1. Spermatogonial proliferation patterns in men with azoospermia of different etiologies 
Batia Bar-Shira Maymon, D.Sc., Leah Yogev, Ph.D., Haim Yavetz, M.D., Beatriz Lifschitz-Mercer, M.D., Letizia Schreiber, M.D., Sandra E Kleiman, Ph.D., Amnon Botchan, M.D., Ron Hauser, M.D., Gedalia Paz, Ph.D. 
Fertility and Sterility 
Volume 80, Issue 5, Pages (November 2003)
DOI: /S (03)

2. FIGURE 1
Immunohistochemical staining for proliferating cell nuclear antigen (PCNA). In all cases, antibody binding was visualized using DAB as a substrate to generate a brown color. Sections were counterstained with Mayer's hematoxylin which stains nuclei blue. SC = Sertoli cell; SPG = spermatogonia; SPC = spermatocyte; RT = round spermatid; MT = mature spermatid. Arrowhead = unstained spermatogonia. (A), Normal spermatogenesis (obstructive azoospermia). PCNA antibody enables nuclear staining in cells of the germ line: prominent staining was demonstrated in the nuclei of the spermatogonia and also in the nuclei of primary spermatocytes. (B), Focal spermatogenesis. The left seminiferous tubule demonstrates full spermatogenesis (i.e., the presence of mature spermatids), whereas the adjacent tubule demonstrates spermato-cyte maturation arrest. PCNA expression can be clearly seen in spermatogonia of the tubule with mature spermatids but is barely detectable in the tubule with spermatocyte arrest. (C), Spermatocyte maturation arrest. This tubule is from a biopsy characterized by a homogenous appearance of spermatocyte arrest. A high labeling rate of PCNA is seen in all the apparent tubules. (A and B: Bar scale indicates 35 μm. C: Bar scale indicates 50 μm.)
Maymon. Patterns of spermatogonial proliferation. Fertil Steril 2003.
Fertility and Sterility  , DOI: ( /S (03) )