bluuebunny/crossref_metadata_2025_split huggingface dataset:
DEPENDENCE ON PROTEIN SYNTHESIS OF THE N6-MONOBUTYRYL CYCLIC AMP PLUS THEOPHYLLINE MEDIATED RELEASE OF LUTEINIZING HORMONE INDUCED BY LUTEINIZING HORMONE RELEASING HORMONE FROM RAT PITUITARY GLANDS IN VITRO
Authors: DE KONING J. , VAN DIETEN J. A. M. J. , TIJSSEN A. M. I. , VAN REES G. P. 
Published: December 2008

The involvement of cyclic AMP in the action of LH releasing hormone (LH-RH) on LH secretion was studied by incubating pituitary glands from adult female rats on day 2 of dioestrus with 1 mm-N6-monobutyryl cyclic AMP (mbcAMP) and 10 mm-theophylline for periods of up to 10 h. This treatment induced a pattern of LH release similar to that observed in the presence of a low concentration of LH-RH (0·1 ng LH-RH/ml), i.e. an initial 4 h period during which the release of LH was minimal was followed subsequently by an increased rate of release. In this system inhibition of protein synthesis by cycloheximide (25 μg/ml) did not impair the initial response of the pituitary tissue but the increase in the rate of LH release during the second phase of the response was blocked.
Preincubation with mbcAMP and theophylline increased the responsiveness of the pituitary tissue to LH-RH. This action could be prevented by including cycloheximide during the preincubation period, whereas addition of this drug during the incubation with LH-RH no longer impaired the increased responsiveness. The size of the sensitizing action of mbcAMP and theophylline mediated through the induction of protein synthesis was comparable with that of a high concentration of LH-RH. From the absence of a significant change in total LH during the preincubation period, it was concluded that the increased responsiveness was not the result of newly synthesized LH.
The present results suggest a role or roles for cyclic AMP in the secretion of LH induced by LH-RH. Besides an effect on the formation of a factor related to the synthesis of protein, other than LH which has a permissive role in the acute release of LH, cyclic AMP might also be concerned in the secretion process through a pathway which does not involve synthesis of protein.
FAILURE OF SHORT-TERM HYPERPROLACTINAEMIA TO INCREASE THE NUMBER OF GONADOTROPHIN RECEPTORS IN THE RAM TESTIS
Authors: BARENTON BRUNO 
Published: December 2008

Hyperprolactinaemia was induced during March in 2-year-old rams which had regressed testes. Five animals were intravenously infused with prolactin for 3 days at a rate that raised concentrations of prolactin in plasma to levels equivalent to those generally found in summer. Five untreated animals acted as controls.
The treatment did not change plasma levels of LH and FSH and had no effect on testicular content of LH and FSH receptors. These results indicate that prolactin is not directly involved in the acute regulation of gonadotrophin receptors in the ram testis.
PHARMACOKINETICS OF PROGESTERONE IN LAYING AND NON-LAYING HENS (GALLUS DOMESTICUS)
Authors: JOHNSON A. L. , VAN TIENHOVEN A. 
Published: December 2008

The metabolic clearance rate (MCR), volumes of distribution (Vd), production rate (PR) and half-life (t½) of progesterone were measured in laying hens 8 h before, during and 8 h after the preovulatory surge of progesterone, and in non-laying hens (pullets and moulting hens) after a single injection of [1,2,6,7-3H]progesterone. A curve-fitting computer program showed that the data of [3H]progesterone metabolism best fit a two-compartment model. The MCR of non-laying birds (163·2±6·4(s.e.m.) ml/min) was significantly greater than that of laying hens (122·4±6·1 ml/min). The mean PR of progesterone in laying hens measured 8 h before and 8 h after the preovulatory peak of progesterone (42·498±6·509 ng/min per kg0·75) was comparable to that of moulting hens (61·771±14·363 ng/min per kg0·75). However, the PR of progesterone in hens when measured during the preovulatory surge of progesterone (254·335±53·972 ng/min per kg0·75) was significantly greater than 8 h before and 8 h after the surge. There were no significant differences among groups in the t½ of the distribution phase (combined mean, 1·03±0·05 min), biologically active t½ (combined mean, 10·93±0·31 min) or Vd of the central compartment (VdA; combined mean, 609·4±46·7 ml). However, the Vd in the peripheral compartment (VdB) was significantly greater in non-laying birds (combined mean, 3891·3±399·5 ml) compared with that of laying hens (combined mean, 2879·2±154·4 ml). There was no significant difference for MCR (ml/min) and PR (ng/min) of progesterone for non-laying pullets between methods using a single injection or continuous infusion. However, when body weight differences between the two groups of pullets were taken into account and the values adjusted by covariance analysis, the MCR obtained with the continuous infusion method was significantly (P<0·05) higher than the value obtained with the single injection method.
It is concluded that (a) the preovulatory surge of progesterone is the result of an increase in the PR and not of a decrease in the MCR; (b) the lower MCR in laying hens compared with pullets and moulting hens is reflected by a smaller Vd B, likely to be due to the presence of progesterone receptors of higher affinity and/or binding capacity in laying hens and to differences in extraction efficiency by progesterone-metabolizing organ systems; (c) t½ in the hen would appear to be shorter than that reported for mammalian species.
BROMOCRIPTINE AND α-ERGOCRYPTINE DO NOT INHIBIT OXYTOCIN SECRETION IN THE LACTATING RAT
Authors: RUSSELL J. A. , HARRISON D. J. , McNEILLY A. S. 
Published: December 2008

