Post-stroke treatment with argon preserved neurons and attenuated microglia/macrophage activation long-termly in a rat model of transient middle cerebral artery occlusion (tMCAO).

In a previous study from our group, argon has shown to significantly attenuate brain injury, reduce brain inflammation and enhance M2 microglia/macrophage polarization until 7 days after ischemic stroke. However, the long-term effects of argon have not been reported thus far. In the present study, we analyzed the underlying neuroprotective effects and potential mechanisms of argon, up to 30 days after ischemic stroke. Argon administration with a 3 h delay after stroke onset and 1 h after reperfusion demonstrated long-term neuroprotective effect by preserving the neurons at the ischemic boundary zone 30 days after stroke. Furthermore, the excessive microglia/macrophage activation in rat brain was reduced by argon treatment 30 days after ischemic insult. However, long-lasting neurological improvement was not detectable. More sensorimotor functional measures, age- and disease-related models, as well as further histological and molecular biological analyses will be needed to extend the understanding of argon's neuroprotective effects and mechanism of action after ischemic stroke.

Percutaneous Argon-Helium Cryoablation for Small Hepatocellular Carcinoma Located Adjacent to a Major Organ or Viscus: A Retrospective Study of 92 Patients at a Single Center.

BACKGROUND Cryoablation of hepatocellular carcinoma (HCC) close to major organs or viscus is challenging because it can cause complications. This retrospective study aimed to investigate the safety and efficacy of percutaneous argon-helium cryoablation of small HCC located adjacent to major organs or viscus. MATERIAL AND METHODS Ninety-two patients who underwent percutaneous argon-helium cryoablation between February 2012 and December 2018 at the Fifth Medical Center of the Chinese People's Liberation Army General Hospital were included. Treatment efficacy was evaluated by magnetic resonance imaging or triphasic computed tomography scan within 1 week after each cryoablation procedure. Local tumor progression, distant recurrence, and overall survival were analyzed using the Kaplan-Meier method and log-rank test. RESULTS A total of 92 patients with small HCC located adjacent to major organs or viscus who underwent cryoablation were retrospectively reviewed. The number of patients with tumors adjacent to the gallbladder, portal or hepatic vein, diaphragm, stomach, heart, and intestine was 22, 1, 39, 6, 8, and 16, respectively. Cumulative local tumor progression rates at 1 and 2 years were 2.8% and 7.3%, respectively. Cumulative distant recurrence rates at 1, 2, and 3 years were 11.1%, 17.6%, and 20.7%, respectively. The overall survival rates at 1, 2, and 4 years were 100%, 93.6%, and 74.9%, respectively. Major complications were observed in 5 (5.4%) patients. Minor complications were observed in 85 (92.4%) patients. CONCLUSIONS This experience from a single center showed that percutaneous argon-helium cryoablation was safe and effective in the management of small HCC that is located adjacent to major organs or viscus.

Efficacy of acute administration of inhaled argon on traumatic brain injury in mice.

BACKGROUND: Whilst there has been progress in supportive treatment for traumatic brain injury (TBI), specific neuroprotective interventions are lacking. Models of ischaemic heart and brain injury show the therapeutic potential of argon gas, but it is still not known whether inhaled argon (iAr) is protective in TBI. We tested the effects of acute administration of iAr on brain oedema, tissue micro-environmental changes, neurological functions, and structural outcome in a mouse model of TBI. METHODS: Anaesthetised adult C57BL/6J mice were subjected to severe TBI by controlled cortical impact. Ten minutes after TBI, the mice were randomised to 24 h treatments with iAr 70%/O2 30% or air (iCtr). Sensorimotor deficits were evaluated up to 6 weeks post-TBI by three independent tests. Cognitive function was evaluated by Barnes maze test at 4 weeks. MRI was done to examine brain oedema at 3 days and white matter damage at 5 weeks. Microglia/macrophages activation and functional commitment were evaluated at 1 week after TBI by immunohistochemistry. RESULTS: iAr significantly accelerated sensorimotor recovery and improved cognitive deficits 1 month after TBI, with less white matter damage in the ipsilateral fimbria and body of the corpus callosum. Early changes underpinning protection included a reduction of pericontusional vasogenic oedema and of the inflammatory response. iAr significantly reduced microglial activation with increases in ramified cells and the M2-like marker YM1. CONCLUSIONS: iAr accelerates recovery of sensorimotor function and improves cognitive and structural outcome 1 month after severe TBI in adult mice. Early effects include a reduction of brain oedema and neuroinflammation in the contused tissue.

