Axoplasmic Transport in the Crayfish Nerve Cord (original) (raw)
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Two rates of fast axonal transport of [3H]glycoprotein in an identified invertebrate neuron
Brain Research, 1981
Recently, the kinetics of fast axonal transport of a single type of organelle, the serotonergic storage vesicle, was described in an identified axon of Aplysia using a pulsing technique combined with intracellular injection of [3H]serotonin. Here we extend the single axon studies by analyzing the movement of pulses of [aH]glycoprotein, following injection into the giant Aplysia cell, R2, of the amino sugar [aH]Nacetylgalactosamine. This glycoprotein precursor has been shown to label several organelles in this neuron. [aH]Glycoprotein is found to move in the axon of R2 at 2 rates of fast transport, 174 and 105 mm per day at room temperature. We suggest that the 2 rates reflect movements of 2 different types of organelle.
Axonal transport of the cytoplasmic matrix
Journal of Cell Biology, 1984
The Cytoplasmic Matrix in Neurons Is Specialized to Support the Elongate Shape of Neurites The cytoplasmic matrix is often highly specialized, making it possible to clearly relate particularaspects ofthe cytoplasmic matrix to the specialized functions of cells. For example, in striated muscle cells the contractile components of the cytoplasmic matrix dominate the cell structurally and functionally. Neurons are another example of cells in which specializations of structure and function can be clearly related to particular aspects of the cytoplasmic matrix (36, 37). The primary function of neurons is to convey information from one location in the organism to another. Pathways for information transfer in the nervous system are provided by specialized neuronal extensions, the axons and the dendrites. Axons, in particular, are specialized to convey information over very long distances, meters in some cases. Accordingly, in the axon the cytoplasmic matrix is specialized to generate and support the extremely elongate shape ofthe axon during development, regeneration, and maturity. To generate and maintain the great volume of cytoplasm within the axon, neurons must produce tremendous amounts of protein (32). Essentially all axonal proteins are synthesized in the neuron cell body and then conveyed into the axon by axonal transport, which provides a lifeline for the axon and its terminus (25, 36). Axonal transport is a process that is initiated when the axon first develops and that continues throughout the life of the neuron. To meet the needs of large animals, which require long axons, axonal transport has become one of the most highly developed mechanisms for the intracellular transport of materials in metazoan cells. Studies of Axonal Transport with Radioisotopes Reveal Processes at the Microscopic Level Although axonal transport occurs on a scale that is properly measured in micrometers, it is possible to study it by macroscopic methods in which the unit used for measurement is the millimeter (12). Axons are often grouped together in parallel bundles, and in long nerves a bundle of axons may extend for 10 cm or more. Axonal transport can be studied in these long axons by radioisotopic labeling methods. Standard radioistopic labeling methods can be employed to study the synthesis, transport, and metabolism of axonal 212s
Comparative Analysis of Rapidly Transported Axonal Proteins in Sensory Neurons of the Frog and Rat
Journal of Neurochemistry, 1980
3sS-labeled proteins carried by fast axonal transport in sciatic sensory axons of bullfrog and rat were separated electrophoretically on discontinuous polyacrylamide gradient slab gels. In contrast to the previously reported similarity in the electrophoretic profiles of rapidly transported proteins from functionally different neurons, we have found that there is very little correspondence in the profiles of these proteins in functionally similar neurons from two widely studied species. We also found very little correspondence between the two species in the profiles of locally synthesized sciatic nerve protein. The results demonstrate the difficulty inherent in comparing the electrophoretic profiles obtained using these two model systems for the study of rapidly transported axonal proteins. In particular, relationships between the major rapidly transported proteins in the two species could-not be analyzed with this technique. Key words: Axonal transport-Nerve-Gel electrophoresis-Sensory neuron-Protein synthesis. Neale J. H. et al. Comparative analysis of rapidly transported axonal proteins in sensory neurons of the frog and rat. ./. Neurochem. 35, 838-843 (1980).
Slab gel analysis of rapidly transported proteins in the isolated frog nervous system
Brain Research, 1977
Studies on intra-axonal transport of newly synthesized proteins in the nervous system have recently shifted from analysis of transport rate kinetics to a characterization of the proteins transported. Several recent studies have focussed on the molecular weight distribution of axonally transported protein utilizing gel electrophoresis techniques. This approach has effectively resolved 5 major proteins which are slowly transported in the nervous system 7. A more complex molecular weight distribution of rapidly transported protein has been found in a variety of neuronal systems%3,'~, 6, 8,10,t3,1~. Despite this heterogeneity, a substantially similar molecular weight distribution appears to exist among proteins rapidly transported in different neuronal systems z,3. The electrophoretic techniques employed in these studies, however, have lacked the resolving power to adequately discriminate individual rapidly transported species. We have reinvestigated the molecular weight distribution of rapidly transported proteins in functionally distinct neuronal systems using analytical slab gel electrophoresis, fluorography and optical scanning techniques. Our results support the proposal z,a that a qualitatively similar population of proteins is transported rapidly by different nerve cell types.
