Particle-free and glycogen-bearing double membrane arrays in extraocular muscle of rabbit.

Smooth double membrane arrays were observed in apparently normal extraocular muscle. These were fully or partially glycogen bearing, or completely particle free. The respective structures were often closely associated. Comparable arrays have been reported in normal and pathologic muscle; in liver cells, particle-free and glycogen-bearing double membrane arrays are frequently seen under an assortment of abnormal conditions. The significance of such structures is not clear. The present observations suggest that particle-free arrays are related to those bearing glycogen and may thus be associated with anabolic functions.