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Biomedical subjects

J Moss

Publications and source records attributed to J Moss.

At least 541 records · Page 30Linked to original sources
PubMed1980

ADP-ribosyltransferase activity of mono- and multi-(ADP-ribosylated) choleragen.

Choleragen (cholera toxin) catalyzed the NAD-dependent auto-ADP-ribosyltation of its A1 peptide. The number of ADP-ribose moieties incorporated into ech A1 peptide was dependent on incubation conditions and time as well as toxin concentration. There was no evidence for the formation of poly(ADP-ribosylated) toxin. The formation of mono- and multi-(ADP-ribosylated) A1 peptides was prevented by the addition of arginine, an alternative ADP-ribose acceptor. Triton X-100 polyacrylamide gel electrophoresis separated the A1 peptide of choleragen from the B complex and multi-(ADP-ribosylated) A1 peptides from unmodified A1. The A1 peptides ADP-ribosylated in the presence of [32P]NAD contained approximately 1, 2, or 3 ADP-ribose molecules/23,500-dalton units; under the conditions used for electrophoresis, the mobilities of the A1 peptides were enhanced by incorporation of ADP-ribose. The mono- and multi-(ADP-ribosylated) A1 peptides catalyzed the NAD-dependent ADP-ribosylation of arginine methyl ester. The turnover numbers of the mono- and multi-(ADP-ribosylated) A1 peptides were consistently 30 to 50% higher than that of the A1 peptide from native toxin.

Adenosine Diphosphate Ribose↗
PubMed1980

Isolation and properties of an NAD- and guanidine-dependent ADP-ribosyltransferase from turkey erythrocytes.

An NAD- and guanidine-dependent ADP-ribosyltransferase has been purified more than 500,000-fold from turkey erythrocytes with an 18% yield. The enzyme in the 100,000 X g supernatant fraction was bound to phenyl-Sepharose, eluted with 50% propylene glycol, and further purified by sequential chromatographic steps on carboxymethylcellulose, NAD-agarose and concanavalin A-agarose. The transferase was specifically eluted from concanavalin A-agarose with alpha-methylmannoside. The enzymatic activity was extremely labile following the first purification step. Both propylene glycol and NaCl stabilized the transferase; significant increases in enzyme recovery were obtained by conducting the NAD- and concanavalin A-agarose chromatography in buffer containing propylene glycol. The purified protein exhibits one predominant protein band on SDS-polyacrylamide gels with an estimated molecular weight of 28,300. On Ultrogel AcA54 chromatography, single coincident peaks of ADP-ribosyltransferase activity and protein were observed. Enzyme activity was independent of DNA; the highly purified transferase was inhibited by thymidine, nicotinamide, and theophylline. The specific activity of the purified enzyme (350 mumol of ADP-ribose transferred from NAD to arginine methyl estermin-1mg-1) is comparable to that reported for purified NAD glycohydrolases and poly(ADP-ribosyl)transferases.

Animals↗
PubMed1980

Effects of GTP on choleragen-catalyzed ADP ribosylation of membrane and soluble proteins.

Choleragen-dependent ADP ribosylation of soluble proteins from bovine thymus, using [32P]NAD as substrate, was increased 3- to 4-fold by GTP. The effect was specific for nucleoside triphosphate, with GTP approximately equal to ITP greater than CTP greater than ATP greater than UTP. Half-maximal enhancement was observed with 0.5 mM GTP. The magnitude of the GTP effect decreased with increasing NAD concentration; GTP had no effect on hydrolysis of NAD at low NAD concentrations. Digestion of ADP-ribosylated proteins with snake venom phosphodiesterase yielded primarily 5'-AMP. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of soluble proteins from thymus after incubation with choleragen and [32P]NAD separated numerous ADP-ribosylated proteins; radioactivity in all bands was increased by nucleoside triphosphate. Choleragen catalyzed the ADP ribosylation of several purified proteins; depending on the protein, GTP either increased, decreased, or had no effect on the extent of ADP ribosylation. Choleragen-dependent ADP ribosylation of a wide variety of proteins is consistent with the possibility that intoxication results in covalent modification of more than one cellular protein and perhaps alters the activity of other enzymes in addition to adenylate cyclase.

Adenosine Diphosphate Ribose↗
PubMed1980

Effect of cyclic AMP on the intracellular degradation of newly synthesized collagen.

Prostaglandin E1 and cholera toxin increased the intracellular levels of cyclic AMP of human lung fibroblasts. With prostaglandin E1, the increase in cyclic AMP occurred within 10 min followed by a decline to less than one-half of peak values in 6 h. With cholera toxin, the increase occurred within 60 min but the level of cyclic AMP remained increased for 6 h. Both agents caused a decrease in collagen production as expressed as the proportion of newly synthesized protein represented by collagen. The increase in cyclic AMP levels was accompanied by a marked increase in the proportion of newly synthesized collagen which was degraded intracellularly prior to secretion. Analysis of the degraded collagen showed it to be predominantly less than 1000 daltons in molecular mass, but still in peptide linkage. The data are consistent with the hypothesis that cyclic AMP levels in diploid fibroblasts regulate the amount of collagen produced by fibroblasts, at least in part, by modulating the level of intracellular collagen degradation.

