Biomedical subjects

S Nandedkar

Publications and source records attributed to S Nandedkar.

4 recordsLinked to original sources

PubMed1992

The development of a technique to estimate the number of motor units in the urethral sphincter.

An electromyographic technique is presented that has been developed in an effort to quantitate the number of motor units in the urinary sphincter. Sphincter contraction was provoked by electrical stimulation and recorded with a catheter mounted electrode. Incremental stimulation produced corresponding increments of sphincter contraction that were recorded as the magnitude of the sphincter electromyogram. Estimates of the number of motor units in the sphincter were made by analysis of variance of a Poisson distribution. Using this method, the mean number of motor units in the sphincter of five dogs was estimated to be 129 with values ranging from 80 to 182. Anatomical correlation was sought by infiltrating this sphincter with horseradish peroxidase, which is taken up by axonal transport to stain the motor neurons in the spinal cord. The mean number of motor neurons was 229 with values ranging from 116 to 358. There are technical and physiologic explanations for the observed differences between the predicted and the actual number of motor neurons stained and this is addressed in the discussion.

Animals↗

PubMed1984

Topographical localization of motor endplates in cryosections of whole human muscles.

The distribution of motor endplates in biceps brachii, tibialis anterior, and sartorius muscles from human adults was studied by staining longitudinal cryosections of whole muscle for cholinesterase. A special freezing technique was used to prevent the muscle from cracking before sectioning on a heavy cryostat microtome. The results from a large number of cryosections from biceps brachii and tibialis anterior muscles were analyzed by a computer and the topographical distributions of endplates in different views of the muscles were reconstructed. In the biceps brachii muscle, the endplates formed a fairly distinct, slightly V-shaped band through the middle of the two heads. In the tibialis anterior muscle, the majority of the endplates were superficially distributed along the whole muscle. In the longitudinal sections from the middle part of the muscle, they gave the pattern of a parabola with its apex at the proximal end of the muscle. In the sartorius muscle, the endplates were scattered throughout the muscle and no endplate band was observed. The findings are in accordance with results obtained 30 years ago in investigations of muscle from small children and stillborn infants.

Adult↗

PubMed1983

Simulation of macro EMG motor unit potentials.

Macro EMG motor unit potentials (MUPs) have been simulated. The effects on MUP parameters of number of fibres, fibre diameter, end-plate scatter, nerve branch delay, motor unit territory and electrode position have been studied. The MUP shape is sensitive to electrode position in the vicinity of the end-plates. It is mainly reflecting the end-plate scatter and the nerve delays. Away from the end-plates the wave shape is principally determined by the fibre diameter distribution. Total number of muscle fibres and their mean diameter act as gain factors at all recording positions. In the simulations the area of the signal appears to be a better measure of the strength of the motor unit than the amplitude. Macro EMG offers a much less selective recording than conventional EMG and single fibre EMG and therefore new aspects of the motor unit can be quantified. Preliminary results from simulations of neuromuscular disorders are consistent with actual findings.

Action Potentials↗

PubMed1983

Automatic analysis of the EMG interference pattern.

A method is described for the automatic analysis of EMG interference patterns obtained at optional non-controlled force levels. It is a modification of Willison's method of measuring turns and amplitude of the signal. In the method, the mean amplitude is plotted against turns obtained during 300 msec for each of 20 recording sites. Different voluntary strengths are used and a scatter of points is obtained. Confidence limits enclosing these points are constructed for healthy subjects for 4 different muscles with concentric and monopolar electrodes. The normal values differ with age, muscle, sex and electrode. The method is tested on patients with myopathic or neurogenic EMG and a high diagnostic yield is obtained. The method is objective, reproducible, fast and needs relatively small computer facilities.

Adolescent↗