Abou-Hamdan M.,Aix - Marseille University |
Gardette B.,COMEX SA |
Cadet J.,Universite de Sherbrooke |
Gharib B.,Aix - Marseille University |
And 3 more authors.
International Journal of Radiation Biology | Year: 2016
Purpose: The main aim of the present study is to gain mechanistic insights into the modulating effect of molecular hydrogen on the γ-radiation-induced alteration pathways of DNA nucleobases. Materials and methods: Aerated aqueous solutions of calf thymus DNA were exposed to a 60Co source at doses ranging from 0 to 55 Gy under normoxic conditions, in the presence or not of 0.7 MPa hydrogen or helium. The measurement of several modified bases was performed using HPLC associated with electrospray ionization tandem pass spectrometry (HPLC-ESI-MS/MS). Bleaching of aqueous solutions of p-nitrosodimethylaniline (p-NDA) solutions was also used to allow the quantification of hydroxyl radical (•OH) formation. Results: pNDA bleaching was significantly reduced in the presence of hyperbaric hydrogen. This is undoubtedly due to •OH scavenging by H2 since, under the same conditions, He had no effect. Similarly, base alterations were significantly reduced in the presence of hydrogen, as compared to controls under normal atmosphere or in the presence of helium. The relative proportions of modified nucleobases were not changed, showing that the only effect of H2 is to scavenge •OH without exhibiting reducing properties. Conclusions: Our findings demonstrate that H2 exerts a significant protection against radiation-induced DNA base damage in aqueous solutions, •OH scavenging being the only mechanism involved. © 2016 Informa UK Limited, trading as Taylor & Francis Group
Lemaitre F.,University of Rouen |
Lemaitre F.,University Hospital Center |
Lafay V.,University Hospital Center |
Taylor M.,University of Ottawa |
And 3 more authors.
Undersea and Hyperbaric Medicine | Year: 2013
The cardiac diving response, 12-lead electrocardiogram (ECG) and the prevalence, time of onset, and possible associations of cardiac arrhythmias were examined during deep breath-hold (BH) dives. Nine elite BH divers (33.2 ± 3.6 years; mean ± SD) performed one constant-weight dive of at least 75% of their best personal performance (70 ± 7 meters for 141 ± 22 seconds) wearing a 12-lead ECG Holter monitor. Diving parameters (depth and time), oxygen saturation (SaO2), blood lactate concentration and ventilatory parameters were also recorded. Bradycardia during these dives was pronounced (52.2 ± 12.2%), with heart rates dropping to 46 ± 10 beats/minute. The diving reflex was strong, overriding the stimulus of muscular exercise during the ascent phase of the dive for all divers. Classical arrhythmias occurred, mainly after surfacing, and some conduction alterations were detected at the bottom of the dives. The BH divers did not show any right shift of the QRS electrical axis during their dives. Copyright © 2013 Undersea & Hyperbaric Medical Society, Inc.
Lartaud F.,CNRS Benthic Ecogeochemistry Laboratory |
Lartaud F.,University Pierre and Marie Curie |
Pareige S.,CNRS Benthic Ecogeochemistry Laboratory |
Pareige S.,University Pierre and Marie Curie |
And 11 more authors.
Aquatic Living Resources | Year: 2013
Research on the biology and ecology of cold-water corals (CWCs) is still in its infancy. The growth patterns of CWCs in their natural environments are poorly known. Growth rate investigations on these deep-sea reef builder species are needed to predict recovery times following damage to their ecosystems. This study investigates a new approach for analysing CWC growth rate, suitable for in situ application. Lophelia pertusa and Madrepora oculata (Scleractinian) were collected from the Lacaze-Duthiers canyon in the northwestern Mediterranean Sea (520 m depth), marked and then either redeployed in situ for 6 months, or maintained in aquaria for growth rate comparison at a constant temperature of 13 C, corresponding to their habitat conditions. Two different types of staining (calcein and manganese) and three different exposure times (30, 60 and 240 min) were tested. The results show that calcein offers rapid incorporation and easy detection, making it particularly suitable for skeletal growth rate investigations compared with other chemical staining. In situ linear polyp growth rates of 7.5 ± 1.2 mm y-1 and 3.5 ± 2.1 mm y-1 were measured in new polyps of L. pertusa and M. oculata, respectively. Those values were significantly higher in young polyps than in older ones, where they decreased to 1.3 ± 1.5 mm y-1 and 1.2 ± 1.2 mm y-1. Beyond the study of coral reef growth processes, this approach offers a methodological basis for habitat quality assessment which could be used in the management of deep-sea marine protected areas (MPA). © EDP Sciences, IFREMER, IRD 2012.
