UMLS:C0022116 - FACTA Search

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

Rats were exposed to insulin-induced hypoglycemia resulting in periods of cerebral isoelectricity ranging from 10 to 60 min. After recovery with glucose, they were allowed to wake up and survive for 1 week. Control rats were recovered at the stage of EEG slowing. After sub-serial sectioning, the number and distribution of dying neurons was assessed in each brain region. Acid fuchsin was found to stain moribund neurons a brilliant red. Brains from control rats showed no dying neurons. From 10 to 60 min of cerebral isoelectricity, the number of dying neurons per brain correlated positively with the number of minutes of cerebral isoelectricity up to the maximum examined period of 60 min. Neuronal necrosis was found in the major brain regions vulnerable to several different insults. However, within each region the damage was not distributed as observed in ischemia. A superficial to deep gradient in the density of neuronal necrosis was seen in the cerebral cortex. More severe damage revealed a gradient in relation to the subjacent white matter as well. The caudatoputamen was involved more heavily near the white matter, and in more severely affected animals near the angle of the lateral ventricle. The hippocampus showed dense neuronal necrosis at the crest of the dentate gyrus and a gradient of increasing selective neuronal necrosis medially in CA1. The CA3 zone, while relatively resistant, showed neuronal necrosis in relation to the lateral ventricle in animals with hydrocephalus. Sharp demarcations between normal and damaged neuropil were found in the hippocampus. The periventricular amygdaloid nuclei showed damage closest to the lateral ventricles. The cerebellum was affected first near the foramina of Luschka, with damage occurring over the hemispheres in more severely affected animals. Purkinje cells were affected first, but basket cells were damaged as well. Rare necrotic neurons were seen in brain stem nuclei. The spinal cord showed necrosis of neurons in all areas of the gray matter. Infarction was not seen in this study. The possibility is discussed that a neurotoxic substance borne in the tissue fluid and cerebrospinal fluid (CSF) contributes to the pathogenesis of neuronal necrosis in hypoglycemic brain damage.
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PMID:The distribution of hypoglycemic brain damage. 649 35

Thirty-eight male Wistar rats were exposed to insulin-induced hypoglycemia resulting in periods of cerebral isoelectricity ranging from 10 to 60 min. Plasma glucose levels during cerebral isoelectricity ranged from 0.12 mM to 1.36 mM. Control rats were injected with insulin, but hypoglycemia was terminated with glucose at the stage of large delta-wave EEG slowing. After recovery, the rats were allowed to wake up and survive for 1 wk. The number of dying neurons was assessed with acid-fuchsin/cresyl-violet-stained, whole-brain, subserial sections using direct visual counting of acidophilic, cytoclastic neurons. Brains from control rats that were not allowed to become isoelectric showed no dying neurons. Ten minutes of cerebral isoelectricity produced very minimal brain damage. The density of neuronal necrosis was positively related to the number of minutes of cerebral isoelectricity up to the maximum examined period of 60 min, but showed no correlation with the blood sugar levels. The cerebral cortex, hippocampus, caudate nucleus, spinal cord, and, to a lesser extent, cerebellar Purkinje cells were affected. The distribution of neuronal necrosis was not identical with that seen in ischemia, but, rather, suggested a CSF-borne neurotoxin operant in contributing to the pathogenesis of neuronal necrosis in hypoglycemic brain damage. Neuronal death does not occur in hypoglycemia unless the EEG becomes isoelectric, whatever the blood sugar level. Serious brain damage does not occur until electrocerebral silence has been established for at least several minutes. Neuronal death accelerates after 30 min of EEG isoelectricity in the rat.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hypoglycemic brain injury in the rat. Correlation of density of brain damage with the EEG isoelectric time: a quantitative study. 650 Jan 89

