Molecular Markers of muscle Plasticity, damage, regeneration and repair.

The motor units of skeletal muscles differ in their ability to sustain power without fatigue and stress. They may therefore be damaged by different levels of exercise, as well as by events involving ischaemia and reperfusion, or administration of myotoxic agents. Quantitation of such damage is often performed morphometrically, but such an approach is vulnerable to the artifacts that can appear in cryostat sections taken from seriously disrupted tissue. Paraffin and acrylic embedding for light and electron microscopy are laborious procedures, and require substantial biopsies whose quantitation can be time-consuming. We will describe scaled-down procedures, based on protein and nucleic acid chemistry, that are sensitive enough to allow several markers of plasticity, damage, regeneration, and repair to be determined on a muscle sample of just a few milligrams. A suitable source of material is a small biopsy specimen removed from the muscle for fibre typing and histopathology; a few additional serial cryostat sections cut from the block constitute a sample that is adequate for biochemical analysis. Since needle biopsies can be taken sequentially, it becomes feasible to construct a time course for the response of skeletal muscle to different demands in either experimental or clinical settings.