Paràmetres cardiorespiratoris durant l'exercici submàxim sota una exposició aguda a hipòxia hipobàrica i normobàrica

Set joves sans i en bona condició física foren sotmesos a dos tests de tolerància a la hipòxia a una altitud simulada de 3.000 m. El primer s’efectuà en una cambra hipobàrica i els segon en un tenda hipòxica. Es registraren diversos paràmetres cardiorespiratoris i la variabilitat de la freqüència cardíaca sota cada condició d’hipòxia. En comparació amb les condicions de normòxia, s’observà un decrement significatiu del 6 al 8% en la saturació de l’oxigen arterial (SpO2) en ambdues condicions d’hipòxia en repòs. L’exercici desencadenà descensos d’un 10% en SpO2 tot i l’increment del 27% del volum ventilatori minut. Tant els components de baixa (BF) com d’alta freqüència (AF) de la variabilitat del ritme cardíac van canviar significativament de la normòxia (BF: 37,1; AF: 62,9; BF/AF: 1,27) a la hipòxia hipobàrica (HH) (BF: 49,1; AF: 50,6; BF/AF: 1,96). Malgrat això, aquests canvis no s’apreciaren en condicions d’hipòxia normobàrica. Per tant, la variabilitat de la freqüència cardíaca té un comportament diferent en les dues condicions d’hipòxia, la qual cosa recolza la hipòtesi que l’hipòxia normobàrica i l’hipobàrica no suposen un estímul igual dels sistemes cardiovacular i respiratori. S’observà una correlació entre la modulació vagal i simpàtica en normòxia i l’SpO2 durant l’exercici en hipòxia hipobàrica (HH). Els subjectes amb major modulació simpàtica (BF%) en normòxia presenten major SpO2 durant l’exercici en HH (r = 0,808; p < 0,05) i els individus amb major modulació vagal (AF%) en normòxia tendeixen a SpO2 més baixa en exercici en HH (r = −0,636; p = 0,125). Sorgeix la possibilitat d’utilitzar aquesta correlació com a eina predictiva de la capacitat individual d’aclimatació a l’altitud

Moderate altitude but not additional endurance training increases markers of oxidative stress in exhaled breath condensate

Oxidative stress occurs at altitude, and physical exertion might enhance this stress. In the present study, we investigated the combined effects of exercise and moderate altitude on redox balance in ten endurance exercising biathletes, and five sedentary volunteers during a 6-week-stay at 2,800m. As a marker for oxidative stress, hydrogen peroxide (H2O2) was analyzed by the biosensor measuring system Ecocheck™, and 8-iso prostaglandin F2α (8-iso PGF2α) was determined by enzyme immunoassay in exhaled breath condensate (EBC). To determine the whole blood antioxidative capacity, we measured reduced glutathione (GSH) enzymatically using Ellman's reagent. Exercising athletes and sedentary volunteers showed increased levels of oxidative markers at moderate altitude, contrary to our expectations; there was no difference between both groups. Therefore, all subjects' data were pooled to examine the oxidative stress response exclusively due to altitude exposure. H2O2 levels increased at altitude and remained elevated for 3days after returning to sea level (p≤0.05). On the other hand, 8-iso PGF2α levels showed a tendency to increase at altitude, but declined immediately after returning to sea level (p≤0.001). Hypoxic exposure during the first day at altitude resulted in elevated GSH levels (p≤0.05), that decreased during prolonged sojourn at altitude (p≤0.001). In conclusion, a stay at moderate altitude for up to 6weeks increases markers of oxidative stress in EBC independent of additional endurance training. Notably, this oxidative stress is still detectable 3days upon return to sea leve

The Physics of the B Factories

This work is on the Physics of the B Factories. Part A of this book contains a brief description of the SLAC and KEK B Factories as well as their detectors, BaBar and Belle, and data taking related issues. Part B discusses tools and methods used by the experiments in order to obtain results. The results themselves can be found in Part C

Melatonin relations with energy metabolism as possibly involved in fatal mountain road traffc accidents

Previous results evidenced acute exposure to high altitude (HA) weakening the relation between daily melatonin cycle and the respiratory quotient. This review deals with the threat extreme environments pose on body time order, particularly concerning energy metabolism. Working at HA, at poles, or in space challenge our ancestral inborn body timing system. This conflict may also mark many aspects of our current lifestyle, involving shift work, rapid time zone crossing, and even prolonged office work in closed buildings. Misalignments between external and internal rhythms, in the short term, traduce into risk of mental and physical performance shortfalls, mood changes, quarrels, drug and alcohol abuse, failure to accomplish with the mission and, finally, high rates of fatal accidents. Relations of melatonin with energy metabolism being altered under a condition of hypoxia focused our attention on interactions of the indoleamine with redox state, as well as, with autonomic regulations. Individual tolerance/susceptibility to such interactions may hint at adequately dealing with body timing disorders under extreme conditions.Comisión Nacional de Investigación Cientifica y Tecnológica (CONICYT) CONICYT FONDECYT Nffi110016

