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PubMed1989

Axonal transport and distribution of endogenous calcitonin gene-related peptide in rat peripheral nerve.

Calcitonin gene-related peptide (CGRP) has been found in both sensory and motor neurons. It has been suggested that CGRP is transported from neuron cell bodies to their terminals, where it may act as an anterograde trophic factor. However, it is not known how fast CGRP is transported or whether CGRP found in the innervated target organ indeed originated in neural tissues. We have quantified endogenous CGRP in the rat peripheral nerve by a newly developed enzyme immunoassay. The CGRP immunoreactive material obtained from neural tissues coincided with synthetic rat CGRP in fractional distributions separated by gel filtration. After ligation of the sciatic nerve, tissue CGRP accumulated in the segment central to the ligature. The rate of anterograde transport of CGRP was about 1 mm/hr in both sensory and motor fibers. In the sciatic nerve, only a small fraction of CGRP measured was found to originate from the motor nerve fibers. This may be due in part to the disproportionately large number of sensory fibers in the sciatic nerve and in part to the possible presence of CGRP in sympathetic nerve fibers. The CGRP content in the dorsal root fibers was significantly lower than that in the peripheral processes of the sensory neurons. The CGRP content in the hind leg muscle was much higher than that expected from the amount of CGRP per nerve fiber in the sciatic nerve. Most CGRP in muscle disappeared following denervation. It is concluded that CGRP highly concentrated in nerve terminals is supplied by axonal transport from the neuron cell bodies.

Animals↗
PubMed1980

Axonal transport of the Ca2+-dependent protein modulator of 3':5'-cyclic-AMP phosphodiesterase in the rabbit visual system.

Water-soluble proteins were extracted from individual retinas, optic nerves, combined optic tracts and lateral geniculate bodies, and superior colliculi of rabbits at 1, 3, and 18 days after injection of [3H]leucine into the right eye. The Ca2+-dependent protein modulator of 3':5'-cyclic-AMP phosphodiesterase (calmodulin) was isolated from these samples by a two-step polyacrylamide gel electrophoresis procedure. An analysis of the radioactivity incorporated into the total soluble proteins and the calmodulin revealed that most of the calmodulin was axonally transported at a slow rate (2--4 mm/day) and represented about 0.45% of the total transported soluble protein.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1987

Axonal transport of dopamine D1 receptors in the rat brain.

Binding of a specific dopamine D1 receptor antagonist, 125I-SCH 23982, was measured in rat brain sections by quantitative autoradiography at various time intervals, following a knife cut through the striatonigral pathway. Twenty-four hours after lesioning, accumulations of D1 receptor binding sites were found in sagittal sections both rostral and caudal to the lesion site. No other regions studied (caudate-putamen, nucleus accumbens, olfactory tubercle, and substantia nigra pars reticulata) showed any change in D1 receptor binding 24 h after the lesion. In brain sections obtained 10 days after lesioning, only the substantia nigra pars reticulata had a significant decrease in D1 receptors ipsilateral to the lesion. These findings suggest the possibility of a presence of bidirectional axonal transport of D1 receptors in rat striatonigral pathway.

Animals↗
PubMed1982

Axonal transport of noradrenaline and noradrenergic transmission in rats with streptozotocin-induced diabetes.

The accumulation of noradrenaline in constricted sciatic nerves was measured in 6 month diabetic rats (streptozotocin 35 mg/kg) and 4 day diabetic rats (streptozotocin 70 mg/kg) together with two groups of age-matched control animals. There was no alteration in the amount of noradrenaline accumulated in the nerves of the diabetic animals when compared with the controls. The vasa deferentia of the long-term diabetic animals showed an impaired response to stimulation of their noradrenergic nerves and a hypersensitivity to exogenous noradrenaline. These vasa were not wasted and showed a normal contractility in response to potassium chloride. Vasa deferentia from the short-term diabetic rats showed no abnormalities of function. Vasa deferentia from all groups of rats were also examined at the ultrastructural level. Specimens from all the chronically diabetic animals contained many abnormal nerve terminals. These lesions were not seen in vasa from the short-term diabetic rats. Taken together these findings indicate that rats with chronic streptozotocin-induced diabetes exhibit pathological changes in the noradrenergic nerves supplying the vas deferens. These animals do not, however, show an impairment of the axonal transport of noradrenaline.

