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PubMed1980

The effect of chronic nicotine and withdrawal on intra-axonal transport of acetylcholine and related enzymes in sciatic nerve of the rat.

The content of acetylcholine (ACh) and activities of the cholinergic enzymes choline (acetyltransferase (CAT) and ACh-esterase (AChE) were studied in intact and crushed rat sciatic nerve after chronic nicotine administration and withdrawal 2 days before the final experiment. Nicotine was given in the drinking water during 8-10 weeks and the final dose reached was about 8 mg/kg/day i.e. equivalent to that of the heavy cigarette smoker. In the chronic nicotine group, ACh levels and AChE activity of uncrushed nerve were significantly decreased as compared to the controls. The accumulation of ACh and AChE proximal to a single crush was also somewhat decreased, but significant only for AChE at 18 hours postoperatively. After withdrawal of nicotine for 2 days the ACh content of both uncrushed and 12 hours crushed nerves were further decreased, while AChE was instead increased to control (uncrushed) or even supranormal (18-hour crush) levels.

Acetylcholine↗
PubMed1978

Further evidence for the involvement of microtubules in the proximo-distal intra-axonal transport of acetylcholine and related enzymes in rat sciatic nerve.

The two mitotic inhibitors colchicine (COL) and podofyllotoxin (POD) and their respective isomers, lumiCOL and picropodofyllin (picPOD) were tested for their effect on the intraaxonal transport (AXT) of acetylcholine (ACh) and the cholinergic enzymes in rat sciatic nerve. The mitotic inhibitors and their isomers were dissolved in saline+10% ethanol (COL and lumiCOL) or dimethylformamid (DMFA) (POD and picPOD) and injected (3-5microliter) subepineurally into the sciatic nerve. As controls the vehicle (saline +10% ethanol or DMFA) alone were injected into some rats. 2 h later a crush operation was performed 15 mm distal to the site of injection. The accumulation of ACh or the two enzymes, ACh-esterase (AChE) and cholineacetyltransferase (CAT), in the nerve segment proximal to the crush (12 h before death) was used as a measure of the AXT. COL and POD were very effective in inhibiting AXT of all 3 substances, while their isomers, lumiCOL and picPOD, were essentially without effect on AXT in equimolar concentrations (0.1 M). The effects on AXT of the 4 test substances thus appear related to their affinity to bind to tubulin, which is several orders of magnitude higher for COL and POD than for their isomers. The results further support the view that intact microtubules are essential for AXT of both membrane-bound (ACh E) and soluble (CAT) enzymes, as well as of ACh in rat motor nerves.

Acetylcholine↗
PubMed1998

The cortico-related zones of the rabbit claustrum-study of the claustrocortical connections based on the retrograde axonal transport of fluorescent tracers.

The claustrocortical connections in the rabbit were assessed for the first time by the method of axonal retrograde transport of two fluorescent tracers (Fast Blue and Diamidino Yellow). The material consisted of 23 adult New Zealand rabbits. Projection zones of spindle-like form, connected with the precentral, postcentral, temporal and occipital cortices have been delineated. They are organized topographically both in the anteroposterior and ventrodorsal direction. The precentral (motor) projection zone is localized in the anterodorsal part of the claustrum. It may be divided into two separate parts that project to the medial and lateral part of the precentral cortex. The large postcentral (somatosensory) zone occupies mainly the central part, whereas the temporal (auditory) and occipital (visual) zones are situated in the posteroventral part of the claustrum. The overlap of various claustral projection zones is differentiated, the largest being that of the somatosensory zones. In comparison to the results of study of claustral projection zones performed on other species, presumably on the rat and cat, its seems plausible to conclude that the extension of claustral projection zones and degree of their overlap in the rabbit represent an intermediate character.

Animals↗
PubMed1987

Axonal transport of receptors: characterization, role in receptor regulation and possible involvement in learning.

There is an increasing amount of evidence indicating that presynaptic receptors move antero- and retrogradely along axons of neurones through axoplasmic transport mechanisms. The main features of this dynamic process will be presented: it is bidirectional, fast, microtubule dependent and associated with vesicles which are presumably recycled in the cell body. Receptor axonal transport is impaired or enhanced in certain pathological conditions. The implications of this process and its possible involvement in long-term memory will be discussed.

Animals↗
PubMed1980

Fast axonal transport in the presence of high Ca2+: evidence that microtubules are not required.

Microtubules have long been associated with the mechanism of fast axoplasmic transport, although experimental evidence to support an involvement has been equivocal. Electron microscopic studies demonstrated that incubation of the axons of excised rat sciatic nerves in media containing 75 mM Ca2+ caused complete loss of microtubules within 6 hr. To evaluate the role of microtubules in fast anterograde transport, studies of transport in nerves exposed to these conditions were undertaken. Prior to measurement of axoplasmic transport, nerves ligated distal to the dorsal root ganglia were preincubated in vitro in 75 mM Ca2+ for 0-6 hr. Fast axonal transport was subsequently monitored by measuring the amount of trichloroacetic acid-insoluble radioactivity that accumulated at the ligature after incubation for 12-18 hr with L-[3H]proline. Nerves in which microtubules had been depolymerized by preincubation in high Ca2+ maintained control levels of transport. We conclude that intact microtubules are not required for fast anterograde axoplasmic transport.

Animals↗
PubMedDate not supplied

Aluminum inhibits neurofilament assembly, cytoskeletal incorporation, and axonal transport. Dynamic nature of aluminum-induced perikaryal neurofilament accumulations as revealed by subunit turnover.

