Untitled

Abstract

The influence of decreased muscle mass and reduced food intake on diaphragm structure and contractility in male Wistar rats was determined after triamcinolone acetate treatment (TR: 0.5 mg per kg per day for 4 weeks) and two degrees of undernutrition (PW: pair-weight, which resulted in a similar (41%) reduction of body weight as TR; PF: pair-fed, which resulted in a moderate (13%) reduction of body weight) and a free-fed control group (FF, with an increase (9%) in body weight). energy intake of TR decreased, but based on daily measurements of food intake and body weight, energy expenditure of the TR rats was increased compared with the other groups. Body (BW) and muscle weights were reduced in proportion to the extent of undernutrition in the nutritionally deprived rates (i.e. BW and diaphragm weight of PF animals were reduced 215 and 16% respectively compared with FF, v. a. 48% and 41% reduction in the PW group). Triamcinolone-induced atrophy was limited to type II fibres (30% of type IIa and 45% of type IIx/b, p < 0.05), while severe chronic undernutrition (PW) induced a generalized fibre type atrophy in the diaphragm (23% type I, 38% type IIa and 49% type IIx/b, p < 0.05), and moderate undernutrition (PF) caused only significant type IIa atrophy (20%, p < 0.05). A leftward shift of the diaphragmatic tension-frequency relationship and a decreased fatiguability of the TR and PW bundles were observed (p < 0.01), while the PF bundles were not significantly different compared with FF. These results suggest that triamcinolone and severe undernutrition cause similar alterations in in vitro contractility of the diaphragm. The effects of triamcinolone treatment on diaphragm structure may be partly explained by the reduced food intake, but the atrophy pattern induced by severe undernutrition (PW) was different.

Impact of diaphragm muscle fiber atrophy on neuromotor control

“…A number of animal studies report that chronic treatment with systemic corticosteroids induces selective atrophy of type IIx and IIb DIAm fibers (Dekhuijzen et al, 1993; Fournier et al, 2003; Koerts-de Lang et al, 2000; Koerts-De Lang et al, 1998; Pellegrino et al, 2004; Sieck et al, 1999; Verheul et al, 2004). Systemic corticosteroid treatment may also result in weight loss and thus studies commonly compare corticosteroid effects with those induced by undernutrition (Dekhuijzen, 1995; Fournier et al, 2003; Koerts-de Lang et al, 2000; Koerts-De Lang et al, 1998; Lewis et al, 1986; Sieck et al, 1989b).…”

“…Systemic corticosteroid treatment may also result in weight loss and thus studies commonly compare corticosteroid effects with those induced by undernutrition (Dekhuijzen, 1995; Fournier et al, 2003; Koerts-de Lang et al, 2000; Koerts-De Lang et al, 1998; Lewis et al, 1986; Sieck et al, 1989b). Regardless of whether corticosteroid effects are compared to weight-matched animals as a result of pair-feeding (undernutrition) or younger age (van Balkom et al, 1997; Verheul et al, 2004), corticosteroid treatment substantially reduces DIAm fiber cross-sectional area in a fiber type selective manner – type IIx and/or IIb DIAm fibers are disproportionately affected.…”

Mechanostimulation, electrostimulation and force measurement in anin vitromodel of the isolated rat diaphragm

“…Most important in vitro investigations of diaphragmatic muscle force were performed on muscle strips. Typically such strips are mounted inside an organ bath, connected to force transducers and stretched in the uniaxial direction (Capdevila et al 2003, Gayan-Ramirez et al 2005, Koerts-De Lang et al 1998, Maes et al 2007. The main advantage of this technique is the highly controllable test condition, which is characterized by precise setting of predistension, controlled electrical stimulation and precise force measurement.…”