bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stimulation of the conversion of corticosterone to aldosterone by sodium and water depletion of potassium-deficient rats. Comparison of different experimental procedures
Authors: Haldy Philippe , Müller Jürg 
Published: December 2008

Abstract.
Sodium depletion, hypovolaemia or both were induced in potassium-depleted rats by various experimental protocols in order to study mechanisms involved in the regulation of late steps in aldosterone biosynthesis. The relative effects of such manoeuvres upon aldosterone biosynthesis and upon the plasma renin activity were compared. The conversion of corticosterone to aldosterone by incubated adrenal glands could be stimulated by a factor of 3 to 4 within 48 h by each of the following procedures: feeding on a sodium- and potassium-deficient diet or on sucrose, water restriction or treatment with furosemide. A 20-fold stimulation was elicited by experimental oedema due to subcutaneous polyethylene glycol solution or formalin. Intermediate responses were obtained by combining the sodium- and potassium-deficient diet with either water restriction or furosemide treatment as well as by the infusion of angiotensin II. Significant increases in the plasma renin activity, which were however not proportional to the stimulation of aldosterone biosynthesis, were seen in rats kept on the sodium- and potassium-deficient diet or treated by furosemide, polyethylene glycol or formalin, but not in rats kept on sucrose or deprived of water. An elevation in the plasma potassium concentration was observed only in the animals treated with water restriction. These results indicate that during potassium deficiency the stimulation of late steps in aldosterone biosynthesis by sodium and water depletion is mediated by the renin-angiotensin system and by an unknown mechanism which enhances the sensitivity of the zona glomerulosa to angiotensin II. Experimental oedema in potassium-deficient rats seems to be a useful model for further investigations of this mechanism.
Influence of gonadotrophins on cAMP formation in theca cells isolated from pre-ovulatory rat follicles
Authors: Nordenström Knut , Hamberger Lars 
Published: December 2008

Abstract.
Pre-ovulatory follicles were obtained from immature PMSG treated rats at various times on the day of pro-oestrus. From these follicles the theca capsules were mechanically isolated and subsequently incubated in the presence or absence of LH and/or FSH. The accumulation of cyclic adenosine 3'5'-monophosphate (cAMP) in tissue plus medium was determined. In certain experiments the rats were injected with LH, FSH or saline 2 h prior to sacrifice.
When the theca cells were isolated from rats sacrificed before the endogenous gonadotrophin surge, FSH added in vitro did not significantly stimulate cAMP formation, while LH had a small but significant stimulatory effect. When isolated 2–5 h after the endogenous gonadotrophin surge the theca cells responded with a marked increase in cAMP formation when exposed to LH in vitro, whereas FSH in vitro still had no stimulatory effect. Theca cells, isolated before the endogenous gonadotrophin surge, from rats pre-treated with a single ip injection of FSH 2 h prior to sacrifice, responded to a subsequent in vitro exposure to LH with a marked increase in cAMP levels.
The results indicate that the FSH component of the endogenous gonadotrophin surge increases the sensitivity of the theca cells to LH - i.e. in vivo exposure to FSH seems to be essential for the development of responsiveness of the cAMP system to LH in the theca cells from pre-ovulatory rat follicles.
Indirect evidence of chronic Leydig cell desensitization in Klinefelter's syndrome
Authors: Smals Anthony G. , Pieters Gerlach F. , Kloppenborg Peter W. 
Published: December 2008

Abstract.
The basal plasma 17α-hydroxyprogesterone (17-OHP) and testosterone (T) levels were proportionally decreased in 10 hypergonadotropic patients with Klinefelter's syndrome. The ratio 17-OHP to T was however about twice as high as in 10 eugonadal male controls, suggesting the presence of a block in the conversion of 17-hydroxylated steroids to androgens in the Klinefelter patients under basal circumstances. Administration of human chorionic gonadotrophin (hCG, 1500 IU im daily for 3 days) to the Klinefelter patients disclosed a response pattern quite different from that observed in controls. In the control subjects 17-OHP and the ratio 17-OHP/T sharply rose to maximum values at 24 h after the first injection. Thereafter both progressively fell to lowest values at 72 h, when T levels reached their maximum. In the Klinefelter patients the T response to hCG administration was greatly diminished but the 17-OHP response was similar to that in the controls. Maximum 17-OHP and 17-OHP/T values however were not achieved until 72 h after the first injection when T levels also reached their maximum. Unlike in the controls in the Klinefelter patients maximum 17-OHP and T increments and the 17-OHP and T levels 48 and 72 h after the injection were positively correlated.
Together the findings of a decreased T synthesis and reserve in the presence of relative 17-OHP accumulation, further increasing after acute hCG administration in a pattern quite different from that in normal men, suggest that in Klinefelter's syndrome the Leydig cells may be chronically desensitized by the persistent endogenous hypergonadotropism.
Effects of two histamine H2-receptor blocking drugs on basal levels of gonadotrophins, prolactin, testosterone and oestradiol-17β during treatment of duodenal ulcer in male patients
Authors: Peden N. R. , Boyd E. J. S. , Browning Margaret C. K. , Saunders J. H. B. , Wormsley K. G. 
Published: December 2008

