Showing papers on "Nervous system published in 1972"

Surgical Disorders of The Peripheral Nerves

Abstract: The Peripheral Nervous System: Gross Anatomy.- The Microscopic Structure of the Nervous System: Its Function.- Reactions to Injury.- Regeneration and Recovery.- Clinical Aspects of Nerve Injury.- Clinical Neurophysiology in Peripheral Nerve Injuries.- Operating on Peripheral Nerves.- Compound Nerve Injury.- The Closed Supraclavicular Lesion.- Birth Lesions of the Brachial Plexus.- Iatrogenous Injuries.- Minimising and Managing Iatrogenous Trigeminal Nerve Injuries in Relation to Dental Procedures.- Pain.- Reconstruction.- Rehabilitation.

The Use of Dopamine β-Hydroxylase as a Marker for the Central Noradrenergic Nervous System in Rat Brain

Abstract: Improvements in the method for localization of dopamine-β-hydroxylase by immunofluorescence allow the observation of noradrenergic-cell bodies, non-terminal fibers, and axon terminals in the rat brain. The distribution of the hydroxylase correlated well with the results obtained by localization of norepinephrine. Dopamine-β-hydroxylase was not observed in dopaminergic neurons or terminals, indicating that these cells do not have the capacity to synthesize norepinephrine. The use of the hydroxylase as a marker, however, has made it possible to visualize noradrenergic nerve terminals on small arteries in the brain parenchyma that have not been described by catecholamine-fluorescence histochemistry. The source of the terminals on small arteries appears to be central noradrenergic neurons rather than the peripheral sympathetic nervous system. Dopamine-β-hydroxylase generally was not observed in the large arteries of the brain parenchyma. These observations suggest that cerebral microcirculation is regulated by central noradrenergic neurons.

N-acetyl-L-aspartic acid content of human neural tumours and bovine peripheral nervous tissues.

Abstract: — Abstract-Tumors of the human nervous system were utilized to investigate the cellular distribution of N-acetyl-L-aspartic acid (NAA). Astroglial tumours contained about 0.144 μmol/g. Oligodendrogliomas and medulloblastomas contained somewhat larger amounts. However, the level of NAA in all gliomas studied was less than that of normal human white matter. NAA was undetectable in meningiomas and acoustic neurinomas. If these results may be taken as representative of normal tissue, they imply a predominantly neuronal localization for NAA. Substantial amounts of NAA were found in peripheral nervous tissues and retina. Neurons seem to vary widely in NAA content.

Fundamental Properties of the Human Nervous System

Abstract: 1: Basic Principles of Approach to the Study of Properties of the Nervous System.- 2: Structure of the Basic Properties of the Nervous System.- 3: Experimental Indices of Dynamism of Nervous Processes.- 4: Orienting Reactions and Their Relationship to Basic Properties of the Nervous System.- 5: Dynamism of the Nervous System as Reflected in Some EEG Indices.- 6: Dynamism of Excitation and Its EEG Correlates in Children.- 7: Referent Indices of Strength of the Nervous System.- 8: Strength of the Nervous System and Absolute Sensitivity.- 9: The Role of the Strength of the Nervous System in the Organism's Reactions to Stimuli of Increasing Intensity.- 10: Mobility of the Nervous Processes and Its Indices.- 11: The Nature of Balance of the Nervous Properties According to the Basic Properties of the Nervous System.- 12: The Problem of Partial Characteristics in the Measurements of Nervous System Properties.- Conclusion.- References.- Author Index.

Acetylcholine and lobster sensory neurones

Abstract: Experiments are presented in support of the hypothesis that acetylcholine functions as a sensory transmitter in the lobster nervous system. 1. Several different peripheral sensory structures incorporate radioactive choline into acetylcholine. The preparation most enriched in sensory as opposed to other nervous elements (the antennular sense organs of the distal outer flagellum) does not incorporate significant amounts of glutamate, tyrosine or tryptophan into any of the other major transmitter candidates. 2. There is a parallel between the distribution of the enzyme choline acetyltransferase and the proportion of sensory fibres in nervous tissue from many parts of the lobster nervous system. 3. Isolated sensory axons contain at least 500 times as much choline acetyltransferase per cm of axon as do efferent excitatory and inhibitory fibres. 4. Abdominal ganglia and root stumps show a decline in the rate of incorporation of choline into acetylcholine 2 to 8 weeks after severing the first and second roots bilaterally (leaving the connectives and third roots intact). Extracts of the root stumps exhibit a significantly lower level of choline acetyltransferase 2 weeks after this operation. 5. Curare and atropine partially block an identified sensory synapse in the lobster abdominal ganglion.

