Reciprocal Ia inhibition from ankle flexors to extensors was studied during voluntary tonic isometric dorsiflexion and plantar flexion in five normal subjects. The Ia inhibition was examined as the short-latency suppression of the soleus H-reflexes by stimulation of the low-threshold afferents in the common peroneal nerve (Mizuno et al. 1971). At rest, weak Ia inhibition was demonstrated in four subjects out of five, the maximal amount being 14.1 +/- 5.0% suppression of the control H-reflex. The absolute amount of inhibition, which was calculated by subtracting the mean size of the conditioned H-reflex from that of the control H-reflex and expressed as a percentage of the maximal M-response, increased during ankle dorsiflexion, and decreased or disappeared during plantar flexion in parallel with the amount of contraction. The neural mechanisms for facilitation of the Ia inhibitory pathway during dorsiflexion were considered to support the hypothesis of "alpha-gamma-linkage in reciprocal inhibition", i.e. combined facilitatory effects on the Ia inhibitory interneuron from the supraspinal centers directly and indirectly via the gamma motoneuron--Ia afferent route. The mechanism for inhibition of the pathway during plantar flexion was considered to be inhibition of the Ia interneuron of the flexor side by Ia interneuron of antagonist extensors. A quantitative aspect of activity in the reciprocal Ia inhibitory pathway on the performance of voluntary movement is revealed in this study.
Joseph's disease is a hereditary ataxia found among descendants of Portuguese from the Azores Islands. We describe the clinical and pathological features of 4 members of a Japanese family who were diagnosed as having Joseph's disease. The illness began with cerebellar ataxia between the ages of 18 and 45 years. Nystagmus, dysarthria, and pyramidal signs were early manifestations. External ophthalmoplegia, dystonia and/or athetotic movements, and muscular atrophy appeared in the late stages. Neuropathological findings in one patient revealed degeneration of the dentatorubral and pallidoluysian systems, substantia nigra, pontocerebellar system, Clarke's column and spinocerebellar tracts, and anterior horn cells, as well as the cranial nuclei in the brainstem. Neurons in the inferior olivary nuclei, Purkinje's and granule cells, the cerebral cortex, thalamus, and striatum were spared. Involvement of the dentatorubral and pallidoluysian systems seems to be a characteristic feature of this disease in Japan.
A case of adrenoleukodystrophy showing neurological features of olivopontocerebellar atrophy is described. A CT scan demonstrated marked atrophy in both cerebellum and pons. ACTH stimulation produced no rise in the plasma cortisol level but a significant rise in the plasma aldosterone level. The ratios of C26:0 to C22:0 in fatty acids of sphingomyelin from erythrocyte membrane and plasma were increased.
SUMMARY Human cord dorsum potential (CDP) was recorded from the posterior epidural space at the levels of cervical and lumbar enlargements, using epidural catheters as the recording electrodes, in 15 normal volunteers and six patients suffering from amyotrophic lateral sclerosis. In normal subjects the CDP elicited by descending volleys consisted of spike potentials followed by sharp negative and slow positive waves which were very similar to the P1, NI, and P2 potentials, respectively, of the CDP evoked segmentally. By contrast, in all patients with amyotrophic lateral sclerosis both the sharp negative and slow positive waves were absent in the CDP elicited by descending volleys, while the pattern of each component of the segmentally evoked CDP remained unchanged. Thus, the sharp negative and slow positive waves of human CDP elicited by descending volleys might reflect the activity of interneurones and primary afferent depolarisation respectively, produced by impulses through the corticospinal tract.
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