Re: Carbon-14

["Bjorn Cedervall" <bcradsafers@hotmail.com>]

>You have to be careful when dealing with retention times of C-14. In >what 
>form was it taken into the body? C-14 is used as a tracer and can >be bound 
>to many tissues types. The retention times will be dependent >upon the 
>chemical form.
-----
The retention time is most probably also related to:
1. The individual's physical and metabolic activity. -A pathway that leads 
to the formation of carboxyl groups may help to ultimately get rid of the 
carbon (including via exhaled CO2) - that is increased carbon turnover 
including the C14.
2. The relative amount of fatty tissue the individual has (and therefore - 
yes the biochemical form of the intake - and stored form will be important).
3. Whether the individual has been starved or not in some form before the 
intake.

I would expect that increased physical activity could decrease the 
biological halflife - and perhaps more so if it is paralleled by an 
appropriate diet (balance carbohydrate, protein and fats) that takes into 
account what may be an assumed major biochemical form in the body.
A wild guess from my side would be that many people could cut their 
biological halflife by say at least 25 % by just changing from a passive 
life to a daily "jogging initiative". (any health benefits would for most 
cases be expected to come from that part - not the lowered C14 levels)

Reasonably the litterature contains compartment models with rate constants 
that can be used for the corresponding calculations. I see systems of 
differential equations where the physical activity would result in shifts in 
the rate constants for transfers between various tissues (not the enzymatic 
rate constants - on that level it is probably only a matter of induced 
activity or not).

All this would make sense to me considering a bunch of biochemistry reading 
I did long ago. Please indicate if you think that these thoughts lack in 
logic or could be improved by actual data.

Bjorn Cedervall   bcradsafers@hotmail.com
PS.
Note that since C14 occurs naturally - we are normally in a steady state 
situation. Any extra C14 taken in (food, injection, or inhalation.) would 
create a pulse on top of the steady state level.


_________________________________________________________________________
Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com.

Share information about yourself, create your own public profile at 
http://profiles.msn.com.

************************************************************************
The RADSAFE Frequently Asked Questions list, archives and subscription
information can be accessed at http://www.ehs.uiuc.edu/~rad/radsafe.html