摘要:

AbstractIn hippocampal slice cultures, the mossy fibers from the dentate granule cells project as normally to cells in the dentate hilus (CA4) and the hippocampal CA3 pyramidal cells. After lesions in vivo and intracerebral transplantation, the mossy fibers can alter their normal distribution within CA3 and even contact CA1 pyramidal cells. The present study examined whether similar changes could be induced in the more simple, virtual two‐dimensionally organized slice cultures. For this purpose slices of 7‐day‐old hippocampal were prepared and subjected to one of the two following manipulations: (1) transection of the mossy fiber layer in CA3 or (2) rearrangement of the geometrical relations between the dentate granule cells in their potential targets (CA3 and CA1) by coculturing dentate slices with CA3 or CA1 slices. Two to 8 weeks later the distribution of the mossy fiber system was visualized by histochemical Timm sulphide silver staining of the terminals.The distribution of the mossy fiber system observed in previous studies of ordinary hippocampal slice cultures was confirmed. In addition, mossy fibers were found to cross the cuts through the mossy fiber layer with formation of a reduced number of characteristic Timm‐stained terminals in CA3 distal to the lesion. Close proximity and contiguity of the cut surfaces were important for such growth to occur. Significantly fewer mossy fiber terminals were found when separate slices of dentate and CA3 tissue were joined and grown as cocultures. Similar apposition of slices of dentate and CA1 tissue only rarely resulted in the ingrowth of mossy fibers into CA1. The Timm‐stained mossy fiber terminals were then of subnormal size.The results show the potentials of the slice culture technique in suplementing lesion and transplant studies in situ. The growth of mossy fibers across a transection of their pathway is thus a new observation, difficult to demonstrate in the brain. The limited growth in the cocultures of aberrant mossy fibers into Cal does, on the other hand, emphasize the importance of close structural contact for the formation of nerve connections, and such contact is apparently more easily obtained in the brain. When the growth of the mossy fibers and that of the cholinergic septohippocampal fibers are compared, it is evident that the cholinergic axons grow better both in vitro and in vivo after lesions and transp

ISSN:0092-7317    

DOI:10.1002/cne.902640102

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe distribution and number of dying cells in the developing retinal ganglion cell layer of the wallabySetonix brachyuruswere assessed by using cresyl violet stained tissue. The density of dying cells has been expressed per 100 live cells for the entire retinal surface, data being presented as a grid of 500 μm squares. For statistical analysis, retinae were divided into 8 regions; dorsal, ventral, nasal, and temporal quadrants, each further divided into center and periphery. This method allowed comparison of the extent of cell death at different retinal locations as the high density area centralis of live cells developed temporal to the optic disk from 60 days onward.Between 30 and 70 days, dying cells were seen across the entire retina; beyond 100 days very few were seen. Initially, there was a significantly higher incidence of dying cells in the central retina compared to the periphery, whereas from 50 days this situation was reversed. Analysis of the central retina before and during area centralis formation consistently indicated a significantly lower number of dying cells per 100 live cells in temporal compared to other retinal quadrants. This differential pattern suggests that cell death lowers live cell densities less in the emerging area centralis than elsewhere, and therefore must play a part in establishing live cell density gradients. However, we cannot exclude the possibility that other factors are also instrumental. Indeed, factors such as areal growth (Beazley et al., in press) presumably operate at later stages since live cell density gradients continue to be accentuated even after cell death is complete.Numbers of dying cells peaked by 50 days, reaching approximately 1% of the live cell population. At this stage, counts were also maximal for live cells with values up to 30% above the adult range

