bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of low concentrations of bovine thyrotrophin by iodide uptake and organification in porcine thyrocytes
Authors: Reader S. C. J. , Davison B. , Ratcliffe J. G. , Robertson W. R.
Published: December 2008

Thyrocytes isolated from porcine thyroids by mechanical and enzymatic dispersion and cultured in Eagle's minimal essential medium, supplemented with 5% (v/v) fetal calf serum, glutamine and cortisol, formed a continuous monolayer within 48 h. This monolayer was without cytochemical peroxidase and diaphorase (NADPH reoxidation) activity. In the presence of bovine thyrotrophin (bTSH; 50 mu./l) the cells developed a follicular-like architecture which was maximal at 4 days before reverting back to a uniform monolayer at 6 days. There were no detectable changes in the total DNA content over this period. The follicular structures had marked diaphorase and peroxidase activity, the latter being apically distributed. Concomitant with follicle formation bTSH induced uptake and organification of iodide presented to the cells during the last 6 h of culture. The extent of this process depended on the dose of bTSH and the duration of stimulation. The most sensitive effects for both iodide uptake and organification occurred with 1 mu. bTSH/1 and were maximal with 100 mu./l. Uptake and organification were increased 20±8-fold and 9·6±2- fold (n = 10) respectively over the control with 100 mu./l and the doses of bTSH at which a half maximal response was seen (ED50) were 15±2 and 7±1 (s.d) mu./l (n = 10) respectively.

On changing the culture medium to a serum-free system using HB101 culture medium the stimulation time for the most sensitive bTSH effect was reduced to 2·5 days. Moreover the sensitivity of iodide uptake to bTSH was dramatically increased being significantly stimulated by 0·1 mu./l, saturated with 10 mu./l, and having an ED50 of 7 ± 0·2 mu. bTSH/1 (n = 7). Over the dose range 0·1–10 mu. bTSH/l intra- and interassay coefficients of variation were 7%±1·5 (n = 15) and 11% ± 2·5 (n = 15) respectively. Cyclic AMP production in cultures incubated under similar conditions (i.e. after chronic TSH stimulation) was also stimulated by bTSH doses in the range 15·6–125 mu./l. Cells stimulated for 2·5 days with dibutyryl cyclic AMP (range 1 μmol/1–2 mmol/l) also actively concentrated iodide in a dose-dependent fashion.

The presence of normal human serum in the medium yielded a progressive and dose-related decrease in TSH-stimulated iodide uptake. This inhibitory effect occurred with serum concentrations as low as 0·1%.

In conclusion, a porcine cell culture system is described in which iodide uptake is significantly stimulated by 0·1 mu. bTSH/l, a sensitivity inferior only to that reported with the cytochemical bioassay.

J. Endocr. (1985) 106, 13–20
The role of neonatal and pubertal gonadal hormones in regulating the sex dependence of the hepatic microsomal testosterone 5-reductase activity in the rat
Authors: Pak R. C. K. , Tsim K. W. K. , Cheng C. H. K.
Published: December 2008

Hepatic microsomal testosterone 5-reductase activity was approximately fourfold higher in adult female rats than in males. This discrepancy was only partly androgen-dependent since gonadectomy of male rats at 68 days of age resulted in only a partial increase of the enzyme activity. This increase was reversible by the administration of testosterone. Similar treatment, however, produced no effect in the female rat, indicating that there is a sex difference in testosterone responsivity. Castration of newborn male rats resulted in a marked increase in the basal enzyme activity. This increase was not affected by treating the adults with testosterone. Giving testosterone to male rats immediately after neonatal gonadectomy, or to newborn female rats, did not produce the male pattern of both the basal enzyme activity and the testosterone responsivity in adulthood. These results suggest that a brief exposure to neonatal androgen is not critical for the expression of the male type of enzyme activity, but that the continuous presence of the male gonads up to and including the pubertal period is essential. Exposure of pubescent female rats to testosterone during the period from 35 to 50 days of age resulted in a significant increase in testosterone sensitivity when tested at 90 days of age, suggesting that pubertal exposure to androgen is important for the expression of testosterone responsivity in adulthood. The sensitivity was potentiated when the animals were ovariectomized before puberty. Furthermore, the enzyme activity in prepubertally ovariectomized female rats was significantly lower than that in adult gonadectomized animals. The decreased level of activity returned to the control value when oestrogen was replaced during puberty, indicating that peripubertal oestrogen exposure is required for maintaining the high level of activity found in adult female rats. The present findings suggest that the pubertal period represents a sensitive phase during which sex hormones act to regulate the sexual differentiation of testosterone 5-reductase activity in the rat.

