Search Results
You are looking at 1 - 10 of 28 items for
- Author: R J Scaramuzzi x
- Refine by access: All content x
Search for other papers by D. R. LINDSAY in
Google Scholar
PubMed
Search for other papers by R. J. SCARAMUZZI in
Google Scholar
PubMed
SUMMARY
Fourteen synthetic steroids and androstenedione were examined in ovariectomized ewes for oestrogenic activity when administered alone and with oestradiol benzoate by intramuscular injection. None of the compounds investigated was active when administered alone, as assessed by the vaginal smear assay, and only androstenedione produced a behavioural response. Androstenedione had a MED of 8·8 mg. but was less active when administered intravenously. Several steroids acted as anti-oestrogens when injected with oestradiol benzoate. Eight steroids inhibited the behavioural response and four the vaginal response. An additive response was found with androstenedione for behavioural response and with 17β-ethyl-17-hydroxy-19-nor-4-androsten-3-one (SC-5914) for vaginal response.
Vaginal and behavioural responses were not necessarily related, and responses obtained in the ewe to particular steroids were not identical with those obtained in laboratory animals by other workers using similar tests.
Search for other papers by I. J. CLARKE in
Google Scholar
PubMed
Search for other papers by R. J. SCARAMUZZI in
Google Scholar
PubMed
M.R.C. Unit of Reproductive Biology, 2 Forrest Road, Edinburgh, EHI 2QW
(Received 31 October 1977)
Exposure to testosterone during development masculinizes the genitalia and behaviour of ewes (Clarke, Scaramuzzi & Short, 1976a; Clarke, 1977) and causes ovulatory failure (Clarke, Scaramuzzi & Short, 1977). Androgenized ewes do not release luteinizing hormone (LH) after oestrogen treatment during anoestrus (Clarke, Scaramuzzi & Short, 1976b). These experiments were performed to determine the site of action (hypothalamus or anterior pituitary gland) of prenatally administered androgens in blocking the preovulatory release of LH.
Finnish Landrace × Dorset Horn ewes were used in their second breeding season after exposure to testosterone between days 30 and 80 (D30–80, n = 6), 50 and 100 (D50–100, n = 1), 70 and 120 (D70–120, n = 6) or 90 and 140 (D90–140, n = 5) of prenatal life (Clarke et al. 1976a). Eight normal ewes served as controls. To facilitate
Search for other papers by R J Scaramuzzi in
Google Scholar
PubMed
Search for other papers by J A Downing in
Google Scholar
PubMed
Abstract
An experiment was conducted to determine the effects of epidermal growth factor (EGF) and fibroblast growth factor (FGF), infused into the ovarian artery, on the secretion of ovarian steroids during the mid-luteal phase in ewes with an autotransplanted ovary. The infusion of EGF (5 μg/h) for 12 h suppressed the secretion of oestradiol and androstenedione during the infusion and for up to 30 h after the infusion. The secretion of progesterone tended to be lower immediately after the infusion (not significant) but had recovered by 24 h after the end of the infusion and then increased significantly (P<0·05) to rates higher than in control animals. There were no effects of the infusion of EGF on the characteristics of pulsatile LH secretion. FSH concentrations increased 24 h after the end of the infusion probably as an indirect consequence of the changes in oestradiol secretion and not as a consequence of a direct effect of EGF on the hypothalamo-pituitary axis although this latter possibility cannot be unequivocally eliminated. The infusion of FGF (1·5 μg/h) for 12 h also suppressed the secretion of oestradiol and androstenedione during and for up to 30 h after the infusion. The infusion of FGF had no detectable effect on the secretion of progesterone or the characteristics of pulsatile LH secretion. FSH concentrations increased steadily during the infusion but declined rapidly to below pre-infusion concentrations after the end of the infusion. These data provide tentative in vivo evidence for paracrine and autocrine effects of EGF and FGF on follicular and luteal function in sheep.
Journal of Endocrinology (1995) 146, 301–311
Search for other papers by B K Campbell in
Google Scholar
PubMed
Search for other papers by R J Scaramuzzi in
Google Scholar
PubMed
Abstract
Recombinant human inhibin A (rhInh) or steroid-free bovine follicular fluid (bFF) were infused into the ovarian artery of anoestrous ewes with ovarian autotransplants induced to ovulate with a pulsatile regimen of GnRH applied after a 10-day pretreatment with progestagen sponges. In the period 12–24 h after sponge withdrawal ewes received ovarian arterial infusions of saline (n=6), 0·3 μg rhInh/h (n=5), 1·6 μg rhInh/h (n=5) or 25 μl bFF/h (n=4).
