bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lack of direct inhibitory action of oxytocin on progesterone production by dispersed cells from human corpus luteum
Authors: Richardson M. C. , Masson G. M. 
Published: December 2008

ABSTRACT
Suspensions of luteal cells were prepared from samples of human corpora lutea obtained during the luteal phase of menstrual cycles. Addition of oxytocin (1 μmol/l) to the various cell preparations had no effect on either basal production of progesterone or on steroidogenic responses to a range of concentrations of gonadotrophin.
J. Endocr. (1985) 104, 149–151
Peripubertal changes in the nature of LH
Authors: Buckingham J. C. , Wilson C. A. 
Published: December 2008

ABSTRACT
Administration of pregnant mare serum gonadotrophin (PMSG) to peripubertal rats, aged 27 days, induces ovulation provided the animals weigh more than 60 g at the time of the injection. In an attempt to determine whether the apparent immaturity of the ovaries in smaller rats is associated with an inability of the pituitary gland to secrete LH, the biological and immunological properties of LH in peripubertal PMSG-treated rats were examined. A single injection of PMSG caused a marked hypersecretion of LH in rats aged 27 days. The LH in the plasma of rats weighing more than 60 g was active in both the radioimmunoassay and the cytochemical bioassay but that in smaller rats was active only in the former. Plasma from both groups of rats stimulated the release of testosterone from dispersed Leydig cells.
Luteinizing hormone-releasing hormone stimulated the secretion, in vitro, of immunoreactive, cytochemically active LH by pituitary tissue from rats weighing over 60 g. The LH released in vitro from tissue from the smaller animals, like that in their plasma, was active in the radioimmunoassay but not in the cytochemical system. The results suggest that an abrupt change in the nature of LH occurs at puberty and that ovulatory cycles commence only when the pituitary gland secretes the adult form of LH with a full spectrum of biological activity.
J. Endocr. (1985) 104, 173–177
Drinking-induced changes in fowl adrenocortical activity: effect of visual and non-visual stimuli
Authors: Harvey S. , Klandorf H. , Lam S.-K. 
Published: December 2008

ABSTRACT
The deprivation of drinking water for 30 h resulted in increased corticosterone concentrations in the plasma of 8- to 10-week-old chickens. When water-deprived birds were allowed to drink ad libitum the corticosterone concentration declined within 45 min, to the level in hydrated controls, and remained suppressed thereafter. Similar reductions in the corticosterone concentrations were also observed in water-deprived chicks which were allowed to drink for only 5 min, 1 min or 5 s. The involvement of visual stimuli in mediating this adrenocortical response was demonstrated by a comparable decline in the corticosterone concentration in water-deprived birds which were presented with water but not allowed access to it. Non-visual stimuli also appeared to be causally involved in the adrenocortical suppression after drinking, since the intraperitoneal injection of tap water (40 ml per bird) also resulted in a lowering of the corticosterone level. However, in the absence of appropriate reinforcement from metabolic stimuli, a rebound in the corticosterone concentration was observed in birds prevented from drinking, in birds unable to satiate their thirst and in birds rehydrated (orally or intraperitoneally) without feeding.
These results demonstrate adrenocortical suppression in water-deprived chickens after free access to food and water and the involvement of visual and non-visual stimuli in mediating this response. The maintenance of adrenocortical suppression is dependent upon metabolic stimuli associated with food and water intake.
J. Endocr. (1985) 104, 225–231
A phylogenetic study of the structural and functional characteristics of corticosteroid binding globulin in primates
Authors: Robinson P. A. , Hawkey C. , Hammond G. L. 
Published: December 2008

