Chronobiologic rhythm

Seasonal variation is another chronobiological rhythm that is manifested by increases in depression and suicide in spring (with smaller peaks in autumn), as opposed to mania, which increases in the summer months. These observations have led to preliminary studies on the alteration of both light and temperature as potential therapies for the two seasonal patterns of affective disturbance. The phenomenon of seasonal variation is discussed in the sections Seasonal Affective Disorders in Chapter 6 and BrighlLight in Chapter 8. 

Both these 5-hydroxyindoles are natural compounds, playing an important role in the brain. 5-hydroxytryptophan (5-HTP) 315 is the metabolic precursor for the neurotransmitter serotonin melatonin 316 is a neurohormone involved in the regulation of chronobiological rhythms such as sleep and fertility306. They have been labelled with F-18, for in vivo metabolic imaging with PET, in reaction of dilute [18F]fluorine gas with melatonin or with 5-hydroxytryptophan in hydrogen fluoride307 at — 70 °C (equation 134). 

Lemmer, B. Genetic aspects of chronobiologic rhythms in cardiovascular disease. In From Molecule to Men Zehen-der, M., Breithardt, G., Just, H., Eds. Darmstadt Germany, 2000 201-213. 

Eating behaviour, in common with many aspects of human activity, is yoked to a number of chronobiological rhythms which oscillate at varying frequencies. Some, such as the sleep-wake cycle, show regular and predictable fluctuations within the 24 hour day their rhythm is said to be diurnal. Others, like the menstrual cycle in women, follow a monthly pattern. There are yet others which have an annual or seasonal periodicity. A number of clinical conditions have been described in which disturbances in eating and changes in body weight follow similar daily, monthly or yearly patterns. 

In the brain, the hypothalamus links the nervous system to the pituitary gland (hypophysis) and this acts on the endocrine system through a number of hypothalamic hormone releasing factors neurohormones (see Chapter 10). The hypothalamus is responsible for the regulation of body temperature, hunger, and thirst and for chronobiological rhythms. 

According to the approach pioneered by Halberg, deterministic, biological rhythms (i.e., chronobiologic rhythms) have four measurable parameters the mean, amplitude, acrophase, and period (Pauly, 1980). These are shown graphically in Fig. 1. 

Arendt, J. 1998. Biological rhythms The science of chronobiology. Journal of the Royal College of Physicians, London 32 27-35. 

Cal, J. C., F. Lemoigne, R. Crockett, and J. Cambar. 1987. Circadian rhythm in gamma glu-tamyltranspeptidase and leucine aminopetidase urinary activity in rats. Chronobiology International 4 153-160. 

Pauly. J. E. (1980). The Spectrum of the Rhythm. Chronobiology. Sijthoff Noordhoff, The Netherlands. 

Reinberg, A. (1983). Chronobiology and Nutrition. Biological Rhythms and Medicine. Springer-Verlag, New York. 

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