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Steiner AR, Rousseau-Blass F, Schroeter A, Hartnack S, Bettschart-Wolfensberger R. Systematic Review: Anaesthetic Protocols and Management as Confounders in Rodent Blood Oxygen Level Dependent Functional Magnetic Resonance Imaging (BOLD fMRI)-Part A: Effects of Changes in Physiological Parameters. Front Neurosci 2020; 14:577119. [PMID: 33192261 PMCID: PMC7646331 DOI: 10.3389/fnins.2020.577119] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Accepted: 09/10/2020] [Indexed: 12/09/2022] Open
Abstract
Background: To understand brain function in health and disease, functional magnetic resonance imaging (fMRI) is widely used in rodent models. Because animals need to be immobilised for image acquisition, fMRI is commonly performed under anaesthesia. The choice of anaesthetic protocols and may affect fMRI readouts, either directly or via changing physiological balance, and thereby threaten the scientific validity of fMRI in rodents. Methods: The present study systematically reviewed the literature investigating the influence of different anaesthesia regimes and changes in physiological parameters as confounders of blood oxygen level dependent (BOLD) fMRI in rats and mice. Four databases were searched, studies selected according to pre-defined criteria, and risk of bias assessed for each study. Results are reported in two separate articles; this part of the review focuses on effects of changes in physiological parameters. Results: A total of 121 publications was included, of which 49 addressed effects of changes in physiological parameters. Risk of bias was high in all included studies. Blood oxygenation [arterial partial pressure of oxygen (paO2)], ventilation [arterial partial pressure of carbon dioxide (paCO2)] and arterial blood pressure affected BOLD fMRI readouts across various experimental paradigms. Conclusions: Blood oxygenation, ventilation and arterial blood pressure should be monitored and maintained at stable physiological levels throughout experiments. Appropriate anaesthetic management and monitoring are crucial to obtain scientifically valid, reproducible results from fMRI studies in rodent models.
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Affiliation(s)
- Aline R. Steiner
- Section of Anaesthesiology, Department of Clinical and Diagnostic Services, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Frédérik Rousseau-Blass
- Department of Clinical Sciences, Faculty of Veterinary Medicine, Université de Montréal, Saint-Hyacinthe, QC, Canada
| | - Aileen Schroeter
- Institute for Biomedical Engineering, University of Zurich and ETH Zurich, Zurich, Switzerland
| | - Sonja Hartnack
- Section of Epidemiology, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
| | - Regula Bettschart-Wolfensberger
- Section of Anaesthesiology, Department of Clinical and Diagnostic Services, Vetsuisse Faculty, University of Zurich, Zurich, Switzerland
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Baron JC. Protecting the ischaemic penumbra as an adjunct to thrombectomy for acute stroke. Nat Rev Neurol 2019; 14:325-337. [PMID: 29674752 DOI: 10.1038/s41582-018-0002-2] [Citation(s) in RCA: 106] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
After ischaemic stroke, brain damage can be curtailed by rescuing the 'ischaemic penumbra' - that is, the severely hypoperfused, at-risk but not yet infarcted tissue. Current evidence-based treatments involve restoration of blood flow so as to salvage the penumbra before it evolves into irreversibly damaged tissue, termed the 'core'. Intravenous thrombolysis (IVT) can salvage the penumbra if given within 4.5 h after stroke onset; however, the early recanalization rate is only ~30%. Direct removal of the occluding clot by mechanical thrombectomy considerably improves outcomes over IVT alone, but despite early recanalization in > 80% of cases, ~50% of patients who receive this treatment do not enjoy functional independence, usually because the core is already too large at the time of recanalization. Novel therapies aiming to 'freeze' the penumbra - that is, prevent core growth until recanalization is complete - hold potential as adjuncts to mechanical thrombectomy. This Review focuses on nonpharmacological approaches that aim to restore the physiological balance between oxygen delivery to and oxygen demand of the penumbra. Particular emphasis is placed on normobaric oxygen therapy, hypothermia and sensory stimulation. Preclinical evidence and early pilot clinical trials are critically reviewed, and future directions, including clinical translation and trial design issues, are discussed.
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Affiliation(s)
- Jean-Claude Baron
- Department of Neurology, Hôpital Sainte-Anne, Université Paris 5, INSERM U894, Paris, France.
