Further Observations on the Fine Structure of “Tubular Aggregates”

Abstract

Accumulations of densely packed long straight tubules, usually at the periphery of skeletal muscle fibers, have been referred to as “tubular aggregates”. They have been described mainly in type II muscle fibers and do not appear to be associated with a specific disease entity. The nature and origin of the abnormal tubular structures remain enigmatic. Some authors have postulated that they arise from lateral sacs of sarcoplasmic reticulum while others maintain that a mitochondrial or sarcolemmal origin is more plausible. This unsettled dispute over their origin prompted us to pursue a more detailed ultrastructural study of their components.A fifty-three year old male presented with a short history of pains in the quadriceps muscles and bitemporal areas. A chronic periarteritis of uncertain etiology was present in the temporal artery and quadriceps muscle. Cryostat sections of the latter revealed numerous subsarcolemmal masses of material which stained basophilic with hematoxylin and eosin, bright red with modified trichrome and intensively with the NADH tetrazolium reductase reaction.