['To gain insight into the function of cyclin-dependent kinase 5 (Cdk5) in spermatogenesis.', 'The expression of the Cdk5 protein was determined with the use of immunohistochemical and immunoblot analysis.', 'Academic research laboratory.', 'Adult mouse and archival human testicular tissue were used for the immunohistochemical analysis. Adult mice were used as the source of tissues for the immunoblot analysis.', 'The immunohistochemical analysis was performed with an anti-Cdk5 antibody. The double immunohistochemical analysis was performed with anti-Cdk5 and alpha-tubulin antibodies. Immunoblotting was used to examine multiple mouse tissues for Cdk5 expression.', 'Analysis of Cdk5 protein distribution.', 'Cdk5 was localized specifically within the cytoplasm of Sertoli cells and meiotic metaphase germ cells. The double immunohistochemistry analysis demonstrated the co-localization of Cdk5 and alpha-tubulin within the Sertoli cells. Western blot analysis revealed a high level of expression of Cdk5 in the testicular lysate.'] Is cyclin-dependent kinase 5 expressed in both Sertoli cells and metaphase spermatocytes?