bluuebunny/crossref_metadata_2025_split huggingface dataset:
Comparison of ramp and square-wave exposure to thyrotrophin-releasing hormone or depolarizing K+ on cytosolic Ca2+ concentration and prolactin secretion in GH4C1 cells
Authors: Sato N , Wang X , Greer M A 
Published: December 2008

Abstract
The standard method of studying hormone secretion in vitro is to make instantaneous changes in the concentration of stimulators in the medium. However, in vivo the extracellular concentration of such substances changes more gradually; secretion does not occur in square-wave bursts and agonists or antagonists transmitted through the bloodstream are diluted and diffused by plasma or tissue fluid to further decelerate the rate of change in concentration at the cell surface. We have therefore compared in GH4C1 cells the dynamics of changes in cytosolic Ca2+ concentration ([Ca2+]i) and prolactin (PRL) secretion in response to two very different secretagogues, thyrotrophin-releasing hormone (TRH) and depolarizing K+, using a square-wave or ramp exposure for 5 min. The dynamics of hormone secretion were analysed by column perifusion (2 × 106 cells/column). Ca2+ dynamics were monitored by dual excitation microfluorimetry from 20–30 optically isolated cells using the Ca2+ indicator, fura-2. With square-wave exposure, both TRH (0·1–100 nm) and K+ (10–50 mm) induced dose-dependent increases in [Ca2+]i and PRL secretion. Concentrations of TRH >1 nm caused a two-phase increase in [Ca2+]i with an initial high-amplitude first phase and a low-amplitude second phase. Depolarizing K+ induced a sharp increase in [Ca2+]i which peaked within 15 seconds, then declined gradually on a sloping plateau. Both TRH and K+ induced an acute dose-dependent PRL secretory burst peaking within 2·5 min with a subsequent rapid decline. With ramp exposure, high doses of TRH (final concentration 10–100 nm) triggered an acute rise in [Ca2+]i; however, the peaks were clearly lower than those induced by the maximum concentration reached given as a square-wave. TRH (0·1–100 nm) induced PRL secretion in a dose-dependent manner. Ramp depolarizing K+ induced dose-dependent parallel 'ramp' increases in [Ca2+]i concentration and PRL secretion without a 'burst' rise in either. These data suggest that a rise in [Ca2+]i plays a more critical role in K+-induced than in TRH-induced PRL secretion; intracellular transduction systems which do not involve [Ca2+]i appear more important for the latter.
Journal of Endocrinology (1994) 142, 145–152
Determination of lignans and isoflavonoids in human female plasma following dietary supplementation
Authors: Morton M S , Wilcox G , Wahlqvist M L , Griffiths K 
Published: December 2008

Abstract
Plasma levels of the lignans enterodiol and enterolactone, and also the isoflavonic phyto-oestrogens daidzein, equol and genistein, are reported for postmenopausal Australian women consuming a traditional diet supplemented with linseed, soya flour or clover sprouts. Analysis was performed by gas chromatography-mass spectrometry, after enzymatic hydrolysis and ion-exchange chromatography. Following linseed supplementation, combined levels of enterolactone and enterodiol reached 500 ng/ml, whereas after soya flour or clover sprouts the respective concentrations of equol, daidzein and genistein reached 43, 312 and 148 ng/ml. Not all subjects were able to produce equol from daidzein. The possible relationship and role of these weak dietary oestrogens as restraining factors in the development of hormone-dependent cancers in Asian populations is discussed.
Journal of Endocrinology (1994) 142, 251–259
The hormonal regulation of the oestrogen receptor in rat liver: an interplay involving growth hormone, thyroid hormones and glucocorticoids
Authors: Freyschuss B , Sahlin L , Masironi B , Eriksson H 
Published: December 2008

