More recently, mooted is the cellulite treatment columbia md that the primary function of eumelanin was augmentation of epidermal barrier function by increasing the skin's resistance to desiccation under arid conditions, and that depigmentation did not occur under positive selection for vitamin D production [ 38 — 40 ]. This hypothesis has been disproved by multiple lines of evidence, including the fact that tanning occurs in the presence of UVR, not desiccation [ 41 ], and that positive selection for depigmented skin capable of producing vitamin D under low and highly seasonal UVB conditions is now well established [ 42 ].
The strongest hypothesis for the evolution of dark skin colour is that it afforded protection against photodegradation of cutaneous and systemic folate under high UVR conditions for early members of the genus Homo.
The physiological effects of photodegradation of folate were explored long before the full extent of folate's roles in DNA biosynthesis, repair, DNA methylation, amino acid metabolism and melanin production were appreciated [ 43 ]. Because folate in its main form of 5-methyltetrahydrofolate or 5-MTHF is sensitive to photodegradation [ 44 — 47 ], protective eumelanin-rich pigmentation evolved in early Homo primarily to prevent reduction of fertility due to loss of folate in cutaneous blood vessels and the systemic circulation [ 2148 ].
Folate deficiencies are associated with potentially fatal birth defects such as neural tube defects and male infertility [ 49 — 52 ]. Folate metabolism is regulated by genes and epigenomic factors, which have evolved to favour conservation of folate under conditions of longer day length and greater potential UVR-related folate loss [ 5354 ].
Recent physiological evidence also indicates the importance of folate in the form of 5-MTHF in thermoregulation, via its effect on controlling nitric oxide-mediated cutaneous vasodilation [ 55 — 58 ]. Maintaining the integrity of folate metabolism is important with respect to evolution because it directly affects reproductive success and survival early in life [ 2159 ].
Natural selection has, thus, affected varied genetic and physiological mechanisms in order to protect folate and 5-MTHF in the face of high UVR.
The primary role of constitutive dark skin colour in hominin and modern human evolution is that of a natural sunscreen to conserve folate. Protection of epidermal DNA against strand breaks was the important secondary role played by dark skin colour.
The genus Homo and the species Homo sapiens emerged in equatorial Africa under conditions of intense and relatively invariant sunlight and UVR. Dispersal of hominins into non-equatorial Africa, Eurasia and the Americas involved movements into habitats with more seasonally variable patterns and differing wavelength mixtures of UVR [ 60 ].
In this review, we shall confine our discussion to the consequences for skin colour of dispersal of Homo sapiens into Eurasia and the Americas, a process which began around 55 years ago [ 61 ]. Dispersing populations were small and bottlenecks further reduced available genetic variation in populations crossing major geographic boundaries [ 62 ].
Note also that there is no evidence that dispersing archaic Homo sapiens used sewn clothing or other methods of full-coverage protection against the sun and elements. Non-sewn animal skins probably afforded some protection, but for the most part people were subjected to the full force of UVR apart from the times when they sought natural shelter.
Skin was thus the primary interface with the environment for most of human evolution. The UVR regimes faced by dispersing hominins were a major selective pressure affecting the evolution of skin pigmentation. Outside of the tropics, consideration of the pattern of UVB is relevant because only some wavelengths of UVB between and nm, with peak synthesis between and nm catalyse production of vitamin D in the skin. Within the tropics, average UVB is high and has two equinoctial peaks, but outside of the tropics, average UVB levels are lower and exhibit but a single peak at the Summer Solstice [ 60 ].
Because eumelanin in skin is a highly effective sunscreen, the potential for pride and prejudice full movie dailymotion vitamin D production is reduced by dark skin [ 2163 — 66 ].
Darkly pigmented hominins dispersing out of equatorial Africa thus faced conditions that significantly affected their vitamin D physiology. Pre-vitamin D production occurs in skin of all colours, but in eumelanin-rich skin, low doses of UVB do not raise 25 OH D levels to physiologically adequate levels at which storage can take place; higher doses over longer periods of time are required for this, and these conditions are not met outside of equatorial latitudes.
