Article

Electrical responses and photopigments of twin cones in the retina of the Walleye

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Abstract

1. The properties of twin and single cones in the retina of the walleye (Stizostedion vitreum vitreum) were studied by intracellular recording, dye injection and microspectrophotometry. 2. Twin cones generate hyperpolarizing responses to central illumination, can receive depolarizing influences (feed-back) from the receptive field surround, and show no detectable dye coupling when injected with Procion yellow. In seventeen of eighteen dye-injected cones, fluorescence was intense in the inner segment and undetectable or weak in the cone pedicle. 3. Both members of the twin cone contain the same photopigment in their outer segments. It absorbs maximally at about 605 nm. 4. A 533 nm green-sensitive photopigment was found in single cones. No blue-sensitive cones have been found. 5. With the exception of a modest discrepancy in the violet, the absorptance spectrum of the 605 nm photopigment of twin cones agrees closely with the action spectrum measured by intracellular recording. 6. The spectral properties established by the twin cone's photopigment are not detectably altered by the hyperpolarizing influences arising from nearby cones or by the depolarizing influences arising from the receptive field surround. 7. The twin cones of the walleye retina are thus "identical twins', both photochemically and physiologically, and seem designed to function as long-wave, spectrally univariant receptor units for colour vision. 8. The available evidence suggests that identical twin cones differ functionally from double cones and non-identical twin cones. 9. Although they outnumber single cones by about three to one in adults, identifiable twin cones were rarely observed in the cone population of retinas examined 3-5 days after birth. If walleye twin cones develop by fusion of single cones this process apparently occurs only for cones containing the 605 nm photopigment.

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... Laboratory studies on walleye retinal physiology have revealed that their photoreceptors have two spectral sensitivities with peak absorbances at 533 nm (green) and 605 nm (orange) (Burkhardt et al., 1980), while the critical flicker-fusion frequency, the highest frequency at which the eye can differentiate flashes, of the walleye retina has a limit of c. 20 Hz (Ali & Anctil, 1977). With this knowledge and the flexibility of LED lights, we hypothesised an optimal combination of strobing and colour may be found to most effectively guide walleye using their sensory biases or sensitivities. ...
... Following esrlier studies using strobing light (Baker, 2008;Johnson et al., 2005), we chose to use constant illumination and a strobe rate of 5 Hz, which is well below walleye critical flickerfusion frequency (20 Hz: Ali & Anctil, 1977). Orange (605 nm) and green (535 nm) were chosen based on the spectral sensitivity of the walleye retina (Burkhardt et al., 1980), generating 5 treatment combinations including a control consisting of the LGD present but turned off. These 5 treatments were presented during the day as well as at night to identify any diel patterning in response. ...
... One possible explanation for our results is that walleye are photosensitive to both colours of light that were tested; i.e., green and orange (Burkhardt et al., 1980). In a similar study, A. transmontanus demonstrated strong levels of attraction to light matching one of their documented spectral sensitivities, green , leaving the possibility that walleye may not demonstrate the same degree of light avoidance if presented with colour spectra that do not match their retinal sensitivities. ...
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... In fact, over 60% of private boat anglers and 82% of charter boat operations in Ohio's Lake Erie waters specifically target walleye (Ohio Department of Natural Resources, 2017). Walleye possess color vision, with two color-absorbing cones, a green cone (max absorbance 533 nm) and an orange-yellow twin cone (max absorbance 605 nm; Burkhardt et al., 1980). Walleyes also possess a specialized morphological structure, the tapetum lucidum, which is a layer of reflective material in the back of the retina that increases low light visual abilities (Ali and Anctil, 1977). ...
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Increasing anthropogenic turbidity alters underwater visual environments, leading to disrupted perception of visual cues with a variety of consequences, such as diet shifts and reduced prey consumption. In this study, we used novel techniques, including a citizen science mobile phone application (app), to investigate the effects of altered water clarity on recreational fisheries. Our objectives were to determine if elevated turbidity (suspended sediments or algae) alters lure success in the recreational Walleye (Sander vitreus) fishery and if the behavior of recreational anglers shifts with algal blooms. We developed a mobile phone app to gather real time data on lure success across water clarity conditions in collaboration with Lake Erie charter captains. Citizen science data collected with the app showed that lure color success shifted with water color and clarity: white lures were most successful in clear water, yellow in sedimentary turbidity, and black in algal conditions. A survey of charter captains suggested that fishing practices and lure usage may change over the long term if algal blooms persist.
... As an alternative method of increasing surface area but maintaining high sensitivity, some species [e.g. the walleye Stizostedion vitreum, Percidae, Burkhardt et al., 1980] have very large diameter cones (25 µm) with enlarged mitochondria. Moreover, the two components of the double cones of shallow-water species have also been found to be either neurally or optically coupled and may, in some circumstances, act as a single cone or macroreceptor [Lythgoe, 1979]. ...
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... This could be achieved by installing light devices in areas that pose potential harm to fish to promote an avoidance response. Further studies will be needed to assess species that are at risk to impingement and entrainment and that possess color vision, such as Bluegill (Hawrynshyn et al. 1988) and Walleye Sander vitreus (Burkhardt et al. 1980;Michaud and Taft 2000). ...
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... Relatively large numbers of twin cones are found in fish that inhabit deeper water, leading to the conclusion that this cone type is more sensitive to light than single cones (Lyall 1957;Tamura 1957;O'Connell 1963). Identical twin cones are likely to be involved in both brightness and colour discrimination (Burkhardt et al. 1980). Furthermore, spatial resolution (see Zaunreiter et al. 1991) and hence motion perception (Gegenfurter et al. 1999), is better in cones than in rods. ...
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... The twin cones of the walleye retina absorb maximally at 605 nm. No blue-sensitive cones have been found (Burkhardt et al. 1980), so the function of sandercyanin in intraspecific signaling would be limited in walleye. ...
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Several fish species, including the walleye (Sander vitreus), have "yellow" and "blue" color morphs. In S. vitreus, one source of the blue color has been identified as a bili-binding protein pigment (sandercyanin), found in surface mucus of the fish. Little is known about the production of the pigment or about its functions. We examined the anatomical localization and seasonal variation of sandercyanin in S. vitreus from a population in McKim Lake, northwestern Ontario, Canada. Skin sections were collected from 20 fish and examined histologically. Mucus was collected from 306 fish over 6 years, and the amount of sandercyanin was quantified spectrophotometrically. Sandercyanin was found solely on dorsal surfaces of the fish and was localized to novel cells in the epidermis, similar in appearance to secretory sacciform cells. Sandercyanin concentrations were significantly higher in fish collected in summer versus other seasons. Yellow and blue morphs did not differ in amounts of sandercyanin, suggesting that the observed blue color, in fact, arises from lack of yellow pigmentation in blue morphs. The function of the sandercyanin remains unclear, but roles in photoprotection and countershading are consistent with available data.
