Skip to main content
PMC home page
The Journal of Cell Biology logoLink to The Journal of Cell Biology
. 1980 Nov 1;87(2):464–479. doi: 10.1083/jcb.87.2.464

Microtrabecular structure of the axoplasmic matrix: visualization of cross-linking structures and their distribution

PMCID: PMC2110738  PMID: 6159361

Abstract

Axoplasmic transport is a dramatic example of cytoplasmic motility. Constituents of axoplasm migrate as far as 400 mm/d or at approximately 5 micron/s. Thin-section studies have identified the major morphological elements within the axoplasm as being microtubules, neurofilaments (100-A filaments), an interconnected and elongated varicose component of smooth endoplasmic reticulum (SER), more dilated and vesicular organelles resembling portions of SER, multivesicular bodies, mitochondria, and, finally, a matrix of ground substance in which the tubules, filaments, and vesicles are suspended. In the ordinary thin-section image, the ground substance is comprised of wispy fragments which, in not being noticeably tied together, do not give the impression of representing more than a condensation of what might be a homogeneous solution of proteins. With the high-voltage microscope on thick (0.5-micron) sections, we have noticed, however, that the so- called wispy fragments are part of a three-dimensional lattice. We contend that this lattice is not an artifact of aldehyde fixation, and our contention is supported by its visability after rapid-freezing and freeze-substitution. This lattice or microtrabecular matrix of axoplasm was found to consist of an organized system of cross-bridges between microtubules, neurofilaments, cisternae of the SER, and the plasma membrane. We propose that formation and deformation of this system are involved in rapid axonal transport. To facilitate electron microscope visualization of the trabecular connections between elements of axoplasm, the following three techniques were used: first, the addition of tannic acid to the primary fixative, OsO4 postfixation, then en bloc staining in uranyl acetate for conventional transmission electron microscope (TEM); second, embedding tissue in polyethylene glycol for thin sectioning, dissolving out the embedding medium from the sections and blocks, critical-point-drying (J. J. Wolosewick, 1980, J. Cell Biol., 86:675-681.), and then observing the matrix-free sections with TEM or the blocks with a scanning electron microscope; and third, rapid freezing of fixed tissue followed by freeze-etching and rotary- shadowing with replicas observed by TEM. All of these procedures yielded images of cross-linking elements between neurofilaments and organelles of the axoplasm. These improvements in visualization should enable us to examine the distribution of trabecular links on motile axonal organelles.

Full Text

The Full Text of this article is available as a PDF (2.3 MB).

