F A Welsh

Hospital of the University of Pennsylvania, Philadelphia, Pennsylvania, United States

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Publications (79)375.53 Total impact

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    ABSTRACT: Intracerebral hemorrhage (ICH) is a devastating stroke subtype in which perihematomal inflammation contributes to neuronal injury and functional disability. Histologically, the region becomes infiltrated with neutrophils and activated microglia followed by neuronal loss, but little is known about the immune signals that coordinate these events. This study aimed to determine the role of Toll-like receptor 4 (TLR4) in the innate immune response after ICH and its impact on neurobehavioral outcome. Transgenic mice incapable of TLR4 signaling and wild-type controls were subjected to striatal blood injection to model ICH. The perihematomal inflammatory response was then quantified by immunohistochemistry, whole brain flow cytometry, and polymerase chain reaction. The critical location of TLR4 signaling was determined by blood transfer experiments between genotypes. Functional outcomes were quantified in all cohorts using the cylinder and open field tests. TLR4-deficient mice had markedly decreased perihematomal inflammation, associated with reduced recruitment of neutrophils and monocytes, fewer microglia, and improved functional outcome by day 3 after ICH. Moreover, blood transfer experiments revealed that TLR4 on leukocytes or platelets within the hemorrhage contributes to perihematomal leukocyte infiltration and the neurological deficit. Together, these data identify a critical role for TLR4 signaling in perihematomal inflammation and injury and indicate this pathway may be a target for therapeutic intervention.
    Annals of Neurology 10/2011; 70(4):646-56. · 11.19 Impact Factor
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    ABSTRACT: Investigation of the pathophysiology of injury after intracerebral hemorrhage (ICH) requires a reproducible animal model. While ICH accounts for 10-15% of all strokes, there remains no specific effective therapy. The autologous blood injection model in mice involves the stereotaxic injection of arterial blood into the basal ganglia mimicking a spontaneous hypertensive hemorrhage in man. The response to hemorrhage can then be studied in vivo and the neurobehavioral deficits quantified, allowing for description of the ensuing pathology and the testing of potential therapeutic agents. The procedure described in this protocol uses the double injection technique to minimize risk of blood reflux up the needle track, no anticoagulants in the pumping system, and eliminates all dead space and expandable tubing in the system.
    Journal of Visualized Experiments 01/2011;
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    ABSTRACT: In vitro-transcribed mRNAs encoding physiologically important proteins have considerable potential for therapeutic applications. However, in its present form, mRNA is unfeasible for clinical use because of its labile and immunogenic nature. Here, we investigated whether incorporation of naturally modified nucleotides into transcripts would confer enhanced biological properties to mRNA. We found that mRNAs containing pseudouridines have a higher translational capacity than unmodified mRNAs when tested in mammalian cells and lysates or administered intravenously into mice at 0.015-0.15 mg/kg doses. The delivered mRNA and the encoded protein could be detected in the spleen at 1, 4, and 24 hours after the injection, where both products were at significantly higher levels when pseudouridine-containing mRNA was administered. Even at higher doses, only the unmodified mRNA was immunogenic, inducing high serum levels of interferon-alpha (IFN-alpha). These findings indicate that nucleoside modification is an effective approach to enhance stability and translational capacity of mRNA while diminishing its immunogenicity in vivo. Improved properties conferred by pseudouridine make such mRNA a promising tool for both gene replacement and vaccination.
