bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of intravenous administration of growth hormone-releasing factor (hpGRF-44) and Tyr-d-Trp-Ala-Trp-d-Phe-NH2 on plasma hormones and metabolites in goats
Authors: Hart I. C. , James S. , Perry B. N. , Simmonds A. D. 
Published: December 2008

ABSTRACT
It has recently been demonstrated that human pancreatic GH-releasing factor (hpGRF-44) and Tyr-d-Trp-Ala-Trp-d-Phe-NH2 (subsequently referred to as 'the peptide') release GH from rat pituitary glands maintained in vitro and, in the former case, increase circulating GH in rats and man. The commercial importance of discovering an agent capable of specifically enhancing GH secretion in ruminants stimulated the present study which examined: (1) the intravenous administration of both peptides on plasma GH, prolactin, insulin, glucose, urea and non-esterified fatty acids in goats and (2) the effect of the peptide on the release of GH from sheep pituitary glands maintained in vitro.
The peptide was injected into the jugular vein of goats in three different forms and at several concentrations (dispersal by shaking, 0·07 μg/kg; 0·7 μg/kg; ball-milled, 7·0 μg/kg, 70 μg/kg; dimethyl sulphoxide (5%), 7·0 μg/kg, 70 μg/kg). None of the treatments stimulated a significant increase in circulating GH. Nevertheless the peptide (20 μg/ml medium) was found to stimulate a 50–60% increase in the production of GH from sheep pituitary glands maintained in vitro.
The effect of intravenously injecting hpGRF-44 (1·0 pg/kg) was investigated in the present and absence of passive immunization with sheep anti-somatostatin immunoglobulin G (IgG) (a bolus of 600 mg, 3 h before treatment with hpGRF-44). Plasma GH was increased (P<0·001) within 15 min of treatment and the magnitude of the response was the same for both the immunized and non-immunized goats. A second peak was measured after approximately 75 min which was only significant (P < 0·05) in the immunized group. Although circulating insulin tended to increase after treatment with sheep anti-somatostatin IgG, neither passive immunization, nor hpGRF-44 nor the peptide stimulated any change in the plasma concentrations of the other parameters which were measured.
J. Endocr. (1984) 103, 173–178
Corticosterone availability in male rats at rest and during shock avoidance: differences among individuals, temporal patterns and effects of dexamethasone
Authors: Wade S. 
Published: December 2008

ABSTRACT
Repeated measurement of the time-integral of interstitial fluid free corticosterone concentration (corticosterone availability) under home-cage conditions, during exposure to recently unfamilar apparatus, and during active shock avoidance over 3 days, demonstrated extreme stability within individuals, and consistent differences among individuals, in corticosterone availability under home-cage conditions. These consistent differences among individuals were preserved, while mean levels were doubled, during exposure to apparatus and during shock avoidance after treatment with dexamethasone. However, this persistent pattern of differences among individuals was not apparent during shock avoidance in the absence of dexamethasone.
Shock avoidance provoked up to fourfold increases in corticosterone availability. Repeated measurements over 3 days showed consistent hour-to-hour increases within days and a gradual decline over days. Dexamethasone given 4 h before shock avoidance resulted in corticosterone availability intermediate between that in home-cage and that in the previous shock-avoidance session.
The situation-dependent loss of consistent interindividual differences is proposed to signal a qualitative change in regulation of corticosterone availability within individuals, and a tactic for using interindividual differences to study some aspects of complex regulatory systems is suggested.
The hour-to-hour increase in corticosterone availability during shock avoidance may be attributable to slow achievement of full adrenal output; the decline over days may be due to behavioural factors.
J. Endocr. (1984) 103, 187–194
Platelet-derived growth factor and multiplication-stimulating activity II, but not multiplication-stimulating activity III-2, stimulate [3H]thymidine and [35S]sulphate incorporation by fetal rat costal cartilage in vitro
Authors: Hill D. J. , Milner R. D. G. 
Published: December 2008

