Fig. 8.

Middle. ArgK is concentrated in neuronal growth cones and can be distributed differentially among growth cones of the same neuron. Three CNS neurons (A/B, C, D) are double-labeled for argK (yellow) and membrane proteins (anti-HRP, blue). ArgK is shown separately in A, and the two labels are shown combined in B–D. The neurons are bipolar (C, D) or have bifurcating axons (A/B, D). Each neuron has one growth cone (white arrowhead) that labels brightly relative to the axon and other growth cones (unfilled arrowhead). The neuron in D has a third growth cone (arrow) that labels at an intermediate level. A low antibody concentration (1:200; see Materials and Methods) was used to reveal differences in argK concentration. Scale bar, 10 μm (all panels).