bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECTS OF HYPOPHYSECTOMY AND SHORT-TERM GROWTH HORMONE REPLACEMENT ON INSULIN RELEASE FROM AND GLUCOSE METABOLISM IN ISOLATED RAT ISLETS OF LANGERHANS
Authors: PARMAN A. Ü. 
Published: December 2008

SUMMARY
The effects of hypophysectomy and short-term GH replacement on insulin release and on some aspects of glucose metabolism in isolated rat islets of Langerhans were investigated. The effects on body, pancreas and adrenal gland weights, and on the levels of blood plasma constituents were also measured. Three to four weeks after hypophysectomy the early and late phases of insulin release from islets incubated with high concentrations of glucose, but not with low concentrations of glucose or with xylitol, leucine, arginine, tolbutamide, citrate or butyrate, were significantly lowered. Short-term GH replacement partially reversed the depression in glucose-stimulated insulin release. This reversal effect was not dependent on the increase in body weight of rats after GH replacement when the fall in adrenal gland but not in pancreas weight was also reversed. Nine out of the 12 plasma constituents measured, including glucose, were maintained in the control range of levels, but albumin, inorganic phosphate and urea nitrogen levels were altered after hypophysectomy or GH replacement.
Three to four weeks after hypophysectomy, total glucose oxidation and glucose utilization by the islets were slightly depressed. Hypophysectomy appeared to slow down glucose 6-phosphate utilization in the islets. However, the functional capacity of the glucose phosphorylating, glucose-6-phosphate and 6-phosphogluconate dehydrogenase activities were not changed. Short-term GH replacement caused improvements in these islet functions.
DISTRIBUTION OF TESTOSTERONE AND 5α-DIHYDRO-TESTOSTERONE IN RAT EPIDIDYMIS AND THEIR CONCENTRATIONS IN EFFERENT DUCT FLUID
Authors: VREEBURG J. T. M. 
Published: December 2008

SUMMARY
5α-Dihydrotestosterone concentrations were found to be appreciably higher in the proximal portion of the rat epididymis than in the distal portion. Following ligation of the efferent ducts of a testis, the 5α-dihydrotestosterone concentration diminished in the proximal half but not in the distal half of the epididymis. Epididymal fluid and spermatozoa were washed out from minces of epididymal tissue. The numbers of spermatozoa present in the wash fluid and in the homogenate of washed minces of epididymal tissue were used as measures for the amounts of epididymal fluid present in these fractions. Of the total amount of 5α-dihydrotestosterone (30·2 ng/g tissue) in the proximal portion, 20·5 ng were localized in the epididymal fluid, whereas of the total amount of 5α-dihydrotestosterone (8·6 ng/g tissue) in the distal portion, 2·8 ng were found in the epididymal fluid. The amounts of testosterone present in the fluids of both proximal and distal portions were 1–2 ng/g tissue. In contrast to the epididymal fluid, efferent duct fluid had a high concentration of testosterone (28·8 ng/ml) and a low concentration of 5α-dihydrotestosterone (1·9 ng/ml). These data suggest that the fluid surrounding the spermatozoa in the testis and the epididymis contains a high concentration of androgen and that as the fluid moves from the testis to the epididymis there is a clear change in the ratio of testosterone to 5α-dihydrotestosterone.
PRESENCE OF SEX PHEROMONE IN PREPUTIAL GLANDS OF MALE RATS
Authors: GAWIENOWSKI A. M. , ORSULAK P. J. , STACEWICZ-SAPUNTZAKIS MARIA , JOSEPH B. M. 
Published: December 2008

SUMMARY
Female rats consistently preferred the odour of male rat preputial gland compared with that of foot pads, submaxillary-sublingual glands, coagulating glands, liver, fat or muscle. Both saline homogenates and ether extracts were effective. Female rats did not respond to the odour of female preputial extract and they preferred the odour of normal male preputial extract to that from castrated rats. The pheromone was not associated with the fatty acids of the preputial extract. The fractionation of the volatile components of preputial extracts by gas chromatography revealed that most of the biological activity resided in a specific fraction.
RAPID INTERACTION BETWEEN LUTEINIZING HORMONE AND ISOLATED RABBIT FOLLICLES
Authors: YOUNGLAI E. V. 
Published: December 2008