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3
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Ellmann S, Langer V, Britzen-Laurent N, Hildner K, Huber C, Tripal P, Seyler L, Waldner M, Uder M, Stürzl M, Bäuerle T. Application of machine learning algorithms for multiparametric MRI-based evaluation of murine colitis. PLoS One 2018; 13:e0206576. [PMID: 30365545 PMCID: PMC6203400 DOI: 10.1371/journal.pone.0206576] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2017] [Accepted: 10/16/2018] [Indexed: 01/15/2023] Open
Abstract
Magnetic resonance imaging (MRI) allows non-invasive evaluation of inflammatory bowel disease (IBD) by assessing pathologically altered gut. Besides morphological changes, relaxation times and diffusion capacity of involved bowel segments can be obtained by MRI. The aim of this study was to assess the use of multiparametric MRI in the diagnosis of experimentally induced colitis in mice, and evaluate the diagnostic benefit of parameter combinations using machine learning. This study relied on colitis induction by Dextran Sodium Sulfate (DSS) and investigated the colon of mice in vivo as well as ex vivo. Receiver Operating Characteristics were used to calculate sensitivity, specificity, positive- and negative-predictive values (PPV and NPV) of these single values in detecting DSS-treatment as a reference condition. A Model Averaged Neural Network (avNNet) was trained on the multiparametric combination of the measured values, and its predictive capacity was compared to those of the single parameters using exact binomial tests. Within the in vivo subgroup (n = 19), the avNNet featured a sensitivity of 91.3% (95% CI: 86.6–96.0%), specificity of 92.3% (95% CI: 85.1–99.6%), PPV of 96.9% (94.0–99.9%) and NPV of 80.0% (95% CI: 69.9–90.1%), significantly outperforming all single parameters in at least 2 accuracy measures (p < 0.003) and performing significantly worse compared to none of the single values. Within the ex vivo subgroup (n = 30), the avNNet featured a sensitivity of 87.4% (95% CI: 82.6–92.2%), specificity of 82.9% (95% CI: 76.1–89.7%), PPV of 88.9% (84.3–93.5%) and NPV of 80.8% (95% CI: 73.8–87.9%), significantly outperforming all single parameters in at least 2 accuracy measures (p < 0.015), exceeded by none of the single parameters. In experimental mouse colitis, multiparametric MRI and the combination of several single measured values to an avNNet can significantly increase diagnostic accuracy compared to the single parameters alone. This pilot study will provide new avenues for the development of an MR-derived colitis score for optimized diagnosis and surveillance of inflammatory bowel disease.
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Affiliation(s)
- Stephan Ellmann
- Institute of Radiology, University Hospital Erlangen, Maximiliansplatz 1, Erlangen, Germany
- * E-mail:
| | - Victoria Langer
- Division of Molecular and Experimental Surgery, Translational Research Center Erlangen, Department of Surgery, Erlangen, Germany
| | - Nathalie Britzen-Laurent
- Division of Molecular and Experimental Surgery, Translational Research Center Erlangen, Department of Surgery, Erlangen, Germany
| | - Kai Hildner
- Department of Medicine 1, University Hospital Erlangen, Kussmaul Campus for Medical Research, Erlangen, Germany
| | - Carina Huber
- Department of Medicine 1, University Hospital Erlangen, Kussmaul Campus for Medical Research, Erlangen, Germany
| | - Philipp Tripal
- Optical Imaging Center Erlangen (OICE), Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Erlangen, Germany
| | - Lisa Seyler
- Institute of Radiology, University Hospital Erlangen, Maximiliansplatz 1, Erlangen, Germany
| | - Maximilian Waldner
- Department of Medicine 1, University Hospital Erlangen, Kussmaul Campus for Medical Research, Erlangen, Germany
| | - Michael Uder
- Institute of Radiology, University Hospital Erlangen, Maximiliansplatz 1, Erlangen, Germany
| | - Michael Stürzl
- Division of Molecular and Experimental Surgery, Translational Research Center Erlangen, Department of Surgery, Erlangen, Germany
| | - Tobias Bäuerle
- Institute of Radiology, University Hospital Erlangen, Maximiliansplatz 1, Erlangen, Germany
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Chen C, Li T, Zhao Y, Qian Y, Li X, Dai X, Huang D, Pan T, Zhou L. Platelet glycoprotein receptor Ib blockade ameliorates experimental cerebral ischemia-reperfusion injury by strengthening the blood-brain barrier function and anti-thrombo-inflammatory property. Brain Behav Immun 2018; 69:255-263. [PMID: 29195783 DOI: 10.1016/j.bbi.2017.11.019] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Revised: 11/17/2017] [Accepted: 11/27/2017] [Indexed: 12/26/2022] Open
Abstract
Blood-brain barrier (BBB) disruption, thrombus formation and immune-mediated inflammation are important steps in the pathophysiology of cerebral ischemia-reperfusion injury but are still inaccessible to therapeutic interventions. Recent studies have provided increasing evidence that blocking of platelet glycoprotein (GP) receptor Ib might represent a novel target in treating acute ischemic stroke. This research was conducted to explore the therapeutic efficacy and potential mechanisms of GPIbα inhibitor (anfibatide) in a model of brain ischemia-reperfusion injury in mice. Male mice underwent 90 min of right middle cerebral artery occlusion (MCAO) followed by 24 h of reperfusion. Anfibatide (1, 2, 4 ug/kg) or tirofiban were administered intravenously 1 h after reperfusion. The results showed that anfibatide could significantly reduce infarct volumes, increase the number of intact neuronal cells and improve neurobehavioral function. Moreover, anfibatide could reduce post ischemic BBB damage by attenuating increased paracellular permeability in the ischemia hemisphere significantly. Stroke-induced increases in activity and protein expression of macrophage-1 antigen (MAC-1) and P-selectin were also reduced by anfibatide intervention. Finally, anfibatide exerted antithrombotic effects upon stroke by decreased the number of microthrombi formation. This is the first demonstration of anfibatide's efficacy in protecting the BBB integrity and decreasing neutrophil inflammation response mediated by MAC-1 besides microthrombus formation inhibition in the brain during reperfusion. Anfibatide, as a promising anti-thrombo-inflammation agent, could be beneficial for the treatment of ischemic stroke.
