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Biomedical subjects

K Wohlfahrt

Publications and source records attributed to K Wohlfahrt.

6 recordsLinked to original sources
PubMed1998

Lack of psychotomimetic or impairing effects on psychomotor performance of acamprosate.

The possible effects on psychomotor performance, concentration, attention, and mood of acamprosate (calciumacetylhomotaurinate) were assessed using a randomized, double-blind, cross-over, placebo-controlled design involving 12 healthy male volunteers. Acamprosate 2 g daily per os or placebo was administered for seven days and separated by washout intervals of at least 21 days. Objective tests evaluated psychomotor functions (simple reaction time measurement, binary choice reaction test, computerized visual searching task, sustained attention test). Mood was assessed using the Beck Depression Inventory and the Beschwerde-Liste to assess subjective physical impairment. Additionally, a visual 3-D illusion paradigm was applied to measure the psychotomimetic effect. A dose of acamprosate of 2 g/day for seven days was free of any significant effects on mood, concentration, attention, psychomotor performance and did not produce any subjective sedation, excitation or psychotomimetic effects.

Acamprosate↗
PubMed1992

F waves and motor unit size.

M responses and twitch contractions were evoked in single motor units (MUs) of the first dorsal interosseus muscle by intramuscular microstimulation of motor axons. Two-hundred nine MUs were studied in 21 subjects. Thirty-five MUs (17%) showed F waves in addition to M responses. Twitch force was used to provide an indirect measure of MU size; additionally, twitch contraction time was measured. There was no select group of MUs generating F waves with regard to the above contraction parameters. However, four of five MUs with very high twitch forces, above 70 mN, generated F waves. We conclude that MUs of all sizes produce F waves with similar probability. Only few MUs with very strong twitch forces, i.e., very large MUs, may be more subject to F-wave production and may be involved in the generation of the so-called repeater F waves.

Action Potentials↗
PubMed1992

Parameters of human motor unit twitches obtained by intramuscular microstimulation.

Intramuscular microstimulation of motor axons was used to study twitch responses of 209 motor units (MUs) in the first dorsal interosseus muscle (FDI) of 20 normal subjects. Twitch peak force (TF), maximum rate of rise of force (MRRF), contraction time (CT) and one-half relaxation time (HRT) were determined. The distributions of TF (mean 16.0 mN, median 10.3 mN) and MRRF (mean 0.88 N s-1, median 0.66 N s-1) were skewed to the right with the majority of the values lying in the lower ranges, whereas CT (mean 63 ms, median 62 ms) and HRT (mean 61 ms, median 58 ms) were approximately normally distributed. TF was significantly correlated with MRRF, but not with CT in contrast with studies of cat gastrocnemius muscle. TF values were similar to those obtained by spike-triggered averaging in the same muscle. The method proved to be reliable and appropriate for use in patients. Examples of MU twitch parameters from three patients with chronic partial denervation of the FDI are described.

Adult↗
PubMed1992

Calcium metabolism in Williams-Beuren syndrome.

Increased 1,25-dihydroxyvitamin D levels and decreased basal and calcium-stimulated calcitonin serum levels have been found in children with Williams-Beuren syndrome (WBS). To determine whether isolated or combined disturbances of secretion or action of the calcium-regulating hormones may cause the tendency to hypercalcemia in WBS, we investigated several aspects of calcium metabolism in 27 normocalcemic children and adults, aged 2 to 47 years, with WBS. With the exception of slightly decreased 25-hydroxyvitamin D and slightly increased calcitonin in serum, all measured basal indexes of calcium and bone metabolism, including the serum levels of intact parathyroid hormone and 1,25-dihydroxyvitamin D, were comparable to control values. Total and extractable calcitonin, the latter representing the monomeric and biologically important form of the hormone, showed the same relative increase after a low-dose calcium infusion in patients and control subjects, indicating a normal capacity of the calcitonin-producing C cells of the thyroid gland in WBS. Furthermore, exogenous parathyroid hormone induced a normal response of 1,25-dihydroxyvitamin D, cyclic adenosine monophosphate, and phosphate excretion, indicating a normal response of the renal 25-hydroxyvitamin D-1 alpha-hydroxylase and the renal receptor-adenylate cyclase system to parathyroid hormone. These findings suggest that neither deficient calcitonin secretion nor increased renal sensitivity to parathyroid hormone is a feature of WBS in normocalcemic patients.

Adolescent↗