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39

This is a interesting question and for a long time it was thought that they do not age. In the meantime there are some new papers which say that bacteria do indeed age. Aging can be defined as the accumulation of non-genetic damages (for example oxidative damage to proteins) over time. If too much of these damages are accumulated, the cell will eventually ...


31

Why do we age is a classical question in Evolutionary Biology. There are several things to consider when we think of how genes that cause disease, aging, and death to evolve. One explanation for the evolution of aging is the mutation accumulation (MA) hypothesis. This hypothesis by P. Medawar states that mutations causing late life deleterious (damaging) ...


17

The 'wear and tear' argument is most likely true but it is also interesting to reason about ageing as inevitable from the evolutionary point of view. To set up the argument, we need two things: First, each individual has got a 'reproductive potential' which is realised throughout life. This means a deleterious mutation which has an effect in early life, ...


15

I've been doing some reading, and have come up with the following interesting information. Telomeres During cell division the DNA is replicated, but the mechanism is imperfect and in each round of cell division a small section is lost from the end of each chromosome. To compensate and protect the genetic information there are caps – regions of excess ...


13

From a certain point of view you could argue that our bodies have an inherently limited lifespan; Telomeres are extensions to the end of chromosomes that prevent damage or loss of genetic information during cell division. Telomeres are not replaced (in normal cells), which gives rise to a replicative lifespan; the number of times a cell can divide before ...


13

Each individuals hair colour is determined by the particular pigment they produce (called melanin - the same stuff in your skin that makes you tan). As the body ages this pigment (produced by the melanonocytes - cells that reside in the hair follicle) is produced less and less, until the hair is no longer coloured, and appears grey. This is unique to each ...


13

This is a very good question. There is a big ongoing field of research called "evolution of aging/senescence" that tackles this question. I won't give you a complete overview of the different hypothesis the could explain why we age but here is a fundamental concept that is to know. We'll assume that there is some extrinsic mortality, mortality against ...


12

It's worth noting that earlier this month a large body of resveratrol research was retracted: The University of Connecticut, in what clearly seems like an attempt to get ahead of damaging news, has announced an “extensive” investigation into research misconduct involving one of its scientists, Dipak K. Das. According to a press release, the ...


11

Well, this needs to be broken down into two parts. Do Crocodilians age (undergo senescence), and are Crocodilians immortal (will only die of external causes)? Are Crocodilians immortal? - No. They appear to live about as long as humans before they die. Measuring crocodile age is unreliable, although several techniques are used to derive a reasonable ...


11

Hydra are just one of the many organisms which are immortal. That is to say all their cells divide forever - there is no senescence (planned cell death) in any of their cells. Interestingly Hydrae that reproduce sexually age and die, but asexual reproduction appear to be immortal. Animals that are immortal more often reproduce asexually... this may only ...


10

Caspase do not directly kill the cell, but rather activate a process known as apoptosis, or programmed cell death. The programmed part is there to distinguish it from other types of cell death, such as necrosis, which are more aspecific death processes. Coming back to caspases, they are a series of proteasis, that can activate in cascade in response to a ...


10

Gametes (sperm and ovum), which fuse to form a zygote, arise from germ cells (spermatogonia and oogonia). Germ cells, like stem cells, are maintained carefully i.e the genome is preserved and transposition/recombination events are tightly controlled via different mechanisms. So these germ cells don't have shortened telomeres. Also, during early embryonic ...


10

Actually, genetically, there is no reason for animals to continue to exist after they have procreated. If you look at salmon, they die immediately after procreating, which is probably the most efficient way to carry the best genes to the next generation. In the case of mammals, they need to teach their offspring where to find food, where to find water and ...


9

Because evolution isn't about individuals: it's about species. What matters to natural selection isn't how long you live, but how many grandchildren you have. A long lifespan can be an evolutionary advantage, but like any trait, it's only an advantage to the extent that allows you to reproduce more. It would seem that a longer lifespan would be advantageous ...


8

Free radicals are damaging because their unpaired electrons (or not fully filled valence shell) makes them highly reactive species. They are often considered together with highly oxidizing "reactive oxygen species" (ROS) such as peroxides. They are especially problematic for cell membranes and DNA. In the latter they can react with (oxidize) heterocyclic ...


