摘要:

AbstractBy using an antibody against tyrosine hydroxylase (TH), the rate‐limiting enzyme in the production of catecholamines, we have examined the morphology and distribution of catecholaminergic cells in the retinas of the rat, guinea pig, cat, and rabbit. In the albino rat, as reported by others, most TH‐immunoreactive (TH‐IR) cells were amacrine cells, and formed two morphological classes. Cells of one class (class 1) are stellate amacrine cells, the somata of most being in the inner part of the inner nuclear layer (INL). Cells of the second class (class 2) were seen only as small somata, also in the inner part of the INL. Cells of both classes were found in all areas of the retina, with a distinct but broad concentration around the superior‐temporal margin of the retina. A small number of TH‐IR interplexiform cells was seen. In the pigmented rat, only class 1 cells were recognized, also concentrating at the superior‐temporal margin. In the guinea pig, cat, and rabbit, TH‐IR cells also seemed to form one morphological class of amacrine cells, which resembled the class 1 cells of the albino rat. In the guinea pig and cat, their distribution resembled that seen in the rat, with the cells concentrating at the superior‐temporal margin of the retina. In the rabbit, TH‐IR cells concentrated weakly in the visual streak, but at both ends of the streak the concentration of TH‐IR cells extended farther peripherally than the concentration of ganglion cells. Overall, the distribution of TH‐IR cells seems largely or (in the rabbit) partially independent of the distribution of ganglion cells. This independence raises questions of the development and function of this gr

ISSN:0092-7317    

DOI:10.1002/cne.902670102

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

年代:1988

数据来源: WILEY

摘要:

AbstractFew studies have dealt with the general ultrastructure and synaptic organization of grafted brain tissue. This study was therefore performed to extend current light microscopic observations on intracerebral and intraocular grafts of hippocampal tissue to the ultrastructural level. Blocks of tissue containing the hippocampus and fascia dentata from day 21 embryonic rats were grafted into the brain of developing and adult rats and to the anterior eye chamber of adult rats. After 100 or 200 days of survival the recipient rat brains or eyes were processed for electron microscopy. Tissue containing the graft dentate molecular layer and adjacent granule cell layer was selected for ultrastructural analysis, together with a few samples of the hilus and CA3. Normal dentate tissue was analyzed as control.At the light microscopic level most intracerebral and intraocular grafts displayed an organotypic organization with clearly recognizable cell and neuropil layers. Under the electron microscope the grafted granule cells had normal‐appearing dendrites bearing the normal types of spines and forming the normal types of synapses. This was the case even in the absence of the normal major extrinsic afferents like the perforant path. The graft dentate granule cells formed axons and terminals with characteristics of the normal mossy fiber system in the hilus and CA3, in addition to aberrant supragranular mossy fiber terminals known from light microscopic studies of dentate transplants. Abnormal structures included a few dendritic growth cones and an increased occurrence of polyribosomes in spines. Their occurrence indicates ongoing dendritic plasticity even 100 days after transplantation. There was also an increased density of glial elements, particularly in the intraocular grafts. In some of these grafts the granule cells displayed immature traits in terms of nuclear indentations. Dentate interneurons of the basket cell type were present in both the intracerebral and the intraocular grafts.We conclude that grafted dentate granule cells, in different surroundings and without the normal, major perforant path input, can develop a basically normal cellular morphology, which includes the normal ultrastructural characteristics of the dendrites with spines and synapses, and the mossy fibers and its terminal

ISSN:0092-7317    

DOI:10.1002/cne.902670103

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

年代:1988

数据来源: WILEY

摘要:

AbstractAs part of an ultrastructural analysis of the normal rat fascia dentata and intracerebral and intraocular dentate transplants the synapses in the dentate molecular layer were quantified. Hippocampal and dentate tissue from 21‐day‐old rat embryos were grafted into the brain of developing and adult rats and to the anterior eye chamber of adult rats. After 100 or 200 days of survival the recipient rat brains and the recipient eyes were processed for electron microscopy, and the graft dentate molecular layer with the adjacent granule cell layer selected for ultrastructural analysis. Tissue from the dentate molecular layer of normal adult rats served as control. The dentate synapses were classified as asymmetric (Gray's type 1) or symmetric (Gray's type 2), and according to the postsynaptic element (cell body, dendritic shaft, dendritic spine). The spine synapses were further classified into simple and complex types according to the spine‐terminal configuration. Also, the length of synaptic contacts of the individual synaptic types was measured in some grafts, just as the percentage of the cross sectional area of the neuropil covered by blood vessels.The results showed that the synaptic density, expressed as number per unit area of neuropil, to a large extent was the same within the different parts of thenormaldentate molecular layer. Compared with this the synaptic density was reduced with 16.4% in dentate molecular layer of the intracerebral graft, primarily because of a 17.6% reduction of simple synapses on dendritic spines and almost halving of the symmetric synapses on dendritic shafts. The synaptic density was independent of the age of the recipient, the intracerebral location of the graft, and the survival time. Although the synaptic length of some of the individual synaptic types increased, this did not compensate for the loss of synapses. In the intraocular grafts the synaptic density was lower than in the intracerebral grafts.Despite the reduced synaptic density, which mainly involved two synaptic types, we conclude that grafted dentate granule cells can develop a remarkably normal, ultrastructural synaptic organization even in the absence of major afferent inputs. This outcome must accordingly be achieved by reorganization of the available intrinsic affe

