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Photoageing
Photoaging or photoageing (also known as "dermatoheliosis") is a term used for the characteristic changes to skin induced by chronic UVA and UVB exposure. Tretinoin is the best studied retinoid in the treatment of photoaging. The deterioration of biological functions and ability to manage metabolic stress is one of the major consequences of the ageing, aging process. Aging is a complex, progressive process that leads to functional and aesthetic changes in the skin. This process can result from both intrinsic (i.e., genetically determined) as well as extrinsic processes (i.e., environmental factors). Photoaging is attributed to continuous, long-term exposure to ultraviolet (UV) radiation of approximately 300–400 nm, either natural or synthetic, on an intrinsically aged skin. Effects of UV light Molecular and genetic changes UVB rays are a primary mutagen that can only penetrate through the epidermis (skin), epidermal (outermost) layer of the skin, resulting in DNA mutati ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ageing
Ageing ( BE) or aging ( AE) is the process of becoming older. The term refers mainly to humans, many other animals, and fungi, whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In a broader sense, ageing can refer to single cells within an organism which have ceased dividing, or to the population of a species. In humans, ageing represents the accumulation of changes in a human being over time and can encompass physical, psychological, and social changes. Reaction time, for example, may slow with age, while memories and general knowledge typically increase. Ageing increases the risk of human diseases such as cancer, Alzheimer's disease, diabetes, cardiovascular disease, stroke and many more. Of the roughly 150,000 people who die each day across the globe, about two-thirds die from age-related causes. Current ageing theories are assigned to the damage concept, whereby the accumulation of damage (such as DNA ox ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tretinoin
Tretinoin, also known as all-''trans'' retinoic acid (ATRA), is a medication used for the treatment of acne and acute promyelocytic leukemia. For acne, it is applied to the skin as a cream, gel or ointment. For leukemia, it is taken by mouth for up to three months. Topical tretinoin is also the most extensively investigated retinoid therapy for photoaging. Common side effects when used as a cream are limited to the skin and include skin redness, peeling, and sun sensitivity. When used by mouth, side effects include shortness of breath, headache, numbness, depression, skin dryness, itchiness, hair loss, vomiting, muscle pains, and vision changes. Other severe side effects include high white blood cell counts and blood clots. Use during pregnancy is contraindicated due to the risk of birth defects. It is in the retinoid family of medications. Tretinoin was patented in 1957, and approved for medical use in 1962. It is on the World Health Organization's List of Essential Medici ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keratinocytes
Keratinocytes are the primary type of cell found in the epidermis, the outermost layer of the skin. In humans, they constitute 90% of epidermal skin cells. Basal cells in the basal layer (''stratum basale'') of the skin are sometimes referred to as basal keratinocytes. Keratinocytes form a barrier against environmental damage by heat, UV radiation, water loss, pathogenic bacteria, fungi, parasites, and viruses. A number of structural proteins, enzymes, lipids, and antimicrobial peptides contribute to maintain the important barrier function of the skin. Keratinocytes differentiate from epidermal stem cells in the lower part of the epidermis and migrate towards the surface, finally becoming corneocytes and eventually be shed off, which happens every 40 to 56 days in humans. Function The primary function of keratinocytes is the formation of a barrier against environmental damage by heat, UV radiation, water loss, pathogenic bacteria, fungi, parasites, and viruses. Pathogen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Actinic Elastosis