Ventilation With Argon Improves Survival With Good Neurological Recovery After Prolonged Untreated Cardiac Arrest in Pigs.

Background Ventilation with the noble gas argon (Ar) has shown neuroprotective and cardioprotective properties in different in vitro and in vivo models. Hence, the neuroprotective effects of Ar were investigated in a severe, preclinically relevant porcine model of cardiac arrest. Methods and Results Cardiac arrest was ischemically induced in 36 pigs and left untreated for 12 minutes before starting cardiopulmonary resuscitation. Animals were randomized to 4-hour post-resuscitation ventilation with: 70% nitrogen-30% oxygen (control); 50% Ar-20% nitrogen-30% oxygen (Ar 50%); and 70% Ar-30% oxygen (Ar 70%). Hemodynamic parameters and myocardial function were monitored and serial blood samples taken. Pigs were observed up to 96 hours for survival and neurological recovery. Heart and brain were harvested for histopathology. Ten animals in each group were successfully resuscitated. Ninety-six-hour survival was 60%, 70%, and 90%, for the control, Ar 50%, and Ar 70% groups, respectively. In the Ar 50% and Ar 70% groups, 60% and 80%, respectively, achieved good neurological recovery, in contrast to only 30% in the control group (P<0.0001). Histology showed less neuronal degeneration in the cortex (P<0.05) but not in the hippocampus, and less reactive microglia activation in the hippocampus (P=0.007), after Ar compared with control treatment. A lower increase in circulating biomarkers of brain injury, together with less kynurenine pathway activation (P<0.05), were present in Ar-treated animals compared with controls. Ar 70% pigs also had complete left ventricular function recovery and smaller infarct and cardiac troponin release (P<0.01). Conclusions Post-resuscitation ventilation with Ar significantly improves neurologic recovery and ameliorates brain injury after cardiac arrest with long no-flow duration. Benefits are greater after Ar 70% than Ar 50%.

Argon treatment after experimental subarachnoid hemorrhage: evaluation of microglial activation and neuronal survival as a subanalysis of a randomized controlled animal trial.

Hereinafter, we evaluate argon's neuroprotective and immunomodulatory properties after experimental subarachnoid hemorrhage (SAH) examining various localizations (hippocampal and cortical regions) with respect to neuronal damage and microglial activation 6, 24 and 72 hours after SAH. One hour after SAH (endovascular perforation rat model) or sham surgery, a mixture of gas containing 50% argon (argon group) or 50% nitrogen (control group) was applied for 1 hour. At 6 hours after SAH, argon reduced neuronal damage in the hippocampal regions in the argon group compared to the control group (P < 0.034). Hippocampal microglial activation did not differ between the treatment groups over time. The basal cortical regions did not show a different lesion pattern, but microglial activation was significantly reduced in the argon group 72 hours after SAH (P = 0.034 vs. control group). Whereas callosal microglial activation was significantly reduced at 24 hours in the argon-treated group (P = 0.018). Argon treatment ameliorated only early hippocampal neuronal damage after SAH. Inhibition of microglial activation was seen in some areas later on. Thus, argon may influence the microglial inflammatory response and neuronal survival after SAH; however, due to low sample sizes the interpretation of our results is limited. The study protocol was approved by the Government Agency for Animal Use and Protection (Protocol number: TVA 10416G1; initially approved by the "Landesamt für Natur, Umwelt und Verbraucherschutz NRW," Recklinghausen, Germany, on April 28, 2009).

Argon Mitigates Impaired Wound Healing Process and Enhances Wound Healing In Vitro and In Vivo.

