摘要:

AbstractThe events that take place along the potential route of distal auditory axons (future vestibular component) prior to and during their outgrowth were examined morphologically using timed mouse embryos. During embry‐onic (E) day 9.5 a discrete zone of cell death appears in the rostrolateral wall of the otic cup. Necrosis is accompanied by outward migration of epitheloid cells from the same region of the otic wall. Temporally and spatially corre‐lated with these two events is the widening of extracellular spaces between otic neuroepithelial cells and the breakdown of basement membrane. During E 10.5 migrating epitheloid cells condense to form a funnel‐shaped configu‐ration. This cellular “funnel” begins narrowly at the dorsorostrolateral wall of the otocyst and broadens as it reaches the auditory ganglion. During E 11.5 through E 12.5, “pioneer” distal auditory axons take a circuitous route and ascend from the auditory ganglion to enter the otocyst. Axons extend toward the otocyst moving along cells of the “funnel,” maintaining an orien‐tation similar to that of the cells that compose it. Axon growth cones enter the otocyst at sites devoid of basement membrane and invade the wall of the otocyst moving tangentially along radially arranged cells that bridge the otocyst and the “funnel.”These observations demonstrate that a preformed, funnel‐shaped tissue exists along the future route of the auditory fibers. We suggest that the “fun‐nel” may influence the growth and directionality of distal auditory axons as they extend from the auditory ganglion to the wall of the otocyst. At the otic wall, the transition provided by “bridge” epitheloid cells, together with the absence of basement membrane at specific sites of the otic wall, provide the auditor

ISSN:0092-7317    

DOI:10.1002/cne.902150402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractContinuous replacement of sensory neurons is a normal process in the olfactory system of adult vertebrates. The capacity for replacement following experimentally induced degeneration of sensory neurons makes this system ideal for the study of the dynamics of neural populations. A quantitative analysis was made to determine the time course and degree of cell replace‐ment in the olfactory epithelium following unilateral bulbectomy in adult hamsters. Histological measurements of number of cells and epithelial thickness were made for up to 194 days postoperatively. Results for each experimental animal were expressed as a percentage of the contralateral control side. There was an immediate degeneration of cells, the number decreasing to 39% by day 4. During days 4–15 new growth resulted in an increase in cell number, which was maintained at a level of 60–70% through day 194. Epithelial thickness decreased to 60–70% during the degeneration period, but there was no recovery during subsequent days 4–194. Analysis of epithelial cells by cell type (supporting, receptor, and basal cells) showed that changes in cell numbers were limited to the neural cell populations (receptor and basal). This study confirms that olfactory sensory neurons are capable of replacement following degeneration in spite of the absence of normal target tissue. However, the observed recovery does not reach control levels and the functional capacity of replacement neurons requires furt

ISSN:0092-7317    

DOI:10.1002/cne.902150403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractBy application of a modified glyoxylic acid‐paraformaldehyde histoflu‐orescence technique, catecholamine perikarya, varicosities, and pathways were delineated within the brainstem of kittens that were either untreated, pretreated pharmacologically, or injected intracerebrally with 6‐OHDA. Three principal catecholamine cell groups were identified within the medulla and pons: the dorsomedial medullary cell group, the dorsolateral pontine cell group, and a ventrolateral cell group extending from the medulla into the pons. Induced axonal accumulation of catecholamines with intracerebral 6‐6‐OHDA injections revealed a majorlongitudinal catecholamine bundlewhich courses in a dorsolateral position through the entire brainstem tegmentum. The dorsomedial medullary and dorsolateral pontine cell groups contribute ascending and descending fibers to this bundle. Axons of the ventrolateral pontomedullary cells also feed into the bundle at successive levels through radially coursing transverse fibers. Via this major dorsolateral conduit and its ventrally and medially coursing tributaries, catecholamine fibers and terminals are distributed to multiple nuclei through the brainstem. The regions of the catecholamine cell groups and the serotonin raphe nuclei all receive a dense catecholamine innervation. Varicosities are also dense in the visceral cranial nerve nuclei, moderately dense in most somatic spinal and cranial nerve motor nuclei, and moderate to light in sensory cranial nerve and relay nuclei. The lateral and ventromedial reticular formation are moderately innervated by varicose catecholamine fibers that traverse these regions. The longitudinal catecholamine bundle continues caudally into the lateral funiculus to descend into and innervate the spinal cord. Rostrally it continues into the tegmental fascicles of the midbrain to ascend into and innervate the diencephalon and there join the medial forebrain bundle to ascend into the telencephalon. Thus, the catecholamine neurons utilize this dorsolateral longitudinal bundle to distribute collaterals to mul‐tiple bulbar nuclei and to travel beyond the brainstem to innervate the spinal cord an

