Biomedical subjects

R Busto

Publications and source records attributed to R Busto.

At least 73 records · Page 4Linked to original sources

PubMed1998

Hyperglycemic exacerbation of neuronal damage following forebrain ischemia: microglial, astrocytic and endothelial alterations.

We undertook a detailed characterization of the cellular responses to acute global cerebral ischemia complicated by hyperglycemia. Anesthetized, physiologically monitored male Wistar rats received 12.5 min of global forebrain ischemia by bilateral common carotid artery occlusions plus hemorrhagic hypotension to 45 mmHg. Cranial temperature was maintained at normothermic levels. Hyperglycemic animals received dextrose (2.5 ml of a 25% solution, intraperitoneally) prior to ischemia; this doubled the mean plasma glucose concentration to 296 mg/100 ml. At 3 days (n = 10) or 24 h (n = 4) after ischemia, brains were perfusion-fixed and paraffin-embedded for light microscopic histopathology and for the histochemical visualization of activated microglia and the immunocytochemical visualization of glial fibrillary acid protein. Normal-neuron counts in the vulnerable hippocampal CA1 sector of hyperglycemic-ischemic (HI) rats were reduced to one-third the number observed in normoglycemic-ischemic (NI) animals. Ischemic cell counts in the striatum were increased fivefold or more in HI compared to NI rats, and normal small-neuron counts were reduced by two-thirds. The neocortex and striatum of NI rats showed only mild damage, while the majority of HI rats had extensive lesions, and several showed large cortical, striatal or thalamic infarcts. In addition, widespread cortical ischemic neuronal changes were evident in HI animals. No endothelial alterations were present in NI rats. By contrast, HI rats showed prominent peri- and intravascular polymorphonuclear and monocytic accumulation evident at 24 h; frequent white cell thrombi in pial arterioles on day 3; and thickening of vascular endothelium, with foci of parenchymal rarefaction or microinfarction adjacent to occluded vessels. Prominent microglial activation, often along the course of penetrating blood vessels, was common in the striatum and neocortex of HI animals but was much less extensive in the NI group. Activated microglia in HI rats were typically hypertrophic and amoeboid. These results suggest that the detrimental influence of hyperglycemia in ischemia is initially mediated by an action on vascular endothelium, which in turn leads to widespread foci of infarction and neuronal loss.

Animals↗

PubMed1998

Posttraumatic cerebral ischemia after fluid percussion brain injury: an autoradiographic and histopathological study in rats.

OBJECTIVES: Mild-to-moderate reductions in local cerebral blood flow (ICBF) have been reported to occur in rats after moderate (1.7-2.2 atm) fluid percussion brain injury. The purpose of this study was to determine whether evidence for severe ischemia (i.e., mean ICBF < 0.25 ml/g/min) could be demonstrated after severe brain injury. In addition, patterns of indium-labeled platelet accumulation and histopathological outcome were correlated with the hemodynamic alterations. METHODS: Sprague-Dawley rats (n = 23), anesthetized with halothane and maintained on a 70:30 mixture of nitrous oxide:oxygen and 0.5% halothane, underwent normothermic (37 degrees C) parasagittal fluid percussion brain injury (2.4-2.6 atm). Indium-111-tropolone-labeled platelets were injected 30 minutes before traumatic brain injury (TBI), while 14C-iodoantipyrine was infused 30 minutes after trauma for ICBF determination. Sham-operated animals (n = 8) underwent similar surgical procedures but were not injured. For histopathological analysis, traumatized rats (n = 5) were perfusion-fixed 3 days after TBI. RESULTS: In autoradiographic images of indium-labeled platelets, abnormal platelet accumulation that was most pronounced overlying the pial surface was commonly associated with severe reductions in ICBF within underlying cortical regions 30 minutes after TBI. For example, within the lateral parietal cortex, ICBF was significantly reduced from 1.67 +/- 0.11 ml/g per minute (mean +/- standard error of the mean) in sham-operated animals to 0.23 +/- 0.03 ml/g per minute within the traumatized group. In addition to focal severe ischemia, moderate reductions in ICBF were detected throughout the traumatized hemisphere, including the frontal and occipital cortices, hippocampus, thalamus, and striatum. Mild decreases in ICBF were also observed throughout the contralateral cerebral cortex. At 3 days after severe TBI, histopathology demonstrated intracerebral and subarachnoid hemorrhage associated with cerebral contusion and selective neuronal necrosis. CONCLUSION: These data indicate that multiple cerebrovascular abnormalities, including subarachnoid hemorrhage, focal platelet accumulation, and severe ischemia, are important early events in the pathogenesis of cortical contusion formation after TBI. Injury severity is expected to be a critical factor in determining what therapeutic strategies are attempted in the clinical setting.

