Observations on the “Cytoskeleton” of Human Platelets

1979 ◽  
Vol 42 (05) ◽  
pp. 1661-1666 ◽  
Author(s):  
V T Nachmias ◽  
J Sullender ◽  
J Fallon ◽  
A Asch
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Structural Study ◽  
Local Anesthetics ◽  
Shape Change ◽  
Human Platelets ◽  
Microtubule Bundle ◽  
High Molecular Weight Band

SummaryStructural study of rapidly lysed platelets supports the view that that shape change involves a change in state of the microfilaments which contain actin. The microtubule “bundle” appears to be a continuous coil. Proteolysis of a high molecular weight band is observed in platelets which can no longer form filopodia after suppression by local anesthetics.

scholarly journals Interaction of high molecular weight kininogen, factor XII, and fibrinogen in plasma at interfaces

Blood ◽  
1980 ◽  
Vol 55 (1) ◽  
pp. 156-159 ◽  
Author(s):  
L Vroman ◽  
AL Adams ◽  
GC Fischer ◽  
PC Munoz
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Marked Change ◽  
Human Platelets ◽  
Blue Staining ◽  
Factor Xii ◽  
High Molecular Weight Kininogen ◽  
Contact Activation ◽  
Coomassie Blue Staining ◽  
Coated Surfaces

Abstract Using ellipsometry, anodized tantalum interference color, and Coomassie blue staining in conjunction with immunologic identification of proteins adsorbed at interfaces, we have previously found that fibrinogen is the main constituent deposited by plasma onto many man- made surfaces. However, the fibrinogen deposited from normal plasma onto glass and similar wettable materials is rapidly modified during contact activation until it can no longer be identified antigenically. In earlier publications, we have called this modification of the fibrinogen layer “conversion,” to indicate a process of unknown nature. Conversion of adsorbed fibrinogen by the plasma was not accompanied by marked change in film thickness, so that we presumed that this fibrinogen was not covered but replaced by other protein. Conversion is now showen to be markedly delayed in plasma lacking high molecular weight kininogen, slightly delayed in plasma lacking factor XII, and normal in plasma that lack factor XI or prekallikrein. We conclude that intact plasma will quickly replace the fibrinogen it has deposited on glass-like surfaces by high molecular weight kininogen and, to a smaller extent, by factor XII. Platelets adhere preferentially to fibrinogen-coated surfaces; human platelets adhere to hydrophobic nonactivating surfaces, since on these, adsorbed firbinogen is not exchanged by the plasma. The adsorbed fibrinogen will be replaced on glass-like surfaces during surface activation of clotting, and platelets failing to find fibrinogen will not adhere.

Human High Molecular Weight Kininogen - A Secreted Platelet Coagulant Protein

1981 ◽  
Author(s):  
A H Schmaier ◽  
J Kuchibhotla ◽  
R W Colman
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Gel Filtration ◽  
Human Platelets ◽  
Metabolic Inhibitors ◽  
Ionophore A23187 ◽  
High Molecular Weight Kininogen ◽  
Contact Phase ◽  
Platelet Factor ◽  
Coagulant Activity

Platelets have been shown to contain a number of secret- able coagulant proteins, which participate as substrates or cofactors in plasma coagulation reactions. Since we have previously demonstrated that high molecular weight kininogen (HMWK) is immunochemically present in platelet extracts, we posited that HMWK is secreted during activation of platelets. Fresh normal platelets were washed by a combination of albumin-gradient and gel-filtration procedures. In 11 experiments the supernates of freeze-thaw lysates of normal human platelets contained a mean of 5.7 Units (range 3.16 to 8.14) of HMWK coagulant activity/3 × 1011 platelets. This coagulant activity was neutralized by a goat antiki- ninogen antibody. Using a 125I-HMWK tracer in PRP, the supernate of washed activated platelets contained 0.082% radioactivity as the starting PRP, suggesting that 14% of the total HMWK coagulant activity could be accounted for by plasma contamination. In four experiments, ionophore A23187 (15μM) induced a net secretion of 39% of the total platelet HMWK (range 16 to 49%). Platelet HMWK secretion by A23187 was concentration dependent (1 to 15 μM) . At A23187 (15μM) platelets released 75% 14C-5HT (range 61 to 99%) and 81% low affinity platelet Factor 4 (range 60 to 99%). Ninety-five percent of A23187-induced secretion of HMWK could be blocked by platelet pretreatment with metabolic inhibitors. LDH determinations indicated that only 5% (range 0 to 10%) of total secreted platelet HMWK could be attributed to lysis. Collagen and PGH2 also caused secretion of platelet HMWK coagulant activity. This study indicates that human platelets contain functional HMWK which may be secreted locally to modulate the reactions of the contact phase of plasma proteolysis.

