Clotting time of blood

No. PET Sample Incorporated pHEMA (%) Clotting Time of Blood (min)... 

Blood that has been stored for 60 min in the presence of heparinized PET films (Sample ho. 4), when put into another glass vessel was clotted within 5 min, which is the clotting time of blood not exposed to heparinized materials (4). Therefore, any reduction in thrombus formation on the heparinized film surface can only be attributed to the activity of bound heparin, i.e. the free heparin was not eluted into the blood. 

The sorbed heparin fully retains its anticoagulant activity the thrombin time for both sorbed heparin and heparin in solution is 20 + 2 s/mg heparin. The clotting time of blood in contact with the gel is proportional to the amount of heparin sorbed and significantly higher than that characteristic for the non-heparinized gel. Heparin may be repeatedly sorbed after it has been removed with saturated NaCl solution. 

Similar results were obtained when polyethylene was modified by grafting acrylamide and cholesterol ester of N-methacryloyl-[3-alanine to get 0.3 + 0.1 mg UChD/ cm2. The efficiency of UChD bound to polymer was close to that of UChD immobilized in a polyacrylamide gel the graft copolymers sorbed from the plasma solution the amount of 0.9 mg heparin/mg of immobilized UChD. The clotting time of blood contacting the modified (but not heparinized) polyethylene was 6 min, whereas on its heparinization the time increased to 30 minutes. The latter figure was actually unaltered after sixfold repetition of the heparin sorption, subsequent washing heparin off the polymer and its repeated sorption. 

Another quinone important in biological systems is vitamin K. This compound was discovered in 1935 as a result of a study of newly hatched chicks with a fatal disease in which their blood was slow to dot. It was later discovered that the delayed clotting time of blood was caused by a deficiency of prothrombin. We now know that a prothrombin deficiency is, in turn, caused by a deficiency in vitamin K, which is essential to the synthesis of prothrombin in the liver. The natural form of vitamin has a chain of five to eight isoprene units bonded to a 1,4-naphthoquinone ring. Figure 21.15 shows seven isoprene units in the side chain. 

Table 9.12 Clotting time of blood from a calf affected by sweet clover disease when treated with the prothrombin fraction from a normal animal or an affected animal...

The thromboresistance of films was determined in vitro as the time of blood-clotting. 

Heparin inhibits reactions that lead to clotting, but does not significantly alter the concentration of the normal clotting factors of blood. Although clotting time is prolonged by full therapeutic doses, in most cases it is not measurably affected by low doses of heparin. Bleeding time is usually unaffected. 

RBCT (relative blood clotting time) the time of blood clot formation on a polymer surface/the time of blood clot formation on a glass surface ... 

Table 22. Whole blood clotting time of PVC with heparin- and/or PGI2-immobilized hydrogels3...

The most common tests are (1) Clotting time of whole blood-, (2) clotting time of whole blood collected and measured in silicone-, (3) prothrombin time Quick)—clotting time of recalcified plasma with added thromboplastin (tissue extract) (4) plasma time Howell)—clotting time of recalcified plasma ... 

Ill-defined alkaloids had already been reported from this plant, but Miller and Chow (1) succeeded in isolating and characterizing the weakly basic achilleine, C14H26O6N2 (m.p. 247-248°, [a]o —14.3°). Doses of 0.5 mg. per kilogram given intravenously to rabbits decreased the clotting time of their blood by 32% without sho ving toxic or other symptoms. 

Sodium xylan polysulphate, an artificially sulphated (1 4)- 3-D-xylan, has been shown to prolong the partial thromboplastin clotting time of plasma. The differential effects of xylan sulphate on different blood serine proteases were discussed in terms of the antithrombin Ill-mediated anticoagulant activity of heparin. 

The symptoms of vitamin K deficiency in chicks are anaemia and a delayed clotting time of the blood birds are easily injured and may bleed to death. It is doubtful whether, in birds, microbially synthesised vitamin K is available by direct absorption from the digestive tract, because the site of its formation is too distal to permit absorption of adequate amounts except by ingestion of faecal material (coprophagy). 

The classical method for the biological testing of vitamin K-active substances is the measuring of their effect on the blood clotting time of the vitamin K-deficient chick. Dam et al. (1951) have described a modified method, by which a linear relationship between vitamin K dosage and clotting time was obtained. 

K Increase in prothrombin time of plasma Hemorrhages Increase in clotting time of whole blood (34, 42, 44, 45) (36, 42, 44) (42)... 

In one such study of PAS-16, average whole blood clotting times of about 26 minutes were obtained (11). 

---