bluuebunny/crossref_metadata_2025_split huggingface dataset:
DEVELOPMENT OF PATHWAYS OF INSULIN SECRETION IN THE RABBIT
Authors: MILNER R. D. G. , LEACH F. N. , ASHWORTH M. A. , CSER A. , JACK P. M. B. 
Published: December 2008

SUMMARY
Insulin release was studied in vitro using pieces of pancreas from rabbits of between 24 days gestational age and 6 weeks postnatal age. When allowance was made for the fraction of pancreas which was endocrine, 16·5 mm-glucose caused increasing stimulation of insulin release as development advanced and 3·3 mm-glucose caused a similar rate of secretion at all ages. Secretion was not significantly influenced by insulin destruction in the incubation medium. Glucagon (5 μg/ml) did not stimulate insulin secretion from 24-day foetal pancreas but did so postnatally. Theophylline (1 mmol/l) stimulated insulin release at all ages and was equipotent on 24-day foetal pancreas in 3·3 or 16·5 mm-glucose. The stimulation of insulin release from 24-day foetal pancreas by 1 mm-theophylline occurred in the absence of extracellular glucose, pyruvate, fumarate and glutamate and in the presence of mannoheptulose and 2-deoxyglucose (each 3 mg/ml). Adrenaline (1 μmol/l) and diazoxide (250 μg/ml) abolished or attenuated the stimulation of insulin release by glucose, leucine plus arginine or theophylline from 24-day foetal, 1 day and 6 weeks postnatal pancreas. The stimulation of insulin release from 6-week-old pancreas by 1 mm-barium was blocked by adrenaline and diazoxide but the effect became less with increasing immaturity.
The experimental results illustrate some of the ways in which insulin secretion by the rabbit β cell changes as a function of development and draw attention to the importance of glucose and cyclic adenosine monophosphate in this process.
THE EFFECTS OF DEXAMETHASONE AND INDOMETHACIN ON THE OUTCOME OF PREGNANCY IN THE RABBIT
Authors: CHALLIS J. R. G. , DAVIES I. J. , RYAN K. J. 
Published: December 2008

SUMMARY
Pregnant rabbits were treated with indomethacin (8–10 mg/kg/day) or dexamethasone (1·2–1·8 mg/kg/day) during late gestation. The effects of these treatments on the concentrations of progesterone and prostaglandin F (PGF) in the peripheral plasma, and the outcome of gestation were studied. Treatment with indomethacin significantly prolonged the length of gestation (P < 0·01) compared with control, untreated animals. In these treated animals, the plasma progesterone levels declined at a similar time to that in control rabbits but the increase in systemic PGF normally seen during late pregnancy was reduced. Dexamethasone treatment reliably induced premature delivery within 3–6 days. The plasma progesterone concentration fell rapidly during the first 24 h of dexamethasone administration, but in no animal was this associated with a significant increase in the plasma levels of PGF.
These results are consistent with the suggestion that prostaglandins are involved in the normal initiation of parturition in the rabbit. They do not support the hypothesis that the effect of dexamethasone on the length of gestation is mediated through an increase in the production of prostaglandin F.
PHYSIOLOGICAL VARIATION IN ABUNDANCE OF OESTROGEN SPECIFIC HIGH-AFFINITY BINDING SITES IN HYPOTHALAMUS, PITUITARY AND UTERUS OF THE RAT
Authors: GINSBURG M. , MACLUSKY N. J. , MORRIS I. D. , THOMAS P. J. 
Published: December 2008

SUMMARY
High-affinity binding of [2,4,6,7-3H]oestradiol-17β has been studied in cytosols prepared from hypothalami, pituitaries and uteri of female rats killed at different stages of the oestrous cycle, and in cytosols prepared from the hypothalami and pituitaries of male rats. In all cases the equilibrium dissociation constant of reaction was of the order of 10−10 mol/l. The number of available high affinity sites per tissue (n) varied with physiological state. In females, n fluctuated with the oestrous cycle. In hypothalamus and pituitary, n fell by about 60 and 40% respectively in pro-oestrus, replenishment occurred during oestrus but could be delayed by phenobarbitone administration during the afternoon of pro-oestrus. In the uterus, n varied biphasically, there being peaks during dioestrus and oestrus, and troughs at pro-oestrus and metoestrus. The numbers of available sites at metoestrus were 12·5 × 109, 10·6 × 1010 and 24·4 × 1010 for hypothalamus, pituitary and uterus respectively. In male rats, values for n were similar to those obtained for females at pro-oestrus (n/hypothalamus = 6·8 × 109, n/pituitary = 4·2 × 1010). Binding was oestrogen specific in all the tissues studied.
THE ROLE OF SHORT DAYS IN THE TERMINATION OF PHOTOREFRACTORINESS IN FEMALE CANARIES (SERINUS CANARIUS)
Authors: STEEL ELIZABETH , FOLLETT B. K. , HINDE R. A. 
Published: December 2008

