Biochemical Adaptation by Peter W. Hochachka and George N. Somero (review)

BOOK REVIEWS Biochemical Adaptation. By Peter W. Hochachka and George N. Somero. Princeton, New Jersey: Princeton University Press, 1984. Pp. 537. $60.00 (cloth); $19.50 (paper). "What do you do for stress?" "Well, I take ..." could be lines from a TV commercial for analgesics, but in this case it is the theme for a very readable book on biological accommodations. The authors have accumulated information from many diverse fields and organized them into several basic strategies used by organisms to adapt to their environments. After reviewing the basic workings of a metabolizing cell, they note how organisms adapt components of their metabolism to such stress situations as strenuous exercise, deep diving (seals and whales), limited oxygen availability, high saline content, extremes of heat and cold, anhydrobiosis and hibernation, and life in the deep sea under hydrostatic pressures 1,000 times that at sea level. In each instance the authors present the strategies that might be used in accommodation: adjusting or altering enzymatic pathways, altering the macromolecular or micromolecular environment of the metabolizing cell. The success of these adjustments to the stress can be assessed when the organism survives and flourishes in an environment closed to other organisms. Short-term or seasonal stress is also considered. For example, as winter approaches goldfish gradually adjust their energy metabolism to life under the ice with limited oxygen supply. Anoxia-adapted goldfish use the fermentation pathway for energy production. This leads to an accumulation of acidic end products (lactate, propionate, etc.) leading to acidosis. The key enzymes of the goldfish, turtles, etc., have distinctly acid pH optima compared to those of terrestrial animals. These anoxia-adapted animals also can detoxify the accumulating lactate by further metabolizing it to pyruvate to acetaldehyde and then to ethanol. The ethanol is lost to the outside water. The authors present these examples to formulate the principles of adaptation. They differentiate the old concept of adjustment—the return to a "normal state" (homeostasis)—from the more modern view of adjustment to conserve function, which is termed enantiostasis. A cogent example of the strategy of enantiostasis is the halophilic bacteria. Living in salt concentrations of 3—5 M (i.e., saturating levels), these organisms cannot function below levels of 1-2 M Na Cl. An examination of the proteins of the organism reveals that there are many acidic amino acids, few strongly hydrophobic residues, and many weakly hydrophobic residues. High KCl concentrations stabilize proteins, and these latter become rigid, often too rigid to function. In the halophilic bacteria, however, the proteins are designed to be unstable at normal solute states but stable and functional at multimolar K+ concentrations. The internal K concentrations of bacteria balance the external Na concentra326 Book Reviews tions of the environment. The organism utilizes solar energy by way of a rhodopsin pigment to concentrate the internal K. Many other areas of stress and strategies of adaptation to it are also covered in the book. These include "on-off' switches for metabolism in both hibernating animals, to ensure survival of cold, and in estivating animals during periods of anhydrobiosis; evolution of respiratory proteins for life at high altitudes; the compensation of altered entropy and enthalpy in accommodating muscle protein to life at great ocean depths; the temporary adjustments that allow animals to dive to great depths in the oceans; the compositional changes in cell membrane permitting adjustment to life at temperatures elevated enough to denature most "normal" cell components; and many more. The interested reader will find this a fascinating book that will give him a feeling of awe page after page. It is not intended to be encyclopedic but is a compilation of the recent investigations on the adaptation of organisms to difficult environments. The style is clear and terse and very readable. John W. Rippon Department of Medicine University of Chicago Selective Nontreatment of Handicapped Newborns. By Robert Weir. New York: Oxford University Press, 1984. Pp. 292. $27.95. The medical management of handicapped neonates constitutes one of the most agonizing and difficult problems in the field of bioethics. What criteria are to be used in fashioning decisions? Who is primarily responsible—and liable— for these decisions? What is the role of the law...