Fast axoplasmic transport of noradrenaline and dopamine in mammalian peripheral nerve

A fast transport of noradrenaline (NA) at a velocity of 392 mm/day was found in cat peroneal nerve using a double-ligation technique and a new sensitive radioenzymatic assay for catecholamines. The velocity of transport of NA is sufficiently close to that of 410 mm/day found for labelled proteins and polypeptides to be considered as moving down within the nerve fibres by the same transport mechanism. In addition, dopamine (DA) was also found to be moved down by anterograde transport at a fast, but not well defined, rate. Disulfiram, a dopamine-beta-hydroxylase inhibiting agent, reduced NA levels and increased DA both in control nerve segments and within the portion of the nerve isolated by ligations where NA-containing densecore vesicles are present. The results are considered to support a dynamic turnover of NA and DA in the dense-core vesicles as they are trasnported in the axons.

Anoxic block and recovery of axoplasmic transport and electrical excitability of nerve

Axoplasmic transport of cat sciatic nerves was studied in vitro in a chamber in which maximal alpha action potentials could also be elicited. After initiation of N2 anoxia, electrical responses fell to zero at an average time of 22 min. A shorter time to zero of 11 min was seen during a second period of anoxia. A good recovery of both action potential responses and axoplasmic transport occurs after a period of anoxia lasting 1--1.5 hr. An apparent failure of recovery of axoplasmic transport was seen after 2 hr of anoxia with a good recovery of electrical responses. Axoplasmic transport tended to return toward normal when more time was allowed for recovery after anoxia. An adequate supply of approximately P was shown to be present by measurement of ATP and creatine phosphate levels. The delay in recovery of transport thus signifies a failure of utilization of approximately P by the transport mechanism. Longer periods of anoxia and recovery were limited in vitro and for this reason, ischemic anoxia was produced in vivo. Blood pressure cuffs were placed on the upper thigh of cats and maintained for times of 1--8 hr at pressures of 300-310 mm Hg. Then, recovery times up to 7 days were allowed. It was shown that axoplasmic transport could gradually recovery after an anoxia lasting up to 6-7 hr if sufficient recovery times were allowed. A possible explanation for the delay in the recovery of axoplasmic transport and the disassociation in the earlier recovery of electrical responses as against the recovery of transport was discussed.

The early history of nerve regeneration beginning with Cruikshank's observations in 1776

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The viscosity of mammalian nerve axoplasm measured by electron spin resonance

1. The microviscosity of the axoplasm of can sciatic nerve was determined by an in vitro electron spin resonance (e.s.r.) method using the spin label tempone. To identify the spin label signal as one arising only from within the axoplasm, Ni2+ was used as a line broadening agent. In one series of experiments in nerves with sheath intact the Ni2+ ion was shown to eliminate the tempone signal arising from the surface water, and in another series of experiments, with the sheath slit, to eliminate the signal from the extracellular space as well. 2. A microviscosity of less than 5 centipoise (cP), i.e. 5x that of water, was determined for the axoplasm. Changes in the viscosity of the nerve axoplasm as a function of temperature over a range of 38 degrees down to 2 degrees C were seen to follow closely the viscosity change found for a water solution. 3. The microviscosity of nerve axoplasm and its change with temperature were related to axoplasmic transport of material in nerve fibres. The results were used to exclude a large increase in viscosity at low temperatures as the cause for the cold-block of fast axoplasmic transport.

Fast axoplasmic transport in the fibres of chromatolysed neurones

1. The rate of fast axoplasmic transport in cat sensory nerves was determined in sciatic nerves above transections made low in the popliteal fossa some 6-165 days beforehand. The pattern and rate of movement of the crest of labelled components in the nerve fibres after injecting the L7 dorsal root with [3H]leucine was used to characterize fast axoplasmic transport. 2. The mean rate and S.D. found on the transected side was 424 + 33 mm/day compared with 432 +/- 34 mm/day for the control nerves. These rates were not significantly different and were similar to the rate of axoplasmic transport previously reported to be 410 +/- 50 mm/day. The results gave little support for the hypothesis that a speeding up of the rate of fast axoplasmic transport is the signal for the initiation of chromatolysis. 3. The amount of transport shown by the level of activity in the crests on the chromatolytic and control sides relative to the "pool" of radioactive materials remaining in the cell bodies of the ganglion were also similar. The significance of these findings was discussed with respect to changes in the cell bodies known to take place during chromatolysis and the stability of the axoplasmic transport mechanism in nerve fibres.

Retention and redistribution of proteins in mammalian nerve fibres by axoplasmic transport

Fast axoplasmic transport is characterized by a crest of labelled activity moving down nerve fibres after injection of the L7 dorsal root ganglion with the amino acid precursor (3H) leucine, the crest followed by a plateau which represents in part a later egress of labelled components from compartments in the cell bodies and in part materials left behind the advancing crest. 2. after making ligations just below the ganglia at different times after injection of the precursor, a small downward slope of locally retained activity of incorporated materials is seen in the plateau remaining in the nerves. The slope becomes changed to a horizontal level when in addition a distal ligation is made as a result of the redistribution of labelled materials within the doubly ligated nerve segments. 3. the outlfow pattern at later times, at a day and longer after injection, shows an additional spread of activity from the cell body region. The pattern of outflow gradually levels off at later times as additions of activity are made to the more distal part of the nerves. The activity retained in the nerves becomes less free to become redistributed in the course of several days. 4. The temporal changes in the outflow patterns can be accounted for by the local retention and redistribution of the labelled materials within the fibres. Later additions of labelled materials compartmented in the cell bodies also contribute to the later pattern of outflow. A "unitary" view for fast and slow transport is presented based on the transport filament hypothesis earlier proposed to account for fast axoplasmic transport.

