bluuebunny/crossref_metadata_2025 huggingface dataset:
Testosterone sensitivity of the seminal sacs of tree sparrows (Spizella arborea) in different reproductive states
Authors: Wilson F. E.
Published: December 2008

Testosterone sensitivity of the seminal sacs of castrated tree sparrows from each of three reproductive states was evaluated by measuring the change in seminal-sac mass per unit change in the logarithm of replacement or plasma testosterone. Birds were exposed to exogenous testosterone for 38 days. Replacement doses less than 0·17 μmol or plasma concentrations less than about 0·7 nmol/l did not induce seminal-sac growth in photosensitive castrated birds held on short days, in photosensitive castrated birds transferred from short to long days, or in photorefractory castrated birds retained on long days. Higher replacement doses or plasma concentrations, however, stimulated log dose-dependent growth of the seminal sacs in castrated birds from all three reproductive states. The change in seminal-sac mass per unit change in the logarithm of the dose of replacement testosterone was less (P= 0·0495) in photosensitive castrated birds held on short days than in photosensitive castrated birds transferred to long days. A more critical test of sensitivity (i.e. the change in seminal-sac mass per unit change in the logarithm of mean plasma testosterone concentration) indicated, however, that sensitivity of the seminal sacs to testosterone is independent of reproductive state. That result, when considered in the context of the plasma testosterone profile of intact males during a simulated reproductive cycle, argues that the seminal sacs of sexually quiescent (photosensitive or photorefractory) tree sparrows are small not because of their insensitivity to androgens, but because of a deficiency of circulating androgens.

J. Endocr. (1986) 109, 125–131
Oxytocin release during parturition in the pelvic-neurectomized rat
Authors: Higuchi T. , Uchide K. , Honda K. , Negoro H.
Published: December 2008

Blood levels of oxytocin during parturition in pelvic-neurectomized rats were determined by radioimmuno-assay. Four out of 29 pelvic-neurectomized rats completed parturition within 23 days of pregnancy. These rats exhibited an increase in blood levels of oxytocin during parturition similar to those of sham-operated control rats, but delivery took longer and there was a higher percentage of still-births. The rise in blood levels of oxytocin was smaller in the 16 rats in which the first fetus was expelled but where delivery did not end within day 23 of gestation than that in sham-operated controls. Levels did not increase in the other nine rats which failed to deliver the first fetus within 23 days of pregnancy. They did, however, show signs indicating delivery, such as stretch movements, vaginal bleeding and/or excretion of mucus within 23 days of gestation. Oxytocin infusion (2 mu./min) for 2–4 h increased uterine contractions in the pelvic-neurectomized rats but failed to reduce the percentage of still-births or the duration of delivery. Immuno-neutralization of circulating oxytocin by anti-oxytocin serum in intact pregnant rats resulted in a significant but much smaller prolongation of the duration of delivery compared with that observed in pelvic-neurectomized rats. The rise in blood levels of oxytocin during pregnancy may be induced, at least in part, by the Ferguson reflex via the pelvic nerve and may thus facilitate the process of delivery. A shortage of oxytocin secretion may not, however, be the main cause of the dystocia in pelvic-neurectomized rats.

J. Endocr. (1986) 109,149–154
Differential effects of passive immunization with somatostatin antiserum on adenohypophysial hormone secretions in starved rats
Authors: Hugues J. N. , Enjalbert A. , Moyse E. , Shu C. , Voirol M. J. , Sebaoun J. , Epelbaum J.
Published: December 2008

The role of somatostatin (SRIF) on adenohypophysial hormone secretion in starved rats was reassessed by passive immunization. Because of the absence of pulsatile GH secretion in starved rats, the effects of the injection of SRIF antiserum on GH levels can be clearly demonstrated. To determine whether starvation modifies the sensitivity of the adenohypophysis to SRIF, we measured 125I-labelled iodo-N-Tyr-SRIF binding. There was no difference in the dissociation constant (Kd) nor in the maximal binding capacity (Bmax) in fed (n = 15) and starved (n = 15) animals (Kd = 0·38 ± 0·09 (s.e.m.) and 0·45 ± 0·09 nmol; Bmax = 204 ± 39 and 205 ± 30 fmol/mg protein respectively).

Administration of SRIF antiserum resulted in a dose-dependent increase in plasma concentrations of GH, TSH and prolactin. The minimal effective dose of SRIF antiserum was 50 μl for GH, 100 μl for TSH and 200 μl for prolactin.

Our results show that: (1) starvation does not modify adenohypophysial SRIF-binding sites, (2) in starved male rats endogenous SRIF exerts a negative control on prolactin secretion in vivo and (3) sensitivity to endogenous SRIF seems to be different for each hypophysial cell type.