ABSTRACT
The actions of partially purified porcine platelet-derived growth factor (PDGF) and highly purified multiplication-stimulating activity (MSA) II and MSA III-2, which are somatomedins, were investigated on the incorporation of [3H]thymidine and [35S]sulphate by fetal rat costal cartilage in vitro. This was compared with their effects in the presence of 1% fetal calf serum (FCS) on the uptake of thymidine by growth-arrested fetal rat fibroblasts. Platelet-derived growth factor at concentrations of 0·21–21 μg/l enhanced the incorporation of both isotopes by fetal cartilage in the presence of 1% FCS, but had an inconsistent action on thymidine uptake and no significant action on sulphate uptake in serum-free medium. Platelet-derived growth factor promoted thymidine uptake by growth-arrested, isolated fetal rat fibroblasts. Multiplication-stimulating activity II (10–100 μg/l) stimulated the uptake of thymidine and sulphate by fetal cartilage in medium containing 1% FCS but had no consistent action in serum-free medium, although MSA II and PDGF had a synergistic effect on thymidine uptake in the absence of serum. Multiplication-stimulating activity III-2 had no consistent action on thymidine or sulphate incorporation by fetal cartilage in either serum-free or serum-supplemented medium. However, the same preparation of MSA III-2 stimulated the uptake of [3H]thymidine into fetal rat fibroblasts with a half-maximal response at a concentration of 5–10 μg/l. The results identify PDGF as a possible mitogenic agent for fetal rat connective tissues in vitro and show a differential sensitivity of fetal cartilage to MSA peptides.
J. Endocr. (1984) 103, 195–203
Secretory dynamics of 1α-hydroxycorticosterone in the elasmobranch fish, Scyliorhinus canicula
Authors: Hazon N. , Henderson I. W. 
Published: December 2008

ABSTRACT
Peripheral plasma concentrations, metabolic clearance rates (MCR) and blood production rates (BPR) of 1α-hydroxycorticosterone (1-OH-B) were determined in female dogfish (Scyliorhinus canicula) under varying environmental conditions. The constant-infusion technique, using high specific activity tritiated 1-OH-B, was applied to measure the MCR, and BPR were derived from the product of plasma concentration and MCR at equilibrium. Urea plasma clearances and apparent BPR were assessed in a similar manner. Fish were adapted stepwise to 140, 120, 90, 80, 70, 60 and 50% normal sea water (about 1000 mosmol/l). In all cases 1-OH-B was the major corticosteroid, cortisol and corticosterone were sought but never detected.
In environments of reduced osmolarity, plasma osmolarity, sodium, chloride and urea concentrations all declined, alongside increases in plasma concentrations, MCR and BPR of 1-OH-B. In fish held in environments at concentrations greater than normal sea water, plasma osmolarity, sodium, chloride and urea concentrations all increased. Plasma clearance of urea increased in fish held in environments more dilute than sea water, while it decreased in the more hyperosmotic waters. It is tentatively concluded that homeostasis of plasma composition, with particular respect to urea, is in part regulated by 1-OH-B in the dogfish.
J. Endocr. (1984) 103, 205–211
Stimulation of milk secretion with inhibition of milk ejection by corticosteroids during extended lactation in the rat
Authors: Flint D. J. , Clegg R. A. , Knight C. H. 
Published: December 2008

ABSTRACT
Milk yield declined significantly between days 22 and 28 of lactation in rats, when lactation was extended by frequent replacement of older litters with younger ones. Corticosterone implants but not cortisol injections or implants prevented this decline. Cortisol, however, appeared to inhibit milk ejection since the mammary glands became engorged with milk and milk yield was improved dramatically by oxytocin injections. In both cases corticosteroid concentrations increased approximately threefold above basal concentrations.
Both corticosteroids increased total mammary gland RNA content and lipoprotein lipase (LPL) activity of the mammary gland but were without effect on insulin binding. They also decreased LPL activity, lipogenesis and the number of insulin receptors on adipose tissue.
Serum prolactin and insulin concentrations were unaffected by any of the treatments.
The results suggest that corticosteroids (1) inhibit milk ejection under certain conditions, (2) may be circulating in lower concentrations, which thereby limit milk production, during prolonged lactation and (3) may improve milk yield during extended lactation in part by suppressing anabolic activity in adipose tissue.
J. Endocr. (1984) 103, 213–218
Differential effects of cryptorchidism and short photoperiod on testicular prolactin and LH/human chorionic gonadotrophin receptors in the golden hamster
Authors: Bartke A. , Klemcke H. G. , Amador A. G. , Talamantes F. 
Published: December 2008