Abstract
The regulation of the formation of the hepatic oestrogen receptor (ER) in adult female rats was studied by assaying steady state levels of ER and ER messenger RNA under different endocrine conditions. Hypophysectomy (HX) drastically reduced ER levels from 67·5 ± 7·9 to 8·4 ± 0·5 (means ± s.e.m.) fmol/mg cytosolic protein. Continuous infusion of growth hormone (GH) to HX animals tripled ER and doubled ER mRNA levels. Treatment with triiodothyronine T3) in a high dose (10 μg/day) doubled ER mRNA levels. The effects of T3 were dose-dependent, since a lower dose (1 μg/day) increased neither ER nor ER mRNA levels. ER mRNA concentrations were increased by GH to 481 ± 44% and by T3 to 372 ± 35% of HX control levels 4 h after single injections of the hormones in HX animals. The glucocorticoid dexamethasone (DEX) alone increased neither ER nor ER mRNA levels in HX animals. DEX and GH in combination increased ER 5-fold and ER mRNA 2-fold compared with control levels in HX animals, whereas DEX and T3 in combination increased neither ER nor ER mRNA levels. Treatment with prolactin affected neither ER nor ER mRNA levels in HX rats.
Insulin-like growth factor I (IGF-I) mRNA and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) mRNA levels were measured. GAPDH mRNA levels were increased 2·5-fold in HX rats by DEX and T3 in combination and almost 2-fold by DEX and GH in combination. IGF-I mRNA levels in HX rats were increased 4·5-fold by continuous infusion of GH alone, 6-fold by GH and T3 in combination, and 2·5-fold by GH and DEX in combination.
These data indicate that both GH and T3 act directly on the liver to increase ER mRNA levels. GH, the most important of these hormones, also acts at the translational and/or post-translational level to increase ER protein levels. DEX treatment suppresses the stimulatory effects of T3, but not of GH.
Journal of Endocrinology (1994) 142, 285–298
Evidence for the presence of pro-oxytocin/neurophysin-converting enzyme in the human ovary
Authors: Guillou M-D , Camier M , Clamagirand C 
Published: December 2008

Abstract
The activity of pro-oxytocin/neurophysin (pro-OT/Np)-processing enzymes was determined in human granulosa cells, follicular fluids and purified secretory granules of corpora lutea. We detected the presence of an endoprotease which releases OT-Gly10-Lys -Arg12 on cleavage of the synthetic pro-OT/Np(1–20) peptide after the dibasic Lys11-Arg12 doublet. This endoprotease was inhibited by EDTA, but was not affected by phenylmethanesulfonyl fluoride and pepstatin. Enzymatic activity was markedly reduced by replacement of l-Arg by d-Arg in the basic amino acid doublet of the substrate. The molecular weight of this enzyme was estimated to be 60 kDa. These features closely resembled those of the endoprotease identified in the bovine pituitary. The endoprotease is a metalloenzyme, specific for the Lys-Arg doublet. We also detected a carboxypeptidasic activity, inhibited by guanidinoethane-mercaptosuccinic acid. In the light of our previous detection of the processing intermediates, OT-Gly-Lys-Arg, OT-Gly-Lys and OT-Gly, in human ovary, these observations are in favour of a pro-OT/Np-processing pathway in the human ovary comparable with that in the bovine ovary. Moreover, these results confirm that oxytocin post-translational processing occurs in the human ovary and strongly suggest that pro-OT/Np is synthesized locally.
Journal of Endocrinology (1994) 142, 345–352
An investigation of the effects of interleukin-1β on plasma arginine vasopressin in the rat: role of adrenal steroids
Authors: Chover-Gonzalez A J , Lightman S L , Harbuz M S 
Published: December 2008

Abstract
While the effects of cytokines on the hypothalamo-pituitary-adrenal axis have received a great deal of attention in recent years the effects of cytokines on posterior pituitary hormone release has been less well characterized. In the present study we have investigated the effects of a single i.p. injection of interleukin (IL)-1β on circulating levels of vasopressin (AVP) in the rat. We have found that the ability of IL-1β to increase plasma AVP is strongly influenced by circulating levels of glucocorticoid steroids. IL-1β did not affect plasma AVP in sham-operated control animals over the 4 h period of study. In contrast, following adrenalectomy we were able to stimulate AVP substantially with increases over the 4 h period. This effect was reduced by treatment of adrenalectomized rats with a low dose of dexamethasone and abolished with a high dose. These data suggest an inverse relationship between circulating levels of glucocorticoids and the ability of IL-1β to stimulate plasma AVP.
Journal of Endocrinology (1994) 142, 361–366
The effects of recombinant human insulin-like growth factor-I (IGF-I) administration on the levels of IGF-I, IGF-II and IGF-binding proteins in adolescents with insulin-dependent diabetes mellitus
Authors: Cheetham T D , Taylor A , Holly J M P , Clayton K , Cwyfan-Hughes S , Dunger D B 
Published: December 2008