J. Endocr. (1986) 109, 169–174
Lactogenic hormone receptors in mammary membrane preparations from prepartum and 60 and 180 day post-partum Holstein cattle
Authors: Kazmer G. W. , Barnes M. A. , Akers R. M. , Whittier W. D.
Published: December 2008

Mammary tissue from nine Holstein cows was collected within 1 week of parturition and at 60 and at 180 days post partum. Blood samples were collected by puncture of the coccygeal vein or artery at 6-h intervals from 2 days before to 2 days after surgery. A membrane-enriched fraction of tissue homogenates was prepared by differential centrifugation. A microcomputer program (LIGAND) provided estimates of the dissociation constant (Kd) and receptor concentrations using Scatchard analysis of competition of radioiodinated human GH by bovine prolactin (NIH-bPRL-6), ovine prolactin (NIH-oPRL-15) and unlabelled human GH (NIH-hGH-I-1). Split-plot analysis of variance of hormone data indicated that mean prolactin concentrations during the periparturient period were greater than those at 60 or 180 days post partum. However, no differences were evident in prolactin content of blood samples collected immediately before biopsy. Analysis of variance of Scatchard data indicated that the Kd of the lactogenic hormone receptor did not differ at different stages of lactation, and averaged 89·7 nmol/l. Receptor concentrations were lower during the prepartum period than at 60 and 180 days post partum (0·65 vs 1·2 and 1·5 fmol/mg membrane protein respectively). The Kd of the lactogenic hormone receptor was similar when estimated with NIH-bPRL-6 or NIH-oPRL-15 competition, but 100-fold greater when estimated with NIH-hGH-I-1. It is concluded that lactogenic hormone receptor concentrations in bovine mammary tissue increase with the onset of lactation, with a pattern similar to that observed in non-ruminants.

J. Endocr. (1986) 109, 175–180
Thyroid function in newborn lambs: influence of prolactin and growth hormone
Authors: Kühn E. R. , Van Osselaer P. , Siau O. , Decuypere E. , Moreels A.
Published: December 2008

Lambs originating from Suffolk, Milksheep and Texel crossbreeds were injected with saline, 500 μg ovine prolactin or 500 μg ovine GH within 30 min of parturition (n = 10). Birth weight was negatively correlated with plasma concentrations of reverse tri-iodothyronine (rT3) but not with thyroxine (T4), free T4 (expressed as the free thyroxine index) or cortisol. At birth, T3 and T4 plasma concentrations were high and remained high during the 3-h observation period. After 3 h a significantly lower rT3 concentration was found. The cortisol concentration at birth was also high (100–400 nmol/l) but decreased rapidly to basal values after 1 h. An injection of 500 μg prolactin after parturition did not influence the hormonal parameters studied except for rT3 where, after 2 h, lower plasma concentrations were found compared with controls.

Growth hormone raised T3 levels from 4·80 ± 0·44 (s.e.m.) nmol/l at birth to 6·74 ± 0·42 nmol/l at 1 h after birth (P < 0·01) and to 6·51 ± 0·42 nmol/l after 2 h (P < 0·05). At both times these values were significantly (P < 0·001) different from saline-injected controls. GH decreased rT3 from 6·77 ± 0·71 nmol/l at birth to 5·42 ± 0·54 nmol/l after 1 h (P < 0·05) and to 5·10 ± 0·45 nmol/l after 2 h (P < 0·01; values were also significantly different from saline controls at P < 0·05 and < 0·005 respectively). At the same time total and free T4 concentrations were increased. No influence of prolactin or GH injection on plasma cortisol concentrations was seen. It is concluded that GH may play an important role in the maturation of thyroid functions during the perinatal period of lambs by increasing T4 secretion and by increasing the conversion of T4 to T3 and decreasing the T4 to rT3 conversion rates.

J. Endocr. (1986) 109, 215–219
Prenatal stress effects over two generations in rats
Authors: Pollard I.
Published: December 2008

Persistent effects of stress were found in second generation rats bred from females whose own mothers had been stressed during pregnancy. The second generation rats grew more slowly, with a plateau in the growth being reached at the same age as in the controls. This resulted in adult animals of both sexes being permanently smaller than their control counterparts. When these offspring were subjected to short-term stress (one session) in adulthood, the response was not significantly different to that for the controls, indicating an intact emergency response. The male offspring from the stressed group, however, had a significantly (P < 0·01) higher plasma progesterone concentration, and a significantly (P < 0·01) lower testicular enzymic 3β-hydroxysteroid dehydrogenase activity at rest, when compared with the control offspring. The fertility of the mature female from the stressed group was not affected as a third generation of litters born did not differ from the controls.

It is suggested that a changed genetic programme in the ovarian germ cells of the first generation and/or a changed uterine environment in the second generation may be implicated.

J. Endocr. (1986) 109, 239–244
Age-related changes in the concentrations of serum gonadotrophins and cholesterol in the female rabbit
Authors: YoungLai E. V.
Published: December 2008

Peripheral serum concentrations of LH, FSH and prolactin were determined by radioimmunoassay on different days after birth in the female rabbit. Serum cholesterol concentrations were also analysed by a colorimetric method. Concentrations of serum LH and FSH showed two distinct peaks occurring on day 9 (LH, 4·05 ± 0·76 (mean ± s.e.m.) μg/l; FSH, 3·62 ± 0·67 μg/l) and either day 35 (LH, 5·90 ± 1·20 μg/l) or day 40 (FSH, 9·01 ± 1·43 μg/l). Concentrations of LH and FSH were in the adult range (LH, < 1 μg/l; FSH, < 0·6 μg/l) by day 100. Serum prolactin showed a progressive increase from day 1 (1·04 ± 0·07 μg/l) to day 100 ( 17·30 ± 2·50 μg/l) with a peak on day 40. Total serum cholesterol in another series of rabbits was high from days 1 to 22 (7·53 ± 0·64 mmol/l) and then decreased to 1·94–3·36 mmol/l by day 106. These data indicate that the two major developmental peaks in gonadotrophins may be related to ovarian function.

