scholarly journals RENEWAL OF GLYCEROL IN THE VISUAL CELLS AND PIGMENT EPITHELIUM OF THE FROG RETINA

1974 ◽  
Vol 62 (2) ◽  
pp. 378-389 ◽  
Author(s):  
Carol Bibb ◽  
Richard W. Young
Keyword(s):  
Pigment Epithelium ◽  
Lipid Synthesis ◽  
Plexiform Layer ◽  
Visual Cell ◽  
Oil Droplets ◽  
Visual Cells ◽  
Rods And Cones ◽  
Outer Segments ◽  
Frog Retina ◽  
Autoradiographic Analysis

The renewal of glycerol in the visual cells and pigment epithelium of the frog retina was studied by autoradiographic analysis of animals injected with [2-3H]glycerol. Assay of chloroform:methanol extracts showed that the labeled precursor was used mainly in lipid synthesis, although there was also some utilization in the formation of protein. Radioactive glycerol was initially concentrated in the myoid portion of rods and cones, indicating that this is the site of phospholipid synthesis in visual cells. The glycogen bodies (paraboloids) of accessory cones were also heavily labeled, suggesting the diversion of some glycerol into glycogenic pathways. In the pigment epithelium, only the oil droplets became significantly radioactive. The outer plexiform layer (which contains the visual cell synaptic bodies) and the cone oil droplets gradually accumulated considerable amounts of labeled material. Within 1–4 h, labeled molecules began to appear in the visual cell outer segments, evidently having been transported there from the myoid portion of the inner segment. Most of these were phospholipid molecules which became distributed throughout the outer segments, presumably replacing comparable constituents in existing membranes. In rods only, there was also an aggregation of labeled material at the base of the outer segment due to membrane biogenesis. These highly radioactive membranes, containing labeled molecules of lipid and protein, were subsequently displaced along the rod outer segments due to repeated membrane assembly at the base. The distribution of radioactivity supported the conclusion that membrane renewal by molecular replacement is more rapid for lipid than it is for protein.

scholarly journals THE RENEWAL OF ROD AND CONE OUTER SEGMENTS IN THE RHESUS MONKEY

1971 ◽  
Vol 49 (2) ◽  
pp. 303-318 ◽  
Author(s):  
Richard W. Young
Keyword(s):  
Rhesus Monkey ◽  
Rhesus Monkeys ◽  
Outer Segment ◽  
Pigment Epithelium ◽  
Renewal Processes ◽  
Visual Cells ◽  
Rods And Cones ◽  
Outer Segments ◽  
Retinal Rod ◽  
Assembly Site

The renewal of retinal rod and cone outer segments has been studied by radioautography in rhesus monkeys examined 2 and 4 days after injection of leucine-3H. The cell outer segment consists of a stack of photosensitive, membranous discs. In both rods and cones some of the newly formed (radioactive) protein became distributed throughout the outer segment. Furthermore, in rods (but not in cones), there was a transverse band of concentrated radioactive protein slightly above the outer segment base 2 days after injection. This was due to the formation of new discs, into which labeled protein had been incorporated. At 4 days, these radioactive discs were located farther from the outer segment base. Repeated assembly of new discs had displaced them away from the basal assembly site and along the outer segment. Measurements of the displacement rate indicated that each retinal rod produces 80–90 discs per day, and that the entire complement of outer segment discs is replaced every 9–13 days. To compensate for the continual formation of new discs, groups of old discs are intermittently shed from the apical end of the cell and phagocytized by the pigment epithelium. Each pigment epithelial cell engulfs and destroys about 2000–4000 rod outer segment discs daily. The similarity between visual cells in the rhesus monkey and those in man suggests that the same renewal processes occur in the human retina.

scholarly journals Rhythmic daily shedding of outer-segment membranes by visual cells in the goldfish.