Diabetic foot ulcers are associated with significant morbidity and mortality, and current treatments are far from optimal. Chronic wounds in diabetes are characterised by impaired angiogenesis, leukocyte function, fibroblast proliferation, and keratinocyte migration and proliferation. Methods: We tested the effect of exposure to argon gas on endothelial cell, fibroblast, macrophage and keratinocyte cell cultures in vitro and in vivo of a streptozotocin-induced diabetic mouse model. Results: Exposure to normobaric argon gas promotes multiple steps of the wound healing process. Argon accelerated angiogenesis, associated with upregulation of pro-angiogenic Angiopoietin-1 and vascular endothelial growth factor (VEGF) signalling in vitro and in vivo. Treatment with argon enhanced expression of transforming growth factor (TGF)-ß, early recruitment of macrophages and keratinocyte proliferation. Argon had a pro-survival effect, inducing expression of cytoprotective mediators B-cell lymphoma 2 and heme oxygenase 1. Argon was able to accelerate wound closure in a diabetic mouse model. Conclusion: Together these findings indicate that argon gas may be a promising candidate for clinical use in treatment of diabetic ulcers.

Argon preconditioning enhances postischaemic cardiac functional recovery following cardioplegic arrest and global cold ischaemia.

OBJECTIVES: Previous studies demonstrated that preconditioning with argon gas provided a marked reduction in inflammation and apoptosis and increased myocardial contractility in the setting of acute myocardial ischaemia-reperfusion (IR). There is substantial evidence that myocardial IR injury following cardioplegic arrest is associated with the enhancement of apoptosis and inflammation, which is considered to play a role in cardiac functional impairment. Therefore, the present study was designed to clarify whether preconditioning with argon gas enhances recovery of cardiac function following cardioplegic arrest. METHODS: Sprague-Dawley rats were anaesthetized and ventilated and allocated to (i) the control group (control IR, n = 10) and (ii) the in vivo group (argon IR), which received 3 cycles of argon (50% argon, 21% oxygen and 29% nitrogen, n = 10) administered for 5 min interspersed with 5 min of a gas mixture (79% nitrogen and 21% oxygen). The hearts were excised and then evaluated in an erythrocyte-perfused isolated working heart system. Cold ischaemia (4°C) for 60 min was induced by histidine-tryptophan-ketoglutarate cardioplegia, followed by 40 min of reperfusion. Cardiac functional parameters were assessed. In left ventricular tissue samples, the expressions of extracellular-regulated kinase (ERK1/2), AKT serine/threonine kinase (Akt), jun N-terminal kinase (JNK), endothelial nitric oxide synthase (eNOS) and HMGB1: high-mobility group box 1 (HMGB1) protein were assessed by western blot, and high-energy phosphates were evaluated by high-performance liquid chromatography. RESULTS: At the end of reperfusion, the rats preconditioned with argon showed significantly enhanced recovery of cardiac output (101 ± 6% vs 87 ± 11%; P < 0.01), stroke volume (94 ± 4% vs 80 ± 11%; P = 0.001), external heart work (100 ± 6% vs 81 ± 13%; P < 0.001) and coronary flow (90 ± 13% vs 125 ± 21%; P < 0.01) compared with the control IR group. These results were accompanied by a significant increase in the levels of myocardial phosphocreatine (23.71 ± 2.07 µmol/g protein vs the control IR group, 13.50 ± 4.75; P = 0.001) and maintained adenosine triphosphate levels (13.62 ±1.89 µmol/g protein vs control IR group adenosine triphosphate: 10.08 ± 1.94 µmol/g; P = 0.017). Additionally, preconditioning with argon markedly reduced the activation of JNK (0.11 ± 0.01 vs 0.25 ± 0.03; P = 0.005) and the expression of HMGB1 protein (0.52 ± 0.04 vs 1.5 ± 0.10; P < 0.001) following reperfusion. CONCLUSIONS: Preconditioning with argon enhanced cardiac functional recovery in rat hearts arrested with histidine-tryptophan-ketoglutarate cardioplegia, thereby representing a potential novel cardioprotective approach in cardiac surgery.

Argon attenuates multiorgan failure following experimental aortic cross-clamping.