Slow axoplasmic transport of mitochondria (MAO) and lactic dehydrogenase in mammalian nerve fibers

The axoplasmic transport of the enzyme monoamine oxidase (MAO) (monoamine:O2 oxidoreductase, (deaminating) EC 1.4.3.4), a marker for mitochondria, and lactic dehydrogenase (LDH) (L-lactate:NAD oxidoreductase, EC 1.1.1927), a soluble component of axoplasm, was studied in cat sciatic nerve. For both these enzymes a linear accumulation was found in the nerve proximal to ligations over a period of at least 20 h. In double-ligation experiments no evidence of a depletion of enzymes within the nerve segment was found over this period of time as would be the case if some portion of the enzymes was carried by fast axoplasmic transport. Both the soluble protein enzyme LDH and the mitochondria, shown by MAO, are thus considered to be moved down the nerve by slow axoplasmic transport. Some differences in the two materials were seen in the greater fall in the level of MAO compared to LDH within the double-ligated segment over the succeeding period from 20 to 48 h. These changes are considered with respect to the transport filament model as modified to take into account slow axoplasmic transport.

Batrachotoxin block of fast axoplasmic transport in mammalian nerve fibers

Batrachotoxin (BTX) irreversibly blocks fast axoplasmic transport in nerve in concentrations as low as 0.2 micromolar. The action of BTX was studied in cat sciatic nerves in vitro by measuring the rate of the crest outflow after injection of the L7 dorsal root ganglion with [3-H]leucine. Tetrodotoxin, which in itself does not affect fast axoplasmic transport, inhibited the blocking action of BTX. Unlike the BTX block of nerve and muscle membrane excitability brought about through increased permeability to sodium ion, the BTX block of fast axoplasmic transport occurs with or without sodium ion in the medium. High concentrations of calcium ion protected against the blocking action of BTX, while magnesium ion did not. An action of BTX on the transport mechanism inside the fibers was indicated by the small reduction of adenosine triphosphate plus creatine phosphate, which in itself did not account for the block of axoplasmic transport.

Low temperature slowing and cold-block of fast axoplasmic transport in mammalian nerves in vitro

1) Fast axoplasmic transport in mammalian nerve in vitro was studied using an isotope labeling technique. The rate of outflow in cat sciatic nerve fibers of 410 mm/day in vitro was reduced at temperatures below 38 degrees C with a Q10 of 2.0 in the range 38-18 degrees C and a Q10 of 2.3 at 38-13 degrees C. 2) At a temperature of 11 degrees C a partial failure of transport occurred. At temperatures below 11 degrees C a complete block of fast axoplasmic transport occurred, a phenomenon termed "cold-block." No transport at all was seen over the temperature range of 10-0 degrees C for times lasting up to 48 hr. 3) Transport was resumed after a period of cold-block lasting up to 22 hr when the nerves were brought back to a temperature of 38 degrees C. Some deleterious effects due to cold-block were seen in the recovery phase as indicated by a reduction in crest amplitude, change in its form, and slowed rate. 4) The approximately P level (combined ATP and creatine phosphate) remained near control level in nerves kept at low or cold-block temperatures for times as long as 64 hr. The reduction in fast axoplasmic transport rate seen at low temperatures for times up to 22 hr was therefore considered due to a decrease in the utilization of ATP, a concept in accord with the "transport filament" model proposed to account for fast axoplasmic transport. 5) The sloping of the front of the crest over the temperature range of 18-13 degrees C suggests an additional factor at the lower temperatures. A disassembly of microtubules is discussed as a possible explanation of the cold-block phenomenon.

Natural abundance carbon-13 nuclear magnetic resonance spectra of the canine sciatic nerve

The proton-decoupled natural abundance carbon-13 nuclear magnetic resonance spectrum of the canine sciatic nerve is virtually identical to that of canine adipose tissue and markedly similar to that of liquid triolein. No resonances assignable to cholesterol, glycolipids, or sphingolipids are detectable in the sciatic nerve spectrum despite their abundance in the myelin sheath of this nerve. However, many such resonances are observed in lipid extracts of the nerve. Chronmatographic analysis of specimens of canine and rabbit sciatic nerve has revealed that these contain sufficient triglyceride to account quantitatively for the observed spectrum. Proton nuclear magnetic resonance and spin-labeling results for preparations containing myelin, especially those derived from the peripheral nerve, should be critically examined for experimental artifacts reflecting the triglyceride content.

Rate of fast axoplasmic transport in mammalian nerve fibres

1. Fast axoplasmic transport in mammalian nerve fibres was determined by the presence of a crest of activity in the sciatic nerve after injection of [(3)H]leucine into the L7 dorsal root ganglion or the L7 motoneurone region in the ventral horn region of the spinal cord. After incorporation into proteins by the cell bodies, a rate of transport close to 410 mm/day was found for cat sensory nerves. A closely similar rate was found in the motor and sensory sciatic nerve fibres of the monkey, dog, rabbit, goat and rat. In the longer nerves where longer downflow times were possible, there was no decrement of rate with distance, or presence of later appearing crests of activity indicative of multiple fast transport systems.2. The rate of fast transport found in the long L7 dorsal roots of the rhesus monkey was the same as that in the corresponding length of sciatic nerve and the same fast rate was shown by the crest of activity ascending in the dorsal columns of the spinal cord.3. Labelled activity was found present inside myelinated nerve fibres ranging in diameter from 3 to 23 mum in nerve segments taken at the forward part of the crest suggesting that the rate of fast axoplasmic transport is independent of fibre diameter.