bluuebunny/crossref_metadata_2025 huggingface dataset:
LHRH pulse frequency in normal and infertile men
Authors: Wu F. C. W. , Taylor P. L. , Sellar R. E.
Published: December 2008

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

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

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

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

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

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

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

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

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

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
Differential activation of the pituitary-adrenocortical axis after stress in the rat: use of two genetically selected lines (Roman low- and high-avoidance rats) as a model
Authors: Walker C.-D. , Rivest R. W. , Meaney M. J. , Aubert M. L.
Published: December 2008

We have examined the activation of the pituitary-adrenal axis in two lines of rats, the Roman high (RHA)- and low (RLA)-avoidance rats known to be emotionally different. These rats are selected for rapid acquisition of a conditioned avoidance response (RHA) compared with failure to acquire this response (RLA). In this study the endocrine response (ACTH, corticosterone, aldosterone) of RLA and RHA rats to two types of stress was examined: exposure to openfield stress for 10 min (Op) or exposure to ether vapours for 3 min (E). Basal plasma ACTH concentrations were lower in RLA than in RHA rats (RLA: 110·8 ± 24·5 ng/l; RHA: 252·7 ± 60·8 ng/l, P<0·05) but the absolute values of ACTH reached after both types of stress were comparable between RLA and RHA rats. Plasma corticosterone and aldosterone under resting conditions were not different between RLA and RHA rats. Plasma corticosterone was higher in RLA following openfield stress (P<0·05) while no differences between RLA and RHA were observed after ether stress (RHA: basal = 66±14·nmol/l, Op =384± 55, E= 606± 75; RLA: basal=121±52, Op = 612 ±92, E= 698 ± 89). Stressinduced increases in plasma aldosterone were higher in the RLA line after both types of stress (RHA: basal = 175±36 pmol/l, Op = 546±53, E= 563± 47; RLA: basal = 272 ± 64, Op =1246 ± 91, E= 863 ± 72). Pituitary responsiveness to exogenous corticotrophinreleasing factor (CRF) in vivo and in vitro differed in the two lines: administration of ovine CRF (10 μg/kg body weight, i.p.) resulted in significant increases in ACTH secretion but the response was significantly lower in RHA rats (RHA: 511·1 ±41·5 ng/l; RLA: 831·4 ± 70·3 ng/l, P<0·01). Dispersed pituitary cells from the RHA line exhibited a smaller response to CRF (10 nmol/l) treatment in vitro compared with cells derived from the RLA rats (RHA: 750 ± 83% of control; RLA: 1374 ±79, P<0·01) suggesting differences in pituitary sensitivity to CRF between the two lines. Additional differences at the pituitary level were observed since the type II glucocorticoid receptor population in RHA rats was higher than in RLA rats (RHA: 246±13 fmol [3H]RU28362 bound/mg protein; RLA: 173±18, P<0·01). Similarly, hippocampal type I glucocorticoid receptor population was increased in RHA rats (RHA: 172·2 ± 8·3 fmol [3H]aldosterone bound/mg protein; RLA: 116·7±7·3, P< 0·01). It is concluded that first, differences in pituitary activity between RLA and RHA rats are distinct from changes observed at the adrenal level, secondly, increased stress-induced ACTH output in the RLA line is associated with enhanced pituitary sensitivity to CRF and possibly with diminished corticosterone inhibitory feedback action on CRF and ACTH secretion, and thirdly, the possible involvement of differences in the pattern of CRF secretion between RLA and RHA rats on resting pituitary ACTH secretion cannot be excluded.

