bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of Leydig cell activity in vivo and in vitro in hypothyroid rats
Authors: Antony F F , Aruldhas M M , Udhayakumar R C R , Maran R R M , Govindarajulu P 
Published: December 2008

Abstract
Leydig cell steroidogenic activity under basal and stimulated conditions was studied in hypothyroid rats. Hypothyroidism was induced at a prepubertal age (30 days postpartum) by surgical thyroidectomy, and l-thyroxine (T4) supplementation (6 μg/100 g body weight/day for 30 days) to hypothyroid rats was begun after 30 days. Hypothyroidism for 60 days reduced serum LH and FSH without affecting prolactin. Serum and intratesticular testosterone and the specific activity of Leydig cell 3β- and 17β-hydroxysteroid dehydrogenases diminished in hypothyroid rats. The stimulatory effect of LH on Leydig cell steroidogenic activity and cAMP was also adversely affected in hypothyroid rats. All these changes were reversed by T4 supplementation. The present results suggest that prepubertal hypothyroidism suppresses both basal and stimulated Leydig cell activity in adult rats.
Journal of Endocrinology (1995) 144, 293–300
Effects of intranasal glucocorticoids on endogenous glucocorticoid peripheral and central function
Authors: Knutsson U , Stierna P , Marcus C , Carlstedt-Duke J , Carlström K , Brönnegård M 
Published: December 2008

Abstract
Glucocorticoids are among the most potent anti-inflammatory agents that can be used in the treatment of rhinitis. Their mechanisms of action are multiple and complex and a number of reports describe significant systemic effects of locally administered glucocorticoids. In order to evaluate the short-term systemic effects of intranasally administered glucocorticoids, 14 normal healthy subjects were treated with two doses of either budesonide (BUD) or fluticasone propionate (FP) for 2 weeks. Before treatment, at regular intervals during the treatment, 1 week and finally 6 weeks after termination of treatment, the effects on glucocorticoid receptor (GR) and methallothionein (MTIIa) mRNA expression levels were examined in peripheral lymphocytes using a solution hybridization assay. Serum cortisol, osteocalcin and urinary cortisol levels were also determined. An insulin tolerance test (ITT) was performed at the end of the second week of treatment and at the end of the 6-week washout period with no statistically significant change in cortisol response. In peripheral lymphocytes, GR mRNA levels were significantly down-regulated. MTIIa mRNA levels increased significantly. Serum osteocalcin decreased significantly during treatment with both BUD and FP. Serum cortisol decreased after 1 week of treatment whereas urinary cortisol was not affected until the second week of treatment. In conclusion, intranasal glucocorticoids at clinically recommended doses have not only significant systemic effects on adrenal function, but also have an effect on specific gene expression in peripheral lymphocytes. These effects are receptor-dependent, reversible, and according to serum and urinary cortisol levels and ITT, leave the hypothalamic-pituitary-adrenal function intact. Finally, these short-term systemic effects were not associated with any of the noticeable side-effects usually observed during long-term treatment with glucocorticoids.
Journal of Endocrinology (1995) 144, 301–310
IGF feedback effects on growth hormone secretion in ewes: evidence for action at the pituitary but not the hypothalamic level
Authors: Fletcher T P , Thomas G B , Dunshea F R , Moore L G , Clarke I J 
Published: December 2008

Abstract
The putative negative feedback effects of IGF-I and IGF-II on GH secretion were tested by intracerebroventricular (icv) and intrapituitary administration to sheep. Over two consecutive days, serial jugular blood samples were taken at 10 min intervals for 6 h from ewes (n=3/group) fitted with indwelling stainless steel cannulae into the lateral or third cerebral ventricles. The sheep were injected (icv) with either vehicle or purified ovine IGF-I (2, 4 or 8 μg). IGF-I injection had no effect on plasma GH secretion. Serial blood samples were taken from a second group of nine ewes in which ovine or recombinant human (rh) IGF-I was infused (2·5 μg/h for 2 h) into the third ventricle; once again, IGF-I failed to affect the episodic pattern of GH secretion. Three ewes fitted with indwelling stainless steel cannulae placed in the anterior pituitary gland were consecutively infused with either ovine or rhIGF-I (2·5 μg/h for 2 h) or vehicle. Plasma GH concentrations were suppressed in 3/3 sheep from 1–1·5 h after the commencement of infusion and GH levels remained low for the remainder of the sampling period. In another group of five ewes synergistic effects of IGF-I and IGF-II on GH secretion were tested by icv infusion of rhIGF-I, rhIGF-II, or rhIGF-I+rhIGF-II (5 μg/h for 2 h) or vehicle (sterile 10 mm HCl/saline). Each sheep received each treatment in a randomised design. Infusion (icv) of IGF-I and IGF-II alone or in combination failed to alter GH secretion.
These observations suggest that IGF-I derived from peripheral tissues may modulate GH release at the pituitary level but that IGF-I acts neither alone nor in conjunction with IGF-II as a negative feedback regulator of GH secretion via the hypothalamus in the ewe.
Journal of Endocrinology (1995) 144, 323–331
Type 1 angiotensin II receptors in rat and human sperm
Authors: Vinson G P , Puddefoot J R , Ho M M , Barker S , Mehta J , Saridogan E , Djahanbakhch O 
Published: December 2008

Abstract
The physiological factors which induce and maintain mammalian sperm maturation and motility generally remain unclear, although several agents are known to be involved. We describe here the application of immunocytochemical and immunoblotting methods to identify the angiotensin II type 1 (AT1) receptor in the tails of ejaculated rat and human sperm. Motility data on stimulated and unstimulated sperm from volunteers and patients attending fertility clinics showed that angiotensin II may increase both the percentage of motile sperm and their linear velocity, while the specific AT1 receptor antagonist DuP753 inhibited the action of angiotensin II on the percentage of motile sperm. In rat seminiferous tubules, AT1 receptors were present in primary spermatogonia and in spermatid tails, but immunoreactivity was not seen in sperm contained in caput or cauda epididymis, showing that AT1 receptor function is regulated during transit through the reproductive tract. Since local tissue reninangiotensin systems are present in both male and female tracts, the data suggest that angiotensin II has a role in the maintenance of sperm function and fertility.
Journal of Endocrinology (1995) 144, 369–
Reduced liver insulin-like growth factor-I gene expression in young zinc-deprived rats is associated with a decrease in liver growth hormone (GH) receptors and serum GH-binding protein
Authors: Ninh N X , Thissen J-P , Maiter D , Adam E , Mulumba N , Ketelslegers J-M 
Published: December 2008

Abstract
Zinc depletion attenuates growth and decreases circulating IGF-I. To investigate the mechanisms responsible for the IGF-I decline, we determined the effects of dietary zinc (Zn) deficiency on body and organ growth, serum IGF-I, serum GH-binding protein (GHBP), liver GH receptors and liver expression of their corresponding gene. After 1 week of adaptation to a normal zinc diet, a zinc-deficient diet (ZD; Zn, 0 p.p.m.) or a zinc-normal diet (CTR; Zn, 75 p.p.m.) was available ad libitum to 4-week-old Wistar rats for 4 weeks. Pair-fed animals (PF) received the zinc-normal diet in the same absolute amount as that consumed the day before by the ZD group. The food intake of ZD and PF rats was reduced by 32% (P<0·001) compared with the CTR group. Zinc depletion specifically reduced body weight gain (−22%, P<0·05), serum IGF-I concentrations (−52%, P<0·001), hepatic GH receptors (−28%; P<0·05) and serum GHBP levels (−51%; P<0·05), compared with the PF group. GH concentrations were reduced in ZD animals compared with CTR rats (P<0·01). The caloric restriction of PF animals also decreased body weight gain (−50%, P<0·001), serum IGF-I concentrations (−21%, P<0·05), liver GH receptors (−38%, P<0·001) and serum GHBP levels (−38%, P<0·01), when compared with the CTR group. Both ZD and PF groups had reduced liver IGF-I and GH receptor/GHBP mRNA levels in comparison with the CTR group (P<0·01). However, only liver IGF-I mRNA levels were specifically reduced by zinc deficiency (ZD vs PF rats; P<0·05). Our observations suggest that beside the decline of GH secretion, decreased hepatic GH receptors and/or GHBP concentrations might be responsible for the decline of circulating IGF-I in ZD animals.
Journal of Endocrinology (1995) 144, 449–456
Differential effect of selective block of α2-adrenoreceptors on plasma levels of tumour necrosis factor-α, interleukin-6 and corticosterone induced by bacterial lipopolysaccharide in mice
Authors: Haskó G , Elenkov I J , Kvetan V , Vizi E S 
Published: December 2008

