bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of gonadal steroid hormones on the hypothalamo-pituitary-liver axis in the control of sex differences in hepatic steroid metabolism in the rat
Authors: Mode Agneta , Norstedt Gunnar 
Published: December 2008

The site of action of gonadal hormones in the regulation of hepatic steroid metabolism was investigated by measuring the effects of (i) implantation of oestradiol into the pituitary gland or anterior hypothalamus of males and (ii) subcutaneous injection of a synthetic androgen in deafferentated male and female rats. The hepatic responses measured in vitro were 5α-reduction, and 6β- and 16α-hydroxylation of androstenedione.
After intrapituitary or intrahypothalamic implantation of oestradiol, 5α-reductase activity increased and 6β- and 16α-hydroxylase activity decreased in males relative to the enzyme activities of cholesterol-implanted animals, indicating a feminizing effect of the oestrogen. This effect could not be accomplished by subcutaneous injection of the same oestrogen preparation.
Deafferentation had no effect on hepatic steroid metabolism in females, but caused a feminization in males. In addition, subcutaneous treatment of intact females with the synthetic androgen caused masculinization of hepatic steroid metabolism, but was without effect in deafferentated animals. Treatment with synthetic androgens had no effect on the hepatic steroid metabolism in deafferentated male animals. Subcutaneous injection of a potent synthetic progestagen had little effect on hepatic steroid metabolism in intact females.
It is concluded that oestrogen feminizes hepatic steroid metabolism by an action at the hypothalamic-pituitary level and that an intact hypothalamic-pituitary axis is required for the masculinizing action of the synthetic androgen on hepatic steroid metabolism. It is possible that the site of action of androgens is in the anterior hypothalamus or in adjacent areas of the brain.
Concentrations of epidermal growth factor in mouse milk throughout lactation
Authors: Beardmore J. M. , Richards R. C. 
Published: December 2008

A radioimmunoassay was used to measure the concentration of epidermal growth factor (EGF) in mouse milk throughout lactation.
The EGF content of mouse milk increased steadily from birth to a concentration of 427 μg/l at day 8 of lactation. These high levels were maintained until the approach of weaning, when values decreased from day 17 to 130 μg/l at day 22.
Milk samples chromatographed on a Biogel P10 column gave a major peak of immunoreactivity at the point at which pure standard EGF was eluted.
The origin of milk EGF is unknown, but the high concentrations of this peptide identified in mouse milk suggest that it must play a role in the neonate.
Plasma immunoreactive gastric inhibitory polypeptide in obese hyperglycaemic (ob/ob) mice
Authors: Flatt P. R. , Bailey C. J. , Kwasowski P. , Page T. , Marks V. 
Published: December 2008

ABSTRACT
Gastric inhibitory polypeptide (GIP), a recognized component of the enteroinsular axis, is raised in the plasma and intestine of obese hyperglycaemic (ob/ob) mice. To evaluate the control of plasma GIP and its role in the hyperinsulinaemia of the ob/ob syndrome, GIP and insulin were determined at different ages in fed mice, and at 10–12 weeks of age after fasting/refeeding and administration of GIP, different nutrients and insulin to mice fasted for 18 h. Plasma GIP and insulin were raised in adult (10- and 20-week-old) compared with younger (3- and 5-week-old) mice, although GIP was not increased in the presence of hyperinsulinaemia at 3 weeks of age. Fasting suppressed and refeeding promptly restored plasma GIP and insulin concentrations. Administration of GIP to mimic postprandial concentrations evoked a marked but transient insulin response which was protracted in the presence of rising hyperglycaemia. Orally administered fat, glucose and amino acids raised GIP concentrations with fat having a particularly strong effect. Glucose and amino acids also evoked prominent increases of insulin, but fat produced only a small rise in insulin in the absence of increasing glucose concentrations. Consistent with glucose-potentiation, a mixture of all three nutrients greatly augmented the insulin response without further increase of plasma GIP. Glucose-induced increase in endogenous insulin and doses of exogenous insulin up to 100 units/kg did not suppress basal, fat-stimulated or glucose-stimulated GIP release. The results indicate that raised GIP concentrations make an important contribution to the hyperinsulinaemia and related metabolic abnormalities of the ob/ob syndrome.
J. Endocr. (1984) 101, 249–256
Effects of background adaptation on the pituitary and plasma concentrations of some pro-opiomelanocortin-related peptides in the rainbow trout (Salmo gairdneri)
Authors: Rodrigues K. T. , Sumpter J. P. 
Published: December 2008

