Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "bipolar disorder and some sleep disorders, are associated with irregular or pathological functioning of circadian rhythms. Recent research suggests that circadian rhythm disturbances found in bipolar disorder are positively influenced by lithium's effect on clock genes.[57]
Disruption to rhythms in the longer term is believed to have significant adverse health consequences on peripheral organs outside the brain, particularly in the development or exacerbation of cardiovascular disease.[58] The suppression of melatonin production associated with the disruption of the circadian rhythm may increase the risk of developing cancer.[59] LED lighting suppresses melatonin production five times more than a high pressure sodium light.[60] Depression symptoms from long term nighttime light exposure can be undone by returning to a normal cycle.[61]"

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "bipolar disorder and some sleep disorders, are associated with irregular or pathological functioning of circadian rhythms. Recent research suggests that circadian rhythm disturbances found in bipolar disorder are positively influenced by lithium's effect on clock genes.[57]
Disruption to rhythms in the longer term is believed to have significant adverse health consequences on peripheral organs outside the brain, particularly in the development or exacerbation of cardiovascular disease.[58] The suppression of melatonin production associated with the disruption of the circadian rhythm may increase the risk of developing cancer.[59] LED lighting suppresses melatonin production five times more than a high pressure sodium light.[60] Depression symptoms from long term nighttime light exposure can be undone by returning to a normal cycle.[61]"

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "These clocks, called peripheral oscillators, are found in the oesophagus, lungs, liver, pancreas, spleen, thymus, and the skin.[34] Though oscillators in the skin respond to light, a systemic influence has not been proven so far.[35][36] There is also some evidence that the olfactory bulb and prostate may experience oscillations when cultured, suggesting that these structures may also be weak oscillators.
Furthermore, liver cells, for example, appear to respond to feeding rather than to light. Cells from many parts of the body appear to have freerunning rhythms."

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "Biological markers
The classic phase markers for measuring the timing of a mammal's circadian rhythm are:
melatonin secretion by the pineal gland
core body temperature[30]
plasma level of cortisol.[31]
For temperature studies, subjects must remain awake but calm and semi-reclined in near darkness while their rectal temperatures are taken continuously. The average human adult's temperature reaches its minimum at about 05:00 (5 a.m.), about two hours before habitual wake time[citation needed], though variation is great among normal chronotypes.
Melatonin is absent from the system or undetectably low during daytime. Its onset in dim light, dim-light melatonin onset (DLMO), at about 21:00 (9 p.m.) can be measured in the blood or the saliva. Its major metabolite can also be measured in morning urine. Both DLMO and the midpoint (in time) of the presence of the hormone in the blood or saliva have been used as circadian markers"

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "he SCN takes the information on the lengths of the day and night from the retina, interprets it, and passes it on to the pineal gland, a tiny structure shaped like a pine cone and located on the epithalamus. In response, the pineal secretes the hormone melatonin. Secretion of melatonin peaks at night and ebbs during the day and its presence provides information about night-length.
Several studies have indicated that pineal melatonin feeds back on SCN rhythmicity to modulate circadian patterns of activity and other processes. However, the nature and system-level significance of this feedback are unknown."

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Retinohypothalamic tract - Wikipedia, the free encyclopedia

Retinohypothalamic tract - Wikipedia, the free encyclopedia: "The origin of the retinohypothalamic tract is the intrinsically photosensitive retinal ganglion cells (ipRGC), which contain the photopigment melanopsin. The axons of the ipRGCs belonging to the retinohypothalamic tract project directly, monosynaptically, to the suprachiasmatic nuclei via the optic nerve and the optic chiasm.[2][3] The suprachiasmatic nuclei receive and interpret information on environmental light, dark and day length, important in the entrainment of the "body clock". They can coordinate peripheral "clocks" and direct the pineal gland to secrete the hormone melatonin."