J. Endocr. (1985) 106, 71–79
Effect of immunoneutralization of thyrotrophin-releasing hormone on the release of thyrotrophin and prolactin during suckling or in response to electrical stimulation of the hypothalamus in the anaesthetized rat
Authors: Sheward W. J. , Fraser H. M. , Fink G.
Published: December 2008

The aim of the present study was to use the technique of immunoneutralization with anti-thyrotrophin-releasing hormone (anti-TRH) serum to investigate the role of TRH in mediating the TSH and prolactin responses to electrical stimulation of the hypothalamus and the prolactin response to suckling in lactating rats. Electrical stimulation of either the median eminence or paraventricular nuclei of male or female rats anaesthetized with urethane resulted in significant increases in the plasma concentrations of both TSH and prolactin. Injection of sheep anti-TRH serum blocked the rise in plasma TSH concentration in response to stimulation of either brain area, but did not block the increase in plasma prolactin concentration. In anaesthetized, lactating female rats, the suckling stimulus produced a significant increase in the plasma prolactin concentration, but did not alter the plasma TSH concentration. Injection of anti-TRH serum, but not control non-immune or anti-bovine serum albumin, significantly decreased the basal release of TSH but did not abolish the prolactin response to suckling. These results show that TRH is the principal mediator of the neural control of TSH release in the rat, but is not crucial for the release of prolactin in response to either hypothalamic stimulation or suckling.

J. Endocr. (1985) 106, 113–119
FSH secretion in pinealectomized rams subjected to artificial photoperiods
Authors: Barrell G. K. , Lapwood K. R. , Elgar H. J.
Published: December 2008

Eight mature Romney rams which had been pinealectomized and another eight sham-operated rams were allocated equally to one of two contrasting lighting regimes. They were housed indoors with the temperature held constant, offered a constant diet and plasma samples were collected each week for 9 months.

Changes in plasma FSH in pinealectomized and sham-operated rams were similar when the rams were subjected to normal seasonal changes in photoperiod, with lower FSH levels recorded under increasing daily photoperiods than during the phase of decreasing (stimulatory) photoperiods. In contrast a reversed pattern of changes in lighting advanced the increase of plasma levels of FSH in the case of sham-operated rams, because the period of decreased daily photoperiods occurred earlier in this situation. In this case, however, pinealectomized rams did not behave like the control animals, but had raised plasma FSH levels at the same time as rams on the normal lighting regime.

These results demonstrate that the pineal-mediated effects of photoperiod on reproduction in sheep directly involve FSH secretion and that seasonal cyclic changes in FSH secretion persist even after pinealectomy.

J. Endocr. (1985) 106, 167–171
Inhibition by prostaglandin E2of the release of vasopressin and β-endorphin from rat pituitary neurointermediate lobe or medial basal hypothalamus in vitro
Authors: Knepel W. , Nutto D. , Vlaskovska M. , Kittel Ch.
Published: December 2008

The present study was performed to examine the effect of the cyclo-oxygenase inhibitor, indomethacin, and that of various prostaglandins on the release of vasopressin and β-endorphin-like immunoreactivity (β-EI) from the rat neurointermediate lobe of the hypophysis, which was superfused in vitro. Indomethacin (2·8 and 28 μmol/l) changed neither basal secretion of vasopressin nor that evoked by electrical stimulation, whereas the resting release of β-EI was enhanced by indomethacin (28 μmol/l). Prostaglandin (PG) E2 did not influence resting release of vasopressin but markedly inhibited (by about 50%) electrically induced release of vasopressin (least effective concentration: 300 nmol/l) as well as spontaneous secretion of β-EI (least effective concentration: 100 nmol/l) in the presence of indomethacin (28 μmol/l). Prostaglandin F2α (5 μmol/l) also inhibited the evoked release of vasopressin, whereas PGD2 (5 μmol/l) did not. Prostaglandin F2α (5 μmol/l), D2 and I2 (1·5 μmol/l each) produced no effects on β-EI release. As observed in the neurohypophysis, PGE2 inhibited the electrically induced release of vasopressin from the medial basal hypothalamus in vitro. We conclude that prostaglandins (especially PGE2) can inhibit (1) the stimulated release of vasopressin when acting on vasopressin-containing nerve terminals of either neurosecretory system (neurohypophysis, median eminence region), and (2) the secretion of β-EI and, as can be inferred, α-MSH, by a direct action on intermediate lobe cells.

J. Endocr. (1985) 106, 189–195
Changes in epidermal growth factor concentrations of submandibular gland, plasma and urine of normal and sialoadenectomized female mice during various reproductive stages
Authors: Kurachi H. , Oka T.
Published: December 2008

The concentrations of epidermal growth factor (EGF) were measured by radioimmunoassay in the submandibular gland, plasma and urine of adult female C3H/HeN mice whilst virgin and during pregnancy, lactation and after lactation. During gestation there was a significant increase in the submandibular EGF concentration which was five to seven times higher than that found in virgin mice. The level of EGF in the gland remained high during the period of lactation and even several weeks after lactation. Plasma EGF levels were also increased during the periods of pregnancy, lactation and after lactation when compared with those of virgin mice. These increases were, however, apparent only between 24.00 and 08.00 h, because of circadian variations in circulating EGF. The level of plasma EGF was significantly (P<0·05) higher during the 24.00–08.00 h period than during the 12.00–20.00 h period in all stages examined. Concentrations of EGF in the urine of virgin, pregnant, lactating and primiparous mice remained relatively constant, and the levels were much higher than those in the plasma. Similar studies using sialoadenectomized pregnant and lactating mice indicated that the plasma levels of EGF were below the level of sensitivity of the assay (<16·5 pmol/l (<0·1 ng/ml)) even during the 24.00–08.00 h period, whereas urinary EGF remained at high levels which were similar to those of normal pregnant and lactating mice. These results suggest that submandibular EGF contributes to the increase in plasma EGF which occurs after gestation, but is not the major source of the urinary EGF.

