bluuebunny/crossref_metadata_2025_split huggingface dataset:
The fate and uptake of murine epidermal growth factor in the sheep
Authors: Tyson L. M. , Browne C. A. , Jenkin G. , Thorburn G. D. 
Published: December 2008

ABSTRACT
125I-Labelled murine epidermal growth factor (EGF) was injected or infused into conscious ewes through the jugular vein. Its disappearance from the circulation and the pattern of its distribution in other body tissues and compartments were observed. Single bolus injections of 125I-labelled EGF resulted in a transient peak of radioactive EGF in the circulation which occurred within 1 min of the injection. This was followed by a very rapid fall in radioactivity in the plasma (t½ ∼ 1 min) and the gradual appearance of 125I-labelled EGF in the urine. Immunoprecipitable 125I-labelled EGF could be detected in urine within 5 min of the start of the experiment. 125I-Labelled EGF accumulated in the urine for several hours following the injection, although with increasing time a substantial amount of non-immunoprecipitable iodide was also found. The rate of disappearance of the 125I-labelled EGF from the plasma of the ewe was found to be faster than the rate of disappearance of free [125I]iodide that had been injected into the ewe.
125I-Labelled EGF was also administered by a continuous infusion following an initial bolus injection. This again resulted in a rapid initial fall in radio-activity in blood, followed by a slow rise throughout the period of the infusion. When the infusion was stopped, there was a 15-min period of rapid readjustment, after which the radioactivity in the blood fell at a much slower rate (t½ ∼70 min) than was seen initially. Again, intact 125I-labelled EGF was transferred to urine throughout the experiment.
At autopsy, 125I-labelled EGF was increased in bile, liver, thyroid and kidney. Although most of the 125I found in the thyroid was free iodide, some EGF-like material was also present. There was also EGF-like material found in both the kidney cortex and the kidney medulla. These results indicate that complex multi-compartment pathways for the uptake, distribution and clearance of 125I-labelled EGF exist in the sheep.
Journal of Endocrinology (1989) 123, 121–130
The angiotensin II receptor of rabbit liver: characterization in isolated hepatocytes and effect of GTP
Authors: Vandekerckhove A. , Keppens S. , De Wulf H. 
Published: December 2008

ABSTRACT
A homologous population of specific angiotensin II receptors is present on the cell surface of isolated rabbit hepatocytes. The binding characteristics of [3H]angiotensin II to the cells were: association rate constant (K+1) 0·08 l/nmol per min and dissociation rate constant (K−1) 1·9/min, yielding a dissociation constant (Kd) of 24 nmol/l. A very similar Kd (32 nmol/l) has been derived from saturation binding data which indicate a maximal binding capacity of about 200 000 sites/cell.
Analysis of the association binding data to purified liver plasma membranes indicated a Kd of 6 nmol/l in the absence and 30 nmol/l in the presence of GTP. Dissociation was clearly dependent upon the presence of the nucleotide, which shifted the K−1 from 0·12/min to 0·42/min.
The studied binding sites are very likely to be involved in the glycogenolytic action of angiotensin II, since a highly significant correlation was established between the biological activity (activation of glycogen phosphorylase) and the binding affinity of a series of agonistic analogues.
The reported characteristics of the rabbit hepatic angiotensin II receptors show much similarity with those of rat liver.
Journal of Endocrinology (1989) 123, 131–136
Kinetic analysis of the uptake of thyroid hormones by the human erythrocyte
Authors: Ball S. G. , Ramsden D. B. 
Published: December 2008