Long-term occupation of non-tropical latitudes, thus, would not have been possible without loss of some constitutive eumelanin pigmentation in order to prevent the serious sequelae of vitamin D deficiency [ 21 ]. At extreme high latitudes, year-round occupation is not possible without a diet that is centred on consumption and storage of vitamin-D rich foods such as oily fish, marine mammals, or caribou and reindeer, which concentrate vitamin D in their muscle meat and fat [ 2170 ].
Melanin produced by the tanning response is the outcome of UV-induced stress and is regulated by melanocortins in the skin [ 71 ]. Melanocortins in the skin reduce the production of reactive oxygen species, enhance repair of DNA damage caused by UVR and inaugurate eumelanin synthesis in individuals who carry specific, naturally expressed variants of MC1R [ 71 ].
Tanning is thus a response to damage caused by UVR. Contrary to popular belief, tanned skin affords little or no protection from damage from subsequent UVR exposure. Recent experimental studies have shown that a tan developed under suberythemal UVB exposure provides minimal photoprotection, but a tan developed under UVA-rich sunlamps such as those used in tanning salons provided no photoprotective benefit [ 72 — 74 ].
Depigmented skin evolved not once, but multiple times in human history, and was accomplished by different combinations of genetic mutations. For modern European populations, different signatures of selection on the MC1R and SLC24A5 genes imply that both natural selection and genetic drift contributed to the evolution of depigmented skin.
These genetic changes affected the amounts of melanin being produced in melanocytes and the size of the melanosomes in which the melanin was packaged [ 75 ]. For modern eastern Asian populations, depigmentation was not achieved through mutations at the SLC24A5 locus [ 75 ], but via a different set of genetic changes, which are still incompletely known [ 7677 ]. The fact that depigmented skin evolved independently in the ancestors of modern Europeans and East Asians suggests that at least two and probably more distinct genetic mutation events occurred and that multiple loci underwent positive selection in these two regions receiving relatively low levels of UVB [ 78 — 80 ].
The most likely reason for this was that it was associated with a loss of skin pigment that favoured vitamin D production under conditions of low UVB [ 697881 ]. Depigmented skin also evolved independently in Homo neanderthalensis [ 82 ] probably for the same reason. There has been a cause and effect relationship between UVR and skin pigmentation in human evolution, and skin colour phenotypes have been modified under the action of natural selection to maintain an optimum balance between photoprotection and photosynthesis over spatially varying conditions of UVR.
Skin colour thus evolved as the product of two opposing clines, one emphasizing dark pigmentation and photoprotection against high loads of UVA and UVB near the equator, the other favouring depigmented skin to promote seasonal, UVB-induced photosynthesis of vitamin D 3 nearer the poles [ 60 ].
Intermediate latitudes with seasonally high loads of UVB favoured the evolution of people with intermediate colour capable of tanning [ 8485 ]. The most important points to reinforce here are that the geographical gradient of human skin colour evolved under the influence of natural selection, and that very similar skin colour phenotypes dark, light and intermediate have evolved independently numerous times under similar UVR conditions.
Diverse combinations of skin colour genes occurred during the course of prehistory as the combined result of natural selection, gene flow due to migration, and founder effect or genetic drift due to population bottlenecks occurring in the course of dispersal events [ 6286 ]. Indigenous populations of the New World have generally lighter skin colours than those of the Old World, probably because they have not resided in their homelands for as long a time and because their adaptations to the environment have been more strongly cultural than biological, as exemplified by the wearing of sewn clothing and the making of shelters [ 212287 ].
Sexual selection does not appear to have been a major influence on the evolution of human skin coloration, but it probably did increase the degree of sexual dimorphism in skin colour in some populations [ 2187 ]. The unexposed skin of females is lighter than that of males in most populations [ 2183 ], possibly because of the greater need of females to produce vitamin D in the skin to absorb and mobilize calcium during pregnancy and lactation.
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A persistent, directional preference for lighter-coloured females as marriage partners has been recognized during historic times in some east- and south-Asian cultures, and it is likely that this has contributed to the greater sexual dimorphism in coloration observed [ 2187 ]. Like skin, the coloration of human hair and eyes is determined primarily by the amount and type of melanin produced and stored in melanosomes [ 8889 ].