Two experiments were performed to study the effects of bromocriptine and α-ergocryptine on oxytocin secretion in lactating rats. In both experiments, after overnight separation from their litters, rats were injected with either vehicle alone or ergot alkaloid plus vehicle; 4 h later the litters were returned.
In the first experiment the mothers were conscious. Treatment did not affect suckling behaviour, number of stretch reactions or litter weight gain in the first 30 min. Oxytocin injection before the second 30 min period of suckling caused no extra milk to be obtained. In the second experiment the mothers were anaesthetized with ethyl carbamate (1·1 g/kg body weight) at the time of the ergot alkaloid or vehicle injection. Changes in intramammary pressure were recorded during suckling. Ergot alkaloids altered neither the number of milk ejections caused by suckling, nor the proportion of milk ejections equivalent to 0·2 mu. or more oxytocin.
In both experiments treatment with ergot alkaloids suppressed secretion of prolactin. It is concluded that (a) in suppressing lactation, bromocriptine and α-ergocryptine do not inhibit oxytocin secretion as well as prolactin secretion, and that (b) prolactin secretion is not a necessary concomitant of oxytocin secretion.
PROGESTERONE CONCENTRATIONS IN PERIPHERAL PLASMA OF NON-PREGNANT AND PREGNANT GREY SQUIRRELS (SCIURUS CAROLINENSIS)
Authors: TAIT A. J. , POPE G. S. , JOHNSON ELIZABETH 
Published: December 2008

Plasma concentrations of progesterone in non-pregnant female grey squirrels were never greater than 3·2 nmol/l and no significant differences were found between levels in anoestrous, pro-oestrous and oestrous animals. During pregnancy, plasma concentrations of progesterone increased significantly and reached a maximum level of 318 nmol/l at around day 35 of the 44 day period of gestation. After parturition, plasma concentrations of progesterone fell sharply. The corpora lutea of pregnancy began to regress in size at about day 30 of gestation, before the maximum levels of progesterone in the plasma were reached, which suggests that there is an extra-ovarian source of progesterone.
Chromatography of pregnancy plasma extracts showed that no significant amount of 5α-or 5β-pregnane-3,20-dione was present and that progesterone accounted for 90% of the assay-positive material in pregnancy plasma from grey squirrels.
ADRENOCORTICOTROPHIC HORMONE IN THE ANTERIOR AND NEUROINTERMEDIATE LOBES OF THE FETAL RAT PITUITARY GLAND
Authors: CHATELAIN ALAIN , DUPOUY J. P. 
Published: December 2008

The concentration of ACTH in the pars distalis and pars intermedia of the fetal rat hypophysis from days 17–21 of pregnancy was measured with a specific radioimmunoassay and a bioassay using isolated adrenal cells from adult rats.
In both lobes of the pituitary gland, a significant correlation was observed between immunoreactive and bioreactive values, expressed as pg equivalents synthetic human 1–39 ACTH per μg protein.
In the pars distalis, ACTH concentrations increased steadily from days 17–20 and then remained unchanged to term. At this time they were tenfold higher than on day 17. In the neurointermediate lobe, ACTH was detected only from day 18; the concentration of ACTH increasing between days 18 and 19. At each of the stages of pregnancy examined, the concentration of ACTH in the pars distalis was greater than that in the pars intermedia.
These data have demonstrated that ACTH is present in both anterior and neurointermediate lobes of the fetal rat hypophysis, that the functional differentiation of the pars distalis takes place earlier than that of the pars intermedia, and that the concentrations of corticotrophin in the pars distalis and in the pars intermedia have different patterns of development as gestation progresses.
COMBINED EFFECTS OF NEONATAL THYROXINE TREATMENT AND NEONATAL CASTRATION ON SEBUM PRODUCTION IN ADULT MALE RATS
Authors: TOH YEE CHU 
Published: December 2008

