clock news
clock | September 15, 2006Students not getting enough sleep:
College students may believe they are being more productive when they sleep less, but in reality it is causing harm to their bodies. The National Sleep Foundation points out that receiving less than six hours of sleep a night is associated with 1.7 times greater risk of disease, according to www.sleepfoundation.org. The chance of decreased academic performance, driving accidents, colds and flu and mental illnesses are all increased.
Workplace fatigue risky business at 30,000 ft.:
Fatigue is worsened when lack of sleep is coupled with a disruption to the body…
clock | September 13, 2006Salivary Melatonin May Help Fight Gum Disease:
Researchers found that melatonin, a hormone created by the pineal gland, may be able to protect the oral cavity against free radicals produced by inflammatory diseases. Melatonin has strong antioxidant effects that can protect cells against inflammatory processes and oxidative damage.
--------------
"Patients with higher salivary and melatonin ratios had lower community periodontal index (CPI). CPI is the score used to assess periodontal status," said Pablo Galindo, DDS, Department of Oral Surgery, School of Dentistry, University of Granada,…
clock | September 11, 2006
Here is the second post on the topic, from March 28, 2006. A couple of links are broken due to medieval understanding of permalinks by newspapers, but you will not miss too much, I hope....
Health Journal: Doctors probe why it's hard for many kids to get up (also Night Owls: Disorder may cause teens to sleep less):
"The parents get stigmatized as not having control over their kids when they can't get them to school in time," says James Wyatt, co-director of the sleep-disorders center at Rush University Medical Center in Chicago who is conducting research looking for ways to better diagnose…
clock | September 7, 2006This is a good article about changes in sleep patterns that occur with old age.
clock | September 1, 2006I rarely write about biological rhythms outside of circadian range (e.g., circannual, circalunar, circatidal rhythms etc.), but if you liked this post on lunar rhythms in antlions, you will probably also like this little review of lunar rhythms in today's Nature:
Pull of the Moon:
-------------------
Studies of fiddler crabs, for example, have shown that even when kept in the lab under constant light and temperature, the animals are still most active at the times that the tide would be out. A similar internal 'circalunar' clock is thought to tick inside many animals, running in synchrony…
clock | August 31, 2006Melatonin improves mood in winter depression:
Alfred Lewy and his colleagues in the OHSU Sleep and Mood Disorders Lab set out to test the hypothesis that circadian physiological rhythms become misaligned with the sleep/wake cycle during the short days of winter, causing some people to become depressed.
Usually these rhythms track to the later dawn in winter, resulting in a circadian phase delay with respect to sleep similar to what happens flying westward. Some people appear to be tracking to the earlier dusk of winter, causing a similar amount of misalignment but in the phase-advance…
clock | August 26, 2006Bumble Bees Can Estimate Time Intervals:
In a finding that broadens our understanding of time perception in the animal kingdom, researchers have discovered that an insect pollinator, the bumble bee, can estimate the duration of time intervals. Although many insects show daily and annual rhythms of behavior, the more sophisticated ability to estimate the duration of shorter time intervals had previously been known only in humans and other vertebrates.
-------------snip------------------
Bees and other insects make a variety of decisions that appear to require the ability to estimate elapsed…
clock | August 26, 2006As we age, our sleep gets less well consolidated: we take more naps during the day and wake up more oftenduring the night. This happens to other mammals as their age. Now we know that it also happens in Drosophila:
"As humans age, so I'm told, they tend not to sleep as well. There are all sorts of reasons -- aches and pains, worries about work and lifelong accumulations of sins that pretty much rule out the sweet sleep of innocence.
But what about fruit flies? Not as a cause of insomnia. What about the problems fruit flies have sleeping?
Yes, Drosophila melanogaster also suffer sleep…
clock | August 24, 2006First 'encyclopedia' of nuclear receptors reveals organisms' focus on sex, food:
Organisms thrive on sex and food, and so do their cells' receptors.
In creating the first "encyclopedia" of an entire superfamily of nuclear receptors - proteins that turn genes on and off throughout the body - UT Southwestern Medical Center researchers found that certain receptors form networks and interact to regulate disease states and physiology in two main areas, reproduction and nutrient metabolism.
Receptor networks also have key roles in metabolism's biological clock, researchers found.
The findings,…
clock | August 21, 2006Three interesting press releases/news-reports today. Click on links to read the whole articles:
Daytime light exposure dynamically enhances brain responses:
Exposure to light is known to enhance both alertness and performance in humans, but little is understood regarding the neurological basis for these effects, especially those associated with daytime light exposure. Now, by exposing subjects to light and imaging their brains while they subsequently perform a cognitive test, researchers have begun to identify brain regions involved in the effects on brain function of daytime light exposure…
clock | August 18, 2006One of the several hypotheses floating around over the past several years to explain the phenomenon of repeated wake-up events in hibernating animals although such events are very energy-draining, is the notion that the immune system needs to be rewarmed in order to fend off any potential bacterial invasions that may have occured while the animal was hibernating:
Now, a group of researchers provided a mathematical model that supports this hypothesis:
"A habit in some animals to periodically wake up while hibernating may be an evolutionary mechanism to fight bacterial infection, according to…
clock | August 15, 2006
This post, from January 25, 2006, describes part of the Doctoral work of my lab-buddy Chris.
