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Ultraviolet light

About: Ultraviolet light is a research topic. Over the lifetime, 49494 publications have been published within this topic receiving 843151 citations.


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Journal ArticleDOI
TL;DR: Hfq function plays a fundamental role in Escherichia coli physiology and that hfq and the hflA region are in the amiB‐mutL‐miaA‐hfq‐hflX superoperon.
Abstract: The region immediately downstream from the miaA tRNA modification gene at 94.8 min contains the hfq gene and the hflA region, which are important in the bacteriophage Q beta and lambda life cycles. The roles of these genes in bacteria remain largely unknown. We report here the characterization of two chromosomal hfq insertion mutations. An omega (omega) cassette insertion near the end of hfq resulted in phenotypes only slightly different from the parent, although transcript mapping demonstrated that the insertion was completely polar on hflX expression. In contrast, an equally polar omega cassette insertion near the beginning of hfq caused pronounced pleiotropic phenotypes, including decreased growth rates and yields, decreased negative supercoiling of plasmids in stationary phase, increased cell size, osmosensitivity, increased oxidation of carbon sources, increased sensitivity to ultraviolet light, and suppression of bgl activation by hns mutations. hfq::omega mutant phenotypes were distinct from those caused by omega insertions early in the miaA tRNA modification gene. On the other hand, both hfq insertions interfered with lambda phage plaque formation, probably by means of polarity at the hflA region. Together, these results show that hfq function plays a fundamental role in Escherichia coli physiology and that hfq and the hflA-region are in the amiB-mutL-miaA-hfq-hflX superoperon.

409 citations

Journal ArticleDOI
TL;DR: The dramatic protective effects of celecoxib suggests that specific COX‐2 inhibitors may offer a way to safely reduce the risk of skin cancer in humans.
Abstract: Epidemiological and dietary studies suggest that nonsteroidal anti-inflammatory drugs (NSAIDs) reduce the risk of colon cancer, possibly through a mechanism involving inhibition of cyclooxygenase (COX)-2, which is overexpressed in premalignant adenomatous polyps and colon cancer. Because ultraviolet light (UV) can induce COX-2 and nonspecific NSAIDs can decrease UV-induced skin cancer, we evaluated the ability of two compounds, celecoxib (a specific COX-2 inhibitor) and indomethacin (a nonspecific NSAID), to block UV-induced skin tumor development in SKH:HR-1-hrBr hairless mice. Mice fed 150 or 500 ppm celecoxib showed a dose-dependent reduction (60% and 89%, respectively) in tumor yield. Indomethacin (4ppm) reduced tumor yield by 78%. Although both acute and chronic UV exposure increased cell proliferation and edema, neither compound reduced these parameters. In contrast, UV-induced prostaglandin synthesis in the epidermis was effectively blocked by both compounds. UV-induced increases in COX-2 expression in skin were also not altered in any of the treatment groups. Similarly, tumors that constitutively express high levels of COX-2 displayed no reduction by treatment with celecoxib or indomethacin. The dramatic protective effects of celecoxib suggests that specific COX-2 inhibitors may offer a way to safely reduce the risk of skin cancer in humans.

407 citations

Journal ArticleDOI
30 Nov 1973-Science
TL;DR: Ultraviolet light has been used to examine urine marks deposited by adult male house mice on filter paper on the floors of their cages during overnight tests, and both the urination frequency and the pattern in which urine was deposited on the filter paper depended upon social rank.
Abstract: Ultraviolet light has been used to examine urine marks deposited by adult male house mice on filter paper on the floors of their cages during overnight tests. Both the urination frequency and the pattern in which urine was deposited on the filter paper depended upon social rank. Dominant males vigorously marked their entire cage floor, whereas subordinate males typically voided urine in only two to four pools in the corners of their cages.

407 citations

Journal ArticleDOI
TL;DR: Reduced epidermal vitamin D3 photosynthesis associated with high skin melanin content and/or decreased UV light intensity at distances from the equator, alone or when coupled with decreased dietary calcium and vitamin D, may be associated with reduced vitamin D stores and increased parathyroid hormone secretion.
Abstract: Mean systolic and diastolic pressures and the prevalence of hypertension vary throughout the world Published data suggest a linear rise in blood pressure at increasing distances from the equator Similarly, blood pressure is higher in winter than summer Blood pressure also is affected by variations in skin pigmentation Altered calcium, vitamin D, and parathyroid hormone status is associated with hypertension and may vary with latitude and season Since changes in UV light affect vitamin D and parathyroid hormone status and UV light intensity are influenced by seasonal change and latitude, these disparate observations suggest an association between blood pressure and ultraviolet light This discussion presents the hypothesis that reduced epidermal vitamin D3 photosynthesis associated with high skin melanin content and/or decreased UV light intensity at distances from the equator, alone or when coupled with decreased dietary calcium and vitamin D, may be associated with reduced vitamin D stores and increased parathyroid hormone secretion These changes may stimulate growth of vascular smooth muscle and enhance its contractility by affecting intracellular calcium, adrenergic responsiveness, and/or endothelial function Thus, UV light intensity and efficiency of epidermal vitamin D3 photosynthesis may contribute to geographic and racial variability in blood pressure and the prevalence of hypertension

404 citations

Journal ArticleDOI
17 Oct 1991-Nature
TL;DR: It is reported that some rodents have a retinal mechanism that is maximally sensitive to ultraviolet light, which was thought not to exist in the eyes of mammals.
Abstract: HIGH sensitivity to near-ultraviolet light is a fundamental feature of vision in many invertebrates1,2 Among vertebrates there are some amphibians, birds and fishes that are also sensitive to near-ultraviolet wavelengths3–6 This sensitivity can be achieved through a class of cone photoreceptor containing an ultraviolet-sensitive pigment7–9 Although these receptors were thought not to exist in the eyes of mammals, we now report that some rodents have a retinal mechanism that is maximally sensitive to ultraviolet light

403 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202346
2022181
20211,101
20201,978
20192,639
20182,772