Transdisciplinary unifying implications of circadian findings in the 1950s (original) (raw)

Timeless spaces: Field experiments in the physiological study of circadian rhythms, 1938-1963

History and Philosophy of the Life Sciences, 2023

In the middle of the twentieth century, physiologists interested in human biological rhythms undertook a series of field experiments in natural spaces that they believed could closely approximate conditions of biological timelessness. With the field of rhythms research was still largely on the fringes of the life sciences, natural spaces seemed to offer unique research opportunities beyond what was available to physiologists in laboratory spaces. In particular, subterranean caves and the High Arctic became archetypal 'natural laboratories' for the study of human circadian (daily) rhythms. This paper is explores the field experiments which occurred in these 'timeless spaces'. It considers how scientists understood these natural spaces as suitably 'timeless' for studying circadian rhythms and what their experimental practices can tell us about contemporary physiological notions of biological time, especially its relationship to 'environmentality' (Formosinho et al. in Stud History Philos Sci 91:148-158, 2022). In so doing, this paper adds to a growing literature on the interrelationship of field sites by demonstrating the ways that caves and the Arctic were connected by rhythms scientists. Finally, it will explore how the use of these particular spaces were not just scientific but also political-leveraging growing Cold War anxieties about nuclear fallout and the space race to bring greater prestige and funding to the study of circadian rhythms in its early years.

In Search of Circasemidian Rhythms

2006

There is controversy over the existence of physiological or behavioral circasemidian (12-h period) rhythms. However, a number of reports have shown a circasemidian error pattern in industrial and transportation environments and a circasemidian pattern in body temperature. We hypothesized that body temperature, subjective sleepiness, simple response time and working memory speed would oscillate with a period of 12 hours (the circasemidian frequency); and that the parameter values describing the circasemidian oscillations of the measures would differ across genders and age groups. Measurements were acquired from 37 male and female participants at half-hourly intervals from 0700h to 1900h in constant conditions. Circasemidian cosine curves were fitted to the data of individual subjects by the least-squares method. A statistically-significant, 12-hour pattern was found for body temperature and for subjective sleepiness, but not for simple response time or working memory speed. No differences in rhythm parameter values were found with respect to gender or age group. Body temperature peaked at 16:49h with a half-wave amplitude of 0.31 deg F. Sleepiness peaked at 17:40h with a half-wave amplitude of 7.7 scale units out of 100 scale units. Considering the large numbers of field observations of a two-peak pattern in errors and accidents, the failure to detect a circasemidian rhythm in task performance was attributed to the task, itself. Future investigations should attempt to replicate our findings, acquire 24 h/day body temperature data, combine circasemidian with circadian cosinor estimates, determine which laboratory tasks display a circasemidian rhythm, try to determine why only some tasks may display that rhythm, and consider models other than the cosine curve.

Chronobiology and circadian rhythms establish a connection to diagnosis

Diagnosis, 2014

Circadian rhythms are synchronized by the light/dark (L/D) cycle over the 24-h day. A suprachiasmatic nucleus in the hypothalamus governs time keeping based on melanopsin messages from the retina in the eyes and transduces regulatory signals to tissues through an array of hormonal, metabolic and neural outputs. Currently, vague impressions on circadian regulation in health and disease are replaced by scientific facts: in addition to L/D cyling, oscillation is maintained by genetic (Clock, Bmal1, Csnk1, CHRONO, Cry, Per) programs, autonomous feedback loops, including melatonin activities, aerobic glycolysis intensity and lipid signalling, among others. Such a multifaceted influential system on circadian rhythm is bound to be fragile and genomic clock acitvities can become disrupted by epigenetic modifications or such environmental factors as mistimed sleep and feeding schedules albeit leaving the centrally driven melatonindependent pacemakter more or less unaffected.

Circadian clocks — the fall and rise of physiology

Nature Reviews Molecular Cell Biology, 2005

| Circadian clocks control the daily life of most light-sensitive organisms -from cyanobacteria to humans. Molecular processes generate cellular rhythmicity, and cellular clocks in animals coordinate rhythms through interaction (known as coupling). This hierarchy of clocks generates a complex, ~24-hour temporal programme that is synchronized with the rotation of the Earth. The circadian system ensures anticipation and adaptation to daily environmental changes, and functions on different levels -from gene expression to behaviour. Circadian research is a remarkable example of interdisciplinarity, unravelling the complex mechanisms that underlie a ubiquitous biological programme. Insights from this research will help to optimize medical diagnostics and therapy, as well as adjust social and biological timing on the individual level. NATURE REVIEWS | MOLECULAR CELL BIOLOGY VOLUME 6 | DECEMBER 2005 | 965 PERSPECTIVES