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Biomedical subjects

A Ratner

Publications and source records attributed to A Ratner.

At least 37 records · Page 2Linked to original sources
PubMed1983

Differences in the stress response of prolactin in young and aged female rats.

The drawing of blood by orbital sinus puncture (OSP) under ether anesthesia is known to produce a marked increase in serum prolactin (PRL levels in young cycling female rats. The effect of this stressful procedure on PRL release was compared in young and aged female rats. Nonstressed PRL levels were obtained from blood drawn by decapitation. Whereas OSP with a one-minute ether exposure induced a marked increase in PRL levels in young rats on all days of the estrus cycle, older cycling female rats on the day of diestrus -1 and aged rats exhibiting prolonged diestrus (PD) showed virtually no increase above nonstressed levels. However, increasing the ether exposure time to five minutes did produce a rise in PRL levels. Old cycling female rats on the day of estrus and aged rats exhibiting constant estrus (CE) did show a PRL increase comparable to that seen in young animals. Ovariectomy (OVX) completely abolished the stress response seen in aged CE rats. The response, though markedly decreased, was still present in young ovariectomized rats. These experiments show that the stress-induced rise in PRL promoted by OSP under either anesthesia is markedly diminished in aged rats exhibiting a diestrus state. The attenuated response seen in these rats is believed due to factors characteristic of the diestrous state of aging.

Aging↗
PubMed1982

Evidence for direct neural control of ovarian steroidogenesis in rats.

Electrical stimulation of the superior ovarian nerve of intact anaesthetized dioestrous rats for 30 min reduced ovarian progesterone levels, even when papaverine and propranolol were also given. The administration of phentolamine (an alpha receptor antagonist) before stimulation reversed this effect. The results suggest that a neural control of ovarian steroidogenesis may be either excitatory through the stimulation of beta receptors or inhibitory through the stimulation of alpha receptors.

Animals↗
PubMed1980

LHRH-induced LH and FSH responses in the aged female rat.

LHRH-induced LH and FSH concentrations were measured in 8 to 12-month-old rats which had just begun to exhibit constant vaginal estrus (CE) or prolonged vaginal diestrus (PD) and in young rats on the day of proestrus (PE). All animals were anesthetized with sodium pentobarbital (31 mg/kg). They received (1) i.v. infusion of LHRH (Beckman 100 ng/ml at a rate of 0.5 ml/hr) for 3 hrs or (2) 2 i.v. injections of LHRH (50 ng/100 g body wt) spaced 120 min apart. LHRH stimulation resulted in a comparable gonadotropin response in young rats and old CE rats; however, old PD rats exhibited a markedly attenuated LH and FSH response to LHRH infusion. These data suggest that pituitary responsiveness to LHRH does not change in 8 to 12-month-old CE rats and therefore does not play a major role in the transition to acyclicity. In contrast, pituitary responsiveness is decreased in old PD rats early during the aging process and therefore may be an important factor in the transition to their acyclic vaginal smear pattern.

Aging↗
PubMed1980

Effect of ovariectomy on plasma LH, FSH, estradiol, and progesterone and medial basal hypothalamic LHRH concentrations old and young rats.

Resting plasma concentrations of LH, FSH, estradiol, and progesterone and medial basal hypothalamic concentrations of LHRH (MBH-LHRH) were measured by RIA in 8- to 12-month-old female rats which had begun to exhibit constant estrous (CE) or prolonged diestrous (PD) vaginal smear patterns and compared to young cycling rats on proestrus, estrus, or diestrus. In addition, we examined the effect of ovariectomy on these hormonal profiles. Old CE rats have normal plasma LH, FSH and progesterone concentrations, but exhibit elevated estradiol levels and decreased MBH-LHRH concentrations compared to young cycling rats on the day of estrus. Ovariectomy results in an attenuated rise in plasma LH and FSH and a much lesser decrease in MBH-LHRH when compared to young rats, despite comparable steroid changes. Old PD rats have normal LH and FSH levels,but have elevated estradiol and progesterone concentrations and decreased MBH-LHRH levels when compared to young rats on the day of diestrus. Ovariectomy causes a normal decrease in MBH-LHRH; however, the increased gonadotropin levels are significantly less than seen in young controls.

Aging↗
PubMed1980

Stimulation by beta 2-adrenergic receptors of the production of cyclic AMP and progesterone in rat ovarian tissue.

