Calcium and light adaptation in retinal rods and cones

Nature ◽  
1988 ◽  
Vol 334 (6177) ◽  
pp. 69-71 ◽  
Author(s):  
K. Nakatani ◽  
K.-W. Yau
Keyword(s):  
Light Adaptation ◽  
Rods And Cones ◽  
Retinal Rods

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.

PHOTOTRANSDUCTION IN RETINAL RODS AND CONES

Vision ◽  
2001 ◽  
Author(s):  
YIANNIS KOUTALOS ◽  
KEI NAKATANI ◽  
WEI-HONG XIONG ◽  
KING-WAI YAU
Keyword(s):  
Rods And Cones ◽  
Retinal Rods

scholarly journals THE FLICKER RESPONSE FUNCTION FOR THE TURTLE PSEUDEMYS

1939 ◽  
Vol 22 (3) ◽  
pp. 311-340 ◽  
Author(s):  
W. J. Crozier ◽  
Ernst Wolf ◽  
Gertrud Zerrahn-Wolf
Keyword(s):  
Flash Intensity ◽  
Rods And Cones ◽  
Sensory Effects ◽  
Retinal Rods ◽  
Fixed Proportion ◽  
Order Of Magnitude ◽  
The Mean ◽  
Probability Integral ◽  
The Individual ◽  
Critical Intensity

1. At constant temperature, with a fixed proportion of light time in a flash cycle (namely, tL/tD = 1), the mean critical intensity for motor response to visual flicker by the turtle Pseudemys scripta follows a probability integral (log I) as a function of flash frequency F. The fit is close and satisfactory; certain quite minor but consistent deviations are adequately explained by features of the experiments. 2. The variation (σI) of critical I is directly proportional to the mean critical intensity (Im), over the entire explorable range. 3. These facts are consistent with the fact that the retina of this turtle is devoid of rods. It contains only cones, histologically, which, with their central representations, provide a single population of sensory effects. The properties of this population are compared with those of homologous populations deduced from corresponding measurements with other forms (various fishes; amphibian; man) which exhibit two such groups of sensory effects associated with the possession of retinal rods and cones. 4. Certain other formulations which have previously been applied to homologous data obtained with other organisms do not properly describe the Pseudemys measurements. 5. The use of a probability integral to describe the data of response to visual flicker for the dissection of the compound curves provided by animals possessing both rods and cones, is accordingly Justified. 6. Persisting differences among individuals of Pseudemys as regards the values of the critical flash intensity under various conditions of experimentation are of the same order of magnitude as are the transitory differences found in lots of other kinds of animals. 7. Determinations of mean critical flash frequency (Fm) at fixed levels of I lie slightly above determinations of Im at fixed values of I, as with other forms. The variation of critical flash frequency goes through a maximum as log I is increased; its height is lower than with certain other forms, in correlation with the low general slope of the F - log I curve (more properly, band). 8. These facts are consistent with the view that the dispersions of the individual critical intensities (and flash frequencies) are determined by organic variation rather than by "experimental error." 9. When the temperature is altered the F - log Im curve is shifted, with no change of Fmax. or of shape; the curve moves to lower intensities as the temperature is raised. 10. The reciprocal of the mean critical intensity, at fixed flash frequency, is a measure of excitability. With increase of temperature (12.5° to 36°) 1/Im for given F follows the Arrhenius equation, exhibiting a "break" at 29.5° (µ = 26,700, 12.5° to 29.5°; 12,400, 29.5° to 36°). This is explained by the necessary theory that, the number of elements of sensory effect required for the index response at fixed F being constant, the ease of their excitation is governed by temperature through its control of the velocity of an interrelated system of catalyzed processes common to all of the sensory elements concerned.

scholarly journals Light adaptation in retinal rods of the rabbit and two other nonprimate mammals.

1991 ◽  
Vol 97 (3) ◽  
pp. 413-435 ◽  
Author(s):  
K Nakatani ◽  
T Tamura ◽  
K W Yau
Keyword(s):  
Light Adaptation ◽  
Evoked Responses ◽  
Flash Intensity ◽  
Exponential Form ◽  
Time To Peak ◽  
Outward Currents ◽  
Retinal Rods ◽  
Response Peak ◽  
Flash Response ◽  
Plateau Level

The responses of rabbit rods to light were studied by drawing a single rod outer segment projecting from a small piece of retina into a glass pipette to record membrane current. The bath solution around the cells was maintained at near 40 degrees C. Light flashes evoked transient outward currents that saturated at up to approximately 20 pA. One absorbed photon produced a response of approximately 0.8 pA at peak. At the rising phase of the flash response, the relation between response amplitude and flash intensity (IF) had the exponential form 1-e-kappa FIF (where kappa F is a constant denoting sensitivity) expected from the absence of light adaptation. At the response peak, however, the amplitude-intensity relation fell slightly below the exponential form. At times after the response peak, the deviation was progressively more substantial. Light steps evoked responses that rose to a transient peak and rapidly relaxed to a lower plateau level. The response-intensity relation again indicated that light adaptation was insignificant at the early rising phase of the response, but became progressively more prominent at the transient peak and the steady plateau of the response. Incremental flashes superposed on a steady light of increasing intensity evoked responses that had a progressively shorter time-to-peak and faster relaxation, another sign of light adaptation. The flash sensitivity changed according to the Weber-Fechner relation (i.e., inversely) with background light intensity. We conclude that rabbit rods adapt to light in a manner similar to rods in cold-blooded vertebrates. Similar observations were made on cattle and rat rods.

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.

Properties of light adaptation in retinal rods

1992 ◽  
Vol 55 ◽  
pp. 71
Author(s):  
L. Cervetto ◽  
S. Bisti ◽  
A. Campagni ◽  
S. Del Bianco ◽  
G.C. Demontis ◽  
...  
Keyword(s):  
Light Adaptation ◽  
Retinal Rods

Morphological Basis for the Photomechanical Response in the Photoreceptors of the Vertebrate Retina

1975 ◽  
Vol 33 ◽  
pp. 476-477
Author(s):  
Gerald E. Adomian ◽  
Fritiof S. Sjöstrand
Keyword(s):  
Electron Microscopy ◽  
Light Adaptation ◽  
Cell Length ◽  
Vertebrate Retina ◽  
Rods And Cones ◽  
Receptor Cells ◽  
Ictalurus Nebulosus ◽  
Morphological Basis ◽  
Ictalurus Melas

The photoreceptors In certain vertebrate retinas respond mechanically to light. This photomechanical response may Involve extensive changes In cell length. These changes are localized within the myoid region of the inner segment. The responses of rod and cone receptor cells to light are reciprocal. In darkness, the cone myoid Is extended, while that of the rod is shortened. In light, the situation is reversed. The machinery responsible for this intriguing phenomenon has not been elucidated. Therefore, the objective of the present study was to Investigate the morphological basis for myoid elongation and shortening.Retinas from a hybrid of Ictalurus melas and Ictalurus nebulosus were prepared for electron microscopy after varying degrees of light adaptation. Six maximally light adapted animals, four semi-adapted animals, and four maximally dark adapted animals were analyzed quantitatively.Myoids from the shortened receptor cells generally consisted of a supranuclear region which measured approximately four and seven microns In diameter and about nine and five microns in length, In rods and cones, respectively.

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