Animals↗
PubMed1999

Visualization of axonally transported horseradish peroxidase using enhanced immunocytochemical detection: a direct comparison with the tetramethylbenzidine method.

Visualization of the neuronal tract tracer horseradish peroxidase (HRP) is commonly achieved through the histochemical detection of its enzymatic activity using 3,3',5,5'-tetramethylbenzidine (TMB) as a chromogen. However, the TMB product is unstable and is incompatible with tissue processing methods that render the enzyme inactive, or when a combination of HRP tract tracing with neuronal phenotype identification is required. In this study we evaluated the applicability of the immunocytochemical detection method for horseradish peroxidase (HRP) visualization using an enhanced detection meth-od based on the Elite ABC peroxidase amplification protocol. The results provide evidence for the immunocytochemical visualization of both anterograde and transganglionic HRP transport in the rat spinal cord. This immunocytochemical method not only showed similar sensitivity to the TMB protocol in detecting HRP-labeled motor neuron perikarya but provided enhanced resolution in the identification of individual neuronal fibers compared to the TMB method. Immunodetection of the HRP tracer also allowed its co-localization with specific neuronal markers using double immunofluorescence techniques. These results offer the first demonstration that sensitive identification of axonally transported HRP can be achieved by immunocytochemistry and provides further support for its use in HRP tract tracing studies.

Animals↗
PubMed1986

Structure-linked latency of muscarinic receptors in axonal transport.

Muscarinic receptors that accumulated above a ligature in rat sciatic nerves were labelled in vitro under isotonic conditions with N-[3H]methylscopolamine. The addition of 0.005% of digitonin doubled the binding in proximal segments above and close to the ligature but not in the intermediary segments between two ligatures. Osmotic shock and freeze-thawing treatments also enhanced the binding. Digitonin did not affect the affinity of muscarinic receptors but revealed a greater number of sites by increasing the membrane permeability to the hydrophilic ligand. We conclude that presynaptic muscarinic receptors that undergo fast axonal transport in rat sciatic nerves exist under a latent form because they are associated with vesicles. This is the first demonstration of a structure-linked latency for receptors.

Animals↗
PubMed1999

A technique for 125I-labelling of neurotrophins and the use of retrograde axonal transport as a bioassay.

The protocol presented here details a technique which enables the neurotrophins nerve growth factor (NGF), neurotrophin-3 (NT-3), neurotrophin-4 (NT-4), and brain-derived neurotrophic factor (BDNF) to be labelled using 125I and the bioactivity of these labelled proteins determined using an in vivo bioassay. We have found that the simplest and most effective method for 125I-labelling of neurotrophic factors is the IODO-GEN method. Following the iodination of neurotrophins it must be established that the labelling procedure has not affected the biological activity of the protein. Traditional methods of assaying the bioactivity of 125I-labelled neurotrophins have several disadvantages and a much easier protocol to use is the retrograde axonal transport of these proteins in sympathetic and sensory neurons of adult mice. High specific activity 125I-labelled neurotrophin, to which known amounts of unlabelled neurotrophin are added, is injected into the right anterior eye chamber of adult mice under anaesthetic and the animals are left to recover for 16 h, after which they are sacrificed and both superior cervical ganglia (SCG) and trigeminal ganglia (TGG) are removed. The accumulated radioactivity in each ganglion is determined using a gamma-counter and the amount of neurotrophin transported is calculated by subtracting the counts obtained on the non-injected side from those present on the injected side. By comparing the amount of protein injected with the amount transported, the specific activity of the bioactive labelled neurotrophin can be determined.

