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

Monitoring motor-evoked responses to transcranial stimulation (tc-MERs) provides information about the functional status of the spinal cord during operations that pose the risk of spinal cord ischemia. Responses can be recorded from the epidural space (epidural tc-MERs) or from muscle (myogenic tc-MERs). In this study the relative sensitivity of epidural and myogenic tc-MERs to acute spinal cord ischemia was compared. Spinal cord ischemia was produced by infrarenal aortic balloon occlusion in nine anesthetized New Zealand White rabbits. Tc-MERs were evoked by transcranial electrical stimuli applied to the scalp. Responses were recorded from the lumbar epidural space and from the soleus muscle, and the effect of aortic occlusion was assessed. The peak-to-peak amplitude of the direct wave of the epidural response decreased gradually during aortic occlusion in eight animals and increased in one. The median (10th to 90th percentiles) time to a 50% reduction in amplitude was 11.3 (3-22) min. In contrast, myogenic responses disappeared within 2 min after the start of occlusion in all animals. Lower extremity ischemia as a cause of changes in myogenic tc-MER amplitude was excluded by ligating the right femoral artery and demonstrating that myogenic responses were preserved for 30 min, before occluding the aorta. We conclude that myogenic responses are more sensitive to acute spinal cord ischemia than epidural responses. The rapid detection of spinal cord ischemia with transcranial myogenic motor-evoked responses could be of clinical use in assessing the adequacy of spinal cord blood flow during operations where the spinal cord is at risk.
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PMID:A comparison of the sensitivity of epidural and myogenic transcranial motor-evoked responses in the detection of acute spinal cord ischemia in the rabbit. 889 79

Altered vascular responsiveness is the hallmark of septic shock. Recently, these changes have frequently been attributed to increased production of nitric oxide (NO). Continued exposure to high levels of NO may alter both endothelial and vascular smooth muscle cell function. Although ex vivo studies demonstrate hyporeactivity of large conduit arteries during established sepsis, it is unclear if the same phenomena exist during early sepsis. This is especially true in the small resistance arterioles of the viscera. We used in vivo microscopy of the rat small intestine to assess (1) endothelial-dependent relaxation and vasomotion (periodic contraction and relaxation of blood vessels) in response to acetylcholine (ACH; 10(-8) to 10(-5) M), (2) endothelial-independent relaxation to nitroprusside (NTP; 10(-5) M), and (3) vascular smooth muscle response to norepinephrine (NE; 10(-10) to 10(-7) M) in normal and bacteremic rats (Escherichia coli). There were no alterations in endothelial-dependent or -independent relaxation during bacteremia as measured by mean diameters. However, acute E. coli bacteremia severely impaired vasomotion in A1 (inflow) and A3 (premucosal) arterioles. Vasomotion was returned to baseline levels in A1 with low-dose ACH (10(-8) M) but only partially improved in A3 arterioles (P < 0.05). A1 response to NE was impaired, while A3 were minimally altered despite being more sensitive to E. coli-induced vasoconstriction. These data suggest that bacteremia causes a rapid, differential impairment of both endothelial-dependent (A3 vasomotion) and vascular smooth muscle cell (A1 constriction) functions. These microvascular impairments occur much earlier than previously described and may contribute to sepsis-induced mucosal ischemia of the intestines.
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PMID:Differential intestinal microvascular dysfunction occurs during bacteremia. 907 Jan 84

This study investigates firstly how far cellular edema correlates with parameters of the anaerobic energy turnover independent of the method used for cardiac arrest, and secondly to what extent cellular edema developing during reversible global ischemia is reduced after reperfusion. Canine hearts were arrested 1. by aortic cross clamping (ACC), 2. by coronary perfusion with St. Thomas solution, or 3. HTK (histidine tryptophan ketoglutarate) solution (Custodiol). Samples for biochemical and structural analysis were taken at different times during ischemia and after reperfusion with Tyrode solution. Cellular edema determined morphometrically and given as volume ratio of sarcoplasm and mitochondria to myofibrils (Vvsp + V vmi/Vvmf) varies significantly in the differently arrested hearts. Reperfusion after a decrease in ATP to 4 mumol/gww (revival time) leads to a nearly complete structural recovery. The relationship between cellular edema and defined over-all metabolite tissue concentrations and extracellular pHe values shows: 1. during the decrease of creatine phosphate to 3 mumol/gww, cellular edema does not change; it is, however, significantly higher after ACC and St. Thomas than after HTK perfusion; 2. at each lactate concentration, cellular edema differs significantly depending on the form of cardiac arrest; 3. during the decrease of ATP and pHe cellular edema increases and is comparable at concentrations < 4 mumol/gww and at pHe values < 6.5 independent of the form of cardiac arrest; 4. beyond 10 mumol/gww of inorganic phosphate (Pi), increasing values for cellular edema correspond to defined Pi values in the differently arrested hearts. Thus, the ratio VVSp+ VVMi/VVMf is a powerful parameter for the determination of cellular edema during ischemia, as well as for correlations with metabolic parameters.
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PMID:Cellular edema and alterations in metabolite content in the ischemic and reperfused canine heart following different forms of cardiac arrest. 912 37