ABSTRACT
Gonadal atrophy induced by short photoperiods in male golden hamsters is accompanied by a decrease in the total content of testicular prolactin and LH/human chorionic gonadotrophin (LH/hCG) receptors and a concomitant rise in the concentration of LH receptors. Atrophic testes are typically abdominal. In this study, we have compared the effects of experimentally induced cryptorchidism and the effects of a short photoperiod on testicular prolactin and LH/hCG receptors. Cryptorchidism produced the expected decrease in testicular weight and an increase in plasma FSH concentrations, without altering plasma concentrations of LH or prolactin and with a relatively small decrease in plasma testosterone. It also produced an increase in the concentration of prolactin and LH/hCG receptors without significant changes in their total content. Exposure to a short photoperiod decreased weights of testes and seminal vesicles and plasma levels of prolactin and testosterone, with no significant effects on plasma gonadotrophin levels. Short photoperiod also increased the concentration of LH/hCG receptors but, in contrast to the effects of cryptorchidism, it produced a precipitous decline in the total content of testicular receptors for both prolactin and LH/hCG. We conclude that changes in prolactin and hCG binding measured in membrane preparations from decapsulated testes of hamsters exposed to a short photoperiod cannot be explained by the abdominal position of the gonads, abnormalities of Sertoli cell function or changes in the relative proportion of Leydig cells in the atrophic testes.
J. Endocr. (1984) 103, 227–231
Central effects of photoperiod on reproduction in the ram revealed by the use of a testosterone clamp
Authors: Lincoln G. A. 
Published: December 2008

ABSTRACT
Over a 3-year period eight adult Soay rams were exposed to an artificial lighting regimen of alternating 16-week periods of long days (16 h light:8 h darkness; 16L:8D) and short days (8L:16D) to induce a seasonal cycle in reproduction and wool growth every 32 weeks. Early in the study the rams were castrated (four during long days and four during short days) and 48 weeks later the castrated animals were each given an s.c. implant of testosterone to increase the blood plasma concentration of testosterone to 14–20 nmol/l. The changes in the concentrations of LH, FSH and testosterone were measured in blood samples collected once or twice weekly while records were made of the changes in the size of the testes (before castration), the intensity of the sexual skin flush, the expression of aggressive and sexual behaviour and the rate of wool growth.
The results showed that in the castrated rams there were only minor changes in the blood levels of LH, FSH and the expression of aggressive behaviour related to the 32-week light cycle, while the sexual skin flush was permanently absent. However, after the commencement of the constant testosterone therapy, there were major changes in all the reproductive parameters related to the lighting regimen with a similar temporal relationship as observed in the rams before castration. Cyclic variation in wool growth occurred throughout the study related to the changes in photoperiod but this was not markedly affected by castration and testosterone replacement.
The conclusion is that photoperiod acts centrally within the brain to dictate the cyclic changes in reproduction and wool growth in the ram, but testosterone is required for the full expression of the effects on reproduction. In the normal seasonal sexual cycle, photoperiod affects both the secretion of testosterone and the responsiveness to testosterone, resulting in a peak of sexuality in autumn.
J. Endocr. (1984) 103, 233–241
Androgen-binding proteins in sheep epididymis: age-related effects on androgen-binding protein, cytosolic androgen receptor and testosterone concentrations. Correlations with histological studies
Authors: Carreau S. , Drosdowsky M. A. , Courot M. 
Published: December 2008

ABSTRACT
The androgen-binding protein (ABP) and the cytosol androgen receptor (Rc) were measured in the epididymis of sheep aged 50, 120 and 200 days. Specific binding protein was not detected at 50 days (infantile); near puberty (120 days), ABP was more concentrated in caput and cauda epididymal cytosols (117 and 183 fmol/mg protein respectively) than in corpus (53 fmol/mg) although Rc levels were low (3–5 fmol/mg). In postpubertal rams (200 days), ABP and Rc concentrations were higher in caput and cauda than in corpus epididymis. Testosterone concentrations at 50 days were not statistically different along the epididymis and varied from 0·3 to 0·8 pmol/mg protein. In 120-day-old animals, testosterone was more concentrated in caput and corpus (0·45 and 0·41 pmol/mg) than in cauda (0·17 pmol/mg); at 200 days, the testosterone contents were low (0·10–0·17 pmol/mg) in all parts of the epididymis. A ten-fold increase in plasma testosterone concentrations was observed between 50 and 200 days (1·31 to 11·71 nmol/l). Histological studies of the epididymis in the three groups of animals showed that the cell differentiation started in the cauda where the principal epithelial cells were higher (47–56 μm) than in the caput (31–38 μm) at 50 days. The principal cells of the caput were two- to threefold higher in postpubertal rams than in infantile lambs, a finding which is correlated with the levels of ABP and Rc. This may suggest an important physiological role of this region in the induction of sperm maturation.
J. Endocr. (1984) 103, 281–286
Effects of long-term administration of high doses of medroxyprogesterone acetate on hormone receptors and target organs in the female rat
Authors: Di Carlo F. , Racca S. , Conti G. , Gallo E. , Muccioli G. , Sapino A. , Bussolati G. 
Published: December 2008

