Biological immortality
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{{Otheruses4|the scientific aspect of immortality|for other uses|Immortality}}
'''[[biology|Biological]] [[immortality]]''' can be defined as the absence of a sustained increase in [[Mortality rate|rate of mortality]] as a function of chronological age. A cell or organism that does not experience, or at some future point will cease [[senescence|aging]], is biologically immortal. However this definition of immortality was challenged in the new "Handbook of the Biology of Aging",<ref>
{{cite book | first=E.J. | last=Masoro | coauthors=Austad S.N. (eds.)| year=2006 | title=Handbook of the Biology of Aging | edition=Sixth | publisher=Academic Press | location=San Diego, CA, USA | id=ISBN 0-12-088387-2 }}</ref> because the increase in rate of mortality as a function of chronological age may be negligible at extremely [[old age]]s (late-life mortality plateau). But even though the rate of mortality ceases to increase in old age, those rates are very high<ref>{{cite journal
| title = Late life: a new frontier for physiology
| author = Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller
| journal = Physiological And Biochemical Zoology
| year = 2005
| month= Nov-Dec
| volume = 78
| number = 6
| pages=869–878
| pmid = 16228927
| doi = 10.1086/498179
}}</ref> (e.g., 50% chance of surviving another year at age 110 or 115 years of age).
There is no known [[organism]] or individual [[cell (biology)|cell]] that is inviolably [[immortality|immortal]]. Any life enjoying ''biological immortality'' can die if exposed to a toxic environment, or otherwise [[kill]]ed or destroyed.
==Cell lines==
{{main|Cell culture}}
[[Biologist]]s have chosen the word immortal to designate cells that are not limited by the [[Hayflick limit]] (where cells no longer divide because of [[DNA repair|DNA damage]] or shortened [[telomere]]s). (Prior to the work of [[Leonard Hayflick]] there was the erroneous belief fostered by [[Alexis Carrel]] that all normal [[somatic]] cells are immortal.)
The term immortalization was first applied to [[cancer]] cells that expressed the telomere-lengthening [[enzyme]] [[telomerase]], and thereby avoided [[apoptosis]] (programmed cell death). Among the most commonly used cell lines are [[HeLa]] and [[Jurkat cells|Jurkat]], both of which are immortalized cancer cells. Normal [[stem cell]]s and [[germ cell]]s can also be said to be immortal.
Immortal cell lines of cancer cells can be created by induction of [[oncogenes]] or loss of [[tumor suppressor gene|tumor suppressor genes]]. One way to induce immortality is through viral-mediated induction of the [[SV40 Large T-antigen|large T-antigen]],<ref>{{cite journal
|title = Expression of the Large T Protein of Polyoma Virus Promotes the Establishment in Culture of "Normal" Rodent Fibroblast Cell Lines
|author = Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller
|journal = PNAS
|year = 1983
|volume = 80
, 4354-4358
}}</ref> commonly introduced through [[SV40|simian virus 40]] (SV-40).
In terms of multi-cellular organisms, immortality may not be a desirable condition, as the main controls over cancer are the apoptotic mechanisms<ref>{{cite journal
| title = Predominant suppression of apoptosome by inhibitor of apoptosis protein in non-small cell lung cancer H460 cells: therapeutic effect of a novel polyarginine-conjugated Smac peptide
| author = Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller
| journal = Cancer Res.
| month = February
| year = 2003
| volume = 63
| number = 19
| pmid = 12591734
}}</ref>.
==Bacteria==
[[Bacteria]] can be said to be biologically immortal, but only as a [[colony (biology)|colony]]. An individual bacterium can easily die. The two daughter bacteria resulting from [[cell division]] of a parent bacterium can be regarded as unique individuals or as members of a [[biology|biologically]] "immortal" colony. The two daughter cells can be regarded as "[[rejuvenation (aging)|rejuvenated]]" copies of the parent cell because damaged [[macromolecule]]s have been split between the two cells and diluted. In the same way [[stem cell]]s and [[gamete]]s can be regarded as "immortal".
==Hydra==
[[Hydra (genus)|Hydra]]s are a genus of simple, fresh-water animals possessing radial symmetry and no post-mitotic cells. The fact that all cells continually divide allows defects and toxins to be "diluted-away". It has been suggested that hydras do not undergo [[senescence]] (aging), and so are biologically immortal<ref>http://www.ucihs.uci.edu/biochem/steele/PDFs/Hydra_senescence_paper.pdf</ref>.