Animals↗
PubMed1980

Prostaglandins increase GTP hydrolysis by membranes from human mononuclear cells.

Both adenylate cyclase and GTPase activities in human mononuclear cell membranes were increased by prostaglandins. Adenylate cyclase activity, however, was enhanced by much lower concentrations of PGE1 (prostaglandin E1) than were required to increase GTPase. PGE2, PGA1, PGB1, and PGF1 alpha also stimulated GTPase activity. These same prostaglandins, with the notable exception of PGF1 alpha, increased adenylate cyclase activity (PGE2 greater than PGA1 greater than or equal to PGB1). Isoproterenol, 100 microM, doubled adenylate cyclase without altering GTPase activity. Choleragen activated adenylate cyclase in mononuclear cell membranes but had no effect on GTPase activity whether or not PGE1 was present. Mononuclear cells were separated into adherent and nonadherent populations by two different methods to examine the possibility that the prostaglandin-stimulated GTPase was confined to a specific type of mononuclear cell. Adenylate cyclase in membranes from both adherent and nonadherent cells was activated by PGE1, but neither PGE1 nor choleragen altered GTPase activity in these preparations. It appears that, although several prostaglandins can increase GTPase activity in mononuclear cell membranes, the increase in GTPase activity is not consistently associated with activation of adenylate cyclase by prostaglandins.

Animals↗
PubMed1980

Loss of choleragen receptors and ganglioside upon differentiation of 3T3-L1 preadipocytes.

3T3-L1 preadipocytes differentiate in culture into cells having the enzymatic and morphological characteristics of adipocytes. Differentiation is accompanied by a decrease in total cellular ganglioside content; the ganglioside level is 1.8 to 2.5-fold higher in undifferentiated than in differentiated cells. Gangliosides GM3 and GD1a constitute a majority of total cell gangliosides in both cell types, while ganglioside GM1, the putative choleragen receptor, constitutes less than 5%. Differentiation results in a 75 to 85% decrease in ganglioside GM1. An inverse correlation exists between the percentage of adipocytes in the cell population and: 1) total ganglioside and ganglioside GM1 content, and 2) surface ganglioside GM1 as estimated by choleragen binding or fluorescent staining of bound choleragen. Nondifferentiating 3T3-C2 control cells do not exhibit changes in total ganglioside, ganglioside GM1, or choleragen binding that are observed with 3T3-L1 cells.

Adipose Tissue↗
PubMed1980

Plasma catecholamines in stress and exercise.

A technique was devised to monitor plasma catecholamines in a minimally obtrusive fashion in subjects going about their working activities. There was a disparity between plasma norepinephrine and epinephrine levels in different situations. During public speaking, epinephrine levels increase twofold, whereas during physical exercise, norepinephrine levels increase threefold. It seemed that while exercise induces a response of the sympathetic nervous system, psychological stress induces primarily an adrenal response.

Catecholamines↗
PubMed1980

Binding of diphtheria toxin to phospholipids in liposomes.

Diphtheria toxin bound to the phosphate portion of some, but not all, phospholipids in liposomes. Liposomes consisting of dimyristoyl phosphatidylcholine and cholesterol did not bind toxin. Addition of 20 mol% (compared to dimyristoyl phosphatidylcholine) of dipalmitoyl phosphatidic acid, dicetyl phosphate, phosphatidylinositol phosphate, cardiolipin, or phosphatidylserine in the liposomes resulted in substantial binding of toxin. Inclusion of phosphatidylinositol in dimyristol phosphatidylcholine/cholesterol liposomes did not result in toxin binding. The calcium salt of dipalmitoyl phosphatidic acid was more effective than the sodium salt, and the highest level of binding occurred with liposomes consisting only of dipalmitoyl phosphatidic acid (calcium salt) and cholesterol. Binding of toxin to liposomes was dependent on pH, and the pattern of pH dependence varied with liposomes having different compositions. Incubation of diphtheria toxin with liposomes containing dicetyl phosphate resulted in maximal binding at pH 3.6, whereas binding to liposomes containing phosphatidylinositol phosphate was maximal above pH 7. Toxin did not bind to liposomes containing 20 mol% of a free fatty acid (palmitic acid) or a sulfated lipid (3-sulfogalactosylceramide). Toxin binding to dicetyl phosphate or phosphatidylinositol phosphate was inhibited by UTP, ATP, phosphocholine, or p-nitrophenyl phosphate, but not by uracil. We conclude that (a) diphtheria toxin binds specifically to the phosphate portion of certain phospholipids, (b) binding to phospholipids in liposomes is dependent on pH, but is not due only to electrostatic interaction, and (c) binding may be strongly influenced by the composition of adjacent phospholipids that do not bind toxin. We propose that a minor membrane phospholipid (such as phosphatidylinositol phosphate or phosphatidic acid), or that some other phosphorylated membrane molecule (such as a phosphoprotein) may be important in the initial binding of diphtheria toxin to cells.