ABSTRACT
A monospecific antiserum against human corticosteroid binding globulin (hCBG) has been used to identify structural similarities between hCBG and CBG in the blood of other primates and representative species of different vertebrate classes. Double immunodiffusion analysis indicated that only CBG in Old World monkeys and apes cross-react with the hCBG antiserum. This was confirmed by a solid-phase radioimmunoassay for hCBG which also demonstrated that CBG in apes is immunologically identical to hCBG and that Old World monkey CBG comprises most, but not all, of the hCBG epitopes. The electrophoretic mobilities of human, gorilla and gibbon CBG were similar (RF 0·50–0·51), but differed from Old World monkey CBG (RF 0·44–0·49) and chimpanzee CBG (RF 0·47). Although serum/plasma cortisol binding capacities were similar in Old World primates, the dissociation half-times (t½) of cortisol were higher from human and ape CBG (18–25 min) than from Old World monkey CBG (14–18 min). The steroid binding specificities of human and ape (CBG corticosterone > cortisol > progesterone ≥ testosterone) were also different from those of Old World monkey CBG (corticosterone >> cortisol ≃ progesterone > testosterone). Lemur plasma cortisol binding capacity and CBG dissociation t½ of cortisol were similar to hCBG, but its steroid binding specificity was different (cortisol > corticosterone > progesterone ≥ testosterone) and it did not cross-react with the hCBG antiserum. We could not detect high affinity cortisol binding activity in blood samples from New World monkeys, and they did not cross-react with the hCBG antiserum. These results suggest that considerable modification in the steroid binding activity and structure of CBG has occurred since the evolutionary appearance of the primates, but that the rate of change decreased after the cladogenesis of Catarrhine primates.
J. Endocr. (1985) 104, 251–257
Identification and characterization of a human corticosteroid binding globulin variant with a reduced affinity for cortisol
Authors: Robinson P. A. , Hammond G. L. 
Published: December 2008

ABSTRACT
A corticosteroid binding globulin variant (CBGv) has been identified in a serum sample taken from an apparently healthy woman during late pregnancy. Identification was based on the observation that it exhibited approximately half the cortisol binding capacity expected when compared to its concentration measured by radioimmunoassay (RIA). Affinity purification of CBGv excluded the possibility that this anomaly was caused by assay interference, and demonstrated that immunoreactive CBGv was capable of binding cortisol. The CBGv had a molecular weight (63 800) similar to normal CBG, and no evidence of molecular aggregation was found by gel filtration. Although the electrophoretic mobility, isoelectric profile and immunochemical identity of CBGv appeared to be similar to normal CBG, it focussed as two distinct bands (pI 5·48 and pI 5·53) after desialylation with neuraminidase, unlike normal CBG which focusses only at pI 5·48. Investigation of the steroid binding characteristics of CBGv revealed a reduced association-rate constant (Ka = 1·05 × 109 1/mol) and dissociation half-time (12·5 min) when compared with normal CBG (Ka = 1·39 × 109l/mol and 25 min at 0 °C) but an apparently normal steroid binding specificity. Although the physiological significance of this variant is not known, the cortisol concentration in the variant serum was within the normal range of women during late pregnancy. No other CBG variants were identified among other normal controls (n = 66) or nine patients with Cushing's syndrome. It is suggested that comparisons between cortisol binding capacity and RIA will reveal other variants of CBG, and lead to greater understanding of their physiological significance.
J. Endocr. (1985) 104, 269–277
Human thyroid cells in monolayer retain the ability to secrete tri-iodothyronine in response to thyrotrophin
Authors: Ollis C. A. , Fowles A. , Brown B. L. , Munro D. S. , Tomlinson S. 
Published: December 2008

ABSTRACT
Confluent monolayer cultures of human thyroid cells secreted low levels of immunoassayable triiodothyronine (T3) and this process could be stimulated by TSH in a concentration-dependent manner. The characteristics of the response to TSH were related to the age of the thyroid cell culture both in terms of the relative sensitivity to TSH and the quantity of T3 released. Cells which had been in culture for 2–3 days (primary cultures) secreted high levels of T3 under unstimulated and TSH-stimulated conditions with a median effective dose (ED50) for TSH of 0·030 mu. TSH/ml. However, cells which had been subcultured and consequently had been in culture for a longer period of 6–7 days secreted lower levels of T3 under basal and stimulated conditions. This was approximately 30% of that released from primary cultures with an ED50 for TSH of 0·1 mu. TSH/ml. Reorganization of human thyroid cells into follicular structures was seen during growth with TSH but these cultures showed little response to subsequent acute stimulation by TSH; the return of a diminished, less sensitive response to TSH was seen after a recovery period of 8 h. The time-course of T3 release was dependent on the TSH concentration with low TSH concentrations stimulating T3 secretion after increased incubation periods. Human thyroid cells had lost the ability to concentrate and organify free iodide after several days in culture but were still secreting T3. This indicates the presence of intracellular stores of T3 which are released on stimulation with TSH, rather than new synthesis of T3.
J. Endocr. (1985) 104, 285–290
Blood pressure and metabolic effects of 9α-fluorocorticosterone and 9α-fluorodeoxycorticosterone in sheep
Authors: Scoggins B. A. , Coghlan J. P. , Denton D. A. , McCarthy P. J. , Mason R. T. , Tresham J. , Whitworth J. A. 
Published: December 2008

