Showing papers in "Endocrinology in 1971"
TL;DR: A rapid and simple method for the measurement of serum “estrogen” concentrations is described which provides a good approximation of estradiol levels.
Abstract: Estradiol and LH levels were measured by radioimmunoassay in daily samples of peripheral serum of rhesus monkeys during 10 normal menstrual cycles. During the 4 days prior to the LH surge, serum estradiol values rose sharply, while the LH levels declined. The midcycle peak of estradiol and LH occurred simultaneously in 9 of the 10 cycles studied. These peaks were followed within 24 to 48 hr by an abrupt fall in estradiol levels, while LH levels declined over a 5-day period. Most animals showed no luteal phase peaks in serum estradiol concentration. A rapid and simple method for the measurement of serum “estrogen” concentrations is described which provides a good approximation of estradiol levels. (Endocrinology 89:177, 1971)
576 citations
TL;DR: A radioimmunoassay of plasma ACTH, useful for several mammalian species, has been adapted for the rat and binding studies showed that the antibody bound most effectively with the 1–24 fragment and nearly as effectively withThe 1–39 native human and porcine molecules.
Abstract: A radioimmunoassay of plasma ACTH, useful for several mammalian species, has been adapted for the rat. The antibody permitting this versatility was produced in the rabbit by immunization with the species-common, steroidogenic 1–24 amino acid sequence of ACTH. Binding studies, using polypeptide fragments of ACTH, showed that the antibody bound most effectively with the 1–24 fragment and nearly as effectively with the 1–39 native human and porcine molecules. The antibody failed to react significantly with αMSH, βP-MSH or with synthetic 1–16 amide or αp 17–39 fragments of ACTH. A close similarity was found between bioactivity and immunoreactivity in 3 tested specimens of rat plasma. Physiological validation of the method was obtained from the following studies. The immunoreactive plasma ACTH concentration at 9 AM in “resting” male rats was 23±4 pg/ml (mean±SE), when the plasma corticosterone concentration was 4 ± 0.4 μg/100 ml. At 4:30 PM, plasma ACTH was 63 ± 9 pg/ml and plasma corticosterone was 13 ± 2 μg/...
422 citations
TL;DR: Melatonin as well as serotonin, when injected into the third ventricle of the brain of male rats, appeared to stimulate the release of prolactin and inhibit the releaseof FSH as judged by the changes in the concentrations of these hormones in the plasma of the recipient animals.
Abstract: Melatonin as well as serotonin, when injected into the third ventricle of the brain of male rats, appeared to stimulate the release of prolactin and inhibit the release of FSH as judged by the changes in the concentrations of these hormones in the plasma of the recipient animals. (FSH and prolactin were determined by radioimmunoassay.) For example, 30 min after the injection into the third ventricle of doses of 1, 5 and 50 μg melatonin, the plasma prolactin concentrations were 199 ± 11.3 % (mean and SE), 235±16.1% and 304±12.7%, respectively, of the pre-injection levels. The corresponding FSH values were 88±3.7%, 85±3.7% and 74±2.6%. After 2 hr, the plasma prolactin concentration had returned to the pre-injection level; however, the plasma FSH concentration after 2 hr was only 50% of the pre-injection level. The effects of intraventricularly administered serotonin were similar to those seen with melatonin. Isotonic saline solution (2.5 μl) had no effect on the release of prolactin and FSH. When melatonin ...
313 citations
TL;DR: In this article, the role of calcium in glucose-induced insulin secretion was examined by measuring 45Ca uptake by isolated islets of Langerhans, which were incubated for 90 min in the presence of 45Ca, submitted to successive washings, and finally examined for their radioactive content.
