chronobiology
clock | June 29, 2006This week, it took me quite a while to figure out how to answer the Ask a ScienceBlogger question: "What are some unsung successes that have occurred as a result of using science to guide policy?"
As a relative newcomer to the United States, and even more a newcomer to American politics, I was not around long enough to pay attention to various science-driven policies of the past. Most of what I know are far from "unsung" successes - from Manhattan Project, through Clean Air and Clean Water acts, to the EWndangered Species Act, to the international Kyoto Protocol. Dealing with DDT, DES,…
clock | June 29, 2006This is in the bread-mold Neurospora crassa. It is unlikely to be universal. I expect to see the connection in some protists and fungi, perhaps in some animals. I am not so sure about plants, and I am pretty sure it is not like this in Cyanobacteria in which the cycle of cell division is independent from circadian timing:
Novel connection found between biological clock and cancer
Hanover, NH--Dartmouth Medical School geneticists have discovered that DNA damage resets the cellular circadian clock, suggesting links among circadian timing, the cycle of cell division, and the propensity for…
clock | June 29, 2006The absence of light-dark cycles in space (e.g., on the shuttle or space station) results in disruptions of sleep. It has been proposed that humans who spend prolonged time in space are suffering from jet-lag - the internal desynchronization of clocks in various tissues.
A new experiment on the space station will take a somewhat different strategy than usual. Instead of measuring EEG (brain activity), it will monitor EKG (heart activity) over a period of 150 days.
The idea, brought by Irish researchers, is that EEG monitoring is not capable of measuring internal desynchronization of the…
clock | June 27, 2006
The origin and early evolution of circadian clocks are far from clear. It is now widely believed that the clocks in cyanobacteria and the clocks in Eukarya evolved independently from each other. It is also possible that some Archaea possess clock - at least they have clock genes, thought to have arived there by lateral transfer from cyanobacteria.[continued under the fold]
It is not well known, though, if the clocks in major groups of Eukarya - Protista, Plants, Fungi and Animals - originated independently or out of a common ancestral clock. On one hand, the internal logic of the clock…
clock | June 26, 2006
In the beginning, there was period.
Before 1995, the only known circadian clock genes were period (Per) in Drosophila melanogaster (wine fly) and frequency (Frq) in Neurospora crassa (bread mold). Some mutations, though not characterized at the molecular level, were also known in Chlamydomonas, Euglena as well as the famous Tau-mutation in hamsters.
I still remember the strained mathematical models attempting to account for a 24-hour rhythm with just a single gene controlling its own expression. We now know that multiple genes are involved in circadian function in invertebrates and…
clock | June 26, 2006
This is the second in the series of posts designed to provide the basics of the field of Chronobiology. See the first part: ClockTutorial #1 - What Is Chronobiology and check out the rest of them here - they will all, over time, get moved to this blog.
Here is a brief overview of the concepts and terms used in the field of chronobiology. I will write much more detailed accounts of various aspects of it in the future.
Seasons of the year, phases of the moon, high and low tides, and alternation between night and day are examples of cyclic changes in the environment. Each presents a different…
clock | June 26, 2006
The persistence of circadian rhythmicity during long bouts of hibernation in mammals has been a somewhat controversial topic in the literature. While some studies suggest that circadian clock is active during hibernation, other studies dispute this. Apparently, the truth is somewhere in-between - it differs between species:
Not all hibernating animals retain apparent circadian rhythmicity during the hibernation season. Whereas some species, such as bats and golden-mantled ground squirrels, maintain circadian rhythmicity in Tb throughout the hibernation season when held in constant…
clock | June 23, 2006Rozerem is a selective melatonin agonist. It acts on melatonin receptors at the suprachiasmatic nucleus. It is prescribed as a non-addictive sleep aid for people having difficulties with the onset of sleep, i.e., falling asleep in the evening.
While melatonin itself appears unlikely to be a molecule that directly induces sleep, it does have phase-resetting effects on the circadian clock. Thus, Rozerem appears ideal as an aid for extreme "owls" to help them fall asleep (if they need to wake up early in the morning, as some jobs require). By mimicking melatonin, it would phase-advance the…
clock | June 21, 2006My post about sleep has been translated by Davide 'Folletto' Casali into Italian, and posted on his blog. You can see the translated post here. If you can read Italian (and even you do not - just for fun, and to reward his hard work), go and look around his blog.
clock | June 19, 2006
Melatonin is secreted in human mother's milk with a daily rhythm - high at night, undetectable during the day (see the figure under the fold):
It has been known for a long time that mother's melatonin entrains the circadian rhythms in the SCN (suprachiasmatic nucleus) of the embryos - thus they are born with a correct phase (time of day). However, a study in rats suggests that melatonin in mother's milk is unlikely to be able to entrain the pups circadian rhythms after they are born.
So, the appearance of melatonin in the milk of breastfeeding humans may either be:
a) just a by-product…
clock | June 16, 2006Interesting:
Melatonin may be found in grapes
MILAN, Italy, June 16 (UPI) -- Scientists in Italy say they have discovered that the grapes used in popular red wines may contain high levels of the sleep hormone melatonin.
Melatonin is naturally secreted by the pineal gland in the brain, especially at night, and it tells the body when it is time to sleep, according to researcher Iriti Marcello at the University of Milan.
Hey, hey, what do you say:
Until recently, melatonin was thought to be exclusively produced by mammals, but has recently been discovered in plants.
Excuse me, but we've known…
clock | June 13, 2006When a news release states that a brain region is crucial for something, one is led to believe that this is the MAIN center controlling that function. If it is crucial for thermoregulation than it is the center for thermoregulation and without it the animal does not thermoregulate. Or am I misunderstanding English (it is a second language for me, after all)?
So, when the article starts with: "Researchers at Northwestern University have pinpointed a brain area in flies that is crucial to sleep, raising interesting speculation over the purpose of sleep and its possible link with learning and…
clock | June 12, 2006So, Wellbutrin is now officially a drug for treating Seasonal Affective Disorder. And chocolate is so unofficially. But, those may only take the edge off of the symptoms - they cannot affect the underlying causes.
clock | June 12, 2006
This post is perhaps not my best post, but is, by far, my most popular ever. Sick and tired of politics after the 2004 election I decided to start a science-only blog - Circadiana. After a couple of days of fiddling with the templae, on January 8, 2005, I posted the very first post, this one, at 2:53 AM and went to bed. When I woke up I was astonished as the Sitemeter was going wild! This post was linked by BoingBoing and later that day, by Andrew Sullivan. It has been linked by people ever since, as recently as a couple of days ago, although the post is a year and a half old.…