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "Biological clock in mammals



Diagram illustrating the influence of light and darkness on circadian rhythms and related physiology and behaviour through the suprachiasmatic nucleus in humans.
The primary circadian "clock" in mammals is located in the suprachiasmatic nucleus (or nuclei) (SCN), a pair of distinct groups of cells located in the hypothalamus. Destruction of the SCN results in the complete absence of a regular sleep–wake rhythm. The SCN receives information about illumination through the eyes. The retina of the eye contains "classical" photoreceptors ("rods" and "cones"), which are used for conventional vision. But the retina also contains specialized ganglion cells which are directly photosensitive, and project directly to the SCN where they help in the entrainment of this master circadian clock."

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "Arctic animals
Norwegian researchers at the University of Tromsø have shown that some Arctic animals (ptarmigan, reindeer) show circadian rhythms only in the parts of the year that have daily sunrises and sunsets. In one study of reindeer, animals at 70 degrees North showed circadian rhythms in the autumn, winter, and spring, but not in the summer. Reindeer at 78 degrees North showed such rhythms only in autumn and spring. The researchers suspect that other Arctic animals as well may not show circadian rhythms in the constant light of summer and the constant dark of winter.[20][21]
However, another study in northern Alaska found that ground squirrels and porcupines strictly maintained their circadian rhythms through 82 days and nights of sunshine. The researchers speculate that these two small mammals see that the apparent distance between the sun and the horizon is shortest once a day, and, thus, a sufficient signal to adjust by.[22]"

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "t is interesting to note that totally-blind subterranean mammals (e.g., blind mole rat Spalax sp.) are able to maintain their endogenous clocks in the apparent absence of external stimuli. Although they lack image-forming eyes, their photoreceptors (which detect light) are still functional; they do surface periodically as well.[18]
Freerunning organisms that normally have one or two consolidated sleep episodes will still have them when in an environment shielded from external cues, but the rhythm is, of course, not entrained to the 24-hour light–dark cycle in nature. The sleep–wake rhythm may, in these circumstances, become out of phase with other circadian or ultradian rhythms such as metabolic, hormonal, CNS electrical, or neurotransmitter rhythms.[19]"

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "hotosensitive proteins and circadian rhythms are believed to have originated in the earliest cells, with the purpose of protecting the replicating of DNA from high ultraviolet radiation during the daytime. As a result, replication was relegated to the dark. The fungus Neurospora, which exists today, retains this clock-regulated mechanism.
Circadian rhythms allow organisms to anticipate and prepare for precise and regular environmental changes; they have great value in relation to the outside world. The rhythmicity appears to be as important in regulating and coordinating internal metabolic processes, as in coordinating with the environment.[11] This is suggested by the maintenance (heritability) of circadian rhythms in fruit flies after several hundred generations in constant laboratory conditions,[12] as well as in creatures in constant darkness in the wild, and by the experimental elimination of behavioural but not physiological circadian rhythms in quail.[13][14]"

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "The rhythms maintain circadian periodicity over a range of physiological temperatures; they exhibit temperature compensation. Some organisms live at a broad range of temperatures, and differences in thermal energy will affect the kinetics of all molecular processes in their cell(s). In order to keep track of time, the organism's circadian clock must maintain a roughly 24-hour periodicity despite the changing kinetics, a property known as temperature compensation."

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "Criteria

To be called circadian, a biological rhythm must meet these four general criteria:
The rhythms repeat once a day (they have a 24-hour period). In order to keep track of the time of day, a clock must be at the same point at the same time each day, i.e. repeat every 24 hours.
The rhythms persist in the absence of external cues (endogenous). The rhythm persists in constant conditions with a period of about 24 hours. The rationale for this criterion is to distinguish circadian rhythms from simple responses to daily external cues."

