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Biomedical subjects

J Moss

Publications and source records attributed to J Moss.

At least 487 records · Page 27Linked to original sources
PubMed1983

Relationship of precipitating antibodies to soluble cellular antigens and histologically defined renal lesions in systemic lupus erythematosus.

Antibodies to nuclear ribonucleoprotein (nRNP), Sm, SS-A, and SS-B, were studied by a quantitative immunodiffusion technique in 48 patients with systemic lupus erythematosus (SLE). There was no correlation between the presence or titre of antibodies to any of these antigens and clinically apparent renal disease. However, among 34 patients who had renal biopsies antibodies to nRNP, Sm, and/or SS-A were seen in all 8 patients with membranous glomerulonephritis. Low-titre antibodies (less than 1:4) were seen in 3 out of 7 patients with diffuse proliferative glomerulonephritis. Longitudinal studies in 4 patients who had serial biopsies indicated that the association between serological and histological findings was maintained for prolonged periods. In 2 patients whose biopsy pattern changed, antibodies to nRNP, Sm, and SS-A antedated the development of membranous nephritis.

Antigens↗
PubMed1983

Receptors for bradykinin in intact cultured human fibroblasts. Identification and characterization by direct binding study.

Bradykinin receptors on cultured human fibroblasts were characterized using [2,3-prolyl-3,4-3H(N)]bradykinin as radioligand. During incubation with intact fibroblasts, intact [3H]bradykinin was lost much more rapidly at 37 degrees than at 4 degrees C as determined by bioassay, high-performance liquid chromatography, and ion-exchange chromatography, and is likely to be degraded. At 4 degrees, but not at 37 degrees C, bradykinin remained intact in the presence of 2 mM bacitracin, but not in the presence of soybean trypsin inhibitor or SQ-20881, an inhibitor of kininase II. Specific binding at 4 degrees C was saturable with a maximum number of binding sites of 230 +/- 18 fmol/mg protein (mean +/- SE, n = 4) and a dissociation constant of 4.6 +/- 0.5 nM (mean +/- SE, n = 4). Linear Scatchard plots, Hill coefficients close to unity (0.95-1.06), and the failure of excess bradykinin to influence dissociation kinetics are consistent with a single component binding system with no significant cooperativity. Na+ at physiological concentrations and Ca++ or Mg++ at 3-10 mM reduced binding by 25%. The relative potencies of bradykinin analogues and unrelated peptides in competing for [3H]bradykinin binding indicated a specificity of the binding sites consistent with that of a B2 type receptor. Potencies of the peptides in displacing [3H]bradykinin correlated with their abilities to release prostacyclin, determined as its metabolite 6-keto-PGF1 alpha. This system, the first in which bradykinin receptors on human cells have been characterized, should prove useful for investigation of the regulation of bradykinin-influenced biological processes.

Binding Sites↗
PubMed1983

Alterations in cyclic AMP phosphodiesterase activities during differentiation of 3T3-L1 cells.

3T3-L1 cells contain multiple forms of cyclic nucleotide phosphodiesterase in both supernatant (100,000 X g, 40 min) and particulate fractions. Supernatant fractions from both undifferentiated and differentiated cells contained calmodulin-sensitive activity. In undifferentiated 3T3-L1 cells, only a small fraction of the total cAMP phosphodiesterase activity was found in the particulate fraction and the specific activity of the particulate was lower than the supernatant. With differentiation the specific activity of the particulate doubled, and there was a dramatic increase in total activity in this fraction, while in the supernatant total cAMP phosphodiesterase activity increased less and specific activity decreased. The particulate fraction accounted for approximately 70% of the total cAMP phosphodiesterase activity in differentiated cells in contrast to about one-third in undifferentiated cells. In addition, there was a qualitative change in particulate phosphodiesterase activity. In fractions from 3T3-L1 adipocytes, with either cAMP or cGMP as substrate, Lineweaver-Burk plots were nonlinear, with low Km components of less than 1 microM, and cGMP inhibited cAMP hydrolysis. In particulate fractions from undifferentiated cells, cGMP did not inhibit and often enhanced hydrolysis of cAMP. With differentiation, there was also a marked increase in particulate cGMP phosphodiesterase activity. cAMP and cGMP phosphodiesterase activities solubilized from particulate fraction of differentiated cells coeluted from DEAE-Biogel and exhibited kinetic properties similar to the crude particulate fractions. During differentiation, there seems to be an alteration in the distribution of phosphodiesterase activity as well as the appearance of a particulate phosphodiesterase with kinetic properties similar to a particulate phosphodiesterase found in mature rat adipocytes.

