• Applied Microscopy
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• v.28 no.3
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• pp.391-398
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• 1998

The morphological phenotype on ocellus of Drosophila rdgC mutant was observed with electron microscope. The result showed the particular phenotype that was not found in other retinal degenarative mutants. The most distinct difference was the orientation of photoreceptor cells. The photoreceptor cells did not attached to corneagenous cells but dropped under corneagenous cells and assembled around newly formed space. Enormous multivesicle bodies caused by the degeneration of photoreceptor cells were frequently found. Rhabdomeres were also severely degenerated in consequence of the mutant. Another degeneration was found in a part of photoreceptor cell, but the degeneration of subrhabdomeric cisternae (SRC) was not found. It was a ovious difference of rdgC comparing with other two retinal degenerative mutants, rdgA and rdgB. As a result, rdgC mutant was affected on the attachment between photoreceptor cells and corneageneous cells, and it suggested the defect of cell-cell attachment. In addition, rdgC mutant was accompanied by the defect not only in retina but nerve system. The results were agreed to the reference discussion that the rdgC molecule is exist in the nerve.

• Journal of Photoscience
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• v.9 no.2
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• pp.41-43
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• 2002

In photoreceptor cells, light activates visual pigments consisting of a chromophore (retinal) and a protein moiety (opsin). Activated visual pigments trigger an enzymatic cascade, called phototransduction cascade, in which more than ten phototransduction proteins are participating. Two types of vertebrate photoreceptor cells, rods and cones, play roles in twilight and daylight vision, respectively. Cones are further classified into several subtypes based on their morphology and spectral sensitivity. Though the diversities of vertebrate photoreceptor cells are crucial for color discrimination and detection of light over a wider range of intensities, the molecular mechanism to characterize the photoreceptor types remains unclear. We investigated the amino acid sequences of about 50 vertebrate opsins, and found that these sequences can be classified into five fundamental subfamilies. Clear relationships were found between these subfamilies and their characteristic spectral sensitivities. In addition to opsins, we studied other phototransduction proteins. The amino acid sequences of phototransduction proteins can be classified into a few subfamilies. Even though their spectral sensitivity is considerably different, cones fundamentally share the phototransduction protein isoforms which are different from those found in rods. It is suggested that the difference in phototransduction proteins between rods and cones is responsible for their sensitivity to light. Isoforms and their selective expression may characterize individual photoreceptor cells, thus providing us with physiological functions such as color vision and daylight/twilight visions.

• Korean Journal of Materials Research
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• v.10 no.1
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• pp.7-14
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• 2000

The object of this study was to improve electrophotographic photoreceptor using metal free-phthalocyanine dye sensitized system. In here a various types of metal free-phthalocyanine and polymers and hydrazone were used as charge generation material(CGM) and binder, respectively, and also the hydrazone derivative or zinc complex was used as charge transport material(CTM). It was found that $x-H_2Pc$ showed the highest sensitivity among the ${\alpha}-$, ${\beta}-$ and x- metal free-phthalocyanine($x-H_2Pc$) as CGM. The photoreceptor made by $x-H_2Pc$ and hydrazone derivative as CGM and CTM, respectively, showed the highest ratio of dark decay having 73.1% and the good sensitivity of $1.50lux{\cdot}sec$ compared to other photoreceptors.

• Proceedings of the Zoological Society Korea Conference
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• 1998.10b
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• pp.218.2-218
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• 1998

No Abstract, See Full Text

• Journal of Photoscience
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• v.9 no.2
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• pp.272-274
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• 2002

The anterior brain vesicle of ascidian larvae contains two distinct pigment cells. Ultrastructure of these pigment cells has been shown that the anterior pigment cell is an otolith for perception of gravity and the posterior pigment cell is an ocellus for light reception. The larva has remarkably simple central nervous system (CNS) composed of about 330 cells. We focused to study neural networks of visual systems. In the present paper, we report the whole structure of the photoreceptors of the ascidian larva visualized by an antibody against arrestin. Visual arrestin is the key protein for the termination of phototransduction and one of the abundant proteins in photoreceptors. Recently, we cloned an arrestin homologue gene, Ci-arr and the expression of Ci-arr was found to be restricted to the photoreceptors in the ocellus. To study the whole structure of the photoreceptors in the larva, we prepared an antibody against Ci-Arr. It is found that anti Ci-Arr antibody specifically stains the photoreceptors, including the cell bodies, the axons, and the nerve terminals. The photoreceptor cell bodies lies in row outside the pigment cup which penetrate the pigment cell and is continuous with the outer segments of the photoreceptor cell, inside the concavity of the pigments. The axons form bundle into a single tract. The tract extends toward the midline, where the nerve terminals diverge and seem to form synapses

