Biomedical subjects

M Wadepuhl

Publications and source records attributed to M Wadepuhl.

3 recordsLinked to original sources

PubMed1992

[24-hour blood pressure decrease with nifedipine with a new galenic action].

OBJECTIVE: Testing of the blood pressure-lowering effect of a slow-release (24 hours) nifedipine preparation. STUDY DESIGN: Single blind, randomized placebo controlled, single cross-over test; duration eight days. PATIENTS: 18 inpatients with essential hypertension and a blood pressure of more than 160/95 mmHg. MEDICATION: A single 60 mg slow-release nifedipine tablet (Aprical long 60 mg) administered daily at 1800 hours. MEASURING PARAMETERS: Pulse and blood pressure measured after 3, 12, 15, 18, 20, 22 and 24 hours post-administration. RESULTS: Even 18 to 24 hours after administration, the systolic blood pressure was reduced on average by 20 mmHg, the diastolic pressure by 14 mmHg. In the case of the test substance, the percentage of blood pressures in the target range (less than 160/95 mmHg) was 40 percentage points (systolic) and 49 percentage points (diastolic) higher than in the case of placebo. In 15 patients, both systolic and diastolic blood pressure was maintained within the defined target range for 24 hours. Reflex tachycardia was not observed, while other side effects such as headache, flushing, hot flashes, and leg edema occurred only rarely. There was evidence that an evening administration of the drug had a favorable effect on the morning blood pressure increase.

Adult↗

PubMed1989

Computer simulation of the hydrostatic skeleton. The physical equivalent, mathematics and application to worm-like forms.

The functional principles of a hydrostatic skeleton were combined to obtain a physical model which includes geometry, number and length-tension relationships of the elastic elements in the body wall, internal volume and internal pressure. The model skeleton with pre-set internal volume assumes a certain shape and develops a specific internal pressure in order to minimize the potential energy stored in the elastic elements. This shape is calculated as equilibrium state by using finite element methods and optimization techniques. This model is flexible enough to accommodate different geometries and length-tension-relationships of the elastic elements. Presently, the model is implemented with linear length-tension relationships and certain geometrical restrictions, such as uniform width over the entire animal, and rectangular cross sections; the general case is outlined. First simulations with the "unit-worm" yield stable solutions, i.e. stable shapes for all combinations of parameters tested so far. They define the conditions for bringing all muscles to an optimal operating point. We detected a pressure maximum with increasing volume, assessed the contribution of circular muscles to bending, and determined the shapes of animals with different muscle activations in each body half (Chapman-matrix). We summarize our results by the volume rule and stabilization rule, two simple concepts which predict changes in shape as the result of muscle activation.

Animals↗

PubMed1989

Depression of excitatory motoneurones by a single neurone in the leech central nervous system.

Intracellular staining techniques have been used to characterize the morphology of a newly identified neurone, cell 151, in the segmental ganglia of the leech. This neurone ramifies extensively within the neuropile and sends multiple extensions into roots and connectives. Strong dye coupling and non-rectifying electrical coupling were observed between the contralateral homologues. No action potentials were recorded from the cell body, but postsynaptic potentials and slow potential changes (greater than 1 s, greater than 15 mV) were observed. Upon injection of hyperpolarizing currents, the efferent spike activity, recorded extracellularly, was depressed in both the ipsi- and the contralateral roots of the ganglion. The depression was gradual and non-adapting and occurred reliably only within the ganglion where cell 151 is situated. Depolarization of cell 151 was without consequence for the tonic firing of isolated ganglia. Many identified excitatory motoneurones follow the hyperpolarization of cell 151. Currents can be exchanged between cell 151 and motoneurones via rectifying electrical synapses. Spontaneous hyperpolarizations of cell 151 were correlated with depression of spike frequencies, recorded in whole nerves as well as in identified motoneurones. The membrane potential of cell 151 was drastically altered by bursts from mechanosensory cells. The ability of cell 151 to distribute inhibition onto a great number of motoneurones and to curtail excessive neuronal activity is discussed.

Animals↗