Abstract: The role of calcium in glucoseinduced insulin secretion was examined by measuring 45Ca uptake by isolated islets of Langerhans. The islets were incubated for 90 min in the presence of 45Ca, submitted to successive washings, and finally examined for their radioactive content. Glucose, but not galactose, stimulated 45Ca uptake by the islets. A sigmoidal curve characterized the relationship between 45Ca uptake and the glucose concentration of the incubation medium. Glucose-induced calcium uptake was increased in media in which Na+ had been partially replaced by K+, and inhibited by mannoheptulose, 2-deoxyglucose, epinephrine, diazoxide, low temperature, low pH, high Mg++ concentration, low Ca++ concentration, and in media in which Na+ had been partially replaced by Li+. Under these experimental conditions, the, changes in 45Ca uptake paralleled those in insulin secretion by the islets. However, although glucose failed to induce insulin release at low Ca++ concentration, the reduced uptake of calcium found un...
299 citations
TL;DR: The accuracy of the isolated adrenal cell method for assay of ACTH is excellent and the cells are highly selective; they do not respond to relatively large quantities of insulin, glucagon, oxytocin, vasopressin or angiotensin II.
Abstract: Rat adrenal tissue is dispersed with a combination of tryptic digestion and mechanical agitation. Production of corticosterone by the isolated cells in response to a given quantity of ACTH is increased when the calcium concentration of the incubation medium is increased to 3 times that of KRB. Production of corticosterone is enhanced when BSA is added to the medium; production is greater at 0.5% than at 2.0 or 3.0% BSA. Minimum effective dose is 0.1 μU (1.0 pg) of ACTH. The accuracy of the isolated adrenal cell method for assay of ACTH is excellent; λ = 0.01–0.06 compared with λ =0.15–0.25 for other currently employed bioassay methods. In addition, the cells are highly selective; they do not respond to relatively large quantities (107 pg) of insulin, glucagon, oxytocin, vasopressin or angiotensin II. At 107 pg, α-MSH exhibits a weak action corresponding to that exhibited by 10 pg of ACTH. (Endocrinology 88: 1063, 1971)
250 citations
TL;DR: To determine whether vasopressin affects the sensitivity of the anterior pituitary to corticotropin-releasing factor, vasopressingin was administered intravenously in doses subthreshold with respect to ACTH release to rats pretreated with dexamethasone (dex), Nembutal (Nem), and, sometimes, also morphine (morph).
Abstract: To determine whether vasopressin affects the sensitivity of the anterior pituitary to corticotropin-releasing factor, vasopressin was administered intravenously in doses subthreshold with respect to ACTH release to rats pretreated with dexamethasone (dex), Nembutal (Nem), and, sometimes, also morphine (morph). Crude ovine CRF was given intravenously immediately following the vasopressin. The adrenocortical response to CRF was increased at least 100% by the prior administration of subthreshold doses of vasopressin. When 1/20 of the intravenous dose of vasopressin was placed into both lobes of the anterior pituitary it again failed to release ACTH itself, but increased 2.5 times the response to CRF given intravenously. This potentiation of CRF-induced ACTH release by vasopressin at the adenohypophysis was not observed if the vasopressin was administered into one lobe only of the anterior pituitary. In rats pretreated with dex +Nem the potentiation was the same as in those pretreated with dex + Nem+morph. Ox...
242 citations
TL;DR: A comparison of the patterns of serum FSH and LH concentrations around the time of pvulation in regularly cycling adult female rat was accomplished by use of recently developed, differential radioimmunoassay systems (NIAMD-Rat F SH and LH radioIMmunoASSay systems).
Abstract: Contrary to a previous report by others, significant FSH activity could not be detected in pooled sera obtained from rats on the late afternoon of proestrus, despite injection of 20 ml of serum/test rat in the HCG-augmentation assay. A comparison of the patterns of serum FSH and LH concentrations around the time of pvulation in regularly cycling adult female rat was accomplished, however, by use of recently developed, differential radioimmunoassay systems (NIAMD-Rat FSH and LH radioimmunoassay systems). A striking difference in these patterns was revealed. Serum LH concentration was elevated only on the late afternoon of proestrus (mean value of approximately 1000 ng NIAMD-Rat-RP-1/ml) and, to a lesser extent, on the evening of proestrus. Serum FSH concentration, largely undetectable during diestrus, also began to rise on the late afternoon of proestrus, but did not attain a maximum until 8–9 PM proestrus (at approximately 500 ng NIAMDRat FSH-RP-1/ml). This maximal elevation of serum FSH persisted until 4...