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Affiliation(s)
- Chunyan Chen
- Department of Pharmacology, School of Basic Medical Science, Key Laboratory of Anti-inflammatory and Immunopharmacology, Ministry of Education, Anhui Medical University, Hefei 230032, PR China
| | - Tingting Li
- Department of Pharmacology, School of Basic Medical Science, Key Laboratory of Anti-inflammatory and Immunopharmacology, Ministry of Education, Anhui Medical University, Hefei 230032, PR China; Department of Pharmacy, The Fourth Affiliated Hospital of Anhui Medical University, Hefei 230032, PR China
| | - Yuchen Zhao
- Department of Pharmacology, School of Basic Medical Science, Key Laboratory of Anti-inflammatory and Immunopharmacology, Ministry of Education, Anhui Medical University, Hefei 230032, PR China
| | - Yinfeng Qian
- Department of Radiology, The First Affiliated Hospital of Anhui Medical University, Hefei 230032, PR China
| | - Xiaoyi Li
- Zhaoke Pharmaceutical Co. Ltd, Hefei 230032, PR China
| | - Xiangrong Dai
- Zhaoke Pharmaceutical Co. Ltd, Hefei 230032, PR China
| | - Dake Huang
- Synthetic Laboratory of Basic Medicine College, Anhui Medical University, Hefei 230032, PR China
| | - Tianzhong Pan
- Department of Pharmacology, School of Basic Medical Science, Key Laboratory of Anti-inflammatory and Immunopharmacology, Ministry of Education, Anhui Medical University, Hefei 230032, PR China
| | - Lanlan Zhou
- Department of Pharmacology, School of Basic Medical Science, Key Laboratory of Anti-inflammatory and Immunopharmacology, Ministry of Education, Anhui Medical University, Hefei 230032, PR China.
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Deuchar GA, Brennan D, Holmes WM, Shaw M, Macrae IM, Santosh C. Perfluorocarbon Enhanced Glasgow Oxygen Level Dependent (GOLD) Magnetic Resonance Metabolic Imaging Identifies the Penumbra Following Acute Ischemic Stroke. Am J Cancer Res 2018; 8:1706-1722. [PMID: 29556351 PMCID: PMC5858177 DOI: 10.7150/thno.21685] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2017] [Accepted: 12/16/2017] [Indexed: 01/27/2023] Open
Abstract
The ability to identify metabolically active and potentially salvageable ischaemic penumbra is crucial for improving treatment decisions in acute stroke patients. Our solution involves two complementary novel MRI techniques (Glasgow Oxygen Level Dependant (GOLD) Metabolic Imaging), which when combined with a perfluorocarbon (PFC) based oxygen carrier and hyperoxia can identify penumbra due to dynamic changes related to continued metabolism within this tissue compartment. Our aims were (i) to investigate whether PFC offers similar enhancement of the second technique (Lactate Change) as previously demonstrated for the T2*OC technique (ii) to demonstrate both GOLD metabolic imaging techniques working concurrently to identify penumbra, following administration of Oxycyte® (O-PFC) with hyperoxia. Methods: An established rat stroke model was utilised. Part-1: Following either saline or PFC, magnetic resonance spectroscopy was applied to investigate the effect of hyperoxia on lactate change in presumed penumbra. Part-2; rats received O-PFC prior to T2*OC (technique 1) and MR spectroscopic imaging, which was used to identify regions of tissue lactate change (technique 2) in response to hyperoxia. In order to validate the techniques, imaging was followed by [14C]2-deoxyglucose autoradiography to correlate tissue metabolic status to areas identified as penumbra. Results: Part-1: PFC+hyperoxia resulted in an enhanced reduction of lactate in the penumbra when compared to saline+hyperoxia. Part-2: Regions of brain tissue identified as potential penumbra by both GOLD metabolic imaging techniques utilising O-PFC, demonstrated maintained glucose metabolism as compared to adjacent core tissue. Conclusion: For the first time in vivo, enhancement of both GOLD metabolic imaging techniques has been demonstrated following intravenous O-PFC+hyperoxia to identify ischaemic penumbra. We have also presented preliminary evidence of the potential therapeutic benefit offered by O-PFC. These unique theranostic applications would enable treatment based on metabolic status of the brain tissue, independent of time from stroke onset, leading to increased uptake and safer use of currently available treatment options.
