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Query: UMLS:C0022116 (ischemia)
 91,303 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Axonal transport of acetylcholinesterase (AChE) and choline acetyltransferase (ChAc) and ultrastructural degenerative changes were compared in isolated nerve segments of rabbit peroneal nerves kept in vivo for 22 h, either with preserved blood supply (control segments) or under conditions of ischemia (ischemic segments). Ischemia abolished the proximo-distal and disto-proximal axonal transport of AChE and the proximo-distal transport of ChAc which, in control segments, were revealed by accumulations of the enzymes at corresponding ends of the segments. Total activities of AChE and ChAc recovered in isolated segments with intact blood supply corresponded to the activities in normal nerves; in ischemic segments, 50% of ChAc activity was lost in 22 h, whereas all AChE activity was preserved. Ultrastructural changes were found in few fibres in control segments and in many fibres in ischemic segments 22 h after nerve interruption. The early changes in control segments correspond to those described in the literature for peripheral stump of severed nerves. The microtubules, neurofilaments and mitochondria were not affected. In ischemic segments, various stages of axoplasmic disintegration occurred in the myelinated and unmyelinated axons:flocculation and clumping of axoplasmic material, decomposition of neurofilaments and microtubules, swelling, formation of amorphous densities and breakdown of mitochondrial cristae. Swelling, amorphous densities, clumping of nuclear chromatin and necrotic mitochondrial changes appeared also in Schwann cells. It is concluded that ischemia blocks axonal transport and brings about, within 22 h, ultrastructural changes both in nerve fibres and in Schwann cells. Cytoplasmic ChAc is affected earlier by necrotic degeneration of the axons than membrane-bound AChE.
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PMID:Effect of ischemia on axonal transport of choline acetyltransferase and acetylcholinesterase and on ultrastructural changes of isolated segments of rabbit nerves in situ. 7 11

Focal brain ischemia was induced by middle cerebral artery occlusion in the rat. The volume of cerebral damage was determined 2 days later by MRI in vivo and in the same animals histologically. The edema volume as measured by MRI and the histologically determined infarction was highly correlated. As a consequence, the neuroprotective effect of the N-methyl-D-aspartate (NMDA) receptor antagonists CGP 40116 and MK 801 were similar with both methods. Excitotoxic neurodegeneration in the rat striatum was induced by direct injection of quinolinic acid. The degree of damage was evaluated in vivo 1 day later by quantitative MRI, and 7 days later by measuring the activities of neuronal marker enzymes choline acetyltransferase and glutamic acid decarboxylase. Striatal damage assessed using the three approaches was highly correlated. Cerebroprotective efficacy of the NMDA receptor antagonist CGP 40116 was indistinguishable based on all methods. MRI was more reproducible than the enzymatic methods and was faster and simpler than histologic examination for routine analysis of excitotoxic damage and cerebroprotection in vivo in a pharmaceutical research environment.
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PMID:Application of magnetic resonance imaging to the measurement of neurodegeneration in rat brain: MRI data correlate strongly with histology and enzymatic analysis. 136 Oct 20

Brief (5 min) bilateral carotid occlusion in the gerbil produces forebrain ischemia resulting, as previously reported, in almost complete neuronal loss in the CA1 region of the hippocampus; this neuronal destruction occurs between the 4th and 7th day post-ischemia. Various hippocampal biochemical indices were measured from just after such ischemia to 21 days of recirculation, and the temporal pattern of changes compared with that of cell loss. The level of thiobarbiturate reacting substances (TBARS), a measure of lipid peroxidation, was greatly elevated at 30 min after ischemia, rapidly returned to normal levels (by 60 min), but was again elevated on days 4-14. The beginning of this second period of elevation correlated closely with the onset of neuronal loss and the very abrupt and large (to about 32%) decrease in specific N-methyl-D-aspartate (NMDA) binding sites, measured with radioactive CPP. The number of muscarinic binding sites, measured with radioactive quinuclidinyl benzilate, showed an even greater decrease (to 13%) at 21 days post-ischemia, but the decrease was delayed (starting at day 7) and much more gradual than the loss in NMDA binding. In neither case was there any change in binding affinity at any time studied. Acetylcholine (ACh) concentrations were initially greatly decreased (to about 15% at 5 min), transiently increased (to about 130% at 30 min), and then decreased again (to about 15% at 60 min), after which gradual recovery occurred and was completed by day 14. Since no inhibition of choline acetyltransferase activity was observed at any time, the reversible depression in ACh must depend upon some factor other than loss of this key synthetic enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Time course of changes in lipid peroxidation, pre- and postsynaptic cholinergic indices, NMDA receptor binding and neuronal death in the gerbil hippocampus following transient ischemia. 182 14