223 citations
TL;DR: Serum LH and FSH, testis weight (TW), ventral prostate weight (VPW) and testicular histology were assessed in the immature male rat from age 21 to 91 days and marked destruction of germinal epithelium by cryptorchidism failed to elev...
Abstract: Serum LH and FSH, testis weight (TW), ventral prostate weight (VPW) and testicular histology were assessed in the immature male rat from age 21 to 91 days. Intact, castrate and cryptorchid male rats were studied at biweekly intervals. In intact animals, TW and VPW increased with age; mature sperm were first observed at 49 days. At 21 days LH was 65% of adult levels and increased progressively with age. In contrast, FSH in immature rats was 2–3 times higher than adult levels. FSH was maximal at 35 days of age and fell with the appearance of mature sperm in the tubules. This fall in FSH and the development of spermatogenesis were prevented by cryptorchidism. FSH values in the cryptorchid rat continued to rise until 49 days, at which time VPW and LH were not different from the controls, indicating unaltered Leydig cell function. Two weeks following castration of 21-day-old rats, LH and FSH were 5 times higher than intact adult levels. Marked destruction of germinal epithelium by cryptorchidism failed to elev...
213 citations
TL;DR: Determination of the structures of TSH and LH has required years of purification and chemical studies, but in just the past two years these efforts have resulted in a major increase in knowledge of the glycoprotein hormones, that is, those polypeptide hormones which contain covalently bound carbohydrate as integral parts of their structures.
Abstract: THIS LECTURE concerns the structure of thyroid stimulating hormone (TSH) and the relationships that have been found between TSH, luteinizing hormone (LH, ICSH) and human chorionic gonadotropin (HCG). Determination of the structures of TSH and LH has required years of purification and chemical studies in many laboratories including our own, but in just the past two years these efforts have resulted in a major increase in our knowledge of the glycoprotein hormones, that is, those polypeptide hormones which contain covalently bound carbohydrate as integral parts of their structures. Particularly important contributions have been made by Condliffe and Bates in the purification of TSH (1) and by Li, Papkoff and their colleagues (2,3) and by Ward and his colleagues (4,5,6) in their structural studies on LH. The major glycoprotein hormones of the pituitary and placenta are listed in Table 1 together with some of their chemical properties as these were known just 2 or 3 years ago. It is obvious that uncertainties...
202 citations
TL;DR: An antiserum to estradiol was used to examine the role of estrogens secreted at diestrus in stimulating the proestrus surges of prolactin and luteinizing hormone (LH) secretion in the rat.
Abstract: An antiserum to estradiol was used to examine the role of estrogens secreted at diestrus in stimulating the proestrus surges of prolactin and luteinizing hormone (LH) secretion in the rat. Plasma prolactin and LH concentrations were measured by radioimmunoassay in blood samples obtained at 1–2 hr intervals on the day of proestrus in 4-day cyclic rats bearing aortic catheters. In control animals, proestrus prolactin values increased above baseline first at 1300 hr, were maximal between 1500–2000 hr, and returned to near baseline titers at 0100 hr on estrus. Proestrus LH concentrations were elevated first at 1500 hr, peaked at 1700–1800 hr, and fell to baseline values at 2300 hr. Estradiol antiserum administered at 1000 hr on proestrus did not affect the proestrus surge of prolactin and LH secretion or the incidence of vaginal cornification (100% vs. 94% in controls) and ovulation (88% vs. 71% in controls). On the other hand, estradiol∧ antiserum administered at 1000 hr on the day prior to proestrus (diestr...
197 citations
TL;DR: Dopamine, epinephrine, or norepinephrine, perfused into the anterior pituitary for 30 min via a hypophysial portal vein, had no effect on prolactin release and dopamine greater than 2.5 jug caused less inhibition of release.
