Ultrastructure of endothelial cells under flow alteration

Endothelial cells are stable and quiet in normal animals. They arrange regularly and have a smooth lumen surface and thin endothelial wall. According to Thoma's principle (1893) and Kamiya and Togawa's principle (1980) on the relationship of the vascular diameter to flow alteration, blood flow is in equilibrium to the diameter and in a physiological state. That is to say, there is no fast flow or slow flow. To understand the nature of the endothelial cells, we should investigate endothelial cells under flow alteration to break the equilibrium state. Endothelial cells under increased flow were studied in arteries with an arteriovenous fistula or in the capillaries of myocardium with volume-overloaded hearts or of the skeletal muscle by electrical stimulation. Those under decreased flow were studied by the closure of the fistula or by ceasing the stimulation. Endothelial cells in the coarctation of the arteries were also observed. Endothelial cells were activated by increased flow in the arteries and capillaries, while they were inactivated by decreased flow. Endothelial activation is characterized as lumen protrusions, increase of cytoplasmic organelles, abluminal protrusions, basement membrane degradation, internal elastic lamina degradation in the arteries, and sproutings in the capillaries. These are ultrastructurally comparable to angiogenesis. Endothelial inactivation is characterized by the decrease of endothelial cell number with apoptosis, which is ultrastructurally comparable to angioregression. We assume that endothelial cells respond to increased flow by angiogenesis and to decreased flow by angioregression.     

Immunocytochemical studies on co-localization of alpha-granule membrane alphaIIbbeta3 integrin and intragranular fibrinogen of human platelets and their cell-surface expression during the thrombin-induced release reaction

We employed a double-staining method to immunocytochemically study the role of alpha-granule membrane alphaIIbbeta3 integrin in the expression of intragranular fibrinogen (Fbg) and albumin on the surface of thrombin-activated human platelets. In unstimulated platelets, alphaIIbbeta3 was distributed along the alpha-granule membrane as well as on the cell-surface membrane, including the open canalicular system (OCS), while Fbg and albumin were exclusively and evenly detected in the granules. At 30 s after activation by 0.1 U ml(-1) thrombin under non-stirred conditions, a small amount of Fbg in the granules was redistributed in association with alpha-granule membrane alphaIIbbeta3, suggesting that co-localization between alphaIIbbeta3and Fbg occurs at this period during platelet activation. At 1-5 min, the shape of the platelets changed from discoid to spheroid with pseudopodia and intact alpha-granules were no longer observed in these cells. Fibrinogen associated with alphaIIbbeta3 became increasingly expressed on the membranes of both the swollen OCS and the cell surface. Nevertheless, abundant Fbg still remained in the lumen of the swollen OCS, the membrane of which had already been depleted of alphaIIbbeta3. By western blot analysis using anti-human Fbg antibody, we detected no Fbg in the surrounding medium of the thrombin-stimulated platelets for 5 min. Unlike Fbg, abundant albumin in the alpha-granules was released into the surrounding medium without association with the membrane of either the alpha-granules or the cell surface. These results suggest that a small portion of the intragranular Fbg may bind to an Fbg binding site expressed on the activated aIIbbeta3 on the alpha-granule membrane, resulting in the formation of an alphaIIbbeta3-Fbg complex, which is then moved through the OCS membrane and expressed on the cell-surface membrane. Thus, alpha-granule membrane aIIbbeta3 may act as a carrier of intragranular Fbg.     

The antiwear property of zinc dialkyldithiophosphates in used engine oils

The change in the lubrication properties of vehicle engine oils with driving distance was studied by using a cross-pin type of lubricant tester and a Fourier transform IR spectrometer. The effect of the thermal decomposition of zinc dialkyldithiophosphates (ZnDTPs) on their antiwear property was also examined. The amount of the ZnDTP in engine oil decreased and the amounts of the decomposition products increased with increasing running distance but a good antiwear property was still observed. After 60 h of heating at 135°C, the ZnDTP in sample oils had decomposed into a precipitate and the antiwear property of the oil had deteriorated. With sample oils containing ZnDTP and a detergent or a dispersant, the decomposition products dissolved in the oil and the antiwear property was maintained even after 80 h of heating. The results suggest that the decomposition products of ZnDTPs have a good antiwear property and that the good antiwear property of the used engine oils was retained because of the solubilization of decomposition products into the oil with the aid of a dispersant or a detergent.