ABSTRACT
The changes in oestrogen, progesterone and prolactin receptor levels in target organs, and the macroscopic and microscopic modifications of uterus, ovary, adrenal and pituitary gland induced by long-term administration of high doses of medroxyprogesterone acetate (MPA) were investigated in female rats. Medroxyprogesterone acetate was injected i.m. for 30 days at daily doses of 7·5, 15 and 75 mg/kg. Oestrogen and/or progesterone-binding capacities were remarkably reduced at all doses of MPA used both in the uterus and pituitary gland. Furthermore, MPA caused a very evident reduction in the weight of pituitary glands, ovaries, adrenals and uterus.
In all MPA-treated rats corpora lutea were absent from the ovaries, whereas the adrenals showed a significant reduction in the thickness of the cortex. In accordance with this, there was no evidence of ACTH-producing cells in the pituitary glands. Prolactin-producing cells were also absent, while GH-producing cells were present. Serum prolactin levels were significantly reduced at all doses of MPA used. A dramatic reduction of prolactin receptor concentrations was observed in the liver and the ovaries of MPA-treated rats.
The results suggest that MPA acts as an antioestrogenic drug both by reducing the number of oestrogen receptors in target tissues and by changing the structure (and perhaps the function) of those organs (pituitary glands, ovaries and adrenals) which are, directly or indirectly, a source of oestrogens. The decreased synthesis of prolactin and the reduction of the number of prolactin receptors (which, on the contrary, are both increased by oestrogens) might be considered as additional antioestrogenic effects of MPA.
J. Endocr. (1984) 103, 287–293
Maintenance of neonatal rat B cells in glucose-depleted medium: effect of medium with galactose and 2-deoxyglucose
Authors: Wakabayashi S. , Kagawa S. , Nakao K. , Mimura K. , Matsuoka A. 
Published: December 2008

ABSTRACT
Monolayer cultures of the pancreas of the neonatal rat were maintained for 7 days in glucose-depleted TCM 199 medium, supplemented with 5·5 mmol galactose/l, with or without 0·1 mmol 2-deoxyglucose/l. Under culture conditions without 2-deoxyglucose, the responsiveness of B cells supported on galactose was totally abolished by day 7 of culture, and islets degenerated. In contrast, the addition of 2-deoxyglucose to the galactose-supplemented medium promoted the survival and the function of B cells even in a glucose-depleted environment and, in addition, yielded the monolayers mostly consisting of endocrine cells by destroying fibroblasts selectively. On day 7 the recovery of insulin in the cells was higher than that of the cells grown in medium with galactose alone (10·7-fold), and than the initial level at day 0 (twofold). Furthermore, the response to an acute challenge with 16·7 mmol glucose/1 was 3·3-fold, to 10 mmol leucine/1 it was 8·5-fold, and to 10 mmol 2-ketoisocaproate/l it was 10·9-fold above each value observed on day 1. In summary, the above data indicate that morphologically intact, functionally competent endocrine B cells can be grown in medium free from glucose.
J. Endocr. (1984) 103, 377–381
Dopamine enters lactotrophs and reaches their secretory granules
Authors: Gallardo M. G. P. , Bilinski M. , Chiocchio S. R. , Tramezzani J. H. 
Published: December 2008

ABSTRACT
The presence of dopamine in the lactotroph cell, as well as in isolated prolactin secretory granules, was demonstrated by means of an histochemical reaction for electron microscopy. Biochemical assays further confirmed the presence of dopamine in the secretory granules.
Autoradiographic preparations examined by light microscopy showed dopamine internalization in dispersed anterior pituitary cells.
Isolated anterior pituitary lactotroph cells incorporated more [3H]dopamine than a fraction containing other anterior pituitary cells.
J. Endocr. (1985) 104, 23–28
Intravenous growth hormone: growth responses to patterned infusions in hypophysectomized rats
Authors: Clark R. G. , Jansson J.-O. , Isaksson O. , Robinson I. C. A. F. 
Published: December 2008

