Oscillatory motion of intra‐axonal organelles of Xenopus laevis following inhibition of their rapid transport.

Abstract

SUMMARY1. The motion of optically detected organelles in myelinated axons of Xenopus laevis was studied in axons bathed in a potassium glutamate based medium and in axons in a similar medium to which various inhibitors ofaxonal transport were added.2. Organelles in the potassium glutamate medium had a motion which was indistinguishable from that previously described for organelles in axons bathed in a conventional physiological saline.3. Colchicine, dimethylsulphoxide, 2,4-dinitrophenol, hyperosmotic solutions, raised concentrations of intracellular calcium ions, and media made up in deuterium oxide caused either a complete or partial inhibition of both anterograde and retrograde organelle transport. 4. When directioned transport had been inhibited by any of the agents used, organelles displayed a longitudinally oriented oscillatory motion.5. An analysis of the variable, or oscillatory, component of organelle motion in axons not treated with inhibitors and in axons in which transport was partially or completely inhibited produced evidence that the dominant frequency components were similar in each case. A maximal estimate of the dominant frequency of oscillatory motion was 0-18+0-02 Hz. The distribution of instantaneous velocities about the mean velocity was not substantially altered as the transport of organelles was inhibited.6. The evidence suggested that the variable component of motion of organelles which show directioned transport is related to the oscillatory motion of organelles whose transport is inhibited.

Axonal mitochondrial transport and potential are correlated

“…Although calcium is a requirement for axonal transport, increases in cytoplasmic calcium levels also inhibit mitochondrial transport (Kanai et al, 2001;Kanje et al, 1981;Kendal et al, 1983). Because mitochondria are involved in calcium regulation (Budd and Nicholls, 1996;Rizzuto, 2001), it will be important to understand how intracellular ionic composition modulates mitochondrial transport.…”

“…For this to occur, it seems likely there is a gradient in a molecule that docked mitochondria create. This could be an ion such as Ca 2+ (Budd and Nicholls, 1996;Kanai et al, 2001;Kanje et al, 1981;Kendal et al, 1983;Ochs and Jersild, 1984;Ochs et al, 1977), a metabolite such as ATP (de Graaf et al, 2000), creatine (van Deursen et al, 1993), ADP or NADH (BereiterHahn and Voth, 1983;Bereiter-Hahn and Voth, 1994), a second messenger such as a small G-protein (Alto et al, 2002;Fransson et al, 2003), or another signal-transduction pathway (Chada and Hollenbeck, 2003). It follows that the concentration of the molecule alters a sensor that regulates activity of a motor (as discussed below) or linker between the mitochondria and cytoskeleton (Boldogh et al, 1998;Trinczek et al, 1999;Wagner et al, 2003).…”

Intermittent myelination of small-diameter sciatic axons inXenopus laevis

“…Living axons were isolated by treating the desheathed sciatic nerve with 1% trypsin in physiological saline for 10 min. Axons were then easily teased apart in a buffered (pH 7.2) 0.12 M solution of potassium glutamate (Kendal et al, 1983) on a microscope slide. The mat of teased axons, mounted under a cover glass, was viewed by video-enhanced differential interference contrast microscopy (Allen et al, 1981).…”