    Molecular Therapy 10/2008; 16(11):1833-40. · 7.04 Impact Factor
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    ABSTRACT: Previous studies have demonstrated that local application of hypertonic KCl or NaCl to the cerebral cortex induces tolerance to a subsequent episode of ischemia. The objective of the present study was to determine whether application of these salts increases the levels of mRNAs encoding inhibitors of inflammation. Hypertonic KCl or NaCl was applied for 2 h to the frontal cortex of Sprague-Dawley rats. After recovery periods up to 24 h, levels of selected mRNAs were measured in samples from frontal and parietal cortex using Northern blots. Application of hypertonic KCl caused a rapid and widespread increase in the levels of mRNA coding for tumor necrosis factor (TNF), tristetraprolin (TTP), suppressor of cytokine signaling-3 (SOCS3), and brain-derived neurotrophic factor (BDNF), and a 24-h delayed induction of ciliary neurotrophic factor (CNTF) mRNA. Application of hypertonic NaCl caused alterations in mRNA levels that were restricted to the frontal cortex. In this region, application of NaCl rapidly increased levels of mRNA encoding TNF, TTP, and SOCS3, but not BDNF, and caused a delayed induction of CNTF mRNA. These results raise the possibility that upregulation of inhibitors of inflammation after preconditioning may contribute to the induction of tolerance to ischemia.
    Brain Research 07/2006; 1097(1):31-8. · 2.88 Impact Factor
  • Journal of Cerebral Blood Flow & Metabolism 07/2005; · 5.40 Impact Factor
  • Journal of Cerebral Blood Flow & Metabolism 07/2005; · 5.40 Impact Factor
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    Katalin Karikó, Drew Weissman, Frank A Welsh
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    ABSTRACT: Cerebral ischemia triggers acute inflammation, which exacerbates primary brain damage. Activation of the innate immune system is an important component of this inflammatory response. Inflammation occurs through the action of proinflammatory cytokines, such as TNF, IL-1 beta and IL-6, that alter blood flow and increase vascular permeability, thus leading to secondary ischemia and accumulation of immune cells in the brain. Production of these cytokines is initiated by signaling through Toll-like receptors (TLRs) that recognize host-derived molecules released from injured tissues and cells. Recently, great strides have been made in understanding the regulation of the innate immune system, particularly the signaling mechanisms of TLRs. Negative feedback inhibitors of TLRs and inflammatory cytokines have now been identified and characterized. It is also evident that lipid rafts exist in membranes and play a role in receptor-mediated inflammatory signaling events. In the present review, using this newly available large body of knowledge, we take a fresh look at studies of ischemic tolerance. Based on this analysis, we recognize a striking similarity between ischemic tolerance and endotoxin tolerance, an immune suppressive state characterized by hyporesponsiveness to lipopolysaccharide (LPS). In view of this analogy, and considering recent discoveries related to molecular mechanisms of endotoxin tolerance, we postulate that inhibition of TLR and proinflammatory cytokine signaling contributes critically to ischemic tolerance in the brain and other organs. Ischemic tolerance is a protective mechanism induced by a variety of preconditioning stimuli. Tolerance can be established with two temporal profiles: (i) a rapid form in which the trigger induces tolerance to ischemia within minutes and (ii) a delayed form in which development of protection takes several hours or days and requires de-novo protein synthesis. The rapid form of tolerance is achieved by direct interference with membrane fluidity, causing disruption of lipid rafts leading to inhibition of TLR/cytokine signaling pathways. In the delayed form of tolerance, the preconditioning stimulus first triggers the TLR/cytokine inflammatory pathways, leading not only to inflammation but also to simultaneous upregulation of feedback inhibitors of inflammation. These inhibitors, which include signaling inhibitors, decoy receptors, and anti-inflammatory cytokines, reduce the inflammatory response to a subsequent episode of ischemia. This novel interpretation of the molecular mechanism of ischemic tolerance highlights new avenues for future investigation into the prevention and treatment of stroke and related diseases.
