bluuebunny/crossref_metadata_2025_split huggingface dataset:
A HORMONAL ASSESSMENT OF BOVINE PARTURIENT PARESIS: EVIDENCE FOR A ROLE OF OESTROGEN
Authors: HOLLIS B. W. , DRAPER H. H. , BURTON J. H. , ETCHES R. J. 
Published: December 2008

A comparative assessment was made of the hormonal control of calcium homeostasis in eight dairy cows which developed parturient paresis and in seven normal animals from the same herd. Plasma levels of calcium, phosphorus, magnesium, free hydroxyproline, 25-hydroxycholecalciferol (25-OHD), 1,25-dihydroxycholecalciferol (1,25-(OH)2D), parathyroid hormone, calcitonin, prolactin and oestrogen were monitored from 30 days prepartum to 15 days post partum.
Prepartum levels of plasma calcium, hydroxyproline and calcitonin were depressed in the paretic animals, and plasma levels of phosphorus and oestrogen were elevated. Plasma levels of 25-OHD remained stable in both groups, whereas levels of 1,25-(OH)2D, parathyroid hormone and prolactin rose sharply at parturition.
Plasma hydroxyproline, an index of bone resorption, began to rise 2 days prepartum in the control cows but not until 2 days post partum in the paretic cows. The data indicate that bone resorption was inhibited in the paretic group at the onset of lactation, and that a decreased capacity for bone resorption is a major factor in the susceptibility of some cows to this disease.
The failure of the paretic animals to resorb bone was not associated with an inability to synthesize the calcium-mobilizing hormones parathyroid hormone or 1,25-(OH)2D, or to regulate the production of calcitonin. However, hypocalcaemia in the affected animals was associated with a significantly higher plasma level of oestrogen (a known inhibitor of bone resorption) in the immediate prepartum period. Following parturition, plasma levels of oestrogen fell rapidly and active bone resorption ensued in the paretic animals.
CONVERSION OF TESTOSTERONE TO 5β-REDUCED METABOLITES IN THE NEUROENDOCRINE TISSUES OF THE MATURING COCKEREL
Authors: MASSA R. , SHARP P. J. 
Published: December 2008

The metabolism in vitro of [4-14C]testosterone to reduced derivatives was studied in the pituitary gland, hypothalamus and hyperstriatum dorsale of cockerels from hatch to sexual maturity. The most important metabolites were 5β-dihydrotestosterone (5β-DHT), 5β-androstane-3α,17β-diol (5β-3α-diol) and 5β-androstane-3β,17β-diol. Trace amounts of androstenedione and, in the hypothalamus only, of 5α-DHT were also detected. The amounts of 5β-reduced metabolites produced by all neuroendocrine tissues declined progressively during maturation with the steepest fall occurring during the first 2 weeks after hatch. At all ages studied, 5β-DHT was formed to the greatest extent by the hyperstriatum dorsale, to a lesser extent by the hypothalamus and in the smallest quantities by the pituitary gland. In the three tissues studied, 5β-3α-diol tended to be formed to the greatest extent by the pituitary gland.
No significant change was observed in the metabolism of testosterone to reduced derivatives in any of the neuroendocrine tissues after castration.
It was concluded that in the cockerel, unlike the rat, a change in 5α-reductase activity of the neuroendocrine tissues is unlikely to be involved in the initiation of puberty. The physiological significance of 5β-reductase activity in the neuroendocrine tissues remains to be established.
EFFECTS OF AN ANTI-OESTROGEN, TAMOXIFEN (ICI 46,474), ON LUTEINIZING HORMONE RELEASE AND OVULATION IN THE HEN
Authors: WILSON SUSAN C. , CUNNINGHAM F. J. 
Published: December 2008

