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Biomedical subjects

M B Zucker

Publications and source records attributed to M B Zucker.

At least 19 recordsLinked to original sources
PubMed1992

Alleviation of immunosuppression in vitro by recombinant platelet factor 4.

To elucidate the mechanism by which platelet factor 4 (PF4), a secreted platelet protein, and its C-terminal peptides alleviate suppression of the antibody response in vivo, their immunoregulatory activity was studied in vitro, using cultured spleen cells from BALB/c mice primed with sheep red blood cells (SRBC). When addition of 48 h cultured concanavalin A (Con A) blasts at 5 x 10(5)/ml significantly suppressed the anti-SRBC plaque-forming cell response, suppression was alleviated in 25 of 29 experiments by 0.2 micrograms/ml recombinant (r)PF4 (6.4 nM if rPF4 is a tetramer). The effect of Con A blasts was abolished by cimetidine, a histamine type 2 (H2) antagonist. Dimaprit, an H2 agonist, at 1-2 x 10(-4) M, or splenic T cells that had been incubated for 1 h with dimaprit and washed, also caused significant suppression that was alleviated by 0.2 micrograms/ml rPF4 (n = 8), and by 0.02 micrograms/ml in six of these tests. The C-terminal 13 amino acid peptide of PF4 was active at 0.02-0.2 micrograms/ml (0.01-0.11 microM), but peptides from the middle or N-terminal end of the molecule, or IL-8, which shares structural homology with PF4, were inactive. IL-1 and IL-2 raised control responses without affecting suppression or its alleviation by rPF4. Neutralizing antibody to transforming growth factor beta 1 (TGF-beta 1) did not affect Con A blast-induced suppression and suppression induced by exogenous TGF-beta 1 (0.5 ng/ml) was not counteracted by rPF4. Blocking prostaglandin production with 0.2 or 2 microM indomethacin did not affect suppression significantly but reduced rPF4 activity; prostaglandin D2 restored the effect of rPF4.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

The effect of agonists and antagonists of platelet aggregation on von Willebrand factor-mediated platelet agglutination.

Ristocetin-induced platelet agglutination (RIPA) in EDTA-treated citrated platelet-rich plasma was reduced to 49 +/- 11% by 1.25 microM ADP, 41 +/- 14% by 1 microM A23187, and 26 +/- 7% by 0.1 microgram/ml platelet activating factor (PAF). The effect of 5-110 microM epinephrine was not dose-dependent, but varied between donors, with RIPA from 56-100% of the control. The inhibitory effects of these agonists were not altered by prior treatment of platelets with aspirin. Prior addition of 200 microM ATP (an ADP receptor antagonist acting at both high and low affinity ADP receptors) prevented the inhibitory action of ADP but not that of A23187 or PAF, suggesting that the inhibitory actions of the latter are not mediated by released ADP. As 700 microM 8-bromoadenosine 5-diphosphate (an ADP receptor antagonist acting mainly at the high affinity receptor) did not prevent ADP-induced inhibition of RIPA, interaction of ADP with the low affinity receptor is presumably responsible for its inhibitory action. As A23187, but not phorbol myristate acetate (0.1 microM) inhibited RIPA, an increase in intracellular calcium ions rather than direct stimulation of protein kinase C appears to mediate agonist-induced inhibition. Cytochalasin B (10.5-21 microM), dibucaine (0.5-1 mM), and prostaglandin E1 (25 nM), added before or after the agonist, prevented or reversed ADP-, A23187-, and PAF-induced inhibition of RIPA, suggesting that the state of the platelet cytoskeleton affects inhibition.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1990

Assembly and GPIIIa content of cytoskeletal core in platelets agglutinated with bovine von Willebrand factor.

The association between occupancy of the von Willebrand factor (vWf) receptor glycoprotein (GP) Ib, agglutination, and the assembly and composition of the cytoskeletal core was studied in 125I-surface-labeled aspirin-treated washed platelets. Binding of ligands to GPIIb-IIIa and platelet aggregation were abolished by addition of EDTA. Platelet agglutination induced by bovine vWf generated a complete cytoskeletal core (Triton-insoluble residue), shown by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to be composed of actin-binding protein (ABP) (260 Kd), 235-Kd protein, myosin heavy chain (200 Kd), alpha-actinin (100 Kd), and actin (43 Kd). In addition, autoradiography of the gels showed a 125I 105-Kd GP, identified by immunoblot as GPIIIa, as well as GPIb, GPIIb, and another band at 87 Kd, probably GPIV. Neither cytoskeletal assembly nor GPIIa incorporation was altered if calpain was inhibited with leupeptin. Platelet suspensions exposed to bovine vWf without stirring (ie, nonagglutinated) or platelets in which agglutination was inhibited with ADP showed smaller cytoskeletons with little ABP, 235 Kd protein, and alpha-actinin. Autoradiographs showed mainly GPIb. Cytochalasin D (CD) and monobromobimane (MB) enhanced agglutination and prevented the inhibitory action of ADP on bovine vWf-induced platelet agglutination. CD markedly inhibited the assembly of the cytoskeletal core as well as GPIIIa retention, whereas MB resulted in a large Triton-insoluble residue which contained GPIIIa. Thus, development of a platelet cytoskeletal core is apparently not required for agglutination, but when a cytoskeletal core is assembled in agglutinated platelets, GPIIIa is retained.

