Showing papers on "Nervous system published in 1978"

efference copy and corollary discharge: implications for thinking and its disorders*

Abstract: Many motor commands in the nervous system are associated with corollary discharges which alter the excitability in both sensory and motor systems. These discharges may assist in the distinction between self-generated and externally produced movements; they also allow (or represent) monitoring of the motor commands before the effector response has occurred. Here, I hypothesize that this mechanism of control and integration is also present in thinking, which as Hughlings Jackson pointed out, may be considered the highest and most complex form of motor activity. I speculate that if corollary discharges are normally part of the motor mechanisms of thought, their derangement could produce many of the symptoms of schizophrenia.

Aging in the rhesus monkey: debilitating effects on short-term memory.

Abstract: The performance of aged rhesus monkeys (18 years and older) was compared to that of young control monkeys (three to five years old) in three experiments designed to define and evaluate the presumed short-term memory impairment associated with aging. An automated, indirect delayed-response procedure was used with special emphasis directed toward controlling or eliminating potentially confounding variables such as attention, motivation, learning disabilities, etc. It was shown that the aged monkeys do suffer from a profound a specific impairment in short-term memory (STM), performing normally on the shortest dealy interval and showing progressively greater impairment as the retention interval was increased. A subsequent study varied deprivation level and demonstrated that it is unlikely that differences in motivation could account for the age-related STM deficits observed on the delayed-response task. Further studies indicated that alterations in stimulus availability did not differentially affect the performance of the two age groups to any measurable extent, suggesting that differences in stimulus processing abilities are neigher necessary nor sufficient conditions for the deficit found in the first experiment. These results suggest that the delayed-response deficity in old monkeys is directly related to age-associated changes in those areas of the nervous system which are important for the expression of short-term memory.

The Fine Structure of the Nervous System: The Neurons and Supporting Cells

Abstract: Motor Neurone Disease Edited by F. Clifford Rose. (Pp. 147; illustrated; £7.00.) Pitman Medical Press: Tunbridge Wells. 1977. It is now some five years since the last symposium on motor neurone disease at the Johns Hopkins Hospital. The present volume is a report on the proceedings of the latest symposium on this condition. The editor has produced a balanced presentation from clinical and epidemiological, pathological and electrophysiological disciplines. The 13 chapters are contained in 140 pages including the references so that each is a fairly short and, in all cases, readable review of a particular approach to the problem. The reader already familiar with the problems of motor neurone disease may find little new information in this book but it does summarise usefully the present state of knowledge of the condition. Some pointers for further research are outlined, the application of studies of axonal transport to motor neurone disease, and the question of slow viruses in the aetiology of the condition. I think, however, that the reader will be left with the impression that, despite the accumulation of much information on the disease, there is as yet little evidence that we are much nearer to an understanding of its aetiology. This is a clear summary of the present state of knowledge of motor neurone disease and it should certainly be read by everyone who has an interest in that condition.

Development of Sensory Systems in Arthropods

Abstract: The arthropods are equipped with a wide variety of receptors, each of which is produced by modified epidermal cells. Groups of these cells cooperate in the construction of a specialized sensory structure such as a lens, a bristle, or a strand, which is linked with the dendrites of a peripherally placed sensory neuron. The first receptors to differentiate appear during embryogenesis, new ones are added in subsequent larval life and in the imaginal discs of the holometabolous insects, and at each moult the cuticular parts of the existing receptors are replaced. Because the sense organs develop quite separately from the central nervous system, the type of receptors, their number, and their distribution are determined by mechanisms that operate at the surface and not by the central connections of the sensory neurons. On the contrary, the connections made by the ingrowing axon of an arthropod sense cell are dictated by the kind of receptor that it innervates and where it lies at the surface, so that new input elements are continually being added to the nervous system by an independent set of morphogenetic mechanisms.

Octopamine distribution in the insect nervous system

Abstract: — Octopamine distribution has been surveyed in the nervous systems of two insect species, the locust, Schistocerca americana gregaria, and the cockroach Periplaneta americana. It is essentially similar for both species, being highly localised in the ganglia of the ventral nerve cord. Large amounts of octopamine are also found in the optic lobes especially, in the locust where it is concentrated in the medulla of the optic lobe. Octopamine can also be shown to be associated with insect neurohae-mal structures such as the corpora cardiaca and the neurohaemal organs of the medial nervous system. The significance of the distribution is discussed.

