Showing posts with label Melanin. Show all posts
Showing posts with label Melanin. Show all posts

May 1, 2015

Eye Colors, Blue

Last in the series of eye colors. Naturally blue eyes are caused by having low melanin levels in the iris - the same stuff that gives skin its pigment and color. In fact, we have all had blue eyes at one point in our lives, because all babies are born with blue eyes. For most people, their eyes change color as they grow older and develop melanin, but for a select few who do not develop as much melanin, their eyes stay blue forever. Eyes appear blue for the same reason as the sky is blue. It is a process called Rayleigh Scattering.

In Iceland, 80% of the population has blue eyes. The statistics are similar in the rest of Northern Europe and Scandinavia, where blue eyes are very common. Blue eyes can also be found in some areas of Western Asia, as well as in Israel. Blue eyes are extremely rare in Africa. People with blue eyes are becoming less common in the US.

For a long time it was believed that blue eyes were caused by a recessive gene, but lately this has been found to be untrue. People with blue eyes tend to have a higher tolerance to alcohol than those without.

Silver eye color is quite rare, although many consider silver eyes to be a variation of blue eye color. Like blue eyes, silver eyes are the result of a very low amount of pigmentation in the eye, which reflects a gray-silver appearance. Silver eye color is most common in eastern European countries, and is one of the more rare eye colors worldwide.

Jul 12, 2013

Change Your Eye Color

Dr. Gregg Homer of Stroma Medical is developing the technology for a laser procedure that will turn brown eyes blue. He says a 20-second procedure that removes melanin, the pigment that gives brown eyes their color, will permanently make them blue without affecting a patient’s eyesight. The change occurs gradually over two weeks. The procedure can not change blue eyes to brown.

The majority of the world’s population has brown eyes, and the number of blue-eyed people is decreasing in America.

The doctor says he expects to do another year of testing before the technique becomes available outside of the United States in less than two years, and within the United States in three. It is estimated the procedure will cost $5,000. 

Jan 22, 2013

What Causes Gray Hair

A few of these gray things have begun to sprout and it made me wonder why. A person’s hair color is the result of pigments known as melanin produced by a specialized group of cells known as melanocytes. Melanocytes are found throughout our body and the melanin they produce is what gives our skin, hair, and eyes their color. Scientists can determine what color your eyes and hair are from DNA.

The melanocytes responsible for hair color are found in the bulbs of your hair follicles.
There are two main types of melanin. Eumelanin produces dark browns and blacks, and pheomelanin produces reddish/yellow. How these cells blend together determines what color hair will be. It is not fully known what makes the melanocytes blend together in the ways they do, but it appears to be genetic.

Once melanin is produced, their granules are transferred to adjacent keratinocytes, also found in the bulbs of your hair follicles. Keratinocytes are what produce keratine, the dead protein cells that make up our visible hair. Gray hair is the result of less melanin within the keratin. The less melanin, the more gray your hair will be and white hair has no melanin.

As we age our melanocytes decrease in number. The result is less and less melanin, until none are present, so hair slowly turns gray, and then white.

In 2009, scientists in Europe found that hair follicles produce small amounts of hydrogen peroxide. Normally this small amount of hydrogen peroxide is broken down by an enzyme called catalase. As we age, catalase production is reduced and there is a build up of hydrogen peroxide, which blocks melanin production by melanocytes.

There are several other things that can cause our hair to turn gray, including: genetic defects; abnormal hormone production, such as stress; abnormal body distribution of melanin; and climate factors, such as pollutants, toxins, and chemical exposure. The time and speed at which you will gray varies greatly.

As an aside, in Britain, Canada, Australia, Ireland, New Zealand, and South Africa, the spelling is commonly grey. In the United States, the preferred spelling is gray, but grey is accepted.