Histological analysis of samples and classification of microarrays. A-F. Histology of selected samples used in the microarray experiment. Characteristic developmental stages I (panel A), II (panel B), III (panel C), V (panel D) and VIII (panel E) are presented. Representative enriched fractions of isolated spermatogonia (F), spermatocytes (G) and spermatids (H) are also shown. Scale bars in panels A-E and F-H represent 50 and 20 μm, respectively. I. Dendogram of sample correlation according to hierarchical classification (uncentered correlation, average linkage) performed on entire microarray signals. Roman numerals (I-VIII) indicate trout developmental stages. Sg = Spermatogonia; SgA and SgB = Type-A and type-B spermatogonia, respectively; Sc = Spermatocytes; St = Spermatids; Sz = Spermatozoa; Ser = Sertoli cell; Ley = Leydig cell; Per = Peritubular cell; Me = Meiosis; Mi = Mitosis; In = Interstitial tissue.