Abstract: In rats, the median eminence, pituitary stalk and anterior pituitary were exposed parapharyngeally and catecholamines were injected into the third ventricle or infused into a stalk portal vessel, peduncular artery, or a tuberalis ramus of an infundibular artery. Ten min after 1.25 μg dopamine hydrochloride was injected into the third ventricle, the plasma prolactin concentration was 70% of the preinjection value; 47% at 20 min; 42% at 30 min; 57% at 60 min; 69% at 90 min; and 93% at 120 min. Similar responses occurred following the administration of 2.5 μg dopamine. Quantities of dopamine greater than 2.5 jug caused less inhibition of release, however. Intraventricular injection of 2.5 or 5 μg of epinephrine or norepinephrine bitartrate did not affect prolactin release although 100 μg did. Dopamine, epinephrine, or norepinephrine, perfused into the anterior pituitary for 30 min via a hypophysial portal vein, had no effect on prolactin release. Dopamine, infused into the stalk-median eminence complex via t...
TL;DR: The findings suggest that the capacity to form dihydrotestosterone in urogenital sinus and tubercle is not the result of androgen action but rather an inherent or obligatory property of the tissue and may fulfill in part the function of an initial androgen receptor in these organs.
Abstract: The rate of conversion of testosterone- l,2-3H to dihydrotestosterone-3H has been measured in a variety of tissues in rabbit embryos from 17 days of development to 3 days following birth and in rat embryos from 15 days of gestation to 4 days after delivery. In the rabbit embryo dihydrotestosterone formation was rapid only in the urogenital sinus and urogenital tubercle of both sexes at the earliest stages studied and was not measurable in wolffian and mullerian ducts until after gender identification was easily demonstrable. A similar pattern of development was observed in the rat embryo. These findings suggest that the capacity to form dihydrotestosterone in urogenital sinus and tubercle is not the result of androgen action but rather an inherent or obligatory property of the tissue and may fulfill in part the function of an initial androgen receptor in these organs. In contrast, in the mullerian and wolffian ducts the ability to form dihydrotestosterone appears to be acquired after the initial stages of...
TL;DR: Subunits of human chorionic gonadotropin have been isolated from carboxymethyl- HCG by preparative poly aery lamide electrophoresis, by chromatography on Sephadex G-25, and from native HCG with significant differences in amino acid composition between the subunits.
Abstract: Subunits of human chorionic gonadotropin have been isolated from carboxymethyl- HCG by preparative poly aery lamide electrophoresis, by chromatography on Sephadex G-25, and from native HCG by chromatography on DEAE-Sephadex A-25. HCG-α subunit has been estimated to have a Stokes’ radius of 23.3 A by gel filtration and a molecular weight by SDSgel electrophoresis of approximately 18,000; the HCG-β subunit has a Stokes' radius of 30.2 A and a molecular weight of approximately 30,000. There are significant differences in amino acid composition between the subunits. Alanine, serine and valine were found as NH2-terminal amino acids of native HCG. Alanine and valine were found to be the NH2-terminal residues of the a subunit, and alanine and serine were found in the NH2-terminus of the β subunit. There appears to be a homology between the sequence of the a subunits of HCG and TSH, and between the 0 subunit of HCG and the CII subunit of LH. The biological activity of the α subunit was less than 1 % of the native...
TL;DR: The concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in serum following progesterone injection into spayed, estrogen-treated rats were measured by radioimmunoassay androgen priming is essential since no effect of progester one was observed in spayed treated animals.
Abstract: The concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in serum following progesterone injection into spayed, estrogen-treated rats were measured by radioimmunoassay. Progesterone (2 mg), injected at noon 2, 3 or 4 days after the injection of a single dose of 20 μg estradiol benzoate, induced, a few hours later, a significant increase in serum LH. On the following 2 days after progesterone injection the LH levels were lower than those in the controls but on the 3rd day the serum LH rose again. The release of LH induced by progesterone was observed in the afternoon up to late in the evening but not in the morning. Estrogen priming is essential since no effect of progesterone was observed in spayed treated animals. Progesterone also exerted an inhibitory effect on the release of LH after the facilitatory period occurred. In fact, the release of LH which can be induced by the injection of either estrogen or progesterone was prevented by the administration of progesterone 1 day ...
