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Query: UMLS:C0038454 (stroke)
 147,016 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A morphological and electrophysiological study was made on a unique primary mechanosensory neuron, the anterior gastric receptor (AGR), previously shown to arise from power-stroke muscle gm1 of the gastric mill system in the lobster foregut. Ultrastructural analysis of horseradish peroxidase injected AGR demonstrated that its peripheral dendrites do not ramify in muscle but are confined strictly to the connective tissue/epidermal interface in the tendon of gm1. These terminals are rich in mitochondria and at their very endings are free of glial cell wrapping, suggesting that they are the site at which mechano-transduction occurs. Extracellular axonal recordings from an in vitro neuromuscular preparation consisting of the gm1 muscle still attached to the stomatogastric nervous system, revealed that AGR is activated by passive stretch of gm1. The response to ramp stimuli displays dynamic and static components, both of which increase with the amplitude of applied stretch, while the dynamic component is also velocity sensitive. AGR is also activated by muscle contraction here elicited either by application of exogenous acetylcholine, the excitatory neurotransmitter for gm1, or by electrical stimulation of the motoneurons (GM) themselves. Consistent with a receptor lying in-series with its muscle, therefore, the effective stimulus of AGR in vivo is probably an increase in tension exerted on the tendon during active muscle contraction. In neuromuscular preparations including the bilateral commissural ganglia, stretching gm1 reflexly activates GM motoneurons at low stimulus strengths but leads to an inactivation of GM motoneurons at high stimulus strengths. This is consistent with earlier findings that both responses can be elicited by direct electrical stimulation of AGR. The functional implications of AGR's anatomical relationship with muscle gm1, the receptor's response properties, and its central effects on motor output to gm1 are discussed. Comparison is also drawn between this first reported example of a true tendon receptor in invertebrates and muscle receptors of vertebrates.
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PMID:Structural and functional characterization of a muscle tendon proprioceptor in lobster. 864 71

This article reviews cellular energy transformation processes and neurochemical events that take place at the time of brain injury and shortly thereafter emphasizing hypoxia-ischemia, cerebrovascular accident, and traumatic brain injury. New interpretations of established concepts, such as diffuse axonal injury, are discussed; specific events, such as free radical production, excess production of excitatory amino acids, and disruption of calcium homeostasis, are reviewed. Neurochemically-based interventions are also presented: calcium channel blockers, excitatory amino acid antagonists, free radical scavengers, and hypothermia treatment. Concluding remarks focus on the role of clinical neuropsychologists in validation of treatment interventions.
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PMID:Neurochemical mechanisms in brain injury and treatment: a review. 894 54

Seven patients with mitochondrial encephalomyopathies were studied for peripheral neuropathy by clinical, electrophysiological and pathological examinations. The clinical manifestation of neuropathy varied from asymptomatic to mild and moderate sensorimotor symptoms with painful paresthesia. Five patients (2 with mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes, and 3 with myoclonic epilepsy and ragged-red fibers, MERRF) had clinical symptoms and signs of polyneuropathy associated mainly with decreased amplitudes of the compound muscle or nerve action potentials in an electrophysiological study indicating axonal degeneration. Sural nerve biopsy from 1 MERRF patient, also confirmed an axonal degeneration with reduction of large myelinated fibers. Mitochondrial DNA analysis of the sural nerve from this patient showed a point mutation from A to G transition at the nucleotide position 8344 with 80% mtDNA mutation. The results of this study suggest that peripheral neuropathy is not uncommon in mitochondrial encephalomyopathies and is predominantly due to axonal degeneration.
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PMID:Peripheral neuropathy in mitochondrial encephalomyopathies. 905 67

The nontoxic C fragment of tetanus toxin (TC) can transport other proteins from the circulation to central nervous system (CNS) motor neurons. Increased levels of CuZn superoxide dismutase (SOD) are protective in experimental models of stroke and Parkinson's disease, whereas mutations in SOD can cause motor neuron disease. We have linked TC to SOD and purified the active recombinant proteins in both the TC-SOD and SOD-TC orientations. Light microscopic immunohistochemistry and quantitative enzyme-linked immunosorbant assays (ELISA) of mouse brainstem, after intramuscular injection, demonstrate that the fusion proteins undergo retrograde axonal transport and transsynaptic transfer as efficiently as TC alone.
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PMID:Delivery of recombinant tetanus-superoxide dismutase proteins to central nervous system neurons by retrograde axonal transport. 921 90