Antagonists for the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor may have therapeutic potential as neuroprotectant agents in conditions of neuronal degeneration that include brain ischemia, Huntington's chorea, and Alzheimer's disease. Here we have investigated the pharmacological actions of LY274614, a structurally novel competitive NMDA receptor antagonist, for pharmacological selectivity and neuroprotectant effects following systemic administration. LY274614 potently displaced NMDA receptor ([3H]CGS19755) binding (IC50 = 58.8 +/- 10.3 nM), but had no appreciable affinity at [3H]AMPA or [3H]kainate receptor sites at up to 10,000 nM. NMDA-induced convulsions in neonatal rats or NMDA-induced lethality in mice are potently and selectively antagonized by i.p. or p.o. LY274614. Oral doses showed a delayed but prolonged duration of effect. In adult rats, the neurodegenerative effects (loss of choline acetyltransferase activity) following the intrastriatal infusions of NMDA or quinolinate, but not kainate, were prevented by LY274614 (2.5 to 20 mg/kg i.p.). LY274614 is an effective neuroprotectant agent against NMDA receptor-induced toxicity when administered systemically and is a promising therapeutic agent for conditions where glutamate plays a role in the pathology of neuronal degeneration.
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PMID:Neuroprotectant effects of LY274614, a structurally novel systemically active competitive NMDA receptor antagonist. 183 88

The pattern of ischemia-induced cell death was examined with histochemical methods in the striatum of adult gerbils 4 and 7 days after transient forebrain ischemia. The results showed a massive loss of immunoreactivity to enkephalin and tachykinins, peptides present in striatal efferent neurons. In contrast, neurons expressing acetylcholinesterase activity, or choline acetyltransferase immunoreactivity, as well as neurons immunoreactive for somatostatin, were relatively preserved in areas of severe neuronal loss. The selective vulnerability of subpopulations of striatal neurons to transient ischemia in the adult is similar to that observed in the neonate and after local injections of agonists of N-methyl-D-aspartate receptors, but not of agonists of other glutamate receptor subtypes. It also presents striking similarities to the pattern of neuronal death observed in Huntington's disease. The results further support a role for overstimulation of a subtype of excitatory amino acid receptor in ischemia-induced cell death and show that the selective sparing of subpopulations of striatal interneurons after ischemic injury is not related to immaturity of these neurons but also occurs in the adult.
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PMID:Ischemic damage in the striatum of adult gerbils: relative sparing of somatostatinergic and cholinergic interneurons contrasts with loss of efferent neurons. 197 9

Little is known about the alterations in the neurochemical anatomy of the brain in the static encephalopathies of childhood, of which one cause is hypoxia-ischemia. We and others have previously shown in neonatal rodent that experimental hypoxia-ischemia results in an increase in the density of striatal cholinergic neurons (number/mm3). There is a rostrocaudal gradient for this effect within the striatum, with as much as a 50% increase in density caudally. It has not been known what effect this injury has on the distribution of striatal cholinergic neuropil. We have therefore investigated effects on striatal cholinergic neuropil, demonstrated with a monoclonal antibody to choline acetyltransferase (CAT) and the immunoperoxidase technique. Because individual CAT-positive fibers in the striatum are too numerous to be directly counted, we have quantified relative effects on neuropil at the population level using segmented field analysis within the same section. We find that hypoxic-ischemic injury results in a significant increase in the proportion of the injured striatum occupied by high density CAT-positive neuropil staining. This change is persistent, as it is also observed in adult rats. The increase is uniform in the rostrocaudal dimension. Our measure of CAT-positive neuropil staining, being relative, cannot determine whether the observed increase in staining is strictly due to striatal shrinkage with compaction of fibers or whether, in addition, there has been sprouting. The latter possibility is suggested by the lack of a correlation between the degree of shrinkage and changes in area occupied by positive staining. While the functional significance of these changes is not known, they support the concept that striatal cholinergic systems are resistant to hypoxic-ischemic injury and that an abnormal predominance of these systems may play a role in the persistent alterations of motor control observed clinically in this form of injury.
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PMID:The effect of neonatal hypoxia-ischemia on striatal cholinergic neuropil: a quantitative morphologic analysis. 204 79