J. Endocr. (1985) 106, 197–202
The role of microfilaments in the priming effect of LH-releasing hormone: an ultrastructural study using cytochalasin B
Authors: Lewis C. E. , Morris J. F. , Fink G.
Published: December 2008

We have investigated the possibility that microfilaments are involved in the priming effect of LH-releasing hormone (LHRH) by ultrastructural morphometry of hemipituitary glands from adult female mice. Glands incubated for 2 consecutive hours with 8·5 nmol LHRH/1 responded with a marked increase in the amount of LH released into the medium during the second hour compared with the first hour of incubation. This priming effect of LHRH on LH secretion was accompanied by a significant margination of secretory granules and a drop in the total granule content of the gonadotrophs. Although the number of microfilaments remained the same, there was an increase in their length and a change in orientation so that the angle between the microfilaments and the plasmalemma was significantly reduced after both the first and second hour of exposure of LHRH. The addition of 14·3 μmol cytochalasin B/l to the incubation medium significantly increased the amount of LH released in the first hour of incubation when compared with the amount of LH released by LHRH alone, but completely abolished the priming effect of LHRH. Cytochalasin B also prevented the LHRH-induced increase in the length and the change in orientation of the microfilaments. These results indicate that LHRH priming involves an increase in length of microfilaments and a change in their orientation relative to the plasmalemma.

J. Endocr. (1985) 106, 211–218
Endocrine control of uterine oxytocin receptors in the ewe
Authors: Sheldrick E. L. , Flint A. P. F.
Published: December 2008

Specific binding of [3H]oxytocin to high affinity sites (hormone receptors) in membrane preparations from uterine tissues of the ewe has been determined at varying stages of the oestrous cycle and in pregnancy. Mean receptor concentrations in caruncular and inter-caruncular endometrium and in myometrium were 14·2, 1·9 and 13·0 fmol/mg protein respectively between days 10 and 13 of the cycle. By the day of oestrus these values had increased to 749, 1085 and 179 fmol/mg protein. These increases in receptor concentrations coincided with luteolysis and falling plasma progesterone levels and followed the preovulatory decline in peripheral oxytocin and rise in ovarian venous oestradiol-17β. Receptor concentrations were low in all uterine tissues from pregnant animals between days 14 and 19 after oestrus. Analysis of binding parameters by Scatchard plot suggested a single population of receptor molecules in each of the tissues studied with apparent dissociation constants in the range 1·9–2·2 nmol/l. A number of naturally occurring neurohypophysial peptides inhibited binding of [3H]oxytocin to the receptor from ewes at oestrus; the cross-reactions of arginine vasopressin and vasotocin exceeded that of oxytocin.

Use of a receptor binding assay to measure oxytocin in extracts of corpora lutea on days 4 and 10 after oestrus gave values similar to those obtained by radioimmunoassay, suggesting the absence of other receptor-active peptides in the corpus luteum.

It is concluded that the oxytocin receptor is present in both components of the endometrium, as well as in the myometrium and that changes in uterine receptor concentrations before oestrus are consistent with receptor activation by steroid hormones.

J. Endocr. (1985) 106, 249–258
Vasoactive intestinal peptide in rat hypophysial portal blood: effects of electrical stimulation of various brain areas, the oestrous cycle and anaesthetics
Authors: Brar A. K. , Fink G. , Maletti M. , Rostene W.
Published: December 2008

Vasoactive intestinal peptide (VIP) was measured by radioimmunoassay in hypophysial portal and peripheral blood from adult male and female Wistar rats. The results confirmed that the concentration of VIP in hypophysial portal blood was significantly greater than in peripheral blood and showed that VIP release into portal blood was not affected by removal of the gut, the largest peripheral source of VIP. Electrical stimulation of the median eminence, several hypothalamic nuclei, the amygdala or hippocampus had no significant effect on the release of VIP into portal blood, possibly because under the conditions of the experiment the spontaneous release of VIP is already at a maximum. In female rats, the VIP released into portal blood collected between 13.00 and 18.30 h of each day of the 4-day oestrous cycle varied under different anaesthetics, and there was no consistent increase in VIP release on pro-oestrus suggesting that VIP is not involved in the pro-oestrous surge of prolactin.

J. Endocr. (1985) 106, 275–280
Growth hormone responses to multiple injections of a fragment of human growth hormone-releasing factor in conscious male and female rats
Authors: Clark R. G. , Robinson I. C. A. F.
Published: December 2008

The GH responses to single i.v. injections of GH-releasing factor (GRF) in conscious male rats are highly variable. Although normal male rats show a pulsatile secretory pattern of GH with pulses occurring at intervals of 3–3·5 h, the peaks occur at different times in individual animals. We have compared the GH responses of young conscious male and female rats to multiple i.v. injections of 1 μg human (h) GRF1-29NH2. The peak GH responses occurred 3–5 min after hGRF1-29NH2 injection and were lower in female than in male rats. Both males and females responded uniformly to hGRF1-29NH2 injections given 180 min apart and the GH responses became entrained with no endogenous GH pulsing. Female rats produced consistent GH peaks in response to hGRF1-29NH2 injections at 90-min intervals, whereas male rats responded only to alternate injections, so that GH peaks occurred only every 180 min despite giving GRF every 90 min. When the frequency of hGRF1-29NH2 administration was increased to once every 40 min female rats again responded consistently to each injection. Male rats responded intermittently, being able to respond to two injections 40 min apart, after which they became refractory to hGRF1-29NH2. This cycle of varying sensitivity to GRF in male rats probably underlies their 3-hourly endogenous GH secretory rhythm. Female rats can respond uniformly to repeated GRF injections, consistent with their more continuous pattern of endogenous GH secretion. Introducing a pulse of 10 μg rat GH into a series of hGRF1-29NH2 injections did not induce refractoriness to hGRF1-29NH2, suggesting that GH does not itself desensitize the pituitary to GRF. Whether the different patterns of GH secretion in males and females result from different patterns of GRF and/or somatostatin secretion remains to be determined.

