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

We occluded the carotid and vertebral arteries of 12 rats for 15 minutes to measure the brain concentrations of choline and acetylcholine and cerebral blood flow at the end of the ischemic period or 15, 30, or 150 minutes after circulation was reestablished. The animals were sacrificed with microwave radiation focused to the head immediately after a brief infusion of [14C]iodoantipyrine with rapid sampling of arterial blood. Brain tissue samples were extracted with ether to separate the tracer, which was subsequently measured by liquid scintillation counting and used to calculate local cerebral blood flow. The aqueous phase was then processed for the measurement of choline and acetylcholine concentrations by gas chromatography/mass spectrometry. The results showed a large increase in tissue choline content and a decrease in tissue acetylcholine content during ischemia. During recirculation, choline levels progressively declined, reaching levels lower than those in four control rats after 150 minutes of recirculation for most brain regions. A reciprocal relation between the brain choline concentration and local cerebral blood flow was found. Acetylcholine levels showed an initial rebound to greater than control during recirculation, with subsequent normalization. Brain acetylcholine concentration was positively correlated with brain choline concentration, provided that cerebral blood flow was greater than 0.3 ml x g-1 x min-1. Because tissue free choline was depleted in most brain regions 150 minutes after transient ischemia, we speculate that prolonged ischemia may produce a greater depletion of tissue free choline with a resulting decline in tissue acetylcholine. This could play an important role in the cognitive deficit associated with vascular dementia.
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PMID:Time-dependent changes in cerebral choline and acetylcholine induced by transient global ischemia in rats. 202 95

Memory is an intellectual function that is initially and consistently impaired in patients with vascular dementia. Experimental approaches to vascular dementia have so far been confined to investigations of memory impairments in rodent ischemic models. Unilateral middle cerebral artery (MCA) occlusion, multiple small embolization or transient four-vessel occlusion in rats produced acute single or multiple infarctions. In such rats, significant memory impairments occurred during the subacute or chronic phases, but were partially reversible. Permanent stenosis of both common carotid arteries in gerbils caused no ischemic changes at 1 day after stenosis but induced multiple infarctions after 1 week of stenosis, probably due either to chronic recurrent ischemia resulting from transient repetitive obstruction of the carotid arteries or to chronic low perfusion. The memory impairments in this model were persistent. Permanent bilateral common carotid artery occlusion in rats produced multiple infarctions plus white matter changes after 1 week of occlusion. Marked memory impairment was also observed in this model. The results of the above studies suggest that memory impairments due to ischemic causes may be partially reversible provided that the infarctions occur only once and are followed by flow recovery. Memory impairments, however, appear to persist if the brain is exposed to chronic recurrent ischemia or chronic moderately low perfusion. A repetitive or persistent low-flow state appears to be an important factor in determining the irreversibility of cognitive impairments.
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PMID:Experimental basis of multi-infarct dementia: memory impairments in rodent models of ischemia. 205 2

In the last 40 years, blood flow and metabolism in the brain have been measured by many methods of varying resolution and reliability. Modern methods have helped to answer some basic pathophysiologic questions, in particular disproving ongoing global ischemia as a cause for dementia. But much of this physiologic work is confounded by swiftly changing clinical and pathologic understandings of ischemic and other forms of dementia: the field remains limited as much by unresolved clinical questions as by technologic feasibility.
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PMID:Cerebral blood flow and metabolism studies in multi-infarct dementia. 205 5

In this study, vascular dementia (VD, 31 cases), senile dementia of Alzheimer type (DAT, 36 cases) and mixed type dementia (14 cases) were studied by means of magnetic resonance imaging (MRI). Diagnosis of dementia was made according to DSM-III and Hachinski's ischemic score. The areas of periventricular high intensity lesions (PVH) and those of brain parenchyma were measured by digitizer which was connected to a computer. The PVH score was obtained by dividing the areas of PVH by those of brain parenchyma at the level of the body of the lateral ventricule. A multiple variable analysis was applied to the PVH scores and risk factors for dementia using Hayashi's quantification method I. The multiple correlation coefficient between the PVH and the risk factors was 0.685. The most significant correlation was found between Hachinski's ischemic score and the PVH score (partial correlation coefficient: 0.58). Significant correlations were also found between ADL and the PVH score (0.25), as well as between the Hasegawa dementia score and the PVH score (0.24). Using the student T test, it was shown that the large PVH group was significantly correlated to poor ADL, whereas the small PVH group was not. The large PVH group in VD showed lower Hasegawa score than the small PVH group. On the other hand, there was no such correlation in DAT. PVH with prolongation of T2 could exist in various pathological states irrespective of their causes. Diffuse PVH tended to be frequently observed in VD together with poor ADL. It was therefore thought that brain ischemia was the main cause of PVH.
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PMID:[Clinical significance of periventricular high intensity lesions on magnetic resonance imaging in dementia]. 206 92