Biochemical Aspects of Transmission at Inhibitory Synapses: The Role of Glycine

Abstract: The biochemical aspects of the neurophysiology of transmission have been clarified during the years since the late 1950s. Thus, it is interesting to recall that during this period many biochemists became aware for the first time that most neurons in the central nervous system of higher vertebrates do not touch. With the aid of the electron microscope, the neuroanatomists have shown that a space of approximately 200 A separates the terminal endings of the axon of one neuron and the cellular membranes of the next neuron. This space is called the synaptic cleft and can vary from 100 to 500 A depending on the tissue and the location; this whole minute region in the nervous system (i.e., the terminal ending of one neuron, the cellular membrane of the second neuron in juxtaposition to the specific nerve ending, and the synaptic cleft) is called a synapse. Various organic compounds can be released from the axonal endings of the presynaptic cell into the synaptic cleft. The compounds which reach and can affect the conductance across the postsynaptic membrane at this region of the synapse in a specific manner are called transmitters and the whole process is called transmission. This latter process is chemical in nature.

Evoked electrical activity in the auditory nervous system

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Development and Plasticity of the Brain: An Introduction

Abstract: This book looks at the development and maintenance of organization in the nervous system of vertebrates, emphasizing the dynamic properties of nerve cells.

Attachment of herpes simplex virus to neurons and glial cells.

Abstract: Summary Cells of brain tissue of rabbits, rats and mice were dissociated and glial cells, neuronal perikarya and synaptosomes were separated by centrifugation on discontinuous Ficoll gradients. HSV was shown to attach well to rat and rabbit glial cells and synaptosomes but not to neuronal perikarya. Of intracerebrally infected mice the fractions with glial cells contained the infective virus. The interactions between HSV and neuronal cells and the implication of the observations on the HSV infection of the nervous system are discussed.

The structure of the nervous system of the pluteus larva of Strongylocentrotus purpuratus.

Abstract: Tissues that have the ultrastructural characteristics of nervous tissues are associated with ciliary and muscular elements of the pluteus larva of Strongylocentrotus purpuratus. The nerve cells are found along the margins of the ciliary bands, which are composed predominantly of spindle-shaped ciliated cells. The nerve cells contribute axonal processes to a tract of axons, which runs at the base of the ciliary band throughout its length. Axonal tracts, in the esophagus, lie beneath the circumesophageal muscles. Branched microvilli, which have been interpreted as sensory receptors, are located on the oral side of the main ciliary band and connect with the nerve cells in the ciliary band. The nervous structures described here, and other tissues of the pluteus that have been previously described as nervous, are compared on the basis of their association with receptor and effector organs, and their ultrastructural characteristics.

Development of Sensory Systems

Abstract: 1 Development of Sensory Systems in Arthropods.- 2 Continuous Nerve Cell Renewal in the Olfactory System.- 3 The Interactions of Periphery and Center in the Development of Dorsal Root Ganglia.- 4 Visual Behavior Development in Nonmammalian Vertebrates.- 5 Ontogeny of Structure and Function in the Vertebrates Auditory System.- 6 The Development of Somatosensory Thalamus in Mammals.- 7 Functional Modification of the Developing Visual System.- 8 Development of Cutaneous Sensory Receptors in Birds.- 9 Cell Death During Development of the Nervous System.- Author Index.

Distribution and release of adenosine triphosphate in rat brain

Abstract: The steady-state level of brain ATP was measured after the tissue had been treated with a focused microwave irradiation system. The brain ATP content (1.50 nmol/mg tissue) obtained by microwave fixation is similar to that observed by others using fast-freezing and microwave fixation techniques. The concentrations of ATP in different brain regions show a rather uniform distribution, ranging from 1.918±0.059 (brainstem) to 2.393±0.19 (caudate) nmol/mg tissue; however, insufficient microwave fixation time seems to produce a greater regional variation of ATP. Release of ATP was investigated by placing a cup on the sensory-motor cortex. The rate for basal release of ATP is 1.43±0.14 femtomole/min/mm2. A 30-fold increase in ATP release was obtained by direct stimulation of the cortex with 5 mA pulses of 0.2 msec duration at a rate of 20/sec over a period of 10 min. These results, in conjunction with others describing the potent pharmacological action of the nucleotide, seem to suggest that ATP could be a mediator in a “purinergic” system in the CNS.

The Structure of the Nervous System

Abstract: The building blocks of the nervous system are the nerve cells, also called neurons. It is estimated that the human brain possesses 25 billion cells. Like all animal cells, each neuron is bounded by a cell membrane that encloses the contents of the cell—that is, the cytoplasm (cell fluid) and the nucleus. The size and shape of these neurons vary widely, but the structural plan always includes certain elements (Fig. 1-1): a cell body, or soma, and the processes from this cell body, namely an axon (neurite), and usually several dendrites. The neuron diagrammed in Fig. 1-1 has one axon and four dendrites.

