Resolution of intraneuronal and transynaptic migration of cobalt in the insect visual and central nervous systems
Conventional cobalt chloride procedures, using either diffusion into cut nerves or application via an electrode, can only incompletely resolve nerve cells for light microscopical observation. Enhanced resolution can be obtained by the addition of small quantities of serum albumin to the cobalt chloride. This allows sufficient contrast many nerve cells and enhances the details of thin fibres and their appendages. That this should be possible is of cardinal importance for combined electrophysiological and structural studies.
The present account also illustrates that in Dipterous insects there are certain conditions where cobalt chloride will move from one neuron into another. This movement is between functionally contiguous neurons and is here described from the visual system, with reference to electrophysiological studies that employ procion yellow identifications. Transynaptically filled neurons are only faintly resoluble in whole mounts. A block modification of the Timm's enhancement procedure is described which will reveal the finest details of neurons in thick sections and will also reveal nerve cells that have taken up minute quantities of CoCl2 after passage across at least two synapses. These observations are discussed with reference to their implications and applications for electrophysiological mappings of structural pathways.
KeywordsCobalt Nerve Cell CoCl2 Fine Detail Minute Quantity
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- Bennet, M.V.L.: Permeability and structure of electrotonic junctions and intracellular movements of tracers. In: Intracellular staining in neurobiology (S.B. Kater and C. Nicholson, eds.), pp. 115–134. Berlin-Heidelberg-New York: Springer 1973Google Scholar
- Dvorak, D.R. Bishop, L.G., Eckert, H.E.: On the identification of movement detectors in the fly optic lobe. J. comp. Physiol.100, 5–23 (1975)Google Scholar
- Gray, E.G.: Presynaptic microtubules and their association with synaptic vesicles. Proc. roy. Soc. B190, 369–372 (1975)Google Scholar
- Goodman, C.: Anatomy of Locust interneurons: constancy and variability. J. comp. Physiol.95, 185–201 (1974)Google Scholar
- Hausen, K.: Functional characterization and anatomical identification of motion sensitive neurons in the lobula plate of the blow flyCalliphora erythrocephala. Z. f. Naturforsch., in press (1976)Google Scholar
- Honegger, H.-W., Schürmann, F.W.: Cobalt sulphide staining of optic fibres in the brain of the cricket,Gryllus campestris. Cell Tiss. Res.159, 213–225 (1975)Google Scholar
- Karnovsky, M.J.: A formaldehyde-glutaraldehyde fixation of high osmolarity for use in electronmicroscopy. J. Cell Biol.27, 137A (1965)Google Scholar
- O'Shea, M.L, Rowell, C.H.F., Williams J.L.D.: The anatomy of a locust visual interneurone; the descending contralateral movement detector. J. exp. Biol.60, 1–12 (1974)Google Scholar
- Payton, B.W., Bennet, M.V.L., Pappas, G.D.: Permeability and structures of junctional membranes at an electrotonic synapse. Science166, 1641–1643 (1969)Google Scholar
- Pitman, R.M., Tweedle, C.D., Cohen, M.J.: Branching of central neurons: intracellular cobalt injections for light and electron microscopy. Science176, 412–414 (1972)Google Scholar
- Pitman, R.M., Tweedle, C.D., Cohen, M.J.: The dendritic geometry of an insect common inhibitory neuron. Brain Res.60, 465–470 (1973)Google Scholar
- Politoff, A., Pappas, G.D., Bennet, M.V.L.: Cobalt ions cross an electrotonic synapse if cytoplasmic concentration is low. Brain Res.76, 343–346 (1974)Google Scholar
- Ramon-Moliner, E.: A source of error in the study of Golgi-stained material. Arch. ital. Biol.105, 139–148 (1967)Google Scholar
- Strausfeld, N.J.: Atlas of an insect brain. Berlin-Heidelberg-New York: Springer 1976Google Scholar
- Székely, G.: The morphology of motorneurons and dorsal root fibres in the frog spinal cord. Brain Res.103, 275–290 (1976)Google Scholar
- Tyrer, N.M., Altman, J.S.: Motor and sensory flight neurons in a locust demonstrated using cobalt chloride. J. comp. Neurol.157, 117–138 (1974)Google Scholar
- Tyrer, N.M., Bell, E.M.: The intensification of cobalt filled neuron profiles using a modification of Timm's sulphide-silver method. Brain Res.73, 151–155 (1974)Google Scholar
- Zawarzin, A.: Zur Morphologie der Nervenzentren. Das Bauchmark der Insekten. Ein Beitrag zur vergleichenden Histologie. Z. wiss. Zool.122 323–424 (1924)Google Scholar