The role of oestradiol in the regulation of LH release in the hen was studied by use of the anti-oestrogen, tamoxifen (ICI 46,474).
Intramuscular injection of laying hens with 2 or 4 mg tamoxifen on 2 successive days delayed or prevented the occurrence of the preovulatory release of LH and ovulation expected on day 3. Ovulation could be restored by i.v. injection of 20 pg LH releasing hormone (LH-RH). Tamoxifen at a dose of 1 mg affected neither the timing of the preovulatory release of LH nor ovulation. Treatment with 2 or 4 mg tamoxifen on 2 successive days reduced the effectiveness of an i.m. injection of progesterone to stimulate a release of LH. Injection of 1, 2 or 4 mg tamoxifen on 2 successive days significantly raised basal levels of LH in the blood at 24 h after the last injection. This was associated with an increase in the capacity of the pituitary gland to respond to an injection of synthetic LH-RH by a release of LH.
These studies suggest that oestradiol has at least two roles in the regulation of LH release in the hen. First, it maintains a low basal level of LH in the blood by reducing the responsiveness of the pituitary gland to LH-RH. Secondly, oestradiol has a facilitative role in the mechanism by which progesterone stimulates the preovulatory release of LH.
EFFECT OF ANAESTHESIA ON THE NEGATIVE FEEDBACK ACTION OF GONADAL STEROIDS ON GONADOTROPHIN SECRETION IN THE OVARIECTOMIZED GUINEA-PIG
Authors: KILPATRICK M. J. , DONOVAN B. T. 
Published: December 2008

The effects of urethane or sodium pentobarbitone anaesthesia on the feedback effects of oestradiol or progesterone on gonadotrophin secretion in the ovariectomized guinea-pig have been investigated. In the control experiments in which no steroids or vehicles were given the concentration of LH and FSH in samples of peripheral blood collected at intervals of 15 min varied in a random episodic manner. The mean level of LH was significantly greater in sodium pentobarbitone- and urethane-anaesthetized animals when compared with conscious animals, and in the conscious animals there was a progressive fall in mean LH level during the course of serial sampling. This effect was not observed in anaesthetized animals.
Oestradiol benzoate (2 μg s.c.) inhibited LH secretion in conscious animals and in those anaesthetized with sodium pentobarbitone, but not in urethane-anaesthetized guinea-pigs. Progesterone (200 μg s.c.) progressively depressed plasma LH levels in conscious and urethane-anaesthetized animals, but not in guinea-pigs anaesthetized with sodium pentobarbitone. The effect of anaesthesia was the converse of that observed with oestradiol treatment.
Significant changes in FSH secretion were not observed under any experimental conditions.
These findings point to the existence of a mechanism in spayed guinea-pigs that restrains LH secretion, the action of which is reduced by anaesthesia and modified by oestradiol and progesterone.
DELAY OF THE SELECTIVE SURGE OF FOLLICLE-STIMULATING HORMONE BY BOVINE FOLLICULAR FLUID DURING THE PERIOD OF OVULATION INDUCED BY HUMAN CHORIONIC GONADOTROPHIN IN DIOESTROUS RATS
Authors: SASAMOTO SHUJI , OTANI TSUYOSHI , SHIROTA MARIKO 
Published: December 2008

When bovine follicular fluid (BFF) was given i.p. three times at intervals of 3 h from 17.00 to 23.00 h to dioestrous rats pretreated with 10 i.u. human chorionic gonadotrophin (HCG) at 17.00 h on the day of dioestrus (day 0), the selective surge of FSH at 02.00 h on day 1 was suppressed in a dose-dependent manner. Three i.p. injections of 0·5 ml BFF completely suppressed the FSH rise in plasma at 02.00 h on day 1, but the time of premature ovulation induced by HCG was not altered. In these animals treated with HCG and BFF, however, the selective surge of FSH occurred as a delayed surge from 05.00 to 23.00 h on day 1. After seven i.p. injections of 0·5 ml BFF (from 17.00 h on day 0 to 11.00 h on day 1) the delayed surge of FSH took place from 17.00 h on day 1 to 11.00 h on day 2, indicating that waning of BFF with a decrease in inhibin secretion by the ovaries may be responsible for the delay of the FSH surge.
The next spontaneous ovulation in rats treated with HCG and BFF occurred on day 5, a delay of ovulation of 1 day compared with animals given HCG on day 0 with no BFF. Initiation of follicular maturation or selection of growing follicles for the succeeding oestrous cycle appeared to be retarded by the delay of the FSH surge in HCG- and BFF-treated animals.
The pituitary content of FSH in animals given HCG and three i.p. injections of 0·5 ml BFF increased strikingly until 11.00 h on day 1, when the delayed FSH surge was already in progress. These results suggest that the ability of the pituitary gland to synthesize FSH is high during the period of ovulation.
PLASMA LEVELS OF ANDROSTENEDIONE, EPITESTOSTERONE, TESTOSTERONE AND OESTROGENS IN COWS AT PARTURITION
Authors: MÖSTL E. , MÖSTL K. , CHOI H. S. , DREIER H. K. , STÖCKL W. , BAMBERG E. 
Published: December 2008

The concentration of total unconjugated oestrogens in the peripheral plasma of cows increased from 2·00±0·20 (s.e.m.) ng/ml 7 days before to 3·87±0·50 ng/ml 1 day before parturition and declined to values below 0·30 ng/ml on day 2 post partum. The concentrations of androstenedione, epitestosterone and testosterone remained approximately constant at 0·90±0·10,0·92±0·08 and 0·40±0·20 ng/ml respectively during the last week of pregnancy. After parturition the concentration of the three androgens declined rapidly.
Similar to data obtained in goats we did not find a marked increase in androgen levels in the peripheral blood of cows before parturition.
MAINTENANCE OF SECRETION OF CALCIUM AND MAGNESIUM DURING INFUSIONS OF PARATHYROID HORMONE TO LACTATING GOATS
Authors: HOVE K. , TOLLMAN R. 
Published: December 2008

Hourly secretion of calcium and magnesium by goat mammary glands was studied following infusions of bovine parathyroid hormone (PTH) into the mammary artery in amounts (6–15 ng/kg per min) giving rise to levels of PTH in mammary venous blood commonly observed during spontaneous hypocalcaemia (2·4–13 μg/l). In two series of experiments a 3 h infusion of PTH was given. The first series was carried out at a normal level of plasma calcium, while the availability of calcium was increased by a 20 h infusion of CaCl2 in the other series. No changes in mammary secretion of calcium or magnesium could be observed during the hormone infusions. A decrease in the urinary excretion of calcium occurred, thus demonstrating the activity of the infused PTH.
In a third experiment an 18·5 h infusion of PTH (6 ng/kg per min) into the mammary artery was given to study possible effects of a more prolonged increase of PTH concentrations. This infusion caused a gradual increase in plasma levels of calcium. Average concentrations of calcium in milk increased slightly (about 5% in both glands (P<0·05). The hourly yield of milk was not significantly changed in the infused gland after 18·5 h of PTH infusion. A small but significant increase occurred in the non-infused gland. Yields of magnesium were not influenced by the infusion of PTH. It was concluded that losses of calcium into milk are independent of the PTH concentration in the circulation.
EARLY INHIBITION BY PROGESTERONE OF OESTROGEN-INDUCED ORNITHINE DECARBOXYLASE ACTIVITY IN THE CHICK OVIDUCT AND RAT UTERUS
Authors: LEVY CARLOS , MEŠTER JAN , BAULIEU ETIENNE-EMILE 
Published: December 2008

The oestradiol-induced increase of ornithine decarboxylase (ODC) activity in the 'withdrawn' chick oviduct was found to be inhibited by progesterone. In vitro (2 h at 37 °C), progesterone (1 μmol/l) abolished the effect of oestradiol (20 nmol/l), progesterone alone having no effect. In vivo, progesterone (3 mg/kg) inhibited ∼70% of the augmentation of ODC activity induced in the oviduct within 2 to 6 h of treatment with oestradiol benzoate (1·5 mg/kg). Administration of progesterone alone in vivo caused an increase in the ODC activity, the maximum level measured after 6 h being similar to that obtained when the chicks were given both oestrogen and progesterone.
In the rat uterus in vivo progesterone also inhibited the rise of ODC activity caused by oestradiol, ∼70% inhibition being observed between 2 and 6 h after treatment. Progesterone alone had no effect on uterine ODC activity during this period.
PLASMA CONCENTRATIONS OF OXYTOCIN AND INTRAMAMMARY PRESSURE IN GOATS DURING MANUAL STIMULATION OF THE UDDER AND HAND-MILKING
Authors: MOSDØL G. , SJAASTAD Ø. V. , BLOM ANNE KRISTINE 
Published: December 2008