Abstract
The effect of selective block of α2-adrenoreceptors on plasma levels of tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6) and corticosterone induced by bacterial lipopolysaccharide (LPS) was investigated in mice using ELISA and RIA. It was found that the LPS-induced TNF-α response was significantly blunted in mice pretreated with CH-38083, a novel and highly selective α2-adrenoreceptor antagonist (the α2/α1 ratio is >2000). In contrast, LPS-induced increases in both corticosterone and IL-6 plasma levels were further increased by CH-38083. Since it has recently been shown that the selective block of α2-adrenoreceptors located on noradrenergic axon terminals resulted in an increase in the release of noradrenaline (NA), both in the central and peripheral nervous systems, and, in our experiments, that propranolol prevented the effect of α2-adrenoreceptor blockade on TNF-α plasma levels induced by LPS, it seems likely that the excessive stimulation by NA of β-adrenoreceptors located on cytokine-secreting immune cells is responsible for this action. Since it is generally accepted that increased production of TNF-α is involved in the pathogenesis of inflammation and endotoxin shock on the one hand, and corticosterone and even IL-6 are known to possess anti-inflammatory properties on the other hand, it is suggested that the selective block of α2-adrenoreceptors might be beneficial in the treatment of inflammation and/or endotoxin shock.
Journal of Endocrinology (1995) 144, 457–462
Effects of indigestible dextrin on glucose tolerance in rats
Authors: Wakabayashi S , Kishimoto Y , Matsuoka A 
Published: December 2008

Abstract
A recently developed indigestible dextrin (IDex) was studied for its effects on glucose tolerance in male Sprague–Dawley rats. IDex is a low viscosity, water-soluble dietary fibre obtained by heating and enzyme treatment of potato starch. It has an average molecular weight of 1600.
An oral glucose tolerance test was conducted with 8-week-old rats to evaluate the effects of IDex on the increase in plasma glucose and insulin levels after a single administration of various sugars (1·5 g/kg body weight). The increase in both plasma glucose and insulin levels following sucrose, maltose and maltodextrin loading was significantly reduced by IDex (0·15 g/kg body weight). This effect was not noted following glucose, high fructose syrup and lactose loading.
To evaluate the effects of continual IDex ingestion on glucose tolerance, 5-week-old rats were kept for 8 weeks on a stock diet, a high sucrose diet or an IDex-supplemented high sucrose diet. An oral glucose (1·5 g/kg body weight) tolerance test was conducted in week 8. Increases in both plasma glucose and insulin levels following glucose loading were higher in the rats given a high sucrose diet than in the rats fed a stock diet. However, when IDex was included in the high sucrose diet, the impairment of glucose tolerance was alleviated. Moreover, IDex feeding also significantly reduced accumulation of body fat, regardless of changes in body weight.
These findings suggest that IDex not only improves glucose tolerance following sucrose, maltose and maltodextrin loading but also stops progressive decrease in glucose tolerance by preventing a high sucrose diet from causing obesity.
Journal of Endocrinology (1995) 144, 533–538
Central effects of growth hormone-releasing hexapeptide (GHRP-6) on growth hormone release are inhibited by central somatostatin action
Authors: Fairhall K M , Mynett A , Robinson I C A F 
Published: December 2008

Abstract
Growth hormone (GH) release is stimulated by a variety of synthetic secretagogues, of which growth hormone-releasing hexapeptide (GHRP-6) has been most thoroughly studied; it is thought to have actions at both pituitary and hypothalamic sites. To evaluate the central actions of this peptide, we have studied GH release in response to direct i.c.v. injections in anaesthetized guinea pigs. GHRP-6 (0·04–1 μg) stimulated GH release >10-fold 30–40 min after i.c.v. injection. The same GH response required >20-fold more GHRP-6 when given by i.v. injection. GH release could also be elicited by a non-peptide GHRP analogue (L-692,585, 1 μg i.c.v.), whereas a growth hormone-releasing factor (GRF) analogue (human GRF 27Nle(1–29)NH2, 2 μg, i.c.v.) was ineffective. A long acting somatostatin analogue (Sandostatin, SMS 201–995, 10 μg i.c.v.) (SMS) given 20 min before 200 ng GHRP-6 blocked GH release. This was unlikely to be due to a direct effect of SMS leaking out to the pituitary, since central SMS injections did not affect basal GH release, nor did they block GH release in response to i.v. GRF injections. We conclude that the hypothalamus is a major target for GHRP-6 in vivo. Since the GH release induced by central GHRP-6 injections can be inhibited by a central action of somatostatin, and other data indicate that GHRP-6 activates GRF neurones, we suggest that somatostatin may block this activation via receptors known to be located on or near the GRF cells themselves. Somatostatin may therefore be a functional antagonist of GHRP-6 acting centrally, as well as at the pituitary gland.
Journal of Endocrinology (1995) 144, 555–560
Increasing gestational age and cortisol alter the ratio of ACTH precursors:ACTH secreted from the anterior pituitary of the fetal sheep
Authors: McMillen I C , Merei J J , White A , Crosby S , Schwartz J 
Published: December 2008

