In vivo detection of apoptotic cells with fluorescently labeled annexin V is an emerging technique that we evaluated for detecting apoptotic germ cells in a mouse model of testicular torsion.Annexin V labeled with an indocyanine fluorophore (bisfunctional succinimidyl ester of cyanine 5.5) (Amersham, Little Chalfont, United Kingdom) was injected intravenously in mice 18 hours after the repair of unilateral 720-degree testicular torsion for 2 hours