... In cones, however, the membrane potential can also be driven in the depolarizing direction. Thus, in various vertebrate species, the receptive field of the cone displays an antagonistic centre-surround organization: light in the centre evokes a hyperpolarizing response which can be reduced by light in the surround (Baylor et al. 1971;O'Bryan, 1973;Burkhardt, 1977;Burkhardt, Hassin, Levine & MacNichol, 1980;Lasansky, 1981Lasansky, , 1984Lasater, 1982;Murakami, Shimoda, Nakatani, Miyachi & Watanabe, 1982;Skryzpek & Werblin, 1983;Perlman, Normann, Itzhaki & Daly, 1985;Byzov & Shura-Bura, 1986). The depolarization induced by light in the surround is generally believed to be mediated by a synaptic feed-back pathway from horizontal cells to cones (Baylor et al. 1971;Piccolino & Gerschenfeld, 1977;Kaneko & Tachibana, 1986) and to play a functional role in aspects of spatial vision, light adaptation and colour vision. ...
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Chapter
Although retinal structure in teleosts does not differ in principle from that found in other vertebrates, it appears more difficult than in other vertebrate species to present a general model for the architecture of the fish retina. This is due to the enormous number of fish species (more than 25 000) and to the tremendous diversity of habitats, behaviours, and modes of life. Suffice it to mention the bioluminescent deep-sea fishes, the nocturnal catfish for which vision seems to be of minor importance, and the diurnal guppy, which uses its eyes for social behaviour, catching prey and avoiding predators (Breden and Stoner, 1987). The consequences of these behavioural and/or environmental factors for structure and function of the visual system have long been realized, and best characterized as ‘adaptive radiation’ by Walls (1967) or later as ‘visual ecology’ by Lythgoe (1979).
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The photoreceptors and eyes of four fish species commonly cohabiting Fennoscandian lakes with different light transmission properties were compared: pikeperch Sander lucioperca, pike Esox lucius, perch Perca fluviatilis and roach Rutilus rutilus. Each species was represented by individuals from a clear (greenish) and a humic (dark brown) lake in southern Finland: Lake Vesijärvi (LV; peak transmission around 570 nm) and Lake Tuusulanjärvi (LT; peak transmission around 630 nm). In the autumn, all species had almost purely A2‐based visual pigments. Rod absorption spectra peaked at c.526 nm (S. lucioperca), c. 533 nm (E. lucius) and c. 540 nm (P. fluviatilis and R. rutilus), with no differences between the lakes. Esox lucius rods had remarkably long outer segments, 1.5–2.8‐fold longer than those of the other species. All species possessed middle‐wavelength‐sensitive (MWS) and long‐wavelength‐sensitive (LWS) cone pigments in single, twin or double cones. Rutilus rutilus also had two types of short‐wavelength sensitive (SWS) cones: UV‐sensitive (SWS1) and blue‐sensitive (SWS2) cones, although in the samples from LT no UV cones were found. No other within‐species differences in photoreceptor cell complements, absorption spectra or morphologies were found between the lakes. However, E. lucius eyes had a significantly lower focal ratio in LT compared with LV, enhancing sensitivity at the expense of acuity in the dark‐brown lake. Comparing species, S. lucioperca was estimated to have the highest visual sensitivity, at least 2 times higher than similar‐sized E. lucius, thanks to the large relative size of the eye (pupil) and the presence of a reflecting tapetum behind the retina. High absolute sensitivity will give a competitive edge also in terms of short reaction times and long visual range. This article is protected by copyright. All rights reserved.
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The connectivity amongst photoreceptors is critical to their function, as it underpins lateral inhibition and effective translation of stimuli into neural signals. Despite much work characterizing second-order interneurons in the outer retina, the synapses directly connecting photoreceptors have often been overlooked. Telodendria are fine processes that connect photoreceptor pedicles. They have been observed in diverse vertebrate groups, yet their roles in vision remain speculative. Here, we visualize telodendria via fluorescent protein expression in photoreceptor subtypes. We characterized short wavelength cone telodendria in adult and larval zebrafish retina. Additionally, in the larval retina, we investigated rod telodendria and UV cone telodendria in mutant and transgenic retinas with altered complements of cone types. In the adult retina, telodendria are twice as abundant and branch almost twice as often on blue cones compared to UV cones. Pedicles of neighbouring UV and blue cones typically converge into contiguous pairs, despite the regular spacing of their cell bodies. In contrast to adults, larval UV cone telodendria are more numerous (1.3 times) than blue cone telodendria. UV cone telodendria are not detectably affected by ablation of blue cones, and are reduced 2-fold in mutant larval retina with few UV cones. We thus saw no evidence that telodendria increase in number in the absence of their typical cellular neighbours. We also found that larval rod telodendria are less abundant than short wavelength cone telodendria. In summary, we describe the development and morphology of zebrafish photoreceptor synaptic connectivity towards appreciating the function of telodendria in visual signal processing. This article is protected by copyright. All rights reserved.
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The optical image focussed on the photoreceptor layer of the retina has distributed within it a variety of informative features that represent visual conditions in the surrounding environment. One of these features is colour. In fact, the functional organization of the vertebrate visual system is such that the colour of a given ‘local’ stimulus is not perceived just according to the wavelengths of light reflected from that point but is also influenced by wavelengths emitted from surrounding areas. This spatio-chromatic phenomenon leads to “colour constancy” whereby the colour of an object appears unchanged under different spectral illumination conditions (Land, 1959). Colour constancy has been demonstrated by both psychophysics and electrophysiology in vertebrates as diverse as fish and primates (Zeki, 1980; 1995; Ingle, 1985).
Chapter
Aquatic habitats are extremely diverse, ranging from deep seas, where hardly any light might be available for vision, to shallow waters, where a wide variety of visual cues would normally be found. Even within a restricted aquatic environment, properties of the light stimulus may change markedly in space and time, thereby making a considerable demand on the functioning of the visual system to remain constantly efficient. Retinal neurones of fish (in common with those of other vertebrates) extract visual information from the optical image focused on the retina. It is not certain that all the available information is used, but presumably at least that portion essential to the animals’ behaviour and ecology would be extracted and processed.
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The intensity and spectral distribution of the light encountered by an animal species set reasonably broad operational limits for the efficient generation and reception of visual signals. This phenomenon is of special importance to fishes because aquatic environments cause profound changes in the nature of light that penetrates to any depth (Blaxter, 1970; Brezonik, 1978; James and Birge, 1938; Jerlov, 1968; Kinney et al., 1967; Tyler, 1959). The complex and variable nature of the underwater photic environment offers a unique opportunity to examine the evolutionary responses of visual receptor systems and body colors to variations in the spectral quality of ambient light. It is of particular interest to determine the extent to which organisms have evolved in directions that either make maximum use of environmental conditions or make optimal compromises in the face of conflicting structural and functional requirements. In other word: how well is the visual communication system of the organism “engineered” to perform the tasks upon which the species depends for its survival?