ABSTRACT
The uptake of 3,5,3′-tri-iodothyronine (T3) by human erythrocytes was shown to occur by two saturable processes. System I (Michaelis constant (Km) 109 ± 40 (mean ± s.d.) nmol/l; maximal velocity (Vmax) = 43 ± 16 pmol/min per 109 cells) was observed over the range 1–50 nmol T3/l whilst system II (Km = 8·8 ± 8·0 pmol/l; Vmax = 29 ± 6 fmol/min per 109 cells) was observed over the range 1–500 pmol T3/l. At low concentrations (1–500 pmol/l) uptake processes equivalent to system II could be demonstrated for thyroxine and 3,3′,5′-tri-iodothyronine also. System II had the properties of a carrier-mediated process.
Journal of Endocrinology (1989) 123, 143–148
LHRH pulse frequency in normal and infertile men
Authors: Wu F. C. W. , Taylor P. L. , Sellar R. E. 
Published: December 2008

ABSTRACT
The aim of this study was to examine the hypothesis that decreased LHRH pulse frequency may be responsible for the preferential rise in FSH in infertile men. The LH pulse pattern was determined as an index of hypothalamic LHRH secretion in 21 infertile patients with idiopathic azoospermia or oligoasthenozoospermia and 14 fertile age-matched controls by frequent blood sampling at 10-min intervals for 24 h. The infertile patients were further divided into three groups according to their relative concentrations of FSH and LH: (1) normal FSH and LH, (2) raised FSH but normal LH, and (3) raised FSH and LH. LH pulses were detected by a computerized algorithm (Munro) validated against a threshold method. Concentrations of FSH, testosterone, sex hormone-binding globulin and oestradiol were measured in pooled plasma.
Luteinizing hormone pulse frequencies in normal men were not significantly different from the infertile group as a whole. Similarly, mean LH pulse frequencies in infertile subgroups 1, 2 and 3 were not significantly lower than normal. Pulse interval, however, was increased in subgroup 1 compared with normal. Mean 24 h LH in group 2 was significantly higher than normal, but still within the normal range. The total testosterone, but not the free testosterone index was significantly decreased in the infertile group compared with normal. There was no correlation between mean FSH and LH pulse frequency or interval.
In conclusion, our results show that in patients with seminiferous tubular dysfunction, the typical pattern of raised plasma FSH, increased LH pulse amplitude, raised FSH: LH ratio and normal or marginally low testosterone was not associated with any significant deviations in LHRH pulse frequency from the range observed in normal fertile men. This is not compatible with the hypothesis that decreased LHRH pulse frequency is associated with or the cause of the preferential rise in FSH in men with idiopathic infertility. Thus unlike anovulatory infertility in females, functional defects of hypothalamic LHRH secretion remain an uncommon finding in male infertility. Attempts to treat idiopathic oligozoospermia by altering LHRH pulse frequency is therefore unlikely to yield any clinical benefit.
Journal of Endocrinology (1989) 123, 149–158
Source of ovarian inhibin secretion during the oestrous cycle of the sheep
Authors: Mann G. E. , McNeilly A. S. , Baird D. T. 
Published: December 2008