Neurobiology of echinodermata.

Abstract: Summary During the past ten years much information has been added to our knowledge of nerve and muscle systems of echinoderms. 1. Electron-microscopy has shown that all the main nerve trunks consist of large numbers of small, parallel-running unmyelinated axons which are packed tightly together. Glial cells are generally absent. Discrete regions of neuropile are recognizable by the interweaving of axons, and the presence of vesicles. It has not yet been found possible to locate synapses with certainty in the nervous system, but it appears that they are chiefly confined to neuropile. The obvious nerve cords are massive accumulations of neurons which do not appear to interact locally. 2. Peripheral axons are difficult to distinguish because both interstitial and muscle cells have processes which often resemble axons. Ultrastructural analysis of this problem is aggravated by difficulties in fixation. However, the electron-microscope has shown that much of the echinoderm body wall contains a thick subepithelial plexus of processes from epithelial cells. Epithelial cells may thus act as sensory cells and supply axons to the plexus. 3. With the exception of striated muscles in some pedicellariae, all echinoderm muscles so far examined are of the smooth type. These muscles characteristically contain large filaments, and in this way do not resemble vertebrate smooth muscle. Some muscles are innervated by simple axonal contact, in others the muscles themselves send processes towards the nervous tissue. 4. Physiological studies of electrical activity in nerve and muscle systems have not added significantly to our knowledge of function. Several authors have demonstrated that massed electrical activity is conducted decrementally along the radial nerve cords, but this does not explain any known aspect of coordination. The only records of electrical activity from single neurons (Takahashi, 1964) have not been repeated. 5. There is strong evidence for two types of neurons in the central nervous system of echinoderms. One of these contains acetylcholine, the other dopamine and/or noradrenaline. Electron-microscopical histochemistry has given good indication that catecholamines are bound in echinoderm nerve tissue to particles similar to those reported in other invertebrate nervous tissues, and there is good evidence that acetylcholine is bound to synaptic vesicles which are morphologically identical to those present in the mammalian brain. The available data further indicate that acetylcholine is a transmitter in sensory and motor neurons, while dopamine and/or noradrenaline are transmitters in interneurons. Such interneurons may be involved in the coordination of the movement of the tube-feet. Other substances which have been implicated in neuro-effector mechanisms in other animal groups have not been found or are present in very small quantities. 6. Studies on the reproductive physiology of starfish have shown that several substances in the radial cords play important roles in its control. Such substances cannot at present be called neurosecretions because it is not known if they are derived from neurons. 7. Pharmacological studies on isolated muscle tissues have not added significantly to our knowledge of their control. The potency of ACh in causing contraction is well documented, and anticholinesterases are similar in effect. Catecholamines, although clearly very important in the nervous system, do not produce clear-cut effects. The published reports of relaxation to noradrenaline may well be due to direct effects on the muscle. No definite information has been obtained on the role of the adrenergic parts of the nervous systems of echinoderms, other than showing that they are not involved in motor responses. Extensive studies with a wide variety of drugs have produced inconsistent and largely negative results.

Effect of Blood Sugar Control on the Accumulation of Sorbitol and Fructose in Nervous Tissues

Abstract: Some products of the sorbitol metabolic pathway of glucose were extracted from peripheral nerves and spinal cords of rats, identified, and measured. Within a few days after a diabetic state was induced with streptozotocin, glucose, sorbitol, and fructose in nerve and cord had risen sharply as blood glucose increased. These levels were partially controlled when the blood sugar was restricted by insulin, but they increased rapidly when the insulin was withheld. Withdrawal of treatment resulted in a much greater rise of the fructose in the nervous system in animals that had been diabetic for six weeks before institution of treatment with insulin than in animals treated from induction. When phen-formin was used as a controlling agent in place of insulin, accumulation of glucose and fructose in the nervous system was enhanced, whereas fructose was found to decrease when tolbutamide was used. Earlier workers have shown that the sorbitol pathway seems to be associated with the Schwann cell and that dysfunction of this cell leads to segmental demyelination. We find that accumulation in nerves of the products of the sorbitol pathway may be minimized when blood sugar is controlled; since we have evidence that in human beings with diabetes good control improves the state of myelination of already damaged nerves, it is postulated that herein lies the mechanism whereby control of diabetes is likely to lead to a reduction in the incidence of nerve damage.

