Transmission and Scanning Electron Microscopic Studies of Human Sperm Heads Extracted with 8 M Urea, 1% Mercaptoethanol and Different Concentrations of Salt

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Abstract
Transmission (TEM) and scanning (SEM) electron microscopic studies were performed on the human sperm heads extracted with (a) 1% Triton X-100, 1% mercaptoethanol (ME) and (b) 8 M urea, 1% ME together with increasing concentrations of NaCl ranging from 0.2 to 0.6 M. In the TEM study, the extraction of the nuclear material was first observed when the heads were treated with 8 M urea and 1% ME, with the majority of the chromatin remaining as 400–550 Å thick interconnecting cords and oval bodies. At 0.2 M NaCl the cords and bodies were further separated but linked together by extremely thin 20–50 A fibers. Between 0.3 and 0.5 M NaCl the chromatin bodies within the sperm heads began to be extracted, first at the central part and progressively towards the periphery. Finally, at 0.6 M NaCl only the chromatin cords forming the periphery of the heads remained. In the SEM study, the sperm heads remained unbroken up to the treatment with 8 M urea, 1% ME and 0.2 M NaCl. Between 0.3 M and 0.5 M NaCl the majority of heads were disrupted to form interlacing chromatin cords of 400–550Å thick while the unbroken heads exhibited surface with cross-weaving cords. At 0.6 M NaCl all heads were disrupted and the remaining chromatin existed mostly as exoskeleton of former sperm heads. Protein gel electrophoresis showed that histones and nonhistones were removed from the chromatin when the treatment reached 0.2 M NaCl, whereas protamines started to be removed at 0.3 M, and totally removed at 0.6 M NaCl; HP1 was the first protamine fraction to be extracted. It is concluded that the thick cords are nucleoprotamines laced together by nucleohistone fibers; and that the cords forming the peripheral exoskeleton are sturdier than those in the interior of the sperm heads.