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R Busto

Publications and source records attributed to R Busto.

At least 91 records · Page 5Linked to original sources
PubMed1996

Posttreatment with intravenous basic fibroblast growth factor reduces histopathological damage following fluid-percussion brain injury in rats.

The purpose of this study was to determine whether treatment with intravenous basic fibroblast growth factor (bFGF) would protect histopathologically in a rat model of traumatic brain injury (TBI). Twenty-four hours prior to TBI, the fluid-percussion interface was positioned parasagittally over the right cerebral cortex. On the second day, fasted rats were anesthetized with 70% nitrous oxide, 1% halothane, and 30% oxygen. Under controlled physiological conditions and normothermic brain temperature (37-37.5 degrees C), rats were injured with a fluid-percussion pulse ranging from 1.6 to 1.9 atm. Rats were randomized into two groups where either bFGF (45 micrograms/kg/h) in vehicle (n = 7) or vehicle alone (n = 7) was infused intravenously for 3 h, beginning 30 min after TBI. Three days later, brains were perfusion-fixed for histopathological assessment and quantitative analysis of contusion volume and numbers of necrotic cortical neurons. In vehicle-treated animals, necrotic neurons were observed throughout the lateral cerebral cortex remote from the impact site. In addition, an intracerebral contusion was present in all rats at the gray-white interface underlying the injured cortical areas. Posttraumatic administration of bFGF significantly reduced the numbers of damaged cortical neuron profiles at several coronal levels and reduced the total number of damaged neurons (696 +/- 148 vs. 1,248 +/- 198, means +/- SEM), p < 0.05, ANOVA). In addition, contusion ares at several coronal levels as well as total contusion volume was significantly reduced (1.13 +/- 0.39 mm(3) vs. 3.18 +/- 0.81 mm(3), p < 0.05). These data demonstrate neuroprotection with intravenous bFGF infusion in the posttraumatic setting.

Animals↗
PubMed1996

Simultaneous measurement of salicylate hydroxylation and glutamate release in the penumbral cortex following transient middle cerebral artery occlusion in rats.

Using the microdialysis technique and laser-Doppler flowmetry, we performed simultaneous measurement of salicylate hydroxylation and glutamate release along with local CBF in the ischemic penumbral cortex of rat brain subjected to normothermic transient middle cerebral artery (MCA) occlusion. Cortical CBF fell to 24 +/- 11% (mean +/- SD) during ischemia and recovered to 84 +/- 16% during reperfusion. Extracellular glutamate levels increased by 6.5-fold above baseline 10 min following MCA occlusion but subsequently returned to near baseline levels in spite of the persistent ischemia. Increase in 2,3- and 2,5-dihydroxybenzoic acid (DHBA) concentrations in the microdialysis perfusate was confirmed during both ischemia and reperfusion phase. Although the temporal profile and amount of salicylate hydroxylation were heterogeneous among individual animals, integrated 2,3-DHBA concentrations during reperfusion were correlated positively with integrated glutamate concentrations during ischemia and negatively with mean postischemic CBF. These relationships suggest a possible association of the enhanced production of 2,3-DHBA during reperfusion with larger amounts of intraischemic glutamate release and lower levels of post-ischemic CBF.

Acid-Base Imbalance↗
PubMed1996

Widespread hemodynamic depression and focal platelet accumulation after fluid percussion brain injury: a double-label autoradiographic study in rats.

Cerebrovascular damage leading to subsequent reductions in local cerebral blood flow (lCBF) may represent an important secondary injury mechanism following traumatic brain injury (TBI). We determined whether patterns of 111-indium-labeled platelet accumulation were spatially related to alterations in lCBF determined autoradiographically 30 min after TBI. Sprague-Dawley rats (n = 8), anesthetized with halothane and maintained on a 70:30 (vol/vol) mixture of nitrous oxide/oxygen and 0.5% halothane, underwent parasagittal fluid percussion brain injury (1.7-2.2 atm). 111-Indium-tropolone-labeled platelets were injected 30 min prior to TBI while [14C]-iodoantipyrine was infused 30 min after trauma. Sham-operated animals (n = 7) underwent similar surgical procedures but were not injured. In autoradiographic images of the indium-labeled platelets, focal sites of platelet accumulation within the traumatized hemisphere were restricted to the pial surface (five of eight rats), the external capsule underlying the lateral parietal cortex (five of eight rats), and within cerebrospinal fluid (CSF) compartments (six of eight rats). In contrast, mild-to-moderate reductions in lCBF, not restricted to sites of platelet accumulation, were seen throughout the traumatized hemisphere. Flow reductions were most severe in coronal sections underlying the impact site. For example, within the lateral parietal cortex and hippocampus, lCBF was significantly reduced [p <0.01; analysis of variance (ANOVA)] from 1.71 +/- 0.34 (mean +/- SD) and 0.78 +/- 0.12 ml/g/min, respectively, versus 0.72 +/- 0.17 and 0.41 +/- 0.06 ml/g/min within the traumatized hemisphere. Significant flow reductions were also seen in remote cortical and subcortical areas, including the right frontal cortex and striatum. These results indicate that focal platelet accumulation and widespread hemodynamic depression are both early consequences of TBI. Therapeutic strategies directed at these early microvascular consequences of TBI may be neuroprotective by attenuating secondary ischemic processes.