Actinic elastosis, also known as solar elastosis, is an accumulation of abnormal elastin (elastic tissue) in the dermis of the skin, or in the conjunctiva of the eye, which occurs as a result of the cumulative effects of prolonged and excessive sun exposure, a process known as photoaging. Signs and symptoms Actinic elastosis usually appears as thickened, dry, wrinkled skin. Several clinical variants have been recorded. One of the most readily identifiable is the thickened, deeply fissured skin seen on the back of the chronically sun-exposed neck, known as cutis rhomboidalis nuchae. These features are a part of the constellation of changes that are seen in photoaged skin. Causes The origin of the elastotic material in the dermis remains a subject of debate. Theories on the formation of the elastotic material include actinic stimulation of fibroblasts, promoting synthesis of this material, or that the material is a degradation product of collagen, elastin, or both. Diagnosis In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lentigo
A lentigo () (plural lentigines, ) is a small pigmented spot on the skin with a clearly defined edge, surrounded by normal-appearing skin. It is a harmless (benign) hyperplasia of melanocytes which is linear in its spread. This means the hyperplasia of melanocytes is restricted to the cell layer directly above the basement membrane of the epidermis where melanocytes normally reside. This is in contrast to the "nests" of multi-layer melanocytes found in moles (melanocytic nevi). Because of this characteristic feature, the adjective "lentiginous" is used to describe other skin lesions that similarly proliferate linearly within the basal cell layer.''Random House Webster's Unabridged Dictionary.'' Random House, Inc. 2001. p. 1101. .''Robbins and Cotran Pathologic Basis of Disease'' Elsevier. 2005. p. 1232. . Diagnosis Conditions characterized by lentigines include: * Lentigo simplex * Solar lentigo (Liver spots) * PUVA lentigines * Ink spot lentigo * LEOPARD syndrome * Mucosal lentig ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Telangiectasia
Telangiectasias, also known as spider veins, are small dilated blood vessels that can occur near the surface of the skin or mucous membranes, measuring between 0.5 and 1 millimeter in diameter. These dilated blood vessels can develop anywhere on the body, but are commonly seen on the face around the nose, cheeks and chin. Dilated blood vessels can also develop on the legs, although when they occur on the legs, they often have underlying venous reflux or "hidden varicose veins" (see Venous hypertension section below). When found on the legs, they are found specifically on the upper thigh, below the knee joint and around the ankles. Many patients with spider veins seek the assistance of physicians who specialize in vein care or peripheral vascular disease. These physicians are called vascular surgeons or phlebologists. More recently, interventional radiologists have started treating venous problems. Some telangiectasias are due to developmental abnormalities that can closely mimic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wrinkle
A wrinkle, also known as a rhytid, is a fold, ridge or crease in an otherwise smooth surface, such as on skin or fabric. Skin wrinkles typically appear as a result of ageing processes such as glycation, habitual sleeping positions, loss of body mass, sun damage, or temporarily, as the result of prolonged immersion in water. Age wrinkling in the skin is promoted by habitual facial expressions, aging, sun damage, smoking, poor hydration, and various other factors. In humans, it can also be prevented to some degree by avoiding excessive solar exposure and through diet (in particular through consumption of carotenoids, tocopherols and flavonoids, vitamins (A, C, D and E), essential omega-3-fatty acids, certain proteins and lactobacilli). Skin Causes for aging wrinkles Development of facial wrinkles is a kind of fibrosis of the skin. Misrepair-accumulation aging theory suggests that wrinkles develop from incorrect repairs of injured elastic fibers and collagen fibers. Repea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinoid X Receptors
The retinoid X receptor (RXR) is a type of nuclear receptor that is activated by 9-cis retinoic acid, which is discussed controversially to be of endogenous relevance, and 9-''cis''-13,14-dihydroretinoic acid, which is likely to be the major endogenous mammalian RXR-selective agonist. In a novel review publication, this 9-''cis''-13,14-dihydroretinoic acid was shown to be a metabolite not originating from the known vitamin A (vitamin A1) pathway and its nutritional precursors all-''trans''-retinol ( vitamin A (vitamin A1) or all-''trans''- beta-carotene (provitamin A (provitamin A1)). An independent pathway for generating this endogenous RXR-ligand 9-''cis''-13,14-dihydroretinoic acid from 9-''cis''-13,14-dihydroretinol present in food source and named vitamin A5 or alternatively via provitamin A5 has been suggested as the first novel vitamin identified since 1948, cobalamin / vitamin B12. There are three retinoic X receptors (RXR): RXR-alpha, RXR-beta, and RXR-gamma, en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Retinoic Acid Receptor
