Time is a dimension tightly associated with the biology of living species. There are cycles of varied lengths in biological activities, from very short (ultradian) rhythms to rhythms with a period of approximately one day (circadian) and rhythms with longer cycles, of a week, a month, a season, or even longer. These rhythms are generated by endogenous biological clocks, i.e. timekeeping structu...

SUMMARY Traditionally the site of impulse formation in so-called A-V nodal rhythms has been considered to be within the upper, middle, and lower portions of the A-V node. In this study, evidence obtained supports the concept that the His bundle and not the A-V node is the pacemaker site in nodal rhythms. His bundle activity was recorded in clinical cases of nodal rhythms and A-V dissociation by...

1997 marks the 25th anniversary of the discovery of the master circadian pacemaker in mammals in the hypothalamic suprachiasmatic nucleus. Remarkable progress has been made over the last 25 years in elucidating the physiological mechanisms involved in the entrainment, generation and expression of circadian rhythms at the cellular and systems levels. The recent discovery and cloning of the first...

Alpha rhythms have been elicited in one of a pair of identical twins as a result of evoking these rhythms in a conventional manner solely in the other.

n-phthaloyl gaba was administrated daily (50 mg/kg body weight-i.p) to wistar rats for 21 days and circadian rhythms of thiobarbituric acid reactive substances (tbars) and antioxidants such as reduced glutathione (gsh), catalase (cat) and superoxide dismutase (sod) were studied under constant light (ll) conditions. delayed acrophase of tbars and advanced acrophase of antioxidants (gsh, cat and ...