The concentration of oxytocin in the jugular venous plasma of goats was studied by radioimmunoassay and the intramammary pressure measured upon manual stimulation of the udder and hand-milking. Before stimulation the concentrations of oxytocin were close to the limit of detection, about 3 pg/ml. Manual stimulation of the udder resulted in a shortlasting increase in plasma oxytocin in 11 out of 18 experiments carried out on nine goats. There were large variations between and within individuals in the magnitude of the oxytocin increase. Hand-milking was in general an efficient stimulus for oxytocin release. In experiments in which manual stimulation had led to a large increase in plasma oxytocin, the ensuing hand-milking did not lead to a further increase. In three experiments neither manual stimulation of the udder nor hand-milking resulted in any significant increase in plasma oxytocin.
The intramammary pressure increased upon manual stimulation of the udder and/or hand-milking in four out of six experiments. There was, in general, a close time-relationship between changes in intramammary pressure and plasma oxytocin.
SECRETION OF ALDOSTERONE IN THE MONOTREME MAMMAL, TACHYGLOSSUS ACULEATUS
Authors: SERNIA CONRAD , McDONALD I. R. 
Published: December 2008

The secretion of aldosterone and its regulation by ACTH and angiotensin II were investigated in conscious, unrestrained echidnas with chronically implanted jugular catheters. Aldosterone was measured by radioimmunoassay after extraction and isolation by silica gel thin-layer chromatography.
The mean concentration of aldosterone in blood plasma of five male and three female echidnas was only 5·4 ± 1·3 (s.e.m.) pg/ml. During stress (surgery and anaesthesia) the mean concentration increased to 17·6 ± 3·8 pg/ml. Infusion of β1–24 ACTH at a rate of 5 units/kg per h increased the plasma concentration of aldosterone to 53·8± 9·8 pg/ml. Infusion of angiotensin II at rates of 100 and 500 ng/kg per h also increased aldosterone concentration, to 24·1 ± 8·6 and 35·1 ± 10·9 pg/ml respectively.
Production and metabolic clearance rates were measured by the constant-rate infusion of [3H]aldosterone and found to be 5·0 ± 2·2 ng/kg per h and 14·3 ±1·3 ml/kg per min respectively in the unstimulated state. Production rate was increased approximately sevenfold by the infusion of ACTH at 5 units/kg per h and fourfold and sixfold by infusion of angiotensin II at 100 and 500 ng/kg per h respectively. Metabolic clearance decreased following the infusion of ACTH or angiotensin II. Direct measurement of secretion rate by the collection of adrenal venous blood from three anaesthetized, laparotomized echidnas gave values of 9·4, 15·6 and 8·8 mg/kg per h.
It is concluded that the adrenal secretion of aldosterone in the echidna is extremely low compared with that in other mammals but the response to stress, ACTH and angiotensin II indicates the presence of typical mammalian control mechanisms for its secretion.
A PERMANENT PREPARATION ALLOWING MEASUREMENTS OF SECRETION OF PARATHYROID HORMONE IN CONSCIOUS GOATS
Authors: HOVE KNUT 
Published: December 2008