ISSN:0092-7317    

DOI:10.1002/cne.902670104

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

年代:1988

数据来源: WILEY

摘要:

AbstractTo visualize and compare the intratectal path of normal and regenerated retinal axons, HRP was applied to localized sites in the dorsotemporal and dorsonasal retina in normal goldfish and in goldfish at 3–12 months after optic nerve section. The anterogradely labeled axons were traced in tectal whole mounts.In normal animals the axons were confined to the appropriate ventral hemitectum. Therein they ran in very orderly routes (Stuermer and Easter:J. Neurosci. 4:1045–1051, '84) and terminated in regions retinotopic to the labeled ganglion cells in the retina. The terminal arbors of dorsotemporal axons resided in the ventrocaudal tectum and those of dorsonasal axons in the ventrocaudal tectum.In regenerating animals the terminal arbors also resided at retinotopic regions, where they sometimes formed two separate clusters. In contrast to normal axons, the regenerating ones traveled in abnormal routes through the appropriate and inappropriate hemitectum. From various ectopic positions, they underwent course corrections to redirect their routes toward the retinotopic target region. In their approach toward their target sites, dorsotemporal and dorsonasal axons behaved differently in that the vast majority of dorsotemporal axons coursed over the more rostral tectum whereas dorsonasal axons progressed into the caudal tectal half.This differential behavior of regenerating dorsonasal and dorsotemporal axons was substantiated by a quantitative evaluation of axon numbers and orientati

ISSN:0092-7317    

DOI:10.1002/cne.902670105

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

年代:1988

数据来源: WILEY

摘要:

AbstractHRP was applied to small sites in the dorsotemporal or dorsonasal retina in fish at 10–36 days after optic nerve section. The anterogradely labeled axons were visualized in tectal whole mounts.Axons traveled through all regions of the tectum in various abnormal routes. Misrouted axons were also seen to alter their orientation and to direct their course toward their target. At all regeneration stages the majority of dorsotemporal axons coursed and achieved target‐related orientations preferentially within the rostral tectal half whereas dorsonasal axons proceeded into the caudal tectum.The growing axons exhibited various morphologies. All axons in the superficial fascicle layer stratum opticum (SO) and some in the synaptic layer stratum fibrosum et griseum superficiale (SFGS) were unbranched and tipped with a leading growth cone. Other axons in the synaptic layer carried one to several growth cones at their ends and often filopodia proximal to the growth cone, or they had sprouted numerous side branches with growth cones and filopodia on the shaft and on branches. Some axons at retinotopic or ectopic sites gave rise to several long branches of several hundred microns in length, with growth cones and filopodia. From 32 days onward axons ending in terminal arbors at retinotopic sites became apparent. Thus, numerous axons at early regeneration stages go through a phase of exploratory growth on their way toward their target si

ISSN:0092-7317    

DOI:10.1002/cne.902670106

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

年代:1988

数据来源: WILEY

摘要:

AbstractIn order to examine the influence of afferent input on nonpyramidal dendrite development in the auditory cortex, unilateral deafening was carried out in neonatal rabbits at birth, approximately 6 days prior to the onset of hearing. Deafening was produced by surgical removal of the incus and stapes ossicles, aspiration of the cochlear perilymph, and kanamycin injection into the oval window. At 60 days of age, acoustic stimulation of the deafened ear was unable to evoke auditory brainstem responses. The brains of experimental and littermate control rabbits were processed according to the Golgi‐Cox Nissl method. The dendritic systems of lamina III/IV spine‐free nonpyramidal cells in the auditory cortex contralateral to the deafened ear were digitized from 340‐μm‐thick coronal sections with the aid of a computer microscope. Three‐dimensional spatial and statistical analyses revealed that nonpyramidal dendrite length in neonatally deafened rabbitsincreased27% relative to littermate controls. A fan‐in projection analysis revealed that the increased dendrite length in the deafened animals was maximum in the tangential direction and toward the white matter. Computer rotation of digitized neurons from neonatally deafened rabbits also revealed evidence of abnormal dendritic growth in the form of recurved dendrites. We interpret our results to indicate that unilateral cochlear destruction early in development causes a reorganization of the ascending auditory pathway which extends to the contralateral cerebral cortex. Because the auditory cortex contralateral to the deafened ear still receives acoustic input from the undamaged ipsilateral ear, normal nonpyramidal dendritic growth in the auditory cortex is, in part, dependent upon afferent activity arising fr

