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Biomedical subjects

U Till

Publications and source records attributed to U Till.

At least 109 records · Page 6Linked to original sources
PubMed1981

Effect of arachidonic acid on the hexose monophosphate shunt and related coenzymes in human blood platelets.

The aggregation of human platelets after addition of arachidonic acid (AA) is accompanied by a 30 fold increase in the net flux through the hexose monophosphate shunt (HMPS). The levels of reduced glutathione (GSH) and NADPH as well as the NADPH/NADPH+NADP quotient show a temporary fall which is restricted to the interval between AA addition and beginning of aggregation suggesting a lag phase between the onset of enhanced coenzyme consumption and that of increased coenzyme regeneration. together with literature data the results point to a possible regulatory function of reduced coenzymes and the HMPS in the process of platelet activation.

Arachidonic Acid↗
PubMed1981

Red cell response to A23187 and valinomycine in Duchenne muscular dystrophy.

Treatment of red cells from Duchenne muscular dystrophy (DMD) patients with A23187 induced identical responses with those in controls in terms of Ca++ flux, shrinkage, ATP depletion, hypotonic lysis protection, and glycolysis stimulation. The level of RC-free calcium seemed not to be altered in DMD. Valinomycine-induced shrinkage was enhanced significantly in DMD red blood cells.

Anti-Bacterial Agents↗
PubMed1981

Glucose-6-phosphate dehydrogenase deficiency in human platelets and its effect on platelet aggregation.

Platelets from patients with known red blood cell G-6-PD deficiency were investigated to find out whether this genetic defect is associated with changes in platelet aggregation. The enzyme defect in platelets could be verified by a decreased G-6-PD activity which was as low as 15% compared to control subjects. The decreased enzyme activity was reflected by lowered levels of NADPH and GSH and by a diminished maximum capacity of the hexose monophosphate shunt. Aggregation measurements in platelet-rich plasma from deficient patients revealed an enhanced dose response to ADP which was higher by about one order of magnitude compared to controls. The same effect was observed in a smaller degree in arachidonic acid induced aggregation.

Blood Platelets↗
PubMed1980

Anticoagulant-free prepared blood platelets and the effect of calcium on their aggregation behaviour.

Human blood platelets were prepared by gel filtration of native blood and subsequent centrifugation in a Ficoll density gradient avoiding any anticoagulant during the preparation. In ADP, ionophore A 23 187 and thrombin induced aggregation an increase in extracellular Ca++ enhanced the velocity of aggregation. From a defined Ca++ concentration threshold on there was a shift from monophasic to biphasic aggregation.

Adenosine Diphosphate↗
PubMed1979

The use of acridine orange for testing blood platelet integrity.

Two processes are involved in the accumulation of acridine orange in human blood platelets. One follows a diffusion like kinetics and is independent of the ATP level whereas the second one can be completely abolished by ATP depletion. The acridine orange incorporation rate seems to be a suitable parameter for testing platelet integrity. It reflects very sensitively the influence of the preparation method as well as of anticoagulating substances used on the stability of platelet suspensions. The rates of acridine orange incorporation and of aggregation were measured in platelet-rich plasma and in saline suspended platelets after gel filtration, respectively, over a period of 120 min storage. Both rates are influenced to a different degree by anticoagulating agents such as citrate, heparin and EDTA. When contact with anticoagulating agents during platelet preparation is avoided, platelets show a constant acridine orange incorporation and aggregation during storage and the smallest morphological alteration.

Acridine Orange↗
PubMed1979

[Preparation of human platelets without the use of anticoagulants and study of the effect of Catt on aggregation].

A method for the preparation of human blood platelets is presented which substitutes the use of anticoagulants by a gelfiltration for the removal of plasma calcium from native blood. In a second step the platelets are separated from the gel filtered blood by a centrifugation on a Ficoll density gradient. The anticoagulant-free platelets reveal an intact morphological feature and a normal aggregation behaviour in response to different aggregation inducers. It was found that in ADP-induced aggregation monophasic aggregation is shifted to a biphasic one by increasing concentrations of extracellular calcium.

Blood Platelets↗
PubMed1977

Relations between ion shifting, ATP depletion and lactic acid formation in human red cells during moderate calcium loading using the ionophore A 23187.

Keeping constant cellular magnesium an A 23 187 mediated moderate calcium loading of human red cells causes isoosmotic cell shrinkage, potassium efflux, slight decrease of cellular pH, ATP depletion connected with an increase of AMP, ADP and Pi and enhanced lactic acid formation. The calcium loading and accompanying effects can be abolished by EGTA or by extracellular magnesium, the latter kept more than two orders of magnitude above that of calcium which was 30 micrometer. Inhibition of the (Mg2+ + Ca2+)-dependent ATPase by ruthenium red or lanthanum decreases the calcium stimulated lactic acid formation after a lag phase. However, the ATP depletion proceeds faster and is much more pronounced under these conditions. (Mg+2 + Na+ +K+)-dependent ATPase, hexokinase, phosphofructokinase and cell shrinkage are ruled out, too, as mediators of the ATP depletion. This suggests that an unknown ATP consuming reaction, apparently not being related to the calcium pump, causes the calcium induced ATP depletion.

Adenosine Triphosphate↗
PubMed1977

The role of red cell membrane in the regulation of glycolysis and the 2,3-bisphosphoglycerate-cycle.

Pyruvate and K-ferricyanide stimulation of net ATP and 2,3-bisphosphoglycerate synthesis is very probably due to enhancement of glyceraldehyde 3-phosphate dehydrogenase activity. Significant peculiarities in the K-ferricyanide effect and its depression by non-penetrating-SH inhibitors at low concentrations were noted and suggested that membrane-bound enzymes play a substantial part in the synthesis of ATP and 2,3-bisphosphoglycerate. Experiments with isolated ghosts showed their ATP-and 2,3-bis-phosphogylcerate-building capacity. Pulse-labeling with 32P-Pi and determination of specific radioactive in intracellular inorganic phosphate and ATP-gamma-P demonstrated that the ferricyanide-stimulated compartment utilizes only intracellular inorganic phosphate for ATP (and 2,3-bisphosphoglycerate) synthesis, and does so only when extracellular inorganic phosphate is present.

Adenosine Triphosphate↗
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↗