On  Fri, 6 Feb 2004 16:36:06 +0000 (UTC)

Tim Tyler wrote:>> >Kola9809  wrote:
>
>> >> Pineal gland cells produce melatonin in response to
day-night cycles.
>The
>> >> generally accepted mechanism is that the photic stimuli
(which do not
>> >> per se activate any gene) are received in retinal
neurons, converted 
>> >> into electrical signals that are processed (and alternatively 
>> >> transformed into chemical-electrical signals) in a neural circuit 
>> >> involving neurons of the superior cervical ganglion, 
>> >> intermediolateral nucleus of the upper thoracal spinal cord, 
>> >> hypothalamic paraventricular nucleus, suprachiasmatic nucleus,
>> >> until it reaches the pineal gland cells where the
chemical output of
>> >> the circuit activates genes involved in the synthesis of
melatonin. 
>> >> 
>> >> My question is: Since the activation of those genes is
not a random 
>> >> process, it requires information. Where does that
information come from?
>> >
>> >>From the environment.
>> 
>> If that information is the environmental stimulus (which you seem to imply)
>> skin cells that are in direct contact with it would produce melatonin as
>well.
>> But, as you know, they can not while pineal cells with the same set of
>genes,
>> do? And the reason is that only (!) pineal cells receive the information on
>the
>> stimulus (but not the stimulus itself).
>>   
>> Nevertheless, you may be be right and I - wrong. But, could you elaborate.
>> 
>> As all we know, the  pineal cells do not receive the stimulus (day-night
>> cycles); they are invariably in darkness. That stimulus is received by
>retinal
>> neurons (they, nevertheless do not produce melatonin), which code it in the
>> form of specific electrical signals (this is the information on the nature
>of
>> the stimulus). But this information still is not
"intelligible" to genes.
>This
>> is why  it is  once more processed in the complex melatonin  circuit, which
>> releases a chemical signal that via signal transduction pathways affects
>the
>> expression of genes responsible for melatonin synthesis in pineal cells.
>> 
>> I'm openminded to listen and change my opinion.
>
>This is like me saying that your friend's voice on the telephone
>comes from your friend - and then you arguing that it is actually
>coming from the speaker in the telephone handset.
>-- 

Let's get serious. I am very interested in  discussing this topic. Do you
really think that information from the environment regulates the function of
our genes ? 

If information implies a sender and a receiver, do you believe that the
environment is the sender and genes are the receivers of environmental
information?
Can you substantiate this Lamarckian concept?

As I have pointed out earlier, I see this differently. A piece of information
from the environment would be used by genes only if it is "intelligible" to
them, but the circadian cycle (the sun light or the lack of it) is not. Neither
the sun light nor the darkness are able to activate/inactivate any gene. This
is the reason why the stimulus is received and converted into an electrical
signal (=information) and further processed in the melatonin neural circuit
which generates the chemical signal (=information) that is intelligible to the
gene as the "receiver". It is not the external stimulus per se, but the
chemical output (=information) generated by  processing of the stimulus in the
neural circuit that via the respective transduction pathways reaches the genes
responsible for the synthesis of melatonin, that is intelligible to (i.e.
contains information for) activating those genes. This information generated in
the neural circuit is processing-dependent, hence epigenetic; it does not exist
but it is computationally generated in response to external/internal stimuli.
 
Let me try an analogy from linguistics (my hobby). When I spell the Messapian
(an ancient indoeuropean language spoken in southern Italy more than 2 thousand
years ago) word "bila" it conveys no information to you as a
receiver, although
it did for the Messapians. Now, I make it intelligible to you by translating it
into the English word "daughter". Similarly, the neural circuits
"translate"
the external stimulus, which is "senseless" to genes, into a specific
epigenetic information for their activation/inactivation.

Do you agree? 
I wait for your input.
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