Search

The effects of C[O.sub.2] water-bath therapy on the hind limb of diabetic animals with or without peripheral ischemia were examined. Diabetes was induced in rats by administering streptozotocin (65 mg x [kg.sup.-1]), and the animals were then divided into 3 groups. After 4 weeks, peripheral ischemia was induced by ligation of the femoral artery for 2 weeks in 2 groups (diabetic ischemic) of diabetic rats, whereas the femoral artery was not occluded in the third group (diabetic). All these animals were subjected to water-bath therapy (with or without C[O.sub.2] mixing; 20 min x [day.sup.-1] for 5 days x [week.sup.-1]) for a period of 4 weeks. Both peak and mean flows, unlike minimal flow, in diabetic ischemic limbs were increased about a twofold by C[O.sub.2] water-bath treatment. Morphological examination of hind limb tissue sections revealed about a twofold increase in the small artery count in diabetic ischemic animals upon C[O.sub.2] water-bath treatment. These results indicate that C[O.sub.2] water-bath therapy augments the blood flow and development of angiogenesis in the skeletal muscle of diabetic ischemic animals and thus may be of some benefit for the treatment of peripheral arterial disease in diabetes. Key words: skeletal muscle angiogenesis, peripheral blood flow, experimental diabetes, peripheral arterial disease, C[O.sub.2] water-bath therapy. Nous avons etudie les effets du traitement en bain d'eau carbogazeuse sur le membre posterieur d'animaux atteints de diabete avec ou sans ischemie peripherique. Nous avons provoque un diabete chez des rats a l'aide de streptozotocine (65 mg x [kg.sup.-1]), et nous avons reparti les animaux dans 3 groupes. Apres 4 semaines, nous avons produit une ischemie peripherique par la ligature de l'artere femorale pendant 2 semaines dans 2 groupes (diabete ischemie) de rats atteints de diabete, alors que l'artere femorale ne subissait pas d'occlusion dans le troisieme groupe (diabete). Nous avons administre un traitement en bain d'eau chez tous ces animaux (avec ou sans melange avec du C[O.sub.2]; 20 min x [jour.sup.-1] pendant 5 jours x [semaine.sup.-1]) pour une periode de 4 semaines. Nous avons observe que, contrairement au flux minimal, les flux maximal et moyen doublaient a peu pres tous 2 dans les membres du groupe diabete ischemie avec bain en eau carbogazeuse. A l'examen morphologique, les coupes de tissu de membre posterieur ont revele que le nombre d'arterioles doublait a peu pres dans le groupe diabete ischemie avec bain en eau carbogazeuse. Ces resultats montrent que le traitement en bain d'eau carbogazeuse permet de faire augmenter le flux sanguin et le developpement de l'angiogenese dans le muscle squelettique d'animaux atteints de diabete avec ischemie, et donc, que ce mode therapeutique pourrait avoir certains avantages dans le traitement de la maladie arterielle peripherique en cas de diabete. [Traduit par la Redaction] Mots-cles : angiogenese dans le muscle squelettique, flux sanguin peripherique, diabete experimental, maladie arterielle peripherique, traitement en bain d'eau carbogazeuse., Introduction Peripheral vascular disease is commonly associated with reduction in blood flow and subsequent ischemia in hind limb skeletal muscle (Carmeliet and Jain 2011; Krishna et al. 2015; Dhalla et [...]

