Beta-like ganglion cells in the retina of the North American opossum

Genesis of neurons of the retinal ganglion cell layer in the opossum

“…Beta-like cells with large-medium somata have been identified by Golgi-like HRP filling (Wilson and Condo 1985) and Golgi impregnation (Hoko~ and Moraes 1991), and may mimick cat beta cells in terms of the naso-temporal division.…”

“…First, development in the visual system of opossums follows a protracted course that favors the resolution of spatial and temporal patterns (Cavalcante and Rocha-Miranda 1978 a, b;Cavalcante et al 1984Cavalcante et al , 1991bMendez-Otero et al 1985;Kirby et al 1988; Barradas et al 1989). Second, studies of the organization of the retinal ganglion cell layer have shown a weak area centralis but no evidence for a visual streak (Hoko~ and Oswaldo-Cruz 1979; Rapaport et al 1981), also a relatively high proportion (> 20%) of cells with uncrossed optic projections (Gawryszewski and Hoko~ 1981;Hoko9 1982;Cavalcante et al 1991 a)and cells with dendritic architecture similar to those of beta, Offprint requests to: L.A. Cavalcante alpha and gamma ganglion cells of the cat retina (cat -Boycott and W/issle ]974; opossums - Wilson and Condo 1985;Hoko9 and Moraes 1991). These features make the ganglion cell layer a suitable place for the search of correlations between developmental patterns and its mature organization.…”

Retinal ganglion cells in the South American opossum (Didelphis aurita)

“…By using Nissl-stained retinal whole-mounts, three groups of ganglion cells have been distinguished in the opossum retina on the basis of their soma size (Freeman and Tancred, 1978;Hokoç and Oswaldo-Cruz, 1979;Rapaport et al, 1981). In the North American opossum, a morphological subtype of ganglion cells similar to the cat beta cell was identified through the use of the horseradish peroxidase (HRP) technique (Wilson and Condo, 1985). Hokoç and Moraes (1992), employing the Golgi technique, reported a ganglion cell with morphology similar to that of the cat beta ganglion cell in the South American opossum (Didelphis aurita).…”

Fiber order in the opossum's optic tract

“…The largest ganglion cells are likely to be homologous to the cat's ~ cell, as every eutherian mammal and two diprotodont marsupials examined display a similar cell type (Wong et al 1986;Peichl et al 1987;Dunlop 1990). A medium-sized cell class in the opossum possesses a dendritic morphology similar to the cat's/~ cell (Wilson and Condo 1985;Hoko9 and Moraes 1992). No good basis exists for relating the other two cell classes (a small-medium class and a small class) with the sub-classes of gamma cell in the cat, although on the basis of the present results and those from the cat's optic tract, a parallel with the tonic and phasic W-cells described by Fukuda and Stone (1974) and by Stanford (1987 a) may eventually be established (Reese et al 1991).…”

“…Despite this, its visual pathways display a differentiation common to other, more visually proficient, mammals: its retina contains ganglion cells that differ in size, dendritic morphology and central projections Rapaport and Wilson 1983;Wilson and Condo 1985;Hoko~ and Moraes 1992), while its optic nerve contains axons of various diameters and conduction velocities (Hoko9 and Oswaldo-Cruz 1978;Rowe et al 1981 ;Kirby et al 1982). Furthermore, its dorsal lateral geniculate nucleus contains cells with receptive fields and latencies similar to those of X, Y and W cells found in the cat (Kirby and Wilson 1986).…”