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Chazalviel L, David HN, Haelewyn B, Blatteau JE, Vallée N, Risso JJ, Besnard S, Abraini JH. The underestimated effect of normobaric hyperoxia on cerebral blood flow and its relationship to neuroprotection. Brain 2018; 139:e62. [PMID: 27412390 DOI: 10.1093/brain/aww178] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Laurent Chazalviel
- Normandie Université, UNICAEN, CNRS, UMR 6301 ISTCT, Equipe Cervoxy, Caen, France
| | - Hélène N David
- Université Laval, Département d'Anesthésiologie, Québec, Canada.,Monatomics Technology, 24 rue Erlanger, 75016 Paris, France
| | - Benoit Haelewyn
- Normandie Université, UNICAEN, Centre Universitaire de Ressources Biologiques, Caen, France
| | - Jean-Eric Blatteau
- Hôpital d'Instruction des Armées (HIA) Sainte-Anne, Service de Médecine Hyperbare et Expertise Plongée (SMHEP), Toulon, France
| | - Nicolas Vallée
- Institut de Recherche Biomédicale des Armées (IRBA), Equipe Résidente de Recherche Subaquatique Opérationnelle (ERRSO), Toulon, France
| | - Jean-Jacques Risso
- Institut de Recherche Biomédicale des Armées (IRBA), Equipe Résidente de Recherche Subaquatique Opérationnelle (ERRSO), Toulon, France
| | | | - Jacques H Abraini
- Université Laval, Département d'Anesthésiologie, Québec, Canada.,Institut de Recherche Biomédicale des Armées (IRBA), Equipe Résidente de Recherche Subaquatique Opérationnelle (ERRSO), Toulon, France.,Normandie Université, UNICAEN, Faculté de Médecine, Caen, France
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7
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Effects of hyperoxia on 18F-fluoro-misonidazole brain uptake and tissue oxygen tension following middle cerebral artery occlusion in rodents: Pilot studies. PLoS One 2017; 12:e0187087. [PMID: 29091934 PMCID: PMC5665507 DOI: 10.1371/journal.pone.0187087] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2017] [Accepted: 10/15/2017] [Indexed: 12/11/2022] Open
Abstract
PURPOSE Mapping brain hypoxia is a major goal for stroke diagnosis, pathophysiology and treatment monitoring. 18F-fluoro-misonidazole (FMISO) positron emission tomography (PET) is the gold standard hypoxia imaging method. Normobaric hyperoxia (NBO) is a promising therapy in acute stroke. In this pilot study, we tested the straightforward hypothesis that NBO would markedly reduce FMISO uptake in ischemic brain in Wistar and spontaneously hypertensive rats (SHRs), two rat strains with distinct vulnerability to brain ischemia, mimicking clinical heterogeneity. METHODS Thirteen adult male rats were randomized to distal middle cerebral artery occlusion under either 30% O2 or 100% O2. FMISO was administered intravenously and PET data acquired dynamically for 3hrs, after which magnetic resonance imaging (MRI) and tetrazolium chloride (TTC) staining were carried out to map the ischemic lesion. Both FMISO tissue uptake at 2-3hrs and FMISO kinetic rate constants, determined based on previously published kinetic modelling, were obtained for the hypoxic area. In a separate group (n = 9), tissue oxygen partial pressure (PtO2) was measured in the ischemic tissue during both control and NBO conditions. RESULTS As expected, the FMISO PET, MRI and TTC lesion volumes were much larger in SHRs than Wistar rats in both the control and NBO conditions. NBO did not appear to substantially reduce FMISO lesion size, nor affect the FMISO kinetic rate constants in either strain. Likewise, MRI and TTC lesion volumes were unaffected. The parallel study showed the expected increases in ischemic cortex PtO2 under NBO, although these were small in some SHRs with very low baseline PtO2. CONCLUSIONS Despite small samples, the apparent lack of marked effects of NBO on FMISO uptake suggests that in permanent ischemia the cellular mechanisms underlying FMISO trapping in hypoxic cells may be disjointed from PtO2. Better understanding of FMISO trapping processes will be important for future applications of FMISO imaging.
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8
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Dani KA, Moreton FC, Santosh C, Lopez R, Brennan D, Schwarzbauer C, Goutcher C, O'Hare K, Macrae IM, Muir KW. Oxygen challenge magnetic resonance imaging in healthy human volunteers. J Cereb Blood Flow Metab 2017; 37:366-376. [PMID: 26787107 PMCID: PMC5363753 DOI: 10.1177/0271678x15627827] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Revised: 11/12/2015] [Accepted: 11/16/2015] [Indexed: 11/15/2022]
Abstract
Oxygen challenge imaging involves transient hyperoxia applied during deoxyhaemoglobin sensitive (T2*-weighted) magnetic resonance imaging and has the potential to detect changes in brain oxygen extraction. In order to develop optimal practical protocols for oxygen challenge imaging, we investigated the influence of oxygen concentration, cerebral blood flow change, pattern of oxygen administration and field strength on T2*-weighted signal. Eight healthy volunteers underwent multi-parametric magnetic resonance imaging including oxygen challenge imaging and arterial spin labelling using two oxygen concentrations (target FiO2 of 100 and 60%) administered consecutively (two-stage challenge) at both 1.5T and 3T. There was a greater signal increase in grey matter compared to white matter during oxygen challenge (p < 0.002 at 3T, P < 0.0001 at 1.5T) and at FiO2 = 100% compared to FiO2 = 60% in grey matter at both field strengths (p < 0.02) and in white matter at 3T only (p = 0.0314). Differences in the magnitude of signal change between 1.5T and 3T did not reach statistical significance. Reduction of T2*-weighted signal to below baseline, after hyperoxia withdrawal, confounded interpretation of two-stage oxygen challenge imaging. Reductions in cerebral blood flow did not obscure the T2*-weighted signal increases. In conclusion, the optimal protocol for further study should utilise target FiO2 = 100% during a single oxygen challenge. Imaging at both 1.5T and 3T is clinically feasible.
