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S Saiduddin

Publications and source records attributed to S Saiduddin.

At least 19 recordsLinked to original sources
PubMed1998

Phosphorylation of bovine prolactin eliminates luteotropic activity in the rat.

Phosphorylated and nonphosphorylated prolactins were isolated from bovine pituitaries and their luteotropic activity determined in female rats. Three groups of rats in day 1 of diestrus were treated i.p. twice daily for three days with 0.25 mg of either prolactin preparation or vehicle. Rats were sacrificed each day of treatment. Serum progesterone concentrations of the groups receiving vehicle or phosphorylated prolactin were similar and the vaginal cytology of these animals indicated that phosphorylated bovine prolactin (bPRL) treatment had not prolonged diestrus. Treatment with nonphosphorylated bPRL significantly increased serum progesterone concentration and the vaginal cytology indicated a diestrus prolonged for up to 4 days. Nonphosphorylated and phosphorylated bPRLs were cleared from the blood at similar rates after i.p. injection. In vitro receptor binding studies demonstrated that phosphorylated bPRL did not bind the ovarian prolactin receptor. Nonphosphorylated, but not phosphorylated, bPRL competed with radiolabeled bovine hormone for occupancy of rat ovarian prolactin receptors. These data are the first to test the activities of phosphorylated bPRL in vivo and indicate; 1) nonphosphorylated bPRL is luteotropic, 2) phosphorylated bPRL is neither luteotropic nor a prolactin receptor agonist or antagonist and 3) phosphorylated bPRL is not dephosphorylated in vivo rapidly enough to provide sufficient biologically-active bPRL to maintain luteal function.

Animals↗
PubMed1993

Reproductive abnormalities in the prepubertal jaundiced Gunn rat.

The female, jaundiced Gunn rat has been previously reported to be infertile. This study describes some abnormalities in the reproductive system of the prepubertal jaundiced female rat. Vaginal opening occurred at the time of weaning, which was approximately 7 days earlier when compared to the nonjaundiced female littermates. Following vaginal opening, the jaundiced rat showed persistent vaginal cornification. The estimated age at first ovulation in the jaundiced rat was 52 days. The uteri of jaundiced rats were significantly larger than those of nonjaundiced rats by 17 days after birth. The accelerated uterine growth and the precocious vaginal opening in the jaundiced rat suggest hyperestrogenism. Feeding activated charcoal to jaundiced rats significantly reduced the uterine weight. These results show that the reproductive abnormalities in the jaundiced female rat appear in the prepubertal life and continue during adult life resulting in infertility.

Animals↗
PubMed1983

Effect of androgens on the ovarian morphology of the hypophysectomized rat.

Experiments were designed to study the short-term effects of androgens on ovarian follicular morphology in immature, hypophysectomized rats. Rats were given 1 mg diethylstilbestrol (DES) daily for 5 days. On the fifth day, they were treated with 5-alpha-dihydrotestosterone (DHT), testosterone (T), and flutamide metabolite, alpha, alpha, alpha-trifluoro-2-methyl-4'-nitro-m-lactotoluidide (FM) alone and in combination and killed 24 hr later. One group of rats received DES alone. Ovarian serial sections (5 mum) were observed in each treatment for the presence of pyknotic nuclei as an index of atresia. Diameter of the follicles was measured, a percentage of atretic follicles was calculated, and the data were analyzed for all size follicles, follicles 150 mum or less (small), and follicles measuring over 150 mum (large). The results show that DHT and DHT plus T increased follicular atresia when all follicle sizes were considered. None of the treatments significantly changed follicular atresia in small follicles. In large follicles, both DHT and T increased follicular atresia. Furthermore, FM prevented T-induced atresia while by itself FM had no effect on follicular morphology. That the FM decreased the action of T in promoting atresia adds support to the conclusion that T promotes atresia by inhibiting the follicular growth promoting action of DES in the ovary. Also, this study shows that DHT promotes follicular atresia.

Animals↗
PubMed1978

Effect of testosterone and progesterone on the estradiol receptor in the immature rat ovary.

The effect of testosterone and progesterone on the estrogen-stimulated ovarian weight increase and es tradiol receptor (ER) levels was examined in immature, hypophysectomized rats. Nuclear translocation and cytosol replenishment of the ER in the ovary exhibited similarities to those events in the uterus. The ovarian weight increase observed on day 4 in response to three daily injections of 2.5 microgram 17beta-estradiol administered sc in sesame oil was effectively suppressed by one injection of 1 mg testosterone on day 3. In contrast, 1 mg progesterone given on day 3 had no effect on the ovarian weight of the estrogen-primed rat. Nor did progesterone alter the ovarian ER levels in the cytosol and nuclei of similarly treated rats. Further, progesterone receptors were undetectable in the ovarian tissue of immature, hypophysectomized rats given two daily injections of 2.5 microgram estradiol-17beta. In contrast, testosterone significantly reduced the ovarian ER levels both in the cytosol as well as in the nuclei. These results suggest that one of the mechanisms by which testosterone acts in the ovarian tissue is by reducing the available ER for estrogen action.

Animals↗
PubMed1977

Estradiol-17beta receptors in the immature rat ovary.

Estradiol binding components in the cytosol and nuclear fractions of the ovary from immature rats (22-28 days old) were characterized by in vitro methods. Several of the biochemical characteristics of the estradiol binding components in the ovarian tissue were compared with the estradiol receptor from the uterus. The results suggest that the ovarian estradiol binding components are similar to the specific high affinity estradiol receptors in the uterus. In the cytosol of intact rat ovary a significant fraction of the total binding sites was found to be occupied, presumably by the endogenous estrogen. Following hypophysectomy there was a significant increase in the available cytosol binding sites. Evidence for translocation of cytosol receptor-estrogen (RE) complex to the nucleus was obtained for the ovary. The sedimentation properties of the RE complex of the ovary and the uterus are similar. The ovarian cytosol RE complex sediments at 7-8S in glycerol gradients at low ionic strength and at 4S in sucrose gradients at high ionic strength. Following extraction with 0.4 M KCl the ovarain nuclear RE complex sediments at 5S in sucrose gradients which is identical to that of the uterine nuclear receptor.

Animals↗