A preparation for estimations of rates of secretion of parathyroid hormone (PTH) in conscious goats is described. The procedure involved surgical isolation of a thyroid with its indwelling parathyroid gland, leaving the blood supply intact. Permanent access to the arterial and venous supplies of the preparation was secured by exteriorization of the jugular vein and carotid artery in skin-covered loops. The remaining parathyroids were removed leaving the isolated parathyroid gland as the only source of the hormone. For the seven goats operated on, the preparation has worked satisfactorily from the start in five and also in the remaining two after a reoperation to cut an accessory venous drainage. The loops have been catheterized repeatedly for extended periods of time and the preparation has proved useful for periods of up to 3 years.
Secretion of PTH was measured in one goat at two consecutive parturitions. In late pregnancy, secretion rates of 0·7–0·9 ng/kg per min were observed when the dietary calcium intake was adequate. In the first weeks of lactation, secretion increased to 1·2–1·5 ng/kg per min when the intake of calcium was adequate and to 2·0–2·2 ng/kg per min when calcium intake was inadequate. Reductions in calcium intake led to increased rates of secretion of PTH both during pregnancy and during lactation. The results indicate that the preparation may be useful in the study of changes in PTH secretion both acutely and in connection with long-term studies of dietary adaptations of the calcium metabolism.
CHARACTERISTICS OF OESTROGEN-INDUCED REFRACTORINESS IN OVINE CERVICAL SECRETION
Authors: ADAMS N. R. 
Published: December 2008

Ovariectomized ewes treated with oestradiol benzoate (OB) had a reduced cervical mucus response to subsequent treatment with OB. This refractory effect was observed 48 h after a single dose of OB, but could be postponed until 72 h by a second dose of OB at 24 h. This postponement did not occur in animals which were recovering from previously induced refractoriness. Less mucus was recovered from refractory ewes, and it had an increased proportion of dry matter and normal Spinnbarkeit.
Pretreatment of ewes with 10 mg progesterone for 10 days decreased the proportion of dry matter and increased the Spinnbarkeit of mucus collected after stimulation with OB. This change was different from that produced by increasing the dose of OB. Progesterone given to ewes after 10 days treatment with OB had a detectable effect on cervical mucus, but it did not specifically decrease refractoriness. The cervix provides a convenient site for studying oestrogen-induced refractoriness in the ewe, without possible confusion by any effects of progesterone.
CLASSIFICATION OF MENSTRUAL CYCLES IN PRE- AND PERIMENOPAUSAL WOMEN
Authors: METCALF MARY G. , DONALD R. A. , LIVESEY J. H. 
Published: December 2008

Urine for the analysis of pregnanediol, oestrogens, FSH and LH, was collected weekly from 50 normal menstruant women. Twenty of these women were aged ≥ 40 years and had a history of regular menstrual cycles; they are termed premenopausal. The other 30 reported a recent break in regular cyclicity and are termed perimenopausal. All menstrual cycles observed in the premenopausal women were ovulatory in type and 25–30 days in length. The 124 cycles observed in the perimenopausal women were 18–260 days in length (median, 29 days), with 52% of the ovulatory type. To describe this diversity, a systematic classification is proposed based on (1) the excretion of pregnanediol in the 12 days preceding menstruation (classes I–IV), (2) gonadotrophin output (categories A–E, and L), and (3) the length of the menstrual cycle in days. The premenstrual surge of pregnanediol was greatest in class I cycles and diminished progressively until it became undetectable in class IV. Gonadotrophin excretion was lowest in category A cycles and increased progressively until all levels were within the postmenopausal range by category E. In cycles of category L only LH (and not FSH) was raised.
In the perimenopausal women 37 cycles included episodes of high gonadotrophin excretion (categories C–L), a phenomenon which was not seen in the premenopausal women. These cycles were usually longer than 50 days and were often anovulatory in type (classes II—IV). Typically they began with the high gonadotrophin levels and the low oestrogens which characterize the postmenopausal state, and ended after a rise in oestrogen output to levels ≥ 70 nmol/24 h. It is concluded that 'anovulatory' cycles and cycles in which there are 'postmenopausal' levels of FSH and LH are common in the perimenopause and that they are rare in premenopausal women.
LACK OF EFFECT OF ANGIOTENSIN ON LEVELS OF CYCLIC AMP IN ISOLATED ADRENAL ZONA GLOMERULOSA CELLS FROM THE RAT
Authors: BELL J. B. G. , TAIT J. F. , TAIT S. A. S. , BARNES G. D. , BROWN B. L. 
Published: December 2008

