On the existence of physiological age based on functional hierarchy: a formal definition related to time irreversibility.
The present approach of aging and time irreversibility is a consequence of the theory of functional organization that I have developed and presented over recent years (see e.g., Ref. 11). It is based on the effect of physically small and numerous perturbations known as fluctuations, of structural units on the dynamics of the biological system during its adult life. Being a highly regulated biological system, a simple realistic hypothesis, the time-optimum regulation between the levels of organization, leads to the existence of an internal age for the biological system, and time-irreversibility associated with aging. Thus, although specific genes are controlling aging, time-irreversibility of the system may be shown to be due to the degradation of physiological functions. In other words, I suggest that for a biological system, the nature of time is specific and is an expression of the highly regulated integration. An internal physiological age reflects the irreversible course of a living organism towards death because of the irreversible course of physiological functions towards dysfunction, due to the irreversible changes in the regulatory processes. Following the works of Prigogine and his colleagues in physics, and more generally in the field of non-integrable dynamical systems (theorem of Poincaré-Misra), I have stated this problem in terms of the relationship between the macroscopic irreversibility of the functional organization and the basic mechanisms of regulation at the lowest "microscopic" level, i.e., the molecular, lowest level of organization. The neuron-neuron elementary functional interaction is proposed as an illustration of the method to define aging in the nervous system.
Chauvet
Gilbert A
GA
Laboratoire Développement et Complexité, Ecole Pratique des Hautes Etudes, 41, rue Gay-Lussac, Paris 75005, France. gilbert.chauvet@univ-angers.fr
D000375:Aging / Q000502:physiology*; D000818:Animals; D002490:Central Nervous System / Q000502:physiology; D003643:Death; D019277:Entropy; D006801:Humans; D008954:Models, Biological; D009415:Nerve Net / Q000502:physiology; D017711:Nonlinear Dynamics; D018384:Oxidative Stress / Q000502:physiology*; D013598:Systems Theory; D013995:Time