The effect of locally infused endotoxin on gracilis muscle glucose uptake was determined in anesthetized mongrel dogs. The effects of infusion of small amounts of Escherichia coli endotoxin into the arteries of isolated, innervated, constant flow perfused gracilis muscles on glucose uptake and other metabolic variables were determined. Locally infused endotoxin consistently caused a significant and substantial increase in skeletal muscle glucose uptake with no alterations in muscle arteriovenous difference of insulin, oxygen, carbon dioxode, or pH, or in venous blood hematocrit or temperature. These data demonstrate that endotoxin can act locally to increase glucose uptake by skeletal muscle, independent of the action of insulin or other metabolic factors. During natural (free flow) conditions, glucose uptake by the muscle increased markedly during six hours of shock. Increased glucose uptake occurred concomitantly with muscle ischemia and hypoxia. However, when muscle blood flow was held constant, thereby preventing local muscle ischemia and hypoxia, glucose uptake by the gracilis muscle did not change during shock. These results implicate local muscle ischemia and/or hypoxia as the mediator(s) of the increased muscle glucose uptake during shock. Further studies demonstrated that local muscle hypoxia was the stimulus for increased glucose uptake by skeletal muscle during endotoxin shock, and muscle ischemia per se did not alter muscle glucose uptake. Since approximately 50% of body mass is composed of skeletal muscle, the contribution of this organ system to the hypoglycemia of endotoxin shock in the dog may be substantial. The ability of insulin to promote glucose diffusion into skeletal muscle before and during gram-negative endotoxin shock was studied in mongrel dogs anesthetized with sodium pentobarbital. The in vivo, isolated, innervated, constant flow perfused gracilis muscle preparation was used. Prior to shock induction, close intra-arterial insulin infusion resulted in a 320% increase in muscle glucose uptake. However, at one, two, and three hours of endotoxin shock, gracilis muscle glucose uptake was unaltered by insulin infusion. This loss of responsiveness to insulin occurred with no alteration in gracilis muscle oxygen uptake, muscle venous P02, or muscle blood flow. During control experiments, however, the muscle response to intra-arterial infusion of insulin (increased glucose uptake) was unaltered during the three-hour control period. These data demonstrate that skeletal muscle insulin resistance develops early and is maintained during three hours of endotoxin shock in the dog.
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PMID:Skeletal muscle metabolism and insulin resistance during endotoxin shock in the dog. 651 86

The neurophysiological alterations associated with transient insulin-induced hypoglycemia were compared in 14 cats anesthetized with halothane and 14 cats anesthetized with pentobarbital fasted for 18 h prior to the study. Each anesthetic group was further divided into acute and chronic preparations which in turn were prepared and studied in an identical manner except for the anesthetic agent employed. In the chronic animals there was no difference in survival between the two groups following a 2-h period of hypoglycemia. In these preparations there were no significant differences in: blood glucose levels, mean arterial blood pressure (MABP); arterial carbon dioxide tension (paCO2), arterial oxygen tensions (paO2), arterial pH (pHa), or acid-base balance during the period of hypoglycemia. Differences in the electroencephalograms were commensurate with the anesthetic used. In the acute preparations cerebral blood flow (CBF), xenon-133 clearance technique; brain pH, pH sensitive fluorescent indicator method; and cerebral metabolic rates of oxygen (CMRO2) and glucose consumption were determined at 15-min intervals in addition to the measurements recorded in the chronic group. During a 3-h period of regular insulin administration at a rate of 30 units/kg/h there were no significant differences in any of the systemic or brain measurements recorded except for CBF (halothane greater than barbiturate). EEGs in the acute group of animals paralleled the chronic group and improved but did not return to normal following glucose resuscitation at the end of the period of hypoglycemia. All the acute animals had a normal paCO2-CBF response curve prior to the insulin administration. CBF and brain pH remained constant during the period of hypoglycemia in both groups. However, following the administration of glucose there was a significant brain acidosis and EEG change without a change in CBF. We conclude that: the protective effects of barbiturates in states of hypoxemia or ischemia do not extend to hypoglycemia, brain pH and blood flow are not altered by moderate (as opposed to severe) hypoglycemia, and brain pH may not be the prime regulator in the CBF-metabolic blood flow couple.
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PMID:Correlation of brain blood flow, intracellular pH and metabolism in hypoglycemic cats under halothane and barbiturate anesthesia. 679 Jan 27

