The olfactory epithelium of vertebrates is known to contain a neurogenic matrix which serves for the replacement of the olfactory receptor neurons under normal or experimental circumstances. This matrix offers a unique opportunity for the study of neural proliferation and differentiation by providing a large homogenous population of developing neurons of a simple bipolar form. The present experiments investigate the ability of the neurogenic matrix to produce young neurons when removed from the nasal cavity and transplanted to the anterior chamber of the eye, and examine the differentiation of these neurons when deprived of both stimulation and appropriate target tissue. Transplants of postnatal olfactory mucosa and of the embryonic nasal pit have been observed with light and electron microscopy. / The matrix continues its production of new neurons for at least four months in oculo. The neurons extend their dendrites and axons, but only occasional receptors exhibiting fully differentiated characteristics (by ultrastructural and cytochemical criteria) are observed in both types of graft. The epithelium contained 50 to 60% of the normal complement of receptor elements, and twice as many mitoses and degenerations as found under normal circumstances. The scarcity of fully differentiated receptors and the frequent occurrence of degenerations indicates that the mature forms are short lived in the transplants, degenerating shortly after maturation. / Olfactory pit transplants consistently produced a convergence of olfactory axons from distant regions of the grafts, which was not observed in olfactory mucosa transplants. This indicates that the guidance mechanism directing the olfactory nerve to its normal target is intrinsic to the olfactory pit. Thus, attraction of the olfactory nerve to the brain by diffusable substances, or guidance along 'substrate pathways' between the nose and brain are not involved in this system. / After converging to form large aggregate bundles, the axons in pit grafts broke up to form a fiber plexus, resembling the fiber layer of the olfactory bulb, which contained isolated olfactory glomeruli. The formation of these glomeruli in the absence of target neurons proves that the signal initiating termination is a property of the olfactory axons, and does not rely on contact with postsynaptic dendrites. / Source: Dissertation Abstracts International, Volume: 47-07, Section: B, page: 2778. / Thesis (Ph.D.)--The Florida State University, 1986.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_75892 |
| Contributors | HECKROTH, JOHN A., Florida State University |
| Source Sets | Florida State University |
| Detected Language | English |
| Type | Text |
| Format | 165 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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