scholarly journals Transient kinetics of the rapid shape change of unstirred human blood platelets stimulated with ADP.

1982 ◽  
Vol 79 (23) ◽  
pp. 7297-7301 ◽  
Author(s):  
D. A. Deranleau ◽  
D. Dubler ◽  
C. Rothen ◽  
E. F. Luscher
Keyword(s):  
Human Blood ◽  
Shape Change ◽  
Blood Platelets ◽  
Transient Kinetics ◽  
Kinetics Of ◽  
Human Blood Platelets

Freeze-Fracture Studies of Human Blood Platelets Activated by Thrombin Using Rapid Freezing

1985 ◽  
Vol 54 (03) ◽  
pp. 574-578 ◽  
Author(s):  
Hans Hols ◽  
Jan J Sixma ◽  
J Leunissen-Bijvelt ◽  
Arie Verkley
Keyword(s):  
Human Blood ◽  
Shape Change ◽  
Blood Platelets ◽  
Secretory Granules ◽  
Freeze Fracture ◽  
Rapid Freezing ◽  
Freeze Fracturing ◽  
Morphological Alterations ◽  
Thrombin Activation ◽  
Human Blood Platelets

SummaryIn this study the influence of thrombin activation on human blood platelets has been followed by freeze-fracturing electron microscopy using rapid freezing in order to catch the initial changes in shape and the morphological alterations during the process of exocytosis of secretory granules. We found that isolation of the platelets by itself leads to some degree of shape change, which made it impossible to study the resting discoid platelet by rapid freezing.Activation of the platelets by thrombin induced dilation of the “surface connecting system (SCS)” with formation of large vacuoles as a result of fusion of the secretory granules with SCS. No intermediary fusion stages or structures were observed even using rapid freezing. Volcano-like protrusions and the corresponding complementary pits were seen at the SCS. These structures were interpreted by us as fractures through protoplasmic channels crossing the SCS. These channels originate during the swelling of the SCS as a result of the fusion of secretory granules with the SCS.

scholarly journals Heterogeneity in filamentous actin content among individual human blood platelets

Blood ◽  
1992 ◽  
Vol 79 (4) ◽  
pp. 920-927
Author(s):  
A Oda ◽  
JF Daley ◽  
C Cabral ◽  
JH Kang ◽  
M Smith ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Fluorescent Probe ◽  
Human Blood ◽  
Actin Polymerization ◽  
Shape Change ◽  
Blood Platelets ◽  
Significant Loss ◽  
Free Calcium ◽  
Filamentous Actin ◽  
Human Blood Platelets

Abstract The content of filamentous actin in individual platelets was measured by flow cytometry, using a fluorescent probe specific for filamentous actin (F-actin), 7-nitrobenz-2-oxa-1,3-phallacidin (NBD-phallacidin). NBD-phallacidin binding to fixed platelets was specific in that either pretreatment of platelets with unlabeled phallacidin or absorption of NBD-phallacidin by rabbit skeletal F-actin, but not globular actin (G- actin), resulted in a significant loss in the bound fluorescent probe. Mean NBD-phallacidin binding to fixed platelets varied with the agonist and paralleled the changes in F-actin reported with the DNAse I inhibition assay. (1) NBD-phallacidin binding increased with stimulation by ADP, U46619 (a prostaglandin H2 analogue), or collagen and paralleled shape change. (2) Epinephrine did not increase NBD- phallacidin binding. (3) Platelets treated at 4 degrees C contained more F-actin than did platelets kept at 37 degrees C. (4) Cytochalasin D (10 mumol/L) inhibited the increase of phallacidin binding to individual platelets stimulated by either ADP or U46619. In measurements of cytosolic free calcium concentration ([Ca2+]i) by flow cytometry in Indo-1-loaded platelets, ADP's dose-response for actin polymerization was similar to that for calcium mobilization. As shown by flow cytometry, a tail population that had a minimal increase in F- actin upon stimulation with ADP or U46619 also contained the platelets with the least forward and right angle light scattering, which are functions of platelet size and shape. When platelets treated with NBD- phallacidin were incubated with S12-murine monoclonal antibody (a marker of alpha-granule secretion detected by phycoerythrin-conjugated antimouse IgG second antibody), phallacidin fluorescence paralleled S12 binding. Thus, human blood platelets are heterogeneous in regard to actin polymerization at rest and in association with platelet activation; different degrees of phallacidin binding may identify functionally different platelet populations.

scholarly journals Heterogeneity in filamentous actin content among individual human blood platelets

Blood ◽  
1992 ◽  
Vol 79 (4) ◽  
pp. 920-927 ◽  
Author(s):  
A Oda ◽  
JF Daley ◽  
C Cabral ◽  
JH Kang ◽  
M Smith ◽  
...  
Keyword(s):  
Flow Cytometry ◽  
Fluorescent Probe ◽  
Human Blood ◽  
Actin Polymerization ◽  
Shape Change ◽  
Blood Platelets ◽  
Significant Loss ◽  
Free Calcium ◽  
Filamentous Actin ◽  
Human Blood Platelets

