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Biomedical subjects

N C Masiello

Publications and source records attributed to N C Masiello.

6 recordsLinked to original sources
PubMed1984

Platelet aggregation caused by dithiothreitol.

MacIntyre et al. showed that over 1 mM dithiothreitol (DTT) aggregates blood platelets in the presence of fibrinogen; aggregation is not inhibited by prostaglandin E1. We confirmed their data and found that 70 mM 2-mercaptoethanol was also active. DDT-induced aggregation was not associated with platelet shape change or secretion of dense granule contents, was not inhibited by tetracaine or metabolic inhibitors, was prevented at pH 6.5, and prevented, reversed, or arrested by EDTA, depending on when the EDTA was added. DTT did not cause aggregation of thrombasthenic, EDTA-treated, or cold (0 degree C) platelets, which also failed to aggregate with ADP. Platelets stimulated with DTT bound 125I-labeled fibrinogen. Thus DTT appears to "expose" the fibrinogen receptors. SDS gel electrophoresis of platelet fractions prepared by use of Triton X-114 showed that aggregating concentrations of DTT reduced proteins of apparent Mr 69,000 and 52,000 (probably platelet albumin) and, to a variable extent, glycoproteins Ib, IIb and III. Exposure of unlabeled or 125I-labeled platelets to ADP had no discernible effect on the electrophoretic patterns.

Adenosine Diphosphate↗
PubMed1984

Novel B-cell maturation factor from spontaneously autoimmune viable motheaten mice.

Both in vivo and in vitro, mice homozygous for the viable motheaten mutation show severe immunodeficiency, polyclonal B-cell activation and Ig secretion, and spontaneous production of a lymphokine [B-cell maturation factor (BMF)] that directly drives the maturation of normal or tumor B cells to the state of active Ig secretion. BMF from motheaten mice is distinct from previously identified forms in its cells of origin (B cells) and biochemical characteristics (apparent Mr 15,000 by gel filtration and NaDodSO4/PAGE; pI 4.3 by chromatofocusing). Among the known murine single-gene models of autoimmunity, only motheaten mice show high levels of spontaneous BMF production, which therefore may be an important component in the development of this form of autoimmunity/immunodeficiency disease. The coincidence of spontaneous BMF production and uncontrolled Ig secretion within the same mutant mouse constitutes the strongest evidence to date for a significant physiological (in vivo) role for BMFs.

Animals↗
PubMed1983

The combining ability of glycoproteins IIb, IIIa and Ca2+ in EDTA-treated nonaggregable platelets.

Platelets deprived of calcium and incubated at 37 degrees C for 10 min lose their ability to bind fibrinogen or aggregate with ADP when adequate concentrations of calcium are restored. Since the calcium complex of glycoproteins (GP) IIb and IIIa is the presumed receptor for fibrinogen, it seemed appropriate to examine the behavior of these glycoproteins in incubated nonaggregable platelets. No differences were noted in the electrophoretic pattern of nonaggregable EDTA-treated and aggregable control CaEDTA-treated platelets when SDS gels of Triton X-114 fractions were stained with silver. GP IIb and IIIa were extracted from either nonaggregable EDTA-treated platelets or aggregable control platelets with calcium-Tris-Triton buffer and subjected to sucrose density gradient centrifugation or crossed immunoelectrophoresis. With both types of platelets, these glycoproteins formed a complex in the presence of calcium. If the glycoproteins were extracted with EDTA-Tris-Triton buffer, or if Triton-solubilized platelet membranes were incubated with EGTA at 37 degrees C for 30 min, GP IIb and IIIa were unable to form a complex in the presence of calcium. We conclude that inability of extracted GP IIb and IIIa to combine in the presence of calcium is not responsible for the irreversible loss of aggregability that occurs when whole platelets are incubated with EDTA at 37 degrees C.

Blood Platelets↗
PubMed1983

Identification of fibrinogen derivatives in the Triton-insoluble residue of human blood platelets.

Several proteins (eg. actin, myosin, and actin-binding protein) in the Triton-insoluble residue of thrombin-stimulated platelets are important in the formation of cytoskeletal structures. Electrophoretic analyses have shown that unidentified protein bands of 68,000, 55,000, and 48-50,000 daltons are also present in larger amounts after thrombin stimulation. Since these molecular weights correspond roughly to those of the alpha, beta, and gamma chains of fibrin, and since fibrinogen is found in platelet alpha-granules, these bands were compared to those obtained when purified fibrinogen was treated with thrombin, exposed to 1% Triton X-100-5 mM EGTA, and the resultant Triton-insoluble residue sedimented. Identification of the 68,000-, 55,000-, and 48-50,000-dalton bands as fibrinogen derivatives was confirmed by identifying them in comigration studies and in autoradiographs of Triton-insoluble residues of platelets that were electrophoretically transferred to nitrocellulose paper and treated with antifibrinogen antibody and 125I-protein A. Furthermore, if the platelet suspension was treated with thrombin in the presence of calcium ions, protein bands characteristic of the action of Factor XIII on fibrin were observed, active platelet Factor XIII apparently having been made available by lysis of platelets during preparations. Making use of the electrophoretic properties of tubulin recently described by Best et al [1981], comigration studies using hog brain tubulin indicated that tubulin is not present in significant amounts in the Triton-insoluble residue of platelets as previously suggested. The identification of these proteins as fibrinogen derivatives does not demonstrate a physiological interaction between fibrin and the platelet cytoskeleton, since fibrin is Triton-insoluble and can be pelleted even in the absence of platelet cytoskeletons.

Blood Platelets↗