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.

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.

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.

scholarly journals THE RENEWAL OF PROTEIN IN RETINAL RODS AND CONES

1968 ◽  
Vol 39 (1) ◽  
pp. 169-184 ◽  
Author(s):  
Richard W. Young ◽  
Bernard Droz
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Electron Microscope ◽  
Golgi Complex ◽  
Outer Segment ◽  
Photoreceptor Cells ◽  
Rods And Cones ◽  
Retinal Rods ◽  
Utilization Of Protein ◽  
Low Levels

The renewal of protein in retinal rods and cones has been analyzed by quantitative electron microscope radioautography in adult frogs injected with a mixture of radioactive amino acids. Protein synthesis occurs predominantly in the ergastoplasm, localized in the myoid region of the photoreceptor cells. Much of the newly formed protein next flows through the Golgi complex. In rods, a large proportion of the protein then moves past the mitochondria of the ellipsoid segment, passes through the connecting cilium into the outer segment, and is there assembled into membranous discs at the base of that structure. Discs are formed at the rate of 36 per day in red rods and 25 per day in green rods at 22.5° C ambient temperature. In cones, a small proportion of the protein is similarly displaced to the outer segment. However, no new discs are formed. Instead, the protein becomes diffusely distributed throughout the cone outer segment. Low levels of radioactivity have been detected, shortly after injection, in the mitochondria, nucleus, and synaptic bodies of rods and cones. Nevertheless, in these organelles, the renewal process also appears to involve the utilization of protein formed in the ergastoplasm of the myoid.

scholarly journals ELECTRON MICROSCOPE OBSERVATIONS ON SYNAPTIC VESICLES IN SYNAPSES OF THE RETINAL RODS AND CONES

1956 ◽  
Vol 2 (3) ◽  
pp. 307-318 ◽  
Author(s):  
Eduardo De Robertis ◽  
Carlos M. Franchi
Keyword(s):  
Electron Microscope ◽  
Synaptic Vesicles ◽  
Sharp Decrease ◽  
Albino Rabbit ◽  
Synaptic Membrane ◽  
Complete Darkness ◽  
Rods And Cones ◽  
Retinal Rods ◽  
Filamentous Material ◽  
Rod Cell

The submicroscopic organization of the rod and cone synapses of the albino rabbit has been investigated with the use of the electron microscope. The most common rod synapse consists of an enlarged expansion of the rod fiber (the so called spherule) into which the dendritic postsynaptic fiber of the bipolar cell penetrates and digitates. The membrane surrounding the terminal consists of a double layer, the external of which is interpreted as belonging to the intervening glial cells. The synaptic membrane has a pre- and a postsynaptic layer with a total thickness of 180 to 300 A. The presynaptic layer is frequently denser and is intimately associated with the adjacent synaptic vesicles. The synaptic membrane shows processes constituted by foldings of the presynaptic layer. The entire spherule is filled with synaptic vesicles varying in diameter between 200 and 650 A with a mean of 386 A. In addition, the spherule contains a few large vacuoles near the rod fiber, interpreted as endoplasmic reticulum, and a matrix in which with high resolution a fine filamentous material can be observed. The postsynaptic fiber is homogeneous and usually does not show synaptic vesicles. In animals maintained in complete darkness for 24 hours vesicles appear to accumulate near the synaptic membrane and its processes. After 9 days there is a sharp decrease in size of the synaptic vesicles. A special rod synapse in which the dendritic postsynaptic expansion penetrates directly into the rod cell body has been identified. In line with Cajal's classification this type of synapse could be considered as a somatodendritic one. The cone synapse has a much larger terminal with a more complex relationship with the postsynaptic fiber. However, the same components recognized in the rod synapse can be observed. In animals maintained for 9 days in complete darkness there is also a considerable diminution in size of the synaptic vesicles.