Vascular dementia is almost always associated with organic brain lesions due to ischemia, not with arteriosclerosis alone. In Japan, more than 50% of dementia in population older than 65 years are of vascular origin. Vascular dementia occurs with diffuse vascular lesions in the cerebral white matter or circumscribed lesions in particular areas such as the thalamus, anterior limb of the internal capsule, and cingulate gyrus, all of which constitute the ascending activating system or the limbic system. Vascular dementia is clinically characterized by stepwise progression, fluctuating course and predominant deterioration of intelligence with relative preservation of personality. Reversibility, disproportionate impairment of intelligence and personality, and dementia caused by a focal lesion observed in vascular dementia pose problems with regard to the classical concept of dementia. The similarity and difference between remitting dementia and disturbance of consciousness remain to be scrutinized.
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PMID:Vascular dementia. 208 4

Ischemic neuronal damage has been believed to make rapid progress in the course of a few days even in delayed selective neuronal death, to say nothing of acute brain necrosis. In the present study, however, we demonstrate for the first time a new type of ischemia-induced neuronal damage which progresses in the course of several weeks or a few months and we tentatively call this process "slowly progressive neuronal damage". We have focused on the chronological changes of neuronal damage in the dorsolateral striatum and neocortex following various durations of transient middle cerebral artery occlusion, which does not cause cerebral infarction and is clinically designated "transient ischemic attack". In the rats subjected to 15 min middle cerebral artery occlusion, the neocortex and lateral striatum were rarely damaged, whereas the small to medium-sized neurons only in the narrow area restricted to the dorsal striatum showed slowly progressive neuronal damage. Prolongation of ischemic duration to 30 min accelerated the evolution of neuronal damage in the dorsolateral striatum and also extended the distribution of neuronal damage to the neocortex, especially to layer III and more superficial layers. Further prolongation of ischemic duration to 45 min resulted in more rapid progress of selective neuronal death in those areas described above, whereas no animal escaped 60 min ischemia, without acute total tissue necrosis in the middle cerebral artery territory. Ischemia-induced slowly progressive neuronal damage may be implicated in the pathogenesis of such slowly progressive neurologic deterioration as dementia or Parkinsonism in patients with cerebral arteriosclerosis.
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PMID:Ischemia-induced slowly progressive neuronal damage in the rat brain. 225 91

Oxygen affinity of hemoglobin, erythrocyte 2,3-diphosphoglycerate (DPG) and adenosine triphosphate (ATP) concentrations were compared before and after oral administration of vinpocetine (TCV-3B) (15 mg/d), a primarily vasodilating agent, for three weeks in eight patients with vascular dementia of the Biswanger type which is characterized by diffuse myelin pallor and multiple lacunes in the cerebral white matter. After vinpocetine administration, oxygen affinity of hemoglobin (P50) was significantly increased (26.5 +/- 0.55 to 27.6 +/- 0.62 mmHg; mean and standard deviation, p less than 0.05), red blood cell (RBC) ATP concentrations were significantly increased (846 +/- 168 to 1,158 +/- 130 mumol/l RBC, p less than 0.05), while DPG concentrations were unaltered (4.46 +/- 0.48 to 4.59 +/- 0.57 mmol/l RBC). There was a significant positive correlation between the increase of P50 and the increase of erythrocyte ATP concentrations (r = 0.67, p less than 0.05). The effect of vinpocetine of enhancing oxygen release of hemoglobin may offer an additional benefit to its primary vasodilating action in the treatment of vascular dementia of the Binswanger type due to chronic ischemia.
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PMID:Effect of vinpocetine on oxygen release of hemoglobin and erythrocyte organic polyphosphate concentrations in patients with vascular dementia of the Binswanger type. 239 97

