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Leukodystrophies are a group of, usually, inherited disorders, characterized by degeneration of the white matter in the brain. [ 1 ] The word leukodystrophy comes from the Greek roots leuko, "white", dys, "abnormal" and troph, "growth". The leukodystrophies are caused by imperfect growth or development of the glial cells which produce the ...
The irises of human eyes exhibit a wide spectrum of colours. Eye color is a polygenic phenotypic trait determined by two factors: the pigmentation of the eye 's iris [ 1 ][ 2 ] and the frequency-dependence of the scattering of light by the turbid medium in the stroma of the iris. [ 3 ]: 9. In humans, the pigmentation of the iris varies from ...
The four pigments in a bird's cone cells (in this example, estrildid finches) extend the range of color vision into the ultraviolet. [1]Tetrachromacy (from Greek tetra, meaning "four" and chroma, meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye.
Lipofuscin. Lipofuscin is the name given to fine yellow-brown pigment granules composed of lipid -containing residues of lysosomal digestion. [ 1 ][ 2 ] It is considered to be one of the aging or "wear-and-tear" pigments, found in the liver, kidney, heart muscle, retina, adrenals, nerve cells, and ganglion cells. [ 3 ]
Pelizaeus–Merzbacher disease is an X-linked neurological disorder that damages oligodendrocytes in the central nervous system. It is caused by mutations in proteolipid protein 1 (PLP1), a major myelin protein. It is characterized by a decrease in the amount of insulating myelin surrounding the nerves (hypomyelination) and belongs to a group ...
Historically from Stargardt's first description of his eponymous disease until recently, the diagnosis was based on looking at the phenotype using examination and investigation of the eye. Since the advent of genetic testing, the picture has become more complex. What was thought to be one disease is, in fact, probably at least three different ...
Colors of confusion include blue/purple and green/yellow. [2] Deuteranopia is a severe form of red-green color blindness, in which the M-cone is absent. It is sex-linked and affects about 1% of males. Color vision is very similar to protanopia. [2] Tritanopia is a severe form of blue-yellow color blindness, in which the S-cone is absent. It is ...
Opponent process. For the universal psychological and neurological model, see opponent-process theory. The opponent process is a color theory that states that the human visual system interprets information about color by processing signals from photoreceptor cells in an antagonistic manner. The opponent-process theory suggests that there are ...