chronobiology
clock | December 18, 2006Back in March 2005, I asked Heinrich of the She Flies With Her Own Wings blog to guest-post on Circadiana. He wrote two nice posts and this is the first of them (March 18, 2005). Perhaps I can get him to do some more...
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I am really excited to introduce to you my first guest blogger here on Circadiana, Heinrich, not Hindrocket whose blog, She Flies With Her Own Wings (http://coeruleus.blogspot.com/) is a worthy daily read. Heinrich does research on mammalian clocks and sleep, and his first contribution is this post…
clock | December 13, 2006Now behind the Wall, but plenty of excerpts available in this March 26, 2005 post...
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Ha! The New York Times has this neat article, that is almost half as good as my early (and so far most frequently linked) post "Everything You Always Wanted To Know About Sleep". Here are some excerpts, go read the rest:
The Crow of the Early Bird
THERE was a time when to project an image of industriousness and responsibility, all a person had to do was wake at the crack of dawn. But in a culture obsessed with status--in which every…
clock | December 11, 2006How does that work? (April 03, 2005)
-------------------------------------------------Alcohol 'binges' in rats during early brain development cause circadian rhythm problems
Rats are nocturnal animals and normally begin their activity slightly after darkness sets in. The rats that had been exposed to alcohol began activities slightly before darkness set in.
When normal rats - or for that matter, humans and other animals - are in situations without environmental cues about day and night, the body's circadian clock generally drives behaviors on a cycle slightly greater than 24 hours.…
clock | December 6, 2006This is an appropriate time of year for this post (February 05, 2006)...
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So, why do I say that it is not surprising the exposure to bright light alleviates both seasonal depression and other kinds of depression, and that different mechanisms may be involved?
In mammals, apart from visual photoreception (that is, image formation), there is also non-visual photoreception. The receptors of the former are the rods and cones that you all learned about in middle school. The receptors for the latter are a couple of thousand Retinal Ganglion…
clock | December 5, 2006
No other aspect of behavioral biology is as well understood at the molecular level as the mechanism that generates and sustains circadian rhythms. If you are following science in general, or this blog in particular, you are probably familiar with the names of circadian clock genes like per, tim, clk, frq, wc, cry, Bmal, kai, toc, doubletime, rev-erb etc.
The deep and detailed knowledge of the genes involved in circadian clock function has one unintended side-effect, especially for people outside the field. If one does not stop and think for a second, it is easy to fall under the impression…
clock | December 3, 2006Sandra Porter is having fun collecting all the new-fangled biological subdisciplines that end with "-omics". The final product of each such project also has a name, ending with "-ome".
You have all heard of the Genome (complete sequence of all the DNA of an organism) and the Genomics (the effort to obtain such a sequence), but there are many more, just look at this exhaustive list! In my written prelims back in 1999, I suggested that sooner or later there will be an organismome...until someone whispers that the term "physiology" already exists.
There are a couple of things that strike me…
clock | December 3, 2006At least once a week on this blog I get down and dirty into some aspect of chronobiology that can get quite technical and requires the use of terminology which, unless you have read my blog in great detail every day since inception or are a chronobiologist yourself, you will not understand. Now I have discovered a searchable Dictionary of Circadian Physiology (compiled by Dr.Roberto Reffinetti) that you can consult for a quick refresher. Do you think it would be useful to put a link to it on the sidebar so it is always accessible?
clock | November 29, 2006
The original title of this post - "Diurnal rhythm of alcohol metabolism" - was more correct, but less catchy (from February 21, 2006).
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Why is breathalyzer a poor method of measuring blood alcohol levels for purposes of DUI tickets? Ed Brayton explains and links to DUI Blog with additional information.
Also, do not forget that every function in the body exhibits a circadian cycle. Likewise, alcohol metabolism:
This is from an old study, from the times when it was OK to recruit some college freshmen to drink alcoholic beverages in the name of…
clock | November 27, 2006
A short-but-sweet study (March 18, 2006):
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I remember from an old review that John Palmer did a study on the diurnal pattern of copulation in humans some years ago. You can see the abstract here.
Now, Roberto Reffinetti repeated the study and published it in the online open-source Journal of Circadian Rhythms here.
The two studies agree: The peak copulatory activity in people living in a modern society is around midnight (or, really, around bedtime) with a smaller secondary peak in the morning around wake-time.
Dig through the papers yourself for…
clock | November 22, 2006Well, it's Thanksgiving tomorrow night so it's time to republish this post from last year, just in time for the ageless debate: does eating turkey meat make you sleepy? Some people say Yes, some people say No, and the debate can escalate into a big fight. The truth is - we do not know.
