A few days before the newspaper know, send an article entitled "crushed slag slag, but also full of blood resurrection of magical creatures," the article ( http://zhidao.baidu.com/daily/view?id=413 ). Crushed slag slag also full of blood resurrection? It sounds really amazing, is not it?
We must ask, hydra this super power is how to do it? In fact, in addition to the Hydra with cattle fork regenerative capacity, as well as a similar biological planarian (biological system "Metamorphosis" who in the planarian head split in half for the manufacture of two-headed planarian music ......), starfish ( chopped sea throw every piece can grow a new one), and so on. Most often heard is earthworms, cut in half may turn into two ......
These are multi-cellular organisms story. If the story passed on to single-celled creature is not magic: they own only one cell, and each time a new division to produce their own. This is eternal life, ah, right? But for single cells, this is actually some kind of asexual reproduction.
According to evolutionary point of view, from a single cell organisms are evolved into multicellular. This means that we can find somewhere between unicellular and multicellular life. In fact, we have found it. Cellular slime mold is a class somewhere between fungi and animal organisms, it (or them?) Just in time for spore germination is free of single cells, and eating bacteria living. At this point they can split their own reproduction. But when the food runs out, many of the original living separately single cells clump together to form a slug and can crawl looks similar move big guy (for single-cell life is really very, very big slug of something not ah ...... slug is to know what your own brain supplement snail without a shell). At this part of the cell which can produce sexual reproduction new single individual cells (that really is confusing).
So, we put this mission into slime molds are countless cells what will happen? You know, these cells originally "interim join as a partner," together, in fact, any of whom live alone can split up such a large group of cells.
So from this perspective, having the ability to generate a single cell throughout the life of the body does not seem surprising.
Group decided to join as a partner to live single cells, and slowly more and more refined division of labor, it is difficult to leave each other - they became multi-cellular organisms. Although this is not a particularly strict interpretation, but it does the more primitive biological, it retains the ability to regenerate stronger.
About Regeneration "Limit" of the biosphere seems to have a magical mechanism. Some multicellular algae cells constituted by the eight, it looks like the next four is four squeeze on eight different cell into a ball ...... (Jiaosha I really forget, this particular piece, see General Biology, Chen wrote that by reading, cover swans that ah, there is not a cover of starfish, "Chen read by general biology" ah) biologists have suspected that they hold tight so forcibly separate them ...... if divided into eight cells, then each the new cells are split into eight cells of a small individual balls!
However, if a separate cell from eight inside, what will happen?
------------------ I let you guess dividers ------------------
The answer is, the remaining seven cells send a representative who make up about split eight individual cells, and a cell is separated themselves split into eight cells, become a new individual. Interestingly Oh, why not split into eight cells above it? I do not really know the secret, but it is equivalent to a finger cut you down, you will not only grow back a new finger, finger to grow out of you a new ......
Obviously finger will not.
This shows that for those of us more high-end atmosphere on the grade of multicellular organisms, a regeneration have become the more difficult task.
This is why it? Why I cut off a finger, the finger can not grow out of the individual?
Of course, because the finger does not eat can not drink no heart blood circulation no lungs can not exchange oxygen ...... sad reminder of the finger away from the body could not survive, you expect it to grow personally? In addition to the division of fingers to get something other than the rest of the needs of other parts of the body, "nurturing."
In multicellular organisms, the more detailed the division of cell regeneration weaker. Nerve cell regeneration was not easy, that there was a time that people think they can not regenerate. Division of our cells are too loyal, too clear. They can not survive independently. A clear division of labor is the price they have lost their freedom.
This is only a popular description. If you want to know more of this stuff, you need to know a new term: cell differentiation. Cell differentiation is the same source of cells each unique structure, physiological function and biochemical characterization of the process of gradual form. The result is a discrepancy between the spatial cells, the same cells over time and its previous state are different.
For example, by a man from the fertilized egg split, but now you are not a bunch of fertilized eggs together look. On the contrary, our brain nerve cells, chondrocytes and our ears heel epithelial cells are no different. But they really come from the same cell division, and they have the same genotype. They are not caused by the same mechanism, called cells.
