摘要:

AbstractA direct pathway from the temporal retina to the contralateral superior colliculus has been demonstrated using anterograde degeneration methods. This observation of a crossed pathway to the most rostral pole of the colliculus confirms electrophysiological evidence that within each colliculus the whole eye, rather than just its hemiretina is represented.Autoradiographic tracing methods have been used to study the total tectal projection of each retina. Following intraocular injections of3H proline, there is dense label in most of the superficial gray of the contralateral colliculus, but in this region there are several small areas of only relatively sparse label. In contrast, the superficial gray of the ipsilateral colliculus contains islands or patches of transported label. These patches are present throughout an extensive region of the colliculus and suggest that the ipsilateral retinocollicular pathway in the cat may be more substantial than earlier reports have indicated. There is no ipsilateral label within the most caudal parts of the colliculus which receives afferents from the monocular crescent of the visual field. In addition, a very small region of the rostral pole is free of ipsilateral input, and we suggest that this corresponds to the region receiving the crossed input from the temporal retina.

ISSN:0092-7317    

DOI:10.1002/cne.901660202

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe spinal cords of newborn and weanling rats were hemisected at the mid‐thoracic level. Control studies revealed that Fink‐Heimer positive debris was absent in the gray matter at three months postoperative. The remaining animals were given a second lesion, a high cervical spinal hemisection, at five to seven months after the original thoracic hemisection. The pattern of degeneration rostral to the thoracic lesion was compared with similar regions of the spinal cord from animals receiving only a cervical hemisection at the adult stage.In neither experimental group of doubly hemisected rats was there any degeneration observed below the thoracic lesion site, even though no glial or connective tissue scar had formed in animals originally operated at birth. Thus no regeneration had occurred. At least one segment above the initial hemisection: 1. the majority of degenerating axons were localized toward the lateral edge of the spinal cord, especially in the doubly lesioned neonatal group; 2. the area of ipsilateral white matter was reduced more in the neonatal than the weanling operates; 3. there was an upward shift in axonal diameter of ipsilateral fibers in both the region of the rubrospinal tract and the ventrolateral portion of the lateral funiculus of the doubly hemisected rats when compared with the cervically lesioned controls; 4. a significantly greater amount of degeneration was present in lamina VII of Rexed in both the neonatal and weanling experimental operates (p<0.05 weanling; p<0.001 neonate); 5. no mean difference in area was seen between the ipsilateral and contralateral gray matter in any group for the segments of the spinal cord in which the judgements and measurements were taken.These data suggest that there has been sprouting of axons from descending nerve tracts rostral to the thoracic lesion in both the neonatal and weanling experimental groups. The question remains whether the sprouting of descending nerve tracts is from collaterals of axons which normally project rostral to the thoracic hemisection and are not cut by the thoracic lesion (collateral sprouting) or from collaterals of lesioned axons (regenerative sprouting). Present evidence favors collateral sprouting, especially in the neonatal operate where much retrograde cell death appears to have taken pl

ISSN:0092-7317    

DOI:10.1002/cne.901660203

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe spinal cords of newborn (0–3 day old) and adult rats were mid‐thoracically hemisected. Ninety days later a glial and connective tissue scar had formed at the lesion site in the adult hemisected rats while in neonatally lesioned animals only normal appearing regions of the contralateral spinal cord were found in the area of hemisection. Comparisons of the magnocellular portions of the red nucleus (MPRN) revealed a decrease in cell number in the MPRN contralateral (C‐MPRN) to the spinal lesion. However, only in the newborn operates was there massive cell loss accompanied by reduction in area and change in shape of the nucleus. These changes were most obvious in the caudal and ventrolateral portions of the C‐MPRN. Pooled data from each group of operates indicated that significantly more cells were lost in the C‐MPRN in the newborn than in the adult operates (p<0.01).Neurons of the C‐MPRN which are known to project to the lower cervical and upper thoracic segments of the spinal cord (Brown, '74; Gwyn, '71) remained undamaged after the mid‐thoracic hemisection in both groups. However, neurons of this region were enlarged in both groups when compared to a similar region of the ipsilateral MPRN. These neurons were found to be more enlarged in the newborn than in the adult operates (p<0.01).This result indicates that massive retrograde cell death takes place after a mid‐thoracic hemisection in the neonatal rat. The retrograde degeneration of axotomized neurons partially may explain why CNS regeneration is not found in the immature mammal even though many of the factors thought to limit regeneration in the adult mammal may not be apparent. The increase in cell size of C‐MPRN neurons which remain in the neonatal animals after mid‐thoracic hemisection may be related to the increase in axonal size found in the region of the rubrospinal tract rostral to the thoracic lesion reported earlier (Prendergast and Stelzner, '76a). Both the increase in axonal and perikaryal size are hypothesized to be related to the increased distribution of supraspinal axons found in the gray matter rostral to a hemisection of the neona

ISSN:0092-7317    

DOI:10.1002/cne.901660204

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

年代:1976

数据来源: WILEY

摘要:

AbstractPeripheral receptive fields of “barrels” in the somatosensory neocortex (SmI) of rats were determined with microelectrode recording and anatomical techniques. A method of flattening each hemisphere prior to embedding was devised so that the organization of layer IV could be seen through the full extent of SmI on a single section. All of the barrels in the rat are located within layer IV of SmI. Sinus hairs on the lateral and rostral face and furry buccal pad project to a continuous sheet of barrels in the head area of the contralateral SmI. The pattern of projections in this area indicates that each barrel receives information from one sinus hair. Large whisking vibrissae project to the largest celldense barrels and smaller non‐whisking sinus hairs project to smaller barrels that are relatively cell‐sparse. Barrels were also found outside of the head area in regions that receive projections from the forepaw and hindfoot. Receptive fields of these barrels are located on glabrous and hairy surfaces of the appendages that do not include any sinus hairs. Other parts of the body project to celldense areas of SmI that do not appear to contain barrels. Barrel subgroups and other somatotopic areas are separated by narrow barrel‐free zones. As a result of this pattern of contrasting cell densities, an outline of the rat's body is delneated within

ISSN:0092-7317    

DOI:10.1002/cne.901660205

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe place of the cells innervating six most important respiratory muscles in the carp (Cyprinus carpio L.) were determined by means of the horseradish peroxidase technique. It was found that these muscles are represented in the rostral and caudal subdivisions of the trigeminal and facial motor nuclei. All connections were ipsilateral. The distribution of the various cell populations over the different subnuclei has been related to the function of the respective muscles in the respiratory cycle. On these grounds it could be concluded that muscles active in the contraction phase of respiration are represented in the rostral subnuclei, the expansion muscles in the caudal subnuclei. This arrangement appears to be a compromise between a somatotopic and functional organization.

ISSN:0092-7317    

DOI:10.1002/cne.901660206

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

年代:1976

数据来源: WILEY

摘要:

AbstractOrganized cultures of newborn rat cerebellum were established in Maximow chambers in order to study the maturation of Purkinje cells in absence of afferent systems. In the first model, standard cultures were devoid of extracerebellar afferents mossy and climbing fibers. Despite this absence, somatic spines appeared upon Purkinje cells during the first week in vitro and maturation proceeded normally except for the almost absence of spiny branchlets. Large dendritic trunks were studded with numerous spines, some of which were naked, a few bearing isolated post‐synaptic densities and others occupied by boutons of parallel fibers. Stellate and basket axons made synapses upon the smooth portions of dendrites and soma.In a second model, the cultures were fed the antimitotic drug methylazoxymethanol (MAM) to prevent multiplication of granule cell precursors. Despite the absence of climbing and parallel fibers, the elongation of Purkinje dendrites was not prevented, but again the dendritic arbor consisted of large trunks studded with spines; somatic as well as dendritic spines were contacted by large boutons identified as Purkinje recurrent collaterals (PRC). It is concluded that the Purkinje cell possesses a large autonomy from afferent systems as to the growth of soma and dendrites.Conversely, the geometry of the dendrite and especially the spiny branchlets depend on the presence of both climbing and parallel fibers. One may conclude from the above experiments that specificity of synaptic contacts is maintained as long as postsynaptic sites are not devoid of their normal afferents. Heterologous synapses are formed when postsynaptic sites are present, their normal afferents absent and aberrant ones increasing by collateral sprouting. Such is probably the case in the second model of this stud

ISSN:0092-7317    

DOI:10.1002/cne.901660207

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

年代:1976

数据来源: WILEY

摘要:

AbstractRats of the BD III strain were injected with a single dose of3H‐thymidine on either the twelfth, fourteenth, sixteenth, eighteenth or twentieth day of gestation (ED 12…‥ED 20) or on the postnatal day one, three, or seven. Animals were killed at age 22 to 24 days. DNA synthesis, as an indicator of cell division, was studied in matrix precursors of nerve and glial cells in the visual centers, including the lateral geniculate body (LGB), the superior colliculus (SC) and the visual cortex (VC).It was found that proliferation of matrix precursors of nerve cells destined for all the regions studied was in progress on ED 12. In the subcortical regions (LGB, SC) this process was substantially more advanced than in the VC. The first neuroblasts appeared in the SC (ED 12) and only later (ED 14) in the LGB and VC. In comparison with the LGB, VC neuroblasts were quite rare on ED 14 and were present only in layer VI. They appeared more frequently in this region only after injection of isotope on ED 16. Matrix cell proliferation and nerve cell formation ceased in the LGB between ED 16 and ED 18. The number of labeled cells arising after injection of the isotope on ED 16 indicates that neurogenesis ceased somewhat earlier in the dorsal nucleus of the LGB than in the ventral. In the SC the last neurons arose between ED 18 and ED 20, and in the VC, with the possible exception of a few granular neurons (which may continue division into the first few days postnatally), proliferation continued until the end of gestation.The origin of neuroblasts initially followed a caudo‐rostral gradient. Later, the times of neurogenesis in the regions studied overlapped significantly. This is clear, for example, on ED 16, when neurogenesis in the mesencephalic SC continued for about two days longer than in the more rostral LGB, and coincided with that in the VC, especially in the deep layers. The end of neurogenesis in the LGB, especially in the ventral nucleus, coincided with the time of neurogenesis in the deep cortical layers.In the VC, and partly also in the SC, an inside‐out pattern of proliferation and neuron formation was confirmed. The times of proliferation of precursor cells, with the exception of the very end of neurogenesis, substantially overlapped within both these regions. The degree of this overlapping, described in terms of Labeling Index values, decreased towards the end of the neurogenetic period.Division of neuroglial cell precursors, started as early as on ED 14 in/for subcortical centers (LGB, SC), but not until ED 18 in/for the VC. A few labeled endothelial‐like cells were observed in all regions studied after isotope injecti

ISSN:0092-7317    

DOI:10.1002/cne.901660208

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

年代:1976

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901660201

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

年代:1976

数据来源: WILEY