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Biomedical subjects

I Kahane

Publications and source records attributed to I Kahane.

At least 91 records · Page 5Linked to original sources
PubMed1978

Adherence of Mycoplasma gallisepticum to human erythrocytes.

Pathogenic mycoplasmas adhere to and colonize the epithelial lining of the respiratory and genital tracts of infected animals. An experimental system suitable for the quantitative study of mycoplasma adherence has been developed by us. The system consists of human erythrocytes (RBC) and the avian pathogen Mycoplasma gallisepticum, in which membrane lipids were labeled. The amount of mycoplasma cells attached to the RBC, which was determined according to radioactivity measurements, decreased on increasing the pH or ionic strength of the attachment mixture. Attachment followed first-order kinetics and depended on temperature. The mycoplasma cell population remaining in the supernatant fluid after exposure to RBC showed a much poorer ability to attach to RBC during a second attachment test, indicating an unequal distribution of binding sites among cells within a given population. The gradual removal of sialic acid residues from the RBC by neuraminidase was accompanied by a decrease in mycoplasma attachment. Isolated glycophorin, the RBC membrane glycoprotein carrying almost all the sialic acid moieties of the RBC, inhibited M. gallisepticum attachment, whereas asialoglycophorin and sialic acid itself were very poor inhibitors of attachment. Only part of the (125)I-labeled glycophorin bound to mycoplasmas could be removed by neuraminidase or by exchange with unlabeled glycophorin. It is suggested that glycophorin, representing the isolated major RBC receptor for M. gallisepticum, binds to the mycoplasmas both specifically, through its sialic acid moieties, and nonspecifically, through its exposed hydrophobic polypeptide moiety.

Calcium↗
PubMed1978

Hydrolase activities in normoblasts of beta-thalassemic patients.

A physiological role for glycosidases in cell membranes has been suggested. Therefore the activities of four glycosidases--beta-galactosidase, beta-glucoronidase, N-acetyl-beta-glucosaminidase and acid phosphatase--were examined in normoblasts and membranes of red blood cells (RBC). The enzymatic assays were based on the hydrolysis of fluorimetric 4-methylumbelliferone from the enzyme substrate. In order to avoid contamination by lysosomal activities derived from RBC, the mature RBC and normoblasts obtained from normal controls and thalassemic patients were separated from other blood elements by cellulose chromatography. The cells were disrupted and lysed by freezing and thawing hypotonic solution. Higher enzymatic activities were found in preparations from thalassemic patients than from normal subjects. With a sucrose density gradient, further separation of normoblasts from RBC membranes was obtained, indicating that the normoblast fraction contributed most of the high specific activity found in the thalassemic preparation. It was concluded that relatively high glycosidase activities are present in normoblasts of thalassemic patients. Lower but significant activities were detected in RBC membranes of normal control subjects and thalassemic patients.

Acetylglucosaminidase↗
PubMed1978

Aberrant congenital dyserythropoietic anemia with negative acidified serum tests and features of thalassemia in a Kurdish family.

Three siblings of a Kurdish Jewish family with clinical and hematologic findings compatible with congenital dyserythropoietic anemia (CDA) are described. All patients presented with mild anemia, marked hyperbilirubinemia and splenomegaly. The bone marrow morphology and ultrastructure of the normoblasts was typical of CDA type II and there was strong agglutination of the patients' red blood cells by anti-i serum. These patients displayed two features that were not characteristic of CDA type II, namely, the acidified serum lysis test was negative on more than 10 occasions, and high levels of Hb A2 were observed in two siblings. In one of the siblings, abnormal globin-chain synthesis was found and alpha-chain production exceeded beta-chain production, as in beta-thalassemia minor. In the light of the above findings, our patients are perhaps best classified as having aberrant CDA with features of thalassemia.

Adult↗
PubMed1977

Cholesterol-phosphatidylcholine dispersions as donors of cholesterol to Mycoplasma membranes.

