June 18, 2021

Why do some people live to be 100 years old? How old is the life limit of a person?

Modern officials recognize that the longest-lived French woman, Yana Carmen, is a record verified by the Guinness Book of World Records. She was born on February 21, 1875 and died on August 4, 1997 at the age of 122 years and 164 days. , She is recognized as the only person on earth who has lived over 120 years old!

How old can a person live?

We ignore these extremely long-lived people, and ignore these unfortunate people who have passed away due to various illnesses and accidents. In theory, how long can people live? There are several aspects to measure human life span:

Calculated from the growth cycle of mammals: the life span of general mammals is 5-7 times the growth cycle, the growth period of humans is about 18-19 years, and the limit life span is between 130 and 140 years.

Estimated from the Gompertz model: This is a model used by the insurance industry to measure the average life expectancy of a person. It is related to the insurance odds and can only be extremely accurate. The earliest basis comes from the “Functional Expression of Human Mortality and Determining Life” published in 1825. “Dangerous New Mode”, this is a function, as shown below:

Starting from the age of 30, the death rate will double for every 8 years of increase. The limit that can be inferred is 130 years old, but the probability is too low. Therefore, going back to 8 years, it happens to be the French woman Yana Calman’s. 122 years old, extremely accurate!

Calculated from the Hayflick limit: In 1961, Leonardo Hayflick, an anatomist at the Wester Institute in Philadelphia, Pennsylvania, did an in vitro cell division experiment. Cells obtained from the fetus were placed in a petri dish After splitting 40-60 times, it enters the senescence stage, which is about 100-150 years old based on the 2.5-year renewal cycle.

The three theoretical basis, the life limit is between 100-150 years old, but there is no doubt that the insurance industry data sought after by capital is the most worthy of reference, and its calculation is so accurate that makes people frightening, Gompertz proposed that function The great god is really a devil.

Why can’t people live forever?

Birth, old age, sickness and death are the laws of nature, but there is no doubt that longevity is one of the pursuits of mankind. Of course, immortality is even better! That’s why some people go to freeze them, and some Russian scientists inject themselves with immortal bacteria. I don’t know if it will work, but there is a question that has been lingering in everyone’s mind. Why can’t people live forever? What is it that limits human life?

In the natural state, lifespan is related to the number of cell divisions. After 40-60 times, it enters the senescence stage. If it can be classified 100 times, 200 times is not longevity. If it can divide indefinitely, isn’t it immortal? What switch affects the number of cell divisions?

In the 1970s, Soviet biologist Alexey Matveyevich Olovnikov (Alexey Matveyevich Olovnikov) proposed that the loss of chromosome end sequences can cause cells to exit the proliferation cycle, but this theory was later developed by Blackburn and Greider discovered the telomere structure of Tetrahymena and it was proved.

Telomeres are repeated sequences of DNA at the ends of chromosomes in eukaryotes. They reduce the length of DNA each time it is copied. It seems to tell the DNA that the copy is almost at the end, so don’t COPY anymore. When the telomeres are used up, the DNA will no longer divide and replicate, and the cell will stop renewing, and will eventually die after aging!

Is there any way to keep the telomeres long and immortal, right? In fact, this is the case. In 1985, Greider and others discovered that telomerase can “fuel” telomeres and keep them long! A large number of scientists have invested in research, but it seems that the effect is not so good. On June 21, 2020, a Harvard University research team said that they have discovered a group of small molecules that can restore the length of mouse telomeres. The research team will find a way to regulate telomeres and reverse the aging process.

Researchers at Harvard University discovered a gene called PARN in 2015, which plays an important role in the action of telomerase. They screened more than 100,000 potentially effective chemical substances and looked for those that can make PARN. They found that compounds that maintain healthy functions of genes can achieve their goals by inhibiting an enzyme called PAPD5. Researchers can restore the length of telomeres through oral drug experiments in mice. Perhaps in the future, they can really study drugs that extend telomeres and increase the number of cell divisions.

Are immortal cells good or bad?

In fact, there are naturally infinitely dividing cells, such as liver cells and hematopoietic stem cells of bone marrow. The outer layer of the skin and the inner layer of the intestine also have a strong ability to divide and regenerate, but it is a pity that there are no other than these, and they are used as wounds or When the missing area is relatively large, the ability of human cells to divide and repair becomes more sloppy, and various scar tissues are formed.

But there is one kind of cell that divides infinitely, and that is cancer cells! For example, the cells obtained from a woman of African descent in 1951 have been multiplied for more than 18,000 generations, with a total weight of more than 50 million tons, and there is no loss of vitality. It’s just that this behavior of cancer cells divides uncontrollably and infinitely.

Naked mole rats are a magical species, about the size of mice, but their life span is ten times that of mice, reaching about 30 years, and they will not get cancer for life, and they will hardly age, so why do they die? ? Most naked mole rats die from bites, kidney stones, liver iron overload, chronic kidney disease, and calcium deposits in the skin. Simply put, they live too long, and even toxin deposits come to their door.

It seems that even if you can live forever, you still have to pay attention to your diet and don’t die, because cells can make you live forever, but they can’t help you want to commit suicide!

In addition to many factors such as slow metabolism, low oxygen demand, cold-blooded animals and other factors for the longevity of tortoises, it is the key that their cell divisions can reach 110 times, so they can easily live over a hundred years old. No surprises for so long!

Another amazing artifact is the planarian. The highest record of this biological energy is that after being cut into 279 pieces, each piece can regenerate a brand-new planarian, although their lifespan is in captivity. But 65 to 140 days, but if you cut it every other time, it seems that it has infinite regeneration ability, then how is its lifespan calculated?

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