Histochemical studies on striated muscle fibres of the beige mutant mouse

Muscle lesions in beige (Chediak-Higashi syndrome) and heterozygous C57BL/6J mice

Muscles from male and female C57BL/6J Chediak-Higashi syndrome (CHS) and phenotypically normal mice with the bgJ allele were studied microscopically and histochemically for the presence of basophilic cytoplasmic structures seen by other investigators in muscles of CHS mice of the SB/Le strain. Triceps brachii, gastrocnemius, quadriceps femoris, and biceps femoris muscles were examined. Multiple basophilic cylindrical lesions were present in hematoxylin and eosin-stained muscle from all groups. Lesions were positive for esterase, Sudan black, and periodic acid-Schiff. Lesions were only seen in type II muscle fibers. Type I muscle cells comprised less than an estimated 5% of the total muscle fibers in the four muscles examined. Scores were assigned based on the presence or absence of lesions in each muscle. Male mice of both phenotypes had significantly more lesions (P less than 0.05) than female mice. When sexes were combined, lesions were significantly (P less than 0.05) more numerous in normal mice than CHS mice for all muscles except the gastrocnemius. Lesions were significantly (P less than 0.05) more numerous in the phenotypically normal male than the CHS male mice for the triceps and quadriceps muscles. There was no significant difference (P greater than 0.05) between lesions of phenotypically normal female and female CHS mice. Basophilic cytoplasmic structures did not prove to be a manifestation of the CHS trait.

Morphology of lesions in striated muscle fibres from the beige mouse

Lesions in striated muscle fibres from the beige mouse are described at both the light- and electronmicroscopical levels. The muscles have two types of lesions, one is well defined cores in the fibres and the other is diffusely enlarged intermyofibrillar spaces (IMS). The cores can be filled with membrane-like structures or a fluffy unstructured material. In the areas with enlarged IMS comparatively few organelles are present and the muscle fibres seem to be fragmented.

Enzyme reactions in beige mouse muscle with central cores

In this paper enzyme activities in cylindric structures from striated muscle fibers of the beige mutant mouse are described. While most of the sarcoplasm possesses a reaction for myosin and sarcoplasmic reticular ATPase, succinic dehydrogenase, and lactic dehydrogenase similar to that described for normal non-mutant mice, the cylinders are totally free from activity of these enzymes. The staining pattern thus resembles earlier reports of the central core disease in humans and suggests that the beige mouse is a suitable animal model for this myopathy.