Animals↗
PubMed1996

L-arginine does not improve cortical perfusion or histopathological outcome in spontaneously hypertensive rats subjected to distal middle cerebral artery photothrombotic occlusion.

The potential of nitric oxide (NO) to influence positively or negatively the outcome of mechanically induced focal cerebral ischemia is still controversial. Recent evidence suggests that NO of vascular origin, whether synthesized from exogenously administered L-arginine (L-Arg) or from NO donor compounds, is beneficial but that of neuronal origin is not. However, the therapeutic potential of NO to ameliorate stroke induced by arterial thrombosis has not been reported. We assessed the therapeutic effect of L-Arg administration in spontaneously hypertensive rats (SHR) subjected to permanent photothrombotic occlusion of the distal middle cerebral artery (dMCA). The ipsilateral carotid artery was left unligated to enhance L-Arg delivery into the putative penumbral region. Local CBF (LCBF) was assessed at 30 min by the [14C]iodoantipyrine technique (n = 9), while histological infarct volumes and index of peripheral ischemic cell change were determined at 3 days (n = 7). Rats (n = 9) given 300 mg/kg L-Arg at 18 and 3 h before photothrombotic dMCA occlusion and at 5 min afterward displayed no significant differences in LCBF compared with animals (n = 8) injected with water (the carrier vehicle) and similarly irradiated. Infarct volumes were also similar, being 37.0 +/- 9.7 mm3 (SD) in the vehicle-treated and 49.1 +/- 17.2 mm3 (SD) in the L-Arg-treated groups (both n = 7), as were assessments of ischemic neuronal density in the penumbra. In contrast, L-Arg administered intravenously in a dose of 300 mg/kg to nonischemic SHR (n = 5) increased cortical CBF by approximately 75% during a 70-min observation period. We conclude that thrombotic processes superimposed upon cerebral ischemia may facilitate tissue reactions that offset the potentially beneficial effect of L-Arg, and this caveat must be considered when proposing L-Arg for clinical treatment of focal thrombotic stroke.

Animals↗
PubMed1996

Neuronal damage following intraspinal injection of a nitric oxide synthase inhibitor in the rat.

Intraspinal microinjection of the nonspecific nitric oxide synthase (NOS) inhibitor N-nitro-L-arginine methyl ester (L-NAME) was used to determine if inhibition of NOS results in morphological changes in the rat spinal cord. Following spinal injections of 100-750 mM L-NAME (pH 7.0), 1.0-500 mM L-NAME (pH 2.5-5.4), or L-NAME + L-arginine, quantitative analysis of morphological changes revealed a positive dose-response relationship between L-NAME and neuronal loss. This effect was blocked by L-arginine and was inversely related to spinal levels of NOS enzyme activity. Results of this study have shown the importance of basal NOS activity in maintaining the structural integrity of spinal neurons. It is proposed that the effects of L-NAME on nitric oxide (NO) production leads to decreased blood flow, secondary to vasoconstriction, and a hypoxic-ischemic reaction in spinal tissue. The results suggest that a potential contributing factor to neuronal damage in pathological conditions such as spinal cord injury may be the decreased production of nitric oxide.

Animals↗
PubMed1996

Delayed posttraumatic brain hyperthermia worsens outcome after fluid percussion brain injury: a light and electron microscopic study in rats.

