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MORTAL NORMAL CELLS. “By mid century the immortality of cancer cells was demonstrated in vitro, followed by the finding that, contrary to prevailing belief, cultured normal cells are mortal.” https://lnkd.in/esfPTAR View in LinkedIn

TUMOR IMMORTALITY. “Most cancer cell populations can be distinguished from normal cells by a progressive acquisition of properties that includes immortality. This was first demonstrated in the early part of the twentieth century by the finding that rodent tumours could be serially transplanted indefinitely.” https://lnkd.in/esfPTAR View in LinkedIn

REPLICOMETER. “Forty years ago we showed that cell mortality and immortality are inextricably linked to longevity determination, ageing and cancer. We suggested that a counting mechanism existed in normal cells and that has now been identified as telomere attrition. This replicometer, in combination with the discovery of the enzyme telomerase, has gone very far in explaining why most normal somatic cells have a finite capacity to replicate both in vivo and in vitro and how immortal cancer cells circumvent this inevitability.” https://lnkd.in/esfPTAR View in LinkedIn

BACTERIAL MORTALITY under some conditions."Bacteria were traditionally thought to have a symmetrical binary fission without a clear distinction between soma and germ-line, being thus considered as immortal biological entities. Yet it has been recently described that bacteria also undergo replicative aging (RA). That is, they exhibit finite replicative abilities under good conditions to growth." https://lnkd.in/esfYya9 View in LinkedIn

IMMORTAL BACTERIA. "Bacteria are said to be biologically immortal, but only at the level of the 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"." http://en.m.wikipedia.org/wiki/Biological_immortality View in LinkedIn

TELOMERE HYPOTHESIS. "A current hypothesis gaining prominence proposes that activation of the enzyme telomerase is necessary for cells to become immortal, or capable of proliferating indefinitely. The theory suggests that almost all cancer cells must attain immortality for progression to malignant states and, hence, require activation of telomerase.” https://lnkd.in/efS2ct4 View in LinkedIn

DISPOSABLE SOMA. "It was considered as “a priori” assumption that bacteria have not separation between soma and germ-line, and therefore under the paradigm of disposable soma theory, that is the soma is the only biological entity that would undergo senescence (aging, the bacteria could not age." https://lnkd.in/d8UFqbd View in LinkedIn

AUTUMN LEAVES seem best to illustrate Weismann’s worn out cell idea; after the wear and tear of a season of respiration, photosynthesis, disease and battering by the elements, leaf defects are multiple and very hard to repair: it is easier to jettison the leaf and start over again than to repair multiple cellular defects. View in LinkedIn

AGING AND SPECIES. “A more parsimonious evolutionary explanation for the existence of aging therefore requires an explanation that is based on individual fitness and selection, not on group selection. This was understood in the 1940's and 1950's by three evolutionary biologists, J.B.S. Haldane, Peter B. Medawar and George C. Williams, who realized that aging does not evolve for the "good of the species". http://www.nature.com/scitable/knowledge/library/the-evolution-of-aging-23651151 View in LinkedIn

FINITE CELL DIVISION."Death takes place because a worn-out tissue cannot forever renew itself, and because a capacity for increase by means of cell division is not everlasting but finite." (Weismann, 1881). http://protein.bio.msu.ru/biokhimiya/contents/v62/full/62111380.html View in LinkedIn