Cardiolipins↗
PubMed1980

Short-term catecholamine response to psychological stress.

The recent development of radioenzymatic assays for plasma catecholamines and of highly portable nonobtrusive blood withdrawal pumps makes possible the investigation of the physiological response to actual stress. However because the half-life of plasma catecholamines is so brief, meticulous care must be taken to obtain blood samples consistently vis-a-vis the stress immersion experience. These points are demonstrated in a study of ten young physicians under the stress of public speaking. Plasma epinephrine levels differ significantly between the initial moments of public speaking and the middle moments of speaking. These differences are large enough to affect the conclusions reached in comparing public speaking values with baseline values.

Blood Specimen Collection↗
PubMed1980

Interferon-induced disease in mice and rats.

Treatment of newborn mice with potent mouse interferon preparations resulted in an acute "early" syndrome characterized by inhibition of growth, delay in maturation of several organs, diffuse liver cell necrosis and death. When interferon treatment was discontinued at 1 week of life, mice appeared to recover, but subsequently developed a progressive glomerulonephritis ("late syndrome"). Treatment of newborn rats with potent rat interferon preparations also resulted in inhibition of growth, delay in maturation, and the subsequent development of glomerulonephritis. After infection at birth with lymphocyte choriomeningitis (LCM) virus, most strains of mice developed a similar acute early syndrome and surviving mice subsequently developed glomerulonephritis. We postulated that the endogenous interferon induced by LCM virus early in life was partially responsible for these syndromes. Administration of a potent anti-mouse interferon serum to LCM virus-infected mice neutralized the circulating endogenous interferon and inhibited the development of both the early and late syndromes. Our results suggest that large amounts of exogenous or endogenous interferon at a crucial stage of rapid growth or development of mice and rats can induce lesions in several different organs. Some lesions (i.e. the kidney) only become apparent weeks or even months after exposure to interferon.

Animals↗
PubMed1979

NAD-dependent ADP-ribosylation of arginine and proteins by Escherichia coli heat-labile enterotoxin.

Escherichia coli heat-labile enterotoxin (labile toxin, LT) catalyzed the hydrolysis of NAD to ADP-ribose and nicotinamide and the ADP-ribosylation of arginine (Moss, J., and Richardson, S.H. (1978) J. Clin. Invest. 62, 281-285). Analysis of the product of the ADP-ribosylation of arginine by nuclear magnetic resonance spectroscopy indicated that the reaction was stereospecific and resulted in the formation of alpha-ADP-ribosyl-L-arginine. This reaction product rapidly anomerized to yield a mixture of the alpha and beta forms. In the presence of [adenine-U-14C]NAD, E. coli enterotoxin catalyzed the transfer of the radiolabel to proteins; the ADP-ribosylation of proteins was inhibited by arginine methyl ester, an alternative substrate. Digestion of the 14C-protein with snake venom phosphodiesterase released predominantly 5'-AMP. No product was obtained with a mobility similar to that of 2'-(5''-phosphoribosyl)-5'-AMP. This result is consistent with the covalent attachment by the enterotoxin of ADP-ribose rather than poly(ADP-ribose) to protein. Thus, LT is catalytically equivalent to choleragen, an enterotoxin of Vibrio cholerae, and activates adenylate cyclase through a similar stereospecific ADP-ribosylation reaction.

Adenosine Diphosphate Sugars↗
PubMed1979

Choleragen (cholera toxin): a bacterial lectin.

Choleragen (cholera toxin) agglutinated erythrocytes and liposomes containing the toxin receptor, galactosyl-N-acetylgalactosaminyl-(N-acetylneuraminyl)-galactosylglucosylceramide (ganglioside GM1). Cells that had been exposed to GM1 were agglutinated, but agglutination was not observed when cells had been exposed to other gangliosides (GM2, GM3, GD1a, GD1b). Choleragen-dependent agglutination of liposomes was slightly less specific, because liposomes containing either GM1 or GD1b, but neither GM2, GD1a, nor GM3 were agglutinated. The oligosaccharide isolated from GM1 inhibited both the agglutination of cells and liposomes containing GM1 and the binding of choleragen to liposomes containing GM1. Galactose and sialic acid were less effective inhibitors of liposomal agglutination and did not inhibit cellular agglutination or binding of choleragen to liposomes. Liposomal agglutination was dependent on choleragen concentration and occurred with the B but not the A protomer of choleragen. These results suggest that choleragen, through its binding to the oligosaccharide portion of a glycolipid, exhibits lectinlike activity, which results in agglutination of liposomes and erythrocytes.

Agglutination↗