摘要:

AbstractEarlier studies in our laboratory have demonstrated that a discrete region of the anterior part of the neonatal subventricular zone (SVZa) contains exclusively neuronal progenitor cells. The descendants of the SVZa progenitor cells are destined for the granule cell and glomerular layers of the olfactory bulb, where they differentiate into granule and periglomerular cells, the interneurons of the olfactory bulb, respectively. In the present set of experiments we examined the neurotransmitter phenotype of the SVZa‐derived cells. In order to label SVZa‐derived cells, the cell proliferation marker bromodeoxyuridine (BrdU) was injected into the SVZa of postnatal day 2 (P2) rats. After 3 weeks, by which time most of the SVZ‐aderived cells have migrated to their final destination in the bulb, the animals were perfused and their brains processed for immunohistochemistry. To identify the neurotransmitter phenotype of the SVZa‐derived cells, sagittal sections of the forebrain, including the olfactory bulb, were double‐labeled with an antibody to BrdU in conjunction with an antibody to γ‐amino‐butyric acid (GABA) or tyrosine hydroxylase (TH), the rate limiting enzyme in the synthesis of dopamine. Using simultaneous indirect immunofluorescence to detect the presence of single‐ and double‐labeled cells, we found that 59% and 51% of the BrdU‐positive cells were immunoreactive for GABA in the granule cell and glomerular layers, respectively. In addition, 10% of the BrdU‐positive periglomerular cells were immunoreactive for TH. The presence of double‐labeled (BrdU‐positive/GABA‐positive and BrdU‐positive/TH‐positive) cells in the olfactory bulb, demonstrates that the SVZa is a source of the GABAergic and dopaminergic interneurons of the olfactory bulb during postnatal development.

ISSN:0736-5748    

DOI:10.1016/S0736-5748(96)00066-4

出版商:Wiley    

年代:1997

数据来源: WILEY

摘要:

AbstractWe determined the time of origin of neurons in the olfactory bulb of the South African clawed frog,Xenopus laevis. Tritiated thymidine injections were administered to frog embryos and tadpoles from gastrulation (stage 11/12) through metamorphosis (stage 65), paraffin sections were processed for autoradiography, and the distribution of heavily and lightly labeled cells was examined. In the ventral olfactory bulb, we observed that the mitral cells were born as early as stage 11/12 and continued to be generated through the end of metamorphosis. Interneurons (periglomerular and granule cells) were not born in the ventral bulb until stage 41, and birth of these cells also continued through metamorphosis. Labeled cells were observed in the accessory olfactory bulb, beginning at stage 41. In contrast, the cells of the dorsal olfactory bulb were not born until the onset of metamorphosis (stage 54); at this stage in the dorsal bulb, the genesis of mitral cells, interneurons, and glial cells completely overlapped. The results indicate that olfactory axon innervation is not necessary to induce early stages of neurogenesis in the ventral olfactory bulb. On the other hand, the results on the dorsal olfactory bulb are consistent with the hypothesis that innervation from new or transformed sensory neurons in the principal cavity induces neurogenesis in the dorsal bulb.

ISSN:0736-5748    

DOI:10.1016/S0736-5748(96)00054-8

出版商:Wiley    

年代:1997

数据来源: WILEY

摘要:

AbstractWhen the olfactory nerve is injured in adult mammals, the axons grow across the PNS‐CNS transitional zone and re‐innervate their synaptic contacts within the olfactory bulb. Some years ago, Liesi [Liesi P. (1985) Laminin‐immunoreactive glia distinguish regenerative adult CNS systems from non‐regenerative ones.EMBO J.4, 2505–2511] reported the presence of laminin in non‐basal lamina locations within the nerve fiber layer (NFL) of the olfactory bulb of adult rats and suggested that this molecule may facilitate olfactory axonal growth into and within the CNS. The purpose of the present study was to compare the expression of laminin, fibronectin, and collagen type IV in: (a) the NFL of developing and adult rats; and (b) the NFL rostral and caudal to a stab wound in the olfactory bulb of adult rats. Numerous punctate deposits of immunofluorescence were seen in the NFL of the E18 (Theiler stage 23) bulb when antisera to laminin, fibronectin or collagen type IV were used. There was a dramatic drop‐off in staining at the border between the NFL and the presumptive glomerular layer. The staining pattern was similar in the newborn bulb, although the immunofluorescence was not as strong. In the unoperated adult rats, only laminin was present consistently as punctate deposits within the NFL, whereas all three antisera stained numerous punctate deposits within the NFL during the first week after a stab wound. Although there was a partial recapitulation of the expression pattern for laminin, fibronectin and collagen type IV in the lesioned adult NFL, it never reached the extent found in the E18 or newborn bulbs and its expression returned to normal levels prior to the re‐innervation of the bulb during the second and third weeks after surgery. The results suggest that the molecular requirements for the successful growth of olfactory axons may differ during development to growth in adult animals.