The biochemical changes of the elements of cholinergic neurotransmission (choline acetyltransferase, ChAT; acetylcholinesterase, AChE; butyrylcholinesterase, BuChE; and muscarinic cholinergic receptors, mAChR) as well as the electrolyte content were studied in ischemic lumbar spinal cord segments of newborn pigs. Ischemia was elicited by ligating the aorta for 30 min. Although no significant changes were observed in the sodium, potassium and calcium content of ischemic spinal cords, the calcium content was slightly elevated, to 119.3% of the control value. Whereas significant depletions were observed in both AChE and ChAT activities (to 69.1 and 87.7% of the control value, respectively), there was no significant change in BuChE activity as compared to the control value. The mAChR were also decreased, from 33.25 +/- 2.2 to 27.18 +/- 1.9 fmol/mg protein, while the Kd value was not significantly altered. It is concluded that even a relatively brief interruption of the oxygen supply can cause severe damage in the lumbar spinal cord of the newborn pig, affecting the cholinergic neurotransmission elements. This animal model might be suitable for studying the effects of hypoxia in newborns and children during chest operations involving the descending aorta.
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PMID:Effects of ischemia on cholinergic neurotransmission and electrolyte content in newborn pig lumbar spinal cord. 215 20

We have observed asymmetries in perfusion between the cerebral hemispheres in immature rats previously subjected to carotid ligation in a model of perinatal hypoxia-ischemia. These asymmetries are associated with marked differences in the number of neurons stained positive by immunoperoxidase protocols for cholinergic neurons utilizing a monoclonal antibody to choline acetyltransferase. These differences are likely to be spurious and due to the asymmetry of perfusion, because fewer stained neurons appear on the unligated side of control animals, in the absence of gliosis or neuron loss. We recommend that quantitative morphologic studies in this model be performed on immersion-fixed specimens.
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PMID:Asymmetrical perfusion fixation in a rodent model of perinatal hypoxia-ischemia may lead to artifactual morphologic asymmetries. 246 11

The fast axonal transport of acetylcholinesterase (AChE) and the slow transport of choline acetyltransferase (ChAT) were measured by the stop-flow ligation technique in the sciatic nerve of rabbits 6 and 24 h after ischemia performed by the occlusion of the abdominal aorta which lasted 40 min. Activities of these enzymes were also measured in punched samples of the spinal cord (L5-6). Results were correlated with those obtained from the sham-operated control group. Six h after ischemia, its only apparent effect was a different distribution of accumulated enzymes in the central nerve segments. Twenty-four h after ischemia, the transport of AChE was markedly depressed; proximodistal accumulation decreased by 68%, whereas enzyme activity in the intact contralateral nerve and in the ventral horns of the spinal cord was preserved. No effect of ischemia on the retrograde axonal transport of AChE was observed in this experimental model. Cytoplasmic ChAT is much more susceptible to necrotic degeneration than membrane-bound AChE; 24 h after ischemia its activity decreased significantly in all investigated parts of the sciatic motoneurones but the rate of slow axonal transport did not seem to be affected.
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PMID:Effect of spinal cord ischemia on axonal transport of cholinergic enzymes in rabbit sciatic nerve. 246 95

Acetylcholine (ACh) is the neurotransmitter related to learning and memory. The activity of its metabolic enzyme - choline acetyltransferase (CAT) is found to be remarkably decreased at autopsy. We consider that there is some relationship between ACh and cerebrovascular dementia such as dementia in ischemia and forgetfulness after ischemia. So we studied the relationship between ischemia and cholinergic neuron. We examined changes of muscarinic cholinergic receptor (m-ChR) in experimental ischemia by binding assay and autoradiography, and performed immunohistochemical study of CAT that is, acetylcholine synthetase, by PAP method. We also studied delayed neuronal death from the aspect of cholinergic system because the hippocampus receives ACh pathway arising from the basal nucleus. Materials used include: Pulsinelli's 4 vessel occluded rats, Tamura's MCA occluded rats and forebrain ischemia mongolian gerbils. In ischemia, the number of m-ChR decreased and binding affinity of m-ChR increased, and recirculation caused increased the number of m-ChR. While m-ChR changed immediately after ischemia, it was not until the fourth day that CAT positive cells decreased in hippocampus. In other words, at first m-ChR in postsynaptic membrane changed in ischemia, and with the progress of neuronal damage, CAT also changed. After m-ChR decreased in the thalamus, stria terminalis and Meynert nucleus 1 day following ischemia, it decreased in hippocampus after 7 days. We can consider receptor changed corresponding to the pathway of cholinergic neuron. Our study suggested that the receptor change in cholinergic system plays some role in the delayed neuronal death in the hippocampus.
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PMID:[Changes in muscarinic cholinergic receptor and choline acetyltransferase in experimental ischemic brain]. 267 78


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