Actinin↗
PubMed1990

Inhibition of von Willebrand factor-induced platelet agglutination by ADP does not result from reduced binding of total von Willebrand factor or its larger multimers.

Earlier experiments showed that platelet agglutination induced by von Willebrand factor (vWf) plus ristocetin was greatly diminished if adenosine diphosphate (ADP) was added first in the presence of ethylenediaminetetraacetic acid (to prevent aggregation). Platelets treated with ADP and then fixed also agglutinated less than control fixed platelets. The studies reported here demonstrate that ADP did not decrease ristocetin-induced binding of vWf whether binding was measured on suspended platelets with iodine 125-labeled vWf or on suspended or agglutinated platelets with the use of any of three 125I-labeled monoclonal antibodies that bind to vWf but that do not interfere with ristocetin-induced agglutination. Equal amounts of vWf were eluted from ristocetin/vWf-treated platelets when they were resuspended without ristocetin, whether or not the platelets had been exposed to ADP, and the vWf recovered in either case was composed only of large multimers. No evidence for an agglutination site other than glycoprotein Ib could be demonstrated by measuring agglutination of a mixture of platelets fixed after inhibition with antibody against glycoprotein Ib and platelets fixed after inhibition with ADP. We conclude that inhibition of agglutination by ADP must involve the way in which vWf is bound, because it does not result from a decreased amount or from a difference in multimer size of bound vWf.

Adenosine Diphosphate↗
PubMed1989

Effect of the thiol group inhibitor monobromobimane and other inhibitors on the composition of the platelet cytoskeletal core and its association with glycoprotein IIIa.

SDS-polyacrylamide gel electrophoresis was used to study the effects of the thiol inhibitor monobromobimane (MB), EDTA, and prostaglandin E1 (PGE1) on the formation and composition of the platelet cytoskeletal core (Triton-insoluble residue) and its association with glycoprotein (GP) IIIa. Stimulation or aggregation of platelets in response to ADP or thrombin increased the amount of Triton-insoluble myosin. Aggregation resulted in incorporation of [125I]GP IIIa and a new band at about 210 kDa into the cytoskeletal core. EDTA and PGE1 caused little disaggregation of platelets that were aggregated in PRP with ADP and that had secreted the contents of their granules. In contrast to EDTA, PGE1 decreased the amount of Triton-insoluble residue and its association with GP IIIa. MB added after ADP-induced aggregation caused an increase in the amount of cytoskeletal core despite marked disaggregation and a substantial decrease in core-associated GP IIIa. With aspirin-treated platelets that had not secreted, EDTA, PGE1, and MB all caused disaggregation and loss of cytoskeletal GP IIIa. MB diminished, but did not reverse, thrombin-induced aggregation of washed platelets and arrested GP IIIa incorporation into the cytoskeletal core. Concanavalin A (Con A) cross-links glycoproteins on a single platelet and induces incorporation of GP IIIa into the Triton-insoluble residue in the absence of platelet aggregation. This induction was not inhibited by MB, although this reagent, as well as aspirin, inhibited Con A-induced secretion. Since GP IIIa incorporation caused by ADP-induced aggregation differs from that caused by Con A in its susceptibility to MB, it seems unlikely that thiol groups are directly involved in the association of GP IIIa with the cytoskeletal core.

Alprostadil↗
PubMed1989

Immunoregulatory activity of peptides related to platelet factor 4.

Platelet factor 4 (PF4), a secreted platelet protein, alleviates concanavalin A-induced immunosuppression in mice. We now find that activity also resides in (i) the C-terminal tridecapeptide of PF4 (P13S), (ii) an analog of this in which arginine replaces the lysine residues and in which the last two amino acids are absent, (iii) the C-terminal 18 amino acids of low-affinity platelet factor 4, which is very similar to P13S, and (iv) peptide fragments of P13S that contain only 5-9 amino acids. P13S treated with fluorescamine to derivatize the free amino groups retained immunoregulatory activity but did not bind to heparin-agarose. The N-terminal and middle portions of PF4, polylysine, protamine, and three unrelated peptides were inactive in this assay.

Amino Acid Sequence↗
PubMed1979

Release of platelet fibronectin (cold-insoluble globulin) from alpha granules induced by thrombin or collagen; lack of requirement for plasma fibronectin in ADP-induced platelet aggregation.

