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Biomedical subjects

I Kahane

Publications and source records attributed to I Kahane.

At least 55 records · Page 3Linked to original sources
PubMed1983

Influence of cell shape and surface charge on attachment of Mycoplasma pneumoniae to glass surfaces.

Attachment of Mycoplasma pneumoniae to glass is reduced in the presence of protein, and fatty acid-free bovine serum albumin is more effective than Cohn fraction V. Cultures in the early log phase (pH 7.45 to 7.25) and cultures in the stationary or decline phase (pH 6.9 to 6.4) were more sensitive to this inhibiting effect of protein-containing buffer. Treatment of the glass surface with bovine serum albumin, concanavalin A, or polylysine reduced attachment of the mycoplasma cells. The inhibiting effects of both proteins in buffer or on the glass surface could be overcome by the addition of glucose. Modification of the mycoplasma surface charge by blocking of carboxyl groups or neutralization of ionic lipids by tetracaine altered the attachment level, whereas fibronectin and its corresponding antiserum were without effect. The results suggest that the mycoplasma interaction with glass is a complex multifactorial process. In protein-free buffer both hydrophobic and electrostatic forces are involved; in protein-containing fluid, other factors seem to be involved. The energy required for this type of attachment could be necessary for maintenance of cell shape or synthesis of polypeptides.

Adhesiveness↗
PubMed1983

Cord blood polymorphonuclear leukocyte chemotaxis. Differential response to formyl peptide and endotoxin-activated serum.

The chemotactic responses of cord blood polymorphonuclear leukocytes (PMN) to two different chemotactic factors, N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys (F-peptide) and the endotoxin-activated serum (EAS), were compared with that obtained with adult PMN. Cord blood PMN chemotactic response to F-peptide was normal, while the response to EAS was decreased (57%). The number of receptor sites for F-peptide on the membranes of cord blood PMN was also found to be normal (120,000 receptors/cell). The differential chemotactic response of cord blood PMN may suggest a poorly developed receptor system for the EAS, in which complement-derived peptides are the major chemoattractants.

Adult↗
PubMed1983

Demonstration of a natural antigalactosyl IgG antibody on thalassemic red blood cells.

A modified antiglobulin test, based on the high affinity between the Fc portion of the red blood cell (RBC) bound IgG and the Fc receptor on the myeloid cell K-562, was utilized for demonstration of immunoglobulins (Ig) on thalassemic RBC. Ig was found on the RBC of 73 out of 80 patients with thalassemia. The immunoglobulins on the thalassemic RBC belonged to the IgG subclass and were autoreactive. Elution studies utilizing various carbohydrates, or by thermal stripping, indicated that at least part of the IgG molecules found on the thalassemic RBC were specifically reactive with terminal galactosyl residues on the RBC membrane. IgG antibodies with similar reactivity were also demonstrated in normal human serum. These natural antigalactosyl IgG antibodies from normal sera could bind to IgG-depleted thalassemic RBC. Thalassemic RBC and normal senescent RBC were previously found to contain reduced amounts of membrane sialic acid (SA). It is suggested that the antigalactosyl IgG antibodies interact with newly exposed galactosyl residues underlying the sialic acid units. Such interaction may lead to the shortened lifespan of thalassemic RBC and may result in sequestration of senescent normal RBC by the reticuloendothelial system.

Adolescent↗
PubMed1982

Effects of ionophores and dicyclohexylcarbodiimide on Mycoplasma gallisepticum adherence to erythrocytes.

To test the influence of the electrochemical ion gradient across mycoplasma membranes on the capacity of organisms to adhere to host cells, Mycoplasma gallisepticum cells were treated with valinomycin, carbonylcyanide m-chlorophenylhydrazone, and N,N'-dicyclohexylcarbodiimide (DCCD) singly or in combination. Uptake of [3H]tetraphenylphosphonium by the treated cells was employed as a measure of the effects of the ionophores on membrane potential. In the absence of K+, valinomycin increased, whereas carbonylcyanide m-chlorophenylhydrazone, and DCCD decreased [3H]tetraphenylphosphonium uptake. However, with a high level of K+ or with DCCD, uptake of [3H]tetraphenylphosphonium in the presence of valinomycin decreased below control levels, indicating that, generally, the ionophores affected membrane potential in the expected manner. The treated organisms were tested for their capacity to attach to glutaraldehyde-fixed human erythrocytes. DCCD was the best inhibitor of mycoplasma attachment, and in combination with valinomycin attachment, capacity decreased by about 40%. The combination of valinomycin plus carbonylcyanide m-chlorophenylhydrazone was less effective; it decreased attachment by about 15 to 25%. It was concluded that the dissipation of ion gradients across cell membranes decreases only partially mycoplasma adherence, in line with previous findings that isolated mycoplasma membranes retain the major part of the attachment capacity of intact cells.

Adhesiveness↗
PubMed1981

Adhesion of mycoplasmas to eukaryotic cells.