Abstract
We have used a perifusion system and slices of the anterior pituitary of the fetal sheep combined with specific immunoradiometric assays to investigate the effect of increasing gestational age and cortisol infusion on the output of ACTH(1–39) and the ACTH precursors, proACTH and pro-opiomelanocortin, from the fetal sheep pituitary. Two slices from each fetal anterior pituitary at 106–113 days (n=3), 120–136 days (n=5) and 140–143 days (n=5) of gestation were used. Slices from each anterior pituitary were perifused with the perifusion buffer for at least 120 min prior to the infusion of cortisol (100 nm) for 30 min or buffer alone (control). The anterior pituitary output (fmol/5 min per mg pituitary) of ACTH(1–39) and the ACTH precursors were measured using specific immunoradiometric assays. There was a significant increase in the anterior pituitary secretion rate of ACTH(1–39) between 120 and 136 days (1·04 ±0·23 fmol/5 min per mg) and between 140 and 143 days of gestation (3·08 ±0·33 fmol/5 min per mg). In contrast, there was no change in the secretory rate of the ACTH precursors between 105 and 143 days of gestation. The ratio of the anterior pituitary output of the ACTH precursors:ACTH(1–39) therefore decreased between 120 and 143 of days gestation from 19·10 ±2·05 to 6·36 ± 0·58. There was no effect of cortisol infusion on the anterior pituitary secretion of either ACTH(1–39) or the ACTH precursors before 116 days of gestation. After 120 days, the anterior pituitary output of ACTH(1–39) was significantly decreased by cortisol with the maximal change (43 ± 7%) occurring 10–15 min after the start of cortisol inclusion in the perifusate. Cortisol also altered the secretion of ACTH precursors. Although there was no significant effect with respect to baseline secretion rates, precursor secretion was elevated at the beginning of perifusion with cortisol, compared with precursor secretion after cortisol. The ratio of the anterior pituitary output of ACTH precursors:ACTH(1–39) increased from basal values of 16 ±4 and 12 ±4 (precortisol infusion) to 48 ± 14 at 15 min after the start and 40 ± 14 at 45 min after the end of the cortisol infusion. The differential effects of increasing gestational age and cortisol infusion on the output of ACTH(1–39) and the ACTH precursors may be explained by a change in the functional populations of corticotrophs in the fetal sheep anterior pituitary. These changes may be important in the stimulation of the fetal adrenal cortex which occurs before delivery.
Journal of Endocrinology (1995) 144, 569–576
Oxytocin antagonists delay the initiation of parturition and prolong its active phase in rats
Authors: Antonijevic I A , Douglas A J , Dye S , Bicknell R J , Leng G , Russell J A 
Published: December 2008

Abstract
The physiological importance of oxytocin for the initiation and maintenance of labour and delivery is controversial. We investigated the effects of two novel peptide oxytocin antagonists on the onset and the progress of delivery in rats implanted with a jugular vein cannula one day before term. During delivery rats were given either an oxytocin antagonist (OVT16, n=10, or F382, n=7, 30 μg/kg) or vehicle (n=10, 9) after the birth of the second pup and the time to deliver five more pups was recorded. Other rats were given an injection of F382 (30 μg/kg, n=7) or vehicle (n=9) after the birth of the fourth pup and the time to deliver three more pups was recorded. In another experiment rats were given repeated injections of F382 (30 or 60 μg/kg, n=13, 11) or vehicle (n=32) prepartum on the day of expected term and the time of onset and the progress of delivery was recorded.
Rats given an antagonist after the second pup delivered the next five pups in 100 ± 8 min (F382) and 83 ± 12 min (OVT16), significantly slower than the respective controls (51 ± 6 and 49 ± 6 min, U-test, P<0·05). Four of the 7 rats given F382 after the fourth pup showed no prolongation of delivery (time between pups 4–7: 24·7±2·9 vs 27·5±3·1 min in controls), while in the other three rats delivery was prolonged (time between pups 4–7: 86 ± 4·3 min). The onset of delivery was significantly delayed in rats given repeated injections of F382 at 60 μg/kg on the afternoon of expected delivery but before labour had begun (median shift 14·5 h vs controls, U-test, P<0·05). These results suggest that in rats oxytocin is involved in both the initiation and the maintenance of parturition and that it is more important during the early rather than the later stages of delivery.
Journal of Endocrinology (1995) 145, 97–103
Epitope mapping and analysis of a growth-enhancing monoclonal antibody by limited tryptic digestion of porcine GH
Authors: Shieh H-M , Bass R T , Wang B S , Corbett M J , Buckwalter B L 
Published: December 2008

