bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECTS OF PREGNANCY IN THE RAT ON THE SIZE AND INSULIN SECRETORY RESPONSE OF THE ISLETS OF LANGERHANS
Authors: GREEN I. C. , TAYLOR K. W. 
Published: December 2008

SUMMARY
The secretory response of rat islets of Langerhans was examined during pregnancy and compared with insulin release in normal rat islets. The threshold for a secretory response to glucose was lowered for islets from pregnant rats by comparison with non-pregnant controls. In addition, such islets showed a greatly increased sensitivity to glucose concentrations over the range 3·5–20 mmol/1. Significantly lower fasting blood glucose levels were found in pregnant rats in vivo, compared with controls.
Insulin secretagogues other than glucose were tested for their effects on islets during pregnancy. Despite the high baseline of insulin secretion in response to glucose in pregnancy, there was an additional increased secretory response to arginine and theophylline. In contrast to their response to glucose, pregnant rat islets did not display an increased sensitivity to leucine. Glucagon, while it increased the insulin response of normal islets, had no significant effect on increasing the insulin response from pregnant rat islets suggesting that adenyl cyclase activity is already highly stimulated in pregnancy.
In addition, the insulin, DNA and protein content of islets during pregnancy were increased significantly above normal values.
The results suggested that rat islets are not only larger in pregnancy, but that they possess a more sensitive mechanism for detecting and responding to glucose and other secretagogues.
ACUTE EFFECTS OF TESTOSTERONE PROPIONATE ON FOLATE COENZYME SYNTHESIS IN THE RAT
Authors: BOVINA C. , TOLOMELLI B. , ROVINETTI C. , MARCHETTI M. 
Published: December 2008

SUMMARY
The early effects of castration and testosterone administration on folic acid metabolism in liver and accessory sex organs were studied in adult male rats. After 3 days, castration did not produce significant variations in the folate coenzyme content of the liver, whereas in the prostate and seminal vesicles it only led to a fall of formylate forms. Testosterone administration did not cause significant changes in normal rats, but in castrated ones it generally raised formylate form levels and lowered the 5-methyltetrahydrofolate content. The capacity to convert folic acid into its activated forms in vivo decreased in castrated animals; after folic acid injection, they eliminated in urine more vitamin and fewer active forms than control rats. Furthermore, the liver content of the reduced forms was less in castrated animals than in intact ones. Testosterone administration partially adjusted this biochemical alteration. Studying in vitro the enzymic activities involved in folate coenzyme metabolism, it was found that the 10-formyltetrahydrofolate synthetase alteration was the more evident and constant one in castrated rats. This enzymic activity was much decreased in the organs studied. The other enzymes showed only a very slight increase in their activity. Testosterone administration to castrated rats not only prevented the fall but stimulated 10-formyltetrahydrofolate synthetase. The present data are discussed in relation to a direct or indirect effect of testosterone on enzymes involved in folate metabolism.
ADRENOCORTICAL FUNCTION IN FOETAL, NEONATAL AND YOUNG PIGS
Authors: DVOŘÁK M. 
Published: December 2008

SUMMARY
Absolute and relative adrenal weight, blood plasma concentrations of 17-hydroxycorticosteroids and their production in vitro on incubation of adrenal slices with corticotrophin (ACTH), were measured in foetal pigs, piglets and older pigs. These criteria all indicated that adrenocortical activity was highest on the day of birth. It developed intensely in about the last 10 days of intra-uterine life. After birth it decreased progressively with age, approaching the adult level after weaning in the second month of life. The adrenal cortex of pigs of all developmental stages investigated in this study was capable of responding markedly to stimulation with ACTH. No significant differences in adrenocortical activity were found between sexes up to 90 days of age.
PERIPHERAL PLASMA PROGESTERONE DURING PREGNANCY AND THE OESTROUS CYCLE IN THE TAMMAR WALLABY, MACROPUS EUGENII
Authors: LEMON MEREDITH 
Published: December 2008

