Showing papers on "Motor neuron published in 1974"

Organization of the stomatogastric ganglion of the spiny lobster

Abstract: The Stomatogastric ganglion ofPanulirus interruptus contains about 30 neurons, and controls the movements of the lobster's stomach When experimentally isolated, the ganglion continues to generate complex rhythmic patterns of activity in its motor neurons which are similar to those seen in intact animals

A quantitative study of synapses on motor neuron dendritic growth cones in developing mouse spinal cord

Abstract: The proportion of synaptic contacts occurring on dendrites as well as on dendritic growth cones and filopodia was determined from electron micrographs of developing mouse (C57BL/6J) spinal cord. Comparable areas of the marginal zone adjacent to the lateral motor nucleus were sampled from specimens on the 13th–16th days of embryonic development (E13–E16). At the beginning of this period, synapses upon growth cones and filopodia comprise about 80% of the observed synaptic junctions, but this proportion decreases with developmental time so that in E16 specimens growth cone synapses account for slightly less than 30% of the synaptic population. Conversely, at E13, synapses upon dendrites comprise less than 20% of the total number of synapses, but increase with developmental time so that they account for about 65% of the synaptic population of E16 specimens. From these data, we suggest the following temporal sequence for the formation of synaptic junctions on motor neuron dendrites growing into the marginal zone. New synapses are initially made upon the filopodia of dendritic growth cones. A synaptically contacted filopodium expands to become a growth cone while the original growth cone begins to differentiate into a dendrite. This process is repeated as the dendrite grows farther into the marginal zone so that synapses originally made with filopodia come to be located upon dendrites. This speculation is briefly discussed in relation to the work and ideas of others concerning synaptogenesis and dendritic development.

Neural Control of Interappendage Phase During Locomotion

Abstract: Interappendage phasing of crayfish swimmeret movements depends upon a central nervous system network of command, oscillator, and coordinating neurons. The command neurons serve to set the general excitation level in each of the segmental oscillators. The oscillator neurons in each hemi-ganglion generate the rhythmic alternations of powerstroke and returnstroke motor neuron activity. The coordinating neurons transmit the precise timing information about the state of one oscillator to other oscillators. This information can serve to advance or to delay the motor bursts driven by the other oscillators. Which effect is observed depends upon the arrival time of the coordinating neuron discharge within the cycle period of the modulated oscillator. This type of modulation leads to the prediction that a stable interappendage phase can result from situations where there is not a fixed excitability gradient among the segmental oscillators. This prediction has been verified using a cut command neuron preparation.

The properties and connections of supernumerary sensory and motor nerve cells in the central nervous system of an abnormal leech.

Abstract: The characteristic features of individual neurons in leech ganglia are highly consistent from animal to animal. Hy chance a leech was dis- covered that had more cells to be seen than usual in many of its ganglia. In some segmental ganglia of the abnormal animal there were four or even five sensory cells responding independently to touch (T cells) instead of the usual complement of three on each side. Ganglia also contained three or four pressure sensitive cells (P cells) and three or four nociceptive cells (N cells) instead of two of each. The membrane properties, as well as the shapes, sizes, and positions, of all these cells were normal. Their axons reached the skin by the appropriate nerve bundles. Two sensory neurons of one modality, often independently innervated, overlay regions of skin that normally would be supplied by one cell. On the other hand, the areas innervated by some supernumerary cells were abnormal in their shape and position. In some ganglia instead of one motor neuron that raised the skin into bumps (the annulus erector, or AE cell) there were two, each of which could independently erect annuli. The regions innervated by the extra AE cells appeared normal and overlapped extensively. Normal synaptic interactions were found between supernumerary sensory cells and motor cells. The results with this animal indicate that two or more nerve cells can form effective connections with other neurons and with skin that normally would be innervated by a single cell.

Reversible forms of motor neuron disease. Lead "neuritis".

Abstract: A 50-year-old battery worker had clinical signs of motor neuron disease: weakness, wasting, and active reflexes. Nerve conduction velocities, electromyogram, and motor unit territory indicated that the disorder was neuronal. Biochemical abnormalities were characteristic of lead intoxication, and the clinical disorder was reversed after treatment with penicillamine. This case and others suggest that "lead neuritis" is a form of motor neuron disease, rather than a neuropathy. Except for those persons who have clearly been exposed to lead, it is doubtful that lead intoxication is responsible for more than a small number of patients with amyotrophic lateral sclerosis (ALS). Considering the prognostic implications, however, prior to making the diagnosis of ALS, lead intoxication should be considered.

Abdominal movements during backward walking in crayfish

Abstract: 1. A study was made of the neuronal connectivity which produces cyclical abdominal flexion and extension in crayfish during backwards terrestrial walking. 2. On the basis of known coupling, intracellular recording and stimulation, and antidromic stimulation, it is concluded that motor neuron properties alone cannot be responsible for the observed output pattern. 3. The properties of a network of intersegmental interneurons isolated in area 85 of the connective are analyzed, and it is concluded that this network is responsible for driving the motor neurons to produce the cyclical pattern described. 4. A model based upon demonstrated connections among the driving neurons and between these neurons and the motor neurons is proposed which accounts for the observed behavior.

Persistent motor neuron discharges of central origin present in the resting state. A case report of alcohol-induced muscle spasms.

Abstract: A 20 year old woman in whom painful muscle cramping developed after she ingested alcohol was found to have persistent motor neuron discharges at rest. Discharges were present during sleep but were abolished by spinal epidural anesthesia, peripheral nerve block, and procaine infiltration into the muscle, suggesting a central site of dysfunction. Cramps were not relieved by diphenylhydantoin or diazepam. Electromyographic findings and pharmacologic responses differentiate our case from syndromes with persistent motor neuron discharges at rest—the Isaacs-Mertens9 Schwartz-Jampel, and stiffman syndromes. The mechanism by which alcohol induces cramping is unknown. Newer agents, such as the gamma aminobutyric acid derivative baclofen, may aid in localizing the defect.

Increased paralysis induced by guanidine in motor neuron disease

Abstract: A marked increase of weakness occurred in two male patients with motor neuron disease during treatment with guanidine hydrochloride. This effect of the drug seemed to be dose-related. Both patients were of Chinese extraction. Oriental men may be more sensitive to the postulated guanidine-induced depletion of axonal acetylcholine.

Second Case of an Infantile Motor Neuron Disease

Abstract: The second case of an unusual motor neuron disease in an infant is described. The disease shows primarily an involvement of motor neurons, less of the proprioceptive and the extrapyramidal systems. Th