bluuebunny/crossref_metadata_2025_split huggingface dataset:
EFFECTS OF AN INTERMITTENT LIGHTING SCHEDULE ON THE TIME OF EGG-LAYING AND THE LEVELS OF LUTEINIZING HORMONE, PROGESTERONE AND CORTICOSTERONE IN THE PLASMA OF THE DOMESTIC HEN
Authors: DUPLAIX MICHELE , WILLIAMS JOHN , MONGIN PIERRE 
Published: December 2008

The use of a complex lighting schedule consisting of five blocks of light and five alternating periods of darkness every 24 h completely abolished the normal pattern of egg-laying characteristic of the domestic hen. Animals tended to lay continuously and not in clutch sequences. Ovipositions were not restricted to an 8- to 10-h period of the day, instead they occurred at any time of the solar day with slightly more occurring during the hours of darkness.
The preovulatory discharge of LH was not restricted to an 8- to 10-h 'open period' and the interval between the peak values of LH in the plasma and the time of lay of the corresponding egg was 32·3 h, i.e. identical to the interval found using a normal lighting schedule of 14 h light: 10 h darkness. There were some indications that minor fluctuations in the concentrations of LH in plasma occurred rhythmically with the changes in illumination, but the concentrations of progesterone showed only a single, preovulatory peak.
The concentrations of corticosterone in the plasma were high and showed marked fluctuations but this did not appear to affect either the levels of progesterone or the time of ovulation.
COMPARISON OF BINDING OF 1,25-DIHYDROXYCHOLECALCIFEROL AND 25-HYDROXYCHOLECALCIFEROL IN INTACT TISSUE AND CYTOSOL PREPARATIONS FROM BONE AND OTHER TISSUES IN THE FETAL RAT
Authors: MUDHER S. , BRAIDMAN I. P. , HALES M. , ANDERSON D. C. 
Published: December 2008

The binding of 1,25-dihydroxy[3H]cholecalciferol (1,25(OH)2[3H]D3) and 25-hydroxy-[3H]cholecalciferol (25(OH)[3H]D3) in vitamin D target and non-target tissues from the fetal rat has been compared using two incubation conditions, each followed by charcoal adsorption and sucrose gradient centrifugation. In intact tissue incubations, equilibrium with the ligand was established overnight at 4 °C before cell disruption. In pre-prepared cytosol incubations, cytosol was prepared from the tissue before incubation with ligand. With both ligands, more sterol was bound during pre-prepared cytosol incubation despite the use of fourfold lower ligand concentrations. With 1,25(OH)2[3H]D3, intact tissue incubation led to most marked binding with calvaria, which was preferentially displaced by unlabelled 1,25(OH)2D3; radioactivity sedimented almost entirely as a 3·2–3·7S peak (peak I) which was completely displaced by 100-fold excess 1,25(OH)2D3 but only partially by 25(OH)D3. Fetal small intestine, another putative target tissue, also showed displaceable binding of 1,25(OH)2D3; however, this was much less marked, and was not accompanied by a significant peak on sucrose gradients. Other fetal tissues (large intestine, kidney, skin, brain and heart) did not show significant displaceable binding of 1,25(OH)2D3 in intact tissue. In contrast, when intact calvaria, kidney, brain and heart were incubated with 25(OH)D3 they all showed significant displaceable binding to a 5·0–5·7S peak (peak II).
Incubations with pre-prepared cytosol confirmed ubiquitous binding of both sterols to peak II with the notable exception of that from small intestine; this peak II binding was preferential for 25(OH)D3, and is believed to be to the plasma vitamin D-binding protein (DBP). Only calvaria showed an additional peak I under these conditions, and even here it was dwarfed by peak II. We conclude that, at least in fetal bone, intact tissue incubations selectively detect receptor (peak I) binding of 1,25(OH)2D3 in the presence of the DBP. The substantial increase in binding of both sterols to peak II in pre-prepared cytosol compared with that in the same fetal tissues incubated intact suggests that some DBP is intracellular and therefore relatively inaccessible to extracellular sterol. The apparent absence of both peak I and peak II binding of cytosol from fetal small intestine merits further investigation.
DIVERGENT PHASES OF RESPONSIVENESS OF THYROID HORMONE BIOSYNTHESIS TO EXOGENOUS THYROID-STIMULATING HORMONE IN THE POSTNATAL RAT
Authors: STOLC V. , KNOPP J. 
Published: December 2008