Animals↗
PubMed2000

Overexpression of neurofilament subunit M accelerates axonal transport of neurofilaments.

Neurofilaments are composed of three polypeptide subunits (NF-H, NF-M and NF-L). They are the most abundant cytoskeletal element in large myelinated axons and play a central role in development of axonal caliber. To perform this role, neurofilaments are transported from their site of synthesis, the cell bodies, to the distal axons. Previous studies showed that overexpression of NF-M in transgenic mice led to accumulation of neurofilaments in neurons and a reduction in the number of neurofilaments in axons, suggesting that axonal transport of neurofilaments was slowed. To determine whether this was the case, we measured axonal transport velocities in the wild type and transgenic mice overexpressing NF-M by the classical pulse-labeling method using 35S-methionine. We found that neurofilament transport in peripheral motor axons can be described with a model consistent with two linear velocities. Contrary to expectations, both velocities were accelerated by overexpression of NF-M. These results suggest that subunit composition in neurofilaments play a regulatory role in neurofilament transport. In addition, these results show that there are regional differences in neurofilament transport along long axons and these differences may be the basis for selective regional accumulation of neurofilaments in various neurological disorders.

Animals↗
PubMed1986

Metabolic correlates and axonal transport in nerves during experimental diabetes.

The most recent biochemical abnormalities, particularly of peripheral nerve, found both in experimental and human diabetic diseases are briefly reviewed. Some of the metabolic features that have fairly well emerged are the following: 1. Correlations exist between reduced nerve myo-inositol level, increased activity of sorbitol pathway and nerve conduction velocity impairment. 2. 32P-labeling of polyphosphoinositides was considerably increased in diabetic rats as compared to controls, whereas inositol and glycerol uptake was decreased. Speculation on this phenomenon is reported. 3. Changes in bidirectional axonal transport of proteins within sciatic and optic nerve fibers were observed. These findings are related to the decrease of perikaryal protein synthesis. 4. Diabetic neuropathy seems to affect the elongation rate of regenerating neurites. 5. Many of the observed abnormalities are reversed by insulin treatment.

Animals↗
PubMed1985

Axonal transport of glycoconjugates in the rat visual system.

Long-Evans rats at 45 days of age were injected intraocularly with 25 mu Ci of [3H]glucosamine. Incorporation of radioactivity into retinal gangliosides, glycoproteins, and glycosaminoglycans (GAGs) was determined at various times after injection. Portions of all three classes of radioactive macromolecules were committed to rapid axonal transport in the retinal ganglion cells. With respect to gangliosides about 60% of those synthesized in the retina were retained in that structure, 30% were committed to transport to regions containing the nerve terminal structures (lateral geniculate body and superior colliculus), and about 10% were deposited in stationary structures of the axons (optic nerve and tract). With the exception of ganglioside GD3 the molecular species distribution of gangliosides synthesized in the retina matched that committed to transport. In contrast to gangliosides a smaller fraction of newly synthesized retinal glycoprotein (less than 12% of that synthesized in the retina) was committed to rapid transport to nerve ending regions and only about 0.5% was retained in the nerve and tract. The molecular-weight distribution of glycoproteins committed to transport differed quantitatively from that of the retina. With respect to GAGs an even smaller portion (1-2%) of that synthesized in the retina was committed to rapid transport; of this portion almost all was recovered in nerve terminal-containing structures. A constant proportion of each retinal GAG species was transported to the superior colliculus. We suggest that most of the retinal gangliosides are synthesized in neurons and preferentially in ganglion cells (possibly a function of the large surface membrane area supported by these cells). Subcellular fractionation experiments indicated that transported gangliosides, glycoproteins, and GAGs may be preferentially distributed into different subcellular compartments.

