摘要:

AbstractThe efferent projections of the telencephalon in the tiger salamander were examined by the Nauta and Fink‐Heimer methods following unilateral hemispherectomies, rostral hemispheric ablations and pallial lesions. The cerebral hemisphere connects with most areas of the contralateral hemisphere via the pallial, anterior and habenular commissures. The descending fibers travel in the medial and lateral forebrain bundles and in the tracts comprising the stria medullaris. Degenerating fibers and terminals were present throughout the diencephalon but were more abundant ipsilaterally. Fibers reach the pretectum and optic tectum via dorsal and ventral pathways. There is a heavy projection to the midbrain tegmentum and a sparse projection to the tectum via the ipsilateral lateral forebrain bundle. This tract continues into the medulla oblongata and the cervical spinal cord. Rostral and dorsal hemispheric ablations revealed that the majority of fibers forming the olfacto‐peduncular tract originate in the ventral, rostral one‐third of the hemisphere. It was also determined that the majority of the descending efferent fibers located in the lateral forebrain bundle originate from the caudal lateral hemispheric wall, and that these fibers form connections characteristic of mammalian corticofugal and striatofugal systems. The cytoarchitecture and connections of the caudal lateral hemispheric wall suggest that it is homologous to parts of motor isocortex and amygdala of amn

ISSN:0092-7317    

DOI:10.1002/cne.901730402

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe differential projections of the three main cellular strata of the superior colliculus have been examined in the cat by the autoradiographic method. The stratum griseum superficiale projects caudally to the parabigeminal nucleus and rostrally to several known visual centers: the nucleus of the optic tract and the olivary pretectal nucleus in the pretectum; the deepest C laminae of the dorsal lateral geniculate nucleus; the large‐celled part of the ventral lateral geniculate nucleus; the posteromedial, large‐celled part of the lateral posterior nucleus of the thalamus. Several of these projections are topographically organized.The stratum griseum profundum gives rise to most of the descending projections of the superior colliculus. Ipsilateral projections pass to both the dorsolateral and lateral divisions of the pontine nuclei, the cuneiform nucleus, and the raphe nuclei, and to extensive parts of the brainstem reticular formation: the tegmental reticular nucleus, and the paralemniscal, lateral, magnocellular, and gigantocellular tegmental fields. Contralateral projections descending in the predorsal bundle pass to the medial parts of the tegmental reticular nucleus and of some of the tegmental fields, the dorsal part of the medial accessory nucleus of the inferior olivary complex, and to the ventral horn of the cervical spinal cord. Ascending projections of the stratum griseum profundum terminate in several nuclei of the pretectum, the magnocellular nucleus of the medial geniculate complex and several intralaminar nuclei of the thalamus, and in the fields of Forel and zona incerta in the subthalamus.The strata grisea profundum and intermediale each have projections to homotopic areas of the contralateral superior colliculus, to the pretectum, and to the central lateral and suprageniculate nuclei of the thalamus. However, the stratum griseum intermediale has few or no descending projecti

ISSN:0092-7317    

DOI:10.1002/cne.901730403

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe origin of spinocerebellar projections from the cranial cervi cal spinal cord was studied in neonatal dogs following cerebellar ablations or the injection of horseradish peroxidase (HRP) into the cerebellum. Cerebellar ablations produced distinct retrograde changes of three types: type I response or cen tral chromatolysis; type II response or ghost cells; and type 111 response or neu ronal loss and gliosis. These ablation‐induced changes were evident in the cells of thenucleus cervicalis centralis. The results of hemicerebellectomy, unilateral cer ebellar pedunculotomy, and cordotomy established that the cells of this nucleus project contralaterally to the cerebellum. Cytoarchitectonic study revealed that this nucleus is composed of clustered medium‐sized, multipolar, chromatophilic neurons located in the zona intermedia of the C1‐C4segments. The retrograde la beling of central cervical neurons following cerebellar injections of HRP con firmed the results obtained with the axonal reaction.Anterograde fiber degeneration was present in the central cervical nucleus following dorsal rhizotomy in the dog and cat. These experiments demonstrated dorsal root fibers among the somata of central cervical neurons rendered chromatolytic following cerebellectomy in the dog. Electron microscopic evidence is presented for the presence of degenerated dorsal root terminals upon the dendrites and somata of central cervical neurons.Thenucleus cervicalis centralisforms a direct link between neck afferents and the cerebellum by way of a crossed cervicospinocerebellar pathway. Evidence could not be found for the presence of a spinocerebellar projection originating in thenucleus ceruicalis late