1978 ◽  
Vol 76 (3) ◽  
pp. 593-604 ◽  
Author(s):  
W T O'Day ◽  
R W Young
Keyword(s):  
Outer Segment ◽  
Dark Period ◽  
Pigment Epithelium ◽  
Light Period ◽  
Rhythmic Pattern ◽  
Light Cycle ◽  
Visual Cells ◽  
Rods And Cones ◽  
Outer Segments ◽  
Pigment Epithelial Cells

Goldfish were placed on a daily light cycle of 12 h light and 12 h darkness for 18 days or longer. The visual cells and pigment epithelium of the retina were then examined by microscopy at many intervals throughout the cycle. Goldfish rods and cones follow a rhythmic pattern in eliminating packets of photosensitive membranes from their outer segments. Rods shed membranes early in the light period. The detached membranes are ingested by pigment epithelial cells or by ameboid phagocytes, which degrade them during the remainder of the light period. Cones discard membranes from the ends of their outer segments early in the dark period. During the next several hours, this debris is digested by the pigment epithelium or by ameboid phagocytes. Thus, the disposal phase of the outer-segment renewal process is similar in rods and cones, but is displaced in time by about 12 h. There is evidence that this daily rhythm of membrane disposal in rods and cones is a general property of vertebrate visual cells.

scholarly journals RENEWAL OF FATTY ACIDS IN THE MEMBRANES OF VISUAL CELL OUTER SEGMENTS

1974 ◽  
Vol 61 (2) ◽  
pp. 327-343 ◽  
Author(s):  
Carol Bibb ◽  
Richard W. Young
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Vitamin A ◽  
Palmitic Acid ◽  
Outer Segment ◽  
Pigment Epithelium ◽  
Radioactive Material ◽  
Visual Cell ◽  
Outer Segments ◽  
Acid Exchange

The renewal of fatty acids in the visual cells and pigment epithelium of the frog retina was studied by autoradiographic analysis of animals injected with tritiated palmitic, stearic, or arachidonic acids. Most of the radioactive material could be extracted from the retina with chloroform-methanol, indicating that the fatty acids had been esterified in lipids. Analysis of the extracts, after injection of [3H]palmitic acid, revealed that the radioactivity was predominantly in phospholipid. Palmitic acid was initially concentrated in the pigment epithelium, particularly in oil droplets which are storage sites for vitamin A esterified with fatty acid. The cytoplasm, but not the nucleus of these cells, was also heavily labeled. Radioactive fatty acid was bound immediately to the visual cell outer segment membranes, including detached rod membranes which had been phagocytized by the pigment epithelium. This is believed to be due to fatty acid exchange in phospholipid molecules already situated in the membranes. Gradually, the concentration of radioactive material in the visual cell outer segment membranes increased, apparently as a result of the addition of new phospholipid molecules, possibly augmented by the transfer from the pigment epithelium of esterified vitamin A. Injected fatty acid became particularly concentrated in new membranes which are continually assembled at the base of rod outer segments. This localized concentration was short-lived, apparently due to the rapid renewal of fatty acid. The results support the conclusion that rods renew the lipids of their outer segments by membrane replacement, whereas both rods and cones renew the membrane lipids by molecular replacement, including fatty acid exchange and replacement of phospholipid molecules in existing membranes.

Microspectrophotometry of visual pigments

1972 ◽  
Vol 5 (3) ◽  
pp. 349-393 ◽  
Author(s):  
Stanley D. Carlson
Keyword(s):  
Vitamin A ◽  
Conformational Change ◽  
Visual Pigments ◽  
Visual Cells ◽  
Rods And Cones ◽  
Outer Segments ◽  
Pigment Molecule ◽  
Receptor Membrane ◽  
Covalently Bonded ◽  
Membrane Changes

Visual pigments are embedded in the disc membranes of the outer segments of vertebrate rods and cones and in the microvilli of invertebrate visual cells. The pigment molecule in both is a most fascinating aggregate of known (the ubiquitous II-cis isomer of vitamin A1 or A2-aldehyde = retinal1 or 2; Hubbard & Wald, 1952) covalently bonded to the unknown (a protein termed opsin) (Anderson, Hoffman & Hall, 1971). This conjugated molecule is called rhodopsin or dehydrorhodopsin (porphryopsin) when the prosthetic portion is retinall or 2 respectively. So sensitive is this sterically hindered, bent and twisted molecule to light that absorption of one photon can initiate its isomerization to the all trans form. This conformational change is but one (but the best known) of the factors leading to receptor membrane changes ushering in the visual impulse.

