We, animals, have inbuilt metronomes with roughly 24 hour oscillation period, called circadian clocks. These clocks allow organisms to be in sync with the day / night cycle.
And it turnes out that human red blood cells have a circadian clock of their own! And it keeps on ticking when the blood is outside the body!
Peroxiredoxins comprise a conserved family of antioxidant proteins, and researchers checked for peroxiredoxin SO2/3 oxidation level in human red blood cell samples over a period of time. Amazingly, it oscillated with ∼24 hour period! What makes it particularly interesting is that human red blood cells have no nucleus, therefore no new mRNA can be produced. This means that the cycle is not transcription-driven.
There are several interesting peculiarities of this cycle.
First - it is temperature-sensitive! So... when you have a fever, do your red blood cells speed up their cycle and you get jet-lagged?!
Second - experiments reported in the paper are made using bulk of blood cells rather than on the single cell level. Observed oscillations suggest that cells are somehow synchronized. How? Is it something in the blood? Can we influence this synchronization? Can we re-set the clock?
All this calls for one simple experiment. Take a blood sample in Europe and fly it to the US and check how is it doing there. Is it jet-lagged? Can it adjust?
O'Neill JS, & Reddy AB (2011). Circadian clocks in human red blood cells. Nature, 469 (7331), 498-503 PMID: 21270888