Cell differentiation characteristics can be summarized into four points:
Persistent: cells throughout the entire life of the organism in the process, in the embryo reaches the maximum level
2. Stability and irreversibility: In general, differentiated cells will remain differentiated state until death
3. Universality: common biosphere, it is the basis for the development of individual organisms
4. genetic material invariance: Cell differentiation is accompanied by cell division, morphology parent and offspring cell structure or function changes, but the genetic material of the cell remain unchanged.
Under normal circumstances, cell differentiation is stable and irreversible. Once the cells by stimulating certain changes after the start of differentiation in one direction, even if the stimulation of change no longer exists, can still be differentiation, cell division and by constantly continue. What this means is that if there would be any cell differentiated into misfortune heel epithelial cells, it can only have been done in the epithelial cells of the heel.
Although there are exceptions, but in most cases this is.
And in the human body, not every cell retains the ability to divide. Those cells retain the ability to divide, called stem cells. Of course, there are some privately infinitely dividing cells, called cancer ...... cancer shows us the consequences of the division limit is broken.
So whether stem cells can solve all medical problems?
Are interested first stem cells to understand it! Self find family members of stem cells: totipotent stem cells (splinter offspring can easily differentiate), multipotent stem cells (splinter offspring can only differentiate one direction) and pluripotent stem cells (splinter offspring can only differentiate into several directions) .
In theory, stem cells can generate a whole new individual through division and differentiation.
But to solve the medical aspect of the problem is not to get out of a new self-ah ...... how to make these cells grow out of what we want? This requires tight control of their differentiation. Scientists gave the cells were grown in mouse ears back, but the "ears" in fact there is an ear-shaped shelves, and there are really ear difference. Grow new organs are good wishes, but we are really very far away from it.
Simple injection of stem cells have not been based on the effect of illegal Stem cell treatment of notorious international touches.
Unlimited division skills quite frightening, because it and the ability of cancer cells is the same. The absence of control who do not know what these cells will grow into something? According to Israeli scientists reported that a desperate Israeli families suffering from fatal brain disease in order to save the son, participated in high-risk infants embryonic stem cells were injected experimental treatment. The results show that injection led to the boy's brain and spinal cord tumors have appeared. This is the first injection on the acceptance of embryonic stem cell treatment caused a brain tumor report records. According to reports, Israel treated the boy suffering from a rare fatal genetic disease "ataxia telangiectasia." The disease causes the brain to disease progression, tumor tissues were boys tests and concluded: the tumor is injected into the body's stem cells result. And because the prevalence of immunocompromised boy, his body only let cancer cell growth. This stem cell scientist at the University of Pennsylvania, Dr. Earhart warned: "Stem cells are not drugs, they may be changed in various ways, people still need to wait for further verification."
Of course, the more likely that it does not grow anything. These cells in vitro must survive harsh environments, enter the body may also be removed immune cells. This situation is called graft failure.
In any case, the stem cells are biomedical frontier. Use of stem cells to cure diseases is still the dream of scientists realized step by step. We often hear of the bone marrow transplant, the purpose is to get inside the bone marrow hematopoietic stem cells. Retained fetal cord blood, also want to keep the inside of the stem cells. Stem cells have the benefit of the public at the Department of Hematology, is indeed gratifying.
But one thing did not estimate how much doubt: Stem cells also can not solve all medical problems. Even if we use stem cells to cure a rare genetic disease causative genes will still continue.
Bring ethical issues of stem cells can not be ignored: "With long fingers out of you" and the original or a person you do? If the brain damage, developed via the brain stem cells to replace the original brain, the person will retain memories? He should do as a new life?
Incidentally, "crushed slag slag, but also full of blood resurrection magical animals," the article, the "keep your head up" issues related to the polar differentiation, differentiation is one of the problems of regulating it. Cell division, differentiation regulation is really a very attractive part of biology which, in the rapid development of technology today, to learn a little more cutting-edge knowledge is a very interesting thing, is not it?
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