AGE AND DIET ALTER SKELETAL-MUSCLE TUBULAR AGGREGATES

Tubular aggregates (TA's) may comprise the major histopathologic findi ng in hyperkalemic and normokalemic periodic paralysis. They also cons titute a conspicuous morphologic abnormality in a number of myopathies , and have been associated with non-specific muscle myalgias/cramps. C aloric restriction (CR) is an experimental manipulation that increases longevity and reduces lesions in mice as compared to animals fed ad l ibitum (AL). However, the impact of CR on the dynamics of muscle tissu e has not been previously established. In this paper we week to charac terize the relationship between tubular aggregates and age and determi ne whether they are modulated by caloric restriction. We examined the effects of 40% caloric restriction (CR) on fiber damage formation in m iddle-aged (19 months of age) and older (27 months) mice. We also exam ined the effects of age and diet restriction on tubular aggregate form ation in 12, 24, and 30 month old mice. Tissue blocks from the 19 and 27 month animals were also examined using electron microscopy for qual itative differences in tubular aggregates which may suggest a diet and age effect. There appeared to be no fiber or Z-disc damage attributab le to age as assessed by quantitative light microscopy (LM). Age and d iet had significant effects on the percent of fibers occupied by tubul ar aggregates. Qualitative LM revealed that many TA's may not have yet penetrated the sarcolemma in the young animals, and in particular, th e young CR mice. The presence of round fibers was evident in the young CR mice whereas fibers were more angular in the AL mice.