Changes in length and disk shedding rate of Xenopus rod outer segments associated with metamorphosis

1978 ◽  
Vol 201 (1143) ◽  
pp. 169-177 ◽  
Keyword(s):  
Histological Examination ◽  
Pigment Epithelium ◽  
Large Change ◽  
Rod Outer Segments ◽  
Cellular Organization ◽  
Dramatic Decrease ◽  
Scotopic Sensitivity ◽  
Rods And Cones ◽  
Outer Segments ◽  
Metamorphic Climax

Histological examination of the retinae of Xenopus tadpoles undergoing the extensive transformations of metamorphic climax revealed a progressive and dramatic decrease in the length of rod outer segments (r. o. s.) (by 1.22 µm/day), which was reversed after the completion of metamorphosis, when r. o. s. grew longer (by 1.11 µm/day). The rate of r. o. s. disk addition during these two periods was determined by examining the incorporation of [ 3 H]-leucine by light microscopic autoradiography. The band of labelled protein in r. o. s. was displaced sclerally at a rate of 1.70 µm/day during the first half of metamorphic climax, and of 1.56 µm/day in young juveniles during the second month after metamorphosis. The similarity of the rate of band displacement at these times indicates that the changes in r. o. s. length associated with metamorphosis result from major changes in the rate of disk shedding and/or phagocytosis, which was about 2.92 µm/day pre-metamorphically and 0.45 µm/day post-metamorphically. E. m. observation at these stages and during the final stages of metamorphic climax revealed no significant alterations in the cellular organization or ultrastructure of rods or pigment epithelium, even though some r. o. s. were only 3 µm long. This large change in r. o. s. length undoubtedly influences the animal’s scotopic sensitivity and the relative mesopic activity of its rods and cones, and may have important effects on the animal’s visual physiology.

scholarly journals THE VISUAL CELLS AND VISUAL PIGMENT OF THE MUDPUPPY, NECTURUS

1963 ◽  
Vol 19 (1) ◽  
pp. 79-106 ◽  
Author(s):  
Paul K. Brown ◽  
I. R. Gibbons ◽  
George Wald
Keyword(s):  
Visual Pigment ◽  
Main Role ◽  
Ciliary Process ◽  
Visual Cells ◽  
Rods And Cones ◽  
Pigment Epithelial ◽  
Outer Segments ◽  
Exciton Migration ◽  
Cytoplasmic Filaments ◽  
Crystalline Array

Electron microscopy of the visual cells of the mudpuppy Necturus have revealed several new or hitherto neglected features of organization: (a) A system of deeply staining micelles in virtually crystalline array, probably located in the lamellae of the rod outer segments. These particles may contain the visual pigment, porphyropsin. Counts of the micelles, and microspectrophotometric measurements of porphyropsin in the retina and single rods yield the estimate that each lamellar micelle may contain about 50 molecules of porphyropsin. (b) Systems of about 30 cytoplasmic filaments (here called dendrites), continuous with the cytoplasm of the inner segment, and standing like a palisade about the outer segments of the rods and cones. In the rods, one such filament stands in the mouth of each of the approximately 30 deep fissures that carve the outer segment into a radial array of lobules. (c) A system of deeply staining particles in the membranes of the dendrites, and another in the membranes of the pigment epithelial processes. It is suggested that these may have a part in interchanges of material with the outer segments. The ciliary process is found to penetrate more deeply than is commonly supposed into the outer segments of the rods and cones. The edge of each double-membrane disc in rods forms a differentiated rim structure, both around the disc circumference and bordering the fissures. These anatomical arrangements are summarized in Figs. 13 and 14, and the relevant measurements in Table I. The dilution of visual pigment in Necturus rods and cones and a general consideration of their microstructures make it seem unlikely that such typically solid state processes as exciton migration or photoconduction can transport the effects of light far from the site of absorption. Excitation must, therefore, be conveyed to the receptor as a whole by some axial structure. Among axial structures, the plasma membrane is most likely to be the site of nervous excitation. The ciliary process probably plays its main role in the embryogenesis and regeneration of outer segments; and the dendrites and pigment epithelial processes in exchanges of material with the outer segments and perhaps with one another.

scholarly journals Localization of antibody binding sites in ultrathin sections of unembedded frog retinal tissue.