ABSTRACT
9α-Fluorocortisol has been postulated to have 'hypertensinogenic' as well as 'mineralocorticoid' and 'glucocorticoid' activity. The present study examined the blood pressure and metabolic effect in sheep of the structurally related steroids 9α-fluorodeoxycorticosterone (9α-FDOC) and 9α-fluorocorticosterone (9α-FB). Infusions of these fluorinated steroids at 0·63 and 0·67 mg/day respectively for 5 days produced falls in plasma potassium, but only 9α-FB increased urine volume. 9α-FDOC raised mean arterial pressure by 11 mmHg and 9α-FB raised it by 14 mmHg. Addition of a 9α-fluoro group appears to increase both 'mineralocorticoid' and 'hypertensinogenic' steroid potencies.
J. Endocr. (1985) 104, 291–294
Increase in plasminogen activator in the involuting uterus of the postpartum rat
Authors: Shimada H. , Okamura H. , Espey L. L. , Mori T. 
Published: December 2008

ABSTRACT
Plasminogen activator (PA) activity in the rat uterus was measured at fixed intervals post partum in order to determine whether this serine protease increases during the acute remodelling of tissue which occurs in the involuting uterus. Plasminogen activator activity was measured by an indirect method based on the hydrolysis of the chromogenic substrate S-2251 by PA-generated plasmin. At the time of parturition the control level of PA activity was 0·033 ± 0·018 (s.d.) μmol/4 mg uterine wet weight per 30 min. This activity increased fourfold to a peak of 0·131 ±0·036 at 3 days post partum, and then it declined steadily towards the control level during the next 7 days. Concomitantly, uterine weight decreased to 25% of the control weight by 3 days post partum, and it continued to decrease until day 15. In the 30 days post partum during which PA activity was monitored there was no significant change in plasmin inhibitors in the uterine extracts. The results suggest a correlation between PA activity and the process of tissue remodelling which occurs during involution of the rat uterus. This increase in PA might serve to activate a latent collagenase since the measured peak in PA activity happens to coincide with a reported increase in collagenolytic activity in the involuting rat uterus.
J. Endocr. (1985) 104, 295–298
Thyroid function in pyridoxine-deficient young rats
Authors: Dakshinamurti K. , Paulose C. S. , Thliveris J. A. , Vriend J. 
Published: December 2008

ABSTRACT
In pyridoxine-deficient young rats hypothalamic serotonin was decreased with no changes in the dopamine and noradrenaline content. Serum thyroxine and tri-iodothyronine concentrations were much lower in the deficient rats as compared to pyridoxine-supplemented controls. No significant difference between deficient and control groups in the serum TSH concentration was detected. Highly significant decreases in the content of pituitary TSH and in the number of pituitary thyrotroph secretory granules were found. These results suggest that the hypothyroidism of pyridoxine-deficient young rats might be of hypothalamic origin.
J. Endocr. (1985) 104, 339–344
Responses to prolactin secretagogues in oestrogen-treated rats suggest that the defect in prolactin regulation produced by oestrogen is at the level of the pituitary gland
Authors: Willoughby J. O. , Pederick H. , Jervois P. , Menadue M. , Judd S. J. 
Published: December 2008