ISSN:0092-7317    

DOI:10.1002/cne.902150404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractHorseradish peroxidase (HRP) applied to the transected mandibular division of the trigeminal (V) ganglion was transported anterogradely to pri‐mary afferent terminal zones in the dorsal and dorsomedial trigeminal brain‐stem nuclear complex (TBNC). Primary V afferents of ganglionic origin were also visible in the ipsilateral cerebellar cortex (crus I and II, paraflocculus) and the dentate, cuneate, solitary, supratrigeminal, and dorsal motor vagal nuclei, parvicellular reticular formation, area postrema and C1–C6 dorsal horn, laminae I–V. Contralateral subnucleus caudalis and C1–C2 dorsal horn were also innervated by primary afferents which crossed in the spinal gray to terminate medially, primarily in laminae I, II, and V. Almost all of these projections were also labeled in various combinations when HRP was applied to individual sensory branches of the mandibular nerve: lingual, infe‐rior alveolar, mylohyoid, and auriculotemporal. Transganglionic transport of HRP in the latter four cases revealed strong evidence for mtradivisional somatotopy among the four branches in both the ganglion and TBNC. Cell bodies innervating posterior and/or lateral portions of the head and face (i.e., auriculotemporal and mylohyoid) were found with greater frequency in dor‐sal mandibular ganglion regions, while somata supplying more rostral oral‐perioral regions (i.e., lingual and inferior alveolar) were predominant ventrally. Components of the mandibular projection to the TBNC were organized topographically in at least some portion of all of its three dimen‐sions. Subnuclear preferences were not clear‐cut; all four nerves innervated at least some portion of principalis, oralis, interpolaris, and caudalis, save for mylohyoid, which did not project to caudalis. Lingual fibers were most prominent in principalis and oralis, occupied medial portions of the mandib‐ular projection to the TBNC, and descended only to rostral caudalis, most notably laminae I‐III. Inferior alveolar afferents were ubiquitous in the mandibular component of the TBNC and C1–C2, save for its far lateral bor‐der. Mylohyoid terminals were sparse, most prominent in interpolaris, and occupied only dorsolateral TBNC regions and laminae III and IV of C1–C3. The auriculotemporal innervation of the mandibular TBNC was heaviest in interpolaris and was restricted to mostly ventrolateral regions. Its primary focus, however, was laminae III and IV of C1–C4. The clinical implications of this topographical organization are discussed, particularly with respect to the rostrocaudal intradivisional lamination in caudal

ISSN:0092-7317    

DOI:10.1002/cne.902150405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe overall distribution of substance P‐like immunoreactivity (SPI) in the wall of the cerebral arteries and their origins were investigated in the guinea pig by using whole‐mounts.Two types of SPI fibers were seen: one forming dense fiber bands and lo‐cated among the periadventitial nerves, and the other forming a meshwork. The SPI fibers located in the periadventitial nerves often leave these nerves to form a meshwork of SPI fibers of varying density according to the diame‐ter or location of the blood vessels.The present study suggests that: (1) SPI fibers located on the circle of Willis and its branches originate from SPI cells in the trigeminal ganglion; (2) SPI fiber's of the rostral one‐third of the basilar artery originate partly from trigeminal SPI cells; and (3) SPI fibers in the caudal two‐thirds of the basilar artery originate exclusively from other SPI cells, apart from the tri‐gem

ISSN:0092-7317    

DOI:10.1002/cne.902150406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractGlial fibrillary acidic protein (GFA) has been visualized by direct peroxi‐dase antiperoxidase (PAP) immunohistochemistry in various vertebrates (cyclostomes, teleosts, amphibians, reptiles, birds, and several placental mammals). In this study GFA‐immunoreactivity (GFA‐I) was observed in all species examined except in cyclostomes and amphibians. Two types of immunoreactive elements were observed: astrocytes and long processes without visible somata.Astrocytic cells with GFA‐I were first found in the snake, and more cells were in birds where the pattern of distribution was similar to that of mam‐mals. Within mammals, few differences in the manner of localization were observed among different species, except in the corpus callosum and the ependymal and subependymal layers.Long straight processes were observed in the lower submammalians‐ the lamprey, carp, and turtle. They radiated through the neuropil from the ventricular wall and followed nerve fiber bundles in the white matter. An un‐common feature was observed in the turtle brain, which possessed very in‐tense GFA‐I within the ependymal layer. The presence of GFA‐containing profiles in the ependyma of adult animals is discussed in relation to GFA‐positive structures seen in the human brain during ontogeny or under cer‐tain