scholarly journals Interaction of high molecular weight kininogen, factor XII, and fibrinogen in plasma at interfaces

Blood ◽  
1980 ◽  
Vol 55 (1) ◽  
pp. 156-159 ◽  
Author(s):  
L Vroman ◽  
AL Adams ◽  
GC Fischer ◽  
PC Munoz
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Marked Change ◽  
Human Platelets ◽  
Blue Staining ◽  
Factor Xii ◽  
High Molecular Weight Kininogen ◽  
Contact Activation ◽  
Coomassie Blue Staining ◽  
Coated Surfaces

Using ellipsometry, anodized tantalum interference color, and Coomassie blue staining in conjunction with immunologic identification of proteins adsorbed at interfaces, we have previously found that fibrinogen is the main constituent deposited by plasma onto many man- made surfaces. However, the fibrinogen deposited from normal plasma onto glass and similar wettable materials is rapidly modified during contact activation until it can no longer be identified antigenically. In earlier publications, we have called this modification of the fibrinogen layer “conversion,” to indicate a process of unknown nature. Conversion of adsorbed fibrinogen by the plasma was not accompanied by marked change in film thickness, so that we presumed that this fibrinogen was not covered but replaced by other protein. Conversion is now showen to be markedly delayed in plasma lacking high molecular weight kininogen, slightly delayed in plasma lacking factor XII, and normal in plasma that lack factor XI or prekallikrein. We conclude that intact plasma will quickly replace the fibrinogen it has deposited on glass-like surfaces by high molecular weight kininogen and, to a smaller extent, by factor XII. Platelets adhere preferentially to fibrinogen-coated surfaces; human platelets adhere to hydrophobic nonactivating surfaces, since on these, adsorbed firbinogen is not exchanged by the plasma. The adsorbed fibrinogen will be replaced on glass-like surfaces during surface activation of clotting, and platelets failing to find fibrinogen will not adhere.

Inhibition of the Platelet Reaction by a High Molecular Weight Phosphoglycoprotein Isolated from Human Platelet Plasma Membranes

1981 ◽  
Vol 45 (02) ◽  
pp. 130-135 ◽  
Author(s):  
R Apitz-Castro ◽  
G Fonseca ◽  
V Michelena ◽  
M R Cruz
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Plasma Membranes ◽  
Human Platelet ◽  
Inhibitory Effect ◽  
Human Platelets ◽  
Secondary Wave ◽  
Platelet Reaction ◽  
Induced Aggregation ◽  
External Calcium

SummaryThe effect of a phospho-glycoprotein (HMW-GP), obtained from human platelet plasma membranes, on the aggregation and secretion of human platelets was studied. Incubation of PRP with 4 to 16 μg/ml of HMW-GP results in inhibition of ADP-, Epinephrine-, Collagen-, and Thrombin-induced platelet aggregation. The effect is mainly reflected on the secondary wave of aggregation. The inhibitory effect is partially overcome by higher concentration of the inducers, however, even under these conditions, a clear tendency towards disaggregation is observed. 5HT release (Col-induced) is strongly decreased from 50% to 4.5. The inhibitory effect on Thrombin-induced aggregation is markedly dependent on external calcium, being maximal at 5 mM calcium. The HMW-GP does not bind ADP or Thrombin. Membrane conformation is markedly affected, as evidenced by the effect of HMW-GP on the iodination of surface polypeptides of intact platelets. It is suggested that interaction of HMW-GP with the platelet membrane blocks the signal(s) transmission that links stimulus to activation. The inhibition observed might just represent an experimental amplification of the endogenous modulatory function that has been proposed for this high molecular weight phosphoglycoprotein.

