Hydroxocobalamin vs cobalt toxicity on rat cardiac and diaphragmatic muscles.

Background: Hydroxocobalamin has been shown to be a rapid and powerful antidote in acute cyanide poisoning and to prevent cyanide poisoning during sodium nitroprusside administration. This cobalt-containing compound has been shown to be devoid of significant immediate side effects during acute administration. However, its potential delayed toxicity related to cobalt accumulation in tissue remains unknown.

Effects of fatigue on force-velocity relation of diaphragm. Energetic implications.

Characteristics of the force (P)-velocity (V) relationship were investigated before and after fatigue in isolated diaphragm muscle of two species: mouse (n = 12), in which diaphragm is composed almost exclusively of fast-twitch fatigue-resistant fiber type, and rat (n = 12), in which diaphragm contains both fatigue-sensitive and fatigue-resistant fiber types. Following fatigue protocol, the mechanical performance of both the contraction and relaxation phases were significantly depressed in the two species. Consequences of the fatigue procedure on P-V characteristics differed markedly according to the two species.

[Mechanical determinants of isotonic relaxation of the isolated diaphragmatic muscle].

The aim of this study was to define the mechanical determinants of isotonic relaxation of isolated diaphragm muscle in the rat over a load range (n = 30). We tested several hypotheses to determine the effect of i) load conditions (preload, post-load), ii) sudden changes in load during contraction, iii) length of the muscle at peak shortening, iv) maximal amplitude of shortening (delta L) and v) stimulation conditions on peak rate of isotonic reelongation (+dL/dmax). At tetanus at 30 Hz, +dL/dmax was linearly correlated to delta L peak shortening and total load.

Relaxant effects of isoproterenol in isolated cardiac muscle: influence of loading patterns.

The purpose of this study was to test the hypothesis that loading patterns (i.e., loading sequence, total load, and preload) modulate the relaxant effects of isoproterenol.

Mechanics of human quadriceps muscle.

Mechanics of human quadriceps muscle strips (vastus lateralis; n = 10) were investigated over the whole load continuum. Mechanical experiments were performed at 29 degrees C and in both twitch and tetanus modes. For a given level of isotonic total load (P) and over a large part of the contraction phase, instantaneous velocity (V) was shown to be a unique function of instantaneous length (L), regardless of time and initial length.