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PubMed2001

Herpesviruses use bidirectional fast-axonal transport to spread in sensory neurons.

Alpha herpesviruses infect the vertebrate nervous system resulting in either mild recurrent lesions in mucosal epithelia or fatal encephalitis. Movement of virions within the nervous system is a critical factor in the outcome of infection; however, the dynamics of individual virion transport have never been assessed. Here we visualized and tracked individual viral capsids as they moved in axons away from infected neuronal cell bodies in culture. The observed movement was compatible with fast axonal flow mediated by multiple microtubule motors. Capsids accumulated at axon terminals, suggesting that spread from infected neurons required cell contact.

Animals↗
PubMed2001

Axonal transport of TNF-alpha in painful neuropathy: distribution of ligand tracer and TNF receptors.

Tumor necrosis factor-alpha (TNF-alpha) is a key player in peripheral nerve injury. In the inflammatory chronic constriction injury (CCI) model of sciatic neuropathy, upregulation of TNF-alpha mRNA and protein at the site of nerve injury has been associated with pain. We now report the distribution of endogenous TNF-alpha protein and its receptors along normal and CCI-injured sciatic nerves, and within the corresponding lumbar dorsal root ganglia (DRG). Using Western blotting, TNF-alpha was found to be distinctly increased at the injury site, as well as in the axons just distal to the corresponding DRG. The TNF-alpha signal between the injury site and DRG (midaxonal) was induced between 2 and 5 days post-CCI, suggesting activation of TNF-alpha axonal transport. Endogenous TNF-alpha was localized in small-diameter, presumably nociceptive, and large-diameter, presumably mechanoceptive, DRG sensory neurons in both normal and CCI animals. Intraneural microinjection of biotin-labeled TNF-alpha showed specific axonal uptake at the injection site, as detected by avidin-biotin-peroxidase histochemistry, and confirmed by co-localization with neurobiotin tracer. In control animals, fast retrograde transport of biotinylated TNF-alpha to both L4 and L5 DRG neurons was apparent 6 h following injection. TNF receptors TNFRI and TNFRII co-localized with biotinylated TNF-alpha tracer along the nerve trunk, suggesting that TNF-alpha transport may be receptor-mediated. In animals with CCI neuropathy, uptake of biotinylated TNF-alpha by neuronal soma was inhibited. Instead, there was signal accumulation in the axons immediately distal to the DRG, and TNFRI and RII were increased at this same anatomic location. These findings highlight a dynamic process of TNF-alpha protein and receptor regulation throughout the peripheral neural axis that bears on both the normal function of DRG neurons and the pathogenesis of painful neuropathies.

Animals↗
PubMed1985

Structural effects in axoplasm of DNase I, an actin depolymerizer that blocks fast axonal transport.

We have studied by electron microscopy the organization of microtubules and neurofilaments in axons of giant identified neurons in Aplysia and the effect upon it of microinjected DNase I, a depolymerizer of actin filaments, to determine whether the block of fast transport caused by this agent might be due to disorganization of the cytoskeleton. Microtubules were thoroughly intermingled with the more numerous neurofilaments rather than segregated into domains. In the axon of the cell, GCN, the morphologically identifiable transmitter storage vesicles, which have been shown previously to move by anterograde fast axonal transport, were distributed non-randomly, tending to be near microtubules. They were found most frequently 10-20 nm from the nearest microtubule. When DNase I was microinjected into the axon of the cell R2, large clumps of organelles formed in areas distributed around the perimeter of the axoplasm. Microtubules were abnormally rare in those areas, though abundant elsewhere in the injected region. In some axons injected with DNase I, axoplasm separated from the axolemma at many places around the perimeter of the axoplasm. When the microtubule stabilizing drug taxol was present in the bathing medium, the inhibition of transport caused by injection of DNase I was reduced by about half. We conclude that a substantial part, at least, of this inhibition is caused by localized losses of microtubules. These results suggest that actin is more likely to play a structural role in the axon than a direct role in force generation for fast axonal transport.

Actins↗
PubMed1986

Afferent projections to the thalamic mediodorsal nucleus in the cat studied by retrograde and anterograde axonal transport of horseradish peroxidase.

