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D I Vaney

Publications and source records attributed to D I Vaney.

45 records · Page 3Linked to original sources
PubMed1980

Coronate cells: displaced amacrines of the rabbit retina?

The rabbit retinal ganglion cell layer contains a soma population which is morphologically distinct from the demonstrated ganglion cells. These "coronate cells" (Vaney, '80) have many features in common with classical neurons and are qualitatively different from typical glial cells. Detailed investigation by specific staining, ribonuclease treatment, and electron microscopy indicates that coronate cells are microneurons. The coronate cells contain somatic subsurface cisternae typical of rabbit amacrine cells, and are similar in appearance to some neurons of the amacrine cell layer. It is suggested that they represent, at least in part, a population of "displaced" amacrine cells.

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PubMed1976

The rabbit optic nerve: fibre diameter spectrum, fibre count, and comparison with a retinal ganglion cell count.

This electron microscopic study indicates that the rabbit optic nerve contains 394,000 +/- 20,000 (p less than 0.05) nerve fibers, of which at least 98% are myelinated. The fibre diameter spectrum of the nerve is unimodal and ranges from 0.25-7 mum with its peak at 0.75 mum. The projection of the visual streak fibres is not apparent in local diameter spectra near the optic nerve head. Integration of a ganglion cell density map of the retina from another rabbit indicates a total ganglion cell count lying between 455,000 and 547,000. The optic nerve fibre and ganglion cell counts are both substantially greater than the maximum fibre count previously reported.

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PubMedDate not supplied

The rod circuit in the rabbit retina.

Mammalian retinae have a well-defined neuronal pathway that serves rod vision. In rabbit retina, the different populations of interneurons in the rod pathway can be selectively labeled, either separately or in combination. The rod bipolar cells show protein kinase C immunoreactivity; the rod (AII) amacrine cells can be distinguished in nuclear-yellow labeled retina; the rod reciprocal (S1 & S2) amacrine cells accumulate serotonin; and the dopaminergic amacrine cells show tyrosine-hydroxylase immunoreactivity. Furthermore, intracellular dye injection of the microscopically identified interneurons enables whole-population and single-cell studies to be combined in the same tissue. Using this approach, we have been able to analyze systematically the neuronal architecture of the rod circuit across the rabbit retina and compare its organization with that of the rod circuit in central cat retina. In rabbit retina, the rod interneurons are not organized in a uniform neuronal module that is simply scaled up from central to peripheral retina. Moreover, peripheral fields in superior and inferior retina that have equivalent densities of each neuronal type show markedly different rod bipolar to AII amacrine convergence ratios, with the result that many more rod photoreceptors converge on an AII amacrine cell in superior retina. In rabbit retina, much of the convergence in the rod circuit occurs in the outer retina whereas, in central cat retina, it is more evenly distributed between the inner and outer retina.

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PubMedDate not supplied

The DAPI-3 amacrine cells of the rabbit retina.

In the rabbit retina, the nuclear dye, 4,6,diamidino-2-phenylindole (DAPI), selectively labels a third type of amacrine cell, in addition to the previously characterized type a and type b cholinergic amacrine cells. In this study, these "DAPI-3" amacrine cells have been characterized with respect to their somatic distribution, dendritic morphology, and neurotransmitter content by combining intracellular injection of biotinylated tracers with wholemount immunocytochemistry. There are about 100,000 DAPI-3 amacrine cells in total, accounting for 2% of all amacrine cells in the rabbit retina, and their cell density ranges from about 130 cells/mm2 in far-peripheral retina to 770 cells/mm2 in the visual streak. The thin varicose dendrites of the DAPI-3 amacrine cells form a convoluted dendritic tree that is symmetrically bistratified in S1/S2 and S4 of the inner plexiform layer. Tracer coupling shows that the DAPI-3 amacrine cells have a fivefold dendritic-field overlap in each sublamina, with the gaps in the arborization of each cell being occupied by dendrites from neighboring cells. The DAPI-3 amacrine cells consistently show the strongest glycine immunoreactivity in the rabbit retina and they also accumulate exogenous [3H]-glycine to a high level. By contrast, the AII amacrine cells, which are the best characterized glycinergic cells in the retina, are amongst the most weakly labelled of the glycine-immunopositive amacrine cells. The DAPI-3 amacrine cells costratify narrowly with the cholinergic amacrine cells and the On-Off direction-selective ganglion cells, suggesting that they may play an important role in movement detection.