Abstract.
In a study of 51 male patients with duodenal ulcer, treatment with cimetidine was accompanied by an increase in basal levels of serum testosterone. Treatment with ranitidine, a new histamine H2-receptor antagonist, produced no such effect. It is concluded that cimetidine has antiandrogenic activity in man which is separate from the histamine H2-receptor blocking activity.
Age-related changes in [125I]hLH specific binding to rat interstitial cells
Authors: Clausen O. P. F. , Purvis K. , Hansson V. 
Published: December 2008

Abstract.
Enriched Leydig cell suspensions were prepared from rats ranging from 5 to 80 days of age. The cells were incubated with [125I]hLH in vitro, and the proportion of LH binding cells determined by means of autoradiography. The proportion of 3β-hydroxy-steroid-dehydrogenase (3β-HSD) positive cells was also determined. By means of Scatchard analysis and determination of grain counts of LH positive cells, an increase in LH receptors per LH binding cells with increasing age was found. LH binding cells from animals 5 and 10 days of age had few LH receptors, more than a doubling occurred between day 10 and day 20, a significant increase was seen between day 20 and 40 whereas only a slight increase in LH receptors per LH binding cell was seen thereafter. Scatchard analysis and grain count analysis of labelled cells gave essentially the same results. The grain count distribution showed cells distributed around low grain values in animals of all ages, whereas a subpopulation of cells with high grain counts appeared in maturing and mature animals. Only a small fraction of LH positive cells had detectable levels of 3β-HSD activity in animals 5 and 10 days of age. With increasing age the proportion of 3β-HSD positive cells approached that of LH binding cells, indicating that rat interstitial cells aquire LH receptors well before any 3β-HSD activity can be traced.
Short- and long-term fluctuations in plasma prolactin concentration in normal subjects
Authors: Djursing Henning , Hagen Claus , Møller Jan , Christiansen Claus 
Published: December 2008

Abstract.
The physiological changes in plasma prolactin concentration were studied in 447 normal subjects, including 65 men, 75 pre-menopausal women and 307 post-menopausal women. The within-day and day-to-day variation as well as the circadian and circannual rhythm of plasma prolactin levels were determined. Furthermore, the relationship between changes in prolactin and oestradiol-17β levels during the normal menstrual cycle and in the climacteric was studied.
Pre-menopausal women had significantly (P<0.01) higher basal plasma prolactin concentration than men and post-menopausal women. Furthermore, they had significantly (P < 0.01) higher day-to-day variation than men. This suggests that prolactin in women is secreted in a pulsatile fashion. Only small seasonal variations in both sexes were seen.
The levels of plasma prolactin during the ovulatory and the luteal phase in the cycle were significantly (P < 0.02) higher than that of the follicular phase, and a positive correlation between changes in plasma concentration of oestradiol-17β and prolactin was found. Also in post-menopausal women a relationship between plasma concentration of prolactin and oestradiol-17β was seen.
It is concluded that the assessment of prolactin concentration in blood is dependent on the physiological variation recorded during sleep in both sexes. However, only in women day-to-day changes and the changes related to the menstrual cycle and the climacteric are of importance.
Existence of multiple molecular forms of luteinizing hormone in rat: differences in immunological and biological activities between stored and circulating forms
Authors: Reddy P. V. , Menon K. M. J. 
Published: December 2008