ABSTRACT
Prolactin responses to pharmacological agents were used to characterize the defect in prolactin regulation which occurs after administration of high doses of oestrogen to rats.
Animals with chronically implanted venous cannulae were injected with 2 mg oestradiol benzoate in oil and 2–3 days later prolactin concentrations were measured after injections of saline, thyrotrophin-releasing hormone (TRH), fenfluramine, apomorphine and butaclamol. The responses were compared with those in oil-injected animals.
Hyperprolactinaemia in oestrogen-treated animals was unresponsive to apomorphine, but was even more sensitive to dopamine receptor blockade than controls. These results suggest that the lactotrophs in oestrogen-treated animals are already maximally suppressed by endogenous dopamine, though ineffectively.
Although there was an increased prolactin response to TRH in oestrogen-treated animals, there was an impaired response to fenfluramine, indicating suppressed serotonergic prolactin-releasing factor mechanisms.
Maximal endogenous dopaminergic activity and suppressed prolactin-releasing factor mechanisms are appropriate hypothalamic responses to hyperprolactinaemia. The operation of these responses in the earliest stages of the development of pituitary hyperplasia indicates that oestrogen induces a disturbance of prolactin regulation in the lactotroph, independent of hypothalamic control.
J. Endocr. (1985) 104, 447–452
Medroxyprogesterone acetate does not perturb the profile of steroid metabolites in urine during pregnancy
Authors: Yovich J. L. , Willcox D. L. , Wilkinson S. P. , Poletti V. M. , Hähnel R. 
Published: December 2008

ABSTRACT
The plasma concentrations of medroxyprogesterone acetate (MPA) in 14 women administered the progestagen for threatened abortion during the first 6 weeks of pregnancy were measured by specific radioimmunoassay. Treatment (52 nmol orally every 6 h) was continued to 18 weeks of gestation. The mean plasma concentration of MPA rose rapidly during day 1 of treatment to 14·1 ±1·84 nmol/l. It reached 21·5 ± 2·3 nmol/l by 7 days and subsequently stabilized at around 26·8±5·0 nmol/l by the end of week 2. Urinary steroid profiles were determined by gas–liquid chromatography and mass spectrometry for six of the MPA-treated women and compared with those of six untreated women of similar gestational age. No differences were detected between the two groups of women, suggesting that the administration of MPA during pregnancy did not alter qualitatively or quantitatively the metabolism and excretion into urine of progesterone and oestrogens.
J. Endocr. (1985) 104, 453–459
Spermatogenesis, seminal characteristics and reproductive hormone levels in mature rams with induced hypothyroidism and hyperthyroidism
Authors: Chandrasekhar Y. , Holland M. K. , D'Occhio M. J. , Setchell B. P. 
Published: December 2008

ABSTRACT
Mature Merino rams were made hypothyroid by daily oral drenching with methylthiouracil or hyperthyroid by daily subcutaneous injections of thyroxine for 8 weeks. Neither hypothyroidism nor hyperthyroidism had any apparent effect on either spermatogenesis or daily sperm production, but motility of ejaculated spermatozoa and circulating testosterone concentrations were reduced in both conditions. The ratio of testosterone concentrations in plasma from the internal spermatic vein to those in peripheral blood plasma was higher in hyperthyroid (21·2 ± 3·5) than in control (11·1 ±4·4 and hypothyroid (7·6±1·4) rams. The basal secretion rate for testosterone was slightly lower in hypothyroid rams and testosterone responses to human chorionic gonadotrophin and after LH-releasing hormone (LHRH) were very much reduced. Basal serum LH levels were low in both hypothyroid and hyperthyroid rams compared with controls whereas there were no differences in FSH levels. The LH response to exogenous LHRH was reduced in hypothyroid rams but not in hyperthyroid rams. Serum prolactin levels on the other hand were higher than control in both hypothyroid and hyperthyroid rams.
Reduced testosterone secretion in hypothyroid rams indicates that the normal function of Leydig cells depends on an adequate level of thyroid hormones. The decrease in circulating testosterone concentrations in hyperthyroid rams with normal secretion rates suggests an increased testosterone clearance rate in these animals. The decreased spermatozoal motility in hypo- and hyperthyroid rams suggests that the lowered testosterone level in these animals has altered the androgen-dependent maturation of spermatozoa in the epididymis. Changes in testis function together with decreased LH secretion in hypothyroid rams indicate that thyroid hormones can act at both the pituitary gland and testes to influence reproductive function in mature rams.
J. Endocr. (1985) 105, 39–46
Levels of dopamine and thyrotrophin-releasing hormone in hypophysial stalk blood during an oestrogen-stimulated surge of prolactin in the ovariectomized rat
Authors: de Greef W. J. , Klootwijk W. , Karels B. , Visser T. J. 
Published: December 2008

