bluuebunny/crossref_metadata_2025_split huggingface dataset:
The passage of 5α-dihydrotestosterone from serum into cerebrospinal fluid and LH negative feedback in castrated rhesus monkeys
Authors: Abbott D. H. , Batty K. A. , Dubey A. K. , Herbert J. , Shiers H. M. 
Published: December 2008

ABSTRACT
Seven castrated monkeys were given either 50 or 100 μg 5α-dihydrotestosterone (DHT) propionate/kg per day. There was no correlation between serum and cerebrospinal fluid (CSF) levels of DHT, which remained very low in the CSF (0·3–0·6% of blood levels) despite the presence of high, supraphysiological amounts in the circulation. There was also no relation between unbound DHT in the blood and the CSF, in which all DHT is unbound. These results differ from previous work on testosterone, the metabolic precursor of DHT.
5α-Dihydrotestosterone propionate at the higher dose maintained suppressed levels of serum LH; LH in two out of four monkeys treated at the lower dose increased to levels observed in castrated, untreated rhesus monkeys. There was no predictable relationship between the amount of DHT in the CSF and levels of LH in the blood: by contrast, DHT in the blood was correlated with serum levels of LH. Levels of LH rose in monkeys in which total blood DHT fell below about 68 nmol/l and, even more obviously, if unbound DHT decreased to less than about 2 nmol/l.
Differences between the distribution of testosterone and DHT between blood and CSF cannot be explained by serum binding, lipid solubility or clearance from the brain, and suggest that there may be some mechanism for excluding DHT from the CSF. Though DHT reaches the CSF from the blood in small amounts, levels there do not relate predictably to those in the vascular compartment. It seems unlikely, therefore, that levels of intracerebral DHT are controlled by changes in those of the blood.
J. Endocr. (1985) 104, 325–330
Characteristics of bovine luteal cells in culture: morphology, proliferation and progesterone secretion in different media and effects of LH, dibutyryl cyclic AMP, antioxidants and insulin
Authors: O'Shaughnessy P. J. , Wathes D. C. 
Published: December 2008

ABSTRACT
The morphological and functional characteristics of cultured bovine luteal cells were examined. Dispersed luteal cells were cultured in either Ham's F12 medium or Dulbecco's Modified Eagle's Medium (DMEM), plus 10% adult bovine serum. After 18 h of culture, fibronectin was observed to be associated with some cells showing histochemical 3β-hydroxysteroid dehydrogenase (3β-HSD) activity. In DMEM, cells adopted a fibroblast-like appearance with a doubling time of 34 h while in Ham's F12, cells retained an epithelial-like morphology with a doubling time of 91 h. Dibutyryl cyclic AMP (dbcAMP) but not LH slowed proliferation and altered cell morphology in DMEM. Addition of insulin and dbcAMP was required to maintain 3β-HSD activity in cells cultured for more than 3 days.
Progesterone secretion was significantly greater in Ham's F12 than in DMEM although there was a rapid decline in basal secretion during culture in either medium. Both LH and dbcAMP stimulated progesterone secretion although the effects of dbcAMP were significantly greater than those of LH after 18 h of culture. Addition of insulin significantly enhanced basal, LH-stimulated and dbcAMP-stimulated progesterone secretion after 3 days of culture whereas several antioxidants were without effect. These studies indicate that the morphological and functional characteristics of cultured luteal cells may be best maintained in Ham's F12 plus dbcAMP and insulin.
J. Endocr. (1985) 104, 355–361
Effects of restricted maternal contact in neonatal rats on sexual behaviour in the adult
Authors: Forsberg G. , Abrahamsson K. , Södersten P. , Eneroth P. 
Published: December 2008

ABSTRACT
Rats, deprived of maternal contact and nutrition every alternate day starting on day 5 of life, attained a body weight at 45 days of age which was 50% of that of rats which had free access to maternal contact and nutrition. After 55 days of unrestricted food availability the body weight of the neonatally deprived rats was approximately 15% lower than that of the controls. Malnourished female rats showed normal behavioural oestrous cycles and became pregnant and lactated normally as young adults. After ovariectomy they showed higher lordosis quotients in response to treatment with oestradiol benzoate and progesterone than controls but lost less body weight in response to treatment with oestradiol-filled constant-release implants. Malnourished male rats ejaculated less frequently than controls in tests with sexually receptive female rats but this difference disappeared with repeated testing. The malnourished males showed longer ejaculation latencies and had somewhat higher serum concentrations of LH than controls after castration and treatment with testosterone-filled constant-release implants which reduced serum androgen concentrations to about 30% of the intact level. The results show that rats are capable of sustaining a rather severe neonatal nutritional deprivation without losing the capacity for essentially normal mating behaviour in adulthood.
J. Endocr. (1985) 104, 427–431
Identification of the major steroids in ovarian and adrenal venous plasma of the brush-tail possum (Trichosurus vulpecula) and changes in the peripheral plasma levels of oestradiol and progesterone during the reproductive cycle
Authors: Curlewis J. D. , Axelson M. , Stone G. M. 
Published: December 2008

