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PubMed1979

Interganglionic axonal transport of neural peptides within the nervous system of Aplysia.

Neurons of the circumesophageal ganglia of Aplysia synthesize 1--2000 dalton peptides and subject them to axonal transport in large quantities in the pleuro-visceral connective and pedal nerves. Most of the protein transported in the connective nerves accumulates in the abdominal ganglion, although some passes out its peripheral nerves. Autoradiography revealed no evidence for terminations of the transporting axons in possible neurohemal areas of this ganglion. It is suggested that these data reflect the existence of a pathway mediating the "directed delivery" of neural peptides in this nervous system.

Animals↗
PubMed1978

Regeneration of motor axons in the rat sciatic nerve studied by labeling with axonally transported radioactive proteins.

Labeling regenerating axons with axonally transported radioactive proteins provides information about the location of the entire range of axons from the fastest growing ones to those which are trapped in the scar. We have used this technique to study the regeneration of motor axons in the rat sciatic nerve after a crush lesion. From 2 to 14 days after the crush the lumbar spinal cord was exposed by laminectomy and multiple injections of [3H]proline were made stereotactically in the ventral horn. Twenty-four hours later the nerves were removed and the distribution of radioactivity along the nerve was measured by liquid scintillation counting. There was a peak of radioactivity in the regenerating axons distal to the crush due to an accumulation of label in the tips of these axons. After a delay of 3.2 +/- 0.2 (S.E.) days, this peak advanced down the nerve at a rate of 3.0 +/- 0.1 (S.E.) mm/day. The leading edge of this peak, which marks the location of the endings of the most rapidly growing labeled fibers, moved down the nerve at a rate of 4.4 +/- 0.2 mm/day after a delay of 2.1 +/- 0.2 days; this is the same time course as that of the most rapidly regenerating sensory axons in the rat sciatic nerve, measured by the pinch test. Another peak of radioactivity at the crush site, presumed to represent the ends of unregenerated axons or misdirected sprouts, declined rapidly during the first week, and more slowly thereafter.

Animals↗
PubMed1975

Mechanism of axonal transport: a proposed role for calcium ions.

In vitro axonal transport of tritiated protein decreased 40 to 60 percent when neuronal cell bodies were incubated in calcium-free medium, but was not affected when only nerve trunks were exposed to calcium-free conditions. In addition, calcium-45 was transported along axons at a rate similar to that of rapidly transported tritiated protein. These data are interpreted to suggest that calcium ions are involved in the initiation of axonal transport and in the coupling of transported proteins to the transport system.

Animals↗
PubMedDate not supplied

Acrylamide-induced alterations in axonal transport. Biochemical and autoradiographic studies.

Alterations in the axonal transport of proteins, glycoproteins, and gangliosides in sensory neurons of the sciatic nerve were examined in adult male rats exposed to acrylamide (40 mg ip/kg body wt/d for nine consecutive days). Twenty-four hours after the last dose, the L5 dorsal root ganglion (DRG) was injected with either [35S]methionine to label proteins or [3H]glucosamine to label glycoproteins and gangliosides. The downflow patterns of radioactivity for [35S]methionine-labeled proteins and [3H]glucosamine-labeled gangliosides were unaltered by acrylamide treatment. In contrast, the outflow pattern of labeled glycoproteins displayed a severely attenuated crest with no alteration in velocity, suggesting a preferential transfer with the unlabeled stationary components in the axolemma. Retrograde accumulation of transported glycoproteins and gangliosides was unaltered for at least 6 h; however, by 24 h, there was a 75% decrease in the amount of accumulated material. The accumulation of [35S]methionine-labeled proteins was not altered. Autoradiographic analysis revealed an acrylamide-induced paucity of transported radiolabeled glycoproteins selectively in myelinated axons with no effect on "nonmyelinated" axons. The pattern of transported proteins was similar in both control and acrylamide-exposed animals. These results suggest a preferential inhibition of glycosylation or axonal transport of glycoproteins in neurons bearing myelinated axons. More importantly, it suggests that interpretations of axonal transport data must be made with the consideration of alterations in selective nerve fibers and not with the tacit assumption that all fibers in the nerve population are equally affected.

Acrylamide↗
PubMed1979

Secretion of axonally transported neural peptides from the nervous system of Aplysia.