Animals↗

PubMed1998

Inducible nitric oxide synthase expression after traumatic brain injury and neuroprotection with aminoguanidine treatment in rats.

OBJECTIVE: We investigated the time course of inducible nitric oxide synthase (iNOS) enzymatic activity and immunocytochemical localization of iNOS expression after traumatic brain injury (TBI), as well as the possible role of iNOS in the pathogenesis of TBI. METHODS: Male Sprague-Dawley rats were anesthetized and underwent moderate parasagittal fluid-percussion brain injury. Rats were decapitated 5 minutes, 6 hours, 1 day, 3 days, 7 days, or 14 days later, and iNOS enzymatic activities were measured (n = 6-8). To determine whether nitric oxide produced by iNOS contributed to the histopathological consequences of TBI, inhibition of iNOS activity using aminoguanidine (intraperitoneal injections of 100 mg/kg aminoguanidine [n = 9] or vehicle [n = 8], twice each day) was conducted for 3 days. RESULTS: Significantly elevated iNOS activity was detected at 3 days (276.8+/-72.3% of contralateral value, means +/- standard errors; P < 0.05), and the most robust increase occurred 7 days after TBI (608.0+/-127.0%, P < 0.01) in the injured parietal cerebral cortex. Immunostaining for iNOS and glial fibrillary acidic protein, at 3 and 7 days after TBI, revealed that the major cellular sources of iNOS expression were cortical Layer 1 astrocytes and macrophages within the subarachnoid space. Administration of aminoguanidine did not reduce contusion volume significantly; however, treatment reduced total cortical necrotic neuron counts (1367.6+/-210.3; P < 0.01, compared with vehicle, 2808.5+/-325.1). CONCLUSION: These data indicate that iNOS is expressed after moderate parasagittal fluid-percussion brain injury, in a time-dependent manner, and that inhibition of iNOS synthesis improves histopathological outcomes. Thus, inhibition of iNOS activation may represent a potential therapeutic strategy for the treatment of TBI.

Animals↗

PubMed1998

Diffusion-weighted magnetic resonance imaging confirms marked neuroprotective efficacy of albumin therapy in focal cerebral ischemia.

BACKGROUND AND PURPOSE: We have recently shown high-dose human serum albumin therapy to confer marked histological protection in experimental middle cerebral artery occlusion (MCAo). We have now used diffusion-weighted magnetic resonance imaging (DWI) in conjunction with morphological methods to expand our understanding of this therapeutic approach. METHODS: Physiologically controlled Sprague-Dawley rats received 2-hour MCAo by the modified intraluminal suture method. Treated rats received 25% human serum albumin solution (1% by body weight) immediately after the MCA was reopened. Vehicle-treated rats received saline. Computer-based image averaging was used to analyze DWI data obtained 24 hours after MCAo and light-microscopic histopathology obtained at 3 days. In a matched series, plasma osmolality and colloid oncotic pressure, as well as brain water content, were determined. RESULTS: Albumin therapy, which lowered the hematocrit on average by 37% and raised plasma colloid oncotic pressure by 56%, improved the neurological score throughout the 3-day survival period. Within the ischemic focus, the apparent diffusion coefficient (ADC) computed from DWI data declined by 40% in vehicle-treated rats but was preserved at near-normal levels (8% decline) in albumin-treated rats (P<0.001). Albumin also led to higher ADC values within unlesioned brain regions. Histology revealed large consistent cortical and subcortical infarcts in vehicle-treated rats, while albumin therapy reduced infarct volume at these sites, on average, by 84% and 33%, respectively. Total infarct volume was reduced by 66% and brain swelling was virtually eliminated by albumin treatment. Microscopically, while infarcted regions of vehicle-treated rats had the typical changes of pannecrosis, infarcted zones of albumin-treated brains showed persistence of vascular endothelium and prominent microglial activation, suggesting that albumin therapy may help to preserve the neuropil within zones of residual infarction. CONCLUSIONS: These findings confirm the striking neuroprotective efficacy of albumin therapy in focal cerebral ischemia and reveal that this effect is associated with DWI normalization and a mitigation of pannecrotic changes within zones of residual injury.