    Journal of Cerebral Blood Flow & Metabolism 12/2004; 24(11):1288-304. · 5.40 Impact Factor
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    ABSTRACT: Cortical application of KCl has previously been shown to induce tolerance to a subsequent episode of cerebral ischemia. KCl triggers recurrent episodes of cortical spreading depression and produces a small lesion at the cortical application site. To determine whether a cortical lesion alone is sufficient to induce tolerance to ischemia, the authors used 5-mol/L NaCl to precondition rat brain 3 days before permanent occlusion of the middle cerebral artery. NaCl produced a small lesion at the application site without evoking cortical spreading depression. Preconditioning with 5-mol/L NaCl significantly attenuated the decrease in CBF after middle cerebral artery occlusion and reduced the volume of cortical infarction by 35%. The results show that a small cortical lesion, by itself, is sufficient to induce tolerance to ischemia.
    Journal of Cerebral Blood Flow & Metabolism 11/2004; 24(10):1167-71. · 5.40 Impact Factor
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    ABSTRACT: Previous studies have demonstrated that traumatic brain injury (TBI) increases the vulnerability of the brain to an acute episode of hypoxia-ischemia. The objective of the present study was to determine whether TBI alters the vulnerability of the brain to a delayed episode of ischemia and, if so, to identify contributing mechanisms. Sprague-Dawley rats were subjected to lateral fluid-percussion (FP) brain injury (n = 14) of moderate severity (2.3-2.5 atm), or sham-injury (n = 12). After recovery for 24 h, all animals underwent an 8-min episode of forebrain ischemia, followed by survival for 6 days. Ischemic damage in the hippocampus and cerebral cortex of the FP-injured hemisphere was compared to that in the contralateral hemisphere and to that in sham-injured animals. Remarkably, the number of surviving CA(1) neurons in the middle and lateral segments of the hippocampus in the FP-injured hemisphere was significantly greater than that in the contralateral hemisphere and sham-injured animals (p < 0.05). Likewise, in the cerebral cortex the number of damaged neurons tended to be lower in the FP-injured hemisphere than in the contralateral hemisphere. These results suggest that TBI decreased the vulnerability of the brain to a delayed episode of ischemia. To determine whether TBI triggers protective metabolic alterations, glycogen levels were measured in cerebral cortex and hippocampus in additional animals 24 h after FP-injury (n = 13) or sham-injury (n = 7). Cortical glycogen levels in the ipsilateral hemisphere increased to 12.9 +/- 6.4 mmol/kg (mean +/- SD), compared to 6.4 +/- 1.8 mmol/kg in the opposite hemisphere and 5.7 +/- 1.3 mmol/kg in sham-injured animals (p < 0.001). Similarly, in the hippocampus glycogen levels in the FP-injured hemisphere increased to 13.4 +/- 4.9 mmol/kg, compared to 8.1 +/- 2.4 mmol/kg in the contralateral hemisphere (p < 0.004) and 6.2 +/- 1.5 mmol/kg in sham-injured animals (p < 0.001). These results demonstrate that TBI triggers a marked accumulation of glycogen that may protect the brain during ischemia by serving as an endogenous source of metabolic energy.
    Journal of Neurotrauma 06/2004; 21(6):707-18. · 4.30 Impact Factor
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    ABSTRACT: The cellular and molecular pathways initiated by traumatic brain injury (TBI) may compromise the function and structural integrity of mitochondria, thereby contributing to cerebral metabolic dysfunction and cell death. The extent to which TBI affects regional mitochondrial populations with respect to structure, function, and swelling was assessed 3 hours and 24 hours after lateral fluid-percussion brain injury in the rat. Significantly less mitochondrial protein was isolated from the injured compared with uninjured parietotemporal cortex, whereas comparable yields were obtained from the hippocampus. After injury, cortical and hippocampal tissue ATP concentrations declined significantly to 60% and 40% of control, respectively, in the absence of respiratory deficits in isolated mitochondria. Mitochondria with ultrastructural morphologic damage comprised a significantly greater percent of the population isolated from injured than uninjured brain. As determined by photon correlation spectroscopy, the mean mitochondrial radius decreased significantly in injured cortical populations (361 +/- 40 nm at 24 hours) and increased significantly in injured hippocampal populations (442 +/- 36 at 3 hours) compared with uninjured populations (Ctx: 418 +/- 44; Hipp: 393 +/- 24). Calcium-induced deenergized swelling rates of isolated mitochondrial populations were significantly slower in injured compared with uninjured samples, suggesting that injury alters the kinetics of mitochondrial permeability transition (MPT) pore activation. Cyclosporin A (CsA)-insensitive swelling was reduced in the cortex, and CsA-sensitive and CsA-insensitive swelling both were reduced in the hippocampus, demonstrating that regulated MPT pores remain in mitochondria isolated from injured brain. A proposed mitochondrial population model synthesizes these data and suggests that cortical mitochondria may be depleted after TBI, with a physically smaller, MPT-regulated population remaining. Hippocampal mitochondria may sustain damage associated with ballooned membranes and reduced MPT pore calcium sensitivity. The heterogeneous mitochondrial response to TBI may underlie posttraumatic metabolic dysfunction and contribute to the pathophysiology of TBI.