AIMS: Argon has been shown to prevent ischaemic injuries in several scenarios of regional ischaemia. We determined whether it could provide a systemic effect in a model of multiorgan failure (MOF) induced by aortic cross-clamping. METHODS: Anaesthetized rabbits were submitted to aortic cross-clamping (30 min) and subsequent reperfusion (300 min). They were either ventilated with oxygen-enriched air throughout the protocol [fraction of inspired oxygen (FiO2 ) = 30%; control group) or with a mixture of 30% oxygen and 70% argon (argon groups). In a first group treated with argon ('Argon-Total'), its administration was started 30 min before ischaemia and maintained throughout the protocol. In the two other groups, the administration was started either 30 min before ischaemia ('Argon-Pre') or at the onset of reperfusion ('Argon-Post'), for a total duration of 2 h. Cardiovascular, renal and inflammatory endpoints were assessed throughout protocol. RESULTS: Compared with control, shock was significantly attenuated in Argon-Total and Argon-Pre but not Argon-Post groups (e.g. cardiac output = 62±5 vs. 29 ± 5 ml min-1 kg-1 in Argon-Total and control groups at the end of the follow-up). Shock and renal failure were reduced in all argon vs. control groups. Histopathological examination of the gut showed attenuation of ischaemic lesions in all argon vs. control groups. Blood transcription levels of interleukin (IL) 1ß, IL-8, IL-10 and hypoxia-inducible factor 1α were not significantly different between groups. CONCLUSION: Argon attenuated clinical and biological modifications of cardiovascular, renal and intestinal systems, but not the inflammatory response, after aortic cross-clamping. The window of administration was crucial to optimize organ protection.

The administration of argon during ex vivo normothermic perfusion in an experimental model of kidney ischemia-reperfusion injury.

BACKGROUND: Argon has shown potential as an organoprotective agent in numerous models of ischemia-reperfusion injury (IRI). The aim of this study was to evaluate the effects of argon gas during ex vivo normothermic perfusion (EVNP) in an experimental porcine model of kidney IRI. MATERIALS AND METHODS: After a warm ischemia time of 15 min and 17 h of static cold storage, porcine kidneys underwent 1 h of EVNP using leukocyte-depleted blood. During EVNP, kidneys were perfused with a gas composition either of 70% argon (n = 6), 70% nitrogen control (n = 6), or standard 95% oxygen (n = 6) balanced with 5% carbon dioxide. After EVNP, kidneys were reperfused with whole blood under standard conditions for 3 h to assess renal function and injury. RESULTS: During 1-h EVNP, the mean renal blood flow was numerically higher in the argon group (49.2 ± 16.2 mL/min/100 g; P = 0.320) compared with the nitrogen and oxygen groups (42.9 ± 18.64 and 37.71 ± 7.0 mL/min/100 g, respectively). Other measures of renal function and hemodynamics were not significantly different between the argon and control groups during this period. During reperfusion, no significant differences were found in functional parameters or inflammatory markers (P < 0.05). Histologic analysis revealed no significant change in morphology or hypoxia-inducible factor-1 alpha staining between gaseous groups. Nuclear hypoxia-inducible factor-1 alpha staining was observed only after 3 h of reperfusion. CONCLUSIONS: Our findings suggest that using 70% argon during 1 h of EVNP does not mediate a measurable organoprotective effect in an experimental porcine model of IRI.

Effect of cold argon plasma on eggs of the blow fly, Lucilia cuprina (Diptera: Calliphoridae).

Non-thermal plasma has been used in many medical applications, including treatment of living cells, blood coagulation, wound healing, and sterilization. The process uses an environmentally friendly gas (e.g., argon, helium, oxygen, nitrogen, or hydrogen) to destroy bacteria cells with no serious adverse effect on humans or animals. However, information on the effect of argon plasma on blow fly eggs is lacking. In this study, we explored the ability of cold argon plasma to destroy the eggs of the Australian sheep blow fly, Lucilia cuprina (Wiedemann, 1830); its larvae are a myiasis-producing agent in both human and animals. We tested the effect of cold argon plasma exposure for 1, 2, 3 and 5min on L. cuprina eggs. Since the temperature of cold Ar plasma is around 30°C, to clarify the effect of temperature on the fly eggs, hot air from an electric dryer was tested for comparison. Cold argon plasma exposure in eggs significantly reduced the survival rates of second instar larvae at all exposures tested; the effects were time dependent, with a stronger effect at longer exposure (32% survival rate after a 1-min treatment; 20%, 2min; 20%, 3min; and 6%, 5min), compared to the control (86%). No significant differences were observed in larval survival rates from eggs treated with hot air (80-84%, after 1- to 5-min treatments) versus the control (86%). These results were supported by observing the treated eggshells under a scanning electron microscope (SEM), we found noticeable aberrations only in the plasma treated groups. The emission spectrum of the argon gas discharge revealed emission lines of hydroxyl radicals at 309.1nm; these may cause the deterioration of the treated L. cuprina eggs. Our results have shown the possibility of using cold argon plasma in medical applications, in particular treating myiasis wounds.