Iris pigmentation is also influenced by structural features within the eye itself and by the degree of pupillary dilation [ 90 — 92 ]. Although skin coloration varies according to the intensity and seasonality of UVR on a global scale, no such regular geographical pattern is observed with hair and eye coloration [ 93 ]. In fact, little variation in hair and eye coloration occurs in indigenous populations outside of Europe for hair and outside of Europe, North Africa, the Middle East, Central Asia and South Asia for eyes [ 888994 ].
The lack of variation in hair and eye coloration in Africa has been assumed to be caused by the importance of eumelanin in affording protection, as it does in the case of skin coloration, but this has not been empirically established.
Hair and eye coloration appear to have not been under as strong natural selection as skin coloration, and loss of genetic variation at one or more population bottlenecks probably contributed to the patterns of phenotypic variation observed in the hair and irises of modern people [ 95 ].
Scalp hair in most non-European populations is very dark brown, with little phenotypic variation [ 96 ]. Many genes appear to contribute to the dark brown hair colour phenotype [ 8893 ], and the relative importance of different loci is not yet known. The relatively high prevalence of blond hair in Northern Island Melanesia has been traced to the 93C allele of the TYRP1 gene [ 9798 ], which has been dispersed throughout the region in the course of human colonization of the Southwest Pacific.
In Europe, blond hair has been traced to establishment of variation in a regulatory enhancer of the KITLG gene, while red hair is produced by a specific range of variants of the MC1R locus [ 99 — ]. Sexual selection is thought to have influenced the high prevalence of blond- and red-hair phenotypes in Europe [ 93 ], but this has not been established empirically. The nature and coloration of human male facial hair—beards and moustaches—have been a matter of curiosity and speculation, but little formal research [ 16, ].
Male facial hair, manifested as moustaches, cheek hair whiskers and beards, occurs in régime sans sel pour maigrir jambes male primates and appears to represent secondary sexual characteristics that evolved as amplified visual signals of rank, dominance and attractiveness [ 8].
This supports claims that age-related changes in human beard and moustache coverage and colour on the male face serve as honest signals of age or social dominance [ ], and that they evolved as products of contest competition between males [ ]. Beards augment the effectiveness of human aggressive facial displays, but are rated as ambivalent or unattractive by females .
Until very recently, studies of human iris coloration focused primarily on European populations, where the greatest range and variety of eye colours—from dark brown to pale blue—are found.
Iris colour phenotypes are determined by amounts of melanin and by the ratio of eumelanin to phaeomelanin in the iris, with brown eyes having a higher ratio than light eyes [ 8889 ]. Other categorical eye colours, such as blue, green and hazel, are common in Europe and parts of the Middle East, and Central and South Asia, with Europeans having the lightest eye colours [ 88 ].
The sets of genetic markers associated with variation in iris coloration in Europe, South Asia and East Asia are distinct, and relatively little is known of the combination of evolutionary forces—including natural and sexual selection—that influenced aha contre rides distribution [ 89 ]. Dark iris coloration is associated with less scattering of intraocular light, a trait that may be protective under conditions of bright sunlight and high UVR.
Blue eye coloration, on the other hand, is associated with greater intraocular light scattering and a higher level of melatonin suppression, traits that may have been adaptive under highly seasonal sunshine regimes in northwestern Eurasia [ ].
Blue-eyed women have been found to be preferred by blue-eyed men, possibly as a manifestation of a male adaptation for the detection of extra-pair paternity based on eye colour, as a phenotypically based assurance of paternity [ ]. Arguments for the action of natural and sexual selection on iris colour need to be examined with great care as more data on the genetic basis of the trait are revealed.
Traduction de "leukoderma" en français
A recent study showing that the genetic markers associated with iris coloration are also associated with skin and hair pigmentation traits suggests that iris coloration was a pleitropic effect associated with selection on pigmentation genes whose primary effect was skin or hair pigmentation, not iris coloration [ 89 ].
The genetic basis of human coloration is complex because some genetic variants affect all pigmentary systems—skin, hair and eyes—through pleiotropic effects, while others affect only one type [ ] and because different genes and gene combinations can create similar coloration phenotypes. Despite the technical difficulties of such studies, the fascination of humans with their own coloration phenotypes will certainly continue to propel research forward quickly.
Skin, hair and eye coloration in humans is variable, and has been influenced by different combinations of evolutionary forces. Skin coloration has been strongly influenced by natural selection, globally and throughout human prehistory, because of the importance of melanin as a natural sunscreen on naked skin. The role of natural selection in the evolution of hair and eye coloration appears to have been negligible, but genetic bottlenecks followed by sexual selection may have played more significant roles in establishing the patterns of variation recognized outside of Africa.
