bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hormonal regulation of epidermal growth factor and insulinlike growth factor-I in adult male hypophysectomized rats treated with ethane dimethane sulphonate
Authors: Spiteri-Grech J. , Bartlett J. M. S. , Nieschlag E. 
Published: December 2008

ABSTRACT
There is increasing evidence implicating growth factors in the regulation of spermatogenesis and in-vitro studies have shown that epidermal growth factor (EGF) and insulin-like growth factor-I (IGF-I) interact with the gonadotrophins in regulating testicular function. In the present study, the effect of FSH, testosterone and GH treatment on serum IGF-I and intratesticular EGF and IGF-I concentrations in adult male hypophysectomized rats treated with ethane dimethane sulphonate (EDS) to destroy Leydig cells has been investigated. Hypophysectomy alone or followed by EDS treatment was associated with a significant increase in intratesticular EGF concentrations compared with normal controls (P<0·05). Treatment of hypophysectomized animals with a combination of GH, FSH and testosterone resulted in a return of intratesticular EGF concentrations to normal control levels. In a second group of animals treated with a 5 cm silicone elastomer implant of testosterone and FSH, intratesticular EGF concentrations were also not significantly different from those of normal controls. Following hypophysectomy alone or hypophysectomy and EDS treatment, a significant increase in circulating IGF-I concentrations occurred, which was only reversed following the administration of GH. In addition, increases in testicular IGF-I concentrations were evident in all treated animals compared with controls, an effect which was only partially reversed in animals treated with a combination of FSH and testosterone (1·5 or 5 cm implant). Similar results were obtained with a combination of GH and FSH or GH and testosterone, although GH alone had no effect on testicular IGF-I concentrations. A combination of GH, FSH and testosterone restored testicular IGF-I to concentrations not significantly different from controls. It is suggested that GH, FSH and testosterone can play an important role in regulating circulating and testicular IGF-I and testicular EGF in the adult rat, but the regulation of growth factor production is a complex process and a number of other factors are probably involved in vivo.
Journal of Endocrinology (1991) 129, 109–117
Mechanisms responsible for suppression of FSH and LH during lactation in the rat
Authors: Taya K. , Sasamoto S. 
Published: December 2008

ABSTRACT
Mechanisms responsible for suppression of FSH and LH secretion during lactation were investigated in rats, with special reference to the suckling stimulus and ovarian inhibin. Concentrations of immunoreactive inhibin in the peripheral plasma and bioactive inhibin in ovarian venous plasma were always low on days 3 and 5 of lactation in dams nursing eight pups, whereas values were always high on days 17 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups. There was an FSH surge within 48 h after removal of litters on days 3 and 5 of lactation in dams nursing eight pups, whereas plasma concentrations of FSH were unchanged within 48 h by removal of litters on days 17 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups. Plasma LH concentrations increased significantly compared with those of control animals within 24 h after removal of the litter on any day of lactation, regardless of the litter size.
Plasma FSH levels increased within 6 h after bilateral or unilateral ovariectomy in lactating rats only on the days when plasma concentrations of inhibin were high before ovariectomy, such as day 17 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups, whereas the mean concentrations of plasma LH showed no significant increase within 12 h after bilateral ovariectomy in these lactating rats. Treatment with progesterone or oestradiol-17β after unilateral ovariectomy did not inhibit the increase in plasma FSH levels, while the increase in plasma concentrations of FSH after surgery was completely inhibited by injecting inhibin (porcine follicular fluid). Treatment with steroid hormones inhibited the basal levels of LH in unilateral ovariectomized lactating rats. Plasma FSH concentrations increased sharply within 6 h after a single i.v. injection of anti-inhibin serum on days 10, 15 and 20 of lactation in dams nursing eight pups and on day 5 of lactation in dams nursing two pups, whereas only a small but significant increase in concentrations of FSH was noted 6 h after the antiserum treatment on day 5 of lactation in dams nursing eight pups. Concentrations of plasma LH were unchanged by treatment with antiserum in lactating rats throughout lactation.
These findings indicate that the suckling stimulus, rather than ovarian factors, is mainly responsible for the suppression of FSH as well as LH secretion during the first half of lactation in rats nursing eight pups. On the other hand, during the second half of lactation in rats nursing eight pups and throughout lactation in rats nursing two pups, ovarian inhibin plays a primary role in the suppression of FSH secretion, whereas ovarian steroids act to suppress LH secretion.
Journal of Endocrinology (1991) 129, 119–130
Concentrations of arachidonate metabolites, steroids and histamine in preovulatory horse follicles after administration of human chorionic gonadotrophin and the effect of intrafollicular injection of indomethacin
Authors: Watson E. D. , Sertich P. L. 
Published: December 2008

