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Results for “Brain function”

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At least 109 records · Page 6Linked to original sources

PubMed1984

Possible role of histamine in brain function: neurochemical, physiological, and pharmacological indications.

Recently accumulated neurochemical, physiological, and pharmacological evidence strongly supports a role for histamine as a central neurotransmitter. Neurochemical methods, which became available within the last years, allow determination of small amounts of histamine and its metabolites in the brain and make possible future studies of central histamine regulation. The demonstration of histamine H1 and H2 receptors in the brain of several species suggests a possible role for histamine in brain function. Microelectrophysiological studies on single central neurones suggest both excitatory and depressant effects of histamine which are receptor mediated. In addition, brain histamine has been demonstrated to be subject to cyclic variations, to play a role in hormonal regulation, and to be altered by stressful conditions. Several psychotropic drugs significantly affect brain histamine regulation and elicit inhibitory effects on central histamine receptors. These findings bring new approaches and stimulus to further research on the significance of brain histamine.

Animals↗

PubMedDate not supplied

Effect of acute doses of controlled-release carbamazepine on clinical, psychomotor, electrophysiological, and cognitive parameters of brain function.

The neurotoxic effect of acute doses of carbamazepine controlled-release (CBZ-CR) divitabs (800, 1,200, and 1,600 mg) was assessed on clinical, psychomotor, electrophysiological, and cognitive parameters of brain function in 10 healthy volunteers in a double-blind, randomised, placebo-controlled, phase I study. Significant changes compared to placebo were demonstrated for the clinical scales, ataxia (AT), convergence of the near-point (CNP), peak saccadic velocity (PSV), critical flicker fusion (CFF), spectral analysis of the EEG, and brainstem auditory evoked potential (BAEP) tests. Digit repetition, digit symbol substitution, Sternberg memory scanning time, Sternberg choice reaction time, saccadic latency, and saccadic accuracy showed important negative findings. Significant clinical tolerance to side effects developed within 20 to 33 h after CBZ-CR dosage during a period in which the mean CBZ blood levels remained virtually unchanged. CBZ-CR, 800, 1,200, and 1,600 mg yielded low, medium, and high therapeutic blood levels, respectively, for +10 to +33 h after dosage without the development of severe clinical side effects.

Adult↗

PubMed1989

Functional brain asymmetry and murine systemic lupus erythematosus.

The role of brain lateralization in antibody production was studied in a murine systemic lupus erythematosus model. Male and female New Zealand black mice that spontaneously produce pathogenic auto-antibodies directed against red blood cells and DNA, were divided into right- and left-handers using a paw preference test, and anti-erythrocyte and anti-DNA antibody production was repeatedly determined. In females, antibodies against erythrocytes and double-stranded DNA appeared earlier in left-handers. These results provide the first evidence of an association between a functional brain asymmetry and auto-antibody production and suggest the involvement of the central nervous system in the pathogenesis of autoimmune processes.

Aging↗

PubMedDate not supplied

[Effect of a high-intensity radiation exposure on brain function in monkeys. Postradiation changes in central coordination of brain bioelectrical processes].

In experiments with Macaca fascicularis exposed to high-energy electrons (45 Gy, 6.5 Gy/s) revealed were early changes in the coherent spectrum of EEG semihemispheric leads. These changes were displayed by the increased interrelation between slow-wave fluctuations and decreased coherence within the mid- and high-frequency EEG-rhythms band. The relationship was noted between the changes observed and the clinical symptoms features of early radiation response as well as the dynamics of the CNS functions of exposed animals. Postirradiation changes in the intracellular bioelectric interaction are considered as one of the manifestations of the systemic response of the brain to the harmful effect of radiation.

Animals↗

PubMed1989

High-altitude mountaineering and brain function: neuropsychological testing of members of a Mount Everest expedition.

Concern has been raised regarding the possibility that hypoxic conditions encountered during high-altitude mountaineering may have lasting harmful effects on the human brain. Members of an expedition to Mount Everest completed a series of neuropsychological tests before and after the expedition. Exposure to altitudes above 7,200 m was limited to a maximum of four consecutive nights, separated by rest periods at lower altitudes. No significant decline in performance was observed on any test. The subjects also completed a short series of tests at different altitudes during the expedition. No significant deterioration was observed at altitudes up to 7,500 m. There do not appear to be lasting harmful effects on brain function under these conditions.

Altitude↗

PubMed1985

Growth hormone, somatomedin and prolactin--relationship to brain function.

In recent years it has been found that the brain of several mammals including have receptors for somatomedin both IGF-I and II and measurable hGH has been identified in human brain tissue. IGF-II has been determined in CSF. The presence of these hormones in brain tissue seems to be of developmental and functional importance as experimental studies in frogs, tadpoles and rats showed that injection of growth hormone enhanced brain growth and increased the ratio of neurons to glia. In man early initiation of hGH therapy to children with hGH (who have a less than normal head circumference) induced a fast catch-up growth of the head and improved their IQ. The data available seems to indicate that growth hormones and/or the somatomedins play an important role in the early brain development, maturation and function. In case of hereditary or congenital GH-RH, hGH or somatomedin deficiency, the effectiveness of therapy seems age limited similar to hypothyroidism. The finding of prolactin receptors in human brain and the report of a child with congenital hypoprolactinemia who had mild mental retardation raises the possibility that also prolactin plays a role in brain function.