1983 ◽  
Vol 31 (1) ◽  
pp. 29-34 ◽  
Author(s):  
D C Pease ◽  
I Nir ◽  
V Clark ◽  
M Hall
Keyword(s):  
Rabbit Antiserum ◽  
External Support ◽  
Rod Outer Segments ◽  
General Technique ◽  
Rods And Cones ◽  
Retinal Tissue ◽  
Outer Segments ◽  
Frog Retina ◽  
Rabbit Igg ◽  
Ultrathin Sections

Much ultrastructural detail is retained in tissue fixed only with aldehydes and subsequently air-dried after suspension in a polyvinyl acetate emulsion. The latter provides an external support only, but permits ultrathin sectioning; thus, an exposure of intracellular contents for potential immunocytochemical reactions is achieved. Sections of unembedded frog retina so prepared have been studied with success. The tissue was incubated first with a rabbit antiserum prepared against gradient purified bovine rod outer segments. Following incubation, reacted sites were labeled with ferritin-conjugated goat anti-rabbit IgG and stained with phosphotungstic acid. Intense labeling of the rod outer segments was clearly achieved, whereas the cone outer segments were without label. Other parts of the retina, including the ellipsoid region of both rods and cones, were also without significant label. These regions provided an intrinsic control for the specificity of the antiserum and established the validity of the general technique.

scholarly journals PROTEIN SYNTHESIS IN THE VISUAL CELLS OF THE HONEYBEE DRONE AS STUDIED WITH ELECTRON MICROSCOPE RADIOAUTOGRAPHY

1972 ◽  
Vol 55 (3) ◽  
pp. 595-605 ◽  
Author(s):  
Alain Perrelet
Keyword(s):  
Protein Synthesis ◽  
Electron Microscope ◽  
Single Injection ◽  
Visual Cell ◽  
Maximal Concentration ◽  
Cell Region ◽  
Photoreceptor Membrane ◽  
Visual Cells ◽  
Rods And Cones ◽  
Honeybee Drone

Protein synthesis was studied in the visual cells of an insect (honeybee drone, Apis mellifera) by electron microscope radioautography. After a single injection of tritiated leucine, the radioactivity first appears in the cytoplasm of the visual cell which contains ribosomes. Later, part of this radioactivity migrates to the rhabdome, the visual cell region which is specialized in light absorption. A maximal concentration of radioactivity is reached there 48 hr after the injection of leucine. This pattern of protein synthesis and transport resembles that described in vertebrate visual cells (rods and cones), where newly synthesized proteins have been shown to contribute to the renewal of the photoreceptor membrane.

The Initial Formation and Subsequent Development of the Double Visual Cells in Amphibia

Development ◽  
1956 ◽  
Vol 4 (1) ◽  
pp. 57-65
Author(s):  
Lauri Saxén
Keyword(s):  
Subsequent Development ◽  
Sufficient Evidence ◽  
Considerable Proportion ◽  
Visual Cell ◽  
Structure Development ◽  
Initial Formation ◽  
Visual Cells ◽  
Rods And Cones ◽  
One Year ◽  
And Function

In 1867 Schultze described the main types of visual cell in the vertebrates, the rod and the cone, and one year later a third type, the double cone. The two first-mentioned types have subsequently been the objects of a large number of investigations; hence their structure, development, and function are largely understood. On the other hand, the double cells have attracted surprisingly little interest. Many writers apparently do not know of their existence, whilst others mention them only as a rarity, not deserving of particular study. Physiologists, too, speak only of rods and cones, without crediting the double cells with any specific function. The very fact, however, that double cells are extremely common in the vertebrates and compose, as a rule, a considerable proportion of the retinal receptors, should be sufficient evidence that they are not an insignificant rarity, and still less artefacts, as has sometimes been alleged.

Ultrastructural Changes of Smoooth Endoplasmic Reticulum in the Retinal Pigment Epithelium by Choline Chloride

1972 ◽  
Vol 30 ◽  
pp. 58-59
Author(s):  
Kazushige Hirosawa ◽  
Eichi Yamada
Keyword(s):  
Endoplasmic Reticulum ◽  
Epithelial Cell ◽  
Smooth Endoplasmic Reticulum ◽  
Pigment Epithelium ◽  
Choline Chloride ◽  
Retinal Pigment ◽  
Ultrastructural Changes ◽  
Lower Vertebrate ◽  
Visual Cells ◽  
Pigment Epithelial

The pigment epithelium is located between the choriocapillary and the visual cells. The pigment epithelial cell is characterized by a large amount of the smooth endoplasmic reticulum (SER) in its cytoplasm. In addition, the pigment epithelial cell of some lower vertebrate has myeloid body as a specialized form of the SER. Generally, SER is supposed to work in the lipid metabolism. However, the functions of abundant SER and myeloid body in the pigment epithelial cell are still in question. This paper reports an attempt, to depict the functions of these organelles in the frog retina by administering one of phospholipid precursors.

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