SUMMARY
Photorefractory intact female canaries were exposed to a photoperiod of 8 h light: 16 h darkness (8L: 16D) for 0, 2, 4 or 6 weeks before photostimulation with 14L:10D for 4 weeks. Photoresponsiveness was measured in terms of plasma immunoreactive LH, ovary and oviduct weights, follicle size and nest-building behaviour. Birds not exposed to 8L:16D were unresponsive to photostimulation while those exposed for 6 weeks to 8L: 16D were as fully photosensitive as females similarly treated immediately before their first breeding season. Birds exposed for 2 or 4 weeks to 8L:16D responded to subsequent photostimulation but were not as responsive as birds exposed to short days for 6 weeks. Positive correlations between the two ovarian parameters and between these ovarian parameters and oviductal weight existed in all groups exposed to short days, but not in birds not exposed to short days. It is concluded that the restoration of photosensitivity at the end of the refractory period is a function of the number of short days experienced; about 6 weeks of short days are needed for its completion.
In another experiment photorefractory birds exposed for 6 weeks to short days without subsequent photostimulation, although potentially photosensitive, were indistinguishable (in terms of the above parameters) from refractory birds kept on long days for the same period; in these birds refractoriness was not broken.
CONTROL OF SEBACEOUS GLAND FUNCTION IN THE RAT BY α-MELANOCYTE-STIMULATING HORMONE
Authors: THODY A. J. , SHUSTER S. 
Published: December 2008

SUMMARY
The effect of α-MSH on sebum secretion and preputial gland weight was examined in intact, castrated and hypophysectomized male rats and in hypophysectomized rats receiving treatment with either testosterone propionate (TP) or progesterone. After treatment with α-MSHMSH for 2 weeks, increases in sebum secretion occurred in intact, castrated and hypophysectomized rats, but larger responses were found in the hypophysectomized rats that had received treatment with either TP or progesterone, suggesting that α-MSH acts synergistically with TP and progesterone to stimulate sebum secretion. α-Melanocyte-stimulating hormone also increased preputial gland weight in intact rats, but there was no response after castration and only a small response after hypophysectomy. However, when the hypophysectomized rats received simultaneous treatment with either TP or progesterone, α-MSH increased preputial gland weight.
It is suggested that α-MSH acts directly on the sebaceous glands to stimulate lipogenesis and, together with steroid hormones, may have an important role in controlling sebaceous gland function in the rat and other hairy mammals. With the evolution of hair, certain of the MSH peptides may have lost their significance as pigmentary hormones and have developed a sebotrophic function. For this reason, it might be more appropriate to refer to these peptides as the 'sebotrophins'.
CHANGES IN THE CONCENTRATION OF FOLLICLE-STIMULATING HORMONE IN PLASMA DURING DEVELOPMENT IN THE GUINEA-PIG
Authors: DONOVAN B. T. , TER HAAR M. B. , LOCKHART A. N. , PEDDIE M. J. 
Published: December 2008

SUMMARY
The concentration of FSH in the plasma of guinea-pigs from day 50 of gestation to day 45 of postnatal life was assayed by a radioimmunological procedure utilizing a cross-reaction with the NIAMDD S6 antiserum to rat FSH.
At 68 days of gestation the mean plasma FSH concentration of female foetuses was greater than that of the males, although the concentrations in the two sexes were similar on day 50 of gestation. Maternal levels remained consistently low throughout gestation. Postnatally there were no marked changes in plasma FSH levels through to maturity, although a transient rise in the male occurred over the first 3 days after birth.
Gonadectomy on days 0, 5, 10, 15, 25 or 35 of postnatal life, or when adult, resulted in a significant increase in plasma levels of FSH within 10 days. The rise in plasma FSH concentration was greater in males than in females at all ages, although a larger increase was observed in females spayed at 5 or 10 days of age than at other times.
DEMONSTRATION OF A SPECIFIC CYTOSOL RECEPTOR IN THE NORMAL AND HYPERPLASTIC CANINE PROSTATE FOR 5α-ANDROSTANE-3α, 17α-DIOL
Authors: EVANS C. R. , PIERREPOINT C. G. 
Published: December 2008