Journal of Endocrinology (1989) 123, 477–485
Enhancement of ectopic β-human chorionic gonadotrophin expression by interferon-α
Authors: Iles R. K. , Chard T.
Published: December 2008

Treatment of three β-human chorionic gonadotrophin (β-hCG)-expressing bladder tumour cell lines with interferon-α (IFN-α) (5000 U/per 106 cells) enhanced the rate of β-hCG secretion from 34·2 ±0·9 to 102·5 ± 0·1 mIU/106 cells per 72 h in cell line 5637; 111·15 ± 11·75 to 261·8± 51·75 mIU/106 cells per 72 h in cell line RT112 and 503·25 ± 28·55 to 1361·65± 110·3 mIU/106 cells per 72 h in cell line SCaBER. IFN-γ had no effect on the rate of β-hCG secretion. Both interferons reduced the growth rate of the cells: incorporation of radiolabelled thymidine was reduced by 15–45% in the presence of IFN-α and by 20–53% with IFN-γ. Enhancement of β-hCG secretion by IFN-α was dose-dependent over the range 5–50 000 U/106 cells. Analysis of cell cycle profiles by flow cytometry showed no increase in the proportion of cells in the G0G1 phase in cultures treated with IFN-α.

The conceptus of some species produces substances which are either luteotrophic or anti-luteolytic. In sheep, the corpus luteum is maintained by ovine trophoblast protein-I, which has been shown to have structural homology with human IFN-α. In primates and a few other higher mammals, early pregnancy is maintained by chorionic gonadotrophin. IFN-α is also an early product of the human conceptus. We have now shown that IFN-α enhances the ectopic production of the β-subunit of hCG by bladder tumour cells. This study suggests a direct transcription/translational effect of this cytokine on the expression of a reproductive endocrine gene.

Journal of Endocrinology (1989) 123, 501–507
Activity of 17β-hydroxysteroid oxidoreductase in tissues of the human fetus
Authors: Milewich L. , MacDonald P. C. , Carr B. R.
Published: December 2008

The interconversion of oestrone and oestradiol, androstenedione and testosterone, and dehydroepi-androsterone and 5-androstene-3β,17β-diol in mammalian tissues is catalysed by 17β-hydroxysteroid oxidoreductase (17β-HSOR). To identify tissue sites of 17β-HSOR activity in the human fetus, microsomal fractions from 15 different fetal tissues obtained from first and second trimester pregnancies were used for evaluation of enzymatic activity by use of [17α-3H] oestradiol as the substrate and NADP+ as the co-factor. With these reagents, the enzyme-catalysed reaction led to the production of both non-radiolabelled oestrone and NADP3H in equimolar amounts; the radioactivity associated with NADP3H was used to quantify 17β-HSOR activity. Activity of 17β-HSOR was present in microsomes of all the tissues evaluated. The specific activity of the enzyme was highest in liver and placental microsomes. The interconversion of oestradiol and oestrone in microsomal fractions of nine different fetal tissues was studied by the use of substrates labelled with tritium at stable nuclear positions ([6,7-3H]oestradiol and [6,7-3H]oestrone). The products, [3H]oestrone and [3H]oestradiol, were quantified by the use of established techniques; other metabolites formed in these incubations were not identified. The reductive pathway of metabolism (oestrone to oestradiol) appeared to be favoured in microsomal fractions prepared from placenta, fetal zone of the adrenal gland and, possibly, lung. The oxidative pathway (oestradiol to oestrone) appeared to be favoured in microsomes prepared from liver, intestine, stomach, kidney, brain and heart. 17β-HSOR activity in fetal liver also was assessed by the use of fresh and frozen-thawed tissue, homogenate, subcellular fractions, and, also, in primary hepatocytes maintained in culture; the specific activity of the enzyme was highest in the microsomal fraction of liver tissue and 17β-HSOR activity in liver microsomes was linear with time of incubation up to 1 h. In hepatocytes, the enzymatic activity was linear with time of incubation up to 2 h and with cell number up to 2·5 × 105 cells/ml; the apparent Michaelis constant of hepatocyte 17β-HSOR for oestradiol was 11 μmol/l. The specific activity of 17β-HSOR did not change after pretreatment of hepatocytes for 24 h with insulin, glucagon or dexamethasone.

