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Biomedical subjects

W Vale

Publications and source records attributed to W Vale.

At least 181 records · Page 10Linked to original sources
PubMed1989

Differential production and regulation of inhibin subunits in rat testicular cell types.

The distributions of the alpha-, beta A-, and beta B subunits of inhibin/activin polypeptides were studied in the testis of adult (60-day-old) and immature (12-day-old) rats. Immunohistochemical techniques using antisera selective for each subunit were used to localize the polypeptide chains. In situ hybridization using radiolabeled complementary RNA probes enabled localization of the messenger RNAs (mRNAs) encoding these subunits. In 12-day-old rats, immunostaining and mRNA signal for the alpha-subunit was found in Leydig cell clusters. The beta A- and beta B-subunit staining and beta A-subunit message were detectable in isolated interstitial cells, but the clusters appeared to lack these subunits. Positive immunostaining for each subunit was localized in a Sertoli cell-like pattern in seminiferous tubules, as was a positive mRNA signal for the alpha- and beta B-subunit over regions containing these cell types. Treatment with human CG (hCG) and PMSG greatly enhanced the production of the alpha-subunit in the Leydig cell clusters, but not within the tubules, of these young rats. In adult rats, alpha- and beta B-subunit staining, and alpha-subunit mRNA signal, was observed in the interstitial cells. As in the immature animals, all three subunits were localized in a Sertoli cell-like pattern in the tubules, and a positive mRNA signal for the alpha- and beta B-subunits was found over these cells. There was, however, no obvious change in the expression of the subunits in the testis of adult rats after gonadotropin treatment. The present findings suggest that: 1) in the rat testis, both Sertoli and interstitial cells produce inhibin/activin subunits; 2) the alpha- and beta-subunits are produced by different types of interstitial cells in immature rats; and 3) the production of the alpha-subunit in the Leydig cells of immature rats is regulated by LH-like hormones.

Animals↗
PubMed1989

Adenohypophysial changes in mice transgenic for human growth hormone-releasing factor: a histological, immunocytochemical, and electron microscopic investigation.

The effect of protracted GH-releasing factor (GRF) stimulation on adenohypophysial morphology was investigated in six mice transgenic for human GRF (hGRF). All animals had significantly higher plasma levels of GH and GRF and greater body weights than controls. Eight-month-old mice were killed, and the markedly enlarged pituitaries were studied by histology, immunocytochemistry, electron microscopy, and immunogold method, using double labeling at ultrastructural level. In all pituitaries, a massive hyperplasia, chiefly of mammosomatotrophs, was found. These bihormonal cells, containing GH and PRL, were demonstrated by light microscopy and ultrastructural immunocytochemistry. Electron microscopy revealed the presence of cells with characteristics of GH cells in three pituitaries and cells resembling human adenomatous mammosomatotrophs in the other three glands. All of these cells, regardless of their ultrastructural features, contained secretory granules heavily labeled for GH by immunogold technique; PRL labeling varied from cell to cell, with the predominance of a weak immunostaining and was colocalized with GH in secretory granules. These results indicate that chronic exposure to GRF excess leads to mammosomatotroph hyperplasia. It is suggested that GH cells proliferate and transform to mammosomatotrophs in response to GRF stimulation. Focal PRL cell hyperplasia noted in three pituitaries could also be due to a GRF effect. Longer exposure to GRF is needed to clarify whether GRF can cause adenoma.

Animals↗
PubMed1989

In the mouse, the activation of the hypothalamic-pituitary-adrenal axis by a lipopolysaccharide (endotoxin) is mediated through interleukin-1.