J. Endocr. (1985) 106, 281–289
Effects of flavonoids on insulin secretion and 45Ca2+ handling in rat islets of Langerhans
Authors: Hii C.S.T. , Howell S.L.
Published: December 2008

The effects of some flavonoids, a group of naturally occurring pigments one of which has been claimed to possess antidiabetic activities, on insulin release and 45Ca2+ handling have been studied in isolated rat islets of Langerhans. Insulin release was enhanced by approximately 44–70% when islets were exposed to either (−)epicatechin (0·8 mmol/l) or quercetin (0·01–0·1 mmol/l); others such as naringenin (0·1 mmol/l) and chrysin (0·08 mmol/l) inhibited hormone release by approximately 40–60%. These effects were observed only in the presence of 20 mmol glucose/l. Quercetin (0·01 mmol/l) and (−)epicatechin (0·8 mmol/l) both inhibited 45Ca2+ efflux in the presence and absence of extracellular Ca2+. In the presence of 20 mmol glucose/l both the short-term (5 min) and steady-state (30 min) uptake of 45Ca2+ were significantly increased by either quercetin or (−)epicatechin. These results suggest that the stimulatory compounds such as quercetin and (−)epicatechin may, at least in part, exert their effects on insulin release via changes in Ca2+ metabolism.

J. Endocr. (1985) 107, 1–8
Pituitary receptors for LH-releasing hormone (LHRH) and responsiveness to LHRH in adult female rats after neonatal monosodium l-glutamate treatment
Authors: Inkster S. E. , Clayton R. N. , Whitehead S. A.
Published: December 2008

The effects of neonatal monosodium l-glutamate (MSG) treatment on pituitary responsiveness to LH-releasing hormone (LHRH) and on pituitary LHRH receptors have been investigated in the intact adult female rat. Three- to four-month-old rats treated with MSG (4 mg/g body wt) on days 2, 4, 6, 8 and 10 after birth had significantly reduced ovarian and pituitary weights, showed an absence or disruption of ovarian cyclicity after puberty, and had significantly higher concentrations of serum prolactin despite normal levels of LH. In-vitro pituitary LH responses to LHRH were in the normal range for one group of treated animals whilst in a second group the LH responses were markedly enhanced. In contrast, the total number of pituitary LHRH receptors were significantly reduced in all MSG-treated animals showing that the increased pituitary responsiveness of MSG-treated animals is not attributable to an increase in pituitary LHRH receptors.

J. Endocr. (1985) 107, 9–13
Ornithine decarboxylase activity and polyamines in the anterior pituitary gland during the rat oestrous cycle
Authors: Persson L. , Nilsson M. , Rosengren E.
Published: December 2008

The biosynthesis of polyamines, an ubiquitous group of amines shown to be essential for normal cellular growth and differentiation, was studied in the rat anterior pituitary gland during the different stages of the oestrous cycle. The activity of ornithine decarboxylase (ODC), which catalyses the rate-limiting step in the biosynthesis of polyamines, was low during oestrus, metoestrus and dioestrus. However, a marked transitory rise in ODC activity was found in the pituitary gland on the evening of pro-oestrus. The rise in ODC activity was accompanied by an increase in the pituitary content of the polyamines putrescine and spermidine.

Ovariectomy did not significantly change the basal ODC activity in the pituitary gland. Oestrogen treatment of ovariectomized rats resulted in a marked stimulation of pituitary polyamine biosynthesis. The largest effects were observed when oestrogen was given as two injections 72 h apart, which gave rise to levels of ODC activity comparable to those observed on the evening of pro-oestrus.

The increase in polyamine synthesis in the anterior pituitary gland during pro-oestrus appeared not to be related to the preovulatory secretion of LH or prolactin, since neither LH-releasing hormone nor thyrotrophin-releasing hormone (which induces a secretion of prolactin) affected pituitary ODC activity. The observed biosynthesis of polyamines may be associated with the cellular proliferation which occurs in the anterior pituitary gland at oestrus.

J. Endocr. (1985) 107, 83–87
Recurrent mammary gland contractions induced by a low tonic release of oxytocin in rats
Authors: Poulain D. A. , Tasker J. G.
Published: December 2008

In urethane-anaesthetized lactating rats, intramammary pressure occasionally displayed recurrent variations or oscillations having a slow rise time, low amplitude, long duration and a periodicity of 1–4 min. These oscillations differed from changes in intramammary pressure characteristic of reflex milk ejections induced by suckling, and were also observed in unsuckled rats. They were suppressed by lesions of the pituitary stalk or by stimulating the septum, a structure that inhibits the activity of the magnocellular system. They could be induced by long-term low frequency stimulation of the pituitary stalk, lesions of the septum or long-term infusions of oxytocin at a low rate of 0·05–0·3 mu./min. We suggest that the recurrent oscillations in intramammary pressure constitute a particular mode of response of the mammary gland to a tonic release of oxytocin resulting from a moderate but sustained increase in the basal level of electrical activity of the oxytocin-secreting neurones.

