Photoreceptors inner segment

In addition to its presence in the RPE, ABCA1 has been found to be localized in the neural retina, particularly in the ganglion cell layer and rod photoreceptor inner segments (Tserentsoodol et al., 2006a), suggesting it may be involved in carotenoid transport throughout the retina. 

Inner nuclear layer Outer plexiform layer Henle fiber layer Photoreceptor outer nuclear layer Photoreceptor inner segment layer... 

Typical The coating of the protein substrate, Opsin, by the chromophore Rhodonine as it is released from the fluid filling the cavity between the RPE and the layer of photoreceptor Inner Segments. 

Figure 5.3C shows a cross-section of the retina, but this tissue came from a donor who had lost useful vision due to a retinal degeneration. There is a complete loss of photoreceptor outer segments, the almost complete absence of cells in the ONL (i.e., photoreceptor inner segments). However, the inner retinal cells are preserved in substantial numbers. 

Photoreceptor Inner Segment, Soma, and Synaptic Terminal... 

Figure 3 Light micrograph of experimental CNV four weeks after PDT. A layer of proliferated RPE (arrow) surrounds the CNV (C) with pigment-laden cells overlying the RPE. The outer nuclear layer, photoreceptor inner segments, and a few rudimentary outer segments remain in the area of CNV. The CNV extends through Bruch s membrane (arrow head) and contains few capillaries. The spaces seen are acinar structures in RPE cells. Bar = 50 pm. Abbreviations PDT, photodynamic therapy RPE, retinal pigment epithelium CNV, choroidal neovascularization. Source From Ref. 24.

Changes in the retina have also been associated with chronic low level lead exposure, also at 300 ppm and 1000 ppm Pb. These include necrosis of photoreceptor inner segments, perikarya and synaptic endings, Mueller cells, and occasional ganglion cells (Santos-Anderson et al., 1980). 

The ox nuclear pellet obtained from retinas homogenized mechanically contains, as shown by EM, heterogeneous populations of nuclei, aggregation of mitochondria derived from photoreceptor Inner segment fragmented outer segments and Isolated photoreceptor terminals.Thus the enzymic activities reported above In crude nuclear fractions are only Indicative of their occurrence as the photoreceptor level without specifying the precise site of their localization In photoreceptors. 

Gerashchenko, D., et al (1998). Dominant expression of rat prostanoid DP receptor mRNA in leptomeninges, inner segments of photoreceptor cells, iris epithelium, and ciliary processes. J. Neurochem. 71, 937-45. 

Figure 14.1 Schematic diagram of the blood-retinal barrier (BRB). The retinal cell layers seen histologically consist of retinal pigment epithelium (RPE) photoreceptor outer segments (POS) outer limiting membrane (OLM) outer nuclear layer (ONL) outer plexiform layer (OPL) inner nuclear layer (INL) inner plexiform layer (IPL) ganglion cell layer (GCL) nerve fiber layer (NFL) inner limiting membrane (ILM).

For simplicity, in this review we will refer to these as GC1 and GC2, respectively. In situ hybridization of the human GC1 and GC2 shows localization in the photoreceptor cell bodies and inner segments (Imanishi et al., 2002) By immunocy-tochemistry, GCs are present in murine rods (Yang and Garbers, 1997 Hallett et al.,... 

First, the absorption spectra of the Outer Segments of the photoreceptor cells rely on the resonant condition of one of the Rhodonines when it is present under specific conditions (Col. R of the Table). These conditions are that it is present as a liquid crystalline surface film on the disks of the segment (8R) and in contact with a de-excitation agent associated with the Inner Segment of the same cell (12R). 

The work of Papermaster and others have clearly shown that the protein used in the substrates (disks) of the outer segment of photoreceptor cells is formed within those cells. The material (opsin + retinal) is secreted by those cells and formed into disks within a cavity associated with the inner segment of the photoreceptor cells. The work of Bridges, et. al. shows clearly that the retinoids used in the functional part of the visual process, the Rhodonines, do not pass through the photoreceptor cells. They are delivered to the outer segments via the RPE. 

Figure 6.7 The rhodopsin-transducin cascade resulting in cGMP hydrolysis. R is rho-dopsin R is "activated rhodopsin" is the transducin ffy-subunit complex Ta is the transducin a subunit. Inset A rod cell showing entry of Na+ ions into the outer segment of the cell through cGMP-sensitive channels and existing from the inner segment via an ATPase pump. (Based, in part, on Lolley RN, Lee RH. Cyclic GMP and photoreceptor function. FASEB J 4 3001-3008, 1990, and partly on Zurer PS. Chemistry of vision. Chem Eng News November, 1983, p. 34.)...

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...

Figure 2. Schematic representations of a prototypic cilium and the photoreceptor cilium in comparison. (A) Scheme of a prototypic cilium, in longitudinal extension and cross sections through subciliary compartments axoneme (9x2 + 2 microtubule arrangement), transition zone (9x2 + 0 microtubule arrangement) and centriole (9x3 + 0 microtubule arrangement) of the basal body. (B) Scheme of the ciliary part of a rod photoreceptor cell. Axonemal microtubules (MX) project into the outer segment (OS). The OS is linked via the connecting cilium (CC) to the inner segment (IS). The CC corresponds to the transition zone of a prototypic cilium. The basal body complex (BB) is localized in the apical region of the IS. The calycal process (CP) of the IS is linked by extracellular fibers with the membrane of the CC.

Figure 30.1. Electron Micrograph of Mitochondria. Numerous mitochondria occupy the inner segment of retinal rod cells. These photoreceptor cells generate large amounts of ATP and are highly dependent on a continuous supply of O2. [Courtesy of Dr. Michael Hogan.]...

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