Focal cerebral infarction (stroke) due to unilateral occlusion of the middle cerebral artery in mature rats produces deficits in sensorimotor function of the contralateral limbs that recover partially over time. We found that biweekly intracisternal injection of basic fibroblast growth factor (bFGF; 0.5 microg/injection), a potent neurotrophic polypeptide, markedly enhanced recovery of sensorimotor function of the contralateral limbs during the first month after stroke without apparent adverse side effects. Immunostaining for growth-associated protein 43 (GAP-43), a molecular marker of axonal sprouting, showed a selective increase in GAP-43 immunoreactivity in the intact sensorimotor cortex contralateral to cerebral infarcts following bFGF treatment. These results show that bFGF treatment can enhance functional recovery after stroke, and that the mechanism may include stimulation of neuronal sprouting in the intact brain.
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PMID:Intracisternal basic fibroblast growth factor enhances functional recovery and up-regulates the expression of a molecular marker of neuronal sprouting following focal cerebral infarction. 922 35

We report the clinical, pathological, and genetic findings of a case of MELAS syndrome. This was a man who died for metabolic failure at the age of 27 years. His familiar history was positive for hypoacusia and stroke. He was of short stature and presented mild mental retardation. Since the age of 21 he suffered from recurrent brain-ischemic lesions mainly in the occipital lobes, documented by repeated CT scans. The laboratory data and muscle biopsy disclosed lactic acidosis with ragged red fibres. Neurophysiological data and peripheral nerve biopsy showed an axonal neuropathy. A point mutation in the tRNALeu(UUR) gene of mitochondrial DNA was detected in 5 post-mortem tissues and in muscle biopsy. No defects of mitochondrial respiratory chain were detected. The histological and ultrastructural studies of the brain showed multiple and heterogeneous ischemic lesions with no obvious alterations of cerebral blood vessels. These lesions do not correspond to the vascular territories of main cerebral arteries. Our observations support the hypothesis that local metabolic alterations would play a crucial role in the pathogenesis of cerebral ischemic lesions in MELAS. The correlation between genetic, biochemical, and pathological data are discussed.
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PMID:Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). 926 44

Axons, the functional elements in CNS white matter, are frequently injured by ischemia, especially in the context of stroke. The pathophysiology of axonal injury induced by energy deprivation has been analyzed in the rat optic nerve and involves excessive calcium influx by way of reverse Na+/Ca2+ exchange and Ca2+ channels. Evidence is presented that CNS axonal function can be supported in the absence of glucose by intrinsic energy reserves provided through the breakdown of astrocytic glycogen. It is argued that energy is transferred from astrocytes to axons in the form of lactate, which is able to maintain axonal function when substituted for glucose. These observations complement the increasingly convincing hypothesis that astrocytes and neurons interact metabolically, both in the course of normal activity and under pathological conditions such as ischemia. The emerging picture would be no surprise to Camillo Golgi, who predicted a close facsimile of this glial-neuronal interaction more than a century ago.
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PMID:Does astrocytic glycogen benefit axon function and survival in CNS white matter during glucose deprivation? 929 56

Recently, we have shown increases in the immunoreactivity for neuropeptide Y and tyrosine hydroxylase in the insular cortex surrounding the focal infarction after middle cerebral artery occlusion. In addition, the immunoreactivity for neuropeptide Y, leucine-enkephalin, dynorphin, and neurotensin increased ipsilaterally in the amygdala. Increases in immunoreactivity were observed in nerve terminals and fibers; changes in the neuropeptides were maximal 3 days after stroke. Local excitotoxic injury of the insular cortex also elicited similar neuropeptide changes unilaterally in the same regions. In this study, immunohistochemistry was used following intracerebroventricular injection of colchicine and stroke to determine whether blockade of axonal transport would prevent these neurochemical changes. These experiments would also locate the putative cellular origins of the neurochemicals involved. Control rats received either colchicine injection or middle cerebral artery occlusion alone. Injection of colchicine enhanced the periinfarct increase in neuropeptide Y but did not alter the increase in tyrosine hydroxylase. The neuropeptide Y increase was observed in local cortical neurons. Colchicine prevented the increases in immunoreactivity for the neuropeptides in the amygdala on the side of stroke, although there were small perikarya that showed immunoreactivity for these neuropeptides within the amygdala on both sides. We conclude that local cortical neurons are responsible for the increase in neuropeptide Y in the periinfarct region, that the cortical increase in tyrosine hydroxylase is not dependent on fast axonal transport, and that axonal transport of signals from the insular cortex to the amygdala is critical in mediating the amygdalar neuropeptide changes seen after stroke.
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PMID:Colchicine affects cortical and amygdalar neurochemical changes differentially after middle cerebral artery occlusion in rats. 933 Nov 69