ISSN:0092-7317    

DOI:10.1002/cne.902670107

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

年代:1988

数据来源: WILEY

摘要:

AbstractPrior studies indicate that vibrissa, guard hair, hairy skin, mucosa, and nociceptive trigeminal primary afferents give rise to morphologically distinct terminal arbors in the medullary dorsal horn. The present study describes the extent to which similar structure‐function relationships exist in the rostrally adjacent subnucleus interpolaris (SpVi). Seventy‐three axons were physiologically characterized and visualized by standard intra‐axonal HRP labeling techniques. They responded to guard hair (GH) or vibrissa (VIB) deflection; gentle pressure applied to hairy skin (HS), glabrous skin (GS), lingual mucosa (LM), or an incisor (PER); or a noxious pinch of the face (NOX). Response latencies to trigeminal ganglion shocks were equivalent for all categories with low threshold receptive fields (mean = 0.44 ms), and these were significantly shorter than those of fibers with high threshold NOX receptive fields (mean = 0.88 ms). All axons gave off transversely oriented collaterals into SpVi with rostrocaudal discontinuities in their arbors. Collaterals were topographically organized. Axons innervating the rostral mouth and face terminated medially, and those that supplied the caudal face innervated successively more lateral SpVi. The dorsal face was represented in the ventral SpVi, whereas the ventral face and mouth were represented more dorsally. This transverse topography extended largely throughout the rostrocaudal extent of SpVi.VIB, GH, GS, and LM collaterals had similar configurations with circumscribed arbors. HS, PER, and NOX arbors had a “stringy” shape without a clear terminal focus, save for the fact that PER and NOX collaterals often terminated in rostrally displaced substantia gelatinosa at the level of the caudal SpVi. Analysis of variance, considering only those data from mystacial VIB, GH, and HS fibers, indicated significant differences for all of the following measures: number of collaterals, number of boutons per collateral, arbor area, arbor circumference, and arbor circularity (form factor). A similar analysis, considering all fiber types, indicated significant differences for only the following measures: number of collaterals, arbor area, and arbor circumference. Individual group comparisons between the more heavily sampled functional categories indicated that GH afferents had sign

ISSN:0092-7317    

DOI:10.1002/cne.902670108

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

年代:1988

数据来源: WILEY

摘要:

AbstractAnterograde transport of wheat germ agglutinin conjugated to horseradish peroxidase was used to determine the terminal domain of the projection from the lumbosacral spinal cord to the midbrain in the rat, cat, and monkey. Results have shown that several midbrain regions receiving afferent input from this level of the spinal cord are common to the three species examined. Structures innervated by this projection were located throughout the full rostrocaudal extent of the midbrain. The strongest projections were to the intercollicular region and caudal midbrain contralateral to injection sites in the spinal cord. Terminal labeling in the rostral midbrain, except that observed in the nucleus of Darkschewitsch, was substantially less than that observed at more caudal midbrain levels. Structures receiving the strongest input from the spinal cord included the central gray, nucleus cuneiformis, the deep and intermediate layers of the superior colliculus, and the intercollicular nucleus. Other structures receiving afferent input from the lumbosacral spinal cord included the anterior and posterior pretectal nuclei, red nucleus, Edinger‐Westphal nucleus, interstitial nucleus of Cajal, and the mesencephalic reticular formation. It is concluded that the spinal projection to the midbrain is a multicomponent projection consisting of several pathways terminating in discrete midbrain regions. Considering the diverse functions associated with midbrain regions receiving spinal input and the response and receptive field properties of cells belonging to this pathway, the results of the present study are discussed in relation to the potential role of the spinomesencephalic tract in somatic, visceral, and motor functio

ISSN:0092-7317    

DOI:10.1002/cne.902670109

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

年代:1988

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902670110

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

年代:1988

数据来源: WILEY