摘要:

AbstractThe effects on rat cranial nerve growth of removing various amounts of extraocular muscle was studied using morphometric techniques. Growth in the third cranial nerves was found to be severely retarded when most of the muscle tissue was removed. By contrast, removal of the eye alone, leaving extraocular muscles relatively intact, was found to have little or no effect on the subsequent growth of third and sixth cranial nerve fibers and of extraocular muscle fibers. This conclusion could be drawn only through the application of statistical methods which take into account several generally unrecognized facts: frequency distributions of axon circumference and myelin sheath thickness are highly variable from nerve to nerve even in normal rats, which often have more large fibers in left than in right nerves. The bimodal nature of peripheral nerve fiber distributions precludes the use of such parametric tests as the commonly and inappropriately used t‐test, but a non‐parametric test such as the Kolmogorov‐Smirnov test, extensively used in these studies, is inadequate for data comprising several sets of distributions to be compared. The application of the analysis of variance to some of the data and the merits of the procedure are disc

ISSN:0092-7317    

DOI:10.1002/cne.901760302

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe retinas of adult goldfish, one to four years of age, 4–23 cm in length, were examined with standard paraffin histology to determine if new cells were being added with growth. Retinal cell nuclei were counted and the area of the retina was measured. An analysis of cell densities in various regions throughout the retina showed that the cells are distributed nearly homogeneously. The density (No./mm2of retinal surface) of ganglion cells, inner nuclear layer cells and cones decreases with growth, but the density of rods remains constant. Thus the rods account for a larger proportion of the cells in larger retinas. The total number of cells per retina increases: the ganglion cells from 60,000 to 350,000; the inner nuclear layer cells from 1,500,000 to 4,000,000; the cones from 250,000 to 1,400,000; the rods from 1,500,000 to 15,000,000. This increase in the number of retinal neurons implies the formation of even more new synapses, and suggests the adult goldfish retina as a model for both neuro‐ and synaptogene

ISSN:0092-7317    

DOI:10.1002/cne.901760303

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe manner in which new cells are added to the growing adult goldfish retina was examined using3H‐thymidine radioutography. Cell proliferation leading to the formation of neurons is restricted to the retinal margin at theora terminalis. New retina is added in concentric rings, with slightly more growth dorsonasally. The rate of cell addition is variable, averaging 12,000 cells/ day. These new cells account for about 20% of the total increase in retinal area; the remaining 80% is due to hypertrophy, or expansin, of the retina. In contrast to all of the other retinal cells, the rods do not appear to participate in the retinal expansion. This hypothesized immobility of the rods would create a shearing strain between the retinal layers resulting in a shift in their position relative to the other cells. Were they to maintain synaptic contacts with the same horizontal and bipolar cells, the rod axons would have to be elongated peripherally or the post‐synaptic cell dendrites displaced centrally. Since neurons with this morphology have not been found in the goldfish retina, these observations suggest that the rods must be changing their synaptic connections as the retina gr

ISSN:0092-7317    

DOI:10.1002/cne.901760304

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

年代:1977

数据来源: WILEY

摘要:

AbstractThespasticmutant of Ambystoma mexicanum shows deficiencies in swimming coordination and equilibrium. Behavior “phenocopy” experiments done previously indicated that vestibular projections to cerebellum and hindbrain interneurons might be responsible for mutant behavior patterns. To test function in mutant vestibular projections, single unit recordings were carried out in the vestibulo‐cerebellum (auricle) and hindbrain area acousticolateralis (AAL) of wild‐type and mutant animals in response to natural vestibular stimulation. Vestibular unit types responding during longitudinal tilting or to sustained tilt were encountered in equal proportions in both animal types. However, mutants showed a significant increase in spontaneously active units in these areas indicating possible deficiencies in inhibitory circuitry. In addition, the topographic location of vestibular units changed under the influence of thespasticgene. In mutants, significant numbers of units were found “translocated” into a ventro‐caudal auricular zone abutting the AAL. Anatomical studies detailed in the following paper have shown this same area to contain grossly “translocated” cerebellar cells and afferent fiber tracts in mutants. These data are drawn together in a model in which deficiencies in the (form and) inhibitory function of the vestibulo‐cerebellum is postulated to underly the behavioral abnormalities of

ISSN:0092-7317    

DOI:10.1002/cne.901760305

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

年代:1977

数据来源: WILEY

摘要:

AbstractThespasticmutant, found in the Mexican axolotl, shows swimming coordination and equilibrium deficiencies. Histological analyses of wildtype andspasticmutant cerebella previously characterized in physiological studies revealed changes in Purkinje cell location in the mutant auricle or vestibulo‐cerebellum. Purkinje cells are “translocated” ventrally correlated with a similar translocation of vestibular single units described previously (Ide, '77). Where wild‐type Purkinje cells are distributed from the surface to a depth of 250 micrometers, mutant Purkinje cells are “crowded” between 250 and 350 micrometers. Although mutant granule cells are present, boundaries between granule cell and Purkinje cell zones are less precise in mutants. Cerebellar nucleus cells are translocated medially, failing to organize into the discrete cell group appearing in wild‐type. Cerebellar white matter tracts and fibers show changes, both in orientation with respect to the underlying tegmentum, and in fascicular organization. Obvious changes in the gross anatomy of the cerebellum are confirmed in reconstructions which define cell and fiber translocations. Thus, thespasticgene is compatible with differentiation of all cerebellar elements, but appears to alter interactions between cells, or between cells and the external milieu. Although all cell types are present in the mutant cerebellum, they fail to attain their proper positions along all th

ISSN:0092-7317    

DOI:10.1002/cne.901760306

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

年代:1977

数据来源: WILEY

摘要:

AbstractEach subdivision of auditory cortex was injected with horseradish peroxidase (HRP). The amount of HRP injected was varied with the result that in some cases the diffusion of HRP was restricted while in other cases, HRP diffused over an entire cortical subdivision and encroached on adjacent subdivisions. In the case of restricted diffusion only a relatively small number of thalamic cells were “labelled”; in the case of extensive diffusion many times that number of cells were labelled. Whether relatively few or many cells, the distribution of labelled cells fell into distinctive patterns. Each pattern consisted of a focus or concentration of labelled cells in one thalamic subdivision and a sparser population of labelled cells in other thalamic subdivisions. The most striking example of a pattern is produced by injecting AI. This injection resulted in a band in the ventral division of the medial geniculate body densely populated with labelled cells; but even after the smallest injection, labelled cells were also found outside the ventral division, in the magnocellular and dorsal divisions of the medial geniculate body, and in the posterior group. (The ventral extremity of the ventral division was always free of cells and this sector is likely a separate nucleus which projects to Ep.) Other patterns are produced by injecting HRP in other cortical subdivisions: temporal injections produced a concentration in the caudal division of the medial geniculate body; insular injections resulted in a concentration in the medial sector of the posterior group; AII injections led to a concentration in the magnocellular and deep dorsal divisions of the medial geniculate body; injections in ventral Epled to a concentration of labelled cells in the dorsal division of the medial geniculate body; finally, dorsal Epseems to be very different from the other divisions inasmuch as injections in it resulted in labelled cells in non‐auditory thalamus–the pulvinar and lateral nuclei, as well as the auditory thalamus.These results lead to the following conclusions. The laminated and principal part of the ventral division of the medial geniculate body projects only to AI. Every other thalamic subdivision projects to two or more cortical subdivisions: the caudal division projects primarily to the temporal area with sparser projections to AII and Ep; the dorsal division projects primarily to Epwith sparser projections to AI, AII, and the temporal area; the medial sector of the posterior group projects primarily to the insular area and to the posterior ectosylvian gyrus; the magnocellular division of the medial geniculate body projects to every subdivision of auditory cortex, including AI

ISSN:0092-7317    

DOI:10.1002/cne.901760307

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

年代:1977

数据来源: WILEY

摘要:

AbstractRat embryos of 15 days gestation were exposedin uteroto 170 R of X‐ray irradiation. Embryos collected 6 hours, 1, 2 and 3 days after irradiation, and animals of 2, 6, 15 and 30 days postanatal age were used for this study. Six hours after irradiation cells in the neuroepithelium and mantle layer along the roof of fourth ventricle were observed destroyed. Neuroepithelium showed only fragmentary regeneration during next two days, and it contributed to a small number of Purkinje cells. During postnatal development of cerebellum the external granular layer, the zone of proliferative cells that gives rise to neurons of postanatal origin, was found reduced. Other structures such as internal granular layer, molecular layer and medullary layer also were reduced. These multiple temporally sequenced developmental events resulted in a subnormal‐sized cerebellum. Various quantitative measures helped established that grossly the cerebellum in the X‐ray irradiated animals was aout half of that in the normal animals. Problems related to regeneration in the embryonic cerebellum, and to the factors determining the subnormal size of the adult cerebellum are discussed. Viewing this as an experimental approach to the study of neuroembryogenesis of cerebellum, the role of Purkinje cells in the regulationo f development of cerebellum is brough

ISSN:0092-7317    

DOI:10.1002/cne.901760308

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

年代:1977

数据来源: WILEY

摘要:

AbstractRat embryso of 18 days gestation were exposed in utero to 170 R of X‐ray irradiation. Embrysos were collected six hours, 1, 2 and 3 days after irradiation, and animals of 2‐, 6‐, 15‐ and 30–day‐old postnatal age were sacrificed. Six hours after irradiation pyknosis of cells was noticed in the external granular layer along the posterior aspect of the cerebellum. Neuroblasts, destined to differentiate into Purkinje cells, were found arrested in their migratory path. During subsequent peoiods of embryogenesis the external granular layer was found recovered, and clustering of the neuroblasts was disorganized and fragmented. This abnormal clustering of neuroblasts was permanent, and the external granular layer followed the same abnormal pattern in its growth. During postnatal development the internal granular layer also was found to follow the abnormal pattern of Purkinje cell layer. These abnormal developmental events were seen to lead to malformed folia in the anterior regions of the cerebellum. In addition to it the cerebellum of X‐ray irradiated animals appeared smaller than the normal. Issues having abearing on the differential radiosensitivity of different cells, factors determining the small size of the cerebellum, and cellular events determining the morphogenetic malformations

ISSN:0092-7317    

DOI:10.1002/cne.901760309

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

年代:1977

数据来源: WILEY

摘要:

AbstractIncorporation of3H‐fucose into hypothalamic tissue of rats was studied between ten minutes and seven days after intraventricular injection. In EM autoradiographs grain densities over perikarya of neurons, astro‐ and oligodendroglia, and neuropil were evaluated. Grain densities were consistently higher over both types of glial cells as compared to neurons. The glia/neuron ratio was especially high after short experimental intervals and declined with increasing time intervals. Concomitantly there was an increase of grain density over the neuropil. The discussion concentrates on the methodical aspects which have to be considered in interpreting the autoradiographic data. It is concluded that both astroglia and oligodendroglia exhibit a considerably higher synthesis rate of glycoproteins per unit volume than nerve cells. The implications of the results for the interpretation of biochemical data on glycoprotein metabolism of brain tissue are discus

ISSN:0092-7317    

DOI:10.1002/cne.901760310

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

年代:1977

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901760301

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

年代:1977

数据来源: WILEY