Epigenetic information for gene expression (Was: Question)

Discussion in 'Health and medical' started by Cncabej, Feb 10, 2004.

  1. Cncabej

    Cncabej Guest

    On Sun. 8 Feb 2004 00:05:30 + 0000 (UTC) r norman wrote: On Sat. 7 Feb 2004 0:52:56 + 000 (UTC),
    [email protected] (CNCabej) wrote:
    .......................................................................... ............
    >>As we well know, 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 ofspecific electrical signals
    (this is the information on the nature of the stimulus). But this information is no "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 expression of genes responsible for
    melatonin synthesis in pineal cells<<
    .......................................................................... .............
    >>It is not the external stimulus per se , but the chemical output
    (=information) generated by processing of the stimulusin the neural circuit that via the respective
    signal transduction pathways reaches the genes responsible for the synthesis of melatonin, which is
    intelligible to (i.e. contains informatio for) activating those genes. This information is processing-
    dependent, hence epigenetic; it does not exist but is computationally generated i response to
    external/internal stimuli.

    Let me try an analogy from linguistics (my hobby). When I spell Messapian (an ancient indoeuropean
    language spoken in southern Italy more than 2 thoussand years ago) the word "bila" it conveys no
    information to you as a receiver, although it did for the Messapians. Now, I make it inteligible to
    you by translating it into the English "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?<<
    ........................................................................... r n:

    >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-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 eventZ. Light in a rod or cone cell is translatedinto electrical potential, but that
    involves a whole series of intermediate steps. Changes in electrical potential inrod 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.<

    If I got it right, you argue that the fact that "a whole series of intermediate steps" are involved
    in the signal cascade from the external stimulus to genes, this fact per se, excludes the
    possibility of any information being transmitted via the cascade. Without the necessary explanation,
    this idea seems hardly defensible to me.

    Applying the same criterium to the process of gene expression, which also involves many
    "intermediate steps", would lead us to the conclusion that no genetic information is transmitted
    from genes to proteins, which is no less difficult to defend.

    You correctly describe those pathways as chains of events where "event A causes event B causes event
    C causes event D causes....causes event Z." where the effect of each element on the downstream
    element (secretion of hypothalamic TRH, e.g. stimulates the pituitary TSH, stimulates thyroid
    hormone, etc.) is determined by stereochemical and thermodynamical properties of the interacting
    molecules and of the environment.

    What takes place in the case of melatonin synthesis is different in an essential respect. The
    external stimulus per se is neutral to any known pathway in metazoans, it can't activate any
    specific gene. In order that it serve as a cue, the input on the stimulus must first be processed in
    the retinal neurons (a computational process), which codes it in the form of a specific pattern of
    electrical signals. But the "electrically coded" stimulus is nothing less than information on the
    stimulus. It is different from the stimulus itself in the same way that my name identifies me but is
    not identical with me.

    The information generated by processing the stimulus is not determined by the stimulus itself but by
    computational properties in which the stimulus is processed. That information is not stimulus-
    dependent but processing-dependent.

    The information contained in the electrical code is still "unintelligible" to genes in the meaning
    that it can't activate the signal transduction pathway for expression of melatonin genes. It must be
    further processed in the described complex neural circuit, which ultimately transforms it in a
    chemical signal that can activate that signal transduction pathway in all the "intermediate steps"
    you talk of. This ultimate chemical form that makes possible the expression of melatonin genes, is
    different from the stimulus itself; it is information on that stimulus that is generated (not
    preexisting) in the neural circuits. No melatonin genes can be expressed without this information.

    This processing of stimuli in the CNS is necessary not only for external stimuli, but for most of
    the internal stimuli, since because of the blood-brain barrier most of the chemical signals (protein
    hormones, growth factors and other secreted proteins) have no access to the CNS. It makes it
    possible for them than in response to the same internal stimuli to activate genes that are not
    expressed in other types of cells.
     