TL;DR: It is concluded that estrogen injection is effective in triggering the release of LH in ovariectomized rats primed with estrogen.
Abstract: The effect of estrogen on the release of luteinizing hormone (LH) and folliclestimulating hormone (FSH) was studied in spayed rats. The concentration of the hormones in serum was determined by a radioimmunoassay procedure. After a single injection of 20 μg estradiol benzoate (EB), the elevated values of LH in ovariectomized rats were reduced the following day and remained low for at least 8 days. A second injection of EB given at noon 3 or 4 days after the first injection significantly increased serum LH a few hours later and a second peak of LH also occurred the next day. When EB was injected on alternate days, beginning 3 days after the priming dose, high serum LH levels were found every day up to the eighth day. The positive feedback effect of EB on LH release was observed only in the afternoon and not in the morning. No significant changes in serum FSH were found. It is concluded that estrogen injection is effective in triggering the release of LH in ovariectomized rats primed with estrogen. (Endocrin...
TL;DR: The incorporation of radioactivity by rat prostate has been measured following administration of seven tritium-labeled natural androgens to separate groups of castrated functionally hepatectomized rats and dihydrotestosterone consistently was found to be the major metabolite.
Abstract: The incorporation of radioactivity by rat prostate has been measured following administration of seven tritium-labeled natural androgens to separate groups of castrated functionally hepatectomized rats. In addition a study has been made of the identity and subcellular localization of metabolites formed from each steroid. With every androgen tested radioactivity was detected in cytoplasmic and nuclear fractions at intervals ranging from 5 min to 1 hour after the administration of the hormone. Highest levels of nuclear radioactivity were achieved with testosterone, dihydrotestosterone and androstanediol; intermediate levels with androstanedione, androstanedione, and androsterone; a low level with dehydroepiandrosterone. Every androgen gave rise to several metabolites in prostatic cytoplasm and invariably one of these was dihydrotestosterone. In nuclei dihydrotestosterone consistently was found to be the major metabolite. There was a striking absence of any other significant nuclear product except for testos...
TL;DR: The hypothesis that tubal transport of ova occurs during and, folio, during and after coitus is supported, suggesting that implantation is preceded by a small rise in estrogen production.
Abstract: The in vivo release of estradiol- 17β (E2), 20α-hydroxypregn-4-en-3-one (20α-OH) and progesterone (P) from the ovary between coitus and implantation was studied in 38 rabbits which had mated with fertile bucks. While P release remained constant, the release of E2 and 20α-OH, as measured in the ovarian venous effluent, increased following coitus to reach peak values between If and 4 hr. After this time the outputs of all 3 steroids began to decline. At ovulation E2 was no longer detectable and both progestins were at nadir ( <5 μg/ov/hr). During the 3-day period of tubal transport steroid output remained very low; but between days 4 and 6, when blastocysts lie free in the uterine lumen, E2 output rose, suggesting that implantation is preceded by a small rise in estrogen production. Between days 8 and 10, E2 release in rabbits with viable fetuses was 20.5 ± 4.1 pg/ov/hr and P release had increased to 23.8 ± 3.0 Mg/ov/hr. These data support the hypothesis that tubal transport of ova occurs during and, folio ...
TL;DR: Blockade of serotonin biosynthesis with p-chlorophenylalanine failed to modify plasma levels of any of the 3 pituitary hormones measured and did not alter the elevation in plasma prolactin produced by concomitant administration of α-MT.
Abstract: DL-α-Methyltyrosine (α-MT), which blocks catecholamine biosynthesis, produced a dramatic rise in plasma prolactin within 30 min of ip injection in castrated rats and treatment with α-MT for 4 days resulted in continued high levels of plasma prolactin and an elevation of pituitary prolactin concentration and content. Plasma FSH and LH were not significantly altered by α-MT. Selective blockade of norepinephrine (NE) biosynthesis with diethyldithiocarbamate (DDC) failed to alter prolactin levels but did lower plasma LH. Blockade of serotonin biosynthesis with p-chlorophenylalanine (p-CPA) failed to modify plasma levels of any of the 3 pituitary hormones measured and did not alter the elevation in plasma prolactin produced by concomitant administration of α-MT. When L-dihydroxphenylalanine (L-DOPA) was administered to elevate brain catecholamines, it lowered plasma prolactin but failed to alter FSH and LH levels. This lowering of piolactin by L-DOPA still occurred if conversion of dopamine (DA) to NE was bloc...
