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Physiology and anatomy of human circ...

Zeitzer, Jamie Marc.

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Physiology and anatomy of human circadian photoreception and melatonin regulation.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Physiology and anatomy of human circadian photoreception and melatonin regulation./
Author:	Zeitzer, Jamie Marc.
Description:	181 p.
Notes:	Source: Dissertation Abstracts International, Volume: 60-06, Section: B, page: 2554.
Contained By:	Dissertation Abstracts International60-06B.
Subject:	Biology, Neuroscience. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9935938
ISBN:	0599371226

Physiology and anatomy of human circadian photoreception and melatonin regulation.
Zeitzer, Jamie Marc.

Physiology and anatomy of human circadian photoreception and melatonin regulation. - 181 p.

Source: Dissertation Abstracts International, Volume: 60-06, Section: B, page: 2554.

Thesis (Ph.D.)--Harvard University, 1999.

Circadian rhythms are endogenous, self-sustained oscillations of &sim; 24 hours that synchronize the internal biology of an organism with the external day/night cycle. Circadian rhythms are nearly ubiquitous in nature, being found throughout the phylogenetic tree. In humans, the circadian pacemaker is localized in the hypothalamic suprachiasmatic nucleus and influences many physiologic and behavioral functions. The pre-eminent external synchronizing influence on this clock is light. Despite the importance of photic input, the identity and physiology of the mechanism responsible for transducing light information to the human circadian pacemaker remains largely enigmatic. Herein, data are presented suggesting that retinal photoreceptors with the same range of spectral sensitivities as those used for image formation in humans may be sufficient for transducing photic information to the circadian pacemaker. Furthermore, the photic response of the human circadian pacemaker appears to follow logistic dynamics. The dynamics of the photic responsiveness are such that light that naturally occurs at night is below the threshold of sensitivity of the pacemaker and light that naturally occurs during the daytime induces a saturating response. Between these two thresholds, the response of the pacemaker increases rapidly with increasing illuminance.

ISBN: 0599371226Subjects--Topical Terms:

1017680
Biology, Neuroscience.

Physiology and anatomy of human circadian photoreception and melatonin regulation.
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035 $a (UnM)AAI9935938
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100 1 $a Zeitzer, Jamie Marc. $3 1907178
245 1 0 $a Physiology and anatomy of human circadian photoreception and melatonin regulation.
300 $a 181 p.
500 $a Source: Dissertation Abstracts International, Volume: 60-06, Section: B, page: 2554.
500 $a Adviser: Charles A. Czeisler.
502 $a Thesis (Ph.D.)--Harvard University, 1999.
520 $a Circadian rhythms are endogenous, self-sustained oscillations of &sim; 24 hours that synchronize the internal biology of an organism with the external day/night cycle. Circadian rhythms are nearly ubiquitous in nature, being found throughout the phylogenetic tree. In humans, the circadian pacemaker is localized in the hypothalamic suprachiasmatic nucleus and influences many physiologic and behavioral functions. The pre-eminent external synchronizing influence on this clock is light. Despite the importance of photic input, the identity and physiology of the mechanism responsible for transducing light information to the human circadian pacemaker remains largely enigmatic. Herein, data are presented suggesting that retinal photoreceptors with the same range of spectral sensitivities as those used for image formation in humans may be sufficient for transducing photic information to the circadian pacemaker. Furthermore, the photic response of the human circadian pacemaker appears to follow logistic dynamics. The dynamics of the photic responsiveness are such that light that naturally occurs at night is below the threshold of sensitivity of the pacemaker and light that naturally occurs during the daytime induces a saturating response. Between these two thresholds, the response of the pacemaker increases rapidly with increasing illuminance.
520 $a Evidence from non-human mammals indicates that the pineal gland must be stimulated by the superior cervical ganglion in order to produce melatonin. From previous reports, it is unclear whether this same regulatory mechanism occurs in humans. Based on studies of humans with spinal cord injury, I conclude that the human pineal gland must be stimulated by sympathetic neurons in order to produce melatonin. Furthermore, a complete loss of melatonin does not result in significant disruption to the circadian rhythms of cortisol or thyrotropin, indicating that these oscillations are not dependent upon or driven by the rhythm of plasma melatonin. Also demonstrated is that the loss or decline in plasma melatonin that has been hypothesized to accompany aging has been substantially overstated, since only a small minority of healthy subjects between 65 and 85 years of age manifest such a reduction. These experiments contribute to the understanding of the basic neurologic and endocrinologic mechanisms that underlie several complex functions in humans, including control of the human circadian pacemaker by light and the control of pineal production of melatonin by the pacemaker.
590 $a School code: 0084.
650 4 $a Biology, Neuroscience. $3 1017680
650 4 $a Biology, Animal Physiology. $3 1017835
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690 $a 0433
710 2 0 $a Harvard University. $3 528741
773 0 $t Dissertation Abstracts International $g 60-06B.
790 1 0 $a Czeisler, Charles A., $e advisor
790 $a 0084
791 $a Ph.D.
792 $a 1999
856 4 0 $u http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9935938