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

Changes in cerebral cortex concentrations of high-energy phosphates, glycolytic metabolites, citric acid cycle intermediates, associated amino acids, and ammonia, were studied after 5, 15 and 30 min of incomplete ischemia in rats anesthetized with 70% N2O or 150 mg.kg-1 of phenobartibal. Previous results have shown that with this type of ischemia (bilateral carotid artery occlusion combined with reduction in blood pressure to 50 mm Hg) cortical blood flow is reduced to below 10% of nitrous oxide values, whether animals are anesthetized with 70% N2O or 150 mg.kg-1 of phenobarbital. In animals under 70% N2O, changes in tissue concentrations of phosphocreatine, ATP, ADP and AMP were similar to those previously obtained in complete ischemia. However, some glucose remained in the tissue, and the lactate concentrations gradually rose to reach excessive values. Changes occuring in glycolytic and citric acid cycle intermediates were similar to those seen in complete ischemia but, after 30 min, there was some reduction in the pool size of amino acids. In those animals given phenobarbital and which lost all EEG activity during ischemia, changes in cerebral metabolites were virtually identical to those observed in nitrous oxide-anesthetized animals. However, some animals exposed to 5 or 15 min of ischemia had some remaining EEG activity. In these, cerebral energy state was significantly less deranged, and levels of glycogen, glucose and pyruvate were higher.
Stroke
PMID:Effects of phenobarbital in cerebral ischemia. Part I: cerebral energy metabolism during pronounced incomplete ischemia. 2 84

The authors determined peripheral-blood ammonia level in patients with cerebral strokes. The determinations were done by the method of Konitzer et al. on the 1st, 3rd and 7th days of the disease. The results of determinations were subjected to statistical analysis with the t test of Student. It was found that the mean serum ammonia level in patients with cerebral stroke on the 1st day of the disease was higher than in the control group. The difference was statistically significant. The level of ammonia in the blood of patients with cerebral haemorrhage was significantly higher on the 1st day of the disease than in patients with encephalomalacia. The difference was statistically significant with error probability of 0.05.
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PMID:[Levels of ammonia in patients with stroke]. 63 30

The changes in mental status during cerebral malaria, heat stroke, and recovery from major surgery are clinically similar, and are associated with high circulating concentrations of cytokines that can induce nitric oxide generation in vascular walls. This vascular nitric oxide could diffuse across the blood brain barrier, causing functional changes that include inhibition of glutamate-induced calcium entry, reduced activity of the calcium-dependent nitric oxide synthase, and thus reduced nitric oxide formation, in post-synaptic neurons. Certain general anaesthetics and ethanol reduce glutamate-induced calcium entry into post-synaptic cells, and so would also reduce the rate of formation of neuronal nitric oxide. In view of the apparent importance of glutamate-induced nitric oxide in excitatory neurotransmission, a reduction in neuronal nitric oxide could help explain why these otherwise unrelated influences alter central nervous system function in a similar manner. In particular, this reduction could rationalise why heat stroke, ethanol excess, morphine poisoning, and conditions with high blood ammonia concentrations are easily confused clinically with cerebral malaria.
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PMID:Possible central role of nitric oxide in conditions clinically similar to cerebral malaria. 138 58

Heat stroke was induced in intact rats in a thermal chamber (45 degrees C) and simultaneously a group of animals was subjected to overheating for the same time but was given intraperitoneal injections of ionol (120 mg/kg) for 2 days and 30 minutes before exposure in the chamber. Significant increase of the concentration of intermediates--lactate, pyruvate, malate, glutamate, ammonia--and decrease of the alpha-ketoglutarate content occurred in the renal tissue in animals of both groups. The NAD/NADH ratio in the cytoplasm and mitochondria reduced essentially, to a greater degree in animals given ionol injections. The last named were distinguished by higher survival and lower degree of hyperthermia.
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PMID:[The effect of ionol on oxidative-reductive processes in the kidney during heat stroke]. 261 12

Viable Hepatocytes were isolated from adult canine liver by in situ collagenase perfusion, and cultured on collagen coated borosilicate glass plates (100 X 200mm) at confluent cell density. The medium of hepatocytes in the primary culture was L-15 supplemented with aprotinin 5000U/L, proline 30mg/L, insulin 10(-8)M, dexamethasone 10(-8)M, glucagon 10(-8)M, and h-EGF 10ng/ml. Long-stroke type bioartificial liver module consisted of 200 glass plates with hepatocytes. It contained 6 billion primary cultured cells in total, that is almost equivalent to 30% of the normal canine liver. All hepatocytes in the module were quite viable during 2 weeks in the perfusion culture, and maintained various liver functions at a high level. Gluconeogenesis was 368.0 +/- 15.4mg/module/hr, albumin synthesis was 19.1 +/- 2.5mg/module/day, ureogenesis was 3.7 +/- 0.1mg/module/hr, and ammonia metabolism was 8.4mg/module/hr. Moreover, those functions were maintained at least 2 weeks in the canine plasma as well as in the culture medium with hormones. This hybrid bioartificial liver may exert various liver functions like a liver in situ.
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PMID:[Hybrid bioartificial liver using canine hepatocytes in primary culture]. 276 24