1-Methyl-3-isobutylxanthine↗
PubMed1983

Experimental interstitial renal fibrosis in rats: nephritis induced by N-(3,5-dichlorophenyl)succinimide.

The nephrotoxic properties of the chemical N-(3,5-dichlorophenyl)-succinimide were investigated in rats with a view to establishing the usefulness of this chemically-induced nephritis as a model of chronic interstitial renal fibrosis. The compound was synthesized and given daily by gastric intubation as a suspension in arachis oil B.P. to male WAG-strain rats, for periods of up to 108 days. Polydipsia and polyuria resulted rapidly in all treated animals and persisted for the duration of the experiment. There was a progressive increase in the extent of proteinuria in all treated animals and, by the end of the experiment, there was an increase in the plasma levels of urea and creatinine. Short term treatment (up to 3 days) resulted in focal areas of necrosis of some proximal convoluted tubules. Treatment for 28 days resulted in patchy but severe tubular interstitial nephritis with which was associated a moderate interstitial fibrosis. By 108 days, the nephritis was more widespread and the interstitial fibrosis was severe. The activity of proline hydroxylase, a part of the intracellular sequence of collagen synthesis, showed progressive increase in the renal cortex throughout the experiment and there was an associated increase in the cortical hydroxyproline content, a measure of the amount of collagen present. Associated with this biochemical evidence of an active, chronic fibrosis, was an increased water content of the cortical tissue. The results indicate that this chemically-induced, tubular interstitial nephritis is indeed a good and reliable model of interstitial renal fibrosis.

Animals↗
PubMed1983

Characterization of NAD: arginine ADP-ribosyltransferases in animal tissues.

Two NAD: arginine ADP-ribosyltransferases (transferase "A" and "B") were identified in turkey erythrocytes and purified to homogeneity. Both transferases in the presence of NAD catalyzed the ADP-ribosylation of arginine, other low molecular weight guanidino compounds and proteins. ADP-ribosyltransferase A was activated by chaotropic salt or histone. Activation was associated with the disaggregation of an inactive, rapidly sedimenting, high molecular weight species to a protomeric form of approximately 28,000 daltons; this protomer in equilibrium aggregate transition was rapidly reversible. In the presence of salt, the Km's for NAD and arginine methyl ester were 15 microM and 1.3 mM, respectively; the turnover number for the purified enzyme was approximately 9,900 mol X min-1 X mol enzyme-1. ADP-ribosyltransferase B exhibited a substrate specificity clearly distinct from that of transferase A. Transferase B had a Mr of 32,000, slightly larger than that of the transferase A protomer. The activity of transferase B was unaffected by histone and inhibited by chaotropic salts; its Km's for NAD and arginine methyl ester of 36 microM and 3 mM, respectively, were similar to those obtained with transferase A. These studies are consistent with the presence of two different NAD: arginine ADP-ribosyltransferases in turkey erythrocytes exhibiting distinct kinetic, regulatory, and physical properties.

ADP Ribose Transferases↗
PubMed1983

Diazepam-fentanyl interaction--hemodynamic and hormonal effects in coronary artery surgery.