ISSN:0092-7317    

DOI:10.1002/cne.902640103

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe projections to the inferior colliculus of the cat are shown in autoradiographs after injections of3H‐amino acids into the anteroventral cochlear nucleus and anterograde axonal transport. Labeled bands of axons are seen in the central nucleus of the inferior colliculus, parallel to the fibrodendritic laminae, and in layers 3 and 4 of the dorsal cortex. A bilateral projection to the lateral, low‐frequency part of the inferior colliculus is observed. In contrast, the more ventromedial, mid‐ and high‐frequency parts receive only a contralateral input. The projections from the cochlear nucleus to both the contralateral midbrain and bilaterally to the superior olivary complex appear to be tonotopically organized. After HRP injections in the inferior colliculus, small numbers of stellate neurons are labeled in the lateral and ventral low‐frequency parts of the anteroventral cochlear nucleus on the ipsilateral side. EM autoradiographs show labeled axonal endings from both sides of the anteroventral cochlear nuclei are present in the same proportion inpars lateralis.Axonal endings from either cochlear nucleus have small, round synaptic vesicles and make asymmetric synaptic contacts on dendrites. Axons from the contralateral side also make axosomatic contacts on large disc‐shaped or stellate cells. Neurons from the ipsilateral anteroventral cochlear nucleus apparently make more synaptic endings per cell as compared to neurons from the contralateral side. Together, bilateral inputs from the anteroventral cochlear nucleus can account for a third of the endings with round synaptic vesicles inpars lateralisof the central nucleus.Morphological similarities among the ascending inputs to the inferior colliculus are discussed. Both direct circuits from the cochlear nucleus to the inferior colliculus and indirect circuits via the superior olivary complex or lateral lemniscus may display banding patterns, nucleotopic organization, or differential synaptic organization. The direct inputs from the anteroventral cochlear nucleus to the colliculus may influence binaural interactions which occur in the superior olivary complex. In addition, direct inputs may create new binaural responses in the inferior colliculus that are independent of lo

ISSN:0092-7317    

DOI:10.1002/cne.902640104

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractRohon‐Beard neurons are primary sensory cells located in the spinal cord of embryonic lower vertebrates. The kinetics of their normal, gradual, but complete disappearance inXenopustadpoles has been followed. Levels of acid phosphatase activity, a common histochemical correlate of cell death, were assayed and found to increase at the time of onset of disappearance of Rohon‐Beard cells. Ultrastructural examination revealed the presence of numerous secondary lysosomes, swelling of endoplasmic reticulum and mitochondria, and a decrease in nuclear density. The disappearance of Rohon‐Beard neurons may be attributed to autophagic cell death involving lysosomal acid hydrolases. This process begins only a few days after the maturation of voltage‐ and neurotransmitter‐dependent membrane conductances and the electrical uncoupling of these neurons. The loss of Rohon‐Beard neurons in embryos whose development was arrested by crowding was appropriate for the developmental stage of the animals rather than their chrono

ISSN:0092-7317    

DOI:10.1002/cne.902640105

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe origin of olivocochlear efferents was studied in the rat, the guinea pig, and the batsRhinolophus,Rhinopoma, Tadarida, andPhylostomusby retrograde labeling with HRP and the fluorescent dye fast blue. In all species with the exception ofRhinolophus rouxitwo types of cochlear efferents could be found: small neurons located in the lateral superior olive (LSO) and larger ones located bilaterally in the periolivary region. In bats and rats small olivocochlear neurons (OCN) were found only in the ipsilateral LSO. In guinea pigs some small OCN were found also in the contralateral LSO. Large OCN were found in all animals exceptRhinolophus.They were organized in a horseshoelike nucleus that extended in a rostrocaudal direction and bent rostrally around the medial superior olive (MSO). This nucleus contains several periolivary nuclei described separately by other authors.InRhinol rouxisomata of all olivocochlear efferents are concentrated in a single nucleus between the MSO and LSO, which we therefore call the nucleus olivocochlearis. This nucleus stains for acetylcholinesterase. We consider its neurons to be similar to small OCN, because they are small, associated with the LSO, and only ipsilaterally labeled. This fits well with the fact thatRhinolophuslacks an efferent innervation of outer hair cells (Bishop: Ph.D. Thesis, University of North Carolina, Chapel Hill, '86; Bruns and Schmieszek:Hear. Res. 3: 27–43, '80), which are normally innervated by large OCN (Guinan et al:J. Comp. Neurol. 221: 358–370, '

