Fig. 7.1.36. These clusters (arrows) containing finely granulofilamentous material are found either attached to granular endoplasmic reticulum, to postsynaptic densities, or lying freely in the cytoplasm (inset). We do not know what their composition and significance exactly are. However, according to their appearance, they perhaps could represent either so called "RNA granules" containing mRNA and ribosomes (according to Knowles et al., 1996, J Neurosci 16:7812-7820, similar formations represent a way by which a specific mRNA and polyribosomes are transported from neuronal soma to dendrites and their postsynaptic regions), or they could be a specific form of CaMKII protein kinase (Dosemeci et al., 2000, J Neurosci 20:3076-3084). Scale = 100 nm. (Human, neocortex.) Download the high resolution image.