The morphological consequences of delayed posttraumatic brain hyperthermia (39 degrees C) after fluid percussion brain injury were assessed in rats. Sprague-Dawley rats anesthetized with 4% halothane and maintained on a 70:30 mixture of nitrous oxide:oxygen and 0.5% halothane underwent moderate (1.5-2.0 atm) traumatic brain injury with the injury screw positioned parasagittally over the right parieto-occipital cortex. At 24 hours after traumatic brain injury, the rats were reanesthetized and randomized into two groups in which either a 3-hour period of brain normothermia (36.5 degrees C, n = 18) or hyperthermia (39 degrees C, n = 18) was maintained. Sham-operated controls (n = 10) underwent all surgical and temperature-monitoring procedures. After the 3-hour monitoring period, the rats were allowed to survive for 3 days for light microscopic analysis or were injected with the protein tracer horseradish peroxidase and were perfusion-fixed 15 minutes later for light and electron microscopic analysis. At 4 days after traumatic brain injury, delayed posttraumatic hyperthermia (n = 12) significantly increased mortality (47%) and contusion volume (1.7 +/- 0.69 mm3, mean +/- standard error of the mean), compared to normothermia (n = 12) (18% mortality and 0.13 +/- 0.21 mm3 contusion volume) (P < 0.01, analysis of variance). At 15 minutes after the 3-hour hyperthermic period, the area of hemorrhage and horseradish peroxidase extravasation overlying the lateral external capsule was significantly increased (2.52 +/- 0.71 mm2, mean +/- standard error of the mean, versus 0.43 +/- 0.16 mm2) (P < 0.01), compared to normothermic rats. Examination of toluidine blue-stained plastic sections demonstrated a higher frequency of abnormally swollen myelinated axons per high microscopic field with hyperthermia. For example, numbers of swollen axons within the sixth layer of the right somatosensory cortex, corpus callosum, and internal capsule were 7.3 +/- 1.3, 4.2 +/- 1.4, and 3.0 +/- 1.2 axons (mean +/- standard error of the mean) with normothermia, respectively, compared with 24.7 +/- 12.1, 33.1 +/- 4.2, and 27.3 +/- 3.1 axons with hyperthermia, respectively (P < 0.01). An ultrastructural examination of the swollen axons demonstrated a severely thinned myelin sheath containing axoplasm devoid of cytoskeletal components. These experimental results indicate that posttraumatic brain hyperthermia might increase morbidity and mortality in patients with head injury by aggravating axonal and microvascular damage.

Animals↗
PubMed1996

Delayed postischemic hyperthermia in awake rats worsens the histopathological outcome of transient focal cerebral ischemia.

BACKGROUND AND PURPOSE: Over the past several years, it has been demonstrated that mild intraischemic or immediate postischemic hyperthermia worsens ischemic outcome in models of global and focal ischemia. Periods of hyperthermia are commonly seen in patients after stroke and cardiac arrest. The hypothesis tested in this study was that a brief hyperthermic period, even when occurring days after an ischemic insult, has detrimental effects on the pathological outcome of focal ischemia. METHODS: Rats were subjected to 60 minutes of transient middle cerebral artery occlusion by insertion of an intraluminal filament. Twenty-four hours after reperfusion, awake rats were subjected to temperature modulation for 3 hours in a heating chamber. The brain temperature was equilibrated to either 37 degrees C to 38 degrees C, or 40 degrees C. Changes in rectal temperature and blood glucose concentration were evaluated during and just after temperature modulation. Behavioral tests were also assessed. Three days after temperature modulation, brains were perfusion-fixed, and infarct volumes were determined. RESULTS: In animals with 40 degrees C hyperthermia, cortical and total infarct volumes were markedly greater (92.2 +/- 63.1 and 126.5 +/- 72.3 mm3 [mean +/- SD], respectively) than in normothermic rats (14.4 +/- 12.7 and 42.4 +/- 19.2 mm3) and in animals with 39 degrees C hyperthermia (16.5 +/- 28.7 and 40.9 +/- 34.3 mm3) (P < .05), whereas there was no significant difference between normothermic and 39 degrees C hyperthermic animals. In addition, animals with 40 degrees C hyperthermia displayed worsened neurological scores compared with normothermic and 39 degrees C hyperthermic rats. In the 39 degrees C hyperthermia group, rectal temperatures were significantly lower (by 0.2 degree C to 0.5 degree C) than brain temperatures throughout the modulation period. CONCLUSIONS: The present findings provide evidence that, after a transient focal ischemic insult, the postischemic brain becomes abnormally sensitive to the effects of delayed temperature elevation, even of moderate degree. The threshold for aggravation of ischemic injury by delayed hyperthermia appears to be approximately 40 degrees C. Body-temperature measurements, in both awake and anesthetized animals, may not accurately reflect brain temperature under these conditions. The present study stresses that fever of even moderate degree in the days following brain ischemia may markedly exacerbate brain injury.