Controls had a normal follicular phase with an LH surge 43 ± 3 h after sponge withdrawal which resulted in ovulation (six out of six). Both doses of rhlnh increased ovarian venous inhibin concentrations in a dose-related fashion (P<0·05) but resulted in depressions (P<0·05) in FSH concentrations of similar magnitude. Both doses of rhInh acutely inhibited ovarian oestradiol and androstenedione secretion (P<0·01) but at the end of rhInh infusion oestradiol secretion was quickly re-established without a corresponding increase in FSH. LH surges were detected in five out of five and three out of five ewes infused with low and high doses of rhInh respectively, and progesterone concentrations during the subsequent luteal phase were depressed (P<0·05). Infusion of bFF had no effect on inhibin or FSH concentrations but resulted in acute inhibition (P<0·01) of ovarian oestradiol, androstenedione and inhibin secretion, a delay (P<0·05) in the time to the LH surge and a depression (P<0·05) in luteal-phase progesterone concentrations.
In conclusion, while the depression in FSH induced by rhlnh cannot be excluded as a cause for the inhibitory effects of rhInh treatment on ovarian function, such a mechanism cannot fully explain the ovarian responses obtained to rhInh infusion. These results therefore support a direct ovarian role for inhibin in the modulation of ovarian function in addition to its indirect role in controlling FSH. This conclusion is supported by the demonstration that bFF can induce similar inhibitory effects on ovarian function without changing FSH.
Journal of Endocrinology (1996) 149, 531–540
Search for other papers by N. D. MARTENSZ in
Google Scholar
PubMed
Search for other papers by R. J. SCARAMUZZI in
Google Scholar
PubMed
Levels of plasma LH, FSH and progesterone during the breeding season were measured by radioimmunoassay in control ewes and ewes actively immunized against androstenedione-11α-hemisuccinyl–bovine serum albumin or testosterone-3(O-carboxymethyl)oxime–bovine serum albumin. Immunization against androstenedione resulted in normal oestrous cycles with raised plasma LH and progesterone levels and a reduction in the concentration of FSH during the luteal phase. It is tentatively suggested that androstenedione, or its metabolites, could modify the oestrogenic control of LH secretion and facilitate the release of FSH in the ewe.
Immunization against testosterone prevented oestrus and resulted in markedly increased levels of LH without alteration of the FSH concentration. Since evidence of increased binding of oestradiol-17β was found in the ewes immunized against testosterone, these results cannot be attributed solely to a reduction in the biologically active fraction of testosterone.
Search for other papers by D. T. BAIRD in
Google Scholar
PubMed
Search for other papers by R. J. SCARAMUZZI in
Google Scholar
PubMed
SUMMARY
The secretion rates of oestradiol, androstenedione and progesterone and the peripheral plasma concentration of LH were measured in 12 ewes with ovarian autotransplants before and after luteal regression induced by a single intramuscular injection of a synthetic prostaglandin (PG) analogue, 16-aryloxyprostaglandin F2α (I.C.I. 80996). Luteal regression was followed by a fourfold rise in the basal concentration of LH and increased secretion of oestradiol. In five out of six ewes there was a discharge of LH with the peak occurring 36–78 h after the injection of the PG analogue. The secretion of oestradiol declined from 3·68± 1·08 to 0·33± 0·6 (s.e.m.) ng/min in the 24 h following the LH peak (P < 0·001). In the remaining six ewes in which progesterone was implanted subcutaneously 24 h after the injection of PG analogue, follicular development was suppressed as indicated by the low secretion of oestradiol and androstenedione. The basal concentration of LH fell to values similar to those observed during the luteal phase after the implant of progesterone. The secretion of androstenedione followed a similar pattern to that of oestradiol in those ewes which showed presumptive evidence of ovulation. These results suggest that progesterone reinforces the negative feedback effects of oestrogen in the ewe.
