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Biomedical subjects

J Moss

Publications and source records attributed to J Moss.

At least 433 records · Page 24Linked to original sources
PubMed1985

Mechanism of inhibition of transducin GTPase activity by fluoride and aluminum.

Transducin, the guanyl nucleotide-binding protein of the retinal light-activated cGMP phosphodiesterase system, is structurally and functionally similar to the inhibitory and stimulatory guanyl nucleotide-binding proteins, Gi and Gs, of the adenylate cyclase complex. All are heterotrimers composed of alpha, beta, and gamma subunits. Gs and Gi can be activated by NaF with AlCl3 as well as by agonists acting through specific receptors. The effects of NaF and AlCl3 on transducin were investigated in a reconstituted system consisting of the purified subunits of transducin (T alpha, T beta, gamma) and rhodopsin. NaF noncompetitively inhibited the GTPase activity of T alpha in a concentration- and time-dependent manner. Inhibition by NaF was enhanced synergistically by AlCl3 which alone only slightly inhibited GTPase activity. None of the other anions tested reproduced the effect of fluoride. Fluoride inhibited [3H]guanosine 5'-(beta, gamma-imido)triphosphate binding to T alpha and release of bound GDP. The ADP-ribosylation of T alpha by pertussis toxin and binding of T alpha to rhodopsin, both of which are enhanced in the presence of T beta gamma, were inhibited by NaF and AlCl3. These findings are consistent with the hypothesis that fluoride enhances the dissociation of T alpha from T beta gamma, resulting in the inhibition of GTP-GDP exchange, and therefore, GTP hydrolysis.

Adenosine Diphosphate Ribose↗
PubMed1985

Kinetic mechanisms of two NAD:arginine ADP-ribosyltransferases: the soluble, salt-stimulated transferase from turkey erythrocytes and choleragen, a toxin from Vibrio cholerae.

A subunit of choleragen and an erythrocyte ADP-ribosyltransferase catalyze the transfer of ADP-ribose from NAD to proteins and low molecular weight guanidino compounds such as arginine. These enzymes also catalyze the hydrolysis of NAD to nicotinamide and ADP-ribose. The kinetic mechanism for both transferases was investigated in the presence and absence of the product inhibitor nicotinamide by using agmatine as the acceptor molecule. To obtain accurate estimates of kinetic parameters, the transferase and glycohydrolase reactions were monitored simultaneously by using [adenine-2,8-3H]NAD and [carbonyl-14C]NAD as tracer compounds. Under optimal conditions for the transferase assay, NAD hydrolysis occurred at less than 5% of the Vmax for ADP-ribosylation; at subsaturating agmatine concentrations, the ratio of NAD hydrolysis to ADP-ribosylation was significantly higher. Binding of either NAD or agmatine resulted in a greater than 70% decrease in affinity for the second substrate. All data were consistent with a rapid equilibrium random sequential mechanism for both enzymes.

ADP Ribose Transferases↗
PubMed1985

Detection of NAD:arginine ADPribosyltransferases in animal tissues using 125I-labeled 1-(p-hydroxyphenyl) 2-guanidinoethane as ADPribose acceptor.

125I-labeled 1-(p-hydroxyphenyl) 2-guanidinoethane (N-guanyltyramine), previously used to assay for the bacterial toxin choleragen (Mekalanos, J.J., Collier, R.J. and Romig, W.R. (1979) J. Biol. Chem. 254, 5849-5854) was utilized to identify NAD:arginine ADPribosyltransferases in animal tissues. The use of this radiolabelled ADPribose acceptor, rather than radiolabelled NAD, would bypass the problem posed by the almost ubiquitous presence of enzymes that degrade NAD. With a homogeneous ADPribosyltransferase from turkey erythrocytes, NAD and 125I-labeled guanyltyramine as ADPribose acceptor, formation of ADPribosyl 125I-guanyltyramine was linear with time and enzyme concentration. The product was indistinguishable on both thin-layer and high-performance liquid chromatography from that formed by choleragen. Using 125I-guanyltyramine, ADPribosyltransferase activity was also demonstrated in crude turkey erythrocyte cytosolic and membrane fractions. When rat liver was fractionated, apparent activity was detected primarily in the microsomes. The NAD-dependent product of the microsomal reaction was, however, distinguished from the turkey erythrocyte transferase product by thin-layer and DEAE-Sephadex chromatography; this product had a retention time identical to that of free 125I on high-performance liquid chromatography. In addition to NAD, the microsomal deiodinase activity was supported by NADH, NADP and NADPH. Phenyl boronate selectively bound ADPribosyl 125I-guanyltyramine and other metabolites of 125I-guanyltyramine which were formed by microsomes in a NAD-dependent process. These metabolites were distinguished from ADPribosyl 125I-guanyltyramine by high-performance liquid chromatography. These results indicate that in some cases, for example, turkey erythrocyte cytosolic and membrane fractions, 125I-guanyltyramine can be used to quantify ADPribosyltransferases in crude mixtures, whereas in others, for example, rat liver microsomes, high-performance liquid chromatographic analysis must be used to identify products.