ABSTRACT
The quantitatively major steroid hormones in ovarian and adrenal venous plasma of the female brush-tail possum were identified by gas chromatography–mass spectrometry. The ovarian vein plasma samples all contained oestradiol and its concentration was highest during the pro-oestrous phase of the reproductive cycle. During this phase the concentration of progesterone was below the limit of detection but at day 13 of the oestrous cycle and pregnancy, the concentration of progesterone exceeded that of oestradiol. Cortisol and corticosterone were the major steroid hormones found in all adrenal vein samples with cortisol predominant. Androgens with a 3-oxo structure, if present, were below the limits of detection in all plasma samples. Radioimmunoassays for the measurement of progesterone and oestradiol in peripheral plasma were used to follow changes in the concentrations of these steroids during the reproductive cycle.
Progesterone in serial blood samples was low at oestrus, rose gradually until day 7 and then increased more rapidly to reach a peak level of 21–29 nmol/l at around day 13. Any differences between the pregnant and non-pregnant cycles were minor. Oestradiol was only detected around oestrus when levels were variable (53·3±20·92 (s.e.m.) pmol/l; n = 4). The results indicate that the reproductive cycle of the brush-tail possum is characterized by a single peak of oestradiol at around pro-oestrus followed by gradually increasing levels of progesterone. Pregnancy appears to have no influence on the circulating concentrations of oestradiol or progesterone.
J. Endocr. (1985) 105, 53–62
Fasting impairs LH secretion in female rats by activating an inhibitory opioid pathway
Authors: Dyer R. G. , Mansfield S. , Corbet H. , Dean A. D. P. 
Published: December 2008

ABSTRACT
Two experiments were undertaken to investigate the way that fasting impairs LH secretion and to assess whether endogenous opioid mechanisms might be responsible for the impairment.
In the first experiment, pulsatile LH secretion was measured in a total of 51 chronically ovariectomized female rats. Initially 29 rats were subjected to food withdrawal for 24, 48, 72 or 120 h before the experiment. When compared with data collected from eight unfasted control rats, the 120-h fast was found to reduce significantly the mean peak and trough values of the LH pulses measured. However, in a subsequent study, the inhibition of pulsatile LH secretion by a 120-h fast was prevented in a group of eight rats given the opioid antagonist naloxone hydrochloride before the start of the blood-sampling period. Naloxone was without effect on pulsatile LH secretion in eight unfasted control rats.
In the second experiment, plasma LH concentrations were measured before and after unilateral electrical stimulation of the ventral noradrenergic tract (VNAT) in ovariectomized female rats pretreated with oestradiol benzoate. In 17 rats VNAT stimulation caused a significant rise in plasma LH, but after a 72-h fast this rise was significantly less than in unfasted control rats. However, pretreatment of fasted rats with naloxone (n = 9) significantly enhanced the VNAT-stimulated release of LH to the control values. Naloxone did not potentiate VNAT-stimulated LH release in unfasted animals (n = 6) or LH release in control unstimulated rats (n = 12).
The experiments indicate that both pulsatile LH secretion, and LH release caused by VNAT stimulation, are impaired by an acute fast. In both cases, the impairment is prevented by pretreatment with naloxone. Thus fasting probably activates an inhibitory opioid pathway within the brain to inhibit LH secretion.
J. Endocr. (1985) 105, 91–97
Mechanisms of release of prolactin from fowl anterior pituitary glands incubated in vitro: effects of calcium and cyclic adenosine monophosphate
Authors: Hall T. R. , Harvey S. , Chadwick A. 
Published: December 2008