Article
This chapter describes the evolution of vertebrate "camera" eyes and concentrates on color vision and visual pigments. The vertebrate camera eye with a lens, a variable pupil aperture, and a photosensitive receptor layer in the retina, evolved in primitive jawless fish under relatively bright light in shallow seas. With the broad spectral range of daylight, four spectral classes of cone photoreceptor rapidly evolved, offering the benefit of tetrachromatic color vision in order to take full advantage of the visual information available in the environment. This highly successful design has been greatly modified as vertebrates evolved into all the major classes, extending their environmental range into the oceans, the deep sea, freshwater, terrestrial habitats, and the air. © 2012 by Olga F. Lazareva, Toru Shimizu, and Edward A. Wasserman. All rights reserved.
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The study of teleosts, as the oldest and most diverse group of vertebrates, has important implications for the comprehension of developmental processes and mechanisms in higher vertebrates, and we hope that it may offer a module for the understanding of human visual development and insult
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Vertebrate rod and cone photoreceptors hyperpolarize when illuminated. However, synaptic input from horizontal cells can depolarize cones and even elicit action potentials. Using the whole-cell tight-seal recording technique, we determined that, in solitary cones isolated from a lizard retina, action potentials can be generated by depolarizing current steps under conditions where only two ionic currents are activated. A dihydropyridine-sensitive, inward Ca2+ current that activates at potentials positive to -40 mV can regeneratively depolarize the cell. Subsequently, a SITS-sensitive, Ca2(+)-dependent outward Cl- current repolarizes the cell. We suggest that these ionic currents may help explain lateral inhibition in the retina.
Article
Spectral sensitivities of photoreceptors in the turtle (Geoclemys) retina were studied by intracellular recording, and each cell was filled with Lucifer yellow (LY). Photoreceptors were classified into seven morphological types: rod, four types of single cones, and two members of a double cone. Single cones contained one of four different oil droplets: red, pale-green, orange, and clear. Double cones consisted of two apposed cones; principal members contained yellow oil droplets, while accessory members contained no oil droplet. Spectral sensitivities recorded from these seven types of photoreceptors were classified into one type of rod and three chromatic types of cones. Rods (n = 19) showed peak sensitivity at 520 nm. Single cones containing either a red (n = 51) or a pale-green (n = 9) oil droplet were red-sensitive (λmax at 620 nm). Single cones containing an orange oil droplet (n = 14) were green-sensitive (λmax at 540 nm). Single cones containing a clear oil droplet (n = 3) were blue-sensitive (λmax at 460 nm). Both members of the double cone, principal (n = 22) and accessory (n = 15), were red-sensitive (λmax at 620 nm) No diffusion of LY was detected between the apposed members of double cones. Red-sensitive cones, therefore, consisted of four different morphological types of cones, and they occupy about 70% of the photoreceptor mosaic in the turtle retina.
Article
Spectral sensitivity curves were measured for bluegills using a heart-rate conditioning technique. A mean spectral sensitivity curve (n=3) determined using a white background exhibited two main peaks, indicating the possible presence of two cone photoreceptors mechanisms. Chromatic adaptation was used to separate the contribution of the cone mechanisms to sensitivity. Peak sensitivities were located at 540 and 640 nm against red and blue-green backgrounds, respectively. Light adaptation curves were measured for each cone mechanism indicating that these cone mechanisms have their greatest contrast sensitivity at higher background intensities. Spatial summation properties were also measured for each cone mechanism revealing a critical diameter (summation area) of 5° for both mechanisms. Microspectrophotometric (MSP) measurements were made on individuals from the same group of bluegills used in the above experiments. The results showed the presence of two cone types: single green-sensitive cones with an average λmax of 536 nm (SD±1.8nm,n=11) and twin redsensitive cones with an average λmax of 620 nm (SD ±1.9 nm,n=11). The correlation between the visual pigment absorption spectra and action spectra of the two cone mechanisms indicate a sound physiological basis for sensitivity. The functional properties of the two cone mechanisms, will be discussed in relation to the ecological and behavioral aspects of bluegills.
Article
Intracellular recordings were made from rods in the superfused retina of the marine toad (Bufo marinus). It was found that injection of a brief depolarizing current pulse (0.04-1 nA) evoked a distinctive, long-lasting response, here called "the prolonged depolarization." The response appears to be regenerative, has a stereotypical waveform, is typically about 6 mV in amplitude and 3 s in duration, and has a relatively long recovery period (10-60 s). As a rule, the response cannot be directly evoked by light but the current-evoked response is significantly enhanced in the presence of steady illumination. The light-evoked hyperpolarization and the depolarizing spikes of the rod are both attenuated in the presence of the prolonged depolarization. The prolonged depolarization is not an altered manifestation of the depolarizing spikes of toad rods since both can be recorded simultaneously and steady illumination suppresses the spikes while enhancing the prolonged depolarization. The response is enhanced in chloride-free superfusate and also appears to be enhanced by the use of electrodes containing chloride. The response is markedly shortened in superfusates that lack calcium or contain 1-5 mM cobalt. On this and other evidence, it is suggested that the response may be generated by the sequential action of calcium channels and calcium-activated chloride channels. Although rarely evoked by light, the prolonged depolarization of toad rods is otherwise remarkably similar to the prolonged depolarization of turtle cones. It is proposed that the prolonged depolarization, in contrast to the feedback depolarization of cones, arises from mechanisms common to both rods and cones.
Article
The ultrastructural localization of endogenous calcium in the retina of adult cichlid fish Oreochromis mossambicus (Teleostei) was studied using the cytochemical osmiate-bichromate method of Probst (1986). The specificity of this method for calcium localization was proven by means of EGTA treatment of ultrathin sections and electron-spectroscopic-imaging technique (ESI) with an energy-filtering transmission electron microscope (CEM 902, Zeiss). Large amounts of electron-dense calcium containing deposits were found in the outer segments of rods, in the synaptic vesicles of receptor terminals and bipolar cells, in the perinuclear space of photoreceptors and in the endoplasmic reticulum of different cell types, especially in the inner segment and fibres of photoreceptor cells. In the inner plexiform layer calcium was detected in the extracellular space with greater accumulations in the synaptic cleft. Principal differences in the localization of calcium between rods and cones and between several types of synapses and vesicles are shown. The possible role of calcium in the subcellular structures of retinal cells is discussed.
