Immunocytochemical Analysis of Ubiquitin. DAB-mediated immunostaining was used to examine the ubiquitin protein abundance in uncompressed and compressed muscles of DMSO- and MG132-treated animals. In DMSO-treated rats, uncompressed muscle did not show any immunoreactivity of ubiquitin whereas compressed muscle demonstrated strong immunoreactivity in the muscle cells (upper panels). The ubiquitin immunoreactivity was distributed in muscle fibres in a scattered pattern. In MG132-treated rats, no immunoreactivity of ubiquitin was detected in both uncompressed and compressed muscles (lower panels).