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Biomedical subjects

W E Nicholson

Publications and source records attributed to W E Nicholson.

At least 55 records · Page 3Linked to original sources
PubMed1981

Simultaneous assay of immunoreactive beta-lipotropin, gamma-lipotropin, and beta-endorphin in plasma of normal human subjects, patients with ACTH/lipotropin hypersecretory syndromes, and patients undergoing chronic hemodialysis.

We have studied the relative concentrations of the human immunoreactive (IR) peptides gamma-lipotropin (hgammaLPH, [1-58]hbetaLPH), beta-lipotropin (hbetaLPH), and beta-endorphin (hbetaEND, [61-91]hbetaLPH) using gel exclusion chromatography together with a specific radio-immunoassay (RIA) for hgammaLPH and a RIA that (because hbetaEND is the COOH-terminus of the hbetaLPH molecule) measures both hbetaEND and hbetaLPH on an equimolar basis. In normal subjects, basal plasma IR-hgammaLPH was often undetectable (<12.5 fmol/ml), but ranged up to 21 fmol/ml, and IR-hbetaEND/hbetaLPH was 10.8+/-0.7 fmol/ml; previous studies by others suggest that most of the IR-hbetaEND/hbetaLPH was probably hbetaLPH. Both IR-hgammaLPH and IR-hbetaEND/hbetaLPH were significantly elevated (P < 0.001) in patients undergoing chronic hemodialysis (101.5+/-12.7 and 23.8+/-2.0 fmol/ml, respectively). Their IR-hgammaLPH coeluted with standard hgammaLPH as a single peak, and IR-hbetaEND/hbetaLPH coeluted with hbetaLPH; no distinct peak of IR-hbetaEND was observed. In patients with ACTH/LPH hypersecretion due to Addison's disease, Nelson's syndrome, or ectopic ACTH syndrome, IR-hgammaLPH and IR-hbetaEND/hbetaLPH were both elevated, and IR-hbetaEND/hbetaLPH eluted as two peaks, one coeluting with hbetaLPH and the other with hbetaEND. The molar concentrations of all three peptides were significantly correlated with one another. The lower concentrations of endogenous IR-hbetaEND observed may be due in part to its apparent shorter plasma half-life, as estimated in an Addison's patient given a cortisol infusion. The biologic significance of these three peptides in circulating blood is still unknown. The increased levels of hbetaLPH and hgammaLPH in plasma of patients with chronic renal failure suggest that the kidney may be an important organ for their metabolism.

ACTH Syndrome, Ectopic↗
PubMed1981

Human gamma-lipotropin radioimmunoassay: identification of immunoreactive gamma-lipotropin in human plasma and tissue.

Disagreement exists concerning the relative contributions to total plasma immunoreactive human lipotropin (hLPH) made by h beta LPH and its amino-terminal fragment, h gamma LPH [h beta LPH-(1-58)]. Using an antiserum (R1547) which requires the free COOH-terminal Asp58 residue of h gamma LPH for full affinity and reacts only 1% as well with h beta LPH and antisera (R3 and G106) that react with both LPHs, we examined gel chromatography eluate fractions of plasma extracts from one normal subject under basal conditions and another after metyrapone administration, of plasma or plasma extracts from patients with ACTH/LPH hypersecretion of various causes, of an extract two normal pituitary glands, and an extract of an ectopic ACTH/LPH-secreting tumor. Immunoreactive h gamma LPH was always a major, frequently the predominant, and sometimes the only immunoreactive LPH observed. We also observed in plasma or tissue of two patients with ectopic ACTH/LPH syndrome a peptide whose immunoreactivity and apparent molecular size were consistent with those of octadecapeptide human beta MSH, a molecule that is not thought to exist in normal man. These studies demonstrate that h gamma LPH is a major LPH component in plasma and tissues and indicate that the h gamma LPH RIA provides a reliable estimate of the h gamma LPH concentration in plasma without prior chromatography.

ACTH Syndrome, Ectopic↗
PubMed1980

[Ectopic secretion of ACTH and of related peptides (LPHs, beta-endorphin, "16K"). Evidence for a common precursor].