Cyclic Adenosine Monophosphate in the Nervous System of Aplysia californica : I. Increased synthesis in response to synaptic stimulation

Abstract: In the isolated abdominal ganglion of Aplysia, previously incubated in adenine-3H, the amount of 3H-labeled adenosine-3',5' monophosphate (cAMP) doubled after electrical stimulation of nerves at a physiological rate (1/sec). No change was detected after 4 min of stimulation. An increase in cAMP was first seen after 15 min; lengthening the period of stimulation to 1 hr did not increase the extent of the effect. ATP contained 50% of the total radioactivity taken up from adenine-3H, cAMP about 0.1%. During stimulation both the total amount and the specific radioactivity of adenosine triphosphate (ATP) did not change. Thus, the increased amount of radioactivity found in cAMP after stimulation represented an increase in its rate of synthesis. During stimulation formation of cAMP-3H was not altered in nerves or in the cell body of an identified neuron (R2). In addition, no changes were detected in the total amounts of cAMP in the ganglion and in the cell body of R2. It seems likely that the increase was initiated by synaptic activity rather than by action potentials. It was blocked by elevating the concentration of Mg, which also blocks synaptic activity without impairing conduction of impulses. Moreover, impulse activity induced by ouabain and glutamate did not result in increased formation of cAMP.

Trichopoliodystrophy. II. Pathological changes in skeletal muscle and nervous system.

Abstract: A skeletal muscle biopsy and the nervous system of a 21-month-old male child who died of trichopoliodystrophy were studied by light and electron microscopy. The fine structural alterations in the muscle consisted of accumulation of glycogen, pronounced interfibrillar vacuolation, "hyaline degeneration," distortion of the tubular system, and disorganization of the mitochondria containing dense granules. In addition to atrophy of the brain with widespread neuronal loss and reduction of the white matter, the Purkinje cells of the cerebellum showed multiple, short, tapering cytoplasmic processes. The changes in the spinal cord consisted of neuronal loss in the Clarke's column and degeneration of the spinocerebellar tracts. Neuronal mitochondria in the postmortem material showed conglomeration and dense granules. The neuropathological changes in this disorder appear to be characteristic. The significance of the muscle changes, however, remains obscure.

Regeneration and Changes in Synaptic Connections between Individual Nerve Cells in the Central Nervous System of the Leech

Abstract: The central nervous system of the leech has been used for the study of the formation of new synaptic connections by regenerating neurons. In control leeches, individual nerve cells in adjacent ganglia are connected in an orderly and stereotyped manner, with only little variation. In the present experiments, a bundle of axons running between two of the segmental ganglia has been severed and allowed to regenerate. Subsequently, the axons reestablish synaptic connections between certain identified nerve cells in the adjacent ganglia, selectively and accurately. Thus, individual sensory cells in one ganglion show a high degree of neural specificity in reestablishing cell to cell connections with a motor cell in the next ganglion. The performance of the regenerated synapses, however, is significantly altered in a consistent manner. The normal balance between the effects of inhibitory and excitatory innervation in leeches with regenerated synapses is different from that seen in normal leeches, with marked overemphasis on inhibition. Similar alterations have also been seen in a series of ganglia at a distance from the site of the lesion. After the operation, therefore, a widespread modification of synapses occurs along the length of the nerve cord.

Synaptogenesis in the chick embryo spinal cord.

Abstract: RECENT advances in the study of the ontogeny of neural function in the chick embryo1 have re-emphasized the need for a better understanding of the morphological details of the developing avian nervous system. With this in mind we have undertaken a correlated programme of study of the ultrastructural and behavioural development of the embryonic nervous system of birds.

Function of catecholamine-containing neurones in mammalian central nervous system.

