Commentaries on Viewpoint: Loopomics: a new functional approach to life
(Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Horvath, A., Simandi, Z., Nagy, L., Kerkhof, P. L. M., Perlitz, V., Handly, N., Zuo, L., Chuang, C.-C. Tags: VIEWPOINT Source Type: research
Loopomics: a new functional approach to life
(Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Burlando, B. Tags: VIEWPOINT Source Type: research
UBC-Nepal expedition: markedly lower cerebral blood flow in high-altitude Sherpa children compared with children residing at sea level
Developmental cerebral hemodynamic adaptations to chronic high-altitude exposure, such as in the Sherpa population, are largely unknown. To examine hemodynamic adaptations in the developing human brain, we assessed common carotid (CCA), internal carotid (ICA), and vertebral artery (VA) flow and middle cerebral artery (MCA) velocity in 25 (9.6 ± 1.0 yr old, 129 ± 9 cm, 27 ± 8 kg, 14 girls) Sherpa children (3,800 m, Nepal) and 25 (9.9 ± 0.7 yr old, 143 ± 7 cm, 34 ± 6 kg, 14 girls) age-matched sea level children (344 m, Canada) during supine rest. Resting gas exchange, blood pressure,...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Flück, D., Morris, L. E., Niroula, S., Tallon, C. M., Sherpa, K. T., Stembridge, M., Ainslie, P. N., McManus, A. M. Tags: RESEARCH ARTICLE Source Type: research
Exposure to intermittent hypoxia and sustained hypercapnia reduces therapeutic CPAP in participants with obstructive sleep apnea
Our purpose was to determine whether exposure to mild intermittent hypoxia leads to a reduction in the therapeutic continuous positive airway pressure required to eliminate breathing events. Ten male participants were treated with twelve 2-min episodes of hypoxia (PETCO2 50 mmHg) separated by 2-min intervals of normoxia in the presence of PETCO2 that was sustained 3 mmHg above baseline. During recovery from the last episode, the positive airway pressure was reduced in a stepwise fashion until flow limitation was evident. The participants also completed a sham protocol under normocapnic conditions, which mimicked the time f...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: El-Chami, M., Sudan, S., Lin, H.-S., Mateika, J. H. Tags: RESEARCH ARTICLE Source Type: research
Dietary nitrate supplementation increases acute mountain sickness severity and sense of effort during hypoxic exercise
In conclusion, dietary nitrate increases AMS and sense of effort during exercise, particularly in those who experience AMS. Dietary nitrate is therefore not recommended as an AMS prophylactic or ergogenic aid in nonacclimatized individuals at altitude.
NEW & NOTEWORTHY This is the first study to identify that the popular dietary nitrate supplement (beetroot) does not reduce acute mountain sickness (AMS) or improve exercise performance during 6-h hypoxia. The consumption of nitrate in those susceptible to AMS exacerbates AMS symptoms (headache) and sense of effort and raises oxygen cost, ventilation, and blood pressure ...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Rossetti, G. M. K., Macdonald, J. H., Wylie, L. J., Little, S. J., Newton, V., Wood, B., Hawkins, K. A., Beddoe, R., Davies, H. E., Oliver, S. J. Tags: RESEARCH ARTICLE Source Type: research
Acclimatization of the systemic microcirculation to alveolar hypoxia is mediated by an iNOS-dependent increase in nitric oxide availability
Rats breathing 10% O2 show a rapid and widespread systemic microvascular inflammation that results from nitric oxide (NO) depletion secondary to increased reactive O2 species (ROS) generation. The inflammation eventually resolves, and the microcirculation becomes resistant to more severe hypoxia. These experiments were directed to determine the mechanisms underlying this microvascular acclimatization process. Intravital microscopy of the mesentery showed that after 3 wk of hypoxia (barometric pressure ~380 Torr; partial pressure of inspired O2 ~68–70 Torr), rats showed no evidence of inflammation; however, treatment ...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Casillan, A. J., Chao, J., Wood, J. G., Gonzalez, N. C. Tags: RESEARCH ARTICLE Source Type: research
The interplay between iron and oxygen homeostasis with a particular focus on the heart
Iron is subject to tight homeostatic control in mammals. At the systemic level, iron homeostasis is controlled by the liver-derived hormone hepcidin acting on its target ferroportin in the gut, spleen, and liver, which form the sites of iron uptake, recycling, and storage, respectively. At the cellular level, iron homeostasis is dependent on the iron regulatory proteins IRP1/IRP2. Unique chemical properties of iron underpin its importance in biochemical reactions involving oxygen. As such, it is not surprising that there are reciprocal regulatory links between iron and oxygen homeostasis, operating both at the systemic and...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Lakhal-Littleton, S., Robbins, P. A. Tags: REVIEW Source Type: research
Regulation of blood volume in lowlanders exposed to high altitude
Humans ascending to high altitude (HA) experience a reduction in arterial oxyhemoglobin saturation and, as a result, arterial O2 content (CaO2). As HA exposure extends, this reduction in CaO2 is counteracted by an increase in arterial hemoglobin concentration. Initially, hemoconcentration is exclusively related to a reduction in plasma volume (PV), whereas after several weeks a progressive expansion in total red blood cell volume (RCV) contributes, although often to a modest extent. Since the decrease in PV is more rapid and usually more pronounced than the expansion in RCV, at least during the first weeks of exposure, a r...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Siebenmann, C., Robach, P., Lundby, C. Tags: REVIEW Source Type: research
