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Biomedical subjects

Z Rácz

Publications and source records attributed to Z Rácz.

At least 19 recordsLinked to original sources
PubMed2001

1/f noise and extreme value statistics.

We study finite-size scaling of the roughness of signals in systems displaying Gaussian 1/f power spectra. It is found that one of the extreme value distributions, the Fisher-Tippett-Gumbel (FTG) distribution, emerges as the scaling function when boundary conditions are periodic. We provide a realistic example of periodic 1/f noise, and demonstrate by simulations that the FTG distribution is a good approximation for the case of nonperiodic boundary conditions as well. Experiments on voltage fluctuations in GaAs films are analyzed and excellent agreement is found with the theory.

Journal Article↗
PubMed2001

[Biological aspects of the effectiveness/ineffectiveness of thrombocyte transfusions].

The clinical effect of platelet transfusions depends on a series of different factors and therefore it is not easy to explain the cause of inefficiency or that of the side-effects. Not only the immunhematological state of the patient, but the medical treatment and the properties of the platelet preparations should be taken into account. Platelet products prepared by standard techniques and stored according to the international recommendations possess different hemostatic effect. The effect of platelet storage conditions, aspects of platelet thermophysiology and current international tendencies regarding preparation and storage of platelet products are discussed. The choice of the proper platelet product has an essential impact on the clinical outcome.

Animals↗
PubMed2000

Characteristics of the specific removal of lymphocytes and granulocytes from whole blood in an automated bottom-and-top processing system.

Characteristics of lymphocyte and granulocyte removal were studied during processing of fresh and overnight-stored human blood in a bottom-and-top semiautomated system using the buffy coat (BC) technique. Blood cells were counted in the resulting components. Removal efficiency of lymphocytes and granulocytes correlated with the loss of erythrocytes due to removal of the BC. Sigmoidal curves showed a good fit to experimental data. Variables of the equations differed substantially concerning removal of lymphocytes and granulocytes. Overnight storage of blood at 20-22 degrees C prior to processing resulted in changes in efficiency of leukocyte removal. Removal of lymphocytes decreased, while that of granulocytes increased due to overnight processing. Lymphocytes may be removed almost quantitatively with less than 10% (fresh blood) or 15% (overnight-stored blood) loss in erythrocyte content of the donated blood, corresponding to less than 28 ml packed red cells in the BC. Granulocytes seem to represent the residual amount of the final leukocyte content in the erythrocyte product. The present study may contribute to the production of erythrocyte products with fewer contaminating leukocytes and to the standardizing of semiautomated blood processing.

Blood Component Removal↗
PubMed1997

Differential reduction in lymphocyte and granulocyte content by removal of the buffy coat from fresh and overnight-stored blood. Comparison of manual and automated blood processing systems.

The efficiency of leukocyte removal was studied by the removal of the buffy coat layer from fresh and overnight-stored whole blood. Manual blood processing was compared with two types of automated separators: the T-ACE (Terumo) and the OPTI system (with the top-and-bottom bag, Baxter). The main characteristics of leukocyte removal were similar for the systems studied. The efficiency of leukocyte removal was consistently higher with overnight-stored blood. When the net red cell content of the buffy coat was 20-30 mL, the figures were: 70% (n = 103) vs 45% (n = 87, manual method), 78% (n = 6) vs 60% (n = 100, T-ACE) and 82% (n = 10) vs 71% (n = 20, OPTI system), respectively. The increase in the efficiency in leukocyte removal was due to a rapid increase in the efficiency of removal of granulocytes: 65% (n = 65) vs 45% (n = 57, manual method), 80% (n = 4) vs 46% (n = 83, T-ACE) and 74% (n = 9) vs 57% (n = 17, OPTI system), respectively. Processing of overnight stored blood may provide red cell concentrates with fewer contaminating leukocytes and granulocytes.

Automation↗
PubMed1997

Increased yield of F VIII from pooled plasma vs. single-donor plasma in the production of cryoprecipitates.

Coagulation factor VIII:C yield was studied in two types of cryoprecipitates. The first group contained products from single-donor plasma units. The other group contained cryoprecipitates which were produced from pooled plasma. The volume of plasma/bag was not different between the two groups, but both the yield and the total content of F VIII:C in cryoprecipitates were significantly different. The yield of F VIII:C was higher (+20% in relative terms) in cryoprecipitates produced from pooled plasma, resulting in higher potency of such products. The positive effect of plasma pooling on the recovery of F VIII:C might be a result of reassembly of factor VIII subunits of different individuals in the plasma pools. The findings may have a role also in large-scale production of F VIII concentrates.

Chemical Precipitation↗
PubMed1995

Storage of platelet concentrates from overnight-stored blood and overnight-stored buffy coat: in vitro studies.

Platelet concentrates (PCs) were prepared from single buffy coats derived from fresh blood and from blood units stored overnight, as well as from buffy coats that were stored overnight. The platelet yield from overnight-stored buffy coats was similar to that of fresh blood or overnight-stored blood. PCs were stored at 20-24 degrees C and on day 5 of storage, platelet aggregation with ADP was tested both at 37 and 25 degrees C. Stored platelets aggregated better at 25 degrees C than 37 degrees C. The maximal, aggregation (10 microM ADP) of stored platelets from overnight-stored buffy coats was 46 +/- 23% (n = 30), while that of stored platelets prepared either from fresh or overnight-stored blood was 27 +/- 21% (n = 29) and 22 +/- 15% (n = 29), respectively. Extracellular lactate dehydrogenase and ammonia levels, as well as elastase activity were similar in stored PCs of different origin. Our conclusion is that PCs prepared from overnight-stored buffy coat might also be suitable for storage and clinical use. In vivo studies are needed to confirm our findings.

Blood Component Removal↗