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Modern gerontology It has several theories, which give an opportunity to understand why a man grows old and dies. They all have a right to exist, but remains the most recognized Molecular-genetic theory of aging . It is based on the hypothesis, which asserts that the cause of aging lies in the primary changes in the unit cell. But with regard to the process, then the views of scientists do not agree, since it can be two options, how it happens and how it is caused.
If you look at these two versions of the process, it is simply impossible to refute them. According to the first theory of the mechanism of aging is genetically incorporated in the cell itself, manifestations of old age - Pattern set by nature. In the second case, it's just a result of the accumulation of errors in the genetic memory that have accumulated over a period of evolution of living beings. As long as the preference for molecular-genetic theory to the first embodiment of the process of aging.
It is believed that the molecular-genetic theory of aging has been created A. Weisman Who put forward the hypothesis of separation of functions between the somatic and germ carriers of genetic material. The basis of this hypothesis is the lack of aging in single-celled organisms. According to Theory Weisman , It is the relationship between sexual and somatic cells determines the lifespan. Sex and germ cells do not die as the main carry genetic information, but are differentiated somatic and die.
The first is responsible for the transmission of information in the population, and the second support them. After the body has fulfilled its purpose, passing information to the population it becomes useless and somatic cells cease to divide. The longer the duration of the function of reproduction, the more generations somatic cells respectively longer lifespan. This can be considered natural selection provided by nature.
For the theory to Weisman confirmed or disproved, we have conducted a lot of research. In the course of these studies it has been established between the pattern of restriction of supply and growth, and thus the aging of the organism. By limiting the power of a young body slows its growth, resulting in delayed puberty, which in turn slows down the aging process. These experiments made it possible to establish that aging is controlled by genes, as well as other stages of ontogeny. By limiting supply the body needs more time for that would reach the final dimensions, to fulfill its purpose in reproduction and start the countdown, that is, to start to grow old.
The first refutation of this theory given experiences A. Carrel . This French surgeon and pathophysiology developed a technique of growing tissue culture using blood plasma and embryonic fluid. His experiment with myocardial tissue cells placed in culture medium showed that molecular genetic theory of aging is not always true, as the layer of cells divided indefinitely.
Molecular-genetic theory of aging Weismann, found its continuation in Theory Heylika . The experiments of scientists proved that the normal somatic cell has a strict number of divisions, the number in honor of the scientist, named number Heylika . According to this theory, somatic cells have limited mitotic potential and a certain life span.
An example of such experiment can be observed in fibroblasts nutrient indoor environment. Connective tissue taken from the body is divided into a certain number of times and dies. But how experiments of Carrel? The difference between these studies is to the material. Carrel mixture was put in a nutrient tissue pieces and Heylik single cells, giving more accurate results. The difference in the nutrient mixture. Carrel In experiments with embryonic blood and fluid samples fell to new cells. Heylik in turn used the solution of amino acids, salts and other low molecular weight components. Thus, molecular genetic theory of aging was reaffirmed, but it did not give an answer as the associated number of division and differentiation of cells in all generations. The answer to this question is not given telomeric theory She only allowed to establish that the structure responsible for the number of divisions - end parts of chromosomes, or telomeres.
Centriolar Tkemaladze theory called into question previous hypotheses, resulting in an indisputable fact. From the somatic cell may grow cloned animals it means that it also carries the genetic information. Then it is logical to assume that the answers are not for aging core, and the structures in the cytoplasm.
Research cells have led to the conclusion that it centrioles are responsible for this process. Before each division they are doubled, and led the formation of the frame cells - cytoskeleton Which plays a vital role in the life of the cell. Cytoskeleton coordinating association cells into the tissue and cell metabolism is responsible for the initial stages of embryonic development. He is responsible for the passage of external signals into the nucleus, until the signal at the destruction of the cells. When the number of cell divisions is exhausted, the centrioles are killed, stops support of the cytoskeleton, and hence, cell aging and dying. The only exceptions are cells capable of regeneration Such as, for example, cells of the liver in adult animals.
In theory centriolar Tkemaladze there immortal cells, such cells are considered of higher plants, fertilized egg and a few other species initially devoid of centrioles and cytoskeleton. To this list and include malignant cancer cells that have broken sharply focus of centrioles and cytoskeleton restructured.
The aging of the body begins when the cells have reached your limit of divisions. Such cells are differentiated Or Specialty. The first humans are differentiated stem cells . Their most fission mechanism is suppressed, it forms the stock all the others go on the formation of the body. Gradually, the stock is expended, for the resumption of tissue cells, when it runs out, the stem cells do not renew it.
As an alternative to all the above hypotheses put forward theory of random mutation Or errors in the human genome. Studies of long-lived cells of over 100 years old showed the predominance allele apoE2 , above apoE4 allele And after the last predisposes to certain diseases for example to giperhodesterinemii and Alzheimer's disease. The dominance of one allele over the other can be considered mutations. That change apolipoprotein Gene, responsible for human longevity and may result in the fact that the body ages.
DNA molecule is the basis of the genetic apparatus, they can be damaged by physical or chemical agents, or so-called free radicals, which violates the process of division and can lead to their modification. Such effects on the genetic material during evolution led to the aging of the organism.
To date, thousands of studies conducted, but it is only another attempt in the long chrede search for eternal youth. All previous theory of aging It is not known until the end. Modern genetics achieved amazing results - from cloned animals. The result of the work of many scientists began to achieve such as increasing the number Heylika 20-30 divisions, highlighted marker of tumor that can help beat cancer and other outstanding achievements. But there is still a lot of work of geneticists, before a person will gain eternal youth and immortality.
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