Ovarian tissue from immature rats treated with pregnant mare serum gonadotrophin (PMSG) or PMSG and human chorionic gonadotrophin was incubated in Medium 199. Stimulation of the formation of cyclic AMP in follicular and luteal tissue by terbutaline (10(-5) mol/l), a selective beta 2-agonist, was blocked by butoxamine (10(-5) mol/l), a selective beta 2-antagonist, whereas practolol (10(-5) mol/l), a selective beta 1-antagonist, was ineffective. Propranolol (10(-5) mol/l) a non-selective beta-antagonist, butoxamine nor practolol affected the increase in cyclic AMP promoted by the addition of 1 microgram LH. Stimulation of the production of progesterone in both follicular and luteal tissue by terbutaline was blocked by butoxamine, but not by practolol. These findings indicated that beta-adrenergic stimulation of ovarian cyclic AMP and progesterone is mediated by beta 2-adrenergic receptors.

Adrenergic beta-Antagonists↗
PubMed1976

Dissociation between LH release and pituitary cyclic nucleotide accumulation in response to synthetic LH-releasing hormone in vivo.

In order to clarify the role of cyclic nucleotides in the mediation of LH-releasing hormone (LH-RH) action on LH release, the effect of LH-RH on LH release and pituitary cyclic AMP and cyclic GMP accumulation was studied in vivo. Pituitary cyclic AMP levels were increased 10 min after the intraveneous injection of 2 mg dibutyryl cyclic AMP (db-cyclic AMP) or 25 mg aminophylline. However, serum LH levels were not altered at 10, 30 or 60 min after the administration of either agent. Synthetic LH-RH (100 ng/rat) increased serum LH levels as measured 10 min after injection, but no effect on either pituitary cyclic AMP or cyclic GMP was seen 1, 5 or 10 min after LH-RH administration. These in vivo results are contradictory to the second messenger hypothesis for either cyclic AMP or cyclic GMP in the mediation of LH-RH-induced LH released and suggest that further work must be done in order to confirm or reject this hypothesis.

Aminophylline↗
PubMed1976

Effects of follicle stimulating hormone and luteinizing hormone upon cyclic AMP and cyclic GMP levels in rat ovaries in vitro.

In vitro effects of FSH and LH on adenosine 3',5'-cyclic monophosphate (cyclic AMP) and guanosine 3',5'-cyclic monophosphate (cyclic GMP) levels in rat ovarian tissue were studied. Ovaries from immature rats treated with either pregnant mare's serum (PMS) or PMS and human chorionic gonadotropin (hCG) were incubated at 37 C for 30 min in defined medium 199 containing aminophylline (0.1 mg/ml). Increasing concentrations of LH (0.4-10.0 mug) when added to the medium containing ovaries with predominantly follicular tissue (PMS-treated) produced progressive increases in cyclic AMP (29-300%) and concomitant decreases in cyclic GMP (41-70%). FSH (4-100 mug) added to the medium produced comparable changes in nucleotide levels: cyclic AMP increased 52-390% and cyclic GMP decreased 45-80%. Ovaries with predominantly luteal tissue (PMS- and hCG-treated) responded differently to the same experimental conditions. LH produced a much greater increase in tissue cyclic AMP levels (209-1280%), whereas FSH produced comparable increases in cyclic AMP as seen with follicular tissue (103-570%). Neither gonadotropin caused any changes in cyclic GMP levels in luteinized ovaries. These results indicate that rat ovarian cyclic GMP is regulated by gonadotropins and the differences in the direction of nucleotide response to gonadotropins suggest divergent roles for cyclic AMP and cyclic GMP in ovarian function.

Animals↗
PubMed1976

Effects of follicle-stimulating hormone and luteinizing hormone on ovarian cyclic AMP and prostaglandin E in vivo in rats treated with indomethacin.

The role of prostaglandins in both FSH- and LH-mediated increases in ovarian cyclic AMP was examined in rats in vivo. Dose-related increases in ovarian cyclic AMP levels were observed 10 min after intravenous injection of FSH or LH. No changes in ovarian prostaglandin E (PGE) content were detected after injection of either gonadotrophin at doses which substantially enhanced cyclic AMP accumulation. Prior treatment of rats with indomethacin produced a greater than 50% decrease in ovarian PGE levels, but did not prevent the FSH- or LH-induced rise in ovarian cyclic AMP concentration. These in vivo experiments do not support the concept that PGE plays a role as an obligatory mediator for the gonadotrophin-induced rise in ovarian cyclic AMP levels.

Animals↗