Newborn Sprague–Dawley rats were castrated within 24 h of birth and control animals were sham-operated. Intact female rats were also included for comparison. One-half of the rats in each group was treated with 28 μg thyroxine (T4) daily for the first week of life. The secretion rate of sebum was measured at the age of 80 days from the amount of skin-surface lipids that could be extracted with acetone and which had been produced during 2 days.
Castration of rats at birth decreased the rate of sebum secretion and neonatal castration plus neonatal thyrotoxicosis produced an even lower level of sebum which more nearly approached that seen in female rats with neonatal T4 treatment. It was concluded that a reduction in the response of the sebaceous glands in adult rats made thyrotoxic with high doses of T4 in the early stage of life is not due to a decreased secretion of gonadal steroids.
SKIN-COLOUR CHANGES IN THE LIZARD, ANOLIS CAROLINENSIS, IN RESPONSE TO LOCALIZED ELECTRICAL STIMULATION AND LESIONS IN THE DIENCEPHALON
Authors: HEMER J. H. , SALAS M. A. , LAPOINTE J. L. 
Published: December 2008

A study was made of changes in skin colour in the lizard, Anolis carolinensis, in response to deep electrical stimulation at 0·2 mm intervals throughout the periventricular region of the diencephalon and the anterior brain stem. Double-barrelled glass microelectrodes with tip diameters of 3 μm were used. A 20 μA pulse-train consisting of a 500 Hz signal lasting for 1 s yielded localized responses. Skin darkening occurred only in response to stimulation delivered in the anterior and dorsal region of the diencephalon and skin lightening only in response to stimulation in a small area in the posterior and ventral region of the hypothalamus. Electrical lesions in the latter region resulted in permanent skin darkening. Surgical interruption of the hypothalamo–hypophysial neurosecretory tract did not block skin-colour change in response to dark or light backgrounds.
It was concluded that MSH release is under tonic inhibitory control by hypothalamic neurones in Anolis. Both inhibitory and stimulatory neurones can be localized stereotaxically in the diencephalon and neither type corresponds with the neurosecretory neurones of the hypothalamo–hypophysial tract. The functional relationship between the stimulatory neurones and the inhibitory neurones and pars intermedia remains unclear.
BINDING OF GLUCOCORTICOSTEROIDS TO HEPATIC ERYTHROPOIETIC CELLS OF THE RAT FETUS
Authors: BILLAT C. , FELIX J. M. , MAYEUX P. , JACQUOT R. 
Published: December 2008

A role for glucocorticosteroids in the evolution of the fetal liver erythron in vivo has been proposed. If direct, such an intervention implies the presence of receptor sites in the cells of the erythroid cell lines. To test this hypothesis cell suspensions were prepared from liver haematopoietic tissue obtained from rat fetuses aged 13, 14, 17 and 20 days. Their composition was determined by light microscopy. The populations consisted essentially of cells of the erythroid line: juvenile cell types (progenitor and basophilic cells) predominated in tissue collected at 13 and 14 days of gestation, more mature types (polychromatic and acidophilic cells) became more abundant at 17 and 20 days of gestation. Suppressible binding of glucocorticosteroid at 4°C was studied on these suspensions, using [3H]dexamethasone. Binding sites were found at all stages of gestation studied. The mean number per cell (for the entire erythroid population) was roughly 3600, 3500, 2300 and 1700 at 13, 14, 17 and 20 days of gestation respectively, without any change in the apparent equilibrium dissociation constant (Kd: 5·5 × 10−9 to 6·5 × 10−9 mol/l). Suspensions containing essentially progenitor cells were prepared from erythropoietic cells from livers obtained at 14 and 16 days of gestation, using a rabbit immune serum against rat erythrocytes in the presence of an excess of complement. These cells had 1800 and 1600 receptor sites per cell respectively (same Kd as above). No receptors were found on circulating adult or fetal erythrocytes.
The results strongly suggest that there is an uneven distribution of the number of the glucocorticosteroid binding sites per cell amongst the different cell types of the erythroid line. These sites were present in progenitors, increased in number in the basophilic cells and then progressively disappeared as the cells matured.
EFFECTS OF NEONATAL EXPOSURE TO MONOSODIUM GLUTAMATE ON THE ELECTRICAL ACTIVITY OF NEURONES IN THE MEDIOBASAL HYPOTHALAMUS, AND ON THE PLASMA CONCENTRATIONS OF THYROID-STIMULATING HORMONE AND PROLACTIN, FOLLOWING STIMULATION OF THE ROSTRAL HYPOTHALAMUS IN ADULT FEMALE RATS
Authors: SAPHIER D. J. , DYER R. G. 
Published: December 2008

