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

Experiments were designed to determine whether endothelial injury contributes to augmented coronary vascular tone seen during myocardial reperfusion. Canine left anterior descending coronary arteries were exposed to ischemia followed by reperfusion (60 minutes each). Rings (3-4 mm) of the reperfused artery and of normal left circumflex (control) coronary artery segments were prepared. Rings were suspended for isometric force measurement in organ chambers containing modified Krebs' Ringer bicarbonate solution (37 degrees C, 95% O2-5% CO2). Endothelium-independent contractions to KCl and prostaglandin F2 alpha were unaltered after reperfusion. Endothelium-dependent relaxations to nitric oxide, sodium nitroprusside, and isoproterenol were comparable in control and reperfused arteries. However, reperfused coronary arteries contracted with prostaglandin F2 alpha lost the ability to express endothelium-dependent relaxations to aggregating platelets. Reperfused arterial rings also exhibited impaired endothelium-dependent relaxations to acetylcholine, the calcium ionophore A23187, and the platelet-derived compounds ADP and serotonin. Quiescent (noncontracted) reperfused arterial rings exhibited larger contractions than controls when exposed to aggregating platelets. In such quiescent rings, the endothelium-dependent increase in tension to hemoglobin was unaltered after reperfusion. Thus, coronary reperfusion impairs the normal endothelium-dependent relaxations to aggregating platelets and vasoactive drugs. This impairment of platelet-mediated coronary relaxation could help explain the increased vascular tone and tendency toward vasospasm commonly observed after reperfusion of the coronary arteries.
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PMID:Acute impairment of endothelium-dependent relaxations to aggregating platelets following reperfusion injury in canine coronary arteries. 211 21

The objective of this study was to determine whether hydrogen peroxide, iron, and/or hydroxyl radicals play a role in ischemia/reperfusion (I/R)-induced granulocyte infiltration in the feline small intestine and whether a chemoattractant is formed when superoxide or hydrogen peroxide reacts with feline extracellular fluid. In vivo determinations of granulocyte infiltration consisted of measurements of tissue myeloperoxidase activity in either the intestinal mucosa (I/R studies) or dermis (chemotaxis studies), whereas in vitro measurements of granulocyte migration were obtained using a Boyden chamber. Treatment with either catalase or the iron chelator deferoxamine significantly attenuated granulocyte infiltration into the mucosa induced by reperfusion of the ischemic intestine. Two hydroxyl radical scavengers, dimethyl sulfoxide (DMSO) and dimethylthiourea (DMTU), were also evaluated for their ability to modulate I/R-induced granulocyte infiltration. DMTU significantly attenuated the I/R-induced granulocyte accumulation, whereas DMSO had no effect. In other experiments, we were unable to stimulate granulocyte migration with feline plasma exposed to superoxide-generating systems using both in vitro and in vivo models of leukocyte chemotaxis. However, hydrogen peroxide in the presence of either ferrous iron or hemoglobin did significantly increase the chemotactic activity of cat plasma. The results obtained from our studies suggest that either hydrogen peroxide or radical species derived from the interaction of superoxide and hydrogen peroxide with iron elicit I/R-induced granulocyte infiltration in the intestine.
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PMID:Role of oxidants in ischemia/reperfusion-induced granulocyte infiltration. 215 38

The endothelial-derived relaxing factor is a vasodilator agent that is formed in the vascular endothelium in response to various stimuli. It has been identified as nitric oxide (NO). Due to its short half-life the endothelial-derived relaxing factor offers certain analytical problems. We present here a method for quantitative analysis of nitrite, the oxidation product of NO, in human plasma. NO binds strongly to hemoglobin. If the resulting NO-hemoglobin (Hb) complex is subjected to a magnetic field and microwave radiation, a characteristic electron paramagnetic resonance spectrum is obtained. This spectrum is highly specific and its amplitude can be used for quantitative determination of NO in the nanomolar range. Columns of bovine Hb covalently bound to agarose were prepared, and an excess amount of dithionite was used to ensure that the Hb was reduced to a ferrous, nonoxygenated state. Samples of human plasma were treated with dithionite to convert nitrite to nitric oxide. They were then passed over the columns, which were subsequently analyzed at 77 degrees K in an electron paramagnetic resonance spectrometer. As an external standard nitrite was used. The amplitude of the spectrum was linear in the range 1-100 nmol. In healthy subjects the venous plasma level of nitrite ranged from 0 to 0.6 microM. Following forearm or leg ischemia the plasma level of nitrite increased substantially. These data are the first to demonstrate circulating levels of an index of the endothelial-derived relaxing factor in human plasma.
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PMID:Detection of endothelial-derived relaxing factor in human plasma in the basal state and following ischemia using electron paramagnetic resonance spectrometry. 216 51

