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.