higher ploidy and mitochondrial maintenance hypothesis

Magnus Lynch mdl24 at cam.ac.uk
Fri Aug 17 14:03:28 EST 2001

Your suggested mechanism may or may not be correct, but even if it is
correct does it have any role in the aging process? The following abstracts
suggests that age related changes in the liver are of secondary rather than
primary importance in aging:

Hepatology 1997 Feb;25(2):421-5 Related Articles, Books, LinkOut
Assessment of the longevity of the liver using a rat transplant model.
Sakai Y, Zhong R, Garcia B, Zhu L, Wall WJ.
Department of Surgery, University of Western Ontario, London, Canada.

To assess the longevity of the liver, arterialized, orthotopic liver grafts
were performed using syngeneic male BN/BiRij rats. Young (5-month-old)
livers were transplanted into 5-month-old recipients (group I, n = 27), and
old (28-month-old) livers were transplanted into 5-month-old rats (group II,
n = 28). Recipient survival after transplantation was similar in both
groups. The average age of the livers at the time of death was 16.7 months
in group I and 39.1 months in group II. Four of the livers in group II
survived for more than 4 years (48.1 to 52.4 months). Early deaths (less
than 1 year) after transplantation were most commonly caused by biliary
obstruction and cholangitis in both groups. Late deaths (more than 1 year)
after grafting were mainly from heart failure or tumors. None of the animals
died of liver failure or liver disease. Weight gain in the rats, total serum
protein levels, and alanine transaminase levels after transplantation did
not differ significantly between the two groups. There was a trend for the
histological features of aging of the liver-fibrosis, bile duct
proliferation, and pigment deposition-to become more prevalent as the livers
became very old (mean age, 46 months). Nevertheless, typical aging changes,
as individual findings, were absent in nearly half of the oldest organs. The
alterations in morphology had no apparent effect on the ability of the
livers to sustain the lives of the recipients. The liver of the BN/BiRij rat
was capable of surviving far beyond the maximum life span of BN/BiRij rats,
and rats in general. It did not become diseased in the process.


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