We have found that the thyroids of postnatal rats respond to administration of thyroid-stimulating hormone (TSH) by significant changes in iodine metabolism and hormone biosynthesis. The specific activity of iodine in thyroxine (T4) and 3,5,3′-tri-iodothyronine (T3) was always higher than that in monoiodotyrosine (MIT) and di-iodotyrosine (DIT) in the TSH-treated rats. The highest sensitivity to TSH in this regard was observed during week 2 of life and again at sexual maturity. The lowest thyroid response to TSH with respect to biosynthesis of MIT, DIT, T4 and T3 was observed in weeks 3 and 4 of life rather than in the younger or older rats. However, the specific activities of MIT and DIT were not changed after TSH administration to 2-day-old pups.
Increase in thyroid weight and in the specific activity of iodine in the thyroid occurred in almost all of the TSH-treated rats. In contrast, the thyroid iodine content decreased after TSH administration, except in the 2-day-old pups. The specific activity of iodine in the thyroid was highest in the 2-day-old pups and then abruptly declined during week 1 of life and continued to do so until maturity. The thyroid protein content decreased during the first 2 weeks of life but thereafter it was increased in the rats receiving TSH.
We conclude that thyroid responsiveness to TSH in terms of thyroid hormone metabolism has several distinct phases in postnatal rats: the first phase, during week 1 of life is characterized by the highest specific activity of iodinated compounds in the thyroid and by the highest percentage representation of T4 and T3; the second, during week 2 of life, by the highest thyroid response to TSH; the third, during weeks 3 and 4 of life, by the lowest thyroid response to TSH; and the last phase in mature rats is characterized by a relatively low specific activity of iodinated compounds in the thyroid but by a good response to TSH stimulation
PROLACTIN RELEASE IN RESPONSE TO INFUSION OF ISOTONIC OR HYPERTONIC SALINE
Authors: BLISS D. J. , LOTE C. J. 
Published: December 2008

In ketamine-anaesthetized rats, the infusion of 10 ml either isotonic (0·9%) or hypertonic (3·0%) saline over a 30-min period was associated with a decrease in the secretory activity of the anterior pituitary prolactin cells (assessed morphologically by electron microscopy), and a decrease in the serum prolactin concentration (determined by radioimmunoassay). The hypertonic saline infusion significantly (P<0·01) increased the serum osmolality whereas the isotonic infusion did not.
The results indicated that prolactin release is reduced in response to volume expansion regardless of whether the fluid load is isotonic or hypertonic, and suggested that, in the rat, the hormone may play a role in volume regulation rather than osmoregulation.
OVARIAN FOLLICULAR DEVELOPMENT LEADING TO FIRST OVULATION AND ACCOMPANYING GONADOTROPHIN LEVELS AS STUDIED IN THE UNILATERALLY OVARIECTOMIZED RAT
Authors: MEIJS-ROELOFS H. M. A. , OSMAN P. , KRAMER P. 
Published: December 2008

Ovarian follicular development was studied in the rat during a 15-day period preceding first ovulation. Ovaries were obtained by unilateral ovariectomy performed at various ages and the rats were allowed to live until the day after first ovulation. The timing of this ovulation was compared with that in unoperated, paired control rats of the same age. For estimation of gonadotrophin levels, blood was taken from the paired control rats at the time when experimental rats were unilaterally ovariectomized. There was no evidence that unilateral ovariectomy had any influence on the timing of first ovulation. Therefore the ovaries obtained could be dated in relation to first ovulation, and follicular growth during the final prepubertal period could thus be studied in a genuine developmental sequence. Results revealed that follicular growth leading to first ovulation starts at ±8 days before this ovulation; follicular processes taking place are comparable to those found during the adult 5-day cycle but proceed more slowly.
Gonadotrophin concentrations accompanying the follicular dynamics and measured at 11·00 h, showed a clear tendency for FSH concentrations to decrease with increasing age, i.e. approaching first ovulation. Concentrations of LH did not show a definite pattern and were generally low, although in some individual rats relatively high LH values (> 100 μg/l) were found in the period of 5–3 days before first ovulation.
CONCENTRATIONS OF TESTOSTERONE IN NEONATAL MALE RATS SUCKLED NATURALLY AND HAND-FED
Authors: ANDERSON P. J. B. , FATINIKUN A. E. , SWIFT A. D. 
Published: December 2008

