Search Details

Word: hayflick (lookup in dictionary) (lookup stats)
Dates: during 1990-1999
Sort By: most recent first (reverse)


Usage:

Eight years ago, scientists discovered that the tips of chromosomes in tissue cells shorten each time the cells replicate--until a point is reached where the cells stop dividing altogether. That point, called the Hayflick limit, comes after about 50 replications, and may be at the heart of the process we call aging...

Author: /time Magazine | Title: On the Horizon | 1/11/1999 | See Source »

...reactivate the enzyme that lengthens the tips, known as telomeres. Last January they succeeded: Andrea Bodnar and colleagues from the Geron Corp. in Menlo Park, Calif., activated the enzyme telomerase, extended the telomeres and lengthened the life-span of cells in culture by at least 20 divisions past the Hayflick limit. In November, Geron scored another first by reconstituting the telomeres of embryonic stem cells, which are renowned for their ability to turn into any type of cell, making it theoretically possible to rejuvenate parts of any organ with a simple injection...

Author: /time Magazine | Title: On the Horizon | 1/11/1999 | See Source »

Although he made history when he discovered the limits on cell replication in the lab, Hayflick left a question unanswered: why the cells die. In the years following his work, biologists mapping human chromosomes looked for a gene that enforced cellular mortality, but found nothing. One thing that did catch their eyes, however, was a small area at the tip of chromosomes that had no discernible purpose. Dubbed a telomere, the sequence of nucleic acids did not appear to code for any traits. Instead it resembled nothing so much as the plastic cuff at the end of a shoelace that...

Author: /time Magazine | Title: CAN WE STAY YOUNG? | 11/25/1996 | See Source »

...telomeres weren't completely inert. One thing they almost always appeared to do was grow shorter. Each time a cell divided, the daughter cells it produced had a little less telomere to play with. Finally, when the cell reached its Hayflick limit of 100 or so replications, the telomere was reduced to a mere nub. At that point, the cell quit replicating. Once it did, researchers theorized, the genes previously covered by the telomere became exposed and active, producing proteins that triggered the tissue deterioration associated with aging...

Author: /time Magazine | Title: CAN WE STAY YOUNG? | 11/25/1996 | See Source »

...moment telomerase was discovered," says Hayflick, "it was clear that for immortal cells at least, this was a way to circumvent the inevitability of aging and dying." Telomerase has now been found in the precursor cells that give rise to human eggs, in the stem cells that give rise to blood cells and in up to 95% of cancer cells...

Author: /time Magazine | Title: CAN WE STAY YOUNG? | 11/25/1996 | See Source »

| 1 | 2 | 3 | Next