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

31P magnetic resonance spectroscopy, using surface coils placed on perfused or surgically exposed animal hearts, shows that unequivocal changes in phosphocreatine (PCr) and adenosine triphosphate (ATP) occur during interventions, such as ischemia. Similar measurements seem warranted in man. We have used a modification of the rotating-frame imaging technique to measure PCr-to-ATP ratio non-invasively in human heart. The subject lay prone on a double-surface coil probe with the apex and the anterior surface of the heart covered by the coil in a 1.9 T magnet. 31P spectra were obtained from slices of tissue approximately 6 cm in diameter and 2 cm in thickness. Though skeletal and cardiac muscle contain similar phosphorus metabolites, animal studies show that the ratio in the two are different. We argued that the ratio should start high (skeletal muscle) and plateau at a low value representing cardiac muscle. Using this criterion, which makes no assumption on what the ratio is in heart muscle, the PCr:ATP in six normal subjects was 1.55 +/- 0.2. This protocol has been used in a preliminary study in patients with cardiomyopathies.
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PMID:Measurement of phosphocreatine to ATP ratio in normal and diseased human heart by 31P magnetic resonance spectroscopy using the rotating frame-depth selection technique. 343 7

Magnetic resonance spectroscopy can be used to characterize the bioenergetic state of the musculoskeletal system, and several marker compounds related to the tissue's biochemistry have been found to exist. Potential new techniques involving better spatial localization, spectral editing, and examination of nuclei other than phosphorus are in the developmental stage. Their development over the next few years will determine the extent to which MRS will become a universally used medical tool. However, the results with 31P alone guarantee a continued role in the study of muscular disease, peripheral vascular disease, and hypoxia and ischemia of the neonatal brain.
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PMID:Magnetic resonance spectroscopy of the musculoskeletal system. 345 10

To assess the applicability of phosphorus-31 magnetic resonance spectroscopy (31P-MRS) in the analysis of renal transplant viability and preservation techniques with respect to pre-transplant ischemia, we studied two rat groups. Twenty-five rat kidneys were subjected to various time increments of warm ischemia (Group A), and 31P-MRS was performed on each kidney at time intervals of up to 72 hours during simple hypothermic storage. We correlated findings of 31P-MRS with simultaneous findings of electron microscopic (EM) ultrastructural viability parameters (in Group A) and subsequent survival and renal function in 30 rats (Group B) subjected to similar amounts of variable ischemia. Intracellular phosphorus metabolite levels were nondestructively monitored by 31P-MRS via spectral peaks of NAD, sugar monophosphates (SP), and inorganic phosphate (Pi). We concluded: SP/Pi and NAD/Pi ratios decay in a time-dependent manner for both warm and cold ischemia, although this process is much slower during cold storage; EM viability parameters correlate with the development of acute tubular necrosis (irreversible damage) versus nonviability (gross cell death) on a qualitative basis only; and 31P-MRS enables a quantitative assessment of renal viability and ischemic renal damage and can predict the degree of acute tubular necrosis and post-ischemic renal function. 31P-MRS is potentially a noninvasive, nondestructive method of assessing viability during simple hypothermic storage of the rat kidney. Preliminary evidence shows that this MRS method can be applied to human kidney viability studies for clinical renal transplantation and urologic research concerning renal preservation.
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PMID:Assessment of renal viability by phosphorus-31 magnetic resonance spectroscopy. 351 65

To evaluate the usefulness of the monophosphate/inorganic phosphate ratio (MP/Pi) in assessing renal viability in a renal transplantation setting, we monitored intracellular phosphorous metabolites of 33 canine kidneys by phosphorus-31 magnetic resonance spectroscopy (MRS) after various amounts of ischemia. Renal viability (adequate perfusion and function) was directly assessed by the presence of intraoperative urine production in each kidney. Twelve normal, well-perfused kidneys (Group 1) exhibited high control MP/Pi ratios, with a mean of 0.87 +/- 0.12. Six in situ kidneys (Group 2), subjected to 45 minutes' warm ischemia followed by reperfusion, had a mean MP/Pi ratio of 0.50 +/- 0.12 after warm ischemia, which increased by a mean of 0.50 +/- 0.11 (to 1.0 +/- 0.07) after two to four hours of reperfusion. Fifteen kidneys (Group 3) were removed, cold-flushed and transplanted after 24 hours of hypothermic storage. In eight (Group 3A), reperfusion was excellent; in seven (Group 3B), reperfusion was inadequate secondary to hypotension in two, hemorrhage in two, and renal vein thrombosis in three. Group 3A kidneys had a mean MP/Pi ratio after cold-storage ischemia of 0.54 +/- 0.08. After successful transplantation and two to four hours of reperfusion, this increased by a mean of 0.23 +/- 0.12 to 0.77 +/- 0.15. Group 3B kidneys all showed a continuous decline of MP/Pi, with a mean loss of 0.26 +/- 0.09 from baseline values (mean 0.56 +/- 0.08) to nonviable levels of 0.28 +/- 0.12 within four hours of transplantation. We conclude that MP/Pi ratios enable assessment of renal viability and ischemic damage and can predict the efficacy of renal preservation maneuvers in the dog kidney. These preliminary data support the theory that MRS can be applied to the noninvasive assessment of viability in ex vivo, cold-stored cadaveric human kidneys awaiting renal transplantation.
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PMID:Assessment of renal preservation by phosphorus-31 magnetic resonance spectroscopy: in vivo normothermic blood perfusion. 353 22