Abstract.
LH from rat anterior pituitary and serum was characterized with respect to its molecular size, and immunological and biological activity. Pituitary extracts prepared by homogenization followed by high speed centrifugation and chromatography on Ultrogel (AcA 44, 1.5 × 80 cm) columns showed two peaks of radioimmunoassayable lutropin (LH) activity, a major peak 1 and a minor peak 2. On the basis of their elution from Ultrogel columns, peak 1 had a larger molecular size (Kav = 0.44) than peak 2 (Kav = 0.53). The biological activities of the two peaks were assessed by testing the ability of the two peaks to stimulate cAMP production and progesterone synthesis using immature rat ovarian cells. Both cAMP production and progesterone synthesis by ovarian cells were stimulated by peak 1 and peak 2 in a dose dependent manner, but differed in the degree of stimulation. At optimal concentrations, stimulation of cAMP production by peak 2 was 1.45-fold higher than peak 1. Similarly, stimulation of progesterone production by peak 2 was 2-fold higher than that produced by peak 1. The molecular size of the LH released from anterior hemipituitaries in response to a gonadoliberin (LRH) agonist, [Des-gly-NH210]LRH ethylaminde, was also determined. Chromatography of control medium as well as the agonist treated medium on the Ultrogel columns showed a single peak of LH activity at a position which corresponded to peak 1 found in the pituitary extract. However, the elution profile of serum LH from animals injected with LRH agonist was found to be similar to that of peak 2 of the pituitary extract. Incubation of the pituitary extract with serum resulted in a shift in the position of elution of peak 1 towards peak 2. From these studies it is concluded that the anterior pituitary contains a major high mol wt form of LH with lower biological activity and a minor low mol wt form with higher biological activity, but only the low mol wt form appears in the circulation.
Oestrogen-like effects of tamoxifen on the concentration of proteins in plasma
Authors: Fex Göran , Adielsson Göran , Mattson Willy 
Published: December 2008

Abstract.
The concentrations of 11 plasma proteins were determined by electroimmunoassay in 6 female and one male patient before and after treatment for 1–4 months with tamoxifen (30 mg/day) for advanced cancer. The concentrations of transcortin, sex hormone binding globulin, pregnancy zone protein, apolipoprotein AI and thyroxine binding globulin increased significantly. The concentrations of orosomucoid and haptoglobin decreased significantly. The concentrations of albumin, transferrin, prealbumin and retinol-binding protein showed no significant change. The changes after treatment with tamoxifen were thus similar to those which occur after the administration of oestrogens or during pregnancy although they were quantitatively less pronounced. There were also differences in the pattern of change between treatment with tamoxifen and during pregnancy. There was no apparent relationship between response to treatment and changes in concentration of plasma proteins.
A model for studies on the response of the ventral prostate to oestrogens
Authors: Corrales J. J. , Høisaeter P. A. , Kadohama N. , Murphy G. P. , Sandberg A. A. 
Published: December 2008

Abstract.
The effects of oestrogen administration on the weight of ventral and dorsolateral prostates were studied in castrated rats of Wistar-Furth and Copenhagen strains. Direct effect of oestradiol (Oe2) on prostatic tissue was also investigated in organ culture. Oe2-treated animals received daily injections of 50 μg for 7 days. Control animals were treated with the vehicle only (peanut oil). In 4 month old Copenhagen rats the mean weight of the ventral prostates (42.4 ± 9.4 mg/100 g body weight) was significantly higher than that in the control animals (19.9 ± 4.6 mg/100 g body weight, P < 0.0001). No such differences were observed in older Copenhagen rats (9 months old) or Wistar-Furth rats (3 and 6 months old). Thus, this effect of Oe2 on ventral prostate seems both strain specific and age specific. Similar strain and age differences in the Oe2 effect were found in the dorsolateral prostate, but to a smaller extent. Direct interaction of Oe2 with target tissue was demonstrated in culture as evidenced by the ability of the steroid to prevent regression in explants derived from prostates of Copenhagen rats.
The in vivo effects of Oe2 on the prostate weights could not be explained by differences in specific androgen or oestrogen receptor contents or in testosterone (T) metabolism. However, the prostates of younger Copenhagen rats differed from those of all other groups in three respects: 1) they contained high levels of oestramustine binding protein (OeBP), 2) they had the highest amount of uptake of radioactivity into the nuclear residue, and 3) their histological picture was characterized by diffuse stromal architecture having the appearance of oedematous tissue.
Effects of water deprivation on immunoreactive angiotensin II levels in plasma, cerebroventricular perfusate and hypothalamus of the rat
Authors: Yamaguchi K. 
Published: December 2008