Influence of argon on temperature modulation and neurological outcome in hypothermia treated rats following cardiac arrest.

AIM OF THE STUDY: Combining xenon and mild therapeutic hypothermia (MTH) after cardiac arrest (CA) confers a degree of protection that is greater than either of the two interventions alone. However, xenon is very costly which might preclude a widespread use. We investigated whether the inexpensive gas argon would enhance hypothermia induced neurologic recovery in a similar manner. METHODS: Following nine minutes of CA and three minutes of cardiopulmonary resuscitation 21 male Sprague-Dawley rats were randomized to receive MTH (33°C for 6h), MTH plus argon (70% for 1h), or no treatment. A first day condition score assessed behaviour, motor activity and overall condition. A neurological deficit score (NDS) was calculated daily for seven days following the experiment before the animals were killed and the brains harvested for histopathological analysis. RESULTS: All animals survived. Animals that received MTH alone showed best overall neurologic function. Strikingly, this effect was abolished in the argon-augmented MTH group, where animals showed worse neurologic outcome being significant in the first day condition score and on day one to three and five in the NDS in comparison to MTH treated rats. Results were reflected by the neurohistopathological analysis. CONCLUSION: Our study demonstrates that argon augmented MTH does not improve functional recovery after CA in rats, but may even worsen neurologic function in this model.

The topical application of low-temperature argon plasma enhances the anti-inflammatory effect of Jaun-ointment on DNCB-induced NC/Nga mice.

BACKGROUND: Jaun-ointment (JO), also known as Shiunko in Japan, is one of the most popular medicinal formulae used in Korean traditional medicine for the external treatment of skin wound and inflammatory skin conditions. Since JO is composed of crude mixture of two herbal extracts (radix of Lithospermum erythrorhizon Siebold & Zucc and Angelica gigas Nakai), those been proved its anti-inflammatory activities in-vitro and in-vivo, JO has been expected as a good alternative treatment option for atopic dermatitis (AD). However, due to the lack of strategies for the penetrating methods of JO's various anti-inflammatory elements into the skin, an effective and safe transdermal drug delivery system needs to be determined. Here, low-temperature argon plasma (LTAP) was adopted as an ancillary partner of topically applied JO in a mice model of AD and the effectiveness was examined. METHODS: Dorsal skins of NC/Nga mice were challenged with DNCB (2,4-dinitrochlorobenzene) to induce AD. AD-like skin lesions were treated with JO alone, or in combination with LTAP. Inflammatory activity in the skin tissues was evaluated by histological analysis and several molecular biological tests. RESULTS: LTAP enhanced the effect of JO on AD-like skin lesion. Topical application of JO partially inhibited the development of DNCB-induced AD, shown by the moderate reduction of eosinophil homing and pro-inflammatory cytokine level. Combined treatment of JO and LTAP dramatically inhibited AD phenotypes. Interestingly, treatment with JO alone did not affect the activity of nuclear factor (NF)κB/RelA in the skin, but combined treatment of LTAP-JO blocked DCNB-mediated NFκB/RelA activation. CONCLUSIONS: LTAP markedly enhanced the anti-inflammatory activity of JO on AD-like skin lesions. The effect of LTAP may be attributed to enhancement of drug penetration and regulation of NFκB activity. Therefore, the combination treatment of JO and LTAP could be a potential strategy for the treatment of AD.

Argon Exposure Induces Postconditioning in Myocardial Ischemia-Reperfusion.