The mechanisms through which endotoxin stimulates the hypothalamic-pituitary-adrenal axis are not well understood. In the studies reported here we tested the hypothesis that endotoxin increases plasma ACTH levels by releasing interleukin-1 (Il-1). Two experimental tools reported to interfere with the biological activity of IL-1 were used: antibodies directed against IL-1 receptors and alpha MSH. In a first series of experiments, adult male mice were injected with a lipopolysaccharide (LPS; 25 micrograms), antibodies against IL-1 receptor, alpha MSH (1-30 micrograms), or LPS and either IL-1 antibodies or alpha MSH. All treatments were administered ip. The endotoxin LPS caused a marked increase in plasma ACTH levels, measured 6 h later. Both alpha MSH and the Il-1 receptor antibodies, while having no effect by themselves, significantly (P less than or equal to 0.01) blocked LPS-induced ACTH release. In a second series of experiments, mice were injected ip with 500 ng recombinant human (rh) Il-1 alpha or 100 ng rhIl-1 beta in the presence or absence of alpha MSH (1-30 micrograms, ip). While not altering ACTH secretion induced by rhIl-1 alpha, 10-30 micrograms alpha MSH significantly (P less than or equal to 0.01) interfered with the effect of rhIl-1 beta. These results suggest 1) that endotoxin activates the hypothalamic-pituitary-adrenal axis through a mechanism involving the activation of interleukin-1 receptors; and 2) that the effect of rhIl-1 beta, but not -alpha, on ACTH secretion by the mouse can be partially blocked by alpha MSH.

Adrenal Glands↗
PubMed1989

In the rat, interleukin-1 alpha and -beta stimulate adrenocorticotropin and catecholamine release.

Recombinant interleukin-1 alpha and -beta (Il-1 alpha and -beta) have been evaluated for their abilities to stimulate ACTH and catecholamine secretion in the intact adult male rat. Additionally, the role of adrenergic-dependent pathways in mediating Il-1-induced ACTH release has been assessed. The iv or intracerebroventricular injection of either Il-1 alpha or Il-1 beta caused dose-related increases in plasma ACTH, epinephrine, and norepinephrine levels. While at low iv doses (less than or equal to 10 ng), Il-1 beta was more effective than Il-1 alpha at releasing ACTH, no measurable differences were noted at higher doses. In contrast, Il-1 beta was significantly more active at all doses in elevating plasma ACTH levels after intracerebroventricular injection. Similarly, Il-1 alpha was more effective than Il-1 beta at stimulating epinephrine, but not norepinephrine, secretion after icv injection. Because of the ability of catecholamines to alter ACTH secretion, we then examined the role of adrenergic-dependent pathways as possible mediators of Il-1-induced ACTH secretion. Blockade of adrenergic receptors by the concomitant administration of prazosin and propanolol prevented the simultaneous actions of phenylephrine and isoproterenol on the corticotrophs, but did not significantly alter the effect of peripherally administered Il-1 alpha on ACTH release. These results suggest that both Il-1 alpha and Il-1 beta stimulate ACTH and catecholamine secretion in the rat. Despite the ability of the lymphokine to elevate plasma epinephrine and norepinephrine values, circulating catecholamines do not appear to represent essential modulators of ACTH release induced by acutely injected Il-1.

Adrenergic alpha-Antagonists↗
PubMed1989

Lack of in vivo somatotroph desensitization or depletion after 14 days of continuous growth hormone (GH)-releasing hormone administration in normal men and a GH-deficient boy.

In vitro and in vivo studies of somatotroph responsivity to GHRH stimulation indicate that partial loss of GH responsiveness occurs during constant GHRH stimulation. To determine if these observations reflect either a short term effect of GHRH or if the absence of somatostatin effects somatotroph desensitization (as occurred in in vitro studies), we administered GHRH-40 (10 ng/kg.min) by continuous iv infusion for 14 days to five normal men and one GH-deficient boy. Serum insulin-like growth factor I (IGF-I) concentrations were measured at frequent intervals to assess the biological effect of GHRH on GH secretion. The GH secretory profiles were assessed by measuring serum GH levels every 20 min for 24 h before (day 0), on the 14th GHRH infusion day, and 14 days after discontinuation of the GHRH infusion in the normal men. The GH-deficient boy was studied before and during the 14th GHRH infusion day. A supramaximal iv GHRH dose was administered at the end of the 24-h sampling period, and the GH responses were compared. Serum IGF-I concentrations increased on the 14th day of GHRH infusion in the normal men [day 0 mean, 0.84 +/- 0.14 (+/- SE) X 10(3); day 14, 1.74 +/- 0.20 X 10(3) U/L; P less than 0.05] and from 0.20 X 10(3) on day 0 to a maximum of 0.67 X 10(3) U/L on day 3 in the GH-deficient boy; they declined to pretreatment levels after discontinuation of GDRH. The mean integrated serum GH concentrations in the normal men were 1.44 +/- 0.10 micrograms/L.h on day 0 and 3.11 +/- 0.95 on day 14 of GHRH infusion. The integrated GH concentration in the GH-deficient boy was 1.53 micrograms/L.h on day 0 and 4.23 on day 14 of GHRH infusion. Pulsatile GH secretion, assessed by cluster analysis, was preserved in the normal men and occurred de novo in the GH-deficient boy on the 14th GHRH infusion day. The GH response to bolus GHRH administration was also preserved; no attenuation of the response occurred in the normal men or the GH-deficient boy after 14 days of GHRH infusion. The increase in IGF-I concentrations during 14 days of continuous GHRH administration, the persistence of pulsatile GH release in normal men, the de novo appearance of GH pulses in the GH-deficient boy, and the preservation of the response to a supramaximal GHRH dose indicates that the somatotrophs remain responsive to prolonged constant stimulation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

