The absorption spectrum of human fibroblast monolayers showed several absorption peaks, among them one at a wave-length of 630 nm. Cultures of these fibroblasts were subjected to He-Ne laser (632.8 nm) irradiation of various energy doses by varying power density and exposure time. On three consecutive days the cell monolayers were irradiated for periods between 0.5 and 10 min. Laser power varied from 0.55 to 5.98 mW. Both cell number and collagen type I production were determined for each irradiation condition within one experiment. Results show that laser power below 2.91 mW could enhance cell proliferation (as determined by cell counting), whereas higher laser power (5.98 mW) had no effect. Stimulatory effects were most pronounced at irradiation times between 0.5 and 2 min. Collagen type I production (as determined by an ELISA) was affected in the opposite direction to cell proliferation: when the cell proliferation was increased, collagen type I production was decreased. From these experiments it is clear that exposure time and power density determine the effects of laser irradiation. Both stimulation and inhibition of the observed cell properties can be obtained with the same laser on the same cells.

Schwann cell proliferation is considered an essential part of Wallerian degeneration after nerve damage. Laminin, an important component of the extracellular matrix and produced by Schwann cells, provides a preferred substrate for outgrowing axons. To study whether low energy (He-Ne) laser irradiation may exert a positive effect on nerve regeneration through an effect on Schwann cells, its effect was evaluated in vivo. Schwann cells were isolated from sciatic nerves of 4-5-day-old Wistar rates and cultured on 96-multiwell plates. The cells were irradiated by a He-Ne laser beam (632.8 nm, 5.98 mW) that was optically expanded to a beam width of 4 mm. During irradiation the plate was kept in an air-tight box equilibrated with humidified air containing 5% CO2 and kept at 37 degrees C. At three consecutive days, starting either at day 5 or day 8, cells were irradiated each day for 0.5, 1, 2, 5 or 10 min. Both cell number and laminin production were determined for each irradiation condition (n = 5) within one experiment. Schwann cells that were irradiated from day 8 on were hardly affected by laser irradiation. However, the proliferation of cells that were irradiated starting on day 5 was significantly increased after 1, 2, and 5 min of daily irradiation, compared to non-irradiated control cultures. The laminin production per cell of these Schwann cells was not significantly altered. From these results we conclude that He-Ne laser irradiation can modulate proliferation of rat Schwann cells in vitro in a dose-dependent manner.

As part of a systematic study of platelet interaction with adhesive proteins under flow conditions, we studied platelet adhesion to multimeric and dimeric von Willebrand factor (vWF) coated to glass. vWF-dependent adhesion to collagen type III was studied for comparison. Adhesion to glass-coated vWF and vWF-mediated adhesion to collagen type III were in many respects similar. Both showed no decrease at increasing shear rates and a decline to 50% of maximum with a low-molecular-weight multimeric fraction. Adhesion to glass-coated vWF was partially inhibited by heparin and completely inhibited by prostaglandin I(2) and anti-glycoprotein (GP) Ib and anti-GPIIb-IIIa antibodies. vWF-dependent adhesion to collagen was not inhibited by heparin, was partially inhibited by anti-GPIIb-IIIa, and was completely inhibited by prostaglandin I(2) and anti-GPIb. Recombinant dimeric vWF was made by deletion of the propeptide and expression in Chinese hamster ovary cells. Adhesion was 50% of that with plasma vWF, and larger concentrations of dimeric vWF were required. Adhesion to dimeric vWF was optimal at 1500 s(-1), with a gradual decrease at higher shear rates. We conclude that adhesion to collagen type III is strongly but not completely determined by the adhesive properties of vWF.

Purified EPA-E in doses of 900 and 1800 mg reduces Platelet-activating factor-induced platelet aggregation without negatively affecting glycemic control. Low-density-lipoprotein cholesterol was elevated in the 1800-mg group.

Platelet adhesion to the vessel wall is initiated by transport of blood platelets from the bulk flow to the wall. The process of diffusion and convection of the platelets is affected by rheological conditions such as well shear rate, red blood cell (RBC) deformability, and viscosity of the medium. To study the effect of plasma viscosity on platelet adhesion, perfusion experiments with a rectangular perfusion chamber were performed. Reconstituted blood, consisting of washed platelets and washed RBCs, was circulated through this chamber for 5 minutes at a wall shear rate of 300 s-1. Different albumin concentrations were made, to obtain different medium viscosities (0.89 to 1.85 mPa.s). Platelet adhesion decreased with increasing medium viscosity up to viscosities of 0.95 mPa.s, but increased with medium viscosity above this value. Instead of human albumin solution, different plasma viscosities were obtained by dilution of Waldenstrom plasma with buffer. Plasma was depleted of fibronectin, which gave a final plasma viscosity of 2.0 mPa.s, and was dialyzed against HEPES buffer and subsequently diluted with the dialysis buffer in different fractions (0.89 to 2.00 mPa.s). Perfusions were performed over a purified von Willebrand factor coating on glass, or over an endothelial cell matrix, preincubated with von Willebrand factor. With both surfaces, platelet adhesion was dependent on the plasma viscosity in a similar way: at low plasma viscosities, adhesion was decreased with increasing plasma viscosity, while at higher plasma viscosities, adhesion increased with plasma viscosity. Adhesion values at higher plasma viscosity or at higher human albumin concentrations could be explained by effects of the medium on the rigidity of the RBCs, since platelet adhesion is known to be increased by enhanced RBC rigidity. Effects of the medium on the deformability of the RBCs were measured separately with the laser diffraction method. These experiments confirmed that presence of human albumin or plasma in the measuring suspension increased the rigidity of RBCs. To prevent influence of the medium on the RBCs in perfusion experiments, the RBCs were fixated with glutaraldehyde. Perfusion experiments with fixated RBCs in plasma over a von Willebrand factor preincubated endothelial cell matrix, showed a consequent decrease in adhesion with increasing plasma viscosity, according to the diffusion theories, whereas the increase of adhesion at high plasma viscosities was lacking. This suggests that the latter effect was entirely due to increased transport of platelets by more rigid RBCs.