Summary: A noble gas with the atomic symbol Xe, atomic number 54, and atomic weight 131.30. It is found in the earth's atmosphere and has been used as an anesthetic.

Top Publications

  1. Coburn M, Baumert J, Roertgen D, Thiel V, Fries M, Hein M, et al. Emergence and early cognitive function in the elderly after xenon or desflurane anaesthesia: a double-blinded randomized controlled trial. Br J Anaesth. 2007;98:756-62 pubmed
    ..b>Xenon, known to be an N-methyl-d-aspartate antagonist, may be advantageous...
  2. Reinhardt J, Ding K, Cao K, Christensen G, Hoffman E, Bodas S. Registration-based estimates of local lung tissue expansion compared to xenon CT measures of specific ventilation. Med Image Anal. 2008;12:752-63 pubmed publisher
    ..We compare the ventral-dorsal patterns of lung expansion estimated across five pressure changes to a xenon CT based measure of specific ventilation in five anesthetized sheep studied in the supine orientation...
  3. Cattano D, Valleggi S, Ma D, Kastsiuchenka O, Abramo A, Sun P, et al. Xenon induces transcription of ADNP in neonatal rat brain. Neurosci Lett. 2008;440:217-21 pubmed publisher
    b>Xenon and other inhalational agents induce cell and organ protection through different and only partially elucidated molecular mechanisms. Anesthesia induced or pharmacologic preconditioning is a recognized mechanism of cell protection...
  4. Nikolaou P, Whiting N, Eschmann N, Chaffee K, Goodson B, Barlow M. Generation of laser-polarized xenon using fiber-coupled laser-diode arrays narrowed with integrated volume holographic gratings. J Magn Reson. 2009;197:249-54 pubmed publisher
    ..Additionally, an anomalous dependence of P(Xe) on the xenon density within the OP cell is reported-including high P(Xe) values (>10%) at high xenon partial pressures (..
  5. Yamamoto Y, Kawaguchi M, Kurita N, Kakimoto M, Inoue S, Furuya H. Effects of xenon on ischemic spinal cord injury in rabbits: a comparison with propofol. Acta Anaesthesiol Scand. 2010;54:337-42 pubmed publisher
    b>Xenon has been shown to reduce cellular injury after cerebral ischemia. However, the neuroprotective effects of xenon on ischemic spinal cord are unknown...
  6. Dickinson R, Peterson B, Banks P, Simillis C, Martin J, Valenzuela C, et al. Competitive inhibition at the glycine site of the N-methyl-D-aspartate receptor by the anesthetics xenon and isoflurane: evidence from molecular modeling and electrophysiology. Anesthesiology. 2007;107:756-67 pubmed
    ..However, the site of action of these agents on the NMDA receptor is unknown. The authors show that xenon and isoflurane compete for the binding of the coagonist glycine on the NMDA receptor NR1 subunit.
  7. Marassio G, Prang T, David H, Santos J, Gabison L, Delcroix N, et al. Pressure-response analysis of anesthetic gases xenon and nitrous oxide on urate oxidase: a crystallographic study. FASEB J. 2011;25:2266-75 pubmed publisher
    The remarkably safe anesthetics xenon (Xe) and, to lesser extent, nitrous oxide (N(2)O) possess neuroprotective properties in preclinical studies...
  8. Vizcaychipi M, Lloyd D, Wan Y, Palazzo M, Maze M, Ma D. Xenon pretreatment may prevent early memory decline after isoflurane anesthesia and surgery in mice. PLoS ONE. 2011;6:e26394 pubmed publisher
    ..We hypothesized that xenon pretreatment prevents POCD by suppressing the systemic inflammatory response or through an associated protective ..
  9. Faulkner S, Downie N, Mercer C, Kerr S, Sanders R, Robertson N. A xenon recirculating ventilator for the newborn piglet: developing clinical applications of xenon for neonates. Eur J Anaesthesiol. 2012;29:577-85 pubmed publisher
    The clinical applications of xenon for the neonate include both anaesthesia and neuroprotection...

More Information


  1. Wappler F, Rossaint R, Baumert J, Scholz J, Tonner P, Van Aken H, et al. Multicenter randomized comparison of xenon and isoflurane on left ventricular function in patients undergoing elective surgery. Anesthesiology. 2007;106:463-71 pubmed
    ..However, these can induce profound cardiovascular alterations. Xenon is a noble gas with potent anesthetic and analgesic properties...