Studies in the experimental mouse pituitary tumor cell line AtT-20/D-16-v have recently shown that ACTH, the lipotropins (beta- and gamma-LPH), beta-endorphin (beta-End) and the 16-K fragment are synthesized through a common precursor molecule which is a 31,000 glycopeptide (pro-ACTH/endorphin). We have investigated whether such a biosynthetic model might exist in man. Radioimmunoassays have been developed against human ACTH, N-terminal LPH, beta-End or C-terminal beta-LPH, C-terminal gamma-LPH, and the 16-K fragment or N-terminal pro-ACTH/endorphin. These radioimmunoassays were used to examine various human samples before and after gel fractionation in ordinary or denaturing buffers. Medium DMS-79, in which human small cell carcinoma cells derived from a lung cancer were cultured, was shown to contain molecules identical to gamma-LPH, beta-LPH, beta-End and ACTH. In addition, it also contained a high molecular weight material with LPH, beta-End, and ACTH immunoreactivity. These three immunoreactivities could not be dissociated under denaturing conditions (6 M guanidine-HCl), and were all absorbed on an ACTH-purified anti-(1-24)-ACTH affinity column. Medium DMS-79 also contained high molecular weight calcitonin immunoreactivity that was not absorbed on the (1-24)-ACTH affinity column and therefore was not part of the pro-ACTH/endorphin molecule. Extracts from two pheochromocytomas responsible for the ectopic ACTH syndrome were found to contain, in addition to ACTH, large amounts of gamma-LPH and beta-End. High levels of beta-LPH and beta-End were also present in the plasma from a patient with the ectopic ACTH syndrome due to pancreatic carcinoma. Plasma immunoreactive 16-K fragment was increased in another patient with this syndrome. These results indicate that a biosynthetic model similar to that described in the AtT-20/D-16-v mouse tumor cell line also exists in man. Tumors responsible for the ectopic ACTH syndrome provide a unique source to study this model in man.

Adrenocorticotropic Hormone↗
PubMed1979

Cell-free synthesis of mouse corticotropin. Evidence for two high molecular weight gene products.

Polysomes or mRNA prepared from cultured AtT-20/D16v mouse pituitary adenocarcinoma cells direct the efficient incorporation of amino acid into newly synthesized material in the presence of wheat germ translational factors. A significant franction of the total cell-free product is specifically immunoprecipitable with corticotropin antibody purified by immune affinity chromatography. Analysis of the cell-free synthesized immunoreactive products by sodium dodecyl sulfate-polyacrylamide gel electrophoresis reveals that two high molecular weight corticotropin species (Mr congruent to 32,500 and 28,000) are synthesized in an approximate 2:1 ratio. Neither product contains carbohydrate based upon concanavalin A chromatography or exposure to polysaccharidases. The smaller molecular weight product does not appear to arise from proteolytic processing since both species are synthesized in approximately the same ratio in cell-free reaction mixtures directed by either polysomes or mRNA. These results suggest that AtT-20/D16v cells contain two distinct mRNA poluations specifying the synthesis of two different high molecular weight forms of mouse corticotropin.

Adenocarcinoma↗
PubMed1979

Adrenoleukodystrophy and adrenomyeloneuropathy associated with partial adrenal insufficiency in three generations of a kindred.

Four cases of adrenoleukodystrophy (ALD) and one case of adrenomyeloneuropathy (AMN) have developed in a kindred over three generations demonstrating that AMN is a clinical variant of ALD. Pituitary-adrenal function studies were performed in 10 family members, including two affected males and four females identified as carriers of ALD/AMN. No pituitary-adrenal abnormality was found in the carriers. However, basal morning plasma adrenocorticotropic hormone (ACTH) levels were markedly elevated in the two males with ALD and AMN, despite the fact that they had no clinical signs of adrenal insufficiency and that morning plasma cortisol levels and their response to maximal exogenous ACTH stimulation appeared to be normal. In addition, the integrated 24-hour response to the administration were also subnormal in these two cases. Thus, people with ALD and AMN may have subclinical partial adrenocrotical insufficiency. No other endocrinologic dysfunction was identified.

Adolescent↗
PubMed1979

Human placental immunoreactive corticotropin, lipotropin, and beta-endorphin: evidence for a common precursor.

