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Biomedical subjects

S Satya-Murti

Publications and source records attributed to S Satya-Murti.

14 recordsLinked to original sources
PubMed1989

Chronic exposure of primates to 60-Hz electric and magnetic fields: III. Neurophysiologic effects.

The neurophysiologic effects of combined 60-Hz electric (E) and magnetic (B) fields, of magnitudes comparable to those produced by high-voltage powerlines, were investigated in 10 monkeys (Macaca nemestrina). Six animals (experimental group) were each exposed to three different levels of E and B fields: 3 kV/m and 0.1 G, 10 kV/m and 0.3 G, and 30 kV/m and 0.9 G. Field exposures were preceded and followed by sham exposures, during which factors of field generation were present (e.g., heat, vibration, noise, etc.) without E and B fields. Each of the five segments (i.e., the three exposure segments and the initial and final sham exposure segments) lasted 3 weeks. Animals were exposed for 18 h/day (fields on at 1600 h, off at 1000 h). Four other animals (external control group) were given sham exposure for the entire 15-week period. Auditory, visual, and somatosensory evoked potentials were recorded twice a week, during the daily 6-h field-off period. E- and B-field exposure had no effect on the early or mid-latency evoked potential components, suggesting that exposure at these levels has no effect on peripheral or central sensory afferent pathways. However, there was a statistically significant decrease in the amplitudes of late components of the somatosensory evoked potential during the 10kV/m and 0.3 G, and 30 kV/m and 0.9 G exposure levels. This result is possibly related to the opiate antagonist effect of electromagnetic field exposure reported by others.

Animals↗
PubMed1979

Abnormal auditory evoked potentials in hereditary motor-sensory neuropathy.

From a kinship with a dominantly inherited motor-sensory neuropathy, we studied 2 brothers with brainstem auditory evoked potentials and behavioral audiometric tests. They had abnormal prolongation of I-III interpeak intervals. Wave V was poorly developed. Conventional audiometric tests did not reveal a peripheral hearing loss. It is probable that their auditory nerves and spiral ganglia are undergoing a pathophysiological process analogous to that of their peripheral nerves.

Adolescent↗
PubMed1979

Isaacs syndrome with laryngeal involvement: an unusual presentation of myokymia.

A woman with widespread myokymia presented initially at age 19 with hoarseness and mild dyspnea on exertion. The diagnosis of Isaacs syndrome was suggested by the clinical findings of widespread continuous muscle activity and depressed tendon reflexes, although she lacked the usually prominent increased muscle tone. The diagnosis was confirmed by the electromyographic demonstration of continuous spontaneous muscle action potentials that were abolished by neuromuscular blockade but not by local nerve blockade. Pulmonary function tests were consistent with fixed extrathoracic obstruction. The vocal cords were closely approximated. Electromyographic studies of the laryngeal muscles under general anesthesia revealed continuous muscle activity, which accounted for the hoarseness and much of the exertional dyspnea. The patient responded well to treatment with phenytoin and carbamazepine. This unusual syndrome should be considered in the differential diagnosis of patients with respiratory complaints and muscle fasciculations, even though they have normal muscle tone.

Action Potentials↗
PubMed1978

Benign cerebellar hemorrhages.

Two patients with cerebellar hemorrhage and a benign outcome stress the potential for spontaneous resolution and clinical recovery in some cases of this disorder. In each patient, resolution of the hemorrhage was noted on the computed tomographic scan. Computed tomography may detect a cerebellar hemorrhage even though on clinical grounds a brainstem localization is favored.

Aged↗
PubMed1977

The declining electrical response of muscle to repetitive nerve stimulation in myotonia.

The electrical response of muscle to repetitive nerve stimulation was studied in patients with various myotonic disorders. A decrementing response was common but not invariable finding, and was unrelated to the severity or diagnosis. The decrement either continued throughout the period of stimulation or "leveled off", sometimes being followed by an increment. If it occurred at low rates of stimulation, a greater decrement occurred at higher rates, usually after a shorter latent period. It was not related consistently to the presence of weakness, but in patients with myotonia congenita it was more conspicuous and elicited by lower rates of stimulation when transient weakness was a feature of the history.

Adolescent↗
PubMed1976

Hypothenar Dimpling. A peripheral equivalent of Hemifacial Spasm?

In two patients, the skin over both hypothenar eminences underwent intermittent, spontaneous, irregular, dimpling contractions. The dimpling was benign, and was the result of spontaneous discharge of motor units in the palmaris brevis muscle. Electrophysiological investigations localized the site of origin of the discharge to the ulnar nerve, possibly at the wrist, but there was no clinical or physiological evidence of neuropathy or of nerve compression. In many respects, the clinical and electrophysiological features of hypothenar dimpling resemble hemifacial spasm.

Aged↗
PubMedDate not supplied

Human middle-latency auditory evoked potentials: vertex and temporal components.

We recorded middle-latency (20-70 msec) auditory evoked potentials (MLAEPs) to monaural and binaural clicks in 30 normal adults (ages 20-49 years) at 32 scalp locations all referred to a balanced non-cephalic reference. Our goal was to define the MLAEP components that were present at comparable latencies and comparable locations across the subject population. Group and individual data were evaluated both as topographic maps and as MLAEPs at selected electrode locations. Three major components occurred between 20 and 70 msec, two well-known peaks centered at the vertex, and one previously undefined peak focused over the posterior temporal area. Pa is a 29 msec positive peak centered at the vertex and present with both monaural and binaural stimulation. Pb is a 53 msec positive peak also centered at the vertex but seen consistently only with binaural and right ear stimulation. TP41 is a 41 msec positive peak focused over both temporal areas. TP41 has not been identified in previous MLAEP studies that concentrated on central scalp locations and/or used active reference electrode sites such as ears or mastoids. Available topographic, intracranial, pharmacologic, and lesion studies indicate that Pa, Pb and TP41 are of neural origin. Whether Pa and/or Pb are produced in Heschl's gyrus, primary auditory cortex, remains unclear. TP41 is probably produced by auditory cortex on the posterior lateral surface of the temporal lobe. It should prove of considerable value in experimental and clinical evaluation of higher level auditory function in particular and of cortical function in general.

Adult↗