    Journal of Cerebral Blood Flow & Metabolism 03/2003; 23(2):219-31. · 5.40 Impact Factor
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    Tatsuo Otori, Joel H Greenberg, Frank A Welsh
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    ABSTRACT: Cortical spreading depression (CSD) has previously been shown to induce tolerance to a subsequent episode of transient cerebral ischemia. The objective of the present study was to determine whether CSD also induces tolerance to permanent focal ischemia and, if so, whether tolerance may be mediated by alterations in cerebral blood flow (CBF). Sprague-Dawley rats were preconditioned by applying potassium chloride to one hemisphere for 2 hours, evoking 19 +/- 5 episodes of CSD (mean +/- SD, n = 19). Three days later, the middle cerebral artery (MCA) was permanently occluded using an intraluminal suture. In a subset of animals, laser Doppler blood flow (LDF) was monitored over the parietal cortex before and during the first 2 hours of MCA occlusion. Preconditioning with CSD reduced the hemispheric volume of infarction from 248 +/- 115 mm3 (n = 18) in sham-conditioned animals to 161 +/- 81 mm3 (n = 19, P< 0.02). Similarly, CSD reduced the neocortical volume of infarction from 126 +/- 82 mm3 to 60 +/- 61 mm3 (P < 0.01). Moreover, preconditioning with CSD significantly improved LDF during MCA occlusion from 21% +/- 7% (n = 9) of preischemic baseline in sham-conditioned animals to 29% +/- 9% (n = 7, P< 0.02). Preconditioning with CSD therefore preserved relative levels of CBF during focal ischemia and reduced the extent of infarction resulting from permanent MCA occlusion. To determine whether CSD may have altered preischemic baseline CBF, [14 C]iodoantipyrine was used in additional animals to measure CBF 3 days after CSD conditioning or sham conditioning. CSD, but not sham conditioning, significantly reduced baseline CBF in the ipsilateral neocortex to values 67% to 75% of those in the contralateral cortex. Therefore, CSD causes a long-lasting decrease in baseline CBF that is most likely related to a reduction in metabolic rate. A reduction in the rate of metabolism may contribute to the induction of tolerance to ischemia after preconditioning with CSD.