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Affiliation(s)
- Krishna A Dani
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Fiona C Moreton
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Celestine Santosh
- Department of Neuroradiology, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Rosario Lopez
- Department of Clinical Physics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - David Brennan
- Department of Clinical Physics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Christian Schwarzbauer
- University of Applied Sciences Munich, School of Applied Sciences and Mechatronics, München
| | - Colin Goutcher
- Department of Anaesthetics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - Kevin O'Hare
- Department of Anaesthetics, Institute of Neurological Sciences, Queen Elizabeth University Hospital Glasgow, Glasgow
| | - I Mhairi Macrae
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Glasgow
| | - Keith W Muir
- Institute of Neuroscience and Psychology, College of Medical Veterinary and Life Sciences, University of Glasgow, Queen Elizabeth University Hospital Glasgow, Glasgow
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9
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Song Y, Garcia S, Frometa Y, Ramella-Roman JC, Soltani M, Almadi M, Riera JJ, Lin WC. Quantitative assessment of hemodynamic and structural characteristics of in vivo brain tissue using total diffuse reflectance spectrum measured in a non-contact fashion. BIOMEDICAL OPTICS EXPRESS 2017; 8:78-103. [PMID: 28101403 PMCID: PMC5231317 DOI: 10.1364/boe.8.000078] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 11/03/2016] [Accepted: 11/08/2016] [Indexed: 05/03/2023]
Abstract
Here we present a new methodology that investigates the intrinsic structural and hemodynamic characteristics of in vivo brain tissue, in a non-contact fashion, and can be easily incorporated in an intra-operative environment. Within this methodology, relative total diffuse reflectance spectra (RTD(λ)) were acquired from targets using a hybrid spectroscopy imaging system. A spectral interpretation algorithm was subsequently applied to RTD(λ) to retrieve optical properties related to the compositional and structural characteristics of each target. Estimation errors of the proposed methodology were computationally evaluated using a Monte Carlo simulation model for photon migration under various conditions. It was discovered that this new methodology could handle moderate noise and achieve very high accuracy, but only if the refractive index of the target is known. The accuracy of the technique was also validated using a series of tissue phantom studies, and consistent and accurate estimates of μs'(λ)/μa(λ) were obtained from all the phantoms tested. Finally, a small-scale animal study was conducted to demonstrate the clinical utility of the reported method, wherein a forepaw stimulation model was utilized to induce transient hemodynamic responses in somatosensory cortices. With this approach, significant stimulation-related changes (p < 0.001) in cortical hemodynamic and structural characteristics were successfully measured.
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10
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Baron JC. Reply: The underestimated effect of normobaric hyperoxia on cerebral blood flow and its relationship to neuroprotection. Brain 2016; 139:e63. [DOI: 10.1093/brain/aww179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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11
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Chazalviel L, Blatteau JE, Vallée N, Risso JJ, Besnard S, Abraini JH. Effects of normobaric versus hyperbaric oxygen on cell injury induced by oxygen and glucose deprivation in acute brain slices. Med Gas Res 2016; 6:169-173. [PMID: 27867486 PMCID: PMC5110143 DOI: 10.4103/2045-9912.191364] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Normobaric oxygen (NBO) and hyperbaric oxygen (HBO) are emerging as a possible co-treatment of acute ischemic stroke. Both have been shown to reduce infarct volume, to improve neurologic outcome, to promote endogenous tissue plasminogen activator-induced thrombolysis and cerebral blood flow, and to improve tissue oxygenation through oxygen diffusion in the ischemic areas, thereby questioning the interest of HBO compared to NBO. In the present study, in order to investigate and compare the oxygen diffusion effects of NBO and HBO on acute ischemic stroke independently of their effects at the vascular level, we used acute brain slices exposed to oxygen and glucose deprivation, an ex vivo model of brain ischemia that allows investigating the acute effects of NBO (partial pressure of oxygen (pO2) = 1 atmospheres absolute (ATA) = 0.1 MPa) and HBO (pO2 = 2.5 ATA = 0.25 MPa) through tissue oxygenation on ischemia-induced cell injury as measured by the release of lactate dehydrogenase. We found that HBO, but not NBO, reduced oxygen and glucose deprivation-induced cell injury, indicating that passive tissue oxygenation (i.e. without vascular support) of the brain parenchyma requires oxygen partial pressure higher than 1 ATA.
