棒とコンの光伝導における視覚的色素特性の役割
Vladimir Kefalov1, Yingbin Fu, Nicholas Marsh-Armstrong
1Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
Nature
|October 3, 2003
まとめ
円と棒の色素は,同様の信号特性を有しています. コーンピグメントの高自発的活性,シグナル差異がないことが,より速いコーン反応と弱光下でのより低い感受性を説明します.
科学分野:
- ビジョン科学 ビジョン科学
- フォトトランスデュークションのメカニズム
- 網膜生理学 網膜の生理学
背景:
- 棒とは周期的なGMP光伝導を共有しているが,感度と運動学では著しく異なっている.
- 異なる棒とコーンタンパク質の変種が存在し,メタII状態の寿命と自発的な異体化などの色素特性における異なる差異が提案されています.
- これらの色素特性差異が,棒-の機能的分岐に及ぼす機能的影響は,主に憶測的なままである.
研究 の 目的:
- 網膜の棒と円の機能的差異に対する視覚色素特性の寄与を調査する.
- 棒とコーンピグメントの固有のシグナル伝達特性が異なるかどうかを判断する.
- 円細胞のより低い光感度と,棒と比較してより速い運動の背後にあるメカニズムを解明する.
主な方法:
- Xenopusの棒で発現したヒト/サラマンダの赤いコーン色素.
- クセノプス (Xenopus) のコーンで発現したヒトの棒の色素.
- 修正されたXenopus細胞における光応答増幅と運動を分析した.
主要な成果:
- 棒とコンのピグメントは,同じ細胞タイプで表現された場合,同じ増幅と運動を持つ光の反応を誘発しました.
- 円色素は,棒色素よりも約1万倍高い自発性イソメリゼーション率を示した.
- 円の色素の高自発的活性が,本来の円が暗闇に適応する重要な要因として特定されました.
結論:
- 視覚色素のシグナル伝達特性における差異は,棒と円の間の機能的差異を説明するものではありません.
- コンピグメントの高自発性イソメリゼーション率は,コンピグメントの感度が低く,運動が速くなり,コンピグメントが昼間の視力に適応する.
- 追加的な,まだ特定されていない要因は,棒と円の間の全体的な機能的な違いに寄与する可能性が高い.
関連する概念動画
The Retina
The retina is a layer of nervous tissue at the back of the eye that transduces light into neural signals. This process, called phototransduction, is carried out by rod and cone photoreceptor cells in the back of the retina.
Vision
Vision is the result of light being detected and transduced into neural signals by the retina of the eye. This information is then further analyzed and interpreted by the brain. First, light enters the front of the eye and is focused by the cornea and lens onto the retina—a thin sheet of neural tissue lining the back of the eye. Because of refraction through the convex lens of the eye, images are projected onto the retina upside-down and reversed.
Channel Rhodopsins
Most organisms use photoreceptors to sense and respond to light. Examples of photoreceptors include bacteriorhodopsins and bacteriophytochromes in some bacteria, phytochromes in plants, and rhodopsins in the photoreceptor cells of the vertebral retina. The light-sensitive property of these receptors is because of the bound chromophores, such as bilin in the phytochromes and retinal in the rhodopsins.
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
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Anatomy of the Eyeball
The eye is a spherical, hollow structure composed of three tissue layers. The outer layer — the fibrous tunic, comprises the sclera — a white structure — and the cornea, which is transparent. The sclera encompasses some of the ocular surface, most of which is not visible. However, the 'white of the eye' is distinctively visible in humans compared to other species. The cornea, a clear covering at the front of the eye, enables light penetration. The eye's middle layer, the vascular tunic,...
Photoreceptors and Visual Pathways
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...
Color Vision
Color perception begins in the retina, the light-sensitive layer at the back of the eye. Two main theories explain how colors are seen: the trichromatic theory and the opponent-process theory. The trichromatic theory, proposed by Thomas Young in 1802 and extended by Hermann von Helmholtz in 1852, suggests that color vision is based on three types of cone receptors in the retina. These cones are sensitive to different but overlapping ranges of wavelengths corresponding to red, blue, and green.


