bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thyroxine concentrations and secretion rates in relation to pregnancy, lactation and energy balance in goats
Authors: Riis P. M. , Madsen A. 
Published: December 2008

ABSTRACT
Plasma thyroxine (T4) concentrations were measured during pregnancy and lactation in goats on diets with different energy concentrations to study the role of T4 secretion in metabolic adaptation to pregnancy and lactation. Thyroxine distribution space (the volume of fluid required to dissolve the total pool of circulating T4 at a concentration equal to that in the plasma) and secretion rates were determined by using 125I-labelled T4 at different stages of lactation and pregnancy.
Plasma concentrations of T4 increased during lactation and reached maximum levels 4–5 months after giving birth. They then remained fairly constant for the following 2–3 months until the goats became pregnant again. Thyroxine concentrations decreased slightly during pregnancy and showed a sudden drop at the onset of lactation. Minimum concentrations were observed during the first 2–3 weeks of lactation after which time concentrations increased slowly. Average concentrations for goats on a low-energy diet were consistently lower than those in goats on a high-energy diet. The mean secretion rate was 10·4 nmol day−1 kg body wt−0·75. The distribution spaces were much lower than the total extracellular space. The average distribution space in non-pregnant and pregnant goats was 11 and 5·3% of the body weight respectively.
The decrease in T4 secretion rate and T4 distribution space during pregnancy is considered to be part of a homeorhetic adaptation to the condition. The drop in T4 secretion rate at the onset of lactation appears to be a homeostatic adaptation to a decreased fuel supply, similar to the situation with fasting or energy malnutrition.
J. Endocr. (1985) 107, 421–427
Effect of epidermal growth factor on reproductive function of ewes
Authors: Shaw G. , Jorgensen G. I. , Tweedale R. , Tennison M. , Waters M. J. 
Published: December 2008

ABSTRACT
Adult Merino ewes were infused via the jugular vein with either saline (n = 5) or epidermal growth factor (EGF) (4·2 μg/kg per h, n = 6) for 24 h in either the luteal phase or the follicular phase of the oestrous cycle and reproductive function was examined.
Infusion of EGF during the luteal phase caused no detectable change in plasma progesterone or prolactin concentrations over a 7-day period compared with the controls.
Infusion of EGF during the follicular phase suppressed the oestrous rise in plasma oestradiol. Luteinizing hormone pulse amplitude was increased and pulse frequency was decreased by the end of the infusion. All control ewes had a pro-oestrous LH surge and mated, but the LH surge and oestrus were prevented by EGF infusion. Nevertheless, plasma progesterone levels rose subsequently in the EGF-infused ewes in parallel with the control ewes, suggesting that the preovulatory follicle had luteinized. Both LH and FSH rose over the 7 days after EGF infusion to levels similar to those in ovariectomized ewes.
Thus EGF appears to inhibit follicular oestradiol production, although it does not affect luteal progesterone production or follicular luteinization. We suggest that the alteration in gonadotrophin secretion patterns results from a disturbance of feedback mechanisms between the ovary and the hypothalamopituitary axis, although a direct effect in the brain or the pituitary gland cannot yet be excluded.
J. Endocr. (1985) 107, 429–436
GROWTH HORMONE-RELEASING FACTOR ANALOGUE (hGRF1-29NH2): IMMUNOREACTIVE-GRF PLASMA LEVELS AFTER INTRAVENOUS AND SUBCUTANEOUS ADMINISTRATION
Authors: Rafferty B. , Poole S. , Clarke R. , Schulster D. 
Published: December 2008

ABSTRACT
A homologous radioimmunoassay (RIA) system for human growth hormone-releasing factor 1-29NH2 (hGRF 1-29-NH2) was developed and applied to the measurement of immunoreactive (IR) concentrations of the peptide in anaesthetized rats to determine some of its pharmacokinetics after i.v. and s.c. administration. Analysis of the biphasic disappearance curve of IR-hGRF-1-29NH2 from plasma after i.v. injection (10μg) gave values for the half-lives of the initial distribution phase (α) and for the elimination phase (β) of 1.9 ± 0.2 min and 10.4 ± 0.2 min respectively. There was rapid uptake of the peptide from the site of s.c. injection but comparison of areas under the plasma IR-hGRF1-29NH2/time curves showed that the estimated total amount in the circulation after s.c. injection was only 4% of that obtained after i.v. administration. A large degree of degradation of the peptide is indicated either at the site of injection or during transfer to plasma; this susceptibility to rapid breakdown is reflected in the short half-life of the peptide in the circulation. Therefore the measurement of the above parameters is a prerequisite when assessing potency of GRF analogues in-vivo and when implementing suitable dosage regimens for clinical purposes.
The involvement of calcitonin in the reproductive physiology of the rainbow trout
Authors: Björnsson B. Th. , Haux C. , Förlin L. , Deftos L. J. 
Published: December 2008

