Dendritic bundles: occurrence and regeneration in the forebrain of the Japanese carp, Cyprinus carpio.

Dendritic bundles were observed in the striatum and cerebellum of the Japanese carp. The striatal bundles were found to regenerate following telencephalic removal. This finding in conjunction with incoming axonal budding suggests that formation of the bundles are under the control of dynamic biological factors and not simple mechanical distortions.

Regeneration of the forebrain of the Japanese carp, Cyprinus carpio: a Golgi analysis.

The regeneration of the forebrain of the Japanese carp, Cyprinus carpio was examined with the rapid Golgi method. Characteristic of both 40 and 70 day regenerated forebrains was a proliferation of the spine processes of ependymal cells. Concomitant with this spinous augmentation was the appearance of swellings in many of the processes. Adjacent to the ependyma were cells that appeared to bud-off the ependyma and become migrating neuroblasts. The examination of the neurons in both normal and regenerated forebrains revealed no obvious and consistent differences between the configurations in both cases. In contrast to this finding, examination of the incoming axons showed numerous swellings and enlargements which were presumed to be immature synapses. The signifiance of these findings to the regeneration of the forebrain is discussed.

The rodent neostriatum: a Golgi analysis.

In the adult rodent, coronal sections of Golgi impregnations of the neostriatum display a compact segregation of axon fascicles, neuronal clusters, and dendritic bundles thus forming an areolar configuration. Isolated neurons are rarely seen. The dorsomedial region of the neostriatum appears free of axon fascicles and dendritic bundles. Horizontal and sagittal sections of the neostriatum show clusters of cells parallel to axon fascicles. The neurons exhibit spine-laden dendrites with an initial spine-free segment. Neonatal impregnations exhibit a different configuration. Neonatally, cells tend to cluster but there is no bundling of dendrites. Neurons are spine-free or have protospines on the soma and the dendrites, including the initial segment. Transition from neonate to adult configuration is discernible at about 15 days after birth. The neostriatum of carnivores exhibits a different structure from the rodent neostriatum. This difference is associated with a developed anterior limb of the internal capsule in the carnivore. The axon fascicle-free portion of the carnivore neostriatum lacks dendritic bundles and pallisades. Portions near the capsule with axon fascicles appear similar to the rodent neostriatum with dendritic bundlings and pallisading. Such findings emphasize the importance of total neuronal configuration (neuronal-architectonics) in morphologic analyses.