In recent centuries, humans have migrated faster and over longer distances than during any time in prehistory. Many of these movements have brought people into regions with markedly different solar regimes than their homelands. Many people now live under levels of solar radiation that are much stronger, or much weaker and more seasonal, than those under which their ancestors evolved.
Traduction de "pigment de la peau" en anglais
These rapid changes in living circumstances have created significant health problems resulting from too much UVR exposure skin cancer, accelerated ageing of the skin and from too little UVR exposure vitamin D deficiency and its many sequelae that have greatly impacted individual well-being and public health. Mitigating these problems is now the focus of considerable attention in many health professions [ — ]. Rapid, long-distance migrations have also brought people together from disparate and widely separated places, creating unprecedented and novel opportunities for gene flow.
The twenty-first century world contains a sepia rainbow of human skin colours, created from old and new combinations of skin colour—related genetic markers.
The effects of these new genetic admixtures on health are not known. More significant to health and overall human well-being, however, are the problems of social segregation and behavioural bias that are rooted in cultural constructions of skin colour—based race categories [ 87 ]. Humans are visually oriented primates, and our varied colours are badges of our recently shared evolutionary history. Our skin colours unite us, not divide us. Tim and two anonymous reviewers provided excellent suggestions for improvement of this contribution.
We thank Theresa Wilson of Penn State for providing comprehensive support and assistance to our research programme, including the maintenance of our reference library and preparation of this manuscript. The authors contributed equally to the conception and design of this paper and to the drafting and revising of the article for important intellectual content; they also gave the final approval of the version to be published.
National Center for Biotechnology InformationU.
Published online May Nina G. Jablonski and George Chaplin. Author information Article notes Copyright and License information Disclaimer. Accepted Dec 9. This article has been cited by other articles in PMC. Abstract Humans are a colourful species of primate, with human skin, hair and eye coloration having been influenced by a great variety of evolutionary forces throughout prehistory.
Keywords: eumelanin, phaeomelanin, ultraviolet radiation, natural selection, sexual selection, genetic drift. Introduction Discussions of the cardinal features of the human lineage usually focus on bipedalism, relative brain size, language and technology, and ignore the remarkable distinctions of the integument and eyes that have figured importantly in human evolution.
Human coloration in context Like most mammals, primates have hair covering most of their bodies. Variation in human skin coloration is mostly a product of natural selection Skin colour as measured by skin reflectance and levels of UVR are highly correlated. Hair and eye coloration are not under strong natural selection Like skin, the coloration of human hair and eyes is determined primarily by the amount and type of melanin produced and stored in melanosomes [ 8889 ].
Conclusion Skin, hair and eye coloration in humans is variable, and has been influenced by different combinations of evolutionary forces. Authors' contributions The authors contributed equally to the conception and design of this paper and to the drafting and revising of the article for important intellectual content; they also gave the final approval of the version to be published.
Competing interests We have no competing interests. Funding We received no funding for this study. References 1. Caro T. The colours of extant mammals. Cell Dev. Walsberg GE. Consequences of skin color and fur properties for solar heat gain and ultraviolet irradiance in two mammals.
These are due to loss of melanocytes, the cells responsible for the pigmentation of the skin. Although the ultimate cause is unknown, vitiligo occurs when immune cells destroy the melanocytes responsible for the production of melanin. It affects both men and women at any age, although there is a higher prevalence in women and in the year age range, but it can occur at any age. It is progressive and has an unpredictable course. Symptoms of vitiligo are very characteristic.
White patches on the skin with normal skin texture. These spots are located anywhere on the body but usually are most noticeable on the hands, feet, arms, face or lips. Vitiligo is more noticeable in people with dark skin. Small dark spots appear occasionally in the lighter area. Usually using a Wood's lamp to examine the skin and confirm the diagnosis.
An ultraviolet light that highlights areas of skin with less pigment. To rule out other causes, a biopsy or blood tests can be used to check hormone levels and vitamin B The main problem that caused by vitiligo is its psychological impact.