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Circadian rhythm - Wikipedia, the free encyclopedia

Circadian rhythm - Wikipedia, the free encyclopedia: "sleepiness increases and decreases with a period of approximately 24 hours.[5] In 1918, J.S. Szymanski showed that animals are capable of maintaining 24-hour activity patterns in the absence of external cues such as light and changes in temperature.[6] Ron Konopka and Seymour Benzer isolated the first clock mutant in Drosophila in the early 1970s and mapped the "period" gene, the first discovered genetic component of a circadian clock.[7] Joseph Takahashi discovered the first mammalian 'clock gene' (CLOCK) using mice in 1994.[8][9]
The term "circadian" was coined by Franz Halberg in the late 1950s.[10]
[edit]Criteria

To be called circadian, a biological rhythm must meet these four general criteria:"

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Circadian Genes, Rhythms and the Biology of Mood Disorders

Circadian Genes, Rhythms and the Biology of Mood Disorders: "The molecular clock
The primary molecular clock is located in the suprachiasmatic nucleus (SCN) in the hypothalamus, and consists of a transcriptional feedback loop which cycles over the course of approximately twenty-four hours in the absence of environmental input (Reppert and Weaver, 2001; Ko and Takahashi, 2006). The major transcriptional activator consists of a dimer between the Circadian Locomotor Output Cycles Kaput Protein (CLOCK) and Brain and Muscle ARNT-like Protein 1 (BMAL1, also known as ARNTL or MOP3). This complex binds to E-box sequences in the promoters of"
 genes including the Period (Per) and Cryptochrome (Cry) genes. The PER and CRY proteins are translated in the cytoplasm, and are phosphorylated by Casein Kinase I ε and δ (CK1) and Glycogen Synthase Kinase 3β (GSK3β)
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Circadian Genes, Rhythms and the Biology of Mood Disorders

Circadian Genes, Rhythms and the Biology of Mood Disorders: "Indeed some of the major hallmarks of diseases like major depressive disorder (MDD) and bipolar disorder (BPD) are abnormal sleep/wake, appetite, and social rhythms (Boivin, 2000; Bunney and Bunney, 2000; Lenox et al., 2002; Grandin et al., 2006). Depression symptoms are also diurnal with the most severe symptoms occurring typically in the morning (Rusting and Larsen, 1998), and depression is more prevalent in areas of the world that receive little sunlight for extended periods of time (Booker et al., 1991). In addition, one of the most common mood disorders, affecting some 2–5% of the population in temperate climates, is seasonal affective disorder (SAD), a syndrome where depressive symptoms occur only in the winter months when there are shorter days and a later dawn (Lam and Levitan, 2000; Magnusson and Boivin, 2003). Thus, it has long been hypothesized that abnormalities in the molecular clock underlie the development of these disorders. "

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Circadian Genes, Rhythms and the Biology of Mood Disorders

Circadian Genes, Rhythms and the Biology of Mood Disorders: "abnormalities in circadian rhythms may underlie the development of mood disorders such as bipolar disorder, major depression and seasonal affective disorder. Furthermore, some of the treatments that are currently employed to treat mood disorders are thought to act by shifting or “resetting” the circadian clock, including total sleep deprivation and bright light therapy. There is also reason to suspect that many of the mood stabilizers and antidepressants used to treat these disorders may derive at least some of their therapeutic efficacy by affecting the circadian clock. Recent genetic, molecular and behavioral studies implicate individual genes that make up the clock in mood regulation. "

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Circadian rhythm sleep disorder - causes, DSM, functioning, effects, therapy, adults, examples, person

Circadian rhythm sleep disorder - causes, DSM, functioning, effects, therapy, adults, examples, person: "The Fourth Edition Text Revision of the Diagnostic and Statistical Manual of Mental Disorders ( DSM-IVTR , a handbook used by mental health professionals to diagnose mental disorders) defines circadian rhythm sleep disorder as one of several primary sleep disorders . Within the category of primary sleep disorders, it is classified as one of the dyssomnias, characterized by irregularities in an individual's quality, timing, and amount of sleep. In earlier versions of the DSM , the disorder is called sleep-wake schedule disorder.

Description

Circadian rhythm sleep disorder involves an alteration of an individual's circadian system or a mismatch between a person's natural, or endogenous, circadian system and the external, or exogenous, demands placed on it. It can lead to insomnia at certain times of the day or excessive sleepiness throughout the day. The insomnia or excessive sleepiness results in impaired functioning in social, occupational, or other environments."

