Defect of platelet aggregation and adhesion induced by autoantibodies against platelet glycoprotein IIIa.

A young patient developed chronic idiopathic thrombocytopenic purpura. Prednisone therapy normalized platelet number, but bleeding symptoms did not disappear. Platelet function was severely impaired, since platelet aggregation, ATP release and adhesion to collagen and subendothelial matrix were significantly reduced. Plasma and purified immunoglobulins of the patient reproduced the functional defects in normal platelets. Immunoblotting revealed that patient's plasma contained an antibody reacting with a component of platelets with the same electrophoretic mobility of glycoproteins IIIa of normal platelets. Moreover, patient's plasma inhibited the binding of an anti-GPIIb/IIIa monoclonal antibody to platelet surface. Additional immunosuppressive therapy with prednisone and azathioprine normalized platelet function and induced the disappearance of bleeding symptoms.

Early diagnosis of deep vein thrombosis following total hip replacement using impedance plethysmography: advantages and limitations of this approach.

Early diagnosis of deep vein thrombosis (DVT) following total hip replacement is of fundamental importance given the particularly high incidence of thromboembolic complications and the limited effectiveness of available preventive measures. The authors report the results of postoperative monitoring of the lower limbs using impedance plethysmography (IPG). The validity of the computerized plethysmograph used in this study has been confirmed by previous clinical studies, in which this instrument demonstrated high sensitivity and specificity of diagnosis of deep vein thrombosis in the symptomatic patient. In the present study, however, the instrument is applied to a group of mostly asymptomatic patients, many of whom have non-occlusive DVT. One hundred thirty-two patients underwent IPG both one the day before surgery and on the seventh day after surgery. The postoperative IPG was positive in seven asymptomatic patients (5.3%). Proximal DVT was confirmed by phlebography in five patients (3.7%) and found to be absent in two patients (false positives: 1.5%), for a positive predictive value of 71%. IPG also found proximal DVT to be absent in three patients with postoperative signs and/or symptoms compatible with a thrombotic complication in the lower limbs. The character of the study did not permit collection of data as to IPG sensitivity in the asymptomatic patient, which is presumably quite lower than in the symptomatic patient. Therefore, phlebography remains the most reliable test for diagnosis of asymptomatic DVT. However, systematic monitoring by phlebography is not feasible for logistic, economic, and ethical reasons. Postoperative use of IPG may at least partially reduce the risks connected with thromboembolic complications.

Centella Asiatica Triterpenic Fraction (CATTF) reduces the number of circulating endothelial cells in subjects with post phlebitic syndrome.

Here we report a study performed in order to assess the number of circulating endothelial cells (EC) in normal subjects and in patients with postphlebitic syndrome (PPS), and the effect of treatment with Centella Asiatica Triterpenic Fraction (CATTF), a drug which has been demonstrated to be effective in promoting wound healing in vivo. EC counts were determined by means of differential centrifugation and phase contrast microscopy. Patients with PPS showed an increased number of circulating EC in comparison to normal subjects (3.8 +/- 1.2 cells versus 1.5 +/- 0.6 per counting chamber). Treatment for three weeks with CATTF caused a statistically significant reduction of circulating EC (1.80 +/- 0.6 cells per counting chamber).

Nicotine alters fibronectin and factor VIII/vWF in human vascular endothelial cells.

Primary cultured human endothelial cells derived from umbilical cord vein were exposed during the growth of the culture to medium containing nicotine at various concentrations (0.5-200 micrograms/ml). Patterns of cellular fibronectin and factor VIII/vWF were compared to control by immunofluorescence technique. The levels of glycoproteins released in the culture medium were quantified by ELISA method. Treated cells showed an important decrease in fibronectin content with fragmentation of the fibronectin pericellular filaments, whereas the levels of secreted fibronectin were reduced in a dose-dependent manner. This reduction of fibronectin availability was correlated with an elongation of cell shape as revealed with phase contrast microscopy. By immunofluorescence, factor VIII/vWF cytoplasmic granules appeared drastically reduced whereas the secretion of the protein was significantly increased. As shown by electron microscopy, there was a concomitant reduction in the number and size of Weibel-Palade bodies. These studies indicate that nicotine modifies fibronectin and factor VIII/vWF distributions but in different ways.

The effect of ticlopidine on human endothelial cells in culture.

The effect of ticlopidine at various concentrations (150, 30, 6 microM), has been studied on cultured endothelial cells derived from human umbilical cord vein. Ticlopidine affects the initial attachment of endothelial cells to artificial substrata and has an inhibitory effect on endothelial cell growth rate which correlates to the concentration of the chemical in the culture medium. These effects are related to a marked reduction of intra- and extracellular fibronectin as evidentiated by immunofluorescence. The drug seems to interfere with the formation of fibronectin filaments from intracellular granules. The reduction of fibronectin availability could affect platelet adhesion to subendothelium as well as endothelial cell repair, and subsequently influence the bleeding time. The inhibition of cell proliferation and its possible effect on the thickness of the vessel wall should be considered as additional mechanisms of action for this substance.

Extracellular matrices produced in the presence of dexamethasone: a natural "growth agent" for human cultured endothelium.

Cultured endothelium synthesizes an extracellular matrix that resembles the basement membrane of the vessels. We studied the aspect of extracellular matrices produced in presence or absence of dexamethasone by immunofluorescent technique for fibronectin; the glycoprotein is more abundant in matrices produced in the presence of dexamethasone than controls and forms a very dense meshwork. When endothelial cells resuspended in medium without FCS were seeded on these preformed matrices they adhered and replicated. The endothelium grown on matrices preformed in the presence of steroid showed a better morphology and covered a greater area indicating the presence of more abundant fibronectin content in basal lamina.

Interactions between tumor cells and vascular endothelium.-I) Adhesion properties of cell lines with different metastasizing capacity.

The authors describe the adhesive properties of four murine tumor lines, chemically and virus induced, with different metastasizing potential. Cancer cells show similar behaviour in attachment kinetics when tested with endothelium monolayer or plastic surfaces, without differences between the lines with high or low malignancy. The time required for a complete adhesion to endothelial cells is three hours while to plastic surfaces is 90 min. The role of divalent cations is not required in the first phases of cellular attachment of tumor lines to plastic dishes.