Distribution of microspheres in plantaris muscles of resting and exercising rats as a function of fiber type

Skeletal muscle perfusion measurements using adiabatic inversion of arterial water

Quantitative NMR measurements of perfusion using magnetic labeling of arterial water have been demonstrated previously in several different highly perfused organs. The success of these previous experiments suggested that arterial labeling may be of use in measuring perfusion in skeletal muscle, where resting perfusion is very low and where increased perfusion after exercise is transient. In the experiments described in this paper, adiabatic inversion of arterial water has been used to make single-voxel measurements of perfusion in the lower hind limb of rats. At rest, the NMR results were quantified to yield a perfusion rate of about 13.8 ml/100g/min. After perturbation due to ischemic exercise, large relative changes in the NMR signal were observed. The peak change of about 2.5% of the NMR signal occurred shortly after perturbation and was followed by a return to resting levels over a period of about 4 min.

Skeletal muscle capillarization and fiber types in urban and homing pigeons (Columba livia)

1. Fiber types, capillary supply and other morphometrical parameters were analysed in pectoral, gastrocnemius and pronator muscles of homing and urban pigeons. 2. The two kinds of birds were analysed before and after a restrainment period of at least 5 months. 3. Only slight differences in fiber type frequencies were noted between urban and homing pigeons in control conditions. 4. The effect of restrainment on the different parameters studied was unclear in gastrocnemius and pronator muscles and negligible in M. pectoralis. 5. Mean diffusion distances for oxygen from capillaries were smaller in oxidative fibers; also, vascularization indexes were higher for these fiber types. 6. The contribution of each fiber type to total sectional ara of muscle remains stable in spite of fiber type frequencies heterogeneity.