Dynamic changes in circulating inhibin levels during the luteal-follicular transition of the human menstrual cycle.

Dynamic changes in serum immunoreactive (ir) inhibin levels during the transition from the luteal to the follicular phase (luteal-follicular transition) were characterized during 3 consecutive cycles in 12 cycling women. Both spontaneous (first to second cycle) and GnRH antagonist-imposed premature luteolysis (second to third cycle) were evaluated. Serum FSH, LH, estradiol (E2), and progesterone (P4) levels were monitored daily by RIA for the entire study. Daily ir-inhibit levels were determined from 7 days before until 7 days after the onset of menses and from 4 days before to 10 days after the GnRH antagonist-induced bleeding by a heterologous RIA. During spontaneous luteolysis, ir-inhibin levels peaked 7 days before menses and declined in a linear fashion (r = -0.99) thereafter, reaching a sustained low level 1 day after the onset of menses. The decline of P4 and E2 levels appears to be coupled to that of ir-inhibin (r = 0.98 and r = 0.95, respectively). FSH levels showed an inverse pattern, with an acute elevation unaccompanied by LH, for 5 days before the onset of menses and reaching a plateau 2 days after. ir-Inhibin and FSH were negatively correlated (r = -0.87; P less than 0.0001). Increased LH levels did not occur until the day of menses and were negatively correlated with ir-inhibin (r = -0.50; P less than 0.05), but not E2 and P4. During the second cycle, at the midluteal phase luteolysis was induced by a single (50 micrograms/kg) im injection of a potent GnRH antagonist, [Ac-D2Nal,D4ClPhe2,D3Pal3,Arg5,DGlu6(AA),+ ++DAla10] GnRH; an acute decline of LH and FSH levels occurred, with maximal suppressions of 51% and 35%, respectively. ir-Inhibin levels decreased rapidly (40 +/- 2.8%) in parallel with E2 and P4 during the first 24 h and continued to decline for 4 days. The inverse relationship and time course of changes between FSH and ir-inhibin levels were similar to those of the spontaneous luteal-follicular transition. Six of the 12 subjects experienced partial reversal of luteolysis; the decline of ir-inhibin and the rise of FSH during the first 2 days were arrested for 4 days, which corresponded to the rebound increases in E2, P4, and LH. The subsequent fall of ir-inhibin was followed by a rise in FSH. Both the complete and incomplete luteolysis groups exhibited an orderly follicular maturation, LH surge, and luteal function during the ensuing cycle.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1989

Activin stimulation of inhibin secretion and messenger RNA levels in cultured granulosa cells.

