Enlarge ImageChanging of the guard. In these nuclei from muscle cells, yellow indicates where nuclear pore proteins are being replaced.Credit: Maximiliano D'Angelo As if gimpy knees, clogged arteries, and forgetfulness weren't bad enough, new research has identified another way our bodies falter as we get older. The pores that permit only certain molecules to enter and exit the nuclei of our cells start leaking. A new study raises the possibility that permissive pores trigger some of the physical decline of old age. Nuclear pores aren't mere portholes. Each consists of about 30 different proteins called nucleoporins that control what...