Concentrations of testosterone were measured daily in plasma of neonatal male rats from the day of birth for 7 days. It was found that a significant (P <0·001) increase in mean plasma levels of testosterone occurs on day 2 of life, followed by a decrease on day 3. Separation of male rat pups from their mothers on the second day of life for as little as 2 h was associated with a significant (P <0·001) fall in plasma testosterone concentration.
Hand-feeding the pups with a proprietary human milk substitute (milk-replacer) from birth until the expected time of the testosterone peak resulted in no increase in plasma levels of testosterone; inclusion of an antiserum to LH-releasing hormone (LH-RH) in the milk-replacer decreased the testosterone levels as did removing any supposed endogenous LH-RH in the milk replacer. Addition of a highly potent analogue of LH-RH, either in the presence or absence of the LH-RH antiserum, to the milk-replacer resulted in mean plasma levels of testosterone similar to those in naturally suckled rats. Rats fed with human milk showed an increase in plasma levels of testosterone.
It is concluded that the increase in the plasma testosterone concentration found in male rat pups on the second day of life, which may have an important effect on the organization of the brain, is provoked indirectly by LH-RH ingested during suckling.
EFFECT OF HUMAN PLASMA ON THE BIOACTIVITY OF ADRENOCORTICOTROPHIN
Authors: READER S. C. J. , DALY J. R. , ROBERTSON W. R. 
Published: December 2008

The effect of plasma on the bioactivity of ACTH was investigated with the cytochemical section bioassay. Levels of ACTH in normal human plasma were underestimated if the plasma concentration in the incubation medium exceeded 2%, and if the plasma ACTH level was > 2 ng/l. A retrospective analysis of 250 plasma ACTH assays revealed that the ACTH concentration was consistently underestimated in the 1: 100 dilution compared with the 1: 1000 dilution, although not to the extent that any assay would be rejected for non-parallelism. The extent of the underestimation increased as the ACTH concentration increased.
Guinea-pig adrenal sections responded faster to 1: 10 or 1: 50 dilutions of human plasma (containing 2 ng ACTH/l) than to either 1: 100 or 1: 1000 dilutions of that same plasma, or to ACTH (over the range 0·005–5 ng/l) in the absence of plasma. This faster response could also be seen in the absence of plasma by increasing the ACTH concentration above 5 ng/l. It seems that plasma contains factors which potentiate the biological effect of ACTH in the cytochemical assay system.
Adrenal circadian system in young and elderly human subjects: a comparative study
Authors: Touitou Yvan , Sulon José , Bogdan André , Touitou Catherine , Reinberg Alain , Beck Hervé , Sodoyez Jean-Claude , Demey-Ponsart Emilie , Van Cauwenberge Henri 
Published: December 2008

Circadian changes in plasma 18-hydroxy-11-deoxycorticosterone (18-OH-DOC), total and unbound cortisol were studied in four groups: seven healthy young men, six elderly men, six elderly women and six elderly demented patients of both sexes. The daily activities of the subjects were synchronous; blood samples were taken every 4 h and 4 hourly urine samples were collected only from the young men. A circadian rhythm was defined for plasma 18-OH-DOC, total and unbound cortisol in all groups; the secretory patterns of these steroids were parallel, as were the profiles of urinary 18-OH-DOC and unconjugated cortisol. When compared with respect to sex, the 24-h mean level of total cortisol was higher in women; that of unbound cortisol was higher in the three groups of elderly patients than in the young men. No major changes in plasma steroids were observed between elderly demented patients (mainly women) and healthy elderly women. The phasing of total and unbound cortisol showed no major modifications with age, sex or senile dementia. Acrophases of 18-OH-DOC were earlier in elderly patients than in young men. Amplitudes were not modified with sex in elderly patients but were always lower in the demented patients. A circadian rhythm was defined for 18-OH-DOC, unconjugated cortisol, 17-hydroxycorticosteroids (17-OH-CS) and 17-ketosteroids in the urine of the young men. The acrophases of 18-OH-DOC and unbound cortisol were close, as were those of 17-OH-CS and 17-ketosteroids. The lag was short between the acrophases of 18-OH-DOC in plasma and urine and between those of plasma unbound cortisol and urinary unconjugated cortisol; it was much larger between the acrophases of plasma total cortisol and 17-OH-CS.
Thus, the process of ageing, and the possible alterations in the central nervous system which are often seen in normal ageing, induced no major modifications in the temporal organization of adrenocortical function, even in subjects who were very advanced in age.
Modulation of gonadal activity by timed injections of melatonin in pinealectomized or intact ferrets kept under two photoperiods
Authors: Carter D. S. , Herbert J. , Stacey Pamela M. 
Published: December 2008

