A global platelet test of thrombosis and thrombolysis detects a prothrombotic state in some patients with non-insulin dependent diabetes and in some patients with stroke.

Platelet aggregation and spontaneous thrombolytic activity were assessed in patients with non-insulin dependent diabetes and stroke using a shear-induced and agonist-induced platelet aggregation test. The Thrombotic Status Analyser (TSA), induces platelet-rich thrombus formation solely by shear forces, while whole blood platelet aggregometry measures platelet reactivity to different agonists. These tests were employed in the present study because in earlier studies they both demonstrated that platelet aggregability in healthy volunteers was unchanged with age. On the other hand, it is known that thrombolytic activity decreases with age in males, but not in females. In diabetic patients shear-induced platelet aggregability varied according to the stage of nephropathy but platelet aggregation to collagen was suppressed at all stages. Platelet reaction to shear stress was enhanced in stroke patients with haemorrhagic episodes but not in patients with lacunar infarction. In contrast, platelet reactivity to collagen was suppressed and changes in ADP-induced platelet aggregability were inconsistent. Suppressed thrombolysis was observed only in diabetes with minor renal defect. Fibrinogen was increased in diabetes with stage III and IV nephropathy. Fibrinopeptide A (FPA) and D-dimer were increased in stroke. Thus, the observed increase in fibrinogen, FPA and D-dimer is inconsistent with changes in platelet aggregability. Our present findings suggest that a shear-induced platelet aggregation test is superior to other tests such as agonist-induced platelet aggregation and thrombotic markers such as fibrinogen, FPA and D-dimer in detecting a prothrombotic state. It is concluded that elderly males may have a prothrombotic state not because of platelet hyper-aggregability but because of suppressed thrombolytic activity. On the other hand, a prothrombotic state in patients with non-insulin dependent diabetes and after stroke may be due to changes in age-independent platelet aggregability.

Effect of pressure on the sol-gel transition of gelatin.

The effects of hydrostatic pressure on the sol-gel transition of gelatins were studied in the concentration range 1.5-12.5% under high pressures up to 300 MPa. The gelatin gels were stabilized by pressure: the pressure-induced elevation of melting temperature, (dT/dP)m, was 3.89 x 10(-2), 3.17 x 10(-2) and 2.92 x 10(-2) K/MPa for gelatins of Bloom No. 60, 225 and 304, respectively. The enthalpy, entropy and volume changes accompanying the gel formation were calculated from the Eldridge-Ferry plots and the Clausius-Clapeyron equation. The volume changes of gelation were estimated to be -25.7, -20.8 and -18.3 ml/mol of cross-links for gelatins of Bloom No. 60, 225 and 304, respectively, which were almost independent of pressure. The kinetic process of gelation was suppressed under high pressure, indicating the positive activation volume of gelation. These volume changes were discussed in terms of the characteristic hydration modes of cross-linking junctions of gelatin gels, comparing them with those of native collagen.