Fig. 6

Immunoelectron microscopy of MIF in the caput region of the rat epididymis. (A) High power magnification shows the specific migration inhibitory factor (MIF) staining of the outer dense fibers (ODF). Note MIF-positive vesicles (arrowhead) around the spermatozoa. (Bar = 60 nm). L = epididymal lumen. (B) The apical cell pole of an epithelial cell in rat caput epididymis. Stereocilia and vesicles pinched off from the apical plasma membrane show accumulation of MIF. (Bar = 50 nm). (C) Gold-labeling is restricted to the cytoplasm of the epididymal epithelium (dark regions). The endoplasmic reticulum is clearly negative for MIF (bright regions). (Bar = 50 nm). (D) Immunoelectron microscopy using the anti-MIF antibody shows the presence of this peptide in vesicles isolated from epididymal fluid. (Bar = 7 nm). (E) Isolated vesicles examined using conventional transmission electron microscopy demonstrate a heterogeneous membrane-bound population similar to vesicles seen in the intact organ. (Bar = 20 nm).