Stem cells - are undifferentiated cells that have the ability to grow in the cells of various tissues and organs. In many tissues they serve as a sort of internal repair system - they can share, supplementing and replacing other cells is almost unlimited, as long as the person or animal is still alive. When a stem cell divides, each of the newly formed cell has the potential either to remain a stem cell or become another type of cell with a more specialized functions - for example, muscle cells, red blood cells, or brain cells.

Cells from other types of stem cells are distinguished by two important characteristics. First - they are undifferentiated cells able to be updated through cell division, sometimes - after long periods of inactivity. The second - under certain physiologic or experimental conditions, can be induced by their transformation into cells of tissues or organs that have certain features. In some organs, such as in bone marrow and gut stem cells divide continuously to repair and replace worn or damaged tissue. In other organs, however, for example, in the pancreas Diabetes and pancreas - the things you need to know   and in the heart, stem cells divide only under special circumstances.

Types of Stem Cells

Until recently, researchers have worked mainly with two kinds of stem cells in animals and humans: embryonic and adult, or somatic, stem cells. On the functions and characteristics of these cells will be discussed below.

For the first time scientists have been able to obtain embryonic stem cells from mouse embryos more than 30 years ago, in 1981. Careful study of stem cell biology has resulted in mice that 1998 was opened method for obtaining stem cells from a human embryo and growing the cells in a laboratory. Embryos used for these studies were created for reproductive purposes by in vitro fertilization. Those embryos that are not useful for this purpose are, with the consent of the donor, transferred for investigation. In 2006, scientists have made another breakthrough - they have identified the conditions under which some of the specialized mature cells can be genetically "reprogrammed" so that they acquired the characteristics of stem cells.

Stem cells are important for living organisms for many reasons. In an embryo at the age of 3 to 5 days - blastocyst already available stem cells that then develop the entire body - heart, lungs, skin, bone, and so on. In some adult tissues stem cells compensate for wear and tear and help authorities recover from injuries and illness.

The unique regenerative capacity of stem cells open up new possibilities for the treatment of diseases such as diabetes and cardiovascular disease. However, there is still a lot of work in laboratory and clinical settings, before we know exactly how to treat the disease with them.

Laboratory studies of stem cells enable scientists to learn more about their features and capabilities. Already, scientists are using stem cells in the laboratory to develop and test new drugs and to study normal growth and identify the causes of birth defects. The study of stem cells - one of the most promising and exciting areas in modern biology and medicine, and here, obviously, it is too soon to know everything.

The unique properties of stem cells

All stem cells, regardless of how they are obtained, there are three general properties: they are able to share and update for extended periods, they are not specialized; They can turn into specialized cells.

Unlike muscle, blood or neuronal cells which do not normally replicate, stem cells may be replicated many times.

Today, scientists are trying to answer two critical questions related to stem cells:

• Why embryonic stem cells can proliferate in the lab for a year or more, without differentiating (without becoming specialized cells of tissues or organs), and most neembrionalnyh stem cells that can not?
• What factors in living organisms normally govern proliferation (growth by cell division), and self-renewal of stem cells?

Answers to these questions help to understand how to regulate the proliferation of normal cells during embryonic development and during abnormal cell division that leads to cancer Breast cancer - the verdict? . This information would also help scientists to more effectively grow in the laboratory embryonic and adult stem cells.

Specific factors and conditions that allow stem cells to remain undifferentiated, are of great interest to scientists. Skilled took many years of research, trial and error, before they were able to allocate stem cells and maintain their livelihoods in the laboratory so as to avoid the spontaneous conversion into specific cells. Once the stem cells were obtained mouse took two decades before scientists were able to grow human embryonic stem cells. Now it is important to understand what signals mature organism stimulate proliferation of stem cells, why they remain undifferentiated until exactly how it will be necessary to use them.

Another fundamental property of stem cells is that they have structures characteristic of cells of certain tissues or organs. For example, stem cells can not interact with its neighbors and to pump blood (heart muscle cells), or transport oxygen molecules through the bloodstream (as red blood cells). However, they can turn into any specialized cells - is called differentiation. When the cell differentiates, it passes through several stages, each of them becoming more and more specialized. While researchers are only beginning to understand the signals inside and outside the cells, which lead to differentiation. Internal signals controlled genes cells which are part of the DNA chain, and wherein coded instructions on cellular structures and functions.

The external signals for cell differentiation are the chemicals that produce other cells; physical contact with adjacent cells; and the activity of certain molecules.

However, the differentiation of stem cells still leaves a lot of questions. For example, whether the internal and external signals are the same for cell differentiation of stem cells of all types? Possible to identify a specific set of signals, which leads to the conversion of stem cells into specific cell types? If these questions will find responses may scientists can find new ways to monitor the differentiation of stem cells in the laboratory and grow cells and tissues, which can then be used, for example, for cell therapy.

Adult stem cells typically generate the cells of the tissues in which they live. For example, hematopoietic (hematopoietic) stem cells in the bone marrow in normal differentiated into different types of blood cells. It is believed that because of hematopoietic stem cells can be formed, for example, nerve cells, or brain cells. In recent years, much research was conducted to show that stem cells from one tissue can generate very different tissue cells, but this has not yet been proven, and is the subject of controversy in the scientific community.

