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Biomedical subjects

R J Scaramuzzi

Publications and source records attributed to R J Scaramuzzi.

At least 127 records · Page 7Linked to original sources
PubMed1976

Endocrine changes associated with luteal regression in the ewe; the secretion of ovarian oestradiol, progesterone and androstenedione and uterine prostaglandin F2alpha throughout the oestrous cycle.

The concentrations of oestradiol, androstenedione, progesterone and prostaglandin F2alpha (PGF2alpha) were measured in utero-ovarian autotransplants. The secretion of oestradiol was closely correlated with that of androstenedione (r = 0-67, P less than 0-001) indicating a common origin from the Graafian follicle. The concentration of these two steroids fluctuated at random throughout the luteal phase with the maximum secretion occurring about 2 days before the onset of oestrus. Functional regression of the corpus luteum, as indicated by a fall in the secretion of progesterone, began on day 12 or day 13, i.e. about 4 days before the onset of oestrus. In five of the six cycles the first significant rise in the secretion of PGF2alpha occurred on days 12-14 at the time of decline of progesterone secretion, although the release of PGF2alpha was maximal on the day before the onset of oestrus. There was very little release of PGF2alpha from the uterus before day 12. The temporal relationship of these events suggests that the uterus will only release PGF2alpha after it has been primed for 7-10 days with progesterone. The initiation of luteal regression is independent of secretion of oestradiol by the pre-ovulatory follicle which may, however, stimulate the further release of PGF2alpha responsible for irreversible structural luteolysis on the day of pro-oestrus.

Androstenedione↗
PubMed1976

Changes in the secretion of ovarian steroid and pituitary luteinizing hormone in the peri-ovulatory period in the ewe: the effect of progesterone.

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 F 2alpha (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 less than 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.

Androstenedione↗
PubMed1976

Effects of testosterone implants in pregnant ewes on their female offspring.

Pregnant ewes were implanted with 1 g testosterone between days 30-80, 50-100, 70-120 or 90-140 of gestation. Ewes treated between days 30-80 and 50-100 showed increased aggressive behaviour and clitoral enlargement, whereas this was not seen in the day 70-120 or 90-140 groups. Although the implants released similar amounts of testosterone at all stages of gestation, plasma testosterone concentrations were lower in the day 70-120 and 90-140 groups. The increased testosterone clearance in late gestation could be a result of increased placental aromatization. Masculinization of the genital tubercle was complete in female lambs in the day 30-80 group, partial in the day 50-100 and 70-120 groups, and absent in the day 90-140 group. These results therefore suggest that the 'critical period' for masculinization of the external genitalia is between days 40 and 50 of foetal life. In contrast to this anatomical masculinization, one aspect of behavioural masculinization had a later critical period, since female lambs of 30-80, 50-100 and 70-120 day groups adopted male-like urination postures, whereas the day 90-140 offspring showed the normal female pattern.

Abnormalities, Drug-Induced↗
PubMed1975

Radioimmunoassay of serum LH and testosterone in male rabbits actively immunized against testosterone.

Five male rabbits were actively immunized against testosterone to determine if this procedure could permanently inactivate circulating testosterone. To assess the response to immunization, serum LH, serum testosterone and antitestosterone titer (titer) were measured by radioimmunoassay at various times after immunization. All rabbits produced antisera to testosterone and developed serum LH levels similar to those measured in castrated males. The rise in serum LH was particularly pronounced after a booster immunization but these elevated levels were not maintained which suggests that biological neutralization was only transient. Serum testosterone rose dramatically after immunization and was directly correlated with titer. High serum testosterone concentrations were associated with both high and low serum LH. No correlation existed between titer ans serum LH. It is concluded that active immunization against testosterone does not necessarily result in a permanent neutralization of circulating testosterone and that titer alone is an inadequate criterion of neutralization.

Animals↗
PubMed1975

Influence of prostaglandins and human chorionic gonadotrophin on progesterone concentration and oocyte maturation in mouse ovarian follicles maintained in organ culture.

The response of mouse ovaries maintained in organ culture to prostaglandin E-2 (PGE2) and prostaglandin F-2alpha (F2alpha) was assessed using quantitative histological and radioimmunoassay procedures. Prostaglandin E2 induced histological changes in the cultured follicles comparable to those induced by human chorionic gonadotrophin (HCG) and the increase in the number of oocytes undergoing preovulatory maturation over the control value was the same irrespective of the treatment (PGE2 alone, HCG alone, or PGE2+HCG). The amount of progesterone/ml of culture medium was also significantly higher with these preparations than in control cultures (about 125 ng/ml compared with 57 ng/ml). By contrast, 5 mug PGF2alpha/ml medium increased neither the number of oocytes undergoing maturation nor the concentration of progesterone in the culture medium. The latter increased when the dose of PGF2alpha was increased to 30 mug/ml, although the proportion of oocytes beyond the dictyate stage remained at the control level. There was no augmentation in the response (above the level for HCG alone) when HCG and PGF2alpha were added to the explant medium simultaneously. These results are discussed in terms of the possible mechanism of action of the various preparations.

Animals↗