Journal of Circadian Rhythms - Latest Comments

Congratulations

Nikola Ilankovic — 2012-01-03T14:38:03Z

It is very interesting!
Congratulations!
Prof.dr Nikola Ilankovic, Belgrade

An interesting article with further scope of research

Priyoneel Basu — 2011-07-01T15:43:32Z

An extremely intriguing and interesting discussion, with scope for further research. The following extensions of this study immediately present themselves:
a) Assessment of periodicity in LOV knock-in and knock-out bacteria
b) A study of the entrainability of this apparent rhythm to zeitgebers of varying periodicity
c) Alterations in periodicity induced by nutrients/ factors
d) The authors present the view that histidine kinase is involved in environmental responses in P. putida, which could be easily checked with a histidine kinase inhibitor (Ref: Gilmour et al., J Bacteriol. 2005 December; 187(23): 8196¿8200.).
In case the authors have already thought of these obvious extensions, then this reader will be looking forward to reading the results in a similarly engaging paper.

Circadian symptoms and responses

Daniel Kripke — 2009-12-08T01:35:43Z

The response of patients to bright light and the circadian expression of bipolar symptoms are some of the evidence supporting the hypothesis that circadian polymorphisms contribute to bipolar disorder.

bipolar disorder linked to circadian clock through sodium

Gregory Marlow — 2009-12-06T21:25:20Z

I had bipolar disorder several years ago and I cured it with light therapy and a high salt diet. The light therapy has an obvious connection to the circadian clock – it lengthens daylight. But it took me a while to find how salt was connected. I discovered that in the evening my urine sodium level rose dramatically. This implies that my sodium blood level falls at this time, probably in preparation for sleep. When my sodium level goes below a certain level it causes a condition called hyponatremia which includes mental symptoms. The high salt diet prevents me from going below that critical level and the extra evening light therapy slows down the loss of sodium during the evening hours.

Teaching Chronobiology and Science

John Araujo — 2009-06-22T15:12:53Z

This review is one of the best chronobiology paper that I have read. It discuss carefully the most important chronobiology concept and it teach us how to make a good and serious Science.

Re: Missing Nighttime Light Exposure?

J. Bullough — 2008-07-29T15:34:05Z

It is standard protocol that participants should wear the device if they get up during normal sleep hours (e.g., to use the bathroom) so such light exposures would be measured. See for example the bottom panel of Figure 1 from a related paper (Figueiro et al. 2006) where the Daysimeter was used.

Missing Nighttime Light Exposure?

Berndette Chasteen — 2008-07-26T00:03:46Z

This new technique for studying the effects of circadian disruption is a wonderful step forward for our understanding of this important area of human health. I just worry that having the Daysimeter device left next to the subject during sleep hours will miss critical nighttime light exposure when the subject gets up in the night (e.g. turning on a bathroom light or passing a window which admits streetlight).

A balance of factors

Daniel Kripke — 2007-08-23T01:16:23Z

Dr. Zivkovic is absolutely right that we might expect the circadian oscillators of older adults to be weaker, and for that reason, easier to phase shift. That is, weaker amplitude in overt circadian rhythms could reflect a lower amplitude central pacemaker leading theoretically to higher-amplitude phase-response curves [1-2]. One indication that older people have weaker oscillators is the lower overt amplitude of many rhythms such as body temperature, activity, and melatonin. Another indication may be the longer duration of melatonin secretion observed, as this may be analogous to increased melatonin duration and activity time (α) in nocturnal rodents [3]. Increased duration of nocturnal wheel-running in hamsters corresponds to a circadian pacemaker which is easier to shift [4,5], and therefore might possibly have a lower functional amplitude. Emerging evidence suggests that increased activity duration (α) may correspond to the dispersion of the phases of the circadian rhythms of individual pacemaker neurons within the suprachiasmatic nucleus. The more dispersed the phases, the weaker the compound oscillator resulting from coupling of these neurons would be. Nonetheless, if decreased pacemaker amplitude contributes importantly to the increased amplitude of light induced phase shifts typical of hamsters exposed to short-photoperiods, oscillator theory predicts that the lower amplitude circadian pacemaker will also show more robust phase shifts to other phase shifting stimuli. However, this expectation was not confirmed for the case for novel wheel-running induced shifts [5], indicating that these relationships warrant further research.

From a different perspective, we expected older adults to have more yellowing of the ocular lens and poorer transmission of the blue-green wave lengths most important in producing phase shifts. Retinal deterioration associated with aging could be another factor. Thus with aging, poorer transmission of the light signal to the retina and from there to the suprachiasmatic nucleii would perhaps tend to produce a weakened phase response.

It would appear that in the particular older adult sample that we studied, the above factors favoring strong phase shifts and those favoring weaker phase shifts were roughly balanced or not as important as suggested above. However, among adults of greater age or poorer health status, the balance might be different.

Regarding the other question, we did not plan to provide all the results for temperature, cortisol, and activity, since as far as we could see, they were entirely consistent with results for aMT6s but merely less statistically significant (for the most part). We have not discerned any reliable differences between variables in the phase responses. To present those data in detail would raise more statistical questions (since several P values were >0.05 or marginal) which might be difficult to resolve or explain.

Daniel F. Kripke, M.D.

Jeffrey A. Elliott, Ph.D.

1. Johnson CH, Elliott JA, Foster R, Honma K-I, Kronauer R: Fundamental properties of circadian rhythms. In: Chronobiology: Biological Timekeeping. Edited by Dunlap JD, Loros JJ, DeCoursey PJ. Sunderland, MA: Sinauer Associates, Inc. 2004:67-105.

2. Johnson CH, Elliott JA, Foster R: Entrainment of circadian programs. Chronobiology Intl. 2003, 20:741-744.

3. Elliott JA and Tamarkin L: Complex circadian regulation of pineal melatonin and wheel running in Syrian hamsters. . Comp Physiol A 1994, 174:469 484.

4. Pittendrigh CS, Elliott JA, and Takamura T: The circadian component in photoperiodic induction. (CIBA. Foundation. Symposium 104). , 1984: 26 47.

5. Evans JA, Elliott JA, Gorman MR: Photoperiod differentially modulates photic and nonphotic phase response curves of hamsters. Am J Physiol 2004, 286:R539-46.

Nice paper, but I have one little question

Bora Zivkovic — 2007-08-01T02:15:08Z

This work is well thought-out and well done. I do not think that the negative result (i.e., no difference between young and old) is a reason to despair - I find it quite informative. I have explained in more detail here:

The Amplitude Problem

Will all the data (e.g., temperature PRC, etc.) be available as Supplementary Information?

Finally, is it a mistake that you expected a smaller sizes of phase-shifts in a lower-amplitude system? Shouldn't you expect greater shifts when the amplitude is lower?

Reply to Professor Kats' query

Roberto Refinetti — 2005-05-15T00:57:14Z

Professor Halberg, as the author of the referenced article, may have a different answer, but my feeling is that more information about the problem is needed before a solution can be sought. In principle, the desynchrony between the circadian clock and the outside clock caused by transmeridian travel could have many effects, including the reported worsening of tremor activity. However, the fact that the tremor improves in a few hours upon return home suggests that circadian desynchrony is not the central issue. More likely, the worsening of tremor activity is an acute effect of the trip (pressure changes in the airplane, change in weather from origin to destination, air-borne allergens, etc.). As for the question of whether targeting genes that encode the proteins governing circadian rhythms could yield new treatments for disorders of circadian rhythm, the answer is certainly "yes", although any such treatment is many years (probably decades) in the future.