ADP Ribose Transferases↗
PubMed1985

Heterologous desensitization of adenylate cyclase with prostaglandin E1 alters sensitivity to inhibitory as well as stimulatory agonists.

Adenylate cyclase in cultured human fibroblasts is activated by prostaglandin E1 (PGE1) or beta-adrenergic agonists, e.g., isoproterenol, and inhibited by muscarinic agonists. Incubation with PGE1 reduced adenylate cyclase responsiveness to both PGE1 and isoproterenol; this so-called heterologous desensitization is believed to result from impaired function of the stimulatory guanyl nucleotide-binding protein of the cyclase complex. The effect of heterologous desensitization by PGE1 on inhibition of adenylate cyclase by the muscarinic agonist oxotremorine was examined. Muscarinic inhibition of basal and isoproterenol-stimulated cAMP accumulation was attenuated following exposure to PGE1; the concentration of oxotremorine required for half-maximal inhibition of cAMP accumulation was increased. In both intact cells and membrane preparations the number of binding sites for [3H]scopolamine, a muscarinic antagonist, was unaltered by desensitization. Following exposure to PGE1, receptor affinity for oxotremorine, assessed by competition with [3H] scopolamine, and the guanyl nucleotide sensitivity of agonist binding were reduced. The amount of inhibitory guanyl nucleotide-binding regulatory protein available for [32P]ADP-ribosylation by pertussis toxin was unaltered by desensitization. Thus, heterologous desensitization of adenylate cyclase with the stimulatory agonist PGE1 alters sensitivity to inhibitory as well as stimulatory ligands.

Adenosine Diphosphate Ribose↗
PubMed1985

Activation and stabilization of the catalytic unit of adenylate cyclase.

The requirements for stability and activity of the catalytic unit (C) of adenylate cyclase were investigated. After solubilization of bovine brain membranes in the zwitterionic detergent 3-[(3-cholamidopropyl)dimethylammonio]propane-1-sulphonate (Chaps), the catalytic unit was separated from the stimulatory guanine-nucleotide-binding protein (Gs) by gel filtration on Ultrogel AcA-34. The partially purified C unit was rapidly inactivated at 30 degrees C; 0.25 mM-ATP stabilized activity. Although C-unit activity was dependent on Mg2+ or Mn2+, stabilization by ATP did not require bivalent cations. Activity of the Ultrogel-AcA-34-purified C unit was increased by Ca2+ plus calmodulin and by phosphatidylcholine plus lysophosphatidylcholine; activity in the presence of both activators was significantly greater than with each alone. Calmodulin plus Ca2+ and phospholipids also stabilized C unit. The column-purified C unit was activated by forskolin; the effect of forskolin was additive to those of calmodulin plus Ca2+ and phospholipids. p[NH]ppG-stimulated adenylate cyclase activity was reconstituted by mixing samples from the gel-filtration column containing Gs with C unit. Activation by Ca2+ plus calmodulin and Gs plus p[NH]ppG was additive; Ca2+ plus calmodulin did not alter the concentration of p[NH]ppG required for half-maximal activation. Results were similar with forskolin and Gs plus p[NH]ppG; the presence of one activator did not alter the effect of the other. These studies define conditions for separation of C unit and Gs from brain adenylate cyclase and demonstrate that ATP (in the absence of bivalent cations), phospholipids, calmodulin plus Ca2+, and forskolin all interact with C unit in a manner that is independent of functional Gs.

Adenosine Triphosphate↗
PubMed1985

Effects of pertussis toxin-catalyzed ADP-ribosylation on interactions of transducin and the inhibitory GTP-binding protein of adenylate cyclase with guanyl nucleotides.

Release of bound [3H]Gpp(NH)p from NG108-15 cell membranes was induced by carbamylcholine, enkephalinamide, and norepinephrine, all of which inhibit adenylate cyclase. Release was blocked by antagonist, was greater with multiple agonists than with one, and required guanyl nucleotides. With membranes from pertussis toxin-treated cells, both total [3H] Gpp(NH)p binding and agonist-induced [3H]Gpp(NH)p release was decreased. ADP-ribosylation by toxin of transducin, the retinal GTP-binding protein which is similar in structure and function to that in cyclase, decreased [3H]Gpp(NH)p binding. Thus, the inability to demonstrate agonist-induced [3H]Gpp(NH)p release from toxin-treated NG108-15 membranes may result in part from absence of bound [3H]Gpp(NH)p.