The effects of pure [Asp1, Val5]- and [Asn1, Val5]-angiotensin II and also [des-Asp1, Ile5]-angiotensin II (angiotensin III) on cyclic AMP and steroid outputs by dispersed rat capsular cells, comprising 95% zona glomerulosa and 5% zona fasciculata cells, have been studied.
The results showed that [Asp1, Val5]- and [Asn1, Val5]-angiotensin II, at doses between 2·5 × 10−1 1 and 2 × 10−4 mol/l, which produced typical increases in steroidogenesis, failed to increase output of cyclic AMP. This lack of effect was observed whether the nucleotide was measured by radioimmunoassay or by adrenal binding protein and under the same conditions in which 8·4 mm-K+ consistently increased the output of cyclic AMP. Instead the results showed a small but significant decrease in cyclic AMP output with angiotensin II. Similar results were obtained with incubations for 60 rather than 120 min and with medium containing a concentration of 5 or 40 g bovine serum albumin/l. Although the levels of cyclic AMP were generally higher in the presence of the phosphodiesterase inhibitor, 3-isobutyl-l-methylxanthine, the same decrease relative to basal outputs was observed with angiotensin II which increased steroidogenesis. Angiotensin III also failed to increase output of cyclic AMP at doses (2·5×10−9 to 2·5×10−6 mol/l) which produced increases in steroid output equivalent to those obtained with angiotensin II.
These results indicate that angiotensin II and III can act through a cyclic AMP- independent mechanism.
INFLUENCE OF INSULIN AND GLUCAGON ON SECRETION OF GROWTH HORMONE IN GROWING DUCKS (ANAS PLATYRHYNCHOS)
Authors: FOLTZER C. , HARVEY S. , STROSSER M. T. , MIALHE P. 
Published: December 2008

An inverse age-related pattern of GH secretion has been identified in immature ducks between 2 and 9 weeks of age, the plasma level of GH falling progressively from 30–40 ng/ml at 2 weeks of age to the adult level (< 10 ng/ml) by 9 weeks of age. This decrease in GH secretion was not accompanied by any age-related changes in the concentrations of plasma immunoreactive insulin or glucagon-like immunoreactivity or in plasma glucose or free fatty acid level.
In 4- to 6-week-old ducklings the intravenous infusion of insulin (2·5 or 10 mu./kg per min for 30 min) and glucagon (0·1 or 0·5 μg/kg per min for 30 min) induced some inhibition of GH secretion, independently of changes in blood glucose level. These results suggest that although insulin and especially glucagon have direct effects on GH secretion in the duck, maturational differences in pancreatic function are unlikely to be causally related to the decrease in GH secretion during growth.
EFFECT OF NON-ESSENTIAL AMINO ACIDS ON FETAL RAT PANCREATIC GROWTH AND INSULIN SECRETION IN VITRO
Authors: MILNER R. D. G. , DE GASPARO M. 
Published: December 2008

Fetal rat pancreatic rudiments explanted on day 14 of gestation were grown for 6 days in organ culture in medium containing glucose (5·5 or 16·5 mmol/l) and essential amino acids (3·5 or 13·1 mmol/l). Non-essential amino acids (alanine, aspartic acid, asparagine, glycine, proline and serine) were added to the culture medium in a number of combinations and at a maximum total concentration of 4·0 mmol/l. At the end of the period of culture rudiments were compared for DNA content, insulin concentration and quantitative morphology. The release of insulin from the rudiments was tested during 6-h incubations on day 6 of culture.
Enrichment of the culture medium with any combination of non-essential amino acids had a slight or no effect on the growth or cellular composition of the rudiment or insulin release from it. Addition of all the non-essential amino acids to medium containing 16·5 mmol glucose and 13·1 mmol essential amino acids/l caused a dramatic reduction in the net insulin accumulation by the cultured rudiment. Combinations of non-essential amino acids in which one or more were omitted did not have the same effect. These findings suggest that fetal rat pancreas grown in vitro may require both essential and non-essential amino acids for the full expression of insulin biosynthesis and secretion.