Animals↗

PubMed1998

Combating hyperthermia in acute stroke: a significant clinical concern.

BACKGROUND: Moderate elevations of brain temperature, when present during or after ischemia or trauma, may markedly worsen the resulting injury. We review these provocative findings, which form the rationale for our recommendation that physicians treating acute cerebral ischemia or traumatic brain injury diligently monitor their patients for incipient fever and take prompt measures to maintain core-body temperature at normothermic levels. SUMMARY OF REVIEW: In standardized models of transient forebrain ischemia, intraischemic brain temperature elevations to 39 degrees C enhance and accelerate severe neuropathological alterations in vulnerable brain regions and induce damage to structures not ordinarily affected. Conversely, the blunting of even mild spontaneous postischemic hyperthermia confers neuroprotection. Mild hyperthermia is also deleterious in focal ischemia, particularly in reversible vascular occlusion. The action of otherwise neuroprotective drugs in ischemia may be nullified by mild hyperthermia. Even when delayed by 24 hours after an acute insult, moderate hyperthermia can still worsen the pathological and neurobehavioral outcome. Hyperthermia acts through several mechanisms to worsen cerebral ischemia. These include (1) enhanced release of neurotransmitters; (2) exaggerated oxygen radical production; (3) more extensive blood-brain barrier breakdown; (4) increased numbers of potentially damaging ischemic depolarizations in the focal ischemic penumbra; (5) impaired recovery of energy metabolism and enhanced inhibition of protein kinases; and (6) worsening of cytoskeletal proteolysis. Recent studies demonstrate the feasibility of direct brain temperature monitoring in patients with traumatic and ischemic injury. Moderate to severe brain temperature elevations, exceeding core-body temperature, may occur in the injured brain. Cerebral hyperthermia also occurs during rewarming after hypothermic cardiopulmonary bypass procedures. Several studies have now shown that elevated temperature is associated with poor outcome in patients with acute stroke. Finally, recent clinical trials in severe closed head injury have shown a beneficial effect of moderate therapeutic hypothermia. CONCLUSIONS: The acutely ischemic or traumatized brain is inordinately susceptible to the damaging influence of even modest brain temperature elevations. While controlled clinical investigations will be required to establish the therapeutic efficacy and safety of frank hypothermia in patients with acute stroke, the available evidence is sufficiently compelling to justify the recommendation, at this time, that fever be combatted assiduously in acute stroke and trauma patients, even if "minor" in degree and even when delayed in onset. We suggest that body temperature be maintained in a safe normothermic range (eg, 36.7 degrees C to 37.0 degrees C [98.0 degrees F to 98.6 degrees F]) for at least the first several days after acute stroke or head injury.

Acute Disease↗

PubMed1998

Role of nitric oxide in traumatic brain injury in the rat.

