摘要:

AbstractGolgi, electronmicroscopic and autoradiographic analyses of the developing cerebellar cortex were carried out in homozygous wild‐type (+/+), heterozygous (+/wv), and homozygous weaver (wv/wv) littermates. At 3 to 15 days after birth, when granule cells normally migrate from the external granular layer inward to their adult position, the somas of postmitotic granule cells in +/+ animals move along straight elongated Bergmann glial fibers which span the molecular layer. As early as postnatal day 3 and increasingly for about the next ten days, some Bergmann fibers in the +/wv cerebellum are enlarged, irregular in caliber, electronlucent and may contain dense bodies and vacuoles. Some granule cells contiguous with the altered Bergmann fibers have round rather than elongated somas, while some have lost contact with Bergmann fibers and appear to degenerate several days after their genesis. Most other granule cells migrate slowly but do eventually reach the granular layer, so that the pathology is less striking in adult than in developing heterozygotes. In wv/wv cerebella, radially‐aligned Bergmann fibers appear reduced in number during the developmental period, and few of them display normal cytological features. Few normally migrating granule cells were observed. Most granule cells fail to form axons and die in the external granular layer close to their site of genesis. While the primary genetic defect is unknown, the Bergmann glial disorder appears to precede the migration failure of granule cells and this in turn, along with impaired axon genesis, appears to be a factor leading to granule cell de

ISSN:0092-7317    

DOI:10.1002/cne.901520202

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

年代:1973

数据来源: WILEY

摘要:

AbstractThis study deals with some consequences of the early postnatal abnormalities of cerebellar Bergmann glial fibers and granule cell neurons. (1) Cerebellar size is mildly reduced in heterozygous weaver (+/wv) mice and markedly reduced in homozygotes (wv/wv), but the pattern of fissures is essentially normal. Comparison with other mutants displaying small cerebella suggests that cell proliferation rate in the external granular layer is a key deteminant of cerebellar cortical folding. (2) Mossy fiber terminals differentiate on schedule despite the reduced number and abnormal positions of granule cells. However, many of them enter the modified molecular layer, and as noted especially in noninbredwv/wvmice one to two years old, form synapses with dendrites of aberrant granule cells. Where granule cells are absent, mossy fibers form more than the normal number of synapses with dendrites of Golgi type II neurons. (3) Purkinje cells are only mildly affected by the disorder of neighbouring cells. Their dendrites grow abnormally into the territory occupied by external granule cells, reach the external surface, and may turn inward. They form few tertiary branches. Dendritic spines are present in profusion and show membrane thickenings akin to normal postsynaptic elements. Although they receive no axonal contacts, the spines persist, enveloped by glial processes, for at least two years. Apart from the absence of parallel fiber contacts, afferent and intrinsic axons form the normal classes of synaptic connections with Purkinje cells. (4) Interneurons of the molecular layer are generated on schedule. At the time of their earliest recognition, they reside in the external granular layer, where they receive synaptic contacts from climbing fibers and other interneurons. In the absence of parallel fibers, interneurons differentiatein situbut their dendrites are abortive and randomly oriented. Growth of their dendrites, in contrast to that of Purkinje cell dendrites, appears to be markedly influenced by the organization of the local cellular milieu.

ISSN:0092-7317    

DOI:10.1002/cne.901520203

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

年代:1973

数据来源: WILEY

摘要:

AbstractTerminal degeneration following lesions of the medial septal nucleus or of the contralateral hippocampus was mapped and compared with the distribution of acetylcholinesterase in the hippocampal formation of the rat. Previously unreported septal projections were found in the supragranular region of the dentate gyrus, an area which is also the locus of a dense band of acetylcholinesterase. This correspondence provides further support for the hypothesis that the enzyme is located in the septal efferents. These findings are combined with those of earlier workers in a hypothetical model of septo‐hippocampal relationship

ISSN:0092-7317    

DOI:10.1002/cne.901520204

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

年代:1973

数据来源: WILEY

摘要:

AbstractIn crayfish peripheral nerve, terminal processes of most sensory fobers degenerated within two to three weeks of nerve severance. First, large clear vesicles appeared in the axoplasm which subsequently lost its substructure, became more dense and compact, and was finally reduced to dense inclusions within glial cytoplasm. Considerable traumatic degeneration was also observed in proximal segments of severed axons. The rate of fiber degeneration was generally more rapid in the smallest fibers and slower in the larger intermediate axons. Large numbers of regenerating axons were first seen crossing the lesion site after four weeks. Growing fibers, found in bundles wrapped by glial processes, were at first small and tightly packed with no glial processes separating them. Later fibers enlarged and acquired wrapping patterns typical of normal sensory fibers. Growth cones were observed during early stages of regeneration. Some secondary degeneration may occur.

ISSN:0092-7317    

DOI:10.1002/cne.901520205

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe trigeminal nerve was unilaterally transected proximal to its ganglion in ten adult bull frogs. The course and termination of the axons were determined with the aid of Nauta and Fink‐Heimer techniques. The trigeminal primary afferents can be traced to five loci within the central nervous system, namely: the main sensory nucleus of the trigeminus, the descending nucleus of the trigeminus, a hitherto undescribed “ventral trigeminal field”, the rostral part of the nucleus of the solitary tract, and to the commissural nucleus of

ISSN:0092-7317    

DOI:10.1002/cne.901520206

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

年代:1973

数据来源: WILEY

摘要:

AbstractMicrochemical techniques correlated with histologic observations were used to study rat optic nerve at 5, 10, 15, 20, 30, 40 and 50 days of postnatal development. Cell enumeration was accomplished by combining DNA as says with previously reported differential cell counts in electron microscopic montages (Vaughn, '69). At 5 days of age, the optic nerve contained unmyelinated axons, and its volume and total number of glia (DNA) were less than 40% of 50‐day‐old values. The cell population was composed of equal numbers of fibrous astrocytes and glial stem cells but contained only 7% oligodendrocytes. Between 5 and 20 postnatal days, mitotic proliferation of these stem cells resulted in a 3‐fold increase of DNA, while numbers of oligodendroglia increased 10‐fold. The cell population of the nerve at 20 postnatal days was similar to that found in the adult, with oligodendrocytes constituting 60% of the total cell population. Although these cells continuously formed myelin throughout postnatal development, their maximal rate of myelin lipid deposition (cerebrosides and cholesterol) occurred between 5 and 20 postnatal days. Hence, the most rapid rate of myelinogenesis in rat optic nerve occurred during the first three weeks of postnatal life and was synchronous with the mitotic proliferation and cellular differentiation of interfascicular oligoden

ISSN:0092-7317    

DOI:10.1002/cne.901520207

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

年代:1973

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901520201

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

年代:1973

数据来源: WILEY