scholarly journals How ribbons make ‘sense’ for vision

2020 ◽  
Vol 42 (5) ◽  
pp. 36-41
Author(s):  
Wallace B. Thoreson ◽  
Cassandra L. Hays
Keyword(s):  
Photoreceptor Cells ◽  
Light Responses ◽  
Electrical Signals ◽  
Rods And Cones ◽  
Planar Structures ◽  
Chemical Signalling ◽  
The Face ◽  
Chemical Messenger ◽  
Spherical Vesicles ◽  
Amino Acid Glutamate

The processing of light by the retina and brain provides the basis for visual perception. Photons are captured and converted to electrical signals by rod and cone photoreceptor cells in the retina. These electrical signals are converted to chemical signals for transmission to downstream neurons. This article provides an overview of the mechanisms involved in transmitting light responses from rods and cones. Chemical signalling occurs at synapses between neurons. In keeping with many other neurons, the chemical messenger released by photoreceptors is the amino acid glutamate, which is packaged into small spherical vesicles. Each photoreceptor synaptic terminal has thousands of synaptic vesicles. Some of these vesicles are attached to the face of planar structures known as ribbons. Ribbons capture and deliver vesicles to release sites at the bottom of the ribbon. Upon stimulation, vesicles fuse with the cell membrane and release their contents. Glutamate molecules diffuse through the extracellular space to reach specialized receptors that regulate the activity of downstream neurons. We discuss how rates of vesicle attachment to ribbons, delivery of vesicles down the ribbon and the release of glutamate shape the information provided to downstream neurons in the visual system.

scholarly journals THE STRUCTURE AND CONCENTRATION OF SOLIDS IN PHOTORECEPTOR CELLS STUDIED BY REFRACTOMETRY AND INTERFERENCE MICROSCOPY

1957 ◽  
Vol 3 (1) ◽  
pp. 15-30 ◽  
Author(s):  
Richard L. Sidman
Keyword(s):  
Photoreceptor Cells ◽  
Interference Microscopy ◽  
Refractive Indices ◽  
Rod Outer Segments ◽  
Vertebrate Species ◽  
Rods And Cones ◽  
Outer Segments ◽  
Retinal Rods ◽  
Cone Cells ◽  
Longitudinal Fiber

Fragments of freshly obtained retinas of several vertebrate species were studied by refractometry, with reference to the structure of the rods and cones. The findings allowed a reassessment of previous descriptions based mainly on fixed material. The refractometric method was used also to measure the refractice indices and to calculate the concentrations of solids and water in the various cell segments. The main quantitative data were confirmed by interference microscopy. When examined by the method of refractometry the outer segments of freshly prepared retinal rods appear homogeneous. Within a few minutes a single eccentric longitudinal fiber appears, and transverse striations may develop. These changes are attributed to imbibition of water and swelling in structures normally too small for detection by light microscopy. The central "core" of outer segments and the chromophobic disc between outer and inner segments appear to be artifacts resulting from shrinkage during dehydration. The fresh outer segments of cones, and the inner segments of rods and cones also are described and illustrated. The volumes, refractive indices, concentrations of solids, and wet and dry weights of various segments of the photoreceptor cells were tabulated. Rod outer segments of the different species vary more than 100-fold in volume and mass but all have concentrations of solids of 40 to 43 per cent. Cone outer segments contain only about 30 per cent solids. The myoids, paraboloids, and ellipsoids of the inner segments likewise have characteristic refractive indices and concentrations of solids. Some of the limitations and particular virtues of refractometry as a method for quantitative analysis of living cells are discussed in comparison with more conventional biochemical techniques. Also the shapes and refractive indices of the various segments of photoreceptor cells are considered in relation to the absorption and transmission of light. The Stiles-Crawford effect can be accounted for on the basis of the structure of cone cells.

scholarly journals Immunocytochemical localization of opsin in outer segments and Golgi zones of frog photoreceptor cells. An electron microscope analysis of cross-linked albumin-embedded retinas