Abstract
Insulin-dependent diabetes mellitus (IDDM) during puberty is associated with a reduction in circulating concentrations of insulin-like growth factor-I (IGF-I) and low IGF bioactivity. Altered levels of the IGF-binding proteins (IGFBPs), including low IGFBP-3 and elevated IGFBP-1, have also been described. These abnormalities have been linked to poor growth and deteriorating blood glucose control. We have therefore examined the effects of recombinant human IGF-I (rhIGF-I) administration on the levels of IGF-I, IGF-II, IGFBP-1, IGFBP-3 and IGF bioactivity in a group of 9 late-pubertal adolescents with IDDM.
This was a double-blind placebo controlled study with each individual admitted on two occasions when either rhIGF-I (40 μg/kg) or placebo was administered by subcutaneous injection in the thigh at 1800 h. Blood samples were then taken for the subsequent 22 h. The half-life of administered rhIGF-I (12·1–22·2 h) was similar to that previously described in normal subjects. There was a small increase in IGFBP-3 concentrations overnight following rhIGF-I administration when compared to placebo, whereas the levels of IGF-II decreased. Under strict euglycaemic conditions, the relationship between insulin and IGFBP-I did not appear to be affected by rhIGF-I administration although the levels of IGFBP-1 tended to be higher overnight. IGF bioactivity was low during the placebo study, and although within the normal adult range following administration of IGF-I, was still relatively low for adolescents in late puberty. Gel filtration chromatography revealed an increase in the fractions corresponding to the 150 kDa complex throughout the duration of the study and to a lesser extent the fractions corresponding to free IGF-I which reached a maximum of 7% of total IGF-I levels. In conclusion, the subcutaneous administration of rhIGF-I in a dose of 40 pg/kg to a group of adolescents with IDDM led to a sustained increase in IGF-I levels and a rise in IGF bioactivity despite a fall in IGF-II and a trend towards higher IGFBP-1 concentrations.
Journal of Endocrinology (1994) 142, 367–374
Short-term oxytocin treatment increases bovine milk yield by enhancing milk removal without any direct action on mammary metabolism
Authors: Knight C H 
Published: December 2008

Abstract
The milk yield-enhancing effect of oxytocin administered either before or after milking was examined using a within-animal model. Eight cows in mid-lactation were changed from normal twice daily milking to a split-milking design, whereby half of the udder was milked at 0500 and 1500 h (control half; normal milking times), and the other half at 0800 and 1800 h (test half). This continued for 3 weeks. During the second week, oxytocin was administered as an i.m. injection immediately before the 0800 and 1800 h milkings. The test half was thus milked immediately after oxytocin administration, whilst the control half was milked 3 h before oxytocin. Milk yield decreased slightly on the adoption of split-milking. The decrease did not differ between udder halves and was not, therefore, due to inadequate milk-ejection in the test half compared with the control. During the week of oxytocin treatment, the yield decreased further in the control half but increased in the test half; consequently, the yield from the test half was significantly greater than that from the control half (P<0·05). The ratio of change in the test half relative to that in the control half was 1·12, significantly different from unity (P=0·002). Analysis of variance demonstrated a significant (P<0·001) interaction between udder half and oxytocin treatment, confirming that the effect of oxytocin was restricted to the test half, treated immediately before milking. This supports the established view that oxytocin acts by enhancing the milk-ejection reflex, and refutes a recent claim that the hormone has a direct stimulatory action on mammary metabolism.
Journal of Endocrinology (1994) 142, 471–473
The development of melatonin-binding sites in the ovine fetus
Authors: Helliwell R J A , Williams L M 
Published: December 2008

Abstract
The pineal hormone, melatonin, is important in the timing of seasonal reproduction in the sheep. Melatonin of maternal origin readily crosses the placenta; its function in the fetal sheep is, however, unclear. To gain an insight into the role of melatonin in ovine development we have identified specific melatonin receptors throughout gestation using 2-[125I]iodomelatonin and quantitative in vitro autoradiography. Specific binding was found at the earliest time studied at 30 days of gestation, over the developing thyroid (term=145 days). At 31 days of gestation specific labelling was found over the thyroid and pituitary glands, the spinal nerves, nasal cavity and developing bronchi. This binding was diminished by over 50% in the presence of 10−4 m GTPγS (an analogue of guanosine triphosphate) indicating that the 2-[125I]iodomelatonin binding at this early stage of gestation represents a receptor coupled to a regulatory G-protein. By 40 days of gestation specific binding was found over the nasal epithelium, cochlear epithelium, regions of the brain, especially the hind brain and the vestibulocochlear and glossopharyngeal nerves, and both the pars distalis and pars tuberalis of the pituitary. As gestation proceeded, labelling over the pars distalis appeared to become more scattered in nature while that on the pars tuberalis remained consistent. Saturation studies of both the neuronal and pituitary binding sites at 121 days of gestation and in the newborn lamb revealed a single class of high-affinity binding sites with Kd values in the picomolar range. Also at 121 days of gestation, binding over the fetal pars tuberalis was diminished in a dose-dependent manner by GTPγS, again confirming that specific binding is indicative of a receptor coupled to a regulatory G-protein. These data demonstrate a potential for sensitivity to melatonin from early in gestation, as well as the developmentally specific expression of the melatonin receptor in certain tissues, and suggest a wider role for melatonin in ovine fetal development than previously considered.
Journal of Endocrinology (1994) 142, 475–484
The evolution of changes in immunoreactive serum insulin-like growth factors (IGFs), IGF-binding proteins, circulating growth hormone (GH) and GH-binding protein as a result of short-term dexamethasone treatment
Authors: Miell J P , Buchanan C R , Norman M R , Maheshwari H G , Blum W F 
Published: December 2008

