Fig. 1. Microinjection of purified anti-dynamin antibodies reduces fluid-phase endocytosis. (A-H) Fluorescence micrographs of Clone 9 cells microinjected with either a control solution (injection buffer or anti-kinesin antibodies) or affinity-purified peptide antibodies targeting Dyn2 and subsequently assayed for the internalization of fluorescently conjugated transferrin (A,C,E,G) or dextran (B,D,F,H). Control cells microinjected with either injection buffer alone (A,B) or purified inhibitory anti-kinesin antibodies (C,D) showed no reduction in the internalization of either fluorescently conjugated transferrin (A,C) or dextran (B,D). By contrast, microinjection of cells with 7.2-8.6 mg/ml of purified polyclonal anti-dynamin antibodies either specific for Dyn2 (E,F) or against a conserved region found in all conventional dynamins, MC65 (G,H), attenuated receptor-mediated and fluid-phase endocytosis. (*) Indicates an injected cell. (I,J) Quantitation of transferrin (I) and dextran (J) internalization in Clone 9 cells microinjected with either buffer alone, anti-kinesin antibodies or anti-dynamin antibodies based on measurement of fluorescence intensity units. Values obtained from microinjected cells were normalized to those of surrounding uninjected cells. Results represent the average ± s.d. of 100 cells measured in each of two independent experiments. Bar, 10 µm.