Bipolar cell

Below the inner segment is the soma and nucleus, which connects at its base to the axon and synaptic terminal. Photoreceptors release glutamate at ribbon synapses (Heidelberger et al., 2005). Synaptic ribbons are specialized for sustained release of neurotransmitter and are also found in the terminals of retinal bipolar cells, as well as vestibular and cochlear hair cells. Synaptic ribbons receive their name because of their planar strnctnre in photoreceptor terminals, although bipolar and hair cell ribbons are more spherical in shape. 

The ribbon is composed mainly of the structural protein, Ribeye, but also includes a kinesin motor protein, KIF3A, and Rab3-interacting protein, RIM. Ribbons are attached to the synaptic active zone by bassoon, and its structural relative, piccolo. Although the ribbon appears to anchor a readily releasable pool of vesicles, molecular motors do not appear to be involved in vesicle movements near the active zone. RDVt protein mutations have been implicated in an autosomal dominant rod-cone dystrophy (Johnson et al., 2003). 

Glutamate release from synaptic terminals of photoreceptor and bipolar cells is regulated by calcium influx through L-type calcium channels (Heidelberger et al., 2005). The use of F-type channels at ribbon synapses contrasts with the reliance on N, P, and Q type channels for neurotransmission at conventional synapses of spiking neurons. A retina-specific L-type channel, alpha IF (CaVl.4), is localized to rod terminals. Mutations in this channel produce a congenital stationary night blindness (Bech-Hansen et al., 1998). 

Opsins. Cone opsins are 40% homologous to rhodopsin, S cone opsins are 40% homologous with M and L cone opsins, but M and L cone opsins are 97% homologous with one another. The differences in spectral absorbance among different opsins result from differences in a small number of amino acid residues that alter the position of hydroxyl groups close to ll-cw-retinal. The 30nm difference in spectral absorbance between primate M and L cones is determined primarily by three amino acids alanine vs. serine at position 180 ( 4nm), phenylalanine vs. tyrosine at position 277 (-10 nm) and alanine vs. threonine at position 285 ( 16nm) (Deeb, 2005). 

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In the electrolysis zone, the electrochemical reactions take place. Two basic electrode configurations are used (/) monopolar cells where the same cell voltage is appHed to all anode/cathode combinations and (2) bipolar cells where the same current passes through all electrodes (Eig. 4). To minimize the anodic oxidation of OCL , the solution must be quickly moved out of this zone to a reaction zone. Because the reaction to convert OCk to CIO (eq. 

Fig. 4. Sodium chlorate cell designs (a) the horizontal bipolar cells used by Huron having narrow gap vertical plates or horizontal mesh where (-)...

Both share more or less the same merits but also the same disadvantages. The beneficial properties are high OCV (2.12 and 1.85 V respectively) flexibility in design (because the active chemicals are mainly stored in tanks outside the (usually bipolar) cell stack) no problems with zinc deposition in the charging cycle because it works under nearly ideal conditions (perfect mass transport by electrolyte convection, carbon substrates [52]) self-discharge by chemical attack of the acid on the deposited zinc may be ignored because the stack runs dry in the standby mode and use of relatively cheap construction materials (polymers) and reactants. 

Benzene hydrogenation, electrochemically promoted, 288, 452 Bipolar cells... 

Zenisek D, Steyer JA, Eeldman ME, Aimers W (2002) A membrane marker leaves synaptic vesicles in nulliseconds after exocytosis in retinal bipolar cells. Neuron 35 1085-1097 Zhang L, He T, Talal A, Wang G, Frankel SS, Ho DD (1998) In vivo distribution of the human immunodeficiency virus/simian immunodeficiency virus coreceptors CXCR4, CCR3, and CCR5. J Virol 72 5035-5045... 

The micro structured platelets, hold in a non-conducting housing, were realized by etching of metal foils and laser cutting techniques [69]. Owing to the small Nemst diffusion layer thickness, fast mass transfer between the electrodes is achievable. The electrode surface area normalized by cell volume amounts to 40 000 m m". This value clearly exceeds the specific surface areas of conventional mono- and bipolar cells of 10-100 m m. ... 