Growing cells of sterol-requiring Mycoplasma hominis and sterol non-requiring Acholeplasma laidlawii were used to test the ability of cholesterol-dipalmitoyl phosphatidylcholine dispersions to serve as cholesterol donors to these organisms. Dispersions with high cholesterol to phosphatidylcholine ratios were more effective than dispersions with low cholesterol to phosphatidylcholine ratios in donating cholesterol to the membranes of both mycoplasmas and in promoting growth of the sterol-requiring species. M. hominis took up almost three times as much cholesterol as did A. laidlawii. In addition, significant quantities of the phosphatidylcholine component of the dispersions were found to be associated with M. hominis membranes as against none in the A. laidlawii membrane preparations. In all cases, the percentage of cholesterol taken up by M. hominis from the dispersions exceeded that of phosphatidylcholine by a factor of 3-5. These results were interpreted to suggest that all the cholesterol taken up by A. laidlawii is transferred from the dispersion to the membranes by a process which involves only a transient contact between the organisms and the lipid dispersions, whereas a certain amount of the cholesterol taken up by M. hominis may also be derived from lipid dispersions adhering to or fusing with the cell membranes.

Acholeplasma laidlawii↗
PubMed1977

Isolation of a glycoprotein from Mycoplasma pneumoniae membranes.

A glycoprotein was detected in Mycoplasma pneumoniae membranes. Its apparent molecular weight was about 60,000, as observed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. It corresponded to the single band that was detected on the gels by the carbohydrate stain, periodic acid-Schiff reagent. The intensity of this stained band varied for membranes derived from cells harvested between 4 and 10 days, with maximal intensity found for cells grown for 6 days. The carbohydrate-containing polypeptide was extracted with lithium diiodosalicylate. The extracted fraction consisted of about 80 to 90% amino acids (mainly glycine and histidine) and about 7% carbohydrates (mainly glucose, galactose, and glucosamine). The fraction was immunologically active, as indicated by the complement fixation and precipitin tests with antisera against whole cells, membranes, and membrane proteins.

Antigens, Bacterial↗
PubMed1976

Isolation of membrane glycoproteins by affinity chromatography in the presence of detergents.

Wheat germ agglutinin has been used in a one-step preparative method to isolate the major sialoglycoprotein (glycophorin A) from the human erythrocyte membrane. The conditions for isolation and purification of the sialoglycopeptide included low concentration of sodium dodecyl sulfate in the presence of relatively high salt concentration. This medium caused complete solubilization of the membrane but still allowed almost quantitative binding of the sialoglycopeptide to wheat germ agglutinin-Sepharose. The eluted protein from such affinity systems was found to be chemically comparable to glycophorin A, as prepared by other procedures.

Amino Acids↗
PubMed1976

Isolation of the major intrinsic transmembrane protein of the human erythrocyte membrane.

The major intrinsic protein of the human erythrocyte membrane commonly referred to as "Band 3", was isolated by a multi-step procedure. Extraction of ghost membranes in dilute solutions of lithium diiodosalicylate removed most of the proteins considered to be extrinsic to the membrane. The resulting membrane fragments were solubilized in sodium dodecyl sulfate, and the major sialoglycoprotein (glycophorin A) was removed by wheat germ agglutinin-Sepharose affinity chromatography. Gel filtration in sodium dodecyl sulfate was used as the final step to yield the band 3 polypeptide in electrophoretically homogeneous form.

Biological Transport, Active↗
PubMed1976

Characterization of the mycoplasma membrane proteins. VI. Composition and disposition of proteins in membranes from aging Mycoplasma hominis cultures.

Membranes of Mycoplasma hominis cells from cultures progressing from the mid to the end of the logarithmic phase of growth became richer in protein, poorer in phospholipids and cholesterol, heavier in density, and more viscous as determined by EPR. The membrane-bound ATPase activity declined steeply. Electrophoretic analysis failed to show marked changes in membrane protein composition on aging, apart from an increase in the staining intensity of one protein band (Mr approximately 130 000) concomitant with a decrease in the staining intensity of several minor protein bands of high molecular weight. To test for possible changes in the disposition of the various membrane proteins on aging of cultures, a comparison was made of the susceptibility of membrane proteins of intact cells and isolated membranes to trypsinization and lactoperoxidase-mediated iodination. The iodination values and the percent of membrane protein released by trypsinization of intact cells were similar in cells from cultures of different ages, indicating no significant changes in the organization of the proteins on the outer surface. On the other hand, trypsinization and iodination of isolated membranes were found to be most markedly affected by the culture age, indicating significant changes in the organization of the proteins on the inner membrane surface. Thus, the iodination values of isolated membranes decreased by almost two fold, while the percentage of protein released from the membrane by trypsin increased from 28% to 50% during the experimental period. It is suggested that aging in M. hominis cultures is accompanied by a continuous increase in the packing density of the protein molecules on the inner surface of the cell membrane.

