By Priv.-Doz. Dr. rer. nat. Dipl.-Biol. H.-J. Wagner (auth.)
In many elements of vertebrate and invertebrate crucial apprehensive structures, teams of nerve or receptor cells are available which are prepared and attached in keeping with an exact, functionally outlined trend (Braitenberg, 1973; Santini, 1975; Strausfeld, 1976; Chan-Palay, 1977). In those situations, teams of mobile our bodies or synapses look as primarily related configurations, which, in spite of the fact that, are assorted 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 cellphone. "Wiring diagrams", accordingly, may be received basically from a large number of person observations. by contrast, in different sensory organs, concrete styles ensue that con sist of a standard, mosaic-like, and geometric association of comparable telephone varieties. The fidelity of the sort of mosaic permits predictions approximately definite devices of the trend at the foundation of just a couple of exemplary observations. usual examples are present in the visible method: within the compound eye of bugs, each one ommatidium includes a yes 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 practical function as model to express environments or modes of feeding.
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Extra resources for Cell Types and Connectivity Patterns in Mosaic Retinas
The rod spherules (rs) are distinguished from cone pedicles by a markedly less electron-dense cytoplasm. They are situated most often in the vicinity of the central single cone. Block-staining, Golgi EM impregnation, double staining of the section 39 Fig. 12. Tangential section through the external plexiform layer of Nannacara anomala. Electron micrograph of a square unit at higher magnification. Eight double cone pedicles (dcp) of equal size surround a central single cone (cscp). In the center of the square, a radial stem of a Muller cell (mfJ is visualized, which is filled with mitochondria.
This is facilitated by incubating the tissue in ethanolic phosphotungstic acid (E-PTA), thereby staining synaptic membranes and paramembranous structures selectively (Bloom and Aghajanian, 1968). Figure 19a shows that, above all, the synaptic ribbon and the arciform density show a strong positive reaction. The cone cytoplasm does not stain with E-PT A in the region of the synaptic ridge; only at the vitread edge is a rim of filamentous material visible, which protrudes into the synaptic cleft in the form of numerous triangular extensions.
At some locations, several profiles of processes are grouped around a central extension of the cone cytoplasm. The membranes that face each other at such sites are slightly enlarged to a thickness of 20 nm. Intercellular accumulations of E-PTA-positive material are observed between these membranes. Because no reconstructions of complete serial sections of teleost cone pedicles are yet available, it is not possible to identify the different constituents of these synapses; however, the configuration of the processes involved strongly resembles spine-like projections of bipolar dendrites in contact with cone pedicles of rabbits, which have been described by Sjostrand (1976) after extensive analsysis of serially sectioned material.
Cell Types and Connectivity Patterns in Mosaic Retinas by Priv.-Doz. Dr. rer. nat. Dipl.-Biol. H.-J. Wagner (auth.)