bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of lithium and phorbol on the dynamics of LH release from dispersed sheep pituitary cells
Authors: Starling L. , McIntosh R. P. , Mclntosh E. A. 
Published: December 2008

ABSTRACT
The possible involvement of polyphosphoinositides in the stimulation of LH release was investigated. Dispersed sheep pituitary cells were incubated in test-tubes, or perifusedns in columns, with gonadotrophin-releasing hormone (GnRH) and Li+, or with a phorbol ester, and the amounts and patterns of LH release over time compared.
Treatment with Li+ (10 mmol/l), which is known to increase levels of inositol phosphates in gonadotrophs, was shown to have effects only on the responses of desensitized cells, significantly decreasing the rate at which the cells desensitize (P<0·005) and decreasing the response to supramaximal levels of GnRH stimulus (P<0·01). It is suggested that these effects could be due to increased levels of inositol monophosphate, inositol bisphosphate inositol 1,3,4-trisphosphate. Responses to single or repeated pulses of GnRH at 18-, 30- and 60-min intervals were not significantly altered.
Phorbol 12-myristate 13-acetate (PMA), an activator of the calcium and phospholipid-dependent protein kinase (protein kinase C), was specifically active in releasing LH with a half-maximal stimulating dose of approximately 3 nmol/l. Phorbol 12,13-diacetate, which is structurally similar to PMA but does not activate protein kinase C, did not release LH, except at high levels in freshly dispersed cells. The timing of PMA-stimulated LH release was similar to that for GnRH-stimulated release, and PMA was able to release greater amounts of LH than could GnRH. This suggests that activation of protein kinase C is likely to be important in the GnRH-stimulated release of LH from gonadotrophs. It also shows that the desensitization to GnRH stimulation observed after 10 min is unlikely to be caused by lack of releasable LH. Cells desensitized to maximally stimulating levels of GnRH still responded strongly to PMA stimulation, indicating that the desensitization to GnRH stimulation involves a step in the transduction mechanism before activation of protein kinase C.
J. Endocr. (1986) 111, 167–173
Cellular interactions in the hormonal induction of α2u-globulin in rat liver
Authors: Sarkar F. H. , Mancini M. A. , Nag A. C. , Roy A. K. 
Published: December 2008

ABSTRACT
The role of hepatocellular interaction in the androgen-dependent synthesis of rat α2u-globulin was examined by immunochemical analysis of liver sections. Both after androgen administration to the ovariectomized female and during puberty in the male, only a subpopulation of hepatocytes became competent to synthesize α2u-globulin. These competent hepatocytes first appeared as discontinuous patches along the wall of the central vein. After the formation of a confluent layer around the central vein, cellular competency was seen to propagate toward the periportal direction through the cords of hepatic cells. Although the periportal progression of cellular competency for the synthesis of α2u-globulin appeared to be an all-or-none phenomenon, it did not require cell division. From these results we conclude that certain components of the central vein are necessary for the hormonal induction of α2u-globulin in the rat liver. We also propose that a primary endocrine influence on the hepatic vein results in the production of a secondary paracrine mediator which can trigger the synthesis of α2u-globulin in adjacent hepatocytes. Perivenous to periportal flow of this putative secondary mediator can explain cell recruitment for the synthesis of α2u-globulin along the hepatic cords.
J. Endocr. (1986) 111, 205–208
The somatotrophic axis in young steers: influence of nutritional status on pulsatile release of growth hormone and circulating concentrations of insulin-like growth factor 1
Authors: Breier B. H. , Bass J. J. , Butler J. H. , Gluckman P. D. 
Published: December 2008

