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Circadian Rhythms and Gene Regulation02:19

Circadian Rhythms and Gene Regulation

The biological clock is involved in many aspects of regulating complex physiology in all animals. It was in 1935 when German zoologists, Hans Kalmus and Erwin Bünning, discovered the existence of circadian rhythm in Drosophila melanogaster. However, the internal molecular mechanisms behind the circadian clock remained a mystery until 1984, when Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered the expression of the Per gene oscillating over a 24-hour cycle. In subsequent years,...
Circadian Rhythms and Gene Regulation02:19

Circadian Rhythms and Gene Regulation

The biological clock is involved in many aspects of regulating complex physiology in all animals. It was in 1935 when German zoologists, Hans Kalmus and Erwin Bünning, discovered the existence of circadian rhythm in Drosophila melanogaster. However, the internal molecular mechanisms behind the circadian clock remained a mystery until 1984, when Jeffrey C. Hall, Michael Rosbash, and Michael W. Young discovered the expression of the Per gene oscillating over a 24-hour cycle. In subsequent years,...
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The circadian—or biological—clock is an intrinsic, timekeeping, molecular mechanism that allows plants to coordinate physiological activities over 24-hour cycles called circadian rhythms. Photoperiodism is a collective term for the biological responses of plants to variations in the relative lengths of dark and light periods. The period of light-exposure is called the photoperiod.
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Light plays a significant role in regulating the growth and development of plants. In addition to providing energy for photosynthesis, light provides other important cues to regulate a range of developmental and physiological responses in plants.
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Sleep, an essential biological state, involves significant reductions in physical activity, sensory awareness, and interaction with the environment. This complex physiological process is primarily regulated by specific brain regions, notably the hypothalamus and pons, which govern the sleep-wake cycle or circadian rhythm.
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Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures
06:53

Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures

Published on: November 11, 2016

Light and the human circadian clock.

Till Roenneberg1, Thomas Kantermann, Myriam Juda

  • 1Institute for Medical Psychology, Centre for Chronobiology, Medical Faculty, Ludwig-Maximilians-University, Goethestrasse 31, 80336, Munich, Germany. till.roenneberg@med.uni-muenchen.de

Handbook of Experimental Pharmacology
|April 23, 2013
PubMed
Summary
This summary is machine-generated.

Rethinking circadian clock dogmas is crucial for understanding entrainment. Social cues likely influence human circadian rhythms through light, leading to social jetlag and potential health issues.

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Last Updated: May 12, 2026

Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures
06:53

Parallel Measurement of Circadian Clock Gene Expression and Hormone Secretion in Human Primary Cell Cultures

Published on: November 11, 2016

Monitoring Cell-autonomous Circadian Clock Rhythms of Gene Expression Using Luciferase Bioluminescence Reporters
10:38

Monitoring Cell-autonomous Circadian Clock Rhythms of Gene Expression Using Luciferase Bioluminescence Reporters

Published on: September 27, 2012

Area of Science:

  • Chronobiology
  • Human Physiology
  • Environmental Health

Background:

  • Circadian clocks require stable entrainment, primarily using light-dark cycles as environmental signals (zeitgebers).
  • Early concepts focused on self-sustained oscillations in constant conditions, influencing our understanding of entrainment.
  • Rethinking these foundational ideas is necessary to fully grasp circadian programming and entrainment mechanisms.

Purpose of the Study:

  • To challenge traditional circadian rhythm dogmas.
  • To propose that social zeitgebers influence human circadian entrainment via light and behavioral feedback loops (zeitnehmer).
  • To investigate human circadian entrainment using real-world conditions outside laboratory settings.

Main Methods:

  • Analysis of real-world human entrainment factors like daylight saving time and time zones.
  • Investigation of the impact of artificial light environments on circadian synchrony.
  • Epidemiological and experimental data on light as a primary human zeitgeber.

Main Results:

  • Human circadian entrainment is influenced by diverse real-world factors, not just laboratory conditions.
  • Social zeitgebers may operate through light entrainment and behavioral feedback loops.
  • Significant discrepancies between biological and social time (social jetlag) have emerged due to modern environmental changes.

Conclusions:

  • Traditional circadian rhythm paradigms need revision to encompass human-specific entrainment factors.
  • Social jetlag, a consequence of modern lifestyles, represents a form of circadian misalignment with potential health implications.
  • The majority of the industrialized population may experience forced synchrony, impacting circadian health.