The possibility that proteins reaching the abdominal ganglion of Aplysia by axonal transport from the circumesophageal ganglia might be subject to secretion in that structure was examined. Transported labeled protein was found to be released from the abdominal ganglion; such release was enhanced by exposure to a high K+ medium and by electrical stimulation of the transporting axons. Stimulation of release was inhibited by lowering the Ca2+/Mg2+ ratio of the medium. The released material is predominantly of 1--2000 daltons in molecular weight and appears to have been derived from a group of transported peptides of about the same size. The possibility is raised that these data may reflect the existence of a peptidergic second-order neurosecretory pathway in this nervous system.

Animals↗
PubMed1992

Local modulation of neurofilament phosphorylation, axonal caliber, and slow axonal transport by myelinating Schwann cells.

Studies in Trembler and control mice demonstrated that myelinating Schwann cells exert a profound influence on axons. Extensive contacts between myelin and axons have been considered structural. However, demyelination decreases neurofilament phosphorylation, slow axonal transport, and axonal diameter, as well as significantly increasing neurofilament density. In control sciatic nerves with grafted Trembler nerve segments, these changes were spatially restricted: they were confined to axon segments without normal myelination. Adjacent regions of the same axons had normal diameters, neurofilament phosphorylation, cytoskeletal organization, and axonal transport rates. Close intercellular contacts between myelinating Schwann cells and axons modulate a kinase-phosphatase system acting on neurofilaments and possibly other substrates. Myelination by Schwann cells sculpts the axon-altering functional architecture, electrical properties, and neuronal morphologies.

Animals↗
PubMed1979

[Impairment of rapid axonal transport and concomitant anomaly of smooth endoplasmic reticulum in acrylamide induced neuropathy].

The axonal transport of proteins was studied by radioautography in preganglionic axons of ciliary ganglia in Leghorn chickens treated by acrylamide. The slow axonal transport of proteins was hardly affected. In contrast, the fast axonal transport was severely impaired. Indeed, radioactive proteins accumulated focally at the periphery of several preterminal axons in regions showing a local disorganization of the smooth endoplasmic reticulum which seemed to be one of the earliest changes induced by acrylamide.

Acrylamides↗
PubMedDate not supplied

[The demonstration of recurrent motor axon collaterals in the chick embryo by using horseradish peroxidase axonal transport].

Motoneurons were labelled by retrograde axonal transport of HRP applied to transected spinal nerves in 9-11-day chick embryos in the in vitro spinal cord preparation. Recurrent motor axon collaterals were revealed in 17 of 48 motor axons which could be followed in the edge regions of labelled motoneuronal pools. The results, coupled with author's earlier electrophysiological data, provide further evidence for the presence of the Renshaw inhibition in the avian spinal cord.

Animals↗
PubMed1992

Rapid axonal transport velocity is reduced in experimental ethylene oxide neuropathy.

Chronic exposure of rats to ethylene oxide (EO) causes distal axonal neuropathy of lumbosacral primary sensory neurons. To study the pathogenesis of this neuropathy, we measured rapid axonal transport in peripheral nerves. Rats were exposed for 6 h to 500 ppm EO in a chamber three times a wk for 15 wk. Rapid axonal transport and quantitative histological alterations of peripheral nerves were studied. After [35S]methionine injection into the dorsal root ganglion, the velocity of rapid anterograde axonal transport of radioisotope-labeled protein was measured. The velocity in the rats exposed to EO was 33% less than that in control rats exposed to filtered room air. However, histological differences were slight. Morphometric studies showed that in EO-exposed rats, only the distal portions of the sural nerve had significantly greater incidental degeneration of myelinated fibers than did controls. There were significantly fewer large myelinated fibers only in the distals peroneal nerve. Therefore, a decrease in the velocity of anterograde axonal transport, related to these slight histological abnormalities of the peripheral nerve, may play a causative role in the development of the distal axonal neuropathy owing to chronic EO exposure.

Animals↗
PubMed1975

Dynamic properties of axonal transport of proteins and glycoproteins: a study based on the effects of metaphase blocking drugs in the developing optic pathway of chick embryos.

Some properties of the axonal transport of proteins and glycoproteins along the optic pathway of chick embryos and newly hatched chicks were studied by labelling retinal ganglion cells with 3H-proline or 3H-fucose. A study of the effects of colchicine (COL) and vinblastine (VLB) on embryonic axonal transport was also carried out. Marked changes in the efficiency of axonal transport were found throughout development. In particular, the fraction of retinal ganglion cell proteins which is rapidly exported toward tectal terminals increases during embryonic life but steadily decreases after hatching. Glycoprotein transport behaves similarly except that its efficiency is relatively higher at stages when critical events of synaptic maturation in the tectum are reported to occur. Embryonic axonal transport is blocked by COL and VLB at very low intravitreal concentrations. Retinal protein synthesis and the morphology of ganglion cells are profoundly altered by the drugs: in general, COL and VLB effects were much more marked in embryonic than in mature neurons. An analysis of the time course of rapid transport along embryonic optic axons was carried out by reducing the efflux of labelled proteins from the eye by giving VLB intravitreally 2 h after the pulse. It revealed some peculiar features in the retino-tectal migration of glycoproteins and confirmed their progressive accumulation within terminals as previously described by radioautography. These results suggest that axonal transport of proteins during embryonic life undergoes changes in parallel with synaptic maturation. It may thus be considered as one of the factors controlling the genesis of neuronal networks.