Abstract.
To examine whether endogenous angiotensin — which has been suggested to produce increased vasopressin (ADH) release and water intake under dehydration, by stimulating the central nervous system — is derived from the brain or from the circulating blood or from both, the effects of water deprivation for 46 h on immunoreactive angiotensin II (AII) concentrations of plasma, cerebroventricular perfusate and the hypothalamus were studied in conscious and urethane-anaesthetized rats. Immunoreactive AII in plasma and the hypothalamus was extracted with acetone and petroleum ether preceding the determination by radioimmunoassay. The water deprivation significantly increased plasma immunoreactive AII concentration (P < 0.002) together with plasma osmolality and sodium concentration, and reduced the potassium concentration. However, neither the immunoreactive AII concentration of the ventricular perfusate nor that of the hypothalamus was affected. Both the perfusate and the hypothalamus were very poor in immunoreactive AII (< 35.0 pg/ml and < 46.7 pg/g wet tissue, respectively). These results may suggest that increased ADH release and water intake under dehydration are brought about by the angiotensin formed in the circulating blood rather than in the brain.
Further evidence of the dual role of noradrenaline in regulation of thyrotrophin secretion in male rats
Authors: Männistö P. T. , Mattila J. , Tuomisto J. 
Published: December 2008

Abstract.
The dual role previously suggested for noradrenergic neurons in TRH-TSH regulation was studied in male rats. α-Methyl-p-tyrosine (αMPT) significantly decreased brain noradrenaline (NA) and dopamine (DA) levels 0.5–6 h after the injection. Maximum inhibition of TSH cold-response occurred at 4 h. One h after administration of l-dopa the brain DA (but not NA) level was considerably elevated. TSH cold-response was not significantly changed. The effects of αMPT and Ca-fusarate on the cold-induced TSH secretion were antagonized by neither dihydroxyphenylserine (DOPS; this drug restores NA stores) nor by l-dopa (which restores DA levels). DOPS even potentiated the depressive effect of αMPT and Ca-fusarate. When given into the third ventricle, NA did not modify basal TSH levels but decreased the cold-induced TSH secretion. When infused directly into the median eminence of the medial basal hypothalamus, NA reduced both basal and cold-induced TSH secretion. Pinealectomy decreased the TSH cold-response but NA seemed to retain its ability to inhibit TSH secretion. These results demonstrate that besides the possible stimulatory action on TSH secretion, noradrenergic neurons also have an inhibitory effect outside the blood-brain barrier, possibly in the median eminence.
Stimulation by serum of aldosterone production from rat adrenal glomerulosa cells in vitro: relationships to K+, serotonin and angiotensin II
Authors: Mendelsohn F. A. O. , Kachel Christine D. 
Published: December 2008

Abstract.
Normal human serum markedly stimulated aldosterone production from rat adrenal glomerulosa cells incubated in Krebs Ringer bicarbonate medium (KRBGA). The effect was dose-related. In [K+] 3.6 mm KRBGA medium, serum stimulated aldosterone output to higher levels than those produced by maximal doses of serotonin (5 HT), angiotensin II (AII) or high [K+] (8.4 mm).
Cells maximally stimulated by high [K+], 5 HT or AII in KRBGA medium were further stimulated by serum. The angiotensin analogue, [Sar1, Ala8]-AII abolished the effect of AII but not that of high [K+] or serum.
Basal and ACTH-stimulated corticosterone outputs of rat fasciculata cells were not significantly affected by sera known to stimulate glomerulosa cells.
Aldosterone stimulating activity of serum was dialysable and fully recovered in a serum ultrafiltrate.
The serotonin blockers methysergide and metergoline abolished the aldosterone stimulating activity of serum but also depressed basal aldosterone output and methysergide reduced K+-stimulated output.
Chymotrypsin digestion abolished the aldosterone stimulating activity of AII but not that of serotonin or serum.
5 HT concentration of sera was measured and found to be near the threshold for aldosterone stimulation.
Sodium loading and depletion of 4 normal subjects did not consistently modify the aldosterone stimulating activity of their sera.
In a supplemented medium (RPMI 1640), basal and K+-stimulated aldosterone outputs were higher than in KRBGA medium. Under these conditions serum stimulated aldosterone output in normal [K+] medium but only marginally in high [K+] medium. In RPMI medium, serum did not further stimulate cells maximally stimulated with serotonin.
Serum appears to stimulate aldosterone production from glomerulsoa cells by two different mechanisms: One is probably due to a serotonin-like substance. A separate effect of serum, seen only in KRBGA medium, is to enhance aldosterone output of glomerulosa cells maximally stimulated by K+, 5 HT or AII.
Effects of 22S-hydroxy-cholesterol and other hydroxylated sterols on the ACTH-stimulated steroid production in rat adrenal cells
Authors: Huijmans J. G. M. , Degenhart H. J. , Kortleve D. J. , Visser H. K. A. 
Published: December 2008