ABSTRACT
The source of inhibin secretion by the ovary in the sheep at different stages of the oestrous cycle was investigated by in-vivo cannulation of the ovarian veins. Twenty-four Scottish Blackface ewes were allocated to four groups of six ewes, i.e. those operated on during the luteal phase (day 10), and those operated on during the follicular phase 24–30, 36 and 60 h following an injection of 125 μg cloprostenol on day 10 of the luteal phase. Samples of jugular and timed ovarian venous blood were collected under anaesthesia before and after enucleation of the corpus luteum. Ovaries were then removed and follicles dissected out.
Following injection of cloprostenol, luteal regression occurred as indicated by a fall in the secretion of progesterone. The concentration of inhibin in jugular venous plasma and its ovarian secretion rate were similar at all stages of the follicular phase and during the luteal phase. In contrast, the secretion rate of oestradiol rose from 2·68 ±0·73 pmol/min during the luteal phase to 8·70± 2·24 pmol/min 24 h after injection of cloprostenol (P<0·05). Following enucleation of the corpus luteum the secretion rate of progesterone fell from 809 ± 270 pmol/min to 86 ± 30 pmol/min (P<0·001). There was also a smaller, artifactual fall in the secretion rate of oestradiol following enucleation of the corpus luteum, which was of similar size to a fall seen in the secretion rate of inhibin. This resulted in a significant (P<0·001) fall in the ratio of progesterone to inhibin, while the oestradiol to inhibin ratio remained unchanged. The secretion rate of inhibin from ovaries containing luteal tissue was similar to that from the contralateral side without luteal tissue (1·41±0·30 compared with 1·32±0·30 ng/min), while ovaries with large antral follicles secreted significantly (P< 0·001) more inhibin than those with no follicles ≥3 mm (2·28 ± 0·36 compared with 0·25 ±0·06 ng/min).
From these results we conclude that, in the sheep, large antral follicles are responsible for most, if not all, the secretion of inhibin by the ovary at all stages of the oestrous cycle, and that the corpus luteum secretes little or no immunoactive or bioactive inhibin. Due to the fact that, unlike inhibin, the secretion rate of oestradiol rises during the follicular phase of the cycle, when the concentration of FSH is suppressed, it seems likely that oestradiol rather than inhibin is the major ovarian factor modulating the change in FSH secretion seen at this stage of the oestrous cycle.
Journal of Endocrinology (1989) 123, 181–188
Epidermal growth factor increases inhibin synthesis by isolated segments of rat seminiferous tubules
Authors: Gonzales G. F. , Risbridger G. P. , de Kretser D. M. 
Published: December 2008

ABSTRACT
The effect of epidermal growth factor (EGF) on the production of immunoreactive inhibin by adult rat isolated seminiferous tubules in vitro has been investigated. EGF (0·1–1000 ng/ml) added to cultures of seminiferous tubules from adult rats caused a dose-dependent increase in inhibin content in the tubules without changing the amount secreted into the media. However, after continuous stimulation with EGF for periods in excess of 5 days, an increase in inhibin secretion was observed. In the presence of 10 and 100 ng FSH/ml, EGF (10 ng/ml) produced a further increment in the inhibin content of the tubules, but this effect was not found with FSH concentrations of 500 or 1000 ng/ml. EGF also increased the tubule content of inhibin after the addition of 100 μg dibutyryl cyclic AMP/ml but no effect of EGF was observed on the FSH- or dibutyryl cyclic AMP-induced secretion of inhibin into the medium.
The effect of EGF on inhibin content in the tubules was partially suppressed by the addition of 4β-phorbol-12β-myristate-13α-acetate (20 ng/ml). Insulin (1–100 ng/ml) decreased basal inhibin secretion without changing the inhibin content of tubules and this effect was antagonized by EGF (10 ng/ml) with insulin doses of 1–50 ng/ml whereas, at 100 ng/ml, the effect of EGF on tubule inhibin content was reversed. The addition of EDTA (2 mmol/l) resulted in an inhibition of basal and EGF-induced inhibin production. These data demonstrate a stimulatory effect of EGF on inhibin production by isolated seminiferous tubules which is inhibited by insulin and phorbol esters, both stimulators of protein kinase C activity.
Journal of Endocrinology (1989) 123, 213–219
The endocrine and metabolic response to feeding in the developing lamb
Authors: Symonds M. E. , Andrews D. C. , Johnson P. 
Published: December 2008