Recent reports suggest that activin (the dimer of inhibin beta subunits with FSH-releasing activity) has specific receptors on ovarian granulosa cells. The present study examined the effects of purified porcine activin on inhibin secretion and mRNA levels in granulosa cells obtained from immature, estrogen-treated rats. Cells were cultured for 48 h in culture media, or media containing FSH (10 ng/ml) and/or activin (30 ng/ml). Western blot analyses performed with affinity-purified antisera to inhibin alpha- and beta A-subunits revealed that treatment with either FSH or activin increased the secretion of inhibin alpha beta dimer (Mr 30,000), with a further increase after cotreatment. These results were confirmed by an inhibin alpha-subunit RIA, which revealed 7-, 14-, and 71-fold increases in the secretion of immunoreactive inhibin-alpha by activin, FSH, and activin plus FSH, respectively. TGF beta, a structural homolog of activin, also stimulated inhibin release, whereas follistatin was ineffective. Total RNA from cultured cells was hybridized with 32P-labeled inhibin alpha-subunit cRNA or beta-actin cDNA probes, and inhibin-alpha message levels were normalized with beta-actin mRNA levels. Northern blot analysis revealed that treatment with FSH and activin increased hybridization of a 1.5 kilobase (kb) message, corresponding to the inhibin alpha-subunit mRNA. Slot blot analyses indicated a 6- and 8-fold stimulation of inhibin alpha-subunit mRNA levels by FSH and activin, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Inhibin, activin, and follistatin: regulation of follicle-stimulating hormone messenger ribonucleic acid levels.

Primary pituitary cell cultures derived from adult male rats were used to explore the direct effects of purified porcine inhibin and follistatin, and recombinant human activin A on FSH beta, as well as LH beta and alpha-subunit mRNA levels. Subunit mRNAs were determined by blot hybridization using alpha, LH beta, and FSH beta cDNA and genomic fragments. Treatment with inhibin for 72 h significantly suppressed alpha and FSH beta mRNA levels with parallel changes in FSH secretion. No change in LH beta mRNA levels was observed. A decrease in FSH beta mRNA to undetectable levels was seen 4 h after inhibin administration. Recombinant human Activin A caused dose-dependent and parallel increases in FSH beta mRNA levels and FSH secretion. This increase was evident at 4 h after activin administration and maintained at longer times. alpha and LH beta mRNA levels remained unchanged. Follistatin addition to cultures for 72 h significantly reduced FSH beta mRNA levels. In a time-course experiment, a reduction in FSH beta mRNA to undetectable levels was observed 24 h after follistatin administration. There were no changes in alpha or LH beta mRNA levels. These data demonstrate that the actions of these gonadal peptides on FSH secretion may be accounted for, at least in part at the level of biosynthesis, by reductions in FSH beta mRNA levels directly at the level of the anterior pituitary gland.

Activins↗
PubMed1989

Periovulatory changes in the expression of inhibin alpha-, beta A-, and beta B-subunits in hormonally induced immature female rats.

Immature female rats were treated with PMSG and human CG to induce ovulation. Sequential treatment with these hormones allowed us to investigate variations in the production of inhibin subunits shortly before ovulation and during the induced luteal phase. Using this model, we found that expression patterns for the alpha-, beta A-, and beta B-subunits were similar to those observed in mature cycling animals: administration of PMSG (to mimic the gonadotropin surge) led to a sharp increase in the expression of all three subunits in large preovulatory follicles whereas injection with human CG (to induce ovulation) caused a decrease in the levels of the respective mRNAs. In contrast to mature females, shortly before ovulation, levels of inhibin alpha-subunit mRNA were low in small antral follicles (approximately 350 microns). In addition, at that time, inhibin beta A- and beta B-subunits mRNAs were present in several large follicles (greater than 500 microns). More than 2 days after ovulation, inhibin beta A- and beta B-subunit mRNAs could not be detected in small antral size follicles (approximately 350 microns) of hormonally induced females. On the other hand, hybridization signals for the inhibin alpha-subunit were observed in some small antral and preantral size follicles, while signals were very low or undetectable in a large number of atretic follicles. Using this synchronized ovulation model, hybridization patterns for inhibin beta A-subunit mRNA was observed in interstitial cells, 8-10 h after ovulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Suppression of bioactive and immunoreactive follicle-stimulating hormone and luteinizing hormone levels by a potent gonadotropin-releasing hormone antagonist: pharmacodynamic studies.

