bluuebunny/crossref_metadata_2025_split huggingface dataset:
METABOLISM OF PROLACTIN IN MICE WITH A HIGH INCIDENCE OF MAMMARY TUMOURS: EVIDENCE FOR GREATER CONVERSION INTO A NON-IMMUNOASSAYABLE FORM
Authors: SINHA Y. N. , BAXTER S. R. 
Published: December 2008

Monomeric mouse prolactin containing small amounts of 125I-labelled prolactin was administered to adult female mice of a high (C3H/St) and low (C57BL/St) mammary tumour strain. Their endogenous prolactin had been suppressed with 2-bromo-α-ergo-cryptine. The chromatographic profile, on Sephadex G-100, of prolactin in the serum of mice injected with mouse prolactin was compared by direct measurement (radioactivity count) and by radioimmunoassay (RIA) at several intervals after injection. With both methods, the injected hormone was found in the serum in predominantly two molecular sizes, the so-called 'big' and 'little' forms. Although 'little' prolactin in both strains constituted a constant 80% of the total hormone at most intervals by direct measurement, it comprised a comparatively smaller proportion by RIA. In addition, the RIA-determined 'little' prolactin, after reaching maximum levels at 15 min, progressively decreased with time, the decrease being greater in the C3H/St than in the C57BL/St strain. Similar experiments with mouse growth hormone revealed no such discrepancies between the radioactivity counts and the RIA measurements. A fraction of both 'big' and 'little' forms in the C3H/St strain failed to precipitate completely after the material had been incubated with an antiserum to mouse prolactin. These results demonstrate that the prolactin injected into mice is metabolized in serum into two non-immunoreactive forms, one that elutes with the same elution volume on Sephadex G-100 column as the monomer and the other that elutes as the 'big' form. Furthermore, the loss of immunoreactivity of monomeric mouse prolactin is greater in the high-tumour C3H/St strain than in the low-tumour C57BL/St strain.
Endogenous immunoreactive prolactin, on the other hand, was found mainly in the 'big' form in the serum of female mice of the C3H/St strain under basal conditions, whereas it was present only in the 'little' form in comparable mice of the C57BL/St strain, even though pituitary extracts of both strains contained mainly the 'little' form. These results support the concept that monomeric prolactin in the systemic circulation of the tumour-prone C3H/St strain is largely in a non-immunoreactive form.
HYPERALDOSTERONISM IN THE SODIUM-DEPLETED RAT: MECHANISM OF ALDOSTERONE STIMULATION BY PERITONEAL DIALYSIS WITH GLUCOSE SOLUTION
Authors: SPÄT A. , NAGY K. , ÉVA TARJÁN 
Published: December 2008

SUMMARY
Peritoneal dialysis with 5% glucose solution was carried out in dexamethasone-pretreated rats. Dialysis brought about a severe loss of sodium and a slight loss of potassium into the peritoneal fluid. This kind of sodium depletion took place without any decrease in total body-water space, thus it evoked a severe fall in plasma sodium concentration.
Plasma renin activity and the serum concentration of aldosterone increased in response to dialysis. Peak values in renin activity were attained within 60 min, whereas aldosterone concentrations exhibited a continuous rise until at least 120 min. Despite the correlation of renin and aldosterone values, neither the administration of an angiotensin I converting enzyme inhibitor (SQ 20,881) nor the reduction of plasma renin activity by indomethacin could reduce hyperaldosteronism evoked by peritoneal dialysis. Therefore, it is assumed that there is no causal relationship between renin and aldosterone in this kind of acute, severe sodium depletion.
EFFECTS OF AGE AND TESTICULAR FUNCTION ON THE PITUITARY–THYROID SYSTEM IN MALE RATS
Authors: CHEN H. J. , WALFISH P. G. 
Published: December 2008