  2. Zhao H, Yoshida A, Xiao W, Ologunde R, O Dea K, Takata M, et al. Xenon treatment attenuates early renal allograft injury associated with prolonged hypothermic storage in rats. FASEB J. 2013;27:4076-88 pubmed publisher
    ..The aim of this study is to investigate the renoprotective effect of xenon on early allograft injury associated with prolonged hypothermic storage...
  3. MOLLER H, Cleveland Z, Driehuys B. Relaxation of hyperpolarized 129Xe in a deflating polymer bag. J Magn Reson. 2011;212:109-15 pubmed publisher
    ..Calculations based on these findings indicate that relaxation may limit HP 129Xe experiments when slow gas delivery rates are employed as, for example, in mouse imaging or vascular infusion experiments...
  4. Peng T, Britton G, Kim H, Cattano D, Aronowski J, Grotta J, et al. Therapeutic time window and dose dependence of xenon delivered via echogenic liposomes for neuroprotection in stroke. CNS Neurosci Ther. 2013;19:773-84 pubmed publisher
    Neurologic impairment following ischemic injury complicates the quality of life for stroke survivors. Xenon (Xe) has favorable neuroprotective properties to modify stroke...
  5. Comment A, Jannin S, Hyacinthe J, Miéville P, Sarkar R, Ahuja P, et al. Hyperpolarizing gases via dynamic nuclear polarization and sublimation. Phys Rev Lett. 2010;105:018104 pubmed
    ..It is illustrated by applications to 129Xe nuclear magnetic resonance in xenon gas, leading to a signal enhancement of 3 to 4 orders of magnitude compared to the room-temperature thermal ..
  6. Georgiev S, Furue H, Baba H, Kohno T. Xenon inhibits excitatory but not inhibitory transmission in rat spinal cord dorsal horn neurons. Mol Pain. 2010;6:25 pubmed publisher
    The molecular targets for the promising gaseous anaesthetic xenon are still under investigation...
  7. Schwiebert C, Huhn R, Heinen A, Weber N, Hollmann M, Schlack W, et al. Postconditioning by xenon and hypothermia in the rat heart in vivo. Eur J Anaesthesiol. 2010;27:734-9 pubmed publisher
    ..Combining mild hypothermia with low-dose xenon, applied either simultaneously or one after the other, protects the neonatal rat brain against reperfusion injury...
  8. Rajakumaraswamy N, Ma D, Hossain M, Sanders R, Franks N, Maze M. Neuroprotective interaction produced by xenon and dexmedetomidine on in vitro and in vivo neuronal injury models. Neurosci Lett. 2006;409:128-33 pubmed
    b>Xenon, an NMDA receptor antagonist and dexmedetomidine (Dex), an alpha(2)-adrenoceptor agonist, both exhibit neuroprotective effects. We investigated the nature of their interaction...
  9. Rex S, Schaefer W, Meyer P, Rossaint R, Boy C, Setani K, et al. Positron emission tomography study of regional cerebral metabolism during general anesthesia with xenon in humans. Anesthesiology. 2006;105:936-43 pubmed
    The precise mechanism by which the gaseous anesthetic xenon exerts its effects in the human brain remains unknown...
  10. Takahashi H, Suzuki M, Ikeda H, Kobayashi M, Sase S, Yotsuyanagi H, et al. Evaluation of quantitative portal venous, hepatic arterial, and total hepatic tissue blood flow using xenon CT in alcoholic liver cirrhosis: comparison with liver cirrhosis C. Alcohol Clin Exp Res. 2007;31:S43-8 pubmed
    b>Xenon computed tomography (Xe-CT) is a noninvasive method of quantifying and visualizing tissue blood flow (TBF). For the liver, Xe-CT allows separate measurement of hepatic arterial and portal venous TBF...
  11. Camp J, Stokol T, Shuler M. Fabrication of a multiple-diameter branched network of microvascular channels with semi-circular cross-sections using xenon difluoride etching. Biomed Microdevices. 2008;10:179-86 pubmed
    ..In this work, the xenon difluoride process for isotropic etching of silicon was optimized for production of channels with semicircular ..