Dose-dependent gonadotropin suppression by a potent gonadotropin-releasing hormone (GnRH) antagonist, Nal1 Glu6 [( Ac-D2Nal1,D4ClPhe2,D3Pal3,Arg5,DGlu(AA)6,- DAla10]GnRH), was determined in five postmenopausal women by frequent sampling for immunoreactive luteinizing hormone (I-LH) and immunoreactive follicle stimulating hormone (I-FSH) for 72 hours after single intramuscular (IM) injections of 10, 50, 150, and 300 micrograms/kg. Bioactive (B) LH and B-FSH also were measured after the IM administration of the 50-micrograms/kg dose. Serum levels of Nal1 Glu6 were determined by a radioreceptor assay for the first 24 hours after the 50-micrograms/kg IM dose and in three women after a 10-micrograms/kg intravenous (IV) dose. While the disappearance rate of serum Nal1 Glu6 after a 10-micrograms/kg IV injection was rapid, gonadotropin suppression persisted longer than detectable serum levels. In contrast, after a 50-micrograms/kg IM injection, the decline from peak circulating levels was slower, contributing to its longer duration of action (greater than 24 hours). All IM doses tested resulted in a similar 51% to 63% decrease in I-LH, which was maximal by 8 hours. The duration of action was dose-dependent, with decreased levels lasting up to 72 hours at the 300-micrograms/kg dose. While decline of I-FSH was smaller (14% to 33%), the duration of suppression was also dose-dependent, although the nadir occurs later (8 to 9 hours after administration) and suppression lasted longer (72 hours at the 150-micrograms/kg dose). The reduction of B-LH was greater than that of I-LH and the suppression of B-FSH also was greater than that of I-FSH.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗
PubMed1989

Studies on the role of oxytocin in late pregnancy in the pregnant rhesus monkey: plasma concentrations of oxytocin in the maternal circulation throughout the 24-h day and the effect of the synthetic oxytocin antagonist [1-beta-Mpa(beta-(CH2)5)1,(Me(Tyr2, Orn8] oxytocin on spontaneous nocturnal myometrial contractions.

Previous observations have demonstrated that under several different circumstances the pregnant rhesus monkey myometrium shows a spontaneous shift in activity from contractures to contractions around the beginning of the hours of darkness. Preliminary studies were conducted to demonstrate that the competitive oxytocin antagonist ([1-beta-Mpa(beta-(CH2)5)1,) Me)Tyr2, Orn8] oxytocin was effective in vivo in inhibiting oxytocin induced contraction type myometrial activity in the pregnant rhesus monkey in the last third of gestation. Four pregnant and one fetectomized rhesus monkey (98-141 days gestation) received one intra-arterial dose of oxytocin antagonist to study its ability to inhibit myometrial contractions occurring spontaneously around the onset of prevailing nighttime. In three pregnant monkeys (105-121 days gestation) maternal arterial plasma oxytocin levels were measured at 4-h intervals for a period of 48 h. Maternal plasma oxytocin concentration was maximal during the early hours of darkness and demonstrated a significant 24-h rhythm. From the combined results of both experiments it may be concluded that circulating oxytocin and/or a change in one of the many potential regulatory sites for oxytocin function plays a role in the switch from contractures to contractions that occurs around the beginning of the hours of darkness.

Animals↗
PubMed1989

Characterization of the potentiation effect of activin on human erythroid colony formation in vitro.

Activin, also named FSH-releasing protein, was previously shown to induce hemoglobin accumulation in K562 cells and potentiate the proliferation and differentiation of CFU-E in human bone marrow cultures. Present studies indicate that the potentiation effect of activin is lineage specific. In addition to CFU-E, activin caused an increase in the colony formation of BFU-E from either bone marrow or peripheral blood. It had little effect on the colony formation of CFU-GM and the mixed colonies from CFU-GEMM. In serum-depleted culture, the effect of activin was shown to be dose-dependent with doses effective at picomolar concentrations. The potentiation effect of activin was exerted indirectly through mediation of both monocytes and T lymphocytes. Activin was also found to increase specifically the proportion of DNA-synthesizing erythroid progenitors from both bone marrow and peripheral blood. It had little effect on DNA synthesis in CFU-GM and in mitogen-stimulated lymphocytes. Addition of the monocytes or T lymphocytes to their respective depleted subpopulations of mononuclear cells reconstituted the enhancing effect of activin on the colony formation and DNA synthesis of erythroid progenitors. These results strongly suggest a specific role of activin in potentiating the proliferation and differentiation of erythroid progenitors in vitro.

Animals↗
PubMed1988

Characterization of activin A binding sites on the human leukemia cell line K562.