BACKGROUND AND PURPOSE: Cardioprotection against ischemia-reperfusion (I/R) damages remains a major concern during prehospital management of acute myocardial infarction. Noble gases have shown beneficial effects in preconditioning studies. Because emergency proceedings in the context of myocardial infarction require postconditioning strategies, we evaluated the effects of argon in such protocols on mammalian cardiac tissue. EXPERIMENTAL APPROACHES: In rat, cardiac I/R was induced in vivo by transient coronary artery ligature and cardiac functions were evaluated by magnetic resonance imaging. Hypoxia-reoxygenation (H/R)-induced arrhythmias were evaluated in vitro using intracellular microelectrodes on both rat-isolated ventricle and a model of border zone in guinea pig ventricle. Hypoxia-reoxygenation loss of contractile force was assessed in human atrial appendages. In those models, postconditioning was induced by 5 minutes application of argon at the time of reperfusion. KEY RESULTS: In the in vivo model, I/R produced left ventricular ejection fraction decrease (24%) and wall motion score increase (36%) which was prevented when argon was applied in postconditioning. In vitro, argon postconditioning abolished H/R-induced arrhythmias such as early after depolarizations, conduction blocks, and reentries. Recovery of contractile force in human atrial appendages after H/R was enhanced in the argon group, increasing from 51% ± 2% in the nonconditioned group to 83% ± 7% in the argon-treated group ( P < .001). This effect of argon was abolished in the presence of wortmannin and PD98059 which inhibit prosurvival phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt) and MEK/extracellular receptor kinase 1/2 (ERK 1/2), respectively, or in the presence of the mitochondrial permeability transition pore opener atractyloside, suggesting the involvement of the reperfusion injury salvage kinase pathway. CONCLUSION AND IMPLICATIONS: Argon has strong cardioprotective properties when applied in conditions of postconditioning and thus appears as a potential therapeutic tool in I/R situations.

Recurrent acute angle-closure attack due to plateau iris syndrome after cataract extraction with or without argon laser peripheral iridoplasty: a case report.

BACKGROUND: We describe two cases of recurrent acute angle-closure attack in patients with plateau iris syndrome after cataract extraction. Argon laser peripheral iridoplasty and cataract extraction have been used to reduce the occurrence of acute angle-closure attack in plateau iris syndrome although the risk cannot be completely eliminated. There is no consensus on the long term management of plateau iris syndrome. This is, as far as we know, the first case report of recurrent acute angle-closure attack in plateau iris syndrome after cataract extraction. CASE PRESENTATION: We report two cases of recurrent acute angle-closure attack in 2 Chinese patients with plateau iris syndrome. The first patient was a 69 year-old woman who received bilateral argon laser peripheral iridoplasty and cataract extraction 2 years prior to the latest acute angle-closure with right eye intraocular pressure 48 mmHg. The attack was aborted medically. Peripheral iridotomy was patent and argon laser peripheral iridoplasty marks were mostly at peripheral 2/3 of the iris. Anterior segment optical coherence tomography confirmed bilateral plateau iris configuration. Use of long term pilocarpine or repeated argon laser peripheral iridoplasty to prevent recurrent angle-closure attack was discussed but she opted for observation. The second patient was a 64 year-old man presented with acute angle-closure after cataract extraction despite placement of laser peripheral iridotomy. Plateau iris syndrome was confirmed by anterior segment optical coherence tomography and he received argon laser peripheral iridoplasty. CONCLUSIONS: Acute angle-closure due to plateau iris syndrome can still occur despite previous cataract extraction and argon laser peripheral iridoplasty. These are the first reported cases of recurrent acute angle-closure attack due to plateau iris syndrome following cataract extraction, with or without previous argon laser peripheral iridoplasty. Repeated treatment with argon laser peripheral iridoplasty or pilocarpine could be considered although the long term efficacy is questionable. Argon laser peripheral iridoplasty should be applied as peripheral as possible so as to open up the drainage angle effectively.

Antibacterial Activity of Cold Atmospheric Pressure Argon Plasma against 78 Genetically Different (mecA, luk-P, agr or Capsular Polysaccharide Type) Staphylococcus aureus Strains.

Previous studies on the antimicrobial activity of cold atmospheric pressure argon plasma showed varying effects against mecA+ or mecA-Staphylococcus aureus strains. This observation may have important clinical and epidemiological implications. Here, the antibacterial activity of argon plasma was investigated against 78 genetically different S. aureus strains, stratified by mecA, luk-P, agr1-4, or the cell wall capsule polysaccharide types 5 and 8. kINPen09® served as the plasma source for all experiments. On agar plates, mecA+luk-P-S. aureus strains showed a decreased susceptibility against plasma compared to other S. aureus strains. This study underlines the high complexity of microbial defence against antimicrobial treatment and confirms a previously reported strain-dependent susceptibility of S. aureus to plasma treatment.