TL;DR: Rat epididymis cytosol contained 2 androgen-binding components, one of which demonstrated a high affinity for dihydrotestosterone, and radioactivity migrated in a single peak with sedimentation coefficient of 4S in comparison with the 3.5S and 8S peaks of prostate cytosols.
Abstract: Rat epididymis cytosol, labeled by incubation with dihydrotestosterone-l,2-3H at 0 C or by injection of testosterone-l,2-3H sc, contained 2 androgen-binding components, one of which demonstrated a high affinity for dihydrotestosterone. The mean constant of dissociation (Kd) of the high affinity component was 7.0 × 109M as determined by methods of dextrancoated charcoal adsorption, sucrose gradient ultracentrifugation and Sephadex gel equilibrium. When epididymis cytosol labeled with dihydrotestosterone-l,2-3H, in amounts which are bound largely by the high affinity binding component, was fractionated by sucrose gradient ultracentrifugation, the radioactivity migrated in a single peak with sedimentation coefficient of 4S in comparison with the 3.5S and 8S peaks of prostate cytosol. Acrylamide gel electrophoresis of similarly labeled epididymis cytosols revealed 2 peaks of radioactivity, while prostate contained only a single peak corresponding to the slower moving epididymis peak. Rat serum and cytosols of...
TL;DR: It is concluded that the “trigger” for LH discharge, in the rhesus monkey, consists of an effective increment in circulating estrogen levels which must be maintained for at least 12 hr and that this positive feedback action of the steroid is clearly operative only in nonlactating adult females.
Abstract: Subcutaneous injections of estradiol benzoate in oil, resulting in a sustained elevation of circulating estrogen levels, induced LH discharges markedly similar to the spontaneous preovulatory LH surges observed during the normal menstrual cycle. Exogenous estrogen leading to high plasma estrogen concentrations for brief periods (less than 12 hr) was ineffective in this regard. The discharge of LH in response to estrogen administration was observed in cycling and in ovariectomized females but not in intact males or in lactating females. It is concluded that the “trigger” for LH discharge, in the rhesus monkey, consists of an effective increment in circulating estrogen levels which must be maintained for at least 12 hr and that this positive feedback action of the steroid is clearly operative only in nonlactating adult females. (Endocrinology 89: 1034, 1971)
TL;DR: The effects of progressive removal of sialic acid (desialylation) on the immunological and biological activity of HCG, as measured by radioimmunoassay (RIA), ovarian ascorbic acid depletion assay (OAAD) and ventral prostate weight assay (VPW), have been evaluated.
Abstract: The effects of progressive removal of sialic acid (desialylation) on the immunological and biological activity of HCG, as measured by radioimmunoassay (RIA), ovarian ascorbic acid depletion assay (OAAD) and ventral prostate weight assay (VPW), have been evaluated. Two highly purified HCG preparations with potencies of about 12,000 IU/mg (bioassay, 2nd Int. Std. HCG) and about 5000 IU/mg (immunoassay, 2nd Int. Std. HCG), were used in these studies. Progressive desialylation was achieved by treating the HCG with varying amounts of Clostridium perfringens neuraminidase. Desialylation did not affect immunological activity. Progressive desialylation up to 25 % reduced biological activity by approximately 75% as measured by OAAD and VPW. Desialylation from 25 to 62% reduced biological activity further, the reduction being much more pronounced when measured by VPW than by OAAD, resulting in a considerable increase in the index of discrimination OAAD /VPW. Desialylation from 62 to 100% did not affect biological a...
TL;DR: Progesterone in the MRF significantly increased lordosis behavior in 15 min, while in the other regions progesterone had no effect even after 2 hr, and an empty tube, tubes containing cholesterol, procaine, or serotonin were similarly implanted to test the specificity of this response.
