Structures identified as lamellar bodies have been observed in neurons of the dorsal sensory nucleus of the vagus of the rat medulla oblongata. They consist of stacks of parallel, regularly spaced cisternae which either run straight or curve forming a whorl. Finely textured, electron-dense fibrils are present between adjacent cisternae which are devoid of ribosomes. Ribosomes are attached only to the outermost surface of outer cisternae which are often continuous with rough endoplasmic reticulum. Cytochemical studies reveal that these intercisternal fibrils contain abundant amino and imidazole groups as well as carboxyl groups. It is suggested that lamellar bodies arise by close alignment of parallel rough surfaced cisternae with subsequent loss of ribosomes from their surface. In addition, it is inferred that polar groups of intercisternal fibrils play an important role in the regular arrangement of cisternal membranes and in the dissociation of ribosomes from cisternae.
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