Animals↗

PubMed1991

Hyperammonaemia does not impair brain function in the absence of net glutamine synthesis.

1. It has been established that chronic hyperammonaemia, whether caused by portacaval shunting or other means, leads to a variety of metabolic changes, including a depression in the cerebral metabolic rate of glucose (CMRGlc) increased permeability of the blood-brain barrier to neutral amino acids, and an increase in the brain content of aromatic amino acids. The preceding paper [Jessy, DeJoseph & Hawkins (1991) Biochem. J. 277, 693-696] showed that the depression in CMRGlc caused by hyperammonaemia correlated more closely with glutamine, a metabolite of ammonia, than with ammonia itself. This suggested that ammonia (NH3 and NH4+) was without effect. The present experiments address the question whether ammonia, in the absence of net glutamine synthesis, induces any of the metabolic symptoms of cerebral dysfunction associated with hyperammonaemia. 2. Small doses of methionine sulphoximine, an inhibitor of glutamine synthetase, were used to raise the plasma ammonia levels of normal rats without increasing the brain glutamine content. These hyperammonaemic rats, with plasma and brain ammonia levels equivalent to those known to depress brain function, behaved normally over 48 h. There was no depression of cerebral energy metabolism (i.e. the rate of glucose consumption). Contents of key intermediary metabolites and high-energy phosphates were normal. Neutral amino acid transport (tryptophan and leucine) and the brain contents of aromatic amino acids were unchanged. 3. The data suggest that ammonia is without effect at concentrations less than 1 mumol/ml if it is not converted into glutamine. The deleterious effect of chronic hyperammonaemia seems to begin with the synthesis of glutamine.

Amino Acids↗

PubMed1991

High-resolution optical imaging of functional brain architecture in the awake monkey.

Optical imaging of the functional architecture of cortex, based on intrinsic signals, is a useful tool for the study of the development, organization, and function of the living mammalian brain. This relatively noninvasive technique is based on small activity-dependent changes of the optical properties of cortex. Thus far, functional imaging has been performed only on anesthetized animals. Here we establish that this technique is also suitable for exploring the brain of awake behaving primates. We designed a chronic sealed chamber and mounted it on the skull of a cynomolgus monkey (Macaca fascicularis) over the primary visual cortex to permit imaging through a transparent glass window. Restriction of head position alone was sufficient to eliminate movement noise in awake monkey imaging experiments. High-resolution imaging of the ocular dominance columns and the cytochrome oxidase blobs was achieved simply by taking pictures of the exposed cortex when the awake monkey was viewing video movies alternatively with each eye. Furthermore, the functional maps could be obtained without synchronization of the data acquisition to the animal's respiration and the electrocardiogram. The wavelength dependency and time course of the intrinsic signal were similar in anesthetized and awake monkeys, indicating that the signal sources were the same. We therefore conclude that optical imaging is well suited for exploring functional organization related to higher cognitive brain functions of the primate as well as providing a diagnostic tool for delineating functional cortical borders and assessing proper functions of human patients during neurosurgery.

Animals↗

PubMed1990

Effects of high dietary sulfur on brain functions using evoked potentials technique.

Brain stem auditory-evoked response (BAER) is a noninvasive technique used for detecting neurophysiological abnormalities of the brain stem along the auditory pathway. Brain stem auditory-evoked response recordings were obtained from subcutaneous skin electrodes from two control sheep and 22 other sheep fed high sulfur (S) diets with low or high concentration of thiamine (B1), copper (Cu), and molybdenum (Mo). At least four peaks (I,II,III,IV) of varied amplitude were observed in all animals. Neurophysiological abnormalities due to decreased conductivity and/or excitability of nerve fibers along the auditory pathway were found on the BAER recordings of sheep fed high S diet. Abnormalities of peaks and interpeak latencies within BAER recordings were related to histopathological observations of brain stem lesions. Lesions in the areas of the cochlear nuclei and lateral lemniscus were seen in conjunction with altered BAER components. However, abnormalities in BAER recordings and lesions in the brain stem also occurred in the absence of overt clinical signs. Analysis of interpeak latencies between peaks I and IV revealed significant differences among dietary groups. Sheep given diets low in Cu, Mo, and B1 were affected most. Factorial analysis indicated B1 and interactions among Cu, Mo, and B1 as significant factors influencing interpeak latencies.

Animals↗

PubMed1968

Anaerobic brain function: effects of stagnant and anoxic anoxia on persistence of breathing in reptiles.

Turtles tolerate anoxic anoxia about 14 times longer than stagnant anoxia. In snakes and crocodiles this difference is much less marked. Apparently, the remarkable anaerobic viability of turtles is dependent on blood circulation, Analyses of plasma indicate that loss of brain function in anoxic crocodiles is not caused by systemic acidosis or hypoglycemia. It is suggested that the ability of the central nervous system of the turtle to function without oxygen is due to a comparatively high rate of anaerobic uptake or metabolism of glucose.

Animals↗

PubMedDate not supplied