METHODS

The generation and characterization of monoclonal antibody Cat-301 and its antigen have been described previously (McKay and Hockfield 1982; Zaremba et al. 1989). For immunochemistry, antigen was partially purified from urea extracts of cat cortex membranes by DEAE chromatography and Sepharose CL-2B gel filtration (Zaremba et al. 1989). Fractions from the Sepharose column containing the Cat-301 antigen were pooled. A second pool was made of fractions eluting at the column void volume. Aliquots of both pools were analyzed for proteoglycan content by incubation with chondroitinase, followed by electrophoresis and immunoblotting with Cat-301 or antibodies to chondroitin sulfate (see below). Final purification of the Cat-301 antigen was performed on a Cat-301 antibody affinity column (Guimaraes et al. 1990). Other methods for immunohistochemical and immunochemical analyses were performed as reported previously (Hockfield and McKay 1983; Kalb and Hockfield 1988; Zaremba et al. 1989; Guimaraes et al. 1990). Antibodies to chondroitin sulfate were obtained from ICN and as a generous gift from B. Caterson (Couchman et al. 1984) and were used according to Watanabe (Watanabe et al. 1989). Antibodies 3B3/C1 (anti-6S), 2B6 (anti-4S), and 1B5/C5 (anti-0S) recog-