SUMMARY
The rapidity of binding of LH to rabbit ovarian follicles was examined using androgen production as the endpoint. Incubations were carried out for about 8 h with medium being changed every 15 min except during the periods when follicles were exposed to LH and/or anti-LH and subsequent washing. Exposure of follicles to LH for 1 s followed by washing in (a) LH-free medium, (b) pure anti-LH or (c) diluted anti-LH, failed to inhibit androgen production which persisted for more than 2 h. Simultaneous addition of anti-LH and LH to the medium before incubation with follicles completely inhibited the response though it could be elicited from the same follicles when LH was added later. These data suggest that the binding of LH to follicular receptors is a rapid process and that either the LH-receptor complex is very stable or that LH initiates a series of reactions which are independent of the presence of hormone.
ABSORPTION OF 125I-LABELLED SHEEP GROWTH HORMONE IN SINGLE PROXIMAL TUBULES OF THE RAT KIDNEY
Authors: STACY B. D. , WALLACE A. L. C. , GEMMELL R. T. , WILSON B. W. 
Published: December 2008

SUMMARY
Techniques of kidney micropuncture and electron microscope autoradiography have been used to study the uptake of 125I-labelled sheep growth hormone (GH) in rat renal proximal tubules. After microperfusion of a proximal tubule with 125I-labelled GH, the transport of label by the tubular epithelium was studied autoradiographically at selected times up to 1 h. The sequential transfer of labelled material from tubule to microvilli, then to small and large apical vacuoles and finally to lysosomes followed the pattern of absorption that has been described for other proteins. Evidence of lysosomal degradation of the transported protein was obtained from studies in vitro; lysosomes isolated from the renal cortex rapidly converted 125I-labelled GH to products of lower molecular weight. In addition to the absorptive pathway through the intracellular vacuolar apparatus it appeared that there was also an alternative pathway, less well defined, whereby GH could be absorbed without being degraded.
PARAMETERS OF ELECTRICAL STIMULATION OF THE MEDIAL PREOPTIC AREA FOR RELEASE OF GONADOTROPHINS IN MALE RATS
Authors: JAMIESON M. G. , FINK G. 
Published: December 2008

SUMMARY
The release of LH and FSH after the application of an electrical stimulus to the anterior diencephalon of male rats has been studied. The stimulus was applied through either platinum or steel electrodes implanted stereotaxically in animals anaesthetized with urethane. The efficacy of various parameters of stimulation by means of a current consisting of balanced biphasic square waves, was tested by systematically changing the frequency, amplitude and duration of the pulses. The effect of direct current (d.c.) stimulation on hormone release was also examined. The concentrations of the hormones in blood withdrawn from the femoral vein before and at frequent intervals up to 80 min after application of the stimulus were determined by radioimmunoassay.
The optimal parameters for the release of LH by square wave stimulation of the medial preoptic area were: frequency, 60 Hz; pulse amplitude, 0·50 mA; pulse duration, 1·00 ms. This stimulus was more effective when applied through steel than through platinum electrodes. Direct current stimulation (15 μA for 10 s) through steel electrodes was most effective of all. When applied through platinum electrodes to the medial preoptic and anterior hypothalamic areas, the optimal square wave stimulus produced significant increases in the concentration of LH after 5 and 10 min respectively. The concentration of plasma FSH in these animals also increased, but the increments were much less than the increments in LH. The magnitude of the respective increases of the gonadotrophins after stimulation of the two brain areas did not differ significantly. Measurement of the milk ejection response to stimulation of the hypothalamo-hypophysial tract in a lactating rat indicated that the spread of the square wave stimulus was no more than 1·5 mm from the electrode tip.
The significance of these findings is discussed with respect to the importance of the medial preoptic area in the male rat, the neurones which may be involved in the regulation of gonadotrophin secretion, and the parameters of stimulation used in studying the hypothalamo-hypophysial system.
EFFECT OF CORTISOL ON UTILIZATION AND HEPATIC RELEASE OF GLUCOSE IN THE MARSUPIAL BRUSH-TAILED OPOSSUM, TRICHOSURUS VULPECULA
Authors: McDONALD I. R. , THAN KHIN AYE 
Published: December 2008

