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Biomedical subjects

T Kenner

Publications and source records attributed to T Kenner.

At least 91 records · Page 5Linked to original sources
PubMed1979

[Feedback by objective tests for coordination of medical teaching (author's transl)].

Within the framework of an experimentally introduced curriculum in Medical Physiology during the past three years, voluntary tests of the multiple-choice type were offered at the end of each term in order to provide students with feedback on their achievements. Positive results contribute to the final grade. Analysis of test results reveals improvement after the first year; results of subsequent tests are fairly stable. Selected items are presented in detail in order to show the distribution of choices. As revealed by item analysis the attractivity of distractors seems to be of a specific nature. Statistical results and interpretation of content of questions derived from different fields indicate that valuable feedback might be obtained from objective tests when interdisciplinary coordination of the curriculum is to be achieved.

Austria↗
PubMed1979

[Development, structure and tasks of the department of physiology in Graz/Austria (author's transl)].

Physiology is concerned with the problems related to the optimal function of biological systems. The field therfore reaches from molecular biology to socio-economic questions. Three basic features have to be considered in science: 1) It is important that the work is being done with enthusiasm, simply because science is interesting and even fun. 2) It is always necessary to consider that the work is a necessary condition of daily life; this is also true for scientific work. 3) Especially in scientific work we have to serve mankind. Science in this sense has to include the idea of serving.--When-ever one of these features or conditions is omitted, the essence of scientific work will suffer, either because the scientist is selfish or because he doesn't take science serious enough. The research in the department of physiology in Graz is concerned with the problem of optimal control in hemodynamics and with research in topics related to biomechanics, exercise physiology and instrumentation. The teaching tasks include teaching of more than thousand second year students and performing laboratory courses and examinations.

Austria↗
PubMed1977

The continuous high-precision measurement of the density of flowing blood.

The "mechanical oscillator" technique for the measurement of the density of fluids is based on the influence of mass on the natural frequency of a mechanical oscillator. The practical application of this principle was worked out by Kratky et al. (1969) and Leopold (1970). It is demonstrated in this study that the method permits the continuous high-precision measurement of the density of flowing blood in anesthetized animals. The accuracy is 10(5) g/ml, the maximum sampling rate 20/min. As found in rabbits and cats during the control state, physiological blood density changes related to spontaneous blood pressure variations are up to 2-10(4) g/ml. The method can be combined with i.v. injections of isotonic and iso-oncotic solutions to determine cardiac output and blood volume on the basis of a "density dilution" principle. Since the density of the interstitial fluid is lower than that of blood, fluid shifts through the capillary walls can be detected. The effects of hypertonic glucose and of hyperoncotic dextran have been examined. Changes in the density of the arterial blood appear within 10 s after i.v. injection of these fluids. Similarly, density changes result from hemorrhage and reinfusion. During and after i.v. administration of vasoactive drugs (noradrenaline, angiotensin II, acetylcholine), marked transient changes in blood density are seen which obviously reflect the effects of fluid shifts through the capillary walls. During hemorrhagic hypotension we found periodic variations in the blood density synchronous with spontaneously occurring Mayer waves. The new method seems to be a promising tool for investigations physiological and pathological capillary fluid dynamics.

Acetylcholine↗
PubMed1977

[The relation between the density of blood and the arterial pressure in animal experiments and in patients during hemodialysis (author's transl)].

The density of arterial blood was measured continuously in animals and in human beings with an accuracy of 10(-5) g/ml by the application of the so-called mechanical oscillator technique. The density measuring device is inserted into an arterio-venous shunt. The continuous reading of the density of arterial blood allows to observe the effect of fluid shifts between the interstitial space and the plasma space. For example, lowering of the capillary pressure by the constriction of the precapillary resistance decreases the blood density by the inflow of interstitial fluid. Strong vasoconstriction apparently increases the capillary pressure and thus raises the blood density by the loss of plasma-ultrafiltrate. During hemodialysis the fluid loss into the dialysator tends to increase the blood density. However, the regulatory mechanisms of the circulation are able to keep the density of the blood at a constant value as long as possible. An increase of the density indicates a decrease of the blood volume. The new method thus allows a continuous control of the course of hemodialysis, and to avoid a critical decrease of the blood volume and of the blood pressure.

Animals↗
PubMed1976

Pulse wave reflection at the collapsed segment of an artery in Riva-Rocci's method.

The contours of pressure and flow of a pulse wave arriving at the entrance of a collapsed segment of an elastic tube can be described by application of the basic laws of reflection. The collapsed segment acts like a valve. It is opened by the pressure of the pulse wave when the pressure within the tube becomes higher than the "collapse pressure", i.e. the pressure exerted on the segment from outside. This opening of the collapsed segment suddenly changes the sign of the pulse wave reflection from positive to negative; thus a typical contour change of the pulse proximal to the segment is observed. The most obvious effect is a reduction of the pulse pressure. The extent of this reduction is a function of the collapse pressure. A typical example of this phenomenon can be observed in an artery proximal to the segment which is collapsed due to pressure exerted by an inflated Riva-Rocci cuff. The effect is explained by the assumption that the sign of reflection changes when the pressure of the pulse wave crosses the level of the cuff pressure. This explanation is supported by the results of model experiments.

Blood Pressure Determination↗
PubMed1976

Spectral analysis of spontaneous contractions of the isolated portal vein of rats.

The spontaneous contractions of segments of rat portal veins have been examined in vitro under isotonic and isometric conditions. The power density spectra of recorded time series lasting 10-60 min were calculated. The spectra usually consist of harmonic frequency components. Only during shorter periods of analysis (10 min time series) we sometimes found additional non-harmonic components. All frequency components are proportionally shifted by changes of the bath temperature according to an average Q10 of 2.0. Increase of the load decreases the frequency of the contractons. The results of the spectral analysi, indicating a preponderance of a single source of periodicity, were supported by direct evidence of a pacemaker region. By recording contractions after systematic dissections of the portal vein segment, we found that spontaneous activity is generated at the central end of the segment.

Animals↗
PubMed1976

Method for the analysis of the entrainment between heart rate and ventilation rate.

A digital computer program was developed which allows to continuously represent the relation between heart rate and ventilation rate. Using this program, experiments in anesthetized rabbits were performed. We found periods of synchronization, periods of transient entrainment and escape, and periods of complete desynchronization. By testing the respective roles for the entrainment mechanism of ventilation rate and heart rate it was found that spontaneous adjustments of the ventilation rate play a more pronounced role. Thus, as soon as spontaneous or induced variations of the heart rate and/or the ventilation rate shift both rhythms close to synchronization, variations of the ventilation pattern, which seem to be of reflex nature, tend to induce entrainment.

Analog-Digital Conversion↗