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pineal-ing away for the good old days...



I realize this has drifted far off topic, but please forgive the
digression.  I won't continue down this line unless forced.

In any case, I've heard from my chronobiological friend--to me he'll
always be "Gumby", but he's asked that I refer to him here as
Mr. Tibbs (something to do with Ethiopian foods--scientists really are
weird people, you know :-)

In any case, this is the relevant section of what he sent me with
regards pineal glands:
        
>The pineal is an endocrine gland and it secretes melatonin. This much is 
>consistent across all species that have it. The function of melatonin is 
>not well understood in general. Reproductive function depends on melatonin 
>in some species (seasonal breeding patterns are in part due to pineal 
>secretions in hamsters and I think in lizards -- not sure about the lizards 
>though). In general,  pineal melatonin output oscillates with peaks at 
>night and troughs in the day (light suppresses melatonin output). The 
>role of the pineal varies a good deal depending on the species. Many birds 
>and enolus apparently rely on the pineal as the circadian pacemaker with an 
>extraocular photoreceptor. Subcutaneous injections of india ink over the 
>pineal produces free running rhythms in these critters and pinealectomy 
>produces arrhythmicity. On the other hand, removal of the pineal does not 
>significantly alter rhythms in adult rats (may alter the sunchrony of 
>fetal rhythms in a pregnant female, ie, melatonin may be a time cue from 
>female to fetus). I have read at least one case in the New England Journal 
>about a boy with delayed an abnormal development of reproductive organs and 
>function at around puberty that was "cured" by melatonin injection. In most 
>of the pineal-containing critters I know about the pineal is considered to 
>be a slave oscillator that is controlled by some neural locus such as the 
>suprachiasmatic nucleus. But  repeat that only a subset of species contain 
>pineal pacemakers (as opposed to neural pacemakers with pineal slave 
>oscillators). These are mostly birds and there is considerable variation 
>between different avian species.

-- 
Mickey Rowe     (rowe@lepomis.psych.upenn.edu)