Acute intestinal ischemia remains a catastrophic event even with the advent of modern diagnostic and vascular surgical techniques. An early noninvasive test would be valuable since early operation yields better survival rates. We have used an in vivo rat model to study acute intestinal ischemia after occlusion of the superior mesenteric artery (SMA). 31Phosphorus magnetic resonance spectroscopy (MRS), a noninvasive nondestructive technique, can detect the phosphorus metabolites most likely to be altered in ischemia: adenosine triphosphate, phosphocreatine (PCr), inorganic phosphate (Pi) and phosphomonoesters and phosphodiesters. Furthermore, intracellular pH can be estimated from the pH dependent position of the Pi spectral line relative to PCr. A tourniquet was loosely placed around the SMA in five Wistar rats through a transabdominal approach to the retroperitoneum. The abdomen was immediately closed. A 20 millimeter MRS surface coil was placed on the abdomen and 31Phosphorus spectra were accumulated. The SMA was then occluded and additional 31Phosphorus spectra were taken for the next 75 minutes. Significant (p less than 10(-4) changes in the position and magnitude of the spectra lines occurred within 20 minutes; the Pi position indicates severe intracellular acidosis and rapidly increases to three times its original magnitude. The PCr line decreases in magnitude. In a similar experiment, occlusion of the superior mesenteric vein (SMV) produced equivalent results. Occlusion of vessels other than the SMA or SMV not accompanied by transmural ischemia resulted in spectra unaltered from control. These findings support the application of phosphorus MRS to clinical studies.
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PMID:In vivo noninvasive observation of acute mesenteric ischemia in rats. 357 17

In order to study the metabolic events surrounding ischemia induced by the graded increase of cerebrospinal fluid (CSF) pressure, the technique of simultaneous phosphorus-31- and hydrogen-1-enhanced nuclear magnetic resonance spectroscopy was applied to five cats as intracranial pressure (ICP) was gradually raised by the instillation of mock CSF. Threshold lactate rose at an average cerebral perfusion pressure (CPP) of 49 torr, and, in general, preceded a threshold decrease in phosphocreatine, which was observed at an average CPP of 29 torr. There was considerable variation among cats in the CPP at which failure of brain energy metabolism occurred, however, suggesting differences in the autoregulatory curves. It is concluded that, with elevated ICP, there is no universally "safe" CPP at which brain energy metabolism may be assumed to be uncompromised.
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PMID:Effects of increased ICP on brain phosphocreatine and lactate determined by simultaneous 1H and 31P NMR spectroscopy. 361 71

Postreperfusion regional myocardial dysfunction may be associated with depletion of high energy phosphate compounds during ischemia and with their relatively slow repletion during reperfusion. However, few studies have correlated relatively rapid changes in regional myocardial function (sonomicrometers) and blood flow (microspheres) with high energy phosphate concentrations measured using phosphorus-31 nuclear magnetic resonance spectroscopy in intact large animal models of regional myocardial ischemia. The left anterior descending coronary artery of mongrel dogs was abruptly occluded for 17.1 +/- 1.9 minutes and then completely released; measurements were made for an additional 22 minutes. Transmural blood flow decreased from 1.07 +/- 0.25 to 0.25 +/- 0.10 ml/(min X g) and holosystolic expansion was observed in all dogs (segmental systolic shortening decreased from 9.3 +/- 3.7 to -6.3 +/- 6.0%). Phosphocreatine (PCr) measured during 4.4 minute sampling intervals decreased to steady state within the first sampling period after occlusion and was 45.9 +/- 17.0% of control at the end of the occlusion, whereas beta-adenosine triphosphate (beta-ATP) reached its lowest level early after reperfusion (72.7 +/- 13.3% of control). The ratio of PCr to inorganic phosphate (Pi) decreased during the occlusion (3.34 +/- 0.75 versus 1.01 +/- 0.61) but returned to control level early during reperfusion. The ratio of PCr to beta-ATP also decreased during coronary occlusion (2.16 +/- 0.39 versus 1.29 +/- 0.39) but did not return to control level during reperfusion. Significant correlations were observed between the intensity of ischemia (reduced blood flow) and reductions in regional contractile function, PCr, beta-ATP, myocardial pH and the increase in Pi during the coronary occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Regional myocardial blood flow, function and metabolism using phosphorus-31 nuclear magnetic resonance spectroscopy during ischemia and reperfusion in dogs. 362 71