J. Endocr. (1985) 107, 89–96
Oxytocin and sexual behaviour in the male rat and rabbit
Authors: Stoneham M. D. , Everitt B. J. , Hansen S. , Lightman S. L. , Todd K.
Published: December 2008

In male New Zealand white rabbits, it was shown that oxytocin but not vasopressin concentrations in plasma were markedly raised after ejaculation. In male Wistar rats, oxytocin infused into the internal carotid artery reduced the number of intromissions made before ejaculation but had no other significant effect. Infusion of oxytocin into the third ventricle increased the latencies to the first mount and intromission and lengthened post-ejaculatory refractory periods. It is suggested that oxytocin released into the periphery during coitus, while not essentially involved in ejaculation, may exert effects on the genital periphery. Behavioural effects of centrally administered oxytocin suggest that it may play a role in the neural mechanisms underlying post-ejaculatory refractoriness.

J. Endocr. (1985) 107, 97–106
Differential effects of melatonin on the stimulated release of LH from dispersed pituitary cells of the prepubertal female rat
Authors: Symons A. M. , Arendt J. , Pryde S. J.
Published: December 2008

The effect of melatonin on the stimulated release of LH from prepubertal female rat pituitary cells in vitro was investigated. Significant inhibition of LH-releasing hormone and calcium ionophore-induced LH release was seen but not of potassium-induced release. These results suggest a specific interaction between melatonin and the endogenous events leading to LH release, and may implicate melatonin as an important neuroendocrine component of pubertal development in this species.

J. Endocr. (1985) 107, 107–112
Endogenous opioids and related peptides: from molecular biology to clinical medicine The Sir Henry Dale Lecture for 1985
Authors: Imura H. , Kato Y. , Nakai Y. , Nakao K. , Tanaka I. , Jingami H. , Koh T. , Yoshimasa T. , Tsukada T. , Suda M. , Sakamoto M. , Morii N. , Takahashi H. , Tojo K. , Sugawara A.
Published: December 2008

Advances in techniques in molecular biology have facilitated the research into endogenous opioids and related peptides in several ways. The organization and expression of genes and the primary structure of three precursor proteins of opioid peptides have been elucidated. These studies predicted the presence of potentially bioactive peptides, which has been confirmed by later studies. Advances in techniques in protein chemistry have helped to elucidate the distribution and molecular forms of endogenous opioids and related peptides in the body, and the processing of precursor proteins. Studies on the function of these peptides have shown a broad spectrum of actions. Leumorphin, a newly identified peptide, has been shown to exhibit unique biological activities. In spite of extensive studies, the physiological and pathophysiological significance of opioid peptide systems are not yet completely understood. This is mainly due to the paucity of our knowledge about opioid receptors. Further studies on the subtypes of opioid receptors will help to elucidate all aspects of the function of endogenous opioids and related peptides.

J. Endocr. (1985) 107, 147–157
Dissociation between emotional and endocrine responses preceding an academic examination in male medical students
Authors: Allen P. I. M. , Batty K. A. , Dodd C. A. S. , Herbert J. , Hugh C. J. , Moore G. F. , Seymour M. J. , Shiers H. M. , Stacey P. M. , Young S. K.
Published: December 2008

A study was made in 2 consecutive years of the emotional states and morning and afternoon serum levels of prolactin, cortisol and testosterone of male medical students during a 4- to 5-week period preceding a major university examination. 'Distress', 'anxiety' and, to a lesser degree, 'depression' increased during the 2 weeks immediately preceding the examination and were positively correlated with personality anxiety or neuroticism traits. Group means for hormones showed no consistent change over the same period. Neither was there evidence for a correlation between endocrine and emotional changes within individual students during the pre-examination period. A restricted study showed that there were significant increments in cortisol in samples taken during the examination itself.

Changes in emotional state before an examination occurred in the absence of equally dramatic changes in levels of the three hormones studied, though this relationship may have altered during the examination itself. This suggests that the factors controlling the two categories of response may relate differently, in some way, to the imminence of this stressful event.

J. Endocr. (1985) 107, 163–170
Measurement of phospholipase A2 activity in human endometrium during the menstrual cycle
Authors: Bonney R. C.
Published: December 2008

Phospholipase A2 activity was measured in human endometrium throughout the menstrual cycle using an assay based on the liberation of oleic acid from 1-palmitoyl-2-[14C]oleoyl phosphatidylcholine. The enzyme was shown to be calcium dependent, to have an optimum pH of 8–9 and an apparent Michaelis constant of 110 μmol/l. Enzyme activity was low in early proliferative-phase tissue (6·08 ±1·42 (s.e.m.) pmol oleic acid released/mg protein per min) but rose significantly (P < 0·01) during the late proliferative phase (10·86 ±2·79 pmol/mg per min). There was a tenfold increase in activity 2–4 days after ovulation (45·6 ± 13·6 pmol/mg per min) which thereafter declined to reach values which at menstruation were not significantly different from those of the proliferative phase (4·5 ± 1·76 pmol/mg per min). The results indicate that phospholipase A2 activity in human endometrium is related to the stage of the menstrual cycle and suggest that arachidonic acid release may be influenced by oestradiol and progesterone.

