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At least 1,099 records · Page 61Linked to original sources
PubMed1989

Metalloendoprotease inhibitors block fast axonal transport.

Metalloendoprotease activity that was sensitive to the metal chelator 1,10-phenanthroline and to synthetic dipeptide substrates of the enzyme was detected in homogenates of dorsal root ganglia (DRG) and spinal nerve from the bullfrog. Exposure of an intact in vitro preparation of DRG and spinal nerves to 1,10-phenanthroline led to a dose-dependent depression in the accumulation of fast-transported 3H-labeled protein proximal to a nerve ligature. In nonligated preparations, the chelator treatment reduced the amount of transported protein entering the nerve; no marked effect on the transport rate was observed. Exposure of a desheathed region of spinal nerve to 1,10-phenanthroline, while DRG were maintained in control medium, resulted in a slight depression of fast transport. This effect was not dose dependent over the range that produced a dose response when both DRG and spinal nerve were exposed to the drug. Treatment of DRG and spinal nerve with the metalloendoprotease substrate analogues carbobenzoxy (CBZ)-Ser-Leu-amide or CBZ-Gly-Leu-amide inhibited fast axonal transport, whereas treatment with CBZ-Gly-Gly-amide, which is not a substrate, had no detectable effect on transport. Selective exposure of desheathed nerve trunk to CBZ-Ser-Leu-amide inhibited fast transport, but the effect was less marked than when DRG and nerve trunk were treated. Although previous studies have focused on the role of metalloendoprotease activity in exocytosis, the present data suggest that the enzyme may also be involved in earlier stages of intracellular transport.

Animals↗
PubMedDate not supplied

Diminished axonal transport of glycoproteins in the senescent rat brain.

At various time intervals (10, 15, 20, 25, 30 min) after injection of 3H-fucose into the medial septal nucleus of young adult (3 months old) and senescent (25 months old) Fischer-344 rats, the specific activities of trichloroacetic acid-phosphotungstic acid (TCA-PTA) soluble and insoluble fractions were determined in the medial area of the septum and in three successive rostro-caudal sections of the hippocampal formation containing mainly the dentate gyrus, but also its hilus with fields CA4 and CA3c of the hippocampus. The rate of 3H-fucose incorporation into glycoproteins of the septum did not differ in young adult and senescent rats. Part of the TCA-PTA soluble and insoluble radioactive material was transported through the septo-hippocampal pathway to the dentate gyrus. This transport was inhibited by the injection of colchicine into the septum prior to 3H-fucose injection and was completely blocked by electrolytic lesion of the medial septal nucleus. The arrival time and the amount of the TCA-PTA soluble radioactive material transported to the dentate gyrus did not differ in young adult and senescent rats. However, the TCA-PTA insoluble labelled glycoprotein was transported to the dentate gyrus in a significantly smaller amount and during a longer period of time in the senescent animals. This age-related change may reflect a reduction in amount and/or in rate of axonal transport of glycoproteins in the septo-hippocampal pathway of senescent rats.

Aging↗
PubMed2001

Direct visualization of the movement of the monomeric axonal transport motor UNC-104 along neuronal processes in living Caenorhabditis elegans.

The formation and function of axons depends on the microtubule-based transport of cellular components from their sites of synthesis in the neuronal cell body to their sites of utilization at the axon terminus. To directly visualize this axonal transport in a living organism, we constructed transgenic lines of Caenorhabditis elegans that express green fluorescent protein fused to the monomeric synaptic vesicle transport motor, UNC-104. This UNC-104:: GFP construct rescued the Unc-104 mutant phenotype and was expressed throughout the nervous system. Using time-lapse confocal fluorescence microscopy, we were able to visualize fluorescent motor proteins moving in both directions along neuronal processes, some of which were identified definitely as axons and others as dendrites. Using kymograph analysis, we followed the movement of >900 particles. Most of them moved in one direction, but not necessarily at the same velocity. Ten percent of the observed particles reversed direction of movement during the period of observation, and 10% exhibited periods of movement interspersed with pauses. During episodes of persistent movement, particles moved at an average velocity of 1.02 microm/sec, which is close to the in vitro velocity of microtubule gliding driven by purified monomeric kinesin at high motor density. To our knowledge, this is the first direct visualization and analysis of the movement of specifically labeled microtubule motor proteins along axons in vivo.

Animals↗
PubMed1983

Selective inhibition of retrograde axonal transport by erythro-9-[3-(2-hydroxynonyl)]adenine.

Retrograde transport of microscopically visible organelles in isolated lobster axons was selectively inhibited by erythro-9-[3-(2-hydroxynonyl)]adenine (EHNA), with little or no effect on anterograde transport. The retrograde velocity was reduced both in living axons and in permeabilized axons in which movement was reactivated with exogenous ATP. This is the first report of an agent that selectively inhibits axonal transport in one direction.