J. Endocr. (1986) 109, 287–290
A modulatory role for cyclic AMP in the control of thyrotrophin release: studies with forskolin and dibutyryl cyclic AMP
Authors: Davis J. R. E. , Sheppard M. C.
Published: December 2008

We have studied the effects of cyclic AMP (cAMP) on TSH secretion by cultured rat pituitary cells, using forskolin and dibutyryl cAMP (dbcAMP) to raise the cellular cAMP content by different mechanisms. Forskolin (10 μmol/l), a stimulator of adenylate cyclase, raised the cAMP content within 10 min, but had a more delayed effect on TSH release, with no significant stimulation for at least 6 h, but a clear dose-dependent effect at 24 h. Incubation with dbcAMP likewise increased TSH release after 6–24 h. By contrast, high cellular cAMP levels induced by either forskolin or dbcAMP augmented the TSH response to TRH at an early stage, before any detectable change in unstimulated TSH release. Pretreatment of cells with forskolin led to a parallel upward shift in the subsequent TRH dose-response curve, without a significant change in median effective dose or any change in cellular TSH content.

These findings suggest that cAMP acts to increase the availability of TSH for acute release by TRH by modulation of an intracellular releasable hormone pool, and indicate synergistic interactions between the adenylate cyclase system and the phospholipid-calcium stimulus-release coupling mechanism of TRH.

J. Endocr. (1986) 109, 365–369
Effects of photoperiod on formation of oestradiol-17β in the dove brain
Authors: Hutchison J. B. , Steimer Th. , Jaggard P.
Published: December 2008

The effects of photoperiod and castration on brain aromatase activity have been examined using an in-vitro radioassay. Formation of oestradiol-17β was lower in the preoptic area of male Barbary doves on a short daylength (6 h light: 18 h darkness) than in males on a long daylength (14 h light: 10 h darkness). This was a specific effect of photoperiod which did not influence aromatase activity in the anterior or posterior hypothalamic areas, and was not accompanied by changes in hormone-sensitive vocal behaviour. Production of 5β-dihydrotestosterone, 5β-androstane-3α,17β-diol and 5α-dihydrotestosterone by the preoptic area did not differ between birds on long or short days. Therefore, a short photoperiod does not appear to influence other pathways of androgen metabolism. In contrast to the effects of photoperiod, castration reduced oestradiol formation in both preoptic and hypothalamic areas. Intramuscular injection of testosterone propionate (TP) in intact males on short days did not restore the pattern of distribution of aromatase activity seen in males on long days. Preoptic aromatase activity was, however, restored by TP in castrated birds. We conclude that a short photoperiod influences both the activity of aromatase and the inductive effect of testosterone on enzyme activity in the preoptic area, which is known to be associated with the behavioural action of oestrogen in the dove. Photoperiod is likely to act both through changes in circulating androgen and by a direct action on preoptic cells.

J. Endocr. (1986) 109, 371–377
Relationship between human chorionic gonadotrophin-induced changes in testicular microcirculation and the formation of testicular interstitial fluid
Authors: Widmark A. , Damber J. E. , Bergh A.
Published: December 2008

The relationship between testicular vascular permeability and testicular microcirculation as measured by laser Doppler flowmetry was studied in adult rats. In untreated control animals there was an oscillatory testicular blood-flow pattern with a frequency of 10·6 ± 0·8 pulses/min and the amount of testicular interstitial fluid (IF) collected was 61·5 ± 2·2 μl/g testis. Treatment of the rats with 25–200 i.u. human chorionic gonadotrophin (hCG) s.c. 8 h before the experiment resulted in a change in the testicular flow pattern from pulsatile to continuous and an increase in IF volume. Treatment with hCG (50 i.u., s.c.) changed the testicular blood-flow pattern from oscillatory to continuous 4, 8 and 16 h after treatment. The flow pattern returned to being pulsatile 32 h after treatment with hCG. The IF information was increased at those times when the blood-flow pattern was continuous. No effects on blood flow or IF formation were observed with 12·5 i.u. hCG s.c.

The present study shows a dose- and time-dependent covariation between the increase in testicular IF volume and the disappearance of the pulsatile flow in testicular microcirculation. It appears that a continuous flow pattern favours the transport of fluid from blood vessels to the interstitium.

J. Endocr. (1986) 109, 419–425
EVIDENCE AGAINST ANP AS A NATRIURETIC HORMONE DURING ATRIAL DISTENSION
Authors: Knapp M. F. , Hicks M. N. , Linden R. J. , Mary D.A.S.G.
Published: December 2008

To determine whether natriuresis attributable to atrial natriuretic peptides (ANP) is obtained in response to atrial stretch after blockade of the afferent input and reflex diuresis from atrial receptors, urine flow and sodium excretion were measured in response to distension of a balloon in the left atrium with the vagi at 37 and 9°C. It is known that during such a distension ANP plasma concentration is increased by the same amount whether or not the afferent vagal fibres are intact.

In 11 chloralose anaesthetized dogs 22 distensions with the vagi at 37°C increased urine flow 117.5% and increased sodium excretion 28.7%. In 11 distensions with the vagi at 9°C, urine flow did not change but sodium excretion decreased significantly (−20.9%).

