Fig. 1.

Endocytically derived organelles in axon shafts and branch points exhibit trimodal and unimodal frequency distributions of pH, respectively. The histograms show the frequency distributions of organelle pH for endocytically derived organelles located in axon shafts (A) and branch points (B).A, Ratiometric pH determination of 95 endocytically labeled organelles located throughout the axon shafts revealed one neutral and two acidified organelle populations. B, Organelles located in axonal branch points exhibited a broad unimodal distribution with a mean pH of 6.39 ± 0.67. Several neutral, but few highly acidified, organelles were observed at branch points.