To determine the characteristic appearance of phosphorus (31P) nuclear magnetic resonance spectra in acute and chronic myocardial infarction in situ, cardiac-gated depth-resolved surface coil spectroscopy (DRESS) at 1.5 T was used to monitor 31P NMR spectra from localized volumes in the left anterior canine myocardium for up to 5 days following permanent occlusion of the left anterior descending coronary artery. Coronary occlusion initially produced regional ischemia manifested as significant reductions in the phosphocreatine (PCr) to inorganic phosphate (Pi) ratios and intracellular pH (P less than 0.05, Student's t test) in endocardially displaced spectra acquired in periods as short as 50 to 150 s postocclusion. Spectra acquired subsequently revealed either (i) restoration of near-normal phosphate metabolism sometime between 10 and about 50 min postocclusion or (ii) advancing ischemic phosphate metabolism at about an hour postocclusion, and/or (iii) maintenance of depressed PCr/Pi ratios for up to 5 days postocclusion with a return of the apparent pH to near normal values between 6 and 15 h postocclusion. Postmortem examination of animals exhibiting the first type of behavior revealed the existence of coronary collateral vessels. The last type of behavior indicates that Pi remains substantially localized in damaged myocardium for days following infarction. The location and size of infarctions were determined postmortem by staining excised hearts. The smallest infarctions detected by 31P DRESS weighed 4.9 and 7.5 g. The most acidic pH measured in vivo was 5.9 +/- 0.2. Infarctions aged 1/2 day to 5 days were characterized by elevated but broad Pi resonances at 5.1 +/- 0.2 ppm relative to PCr and significantly depressed PCr/Pi ratios (P less than 0.002, Student's t test) relative to preocclusion values. Contamination of Pi resonances by phosphomonoester (PM) components is a significant problem for preocclusion Pi and pH measurements. These results should be applicable to the detection and identification of human myocardial infarction using 31P NMR and DRESS.
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PMID:The fate of inorganic phosphate and pH in regional myocardial ischemia and infarction: a noninvasive 31P NMR study. 365 2

A phosphorus 31-nuclear magnetic resonance method was used to study the effect of exogenous phosphocreatine on the isolated perfused rat heart. The hearts were chemically arrested by St. Thomas' Hospital solution and made totally ischemic for 35 minutes at 37 degrees C. In the presence of phosphocreatine, 10 mmol/L, during ischemia, almost complete recovery of heart function and phosphocreatine content and 61% recovery of adenosine triphosphate content were observed after 30 minutes of postischemic reperfusion; in the control experiments without phosphocreatine, contractile function, intracellular phosphocreatine, and adenosine triphosphate contents were restored to 33%, 43%, and 26% of their normal values, respectively. Ultrastructural studies with a lanthanum tracer method showed remarkable protection of sarcolemma against ischemic injury by exogenous phosphocreatine at the level of the glycocalyx.
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PMID:Protection of ischemic myocardium by exogenous phosphocreatine. I. Morphologic and phosphorus 31-nuclear magnetic resonance studies. 366 3

Phosphorus-31 MR spectroscopy allows non-invasive evaluation of the energy state of a tissue and was used to study effects of acute ischemia in rat skeletal muscle. Male Wistar rats were anesthetized with pentobarbital (50 mg.kg-1) and the femoral artery ligated on leaving the abdominal cavity. Animals were then set inside a superconducting magnet (Bruker 2.35 T) and a circular coil (15 mm diameter) placed on leg facing gastrocnemius muscle. Pulse lengths were chosen in such a may that the sensitive zone would include mainly gastrocnemius muscle. Signals were accumulated over 2 or 18 minutes. One hour after insertion of ligature muscular exercise was provoked over 20 minutes by electrical stimulation of sciatic nerve (4 Hz, 2 to 5 V). Muscles were removed at different stages of the test for biochemical assays. Figure 1 includes spectra at 2 and 18 minutes showing the effects of ischemic when compared with normoxic muscle exercise. Figure 2, showing phosphocreatine (PC) and ATP levels, illustrates the accentuation under the effect of ischemia of degradation in PC during muscular exercise and its subsequent slow reconstitution. Table I lists more precise MR data obtained during 18 minutes and compares them with biochemical findings. Ischemic exercise appears also to induce significant degradation of ATP, accumulation of inorganic phosphate (Pi) and phosphomonoesters (PME) as well as persistent intracellular acidosis (pH 6.5 as against 7.1).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Effects of acute arterial occlusion on muscle energy metabolism. An experimental model using phosphorus NMR spectroscopy in the rat]. 369 56


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