Monolayer cultures of hepatocytes were shown to have good function when compared with suspended cells. The authors manufactured a new hybrid artificial liver containing hepatocyte monolayers and evaluated its function. Hepatocytes isolated from an adult dog liver were cultured on collagen coated borosilicated glass (10 X 20 X 0.04 cm). A long-stroke artificial liver module was constructed by stacking 200 glass plates bearing hepatocytes, which were viable and functioned well during 4 weeks in perfusion culture; glyconeogenesis = 110 ng/micrograms DNA/min, urea synthesis = 3.6 ng/micrograms DNA/min and albumin synthesis = 29 micrograms/10(6) cells/day at the 5th day of perfusion. The levels were maintained for 2 weeks. The new device was applied to anhepatic dogs (Group 3) and compared with untreated (Group 1) and plasma exchange dogs (Group 2). The survival times were 21.3 +/- 5.6 hours in Group 1 (N = 6), 27.8 +/- 4.0 hours in Group 2 (N = 3), and 55.0 +/- 10.3 hours in Group 3 (N = 4). The longest survival was 65 hours. Serum ammonia increased to over 2,000 micrograms/dl after 12 hours in Groups 1 and 2, but remained under 400 micrograms/dl in Group 3. This new type of hybrid system may be a pilot design for the complete artificial liver.
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PMID:A hybrid bioartificial liver composed of multiplated hepatocyte monolayers. 321 60

The decrease in myocardial contractility during ischemia, hypoxia, and extracellular acidosis has been attributed to intracellular acidosis. Previous studies of the relationship between pH and contractile state have utilized respiratory or metabolic acidosis to alter intracellular pH. We developed a model in the working perfused rat heart to study the effects of intracellular acidosis with normal external pH and optimal O2 delivery. Intracellular pH and high-energy phosphates were monitored by 31P nuclear magnetic resonance spectroscopy. Hearts were perfused to a steady state with a medium containing 10 mM NH4Cl (extracellular pH, 7.4). The subsequent washout of NH3 from the cytosol generated a slight acidosis (from intracellular pH 7.0 to 6.8) which was associated with little change in the determinants of O2 consumption (rate-pressure product) and O2 delivery (coronary flow). Acidosis induced a substantial decrease in aortic flow and stroke volume which was associated with little change in peak systolic pressure. Results were qualitatively similar at different external [Ca2+] (1.75, 2.5, 3.15 mM) and preload (12 or 21 cmH2O) but were most prominent at the lowest external [Ca2+] and left atrial pressure. In contrast to this model of isolated intracellular acidosis, hearts subject to a respiratory (extracellular plus intracellular) acidosis showed a marked reduction in pressure development. It was concluded that 1) for the same intracellular acidosis the influence on tension development was more pronounced with a combined extra- and intracellular acidosis than with an isolated intracellular acidosis, and 2) stroke volume at constant preload was impaired by intracellular acidosis even though changes in developed pressure were minimal. These observations suggest that isolated intracellular acidosis has adverse effects on diastolic compliance and/or relaxation.
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PMID:Influence of intracellular acidosis on contractile function in the working rat heart. 342 50

By means of emission computed tomography (ECT), we used 18F-fluorodeoxyglucose (18FDG) and 13N-ammonia (13NH3) as indicators of abnormalities in local cerebral glucose utilization (LCMRglc) and relative perfusion, respectively. The ECAT positron tomograph was used to scan normal control subject and 10 stroke patients at various times during recovery. In normal subjects, mean CMRglc was 5.28 +/- 0.76 mg per 100 gm tissue per minute (mean +/- SD; N = 8). In patients with stroke, mean CMRglc in the contralateral hemisphere was moderately decreased during the first week, profoundly depressed in irreversible coma, and normal after clinical recovery. Quantification was restricted by incomplete understanding of tracer behavior in diseased brain, but relative local distributions of 18FDG and 13NH3 trapping qualitatively reflected the increases and decreases as well as coupling and uncoupling expected for local alterations in glucose utilization and perfusion in stroke. Early after cerebrovascular occlusion there was a greater decrease in local trapping of 13NH3, than 18FDG within the infarct, probably because of increased anaerobic glycolysis. Otherwise, 18FDG was a more sensitive indicator of cerebral dysfunction than was 13NH3. Hypometabolism, due to deactivation or minimal damage, was demonstrated with the 18FDG scan in deep structures and broad zones of cerebral cortex that appeared normal on x-ray computed tomography and technetium 99m pertechnetate scans. In its present state of development, the 18FDG ECT method should aid in defining the location and extent of altered brain in studies of disordered function after stroke. With improved knowledge of tracer behaviour in diseased brain, the method has promise for mapping the response to therapeutic intervention and increasing our understanding of how the human brain responds to stroke.
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PMID:Effects of stroke on local cerebral metabolism and perfusion: mapping by emission computed tomography of 18FDG and 13NH3. 696 12