Mammals have only one circadian pacemaker - the suprachiasmatic nucleus (SCN). Apparently all the other cells in the body contain circadian clocks, too, but only the SCN drives all the overt rhythms. Without the SCN, there are no rhythms - the peripheral clocks either get out of phase with each other, or their clocks stop ticking altogether.
If you place various tissues in a dish, the SCN cycles indefinitely. All other tissues are capable of only a few oscillations in the absence of a daily signal…
clock | August 10, 2006This is an interesting idea:
A novel way to advance the circadian cycle has been proposed as a way to solve the problem associated with the early starting times of middle and high schools. It has been recognized for some time that teen age students do not really wake up until well past the time they physically arrive at school. Researchers at Brown University have found that the student's blood contains large amounts of the sleep hormone, melatonin. Researchers at the Lighting Innovations Institute of John Carroll University are seeking funding to carry out a study to find out if their method…
clock | August 10, 2006A nice new study on ecological aspects of circadian rhythms:
To a tiny tadpole, life boils down to two basic missions: eat, and avoid being eaten. But there's a trade-off. The more a tadpole eats, the faster it grows big enough to transform into a frog; yet finding food requires being active, which ups the odds of becoming someone else's dinner.
Scientists have known that prey adjust their activity levels in response to predation risk, but new research by a University of Michigan graduate student shows that internal factors, such as biorhythms, temper their responses.
Michael Fraker, a…
clock | August 10, 2006As the temperatures rise, different organisms respond differently. Some migrate to higher latitudes or altitudes. Others stay put but change the timing of reproduction and other seasonal activities. As a result, ecosystems get remodeled.
So, for instance, insect pollinators and flowers they pollinate may get out of sync.
Animals tend to use photoperiod as a major clue for seasonal timing, with temperature only modulating the response to some extent.
Plants, on the other hand, although they certainly can use photoperiod, are much more strongly influenced by temperature. Non-biologists who…
clock | August 8, 2006A couple of months ago I wrote about a study in primates, suggesting that there is a circadian clock in the adrenal gland. This was hyped like a big break-through, but, while that was a good and useful study, it did not show anything surprising, e.g., that the adrenal is a pacemaker, only that it is a peripheral clock, which was known for decades, before the whole paradigm of perihperal clocks matured within the field.
Now, there is a new study, this time in mice, on the same question: How the adrenal 'clock' keeps the body in synch.
Again, it is touted as something that will fundamentaly…
clock | August 3, 2006Interesting, if you are in the field:The Neurospora Checkpoint Kinase 2: A Regulatory Link Between the Circadian and Cell Cycles
by António M. Pregueiro, Qiuyun Liu, Christopher L. Baker, Jay C. Dunlap, Jennifer J. Loros
The clock gene period-4 (prd-4) in Neurospora was identified by a single allele displaying shortened circadian period and altered temperature compensation. Positional cloning followed by functional tests show that PRD-4 is an ortholog of mammalian checkpoint kinase 2 (Chk2). Expression of prd-4 is regulated by the circadian clock and, reciprocally, PRD-4 physically interacts…
clock | July 31, 2006It has been known for decades that scheduled meals can entrain the circadian clock. In some species (e.g., in some birds), regular timing of feeding entrains the main circadian system of the body in the suprachiasmatic (SCN) area of the hypothalamus, the retina and the pineal. In other species (e.g., rodents), it appears that the food-entrainable oscillator is anatomically and functionally distinct from the main pacemaker in the SCN.
Researchers working on different species discovered different properties and different anatomical locations for the food-entrainable clock. Now, a study…
clock | July 25, 2006
You and I, as well as all of our mammalian brethren, have just a few photopigments, i.e., colored molecules that change shape when exposed to light and subsequently trigger cascades of biochemical reactions leading to changes in electrical properties of sensory neurons, which lead to modulation of neurotransmitter release, which propagates the information from one neuron to the next until it is integrated and interpreted somewhere in the brain - we see the light!
More under the fold....
Mammals have rhodopsin (in rod-shaped photoreceptor cells in the retina of the eye), three or four color-…
clock | July 19, 2006Sometimes a metaphor used in science is useful for research but not so useful when it comes to popular perceptions. And sometimes even scientists come under the spell of the metaphor. One of those unfortunate two-faced metaphors is the metaphor of the Biological Clock.
First of all, there are at least three common meanings of the term - it is used to describe circadian rhythms, to describe the rate of sequence change in the DNA over geological time, and to describe the reaching of a certain age at which human fertility drops off ("my clock is ticking").
I prefer the Rube-Goldberg Machine…