Action of group A streptococcus extracellular product(s) on the connective tissue of the human heart valve

Summary The cultivation of a rheumatogenic strain of group A streptococcus in presence of human heart valve connective tissues leads to the release of substance(s) reacting with antistreptococcal polysaccharide and antihuman glycoprotein antibodies.     

Effect of aloe lectin on deoxyribonucleic acid synthesis in baby hamster kidney cells

Summary A homogeneous glycoprotein (mol.wt 40,000) containing 34% carbohydrate was isolated fromAloe arborescens var.natalensis. At a concentration of 5 g/ml, this glycoprotein was shown to stimulate deoxyribonucleic acid (DNA) synthesis in baby hamster kidney (BHK) cells and to have the properties of a lectin which reacts with sheep blood cells. The chemical and physical properties of the glycoprotein (aloe lectin) are also discussed.     

Platelet aggregation is inhibited by phycolectins

Lectins from four marine algal species were examined for interaction with human platelets. The lectin designated hypnin A, from the red algaHypnea japonica, inhibited adenosine diphosphate (ADP)-or collagen-induced human platelet aggregation in a dose-dependent manner. Complete inhibition was observed at concentrations of 100 and 5 g/ml of the lectin with, ADP (2 M) and collagen (0.2 g/ml)-induced platelet aggregation, respectively. At the inhibitory concentration of 0.5 to 100 g/ml, the lectin did not induce aggregation of resting platelets. Lectins from the other three algal species also inhibited ADP-induced human platelet aggregation. These results indicate that the algal lectins are a new group of inhibitors and may be useful to study glycoconjugates on platelet membranes and to design novel platelet aggregation inhibitors.     

Effect of clofibrate on the enzyme activity of rat liver plasma membranes

Summary The activity of 3 plasma membranes marker enzymes (5-nucleotidase, Mg⁺⁺-ATPase and alkaline phosphodiesterase-I) was determined in plasma membranes isolated from liver of control and of clofibrate-treated rats. A complete identity of plasma membranes enzyme activity in the 2 groups of experimental animals was observed for the 3 enzymes studied.     

Changes in erythrocyte membrane lipid composition affect the transient decrease in membrane order which accompanies insulin receptor down-regulation

We have recently demonstrated, using electron paramagnetic resonance (EPR) spectroscopy, that insulin receptor internalization in response to insulin incubation (down-regulation) in human erythrocytes is accompanied by a transient decrease in membrane order, as measured by the 2T order parameter. Since membrane lipids play such an important role in receptor internalization, we investigated the possible effects that an alteration of the normally-occurring lipid profile might have on down-regulation and the concomitant transient decrease in membrane order. Consequently, human erythrocytes enriched with cholesterol and erythrocytes from cirrhotic patients were examined, because both of these groups of cells have a higher cholesterol/phospholipid molar ratio (CH/PL) than controls. The 5-nitroxystearate spin label, which inserts into the lipid bilayer of cell membranes, was used to monitor changes in 2T for a 3-h period at 37°C. We report here that both cholesterol-enriched and cirrhotic erythrocytes do not down-regulate, as demonstrated by binding assays, and that they do not show the typical transient decrease in membrane order observed in controls. The results seem to indicate that a more ordered membrane inhibits internalization of the insulin receptor in erythrocytes, and that an increase in membrane disorder is necessary for insulin receptor down-regulation.     

Effects of atmospheric pollution on human health

Most air pollutants do not lead to specific diseases. Depending on the pollutant, the concentration and the duration of exposure, some organs are more affected than others. The most frequent disorders are those caused by irritant gases and particulates on the mucous membranes and respiratory organs. The consequences are eye, nose and throat inflammations, diminished lung function, increased susceptability to respiratory infection and a higher incidence of chronic bronchitis. These disorders and diseases are, of course, influenced by other factors as well, such as immune deficiency, allergies, occupational exposure to pollutants, and particularly smoking. The effects of air pollutants are, therefore, multifactorially conditioned and nonspecific disorders are placed in the foreground. Evidence for an association of air pollution with adverse effects on human health is drawn from three sources: animal experiments, experimental human exposures, and epidemiologic studies of exposed human populations. The burden of atmospheric pollution must be reduced to protect human health by an adequate safety margin. In particular, the increased sensitivity of sick and aged people as well as children should be taken into account. In defining the maximum emmission levels, preventive aspects should have priority so as to keep the risk of damage to health and the harmful influences on the environment to a minimum.This article Effects of atmospheric pollution on human health by H. U. Wanner is a revised version of the same article that was first published in the Proceedings of the 1990 European Aerosol Conference; special issue of the J. Aerosol Sci., Vol. 21, Suppl. 1 (1990) 389–396.Reprinted with kind permission from Pergamon Press Ltd, Headington Hill Hall, Oxford OX3 0BW, Great Britain.     

