bluuebunny/crossref_metadata_2025_split huggingface dataset:
The identification and characterization of 125I-labelled iodomelatonin-binding sites in the duck kidney
Authors: Song Y. , Ayre E. A. , Pang S. F. 
Published: December 2008

ABSTRACT
The melatonin-binding sites in membrane preparations of duck kidney were demonstrated by utilizing 125I-labelled iodomelatonin as a radioligand. Binding at these sites was found to be reversible, saturable, specific and of high affinity. Scatchard analysis of the specific binding revealed an equilibrium binding constant (Kd) of 44·6±4·4 pmol/l (n= 6) and a total number of binding sites (Bmax) of 6·43 ±0·60 fmol/mg protein (n= 6) at the mid-point of the light period (mid-light). The Hill coefficient approached 1·0, suggesting a single class of 125I-labelled iodomelatoninbinding site in the duck kidney. Diurnal variation in 125I-labelled iodomelatonin binding showed that the Bmax was 53·4% higher at mid-light than at mid-point of the dark period (P<0·05), with no significant variation in Kd. The Kd value determined from kinetic analysis was 22·5 pmol/l in birds at mid-light, which was comparable with values determined from equilibrium studies. The order of pharmacological affinity for 125I-labelled iodomelatonin-binding sites in the duck kidney membrane preparations was: 2-iodomelatonin > melatonin > 6-chloromelatonin > 6-hydroxymelatonin > N-acetylserotonin » 5-methoxytryptamine, 5-methoxytryptophol, 5-hydroxytryptamine, tryptamine, 1-acetylindole-3-carboxaldehyde, 5-hydroxyindole-3-acetic acid, l-tryptophan, 5-methoxyindole-3-acetic acid, 3-acetylindole, acetylcholine, epinephrine, norepinephrine and harmaline. The pharmacological characteristics indicated that 125I-labelled iodomelatonin-binding sites are highly specific for melatonin. Our finding of 125I-labelled iodomelatonin-binding sites in the kidney suggests that melatonin may regulate kidney function. The possibility of a direct effect of melatonin on renin secretion and daily urine production is hypothesized.
Journal of Endocrinology (1992) 135, 353–359
Noradrenergic peripheral denervation of the female rat accelerates the positive feedback mechanisms resulting in pubertal ovulation, and blocks the modifications induced by administration of testosterone propionate at birth
Authors: Flores A. , Domínguez R. 
Published: December 2008

ABSTRACT
The noradrenergic innervation of the ovary of prepubertal rats causes an inhibitory response of the follicles to gonadotrophins, leading to ovulation. We investigated the possibility that noradrenergic peripheral denervation at birth, produced by treatment with guanethidine, modifies the positive feedback effects of gonadotrophins and oestradiol in prepubertal rats, and also the possibility that peripheral denervation can modify the anovulatory syndrome induced by androgenization at birth.
Noradrenergic peripheral denervated rats of 18 days of age treated with pregnant mare serum gonadotrophin (PMSG) ovulated 96 h later, while normal animals did not ovulate (4/9 vs 0/12, P < 0·05) and the number of ova shed was lower than in rats which ovulated spontaneously at first vaginal oestrus (3·5 ± 0·6 vs 8·3 ± 0·4 (s.e.m.), P < 0·01). Oestradiol benzoate (10 μg) did not induce ovulation in either normal or denervated animals (0/11 and 0/11). The anovulatory syndrome induced by the administration of testosterone propionate (75 μg) at birth was partially blocked by noradrenergic peripheral denervation (4/7 ovulated vs 0/10).
The results suggest that some neural information arising from the ovary modulates, in an inhibitory way, the stimulatory feedback mechanisms required to induce ovulation. Partial inhibition of the anovulatory syndrome resulting from androgenization caused by peripheral noradrenergic denervation suggests that noradrenergic neural information sent by the ovary to the hypothalamus results in a decreased concentration of noradrenaline in the hypothalamus and in the aromatization of androgens to oestrogens.
Journal of Endocrinology (1992) 135, 415–420
Oestradiol increases the extracellular levels of amine metabolites in the ewe hypothalamus during anoestrus: a microdialysis study
Authors: Gayrard V. , Malpaux B. , Thiéry J. C. 
Published: December 2008

ABSTRACT
Giving a subcutaneous oestradiol implant during anoestrus to ovariectomized ewes inhibits pulsatile LH secretion. This effect results from an increased negative feedback of oestradiol and depends on the synthesis of biogenic amines, mainly from the mediobasal hypothalamus. In the present study, we examined the effect of oestradiol on the extracellular levels of amines and their metabolites. Eight ewes were sampled by microdialysis from the lateral retrochiasmatic area, including the dopaminergic A15 nucleus, during inhibition of LH secretion by long days. Two dialysis sessions were carried out on each ewe; one after a 10-day oestradiol treatment and the other one after 10 days without oestradiol treatment. Half of the ewes were first oestradiol-treated then untreated, the other half received the treatment in the reverse order.
Oestradiol caused a decline in pulsatile LH secretion without affecting the secretion of prolactin. This steroid also led to a significant increase in the levels of amine metabolites: 3,4-dihydroxyphenylacetic acid, homovanillic acid and 5-hydroxyindolacetic acid in the extracellular medium. These results demonstrate the effect of oestradiol on aminergic activity as related to changes in hormonal secretions during long days (16 h of light per 24 h). Thus our data support the hypothesis that amines inhibit gonadotrophic secretion during anoestrus in the ewe and suggest that there is an activation of the aminergic neurones from the retrochiasmatic area in this regulatory mechanism.
Journal of Endocrinology (1992) 135, 421–430
The processing of β-endorphin and α-melanotrophin in the pars intermedia of Xenopus laevis is influenced by background adaptation
Authors: Maruthainar K. , Peng-Loh Y. , Smyth D. G. 
Published: December 2008

ABSTRACT
β-Endorphin-and α-melanotrophin (α-MSH)-related peptides were extracted from the pars intermedia of Xenopus laevis maintained for 2, 4 or 6 weeks on a white background and for the same periods on a black background. The peptides were resolved under dissociating conditions by gel exclusion chromatography on Sephadex G-50 and they were detected by radioimmunoassay with antibodies to β-endorphin, α,N-acetyl β-endorphin and α-MSH. The β-endorphin-related peptides separated into two fractions of different molecular size. Further purification of the peptides in each fraction was by ion exchange chromatography on SP-Sephadex C-25 and by high-pressure liquid chromatography. The α-MSH-related peptides were resolved by gel exclusion and ion exchange chromatography. The purified β-endorphin- and α-MSH-immunoreactive peptides were identified by comparison of their chromatographic properties with the corresponding peptides from porcine pituitary or by comparison with synthetic peptides.
The major form of β-endorphin in the pars intermedia of the frog adapted to a white background was identified as α,N-acetyl β-endorphin (1–8); it was accompanied by a small quantity of acetylated peptides with molecular size similar to β-endorphin. In contrast, the pars intermedia of the frogs adapted to a black background contained approximately equal amounts of α,N-acetyl β-endorphin (1–8) and the larger forms of β-endorphin. The higher molecular weight forms were identified as the α,N-acetyl derivatives of β-endorphin (1–26), (1–27) and (1–31); however after 6 weeks of white adaptation the sole remaining peptide in this group was the 26-residue peptide. An additional β-endorphin immunoreactive peptide, provisionally identified as β-endorphin (10–26), was present in both black- and white-adapted animals; the amounts of this peptide increased during white adaptation. Major differences in the processing of α-MSH were also observed. In the frogs adapted to a black background des-acetyl α-MSH greatly predominated over the acetyl form whereas after 6- weeks adaptation to a white background the acetylated peptide proved to be the principal component.
The results demonstrate that the proteolytic processing of β-endorphin and the acetylation of α-MSH in Xenopus laevis are influenced by background adaptation. The formation of β-endorphin (1–8) appears to reflect the action of an endopeptidase that acts at the single arginine residue present at position 9. This cleavage does not appear to take place in mammalian β-endorphins where position 9 is occupied by lysine.
Journal of Endocrinology (1992) 135, 469–478
Paradoxical hypertrophy and plasticity of the testis in rats recovering from early thyroid deficiency: a growth study including effects of age and duration of hypothyroidism
Authors: Meisami E. , Sendera T. J. , Clay L. B. 
Published: December 2008

ABSTRACT
The effects of various durations of postnatal hypothyroidism followed by recovery were studied on testicular growth in Long–Evans and Sprague–Dawley rats from birth to 7 months. Hypothyroidism was induced by adding propylthiouracil (PTU) in drinking water (0·1%, w/v). Recovery was induced by withdrawal of PTU. Testicular growth was reduced in rat pups by 20, 65 and 90% at days 10, 25 and 50. Upon withdrawal of PTU at weaning (25 days), testicular growth resumed and became compensatory; catch-up growth occurred by day 65. Paradoxically, testicular growth progressively increased, surpassing the control weights by 40, 50 and 100% at days 75, 90 and 210. Maximal testicular growth rate in the recovery group was 35% higher, occurred 2 weeks later and lasted 2 weeks longer than controls. Testes of rats subjected to prolonged postnatal hypothyroidism (60 or 120 days) also showed recovery and hypertrophy, amounting to nearly twice the normal maximal growth levels, after at least 6 months of recovery. Body weights of recovering rats remained always significantly below those of controls. When the suckling pups were exposed to short, week-long regimes of PTU treatment, only rats treated during the early postnatal weeks (days 1–8 or 9–16) had enlarged testes; PTU treatment during the late suckling period (days 17–24) or later had no effects. Total duration of hypothyroidism in the suckling period was positively correlated with testicular enlargement. The results indicate that hypothyroidism early in life is stimulatory to testicular growth, resulting in a paradoxical twofold increase in final testicular size which occurs even if hypothyroidism is prolonged. These effects occur similarly in different strains of rat with differing sized testes. It is suggested that there is a sensitive period for this effect, i.e. during the first 2 weeks after birth. The marked plasticity of testicular growth as shown by its recovery and hypertrophy, even after long periods of hypothyroid retardation, is unique in the body and may be a useful model for studying hormonal factors regulating testicular growth and for animal breeding and research into infertility.
Journal of Endocrinology (1992) 135, 495–505
Transforming growth factor-β is a potent inhibitor of basal and stimulated relaxin release by porcine luteal cells maintained in monolayer culture
Authors: Taylor M. J. , Clark C. L. 
Published: December 2008

ABSTRACT
The effect of transforming growth factor-β (TGF-β) on relaxin release by porcine large luteal cells (LLC) was examined by use of a reverse haemolytic plaque assay. In this assay, mixed luteal cells were co-cultured in monolayers with protein A-coupled sheep erythrocytes. In the presence of complement and porcine relaxin antiserum, a zone of haemolysis (a plaque) developed around relaxin-releasing LLCs. The rate of plaque development in time-course experiments and the average size of plaque areas were used to monitor the rate of relaxin release and cumulative amounts of hormone respectively. Monolayers were bathed in medium containing TGF-β alone, or in the co-presence of a stimulatory secretagogue (prostaglandin E2; PGE2).
Exposure of luteal cell-containing monolayers to TGF-β (1 ng/1–100 μg/l) elicited a dose-related inhibition in the rate of basal relaxin release. Minimal and maximal concentrations were approximately 10 ng/l and 10 μg/l respectively. Treatment with 1 μg TGF-β/l reduced the cumulative amount of relaxin released to 63 ± 6% of control values (mean ± s.d., P < 0·05, n = 6; averaged over the whole course of the experimental incubation). Exposure of monolayers treated with TGF-β to the relaxin-stimulatory secretagogue PGE2 (0·1 μmol) resulted in a significant (P < 0·05) increase in the amount of relaxin released by TGF-β-suppressed LLCs, and restored rates of hormone release to control levels. This is evidence that TGF-β and PGE2 interact antagonistically in the modulation of relaxin. The effect of TGF-β was strictly time-dependent. A period of at least 16 h of treatment with TGF-β was required to induce an inhibitory effect on relaxin.
These results implicate TGF-β as a novel inhibitor of relaxin release, and the presence of TGF-β in porcine luteal tissue suggests that such regulation may be achieved via paracrine or autocrine routes. It is possible that TGF-β interacts functionally during luteal life with other secretagogues to achieve integrated control of hormone release.
Journal of Endocrinology (1992) 135, 543–550
Human chorionic gonadotrophin and subunit composition of maternal serum and coelomic and amniotic fluids in the first trimester of pregnancy
Authors: Iles R. K. , Wathen N. C. , Campbell D. J. , Chard T. 
Published: December 2008

