Biomedical subjects

Elizabeth S Yamada

Publications and source records attributed to Elizabeth S Yamada.

6 recordsLinked to original sources

PubMed2006

Synaptic input to OFF parasol ganglion cells in macaque retina.

A Neurobiotin-injected OFF parasol cell from midperipheral macaque retina was studied by reconstruction of serial ultrathin sections and compared with ON parasol cells studied previously. In most respects, the synaptic inputs to the two subtypes were similar. Only a few of the amacrine cell processes that provided input to the labeled OFF parasol ganglion cell dendrites made or received inputs within the series, and none of these interactions were with the bipolar cells or other amacrine cells presynaptic to the OFF parasol cell. These findings suggest that the direct inhibitory input to OFF parasol cells originates from other areas of the retina. OFF parasol cells were known to receive inputs from two types of diffuse bipolar cells. To identify candidates for the presynaptic amacrine cells, OFF parasol cells were labeled with Lucifer yellow by using a juxtacellular labeling technique, and amacrine cells known to costratify with them were labeled via immunofluorescent methods. Appositions were observed with amacrine cells containing immunoreactive calretinin, parvalbumin, choline acetylatransferase, and G6-Gly, a cholecystokinin precursor. These findings suggest that the inhibitory input to parasol cells conveys information about several different attributes of visual stimuli and, particularly, about their global properties.

Acetylcholine↗

PubMed2005

Peripheral variability and central constancy in mammalian visual system evolution.

Neural systems are necessarily the adaptive products of natural selection, but a neural system, dedicated to any particular function in a complex brain, may be composed of components that covary with functionally unrelated systems, owing to constraints beyond immediate functional requirements. Some studies support a modular or mosaic organization of the brain, whereas others emphasize coordination and covariation. To contrast these views, we have analysed the retina, striate cortex (V1) and extrastriate cortex (V2, V3, MT, etc.) in 30 mammals, examining the area of the neocortex and individual neocortical areas and the relative numbers of rods and cones. Controlling for brain size and species relatedness, the sizes of visual cortical areas (striate, extrastriate) within the brains of nocturnal and diurnal mammals are not statistically different from one another. The relative sizes of all cortical areas, visual, somatosensory and auditory, are best predicted by the total size of the neocortex. In the sensory periphery, the retina is clearly specialized for niche. New data on rod and cone numbers in various New World primates confirm that rod and cone complements of the retina vary substantially between nocturnal and diurnal species. Although peripheral specializations or receptor surfaces may be highly susceptible to niche-specific selection pressures, the areal divisions of the cerebral cortex are considerably more conservative.

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PubMed2004

Morphology and physiology of primate M- and P-cells.

Catarrhines and platyrrhines, the so-called Old- and New-World anthropoids, have different cone photopigments. Postreceptoral mechanisms must have co-evolved with the receptors to provide trichromatic color vision, and so it is important to compare postreceptoral processes in these two primate groups, both from anatomical and physiological perspectives. The morphology of ganglion cells has been studied in the retina of catarrhines such as the diurnal and trichromatic Macaca, as well as platyrrhines such as the diurnal, di- or trichromatic Cebus, and the nocturnal, monochromatic Aotus. Diurnal platyrrhines, both di- and trichromats, have ganglion cell classes very similar to those found in catarrhines: M (parasol), P (midget), small-field bistratified, and several classes of wide-field ganglion cells. In the fovea of all diurnal anthropoids, P-cell dendritic trees contact single midget bipolars, which contact single cones. The Aotus retina has far fewer cones than diurnal species, but M- and P-cells are similar to those in diurnal primates although of larger size. As in diurnal anthropoids, in the Aotus, the majority of midget bipolar cells, found in the central 2 mm of eccentricity, receive input from a single cone and the sizes of their axon terminals match the sizes of P-cell dendritic fields in the same region. The visual responses of retinal ganglion cells of these species have been studied using single-unit electrophysiological recordings. Recordings from retinal ganglion cells in Cebus and Aotus showed that they have very similar properties as those in the macaque, except that P-cells of mono- and dichromatic animals lack cone opponency. Whatever the original role of the M- and P-cells was, they are likely to have evolved prior to the divergence of catarrhines and platyrrhines. M- and P-cell systems thus appear to be strongly conserved in the various primate species. The reasons for this may lie in the roles of these systems for both achromatic and chromatic vision.