Platelets lysed with Triton X-100 contain 3.44 +/- 1.27 (SD) microgram of fibronectin (cold-insoluble globulin) per 10(9) platelets. Fibronectin was partially released from washed whole platelets by collagen or thrombin, and its release by collagen was inhibited by aspirin. Analysis of subcellular fractions obtained by density-gradient centrifugation of disrupted platelets indicated that fibronectin was contained in the alpha granules. Fibrinogen depleted of fibronectin (less than 2 microgram/mg) supported ADP-induced aggregation as effectively as fibrinogen contaminated with this protein, thus reinforcing the generally held view that fibrinogen itself is the necessary protein cofactor in this reaction.

Adenosine Diphosphate↗
PubMed1979

Factor VIII-related antigen in human blood platelets: localization and release by thrombin and collagen.

Human platelets contain 0.61 +/- 0.06 (S.E.) U of VIIIR:Ag per 10(9) platelets or about 25% of the circulating antigen in whole blood. Assay of subcellular fractions obtained by sucrose density-gradient centrifugation of disrupted platelets indicates that over 85% of the VIIIR:Ag is in the alpha granule fraction with other nonenzymatic proteins which can be released by treating platelets with collagen or thrombin. Seven percent or less is in the membrane fraction. After exposure of platelet suspensions to an optimal concentration of collagen, the supernatants contain, at most, 30% of the total amount of VIIIR:Ag in the platelets but a higher percentage of other releasable substances. After exposure to thrombin, the supernatants contain virtually no VIIIR:Ag. These low values are attributed to release of a limited amount of VIIIR:Ag by collagen or thrombin rather than to adsorption or destruction of antigen, for several reasons. (1) VIIIR:Ag can be recovered in the platelet residue as effectively as in control samples. (2) The antigen cannot be detected on the surface of collagen- or thrombin-stimulated platelets. (3) Relatively little released antigen is adsorbed by collagen or destroyed by thrombin. Release of VIIR:Ag by collagen is markedly reduced by aspirin, and release of the antigen as well as fibrinogen from platelets is much slower than release of 14C-serotonin and beta-TG.

Antigens↗
PubMed1978

Nonreversible loss of platelet aggregability induced by calcium deprivation.

Platelets lose their ability to aggregate when deprived of divalent cations. This usually was studied by incubating human citrated platelet-rich plasma with EDTA or EGTA and then adding enough CaCl2 to combine with the chelating agent. Incubation for 5-7 min at 37 degrees C caused irreversible loss of the platelets' ability to adhere to glass and to aggregate with ADP, epinephrine, A23187, vasopressin, or serotonin or upon rewarming after chilling and markedly reduced aggregation with collagen or thrombin. Control samples incubated with saline, CaEDTA, or CaEGTA were not inhibited. Untreated platelets washed and incubated in solutions treated with resins that remove divalent cations lost their ability to aggregate in 30 min. More than about 0.26 mM Mg2+ partially protected the platelets. Unlike aggregation, ADP-induced shape change, clot retraction caused by thrombin or ADP plus reptilase, and thrombin-induced 14C-serotonin release were not inhibited after incubation. Aggregability was not restored by prolonged incubation with CaCl2, adding normal plasma, or washing the platelets. Its loss was temperature and pH dependent, occurring in 2 min at 43 degrees C but not in 7 min at 30 degrees C, and at pH 7.8 but much less at pH 7.2. The defect was not associated with an increase in platelet cyclic AMP, a decrease in metabolic ATP, or the presence of free ADP.

Calcium↗
PubMed1977

Increased activity of vitamin K-dependent clotting factors in human hyperlipoproteinaemia - association with cholesterol and triglyceride levels.

Levels of blood coagulation factors, cholesterol and triglyceride were measured in human plasma. Prothrombin was significantly elevated in type IIa hyperlipidaemia; prothrombin and factors VII, IX and X in type IIb; and prothrombin and factors VII and IX in type V. Multiple regression analysis showed significant correlation between the levels of these plasma lipids and the vitamin K-dependent clotting factors (prothrombin, factors VII, IX and X). Higher cholesterol levels were associated with higher levels of prothrombin and factor X while higher triglyceride levels were associated with higher levels of these as well as factors VII and IX. Prothrombin showed a significant cholesterol-triglyceride interaction in that higher cholesterol levels were associated with higher prothrombin levels at all levels of triglyceride, with the most marked effects in subjects with higher triglyceride levels. Higher prothrombin levels were noted in subjects with high or moderately elevated (but not low) cholesterol levels. Ultracentrifugation of plasma in a density of 1.21 showed activity for prothrombin and factors VII and X only in the lipoprotein-free subnatant fraction. Thus, a true increase in clotting factor protein was probably present. The significance of the correlation between levels of vitamin K-dependent clotting factors and plasma lipids remains to be determined.

Adult↗