SUMMARY
Progesterone or progestin concentrations were measured in the peripheral plasma of the tammar wallaby (Macropus eugenii) during pregnancy and the oestrous cycle, using a competitive protein-binding method. In common with most other members of the marsupial family Macropodidae, the tammar has a gestation period slightly shorter than one oestrous cycle, and the occurrence of pregnancy does not affect the time of onset of the following oestrus. This study was an attempt to obtain direct evidence for the common assumption that most macropodid marsupials secrete the same amounts of ovarian hormones during pregnancy as they do during the oestrous cycle. The effect on progesterone levels of ovariectomy and removal of the corpus luteum was also studied to discover whether an extra-ovarian source of progesterone exists during pregnancy. Circulating levels of both total plasma progestins and progesterone are very low compared with other mammalian species—less than 1 ng/ml at all stages of the reproductive cycle. An increase in plasma progesterone concentration, apparently of ovarian origin, occurs before birth and/or oestrus, and this may possibly be associated with parturition. The plasma progestin concentration during pregnancy, and that of progesterone during the last 10 days of pregnancy, were significantly greater than during the oestrous cycle.
OESTRADIOL LEVELS IN THE PERIPHERAL BLOOD OF COWS DURING THE OESTROUS CYCLE
Authors: SHEMESH M. , AYALON N. , LINDNER H. R. 
Published: December 2008

SUMMARY
Changes in the peripheral plasma level of oestradiol during the bovine oestrous cycle were determined by a competitive protein-binding assay, following chromatographic purification of the steroid. Oestradiol concentration increased during the 3 days preceding oestrus and attained its peak value [17 ± 1·9 (s.e.m.) ng/100 ml] 4 h before oestrous behaviour could be detected. The level declined steeply during the day of oestrus to reach a nadir (0·8 ± 0·11) before the time of ovulation. A minor rise was observed on day 4 and a more sustained increase on days 10–13, with a peak on day 11 (8·1 ± 3·6). Comparison with published data on luteinizing hormone (LH) levels suggests that the pre-oestrous surge of oestradiol precedes the pre-ovulatory surge of LH in the cow.
THE OCCURRENCE OF TESTOSTERONE AND 5α-DIHYDROTESTOSTERONE IN THE SUBMAXILLARY SALIVARY GLAND OF THE BOAR
Authors: BOOTH W. D. 
Published: December 2008

SUMMARY
Testosterone and 5α-dihydrotestosterone were extracted from the submaxillary salivary glands of boars at different ages, but were not detected in these glands of the female pig. After purification by thin-layer and paper chromatography the steroids were identified by gas—liquid chromatography and combined gas—liquid chromatography—mass spectrometry. In the submaxillary gland of the mature boar, a high concentration of androgen (> l μg/100 g) was found, and the concentration of 5α-dihydrotestosterone was two to four times higher than testosterone. Immediate steroid precursors of testosterone which are found in boar testis were not isolated. The isolation of the two potent androgens, and the known occurrence of 16-unsaturated C19 steroids in the boar submaxillary gland, shows that there is a biochemical sexual dimorphism in this gland of the pig, which is primarily under the influence of testicular hormones.
PROTEIN SYNTHESIS IN DIFFERENT HYPOTHALAMIC AREAS DURING THE SEXUAL CYCLE IN RATS: INFLUENCE OF CASTRATION
Authors: MOGUILEVSKY J. A. , CHRISTOT JANINE 
Published: December 2008

SUMMARY
In-vitro incorporation of l-[3H]phenylalanine into proteins of the anterior, middle and posterior hypothalamus was measured in female rats given androgen soon after birth and in castrated rats. The results were compared with control animals during the sexual cycle.
Protein synthesis in the anterior hypothalamic area was higher during pro-oestrus than during oestrus and dioestrus, and lower in dioestrous than in oestrous rats. Castrated rats showed a similar rate of incorporation in this area as in the oestrous group. Protein synthetic activity in the anterior hypothalamus of androgenized rats was as low as in normal rats during dioestrus.
The highest radioactivity in the proteins of the posterior hypothalamus was found in oestrous rats. The androgenized group showed a rate of incorporation significantly higher than in dioestrus and pro-oestrus, but lower than during oestrus. Castration significantly increased the rate of incorporation of labelled amino acid into protein of the posterior hypothalamic area, as compared with the specific activity found in dioestrous and pro-oestrous groups.
EFFECT OF PORCINE, SALMON AND HUMAN CALCITONIN ON URINARY EXCRETION OF SOME ELECTROLYTES IN SHEEP
Authors: BARLET J. P. 
Published: December 2008

SUMMARY
Purified porcine and salmon calcitonin and synthetic salmon and human calcitonin were infused at the rate of 20 MRC mu./kg/h over a 96 h period in intact male lambs. Every calcitonin preparation significantly increased the urinary excretion of inorganic phosphorus, sodium, potassium and calcium, while the urinary excretion of magnesium was always significantly inhibited. Similar significant effects were observed with purified porcine calcitonin in thyroparathyroidectomized lambs supplemented with thyroxine. Oxidation of calcitonin with performic acid completely abolished its effects on plasma calcium and on the kidney. It is concluded that, when used at physiological doses, in sheep calcitonin has an important effect on urinary excretion of inorganic phosphorus, sodium and magnesium.
DIRECT MEASUREMENT OF SODIUM UPTAKE BY TOAD BLADDER MUCOSAL CELLS
Authors: FERGUSON D. R. , SMITH M. W. 
Published: December 2008