Adenosine Diphosphate Ribose↗
PubMed1985

Identification of enzymatic activities which process protein bound mono(ADP-ribose).

Enzymatic activities have been identified in extracts of cultured mouse cells which catalyze the removal of intact mono(ADP-ribosyl) residues linked to proteins at arginine. Activities that sequentially remove AMP and ribose 5-phosphate have also been identified. These results suggest that mono(ADP-ribosylation) of proteins is a reversible post translational modification.

Adenosine Diphosphate Ribose↗
PubMed1985

Cytochemistry of the tubular aggregates found in hepatocytes of interferon-treated suckling mice.

Administration of mouse interferon to neonatal mice induces the formation of tubular aggregates within hepatocytes. These aggregates are composed of networks of small tubules which are continuous with the granular endoplasmic reticulum. The tubules are bounded by trilaminar unit membranes and exhibit glucose-6-phosphatase activity. These features suggest that the tubular aggregate is an interferon-induced alteration of the endoplasmic reticulum.

Animals↗
PubMed1985

Use of prophylactic combined H1 and H2 antagonists reduces mortality in chymopapain anaphylaxis.

The American experience concerning the epidemiology of anaphylactic reactions following chemonucleolysis with chymopapain (Chymodiactin) were presented. The first study involved 1,585 patients of whom 17% were premedicated with some drug with either an H1 or H2 antagonist or both. The rate of anaphylaxis was 0.82%. Following its clinical introduction, a postmarketing surveillance study was undertaken. During the first 30,000 cases of which 93% were premedicated with combined H1 and H2 antagonists, the frequency of anaphylactic reactions was 0.78%. Subsequently, following the introduction of an immunologic test to screen for circulating IgE, the reaction rate fell to 0.44% in 45,000 cases of which 92% were premedicated with combined H1 and H2 antagonists. Females were far more likely to experience an anaphylactic event. Overall mortality from anaphylaxis decreased from one in 800 to one in 25,000 administrations. The decreased number and severity of these reactions correspond to the development of an immunologic screening test and utilization of prophylactic antihistamines.

Anaphylaxis↗
PubMed1985

Reversibility of arginine-specific mono(ADP-ribosyl)ation: identification in erythrocytes of an ADP-ribose-L-arginine cleavage enzyme.

Enzymes have been identified in animal tissues that catalyze the mono(ADP-ribosyl)ation of arginine and proteins. Since these NAD:arginine ADP-ribosyltransferases under physiological conditions do not appear to catalyze the degradation of the product ADP-ribose-arginine, the possibility was investigated that a different family of enzymes exists that cleaves the ADP-ribose-arginine linkage. An enzyme was identified in and partially purified from turkey erythrocytes that catalyzed the degradation of ADP-ribose-[14C]arginine synthesized by a salt-activated NAD:arginine ADP-ribosyl-transferase, resulting in the release of a radiolabeled compound that was characterized chromatographically and by amino acid analysis as arginine. This putative arginine product was converted in a reaction dependent on NAD and the NAD:arginine ADP-ribosyltransferase to a compound exhibiting properties characteristic of ADP-ribose-arginine. Action of cleavage enzyme on [adenine-U-14C]ADP-ribose-arginine resulted in the release of a radiolabeled compound that behaved chromatographically like [adenine-U-14C]ADP-ribose. Since degradation of ADP-ribose-arginine appears to generate an arginine moiety that is a substrate for the NAD:arginine ADP-ribosyltransferase, it appears that ADP-ribosylation may be a reversible modification of proteins.

ADP Ribose Transferases↗
PubMed1985

Effects of phospholipids and ADP-ribosylation on GTP hydrolysis by Escherichia coli-synthesized Ha-ras-encoded p21.

