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Biomedical subjects

A Horn

Publications and source records attributed to A Horn.

At least 127 records · Page 7Linked to original sources
PubMed1977

Principle and application of a multicuvette for determination of enzyme activities and substrate concentrations in microsamples.

A method of photometric analysis is described that allows to determine enzyme activities or substrate concentrations of 50 samples simultaneously in a multicuvette. Test volume is in the range of 30-85 micronl, light path between 0.5 and 2.0 mm. The testing principle can be used for colorimetric measurements and for NADH dependent reactions as well. The procedure is particularly suited for kinetic determinations. Variation coefficients for determinations of substrate concentrations and enzyme activities are in the range of conventional enzymatic tests.

Kinetics↗
PubMed1976

Purification and characterization of commercial NADH and accompanying dehydrogenase inhibitors.

The anion-exchange chromatography of commercial NADH using a potassium bicarbonate solution as eluent yields highly pure NADH with good stability. Twelve compounds are also separated which act as dehydrogenase inhibitors. The main impurities are further characterized. The compound mainly responsible for residual optical density in commercial NADH preparations is probably a stereoisomer of NADH which is in reversible equilibrium with NADH at pH values in the range 5-7. A method of thin-layer chromatography, to check commercial NADH preparations for impurities, is described.

Bicarbonates↗
PubMed1976

Preservation of dog kidneys by hypothermic perfusion with glucose-free and glucose-rich perfusates.

Dog kidneys were perfused for 48 h at 8-10 degrees C with two different perfusion fluids: one fluid rich in glucose, and another in which mannitol was a substitute for glucose. Immediately after reimplantation of the perfused kidneys, contralateral nephrectomy was performed. Kidney function, estimated by serum creatinine, was the same in both groups of animals, and 2 weeks after implantation it was identical to that of dogs with a single normal kidney. In a second series of experiments the renal utilization of glucose and glycogen was studied. Although small amounts of perfusate glucose were metabolized to lactate and CO2, the results of this study indicate that the kidney is not dependent upon glucose for its metabolic needs in order to retain function during 48 h hypothermic preservation.

Animals↗
PubMed1976

Substrate-stat: a method for characterization of enzymes in concentrated solutions at low substrate concentrations.

A method is proposed, which is suitable for kinetic studies with concentrated enzyme preparations, and its principal features are described. The method makes it possible to keep constant the concentration of substrate(s) or product(s) during the observation time. For this purpose, the increase or decrease of an indicator extinction signal, dependent on enzyme velocity, is monitored and automatic titration is performed using a suitable titer solution. This latter contains equimolar amounts of indicator and substrate(s). The whole system operates in a similar manner as in pH-stat devices. The technical set-up, model reaction systems and practical applications are shown. Operation problems and possible sources of error are examined. Finally, the main limitations as well as possible improvements are discussed.

Enzymes↗