Article
An investigation of retinal specializations was carried out in larval and juvenile dhufish, Glaucosoma hebraicum (Glaucosomidae, Teleostei). The development of photoreceptors and formation of the retinal mosaic was followed by light and electron microscopy. At hatching the eye was undifferentiated. Cone photoreceptors were present by day 3 posthatch (dph), when exogenous feeding began. Single and multiple cones were present in a row arrangement from 3 dph to 20 dph, when the first rod nuclei were observed. Between 20 dph and approximately 3 months posthatch (mph), the row arrangement was replaced by a square mosaic of four double cones surrounding a single cone, and the cones increased in size, with the outer segments reaching up to 30 microm in length. During the period of spatial rearrangement, triple cones were often observed. From their first appearance, rod photoreceptors were added rapidly. Investigation of ganglion cell topography in 3-mph fish that had attained the adult-like square photoreceptor mosaic was carried out using retinal wholemounts. The highest densities of neurones in the ganglion cell layer were in temporal retina but no well-defined area centralis was observed. Microspectrophotometric measurements of the visual pigments within the outer segments of the photoreceptors of 3-mph fish revealed double cones with identical absorption spectra in each member of the outer segment, and the wavelength of maximum absorption (lambda(max)) located at 522 nm. Single cones were found to possess a visual pigment with lambda(max) at 460 nm and rods with a lambda(max) of 498 nm. The results imply that the larvae and juveniles are adapted for survival in coastal waters and may be active in relatively low light levels from early stages of development.
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A review of the literature indicated contrasts in retinal structure and function between perches (Perca spp.) and pikeperches (Stizostedion spp.). Foremost among these were differences in size and distribution of rods, size and shape of cones, extent of retinomotor responses, possession or lack of reflecting material, and relative concentrations of melanin. The perches are primarily active by daylight, whereas the pikeperches are most active during twilight or at night. The coincidental occupancy of shoal areas by yellow perch (Perca flavescens) and walleye (Stizostedion vitreum vitreum) at twilight is related to decreasing visual acuity of the former and the approach of optimum visual performance in the latter species. On this basis the two species have a classic predator–prey relationship. Key words: histology, light, Perca sp., photopic vision, predation, retina, Stizostedion vitreum vitreum, symbiosis, tapetum lucidum
Article
In order to have a satisfactory description of how the visual system works, particularly a description on which one can base adequate quantitative as well as qualitative theories of visual function, including both normal and abnormal color perception, it’s obviously necessary to understand how photoreceptor cells transduce light signals. This paper concerns two techniques that may be useful in improving our knowledge in this area. The first is an improved microspectrophotometer for studying the pigments in single receptors. The second is a microchemical technique for the measurement of light induced reactions in single receptor outer segments. To begin with I would like to go briefly into some of the history of single receptor microspectrophotometry. Until reasonably accurate measurements on single cones in the goldfish were reported by MARKS and myself (1), MARKS (2, 3), and confirmed by LIEBMAN and ENTINE (4), and in human and rhesus monkey receptors by MARKS, DOBELLE and MACNICHOL, (5), and by BROWN and WALD (6), there was no direct evidence that there are three kinds of cones each having a different pigment in organisms known to have trichromatic vision, although much indirect evidence has accumulated over the course of many years from psychophysical and behavioral measurements, the study of defective color perception, and more recently, retinal densitometry. However, for a variety of reasons, the promising work on primate cones of the early 1960’s was soon dropped in the two laboratories in which it was done. Although LIEBMAN has reported confirmatory work, neither he nor anyone else to my knowledge has published any more data on single primate cones since then.
Article
The formation of double cones in the retina of fry of Perca fluviatilis has been investigated by light and electron microscopy. The retina of newly hatched fry is provided with single cones and rods, single cones being the predominant receptor type. Double cones are seen for the first time 22 days after hatching. Mitoses are observed at the periphery of the retina, but are also seen in more central parts of the retina containing differentiated receptors and a cone mosaic. The fate of the cells resulting from the centrally located mitoses is not known. No signs of longitudinal fission of differentiated single cones are seen. It is suggested that double cones in the retina of perch fry arise by fusion of single cones which associate closely and develop subsurface cisterns coextensive with the region of intimate contact in the ellipsoid. During the first few weeks after hatching, there is a gradual shift in arrangement of the cones. In the newly hatched fry, the single cones are arranged in rows. When double cones are first seen, square pattern units appear, built up from four double cones and a single cone.
Article
Freshly isolated retinal photoreceptors of goldfish were studied microspectrophotometrically. Absolute absorptance spectra obtained from dark-adapted cone outer segments reaffirm the existence of three spectrally distinct cone types with absorption maxima at 455 ± 3,530 ± 3, and 625 ± 5 nm. These types were found often recognizable by gross cellular morphology. Side-illuminated cone outer segments were dichroic. The measured dichroic ratio for the main absorption band of each type was 2–3:1. Rapidly bleached cells revealed spectral and dichroic transitions in regions near 400–410, 435–455, and 350–360 nm. These photoproducts decay about fivefold as fast as the intermediates in frog rods. The spectral maxima of photoproducts, combined with other evidence, indicate that retinene2 is the chromophore of all three cone pigments. The average specific optical density for goldfish cone outer segments was found to be 0.0124 ± 0.0015/µm. The spectra of the blue-, and green-absorbing cones appeared to match porphyropsin standards with half-band width Δν = 4,832 ± 100 cm–1. The red-absorbing spectrum was found narrower, having Δν = 3,625 ± 100 cm–1. The results are consistent with the notion that visual pigment concentration within the outer segments is about the same for frog rods and goldfish cones, but that the blue-, and green-absorbing pigments possess molar extinctions of 30,000 liter/mol cm. The red-absorbing pigment was found to have extinction of 40,000 liter/mol cm, assuming invariance of oscillator strength among the three cone spectra.
Article
This treatise on comparative ophthalmology is written both for the layman and the specialist. Part 1 outlines the essentials of the vertebrate (human) eye, the histology and physiology of the vertebrate retina, and discusses scotopic and photopic vision. To this is added an account of the embryological and evolutionary genesis of the eye. Part 2 discusses the following topics: adaptations to arhythmic activity as seen in photomechanical retinal changes and in pupil mobility; adaptations to diurnal activity; adaptations to nocturnal activity; adaptations to space and motion; adaptations to media and substrates including aquatic and aerial vision; and adaptations to photic quality including color vision in animals, dermal color-changes, and coloration of the eye. Part 3 traces the history of the eye from the lowest to the highest living vertebrates. There is a 24-page bibliography and an index and glossary. (PsycINFO Database Record (c) 2012 APA, all rights reserved)
Article
The formation of double cones in the retina of fry of Perca fluviatilis has been investigated by light and electron microscopy. The retina of newly hatched fry is provided with single cones and rods, single cones being the predominant receptor type. Double cones are seen for the first time 22 days after hatching. Mitoses are observed in the periphery of the retina, but are also seen in more central parts of the retina containing differentiated receptors and a cone mosaic. The fate of the cells resulting from the centrally located mitoses is not known. No signs of longitudinal fission of differentiated single cones are seen. It is suggested that double cones in the retina of perch fry arise by fusion of single cones which associate closely and develop subsurface cisterns coextensive with the region of intimate contact in the ellipsoid. During the first few weeks after hatching, there is a gradual shift in arrangement of the cones. In the newly hatched fry, the single cones are arranged in rows. When double cones are first seen, square-pattern units appear, built up from four double cones and a single cone.