The Ha-ras protooncogene product p21, which may be involved in control of cellular growth, is a membrane protein that binds guanine nucleotides and hydrolyzes GTP. p21 GTPase activity is stimulated by lysophosphatidylcholine; a delay in activation was observed unless p21 was incubated with the phospholipid prior to assay. Maximal activation by the phospholipid was observed over a narrow concentration range; the presence in the assay mixture of lysophosphatidylcholine at concentrations above this optimum markedly inhibited p21 GTPase. GTP hydrolysis was also stimulated, but to a lesser degree, by phosphatidylcholine. Phosphatidylinositol and phosphatidylserine did not significantly enhance GTPase activity. The stimulatory effect of phospholipid was mimicked, in part, by nonionic detergents. p21 may be related to other GTPases, the regulatory guanine nucleotide-binding G proteins of the hormone-sensitive adenylate cyclase complex and transducin of the retinal light-activated phosphodiesterase system. The G proteins and transducin are heterotrimers; the alpha subunits possess GTPase activity and the beta gamma subunit complex along with agonist-receptor complex or light-activated rhodopsin enhance GTP hydrolysis. p21 GTPase activity was slightly stimulated by rhodopsin, but, in contrast to the GTPase activity of transducin, stimulation was not light-dependent. GTP hydrolysis was enhanced somewhat by beta gamma subunit complex in the absence, but not in the presence, of rhodopsin. Like the G proteins and transducin, activity of p21 was altered by ADP-ribosylation. Modification of p21 catalyzed by an NAD: arginine ADP-ribosyltransferase purified from turkey erythrocytes decreased both GTPase activity and guanine nucleotide binding activity.

Adenosine Diphosphate Ribose↗
PubMed1985

Fluorescent gangliosides as probes for the retention and organization of fibronectin by ganglioside-deficient mouse cells.

Ganglioside-deficient transformed mouse fibroblasts (NCTC 2071A cells), which grow in serum-free medium, synthesize fibronectin but do not retain it on the cell surface. When fluorescent derivatives of gangliosides, containing either rhodamine or Lucifer yellow CH attached to the sialic acid residues, were added to the culture medium, the cells incorporated the derivatives and their surfaces became highly fluorescent. When the cells were stained with anti-fibronectin antibodies and a fluorescent second antibody, fibrillar strands of fibronectin were observed to be attached to the cell surface, with partial coincidence of the patterns of direct ganglioside fluorescence and indirect fibronectin immunofluorescence at the cell surface. When the cells were exposed to bacterial neuraminidase during the time of ganglioside insertion, similar patterns of fluorescence were observed. Because the fluorescent gangliosides are resistant to the enzyme, these results suggest that neuraminidase-sensitive endogenous glycoconjugates were not involved in the ganglioside-mediated retention and organization of endogenous fibronectin. After cells were exposed to exogenous chicken fibronectin, most of the fibronectin was attached to the substratum and only a few fibrils were attached to the cells. When exogenous gangliosides were included in the incubation, there was a striking increase in cell-associated exogenous fibronectin, which was highly organized into a fibrillar network. Conversely, cells incubated for 18 h with exogenous unmodified gangliosides exhibited a highly organized network of endogenously derived fibronectin. Upon further incubation of the cells for 2 h with fluorescent gangliosides, there was considerable co-distribution of the fluorescent gangliosides with the fibronectin network as revealed by immunofluorescence. Our results support the concept that gangliosides can mediate the attachment of fibronectin to the cell surface and its organization into a fibrillar network.

Animals↗
PubMed1985

Histamine release in anesthesia and surgery.

Histamine release can occur in response to anaphylactic or chemically mediated anaphylactoid reactions during general anesthesia. Narcotics and muscle relaxants have been demonstrated both in vitro and in vivo to cause significant histamine release. This histamine release appears to be directly related to changes in the cardiovascular system that are often seen during anesthesia. The use of combined H1 and H2 antagonists to attenuate the effects of anaphylactoid reactions in humans has been shown in several controlled trials. In addition, recent experience with chymopapain administration suggests that the use of H1 and H2 antagonists may be useful in the prophylaxis of immunologically mediated reactions.

Anaphylaxis↗
PubMed1985

Decreased incidence and mortality of anaphylaxis to chymopapain.

A recognized side effect of chemonucleolysis is life-threatening anaphylaxis to chymopapain. In the clinical trials of chymopapain, 13 cases of anaphylaxis were reported in 1585 administrations (0.82%). Two patients died. Data from a postmarketing survey (48,239 questionnaires) were reviewed to identify factors influencing the incidence and severity of anaphylaxis. The results indicate the incidence of anaphylaxis decreased to 0.44% in the 1983-1984 period (126/23,736), a level significantly (P less than or equal to 0.001) below the incidence of 0.82% observed in initial clinical trials. Only three deaths from complications related to anaphylaxis occurred in approximately 75,000 administrations (producing 252 anaphylactic episodes) reported since December 1982. The prophylactic use of antihistamines and pretreatment with intravenous fluids coincide with the dramatic reduction in mortality due to anaphylaxis. However, overdiagnosis of anaphylaxis in the clinical trials and avoidance of chemonucleolysis in patients with IgE antibodies to chymopapain may account, in part, for the reduction in incidence.

Adult↗