8

If you search clinicaltrials.gov (maintained by the NIH) for "resveratrol", you'll find 44 clinical trials, many of them ongoing or not yet started. A recent review by Smoliga JM et al states in the abstract: "Although the supporting research in laboratory models is quite substantial, only recently data has emerged to describe the effects of resveratrol ...


7

I think it is the wrong question. You assume that eukaryotes developed from a single-cell organism with circular DNA. Then, clearly, there must have been an advantage of (newly) developing a linear genome. But eukaryotes could have developed from an organism with linear DNA, too. There are still a few bacterial species with linear chromosomes, so this is not ...


7

Well, Erickson et al (2011) attribute the increase in brain volume in the aerobic exercise group to brain-derived neurotrophic factor (BDNF). Specifically (p. 3020): In fact, we found here that changes in serum BDNF levels were associated with changes in anterior hippocampal volume; an important link because the hippocampus is rich in BDNF, and BDNF ...


7

This isn't so precisely focused on tortoises, but a general theory in evolutionary biology for why some animals live longer is K vs r selection theory. The idea here is that animals will make a sort of evolutionary 'choice' and configure themselves to breed as numerously and quickly as they can. This is called 'r' selection, named after the constant that ...


7

Interesting question. My answer is no, but it requires a rather science-fiction style answer - at least it's beyond current technology, but here goes: My Assumptions I make the simplifying assumption that ageing is only related to telomere length. Thus by "avoid ageing" I assume you mean "avoid telomere shortening". Also to clarify things for others, I'll ...


6

p16-INK4a is a part of a very important checkpoint mechanism. It's the "bad guy" in the context of aging because it induces senescence, and too much senescence leads to aging-related tissue degradation. But senescence is important. It's one of the responses cells take when something goes wrong-- DNA damage, viral infection, telomere depletion, that sort of ...


6

Once could argue that we die because it is advantageous to get rid of mature individuals once they have reproduced. Because mature individuals have no more offspring to convey beneficial genes, those offspring which will benefit from knocking off their ancestors will have an evolutionary advantage.


6

There are many papers suggesting a link between AMPK (the major cellular sensor of the AMP/ATP ratio) and lifespan. As with most of these sorts of experiments, I think it is currently unclear precisely what the mechanism for this is, but AMPK regulates TORC1 and autophagy, both of which are also important for lifespan regulation. Here is a PubMed link to ...


6

In a study on longevity in 121 countries, women tended to outlive men by about 5 years [1]. The suggested causes for this are numerous, some of which are temporally, geographically, or culturally specific. On the terminology, sex tends to refer to the absolute biological differences, whereas gender relates more to differences in perception/lifestyle (for ...


5

I can find no examples of immortal plants, but then again immortality is rather hard to prove, it's rather like trying to prove that space will never turn in to a pony - as long as time exists it could still occur, only if you go beyond the end of all time would you be able to say that it has or has not happened but then time would no longer exist and nor ...


5

The answer is that the majority of the cells were frozen from very early in their Hayflick lifetimes e.g. after 9 population doublings. They have been thawed out judiciously and only as needed thus preserving a lot of frozen stocks. When an ampule of cells frozen at, for instance 9 population doubling, is thawed, the cells pick up where they left off and ...


5

First of all, in eukaryotes (as far as I'm aware), older cells can be distinguished from younger cells due to telomere shortening, so there is an ageing process. HeLa cells mentioned by @Gary Chou have a more active telomerase which mitigates telomere shortening, allowing cells to continue to divide indefinitely. I think it's a very interesting question ...


5

In men, gout is associated with a higher risk of death from all causes. This would imply that their life expectancy is shorter. From a review by Kim et al. (1): Among men who did not have pre-existing coronary heart disease, the increased mortality risk is due primarily to an elevated risk of cardiovascular death, particularly from coronary heart ...


4

Resveratrol has recently been shown to induce cellular senescence (at least at high concentrations, see here) which has the potential to accelerate ageing. Senescent cells display and highly inflammatory phenotype which could damage tissues if not removed. However, Resveratrol itself is rapidly metabolised and it may be these metabolites that have health ...


4

There is a pretty good discussion on this topic in chapter 2 of Geriactric Medicine - An Evidence Based Approach (4th ed) by Cassel. This is the main reference for the info below which can hopefully add something to the answers already given. In terms of views on ageing, there's evidence to support both: general principles that may apply to it; and it ...



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