    Tags:


  2. R Norman

    R Norman Guest

    On Tue, 10 Feb 2004 00:14:46 +0000 (UTC), [email protected] (CNCabej)
    wrote:

    >On Sun. 8 Feb 2004 00:05:30 + 0000 (UTC) r norman wrote: On Sat. 7 Feb 2004 0:52:56 + 000 (UTC),
    >[email protected] (CNCabej) wrote:
    >.......................................................................... ............
    >>>As we well know, 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 ofspecific electrical signals
    >(this is the information on the nature of the stimulus). But this information is no "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 expression of genes responsible for
    >melatonin synthesis in pineal cells<<
    >.......................................................................... .............
    >>>It is not the external stimulus per se , but the chemical output
    >(=information) generated by processing of the stimulusin the neural circuit that via the respective
    >signal transduction pathways reaches the genes responsible for the synthesis of melatonin, which is
    >intelligible to (i.e. contains informatio for) activating those genes. This information is processing-
    >dependent, hence epigenetic; it does not exist but is computationally generated i response to
    >external/internal stimuli.
    >
    >Let me try an analogy from linguistics (my hobby). When I spell Messapian (an ancient indoeuropean
    >language spoken in southern Italy more than 2 thoussand years ago) the word "bila" it conveys no
    >information to you as a receiver, although it did for the Messapians. Now, I make it inteligible to
    >you by translating it into the English "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?<<
    >........................................................................... r n:
    >
    >>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-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 eventZ. Light in a rod or cone cell is translatedinto electrical potential, but that
    >involves a whole series of intermediate steps. Changes in electrical potential inrod 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.<
    >
    >If I got it right, you argue that the fact that "a whole series of intermediate steps" are involved
    >in the signal cascade from the external stimulus to genes, this fact per se, excludes the
    >possibility of any information being transmitted via the cascade. Without the necessary
    >explanation, this idea seems hardly defensible to me.
    >
    >Applying the same criterium to the process of gene expression, which also involves many
    >"intermediate steps", would lead us to the conclusion that no genetic information is transmitted
    >from genes to proteins, which is no less difficult to defend.
    >
    >You correctly describe those pathways as chains of events where "event A causes event B causes
    >event C causes event D causes....causes event Z." where the effect of each element on the
    >downstream element (secretion of hypothalamic TRH, e.g. stimulates the pituitary TSH, stimulates
    >thyroid hormone, etc.) is determined by stereochemical and thermodynamical properties of the
    >interacting molecules and of the environment.
    >
    >What takes place in the case of melatonin synthesis is different in an essential respect. The
    >external stimulus per se is neutral to any known pathway in metazoans, it can't activate any
    >specific gene. In order that it serve as a cue, the input on the stimulus must first be processed
    >in the retinal neurons (a computational process), which codes it in the form of a specific pattern
    >of electrical signals. But the "electrically coded" stimulus is nothing less than information on
    >the stimulus. It is different from the stimulus itself in the same way that my name identifies me
    >but is not identical with me.
    >
    >The information generated by processing the stimulus is not determined by the stimulus itself but
    >by computational properties in which the stimulus is processed. That information is not stimulus-
    >dependent but processing-dependent.
    >
    >
    >The information contained in the electrical code is still "unintelligible" to genes in the meaning
    >that it can't activate the signal transduction pathway for expression of melatonin genes. It must
    >be further processed in the described complex neural circuit, which ultimately transforms it in a
    >chemical signal that can activate that signal transduction pathway in all the "intermediate steps"
    >you talk of. This ultimate chemical form that makes possible the expression of melatonin genes, is
    >different from the stimulus itself; it is information on that stimulus that is generated (not
    >preexisting) in the neural circuits. No melatonin genes can be expressed without this information.
    >
    >This processing of stimuli in the CNS is necessary not only for external stimuli, but for most of
    >the internal stimuli, since because of the blood-brain barrier most of the chemical signals
    >(protein hormones, growth factors and other secreted proteins) have no access to the CNS. It makes
    >it possible for them than in response to the same internal stimuli to activate genes that are not
    >expressed in other types of cells.