    Journal of Cerebral Blood Flow & Metabolism 01/2003; 23(1):43-50. · 5.40 Impact Factor
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    ABSTRACT: Previous studies have demonstrated that preconditioning the brain with cortical spreading depression (CSD) induces tolerance to a subsequent episode of ischemia. In other models of preconditioning, induction of ischemic tolerance has been associated with increased expression of the antioxidant enzyme, superoxide dismutase (SOD). The objective of the present study was to determine whether CSD upregulates Cu/Zn-SOD or Mn-SOD. CSD was induced in one hemisphere by applying 2 M KCl to the frontal cortex in Wistar rats. After 2 or 24 h of recovery, Cu/Zn-SOD and Mn-SOD mRNA levels were determined in both hemispheres using Northern blot analysis. In separate rats, Cu/Zn-SOD and Mn-SOD protein levels were determined 24 and 72 h after CSD using Western blot analysis. In addition, total SOD, Cu/Zn-SOD and Mn-SOD enzymatic activities were measured 24 and 72 h after CSD using spectrophotometric and zymographic assays. At the times investigated, no significant differences in mRNA or protein levels for Cu/Zn-SOD or Mn-SOD were observed between the ipsilateral and contralateral cortex. Further, there were no significant differences in Cu/Zn-SOD or Mn-SOD enzymatic activities between the two hemispheres at 24 or 72 h after CSD. In addition, CSD did not alter the activities of Cu/Zn-SOD or Mn-SOD in either hemisphere, relative to those in unoperated animals. Taken together, these results fail to support the hypothesis that CSD-induced tolerance is mediated through the upregulation of Cu/Zn-SOD or Mn-SOD.
    Molecular Brain Research 12/2001; 96(1-2):50-8. · 2.00 Impact Factor
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    ABSTRACT: Activity of the Ca(2+)-dependent protease calpain is increased in neurons after global and focal brain ischemia, and may contribute to postischemic injury cascades. Understanding the time course and location of calpain activity in the post-ischemic brain is essential to establishing causality and optimizing therapeutic interventions. This study examined the temporal and spatial characteristics of brain calpain activity after transient forebrain ischemia (TFI) in rats. Male Long Evans rats underwent 10 min of normothermic TFI induced by bilateral carotid occlusion with hypovolemic hypotension (MABP 30 mm Hg). Brain calpain activity was examined between 1 and 72 h after reperfusion. Western blot analysis of regional brain homogenates demonstrated a bimodal pattern of calpain-mediated alpha-spectrin degradation in the hippocampus, cortex, and striatum with an initial increase at 1 h followed by a more prominent secondary increase at 36 h after reperfusion. Immunohistochemical analysis revealed that calpain activity was primarily localized to dendritic fields of selectively vulnerable neurons at one hour after reperfusion. Between 24 and 48 h after reperfusion neuronal calpain activity progressed from the dorsal to ventral striatum, medial to lateral CA1 hippocampus, and centripetally expanded from watershed foci in the cerebral cortex. This progression was associated with fragmentation of dendritic processes, calpain activation in the neuronal soma and subsequent neuronal degeneration. These observations demonstrate a clear association between calpain activation and subsequent delayed neuronal death and suggest broad therapeutic window for interventions aimed at preventing delayed intracellular Ca(2+) overload and pathologic calpain activation.
    Experimental Neurology 08/2001; 170(1):27-35. · 4.65 Impact Factor
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    ABSTRACT: Previous studies have demonstrated that cortical spreading depression (CSD) increases the expression of putative neuroprotective proteins. The objective of the present study was to elucidate the relationship between the number of episodes of CSD and steady-state levels of mRNAs encoding brain-derived neurotrophic factor (BDNF), heat-shock protein-72 (hsp72) and c-fos. Wistar rats were administered one, five, or twenty-five episodes of CSD evoked by application of 2 M KCl to the frontal cortex of one hemisphere. Animals were permitted to recover for 30 min, 2 h or 24 h prior to sacrifice. Total RNA was isolated from the parietal cortex of each hemisphere and analyzed using Northern blots. At 30 min recovery, levels of BDNF mRNA were not significantly elevated after 1 episode of CSD, but were increased 4-fold after five episodes of CSD and 11-fold after twenty-five episodes of CSD, relative to levels in the contralateral hemisphere. At 2 h recovery, BDNF mRNA levels increased 2-, 3- and 9-fold, respectively. At 24 h, BDNF mRNA had returned to control levels in all groups. Thus, CSD increased levels of BDNF mRNA in a dose-dependent fashion at the early recovery times. Hsp72 mRNA was below the level of detection after 1 and 5 episodes of CSD. However, after twenty-five episodes of CSD, hsp72 mRNA levels were increased in the ipsilateral hemisphere at 30 min and 2 h recovery. Unlike levels of BDNF and hsp72 mRNA, levels of c-fos mRNA were increased nearly to the same extent at 30 min and 2 h after one, five or twenty-five episodes of CSD before returning to control by 24 h recovery. These results demonstrate that CSD triggers a dose-dependent increase in the expression of genes encoding neuroprotective proteins, which may mediate tolerance to ischemia induced by CSD.
