Apocynin attenuates diaphragm oxidative stress and protease activation during prolonged mechanical ventilation.

Objective: To investigate whether apocynin protects the diaphragm from wasting and oxidative stress during mechanical ventilation (MV).

Design: Prospective, randomized, controlled study.

Setting: Research laboratory.

The IkappaB kinases IKKalpha and IKKbeta are necessary and sufficient for skeletal muscle atrophy.

Nuclear factor-kappaB (NF-kappaB) signaling is necessary for many types of muscle atrophy, yet only some of the required components have been identified. Gene transfer of a dominant negative (d.n.

Diaphragmatic nitric oxide synthase is not induced during mechanical ventilation.

Mechanical ventilation (MV) is associated with diaphragmatic oxidative stress that contributes to both diaphragmatic atrophy and contractile dysfunction. However, the pathways responsible for oxidant production in the diaphragm during MV remain unknown. To address this issue, we tested the hypothesis that diaphragmatic nitric oxide synthase (NOS) activity is elevated during MV, resulting in nitration of diaphragmatic proteins.

Diaphragm unloading via controlled mechanical ventilation alters the gene expression profile.

Rationale: Prolonged controlled mechanical ventilation results in diaphragmatic inactivity and promotes oxidative injury, atrophy, and contractile dysfunction in this important inspiratory muscle. However, the impact of controlled mechanical ventilation on global mRNA alterations in the diaphragm remains unknown.

Objectives: In these experiments, we used an Affymetrix oligonucleotide array to identify the temporal changes in diaphragmatic gene expression during controlled mechanical ventilation in the rat.

Reloading the diaphragm following mechanical ventilation does not promote injury.

Study Objective: Mechanical ventilation (MV) is used clinically to treat patients who are incapable of maintaining adequate alveolar ventilation. Prolonged MV is associated with diaphragmatic atrophy and a decrement in maximal specific force production (P(O)). Collectively, these alterations may predispose the diaphragm to injury on the return to spontaneous breathing (ie, reloading).

Mechanical ventilation induces alterations of the ubiquitin-proteasome pathway in the diaphragm.

Prolonged mechanical ventilation (MV) results in diaphragmatic atrophy due, in part, to an increase in proteolysis. These experiments tested the hypothesis that MV-induced diaphragmatic proteolysis is accompanied by increased expression of key components of the ubiquitin-proteasome pathway (UPP). To test this postulate, we investigated the effect of prolonged MV on UPP components and determined the trypsin-like and peptidylglutamyl peptide hydrolyzing activities of the 20S proteasome.

Trolox attenuates mechanical ventilation-induced diaphragmatic dysfunction and proteolysis.

Prolonged mechanical ventilation results in diaphragmatic oxidative injury, elevated proteolysis, fiber atrophy, and reduced force-generating capacity. We tested the hypothesis that antioxidant infusion during mechanical ventilation would function as an antioxidant to maintain redox balance within diaphragm muscle fibers and therefore prevent oxidative stress and subsequent proteolysis and contractile dysfunction. Sprague-Dawley rats were anesthetized, tracheostomized, and mechanically ventilated with 21% O(2) for 12 hours.

Mechanical ventilation depresses protein synthesis in the rat diaphragm.

Prolonged mechanical ventilation results in diaphragmatic atrophy and contractile dysfunction in animals. We hypothesized that mechanical ventilation-induced diaphragmatic atrophy is associated with decreased synthesis of both mixed muscle protein and myosin heavy chain protein in the diaphragm. To test this postulate, adult rats were mechanically ventilated for 6, 12, or 18 hours and diaphragmatic protein synthesis was measured in vivo.

Cumulative effects of aging and mechanical ventilation on in vitro diaphragm function.

Study Objective: Unloading the diaphragm, via mechanical ventilation (MV), results in significant diaphragmatic atrophy, contractile dysfunction, and oxidative stress in young adult animals. Since aging increases skeletal muscle susceptibility to atrophy and injury, we tested the hypothesis that MV-induced diaphragmatic contractile dysfunction would be exacerbated in aging rats.

Methods: Fisher 344/Brown Norway hybrid rats (4 months old [young] and 30 months old [old]) were assigned to either control or MV groups.

Mechanical ventilation-induced oxidative stress in the diaphragm.

Prolonged mechanical ventilation (MV) results in oxidative damage in the diaphragm; however, it is unclear whether this MV-induced oxidative injury occurs rapidly or develops slowly over time. Furthermore, it is unknown whether both soluble (cytosolic) and insoluble (myofibrillar) proteins are equally susceptible to oxidation during MV. These experiments tested two hypotheses: 1).

Effects of norandrostenedione and norandrostenediol in resistance-trained men.

The purpose of this study was to determine the effects of norsteroid supplementation (224 mg of 19-nor-4-androstene-3,17-dione and 120 mg of 19-nor-4-androstene-3,17-diol, total daily dose = 344 mg) on body composition and strength in resistance-trained men. In a placebo-controlled, double-blind, randomized fashion, 10 subjects received the norsteroid (11 capsules containing a combination of both norsteroids) or a placebo for 8 wk (five subjects per group). Each subject participated in resistance training an average of 4 d/wk for the duration of the study.

Mechanical ventilation results in progressive contractile dysfunction in the diaphragm.

These experiments tested the hypothesis that a relatively short duration of controlled mechanical ventilation (MV) will impair diaphragmatic maximal specific force generation (specific P(o)) and that this force deficit will be exacerbated with increased time on the ventilator. To test this postulate, adult Sprague-Dawley rats were randomly divided into one of six experimental groups: 1) control (n = 12); 2) 12 h of MV (n = 4); 3) 18 h of MV (n = 4); 4) 18 h of anesthesia and spontaneous breathing (n = 4); 5) 24 h of MV (n = 7); and 6) 24 h of anesthesia and spontaneous breathing (n = 4). MV animals were anesthetized, tracheostomized, and ventilated with room air.