ABSTRACT
The relationship between plasma GH profiles and circulating concentrations of insulin-like growth factor 1 (IGF-1) at three different planes of nutrition, chosen to represent a high, medium and low level of nutrition (3%, 1·8% and 1% dry matter of liveweight per day) was studied in 15 young Angus steers. All steers were maintained on 3% dry matter for 5 weeks, then on one of the three nutritional planes for 4 weeks and then all were returned to 3% dry matter for 3 weeks. Blood was sampled through jugular catheters at 15-min intervals for 25 h at the end of each phase of the study and additional samples were taken on 2 days each week.
Pulsatile release of GH occurred episodically with a diurnal increase during night and morning hours only in steers on high nutritional intakes. Reduced feeding at both the medium and the low plane abolished the diurnal rhythm and significantly increased mean plasma GH concentrations, the amplitude of GH pulses and the area under the GH profiles. Baseline concentrations of GH and pulse frequency did not change through nutritional manipulation. Upon realimentation, plasma GH concentrations decreased in both previously undernourished groups, with those fed 1% dry matter still having increased levels 10 days after refeeding. Plasma IGF-1 concentrations showed no periodicity. With nutritional deprivation, a decrease in IGF-1 concentration was observed only at negative energy balance (1% group). In this group plasma IGF-1 concentrations were progressively restored within 1 week of realimentation.
The different relationship between GH and IGF-1 release at each plane of nutrition suggests that at both medium and low levels of feed intake, tissue insensitivity to GH may exist peripherally and perhaps centrally. It is suggested that nutritional status may, through modulation of tissue sensitivity to GH, be a primary factor in determining growth and the regulation of the somatotrophic axis in the postnatal ruminant.
J. Endocr. (1986) 111, 209–215
Characterization of particle-associated choriomammotrophin and progesterone in ovine placentomes
Authors: Rice G. E. , Thorburn G. D. 
Published: December 2008

ABSTRACT
The subcellular distribution and compartmentalization of choriomammotrophin (CM) and progesterone within ovine placentomes was investigated using differential and density gradient centrifugation techniques. Approximately 67% of placental CM and 45% of progesterone was associated with subcellular particles. The 10 000 g particulate fraction contained the highest specific activity of both CM and progesterone (19·1 ±3·8 (s.e.m.) μg/mg and 71·5 ± 9·2 pmol/mg protein respectively). This fraction was also shown to contain electron-dense granules with morphology similar to that of hormone-containing secretory granules isolated from other endocrine tissues. Particle-associated CM sedimented to a density of 1·051–1·054 g/ml in colloidal silica gradients and displayed physicochemical characteristics consistent with its storage in secretory granules. During in-vitro incubations, particle-associated CM was stable for up to 90 min, but dissociated when incubated in hypoosmotic medium. Particulate progesterone, which was also present in the CM-rich fraction and was stable for up to 90 min of incubation, was not affected by decreasing the osmolality of the incubation medium. These data suggest that ovine CM (but not progesterone) is stored within a population of secretory granules located within placentomes.
J. Endocr. (1986) 111, 217–223
The characteristics of β-adrenergic binding sites on pancreatic islets of Langerhans
Authors: Fyles J. M. , Cawthorne M. A. , Howell S. L. 
Published: December 2008

ABSTRACT
The sympathetic nervous system is believed to play a part in the control of insulin release from the pancreatic islets of Langerhans. Stimulation of α-adrenoceptors is thought to inhibit the release of insulin whereas stimulation of β-adrenoceptors enhances insulin release. The present experiments were conducted to establish the existence of β-adrenergic receptors on guinea-pig and rat islet cells and to quantify them using the selective β-adrenergic ligands [3H]dihydroalprenolol (DHA) and [125I]cyanoiodopindolol (CYP).
Guinea-pig islets had 62 fmol β-adrenoceptors/mg protein using [3H]DHA, corresponding to 43 700 binding sites/cell and 25 fmol β-adrenoceptors/mg protein using [125I]CYP, corresponding to 17 400 sites/cell. Rat islet cells were found to have 4·6 fmol β-adrenoceptors/mg protein using [125I]CYP, corresponding to 7200 sites/cell. Adenylate cyclase activation exhibited a positive dose–response relationship when exposed to the β-adrenoceptor agonist isoprenaline, with a maximum response (190 ± 21% above basal) at 10 μmol isoprenaline/l. This response was abolished with 1 μmol/l of the β-adrenergic antagonist 1-alprenolol. Insulin secretion in the presence of 10 mmol glucose/l, but in the absence of the α-adrenoceptor blocker phentolamine, was not affected by 10 μmol isoprenaline/l. However, perifusion experiments showed that secretion of insulin from isolated rat islets in the presence of 10 mmol glucose/l was significantly increased (332%) by 10 μmol isoprenaline/l in the presence of 10 μmol phentolamine/l.
These results suggest that binding of selective radio-labelled ligands occurs to β-adrenergic receptors on the B cell surface of the islets of Langerhans, and that these receptors are functionally coupled to insulin secretion through modulation of adenylate cyclase activity.
J. Endocr. (1986) 111, 263–270
Serotonin induces gonadotrophin release through stimulation of LH-releasing hormone release from the median eminence
Authors: Vitale M. L. , Parisi M. N. , Chiocchio S. R. , Tramezzani J. H. 
Published: December 2008

