scholarly journals Uncoordinated expression of fibrinogen compared with thrombospondin and von Willebrand factor in maturing human megakaryocytes

Blood ◽  
1989 ◽  
Vol 73 (5) ◽  
pp. 1123-1129 ◽  
Author(s):  
EM Cramer ◽  
N Debili ◽  
JF Martin ◽  
AM Gladwin ◽  
J Breton-Gorius ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Von Willebrand Factor ◽  
Blood Platelets ◽  
Normal Subjects ◽  
Culture Conditions ◽  
Normal Serum ◽  
Maturation Stage ◽  
Megakaryoblastic Leukemia ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract The localization of three known alpha-granule proteins, thrombospondin (TSP), von Willebrand factor (vWF), and fibrinogen (Fg) has been studied in human megakaryocytes (MK) by immunofluorescence and immunoelectron microscopy. For this study, highly purified populations of MK were prepared from human bone marrow either by counterflow centrifugal elutriation or by cell culture from normal subjects and from two patients with megakaryoblastic leukemia. In normal bone marrow immature MK, TSP, and vWF were observed in the Golgi-associated vesicles and in small immature alpha-granules; in mature MK, they were found in the matrix of the mature large alpha-granules. Surprisingly, Fg was detected neither in the Golgi area, nor in the small precursors of alpha-granules; it was only found in the mature alpha-granules but this labeling was generally weaker than in blood platelets. In order to confirm these differences between the expression of Fg and vWF or TSP additional studies were performed on cultured maturing MK: immunofluorescent and ultrastructural immunogold labeling confirmed that vWF appeared early in the maturation while the same immature MK were negative for Fg. In the late maturation stage, the three proteins were detected in the alpha-granules. In order to know whether Fg was lately synthesized or endocytosed from the outside medium, normal MK were grown in the presence of either normal or afibrinogenemic plasma, and normal serum. Fg was detected only in the alpha-granules of MK grown in normal plasma. Similar results were observed with malignant MK, whose maturation was independent of the culture conditions. In conclusion, this study brings immunocytochemical evidence that vWF and TSP are synthesized by immature MK, whereas Fg appears later in the MK alpha-granules and its expression is dependent of the presence of an exogenous Fg source.

scholarly journals Uncoordinated expression of fibrinogen compared with thrombospondin and von Willebrand factor in maturing human megakaryocytes

Blood ◽  
1989 ◽  
Vol 73 (5) ◽  
pp. 1123-1129 ◽  
Author(s):  
EM Cramer ◽  
N Debili ◽  
JF Martin ◽  
AM Gladwin ◽  
J Breton-Gorius ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Von Willebrand Factor ◽  
Blood Platelets ◽  
Normal Subjects ◽  
Culture Conditions ◽  
Normal Serum ◽  
Maturation Stage ◽  
Megakaryoblastic Leukemia ◽  
Von Willebrand ◽  
Willebrand Factor

The localization of three known alpha-granule proteins, thrombospondin (TSP), von Willebrand factor (vWF), and fibrinogen (Fg) has been studied in human megakaryocytes (MK) by immunofluorescence and immunoelectron microscopy. For this study, highly purified populations of MK were prepared from human bone marrow either by counterflow centrifugal elutriation or by cell culture from normal subjects and from two patients with megakaryoblastic leukemia. In normal bone marrow immature MK, TSP, and vWF were observed in the Golgi-associated vesicles and in small immature alpha-granules; in mature MK, they were found in the matrix of the mature large alpha-granules. Surprisingly, Fg was detected neither in the Golgi area, nor in the small precursors of alpha-granules; it was only found in the mature alpha-granules but this labeling was generally weaker than in blood platelets. In order to confirm these differences between the expression of Fg and vWF or TSP additional studies were performed on cultured maturing MK: immunofluorescent and ultrastructural immunogold labeling confirmed that vWF appeared early in the maturation while the same immature MK were negative for Fg. In the late maturation stage, the three proteins were detected in the alpha-granules. In order to know whether Fg was lately synthesized or endocytosed from the outside medium, normal MK were grown in the presence of either normal or afibrinogenemic plasma, and normal serum. Fg was detected only in the alpha-granules of MK grown in normal plasma. Similar results were observed with malignant MK, whose maturation was independent of the culture conditions. In conclusion, this study brings immunocytochemical evidence that vWF and TSP are synthesized by immature MK, whereas Fg appears later in the MK alpha-granules and its expression is dependent of the presence of an exogenous Fg source.

