Most forensic laboratories like to observe spermatozoa as part of confirming the presence of semen in an evidentiary sample. A common method of doing this is to recover dried semen evidence from fabric or on human skin with a deionized water-moistened swab. A portion of the recovered cells are then placed onto a microscope slide and fixed to the slide with heat. The immobilized cells are stained with a 'Christmas Tree' stain consisting of aluminum sulfate, nuclear fast red, picric acid, and indigo carmine (Shaler 2002). The stained slide is then examined under a light microscope for sperm cells with their characteristic head and long tail. The Christmas Tree stain marks the anterior sperm heads light red or pink, the posterior heads dark red, the spermatozoa's mid-piece blue, and the tails stain yellowish green (Shaler 2002). John Herr at the University of Virginia is developing some 'sperm paints' to fluores-cently label the head and tail portions of spermatozoa with antibodies specific to sperm and thus make it easier to observe sperm cells in the presence of excess female epithelial cells.
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Discover Simple Techniques to Help Control Your Stutter. Stuttering is annoying and embarrassing. If you or a member of your family stutters, you already know the impact it can have on your everyday life. Stuttering interferes with communication, and can make social situations very difficult. It can even be harmful to your school or business life.