Abstract
Inhibition of growth in man and laboratory animals by glucocorticoid treatment is well recognized, yet we have previously shown that glucocorticoids may paradoxically enhance GH secretion and increase serum insulin-like growth factor (IGF) levels. IGFs circulate bound to high-affinity binding proteins (IGFBPs) which modulate their actions, and circulating GH may be associated with two binding proteins (GHBPs) of which the high-affinity GHBP has been characterized and is structurally identical to the extracellular domain of the GH receptor.
We have investigated the time-course of changes in GH, IGFs and their binding proteins induced by glucocorticoid treatment in normal male volunteers (n=12, age range 22–31 years) sampled at 0800 h daily before and during treatment with dexamethasone (2 mg twice daily) for 5 days. In addition, subjects were sampled at 30-min intervals over 7-h periods (0730–1430 h) during the day prior to dexamethasone (day 0), on day 1 following the first dose of dexamethasone and on day 5 following the last dose of dexamethasone. Mean serum IGF-I rose over the initial 72 h and remained elevated at 96 h (297 ± 11·5 compared with basal levels of 215·5 ± 9·3 μg/l, P<0·001) whereas IGF-II levels did not change (472·6 ± 20·5 vs 450·3 ± 21·7 μg/l, P=0·97). There was a concomitant rise in serum IGFBP-3 from basal levels of 3·69 ± 0·23 mg/l to a peak at 5 days of 4·16 ± 0·21 (P=0·003 vs day 1). Mean fasting IGFBP-1 levels fell significantly within 24 h, remaining low throughout the 5-day period whilst fasting insulin and C-peptide levels increased. IGFBP-2 rose within 24 h from basal levels of 315·5 ± 27·9 to 407·8 ± 27·3 μg/l at 24 h (P=0·01), then fell steadily to reach a nadir at 5 days of 240·4 ± 18·9 μg/l (P=0·02 vs basal levels). Peak GH secretion on day 1 (14·5 ± 3·7 μg/l) occurred between 4 and 5 h after dexamethasone administration. On day 5, the time of peak GH secretion was similar but the peak was attenuated (7·9 ± 1·2 μg/l, P<0·01 vs day 1). No morning rise in GH secretion had been observed prior to dexamethasone (day 0). GHBP fell steadily during the 5-day treatment period from basal levels of 29·3 ± 1·9% to day 5 levels of 24·4 1·6%, P=0·001.
The fall in GHBP as a result of dexamethasone treatment is in accordance with the reported inverse relationship between 24-h GH secretion and GHBP in health and disease states in man. This study has demonstrated clear temporal relationships between alterations in circulating levels of GH, IGF-I and IGFBP-1, -2 and -3 during dexamethasone treatment which support possible mechanisms whereby glucocorticoids induce a catabolic state through their endocrine and local tissue effects.
Journal of Endocrinology (1994) 142, 547–554
The effect of ovarian arterial infusion of transforming growth factor α on ovarian follicle populations and ovarian hormone secretion in ewes with an autotransplanted ovary
Authors: Campbell B K , Gordon B M , Scaramuzzi R J 
Published: December 2008

