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Biomedical subjects

A Ehlert

Publications and source records attributed to A Ehlert.

4 recordsLinked to original sources
PubMed2001

Evolution of fractal patterns during a classical-quantum transition.

We investigate how fractals evolve into nonfractal behavior as the generation process is gradually suppressed. Fractals observed in the conductance of semiconductor billiards are of particular interest because the generation process is semiclassical and can be suppressed by transitions towards either fully classical or fully quantum-mechanical conduction. Investigating a range of billiards, we identify a "universal" behavior in the changeover from fractal to nonfractal conductance, which is described by a smooth evolution rather than deterioration in the fractal scaling properties.

Journal Article↗
PubMed1995

Endogenous tissue plasminogen activator and platelet reactivity as risk factors for reocclusion after recanalization of chronic total coronary occlusions.

A prospective study was performed to investigate the role of the endogenous fibrinolytic system and platelet function for the occurrence of reocclusion after successful recanalization of chronic coronary occlusions. At control coronary angiography 8 +/- 2 weeks after recanalization, reocclusion was found in 10 (21%) of 47 patients. After correction for angiographic and clinical confounding factors, endogenous concentrations of tissue plasminogen activator (TPA) were lower in patients with reocclusion than in patients without. In contrast, plasma levels of plasminogen activator inhibitor-1 and alpha 2-antiplasmin were similar in the two groups. The mean platelet volume was significantly higher in patients with reocclusion than in patients without. In addition, agonist-induced platelet aggregation in platelet-rich plasma was enhanced in the patients with reocclusion. Decreased endogenous plasma TPA concentrations and enhanced platelet reactivity may contribute to the occurrence of reocclusion after primarily successful coronary artery recanalization.

Aged↗
PubMedDate not supplied

Tryptophan metabolism in alcoholism. Tryptophan but not excitatory amino acid availability to the brain is increased before the appearance of the alcohol-withdrawal syndrome in men.

Tryptophan (Trp) metabolism and disposition and excitatory and other amino acid concentrations were determined in alcohol-dependent subjects in relation to the alcohol-withdrawal syndrome (AWS). Parameters were examined in 12 alcohol-dependent male subjects, undergoing elective upper digestive tract tumour resection, and 12 age-, gender-, and medication-matched controls on three occasions: pre-operatively, post-operatively, and immediately before (i.e. within 24 h of) the appearance of the AWS. No significant differences were observed between controls and alcoholic subjects on the first or second of these occasions. On the third occasion, within 24 h of the appearance of the AWS, alcoholics showed a dramatic elevation (117%) in free serum Trp concentration and a consequent increase (111%) in the ratio of [free Trp]/[competing amino acids], which is an accurate predictor of Trp entry into the brain. Increases were also observed on this third occasion in concentrations of total Trp (49%), cortisol (123%), and norharman (137%). Concentrations of glutamate, glycine, aspartate, serine, and taurine did not differ significantly within or between the control and alcohol-dependent groups of subjects on any of the three occasions. The possible significance of the Trp and related metabolic changes in relation to the behavioural features of the AWS is discussed.

Alcoholism↗