Function of the Nervous System During Prenatal Life

Abstract: That the nervous system begins to function early during prenatal life is demonstrated only by the movements resulting from its activity. The skeletal muscle reflexes of the fetus are one manifestation of function, and constitute its overt behavior. (35) Another way that function is revealed is through visceral reactions, such as cardiac action, intestinal activity due to smooth muscle contraction, or glandular secretion. The neural regulation of the heart is probably the earliest evidence for function of the nervous system in visceral reactions, for nerve fibers invade the heart at about 16–19 mm,(60) and ECGs have been obtained as early as at 9.5 weeks of menstrual age [36.0 mm crown-rump length (CR), Hooker fetal series].(30)

Nervous system and hypertension.

Abstract: 1. Presynaptic regulation. The regulation of noradrenaline release by a wide variety of substances acting on presynaptic receptors suggests that local factors may play a greater role in the control of blood pressure than was previously believed and that a number of new approaches to the drug treatment of hypertension could be developed. It also raises the possibility that there might be differences in the presynaptic receptor populations of hypertensive and normotensive subjects or animals. 2. Central nerve pathways. There is a need for more precise delineation of central nerve tracts subserving a cardiovascular function and for greater use of morphological techniques to confirm the reliability of biochemical and physiological experiments in the central nervous system. Two appropriate techniques are described. 3. Models of experimental hypertension. (a) Neurogenic hypertension: interference with baroreceptor afferents can cause a permanent elevation of arterial pressure mediated by increased activity of peripheral sympathetic nerves and of descending noradrenergic nerves terminating in the spinal cord. Catecholamine nerve connections of the nucleus tractus solitarius serve mainly to modulate rather than to mediate baroreceptor reflexes. (b) DOCA—salt hypertension: increased peripheral sympathetic activity is important in both the initiation and the maintenance of this form of hypertension. The decrease in brain-stem noradrenaline turnover found in this model could play a determinant role in the development of the high blood pressure. (c) Renal hypertension: both central and peripheral nervous mechanisms contribute to the development and the early phase of ‘one-kidney’ hypertension in animals. Their role in the maintenance of this form of hypertension is still controversial. (d) Spontaneously hypertensive rats: peripheral and central mechanisms do not appear to have a major role in the maintenance of this form of hypertension. However, it seems possible that centrally evoked increases in peripheral sympathetic activity could be important in the initiation of the high blood pressure. (e) Central catecholamines and blood pressure control; central catecholaminergic nerves do not make up a single homogeneous system. For example, the activity of descending noradrenergic nerves in the spinal cord contributes to an elevation of arterial pressure, whereas the activity of catecholaminergic nerves in the dorsomedial medulla appears to have a depressor effect. 4. Human essential hypertension. (a) There is no good evidence that the nervous system plays the major primary role in the development or maintenance of essential human hypertension. (b) Effective treatment of raised blood pressure through nervous mechanisms requires an understanding of the factors that normally control the pressure and does not necessarily depend on reversing specific nervous processes responsible for producing the increase in pressure.

The chemical differentiation of nerve cells.

Abstract: The development of the intricate network of nerve cells that make up the nervous system requires each cell to "choose" a transmitter substance appropriate to its specific connections with other cells.

Effects of Electromagnetic Fields on Isolated Nerve and Muscle Preparations

Abstract: An S-band waveguide exposure system was designed to study the electromagnetic fields on the isolated tissues. The temperature of the exposed tissue was maintained at a constant temperature by circulating temperature controlled Ringer's solution through the waveguide. Isolated frog sciatic nerves, cat saphenous nerves, rabbit vagus nerves and superior cervical ganglia, as well as rat diaphragm muscles were placed in the waveguide either parallel or perpendicular to the electric field of the TE/sub 10/ mode. Compound action potentials of nerves or contractile tensions of muscles were recorded before, during and after the 2450-MHz microwave irradiation. Results showed no significant change in characteristics of nerves or muscles exposed to CW specific absorption rate (SAR) of 0.3-1500 W/kg and pulsed peak SAR of 0.3-220 kW/kg. The effects observed during high-power radiation were reproducible by changing the solution temperature. No direct field stimulation of nerves or muscles was observed during microwave irradiation.