ABSTRACT
Plasma from rainbow trout (Salmo gairdneri) of both sexes was sampled every month throughout an annual reproductive cycle in order to elucidate possible relationships between plasma calcitonin and free and protein-bound calcium and magnesium. This was then studied in greater detail around the time of ovulation in the female fish.
The plasma levels of the parameters studied were stable in males during the whole annual cycle and were similar to the levels found in females during at least 6 months of the cycle. Plasma levels of protein-bound calcium and magnesium as well as calcitonin were raised in the females for 6, 4 and 3 months respectively. These increases occurred concomitantly during the months before and after ovulation, but no correlations between the protein-bound ion and calcitonin levels were found during this period. With the exception of a decrease observed in December, the free plasma levels of calcium and magnesium were stable in both males and females throughout the cycle. This decrease was attributed to the high production rate of the yolkprotein precursor vitellogenin, which binds both calcium and magnesium.
In the detailed study on the ovulating females, plasma calcitonin levels were high 4 weeks before, and continued to increase until the time of ovulation, when a sharp decrease towards normal was noted. The free plasma calcium and magnesium levels were not affected, while the protein-bound levels of calcium and magnesium were found to decline towards normal for the duration of the experiment, without any obvious correlation with the time of ovulation. Regulation of calcitonin secretion seems not to be directly related to free plasma calcium levels, and it is suggested that ovarian steroids and/or gonadotrophins are involved. It is still possible, however, that calcitonin in rainbow trout may play a role in protecting the skeleton during periods of the increased calcium demand of oogenesis.
It is concluded that calcitonin plays a specific role in the reproductive physiology in female rainbow trout, which is apparently not reflected by measurable changes in blood calcium.
J. Endocr. (1986) 108, 17–23
Prolactin stimulates Na+-K+-ATPase activity located in the outer renal medulla of the rat
Authors: Pippard C. , Baylis P. H. 
Published: December 2008

ABSTRACT
The effect of rat prolactin on rat renal Na+-K+-ATPase activity was investigated by a cytochemical technique. Rat prolactin caused stimulation of Na+-K+-ATPase activity only in the outer medulla of the kidney, and not in renal cortical structures. Peak enzyme activity in cultured rat renal segments occurred after tissue had been exposed to rat prolactin for 2 min, and the time of maximal stimulation did not vary with the concentration of prolactin. There was a curvilinear response in Na +-K+-ATPase activity over the rat prolactin concentration range, 0·04–40 ng/1, but higher prolactin concentrations caused inhibition of enzyme activity. Na+-K+-ATPase response was totally blocked by specific rat prolactin antiserum. Human prolactin had no consistent effect on rat medullary Na+-K+-ATPase activity. Addition of specific tri-iodothyronine and arginine vasopressin antisera to rat prolactin was without effect, confirming that the stimulatory action of rat prolactin on Na+-K+-ATPase was not due to contamination with these hormones which are known to stimulate this enzyme.
J. Endocr. (1986) 108, 95–99
Changes in aromatase activity in the neuroendocrine tissues of red grouse (Lagopus lagopus scoticus) in relation to the development of long-day refractoriness
Authors: Sharp P. J. , Armstrong D. G. , Moss R. 
Published: December 2008

