Fig. 1. Distribution of BC1 RNA in murine testis. Signal is represented as white autoradiographic silver grains in dark field photomicrographs. Labeling patterns in seminiferous tubules indicate an annular but patchy distribution of BC1 RNA along the tubular periphery (see low-power photomicrograph A with corresponding bright field B). Central adluminal regions are devoid of significant labeling (asterisk in A). Highest relative BC1 labeling appears concentrated in distinct patches overlying several neighboring cells (C-F; arrowheads in D,F) that are located adjacent to the basement membrane. Such cells often show the irregular nuclear outlines typical of enlarged A_al spermatogonia (Huckins, 1971). A sense-strand control is shown in G. Gold-colored silhouettes apparent in these and other dark field photomicrographs are produced by reflections from elongated spermatids in the adluminal regions of seminiferous tubules. (A,C,E,G) Dark field photomicrographs; (B,D,F) bright field photomicrographs. Bar, 100 µm (A,B); 50 µm (G); 30 µm (C-F).