1978 ◽  
Vol 77 (1) ◽  
pp. 196-210 ◽  
Author(s):  
DS Papermaster ◽  
BG Schneider ◽  
MA Zorn ◽  
JP Kraehenbuhl
Keyword(s):  
Electron Microscope ◽  
Outer Segment ◽  
Specific Binding ◽  
Photoreceptor Cells ◽  
Indirect Detection ◽  
Thin Sections ◽  
Rods And Cones ◽  
Outer Segments ◽  
Cell Structures ◽  
Cone Photopigments

Adult vertebrate retinal cells (rod and cones) continuously synthesize membrane proteins and transport them to the organelle specialized for photon capture, the outer segment. The cell structures involved in the synthesis of opsin have been identified by means of immunocytochemistry at the electron microscope level. Two indirect detection systems were used: (a) rabbit antibodies to frog opsin were localized with ferritin conjugated F(ab')2 of sheep antibodies to rabbit F(ab')2 and (b) sheep antibodies to cattle opsin were coupled to biotin and visualized by means of avidin-ferritin conjugates (AvF). The reagents were applied directly to the surface of thin sections of frog retinal tissues embedded in glutaraldehyde cross-linked bovine serum albumin (BSA). Specific binding of anti-opsin antibodies indicates that opsin is localized in the disks of rod outer segments (ROS), as expected, and in the Golgi zone of the rod cell inner segments. In addition, we observed quantitatively different labeling patterns of outer segments of rods and cones with each of the sera employed. These reactions may indicate immunological homology of rod and cone photopigments. Because these quantitiative variations of labeling density extend along the entire length of the outer segment, they also serve to identify the cell which has shed its disks into adjacent pigment ipithelial cell phagosomes.

An enzymatically enhanced recording technique for Limulus ventral photoreceptors: Physiology, biochemistry, and morphology

1994 ◽  
Vol 11 (1) ◽  
pp. 41-52 ◽  
Author(s):  
Hui-Juan Zhang ◽  
Robert N. Jinks ◽  
Anne C. Wishart ◽  
Barbara-Anne Battelle ◽  
Steven C. Chamberlain ◽  
...  
Keyword(s):  
Photoreceptor Cells ◽  
Enzyme Treatment ◽  
Light Responses ◽  
Whole Cell ◽  
Transmembrane Potentials ◽  
Lateral Eye ◽  
Electrophysiological Recordings ◽  
Transmission Electron ◽  
Whole Cell Recordings

AbstractEnzymatic treatments that facilitated whole-cell electrophysiological recordings were used on Limulus ventral photoreceptor cells. Ventral optic nerves were treated with either collagenase or collagenase, papain, and trypsin. Either treatment greatly increased the ease of making whole-cell recordings of transmembrane potentials. Light responses obtained from enzyme-treated photoreceptor cells were nearly identical to results obtained without enzyme treatment and compared favorably to in vivo recordings of light responses from the compound lateral eye. Enzyme-treated cells also responded to applied octopamine, as do untreated cells, with an increased phosphorylation of a 122-kD protein. This suggests that the external receptors and internal biochemical machinery required for at least one second-messenger cascade are present after enzyme treatment. The morphological integrity of enzyme-treated photoreceptor cells was examined with light microscopy as well as with scanning and transmission electron microscopy. In general, we found that each enzyme treatment greatly reduced the integrity of the layers of glial cells that surround the photoreceptor cells thereby making these cells easily accessible for whole-cell recordings of transmembrane potentials. The morphology of the rhabdomere was normal after enzymatic degradation of the adjacent glial covering.

scholarly journals Jellyfish vision starts with cAMP signaling mediated by opsin-Gs cascade

2008 ◽  
Vol 105 (40) ◽  
pp. 15576-15580 ◽  
Author(s):  
Mitsumasa Koyanagi ◽  
Kosuke Takano ◽  
Hisao Tsukamoto ◽  
Kohzoh Ohtsu ◽  
Fumio Tokunaga ◽  
...  
Keyword(s):  
G Protein ◽  
Molecular Level ◽  
Ganglion Cells ◽  
Photoreceptor Cells ◽  
Retinal Ganglion ◽  
Box Jellyfish ◽  
Visual Cells ◽  
Rods And Cones ◽  
Light Sensing ◽  
Phototransduction Cascade