ABSTRACT
Changes in aromatase activity in the neuroendocrine tissues of captive male and female red grouse (Lagopus lagopus scoticus) were measured during a photoinduced breeding cycle. The gonads enlarged and subsequently regressed, as a consequence of the development of long-day refractoriness, within 84 days of transferring photoinsensitive birds from a non-stimulatory to a stimulatory daylength. The object of the study was to determine whether long-day refractoriness is related to an increase in aromatase activity in the neuroendocrine tissues which might result in a greater inhibitory action of locally produced oestrogens on the release of LH-releasing hormone.
Aromatase activity was measured and found to be present in the anterior pituitary gland, the anterior/ preoptic hypothalamus, the posterior hypothalamus and the hyperstriatum dorsale. It was higher in the hypothalamus than in the hyperstriatum dorsale and higher in the posterior than in the anterior/preoptic hypothalamus.
Aromatase activity in the posterior hypothalamus was higher in males than in females in short-day photosensitive and reproductively active birds, but not in long-day refractory birds. A similar sex difference was also observed in the anterior/preoptic hypothalamus in reproductively active birds.
Hypothalamic aromatase activity in both sexes was directly related to gonadal function, being highest in reproductively active birds and lowest in long-day refractory birds.
It is concluded that the development of long-day refractoriness is not related to an increase in aromatase activity in the neuroendocrine tissues. The decrease in aromatase activity in the neuroendocrine tissues in long-day refractory birds parallels a decrease in aggressive and territorial behaviour.
J. Endocr. (1986) 108, 129–135
Corticotrophin-releasing factor-like immunoreactivity and bioactivity of human fetal and adult hypothalami
Authors: Ackland J. F. , Ratter S. J. , Bourne G. L. , Rees L. H. 
Published: December 2008

ABSTRACT
Corticotrophin releasing factor-like immunoreactivity (CRF-LI) and bioactivity, and arginine vasopressinlike immunoreactivity (AVP-LI) have been measured in extracts of human fetal and adult hypothalamic tissue and their development with the gestational age of the fetuses (12–27 weeks) studied. CRF-LI was measured by a radioimmunoassay developed for ovine corticotrophin-releasing factor (oCRF-41). Corticotrophin-releasing factor bioactivity was measured in a rat isolated anterior pituitary cell perfusion system. CRF-LI and bioactivity and AVP-LI were all detectable in fetal hypothalamic extracts from 12 to 13 weeks of gestational age. CRF-LI was also present in human fetal pituitary glands from 12 weeks of gestational age. The concentration of CRF-LI in the fetal hypothalamic extracts (9·2±11·4 ng/g, mean ± s.e.m., n = 33) showed no significant correlation with the gestational age of the fetuses. However the concentration of AVP-LI (25·0–36·8 ng/g, n = 17) did show a positive correlation (r = 0·508, P<0·05) with gestational age, as did the concentration of CRF bioactivity (471·3–556·3 ng ACTH released/g tissue, n = 13, r = 0·725, P < 0·01).
The CRF bioactivity of all fetal hypothalamic extracts was potentiated by the addition of synthetic human (h)AVP, but the bioactivity of the adult hypothalamic extracts was not, presumably because of the higher levels of AVP-LI already present in the adult extracts. Pretreatment of tissue extracts with antisera to oCRF-41 and/or hAVP reduced the CRF bioactivity of all hypothalamic extracts. Sephadex chromatography of fractions which co-eluted with synthetic oCRF-41 or hAVP contained CRF bioactivity and this bioactivity was potentiated when synthetic hAVP or oCRF-41, respectively, were added to the fractions. However, a larger molecular weight form of CRF-LI (8000–10 000 daltons), which was observed only in fetuses of 20 weeks of gestational age or less, did not contain any significant CRF bioactivity.
J. Endocr. (1986) 108, 171–180
Sex difference in the cytosolic and nuclear distribution of androgen receptor in mouse submandibular gland
Authors: Kyakumoto S. , Kurokawa R. , Ohara-Nemoto Y. , Ota M. 
Published: December 2008

ABSTRACT
Cytosol and nuclear androgen receptors in submandibular glands of male and female mice were measured by an exchange assay at 0 °C. The binding of [3H]methyltrienolone to cytosol receptors in females was mostly saturated within a short period of incubation (3 h), whereas the saturation was much slower in males; suggesting that almost all of the cytosol receptors were unoccupied in females and the receptors were partially occupied in males. Nuclear receptors were extracted with pyridoxal 5′-phosphate (5 mmol/l) from nuclear fractions with 93–95% efficiency. The exchange of the bound steroids occurred by 24–48 h at 0 °C, suggesting that most of the nuclear androgen receptor was occupied. The binding was low at higher temperatures, probably due to inactivation of the receptor. Scatchard analysis showed that the apparent dissociation constants of cytosol and nuclear receptors were similar (0·8 and 0·9 nmol/l respectively) in both sexes. On the other hand, the number of androgen-binding sites in the nucleus was much higher in males than in females (1052 fmol/mg DNA and 32 fmol/mg DNA respectively), while the number in the cytosol was higher in females than in males (512 fmol/mg DNA and 368 fmol/mg DNA respectively). These observations show that androgen receptors exist mainly (74%) in the nuclei of males, while they exist mostly (94%) in the cytosol of females.
J. Endocr. (1986) 108, 267–273
Effects of a prenatal androgen peak on rat brain sexual differentiation
Authors: Perakis A. , Stylianopoulou F. 
Published: December 2008