SUMMARY
Old male rats of 22–24 months and young ones of 3–5 months were studied to find the effects of ageing, of orchidectomy and of orchidectomy and treatment with testosterone propionate (TP) on the basal serum concentrations of thyrotrophin (TSH) and on the total and free concentrations of tri-iodothyronine (T3) and thyroxine (T4) in the serum. The changes in TSH after treatment with thyrotrophin releasing hormone (TRH) were also observed. Intact old rats had significantly (P < 0·001) lower basal T4 and T3 as well as lower (P < 0·05) testosterone concentrations than were present in young rats. They also had higher basal TSH and per cent free T4 but lower absolute free T3 concentrations than had young rats. Two weeks after orchidectomy, basal TSH concentrations were slightly but significantly (P < 0·05) decreased in both young and old rats while T4 decreased significantly (P < 0·05) only in the young. The responses of TSH to TRH were also reduced by orchidectomy in both age groups with the old rats being less responsive than the young. Orchidectomy and treatment with pharmacological doses of TP produced similar effects on the pituitary-thyrotrophic response for both old and young rats but a greater effect occurred in the basal T4 response in young rats. In all groups basal TSH was influenced by orchidectomy or by treatment with TP but was always higher in the aged rat. Tri-iodothyronine concentration was always lower in the older rat and was not altered by orchidectomy or by treatment with TP in either young or old rats.
These results indicate that (1) in the male rat these age-specific effects on the thyroid–pituitary system are probably due, not only to a reduction in thyroid gland function and plasma T4 protein-binding, but also to a concomitant hyporesponsiveness of the aged male rat pituitary thyrotroph to TRH stimulation and (2) there is probably a significant influence of testicular function on the pituitary–thyroid system of the male rat.
EFFECT OF PREPUBERTAL HEMIORCHIDECTOMY ON THE RESPONSE OF THE TESTIS TO LUTEINIZING HORMONE
Authors: SELIN LIISA , MOGER W. H. 
Published: December 2008

SUMMARY
Administration of FSH to hypophysectomized male rats has been shown to increase the capacity of the testes to secrete testosterone in response to LH. Studies were done to assess the effect of increased endogenous FSH on the response of the testis to LH. At 17 and 24 days of age, animals hemiorchidectomized at 10 days of age had significantly higher serum FSH levels and testicular weights than sham-operated rats. To study the testicular response to LH in vivo, hemiorchidectomized animals were sham-operated and the sham-operated animals were hemiorchidectomized at 17 or 24 days of age. Luteinizing hormone (30 μg/100 g body wt) or saline was administered immediately after the operation and the animals were autopsied 90 min later. Chronic hemiorchidectomy significantly increased the serum testosterone response to LH at 17 but not at 24 days of age. The testicular response to LH in vitro was also investigated. Testes from rats hemiorchidectomized or sham-operated at 10 days of age and killed at 17 and 24 days of age were incubated for 3 h in the presence or absence of 100 ng LH/ml incubation medium. Significantly more 5α-androstane-3α,17β-diol and androsterone were produced by the testes from hemiorchidectomized than from sham-operated animals at 17 days of age but not at 24 days of age. The production of testosterone in vitro was not influenced by hemiorchidectomy at either age. These results suggest that serum FSH concentration is the factor limiting LH responsiveness before but not after the prepubertal increase in FSH levels. However, treatment of intact rats from 10 to 16 days of age with 20 μg rat FSH/day did not increase the serum testosterone response to LH.
SEROTONIN INVOLVEMENT IN THE CONTROL OF PHASIC LUTEINIZING HORMONE RELEASE IN THE RAT: EVIDENCE FOR A CRITICAL PERIOD
Authors: COEN C. W. , MacKINNON P. C. B. 
Published: December 2008