Vascularization of the crayfish abdominal nerve cord
Journal of Comparative Physiology ? A, 1981
The anatomy of the vascular supply to the abdominal nerve cord of the crayfish Procambarus clarkii was investigated by filling the arterial supply with ink injected into the heart. The abdominal nerve cord was found to receive all of its blood supply from the ventral artery, which parallels the ventral midline of the nerve cord. Extensive vascularization of the abdominal nerve cord was revealed, with more major arterial inputs entering the ganglia than the connectives ). Both the neuronal somata and the neuropil are heavily vascularized . The connectives contained little of the fine vascularization found within the ganglia, and the roots were lightly and variably vascularized .
Quantitative Analysis of Axonal Transport of Cytoskeletal Proteins in Chicken Oculomotor Nerve
Journal of Neurochemistry, 1982
We studied the axonal transport characteristics of major cytoskeletal proteins: tubulin, the 69,000 molecular weight protein of chicken neurofilaments, and actin. After intracerebral injection of [35S]methionine, we monitored the specific radioactivity of these proteins as they passed through a very short nerve segment of the chicken oculomotor nerve. Specific radioactivities were assessed by quantitative sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography. The transport patterns obtained for tubulin and the neurofilament protein were very similar, corresponding to transport rate ranges of 1-15 and 1-10 mndday, rcspectively. A narrower velocity range of 3 to 4.3 mrn/day was found for actin. Tubulin and the neurofiiament protein appeared to be largely dispersed during the course of their transit along the nerve. The radioactivity associated with the proteins studied persisted in the nerve segment for a long time after the bulk of the labeled molecules had swept down. Finally, none of these proteins was observed to be transported with the fast axonal transport.
Ventral Nerve Cord Transection in Crayfish: A Study of Functional Anatomy
Journal of Crustacean Biology, 1998
In crayfish, neural degeneration and regeneration in the ventral nerve cord occur in one of two ways, depending on the injured fiber. Most fibers degenerate in 1 or 2 weeks, while giant fibers degenerate slowly. Although degenerative changes are similar in both cases, they do not seem to correlate with motor behavioral alterations. The aim of this work was to characterize the time course of behavioral and anatomical changes following ventral nerve cord (VNC) transection in crayfish. The behavioral analysis was focused on the righting reflex whose changes were correlated with morphological studies performed on longitudinal sections and analyzed with transmission (TEM) and scanning electron microscope (SEM). Latency for the righting reflex increased after VNC transection and then slowly decreased toward control values. Anatomically, degenerative changes began to appear 10 days after VNC transection. Disruption in membrane arrangement, subcellular organelles, and a strong increase in glia appeared in small fibers. To a lesser degree, similar changes could be detected in medial and lateral giant fibers. Glial growth reconnected the transected VNC where regeneration signs were detected in small fibers. Both stumps were reconnected at least by glial tissue 90 days after transection, while giant axons were still degenerating; at this time, the righting reflex returned to control values.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
Protein maintenance and degradation are examined in the severed distal (anucleate) portions of crayfish medial giant axons (MGAs), which remain viable for over 7 months following axotomy. On polyacrylamide gels, the silver-stained protein banding pattern of anucleate MGAs severed from their cell bodies for up to 4 months remains remarkably similar to that of intact MGAs. At 7 months postseverance, some (but not all) proteins are decreased in anucleate MGAs compared to intact MGAs. To determine the half-life of axonally transported proteins, we radiolabeled MGA cell bodies and monitored the degradation of newly synthesized transported proteins. Assuming exponential decay, proteins in the fast component of axonal transport have an average half-life of 14 d in anucleate MGAs and proteins in the slow component have an average half-life of 17 d. Such half-lives are very unlikely to account for the ability of anucleate MGAs to survive for over 7 months after axotomy.
1987
Cytoskeletal protein transport and metabolism are studied in the somatic motor and parasympathetic axons of the chicken oculomotor system. Kinetic analyses of pulse-labeled proteins indicate that the neurofilaments are transported 2–3 times more rapidly in the somatic motor axons than in the parasympathetic axons. By contrast, the transport rates of the slow component b (SCb) proteins are very similar in these axons. The parasympathetic axons terminate in the ciliary ganglion, and radiolabeling curves from the ciliary ganglion can be used to study the kinetics of cytoskeletal protein removal from the terminals. The rate of removal directly determines the residence time of the cytoskeletal proteins in the ciliary ganglion, and the residence time directly affects the shape and amplitude of the transport curves of the ganglion. A computer model was used to analyze these transport curves and to determine the half-residence time of the cytoskeletal proteins in the terminal regions. From ...