The Cytological and Chemical Orqanization

The prostatic complex of Didelphis virginiana Kerr has been studied by a variety of cytological and cytochemical means. Segment I was characterized by an apocrine type secretory mechanism. The apical parts of the epithelial cells, which were shed into the glandular lumen, contained vesicles which give positive cytochemical reactions for acid phosphatase, aliesterase, 5'-nucleotidase, and nucleoside diphosphatase. These vesicles also contained material which was reactive with the periodic acid-Schiff test for mucopolysaccharide and Baker's test for phospholipid. Segment I1 was characterized by the presence of two types of cells in the glandular epithelium. Type A cells contained large rounded secretory granules which gave positive reactions for acid mucopolysaccharides but not for proteins. Type B cells contained large elongate secretory granules which gave positive reactions for proteins but not for polysaccharides. Electronmicrographs indicated these secretory granules to have distinctive morphologies and to contain complex crystalloid material. No cells with characteristics intermediate between those of the A and B types were observed. Segment I11 of the prostatic complex was characterized by the presence of large amounts of glycogen both in the epithelial cells and within the glandular lumen. These observations indicate a remarkable degree of morphological and biochemical heterogeneity on the part of the prostatic complex of this animal. In spite of the fact that the Virginia opossum has been widely used during more than three decades of research on problems of reproductive physiology, no modern study of the cytological organization of the prostatic complex of this animal has been carried out. Chase ('39) described the gross morphology and histological organization of the prostate gland in this form. In common with the prostate glands of other mammals, that of the opossum is of the tubulo-alveolar variety. The secretory acini are embedded in the urethral stroma and the gland is thus of the disseminate or diffuse type (Price, '63). Grossly, three regions of the gland may be recognized in adult males. Segment I is the most craniad portion and is light brown in color; Segment I1 is the medial portion and is pink in color; and Segment I11 is most caudad and is dark grey in color. The histological organizations of these segments differ (Chase, '39). Underlying this histological differentiation is a series of cytological and chemical differences which we believe are unique in the area of prostatic morphology. A description of the cytological and some of the cytochemical characteristics J. EXP. ZOOL. , 159: 209-230. of the three segments of the prostatic complex of Didelphis virginiana Kerr are the subject of this paper. MATERIALS AND METHODS The eight adult, male animals used in this study were obtained from the Carolina Biological Supply House, Elon College, North Carolina during the months of October to May. They were judged to be in a state of full reproductive development on the basis of the curvature of the prostatic urethra and by the distinctive colors of the various prostatic segments (Chase, '39). Tissue for the following cytological and cytochemical procedures was embedded in paraffin by standard procedure : Mitochondria were visualized by Kull's aurantia method (Baker, '50) or by the methods of Mallory or Regaud (Lillie, '54) after fixation in the solution of Helly (Lillie, '54). Golgi material was stained by the Aoyama method (Lillie, '54) after fixation in 4.0% aqueous formaldehyde contain-