SUMMARY
A marked surge of luteinizing hormone (LH) occurs daily at 18.00 h in oestrogen-treated ovariectomized rats maintained under regular lighting from 06.00 to 20.00 h. The administration of p-chlorophenylalanine (PCPA), p-chloroamphetamine or 5,6-dihydroxytryptamine in treatments designed to cause a severe depletion of brain serotonin abolished this daily surge. Synthesis of serotonin may be temporarily restored in PCPA-treated animals by the administration of the serotonin precursor, 5-hydroxytryptophan. The effectiveness with which restoration of synthesis resulted in restoration of the LH surge varied according to the time at which the precursor was administered, the optimal time being 10.00 h. The results suggest that there is an essential, permissive function performed by serotonin in the production of the LH surge and that this function occurs during a critical period.
EFFECTS OF CHEMORECEPTOR AND BARORECEPTOR STIMULATION ON THE DISCHARGE OF HYPOTHALAMIC SUPRAOPTIC NEURONES IN RATS
Authors: HARRIS M. C. 
Published: December 2008

SUMMARY
Experiments have been performed to examine the effects of activating the carotid body chemoreceptors and the arterial baroreceptors on the discharge of neurones within the hypothalamic supraoptic nucleus of the rat. Chemoreceptors were activated by intracarotid injection of 0·9% NaCl solution equilibrated with 100% CO2. The baroreceptors of the carotid sinus and aortic arch were activated by raising the blood pressure with an intravenous injection of phenylephrine.
Chemoreceptor stimulation activated and baroreceptor stimulation inhibited the discharge of all the phasically discharging neurones tested. Neither stimulus had any consistent effect on non-phasically discharging neurones, although slight inhibition occasionally occurred. Anaesthesia of the carotid bifurcation abolished the effects of cardiovascular stimulation on the supraoptic neurones. Responses resumed when the anaesthesia wore off. However, the anaesthesia also seemed to alter the phasic pattern of discharge.
The results are discussed with reference to the influence of the cardiovascular receptors upon the neurones in the supraoptic nucleus, and with reference to possible roles for the cardiovascular reflexes in control of vasopressin secretion.
PROLACTIN RELEASE IN PARENT RING DOVES AFTER BRIEF EXPOSURE TO THEIR YOUNG
Authors: BUNTIN J. D. 
Published: December 2008

SUMMARY
A pigeon crop sac radioreceptor assay was used to measure changes in pituitary prolactin levels in parent ring doves of both sexes on the third day after hatching of their young. After a deprivation of 17 h from the squabs, exposure to a 3-day-old squab for 1 h resulted in a significant decrease in the prolactin content of the pituitary gland as compared with levels obtained in control birds deprived of their young for 18 h. No significant sex differences in prolactin levels were observed in either group. Because exposure to the young also promotes prolactin-induced crop sac growth, it appears probable that the squab-induced decrease in prolactin content of the pituitary gland reflects the release of prolactin into the circulation. Accordingly, the environmental regulation of prolactin secretion in parent ring doves appears similar to that observed in lactating mammals.
DEPENDENCE OF SPONTANEOUS AND ANGIOTENSIN-INDUCED DRINKING IN THE RAT UPON THE OESTROUS CYCLE AND OVARIAN HORMONES
Authors: FINDLAY A. L. R. , FITZSIMONS J. T. , KUCHARCZYK J. 
Published: December 2008