SUMMARY
A technique is described by which the unidirectional influx of sodium into toad bladder mucosal cells can be measured over short periods.
The uptake of sodium, which is linear over a 60 s contact period, changes in a non-linear way when the external sodium concentration is varied from 5 to 115mm.
Vasotocin applied to the serosal surface increases significantly the influx of sodium; amiloride applied to the mucosal surface inhibits influx. This is true whether high or low concentrations of sodium are used to bathe the mucosal surface.
The kinetics for the unidirectional influx of sodium provide direct evidence that the passage of sodium into this tissue is by some means other than simple diffusion.
DEVELOPMENT OF A RADIOIMMUNOASSAY FOR CANINE LUTEINIZING HORMONE
Authors: BOYNS A. R. , JONES GWYNETH E. , BELL E. T. , CHRISTIE D. W. , PARKES M. F. 
Published: December 2008

SUMMARY
A double antibody radioimmunoassay for canine luteinizing hormone (LH) was devised. The assay can measure immunoreactive LH in the peripheral plasma of the normal male and female dog. An increase in hormone concentration was found on the 2nd day of oestrus in the female. Ovariectomy raised plasma concentrations of the hormone to levels greater than those observed during oestrus. The administration of LH-releasing factor induced a rapid increase in the plasma concentrations of LH.
TEMPORAL EFFECTS OF PARATHYROID HORMONE ON SERUM AND URINARY CALCIUM IN THE HAMSTER
Authors: BIDDULPH D. M. , GALLIMORE L. B. 
Published: December 2008

SUMMARY
The temporal aspects of calcium addition to blood and renal conservation of calcium were compared in fasted, parathyroidectomized (PTX) hamsters after a single, intravenous injection of parathyroid hormone (PTH). Injection of 110 units of hormone rapidly stabilized urinary excretion of calcium at normal (sham-PTX) levels during a following 3-h period in contrast to the progressive and rapidly occurring hypercalciuria in animals without hormone replacement. Serum calcium concentrations increased rapidly after hormone replacement, rising 3 mg/100 ml within the first 2 h. No further increase was detected after 2 h with a significant decrease in concentration apparent between 3 and 4 h after injection of hormone. Nephrectomy, performed at intervals during the first 2-h period, resulted in significantly increased serum calcium concentrations by 4 h relative to animals with kidneys during the first 2-h period. The magnitude of this increase was directly related to the length of time kidneys were absent during the first 2 h after injection of hormone. These findings indicate that, in the hamster, the effects of PTH on the addition of calcium to blood and conservation of calcium by the kidney occur simultaneously and are both of very short duration (2 to 3 h). These short-lived effects of PTH in this species seem to be due, at least in part, to the participation of a renal influence.
INFLUENCE OF HEMITHYROIDECTOMY ON ENDOGENOUSLY LABELLED THYROXINE AND TRI-IODOTHYRONINE IN RATS
Authors: EMRICH D. , von zur MÜHLEN A. , LINDNER J. , ZIMMERMANN H. D. , BECKMANN R. 
Published: December 2008

SUMMARY
In order to investigate the influence of thyroid-stimulating hormone (TSH) on the ratio of newly synthesized thyroxine( T4):tri-iodothyronine (T3), hemithyroidectomy was performed on rats maintained on an iodinerich diet. One and two weeks after the operation the concentration of TSH increased in the plasma. As a result, the weight of the residual lobes and their thyroidal uptake of 131I/mg increased and significant histological signs of increased function in the remaining lobes were observed. The most prominent effect was a significant alteration of the ratio of newly synthesized T4:T3 in favour of T3, both in the thyroid and plasma. Four weeks after the operation, when the residual lobes weighed 57% more than those in the controls, the alterations decreased or returned to normal. The total hormone concentration in the plasma (measured as protein-bound 127I) and the oxygen consumption of the animals remained unchanged during the entire study. These findings support the hypothesis that alteration of the production and secretion ratio of T4:T3 induced by TSH might act as another regulatory factor, if a hormone deficiency originates in the peripheral cells. The results show also that changes of the T4:T3 ratio induced by TSH occur in animals on an iodine-rich diet.
PATHWAYS FOR ANDROGEN SYNTHESIS IN VITRO BY THE TESTES OF JAPANESE QUAIL (COTURNIX COTURNIX JAPONICA)
Authors: NAKAMURA TAKAO , TANABE YUICHI 
Published: December 2008