ABSTRACT
Fowl anterior pituitary glands were bisected and each half was pretreated in either Medium 199 or medium containing EGTA to deplete endogenous calcium (Ca2+) stores, after which they were incubated in Medium 199, or Ca2+-free medium, containing prolactin release-stimulating agents and verapamil, a Ca2+ channel blocker. High K+ concentrations, hypothalamic extract, synthetic thyrotrophin-releasing hormone (TRH) and dibutyryl cyclic AMP (dbcAMP) all stimulated release of prolactin from control (non EGTA-treated) hemianterior pituitary glands. The effects of TRH and dbcAMP were not additive, but the response to submaximal concentrations of TRH was augmented by theophylline, a phosphodiesterase inhibitor. Reduction of Ca2+ availability with EGTA or verapamil reduced basal release of prolactin, prevented the prolactin-stimulating effects of high K+ concentrations and TRH, and markedly attenuated responses to hypothalamic extract and dbcAMP, EGTA being more effective than verapamil. Increasing the Ca2+ concentration of the medium did not augment basal or stimulated release of prolactin.
These results suggest that both Ca2+ and cyclic AMP may act as intracellular mediators in the release of prolactin. Both basal and stimulated release of prolactin depend upon the presence of Ca2+. Although influx from the medium may be the major source of Ca2+, endogenous stores of Ca2+, perhaps mobilized by dbcAMP, may be able to maintain some release of prolactin. The prolactin-stimulating effects of TRH may be mediated by cyclic AMP.
J. Endocr. (1985) 105, 183–188
Effect of intravenous bovine growth hormone or human pancreatic growth hormone-releasing factor on milk production and plasma hormones and metabolites in sheep
Authors: Hart I. C. , Chadwick P. M. E. , James S. , Simmonds A. D. 
Published: December 2008

ABSTRACT
Although it is well known that exogenous bovine GH (bGH) increases milk yield in ruminants it has not been possible to determine whether an increase in endogenous GH secretion has the same effect. The recent isolation of human pancreatic GH-releasing factor (hpGRF-44) has enabled this comparison of the effects of bGH and hpGRF-44 on milk production in sheep.
Three pairs of Dorset ewes underwent three 4-day treatments according to a Latin square design. Treatment 1 involved: 2-hourly i.v. injections (∼ 3·0 ml) of bGH (15 μg/kg; 1·8 units/mg); treatment 2: 2-hourly i.v. injections (∼3·0 ml) of hpGRF-44 (0·6 μg/kg); treatment 3: 2-hourly i.v. injections (3·0 ml) of the vehicle. Treatment periods were separated by 10 days. Sheep were milked twice daily and the milk was analysed for fat, protein and lactose. Blood samples (5·0 ml) were taken before and at 15, 45, 75 and 100 min after every third injection throughout the 4 days. Plasma was analysed for insulin, glucose, urea and non-esterified fatty acids (NEFA).
The changes in plasma GH stimulated by hpGRF-44 were consistent and repeatable throughout the 4 days of treatment. In comparison to the controls, treatment with hpGRF-44 and bGH significantly increased average plasma GH (μg/l) for the 4 days (control, 5·7±0·2 (s.e.m.); hpGRF-44, 12·3±0·4, P<0·001; bGH, 14·5±0·5, P<0·001), and this was accompanied by similar increases in milk yield (hpGRF-44, 26·7±2·6%, P<0·001; bGH, 30·7±2·9%, P<0·001) and the concentration of milk fat (g/kg) (control, 28·6±0·5; hpGRF-44, 33·2±0·5; bGH 34·8±1·5, P<0·01 for both treatments). The post-treatment decline in milk yield was much slower after hpGRF-44 than after bGH injections. Both treatments stimulated significant increases in the average concentrations of plasma insulin, glucose and NEFA, and plasma urea was significantly reduced by treatment with bGH only.
It is concluded that raising endogenous GH secretion is equally as effective as exogenous bGH in stimulating milk production in sheep.
J. Endocr. (1985) 105, 189–196
Oestrogenic regulation of testicular androgen production during development in the rat
Authors: Keel B. A. , Abney T. O. 
Published: December 2008