Myocardial oxygenation may be altered markedly by changes in tissue blood flow. During brief ischemia and reperfusion produced by transient occlusion of the left anterior descending artery in 10 open-chest dogs, changes in the oxygenation of tissue hemoglobin (Hb) plus myoglobin (Mb) and the oxidation-reduction (redox) state of mitochondrial cytochrome aa3 were monitored continuously using near-infrared spectroscopy. The nondestructive optical technique indicated that coronary occlusion produced an abrupt drop in tissue oxygen stores (tHb02 + Mb02), tissue blood volume (tBV), and the oxidation level of cytochrome aa3. Changes in the cytochrome oxidation state were related inversely to transmural collateral blood flow within the ischemic region (r = 0.77) measured with radiolabeled microspheres. Furthermore, there was a direct relationship (r = 0.91) between collateral blood flow and the tissue level of desaturated Hb and Mb (tHb + Mb). Reperfusion after 2 min of ischemia led to a synchronous overshoot of baseline in coronary flow and tBV followed by supranormal increases in tHb + Mb02 and the oxidation level of cytochrome aa3. The tHb + Mb level increased transiently during reperfusion. This response correlated inversely with collateral flow during ischemia (r = 0.91). Accordingly, the time required to reach peak tHb + Mb levels was shortest in dogs with high collateral flows (r = 0.75). Thus collateral blood flow partially sustains myocardial oxygenation during coronary artery occlusion and influences tissue reoxygenation early during reperfusion.
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PMID:Dynamic mechanisms of cardiac oxygenation during brief ischemia and reperfusion. 217 24

This study documents the value of continuous observation of nicotinamide adenine dinucleotide (NADH) fluorescence (NADH-F). NADH-F monitoring is used to identify ischemic regions for the recognition of minor technical failures associated with ischemia and reperfusion experiments in the isolated perfused heart system. The visualization of NADH-F is possible by simply irradiating the heart with ultraviolet light. Rat hearts, in the working-heart mode, were subjected to occlusion/reperfusion of the left coronary artery, and analyzed. The perfusate was filtered through a 5 micron pore membrane. Out of 281 hearts which were judged to be free of technical failures by conventional physiological indices (heart rate greater than 200/min, cardiac output greater than 34 ml/min, and coronary flow 9-14 ml/min), 43 (15%) disclosed an abnormal NADH-F area prior to the coronary intervention. During coronary intervention, 29 technical failures were detected as indicated by sparse NADH-F distribution with occlusion, delayed disappearance of NADH-F upon reperfusion, or the exhibition of an abnormal NADH-F region unassociated with the coronary artery supply area. These technical failures are not detectable without the use of NADH-F, although the actual number of failures detected may depend on the skill of the operator. We recommend NADH-F monitoring for any preparations which do not contain hemoglobin, since NADH-F is an intrinsic probe for ischemia and is easily applicable to a variety of experiments.
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PMID:The detection of technical failures in perfused heart with ischemia and reperfusion by epicardial NADH fluorescence. 222 7

We tested the hypothesis that 1- to 2-wk-old pigs (piglet) have improved recovery of cerebral blood flow (CBF), cerebral oxygen consumption (CMRO2), and somatosensory-evoked potentials (SEP) compared with 6- to 8-mo-old pigs (pig) after transient global cerebral ischemia. All animals were anesthetized with pentobarbital sodium. After tracheostomy ventilation was adjusted to maintain normoxia (arterial oxygen pressure, 100-150 mmHg) and normocarbia (arterial carbon dioxide pressure, 35-40 mmHg). Arterial blood gases, blood pressure, and hemoglobin concentration remained within physiological limits throughout the experiment. Cerebral ischemia was produced by sequentially tightening ligatures around the inferior vena cava and ascending aorta. During ischemia the electroencephalogram and SEP became isoelectric within 40 and 120 s, respectively. At 10 min of reperfusion hyperemia occurred in most brain regions (e.g., whole brain: piglet, 270 +/- 45%; pig, 316 +/- 48%). In pigs delayed hypoperfusion occurred in all regions except white matter. In contrast, piglets only had delayed hyperperfusion to the brain stem and caudate nucleus. Throughout reperfusion CMRO2 was decreased in pigs (3.3 +/- 0.4 to 1.9 +/- 0.2 ml.min-1.100 g-1) but was not different from control (2.7 +/- 0.3 ml.min-1.100 g-1) in piglets. By the end of reperfusion SEP amplitude was closer to control in piglets than pigs (55 +/- 9 vs. 32 +/- 4% of control). We conclude that 1- to 2-wk-old piglets have quicker return of CBF, CMRO2, and SEP to control values after global ischemia, which mechanistically may explain previous reports of improved neurological recovery in young animals after transient ischemia.
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PMID:Age-related cerebrovascular response to global ischemia in pigs. 224 Feb 52

