(A) Representative electrophoretogram showing coomassie stained histone bands in the rat testis, separated by 15% Acid Urea Polyacrylamide Gel Electrophoresis. Lane M: Calf thymus core somatic histone standard (H1 21.5Kd; H2A 14Kd; H2B 13.8Kd; H3 15.3Kd; H4 11.3Kd); Lane Fh1: H1 histones in FD-treated samples; Lane Ch1: H1 histones in control samples; Lane Ph1: H1 histones in CPA-treated samples; Lane Fc: Core histones in FD treated samples; Lane Cc: Core histones in control samples; Lane Pc: Core histones in CPA treated samples. Arrows indicate histone bands in standard and samples. (B) Representative ultramicrographs of immature caput epididymal rat sperm heads, treated in vitro with dithiothreitol (DTT). Left panel: Ultramicrographs of sperm heads of control rats at: (a) 30,000; (b) 68,000; (c) 68,000 magnification showing normal nuclei. Middle panel: Ultramicrographs of rat sperm heads of CPA-treated rats at: (d) 30,000; (e) 68,000; (f) 68,000 magnification showing subtle nuclear defects. Right panel: Ultramicrographs of rat sperm heads of FD-treated rats at: (g) 30,000; (h) 49,000; (i) 68,000 magnification showing subtle nuclear defects. (→) Arrows indicate immature epididymal sperm nuclei with condensed chromatin and normal perforatoria. (*) indicates immature epididymal sperm nuclei with loosely packaged chromatin and abnormal perforatoria with distended plasmalemma. SN, sperm nucleus.