Use of UF-bonded recycling particle- and fibreboards in MDF-production

International audienceDie Untersuchungen betreffen die Eignung von TMP (thermo-mechanisch hergestellte Fasern) aus gebrauchten Holzspan- und -faserplatten als Rohstoff für die Herstellung von mitteldichten Faserplatten. Die Untersuchungsergebnisse lassen folgende Schlüsse zu: TMP aus gebrauchten Holzspan- und Holzfaserplatten weisen charakteristische morphologische und chemische Unterschiede zu TMP aus Holz auf. TMP aus Gebrauchtfaser- und -spanplatten sind kürzer in der Faserlänge und verfügen über einen höheren Feinanteil. Die Kaltwasserextrakte der TMP aus Gebrauchtspanplatten und Gebrauchtfaserplatten weisen einen deutlich höheren pH-Wert und einen höheren Gehalt an Acetat- und Formiationen auf. Auch die Formaldehydabgabe der TMP aus gebrauchten Span- und Faserplatten ist höher als die des aus Holz hergestellten TMP. TMP aus Holz lässt sich bei der Herstellung von UF-Harz-gebundenen MDF zu 30% durch TMP aus Gebrauchtspan- und -faserplatten ersetzen, ohne dass die mechanisch-technologischen Eigenschaften der hergestellten Platten eine nennenswerte Beeinträchtigung erfahren. Auch die Formaldehydabgabe der hergestellten Platten wird hierdurch nicht erhöht. Es sind weiterhin keine signifikanten Unterschiede in der Abgabe an flüchtigen Säuren zwischen den direkt aus Holz hergestellten Platten und denen unter Zusatz von TMP aus Gebrauchtspan- und -faserplatten gefertigten MDF feststellbar. Dies kann als hinreichendes Kriterium dafür angesehen werden, dass zwischen dem eingesetzten Bindemittel und den chemischen Abbauprodukten der Gebrauchtholzspan- und -faserplatten chemische Wechselwirkungen bestehen

Lipid monolayer expansion by calcium-chlorotetracycline at the air/water interface and, as inferred from cell shape changes, in the human erythrocyte membrane

Chemically induced shape changes of the human erythrocyte may result from cell membrane bending by surface tension changes at the lipid bilayer (Evans, E.A. (1947) Biophys. J. 14, 923-931) implicating differential expansion of the monolayers coupled to form the red cell membrane (Sheetz, M.P. and Singer, S.J. (1974) Proc. Natl. Acad. Sci. U.S.A. 71, 4457-4461). Interacting with calcium, the antibiotic chlorotetracycline (CTC) transforms crenated cells (echinocytes) into cup-shaped ones (stomatocytes), presumably expanding thereby the red cell membrane inner leaflet relative to the outer one (Behn, C., Lübbemeier, A. and Weskamp, P. (1977) Pflügers Arch. 372, 259-268). Whether the Ca-CTC interaction with lipid monolayers may in fact expand the latter, has now been examined by surface tension measurements at the air/water interface. CTC and lipids appeared to compete for the available sites at the air/water interface, contributing additively to its surface pressure. Ca increased both th

Long-term intermittent hypoxia increases O2-transport capacity but not VO2max

Long-term intermittent hypoxia, characterized by several days or weeks at altitude with periodic stays at sea level, is a frequently occurring pattern of life in mountainous countries demanding a good state of physical performance. The aim of the study was to determine the effects of a typical South American type of long-term intermittent hypoxia on VO2max at altitude and at sea level. We therefore compared an intermittently exposed group of soldiers (IH) who regularly (6 months) performed hypoxic-normoxic cycles of 11 days at 3550 m and 3 days at sea level with a group of soldiers from sea level (SL, control group) at 0 m and in acute hypoxia at 3550 m. VO2max was determined in both groups 1 day after arrival at altitude and at sea level. At altitude, the decrease in VO2max was less pronounced in IH (10.6 ± 4.2%) than in SL (14.1 ± 4.7%). However, no significant differences in VO2max were found between the groups either at sea level or at altitude, although arterial oxygen content (C