Circadian rhythms are biological processes that oscillate with an approximate 24 hour periodicity when there are no external timing cues. Basically, a circadian rhythm is an internal daily biological clock. Time lapse video of Neurospora Circadian Conidiation Rhythms by Van Gooch and Jason Thoen.
Van D. Gooch, Arun Mehra, Luis F. Larrondo, Julie Fox, Melissa Touroutoutoudis, Jennifer J. Loros, and Jay C. Dunlap
Fully Codon-Optimized luciferase Uncovers Novel Temperature Characteristics of the Neurospora Clock
Eukaryotic Cell 2008 7: 28-37.
Watch bioluminescent movies in the supplemental materail in the Eukaryotic Cell reference mentioned above.
Neurospora Growth rate is Dramatically Circadian:
Van D. Gooch, Laura Freeman, and Patricia L. Lakin-Thomas
Time-Lapse Analysis of the Circadian Rhythms of Conidiation and Growth Rate in Neurospora
J Biol Rhythms 2004 19: 493-503.
Phase Response Experiments: First consider a control where an organism is demonstrating a cycling (appx 24 hours) of some physiological feature under constant conditions. For example a sleep wake cycle of a mouse in constant dark and with constant temperature; or the leaf movement of a plant in constant dim light and constant temperature. Now ask what happens if during those constant conditions an experimenter applies some perturbation that one suspects might influence the circadian clock. For example turning on the lights for five minutes, or raising the temperature 10C for 2 hours, or applying a drug for three hours. When one applies such a perturbation, it is common to observe that the time at which an event occurs (i.e. the phase) is often now different than a control that did not receive the perturbation. This is called a phase shift and is usually measured in hours from the control (or in degrees from a 360 cycle or in circadian time). One usually finds that the magnitude of the phase shift usually depends on the time in the cycle at which the perturbation was applied.
A Phase Response Curve (PRC) is a plot of the magnitude of phase shifting due to a pulse versus the time at which the pulse was applied. Experimenters have determined phase response curves for many organisms, many oscillating types of physiology, and using many forms of perturbation. Carl Johnson of Vanderbilt University has compiled the data for most of the published phase response curves and has termed the compilation the PRC Atlas. With my help, that data has been put into computer format and is available for the asking. The best way to view the data is via the PRC Atlas that can be downloaded from Carl Johnson's web site.
You can get the text format of the data by downloading one of the formats below. In this case you will have to put the data into your own plotting program to see the actual plots. The data are fairly well structured so that it should be easy to insert into your favorite data spreadsheet program.
Last updated January 13 2010
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