Thus natriuresis could not be demonstrated in response to atrial stretch in anaesthetised dogs after blockade of the atrial receptor reflex. These results imply that under these conditions, in which ANP is reportedly released into plasma, ANP is not acting as a hormone. The results must call into question the suggestion that ANP is released into plasma in a concentration capable of causing a natriuresis as its normal physiological function.
Steroid regulation of Na+/K+-ATPase activity in the rat kidney: effect of a new 19-nor-progestagen
Authors: Botella J. , Paris J. , Lahlou B.
Published: December 2008

The effects of Nomegestrol acetate (17α-acetoxy-6-methyl-19-nor-4,6-pregnadiene-3,20-dione), a new 19-nor-progesterone derivative, on renal Na+/K+-ATPase activity were assessed in normal and adrenalectomized rats, and compared with the stimulatory or inhibitory actions produced by other steroids. This compound displayed an inhibitory effect which was similar to, but smaller than, that induced by progesterone and quite distinct from the stimulation produced by 19-nor-progesterone and corticosteroids. In addition, unlike progesterone, it did not antagonize the effect of aldosterone in adrenalectomized rats. This result, together with previous in-vivo and in-vitro observations on this compound indicates that additional modifications introduced in the molecular structure of 19-nor-progesterone produces a potent progestagenic substance virtually devoid of effects on renal Na+/K+-ATPase activity and sodium loss in urine.

J. Endocr. (1986) 110, 37–41
Control of leucocyte infiltration into the decidualized mouse uterus
Authors: Finn C. A. , Pope M.
Published: December 2008

Ovariectomized mice were treated with oestrogen and progesterone on a schedule to mimic early pregnancy. Decidualization was induced with oil and uteri were examined at various times after the last progesterone injection.

The first morphological change detected in the uterus of decidualized mice following withdrawal of progesterone was infiltration of leucocytes into the stroma. This preceded overt tissue breakdown and extravasation of blood cells, and did not occur following withdrawal of progesterone without decidualization. It is suggested either that there is a release of a chemoattractant from decidual cells before any morphological changes are apparent or that the signal for attracting the leucocytes is released at the time of decidual induction, but that their migration is suppressed by progesterone.

J. Endocr. (1986) 110, 93–96
Effects on growth and body composition of androgen deprivation by castration or autoimmunization to LH-releasing hormone in the male rat under conditions of controlled food intake
Authors: Fletcher J. M. , Lobley G. E. , Connell A.
Published: December 2008

The effects of endogenous gonadal hormones on the regulation of body composition and energy retention have been investigated under conditions of controlled food intake. Male and female rats were fed the same amount from weaning to 82 days of age. The carcases of males contained more protein, less lipid and yielded more ash than females, but they had the same amount of total energy in their carcases as females. In a second experiment, male rats were sham-operated or castrated at 19 days and then fed equal amounts from weaning. At 40 days, intact and castrated rats did not differ in total carcase energy content nor in carcase composition. At 82 days the carcases of intact rats had more protein but had retained the same amount of energy as castrated rats. By 131 days, the difference in protein content was larger and intact rats had less carcase lipid, less carcase energy and gave less ash than castrated rats. At the same age and with a similar food intake, the differences in carcase composition between intact males and females were considerably larger than between intact and castrated males. In a third experiment, male rats were sham-operated or castrated at 1 day post partum and fed the same amount as in the second experiment from weaning to 82 days. Both sham-castrated and castrated rats grew less well than rats operated on at 19 days. The differences in carcase composition between intact and castrated rats were in the same direction but of greater magnitude than in rats operated at the later age. In a fourth experiment the effects on body compositon and energy retention of sham-operation, castration or immunization to LH-releasing hormone (LHRH) at weaning were compared in male rats fed the same amount from weaning to 131 days. Intact rats retained less carcase energy, less lipid and produced less ash than castrated and LHRH-immunized animals. Castrated and LHRH-immunized rats did not differ in carcase composition or amount of energy retained. It is concluded that (1) endogenous sex steroids affect growth and carcase composition independently of food intake, (2) the characteristic carcase composition of the female rat is largely due to the presence of ovarian steroids rather than lack of testicular steroids, (3) in the absence of increased food intake the effects of testicular steroids upon growth and energy expenditure are small but similar to those found in animals with free access to food, (4) the long-terms effects of perinatal exposure to testicular steroids upon growth and carcase composition are not only a consequence of changed food intake and (5) surgical castration and functional castration, induced by LHRH auto-immunization, produce the same effects on carcase composition.

J. Endocr. (1986) 110, 97–102
Gonadotrophin-releasing hormone (GnRH) overcomes GnRH antagonist-induced suppression of LH secretion in primates
Authors: Marshall G. R. , Bint Akhtar F. , Weinbauer G. F. , Nieschlag E.
Published: December 2008

