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Biomedical subjects

W Schön

Publications and source records attributed to W Schön.

10 recordsLinked to original sources
PubMed1994

Heavy ion induced membrane damage: hemolysis of erythrocytes and changes in erythrocyte membrane fluidity.

Human erythrocytes were irradiated with heavy ions of energies between 4 and 18 MeV/u having linear energy transfer (LET) values between 92 and 14,000 keV/microns. Hemolysis has been studied as a macroscopic parameter for membrane damage and changes of the fluidity as a more microscopic parameter. The membrane fluidity changed in a characteristic dose-dependent manner as detected by electron spin resonance employing 12-doxylstearic acid methyl ester spin label (SL 12). Lysis cross sections and RBE values were determined from dose effect curves. The results demonstrate a high hemolytic efficiency of heavy ions compared to X rays. With increasing LET values the measured relative biological efficiency (RBE) values increase continuously. In the complete LET range the cross sections formed one common curve as function of LET and no saturation effects are observed. This is in direct contrast to other biological endpoints such as cell inactivation or DNA damage.

DNA Damage↗
PubMed1992

Irradiation increases proteolysis in erythrocyte ghosts: a spin label study.

X- and gamma-irradiation of human erythrocyte membranes (250-1000 Gy) was found to decrease the ratio of weakly to strongly immobilized signal height of membrane-bound maleimide spin label (Mal-6). Subsequent incubation of spin-labeled membranes at ambient temperature (21 degrees C) induced a progressive increase in this ratio, faster for membranes irradiated with low doses which was hampered by protease inhibitors. These results demonstrate that ionizing radiation stimulates proteolysis of erythrocyte membrane proteins by membrane-associated proteases.

Blood Proteins↗
PubMed1992

Fluidity alterations induced by chemical modification of erythrocyte membrane proteins.

Using EPR technique we have examined the effect of chemical agents on pig erythrocyte membranes. Treatment of the erythrocyte membranes with SH-oxidizing and denaturing or specific for amino groups reagents affects both the membrane proteins and lipids. These results suggest that modified proteins may perturb the interactions of the membrane components and lead to alterations of the membrane organization in the polar region.

Animals↗
PubMed1987

[Correlation between the ST/heart rate slope and the severity of coronary disease in inferior infarcts. A new criterion of positivity of the ergometric test].

We reviewed a group of 80 patients who had bicycle exercise stress testing and cardiac catheterization: 60 patients with known coronary artery disease (CAD) had a remote myocardial infarction, anterior, inferior, Q and no Q wave (post MI), 20 patients evaluated for suspected CAD resulted to have normal coronary arteries or lesions less than 50%. Patients were divided into three groups according to the extent of CAD. Group I with anatomically or functionally high risk CAD: left main (LM) stenosis greater than or equal to 50%, 3 vessels CAD greater than or equal to 70%, proximal left anterior descending stenosis (PLAD) greater than or equal to 90% with another vessel CAD; group II with one or two vessels CAD greater than or equal to 70%; group III with no or insignificant CAD. Linear regression analysis of the heart rate (HR)--related change in ST segment depression (ST/HR slope) was compared with six conventional electrocardiographic exercise test criteria to evaluate whether ST/HR slope can identify with improved accuracy group I. When all 80 patients are assessed together, ST/HR slope greater than or equal to 60 mm/beat/min 10(3) compared with standard electrocardiographic criteria failed to discriminate significantly between high-risk CAD (group I) and less extensive (group II) or insignificant CAD (group III). When only Q wave inferior post MI are considered, ST/HR slope greater than or equal to 60 mm/beat/min. 10(3) compared with ST segment depression greater than or equal to 1 mm identifies group I with 90% +/- 4 versus 75% +/- 6 overall predictive accuracy (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Coronary Disease↗