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Experimental reorganization of the cerebellar cortex. III. Regeneration of the external germinal layer and granule cell ectopia
Author(s) -
Altman Joseph
Publication year - 1973
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.901490203
Subject(s) - biology , granule (geology) , granule cell , regeneration (biology) , anatomy , microbiology and biotechnology , cerebellar cortex , cerebellum , neuroscience , central nervous system , dentate gyrus , paleontology
Abstract The heads of Long‐Evans hooded rats were irradiated daily from day 3, 4 or 6 onward with schedules of low‐level x‐ray which differentially delayed the regeneration of the subtotally eradicated external germinal layer or prevented its regeneration altogether. Most schedules that permitted regeneration led to the arrest of many granule cells in the molecular layer where they formed an ectopic zone. The dendrites of ectopic granule cells had synapses with mossy fibers located in their vicinity in the molecular layer. The position of the ectopic zone varied in different lobules depending on several factors: the time when regeneration began, the estimated date of descent of granule cells, regional differences in cortical maturation and in the estimated upward growth rate of mossy fibers. Within the same lobule, the longer regeneration was delayed the higher in the molecular layer the differentiating and descending granule cells were captured by the apparently autonomously ascending mossy fibers. If regeneration started early and allowed the descent of granule cells into the granular layer (early irradiation) or if regeneration of granule cells was prevented altogether (late irradiation) an ectopic zone was not formed. The technique was used for estimating the normal growth pattern of mossy fibers in the different lobules.