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Biomedical subjects

E G Walsh

Publications and source records attributed to E G Walsh.

At least 55 records · Page 3Linked to original sources
PubMed1984

Resonance at the wrist demonstrated by the use of a torque motor: an instrumental analysis of muscle tone in man.

The resonance of the relaxed wrist for flexion-extension movements in the horizontal plane has been investigated by using rhythmic torques generated by a printed motor. In the normal subject the resonant frequency of the wrist is ca. 2 Hz unless the torque is reduced below a certain critical value when the system is no longer linear and the resonant frequency rises. This critical torque level, and the damping are both less in women than men. The resonant frequency is uninfluenced by surgical anaesthesia. With added bias the increase of resonant frequency at low torques still occurs although the hand is now oscillating about a displaced mean position. It follows that the stiffening implied by this elevation of resonant frequency for small movements is neither the result of pre-stressing of the muscles nor of reflex activity. With velocity feed-back of appropriate polarity the system will oscillate spontaneously at its resonant frequency. If the peak driving torque is progressively reduced the resonant frequency increases abruptly, indicating that the system has stiffened. Perturbations delivered to the wrist may reduce its stiffness. The postural system is thixotropic with a 'memory time' of 1-2 s. The resonant frequency is elevated in voluntary stiffening.

Anesthesia↗
PubMed1981

Platelet number and function in Diamond-Blackfan anemia.

Congenital red cell aplasia (Diamond-Blackfan anemia) is occasionally associated with hematologic defects other than a deficiency of red blood cell progenitors, but such alterations have not been well studied. The frequency and magnitude of abnormalities in platelet count and platelet function were therefore examined in 38 patients. Thrombocytosis was seen in 21 patients, and 12 had mild thrombocytopenia on at least one occasion. Elevated platelet counts were demonstrated repeatedly in nine children. The three patients with the lowest platelet counts also had leukopenia. Platelet aggregation was normal in all 16 patients in whom it was studied, and bleeding times were within the normal range in 14 of them. Bleeding signs and symptoms were not observed. It is concluded that thrombocytosis or thrombocytopenia often occurs but that platelet function is normal in patients with Diamond-Blackfan anemia.

Adolescent↗
PubMed1979

Beats produced between a rhythmic applied force and the resting tremor of Parkinsonism.

Rhythmic forces have been applied to the wrist of patients with Parkinsonism tremor by means of a printed motor. The tremor rate was not altered to that of the applied force. On the contrary, beats were established, the rate of which depended on the difference in rate between the tremor and the applied rhythm. Most of the observations have been for horizontal motion of the hand but similar phenomena have been seen for vertical movements, and for other parts of the body--for example, foot, elbow, finger joint, and head. The observations are regarded as supporting the view that the tremorgenic mechanism is central. There was no electromyographic evidence of servo driving or servo assistance in the genesis of the tremor.

Electromyography↗
PubMed1976

Clonus: beats provoked by the application of a rhythmic force.

(1) Clonus has been elicited by using a printed motor in nine patients with sustained ankle clonus. (2) When a dorsiflexing biasing force was applied to the foot the amplitude, but not the frequency, of the clonus varied according to the strength of the force. (3) When the biasing force was withdrawn there could be, for some seconds, continuing EMG evidence of a rhythmic discharge. (4) The clonus did not synchronise with an externally applied rhythmic force. In all relevant observations beats were set up between the clonus and the applied force. (5) When clonus was started by the abrupt application of bias the waveform in successive trials was fairly closely repeatable. (6) Beats were also established in two cases of wrist clonus. (7) It is concluded that clonus is not due to the self re-excitation of proprioceptive reflexes but is dependent on a spinal generator, the rate of beating of which is normally independent of peripheral circumstances, although it may be switched on and its activity maintained by appropriate events.

Adolescent↗
PubMed1974

'Pugnatron'-like reaction in a patient with familial dystonia: torque induced motion analysis.

A patient is described who suffered from an unusual extrapyramidal syndrome involving both legs and one arm. In the affected parts there was an extreme degree of rigidity. Measurements have been made of the motion that occurred as a result of applying force to the left foot. The torque was provided by a printed motor. The effect of a maintained plantar flexing force was anomalous for the foot moved to a dorsiflexed position. A model illustrating possible principles of feedback control-the Pugnatron-is described.

Action Potentials↗