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Biomedical subjects

H B Boom

Publications and source records attributed to H B Boom.

67 records · Page 4Linked to original sources
PubMed1982

Calculation and registration of the same motor unit action potential.

In order to increase insight into the electrical phenomena of active motor units, a computer simulation model has been developed. With this model motor unit action potentials (MUAPs) have been calculated. The model has been based on the superposition of the muscle fibre potentials of the fibres of one motor unit. For verification, calculated MUAPs have been compared with the matching recorded MUAPs. During experiments one motor unit was stimulated and the MUAP of this unit was measured with intramuscular wire electrodes. After the experiments the positions of the activated fibres of this unit and of the electrodes were determined by means of histochemical techniques. Other parameters were derived from other experiments or the literature. Using the obtained set of parameters in the model MUAPs were calculated. These MUAPs were compared with the measured MUAPs. From this comparison it has been concluded that the model predicts the MUAP to an appreciable degree. The results clearly show the dominating effect of muscle fibres in close vicinity of the electrode and the important effect of the activation moment of those fibres on the shape of the MUAP.

Action Potentials↗
PubMed1980

Force development of fast and slow skeletal muscle at different muscle lengths.

It is known that the behavior of fast and slow skeletal muscles differs, but a comparison between fast and slow muscles with different stimulation patterns at various muscle lengths is lacking. The twitch, tetanus, and double pulse responses with a number of interval times have been investigated for a fast (EDL) and a slow (soleus) muscle of the rat at three muscle lengths (in vivo, at 37 degrees C, pentobarbital sodium anesthesia). The twitches of EDL and soleus change with muscle length, but the relative form of the ascending phase is independent of muscle length. The tetanus amplitude is independent of the muscle length over a considerable length range below the optimum twitch length. The form of the ascending phases of EDL-tetanus and double pulse responses (with certain interval times between the stimuli) varies with muscle length in contrast with the comparable soleus force patterns. The maximum slope in the descending phase of all contraction patterns decreases with increasing muscle length above the optimum twitch length.

Action Potentials↗
PubMed1978

Left ventricular active stiffness: dependency on time and inotropic state.

Left ventricular systolic stiffness was measured by rapidly changing ventricular volume (within 7 ms) of isovolumically contracting isolated rabbit hearts. Instantaneous pressure-volume relations were found to be linear with slopes that depended upon the moment during contraction at which the volume change was induced. These slopes were proportional to the total pressure developed in the ventricle just prior to the volume change. The same was found when the time course of pressure was influenced by changing the Ca++ content of the perfusate. An influence, however, also could be detected when end-diastolic volume was changed. At the same pre-release pressure a greater volume caused a decrease of active stiffness. The results indicate the possibility of an active component in ventricular systolic stiffness.

Animals↗
PubMed1977

The combined influence of the stimulus frequency of the vagal nerves and the atrial stimulus interval on the atrioventricular conduction time.

The way in which the A-V node adapts its conduction time to stepwise alterations of atrial stimulation rates was studied under different conditions of vagal nerve activity (open chest, anaesthetised rabbit). Increase of stimulation rate induced oscillatory adaptation to a longer conduction time. Decrease caused shorter conduction times without oscillation. The time constant did not differ. Oscillation amplitude and time constants were markedly influenced by vagal activity. The observed phenomena can be explained on the basis of a time and voltage dependent K+ conductance.

Animals↗
PubMed1976

A note on the phase-plane technique representation of cardiac action potentials.

In this study the applicability of the phase-plane technique for interpreting membrane properties of cardiac cells in a two-dimensional structure is discussed. The conditions are derived for which the effects of two-dimensionality of a sheet can be neglected and for which the one-dimensional phase-plane technique for estimation of the membrane current densities remains valid. The usual phase-plane technique appears to be applicable to nodal and atrial tissue.

Action Potentials↗
PubMedDate not supplied

Interactive control of physiological experiments.

Physiological and biological experiments often require the imposition of repeated influences on an organ or organic system. Then the experimental protocol requires many repetitive functions with adjustable interval times and magnitudes, which are prepared or dictated by experimental results. To control such an experimental set-up interactively with a small computer we chose a more or less general approach. A special language syntax has been developed for: experiment definition; experiment composition in advance; real-time control during the actual experiment; and registration of the actual protocol parameters. The interactive control was realized using the special language and an interpreter as one of the parallel processes for the experimental control.

Animals↗