These experiments investigated the way that the effects of melatonin on gonadal activity of ferrets depended upon either reproductive status or environmental lighting conditions. Melatonin (1 mg/day) injected once daily 8 h into the photoperiod prevented the retiming of oestrus by long photoperiods; oestrus occurred in animals treated in this way at the same time as in controls kept under short non-stimulatory photoperiods of 8 h light: 16 h darkness (8L : 16D). This suggests that the 'intrinsic' timing mechanism was not altered by melatonin. Melatonin injected daily into oestrous ferrets terminated oestrus prematurely when the injection was given either 8 or 14 h after the onset of the photoperiod in animals kept under either long (14L : 10D) or short (8L : 16D) photoperiods, though injections given 14 h after onset were more potent in long (but not short) light periods. Melatonin was equally effective in driving pinealectomized ferrets out of oestrus as it was in intact animals.
Melatonin could also induce as well as terminate oestrus in ferrets, but only if injections were discontinued. Thus, shifting the time of two daily injections from 8 and 11 h after 'lights on' to 14 and 17 h was ineffective, but withdrawal of melatonin from anoestrous ferrets (pinealectomized or intact) reliably induced oestrus 4–6 weeks later, irrespective of the lighting conditions. Withdrawal of oil injections had no effect.
These experiments suggest that melatonin acts on the neural mechanisms resetting the timing of oestrus, rather than by a direct 'anti-gonadotrophic' effect. Furthermore, the effect of changes in duration of photoperiod could not be replicated by simply changing the time of melatonin injections to correspond with the presumed night-time surge of endogenous melatonin. Some of the effects of melatonin on retiming oestrus can only be expressed in the absence of melatonin itself.
Hepatic receptors for insulin and glucagon in relation to plasma hormones and metabolites in pregnant and unmated ewes
Authors: Gill R. D. , Hart I. C. 
Published: December 2008

Glucagon and insulin receptors were examined in relation to plasma concentrations of hormones and metabolites in unmated and in 110- and 140-day pregnant ewes (four animals per group). The concentrations of insulin, growth hormone and non-esterified fatty acids in the circulation, together with the maintenance of body weight, suggested that the animals were in energy surplus. When compared with the unmated group the binding of insulin to isolated hepatocytes increased by 110 days of pregnancy, attaining statistical significance (P < 0·02) after 140 days. Conversely, glucagon binding was reduced by 110 days of pregnancy, also attaining statistical significance (P < 0·02) after 140 days.
The changes in both insulin and glucagon binding were primarily due to changes in the number of receptors on each hepatocyte, although some fluctuations in receptor affinity were also found.
These observations suggested that the number of hepatic insulin and glucagon receptors are altered during the metabolic demands of pregnancy in sheep, but unlike the changes reported during lactation in the ewe and restricted energy intake in the goat, they are not related either to energy deficit or to changes in the concentration of insulin, and probably of glucagon, in the circulation.
Blood–cerebrospinal fluid barrier to arginine-vasopressin, desmopressin and desglycinamide arginine-vasopressin in the dog
Authors: Ang V. T. Y. , Jenkins J. S. 
Published: December 2008

The passage of 125I-labelled arginine-vasopressin (AVP) and its analogues desmopressin (DDAVP) and desglycinamide arginine-vasopressin (DGAVP) into cerebrospinal fluid (CSF) has been studied in the dog. After intravenous injection or infusion of these peptides radioactive sustances were found in the CSF in amounts ranging from 0·5 to 1·4% of the total plasma radioactivity. However, only DDAVP could be identified in the CSF as the unmetabolized peptide. This observation may be related to the long plasma half-life of DDAVP which was found to be 50 min, compared with a half-life of 13 min for AVP and 8 min for DGAVP.
After the intranasal administration of either [3H]AVP or 125I-labelled AVP similar results were obtained. Radioactivity was again present in the CSF but no AVP could be identified. These observations showed that the intranasal route of administration provides no increased access to the CSF.
The existence of a blood–CSF barrier to AVP is confirmed and indicates that the concentrations of the hormone normally found in CSF arise from sources other than the blood.
Effect of Ca2+ deprivation on release of luteinizing hormone induced by luteinizing hormone releasing hormone from female rat pituitary glands in vitro
Authors: de Koning J. , Tijssen A. M. I. , van Dieten J. A. M. J. , van Rees G. P. 
Published: December 2008