The objective of this study was to assess the protective capacity of UW solution in comparison to Bretschneider's (HTK) cardioplegic solution under moderate hypothermic conditions (25 degrees C), as those usually present during intraoperative myocardial protection. Ischemia-induced alterations of cardiac function parameters were analyzed and compared for each solution after 45 min of ischemic storage and 60 min of reperfusion with oxygenated Krebs-Henseleit buffer (KHB), using a rat working-heart model. Compared to nonischemic values, left-ventricular systolic and diastolic pressure, +dp/dtmax and -dp/dtmax were significantly better maintained in the HTK (95 mm Hg, 7 mm Hg, 2,657 mm Hg/s and 2,122 mm Hg/s) than in the UW group (76 mm Hg, p < 0.05, 11 mm Hg, p < 0.05, 1,745 mm Hg/s, p < 0.05 and 1,600 mm Hg/s, p < 0.05). Concerning the myocardial contents of ATP, creatine phosphate and the energy charge, a minor decrease was observed after preservation in HTK compared to UW solution. The results of this study indicate superior myocardial protection with the use of HTK solution for protection of the heart at 25 degrees C compared to UW solution.
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PMID:HTK versus UW solution for myocardial protection during moderate hypothermia. 925 98

Hypoxia is a pathophysiological condition that occurs during injury, ischemia, and stroke. It is characterized by a decrease of reactive oxygen intermediates and a change of the intracellular redox level. In tumors hypoxia is regarded as a trigger for enhanced growth and metastasis. Here we report that in HeLa cells, hypoxic conditions induce the transcriptional activation of c-fos transcription via the serum response element. Mutations in the binding site for the ternary complex factor Elk-1 and the serum response factor abolished this induction, indicating that a ternary complex at the serum response element is necessary for the induction of the c-fos gene under hypoxia. The transcription factor Elk-1 was covalently modified by phosphorylation in response to hypoxia. Furthermore this hyperphosphorylation of Elk-1, the activation of mitogen-activated protein kinase (MAPK), and the induction of c-fos transcripts were blocked by PD98059, a specific inhibitor of mitogen-activated protein kinase kinase/extracellular signal-regulated protein kinase kinase 1. An in vitro kinase assay with Elk-1 as substrate showed that MAPK is activated under hypoxia. The activation of MAPK corresponds temporally with the phosphorylation and activation of Elk-1. Thus, a decrease of the intracellular reactive oxygen intermediate level by hypoxia induces c-fos via the MAPK pathway. These results suggest that the intracellular redox levels may be directly coupled to tumor growth, invasion, and metastasis via Elk-1-dependent induction of c-Fos controlled genes.
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PMID:Hypoxia induces c-fos transcription via a mitogen-activated protein kinase-dependent pathway. 928 59

During myocardial ischemia, inhibition of the carnitine-mediated transportation of fatty acid may be beneficial because it facilitates glucose utilization and prevents an accumulation of fatty acid metabolites. We orally administered 3-(2,2,2-trimethyl hydrazinium) propionate (MET), an inhibitor of carnitine synthesis, for 20 days to rats. Then we evaluated left ventricular (LV) function during brief ischemia by using a buffer-perfused isovolumic heart model. After 15 min of reoxygenation after the transient ischemia, LV peak systolic pressure (PSP) almost completely returned to the baseline level in rats given MET (96 +/- 4%), whereas it was only partially (77 +/- 16%) recovered in the placebo-treated rats. We induced myocardial infarction in other rats by ligating the left anterior descending coronary artery. Then the animals were given MET for 20 days, and LV function was compared. In the placebo-treated rats (with myocardial infarction, but without drug treatment), LVPSP was lower than that in the sham group [108 +/- 19 (n = 10) vs. 136 +/- 15 mm Hg (n = 13); p < 0.05], and the time constant (T) of LV pressure decay was elongated (36 +/- 4 vs. 30 +/- 7 ms; p < 0.05). In MET-treated groups, however, neither PSP nor T differed from those in the sham group. In conclusion, inhibition of the carnitine-mediated transportation of fatty acid by MET protected against left ventricular dysfunction in acute and chronic myocardial ischemia.
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PMID:Inhibition of carnitine synthesis protects against left ventricular dysfunction in rats with myocardial ischemia. 933 6

Warm ischemia is known to induce substantial damage to the liver parenchyma. With respect to clinical liver transplantation, the tolerance of the liver to warm ischemia and the preservation of these organs have not been studied in detail. In isolated reperfused pig livers we proceeded according to the following concept: Livers were subjected to 1 or 3 h of warm ischemia. Subsequently, these organs were preserved by either normothermic perfusion or cold storage (histidine-tryptophan-alpha-ketoglutarate, HTK) for 3 h each. After storage, liver function was assessed in a reperfusion circuit for another 3 h. Parameters under evaluation were bile flow, perfusion flow, oxygen consumption, enzyme release into the perfusate (creatine kinase, glutamic oxaloacetic transaminase (GOT), lactic dehydrogenase, and glutamic pyruvic transaminase), and histomorphology. Damage to the liver was lowest after warm ischemia of 1 h. The results after cold storage were superior to those after normothermic perfusion (GOT: 3.2 +/- 0.3 and 2.6 +/- 0.2 U/g liver; cumulative bile production: 14.7 +/- 2.1 and 9.4 +/- 1 ml, respectively; P < 0.05). In contrast, we found substantial damage at the end of reperfusion in livers undergoing 3 h of warm ischemia under both preservation techniques with severe hepatocellular pyknoses and essentially altered nonparenchymal cells. The results suggest that pig livers undergoing 1 h of warm ischemia and cold storage for 3 h with HTK solution may lead to functioning after transplantation.
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PMID:Preservation of pig liver allografts after warm ischemia: normothermic perfusion versus cold storage. 939 99