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The Pineal Gland

The Pineal Gland: "elevating melatonin synthesis in the pinealocytes (Ganguly et al., 2001; Schomerus and Korf 2005). Recent studies have also shown that the removal of the SCN results in a daytime increase in Aa-nat mRNA levels, suggesting that the presence of an inhibitory SCN output contributs to the control of pineal melatonin rhythm (Kalsbeek et al., 2000). It has also been suggested that the GABA-ergic output of the SCN terminals on to the pre-autonomic PVN neurons may be the daytime inhibitory signal contributing to the morning decline of melatonin synthesis (Kalsbeek et al., 2000).

Another important factor in the regulation of the melatonin level is represented by light. Light is the dominant environmental factor that regulates melatonin biosynthesis in vertebrates, and regardless of whether a species is diurnal/nocturnal or exhibits crepuscular activity, pineal melatonin levels are high during the dark phase of a natural or imposed illumination cycle (Reiter, 1991; Arendt, 1999)."

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The Pineal Gland

The Pineal Gland: "Light signals perceived by the retina are conveyed via the retinohypothalamic tract to the SCN, and then to the mammalian pineal gland via the previously mentioned pathway (Korf et al., 1998; Korf, 1999). Light exerts a distinct suppressive effect on melatonin production irrespective of whether it is full spectrum white light, monochromatic light or UV-A light. The amount of light required to suppress melatonin production at night varies with species, previous light exposures, and the particular time of the night (Bojkowski et al., 1987; Brainard et al., 1988, 2001). Blue light (446-477 nm) is the most effective light to suppress melatonin (Brainard et al., 2001), thus suggesting that the intrinsically photosensitive retinal ganglion cells (ipRGCs) are involved in this phenomenon (Paul et al., 2009). Another important factor involved in the regulation of melatonin synthesis and levels is age."

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The Pineal Gland

The Pineal Gland: "
The suprachiasmatic nuclei (SCN) of the hypothalamus via a sympathetic multisynaptic pathway regulates rhythmic melatonin synthesis by acting on Aa-nat transcription (Klein et al., 1983; Tessonneaud et al., 1995; Garidou et al., 2002; Perreau-Lenz et al., 2005). The SCN uses a combination of daytime inhibitory and nighttime stimulatory signals to control the daily rhythm of pineal melatonin synthesis (Perreau-Lenz et al., 2003, 2004). At night the sympathetic neurotransmitter, Norepinephrine (NE), is released from the postganglionic nerve terminals innervating the pineal, thus stimulating (ß1 and 1 adrenoreceptors on the pinealocytes, leading to an increase in intracellular calcium levels."

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The Pineal Gland

The Pineal Gland: "Finally, it has also been suggested that melanopsin may mediate the photosensitivity observed in the neonatal pineal (Saafir et al., 2006). The reason why the mammalian pineal has lost the capability to directly respond to light is unknown, but it is believed to be a consequence of the evolutionary history of mammals (Menaker et al., 1997).


Melatonin Synthesis in the Pineal Gland
The pineal hormone melatonin is primarily synthesized in the pineal gland at night regardless of the diurnal or nocturnal activity of the animals. "

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The Pineal Gland

The Pineal Gland: "Introduction
The Pineal Gland (epiphysis cerebri in mammals), conferred as "the seat of Human soul" by Rene Descartes in 17th century,

was considered as an epithalamic appendage of the vertebrate brain, and a vestigial evolutionary element until the 19th century.

http://www.photobiology.info/Tosini.html


 The endocrine aspect of the pineal gland reported in the early 20th century was confirmed through isolation of the hormone melatonin by Aaron B. Lerner in 1958.

The pineal thus attracted scientific attention in the late 20th century due to its crucial role of transducing photoperiodic information through the rhythmic secretion of the daily and annual timekeeping hormone melatonin."

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The Pineal Gland

The Pineal Gland: "Melatonin Synthesis in the Pineal Gland
The pineal hormone melatonin is primarily synthesized in the pineal gland at night regardless of the diurnal or nocturnal activity of the animals. The initial step of the biosynthesis of this indoleamine involves the uptake of its precursor L-tryptophan from the circulation into the pinealocytes, "

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