But for this hypothesis to be true, several things need to happen. In this post I look at the evidence for each of the those several things. Unfortunately, nobody has put all the elements together yet, and certainly not in a human. I am wondering...is there a simple easily-controlled experiment that…
clock | November 20, 2006
Often a press release inflates the meaning of a research paper. Here is one example of it (from May 23, 2006):
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From Afarensis, I got a new paper about circadian rhythms in primates: Twenty-four hour rhythmic gene expression in the rhesus macaque adrenal gland (PDF), by Dario Lemos, Jodi Downs and Henryk Urbanski.
The way the study is presented in the press release (now offline!), it sounds like this is a big surprising breakthrough, but I am not too impressed. The work is good and useful, but the findings are far from Earth-shattering.
Using…
clock | November 15, 2006An oldie but goodie (June 12, 2005) debunking one of the rare Creationist claims that encroaches onto my territory.
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I got homework to do. PZ Myers alerted me to an incredible argument that the existence of circadian rhythms denies evolution!
bryanm, the proprietor of the aptly-named The Narrow blog, describes himself as "...nobody who wants to tell everybody that there is somebody who can save anybody." In other words he is a know-nothing who keeps bothering everybody trying to push his idea that there is this non-existent being who…
clock | November 13, 2006
This post is a relatively recent (May 24, 2006) critique of a PLoS paper.
----------------------------------------------------There is a new study on PLoS - Biology that is getting some traction in the media and which caught my attention because it was supposed to be about circadian rhythms. So, I downloaded the paper and read it through to see what it is really about.
Well, it is a decent study, but, unfortunately, it has nothing to do with circadian rhythms. Many examples of tritrophic relationships involve parasitoids (usually small wasps) being attracted by plant volatiles which are…
clock | November 6, 2006Chronic Jet-Lag Conditions Hasten Death in Aged Mice
Researchers at the University of Virginia have found that aged mice undergoing weekly light-cycle shifts - similar to those that humans experience with jet lag or rotating shift work - experienced significantly higher death rates than did old mice kept on a normal daylight schedule over the same eight-week period. The findings may not come as a great surprise to exhausted globetrotting business travellers, but the research nonetheless provides, in rather stark terms, new insight into how the disruption of circadian rhythms can impact well-…
clock | November 6, 2006
Making connections (from January 22, 2006)...
---------------------------------------------------I love Miss Frizzle from the cartoon "The Magic School Bus". She always says "Make connections, kids, make connections!" Here I'll try to make some tentative connections between two recent papers, both concerning health issues in humans.
The first paper, brought to my attention by Corpus Callosum, a blog I belatedly placed on my blogroll here only today, is titled Commonly Used Antidepressants May Also Affect Human Immune System, which is a high-hype way of presenting a finding that some types…
clock | November 1, 2006Eva of Easternblot just published a nice article about circadian clocks in her school newspaper. Much good stuff was cut out during the editing process, but she posted those good parts on her blog so you can see what the editors left out.
clock | November 1, 2006One of th efirst posts on Circadiana, just defining what the blog was about (January 17, 2005):
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When I first took a class on Biological Clocks (eleven years ago), the instructor explained why biorhythms are not science. This was done with such fun, and as aside, I did not take it seriously. I did not realize I was supposed to study this exercise in Baloney Detection. I was surprised when I saw the question on the first mid-term exam, asking us to debunk biorhythms point-by-point. I lost several points there. I have learned since then to pay…
clock | October 31, 2006Apparently, the timing of sporting events in Beijing, probably driven by needs of American TV audiences, did not take into consideration the best time of day for athletic performance. But who cares about athletes, or even about breaking Olympic and world records, when delivering Joe Schmoe to the Budweiser commercial is much, much more important for the success of Olumpic games?!
This article provides a nice summary of the issue and the current state of understanding of the way circadian clocks affect athletic performance:Science Says Athletes Perform Better At Night
clock | October 26, 2006
There is nothing easier than taking a bad paper - or a worse press release - and fisking it with gusto on a blog. If you happen also to know the author and keep him in contempt, the pleasure of destroying the article is even greater.
It is much, much harder to write (and to excite readers with) a blog post about an excellent paper published by your dear friends. But I'll try to do this now anyway (after the cut).
Paul Shaw is a friend, and Indrani Ganguli is a good, good, good friend. Faculty and graduate students in biology are usually a pretty smart lot. A subset of those, as self-…
clock | October 24, 2006As the paper linked to in the previous post explains, everything is connected - clocks, sleep, hunger, obesity and diabetes.
An important part of understanding all these interconnections between clocks and food is to understand the food-entrainable clocks, i.e., how timing of meals affects the performance of the circadian clock.
A new paper provides a molecular link between scheduled meals and circadian timing, implicating our old friend PERIOD2 as part of the mechanisms by which timing of the meal entrains the brain clock (but not the mutual entrainment of peripheral clocks):
Circadian gene…