Showing papers on "Motor neuron published in 1975"

The fine structure of the cervical spinal cord, ventral root and brachial nerves in the wobbler (wr) mouse.

Abstract: Much indirect evidence supports the prevailing concept that the wobbler mouse represents an inherited form of lower motor neuron degeneration, with resultant neurogenic muscular atrophy, due to an autosomal recessive gene (wr). This report, which emphasizes the fine structural changes in the wobbler mouse cervical spinal cord, ventral root and brachial nerves, both extends and modifies previously published data concerning the ultrastructural changes in this disorder. In addition to the more obvious neuronal cytoplasmic vacuolization known to occur, studies extended to a broader age range of wobbler mice have revealed neuronal alterations such as nonvacuolar dissolution of granular endoplasmic reticulum, proliferation of cytoplasmic microtubules and neurofilaments, proliferation of branched tubules resembling smooth endoplasmic reticulum, development of lipid droplets, and increased numbers of pleomorphic dense and lamellar cytoplasmic bodies. The spectrum of pathological changes in this murine form of motor neuron disease thus appears more complex and varied than has hitherto been appreciated, and may be relevant to the formulation of pathogenetic hypotheses.

Command fiber control of crayfish abdominal movement

Abstract: 1. The control of abdominal extension and flexion movements in the crayfishOrconectes rusticus, O. virilis andProcambarus clarkii was examined by monitoring the afferent and efferent unit activities in the dorsal nerve of the second abdominal segment during unrestrained abdominal extensions and flexions which were evoked by stimulation of command fibers (CFs) in the circumesophageal connective (CC). 2. CFs which when stimulated generate coordinated extensions and flexions are present in the CC ofP. clarkii. 3. Two classes of extension CFs are present in the CC ofP. clarkii: 1. those which excite the motor neuron (#4) which innervates the tonic receptor muscle (RM1) of the muscle receptor organ; 2. those which excite one or more of the excitatory motorneurons which do not innervate RM1 (#2, #3 and #6). 4. The extensor motorneurons are activated in reciprocal sets by CF stimulation. The inhibitory motor neuron (#5) is silent during CF evoked extensions (inP. clarkii.) 5. During flexion CF stimulation the inhibitory extensor motorneuron is excited while activity in the excitatory extensor motorneurons is suppressed. 6. The strong reciprocity observed in the superficial extensor motor neuron (SEMN) activities evoked by CF stimulation contrasts with the weak reciprocity which is characteristic of extensor motorneuron activities generated by the intact animal which moves its abdomen in response to a strong sensory stimulus (Sokolove, 1973). This difference in reciprocity supports the hypothesis that an intact animal initiates a postural movement of its abdomen by the conjoint excitation of several CFs. 7. Few if any extension CFs are present in the CC ofO. rusticus orO. virilis.

Dantrolene in Amyotrophic Lateral Sclerosis

Abstract: To the Editor.— In relation to the article by Dr. Michael H. M. Dykes (231:862, 1975), our experience using the muscle relaxant dantrolene sodium (Dantrium) in patients with amyotrophic lateral sclerosis (ALS) may provide additional information on side effects and precautions. Dantrolene has been used in controlling spasticity resulting from disorders such as spinal cord injury, brain damage secondary to birth trauma, multiple sclerosis, and stroke. Although the spastic syndromes associated with motor neuron manifestations in ALS are not mentioned in the literature 1-3 or in the package insert by the company producing the drug, it would seem justifiable to use this muscle relaxant because this syndrome affects the corticospinal pathways, producing spasticity that interferes with motor function and rehabilitation. Amyotrophic lateral sclerosis comprises a group of progressive diseases in which variable degrees of atrophy of motor neurons and degeneration of the corticospinal tracts are the common pathological results: Progressive

Silent period measurement in the differentiation of central demyelination and axonal degeneration.

Abstract: The investigators recorded the silent period from the abductor policies brevis and gastrocnemius soleus muscles in normal subjects and in patients with multiple sclerosis and motor neuron disease. In the multiple sclerosis group the termination of the silent period recorded from the leg was significantly delayed, and the arm and leg silent period differences were increased threefold as compared with normal subjects. Silent period measurements in the motor neuron disease group were normal. The silent period probably participates in a “long loop reflex,” and its delay in multiple sclerosis could therefore be due to a block in central conduction resulting from demyelination. This would not occur in motor neuron disease, in which axonal degeneration is the primary lesion. The techniques used are relatively simple and are a valuable means of differentiating central demyelination from axonal degeneration in man.

Changes in neuromuscular relationships in aging

Abstract: Old age is the period when disorders of the locomotor system prevail (McKeown, 1965). The motor performance is characterized by decrease of muscle strength, slowness and lack of fine coordination of movement. Behaviorally the decrease in speed of response is one of the most characteristic changes in an aging organism (Magladery, 1959). Motor performance is, of course, the result of interaction of complex mechanisms, including motivation, receptors, central synaptic mechanisms at different levels of organization, peripheral synaptic mechanisms and effectors. Whatever the nature of this interaction, the age-dependent disturbance of motor function will most clearly be exposed by changes in motor units, defined by Sherrington (1929) as the population of muscle fibres innervated by a single motor neuron.