Academia.edu no longer supports Internet Explorer.
To browse Academia.edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser.
1971, American Journal of Physiology-- …
In Vitro Cellular & Developmental Biology - Animal
The American Journal of Pathology, 2004
Journal of Applied Physiology, 2001
Intermittent hypoxia (IH), associated with obstructive sleep apnea, initiates adaptive physiological responses in a variety of organs. Little is known about its influence on diaphragm. IH was simulated by exposing rats to alternating 15-s cycles of 5% O2 and 21% O2 for 5 min, 9 sets/h, 8 h/day, for 10 days. Controls did not experience IH. Diaphragms were excised 20–36 h after IH. Diaphragm bundles were studied in vitro or analyzed for myosin heavy chain isoform composition. No differences in maximum tetanic stress were observed between groups. However, peak twitch stress ( P < 0.005), twitch half-relaxation time ( P < 0.02), and tetanic stress at 20 or 30 Hz ( P < 0.05) were elevated in IH. No differences in expression of myosin heavy chain isoforms or susceptibility to fatigue were seen. Contractile function after 30 min of anoxia (95% N2-5% CO2) was markedly preserved at all stimulation frequencies during IH and at low frequencies after 15 min of reoxygenation. Anoxia-ind...
Progress in clinical and biological research, 1989
In isolated rabbit papillary muscles at 20 degrees C, we studied the relationship between demand, supply, and utilisation of energy in hypoxia. Since shortage of energy is an important factor in loss of contractile performance following an hypoxic period, we tried to find a relationship between the loss of force production upon reoxygenation and the demand, supply, and utilisation of energy. Energy demand in hypoxia was defined as the -P turnover found in oxygen under further identical conditions. Energy supply in hypoxia was determined from lactate formation, using a P/lactate ratio of 1, while energy utilisation in hypoxia was obtained from the sum of: -P supply, the decrease of PCr and ATP, and the increase of AMP. Energy demand in hypoxia was varied by stimulating the hypoxic muscles at 0.2 Hz or not at all. For contracting hypoxic muscles energy supply by glycolysis was only 23% of energy demand. After 40 min of hypoxia force did only partially recover (78%) upon reoxygenation....
Journal of Applied Physiology, 2001
Intermittent hypoxia (IH) describes conditions of repeated, transient reductions in O2 that may trigger unique adaptations. Rest periods during IH may avoid potentially detrimental effects of long-term O2 deprivation. For skeletal muscle, IH can occur in conditions of obstructive sleep apnea, transient altitude exposures (with or without exercise), intermittent claudication, cardiopulmonary resuscitation, neonatal blood flow obstruction, and diving responses of marine animals. Although it is likely that adaptations in these conditions vary, some patterns emerge. Low levels of hypoxia shift metabolic enzyme activity toward greater aerobic poise; extreme hypoxia shifts metabolism toward greater anaerobic potential. Some conditions of IH may also inhibit lactate release during exercise. Many related cellular phenomena could be involved in the response, including activation of specific O2 sensors, reactive oxygen and nitrogen species, preconditioning, hypoxia-induced transcription facto...
Journal of Applied Physiology, 2004
Patients with obstructive sleep apnea (OSA) often exhibit fatigued or inefficient upper airway dilator and constrictor muscles; an upper airway dilator, the geniohyoid (GH) muscle, is a particular example. Intermittent hypoxia (IH) is a frequent concomitant of OSA, and it may trigger muscle fiber composition changes that are characteristic of a fatigable nature. We examined effects of short-term IH on diaphragmatic and GH muscle fiber composition and fatigue properties by exposing 24 rats to alternating 10.3% O2-balance N2 and room air every 480 s (240 s duty cycle) for a total duration of 5, 10, 15, 20, or 30 h. Sternohyoid fiber composition was also examined. Control animals were exposed to room air on the same schedule. Single-fiber analyses showed that GH muscle fiber types changed completely from myosin heavy chain (MHC) type 2A to MHC type 2B after 10 h of exposure, and the conversion was maintained for at least 30 h. Sternohyoid muscle fibers showed a delayed transition from ...
Quarterly journal of experimental physiology and cognate medical sciences
Circulation research, 1990
The FASEB Journal, 2000
Academia Medicine, 2024
SAE Technical Paper Series, 2001
Progress in Biophysics and Molecular Biology, 2015
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 2006
Clinical Immunology and Immunopathology, 1975
IOP Publishing
Physical review, 2017
RePEc: Research Papers in Economics, 2010
Zenodo (CERN European Organization for Nuclear Research), 2023
Zenodo (CERN European Organization for Nuclear Research), 2023
Revista Peruana de Biología, 2013
Asian-Australasian Journal of Animal Sciences, 2015