Article
Morphologically speaking, there are five kinds of cone cells in the retina of the rudd (Scardinius erythrophthalmus). But two of them, the principal elements of the double cones and the free principal cones, are probably functionally equivalent, while another, sparse, population of small (oblique) cones (which disappear in older fish), is unlikely to make a significant contribution to visual spectral sensitivity. Thus, principal and accessory cones (usually paired with one another), and single cones seem to be the three receptors which underlie the fish's trichromacy. Photographic densitometry of individual cone cells was used to provide evidence that accessory cones contain a green-absorbing photopigment and the single cones a blue one. Other arguments are given in support of those identifications, and they also strongly suggest that principal cones contain the red-absorbing pigment. Golgi-impregnated bipolar cells were examined electron-microscopically to determine the specific patterns of synaptic connexion they make with these different, anatomically identifiable, colour cones and with the retinal rods. Three principal arrangements were distinguished (see figure 69, page 100). (1) Rod bipolar cells comprise two distinct morphological types, both of which connect exclusively to principal (red) cones as well as to the rods within the outlines of their dendritic fields. (2) Selective cone bipolar cells, more delicate neurons with considerably wider dendritic fields, connect (according to type) to one or other of the different colour cone populations. Examples analysed were specific for the accessory (green) or for the single (blue) cones; no bipolar cells were found connected only to red cones. (3) Mixed cone bipolars have the smallest dendritic fields, and connect to combinations of cones (for example, red and green, or green and blue, but not red and blue). They also have synaptic input (usually relatively sparse) from the rods. Cells were encountered connecting to all three cone types, but they were only partially analysed, and are not described at length. The light microscopic morphology of these bipolar cell types consistently reflects the detailed pattern of connexion each makes with the different receptor populations (just as the morphology of the cones reflects the spectral properties of their photopigment). But while their synaptic connectivity is generally highly specific for cone type, they do occasionally make anomalous connexions with the 'wrong' receptors. There is a high degree of divergence (page 85) at the receptor-bipolar synapses, and the different kinds of cones each characteristically connect to different numbers of bipolar cells. Principal (red) cones, which are the most numerous, individually connect to more bipolars than cones of other types, whose characteristic synaptic divergence is likewise related to the frequency with which they occur in the retina. However, rods, which are much more numerous than cones, do not conform with this generalization. The selectivity with which the synaptic terminals of the different cones are connected together by their invaginating basal processes was also examined. These processes link neighbouring synaptic terminals of differently coloured cones: specifically, principal (red) cone basal processes invaginate accessory (green) cone pedicles, and vice versa. Single (blue) cone basal processes connect only to accessory cone pedicles, but that synaptic relation is not reciprocated. These synapses between the cones have important bearing upon interpretation of the bipolar cell connectivity patterns. In their light, the interaction between colour channels which the convergence of different cones onto the mixed cone bipolar dendrites mediates, seems to re-iterate a process already undertaken more peripherally. Likewise, whereas the anatomy of the selective cone bipolars appears designed to convey activity from the individual cone populations, the responses of the receptors they sample must already be influenced by activity in other colour channels.
Article
Microspectrophotometric investigations of visual pigments in the teleost family Cichlidae determined that morphological "twin cones" need not be "pigment twins" as well. In each species there were two pigments that could be found in these cells; a "longwave" and a "shortwave" type whose precise spectral location varies for each species, making the terms red and green inadequate to describe them. Studies of the receptor mosaic with the nitro-blue tetrazolium chloride reduction technique permitted the sampling of larger receptor populations and confirmed that twin cones in several cichlid species could be either longwave-longwave, longwave-shortwave, or shortwave-shortwave pairs, and that the relative proportions of these twin cone types vary in different parts of the retinas. Nonuniform distribution of pigment types was also evident in the eyes of several other species from a variety of piscine taxa.
Article
The voltage-current relations of the cone membrane were measured by means of pulses of current injected into single cones of turtle retina. In darkness the voltage-current curve was almost linear. During illumination with a small (dia. 115 μm) spot the steepness of the curve increased but its linearity was preserved. However, during illumination with a big (dia. 2 mm) spot the positive pulses of current evoked considerably higher potential drops than negative pulses of the same intensity. Accordingly, the depolarizing portion of the voltage-current curve was steeper than the hyperpolarizing one. This non-linear behaviour of cone membrane displayed only with a large-area illumination can be explained as a combined effect of non-linearity of presynaptic membrane of the cone and of the mechanism of feedback between the horizontal cells and cones. The equivalent circuit of synapse between the photoreceptor and the horizontal cell, realized as a physical model, is described. The model reproduces the effect of area illuminated on the shape of the voltage-current curves of the cone, as well as some other experimental manifestations of the feedback mechanism in cones.
Article
Microspectrophotometer measurements of the oil droplets and visual pigments in the receptors of the pigeon have demonstrated the presence of at least five types of oil droplet and four visual pigments. The oil droplets act as cut-off filters, their wavelengths of 50% transmission varying depending from which area of the retina they come, but lying between 600 and 610, 560 and 570, 470 and 554, 470 and 476 and below 430 nm, and effectively cutting off light below these wavelengths. The rod receptors contain a rhodopsin withλmax 503 nm. The dominant cone visual pigment hasλmax 567 nm and is found in both members of the double cone and three types of single cone. Two further types of single cone contain a green-absorbing pigment (λmax about 515 nm) and another type of single cone a blue-absorbing pigment (λmax about 460 nm). From the transmission characteristics of the oil droplets and the absorbance spectra of the cone visual pigments, the effective spectral sensitivities of each cone type has been derived and directly related to the spectral sensitivities of isolated units in the retina and optic tectum and to the overall photopic sensitivity of the pigeon as measured behaviourally and electrophysiologically.
Article
Ellipsosomes are dense spherical bodies containing a very large concentration of a heme pigment spectroscopically resembling pure cytochrome c. They are located at the outer ends of the inner segments of the cones of certain fishes. Although, superficially, they resemble the similarly located oil droplets in the cones of birds and reptiles, their ultrastructure and staining properties resemble those of the neighboring mitochondria. However, like the oil droplets, they may serve as intracellular color filters.