ABSTRACT
Sixteen matched samples of first trimester amniotic fluid (AF), extraembryonic coelomic fluid (EECF) and maternal serum (MS) were assayed for intact human chorionic gonadotrophin (hCG) and free subunits. Total β-hCG (free β-subunit and intact hCG) levels in the EECF (median 410 kIU/l) were 61 times greater than levels in AF (median 6·73 kIU/l) and 2·8 times greater than in MS (median 141·5 kIU/l). Levels of intact hCG in the EECF (median 245 kIU/l) were 142 times greater than in AF (median 1·73 kIU/l) and 1·6 times greater than in MS (median 157 kIU/l). Free α-subunit levels in EECF (median 17·3 mg/l) were 66 times greater than in AF (median 0·262 mg/l) and 12 times greater than in MS (median 1·3 mg/l). Virtually all of the total β-hCG immunoreactivity in MS can be attributed to intact hCG, but only 60% of total β-hCG in the EECF and 20% of that in AF can be accounted for by the intact hormone. In both EECF and AF the free α-subunit was a major constituent; on a molar basis the ratio of free α:free β:intact hCG was 1:1·2:0·3 in AF, 1:0·6:0·5 in EECF and 1:0:5 in MS. Chromatography of MS, EECF and AF on Sephadex G-100 confirmed the hCG and subunit composition of the fluids. On the basis of these findings it seems likely that previous studies showing very high levels of hCG in AF during the first trimester may have incorrectly sampled the EECF. In reality, the levels of total hCG (and free subunits) are low in the AF, and only 20% is intact hCG. In both AF and EECF the free subunits may have been derived by dissociation of intact hormone, or possibly by independent synthesis. These and other findings suggest that either the amnion acts as a barrier to the transfer of proteins or that there may be dynamic removal from this compartment. By contrast, the EECF might act as a relatively stable reservoir for these proteins.
Journal of Endocrinology (1992) 135, 563–569
Immunohistochemical localization of 17α-hydroxylase/C17–20 lyase and aromatase cytochrome P-450 in the human ovary during the menstrual cycle
Authors: Tamura T. , Kitawaki J. , Yamamoto T. , Osawa Y. , Kominami S. , Takemori S. , Okada H. 
Published: December 2008

ABSTRACT
Immunohistochemical localization of 17α-hydroxylase/C17–20 lyase (P-45017α,lyase) and aromatase cytochrome P-450 (P-450arom) in normal human ovaries during the menstrual cycle was studied using specific polyclonal antibodies which were raised against corresponding enzymes. In the follicular phase of matured follicles, P-45017α,lyase was localized in theca interna cells and P-450arom in granulosa cells. P-45017α,lyase was expressed in theca interna cells before P-450arom was expressed in granulosa cells. The corpus luteum showed immunoreactivity to both enzymes and, after menstruation, immunoreactivity decreased gradually until it could not be detected in the corpus albicans. In corpus luteum graviditatis the immunoreactivity continued to be expressed strongly. In some atretic follicles, P-45017α,lyase and/or P-450arom continued to be expressed. In the stromal layer, P-45017α,lyase was detected in secondary interstitial cells, which originated from the theca interna of atretic follicles, and P-450arom was detected in hilar cells. Immunoreactivity to both enzymes was also detected in oocytes of developing follicles. These results are consistent with the two cell theory in the human ovary. They also suggest that androgens and oestrogens are produced not only by follicles and corpora lutea but also by stroma and oocytes.
Journal of Endocrinology (1992) 135, 589–595
Russell's viper venom stimulates insulin secretion from rat islets of Langerhans
Authors: Jones P. M. , Mann F. M. 
Published: December 2008

ABSTRACT
Burmese Russell's viper venom (RVV) caused a dose-and temperature-dependent stimulation of insulin secretion from islets of Langerhans isolated from rat pancreas by collagenase digestion. RVV stimulated both basal and glucose-induced insulin secretion at concentrations which did not compromise islet cell viability as assessed by exclusion of trypan blue dye. The effects of RVV on insulin secretion could not be attributed to the activation of protein kinase C (PKC), since down-regulation of PKC by prolonged exposure to a tumour-promoting phorbol ester did not abolish subsequent secretory responses to RVV. However, RVV-induced insulin secretion was inhibited in the absence of extracellular Ca2 +, and RVV did not stimulate insulin secretion from Ca2+-clamped electrically permeabilized islets at either substimulatory (50 nmol/l) or stimulatory (10 μmol/l) concentrations of Ca2 +, suggesting that changes in cytosolic Ca2+ are important in the stimulation of insulin secretion by RVV. The phospholipase A2 (PLA2) inhibitor quinacrine caused a dose-dependent inhibition of RVV-induced insulin secretion, suggesting that the activation of PLA2, perhaps in response to Ca2+ influx, may be partially responsible for RVV-induced insulin secretion.
Journal of Endocrinology (1993) 136, 27–33
Distribution, molecular characterization of pituitary adenylate cyclase-activating polypeptide and its precursor encoding messenger RNA in human and rat tissues
Authors: Ghatei M. A. , Takahashi K. , Suzuki Y. , Gardiner J. , Jones P. M. , Bloom S. R. 
Published: December 2008