J. Endocr. (1985) 107, 183–189
Influences of thyroidectomy and thyroxine replacement on photoperiodically controlled reproduction in quail
Authors: Follett B. K. , Nicholls T. J.
Published: December 2008

The breeding season in quail ends when they become relatively refractory to long photoperiods. The processes underlying the development of this refractoriness are dependent upon the thyroid gland.

Thyroidectomized male Japanese quail transferred from short (8 h light: 16 h darkness; 8L: 16D) to long (20L: 4D) daily photoperiods mature their gonads and develop the androgen-dependent cloacal gland at rates only marginally slower than controls. However, when the birds are retransferred to short days thyroidectomized individuals do not show the rapid testicular regression and moult which occurs in controls under such conditions. The testes remain large for a long period, eventually decreasing in size slowly and irregularly. Once such thyroidectomized birds are transferred back to short days the administration of thyroxine has little effect upon the slow rate of gonadal regression but if the hormone is administered during the preceding period of long days normal regression does occur under short days, even though treatment has ceased. This suggests that a process dependent upon thyroid hormones takes place under long daylengths that ensures the termination of reproduction when they are exposed either to short daylengths or to decreasing daylengths after the summer solstice. This view was substantiated by further experiments in which thyroidectomy was performed after the birds had been exposed to long daylengths. When transferred to 8L: 16D normal testicular regression and moult occurred rapidly. Presumably the thyroiddependent process had proceeded to an adequate extent in these quail before the thyroid glands were destroyed. Further support came from treating intact quail chronically with thyroxine. Its administration to quail on 20L: 4D had no observable effect; the testes grew rapidly to maximal size and remained large. However, if the birds were given thyroxine under 12L: 12D the gonads first developed to maximal size and then, after about 12 weeks of treatment, regressed spontaneously whether or not thyroxine was still being administered. It seems that thyroxine had made the quail so relatively refractory that 12L: 12D was no longer sufficiently stimulatory to overcome the developing inhibition on the photoperiodic system. The results in quail are very reminiscent of the finding that the absolute photorefractoriness and spontaneous testicular regression which develops in starlings under long daylengths is thyroid dependent. Quail do not become absolutely refractory on long daylengths and regress their gonads spontaneously but they do develop a 'relative' refractoriness so that only a small decrease in photoperiod is necessary to switch off the reproductive system. We suggest that quail-type refractoriness is homologous with that in starlings and that both involve progressive changes induced by exposure to long daylengths which profoundly alter the photoperiodic response: these changes will not occur without a functional thyroid gland.

J. Endocr. (1985) 107, 211–221
Amplitude of episodic release of LH as a measure of pituitary function analysed from the time-course of hormone levels in the blood: comparison of four menstrual cycles in an individual
Authors: McIntosh R. P. , McIntosh J. E. A.
Published: December 2008

Pulse amplitude and frequency are often used to describe measurements of LH in blood. Such analyses are compatible with models of LH being released from the pituitary in episodes that are controlled by pulses of hypothalamic gonadotrophin-releasing hormone. The amplitudes of these secretory episodes as seen in blood are usually defined as the net heights of peaks above a baseline. As a measure of each pituitary secretory episode, this is valid only if peaks are regularly and widely spaced, making overlap negligible. When episodes are erratic and frequent so that only fractions of peaks have been cleared from the circulation before others follow, nadirs between peaks include output from previous episodes and do not define a physiologically meaningful baseline. Applied to overlapping peaks, such measures of amplitude usually underestimate pituitary secretory episodes and imply a tonic mode of LH secretion in addition to pulsatile release.

Using the additional information of fitted LH clearance coefficients to define the shapes of LH peaks, a simple method based on an episodic mode of release alone is described, for estimating more accurately the relative sizes of secretory episodes as observed in blood, free of the effects of overlapping peaks. Using this analysis we have described the variation in amplitude, interval and clearance rates of LH secretory episodes within and between four normal menstrual cycles of a single individual. Thirteen, 3–6 h blood sampling sessions were performed during early follicular growth at the transition from luteal to follicular phases when the frequencies of LH peaks, LH/FSH ratios and progesterone concentrations were changing markedly.

Our secretory episode model described all data well without the need to introduce a tonic mode of release. When frequent pulses overlapped we found that amplitudes of episodes were usually higher than peaks estimated by conventional methods, but a decrease in both amplitude and pulse interval occurred after the start of menstruation. Highly variable patterns of LH release were demonstrated in the late luteal phase of this normal individual while FSH levels rose consistently.