Animals↗
PubMed1996

Middle cerebral artery occlusion in the rat by intraluminal suture. Neurological and pathological evaluation of an improved model.

BACKGROUND AND PURPOSE: The purpose of the present study was to evaluate a modified method of intraluminal suture occlusion of the middle cerebral artery (MCA) on the volume of brain infarction and on neurobehavioral function in rats subjected to a temporary focal ischemic insult. METHODS: Male Sprague-Dawley rats were anesthetized with halothane and subjected to 60 minutes or 2 hours of temporary MCA occlusion (MCAo) by an intraluminal thread. In one group of rats, the suture was coated with poly-L-lysine, while in a second group, a conventional uncoated suture was used. Behavioral function was evaluated at 50 to 60 minutes after occlusion and during a 3-day period after MCAo. Three days after MCAo brains were perfusion-fixed and infarct volumes were measured. RESULTS: In rats with 60-minute MCAo, only 3 of 7 animals with uncoated sutures had infarcts, whereas in the group with poly-L-lysine-coated sutures, all rats (n = 7) exhibited infarction (P = .009, Fisher's exact test). With 2 hours of MCAo, total infarct volume (corrected for brain edema) was significantly larger in rats with poly-L-lysine-coated sutures than in the group with uncoated sutures (mean +/- SEM, 122.1 +/- 4.8 versus 67.0 +/- 18.2 mm3, respectively; P = .03; n = 4 in each group). In the 2-hour MCAo study, infarct volumes in the uncoated-suture group tended to be variable and inconsistent (coefficient of variation, 54%) compared with the group in which sutures were coated with poly-L-lysine, in which a highly consistent infarct was produced (coefficient of variation of infarct volume, 8%). CONCLUSIONS: Reversible MCAo in which a poly-L-lysine-coated intraluminal suture was used proved to be a reliable and effective modification of this technique, yielding consistently larger infarcts and greatly reduced interanimal variability.

Animals↗
PubMed1995

Combined postischemic hypothermia and delayed MK-801 treatment attenuates neurobehavioral deficits associated with transient global ischemia in rats.

The present study was designed to determine whether postischemic hypothermia, delayed MK-801 (dizocilpine) administration, or a combination of these treatments can provide lasting neurobehavioral protection following transient global ischemia in rats. Rats were subjected to 10 min of normothermic (37 degrees C) ischemia induced by 2-vessel occlusion and hypotension (50 mmHg) or sham procedures. Ischemia was followed by either: (a) 3 h at normothermic brain temperatures, (b) 3 h of postischemic brain hypothermia at 30 degrees C, (c) hypothermia coupled with MK-801 (4 mg/kg, i.p.) on postischemic days 3, 5 and 7, or (d) postischemic MK-801 treatment alone. Neurobehavioral evaluation 6-8 weeks following surgery showed that normothermic ischemia (NI) was associated with water maze navigational deficits, including performance on a simple place task involving finding a hidden platform maintained in one position for 6 days, and a learning set task in which the platform was moved to a different location each day (both P's < 0.02 vs. sham). NI was also associated with increased locomotion in an open field (P < 0.01 vs. sham). A combination of postischemic hypothermia and delayed MK-801 injections provided partial protection from ischemic-associated hyperactivity in the open field (P < 0.02 vs. NI), and robust protection from simple place task deficits (P < 0.02 vs. NI). Evidence for significant protective effects of MK-801 or hypothermia alone was observed in the learning set, during the final trial blocks each day. These results provide further evidence for neuroprotective effects of these treatments at chronic survival intervals, and indicate that the therapeutic window for attenuating ischemic damage is considerably longer than has heretofore been appreciated.

Animals↗
PubMed1995

Post-ischemic administration of HU-211, a novel non-competitive NMDA antagonist, protects against blood-brain barrier disruption in photochemical cortical infarction in rats: a quantitative study.