SUMMARY
The influence of the oestrous cycle on spontaneous and dipsogen-induced drinking was studied in female rats. Spontaneous fluid intake was lowest on the day of oestrus. Drinking induced by subcutaneous isoprenaline, and by angiotensin II (injected into the preoptic area), also showed marked cyclical variation, being lower at pro-oestrus and oestrus than at other stages of the cycle. Drinking induced by subcutaneous hypertonic NaCl or by intracranial carbachol did not vary with the oestrous cycle. Cyclicity of spontaneous and of angiotensin-induced water intake was not apparent in rats before puberty or after ovariectomy. Ovariectomy reduced drinking in response to isoprenaline. Treatment with oestradiol benzoate (20 μg) caused a reduction in spontaneous water intake, but a marked increase in the drinking response to isoprenaline. Treatment with oestradiol benzoate and progesterone (2·5 mg) caused a larger decrease in spontaneous water intake and an insignificant increase in isoprenaline-induced drinking. Water intake induced by subcutaneous hypertonic saline was unaffected by gonadal steroids. The results provide further evidence for the view that the thirst of extracellular origin, in which the renin–angiotensin system is involved, is brought about by mechanisms different from those that respond to cellular dehydration. Only drinking caused by activation of extracellular mechanisms appeared to be sensitive to the ovarian cycle and to ovarian hormones.
IDENTIFICATION AND PURIFICATION OF A NEW PROTEIN FROM WATER-SOLUBLE EXTRACTS OF HUMAN ADRENAL GLAND
Authors: AL-AWQATI M. A. , GORDON Y. B. , CHARD T. 
Published: December 2008

An homogenate of human foetal adrenal gland was subjected to negative immunoabsorption by column chromatography using anti-whole human serum coupled to Sepharose 4B. Two peaks were eluted and used to immunize rabbits. The antisera produced were absorbed and tested for specificity by double immunodiffusion.
Two antigens, which appeared to be specific to the adrenal gland, were identified having molecular weights of 25 000 and 65 000 as determined by gel filtration. The lower molecular weight antigen was isolated by physicochemical methods and found to be a protein. The amino acid composition is reported.
EFFECTS OF HYDROXYLATED DERIVATIVES OF VITAMIN D3 AND OF AQUEOUS EXTRACTS OF SOLANUM MALACOXYLON ON THE ABSORPTION OF CALCIUM, PHOSPHATE, SODIUM, POTASSIUM AND WATER FROM THE JEJUNUM OF PIGS
Authors: FOX J. , CARE A. D. 
Published: December 2008

The effects of hydroxylated derivatives of vitamin D3 and aqueous extracts of Solanum malacoxylon on the intestinal absorption of calcium, phosphate, sodium, potassium and water have been studied in unstressed vitamin D-replete pigs each of which was surgically prepared beforehand with a Thirty–Vella loop of jejunum. The addition, for six 1 h periods of perfusion, of 1,25-dihydroxycholecalciferol (1,25-(OH)2D3) or 1α-hydroxycholecalciferol at similar concentrations (3·6–3·75 pmol/ml) to the solution used to perfuse the intestinal loop caused a rapid increase in the absorption of calcium but increased the absorption of phosphate only after a delay of at least 12 h. The absorption of both calcium and phosphate reached a maximum on the day following the addition of the vitamin D derivative to the perfusate. The addition of 25-hydroxycholecalciferol (25-(OH)D3) at a concentration of 3·75 pmol/ml was without effect on absorption except for a small increase in the absorption of phosphate on the following day. However, at higher concentrations (> 250 pmol 25-(OH)D3/ml) the absorptions of calcium and phosphate were both increased rapidly. 24,25-Dihydroxycholecalciferol was without effect on absorption at the concentration tested (3·6 pmol/ml).
Aqueous extracts (1%) of the leaf of S. malacoxylon showed similar effects on absorption to those of 1,25-(OH)2D3. However, there was one point of difference; the absorption of phosphate was stimulated with a similar time course to that of calcium in contrast to its delayed response to 1,25-(OH)2D3.
The absorption rates of water, sodium and potassium were not consistently affected by 1,25-(OH)2D3 or S. malacoxylon. However, the major effects of these derivatives were usually seen on the day following the day of addition to the perfusate. In contrast, 25-(OH)D3 at high concentrations had a marked effect on the absorption of water, sodium and potassium on the day of addition.
VARIATION IN SIZE OF THE 'READILY RELEASABLE POOL' OF LUTEINIZING HORMONE DURING THE OESTROUS CYCLE OF THE RAT
Authors: PICKERING A. J.-M. C. , FINK G. 
Published: December 2008

