[Morphological changes in human diaphragm--ragged red fiber, core/targetoid fiber, cytoplasmic body, and ring fiber]

We have already described that ragged red fiber (RRF), core/targetoid fiber and type 1 fiber predominance were found at autopsy in the diaphragm taken from patients with chronic obstructive pulmonary diseases. The purpose of the present study is to investigate morphological and histochemical changes in the diaphragm in denervating neurologic disorders. The diaphragm in the costal portion was taken from 22 autopsy cases including 4 with amyotrophic lateral sclerosis (ALS), 4 cerebrovascular diseases, 3 Parkinson disease, 2 olivopontocerebellar atrophy. In addition, 4 diaphragm muscles were biopsied at the time of surgery for lung cancer. In the diaphragm we observed not only RRF and core/targetoid fiber but also cytoplasmic body and ring fiber in many cases. These findings were, however, not specific for neurologic disorders. Focal cytochrome c oxidase deficiency was found in muscles with RRF. It should be emphasized that RRF was absent in 3 of 4 cases with ALS and in a case with elevated hemidiaphragm from phrenic nerve paralysis. In the previous report, we suggested that RRF was formed under the relative ischemic state in overworking diaphragm. The relative ischemia means a condition that oxygen (energy) demand for respiratory work exceeds over oxygen supply from the blood in the overworking diaphragm. The reason why no RRF was found in the denervated muscle is that the ischemic state in the denervated muscles is relieved by immobilization after denervation. Karpati et al conformed that denervation prevented ischemic state in the muscle. Other histochemical features in the diaphragm included cytoplasmic body and ring fiber.(ABSTRACT TRUNCATED AT 250 WORDS)