If the suppressive effects of gonadotrophin-releasing hormone (GnRH) antagonists on gonadotrophin secretion are mediated through GnRH-receptor occupancy alone, it should be possible to restore serum gonadotrophin levels by displacing the antagonist with exogenous GnRH. To test this hypothesis, eight adult crab-eating macaques (Macaca fascicularis), weight 4·7–7·6 kg, were subjected to the following treatment regimens. A GnRH-stimulation test was performed before and 4, 12 and 24 h after a single s.c. injection of the GnRH antagonist (N-Ac-d-p-Cl-Phe1,2,d-Trp3,d-Arg6,d-Ala10)-GnRH (ORG 30276). The stimulation tests were performed with 0·5, 5·0 or 50 μg GnRH given as a single i.v. bolus. Blood was taken before and 15, 30 and 60 min after each bolus for analysis of bioactive LH and testosterone. The GnRH-challenging doses were given as follows: 0·5 μg GnRH was injected at 0 and 4 h, followed by 5·0 μg after 12 h and 50 μg after 24 h. One week later, 5·0 μg GnRH were given at 0 and 4 h, followed by 50 μg after 12 h and 0·5 μg after 24 h. Finally, after another week, the GnRH challenges began with 50 μg at 0 and 4 h, followed by 0·5 μg at 12 h and 5·0 μg at 24 h. This design permitted comparison of the LH and testosterone responses with respect to the dose of GnRH and the time after administration of GnRH antagonist. The areas under the response curves were measured and statistical evaluation was carried out by means of non-parametric two-way analysis of variance followed by the multiple comparisons of Wilcoxon and Wilcox. Four hours after the antagonist was injected, the LH and testosterone responses to all three doses of GnRH were suppressed. At the lowest dose of GnRH (0·5 μg) the responses remained reduced even after 24 h, whereas the higher doses of GnRH elicited an LH and testosterone response at 12 and 24 h which was not significantly different from that at 0 h. These data demonstrate that the suppression of LH secretion by a GnRH antagonist in vivo can be overcome by exogenously administered GnRH in a dose- and time-dependent manner, thus strongly supporting the contention that GnRH antagonists prevent gonadotrophin secretion by GnRH-receptor occupancy.

J. Endocr. (1986) 110, 145–150
Plasma testosterone-binding globulin-binding capacity in the male lesser mouse lemur (Microcebus murinus): relationship to seasonal and social factors
Authors: Perret M.
Published: December 2008

Plasma testosterone-binding globulin (TeBG)-binding capacity was determined by equilibrium dialysis in the lesser mouse lemur (Microcebus murinus), a prosimian which exhibits a clear photoperiod-dependent sexual cycle. Plasma TeBG-binding capacity showed significant seasonal changes which were inversely correlated to those of plasma testosterone concentrations. The capacity of TeBG was at its maximum (1·72 ± 0·4 μmol/l) during the sexual rest period and decreased to 0·98 ±0·24 μmol/l during the breeding season when testosterone concentrations were about 200–280 nmol/l. In addition, when males developed a social hierarchy in groups, the decreased sexual function in non-dominant animals was associated with a higher TeBG-binding capacity. However, although TeBG-binding capacity increased when testosterone concentrations decreased either during sexual rest or under social dominance, a positive correlation was found between TeBG-binding capacity and testosterone levels during the breeding season in males with a normal reproductive cycle, i.e. in both isolated and dominant males. This suggests that factors other than sex steroids are involved in the changes in TeBG-binding capacity occurring under seasonal and social influences.

J. Endocr. (1986) 110, 169–175
Effect of haemodialysis on plasma concentrations of atrial natriuretic peptide in adult patients with chronic renal failure
Authors: Anderson J. V. , Raine A. E. G. , Proudler A. , Bloom S. R.
Published: December 2008

Twenty patients with chronic renal failure were studied before and after haemodialysis. Plasma atrial natriuretic peptide (ANP) concentrations were markedly elevated (P < 0·01) before dialysis in comparison with healthy control subjects. After haemodialysis the plasma ANP concentration was lower in 19 patients (P < 0·01) but remained above the normal range in all but three cases. Systolic and diastolic blood pressure and body weight fell during dialysis but none of these changes correlated with the reduction of the plasma ANP concentration. Chromatographic analysis of plasma extracts indicated that α-ANP is the predominant circulating molecular form. The increase in concentration of ANP in plasma between dialyses, at a time when many patients are susceptible to sodium and water overload, and its return towards normal after dialysis supports the putative role of ANP as a circulating factor released in response to sodium and water accumulation.

J. Endocr. (1986) 110, 193–196
Effects of pancreatectomy on the growth and metabolite concentrations of the sheep fetus
Authors: Fowden A. L. , Mao X. Z. , Comline R. S.
Published: December 2008

The effects of fetal pancreatectomy on the growth and metabolism of the fetal sheep were investigated in chronically catheterized animals during the last third of gestation. Fetal pancreatectomy reduced body weight and crown–rump length at delivery near term (term 145 days). Body weight was affected more than body length so the ratio of weight to length was significantly less after pancreatectomy than in intact animals (P < 0·05). Pancreatectomized fetuses appeared to maintain a normal growth rate for 5–10 days after surgery but thereafter showed no further significant increase in body weight. When all the data from the intact and pancreatectomized fetuses were combined, there was a significant positive correlation between the plasma insulin concentration in utero and the body weight at delivery near term. The majority of organs studied were reduced in absolute weight after pancreatectomy but only the spleen and thymus were proportionally lighter when the weights were expressed as a percentage of body weight. Brain and placental weights were similar in intact and pancreatectomized fetuses. Over the range of values observed in utero, there were significant inverse correlations between the log plasma insulin level and the mean plasma concentrations of glucose, lactate, fructose and α-amino-nitrogen in individual intact and pancreatectomized fetuses. Insulin infusion into pancreatectomized fetuses restored the metabolite concentrations to their normal values within 48 h of infusion. The results demonstrate that insulin has a vital role in regulating fetal growth and metabolism in utero.