OBJECT: Although nitric oxide (NO) has been shown to play an important role in the pathophysiological process of cerebral ischemia, its contribution to the pathogenesis of traumatic brain injury (TBI) remains to be clarified. The authors investigated alterations in constitutive nitric oxide synthase (NOS) activity after TBI and the histopathological response to pharmacological manipulations of NO. METHODS: Male Sprague-Dawley rats underwent moderate (1.7-2.2 atm) parasagittal fluid-percussion brain injury. Constitutive NOS activity significantly increased within the ipsilateral parietal cerebral cortex, which is the site of histopathological vulnerability, 5 minutes after TBI occurred (234.5+/-60.2% of contralateral value [mean+/-standard error of the mean ¿SEM¿], p < 0.05), returned to control values by 30 minutes (114.1+/-17.4%), and was reduced at 1 day after TBI (50.5+/-13.1%, p < 0.01). The reduction in constitutive NOS activity remained for up to 7 days after TBI (31.8+/-6.0% at 3 days, p < 0.05; 20.1+/-12.7% at 7 days, p < 0.01). Pretreatment with 3-bromo-7-nitroindazole (7-NI) (25 mg/kg), a relatively specific inhibitor of neuronal NOS, significantly decreased contusion volume (1.27+/-0.17 mm3 [mean+/-SEM], p < 0.05) compared with that of control (2.52+/-0.35 mm3). However, posttreatment with 7-NI or pre- or posttreatment with nitro-L-arginine-methyl ester (L-NAME) (15 mg/kg), a nonspecific inhibitor of NOS, did not affect the contusion volume compared with that of control animals (1.87+/-0.46 mm3, 2.13+/-0.43 mm3, and 2.18+/-0.53 mm3, respectively). Posttreatment with L-arginine (1.1+/-0.3 mm3, p < 0.05), but not 3-morpholino-sydnonimine (SIN-1) (2.48+/-0.37 mm3), significantly reduced the contusion volume compared with that of control animals. CONCLUSIONS: These data indicate that constitutive NOS activity is affected after moderate parasagittal fluid percussion brain injury in a time-dependent manner. Inhibition of activated neuronal NOS and/or enhanced endothelial NOS activation may represent a potential therapeutic strategy for the treatment of TBI.

Animals↗

PubMed1997

The role of nitric oxide in the pathophysiology of thromboembolic stroke in the rat.

Although nitric oxide (NO) has been shown to play an important role in the pathophysiology of cerebral ischemia, its contribution to the pathogenesis of experimentally induced thromboembolic stroke is unknown. In this study, we pharmacologically manipulated NO levels in the acute post-thrombotic stage and determined the effects on behavior and histopathology. The following drugs were used: nitro-L-arginine-methyl ester (L-NAME), a non-specific endothelial and neuronal nitric oxide synthase (eNOS and nNOS) inhibitor, 3-bromo-7-nitroindazole (7-NI), a specific inhibitor for nNOS, the NO precursor, exogenous L-arginine and the NO-donor, 3-morpholino-sydnonimine (SIN-1). Male Wistar rats (n = 76) were randomly assigned to receive vehicle or drug immediately after common carotid artery thrombosis (CCAT). Regional measurements of cortical NOS activity using the [3H]L-arginine to [3H]L-citrulline conversion assay were decreased 1 h after treatment with L-NAME and 7-NI by 50 and 65%, respectively; hippocampal NOS activity was reduced with L-NAME by 35% and with 7-NI by 65%. L-NAME significantly worsened forelimb placing as compared to other groups. 7-NI accelerated sensorimotor recovery. Water maze retention deficits were noted 48 h after CCAT and these were exacerbated by L-NAME treatment. Histopathological protection was conferred in the hippocampus by 7-NI and SIN-1; conversely, L-NAME increased neuronal injury in the contralateral cortex. L-arginine had no effect on these outcomes. In conclusion, both structural and functional consequences of CCAT can be aggravated by limiting endothelial NO production in the acutely post-thrombotic brain. In contrast, inhibition of nNOS and infusion of an NO donor has a beneficial effect on pathology.

Animals↗

PubMed1997

Chronic histopathological consequences of fluid-percussion brain injury in rats: effects of post-traumatic hypothermia.