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Affiliation(s)
- Laurent Chazalviel
- Normandie Université, UNICAEN, CNRS, UMR 6301 ISTCT, Equipe Cervoxy, Caen, France
| | - Jean-Eric Blatteau
- Hôpital d'Instruction des Armées (HIA) Sainte-Anne, Service de Médecine Hyperbare et Expertise Plongée (SMHEP), Toulon, France
| | - Nicolas Vallée
- Institut de Recherche Biomédicale des Armées (IRBA), Equipe Résidente de Recherche Subaquatique Opérationnelle (ERRSO), Toulon, France
| | - Jean-Jacques Risso
- Institut de Recherche Biomédicale des Armées (IRBA), Equipe Résidente de Recherche Subaquatique Opérationnelle (ERRSO), Toulon, France
| | | | - Jacques H Abraini
- Institut de Recherche Biomédicale des Armées (IRBA), Equipe Résidente de Recherche Subaquatique Opérationnelle (ERRSO), Toulon, France; Normandie Université, UNICAEN, Faculté de Médecine, France; Université Laval, Département d'Anesthésiologie, Québec, Canada
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Abstract
PURPOSE OF REVIEW This article provides an overview of the recent literature regarding the application of in-vivo brain imaging techniques to animal models of ischemic stroke. RECENT FINDINGS Major breakthroughs concerned the effects of sensory stimulation on neuronal function, local hemodynamics, and tissue outcome in the hyperacute phase of stroke; the novel application to stroke of hybrid scanners allowing simultaneous PET and magnetic resonance; the refinements of magnetic resonance-based oxygen imaging, allowing to map the ischemic penumbra in a completely noninvasive way; the implementation of new PET ligands to selectively map poststroke neuronal death and neuroinflammation; and the use of novel mesoscale imaging techniques to demonstrate the major role of interhemispheric connectivity in poststroke plasticity and functional recovery. SUMMARY The array of techniques to map in vivo the key pathophysiological brain processes involved in stroke is currently enlarging at an amazing pace. This is paralleled by ever-increasing sophistication in postprocessing tools. The combination of techniques allowing simultaneous access to several variables is particularly powerful as it affords unprecedented insights into the intimate processes underlying the tissue and neuronal changes that follow a stroke. These major leaps forward will hopefully lead to therapeutic breakthroughs aiming at improving functional outcome after stroke.
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13
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Ejaz S, Emmrich JV, Sitnikov SL, Hong YT, Sawiak SJ, Fryer TD, Aigbirhio FI, Williamson DJ, Baron JC. Normobaric hyperoxia markedly reduces brain damage and sensorimotor deficits following brief focal ischaemia. Brain 2016; 139:751-64. [PMID: 26767570 DOI: 10.1093/brain/awv391] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Accepted: 11/16/2015] [Indexed: 01/02/2023] Open
Abstract
'True' transient ischaemic attacks are characterized not only clinically, but also radiologically by a lack of corresponding changes on magnetic resonance imaging. During a transient ischaemic attack it is assumed that the affected tissue is penumbral but rescued by early spontaneous reperfusion. There is, however, evidence from rodent studies that even brief focal ischaemia not resulting in tissue infarction can cause extensive selective neuronal loss associated with long-lasting sensorimotor impairment but normal magnetic resonance imaging. Selective neuronal loss might therefore contribute to the increasingly recognized cognitive impairment occurring in patients with transient ischaemic attacks. It is therefore relevant to consider treatments to reduce brain damage occurring with transient ischaemic attacks. As penumbral neurons are threatened by markedly constrained oxygen delivery, improving the latter by increasing arterial O2 content would seem logical. Despite only small increases in arterial O2 content, normobaric oxygen therapy experimentally induces significant increases in penumbral O2 pressure and by such may maintain the penumbra alive until reperfusion. Nevertheless, the effects of normobaric oxygen therapy on infarct volume in rodent models have been conflicting, although duration of occlusion appeared an important factor. Likewise, in the single randomized trial published to date, early-administered normobaric oxygen therapy had no significant effect on clinical outcome despite reduced diffusion-weighted imaging lesion growth during therapy. Here we tested the hypothesis that normobaric oxygen therapy prevents both selective neuronal loss and sensorimotor deficits in a rodent model mimicking true transient ischaemic attack. Normobaric oxygen therapy was applied from the onset and until completion of 15 min distal middle cerebral artery occlusion in spontaneously hypertensive rats, a strain representative of the transient ischaemic attack-prone population. Whereas normoxic controls showed normal magnetic resonance imaging but extensive cortical selective neuronal loss associated with microglial activation (present both at Day 14 in vivo and at Day 28 post-mortem) and marked and long-lasting sensorimotor deficits, normobaric oxygen therapy completely prevented sensorimotor deficit (P < 0.02) and near-completely Day 28 selective neuronal loss (P < 0.005). Microglial activation was substantially reduced at Day 14 and completely prevented at Day 28 (P = 0.002). Our findings document that normobaric oxygen therapy administered during ischaemia nearly completely prevents the neuronal death, microglial inflammation and sensorimotor impairment that characterize this rodent true transient ischaemic attack model. Taken together with the available literature, normobaric oxygen therapy appears a promising therapy for short-lasting ischaemia, and is attractive clinically as it could be started at home in at-risk patients or in the ambulance in subjects suspected of transient ischaemic attack/early stroke. It may also be a straightforward adjunct to reperfusion therapies, and help prevent subtle brain damage potentially contributing to long-term cognitive and sensorimotor impairment in at-risk populations.
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Affiliation(s)
- Sohail Ejaz
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Julius V Emmrich
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, UK 2 Department of Neurology, Charité - Universitätsmedizin Berlin, Germany
| | - Sergey L Sitnikov
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Young T Hong
- 3 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Stephen J Sawiak
- 3 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Tim D Fryer
- 3 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Franklin I Aigbirhio
- 3 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, UK
| | - David J Williamson
- 3 Wolfson Brain Imaging Centre, Department of Clinical Neurosciences, University of Cambridge, UK
| | - Jean-Claude Baron
- 1 Stroke Research Group, Department of Clinical Neurosciences, University of Cambridge, UK 4 INSERM U894, Hôpital Sainte-Anne, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
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Abstract
Hyperoxia has been uniformly efficacious in experimental focal cerebral ischemia. However, pilot clinical trials have showed mixed results slowing its translation in patient care. To explain the discordance between experimental and clinical outcomes, we tested the impact of endothelial dysfunction, exceedingly common in stroke patients but under-represented in experimental studies, on the neuroprotective efficacy of normobaric hyperoxia. We used hyperlipidemic apolipoprotein E knock-out and endothelial nitric oxide synthase knock-out mice as models of endothelial dysfunction, and examined the effects of normobaric hyperoxia on tissue perfusion and oxygenation using high-resolution combined laser speckle and multispectral reflectance imaging during distal middle cerebral artery occlusion. In normal wild-type mice, normobaric hyperoxia rapidly and significantly improved tissue perfusion and oxygenation, suppressed peri-infarct depolarizations, reduced infarct volumes, and improved neurological function. In contrast, normobaric hyperoxia worsened perfusion in ischemic brain and failed to reduce infarct volumes or improve neurological function in mice with endothelial dysfunction. These data suggest that the beneficial effects of hyperoxia on ischemic tissue oxygenation, perfusion, and outcome are critically dependent on endothelial nitric oxide synthase function. Therefore, vascular risk factors associated with endothelial dysfunction may predict normobaric hyperoxia nonresponders in ischemic stroke. These data may have implications for myocardial and systemic circulation as well.
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15
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Shen Q, Du F, Huang S, Duong TQ. Effects of cerebral ischemic and reperfusion on T2*-weighted MRI responses to brief oxygen challenge. J Cereb Blood Flow Metab 2014; 34:169-75. [PMID: 24129750 PMCID: PMC3887355 DOI: 10.1038/jcbfm.2013.179] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/24/2013] [Revised: 08/19/2013] [Accepted: 09/19/2013] [Indexed: 11/09/2022]
Abstract
This study characterized the effects of cerebral ischemia and reperfusion on T2*-weighted magnetic resonance image (MRI) responses to brief oxygen challenge (OC) in transient (60 minutes) cerebral ischemia in rats. During occlusion, the ischemic core tissue showed no significant OC response, whereas the perfusion-diffusion mismatch tissue showed markedly higher percent changes relative to normal tissue. After reperfusion, much of the pixels with initial exaggerated OC responses showed normal OC responses, and the majority of these tissues were salvaged as defined by endpoint T2 MRI. The initial core pixels showed exaggerated OC responses after reperfusion, but the majority of the core pixels eventually became infarct, suggesting exaggerated OC responses do not necessarily reflect salvageable tissue. Twenty-four hours after stroke, basal T1 increased in the ischemic core. Oxygen challenge decreased T1 significantly in the core, indicative of the substantial increases in dissolved oxygen in the core as the result of hyperperfusion. We concluded that exaggerated T2*-weighted MRI responses to OC offer useful insight in ischemic tissue fates. However, exaggerated OC pixels are not all salvageable, and they exhibited complex dynamics depending on reperfusion status, hyperperfusion, and edema effects.
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Affiliation(s)
- Qiang Shen
- 1] Department of Research Imaging Institute, San Antonio, Texas, USA [2] Department of Ophthalmology, San Antonio, Texas, USA [3] Department of Radiology, University of Texas Health Science Center, San Antonio, Texas, USA
| | - Fang Du
- Department of Research Imaging Institute, San Antonio, Texas, USA
| | - Shiliang Huang
- Department of Research Imaging Institute, San Antonio, Texas, USA
| | - Timothy Q Duong
- 1] Department of Research Imaging Institute, San Antonio, Texas, USA [2] Department of Ophthalmology, San Antonio, Texas, USA [3] Department of Radiology, University of Texas Health Science Center, San Antonio, Texas, USA [4] South Texas Veterans Health Care System, Department of Veterans Affairs, San Antonio, Texas, USA
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16
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Deuchar GA, Brennan D, Griffiths H, Macrae I M, Santosh C. Perfluorocarbons enhance a T2*-based MRI technique for identifying the penumbra in a rat model of acute ischemic stroke. J Cereb Blood Flow Metab 2013; 33:1422-8. [PMID: 23801243 PMCID: PMC3764387 DOI: 10.1038/jcbfm.2013.86] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/28/2013] [Revised: 04/22/2013] [Accepted: 05/01/2013] [Indexed: 02/05/2023]
Abstract
Accurate imaging of ischemic penumbra is crucial for improving the management of acute stroke patients. T2* magnetic resonance imaging (MRI) combined with a T2*oxygen challenge (T2*OC) is being developed to detect penumbra based on changes in blood deoxyhemoglobin. Using 100% O2, T2*OC-defined penumbra exhibits ongoing glucose metabolism and tissue recovery on reperfusion. However, potential limitations in translating this technique include a sinus artefact in human scans with delivery of 100% OC and relatively small signal changes. Here we investigate whether an oxygen-carrying perfluorocarbon (PFC) emulsion can enhance the sensitivity of the technique, enabling penumbra detection with lower levels of inspired oxygen. Stroke was induced in male Sprague-Dawley rats (n=17) with ischemic injury and perfusion deficit determined by diffusion and perfusion MRI, respectively. T2* signal change was measured in regions of interest (ROIs) located within ischemic core, T2*OC-defined penumbra and equivalent contralateral areas during 40% O2±prior PFC injection. Region of interest analyses between groups showed that PFC significantly enhanced the T2* response to 40% O2 in T2*-defined penumbra (mean increase of 10.6±2.3% compared to 5.6±1.5% with 40% O2, P<0.001). This enhancement was specific to the penumbra ROI. Perfluorocarbon emulsions therefore enhances the translational potential of the T2*OC technique for identifying penumbra in acute stroke patients.