ABSTRACT
This study investigated the sequence of hormonal changes within the preovulatory follicles of mares. Mares were injected i.v. with 2500 IU human chorionic gonadotrophin (hCG) when a preovulatory follicle of 35 mm in diameter was detected. Fluid was aspirated from preovulatory follicles before (0 h), and 12, 24 and 36 h after administration of hCG. Concentrations of progesterone, prostaglandin (PG) E2, PGF, 6-keto-PGF1α and thromboxane B2 in follicular fluid increased significantly (P<0·01) between 0 and 36 h. At 36 h, PGE2 was present in highest concentrations, followed by PGF and 6-keto-PGF1α; thromboxane B2 was present at lower concentrations than other prostanoids. Concentrations of 13,14-dihydro-15-keto-PGF2α increased significantly (P<0·05) between 24 and 36 h. Leukotriene B4, leukotriene C4 and histamine were present in follicular fluid at all sampling periods and did not change significantly over time.
In another experiment, buffered saline or indomethacin (either 100 or 500 μg) was injected into preovulatory follicles on the day that they reached 35 mm in diameter to determine whether blocking intrafollicular PG synthesis would affect ovulation. The interval between intrafollicular injection and ultrasonographic detection of luteinization was significantly longer (P<0·05) in mares treated with 500 μg indomethacin. Plasma progesterone concentrations were significantly (P<0·05) lower in indomethacin-treated mares than in control mares on the first 5 days after injection.
These results indicate that intrafollicular concentrations of PGs increase significantly before ovulation in mares and may be involved in the ovulatory process.
Journal of Endocrinology (1991) 129, 131–139
Binding sites for iodinated endothelin-1, endothelin-2 and endothelin-3 demonstrated on human uterine glandular epithelial cells by quantitative high-resolution autoradiography
Authors: Davenport A. P. , Cameron I. T. , Smith S. K. , Brown M. J. 
Published: December 2008

ABSTRACT
Quantitative in-vitro receptor autoradiography has been used to localize and compare the anatomical distribution of binding sites for iodinated endothelins (ET-1, ET-2 and ET-3) in human uterus. Binding sites for the three iodinated isoforms had a similar gross anatomical distribution. The density of binding sites was significantly higher in the endometrium compared with the myometrium and greatest at the endometrial–myometrial junction.
In cross-competition experiments, unlabelled ET-1, ET-2, ET-3, sarafotoxin S6b and mouse vasoactive intestinal contractor (1 μmol/l) competed for the binding sites of all the iodinated peptides suggesting that ETs may bind to the same receptor. However, preproendothelin(110–130) (endothelin-like peptide) or preproendothelin(124–130) and other non-endothelin vasoactive peptides tested as a concentration of 1 μmol/l did not compete.
Micro-autoradiography revealed that high densities of iodinated ET-1, ET-2 and ET-3 binding sites were localized to glandular epithelial cells and blood vessels with lower levels in the myometrium and vascular smooth muscle, suggesting that these potent vasoactive and proliferative agents could play a role in the control of menstruation.
Journal of Endocrinology (1991) 129, 149–154
Regulation of differential release of α-melanocyte-stimulating hormone forms from the pituitary of a teleost fish, Oreochromis mossambicus
Authors: Lamers A. E. , Balm P. H. M. , Haenen H. E. M. G. , Jenks B. G. , Bonga S. E. Wendelaar 
Published: December 2008

ABSTRACT
Using high-performance liquid chromatography (HPLC) in combination with radioimmunoassay, three forms of α-MSH (des-acetyl, mono-acetyl and di-acetyl α-MSH) were separated and identified in tilapia neurointermediate lobes and plasma, and in medium from lobes superfused in vitro. The presence of acetylated forms in lobe extracts indicated that the peptides are acetylated intracellularly. Di-acetyl α-MSH was, especially in comparison with monoacetyl α-MSH, relatively more abundant in lobe extracts than in plasma. This suggests that the three forms of α-MSH are not released according to their relative intracellular abundances. The possibility of regulation of this differential release by dopamine and TRH was investigated, using a microsuperfusion system. Dopamine was a potent inhibitor of α-MSH release, but did not modulate the relative abundance of the different forms of α-MSH released from the MSH cells. TRH was a potent stimulator of α-MSH release. It enhanced in vitro the release of di-acetyl α-MSH more than the release of mono-acetyl α-MSH. Thus tilapia may be able to modulate not only the quantitative but also the qualitative signal from the MSH cells. This might enhance the flexibility of the animals to respond to environmental challenges.
Journal of Endocrinology (1991) 129, 179–187
Inherited primary hypothyroidism with thyrotrophin resistance in Japanese cats
Authors: Tanase H. , Kudo K. , Horikoshi H. , Mizushima H. , Okazaki T. , Ogata E. 
Published: December 2008