ABSTRACT
Radioimmunoassays for α-MSH, β-MSH, ACTH and endorphin were used to measure pituitary concentrations of these peptides in rainbow trout during adaptation to black and white backgrounds. There was no difference in the pituitary content of any of these peptides between long-term black- and white-adapted trout. Plasma levels of α-MSH immunoreactivity were significantly higher in black-adapted trout than in white-adapted trout. Time-course studies revealed that although the body colour of trout showed an initial rapid adaptation to background colour, this was not paralleled by a corresponding change in plasma α-MSH levels. These only showed significant changes after 7 or more days of background adaptation, when melanophore recruitment or degradation occurred on black or white backgrounds respectively. Intravenous administration of mammalian α-MSH, salmon β-MSH I or antibodies to these peptides did not affect short-term background adaptation. However, long-term administration of mammalian α-MSH via osmotic minipump maintained melanophore numbers in grey-adapted trout transferred to a white background, although this observation was based on only two fish. It is concluded that peptides derived from pro-opiomelanocortin do not appear to be involved in controlling physiological colour change but may be involved in regulating morphological colour change of the rainbow trout.
J. Endocr. (1984) 101, 277–284
Effects of hypophysectomy and growth hormone treatment on renal hydroxylation of 25-hydroxycholecalciferol in rats
Authors: Wongsurawat N. , Armbrecht H. J. , Zenser T. V. , Forte L. R. , Davis B. B. 
Published: December 2008

ABSTRACT
Growth hormone stimulates intestinal calcium absorption. This action has been linked to vitamin D metabolism. We have investigated the effects of hypophysectomy and GH treatment on renal metabolism of 25-hydroxycholecalciferol (25-OH-D3). Renal hydroxylation of 25-OH-D3 was measured in vitro using the renal slice technique. Experiments were performed in young F344 rats fed a vitamin D-replete, low calcium diet for 4 weeks. In hypophysectomized rats, renal conversion of 25-OH-D3 to 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) was markedly reduced compared with sham-operated rats. Renal conversion of 25-OH-D3 to 24,25-(OH)2D3 was markedly increased in hypophysectomized rats compared with sham-operated rats. Treatment of hypophysectomized rats with rat GH (rGH) for 10 days resulted in a significant increase in renal conversion of 25-OH-D3 to 1,25-(OH)2D3 and a significant decrease in conversion to 24,25-(OH)2D3. Rat GH treatment caused no significant changes in serum levels of immunoreactive parathyroid hormone. Serum calcium concentrations were similar in all groups, and serum phosphorus was low in hypophysectomized rats. Treatment of hypophysectomized rats with ovine GH for 6 days caused changes which were much less pronounced than those induced by rGH. Renal conversion of 25-OH-D3 to 1,25-(OH)2D3 and 24,25-(OH)2D3 correlated well with growth rate (weight gain). These results suggest that GH, either directly or indirectly, modulates renal metabolism of 25-OH-D3.
J. Endocr. (1984) 101, 333–338
In-vitro effects of corticosterone, synthetic ovine corticotrophin releasing factor and arginine vasopressin on the release of adrenocorticotrophin by fetal rat pituitary glands
Authors: Dupouy J. P. , Chatelain A. 
Published: December 2008

ABSTRACT
The in-vitro release of ACTH by fetal rat pituitary glands on days 17, 19 and 21 of pregnancy was measured using radioimmunoassay.
The spontaneous release of ACTH, expressed in pg ACTH/gland per h, increased with fetal age, in correlation with the sharp rise in pituitary ACTH content. However, since pituitary ACTH content was nearly sevenfold higher at term than on day 17, while basal release of ACTH was only threefold higher, one can speculate that the spontaneous release of ACTH was proportionally greater on day 17 than on day 21 of gestation.
As corticosterone, at a physiological concentration (865 nmol/l), reduced ACTH release, it was concluded that the pituitary gland was one site of the negative feedback action of the corticosteroids during fetal life.
Quantities of synthetic ovine corticotrophin releasing factor (CRF) which gave concentrations of 0·3–30 nmol/l in the incubation medium induced a sharp rise in ACTH release which was log-dose dependent between 0·3 and 3 nmolCRF/1 on day 17 and between 0·3 and 30 nmolCRF/1 on days 19 and 21. The response to CRF increased with fetal age.
Quantities of arginine vasopressin (AVP) which gave concentrations of 2–200 nmol/l stimulated ACTH release at all stages of gestation investigated. However, the response to AVP was much lower than that to CRF.
Potentiation of CRF-induced ACTH release was not observed when whole pituitary glands from 21-day-old fetuses were incubated with AVP (20 nmol/l) + CRF (3 nmol/l).
Such results were correlated with the ontogenesis of immunoreactive vasopressin- and CRF-containing fibres in the median eminence of the rat fetus, as well as with the CRF-like immunoreactivity present in adult rat pituitary portal plasma and the AVP content of the fetal rat hypophysis.
J. Endocr. (1984) 101, 339–344
Further characterization of the second oestrogen-binding species of the rat granulosa cell
Authors: Kudolo G. B. , Elder M. G. , Myatt L. 
Published: December 2008

ABSTRACT
Rat granulosa cell cytosol contains a second oestrogen-binding species (SOB) distinguished from the classical oestrogen receptor by its lower dissociation constant (approx. 45 nmol/l) and the ability to bind oestrogens, antioestrogens, androgens and progesterone but not diethylstilboestrol. The SOB and the oestrogen receptor can be further distinguished by their differential adsorption to spheroidal hydroxylapatite and Concanavalin A–Sepharose. Addition of chaotropic salts or molybdate to granulosa cell cytosol did not alter the concentration of SOB or oestrogen receptor measured, indicating that there are no 'masked' binding sites in the two species caused by aggregation phenomena. The association rate of oestradiol with SOB at 4°C (1·72 ± 0·27(s.e.m.) × 108 mol/h) and 25°C (4·50 ± 0·36 × 108 mol/h) was faster than with the oestrogen receptor (7·20 ± 0·15 × 107 mol/h and 1·23 ± 0·15 × 108 mol/h respectively). The biphasic dissociation kinetics of [3H]oestradiol from the oestrogen receptor at 25°C (rate constants k−1 = 0·30±0·07/min and k−2 = 3·73±0·57 × 10−3/min) were similar to those reported in other target tissues but the dissociation of [3H]oestradiol from SOB appeared to be much more rapid and could not be measured by the Sephadex LH-20 separation method employed for determining receptor kinetics. Using sucrose density-gradient (SDG) analysis and Sephacryl S-200 gel chromatography the oestrogen receptor fractionated in an aggregated form (10·3S, Stokes radius >5·2 nm) in low ionic strength buffers and as a small species (4·4S, Stokes radius 3·5 nm) in buffers containing 0·4 m-KCl. However, the SOB fractionated as 2–3S, Stokes radius 3·7–4·0 nm at low ionic strength and as 5·8S, Stokes radius 3·5 nm in 0·4 m-KCl. In contrast to the receptor from other target tissues the granulosa cell oestrogen receptor did not bind to the artificial acceptor matrix oligo(dT)-cellulose and heat activation did not promote a 4S to 5S conversion when analysed on SDG. The salt-extracted form of nuclear receptor sedimented at 4·6S, mol. wt 69–72 000 on SDG.
J. Endocr. (1984) 102, 93–102
Activity of the genital tract and plasma levels of oxytocin and cortisol at the time of mating in the ewe
Authors: Garcia-Villar R. , Schams D. , Alvinerie M. , Laurentie M. P. , Toutain P. L. 
Published: December 2008

ABSTRACT
Experiments were conducted in the ewe to determine the effects of mating on the activity of the genital tract and on blood levels of oxytocin and cortisol. The activity of the uterus and cervix was recorded by electromyography, oxytocin was measured by radioimmunoassay, and cortisol by high performance liquid chromatography. Mating itself did not increase circulating oxytocin or cortisol; uterine motility remained unchanged during and after copulation but the cervix was significantly stimulated during teasing and after copulation. It is suggested that increased cervical activity resulting from adrenergic mechanisms may facilitate the generation of a cervical reserve of spermatozoa.
J. Endocr. (1985) 105, 323–329
Release of oxytocin during suckling and parturition in the rat
Authors: Higuchi T. , Honda K. , Fukuoka T. , Negoro H. , Wakabayashi K. 
Published: December 2008

ABSTRACT
A highly sensitive and specific radioimmunoassay (RIA) for oxytocin was developed and used to measure oxytocin concentrations during both suckling and parturition in individual rats. In urethane-anaesthetized rats, the suckling stimuli, provided by ten pups, induced intermittent increases in intramammary pressure of about 10 mmHg. This was associated with a significant (P < 0·01) increase in serum oxytocin levels from 19·5 ± 4·5 (s.e.m., n = 9) to 49·1 ± 7·4 pmol/l (n = 9) in the samples taken within 30 s from the time of the peak in the pressure. These rises in serum oxytocin returned rapidly to the basal levels as expected from the short half-life (1·46 min) of oxytocin in general circulation.
On day 22 or 23 of gestation, serum oxytocin levels remained stable until 0–0·5 h before the first fetus was expelled. They then increased significantly (P < 0·01) from 27·6± 4·6 pmol/l (n = 19) in samples taken 0–0·5 h before to 45·1 ± 5·6 pmol/l in samples taken after the expulsion of the first fetus and gradually increased until the last fetus was expelled. Serum oxytocin concentrations then declined but remained higher than those observed before the first fetus had been born until at least 1–1·5 h after the expulsion of the last fetus. Thus, this oxytocin RIA revealed increased concentrations of the hormone in blood during both suckling and parturition in the rat.
J. Endocr. (1985) 105, 339–346
Calcium-independent stimulation of glycogenolysis by arginine vasotocin and catecholamines in liver of the axolotl (Ambystoma mexicanum) in vitro
Authors: Janssens P. A. , Kleineke J. , Caine A. G. 
Published: December 2008

ABSTRACT
Arginine vasotocin (AVT) caused a concentrationdependent increase of glycogen phosphorylase a activity, breakdown of glycogen and release of glucose, when added to pieces of axolotl liver in organ culture. The concentration causing half-maximal response (EC50) was about 1 nmol/l. These actions of AVT were unaffected by the adrenergic antagonists propranolol, yohimbine and prazosin, but were blocked by equimolar amounts of d(CH2)5Tyr(Me)AVT, a synthetic antagonist of vasopressin. Arginine vasotocin similarly caused glycogenolysis in isolated perfused axolotl liver where the EC50 was about 0·1 nmol/l.
The glycogenolytic action of AVT (10 nmol/l) was sustained for at least 3 h in Ca2+ -free perfusion and longer in organ culture. No increase in Ca2+ concentration in the effluent perfusion medium was apparent during AVT-induced glucose release. Omission of Ca2+ from the medium, together with addition of EGTA (2·5 mmol/l) to the organ culture, had only a slight inhibitory effect upon the rate of glycogenolysis brought about by AVT and did not inhibit the glycogenolytic action of catecholamines.
Addition of the calcium ionophore A23187 (5 μmol/l) neither caused glucose release nor abolished the glycogenolytic action of AVT added subsequently. Nevertheless, A23187 caused increased loss of 45Ca from Ca2+-loaded liver pieces whereas AVT was without effect.
There was a slight accumulation of cyclic AMP (cAMP), but not cGMP, in axolotl liver pieces cultured in the presence of 0·1 μmol AVT/l and this was accentuated in the presence of phosphodiesterase inhibitors.
We conclude that, in contrast to the position in mammals, Ca2+ is not involved in the glycogenolytic actions of AVT or catecholamines in axolotl liver. Preliminary experiments suggest that the same is true in the carp and we suggest that the involvement of Ca2+ in regulation of hepatic glucose release may not have evolved until after the amphibians separated from the ancestors of the mammals.
J. Endocr. (1986) 109, 75–84
Single channel recordings of potassium currents in an insulin-secreting cell line
Authors: Sturgess N. C. , Ashford M. L. J. , Carrington C. A. , Hales C. N. 
Published: December 2008

ABSTRACT
Using the patch-clamp technique we observed three distinct classes of K+ channels which were spontaneously active in excised 'inside-out' membrane patches from an insulin-secreting rat pancreatic islet cell line (CRI-G1). Two of these occurred infrequently, one with a conductance of approximately 7 pS, and the other a conductance of 220 pS. The activation of the 220 pS K+ channel was dependent upon the membrane voltage and was sensitive to the concentration of calcium ions at the cytoplasmic surface of the membrane. The third, and by far the most common class of K+ channel, was characterized by its sensitivity to ATP. Application of ATP to the cytoplasmic side of the membrane reversibly inhibited this K+ channel in a dose-dependent manner, but had no effect when applied to the external side. The properties of the ATP-sensitive K+ channel appear to be indistinguishable from those of a channel found in rat neonatal β cells. Thus this insulin-secreting cell line should prove valuable in the investigation of the role of K+ channels in the regulation of insulin secretion.
J. Endocr. (1986) 109, 201–207
Autocrine tumour growth regulation by somatomedin C: an in-vitro model
Authors: Pavelić K. , Vrbanec D. , Marušić S. , Levanat S. , Čabrijan T. 
Published: December 2008

ABSTRACT
A human primary haemangiosarcoma was derived from a patient with severe hypoglycaemia. Cell line established from that tumour secreted somatomedin C in serum-free culture media. Immunoreactive somatomedin from the media eluted from Sephacryl S-200 in two peaks of 160 000 and 8000 molecular weights. Similar results were obtained when medium was acidified and chromatographed on Sephadex G-50. Binding of tracer concentrations of 125I-labelled somatomedin C to human haemangiosarcoma cells was much higher than that of 125I-labelled insulin. Half-maximal displacement of 125I-labelled somatomedin C binding occurred at an unlabelled somatomedin C concentration of 0·7 nmol/l. Insulin competed with 125I-labelled somatomedin for binding to this receptor, but 150-fold more insulin was required for half-maximal displacement. Somatomedin secreted by human haemangiosarcoma cells and purified from serum-free media strongly stimulated [methyl-3H]thymidine incorporation into the DNA of these cells. Inhibition of somatomedin C secretion by cortisol resulted in the inhibition of tumour cell proliferation but stimulation of somatomedin secretion by human GH stimulated the cell proliferation rate. It appears that production of somatomedin C in human haemangiosarcoma cells plays a part in the regulation of tumour growth by an autocrine mechanism.
J. Endocr. (1986) 109, 233–238
Reduced adrenal cortical sensitivity to ACTH in lambs with cut splanchnic nerves
Authors: Edwards A. V. , Jones C. T. , Bloom S. R. 
Published: December 2008

ABSTRACT
The possibility that the sensitivity of the adrenal cortex to endogenous ACTH may be affected by splanchnic nerve activity has been investigated in conscious, weaned, 5- to 8-month-old lambs. The animals were atropinized (0·5 mg/kg) and tested with an i.v. infusion of noradrenaline (333 ng/kg per min for 10 min), which produced a significant rise in the mean concentration of both ACTH and cortisol in the arterial plasma. In lambs tested at least 7 days after section of both splanchnic nerves, just below the diaphragm, the rise in plasma ACTH concentration was significantly greater, and that in plasma cortisol significantly less, than in control lambs. The mean plasma ACTH and cortisol concentrations were linearly related to one another in both groups (r = 0·93 and 0·92) but the sensitivity of the adrenal cortex to the steroidogenic action of ACTH appeared to have been roughly halved 1 week after bilateral splanchnic nerve section.
J. Endocr. (1986) 110, 81–85
LH and testosterone cause the development of seminiferous tubule contractile activity and the appearance of testicular oxytocin in hypogonadal mice
Authors: Nicholson H. D. , Worley R. T. S. , Charlton H. M. , Pickering B. T. 
Published: December 2008

ABSTRACT
Immunoreactive oxytocin is present in the testis and it has been shown that this hormone increases the contractility of seminiferous tubules. We have investigated the relationship between testicular oxytocin, tubular movements and the effects of LH and testosterone using, as a model, the hypogonadal (hpg/hpg) mouse, which is deficient in hypothalamic LH-releasing hormone (LHRH). Whilst both testicular oxytocin and seminiferous tubule movements, resembling those seen in the rat, can be found in normal adult mice, neither can be found in hypogonadal mice. After 2 weeks of treatment with LH (200 ng to 100 μg daily) low levels of testicular oxytocin and tubular movements were observed. Treatment with large doses of testosterone for 2–12 weeks led to higher concentrations of testicular oxytocin and tubular movements resembling those seen in the normal adult mouse. The results support the evidence that testicular oxytocin modulates seminiferous tubule movements. We suggest that testosterone may play a part in the accumulation of oxytocin in the testis.
J. Endocr. (1986) 110, 159–167
Reappearance of the thymus in old rats after orchidectomy: inhibition of regeneration by testosterone
Authors: Greenstein B. D. , Fitzpatrick F. T. A. , Adcock I. M. , Kendall M. D. , Wheeler M. J. 
Published: December 2008

ABSTRACT
The thymus is a critically important organ during development, but atrophies progressively during the ageing process after puberty and is often considered to be unimportant in adult life. We have found that the thymus, which is grossly atrophied in 12- to 15-month-old male rats, is markedly restored in size 30 days after orchidectomy. The organ then appears normal histologically, having a well-defined cortex and medulla, is vascularized and filled with thymocytes. The regeneration of the thymus after orchidectomy was inhibited in a dose–related fashion by testosterone implants which produced serum concentrations of testosterone within the physiological range. The thymus was also increased in size after orchidectomy of 10-week-old rats, and testosterone inhibited the enlargement of the thymus. These results have important implications for the possible enhancement of the immune system with associated improvement of health during ageing and disease. They also point to an important physiological link between the endocrine and immune systems.
J. Endocr. (1986) 110, 417–422