ISSN:0092-7317    

DOI:10.1002/cne.902640106

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractAntisera to glutamic acid decarboxylase (GAD) and γ‐aminobutyric acid (GABA) have been used to characterize the morphology and distribution of presumed GABAergic neurons and axon terminals within the macaque striate cortex. Despite some differences in the relative sensitivity of these antisera for detecting cell bodies and terminals, the overall patterns of labeling appear quite similar. GABAergic axon terminals are particularly prominent in zones known to receive the bulk of the projections from the lateral geniculate nucleus; laminae 4C, 4A, and the cytochrome‐rich patches of lamina 3. In lamina 4A, GABAergic terminals are distributed in a honeycomb pattern which appears to match closely the spatial pattern of geniculate terminations in this region. Quantitative analysis of axon terminals that contain flat vesicles and form symmetric synaptic contacts (FS terminals) in lamina 4Cβand in lamina 5 suggest that the prominence of GAD and GABA axon terminal labeling in the geniculate recipient zones is due, at least in part, to the presence of larger GABAergic axon terminals in these regions.GABAergic cell bodies and their initial dendritic segments display morphological features characteristic of nonpyramidal neurons and are found in all layers of striate cortex. The density of GAD and GABA immunoreactive neurons is greatest in laminae 2–3A, 4A, and 4Cβ. The distribution of GABAergic neurons within lamina 3 does not appear to be correlated with the patchy distribution of cytochrome oxidase in this region; i.e., there is no significant difference in the density of GAD and GABA immunoreactive neurons in cytochrome‐rich and cytochrome‐poor regions of lamina 3.Counts of labeled and unlabeled neurons indicate that GABA immunoreactive neurons make up at least 15% of the neurons in striate cortex. Layer 1 is distinct from the other cortical layers by virtue of its high percentage (77–81%) of GABAergic neurons. Among the other layers, the proportion of GABAergic neurons varies from roughly 20% in laminae 2–3A to 12% in laminae 5 and 6.Finally, there are conspicuous laminar differences in the size and dendritic arrangement of GAD and GABA immunoreactive neurons. Lamina 4Cαand lamina 6 are distinguished from the other layers by the presence of populations of large GABAergic neurons, some of which have horizontally spreading dendritic processes. GABAergic neurons within the superficial layers are significantly smaller and the majority appear to have vertically oriented dendritic processes. These results provide support for the idea that GABAergic neurons make up a significant proportion of the neurons within the macaque striate cortex and that there are laminar differences in the number and the types of GABAergic neurons—differences that may be relevant for understanding the contributions of GABA‐mediated inhibition to st

ISSN:0092-7317    

DOI:10.1002/cne.902640107

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe terminal areas and cells of origin of the somatosensory projection to the mesencephalon in the monkey were investigated by the intraaxonal transport method.Following injection of wheat germ agglutinin‐horseradish peroxidase conjugate (WGA‐HRP) into the spinal enlargements, the lateral cervical nucleus (LCN), the dorsal column nuclei (DCN), or the spinal trigeminal nucleus,anterograde labelingwas observed in several regions of the mid‐brain. (1) Injection of tracer into thespinal enlargementsresulted in dense terminal labeling in the parabrachial nucleus (PBN) and the periaqueductal gray matter (PAG); moderate termination was observed in the intercollicular nucleus (Inc), the intermediate and deep gray layers of the superior colliculus (SGI, SGP), the posterior pretectal nucleus (PTP), and the nucleus of Darkschewitsch (D); and scattered terminal fibers were seen in the cuneiform nucleus (CNF) and the pars compacta of the anterior pretectal nucleus (PTAC). The projections from the cervical enlargement to PAG, Inc, and the superior colliculus terminated more rostrally than those from the lumbar segments, indicating a somatotopic organization. (2) Terminal labeling after injection of tracer intoLCNwas found mainly in Inc, SGI, and SGP, but sparse labeling was also observed in the nucleus of the brachium of the inferior colliculus (BIN), PAG, PBN, PTP, and D. (3) The projection fromDCNterminated densely in the external and pericentral nuclei of the inferior colliculus (ICX, ICP), Inc, SGI, SGP, PTP, PTAc, the nucleus ruber, and D, and weak terminal labeling was seen in BIN, PAG, and PBN. Comparisons of the anterograde labeling following injections involving both the gracile nucleus and the cuneate nucleus with that after injection restricted to the gracile nucleus alone suggested a somatotopic termination pattern in Inc, the superior colliculus, and the pretectal nuclei. (4) The patterns of projection from the laminar and alaminar parts of thespinal trigeminal nucleusdiffered: injection of tracer into the caudal part of the alaminar spinal trigeminal nucleus (nucleus interpolaris) resulted in dense anterograde labeling in SGI and SGP, moderate termination in Inc, and minor projections to PBN, PAG, and PTP, whereas after tracer injection into the laminar trigeminal nucleus (nucleus caudalis) terminal labeling was present only in PBN and PAG.Following injection of tracer into the midbrain terminal areasretrogradely labeled neuronswere found in the spinal cord, LCN, DCN, and the spinal trigeminal nucleus, with the majority of labeled cells situated on the side contralateral to the injection site. (1) In thespinal cordthe retrogradely labeled neurons were concentrated to the cervical segments and to the lumbosacral enlargement, with more sparse retrograde labeling in the thoracic and upper lumbar segments. The majority of the labeled neurons were situated in lamina I, with smaller fractions in laminae IV and V, and, in the upper cervical, thoracic, and sacral segments, also in the deeper laminae. (2) Heavy retrograde labeling was observed throughout the rostrocaudal extent ofLCN. (3) The retrogradely labeled neurons inDCNwere located along the periphery of the nuclei; in the cuneate nucleus the labeled neurons were found in the pars triangularis, but not in the pars rotunda, and in the gracile nucleus they were situated along the dorsal and medial borders of the nucleus. (4) In thesensory trigeminal nucleiperoxidase‐positive neurons were present throughout the entire nuclear complex except for the principal sensory trigeminal nucleus. The most dense labeling was observed in the laminar spinal trigeminal nucleus (nucleus caudalis), with the majority of the labeled neurons situated in its marginal layer (lamina I) and along the ventral and lateral parts of the alaminar spinal trigeminal nucleus (nuclei interpolaris and oralis).The results of this study show that the somatosensory projection to the midbrain in the monkey is organized in a way similar to that previously demonstrated in the cat. The possible functional role of these projections is discussed in relation to the orientational behavior and central pain mec

