Free radicals are molecules with one or more unpaired electron(s) commonly found in seminal plasma. Physiologically, free radicals control sperm maturation, capacitation and hyperactivation, the acrosome reaction, and sperm-oocyte fusion. Pathologically, free radicals induce lipid peroxidation, DNA damage and apoptosis of spermatozoa. The present review deals with both the beneficial and detrim...

The rewiring of metabolism in cancer is thought to result from hyperactivation of signaling pathways that instruct cells to grow. Sebastian et al. show that loss of the tumor suppressor SIRT6 transforms cells by activating tumor metabolism. This occurs independently of mutations in canonical growth signaling pathways and reveals a tumorigenic role for cancer metabolism.

Under inflammatory conditions after burn/trauma injuries, circulating neutrophils are frequently hyperactive, contributing to excessive superoxide production and related tissue damage. Although normal neutrophil activation is cooperatively controlled by Ca(2+)-independent and Ca(2+)-linked signaling pathways, exuberant Ca(2+)-linked signaling appears to cause neutrophil hyperactivation in the i...

Mammalian sperm must hyperactivate in order to fertilize oocytes. Hyperactivation is characterized by highly asymmetrical flagellar bending. It serves to move sperm out of the oviductal reservoir and to penetrate viscoelastic fluids, such as the cumulus matrix. It is absolutely required for sperm penetration of the oocyte zona pellucida. In order for sperm to hyperactivate, cytoplasmic Ca(2+) l...