Anatomy & Reproductive Biology, School of Medicine, University of Hawaii, Honolulu, Hawaii 96822, U.S.A., and Reproductive Research Section, University of Melbourne, S.S. Cameron Laboratory, Werribee 3030, Australia

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W. A. CHAMLEY, J. K. FINDLAY, HELEN JONAS, I. A. CUMMING and J. R. GODING

Summary.

Synthetic gonadotrophin-releasing hormone (Gn-RH) was infused at 1·5 μg/hr for 5 hr into ewes at 6, 13 and 18 weeks of gestation, around the time of parturition and at 3 and 6 weeks post partum. Changes in the concentration of FSH in plasma were measured by radioimmunoassay. Pituitary response to Gn-RH decreased during gestation with no detectable release of ovine FSH by 18 weeks. There was a marginal response in two of three ewes treated around parturition. No response was observed in two ewes treated at 3 weeks but a slight response was observed in one of the two ewes treated at 6 weeks post partum. These findings suggest that the ovine pituitary is progressively depleted of FSH or becomes refractory to Gn-RH during pregnancy.

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Salei'a Afele, Gillian D. Bryant-Greenwood, W. A. Chamley and Elizabeth M. Dax

Summary. One sow bled at 30–60-min intervals for 48 h at 5 and 4 days before parturition had mean ± s.e.m. relaxin levels of 5·0 ± 0·48 ng/ml and 5·5 ± 0·44 ng/ml for each 24-h period respectively. This sow and another were bled at frequent intervals during parturition; both showed considerable fluctuations in their relaxin levels but no consistent peaks in relation to each birth. Mean levels during parturition were 10·7 ± 0·46 ng/ml and 13·4 ± 0·81 ng/ml respectively, both significantly higher than the levels at 4 and 5 days before birth.

Relaxin levels in two lactating sows rose acutely during nursing, showing a 3-fold rise in one animal and an 8-fold rise in the other. Results from a third sow during an extended period of nuzzling and sucking by the piglets showed multiple peaks of relaxin immunoactivity associated with each nuzzling/sucking stimulus.

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A Bhalla, P R Stone, H S Liddell, A Zanderigo and L W Chamley

Recurrent miscarriage affects 1% of all couples attempting pregnancy. Immunological factors are postulated to play a role in the aetiology of recurrent miscarriage because the fetus and placenta are immunologically different from the mother. In particular, altered expression of the, non-classical, class I histocompatibility leukocyte antigen (HLA) molecules has been postulated to play a role in the aetiology of recurrent miscarriage as the fetus and placenta are semi-allogenic to the mother. This study was conducted to examine whether altered expression of the non-classical class I HLA molecules, HLA-G and HLA-E, by cells at the maternofetal interface could play a role in the aetiology of recurrent miscarriage. First-trimester placental and decidual biopsies were obtained from 45 women with recurrent miscarriage and 17 gestation-matched normal controls. These biopsies were screened by immunohistochemistry for HLA-G and HLA-E and isotype-matched control antibodies. Staining was analysed by light microscopy and digital image analysis. In both recurrent miscarriage and normal pregnancy, HLA-G was localised to the extravillous trophoblast. There was no difference in the pattern of HLA-G expression between women with recurrent miscarriage and those with normal pregnancies. HLA-E was localised to the syncytiotrophoblast, villous mesenchymal cells, extravillous trophoblast and several decidual cell types, but staining for HLA-E appeared to be confined primarily to the cytoplasm. There was no difference in the pattern of HLA-E expression between women with recurrent miscarriage and those with normal pregnancies.

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L. P. Cahill, M. A. Driancourt, W. A. Chamley and J. K. Findlay

Summary. Manipulation of circulating concentrations of hormones and ovarian follicle status was carried out on Day 11–12 of the oestrous cycle in sheep. All follicles visible on the ovary were ablated by cautery and ewes were treated with oestradiol or ovine follicular fluid (oFF) to suppress FSH or with PMSG to increase circulating gonadotrophic activity. One group underwent unilateral ovariectomy which greatly increased endogenous FSH and was the only treatment which significantly affected LH pulse frequency. The size distribution of antral follicles, the extent of atresia and the mitotic index of granulosa cells of follicles on Day 15 showed that (a) treatment with oFF inhibited the growth of follicles beyond 2 mm diameter by suppressing the mitotic index of the granulosa cells and (b) the concentration of FSH in peripheral plasma was related to the ability of small antral follicles to grow during the late luteal—early follicular phase of the cycle.

Subsequently, it was demonstrated that oFF inhibits, in a dose-dependent manner, folliculogenesis sustained by PMSG in ewes on Days 12–15. Inhibition of folliculogenesis was represented by a decrease in those follicles > 4 mm, an increase in the relative proportion of follicles < 2 mm, and minimal change in the average number of follicles visible on the ovarian surface, and a decrease in the mitotic index of granulosa cells of follicles < 2 mm. There was no change in the extent of atresia. This supports the concept of a mitotic inhibitor present in charcoal-treated oFF, which can act at the ovarian level to prevent follicles passing beyond 2 mm diameter, even in the presence of excess exogenous gonadotrophin. Such a factor could be involved in selection of the follicle(s) destined to ovulate.

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I. J. Clarke, P. J. Wright, W. A. Chamley and K. Burman

Summary. More (P < 0·05) post-partum acyclic ewes (8/9) showed evidence of pulsatile LH release than did seasonally anoestrous ewes (2/8). Mean plasma prolactin concentrations were higher (P < 0·05) in the post-partum ewes than in the seasonally anoestrous ewes. Hypothalamic and pituitary cytosol oestrogen receptor number, median eminence GnRH content and pituitary LH, FSH and prolactin contents were similar in the two groups of ewes. The number of nuclear-bound oestrogen receptors was greater (P < 0·01) in pituitaries from seasonally anoestrous ewes than in pituitaries from post-partum ewes.

These data suggest that the basis of acyclicity in seasonally anoestrous ewes and in post-partum ewes is probably due to their inability to generate LH pulse frequencies similar to that in the follicular phase of the oestrous cycle. The higher LH pulse frequency in post-partum ewes, compared to that in seasonally anoestrous ewes, suggests that pregnancy may partly negate the reduction in LH secretion that is associated with photoperiod-induced acyclicity. The lower number of nuclear-bound oestrogen receptors in post-partum ewes suggests that there may be lower plasma oestrogen levels and less ovarian follicular growth than in non-suckling anoestrous ewes.