Very low levels

A severe challenge to the idea that mitochondrial DNA mutations play a major role in the aging process in mammals is that clear loss-of-function mutations accumulate only to very low levels (under 1% of total) in almost any tissue, even by very old age. Their accumulation is punctate: some cells become nearly devoid of wild-type mitochondrial DNA and exhibit no activity for the partly mitochondrially encoded enzyme cytochrome c oxidase. Such cells accumulate in number with aging, suggesting that they survive indefinitely, which is itself paradoxical....

7p research12 01-06-2013 27 3   Download

Undifferentiated human promyelocytic leukemia HL-60 cells show little or no superoxide production, but generate a very low O2 – concentration upon incubation with all-trans-retinoic acid (ATRA). Its production reaches a maximum within 20 h, and thereafter is maintained at an almost con-stant level. The differentiated cells show phorbol 12-myri-state 13-acetate (PMA)-stimulatedNADPHoxidase activity consistent with the amount of gp91phox(phagocytic oxid-ase) expressed in the plasma membrane.

8p research12 29-04-2013 35 5   Download

The orphan receptors, Rev-erba and Rev-erbb, are members of the nuclear receptor superfamily and specifically repress apolipoprotein CIII (apoCIII) gene expression in rats and humans. Moreover, Rev-erbanull mutant mice have elevated very low density lipoprotein triacylglycerol and apoCIII levels.

12p media19 04-03-2013 33 2   Download