SUMMARY
Brush-tailed opossums were prepared surgically with indwelling hepatic and jugular venous catheters for blood sampling without disturbance in the conscious state.
Hepatic extraction of [125I]Rose Bengal was 21 ± 3 (s.d.)% and hepatic clearance, used as a measure of hepatic blood flow, was 42·5 ± 7 ml/kg/min. Hepatic release of new glucose, calculated from the thoracic vena caval-hepatic venous difference in glucose specific activity at equilibrium during i.v. infusion of [14C]glucose and hepatic blood flow, was 3·5 ± 0·8 mg/ kg/min. This was not changed by i.v. infusion of 10% ethanolic saline or cortisol in ethanolic saline, at 1 mg/kg/h for 90 min, although the cortisol infusion caused the peripheral blood glucose concentration to rise from 56·5 ± 7·3 to 83·2 ± 10·3 mg/100 ml.
The rate of metabolic clearance of glucose fell from 6·1 ± 1·1 to 4·2 ± 0·9 ml/kg/min during i.v. cortisol infusion. Daily i.m. injection of 1 mg cortisol acetate/kg for 5 days caused an increase in hepatic new glucose release to 8·0 ± 1·6 mg/kg/min.
The findings support the proposition that, in this marsupial, the short-term effect of cortisol on plasma glucose concentration is due to inhibition of peripheral glucose utilization, whereas the long-term effect is due to increased hepatic glucose production.
METABOLIC CLEARANCE RATE AND PRODUCTION RATE OF OESTRADIOL IN CONSCIOUS RABBITS
Authors: FRASER I. S. , CHALLIS J. R. G. , THORBURN G. D. 
Published: December 2008

SUMMARY
A continuous isotope infusion technique was used to measure the metabolic clearance rate (MCRB) and production rate (PRB) of oestradiol-17β in a group of six non-pregnant conscious Chinchilla rabbits. The mean MCRB of oestradiol was 162 ml/min (0·079 1/ min/weight0·75), and at equilibrium a significant proportion of the radioactivity in the circulation was present as oestrone (conversion ratio oestradiol to oestrone, 27·6%). The mean PRB of oestradiol was 4·3 ng/min, which is equivalent to about 5 μg/day. Some day-to-day variation was seen in the endogenous concentrations of oestradiol, oestrone and progesterone although in general the levels of the two oestrogens were less than 30–40 pg/ml, and progesterone levels were below 300 pg/ml apart from short peaks up to 600 pg/ml. These values were compared with previous measurements of the ovarian secretion rate of oestradiol measured directly in anaesthetized animals.
EGG TRANSPORT IN OVARIECTOMIZED RABBITS AS AFFECTED BY DIFFERENT COMBINATIONS OF OESTROGEN AND PROGESTERONE
Authors: EL-BANNA A. A. , SACHER B. 
Published: December 2008

SUMMARY
A total of 1548 eggs was transferred to the oviducts of rabbits ovariectomized 45 days to 7 months earlier. The pattern of egg transport was disrupted, and the majority of eggs were in the vagina 60–72 h after transfer.
To determine the role of the ovarian hormones on egg transport, the effects of various combinations of oestrogen and progesterone were studied. None of the hormonal treatments produced the normal transport pattern and large proportions of transferred eggs were retained in the oviducts.
It is concluded that as long as progesterone is the dominant hormone, eggs move very slowly through the isthmus, and that a surge of oestrogen is required to modify the action of progesterone and to speed the movement of eggs to the uterus.
PROLACTIN STIMULATION TEST WITH PERPHENAZINE: AN EVALUATION OF PLASMA PROLACTIN LEVELS AND PITUITARY SECRETORY ACTIVITY IN THE RAT
Authors: VAN DER GUGTEN A. A. , SAHULEKA P. C. , VAN GALEN G. H. , KWA H. G. 
Published: December 2008

SUMMARY
Many investigations of the regulation of prolactin synthesis and release are based on single plasma prolactin determinations. The purpose of the present experiment was to ascertain whether groups of rats (i.e. young or adult, male or female animals, being either intact, gonadectomized or gonadectomized and treated with oestrone), differing in age and/or endocrine status, will react to a single dose of perphenazine by an acute release of pituitary prolactin in proportion to their initial plasma prolactin levels.
No consistent relation existed between the classification of the twelve groups of rats into three categories of basal plasma prolactin levels (i.e. < 20, 25–50, > 125 ng/ml) and their response to perphenazine. Even though all groups showed a highly significant increase of plasma prolactin levels the magnitude of the maximum prolactin response at 30 min varied greatly within the groups of one category and thus was not related to the initial prolactin levels.
The effect of 14 days of oestrone treatment in increasing plasma prolactin levels in gonadectomized animals was greatest in young and adult male rats, less in young females and not significant in adult females. The results obtained after perphenazine treatment in the latter group made it clear that the effect of oestrogen treatment on prolactin release can be completely blocked by increasing synthesis and/or release of the prolactin-release inhibiting factor (PIF). Since perphenazine induces decrease of pituitary prolactin and a concomitant increase of plasma prolactin levels through lowered PIF-action, the positive effect of oestrogens on prolactin release (as observed in gonadectomized male and young female rats) apparently is caused by a different mode of action. The implications of these findings for the regulation of prolactin release, as affected by the endocrine status of the rat, is discussed.
Moreover, comparison of prolactin lost from the pituitary and gained in the circulation of the experimental animals, with amounts of prolactin that were observed to disappear from plasma during the experiment, provided suggestive evidence that the capacity to synthesize and/or eliminate prolactin, after a sudden provoked release of the hormone, differed among the groups.
The rates of synthesis by the pituitary, of release from the pituitary into the circulation as well as of elimination of the hormone from the circulation (equally involved in determining actual plasma levels) are thought, therefore, to be far more important for the elucidation of prolactin regulation than single plasma prolactin determinations.
ROLE OF MATERNAL AND FOETAL ADRENAL ACTIVITY IN THE DEVELOPMENT OF THE RAT MAMMARY GLAND NEAR TERM
Authors: BARRENA J. C. , GRIFFITH D. R. 
Published: December 2008

