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

Using in vivo 1H NMR spectroscopy (1H MRS) and biochemical analysis, the effects of hyperammonemia on cerebral function were studied in three rat models: acute liver ischemia (LIS), administration of urease (UREASE) and administration of methionine sulfoximine (MSO). By means of localization in three dimensions signals were obtained exclusively from the cerebral cortex. Specially developed lineshape correction and fitting methods were used to quantitate the MRS signals. The following concentration changes were observed; a decrease in glutamate and (phospho)choline for all the models; an increase in glutamine in the LIS and UREASE model but a decrease in the MSO model; a marked increase in lactate in the LIS and UREASE group; a tendency to a decrease in N-acetylaspartate in all the models. These changes agree well with the changes in the post-mortem biochemically determined cerebral cortex glutamine and glutamate concentrations. Estimated absolute 1H MRS metabolite concentrations agree well with those obtained by other techniques; cerebral cortex glutamate, however, is underestimated by about 35% by NMR. The present data support the hypothesis that hyperammonemia is associated with a decreased availability of glutamate for neurotransmission.
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PMID:The use of in vivo proton NMR to study the effects of hyperammonemia in the rat cerebral cortex. 167 7

Two ester-type prostaglandin oligomeric compounds were synthesized, one from prostaglandin E1 (termed MR-356) and the other from prostaglandin B2 (termed OC-5186). Using in vivo [31P]MRS, the protective effects of these oligomers on forebrain ischemia (15 min) were evaluated in a rat model. Forebrain ischemia caused a decrease in intracellular high energy phosphates and intracellular pH (pHi) in the control and compounds-treated groups, but changes of these values in the OC-5186-treated group were significantly smaller than those in the control group. Moreover, the cerebral energy metabolism of the OC-5186-treated group returned to the preischemia level more rapidly than in the control group after forebrain ischemia. MR-356 had some effects, but the differences were not significant.
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PMID:[31P]MRS study of the protective effects of prostaglandin oligomers on forebrain ischemia in rats. 186 52

Two metabolically distinct cell populations were detected when two peaks of inorganic phosphate (Pi), corresponding to two pHi values, were recorded by Phosphorus Magnetic Resonance Spectroscopy (31P MRS). One cell population, having intracellular pH (pHi) values less than 6.3, was thought to contain neither PCr (phosphocreatine) nor ATP and was thus considered metabolically unstable or inactive. The second cell population, having normal or near normal pHi, was considered metabolically active with adequate values of ATP and PCr. We can therefore further analyze the bioenergetics in this cell population. The results were based upon studies of 14 ischemic dogs that were anesthetized with 2% isoflurane and ventilated. The amount of Pi associated with the acidic cell population (low pHi) was used to calculate the fraction of metabolically inactive brain tissues. This value correlated well with the ATP depletion of the total cell population. This suggests that in the acidic cell population, PCr and ATP supplies were depleted by dephosphorylation during ischemia, leading to an accumulation of acidic Pi. In addition, ATP synthesis in this population may be inhibited by the low intracellular pH. On the other hand, the bioenergetic state of the metabolically stable cell population having a nearly neutral pHi changed markedly during ischemia. The PCr/Pi dropped to 0.8 and the phosphorylation potential (PP) dropped to 10 mM-1 from 40 mM-1. With reperfusion, two distinct patterns of responses were observed. One group showed the restoration of ATP (recovery group) whereas the second group did not (non-recovery group). After 3 h of reperfusion, the ATP restored group showed complete recovery of PCr.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Metabolic heterogeneity in brain tissue during incomplete ischemia and reperfusion. 209 39