Boussen S.,Aix - Marseille University |
Coulange M.,Hopital de la Timone |
Coulange M.,Aix - Marseille University |
Fournier M.,Hopital de la Timone |
And 4 more authors.
Respiratory Care | Year: 2014
BACKGROUND: Previous studies on ventilators used for air transport showed significant effects of altitude, in particular with regard to accuracy of the tidal volume (VT) and breathing frequency. The aim of the study was to evaluate transport ventilators under hypobaric conditions. METHODS: We conducted a bench study of 6 transport ventilators in a Comex hypobaric chamber to simulate mild altitude (1,500 m [4,920 feet] and 2,500 m [8,200 feet]). The ventilators were connected to a test lung to evaluate their accuracy: (1) to deliver a set VT under normal resistance and compliance conditions at FIO2 = 0.6 and 1, (2) to establish a set PEEP (0, 5, 10, and 15 cm H2O), and (3) to establish a set inspiratory pressure in pressure controlled mode, (4) at a FIO2 setting, and (5) and at a frequency setting. RESULTS: Four ventilators kept an average relative error in VT of < 10% without effect of altitude. The Medumat ventilator was affected by the altitude only at FIO2 = 1. The Osiris 3 ventilator had > 40% error even at 1,500 m. We found no change in frequency as a function of altitude for any ventilators studied. No clinically important differences were found between all altitudes with the PEEP or inspiratory pressure setting. Although FIO2 was affected by altitude, the average error did not exceed 11%, and it is unclear whether this fact is an experimental artifact. CONCLUSIONS: We have shown that most of the new transport ventilators tested require no setting adjustment at moderate altitude and are as safe at altitude as at sea level under normal respiratory conditions. Older technologies still deliver more volume with altitude in volumetric mode. © 2014 by Daedalus Enterprises.
Weiss P.,COMEX SA |
Gardette B.,COMEX SA |
Chirie B.,Ecoles dOfficiers delArmee delAir |
Collina-Girard J.,French National Center for Scientific Research |
Delauze H.G.,COMEX SA
Planetary and Space Science | Year: 2012
Extravehicular activity (EVA) of astronauts during space missions is simulated nowadays underwater in neutral buoyancy facilities. Certain aspects of weightlessness can be reproduced underwater by adding buoyancy to a diver-astronaut, therefore exposing the subject to the difficulties of working without gravity. Such tests were done at the COMEX' test pool in Marseilles in the 1980s to train for a French-Russian mission to the MIR station, for the development of the European HERMES shuttle and the COLUMBUS laboratory. However, space agencies are currently studying missions to other destinations than the International Space Station in orbit, such as the return to the Moon, NEO (near-Earth objects) or Mars. All these objects expose different gravities: Moon has one sixth of Earth's gravity, Mars has a third of Earth's gravity and asteroids have virtually no surface gravity; the astronaut floats above the ground. The preparation of such missions calls for a new concept in neutral buoyancy training, not on man-made structures, but on natural terrain, underwater, to simulate EVA operations such as sampling, locomotion or even anchoring in low gravity. Underwater sites can be used not only to simulate the reduced gravity that astronauts will experience during their field trips, also human factors like stress are more realistically reproduced in such environment. The Bay of Marseille hosts several underwater sites that can be used to simulate various geologic morphologies, such as sink-holes which can be used to simulate astronaut descends into craters, caves where explorations of lava tubes can be trained or monolithic rock structures that can be used to test anchoring devices (e.g., near Earth objects). Marseilles with its aerospace and maritime/offshore heritage hosts the necessary logistics and expertise that is needed to perform such simulations underwater in a safe manner (training of astronaut-divers in local test pools, research vessels, subsea robots and submarines). COMEX is currently preparing a space mission simulation in the Marseilles Bay (foreseen in June 2012), and the paper will give an overview of the different underwater analogue sites that are available to the scientific community for the simulation of surface EVA or the test of scientific instruments and devices. © 2012 Elsevier Ltd. All rights reserved.