ABSTRACT
Oxygen consumption (VO2), carbon dioxide production (VCO2), heart rate and the arterial plasma concentrations of glucose, non-esterified fatty acids, thyroxine (T4), 3,5,3′-tri-iodothyronine (T3), TSH, insulin, cortisol and GH were measured before and after feeding a formula milk diet to lambs aged 9, 21, 33 and 46 days. In all age groups, VO2, VCO2 and heart rate increased significantly following feeding and this effect was greatest at 9 days of age. Both VO2 and VCO2 before and after feeding decreased with age. Plasma concentrations of T3 before feeding did not change with age, but plasma T3 levels after feeding were significantly higher in lambs aged 9 days compared with 33 and 46 days. There was no effect of feeding on TSH or age on plasma TSH and T4 concentrations. In all age groups, glucose concentration increased after feeding and was paralleled by a rise in insulin concentration. At 9 and 21 days of age plasma glucose and insulin concentrations reached a plateau after the initial postprandial increase and together with a rise in respiratory quotient was indicative of a stimulation of carbohydrate oxidation. Plasma concentrations of GH increased after feeding at 21 days and older, when the mean growth rate was also stimulated by 75%. Basal metabolic rate and dietary-induced thermogenesis both decreased with age and, as a result, metabolism associated with an increase in GH levels after feeding became more efficient in terms of growth rate after 21 days. It is therefore concluded that there are major endocrine and cardiorespiratory changes in response to feeding of the young lamb which are important in stimulating and/or facilitating its growth and development.
Journal of Endocrinology (1989) 123,295–302
Sustained inhibition of sperm production and inhibin secretion induced by a gonadotrophin-releasing hormone antagonist and delayed testosterone substitution in non-human primates (Macaca fascicularis)
Authors: Weinbauer G. F. , Khurshid S. , Fingscheidt U. , Nieschlag E. 
Published: December 2008

ABSTRACT
Since the concomitant administration of a gonadotrophin-releasing hormone (GnRH) antagonist and testosterone suppresses sperm production only incompletely, the feasibility of treatment with a GnRH antagonist and delayed testosterone supplementation for sustained suppression of sperm production in a non-human primate model was investigated. Adult cynomolgus monkeys (Macaca fascicularis; five/group) received daily s.c. injections of the GnRH antagonist [N-acetyl-d-2-naphthyl-Ala1,d-4-chloro-Phe2,d-pyridyl-Ala3,nicotinyl-Lys5,d- nicotinyl - Lys6, isopropyl-Lys8,d-Ala10]-GnRH of either 450 or 900 μg/kg for 18 weeks. During week 6 of the GnRH antagonist treatment, all monkeys were given a single i.m. injection of 40 mg of a long-acting testosterone ester (testosterone-trans-4-n-butylcyclo-hexanecarboxylate; 20-Aet-1). Within 1 week, serum LH bioactivity was suppressed in both groups and remained low throughout the entire treatment period. Similarly, concentrations of serum testosterone declined precipitously. During week 6, substitution with testosterone restored concentrations of serum testosterone into the pretreatment range. Concentrations of serum inhibin declined within 1 week and remained suppressed during the period of treatment with the GnRH antagonist. Testicular volumes were reduced to approximately 25% of pretreatment values in both groups by week 8 and stayed in that range during the remaining period of administration of the GnRH antagonist. During the first 6 weeks of administration of the GnRH antagonist, the ejaculatory response to electrostimulation and the volume of the ejaculates diminished with time. Supplementation with testosterone during week 6 restored the ejaculatory responses within 2–3 weeks. From week 9 of GnRH antagonist treatment onwards, all monkeys given 450 μg/kg and four monkeys given 900 μg/kg produced azoospermic ejaculates. The fifth animal in the latter group became azoospermic during week 13. Azoospermia persisted throughout the entire period of treatment with the GnRH antagonist and for a further 7–13 weeks. All suppressive effects of administration of GnRH antagonist were reversible. During the recovery phase the increase in testicular volumes paralleled an increase in concentrations of serum inhibin. The suppression of inhibin levels during the period of administration of testosterone indicates that Sertoli cell activity was not restimulated by testosterone. In conclusion, GnRH antagonist treatment with delayed supplementation with testosterone might serve as a model for further research towards the development of an endocrine male contraceptive. The recovery pattern of serum levels of inhibin suggests that inhibin could serve as a marker for Sertoli cell activity.
Journal of Endocrinology (1989) 123, 303–310
Stimulation of DNA synthesis in cultures of ovine mammary epithelial cells by insulin and insulin-like growth factors
Authors: Winder S. J. , Turvey A. , Forsyth I. A. 
Published: December 2008