Nimodipine, a Ca2+ antagonist with cerebrovasodilatory and anti-ischemic effects, binds to rat, guinea pig, and human brain membranes with high affinity (less than 1 nM). Only at higher concentrations has nimodipine been reported to block the release of some neurotransmitters and hormones from neuronal tissue. Nimodipine has no consistent effect on brain oxygen consumption or cortical ATP or phosphocreatine levels, although the ischemia-induced fall of brain ATP levels in gerbils or the lowering of intracellular brain pH in rabbits with focal cerebral ischemia were antagonized by the drug. In rats and baboons with middle cerebral artery occlusion, nimodipine was found to reduce neurological deficits without an increase in intracranial pressure or brain edema. Electrophysiological studies with nimodipine suggested a direct neuronal action. In rabbit dorsal root ganglion cells, concentrations as low as 20 nM were reported to block inward Ca2+ currents. Recent studies have suggested that nimodipine may also improve memory in brain-damaged or old rats, restore sensorimotor function and abnormal walking patterns of old rats, and accelerate acquisition of associative learning in aging rabbits. Blockade of age-related changes in Ca2+ fluxes in rat hippocampal neurones by nimodipine in vitro pointed to neuronal plasma membrane as the site of nimodipine action. The therapeutic usefulness of nimodipine appears not to be limited to cerebral ischemia, but may include dementia, age-related degenerative diseases, epilepsy, and ethanol intoxication.
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PMID:Pharmacological basis for the use of nimodipine in central nervous system disorders. 256 39

Computed tomography is often insensitive to such lesions as atrophic demyelination, enlarged perivascular spaces and infarction in the periventricular white matter. In attempt to better understand the discrepancy between the pathologic and X-CT findings, the author correlated areas that had focal, patchy on X-CT and brains with gross and microscopic findings. Patients with cerebral strokes had larger volume infarcts characterized centrally by necrosis, axonal loss, and demyelination. The progressive subcortical vascular encephalopathy (Binswanger's disease) is characterized by ischemic demyelinization of white matter provoked by hypertensive vascular changes in small vessels and is usually accompanied by multiple lacunar infarcts in a periventricular area and the basal ganglia. Small, deep hemispheric infarcts may be of no clinical significance unless a sufficient aggregate of these occurs. It should be pointed out that many small infarcts are clinically silent, and chronic multifocal ischemia may be responsible for observed senescent changes in cerebral tissue. The extension of the infarcted area might be most important in the development of cerebrovascular dementia. Mixed forms of degenerative dementia and any type of cerebral vascular disease are common and account for 10-20% of all dementias.
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PMID:[Cerebrovascular dementia; correlation of computed and histopathologic findings]. 260 Oct 93

To investigate the relationship between middle cerebral artery (MCA) trunk lesions and the etiology of Binswanger type (B type) infarction, which was demonstrated as a diffuse subcortical low density area/high intensity area by CT/MRI, patients with both MCA lesions and B type infarction were studied clinically. Eighteen patients with B type infarction were diagnosed among 224 patients with MCA occlusion/stenosis on angiography accounting for 8%. The incidence was as high as 25% in M2 stenosis. The mean age of B type infarction patients was 64 years and 16 of them were men. Chronologically stepwize/slowly-progressive deterioration of clinical manifestations were observed in 14. All patients had hemiplegia, though half of them were mild or moderate in severity. Furthermore, aphasia, Gerstmann syndrome and dementia were present in 10, 1 and 2 patients, respectively. Twelve had a history of hypertension, while 11 showed transient decreases with marked changes (more than 31 mmHg in mean arterial blood pressure) in arterial blood pressure during their clinical course. Out of 9 patients in whom cerebral blood flow (CBF) was measured by 133Xe injection method/inhalation method, 7 demonstrated mild to moderate decreases in mean CBF (more than 30 ml/100 g/min) with no relation to the severity of MCA lesions. These findings suggested that hemodynamic mechanisms associated with hypoperfusion due to marked fluctuations in blood pressure are accelerating factors of B type infarction and MCA lesions, even though ischemia in the subcortical area due to leptomeningeal anastomosis may be mild or moderate.
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PMID:[Clinical study on the relationship between middle cerebral artery lesions and Binswanger type infarction]. 260 75


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