The content of filamentous actin in individual platelets was measured by flow cytometry, using a fluorescent probe specific for filamentous actin (F-actin), 7-nitrobenz-2-oxa-1,3-phallacidin (NBD-phallacidin). NBD-phallacidin binding to fixed platelets was specific in that either pretreatment of platelets with unlabeled phallacidin or absorption of NBD-phallacidin by rabbit skeletal F-actin, but not globular actin (G- actin), resulted in a significant loss in the bound fluorescent probe. Mean NBD-phallacidin binding to fixed platelets varied with the agonist and paralleled the changes in F-actin reported with the DNAse I inhibition assay. (1) NBD-phallacidin binding increased with stimulation by ADP, U46619 (a prostaglandin H2 analogue), or collagen and paralleled shape change. (2) Epinephrine did not increase NBD- phallacidin binding. (3) Platelets treated at 4 degrees C contained more F-actin than did platelets kept at 37 degrees C. (4) Cytochalasin D (10 mumol/L) inhibited the increase of phallacidin binding to individual platelets stimulated by either ADP or U46619. In measurements of cytosolic free calcium concentration ([Ca2+]i) by flow cytometry in Indo-1-loaded platelets, ADP's dose-response for actin polymerization was similar to that for calcium mobilization. As shown by flow cytometry, a tail population that had a minimal increase in F- actin upon stimulation with ADP or U46619 also contained the platelets with the least forward and right angle light scattering, which are functions of platelet size and shape. When platelets treated with NBD- phallacidin were incubated with S12-murine monoclonal antibody (a marker of alpha-granule secretion detected by phycoerythrin-conjugated antimouse IgG second antibody), phallacidin fluorescence paralleled S12 binding. Thus, human blood platelets are heterogeneous in regard to actin polymerization at rest and in association with platelet activation; different degrees of phallacidin binding may identify functionally different platelet populations.

Change in electrophoretic mobility associated with the shape change of human blood platelets

1977 ◽  
Vol 196 (1125) ◽  
pp. 471-474 ◽  
Keyword(s):  
Electrophoretic Mobility ◽  
Human Blood ◽  
Shape Change ◽  
Blood Platelets ◽  
Sialic Acids ◽  
Membrane Glycoproteins ◽  
Platelet Surface ◽  
Human Blood Platelets

All physiological pH platelets, like other cells, have an excess of negative electric charges on the surface which determine their electrophoretic mobility (Seaman & Vassar 1966; Hampton & Mitchell 1974). The greater part of these negative charges are due to sialic acids bound to membrane glycoproteins (Madoff, Ebbe & Baldini 1964). Removal of sialic acids from the platelet surface by neuraminidase diminishes the electrophoretic mobility of platelets (Bray & Alexander 1969). It has been shown recently that the rapid shape change of platelets which precedes their aggregation by ADP or 5-hydroxytryptamine is associated with an increase in sialic acids removable by neuraminidase (Motamed, Michal & Born 1976). If this increase in sialic acids were on the platelet surface which determines their electrophoretic mobility, it should show itself as an increase in that mobility. This paper shows that the mobility increases when the shape change is induced by ADP.

ADP Induced Depolarization of Human Platelet Membrane Potential

1985 ◽  
Vol 53 (01) ◽  
pp. 075-079 ◽  
Author(s):  
June D Wencel-Drake ◽  
Harold Feinberg
Keyword(s):  
Membrane Potential ◽  
Platelet Activation ◽  
Human Blood ◽  
Transmembrane Potential ◽  
Human Platelet ◽  
Shape Change ◽  
Blood Platelets ◽  
Positive Current ◽  
Initial Interaction ◽  
Human Blood Platelets

SummaryThe transmembrane potential of human blood platelets suspended in plasma was investigated by studying the distribution of a radiolabeled permeant ion [14C] thiocyanate. The membrane potential of resting platelets was found to be -54.50 mV ± 9.23 S.D. with a range of -39 to -76 mV (n = 27). The possibility that platelet activation alters membrane potential or that changes in membrane potential serve as an activation trigger was investigated. Stimulation by ADP (10 ¼M) resulted in a significant (p :0.05) depolarization of the membrane potential. Preincubation with 6 mM EGTA failed to inhibit ADP-induced depolarization even though EGTA effectively prevented primary and secondary aggregation but not shape change. Preincubation with PGE1 inhibited shape change, aggregation, and the ADP- induced depolarization. No significant change in membrane potential was observed following stimulation by epinephrine (50 ¼M). These results suggest that the initial interaction of ADP and its receptor may involve an inward positive current which can be determined by thiocyanate distribution.

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