ISSN:0092-7317    

DOI:10.1002/cne.901730404

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe origin of spinocerebellar projections from the caudal cervical, the thoracic, and the cranial lumbar regions of the spinal cord was studied in neonatal dogs.The present cytoarchitectonic and experimental studies of the cervical intumescence of the spinal cord led to the description of a cell group prominent in the dorsal horn, the nucleus centrobasalis. This nucleus, comprised of neurons of varying size and shape, extended over the length of the cervical intumescence. The largest neurons of then. centrobasahexhibited retrograde reaction following cerebellar injury or they accumulated horseradish peroxidase (HRP) after injection of the enzyme into the cerebellum. Unilateral cerebellar ablation or cordotomy evoked retrograde changes in the ipsilateral nucleus. The cerebellar‐projecting neurons were large, multipolar and chromatophilic. They occured singly, in small clusters, or in columns. The columnar arrangement was common at caudal levels of the cervical intumescence where these large cells were most abundant.The results of earlier experiments with cats and rhesus monkeys have demonstrated massive fiber degeneration in then. centrobasahfollowing dorsal rhizotomy (Petras, '65, '66; Petras and Cummings, '72). The presence of spinal afferents in this nucleus suggests that its largest neurons may serve as a link for the passage of forelimb afferent information to the cerebellum by way of an uncrossed brachiospinocerebellar projection. The present anatomical data suggest too that these large neurons are the cells of origin for the rostral spinocerebellar tract (Oscarsson and Uddenberg, '64; Oscarsson, '65).The cellular composition of the nucleus dorsalis was studied also, and the results compared with Loewy's ('70) findings in the cat. Three types of neurons were present in then. dorsalis. These have been classified as giant, medium, and small‐sized neurons. The giant and medium‐sized neurons responded to cerebellectomy, and accumulated enzyme following HRP injections into the cerebellum. The retrograde responses, generally, were most pronounced in cranial thoracic segments and diminished progressively in more caudal segments. Unilateral cerebellar ablations, cerebellar pedunculotomy, and cordotomy almost exclusively affected ipsilateral neurons. The present study provides the first demonstration of discrete retrograde changes in the giant cells of Clarke's column following cerebellectomy. The contribution of the medium‐sized neurons of then. dorsalisto spinocerebellar projections is established for the fir

ISSN:0092-7317    

DOI:10.1002/cne.901730405

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe distribution and activity pattern of acetylcholinesterase in the central nervous system of salticid and lycosid spiders has been studied. Enzyme activity was limited to the neuropile mass. The salticid and lycosid species investigated showed different intensities of enzyme reactions in the protocerebrum. The differences observed may be related to the some what contrasting habits of these spider families. Reactions were strong especially in the optic ganglia (lamina glomerularis, corpora pedunculata) and in the cerebral ganglion, while the central body showed only weak to moderate activity. In the cheliceral ganglia, as in the pedipalpal and the leg ganglia, including the fibre tracts of the ventral cord the demonstration of acetylcholinesterase was of moderate to strong intensity.

