Horizontal Cells

Corrosion susceptibility in aqueous media is assessed on the basis of the rating numbers [3, 14], which are different from those of soils. An increased likelihood of corrosion is in general found only in the splash zone. Particularly severe local corrosion can occur in tidal regions, due to the intensive cathodic action of rust components [23, 24]. Since cathodic protection cannot be effective in such areas, the only possibility for corrosion protection measures in the splash zone is increased thickness of protective coatings (see Chapter 16). In contrast to their behavior in soils, horizontal cells have practically no significance. 

Studies on teleost fish and mammals have demonstrated the existence of non-rod, non-cone ocular photoreceptors. In the case of VA opsin in the roach, electrophysiological evidence suggests that one function of this photosensory photopigment is to modulate the activity of retinal horizontal cells. To what end remains unclear, but this fits with the general role of horizontal cells in the teleost... 

Kojima D, Mano H, Fukada Y 2000 Vertebrate ancient-long opsin a green-sensitive photoreceptive molecule present in zebrafish deep brain and retinal horizontal cells. J Neurosci 20 2845-2851... 

In horizontal cells of turtle and fish retinae, a dopamine-induced increase in intracellular cAMP levels is associated with cellular uncoupling [DeVries and Schwartz, 1989 McMahon et al., 1989] (the connexin isoform involved is not identified). Inhibition of phosphodiesterase with IBMX after stimulation of adenylate cyclase using forskolin resulted in an increase in intracellular... 

De Vries SH, Schwartz EA Modulation of an electrical synapse between solitary pairs of catfish horizontal cells by dopamine and second messengers. J Physiol 1989 414 351-375. 

McMahon DG, Kanpp AG, Dowling JE Horizontal cells gap junctions Single channel conductance and modulation by dopamine. Proc Natl Acad Sci USA 1989 86 7639-7643. 

Piccolino M, Neyton J, Gerschenfeld HM Decrease of gap junction permeability induced by dopamine and cyclic adenosine 3, 5 -monophosphate in horizontal cells of turtle retina. J Neurosci 1984 4 ... 

Figure 30-10 (A) Schematic drawing of a synapse. (B) Electron micrograph showing the synaptic junctions in the basal part (pedicle) of a retinal cone cell of a monkey.403 Each pedicle contains synaptic contacts with 12 triads, each made up of processes from a bipolar cell center that carries the principal output signal and processes from two horizontal cells that also synapse with other cones. A ribbon structure within the pedicle is characteristic of these synapses. Note the numerous synaptic vesicles in the pedicle, some arranged around the ribbon, the synaptic clefts, and the characteristic thickening of the membranes surrounding the cleft (below the ribbons). Micrograph courtesy of John Dowling.

Figure 2.2 The retina consists of three layers. Retinal ganglion cells are located at the top followed by a layer of bipolar cells and receptors at the bottom. Light has to pass through the top two layers to reach the light-sensitive sensors. Information then travels upward from the receptors to the bipolar cells and on to the retinal ganglion cells. Information is also exchanged laterally through amacrine and horizontal cells. (Retina illustration from LifeART Collection Images 1989-2001 by Lippincott Williams Wilkins, used by permission from SmartDraw.com.

At a mesoscopic level, the hollow cylindrical-shaped cells are orientated in the same direction as the trunk. Radial sheets of horizontal cells rich in lignin go from... 

Rodrigues Pdos S, Dowling JE (1990) Dopamine induces neurite retraction in retinal horizontal cells via diacylglycerol and protein kinase C. Proc Natl Acad Sci USA 87 9693-9697. 

Based on results in vertebrates Bodis-Wollner (1990) assumed that in primates the surround organization of the retinal ganglion cell is under D1 receptor control. D1 receptor activation causes disjunction of horizontal cells, otherwise coupled in... 

Figure I. Structure of a ciliated photoreceptor cell in vertebrates. (A) Scheme of a rod photoreceptor cell. (B) Transmission electronmicroscopy image of a part of a mouse rod photoreceptor cell. The apical extensions of cells of the retinal pigment epithelium (RPE) evolve the tips of photoreceptors light-sensitive outer segments (OS). The OS is linked via a connecting cilium (CC) to an inner segment (IS) which bears the basal body complex (BB) in its apical region. Synaptic terminals (S) link the photoreceptor cell and the 2nd-order neurons, bipolar and horizontal cells. N = nucleus in B, arrow point to axonemal microtubules projecting into the OS. Bar in B = 0.2 p,m...

This admits periodic solutions for each value of A, and in general A = m. This indicates multiple cells in the horizontal direction. We restrict ourselves to just one horizontal cell, i.e., n = 1. The value of n = 1 corresponds to one horizontal cell, and all the values of n that are greater than 1 correspond to multiple cells in the horizontal direction. In bubble column transitions, the multiple cells in horizontal direction have been observed only in shallow bubble columns in which the height-to-diameter ratio is less than 1. In the present case, we have considered HID > 1. Therefore, the transition to the heterogeneous regime is characterized by one cell in the horizontal direction. Thus, the first transition appears to correspond to a single cell in the horizontal direction ... 

Keywords Amacrine cell Bipolar cell Cone Fovea Horizontal cell Muller cells Photoreceptor Retina Retinal ganglion cell Rod... 

Figure 11.2. The five major retinal cell types (photoreceptors, bipolai cells, horizontal cells, amacrine cells, and ganglion cells) and tlieir synaptic connections.

Twig G, Levy H, Perlman I (2003) Color opponency in horizontal cells of the vertebrate redna. Prog Redn Eye Res 22 31-68. 

The GABA receptor is insensitive to allosteric modulators, such as benzodiazepines and barbiturates. Native responses of the GABA receptor type occur in retinal bipolar or horizontal cells across vertebrate species. Although the term GABA receptors is still being used frequently they have been reassigned as part of GABA receptor family. 

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