SUMMARY
The essential role of adrenal corticosteroids in the initiation of mammary gland secretory activity near term in the rat has been investigated. Mammary gland DNA and RNA were estimated as a quantitative indication of the extent of mammary gland development. Maternal adrenalectomy or hypophysectomy resulted in a decrease in the mammary gland RNA:DNA ratio. Treatment of adrenalectomized animals with cortisol acetate completely restored the RNA:DNA ratio to the control level. Treatment of hypophysectomized animals with cortisol acetate resulted in an increase in the RNA:DNA ratio but did not restore the ratio to the control level. Removal of the pups had no effect on the RNA:DNA ratio. The findings are discussed in relation to the foetal and maternal contribution to the level of glucocorticoids in the circulation and with respect to changes in mammary gland sensitivity to lactogenic stimulation near term.
TAMOXIFEN AS AN ANTI-TUMOUR AGENT: OESTROGEN BINDING AS A PREDICTIVE TEST FOR TUMOUR RESPONSE
Authors: JORDAN V. C. , JASPAN T. 
Published: December 2008

SUMMARY
Rats with growing 7,12-dimethylbenz(a)anthracene (DMBA)-induced rat mammary carcinomata were biopsied and oestrogen-binding capacity was measured using a Sephadex LH-20 chromatography method. Tumours were measured with calipers and animals were treated for 3 weeks with tamoxifen (50 μg/day, s.c.). Tumour response was determined by the size (cm2) before and after therapy. An increase in tumour regression (ten tumours) was seen with increasing oestrogen-binding sites determined by Scatchard analysis (P < 0·01). Thirty tumours were used to determine oestrogen binding with a single dose of [3H]-oestradiol. The percentage tumour regression was linearly correlated with oestrogen-binding capacity (P < 0·01), although some tumours with high oestrogen-binding capacities only partially regressed in response to tamoxifen therapy. The time of the oestrous cycle when biopsy occurred was not a critical factor in determining oestrogen binding for prediction of response. Oestrogen binding was reduced during tamoxifen therapy.
SERUM GONADOTROPHINS AND FOLLICULAR DEVELOPMENT IN IMMATURE RATS AFTER EARLY ANDROGEN ADMINISTRATION
Authors: UILENBROEK J. TH. J. , DE WOLFF-EXALTO E. ARENDSEN , BLANKENSTEIN M. A. 
Published: December 2008

SUMMARY
Follicular development and serum gonadotrophin levels were studied in female rats after neonatal androgen administration.
After injection of 1250 μg testosterone propionate (TP) on day 5 after birth the composition of the follicular population was altered: at nearly all ages the number of pre-antral follicles (follicular volume 2–20 × 105 μm3) was lower than in oil-treated rats, in some cases the number of small antral follicles (21–249 × 105 μm3) was also lower. Furthermore levels of serum follicle-stimulating hormone and luteinizing hormone were decreased from day 7 to day 20 suggesting that the high gonadotrophin levels before day 20 are of importance for normal follicular development.
In contrast, final follicular maturation in TP-treated rats was enhanced; at day 35 more large antral follicles (follicular volume ≥ 500 × 105μm3) were present in TP-treated rats than in oil-treated rats. The presence of more large antral follicles was accompanied by higher plasma oestradiol concentrations, higher uterine weights and advanced vaginal opening.
These results demonstrate an inhibition of normal follicular growth and an acceleration of ovarian maturation after neonatal androgen administration.
EFFECT OF LUTEINIZING HORMONE RELEASING HORMONE ON PLASMA LEVELS OF LUTEINIZING HORMONE, OESTRADIOL AND TESTOSTERONE IN THE MALE DOG
Authors: JONES GWYNETH E. , BAKER KAY , FAHMY DIAN R. , BOYNS A. R. 
Published: December 2008

