摘要:

AbstractThe development of the spatial organization of Purkinje cell perikarya was examined in the rat cerebellum from birth to adulthood. Dispersion of the perikarya following birth is made possible by the rapid expansion of the cortical surface. Their subsequent regular monocellular alignment is ensured by mechanical factors, the pressure exerted from below by the expanding granular layer and the barrier formed above by the pile of parallel fibers which prevent the penetration of the bulky perikarya into the molecular layer. The perikarya remain in this position even after the slender stem dendrite pierces the molecular layer along the descending axons of basket cells.The increase in interperikaryal distance between Purkinje cells is rapid up to day 12, then declines. This is temporally associated with the growth of the basket cell plexus and glial envelope around the perikaryon. The increase in perikaryal size continues up to day 30. This may be temporally associated with the growth of the Purkinje cell dendritic arbor as reflected by the expansion of the molecular layer up to day 30.The spatial arrangement of Purkinje cells within the monocellular sheet was graphically displayed with computer aid. In the adult cerebellum a hexagonal arrangement could be recognized in a proportion of “near‐neighborhoods,” consisting of about six Purkinje cells and their neighbors. When the neighborhoods were extended with fixed orientation with respect to the axis of the folium, the hexagonal arrangement disappeared. When orientation was ignored, the superimposed nearneighborhoods could be rotated to produce a hexagonal pattern. In the infant cerebellum the hexagonal arrangement could not be demonstrated before the alignment of Purkinje cells in a monolayer. Thereafter there appeared to be an increase with age in the proportion of hexagonally arranged near‐neighborhoods.It was concluded that in the monocellular ganglionic layer Purkinje cells are not aligned in regular rows with respect to the geometrically arranged elements of the supraganglionic layer. The formation of an imprecise hexagonal pattern, like the alignment of Purkinje cells in a monolayer, was attributed to mechanical

ISSN:0092-7317    

DOI:10.1002/cne.901710102

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractWhole head fractionated doses of 200 r and 150 r were initiated postnatally in five experimental age groups (birth, 1‐week, 2‐week, 3‐week and 4‐week) and continued over a period of 14 or 20 days to prevent reconstitution of the external granular layer. Animals irradiated at birth displayed minor deficits in behavior, which included ataxia, tremor, hypertonus and dysmetria, while animals irradiated at 1‐week showed only mild symptoms of hypermetria. All other animals displayed no motor deficits. Animals irradiated at birth had smaller eyes and ears, a reduction in the size of the entire head and were susceptible to seizures. All animals were sacrified at 70 days of age. The cerebellum was found to be reduced in size and weight, the greatest deficit being seen in animals x‐irradiated at the very early ages. Newborn condition animals were found to have large compliments of interneurons in the molecular layer, an established internal granular layer, and Purkinje cells were found to have a normal orientation, position, and to be unreduced in number or size. Total granule cell deficits were found to range from 83% at birth to 29% at four weeks. Quantitative changes for the molecular layer, internal granular layer, medullary layer, Purkinje cell to granule cell ratio, and granule cell density, all depicted the greatest changes in the newborn, 1‐week and 2‐week conditions. This experiment confirmed that the critical period in the development at which damage would result in behavioral abnormalities was from birth to five days, while for neuroanatomical abnormalities, this critical period was from b

ISSN:0092-7317    

DOI:10.1002/cne.901710103

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe whole‐head of infant kittens was irradiated with fractionated doses of 150 R and 200 R at different postnatal intervals. Experimental age conditions consisted of an irradiated newborn, 1‐week, 2‐week, 3‐week, and a 4‐week age condition while the age of sacrifice remained constant at 70 days. The molecular layer thickness was reduced by 47% in the newborn, 40% in the 1‐week group, 17% in the 2‐week group, 19% in the 3‐week group and by 9% in the 4‐week group. An evaluation of Golgi impregnated material revealed that the dendritic arborizations of Purkinje cells were consistently reduced the earlier the age at which radiation was begun. A reduction in spiny branchlets was seen in all of the experimental conditions. All experimental age conditions displayed the phenomenon of dendritic “damming” at the pial surface, which consisted of an excessive crowding of spiny branches at this level. An increased growth of the primary dendrite before branching tood place was seen in the newborn and 1‐week group. This became less but was still significant in the 2‐week group. A correlation of this phenomenon with the presence or lack of stellate cells is discussed. Purkinje cells with two or more dendrites emerging from their soma were classified and analyzed separately. It was found that the primary dendritic branching in these cells often followed separate morphological patterns and appeared to be independent of each other. Climbing fibers were found to conform to the abnormal dendritic arborizations of the Purkinje cells, and were reduced in complexity in the early radiation treatment groups. This suggested that climbing fibers had no influence upon the dendritic growth pattern, but instead were under the influence of the Purki