Structure of the porcine thyrotropin receptor: a 200 kilodalton glycoprotein heterocomplex

Summary We have determined that the porcine thyroidal TSH receptor is a glycoprotein heterotetramer composed of two M_r 35,000 () covalently linked subunits which interact noncovalently with two copies of (M_r 66,000) chains.Acknowledgments. This work was supported by grants from the Medical Research Council of Canada.     

Purification and some properties of hemagglutinin from the Myxomycete,Physarum polycephalum

A new hemagglutinin was isolated from the plasmodium ofPhysarum polycephalum by salting out with ammonium sulphate followed by chromatography on DE-32, DEAE-Toyopearl and hydroxyapatite. This hemagglutinin, named physarumin, was purified 1000-fold over crude extracts. The molecular weight of physarumin was determined to be 22,000 by size exclusion chromatography on Bio-Gel P-60 and 8,700 by SDS-polyacrylamide gel electrophoresis. Physarumin agglutinated rabbit, guinea pig, horse and human erythrocytes. Physarumin-induced hemagglutination was inhibited by fetuin and ₁ glycoprotein, but not by commercially available mono-and disaccharides. Hemagglutinating activity was blocked by EDTA, and was restored by adding Ca²⁺ but not by Mg²⁺.     

Tangential flow filtration ofBordetella pertussis submerse cultures

Summary A procedure is reported for the large scale separation ofBordetella pertussis microorganisms from liquid culture media by tangential flow filtration (cross flow filtration) using anisotropic membranes with a cut-off limit of 1×10⁶ daltons, and microporous membranes with a pore size of 0.22 m.     

Identification of ϱ-antigenic determinants on the surface,of mouse T-lymphocytes

Summary A monospecific antiserum has been prepared in rabbits against purified -antigen, a 100,000 mol.wt glycoprotein found on the surface of mouse L-cells. This antiserum has been employed to demonstrate the presence of -antigenic determinants selectively on the surface of mouse T-, but not B-lymphocytes.We thank Drs A. Christopher and R. Hunt for advice during the course of these studies. This work was supported by grants from the U.S. Public Health Service and the American Cancer Society.     

Influence of electrical stimulation on the subcellular distribution of dopamine-β-hydroxylase in the dog spleen

Résumé Une stimulation électrique in situ de la rate du chien provoque l'apparition de membranes contenant de la dopamine--hydroxylase. Les membranes sont très probablement le résultat d'une fusion de la membrane axonale et de la membrane vésiculaire, pendant le processus de décharge. Une telle formation de membranes indique que les particules chargées de noradrénaline ne peuvent être utilisées qu'une seule fois.     

Inhibition of hepatic Na+, K+-adenosinetriphosphatase in taurolithocholate-induced cholestasis in the rat

Summary Na⁺, K⁺-adenosinetriphosphatase (Na⁺, K⁺-ATPase) activity was decreased in liver plasma membranes from rats in which cholestasis had been induced by i.v. administration of sodium taurolithocholate (5 moles/100 g b. wt). Incubation of liver plasma membranes with taurolithocholate (10–1300 M) caused significant and dose dependent reductions of Na⁺, K⁺-ATPase activity at taurolithocholate concentrations above 100 M. These findings lend support to the hypothesis that cholestasis induced by monohydroxy bile acids is at least partially the result of an inhibition of hepatic Na⁺, K⁺-ATPase activity.This work was supported by the Swiss National Science Foundation.The authors thank Mr H. Sägesser and Miss B. Schütz for technical assistance.     