    Molecular Brain Research 04/2001; 88(1-2):103-12. · 2.00 Impact Factor
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    ABSTRACT: The expression of proteins after local mRNA delivery has a great potential for analysis of protein function in vivo. To explore the feasibility of such a technique within the central nervous system (CNS), we delivered luciferase-encoding mRNA into the rat brain. The tissue distribution and stability of injected mRNA were analyzed using in situ detection and Northern hybridization, while luciferase expression was measured by enzymatic assay. Following intracerebral injection of lipofectin-complexed mRNA, expression of luciferase was detectable as early as 1 h, was maximal at 2-3 h, but was below the level of detection by 24 h. The extent of luciferase expression correlated with the amount of mRNA delivered. Luciferase expression was higher when lipofectin-complexed rather than naked mRNA was injected. In addition, the luciferase expression increased significantly by adding a 50 nt-long poly(A) tail to the 3'-end of the mRNA. Delivering mRNA to the cerebral cortex or hippocampus resulted in measurable luciferase activity at the injection sites but not in adjacent areas. Accordingly, the luciferase mRNA was also localized to the injection site, and the amount of intact transcript was significantly higher at 3 h compared to 24 h after injection. These results demonstrate that in vivo mRNA delivery is a feasible technique for immediate, transient overexpression of desired proteins in the CNS and, therefore, can serve as a model system to study the neurobiological effects of specific proteins.
    Journal of Neuroscience Methods 02/2001; 105(1):77-86. · 2.11 Impact Factor
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    ABSTRACT: PURPOSE: One of the downstream consequences of glutamate-induced NMDA (N-methyl-D-aspartate) receptor activation following trau-matic brain injury (TBI) is production of nitric oxide (NO). In this study, we evaluated the ability of lubeluzole, a novel neuroprotective com-pound which downregulates the glutamate-activated nitric oxide pathway and blocks sodium and voltage-sensitive calcium channels, to improve behavioral and histological outcome in rats following TBI. METHODS: Rats were anesthetized and subjected to moderate lateral fluid percussion brain injury (2.4-2.6 atm) or were surgically prepared but not injured (sham). Fifteen minutes after injury, animals received a bolus of either vehicle (n = 12 injured, n = 14 uninjured) or lubeluzole (0.31 mg/kg, n = 12 injured, n = 8 uninjured) through the jugular vein followed by a one hour infusion of vehicle or lubeluzole (0.31 mg/kg). Animals were tested at 48 hours post-injury for cognitive performance in the Morris water maze, neuromotor function, and limb placing func-tion, and then sacrificed. RESULTS: While brain injury resulted in significant cognitive and motor deficits, injured animals treated with lubeluzole did not differ in spa-tial memory performance, neuromotor score, or limb placing function from injured, vehicle-treated animals. Furthermore, there was no differ-ence in the mean number of ipsilateral hippocampal CA3 neurons between injured rats treated with vehicle and those treated with lubeluzole. CONCLUSIONS: This single-dose study failed to demonstrate a beneficial effect of lubeluzole on the acute behavioral or histological sequelae following TBI.
    Restorative neurology and neuroscience 02/2000; 16(2):127-134. · 2.93 Impact Factor
  • F A Welsh
    Nippon Ika Daigaku Zasshi 01/1999; 65(6):447-9.