Article
The visual pigments in the retinae of 18 species of fishes were measured microspectrophotometrically and assigned to specific cone types. The major ecological implications of these data are seen by grouping the fishes into habitat classes based on spectral quality of the water and depth. It is seen that double and twin cones in the examined species contain a visual pigment roughly matching the water background spacelight, while single cones occupying typically the “additional” position in a square mosaic unit are invariably blue-sensitive and offset from the water transmission maximum. In photopic dichromats the central single cone of a square unit was found to contain a pigment identical to that found in the twin cones.The relevance of these findings to contrast enhancement, adaptation to rapid changes in spectral quality of the water, and formation of “ghost” pigments through opponancy is also discussed.
Article
Retinal growth in young Sebastes diploproa involves the succession of three distinct cone patterns. Development of the final pattern with the loss of single cones occurs in close temporal association with a permanent migration from the surface to deep water. The results suggest that loss of single cones depends upon the change in environment and that the loss occurs through fusion to double elements.
Article
1. The spectral sensitivity and spatial organization of cones and horizontal cells have been analysed by intracellular recording in pikeperch retinas. 2. The vast majority of cone recordings were obtained from orange-sensitive cones. They have an action spectrum which peaks at about 605 nm. Recordings from several green-sensitive cones have also been obtained. 3. The results of action spectrum measurements and spectral screening tests indicate that the vast majority of luminosity-type horizontal cells receive predominant input from the orange-sensitive cones. 4. Chromatic-type horizontal cells were recorded at more proximal levels of the retina than luminosity-type cells and were the classic red-depolarizing, green hyperpolarizing (R/G) type. 5. The action spectra of the depolarizing and hyperpolarizing responses of chromatic horizontal cells peak at about 650 and 530 nm, respectively. When the depolarizing mechanism is selectively depressed by a red background field, the action spectrum of the hyperpolarizing mechanism shows an enhanced sensitivity, peaks at 530--540 nm, and may approximate the action spectrum of the green-sensitive cones. 6. Small red fields evoke depolarizing responses from chromatic-type horizontal cells but do not seem to significantly activate the depolarizing surround mechanism of cones. 7. These and other results suggest that the colour-opponent properties of the chromatic-type horizontal cells are not fundamentally dependent upon feed-back to cones but rather originate from antagonistic interactions generated in post-receptor networks.
Article
Six types of photoreceptors in the red area (dorso-temporal quadrant) of the pigeon retina are identified using Golgi impregnation, light microscopy and electron microscopy. Golgi impregnation is used to categorize the receptors into morphological types. Examination of oil droplets in the inner segments of cones in fresh, unfixed tissue shows five different types which can be characterized by color, size and stratification. Therefore, in sections through the length of the receptors examined by electron microscopy, the oil droplets contained in the inner segments of the cones can be identified as to their color by their characteristics (i.e., size and stratification), and the groups of receptors thus classified, further characterized as to the morphology of their terminals. Rods have no oil droplets in their inner segments, and their synaptic terminals are located in the outermost stratum of the outer plexiform layer OPL). Principal members of double cones have yellow oil droplets in their inner segments, while accessory members contain small colorless oil droplets. The synaptic terminals of double cones are located in the same (outermost) stratum of the OPL as rod synaptic terminals. Two types of single, straight cones house either red or orange oil droplets and terminate in the intermediate stratum of the OPL. Oblique single cones with yellow-green oil droplets in their inner segments contribute synaptic terminals to the innermost stratum of the OPL.
Article
The permeability of the cell-to-cell membrane channels in salivary gland cell junction (Chironomus thummi) was probed with fluorescent-labeled amino acids and synthetic or natural peptides. Molecules up to 1200 daltons pass through the channels with velocities depending on molecular size. Molecules of 1900 daltons or greater do not pass. This passage failure seems to reflect the normal size limit for junctional channel permeation; the channels continue to be permeated by the molecules up to 1200 daltons when these are mixed with the nonpermeant molecules. From this size limit a channel diameter of 10 to 14 angstroms is estimated.
Article
1. Cones in the retinas of two closely related species of perch, the walleye and sauger (S, vitreum vitreum and S. canadense), are remarkably large. This paper reports a first series of intracellular recordings obtained from 77 of these cones. 2. A small spot of light evokes a sustained hyperpolarizing response from perch cones which may exceed 10 mV in amplitude, is graded with stimulus intensity, and is markedly reduced when the spot is decentered. Most cones seem to be orange sensitive with peak sensitivity at about 600 nm. 3. Enlarging the stimulus diameter from 0.04 to 0.25 mm produces a modest increase in the hyperpolarizing response. However, larger stimuli which illuminate surrounding regions of the retina often evoke a delayed depolarizing potential which antagonizes the sustained phase of the cone's hyperpolarizing response to central illumination. 4. The outer diameter of the region of the antagonistic surround is at least 2.2 mm in extent. An annulus evokes a depolarizing response only if the central region of the receptive field is simultaneously activated. 5. The present results provide the first direct evidence that the receptive fields of cones in fish retinas have an antagonistic center-surround organization. Luminosity-type horizontal cells probably serve as the interneurons which mediate the depolarizing influence of the surround.
Article
Dark-adapted retinal cones of goldfish were measured microspectrophotometrically. The three types of spectra so obtained were subjected to a new method of data analysis. In order of types blue (B), green (G), and red (R), the best estimates for lambdamax were 453, 533, and 620 nm; for main band half width, 6,700, 4,700, and 3,900 cm-1. The extinction spectra of 11-cis 3,4-dehydroretinal and those of the three goldfish pigments were progressively fitted with Gaussian curves starting at the low-energy end of their spectra. The sum of the oscillator strengths of the first three Gaussian components throughout the four spectra were found to have nearly equal magnitudes. Functional relationships that connect the Gaussian parameters were obtained by curve-fitting, enabling partial absorption spectra to be generated for any lambdamax. The generated curves predicted the half width and peak extinction of porphyropsin-type absorption spectra more accurately than previously existing nomograms or hypothesis. The epsilonmax values thus obtained were 28,500, 32,000, and 35,700 liter/mole cm for the B-, G-, and R-type goldfish pigments; these were found to be consistent with the experimental determinations of +/- 10% estimated accuracy.
