clock

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clock

(klok) a device for measuring time.
biological clock  the physiologic mechanism which governs the rhythmic occurrence of certain biochemical, physiologic, and behavioral phenomena in living organisms.

clock

(klŏk)
n.
1. An instrument other than a watch for measuring or indicating time, especially a mechanical or electronic device having a numbered dial and moving hands or a digital display.
2. A biological clock.
v. clocked, clocking, clocks
v.tr.
To register or record with a mechanical device: clocked the winds at 60 miles per hour.

clock′er n.

CLOCK

A gene on chromosome 4q12 that encodes a ubiquitously expressed human homolog of the mouse clock gene, which forms a heterodimer with ARNTL and activates E-box element transcription of several circadian clock proteins (e.g., PER1 and PER2). CLOCK is highly expressed in the suprachiasmatic nucleus.

Molecular pathology
CLOCK-ARNTL double mutations in the PAS domains result in syngernistic desensitisation to high levels of CRY on repression of CLOCK-ARNTL transcriptional activity of PER1, disrupting circadian rhythmicity.

clock

(klok)
A device for measuring time.

biological clock

1. An internal system in organisms that influences behavior in a rhythmic manner. Functions such as growth, feeding, secretion of hormones, the rate of drug action, the wake-sleep cycle, the menstrual cycle, and reproduction coincide with certain external events such as day and night, the tides, and the seasons. Biological clocks appear to be set by environmental conditions in some animals, but if these animals are isolated from their environment they continue to function according to the usual rhythm. A gradual change in environment does produce a gradual change in the timing of the biological clock. See: circadian; maladaptation to night work; zeitgeber
2. A colloquial term for the decrease in fertility that accompanies aging, particularly as women approach the age of 35.

Patient discussion about clock

Q. How do you wake up in the morning if your narcolepsy is so severe you can't hear the alarm clock, phone ring? biggest problem is sleep paralysis, can't wake up. Late for work, everything, life is suffering because of severity. Have tried ritalin, natural supplements, hypnosis therapy, Provigal, antidepressants, nothing seems to work. Employer thinks it's an excuse, friends are irritated, I'm at my wits end. Life is spent sleeping more than awake.

A. Narcolepsy cannot yet be cured. But EDS and cataplexy, the most disabling symptoms of the disorder, can be controlled in most patients with drug treatment. Often the treatment regimen is modified as symptoms change. For decades, doctors have used central nervous system stimulants-amphetamines such as methylphenidate, dextroamphetamine, methamphetamine, and pemoline-to alleviate EDS and reduce the incidence of sleep attacks. For most patients these medications are generally quite effective at reducing daytime drowsiness and improving levels of alertness. However, they are associated with a wide array of undesirable side effects so their use must be carefully monitored. Common side effects include irritability and nervousness, shakiness, disturbances in heart rhythm, stomach upset, nighttime sleep disruption, and anorexia. For full article: http://www.ninds.nih.gov/disorders/narcolepsy/detail_narcolepsy.htm#120393201 Hope this helps.

More discussions about clock
References in periodicals archive ?
In vivo endotoxin synchronizes and suppresses clock gene expression in human peripheral blood leukocytes.
Through the use of antibodies specific to the Clock gene and tyrosine hydroxylase, McClung et al.
Circadian clock gene polymorphisms in alcohol use disorders and alcohol consumption.
Disruption of clock gene expression alters responses of the aryl hydrocarbon receptor signaling pathway in the mouse mammary gland.
Circadian clock genes play an important role in regulating many body rhythms over a 24-hour cycle.
How does altering clock gene function affect cell cycle checkpoint genes and genes of apoptosis in susceptible tissue such as breast and prostate?
The researchers then showed that longdaysin had the same effect of lengthening the biological clock in mouse tissue samples and in zebrafish larvae that carried luciferase genes attached to their clock genes.
assistant professor, and his colleagues undertook the first study to establish a relationship between circadian clock gene expression and the growth rate of tumors.
He is the author of more than 140 scientific publications, and is widely recognized for identification, isolation and characterization of the Clock gene in mice, the first vertebrate circadian gene to be isolated using forward genetics.
It's surprising to find a clock gene that is performing the same function across such widely unrelated groups," said Stacey Harmer, associate professor of plant biology in the UC Davis College of Biological Sciences and senior author on the paper.
A statistical analysis indicated that people with two thymine versions of the Clock gene are more morning oriented than those with one or two copies of the cytosine form.
As expected, Takahashi's group observed that the clock gene is active in the mouse SCN and retina.