J. Endocr. (1986) 110, 225–231
Serotoninergic inhibition of LH secretion in the domestic fowl
Authors: Hall T. R. , Cheung A. , Harvey S.
Published: December 2008

Immature cockerels were injected with drugs known to affect serotoninergic activity. The receptor agonist quipazine as well as pargyline, an inhibitor of serotonin breakdown, both reduced plasma LH concentrations in a time-dependent fashion. The effect of pargyline was also dose-related. The serotonin precursor, tryptophan, reduced plasma LH levels. Tryptophan and pargyline were as effective in pubertal cockerels as in 3-week-old birds. Responses to quipazine were attenuated by the antagonist, methysergide, although another antagonist, cyproheptadine, also reduced plasma LH levels. Serotonin itself had no effect on plasma LH levels. Parachlorophenylalanine, which blocks serotonin synthesis, had no effect on plasma LH by itself, but attenuated the tryptophan-induced inhibition of LH. These data indicate that serotoninergic mechanisms inhibit secretion of LH in domestic fowl. This mechanism probably operates through the central nervous system.

J. Endocr. (1986) 110, 239–244
Influence of oestrogen and noradrenergic afferent neurones on the response of LH and oxytocin to immobilization stress
Authors: Higuchi T. , Honda K. , Negoro H.
Published: December 2008

The influence of oestrogen on LH and oxytocin responses to immobilization stress, and the involvement of noradrenergic afferent neurones in these responses, was examined in ovariectomized rats with or without pretreatment with oestrogen or after noradrenergic transmitter blockade. Immobilization of the rats on a board in a supine position for 1 h brought about a rapid decrease in LH levels and an increase in oxytocin levels in the blood of ovariectomized rats. Oestradiol benzoate (20 μg) injected s.c. the day before immobilization, decreased basal LH levels but had no effect on basal oxytocin levels. Immobilization stress applied to oestrogen-treated rats induced a small but significant increase in LH concentrations and a rise in oxytocin concentrations similar to that in rats without oestrogen pretreatment. A dopamine-β-hydroxylase inhibitor or phenoxybenzamine (α-adrenoceptor blocker) injected into ovariectomized rats reduced basal LH levels and increased basal oxytocin levels in the blood. Immobilization stress induced an increase in LH levels in rats treated with dopamine-β-hydroxylase inhibitor, but had no effect in rats treated with phenoxybenzamine. Stress induced a larger increase in blood oxytocin levels in rats treated with either drug compared with that in control rats injected with vehicle. On the other hand, propranolol (β-adrenoceptor blocker) had no effect on basal or stress-induced changes in LH or oxytocin levels in the blood. These results indicate that the LH response to stress, which might be mediated through α-adrenergic neurones, depends on the circulating oestrogen or LH levels before the stress. In contrast, the oxytocin response to stress may not be mediated by noradrenergic neurones and may not be influenced by oestrogen.

J. Endocr. (1986) 110, 245–250
Detailed analysis of blood oxytocin levels during suckling and parturition in the rat
Authors: Higuchi T. , Tadokoro Y. , Honda K. , Negoro H.
Published: December 2008

A detailed secretory profile of oxytocin during suckling and parturition was determined in unanaesthetized freely moving rats. Ten pups were reunited with their mothers after 12–15 h of separation. Unless the milk-ejection reflex occurred, there was no difference in serum oxytocin levels before separation and during the suckling of either four or five, or nine or ten pups. Serum oxytocin levels increased abruptly by 50·1 ± 4·2 (s.e.m.) pmol/l (n = 9) at milk ejection, and declined rapidly with a half-life of about 1·5 min. The peak concentration of blood oxytocin at each milk ejection was independent of the previous suckling period; values from the first three milk-ejection reflexes following the introduction of the pups and those observed 3–5 h after introduction were similar. The process of parturition was monitored by recording intra-uterine pressure with a balloon implanted in the uterus. On day 22 or 23 of pregnancy, continuous and rhythmical contractions of the uterus occurred (onset of parturition), but serum levels of oxytocin (21·1 ± 1·9 pmol/l; n = 13) did not alter until the expulsive phase. During the expulsive phase, fetuses were delivered after fetus-expulsion reflexes which were recorded as sudden large increases in intra-uterine pressure. Basal levels of oxytocin in the blood increased during this phase (32·5 ± 4·4 pmol/l; n = 13) and, in addition, rose by about 15 pmol/l and declined slowly after fetus-expulsion reflexes. The increase, however, was quite different from that seen at milk-ejection reflexes.

J. Endocr. (1986) 110, 251–256
Development and amplification of mid-afternoon surges of prolactin secretion in ovariectomized immature rats
Authors: Urbanski H. F. , Ojeda S. R.
Published: December 2008