Early outcome measures of experimental traumatic brain injury (TBI) are useful for characterizing the traumatic severity as well as for clarifying the pathomechanisms underlying patterns of neuronal vulnerability. However, it is increasingly apparent that acute outcome measures may not always be accurate predictors of chronic outcome, particularly when assessing the efficacy of potential therapeutic regimens. This study examined the chronic histopathological outcome in rats 8 weeks following fluid-percussive TBI coupled with moderate post-traumatic brain hypothermia, a protocol that provides acute neuronal protection. Animals received a moderate parasagittal percussive head injury (2.01-2.38 atm) or sham procedure followed immediately by 3 h of brain hypothermia (30 degrees C) or normothermia (37 degrees C). Eight weeks following TBI, serial tissue sections were stained with hematoxylin and eosin or immunostained for glial fibrillary acidic protein. Tissue damage, gliosis and immunoreactive astrocytes were observed in the ipsilateral thalamus, hippocampus, and in the neocortex lateral to the injury site. Within the thalamus, focal necrosis was restricted to selective thalamic nuclei. Significant hippocampal cell loss was found in the ipsilateral dentate hilar region of both TBI groups. Quantitative volume measurements revealed significant decreases in cortical, thalamic and hippocampal volume ipsilateral to the impact in both TBI groups. Lateral ventricles were substantially enlarged in the TBI-normothermia group, an effect which was significantly attenuated by post-TBI hypothermia. The attenuation of lateral ventricular dilation by post-traumatic hypothermia is indicative of chronic neuroprotection in this TBI model. These data provide new information concerning the chronic histopathological consequence of experimental TBI and the relevance of this trauma model to chronic human head injury.

Animals↗

PubMed1997

Ontogenic development of the adenylyl cyclase enzyme and the alpha s, alpha i1 and alpha i2 G-protein regulatory subunits from rat prostate.

The expression of alpha s, alpha i1 and alpha i2 G-protein subunits measured by immunoblot increased in the rat prostate during sexual maturation, supporting their involvement in proliferation/differentiation. Northern blotting gave transcripts of 1.8 and 4 kb for alpha s, 1.4 and 4.5 kb (mainly) for alpha i1, and 2.4 kb for alpha i2 with levels suggesting a differential regulation (at transcription or post-transcription for alpha s, transcription for alpha i1, and translation for alpha i2). The stimulatory effects of forskolin, vasoactive intestinal peptide (VIP) and isoproterenol on adenylyl cyclase activity increased between 0.5-3 mo, remained constant up to 12 mo and decreased thereafter, conceivably following the expression of VIP and beta-adrenergic receptors. However, G-protein activation of adenylyl cyclase (by GTP and Gpp[NH]p) was maximal at 0.5 mo and then decreased as it occurred with toxin-catalyzed ADP-ribose incorporation to alpha subunits suggesting that other factors are also involved in the regulation of G-protein activity during rat prostatic development.

Adenosine Diphosphate Ribose↗

PubMed1997

Extracellular release of serotonin following fluid-percussion brain injury in rats.

Serotonin has been implicated in the pathobiology of central nervous system trauma. Using microdialysis techniques, we performed measurements of extracellular serotonin release within the traumatized cerebral cortex of rats subjected to moderate fluid-percussion (F-P) brain injury. Twenty-four hours prior to TBI, a F-P interface was positioned parasagitally 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 (n = 6) with a F-P pulse ranging from 1.8 to 2.0 atm. Following trauma, brain temperature was maintained for 4 h at 37 degrees C. Sham trauma animals (n = 7) were treated in an identical manner. Brain trauma induced acute elevations in the extracellular levels of serotonin (p < 0.01, ANOVA) compared to sham-operated controls. For example, serotonin levels increased from 18.85 +/- 7.12 pm/mL (mean +/- SD) in baseline samples to 65.78 +/- 11.36 in the first 10 min after trauma. The levels of serotonin remained significantly higher than control for the first 90-min sampling period. In parallel to the increase in serotonin levels after TBI, a significant 71.1% decrease (i.e., 182.29 +/- 30.08 vs 52.75 +/- 16.92) in extracellular 5-hydroxyindoleacetic acid (5-HIAA) levels was observed during the first 10 min after TBI. These data indicate that TBI is followed by a prompt increase in the extracellular levels of serotonin in cortical regions adjacent to the impact site. These neurochemical findings indicate that serotonin may play a significant role in the pathophysiology of TBI.

Animals↗

PubMed1997

Transient middle cerebral artery occlusion by intraluminal suture: I. Three-dimensional autoradiographic image-analysis of local cerebral glucose metabolism-blood flow interrelationships during ischemia and early recirculation.