Many pathogenic mycoplasmas are surface parasites, adhering to the epithelial linings of the respiratory and urogenital tracts. Since mycoplasmas lack cell walls their plasma membrane comes in close contact with that of their host, allowing exchange of components between the two membranes and possibly fusion. The tight association of the parasite with its host is illustrated in scanning electron micrographs of Mycoplasma pneumoniae and M. gallisepticum adhering to human red blood cells. Specialized structure at the tips of the mycoplasma cells appear to function as attachment organelles. Our main aim has been to chemically define the receptors on the host cell and the binding sites on the mycoplasma cells responsible for adhesion. Glycophorin (the major sialoglycoprotein of human red blood cells) serves as the main or sole receptor for M. gallisepticum whereas M. pneumoniae binds to additional receptors on human red blood cells. Trypsin treatment of M. pneumoniae cells abolishes their ability to attach to human red cells, suggesting the protein nature of the binding sites. M. pneumoniae membranes solubilized by detergents were subjected to affinity chromatography on glycophorin-Sepharose so that membrane components with high affinity for glycophorin could be isolated. The fraction isolated consisted of several proteins (relative molecular mass 25 000 and 45 000). The binding of this fraction to red cells was relatively low but appeared to be specific, as it was inhibited by glycophorin but not by its hydrophobic moiety. The possibility is discussed that the exposure of the binding sites on the mycoplasma cell surface is influenced by the electrochemical ion gradient across the membrane.

Adhesiveness↗
PubMed1981

Attachment of killed Mycoplasma gallisepticum cells and membranes to erythrocytes.

To correlate viability with attachment capacity, Mycoplasma gallisepticum cell harvested at different growth phases and treated by various agents were tested for their capacity to attach to human erythrocytes. The results show that viability per se is not essential for M. gallisepticum attachment to erythrocytes, as cells killed by ultraviolet irradiation anmd membranes isolated by lysing M. gallisepticum cells by various means retained attachment capacity. However, treatment of the mycoplasmas by protein-denaturing agents, such as heart, glutaraldehyde, or prolonged exposure to low pH, drastically affected or even abolished attachment, supporting the protein nature of the mycoplasma membrane components responsible for specific binding to the sialoglycoprotein receptors on the erythrocytes.

Adhesiveness↗
PubMed1981

Acetate kinase activity in mycoplasmas.

Acetate kinase activity was assayed in 13 mycoplasmas. Nine species exhibited the enzymic activity in the direction of either synthesis of acetylphosphate or adenosine triphosphate. On the other hand Mycoplasma orale, Mycoplasma arthritidis, Ureaplasma urealyticum (10 serotypes), and two strains of Anaeroplasma species exhibited only minimal levels of the enzymic activity. In these four species, the enzyme does not seem to play a key role in adenosine triphosphate formation.

Acetate Kinase↗
PubMed1981

Cytoplasmic helical structure associated with Acholeplasma laidlawii.

A distinct spiral protein structure was found in three species of Acholeplasma, but was not found in the Mycoplasma species studied. The spirals, which are 14 nm in width and of variable length from 50 to 300 nm, are formed by a helical arrangement of 7-nm subunits. A rosette-like structure 45 nm in diameter also composed of 7-nm subunits was found in close association with the spirals and may be a taut in vivo form of the spiral. The electrophoretic profile in sodium dodecyl sulfate-polyacrylamide gels indicated that the spirals are composed of a predominant polypeptide with an apparent molecular weight of 100,000. No evidence can be found for inferring actin-like properties for this structure.

Acholeplasma↗
PubMed1981

Functional study of lipids of PNH red cell membranes: susceptibility of liposomes to reactive lysis.

Lipids extracted with chloroform-methanol from red blood cell membranes of 7 PNH and 13 control subjects were used for the preparation of liposomes, which were then examined with the reactive lysis test. PNH liposomes lysed to a higher extent than control liposomes as indicated by the higher dilution of the limiting complement reagent that was necessary to lyse 50% of the PNH liposomes. A similar finding was also observed with liposomes made of lipids from AET-treated red cells. The enhanced reactive lysis can be attributed to the polar lipid fraction, as indicated by the increased lysis of hybrid liposomes prepared from this polar lipids extracted from PNH erythrocyte membrane and lipids extracted from normal erythrocyte membrane. The increased susceptibility to reactive lysis does not seem to be specific of PNH liposomes, since it was also observed with liposomes prepared from lipids of red cells from beta-thalassemia major and autoimmune hemolytic disease.

Adult↗
PubMed1981

Attachment of mycoplasmas to erythrocytes: a model to study mycoplasma attachment to the epithelium of the host respiratory tract.