Article
Histologic examination of the retina in comet goldfish 11 cm long (nose to base of tail) reveals at least six distinct varieties of cones. Unequal double cones (DC) comprise long (LD) and short (SD) members which differ in form as well as length. Long single (LS) cones are similar in length and form to SD cones. Although evidence indicates that there are two subpopulations of LS cones, normally they are structurally indistinguishable. Short single (SS) cones have short, broad outer segments and ellipsoids and virtually no myoids. Miniature long single (MLS) cones have the same shape as LS cones, but they are shorter and more slender and their nuclei project farther into the outer nuclear layer. Miniature short single (MSS) cones have the same shape as SS cones, but they are shorter and more slender and their nuclei are found with those of MLS cones. The average cone densities, relative to SS = 1.0, are: DC (pairs) ≅ 2.0, LS (total) ≅ 1.4–2.0, MSS ≅ 0.4–0.8, and MLS < 0.1. The form, dimensions, and densities of cones do not vary systematically with location in the retina.
Article
1. The directional selectivity of individual cones was examined by intracellular recording in the eye of the turtle. Sensitivites were determined from linear responses to dim flashes of monochromatic light incident on a cell over a range of angles to its long axis. 2. With light near the optimum wave-length, some red- and green-sensitive cones showed a high sensitivity for light entering axially and lower sensitivities for light entering obliquely. In contrast, other cells had lower peak sensitivities and less pronounced directional selectivities. The highest axial sensitivities observed in red receptors were about 320 muV photon(-1) mu2; in these cells, the sensitivity declined to half for rays 6-9 degrees off the axis as measured in the retina. Green receptors had lower axial sensitivities and broader angular profiles. 3. On the assumption that rays at all angles contribute independently to the over-all sensitivity, the sensitivity of a cell to large cones of rays was successfully predicted from the angular selectivity determined with a narrow pencil of rays. The shape of small responses to dim stimuli delivered on and off the axis of the cell was invariant, implying that a cone signals the number of photons absorbed but not their angle of incidence. 4. Short wave-lengths have previously been shown to be filtered out by the oil droplets present in turtle cones. At short wave-lengths, the angular profiles showed a depression in axial sensitivity consistent with this filtering action. 5. Diameters of inner segments, oil droplets, and outer segments were measured in red-, green-, and blue-sensitive cones, since these dimensions are expected to influence the cones' angular acceptances and ability to collect light. The diameters of the structure were in approximately the same proportions for each type of receptor, but the absolute values of the diameters were found to be scaled in relation to the wave-length of maximum sensitivity. 6. Optical determinations of the efficiency with which axial rays are concentrated by red receptors gave a mean value of 55%. 7. Receptors in histological sections of the whole eye were found to be oriented with their long axes directed approximately toward the pupil. 8. The observed directional selectivities and collecting efficiencies agree well with the behaviour of a model retinal cone developed by Winston & Enoch (1971) on a geometrical optical treatment. 9. Effective collecting areas are derived for red-, green- and blue-sensitive cones; these permit conversion of observed flash sensitivities into the mean peak hyperpolarization produced by isomerization of a visual pigment molecule. The figure obtained is about 25 muV for red-sensitive cones and 21muV for green-sensitive cones.
Article
1. Responses to monochromatic flashes were recorded intracellularly from double cones in the retina of the turtle, Pseudemys scripta elegans. Double cones have been identified by intracellular marking with Procion Yellow dye.2. The direct light response of a double cone is a hyperpolarization graded with the intensity of a flash and similar to the response of single cones.3. When flashes were dim, responses were proportional to light intensity but varied in time course as a function of wave-length. They reached peak in about 120 msec for deep red stimuli and about 143 msec for green stimuli.4. When applied over red backgrounds, responses to red flashes became smaller, faster and frequently diphasic, but responses to green remained similar to those recorded from darkness. Green backgrounds made responses to all colours small and fast.5. Linear spectral sensitivity curves have peaks corresponding to the peak sensitivities of single red-sensitive and green-sensitive cones. Red and green backgrounds suppressed red and green sensitivity respectively.6. Large fields of illumination evoked composite responses which included the direct light response, its enhancement from illumination of nearby receptors and the depolarizing effect of luminosity horizontal cell impingement. In the green-sensitive element the depolarizing effect was larger for red than for green flashes, and stimulation with red annuli evoked net depolarizing responses.7. It is concluded that the responses of double cones may be explained by coupling of the responses from red-sensitive and green-sensitive elements each of which has properties otherwise similar to single red-sensitive and green-sensitive cones.
Article
1. Intracellular recordings of cone and horizontal cell responses to circles or annuli of light were made with the purpose of determining the properties of and the mechanisms underlying the horizontal-cell-mediated depolarization of cones which is evoked by surround illumination.2. A comparison of the responses of a cone and a near-by horizontal cell to a peripheral stimulus revealed a striking similarity in their time courses and amplitudes, indicating that a correlation exists between the depolarizing synaptic potential in the cone and the response of the horizontal cell.3. The depolarizing synaptic potential in cones was separated from the direct response of the cell to light by illuminating the periphery with an annulus during steady, bright illumination of the central cone. The synaptic potentials were graded with the intensity or area of peripheral illumination. In some cones a spike-like depolarization, which overshot the dark resting potential, occurred with bright illumination of the periphery.4. The effects of extrinsic current on the synaptic potential demonstrated that this response was generated by a change in membrane conductance consisting of two separate components with different time-dependences and reversal levels. The slower of the two components, which often outlasts the stimulus, represents an increase in membrane conductance.5. The progressive decline in the amplitude of the responses of horizontal cells under a large spot from centre to periphery was found to result in a diminished feed-back effect in cones near the edge of the spot. This leads to a Mach-band effect during the plateau phase of cone responses, suggesting that one function of the feed-back might be to enhance contrast discrimination.
Article
Freshly isolated retinal photoreceptors of goldfish were studied microspectrophotometrically. Absolute absorptance spectra obtained from dark-adapted cone outer segments reaffirm the existence of three spectrally distinct cone types with absorption maxima at 455 +/- 3,530 +/- 3, and 625 +/- 5 nm. These types were found often recognizable by gross cellular morphology. Side-illuminated cone outer segments were dichroic. The measured dichroic ratio for the main absorption band of each type was 2-3:1. Rapidly bleached cells revealed spectral and dichroic transitions in regions near 400-410, 435-455, and 350-360 nm. These photoproducts decay about fivefold as fast as the intermediates in frog rods. The spectral maxima of photoproducts, combined with other evidence, indicate that retinene(2) is the chromophore of all three cone pigments. The average specific optical density for goldfish cone outer segments was found to be 0.0124 +/- 0.0015/microm. The spectra of the blue-, and green-absorbing cones appeared to match porphyropsin standards with half-band width Deltanu = 4,832 +/- 100 cm(-1). The red-absorbing spectrum was found narrower, having Deltanu = 3,625 +/- 100 cm(-1). The results are consistent with the notion that visual pigment concentration within the outer segments is about the same for frog rods and goldfish cones, but that the blue-, and green-absorbing pigments possess molar extinctions of 30,000 liter/mol cm. The red-absorbing pigment was found to have extinction of 40,000 liter/mol cm, assuming invariance of oscillator strength among the three cone spectra.
