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Biomedical subjects

B H Brown

Publications and source records attributed to B H Brown.

At least 109 records · Page 6Linked to original sources
PubMed1976

Somatosensory evoked cortical responses: detection in normal infants.

The detection of evoked cortical potentials to a peripheral stimulus is a possible method of studying sensory innervation in children. The purpose of the present study was to determine the consistency with which evoked responses to the electrical stimulation of nerve trunks can be recorded, and to assess the validity of computer analysis of the records. Automated analysis was felt to be desirable because the identification of evoked potentials is usually subjective. Recording sessions were carried out on 37 normal children between the ages of one and six months, and where possible were repeated on three occasions at intervals of at least one month. Using a rigid recording regime, evoked responses could be obtained in 90 to 95 per cent of sessions, the success rate varying with the site of stimulation. An objective computer analysis of records has been developed which is able to recognise evoked potentials as successfully as an experienced human observer.

Evoked Potentials↗
PubMed1976

Somatosensory evoked cortical responses in children with spina bifida.

The sensory pathways of 18 infants and children with myelomeningocele were studied by recording somatosensory evoked cortical responses to standardised electrical stimuli over major nerve trunks in the arms and legs. The 12 infants were tested between the ages of three days and eight months and the six children were tested between two and three years of age. In the majority of patients the results obtained by this technique correlated well with the clinical testing of sensation.

Child, Preschool↗
PubMed1976

Nerve fibre velocity and refractory period distributions in nerve trunks.

With the use of a double stimulus technique, nerve fibre velocity range measurements were performed over a single conduction distance in 13 normal subjects and over two conduction distances in another 12 normal subjects. The velocity ranges were found to be dependent upon the conduction distance, owing to unknown refractory period delays. Refractory period values were calculated for the 12 subjects and also direct refractory period distribution measurements were made on 15 normal subjects using a twin stimulus and automatic subtraction technique. Corrections to the velocity range measurements were made upon differing assumptions as to the correlation between refractory period and fibre conduction velocity. It was concluded that a single median value refractory period obtained from the distribution was the best correction to use, based upon the hypothesis that for group A fibres the random scatter of refractory period values is far greater than any variation due to a correlation between refractory period and fibre conduction velocity. It was found important to recognize that calculated values of velocity range are a function not only of the spread of fibre conduction velocities but also of refractory periods.

Adult↗
PubMed1975

The immediate and delayed effects of different types of vagotomy on human gastric myoelectrical activity.

The immediate and delayed effects of different types of vagotomy on the antral myoelectrical activity have been studied in 52 patients who had previously undergone either highly selective vagotomy (HSV) or truncal vagotomy and pyloroplasty (TV + P) for the treatment of chronic duodenal ulceration up to eight years previously. The frequency of the electrical activity was not statistically different between the two types of operation. After HSV the triphasic waveshape of the antral myoelectrical activity was retained; it was recorded more frequently in the delayed tests (98.0 plus or minus 1-7%) of the recording period than in immediate tests (74-7 plus or minus 6-5%) whereas mean amplitude in the immediate tests (1-59 plus or minus 0-13 mV) was not significantly changed in the delayed tests (1-49 plus or minus 0-08mV). After TV + P the waveform was more sinusoidal in shape, being recorded more often in the delayed tests (91-7 plus or minus 2-7%) than in the immediate tests (41-4 plus or minus 8-9%) although the mean amplitude between the immediate (0-090 plus or minus 0-06 mV) and delayed tests (0-94 plus or minus 0-07 mV) was not significantly different. The only significant change in the myoelectrical activity with the passage of time after vagotomy was an increase in the percentage activity.

Action Potentials↗
PubMed1975

A linked oscillator model of electrical activity of human small intestine.

The electrical slow-wave activity of the human small intestine has been simulated by a chain of 64 coupled electronic relaxation oscillators. The model simulates the frequency gradient of recorded patoentials in the human small intestine and when transected, behaves in a similar way to the transected canine small intestine. The model exhibits a spontaneous effect whereby several adjacent oscillators periodically are in the same state. This effect travels down the model in the time of 20-30 min.

Electrophysiology↗
PubMed1975

New apparatus for measuring forces in strabismus.

An apparatus for measuring muscle forces in strabismus has been developed. The globe is fixed with a modified suction cup, force applied is measured by strain gauges, and the excursion of the globe is measured by a light pointer and tangent screen. The values of force generation tests for normal horizontal rectus muscles performing 30 degrees saccades lie mainly within the range of 60 to 80 G.

Eye Movements↗
PubMed1974

The effect of stimulation on the myoelectrical activity of the rectosigmoid in man.

The myoelectrical activity of the rectosigmoid has been studied in 66 subjects at rest and after stimulation with either pentagastrin 6.0 mug/kg hr intravenously in 21 cases, neostigmine 0.5 mg intramuscularly in 20 cases, or two bisacodyl suppositories in 19 cases. Two electrical rhythms were present at rest. A faster rhythm (frequency 6-9 cycles/min) predominated and its incidence was significantly increased by neostigmine at all levels in the rectosigmoid and by bisacodyl in the rectum only. The incidence of the slower rhythm (frequency 2.5-4.0 cycles/min) was significantly increased by pentagastrin which had no effect on the faster rhythm. The amplitude of each basic electrical rhythm rose when its incidence was increased. Motor waves were augmented corresponding to which of the two electrical rhythms was increased after stimulation.

Bisacodyl↗
PubMed1973

The effects of varying the extent of the vagotomy on the myoelectrical and motor activity of the stomach.

The effects of varying the extent of vagotomy on the myoelectrical and motor activity of the stomach have been successfully studied in 21 patients undergoing either truncal, selective, or highly selective vagotomy for the treatment of chronic duodenal ulceration. The mean percentage time that regular antral myoelectrical activity was recorded preoperatively was 95.8% +/- 1.0 and this was decreased following highly selective vagotomy (74.0% +/- 6.6), selective vagotomy (37.8% +/- 12.4), and truncal vagotomy (30.2% +/- 10.4). The mean amplitude of the pacesetter potential was less following truncal (0.86 mV +/- 0.05), selective (1.32 mV +/- 0.09), and highly selective vagotomy (1.67 +/- 0.09) than in preoperative studies (2.21 mV +/- 0.12). Following truncal and selective vagotomies the triphasic waveform of the pacesetter potential changed to a sinusoidal shape. No significant change in the mean preoperative frequency of the myoelectrical activity (3.03 cpm +/- 0.08) occurred after vagotomy. Thus the changes in the electrical activity of the stomach are related to the extent of the vagal denervation. Intravenous administration of insulin did not alter these patterns except after highly selective vagotomy when the amplitude of the electrical waves, the incidence of action potentials, and percentage motor activity were increased.

Action Potentials↗
PubMed1973

The electrical and motor actions of gastrointestinal hormones on the duodenum in man.

The electrical and motor activity was recorded from the duodenum in 16 conscious human subjects in resting conditions. The main electrical wave form variously known as the pace-setter potential or slow wave was constantly present and periodically accompanied by a second electrical trace consisting of rapid bursts of fast waves or action potentials which were related to motor waves. Secretin and the synthetic analogue of gastrin, pentagastrin, were given in separate tests and their complementary actions on myoelectrical activity are reported. In general, secretin (in six subjects) depressed and pentagastrin (in eight subjects) enhanced motor activity and bursts of action potentials.

Action Potentials↗