These are direct effects that are also present in astrocyte cell cultures not containing neurons. GFAP is expressed in the central nervous system in astrocyte cells. A gemistocyte ( ; ) is a swollen, reactive astrocyte. Demethylation of HES1 target sites in the promoter region of astrocyte-specific genes hastens astrocyte differentiation. Proteins expressed in glial cells are astrocyte markers GFAP, and S100B. Another perspective is that astrocyte swelling is due to glutamine accumulation. Both adenosine and ATP induce astrocyte cell proliferation. Astrocyte and oligodendrocyte glial cells were pooled for these results. These astrocytes have an unhealthily large amount of GFAP that affects astrocyte formation and function. FGF2 has also been shown to increase astrocyte proliferation "in vitro". This astrocyte remodeling appears to be mediated through ammonia-induced mitochondrial permeability transition.