Current progress in chronohaematology

Circadian oscillators in eukaryotes

The biological clock, present in nearly all eukaryotes, has evolved such that organisms can adapt to our planet's rotation in order to anticipate the coming day or night as well as unfavorable seasons. As all modern high-precision chronometers, the biological clock uses oscillation as a timekeeping element. In this review, we describe briefly the discovery, historical development, and general properties of circadian oscillators. The issue of temperature compensation (TC) is discussed, and our present understanding of the underlying genetic and biochemical mechanisms in circadian oscillators are described with special emphasis on Neurospora crassa, mammals, and plants.

Daily rhythms of serum and salivary parameters in goats

OBJECTIVE

Determine the daily rhythms of urea, bicarbonate, sodium, potassium, chloride, calcium, magnesium and inorganic phosphorus secretion in the serum and saliva of goats and whether there is a relationship between them.

DESIGN

Ten non-gravid, non-lactating does underwent a 30-day preconditioning period (natural 24-h photoperiod, environmental temperature 19-21 degrees C, relative humidity 40-50%, the same feeding regimen, offered as a single meal at 07:00 hours, and water ad libitum), following which saliva and blood samples were collected from each subject every 4 h for 2 days (starting at 08:00 hours) for measurement of urea and electrolytes.

RESULTS

Data analysis was conducted by one-way repeated measures analysis of variance (ANOVA) and by the single cosinor method. ANOVA showed a significant effect of time (0.001 < P < 0.01) on all the studied parameters in saliva and serum on both days. Cosinor analysis identified the periodic parameters and their acrophases (expressed in hours) during the 2 days of monitoring. Serum and salivary acrophases were all diurnal and were observed between 11:40 and 16:24 hours. No circadian rhythmicity was found for bicarbonate, magnesium or potassium in either saliva or serum.

CONCLUSION

There was a daily rhythm of secretion for the majority of the measured parameters, suggesting the potential role of saliva as an additional, reliable index for physiological, clinical, nutritional and chronophysiological studies.

Effects of different electromagnetic fields on circadian rhythms of some haematochemical parameters in rats

OBJECTIVE

To investigate the effects of different electromagnetic fields on some haematochemical parameters of circadian rhythms in Sprague-Dawley rats.

METHODS

The study was carried out in 18 male and 18 female rats in good health conditions exposed to 50 Hz magnetic sinusoid fields at the intensity of 1000 microT, 100 microT, and 0 microT (control group) respectively, and in 18 male and 18 female rats in good health conditions exposed to 1.8 GHz electromagnetic fields at the intensity of 50 V/m, 25 V/m and 0 V/m (control group), respectively. Following haematochemical parameters for glucose, triglycerides, and total cholesterol were measured.

RESULTS

Different effects of electromagnetic fields on circadian rhythms of both male and female rats were observed. Different changes occurred in some haematochemical parameters for glucose, triglycerides, and total cholesterol (P < 0.05).

CONCLUSION

Exposure to different electromagnetic fields is responsible for the variations of some haematochemical parameters in rats.

A two-clock model of circadian timing in the immune system of mammals

It has been confirmed that clock genes, as well as the pineal hormone, have a role in the hypothalamic suprachiasmatic nucleus, the circadian endogenous pacemaker. It seems that the peripheral clock genes in the cells of the immune system subtly control biorhythms; their seeming lack of impact only showing that they work well. Some biorhythms even seem to be independent of a light/dark circadian regime. This apparent conflict in the mammalian time structure can be resolved by a two-clocks control model involving: (a) the endogenous gene clock, which is dominant in the neural system and (b) the exogenous clock of the immune system. Interactions between these two clocks can explain both the frequently observed individual differences in circadian rhythms and the subtle role of the peripheral clock genes. The endogenous clock facilitates an alternation in the immune system which counters external attacks in daytime and induces repair and advancement by night.