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

Our model of severe nerve ischemia consistently results in extinction of the compound nerve and muscle action potentials (NAP; CMAP) within 30 min. Since impulse transmission may depend on nerve energy metabolism (NEM), we studied the effects of ischemia with reperfusion on sciatic-tibial nerve NEM in vivo and compared these results with NEM of this nerve in deoxygenated Ringer's solution in vitro and postmortem. Ischemia for 30 min postmortem or in deoxygenated Ringer's solution resulted in marked depletion of adenosine triphosphate (ATP) and creatine phosphate (CP) and an increase in lactate (LAC) of sciatic-tibial nerve of adult male Sprague-Dawley rats. In vivo ischemia for up to 3 h to sciatic-tibial nerve was sufficient to extinguish CMAP but not NAP and did not deplete ATP, CP, or GLU nor did it increase LAC. Ischemia sufficient to extinguish NAP resulted in reduction of energy substrates to about 50% of resting. Muscle fails to conduct impulses before nerve and in vivo reductions of energy substrates are milder than in vitro changes. These changes are explainable in terms of energy requirements and supply. These findings support an energetic basis of ischemic conduction failure.
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PMID:Effect of ischemia and reperfusion in vivo on energy metabolism of rat sciatic-tibial and caudal nerves. 174 5

The benefit of perfusion washout in both experimental and clinical skin flaps has long been debated. By perfusing ischemic rat pedicled flaps with UW solution, a recently developed, high-molecular-weight, organ-preservation medium, a 170 percent increase in the critical ischemia time of treated versus untreated control flaps was demonstrated. Sixty rats were used in this study. A 3- x 6-cm unilateral abdominal skin flap based on the superficial inferior epigastric artery and vein was raised. The flaps were divided into three groups: Group 1 (control--no perfusion washout (n = 15); Group 2 (LR)--perfusion washout with lactated Ringer's solution (n = 15); Group 3 (UW)--perfusion washout with UW solution (n = 30). Flaps were subjected to varying periods of ischemia, ranging between 8 and 30 hr. The primary ischemia time at which 50 percent of the flaps survived clinically was 10 hr for Group 1, 15 hr for Group 2, and 27 hr for Group 3. The differences between the survival rates for flaps in Groups 1, 2, and 3 were statistically significant (p less than .0005). By bathing the vascular and parenchymal cells in an impermeant preservation solution, it was hypothesized that cellular swelling would be inhibited, thereby significantly improving a skin flap's tolerance to warm ischemia. Furthermore, after reviewing the pertinent literature, it is evident that the primary critical ischemia time of 27 hr is the highest reported to date for the normothermic experimental rat pedicled flap. Clinical application of these findings, as well as the need for further studies, are discussed.
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PMID:The use of a new perfusate in experimental microvascular flaps: a threefold increase in ischemic tolerance. 175 71

Temperature increases membrane fluidity and decreases vascular resistance in isolated organs. Therefore, these studies were designed to determine if a rinse with warm buffer could increase survival time in the rat model of orthotopic liver transplantation by improving hepatic microcirculation. Brief periods of warm ischemia (3-8 min) did not damage the liver as indexed by minimal release of LDH. Survival of rats for 30 days was greater than 90% in this model when livers were stored for 1 hr in Ringer's solution; yet grafts stored for 8 hr in Euro-Collins solution and rinsed with 20 ml of cold (0-4 degrees C) Ringer's solution survived postoperatively only around 3 days. However, livers stored for 8 hr in Euro-Collins and rinsed with 20 ml of warm (37 degrees C) Ringer's survived longer than 30 days (i.e., permanently). Serum transaminase levels reached peak values around 6000 U/L one day postoperatively in the cold-rinsed group, and liver injury assessed histologically was substantial. Under these conditions, pulmonary infiltration of inflammatory cells was observed in about 23% of lung tissue examined and was associated with massive bleeding. Following a warm rinse, however, maximal SGOT levels and injury to both liver and lung were reduced significantly by 80-90% 24 hr postoperatively. Moreover, the warm rinse improved hepatic microcirculation. It accelerated blood flow into the liver approximately two-fold, as indexed by the half-time of changes in hemoglobin reflectance from the liver surface, improved the distribution of colloidal carbon in the organ observed macroscopically, and decreased vascular resistance by over 50%. These data support the hypothesis that a brief rinse of liver grafts with warm buffer markedly improves the hepatic microcirculation, leading to dramatic improvement in graft survival. This work demonstrates clearly that a brief warm rinse may be useful clinically in liver transplantation.
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PMID:Increase in survival of liver grafts after rinsing with warm Ringer's solution due to improvement of hepatic microcirculation. 187 93