ABSTRACT
Young hypophysectomized rats were maintained with chronic indwelling i.v. cannulae attached via swivels to a multichannel pumping system programmed to deliver GH in a continuous or pulsatile pattern for several days. Continuous i.v. infusions of human GH for 5 days produced dose-dependent increases in body weight and tail length, without increasing food intake. A comparison of GH infusions by the s.c. or i.v. route showed that the direct i.v. route was threefold more effective. Pulsatile i.v. infusions of human or bovine GH at two doses (12 or 36 mu./day, eight pulses/day, 5-min duration, every 3 h) produced greater increases in body weight than continuous i.v. infusions of GH at the same daily dose. Continuous infusions of bovine GH produced a lower growth rate in the second of two consecutive 5-day treatment periods, whereas the responses to pulsatile GH did not diminish with time. Both body weight gain and long-bone growth were affected by the frequency of GH pulses; nine pulses per day were more effective than three pulses per day which in turn produced larger growth responses than one pulse per day. Keeping GH pulse frequency constant and varying pulse duration (4, 16 or 64 min) did not affect growth rates. In conclusion, long-term pulsatile i.v. infusions of GH mimic the endogenous secretory pattern, and are most effective when given at the physiologically appropriate pulse frequency.
J. Endocr. (1985) 104, 53–61
Hormone concentrations, mammary development and milk yield in goats given long-term bromocriptine treatment in pregnancy
Authors: Forsyth I. A. , Byatt J. C. , Iley S. 
Published: December 2008

ABSTRACT
Ten British Saanen goats were treated daily with 5 mg bromocriptine intramuscularly from week 8 of pregnancy until week 20 (day 140). By comparison with untreated control goats (n = 8), concentrations of prolactin in plasma were suppressed throughout the treatment period and remained significantly lower until 3 days prepartum, parturition occurring on day 153 ± 0·7 (mean ± s.e.m., n = 10). Growth hormone concentrations were low, but the incidence of levels exceeding 1 μg/l was increased in bromocriptine-treated goats. Plasma concentrations of placental lactogen, progesterone and oestrone sulphate were unaffected. The accumulation of pre-colostrum in the udder (lactogenesis stage I) was not affected by bromocriptine treatment in goats carrying twin fetuses, but in goats with single kids it was delayed by about 4–6 weeks to week 17 of pregnancy. Secretion could not be expressed from the udder and the concentration of α-lactalbumin in plasma remained low. Udder volume was significantly reduced in week 15–16 but not week 20–21 of pregnancy by bromocriptine treatment. Milk yields after 50 or 203 days of lactation were not significantly different from those in control goats. Placental lactogen concentrations in late pregnancy and udder volume in week 20–21 were the only variables measured which correlated with milk yield post partum. It is concluded that in vivo placental lactogen is an effective mammotrophic hormone, although less potent than prolactin as evidenced by the delay in lactogenesis stage I in bromocriptine-treated goats bearing single kids.
J. Endocr. (1985) 104, 77–85
Menstrual cycle and exposure to oestrogens unopposed by progesterone: relevance to studies on breast cancer incidence
Authors: Metcalf M. G. , Mackenzie J. A. 
Published: December 2008

ABSTRACT
It is claimed that the exposure of women to oestrogens unopposed by progesterone increases the risk of breast cancer. Despite indirect evidence in support of this claim, the impracticability of monitoring oestrogen and progesterone levels in large numbers of women for prolonged periods of time has meant that no direct demonstration of the effect has been made. A possible technique is suggested.
The ratio (R) of oestrogens to pregnanediol in urine has been used as an index of oestrogen exposure relative to progesterone. Samples were collected at weekly intervals on 700 occasions from 30 perimenopausal women, and on 519 occasions from 66 women with a history of regular menstrual cyclicity. Unusually prolonged episodes of unopposed high oestrogen excretion (R ≥ 100 for ≥ 2 successive weeks) were observed on 30 occasions in 15 of the perimenopausal women and on four occasions in the other women. In the perimenopausal group, these episodes occurred in 46·9% of the 32 menstrual cycles which were longer than 50 days compared with 6·9% of the 72 cycles which were shorter than 35 days (P < 0·001). The association of prolonged episodes of unopposed high oestrogen excretion with long menstrual cycles suggests the possibility of using menstrual cycle length as an index of oestrogen exposure during the menopausal transition.
J. Endocr. (1985) 104, 137–141