Glucose, lactate, pyruvate and adenosine triphosphate (ATP) concentrations in the supratentorial brain tissue frozen in situ were measured one hour after bilateral carotid occlusion in spontaneously hypertensive rats, of which blood glucose levels were varied by intraperitoneally injected insulin (hypoglycemia), saline (normoglycemia) and 50% glucose (hyperglycemia). Cerebral glucose concentrations as well as blood glucose levels were significantly increased in hyperglycemic animals, and decreased in hypoglycemic ones. Cerebral lactate, and lactate/pyruvate ratio at one-hour ischemia tended to increase in hyperglycemic animals comparing with those in normoglycemic ones, although cerebral ATP levels were slightly higher in the former. In hypoglycemic animals with one-hour ischemia, cerebral lactate was less increased but ATP was significantly reduced. It has been reported that hyperglycemia has vulnerable effects on brain metabolism of complete cerebral ischemia, presumably due to hyperglycemia-induced lactic acidosis of the brain. In incomplete cerebral ischemia as demonstrated in the present study, however, ATP concentrations remained at slightly higher level, despite tendency to more increase in lactate in hyperglycemic animals, indicating that high blood glucose level might be beneficial, rather than vulnerable, to incomplete cerebral ischemia. On the other hand, hypoglycemia causes more severe impairment of the brain energy metabolism because of an insufficient supply of substrates to the brain.
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PMID:[Effects of hypo- or hyperglycemia on brain metabolism in experimental cerebral ischemia]. 684 11

Neuronal lesions in the brain occur in conditions associated with a reduced supply of oxygen (hypoxia and ischemia) and glucose (hypoglycemia) as well as in those associated with a pathologically enhanced neuronal activity (status epilepticus). In only two of these conditions (hypoxia and ischemia) are the lesions correlated to cellular oxygen lack, and gross energy failure is absent in one condition (status epilepticus). Although anaerobic mechanisms seem responsible for the cell injury in hypoxia and ischemia, oxidative mechanisms could operate in hypoglycemia and status epilepticus. Since the supply of oxygen has not ceased altogether in hypoxia and incomplete ischemia, and since reoxygenation/recirculation leads to a transient increase in tissue oxygen tensions, one cannot exclude the possibility that oxidative mechanisms contribute to the final damage following all types of cellular oxygen lack. We have failed to obtain evidence that peroxidative degradation of cellular constituents occurs in hypoglycemia and status epilepticus. Thus, there is neither a perturbation of the redox state of the glutathione pool of the tissue nor a measurable degradation of polyenoic phospholipid-bound fatty acids. It is emphasized that the cascade of events triggered by an accumulation of free polyenoic fatty acids, mainly arachidonic acid, may contribute to cell lesions by leading to cell edema and/or microcirculatory changes. During seizures, such an accumulation occurs even though energy failure is moderate and it may conceivably contribute to cell damage. In general, though, mechanisms of cell damage in the brain remain partly elusive.
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PMID:Neuronal cell damage in the brain: possible involvement of oxidative mechanisms. 693 2

Carbohydrate metabolism of skeletal muscle was studied during 2 mg/kg E coli endotoxin shock in dogs. During natural (free-flow) conditions, glucose uptake by the muscle increased markedly during 6 hours of shock. Increased glucose uptake occurred concomitant with muscle ischemia and hypoxia. However, when muscle blood flow was held constant, thereby preventing local muscle ischemia and hypoxia, glucose uptake by the gracilis muscle did not change during shock. These results implicate local muscle ischemia and/or hypoxia as the mediator(s) of the increased muscle glucose uptake during shock. Further studies demonstrated that local muscle hypoxia was the stimulus for increased glucose uptake by skeletal muscle during endotoxin shock, and muscle ischemia per se did not alter muscle glucose uptake. Since approximately 50% of body mass is composed of skeletal muscle, the contribution of this organ system in the hypoglycemia of endotoxin shock in the dog may be substantial.
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PMID:Mechanism of increased glucose uptake by skeletal muscle during E coli endotoxin shock in the dog. 701 61

Previous results have shown that severe, prolonged hypoglycemia leads to neuronal cell damage in, among other structures, the cerebral cortex and the hippocampus but not the cerebellum. In order to study whether or not this sparing of cerebellar cells is due to preservation of cerebellar energy stores, hypoglycemia of sufficient severity to abolish spontaneous EEG activity was induced for 30 and 60 min. At the end of these periods of hypoglycemia, as well as after a 30 min recovery period, cerebellar tissue was sampled for biochemical analyses or for histopathological analyses or for histopathological analyses by means of light and electron microscopy. After 30 min of hypoglycemia. the cerebellar energy state, defined in terms of the phosphocreatine, ATP, ADP, and AMP concentrations, was better preserved than in the cerebral cortex. After 60 min, gross deterioration of cerebellar energy state was observed in the majority of animals, and analyses of carbohydrate metabolites and amino acids demonstrated extensive consumption of endogenous substrates. In spite of this metabolic disturbance, histopathologic alterations were surprisingly discrete. After 30 min, no clear structural changes were observed. After 60 min, only small neurons in the molecular layer (basket cells) were affected, while Purkinje cells and granule cells showed few signs of damage. The results support our previous conclusion that the pathogenesis of cell damage in hypoglycemia is different from that in hypoxia-ischemia and indicate that other mechanisms than energy failure must contribute to neuronal cell damage in the brain.
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PMID:Hypoglycemic brain injury: metabolic and structural findings in rat cerebellar cortex during profound insulin-induced hypoglycemia and in the recovery period following glucose administration. 703 72