The concentrations and molecular sizes of immunoreactive corticotropin (ACTH), lipotropin (LPH, beta LPH plus gamma LPH), gamma LPH, and beta-endorphin (beta END) were determined in human placental extracts. Serial dilutions of a water extract of placenta generated competitive binding curves parallel with that of the standard in each assay. The concentrations of ACTH, LPH, gamma LPH, and beta END were 3.3, 0.8, 0.7, and 1.1 ng/g wet weight of tissue, respectively. A partially purified extract applied to a Sephadex G-50 column contained high Mr components with ACTH, LPH, gamma LPH, and beta END immunoreactivities. The extract was applied to an immune affinity chromatography column consisting of affinity-purified (1-24)ACTH antiserum covalently bound to agarose. The material that adsorbed to the column and eluted with buffer containing sodium dodecyl sulfate had ACTH, LPH, and beta END immunoreactivities, indicating that there was a component or components containing antigenic determinants for all of these peptides. Sodium dodecyl sulfate/polyacrylamide gel electrophoresis of the affinity-purified placental extract revealed at least two high Mr components (Mr approximately 48,000 and 36,000) with all three immunoreactivities. These data suggest, but do not prove, that the placenta synthesizes ACTH, the LPHs, and beta END from a common precursor molecule.

Adrenocorticotropic Hormone↗
PubMed1979

Free-running circadian plasma cortisol rhythm in a blind human subject.

The plasma cortisol rhythm in man has been presumed to be an endogenous circadian rhythm, synchronized by some external stimulus to an exact 24-h period. Sleep/wake and 'social activity' cycles have been considered as candidates for this synchronizer. Previous studies have suggested that the dark/light phase shifts associated with the sleep-wake cycle may be the external synchronizer, rather than the sleep/wake cycle itself. A totally blind, but otherwise normal subject was studied for a period of 50 days. Her hourly sleep/wake status and hourly integrated mean plasma cortisol concentrations were determined, and the data were subjected to non-parametric mathematical analysis. The subject was found to have a free-running rhythm in plasma cortisol with a period of approximately 24.5 h. Her sleep/wake rhythm, determined by similar analysis, had a period of exactly 24 h. In addition to the dominant 24.5-h cortisol rhythm, there appeared to be a minor 24-h cortisol rhythm with a peak that coincided approximately with the time of awakening. It was not possible to determine whether this sleep/wake-related peak represented a minor component of the circadian rhythm, synchronized by some stimulus associated with sleep/wake activity, or merely an acute response to awakening itself. Nevertheless, the two rhythms exhibited 'beating' behaviour, resulting in maximal peak cortisol concentrations when they were in synchrony and minimal peak concentrations when they were not. It is concluded that environment dark/light phase shifts are the dominant synchronizer of the circadian rhythm in plasma cortisol concentrations in man, as they are for a variety of circadian rhythms in other living things.

Blindness↗
PubMed1979

Dopamine inhibits angiotensin-stimulated aldosterone biosynthesis in bovine adrenal cells.

The possibility that dopamine may play a role in the in vivo control of aldosterone production in man was suggested to us by reports from others; (a) that bromocriptine, a dopaminergic agonist, inhibits the aldosterone response to diuresis and to the infusion of angiotensin or ACTH; and (b) that metaclopramide, a dopamine blocking agent, causes elevations in plasma aldosterone levels. To determine whether such effects were direct or indirect, we examined the action of dopamine on aldosterone biosynthesis in isolated, bovine adrenal cells. Dopamine significantly inhibits the aldosterone response to angiotensin (P < 0.001), but does not influence basal aldosterone biosynthesis. It has previously been reported that angiotensin stimulates both the early and late phases of aldosterone biosynthesis. The present experiments demonstrated that the enhancing effect of angiotensin on the conversion of deoxycorticosterone to aldosterone (late phase of aldosterone biosynthesis) was almost completely inhibited by dopamine (P < 0.001). A significant inhibitory effect of dopamine (10 nM) was seen even when aldosterone biosynthesis was stimulated by a grossly supraphysiological concentration of angiotensin II (10 muM). However, these studies did not demonstrate any direct effect of dopamine on the early phase of aldosterone biosynthesis (cholesterol to pregnenolone) basally or when stimulated, or on the late phase of aldosterone biosynthesis under basal conditions. These in vitro studies suggest a direct inhibitory role for dopamine on the late phase of aldosterone biosynthesis, which may account for the in vivo inhibition of the aldosterone response to angiotensin in subjects treated with a dopaminergic agent.

