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This process of absorption works to reduce the risk of DNA damage and the formation of pyrimidine dimers. UVA light makes up 95% of the UV light that reaches earth, whereas UVB light makes up only about 5%. UVB light is the form of UV light that is responsible for tanning and burning. Sunscreens work to protect from both UVA and UVB rays.
UV-B light causes crosslinking between adjacent cytosine and thymine bases creating pyrimidine dimers. This is called direct DNA damage. UV-A light creates mostly free radicals. The damage caused by free radicals is called indirect DNA damage. Ionizing radiation such as that created by radioactive decay or in cosmic rays causes breaks in DNA ...
The excited state lifetime of compounds used in sunscreens such as menthyl anthranilate, avobenzone or padimate O is 1,000 to 1,000,000 times longer than that of melanin, [2] and therefore they may cause damage to living cells that come in contact with them.
Xeroderma pigmentosum (XP) is a genetic disorder in which there is a decreased ability to repair DNA damage such as that caused by ultraviolet (UV) light. [1] Symptoms may include a severe sunburn after only a few minutes in the sun, freckling in sun-exposed areas, dry skin and changes in skin pigmentation. [1]
One cause of cataracts is exposure to ultraviolet light. Provided the level of UV emission from lamps is within safe limits, and the lamp a sufficient distance away from the individual, there should be no increased risk of developing cataracts. Photophobia is a symptom of excessive sensitivity to light which affects 5 to 20% of the population ...
Particular medications make the skin more sensitive to sunlight; these include most of the tetracycline antibiotics, heart drugs amiodarone, and sulfonamides. Some dietary supplements, such as St. John's Wort, include photosensitivity as a possible side effect. Particular conditions lead to increased light sensitivity.
Prolonged optical exposure to sunlight, especially intense ultraviolet light, may be linked to cortical cataracts, [50] [15] and high levels of visible light is maybe linked to macular degeneration. However, significant daily exposure to bright light may be necessary for children to avoid myopia (nearsightedness). [51]
[70] γH2AX does not, itself, cause chromatin decondensation, but within 30 seconds of irradiation, RNF8 protein can be detected in association with γH2AX. [71] RNF8 mediates extensive chromatin decondensation, through its subsequent interaction with CHD4 , [ 72 ] a component of the nucleosome remodeling and deacetylase complex NuRD .