The retinoic acid receptor (RAR) is a type of nuclear receptor which can also act as a ligand-activated transcription factor that is activated by both all-trans retinoic acid and 9-cis retinoic acid the retinoid active derivatives of Vitamin A . They are typically found within the nucleus. There are three retinoic acid receptors (RAR), RAR-alpha, RAR-beta, and RAR-gamma, encoded by the , , genes, respectively. Within each RAR subtype there are various isoforms differing in their N-terminal region A. Multiple splice variants have been identified in human RARs: four for , five for , and two for . As with other type II nuclear receptors, RAR heterodimerizes with RXR and in the absence of ligand, the RAR/RXR dimer binds to hormone response elements known as retinoic acid response elements (RAREs) complexed with corepressor protein. Binding of agonist ligands to RAR results in dissociation of corepressor and recruitment of coactivator protein that, in turn, promotes transcript ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metalloproteinase
A metalloproteinase, or metalloprotease, is any protease enzyme whose catalytic mechanism involves a metal. An example is ADAM12 which plays a significant role in the fusion of muscle cells during embryo development, in a process known as myogenesis. Most metalloproteases require zinc, but some use cobalt. The metal ion is coordinated to the protein via three ligands. The ligands coordinating the metal ion can vary with histidine, glutamate, aspartate, lysine, and arginine. The fourth coordination position is taken up by a labile water molecule. Treatment with chelating agents such as EDTA leads to complete inactivation. EDTA is a metal chelator that removes zinc, which is essential for activity. They are also inhibited by the chelator orthophenanthroline. Classification There are two subgroups of metalloproteinases: * Exopeptidases, metalloexopeptidases ( EC number: 3.4.17). * Endopeptidases, metalloendopeptidases (3.4.24). Well known metalloendopeptidases include ADAM pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AP-1 Transcription Factor
Activator protein 1 (AP-1) is a transcription factor that regulates gene expression in response to a variety of stimuli, including cytokines, growth factors, stress, and bacterial and viral infections. AP-1 controls a number of cellular processes including differentiation, proliferation, and apoptosis. The structure of AP-1 is a heterodimer composed of proteins belonging to the c-Fos, c-Jun, ATF and JDP families. History AP-1 was first discovered as a TPA-activated transcription factor that bound to a cis-regulatory element of the human metallothionein IIa ( hMTIIa) promoter and SV40. The AP-1 binding site was identified as the 12-O-Tetradecanoylphorbol-13-acetate ( TPA) response element (TRE) with the consensus sequence 5’-TGA G/C TCA-3’. The AP-1 subunit Jun was identified as a novel oncoprotein of avian sarcoma virus, and Fos-associated p39 protein was identified as the transcript of the cellular Jun gene. Fos was first isolated as the cellular homologue of two ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kinase
In biochemistry, a kinase () is an enzyme that catalyzes the transfer of phosphate groups from high-energy, phosphate-donating molecules to specific substrates. This process is known as phosphorylation, where the high-energy ATP molecule donates a phosphate group to the substrate molecule. This transesterification produces a phosphorylated substrate and ADP. Conversely, it is referred to as dephosphorylation when the phosphorylated substrate donates a phosphate group and ADP gains a phosphate group (producing a dephosphorylated substrate and the high energy molecule of ATP). These two processes, phosphorylation and dephosphorylation, occur four times during glycolysis. Kinases are part of the larger family of phosphotransferases. Kinases should not be confused with phosphorylases, which catalyze the addition of inorganic phosphate groups to an acceptor, nor with phosphatases, which remove phosphate groups (dephosphorylation). The phosphorylation state of a molecule, whet ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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