ABSTRACT
Mutant cats were developed with non-goitrous primary hypothyroidism. They were clinically characterized by severely retarded growth, mild anaemia and high mortality in the young. They responded markedly to thyroid hormone replacement. Thyroid glands in the mutants were normal in position but slightly reduced in size. Laboratory studies revealed low serum concentrations of thyroxine (T4) and tri-iodothyronine (T3), and increased serum concentrations of TSH. Administration of TRH induced no further increase in TSH. Administration of exogenous TSH after suppression of endogenous TSH by T3 did not increase the serum concentration of T4 in the mutants, in sharp contrast with the threefold increase in serum T4 observed in the normal litter-mates. These findings suggest that the underlying pathogenesis of this disorder is unresponsive to TSH. Moreover, we found that the mutants were transmitted in an autosomal recessive manner.
Journal of Endocrinology (1991) 129, 245–251
Occurrence of sexual maturation in chronic opiate-treated female rats
Authors: MacDonald M. C. , Wilkinson M. 
Published: December 2008

ABSTRACT
We have investigated the consequences of chronic morphine or fentanyl exposure on the timing of puberty in female Sprague–Dawley rats. The μ-receptor agonists morphine and fentanyl were either added to the drinking water or, in the case of fentanyl, in osmotic minipumps. Morphine and fentanyl treatment, beginning at postnatal day 22, delayed the time of the first ovulation/vaginal opening (VO). For example, morphine included in the drinking water (800 mg/l) delayed VO by 5 days. Fentanyl gave similar results but at lower concentrations (30 mg/l). Surprisingly, these treatments delayed but did not prevent VO; i.e. in the face of continued opiate treatment most rats ovulated normally. In contrast, identical doses of morphine blocked oestrous cyclicity in drug-naive adults rats. However, morphine-dependent rats, which have reached VO (and first ovulation) then became briefly acyclic before beginning regular cycles even though opiate treatment was continued. The effects of fentanyl on immature rats were identical with those of morphine, i.e. VO was delayed but ovulation occurred in spite of continued drug treatment. On the other hand, fentanyl did not prevent cyclicity subsequent to VO.
Our observation that immature female rats can reach first ovulation despite chronic opiate treatment suggests that some degree of tolerance to opiates may develop. Such a mechanism could operate in normal drug-free rats, via endogenous opioid peptides, in the timing of puberty.
Journal of Endocrinology (1991) 129, 253–259
Effect of hypophysectomy and acute administration of growth hormone (GH) on GH-receptor binding in chick liver membranes
Authors: Vanderpooten A. , Darras V. M. , Huybrechts L. M. , Rudas P. , Decuypere E. , Kühn E. R. 
Published: December 2008

ABSTRACT
The effects of hypophysectomy on GH binding to liver membranes of young chicks were studied 3 days and 1 week after surgery. Specific binding of 125I-labelled chicken GH (cGH) to MgCl2-treated liver microsomal fractions of hypophysectomized animals was two- to fivefold greater than to those of sham-operated or control (non-operated) birds. This effect was due to a rise in binding capacity rather than a change in binding affinity of the GH receptor. Two daily injections of cGH (20 μg/animal) returned the number of hepatic GH receptors from hypophysectomized chicks to the level of the sham-operated ones. Administration of GH to the latter group did not cause a significant lowering of specific binding or number of receptors. No positive correlation between GH binding and plasma concentrations of insulin-like growth factor-I (IGF-I) was observed; although GH binding increased, IGF-I levels were lower for the hypophysectomized group. Since the number of hepatic GH receptors and the plasma GH levels were inversely correlated, it was concluded that the GH receptors in the liver of the chicken can be down-regulated by GH. This possibly explains why GH binding is low in posthatch and young chicks, because circulating GH concentrations are high during this period.
Journal of Endocrinology (1991) 129, 275–281
Circadian variation in the distribution of cells throughout the different phases of the cell cycle in the anterior pituitary gland of adult male rats as analysed by flow cytometry
Authors: Carbajo-Pérez E. , Carbajo S. , Orfao A. , Vicente-Villardón J. L. , Vázquez R. 
Published: December 2008