Action potentials were recorded from 174 neurones in the mediobasal hypothalamus of ovariectomized adult female rats exposed neonatally to monosodium glutamate (MSG) and from 145 neurones in control rats. All of the animals, which were anaesthetized with urethane, had been ovariectomized for at least 3 weeks and received two injections of oestradiol benzoate (20 μg/100 g body weight, i.m.) 72 h and immediately before the recording experiments. The response of each neurone to electrical stimulation of the median eminence and rostral hypothalamus (preoptic and anterior hypothalamic areas; PO/AH) was analysed. The most striking feature of the results obtained was the significant (P < 0·001) loss of inhibitory responses in those neurones remaining in the adult rats after neonatal treatment with MSG. The loss of inhibitory responses applied to both stimulation sites.
In each rat the response of one neurone, which was antidromically identified as projecting to the median eminence, was recorded before and during stimulation of the PO/AH at 50 Hz for 30 s in every min for 15 min. Before and after this stimulation blood was collected from a jugular vein for estimation by radioimmunoassay of concentrations of prolactin and TSH. In the MSG-treated rats significantly (P < 0·05) fewer neurones were inhibited by the 50 Hz stimulation than in control rats. In control rats the plasma concentrations of prolactin nearly quadrupled as an immediate consequence of this treatment, whereas in MSG-treated rats plasma concentrations barely doubled. However, in the MSG-treated rats plasma concentrations of prolactin continued to rise after stimulation ceased, possibly as a consequence of enhanced secretion of thyrotrophin releasing hormone.
EFFECTS OF AN ANTISERUM TO LUTEINIZING HORMONE AND STEROID REPLACEMENT THERAPY ON MAINTENANCE OF PREGNANCY IN THE RAT: SERUM AND LUTEAL LEVELS OF PROGESTERONE, TESTOSTERONE AND OESTRADIOL
Authors: TERRANOVA P. F. , GREENWALD G. S. 
Published: December 2008

Pregnant rats were injected s.c. with antiserum to LH (anti-LH) on days 8 or 10 of pregnancy (day 1 = day of sperm-positive vaginal smear) and subsequently given various steroids s.c. to prevent luteolysis and/or abortion. A single injection of 4 mg progesterone on day 8 prevented abortion and luteolysis as shown on day 12 by the presence of fetal swellings and levels of progesterone in serum (88 ±6 (s.e.m.) ng/ml) and corpora lutea (26±3 ng/mg) comparable to control values. After 0·5 ml anti-LH on day 10, a daily dose of 4 mg progesterone prevented abortion in five out of eight animals but by day 13 luteal progesterone was 3·0 ± 0·7 compared with 24±3 ng/mg in controls.
After anti-LH on day 8 or 10, daily injections of 1 or 4 mg testosterone propionate or 10 μg, 100 μg or 1 mg oestradiol failed to prevent abortion or to raise luteal concentrations of progesterone to normal values. However, 4 mg testosterone propionate on day 8 or 100 or 500 μg oestradiol on day 10 maintained serum progesterone levels at approximately half those of control values. Treatment with 4 mg testosterone propionate on days 8–11 led to significant increases in serum and luteal levels of testosterone and oestradiol on day 12; on day 10 exogenous oestradiol (100 or 500 μg) increased serum and luteal levels of oestradiol by day 13.
These results, especially treatments begun on day 8, are difficult to reconcile with the current concept that the luteotrophic action of LH in the pregnant rat is exerted by increasing luteal androgens that are aromatized to oestrogens which then act as the direct luteotrophic stimulus.
INSULIN RELEASE AND STEROID-HORMONE BINDING IN ISOLATED ISLETS OF LANGERHANS IN THE RAT: EFFECTS OF OVARIECTOMY
Authors: EL SEIFI S. , GREEN I. C. , PERRIN D. 
Published: December 2008

