Re: AAT Questions...
Gerrit Hanenburg (ghanenbu@inter.nl.net)
Mon, 21 Aug 1995 23:37:46 GMT
Elaine Morgan <Elaine@desco.demon.co.uk> wrote:
>Could you please tell me more about the kind of active transport
>required to excrete a substance against a gradient?
If the salt concentration on the outside of the cell is higher than inside it
cannot excrete more salt by diffusion.It can only be done by a pump
mechanism.Such a pump may consist of a transmembral protein complex which
functions as a one way channel or a mobile carrier that switches sides.
These contragradient biopumps or known to use ATP.
For the details you will have to resort to the literature on molecular
biology.
>You say : "As far as I know there is not a trace of a "scar" of
>such inside-outside transport in the human eccrine sweat gland."
> Would I be right in thinking that one indication that this kind of
>active transport was taking place would be the need to consume energy?
>and an indication that such consumption of energy had taken place
>after thermoregulatory sweating?
The use of energy would have to be associated with increasing osmolarity of
sweat on the way out and preferably independent of thermoregulatory sweating.
(It would also be nice if this were associated with the intake of excess
salt.)
>Quote from Weiner & Hellman on human thermoregulatory sweating:
>"The only change, and it is a notable one, found by Shelley and Mescon
>(1952) in association with glandular activity was reduction, and in
>some cells, a disappearance, of glycogen - an effect inhibited by
>atropine. After recovery from the effects of the heat there was a
>restoration of the cellular glycogen. These changes were in fact noted
>earlier by Gualdi and Baldino (1930) and by Yuyama (1935). It is clear
>that glycogen depletion is closely related to glandular activity" ...
This shows that glycogen is broken down and probably used as an energy
source,but it doesn't show you for which activities it is used.If the
breakdown of glycogen were somehow associated with an increase in the
osmolarity of sweat this would be a more convincing indication of active
contragradient transport.
>At that date (1959) no investigation of the glycogen content of eccrine
>glands other than those in man had been made. If I am right in
>thinking (along with Montagna) that our non-volar eccrine glands had a
>different evolutionary history from those on the pads of quadrupeds and
>on our own palms, there should be a distinction in this regard , as
>well as in the factor which activates them (emotion versus temperature
>change) between our volar and non-volar eccrine glands.
>Can you tell me whether there is any difference between the two types
>either in (a) degree of salt retention or (b) depletion of glycogen?
(a) not to my knowledge and (b) idem.
Gerrit.
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