SUMMARY
The microsomal fraction of testicular tissue from Japanese quail (Coturnix coturnix japonica) was incubated with 4-14C-labelled pregnenolone, progesterone, 17α-hydroxyprogesterone, androstenedione, dehydroepiandrosterone and testosterone and [7-3H]17α-hydroxypregnenolone in a medium containing either NAD or NADPH. The metabolic products were identified by their mobilities on thin-layer chromatograms, derivative formation after oxidation and acetylation of the metabolites, and recrystallization to constant specific activity.
Three pathways for testosterone formation by the testes are suggested by the results: the first via progesterone, 17α-hydroxyprogesterone and androstenedione; the second via 17α-hydroxypregnenolone, dehydroepiandrosterone and androstenedione; and the third via 17α-hydroxypregnenolone, dehydroepiandrosterone and androst-5-ene-3β,17β-diol.
DISTRIBUTION OF SOLUBLE PROTEINS IN THE MAMMALIAN NEUROHYPOPHYSIS AND THEIR CROSS-SPECIES REACTIVITY WITH ANTI-NEUROPHYSIN
Authors: ELLIS H. K. , WATKINS W. B. , EVANS J. J. 
Published: December 2008

SUMMARY
Pituitary glands were collected from a selection of 22 domestic and exotic mammalian species. The soluble proteins extracted from the neurohypophyses were characterized by horizontal starch-gel electrophoresis at pH 8·1. Those species which were closely related phylogenetically, e.g. fallow deer and muntjac deer, pig and hippopotamus, dog and coatimundi, and members of the primates, had similar and in some cases identical protein profiles. The ability of proteins extracted from the starch-gel to cross-react immunologically with an antiserum raised against porcine neurophysin-II was determined by microimmunodiffusion. Using this technique for the identification of neurophysins in conjunction with osmotic stimulation experiments, it was found that the number of major neurophysins present in the mammalian neurohypophyses studied varied from one in the guinea-pig and hedgehog to four in man. The concept of multiple neurophysins is discussed.
THE TENTATIVE IDENTIFICATION OF THREE NEUROPHYSINS FROM THE RAT POSTERIOR PITUITARY GLAND
Authors: WATKINS W. B. 
Published: December 2008

SUMMARY
Acetone-dried rat posterior pituitary glands were extracted with 0·1mhydrochloric acid and the soluble proteins fractionated by Sephadex gel exclusion and ion exchange chromatography. Three proteins had chromatographic and biochemical properties expected of neurophysins and also cross-reacted immunologically (as demonstrated by microimmuno-diffusion and -electrophoresis in agarose) with an anti-serum raised against porcine neurophysin-II. The three proteins were named neurophysin-I, -II and -III in order of their electrophoretic mobility on starch-gel and accounted for approximately 8, 70 and 22% respectively of the total neurophysin present in the gland. The assignment of the major rat posterior pituitary lobe protein as a neurophysin (neurophysin-II) is confirmed by its ability to bind oxytocin and [8-arginine]-vasopressin. A minimum molecular weight of 10056 was calculated for neurophysin-II from its amino acid analysis and based upon the presence of one molecule of methionine and one molecule of tyrosine per molecule of protein. The stoicheiometry of the neurophysins relative to the neurohypophysial hormones is discussed.
INITIAL OBSERVATIONS ON PINEALECTOMIZED FERRETS KEPT FOR LONG PERIODS IN EITHER DAYLIGHT OR ARTIFICIAL ILLUMINATION
Authors: HERBERT J. 
Published: December 2008

SUMMARY
Removal of the pineal gland from ferrets kept entirely in daylight prevented the appearance of the normal annual oestrous rhythm. Animals were operated upon in the autumn; that is, at the start of their anoestrum. Oestrus in pinealectomized ferrets began at the usual time the following spring, as in control-operated and normal animals. However, during the second year after operation, pinealectomized ferrets came into oestrus 20–30 weeks after controls. Mean intervals between onsets of successive oestrous periods were: pinealectomized, 73·8 weeks (4 animals); control-operated, 52·9 weeks (7 animals); and normal animals, 52·5 weeks (10 animals). The duration of the oestrous period was not altered by removing the pineal.
Three other pinealectomized ferrets kept in artificial photoperiods (14 h light: 10 h darkness) showed an oestrous rhythm indistinguishable from those pinealectomized and kept in daylight, whereas four controls that had also been put into artificial light showed greatly prolonged oestrous periods lasting more than a year.
These experiments indicate that the pineal is concerned with timing the annual breeding season of ferrets in natural daylight as well as in artificial illumination. The anterior pituitary gland of pinealectomized ferrets seems unresponsive to either natural or artificial light under the conditions used in these studies. The duration of oestrus may be self-limited, but can be prolonged if the pineal gland is stimulated by the artificial 'long day'.
GONADAL HORMONES AND THE CONTROL OF OVULATION IN THE GUINEA-PIG
Authors: DONOVAN B. T. , LOCKHART A. N. 
Published: December 2008

