An ultrastructural study of the origin and function of basophilic degeneration in human cardiac muscle-cardiac colloid. Type 1

The myofibres in biopsies obtained from the left ventricle during cardiopulmonary bypass, in patients undergoing surgery for mitral and aortic valve replacement and the correction of atrial septal defect, contained inclusions thought to be type 1 cardiac colloid. Electron microscopy showed this material to be synthesised by and contained within a grossly dilated rough endoplasmic reticulum. The presence of membrane‐bound aggregates of non‐fibrillar sarcoplasmic organelles within colloid deposits, together with osmiophilic inclusions thought to be related to lipofuscin, both within and moving from this structure, suggest that type 1 cardiac colloid is an autophagic vacuole designed to degrade ageing or redundant sarcoplasmic organelles.