Abstract
Transforming growth factor α (TGFα) inhibits hormone production by cultured follicular cells but evidence of an effect of TGFα on ovarian hormone secretion in vivo is still required. Eleven ewes with an autotransplanted ovary received, by ovarian arterial infusion, either 5 μg/h recombinant rat TGFα (n=6) or placebo (n=5) for 12 h on day 10 of the luteal phase. Two hours before the start and 1 hour before the end of the infusion each ewe received a single injection of gonadotrophin-releasing hormone (GnRH; 150 ng i.v.). Two hours after the end of the infusion luteal regression was induced with prostaglandin F2α (PGF2α; 125 μg i.m.). Ovarian and jugular venous blood samples were taken at 10-min, 15-min or 4-h intervals from 2 h before the start of the infusion until 96 h after PGF2α and the rates of secretion of ovarian oestradiol, inhibin, progesterone and androstenedione were determined. Jugular venous concentrations of LH and FSH were also measured and follicle populations monitored by real-time ultrasound scanning.
Infusion of TGFα resulted in a significant (P<0.05) depression in the amplitude of the pulsatile response of oestradiol and androstenedione secretion to the GnRH-induced LH pulse at the end of the infusion. Ovarian inhibin secretion was acutely suppressed by TGFα infusion (P<0·001) and remained lower than controls for the period of the experiment. Luteal phase progesterone secretion was also acutely inhibited (P<0·001) by infusion of TGFα and in one treated ewe progesterone secretion was elevated 48–84 h after PGF2α. Jugular venous concentrations of FSH in TGFα-treated ewes were significantly (P<0·001) elevated over controls during the first 48 h of the follicular phase and the LH surge was delayed for about 10 h (P<0·05). Infusion of TGFα caused a marked decline (P<0·05) in the number of large follicles within 12 h of the end of the infusion. Two of the six treated ewes, including the one with high follicular phase progesterone, had unusually large (8·7 and 10 mm) follicles present from 48–96 h after PGF2α.
We conclude that direct arterial infusion of TGFα results in acute inhibition of ovarian steroid and inhibin secretion that is associated with induction of atresia in the population of large follicles. The lack of feedback of ovarian hormones results in a rebound increase of FSH which stimulates the growth of more ovarian follicles and the eventual re-establishment of ovarian hormone secretion and normal cyclicity.
Journal of Endocrinology (1994) 143, 13–24
Photoperiodic modulation of the dopaminergic control of pulsatile LH secretion in sheep
Authors: Tortonese D J , Lincoln G A 
Published: December 2008

Abstract
This study was conducted to investigate whether the photoperiodic regulation of the seasonal changes in pulsatile LH secretion in the ram involves changes in the activity of inhibitory hypothalamic dopaminergic (DA) pathways. To test this hypothesis, a series of experiments was carried out in Soay rams in which the effects of a DA-D2 receptor antagonist (sulpiride) or a DA-D2 receptor agonist (bromocriptine) on the pulsatile secretion of LH were determined under both long and short days. In each experiment blood samples were collected every 10 min for 8 h starting at the time of vehicle, sulpiride or bromocriptine injections to assess concentrations of LH. Sulpiride (0·59 mg/kg, s.c.) administered to rams under long days induced an immediate and sustained increase in the secretion of LH that lasted for approximately 4 h (P<0·05; ANOVA); this LH response reflected both a rise in mean concentrations (0·247 ± 0·03 vs.0·452 ± 0·1 μg/1) and an increase in the frequency of LH pulses (0·5±0·5 vs. 2·33±0·42 pulses/8 h; P<0·01). In contrast, under short days sulpiride had no effect. Bromocriptine (0·06 mg/kg, s.c.) administered to rams under long days, when LH concentrations were low, was without effect, but when given to rams under short days significantly (P<0·05) suppressed mean LH concentrations (0·627 ±0·08 vs. 0·320 ± 0·02 μg/l) and LH pulse frequency (4·86 ±0·46 vs. 2·43 ±0·37 pulses/8 h). In an additional experiment, pimozide (total dose: 0·16 mg/kg, i.m.), a DA antagonist less specific for DA-D2 receptors than sulpiride, was ineffective in modifying LH secretion in sexually inactive rams exposed to long days. These results are consistent with the hypothesis that an inhibitory dopaminergic system is involved in the regulation of pulsatile LH secretion in the ram. The induced changes in LH pulse frequency under long days (increased by sulpiride) and under short days (decreased by bromocriptine) indicate that, under both photoperiods, DA acts within the hypothalamus, via a specific DA-D2 receptor, to influence pulsatile GnRH secretion. A photoperiodic-induced activation of this inhibitory system may therefore represent the mechanism whereby long days suppress LH secretion and lead to the sexually inactive state characteristic of the non-breeding season.
Journal of Endocrinology (1994) 143, 25–32