This study examines the hydrological recovery of two regenerating boreal trembling aspen (Populus tremuloides Michx.) dominated stands and the sensitivity of that regeneration to drought within the first 5 years of establishment. The results indicate that evapotranspiration fluxes and water-use efficiency rebounded quickly as a result of new vegetation foliage growth and wet conditions found within the first 2 years following the harvest. However, a period of dry years had a significant influence on rates of postharvest growth, carbon dioxide (C[O.sub.2]), and water fluxes at these sites. The northern study area (NSA) and southern study area (SSA) were harvested in the winters of 2007 and 2008, respectively. The first and second years of regeneration at the SSA and NSA, respectively, were marked by an early spring thaw and higher-than-normal precipitation, while air temperatures remained slightly above the 30-year normal. During this period, mean measured height of vegetation tripled at both sites, and cumulative evapotranspiration was approximately 60% of that prior to harvest by the end of the second year of growth. By the third year (2009), the NSA became a sink for atmospheric C[O.sub.2] during the snow free season (days of the year 128- 238) despite low precipitation during the latter half of the summer. Volumetric soil moisture content in 2009 was the highest (on average) of the 5 years examined due to heavy snowfall and a late start to the growing season (where air temperatures consistently exceeded 0°C), resulting in sustained productivity. However, cumulative annual precipitation also declined to 79% and 57% in 2009 and 2010, respectively, of the 30-year normal for that region, leading to significant (lagged) declines in forest productivity at the NSA in 2010 and 2011. This resulted in the site becoming a source of C[O.sub.2] to the atmosphere during the 2010 and 2011 growing seasons (annual balance was not measured). Throughout the drought period (2009, 2010, and 2011), mean stand height increased by only 15%, 11%, and 14%, respectively, compared with the mean stand height in 2008. Water-use efficiency also declined in 2010 and 2011, whereas differences in light-use efficiency did not vary significantly because foliage was maintained (i.e., leaves did not abscise as a result of drought). The results of this study indicate that regenerating aspen stands are sensitive to drought and respond relatively quickly to changes in the soil moisture regime. This is important because regional drying as a result of predicted climatic changes combined with increased industrial activity may result in significant decline in productivity within these stands over broad regions. Key words: trembling aspen, evapotranspiration, net ecosystem exchange, water-use efficiency, harvest. Cette etude s'interesse a la recuperation hydrologique de deux peuplements boreaux en regeneration domines par le peuplier faux-tremble (Populus tremuloides Michx.) ainsi qu'a la sensibilite de la regeneration a la secheresse au cours des cinq annees suivant son etablissement. Les resultats de cette etude indiquent que le flux d'evapotranspiration (ET) et l'efficacite d'utilisation de l'eau (EUE) se sont rapidement retablis avec la croissance du feuillage de la nouvelle vegetation et les conditions humides observees au cours des deux premieres annees apres la recolte. Cependant, une periode d'annees seches a eu une influence significative sur les taux de croissance postrecolte, de dioxyde de carbone (C[O.sub.2]) et de flux de l'eau dans ces sites. L'aire d'etude septentrionale (AES) et l'aire d'etude meridionale (AEM) ont ete recoltees respectivement durant les hivers 2007 et 2008. La premiere annee de regeneration dans l'AEM et la seconde dans l'AES ont ete marquees par un degel printanier hatif et des precipitations plus elevees que la normale tandis que les temperatures de l'air sont demeurees legerement au-dessus de la normale 30 ans. Durant cette periode, la hauteur moyenne mesuree de la vegetation a triple dans les deux sites et, a la fin de la deuxieme annee de croissance, la valeur cumulative de ET correspondait a environ 60 % de la valeur prerecolte. A la troisieme annee (2009), l'AES est devenue un puits pour le C[O.sub.2] atmospherique pendant la saison exempte de neige (jours de l'annee 128-238) malgre les faibles precipitations durant la derniere moitie de l'ete. Au cours des cinq annees de l'etude, l'humidite volumique du sol (Hv) a ete la plus elevee en 2009 (en moyenne) a cause des chutes de neige importantes et du debut tardif de la saison de croissance (lorsque la temperature de l'air etait constamment au-dessus de 0°C), entrainant une production soutenue. Cependant, la precipitation annuelle cumulative a aussi diminue, atteignant seulement 79 % (2009) et 57 % (2010) de la normale 30 ans dans cette region, ce qui a entraine un declin important (differe) de la production de la foret dans l'AES en 2010 et 2011. Ce site est par consequent devenu une source de C[O.sub.2] atmospherique durant les saisons de croissance de 2010 et 2011 (le bilan annuel n'a pas ete mesure). Durant la periode de secheresse (2009, 2010 et 2011) la hauteur moyenne du peuplement a augmente de seulement 15 % (2009), 11 % (2010) et 14 % (2011) par rapport a 2008. L'EUE a aussi diminue en 2010 et 2011 tandis que les differences dans l'efficacite d'utilisation de la lumiere n'ont pas varie de facon significative parce que le feuillage s'est maintenu (c.-a-d. que les feuilles ne sont pas tombees a cause de la secheresse). Les resultats de cette etude indiquent que les peuplements de peuplier faux-tremble en regeneration sont sensibles a la secheresse et reagissent assez rapidement aux variations du regime d'humidite du sol. Cela est important etant donne que des conditions regionales plus seches a cause des changements climatiques a venir combinees a l'activite industrielle accrue pourraient engendrer un declin de la productivite dans ces peuplements sur de vastes etendues. [Traduit par la Redaction] Mots-cles : peuplier faux-tremble, evapotranspiration, echanges nets de l'ecosysteme, efficacite d'utilisation de l'eau, recolte., Introduction The northern boreal forest covers approximately 29% of North America (Brandt 2009) and is a significant sink for atmospheric carbon dioxide (C[O.sub.2]) due to broad area coverage and the [...]

Author(s): Thomas Bein [sup.1] , Cécile Aubron [sup.2] , Laurent Papazian [sup.3] Author Affiliations: (1) 0000 0000 9194 7179, grid.411941.8, Department of Anesthesia and Operative Critical Care, University Hospital Regensburg, [...]

Early life stages of the coral Seriatopora caliendrum were used to test the hypothesis that the depression of dark respiration in coral recruits by high pC[O.sub.2] is caused by perturbed protein metabolism. First, the contribution of protein anabolism to respiratory costs under high pC[O.sub.2] was evaluated by measuring the aerobic respiration of S. caliendrum recruits with and without the protein synthesis inhibitor emetine following 1 to 4 days at 45 Pa versus 77 Pa pC[O.sub.2]. Second, protein catabolism under high pC[O.sub.2] was evaluated by measuring the flux of ammonium (N[H.sub.4.sup.+]) from juvenile colonies of S. caliendrum incubated in darkness at 47 Pa and 90 Pa pC[O.sub.2]. Two days after settlement, respiration of recruits was affected by an interaction between emetine and pC[O.sub.2], with emetine reducing respiration 63% at 45 Pa pC[O.sub.2] and 27% at 77 Pa pC[O.sub.2]. The interaction disappeared 5 days after settlement, when respiration was reduced 27% by emetine under both pC[O.sub.2] conditions. These findings suggest that protein anabolism accounted for a large proportion of metabolic costs in coral recruits and was affected by high pC[O.sub.2], with consequences detected in aerobic respiration. Juvenile S. caliendrum showed net uptake of N[H.sub.4.sup.+] at 45 Pa pC[O.sub.2] but net release of N[H.sub.4.sup.+] at 90 Pa pC[O.sub.2], indicating that protein catabolism, N[H.sub.4.sup.+] recycling, or both were affected by high pC[O.sub.2]. Together, these results are consistent with the hypothesis that high pC[O.sub.2] affects protein metabolism in corals., Introduction Ocean acidification (OA) caused by the dissolution of atmos[pH.sub.e]ric pC[O.sub.2] in seawater is a serious threat to marine life (Hoegh-Guldberg et al., 2007). Of the many taxa likely to [...]

Dietary deficiencies of zinc and iron are a substantial global public health problem. An estimated two billion people suffer these deficiencies (1), causing a loss of 63 million life-years annually (2,3). Most of these people depend on [C.sub.3] grains and legumes as their primary dietary source of zinc and iron. Here we report that [C.sub.3] grains and legumes have lower concentrations of zinc and iron when grown under field conditions at the elevated atmospheric C[O.sub.2] concentration predicted for the middle of this century. [C.sub.3] crops other than legumes also have lower concentrations of protein, whereas [C.sub.4] crops seem to be less affected. Differences between cultivars of a single crop suggest that breeding for decreased sensitivity to atmospheric C[O.sub.2] concentration could partly address these new challenges to global health., In the 1990s, several investigators found that elevated atmospheric C[O.sub.2] concentration (hereafter abbreviated to [C[O.sub.2]]) decreased the concentrations of zinc, iron and protein in grains of wheat (4-7), barley (5) [...]