SUMMARY
An injection of luteinizing hormone releasing hormone (LH-RH) increased plasma LH and testosterone concentrations in the male dog, but no significant increase in plasma oestradiol-17β levels was observed. Repeated injections of LH-RH produced an increase in plasma LH levels but there was a progressive decline in the response with each injection. The concentration of plasma testosterone reached a maximum within 40 min of the first injection of LH-RH and remained constant thereafter while plasma oestradiol concentration gradually increased with successive injections of LH-RH.
INHIBITION BY OESTRADIOL OF THE PITUITARY RESPONSE TO LUTEINIZING HORMONE RELEASING HORMONE IN THE DOG
Authors: JONES GWYNETH E. , BOYNS A. R. 
Published: December 2008

SUMMARY
Intravenous injections of synthetic LH-RH stimulated LH secretion in male dogs. Pretreatment with 50 μg oestradiol-17β, 60 or 165 min but not 15 min before LH-RH, inhibited LH secretion. Injection of 0·1–10 μg oestradiol 165 min before administration of LH-RH, blocked LH secretion. Basal plasma LH levels before LH-RH administration were lower in dogs given oestradiol than in controls.
ANDROGEN-CONTROLLED SPECIFIC PROTEINS IN RAT EPIDIDYMIS
Authors: CAMEO MÓNICA S. , BLAQUIER J. A. 
Published: December 2008

SUMMARY
The pattern of proteins in the soluble fraction of the cytoplasm of the rat epididymis was studied by acrylamide gel electrophoresis. The components of five distinct bands, labelled A, B, C, D and E, were found to be sensitive to changes in androgen in the blood. Castration for 14 days produced a sharp decrease in the colour intensity of bands B–E when stained with Amido black. After 21 days of castration, bands D and E were undetectable, bands B and C were severely diminished and band A was more intense. Seven days of replacement with testosterone (1 mg/day) induced a return towards a normal pattern. The degree of restoration was inversely proportional to the duration of castration. Quantitation by densitometry showed that the relative contributions of bands B–E to the region A–E were 61% in the control rat, only 27% after 21 days of castration and 35% when testosterone was given between days 14 and 21 of castration. The components of bands A–E are presumed to be proteins since the electrophoretic pattern was altered by digestion with pronase but not by ribonuclease, phospholipase C or neuraminidase. Epididymides from castrated and androgen-treated castrated rats were incubated with 14C- and 3H-labelled mixed amino acids respectively. After co-electrophoresis the ratio 3H: 14C rose from a baseline of 2–5 in band B, 32 in band C and 7 in bands D and E. Molecular weights were estimated as 27900 for B, 23100 for C and 34400 for D. Band A had the same electrophoretic mobility as serum albumin. Bands B and C were also present in testicular cytosol. Bands D and E were only found in the epididymis, localized mainly within the lumen of the tubules. Bands B–E increased with age during sexual maturation, bands D and E became detectable in the 20-day-old rats. Preliminary evidence indicates that the proteins in bands C, D and E can be removed from caput spermatozoa by washing.
UPTAKE OF [125I]IODODEOXYURIDINE IN CULTURED RAT AND HUMAN PROSTATE: EFFECTS OF INSULIN AND TESTOSTERONE
Authors: DONALDSON L. J. , THOMAS G. H. 
Published: December 2008

SUMMARY
DNA synthetic activity was monitored in rat and human prostate using [125I]iododeoxyuridine ([125I]UdR). Fresh prostate tissue from 6-week-old rats showed higher incorporation of [125I]UdR than that from 12- or 26-week-old rats. During culture for up to 6 days in the absence of hormones, the incorporation of [125I]UdR fell to a low level for all three age groups. Stimulatory effects were seen when rat prostates were cultured in the presence of insulin (3 μg/ml) and testosterone (10−7 mol/l), the incorporation on day 4 of culture being commensurate with that of fresh prostate of the corresponding age. Thus the magnitude of the response was higher for the 6-week-old prostate than that for the other two age groups. A similar age-related pattern of androgen stimulation was observed in experiments in which immature and adult castrated rats were injected daily with testosterone and the freshly removed prostates were incubated with [125I]UdR.
Although insulin, by itself, had a stimulatory effect on [125I]UdR incorporation in cultured prostate, the magnitude of the response did not differ in the 6- and 26-week-old prostate tissue. Maximal stimulation was obtained using 25 μg insulin/ml.
Tissue from a benign prostatic hyperplasia was also responsive to insulin in culture but it differed from rat prostate in that increased proliferative activity occurred even in the absence of hormone stimulation. This spontaneous surge in activity during culture tended to mask the stimulatory effects of insulin and testosterone at concentrations of 3 μg/ml and 10−7 mol/l respectively.