    We seem to be talking at such cross purposes that we cannot understand each other. I find your
    discussion of the requirement for information processing (as in your final paragraph) to be
    essentially incomprehesible.

    I do not understand why you are making a simple situation very complicated. If you chill me for a
    substantial period of time, my thyroid gland secretes thyroxin. That process may also be associated
    with the transcription of genes coding for proteins in the thyroxin synthesis pathway. If you shine
    light into my eyes, it affects the way that my pineal gland secretes melatonin. That process may
    also be associated with the transcription of genes coding for proteins in the melatonin synthesis
    pathway. There is no conceptual difference. There is absolutely NOTHING in the nervous system that
    codes for "thyroxin" or for "melatonin" or for "transcribe this particular gene" or anything at all
    like that. All that happens is that a chemical binds to a receptor in the membrane of the thyroid or
    pineal gland cell and makes that cell "do its thing". That "thing" may involve gene transcription,
    or maybe not. Whatever, the stimulus simply "doesn't care" what the target cell does with the
    signal. The signal, in fact, doesn't carry any information other than "I have a message for you". It
    is completely up to the target cell to "know" how to respond.
     
  3. Cncabej

    Cncabej Guest

    On Wed, 11 Feb 2004 00:46:11 +0000 (UTC) r norman [email protected]_comcast.net wrote:

    N.C. wrote: ..............
    >>r n:
    >>
    >>>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-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 eventZ. 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.<
    >>

    >>If I got it right, you argue that the fact that "a whole series of
    >intermediate
    >>steps" are involved in the signal cascade from the external stimulus to
    >genes,
    >>this fact per se, excludes the possibility of any information being
    >transmitted
    >>via the cascade. Without the necessary explanation, this idea seems hardly defensible to me.
    >>
    >>Applying the same criterium to the process of gene expression, which also involves many
    >>"intermediate steps", would lead us to the conclusion that no genetic information is transmitted
    >>from genes to proteins, which is no less difficult to defend.
    >>
    >>You correctly describe those pathways as chains of events where "event A
    >causes
    >>event B causes event C causes event D causes....causes event Z." where the effect of each element
    >>on the downstream element (secretion of hypothalamic TRH, e.g. stimulates the pituitary TSH,
    >>stimulates thyroid hormone, etc.)
    >is
    >>determined by stereochemical and thermodynamical properties of the
    >interacting
    >>molecules and of the environment.
    >>
    >>What takes place in the case of melatonin synthesis is different in an essential respect. The
    >>external stimulus per se is neutral to any known
    >pathway
    >>in metazoans, it can't activate any specific gene. In order that it serve as
    >a
    >>cue, the input on the stimulus must first be processed in the retinal
    >neurons
    >>(a computational process), which codes it in the form of a specific pattern
    >of
    >>electrical signals. But the "electrically coded" stimulus is nothing less
    >than
    >>information on the stimulus. It is different from the stimulus itself in the same way that my name
    >>identifies me but is not identical with me.
    >>
    >>The information generated by processing the stimulus is not determined by
    >the
    >>stimulus itself but by computational properties in which the stimulus is processed. That
    >>information is not stimulus-dependent but
    >processing-dependent.
    >>
    >>
    >>The information contained in the electrical code is still "unintelligible"
    >to
    >>genes in the meaning that it can't activate the signal transduction pathway
    >for
    >>expression of melatonin genes. It must be further processed in the described complex neural
    >>circuit, which ultimately transforms it in a chemical signal that can activate that signal
    >>transduction pathway in all the "intermediate steps" you talk of. This ultimate chemical form that
    >>makes possible the expression of melatonin genes, is different from the stimulus itself; it is
    >>information on that stimulus that is generated (not preexisting) in the
    >neural
    >>circuits. No melatonin genes can be expressed without this information.
    >>
    >>This processing of stimuli in the CNS is necessary not only for external stimuli, but for most of
    >>the internal stimuli, since because of the
    >blood-brain
    >>barrier most of the chemical signals (protein hormones, growth factors and other secreted
    >>proteins) have no access to the CNS. It makes it possible for them than in response to the same
    >>internal stimuli to activate genes that
    >are
    >>not expressed in other types of cells.
    >
    >We seem to be talking at such cross purposes that we cannot understand each other. I find your
    >discussion of the requirement for information processing (as in your final paragraph) to be
    >essentially incomprehesible.
    >
    >I do not understand why you are making a simple situation very complicated. If you chill me for a
    >substantial period of time, my thyroid gland secretes thyroxin. That process may also be associated
    >with the transcription of genes coding for proteins in the thyroxin synthesis pathway. If you shine
    >light into my eyes, it affects the way that my pineal gland secretes melatonin. That process may
    >also be associated with the transcription of genes coding for proteins in the melatonin synthesis
    >pathway. There is no conceptual difference. There is absolutely NOTHING in the nervous system that
    >codes for "thyroxin" or for "melatonin" or for "transcribe this particular gene" or anything at all
    >like that. All that happens is that a chemical binds to a receptor in the membrane of the thyroid
    >or pineal gland cell and makes that cell "do its thing". That "thing" may involve gene
    >transcription, or maybe not. Whatever, the stimulus simply "doesn't care" what the target cell does
    >with the signal. The signal, in fact, doesn't carry any information other than "I have a message
    >for you". It is completely up to the target cell to "know" how to respond.