ABSTRACT
Flow cytometric analysis of nuclei stained with propidium iodide (PI) has been used to study the distribution of cells throughout the different phases of the cell cycle in the anterior pituitary gland of adult male Sprague–Dawley rats at different times of the day. According to PI fluorescence intensity the relative numbers of cells in S phase (cells with a DNA content between that of somatic cells in interphase (2n) and that of somatic cells after duplication of the DNA prior to cell division (4n)) and G2/M phase (4n) were calculated. A significant circadian rhythm was found for cells in both the S phase (P < 0·05) and the G2/M phase (P < 0·01). The wave of cells in S phase with a peak at the middle of the light period (14.00 h) precedes by about 6 h the wave of cells in G2/M phase (peak at 20.00 h). Most of the DNA-replicating cells were found during the early S phase at 11.00 h, advancing further up to the middle of this phase at 14.00 h. Cells were distributed homogeneously throughout the S phase at 17.00 h. These data strongly suggest that the beginning of the light period triggers a wave of cells to leave G0/G1 into S phase.
Journal of Endocrinology (1991) 129, 329–333
The concentration of insulin-like growth factor-I and insulin-like growth factor-binding protein-1 in human umbilical cord serum at delivery: relation to fetal weight
Authors: Wang H. S. , Lim J. , English J. , Irvine L. , Chard T. 
Published: December 2008

ABSTRACT
Serum levels of insulin-like growth factor-I (IGF-I) and insulin-like growth factor-binding protein-1 (IGFBP-1) have been determined by radioimmunoassay in the maternal circulation (n = 91) and in the umbilical artery (n = 56) and vein (n = 90) of man. In both the umbilical artery and vein, the concentration of serum IGF-I showed an inverse correlation with birthweight (P < 0·005 and P < 0·001 respectively); the mean serum IGF-I levels in the small-for-gestational-age (SGA) group were significantly higher than those in average-for-gestational-age (AGA) neonates (P <0·01 and P < 0·001 respectively). However, maternal serum IGF-I showed no association with birthweight and there was no significant difference between the SGA and AGA groups. These observations imply that the production of IGF-I in the maternal and fetal compartments is independent and that there is unlikely to be transfer of IGF-I across the placenta. Serum IGFBP-1 levels in both maternal and umbilical cord blood (artery and vein) showed an inverse relation to birthweight (P <0·001, P<0·005 and P<0·001 respectively). Increased IGFBP-1 levels in the umbilical artery and vein were observed in the SGA group. These findings suggest that IGFBP-1 might inhibit the action of IGF-I in both the maternal and the fetal compartments and that the rise in IGFBP-1 could be a primary factor in retardation of fetal growth. Alternatively, circulating IGF-I and IGFBP-1 levels may only be a secondary reflection of local tissue events involved in fetal growth.
Journal of Endocrinology (1991) 129, 459–464
Stimulation of body weight gain of the mature female rat by bovine GH and bovine placental lactogen
Authors: Byatt J. C. , Staten N. R. , Schmuke J. J. , Buonomo F. C. , Galosy S. S. , Curran D. F. , Krivi G. G. , Collier R. J. 
Published: December 2008

ABSTRACT
Mature female rats (200 g) were treated for 10 days with either recombinant bovine GH (bGH) or recombinant bovine placental lactogen (bPL) to compare the somatogenic responses elicited by these hormones. The treatments were administered by daily s.c. injection at four dose levels (0·19, 0·56, 1·67 and 5·0 mg/day). Both bGH and bPL stimulated significant increases in weight gain, but the slopes of the dose–response curves were different (P<0·05). Bovine PL was more potent than bGH (P<0·01) at the lowest dose, although there were no differences between treatment groups at the three higher doses. Feed consumption was stimulated more by bPL than bGH at all doses (P<0·001). The concentration of insulin-like growth factor-I (IGF-I) in blood plasma was increased by bGH in a dose-responsive manner and was higher than control at doses of 1·67 and 5 mg/day (P<0·05). Low doses of bPL stimulated increases in IGF-I similar to those with bGH. At the highest dose of bPL, however, there was no concomitant increase in plasma IGF-I. Nevertheless, the growth rate of the animals in this group matched that of the group given the highest dose of bGH. Receptor binding studies indicated that bPL bound to both GH and prolactin receptors. This is consistent with the growth data which suggest that bPL stimulated weight gain through a somatogenic mechanism as well as by another route, possibly mediated by lactogenic receptors.
Journal of Endocrinology (1991) 130, 11–19
Substance P stimulation of polyphosphoinositide hydrolysis in rat anterior pituitary membranes involves a GTP-dependent mechanism
Authors: Mau S. E. , Saermark T. 
Published: December 2008

