Department of Physiology, Ibrahim Medical College and Oxford Centre for Diabetes, Endocrionolgy & Metabolism, University of Oxford, Oxford, UK
Department of Physiology, Ibrahim Medical College, 122 Kazi Nazrul Islam Avenue, Shahbag, Dhaka
Throughout the annals of time, men even the prehistoric ones have been fascinated by the ever-existing rhythmic processes in living systems. However, this idea wasn’t completely in the open till 1797 when Hufeland proposed rhythmic events of life in relation to 24 hours or solar day as a prime unit of functional chronology1. In Florida, nose and throat surgeons found that hemorrhages in throat operation were 82% higher during the second quarter of the cycle of the moon than at other times2. Similarly, insulin sensitivity index was found to be lower during winter than summer in Swedish population3. Seasonal variations of HbA1C in diabetic subjects and glycemic variations in healthy subjects have also been reported4-6.Thus, it seems that periodic biological events are intimately related to the non-biological cycles, whether terrestrial, astronomical, physical, electrical or others. But certainly it has been realized by the early scientists that the universe is rhythmic and displays incessant movement in the form of periodicity. The capacity to follow them, to oscillate, would enhance the survival potential of a species, including we, the human beings.
In 1843, nearly half a century after Hufeland’s Publication, Chossat presented his report of 20 years of study on the changes in cloacal temperature of pigeons under various experimental conditions as to environmental temperature and nutrition1. Further analyses on biological rhythms revealed that ‘a close study of these rhythms should yield vital information concerning the construction of various biochemical reactions in the body, especially if cybernetic and thermodynamic principles are applied’. Many enthusiastic scientists and clinicians then devoted themselves for basic understanding of the fundamentals of biological rhythms. In the 30’s of the twentieth century, the periodic behavior of the normal blood glucose was characterized. In this case small meals were given regularly throughout the day and generally each meal produced a variable, transient increase. However, it was found that the glucose concentration often tended to drop somewhat at about 2 to 3 p.m. even if food was given7. The essential feature of this periodic behavior is that the blood glucose level is relatively stable, varying between 4.4 and 6.6 mM/L. It was discovered later, that under physiological conditions the blood glucose level is kept at around 5 mM/L in fasting mammals, including humans due to the pulsatile release of the glucostatic hormone insulin.
Ibrahim Med. Coll. J. 2007; 1(1): 21-31
Address for Correspondence: Prof. KM Fariduddin, Department of Physiology, Ibrahim Medical College, 122 Kazi Nazrul Islam Avenue, Shahbag, Dhaka-1000