Journal of Endocrinology (1989) 123, 509–518
UNCOUPLING OF RECEPTOR-MEDIATED CELLULAR RESPONSES BY IONIC LITHIUM
Authors: Zaidi M. , Patchell A. , Datta H.K. , MacIntyre I.
Published: December 2008

The propensity of ionic lithium to interfere with the coupling of receptors to guanine nucleotide binding proteins (G-proteins) has only recently been investigated using rat cortical membranes. In the present study we have used intact isolated osteoclasts to investigate lithium-induced uncoupling of the receptor-mediated actions of calcitonin. All actions of calcitonin on the osteoclast were abolished by ionic lithium. We believe that the cation prevents signal transduction by inhibiting G protein-receptor interaction, the first step in intracellular signalling.
THE RESPONSE OF INHIBIN TO HUMAN CHORIONIC GONADOTROPHIN IS DECREASED IN SENESCENT MEN COMPARED WITH YOUNG MEN
Authors: Fingscheidt U. , Nieschlag E.
Published: December 2008

Inhibin and testosterone were measured in the serum of young and old men with proven fertility before and after stimulation with human chorionic gonadotrophin (hCG) in order to characterize endocrinological changes in senescence further. While there was a significant increase of both hormones in all young men, there was a decreased response of serum testosterone and an insignificant increase in inhibin in the older men. Although basal hormone levels and ejaculate parameters were not different, hCG stimulation revealed that there were decreased secretory capacities of Leydig as well as of Sertoli cells in old age.
Occurrence of rare somatomammotrophs in ovine anterior pituitary tissue studied by immunogold labelling and electron microscopy
Authors: Thorpe J. R. , Ray K. P. , Wallis M.
Published: December 2008

Prolactin and GH are distinct hormones that have been conventionally thought to be produced and secreted by separate cells in the anterior pituitary gland. Recently it has been suggested that some cells (somatomammotrophs) may secrete both hormones. We have examined the occurrence of somatomammotrophs in sheep anterior pituitary tissue using immunogold labelling. Of a number of procedures used, double labelling using first antibodies raised in different species proved the least susceptible to apparent co-localization of hormones due to artifacts. Using this approach it was shown that a large proportion of the cells in the sheep anterior pituitary glands examined were mammotrophs or somatotrophs, showing no significant co-localization of GH and prolactin. Of 1800 cells examined, only two were somatomammotrophs. One of these, from a female animal, contained GH and prolactin in different granules within the same cell. The other, from a male animal, showed co-localization of these two hormones within the same granules.

Journal of Endocrinology (1990) 124,67–73
Premature birth of live lambs induced by pulsatile infusion of ACTH
Authors: MacIsaac R. J. , Carson R. S. , Horvath A. P. , Wintour E. M.
Published: December 2008