ABSTRACT
The effects of serotonin (5-HT) on the release of gonadotrophins and LH-releasing hormone (LHRH) were examined in an in-vitro perifusion system using median eminences and/or anterior pituitaries obtained from male or pro-oestrous female rats. Animals were killed by decapitation between 12.00 and 13.00 h. A serial double-chamber perifusion system was employed. Three types of experiments were performed. In the first, median eminences were placed in the first chamber and one anterior pituitary in the second chamber. In the second group, only the anterior pituitary was perifused. In the third group, only five median eminences were perifused. In the first and second experiments, LH, FSH and prolactin were determined in the perifusion efflux by radioimmunoassay (RIA). In the third experiment, LHRH was determined by RIA.
Addition of 5-HT (final concentrations 0·06, 0·6 and 6·0μmol/l) into the first chamber containing the median eminences stimulated the release of LH and FSH from the pituitary, but did not affect the levels of prolactin in the effluent in the same experiment (prooestrous rats). The stimulatory effect of 5-HT was blocked by the addition of cyproheptadine (1 μmol/l) in the perifusion fluid. The introduction of 5-HT (0·6 μmol/l) into the tube connecting the first and second chambers did not modify the release of LH, nor did 5-HT added to the pituitaries perifused alone.
Injection of 5-HT into the first chamber (median eminences), containing tissue samples from male rats, stimulated LH release, but to a significantly (P< 0·001) lower degree than that found when samples from pro-oestrous females were used (P< 0·0001).
When median eminences from pro-oestrous rats were perifused alone, injection of 5-HT produced an immediate release of LHRH which peaked during the first 10 min of collection and lasted for 30 min; in these experiments, a clear relationship existed between dose of 5-HT and release of LHRH (P<0·02). The stimulatory effect of 5-HT was blocked by the addition of cyproheptadine (5 μmol/l) or methiothepin (5 μmol/l).
These results demonstrate that 5-HT stimulates gonadotrophin release by acting directly on LHRH terminals in the median eminence from pro-oestrous rats. Furthermore, the effect of 5-HT on LHRH release was dose dependent and was nullified by 5-HT receptor blockers (cyproheptadine and methiothepin).
J. Endocr. (1986) 111, 309–315
Biochemical characterization of circulating Met-enkephalins in canine endotoxin shock
Authors: Watson J. D. , Varley J. G. , Tomlin S. J. , Medbak S. , Rees L. H. , Hinds C. J. 
Published: December 2008

ABSTRACT
The alterations in arterial, venous and adrenal vein levels of immunoreactive Met-enkephalins following endotoxin administration have been investigated in dogs by direct measurement and gel filtration chromatography. Animals were anaesthetized with α-chloralose and allowed to breath spontaneously. The left lumbar adrenal vein, limb vein and femoral artery were cannulated for blood sampling. Severe shock was produced by the administration of a large bolus of E. coli endotoxin followed by a continuous infusion. The production of endotoxin shock was associated with significant increases in adrenal vein and systemic venous plasma immunoreactive Met-enkephalin levels. Forty-five minutes after induction of endotoxin shock arterial immunoreactive Met-enkephalin levels were generally higher than baseline values. In resting anaesthetized animals a large 31 000 molecular weight form of Met-enkephalin, presumably proenkephalin, was found in plasma obtained from the adrenal vein, systemic and pulmonary circulations. Following endotoxin this enkephalin-containing peptide still predominated in arterial and venous plasma, whereas in the adrenal vein the proportion of Met-enkephalin immunoreactivity attributable to this large peptide fell. This was associated with the appearance of increasing amounts of smaller molecular forms (18 000, 8000, 3–5000 molecular weight and the pentapeptide itself). In this model enkephalin-containing peptides were not biochemically modified by their passage through the lungs.
J. Endocr. (1986) 111, 329–334
The distribution of immunoreactive α-melanocyte-stimulating hormone cells in the adult human pituitary gland
Authors: Coates P. J. , Doniach I. , Hale A. C. , Rees L. H. 
Published: December 2008