• KSBB Journal
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• v.14 no.6
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• pp.643-650
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• 1999

An artificial photoreceptor composed of bacteriorhodopsin(bR)/flavin complex Langmuir-Blodgett(LB) films was developed by mimicking the human visual system. bR and flavin molecules were deposited onto solid substrate by LB technique, and the deposition of two molecules was proved by UV/VIS absorption spectroscopy and atomic force microscopy(AFM). Based on AFM images and photocurrent generation from the LB films, the optimal conditions for device fabrication were determined. With a series of light illuminations, the generated photocurrent could be detected, and the response characteristics of two molecules could be clearly distinguished from each other. According to the obtained signal shapes, three distinctive regions could be found in the obtained action spectrum. Using a correlation between the photocurrent generation and the wavelength of the input light, it was possible to organize the basic rules to interpret the wavelength of the input light. It is concluded that the proposed artificial photoreceptor would e applicable to the bioelectronic device for color recognition.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.295-296
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• 1998

With xeroradiography appearance, DR (Digital Radiography) system have been studying for X-ray detection using photoreceptor. Also detection method for receptor charge change have been developing variably. We use photoreceptor material of a-Se(Amorphous Selenium) with high DQE, high SNR(Signal to Noise Ratio) and high transformation efficiency of X-ray signals into electrical signals. After a-Se receptor is uniformly charged by using Arc discharge, X-ray is exposed. Then a-Se receptor produce subtle charge variation and MOSFET detect charge variations. The detected signal pass A/D converter and signal processing by PC. As results, the initial voltage is 8V. It has wide dynamic range needed digital radiography system. In this study, we obtained data with changing kVp(tube potential voltage) and fixed 8mAs(tube current by exposure time) in X-ray system. However MOSFET detector for X-ray signal is not tested X-ray mAs variations. But if MOSFET detector is tested X-ray mAs variation and exactly calibrated multichannel is made and noise-reduction is done, suitable DR system readout method will be done.

• Korean Journal of Materials Research
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• v.3 no.5
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• pp.505-513
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• 1993

To make the electrophotographic photoreceptor that srnsirizes for panchromatic matcrial, the dying element of sunfasr yellow which has an absorption ivavclength at near 400nm, and $\alpha,\beta$-copper phthalocyaninc dying elements with 700nm absorption wavelength were adsorbed and then dispersed onto the zine oxide(Zn0). In ordcr to characterize rhe change In sensitivity the various binders and different mole ratio of ZnO to binder were employed in here. It was found rhat the optimum sensitivity was obtained with 5.5 ratio. I;rom the measurements of electrostatic and spectral sensitivity, it was found that the maximum photographic properties were obtained for mixing the sunfast yellow and $\beta$-copper phthalocyaninr. In this case the electrophotographic sensiri\ity was found to he $E{1:2}$= 1440 lux . sec. And also the spectral sensitivity shows that it had a good properties for panchromatic matcrial.

• Journal of Photoscience
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• v.9 no.2
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• pp.47-50
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• 2002

Raft is a distinctive membrane domain enriched in a certain class of lipids, cholesterol, and proteins observed on the plasma membrane. Growing evidence has revealed that such membrane domains play key roles in signal transduction, fertilization, development, transmitter release, and so on. Recently, we have isolated raft-like detergent-resistant membrane (DRM) fraction from bovine photoreceptor rod outer segments. Transducin and its effecter, cGMP-phosphodiesterase, elicited stimulus-dependent translocation between detergent-soluble membrane and DRM. This suggested potential importance of such distinct membrane domains in vertebrate phototransduction. Here, we will discuss physiological meaning of the translocation of major components of cGMP cascade to raft-like membrane in phototransduction. We would like to propose a hypothesis that raft-like membrane domains on the disk membrane are the place where cGMP cascade system could be quenched.

• Journal of Photoscience
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• v.3 no.3
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• pp.133-136
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• 1996

Calcium modulates the activity of guanylate cyclase and plays a key role in dark and light adaptation in the visual system. We have measured the Ca$^{2+}$, K$^+$ and Na$^+$ concentration in dark and light adapted bullfrog's (Rana catesbeiana) vitreous humor by using the atomic absorption spectrophotometer. The calcium concentration of the light adapted bullfrog's vitreous humor was higher than that of the dark adapted bullfrog's vitreous humor. This means that ion activity between the photoreceptor and vitreous humor side is light dependent and we have found that a Ca$^{2+}$ channel and Na$^+$ - Ca$^{2+}$ exchanger exist in the vitreous humor.