Animals↗
PubMed1985

A quantitative comparison of the efficiency of orthograde axonal transport and transsynaptic transport of iodinated (125I) wheat germ agglutinin (I-WGA) and horseradish peroxidase labeled I-WGA (I-WGA-HRP) in the rat visual system.

A quantitative study of the orthograde axonal transport of iodinated wheat germ agglutinin (I-WGA) and I-WGA conjugated to horseradish peroxidase (I-WGA-HRP) demonstrated labeling of both the lateral geniculate nucleus and the visual cortex following intraocular injections. I-WGA was 13 times more efficient than I-WGA-HRP as a marker of the primary projection from the retina to the geniculate and 3 times more efficient than I-WGA-HRP as a marker of the second order projection to the cortex.

Animals↗
PubMed1983

Mechanism of uptake and retrograde axonal transport of noradrenaline in sympathetic neurons in culture: reserpine-resistant large dense-core vesicles as transport vehicles.

The uptake and retrograde transport of noradrenaline (NA) within the axons of sympathetic neurons was investigated in an in vitro system. Dissociated neurons from the sympathetic ganglia of newborn rats were cultured for 3-6 wk in the absence of non-neuronal cells in a culture dish divided into three chambers. These allowed separate access to the axonal networks and to their cell bodies of origin. [3H]NA (0.5 X 10(-6) M), added to the axon chambers, was taken up by the desmethylimipramine- and cocaine-sensitive neuronal amine uptake mechanisms, and a substantial part was rapidly transported retrogradely along the axons to the nerve cell bodies. This transport was blocked by vinblastine or colchicine. In contrast with the storage of [3H]NA in the axonal varicosities, which was totally prevented by reserpine (a drug that selectively inactivates the uptake of NA into adrenergic storage vesicles), the retrograde transport of [3H]NA was only slightly diminished by reserpine pretreatment. Electron microscopic localization of the NA analogue 5-hydroxydopamine (5-OHDA) indicated that mainly large dense-core vesicles (700-1,200-A diam) are the transport compartment involved. Whereas the majority of small and large vesicles lost their amine dense-core and were resistant to this drug. It, therefore, seems that these vesicles maintained the amine uptake and storage mechanisms characteristic for adrenergic vesicles, but have lost the sensitivity of their amine carrier for reserpine. The retrograde transport of NA and 5-OHDA probably reflects the return of used synaptic vesicle membrane to the cell body in a form that is distinct from the membranous cisternae and prelysosomal structures involved in the retrograde axonal transport of extracellular tracers.

Animals↗
PubMed1984

Slow orthograde axonal transport of radiolabelled protein in sciatic motoneurones of rats with short-term experimental diabetes: effects of treatment with an aldose reductase inhibitor or myo-inositol.

This study examined the effect of streptozotocin diabetes of 5 weeks duration on the profile of slow orthogradely transported radiolabelled protein in rat sciatic motoneurones. The diabetic rats showed a retardation of the tail of the slow-component profile. This selective retardation was unaffected by treatment with an aldose reductase inhibitor, although this treatment reduced the accumulation of sorbitol and prevented the depletion of myo-inositol in the sciatic nerves of the treated diabetic rats. Other groups, treated with myo-inositol, had normal or elevated sciatic nerve myo-inositol levels in the presence of accumulated sorbitol. The axonal transport profiles from both control and diabetic myoinositol-treated groups gave normal tail velocities but an altered shape such that retardation of the tail of the profile may have been present in both. The study concludes that rats with 5 weeks streptozotocin diabetes show retardation of the velocity of the most slowly transported proteins in sciatic motoneurones, and that this defect is not linked to the polyol pathway.

Aldehyde Reductase↗
PubMed1985

Retrograde axonal transport of horseradish peroxidase by the rat sympathetic neurons.