Ocean acidification (OA) is expected to have a major impact on marine species, particularly during early life-history stages. These effects appear to be species-specific and may include reduced survival, altered morphology, and depressed metabolism. However, less information is available regarding the bioenergetics of development under elevated [CO.sub.2] conditions. We examined the biochemical and morphological responses of Strongylocentrotus purpuratus during early development under ecologically relevant levels of p[CO.sub.2] (365, 1030, and 1450 µatm) that may occur during intense upwelling events. The principal findings of this study were (1) lipid utilization rates and protein content in S. purpuratus did not vary with p[CO.sub.2]; (2) larval growth was reduced at elevated p[CO.sub.2] despite similar rates of energy utilization; and (3) relationships between egg phospholipid content and larval length were found under control but not high p[CO.sub.2] conditions. These results suggest that this species may either prioritize endogenous energy toward development and physiological function at the expense of growth, or that reduced larval length may be strictly due to higher costs of growth under OA conditions. This study highlights the need to further expand our knowledge of the physiological mechanisms involved in OA response in order to better understand how present populations may respond to global environmental change., Introduction Ocean acidification--the decrease of ocean pH via absorption of anthropogenic [CO.sub.2] by surface waters--has emerged as a major priority in the marine science research community (e.g., National Research Council, [...]

There is a long-standing controversy about the role of serotonin in sleep/wake control, with competing theories that it either promotes sleep or causes arousal. Here, we show that there is a marked increase in wakefulness when all serotonin neurons are genetically deleted in mice hemizygous for ePet1-Cre and homozygous for floxed Lmx1b ([Lmx1b.sup.f/f/p]). However, this only occurs at cool ambient temperatures and can be explained by a thermoregulatory defect that leads to an increase in motor activity to generate heat. Because some serotonin neurons are stimulated by C[O.sub.2], and serotonin activates thalamocortical networks, we hypothesized that serotonin neurons cause arousal in response to hypercapnia. We found that [Lmx1b.sup.f/f/p] mice completely lacked any arousal response to inhalation of 10% C[O.sub.2] (with 21% [O.sub.2] in balance [N.sub.2]) but had normal arousal responses to hypoxia, sound, and air puff. We propose that serotonin neurons mediate the potentially life-saving arousal response to hypercapnia. Impairment of this response may contribute to sudden unexpected death in epilepsy, sudden infant death syndrome, and sleep apnea. chemoreception | hypercapnia | sleep | thermoregulation | Lmx1b www.pnas.org/cgi/doi/ 10.1073/pnas.1004587107

Keywords: stomata, ion channel, ABA, calcium, drought, carbon dioxide Author Notes: These authors contributed equally. Abstract Stomatal pores are formed by pairs of specialized epidermal guard cells and serve as major gateways for both CO.sub.2 influx into plants from the atmosphere and transpirational water loss of plants. Because they regulate stomatal pore apertures via integration of both endogenous hormonal stimuli and environmental signals, guard cells have been highly developed as a model system to dissect the dynamics and mechanisms of plant-cell signaling. The stress hormone ABA and elevated levels of CO.sub.2 activate complex signaling pathways in guard cells that are mediated by kinases/phosphatases, secondary messengers, and ion channel regulation. Recent research in guard cells has led to a new hypothesis for how plants achieve specificity in intracellular calcium signaling: CO.sub.2 and ABA enhance (prime) the calcium sensitivity of downstream calcium-signaling mechanisms. Recent progress in identification of early stomatal signaling components are reviewed here, including ABA receptors and CO.sub.2-binding response proteins, as well as systems approaches that advance our understanding of guard cell-signaling mechanisms.

Elevated C[O.sub.2] levels (hypercapnia) frequently occur in patients with obstructive pulmonary diseases and are associated with increased mortality. However, the effects of hypercapnia on non-neuronal tissues and the mechanisms that mediate these effects are largely unknown. Here, we develop Drosophila as a genetically tractable model for defining non-neuronal C[O.sub.2] responses and response pathways. We show that hypercapnia significantly impairs embryonic morphogenesis, egg laying, and egg hatching even in mutants lacking the Gr63a neuronal C[O.sub.2] sensor. Consistent with previous reports that hypercapnic acidosis can suppress mammalian NF-[kappa]B-regulated innate immune genes, we find that in adult flies and the phagocytic immune-responsive S2* cell line, hypercapnia suppresses induction of specific antimicrobial peptides that are regulated by Relish, a conserved Rel/NF-[kappa]B family member. Correspondingly, modest hypercapnia (7-13%) increases mortality of flies inoculated with E. faecalis, A. tumefaciens, or S. aureus. During E. faecalis and A. tumefaciens infection, increased bacterial loads were observed, indicating that hypercapnia can decrease host resistance. Hypercapnic immune suppression is not mediated by acidosis, the olfactory CO2 receptor Gr63a, or by nitric oxide signaling. Further, hypercapnia does not induce responses characteristic of hypoxia, oxidative stress, or heat shock. Finally, proteolysis of the Relish I[kappa]B-like domain is unaffected by hypercapnia, indicating that immunosuppression acts downstream of, or in parallel to, Relish proteolytic activation. Our results suggest that hypercapnic immune suppression is mediated by a conserved response pathway, and illustrate a mechanism by which hypercapnia could contribute to worse outcomes of patients with advanced lung disease, who frequently suffer from both hypercapnia and respiratory infections. COPD | hypercapnia | Relish | NF-[kappa]B | Gr63a www.pnas.org/cgi/doi/10.1073/pnas.0905925106

