Macroscopic to Ultrastructural Analyses Identify the Loss of Myofibrils as the Primary Mediator of Muscle Fiber Atrophy in Aging and Disuse. - Sayed RKA; Lange AN; Paez HG; Hibbert JE; Meinhold M; Flynn CGK; Vergara MBZ; Dobrzycki I; Wrucke DJ; Zepeda CS; James JJ; Sundberg CW; et al. (BioRxiv : the preprint server for biology, 2026)