A randomized trial of the effects of the noble gases helium and argon on neuroprotection in a rodent cardiac arrest model.

BACKGROUND: The noble gas xenon is considered as a neuroprotective agent, but availability of the gas is limited. Studies on neuroprotection with the abundant noble gases helium and argon demonstrated mixed results, and data regarding neuroprotection after cardiac arrest are scant. We tested the hypothesis that administration of 50% helium or 50% argon for 24 h after resuscitation from cardiac arrest improves clinical and histological outcome in our 8 min rat cardiac arrest model. METHODS: Forty animals had cardiac arrest induced with intravenous potassium/esmolol and were randomized to post-resuscitation ventilation with either helium/oxygen, argon/oxygen or air/oxygen for 24 h. Eight additional animals without cardiac arrest served as reference, these animals were not randomized and not included into the statistical analysis. Primary outcome was assessment of neuronal damage in histology of the region I of hippocampus proper (CA1) from those animals surviving until day 5. Secondary outcome was evaluation of neurobehavior by daily testing of a Neurodeficit Score (NDS), the Tape Removal Test (TRT), a simple vertical pole test (VPT) and the Open Field Test (OFT). Because of the non-parametric distribution of the data, the histological assessments were compared with the Kruskal-Wallis test. Treatment effect in repeated measured assessments was estimated with a linear regression with clustered robust standard errors (SE), where normality is less important. RESULTS: Twenty-nine out of 40 rats survived until day 5 with significant initial deficits in neurobehavioral, but rapid improvement within all groups randomized to cardiac arrest. There were no statistical significant differences between groups neither in the histological nor in neurobehavioral assessment. CONCLUSIONS: The replacement of air with either helium or argon in a 50:50 air/oxygen mixture for 24 h did not improve histological or clinical outcome in rats subjected to 8 min of cardiac arrest.

Inhaled 45-50% argon augments hypothermic brain protection in a piglet model of perinatal asphyxia.

Cooling to 33.5°C in babies with neonatal encephalopathy significantly reduces death and disability, however additional therapies are needed to maximize brain protection. Following hypoxia-ischemia we assessed whether inhaled 45-50% Argon from 2-26h augmented hypothermia neuroprotection in a neonatal piglet model, using MRS and aEEG, which predict outcome in babies with neonatal encephalopathy, and immunohistochemistry. Following cerebral hypoxia-ischemia, 20 Newborn male Large White piglets<40h were randomized to: (i) Cooling (33°C) from 2-26h (n=10); or (ii) Cooling and inhaled 45-50% Argon (Cooling+Argon) from 2-26h (n=8). Whole-brain phosphorus-31 and regional proton MRS were acquired at baseline, 24 and 48h after hypoxia-ischemia. EEG was monitored. At 48h after hypoxia-ischemia, cell death (TUNEL) was evaluated over 7 brain regions. There were no differences in body weight, duration of hypoxia-ischemia or insult severity; throughout the study there were no differences in heart rate, arterial blood pressure, blood biochemistry and inotrope support. Two piglets in the Cooling+Argon group were excluded. Comparing Cooling+Argon with Cooling there was preservation of whole-brain MRS ATP and PCr/Pi at 48h after hypoxia-ischemia (p<0.001 for both) and lower (1)H MRS lactate/N acetyl aspartate in white (p=0.03 and 0.04) but not gray matter at 24 and 48h. EEG background recovery was faster (p<0.01) with Cooling+Argon. An overall difference between average cell-death of Cooling versus Cooling+Argon was observed (p<0.01); estimated cells per mm(2) were 23.9 points lower (95% C.I. 7.3-40.5) for the Cooling+Argon versus Cooling. Inhaled 45-50% Argon from 2-26h augmented hypothermic protection at 48h after hypoxia-ischemia shown by improved brain energy metabolism on MRS, faster EEG recovery and reduced cell death on TUNEL. Argon may provide a cheap and practical therapy to augment cooling for neonatal encephalopathy.

[The Status of Hemostasis System in Hypoxic Nitrogen-Oxygen and Argon-Oxygen Diving Gases].

