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Biomedical subjects

I Kahane

Publications and source records attributed to I Kahane.

At least 73 records · Page 4Linked to original sources
PubMed1980

Scanning electron microscopy of mycoplasmas adhering to erythrocytes.

The interaction of Mycoplasma pneumoniae and Mycoplasma gallisepticum with human erythrocytes (RBC) was studied by scanning electron microscopy. The tight nature of the attachment of the microorganisms to the RBC was indicated by the indentation of the RBC surface at the site of attachment of M. gallisepticum cells and by traction and resulting distortion in the shape of the RBC at the point of its attachment to M. pneumoniae filaments growing on glass or plastic. In many cases attachment took place via the tip of the filaments, the membrane of the parasite appearing to be fused with that of the RBC. The morphology of the mycoplasmas growing on cover slips conformed in general with previous descriptions obtained by scanning electron microscopy. Growth of M. pneumoniae on glass or plastic consisted of branching filaments spread on the inert surface and microcolonies made up of intertwining filaments projecting into the medium. The filaments had a bulbous swelling adjacent to a tapered tip end. A few filaments were shown to have a ropelike helical twist. M. gallisepticum grown on the cover slips of Leighton tubes had a peculiar fusiform or teardrop shape with blebs at one or both poles of the cells. Elongated filamentous forms and chains of coccobacillary bodies were observed as well.

Cell Adhesion↗
PubMed1980

Isolation of binding sites to glycophorin from Mycoplasma pneumoniae membranes.

Sialoglycoproteins are major receptor sites for attachment of Mycoplasma pneumoniae to respiratory epithelium and erythrocytes (RBC). We used glycophorin, the major sialoglycoprotein of human RBC, as a ligand in affinity chromatography for the isolation of the binding sites from M. pneumoniae membranes. Membranes isolated from M. pneumoniae cells, radioiodinated by the lactoperoxidase technique, were treated with 0.5% deoxycholate. The insoluble residue, exhibiting an increased capacity to bind to RBC, was solubilized by 0.1% sodium dodecyl sulfate. The solubilized material was subjected to chromatography on a glycophorin-Sepharose column. The fraction retained on the column was eluted with 0.2% sodium dodecyl sulfate. It lacked the high-molecular-weight polypeptides and was highly enriched with two polypeptides (apparent molecular weights, 45,000 and 25,000). The eluted fraction exhibited a high capacity to bind to glycophorin-Sepharose beads and a lower capacity to bind to RBC. The binding of the eluted fraction to RBC was almost completely abolished by glycophorin, but not by its hydrophobic moiety. Binding of the fraction to glycophorin-Sepharose beads was inhibited to about the same extent by both glycophorin and its hydrophobic moiety, suggesting that components of the eluted fraction are also capable of binding to the hydrophobic moiety of glycophorin, which is apparently exposed on the beads but not on the RBC surface.

Binding Sites↗
PubMed1980

Distribution of myosin, actin and actin-binding protein in thrombasthenic platelets.

The quantity of myosin, actin, and actin-binding protein (ABP) in platelets and platelet fractions of 5 patients with Glanzmann's thrombasthenia were compared to those of normal individuals. No significant differences were observed between the average amounts of these contractile proteins in unfractionated platelets or platelet membrane obtained after osmotic shock. However, the amount of myosin was significantly decreased in the KCl extract of thrombasthenic platelets ruptured by freezing and thawing,while its specific ATPase activity was increased.

Actins↗
PubMed1979

Receptor-mediated internalization of fluorescent chemotactic peptide by human neutrophils.

Tetramethylrhodamine labeled N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys is a potent chemoattractant for human neutrophils. Binding of this peptide to living neutrophils was observed by means of video intensification microscopy. At 37 degrees C, diffuse membrane fluorescence was seen initially, followed by rapid aggregation and internalization of the fluorescent peptide. These processes are dependent on specific binding to the formal peptide chemotactic receptor.

Cell Membrane↗
PubMed1979

"Lysosomal" enzyme activities in red blood cells of normal individuals and patients with homozygous beta-thalassaemia.

