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Biomedical subjects

P Wach

Publications and source records attributed to P Wach.

16 recordsLinked to original sources
PubMed1991

[Further advances in the salt sensitivity hypothesis in man].

The hypothesis, proposed by us since 1981, that genetically determined salt sensitivity exists in the normotensive population has been confirmed by other groups. We propose that in salt sensitive subjects an augmented upregulation of alpha-2 combined with simultaneous downregulation of beta-2 adrenoceptors by a high salt diet (resulting in an increase in the "operative" adrenoceptor ratio) is responsible for the rise of blood pressure. In salt resistant subjects the "operative alpha-2/beta-2 adrenoceptor ratio" does not increase on a high salt intake. The adrenoceptor changes in salt sensitive subjects probably lead to an increased central sympathetic outflow (through receptor changes in certain brain areas) and to simultaneous enhanced end-organ response in resistance vessels and in the kidney, causing enhanced vasoconstriction and enhanced sodium reabsorption. Long term follow up of salt sensitive normotensives will show, whether they develop "essential hypertension" in the future.

Absorption↗
PubMed1990

Light scattering by blood components after supplying glucose.

Investigations were performed in order to find out whether the glucose concentration in liquids can be determined by means of light scattering. Both static light scattering and photon correlation spectroscopy (PCS) were used. Neither of them revealed a possibility of determination of glucose concentration in a pure glucose solution. But for glucose-protein-solutions a clear correlation between intensity of light scattering and glucose concentration was detected due to glycosylation of proteins. In blood serum it is solely possible to measure non-enzymatic reaction products between glucose and proteins and to determine the influence of Amadori products on protein structure. Therefore not even indirect conclusions on the present glucose concentration are possible.

Blood Glucose↗
PubMed1989

[Glucose determination by means of NMR spectrometry].

NMR spectroscopy could be a method for non-invasive determination of glucose concentration in the future. In this connection, 13C-NMR spectroscopy is of special interest. In vitro investigation of blood serum samples in 13C-NMR revealed significant changes in signal intensities reflecting the different glucose concentrations in these samples. The further development of noninvasive in vivo glucose determination by means of NMR spectroscopy is closely associated with technological progress.

Blood Glucose↗
PubMedDate not supplied

Three-dimensional computer model of the entire human heart for simulation of reentry and tachycardia: gap phenomenon and Wolff-Parkinson-White syndrome.

A computer model of the entire human heart has been developed for simulation of the excitation and repolarization process. Spatial distribution of refractory periods and conduction velocities in the different cardiac tissues, the anisotropy of conduction in the ventricles, and the cycle length dependence of refractory periods and conduction velocities are taken into account. The algorithm calculating the activation process is based on a modified version of Huygen's principle for constructing wavefronts. This study presents simulations concerning the gap phenomenon of the conduction system and the initiation of tachycardias in a heart with Wolff-Parkinson-White syndrome. Results are compared for different basic cycle lengths and for normal and prolonged refractory periods in the His-Purkinje system. The gap phenomenon was found to be present only when using the prolonged refractory periods in the His-Purkinje-system at a cycle length of 700 ms. Induction of tachycardia by a single extrastimulus in the high right atrium in a heart with a bidirectionally conducting accessory pathway is possible by properly timed extrastimuli. The coupling interval of the stimulus for initiating a reentrant tachycardia depends on the cycle length, the conduction velocities and the set of refractory periods used. The same parameters determine whether or not a gap phenomenon in atrioventricular conduction occurs. The model may be useful for investigating similar questions concerning the reentry phenomena of tachycardia.

Atrioventricular Node↗
PubMedDate not supplied

A computer model of human ventricular myocardium for simulation of ECG, MCG, and activation sequence including reentry rhythms.

A computer model is presented for simulation of the spread of activation and repolarization in ventricular myocardium. The program calculating the activation sequence is based on an algorithm similar to Huygen's principle of constructing wavefronts. Physiological parameters of the heart, such as areas of early activation on the endocardium, conduction velocity, anisotropy of propagation, duration of action potentials and refractory periods are taken into account. The time-course of ECG and MCG is calculated using the equations of the bidomain model. Simulation of pathologic cases of activation is performed through variation of the physiological heart parameters. The simulations presented here show good agreement of ECG and MCG with measurements in the normal case, the case of bundle branch block and abnormal repolarization. A special feature of the model is the possibility of simulating reentry rhythms following a premature stimulus in ventricular myocardium. Two kinds of reentry are simulated: reentry around an anatomical obstacle and the leading-circle model. The widespread capability for investigating not only ECG but also MCG and various kinds of pathologic activation patterns including reentry rhythms indicates that the model may be useful in studying numerous problems in cardiologic research.

Action Potentials↗