Actually, it is not harmful to the health. However there is no definitive cure and usually get worse over time. Symptoms can improve if appropriate treatment is used. Depigmented skin is at greater risk when exposed to the sun. Antioxidant, immunomodulation, increases the absorption of iron. Hypopigmented plaque increases tolerance to sunlight, and helps prevent burns pigmentation. Vitilox Cover Cream gives you the advantage of covering your Vitiligo spots or patches while treatment is in progress.
Our Treatment range includes treatment for joint areas, high body coverage, low body coverage, genetically caused Vitiligo as well as face and lip treatment. We also have products suitable for children who suffer from Vitiligo.
From our feedback we generally find that the average time taken to see results is three to four weeks. Around this time frame, you should see the small pigmentation freckles appearing within the white patches. However, we have had report backs of pigmentation starting within the first 2 weeks of treatment. Pigmentation may be a slow but steady process but saying this we have had remarkable cases of full restoration in under 6 weeks.
Follow-up Treatment: Once the pigment has returned we advise using the Vitilox Serum to smooth and even the skin tone. Many patients ask if there is a possibility of the Vitiligo returning after Treatment. The answer to that is yes. Vitiligo can manifest in other areas of the body though it is highly unlikely to return to the treated areas. As Vitiligo patients generally lack Vitamin B and Folic acid, which gives rise to the onset of Vitiligo, we recommend continuing with these tablets or the T-Cell-V tablets for at least 3 months after treatment.
From our ongoing assessments, and also patient consultations, we have noticed that Allergies do cause Vitiligo to trigger, or spread.
Vitiligo and Allergies are very closely connected, and many of our new patients see the first signs of Vitiligo appearing once they become effected or have an allergic reaction to the change of seasons or chemical induced allergies.
Why are Allergies more prone in Spring? The difference in temperature and rainfall patterns affect the pollination of plants and the growth of mold spores. Grass pollen allergy commonly causes nasal symptoms such as itching, sneezing, congestion or a watery, streaming nose, while tree pollen may trigger allergic rhinitis, or a runny nose, hay fever, and red, itchy eyes. It is the scratching of these irritants that causes the damage to the skin which in turn causes Vitiligo to appear in predisposed individuals.
What about other Seasons? However, rain also fosters the growth of mold spores, which are another common natural allergen. It is important for you to get treatment for your allergies to prevent side effects and conditions such as Vitiligo from manifesting. Saying all this, there are many treatments available for allergies. Detergents, soaps, cleaners are some of the chemicals and substances that can irritate the skin.
They can wear down the oily, protective layer on skin surface and lead to irritant contact dermatitis. Irritant contact dermatitis is common among people who regularly work with strong chemicals or detergents, such as at restaurant, maintenance workers, and chemical workers.
It is also seen in people who do a lot of housework due to contact with cleaning products. Initially the skin reacts by swelling and then very small lacerations will appear. These small itchy spots can very easily trigger Vitiligo if you are predisposed to it, or cause the further spread of the condition if you do have Vitiligo.
If you have just seen the first signs of Vitiligo appearing, or are now noticing an increase in the spread of your Vitiligo condition, please do not rule out Allergies, either air borne or chemical. We are here to help. Please feel free to ask any questions or complete our free Vitiligo assessment form for further treatment information. The colour of our skin depends on our melanin production. The more melanin your body produces the darker your skin tone. When the melanocytes, melanin producing cells in the skin die or are damaged, they stop producing melanin.
When this happens, we develop white spots or patches on our skin. We can also loose the pigmentation in our nasal cavity and gums as well as our hair. This is known as Vitiligo. To do this we need to replace the vitamins and metallic elements that have been depleted and are missing from the body of the Vitiligo patient. Vitilox Vitiligo T-Cell-V contains all the ingredients researchers have found to be lacking in Vitiligo sufferers.
The metallic elements in the T-Cell-V stimulates the process of melanogenesis resulting in the production of melanin and the return of your natural skin tone. These elements also address the inflammatory effects of the condition. The Biotin found in T-Cell-V is also important for maintaining a healthy skin. And finally, the Selenium is your essential ingredient required by the immune system to keep your overall body healthy. Apply the Cream to the affected areas once a day to start the Pigmentation process again.