Association Between Bleeding Time and Platelet Adherence to Artery Subendothelium

1984 ◽  
Vol 52 (02) ◽  
pp. 144-147 ◽  
Author(s):  
K S Sakariassen ◽  
P A Bolhuis ◽  
Margaretha Blombäck ◽  
L Thorell ◽  
Birger Blombäck ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Bleeding Time ◽  
Blood Platelets ◽  
Normal Subjects ◽  
Commercial Preparation ◽  
Normal Platelet ◽  
Platelet Adherence ◽  
Von Willebrand ◽  
Willebrand Factor

SummaryThe efficacy of five different factor VUI-von Willebrand factor (FVIII-VWF) preparations in mediating adherence of blood platelets to damaged vessel walls was tested in an annular perfusion chamber utilizing human arteries and reconstituted blood.FVIII-VWF-purified by Sepharose CL-4B chromatography and von Willebrand factor prepared from this preparation by dissociation with 0.25 M CaCl2 followed by Sepharose CL-6B chromatography were equally effective in mediating platelet adherence as FVIII-VWF in cryoprecipitate and in plasma from normal subjects. A commercial concentrate of FVIII-VWF (Hemofil, Hyland) used for the treatment of haemophiliacs did not mediate platelet adherence at normal levels of FVIII-VWF related properties. A recently developed high-purity FVIII-VWF preparation (Concentrate II) containing multimers of high molecular weight normalized the platelet adherence. Platelet adherence in plasma obtained from two patients with von Willebrand’s disease (VWD) was impaired, but plasma samples obtained following treatment with Concentrate II mediated normal platelet adherence. The normalization of platelet adherence paralleled the normalization of the bleeding time.This platelet adherence assay offers an inexpensive and efficient in vitro tool to test the efficacy of FVIII-VWF preparations designed for VWD patients. Preparations such as cryoprecipitate and Concentrate II mediated the platelet adherence and normalized the bleeding time. The commercial preparation did not mediate platelet adherence and had no effect on the bleeding time.

EFFECTS OF SOME ORGANIC SOLVENTS ON GP lb AND ACTIN-BINDING PROTEIN IN BLOOD PLATELETS

1987 ◽  
Author(s):  
A M Aakhus ◽  
N O Solum ◽  
I Hagen
Keyword(s):  
Organic Solvents ◽  
Von Willebrand Factor ◽  
Early Stage ◽  
Binding Protein ◽  
Blood Platelets ◽  
Cytoskeletal Proteins ◽  
Actin Binding ◽  
Actin Binding Protein ◽  
Von Willebrand ◽  
Willebrand Factor

Effects on filamentous proteins appear to be a central phenomenon in the neuronal toxic effects of organic solvents. We have therefore compared the effects of some organic solvents (particularly isopropylalcohol, IPA) to the previously observed effects of dibucaine (DBC) on platelet cytoskeletal proteins. Incubation of platelets with 6% IPA at 37° C, like DBC, initiates a degradation of actin-binding protein (ABP) as substrate for a calcium activated protease (CAP), shown by SDS-PAGE. IPA leads to an increase followed by a decrease in bovine von Willebrand factor-induced agglutination. The decrease is accompanied by a release of glycocali-cin from the GP lb α-chain. The process was also studied using CIE of Triton X-100 extracts of platelets against antiserum to glycocalicin. Incubation of platelets with IPA before extraction in the presence of 4.2 mM leupeptin leads to a time-dependent transformation of GP Ib-related immunoprecipitates from that of the slow-migrating peak III complex (probably between ABP and GP lb) to the faster migrating GP Ib-precipitate. Our working hypothesis is that IPA induces an activation of the CAP by mobilizing calcium. This leads to degradation of ABP and liberation of GP lb from the cytoskeleton accompanied by an increased tendency for agglutination. The following decrease is explained by degradation of the glycocalicin part of the GP lb enchain which contains the binding-site for von Willebrand factor. We conclude that IPA has a similar effect on GP lb and ABP as DBC. Preliminary studies with 1% DMSO and 0,005% toluene at 37° C revealed that these organic solvents have some similar effects on platelets as described for IPA. Possibly the described effects are characteristic of certain cells at an early stage in a process ultimately leading to cell lysis.