Light sensing starts with phototransduction in photoreceptor cells. The phototransduction cascade has diverged in different species, such as those mediated by transducin in vertebrate rods and cones, by Gq-type G protein in insect and molluscan rhabdomeric-type visual cells and vertebrate photosensitive retinal ganglion cells, and by Go-type G protein in scallop ciliary-type visual cells. Here, we investigated the phototransduction cascade of a prebilaterian box jellyfish, the most basal animal having eyes containing lens and ciliary-type visual cells similar to vertebrate eyes, to examine the similarity at the molecular level and to obtain an implication of the origin of the vertebrate phototransduction cascade. We showed that the opsin-based pigment functions as a green-sensitive visual pigment and triggers the Gs-type G protein-mediated phototransduction cascade in the ciliary-type visual cells of the box jellyfish lens eyes. We also demonstrated the light-dependent cAMP increase in the jellyfish visual cells and HEK293S cells expressing the jellyfish opsin. The first identified prebilaterian cascade was distinct from known phototransduction cascades but exhibited significant partial similarity with those in vertebrate and molluscan ciliary-type visual cells, because all involved cyclic nucleotide signaling. These similarities imply a monophyletic origin of ciliary phototransduction cascades distributed from prebilaterian to vertebrate.

scholarly journals Mathematical Analysis of Electrical Responses in Photoreceptor Cells Reveals Distinct Chemical Control of Visual Signal Transduction in Rods and Cones.

2021 ◽  
Author(s):  
Yukari Takeda ◽  
Kazuma Sato ◽  
Yukari Hosoki ◽  
Shuji Tachibanaki ◽  
Chieko Koike ◽  
...  
Keyword(s):  
Light Intensity ◽  
Current Model ◽  
Photoreceptor Cells ◽  
Light Sensitivity ◽  
Visual Signal ◽  
Visual Transduction ◽  
Rods And Cones ◽  
Experimental Systems ◽  
Lower Light

Abstract Retinal photoreceptor cells, rods and cones, convert photons of light into chemical and electrical signals as the first step of the visual transduction cascade. Although the chemical processes in the phototransduction system are very similar to each other in these photoreceptors, the light sensitivity and time resolution of the photoresponse in rods are functionally different than those in the photoresponses of cones. To systematically investigate how photoresponses are divergently regulated in rods and cones, we have developed a detailed mathematical model on the basis of the Hamer model. The current model successfully reconstructed light intensity-, ATP- and GTP-dependent changes in concentrations of phosphorylated visual pigments (VPs), activated transducins (Tr*s) and phosphodiesterases (PDEs), as well as cyclic nucleotide-gated currents (ICNG) in rods and cones. In comparison to rods, the lower light sensitivity of cones was attributed not only to the lower affinity of activated VPs for Trs but also to the faster desensitization of the VPs. The assumption of an intermediate inactive state, MIIi, in the thermal decay of activated VPs was pivotal for inducing faster inactivation of VPs. In addition to the faster inactivation of VPs, calculating a faster rate of RGS9 intervention for PDE-induced Tr* inactivation in cones was indispensable for simulating the electrical waveforms of the light intensity-dependent ICNG at higher temporal resolution in experimental systems in vivo.

scholarly journals Melanopsin expression in the cornea

2018 ◽  
Vol 35 ◽  
Author(s):  
ANTON DELWIG ◽  
SHAWNTA Y. CHANEY ◽  
ANDREA S. BERTKE ◽  
JAN VERWEIJ ◽  
SUSANA QUIRCE ◽  
...  
Keyword(s):  
Ganglion Cells ◽  
Nerve Fibers ◽  
Visual Signals ◽  
Light Responses ◽  
Rods And Cones ◽  
Retinal Tissue ◽  
Antibody Staining ◽  
Electrophysiological Recordings ◽  
Pupil Constriction ◽  
Sensory Fibers