Permissive hypercapnia, achieved using low tidal volume ventilation, has been an effective protective strategy in patients with acute respiratory distress syndrome. To date, no such protective effect has been demonstrated for the chronic neonatal lung injury, bronchopulmonary dysplasia. The objective of our study was to determine whether evolving chronic neonatal lung injury, using a rat model, is resistant to the beneficial effects of hypercapnia or simply requires a less conservative approach to hypercapnia than that applied clinically to date. Neonatal rats inhaled air or 60% [O.sub.2] for 14 days with or without 5.5% C[O.sub.2]. Lung parenchymal neutrophil and macrophage numbers were significantly increased by hyperoxia alone, which was associated with interstitial thickening and reduced secondary crest formation. The phagocyte influx, interstitial thickening, and impaired alveolar formation were significantly attenuated by concurrent hypercapnia. Hyperoxic pups that received 5.5% C[O.sub.2] had a significant increase in alveolar number relative to air-exposed pups. Increased tyrosine nitration, a footprint for peroxynitrite-mediated reactions, arteriolar medial wall thickening, and both reduced small peripheral pulmonary vessel number and VEGF and angiopoietin-1 (Ang-1) expression, which were observed with hyperoxia, was attenuated by concurrent hypercapnia. We conclude that evolving chronic neonatal lung injury in a rat model is responsive to the beneficial effects of hypercapnia. Inhaled 5.5% C[O.sub.2] provided a significant degree of protection against parenchymal and vascular injury in an animal model of chronic neonatal lung injury likely due, at least in part, to its inhibition of a phagocyte influx. carbon dioxide; lung growth; inflammation doi: 10.1152/ajplung.00139.2009.

The aim of this study was to assess whether one of the most common poisons of cellular respiration, i.e., carbon dioxide, is proinflammatory. C[O.sub.2] is naturally present in the atmosphere at the level of 0.038% and involved in numerous cellular biochemical reactions. We analyzed in vitro the inflammation response induced by exposure to C[O.sub.2] for 48 h (0-20% with a constant [O.sub.2] concentration of 21%). In vivo mice were submitted to increasing concentrations of C[O.sub.2] (0, 5, 10, and 15% with a constant [O.sub.2] concentration of 21%) for 1 h. The exposure to concentrations above 5% of C[O.sub.2] resulted in the increased transcription (RNase protection assay) and secretion (ELISA) of proinflammatory cytokines [macrophage inflammatory protein-l[alpha] (MIP-1[alpha]), MIP-1[beta], MIP-2, IL-8, IL-6, monocyte chemoattractant protein-1, and regulated upon activation, normal T cell expressed, and, presumably, secreted (RANTES)] by epithelial cell lines HT-29 or A549 and primary pulmonary cells retrieved from the exposed mice. Lung inflammation was also demonstrated in vivo by mucin 5AC-enhanced production and airway hyperreactivity induction. This response was mostly mediated by the nuclear translocation of p65 NF-[kappa]B, itself a consequence of protein phosphatase 2A (PP2A) activation. Short inhibiting RNAs (siRNAs) targeted toward PP2Ac reversed the effect of carbon dioxide, i.e., disrupted the NF-[kappa]B activation and the proinflammatory cytokine secretion. In conclusion, this study strongly suggests that exposure to carbon dioxide may be more toxic than previously thought. This may be relevant for carcinogenic effects of combustion products. tobacco smoke; protein phosphatase 2A; nuclear factor-[kappa]B

Hypercapnia (high C[O.sub.2] levels) occurs in a number of lung diseases and it is associated with worse outcomes in patients with chronic obstructive lung disease (COPD). However, it is largely unknown how hypercapnia is sensed and responds in nonneuronal cells. Here, we used C. elegans to study the response to nonanesthetic C[O.sub.2] levels and show that levels exceeding 9% induce aberrant motility that is accompanied by age-dependent deterioration of body muscle organization, slowed development, reduced fertility and increased life span. These effects occur independently of the IGF-R, dietary restriction, egg laying or mitochondrial-induced aging pathways. Transcriptional profiling analysis shows specific and dynamic changes in gene expression after 1, 6, or 72 h of exposure to 19% C[O.sub.2] including increased transcription of several 7-transmembrane domain and innate immunity genes and a reduction in transcription of many of the MSP genes. Together, these results suggest specific physiological and molecular responses to hypercapnia, which appear to be independent of early heat shock and HIF mediated pathways. aging | gene expression | hypercapnia | muscle deterioration | physiology

Byline: Fabrice Vallee (1,3), Benoit Vallet (2), Olivier Mathe (1), Jacqueline Parraguette (1), Arnaud Mari (1), Stein Silva (1), Kamran Samii (1), Olivier Fourcade (1), Michele Genestal (1) Keywords: Venous CO.sub.2; ScvO.sub.2; Lactate; Septic shock; Goal-directed therapy; Cardiac index Abstract: Objective To test the hypothesis that, in resuscitated septic shock patients, central venous-to-arterial carbon dioxide difference [P(cv-a)CO.sub.2] may serve as a global index of tissue perfusion when the central venous oxygen saturation (ScvO.sub.2) goal value has already been reached. Design Prospective observational study. Setting A 22-bed intensive care unit (ICU). Patients After early resuscitation in the emergency unit, 50 consecutive septic shock patients with ScvO.sub.2 > 70% were included immediately after their admission into the ICU (T0). Patients were separated in Low P(cv-a)CO.sub.2 group (Low gap n = 26) and High P(cv-a)CO.sub.2 group (High gap n = 24) according to a threshold of 6 mmHg at T0. Measurements Measurements were performed every 6 h over 12 h (T0, T6, T12). Results At T0, there was a significant difference between Low gap patients and High gap patients for cardiac index (CI) (4.3 +- 1.6 vs. 2.7 +- 0.8 l/min/mA2, P < 0.0001) but not for ScvO.sub.2 values (78 +- 5 vs. 75 +- 5%, P = 0.07). From T0 to T12, the clearance of lactate was significantly larger for the Low gap group than for the High gap group (P < 0.05) as well as the decrease of SOFA score at T24 (P < 0.01). At T0, T6 and T12, CI and P(cv-a)CO.sub.2 values were inversely correlated (P < 0.0001). Conclusion In ICU-resuscitated patients, targeting only ScvO.sub.2 may not be sufficient to guide therapy. When the 70% ScvO.sub.2 goal-value is reached, the presence of a P(cv-a)CO.sub.2 larger than 6 mmHg might be a useful tool to identify patients who still remain inadequately resuscitated. Author Affiliation: (1) Pole d'Anesthesie et Reanimation, Unite de Reanimation Polyvalente de Purpan, GRCB 48, Universite Paul Sabatier, CHU de Toulouse, France (2) Pole d'Anesthesie et Reanimation, Hopital Huriez, Universite Lille II, CHU de Lille, France (3) Reanimation polyvalente adulte, Hopital Purpan, Place du Dr Baylac, TSA 40031, 31059, Toulouse Cedex 9, France Article History: Registration Date: 24/06/2008 Received Date: 26/10/2007 Accepted Date: 06/06/2008 Online Date: 08/07/2008 Article note: Electronic supplementary material The online version of this article (doi: 10.1007/s00134-008-1199-0) contains supplementary material, which is available to authorized users.