ABSTRACT
Substance P (SP) stimulates polyphosphoinositide breakdown in the rat anterior pituitary through an NK-1 receptor. In the present study we present evidence that the coupling between the SP–NK1 receptor complex and polyphosphoinositide-specific phospholipase C (PI-PLC) in rat anterior pituitary membranes may involve a mechanism consistent with a GTP-binding protein. The formation of inositol phosphates from [3H]myo-inositol-labelled anterior pituitary membranes induced by SP was potentiated by GTP and non-hydrolysable guanine nucleotides. The stimulatory effects of SP alone and SP plus GTP could be blocked by addition of GDP-β-S (guanosine 5-O-(thiodiphosphate)) in excess. Basal and SP plus guanine nucleotide-induced inositol phosphate formation were stimulated by fluoride, whereas the effect of SP alone was inhibited. Pretreatment of anterior pituitary membranes with sodium deoxycholate attenuated the inositol phosphate response elicited by GTP and GTP-γ-S, whereas basal and SP-stimulated inositol phosphate production showed a peak at 1 mg sodium deoxycholate/ml. SP, fluoride and guanine nucleotide stimulatory effects on hydrolysis of polyphosphoinositide (PPI) were unaffected by pretreatment of anterior pituitary cells with cholera or pertussis toxin for 12 h. Treatment of anterior pituitary membranes with cholera and pertussis toxin yielded [32P]ADP-ribosylation of two proteins with molecular masses of 45 and 41 kDa respectively.
We conclude that SP coupling to PI-PLC through the NK1 receptor in the rat anterior pituitary involves a GTP-binding mechanism distinct from the G-proteins associated with adenylate cyclase, Gs and Gi.
Journal of Endocrinology (1991) 130, 63–70
Effects of RU 486 on adrenal steroidogenesis in the guinea-pig
Authors: Provencher P. H. , Bélanger A , Fiet J. 
Published: December 2008

ABSTRACT
Recent reports have shown that RU 486, a synthetic glucocorticoid and progestin antagonist, has direct effects on tissues secreting steroids. In order to characterize the effects of RU 486 on steroidogenesis further, guinea-pig fasciculata-glomerulosa (FG) cells in primary culture were treated for 48 h with RU 486. RU 486 caused an alteration of basal as well as ACTH-stimulated steroid secretion. Corticosterone and cortisol secretion decreased by 50% while the secretion of 17-hydroxyprogesterone and C19 steroids were increased. The activity of steroidogenic enzymes was measured using tritiated steroids. In RU 486-treated cells, the activity of 21-hydroxylase was dramatically inhibited while there was an increase in 17-hydroxylase and 17,20-desmolase activities. The effects of RU 486 on enzyme activities were dependent upon dose and time. The effects of the compound were not reversed by concomitant treatment of FG cells with R-5020 or dexamethasone, thus suggesting that RU 486 acted directly on steroidogenic enzymes to alter their activity.
Journal of Endocrinology (1991) 130, 71–78
Osmoregulatory actions of insulin-like growth factor-I in rainbow trout (Oncorhynchus mykiss)
Authors: McCormick S. D. , Sakamoto T. , Hasegawa S. , Hirano T. 
Published: December 2008

ABSTRACT
The ability of insulin-like growth factor-I (IGF-I), insulin and GH to promote hypoosmoregulatory ability was examined in juvenile rainbow trout (Oncorhynchus mykiss). Following adaptation to 12 parts per thousand (p.p.t.) seawater for 5 days, fish were given a single injection of hormone or vehicle, then exposed to 29 p.p.t. for 24 h and examined for changes in plasma osmolarity, ions and glucose. Ovine GH (oGH; 0·2 μg/g) significantly improved the ability of rainbow trout to maintain plasma osmolarity and sodium levels following transfer to 29 p.p.t. seawater. Recombinant bovine IGF-I (0·01, 0·05 and 0·2 μg/g) also improved the hypoosmoregulatory ability of trout; the effect being dose-dependent and greater than that of oGH. Bovine insulin (0·01, 0·05 and 0·2 μg/g) had no statistically significant effect on plasma ions. The results indicate that IGF-I is a potential mediator of the action of GH in seawater adaptation of salmonids.
Journal of Endocrinology (1991) 130, 87–92