Abstract: In an attempt to localize the site of action of progesterone in facilitating sexual receptivity, ovariectomized rats were primed sc with 2 μg estradiol benzoate (EB) for 3 days, and on the fourth day progesterone crystals were applied directly to the brain by inserting a hormone-containing tube into chronic cannulae implanted unilaterally in the lateral and medial preoptic area (MPOA), anterior hypothalamus, ventromedial-arcuate area, or the caudal mesencephalic reticular formation (MRF). Also, in similarly primed animals bearing chronic cannulae in the MPOA or the MRF, EB was applied directly to the brain. Lordosis behavior was quantified 15, 30, 60, 90 and 120 min after progesterone application and compared to pretest values. Progesterone in the MRF significantly increased lordosis behavior in 15 min, while in the other regions progesterone had no effect even after 2 hr. To test the specificity of this response an empty tube, tubes containing cholesterol, procaine, or serotonin were similarly implanted ...
TL;DR: Estrogen and progesterone concentrations were determined in plasma for the periods of proestrus (4 days prior to estrus) and estrus and progesterone levels were highest on the fourth day before estrus, then progressively decreased to a nearly nondetectable level on the day prior to Esther.
Abstract: Estrogen and progesterone concentrations were determined in plasma for the periods of proestrus (4 days prior to estrus) and estrus. In trial I, blood was obtained at 0630 and 1800 hr every day for 4 days preceding estrus in 10 heifers. In trial II, blood was obtained on the day prior to estrus and every 2–4 hr on the day of estrus in four cows. Estrogen concentrations were determined by radioimmunoassay. Progesterone concentration was determined by the competitive protein binding assay. Plasma estrogen concentrations were less than 10 pg/ml until the day prior to estrus when the concentrations were 15–25 pg/ml. There were transient increases between 3 and 10 pg/ml during the first 3 days of proestrus. Progesterone levels were highest (5–12 ng/ml) on the fourth day prior to estrus, then progressively decreased to a nearly nondetectable level on the day prior to estrus. An estrogen concentration greater than 10 pg/ml was not detected until the progesterone concentration was below 2 ng/ml. Upon the onset of...
TL;DR: The data indicate that estrogens exert both negative and positive actions on LH release from the hypothalamo-hypophyseal system, and that progesterone exerts a block on only the positive action of estrogen.
Abstract: A series of experiments were con- ducted which involved the exogenous administra- tion of progesterone and estrogens to 15 ovariec- tomized ewes Plasma LH levels were measured by radioimmunoassay and the occurrence of behavioral estrus was determined by vasec- tomized rams Injection of estradiol benzoate (EDB) either at 2 or at 16 days after the end of progesterone priming produced 2 effects In- itially, a depression (0-12 hr post injection) of plasma LH, followed by an LH surge (12-24 hr post injection) EDB (50 tig) injected at 2, 8 and 14 days after the end of progesterone priming resulted in typical LH surges to all 3 injections However, the behavioral responses decreased with repeated injections of EDB When pro- gesterone was injected simultaneously with EDB on day 2 after the end of progesterone priming, both estrous behavior and the LH surge were totally inhibited but the initial de- pression in plasma LH was still apparent These data indicate that estrogens exert both negative and positive actions on LH release from the hypothalamo-hypophyseal system, and that progesterone exerts a block on only the positive action of estrogen (Endocrinology 88: 1184, 1971)
TL;DR: Plasma glucose and insulin of future obese mice were indistinguishable from those of future normal weight mice prior to weaning and the onset of obesity in affected animals, suggesting that insulin resistance was not structurally determined.