The Question of Relationship Between Golgi Vesicles and Synaptic Vesicles in Octopus Neurons

1970 ◽  
Vol 7 (1) ◽  
pp. 189-201
Author(s):  
E. G. GRAY
Keyword(s):  
Electron Microscopy ◽  
Golgi Apparatus ◽  
Frontal Lobe ◽  
Synaptic Vesicles ◽  
Optic Lobe ◽  
Visual Cell ◽  
Visual Cells ◽  
Golgi Vesicles

Electron microscopy of the vertical lobe of octopus brain shows that the synaptic knobs of axons with perikarya in the median superior frontal lobe have synaptic vesicles, approximately 28% of which are dense-cored (or granulated). In contrast, the endings of the amacrine neurons in the vertical lobe and the endings in the retina and optic lobe, both of which are derived from the retinal visual cells, have only agranular synaptic vesicles. The Golgi apparatuses of the median superior frontal perikarya have vesicles, approximately 4.3% of which are granulated. The amacrine Golgi apparatuses have 1.5% granulated vesicles. The visual cell Golgi apparatuses have virtually no dense-cored vesicles, only agranular ones. The question of the formation of dense-cored and agranular synaptic vesicles at the Golgi apparatus and their subsequent transport to the terminals are related to these observations.

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.

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.

Early Dissociation of Protein Synthesis and Amylase Secretion Following Hormonal Stimulation of the Pancreas

1974 ◽  
Vol 52 (2) ◽  
pp. 198-205 ◽  
Author(s):  
R. Mongeau ◽  
Y. Couture ◽  
J. Dunnigan ◽  
J. Morisset
Keyword(s):  
Protein Synthesis ◽  
Incubation Medium ◽  
Single Injection ◽  
Pancreatic Enzyme ◽  
Amylase Secretion ◽  
Hormonal Stimulation ◽  
Pancreatic Enzyme Secretion ◽  
Metabolic Conditions

The secretion of the various pancreatic enzymes can be increased by hormonal and cholinergic stimulation. However, it is not yet clear among the different investigators if their synthesis remains constant or can be modified according to different metabolic conditions. The secretion and synthesis of the pancreatic proteins were then studied in parallel to evaluate if secretion triggers synthesis or both phenomenons are controlled by separate mechanisms.The approach for these studies consists mainly in a combination of in vivo and in vitro experiments. The stimulants were injected in vivo and the pancreatic secretions were collected for different periods of time. The animals were then sacrificed and protein synthesis was measured in vitro along with the amylase secreted into the incubation medium. The results show that protein synthesis is decreased during the first 15 min after a single injection or infusion of both cholecystokinin–pancreozymin (CCK–PZ) and secretin. This reduction was associated with an increase in amylase secreted into the incubation medium. However, at 30 min after the hormonal stimulation, protein synthesis is increased while secretion into the incubation medium had returned to control levels. This increase in protein synthesis lasts for at least 1 h. These results strongly suggest that pancreatic enzyme secretion and synthesis are dissociated in the early minutes following hormonal stimulation.

scholarly journals Submicroscopic Changes in Visual Cells of the Rabbit Induced by Iodoacetate

1959 ◽  
Vol 5 (2) ◽  
pp. 245-250 ◽  
Author(s):  
Arnaldo Lasansky ◽  
Eduardo De Robertis
Keyword(s):  
Body Weight ◽  
Synaptic Vesicles ◽  
Single Injection ◽  
Synaptic Membrane ◽  
Visual Cells ◽  
Rod Cells ◽  
Complete Destruction ◽  
Cone Cells ◽  
The Matrix ◽  
Myelin Figures

Alterations produced by iodoacetate in visual cells have been studied under the electron microscope. Lesions of the outer segments of the rods are visible as early as 3 hours after a single injection of 20 mg. iodoacetate per kg. body weight. After 6 hours the changes are more marked and consist then of disorganization, vesiculation, and lysis of the rod sacs. The inner segments of most rod cells show swelling and vacuolization of the matrix, the endoplasmic reticulum, and the Golgi complex. The mitochondria of the ellipsoid show a tendency to disintegrate. In some inner segments the changes consist primarily in an increase in density of the matrix and deposition of a granular material. The rod synapses are also affected, showing lysis of the synaptic vesicles and alterations of the synaptic membrane. With a second injection of 20 mg. iodoacetate per kg. body weight, all these changes become more marked and lead to complete destruction of the rod cells. The cones seem more resistant than the rods. A single injection produces no visible changes in the outer or inner segments of the cones. At cone synapses, however, there are changes consisting of fusion of synaptic vesicles and other membranous material to form large concentric membranes characteristic of myelin figures. A second dose of the drug causes complete destruction of the cone cells. All these, and other submicroscopic changes, are discussed in relation to various hypotheses put forward to explain the mode of action of iodoacetate on visual cells. The pronounced alterations of submicroscopic intracellular membranes suggest that the locus of action of iodoacetate may be a component widely dispersed throughout the visual cells and related, in some way, to the maintenance of these lipoprotein structures.

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