Biomedical subjects

A Tzipiniuk

Publications and source records attributed to A Tzipiniuk.

3 recordsLinked to original sources

PubMed1984

Tailor-made agarose-based reactive beads for hemoperfusion and plasma perfusion.

Composite beads of approximately 1 mm diameter, made of crosslinked agarose and containing Fuller's Earth or zirconium oxide powders, were prepared and used in extracorporeal systems for blood detoxification. The former was used for the removal of Paraquat, while the latter was used to remove inorganic phosphate from hyperphosphatemic animals with or without acute renal failure. The high surface area of the powder, combined with the low resistance to diffusion in the crosslinked agarose matrix, are highly advantageous. The crosslinking provides high mechanical strength, heat stability, prolonged shelf life, good blood flow characteristics, and prevents the release of fine particles into the blood. Crosslinked agarose beads of 1 mm diameter, containing chemically-bound heparin were also prepared, and used as a model for direct contact removal of LDL-cholesterol from the blood of familial hypercholesterolemic patients by hemoperfusion. The high capacity of these beads (over 5 mg LDL/mL beads) indicates that this clinical modality can replace the highly expensive plasmapheresis procedure presently used.

Animals↗

PubMed1984

Controlling anticoagulation in extracorporeal blood circuits (hemoperfusion).

The study demonstrates that different individuals (monkeys) need different heparin doses so as to avoid either clotting or bleeding when an extracorporeal blood system is involved. The linear correlation between PT and WBPTT values enables to utilize the latter for monitoring the heparin level in the blood. One procedure is based on the application of the Gotch and Keen intravenous heparinization model in its steady state limit by utilizing the pre-treatment evaluation of k/S, the ratio of the elimination rate constant to the individual's sensitivity to heparin. A second procedure involves the direct heparinization of the extracorporeal system. The heparin infusion rate is monitored through the arterial WBPTT values after relating the individual's PT or WBPTT values to the in vitro heparin concentration in the blood. In vitro and in vivo study of the effect of hemoperfusion through a column containing anion exchange particles on the amount and rate of heparin administration indicates that only the in vivo results are meaningful. The sharp response of WBPTT to relatively small changes of citrate concentration in the blood precludes individual monitoring by WBPTT. Work on the advantage of utilizing heparin together with citrate is required.

Animals↗

PubMedDate not supplied

Cholesterol removal by haemoperfusion of whole blood in vivo.

Familial hypercholesterolaemia is caused by genetic defects in the cellular metabolism of cholesterol (C) and is characterized by high levels of low-density lipoproteins (LDL) and premature atherosclerosis. The C is carried in the plasma mainly as an LDL-C complex, and removal of the latter from plasma is highly desirable. This task can be achieved by selective haemoperfusion (HP), thereby eliminating the need for plasmapheresis. Agarose beads (2 per cent agarose, 0.85 to 1.4 mm in diameter) were prepared, and crosslinked with epichlorohydrin. Heparin and/or ethanolamine were subsequently attached. The beads thus obtained were found to be suitable for the removal of LDL-C from the whole blood of hypercholesterolaemic rabbits, using a simple HP technique. A single two-hour HP treatment with a 40 ml column packed with active agarose beads resulted in a 30 per cent decrease in the C plasma level in the experimental animals. Our previous, in vitro, studies with the plasma of hypercholesterolaemic patients showed a high selectivity of the beads for LDL. Yet when used with hypercholesterolaemic rabbits, a relatively high amount of HDL was also removed from the blood. This can be attributed to a significant difference between the structure of human hypercholesterolaemic lipoproteins and that of rabbits. Upon treatment of blood using the active agarose beads, no abnormalities in plasma and blood composition were detected, except for some prolongation of PT. It is to be hoped that this new system will replace the presently used and highly expensive plasmapheresis.

Animals↗