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Biomedical subjects

R L Nachman

Publications and source records attributed to R L Nachman.

At least 127 records · Page 7Linked to original sources
PubMed1971

Rabbit platelet bactericidal protein.

The heat-stable antibacterial activity of rabbit serum against Gram-positive microorganisms has been shown to reside in a cationic protein fraction of platelet lysosomal granules. The activity is released during platelet aggregation. No plasma or serum component is required for the bactericidal effect. The platelet bactericidin resembles the antibacterial proteins of leukocyte granules both in cellular localization and in biochemical characteristics. It can be differentiated from platelet factor 4, the antiheparin factor, which is also a basic protein in platelet granules. The antibacterial effect of the platelet bactericidin may be related to the metabolic activity of the organisms. This antibacterial activity of platelets may represent another means by which platelets can participate in host inflammatory defense reactions.

Adenosine Diphosphate↗
PubMed1971

Macrophage plasma membranes. I. Isolation and studies on protein components.

Plasma membranes have been isolated from pure populations of rabbit alveolar macrophages which were swollen in water, fixed briefly with glutaraldehyde, disrupted by Dounce homogenization, and separated by sucrose gradient centrifugation. The recovered membranes exhibited good structural preservation and enzymatic activity; both morphologic and biochemical evidence indicated a high degree of purity (>90%) of the membrane preparation. Interiorized plasma membranes were also prepared without exposure to glutaraldehyde from phagocytic vacuoles recovered from alveolar macrophages which had ingested large numbers of polystyrene spheres. These membranes were contaminated with lysosomal constituents, but they were nevertheless of value for comparison to the "pure" membranes isolated by the glutaraldehyde procedure. Acrylamide gel electrophoresis of the solubilized plasma membranes and phagolysosomal membranes revealed similar protein patterns, with seven to nine individual components ranging in molecular weight from 70,000 to 140,000. The two most rapidly migrating components gave positive reactions for lipid as well as protein. A band containing carbohydrate was detected near the origin of the plasma membrane gels. Antisera were made by injecting guinea pigs with the purified rabbit alveolar macrophage plasma membranes. Gel diffusion and immunoelectrophoretic study of these antisera established the presence of rabbit immunoglobulin G and of one or two other antigenic constituents in the membrane preparation.

Acid Phosphatase↗
PubMed1971

Macrophage plasma membrane. II. Studies on synthesis and turnover of protein constituents.

Rabbit alveolar macrophages were incubated in vitro with radioactive protein precursors. Plasma membranes were isolated from these cells, dissolved in phenol-urea-acetic acid, and separated by acrylamide gel electrophoresis. (3)H-leucine was rapidly incorporated into membrane protein. The rate of labeling with (3)H-leucine was markedly different from one protein band to another, indicating heterogeneous or multistep synthesis and assembly of proteins in the alveolar macrophage plasma membrane. Cells incubated with (3)H-choline incorporated this compound into membrane lecithin. On gel electrophoresis the label derived from choline was located in the two bands migrating most rapidly towards the cathode. Studies on cells incubated with (3)H-glucosamine revealed incorporation of label into two protein bands, one located near the origin and the other migrating rapidly towards the cathode. The in vitro techniques were also employed for pulse-chase studies to gain information on rate of turnover of macrophage plasma membrane proteins. This turnover rate was rapid, with a half-life of approximately 8 hr. The radioactivity disappeared from the several protein bands at the same rate, suggesting bulk removal of membrane rather than catabolism of the individual proteins in situ. Endocytosis seems a likely mechanism to account for a major part of the plasma membrane removal. Studies on the protein components of phagolysosomal membranes from cells which had been labeled with (3)H-leucine revealed the presence of all of the major labeled protein bands characteristic of the plasma membrane except one, thus confirming the bulk interiorization of large segments or units of plasma membrane by endocytic processes.

Animals↗
PubMed1970

Increased vascular permeability produced by human platelet granule cationic extract.

A cationic protein extract obtained from isolated human platelet granules increased vascular permeability in mouse and rabbit skin. The permeability-enhancing effect was not inhibited by soybean trypsin and pancreatic trypsin inhibitor, methylsergide maleate, carboxypeptidase B, and C[unk]1 inactivator. Permeability-enhancing activity was blocked by prior treatment of challenged animals with antihistamine. The nondializable relatively heat-stable cationic granule protein extract possessed potent mastocytolytic activity. The experiments described suggest that human platelets exert a permeability-enhancing effect by lysosomal release of cationic proteins which cause histamine release from adjacent tissue mast cells.

Animals↗
PubMed1969

Studies on human platelet protease activity.

SOLUBILIZED PROTEIN DERIVED FROM HUMAN PLATELETS WAS FRACTIONATED BY DEAE CELLULOSE COLUMN CHROMATOGRAPHY AND ANALYZED FOR PROTEASE ACTIVITY USING THREE SUBSTRATES: denatured bovine hemoglobin, alpha casein, and purified plasminogen-free human fibrinogen. A protein fraction was found with proteolytic activity which was heat labile and not attributable to plasmin. The activity was not potentiated by cysteine or inhibited by iodoacetamide. Studies of pH optima indicated a broad range of enzyme activity with peaks in both the acid and alkaline region. Cathepsin A activity was detected in the platelet protease fraction by hydrolysis of the synthetic substrate N-carbobenzoxy-alpha-L-glutamyl-L-tyrosine. Similar proteolytic activity was found when the proteins derived from isolated platelet granules were examined. The results indicate that human platelets possess potent intracellular proteolytic enzymes. The relationship of this proteolytic activity to the hemostatic process is discussed.

Blood Coagulation↗
PubMed1967

Ultrastructure of thrombosthenin, the contractile protein of human blood platelets.

Partially purified thrombosthenin with adenosine triphosphatase activity similar to that of actomyosin was subjected to electron microscopy. More than 50 percent of the material consisted of fibrils 80 to 100 angstroms in width. Occasional fibrils suggested a periodic structure. The morphology of isolated thrombosthenin resembled that of microfibrils in the cytoplasm and pseudopods of intact platelets.

Blood Platelets↗
PubMed1967

Platelet thrombosthenin: subcellular localization and function.

Thrombosthenin, an immunologically distinct contractile protein was isolated in relatively pure form from human platelets. The protein, which was of high molecular weight appeared to be composed of multiple polypeptide subunits, probably polymeric in nature.Thrombosthenin had magnesium-dependent ATPase activisty, releasing an average of 3 mug phosphorus per mg protein in 30 min. After the addition of ATP, there was a reversible alteration in viscosity with calculated ATP sensitivity ranging from 64 to 90%. These biochemical properties of thrombosthenin resemble those of smooth muscle.Specific antisera to thrombosthenin significantly inhibited the ATPase activity of the protein. Clot retraction of recalcified platelet-rich plasma and clot retraction of clotted fibrinogen-platelet mixtures were also inhibited by the antisera. The findings suggest that thrombosthenin is an important component of the clot retraction system.Thrombosthenin was extracted from isolated platelet granule and membrane fractions. The contractile protein derived from the membrane compartment was more active as an ATPase and appeared to be more homogeneous on immunologic analysis.

Journal Article↗