    >

    Let me try once again to show you the "conceptual" difference between the classical way of gene
    expression and the expression of genes in neural tissues? In the classical mode of gene expression,
    the effect of the stimulus is determined by stereochemical and thermodynamical properties of the
    stimulus and the respective pathway. Unlike that, the activation/inactivation of genes in the CNS
    does not depend on the stereochemical and thermodynamical properties of the stimulus but on the
    computational properties of the neural circuit that processes the stimulus: in response to the same
    external stimulus ( with the same stereochemical and thermodynamical properties) the CNS is able to
    manipulatively and adaptively activate different genes (examples bound). This does not happen
    anywhere else in the body. It is the processing of the stimulus in neural circuits that makes
    possible "manipulative" activation in the CNS of genes (such as melatonin and thyroxin you mention)
    that can't be activated in other types of cells.

    You say that "All that happens is that a chemical binds to a receptor in the membrane of the thyroid
    or pineal gland cell and makes the cell "do its thing"". Unfortunately, this is neither "all" nor
    the essential that happens. In both examples you see just the proximal link in a long cascade,
    ignoring the series of signals and especially the "essential" processing of those stimuli (chill and
    darkness) in neural circuits, without which neither thyroxin nor melatonin is produced. You know
    better than me that chill applied to thyroid won't make it synthesize thyroxin (only hypothalamic
    TRH will, which in turn is synthesized according to signals generated computationally by processing
    of the stimulus in neural circuits in other parts of the brain). The same I have explained for
    melatonin synthesis.

    What makes unique the thyroid in producing thyroxin and pineal in producing melatonin is the
    INFORMATION (computationally generated in neural circuits) they receive on the external stimulus
    (not the stimulus itself). Deprived of this INFORMATION generated in neural circuits, no other type
    of cell in the animal body is capable of synthesizing those chemicals.

    Is this manipulative (processing-dependent) activation/inactivation of genes in the CNS requiring
    information ON THE STIMULUS "essentially different both in the the mechanism that makes it possible
    and the outcome?
     
