The influence of light on cone disk shedding in the lizard, Sceloporus occidentalis.

Bernstein, Steven A.; Breding, David J.; Fisher, Steven K.

doi:10.1083/jcb.99.2.379

Cited by 27 publications

(6 citation statements)

References 13 publications

(45 reference statements)

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“…Red-eared slider Pseudemys scripta elegans Baylor and Fettiplace, 1975;Leeper, 1978;Jones, 1982, 1987;Ohtsuka and Kawamata, 1990 Snapping turtle Chelydra serpentina Baylor and Fettiplace;Leeper; Reeve's turtle Geoclemys reevesii Ohtsuka, 1985;Ohtsuka and Kawamata; Garter snake Thamnophis sirtalis Wong;1989;Sillman et al, 1997 Ball python Python regius Sillman et al, 1999b Common boa Boa constrictor imperator Sillman et al, 2001 Mississippi alligator Alligator mississippiensis Kalberer and Pedler, 1963;Sillman et al, 1991 Caiman Caiman crocodilus Govardovskii et al, 1988 Tokay gecko Gekko gecko Pedler and Tilly, 1964;Crescitelli, 1972 Blue-tailed day gecko Phesulma inunguis Pedler and Tansley, 1963;Pedler and Tilly, 1964 Coastal banded gecko Coleonyx variegates Dunn, 1966 Mediterranean gecko Hemydactilus turcicus Pedler and Tilly, 1964;Loew et al, 1996 House gecko Hemydactilus garnotii Loew et al, 1996 Scinc gecko Teratoscincus scincus Govardovskii et al, 1984;Loew et al, 1996 Chameleon Chamaleo chamaleo Armengol et al, 1981 Western fence lizard Sceloporpus occidentalis Young, 1977;Bernstein et al, 1984 Ornate dragon lizard Ctenophorus ornatus Barbour et al, 2002 Tuatara Sphenodon punctatu Meyer-Rochow et al, 2005 Bouton's skink Cryptoblepharus boutonii Röll, 2001…”

Section: Reptilesmentioning

confidence: 99%

Functional significance of the taper of vertebrate cone photoreceptors

Hárosi

Flamarique

2012

Journal of General Physiology

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Vertebrate photoreceptors are commonly distinguished based on the shape of their outer segments: those of cones taper, whereas the ones from rods do not. The functional advantages of cone taper, a common occurrence in vertebrate retinas, remain elusive. In this study, we investigate this topic using theoretical analyses aimed at revealing structure–function relationships in photoreceptors. Geometrical optics combined with spectrophotometric and morphological data are used to support the analyses and to test predictions. Three functions are considered for correlations between taper and functionality. The first function proposes that outer segment taper serves to compensate for self-screening of the visual pigment contained within. The second function links outer segment taper to compensation for a signal-to-noise ratio decline along the longitudinal dimension. Both functions are supported by the data: real cones taper more than required for these compensatory roles. The third function relates outer segment taper to the optical properties of the inner compartment whereby the primary determinant is the inner segment’s ability to concentrate light via its ellipsoid. In support of this idea, the rod/cone ratios of primarily diurnal animals are predicted based on a principle of equal light flux gathering between photoreceptors. In addition, ellipsoid concentration factor, a measure of ellipsoid ability to concentrate light onto the outer segment, correlates positively with outer segment taper expressed as a ratio of characteristic lengths, where critical taper is the yardstick. Depending on a light-funneling property and the presence of focusing organelles such as oil droplets, cone outer segments can be reduced in size to various degrees. We conclude that outer segment taper is but one component of a miniaturization process that reduces metabolic costs while improving signal detection. Compromise solutions in the various retinas and retinal regions occur between ellipsoid size and acuity, on the one hand, and faster response time and reduced light sensitivity, on the other.

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Section: Reptilesmentioning

confidence: 99%

Functional significance of the taper of vertebrate cone photoreceptors

Hárosi

Flamarique

2012

Journal of General Physiology

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“… ND: Not determined a (Carter-Dawson and LaVail, 1979) b (Galliard, et al, 2008) c (Reme and Young, 1977) d (Bernstein, et al, 1984) e (Braekevelt, 1983) f (Braekevelt, 1998) g (Yuodelis and Hendrickson, 1986), survey of fovea from a 37 year old patient …”

Section: Figures and Tablesmentioning

confidence: 99%

Structure of cone photoreceptors

Mustafi

Engel

Palczewski

2009

Progress in Retinal and Eye Research

197

166

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Although outnumbered more than 20:1 by rod photoreceptors, cone cells in the human eye mediate daylight vision and are critical for visual acuity and color discrimination. A variety of human retinal diseases, e.g. age-related macular degeneration (AMD), are characterized by a progressive loss of cone photoreceptors, but the low abundance of cones and the absence of a macula in non-primate mammalian retinas have made it difficult to investigate them directly owing to lack of suitable experimental models. Conventional rodents (laboratory mice and rats) are nocturnal rod dominated species with few cones in the retina, while investigating other animals with cone-rich retinas presents various logistic and technical difficulties. Past work, originating in the early 1900s, has begun to provide insights into cone ultrastructure, but has yet to afford a unified model of cone cell organization. This review summarizes this past work and focuses on the recent introduction of special mammalian models (transgenic mice and diurnal rats rich in cones) that promise to reveal a more unified model of cone photoreceptor organization and its role in retinal diseases. These new mammalian models should allow new investigative techniques such as atomic force microscopy and cryo-electron tomography to advance our understanding of cone photoreceptors, much as has been done with rod photoreceptors.

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“…Most studies show cone peak phagocytosis as occurring within the dark period, as in diurnal chickens, 31 fence lizards, 32 tree squirrels, 29 ground squirrels, 30 and rhesus monkeys. 25 A few studies show the maximum activity being coincident with that of rods (in nocturnal species such as cat 28 and diurnal species such as Tupaia 33 or Arvicanthis 20 ). In the present study, advances or delays in the lighting regimen led to immediate adjustments in the phagocytic profiles, with peak activities after the modified light schedule, in a time course expected for light-triggered responses (although there was increased phagocytosis outside of peak times compared to LD).…”

Section: Discussionmentioning

confidence: 99%