摘要:

AbstractThe long term consequences of graduated interference with the acquisition of hippocampal neurons and glia during early infancy were examined with quantitative histology and3H‐thymidine autoradiography. The head region containing the hippocampus was irradiated from day two on with either two (2X), four (4X), six (6X) or eight (8X) doses of 150–200r X‐rays. The animals were killed at 30, 60, 90 and 120 days of age.The morphology of the hippocampus was normal in all irradiated groups with the characteristic interlocking folds of the pyramidal and granular layers. While the number of pyramidal cells of Ammon's horn was unaffected, the number of granule cells of the dentate gyrus was progressively and permanently reduced from control levels by the different dosage schedules (2X, 59% reduction; 4X, 77%; 6X, 83%; 8X, 84%). Incidental observations in control animals indicated a 20% increase in granule cells between 30 and 120 days of age in agreement with earlier observations of granule cell labelling after3H‐thymidine injections in adult rats.The time of origin of the approximately 15–16% of the granule cells surviving irradiation in the 8X group was determined by injecting either pregnant females (gestation days 19–20) or pups (days 0 and 1) with two successive doses of3H‐thymidine; the animals were irradiated from day two on with eight X‐ray doses. The granule cells surviving in the postnatally injected group were all unlabelled and comparable in number to the unlabelled cells in control animals that were given five successive postnatal injections of3H‐thymidine. This established that the radioresistant complement of granule cells is formed prenatally. In the prenatally injected group, over half the surviving cells were labelled; it was assumed that those not labelled were formed before gestation day 19.In contrast to the permanent reduction in the number of granule cells, there was some reestablishment of the number of cells in the dentate molecular layer and the Ammonic stratum oriens; in the fimbria, recovery in cell number was complete by 60 days. In a supplementary autoradiographic experiment, cell proliferation in the granular layer and in the fimbria was determined at 60 days of age after a single postnatal injection of3H‐thymidine on either day 15 or day 20 in the control, 2X, 4X and 6X groups. The number of labelled cells in the irradiated groups was always well below control levels in the granular layer, but it was either above or at the same level as controls in the fimbria. Tentative interpretations were offered for the differential long‐term effects of variable X‐ray schedules on the neuronal and glial populat

ISSN:0092-7317    

DOI:10.1002/cne.901630102

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe topographical organization of cerebellar cortical efferents of the posterior lobe vermis was studied in a prosimian primate (Galago senegalensis) and the tree shrew (Tupaia glis). Two patterns emerge; one which shows longitudinal zones of the entire vermis and a second which shows that individual lobules within the overall longitudinal pattern terminate in specific areas of the ipsilateral medial cerebellar nucleus (NM) and vestibular complex.The posterior lobe vermis consists of a narrow midline portion which projects bilaterally into the NM and a paramidline zone which projects only into the ipsilateral NM. These two zones are probably comparable to, and subdivisions of, Zone A of Voogd ('69). The lateral vermal zone projects primarily into the ipsilateral vestibular complex and/or interposed nuclei and appears to correspond to Zone B of Voogd ('69). Within this overall pattern individual lobules project into specific portions of the NM. From rostral to caudal (lobules VI to IX) terminal fields in the NM shift from dorsal and dorsomedial to ventral and ventrolateral. This is the inverse of the pattern of termination seen in the vestibular complex from lesions of the same lobules where from rostral to caudal (VI to IX) there are overlapping terminal fields from lateral to medial. With the exception of the narrow midline zone cerebellar corticonuclear projections of the posterior lobe vermis are ipsilateral. There is a more complex and more precise relationship between the posterior lobe vermis, NM and vestibular complex than previously suggested.