The present study was undertaken to assess the role of oxygen free radicals relating to cell damage upon reoxygenation of the ischemically altered isolated rat liver. Livers were excised and flushed via the portal vein with Ringer's solution and Euro-Collins solution, to which superoxide dismutase (SOD) was added in the experimental group. After warm ischemia at 37 degrees C and cold storage at 4 degrees C, the livers were reperfused via the portal vein with carbogen-saturated Krebs-Henseleit solution. Other livers were subjected to a retrograde persufflation via the infrahepatic caval vein with either oxygen or nitrogen and then rinsed with Ringer's solution. During reperfusion, SOD-treated livers showed markedly reduced vascular resistance, lower enzyme release and enhanced VO2 accordingly, energy charge at the end of reperfusion was significantly higher in the treated group. With reference to the tissue content of malondialdehyde, SOD-treated livers showed significantly less damage than the corroboration for these data. Enzyme activities in the eluate were significantly reduced under anoxic conditions as well as in the presence of SOD. We conclude from these data that oxygen free radicals do exert a detrimental impact on the reoxygenated liver, which could be specifically suppressed by application of exogenous SOD.
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PMID:Involvement of oxygen in harvesting injury of the liver. An experimental study including substrate free organ persufflation to evaluate a specific therapeutic approach. 192 67

The effects of physiologic and pharmacologic manipulations on contact lens-induced edema were studied. In isolated superfused rabbit corneas bathed in Ringer's solution and covered with large-diameter polymethylmethacrylate (PMMA) lenses, corneal swelling rates of 17-26 microns/hr (versus -5-5 microns/hr in paired controls) were observed. Neither the calcium antagonist diltiazem (10(-4) M), the glucocorticoid dexamethasone (10(-7) M), the glucose substitute fructose (20 mM), nor 0.5 mM adenosine and 0.3 mM reduced glutathione mitigated the edema. Lens-induced edema was 25 microns/hr in corneas bathed at pH 8.2 and decreased to 9 microns/hr at pH 7.0. In corneas without lenses, however, decreasing the pH from 7.4-7.0 caused significant swelling (P less than 0.05). The pyruvate dehydrogenase stimulant sodium dichloroacetate (3.2 mM) on the tears side ameliorated the edema, and its congener, 3.2 mM 2-chloropropionate, was less effective. These latter agents are known to relieve lactic acidosis systemically and had no significant effect on corneas without lenses. In tissues bathed with 20 mM lactate Ringer's, normal thickness was maintained in both control and PMMA-treated corneas throughout the 3-hr period. These findings suggest that the contact lens-induced edema does not involve the acute cytotoxic mechanisms seen in severe tissue ischemia or hypoxia. The edema appears to result in part from acidosis but mainly from stromal lactate accumulation.
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PMID:Contact lens-induced edema in vitro. Pharmacology and metabolic considerations. 199 86

A central noradrenergic process may permit expression of the stress-related increase in cardiac vulnerability to ventricular fibrillation (VF). Thus, the effect of central beta-adrenergic receptor blockade with L-propranolol (0.01 and 0.05 mg/kg) on ischemia-induced VF vulnerability was evaluated in the psychologically stressed pig model and compared with Ringer's solution and D-propranolol (0.05 mg/kg). The ischemia of a maximum 15-minute left anterior descending coronary artery occlusion was used since we previously determined that pigs surviving 15 minutes usually do not fibrillate. Time to the onset of VF was analyzed by time-to-event analysis and ranged from 0.75 to 13.8 minutes in vulnerable pigs. Intracerebroventricular administration of L-propranolol (0.05 mg/kg) prolonged the time to VF compared with Ringer's solution and D-propranolol (p less than 0.05). The high dose of L-propranolol also reduced the incidence of VF (7/15 fibrillated) compared with Ringer's solution (12/12 fibrillated) and D-propranolol (6/7 fibrillated). The lower dose of L-propranolol was without effect on VF vulnerability (7/9) fibrillated). The plasma concentration resulting from central administration of 0.05 mg/kg L-propranolol was found to be 9.05 +/- 3.25 ng/ml, which is significantly below therapeutic antiarrhythmic blood levels. We conclude that the reduced vulnerability to ischemia-induced VF after intracerebroventricular administration of propranolol is due to alteration of a central beta-adrenergic receptor-mediated phenomenon as opposed to an effect on the heart directly or to nonspecific membrane stabilization.
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PMID:Central beta-adrenergic mechanisms may modulate ischemic ventricular fibrillation in pigs. 215 67