This study was designed to investigate the effects of pulsatile infusion of ACTH into ovine fetuses on the endocrine changes that precede parturition, the timing of birth and the subsequent survival of the lamb. Where appropriate, these parameters were compared with fetuses infused with pulses of saline and uninfused normal term fetuses. Ten fetuses received a 15-min infusion of synthetic ACTH(1–24) (79 ng/min) from day 125 (n=9) or day 126 (n=1) of gestation. Seven fetuses were born prematurely within 174±14 h (mean ± s.e.m.) after the commencement of the infusion, i.e. at 132 ± 0·6 days, whilst three died in utero at 130–131 days. When born all lambs could breath, walk and suckle. Of the seven premature lambs, four died 2–10 days after parturition but three survived for at least 12 months after birth. Fetuses infused with pulses of ACTH exhibited intermittent but very large increases in plasma ACTH values, with the first pulse, on day 1, increasing ACTH values from 5·1 ± 1·1 to 140 ± 31·3 pmol/l (P<0·001). At the next sampling time, ACTH values were not significantly different from preinfusion values. A similar plasma ACTH profile was observed on each subsequent day of ACTH treatment. In contrast, fetuses (n=4) infused with pulses of saline between 125 and 131 days exhibited fetal plasma concentrations of ACTH which ranged between 2 and 12 pmol/l for the majority of the time. Of the uninfused fetuses (n=8) that were studied during the last week of normal gestation, seven were born alive at 148·9± 1·0 days of gestation, whilst one lamb was stillborn at 146 days. In these fetuses, plasma concentrations of ACTH increased slowly to 35·6 ±2·4 pmol/l on the day before delivery with a further increase to 76·4± 3·9 pmol/l occurring on the day of delivery. In fetuses infused with pulses of ACTH there was also a significant (P< 0·001) increase in the fetal cortisol to corticosterone ratio from a value of 2·9 before the commencement of the infusion to 69·1 just before birth. In ewes bearing uninfused fetuses born at normal term, maternal plasma concentrations of progesterone on day 4 before delivery were significantly (P<0·05) lower than on day 5 before delivery. In comparison, in ewes bearing fetuses infused with pulses of ACTH, a significant (P<0·05) decrease from maternal plasma concentrations of progesterone on day 5 before delivery did not occur until day 1 before delivery. In ewes bearing uninfused or prematurely delivered fetuses infused with pulses of ACTH, maternal plasma concentrations of oestrogen did not significantly (P<0·01) increase until the day of parturition. It is concluded that a minimum of 6–7 days of ACTH treatment is required by the fetal adrenal for the induction of cortisol synthesis sufficient to produce the birth of viable lambs. However, premature lambs have a 57% mortality rate in the 2- to 10-day period after birth.

Journal of Endocrinology (1990) 124, 99–107
Effects of epidermal growth factor on gastrointestinal electromyographic activity of conscious sheep
Authors: McLeay L. M. , Comeskey M. A. , Waters M. J.
Published: December 2008

Adult sheep were infused with depilating doses of epidermal growth factor (EGF) at 4 pg/kg per h for 24 h. Food was available ad libitum during recording of integrated electromyographic (EMG) activity of the gastrointestinal tract. In comparison with control sheep infused with saline, EGF reduced the frequency of A and B sequences of contraction of the reticulum and rumen over the 24-h period, an effect attributable to the consumption of less food. During the 24-h infusion, EGF stimulated phase III migrating myoelectric complex (MMC)-like activity of the duodenum with an associated decline in the EMG of the abomasal antrum.

Infusion of EGF for 1 h at 2·5 and 5·0 μg/kg per h in fasted animals produced inhibitory effects on the frequency of A sequences of contraction of the reticulum and rumen during the infusion, and on the amplitude of the ruminal EMG during, and in the hour following, infusion. Phase III MMC-like activity of the duodenum was stimulated by EGF in fasted animals.

It is concluded that in fed sheep, depilating doses of EGF have inhibitory effects on the EMG activity of the reticulum and rumen through reductions in food consumption and by other undefined mechanisms. Additional effects of EGF on the gastrointestinal tract of sheep include stimulation of duodenal phase III MMC-like activity.

Journal of Endocrinology (1990) 124, 109–115
Effect of high-density lipoprotein on bovine granulosa cells: progesterone production in newly isolated cells and during cell culture
Authors: O'Shaughnessy P. J. , Pearce S. , Mannan M. A.
Published: December 2008

