PubMed Health⌕ Search

Biomedical subjects

C D Marsden

Publications and source records attributed to C D Marsden.

At least 937 records · Page 52Linked to original sources
PubMed1977

The effect of lesions of the sensorimotor cortex and the capsular pathways on servo responses from the human long thumb flexor.

Lesions of the sensorimotor cortex, or of the capsular pathways beneath it, caused (with one exception out of 14 cases) diminution "r loss of the servo responses in the thumb, which are based on the long-latency stretch reflex. When not absent the long-latency stretch reflex tended to be late in onset. When absent it was often replaced by a large early reflex response at spinal latency. In general the results are consistent with the transcortical theory of the long-latency stretch reflex for the thumb, but, in detail, they indicate that the theory will require elaboration.

Adult↗
PubMed1977

Nomifensine in Parkinson's disease.

1. Eight patients who failed or ceased to respond to levodopa, or who had developed the "on-off" phenomenon were treated additionally with nomifensine. 2. The dosage of nomifensine started at 50 mg, was increased to 150 mg daily, and other medication was continued unchanged. The duration of treatment was from 2-5 months. Assessments were carried out at 2-week intervals using a validated rating scale. 4. Loss of dopaminergic nigrostriatal neurones characterizes Parkinson's disease, and it is probably for this reason that indirect dopamine (DA) agonists, whose actions depend on intact presynaptic mechanisms, are less active. 3. Nomifensine was not shown to be of antiparkinsonian value in these patients but may be of value as an antidepressant in patients with Parkinson's disease.

Adult↗
PubMed1977

The sensory mechanism of servo action in human muscle.

1. Anaesthesia of the thumb suppresses servo action in the long flexor of the thumb during movements of the terminal phalanx. 2. It needs a greater subjective effort to flex an anaesthetized thumb than a normal one. 3. Anaesthesia of other digits is without effect on the thumb flexor. 4. In an anaesthetic thumb without servo responses the changes in force exerted when a mechanical perturbation is applied which are due purely to the passive mechanical properties of the muscle can be measured. Subtraction of these gives the active components of servo action in the normal thumb and thus an estimate of the mechanical gain of the servo. 5. Giving the subject a visual tracking task can partially restore servo action when the thumb is anaesthetic. 6. After some years subjects become resistant to the effect of peripheral anaesthesia. 7. Peripheral anaesthesia has no detectable effect on servo responses in the long flexor of the great toe, in infraspinatus or in pectoralis major. Servo action in these muscles is presumably based predominantly on muscle receptors. 8. Tendon jerks are not apparently influenced by peripheral anaesthesia. 9. The Discussion considers the possibility that, for the thumb, muscle afferents co-operate with a somatic and a visual input in a servo loop via the cerebral cortex.

Afferent Pathways↗
PubMed1977

Plasma DOPA levels and growth hormone response to levodopa in parkinsomism.

It has been suggested that the therapeutic response to levodopa in patients with Parkinson's disease may be related to changes in plasma growth hormone concentration. In order to examine this problem, we have determined plasma DOPA and growth hormone levels after a standard oral levodopa load in 32 patients with Parkinson's disease. Levodopa caused an increase in plasma growth hormone concentration in 30 subjects. The magnitude and timing of this growth hormone response was not related to the clinical response, the presence or absence of response swings, or the occurrence of dyskinesias. The growth hormone response to levodopa is normal in patients with Parkinson's disease and not altered by long-term levodopa treatment.

Adult↗
PubMed1977

Reticular reflex myoclonus: a physiological type of human post-hypoxic myoclonus.

A patient with post-hypoxic myoclonus, sensitive to therapy with 5-hydroxytryptophan and clonazepam, was subjected to detailed electrophysiological investigation. Brief generalised jerks followed the critical stimulus of muscle stretch. The electroencephalogram showed generalised spikes that were associated with, but not time locked to, the myoclonus. The cranial nerve nuclei were activated upward. Analysis of the findings suggests that the mechanism of the myoclonus is hyperactivity of a reflex mediated in the reticular formation of the medulla oblongata.

5-Hydroxytryptophan↗
PubMed1976

The relationship between striatal and mesolimbic dopamine dysfunction and the nature of circling responses following 6-hydroxydopamine and electrolytic lesions of the ascending dopamine systems of rat brain.

The importance of extrapyramidal and mesolimbic function for circling behaviour was investigated by placing 6-hydroxydopamine (6-OHDA) and electrolesions in the cell bodies, axons and terminals of each system. Circling behaviour was weak when 6-OHDA was placed at the centre of the substantia nigra (SN), but the characteristic contralateral/ipsilateral turning to apomorphine/amphetamine were recorded. Circling was more marked when 6-OHDA was placed anterior to the SN but was generally absent following injections posterior to the SN. However, 6-OHDA placed in the medial forebrain bundle in the lateral hypothalamus resulted in intense contralateral/ipsilateral turning to apomorphine/amphetamine. Generally, the intensity of circling responses was related to the degree of striatal dopamine (DA) depletion but the more effective lesions also caused reductions in mesolimbic DA content. However, circling was not observed following any 6-OHDA injection into the mesolimbic DA system and it is concluded that mesolimbic DA function is not essential for the initiation of circling. In contrast to the 6-OHDA lesions, rats circled ipsilateral to both apomorphine and amphetamine when the SN was damaged by electrocoagulation to cause marked depletion of striatal dopamine. Lesser depletions of striatal dopamine after electrocoagulation in different regions of the medial forebrain bundle were associated with a lower intensity of ipsilateral circling to both drugs. In general, the differences between 6-OHDA and electrolesions could not be explained by additional damage to ascending noradrenaline or 5-hydroxytryptamine pathways. Lower doses of apomorphine were effective in the 6-OHDA circling rats, and the ipsilateral striatum of such rats was more sensitive to directly applied DA. Higher doses of apomorphine were required to produce circling after chronic electrolesions which rendered the ipsilateral striatum insensitive to DA. The contralateral circling to apomorphine after 6-OHDA lesions was abolished by chronic but not by acute electrolesion of the SN. It is suggested that electrolesions of the SN cause different effects to 6-OHDA because they destroy neuronal pathways in addition to the dopaminergic nigrostriatal tract. These appear to be required for the expression of circling behaviour caused by stimulation of the denervated striatum. Whereas 6-OHDA lesions result in super-sensitivity of the denervated strital DA receptors, electrolesions may cause a hypo-sensitivity of the same receptor sites.

Afferent Pathways↗