ISSN:0092-7317    

DOI:10.1002/cne.901730406

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractDevelopmental alterations in the rate and severity of axon reaction are thought to be influenced by the level of neuronal maturation and synaptogenesis. As an initial step in more carefully examining this issue, two concurrent series of studies were performed using the ventrobasal complex as a model.Sprague‐Dawley albino rats, ranging in age from neonate through 60 days postnatal (dpn) were subjected to unilateral aspiration lesions encompassing somato‐sensory cortex. Two to four animals were sacrificed at various postoperative periods of from one through 40 days. The reactive ventrobasal (VB) complex was qualitatively and quantitatively analysed employing electron microscopy and the Cajal‐DeCastro reduced silver technique or a hematoxylin‐eosin‐Orange‐G method for light microscopic study. Neuronal degenerative changes are prominent within 48 hours following ablation of neonate through 9 dpn animals. These alterations include a loss of cytoplasmic basophilia together with vacuolization, and rapid disappearance of the cell. Swelling and vacuolization of axons and dendrites is seen throughout the zone of degeneration accompanied by the rapid accumulation of numerous reactive non‐neuronal elements, some of which resemble those mesodermal elements designated as “M” cells. Following equivalent lesions of animals 12 through 60 dpn, neurons within the VB undergo degenerative changes which are qualitatively similar to those seen in younger animals but require between 6 and 20 days postoperative to appear. While most such cells will disappear the degenerative process is temporally extended by as much as one order of magnitude.The normal ventrobasal complex was examined in 7,12,15,20, and 60 dpn rats. Golgi‐Cox impregnations of thalamic neurons reveal such cells at 7 dpn to be characterized by short, stubby, irregular dendrites with distinct growth cones and filopodia, whereas by 12 dpn Golgi analysis demonstrates prominent morphological changes indicative of considerable progress in thalamic neuronal differentiation including dendritic elongation with secondary and tertiary branching, and the appearance of spinous protrusions. The use of the Rasmussen stain for synapses, as well as electron microscopy, shows distinctive trends of synaptogenesis typified by a paucity of synaptic complexes but large numbers of dendritic and axonal growth cones at 7 dpn. However, by 12 dpn a 3‐fold increase in the number of synapses has taken place together with an enhanced morphological complexity and variety of individual synaptic profiles, some of which are known to represent lemniscal input. Further prominent increases in synaptic population density are observed at 15dpn but the rate of synaptogenesis appears to become attenuated after this period. Finally, patterns of distribution of perikaryal RNA become altered from a predominance of polyribosomes at 7 dpn to characteristic multilamellate aggregations of granular endoplasmic reticulum initially observed at 12 dpn. With subsequent neuronal enlargement this component proportionally increases in amount but is qualitatively unchanged with respect to morphological arrangement. The close temporal correlation between the specific developmental events documented in this study and the postnatal age during which VB neurons become less susceptible to injury suggests that important changes in maturation of intrinsic neuronal metabolism involving rates of RNA and protein synthesis may be, in part, initiated and regulated by extrinsic factors related to the establishment of pre‐synaptic input upon VB neurons. A number of putative molecular substrates for these i

ISSN:0092-7317    

DOI:10.1002/cne.901730407

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractDescending projections to the spinal card from the dorsal column nuclei were studied in the cat, rat and monkey with the retrograde horseradish peroxidase (HRP) technique, and in the cat with the autoradiographic anterograde axonal transport technique. Retrogradely labeled neurons were seen in the dorsal column nuclei after HRP injections at all levels of the spinal cord and additionally in the magnocellular division of the spinal caudalis nucleus of the trigeminal nerve after injections into cervical spinal segments in all three species. HRP‐positive neurons were predominantly located along the middle of the rostro‐caudal axis of the dorsal column nuclei and amongst the fusiform, triangular and polygonal cells that surround, especially ventrally, the cell nest zone containing thalamic relay neurons. The labeled neurons are densely concentrated in those portions of the dorsal column nuclei where most corticofugal and non‐primary afferent projections terminate and where the terminal distribution of primary afferent fibers is overlapping and diffuse. Previous studies have shown that most neurons in this middle and ventral region do not project to the thalamus or cerebellum. The majority of the cells in the dorsal column nuclei with descending axons or axon collaterals project by way of the ipsilateral dorsal columns, but some fibers project into the dorsolateral funiculus; the descending trigeminal fibers course in the dorsolateral funiculus. The terminal fields for these fibers in the cervical spinal cord include the lateral cervical nucleus, laminae IV and V, and possibly lamina I. These results indicate that the dorsal column nuclei may contribute to a feedback mechanism regulating the flow of sensory information ascending along other somatosensory spinal pat

ISSN:0092-7317    

DOI:10.1002/cne.901730408

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901730401

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY