bluuebunny/crossref_metadata_2025_split huggingface dataset:
INHIBITION BY DEXAMETHASONE OF ADRENOCORTICOTROPHIN AND CORTISOL RELEASE INDUCED BY INTRAVENOUS INFUSION OF ATP AND DIBUTYRYL CYCLIC AMP IN PIGLETS
Authors: COOK D. B. , GILL G. V. , JACKSON I. M. D. , SMART G. A. 
Published: December 2008

SUMMARY
The effect of intravenous infusions of ATP and dibutyryl cyclic AMP (DB cyclic AMP) on adrenocorticotrophin (ACTH) and corticosteroid release was investigated in piglets.
A consistent increase of both plasma ACTH and plasma cortisol was observed in response to infusions of 600 mg ATP/h. These responses were abolished by pretreating the animals with dexamethasone. A similar pattern of response was observed with DB cyclic AMP infused intravenously. No response occurred when 100 mg DB cyclic AMP were infused in 1 h, but there was a marked plasma corticosteroid response to an infusion of 600 mg DB cyclic AMP in 1 h. Surprisingly, this response was also abolished by pretreatment with dexamethasone.
SEASONAL VARIATIONS IN BLOOD LUTEINIZING HORMONE AND TESTOSTERONE LEVELS IN RAMS
Authors: KATONGOLE C. B. , NAFTOLIN F. , SHORT R. V. 
Published: December 2008

SUMMARY
Three adult Suffolk rams were bled at weekly intervals for 14 months, and at hourly intervals for 24 h during the summer (one ram) and autumn (two rams). Luteinizing hormone (LH) was measured by radioimmunoassay, and testosterone by a competitive protein binding assay.
There were episodic bursts of LH secretion during the 24 h period in both the summer and the autumn; the frequency of discharge was lower in the summer, but the amplitude (0·1–8·0 ng/ml) did not appear to change. It was not always possible to detect seasonal changes in LH concentration in single blood samples taken once a week throughout the year.
The blood testosterone levels also showed marked fluctuations throughout the 24 h, and the frequency of the peaks was lower in the summer. But in contrast to LH, the magnitude of the testosterone peaks also changed throughout the year; from January to September the testosterone concentration ranged from 0·5 to 10 ng/ml plasma, whereas from October to December it ranged from 3 to 28 ng/ml. Thus in temperate regions the ram, like the ewe, shows seasonal changes in gonadal endocrine activity, although some degree of spermatogenesis continues throughout the whole year.
STEROIDS OF ADRENAL ORIGIN METABOLIZED BY HUMAN PROSTATIC TISSUE BOTH IN VIVO AND IN VITRO
Authors: HARPER M. E. , PIKE A. , PEELING W. B. , GRIFFITHS K. 
Published: December 2008

SUMMARY
The pattern of metabolites present in human benign prostatic tissue after infusion of either [7α-3H]testosterone, [7α-3H]androstenedione or [7α-3H]dehydroepiandrosterone (DHA) sulphate 30 min before prostatectomy were investigated. Infusion of [7α-3H]testosterone yielded 5α-dihydrotestosterone (17β-hydroxy-5α-androstan-3-one) as the major metabolite present in the prostatic tissue together with other 5α-androstane compounds. The major radioactively labelled steroids identified in the prostatic tissue after [7α-3H]androstenedione infusion were epiandrosterone and androsterone, and dehydroepiandrosterone after [7α-3H]DHA sulphate infusion, although various other 5α-androstane compounds were also present after both infusions. The proportion and identity of radioactive steroids present in the epithelial and stromal portions of the tissue after in-vivo infusion of [7α-3H]testosterone was investigated. Also the ability of separated epithelial and stromal elements of prostatic tissue to metabolize steriods in vitro was studied. Dehydroepiandrosterone sulphate and DHA metabolism in vitro by minced human prostatic tissue yielded various 5α-androstane compounds in addition to DHA and androstenediol (androst-5-ene-3β,17β-diol).
BLASTOCYST-ENDOMETRIAL CONTACT AND PONTAMINE BLUE REACTION DURING NORMAL IMPLANTATION IN THE RAT
Authors: LJUNGKVIST I. , NILSSON O. 
Published: December 2008

SUMMARY
Pregnant rats were injected with pontamine blue on the afternoon of day 5 of normal pregnancy to study, by electron microscopy, blastocyst-epithelial contact at implantation sites negative and positive to the dye. Implantation sites negative to the dye contained merely zona-encased blastocysts. Positive sites contained zona-free blastocysts or blastocysts only partly covered by a zona. Remnants of the zona were often observed. At positive sites intimate cell-membrane contacts between blastocyst and uterine epithelium were always noted. The results obtained suggest zona disappearance by uterine lysis and do not contradict the concept that blastocyst—epithelial contact is involved in decidua induction during normal pregnancy.
EFFECTS OF OESTROGEN ANTAGONISTS ON MITOSIS AND [3H]OESTRADIOL BINDING IN THE MOUSE UTERUS
Authors: LEE AUDREY E. 
Published: December 2008

SUMMARY
Progesterone and megestrol acetate reduced oestrone-stimulated epithelial mitosis in the mouse uterus and increased it in the stroma. Neither progestin reduced the uptake of [3H]oestradiol by the uterus in vivo. Compounds ICI 46,474 and U11,100A were mitogenic in both luminal epithelium and stroma but did not antagonize the epithelial response to oestrone. U11,100A reduced the uptake of [3H]oestradiol by the uterus in a way similar to that shown by unlabelled oestradiol, but there was no evidence that ICI 46,474 competed for oestrogen receptors.
EXTRAHEPATIC AND EXTRARENAL RENIN INACTIVATION IN THE DOG
Authors: FAGARD R. , FOSSION E. , CAMPFORTS M. , AMERY A. 
Published: December 2008

SUMMARY
It was demonstrated previously that renin disappears quickly from the circulation after nephrectomy in the hepatectomized dog. In the present study the plasma renin concentration (PRC) was measured in the efferent and afferent blood vessels of several vascular beds (pulmonary circulation, splanchnic region, spleen, both inferior limbs and pelvis, head) in the anhepatic and in the anhepatic and anephric dog in order to investigate extrarenal and extrahepatic renin inactivation. However, no significant arteriovenous differences in PRC could be traced. The blood of these dogs kept in vitro at 37 °C in a glass container showed no decline in PRC within 3 h of removal.
Therefore no specific extrahepatic and extrarenal renin-inactivating mechanism was found which could explain the rapid disappearance of renin from the blood in vivo in the anhepatic and anephric dog.
EVIDENCE FOR DUAL CORTICOSTEROID-RECEPTOR MECHANISMS IN THE FEEDBACK CONTROL OF ADRENOCORTICOTROPHIN SECRETION
Authors: JONES M. T. , TIPTAFT ELIZABETH M. , BRUSH F. R. , FERGUSSON D. A. N. , NEAME R. L. B. 
Published: December 2008

SUMMARY
The influence of several corticosteroids on stress-induced secretion of adrenocorticotrophin was studied. Two periods of inhibition were demonstrated. Fast feedback occurred within minutes with small doses of corticosterone, and was of short duration which was further curtailed as the dose of corticosterone was raised. Delayed feedback occurred after 1 h or later, required larger doses and the duration of inhibition was increased with increased dosage. Corticosterone and cortisol were agonists on both fast and delayed feedback. However, 11-deoxycorticosterone and 11-deoxycortisol were antagonists on fast feedback but agonists on delayed feedback. It is concluded that the two feedback mechanisms have different dynamics and separate receptors.
INHIBITORY EFFECT OF SEROTONIN ON OVULATION IN ADULT RATS
Authors: WILSON CATHERINE A. , McDONALD P. G. 
Published: December 2008

SUMMARY
Serotonin (5HT, 100 mg/kg) given subcutaneously between 16.00 and 18.00 h on the day of pro-oestrus, at 17.00 h on day 2 of dioestrus and at 13.00 and 17.00 h on day 1 of dioestrus, inhibited ovulation in adult rats. It was ineffective at 13.00 h on the day of pro-oestrus and on day 2 of dioestrus. The anti-ovulatory effect at 17.00 h during pro-oestrus was reversed by pretreatment with 2–4 mg progesterone or 2·5 mg dipyridamole/kg. The effect at 17.00 h on day 2 of dioestrus was reversed by 2 μg oestradiol benzoate. Subcutaneous injection of 5HT antagonized the ovulatory action of exogenous luteinizing hormone and inhibited the passage of 22Na into ovary, uterus and muscle but not the pituitary. Intraventricular administration of 5HT (200 μg/rat) between 13.00 and 18.00 h during pro-oestrus had no effect on ovulation. These results suggest that subcutaneous administration of 5HT does not inhibit ovulation at a central site, but acts as a peripheral vasoconstrictor preventing the passage of hormones to their target organs.
STIMULATION OF DNA SYNTHESIS IN RAT LIVER BY ADRENALECTOMY
Authors: DESSER-WIEST LUCIA 
Published: December 2008

SUMMARY
The following effects were observed in the liver of male rats in the first few days after adrenalectomy: the rate of thymidine incorporation into DNA was increased three- to fourfold in the 2 days after adrenalectomy. The mitotic index was increased 5·5-fold on the first day and 15-fold on the second day after the operation. The number of tetraploid cells rose from 40 to 68%. While the subsequent administration of cortisol, cortisone or corticosterone to the adrenalectomized animals reduced DNA synthesis to the normal level, testosterone and oestrone were without effect. It is suggested that liver growth is regulated by the concentration of corticosteroids in the blood.
EFFECT OF MELATONIN AND SHORT PHOTOPERIOD ON Δ4-REDUCTASE ACTIVITY IN LIVER AND HYPOTHALAMUS OF THE HAMSTER AND THE RAT
Authors: FREHN J. L. , URRY R. L. , ELLIS L. C. 
Published: December 2008

SUMMARY
Adult, male hamsters exposed to a photoperiod of 1 h light: 23 h darkness for either 2, 3, 4, 6, 8, or 10 weeks exhibited significantly lower testicular weights than did controls after 3 and 4 weeks of exposure to 14 h light: 10 h darkness. Liver Δ4-reductase activity was significantly decreased by 4 weeks of exposure to the short photoperiod. Exogenous melatonin decreased Δ4-reductase activity when incubated with either hamster liver (at 10−7 and 10−5 mol melatonin/l) or hamster hypothalamus (at 10−6 mol melatonin/l). In contrast, exogenous melatonin stimulated Δ4-reductase activity in preparations of rat liver (at 10−7 and 10−6 mol/l) and rat hypothalamus (at 10−9, 10−8, 10−7, and 10−6 mol/l). The possible role of melatonin in influencing the testosterone: dihydrotestosterone ratio is discussed in relation to possible regulation of gonadotrophin release.
EFFECT OF MAGNESIUM STATUS ON THYROID ACTIVITY AND IODIDE METABOLISM
Authors: HEATON F. W. , HUMPHRAY H. P. 
Published: December 2008

SUMMARY
The close positive correlation between the magnesium concentration in serum and the activity of the thyroid gland, as indicated by the ratio of (protein-bound 125I): (total serum 125I) 24 h after injection of a tracer dose of [125I]iodide, was investigated in young male rats. Dietary deficiency or loading with magnesium salts had no effect on the concentration of cyclic AMP within the thyroid gland or the release of thyroid hormone from glands incubated in vitro.
Accumulation of radioactive iodide by thyroid glands in vivo was stimulated by magnesium loading and inhibited by magnesium deficiency, but there was no selective effect on the synthesis of iodinated tyrosines or thyronines within the gland. As similar differences in radioactive iodide uptake were observed in other soft tissues, this appears to be part of a general influence of magnesium status on iodide transport, rather than a specific action on the thyroid gland.
TEMPORAL VARIATIONS OF TESTOSTERONE LEVELS IN THE PERIPHERAL BLOOD PLASMA OF MEN
Authors: ROWE P. H. , LINCOLN G. A. , RACEY P. A. , LEHANE J. , STEPHENSON M. J. , SHENTON J. C. , GLOVER T. D. 
Published: December 2008

SUMMARY
Testosterone was measured in the peripheral blood plasma of normal men by radioimmunoassay. The results were analysed to test for the possible existence of a circadian rhythm, for fluctuations superimposed on any such rhythm, and for day-to-day variations. Unequivocal evidence of a circadian rhythm was found in all but one of the subjects studied and the cycle appeared to be accompanied by a series of fluctuations of lower amplitude lasting for 1–2 h. Samples taken from the same subjects on consecutive days showed marked variation between days, but no regular cyclic pattern. The possible existence of such a cycle is not, however, eliminated. On the basis of all the data obtained a regime is suggested for the collection of blood samples from individuals whose androgenic status is to be assessed.
CALCITONIN AND INTESTINAL CALCIUM ABSORPTION
Authors: SWAMINATHAN R. , KER J. , CARE A. D. 
Published: December 2008

SUMMARY
The effect of calcitonin (CT) on small intestinal calcium absorption was studied using Thiry—Vella loops in one intact sheep, one intact pig and three parathyroidectomized pigs. Net calcium absorption rate was measured after recirculating through the loop a known volume of a solution containing calcium and polyethylene glycol 4000. Calcitonin was infused intravenously and its effect on the net calcium absorption rate was measured. When relatively high doses of CT (10 mu./min/kg) were infused for up to 45 h, there was an initial rise in net calcium absorption associated with hypocalcaemia, followed by a marked reduction in calcium absorption. When small doses of CT (0·5 mu./min/kg) were infused for 100 h, the increase in the net absorption rate was not observed or was less marked, but there was a significant reduction in net calcium absorption 2 days after the CT infusion was stopped. A reduction in net calcium absorption rate was seen both in intact and parathyroidectomized animals. In one experiment in which the true absorption rate of calcium from lumen to blood was measured using 47Ca, a reduction in unidirectional transfer of calcium from lumen to blood was seen 2 days after the CT infusion was stopped. The possible mechanism of this action of CT and its significance in calcium homeostasis during the ingestion of a high calcium diet is discussed.
EFFECTS OF 17β-HYDROXY-4-ANDROSTEN-19-OL-3-ONE (19-HYDROXYTESTOSTERONE) AND 5α-ANDROSTAN-17β-OL-3-ONE (DIHYDROTESTOSTERONE) ON ASPECTS OF SEXUAL BEHAVIOUR IN CASTRATED MALE RATS
Authors: PARROTT R. F. 
Published: December 2008

SUMMARY
The ability of 19-hydroxytestosterone propionate (150 μg/day) to maintain sexual behaviour, accessory organ weights and the number of penile spines in experienced adult male rats in the 5 weeks after castration was compared with intact males and castrated animals receiving testosterone propionate (75 μg/day) or oil treatment. In a second experiment a group of male rats receiving dihydrotestosterone propionate (150 μg/day) was also included. 19-Hydroxytestosterone did not maintain ejaculatory performance but animals that ejaculated had refractory periods similar to those in intact and testosterone-treated groups. Dihydrotestosterone, however, slowed the rate of decline of ejaculatory performance but the refractory periods were comparable to those in castrated controls. The former action of dihydrotestosterone was attributed to its stimulatory effect on peripheral structures, especially the penile spines. 19-Hydroxytestosterone was shown to have no peripheral effect at doses up to 1800 μg every other day. The results are discussed in terms of a theory of testosterone action involving aromatization in the brain and 5α-reduction peripherally.
POSSIBLE INVOLVEMENT OF CYCLIC AMP IN REGULATION OF MASCULINE SEXUAL BEHAVIOUR BY TESTOSTERONE
Authors: CHRISTENSEN L. W. , CLEMENS L. G. 
Published: December 2008

SUMMARY
Experiments were carried out to assess the possible involvement of cyclic AMP in the regulation of masculine sexual behaviour by testosterone in the laboratory rat. Doses of testosterone propionate which were ineffective in maintaining or inducing male sexual behaviour were potentiated by concurrent administration of theophylline. Since removal of the adrenal glands had no effect on this potentiation, the possibility that theophylline increased adrenal androgen secretion and thereby influenced sexual behaviour, can be ruled out. A major effect of theophylline is to increase levels of cyclic AMP by inhibiting the enzyme which inactivates this nucleotide. These results suggest that cyclic AMP may play a mediating role in the regulation of masculine sexual behaviour by testosterone.
PLASMA TESTOSTERONE CONCENTRATIONS IN THE RAM
Authors: PURVIS K. , ILLIUS A. W. , HAYNES N. B. 
Published: December 2008

SUMMARY
Testosterone levels in plasma obtained from the jugular vein of rams were measured using a radioimmunoassay. The assay antiserum had a specificity for testosterone such that chromatography was not used during determinations. Blood was taken every ½-1 h under conditions approximating to the natural environment at the particular time of year. Measurements during a 48 h period in January demonstrated that marked episodic bursts of testosterone occurred. Two rams showed eight peaks of testosterone in 24 h with levels reaching 12–14 ng/ml. Two other animals showed four peaks in 24 h, the levels reaching 8 ng/ml. The pattern for all animals was similar in the second 24 h period. In one animal, a testosterone profile obtained over 24 h in the previous November corresponded to that obtained in January although the animal had been serving ewes in the interim period and suggests tentatively that a particular pattern may be inherent in an individual animal.
The rams were maintained in the absence of females until early March and sampled again for 7 h during which time they were allowed contact with an ovariectomized ewe induced into oestrus. The libido of the rams appeared normal. Testosterone levels were low throughout, exceeding 5 ng/ml on one occasion only, and were not affected by copulation. A testosterone profile obtained for two of the rams over a 24 h period in late March demonstrated that the levels were still low. A further testosterone profile was obtained for one of these rams in June. Levels were high and the pattern had reverted to that found the previous November and January.
To obtain evidence that the low levels of testosterone found in March were a result of season rather than lack of regular copulation at this time, blood was obtained from four rams maintained at the Meat and Livestock Commission A.I. Centre, Selby. Two of these animals had not been used for semen collection since January and two were in regular use with a teaser female and semen was collected twice weekly. Maximum testosterone levels of 5 ng/ml were obtained over 12 h in both groups.
During this work, in periods when the testosterone levels were high, there were disruptions in apparently periodic fluctuations in testosterone levels which could be correlated with the proximity of other animals.
THE EXTRACTION OF OESTROGENS, AND THE RATE OF SECRETION OF OESTRONE AND OESTRADIOL-17β BY THE UTERUS IN THE PREGNANT SHEEP
Authors: CHALLIS J. R. G. , HARRISON F. A. , HEAP R. B. 
Published: December 2008

SUMMARY
The sharp increase in oestrone and oestradiol-17β production during the 48 h before parturition in the ewe does not always result in the uterine venous concentration of these steroids being greater than that found in peripheral blood, even though the gravid uterus is considered to be the major source of enhanced oestrogen synthesis in late pregnancy. This anomaly has been partly resolved by the results from tracer kinetic studies. During the infusion of labelled oestradiol-17β or oestrone into a jugular vein to steady state, 53% of [3H]oestradiol-17β and 62% of [3H]oestrone in the peripheral circulation were extracted by a gravid uterine horn. The extraction of [3H]oestradiol-17α, a product of the infused steroids, was 53% and 45% during the infusion of [3H]oestrone and [3H]oestradiol-17β, respectively.
Calculations of the secretion rate of these steroids by one gravid horn, after correcting for uterine extraction, gave values that represented a substantial proportion of the kinetically determined production rate. This confirms that an appreciable part of the oestrogen produced just before term is in fact derived from the gravid uterus. However, the possibility that other sources may contribute to oestrogen synthesis in late pregnancy cannot be excluded. The findings show that a direct measurement of arteriovenous difference and uterine blood flow is inadequate to determine oestrogen secretion rates by the gravid uterus.
VAGINAL MUCIFICATION IN THE OVARIECTOMIZED RAT IN RESPONSE TO 5α-PREGNANE-3,20-DIONE, TESTOSTERONE AND 5α-ANDROSTAN-17β-OL-3-ONE: TEST FOR PROGESTOGENIC ACTIVITY
Authors: KENNEDY T. G. 
Published: December 2008

SUMMARY
In an attempt to examine the hypothesis that progesterone, like testosterone, is active through its 5α-reduced metabolite, the ability of 5α-pregnane-3,20-dione (5α-P), testosterone and 5α-androstan-17β-ol-3-one (5α-DHT) to induce vaginal mucification when given subcutaneously for 7 days to oestrogen-pretreated ovariectomized rats was examined. Vaginal mucification was quantified by measuring vaginal sialic acid concentration. When given at the rate of 4 mg/day in either sesame oil or propylene glycol, with or without oestradiol-17β (E2), 5α-P was ineffective in increasing vaginal sialic acid concentration. When given at the rate of 8 mg/day suspended in 16% aqueous gelatin, 5α-P in the absence, but not in the presence of E2, brought about a small increase in vaginal sialic acid concentration. In contrast, testosterone and 5α-DHT, either with or without E2, markedly increased vaginal sialic acid concentration. In terms of its effects on vaginal sialic acid content and concentration, 5α-DHT was estimated to be approximately 45% as potent as testosterone. The difference in the abilities of 5α-P and 5α-DHT to mimic the action on the vagina of progesterone and testosterone, respectively, is discussed.
CORTICOTROPHIN-LIKE PEPTIDES IN THE RAT PITUITARY
Authors: SCOTT A. P. , LOWRY P. J. , RATCLIFFE J. G. , REES LESLEY H. , LANDON J. 
Published: December 2008

SUMMARY
The pars intermedia of the rat pituitary contains a peptide resembling the 18–39 portion of adrenocorticotrophic hormone (ACTH), which has been termed 'corticotrophin-like intermediate lobe peptide' (CLIP). It can be detected by its cross-reaction with an antiserum directed against the CO2H-terminal portion of the ACTH molecule; it has an amino acid composition identical to the 18–39 portion of human ACTH, except for one less glycine and an extra valine residue, and it is rapidly released from neurointermediate lobes maintained in organ culture. The pars intermedia also contains a peptide with an amino acid composition and biological potency identical to that of melanocyte-stimulating hormone (α-MSH) isolated from other mammals, and which accounts for the bulk of melanocyte-stimulating activity in the pituitary. Rat ACTH resembles human ACTH in amino acid composition, except for an extra valine and one less glycine residue. On the basis of these data it is proposed that ACTH is the precursor of α-MSH and CLIP, which are both present in the cells of the pars intermedia.
PURIFICATION AND CHARACTERIZATION OF PORCINE CORTICOTROPHIN-LIKE INTERMEDIATE LOBE PEPTIDE
Authors: SCOTT A. P. , LOWRY P. J. , BENNETT H. P. J. , McMARTIN C. , RATCLIFFE J. G. 
Published: December 2008

SUMMARY
Pig posterior pituitary lobe powder contains a peptide structurally identical to the 18–39 portion of porcine adrenocorticotrophin (ACTH). Its extraction by several different procedures is described and its susceptibility to degradation in the presence of 5% acetic acid has been noted. This degradation has been ascribed to the presence of acid proteases in the acetone-dried powder of the posterior pituitary lobe. The peptide has been isolated by chromatography on Biogel P6 and DEAE-cellulose, and characterized by enzyme fragmentation studies. It resembles the peptide isolated from rat neurointermediate lobes termed 'corticotrophin-like intermediate lobe peptide' and it is suggested that it is derived by the intracellular cleavage of ACTH in the pars intermedia cells, with subsequent formation of α-melanocyte-stimulating hormone from the other adrenocorticotrophic fragment.