Abstract
In this study, the epitope of a murine PS-7·6 monoclonal antibody (mAb) which was raised against the recombinant porcine GH (pGH) and subsequently shown to enhance the growth-promoting activity of pGH in a hypophysectomized rat model, was mapped by the limited tryptic digestion of pGH. A pGH fragment corresponding to amino acid residues 70–95 was separated by reverse-phase HPLC and also immunoprecipitated by PS-7·6 mAb. This fragment was found in an RIA to compete with radiolabelled pGH for the binding of PS-7·6 mAb in a dose-dependent fashion. Several peptides covering this potential epitope region of pGH(70–95) were synthesized and assayed by competitive RIA. The results suggested that pGH(75–90) was the optimal sequence recognized by PS-7·6 mAb. Sequential alanine substitution of each residue of pGH(75–90) revealed that the side chains of Leu76, Ile83 and Leu87 were critical for binding to PS-7·6 mAb. Other residues could be replaced by alanine without substantially altering the binding affinity. The region of amino acids 75–95 comprises the C-terminal end of the second helix of pGH and the repeating pattern of i and i+3 (i+7) of the critical amino acids appears consistent with PS-7·6 mAb binding to the hydrophobic side of the helix. The sequence and the helical structure of the epitope of PS-7·6 mAb provide the basis for designing the effective peptide vaccines to enhance the growth performance of animals.
Journal of Endocrinology (1995) 145, 169–174
Corpuscles of Stannius and blood flow regulation in freshwater North American eels, Anguilla rostrata LeSueur
Authors: Butler D G , Oudit G Y 
Published: December 2008

Abstract
Cardiac output (CO), heart rate (HR), stroke volume (SV), dorsal aortic blood flow (DABF), dorsal aortic blood pressure (PDA) and plasma electrolytes were monitored in stanniectomized and sham-operated freshwater eels over a 3-week period; branchial shunting and systemic resistance (RSYS) were estimated. DABF was significantly reduced by 45% from 11·72±0·48 (control) to 6·55±0·41 (n=6; day 21) ml.min−1.kg−1 within 3 weeks after the removal of the corpuscles of Stannius. This large reduction in blood flow was due to a 25% decrease in CO and a 100% increase in estimated branchial shunting which preceded the fall in CO. CO was decreased from 16·07 ±0·31 (control) to 11·91 ±1 (n=6; day 21) ml.min−1.kg−1 through a reduction in SV; there was no significant change in HR. Estimated branchial shunting, a relative measure of branchial arterio-venous blood flow, corresponded to 2·53±0·18 ml.min−1.kg−1 (control; n=12), which represents 16% of baseline CO. Ventral and dorsal aortic pulse flows also decreased following stanniectomy. The decrease in DABF occurred in conjunction with a reduction in PDA which was measured for 12 days in a separate group of eels. Baseline PDA (3·03 ±0·1 kPa) significantly decreased by 15% to 2·55 ±0·13 kPa 4 days after stanniectomy. However, this fall in PDA was transient and accompanied by an elevation in derived RSYS. These results support the hypothesis that the corpuscles of Stannius are closely linked to cardiovascular regulation in freshwater eels. Electrolyte changes (hypercalcemia, hypomagnesia, hyperkalemia and hyponatremia) were temporally coupled to the changes in blood flows. Impaired cardiovascular function and altered patterns of blood flow to osmoregulatory organs such as the gills, kidney and skin may have led to some or all of the electrolyte disturbances which followed stanniectomy.
Journal of Endocrinology (1995) 145, 181–194