Cover photograph (Copyright © 2006, American Society for Microbiology. All Rights Reserved.): Adenovirus-mediated expression of |gb-galactosidase in perivascular astrocytes in the brain parenchyma (striatum). Mice were injected with an adenoviral vector expressing |gb-galactosidase. Six days after infection, brain sections were stained for |gb-galactosidase (red) and astrocytes (magenta). Serial confocal optical sections were combined to produce the three-dimensional projection shown. Note that |gb-galactosidase is expressed within brain astrocytes surrounding a blood vessel in the brain parenchyma. (See related article on page 5655.)