ISSN:0092-7317    

DOI:10.1002/cne.901630103

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

年代:1975

数据来源: WILEY

摘要:

AbstractTo determine whether the largely ipsilateral, inverted representation of mouth parts in the ventrobasal thalamus of sheep was unique to that species or an expansion of a general mammalian pattern, the corresponding thalamic projections were mapped electrophysiologically in a selected series of mammals (opossums, agoutis, squirrel monkeys, cats, raccoons, and sheep) representing major branches of evolution among therian mammals. In mapping, tungsten microelectrodes were used to record multi‐unit discharges in the thalamus in response to mechanical stimulation of oral surfaces. The pattern of projections seen in sheep is not a general mammalian pattern; there is extensive variability among mammals in the laterality and internal organization of the projections from the mouth. In spite of the great variability, the results suggest an hypothesis concerning phylogenetic trends: descendants of palaeoryctoid insectivores (cats, raccoons, and sheep in our sample) have extensive ipsilateral projections from the mouth, in other therian mammals (opossums, agoutis, and squirrel monkeys in our sample) the ipsilateral component is small or absen

ISSN:0092-7317    

DOI:10.1002/cne.901630104

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe central projections of the retinal ganglion cells of the cat were examined using the method of retrograde transport of horseradish peroxidase. Peroxidase was injected into the lateral geniculate nucleus and into the superior colliculus by means of a recording micropipette. After injections at retinotopically homologous points in these two structures in separate animals, the patterns of retinal ganglion cell labeling were compared. We found that there were three populations of ganglion cells: small cells, that projected predominantly to the superior colliculus; medium‐sized cells, that projected predominantly to the lateral geniculate nucleus; and large cells, some of which projected to both structures, and some of which projected to the lateral geniculate nucleus alone. Quantitative studies showed that the average size of the cells in each population was smaller at the area centralis than in the periphery. These results could be directly related to physiological classifications of retinal ganglion cells proposed by other author

ISSN:0092-7317    

DOI:10.1002/cne.901630105

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe projection of cells in different layers of several cortical visual areas in the cat were studied using the method of retrograde transport of horseradish peroxidase. Injections of the enzyme were made through a recording micropipette, making it possible to localize the injection site by physiological criteria. We found that layer VI cells projected to the lateral geniculate nucleus, while a distinct population of cells in layer V projected to the superior colliculus. Cells in layers II and III were the major sources of ipsilateral cortico‐cortical connections. This pattern of projection was consistent from one visual area to another. Pyramidal cells appeared to be the source of cortico‐geniculate, cortico‐collicular and cortico‐cortical projections. The proportion of cells within a layer that terminated in a given site varied from layer to layer: apparently all of the large pyramids in layer V had terminals in the superior colliculus, about half of the pyramids in layer VI had terminals in the lateral geniculate nucleus, while only a small proportion of the pyramids in layers II and III had terminals in any single cortical area. The results indicated a remarkable specificity in the projections of the cortical layers.The cortical connections of the different cell types in layers A and A1 of the lateral geniculate nucleus were also examined: the cells that projected to area 17 were much more numerous and were on the average smaller than those that projected to area 18. Projections to the cortex were also found from the pulvinar, the medial interlaminar nucleus and the posterior nucleus. Direct connections were observed to the lateral geniculate nucleus from several midbrain reticular nuclei. Finally, projections were found to the superior colliculus from the zona incerta, the reticular nucleus of the thalamus and the ventral lateral geniculate

ISSN:0092-7317    

DOI:10.1002/cne.901630106

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

年代:1975

数据来源: WILEY

摘要:

AbstractA retinal ganglion cell distribution map has been prepared for the cresyl violet stained cat retina. It differs from previously published maps in revealing the visual streak to be more substantial and in showing a higher peak density of 9–10,000 ganglion cells/mm2at the presumed visual pole. The map was used to obtain a minimum estimate of the retinal ganglion cell population as 217,000 cells, more than double the total previously reported. The problem of classifying the cells of the ganglion cell layer is discussed in detail and examples of criterion cells illustrated. The paper also includes an account of retinal mensuration (dimensions, area, etc.) and a discussion of the visual streak orientatio

ISSN:0092-7317    

DOI:10.1002/cne.901630107

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

年代:1975

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901630101

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

年代:1975

数据来源: WILEY