Bacterial Proteins↗
PubMed1976

Binding of plant lectins to mycoplasma cells and membranes.

The binding of iodinated wheat germ agglutinin, Ricinus communis agglutinin, and concanavalin A to mycoplasma cells and membranes was examined. All mycoplasmas studied specifically bound concanavalin A or R. communis agglutinin and, to a lesser degree, wheat germ agglutinin. The binding of lectins to whole cells was similar to that recorded for membranes, suggesting that significant binding only occurred on the outer surface of the mycoplasma membrane. Proteolysis of the membrane almost always increased the capacity to bind lectins, which indicates that additional carbohydrate groups on the mycoplasma membrane are masked by a protein layer or protein complexes on the membrane. The observation that carbohydrates are apparently exposed on the surface of mycoplasma membranes should stimulate more concentrated study on the isolation and chemical characterization of these substances since it is quite likely that they are responsible for a variety of reactions between mycoplasmas and host cells.

Acholeplasma↗
PubMed1976

Alterations in the red blood cell membrane and the effect of vitamin E on osmotic fragility in beta-thalassemia major.

Red blood cell membranes from patients with beta-thalassemia major and intermedia had an average of 25% less sialic acids, and a 50% decrease in titratable SH groups, as compared with normal controls. Membranes from 12 of 13 splenectomized patients were less dense and could be clearly distinguished from normal membranes on a sucrose linear density gradient, indicating a change in lipid-to-protein ratio. The impaired osmotic fragility of thalassemic erythrocytes almost returned to normal following administration of vitamin E, a potent antioxidant, in a daily dose of 750 IU for three to six months. These observations provide more evidence that membrane properties of thalassemic red blood cells differ from those of normal erythrocytes, the difference being due, in part, to increased oxidative stress.

Adolescent↗
PubMed1975

Stimulation of lymphoid cells by components of BCG.

BCG was fractionated into a delipidated mycobacterial cell fraction (DMC) and lipid by exhaustive chloroform-methanol extraction. The effects of these fractions were tested on mouse spleen cells, nonadherent spleen cells (lymphocytes), thymus cells, and adherent spleen cells (macrophages) in vitro and were compared with effects of the whole bacilli and a methanol-extraction residue (MER). Tritiated thymidine incorporation into spleen cells, purified spleen lymphocytes, and thymus cells was measured as an indicator of activity on these cells; lymphocyte-activating factor (LAF) production was used to measure activation of macrophages. DMC and MER were at least equivalent to, and often exceeded, whole BCG in their stimulation of spleen cells and spleen lymphocytes. DMC was a poor thymic mitogen in contrast to MER, which was as strong as BCG in this regard. Lipid was far less effective a mitogen for all cells tested, and failed to augment the effectiveness of DMC on thymus cells when both were present in the incubation mixture. LAF production was significantly increased by whole BCG (18-fold above controls), whereas each fraction increased production threefold to sixfold. These in vitro results seemed to reflect the known in vivo activity of BCG and its components and suggest further antitumor applications.

Animals↗
PubMed1973

Divalent cations in native and reaggregated mycoplasma membranes.

The Mg(2+) content of membranes of several Mycoplasma and Acholeplasma species varied between 0.88 and 1.98 mug of Mg(2+) per mg of protein, depending on the species and on growth conditions. Ca(2+) could be detected only when it was added to the growth medium. The Mg(2+) content of isolated A. laidlawii membranes could be increased almost threefold by dialysis against 20 mm Mg(2+), whereas aggregated A. laidlawii membranes contained about six to eight times more Mg(2+) per mg of protein than the native membranes. This was taken to indicate that the molecular organization of the lipid and protein in the reaggregated membranes differs from that of the native membranes. Between 60 and 83% of the Mg(2+) in native and reaggregated A. laidlawii membranes was associated with the lipid fraction extracted with chloroform-methanol. The removal of over 80% of membrane protein by Pronase digestion did not release any significant amount of Mg(2+). Hence, most of the divalent cation appears to be bound to membrane lipids, most probably to phospholipids. Ethylenediaminetetraacetic acid released the bulk of Mg(2+) bound to the native and reaggregated A. laidlawii membranes, except for about 0.5 mug of Mg(2+) per mg of protein which was too tightly bound. Hence, a small but fairly constant amount of Mg(2+) is unavailable for chelation.

Acholeplasma laidlawii↗