SUMMARY
A specific receptor protein has been demonstrated for 5α-androstane-3α, 17α-diol in cytoplasmic extracts of normal and hyperplastic canine prostates. The receptor molecule, with a sedimentation coefficient of 4–5S, has been identified by the use of sucrose gradient centrifugation of tissue fractions which had been labelled in vitro with tritiated 5α-androstane-3α, 17α-diol. The receptor showed a relatively high affinity for this compound whereas binding could not be demonstrated with other labelled C19 steroids. In addition binding of tritiated 5α-androstane-3α, 17α-diol was not affected by the presence of 50-fold excesses of other C19 steroids.
PLASMA HORMONES AND PITUITARY LUTEINIZING HORMONE IN THE RAT DURING THE EARLY STAGES OF PREGNANCY AND AFTER POST-COITAL TREATMENT WITH TAMOXIFEN (ICI 46,474)
Authors: WATSON J. , ANDERSON F. B. , ALAM M. , O'GRADY J. E. , HEALD P. J. 
Published: December 2008

SUMMARY
Plasma levels of oestradiol-17β, progesterone and luteinizing hormone (LH) and pituitary levels of LH have been measured during the first 6 days of pregnancy, in normal rats and in rats receiving two doses of Tamoxifen (trans-1-(p-β dimethylamino-ethoxyphenyl)-1-2 diphenylbut-1-ene) on day 2 of pregnancy.
In normal rats oestradiol rose strongly from early on day 3 to reach a peak concentration between 22.00 h on day 3 and 08.00 h on day 4. Progesterone concentrations rose from day 2 to reach peak values on day 3–4. In animals in which implantation was delayed 20–24 h by administration of Tamoxifen (0·1 mg/kg) orally on day 2 the increased level of plasma oestrogen was also delayed by 20 h. A higher dose of Tamoxifen (0·2 mg/kg) on day 2, which prevented implantation, completely eliminated the increase in plasma oestradiol. Neither dose of Tamoxifen affected the levels of progesterone.
In both normal rats and rats treated with 0·1 mg Tamoxifen/kg, plasma LH levels declined by day 3 while pituitary levels rose steadily. There was no detectable change in either plasma or pituitary LH levels, accompanying the increase in plasma oestradiol in the normal rats. In animals receiving Tamoxifen (0·2 mg/kg), plasma LH increased to a maximum by day 4 while levels of pituitary LH decreased.
The results show that the oestrogen ' surge' of early pregnancy, occurs normally about midnight on day 3 and not late on day 4 as previously thought. It is considered that the plasma oestradiol peak in early pregnancy results from an increased release of FSH rather than an increased release of LH. Tamoxifen may owe part of its antifertility action to a capacity to inhibit the synthesis of oestradiol from progesterone.
PRODUCTION OF SPECIFIC ANTISERA TO FOLLICLE-STIMULATING HORMONE AND OTHER HORMONES
Authors: LYNCH S. S. , SHIRLEY A. 
Published: December 2008

SUMMARY
Specific high titre antisera were raised in three out of four rabbits injected with 100/μg each of a highly purified FSH preparation by the multi-site intradermal immunization technique. High titre antisera were also raised to LH, TSH, HCG, and the α sub-unit of HCG. Immunization with human GH- and LH-releasing hormone did not result in such high titre antisera. The implications of the results are discussed.
REVERSAL BY PROGESTERONE OF PHENOBARBITONEBLOCKADE OF OVULATION IN THE PREPUBERTAL RAT PRIMED WITH PREGNANT MARE SERUM GONADOTROPHIN
Authors: McCORMACK C. E. , STRAUSS W. F. 
Published: December 2008

SUMMARY
In immature female rats injected with PMSG at 30 days of age (day 30), ovulation occurs between the hours of 02.00 and 03.00 on day 33. If progesterone is injected at 10.00 h on day 32, the onset of ovulation is advanced by 1–2 h. In rats that were not given progesterone, ovulation was blocked by phenobarbitone sodium administered on day 32 before 13.50 h. However, pretreatment with progesterone at 10.00 h caused ovulation to occur in spite of phenobarbitone treatment at 13.50 h. An early release of ovulatory gonadotrophin from the anterior pituitary gland cannot completely account for progesterone's capacity to reverse the blockade of ovulation by phenobarbitone, because when phenobarbitone treatment was advanced by 2–4 h, ovulation still occurred in most progesterone-treated rats.
UPTAKE OF 125I-LABELLED HUMAN PLACENTAL LACTOGEN AND HUMAN PLACENTAL LACTOGEN BY THE TISSUES OF NORMAL AND LACTATING RATS
Authors: REDDY S. , WATKINS W. B. 
Published: December 2008

