By Priv.-Doz. Dr. rer. nat. Dipl.-Biol. H.-J. Wagner (auth.)
In many components of vertebrate and invertebrate important fearful platforms, teams of nerve or receptor cells are available which are prepared and hooked up in keeping with an actual, functionally outlined trend (Braitenberg, 1973; Santini, 1975; Strausfeld, 1976; Chan-Palay, 1977). In those circumstances, teams of phone our bodies or synapses seem as essentially related configurations, which, although, are diverse intimately from one another. Such summary styles of connectivity are of a statistical nature and don't enable, in a given instance, for the prediction of the localization or connections of a specific phone. "Wiring diagrams", for this reason, will be bought in basic terms from a large number of person observations. against this, in numerous sensory organs, concrete styles happen that con sist of a standard, mosaic-like, and geometric association of comparable mobile varieties. The fidelity of the sort of mosaic permits predictions approximately definite devices of the development at the foundation of just a couple of exemplary observations. general examples are present in the visible procedure: within the compound eye of bugs, every one ommatidium encompasses a convinced variety of visible cells which are grouped round the optical axis in a hexogonal array (Kirsch feld, 1967); within the vertebrate retina, mosaics of geometrically prepared cones are came upon most often in decrease vertebrates; they're universal between teleosts. a few reports have handled their phylogenetic value and their useful position as model to precise environments or modes of feeding.
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Extra resources for Cell Types and Connectivity Patterns in Mosaic Retinas
Hiodon alosoides: Bundles of about 35 photoreceptor cells are arranged in a hexagonal pattern. ) 35 If the rows of single cones are located at right angles, double cones may be arranged in this lattice in such a way that the clefts which separate the double cone partners are oriented parallel to each other (Fig. 9f). The resulting row patterns appears to be the more primitive form of mosaic - at least during ontogeny - from which patterns described below may develop (Lyall, 1957b; Engstrom, 1963b; Wagner, 1974).
In the internal plexiform layer, they are localized at the ribbon synapses between bipolar terminals and processes of amacrine cells. 54 Electrophysiologic experiments have shown that there are interactions between cones and horizontal cells that are in accordance with the morphologic observation of reciprocal synapses. Stimulation of visual cells with light leads to a hyperpolarization of horizontal and bipolar cells; the same cells are depolarized in response to darkness. According to Byzov (1968), visual cells during darkness liberate permanently transmitter substances that depolarize the membrane of horizontal and bipolar cells (Cervetto, 1976; Fuortes, 1976; also see Sect.
These rows are in register with the mosaic of cone pedicles that is visible in the upper right corner. g. The nuclei of rod horizontal cells in the center show no regular arrangement. h. Layer of bipolar cell nuclei; no pattern formation is detectable cone mosaics are best demonstrated a few micrometers sclerad of this layer at the level of the cell ellipsoids; at the level of the cone outer segments they are more difficult to observe. At the level of the visual cell nuclei in the external nuclear layer, only the nuclei of those cells show a regular arrangement that are situated directly vitread of the external limiting membrane; in most cases, these are the single cones (Figs.
Cell Types and Connectivity Patterns in Mosaic Retinas by Priv.-Doz. Dr. rer. nat. Dipl.-Biol. H.-J. Wagner (auth.)