ISSN:0092-7317    

DOI:10.1002/cne.902150407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractFrom the earliest stage of its ontogenesis, the mammalian cerebral cor‐tex displays a remarkable cytoarchitectonic organization, with its neurons oriented radially within the cortical plate (CP).It is not known whether this radial organization of cortical neurons is characteristic of every cerebral cortex or whether it reflects a progressive phylogenetic acquisition. In order to study this question, the embryonic de‐velopment of the cortex has been examined in reptiles, where it is the most primitive. Two species,Emys orbicularisandLacerta agilis, representative of the two principal reptilian orders (chelonians and squamates), have been studied with histological methods, Golgi impregnation, and electron micros‐copy. Very similar patterns of cell proliferation, migration, maturation, and synaptogenesis have been observed. However, important species differences are present in the cellular organization of the cortical plate. Whereas inEmysthe structure of the cortical plate is rudimentary, inLacertait appears well developed and quite reminiscent of its mammalian counterpart. Prelimi‐nary comparisons with embryological preparations ofSphenodonandCroco‐dilus niloticusshow that the organization of the cortical plate displays significant variations among the different reptilian groups.The present results suggest that the radial organization of cortical neu‐rons is not an all or nothing phenomenon but has been acquired indepen‐dently and is thus acase of homoplasy, probably due to convergence (North‐cutt, 1981). Several possible implications of these findings are discussed and a working hypothesis based on the role of radial glial cells in the formation of cytoarchitectonic patterns (Rakic, 198

ISSN:0092-7317    

DOI:10.1002/cne.902150408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractSpinothalamic (STT) cells were investigated in the rat to determine the distribution of subpopulations with terminals in both the lateral and medial thalamus, the thalamus bilaterally, or the thalamus and the medullary retic‐ular formation. Two or more retrogradely transported substances (fluores‐cent dyes, and/or horseradish peroxidase) were injected in each animal. Three combinations of injections were most commonly used: (1) injections of the medullary reticular formation and thalamus, (2) separate injections into each side of the thalamus, and (3) separate injections into the medial and lat‐eral thalamus. The distribution of single labeled cells after each injection was compared with previously published results for rats. The distribution of cells which contained both tracers, double‐labeled (DL) cells, was the focus of this study. An average of 15% of STT cells and 8% of spinoreticular cells projected to both the reticular formation and thalamus. However, only a small component of STT cells (less than 2%) projected bilaterally into the thalamus. Most DL cells were found in upper cervical segments. The laminar distributions of all three groups of DL neurons were similar. These cells were most often located in the reticulated part of lamina V and the intermediate zone, lamina VII. STT cells that had terminals in both the medial and lateral thalamus and STT cells with collaterals in the reticular formation were con‐centrated on the side contralateral to their terminals. These DL neurons pro‐vide an anatomical substrate for noxious stimuli to activate the reticular for‐mation and thalamus and/or specific sensory and intralaminar thalamus s

ISSN:0092-7317    

DOI:10.1002/cne.902150409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

摘要:

AbstractThe rat olfactory tubercle contains high concentrations of γ‐aminobu‐tyric acid (GABA) and its synthetic enzyme, glutamic acid decarboxylase (GAD). We previously demonstrated that GABA and GAD are most concen‐trated in the polymorphic layer of the tubercle and relatively absent from the plexiform and pyramidal layers. Here we report that the granule cells (the islands of Calleja) in the polymorphic layer.accumulate3H‐GABA.3H‐GABA Ci/mmole; 1.5 μ1 was injected trie tubercle and an hour later the rat was perfused with a mixture of paraformaldehyde and glu‐taraldehyde. The tissue was osmicated, dehydrated, and embedded in epon. Silver grains were sparse over the pyramidal and polymorphic cell bodies but numerous over the granule cell bodies in the islands of Callejaanddendrites in the surrounding.neuropjl. Grain densities for the granule cells were 41/100 μm3compared to 4.2 for pyramidal and polymorphic cells. Witnm the island, all the granule cells appeared to be labeled. These results, com‐bined with previous demonstrations of the presence in this region of endo‐genous GABA and GAD, suggest that the granule neurons of the rat olfac‐tory tubercle are GABA‐ergic. These neurons also appear to receive dopamine input and therefore form part of a circuit that includes targets for both major a

ISSN:0092-7317    

DOI:10.1002/cne.902150410

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902150411

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1983

数据来源: WILEY