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PubMedDate not supplied

The fountain amacrine cells of the rabbit retina.

We have characterized a distinctive type of bistratified amacrine cell in the rabbit retina at both the single cell and population levels. These cells correspond to the "fountain" amacrine cells recently identified by MacNeil and Masland (1998). The fountain cells can be distinguished in superfused retinal wholemounts labeled with nuclear dyes, thus enabling them to be targeted for intracellular injection with Neurobiotin. This revealed that the primary dendrites ascend steeply to sublamina b of the inner plexiform layer, where they form an irregular arbor at the border of strata 4 and 5. These dendrites then give rise to multiple varicose processes that descend obliquely to sublamina a, where they form a more extensive arbor in stratum 1. The fountain amacrine cells show strong homologous tracer coupling when injected with Neurobiotin, and this has enabled us to map their density distribution across the retina and to examine the dendritic relationships between neighboring cells. The fountain amacrine cells range in density from 90 to 360 cells/mm2 and they account for 1.5% of the amacrine cells in the rabbit retina. The thick tapering dendrites in sublamina b form highly territorial arbors that tile the retina with minimal overlap, whereas the thin varicose processes intermingle in sublamina a. The fountain cells are immunopositive for y-aminobutyric acid and immunonegative for glycine. We further propose that these cells are homologous to the substance P-immunoreactive (SP-IR) amacrine cells in the cat retina and that they may account for a subset of the SP-IR amacrine cells in the rabbit retina.

3,3'-Diaminobenzidine↗
PubMedDate not supplied

Distinguishing direction selectivity from orientation selectivity in the rabbit retina.

Direction selectivity and orientation selectivity were examined in the direction-selective (DS) and orientation-selective (OS) ganglion cells in the rabbit retina. Spike activities were recorded in vivo using tungsten-in-glass electrodes. Three types of visual stimuli (flashing slit, moving edges behind a slit, and whole-field drifting gratings) were used to distinguish these attributes. Fourier analysis was performed on data obtained using drifting gratings as proposed by Worgotter and Eysel (1987). Results from both angular and Fourier (polar angle frequency) domains were consistent. DS cells had strong directional components and varying strength of orientational components; they also had intact inhibitory surrounds. The phase of the biased orientation did not have a consistent relationship with the preferred direction. OS cells had predominant orientational components and very weak directional components. We conclude that the orientation bias does not contribute to the generation of direction selectivity, and that the mechanism of this bias of DS cells is rather different from the mechanism that generates orientation selectivity in rabbit OS cells. There are indications that it is similar to the mechanism shown to cause orientation bias in cat concentric cells.

Action Potentials↗
PubMedDate not supplied

The fountain amacrine cells of the rabbit retina.

We have characterized a distinctive type of bistratified amacrine cell in the rabbit retina at both the single cell and population levels. These cells correspond to the "fountain" amacrine cells recently identified by MacNeil and Masland (1998). The fountain cells can be distinguished in superfused retinal wholemounts labeled with nuclear dyes, thus enabling them to be targeted for intracellular injection with Neurobiotin. This revealed that the primary dendrites ascend steeply to sublamina b of the inner plexiform layer, where they form an irregular arbor at the border of strata 4 and 5. These dendrites then give rise to multiple varicose processes that descend obliquely to sublamina a, where they form a more extensive arbor in stratum 1. The fountain amacrine cells show strong homologous tracer coupling when injected with Neurobiotin, and this has enabled us to map their density distribution across the retina and to examine the dendritic relationships between neighboring cells. The fountain amacrine cells range in density from 90 to 360 cells/mm2 and they account for 1.5% of the amacrine cells in the rabbit retina. The thick tapering dendrites in sublamina b form highly territorial arbors that tile the retina with minimal overlap, whereas the thin varicose processes intermingle in sublamina a. The fountain cells are immunopositive for gamma-aminobutyric acid and immunonegative for glycine. We further propose that these cells are homologous to the substance P-immunoreactive (SP-IR) amacrine cells in the cat retina and that they may account for a subset of the SP-IR amacrine cells in the rabbit retina.

3,3'-Diaminobenzidine↗