We examined the effect of HU-211, a synthetic non-psychotropic cannabinoid with non-competitive N-methyl-D-aspartate (NMDA) antagonist properties, on blood-brain barrier (BBB) integrity after photochemically induced cortical infarction. Evans blue dye was used as a BBB permeability indicator after unilateral thrombotic cortical infarction was produced photochemically by 560 nm light irradiation of the cortex in male Wistar rats receiving rose bengal intravenously. HU-211 was injected in a dose of 4 mg/kg i.v. 30 min after stroke. Fluorometric measurement of Evans blue was performed 24 h later in six brain regions. Treatment with HU-211 significantly decreased extravasation of dye into the area of infarct (406 +/- 19 vs. 539 +/- 33 micrograms/g, mean +/- S.E.M.) as well as other sites of the affected hemisphere (866 +/- 68 vs. 1096 +/- 68 micrograms/g) compared to the vehicle group. These data indicate that HU-211 is an effective drug in protecting against the effects of focal ischemia-induced BBB disruption in the rat and suggest that the drug may be an effective treatment against the ischemic cell death and BBB disruption that can occur clinically following a stroke or cardiac arrest.

Animals↗
PubMed1995

Ischemia-induced changes in extracellular levels of striatal cyclic GMP: role of nitric oxide.

Using microdialysis, we evaluated temporal changes in striatal extracellular cGMP level following ischemia and its relationship to nitric oxide (NO) production. In untreated animals, significant elevation of cGMP was observed during ischemia and during 4 h of recirculation. In animals treated with L-NAME ischemia induced a modest increase in the cGMP level, but this level was significantly lower than that observed in the untreated animals. These results demonstrate first, that the microdialysis technique can be used to detect changes in extracellular cGMP levels during ischemia and second, that ischemia and recirculation induce a rise in cGMP which is diminished by nitric oxide synthase inhibition, suggesting a linkage to NO production.

Analysis of Variance↗
PubMed1995

Local hemodynamic changes during transient middle cerebral artery occlusion and recirculation in the rat: a [14C]iodoantipyrine autoradiographic study.

We evaluated acute alterations of local cerebral perfusion following 30 min of transient right proximal middle cerebral artery (MCA) clip-occlusion in the rat and following two intervals of postischemic reperfusion. Local cerebral blood flow (lCBF) was assessed by [14C]iodoantipyrine autoradiography. Brain temperature was controlled at 35.5-36.5 degrees C throughout the experiment. We measured lCBF in four groups of rats: (a) sham-operated controls (n = 5), (b) following 30 min MCA occlusion (n = 5), (c) following 30 min of MCA occlusion with 15-min reperfusion (n = 6) and (d) following 30 min of MCA with 120-min reperfusion (n = 6). lCBF was measured in seven regions of the ischemic and non-ischemic hemispheres. MCA occlusion induced an ipsilateral reduction of lCBF, which was most severe in the parietal cortex (8.4 +/- 4.0% of control, mean +/- S.D.), and dorsolateral caudoputamen (20.0 +/- 13.4% of control). lCBF in the non-ischemic hemisphere and in ipsilateral regions lying outside the MCA territory also decreased significantly. lCBF recovery was incomplete when assessed following only 15 min of reperfusion. Reperfusion of 120 min led to return of cortical CBF to control levels, but lCBF in the caudoputamen remained depressed (50-55% of control values). Caudoputaminal CBF and cortical CBF values were highly correlated with one another under normal and ischemic conditions, but this correlation was disrupted following reperfusion. On the basis of these results, we speculate that, if a means were found to enhance the early recovery of lCBF following transient ischemia, this might expand the therapeutic window of opportunity for the institution of other neuroprotective strategies.

Acute Disease↗
PubMed1995

A dual role for nitric oxide in NMDA-mediated toxicity in vivo.