J. Endocr. (1985) 107, 231–239
Central nervous system-mediated growth inhibition of a rat prostate carcinoma by an opioid
Authors: Reubi J. C.
Published: December 2008

Long-term treatment for more than 3 months with a central nervous system (CNS)-active drug, the opioid agonist bremazocine, at a dose of 1 mg/kg per day elicited an 80% inhibition of the volume of the subcutaneously transplanted rat prostate adenocarcinoma Dunning R3327H. Whereas, under this therapy, prostate tumour and prostatic weights were decreased, testes and pituitary weights remained normal. Bremazocine inhibited not only the growth of freshly transplanted tumours but also that of well-grown Dunning prostate carcinomas since, after 41 days of treatment, such tumours showed a volume inhibition of 52%. In these experiments bremazocine decreased LH and testosterone plasma levels significantly. Bremazocine, therefore, probably acts mainly through suprapituitary CNS-opiate receptor sites, which indirectly, rather than locally, mediate LH inhibition. Indeed, no specific receptors for bremazocine could be found in the Dunning tumour, which makes a local action of bremazocine in this tissue unlikely. The efficient tumour growth inhibition through the supra-pituitary action of bremazocine makes such opiate drugs, which lack respiratory and side effects due to improper use, of potential interest for treatment of prostatic tumours.

J. Endocr. (1985) 107, 247–250
Superovulation in the cow: comparison of oestradiol-17β and progesterone patterns in plasma and milk of cows induced to superovulate; relationships with ovarian responses
Authors: Saumande J. , Batra S. K.
Published: December 2008

Free oestradiol-17β, free+conjugated oestradiol-17β (total oestradiol-17β) and progesterone in milk, and free oestradiol-17β and progesterone in plasma were measured in 16 cyclic cows injected with FSH to induce superovulation during the treatment and periovulatory periods. The patterns of steroid secretion were the same in milk as in plasma but at different concentrations. Among oestrogens, the highest concentrations were measured for total oestradiol-17β in milk, followed by free oestradiol in plasma and free oestradiol in milk. Progesterone concentrations in milk were higher than in plasma. The peak concentrations of oestrogens were related to ovulation rate: Spearman Rank Correlation coefficient (r.s.) = 0·87 (P < 0·001), 0·78 (P < 0·001) and 0·69 (P < 0·001) for total oestradiol, free oestradiol in milk and free oestradiol in plasma respectively. The increase in progesterone concentrations in milk between the beginning of treatment and prostaglandin injection was negatively correlated with the percentage of viable embryos among those recovered (r.s. = −0·68; P < 0·001). This was not observed for progesterone in plasma. These results therefore show that the steroid pattern in milk gives a better indication as to the ovarian response to a superovulatory treatment than does the steroid pattern in plasma. In addition the fact that milk samples are easier to obtain and handle than blood plasma have led us to conclude that, to follow the effect of gonadotrophin stimulation, it would be more informative to assay oestradiol-17β and progesterone in milk rather than in plasma.

J. Endocr. (1985) 107, 259–264
The functional significance of glycosylation of proopiomelanocortin in melanotrophs of the mouse pituitary gland
Authors: Jenks B. G. , Ederveen A. G. H. , Feyen J. H. M. , van Overbeeke A. P.
Published: December 2008

Pro-opiomelanocortin (POMC) is a glycoprotein precursor for a number of neuropeptides and peptide hormones. The functional significance of the glycosylation of POMC has never been established. Using the antibiotic tunicamycin to block glycosylation of the prohormone in the mouse pars intermedia, we have compared processing of non-glycosylated prohormone with that of glycosylated prohormone in pulse-chase experiments. The peptides produced from non-glycosylated prohormone were shown to be correct cleavage products. Therefore it was concluded that, with the possible exception of peptides from the N-terminal region of the prohormone, the carbohydrate on POMC plays no role in directing cleavage or in protecting the prohormone from random proteolysis. Tunicamycin treatment retarded N-terminal acetylation of melanotrophin but had no apparent effect on acetylation of β-endorphin. The mouse pars intermedia synthesizes two forms of POMC which differ in their degree of glycosylation. Our results indicated that, during secretion, the melanotrophs make no distinction between peptides derived from the two prohormones.

J. Endocr. (1985) 107, 365–374
Identification and measurement of 4-oestren-3,17-dione (19-norandrostenedione) in porcine ovarian follicular fluid using high performance liquid chromatography and capillary gas chromatography–mass spectrometry
Authors: Khalil M. W. , Walton J. S.
Published: December 2008

4-Oestren-3,17-dione (19-norandrostenedione) has been identified as a major steroid in porcine ovarian follicular fluid for the first time. This steroid was isolated by C18 reverse-phase high performance liquid chromatography (HPLC) and its structure was established unambiguously by capillary gas chromatography–mass spectrometry. The mean concentration in pooled fluid obtained from prepubertal gilts determined by HPLC and capillary gas chromatography was 1·71 μmol/l. The level of this steroid in fluid obtained from large preovulatory follicles of sows exceeded 21·0 μmol/l on days 19 and 20 of the oestrous cycle. The high levels of this steroid within the follicle during the follicular phase might imply a possible biological role in follicular development and oocyte maturation.

J. Endocr. (1985) 107, 375–381
Identification of 3β-hydroxy-5,7-androstadien-17-one as a secretory product of the fetal horse gonad in vivo and in vitro
Authors: Raeside J. I. , Renaud R. L.
Published: December 2008

Isolation of 3β-hydroxy-5,7-androstadien-17-one, as a major component of steroids extracted from vein blood of the fetal gonads of the horse, supports the proposed role for the compound as a precursor for equilin formation in the placenta of the mare. The 5,7-diene was extracted from blood collected from gonadal veins of fetal ovaries and testes in situ, and from a fetal testis connected to an artery in the neck region of the mare. Perfusion of fetal gonads in the laboratory was carried out to allow longer periods of collection. In addition, isolated cell preparations from a fetal testis were incubated for 4–8 h in tissue culture to investigate steroid secretion in vitro. Final purification of neutral steroids in the extracts was carried out by high performance liquid chromatography, and identification was made by u.v. and mass spectrometry. The presence of 3β-hydroxy-5,7-androstadien-17-one in extracts from all sources provided evidence for its secretion in vivo and in vitro. Other 5,7-dienes, which were less polar than the C19 compound, were noted in extracts of media but not identified. These data support the view that a 5,7-diene pathway is involved in the biosynthesis of 3β-hydroxy-5,7-androstadien-17-one in the fetal horse gonad.

