Cell's Cycle & Lifespan

K

Kumar

Registered Senior Member
Hello all,

I want to know the following details:-

1. What is the lifespan & life cycle of human body cells.

2. If cells are born & die OR just multiply & die. Born-I mean new cell which do not have any aquired manifestations but may just have inherited predispositions. Multiply-I mean by dividing of specialized cells, which may carry both a.m. & i.p.

3. Is there any limit to the the lifespan of cells from borned to death of all its generations/multiplications.

4. If the cells are borned then these will carry any aquired manifestations or not- means that if these will be just like 'refreshed' child like cells.

Thanks in advance.
 
There is a lot known about this topic, but it's difficult to explain properly without a strong background in biology. But, here goes.

1. Depends entirely on the cell type. Nerve cells don't divide once you are past the developmental stage, so they are with you until you die (more or less, just generally speaking). Blood cells on the other hand turnover on the order of days, but do not replicate. It's different for each cell type.

2. Cells divide. They are exact replicas of the 'parent' cell.

3. Cells can generally only divide about 80 times in a human cell line before they senesce (this is from memory, please correct me if I am mistaken, and you think it's important). There are a limited number of cell divisions a cell line can undergo, unless they become cancerous, then they are essentially immortal.

4. They are exact replicas of the parent cell.
 
1. Depends on the cell...
2. Again depends on the cell. Cell specialize as they develop based off gene activation and developmental biology. Signals from other cells say “you become a skin cell, you become a muscle cell, ect” well it get really complicated and the details on how cells organize are still being worked on.
3. Depends on the cell, stem cell lines can divide thousand of time, most cell lines like mention before can't pass 80 in vitro (in laboratory). As the cell divide the telomeres grow shorter and eventually the telomeres are removed and the chromosome get worn down, cell senescence (old age or senility, can’t reproduce) and apoptosis (cell death) will follow. Telomeres are re-grown at a continues rate during meiosis (reproductive cells) in some stem cells lines and cancer cells those allowing them to divide indefinitely
4. Cells can be made to revert to stem cell lines in vitro (in laboratory) it not know if these happens in vivo (in the body) so a cell can revert artificially at least.
 
Idle mind,WellCookedFetus,

Thanks for explaining. Depending on the type of cell, lifespan of some cellls is limited. Cancer is said to develop in several years. Then a cell-line with a shorter lifespan will not die before they could develop & carry cancer & become immortal. How it is possible that cells with shorter lifespan develop cancer- whose development time is much more than the lifespan of cells/celllines? Can it be assumed that cancer starts in stem cells.
 
Cells with short cell lines need to have a mutation in telemerase production so that they can keep growing back their telomeres after every division thus extending their life span indefinitely. They could also have a mutation in telomerlyase production so they can not cut down there telomeres after every division.
To become cancerous a cell needs at least three groups of mutations
1. Immortality by telomere regeneration also by damage to cell DNA repair and cell death activation.
2. Constant division rate, if not the tumor is very slow growing
3. Metastasize, the cells must be able to leave and start new tumors.
 
WellCookedFetus, spuriousmonkey,

Thanks for the information. It means that the mutation in Cells with short cell lines can take place in telemerase production so that they can keep growing back their telomeres after every division thus extending their life span indefinitely-- in any shortest time but the development in cancer tumor & metastatis ( with angiogenesis) may take any longer time ( may be called as cancer development stage). Does it mean that so many persons may be already having cancer cells but they will not be called cancer patients unless their development in cancer tumor & metastatis takes place? We can say- there can be following stages:-

1. Mutation (as mentioned), 2. Cancer Tumor Development(with angiogenesis) & 3. Metastatis.

No.1 will be called as due to mutagenic effect of responsible factor. No.2 & 3. will not be mutagenic but the habit of those cells effected by no.1 will cause the progress of cancer. It can be now thought that If caricinogenic substances are responsible for No.1 effect only OR can also cause No.2 & No.3 effects.

Am I correct?
 