Thromboembolic stroke in rats leads to a well-described pattern of histopathological and behavioral abnormalities. However, limited data are available in animal models concerning the response of the white matter to embolic events. The purpose of this study was to document patterns of white matter abnormalities using beta-amyloid precursor protein (betaAPP) immunocytochemistry as a marker of axonal damage. Twelve male Wistar rats underwent photochemically induced right common carotid artery thrombosis (CCAT) or sham procedures. At 3 days after CCAT, rats were perfusion-fixed and sections immunostained for the visualization of betaAPP or stained with hematoxylin and eosin for routine histopathological analysis. As previously described, CCAT produced small ipsilateral embolic infarcts and ischemic cell change within gray matter structures including the medial cerebral cortex, striatum, hippocampus and thalamus. In areas of frank infarction, numerous reactive profiles were observed within borderzones of the damaged site. However, betaAPP immunocytochemistry also revealed reactive axonal profiles within various white matter tracts including the corpus callosum, external capsule and fimbria of the hippocampus. In many cases, the presence of axonal damage could not be appreciated with routine hematoxylin and eosin staining. These data indicate that CCAT leading to platelet embolization to the brain not only produces embolic infarcts but also produces more subtle white matter abnormalities. Previously undetected white matter damage would be expected to participate in the sensorimotor and cognitive behavioral deficits following embolic stroke.
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PMID:White matter alterations following thromboembolic stroke: a beta-amyloid precursor protein immunocytochemical study in rats. 960 May 99

Axonal injury following cerebral ischaemia has attracted less attention than damage in grey matter. However, it is becoming increasingly recognised that axons are highly vulnerable to focal ischaemia [D. Dewar, D.A. Dawson, Changes of cytoskeletal protein immunostaining in myelinated fibre tracts after focal cerebral ischaemia in the rat, Acta. Neuropathol., 93 (1997) 71-77] [2]; [L. Pantoni, J.H. Garcia, J.A. Gutierrez, Cerebral white matter is highly vulnerable to ischemia, Stroke, 27 (1996) 1641-1647] [10]; [P. S. Yam, T. Takasago, D. Dewar, D.I. Graham, J. McCulloch, Amyloid precursor protein accumulates in white matter at the margin of a focal ischaemic lesion, Brain Res., 760 (1997) 150-157] [15]. Since white matter does not contain neuronal cell bodies or synapses it is likely that the mechanisms of injury and strategies for its protection are different from those in grey matter. In order that the effect of therapeutic intervention on the protection of axons can be assessed, a method by which axonal injury can be mapped and quantified is required. For this purpose, we investigated immunocytochemical methods using amyloid precursor protein (APP) following permanent middle cerebral artery occlusion in the rat. APP is transported by fast anterograde axonal transport [E.H. Koo, S.S. Sisodia, D.R. Archer, L.J. Martin, A. Weidemann, K. Beyreuther, P. Fischer, C.L. Masters, D.L. Price, Precursor of amyloid protein in Alzheimer disease undergoes fast anterograde axonal transport, Proc. Natl. Acad. Sci. U.S.A. 87 (1990) 1561-1565] [7] and has been shown to accumulate following a variety of insults to axons, indicative of dysfunction of axonal transport [R.N. Kalaria, S.U. Bhatti, E.A. Palatinsky, D.H. Pennington, E.R. Shelton, H.W. Chan, G. Perry, W.D. Lust, Accumulation of the beta amyloid precursor protein at sites of ischemic injury in rat brain, Neuroreport, 4 (1993) 211-214] [4]; [T. Kawarabayashi, M. Shoji, Y. Harigaya, H. Yamaguchi, S. Hirai, Expression of APP in the early stage of brain damage, Brain Res., 563 (1991) 334-338] [5]; [N. Otsuka, M. Tomonaga, K. Ikeda, Rapid appearance of beta-amyloid precursor protein immunoreactivity in damaged axons and reactive glial cells in rat brain following needle stab injury, Brain Res., 568 (1991) 335-338] [9]; [K. Shigematsu, P. L. McGeer, Accumulation of amyloid precursor protein in neurons after intraventricular injection of colchicine, Am. J. Pathol., 140 (1992) 787-794] [12]. We have been able to map the topographical relationship between APP accumulation and region of infarction using immunocytochemistry and image analysis techniques. Additionally, using a semi-quantitative scoring system, we have demonstrated that there is a relationship between the amount of APP accumulation and the volume of infarction following middle cerebral artery occlusion. These methods will be useful in the future for the assessment of therapeutic interventions on the protection of axons following ischaemic injury.
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PMID:Topographical and quantitative assessment of white matter injury following a focal ischaemic lesion in the rat brain. 963 Jul


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