Byline: Fabrizio Racca (1), Lorenzo Appendini (2), Cesare Gregoretti (3), Ilaria Varese (1), Giacomo Berta (1), Ferdinando Vittone (1), Gabriela Ferreyra (1), Elisa Stra (1), V. Marco Ranieri (1) Keywords: Noninvasive ventilation; Pressure support ventilation; Continuous positive airway pressure; Carbon dioxide rebreathing; Helmet; Air leaks Abstract: Objective We examined whether additional helmet flow obtained by a single-circuit and a modified plateau valve applied at the helmet expiratory port (open-circuit ventilators) improves CO.sub.2 wash-out by increasing helmet airflow. Design and setting Randomized physiological study in a university research laboratory. Participants Ten healthy volunteers. Interventions Helmet continuous positive airway pressure and pressure support ventilation delivered by an ICU ventilator (closed-circuit ventilator) and two open-circuit ventilators equipped with a plateau valve placed either at the inspiratory or at the helmet expiratory port. Measurements and results We measured helmet air leaks, breathing pattern, helmet minute ventilation ( .sub.Eh), minute ventilation washing the helmet ( .sub.Ewh), CO.sub.2 wash-out, and ventilator inspiratory assistance. Air leaks were small and similar in all conditions. Breathing pattern was similar among the different ventilators. Inspiratory and end-tidal CO.sub.2 were lower, while .sub.Eh and .sub.Ewh were higher only using open-circuit ventilators with the plateau valve placed at the helmet expiratory port. This occurred notwithstanding these ventilators delivered a lower inspiratory assistance. Conclusions Additional helmet flow provided by open-circuit ventilators can lower helmet CO.sub.2 rebreathing. However, inspiratory pressure assistance significantly decreases using open-circuit ventilators, still casting doubts on the choice of the optimal helmet ventilation setup. Author Affiliation: (1) Dipartimento di Anestesia e Rianimazione, Universita di Torino, Ospedale S. Giovanni Battista-Molinette, Turin, Italy (2) Divisione di Pneumologia, Fondazione Salvatore Maugeri, IRCCS, Istituto Scientifico di Veruno, Via Revislate, n. 13, 28010, Veruno, Italy (3) Servizio di Anestesia e Rianimazione, Azienda Ospedaliera CTO-CRF-Maria Adelaide, Turin, Italy Article History: Registration Date: 27/03/2008 Received Date: 25/09/2007 Accepted Date: 24/03/2008 Online Date: 06/05/2008 Article note: Electronic supplementary material The online version of this article (doi: 10.1007/s00134-008-1120-x) contains supplementary material, which is available to authorized users.

Byline: Mauro Maniscalco (1,2), Anna Zedda (1), Stanislao Faraone (1), Pierluigi Carratu (2), Matteo Sofia (2) Keywords: Transcutaneous carbon dioxide; Non-invasive monitoring; Obese; Arterial blood analysis; COPD; OSAS Abstract: Objective To determine the reliability of estimating arterial CO.sub.2 pressure (PaCO.sub.2) using a recently introduced transcutaneous CO.sub.2 pressure (PtcCO.sub.2) monitor in severe obese patients. Design Observational and interventional study. Setting District hospital with respiratory ward and bariatric surgery unit. Patients and methods PtcCO.sub.2 was measured in 35 obese patients with varied pathology, including chronic obstructive pulmonary disease, obstructive sleep apnea syndrome and hypoventilation syndrome. Ten minutes after the probe had been attached to an earlobe, PtcCO.sub.2 was recorded immediately before arterial blood sampling. The PtcCO.sub.2 and PaCO.sub.2 values obtained with two methods were compared by Bland--Altman analysis. In a subgroup of 18 obese patients with chronic obstructive pulmonary disease and/or obstructive sleep apnea syndrome with moderate to severe hypercapnia both PtcCO.sub.2 and PaCO.sub.2 were re-evaluated during continuous positive airways pressure (CPAP) or bi-level positive airway pressure (Bi-PAP) treatment. Results The mean difference between PaCO.sub.2 and PtcCO.sub.2 was -1.4a-mmHg, and the standard deviation of the difference was 1.3a-mmHg. Bland--Altman analysis showed generally good agreement between the two methods with a 95% limit of agreement of -4 to 1.1. The agreement between methods did not significantly change before and during cPAP or Bi-PAP treatment in hypercapnic patients. Conclusions The accuracy of estimation of PaCO.sub.2 by transcutaneous monitoring was generally good in comparison with standard arterial blood gases examination. The device appears to be promising for use in obese patients to evaluate abnormalities in their alveolar ventilation. Author Affiliation: (1) Section of Respiratory Medicine, Hospital S. Maria della Pieta, Via San Rocco ndeg 9, CAP 80026, Casoria, Naples, Italy (2) Department of Respiratory Medicine, AO Monaldi, University Federico II of Naples, Via Leonardo Bianchi ndeg 1, CAP 80131, Naples, Italy Article History: Registration Date: 29/02/2008 Received Date: 02/07/2007 Accepted Date: 27/02/2008 Online Date: 26/03/2008 Article note: Present address: M. Maniscalco, Largo delle Mimose 1, 80131 Napoli, Italy