Mycoplasma pneumoniae, M. gallisepticum and M. pulmonis are pathogens of the respiratory tract. Their adherence to the host tissue is a prerequisite for manifestation of the disease. The attachment occurs between membrane components of the mycoplasmas and the host cells. In the attachment of M. pneumoniae and M. gallisepticum, binding sites of a protein nature of the mycoplasma membranes interact primarily with sialic acid residues of sialoglycoproteins of the host cell membranes. The latter was clearly indicated in studies on the pathogenic strain of M. pneumoniae and its nonpathogenic nonhemadsorbing mutants, and by the assessment of the direct binding of glycophorin [the major sialoglycoprotein of human red blood cells (RBC)] and other sialoglycoproteins to M. pneumoniae and M. gallisepticum. The components involved in the interaction of M. pulmonis with the host cells are not as well characterized, since the attachment is not affected by proteolytic treatment of the mycoplasmas, nor by removal of sialic acid residues from the host cell membranes. The attachment of the mycoplasmas to the host cells also occurs with nonviable organisms and can, in addition, by reproduced by isolated membranes. The binding sites of M. pneumoniae and M. gallisepticum were partially purified by affinity chromatography, using the high affinity of the binding sites for glycophorin. By this procedure the membranes were solubilized with detergents and chromatographed through glycophorin attached to Sepharose 4B as an affinity matrix. The binding sites retained the high affinity for glycophorin and bound to RBC membranes. Are the binding sites distributed throughout the membrane? Since the binding of the mycoplasma is via a polar structure (the tip or bleb), one may suggest that these structures harbor them. Experimental evidence for their distribution is being sought.

Adhesiveness↗
PubMed1981

Adherence of mycoplasmas to cells and inert surfaces: phenomena, experimental models and possible mechanisms.

Mycoplasmas are typical surface parasites colonizing the mucous membranes of animals and man. Efficient adherence mechanisms are therefore a prerequisite for survival and, in some species, for pathogenicity. The lack of a rigid cell wall enables the mycoplasmas, in contrast to bacterial mechanisms, to actively rearrange their surface structure in a vertical or horizontal direction. The energy requirement for attachment of M. pneumoniae in inert surfaces strongly suggests such a mechanism, although no supporting morphological data are yet available. There seem to exist different kinds of adherence mechanisms depending on the species of mycoplasma and the host involved. The receptors of sheep erythrocytes for M. pneumoniae, M. gallisepticum and M. dispar are neuraminidase-sensitive, whereas those for M. hominis and M. salivarium are not, but are protease-sensitive. On the other hand the receptors of rabbit red blood cells for M. pneumoniae and M. dispar are neuraminidase-resistant. The binding sites on the mycoplasma surface too differ in some properties. Data on M. pneumoniae suggest a protein as major constituent of the binding mechanism. The results of all studies are to some extent also dependent on the method used to examine adherence. Most work was done with either hemagglutination and hemadsorption or with attachment to cells and organ cultures. A special experimental system is provided by the adherence of some species to glass or plastic surfaces. On this model the role of energy metabolism could be studied in more detail. Further strategy of research must include biochemical methods as well as morphological and immunological approaches.

Adhesiveness↗
PubMed1980

The erythrocyte membranes in beta-thalassemia. Lower sialic acid levels in glycophorin.

The sialic acids content of glycophorin of thalassemic erythrocyte membranes is about 25% lower than in glycophorin of normal erythrocyte membranes. Glycophorin extracted from old thalassemic erythrocytes separated by density centrifugation, has about half the sialic acids content found in glycophorin extracted from young thalassemic erythrocytes. Possible sialidase activty was sought in the plasma and erythrocyte membranes of thalassemic erythrocytes. No increased sialidase activity was detected in the plasma of the patients as compared to that of normal donors. Thus, other sites for sialidase activity, or other possibilities have to be explored to account for the increased sialic acid hydrolysis of glycophorin of the thalassemic erythrocytes.

Centrifugation, Density Gradient↗
PubMed1980

A subpopulation of cultured human promyelocytic leukemia cells (HL-60) displays the formyl peptide chemotactic receptor.

The chemotactic peptide N-formyl-Nle-Leu-Phe-Nle-Tyr(125I)-Lys (formyl 125I-peptide) binds in a saturable manner to human promyelocytic leukemia cells (HL-60) grown in suspension culture. The binding is of high affinity (50% binding at 0.4--0.75 nM), is rapid (half-time at 22 degrees C = 10 min), is enhanced by divalent cations, but is poorly reversible. These characteristics are similar to those of the formyl peptide chemotactic receptor on human peripheral blood neutrophils. The relative potencies of a series of synthetic peptides in inhibiting binding to the HL-60 cell receptor correlate closely with their potencies in inhibiting binding to the peripheral neutrophil receptor. However, whereas all peripheral human neutrophils display the receptor, only a subpopulation of the cultured cells will bind and internalize tetramethylrhodamine-labeled N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys. This subpopulation is distinct from the rest of the culture, displays morphological characteristics typical of well-differentiated promyelocytes, and appears to account for all of the measured fromyl 125I-peptide binding. Binding of both 125I-labeled and tetramethylrhodamine-labeled formyl peptide increases in response to treatment of the culture with polar compounds that induce cell differentiation. Cells from the differentiated culture demonstrate a chemotactic response to N-formyl-Nle-Leu-Phe-Nle-Tyr-Lys, whereas cells from the undifferentiated culture do not.

Cell Differentiation↗