SUMMARY
The size of the 'readily releasable pool' of luteinizing hormone at various times of the oestrous cycle has been determined by injecting a supramaximal dose of luteinizing hormone releasing factor (LH-RF) i.v. into rats anaesthetized with sodium pentobarbitone. In an attempt to block replenishment of the 'pool' during release, cycloheximide was administered 30 min before LH-RF. A 20-fold increase in pool size occurred between the morning of dioestrus and the evening of pro-oestrus in the absence of any significant change in total pituitary content of LH. This suggests that increased responsiveness may be brought about by a change in the receptor-release apparatus and/or a transfer of LH from a 'storage pool' which leads to an apparent increase in the proportion of LH available for release.
PROLACTIN RECEPTORS IN THE MAMMARY GLAND, CORPUS LUTEUM AND OTHER TISSUES OF THE TAMMAR WALLABY, MACROPUS EUGENII
Authors: SERNIA C. , TYNDALE-BISCOE C. H. 
Published: December 2008

SUMMARY
Specific binding of radio-iodinated ovine prolactin to subcellular tissue fractions of the tammar wallaby (Macropus eugenii) was investigated. Specific binding was found, in order of decreasing binding activity, in the lactating mammary gland, corpus luteum, corpus albicans, adrenal gland and ovary. Specific binding was absent in kidney, liver, brain and inactive mammary gland.
The mean association constant (Ka at 23 °C) was determined as 0·90 × 109, 2·20 × 109, 2·44 × 109, 3·38 × 109 and 10·98 × 1091/mol for mammary gland, adrenal, corpus albicans, corpus luteum and ovary respectively. The mean receptor concentration (N) varied from 92·87 × 10−14 mol/mg protein for the mammary gland to 1·03 × 10−14 mol/mg protein for the ovary. The concentration in the corpus luteum varied between tissue pools collected at different times of the annual breeding cycle.
The specificity for prolactin was shown in the mammary gland and corpus luteum by the failure of ovine FSH, LH, GH and TSH to displace 125I-labelled ovine prolactin, whereas it was displaced readily by both ovine and bovine prolactin.
URINARY EXCRETION OF OESTRONE, OESTRADIOL-17β AND OESTRIOL IN PREGNANCIES COMPLICATED BY STEROID SULPHATASE DEFICIENCY
Authors: MUJAJI B. W. , TOUMBA K. J. , OAKEY R. E. 
Published: December 2008

SUMMARY
The urinary excretion of oestrone, oestradiol-17β and oestriol was measured by gas–liquid chromatography in 24 h urine specimens, collected after 34 weeks of gestation from each of eight women whose pregnancies were complicated by steroid sulphatase deficiency and from each of 21 pregnant women without this complication. Mean (±s.d.) values μmol/24 h, sulphatase deficient; normal) were: oestrone, 0·7 ± 0·2; 2·5 ± 1·3; oestradiol-17β, 0·5 ± 0·2; 1·6 ± 0·5: oestriol, 2·0 ± 0·9; 54·4 ± 19·9. Thus, mean oestrone and oestradiol-17β excretions were only 30% of normal whilst mean oestriol excretion was reduced by more than 90%. Consequently, the mean ratio of urinary oestriol/(oestrone + oestradiol-17β changed from 13·7 ± 2·3 in normal pregnancy to 1·6 ± 0·6 in pregnancies complicated by steroid sulphatase deficiency. The greater fall in oestriol excretion in this condition, in comparison with that of oestrone and oestradiol-17β, emphasizes the importance of conjugated 16-oxygenated C19 steroids in the biosynthesis of oestriol in human pregnancy. The change in the relative proportions of the three urinary oestrogens implies that in the precursor pool of normal pregnancy the concentration of 16-oxy-C19 steroids relative to that of the 16-deoxy-C19 steroids, is much greater in the sulphate fraction than it is in the unconjugated fraction.
The measurement of the urinary oestriol/(oestrone+oestradiol-17β) ratio may have the potential to make it possible to distinguish, before birth, between pregnancies complicated by steroid sulphatase deficiency and those with foetal adrenal hypoplasia.
VARYING RESPONSE TO LUTEINIZING HORMONE OF TWO LUTEAL CELL TYPES ISOLATED FROM BOVINE CORPUS LUTEUM
Authors: URSELY JOCELYNE , LEYMARIE PIERRE 
Published: December 2008

