Fig. 3. A, Electron micrograph of the soma of a labeled cerebral cortical pyramidal neuron. Immunogold particles are present both in the nucleus (n) and perikaryon. Little of the cytoplasmic label is associated with the plasma membrane, mitochondria, or Golgi apparatus (arrow).B, C, Few particles were found in the nuclei or cytoplasm of astrocytes (a) or oligodendrocytes (o). D, Tangential section through the nuclear envelope of a pyramidal cell showing three nuclear pores (arrows), one of which (longer arrow) contains an immunogold particle. E, Cross-section through the nuclear envelope showing immunogold particles within nuclear pores (arrows).F–H, In perikarya, most immunogold particles are clustered between the cisternae of RER. These regions are especially rich in free ribosomes, visible here as fine electron-dense particles (asterisks). A few immunogold particles are also seen in direct contact with the cisternae (arrows). Scale bars: A–C, 1 μm;D–H, 500 μm.