ISSN:0092-7317    

DOI:10.1002/cne.902640108

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe total number of ventral horn motoneurons throughout the spinal cord was determined for 19 human fetuses ranging in age from 11 to 32 menstrual weeks. There was a significant (∽35%) decline in motoneuron number between wks 11 and 25 of gestation, but no further decline from wks 25–32. Counts of pyknotic cells indicated a peak of motoneuronal degeneration between about wks 12 and 16 of age. The normal period of motoneuronal death observed here overlaps with the initiation of functional neuromuscular contact as well as the period of androgen production by the human fetal testes. As in rats, androgen may influence final motoneuron number in the human spinal cord by attenuating cell death in sexually dimorphic motor nuc

ISSN:0092-7317    

DOI:10.1002/cne.902640109

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to identify thalamic areas receiving convergent sensory inputs from acoustic and spinal projection systems in the rat. The topographic distribution of afferents to the thalamus from the inferior colliculus and spinal cord was examined by using WGA‐HRP as an anterograde axonal tracer. Following injections in the inferior colliculus, terminal labeling was present in ventral, medial, and dorsal divisions of the medial genicuate body (MGB) and in adjacent areas of the posterior thalamus, including the posterior limitans nucleus, the posterior intralaminar nucleus, the marginal zone, the peripeduncular region, the lateral or parvicellular part of the subparafascicular nucleus, and a region intercalated between the posterior limitans nucleus and the suprageniculate nucleus. In the caudal thalamus spinal projections remained in the reticular formation medial to the collicular terminal field. At intermediate levels of the MG, however, the spinal projection began to overlap the collicular field, terminating in the medial division of the MG and in the posterior intralaminar nucleus, the marginal zone, the lateral subparafascicular nucleus, and the area between the suprageniculate and posterior limitans nuclei. More rostrally, the convergent field expanded to include aspects of the dorsal MG division. The extent to which afferent projections to the thalamus from the inferior colliculus and spinal cord converge is thus graded in the caudorostral plane, with the greatest overlap occurring at the level of the rostral third of the MGB. These observations identify potential areas of acoustic and somesthetic integration and may account for observations of neuronal plasticity in the thalamus in response to the pairing of acoustic and somesthetic input

ISSN:0092-7317    

DOI:10.1002/cne.902640110

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.902640101

出版商:Alan R. Liss, Inc.    

年代:1987

数据来源: WILEY