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Black M. M., Lasek R. J. Axonal transport of actin: slow component b is the principal source of actin for the axon. Brain Res. 1979 Aug 10;171(3):401–413. doi: 10.1016/0006-8993(79)91045-x. [DOI] [PubMed] [Google Scholar]
  2. Black M. M., Lasek R. J. Slow components of axonal transport: two cytoskeletal networks. J Cell Biol. 1980 Aug;86(2):616–623. doi: 10.1083/jcb.86.2.616. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Broadwell R. D., Oliver C., Brightman M. W. Neuronal transport of acid hydrolases and peroxidase within the lysosomal system or organelles: involvement of agranular reticulum-like cisterns. J Comp Neurol. 1980 Apr 1;190(3):519–532. doi: 10.1002/cne.901900308. [DOI] [PubMed] [Google Scholar]
  4. Burton P. R., Fernandez H. L. Delineation by lanthanum staining of filamentous elements associated with the surfaces of axonal microtubules. J Cell Sci. 1973 Mar;12(2):567–583. doi: 10.1242/jcs.12.2.567. [DOI] [PubMed] [Google Scholar]
  5. Byers H. R., Porter K. R. Transformations in the structure of the cytoplasmic ground substance in erythrophores during pigment aggregation and dispersion. I. A study using whole-cell preparations in stereo high voltage electron microscopy. J Cell Biol. 1977 Nov;75(2 Pt 1):541–558. doi: 10.1083/jcb.75.2.541. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Chalfie M., Thomson J. N. Organization of neuronal microtubules in the nematode Caenorhabditis elegans. J Cell Biol. 1979 Jul;82(1):278–289. doi: 10.1083/jcb.82.1.278. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Cooper P. D., Smith R. S. The movement of optically detectable organelles in myelinated axons of Xenopus laevis. J Physiol. 1974 Oct;242(1):77–97. doi: 10.1113/jphysiol.1974.sp010695. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Droz B., Rambourg A., Koenig H. L. The smooth endoplasmic reticulum: structure and role in the renewal of axonal membrane and synaptic vesicles by fast axonal transport. Brain Res. 1975 Jul 25;93(1):1–13. doi: 10.1016/0006-8993(75)90282-6. [DOI] [PubMed] [Google Scholar]
  9. Ellisman M. H., Brooke M. H., Kaiser K. K., Rash J. E. Appearance in slow muscule sarcolemma of specializations characteristic of fast muscle after reinnervation by a fast muscle nerve. Exp Neurol. 1978 Jan 1;58(1):59–67. doi: 10.1016/0014-4886(78)90120-6. [DOI] [PubMed] [Google Scholar]
  10. Ellisman M. H., Friedman P. L., Hamilton W. J. The localization of sodium and calcium to schwann cell paranodal loops at nodes of Ranvier and of calcium to compact myelin. J Neurocytol. 1980 Apr;9(2):185–205. doi: 10.1007/BF01205157. [DOI] [PubMed] [Google Scholar]
  11. Forman D. S., Padjen A. L., Siggins G. R. Axonal transport of organelles visualized by light microscopy: cinemicrographic and computer analysis. Brain Res. 1977 Nov 11;136(2):197–213. doi: 10.1016/0006-8993(77)90798-3. [DOI] [PubMed] [Google Scholar]
  12. Forman D. S., Padjen A. L., Siggins G. R. Effect of temperature on the rapid retrograde transport of microscopically visible intra-axonal organelles. Brain Res. 1977 Nov 11;136(2):215–226. doi: 10.1016/0006-8993(77)90799-5. [DOI] [PubMed] [Google Scholar]
  13. Henkart M. P., Reese T. S., Brinley F. J., Jr Endoplasmic reticulum sequesters calcium in the squid giant axon. Science. 1978 Dec 22;202(4374):1300–1303. doi: 10.1126/science.725607. [DOI] [PubMed] [Google Scholar]
  14. Heslop J. P. Axonal flow and fast transport in nerves. Adv Comp Physiol Biochem. 1975;6:75–163. doi: 10.1016/b978-0-12-011506-8.50008-1. [DOI] [PubMed] [Google Scholar]
  15. Heuser J. E., Salpeter S. R. Organization of acetylcholine receptors in quick-frozen, deep-etched, and rotary-replicated Torpedo postsynaptic membrane. J Cell Biol. 1979 Jul;82(1):150–173. doi: 10.1083/jcb.82.1.150. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Hoffman P. N., Lasek R. J. The slow component of axonal transport. Identification of major structural polypeptides of the axon and their generality among mammalian neurons. J Cell Biol. 1975 Aug;66(2):351–366. doi: 10.1083/jcb.66.2.351. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. Holtzman E. The origin and fate of secretory packages, especially synaptic vesicles. Neuroscience. 1977;2(3):327–355. doi: 10.1016/0306-4522(77)90001-x. [DOI] [PubMed] [Google Scholar]
  18. Karlsson J. O., Sjöstrand J. Transport of microtubular protein in axons of retinal ganglion cells. J Neurochem. 1971 Jun;18(6):975–982. doi: 10.1111/j.1471-4159.1971.tb12027.x. [DOI] [PubMed] [Google Scholar]
  19. Khan M. A., Ochs S. Magnesium or calcium activated ATPase in mammalian nerve. Brain Res. 1974 Dec 13;81(3):413–426. doi: 10.1016/0006-8993(74)90840-3. [DOI] [PubMed] [Google Scholar]
  20. Lane N. J., Treherne J. E. Lanthanum staining of neurotubules in axons from cockroach ganglia. J Cell Sci. 1970 Jul;7(1):217–231. doi: 10.1242/jcs.7.1.217. [DOI] [PubMed] [Google Scholar]
  21. Levin B. E. Axonal transport of [3H]proteins in a noradrenergic system of the rat brain. Brain Res. 1978 Jul 7;150(1):55–68. doi: 10.1016/0006-8993(78)90653-4. [DOI] [PubMed] [Google Scholar]