Furan was dimethoxylated to give 2,5-dihydro-2,5-dimethoxyfuran, using electrogenerated bromine molecules generated from bromide salts in electrolyte solutions [71]. This reaction was characterized in classical electrochemical reactors such as pump cells, packed bipolar cells and solid polymer electrolyte cells. In the last type of reactor, no bromide salt or electrolyte was used rather, the furan was oxidized directly at the anode. H owever, high consumption of the order of 5-9 kWh kg (at 8-20 V cell voltage) was needed to reach a current efficiency of 75%. 

The OSN is a bipolar cell that extends a single dendrite to the apical surface of the epithelium. From the dendritic... 

DeVries, S. H. and Schwartz, E. A. (1999) Kainate receptors mediate synaptic transmission between cones and Off bipolar cells in a mammalian retina. Nature 397,157-160. 

The core of the electrolyser is the cell block, which is made up of a large number of usually bipolar cells in a modular structure.8 Typical sizes of a cell block range from 1 to 800Nm3/h. (Most electrolysers sold today to laboratories, the semiconductor industry, etc., have a capacity less than 60 Nm3/h.) The biggest capacities realised are about 150 MW. An alkali solution, usually 20% to 40% potassium hydroxide (KOH), is used as the electrolyte that flows between the electrodes. In alkaline solutions, the electrodes must be resistant to corrosion, have good electronic... 

Two distinct classes of cell design exist the monopolar and the bipolar. Most commercial stacks have the bipolar design, which means that the single cells are connected in series both electrically and geometrically. The bipolar cell design has the advantages of compactness and shorter current paths with lower voltage losses. 

In this undivided, bipolar cell, the top-sides of all the graphite plates are working as anodes and the bottom sides as... 

Because the membrane is partially depolarized in the dark, its neurotransmitter glutamate is continuously released. Glutamate inhibits the optic nerve bipolar cells with which the rod cells synapse. By hyperpolarizing the rod cell membrane, light stops the release of glutamate, relieving inhibition of the optic nerve bipolar cell and thus initiatii a signal into the brain. 

The Na" channel has a receptor site for cyclic GMP when cyclic GMP is bound, the channel is closed. This leads to a decrease in the intracellular Na ion concentration, resulting in hyperpolarisation of the cell membrane. This decreases the release of the neurotransmitter glutamate into the synapse that connects the photoreceptor cell to the bipolar neurones. In this specific case, a decrease in the neurotransmitter concentration in the synapse is a signal that results in depolarisation of the bipolar cell. The action potential in the bipolar cells communicate with ganglion cells, the axons of which form the optic nerve. Thus action potentials are generated in the axons which are... 

Physiological studies have identified both post- and presynaptic roles for ionotropic kainate receptors. Kainate receptors contribute to excitatory post-synaptic currents in many regions of the CNS including hippocampus, cortex, spinal cord and retina. In some cases, postsynaptic kainate receptors are codistributed with AMPA and NMDA receptors, but there are also synapses where transmission is mediated exclusively by postsynaptic kainate receptors for example, in the retina at connections made by cones onto off bipolar cells. Extrasynaptically located postsynaptic kainate receptors are most likely activated by spill-over glutamate (Eder et al. 2003). Modulation of transmitter release by presynaptic kainate receptors can occur at both excitatory and inhibitory synapses. The depolarization of nerve terminals by current flow through ionotropic kainate receptors appears sufficient to account for most examples of presynaptic regulation however, a number of studies have provided evidence for metabotropic effects on transmitter release that can be initiated by activation of kainate receptors. The hyperexcitability evoked by locally applied kainate, which is quite effectively reduced by endocannabinoids, is probably mediated preferentially via an activation of postsynaptic kainate receptors (Marsicano et al. 2003). 

A more recent LPB development in Israel involves the fabrication of bipolar cells using a composite polymer electrolyte (CPE), and a pyrite-based positive... 

Table 8.3 Specific energy and power of 13 cm diameter bipolar cells...

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 19.17. Overvoltage and distribution of voltage drops in cells (Jtiine, 1985). (a) Overvoltage of hydrogen on some metals, (b) Voltage distribution in two kinds of cells for electrolysis of brine, (c) Variation of voltage distribution with current density in the electrolysis of HC1. (d) Schematic of voltage profile in a bipolar cell with five pairs of electrodes.

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