Most protons remained uncombined as hydrogen nuclei. Mature monocytes have large, smooth, lobed nuclei and abundant cytoplasm that contains granules. The electromagnetic attraction between atomic nuclei and their orbital electrons holds atoms together. When neutrons strike the hydrogen nuclei, proton radiation (fast protons) results. Alpha particles are identical with helium-4 nuclei. The serotonergic system has almost all of its serotonergic neurons originating in the raphe nuclei. Th is an isotope of thorium whose nuclei contain 144 neutrons. All fission reactions generate fission products, the remains of the split atomic nuclei. Degeneration is also present in brainstem nuclei like the locus coeruleus. The fibers arise from the deep cerebellar nuclei. Inert gas can diffuse into bubble nuclei between tissues. The queen cells hatch inside of the mating nuclei. Other nuclei, such as alpha particles, are less prevalent. Ventricaria ventricosa has a coenocytic structure with multiple nuclei and chloroplasts. Ependymomas are composed of cells with regular, round to oval nuclei.