AbstractA unique class of intrinsically photosensitive retinal ganglion cells in mammalian retinae has been recently discovered and characterized. These neurons can generate visual signals in the absence of inputs from rods and cones, the conventional photoreceptors in the visual system. These light sensitive ganglion cells (mRGCs) express the non-rod, non-cone photopigment melanopsin and play well documented roles in modulating pupil responses to light, photoentrainment of circadian rhythms, mood, sleep and other adaptive light functions. While most research efforts in mammals have focused on mRGCs in retina, recent studies reveal that melanopsin is expressed in non-retinal tissues. For example, light-evoked melanopsin activation in extra retinal tissue regulates pupil constriction in the iris and vasodilation in the vasculature of the heart and tail. As another example of nonretinal melanopsin expression we report here the previously unrecognized localization of this photopigment in nerve fibers within the cornea. Surprisingly, we were unable to detect light responses in the melanopsin-expressing corneal fibers in spite of our histological evidence based on genetically driven markers and antibody staining. We tested further for melanopsin localization in cell bodies of the trigeminal ganglia (TG), the principal nuclei of the peripheral nervous system that project sensory fibers to the cornea, and found expression of melanopsin mRNA in a subset of TG neurons. However, neither electrophysiological recordings nor calcium imaging revealed any light responsiveness in the melanopsin positive TG neurons. Given that we found no light-evoked activation of melanopsin-expressing fibers in cornea or in cell bodies in the TG, we propose that melanopsin protein might serve other sensory functions in the cornea. One justification for this idea is that melanopsin expressed in Drosophila photoreceptors can serve as a temperature sensor.

scholarly journals Co-expression of xenopsin and rhabdomeric opsin in photoreceptors bearing microvilli and cilia

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Oliver Vöcking ◽  
Ioannis Kourtesis ◽  
Sharat Chandra Tumu ◽  
Harald Hausen
Keyword(s):  
Visual Pigment ◽  
Photoreceptor Cell ◽  
Gene Loss ◽  
Photoreceptor Cells ◽  
Common Origin ◽  
Opsin Gene ◽  
Cell Type ◽  
Rods And Cones ◽  
Gene Structures ◽  
And Function

Ciliary and rhabdomeric opsins are employed by different kinds of photoreceptor cells, such as ciliary vertebrate rods and cones or protostome microvillar eye photoreceptors, that have specialized structures and molecular physiologies. We report unprecedented cellular co-expression of rhabdomeric opsin and a visual pigment of the recently described xenopsins in larval eyes of a mollusk. The photoreceptors bear both microvilli and cilia and express proteins that are orthologous to transporters in microvillar and ciliary opsin trafficking. Highly conserved but distinct gene structures suggest that xenopsins and ciliary opsins are of independent origin, irrespective of their mutually exclusive distribution in animals. Furthermore, we propose that frequent opsin gene loss had a large influence on the evolution, organization and function of brain and eye photoreceptor cells in bilaterian animals. The presence of xenopsin in eyes of even different design might be due to a common origin and initial employment of this protein in a highly plastic photoreceptor cell type of mixed microvillar/ciliary organization.

scholarly journals Shedding light on dark adaptation

2020 ◽  
Vol 42 (5) ◽  
pp. 44-50
Author(s):  
Ellen Weiss
Keyword(s):  
Dark Adaptation ◽  
Bright Light ◽  
Photoreceptor Cells ◽  
Light Sensitivity ◽  
Visual Sensitivity ◽  
Rods And Cones ◽  
Light Sensing ◽  
Light Intensities ◽  
Visual Signalling ◽  
G Protein Coupled