ABSTRACT
The influence of age on the sensitivity of the testis to oestrogens was investigated. Intact male rats at 10, 25, 40 and 53 days of age were injected s.c. with vehicle, 5 or 50 μg oestradiol or diethylstilboestrol (DES)/100 g body wt twice daily for 2 days; the animals were killed 12 h after the last injection. Subsequently, the concentrations of testicular androgens and serum LH, prolactin, testosterone and androstanediol (5α-androstane-3α, 17β-diol) were measured. Testicular androgen production was determined in vitro in the presence or absence of human chorionic gonadotrophin (hCG) or dibutyryl cyclic AMP (dbcAMP). Androgens in the serum and testes displayed an age-related alternating pattern with androstanediol being the major androgen produced at 27 days of age. As a result of oestrogen treatment, serum LH concentrations were decreased while serum prolactin was increased. Serum testosterone was decreased by 36–55% in the 12-day-old group and further reduced by 95% of control values by day 55; serum androstanediol was less sensitive to oestrogen suppression. Testicular concentrations of both testosterone and androstanediol exhibited a marked reduction in 12-day-old animals as a result of oestrogen administration. These values were reduced by 85–95% at day 27 and remained suppressed even at 55 days. Basal production of testosterone was unaffected by oestrogen treatment in 12- and 27-day-old animals but was markedly decreased by day 42. Significant suppression of basal production of androstanediol was observed as early as day 12. Oestradiol treatment caused a significant reduction in hCG responsiveness of both androgens at days 12, 42 and 55. Oestrogen administration resulted in a significant (32–59%) decline in dbcAMP-responsive testosterone production in the 42-day group and a further suppression in the 55-day group. A marked inhibition of dbcAMP-stimulated androstanediol production was also observed in the 42- and 55-day groups. Testosterone production in response to dbcAMP was not significantly altered in the 12- and 27-day groups. With few exceptions the effects of oestradiol and DES on testicular function were similar. The data presented here suggest that the inhibitory effects of oestrogens become more pronounced as the animal approaches adulthood, that oestradiol and DES are similarly effective in regulating testicular function at all ages studied and that the production of both testosterone and androstanediol are suppressed by oestrogen administration.
J. Endocr. (1985) 105, 211–218
Subcellular compartmentation of prolactin in rat lactotrophs
Authors: Torres A. I. , Aoki A. 
Published: December 2008

ABSTRACT
The intracellular localization of different molecular forms of prolactin was studied in various experimental models covering a wide range of secretory states.
By correlating electron microscopy, morphometry and quantification of monomeric (small) and polymeric (big) prolactin after differential extraction procedures, big prolactin was found stored in secretory granules while small prolactin was loosely associated with all organelles involved in hormone synthesis and processing. No correlation with levels of lactotrophic secretory activity was detected by either the number of secretory granules or prolactin content in lactotrophs.
J. Endocr. (1985) 105, 219–225
Influence of vitamin D on mineral metabolism, hormonal status and bone histology in lactating rats and their pups
Authors: Cancela L. , Marie P. J. , Le Boulch N. , Miravet L. 
Published: December 2008

ABSTRACT
Mineral, hormonal and skeletal changes were determined in vitamin D-deficient (−D) and vitamin Dreplete (+D) mother rats and in their litters on day 20 of lactation. These results were compared with those obtained in −D mothers and pups, after giving the mothers an oral supplement (10 i.u. vitamin D3/day) during the period of lactation (20 days). Compared to +D animals, both −D lactating mothers and their pups exhibited extremely low plasma levels of 25-hydroxyvitamin D3 (25-OH-D3), diminished 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) and increased levels of immunoreactive parathyroid hormone (iPTH). Vitamin D-deficient mothers also had higher levels of calcitonin and lower levels of prolactin than +D mothers. All − D animals (mothers and pups) showed increased osteoclastic bone resorption and severe osteomalacia as shown by decreased bone ash, decreased calcification rate and increased endosteal osteoid surface, volume and thickness. In mothers treated with vitamin D3 during lactation, nearly all the plasma variables measured, as well as bone histomorphometric features, were normal. In contrast, their pups still showed rickets and osteomalacia, despite normal levels of 25-OH-D3 and calcium in the plasma. These pups had raised plasma levels of 1,25(OH)2D3 and iPTH associated with persistent stimulation of bone resorption. This study showed that (1) severe vitamin D deficiency in lactating rats produced marked osteomalacia and secondary hyperparathyroidism in both mothers and pups, and (2) vitamin D treatment of − D mother rats during lactation (10 i.u. vitamin D3/day) reversed the mineral, hormonal and skeletal abnormalities in mothers but not in pups.
J. Endocr. (1985) 105, 303–309
Leydig cell resistance to the cytotoxic effect of ethylene dimethanesulphonate in the adult rat testis
Authors: Morris I. D. 
Published: December 2008

