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E A Mauss

Publications and source records attributed to E A Mauss.

10 recordsLinked to original sources
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↗
PubMed1988

Erythrocyte aggregation in iohexol and other nonionic media.

Erythrocytes aggregate when blood comes into contact with solutions of nonionic substances such as glucose or the contrast medium iohexol, especially at a reduced pH (eg, 6.8). The aggregates are not clots because they form rapidly even in heparinized blood, do not contain fibrin, and disappear at once when they are added to plasma or other ionic media. Formation of these aggregates in solutions of glucose or iohexol can be decreased by including a low concentration of an ionic solute such as NaCl or by maintaining the pH close to 7.4.

Buffers↗
PubMed1986

Modification of platelet functions by monobromobimane, a fluorescent thiol group label.

Monobromobimane (mBBr, bimane), a compound that penetrates cells and forms a fluorescent adduct with thiol groups, was used to asses the significance of thiols in platelet function. Exposure of washed platelets for 1 min to 100 microM mBBr abolished ADP-induced aggregation; shape change was not inhibited by 500 microM mBBr. The nonpenetrating compound monobromotrimethylammoniobimane was ineffective. Established ADP-induced aggregation was reversed by bimane, and fibrinogen binding to ADP-stimulated platelets was inhibited, an effect mainly due to decreased number of binding sites. Aggregation stimulated by A23187 and arachidonate was less effectively inhibited whereas epinephrine- and collagen-induced aggregation were abolished by 50 microM mBBr. Similar effects on aggregation and secretion were observed in platelet-rich plasma except that higher mBBr concentrations were usually necessary. Aggregation and 14C-serotonin secretion stimulated by 0.1 U/ml thrombin were partially inhibited by pretreatment with bimane. With lower thrombin concentrations, they were often enhanced, as was 3H-arachidonate release. Bimane inhibited epinephrine-induced arachidonate release in gel-filtered platelets, possibly because it abolished the primary aggregation necessary for this release. mBBr did not elevate cyclic AMP but enhanced the increase induced by PGE1 and prevented the subsequent decrease typically caused by ADP. Examination of SDS polyacrylamide gels with ultraviolet light showed that mBBr reacted with many platelet proteins but not with GP IIb or IIIa. This observation, and the fact that bimane did not inhibit the fibrinogen-induced aggregation of DTT- or chymotrypsin-treated platelets suggest that it reacts with thiol group(s) that are involved in "exposing" the fibrinogen receptor.

Adenosine Diphosphate↗