ABSTRACT
Ovine mammary epithelial cell clumps (30–90 μm) were plated onto attached gels of rat tail collagen in serum-free medium. Synthesis of DNA by these cultures could be stimulated by insulin-like growth factor-I (IGF-I) with a median effective dose of 5 μg/l, irrespective of stage of pregnancy. The time-course of response, however, was significantly slower in cells prepared from mammary tissue of non-pregnant and early pregnant sheep compared with sheep later in pregnancy. IGF-II had approximately 10% of the potency of IGF-I in stimulating DNA synthesis. Insulin acted over a wide concentration range and produced a maximum rate of stimulation not significantly different from that produced by IGF-I. These results are consistent with actions through the type-I IGF receptor although insulin may also act through its own receptor, possibly stimulating local IGF-I production. It is concluded that IGF-I is an important mitogen for ovine mammary epithelial cells.
Journal of Endocrinology (1989) 123, 319–326
Characterization of the growth hormone-binding protein of human serum using a panel of monoclonal antibodies
Authors: Barnard R. , Quirk P. , Waters M. J. 
Published: December 2008

ABSTRACT
A panel of monoclonal antibodies (MAbs) reactive with distinct epitopes on the rabbit liver GH receptor and rabbit serum GH-binding protein (GHBP) were tested for cross-reactivity with the GHBP from human serum. Four of seven MAbs reacted with the human serum GHBP. Immunoprecipitation of the human binding protein enabled hormonal specificity identical to that previously reported for human GH receptors to be demonstrated. Scatchard analyses of 125I-labelled human GH binding to the serum GHBP were carried out with correction made for endogenous human GH which was measured by radioimmunoassay of each serum sample. This approach yielded the first reliable estimates of the affinity and capacity of the human GHBP. The binding capacity (mean ± s.e.m.) of female sera (804±126 pmol/l; n= 6) was greater than that of male sera (505 ± 36 pmol/l; n=9; P < 0·02). The affinity of the GHBP was 0·91 ±0·10 litres/nmol (n= 15).
The presence of multiple epitopes common to the human serum GHBP and the rabbit liver GH receptor is consistent with identity between the extracellular domains of the human GHBP and the human GH receptor, as is the case for the rabbit GHBP and GH receptor.
Journal of Endocrinology (1989) 123, 327–332
Effects on oestrous cyclicity and ovulation of unilateral section of the vagus nerve performed on different days of the oestrous cycle in the rat
Authors: Chávez R. , Sánchez S. , Ulloa-Aguirre A. , Domínguez R. 
Published: December 2008

ABSTRACT
The effects of unilateral section of the right or left vagus nerve (SRVN, SLVN) performed on different days of the oestrous cycle of the rat were analysed. Vagal nerve section on the day of oestrus or on day 1 of dioestrus (D1) altered oestrous cyclicity in a more significant way than when it was performed on day 2 of dioestrus (D2) or pro-oestrus (6/58 maintained normal oestrous cycles compared with 32/39 that did not; P<0.01). Ovulation rate at oestrus was lower in rats with SLVN than in the sham-operated group (32/47 vs 28/32; P < 0.05). The number of ova shed by the left ovary was reduced in sham-operated rats and in animals with SRVN and SLVN, whereas the number shed by the right ovary was not modified. The day of the oestrous cycle on which the vagus nerve was cut also influenced the number of ova shed. No changes in plasma levels of FSH at oestrus were observed in animals with SRVN or SLVN. The results indicate that vagal manipulations performed at the beginning of the oestrous cycle (day of oestrus and D1) induce more changes on oestrous cyclicity and ovulation than when they are performed during the second half of the cycle (D2 and pro-oestrus). In addition, the left ovary is more sensitive to neural manipulation than is the right one.
Journal of Endocrinology (1989) 123, 441-444
Role of angiotensin II in aldosterone regulation in the Pekin duck
Authors: Gray D. A. , Gerstberger R. , Simon E. 
Published: December 2008