Luteal cell suspensions obtained by enzymatic digestion of pregnant cow corpus luteum were found to be heterogenous and mainly made up of two types of cells of different sizes. The large cells (37 μm, average diameter) could be separated from the small ones (18 μm, average diameter) by sedimentation at unit gravity in a gradient of Ficoll–bovine serum albumin. A comparative in-vitro study of the synthesis of progesterone by the two types of cells indicated striking differences between them. The average content and the synthesis of progesterone in the absence and presence of a saturating dose of bovine LH after incubation for 2 h were 0·07, 0·12 and 6·9 pg/cell for the small cells and 0·65, 2 and 10 pg/cell for the large ones. Moreover, the sensitivity to low concentrations of LH was 100 to 1000 times higher for the small cells than for the large ones. oestradiol-17β at concentrations ranging from 5 × 10−10 to 5 × 10−4 mol/l exerted a dose–dependent inhibition on the stimulation of LH in both cell types.
These results suggest a possible involvement of both cell types in the synthesis of progesterone in vivo with a greater contribution by the small cells to stimulation induced by LH.
Moreover, it appears that small cell suspensions could be a useful model system for in-vitro studies of the control of the synthesis of progesterone in cow corpus luteum.
EFFECTS OF TAMOXIFEN ON THE BINDING AND METABOLISM OF TESTOSTERONE BY HUMAN PROSTATIC TISSUE AND PLASMA IN VITRO
Authors: HABIB F. K. , RAFATI G. , ROBINSON M. R. G. , STITCH S. R. 
Published: December 2008

The in-vitro metabolism of testosterone in benign and malignant prostatic tissue was examined and distinct quantitative differences between the two types of specimens were observed. The major metabolite of testosterone in the hyperplastic prostate was 5α-dihydrotestosterone and a high 3α(β)-hydroxysteroid dehydrogenase activity was also detected.
In the malignant tissue, 5α-reductase activity was considerably reduced and there was little or no androstanediol formed; the 17β-dehydrogenase activity was, however, higher than in the benign tissue. The decrease in 5α-reductase was always followed by a compensatory change in the 3α(β)-hydroxysteroid dehydrogenase of the malignant prostate. The present study revealed that the ratio of the mean activities of 5α-reductase to 3α(β)-hydroxysteroid dehydrogenase in the two types of specimen always remained a constant.
Although the antioestrogen, tamoxifen, induced an inhibitory effect on the activities of 5α-reductase and 17β-hydroxysteroid dehydrogenase in the gland, the present investigation also suggested that tamoxifen stimulated the activity of 3α(3β)-hydroxysteroid dehydrogenase. In blood, the action of tamoxifen appeared to be confined to the displacement of androgens from the binding sites on the sex hormone binding globulin.
RELATIONSHIP BETWEEN PLASMA SOMATOMEDIN ACTIVITY AND LEVELS OF CORTISOL AND FREE FATTY ACIDS FOLLOWING STRESS IN PIGS
Authors: SPENCER G. S. G. 
Published: December 2008

Somatomedin activity, cortisol and free fatty acids have been measured in the plasma of eight Pietrain pigs at various times after stress. Somatomedin activity decreased immediately, reached a minimum after 15 min and remained low throughout a 3·5 h period. Cortisol levels rose to a peak after 15 min and regained normal levels after 60 min. Free fatty acid levels increased to a peak level about 3 h after stress.
The possibility of inhibitors of the bioassay for somatomedin activity influencing the results are discussed.