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PubMed2003

Synaptic connections of starburst amacrine cells and localization of acetylcholine receptors in primate retinas.

Starburst amacrine cells in the macaque retina were studied by electron microscopic immunohistochemistry. We found that these amacrine cells make a type of synapse not described previously; they are presynaptic to axon terminals of bipolar cells. We also confirmed that starburst amacrine cells are presynaptic to ganglion cell dendrites and amacrine cell processes. In order to determine the functions of these synapses, we localized acetylcholine receptors using a monoclonal antibody (mAb210) that recognizes human alpha3- and alpha5-containing nicotinic receptors and also antisera against the five known subtypes of muscarinic receptors. The majority of the mAb210-immunoreactive perikarya were amacrine cells and ganglion cells, but a subpopulation of bipolar cells was also labeled. A subset of bipolar cells and a subset of horizontal cells were labeled with antibodies to M3 muscarinic receptors. A subset of amacrine cells, including those that contain cholecystokinin, were labeled with antibodies to M2 receptors. Taken together, these results suggest that acetylcholine can modulate the activity of retinal ganglion cells by multiple pathways.

Acetylcholine↗

PubMedDate not supplied

Synaptic input to an ON parasol ganglion cell in the macaque retina: a serial section analysis.

A labeled ON parasol ganglion cell from a macaque retina was analyzed in serial, ultrathin sections. It received 13% of its input from diffuse bipolar cells. These directed a large proportion of their output to amacrine cells but received a relatively small proportion of their amacrine cell input via feedback synapses. In these respects, they were similar to the DB3 bipolar cells that make synapses onto OFF parasol cells. Bipolar cell axons that contacted the ON parasol cell in stratum 4 of the inner plexiform layer always made synapses onto the dendrite, and therefore, the number of bipolar cell synapses onto these ganglion cells could be estimated reliably by light microscopy in the future. Amacrine cells provided the majority of inputs to the ON parasol cell. Only a few of the presynaptic amacrine cell processes received inputs from the same bipolar cells as the parasol cells, and most of the presynaptic amacrine cell processes did not receive any inputs at all within the series. These findings suggest that most of the inhibitory input to the ON parasol cell originates from other areas of the retina. Amacrine cells presynaptic to the parasol ganglion cell interacted very infrequently with other neurons in the circuit, and therefore, they would be expected to act independently, for the most part.

Animals↗

PubMedDate not supplied

Wide-field ganglion cells in macaque retinas.

To describe the wide-field ganglion cells, they were injected intracellularly with Neurobiotin using an in vitro preparation of macaque retina and labeled with streptavidin-Cy3. The retinas were then labeled with antibodies to choline acetyltransferase and other markers to indicate the depth of the dendrites within the inner plexiform layer (IPL) and analyzed by confocal microscopy. There were eight different subtypes of narrowly unistratified cells that ramified in each of the 5 strata, S1-5, including narrow thorny, large sparse, large moderate, large dense, large radiate, narrow wavy, large very sparse, and fine very sparse. There were four types of broadly stratified cells with dendritic trees extending from S4 to S2. One type resembled the parvocellular giant cell and another the broad thorny type described previously in primates. Another broadly stratified cell was called multi-tufted based on its distinctive dendritic branching pattern. The fourth type had been described previously, but not named; we called it broad wavy. There was a bistratified type with its major arbor in S5, the same level as the blue cone bipolar cell; it resembled the large, bistratified cell with blue ON-yellow OFF responses described recently. Two wide-field ganglion cell types were classified as diffuse because they had dendrites throughout the IPL. One had many small branches and was named thorny diffuse. The second was named smooth diffuse because it had straighter dendrites that lacked these processes. Dendrites of the large moderate and multi-tufted cells cofasciculated with ON-starburst cell dendrites and were, therefore, candidates to be ON- and ON-OFF direction-selective ganglion cells, respectively. We concluded that there are at least 15 morphoplogical types of wide-field ganglion cells in macaque retinas.

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