ABSTRACT
The response of plasma aldosterone to increased plasma angiotensin II (AII) was evaluated in normally hydrated Pekin ducks as well as in birds in which plasma sodium had been acutely increased (+12 mmol/l) or reduced (−4 mmol/l) by the prior infusion of hypertonic saline or hypotonic glucose. In all cases, the i.v. infusion of AII at rates of 5, 15 and 45 pmol/kg per min for 1 h produced dose-dependent increases in the plasma concentration of aldosterone, with a potency that was inversely related to the sodium status. In addition, adrenal receptors for AII were demonstrated by in-vitro autoradiography and membranebinding techniques, suggesting that the AII effect on aldosterone secretion is direct. Angiotensin II produced no change in plasma corticosterone.
The infusion of KC1 at 1, 2 and 5 mmol/l for 1 h increased plasma potassium by as much as 2 mmol/l, but had no influence on plasma aldosterone. Similarly, the heptapeptide angiotensin III, infused at 5, 15 and 45 pmol/kg per min for 1 h had no effect on circulating aldosterone.
The results show that in ducks, AII has a physiological role in the control of aldosterone, whereas plasma potassium and angiotensin III have no such secretagogue function.
Journal of Endocrinology (1989) 123, 445–452
Improved estimates of clearance of 131I-labelled insulin-like growth factor-I carrier protein complexes from blood plasma of sheep
Authors: Davis S. R. , Hodgkinson S. C. , Moore L. G. , Gluckman P. D. 
Published: December 2008

ABSTRACT
Clearance of protein-bound forms of insulin-like growth factor-I (IGF-I) from the circulation of sheep was determined using single injections of 131I-labelled ovine or [Thr59]-human IGF-I, in the 'free' form or prebound to 50 or 150 kDa plasma binding protein fractions. The half-life of circulating protein-bound forms of IGF-I was determined by size-exclusion chromatography of plasma samples taken over a 24-to 26-h experimental period.
IGF-I bound to lower molecular weight binding protein(s) (approximately 50 kDa) showed a half-life of 26–40 min (mean 34 min; n = 6), while the half-life of a high molecular weight fraction (150 kDa) was considerably longer (range 398–603 min; mean 545 min; n =8). Metabolic clearance of IGF-I following administration of free tracer ranged from 3.0 to 5.3 ml/min in sheep (n = 4) weighing 26.0–28.5 kg. Tracer distribution volume was 59 ml/kg liveweight (n=4).
Tracer degradation products were first detected in plasma 8 h after i.v. administration. No differences in stability of the purified ovine and recombinant human IGF-I tracer preparations were observed. However, a fraction of the [Thr59]-IGF-I tracer did not possess binding activity and this was associated with excretion of a greater proportion of administered radioactivity (over 22 h) in urine in animals receiving [Thr59]-IGF-I tracer (18.4–19.3%) compared with ovine IGF-I (7.1–11.0%).
Following administration of free tracer or tracer bound to the 50 kDa protein, the proportion of radioactivity bound to the 150 kDa fraction increased over the first 20-30 min of observation. However, this was not apparent following administration of tracer bound to the 150 kDa protein, indicating that the more rapid turnover of IGF-I bound to the 50 kDa protein was associated, in part, with transfer of IGF-I to the 150 kDa binding protein fraction.
The calculated secretion rates of the IGFs were two- to threefold and twentyfold higher, for IGF-I and -II respectively, relative to that of insulin. These data are evidence supporting roles for IGFs in the regulation of metabolism.
Journal of Endocrinology (1989) 123, 469–475