Diazepam has been reported to produce hypotension when administered with anesthetic doses of fentanyl. Twenty patients undergoing coronary bypass surgery were randomly assigned to one of four treatment groups: group 1, no diazepam; groups 2, 3, and 4, 0.125, 0.25, and 0.5 mg X kg -1 of diazepam, respectively. All patients then received 50 micrograms X kg -1 fentanyl at 400 micrograms X min -1 and 0.4 mg X kg -1 metocurine at 2 mg X min -1. Hemodynamic parameters were recorded and blood was sampled for measurement of plasma catecholamine and histamine concentrations. Heart rate, cardiac index, stroke volume index, central venous pressure, pulmonary arterial and wedge pressures, and pulmonary vascular resistance did not change significantly in any group. Patients in groups 2-4 had significant decreases in mean arterial pressure and systemic vascular resistance during fentanyl infusion. These hemodynamic changes were accompanied by decreases in plasma epinephrine and norepinephrine levels. These hemodynamic and hormonal changes did not occur in patients given fentanyl only. Plasma histamine levels did not change significantly in any group. Caution should be used when diazepam in doses as small as 0.125 mg X kg -1 are combined with high-dose fentanyl anesthesia.

Adult↗
PubMed1983

Uptake and metabolism of exogenous gangliosides by cultured cells: effect of choleragen on the turnover of GM1.

When added to the culture medium, 3H-labeled GM1 (tritiated predominantly in the terminal galactose residue) was taken up by murine NCTC 2071 and rat glioma C6 cells, both of which are GM1-deficient. Upon incubating the labeled cells in fresh medium, the cell-associated GM1 was metabolized by the cells with a half-life of 1 to 2 days. Some of the GM1 was converted to GD1a but the bulk of the label appeared in the medium as degradation products. When GM1 labeled in the sialic acid or lipid portion of the molecule was utilized, GM2 also was detected with time in the cells and only a small fraction of the radioactivity was detected in the medium. The rat glioma C6 cells appeared unable to degrade the GM2 that they accumulated; this was demonstrated directly by incubating the cells with labeled GM2. The uptake and subsequent metabolism of GM1 was observed over a wide range of GM1 concentrations (10(-8) to 10(-4) M). The GM1-treated cells initially bound more iodinated choleragen than did untreated cells; but with time, binding capacity decreased. When GM1-treated cells were transferred to fresh medium in the presence of excess choleragen, the amount of cell-associated GM1 remained relatively constant for several days; the conversion of GM1 to GD1a also was blocked. Although labeled GM3 and GD1b also were taken up by the cells, choleragen had no effect on their subsequent metabolism. Choleragenoid, the binding subunit of choleragen, also inhibited GM1 metabolism without activating adenylate cyclase. These results indicate that exogenous gangliosides taken up by cultured cells are metabolized and that choleragen, which binds with high affinity to GM1, specifically prevents the metabolism of this ganglioside.

Animals↗
PubMed1983

Reliability of faculty assessments of student case histories: a problem in chiropractic education.

A competency based educational model necessitates reliable evaluation. This study examined faculty reliability in assessing students' case histories at one chiropractic college. Previous studies have found great variation in faculty assessment of clinical performance in medical residents. In this study, sixteen faculty members at the Canadian Memorial Chiropractic College evaluated three case histories by completing five rating scales on each one. The study found little faculty agreement in judging the case histories. Faculty evaluations ranged from extremely poor to extremely excellent for the same case history. In addition, the data indicate that the faculty's ratings were influenced by a halo effect. Evaluators made a general judgement, which influenced the ratings on the five scales. It is suggested that meetings of clinical instructors to standardize criteria of assessment may be beneficial.

Chiropractic↗
PubMed1982

Effect of differentiation on the adenylate cyclase system of 3T3-C2 and 3T3-L1 cells. Determination of choleragen substrates in differentiating 3T3-L1 and nondifferentiating 3T3-C2 cells.

