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Biomedical subjects

J Racek

Publications and source records attributed to J Racek.

At least 19 recordsLinked to original sources
PubMed1991

A yeast biosensor for glucose determination.

A yeast potentiometric biosensor for glucose determination is described. After induction of glycolytic enzyme synthesis a cell suspension of the yeast Hansenula anomala is retained in calcium alginate gel on the surface of a glass electrode. This biosensor gives a Nernstian response in glucose concentration of 5 x 10(-4)-5 x 10(-3) mol/l with a response time of 5 min and a life-time of at least 2 months. Mannose and fructose are the only significantly interfering substances. The biosensor was used for measurement of glucose concentration in urine with results comparable to those obtained by a photometric enzymatic method.

Biological Assay↗
PubMed1991

What are the factors contributing to the changes in tissue-type plasminogen activator during haemodialysis?

Haemodialysis (HD) is associated with stimulation of the fibrinolytic system. The increase of fibrinolytic activity seems to be primarily due to tissue-type plasminogen activator (t-PA) released from the vessel wall. The aim of our study was to determine whether the t-PA release is the consequence of uraemic intoxication adjustment, extracorporeal circulation effect, heparin administration, or whether a mere reflection of the circadian rhythm of fibrinolysis is involved. To identify the factor, fibrinolytic system parameters were determined during HD, sham HD (SD), after the administration of heparin alone outside HD, and during a control period (CP). The plasma concentrations of t-PA antigen indicate that HD is associated with the release of t-PA from the vessel wall; 3.70 ng/ml before HD, 4.35 (NS) at the 15th min, 4.88 (P less than 0.05) at the 20th min, and 5.09 (P less than 0.05) after HD (medians). The respective values for a CP are 4.05, 4.37 (NS), 4.40 (NS), and 4.22 (NS). The effect of heparin alone and SD was evaluated for 120 min only, with the following t-PA concentrations determined after heparin: 5.10, 6.22 (NS), 4.72 (NS), 4.72 (NS); during SD and 4.50, 5.14 (NS), 5.20 (P less than 0.05). We conclude that t-PA is released from the vessel wall during HD. A factor contributing to its release is the extracorporeal circulation system.

Adult↗
PubMed1987

Biosensor for lactate determination in biological fluids. 2. Interference studies.

The selectivity of a yeast lactate biosensor with immobilized cells of aerobic yeast Hansenula anomala was studied. Reducing substances potentially present in blood plasma influenced both enzyme and yeast biosensors in the same way; the highest positive error was observed in the case of uric acid. With respect to the metabolic activity of the yeast cells the biosensor was absolutely specific for lactate during the first two weeks; later on the biosensor responded slightly to some other metabolites, especially some sugars and amino acids. Glucose could cause the highest degree of interference, its effect was however completely eliminated by adding sodium fluoride to the reaction solution. The concentration of other metabolites present in blood plasma is not great enough to call a significant positive error. The results thus support the general use of the yeast lactate biosensor for lactate determination in biological material.

Humans↗
PubMed1987

Biosensor for lactate determination in biological fluids. I. Construction and properties of the biosensor.

The preparation of a biosensor for lactate determination is described. The biosensor is based on an immobilized suspension of the aerobic yeast Hansenula anomala, containing flavocytochrome b2 in high activity. The conditions for yeast cultivation were optimized to gain a sufficiently high activity of this enzyme converting lactate in the cells. The properties of the biosensor are compared with those of a sensor based on immobilized enzyme flavocytochrome b2. The yeast lactate biosensor has a sufficient sensitivity and linearity and short time of response. The precision and accuracy of lactate determination as well as the results of comparisons using an enzyme electrode and the spectrophotometric UV-test, enables this biosensor to be used in routine work. Analysis can be performed in blood plasma or whole blood. The stability of the biosensor makes it possible to work for 4 weeks with one yeast cell pellet.

Drug Stability↗