ABSTRACT
It has been suggested that a proportion of the adenomas and the nodular hyperplasia of cells in the pituitary gland in cases of Cushing's disease are derived from cells of the pars intermedia rather than the pars anterior. The evidence can be summarized as follows: (1) the posterior site of adenoma or nodular hyperplasia in the pituitary, (2) the innervation of cells and (3) the suppressive response to the dopamine agonist bromocriptine in vivo or to dopamine in vitro. All these observations infer analogy with cells of the pars intermedia of other species, which are controlled by direct neural tonic dopaminergic inhibition. The adult human pituitary gland, however, does not possess a morphologically distinct pars intermedia, due to regression of the rudimentary fetal pars intermedia after birth, with mixing of cells into the pars anterior and pars nervosa. Since cells of the pars intermedia characteristically synthesize α-MSH, we have studied this peptide in order to assess the occurrence and distribution of intermedia-derived cells in the adult human pituitary.
Sections from 100 pituitaries, removed at autopsy, were stained by an indirect immunoperoxidase technique using non-cross-reacting antisera specific for α-MSH and ACTH. Immunoreactive α-MSH (IR-α-MSH) cells were found in a total of 97 specimens. Of these, only ten cases showed a marked concentration of IR-α-MSH cells in the zona intermedia. In the majority of pituitaries, IR-α-MSH cells were more commonly seen in the pars anterior than in the zona intermedia; in 41 cases, IR-α-MSH cells were completely absent from the zona intermedia. The number of IR-α-MSH cells varied greatly, from less than ten cells per section to many hundreds, regardless of the age or sex of the individual. Additionally, no correlation could be made between the number of IR-α-MSH cells and the cause of death, treatment or the period of time between death and removal of the pituitary.
We conclude that cells containing IR-α-MSH are present in varying numbers in the normal adult human pituitary gland. These cells do not show a specific distribution pattern, but may be found in both the zona intermedia and are spread throughout the pars anterior.
J. Endocr. (1986) 111, 335–342
Release of aldosterone and corticosterone from the adrenal cortex of the Brattleboro rat in response to administration of ACTH
Authors: Brudieux R. , Krifi M. N. , Laulin J. P. 
Published: December 2008

ABSTRACT
The time-course and dose–response of the in-vivo secretion of aldosterone and corticosterone after administration of ACTH(1–24) were measured in adrenal venous blood from female Brattleboro rats, homozygous for hypothalamic diabetes insipidus and lacking arginine vasopressin (AVP). Female Long–Evans rats were used as controls. All animals were pretreated with dexamethasone and anaesthetized with pentobarbital. Basal secretions of aldosterone and corticosterone were four- to sixfold lower in Brattleboro than in Long–Evans rats. Administration of ACTH consistently increased the secretion of aldosterone and corticosterone similarly in the two groups of rats; maximum values were observed 20–30 min after ACTH injection. However, for all the doses of ACTH (0·05, 0·5 and 5·0 mi.u./100 g body wt) and at every stage of response the secretion rates of aldosterone and corticosterone were twofold lower in Brattleboro than in Long–Evans rats. Furthermore the absolute increase in steroid secretion induced by ACTH was reduced by half in Brattleboro rats. These results show that the impairment of adrenal activity is largely due to a reduced capacity for corticosteroidogenesis in the adrenal cortex of Brattleboro rats. The mechanisms of action of AVP are discussed.
J. Endocr. (1986) 111, 375–381
Transient increase in prolactin secretion following hypothalamo-pituitary disconnection in ewes during anoestrus and the breeding season
Authors: Thomas G. B. , Cummins J. T. , Cavanagh L. , Clarke I. J. 
Published: December 2008

ABSTRACT
Hypothalamic control of prolactin secretion was studied in ovariectomized ewes by comparing the effects of hypothalamo-pituitary disconnection (HPD) and sham-operation (sham-HPD). HPD caused a two-fold increase in plasma prolactin concentrations on days 1 and 7 following surgery during anoestrus and a tenfold increase during the breeding season. Thereafter, concentrations gradually declined to be similar to those in sham-HPD ewes by day 43 (breeding season) and day 145 (anoestrus). The maximum plasma prolactin response to HPD was similar during the two seasons (anoestrus: 128 ± 15 vs breeding season: 118 ± 13 μg/l). Sham-HPD had no effect on plasma prolactin concentrations. Prolactin pulse frequency was not affected by HPD, but increases in plasma prolactin concentrations were associated with increases in pulse amplitude. At the time of the normal anoestrus, plasma prolactin concentrations rose in both the HPD and sham-HPD ewes, raising the question of extra-hypothalamic regulation of seasonal changes in prolactin secretion. Plasma LH and FSH concentrations became undetectable in HPD ewes but were unaltered in sham-HPD ewes. We conclude that hypothalamic inhibition of pituitary prolactin secretion in the sheep can be demonstrated by HPD but that this effect is not sustained. This transience may indicate the additional requirement of hypothalamic-releasing factors in the control of prolactin release. In addition, the surgically isolated ovine pituitary of the HPD animal has an inherent pulsatile secretion of prolactin.
J. Endocr. (1986) 111, 425–431
The streaming adrenal cortex: direct evidence of centripetal migration of adrenocytes by estimation of cell turnover rate
Authors: Zajicek G. , Ariel I. , Arber N. 
Published: December 2008

