1,721,113 research outputs found
Heptadecapeptide ACTH 1-17 : the first analogue in chronobiology
No full textThe heptadecapeptide ACTH 1-17 is the analogue of corticotropin with β-alanine in position 1, lysine instead of 17-arginine and a basic amide instead of 18 arginine-amide. These modifications give enhanced biological activity and longer duration of the action. Several researchers investigated the acute effect of the analogue after administration at different time points along the 24 h cycle, and discovered that glucocorticoid and mineralocorticoid responses are dissociated in terms of doses and timing. Cortisol and urinary 17 OH-CS rise more after morning injections whereas for aldosterone the maximum effect was noted at 1400. The most interesting finding that concerns ACTH 1-17 is the chronizing effect. ACTH 1-17 can be a chronizer because its administration resets, for instance, the toleration to antimitotic drugs, to a more convenient time. At clinical level, a group of researchers studied, in some case correctly from a chronobiological point of view, the effect of the ACTH 1-17 on patients and on healthy subjects. It is useful to remember the concept of hierarchies of rhythms: each different periodic function is regulated or, better, intermodulated by a network of other periodic variables of the same organ or of other organs and systems. So the necessity of large samplings to evidentiate periodic phenomena, and the utility of investigating pertiment marker rhythms significantly correlated with those to be studied are evident. Autorhythmometry and automatic monitoring can help very much on this purpose
Ricerche sperimentali nel ratto con metodica cronobiologica simulante diversi turni di lavoro nell'uomo
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Chronobiology principles and methods of studying biological rhythms
No full textIn studying many diseases we meet with periodic phenomena. The appearance of some symptoms and the relevant remissions often have a cyclic pattern. The temporal structure of living organisms is at the root of these phenomena: the correct intermodulation, in terms of time, of the biological variables, realizes the conditions of well being. If the harmony between the biological rhythms is disturbed for some reason, the subjects find themselves in the state of proneness to disease or of overt disease. To evaluate this different situation it is necessary to follow the biological phenomena during the time and estimate, with correct statistical methods, the periodicity, the relevant parameters and the ratios. So research has to be completed with a sufficient number of measurements of pertinent variables and of the variables to be utilized as marker rhythms. For this purpose, autorhythmometry and automatic monitoring can help greatly. Evaluation of the parameters and ratios between the biological rhythms pertinent to the studied disease and marker rhythms constitute the ground on which the discussion and conclusions of the research have to be founded
Experimental peptic ulcerogenesis : the promise of international cooperation and its implications for the clinic
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