J. Endocr. (1985) 107, 415–419
Effects of β-aminobutyric acid receptor agonists on the secretion of growth hormone, luteinizing hormone, adrenocorticotrophic hormone and thyroid-stimulating hormone from the rat pituitary gland in vitro
Authors: Anderson R. A. , Mitchell R.
Published: December 2008

The effects of the γ-aminobutyric acid receptor agonists muscimol and baclofen were investigated on the secretion of GH, LH, ACTH and TSH from the anterior pituitary in vitro using a rapid superfusion system. A bicuculline-sensitive stimulatory effect of muscimol was demonstrated on the secretion of GH, LH and ACTH but not TSH. Baclofen had no effect on the basal secretion of any of the hormones, but inhibited LH-releasing hormone-stimulated release of LH and K+- and Ba2+-stimulated release of ACTH. The benzodiazepine Roll-6896 and the barbiturate secobarbital were found to potentiate the effect of muscimol on GH secretion. These results demonstrate the presence of GABAA receptors on somatotrophs, gonadotrophs and corticotrophs, and the presence of GABAB receptors on gonadotrophs and corticotrophs. Thyrotrophs appear devoid of GABA receptors.

J. Endocr. (1986) 108, 1–8
Failure of glucocorticoid feedback in males of a population of small marsupials (Antechinus swainsonii) during the period of mating
Authors: McDonald I. R. , Lee A. K. , Than K. A. , Martin R. W.
Published: December 2008

In an investigation of the factors leading to the increase in the concentration of plasma free glucocorticoid, which results in immunosuppression and death after mating of all males in natural populations of a small shrew-like marsupial, the dusky antechinus (Antechinus swainsonii), the integrity of the glucocorticoid feedback control of the concentration of plasma cortisol was examined by use of dexamethasone-suppression tests.

Injection of 0·2 mg dexamethasone/kg i.m. caused a marked fall in the concentration of plasma cortisol 17 h later, approximately 2 months and 2 weeks before the annual mating period in mid-July. However, the same dose had no significant effect on the increased concentration of plasma cortisol characteristic of the mid- to late July mating period.

Injection of 100 i.u. ACTH/kg i.m. caused a significant increase in the concentration of plasma cortisol 6–7 h later on all occasions, indicating that the responsiveness of the adrenal cortex to ACTH did not change. Pretreatment with dexamethasone had no effect on the ACTH-stimulated cortisol concentration, ruling out a possible direct effect of dexamethasone on adrenocortical secretion in this species. Dexamethasone also reduced the concentration of plasma testosterone when the level was low, before the mating period, but not when the level was high, at the beginning of the mating period.

It is concluded that, in association with a rapid increase in the concentration of plasma testosterone, an increase in aggression and intense mating activity, glucocorticoid feedback control of ACTH secretion is impaired. This contributes to the rapid and sustained rise in the concentration of plasma free cortisol to immunosuppressive levels.

J. Endocr. (1986) 108, 63–68
Pancreatic α cell function in the fetal and newborn pig
Authors: Silver M. , Fowden A. L. , Comline R. S. , Bloom S. R.
Published: December 2008

Plasma glucagon concentrations were measured in chronically catheterized fetal pigs during the last third of gestation and compared with the values observed in anaesthetized fetuses of similar gestational age. The mean plasma concentration of glucagon in the chronically catheterized fetuses was 10·0 ± 1·4 (s.e.m.) pmol/l (n = 11; term = 114 ± 2 days). Concentrations were increased after catheterization and fell to baseline values within 48 h of surgery. Arginine infusion evoked a rapid release of glucagon in chronically catheterized fetuses between 105 and 108 days of gestation; the mean maximum increment in plasma glucagon was 15·4 ± 4·5 pmol/l (n = 5). Plasma glucagon concentrations increased with increasing gestational age in both anaesthetized and chronically catheterized fetuses. Between 95 and 110 days of gestation, glucagon levels were significantly higher in anaesthetized fetuses than in chronically catheterized animals with similar normal pH values. Catheterization and prematurity had no apparent effect on plasma glucagon levels at birth. The plasma concentrations at birth were similar to those observed in the chronically catheterized fetuses in utero provided the piglets did not become acidotic during delivery. Significantly higher plasma levels of glucagon were found in newborn piglets with acidaemia (pH < 7·3) than in piglets with normal pH values at birth (pH > 7·3). When all the data from the newborn piglets were combined, there was a significant negative correlation (r= − 0·79, n = 39, P < 0·01) between blood pH and the plasma concentration of glucagon at birth. These observations demonstrate that the fetal α cells are functional and responsive in utero and at birth.

J. Endocr. (1986) 108, 137–142