ABSTRACT
Thirty adult male rats were injected with 0·5 μCi [3H]thymidine/g body weight (specific activity 5 Ci/ mmol) and killed, in groups of five, 1 h and 14, 30, 60, 90 and 120 days after injection. The displacement of labelled adrenocytes with time was estimated in autoradiograms of adrenal sections. The radial distance of the labelled cell from the capsule was measured with an eyepiece micrometer and expressed in cell location units, i.e. the number of cells separating the labelled cell from the capsule. One hour after labelling, 95% of labelled cells were confined to the outer quarter of the cortex. During the following days, adrenocytes were displaced inwardly, approaching the medulla at a velocity of 0·24 locations/day. They traversed the three cortex zones, reaching the medulla after 104 days. The three adrenal zones represent three differentiation states of the adrenocyte. When young, the adrenocyte secretes aldosterone, after leaving the glomerulosa it produces corticosteroids and on reaching the reticularis it produces sex hormones. The adrenal cortex is a cell renewal system made of two compartments. A progenitor compartment extending between locations 1 and 15, and a functional compartment, covering locations 16–64. The first compartment produces 0·47 cells daily, which enter the second. Half of them die on their way while the rest are eliminated in the reticular zone. The cell stream is nourished by a subcapsular stem cell.
J. Endocr. (1986) 111, 477–482
Differences in prolactin and LH responses to acute stress between peripuberal and adult male rats
Authors: Armario A. , Restrepo C. , Hidalgo J. , Lopez-Calderón A. 
Published: December 2008

ABSTRACT
Pituitary-adrenal, pituitary-gonadal and prolactin responses to acute stress (restraint) were studied in peripuberal and adult male rats. The pituitary-adrenal response to restraint stress did not differ in peripuberal and adult rats. Prolactin increase during stress was less marked in peripuberal animals. While an increase in LH during stress was observed in adult rats, peripuberal animals did not respond to stress. Testosterone levels were also lower in peripuberal than in adult rats. Diminished LH and prolactin responses to stress in peripuberal rats did not appear to be due either to increased pituitary-adrenal activity or to altered pituitary responsiveness to LHRH and dopamine respectively. Peripuberal rats were also more sensitive to the action of morphine on LH and prolactin release than were adult rats, suggesting that endogenous opioids may be involved in the LH and prolactin responses to acute stress. Differences in the maturation of central mechanisms rather than in pituitary response appear to be responsible for the differing responses to acute stress.
J. Endocr. (1987) 112, 9–13
Enhanced corticosterone-binding capacity in plasma after stimulation of the rat adrenal cortex: the possibility of a simultaneous release of protein and corticosterone
Authors: Bassett J. R. 
Published: December 2008

ABSTRACT
Exposure of rats to either footshock or handling stress produced a significant increase in both plasma corticosterone concentration and specific binding capacity. Non-specific binding was eliminated using the synthetic glucocorticoid, dexamethasone. The increase in both plasma corticosterone and specific binding capacity was biphasic following exposure to footshock. Adrenalectomy and pretreatment with betamethasone abolished both phases of the enhanced binding capacity and plasma steroid concentration. Intraperitoneal injection of ACTH (1–24) in animals pretreated with betamethasone resulted in a biphasic rise in plasma concentrations of corticosterone but only the initial increase in binding capacity. Dissociation constant (Kd) values, determined by Scatchard analysis, for adrenalectomized and betamethasone-pretreated animals were 546 and 556 pmol/l respectively. These values were significantly different from the Kd in animals with functional adrenals (631 pmol/l). The results are discussed in the light of a possible specific corticosteroid-binding globulin (CBG)-like binding protein of adrenal origin released in conjunction with corticosterone. This binding protein has a lower affinity for corticosterone and a shorter half-life than CBG.
J. Endocr. (1987) 112, 33–41