  12. Zhu Q, Jung D, Oganov A, Glass C, Gatti C, Lyakhov A. Stability of xenon oxides at high pressures. Nat Chem. 2013;5:61-5 pubmed publisher
    b>Xenon, which is quite inert under ambient conditions, may become reactive under pressure...
  13. Zhuang L, Yang T, Zhao H, Fidalgo A, Vizcaychipi M, Sanders R, et al. The protective profile of argon, helium, and xenon in a model of neonatal asphyxia in rats. Crit Care Med. 2012;40:1724-30 pubmed publisher
    b>Xenon provides neuroprotection in multiple animal models; however, little is known about the other noble gases. The aim of the current study was to compare xenon, argon, and helium neuroprotection in a neonatal asphyxia model in rats.
  14. Laitio R, Långsjö J, Aalto S, Kaisti K, Salmi E, Maksimow A, et al. The effects of xenon anesthesia on the relationship between cerebral glucose metabolism and blood flow in healthy subjects: a positron emission tomography study. Anesth Analg. 2009;108:593-600 pubmed publisher
    ..In this positron emission tomography study, our aim was to assess both rCMR(glc) and rCBF in the same individuals during xenon anesthesia.
  15. Coburn M, Maze M, Franks N. The neuroprotective effects of xenon and helium in an in vitro model of traumatic brain injury. Crit Care Med. 2008;36:588-95 pubmed publisher
    The "inert" gas xenon has been shown to be an effective neuroprotectant in a variety of in vitro and in vivo models of neuronal injury. We examined its neuroprotective properties in an in vitro model of traumatic brain injury.
  16. Schubert G, Seiz M, Hegewald A, Manville J, Thome C. Acute hypoperfusion immediately after subarachnoid hemorrhage: a xenon contrast-enhanced CT study. J Neurotrauma. 2009;26:2225-31 pubmed publisher
    ..b>Xenon contrast-enhanced CT scanning was performed in 17 patients (Hunt and Hess grade [HH] 1-3, n = 9; HH 4-5, n = 8) ..
  17. Rawat S, Dingley J. Closed-circuit xenon delivery using a standard anesthesia workstation. Anesth Analg. 2010;110:101-9 pubmed publisher
    b>Xenon (Xe) is an anesthetic with minimal side effects, now also showing promise as a neuroprotectant both in vitro and in vivo...
  18. Widmer R, Passerone D, Mattle T, Sachdev H, Gröning O. Probing the selectivity of a nanostructured surface by xenon adsorption. Nanoscale. 2010;2:502-8 pubmed publisher
    ..The insight into this interplay of interactions should pave the way to gain a more general knowledge on such site-specific adsorption processes...
  19. Neukirchen M, Hipp J, Schaefer M, Brandenburger T, Bauer I, Winterhalter M, et al. Cardiovascular stability and unchanged muscle sympathetic activity during xenon anaesthesia: role of norepinephrine uptake inhibition. Br J Anaesth. 2012;109:887-96 pubmed publisher
    ..The N-methyl-d-aspartate (NMDA) receptor (NMDA-R) antagonist xenon (Xe) induces general anaesthesia without impairment of cardiac output and vascular resistance...
  20. Shigefuku R, Takahashi H, Kobayashi M, Ikeda H, Matsunaga K, Okuse C, et al. Pathophysiological analysis of nonalcoholic fatty liver disease by evaluation of fatty liver changes and blood flow using xenon computed tomography: can early-stage nonalcoholic steatohepatitis be distinguished from simple steatosis?. J Gastroenterol. 2012;47:1238-47 pubmed publisher
    ..Our aim was to determine the possibility of noninvasively distinguishing early-stage NASH from SS...
  21. Goldinger S, Dummer R, Schmid P, Burg G, Seifert B, Lauchli S. Combination of 308-nm xenon chloride excimer laser and topical calcipotriol in vitiligo. J Eur Acad Dermatol Venereol. 2007;21:504-8 pubmed
    ..Recently, monochromatic phototherapies such as 311-nm narrowband ultraviolet B therapy and 308-nm xenon chloride excimer laser have been reported to be an effective and safe therapeutic option in children and adult ..