Animals↗
PubMed1979

Axonal transport of actin: slow component b is the principal source of actin for the axon.

Axonally transported proteins were studied in guinea pig retinal ganglion cells using the standard radioisotopic labeling procedure. Two slowly moving groups of proteins were identified in guinea pig retinal ganglion cells. The more slowly moving group of proteins, designated slow component a (SCa) was transported at 0.2-0.5 mm/day. Five polypeptides contained greater than 75% of the total radioactivity transported in SCa. Two of these polypeptides correspond to the subunits of tubulin, while the other three correspond to the slow component triplet. The other slowly moving group of proteins, which is designated slow component b (SCb), was transported at approximately 2 mm/day. Twenty labeled polypeptides were identified in SCb. The major labeled polypeptides transported in SCb differ from those transported in SCa. One of the polypeptides transported in SCb co-migrates with skeletal muscle actin in SDS-polyacrylamide slab gels. This polypeptide behaved identically to skeletal muscle actin on DNaseI affinity columns. Since DNaseI is a highly specific affinity ligand for actin, we conclude that the labeled SCb polypeptide which comigrates with actin in SDS-gels is actin. Between 1.4 and 5.7% of the total radioactivity transported in SCb is attributable to action. Detailed comparison of the distribution of total radioactivity in the optic axons with the distribution of radioactive actin in the optic axons at post-injection times between 6 and 77 days showed that actin was transported specifically in SCb, and not in SCa. Furthermore, analyses of the proteins transported in the fast component of guinea pig retinal ganglion cells by DNaseI affinity chromatography failed to reveal an actin-like moiety. Slow component a, SCb and the fast component are the major components of axonal transport in guinea pig retinal ganglion cells. Thus, in these neurons, actin is transported principally and possibly only in SCb. Guinea pig retinal ganglion cell axons project principally to the lateral geniculate nucleus and superior colliculus. The fate of actin axonally transported to the region of the axon terminals was studied by determining the kinetics by which radioactivity associated with actin accumulates and then decays in the superior colliculus. The results of these studies indicate that labeled actin has a half-life in the superior colliculus of approximately 28 days.

Actins↗
PubMed1978

Changes in synaptic function induced by blockage of axonal transport in the rabbit optic pathway.

This study was undertaken to elucidate the physiological significance of material involved in the rapid axonal transport. The effects of colchicine-induced inhibition of axonal transport in the retinal ganglion cells on the electrophysiological properties of the retrobulbar visual pathways were investigated in Albino rabbits. An impaired signal transmission to the contralateral visual cortex, superior colliculus and lateral geniculate body following flash light stimulation as well as direct optic nerve stimulation appeared 4--6 days after an intravitreous injection of 10--25 microgram colchicine. It was concluded that inhibition of the fast axonal transport within the retinal ganglion cells interferes with transsynaptic signal transmission from optic nerve terminals in the subcortical nuclei. This indicates a functional relationship between material supplied via the rapid phase of axonal transport and an unimpaired transsynaptic signal transmission, previously not revealed in the central nervous system of mammals.

Animals↗
PubMed1992

Sabeluzole, a memory-enhancing molecule, increases fast axonal transport in neuronal cell cultures.

Morphological rearrangements, such as synapse number changes, have been observed in the adult mammalian brain after various experimental paradigms of learning and behavioral experience. The role of axonal transport in the physical translocation of material during this form of brain plasticity has not been fully appreciated. We show here by quantitative video microscopy that sabeluzole (R58735), a new memory-enhancing drug in humans, effectively increases fast axonal transport in rat neuronal cell cultures. Long-term incubation (24 hr) with sabeluzole in the concentration range between 0.1 and 1 microM increases both velocity and jump length of saltatory movements maximally by 20-30% in embryonic hippocampal neurons. Acute treatment only increases the velocity by 15-20%. Furthermore, the inhibition of axonal transport by 0.1 mM vanadate in N4 neuroblastoma cells is reversed by 1 microM sabeluzole. Observations on the kinesin-induced microtubule mobility in a reconstituted system show a 10% enhancement by sabeluzole at an optimal concentration of 2 microM, but no increase in kinesin ATPase activity. To our knowledge, this is the first pharmacological compound shown to increase fast axonal transport. The mechanism of fast axonal transport enhancement is discussed as a rationale for new therapeutic treatment in neuropathology.

