Properties of the ipRGC Photopigment: Melanopsin IpRGC’s are unique in that they contain their own photopigment, melanopsin (source). Melanopsin is categorized in the opsin family because of its ability to receive a photon of light and translate it into an electrochemical signal. This ability has been observed and is well understood in the photoreceptor rods and cones. The photoreceptors are key players in translating visual stimuli to a language the brain can understand. Their ability to interpret visual cues on their own depends on the opsins that are integrated into their structure (SOURCE). Comparing photoreceptor opsins and the opsin expressed in ipRGC’s is helpful because they both act to relay signals to the brain. The pathway however, that transfers signals from each is quite different and will be discussed in the following section. Provencio and colleagues isolated an unknown type of opsin from photosensitive dermal melanophores of Xenopus laevis, also known as the African clawed frog WHAT YEAR?(pickers). Due to this discovery they named this new opsin, melanopsin (pickers)(hankins). Despite the fact the african clawed frog is a vertebrate, tests showed this opsin identified more closely with invertebrate opsins (39%), than with vertebrates (~27%) (hankins). ...? More recent studies have revealed there are actually two types of melanopsin: mammalian-like Opn4m and Xenopus-like Opn4x (hankins). All opsins are G-protein coupled receptors (GPCRs) and their most distinctive feature is located on their seventh transmembrane domain (source). This feature is the presence of a retinal attachment site which binds to the chromophore through a schiff base linkage (davies). The chromophore is a region on the opsin where two ... ... middle of paper ... ...d-messenger systems but it is uncertian which of these pathways are involved in ipRGC phototransduction. Studies are being conducted to better understand these pathways but the pharmacological tools available are not sufficient to make concrete conclusions. Despite the lack of technological advancements, pharmacological approaches and tedious studies have devised a potential model for the melanopsin phototransduction cascade in ipRGC. (figure 4? hankins). It has been noted that melanopsin interacts with Gq/G11. This G-protein then activates a PLC-β which creates Ins(1,4,5)P3 and diacylglycerol (DAG). These activated messengers may regulate the TRPC6 or TRPC7 channel, possibly by a PKC (hankins.. all of it). Again, these components are not confirmed. and future studies should aim to better understand the pathway through which melanopsin in the ipRGC is activated.
The widespread involvement of Retinal Pigment Epithelium (RPE), flat (placoid) nature of the lesions and absence of overlying serous retinal detachment and minimal choroidal involvement lead Gass to conclude RPE was primary focus of inflammation.(1) ...
4) I predict the amount of DPIP reduced will vary for each condition and increase over the time intervals. I hypothesize under the light condition the amount of DPIP will drastically be reduced within each five minute time interval. However, under the dark condition the DPIP will not be reduced due to the fact that light is required for photosynthesis.
...s to interfere with bonding to the receptors. The final possibility uses CNP, which downregulates the activation in MAP kinase pathways in the chondrocytes (4).
The sun makes Vitamin D therefore those in colder regions with less sunlight are at a disadvantage although there are other supplements such as tanning salons and cod-liver fish oils. Although the sun produces Vitamin D, it also destroys folic acid. People with darker skin can prevent the depletion of folic acid better than those with lighter skin, but people with darker skin would have to carry more cholesterol to utilize the sun’s benefits. Folic acid aids in cell replication and the cell growth system. Melanin is a pigment that absorbs light and determines the darkness of skin color along with hair and eye color. This chapter also introduces the gene ApoE4, which is related to evolution. ApoE4 makes sure that people with darker skin have higher levels of cholesterol, therefore aiding the production of Vitamin D. But we also learn the flaw that ApoE4 can also increase the chances of heart attacks and
Once binding has occurred, a cascade of signalling reactions will initiate, with Rho guanosine-5'-triphosphate (Rho GTPases) such as rho-asso...
The prominent theory today about how and why skin pigment in humans developed with the color diversity that exists today, is that ancestral populations of humans inhabited areas with different UV radiation concentration. As a result, the effects of UV radiation put positive evolutionary pressure on skin pigment to develop for sufficient folate protection and Vitamin D production. For a long time, paleontologists have known that human ancestors had dense hair that covered their bodies. The reason that modern humans lack such covering is probably due to changes in climate and habitation choice, but for whatever reason the dense hair covering disappeared, it ultimately did, rendering the skin much more exposed to both the elements and to UV rays. Scientists believe that in response to this change in UV concentrations, the human skin became tougher, and developed a protective pigment called ‘melanin’ which protects against the effects of UV radiation.