ABSTRACT
Exposure of the developing female brain to a 5α-dihydrotestosterone surge on day 18 of gestation resulted in defeminization and slight masculinization of the brain. In contrast, abolition of the androgenic effects of the testosterone peak naturally occurring in male fetuses on day 18 of gestation by exposure of the developing male brain to cyproterone acetate, at that time, resulted in demasculinization while feminization was not affected. On the basis of these results, we suggest that both the prenatal testosterone peak and the high testosterone levels occurring in males neonatally are necessary for aromatization sufficient to effect complete male rat brain sexual differentiation.
J. Endocr. (1986) 108, 281–285
Neonatal screening for congenital adrenal hyperplasia: a programme based on a novel direct radioimmunoassay for 17-hydroxyprogesterone in blood spots
Authors: Wallace A. M. , Beastall G. H. , Cook B. , Currie A. J. , Ross A. M. , Kennedy R. , Girdwood R. W. A. 
Published: December 2008

ABSTRACT
We have assessed the feasibility of screening newborn babies for congenital adrenal hyperplasia (CAH) by the direct measurement of 17-hydroxyprogesterone (17-OHP) in blood spots collected on filter paper (Guthrie cards) for the phenylketonuria, hypothyroidism and galactosaemia screening programmes run in Scotland. The procedure described for CAH uses an iodinated 17-OHP tracer and a specific 17-OHP antiserum sheathed within semipermeable nylon microcapsules. The method does not require a solvent extraction step, is inexpensive, precise, efficient and, therefore, practical for large-scale use. With this system the value of a neonatal screening programme was assessed in a retrospective analysis and a prospective trial.
The retrospective study of 15 paediatric cases of CAH illustrated that at least half were not diagnosed within 3 weeks of birth. Analysis of the original Guthrie card samples revealed increased levels of 17-OHP in all cases. The prevalence of CAH as calculated in the retrospective study was 1 in 20 907 with a range (within 95% confidence limits) of from 1 in 12 675 to 1 in 32 604 (n = 301 450). In the prospective trial a total of 92 051 consecutive samples was screened. Five cases of CAH were correctly identified with a current false positive rate of 0·042%. Analysis of urinary steroids confirmed defective adrenal 21-hydroxylase activity in all positive cases. In the prospective trial the prevalence was 1 in 18 401 with a range of from 1 in 7 422 to 1 in 50006.
We conclude that mass screening for CAH is both feasible and desirable.
J. Endocr. (1986) 108, 299–308
The physiological significance of arginine vasopressin in potentiating the response to corticotrophin-releasing factor in sheep
Authors: Redekopp C. , Livesey J. H. , Sadler W. , Donald R. A. 
Published: December 2008

ABSTRACT
In order to assess the physiological importance of endogenous arginine vasopressin (AVP) in augmenting the ACTH response to corticotrophin-releasing factor (CRF), the response to CRF during hypertonic saline infusion in six Coopworth sheep was examined. A 4-h infusion of 5% (w/v) NaCl (3·8 ml/min) resulted in significantly (P < 0·01) greater rises in ACTH and cortisol, but not aldosterone, than were observed after CRF alone. Infusion of hypertonic saline without CRF resulted in a highly significant (P < 0·001) rise in plasma osmolality and AVP but no significant change in plasma ACTH, cortisol or aldosterone.
It is concluded that a marked but physiological increase in peripheral (and presumably central) levels of AVP does not result in any demonstrable change in plasma ACTH concentration. However, under these conditions, the ACTH and cortisol responses to CRF are considerably augmented.
J. Endocr. (1986) 108, 309–312
FSH-induced aromatase activity in porcine granulosa cells: non-competitive inhibition by non-aromatizable androgens
Authors: Chan W. K. , Tan C. H. 
Published: December 2008