  4. R Norman

    R Norman Guest

    On Fri, 13 Feb 2004 16:49:38 +0000 (UTC), [email protected] (CNCabej)
    wrote:

    >On Wed, 11 Feb 2004 00:46:11 +0000 (UTC) r norman [email protected]_comcast.net wrote:
    >
    >N.C. wrote: ..............
    >>>r n:
    >>>
    >>>>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-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 eventZ. 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.<
    >>>
    >
    >>>If I got it right, you argue that the fact that "a whole series of
    >>intermediate
    >>>steps" are involved in the signal cascade from the external stimulus to
    >>genes,
    >>>this fact per se, excludes the possibility of any information being
    >>transmitted
    >>>via the cascade. Without the necessary explanation, this idea seems hardly defensible to me.
    >>>
    >>>Applying the same criterium to the process of gene expression, which also involves many
    >>>"intermediate steps", would lead us to the conclusion that no genetic information is transmitted
    >>>from genes to proteins, which is no less difficult to defend.
    >>>
    >>>You correctly describe those pathways as chains of events where "event A
    >>causes
    >>>event B causes event C causes event D causes....causes event Z." where the effect of each element
    >>>on the downstream element (secretion of hypothalamic TRH, e.g. stimulates the pituitary TSH,
    >>>stimulates thyroid hormone, etc.)
    >>is
    >>>determined by stereochemical and thermodynamical properties of the
    >>interacting
    >>>molecules and of the environment.
    >>>
    >>>What takes place in the case of melatonin synthesis is different in an essential respect. The
    >>>external stimulus per se is neutral to any known
    >>pathway
    >>>in metazoans, it can't activate any specific gene. In order that it serve as
    >>a
    >>>cue, the input on the stimulus must first be processed in the retinal
    >>neurons
    >>>(a computational process), which codes it in the form of a specific pattern
    >>of
    >>>electrical signals. But the "electrically coded" stimulus is nothing less
    >>than
    >>>information on the stimulus. It is different from the stimulus itself in the same way that my
    >>>name identifies me but is not identical with me.
    >>>
    >>>The information generated by processing the stimulus is not determined by
    >>the
    >>>stimulus itself but by computational properties in which the stimulus is processed. That
    >>>information is not stimulus-dependent but
    >>processing-dependent.
    >>>
    >>>
    >>>The information contained in the electrical code is still "unintelligible"
    >>to
    >>>genes in the meaning that it can't activate the signal transduction pathway
    >>for
    >>>expression of melatonin genes. It must be further processed in the described complex neural
    >>>circuit, which ultimately transforms it in a chemical signal that can activate that signal
    >>>transduction pathway in all the "intermediate steps" you talk of. This ultimate chemical form
    >>>that makes possible the expression of melatonin genes, is different from the stimulus itself; it
    >>>is information on that stimulus that is generated (not preexisting) in the
    >>neural
    >>>circuits. No melatonin genes can be expressed without this information.
    >>>
    >>>This processing of stimuli in the CNS is necessary not only for external stimuli, but for most of
    >>>the internal stimuli, since because of the
    >>blood-brain
    >>>barrier most of the chemical signals (protein hormones, growth factors and other secreted
    >>>proteins) have no access to the CNS. It makes it possible for them than in response to the same
    >>>internal stimuli to activate genes that
    >>are
    >>>not expressed in other types of cells.
    >>
    >>We seem to be talking at such cross purposes that we cannot understand each other. I find your
    >>discussion of the requirement for information processing (as in your final paragraph) to be
    >>essentially incomprehesible.
    >>
    >>I do not understand why you are making a simple situation very complicated. If you chill me for a
    >>substantial period of time, my thyroid gland secretes thyroxin. That process may also be
    >>associated with the transcription of genes coding for proteins in the thyroxin synthesis pathway.
    >>If you shine light into my eyes, it affects the way that my pineal gland secretes melatonin. That
    >>process may also be associated with the transcription of genes coding for proteins in the
    >>melatonin synthesis pathway. There is no conceptual difference. There is absolutely NOTHING in the
    >>nervous system that codes for "thyroxin" or for "melatonin" or for "transcribe this particular