Search for other papers by I. J. CLARKE in
Google Scholar
PubMed
Search for other papers by R. J. SCARAMUZZI in
Google Scholar
PubMed
Search for other papers by R. V. SHORT in
Google Scholar
PubMed
M.R.C. Unit of Reproductive Biology, 2 Forrest Road, Edinburgh, EH1 2QW
(Received 11 June 1976)
Testosterone treatment of female mammals during a critical period of foetal or neonatal life affects their postpubertal endocrine and behavioural activity. For example, it prevents the occurrence of regular ovulatory cycles in adult rats (Barraclough & Gorski, 1961), guinea-pigs (Brown-Grant & Sherwood, 1971), hamsters (Swanson & Brayshaw, 1973) and sheep (Short, 1974), which is apparently due to a failure of oestrogen to facilitate the release of luteinizing hormone (positive feedback) (Brown-Grant, 1974; Short, 1974). Positive feedback is a sexually dimorphic character in sheep and is only shown by ewes (Short, 1974; Karsch & Foster, 1975). Female sheep foetuses exposed to testosterone from days 20 or 60 of gestation until birth not only failed to show positive feedback (Short, 1974), but were incapable of displaying behavioural oestrus, even when given 800 μg oestradiol benzoate (OB) (I.
Search for other papers by R. J. SCARAMUZZI in
Google Scholar
PubMed
Search for other papers by D. R. LINDSAY in
Google Scholar
PubMed
Search for other papers by J. N. SHELTON in
Google Scholar
PubMed
Most investigators studying oestrous behaviour in sheep use the incidence of such behaviour as a quantal response, an animal being scored as showing or as not showing behavioural oestrus. This procedure has been useful in studying the endocrinology of oestrus in this species but has not clarified the effects of the ovarian hormones on certain quantitative aspects of oestrus such as its duration. In only one study (Lindsay, 1966) have quantitative measurements of the duration of oestrous behaviour in the ovariectomized ewe been recorded and these results suggest that the length of the induced oestrus might be related to the dose of oestradiol benzoate.
Fifty Border Leicester × Merino ewes, ovariectomized 2 years previously, were randomly divided into five groups. The ewes were then injected with 20 mg progesterone every second day for 10 days, followed by a final injection of 10 mg progesterone 2 days later. Forty-eight hours after
Search for other papers by R. J. SCARAMUZZI in
Google Scholar
PubMed
Search for other papers by D. R. LINDSAY in
Google Scholar
PubMed
Search for other papers by J. N. SHELTON in
Google Scholar
PubMed
SUMMARY
The effects of repeated injections of oestradiol benzoate (ODB) on the behavioural oestrous responses of ovariectomized ewes were studied using a pool of 144 animals. Oestradiol benzoate (15·6–421·2 μg) injected at intervals of 4 or 6 days produced a gradual decrease in the number of ewes showing induced oestrous behaviour. The response eventually fell below 10% at which time the ewes were defined to be refractory to oestrogenic stimulation of behavioural oestrus. When a continuous variable was used as a measure of response an immediate effect was observed; after the second injection of ODB the duration of oestrous behaviour decreased while the time to onset of oestrous behaviour showed a corresponding increase when compared with the first injection. However the proportion of ewes responding remained unaltered, indicating that continuous variables are a more sensitive measure of refractoriness. Treatment of refractory ewes with the progestagens progesterone, SC-9880 or Nilevar restored normal oestrous behaviour. These results are interpreted to mean that oestrogens (15–400 μg) act to increase thresholds for subsequent oestrogen stimulation of behavioural oestrus, while progestagens (1–10 mg) act to decrease this threshold.
Search for other papers by I. J. CLARKE in
Google Scholar
PubMed
Search for other papers by R. J. SCARAMUZZI in
Google Scholar
PubMed
Search for other papers by R. V. SHORT in
Google Scholar
PubMed
SUMMARY
The ovarian activity of prenatally androgenized ewes was studied by measuring plasma progesterone concentrations in daily samples of peripheral blood, and by examining the ovaries at laparotomy.
Ewes that were exposed to testosterone between days 30 and 80, 50 and 100 or 70 and 120 of foetal life by implanting their mothers with 1 g testosterone, failed to show regular overt oestrous cycles, although some of them ovulated, whereas ewes exposed to testosterone between days 90 and 140 of foetal life had normal oestrous cycles. The incidence of ovulatory failure appeared to increase with age in ewes treated between days 50 and 100 or days 70 and 120 of foetal life.