It has been proposed that changes in steroidogenesis which occur during early development of the corpus luteum may be due to increased availability of lipoproteins. Bovine follicular fluid, however, contains significant amounts of high-density lipoprotein (HDL), and granulosa cells are exposed to this lipoprotein before ovulation. To determine whether bovine granulosa cells can utilize HDL the effects of this lipoprotein on freshly isolated, non-luteinized granulosa cells and on granulosa cells undergoing luteinization in serum-free culture were examined. Cells were isolated from non-atretic, antral follicles and cultured for 12 h in 10% (v/v) lipoprotein-deficient serum to allow cell attachment. After this time cells were cultured in serum-free medium. During culture the cells underwent functional luteinization as assessed by an increase in basal progesterone output (9·6-fold in 7 days) which was associated with a marked increase in activity of cholesterol side-chain cleavage and loss of aromatase activity. Dibutyryl cyclic AMP (dbcAMP) increased basal production of progesterone about twofold but HDL alone had no effect. Addition of HDL plus dbcAMP, in contrast, caused a very marked stimulation (up to ten times) of basal steroidogenesis. This trophic effect of HDL and dbcAMP lasted at least 2 weeks. Activity of cholesterol side-chain cleavage was stimulated (threefold over basal) by dbcAMP during culture but HDL was without effect, alone or with dbcAMP.

Addition of HDL (in the presence or absence of dbcAMP) to freshly isolated granulosa cells had no significant stimulatory effect on progesterone production over 12 h in six experiments, and in two of these experiments a significant inhibitory effect was seen. Incubation with 22R-hydroxycholesterol, in contrast, caused a marked stimulation of progesterone production, indicating that the steroidogenic capacity of the cells was not already saturated. Results presented here suggest that bovine granulosa cells are able to utilize HDL for steroidogenesis only after luteinization. The massive secretion of progesterone by luteinized granulosa cells which occurs in the presence of HDL suggests that this lipoprotein is very important in the development and maintenance of luteal cell function in cattle.

Journal of Endocrinology (1990) 124, 255–260
Effect of ovariectomy and treatment with ovarian steroids on vasopressin release and fluid balance in the rat
Authors: Peysner K. , Forsling M. L.
Published: December 2008

Plasma vasopressin concentrations have previously been shown to vary during the oestrous cycle of the rat, being highest on the morning of pro-oestrus and lowest on dioestrus day 1. To determine the effect of gonadal steroids on vasopressin secretion and fluid balance, mature rats were ovariectomized and given oestrogen, progesterone or vehicle alone s.c. for periods of up to 16 days. Plasma vasopressin concentrations fell after ovariectomy and this was reflected in an increase in 24-h urine volume. The normal increase in plasma vasopressin concentrations seen over daylight hours was also suppressed. The change in vasopressin concentrations observed on steroid treatment depended upon both the dose and the duration. High doses of oestrogen were associated with a fall in plasma vasopressin, probably as a result of fluid retention. Thus, of an initial group of rats given silicone elastomer implants containing 50, 500 or 1000 μg oestradiol in oil, plasma vasopressin concentrations were reduced after 7 days treatment with 1000 μg oestradiol implants in association with reduced plasma sodium concentrations. Daily s.c. injections of 100 μg oestradiol benzoate/100 g body weight produced an immediate small increase in plasma vasopressin concentrations, but by 14 days the plasma concentrations of 0·7 ± 0·16 pmol/l (mean ± s.e.m.) had fallen significantly and were less than those in the vehicle-treated group (1·2± 0·26 pmol/l). However, after treatment for 14 days with implants containing only 50 μg oestradiol, plasma vasopressin concentations were higher compared with the group receiving vehicle alone, despite the fact that the plasma osmolality was lower in the latter group, suggesting a long term resetting of the osmoreceptors. Progesterone treatment with two implants containing 17·5 mg progesterone in oil was associated with an initial suppression of plasma vasopressin concentrations, but 16 days after the implant the plasma concentrations were higher than in the control group. Neither oestrogen nor progesterone restored the vasopressin concentrations to those seen in the intact animal. Oestrogen treatment resulted in a reduction in food and water intake, whereas progesterone treatment produced an initial increase in food and water intake, and a fall in plasma osmolality which could account for the reduced plasma vasopressin. This was followed by an increase in urine flow over days 6 to 15. Thus ovariectomy had a marked effect on circulating vasopressin concentrations, probably as a result of complex changes since administration of either oestrogen or progesterone in doses giving normal circulating concentrations had little effect.