The aim of this study was to investigate the oxygenation of the gastrointestinal tract mucosa using indirect pH measurements in a porcine septic model (intravenous infusion of live E. coli). By means of intraluminally placed balloon catheters (Tonomitior) permeable to CO2, intramucosal pH (pHi) was calculated using the Henderson-Hasselbalch equation. Cardiopulmonary hemodynamics and portal blood flow were measured using Swan-Ganz catheters. Samples were taken from the gastrointestinal tract for histological examination. Nine pigs were given i.v. E. coli infusion while six pigs served as sham controls and were given an equivalent amount of Ringer's solution only. All septic animals developed hemodynamic signs of septic shock. Gastric, small intestinal and sigmoid colonic pHi decreased gradually during the four hour observation period. In the small intestine and the sigmoid colon the decrease was significant already after one hour (p less than 0.01 and p less than 0.02, respectively). Microscopic examination of tissue specimens obtained 4 hours following induction of sepsis revealed normal or close to normal findings in all the sham and in more than half of the septic animals. These findings indicate that abnormally low gastrointestinal intramucosal pH may be found early in septicemia, preceding microscopically detectable damage by several hours. It is concluded that the tonometer technique does provide early detection of gastrointestinal ischemia in septic shock.
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PMID:Early detection of gastrointestinal mucosal ischemia in porcine E. coli sepsis. 226 40

We devised the present experiments to assess the effects of ischemia on the production of dopamine in the caudate nucleus of spontaneously hypertensive stroke-resistant rats. Ringer's solution was continuously perfused at a rate of 10 microliters/min through 0.2-mm-diameter dialysis tubing implanted in the rat's caudate nucleus. After bilateral occlusion of the common carotid artery, perfusate was collected at 20-minute intervals for 120 minutes and was analyzed for monoamines and their metabolites using high-performance liquid chromatography and an electrochemical detection system. The extracellular concentration of dopamine increased abruptly approximately 3 minutes after the ischemic insult, reached a maximum at between 20 and 40 minutes after the insult, and subsequently decreased. During the 120 minutes, 3,4-dihydroxyphenylacetic acid and 5-hydroxyindole-3-acetic acid concentrations decreased significantly, whereas 5-hydroxytryptamine was not detected. Our results indicate that during cerebral ischemia a large increase in extracellular dopamine concentration in the caudate nucleus occurs, probably as a result of energy failure of the cell membranes. This leakage of dopamine may be a causal factor in the neuronal damage associated with cerebral ischemia.
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PMID:Striatal dopamine in acute cerebral ischemia of stroke-resistant rats. 246 90

We studied the effect of iv administration of biodegradable macromolecules on microvascular permeability after ischemia-reperfusion injury in a rat gastrocnemius model. After 2 h of tourniquet ischemia of the rats' hind limb, groups of animals were given iv lactated Ringer's solution (RL), serum albumin 5%, or varying MW fractions of biodegradable macromolecules of hydroxyethyl starch (HES), glycogen, and dextran. At the conclusion of the 24-h reperfusion period, the rat gastrocnemius muscles were collected. Water and K+ differences between the ischemic and control muscles were compared. Rats given a 100,000 to 300,000-dalton fraction of HES had significantly decreased water content (5.1 +/- 3.4%) when compared to rats receiving RL (8.3 +/- 2.2, p less than .01), less than 100,000 dalton HES (8.3 +/- 3.2, p less than .05), less than 300,000 glycogen (7.9 +/- 2.5, p less than .01), or dextran 150,000 (8.3 +/- 1.5, p less than .05). Rats given 100,000 to 300,000-dalton HES also had significantly higher ischemic muscle K+ content as compared to the nontourniquet control (difference 14.2 +/- 9.7 mEq/g) than rats receiving any of the other solutions (range 32.5 to 39.3) except the 300,000 to 1,000,000-dalton fraction of HES. Regression analysis comparison of K+ difference to the histologic evaluation of the muscles on the criteria of polymorphonuclear infiltration and interstitial edema (0, best; 3, worst) had a Pearson correlation coefficient of r = .73. Reduction of abnormally increased microvascular permeability may be accomplished by the iv use of appropriate sized biodegradable macromolecules.
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PMID:Macromolecules reduce abnormal microvascular permeability in rat limb ischemia-reperfusion injury. 248 Feb 5

This study examined the microcirculatory alterations in the hindlimb of the rat caused by ischemia and vascular washout with lactated Ringer's solution. Experimental groups consisted of innervated and denervated animals, each subjected to 2 hours of hindlimb ischemia. The ischemic period was then followed by either vascular washout or no washout prior to reperfusion. The cutaneous capillary blood flow was measured using laser Doppler velocimetry. The results demonstrated a substantial increase in early reperfusion flow above baseline in the innervated groups, more apparent in the group subjected to vascular washout. In all cases where there was elevated early flow, later flow levels were decreased. The results and proposed mechanisms of the response are discussed.
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PMID:Microcirculatory responses to vascular washout following ischemia. 259 95


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