The interrelationships between hemodynamics and hypoglycemia during the course of endotoxin shock (ES) has not been fully defined. In the following study, ES (E. coli, 1 mg/kg; n = 7) was induced in a canine model and systemic hemodynamics, glucose metabolism, and hepatic and pancreatic function monitored for 5 hr and compared to time-matched controls (TMC, n = 7). Total peripheral resistance (TPR, dynes-sec-cm-5) increased from 3227 +/- 430 to 4050 +/- 750 at 30 min and then declined to 3050 +/- 1100 at 90 minutes. TPR progressively increased to 6225 +/- 749 by 5 hours. Plasma glucose did not significantly differ from control values (105 +/- 4 mg%) for the first 90 min but then declined to 68 +/- 6 mg% at 4.5 hours. (TMC = 103 +/- 17, P less than 0.05). Serum amylase during the 5 hr protocol was not elevated (TMC = 110.9 +/- 2.4; ES = 100 +/- 1.97%; P greater than 0.1), and light microscopy of the exocrine pancreas demonstrated normal acinar structure. Islet cell structure from the ES group is not significantly different from the TMC. Hepatic histology in the ES group demonstrated periportal and perilobular degranulation and hepatocyte disruption not seen in the TMC. It is hypothesized that ES results in a circle of positive feedback initiated by an increase in TPR and subsequent decrease in flow resulting in hepato-pancreatic ischemia. Ischemic damage is most apparent at the liver and leads to changes in hepatic metabolic activities which contribute to the developing hypoglycemia of the late phase of ES.
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PMID:Hemodynamics, hypoglycemia, and hepato-pancreatic pathology during the course of endotoxin shock. 734 83

In order to assess the influence of severe hypoglycemia on local cerebral blood flow (1-CBF) artificially ventilated rats, maintained on 70% N2O, were injected with insulin to provide either an EEG pattern of slow-wave polyspikes, or cessation of spontaneous EEG activity for 5, 15 or 30 min ("coma"). In other animals, glucose was injected at the end of a 30 min period of "coma" and 1-CBF was measured after recovery periods of 5, 30, 90, or 180 min. Local CBF was measured autoradiographically with 14C-iodoantipyrine as the diffusible tracer. In the slow-wave polyspike period 1-CBF was increased in most of the structures studied, and reached values that were 1.4 to 3.2 times greater than control. In many structures, cessation of EEG activity was accompanied by a further increase in 1-CBF, with some structures (thalamus, hypothalamus, pontine gray, and cerebellar cortex) showing flow rates of 400--500% of control. The increase in 1-CBF was unrelated to arterial hypertension, hypercapnia, or hypoxia. 5 min after glucose injection the hyperemia persisted in only some of the structures studied; in others, the 1-CBF were close to, or below, control values. During the subsequent recovery period 1-CBF was markedly reduced with some structures (cerebral cortical areas, hippocampus, and caudate-putamen) showing flow rates of only 20--35% of control. In others, notably pontine gray and cerebellar cortex, secondary hypoperfusion was never observed. The hypoperfusion was unrelated to arterial hypertension, hypocapnia, or increase in intracranial pressure. It is concluded that, like hypoxia and ischemia, substrate deficiency due to hypoglycemia is accompanied by vasodilatation in the brain. Furthermore, like long-lasting ischemia, severe hypoglycemia is followed by a delayed hypoperfusion syndrome that, by restricting oxygen supply, may well contribute to the final cell damage incurred.
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PMID:Local cerebral blood flow in the rat during severe hypoglycemia, and in the recovery period following glucose injection. 744 74

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