Animals↗
PubMed1979

Axonal transport of adrenaline, noradrenaline and phenylethanolamine-N-methyl transferase (PNMT) in sympathetic neurons of the cod, Gadus morhua.

The axonal transport of adrenaline, noradrenaline and phenylethanolamine-N-methyl transferase (PNMT) has been studied in vivo in sympathetic neurons of the splanchnic nerve in the cod, Gadus morhua. Adrenaline and noradrenaline are transported at a mean axonal transport rate of 16 mm/day. After correction for a non-mobile fraction of adrenaline and noradrenaline, which does not contribute to the amine accumulation proximal to a ligature, a maximal rate of transport was calculated to about 45 mm/day for both amines. The increased level of catecholamines in front of a ligature could be depleted by reserpine treatment, which strongly suggests that both amines are stored in granules. PNMT is transported at a slow rate of 2 mm/day. The subcellular distribution of the cod PNMT was exclusively non-particular. The cod PNMT was further characterized by studying substrate specificity, temperature and pH optima. It is concluded that adrenaline and noradrenaline, stored in granules, are transported in a proximo-distal direction at a high rate compared to PNMT.

Animals↗
PubMed1977

Axonal transport of putrescine, spermidine and spermine in normal and regenerating goldfish optic nerves.

Radopactove putrescine, spermidine or spermine was injected into the right eye of normal goldfish and fish in which both optic nerves had been crushed 18 days earlier. Fish were sacrificed 0.25-21 days after injection. Trichloroacetic acid-soluble and -insoluble material was extracted from the right retina and both tecta and assayed for radioactivity (significant differences between left and right tecta suggesting axonal transport). The nature of the radioactivity in the TCA-soluble fraction was determined on an amino acid analyzer. Results indicate that putrescine is not axonally transported in intact goldfish optic nerves, but that during regeneration of the optic nerve large amounts of putrescine are axonally transported at rates similar to the fast component of protein transport. Spermidine appears to be axonally transported both in intact optic nerves and in regenerating optic nerves, and at an intermediate rate of transport; the amount of spermidine transported is significantly increased during regeneration. Spermine is also axonally transported in intact and regenerating nerves, at a rate similar to the rapid rate of protein transport. The amount of spermine transported appears to be slightly less in regenerating than in intact nerves during early stages of regeneration, but increases during later stages of nerve regeneration. The results suggest that putrescine and spermidine may be preferentially transported during nerve regeneration, while spermine and spermidine are transported extensively in intact nerves.

Animals↗
PubMed1978

Slow axonal transport of neurofilament proteins: impairment of beta,beta'-iminodipropionitrile administration.

beta,beta'-Iminodipropionitrile (IDPN) administration prevented normal slow axonal transport of [35S]methionine- or [3H]leucine-labeled proteins in rat sciatic motor axons. Ultrastructural and electrophoretic studies showed that the neurofilament triplet proteins in particular were retained within the initial 5 millimeters of the axons, resulting in neurofilament-filled axonal swellings. Fast anterograde and retrograde axonal transport were not affected. The IDPN thus selectively impaired slow axonal transport. The neurofibrillary pathology in this model is the result of the defective slow transport of neurofilaments.

Axonal Transport↗
PubMed1979

Axonal transport in early experimental diabetes.

In the present study fast axonal transport was examined in streptozotocin rats with 4 weeks duration in diabetes. Tritiated leucine and 14C-labelled glucosamine were injected into the fifth lumbar ganglion and TCA-soluble as well as insoluble activity were measured in segments of the sciatic nerve at various time intervals. (1) Time from injection until start of fast axonal transport was prolonged in diabetic rats whereas anterograde transport velocity was unchanged. (2) Incorporation of labelled leucine was reduced by 40%, whereas labelled glucosamine incorporation was unchanged. (3) Alterations observed in accumulations of labelled glycoconjugates proximal and distal to a collection crush might represent a decreased amount of retrograde transported material. The changes found in protein and glycoconjugate synthesis and transport could be related to the early reduction in axon calibre and conduction velocity in peripheral nerve of streptozotocin-diabetic rat.

Animals↗