title: B-50/GAP43 localization in polarized hippocampal neurons in vitro: an ultrastructural quantitative study.
abstract: Hippocampal pyramidal neurons cultured in vitro gradually develop morphologically and biochemically distinct axons and dendrites, resulting in functional neuronal polarization [Dotti C. G. et al. (1988) J. Neurosci. 8, 1454-1468]. We have studied the distribution of the growth-associated protein B-50 in hippocampal neurons of the rat at stage 3 of development by means of light and electron microscopic immunocytochemistry. Hippocampal neurons grown for two to three days in vitro were aldehyde fixed and immunolabelled using polyclonal rabbit antibodies to B-50 and goat anti-rabbit immunoglobulins tagged with 1 nm gold particles. In order to permit visualization by both light and electron microscopy, the gold probes were silver intensified. Light microscopy demonstrated the absence of B-50 immunostaining in living neurons and the presence after permeabilization by fixation and subsequent treatment of the neurons with sodium borohydride, indicating that B-50 is located intracellularly. Both immunofluorescence and immunogold-silver labelling revealed that B-50 immunoreactivity outlined all neurites of the morphologically polarized neurons. For quantitative electron microscopy, six morphologically polarized neurons (developmental stage 3) were carefully selected from immunolabelled Epon-embedded neurons and processed completely to ultrathin sections. In this way the ultrastructural localization of B-50 has been studied in the cell body, the neurites and their growth cones. For each sectioned neuron, the relative distribution of the gold-silver deposits (representing B-50) over the plasma membrane of various cellular compartments was quantitated. B-50 is located at the plasma membrane of the neuronal cell body and all neurites including their growth cones. The density of B-50 on the plasma membrane of growth cones is not different from that of the neuritic shaft. In addition, B-50 is present on the cytosolic side of the membrane of small electron-lucent vesicles (average diameter 102.7 +/- 2.5 nm) resembling transport vesicles. These vesicles are present in the cell body and the neurites. A two-fold concentration is found in the central region of the growth cones, suggesting a role of these vesicles in axonal transport, membrane insertion and (or) recycling. Since, at the onset of neuronal polarization, B-50 is present at the plasma membrane in all compartments of the hippocampal neuron, we suggest that at this stage of development B-50 does not participate directly in the processes leading to morphological polarization.(ABSTRACT TRUNCATED AT 400 WORDS)
authors.affiliation: Rudolf Magnus Institute, Division of Molecular Neurobiology, Utrecht, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Van Lookeren Campagne
authors.forename: C G
authors.initials: CG
authors.lastname: Dotti
authors.forename: E R
authors.initials: ER
authors.lastname: Jap Tjoen San
authors.forename: A J
authors.initials: AJ
authors.lastname: Verkleij
authors.forename: W H
authors.initials: WH
authors.lastname: Gispen
authors.forename: A B
authors.initials: AB
authors.lastname: Oestreicher
mesh_terms: D000818:Animals; D000906:Antibodies; D015153:Blotting, Western; D002462:Cell Membrane / Q000648:ultrastructure; D002478:Cells, Cultured; D003712:Dendrites / Q000648:ultrastructure; D005333:Fetus; D005455:Fluorescent Antibody Technique; D019922:GAP-43 Protein; D006624:Hippocampus / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure*; D008562:Membrane Glycoproteins / Q000032:analysis*; D016253:Microscopy, Immunoelectron; D009419:Nerve Tissue Proteins / Q000032:analysis*; D016501:Neurites / Q000648:ultrastructure; D016900:Neurofilament Proteins / Q000032:analysis; D009474:Neurons / Q000166:cytology / Q000502:physiology / Q000648:ultrastructure*; D051381:Rats; D017208:Rats, Wistar
chemical_list: D000906:Antibodies; D019922:GAP-43 Protein; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D016900:Neurofilament Proteins