Research Article

Activation of Cyclin-Dependent Kinase 5 Is a Consequence of Cell Death

Figure 5

Inhibition of Cdk5 expression does not protect cells from death. COS-7 cells treated with CPT at 48 hours with or without transfection of Cdk5 dsRNA were fixed for electron microscopy. (a) and (b) Untreated cells transfected with Cdk5-1 (a) or Cdk5-2 (b) are elongated and display large nuclei, comparable to controls that were not transfected (see Figure 3(b)(A); otherwise not illustrated). (c) and (d) CPT-exposed dying cells in control (c) and transfected with Cdk5-1 dsRNA (d) were apoptotic. An apoptotic cell has a condensed nucleus and cytoplasm and increased electron density while the chromatin is coalesced and electron-dense. Cells killed by CPT are apoptotic regardless of the concentration of Cdk5.
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