The immature female rat shows a mid-afternoon surge of prolactin secretion which reaches a maximum on the day of first pro-oestrus. The present experiments were undertaken to elucidate the mechanisms which underly the development of this prolactin discharge. Detailed plasma prolactin profiles were obtained from short-term (48 h) ovariectomized rats at 23, 28 or 37 days of age. In the two older groups, but not the youngest, a mid-afternoon surge of prolactin secretion occurred in spite of the absence of the ovaries. To exclude the possibility that such an apparent ovarian-independent discharge of prolactin was due to an oestradiol effect which persisted for 2 days following ovariectomy, another study was conducted using long-term ovariectomized animals. Plasma profiles were obtained from neonatally ovariectomized rats at ages equivalent to juvenile (26–28 days), peripubertal (38–41 days) or adult (46–49 days) phases of development. A mid-afternoon surge of prolactin secretion was observed in the majority of animals (eight out of twelve) irrespective of the interval after ovariectomy; this finding further indicates that in the female rat there is a centrally originated mid-afternoon episode of prolactin secretion which is expressed during juvenile development even in the absence of the ovaries. The relatively small magnitude of these ovarian-independent prolactin discharges (c.f. the preovulatory prolactin surge) suggested that in the intact animal they are amplified by ovarian secretions. To test this hypothesis, oestradiol-containing silicone elastomer capsules were implanted s.c. into juvenile rats, immediately after ovariectomy, and plasma prolactin profiles examined 2 days later (28 days of age). In all cases the prolactin surge was greatly amplified and in many instances the magnitude was identical to that observed at first pro-oestrus. These data suggest that development of the large pro-oestrous surge of prolactin secretion involves the interplay of at least two distinct neuroendocrine mechanisms: (1) a centrally originated ovarian-independent signal and (2) an amplification effect exerted by ovarian oestradiol.

J. Endocr. (1986) 110, 361–366
Adrenocortical functions in a macropodid marsupial Thylogale billardierii
Authors: Martin I. K. , McDonald I. R.
Published: December 2008

In a study of adrenocortical functions in macropodid marsupials, measurements were made of the effects of ACTH infusion, ether stress and adrenaline infusion on plasma corticosteroid and glucose concentrations in wallabies (Thylogale billardierii) provided with indwelling venous catheters.

The mean plasma total glucocorticoid concentration in undisturbed males and females was 80 ± 5 (s.e.m.) μg/l, of which more than 90% was cortisol. This fraction declined to 68% of the total at the highest ACTH-stimulated concentration of 225 μg/l, due to an increase in the contribution by 11-deoxycortisol.

Although maximal ACTH stimulation (4·5 i.u./kg per h) caused a five- to sixfold increase in cortisol secretion rate, as measured by isotope dilution during constant-rate tracer infusion, plasma cortisol concentration rose only two- to threefold, due to a marked increase in metabolic clearance.

Plasma glucose concentration did not change significantly during either short-term (1 h) i.v. infusion or long-term (8 days) i.m. injection of ACTH, even though plasma cortisol concentration was significantly increased.

Ether anaesthesia caused a marked hyperglycaemia that preceded an increase in plasma cortisol concentration and was not sustained while plasma cortisol concentration continued to increase.

Infusion of adrenaline i.v. at rates sufficient to cause a similar hyperglycaemia had no significant effect on plasma cortisol concentration. A marked hyperglycaemia during xylazine anaesthesia was not associated with an increase in plasma cortisol concentration and was attributable to suppression of insulin secretion.

It is concluded that, as in the red kangaroo (Macropus rufus) and the quokka (Setonix brachyurus) and in contrast to the reported effects in the tammar wallaby (Macropus eugenii), neither ACTH, nor the increase in plasma glucocorticoid concentration caused by ACTH administration, influence plasma glucose concentration in Thylogale billardierii.

J. Endocr. (1986) 110, 471–480
Effects of multiple injections of LH on the secretion of pregnane compounds from polycystic ovaries of androgen-sterilized rats
Authors: Sawada T.
Published: December 2008

Differences in the secretion of pregnane compounds by follicular polycystic ovaries of androgen-sterilized rats and by normal preovulatory ovaries of early prooestrous rats were compared. Some rats were injected i.v. with LH 30 min before bleeding, in order to stimulate the secretion of steroids. This injection of LH greatly increased the secretion of progesterone, 5α-pregnane-3,20-dione and 3α-hydroxy-5α-pregnan-20-one by both types of ovaries. The response of the two progesterone metabolites in the polycystic ovaries was low, suggesting low 5α-reductase activity.

Because it is known that the preovulatory LH surge is absent in androgen-sterilized rats, a classical approach was taken to circumvent the probable deficit in cyclic release of LH by giving an i.v. injection of LH (25 μg) every 4 days for 16 days. Ovarian venous blood was collected 4 days after the last injection. The mean secretion of 5α-pregnane-3,20-dione and 3α-hydroxy-5α-pregnan-20-one from the ovaries of such androgen-sterilized rats became much (P <0·01) higher than that of multiple saline-treated controls. These results suggest that low 5α-reductase activity of polycystic ovaries in androgen-sterilized rats may be due to the absence of cyclic release of LH from the pituitary gland.

J. Endocr. (1986) 110, 507–510
Effects of physiological concentrations of parathyroid hormone on acid phosphatase activity in cultured rat bone cells
Authors: Braidman I. P. , St John J. G. , Anderson D. C. , Robertson W. R.
Published: December 2008

The mechanism by which parathyroid hormone (PTH) induces osteoclastic bone resorption is still incompletely understood. Recent evidence suggests that the hormone exerts its effects indirectly, via the osteoblasts. Bone cells isolated from fetal rat calvaria by enzymatic digestion were used. Two heterogeneous cell populations were isolated by equilibrium density centrifugation on Percoll gradients and maintained by differential culture conditions. These two populations, which are morphologically distinguishable from one another by light and electron microscopy, have been characterized previously both biochemically and with regard to their hormonal (PTH and calcitonin) responses. We have called them type C cells (containing cells with some of the properties of osteoclasts) and type B cells (containing osteoblast-like cells, as well as fibroblasts, chondrocytes and other stromal cells). In the present study, we have further characterized the functional relationship between the two cell populations, with particular regard to the hormonal responses of type C cultures. Acid phosphatase, measured cytochemically in individual cells, was used as a marker for C cell responses.