    >>gene" or anything at all like that. All that happens is that a chemical binds to a receptor in the
    >>membrane of the thyroid or pineal gland cell and makes that cell "do its thing". That "thing" may
    >>involve gene transcription, or maybe not. Whatever, the stimulus simply "doesn't care" what the
    >>target cell does with the signal. The signal, in fact, doesn't carry any information other than "I
    >>have a message for you". It is completely up to the target cell to "know" how to respond.
    >
    >>
    >
    >Let me try once again to show you the "conceptual" difference between the classical way of gene
    >expression and the expression of genes in neural tissues? In the classical mode of gene expression,
    >the effect of the stimulus is determined by stereochemical and thermodynamical properties of the
    >stimulus and the respective pathway. Unlike that, the activation/inactivation of genes in the CNS
    >does not depend on the stereochemical and thermodynamical properties of the stimulus but on the
    >computational properties of the neural circuit that processes the stimulus: in response to the same
    >external stimulus ( with the same stereochemical and thermodynamical properties) the CNS is able to
    >manipulatively and adaptively activate different genes (examples bound). This does not happen
    >anywhere else in the body. It is the processing of the stimulus in neural circuits that makes
    >possible "manipulative" activation in the CNS of genes (such as melatonin and thyroxin you mention)
    >that can't be activated in other types of cells.
    >
    >You say that "All that happens is that a chemical binds to a receptor in the membrane of the
    >thyroid or pineal gland cell and makes the cell "do its thing"". Unfortunately, this is neither
    >"all" nor the essential that happens. In both examples you see just the proximal link in a long
    >cascade, ignoring the series of signals and especially the "essential" processing of those stimuli
    >(chill and darkness) in neural circuits, without which neither thyroxin nor melatonin is produced.
    >You know better than me that chill applied to thyroid won't make it synthesize thyroxin (only
    >hypothalamic TRH will, which in turn is synthesized according to signals generated computationally
    >by processing of the stimulus in neural circuits in other parts of the brain). The same I have
    >explained for melatonin synthesis.
    >
    >What makes unique the thyroid in producing thyroxin and pineal in producing melatonin is the
    >INFORMATION (computationally generated in neural circuits) they receive on the external stimulus
    >(not the stimulus itself). Deprived of this INFORMATION generated in neural circuits, no other type
    >of cell in the animal body is capable of synthesizing those chemicals.
    >
    >Is this manipulative (processing-dependent) activation/inactivation of genes in the CNS requiring
    >information ON THE STIMULUS "essentially different both in the the mechanism that makes it possible
    >and the outcome?

    I still think we are so far apart that we cannot understand each other. I have a great deal of
    difficulty with statements like "the effect of the stimulus is determined by stereochemical and
    thermodynamical properties of the stimulus" .

    Let me try to be clear. Pineal gland cells are highly differentiated by whatever developmental
    processes produce those cells. As a result, they express the genes involved in melatonin synthesis
    and are capable of secreting melatonin. That is what I referred to as "their thing". Neural
    computation has absolutely nothing to do with it. Other cells express different genes and make
    different proteins and secretory products. When you stimulate a pineal gland cell, it "does its
    thing" which is actually to secrete melatonin. The computational properties of neurons have nothing
    whatsoever to do with it.

    In fact, the stmulation of the pineal is through the sympathetic nervous system. That is, if you
    drop norepinephrine onto the pineal gland or artificially stimulate the superior cervical ganglion,
    the gland will release melatonin just as effectively as if you stopped shining light into the eye.
    The nervous system "calculates" only that during daylight it should refrain from sending action
    potentials to the superior cervical ganglion destined for the pineal and to resume those action
    potentials during the night time. Nowhere does the nervous system calculate just how to activate any
    specific genes or how to secrete any specific chemical.
     
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