Four hydrolases, beta-galactosidase, beta-glucuronidase, beta-N-acetylglucosaminidase and acid phosphatase were examined in red blood cells (RBC) of normal donors and patients with homozygous beta-thalassaemia. Highly sensitive fluorimetric substrates were used to determine the specific activities of these enzymes. In order to avoid contamination by lysosomal activities derived from white blood cells (WBC), the mature RBV were separated from other blood elements by cellulose chromatography. The hydrolase activities in normal RBC were detected only in their plasma membranes and were found to be considerably lower than in WBC or platelets. In thalassaemic RBC, hydrolase activities were present in both plasma membranes and in the soluble fraction. The normoblast fraction contributed most of the hydrolase activity found in these preparations, suggesting the presence of lysosomal particles in thalassaemic RBC. No differences in the enzymatic activities were found when purified membranes of mature RBC from thalassemic and normal preparations were compared. The origin and roles of these hydrolytic enzymes in normal and thalassaemic RBC membranes are not known.

Acetylglucosaminidase↗
PubMed1979

Adherence of Mycoplasma gallisepticum to glass.

Attachment of washed Mycoplasma gallisepticum cells to glass was quantified with organisms in which membrane lipids were labelled with 3H. Siliconization of the test tubes decreased attachment, while centrifugation increased it. Attachment increased with temperature, decreased with increasing pH and ionic strength of the attachment mixture, but was unaffected by Ca2+, Mg2+ and EDTA. This suggests that ionic bonds, but not salt bridges, participate in the attachment process. Glycophorin, the major receptor responsible for M. gallisepticum attachment to erythrocytes, partially inhibited the attachment of the organisms to glass. However, bovine serum albumin also decreased attachment. Extensive pretreatment of the organisms with trypsin decreased their ability to attach to glass by about 35 to 40%. Trypsin and pronase failed to detach the organisms already bound to glass, suggesting that external mycoplasma cell components, other than membrane proteins, also participate in attachment of the organisms to glass.

Cell Count↗
PubMed1979

Phagocytosis of nucleated and mature beta thalassaemic red blood cells by mouse macrophages in vitro.

Physiological or experimental decrease in sialic acid (SA) content on the red blood cell (RBC) membrane is believed to play an important role in the recognition of these cells by macrophages. Since there is a 20-30% decrease in the SA content on the membrane of thalassaemic RBC, the interaction between macrophages and these RBC was studied in vitro. Using mouse peritoneal macrophages, it was found that these macrophages 'recognize' and phagocytize thalassaemic RBC while RBC from normal donors are hardly phagocytized. The average level of phagocytosis of thalassaemic RBC from splenectomized patients was found to be 22-fold higher than that of RBC from normal donors. The phagocytized cells consisted of both mature and nucleated RBC. Mouse peritoneal macrophages seem to be a useful in vitro system for the study of the accelerated sequestration and shortened life span of thalassaemic RBC.

Animals↗
PubMed1979

Adherence of erythrocytes to Mycoplasma pneumoniae.

The human pathogen Mycoplasma pneumoniae adheres to a variety of cells, including erythrocytes. A hemadsorption technique was developed to quantitate adherence by photometric measurement of lysates of erythrocytes that attached to sheets of M. pneumoniae grown in cups of Linbro plates. Attachment of sheep erythrocytes (SE) increased with higher ionic strength, was unaffected by minor pH variations (6 to 9), and was blocked by anti-M. pneumoniae antiserum, but was not inhibited by a variety of sugars, amino acids, and bovine serum albumin. The reaction was time and temperature dependent. The temperature curve showed peaks at 14 and 28 degrees C with untreated SE but only one peak at about 38 degrees C with glutaraldehyde-treated SE. The temperature dependence indicated involvement of either metabolic or membrane activities in the binding process. Trypsin treatment of the M. pneumoniae sheet abolished adherence of SE but was only partially effective with human erythrocytes and noneffective with rabbit erythrocytes. The binding capacity of the mycoplasma cells for SE was restored by incubation in growth medium for 3 to 4 h; this restoration was inhibited by 10 mug of chloramphenicol per ml. Neuraminidase treatment of SE removed their attachment capacity but had no effect on attachment of rabbit erythrocytes and only a slight effect on attachment of human erythrocytes. Pretreatment of M. pneumoniae with neuraminic acid partially blocked the adherence of SE, whereas rabbit erythrocyte attachment was not affected. Attached SE could be detached by trypsin, but not by neuraminidase. For human and rabbit erythrocytes, the results suggest binding mechanisms other than the interaction between neuraminidase-sensitive receptors and protein-containing binding sites shown for SE.