Using autoradiographic image-averaging strategies, we studied the relationship between local glucose utilization (LCMRglc) and blood flow (LCBF) in a highly reproducible model of transient (2-hour) middle cerebral artery occlusion (MCAO) produced in Sprague-Dawley rats by insertion of an intraluminal suture coated with poly-L-lysine. Neurobehavioral examination at 60 minutes after occlusion substantiated a high-grade deficit in all animals. In two subgroups, LCBF was measured with 14C-iodoantipyrine at either 1.5 hours of MCAO, or at 1 hour of recirculation after suture removal. In two other matched subgroups, LCMRglc was measured with 14C-2-deoxyglucose at 1.5 to 2.25 hours of MCAO, and at 0.75 to 1.5 hours of recirculation after 2 hours of MCAO. Average image data sets were generated for LCBF, LCMRglc, and the LCMRglc/LCBF ratio for each study time. Middle cerebral artery occlusion for 2 hours induced graded LCBF decrements affecting ipsilateral cortical and basal ganglionic regions. After 1 hour of recirculation, LCBF in previously ischemic neocortical regions increased by 40% to 200% above ischemic levels, but remained depressed, on average, at about 40% of control. By contrast, frank hyperemia was noted in the previously ischemic caudoputamen. Mean cortical LCBF values during MCAO correlated highly with their respective LCBF values after 1 hour of recirculation (R = 0.93), suggesting that post-ischemic LCBF recovery is related to the depth of ischemia. Despite focal ischemia, LCMRglc during approximately 2 hours of MCAO was preserved, on average, at near-normal levels; but following approximately 1 h of recirculation, LCMRglc became markedly depressed (on average, 55% of control in previously densely ischemic cortical regions). Regression analysis indicated that this depressed glucose utilization was determined largely by the intensity of antecedent ischemia. By pixel analysis, the ischemic core (defined as LCBF 0% to 20% of control) comprised 33% of the ischemic hemisphere, and the penumbra (LCBF 20% to 40%) accounted for 26%. The penumbra was concentrated at the coronal poles of the ischemic lesion and formed a thin shell around the central ischemic core. During 2 hours of MCAO, the LCMRglc/LCBF ratio within the ischemic penumbra was increased four-fold above normal (average, 179 umol/100 mL). In marked contrast, after approximately 1 h recirculation, this uncoupling had almost completely subsided. The companion study (Zhao et al., 1997) further analyzes these findings in relation to patterns of infarctive histopathology.

Animals↗

PubMed1997

Uncoupling of local cerebral glucose metabolism and blood flow after acute fluid-percussion injury in rats.

We assessed local cerebral glucose metabolism (lCMRGlc) and blood flow (lCBF) interrelationships in the first hour after parasagittal fluid-percussion head injury (FPI) in rats. Matched series were studied autoradiographically for lCMRGlc and lCBF with 2-[14C]deoxyglucose and 14C-labeled iodoantipyrine, respectively. Three-dimensional autoradiographic-image mapping was to generate average data sets from which a mean ICMRGlc-to-lCBF ratio data set was derived. lCBF in neocortical regions ipsilateral to the trauma were depressed, on average, by 44% compared with sham-FPI rats, whereas contralateral lCBF values were not altered. By contrast, ICMRGlc was elevated in many cortical and subcortical sites of both hemispheres; this amounted to 1.3- to 1.4-fold increases in neocortical regions in the thalamus and 1.6- to 1.7-fold increases in the hippocampus. The lCMRGlc-to-lCBF ratio data revealed striking elevations both ipsilateral (P = 7 x 10(-7) and contralateral to the FPI (P = 0.003). The extent of metabolism-flow uncoupling, on average, amounted to 2.5-fold in the ipsilateral hippocampus and neocortex and 1.7-fold contralaterally. The loci of pronounced metabolism-flow dissociation corresponded closely to the previously documented histological distribution of neuronal necrosis. Our findings resemble events occurring in the acute focal ischemic penumbra and suggest that similar injury mechanisms may be operative.

Acute Disease↗

PubMed1997

Hyperthermia delayed by 24 hours aggravates neuronal damage in rat hippocampus following global ischemia.

