Thermodynamic aspects of developmental biology.

Abstract This article examines theoretical and experimental evidence of the validity of the Prigogine-Weame thermodynamic theory of the development and growth of living organisms. It shows that for the process of development and growth a condition of linear relations is achieved between fluxes and forces. A continual reduction in the rate of specific entropy production—measured from the rate of heat production or respiration—takes place during development, growth and ageing. While this is going on living organisms move towards the final steady state defined as the minimum rate of entropy production. The processes of injury, regeneration and malignant growth fit the framework of the thermodynamic theory of development very well. Proceeding from the Prigogine-Weame theory and an equation of animal growth we have derived a new relationship between the rate of specific heat production and the weight of growing animals. The article indicates the main periods in the life of organisms when deviation from the steady state occurs, i.e. the period of oogenesis, and the period of initial changes during regeneration and malignant growth. During these periods rejuvenation of the cells takes place (in the thermodynamic sense) and this allows them to reaccomplish the processes of development which are again accompanied by a reduction in the rate of specific entropy production.