Animals↗
PubMed1979

Purification and properties of acetate kinase from Acholeplasma laidlawii.

Acetate kinase (EC 2.7.2.1) was purified from Acholeplasma laidlawii cytoplasm by a combination of ammonium sulfate fractionation, gel filtration, diethylaminoethyl-cellulose chromatography, and affinity chromatography on 8-(6-aminohexylamino)-adenosine 5'-triphosphate conjugated to Sepharose 4B. The enzyme was composed of polypeptide chains of about 50,000 molecular weight as estimated from sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Under nondenaturating conditions, apparent molecular weights between 64,000 and 130,000 were obtained, depending upon mainly the ionic strength of the test solution. The enzyme had a narrow specificity for phosphate acceptor acids, whereas both purine and pyrimidine nucleoside triphosphates were suitable phosphate donors. Na(+) and K(+) inhibited both acetyl phosphate and adenosine 5'-triphosphate synthesis, and the latter was also inhibited by high concentrations of adenosine 5'-diphosphate and acetyl phosphate. This substrate inhibition was partially abolished by 0.5 M NaCl. The enzyme catalyzed the independent adenosine 5'-diphosphate<-->adenosine 5'-triphosphate and acetate<-->acetyl phosphate exchanges. The rate of the latter was enhanced by the addition of cosubstrate Mg(2+)-adenosine 5'-triphosphate. The high affinity for substrates, except for acetate, indicated that under physiological conditions the direction of the enzymic reaction favors adenosine 5'-triphosphate synthesis. Thus, a mechanism for adenosine 5'-triphosphate generation in mycoplasmas is suggested.

Acetate Kinase↗
PubMed1979

Binding of lectins to membranes of mycoplasmas from aging cultures.

The binding of iodinated concanavalin A (Con A) and Ricinus communis agglutinin (RCA) to intact cells and isolated membranes of Acholeplasma laidlawii, Mycoplasma hominis and Mycoplasma capricolum decreased with the progression of the culture from the mid- to the late-logarithmic phase of growth. The binding of the lectins to Acholeplasma laidlawii membranes had no significant effect on membrane fluidity, as assessed by electron-paramagnetic resonance spectroscopy of spin-labelled fatty acids, and had no effect on several membrane-associated enzymic activities. Temperature affected the binding of Con A and RCA in an opposite manner: the binding of Con A increased, whereas that of RCA decreased, on raising the temperature from 4 degrees C to 37 degrees C. No significant difference in lectin binding was found between oleate- and elaidate-enriched membranes at low temperatures where the former was in the liquid-crystalline state and the latter in the gel state, suggesting that membranes fluidity does not influence the binding of Con A and RCA to Acholeplasma laidlawii membranes.

Acholeplasma laidlawii↗
PubMed1978

Red cell membrane glycophorin labeling from within the lipid bilayer.

Human red blood cell membranes were labeled from within the lipid bilayer by the apolar photosensitive reagent, 5-[125I]iodonaphthyl-1-azide. Glycophorin, the major sialoglycoprotein of the red cell membrane, was purified by two different methods; it contained approximately half of the total label incorporated into membrane proteins. The label was confined to the trypsin-insoluble peptide of glycophorin that includes a sequence of 20, mainly apolar, amino acids. These findings provide direct evidence that the labeled segment resides within the membrane in direct contact with the lipid bilayer, and support the suggestion that glycophorin spans the bilayer through its hydrophobic domain.

Azides↗
PubMed1978

A new mutant erythrocyte glucosephosphate isomerase (GPI) associated with GSH abnormality.

A case of congenital nonspherocytic haemolytic anaemia associated with a new abnormal glucosephosphate isomerase (GPI), GSH (reduced glutathione) deficiency, and instability and altered carbohydrate membrane composition is reported. The only functional abnormality of the mutant enzyme seems to be a marked instability to heat, urea, and guanidine-HCl. Family studies suggest that the propositus is doubly heterozygous for a maternal gene producing an inactive enzyme and a paternal gene responsible for a structural alteration causing marked lability of the coded enzyme. Experiments of incubation of normal GPI and the propositus's GPI with oxidizing and reducing agents seem to indicate that the abnormality resides in the SH groups of the mutant GPI.

Adolescent↗