Recombinant activin A was radioiodinated to a high specific activity with maintenance of bioactivity using the Bolton-Hunter method. The human leukemia cell line K562, known to differentiate in response to activin A, was found to possess high affinity [125I]BH-activin A receptors (Kd approximately 0.13 nM) with a low number of receptors per cell (approximately 600 per cell). This receptor was found to be specific as FSH, LH, GnRH, and TGF-beta 1 do not compete for binding. This is the first description of binding sites for this protein hormone on K562 cells.

Activins↗
PubMed1988

Inhibin beta in central neural pathways involved in the control of oxytocin secretion.

Inhibin (I) a gonadal hormone glycoprotein which suppresses follicle-stimulating hormone (FSH) secretion from the anterior pituitary, is a heterodimer consisting of an alpha subunit and one of two distinct beta subunits. S1 nuclease analysis has revealed that RNAs encoding all three subunits (alpha, beta A and beta B) are expressed in rat brain. We report here on the localization, and a potential function, of inhibin beta in the rat brain. A cell group centred in the nucleus of the solitary tract (NTS), a major recipient of visceral sensory information, was stained immunohistochemically with antisera against synthetic fragments of I beta, but not I alpha. The distribution of I beta-stained fibres is consistent with known NTS projections, and includes a prominent projection to oxytocinergic aspects of the magnocellular neurosecretory system.

Animals↗
PubMed1988

Effects of somatostatin antiserum on growth hormone levels in rats with periventricular lesions in the anterior hypothalamus.

To determine whether residual inhibitory control of growth hormone (GH) secretion in rats with lesions of the periventricular nucleus (PVN) and depleted median eminence content of somatostatin (SRIF) is due to SRIF, PVN-lesioned rats were treated with SRIF antiserum. Such treatment, in contrast to normal sheep serum, caused increased (P less than 0.0001) plasma GH in lesioned and control groups. These results indicate that biologically important amounts of SRIF are available in the PVN-lesioned rat.

Animals↗
PubMed1988

Centrally administered hypothalamic growth hormone-releasing factor stimulates food intake in free-feeding rats.

Intracerebroventricular injections of rat hypothalamic growth hormone-releasing factor (rhGRF) were examined for effects on food intake in free-feeding rats. It was found that, in picomole doses, rhGRF had a stimulatory effect on food intake. Examination of higher doses of rhGRF revealed a decrease in the facilitatory effects and an inhibitory trend at the highest dose (4 nanomoles). The present results are consistent with previous results from our laboratory showing that central injections of rhGRF stimulate food intake in food-deprived rats.

Animals↗
PubMed1988

Design of potent cyclic gonadotropin releasing hormone antagonists.

In order to improve the biological potency of cyclic gonadotropin releasing hormone (GnRH) antagonists, we have synthesized analogues, the conformations of which were restrained through internal side chain/side chain amide bridges linking aspartic acid or glutamic acid and L-2,3-diaminopropionic acid or L-ornithine. A disulfide bridge linking L-cysteine residues was also introduced. Residues belonging to the bridge spanned from position 4 to positions 9 or 10. Two series of analogues were synthesized and are characterized by residues at positions 1 [Ac-D-3-(2'-naphthyl)alanine], 2 [D-(4-chlorophenyl)alanine or D-(4-fluorophenyl)alanine], 3 [D-3-(3'-pyridyl)alanine or D-tryptophan], 5 (arginine or tyrosine), and 6 [D-3-(3'-pyridyl)alanine or D-arginine], respectively. These substitutions were selected in an effort to optimize high biopotency for inhibition of luteinizing hormone secretion, minimization of histamine release activity, and high (relative) hydrophilicity. The most potent analogues in the antiovulatory assay were cyclo(4-10) [Ac-DNal1,DCpa2,DPal3,(Asp4 or Glu4),Arg5,DPal]6,Dpr10]GnRH (compounds 5 and 7), which were fully active at ca. 12.5 micrograms/rat in the first series, and cyclo(4-10)[Ac-DNal1,DFpa2,DTrp3,Asp4,DArg6++ +,Dpr10]GnRH (compound 12), which was fully active at 2.5 micrograms/rat in the second.

Amino Acid Sequence↗