Homeostasis of internal carbon dioxide (C[O.sub.2]) and oxygen ([O.sub.2]) levels is fundamental to all animals. Here we examine the C[O.sub.2] response of the nematode Caenorhabditis elegans. This species inhabits rotting material, which typically has a broad C[O.sub.2] concentration range. We show that well fed C. elegans avoid C[O.sub.2] levels above 0.5%. Animals can respond to both absolute C[O.sub.2] concentrations and changes in C[O.sub.2] levels within seconds. Responses to C[O.sub.2] do not reflect avoidance of acid pH but appear to define a new sensory response. Sensation of C[O.sub.2] is promoted by the cGMP-gated ion channel subunits TAX-2 and TAX-4, but other pathways are also important. Robust C[O.sub.2] avoidance in well fed animals requires inhibition of the DAF-16 forkhead transcription factor by the insulin-like receptor DAF-2. Starvation, which activates DAF-16, strongly suppresses C[O.sub.2] avoidance. Exposure to hypoxia (< 1% [O.sub.2]) also suppresses C[O.sub.2] avoidance via activation of the hypoxia-inducible transcription factor HIF-1. The npr-1 215V allele of the naturally polymorphic neuropeptide receptor npr-1, besides inhibiting avoidance of high ambient [O.sub.2] in feeding C. elegans, also promotes avoidance of high C[O.sub.2]. C. elegans integrates competing [O.sub.2] and C[O.sub.2] sensory inputs so that one response dominates. Food and allelic variation at NPR-1 regulate which response prevails. Our results suggest that multiple sensory inputs are coordinated by C. elegans to generate different coherent foraging strategies. carbon dioxide sensing | natural variation | oxygen sensing

Carbon dioxide is produced as a by-product of cellular respiration by all aerobic organisms and thus serves for many animals as an important indicator of food, mates, and predators. However, whether free-living terrestrial nematodes such as Caenorhabditis elegans respond to C[O.sub.2] was unclear. We have demonstrated that adult C. elegans display an acute avoidance response upon exposure to C[O.sub.2] that is characterized by the cessation of forward movement and the rapid initiation of backward movement. This response is mediated by a cGMP signaling pathway that includes the cGMP-gated heteromeric channel TAX-2/TAX-4. C[O.sub.2] avoidance is modulated by multiple signaling molecules, including the neuropeptide Y receptor NPR-1 and the calcineurin subunits TAX-6 and CNB-1. Nutritional status also modulates C[O.sub.2] responsiveness via the insulin and TGF[beta] signaling pathways. C[O.sub.2] response is mediated by a neural circuit that includes the BAG neurons, a pair of sensory neurons of previously unknown function. TAX-2/TAX-4 function in the BAG neurons to mediate acute C[O.sub.2] avoidance. Our results demonstrate that C. elegans senses and responds to C[O.sub.2] using multiple signaling pathways and a neural network that includes the BAG neurons and that this response is modulated by the physiological state of the worm. behavioral genetics | cGMP signaling | chemosensation

Byline: Elisabet Astrom (1), Leif Uttman (1), Lisbet Niklason (1), Jerome Aboab (2), Laurent Brochard (2), Bjorn Jonson (1) Keywords: Pulmonary gas exchange; Respiration, artificial; Capnography; Breath tests; Swine Abstract: Objective To avoid ventilator induced lung injury, tidal volume should be low in acute lung injury (ALI). Reducing dead space may be useful, for example by using a pattern of inspiration that prolongs the time available for gas distribution and diffusion within the respiratory zone, the mean distribution time (MDT). A study was conducted to investigate how MDT affects CO.sub.2 elimination in pigs at health and after ALI. Design and setting Randomised crossover study in the animal laboratory of Lund University Biomedical Center. Subjects and intervention Healthy pigs and pigs with ALI, caused by surfactant perturbation and lung-damaging ventilation were ventilated with a computer-controlled ventilator. With this device each breath could be tailored with respect to insufflation time and pause time (T .sub.I and T .sub.P) as well as flow shape (square, increasing or decreasing flow). Measurements and results The single-breath test for CO.sub.2 allowed analysis of the volume of expired CO.sub.2 and the volume of CO.sub.2 re-inspired from Y-piece and tubes. With a long MDT caused by long T .sub.I or T .sub.P, the expired volume of CO.sub.2 increased markedly in accordance with the MDT concept in both healthy and ALI pigs. High initial inspiratory flow caused by a short T .sub.I or decreasing flow increased the re-inspired volume of CO.sub.2. Arterial CO.sub.2 increased during a longer period of short MDT and decreased again when MDT was prolonged. Conclusions CO.sub.2 elimination can be enhanced by a pattern of ventilation that prolongs MDT. Positive effects of prolonged MDT caused by short T .sub.I and decreasing flow were attenuated by high initial inspiratory flow. Author Affiliation: (1) Department of Clinical Physiology, University Hospital, SE-221 85, Lund, Sweden (2) Medical Intensive Care Unit, Hospital Henri Mondor, 51, av. du Marechal de Lattre de Tassigny, 94010, Creteil, France Article History: Registration Date: 27/07/2007 Received Date: 30/11/2006 Accepted Date: 26/07/2007 Online Date: 01/09/2007 Article note: Electronic supplementary material The online version of this article (doi: 10.1007/s00134-007-0840-7) contains supplementary material, which is available to authorized users.

Byline: Murali. Vinodh, Vijaykumar. Mohankumar, Arvind. Ganpule, Banibrata. Mukhopadhyay, Ravindra. Sabnis, Mahesh. Desai Context: Although the technical feasibility of laparoscopic donor nephrectomy (LDN) has been established, concerns have been raised [...]

