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.

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.

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.

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.

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.

Quantitative electromyography: carrier detection in Duchenne type muscular dystrophy using a new automatic technique

An automated method of quantitating small electromyographic changes, based on the ratio of action potential duration to the number of phases per potential, was applied to carriers of X-linked Duchenne type muscular dystrophy. The ratio was found to be significantly raised in a proportion of these cases.

The effects of humoral agents on the myoelectrical activity of the terminal ileum

Electrical and motor activities of the terminal ileum have been recorded in 25 patients with a permanent ileostomy. Records made within a week of formation of the ileostomy show an increased motor activity which is significantly reduced after four weeks. Intravenous infusion of gastrin, 1 mug/kg-hr, was accompanied by a significant increase in action potentials and in the percentage motility. Conversely, secretin 1 unit/kg-hr was associated with a decrease in action potentials and in percentage motor activity.

Quantitative electromyography: a new analogue technique for detecting changes in action potential duration

An automatic method using an analogue analyser is described for obtaining an index which is based on the mean phase duration of an EMG signal. This method gives similar values for motor unit action potential duration to an alternative digital method of analysis based on the distribution of time intervals between zero crossings of the EMG signal. The analysis has been found to give good discrimination of normal and myopathic EMG signals.

Pacesetter potential of the human gastroduodenal junction

The pacesetter potential of the gastric antrum and proximal duodenum has been recorded in man by electrodes placed under the serosal coat of the gut. The typical 3 cycle/min of the stomach was found to be conducted across the pylorus into the first part of the duodenum at a rate (2 cm/sec) about four times as fast as its conduction in the more proximal antrum (0.5 cm/sec). A 3 cycle/min pacesetter potential could be detected as far distally in the duodenum as 10 cm from the pylorus.

Electrical activity of the gastric antrum in man

The electrical activity of the gastric antrum, up to 6 cm. from the pylorus, has been studied at operation by means of electrodes implanted through the serosa in 68 patients; electrodes were also attached to the mucosa in 13. Records made from the mucosal electrodes show the same frequency as the serosal electrodes. Control records made in 12 patients with gall-stones showed a frequency of electrical waves in the region of 3 per minute (median 2.85 cycles per minute), which is significantly less than the frequency in 11 patients with gastric cancer, in 8 patients with gastric ulcer, and in 24 patients with duodenal ulcer.