TNF and glioblastoma: Ca2+‐ATPase activity in membranes from human glioblastoma (U‐251, U‐138) and rat glioma (C6) cell lines, untreated (Control) and treated with cytokines (3 ng·mL−1 of IL‐1α, 30 ng·mL−1 of TNF‐α, and 400 ng·mL−1 of C1q), or with 5 μm Aβ1‐42 or 10 nm tau.