Adenine↗
PubMed1974

Cellular specificity of serotonin storage and axonal transport in identified neurones of Aplysia californica.

1. [(3)H]D,L-5-hydroxytryptophan ([(3)H]5HTP) was injected under pressure into cell bodies of identified cholinergic and serotonergic neurones in the central nervous system of the marine mollusc, Aplysia californica.2. Both serotonergic and cholinergic neurones converted [(3)H]5HTP to [(3)H]5-hydroxytryptamine ([(3)H]5HT).3. The fate of [(3)H]5HT in the two types of neurones differed. In serotonergic cells, 5HT was present primarily in particulate form; the transmitter readily moved from cell bodies into nerves by selective transport. In contrast, 5HT remained free in the cytoplasm of the cholinergic neurone, and was not transported from the cell body.4. Treatment of Aplysia with reserpine decreased the proportion of [(3)H]5HT associated with particulate material, and also decreased the amount of [(3)H]5HT recovered.5. Serotonergic neurones possess specific mechanisms for the storage and axonal transport of 5HT which are absent in cholinergic cells.

5-Hydroxytryptophan↗
PubMed2006

Axonal transport and Alzheimer's disease.

In contrast to most eukaryotic cells, neurons possess long, highly branched processes called axons and dendrites. In large mammals, such as humans, some axons reach lengths of over 1 m. These lengths pose a major challenge to the movement of proteins, vesicles, and organelles between presynaptic sites and cell bodies. To overcome this challenge axons and dendrites rely upon specialized transport machinery consisting of cytoskeletal motor proteins generating directed movements along cytoskeletal tracks. Not only are these transport systems crucial to maintain neuronal viability and differentiation, but considerable experimental evidence suggests that failure of axonal transport may play a role in the development or progression of neurological diseases such as Alzheimer's disease.

Aging↗
PubMedDate not supplied

Organization and slow axonal transport of cytoskeletal proteins under normal and regenerating conditions.

The organization of the axonal cytoskeleton was investigated by analyzing the solubility and transport profile of the major cytoskeletal proteins in motor axons of the rat sciatic nerve under normal and regenerating conditions. When extracted with the Triton-containing buffer at low temperature, 50% of tubulin and 30% of actin were recovered in the insoluble form resistant to further depolymerizing treatments. Most of this cold-insoluble form was transported in slow component a (SCa), the slower of the two subcomponents of slow axonal transport, whereas the cold-soluble form showed a biphasic distribution between SCa and SCb (slow component b). Changes in slow transport during regeneration were studied by injuring the nerve either prior to (experiment I) or after (experiment II) radioactive labeling. In experiment I where the transport of proteins synthesized in response to injury was examined, selective acceleration of SCb was detected together with an increase in the relative proportion of this component. In experiment II where the response of the preexisting cytoskeleton was examined, a shift from SCa to SCb of the cold-soluble form was observed. The differential distribution and response of the two forms of tubulin and actin suggest that the cold-soluble form may be more directly involved in axonal transport.

Actins↗
PubMed1985

Retrograde axonal transport of cadmium in the rat hypoglossal nerve.

A small volume of radioactively labelled cadmium was injected into the tongue of rats. Two weeks later, the rats were killed and the lower brainstem with the hypoglossal nuclei was dissected out and sectioned in a cryostat. Autoradiography of freeze-dried sections showed accumulation of cadmium in both hypoglossal nuclei. When unilateral nerve section was performed prior to the injection, only the contralateral nucleus was labelled. The results are interpreted as strong evidence for retrograde axonal transport of cadmium in the hypoglossal nerve.

Animals↗
PubMed1991

Axonal transport and release of transferrin in nerves of regenerating amphibian limbs.

Transferrin, a plasma protein required for proliferation of normal and malignant cells, is abundant in peripheral nerves of birds and mammals and becomes more concentrated in this tissue during nerve regeneration. We are testing the hypothesis that this factor is involved in the growth-promoting effect of nerves during the early, avascular phase of amphibian limb regeneration. A sensitive enzyme-linked immunosorbent assay for axolotl transferrin was developed and used to determine whether this protein meets certain criteria expected of the trophic factor(s) from nerves. During limb regeneration adult sciatic nerves greatly increased their content of transferrin, which immunohistochemistry revealed was distributed in both axons and Schwann cells. Using the double ligature method with sciatic nerves in vivo, it was determined that transferrin is carried by fast anterograde axonal transport at all stages of limb regeneration. An approach based on multicompartment organ culture demonstrated that fast-transported transferrin was secreted in physiologically significant amounts at distal ends of regenerating axons. Finally, the concentration of transferrin in the distal region of larval axolotl limb stumps was found to decrease directly and rapidly in response to axotomy. Since transferrin is important for both axonal regeneration and cell cycling, the present data have significance for various aspects of nerve's trophic activity during limb regeneration.

Ambystoma↗