  22. Lin C. T., Dedman J. R., Brinkley B. R., Means A. R. Localization of calmodulin in rat cerebellum by immunoelectron microscopy. J Cell Biol. 1980 May;85(2):473–480. doi: 10.1083/jcb.85.2.473. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Metuzals J. Configuration of a filamentous network in the axoplasm of the squid (Loligo pealii L.) giant nerve fiber. J Cell Biol. 1969 Dec;43(3):480–505. doi: 10.1083/jcb.43.3.480. [DOI] [PMC free article] [PubMed] [Google Scholar]
  24. Ochs S., Worth R. M., Chan S. Y. Calcium requirement for axoplasmic transport in mammalian nerve. Nature. 1977 Dec 22;270(5639):748–750. doi: 10.1038/270748a0. [DOI] [PubMed] [Google Scholar]
  25. Pearse B. M. Coated vesicles from pig brain: purification and biochemical characterization. J Mol Biol. 1975 Sep 5;97(1):93–98. doi: 10.1016/s0022-2836(75)80024-6. [DOI] [PubMed] [Google Scholar]
  26. Peters A. The node of Ranvier in the central nervous system. Q J Exp Physiol Cogn Med Sci. 1966 Jul;51(3):229–236. doi: 10.1113/expphysiol.1966.sp001852. [DOI] [PubMed] [Google Scholar]
  27. Sannes P. L., Katsuyama T., Spicer S. S. Tannic acid-metal salt sequences for light and electron microscopic localization of complex carbohydrates. J Histochem Cytochem. 1978 Jan;26(1):55–61. doi: 10.1177/26.1.74385. [DOI] [PubMed] [Google Scholar]
  28. Simionescu N., Simionescu M. Galloylglucoses of low molecular weight as mordant in electron microscopy. I. Procedure, and evidence for mordanting effect. J Cell Biol. 1976 Sep;70(3):608–621. doi: 10.1083/jcb.70.3.608. [DOI] [PMC free article] [PubMed] [Google Scholar]
  29. Smith D. S., Järlfors U., Beránek R. The organization of synaptic axcplasm in the lamprey (petromyzon marinus) central nervous system. J Cell Biol. 1970 Aug;46(2):199–219. doi: 10.1083/jcb.46.2.199. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Smith D. S. On the significance of cross-bridges between microtubules and synaptic vesicles. Philos Trans R Soc Lond B Biol Sci. 1971 Jun 17;261(839):395–405. doi: 10.1098/rstb.1971.0074. [DOI] [PubMed] [Google Scholar]
  31. Smith R. S. The short term accumulation of axonally transported organelles in the region of localized lesions of single myelinated axons. J Neurocytol. 1980 Feb;9(1):39–65. doi: 10.1007/BF01205226. [DOI] [PubMed] [Google Scholar]
  32. Tani E., Ametani T. Substructure of microtubules in brain nerve cells as revealed by ruthenium red. J Cell Biol. 1970 Jul;46(1):159–165. doi: 10.1083/jcb.46.1.159. [DOI] [PMC free article] [PubMed] [Google Scholar]
  33. Tsukita S., Ishikawa H. The movement of membranous organelles in axons. Electron microscopic identification of anterogradely and retrogradely transported organelles. J Cell Biol. 1980 Mar;84(3):513–530. doi: 10.1083/jcb.84.3.513. [DOI] [PMC free article] [PubMed] [Google Scholar]
  34. Tsukita S., Ishikawa H. Three-dimensional distribution of smooth endoplasmic reticulum in myelinated axons. J Electron Microsc (Tokyo) 1976;25(3):141–149. [PubMed] [Google Scholar]
  35. VANHARREVELD A., CROWELL J. ELECTRON MICROSCOPY AFTER RAPID FREEZING ON A METAL SURFACE AND SUBSTITUTION FIXATION. Anat Rec. 1964 Jul;149:381–385. doi: 10.1002/ar.1091490307. [DOI] [PubMed] [Google Scholar]
  36. Van Harreveld A., Trubatch J., Steiner J. Rapid freezing and electron microscopy for the arrest of physiological processes. J Microsc. 1974 Mar;100(2):189–198. doi: 10.1111/j.1365-2818.1974.tb03928.x. [DOI] [PubMed] [Google Scholar]
  37. Webster R. E., Henderson D., Osborn M., Weber K. Three-dimensional electron microscopical visualization of the cytoskeleton of animal cells: immunoferritin identification of actin- and tubulin-containing structures. Proc Natl Acad Sci U S A. 1978 Nov;75(11):5511–5515. doi: 10.1073/pnas.75.11.5511. [DOI] [PMC free article] [PubMed] [Google Scholar]
  38. Willard M. B., Hulebak K. L. The intra-axonal transport of polypeptide H: evidence for a fifth (very slow) group of transported proteins in the retinal ganglion cells of the rabbit. Brain Res. 1977 Nov 11;136(2):289–306. doi: 10.1016/0006-8993(77)90804-6. [DOI] [PubMed] [Google Scholar]
  39. Willard M., Cowan W. M., Vagelos P. R. The polypeptide composition of intra-axonally transported proteins: evidence for four transport velocities. Proc Natl Acad Sci U S A. 1974 Jun;71(6):2183–2187. doi: 10.1073/pnas.71.6.2183. [DOI] [PMC free article] [PubMed] [Google Scholar]
  40. Wolosewick J. J., Porter K. R. Microtrabecular lattice of the cytoplasmic ground substance. Artifact or reality. J Cell Biol. 1979 Jul;82(1):114–139. doi: 10.1083/jcb.82.1.114. [DOI] [PMC free article] [PubMed] [Google Scholar]
  41. Wolosewick J. J. The application of polyethylene glycol (PEG) to electron microscopy. J Cell Biol. 1980 Aug;86(2):675–661. doi: 10.1083/jcb.86.2.675. [DOI] [PMC free article] [PubMed] [Google Scholar]
  42. Yamada K. M., Spooner B. S., Wessells N. K. Ultrastructure and function of growth cones and axons of cultured nerve cells. J Cell Biol. 1971 Jun;49(3):614–635. doi: 10.1083/jcb.49.3.614. [DOI] [PMC free article] [PubMed] [Google Scholar]

Articles from The Journal of Cell Biology are provided here courtesy of The Rockefeller University Press

RESOURCES