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Chemical modification of chitin led to a series of derivatives: chi tosan, N-acetylchitosan, monoacetylchitin, dibutyrylchitin, chitosan acetate, chitosan butyrate, chitosan citrate and chitosan-poly(acrylic acid) complex. These were used to coat glass surfaces and studied with respect to their wetting properties and thrombogenic characteristics. All materials had much better wetting properties than siliconized glass surface The surface tension of these chitin derivatives was calculated and found to correlate with substrate throm bogenicity. The clotting time of whole blood depended on the chemical modification of the polyaminosaccharide structure and was significantly higher than the silicone surface. Gamma radiation treatment of chitosan led to a decrease in intrinsic viscosity but a small influence on the clotting time of blood in contact with the polymer samples. Solid coatings of acetate, butyrate and citrate salts of chitosan exhibited the greatest thromboresistance of all the investigated derivatives. The kaolin clotting time of plasma shaken in tubes coated with the salts did not show any leachable substances that affected blood coagulation factors except for chitosan-poly(acrylic acid) complex.

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The high specificity of the "pink test" for the detection of hereditary spherocytosis has been confirmed. A modification of the test is proposed that requires only 10 microliter of blood taken without anticoagulant (a "direct pink test"), thus eliminating the necessity of venipuncture, especially cumbersome in newborns and infants.