We investigated whether moderate, transient whole-body hyperthermia (approximately 39.6 degrees C), if imposed 1 day following a brief episode of forebrain ischemia, would affect the neuropathologic outcome. Forty-two Wistar rats were subjected to either a 5- or 7-minute period of bilateral common carotid artery occlusion plus hypotension (50 mm Hg), or to the equivalent sham procedure. Twenty-four hours later, rats of one subgroup were placed into a hyperthermic chamber containing high-intensity lamps designed to elevate rectal temperature to 39 to 40 degrees C for 3 hours. Normothermic subgroups received the same procedures, but the heating lamps were turned off. Eight days after brain ischemia or the sham procedure, brains were perfusion-fixed, and numbers of ischemic-appearing CA1 pyramidal neurons were counted. In rats with 7-minute forebrain ischemia, delayed hyperthermia increased mean numbers of ischemic neurons by 2.6- to 2.7-fold in all subsectors of area CA1 (p < 0.05, ANOVA). Delayed hyperthermia in 5-minute ischemic rats also tended to increase mean numbers of ischemic neurons (by 11-fold in lateral, 6-fold in middle, and 5-fold in medial CA1 subsectors), but these differences were not statistically significant. We conclude that moderate, transient hyperthermia, even if occurring 1 day after a 7-minute global ischemic insult, exacerbates the extent of ischemic neuronal injury.

Analysis of Variance↗

PubMed1997

Effect of delayed albumin hemodilution on infarction volume and brain edema after transient middle cerebral artery occlusion in rats.

The authors examined the effect of delayed high-concentration albumin therapy on ischemic injury in a highly reproducible model of middle cerebral artery (MCA) occlusion in rats. Male Sprague-Dawley rats weighing 270 to 320 g were anesthetized with halothane and subjected to 120 minutes of temporary MCA occlusion induced by means of a poly-L-lysine-coated intraluminal nylon suture inserted retrograde via the external carotid artery into the internal carotid artery and MCA. The agent (20% human serum albumin [HSA]) or control solution (sodium chloride 0.9%) was administered intravenously at a dosage of 1% of body weight immediately after suture removal following a 2-hour period of MCA occlusion. The animals' neurological status was evaluated during MCA occlusion (at 60 minutes) and daily for 3 days thereafter. The brains were perfusion-fixed, and infarct volumes and brain edema were determined. The HSA significantly improved the neurological score compared with saline at 24 hours after MCA occlusion. The rats treated with HSA also had significantly reduced total infarct volume (by 34%) and brain edema (by 81%) compared with saline-treated rats. There was a strong correlation between hematocrit level and brain edema (p < 0.01), and between total infarct volume or brain edema and neurological score at 24, 48, and 72 hours postinjury (p < 0.0002). These results strongly support the beneficial effect of delayed albumin therapy in transient focal ischemia and indicate its possible usefulness in treating patients with acute ischemic stroke.

Anesthetics, Inhalation↗

PubMed1996

Bilateral ischemic tolerance of rat hippocampus induced by prior unilateral transient focal ischemia: relationship to c-fos mRNA expression.

The purpose of this study was to determine whether transient unilateral (2 h) middle cerebral artery occlusion (MCAo) is capable of inducing bilateral ischemic tolerance in hippocampal CA1 neurons when temporary bilateral forebrain ischemia by two-vessel occlusion (2VO) is carried out 3 days later, and to explore the relationship of this tolerance to the regional expression of c-fos and hsp-70 mRNA. Rats were sacrificed 4 days after 2VO, and normal-appearing neurons in CA1 subregions were counted. Rats subjected to MCAo and 2VO showed significant protection of CA1 neurons in both hippocampi, whereas rats which underwent sham MCAo and 2VO typically had severe bilateral destruction of CA1 neurons (normal neuron counts, ipsilateral medial CA1: 59.8 +/- 7.2 vs 16.6 +/- 7.8 (mean +/- s.e.m.); middle CA1: 50.0 +/- 4.7 vs 16.0 +/- 8.8; lateral CA1: 43.5 +/- 5.7 vs 13.8 +/- 6.3; contralateral, medial CA1: 52.3 +/- 6.3 vs 17.0 +/- 6.4; middle CA1: 43.3 +/- 4.7 vs 19.8 +/- 8.1; lateral CA1: 45.5 +/- 4.6 vs 26.0 +/- 10.3, respectively). This neuronal tolerance was preceded by the early bilateral induction of c-fos mRNA, which may in turn lead to expression of critical target genes that promote cell recovery.

