Learning and physiological regulation

Book Reviews Role of Free Radicals in Biological Systems--Edited by J. Feher, A. Blazovics, B. Matkovics and M. Mezes. 258 pp. 1993. Akademiai Kiado, Budapest, $52. Free radicals are formed in many biological systems such as arachidonic acid metabolism, microsomal enzyme metabolism of drugs, electron transport, and the oxygen dependent killing of bacteria by phagocytes. Free radicals probably are important in the pathology of inflammation, ischaemia-reperfusion damage, hyperlipidemia, liver cirrhosis, streptozotocin induced diabetes, atherosclerosis, and in the ageing process. Naturally occuring antioxidants, ascorbic acid, alpha tocopherol, glutathione, the P450 system, melanins, and specific enzymes protect against reactive oxygen intermediates and lipid peroxides. This volume deals with the role of free radicals in a range of systems with special relevance to enzyme and tissue damage and the extent to which it can be prevented. Learning and Physiological Regulation--B. R. Dworkin. 215 pp. 1993. University of Chicago Press, Chicago. £19.25, $27.50. Homeostasis is often explained in terms of fixed negative feedback networks. Dworkin thinks that the systems are more dynamic and that the stability and regulation of heart rate, blood pressure, glucose, electrolytes and temperature are due not only to hard wired systems but that learning mechanisms in the nervous system are essential to regulation. He deals with the history

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of homeostasis; classical conditioning; the Russian school; conditioned drug responses; long term regulation of the physiological state; models of steady state regulation. The book provides a welcome review of the adaptability of living systems to adjust and change their set point.

Regulation and Control Mechanisms in Biological Systems--V. S. Vaidhyanathan. 294pp. 1993. Prentice Hall, New Jersey. Biochemistry, biophysics and mathematics have all developed approaches to control theory. This book deals with the application of some of these to the study of living systems. The chapters deal with characteristics of living systems (systems theory, reduction of errors, feed back, step responses of 1st, 2nd and 3rd order, stability); thermodynamics; homeostatic systems (membranes, cell cycle, acid-base regulation); system behavior in stationary state (stability, continuity, carrier-transport model, irreversible processes, network thermodynamics, catastrophy); biochemical control mechanisms (kinetics, open systems, enzymes, large substrate concentration, feedback, allosterism, free energy coupling); mathematical aspects (oscillations, harmonics, stability, phase plane, linear stability, natural, forced and van de Pol oscillations, fields of oscillators); control mechanisms (genetic control, insulin release, growth, conflict and pursuit, antibody-tumor interactions); nonlinear nonequilibrium thermodynamics; rhythmic phenomena in biology. The book is aimed at the undergraduate/postgraduate level.