Nitric oxide has been implicated in N-methyl-D-aspartate (NMDA)-mediated damage in vitro; however, its role in excitotoxic damage in vivo is not clear. In the present study we evaluated the histopathological and hemodynamic consequences of intrastriatal injections of various doses of NMDA and determined the effects of nitric oxide synthase inhibition on these changes. NMDA was injected into the striatum at doses of 50, 150, and 300 nmol with or without N omega-nitro-L-arginine methyl ester (L-NAME; 100 micrograms, locally). Three days following injections histopathological assessment was performed by morphometric analysis of the lesion area in multiple sections taken from the anterior to the posterior borders of the lesion. In animals injected with 150 and 300 nmol of NMDA (+/- L-NAME), local CBF (lCBF) was determined 30 min following injections using 14C-iodoantipyrine autoradiography. All NMDA-treated animals showed a well-demarcated lesion extending beyond the injection site. The volume of the lesion correlated significantly with the NMDA dose injected. The effects of L-NAME on lesion size were dependent on the dose of the NMDA. The lesion induced by 50 nmol of NMDA was not affected by L-NAME. With a dose of 150 nmol of NMDA, L-NAME induced a 43% increase in lesion volume. In contrast, a 38% decrease in lesion size was observed in animals treated with 300 nmol of NMDA combined with L-NAME. At a dose of 150 nmol, NMDA induced a significant elevation in lCBF, which was restricted to regions close to the injection site including the center areas of the anterior and middle striatum. The increase in lCBF observed with 150 nmol of NMDA was significantly attenuated in the NMDA + L-NAME-treated group. The lCBF changes induced by 300 nmol of NMDA were not significantly different from those in the 150-nmol group; however, the extent of the regions involved was larger. The increases in lCBF were observed in all striatal regions including the central and peripheral areas. L-NAME did not have a significant effect on the lCBF changes induced by NMDA at a dose of 300 nmol. These data suggest that in vivo the involvement of nitric oxide in NMDA toxicity depends on the NMDA dose and on the participation of hemodynamic mechanisms secondary to NMDA exposure.

Animals↗
PubMed1995

Effect of delayed MK-801 (dizocilpine) treatment with or without immediate postischemic hypothermia on chronic neuronal survival after global forebrain ischemia in rats.

In contrast to intraischemic hypothermia, immediate postischemic hypothermia (30 degrees C) has been shown to delay but not chronically protect the CA1 hippocampus from transient global forebrain ischemia. The inability of a relatively short postischemic hypothermic period to protect chronically might involve a delayed or secondary injury mechanism. We determined whether delayed treatment with the noncompetitive N-methyl-D-aspartate receptor antagonist MK-801 (dizocilpine), alone or in combination with immediate postischemic hypothermia, would chronically protect histopathologically. Wistar rats underwent 10 min of normothermic forebrain ischemia induced by bilateral common carotid artery occlusion plus hypotension (50 mg Hg). Four ischemia groups were studied after normothermic (37 degrees C) ischemia: no treatment; 3 h of immediate postischemic hypothermia (30 degrees C); delayed MK-801 treatment (4 mg/kg) on postischemic days 3, 5, and 7; and postischemic hypothermia combined with multiple MK-801 treatments. Two months after the ischemic insult, rats were perfusion-fixed for quantitative histopathological assessment. Postischemic hypothermia alone or MK-801 treatment alone failed to protect the CA1 hippocampus chronically. However, immediate postischemic hypothermia combined with delayed MK-801 treatment led to significant increases in normal CA1 neuron counts per microscopic field compared with normothermic ischemia. For example, neuronal counts within the hippocampal CA1 areas were 58 +/- 39 (mean +/- SD) in normothermic ischemic rats compared with 395 +/- 198 in rats treated with postischemic hypothermia and MK-801. Chronic survival also led to pronounced striatal damage. Within the dorsolateral striatum, significant protection was documented with either postischemic hypothermia alone or delayed MK-801 treatment alone.

Animals↗
PubMed1995

Local cerebral glucose utilization and cytoskeletal proteolysis as indices of evolving focal ischemic injury in core and penumbra.

To ascertain the tempo of progression to irreversible injury in focal ischemia, we subjected halothane-anesthetized Sprague-Dawley rats to photochemically induced distal middle cerebral artery occlusion (dMCAO) combined with permanent ipsilateral and 1 h contralateral common carotid artery occlusions. Head temperature was maintained at 36 degrees C. At times centered at either 1.5 or 3 h post-dMCAO, the rate of local glucose metabolism (lCMRgl) was measured by 2-deoxyglucose autoradiography, and cytoskeletal proteolysis was assessed regionally by an immunoblotting procedure to detect spectrin breakdown products. At 1.5 h (n = 5), the cortical ischemic core was already severely hypometabolic (lCMRgl 15.5 +/- 10.8 mumol 100 g-1 min-1, mean +/- SD), whereas the cortical penumbral zone was hypermetabolic (69.0 +/- 9.7). (The lumped constant was verified to be unchanged by methylglucose studies). Neutral red pH studies at this time point showed that both the core and penumbral zones were equally acidotic. By 3 h post-dMCAO (n = 6), lCMRgl in the penumbral zone had fallen to low levels (15.4 +/- 2.2 mumol 100 g-1 min-1) equal to those of the ischemic core (16.7 +/- 4.5). Correspondingly, spectrin breakdown in the ischemic core was advanced at both 2 and 3.5 h post-dMCAO (36 +/- 18% and 33 +/- 18% of total spectrin, respectively), whereas in the penumbral zone spectrin breakdown was less extensive and more highly variable at both times (22 +/- 23% and 29 +/- 16%). We conclude that irreversible deterioration of the ischemic core, as evidenced by the onset of local cytoskeletal proteolysis, begins within 2 h of middle cerebral artery occlusion. In the ischemic penumbra, the transition from glucose hyper- to hypometabolism occurs by 3.5 h and is associated with a milder and more variable degree of spectrin breakdown.