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Affiliation(s)
- Graeme A Deuchar
- Wellcome Surgical Institute, Glasgow Experimental MRI Centre, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - David Brennan
- Department of Neuroradiology, Institute of Neurological Sciences, Southern General Hospital, Glasgow, UK
| | - Hugh Griffiths
- Department of Neuroradiology, Institute of Neurological Sciences, Southern General Hospital, Glasgow, UK
| | - I Mhairi Macrae
- Wellcome Surgical Institute, Glasgow Experimental MRI Centre, Institute of Neuroscience and Psychology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, UK
| | - Celestine Santosh
- Department of Neuroradiology, Institute of Neurological Sciences, Southern General Hospital, Glasgow, UK
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17
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Dynamic functional cerebral blood volume responses to normobaric hyperoxia in acute ischemic stroke. J Cereb Blood Flow Metab 2012; 32:1800-9. [PMID: 22739619 PMCID: PMC3434635 DOI: 10.1038/jcbfm.2012.87] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Studies suggest that neuroprotective effects of normobaric oxygen (NBO) therapy in acute stroke are partly mediated by hemodynamic alterations. We investigated cerebral hemodynamic effects of repeated NBO exposures. Serial magnetic resonance imaging (MRI) was performed in Wistar rats subjected to focal ischemic stroke. Normobaric oxygen-induced functional cerebral blood volume (fCBV) responses were analyzed. All rats had diffusion-weighted MRI (DWI) lesions within larger perfusion deficits, with DWI lesion expansion after 3 hours. Functional cerebral blood volume responses to NBO were spatially and temporally heterogeneous. Contralateral healthy tissue responded consistently with vasoconstriction that increased with time. No significant responses were evident in the acute DWI lesion. In hypoperfused regions surrounding the acute DWI lesion, tissue that remained viable until the end of the experiment showed relative preservation of mean fCBV at early time points, with some rats showing increased fCBV (vasodilation); however, these regions later exhibited significantly decreased fCBV (vasoconstriction). Tissue that became DWI abnormal by study-end initially showed marginal fCBV changes that later became moderate fCBV reductions. Our results suggest that a reverse-steal hemodynamic effect may occur in peripheral ischemic zones during NBO treatment of focal stroke. In addition, CBV responses to NBO challenge may have potential as an imaging marker to distinguish ischemic core from salvageable tissues.
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18
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Jensen-Kondering U, Baron JC. Oxygen imaging by MRI: can blood oxygen level-dependent imaging depict the ischemic penumbra? Stroke 2012; 43:2264-9. [PMID: 22588263 DOI: 10.1161/strokeaha.111.632455] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Affiliation(s)
- Ulf Jensen-Kondering
- Stroke Research Group, University of Cambridge, Department of Clinical Neurosciences, Addenbrooke's Hospital, Cambridge, UK
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19
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David HN, Haelewyn B, Degoulet M, Colomb DG, Risso JJ, Abraini JH. Prothrombolytic action of normobaric oxygen given alone or in combination with recombinant tissue-plasminogen activator in a rat model of thromboembolic stroke. J Appl Physiol (1985) 2012; 112:2068-76. [PMID: 22492935 DOI: 10.1152/japplphysiol.00092.2012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The potential benefit of 100 vol% normobaric oxygen (NBO) for the treatment of acute ischemic stroke patients is still a matter of debate. To advance this critical question, we studied the effects of intraischemic normobaric oxygen alone or in combination with recombinant tissue-plasminogen activator (rtPA) on cerebral blood flow and ischemic brain damage and swelling in a clinically relevant rat model of thromboembolic stroke. We show that NBO provides neuroprotection by achieving cerebral blood flow restoration equivalent to 0.9 mg/kg rtPA through probable direct interaction and facilitation of the fibrinolytic properties of endogenous tPA. In contrast, combined NBO and rtPA has no neuroprotective effect on ischemic brain damage despite producing cerebral blood flow restoration. These results 1) by providing a new mechanism of action of NBO highlight together with previous findings the way by which intraischemic NBO shows beneficial action; 2) suggest that NBO could be an efficient primary care therapeutic intervention for patients eligible for rtPA therapy; 3) indicate that NBO could be an interesting alternative for patients not eligible for rtPA therapy; and 4) caution the use of NBO in combination with rtPA in acute stroke patients.
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Affiliation(s)
- H N David
- Centre de Recherche, Centre Hospitalier Affilié Universitaire Hôtel-Dieu de Lévis, Lévis, Quebec, Canada
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