The maintenance of axoplasmic transport by strontium and its localization in nerve fibers

A new technique for the detection of the axoplasmic transport of β-radioactively labelled materials is described wherein a multiwire proportional chamber is used to measure the distribution of activity along peripheral nerve fibers which are maintained in vitro. The operating principles of the chamber are described and basic construction parameters given. Potential radiolabels are discussed.Two types of studies were performed at room temperature in vitro using sciatic nerves of the amphibian Xenopus laevis: static and dynamic. In the static study the nerve ganglion was incubated for a suitable period of time in either L-[U-14C]leucine or L-[35S]methionine after which the ganglion was removed and the activity in the remaining nerve assayed with the chamber. In the dynamic study the nerve activity was assayed by the chamber while incubation proceeded so that a dynamic picture of transport could be observed. Using the second approach, transport rates were observed which are in agreement with others which have been reported in the literature.Some advantages and limitations of the technique are discussed.

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Microtubule and Neurofilament Densities in Amphibian Spinal Root Nerve Fibers: Relationship to Axoplasmic Transport

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y73-123 ◽

1973 ◽

Vol 51 (11) ◽

pp. 798-806 ◽

Cited By ~ 43

Author(s):

Richard S. Smith

Keyword(s):

Dorsal Root ◽

Dark Field ◽

Nerve Fibers ◽

Axoplasmic Transport ◽

Spinal Root ◽

Myelinated Nerve ◽

Dorsal Roots ◽

Dark Field Microscopy ◽

Spinal Roots ◽

Ventral Roots

Dark-field microscopy of living myelinated nerve fibers from the spinal roots of Xenopus laevis revealed many spherical organelles moving in the axoplasm of fibers from the ventral roots and in fibers just distal to the dorsal root ganglion. Similar organelles were present but few were seen to move along fibers from the dorsal roots central to the ganglion. This observation prompted an ultrastructural study of microtubule and neurofilament densities in the myelinated fibers of the spinal roots. The density of microtubules was significantly less in fibers from the central part of the dorsal roots than in the rest of the spinal root system. Neurofilament densities were equivalent in all parts of the roots. Microtubules showed a significant association with mitochondria in the ventral roots and in the dorsal roots distal to the ganglion, but no significant association was obtained for the dorsal roots central to the ganglion. The meaning of these results in the axoplasmic transport of large organelles is discussed.

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