Causes of baldness

Because of hormonal changes, irritation or damage, some hair follicles have a shorter growth phase and produce thinner, shorter hair shafts. Tested hair cycle during which the alternating phases of growth and rest. Proceedings of each cycle depend on the individual. But in general, the growth phase of scalp hair, known as anagen, usually lasts two to three years. At this time the hair grow about 1 cm per month. Resting phase called telogen. This stage usually lasts three to four months. At the end of the resting phase the hair falls out, and in its place begins to grow a new one. Once the hair falls out, the growth stage begins again.

Most people generally falls between 50 to 100 hairs a day. But as on the scalp grows about 100,000 hair is the number of lost hair should not cause noticeable thinning hair.

Gradual thinning hair is a normal part of the aging process. However, hair loss may lead to baldness, if the rate exceeds the rate of regrowth of hair loss, if the new hair thinner than dropped or when the hair falls out scraps.

Reasons for certain types of hair loss

• Androgenic alopecia (androgenic alopecia)

The female and male pattern baldness types of hair growth time is shortened, and the hair is not as thick or sturdy. Each hair growth cycle rooted more superficially and is easy to fall out. A key role is probably played by heredity. Cases of androgenetic alopecia on the part of both parents increase the risk of baldness. Heredity also affects the age at which a person begins to lose her hair, and the rate of development, the structure and the degree of baldness.

• Cicatrical alopecia

This type of permanent hair loss occurs when inflammation damages the hair follicle and leaves a scar on it. It prevents the growth of new hair. This condition can be observed in some diseases of the skin, including such as lupus erythematosus or lichen planus. The causes of inflammation is unknown.

• Alopecia areata

It is classified as an autoimmune disease, but the cause is unknown. People who develop alopecia areata are generally in good health. Some people may have other autoimmune diseases, including thyroid disease Thyroid disease - women at risk . Some scientists believe that some people are genetically predisposed to develop alopecia areata and that the kakoy- factor, such as a virus or something in the environment triggers the development of this condition. Took place in the family history of alopecia areata makes a person more prone to its development. With alopecia areata hair usually grows back, but sometimes the hair fall out and grow back several times.

• Telogen alopecia

This type of alopecia generally occurs due to changes in the normal growth cycle of hair. This can happen when something yavivsheesya shock to the body - emotional or physical - prematurely pushed the hair roots to rest. The victims of these growing root hairs fall out. After a month or two, the hair follicles become active again and new hair starts to grow. Telogen alopecia may follow emotional disorder, such as a death in the family or a physiological stress, such as high fever, sudden or excessive weight loss, extreme diets, nutritional deficiencies, surgery, or metabolic disorders. Hair usually grow back once the cause disappears, causing the hair loss, but it usually takes months.

• Traction alopecia

Excessively frequent styling or hairstyles in which the hair too tight can cause traction alopecia. If you stop to pull hair is not formed scar the scalp and the roots of irreversible damage has occurred, the hair grow normally again.

Other causes of baldness

• Poor diet

Insufficient amount of protein or iron in the diet or otherwise poor nutrition can result in hair loss. Quaint and strict diet, as well as some diseases, such as eating disorders, are also causes of hair loss.

• Medication

Some drugs that are prescribed to treat gout, arthritis, depression, heart disease and high blood pressure in some people can cause hair loss. In some women, the hair can fall out while taking birth control pills.

• Diseases

Hair loss can cause diseases such as diabetes mellitus Diabetes - threatening and incurable disease   and lupus.

• Medication

Chemotherapy and radiation therapy can lead to baldness. In these circumstances, could be affected healthy, growing hair. After the treatment the hair is usually started to grow again.

• Hormonal changes

Hormonal changes and imbalance of hormones can sometimes cause hair loss. The reason could be pregnancy, childbirth, discontinuation of birth control pills, menopause, thyroid dysfunction. Hair loss can occur three months after the hormonal change and another three months need to hair may grow back. During pregnancy naturally be thicker, more luxuriant hair. It is also normal to lose more hair than normal about three months after birth. If a hormonal imbalance is associated with excessive production of testosterone can occur thinning hair on the crown of the head. Restoring hormonal balance can stop hair loss.

• Hair Treatments

Chemicals used for coloring, tinting, lightening, straightening or perm hair can cause damage and loss of hair if overused or do them wrong. If your hair is damaged, too frequent styling and excessive brushing also can cause hair loss.

• Infections of the scalp

Infections, such as ringworm Ringworm Ringworm - not only infectious disease   - How not to be left without hair May penetrate into the hair and scalp, resulting in the loss of hair. Once infections are treated, hair generally grows back. Ringworm is a fungal infection, and usually can be cured by external or antifungal medications taken orally.

• Trichotillomania

Trichotillomania is a type of mental illness in which patients feel an irresistible urge to pull your hair out of your head, eyebrows, or other body parts. Pulling hair out of my head often leaves them bald spots on the head inhomogeneous. To demolish these bald spots, patients may go to great lengths. Causes of trichotillomania are still being studied and no specific cause is found.