On Sat, 7 Feb 2004 05:52:56 +0000 (UTC),
[email protected] (CNCabej)
wrote:
>On Fri, 6 Feb 2004 16:36:06 +0000 (UTC)
>
>Tim Tyler wrote:>> >Kola9809 <
[email protected]> 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.
>
I still think that "information translation" is not a proper way of looking at the situation.
Light entering the eye causes genes to be expressed in specific cells. There are a lot of
intermediate steps, but there is a demonstrable chain of cause-and-effect events that can be
described linking stimulus to response. It is not necessary to talk in terms of information
generation, merely in terms of "event A causes event B causes event C causes event D causes .....
causes event Z. Light in a rod or cone cell is translated into electrical potential, but that
involves a whole series of intermediate steps. Changes in electrical potential in rod and cone cells
in the retina cause release of synaptic transmitter onto melatonin secreting cells in the pineal,
but that involves a whole series of intermediate steps. Synaptic transmitter binding to receptors on
melatonin secreting cells in the pineal activate genes in the cell nucleus, but that involves a
whole series of intermediate steps.
The problem is one of cell physiology, not of information translation.