Possibilities of selective and unselective adsorbent development in blood purification.
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Biomedical subjects
Publications and source records attributed to F Loth.
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Results of in vitro and ex vivo experiments with a newly developed LDL-binding material are presented. This material consists of macroporous bead cellulose which is capable to bind selectively LDL. LDL-cholesterol is considerably decreased after contacts of plasma or serum samples with this bead cellulose. On the other hand high density lipoproteins (HDL) and other plasma components (proteins, enzymes, electrolytes, and metabolic substances) remained high or unchanged. Triglycerides (TG)--transported by very low density lipoproteins--are also bound up to a certain degree. 1 g of the adsorbent wet mass binds at least 20 mg cholesterol. The capacity suffices to decrease two- to threefold increased cholesterol and LDL plasma levels to the low normal range following passage of the sevenfold plasma volume' through two the three LDL adsorbent columns (results of perfusion experiments). In vitro and dog experiments revealed only slight drops of the hemolytic capacities of the classic complement pathway and moderate decreases of the alternative one. But no detectable side effects were noticed in the dog experiments.
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Cellulose of a certain macroporous structure is capable of binding selectively low density lipoproteins (LDL) whilst maintaining high density lipoprotein (HDL) levels. It was ascertained that the porous structure of the cellulose causes binding of LDL and that also diffusion processes play a role. To a certain extent special bindings such as hydrogen bonds between cellulose and LDL and/or hydrophobic interactions may furthermore be of importance for the LDL fixation.
A biomaterial on cellulose basis capable of swelling was developed for a progressive occlusion of vessels. Pathologic courses of the human arteriosclerosis can be imitated in animal experiment by means of this material.
Occlusions of different visceral arteries were imitated by progressive swelling substance constriction in 30 mongrel dogs. The variants of the developed collateral circulation could be proved by the postoperative angiographies. There is given reference to the importance of the connections of the visceral vascular system among one another and for the abdominal surgery of the human. Evidence is given that occlusions of the celiac artery and of the superior mesenteric artery are compensable only with the formation of large collateral vascular systems. But on certain circulation conditions the inferior mesenteric artery has a great significance too.
In vitro studies were carried out with IM-T. This adsorbent consists of polyvinyl alcohol joined with tryptophan side chains and was delivered by ASAHI Medical Co., Ltd., Tokyo/Japan. It was found that IM-T binds immunoglobulins G and M and also immune complexes only moderately but IgE was adsorbed in remarkable amounts. A clear dose-dependent was adsorbed in remarkable amounts. A clear dose-dependent manner of the IgE adsorption could be stated. Kinetic studies revealed that the binding was only slow and gradual.
A new procedure of microencapsulation was studied with regard to substance release and quantification of diffusion processes on the capsule membrane. The permeability behaviour on the capsule membrane was especially studied in metabolites, which are essential for immobilized biological objects (i.g. preimplantative mammal embryos). Peptide and proteohormones, cyanmethemoglobin and proteins were enclosed in simple and multiple Symplex Capsules. All substances examined are able to pass the Symplex membrane. The speed of release is influenced by the size of the capsule, the ion force, temperature, concentration of immobilized substances as well as their linear and globular structur. Compared with simple capsules the release of substances from multiple capsules was delayed. Corresponding to the results found under the experimental design described the Symplex membrane can be considered as coating for the compartmentation of cells, that allows the passage of essential substances for the immobilized objects. The method of microencapsulation used and described has various ways of application.
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Polyelectrolyte complex capsules from cellulose sulphate can be formed by precipitation in a polycation bath. The application of this new method for encapsulation of pancreatic islets requires investigations whether and to what extent cellulose sulphate injures viability and functionality of the pancreatic islets. Islets cultures in the presence of 2% cellulose sulphate for up to 3 weeks are characterized by unchanged insulin content, secretion and biosynthesis when compared to appropriate controls.
Cytochrome c, hemoglobin, urease and liver microsomes were microencapsulated in aqueous solution by use of a new method. The membrane of the microcapsules consist of a symplex, which is formed predominantly by electrostatic interactions between a polymeric polyanion and a polymeric polycation. The membrane is characterized by high mechanical stability and is a barrier for globular substances with molecular weights larger than 12000, but permeable for substances with lower molecular weight. The microcapsules contain the protein or microsomes and additionally the polymeric polyanion in the liquid interior. Structure and function of microencapsulated proteins and microsomes are preserved. The developed method of microencapsulation opens new possibilities for the application of biomacromolecules, particularly for extracorporal detoxification.
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