Adrenal Glands↗
PubMed1979

A case of pituitary adrenocorticotropin-dependent Cushing's syndrome in the horse.

In the horse, a syndrome of hirsutism, hyperglycemia, glucosuria, polydipsia, polyuria, polyphagia, and progressive debilitation has been recognized. Most often the syndrome has been associated with adenomas of the pars intermedia of the pituitary and bilateral adrenal hyperplasia or nodular hyperplasia involving primarily the zona fasciculata. Previously, the syndrome has been ascribed to compression of the hypothalamus by an expanding but functionally inactive pituitary neoplasm. In the present case, with RIA determination of plasma ACTH concentrations, the syndrome was ascribed to pituitary ACTH-dependent hyperadrenocorticism and likened to human Cushing's disease.

Adrenocorticotropic Hormone↗
PubMed1979

Circulating big human prolactin: conversion to small human prolactin by reduction of disulfide bonds.

The heterogeneity of circulating human PRL (hPRL) in sera of patients with hyperprolactinemia was studied by exclusion chromatography on Sephadex G-100. Big hPRL, which elutes between the void volume and the elution position of monomeric small hPRL, is stable upon rechromatography but is almost entirely converted into small hPRL after reduction with 0.5% mercaptoethanol. These results suggest that the existence of circulating big hPRL is dependent upon the formation of interpolypeptide disulfide bonds and does not represent a classical biosynthetic precursor of hPRL.

Adolescent↗
PubMed1978

Corticotropin, lipotropin, and beta-endorphin production by a human nonpituitary tumor in culture: evidence for a common precursor.

A continuous line (DMS-79) of human pulmonary small cell carcinoma cells was shown to secrete immunoreactive adrenocorticotropin (ACTH), lipotropin, and beta-endorphin concomitantly into the culture medium. Gel filtration of the culture medium demonstrated at least five components: high molecular weight material(s) that had ACTH, lipotropin, and beta-endorphin immunoreactivities and materials similar to ACTH, beta-lipotropin, gamma-lipotropin, and beta-endorphin in their immunoreactivities and apparent molecular weights. The same components were observed when gel filtration was carried out in 6 M guanidine-HCl, and the high molecular weight material(s) appeared to consist of more than one component, with molecular weights in the range of 15,000-40,000. Immune affinity chromatography of the high molecular weight component(s) from gel filtration with a specific anti-(1-24)ACTH serum demonstrated that the ACTH, lipotropin, and beta-endorphin immunoreactivities were possessed by the same molecule(s), suggesting that ACTH, lipotropins, and beta-endorphin were derived from a common, high molecular weight precursor.

Adrenocorticotropic Hormone↗
PubMed1978

The nature of the immunoreactive lipotropins in human plasma and tissue extracts.

This study was designed to establish definitively the nature of immunoreactive lipotropin (IR-LPH) in human plasma and tissue extracts. Using gel filtration, gel filtration under denaturing conditions, cationic exchange chromatography, immunoprecipitation, and radioimmunoassay, we have studied normal and tumorous human pituitaries, ectopic ACTH- and LPH-secreting tumors, plasma from normal subjects before and after dexamethasone administration, and plasma from patients with primary adrenal insufficiency and pituitary and nonpituitary ACTH- and LPH-secreting tumors. Except in the plasma and tumors of occasional patients with ectopic ACTH syndrome, the smallest IR-LPH appears to be lambda-lipotropin (lambdaLPH), which is often the predominant and occasionally the only IR-LPH present. The other major peptide appears to be betaLPH, a 91-amino acid molecule that contains lambdaLPH as its 1-58 sequence. Larger immunoreactive materials were observed in some specimens, but the "big" LPH in one plasma was shown to be lambdaLPH bound to IgG.The weak melanocyte-stimulating activity of LPH suggests that ACTH may be the principal pigmentary hormone in man. The fact that lambdaLPH, rather than betaLPH, is the predominant form in plasma suggests that the enkephalin-endorphin opiate peptides, which are contained in the "missing" 59-91 sequence from the betaLPH precursor of lambdaLPH, may be secreted in parallel with ACTH under both physiological and pathological conditions in man.

Chromatography, Gel↗