==Life extensionists==
Some [[life extension]]ists, such as those who practice [[cryonics]], have the hope that humans may someday become biologically immortal. This would not be the same as literal [[immortality]], since people can always be murdered or die in accidents. ([[Mind uploading]], however, could allow literal immortality in a sense, by uploading backups into cloned or artificial bodies after an accident. See [[Mind_uploading#Mind_uploading_in_science_fiction|Mind uploading in science fiction]].)
[[Nanotechnology]], and specifically of [[nanomedicine]], have recently increased awareness of the possibilities for biological immortality in humans. A study published in Physiological and Biochemical Zoology in 2005 indicates that biological immortality may exist in humans at a late stage in life: "the exponential increase in age-specific death rate seemed to slow down considerably, if not cease."<ref>http://darwin.bio.uci.edu/~mueller/pdf/PBZ%2005.pdf</ref>
The [[gerontologist|biogerontologist]] [[Aubrey de Grey]] of [[University of Cambridge|Cambridge University]] has proposed that damage to [[macromolecule]]s, [[cell (biology)|cell]]s, [[biological tissue|tissue]]s and [[organ (anatomy)|organ]]s could be repaired by advanced [[biotechnology]]. He calls his project [[Strategies for Engineered Negligible Senescence|SENS]] (Strategies for Engineered Negligible Senescence). Dr. de Grey has created the [[Methuselah Mouse Prize]] to award money to researchers who can significantly extend the lifespan of, or [[rejuvenation (aging)|rejuvenate]] mice. It is his hope that if a monetary reward is offered, it will increase the likelihood of mice being rendered extremely, unnaturally long-lived by science, and that such a feat will inspire research into replicating this achievement in humans which may spark a "''buy-in''" with many people willing to pay large amounts of money for the benefits of such research.
==See also==
*[[DNA damage theory of aging]]
*[[Aging Research Centre]]
*[[American Academy of Anti-Aging Medicine]]
*[[Strategies for Engineered Negligible Senescence]] (SENS)
*[[Immortality Institute]]
*[[Hayflick limit]]
*[[Hydra (genus)|Hydra]]
*[[Life extension]]
*[[Maximum lifespan]]
*[[Methuselah Mouse Prize]]
*[[Senescence]]
==References==
<references />
* [[James L. Halperin]]. ''The First Immortal'', Del Rey, 1998. ISBN 0-345-42092-6
* [[Robert Ettinger]]. ''The Prospect of Immortality'', Ria University Press, 2005. ISBN 0-9743472-3-X
* Dr. R. Michael Perry. ''Forever For All: Moral Philosophy, Cryonics, and the Scientific Prospects for Immortality'', Universal Publishers, 2001. ISBN 1-58112-724-3
* *Martinez, D.E. (1998) "Mortality patterns suggest lack of senescence in hydra." ''Experimental Gerontology'' 1998 May;33(3):217-225. [http://www.ucihs.uci.edu/biochem/steele/PDFs/Hydra_senescence_paper.pdf Full text.]
==External links==
* [http://www.benford-rose.com/bioimm-atlanta05.htm Biological Immortality] Slide show by Michael R. Rose
* [http://www.benbest.com/lifeext/aging.html#senescence Cellular Senscence and Apoptosis in Aging]
*[http://websites.afar.org/site/PageServer?pagename=IA_b_sene_home Cellular Senescence Information Center]
* [http://www.genomicsproteomics.com/index.aspx?ID=69329 Geron Announces Launch of Telomerase-Immortalized Cell Line] [[Geron Corporation]]
* [http://darwin.bio.uci.edu/~mueller/pdf/PBZ%2005.pdf Late Life: A New Frontier for Physiology] study indicates biological immortality in humans late in life
* [http://longevity-science.org/Betterhumans-2004.pdf No Limit to Lifespan if We're Machines] (pdf) - ''Betterhumans'', August 26, 2004
* [http://www.firstimmortal.com/ The First Immortal]: free download
* [http://www.cryonics.org/book1.html The Prospect of Immortality]: free download
[[Category:Aging]]
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