Anterior segment ischemia (ASI) is a dreaded complication of retinal detachment surgery particularly in patients with predisposing factors such as sickle cell disease. We report a case of ASI after scleral buckling in an otherwise healthy black patient with sickle cell trait. Conditions of relative hypoxia intraoperatively from either anesthesia or surgical manipulation may precipitate vasoocclusive phenomena in these normally asymptomatic patients. Since the incidence of sickle cell trait in the black population in the United States is 8.5%, we recommend these patients have a preoperative sickle test followed by hemoglobin electrophoresis with quantification if positive. The presence of sickle cell trait should alert the surgeon to the risk of ASI, and factors predisposing to hypoxia should be minimized when possible.
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PMID:Anterior segment ischemia: a complication of retinal detachment repair in a patient with sickle cell trait. 224 89

Delayed cerebral ischemia is the major cause of death and disability in patients who initially survive an aneurysmal subarachnoid hemorrhage (SAH). In the present study, a protocol for prophylactic hypertensive hypervolemic hemodilution ("triple-H" therapy) was utilized in the treatment of SAH, and the response of cerebral blood flow (CBF) was evaluated. Serial CBF measurements, f1 and CBF15, were performed using the xenon-133 inhalation technique to maximize therapy. Surgery within 24 hours of subarachnoid hemorrhage was preferred. In 43 patients with SAH, mean hemoglobin and hematocrit were lowered 3.0 +/- 0.3 g/dL and 8.9 +/- 0.5%, respectively, over the first 24 hours. Mean f1 and mean CBF15 over the same period increased 34.2 +/- 5.8% and 21.2 +/- 3.6%, respectively. The maximum mean increase in CBF was 47.2 +/- 4.7% for f1 and 30.1 +/- 3.2% for CBF15. Cerebral blood flow remained elevated during the 21 days after SAH, irrespective of neurological grade on admission, age, sex, or angiographic arterial narrowing. This is the first report of a consistent method for establishing sustained improvement in CBF after SAH. All patients managed in total compliance with the protocol remained neurologically stable or improved. Two patients developed delayed ischemia and infarction because of the inability to sustain protocol requirements. Thirty-six of the 43 patients (84%) were discharged capable of an independent lifestyle. Triple-H therapy is a safe and effective modality for elevating and sustaining CBF after SAH. In combination with early aneurysm surgery, it can minimize delayed cerebral ischemia and lead to an improved overall outcome.
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PMID:Sustained increased cerebral blood flow with prophylactic hypertensive hypervolemic hemodilution ("triple-H" therapy) after subarachnoid hemorrhage. 225 3

Results of subarachnoid hemorrhage (SAH) in the acute phase are represented by the direct threat of vasospasm. The first step still is to recognise SAH, so that all misleading clinical aspects of arterial aneurysm rupture do not misguide, or even fail to do the right diagnosis. If so, rebleeding still remains a real danger. Among biological patterns, hyponatremia is an important factor of vasospasm. Cardiovascular symptoms are represented by a sudden and transient arterial hypertension which can drive to a diagnostic error and electrocardiographic abnormalities, which are directly related with the degree of vasospasm; their evolution is completely regressive. Main intracranial consequences are early hydrocephalus, worsening of consciousness and progressive ventricular distension on CT scan and vasospasm, which occurs between the 4th and the 12th day, may be asymptomatic or symptomatic, responsive for delayed ischemia, followed by deterioration of consciousness and focal neurological signs. The main factors responsible for the vasospasm are a high amount of blood in basal cisterns on CT scan; an increase of substances released by the lysis of hemoglobin in CSF; hyponatremia, hypovolemia, and decrease in cerebral blood flow. Consequences of these disorders have to be well known in the medical treatment before and after operation.
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PMID:[Consequences of meningeal hemorrhage during the first days after its onset]. 228 34

Disorders of hemoglobin synthesis affect the musculoskeletal system by either causing replacement of bone by hematopoietic tissue, precipitating bone and soft tissue ischemia and necrosis, or a combination of both processes. Less frequently, joints are involved by synovial ischemia, synovial deposition of iron, or microfracture of subchondral bone. Osteopenia is a significant problem in both thalassemia and sickle cell anemia and may result in vertebral and long bone fractures. Growth disturbances are frequently seen but are not often appreciated until adolescence because of improved hematologic management. The cause of the growth problems is multifactorial and may be related to hormonal deficiencies, iron overload, hypoxia, or local trauma to the growth plate secondary to significant osteopenia.
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PMID:Musculoskeletal problems in hemoglobinopathy. 229 57


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