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Biomedical subjects

J Illés

Publications and source records attributed to J Illés.

14 recordsLinked to original sources
PubMed2001

Metal ion coordination of macromolecular bioligands: formation of zinc(II) complex of hyaluronic acid.

The coordination of zinc(II) ion to hyaluronate (Hya), a natural copolymer, in aqueous solution at pH 6 was investigated by potentiometric and circular dichroism (CD) spectroscopic methods, and by monitoring the changes in macroscopic properties by high-precision measurements. The zinc(II)-selective electrode, and CD measurements proved the binding of zinc(II) by Hya. A number of Hya fragments (Mr approximately 3.3 x 10(3)-1.4 x 10(6)) were studied to estimate the contributions of the polyelectrolyte effect, the solvation and host-guest interactions to the extra stabilization of the macromolecular zinc(II) complexes as compared with the monomeric unit. The zinc(II) ion activity increase reflected a stability decrease for the fragments with Mr < 4 x 10(4). This molecular weight differs from that where cleavage of the Hya skeleton starts (approximately 5 x 10(5), according to the size-exclusion gel, and anion-exchange chromatographic behavior of the Hya fragments) and from that where the polyelectrolyte effect stops (approximately 6 x 10(3)). The excess volumes and Bingham shear yield values of the solutions revealed the transformation of the coherent random coil structure stabilized by intermolecular association in the NaHya to an intramolecular association producing the globular structure of the ZnHya molecule, with a smaller but more strongly bound solvate water sheet.

Chromatography, Gel↗
PubMed1998

[Filtration of solutions with high viscosity: from laboratory experiments to production].

The Zinc Hyaluronate complex has several advantages from the point of view of woundhealing. The author's task was the elaboration of the sterile filtration technology of the 0.2% Zinc Hyaluronate solution. In the first step 0.2 micron pore diameter filters were used. During the scale up process we found that the filter boards are not suitable. The filtration time extremely increased and sometimes the whole process stopped because of the relatively small filtration area. For larger batches polypropylene capsule filters have been applied. The mean pore diameter of the filter was 0.2 micron but the unregular pore size distribution did not make the filtrate microbe free. In the next experience inlet pore diameter was 0.65 micron--the outlet pore diameter 0.45 micron. This filtration process resulted in a sterile filtrate with reduced active content. This means that the solution has been ultrafiltrated. Applying too high pressure and form a compact layer on the filter's surface which is functioning as a secondary filter layer. The filtration should begin with low pressure and it has to increase it gradually from 0 to 2 bar in 0.5 bar steps. It was supposed that at high temperature filtration could be easier and faster. On the contrary we found that depending on the concentration above 35-45 degrees C the active content of the filtrate is decreasing. In the case of the filtration of the fraction with a lower temperature the fractions with high molecular weight can be filtrated because of the anisometric distribution of the molecules. The filtration of these products is very difficult even at laboratory scale.

Capsules↗
PubMed1982

Importance of cell-to-cell contact and transfer in white cell activity.

Formation of cell junctions and the occurrence of cell-to-cell transfer through these was examined in mixed cultures of PK 15 pig kidney and mouse peritoneal cells. Under standardized conditions of experiment, a close contact developed between peritoneal and target cells within 90 min. Light and scanning electron microscopic examinations of the area of close contact indicated extension of cytoplasmic processes from peritoneal cells towards the nucleoli of target cells. The size and localization of the nucleolus and the incorporation of a considerable amount of label by the nucleolar associated chromatin also indicated the decisive role of the nucleolus in the events following upon the establishment of close contact. Autoradiographic examinations showed that part of the 6-3H-thymidine labelled material migrated from the nucleus of target cells into the cytoplasm of peritoneal cells within 30 min. A greater cytoplasmic accumulation of label took place in peritoneal cells exclusively in the presence of actinomycin-D, indicating a rapid breakdown of transferred material under normal conditions. The development of cell-to-cell contact and transfer was found to depend greatly on the composition of the nutrient medium.

Animals↗
PubMed1975

[Protective oral immunization against coli enterotoxemia in swine (author's tranls)].

The issue of immunity in the case of enteric infections caused by bacteria is still widely unresolved. To clarify this, weaned piglets 6-7 weeks of age were used as a model, because of the particular susceptibility to colienterotoxemia shown by them at this particular age. The experimental design was as follows. The animals were immunized orally and parenterally (i.v. and i.p. routes) by means of a vaccine consisting of bacteria incapable of reproduction. 14 days later, the animals were challenged orally with virulent EC-O 141 B 85 and EC-O 139 B 82. The results have shown that a) parenteral immunization did not induce protection against oral infection with virulent E. coli; b) repeated oral immunization produced measurable immunity against oral infection; and c) 1 7-hour broth culture proved to be particularly suitable for oral infection. Results also point to the fact local immunity in the intestine as present after enteric infection by bacteria may be artificially induced only by protective oral immunization.

Administration, Oral↗
PubMedDate not supplied

[Positron lifetime studies of sodium- and zinc-hyaluronates].

The aim of this work was to test the positron lifetime technique (PLT) as a tool of the structure study of sodium- and zinc-hyaluronates. The information based on the PLT measurements (outlined as follows) proved that this method can be useful in this field as well. The lifetime of ortho-positronium (o-Ps) significantly increased and its intensity decreased in the samples containing Zn2+, comparing to Na-hyaluronates. It showed that the electronic orbitals are more closed in the case of Zn2+ cation that means the overlapping between the wave functions of the positron and of the electrons decreased. (See equation No 1.) The study of the effect of water content suggested that the hydrogen-bridge-bonds "localised" the free electron pairs. The increasing pressure increased the lifetime and it is an evidence that the effect of the cations (Na+ and Zn2+) can be explained rather with the change of the electronic structure than with the altering of the free volumes of the samples.

Adjuvants, Immunologic↗