Article
A novel microspectrophotometer is described, which simultaneously resolves cell absorption into two mutually orthogonal components allowing the determination of linear dichroism as a function of wavelength in the range of 325–695 nm. This instrument uses a single plane-polarized light beam and a small general-purpose digital computer, and is equipped with a photo-flash apparatus for rapid photolysis. Following visual pigment bleaching, it can detect changes occurring on a time scale of seconds in the orientation and spectral character of chromophores in isolated cells. The spectral scanning is performed in either single or multiple sweeps which may be unidrectional or bidirectional. The scanning rate is set to 500 nm/s. Spectral resolution is 5 nm. Its signal and data processing are discussed. Its performance is illustrated on subcellular organelles of retinal photoreceptors from turtle and frog. Rhodopsin and its photoproducts are shown to lend dichroism to frog rod outer segments. Metarhodopsin II, when formed, is transversely dichroic as rhodopsin. The late products (retinol, retainal oxime, etc.) show axial dichroism. The corrected specific optical density (transverse component) of frog rod outer segments (in hydroxylamine) is found to be 0.0182±0.002/ µm. The average absorption spectrum is presented for in situ rhodopsin.
Article
Glutamate and aspartate completely suppress the activity of horizontal cells but only partially affect the response of receptor cells to light. The changes observed in the receptor responses are consistent with the interruption of a synaptically mediated process rather than with a direct action on the receptor membrane.
Article
1. Intracellular recordings have been made of the responses to light of single cones in the retina of the turtle. The shape of the hyperpolarizing response to a flash depends on the pattern of retinal illumination as well as the stimulus intensity.2. Although changes in the stimulus pattern can produce changes in the effective stimulus intensity, the responses to certain patterns cannot be matched by any adjustment of stimulus intensity.3. The initial portion of responses to large or small stimulating spots is proportional to light intensity; this allows comparison of responses when the amount of light on a cone is kept constant but the light on surrounding cones is changed. For equal light intensity on the cone, the response to a spot 2 or 4 mu in radius is smaller than that to a spot 70 mu in radius.4. Responses to spots 70 and 600 mu in radius coincide over their rising phases and peaks without any adjustment of stimulus intensity. The responses to the larger spot, however, contain a delayed depolarization not present with the smaller spot.5. During steady illumination of a cone with a small central spot, the response to transient illumination superimposed on the same area is greatly reduced. Illumination of cones in the near surround, however, produces a hyperpolarizing response, and illumination of cones in the more distant surround generates a delayed depolarization.6. The results described above suggested that synaptic signals might impinge on cones. This possibility was tested by electrically polarizing one retinal cell while recording from another.7. Currents passed through a cone within 40 mu of another cone can change the membrane potential of the latter. Not all cones within this distance show the interaction, however, and it has never been detected at distances greater than 50 mu.8. Hyperpolarization of a horizontal cell with applied current can produce a depolarization of a cone in the vicinity. During this depolarization, the response of the cone to a flash is reduced in size and altered in shape.9. It is concluded that the response of a cone to light may be modified by synaptic mechanisms which are activated by peripheral illumination.
Article
1. S-potentials recorded from the excised tench retina left undisturbed in the optic cup show colour cells of the two types originally described by Svaetichin & MacNichol (1958).2. One type (green/blue, G/B) is depolarized by signals from green cones and hyperpolarized by blue cones. The other type (red/green, R/G) is depolarized by deep red and hyperpolarized by green cones.3. By superposing spectral flashes upon steady adapting lights it is possible to find a spectral range in which only one kind of cone is effective. In this range the effect of any spectral light may be matched with that of any other provided the energies are linked in a fixed ratio that defines the action spectrum of the pigment.4. The green pigment has an action spectrum with maximum at 540 nm and corresponds well with the pigment that Marks measured in ;green' cones. The blue pigment has not been measured, but it probably corresponds with that found by Marks in ;blue' cones. However, the red pigment whose action spectrum we measured had its maximum at 680 nm, whereas the difference spectrum of Marks's red cone pigment peaked at 620 nm. The 620 nm cones excite the luminosity S-units but not the R/G units.5. In the range where only one type of cone is effective the relation between the light intensity, I(0), and V(0), the S-potential generated (both expressed in suitable units), is given by equation (1) p. 545. It is the relation that would be found if cone signals increased the conductance through a polarized ;S-membrane' in proportion to the flux of caught quanta.
Article
Cones and horizontal cells of the pikeperch retina were studied with morphological and physiological techniques. Gap junctions were observed between cone pedicles and basal processes emitted by neighboring cones. Intracellular recordings showed that the light-evoked hyperpolarizing cone response was enhanced by light falling upon neighboring receptors within a radius of 50μm. We suggest that the network of gap junctions between cones mediates the summative lateral interaction described. Three sub-classes of horizontal cells (H1, H2, H3) send dendrites to cones; H1 and H2 cells appear to appear to contact twin cones, exclusively or preferntially, whereas H3 cells appear to synapse only with single cones. Horizontal cells of the same sub-class are joined by gap junctions between dendrites or at the lateral faces of perikarya. These unions extend over several μm2 and as seen in transmission electron microscopy consist of patches of close apposition alternating with areas of membrane separation, folding and occasional zonulae adherentes. Freeze-fracture profiles of horizontal gap junctions show localized areas of dense particle aggregation on the P-face and pits on the E-face flanked by regions of unspecialized membrane. These morphological findings provide support for the known spatial and color-coding properties of pikeperch horizontal cells.
Article
Micropipettes filled with Procion yellow dye were used to record from and to stain pikeperch horizontal cells intracellularly. Three major types were found: a distal layer (H1) of relatively small cells which were luminosity or L-type; a second and more proximal layer of larger L-type cells (H2); and a third and yet more proximal layer of very stellate chromatic or C-type cells (H3). A few anucleate processes which displayed slow-potentials were found in the proximal area of the inner nuclear layer. Cells of each of the three layers were shown to be cone related by both anatomical and physiological methods. L-type cells were further categorized by the area over which each exhibited spatial summation and the relative sensitivity of each to red and green lights. Receptive field sizes of H2's were found to range from less than 2 mm to greater than 5 mm in diameter, whereas those of the few H1's tested were all less than 2 mm. Results from spectral screening tests indicate that most H1 and H2 cells are maximally sensitve to orange light, whereas the H3 cells hyperpolarize maximally to green and depolarize maximally to red. A small percentage of sampled C-cells displayed an additional depolarization to violet.
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Electrical responses of double cones in turtle retina
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Cone structure and visual pigment content in the retina of the goldfish. Vision Re8
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Synaptic connections linking cones and horizontal cells in the retina of the pikeperch (Stizoatedion vitreum)
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