Fetal Rat Cerebellar Fragment Transplantation into Adult Rat Forebrain Lesion Cavities

Fragments of fetal rat cerebellar tissue were grafted into forebrain cortical lesion cavities of adult rats. After a survival ranging from 12-151 days, no graft was found to fill the cavity completely. Large neurons, occasionally grouped into nests, were identifiable from the 22nd day. Myelinated graft fibers, first seen at 32 days, failed to enter host brain. Although grafts demonstrated elements resembling cerebellar tissue, overall organization did not resemble that of the cerebellum

Development of the retinofugal projections in the embryonic and larval zebrafish ( Brachydanio rerio )

Studies of the projection from the vertebrate retina have contributed significantly to current concepts of neural development. The zebrafish has recently become a favored system for the study of development in general and neural development in particular. Although the development of both the optic nerve and the retinotectal projection of the zebrafish has been described, the retinofugal projection in its entirety has not. This paper describes it and also addresses the issue of projectional exuberance: i. e., transient projections to targets that are not innervated in the adult. The retinofugal projection of embryonic and larval zebrafish (32 hours to 7 days post-fertilization) was labeled by intraocular injection of DiI (1,1′-dioctadecyl-3,3,3′,3′, tetramethylindocarbocyanine perchlorate) and then studied in wholemounts and sections. The first optic axons crossed the chiasm at 32 hours post-fertilization and projected in a straight line to reach the tectum at about 44 hours. At 48 hours, a few optic axons deviated along either the tract of the posterior commissure or the tract of the postoptic commissure. By 72 hours (about the time of hatching) optic axons arborized in ten distinct regions, termed arborization fields. At 6–7 days post-fertilization, the same ten arborization fields (nine contralateral, one bilater) were evident. Most of the arborization fields were located in the superficial neuropil and were not associated with morphologically identifiable clusters of somata. On the basis of various landmarks, the ten arborization fields are identified as precursors of retinorecipient nuclei previously described in other adult cypriniform fishes. The development was characterized by the nearly complete absence of any transient projections. Thus, the idea that axonal outgrowth is initially exuberant and trimmed back later is not supported by these results. © 1994 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50063/1/903460410_ftp.pd

Mask for Controlling Visual Input in Cats

Analysis of visual function frequently requires control of visual input. The present report describes a mask which can be used for achieving this control in a variety of experimental situations