Abstract.
Several effects of hydroxylated sterols on cell cultures are known. Most of these can be explained by an inhibition of the cholesterol synthesis at the level of the 3-hydroxy-3-methylglutaryl CoA reductase.
When studying cholesterol metabolism in rat adrenal cells, an inhibitory action of some sterols on the ACTH-stimulated corticosterone production was observed. The effects of one sterol, 22S-OH-cholesterol, were investigated further.
The sterol had no effect on the ACTH-stimulated cyclic AMP production, suggesting an intact receptor-adenylate cyclase complex and cellular membrane. In the presence of ACTH and 22S-OH-cholesterol particularly the free cholesterol concentration was elevated; 22S-OH-cholesterol therefore probably exerts its inhibitory effect at a step located after hydrolysis of the cholesterol esters. 22S-OH-cholesterol had no effect on the conversion of exogenous pregnenolone into corticosterone.
These results make it probable, that the inhibitory effect of 22S-OH-cholesterol on the ACTH-stimulated corticosterone production is situated at the level of the cholesterol side-chain cleavage.
Delayed stimulatory effect of cyclic AMP on bone resorption in vitro
Authors: Lerner Ulf , Gustafson Gunnar T. 
Published: December 2008

Abstract.
The effect of dibutyryl cyclic AMP (dbcAMP) and the phosphodiesterase inhibitors 3-isobutyl methylxanthine (IBMX) and theophylline on bone resorption was studied in an organ culture system for 96– 144 h using half calvaria from 6–7 day old mice. The magnitude of resorption was assessed by measuring the release from the bones of previously incorporated 45Ca. It was observed that dbcAMP, IBMX and theophylline, following a lag period or a period of reduced bone resorption, all progressively increased mineral mobilization. Although the continuous presence of dbcAMP increased mineral mobilization more than a temporary exposure, a limited treatment of 24 h with the nucleotide was sufficient to bring about the delayed stimulatory response. It is concluded that the observations support our earlier proposal that cAMP is not a mediator of the early stages of parathyroid hormone (PTH)- and prostaglandin E2 (PGE2)-stimulated bone resorption. We suggest that the role played by cAMP may be related to the capacity of PTH and PGE2 to develop new osteoclasts, a phenomenon which takes more than 24 h to be observed.
Dopaminergic and adrenergic effects on plasma LH levels in rats with hypothalamic islands
Authors: van Dieten J. A. M.J. , van Valkenburg C. F. M. , de Koning J. , van Rees G. P. 
Published: December 2008

Abstract.
In female rats hypothalamic islands were prepared by making a cut around the mediobasal hypothalamus. Three weeks later the rats were ovariectomized. Two weeks after ovariectomy, part of the animals showed elevated blood LH levels with oscillations, although the mean LH levels were significantly lower than in sham-operated ovariectomized animals. There was a significant correlation between the occurrence of elevated blood LH levels after ovariectomy and the inclusion of at least part of the suprachiasmatic nucleus within the islands. Noradrenaline content of the hypothalamus was decreased significantly, but there was no significant change in hypothalamic dopamine content. Injection of doses of apomorphine, ranging from 2.5 μg/kg to 25 mg/kg sc into island-bearing and sham-operated animals caused a dose-dependent decrease of plasma LH. However, the magnitude of the decrease was smaller in rats with hypothalamic islands than in controls. Even the highest doses of apomorphine did not decrease plasma LH further than to about 100 ng of LH-RP-1/ml. Phenoxybenzamine (10 and 40 mg/kg ip) and phentolamine (20 mg/kg ip) caused a decrease of plasma LH in ovariectomized control rats, but in ovariectomized rats with hypothalamic islands these drugs caused an increase. Clonidine (100 μg/kg sc followed by 100 μg/kg ip) had no effect in ovariectomized control rats, but in ovariectomized rats with a hypothalamic island an increase was induced. These results may have been caused by an increased sensitivity of hypothalamic α-receptors resulting from severing afferent noradrenergic fibres.