ABSTRACT
The distribution of a novel neuropeptide, pituitary adenylate cyclase-activating polypeptide (PACAP), was studied in the brain of the rat and man and a variety of other rat tissues using Northern blot hybridization and two radioimmunoassays for PACAP 1–38 and PACAP 1–27. The assay, using PACAP 1–38 as standard and an antibody to PACAP 21–38 and radiolabelled tracer, revealed immunoreactive PACAP in all brain regions examined, with the highest concentrations in the rat being in the hypothalamus, nucleus accumbens and substantia nigra (380 ± 34, 310 ± 37 and 346 ± 30 pmol/g wet tissue, means±s.e.m., n = 5 respectively), whilst in man the highest concentrations were found in the pituitary gland (15·8 ± 4·7 pmol/g). Immunoreactive PACAP 1–38 was also detected in the rat gastrointestinal tract, adrenal gland and testis. The assay using PACAP 1–27 as standard and label and an antibody to PACAP 1–27 detected immunoreactive PACAP only in the rat hypothalamus (12·6 ± 1·8 pmol/g wet tissue, n = 5). PACAP mRNA of approximately 2·7 kb in size was detectable in all brain regions of both rat and man, and its distribution paralleled that of the immunoreactive peptide.
Gel permeation chromatography of different regions of human and rat hypothalamus, and also rat spinal cord and small intestine, showed a broad immunoreactive peak corresponding to PACAP 1–38. Fast protein liquid chromatography (FPLC) resolved this peak into two immunoreactive peaks, the majority eluting in the position of synthetic PACAP 1–38. Presence of immunoreactivity corresponding to PACAP 1–27 was also confirmed in rat hypothalamic extracts using FPLC. The presence of immunoreactive PACAP and its precursor encoding mRNA in various neural and other tissues is in accord with a role for PACAP as a neurotransmitter, neuromodulator or neurohormone.
Journal of Endocrinology (1993) 136, 159–166
Immunoreactive and receptor-active insulin-like growth factor-I (IGF-I) and IGF-binding protein in blood plasma from the freshwater fish Macquaria ambigua (golden perch)
Authors: Anderson T. A. , Bennett L. R. , Conlon M. A. , Owens P. C. 
Published: December 2008

ABSTRACT
The presence of insulin-like growth factor-I (IGF-I)-related molecules and IGF-binding factors in blood from golden perch, Macquaria ambigua, an Australian native freshwater fish, was investigated.
Serum was acidified to dissociate IGF and IGF-binding protein complexes that might be present, and fractionated by size-exclusion high-performance liquid chromatography at pH 2·8. Fractions were neutralized and their activities assessed by (i) an immunoassay for mammalian IGF-I which also detects chicken IGF-I but in which all known forms of IGF-II react very poorly, (ii) a receptor assay for IGF-II in which all known forms of IGF-I react poorly, and (iii) a type-I IGF receptor assay in which mammalian IGF-I and IGF-II polypeptides are almost equivalent. No IGF-II-like activity was detected. Three peaks of IGF-I-like activity were detected by IGF-I immunoassay and type-I IGF receptor assay. The major peak of activity was similar in molecular size to human IGF-binding protein-3, 45–55 kDa ('large IGF'), and a minor peak of activity which was similar in size to mammalian IGFs, 7·5 kDa. A third peak of activity was observed eluting at a time which indicates that it is a smaller molecule than any previously described IGF. The large IGF was temperature-sensitive, but was not a binding protein for 125I-labelled human IGF-I (hIGF-I). This material therefore was able to bind to anti-hIGF-I antibodies and to human type-I IGF receptors, and may represent the fish equivalent of mammalian prepro-IGFs.
The two smallest forms of IGF activity identified by IGF-I radioimmunoassay and type-I radioreceptor assay following acidic size-exclusion chromatography were able to stimulate protein synthesis by L-6 myoblasts in culture, although large IGF did not.
When fresh (but not frozen and thawed) golden perch serum was incubated with 125I-labelled hIGF-I and then fractionated by size-exclusion liquid chromatography at pH 7·4 through Sephadex G-100, the radioactivity became associated with a complex, intermediate in size between free IGF-I and the major IGF-binding protein in human serum. The association of 125I-labelled hIGF-I with the complex was inhibited by the presence of unlabelled hIGF-I in the incubation.
These studies show that receptor-active, immunoreactive and bioactive IGF-I-like activity is present in golden perch serum, and demonstrate the presence of an IGF-I-binding factor in this species.
Journal of Endocrinology (1993) 136, 191–198