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Ученые раскрыли секрет появления седины - анемия/недостаток В12

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Группа европейских исследователей обнаружила, что механизм появления седины заключается в нарушении процессов расщепления перекиси водорода, образующейся в волосяных луковицах.
В результате ее накопления снижается активность ферментов синтеза пигмента меланина, который придает волосам их натуральный цвет.

Пользуясь методикой инфракрасной Фурье и Рамановской спектроскопии, ученые обнаружили, что в луковицах седых волос накапливается перекись водорода, которая в микроскопических количествах образуется во всех волосяных луковицах, но в норме быстро расщепляется ферментом каталазой (пероксидазой).

Седина появляется, когда под влиянием возрастных изменений, генетической предрасположенности или заболеваний в волосяных луковицах значительно снижается активность каталазы, а также метионинсульфоксидредуктаз А и Б – ферментов, которые принимают участие в синтезе меланина. В результате этого продукция меланина снижается, что приводит к обесцвечиванию волос.

Помимо этого, исследователи установили, что в лабораторных условиях повреждающее действие перекиси водорода на ферменты синтеза меланина можно предотвратить аминокислотой L-метионином.

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It all begins when your body stops producing melanin. Each strand of your hair grows out of a follicle that has cells filled with melanin. These melanin-filled cells are called melanocytes.
"Melanocytes pass melanin to adjoining cells called keratinocytes, which produce keratin -- hair's chief component," explains Laurence Meyer, M.D., Ph.D., professor of dermatology at the University of Utah. "When keratinocytes undergo their scheduled death, they retain melanin. The pigment visible in hair and in the skin lies in these dead keratinocyte bodies."
Over time, the amount of melanin in the keratinocytes decreases. Gray hair is simply hair with declining levels of melanin. White hair has no melanin at all.
The declining presence of melanin also appears to contribute to the lack of moisture in gray or white hair. So as your hair becomes lighter in color, its texture becomes dryer and coarser. That’s why gray hair tends to be more curly or wiry.
At the beginning of the graying process, follicles produce colorless strands in a random pattern. For unknown reasons, the first gray or white strands usually appear on your temples and the top of your head.
Your hair doesn't actually "turn" gray -- it grows in this way. Every day, hairs fall out and new ones replace them. At any given time, about 85% to 90% of your hairs are actively growing, while the rest are in a resting state.
Typically, one strand grows for two to four years. It then naturally enters a resting state for about two to four months, after which it falls out and is replaced by a new hair. On average, most people lose about 50 to 100 strands of head hair a day.
Some Potential Reasons
Despite the lack of funded research into the role of genetics and gray hair, medical experts have been able to find a relationship between graying and the environment and graying and lifestyle choices. They have also shown a relationship, to some degree, between graying and illnesses and conditions.
Smoking. A 1996 British Medical Journal study reported that smokers are four times more likely to go gray at a young age. Why is not clear.
Illnesses. Sometimes, the arrival of gray hair can be a sign of an underlying health problem. Werner's syndrome, a disease that mirrors the symptoms of aging in people as young as 20, can spur the premature growth of gray hair. Pernicious anemia, a disease marked by a vitamin B12 deficiency, is sometimes associated with decreased melanin production. Any illness or condition that causes your hair to fall out may reveal graying strands formerly hidden by your original hair color or sheen. For example, slow-growing or new gray wisps may become more obvious if you are coping with alopecia areata, an autoimmune disease that causes hair to fall out in small patches. Other examples include thyroid disease and vitiligo, a condition of unknown cause in which melanocytes are lost or destroyed, perhaps because the immune system "misfires" and attacks normal skin. If the scalp is involved, areas of white hair may develop.
Drug treatment and alternative medicine. Several drugs can cause growing hair to stop its growth cycle and fall out. For example, drugs such as lithium (used to treat manic depression) and methotrexate (used to treat some forms of arthritis and cancer) can contribute to hair loss, revealing more gray strands. Interestingly, some cancer patients, whose gray hair falls out as a result of chemotherapy, experience regrowth of the lost strands in their original color. This phenomenon suggests that melanocytes that are producing less melanin can be stimulated to make more, although how this occurs remains a mystery.

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Краткий перевод -
"Анемия и недостаток витамина В12 правоцирируют появление  ранней седины."

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