Abstract: SEVERAL chemical substances are involved in synaptic transmission in the mammalian central nervous system1–3. The Falck-Hillarp technique4 has demonstrated noradrenaline, dopamine and 5-hydroxytryptamine within nerve cell bodies and terminals5,6 and the belief that these amines act as neurohumours is strengthened by observations that nerve fibre activation leads to their release from the terminals7,8. Histo-chemical evidence suggests that discrete systems of neurones can be identified by their content of particular amines, and it seems possible that such neurohumorally homogeneous systems have a functional as well as a chemical identity. Before the anatomical distribution of amine-containing neurones had been described, Brodie and Shore9 proposed that noradrenaline functions as the central neurohumour of the sympathetic and 5-hydroxytryptamine of the parasympathetic system. This suggestion has not been supported by anatomical evidence; the amine-containing neurones form systems of small diameter fibres of very diffuse terminal distribution, which do not correspond to recognized ascending or descending pathways5,6, although amine-containing neurones in invertebrates have been identified as sensory systems10.

Nature and significance of spontaneous degeneration of axons in the pyramidal tract.

Abstract: During postnatal development of the rat the nature of spontaneous degeneration of axons in the pyramidal tract was studied electron microscopically. The degenerating axons were found more frequently in young animals than in old animals, and they were generally found in bundles. On the basis of electron-opacity and visibility of ultrastructural details in the degenerating axons, and frequency of their occurrence at various developmental stages the degenerating axons were classified into four groups representing four stages of severity of spontaneous degeneration of axons in the pyramidal tract. In the context of neuroembryological material, autoradiographic as well as silver-impregnated, it was established that these spontaneously degenerating axons arose from the reticular formation of the brain stem and that they had ascending as well as descending components, the latter descending in the spinal cord. Possible significance of such reticulo-spinal axons in the primitive organization of the embryonic nervous system and its determination of the spontaneous motility in early embryos, and in the apparently directed growth of the cortico-spinal axons during late stages of embryonic development are discussed.

The control of foregut movements by the stomatogastric nervous system in the European house cricketAcheta domesticus L.

Abstract: 1. The morphology of the stomatogastric nervous system inAcheta domesticus L. is briefly described. 2. Removal of the ventricular ganglia and the hypocerebral ganglion as well as severing the oesophageal nerves and their sidebranches to the gut show that the foregut movements are under nervous control. The neural co-ordinating mechanism is located in the oesophageal nerves, whereas the ganglia seem to play merely a stabilizing role. Foregut movements seem to be under additional myogenic control. 3. Simultaneous recordings of gut movements and the activity in the oesophageal nerves demonstrate a correlation between nervous activity and the contraction waves. This correlation is not very obvious in any single event, however, it becomes clear when the average of activity is taken. 4. The stretch receptors on the gutwall respond phasically to the most part to trapezoid and sinusoidal stretches of the gutwall. 5. There exist interactions between sensory elements within the gutwall and motor elements in the oesophageal nerves. The motor elements react to stretching the gutwall with a decrease of their spike activity; this decrease is greatest during the maximum stretch. However, it is often preceded by a short increase which is dependent on the stretching speed. After removal of the hypocerebral ganglion and the ventricular ganglia these relations show no qualitative change. 6. The co-ordinating mechanism includes stretch receptors on the gutwall and motor neurones in the oesophageal nerves between which interactions do occur. The mechanism can be described functionally as a system of spontaneously active motor elements which are modulated by sensory input from the gutwall.

The differentiation of glial cells and glia limitans in organ cultures of chick spinal cord.

Abstract: Differentiation of glial cells and the glia limitans in organ cultures of chick spinal cord explanted at early neural tube stages, alone or with adjacent tissues, was studied by electron microscopy. Oligodendrocytes and astrocytes comparable to those seen in the chicken in vivo were observed, mainly in areas of good neuronal differentiation. A glia limitans with basal lamina, comparable to that in vivo, was found when spinal cord was bordered by normally adjacent tissues. When it was surrounded by vitelline membrane only, a characteristic limiting layer of glial processes, but no basal lamina, was seen. Contact with a filter membrane (Millipore) elicited excessive differentiation of glial filaments and modified cell fine structure; no glia limitans was formed.