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15

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, ...


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

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 ...


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

It's worth noting that earlier this month a large body of resveratrol research was retracted: The University of Connecticut, in what clearly seems like an attempt to get ahead of damaging news, has announced an “extensive” investigation into research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 ...


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 ...


9

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. So these germ cells don't have shortened telomeres. Also, during early embryonic development the future ...


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 ...


7

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

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

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

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

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

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

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 ...


6

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 ...


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

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

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 ...


4

Nice answer by Poshpaws +1. Free radicals can damage membranes (especially important for mitochondrial and endoplasmic reticulum membrane function), DNA (genes, telomeres, and mitochondrial DNA, eg), and microsomes. These are the things we consider with regard to ROS for our research on aging. The role of diet is not clear. Smoking and alcohol may have ...


4

Although many studies have shown that there are trade-offs between longevity and reproduction, whether such trade-offs exist in humans has been a matter of debate [1,2]. In many species, including humans, males live shorter than females, which could be due to the action of male sex hormones. Castration, which removes the source of male sex ...


4

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 ...


3

Dementia with Lewy bodies (DLB): It is characterized anatomically by the presence of Lewy bodies, clumps of alpha-synuclein and ubiquitin protein in neurons, detectable in post-mortem brain histology.[1] Lewy Body dementia affects 1.3 million individuals in the United States alone. http://en.wikipedia.org/wiki/Dementia_with_Lewy_bodies ...


3

Looking at the articles referenced in the Wikipedia article, there's probably no direct physiological link between senescence and beta-galactosides. Lee et al (2006) and others before them have shown that the "hypothetical" protein is just regular lysosomal beta-galactosidase, which is present in higher concentrations in aging and stressed cells because the ...


3

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 ...


3

Therapeutic hypothermia certainly is an extremely useful short-term treatment for hypoxic and ischaemic injury to tissues (caused by loss of blood flow and/or oxygen) and is part of the protocol for treating people in intensive care who have had out of hospital cardiac or respiratory arrest as well as being used during heart surgery in cardiopulmonary ...


3

A database that answers the question, charting telomere repeat sequences for all known species, is: http://telomerase.asu.edu/sequences_telomere.html For example in Yeast:



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