scholarly journals Role of hemichrome binding to erythrocyte membrane in the generation of band-3 alterations in beta-thalassemia intermedia erythrocytes

Blood ◽  
1995 ◽  
Vol 86 (5) ◽  
pp. 2014-2020 ◽  
Author(s):  
F Mannu ◽  
P Arese ◽  
MD Cappellini ◽  
G Fiorelli ◽  
M Cappadoro ◽  
...  
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Band 3 ◽  
Beta Thalassemia ◽  
Thalassemia Intermedia ◽  
Sequence Of Events ◽  
High Molecular Weight Band ◽  
Oxidative Modifications ◽  
Membrane Bound

Nine splenectomized, hematologically well-compensated beta-thalassemia intermedia patients randomly chosen from a pool of 60 similar patients were studied. Membrane proteins solubilized with nondenaturing detergent C12E8 were gel filtered on Sepharose CL-6B (Pharmacia Fine Chemicals, Uppsala, Sweden). Fractions containing higher than 4,000-kD molecular-weight aggregates were isolated and analyzed. Four patients had remarkably increased amounts of membrane-bound hemichromes and Igs. In those patients, band 3 underwent oxidative modifications such as aggregation and a decrease in sulfhydryl groups. The other five patients had low amounts of membrane-bound hemichromes and less modifications of band 3. The same band-3 modifications could be reproduced by challenging normal membranes with artificially generated hemichromes or with hemolysates prepared from thalassemic erythrocytes of the high-hemichrome group. Addition of reduced glutathione to the challenged membranes did not hinder hemichrome binding, but prevented oxidative modifications of band 3 and Ig binding to high-molecular- weight band-3 aggregates. Hemichrome binding to band 3, hemichrome- mediated oxidation of band-3 cytoplasmic domains, generation of high- molecular-weight band-3 aggregates, and enhanced opsonization by anti- band-3 antibodies is a possible sequence of events leading to phagocytic removal of erythrocytes in thalassemia.

scholarly journals Effects of local anesthetics on human platelets: filopodial suppression and endogenous proteolysis

Blood ◽  
1979 ◽  
Vol 53 (1) ◽  
pp. 63-72 ◽  
Author(s):  
VT Nachmias ◽  
JS Sullender ◽  
JR Fallon
Keyword(s):  
Local Anesthetics ◽  
Shape Change ◽  
Human Platelets ◽  
Time Intervals ◽  
Drug Concentrations ◽  
Low Concentrations ◽  
Low Ionic Strength ◽  
Short Time ◽  
Cytoskeletal System ◽  
Platelet Shape

Abstract Agents that affect platelet shape may be useful in understanding the mechanism of shape change; for this reason the effects of local anesthetics are worthy of further study. Local anesthetics cause platelets to retract filopodia. At short time intervals (up to about 30 min) and low concentrations of the drugs, the filopodia are reextended when the platelets are gel filtered with eluant free of anesthetic. At longer time intervals (1–2 hr) or higher drug concentrations, the retraction becomes irreversible. When the polypeptide composition of the total platelet lysate was examined on SDS gels, proteolysis of two high molecular weight bands was seen when the suppression became irreversible. These polypeptides, estimated as 250,000 and 230,000 daltons, were major components of a precipitate that formed when platelets were lysed at low ionic strength and were also enriched in a “cytoskeletal” preparation made by lysing platelets attached to glass beads and analyzing the adherent residue. Electron micrographs of platelets lysed on surfaces showed an intermeshed network of filaments to be a major component of the residue. The results suggest that the proteins comprised of these bands may be part of the cytoskeletal system and that their integrity may be necessary for the platelet to reextend filopodia following suppression.

Sign in / Sign up

Export Citation Format

Share Document