ABSTRACT
The aim of this study was to examine the inhibitory effect of the non-aromatizable androgens on FSH-stimulated aromatase activity in porcine granulosa cells. The cells were isolated from medium-sized follicles (4–6 mm) of prepubertal pigs, and cultured under chemically defined conditions in the presence of FSH (1 μg/ml, NIADDK-oFSH-S13) with and without the androgens for an initial 48-h induction period. Subsequently, the spent medium was replaced with fresh medium containing only testosterone as substrate and the cells were reincubated for a further 6 h. The conversion of this steroid to oestradiol-17β during this latter 'test' period was taken as a measure of the aromatase activity. The addition of 5α-dihydrotestosterone (DHT) into cultures of FSH-stimulated cells during the induction period resulted in a definite dose-dependent inhibition (30–70%) of the aromatase activity expressed in the test period. This inhibitory action, of the mixed non-competitive type, is characterized by a decrease in the apparent Vmax and an increase in the Km value, suggestive of an androgen inhibition of FSH-stimulated aromatase synthesis. This inhibition was also shown by the other 5α- and 5β-reduced androgens: 5β-androstanedione was the most effective, while DHT was the least. Other steroids such as pregnenolone and progesterone were inhibitory, but testosterone and diethylstilboestrol were stimulatory. These results suggest an important mechanism for the intrafollicular control of oestrogen synthesis, involving a possible reciprocal relationship between aromatase and 5α-reductase activities.
J. Endocr. (1986) 108, 335–341
Seasonal changes in concentrations of plasma hormones in the male ring dove (Streptopelia risoria)
Authors: Lea R. W. , Sharp P. J. , Klandorf H. , Harvey S. , Dunn I. C. , Vowles D. M. 
Published: December 2008

ABSTRACT
Seasonal changes in concentrations of plasma LH, prolactin, thyroxine (T4), GH and corticosterone were measured in captive male ring doves exposed to natural lighting at latitude 56 °N. Plasma LH levels decreased steeply in autumn when the daylength fell below about 12·5 h but increased in November as the birds became short-day refractory. In comparison with plasma LH concentrations in a group of short-day refractory birds exposed to 6 h light/day from the winter solstice, plasma LH levels in birds exposed to natural lighting increased further in spring after the natural daylength reached about 12·5 h. There were no seasonal changes in plasma prolactin concentrations and plasma T4 concentrations were at their highest during December, January and February, the coldest months of the year. The seasonal fall in plasma LH levels in September was associated with a transitory increase in plasma T4, a transitory decrease in plasma corticosterone and a sustained increase in plasma GH.
It is suggested that in the ring dove, short-day refractoriness develops rapidly in November to allow the bird to breed when the opportunity arises, during the winter and early spring. The annual breeding cycle is synchronized by a short-day induced regression of the reproductive system in the autumn, the primary function of which may be to enable the birds to meet the energy requirements for the annual moult. The changes in plasma T4, corticosterone and especially of GH at this time of year are probably concerned with the control of moult or the associated changes in energy requirements.
J. Endocr. (1986) 108, 385–391
Measurement of lipogenesis in isolated preputial gland cells of the rat and the effect of oestrogen
Authors: Alves A. M. , Thody A. J. , Fisher C. , Shuster S. 
Published: December 2008

ABSTRACT
Lipogenesis was measured in isolated preputial gland cells of female rats after ovariectomy and after the administration of oestradiol benzoate. Ovariectomy decreased preputial gland cell lipogenesis and also altered the pattern of lipid synthesis, producing a relative decrease in the proportion of polar lipids and an increase in the proportion of 'triglycerides'. Although daily administration of 2 or 10 μg oestradiol benzoate for 7 days produced slight increases in preputial gland cell lipogenesis in ovariectomized rats, the effects were not significant. A single injection of 10 μg oestradiol benzoate, however, produced significant increases in preputial gland cell lipogenesis of ovariectomized rats at both 2 and 24 h and, moreover, at 24 h the pattern of polar lipid and triglyceride labelling was restored to normal. Prior administration of actinomycin D reduced the lipogenic effect of oestradiol benzoate. Oestradiol benzoate had little or no effect on preputial gland cell lipogenesis in male rats. These results confirm that oestrogen is able to stimulate preputial lipogenesis in female rats. Whether this action of oestrogen is related to its pheromone-producing effect on the preputial glands is not yet known.
J. Endocr. (1986) 109, 1–7