Guy Brown wrote:
> As others have noted the paper on a revised nomenclature
> is mostly clear, well written and well intended.
Thanks.
> I have only a few comments:
>> 1. Why are co-response and co-control coefficients to be
> defined as fundamental symbols in MCA on a par with control
> and eleasticity coefficients?
> I do not think that this can be seriously justified.
We do not define them as fundamental symbols, but clearly as derived
symbols. The point is, however, that this is a nomenclature document,
not a minimalist treatment of MCA (in which, I agree,
co-control and co-response coefficients would have no place). It
seems that other workers besides ourselves also find these
coefficients useful for analysing regulation - David's group uses
them routinely, as does Reinhart (see the Schuster-Rapoport book).
There is clearly a need here for consensus on which symbols to use.
Note that concepts such as regulatory potential (which I at least
have found useful in my own thinking) has not made it into the
recommendations.
> 4. In the definition of control coefficient the fractional change
> d ln p rather than the absolute change in p is used. Will this
> not cause C to be undefined where p is initially zero?
Yes, but this is not only a problem for the definition of control
coefficients but for all coefficients defined as dln x/dln y. If it
is of fundamental importance that coefficients be defined when y = 0,
then it follows that we must define all of them as unscaled
derivatives. In our opinion, definability (?) when y = 0 is of little
importance in practice. It is always possible to consider the value
of any coefficient in the limit when y -> 0. What do you all think
about this?
Guy, I'll get to your other comments later.
Best regards
Jannie
Prof. Jannie Hofmeyr Tel: +27 21 808 3039
Dept. of Biochemistry Fax: +27 21 808 3022
University of Stellenbosch e-mail: jhsh at maties.sun.ac.za
Stellenbosch 7600
South Africa