Continuous exposure of hemi-pituitary glands from intact female rats to LH releasing hormone (LH-RH) in vitro displayed three phases in the pattern of LH release: during the first hour release of LH was low (first phase response), then it increased to a higher level during the second hour and remained constant during the next 2 h (second phase response), after which there was a refractoriness of LH release (third phase response). The initial phase response of pituitary glands from intact rats was blocked by EGTA (a Ca2+ chelator) but there was a small but significant increase in the rate of LH release during the second phase response. This increase could be prevented by inhibition of protein synthesis by cycloheximide. Cycloheximide and EGTA did not affect basal release of LH by glands from intact rats, neither did EGTA affect the high basal release of LH by glands from ovariectomized rats. However, the LH-RH-induced release of LH from pituitary glands of ovariectomized rats, which did not show the initial phase of low LH release, was completely suppressed by EGTA throughout a 4-h incubation period.
The pattern of LH release stimulated by the combination of N6-monobutyryl cyclic AMP and theophylline (mbcAMP/theophylline) showed an initial phase of low LH release lasting 4 h after which it increased. The magnitude of the effect was small compared with the action of LH-RH. As it did with LH-RH, EGTA completely blocked the initial response, but allowed a small increase in the rate of LH release thereafter; this increase could also be blocked by inhibition of protein synthesis.
Addition of EGTA to media during pretreatment of pituitary glands from intact rats with either LH-RH or mbcAMP/theophylline did not impair the facilitatory effect of these secretagogues on the responsiveness of the glands to subsequent exposure to LH-RH and cycloheximide and normal Ca2+ levels. The restoration of Ca2+ levels after withdrawal neither affected basal nor LH-RH-induced release of LH.
Exclusion of Ca2+ from the media during a 6-h incubation of pituitary glands from intact rats with LH-RH prevented the glands from becoming refractory to subsequent stimulation by LH-RH, which occurs when normal Ca2+ concentrations are present.
The results suggested that extracellular Ca2+ is obligatory for LH release and the induction of refractoriness by LH-RH. In contrast, that part of the action of LH-RH which is cyclic AMP-mediated and protein synthesis-dependent is not affected by withdrawal of extracellular Ca2+.
Molecular composition of human luteinizing hormone: biological and immunological profiles of highly purified preparations after electrofocusing
Authors: Zaidi A. A. , Qazi M. H. , Diczfalusy E. 
Published: December 2008

Five highly purified human pituitary LH preparations (candidate preparations for a new International Reference Preparation (IRP) and coded A to E) and three highly purified commercial preparations (referred to as Kabi I, II and III) were fractionated by electrofocusing on a sucrose density gradient with ampholytes in the pH range of 3·5–10·0 The LH activity was monitored in each of the eluted fractions by an in-vitro bioassay and a radioimmunoassay procedure and the profiles of biological activity and immunoreactivity were compared with those of the first IRP of Human Pituitary Luteinizing Hormone for Immunoassay (code no. 68/40).
The overall recovery of the biological activity after electrofocusing of the nine preparations ranged between 75 and 92% (mean 86%) and was higher (P < 0·05) than that of the immunological reactivity which varied between 71 and 94% (mean 79%).
The profiles of the biological activity and immunological reactivity were in close agreement with each other in all preparations. Significant differences were, however, observed in the distribution of various molecular species between the currently used standard and the eight other highly purified preparations.
The ratios of biological activity (B) to immunoreactivity (I) of preparation B and of the three Kabi preparations were significantly higher than those of the other five preparations, both before and after electrofocusing. After electrofocusing, a slight but significant (P < 0·05) rise in the B/I ratios was observed, suggesting that some biologically inactive immunoreactive material was removed during fractionation. All purified preparations lacked the characteristic 'acidic' human LH species which accompanies FSH and which is abundant in the IRP (69/104) and is also present in aqueous extracts of postmenopausal pituitary glands.
A comparison of the electrofocusing profiles of the nine highly purified preparations with those of human LH from plasma and individual pituitary glands revealed marked differences, suggesting that the methods used for the purification of the hormone significantly altered its molecular composition.