This review has attempted to indicate areas of investigation that in vivo MRS methodology is particularly suited for and would answer important questions related to neonatal cerebral development or injury. There are several metabolites (PEth, PCr, NAA, taurine, glutamate) and lipids detectable by in vivo 31P or 1H MRS, which show substantial changes in concentration during ontogenesis. Do these biochemical markers correlate with major morphological changes, such as myelination? If they do, can this be used to quantitate abnormalities in brain development from congenital abnormalities or metabolic encephalopathies? In the neutral to mild acidic range (7.0 greater than pHi greater than 6.5) adult and neonatal brain appear to have similar intrinsic physicochemical buffering capacity. However, at the extremes of pHi induced by respiratory alkalosis or severe acidosis from partial ischemia, the possibility exists that the buffering capacities of adult and neonatal brain differ. Whether this is true requires further investigations using both neonates and adults, or perhaps more preferably, multiple measurements on a single species throughout its developmental period. Such studies are now feasible because multinuclear in vivo MRS can provide a large body of information from individual animals. A similar study design could prove useful for investigations of changes in cerebral resistance to hypoxia, ischemia, or asphyxia during development. The roles that blood pressure, glucose, temperature, or the administration of extrinsic buffers and drugs have on modulating the severity of and relationship between changes in blood flow, energy metabolites, or pHi, are all amenable to study using in vivo MRS. Furthermore, all of these variables can be measured simultaneously. The kinetics of brain acid and lactate homeostasis during chronic cerebral insults or following acute insults has not been thoroughly examined in either neonates or adult animals. There is evidence to suggest that following ischemia or seizures, brain acidosis resolves before brain lactosis. However, the clinical diagnostic significance of this post-insult uncoupling between pHi and lactate remains to be established. Finally, the application of in vivo MRS methodology to study the effects of trauma, drugs, environmental toxins, and other metabolic encephalopathies on neonatal cerebral perfusion and metabolism are virtually unexplored. Hopefully, the material presented here will prompt researchers to consider the application of in vivo MRS to new avenues of investigation.
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PMID:In vivo multinuclear magnetic resonance spectroscopy investigations of cerebral development and metabolic encephalopathy using neonatal animal models. 219 84

The authors report on an acute compartment syndrome occurring symmetrically in the extensors of both forearms. The etiology of this unique compartment syndrome, not previously described, could be attributed to the inhalation of a propane-butane gas mixture, low in oxygen, while sleeping, in combination with external compression of both forearms, due to the patient's head lying on both forearms while sleeping. Ischemic damage to muscles was precisely located using non-invasive MRI (Magnetic Resonance Imaging). The extent of cellular damage due to ischemia after fasciotomy and healing by secondary intention was quantitatively assessed using non-invasive 31P-MRS (Phosphorus Magnetic Resonance Spectroscopy). The results correlate with the clinical and histological findings and indicate a bioenergetic regeneration of the ischemic skeletal muscle's cells.
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PMID:[Monitoring of an acute compartment syndrome of unusual etiology using MRI (magnetic resonance tomography) and MRS (magnetic resonance spectroscopy)]. 222 41

In vivo MRS measurement of deoxymyoglobin (deoxy-Mb) in human forearms was performed by observing the N-delta proton of F8 proximal histidine. The concentration of deoxy-Mb reflects the oxygen level in the muscle. In resting muscles, the deoxy-Mb level was below the detection sensitivity. When ischemia was introduced by arterial occlusion, the time-resolved NMR spectra (with 1 min resolution) was recorded to follow the change in the deoxy-Mb signal. The result shows that deoxy-Mb signal builds up and levels off within 6 min. This technique may be used to study bioenergetics of muscle during exercise and under pathological conditions.
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PMID:In vivo MRS measurement of deoxymyoglobin in human forearms. 235 38

Angina is characterized by brief periods of ischemia followed by reperfusion; the cumulative effect of these episodes on energetics of the myocardium has not been fully elucidated. This study used an in vivo feline model for the assessment of high-energy phosphate compounds during brief sequential periods of ischemia and reperfusion. Nine adult, open-chest, anesthetized cats were prepared with a reversible occluder around the proximal left anterior descending artery and a 1.2-cm-inside diameter coil sutured on the myocardial surface in the distribution of the left anterior descending coronary artery. Levels of PCr, Pi, and ATP (beta-phosphate signal) were measured by 31P MRS in a GE CSI 2-T NMR spectrometer/imager. Measurements were obtained during a control period and during three successive occlusion-deocclusion periods of roughly 12 and 20 min' duration, respectively. The last deocclusion period was observed for 60 min. Electron microscopy was performed in two animals. PCr declined (P less than 0.01) rapidly following each occlusion to 51 +/- 5.2% (occlusion 1), 53 +/- 5.8% (occlusion 2), and 48 +/- 5.7% (occlusion 3) of the control value by 6 min. Pi rose (P less than 0.01) with the three sequential occlusions to 253 +/- 46, 288 +/- 57, and 277 +/- 46%, respectively. PCr and Pi returned to baseline promptly with reperfusion, while ATP showed a gradual decline throughout the experiment, decreasing to 77 +/- 7.2% of control at the end of the last reperfusion (P less than 0.05). Although PCr returned to baseline during reperfusion, ATP did not, suggesting a reduction in the nucleotide pool. These findings indicate that the repeated episodes of ischemia, which are insufficient to produce necrosis, can have an effect on myocardial high-energy phosphate metabolism as evidenced by mild depletion of ATP.
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PMID:Effect of repetitive brief episodes of cardiac ischemia on 31P magnetic resonance spectroscopy in the cat. 237 1

