Open Systems in Biology

The model of open systems is applicable to many problems and fields of biology (Beier, 1962, 1965; Locker et al., 1964, 1966a). A survey of the biophysics of open systems, including theoretical foundations and applications, was given some years ago (von Bertalanlfy, 1953a); a revised edition (with W. Beier, R. Laue and A. Locker) is presently in preparation. The present survey is restricted to some representative examples.

There is, first, the large field of Goethe’s Stirb und werde, the continuous decay and regeneration, the dynamic structure of living systems at all levels of organization (Tables 6.1-6.3). Gen-erally it may be said that this regeneration takes place at far higher turnover rates than was anticipated. For example, it is certainly surprising that calculation on the basis of open system revealed that the proteins of the human body have a turnover time of not much more than a hundred days. Essentially the same is true for cells and tissues. Many tissues of the adult organism are maintained in a steady state, cells being continuously lost by desquamation and replaced by mitosis (F. D. Bertalanffy and Lau, 1962). Techniques such as the application of colchicine that arrests mitosis and thus permits counting of dividing cells over certain periods, as well as labelling with tritiated thymidine, have revealed a sometimes surprisingly high renewal rate. Prior to such investigations, it was hardly expected that cells in the digestive tract or respiratory system have a life span of only a few days.

After the exploration of the paths   of individual metabolic reactions, in biochemistry, it has now become an important task to understand integrated metabolic systems as functional units (Chance et al., 1965). The way is through physical chemistry of enzyme reactions as applied in open systems. The complex network and interplay of scores of reactions was clarified in functions such as photosynthesis (Bradley and Calvin, 1956), respiration (B. Hess and Chance, 1959; B. Hess, 1963) and glysolysis, the latter investigated by a computer model of some hundred nonlinear differential equations (B. Hess, 1969). From a more general viewpoint, we begin to understand that besides visible morphologic organization, as observed by the electron microscope, light microscope and macroscopically, there is another, invisible, organization resulting from interplay of processes determined by rates of reaction and transport and defending itself against environmental disturbances.

Hydrodynamic (Burton, 1939; Garavaglia et al., 1958; Rescigno, 1960) and particularly electronic analogs provide another approach besides physiological experiment, especially permitting solutions of multivariable problems which otherwise exceed time limits and available mathematical techniques. In this way Zerbst et al. (1963fE.) arrived at important results on temperature adaptation of heart frequency, action potentials of sensory cells (amending the Hodgkin- Huxley feedback theory), etc.

Furthermore, energetic conditions have to be taken into account. The concentration, say, of proteins in an organism does not correspond to chemical equilibrium; energy expense is necessary for the maintenance of the steady state. Thermodynamic consideration permits an estimate of energy expense and comparison with the energy balance of the organism (Schulz, 1950; von Bertalanffy, 1953a).

Another field of investigation is active transport in the cellular processes of import and export, kidney function, etc. This is con- nected with bioelectrical potentials. Treatment requires application of irreversible thermodynamics.

In the human organism, the prototype of open system is the blood with its various levels of concentrations maintained constant. Concentrations and removal of both metabolites and administered test substances follow open-systems kinetics. Valuable clinical tests have been developed on this basis (Dost, 1953-1962). In a broader context, pharmacodynamic action in general represents processes taking place when a drug is introduced into the open system of the living organism. The model of the open system can serve as foundation of the laws of pharmacodynamic effects and dose-effect relations (Loewe, 1928; Druckery and Kuepfmiiller, 1949; G. Werner, 1947).

Furthermore, the organism responds to external stimuli. This can be conceived of as disturbance and subsequent reestablishment of a steady state. Consequently, quantitative laws in sensory physiology, such as the Weber-Fechner law, belong to open systems kinetics. Hecht (1931), long before the formal introduction of open systems, expressed the theory of photoreceptors and existing laws in the form of “open” reaction kinetics of sensitive material.

The greatest of biological problems, remote from exact theory, is that of morphogenesis, the mysterious process whereby a nearly undifferentiated droplet of protoplasm, the fertilized ovum, becomes eventually transformed into the marvelous architecture of the multicellular organism. At least a theory of growth as quantitative increase can be developed (cf. pp. 17Iff.). This has become a routine method in international fisheries (e.g., Beverton and Holt, 1957). This theory integrates physiology of metabolism and of growth by demonstrating that various types of growth, as encountered in certain groups of animals, depend on metabolic constants. It renders intelligible the equifinality of growth whereby a species-specific final size is attained, even when starting conditions were different or the growth process was interrupted. At least part of morphogenesis is effectuated by so-called relative growth (J. Huxley, 1932), i.e., different growth rates of the various organs. This is a consequence of the competition of these components in the organism for available resources, as can be derived from open system theory (Chapter 7).

Not only the cell, organism, etc., may be considered as open system, but also higher integrations, such as biocoenoses, etc. (cf. Beier, 1962, 1965). The open-system model is particularly evident (and of practical importance) in continuous cell culture as applied in certain technological processes (Malek, 1958, 1964; Brunner, 1967).

These few examples may suffice to indicate briefly the large fields of application of the open-system model. Years ago it was pointed out that the fundamental characteristics of life, metabolism, growth, development, self-regulation, response to stimuli, spontaneous activity, etc., ultimately may be considered as consequences of the fact that the organism is an open system. The theory of such systems, therefore, would be a unifying principle capable of combining diverse and heterogeneous phenomena under the same general concept, and of deriving quantitative laws. I believe this prediction has on a whole proved to be correct and has been testified by numerous investigations.

Behind these facts we may trace the outlines of an even wider generalization. The theory of open systems is part of a general system theory. This doctrine is concerned with principles that apply to systems in general, irrespective of the nature of their components and the forces governing them. With general system theory we reach a level where we no longer talk about physical and chemical entities, but discuss wholes of a completely general nature. Yet, certain principles of open systems still hold true and may be applied successfully to wider fields, from ecology, the competition and equilibrium among species, to human economy and other sociological fields.

Source: Bertalanffy Ludwig Von (1969), General System Theory: Foundations, Development, Applications, George Braziller Inc.; Revised edition.

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