Biological immortality (sometimes referred to as bio-indefinite mortality) is a state in which the rate of mortality from senescence is stable or decreasing, thus decoupling it from chronological age. Various unicellular and multicellular species, including some vertebrates, achieve this state either throughout their existence or after living long enough. A biologically immortal living being can still die from means other than senescence, such as through injury, poison, disease, predation, lack of available resources, or changes to environment.

This definition of immortality has been challenged in the 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, an idea referred to as the late-life mortality plateau. The rate of mortality may cease to increase in old age, but in most cases that rate is typically very high.[2]

The term is also used by biologists béo describe cells date calculator age
are not subject phệ the Hayflick limit on how many times they can divide .

Cell lines[edit]

Biologists chose the thế giới ” immortal ” mập designate cells that are not subject béo the Hayflick limit, the point at which cells can no longer divide due phệ DNA damage or shortened telomeres. Prior lớn Leonard Hayflick ‘ s theory, Alexis Carrel hypothesized that all normal somatic cells were immortal. [ ba ]The term ” immortalization ” was first applied bự cancer cells that expressed the telomere-lengthening enzyme telomerase, & thereby avoided apoptosis — i. e. cell death caused by intracellular mechanisms. Among the most commonly used cell lines are HeLa và Jurkat, both of which are immortalized cancer cell lines. HeLa cells originated from a sample of cervical cancer taken from Henrietta Lacks in 1951. [ bốn ] Thes e cells have been và still are widely used in biological research such as creation of the polio vaccine, [ 5 ] sex hooc môn steroid research, [ 6 ] và cell metabolism. [ 7 ] Embryonic stem cells và germ cells have also been described as immortal. [ tám ] [ 9 ]Immortal cell lines of cancer cells can be created by induction of oncogenes or loss of tumor suppressor genes. One way béo induce immortality is through viral – mediated induction of the large T-antigen, [ 10 ] commonly introduced through simian vi khuẩn 40 ( SV-40 ). [ 11 ]

Organisms[edit]

According Khủng the Animal Aging và Longevity Database, the danh sách of animals with negligible aging ( along with estimated longevity in the wild ) includes : [ 12 ]

In 2018, scientists working for Calico, a company owned by Alphabet, published a paper in the journal eLife which presents possible evidence that Heterocephalus glaber (Naked mole rat) do not face increased mortality risk due to aging.[13][14][15]

Bacteria và some yeast[edit]

Many unicellular organisms age : as phút giây passes, they divide more slowly & ultimately die. Asymmetrically dividing bacteria & yeast also age. However, symmetrically dividing bacteria và yeast can be biologically immortal under ideal growing conditions. [ 16 ] In these conditions, when a cell splits symmetrically lớn produce two daughter cells, the process of cell division can restore the cell phệ a youthful state. However, if the parent asymmetrically buds off a daughter only the daughter is reset lớn the youthful state — the parent isn’t restored & will go on mập age & die. In a similar manner stem cells & gametes can be regarded as ” immortal ” .

Hydra[edit]

HydraHydras are a genus of the Cnidaria phylum. All cnidarians can regenerate, allowing them phệ recover from injury & phệ reproduce asexually. Hydras are simple, freshwater animals possessing radial symmetry và contain post – mitotic cells ( cells that will chưa bao giờ divide again ) only in the extremities. [ 17 ] All hydra cells continually divide. [ 18 ] It has been suggested that hydras do not undergo senescence, &, as such, are biologically immortal. In a four-year study, ba cohorts of hydra did not show an increase in mortality with age. It is possible that these animals live much longer, considering that they reach maturity in 5 Khủng 10 days. [ 19 ] However, this does not explain how hydras are subsequently able Khủng maintain telomere lengths .

Jellyfish[edit]

Turritopsis dohrnii, or Turritopsis nutricula, is a small (5 millimeters (0.20 in)) species of jellyfish that uses transdifferentiation to replenish cells after sexual reproduction. This cycle can repeat indefinitely, potentially rendering it biologically immortal. This organism originated in the Caribbean sea, but has now spread around the world.[citation needed] Key molecular mechanisms of its rejuvenation appear to involve DNA replication and repair, and stem cell renewal, according to a comparative genomics study.[20][21]

Similar cases include hydrozoan Laodicea undulata[22] and scyphozoan Aurelia sp.1.[23]

Lobsters[edit]

Research suggests that lobsters may not slow xuống dốc, weaken, or thất bại fertility with age, & that older lobsters may be more fertile than younger lobsters. This does not however make them immortal in the traditional sense, as they are significantly more likely phệ die at a shell moult the older they get ( as detailed below ) .Their longevity may be due béo telomerase, an enzyme that repairs long repetitive sections of DNA sequences at the ends of chromosomes, referred bự as telomeres. Telomerase is expressed by most vertebrates during embryonic stages but is generally absent from adult stages of life. [ 24 ] However, unlike vertebrates, lobsters express telomerase as adults through most tissue, which has been suggested béo be related lớn their longevity. [ 25 ] [ 26 ] [ 27 ] Contrary bự popular belief, lobsters are not immortal. Lobsters grow by moulting which requires considerable energy, và the larger the shell the more energy is required. [ 28 ] Eventually, the lobster will die from exhaustion during a moult. Older lobsters are also known lớn stop moulting, which means that the shell will eventually become damaged, infected, or fall apart và they die. [ 29 ] The European lobster has an average life span of 31 years for males và 54 years for females .

Planarian flatworms[edit]

Polycelis felina, a freshwater planarian, a freshwater planarianPlanarian flatworms have both sexually và asexually reproducing types. Studies on genus Schmidtea mediterranea suggest these planarians appear mập regenerate ( i. e. heal ) indefinitely, & asexual individuals have an ” apparently limitless [ telomere ] regenerative capacity fueled by a population of highly proliferative adult stem cells “. ” Both asexual và sexual animals display age-related decline in telomere length ; however, asexual animals are able béo maintain telomere lengths somatically ( i. e. during reproduction by fission or when regeneration is induced by amputation ), whereas sexual animals restore telomeres by extension during sexual reproduction or during embryogenesis lượt thích other sexual species. Homeostatic telomerase activity observed in both asexual & sexual animals is not sufficient lớn maintain telomere length, whereas the increased activity in regenerating asexuals is sufficient phệ renew telomere length … ” [ 30 ]For sexually reproducing planaria : ” the lifespan of individual planarian can be as long as ba years, likely due Khủng the ability of neoblasts phệ constantly replace aging cells “. Whereas for asexually reproducing planaria : ” individual animals in clonal lines of some planarian species replicating by fission have been maintained for kết thúc 15 years “. [ 31 ] [ 32 ]

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