The retina is famous for its ability to operate under a broad range of light intensities. This is partly due to the presence of two types of photoreceptor cells, rods and cones. Rods are used mostly for dim light vision, and cones are used for bright light and colour vision. These cells are also able to adapt to a broad range of light intensities using light- and dark-adaptation mechanisms. Dark adaptation is used by the vertebrate retina to increase its visual sensitivity when moving from a brightly lit environment to a dark environment. The brighter the surrounding light, the longer it takes for the retina to adapt to the dark. Most retina biologists have studied dark adaptation by exposing animals to a 90% bleach, meaning that 90% of the light-sensing proteins in these photoreceptor cells have been activated, followed by transfer of these animals to a dark room and analysis of their light sensitivity using electrophysiological methods. In this report, we introduce the basic elements of the visual system and describe how the system might operate during dark adaptation. We also introduce a novel role for cAMP-mediated phosphorylation of G protein-coupled receptor kinase 1 (GRK1), a major kinase in visual signalling.

scholarly journals An Electrogenic Sodium Pump in Limulus Ventral Photoreceptor Cells

1972 ◽  
Vol 59 (6) ◽  
pp. 720-733 ◽  
Author(s):  
J. E. Brown ◽  
J. E. Lisman
Keyword(s):  
Sodium Pump ◽  
Light Stimulus ◽  
Bright Light ◽  
Receptor Potential ◽  
Photoreceptor Cells ◽  
Intracellular Accumulation ◽  
Light Responses ◽  
Electrogenic Sodium Pump ◽  
Electrogenic Na Pump ◽  
Intracellular Ca

A hyperpolarization can be recorded intracellularly following either a single bright light stimulus or the intracellular injection of Na+. This after-hyperpolarization is abolished by bathing in 5 x 10-6 M strophanthidin or removal of extracellular K+. Both treatments also lead to a small, rapid depolarization of the dark-adapted cell. When either treatment is prolonged, light responses can still be elicited, although with repetitive stimuli the responses are slowly and progressively diminished in size. The rate of diminution is greater for higher values of [Ca++]out; with [Ca++]out = 0.1 mM, there is almost no progressive diminution of repetitive responses produced by either K+-free seawater or strophanthidin. We propose that an electrogenic Na+ pump contributes directly to dark-adapted membrane voltage and also generates the after-hyperpolarizations, but does not directly generate the receptor potential. Inhibition of this pump leads to intracellular accumulation of sodium ions, which in turn leads to an increase in intracellular Ca++ (provided there is sufficient extracellular Ca++). This increase in intracellular calcium probably accounts for the progressive decrease in the size of the receptor potential seen when the pump is inhibited.

scholarly journals Multiple rod–cone and cone–rod photoreceptor transmutations in snakes: evidence from visual opsin gene expression

2016 ◽  
Vol 283 (1823) ◽  
pp. 20152624 ◽  
Author(s):  
Bruno F. Simões ◽  
Filipa L. Sampaio ◽  
Ellis R. Loew ◽  
Kate L. Sanders ◽  
Robert N. Fisher ◽  
...  
Keyword(s):  
Photoreceptor Cells ◽  
Opsin Gene ◽  
Future Research ◽  
Rod Photoreceptor ◽  
Radical Theory ◽  
Rods And Cones ◽  
Fundamental Properties ◽  
Light Levels ◽  
Reverse Complement ◽  
Functional Implications

In 1934, Gordon Walls forwarded his radical theory of retinal photoreceptor ‘transmutation’. This proposed that rods and cones used for scotopic and photopic vision, respectively, were not fixed but could evolve into each other via a series of morphologically distinguishable intermediates. Walls' prime evidence came from series of diurnal and nocturnal geckos and snakes that appeared to have pure-cone or pure-rod retinas (in forms that Walls believed evolved from ancestors with the reverse complement) or which possessed intermediate photoreceptor cells. Walls was limited in testing his theory because the precise identity of visual pigments present in photoreceptors was then unknown. Subsequent molecular research has hitherto neglected this topic but presents new opportunities. We identify three visual opsin genes, rh1 , sws1 and lws , in retinal mRNA of an ecologically and taxonomically diverse sample of snakes central to Walls' theory. We conclude that photoreceptors with superficially rod- or cone-like morphology are not limited to containing scotopic or photopic opsins, respectively. Walls' theory is essentially correct, and more research is needed to identify the patterns, processes and functional implications of transmutation. Future research will help to clarify the fundamental properties and physiology of photoreceptors adapted to function in different light levels.

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