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Transducin (G t) is a protein naturally expressed in vertebrate retina rods and cones and it is very important in vertebrate phototransduction. It is a type of heterotrimeric G-protein with different α subunits in rod and cone photoreceptors. [1]
Visual phototransduction is the sensory transduction process of the visual system by which light is detected by photoreceptor cells (rods and cones) in the vertebrate retina.A photon is absorbed by a retinal chromophore (each bound to an opsin), which initiates a signal cascade through several intermediate cells, then through the retinal ganglion cells (RGCs) comprising the optic nerve.
Leydig cells release a class of hormones called androgens (19-carbon steroids). [8] They secrete testosterone, androstenedione and dehydroepiandrosterone (DHEA), when stimulated by the luteinizing hormone (LH), which is released from the anterior pituitary in response to gonadotropin releasing hormone which in turn is released by the hypothalamus.
The prevailing theory of how simple and complex cells interact is that cells in the lateral geniculate nucleus stimulate simple cells, and simple cells in turn stimulate complex cells where then a combination of complex cells create depth perception. [1] [7] [10] Three different cell types exist: far cells, near cells, and tuned zero cells.
A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The great biological importance of photoreceptors is that they convert light (visible electromagnetic radiation ) into signals that can stimulate biological processes.
Peripherin-2 is a protein, that in humans is encoded by the PRPH2 gene. [5] [6] Peripherin-2 is found in the rod and cone cells of the retina of the eye. Defects in this protein result in one form of retinitis pigmentosa, an incurable blindness. Mutations in the PRPH2 gene are associated with Vitelliform macular dystrophy.
The first parietopsin was found in the photoreceptor cells of the lizard parietal eye. The lizard parietopsin is green-sensitive ( λ max = 522 nm), and despite it is a c-opsin, like the vertebrate visual opsins, it does not induce hyperpolarization via a Gt-protein, but induces depolarization via a Go-protein.
To identify expressing cells, they replaced the cytoplasmic tail of the algal protein with a fluorescent protein YFP, generating the first generally applicable optogenetic tool. [27] They stated in the 2003 paper that "expression of ChR2 in oocytes or mammalian cells may be used as a powerful tool to increase cytoplasmic Ca 2+ concentration or ...