chronobiology
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 7, 2006A short post from April 17, 2005 that is a good starting reference for more detailed posts covering recent research in clock genetics (click on spider-clock icon to see the original).
As I have mentioned before, there was quite an angst in the field of chronobiology around 1960s about the lack of undestanding of circadian and other rhythms at cellular and subcellular levels. Experiment involved manipulation of the environment (e.g,. light cycles) and observing outputs (e.g., wheel-running rhythms), while treating the clock, even if its anatomical location was known, as a "black box".…
clock | August 4, 2006We have recently covered interesting reproductive adaptations in mammals, birds, insects, flatworms, plants and protists. For the time being (until I lose inspiration) I'll try to leave cephalopod sex to the experts and the pretty flower sex to the chimp crew.
In the meantime, I want to cover another Kingdom - the mysterious world of Fungi. And what follows is not just a cute example of a wonderfully evolved reproductive strategy, and not just a way to couple together my two passions - clocks and sex - but also (at the very end), an opportunity to post some of my own hypotheses online.…
clock | August 4, 2006Oversimplified, but much believed idea: Many cancer drugs target cells during cell division. Healthy cells divide at a particular time of day (exact timing may differ between cell types). Cancer cells are not under the control of the circadian clock so they divide at all times of the day (and they divide more often anyway). Thus, incorrect timing of chemotherapy - given during the time most healthy cells divide as well as some cancer cells - will kill more healthy than cancerous cells, leading to early termination of treatment and worse prognosis. Correct timing - during the time when…
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…
clock | August 3, 2006A number of media outlets are reporting on the new Duke University study on the effects of time-of-day on the outcome of surgery:
Patients who undergo surgery late in the afternoon are more likely to experience unexpected adverse events related to their anesthesia than are patients whose operations begin in the morning, a new analysis by Duke University Medical Center researchers suggests.
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In addition to spotting problems related to anesthesia, Wright and her colleagues also found that surgery patients experienced a significant increase in "…
clock | August 3, 2006
Being out of the lab, out of science, and out of funding for a while also means that I have not been at a scientific conference for a few years now, not even my favourite meeting of the Society for Research on Biological Rhythms. I have missed the last two meetings (and I really miss them - they are a blast!).
But it is funny how, many years later, one still remembers some posters from poster sessions. What makes a poster so memorable?
I guess it has something to do with one's interests - there is just not enough time during a session to check out every single one out of hundreds (or…
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 31, 2006 I wrote this post back on January 23, 2005. It explains how clock biologists think and how they design their experiments:
So, are you ready to do chronobiological research? If so, here are some of the tips - the thought process that goes into starting one's research in chronobiology.
First, you need to pick a question. Are you interested in doing science out of sheer curiosity to discover stuff that nobody knew before (a very noble, but hard-to-fund pursuit)? Or would you prefer your work to be applicable to human medicine or health policy, veterinary medicine, conservation biology, or…
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…
clock | July 17, 2006From Financial Times: 'Social jet lag' causes fatigue and illness (also on MSNBC):
Half the people in modern urban societies suffer from "social jet lag" because their body clocks are seriously out of step with their real lives, the Euroscience forum in Munich heard on Monday.
The result was chronic fatigue and an increased susceptibility to disease, researches found. They concluded that employers should tell staff to wake up in their own time and come in to work when they feel ready to.
Till Roenneberg, a circadian rhythm researcher at Ludwig Maximilians University in Munich, coined the…
clock | July 17, 2006This post about the origin, evolution and adaptive fucntion of biological clocks originated as a paper for a class, in 1999 I believe. I reprinted it here in December 2004, as a third part of a four-part post. Later, I reposted it here.
III. Whence Clocks?
Origin, Evolution, and Adaptive Function of Biological Clocks
The old saw about the early bird just goes to show that the worm should have stayed in bed. (Heinlein 1973)
Now darkness falls.
Quail chirps.
What use Hawk eyes?
(Basho)
Local/temporary and global/universal environments. In the study of adaptive functions, usually the question…
clock | July 13, 2006This is so basic that I even teach it in Intro Bio:
Wherever the master clock may be located (SCN, pineal or retina) in any particular species, its main function is to coordinate the timing of peripheral circadian clocks which are found in every single cell in the body. Genes that code for proteins that are important for the function of a particular tissue (e.g., liver enzymes in liver cells, neurotransmitters in nerve cells, etc.) show a daily rhythm in gene expression. As a result, all biochemical, physiological and behavioral functions exhibit daily (circadian) rhythms, e.g., body…
clock | July 10, 2006This post, originally published on January 16, 2005, was modified from one of my written prelims questions from early 2000.
EVOLUTIONARY PHYSIOLOGY OF BIOLOGICAL CLOCKS
"Circadian clocks allow organisms to predict, instead of merely react to, cyclic (predictable) changes in the environment". A sentence similar to this one is the opening phrase of many a paper in the field of chronobiology. Besides becoming a truth by virtue of frequent repetition, such a statement appeals to common sense. It is difficult to imagine a universe in which it was not true. Yet, the data supporting the above…
clock | July 4, 2006
I got several e-mails yesterday about a new study about the molecular mechanism underlying circadian rhythms in mammals ("You gotta blog about this!"), so, thanks to Abel, I got the paper (PDF), printed it out, and, after coming back from the pool, sat down on the porch to read it.
After reading the press releases, I was in a mind-frame of a movie reviewer, looking for holes and weaknesses so I could pounce on it and write a highly critical post, but, even after a whole hour of careful reading of seven pages, I did not find anything deeply disturbing about the paper. Actually, more I read…
clock | July 4, 2006Writing a chronobiology blog for a year and a half now has been quite a learning experience for me. I did not know how much I did not know (I am aware that most of my readers know even less, but still....). Thus, when I wrote about clocks in birds I was on my territory - this is the stuff I know first-hand and have probably read every paper in the field. The same goes for topics touching on seasonality and photoperiodism as my MS Thesis was on this topic. I feel equally at home when discussing evolution of clocks. I am also familiar with the clocks in some, but not all, arthropods. And…
clock | July 3, 2006
This is the third in the series of posts designed to provide the basics of the field of Chronobiology. This post is interesting due to its analysis of history and sociology of the discipline, as well as a look at the changing nature of science. You can check out the rest of Clock Tutorials here.
It appears that every scientific discipline has its own defining moment, an event that is touted later as the moment of "birth" of the field. This can be a publication of a paper (think of Watson and Crick) or a book ("Origin of Species" anyone?). In the case of Chronobiology, it was the 1960…
clock | July 3, 2006Believe me, I love the word "circadian". It is a really cool word, invented by Franz Halberg in the late 1950s, out of 'circa' (Latin - "about") and diem ("a day"), to denote daily rhythms in biochemistry, physiology and behavior generated by the internal, endogenous biological clocks within living organisms.
It's been a while since the last time I found someone mistaking the word for 'cicada' which is a really cool insect. 'Circadian' has become quite common term in the media and, these days increasingly, in popular culture. Names of some bands contain the word. A few blogs' names…