Animals↗

PubMed1996

Quantitative evaluation of blood-brain barrier permeability following middle cerebral artery occlusion in rats.

A sensitive quantitative fluorescence method was used to explore the time course and regional pattern of blood-brain barrier (BBB) opening after transient middle cerebral artery occlusion (MCAo). Male Sprague-Dawley rats were anesthetized with halothane and subjected to 2 h of temporary MCAo by retrograde insertion of an intraluminal nylon suture, coated with poly-L-lysine, through the external carotid artery into the internal carotid artery and MCA. Damage to the BBB was judged by extravasation of Evans Blue (EB) dye, which was administered either 2, 3, 24 or 48 h after onset of MCAo. Fluorometric quantitation of EB was performed 1 or 2 h later in six brain regions. Cerebral infarction volumes were quantitated from histopathological material at 72 h. EB extravasation first became grossly visible in the ipsilateral caudoputamen and neocortex following 3 h of MCAo, was grossly unapparent at 24-26 h, and was maximal at 48-50 h. Fluorescence quantitation confirmed that BBB opening was absent at 2-3 h but present at all later times. In the hemisphere ipsilateral to MCAo, a 179% mean increase in extravasation of EB (compared to sham rats) was measured at 4 h, 407% at 5 h, 311% at 26 h and 264% at 50 h. (in each case, P < 0.05 vs. sham). The volume of infarcted tissue at 72 h in this model was 163.6 +/- 7.7 mm3. Our results indicate that an initial, acute disruption of the BBB occurs between 3 and 5 h following MCAo, and that a later, more widespread increase in regional BBB permeability is present at 48 h. Regional measurement of Evans Blue extravasation offers a precise means of quantitating BBB disruption in focal cerebral ischemia; this method will be of considerable utility in assessing the BBB-protective properties of pharmacological agents.

Analysis of Variance↗

PubMed1996

Computer-assisted image-averaging strategies for the topographic analysis of in situ hybridization autoradiographs.

We report the application of a computer-based image-averaging strategy to the quantitative topographic analysis of in situ hybridization autoradiographs, based upon a disparity-analysis algorithm. We illustrate this approach for a representative antisense riboprobe-the astrocytic marker, glial fibrillary acid protein (GFAP)-in the setting of fluid-percussion brain injury in rats. Sequential coronal autoradiographs in individual animals are first digitized and aligned by disparity analysis. Next, coronal sections of all brains of a given experimental group are placed in register with one another, using a common anatomic reference level. One brain of the series serves as a template, and corresponding sections of other brains are mapped into its contour at each level. In this manner, average and standard deviation image data sets may be generated. With thresholding techniques, individual data sets can be dichotomized with respect to a chosen threshold, and frequency maps can be generated at each coronal level, displaying numbers of brains showing supra-threshold levels of mRNA at each pixel location. Pixel-by-pixel statistical comparison of data sets obtained under two different conditions (e.g., 30 min vs. 24 h following brain trauma) is then feasible. A digitized functional-anatomic brain atlas may be fitted to the images to assist analysis. Computer-based image analysis of in situ hybridization autoradiographs greatly extends the utility and applicability of this technique.

Animals↗

PubMed1996

Macroscopic indices of lipid peroxidation in cerebral ischemia/reperfusion: validity and sensitivity enhancement in terms of conjugated diene detection.

Recent evidence for the occurrence of in vivo lipid peroxidation in the context of cerebral ischemia/reperfusion, as detected by classical tests such thiobarbituric acid reactivity and conjugated diene absorbance, is critically reviewed. Despite the widespread perception that lipid peroxidation is well-established and to be expected under such circumstances, in general these detection methods have not been applied with rigor sufficient to prove the quantitative existence of lipid peroxides unequivocally. The development of sensitive methods which can be utilized in small tissue samples at early times after brain injury is needed. In particular, the conditions necessary for the establishment of a more rigorous and sensitive method of conjugated diene detection in terms of difference spectral analysis are detailed and illustrated. In addition, a new autofluorescence in the far-ultraviolet region is shown to be associated with oxygenated conjugated diene-containing compounds.

Animals↗