Seven hours after injection of 5 mg of horseradish peroxidase (HRP) dissolved in 10 microliter normal saline into the anterior chamber of the eye directly into the iris of rats, sympathetic ganglion cells projecting to these regions were detected by numerous HRP-positive granules in their cytoplasm. By light microscopy, these HRP-labelled granules appeared as heavy brown granules, ultrastructurally they were demonstrated in the vesicles and tubules of smooth endoplasmic reticulum and in the lysosome-like dense bodies in the perikaryon of the neuron. The HRP reaction product was also detected in the vesicles and tubules of smooth endoplasmic reticulum within the axons in the superior cervical ganglion. The neurons projecting to the iris dilator muscles, which showed an HRP-positive reaction were scattered in the ganglion, and the rate of retrograde axonal transport of HRP was 4 mm/hour. The present study revealed that the greatest amount of strong reaction product was found in the neurons from animals 2 days after injection of HRP, and that HRP-labelled ganglion cells also have the capacity for dendritic transport of HRP. The HRP reaction product that disappeared from ganglion cells by 7 days post-injection of HRP was probably due to the lysosomal degradation.

Animals↗
PubMed2005

Axonal transport of rubidium and thallium in the olfactory nerve of mice.

Following intranasal administration of radioactive (86)Rb(+) and (201)Tl(+) in mice, we observed this direct transport via the olfactory nerve pathway. The (86)RbCl and (201)TlCl solutions were administered to two groups of mice, the unilateral intranasal and intravenous administration groups. After sacrifice, their heads were divided into the right and left side, which were then subdivided into seven parts; the nasal mucosa and brain regions were separated. Following the unilateral intranasal administration, uptake after 6 h by the olfactory bulb was significantly higher on the ipsilateral side ((86)Rb, 0.7 %dose; (201)Tl, 0.5 %dose) than on the contralateral side ((86)Rb, 0.08 %dose; (201)Tl, 0.15 %dose). Moreover, the (86)Rb and (201)Tl that accumulated in the olfactory bulb were gradually transported to other brain regions of the olfactory tract, the telencephalon and the diencephalon on the side corresponding to the nostril used for administration. Significant differences were observed between the right and left side of the brain regions 6 and 12 h after administration. Further, (201)Tl autoradiography clearly showed striped patterns of dense accumulation, localized in the region around the glomerular layer and granule cell layer of the olfactory bulb and around the olfactory cortex. These results provide clear evidence of axonal transport via the olfactory nerve pathway, from nasal cavity to the olfactory bulb, as well as to the olfactory cortex through the synaptic junctions. The olfactory transport of the (86)Rb(+) and (201)Tl(+) is thought to represent the behavior of K(+) in the olfactory system.

Animals↗
PubMed1992

Biosynthesis and axonal transport of multiple molluscan insulin-related peptides by the neuroendocrine light green cells of Lymnaea stagnalis.

The neuroendocrine light green cells (LGCs) control body growth and metabolism of the freshwater snail, Lymnaea stagnalis. These cells, located in the cerebral ganglia, use the peripheries of the median lip nerves (MLNs) as the neurohemal area. The LGCs express four members of a gene family encoding the precursors of distinct though related molluscan insulin-related peptides (MIPs). The molecular characterization and biosynthesis of MIPs have been investigated. MLN extracts were first size fractionated using gel permeation chromatography, and a major peak that coeluted with bovine insulin was further resolved using reverse phase high performance liquid chromatography. Amino acid composition analysis revealed that the four MIPs were present, as encoded by the MIP genes. Biosynthesis and axonal transport of the MIPs were studied in vitro with LGC systems in a series of pulse-chase incubations in combination with gel permeation chromatography analysis. During the pulse period of 20 min MIP precursors were formed in the LGC cell bodies. During the subsequent chase period these precursors were converted to MIPs and C peptides, which were transported to the LGC axon terminals in the MLNs for storage and release. The MIP precursors seem to be processed similarly to the insulin precursor in pancreatic islets.

Animals↗