The growth rate of atmospheric carbon dioxide (C[O.sub.2]), the largest human contributor to human-induced climate change, is increasing rapidly. Three processes contribute to this rapid increase. Two of these processes concern emissions. Recent growth of the world economy combined with an increase in its carbon intensity have led to rapid growth in fossil fuel C[O.sub.2] emissions since 2000: comparing the 1990s with 2000-2006, the emissions growth rate increased from 1.3% to 3.3% [y.sup.-1]. The third process is indicated by increasing evidence (P = 0.89) for a long-term (50-year) increase in the airborne fraction (AF) of C[O.sub.2] emissions, implying a decline in the efficiency of C[O.sub.2] sinks on land and oceans in absorbing anthropogenic emissions. Since 2000, the contributions of these three factors to the increase in the atmospheric C[O.sub.2] growth rate have been [approximately equal to] 65 [+ or -] 16% from increasing global economic activity, 17 [+ or -] 6% from the increasing carbon intensity of the global economy, and 18 [+ or -] 15% from the increase in AF. An increasing AF is consistent with results of climate-carbon cycle models, but the magnitude of the observed signal appears larger than that estimated by models. All of these changes characterize a carbon cycle that is generating stronger-than-expected and sooner-than-expected climate forcing. airborne fraction | anthropogenic carbon emissions | carbon-climate feedback | terrestrial and ocean carbon emissions | vulnerabilities of the carbon cycle

Abstract The inhalation of 7.5% carbon dioxide (C[O.sub.2]) in healthy subjects produces an increase in blood pressure and heart rate, and increased feelings of anxiety, fear and tension (Bailey et [...]

Induction of hypercapnia by breathing high concentrations of carbon dioxide (C[O.sub.2]) may have beneficial effects on the pulmonary circulation. We tested the hypothesis that exposure to C[O.sub.2] would protect against chronic pulmonary hypertension in newborn rats. Atmospheric C[O.sub.2] was maintained at carbon dioxide; endothefin; oxidant stress; 8-isoprostane; echocardiography

We hypothesized that long-term facilitation (LTF) of minute ventilation and peak genioglossus muscle activity manifests itself in awake healthy humans when carbon dioxide is sustained at elevated levels. Eleven subjects completed two trials. During trial 1, baseline carbon dioxide levels were maintained during and after exposure to eight 4-min episodes of hypoxia. During trial 2, carbon dioxide was sustained 5 mmHg above baseline levels during exposure to episodic hypoxia. Seven subjects were exposed to sustained elevated levels of carbon dioxide in the absence of episodic hypoxia, which served as a control experiment. Minute ventilation was measured during trial 1, trial 2, and the control experiment. Peak genioglossus muscle activity was measured during trial 2. Minute ventilation during the recovery period of trial 1 was similar to baseline (9.3 [+ or -] 0.5 vs. 9.2 [+ or -] 0.7 1/min). Likewise, minute ventilation remained unchanged during the control experiment (beginning vs. end of control experiment, 14.4 [+ or -] 1.7 vs. 14.7 [+ or -] 1.4 1/min). In contrast, minute ventilation and peak genioglossus muscle activity during the recovery period of trial 2 was greater than baseline (minute ventilation: 28.4 [+ or -] 1.7 vs. 19.6 [+ or -] 1.0 1/min, P < 0.001; peak genioglossus activity: 1.6 [+ or -] 0.3 vs. 1.0 fraction of baseline, P < 0.001). We conclude that exposure to episodic hypoxia is necessary to induce LTF of minute ventilation and peak genioglossus muscle activity and that LTF is only evident in awake humans in the presence of sustained elevated levels of carbon dioxide. genioglossus muscle; episodic hypoxia

Byline: Annika I. Schmidt (1), Marc Reismann (1), Joachim F. Kubler (1), Gertrud Vieten (1), Catherine Bangen (1), Akihiro Shimotakahara (1), Sylvia Gluer (1), Rainer Nustede (1), Benno M. Ure (1) Keywords: Proliferation; Neuroblastoma; CO.sub.2; Helium; Laparoscopy Abstract: Background: Minimally invasive techniques are increasingly applied to children with malignant tumors. We showed previously that CO.sub.2 used for pneumoperitoneum modulates the function of macrophages and polymorphonuclear cells via direct effects and via acidification. Numerous in vitro and small animal model studies also confirmed an alteration of the behavior of several types of adult tumor cells by CO.sub.2. The impact of CO.sub.2 and other gases used for pneumoperitoneum on the behavior of various pediatric tumors has not yet been determined. Methods: Cell lines of neuroblastoma (IMR 32, SK-N-SH, Sy5y), lymphoma (Daudi), hepatoblastoma (Huh 6), hepatocellular carcinoma (Hep G2), and rhabdomyosarcoma (Te 671) were incubated for 2 h. Incubation was performed with 100% CO.sub.2, 100% helium, and 5% CO.sub.2 as control. Cell proliferation was determined by the MTT-assay [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] by actively growing cells to produce a blue formazan product. The MTT-assay was performed before, directly after incubation, and daily for 4 days. Vitality of the cells was determined by trypan blue. The extracellular pH during incubation was measured during gas exposition every 10 min using Bayer Rapid Lab 855. Results: CO.sub.2 for 2 h significantly decreased the proliferation of neuroblastoma, lymphoma, hepatoblastoma, and hepatocellular carcinoma cells. This decrease persisted over 4 days in neuroblastoma, lymphoma, and hepatocellular carcinoma cells. The CO.sub.2 had no impact on hepatoblastoma and rhabdomyosarcoma cells. Helium had a similar effect on neuroblastoma cells. After 4 days, a significant decrease of cell activity was found in two neuroblastoma cell lines and in hepatoblastoma cells. Helium had no effect on lymphoma and hepatocellular carcinoma cells. The extracellular pH was 6.2 during incubation with CO.sub.2, and 7.6 during incubation with helium. Conclusion: CO.sub.2 and helium may affect the proliferation of some pediatric tumor cell lines in vitro. However, some of these effects and the impact on the extracellular pH are differential. The role of pH modulation, hypoxia and direct effects of gases remain to be investigated before a general recommendation on the use of minimally invasive techniques in pediatric oncology can be given. Author Affiliation: (1) Department of Pediatric Surgery, Hannover Medical School, Carl-Neuberg-Str. 1, 30625, Hannover, Germany Article History: Registration Date: 17/10/2005 Online Date: 08/11/2005