ISSN:0092-7317    

DOI:10.1002/cne.901710104

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe whole head of infant kittens was irradiated with fractionated doses of 150 R and 200 R at different postnatal intervals. Experimental age conditions consisted of a newborn, 1‐week, 2‐week, 3‐week, and a 4‐week age condition while the age of sacrifice remained constant at 70 days. Golgi analysis revealed that the interneurons found in the molecular layer of the newborn, 1‐week and 2‐week condition were basket cells. Stellate cells were found in increasing numbers in the 3‐week and 4‐week conditions. Basket cells were found to occupy the entire molecular layer in the newborn and 1‐week conditions resulting in an abnormal axonal plexus. The position of the basket cell soma was found to be in the same plane as its axonal projection. The branching point of the primary dendrite of Purkinje cells was found to correlate with the amount of molecular layer occupied by the abnormal basket cell plexus. Interneurons in the molecular layer were found to show different dendritic growth patterns dependent upon where their soma was located. Interneurons in the deep molecular layer showed only a decreased dendritic field, whereas interneurons in the middle and superficial molecular layer had an abnormal growth of dendrites into the deep molecular layer. A hypothesis is presented to account for the decreased dendritic arborization and the increased length of the primary dendrite before branching, the ectopic basket cell and their abnormally directed dendritic growth, and the difference in behavioral deficits between the newborn and the

ISSN:0092-7317    

DOI:10.1002/cne.901710105

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractA quantitative study has been made of the retrograde neuronal changes that occur in the large neurons of Clarke's column in the L3 spinal segment, 100 days after dorsolateral column lesions at the medullary, C5, T1, T8, and L1 levels in a series of 10‐week‐old kittens. Cell counts, and nuclear and perikaryal areal measurements, have been made in thionin stained material. The results indicate that following L1 level lesions, there is about a 30% loss of Clarke neurons and the remaining neurons are reduced in size to about 75% of their normal cross‐sectional perikaryal area (as judged from the cells on the opposite side) and about 65% of their normal nuclear area. Lesions at the T8 and T1 level both cause about a 20% Clarke cell loss; but after the T8 lesions, there is about a 65% decrease in perikaryal area and a 55% decrease in nuclear area while the T1 lesions cause about a 55% decrease in perikaryal area and a 45% reduction in nuclear area. Lesions at the C5 level result in about a 15% cell loss, a 50% decrease in perikaryal area, and a 40% decrease in nuclear area. Medullary lesions produce about a 5% cell loss, a 50% decrease in perikaryal area, and a 40% decrease in nuclear area. In unoperated control preparations, the left‐right differences in the number of cells are less than 2% and the areal measurements are within 5% of each other.The results of this study suggest that the severity of the retrograde neuronal reaction in Clarke's column is related to the proximity of the lesion to the cell body, but that this relationship is non‐linear. Several possible interpretations of these results are

ISSN:0092-7317    

DOI:10.1002/cne.901710106

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractNucleus cuneatus projections to nucleus ventralis posterolateralis pars medialis (VPLm) and other thalamic as well as midbrain and medullary nuclei were studied in cats using the Fink‐Heimer I silver technique. Single electrolytic lesions of very small size were made stereotaxically in different zones of nucleus cuneatus under electrophysiological control. All zones studied projected to contralateral VPLm in a pattern of discrete terminal arborizations or clusters, which were organized in onionskin‐like dorso‐ventral laminae.The clusters of degeneration varied in size and density according to their dorsoventral location within VPLm. Those in dorsal areas were smaller in diameter (50–125 μ) and contained less dense amounts of degeneration than clusters (150–300 μ) in more ventral regions. The clustered terminal arborizations mirrored the organization of the VPLm neuronal clusters, themselves.Terminations within VPLm were topographically organized, but were completely inverted, i.e. dorsal nucleus cuneatus projected to ventral VPLm and ventral to dorsal, lateral to medial, and medial to lateral VPLm. A ventral zone of nucleus cuneatus, which contained “deep” units, projected to a separate dorsal zone of VPLm. In addition to its classical connection with VPLm, nucleus cuneatus projected to the following contralateral brainstem or thalamic nuclei: medial and dorsal accessory olives, external nucleus of the inferior colliculus, ventrolateral part of the superior colliculus, nucleus ruber, medial geniculate nucleus pars magnocellularis, suprageniculatus, medial and lateral divisions of the posterior thalamic nuclear group, zona incerta, and Fields of Forel. Very sparse amounts of degeneration were also present within nuclei ventralis posteromedialis (caudal pole) and ventralis posterolateralis pars lateralis. The brainstem and thalamic projections of the dorsocaudal part (cell nest region) of the cuneate nucleus were more restricted than those of its rostral and ventral regions. The clusters of both the VPLm neurons and cuneate terminations within VPLm provides an anatomical basis for the functional characteristics of synaptic security, fine grain somatotopia and modality specificity so prominent in the dorsal column nuclei‐medial

ISSN:0092-7317    

DOI:10.1002/cne.901710107

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY

摘要:

AbstractThe region of cerebral cortex in the owl monkey that is responsive to acoustic stimulation is located on the dorsal and lateral surfaces of the rostral half of the superior temporal gyrus. Systematic microelectrode mapping of this area has revealed multiple frequency representations. The boundaries of these fields determined electrophysiologically correlate with the architectural bound aries apparent in Nissl stained material. On the basis of combined cytoarchitectonic and electrophysiological maps we have divided auditory cortex into five fields. Two of them, the primary field (AI) and the field rostral to it (R) are somewhat similar architectonically and constitute the central core of auditory cortex. Each of these two fields has a complete and orderly representation of the audible frequency spectrum within it. Surrounding these fields is a belt of cortex in which units are generally less responsive to acoustic stimulation and the frequency organization is more complex than in AI or R. Electrophysiological and cytoarchitectonic evidence suggest that this belt is composed of at least three and possibly four separate auditory fields.

ISSN:0092-7317    

DOI:10.1002/cne.901710108

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.901710101

出版商:The Wistar Institute of Anatomy and Biology    

年代:1977

数据来源: WILEY