In this study the effect of factors of hermetic chamber with modified gas medium on the hemostasis system is analyzed in order to estimate and to compare different diving breathing gases. The parameters characterizing pro-, anticoagulant as well as fibrinolytic components of hemostasis were determined using clotting, chromogenic and immunological methods. The applied exposure did not affect the activity and regulatory potential of hemostasis significantly; however, the nitrogen-oxygen and argon-oxygen diving gases have a different effect on the hemostasis functioning, especially in the recovery period.

Hydrogen production by the engineered cyanobacterial strain Nostoc PCC 7120 ΔhupW examined in a flat panel photobioreactor system.

Nitrogenase based hydrogen production was examined in a ΔhupW strain of the filamentous heterocystous cyanobacterium Nostoc PCC 7120, i.e., cells lacking the last step in the maturation system of the large subunit of the uptake hydrogenase and as a consequence with a non-functional uptake hydrogenase. The cells were grown in a developed flat panel photobioreactor system with 3.0L culture volume either aerobically (air) or anaerobically (Ar or 80% N2/20% Ar) and illuminated with a mixture of red and white LED. Aerobic growth of the ΔhupW strain of Nostoc PCC 7120 at 44µmolar photons m(-2)s(-1) PAR gave the highest hydrogen production of 0.7mL H2 L(-1)h(-1), 0.53mmol H2 mg chlorophyll a(-1)h(-1), and a light energy conversion efficiency of 1.2%. Anaerobic growth using 100% argon showed a maximal hydrogen production of 1.7mLL(-1)h(-1), 0.85mmol per mg chlorophyll a(-1) h(-1), and a light energy conversion efficiency of 2.7%. Altering between argon/N2 (20/80) and 100% argon phases resulted in a maximal hydrogen production at hour 128 (100% argon phase) with 6.2mL H2L(-1)h(-1), 0.71mL H2 mg chlorophyll a(-1)h(-1), and a light energy efficiency conversion of 4.0%. The highest buildup of hydrogen gas observed was 6.89% H2 (100% argon phase) of the total photobioreactor system with a maximal production of 4.85mL H2 L(-1)h(-1). The present study clearly demonstrates the potential to use purpose design cyanobacteria in developed flat panel photobioreactor systems for the direct production of the solar fuel hydrogen. Further improvements in the strain used, environmental conditions employed, and growth, production and collection systems used, are needed before a sustainable and economical cyanobacterial based hydrogen production can be realized.

Neuroprotective effects of Argon are mediated via an ERK-1/2 dependent regulation of heme-oxygenase-1 in retinal ganglion cells.

Retinal ischemia and reperfusion injuries (R-IRI) damage neuronal tissue permanently. Recently, we demonstrated that Argon exerts anti-apoptotic and protective properties. The molecular mechanism remains unclear. We hypothesized that Argon inhalation exert neuroprotective effects in rats retinal ganglion cells (RGC) via an ERK-1/2 dependent regulation of heat-shock proteins. Inhalation of Argon (75 Vol%) was performed after R-IRI on the rats' left eyes for 1 h immediately or with delay. Retinal tissue was harvested after 24 h to analyze mRNA and protein expression of heat-shock proteins -70, -90 and heme-oxygenase-1, mitogen-activated protein kinases (p38, JNK, ERK-1/2) and histological changes. To analyze ERK dependent effects, the ERK inhibitor PD98059 was applicated prior to Argon inhalation. RGC count was analyzed 7 days after injury. Statistics were performed using anova. Argon significantly reduced the R-IRI-affected heat-shock protein expression (p < 0.05). While Argon significantly induced ERK-1/2 expression (p < 0.001), inhibition of ERK-1/2 before Argon inhalation resulted in significantly lower vital RGCs (p < 0.01) and increase in heme-oxygenase-1 (p < 0.05). R-IRI-induced RGC loss was reduced by Argon inhalation (p < 0.001). Immunohistochemistry suggested ERK-1/2 activation in Müller cells. We conclude, that Argon treatment protects R-IRI-induced apoptotic loss of RGC via an ERK-1/2 dependent regulation of heme-oxygenase-1. We proposed the following possible mechanism for Argon-mediated neuroprotection: Argon exerts its protective effects via an induction of an ERK with subsequent suppression of the heat shock response. In conclusion, ischemia and reperfusion injuries and subsequent neuronal apoptosis are attenuated. These novel findings may open up new opportunities for Argon as a therapeutic option, especially since Argon is not toxic.