This study was designed to assess whether the protective effect of ischemic preconditioning can be adapted for myocardium undergoing 6 h of no-flow ischemia. Twelve isolated rat hearts were either perfused with oxygen-bicarbonated Krebs-Henseleit buffer in the Langendorff mode for 35 min (n=6), or perfused in the same way for 20 min, following 5 min of global normothermic ischemia and 100 min of buffer-perfusion (n=6). The 12 hearts were then preserved for 6 h in HTK solution at 4 degrees C, followed by 30 min of reperfusion. Recovery of cardiac function, metabolic activity and intracellular free calcium concentration were compared between the two groups. After 6 h ischemia, the hearts that underwent preconditioning showed better recovery of left ventricular developed pressure (P<0.01), a lower end-diastolic pressure level (P<0.05), less creatine kinase leakage and a lower calcium concentration. There was no statistical difference in the recovery rate of coronary flow and leakage rate of LDH between the two groups. In conclusion, this experiment demonstrates that ischemic preconditioning improved myocardial functional recovery after 6 h of hypothermic ischemic preservation in the isolated rat heart. Preconditioning might be a potential mechanism for preserving the heart against long-term ischemia/reperfusion injury.
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PMID:Cardioprotective efficacy of ischemic preconditioning on long-term myocardial ischemia. 946 84

"Stress-regulated" mitogen-activated protein kinases (SR-MAPKs) comprise the stress-activated protein kinases (SAPKs)/c-Jun N-terminal kinases (JNKs) and the p38-MAPKs. In the perfused heart, ischemia/reperfusion activates SR-MAPKs. Although the agent(s) directly responsible is unclear, reactive oxygen species are generated during ischemia/reperfusion. We have assessed the ability of oxidative stress (as exemplified by H2O2) to activate SR-MAPKs in the perfused heart and compared it with the effect of ischemia/reperfusion. H2O2 activated both SAPKs/JNKs and p38-MAPK. Maximal activation by H2O2 in both cases was observed at 0.5 mM. Whereas activation of p38-MAPK by H2O2 was comparable to that of ischemia and ischemia/reperfusion, activation of the SAPKs/JNKs was less than that of ischemia/reperfusion. As with ischemia/reperfusion, there was minimal activation of the ERK MAPK subfamily by H2O2. MAPK-activated protein kinase 2 (MAPKAPK2), a downstream substrate of p38-MAPKs, was activated by H2O2 to a similar extent as with ischemia or ischemia/reperfusion. In all instances, activation of MAPKAPK2 in perfused hearts was inhibited by SB203580, an inhibitor of p38-MAPKs. Perfusion of hearts at high aortic pressure (20 kilopascals) also activated the SR-MAPKs and MAPKAPK2. Free radical trapping agents (dimethyl sulfoxide and N-t-butyl-alpha-phenyl nitrone) inhibited the activation of SR-MAPKs and MAPKAPK2 by ischemia/reperfusion. These data are consistent with a role for reactive oxygen species in the activation of SR-MAPKs during ischemia/reperfusion.
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PMID:Stimulation of "stress-regulated" mitogen-activated protein kinases (stress-activated protein kinases/c-Jun N-terminal kinases and p38-mitogen-activated protein kinases) in perfused rat hearts by oxidative and other stresses. 951 15

Extracellular stimuli such as neurotransmitters, neurotrophins, and growth factors in the brain regulate critical cellular events, including synaptic transmission, neuronal plasticity, morphological differentiation and survival. Although many such stimuli trigger Ser/Thr-kinase and tyrosine-kinase cascades, the extracellular signal-regulated kinases, ERK1 and ERK2, prototypic members of the mitogen-activated protein (MAP) kinase family, are most attractive candidates among protein kinases that mediate morphological differentiation and promote survival in neurons. ERK1 and ERK2 are abundant in the central nervous system (CNS) and are activated during various physiological and pathological events such as brain ischemia and epilepsy. In cultured hippocampal neurons, simulation of glutamate receptors can activate ERK signaling, for which elevation of intracellular Ca2+ is required. In addition, brain-derived neurotrophic factor and growth factors also induce the ERK signaling and here, receptor-coupled tyrosine kinase activation has an association. We describe herein intracellular cascades of ERK signaling through neurotransmitters and neurotrophic factors. Putative functional implications of ERK and other MAP-kinase family members in the central nervous system are give attention.
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PMID:Role of MAP kinase in neurons. 955 3


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