The physiological properties of amine-containing neurones in the lobster nervous system

Abstract: 1. Our previous studies have shown that octopamine and serotonin are found associated with a system of neurones in the connective tissue sheath of the second roots of lobster thoracic ganglia. To try to understand the mechanism of activation of these neurones, we undertook an examination of their general physiological properties. 2. All of the neurones receive excitatory synaptic input that has a cholinergic pharmacology, which suggests that it may be from sensory neurones. A very limited number of cells, possibly one, provdes the total synaptic input to all the cells in the roots of the second and third thoracic segments. 3. The cells within one root are electronically coupled to each other. The extent of coupling varies widely between cells; on occasion the coupling is sufficiently tight for action potentials originating in one cell to trigger action potentials in the neighbouring cell. 4. The majority of the cells show no spontaneous activity at temperatures below 14 degrees C, but become spontaneously active above that temperature. Cells cycle reversibly from silent to continuously active to bursting and back as the temperature is increased and decreased. 5. Octopamine and serotonin both inhibit the bursting activity. The octopamine response is blocked by phentolamine but not by propranolol, while the inhibitory action of serotonin is unaffected by either of these drugs. The amine-inhibition of the firing could be an autoregulatory mechanism for cell activity. 6. The physiological properties described in this paper suggest that the widely dispersed amine-containing neurones in lobsters behave like a neurosecretory organ in terms of their mechanism of activation.

3-Oxo acid coenzyme A transferase activity in brain and tumors of the nervous system.

Abstract: THE ABILITY of the CNS to utilize the ketone body acetoacetate is dependent on its capability to form the corresponding CoA derivative (PAGE er a/.. 1971). The enzyme succinyl-CoA-3-oxo acid transferase (EC 2.8.3.5) is principally responsible for the conversion of acetoacetate to acetoacetyl-CoA (STERN et a/.. 1956). The formation of acetoacetyl-CoA appears to be quite important to the CNS, because exogenous acetoacetate and the other major ketone body. 3-hydroxybutyrate. are major carbon sources for energy production (HAWKINS er a/.. 1971; WILLIAMSON & BUCKLEY. 1973; DEVIVO et al., 1975) and lipid synthesis (WENG et a/.. 1973: DEVIVO et a/.. 1973; EDMOND, 1974; PATEL rr a/.. 1975: RAMSEY, 1976; PATEL & OWEN, 1977) in this tissue. particularly during the developmental period. Although CoA transferase has been shown to have a mitochondrial synaptosomal subccllular localization in the CNS (DEVIVO t't a!.. 1976). neural cell-specific activities have not been previously determined. Whole brain activity of the CoA transferase in the adult rat has been found to be approx 14\"\" of that of kidney, the organ of greatest activity (FENS~LAU & WALLIS. 1974). With regard to neoplastic tissue, F E N S ~ L A ~ et a/. (1975) have demonstrated that CoA transferase activity is present in hepatomas but not normal liver. A positive correlation was shown in these tumors between increased malignancy and increased enzyme activity. The mitochondial localization of the enzyme suggested that the acetoacetate was being used for increased energy production (FENSELAU et a/.. 1976). Since the CNS can normally utilize ketone bodies. including acetoacetate. we sought to establish if this ability was enhanced in tumors of the nervous system.

Central Nervous System Susceptibility to Herpes Simplex Infection

Abstract: Four days after inoculation of herpes simplex virus (HSV) on the rabbit cornea, distinctive and reproducible lesions appear in the trigeminal root entry zone. These viral lesions, situated in the central nervous system (CNS) portion of the root, consist of severe myelin destruction accompanied by mononuclear cell infiltration and partial sparing of axons. Immunofluorescent study demonstrated abundant viral antigen, and by electron microscopy viral nucleocapsids were found to be numerous within astrocytes and were rarely found in other cell types. In contrast, the adjacent peripheral nervous system (PNS) tissue appears unaffected by the presence of virus. The mechanism for this marked difference in response of the central nervous system and the peripheral nervous system may depend upon the susceptibility of astrocytes to viral infection and replication. The selective nature of the lesion provides an easily reproducible model for further investigation of the response of nervous system tissue to HSV.

Brain development influences the appearance of glial factor-like activity in rat brain primary cultures

Abstract: THE development of the nervous system in mammals is thought to be a complex process which involves the orderly expression of a pattern of signals and events. The understanding of how development is controlled requires the identification of the biochemical events which are causally related to this process. Established cultured cell lines provide useful model systems which have yet to be validated by careful examination in conditions more closely related to those in vivo. We have shown previously that established glial cell lines release a macromolecular factor(s) which can induce morphological differentiation of neuroblastoma cells1 and this glial factor(s) is distinct from the well characterised nerve growth factor2. Here we report that glial factor (GF) activity is not confined to established cell lines, as a similar activity is also detected in the medium conditioned by certain primary cultures of rat brain. We further demonstrate that there is a correlation between the presence of GF activity in the medium from cultures of various brain regions and the age of the animal at the autopsy from which the primary culture was derived. Our results provide experimental evidence that primary cultures initiated at different developmental stages can parallel the cellular and biochemical development of the brain in vivo.