ISSN:0736-5748    

DOI:10.1016/S0736-5748(96)00042-1

出版商:Wiley    

年代:1997

数据来源: WILEY

摘要:

AbstractIn an effort to identify and understand the laminar disorganization that occurs in the transplanted (TX) rat olfactory bulb (OB), we examined the development of fiber systems within these TX OBs. One antibody for olfactory marker protein (OMP) was used to identify axons of mature olfactory receptor neurons (ONs) and a second antibody, for a growth‐associated protein (GAP‐43), provided a marker for all extending or immature fibers. Donor OBs were taken from fetuses on embryonic days 14 or 15 (sperm‐positive day is zero) and TX directly into the cavity produced by removal of an OB in 1‐day‐old hosts of the same strain. After survival times of I and 2 weeks and at maturity, adjacent 8 pm paraffin sections from the TX material were examined for OMP and GAP‐43 reactivity.Fiber bundles, reactive for OMP, were found within the TX by 1 week post‐TX, indicating rapid reinnervation of the donor OB by ONs. The appearance of OMP reactivity gradually shifted from tightly packed, well‐defined fiber bundles at 1 week post‐TX to a diffuse reticulated pattern of individual fibers emerging from bundles at maturity. The OMP‐reactive fiber bundles of the TX OB also contained GAP‐43‐reactive fibers, but GAP‐43 reactivity also extended to other (OMP‐negative) bundles and fields. Reactivity for GAP‐43 in the TX OB was nearly ubiquitous at 2 weeks post‐TX but, as development progressed (in both the TX and normal OB), such reactivity gradually decreased. Thus, while maturation in sensory afferent fiber systems in the TX OB may be delayed, it eventually follows a pattern similar to that in the normal OB, suggesting that factors other than the timing of fiber extension may be responsible for the laminar disorganization of the TX OB.

ISSN:0736-5748    

DOI:10.1016/S0736-5748(96)00043-3

出版商:Wiley    

年代:1997

数据来源: WILEY

摘要:

AbstractOdorant deprivation, produced by unilateral naris closure, profoundly reduces tyrosine hydroxylase (TH) expression within intrinsic olfactory bulb dopamine neurons. The TH gene contains an AP‐1 site, which interacts with the product of the immediate early gene, c‐fos. c‐Fos exhibits activity dependent regulation in the CNS. The hypothesis that odorant stimulation and deprivation might modify c‐fos expression in TH neurons was tested in adult CD‐1 mice, subjected to unilateral naris closure. After 2 months, naris closed and control mice were exposed to either clean air for 60 min or clean air for 60 min followed by 30 min of alternating exposure to 10% isoamyl acetate (1 min) and air (4 min). A parallel reduction occurred in TH and fos expression (both c‐fos mRNA and fos‐like immunoreactivity) in the glomerular layer of the odorant‐deprived olfactory bulb. Odor stimulation induced a short‐lived increase in c‐fos mRNA and fos‐like immunoreactivity in olfactory bulbs contralateral to naris closure. The increase in fos expression was region‐specific in the glomerular layer but more diffuse in mitral and granule cell layers. In olfactory bulbs ipsilateral to naris closure, odor stimulation also induced c‐fos mRNA expression in the mitral and granule cell layers and sparsely within limited periglomerular regions. Odor induced expression in mitral and granule cell layers may represent increased centrifugal activity acting on as yet unknown genes. These results suggest a correlation between c‐fos mRNA expression and increased neuronal activity in the olfactory bulb which, in turn, acts to regulate TH expression in periglomerular neurons.

ISSN:0736-5748    

DOI:10.1016/S0736-5748(96)00044-5

出版商:Wiley    

年代:1997

数据来源: WILEY

摘要:

AbstractDuring metamorphic development, the arrival at the olfactory (antennal) lobe of olfactory receptor axons initiates the process of glomerulus formation. The glomeruli are discrete spheroidal regions of neuropil that are the sites of synaptic interactions among receptor neurons and their target antennal‐lobe neurons. The process of glomerulus formation begins as groups of receptor axons form protoglomeruli. These dense clusters of terminal branches mostly are discrete entities from the time they can be recognized, although a few branches from neighboring protoglomeruli overlap laterally. A previous study by Schweitzeret al.[Schweitzer E. S., Sanes J. R. and Hildebrand J. G. (1976) Ontogeny of electroantennogram responses in the moth,Manduca sexta. J. Insect Physiol.22, 955–960] has shown that odor‐induced activity in the receptor neurons can be detected first in recordings from the axons in the antennal nerve only in the last few days of metamorphic development and thus could not influence the process of glomerulus formation. In this study, we have tested directly the possibility that an earlier presence of spontaneous activity in either the receptor axons or the antennal‐lobe neurons could affect the process. Tetrodotoxin, a Na+‐channel blocker, was injected into the hemolymph prior to the onset of glomerulus formation to block any spontaneous Na+‐dependent activity. Subsequent intracellular recordings from antennal‐lobe neurons revealed no spike activity. Comparison with vehicle‐injected control animals at stages during and after glomerulus formation revealed no differences in the localization of receptor‐axon terminal branches in the glomeruli, in the border of glial cells that forms around each glomerulus, or in the morphology of the tufted glomerular arbors of one of the antennal‐lobe neurons. We conclude that: (1) the process of glomerulus formation is largely independent of activity; and (2) glomeruli as modular units of the CNS more closely resemble cortical barrels than cortical columns, both in their ontogeny and in the lack of an obvious effect of activity on the morphology of the neurons arborizing within them.

ISSN:0736-5748    

DOI:10.1016/S0736-5748(96)00045-7

出版商:Wiley    

年代:1997

数据来源: WILEY

摘要:

AbstractIn order to identify molecules involved in the development of the honeybee olfactory pathway, hybridoma technology has been used. Among different cell lines, A2B7 has been selected. It produces a specific antibody for a surface glycoprotein of 91 kDa. This protein is mainly expressed by both the antennal receptor cells and mushroom body neurons. Based on (i) the spatio‐temporal pattern of expression during pupal development; (ii) the cell surface location of the antigen; and (iii) the partial molecular characterization of the antigen, a putative role for this protein in axonal fasciculation and guidance is discussed.

ISSN:0736-5748    

DOI:10.1016/S0736-5748(96)00065-2

出版商:Wiley    

年代:1997

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/S0736-5748(96)90007-6

出版商:Wiley    

年代:2005

数据来源: WILEY

ISSN:0736-5748    

DOI:10.1016/S0736-5748(96)90008-8

出版商:Wiley    

年代:2005

数据来源: WILEY