Ovariectomized rats showed a 30% increase in body weight and food intake over a 9 day period after operation. When pair-fed with normal controls, they had comparatively higher fasting serum levels of glucose and lower levels of insulin and progesterone than the normal rats. Treatment with oestradiol reversed these results. Insulin release from islets isolated from ovariectomized rats was significantly lower than from those of normal controls; the secretory responses were improved after administration of oestradiol to ovariectomized rats.
Cytosol receptors for progesterone and oestradiol were measured in a 105 000g supernatant fraction of islets from normal, ovariectomized and oestrogen-treated ovariectomized rats. Progesterone-receptor binding was dramatically reduced after ovariectomy but was restored to normal levels by oestradiol treatment of the rats. Oestradiol-receptor binding was not significantly affected by ovariectomy but was increased several fold by oestrogen treatment of ovariectomized rats.
These results suggest that islets of Langerhans contain receptors for both progesterone and oestradiol, and that this receptor population is subject to change. Progesterone—but not oestradiol—receptor measurements could be correlated with alterations in the rates of secretion of insulin from islets. Oestrogen administration in vivo had profound effects on subsequent insulin release from islets, though this may have been mediated by way of an increase in the quantity of the progesterone receptor.
FOLLICLE FORMATION AND IODIDE METABOLISM IN CULTURES OF HUMAN THYROID CELLS
Authors: DICKSON J. G. , HOVSÉPIAN S. , FAYET G. , LISSITZKY S. 
Published: December 2008

Primary cultures were initiated using thyroid tissue obtained at operation from patients with Graves's disease. The in-vitro conditions which permitted the formation of functional follicular structures in both primary cultures and derived sub-cultures were examined. In both situations, culture without the addition of calf serum to the medium resulted in the formation of follicles in response to thyrotrophin. In primary cultures the response to stimulation by exogenous thyrotrophin was variable. However, cells derived from long-term primary monolayers responded to thyrotrophin stimulation in a more predictable manner.
In sub-cultures, the ability of cells to concentrate and organify iodide was augmented in a dose-dependent fashion in response to thyrotrophin (0 to 0·2 mu./ml); maximal values of 20 to 80 times those of control cultures being obtained. While follicular structure was maintained at higher hormone concentrations, iodide-trapping capacity declined. Similar effects were produced by both low and high purity thyrotrophin and by dibutyryl cyclic AMP.
Thyroid cells from two patients with a genetic defect of iodide organification exhibited the same lesion in vitro.
ONTOGENESIS OF THE ADRENAL GLUCOCORTICOIDS AND OF THE TARGET FUNCTION OF THE ENZYMATIC TYROSINE TRANSAMINASE ACTIVITY IN THE CHICK EMBRYO
Authors: MARIE C. 
Published: December 2008

Adrenal and plasma glucocorticoids were determined in developing chick embryos of Gallus domesticus from days 8 to 19 of incubation, using a competitive protein-binding assay. At the same time, tyrosine transaminase activity in the liver was studied as an adrenal-dependent target function.
Total amounts of glucocorticoids in the adrenal gland increased from day 11 and reached 7 ng/pair of glands on day 19. This increase was related to growth of the adrenal since concentrations remained constant at about 380 pg/μg dry weight from days 9 to 18. Glucocorticoids appeared in the plasma on day 12 and their concentrations rose to 10 ng/ml on day 19, with a marked peak on day 13. This peak was not reflected in the tyrosine transaminase activity which appeared and developed independently of the variations in the circulating glucocorticoids.
STIMULATION BY POLYPEPTIDES OF DEHYDROEPIANDROSTERONE SULPHATE SYNTHESIS IN HUMAN FETAL ADRENAL SLICES
Authors: BROWN T. J. , GINZ BERYL , MILNE CATHERINE M. , OAKEY R. E. 
Published: December 2008

Slices of human fetal adrenal glands (obtained after abortion at 10–18 weeks of gestation) were superfused sequentially with buffer or with buffer incorporating human ACTH, synthetic ACTH(1–24), human GH, human chorionic gonadotrophin, α-melanocyte stimulating hormone, metenkephalin, ovine prolactin, β-lipotrophic hormone or corticotrophin-like intermediate lobe peptide in concentrations from 10−6 to 10−9 mol/l. Changes in the concentration of dehydroepiandrosterone sulphate (DHAS) in the effluent in response to addition or removal of the polypeptides were measured by radioimmunoassay. Comparison of the quantity of DHAS in the effluent collected during superfusion (5 h) with that present in the tissue initially indicated that synthesis of this conjugated steroid occurred during superfusion.
Increases in the concentration of DHAS in the effluent were provoked by exposure of the tissue to all the polypeptides except corticotrophin-like intermediate lobe peptide.
These effects were unlikely to be non-specific since incorporation of gonadotrophins, albumin or dextran into the superfusate did not stimulate corticosteroid synthesis from viable bovine adrenal tissue.
It was concluded that a number of pituitary polypeptides have the potential to provoke androgen sulphate synthesis by the human fetal gland in early gestation. Consequently there may be no single fetal corticotrophin at this stage and androgen production may be regulated by a number of trophic factors.