Abstract. C[O.sub.2] capture and storage (CCS) in geological reservoirs may be part of a strategy to reduce global anthropogenic C[O.sub.2] emissions. Insight in the risks associated with underground C[O.sub.2] storage is needed to ensure that it can be applied as safe and effective greenhouse mitigation option. This paper aims to give an overview of the current (gaps in) knowledge of risks associated with underground C[O.sub.2] storage and research areas that need to be addressed to increase our understanding in those risks. Risks caused by a failure in surface installations are understood and can be minimised by risk abatement technologies and safety measures. The risks caused by underground C[O.sub.2] storage (C[O.sub.2] and C[H.sub.4] leakage, seismicity, ground movement and brine displacement) are less well understood. Main R&D objective is to determine the processes controlling leakage through/along wells, faults and fractures to assess leakage rates and to assess the effects on (marine) ecosystems. Although R&D activities currently being undertaken are working on these issues, it is expected that further demonstration projects and experimental work is needed to provide data for more thorough risk assessment.

Lower than normal blood levels of carbon dioxide can have adverse effects on the body and should not be induced therapeutically except in emergencies. The health consequences of low carbon dioxide levels are reviewed.

Byline: G. Cinnella (1), M. Dambrosio (1), N. Brienza (2), R. Giuliani (2), F. Bruno (2), T. Fiore (2), A. Brienza (2) Keywords: ILV Vt EtCO2 Pplat Compliance Barotrauma Abstract: Objective: a) to describe a non-barotraumatic ventilatory setting for independent lung ventilation (ILV) b) to determine the utility of single lung end-tidal CO.sub.2 (EtCO.sub.2) monitoring to evaluate the ventilation to perfusion (V/Q) matching in each lung during ILV and for ILV weaning. Design: prospective study. Setting: general intensive care unit in a university teaching hospital. Patients: twelve patients with unilateral thoracic trauma needing ILV. Interventions and results: ILV was started with each lung ventilated with the same tidal volume (Vt): plateau airway pressure (Pplat) was 34.2+-3.2 cmH2O in diseased lungs (DL) and 18.1+-1.9 cmH2O in normal lungs (NL) (P Author Affiliation: (1) Department of Anesthesia and Intensive Care, University of Foggia, Italy (2) Department of Anesthesia and Intensive Care, University of Bari, Italy (3) Istituto di Rianimazione, Policlinico, Piazza G. Cesare, 70124 Bari, Italy Article History: Received Date: 14/02/2001 Accepted Date: 09/10/2001 Article note: Final revision received: 11 September 2001 Electronic Publication

The increasing recognition that panic attacks are heterogeneous phenomena necessitates better and more objective criteria to define and examine what constitutes a panic attack. The central aim of the present study was to classify subtypes of panic attacks (i.e. prototypic, cognitive, and non-fearful) in a nonclinical sample (N = 96) based on the concordance/discordance between subjective and physiological responding to multiple inhalations of 20 and 13% CO(sub 2)-enriched air. Results show that a substantial proportion of this nonclinical sample (55.2%) responded to the CO(sub 2) challenge in a manner consistent with clinical and research definitions of different subtypes of panic attacks. The implications of this dimensional approach for discriminating subtypes of panic in the laboratory are discussed as a means to better understand the phenomenology and nature of panic attacks.

Byline: B. Venkatesh (1), T. J. Morgan (1), J. Lipman (1) Keywords: Key words Shock; Tonometry; Mucosal; Subcutaneous; Oxygen; Carbon dioxide; Lactate; Haemorrhage; Resuscitation; Ischaemia Abstract: Objectives: The cutaneous and splanchnic circulations undergo early vasoconstriction in shock. Methodological problems and insufficient information on subcutaneous carbon dioxide partial pressures limit the usefulness of previous studies on splanchnic and subcutaneous gas tensions in shock. Little comparative data exist on the responses of these tissues to shock and resuscitation. We therefore compared continuous subcutaneous PO.sub.2 (PO.sub.2sc) and PCO.sub.2 (PCO.sub.2sc) with simultaneous continuous gut luminal PCO.sub.2 (PCO.sub.2gi) in an animal model of haemorrhagic shock and resuscitation. Design: Prospective observational study. Setting: Intensive care laboratory in a teaching hospital. Subjects: Five anaesthetised rats. Interventions: Electrochemical-fiberoptic gas sensors inserted into Silastic tubing placed in the subcutaneous tissue and in the ileal lumen measured PCO.sub.2sc, PO.sub.2sc and PCO.sub.2gi continuously in five anaesthetised rats. After steady state conditions, hypotension [mean arterial blood pressure (MAP) 40 mmHg] was induced by controlled haemorrhage. The rats were allowed to remain hypotensive for 15 min and then resuscitated with shed blood and crystalloids. Arterial plasma lactate concentrations were measured at defined periods during the study. Measurements and main results: Hypovolaemia resulted in a significant decrease in PO.sub.2sc (P < 0.01) and a significant increase in PCO.sub.2gi and PCO.sub.2sc (P < 0.05). These values returned to baseline with resuscitation. PO.sub.2sc appeared to respond to haemorrhage earlier than PCO.sub.2gi and PCO.sub.2sc (P = 0.02). PO.sub.2sc was inversely correlated with PCO.sub.2gi (r .sup.2 0.7, P < 0.001). There were no significant changes in arterial plasma lactate concentrations. Conclusions: In our rat model, subcutaneous oxygen tension provided similar information to ileal luminal PCO.sub.2 and was more rapidly responsive than subcutaneous carbon dioxide tensions and arterial lactate during evolving haemorrhagic shock and resuscitation. Author Affiliation: (1) Department of Intensive Care, Royal Brisbane Hospital, Herston 4029, Queensland, Australia e-mail: venkateshb@health.qld.gov.au Tel.: + 61-7-32 53 81 11 Fax: + 61-7-32 53 35 42, AU Article note: Received: 21 July 1999 Final revision received: 28 January 2000 Accepted: 3 February 2000