The afferent pathways to the thalamic mediodorsal nucleus (MD) in the cat were studied using the methods of anterograde and retrograde axonal transport of horseradish peroxidase (HRP) and wheat germ agglutinin conjugated to HRP (WGA-HRP). The MD receives fibers from the prefrontal cortex in a topically organized manner in accordance with the thalamocortical projections. The medial or ventral portion of the MD receives afferents from the islands of Calleja of the olfactory tubercle, the nucleus of the diagonal band, the amygdala and the claustrum. The lateral hypothalamic nucleus sends a moderate number of fibers to the medial MD, but other hypothalamic nuclei send only a few fibers to the MD. The lateral or dorsal portion of the MD receives fibers from the nucleus of the diagonal band, the ventral pallidum and the entopeduncular nucleus, but only few from the olfactory tubercle and the amygdala. The thalamic reticular nucleus sends many fibers to the MD without showing any topography. The MD, particularly its lateral part, receives afferents from brainstem structures, such as the substantia nigra, superior colliculus, reticular formation, raphe nuclei and nucleus loci coerulei. Only the interpeduncular nucleus sends fibers mainly to the medial part of the MD. The cerebellar nuclei send only a few fibers to the lateral part of the MD at posterior levels.

Afferent Pathways↗
PubMed1986

Impaired axonal transport of acetylcholinesterase in the sciatic nerve of alloxan-diabetic rats: effect of ganglioside treatment.

The anterograde and retrograde axonal flow of acetylcholinesterase were studied in the sciatic nerve of alloxan-diabetic rats after five weeks of experimental diabetes. A slight reduction of the anterograde axonal flow of the enzyme was found in alloxan-diabetic compared to control rats. Sedimentation analysis revealed a major reduction of anterograde axonal flow of the light globular forms of the enzyme (G1 + G2), which are probably conveyed by slow transport. There was also a minor reduction of the anterograde flow of the globular form G4, while no modification of the axonal flow of the heavy asymmetric form A12 was found. Both G4 and A12 molecular forms are conveyed by fast axonal transport. In contrast, no abnormality of the retrograde axonal flow of acetylcholinesterase was observed. Ganglioside treatment antagonized the decline of the anterograde axonal flow of the enzyme in alloxan-diabetic rats. These results are consistent with the view that experimental diabetic neuropathy is associated with axonal transport defects, and suggest a protective effect of ganglioside treatment against neuronal damage(s) related to the diabetic syndrome.

Acetylcholinesterase↗
PubMed1991

Axonal transport of neuropeptide encoding mRNAs within the hypothalamo-hypophyseal tract of rats.

Hypothalamic vasopressin and oxytocin transcripts have been detected in the posterior pituitary suggesting either transcription of the respective genes in pituicytes or axonal mRNA transport from the hypothalamus to the nerve terminals of the posterior pituitary. The concept of axonal mRNA transport is supported firstly, by Northern blot and in situ hybridization analysis indicating that vasopressin and oxytocin mRNAs are also present in the neural stalk; secondly, by intron analysis and transcription run on experiments demonstrating the absence of primary vasopressin and oxytocin transcripts in non-neuronal cells of the posterior pituitary; thirdly, by embryonic developmental studies showing that appearance of vasopressin transcripts in the hypothalamus and the pituitary anlage is correlated. Furthermore, during axonal transport the respective mRNAs are subject to specific modification at the poly(A) tails.

Animals↗
PubMed1972

Intra-axonal transport and turnover of neurohypophysial hormones in the rat.

1. The specific radioactivities of isotopically pure oxytocin and vasopressin prepared from the neural lobe of the pituitary gland have been measured at various times after an intracisternal injection of [(3)H]tyrosine.2. Radioactive hormone began to appear in the gland 1-2 hr after the injection which suggests an intra-axonal transport velocity of 1-2 mm/hr.3. From 7 days onwards the specific radioactivity of each hormone declined exponentially with the same rate constant and a half-life of about 13 days.4. If the decline in radioactivity can be equated with the release of the hormones, the rates of secretion for the male rat in water balance are 18.7 m-u./day for oxytocin and 28.9 m-u./day for vasopressin.5. Calculation from the secretion rates gave steady-state plasma concentrations of about 3 muu./ml. for each hormone.

Animals↗
PubMed1987

Subsets of axonally transported and periaxonal polypeptides are released from regenerating nerve.

Using two-dimensional polyacrylamide gel electrophoresis to analyze proteins, we have found subsets of periaxonal and fast-transported axoplasmic proteins that are released in vitro from regenerating sciatic nerve into a surrounding bath. Of the fast-transported proteins that are released from nerve, there is a subset of at least five polypeptides that appears in greater relative abundance in the bath than in the nerve. Some of these released, fast-transported proteins are glycosylated. Several periaxonally synthesized polypeptides are released in significantly greater amounts from regenerating nerve, and of these polypeptides, two are released in greater amounts from nerve only at regions of regeneration or distal to regeneration. These released polypeptides do not represent the most abundant of the locally synthesized proteins. The released, fast-transported and periaxonal proteins may play a role in intercellular signaling or in modulation of the extracellular environment during nerve regeneration.

Animals↗