Roger W. Harms, M. D. U.S. National Library of Medicine, National Library of Medicine. (2014). Oculocutaneous Albinism. Retrieved from U.S. National Library of Medicine website: http://ghr.nlm.nih.gov/condition/oculocutaneous-albinism
...ethanolamine, forming a complex known as N-retinylidene-PE to facilitate the all-trans retinal transport from the disk lumen to the photoreceptor cytoplasm. In the mice study it was found that N-RPE is converted into A2E, a major component of lipofuscin. The A2E produced then accumulates in the RPE, which dissolves cell membranes and destroys the RPE cells that store it.
The mouse eyes were significant in that they provided results that can be compared with the data obtained from the frogs. These frog and mouse eyes were studied using X-ray diffraction. The changes regarding light induced reflections were recorded at 0.1seconds and 1.0 seconds in frog and mouse cells. (Chabre and Cavaggioni, 1973). The diffraction of disk membranes was measured to the 10th order to maintain specificity and detailed differences between mammalian and amphibian rod outer segments. For the experiment, a bullfrog ( Rana catesbeiana) eye was used and the frogs were in an environment that provided 12 hours of light and 12 hours of dark at a constant temperature of 8 degrees celsius for one to four weeks. A frog from the group was killed and the head was cut along the middle so that both eyes could be further studied. For the mouse eyes, BALB/C mice also maintained under the same conditions as the frogs were used. However, the eyes from the mice were removed from the sockets by cutting the optical nerve and tissues whereas the eyes on the frog remained intact. A similar X-ray analysis was used for both specimen and involved a beam passing from the back of the eye to the side where the light illuminates the eye from the front. (Corless 1972). A
gland has no direct access to sunlight. Our eyes send it a message of how much
...2007).Evolution of the vertebrate eye: opsins, photoreceptors, retina and eye cup. Nat. Rev. Neurosci. 8: 960–976.
With over 600 carotenoids known to humankind, only 60 carotenoids are known to demonstrate vitamin A activity. When discussing AMD, the carotenoids of particular interest are known as xanthophylls – specifically lutein and zeaxanthin. Carotenoids are lipophilic and as a result they are absorbed via a similar mechanism to fat absorption. Similarly, carotenoids are integrated into chylomicrons and are transported throughout the body via the lipoprotein cycle. High-density lipoprotein is the primary transporter for xanthophylls, accounting for 53 percent of their transport to the retina.2, 6 Additionally, low-density lipoprotein and very-low-density lipoprotein account for 31 and 16 percent of xanthophyll transport respectively.2Lutein and zeaxanthin function as antioxidants; thus, they are capable of providing the Bruch’s membrane with a coping mechanism preventing ROS from damaging the RPE. Additionally, lutein and zeaxanthin are capable of filtering blue light and preventing excessive oxidative
The variations of pigmentation between alleles of the brown gene are likely to be caused by repressing pteridines in the pigment cells. Mutations in the brown (bw) gene result in a modification of pigmentation in the eye color. The reduction of screening pigments in primary pigment cells of the ommatidium, consisting of brown ommochromes and red pteridines, cause variations of darker or lighter shades of
Nagel, G. et al. Channelrhodopsin-2, a directly light-gated cation-selective membrane channel. Proc. Natl. Acad. Sci. USA 100, 13940-13945 (2003).
The system involved in this lab was L-dopa as a substrate, enzyme was Tyrosinase, and the product was Dopachrome. Tyrosinase is commonly known as polyphenol oxidase, an enzyme that present in plant and animal cell (#1 Boyer). In plant cell, the biological function if Tyrosinase is unknown, but its presence is readily apparent. Tyrosinase is also involved in the browning of fruits, tubers, and fungi that have been damaged. In mammalian cell, Tyrosinase is involved in melanin synthesis, which gives skin its color. It will act on the substrate L-dihydroxyphenylalanine (L-Dopa) and convert to Dopachrome, which is the product that has color, and it can measure at 475nm using the Spectrophotometer. This work based on the Beer-Lambert’s Law (A=εlc), A stands for Absorbance, ε is extinction coefficient or the molar absorptivity (M-1 cm-1), and l is the path length (distance) that light passes through the sample (cm), c is a concentration of solution (M) (#3 Ninfa, Ballou, Benore). Beer- Lambert Law predicts a linear relationship between absorbance and the concentration of a chemical species being analyzed. It states that the absorbance (A) of a sample solution is directly proportional to the concentration (c) of the absorbing colored