3T3-L1 preadipocytes, when treated with 3-isobutyl-1-methylxanthine, dexamethasone, and insulin, differentiate into cells with the morphological and biochemical properties of adipocytes; the closely related 3T3-C2 cells, under identical conditions, exhibit a low frequency of adipocyte conversion. During differentiation, 3T3-L1 preadipocytes acquire an increased responsiveness to certain agonists (e.g. isoproterenol and adrenocorticotropic hormone) that influence lipolysis and lipogenesis through activation of adenylate cyclase, whereas 3T3-C2 cells do not. It has been suggested that changes in hormone responsiveness of 3T3-L1 cells during differentiation result from increased amounts of the guanyl nucleotide-binding protein of adenylate cyclase, as demonstrated by choleragen-catalyzed [32P]ADP ribosylation of 42 and 49-50-kilodalton particulate peptides. Particulate fractions from nondifferentiating 3T3-C2 cells, like those from 3T3-L1 cells, contained choleragen substrates of 42 and 46-47 (doublet) kilodaltons. Incubation of intact 3T3-L1 or 3T3-C2 cells with choleragen prior to preparation of particulate fractions prevented the subsequent in vitro choleragen-dependent [32P]ADP ribosylation of only these peptides. Increased incorporation of radioactivity into both the 42 and 46-47-kilodalton peptides was observed during differentiation of 3T3-L1 cells. However, a similar increase was also observed in nondifferentiating 3T3-C2 cells subjected to the differentiation protocol. Therefore, increased hormone responsiveness of 3T3-L1 adipocytes cannot be explained solely on the basis of increased labeling, and perhaps increased amounts, of the guanyl nucleotide-binding protein.

Adenosine Diphosphate Ribose↗
PubMed1982

Mechanism of action of cholera toxin on intact cells. Generation of A1 peptide and activation of adenylate cyclase.

When intact mouse neuroblastoma NB cells were incubated with choleragen at 4 degrees C, washed, and incubated at 37 degrees C, activation of adenylate cyclase occurred rapidly after a delay of 15 min. The cells were incubated under the same conditions with 125I-labeled toxin, lysed, and solubilized with sodium dodecyl sulfate under mild conditions. Soluble proteins were subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis in the absence of dithiol reductants to separate labeled toxin products. Initially, only 0.1 to 0.2% of the cell-associated radioactivity migrated on the gels as the A1 peptide of choleragen. After a 15-min delay, the amount of A1 peptide increased rapidly with time and paralleled the activation of adenylate cyclase. Similar results were observed with human skin fibroblasts, Friend erythroleukemic cells, and II3-alpha-N-acetylneuraminosyl-gangliotetraosylceramide-treated rat glioma C6 cells. When toxin-treated NB cells were incubated at increasing temperatures, generation of A1 peptide and activation of adenylate cyclase increased in parallel. Both processes were prevented by incubation of cells at 4 or at 37 degrees C in the presence of anticholeragen antibodies. These results indicate that there is delay both in the formation of A1 peptide and in the activation of adenylase cyclase in intact cells. As A1 is believed to be the catalytically active component of choleragen, it is suggested that the lag period may be related in part to the time required to generate A1 peptide from choleragen.

Adenylyl Cyclases↗
PubMed1982

Kinetic analysis of agonist-receptor interactions. Model for the "irreversible" binding of choleragen to human fibroblasts.

Current studies on receptor-ligand interactions usually employ a "binding" step followed by extensive washing to remove free ligand. This procedure, by definition, removes reversibly bound ligand from the receptor; the equations used by most workers to analyze the data, however, require an equilibrium between free and bound ligand and are not applicable given the design of most binding assays. The assay, in fact, measures binding that is slowly reversible or irreversible. Assuming that ligand receptor interaction involves two stages with a reversible step followed by an "irreversible" event, the Ka for the reversible reaction may be obtained from the rate of the irreversible step. 125I-Choleragen binding to human fibroblasts was only slowly reversible at both 0 and 37 degrees C. The two-step model was, therefore, applied experimentally to determine the Ka for the reversible step in 125I-choleragen binding to human fibroblasts at 0 degrees C (Ka = 1.9 x 10(8) M-1) and at 37 degrees C (Ka = 3.6 x 10(8) M-1). As predicted by the two-step model for ligand binding, the addition of 50 micrograms/ml of unlabeled toxin enhanced the rate of release of radioactivity at 37 degrees C; the rate of radiolabel release remained low at 0 degrees C, even with unlabeled toxin present in the medium. The rate of release of previously incorporated 125I-toxin was accelerated by 50 micrograms/ml of toxin greater than 5 micrograms/ml of toxin. The two-step model for ligand binding appears to be applicable to the study of 125I-choleragen binding to fibroblasts and should be useful, in general, for the analysis of receptor-ligand interaction.

Binding, Competitive↗