The mechanism by which aluminum induces formation of perikaryal neurofilament (NF) inclusions remains unclear. Aluminum treatment inhibits: 1. The incorporation of newly synthesized NF subunits into Triton-insoluble cytoskeleton of axonal neurites; 2. Their degradation and dephosphorylation; 3. Their translocation into axonal neurites. It also fosters the accumulation of phosphorylated NFs within perikarya. In the present study, we addressed the relationship among these effects. Aluminum reduced the assembly of newly synthesized NF subunits into NFs. During examination of those subunits that did assemble in the presence of aluminum, it was revealed that aluminum also interfered with transport of newly assembled NFs into axonal neurites. Similarly, a delay in axonal transport of microinjected biotinylated NF-H was observed in aluminum-treated cells. Aluminum also inhibited the incorporation of newly synthesized and microinjected subunits into the Triton-insoluble cytoskeleton within both perikarya and neurites. Once incorporated into Triton-insoluble cytoskeletons, however, biotinylated subunits were retained within perikarya of aluminum-treated cells to a greater extent than within untreated cells. Notably, these subunits were depleted in the presence and absence of aluminum within 48 h, despite the persistence of the aluminum-induced perikaryal accumulation itself, suggesting that individual NF subunits undergo turnover even within aluminum-induced perikaryal accumulations. These findings demonstrate that aluminum interferes with multiple aspects of neurofilament dynamics and furthermore leaves open the possibility that aluminum-induced perikaryal NF whorls may not represent permanent structures, but rather may require continued recruitment of cytoskeletal constituents.

Aluminum↗
PubMed1983

N-[acetyl-3H] wheat germ agglutinin: anatomical and biochemical studies of a sensitive bidirectionally transported axonal tracer.

Both retrograde and anterograde autoradiographic axonal labeling were associated with the appropriate pathways after injections of N-[acetyl-3H] wheat germ agglutinin within numerous structures in the central nervous system of mice. Sections processed for light microscopic autoradiography following the placement of injections mainly within the neocortex, neostriatum, or cerebellum have revealed patterns of bidirectional axonal labeling in various thalamic, monoaminergic, deep cerebellar and precerebellar nuclei that were similar to that seen after similarly placed horseradish peroxidase injections. Small injections of N-[acetyl-3H] wheat germ agglutinin, by way of an extremely limited extracellular spread of the tracer, yield large amounts of autoradiographic retrograde and anterograde axonal labeling. High specific activities, in addition to the sensitivity displayed by this tracer, allow the use of relatively short autoradiographic exposure times that still lead to an extensive signal over labeled neurons. Biochemical analysis of this radiolabeled derivative of wheat germ agglutinin was carried out using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Results from Coomassie blue staining and fluorography of the gels have revealed that affinity-purified N-[acetyl-3H] wheat germ agglutinin migrates predominantly as a monomer (molecular weight 18,000 +/- 1000 daltons) as well as a dimer (35,100 +/- 1000 daltons) when compared with native wheat germ agglutinin and molecular weight standards. Gels run on the native preparation, prior to derivatization, radiolabeling and affinity purification, in addition to containing species that co-migrate with the monomeric and dimeric forms of the tagged lectin, also reveal several other bands with molecular weights above and below those values for the monomer and dimer. When scintillation counting was performed on fresh gels of N-[acetyl-3H] wheat germ agglutinin, the predominant species was again found to be the monomeric and dimeric forms; however, small peaks were also present around 12,000 daltons as well as above 43,000 daltons. Coomassie blue staining and fluorography never revealed banding below 18,000 daltons, though some trace of labeling was present, but not in the form of discrete bands, above 36,000 daltons. The presence, albeit small in comparison to the monomer and dimer, of these other higher and lower molecular weight species might in part result from fragments produced by proteolytic digestion of intact subunits of N-[acetyl-3H] wheat germ agglutinin that may or may not possess intact binding sites.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1999

Kinesin-II is required for axonal transport of choline acetyltransferase in Drosophila.

KLP64D and KLP68D are members of the kinesin-II family of proteins in Drosophila. Immunostaining for KLP68D and ribonucleic acid in situ hybridization for KLP64D demonstrated their preferential expression in cholinergic neurons. KLP68D was also found to accumulate in cholinergic neurons in axonal obstructions caused by the loss of kinesin light chain. Mutations in the KLP64D gene cause uncoordinated sluggish movement and death, and reduce transport of choline acetyltransferase from cell bodies to the synapse. The inviability of KLP64D mutations can be rescued by expression of mammalian KIF3A. Together, these data suggest that kinesin-II is required for the axonal transport of a soluble enzyme, choline acetyltransferase, in a specific subset of neurons in Drosophila. Furthermore, the data lead to the conclusion that the cargo transport requirements of different classes of neurons may lead to upregulation of specific pathways of axonal transport.

Amino Acid Sequence↗
PubMed1978

New technique for measuring dynamic axonal transport and its application to temperature effects.

A new technique was devised for the dynamic detection of the axoplasmic transport of beta-radioactively labeled materials in which a semiconductor radiation detector was used as the beta-ray counter. The detector element is a silicon p-n junction diode and has a diameter of 2.0 mm. With this detector, the beta-radioactive distribution of axoplasmic transport could be measured in a axon maintained physiologically without cutting nerves. This method makes possible determination of the transport rate using one bundle of peripheral nerves. The rate in the bullfrog was 6.4 mm per hour at 24.0 degrees D. Temperature effects on the bullfrog axoplasmic transport were also observed at different temperatures, ranging from 5.0 to 24.0 degrees C. At these temperatures the rate increased as an exponential function of temperature from 1.1 to 6.4 mm per hour. Within this temperature range, the Q10 is 2.5 and an Arrhenius plot of the natural logarithm of velocity versus the reciprocal of absolute temperature yielded an apparent activation energy of 14.8 Kcal. this technique offers great advantages in permitting direct study of the axoplasmic flow of the axon in a physiological condition.

Animals↗