Journal of Endocrinology (1990) 124, 277–284
Effect of maternal hypothyroxinaemia in the rat on brain biochemistry in adult progeny
Authors: Hadjzadeh M. , Sinha A. K. , Pickard M. R. , Ekins R. P.
Published: December 2008

The effects of maternal hypothyroxinaemia during pregnancy on subsequent brain biochemistry in progeny was studied. Normal and partially thyroidectomized rat dams were mated and progeny allowed to grow to adulthood. Brain regions (cerebellum, medulla, midbrain, cerebral cortex and paleocortex) were dissected out and the activities of various cell marker enzymes were determined, along with cholesterol contents.

Maternal hypothyroxinaemia was without effect on body weight, brain weight or thyroid status of adult progeny. Oligodendroglial marker enzyme activities were altered in progeny from thyroidectomized dams. 2′,3′-Cyclic nucleotide 3′-phosphohydrolase was decreased in the medulla (by 37%) and midbrain (by 32%). 5′-Nucleotidase was also diminished in the same brain regions, by 33% in the medulla and by 35% in the midbrain. In contrast, oleate esterase was increased (by 39%) in the paleocortex. Although these enzymes are putatively involved in myelin metabolism, no changes were observed in the concentration of a major myelin lipid (cholesterol). The activity of β-d-glucuronidase (a general neuronal marker) was decreased (by 30%) in the paleocortex, whereas N-acetyl-β-d-galactosaminidase (a general glial marker) was unchanged in all brain regions.

In summary, maternal hypothyroxinaemia has irreversible effects on brain biochemistry in adult progeny. The damage is parameter-selective and brain region-specific, analogous to the pattern of neurological damage seen in offspring born to hypothyroxinaemic women in iodine-deficient endemias.

Journal of Endocrinology (1990) 124, 387–396
Induction of lactogenic receptors in liver of hypophysectomized rats treated with bovine growth hormone–monoclonal antibody complexes
Authors: Thomas H. M. , Green I. C. , Wallis M. , Aston R.
Published: December 2008

Male hypophysectomized rats treated with bovine (b)GH–monoclonal antibody complexes showed enhanced weight gain compared with animals treated with bGH alone over a 12-day treatment period. Liver microsomes prepared from animals showing enhanced weight gain exhibited increased specific binding of human (h)GH. Studies on the specificity of these binding sites showed that they were lactogenic, 125I-labelled hGH being displaced by ovine prolactin, but not by non-mammalian growth hormones. In this respect they were similar to lactogenic binding sites in the liver of pregnant rats. Monoclonal antibodies to hGH blocked binding to lactogenic receptors to different extents. The pattern of such inhibition was similar, but not identical, for the receptors induced in hypophysectomized rats and those from pregnant rat liver. The evidence available suggests that the lactogenic receptors induced by bGH–monoclonal antibody complexes are not directly involved in the enhancement of growth.

Journal of Endocrinology (1990) 124, 469–474
Evidence for steroid control of a putative angiogenic factor in the porcine uterus
Authors: Ashworth C. J. , Fliss M. F. V. , Bazer F. W.
Published: December 2008

The formation of new capillaries, both in extraembryonic membranes and in the maternal endometrium, is an essential prerequisite for appropriate feto-maternal relationships throughout pregnancy. At present there is no indication of the nature of the uterine angiogenic stimulus. In-vitro, degradation products of hyaluronic acid, following its catalysis by hyaluronidase, have been shown to have angiogenic properties. In the current study, levels of hyaluronic acid in endometrial tissues and of hyaluronidase and hyaluronic acid in uterine flushings were measured during the oestrous cycle and early pregnancy.