  22. Fahlenkamp A, Krebber F, Rex S, Grottke O, Fries M, Rossaint R, et al. Bispectral index monitoring during balanced xenon or sevoflurane anaesthesia in elderly patients. Eur J Anaesthesiol. 2010;27:906-11 pubmed publisher
    ..We evaluated the bispectral index (BIS) for monitoring depth of anaesthesia during clinically guided balanced xenon or sevoflurane anaesthesia in aged patients.
  23. Saravanan P, Exley A, Valchanov K, Casey N, Falter F. Impact of xenon anaesthesia in isolated cardiopulmonary bypass on very early leucocyte and platelet activation and clearance: a randomized, controlled study. Br J Anaesth. 2009;103:805-10 pubmed publisher
    Cardiopulmonary bypass (CPB) is associated with leucocyte and platelet activation and also organ dysfunction. Xenon has been found to have organ-protective effects...
  24. Bantel C, Maze M, Trapp S. Neuronal preconditioning by inhalational anesthetics: evidence for the role of plasmalemmal adenosine triphosphate-sensitive potassium channels. Anesthesiology. 2009;110:986-95 pubmed publisher
    ..Here, the authors explore the neuronal preconditioning effect of modern inhalational anesthetics and investigate their effects on K(ATP) channels...
  25. Coburn M, Kunitz O, Apfel C, Hein M, Fries M, Rossaint R. Incidence of postoperative nausea and emetic episodes after xenon anaesthesia compared with propofol-based anaesthesia. Br J Anaesth. 2008;100:787-91 pubmed publisher
    b>Xenon has been proved to be safe and efficacious for general anaesthesia in numerous trials. In addition, experimental studies demonstrate that xenon inhibits the 5-hydroxytryptamine type 3 (5-HT(3)) receptor...
  26. Doukov T, Blasiak L, Seravalli J, Ragsdale S, Drennan C. Xenon in and at the end of the tunnel of bifunctional carbon monoxide dehydrogenase/acetyl-CoA synthase. Biochemistry. 2008;47:3474-83 pubmed publisher
    ..Here, we report a 2.5 A resolution structure of xenon-pressurized mtCODH/ACS and examine the nature of gaseous cavities within this enzyme...
  27. Valleggi S, Cavazzana A, Bernardi R, Ma D, Natale G, Maze M, et al. Xenon up-regulates several genes that are not up-regulated by nitrous oxide. J Neurosurg Anesthesiol. 2008;20:226-32 pubmed publisher
    b>Xenon and other inhalational agents induce cell and organ effects through different and only partially elucidated molecular mechanisms...
  28. Stibich M, Stachowiak J, Tanner B, Berkheiser M, Moore L, Raad I, et al. Evaluation of a pulsed-xenon ultraviolet room disinfection device for impact on hospital operations and microbial reduction. Infect Control Hosp Epidemiol. 2011;32:286-8 pubmed publisher
    This study evaluated the use of pulsed-xenon ultraviolet (PX-UV) room disinfection by sampling frequently touched surfaces in vancomycin-resistant enterococci (VRE) isolation rooms...
  29. Dregely I, Mugler J, Ruset I, Altes T, Mata J, Miller G, et al. Hyperpolarized Xenon-129 gas-exchange imaging of lung microstructure: first case studies in subjects with obstructive lung disease. J Magn Reson Imaging. 2011;33:1052-62 pubmed publisher
    ..To develop and test a method to noninvasively assess the functional lung microstructure...
  30. Ma D, Williamson P, Januszewski A, Nogaro M, Hossain M, Ong L, et al. Xenon mitigates isoflurane-induced neuronal apoptosis in the developing rodent brain. Anesthesiology. 2007;106:746-53 pubmed
    ..b>Xenon, also an N-methyl-D-aspartate antagonist, not only lacks the characteristic toxicity produced by other N-methyl-D-..
  31. Salmi E, Laitio R, Aalto S, Maksimow A, Långsjö J, Kaisti K, et al. Xenon does not affect gamma-aminobutyric acid type A receptor binding in humans. Anesth Analg. 2008;106:129-34, table of contents pubmed publisher
    The noble gas xenon acts as an anesthetic with favorable hemodynamic and neuroprotective properties...
  32. Honda M, Sase S, Yokota K, Ichibayashi R, Yoshihara K, Masuda H, et al. Early cerebral circulation disturbance in patients suffering from different types of severe traumatic brain injury: a xenon CT and perfusion CT study. Acta Neurochir Suppl. 2013;118:259-63 pubmed publisher
    ..In particular, secondary brain insults have been reported to decrease CBF. The purpose of this study was to clarify the cerebral circulation in different types of TBI...
  33. Bantel C, Maze M, Trapp S. Noble gas xenon is a novel adenosine triphosphate-sensitive potassium channel opener. Anesthesiology. 2010;112:623-30 pubmed publisher
    ..This is different with the inhalational anesthetic xenon, which recently has been suggested to activate KATP channels; it partitions freely into the brain.
  34. Murray J, Maghlaoui K, Kargul J, Sugiura M, Barber J. Analysis of xenon binding to photosystem II by X-ray crystallography. Photosynth Res. 2008;98:523-7 pubmed publisher
    In order to investigate oxygen binding and hydrophobic cavities in photosystem II (PSII), we have introduced xenon under pressure into crystals of PSII isolated from Thermosynechococcus elongatus and used X-ray anomalous diffraction ..
  35. Fries M, Nolte K, Coburn M, Rex S, Timper A, Kottmann K, et al. Xenon reduces neurohistopathological damage and improves the early neurological deficit after cardiac arrest in pigs. Crit Care Med. 2008;36:2420-6 pubmed publisher
    ..Treatment options to ameliorate brain damage following cardiopulmonary resuscitation from cardiac arrest are limited...
  36. Baumert J, Hein M, Hecker K, Satlow S, Neef P, Rossaint R. Xenon or propofol anaesthesia for patients at cardiovascular risk in non-cardiac surgery. Br J Anaesth. 2008;100:605-11 pubmed publisher
    The results of two European multi-centre trials on xenon anaesthesia led to the hypothesis that a xenon-based anaesthetic would keep left ventricular (LV) and circulatory function more stable than a propofol-based anaesthetic, in ..
  37. Kim W, Lee C, Goo J, Park S, Kim J, Park E, et al. Xenon-enhanced dual-energy CT of patients with asthma: dynamic ventilation changes after methacholine and salbutamol inhalation. AJR Am J Roentgenol. 2012;199:975-81 pubmed publisher
    The purpose of this study was to evaluate the use of xenon-enhanced dual-energy CT of the chest to assess ventilation changes after methacholine and salbutamol inhalation in subjects with asthma and healthy subjects.
  38. Schröder L. Xenon for NMR biosensing--inert but alert. Phys Med. 2013;29:3-16 pubmed publisher
    NMR studies with hyperpolarized xenon as functionalized sensor or contrast agent recently made notable progress in developing a new approach for detecting molecular markers and parameters of biomedical interest...
  39. Faulkner S, Bainbridge A, Kato T, Chandrasekaran M, Kapetanakis A, Hristova M, et al. Xenon augmented hypothermia reduces early lactate/N-acetylaspartate and cell death in perinatal asphyxia. Ann Neurol. 2011;70:133-50 pubmed publisher
    ..We assessed neuroprotective effects of combining inhaled xenon with therapeutic hypothermia after transient cerebral hypoxia-ischemia in a piglet model of perinatal asphyxia ..
  40. Baumert J, Hein M, Hecker K, Satlow S, Schnoor J, Rossaint R. Autonomic cardiac control with xenon anaesthesia in patients at cardiovascular risk. Br J Anaesth. 2007;98:722-7 pubmed
    The cardiovascular stability found with xenon anaesthesia may be caused by absence of circulatory depression. Xenon may also act directly on autonomic cardiovascular control.
  41. Baumert J, Hein M, Gerets C, Baltus T, Hecker K, Rossaint R. The effect of xenon anesthesia on the size of experimental myocardial infarction. Anesth Analg. 2007;105:1200-6, table of contents pubmed
    ..Volatile anesthetics protect the myocardium from ischemia reperfusion damage. Our hypothesis for this study was that xenon reduces the size of myocardial infarction similar in extent to the reduction associated with ischemic ..
  42. Hein M, Roehl A, Baumert J, Bantes B, Bleilevens C, Bernstein N, et al. Establishment of a porcine right ventricular infarction model for cardioprotective actions of xenon and isoflurane. Acta Anaesthesiol Scand. 2008;52:1194-203 pubmed publisher
    ..Therefore, we used a porcine model of RV ischemia and reperfusion (IR) injury to study the influence of isoflurane and xenon on the extent and degree of myocardial injury.
  43. Lam W, Holdsworth D, Du L, Drangova M, McCormack D, Santyr G. Micro-CT imaging of rat lung ventilation using continuous image acquisition during xenon gas contrast enhancement. J Appl Physiol (1985). 2007;103:1848-56 pubmed
    ..using a dynamic, flat-panel volumetric micro-computed tomography (micro-CT) scanner during ventilation with a xenon/oxygen (Xe-O(2)) gas mixture. Forty time-resolved volumes consisting of eighty 0...
  44. Fahlenkamp A, Coburn M, Haase H, Kipp M, Ryang Y, Rossaint R, et al. Xenon enhances LPS-induced IL-1? expression in microglia via the extracellular signal-regulated kinase 1/2 pathway. J Mol Neurosci. 2011;45:48-59 pubmed publisher
    ..In this study, we show the influence of xenon on phosphatase activity, ERK 1/2 signalling and cytokine expression in microglia...
  45. Hill P, Wei Q, Troxler T, Dmochowski I. Substituent effects on xenon binding affinity and solution behavior of water-soluble cryptophanes. J Am Chem Soc. 2009;131:3069-77 pubmed publisher
    ..was synthesized and determined by isothermal titration calorimetry and fluorescence quenching assay to have a xenon association constant of 33,000 M(-1) at 293 K, which is the largest value measured for any host molecule to date...
  46. Sabir H, Bishop S, Cohen N, Maes E, Liu X, Dingley J, et al. Neither xenon nor fentanyl induces neuroapoptosis in the newborn pig brain. Anesthesiology. 2013;119:345-57 pubmed publisher
    Some inhalation anesthetics increase apoptotic cell death in the developing brain. Xenon, an inhalation anesthetic, increases neuroprotection when combined with therapeutic hypothermia after hypoxic-ischemic brain injury in newborn ..
  47. Kratzer S, Mattusch C, Kochs E, Eder M, Haseneder R, Rammes G. Xenon attenuates hippocampal long-term potentiation by diminishing synaptic and extrasynaptic N-methyl-D-aspartate receptor currents. Anesthesiology. 2012;116:673-82 pubmed publisher
    ..The inhalational anesthetic xenon antagonizes N-methyl-D-aspartate (NMDA) receptors...
  48. Hobbs C, Thoresen M, Tucker A, Aquilina K, Chakkarapani E, Dingley J. Xenon and hypothermia combine additively, offering long-term functional and histopathologic neuroprotection after neonatal hypoxia/ischemia. Stroke. 2008;39:1307-13 pubmed publisher
    ..b>Xenon is a noble anesthetic gas with an excellent safety profile, showing great promise in vitro and in vivo as a ..
  49. Natale G, Cattano D, Abramo A, Forfori F, Fulceri F, Fornai F, et al. Morphological evidence that xenon neuroprotects against N-methyl-DL-aspartic acid-induced damage in the rat arcuate nucleus: a time-dependent study. Ann N Y Acad Sci. 2006;1074:650-8 pubmed
    ..Since the anesthetic gas xenon behaves as an NMDA antagonist, the present article investigated, by distinct morphological approaches and after ..
  50. Hein M, Roehl A, Baumert J, Bleilevens C, Fischer S, Steendijk P, et al. Xenon and isoflurane improved biventricular function during right ventricular ischemia and reperfusion. Acta Anaesthesiol Scand. 2010;54:470-8 pubmed publisher
    ..b>Xenon, on the other hand, does not influence myocardial contractility...
  51. Rex S, Meyer P, Baumert J, Rossaint R, Fries M, Bull U, et al. Positron emission tomography study of regional cerebral blood flow and flow-metabolism coupling during general anaesthesia with xenon in humans. Br J Anaesth. 2008;100:667-75 pubmed publisher
    The effects of xenon on regional cerebral blood flow (rCBF) are controversial. Moreover, the precise sites of action at which xenon exerts its effects in the human brain remain to be established.
  52. Banks P, Franks N, Dickinson R. Competitive inhibition at the glycine site of the N-methyl-D-aspartate receptor mediates xenon neuroprotection against hypoxia-ischemia. Anesthesiology. 2010;112:614-22 pubmed publisher
    The general anesthetic gas xenon is neuroprotective and is undergoing clinical trials as a treatment for ischemic brain injury...