In vitro modulation of rat adipocyte ghost membrane fluidity by cholesterol oxysterols

The effects of cholesterol and cholesterol-derived oxysterols (cholestanone, cholestenone, coprostanone and epicoprostanol) on adipocyte ghost membrane fluidity were studied using a fluorescence depolarization method. The fluorescence anisotropy of the treated membranes was determined using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH). Cholestanone and cholesterol decreased membranes fluidity at both the concentrations tested (10 & 50 M) while the rest of the sterols did not exert any significant effect on membrane fluidity. In the presence of epinephrine, cholestanone partitioned more towards the lipid core but cholesterol partitioning was not affected. The fusion activation energies (E) obtained for membranes preincubated with cholestanone (8.6 kcal/mol) and cholesterol (8.2 kcal/mol) were not significantly different from that of untreated membranes (8.3 kcal/mol). Membranes preincubated with cholestanone and cholesterol did not exhibit any change in lipid phase throughout the temperature range (10–45°C) tested. The sterols were found to inhibit fisetin-induced phospholipid methylation in isolated rat adipocytes in the rank order of cholesterol > epicoprostanol > cholestanone=cholestenone=coprostanone, while basal methylations was unaffected. When adipocytes were preincubated with the sterols before the addition of fisetin, cholestanone and cholestenone showed 74% and 66% inhibition of maximal methylation respectively. These results indicated that cholesterol oxysterols interact differently with rat adipocyte membranes, with cholestanone interacting more with phospholipids located at the inner lipid bilayer (e.g. phosphatidylethanolamine) while cholesterol interacts more with phosphatidylcholine located at the outer lipid bilayer. This differential interaction may cause selective changes in membrane fluidity at different depths of the bilayer and thus may modulate the activities of membrane-bound proteins such as enzymes and receptors.     

Preparation of a plasma membrane fraction from the brown adipose tissue

Résumé Les membranes plasmatiques des tissus adipeux brun et blanc sont isolées de la fraction microsomale selon une modification de la technique décrite parKamat etWallach ⁸. Les résultats de l'analyse enzymatique démontrent un degré de purification satisfaisant des membranes plasmatiques et des microsomes.

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This work was supported by a grant from the Fonds national suisse de la Recherche scientifique.     

Role of phospholipids in the binding activity of vasoactive intestinal peptide receptors

Summary Phospholipase digestion of rat intestinal epithelial cell membranes was performed in order to study the influence of membrane phospholipids on the binding activity of VIP receptors. Phospholipases A₂ and C strougly (ED₅₀4×10^–2 and 4×10^–1 g/ml, respectively) and rapidly reduced¹²⁵I-VIP binding to membranes whereas phospholipase D was ineffective. This suggests an important role of both hydrophobic and hydrophilic groups of phospholipids on VIP receptor binding activity.This work was supported by INSERM (CRL 827017) and the Fondation pour la Recherche Médicale Française.     

Ultrastructural localization of catalase and D-amino acid oxidase in ‘normal’ fetal mouse liver

Summary In the hepatocytes of normal fetal mice from mothers which were carriers of muscular dysgenesis, catalase and D-amino acid oxidase (DAAO) positive as well as negative peroxisomes were observed. DAAO reaction product was occasionally localized in patches around cell membranes and DAAO-positive peroxisomes were frequently observed near mitochondria.     

Proteoglycans of basement membranes

Proteoglycans carrying either heparan sulfate and/or chondroitin sulfate side chains are typical constituents of basement membranes. The most prominent proteoglycan (perlecan) consists of a 400–500 kDa core protein and three heparan sulfate chains. Electron microscopy and cDNA sequencing show a complex and elongated domain structure for the core protein which in part is homologous to that of the laminin A chain. This structure may be varied by alternative splicing and proteolysis. Integration into basement membranes probably occurs by heparan sulfate binding to laminin and collagen IV, core protein binding to nidogen and by limited self assembly. The proteoglycan is in addition a cell-adhesive protein which is recognized by 1 integrins. Several more proteoglycans with smaller core proteins (10–160 kDa) apparently exist in basement membranes but are less well characterized. Biological functions include control of filtration through basement membranes and binding of growth factors and protease inhibitors.     

Zone immunoelectrophoresis assay applied to α1 glycoprotein secretion by isolated rat hepatocytes

Summary A method for measuring proteins in low concentrations applying the zone immunoelectrophoresis assay is reported. The low detection limit makes it possible to measure ₁-acid glycoprotein in rat serum and also to quantify the secretion of this protein after concentration of the incubation media containing less than 10⁷ isolated rat hepatocytes. The method is simple and consumes very small quantities of antiserum.     

5′-Nucleotidase activity in liver homogenates of rats treated with CCl4, colchicine,cycloheximide, emetine,ethanol, ethionine and 5-fluorotryptophan

Summary 5-Nucleotidase activity, an enzyme marker of the plasma membranes, increases in female rat liver homogenates following ethionine administration, while homogenates from males show no changes. Treatment with CCl₄, colchicine, cycloheximide, emetine, ethanol and 5-fluorotryptophan does not significantly modify the 5-nucleotidase activity of liver homogenates of either female or male rats.