SUMMARY
The rate of clearance from the circulation and uptake into tissues of radioactive label was studied after i.v. injection of 125I-labelled human placental lactogen (HPL) into rats at various stages of pregnancy. The half-life was obtained for the disappearance of the trichloroacetic acid-precipitable material from the plasma. The half-life, t½(S), calculated over the first 5 min after injection of the hormone was 5·4 ± 1·1 (s.d.) min, while a half-life, t½(L), of 27·9 ± 2·3 min was obtained from the decay period of 15–35 min.
In the non-pregnant and pregnant rat the highest ratio of the radioactivity in an organ to that in the blood was 12–14:1 in the kidney. That the kidney is mainly involved in the uptake of exogenous HPL is further confirmed by the application of the histochemical immunoperoxidase technique. Human placental lactogen was localized in the cells of the proximal tubules of the cortex and to a lesser extent in the tubular lumen and the tubules of the medulla region.
Uptake of HPL in vivo also occurs in the mammary gland tissue of the post-partum rat and reaches a maximum uptake between 15 and 30 min after injection of the hormone. Furthermore, specific uptake of HPL was observed on the alveolar cell membranes after the incubation of paraffin-embedded sections of formalin-fixed mammary gland and subsequent treatment by the peroxidase-labelled antibody method.
These findings support the work of others who have demonstrated the presence of specific membrane receptors in the mammary gland for hormones with prolactin-like activity.
CHANGES IN THE ENDOMETRIUM OF MICE AFTER THE INDUCTION OF IMPLANTATION BY ACTINOMYCIN D
Authors: FINN C. A. , DOWNIE JENIFER M. 
Published: December 2008

SUMMARY
Actinomycin D can induce a small number of implantations in pregnant mice undergoing progestin-induced delayed implantation following ovariectomy. However, the response of the uterus to the blastocyst is considerably retarded compared with the response observed when implantation is precipitated by oestradiol.
With the electron microscope the attachment reaction between the trophoblast and uterine epithelium is evident about 48 h after administration of the drug. However, the differentiation of the luminal surface of the epithelial cells in areas of uterus distant from a blastocyst (2nd stage of closure), which normally accompanies implantation, and can be induced by oestradiol in progesterone-treated animals, is not seen. Thus actinomycin D, although allowing implantation to proceed, does not completely mimic the actions of oestradiol on the progesterone-treated uterus.
DISCREPANCY BETWEEN RADIOIMMUNOASSAY AND RADIOLIGAND-RECEPTOR ASSAY OF LUTEINIZING HORMONE RELEASED IN VITRO BY PITUITARY TISSUE FROM MALE RATS OF DIFFERENT AGES
Authors: SHARPE R. M. , SHAHMANESH M. , ELLWOOD M. G. , HARTOG M. , BROWN P. S. 
Published: December 2008

SUMMARY
Anterior pituitary glands from male rats aged 21, 40, 60 or 95 days were incubated in medium containing 0, 2 or 20 ng luteinizing hormone-releasing hormone (LH-RH)/ml. Incubates were assayed for LH by radioimmunoassay (RIA), by the radioligand-receptor assay (RLA) using testicular homogenates as the source of receptor and, in some instances, by the ovarian ascorbic acid depletion assay (OAAD). Irrespective of the dose of added LH-RH, glands from rats aged 40 and 60 days always showed a higher release of LH, as determined by RLA, than glands from animals aged 21 or 95 days. Measurement by RIA showed a similar pattern to RLA in the basal release of LH, but in the presence of LH-RH showed little difference in LH release by glands from rats aged 40, 60 or 95 days. The LH release caused by the higher concentration of LH-RH was always greater when measured by RLA than by RIA. Assay of comparable incubates by OAAD showed close agreement with RLA estimates in four incubations (mean index of discrimination 1·07; range 0·86–1·18) and consistent disagreement with RIA estimates (1·64; range 1·38–1·99). In contrast to the results with incubates, homogenates of pituitary glands from male rats of various ages showed close agreement of estimates by RLA, RIA and OAAD. These results suggest that RIA underestimates the LH-RH-stimulated release of LH in vitro from the male rat pituitary during some stages of sexual maturation.
THE PRODUCTION OF CARDIAC HYPERTROPHY BY TRI-IODOTHYROACETIC ACID
Authors: SYMONS CECIL , OLSEN E. G. J. , HAWKEY C. M. 
Published: December 2008