Kumar,

See any moles on your skin? Many of those are cancers potential cells.

I would assume so... sorry logic statements have not been making sense to me lately :confused:
 
WellCookedFetus,

Sorry, it looked bit otherwise to you. But I just want to assess that why long exposure(not short) of carcinogenic substance say tobacco/smoking is linked to the cause of cancer--when mutation can take place instantly?

Bit fearful, as I have so many moles. :(
 
most carcinagens are mutatgens, some though could as you said induce cell growth and/or Metastatis wihtout mutation.

it take many mutations in specific parts genes for a cell to become cancerous, so mutation induce cancer is usually slow.
 
It may mean that first few mutations can create immortality(as discussed) & furthur mutations make them to grow & & induce metastatis.
 
it would be a event of very bad luck if it happens quickly. to many mutation at once will induce apoptosis, unless of course the genes for induce cell death have been mutated before hand.
 
WellCookedFetus,

I am sorry it is not clear to me. Cells which have limited lifespan of their celllines- With in this period they should be able to become cancerous or at least mutated to become immortal-otherwise they will die. Now this mutation should be done with in their cellline lifespan. As you said there can be furthur mutations or otherwise-which will induce their growth & metastatis or stimulation to become cancerous. Is is correct-then I will mention furthur. Thanks.
 
Cells which have a limited lifetime will undergo senescence unless they gain immortality. While some mouse cells have been able to sponatneously overcome senescence, human cells apparently cannot. So, in order to do so, to gain immortality, they have to become cancerous. If they don't, they will die after a determined number of divisions.
 
Idle Mind,

It looks that normal cells with short lifespan can't become cancerous within their lifespan, because it may take more time to become cancerous then their lifespan. How the cancer will develop in these cells?

Can you please give total lifespan of all celllines of some short life cells & which can aquire cancer? It will add for better discussions.

Hello spuriousmonkey,

"longevity of cell live can also be attained by dividing slowly"

If you mean to say that something happens which can convert short life of cells to attain longevity by dividing slowly during a cancer sequence? Can you bit explain this sequence?

Ps; If we see the belowmentioned quote, it may help to understand this subject:-

"Normal body cells grow, divide, and die in an orderly fashion. During the early years of a person's life, normal cells divide more rapidly until the person becomes an adult. After that, cells in most parts of the body divide only to replace worn-out or dying cells and to repair injuries.

Because cancer cells continue to grow and divide, they are different from normal cells. Instead of dying, they outlive normal cells and continue to form new abnormal cells. "
 
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I am not talking about cancer. The lifespan of a cell is dependent on its function. For some functions you do not need a short cell lifespan. Quite the opposite, a long lifespan is a necessity. Stem cells are slowly dividing cells with a long lifespan. Certain neurons don't regenerate, so better pray that they are long lived. A cell of the outer layer of your skin has a short lifespan. It is under stress and will wear off, ending its life as housedust, and food for your house mites.

It is a simple minded view to think that you can extend the lifespan of an organism by making cells proliferate longer. They proliferate for a certain amount for a reason. That is to make a functional organism.

A cancer are cells that are out of control of this pogram of replication, with sometimes dreadful consequences for the whole organism.

Too much proliferation however is a general tool to build a structure during the development of an organism. You make too much and then start deleting the cells that you don't need, or don't want. A general change in the proliferation profile of all the cells in the body would probably result in a 'monster', or an organism with some serious problems.


did I explain anything that you requested or was it too much of a rant?
 
Thanks for detailed explaination. I want to understand few things.

Cells can have differant lifespans depending upon their functional requirements & ability to regenerate. But the question remains-how cancer can develop in cells which have shorter life span then cancer's causing lifespan? Btw, if rapid proliferation rate or rapid replication of healthy cells is sign of avoiding the cancer?
 
Originally posted by Kumar
But the question remains-how cancer can develop in cells which have shorter life span then cancer's causing lifespan?
Click to expand...

the cells are mutated and have acquired different proliferating characteristics.
 
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