ABSTRACT
Weekly doses of the Leydig cell cytotoxic ethylene dimethanesulphonate (EDS) were administered to adult male rats in an attempt to study the endocrine activity of the testis in the absence of Leydig cells. One week after the first dose serum testosterone and LH concentrations and seminal vesicle weights were close to levels in castrated rats and testicular human chorionic gonadotrophin (hCG) binding was severely depressed. These changes were maintained for a further week but subsequently began to return to, but did not achieve, control levels. After six weekly doses seminal vesicle weight and serum testosterone concentrations were significantly higher than in the castrated rats. Serum LH concentrations were declining towards control values at 4 weeks but had risen again at 6 weeks. Serum FSH concentrations were raised to about 50% of the value in castrated rats throughout the period studied. Testis weight and hCG binding, which initially fell, were partially restored at 6 weeks and spermatogenesis was recovering. The data show that responses of the testis to multiple doses of EDS are similar to those after a single dose. This apparent resistance indicates that the regenerating Leydig cells are functionally different from the mature Leydig cell. The similarities between the maturing Leydig cell seen after EDS destruction and those in the immature rat suggest that EDS will provide a valuable model for the investigation of Leydig cell physiology.
J. Endocr. (1985) 105, 311–316
Effect of hypophysectomy on cyclic 3′,5′-nucleotide-metabolizing enzymes in the rat thyroid gland
Authors: Nagasaka A. , Hidaka H. , Itoh H. , Nakagawa H. , Kataoka K. , Yamaguchi A. , Iwase K. , Nakai A. , Ohyama T. , Aono T. , Miyakawa S. , Kawase K. , Miura K. 
Published: December 2008

ABSTRACT
Adenylate cyclase and cyclic AMP phosphodiesterase activities in the thyroid gland were significantly reduced after hypophysectomy, followed by a gradual restoration of the enzyme activities to the levels seen in sham-operated rats whereas a slight and persistent reduction was evident in guanylate cyclase and cyclic GMP phosphodiesterase activities in the same tissue. These changes in enzyme activities were restored by TSH administration but not by ACTH. The recovery of activity produced by TSH administration was inhibited by cycloheximide. Hypophysectomy, or TSH and cycloheximide administration, did not produce any significant changes in the concentrations of calmodulin, suggesting that the alteration of these enzyme activities is not induced by a decrease in the concentration of calmodulin. Since forskolin activation of adenylate cyclase did not restore the reduced activity in the hypophysectomized rat thyroid to the level found in the sham-operated control rat thyroid, we conclude that there is a reduction of the amount of enzyme after hypophysectomy rather than a change of the active site on adenylate cyclase. The spontaneous restoration of adenylate cyclase and cyclic AMP phosphodiesterase activities after hypophysectomy implies that cyclic AMP-metabolizing enzymes are responsive to an autoregulatory mechanism in thyroid follicular cells.
J. Endocr. (1985) 105, 363–369
Antagonism by growth hormone of insulin action in fetal sheep
Authors: Parkes M. J. , Bassett J. M. 
Published: December 2008

ABSTRACT
Insulin, glucose, lactate and alpha-amino acid nitrogen concentrations were measured in the plasma of ewes and their hypophysectomized fetal lambs during intravenous infusions of GH, prolactin or saline into the fetus in utero. Prolactin and saline had no effect on mother or fetus. Infusion of GH at 1·2 mg/kg per day for 2 days or at 0·4 mg/kg per day for 4 days caused a sustained twofold increase in the level of insulin and a smaller, but sustained, increase in the level of glucose in fetal plasma. We suggest that GH antagonizes the action of insulin in the fetus. Glucose supplies to the fetal brain and placenta may be protected by such antagonism of insulin use during glucose shortage.
J. Endocr. (1985) 105, 379–382
CHARACTERISATION BY HIGH PERFORMANCE LIQUID CHROMATOGRAPHY OF CIRCULATING GROWTH HORMONE RELEASING FACTORS IN A HUMAN PLASMA
Authors: Penny E.S. , Patience R.L. , Sopwith A.M. , Wass J.A.H. , Besser G.M. , Rees L.H. 
Published: December 2008

ABSTRACT
Three forms of circulating immunoreactive human growth hormone-releasing factor (ir-hGRF) have been identified from a patient whose acromegaly was associated with a disseminated carcinoid tumour. This is the first known report of the molecular forms of ir-hGRF in human plasma. High performance liquid chromatography (HPLC) on a C3, wide pore reversed-phase column and gel filtration chromatography were used in conjunction with a sensitive radioimmunoassay (RIA). The greatly elevated concentration of the ir-hGRF in plasma from this patient was 25,000 ng/l (normal range <60 ng/l). Gel filtration (G50) chromatography of the plasma revealed a single peak which coeluted with synthetic hGRF-40. However, reversed-phase HPLC of Vycorextracted plasma resolved the ir-hGRF into three components, which coeluted with synthetic hGRF-40 (69%), hGRF-44 (22%) and hGRF-37 (9%). At present it is not clear if the three forms are natural variants or whether either or both hGRF-40 and hGRF-37 are cleavage products of hGRF-44.