ABSTRACT
The changes in hypothalamic release of dopamine and thyrotrophin-releasing hormone (TRH) into the hypophysial portal vascular system during an oestrogen-stimulated surge of prolactin in ovariectomized rats were investigated.
A single injection of 5 μg oestradiol benzoate resulted in a reliable increase in the plasma levels of prolactin during the afternoon 3 days later. Anaesthesia did not block this afternoon surge of prolactin, although its magnitude was only half of that of unanaesthetized rats. Before and during this surge, hypophysial stalk blood was collected into methanol to analyse the hypothalamic release of dopamine and TRH. Immunoreactive TRH in these methanolic extracts eluted as a single peak with the same retention time as authentic TRH on reverse-phase high performance liquid chromatography. In comparison to the morning values, levels of dopamine decreased and those of TRH increased in hypophysial stalk blood by 50 and 240% respectively. These data indicate that hypothalamic dopamine and TRH may be involved in the afternoon surge of prolactin.
Daily treatment with parachlorophenylalanine, an inhibitor of serotonin synthesis, reduced the hypothalamic release of TRH by 50%, but did not prevent the afternoon surge of prolactin and TRH induced by oestradiol benzoate.
J. Endocr. (1985) 105, 107–112
Reappraisal of the influence of mammary distension on the frequency of milk ejection in the rat
Authors: Riggs C. M. , Sutherland R. C. , Wakerley J. B. 
Published: December 2008

ABSTRACT
Experiments were performed to reinvestigate the importance of mammary engorgement for activation of the milk-ejection reflex in the rat. Reflex milk ejection (measured by intramammary pressure recordings during a 2-h suckling test under anaesthesia) was compared in rats with engorged mammary glands (15-h separation from the pups, followed by sham-removal of milk) and in rats with drained mammary glands (15-h separation, followed by milk removal using a foster litter and exogenous oxytocin).
In experiment 1, multiple small (2 mu.) doses of oxytocin were used for milk removal: these were effective in emptying the mammary glands and caused no subsequent impairment or change in sensitivity of the mammary response to oxytocin. Using this draining procedure, no significant differences were observed in either the number or relative amplitude of the milk ejections, or the occurrence of pup stretch reactions between engorged and drained rats. Similar results were seen in experiment 2, where an identical draining protocol was used, but the rats were pretreated with propranolol before the suckling test. In experiment 3, large (250 mu.) oxytocin doses were used for milk removal, as in previous studies. Again mammary draining had no effect on milk ejection in a subsequent suckling test (with propranolol pretreatment). However, the number of stretch reactions shown by the pups was significantly (P < 0·001) reduced from 8·6 ± 1·4/2 h to 1·9 ± 0·6/2 h. This effect probably related to long-term impairment of the oxytocin response of the mammary glands following the draining procedure, and could not be attributed to the draining per se. The dissociation of milk ejections and pup behavioural responses using this method of draining the glands explains previous reports, based on behavioural observations, that mammary draining profoundly disrupts milk ejection. It is concluded that mammary engorgement in fact has little influence on the activation of the milk-ejection reflex in the rat.
J. Endocr. (1985) 105, 127–132
Immunocytochemical localization of vasopressin-binding sites in the rat kidney
Authors: Ravid R. , Swaab D. F. , Pool Chr. W. 
Published: December 2008

ABSTRACT
The rat kidney and brain are major target organs for vasopressin (VP). A procedure was developed for immunocytochemical staining of VP and its binding sites in the kidney. This procedure involved preincubation of kidney sections with the ligand, followed by immunocytochemical detection of VP.
The staining in renal tubules from Wistar rats was enhanced by preincubation of tissue sections with increasing concentrations of VP (6–6000 nmol/l). Staining was present in the epithelium of distal convolutions and collecting ducts (medullary and cortical portions) and more pronounced in the apical zone of the tubular epithelium. With high concentrations of VP in the preincubation, staining was also obtained in the thick ascending limb of the loop of Henle. There was no staining under any circumstances in proximal tubules. In the kidney of the Brattleboro rat homozygous for hypothalamic diabetes insipidus (DI) which congenitally lacks VP but responds to the peptide, exactly the same staining pattern was observed after preincubation with VP, but the maximal staining was less intense. The VP binding to the DI rat kidney, after 2 weeks treatment with VP (using Accurel implants), reached levels seen in the Wistar kidney after in-vitro preincubation with high doses of VP.
J. Endocr. (1985) 105, 133–140