scholarly journals New Method for Assessment of Plasma Von Willebrand Factor

1977 ◽  
Author(s):  
T. Sano ◽  
T. Motomiya ◽  
N. Mashimo ◽  
H. Yamazaki
Keyword(s):  
Platelet Aggregation ◽  
Von Willebrand Factor ◽  
Platelet Rich Plasma ◽  
Normal Subjects ◽  
Induce Platelet Aggregation ◽  
Platelet Suspension ◽  
Maximal Plasma ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Diabetes Melitus

As much interests have been focused on von Willebrand factor (vWF) in diabetes melitus and atherosclerosis, request to determine vWF has been increasing recently. Two methods for assessment of plasma vWF level, without platelet aggregometer, were devised. 1) Platelet-rich plasma (PRP) sensitivity to ristocetin-induced platelet aggregation (RIPA): PRP was separated without centrifugation from citrated blood. Serially two-fold diluted restocetin (16 to 16x2-10 mg/ml) was prepared in a Cooke Microtiter tray and PRP (25 μl each) was added to each concentration of ristocetin. Then the ristocetin-PRP mixture was agitated for 15 seconds using a Kowa Kizai Micromixer and the minimum effective final concentration of ristocetin to give platelet aggregation was obtained microscopically and this was defined as PRP sensitivity to RIPA. This method is convenient for screening test. 2) vWF assay:Serially two-fold diluted plasma (2 to 1024 times, in Tris-salin pH 7.2 containing 12 mg/ml bovine serum albumin), fixed and washed platelet suspension (6x105 /μl, Macfarlane et al.1975) and 3 mg/ml ristocetin were mixed (25 μl each) in a microtiter tray and agitated for 15 seconds. The maximal plasma dilution to induce platelet aggregation was obtained microscopically and defined as the titer of plasma vWF. In normal subjects, minimum effective ristocetin concentration (PRP sensitivity to RIPA) was around 1 to 0.5 mg/ml and maximal plasma dilution to give platelet aggregation (vWF titer) was around 16 to 32 times. The present methods have a good reproducibility and are performed easily without aggregometer and thought to be useful clinically.

scholarly journals Platelet adhesion to collagen in healthy volunteers is influenced by variation of both α2β1 density and von Willebrand factor

Blood ◽  
2000 ◽  
Vol 96 (4) ◽  
pp. 1433-1437 ◽  
Author(s):  
Mark Roest ◽  
Jan J. Sixma ◽  
Ya-Ping Wu ◽  
Martin J. W. Ijsseldijk ◽  
Mariëlle Tempelman ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Platelet Adhesion ◽  
Collagen Type ◽  
Normal Subjects ◽  
Collagen Type Iv ◽  
Collagen Types ◽  
Platelet Surface ◽  
Type Iv ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Platelet thrombus formation on collagen is initiated by platelet GPIb interaction with von Willebrand factor (vWF) bound to collagen, followed by firm attachment of the platelet to collagen by the integrin α2β1. Platelet and plasma vWF levels and α2β1 density on the platelet surface are highly variable among normal subjects; however, little is known about the consequences of this variability on platelet adhesion to collagen. A population of 32 normal subjects was studied to evaluate the relation between genetic and phenotypic variations of α2β1 density on the platelet surface, plasma vWF levels, platelet vWF levels, and adenosine diphosphate and adenosine triphosphate concentrations on the one hand and platelet adhesion to collagen under flow on the other hand. Platelet adhesion to collagen types I and III under flow was correlated with plasma levels of vWF (r2 = 0.45 and 0.42, respectively) and α2β1 density on the platelet surface (r2 = 0.35 and 0.17, not significant). Platelet adhesion to collagen type IV under flow was significantly correlated with platelet vWF levels (r2 = 0.34) and α2β1 density on the platelet surface (r2 = 0.42). Platelet adhesion to collagen types I and III depends on both plasma levels of vWF and α2β1 density on the platelet surface, whereas platelet adhesion to collagen type IV is mediated by both platelet vWF levels and α2β1 density on the platelet surface.

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