SUMMARY
The release of ovulating hormone after acute treatment with gonadal steroids, or corpus luteum removal on different days of the oestrous cycle, was studied in the guinea-pig. Injection of 25, 50 or 100 μg oestradiol or 2·5 mg progesterone on day 13 of the cycle had no effect upon gonadotrophin secretion as judged by follicular histology, but markedly altered the sizes of the corpora lutea of the previous ovulation. Treatment with oestradiol on day 14 did not elicit gonadotrophin secretion. However, administration of the same hormones to animals given 10 μg oestradiol benzoate 24 h earlier caused ovulation or follicular luteinization. Progesterone (2·5 mg) appeared least effective in stimulating gonadotrophin release; 25 μg oestradiol were more effective when given at 12.00 h than at 24.00 h but treatment with both hormones caused ovulation when given at either time of day. Luteal volumes were not affected. Removal of corpora lutea during the second half of the cycle advanced the time of expected ovulation to day 15 or earlier when the procedure was carried out on days 8 or 9, but not on days 10–13. It is concluded that 4–5 days must elapse between the fall in plasma progesterone level associated with corpus luteum regression and the release of ovulating hormone.
LIPOLYSIS AND ADENOSINE 3′,5′-CYCLIC MONOPHOSPHATE IN ADIPOSE TISSUE OF THE NEW ZEALAND OBESE MOUSE
Authors: LOVELL-SMITH C. J. , SNEYD J. G. T. 
Published: December 2008

SUMMARY
Isolated fat cells from young New Zealand obese mice (NZO/Bl) showed an impaired rate of glycerol release in response to isoprenaline. Old animals showed an increased rate of glycerol release.
The impaired lipolysis in young animals may be caused by failure of the adenosine 3′,5′-cyclic monophosphate level to rise normally when isolated fat cells are treated with isoprenaline. It is proposed that the impaired lipolysis in young NZO/Bl mice is important in the development of obesity.
RAPIDLY-LABELLED RNA IN THE MOUSE MAMMARY GLAND BEFORE AND DURING LACTATION
Authors: BANERJEE D. N. , BANERJEE M. R. 
Published: December 2008

SUMMARY
Linear sucrose density gradient analysis showed that the synthesis of rapidly-labelled high molecular weight RNA was virtually absent in the mammary glands of virgin mice. The rapidly-labelled RNA was first evident in the mammary gland in pregnancy and was also present during lactation. The bulk of this newly-made nuclear RNA sedimented as 45S and 32S fractions after a 15-min [3H]uridine pulse period in vivo. No labelled 18S RNA was detectable in the nuclear fraction after the 15-min pulse but it was present in the cytoplasm, suggesting that the 18S RNA migrates to the cytoplasm almost immediately after its formation. Thirty minutes after injection of [3H]uridine, the initial radioactivity of the 45S region migrated to the 32S fraction and a labelled 28S peak was also present in the cytoplasmic RNA at 60 min, suggesting that the processed 28S ribosomal RNA in the mammary gland began to migrate to the cytoplasm between 30 and 60 min after the nuclear synthesis of the precursor molecule.
MEASUREMENT OF PLASMA RENIN-SUBSTRATE IN MAN
Authors: TREE MALCOLM 
Published: December 2008

SUMMARY
Values of plasma renin-substrate concentration in man vary widely according to the method of measurement used. Potential sources of variation have been tested and, as far as possible, excluded in the method described here.
Blood was diluted rapidly in an angiotensinase-inhibitor solution containing EDTA and phenanthroline; plasma was separated by centrifugation and the renin-substrate in the specimen was hydrolysed by renin to angiotensin I which was identified as such by chromatography and radioimmunoassay. Angiotensin I was used as a standard to determine the amount of angiotensin formed on incubation. Use of angiotensin II for a standard, as in other methods, led to falsely low values of plasma renin-substrate concentration. Recovery of added substrate was 94%.
Changes of plasma renin-substrate concentration in some physiological and pathological states are reported briefly.