C cells had significantly higher levels of acid phosphatase activity than either B cells or spleen macrophages. Calcitonin (0–10 pg/ml) decreased C cell acid phosphatase activity but was without effect on B cells or spleen macrophages. Co-culture of C cells with B cells produced increased enzyme activity only in the former; this effect could be mimicked if fibroblasts replaced B cells and cell contact was essential for this response. PTH (0–10 pg/ml) raised enzyme activity further in C cells only when they were cultured with B cells. When C cells were cultured so that they shared medium, but were not in contact, with B cells, PTH (2 pg/ml) still increased enzyme activity in the former. Fibroblasts were ineffective in this system. Spleen macrophages were also unresponsive to PTH when substituted for C cells. Calcitonin (10 pg/ml) blocked the effects of PTH on C cells. These results indicate that macrophages are probably not a significant proportion of the C cell population, and that PTH may produce increased acid phosphatase activity in C cells via a humoral factor produced by cells present in B cell cultures.

J. Endocr. (1986) 111, 17–26
Somatostatin tonically inhibits growth hormone secretion in domestic fowl
Authors: Harvey S. , Lam S.-K. , Hall T. R.
Published: December 2008

Passive immunization of immature chickens with sheep somatostatin (SRIF) antiserum promptly increased the basal plasma GH concentration and augmented TRH-induced GH secretion. Although exogenous SRIF had no inhibitory effect on the basal GH concentration in untreated birds or birds pretreated with non-immune sheep serum, it suppressed the stimulatory effect of SRIF immunoneutralization on GH secretion. These results suggest that SRIF is physiologically involved in the control of GH secretion in birds, in which it appears to inhibit GH release tonically.

J. Endocr. (1986) 111, 91–97
Effects of lithium and phorbol on the dynamics of LH release from dispersed sheep pituitary cells
Authors: Starling L. , McIntosh R. P. , Mclntosh E. A.
Published: December 2008

The possible involvement of polyphosphoinositides in the stimulation of LH release was investigated. Dispersed sheep pituitary cells were incubated in test-tubes, or perifusedns in columns, with gonadotrophin-releasing hormone (GnRH) and Li+, or with a phorbol ester, and the amounts and patterns of LH release over time compared.

Treatment with Li+ (10 mmol/l), which is known to increase levels of inositol phosphates in gonadotrophs, was shown to have effects only on the responses of desensitized cells, significantly decreasing the rate at which the cells desensitize (P<0·005) and decreasing the response to supramaximal levels of GnRH stimulus (P<0·01). It is suggested that these effects could be due to increased levels of inositol monophosphate, inositol bisphosphate inositol 1,3,4-trisphosphate. Responses to single or repeated pulses of GnRH at 18-, 30- and 60-min intervals were not significantly altered.

Phorbol 12-myristate 13-acetate (PMA), an activator of the calcium and phospholipid-dependent protein kinase (protein kinase C), was specifically active in releasing LH with a half-maximal stimulating dose of approximately 3 nmol/l. Phorbol 12,13-diacetate, which is structurally similar to PMA but does not activate protein kinase C, did not release LH, except at high levels in freshly dispersed cells. The timing of PMA-stimulated LH release was similar to that for GnRH-stimulated release, and PMA was able to release greater amounts of LH than could GnRH. This suggests that activation of protein kinase C is likely to be important in the GnRH-stimulated release of LH from gonadotrophs. It also shows that the desensitization to GnRH stimulation observed after 10 min is unlikely to be caused by lack of releasable LH. Cells desensitized to maximally stimulating levels of GnRH still responded strongly to PMA stimulation, indicating that the desensitization to GnRH stimulation involves a step in the transduction mechanism before activation of protein kinase C.

J. Endocr. (1986) 111, 167–173
Cellular interactions in the hormonal induction of α2u-globulin in rat liver
Authors: Sarkar F. H. , Mancini M. A. , Nag A. C. , Roy A. K.
Published: December 2008

The role of hepatocellular interaction in the androgen-dependent synthesis of rat α2u-globulin was examined by immunochemical analysis of liver sections. Both after androgen administration to the ovariectomized female and during puberty in the male, only a subpopulation of hepatocytes became competent to synthesize α2u-globulin. These competent hepatocytes first appeared as discontinuous patches along the wall of the central vein. After the formation of a confluent layer around the central vein, cellular competency was seen to propagate toward the periportal direction through the cords of hepatic cells. Although the periportal progression of cellular competency for the synthesis of α2u-globulin appeared to be an all-or-none phenomenon, it did not require cell division. From these results we conclude that certain components of the central vein are necessary for the hormonal induction of α2u-globulin in the rat liver. We also propose that a primary endocrine influence on the hepatic vein results in the production of a secondary paracrine mediator which can trigger the synthesis of α2u-globulin in adjacent hepatocytes. Perivenous to periportal flow of this putative secondary mediator can explain cell recruitment for the synthesis of α2u-globulin along the hepatic cords.

J. Endocr. (1986) 111, 205–208