To investigate the mechanisms of development in ischemic myocardial injury, intracellular pH and high energy phosphates in perfused guinea-pig hearts were measured using 31P-MRS method. During 60 minutes' global ischemia, intracellular ATP level decreased to 1.2% and 26.4% of control, respectively with and without preischemic administration of isoproterenol, while intracellular pH declined to 6.48 and 6.03. In hearts loaded with isoproterenol, approximately 50% of ATP was depleted with little pH decline. After 40 minutes' reperfusion with a standard perfusate, ATP levels were 23.3% and 46.1%. Cardiac contractility (LVdp/dt) were 16.3% and 45.0% of control value respectively. When hearts were reperfused with inosine, cardiac functions recovered to 52.3% and 81.6% respectively with and without preischemic administration of isoproterenol, while ATP increased to 59.4% and 78.1% after 6 hours' reperfusion. Recovery of ATP level correlated with recovery of contractility. Isoproterenol stole the ability of ATP synthesis from a plenty of ischemic myocytes and progressed irreversible myocardial ischemic injury. ATP depletion was a critical factor in the onset of irreversibility rather than accumulation of anerobic glycolytic products. Measurement of ability of ATP synthesis, with administration of inosine, was supposed to be an usable method to evaluate any organ's viability using 31P-MRS.
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PMID:Mechanisms of myocardial ischemic injury assessed by phosphorus-31 magnetic resonance spectroscopy (effects of catecholamine on ischemic hearts). 238 36

Phosphorus-31 (31P) magnetic resonance spectroscopy of the kidneys promises to provide metabolic information leading to better assessment of renal physiology. However, the problems of studying the metabolism of the heterogeneous renal architecture by precisely localizing the origin of the signal obtained from small voxels and eliminating motion artifacts have not been solved as yet. The normal 31P MRS spectra show a characteristic fingerprint of six peaks including phosphomonoesters, phosphodiesters, inorganic phosphorus, and gamma, alpha, beta adenosine triphosphate (ATP). Renal failure, regardless of its etiology and mechanism of inducement (hypoxia, ischemia, acidosis, or obstruction) produces a loss of ATP with a progressive increase of inorganic phosphorus and a decline in intracellular pH. The severity of renal failure correlates with the severity of the metabolic disturbance. The potential use of 31P MRS in the assessment of renal viability has been applied to the study of renal preservation methods and prediction of renal function following transplantation.
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PMID:Phosphorus-31 MRS of the kidney. 269 45

In research cardiology large numbers of in vivo animal experiments, mostly with dogs or pigs, are necessary. It was the aim of this study to test a simple in vitro perfusion heart model from swine harvested in the slaughterhouse as a potential substitute for in vivo animal studies. 32 unselected hearts of slaughterhouse swine after 10 to 15 min of warm ischemia were subjected to reperfusion with warm oxygenized blood and were examined for mechanical recovery, which occurred in 56%, increasing to 95% if primarily using only hearts that were in relaxation. In 21 of selected relaxed heart models the energy phosphate pattern as an index of viability was measured by P-31 MRS on a 4.7 Tesla NMR tomograph in 37 experimental runs with the following perfusion protocols: 1) immediate cardioplegia with cold Bretschneider or Collins solution, transportation under cooling, MRS after approximately 1 h; 2) immediate cardioplegia, transportation, reperfusion with oxygenated warm blood, MRS; 3) immediate blood perfusion with genuine fresh arterial blood from the slaughterhouse, cold plegia perfusion, transportation, MRS; 4) immediate blood perfusion with transportation MRS; 4) immediate blood perfusion with genuinefresh arterial blood, cold plegia perfusion, transportation, reperfusion with oxygenated warm blood, MRS during reperfusion; 5) An experimental pig heart was made plegic in vivo and reperfused with oxygenated warm blood during MRS as reference.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Studies of myocardial metabolism using P-31-NMR spectroscopy and a simple heart perfusion model of slaughtered animals--an approach to avoiding in vivo animal experiments]. 281 11


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