SUMMARY
Severe cardiac hypertrophy has been produced experimentally in rats by long-term, lowdose treatment with tri-iodothyroacetic acid. The dose used was insufficient to cause any apparent systemic or metabolic effect. It is suggested that similar iodinated substances in the blood in man, resulting from normal or abnormal thyroid hormone catabolism, may be causally related to some forms of cardiomyopathy.
THE PROLIFERATIVE RESPONSE OF THE COAGULATING GLAND OF THE CASTRATED MOUSE UNDER CONTINUOUS ANDROGEN STIMULATION: AN EXPERIMENTAL AND COMPUTER SIMULATION MODEL
Authors: MORLEY A. R. , APPLETON D. R. , WRIGHT N. A. , ALISON M. R. 
Published: December 2008

SUMMARY
The proliferative response of the coagulating gland of the castrated male mouse has been examined during continuous treatment with testosterone propionate. Fourteen days after castration, s.c. daily injections of testosterone propionate were begun. Mitotic (Im) and labelling (IL) index values were obtained at 3 h intervals for up to 100 h after the initial injection. These showed a biphasic response, in which IL reached a maximum at 30 and 70 h, and Im at approximately 45 and 75 h. Fraction-labelled mitoses (FLM) curves were begun 24, 48, and 72 h after the first androgen injection. In each curve the first wave of labelled mitoses rose to 100% and showed a square form indicating little spread in the durations of the G2 and S phases. Values of 7·5, 1·3 and 0·7 h, were obtained for the durations of DNA synthesis (ts), the post-synthetic period (tG2) and of mitosis (tm) respectively. In none of the FLM curves was it possible to demonstrate a second wave of labelled mitoses and direct measurement of the cell cycle time (Tc) was not obtained. Continuous tritiated thymidine labelling indices revealed that after a latent period of 25 h, DNA synthesis began and labelling rose rapidly to 80% by 45 h and then more slowly to 95% by 97 h. Cell population changes during androgen stimulation estimated from measurements of total glandular DNA indicated that the number of cells present in the glands remained constant during the first 30 h after stimulation and thereafter increased to approximately 2·3 times the original value.
The data are compared with a mathematical model which assumes that the cell population of castrated mice when stimulated passes from a G0 compartment through successive waves of DNA synthesis and mitosis. After each cell division the cells may leave or remain in the proliferative cycle. This model has been subjected to computer simulation using the cell cycle parameters obtained in the kinetic experiments. There was good agreement between the simulation and experimental results in the Im and IL curves, continuous labelling, and total cell number experiments. The simulation of FLM curves was less successful. Although the first wave of labelled mitoses was clearly seen the model predicts a distinct second wave of labelled mitoses. It is concluded that this does not appear because of variation in the duration of G1.
EVIDENCE FOR A POSSIBLE FOETAL CONTROL OF PROSTAGLANDIN RELEASE FROM THE PREGNANT RAT UTERUS IN VITRO
Authors: PARNHAM M. J. , SNEDDON J. M. , WILLIAMS K. I. 
Published: December 2008

SUMMARY
The release of prostaglandin-like material and the spontaneous contractions of individual horns from the pregnant rat uterus in vitro have been studied on day 22 of pregnancy – the expected day of delivery. Removal of foetuses (retaining placentae in utero) from one or both uterine horns on day 16 or 17 significantly reduced prostaglandin F release and spontaneous activity. Rats which had been made unilaterally pregnant after ligation of one uterine horn, exhibited a decrease in prostaglandin F output from both horns. Uterine activity and prostaglandin release were increased in quiescent uteri by the addition of arachidonic acid (5 μg/ml) or phospholipase A (160 mu./ml); these effects were abolished by indomethacin (20 μg/ml). However, the stimulation of uterine activity by PGF2α (30–60 ng/ml) was not affected by indomethacin. It is concluded that the release of prostaglandins from the pregnant rat uterus in vitro at term is related to the presence of viable foetuses.