Summary
Previous studies have demonstrated that astrocyte processes are responsible for a spontaneously occurring phagocytosis of boutons on cat spinal motoneurons during the second postnatal week. In the present investigation, the astrocytes and the astrocyte processes in contact with the motoneurons were studied qualitatively and quantitatively during the early postnatal period. It could be concluded that the cells responsible for the phagocytosis of boutons are immature astrocytes. These cells were present not only during the period of phagocytosis but also prior to this period. The type of process responsible for the phagocytosis was present not only during the period of phagocytosis but also prior to and after that period although the relative contribution of such processes to the glia-covered membrane area of the motoneurons was reduced in the older animals. On the basis of these results, the possible specificity of the immature astrocyte as the element responsible for the phagocytosis of boutons during normal development is discussed.
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Alksne, J.F., Blackstad, Th. W., Walberg, F., White, L.E., Jr.: Electron microscopy of axon degeneration: A valuable tool in experimental neuroanatomy. Ergebn. Anat. Entwickl.-Gesch. 39, (1966)
Berthold, C.-H.: A study on the fixation of large mature feline myelinated ventral lumbar spinal-root fibres. Acta Soc. Med. upsalien. 73, Suppl. 9, 1–36 (1968)
Blunt, M.J., Baldwin, F., Wendell-Smith, C.P.: Gliogenesis and myelination in kitten optic nerve. Z. Zellforsch. 124, 293–310 (1972)
Brody, I.: The keratinization of epidermal cells of normal guinea pig skin as revealed by electron microscopy. J. Ultrastruct. Res. 2, 482–511 (1959)
Conradi, S.: Ultrastructure and distribution of neuronal and glial elements on the motoneuron surface in the lumbosacral spinal cord of the adult cat. Acta physiol. scand., Suppl. 332, 5–48 (1969)
Conradi, S., Ronnevi, L.-O.: Spontaneous elimination of synapses on cat spinal motoneurons after birth: do half of the synapses on the cell bodies disappear? Brain Res. 92, 505–510 (1975)
Conradi, S., Ronnevi, L.-O.: Ultrastructure and synaptology of the initial axon segment of cat spinal motoneurons during early postnatal development. J. Neurocytol. 6, 195–210 (1977)
Fleischhauer, K.: Postnatale Entwicklung der Neuroglia. Acta neuropath. (Berl.), Suppl. IV, 20–32 (1968)
Griffin, R., Illis, L.S., Mitchell, J.: Identification of neuroglia by light and electronmicroscopy. Acta neuropath. 22, 7–12 (1972)
Maxwell, D.S., Kruger, L.: The fine structure of astrocytes and their response to focal injury produced by heavy ionizing particles. J. Cell Biol. 25, 141–157 (1965)
McMahan, U.J.: Fine structure of synapses in the dorsal nucleus of the lateral geniculate body of normal and blinded rats. Z. Zellforsch. 76, 116–146 (1967)
Meller, K., Breipohl, W., Glees, P.: The cytology of the developing molecular layer of mouse motor cortex. Z. Zellforsch. 86, 171–183 (1968)
Mellström, A., Skoglund, S.: Quantitative morphological changes in some spinal cord segments during postnatal development. A study in the cat. Acta physiol. scand., Suppl. 331 (1969)
Millonig, G.: Advantages of a phosphate buffer for OsO4 solutions in fixation. J. appl. Phys. 32, 1637 (1961)
Mori, S., Leblond, C.P.: Identification of microglia in light and electron microscopy. J. comp. Neurol. 135, 57–80 (1969)
Mugnaini, E., Walberg, F.: Ultrastructure of neuroglia. Ergebn. Anat. Entwickl.-Gesch. 37, 194–236 (1964)
Mugnaini, E., Walberg, F., Brodal, A.: Mode of termination of primary vestibular fibres in the lateral vestibular nucleus. An experimental electron microscopic study in the cat. Exp. Brain Res. 4, 187–211 (1967)
Phillips, D.E.: An electron microscopic study of macroglia and microglia in the lateral funiculus of the developing spinal cord in the fetal monkey. Z. Zellforsch. 140, 145–167 (1973)
Reynolds, E.S.: The use of lead citrate at high pH as an electron opaque stain in electron microscopy. J. Cell Biol. 17, 208–212 (1963)
Ronnevi, L.-O.: Spontaneous phagocytosis of boutons on spinal motoneurons during early postnatal development. An electron microscopical study in the cat. J. Neurocytol. 6, 487–504 (1977)
Ronnevi, L.-O., Conradi, S.: Ultrastructural evidence for spontaneous elimination of synaptic terminals on spinal motoneurons in the kitten. Brain Res. 80, 335–339 (1974)
Schultz, R.L.: Macroglial identification in electron micrographs. J. comp. Neurol. 122, 281–295 (1964)
Scott, P.P., da Silva, A.C., Lloyd-Jacob, M.A. The cat. In: The UFAW handbook on the care and management of laboratory animals (Worden, A.N. and Lane-Petter, W., eds.). London: UFAW 1957
Špaček, J.: Three dimensional reconstructions of astroglia and oligodendroglia cells. Z. Zellforsch. 112, 430–442 (1971)
Vaughn, J.E.: An electron microscopic analysis of gliogenesis in rat optic nerve. Z. Zellforsch. 94, 293–234 (1969)
Vaughn, J.E., Peters, A.: Electron microscopy of the early postnatal development of fibrous astrocytes. Amer. J. Anat. 121, 131–152 (1967)
Vaughn, J.E., Peters, A.: The morphology and development of neuroglial cells. In: Cellular aspects of neural growth and differentiation (Pease, D.C., ed.). Berkely-Los Angeles-London: University of California Press 1971
Watson, M.L.: Staining of tissue sections for electron microscopy with heavy metals. J. biophys. biochem. Cytol. 4, 475–485 (1958)
Wendell-Smith, C.P., Blunt, M.J., Baldwin, F.: The ultrastructural characterization of macroglial cell types. J. comp. Neurol. 127, 219–240 (1966)
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The author is indebted to Miss Maj Berghman, Mrs. Anna-Stina Höijer and Mrs. Lillebil Stuart for excellent technical assistance. This work was supported by grants from Karolinska Institutet and the Swedish Medical Research Council (proj. 2886).
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Ronnevi, LO. Origin of the glial processes responsible for the spontaneous postnatal phagocytosis of boutons on cat spinal motoneurons. Cell Tissue Res. 189, 203–217 (1978). https://doi.org/10.1007/BF00209270
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DOI: https://doi.org/10.1007/BF00209270