Abstract: The relationships between obesity, hyperglycemia, hyperinsulinism and insulin resistance have been studied in mice with congenital obesity (obob). Plasma glucose and insulin of future obese mice were indistinguishable from those of future normal weight mice prior to weaning and the onset of obesity in affected animals. Insulin sensitivity as determined by in vitro uptake of 2-deoxyglucose by intact diaphragm muscle was demonstrable prior to weaning in obob mice. Plasma insulin first rose significantly at age 26 to 32 days, preceding hyperglycemia. By 6 weeks insulin resistance was well developed, as shown by markedly elevated plasma insulin to glucose ratios and poor response of diaphragm muscle to insulin in vitro. Subsequent further rises in plasma insulin paralleled body weight rather than plasma glucose. No abnormalities in diaphragm muscle structure were seen by electron microscopy, suggesting that insulin resistance was not structurally determined. Intravenous and oral glucose tolerances were diabet...
TL;DR: In studies of parathyroid hormone secretion in organ culture, the quantitative aspects of calcium and magnesium ion control were compared, and the response of the glands in vitro paralleled their function in vivo, indicating that the system was a valid model for studying hormone regulation.
Abstract: In studies of parathyroid hormone secretion in organ culture, the quantitative aspects of calcium and magnesium ion control were compared. The response of the glands in vitro paralleled their function in vivo, indicating that the system was a valid model for studying hormone regulation. There was a first-order relationship between hormone release and the total concentration of divalent cation (calcium plus magnesium); calcium and magnesium ions were equivalent in blocking the release of hormone. These observations emphasize the physiologic regulation of parathyroid hormone secretion by both calcium and magnesium ions and suggest the possibility of a cation-ligand interaction in or at the surface of the parathyroid cell. (Endocrinology 88: 1477, 1971)
TL;DR: These behaviors were considered to be controlled by a common neuroendocrine activational mechanism in this species of ring doves.
Abstract: The site of action of androgen in the activation of sexual and aggressive behavior in castrate male ring doves was investigated by means of intracerebral implantation of testosterone propionate (TP). Pellet TP implants (large TP surface) area and 22, 25, and 27 gauge hypodermic tubing TP implants (surface area equal to cross sectional area of lumen) had a range of effectiveness that was inversely correlated with their surface areas. Bilateral 27 guage implants proved most effective in localization of activational sites. Most 27 gauge implants in the anterior hypothalamic-preoptic area activated sexual and aggressive behavior, but those in the preoptic area proper were particularly effective, w No distinction between the activation of copulatory, courtship, or aggressive behavior according to the location of the implants could be found. Thus these behaviors were considered to be controlled by a common neuroendocrine activational mechanism in this species. (Endocrinology 89: 1470, 1971)
TL;DR: Ovarian dysgenesis characterized by absence of follicles and corpora lutea associated with hyperplastic interstitial cells can be induced by removal of the thymus at the age of 2–4 days in all strains of mice examined.
Abstract: Ovarian dysgenesis characterized by absence of follicles and corpora lutea associated with hyperplastic interstitial cells can be induced by removal of the thymus at the age of 2–4 days in all strains of mice examined. Thymectomy before this age resulted in death due to wasting disease and thymectomy after the age of 7 days was no longer associated with postnatal ovarian development. Chronologic studies on the ovarian histology of thymectomized mice indicated that degeneration of follicles at early growing stages and subsequent arrest of their development might be fundamental histologic changes evoked by ablation of the thymus. The hypertrophy and hyperplasia of the interstitial cells in the fully advanced dysgenetic ovaries might suggest that these small ovaries perform an endocrinologic function. This assumption is supported by the fact that the uteri of thymectomized mice are not hypoplastic and they undergo rapid atrophic changes after removal of the dysgenetic gonads. Abnormal function of the small o...
TL;DR: A rhythm of pineal melatonin content persists and is phase-locked with the free-running, circadian rhythm of locomotor activity, however, the melatonin cycle was suppressed in intact rats that were maintained in continuous light.
Abstract: Male rats that were maintained in continuous darkness or blinded by enucleation exhibited circadian rhythms of wheel-running activity. Pineal bodies taken from rats that were killed during the phase of greater locomotor activity contained significantly more melatonin than the pineal bodies of rats killed during the phase of lesser activity. Thus, a rhythm of pineal melatonin content persists and is phase-locked with the free-running, circadian rhythm of locomotor activity. However, the melatonin cycle was suppressed in intact rats that were maintained in continuous light. (Endocrinology 89: 1361, 1971)