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    ABSTRACT: Previous studies have demonstrated that cortical spreading depression (CSD) induces neuronal tolerance to a subsequent episode of ischemia. The objective of the present investigation was to determine whether CSD alters levels of mRNA coding for putative neuroprotective proteins. Unilateral CSD was evoked in male Wistar rats by applying 2 mol/L KCl over the frontal cortex for 2 hours. After recovery for 0, 2, or 24 hours, levels of several mRNA coding for neuroprotective proteins were measured bilaterally in parietal cortex using Northern blot analysis. Levels of c-fos mRNA and brain-derived neurotrophic factor (BDNF) mRNA were markedly elevated at 0 and 2 hours, but not 24 hours after CSD. Tissue plasminogen activator (tPA) mRNA levels were also significantly increased at 0 and 2 hours, but not 24 hours after CSD. Levels of the 72-kDa heat-shock protein (hsp72) mRNA were not significantly increased by CSD, except for a small elevation (20%) at 2 hours recovery. Levels of the 73-kDa heat-shock cognate (hsc73) mRNA were slightly, but significantly, increased at 2 and 24 hours of recovery. Finally, levels of mRNA for protease nexin-1 and glutamine synthetase were not significantly altered by CSD at any time studied. The current results support the hypothesis that neuronal tolerance to ischemia after CSD may be mediated by increased expression of FOS, BDNF, or tPA, but not by increased expression of hsp72, hsc73, nexin-1, or glutamine synthetase.
    Journal of Cerebral Blood Flow & Metabolism 01/1999; 18(12):1308-15. · 5.40 Impact Factor
  • Critical Care Medicine - CRIT CARE MED. 01/1999; 27.
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    G Bronner, K Mitchell, F A Welsh
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    ABSTRACT: To investigate long-term adaptations after unilateral carotid artery ligation, the effect of forebrain ischemia on cerebral blood flow and ATP levels was determined at various times after ligation. Unilateral carotid artery ligation was performed in male Wistar rats 0, 3, or 7 days before forebrain ischemia. Laser-Doppler blood flow was monitored bilaterally over the parietal cortex and ATP was measured in the subadjacent cortex of both hemispheres at the end of a 10-minute episode of ischemia. In the 0-day group, forebrain ischemia reduced cortical blood flow to 12% +/- 8% (mean +/- SD) of preischemic values and lowered cortical ATP to 26% +/- 35% of control levels in the ipsilateral hemisphere. Delaying the onset of forebrain ischemia for 3 days after carotid artery ligation significantly improved cortical blood flow (29% +/- 12%, P < 0.05) and ATP levels (92% +/- 11%, P < 0.05) in the ipsilateral hemisphere. Delaying forebrain ischemia for 7 days also significantly improved ipsilateral blood flow (36% +/- 11%, P < 0.05) and ATP levels (81% +/- 29%, P < 0.05) compared with the 0-day group. In the contralateral hemisphere, the reduction in blood flow and ATP levels was not significantly altered by delaying the onset of forebrain ischemia for 3 or 7 days. These results show that unilateral carotid artery ligation induces long-term vascular adaptations that improve the collateral circulation and preserve ATP levels during a subsequent episode of ischemia.
    Journal of Cerebral Blood Flow & Metabolism 01/1998; 18(1):118-21. · 5.40 Impact Factor

Publication Stats

2k Citations
375.53 Total Impact Points

Institutions

  • 1977–2005
    • Hospital of the University of Pennsylvania
      • Department of Neurosurgery
      Philadelphia, Pennsylvania, United States
  • 1975–2005
    • University of Pennsylvania
      • • Department of Neurosurgery
      • • Department of Neurology
      Philadelphia, PA, United States
  • 1990–1992
    • The Children's Hospital of Philadelphia
      • Department of Neurosurgery
      Philadelphia, Pennsylvania, United States