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Biological immortality is the absence of a sustained increase in rate of mortality as a function of chronological age. A cell or organism that does not experience, or at some future point will cease, aging, is biologically immortal. However this definition of immortality was challenged in the new "Handbook of the Biology of Aging",[1] because the increase in rate of mortality as a function of chronological age may be negligible at extremely old ages (late-life mortality plateau). But even though the rate of mortality ceases to increase in old age, those rates are very high[2] (e.g., 50% chance of surviving another year at 110 or 115 years of age).

No actual organism or individual cell is inviolably immortal (i.e. "invincible" or "indestructible"). Any real living object enjoying biological immortality would still be able to die, for example, upon receiving sufficient injury or otherwise having its body destroyed or diseased.

Contents

Cell lines

Biologists have chosen the word immortal to designate cells that are not limited by the Hayflick limit (where cells no longer divide because of DNA damage or shortened telomeres). (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, both of which are immortalized cancer cell lines. Normal stem cells and germ cells can also be said to be immortal (when we refer to the cell line).

Immortal cell lines of cancer cells can be created by induction of oncogenes or loss of tumor suppressor genes. One way to induce immortality is through viral-mediated induction of the large T-antigen,[3] commonly introduced through 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[4].

Bacteria

Bacteria are said to be biologically immortal, but only as a 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 biologically "immortal" colony. The two daughter cells can be regarded as "rejuvenated" copies of the parent cell because damaged macromolecules have been split between the two cells and diluted. In the same way stem cells and gametes can be regarded as "immortal".

Hydra

Hydras 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 as such are biologically immortal[5]. However, this does not explain how hydras are consequently able to maintain telomere lengths.

Jellyfish

Turritopsis nutricula is a small (5 mm or 0.2 in) species of jellyfish which uses transdifferentiation to replenish cells after sexual reproduction. This cycle can repeat indefinitely, rendering it biologically immortal. It originates from the Caribbean sea, but has now spread around the world.

Life extensionists

Some life extensionists, 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 humans are still susceptible to death through external circumstances.

See also

References

  1. ^ Masoro, E.J.; Austad S.N. (eds.) (2006). Handbook of the Biology of Aging (Sixth ed.). San Diego, CA, USA: Academic Press. ISBN 0-12-088387-2. 
  2. ^ Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller (Nov-Dec 2005). "Late life: a new frontier for physiology". Physiological And Biochemical Zoology 78 (6): 869–878. doi:10.1086/498179. PMID 16228927. 
  3. ^ Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller (1983). "Expression of the Large T Protein of Polyoma Virus Promotes the Establishment in Culture of "Normal" Rodent Fibroblast Cell Lines". PNAS 80 , 4354-4358. 
  4. ^ Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller (February 2003). "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". Cancer Res. 63 (19). PMID 12591734. 
  5. ^ http://www.ucihs.uci.edu/biochem/steele/PDFs/Hydra_senescence_paper.pdf
  • 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. Full text.

External links


Biological immortality is the absence of a sustained increase in rate of mortality as a function of chronological age. A cell or organism that does not age, or which at some point in its life will cease to age, is one which is deemed to be biologically immortal. However, this definition of immortality has been challenged in the new "Handbook of the Biology of Aging",[1] because the increase in rate of mortality as a function of chronological age may be negligible at extremely old ages (late-life mortality plateau). But even though the rate of mortality ceases to increase in old age, those rates are very high[2] (e.g., 50% chance of surviving another year at 110 or 115 years of age).

No actual organism or individual cell is inviolably immortal (i.e. "invincible" or "indestructible"). Any real living object enjoying biological immortality would still be able to die, for example, upon receiving sufficient injury or otherwise having its body destroyed or diseased.

Contents

Cell lines

Biologists have chosen the word immortal to designate cells that are not limited by the Hayflick limit (where cells no longer divide because of DNA damage or shortened telomeres). (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, both of which are immortalized cancer cell lines. Normal stem cells and germ cells can also be said to be immortal (when humans refer to the cell line).

Immortal cell lines of cancer cells can be created by induction of oncogenes or loss of tumor suppressor genes. One way to induce immortality is through viral-mediated induction of the large T-antigen,[3] commonly introduced through 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[4].

Tardigrades

Tardigrades, otherwise known as "water bears" are highly resilient microscopic animals. They have indefinite senescence; moreover, unlike bacteria, they are quite difficult to destroy. A current mission is planned by the Russian Space Administration to launch water bears at Phobos to study the scientific theory of panspermia.

Bacteria

Bacteria are said to be biologically immortal, but only as a 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 biologically "immortal" colony. The two daughter cells can be regarded as "rejuvenated" copies of the parent cell because damaged macromolecules have been split between the two cells and diluted. In the same way stem cells and gametes can be regarded as "immortal".

Hydra

Hydras 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 as such are biologically immortal[5]. However, this does not explain how hydras are consequently able to maintain telomere lengths.

Jellyfish

Turritopsis nutricula is a small (5 mm or 0.2 in) species of jellyfish which uses transdifferentiation to replenish cells after sexual reproduction. This cycle can repeat indefinitely, potentially rendering it biologically immortal. It originates from the Caribbean sea, but has now spread around the world.

Life extensionists

Some life extensionists, 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 humans are still susceptible to death through external circumstances.

Biogerontologist Marios Kyriazis suggested that biological immortality in humans is an inevitable consequence of natural evolution. His ELPIs (Extreme Lifespans through Perpetual-equalising Interventions) theory proposes that the ability to attain indefinite lifespans is inherent in human biology, and that there will come a time when humans will continue to develop their intelligence and sophistication by living indefinitely, rather through Darwinian evolution.

See also

References

  1. ^ Masoro, E.J.; Austad S.N. (eds.) (2006). Handbook of the Biology of Aging (Sixth ed.). San Diego, CA, USA: Academic Press. ISBN 0-12-088387-2. 
  2. ^ Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller (Nov-Dec 2005). [Expression error: Unexpected < operator "Late life: a new frontier for physiology"]. Physiological and Biochemical Zoology 78 (6): 869–878. doi:10.1086/498179. PMID 16228927. 
  3. ^ Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller (1983). [Expression error: Unexpected < operator "Expression of the Large T Protein of Polyoma Virus Promotes the Establishment in Culture of "Normal" Rodent Fibroblast Cell Lines"]. PNAS 80 , 4354-4358. 
  4. ^ Michael R. Rose; Casandra L. Rauser; Laurence D. Mueller (February 2003). [Expression error: Unexpected < operator "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"]. Cancer Res. 63 (19): 831–7. PMID 12591734. 
  5. ^ http://www.ucihs.uci.edu/biochem/steele/PDFs/Hydra_senescence_paper.pdf

External links








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