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Early neuron differentiation in the mouse olfactory bulb. II. Electron microscopy
Author(s) -
Hinds James W.
Publication year - 1972
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901460208
Subject(s) - olfactory bulb , biology , axon , anatomy , microtubule , olfactory nerve , golgi apparatus , cytoarchitecture , endoplasmic reticulum , neuroscience , microbiology and biotechnology , central nervous system
Differentiating mitral cells were followed in serial section analysis of mouse embryos from day 12 of gestation (E12) to E14. Animals at E11 and E15 were also examined. Olfactory nerve axons reach the presumptive olfactory bulb at E12 and many penetrate deeply into the intermediate (mantle) layer at this time. The first identified young neurons (postmitotic neuroblasts) were also seen at E12. Many had a tangential orientation, and they occurred only in the region where olfactory nerve axons were present. Olfactory nerve axons (and also mitral cell axons formed later) are characterized by numerous longitudinallyoriented microtubules and an extensive system of transversely and longitudinallyorinted cisternae of smooth endoplasmic reticulum (SER). Near the growing tips of olfactory nerve axons, the microtubules disappear and the SER becomes more extensive and irregular. The four stages of early mitral cell differentiation determined in the companion paper (Hinds, '72) were confirmed by electron microscopic analysis. In the earliest cells of the primitive radial stage few organelles occur in the perikaryon, but in later cells of this stage and in cells of the pre‐axonic tangential stage a Golgi complex and a pair of centrioles occurs on one side of the nucleus at the base of the largest tangential process, thus determining a cell polarity within the tangential plane. This initial polarity at E12 seems to be random and unrelated to the polarity attained when axon outgrowth occurs at E13 and E14, suggesting a re‐orientation prior to axon outgrowth. The growing tips of primitive tangential processes were studied and compared with those of growing primitive radial processes and growing axons.