Hormones and blood pressure: clues from chronobiology

Results relating to the study of several hormones homeostatically related to blood pressure (renin-angiotensins, mineralocorticoids, glucocorticoids, atrial natriuretic factor) are reviewed. Most experimental data and clinical observations concerning 'hypertension' are specified neither as to circadian stage nor do they assess rhythm parameters. Such homeostatic data suggest that several groupings of hormones play a major role in coordinating blood pressure. The majority of hormones involved have multiple actions and the diversity of effects is often unexplained in homeostatic terms. In chronobiology, opposite effects are seen in response to the same stimulus depending upon the stage of the organism's multifrequency rhythms and their intermodulation. The periodic pattern exhibited by some of the hormones coordinating blood pressure in health and the capability of these hormones to modify temporal structure, either inducing a change in timing (circadian blood pressure ecphasia) or in amplitude (amplitude-hypertension) or in mean level of the values (MESOR-hypertension) are reviewed as well.     

Learning chronobiology by improving wikipedia

Although chronobiology is of growing interest to scientists, physicians, and the general public, access to recent discoveries and historical perspectives is limited. Wikipedia is an online, user-written encyclopedia that could enhance public access to current understanding in chronobiology. However, Wikipedia is lacking important information and is not universally trusted. Here, 46 students in a university course edited Wikipedia to enhance public access to important discoveries in chronobiology. Students worked for an average of 9 h each to evaluate the primary literature and available Wikipedia information, nominated sites for editing, and, after voting, edited the 15 Wikipedia pages they determined to be highest priorities. This assignment (http://www.nslc.wustl.edu/courses/Bio4030/wikipedia_project.html) was easy to implement, required relatively short time commitments from the professor and students, and had measurable impacts on Wikipedia and the students. Students created 3 new Wikipedia sites, edited 12 additional sites, and cited 347 peer-reviewed articles. The targeted sites all became top hits in online search engines. Because their writing was and will be read by a worldwide audience, students found the experience rewarding. Students reported significantly increased comfort with reading, critiquing, and summarizing primary literature and benefited from seeing their work edited by other scientists and editors of Wikipedia. We conclude that, in a short project, students can assist in making chronobiology widely accessible and learn from the editorial process.     

Time is ripe: maturation of metabolomics in chronobiology

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The birth of chronobiology: Julien Joseph Virey 1814

Julien-Joseph Virey (1775-1846) held the position of pharmacist-in-chief at the Val-de-Grace, a military hospital. He was an innovative pharmacist, naturalist, anthropologist, and philosopher and a prolific author. His writings encompassed a wide range of topics, although many of his ideas were sometimes harshly questioned. Interest in Virey's work today stems from renewed appreciation of his doctoral thesis in medicine, which was completed in 1814 in Paris and was the first devoted to biological rhythms. Virey envisioned biological rhythms to be innate in origin and controlled by living clocks entrained by periodic environmental changes, such as the day-night alternation in light and darkness. He also reported that the effects of drugs vary according to their administration time. But, above all, he collected and published quantified time series that demonstrated human circadian and annual mortality rhythms. Statistical analysis of Virey's data using modern time series methods confirms his deduction that human mortality exhibits rhythmicity. Comparison of his findings with those derived from analyses of more recent human mortality time series shows the characteristics of these rhythms have changed little since 1807 despite differences in environmental conditions. Virey deserves credit for establishing the field of chronobiology based on his insights and writings.     

Perspectives in chronobiology of air pollution

In a series of experiments, male and female Sprague Dawley rats, kept in light (L) from 06(00) to 18(00) alternating with darkness (LD 12:12) inhaled different concentrations of carbon monoxide (50-1,700 ppm) at each of two test times, 12 h apart. A decrease in flow of CO2 (VCO2) resulting from CO inhalation was greater in the active dark (D) than resting light (L) span. Experimental hypoxic mortality of male and female mice also shows circadian variations, being greater in the D than in the L span. Moreover, a difference of mortality was observed betwen hypoxic exposures performed at 12(00) (in LD or DL) and hypoxic exposures performed at 00(00) (in LD or DL). Such results await tests of any extent to which they model responses of human beings to air pollution. In human beings any external environmental circadian, circaseptan and circannual variations in air pollution as such may serve to variable extent as socioeconomic synchronizers of innate rhythms with a corresponding frequency, rather than as solely generators of time patterns in any physiopathologic response to air pollution.     

Application of flow cytometry in chronobiology

A survey is given on flow cytometric techniques and their applications in chronobiology. Rapid automatic single cell measurements with a high rate (1,000-5,000 single cells/sec) enable the accumulation of large numbers of data at short intervals, thus obtaining important knowledge on circadian variations of cell proliferation in epidermis and other types of surface epithelium as well as hemopoiesis. In addition, the method has to some extent been used for monitoring cancer chemotherapy, and is thus available for the application in chronotherapy of malignancy. The introduction of rapid automatic techniques such as flow cytometry is a great advantage for any study on single cells and tissues where rhythmic variations in different functions have to be taken into consideration.