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Biomedical subjects

D Burke

Publications and source records attributed to D Burke.

At least 361 records · Page 20Linked to original sources
PubMed1971

"Intal" intake.

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Chromones↗
PubMed1971

Hamstrings stretch reflex in human spasticity.

In 16 patients with spastic paralysis the hamstrings stretch reflex was found to increase as the velocity of stretch increased, and generally to subside after movement ceased. These effects are attributable to the dynamic property of the primary spindle ending. The stretch reflex commonly appeared in only the last third of the stretching movement and was maximal as the knee became fully extended. This is consistent with the static properties of the primary and secondary spindle endings, and accounts for the absence of the clasp-knife phenomenon in the spastic hamstrings. The difference in the nature of the stretch reflex in spastic flexor and extensor muscles is best explained by the differential reflex effects of group II afferent fibres which facilitate flexor motoneurones and inhibit extensor motoneurones.

Electromyography↗
PubMed1971

Stretch reflexes in the upper limb of spastic man.

The reflex response to stretch has been studied in the upper limb of 20 spastic patients. The amplitude of reflex EMG was found to be closely related to the velocity of stretch. Reflex EMG in biceps and triceps muscles was augmented by increasing the length of the muscle, although minimal inhibition of reflex EMG in biceps was obtained in two patients by extreme stretch. The clasp-knife sensation in the upper limb cannot be related to autogenic inhibition but may be explained by the characteristics of a velocity-dependent reflex in which limb movement is braked by the mechanical effect of increasing muscle tension. It is suggested that this be called the pseudo-clasp-knife reaction to distinguish it from the clasp-knife phenomenon of the quadriceps muscle, since the underlying neurophysiological mechanism is quite different.

Cerebrovascular Disorders↗
PubMed1970

A new agent for the control of spasticity.

In a preliminary controlled trial, CIBA 34,647-Ba, a gamma aminobutyric acid derivative, was found to be more effective than placebo in reducing spasticity due to spinal injuries. In an uncontrolled trial, 34,647-Ba also appeared more effective than diazepam. The intensity of spasticity was measured electromyographically by the amplitude of the stretch reflex at various velocities, and the results were correlated with those obtained by clinical assessment. 34,647-Ba was effective in both complete and incomplete spinal cord lesions and it is suggested that it has an action at the spinal level. No significant side-effects were encountered.

Amines↗
PubMedDate not supplied

Power spectrum and optimal filtering for visual evoked potentials to pattern reversal.

The optimal bandwidth for recording the visual evoked potential (VEP) to pattern reversal was investigated in 8 normal subjects by re-analyzing off-line data recorded on tape using an open bandwidth of 0.1 Hz-3 kHz. Power spectral analysis of the VEP revealed little energy above 50 Hz. With digital filtering, the amplitude N70-P100 was significantly attenuated only when the low-pass filter was reduced to 50 Hz or when the high-pass filter was raised to 8 Hz. With analogue filtering, there was significant prolongation of latency of P100 when the low-pass filter (12 dB/octave) was reduced to 250 Hz and a significant decrease in latency when the high-pass filter (6 dB/octave) exceeded 3 Hz. However, the effects of analogue filtering were not uniform across subjects: in 2 subjects the latency of P100 was prolonged using a low-pass filter of 600 Hz and in 2 other subjects the latency was shortened when the 1 Hz high-pass filter was introduced. If a restricted bandwidth is used, non-uniform distortion of latency could make a significant contribution to the variability in latency of P100. The optimal bandwidth is one which minimises this contribution to the variability, 0.3 Hz to greater than 600 Hz.

Adult↗
PubMedDate not supplied

Projection of thenar muscle afferents to frontal and parietal cortex of human subjects.

There is some controversy about the projection of muscle afferents from the human upper limb to cerebral cortex and about their contribution to somatosensory evoked potentials. In 8 normal volunteers, the somatosensory projections of muscle and cutaneous afferents from the hand were recorded at 21 scalp sites, using a non-cephalic reference. Low-threshold thenar muscle afferents were selectively activated by intramuscular microstimulation. In addition, the averaged data for the projections were mapped for each individual. In each subject a focal parietal negativity was detected over the contralateral parietal cortex at a mean latency of 20.8 msec (S.D. 1.15 msec) following stimulation of thenar muscle afferents. The amplitude of the parietal 'N20-P25' was relatively small (mean 0.49 microV, range 0.18-1.56 microV). A small focal positivity was detected, maximal over contralateral frontal cortex at 22.8 msec (S.D. 2.05 msec) but recorded bilaterally. In all subjects subcortical positive waves (P9 and P14) were defined for the muscle afferent volley. This pattern of cortical activity was similar to that for the projection from the digital nerves of the index finger. For the cutaneous input the latency of the parietal 'N20' was 21.7 msec (S.D. 1.17 msec) and of the frontal 'P22' was 24.2 msec (S.D. 3.09 msec). The amplitude of the parietal 'N20-P25' was larger for the cutaneous projection (mean 1.59 microV; range 0.65-4.28 microV).

Adult↗