Erythrocyte purinergic signaling components underlie hypoxia adaptation
Erythrocytes are vital to human adaptation under hypoxic conditions because of their abundance in number and irreplaceable function of delivering oxygen (O2). However, although multiple large-scale altitude studies investigating the overall coordination of the human body for hypoxia adaptation have been conducted, detailed research with a focus on erythrocytes was missing due to lack of proper techniques. The recently maturing metabolomics profiling technology appears to be the answer to this limitation. Metabolomics profiling provides unbiased high-throughput screening data that reveal the overall metabolic status of eryt...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Sun, K., Liu, H., Song, A., Manalo, J. M., DAlessandro, A., Hansen, K. C., Kellems, R. E., Eltzschig, H. K., Blackburn, M. R., Roach, R. C., Xia, Y. Tags: REVIEW Source Type: research
High-altitude champions: birds that live and migrate at altitude
High altitude is physiologically challenging for vertebrate life for many reasons, including hypoxia (low environmental oxygen); yet, many birds thrive at altitude. Compared with mammals, birds have additional enhancements to their oxygen transport cascade, the conceptual series of steps responsible for acquiring oxygen from the environment and transporting it to the mitochondria. These adaptations have allowed them to inhabit a number of high-altitude regions. Waterfowl are a taxon prolific at altitude. This minireview explores the physiological responses of high-altitude waterfowl (geese and ducks), comparing the strateg...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Laguë, S. L. Tags: REVIEW Source Type: research
Beyond just hemoglobin: Red blood cell potentiation of hemoglobin-oxygen unloading in fish
Teleosts comprise 95% of fish species, almost one-half of all vertebrate species, and represent one of the most successful adaptive radiation events among vertebrates. This is thought to be in part because of their unique oxygen (O2) transport system. In salmonids, recent in vitro and in vivo studies indicate that hemoglobin-oxygen (Hb-O2) unloading to tissues may be doubled or even tripled under some conditions without changes in perfusion. This is accomplished through the short circuiting of red blood cell (RBC) pH regulation, resulting in a large arterial-venous pH difference within the RBC and induced reduction in Hb-O...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Brauner, C. J., Harter, T. S. Tags: REVIEW Source Type: research
Functional roles of globin proteins in hypoxia-tolerant ectothermic vertebrates
Globins are heme-containing proteins ubiquitously expressed in vertebrates, where they serve a broad range of biological functions, directly or indirectly related to the tight control of oxygen levels and its toxic products in vivo. Perhaps the most investigated of all proteins, hemoglobin and myoglobin are primarily involved in oxygen transport and storage, but also in facilitating arterial vasodilation, suppressing mitochondrial respiration, and preventing tissue oxidative damage via accessory redox enzymatic activities during hypoxia. By contrast, the more recently discovered neuroglobin and cytoglobin do not seem to fu...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Fago, A. Tags: REVIEW Source Type: research
Translation in Progress: Hypoxia 2017
(Source: Journal of Applied Physiology)
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Roach, R. C., Wagner, P. D., Ainslie, P. N., Hackett, P. H. Tags: EDITORIAL Source Type: research
Effects of different input pressure waveforms on the carotid sinus baroreflex-mediated sympathetic arterial pressure response in rats
In conclusion, the FSW was more effective than the BSW in reducing mean SNA and AP. The finding could be applied to designing an artificial pulsatile pressure such as that generated by left ventricular assist devices.
NEW & NOTEWORTHY This study examined whether the waveforms of an input pressure alone can affect the baroreflex function by using a forward saw wave and a backward saw wave with the same mean pressure, pulse pressure, and pulse frequency. The forward saw wave was more effective than the backward saw wave in reducing sympathetic nerve activity and arterial pressure. The finding could be applied to designin...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Kawada, T., Shimizu, S., Yamamoto, H., Miyamoto, T., Kamiya, A., Shishido, T., Sugimachi, M. Tags: RESEARCH ARTICLE Source Type: research
Running training experience attenuates disuse atrophy in fast-twitch skeletal muscles of rats
Responsiveness to physiological stimuli, such as exercise and muscular inactivation, differs in individuals. However, the mechanisms responsible for these individual differences remain poorly understood. We tested whether a prior experience of exercise training affects the responses of skeletal muscles to unloading. Young rats were assigned to perform daily running training with a treadmill for 8 wk. After an additional 8 wk of normal habitation, the rats were hindlimb unloaded by tail suspension for 1 wk. Fast-twitch plantaris, gastrocnemius, and tibialis anterior muscles did not atrophy after unloading in rats with train...
Source: Journal of Applied Physiology - October 26, 2017 Category: Physiology Authors: Nakamura, K., Ohsawa, I., Masuzawa, R., Konno, R., Watanabe, A., Kawano, F. Tags: RESEARCH ARTICLE Source Type: research