Animals↗
PubMed1995

Detection of free radical activity during transient global ischemia and recirculation: effects of intraischemic brain temperature modulation.

To obtain direct evidence of oxygen radical activity in the course of cerebral ischemia under different intraischemic temperatures, we used a method based on the chemical trapping of hydroxyl radical in the form of the stable adducts 2,3- and 2,5-dihydroxybenzoic acid (DHBA) following salicylate administration. Wistar rats were subjected to 20 min of global forebrain ischemia by two-vessel occlusion plus systemic hypotension (50 mm Hg). Intraischemic striatal temperature was maintained as normothermic (37 degrees C), hypothermic (30 degrees C), or hyperthermic (39 degrees C) but was held at 37 degrees C before and following ischemia. Salicylate was administered either systemically (200 mg/kg, i.p.) or by continuous infusion (5 mM) through a microdialysis probe implanted in the striatum. Striatal extracellular fluid was sampled at regular intervals before, during, and after ischemia, and levels of 2,3- and 2,5-DHBA were assayed by HPLC with electrochemical detection. Following systemic administration of salicylate, stable baseline levels of 2,3- and 2,5-DHBA were observed before ischemia. During 20 min of normothermic ischemia, a 50% reduction in mean levels of both DHBAs was documented, suggesting a baseline level of hydroxyl radical that was diminished during ischemia, presumably owing to oxygen restriction to tissue at that time. During recirculation, 2,3- and 2,5-DHBA levels increased by 2.5- and 2.8-fold, respectively. Levels of 2,3-DHBA remained elevated during 1 h of reperfusion, whereas the increase in 2,5-DHBA persisted for 2 h. The increases in 2,3- and 2,5-DHBA levels observed following hyperthermic ischemia were significantly higher (3.8- and fivefold, respectively). In contrast, no significant changes in DHBA levels were observed following hypothermic ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Glutamate release and free radical production following brain injury: effects of posttraumatic hypothermia.

Posttraumatic hypothermia reduces the extent of neuronal damage in remote cortical and subcortical structures following traumatic brain injury (TBI). We evaluated whether excessive extracellular release of glutamate and generation of hydroxyl radicals are associated with remote traumatic injury, and whether posttraumatic hypothermia modulates these processes. Lateral fluid percussion was used to induce TBI in rats. The salicylate-trapping method was used in conjunction with microdialysis and HPLC to detect hydroxyl radicals by measurement of the stable adducts 2,3- and 2,5-dihydroxybenzoic acid (DHBA). Extracellular glutamate was measured from the same samples. Following trauma, brain temperature was maintained for 3 h at either 37 or 30 degrees C. Sham-trauma animals were treated in an identical manner. In the normothermic group, TBI induced significant elevations in 2,3-DHBA (3.3-fold, p < 0.01), 2,5-DHBA (2.5-fold, p < 0.01), and glutamate (2.8-fold, p < 0.01) compared with controls. The levels of 2,3-DHBA and glutamate remained high for approximately 1 h after trauma, whereas levels of 2,5-DHBA remained high for the entire sampling period (4 h). Linear regression analysis revealed a significant positive correlation between integrated 2,3-DHBA and glutamate concentrations (p < 0.05). Posttraumatic hypothermia resulted in suppression of both 2,3- and 2,5-DHBA elevations and glutamate release. The present data indicate that TBI is followed by prompt increases in both glutamate release and hydroxyl radical production from cortical regions adjacent to the impact site. The magnitude of glutamate release is correlated with the extent of the hydroxyl radical adduct, raising the possibility that the two responses are associated.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