If you are treating your face or hands, you may want to apply the Pigmentation Cream in the mornings and evenings for faster results. If you find that your Pigmentation returning is slow, we do recommend the UVB Lamps to speed up the Pigmentation process. Joint areas — Hands, Feet, Knees, Elbows, etc. Once pigmentation has been restored it is recommended that the patient continue with the Vitamin B12 and folic acid for at least a further 6 months to make sure there is no further outbreak of the condition.
If you have localised Vitiligo to the lips, or are suffering from Vitiligo around the lips and on the inner lips, we recently introduced our Vitilox Vitiligo Lip Treatment product to help soothe the inner lips, and to treat this very sensitive area. Vitiligo is a skin disorder that causes the pigment-producing cells melanocytes to die. It is common for a loss of pigmentation to occur on the lips and inside the mouth.
It may have to do with the consta … nt rubbing that people tend to do in this area, which is a risk factor for Vitiligo patches in susceptible people. This product is specially formulated for the treatment of Vitiligo. Vitilox Lip Balm contains stimulating elements which are absorbed deep down triggering the Melanocytes thus releasing the pigment Melanin. The Lip Balm is an excellent way to treat your inner or lip surface. The formulation of this product enables it to be rubbed onto the lip and remain there for a good few hours.
The element used for the pigmentation of the lips is therefore able to remain intact, and active for longer.
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We have combined the healing properties of our cream into a pleasant tasting easy to use lip balm. There are no known side effects when using this Lip Balm as instructed, as it is made from natural ingredients. At Vitiligo Treatment we do not use any scheduled drugs! Conveniently packaged to carry in your bag or pocket it can be used up to 3 times a day.
Vitilox works quickly in stimulating the pigmentation process. Vitiligo Lip Treatment is now achievable! Remember that if you are unsure of the correct product required to successfully treat your own Vitiligo condition, please submit the Free Vitiligo Assessment and one of our qualified consultants shall respond with the correct treatment for you.
VitiligoTreatments Vitilox Vitiligoliptreatment. Many people with Vitiligo also have a family history of the condition. As it runs in the family, it does suggest that Genetics plays a role. In the past many Vitiligo patients have felt that if their Vitiligo is hereditary, treatment is not possible.
We have found that by using the correct product, it can be treated successfully. The pigmentation loss is decentralized with one side of her body seemingly affected completely differently to the other. It is even worse for the person diagnosed to deal with — further aggravated when diagnosed in your teenage years.
In Augustwe tried juicing specific veggies and ginger etc. Below are the Before and After pics of just her left arm and we can definitely see an improvement!! The product has certainly given her hope in meilleur anti rides contour des yeux 60 millions de consommateur the effects of Vitiligo and re-pigmentation of affected areas.
The before and after pics are loaded on the blog section of our website. If you require any further information on Genetic Vitiligo, or any of the products listed here, please do not hesitate to contact us. This year it shall be focusing on the mental and medical journey of vitiligo as well as the social impact of vitiligo. Since inception inVitiligo Treatment has offered community support and formed groups where we would discuss the difficulties of living with the condition.
As the groups grew, we opened our website, and concentrated on online consultations and assessments. At his stage the preferred treatment for Vitiligo was the UVB narrow band lamps. As the company grew, and from evaluating vitiligo assessments, we began to realise that many products being offered to the Vitiligo public were not safe, and also many did not work. After years of studying the condition, we found the ingredients for a safe and effective product that worked.
We took this formula and this was the beginning of the Vitilox Range of Products. We now have offices in three continents, and our product range has expanded as the need arose though feedback and discussions with Vitiligo patients. We have tried to address all issues that caused concern for our patients, and have a range of products available to treat all cases of Vitiligo. We have upgraded our websites as technology has evolved, improving it for ease of use and embracing all the modern conveniences available to us.
We have taken to social media to connect with, update and offer emotional support to everyone who has Vitiligo. White patches or spots on your lips or around the corner of your mouth could very well be caused by Vitiligo. Vitiligo on the corner of the mouth may spread to the inner lip area as well.
It may depigment the inner lip and top of the lips. Recently we have had more and more requests for a treatment specifically for the lip. We have had our researchers and chemist working on a lip balm specifically for Vitiligo. We have combined the healing properties of our cream and combined it into a pleasant tasting easy to use lip balm that will re-pigment the lips. If you require more detailed information on this product, please visit our website.
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