The concentration of both hyaluronic acid and hyaluronidase in uterine flushings followed the growth and regression of the corpus luteum, in that basal levels detected on days 0 and 6 increased to peak concentrations on days 12 and 15. By day 18, levels of both hyaluronidase and hyaluronic acid had decreased in cyclic gilts, but remained increased in pregnant pigs. Tissue concentrations of hyaluronic acid were not affected by pregnancy or by the day of the oestrous cycle. In a subsequent experiment, four groups of gilts were ovariectomized on day 4 and thereafter received daily injections of corn oil, progesterone, oestrogen or a combination of oestrogen and progesterone. Hyaluronidase was undetectable in uterine flushings collected on day 15 from corn oil-and oestrogen-treated gilts, but present in similar amounts in uterine flushings from gilts treated with progesterone and progesterone plus oestrogen. Similarly, uterine fluid concentrations of hyaluronic acid were increased in progesterone- and progesterone plus oestrogen-treated gilts, but not in corn oil-or oestrogen-treated pigs. Tissue concentrations of hyaluronic acid were unaffected by steroid treatment.

These results indicate that progesterone stimulates secretion of hyaluronidase and hyaluronic acid; both substances believed to be associated with the presence of an angiogenic factor in the pig uterus, but there was no evidence of a synergistic interaction between progesterone and oestrogen.

Journal of Endocrinology (1990) 125, 15–19
Comparison of ACTH and ACTH precursor peptides secreted by human pituitary and lung tumour cells in vitro
Authors: Crosby S. R. , Stewart M. F. , Farrell W. E. , Gibson S. , White A.
Published: December 2008

The molecular forms of ACTH secreted by established human small cell lung cancer (SCLC) cells and primary cultures derived from a bronchial carcinoid tumour, a pituitary adenoma and hyperplastic pituitary tissue have been characterized by Sephadex G-75 chromatography and quantified with two novel immunoradiometric assays for ACTH and ACTH precursor peptides. Pro-opiomelanocortin (POMC; Mr 31 000) and pro-ACTH (Mr 22 000) were secreted by all cell types. No smaller peptides were identified in the culture media from SCLC and bronchial carcinoid cells, implying a deficiency in the enzymes and/or intracellular organelles required for extensive POMC processing. A more heterogeneous profile of ACTH-containing peptides was produced by cells of pituitary origin, indicating more extensive proteolytic processing of POMC. However, the major peptide secreted by cells from a large aggressive pituitary adenoma was unprocessed POMC (Mr 31 000). These results suggest that both lung and pituitary cells in vitro retain their in-vivo pattern of POMC processing and provide valuable models in which to study the regulation of ACTH synthesis and secretion.

Journal of Endocrinology (1990) 125, 147–152
The International Reference Reagent for Insulin-like Growth Factor-I
Authors: Bristow A. F. , Gooding R. P. , Gaines Das R. E.
Published: December 2008

Three preparations of recombinant DNA-derived insulin-like growth factor-I (IGF-I) were obtained, prepared in ampoules coded 86/522, 86/720 or 87/518, and evaluated as candidate International Reference Reagents in an international collaborative study (nine laboratories in four countries) in response to a request by the World Health Organization (WHO).

Immunoassay dose–response curves for each of the three preparations did not in general differ significantly from those of local standards or from those of ampouled preparations of serum-derived IGF-I which were included in the study. The estimates of ampoule contents in terms of local standards showed considerable heterogeneity; the between-laboratory variability of estimates in terms of local standards was ten times greater than the inherent variability of estimates from these systems as estimated from comparisons of coded duplicates. Bioassay data were limited, and those available were inconsistent with immunoassay data. Of the three preparations, ampoules coded 86/720 were derived from an IGF-I preparation that was heterogeneous by high-performance liquid chromatography, and stability data for the preparation 86/522 were anomalous.

As a result, the ampouled preparation coded 87/518 has been established by WHO as the International Reference Reagent for IGF-I for immunoassay, with an assigned ampoule content of 3·1 μg/ampoule, and is available from the National Institute for Biological Standards and Control.

Journal of Endocrinology (1990) 125, 191–197