13N-labeled ammonia was used to investigate 1) the cerebral extraction and clearance of ammonia, 2) the mechanism by which capillaries accommodate changes in cerebral blood flow (CBF) and 3) its use for the measurement of CBF. The unidirectional extraction of 13NH3 in rhesus monkeys was measured during PaCO2 induced changes in CBF and dog studies were performed using in vitro tissue counting techniques to examine 13NH3 extraction in gray and white matter, mixed tissue and cerebellum during variations in CBF produced by combinations of embolization, local brain compression, and changes in PaCO2. The single pass extraction fraction of 13NH3 varied from about 70 to 20% over a CBF range of 12 to 140 cc/min/100 g. Capillary permeability-surface area product (PS) estimates with a Renkin/Crone model show PS increasing with CBF. The magnitude and rate of increase in PS with CBF was highest in gray matter greater than mixed tissue greater than white matter. Tissue extraction of 13NH3 vs CBF relationship was best described by a unidirectional transport model in which CBF increases by both recruitment of capillaries and by increases of blood velocity in open capillaries. This saturable-recruitment model provides a possible explanation for the mechanism of flow changes at the capillary level. The net 13NH3 extraction subsequent to an i.v. injection increases non-linearly with CBF. Doubling or halving basal CBF produced from 35 to 50% changes in the 13N tissue concentrations with further increases in CBF associated with progressively smaller changes in 13N concentrations.
Stroke
PMID:Cerebral extraction of N-13 ammonia: its dependence on cerebral blood flow and capillary permeability -- surface area product. 730 45

Brain imaging is performed using radiopharmaceuticals by single photon emission computed tomography (SPECT) and positron emission tomography (PET). SPECT and PET radiopharmaceuticals are classified according to blood-brain-barrier permeability, cerebral perfusion and metabolism receptor-binding, and antigen-antibody binding. The blood-brain-barrier (BBB) SPECT agents, such as 99mTcO4-, [99mTc]DTPA, 201TI and [67Ga]citrate are excluded by normal brain cells, but enter into tumor cells because of altered BBB. These agents were used in the earlier period for the detection of brain tumors. SPECT perfusion agents such as [123I]IMP, [99mTc]HMPAO, [99mTc]ECD are lipophilic agents and therefore, diffuse into the normal brain. These tracers have been successfully used to detect various cerebrovascular diseases such as stroke, Parkinson disease, Huntington's disease, epilepsy, dementia, and psychiatric disorders. Xenon-133 and radiolabeled microspheres have been used for the measurement of cerebral blood flow (CBF). Important receptor-binding SPECT radiopharmaceuticals include [123I]QNE, [123I]IBZM, and [123I]iomazenil. These tracers bind to specific receptors in the brain, thus displaying their distribution in various receptor-related cerebral diseases. Radioiodinated monoclonal antibodies were used for the detection of brain tumors. PET radiopharmaceuticals for brain imaging are commonly labeled with positron-emitters such as 11C, 13N, 15O, and 18F, although other radionuclides such as 82Rb, 62Cu and 68Ga also were used. The brain uptake of [13N]glutamate, [68Ga]EDTA and [82Rb]RbCl depends on the BBB permeability, but these are rarely used for brain imaging. Several cerebral perfusion agents have been introduced, of which [15O]water, [13N]ammonia, and [15O]butanol have been used more frequently. Regional CBF has been quantitated by using these tracers in normal and different cerebral disease states. Other perfusion agents include [15O]O2, [11C]CO, [11C]CO2, [18F]fluoromethane, [15O]O2, [11C]butanol, and [62Cu]PTSM. Among the PET cerebral metabolic agents, [18F]fluorodeoxyglucose (FDG) is most commonly used to detect metabolic abnormalities in the brain. Various brain tumors have been graded by [18F]FDG PET. This technique was used to detect epileptic foci by showing increased uptake in the foci during the ictal period and decreased uptake in the interictal period. Differentiation between recurrent tumors and radiation necrosis and the detection of Alzheimer's disease have been made successfully by [18F]FDG PET. Other PET metabolic agents such as [11C]deoxyglucose, and [11C]methylmethionine have drawn attention in the detection of brain tumors. [18F]fluorodopa is a cerebral neurotransmitter agent, which has been found very useful in the detection of Parkinson disease that shows reduced uptake of the tracer in the striatum of the brain.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Radiopharmaceuticals for brain imaging. 781 3


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