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Transcript
Books Behold the fowls of the air Avian Biochemistry and Molecular Biology. Lewis Stevens. Camhridge University Press, Cambridge, UK, 1996. 286 pp., illus. $80.00 (ISBN 0-521-45510-3 cloth). Among OUf vertebrate cousins, hirds have a unique way of inspiring and intriguing humans. Other animals take to the air, bur ooly birds cause hoth paets to rhapsodize and scien rists to ruminate about the mysrery of flight. The legendary distances and hardships of bird migrations are sources of wander to the layperson and expert alike. Much of bird biology is as familiar as the backyard robin, so many avian features appear to be just twists on our own: erythrocytes wirh or without nuclei still da essentially the same thing; both feathers and hair are made of keratin. Yet it is also clear that birds are the exotic "other," with their bursa of Fahricius and uric acid excretion. Biologists continue to wonder whether birds are descended frorn dinosaurs, and we are still haunted hy Martha, the last passenger pigeon, and hy other hird extinctions. Sornewhere deep within rnany of us is a need to know: What are hirds and how do they work? Lewis Stevens' Avian Biochemistry and Molecular Biology is one answer to these questions.lts avowed purpose is to be the " ... only cornprehensive and up-to-date survey of avian biochemistry and molecular biology available. It emphasizes the similarities and differences between hirds and other vertebrates, concentrating on new developments" (p. i). It succeeds in being both comprehensive, with over 1000 references, and up-ta-date, with references dating back from 1994, most of them published sinee 1980. The book covers two major areas: avian metaboIism and the avian genome and its expression. Recognizing that many w 478 mechanisms of metabolism and of gene expression are conserved among vertebrates and have been covered thoroughly elsewhere, Stevens has chosen to focus on particular adaptations of avian metabolism and on unique features of genome structure and gene expression. This focus is what gives this book its strength; it frees Stevens to cover these areas with an impressive degree of depth. The first half of the book includes chapters on avian nutrition, carbohydrate metabolism, lipid metabolism, protein and amino acid metabolism, metabolie adaptations, and hormonal contral of metabolism. Although Stevens writes in his preface that he assumes the reader will have had at least one year of both undergraduate biochemistry and molecular biology course work, these chapters are written at a high level that could challenge even a doctaral-level hiochemist. The material is made more accessible hy a multitude of figures and tables (79 in 105 page,), whieh should be help ornithologists without a strong hiochemical background to benefit from this material. However, at times, even the tables go into too much depth. For example, Table 7.1 includes plasma levels of insulin from eight species of birds; although these data make a point ahout hormone concentration, they do litde to explain anything else in the text and are more detail than is prohably nec- essary. Moreover, on rare occasions there is some confusion in coordinating the figures and the text, as with Figure 4.10, in which it is unclear whether hrain and kidney or skeletal museIe is the primary site of ketone body utilization in birds. Gther than these admittedly minor problems, this section of the book is a thorough, satisfying survey of the current understanding of avian metaholism. Somewhat less satisfying is the second half of the book, which covers avian molecular biology; I suspect my disappointment has more to do with the current state of research in this area than with Stevens' survey of it. In many ways, avian molecular genetics is still suffering from growing pains, with an inability to emulate such innovations as transgenic "knockout" mice and genome sequencing projects. As Stevens notes, these limitations are understandable; transgenesis in birds is complicated hy oviposition late in embryonic development, and the organization of avian genomes into numerous (2N = 40-126) minichromosomes and macrachromosomes will no doubt challenge eHons to map and sequence avian genomes. Nevertheless, much valuable research has been done in avian molecular genetics, especially in the last 15 years, and Stevens does a solid job of reviewing this work. Chapters in this half of the book cover genome organization, multi- BioScience Vol. 48 No. 6 domain genes and multiple gene families, gene regulation by steroid hormones, oncogenes, and the molecular genetics of developrnent and of the immune system. Of particular interest to molecular geneticists will be cha pter 8, on genome structure and organization. As DNA sequence information is increasingly applied to taxonomic and population problems, it is important to realize that avian genomes are both poorly characterized at a molecular level and significantly different from other vertebrate genomes. Biologists are still a long way from understanding how evolution affects genome structure and the converse. As happens so often these days in biology, readers will be struck simultaneously by how much is known about avian biochemistry and molecular biology and how much is still to be learned. For example, much can be explained about metabolic adaptations associated with the energy demands of flight, but why are bird lifespans surprisingly long relative to their metabolic rates? Detailed sequence information is availahle on repetitive elements of the avian W chromosome, but what is the relationship between the ZZ/ZW sex determination system in birds and the better characterized XX/XY system in mammals? In this era of genome sequencing projects, DNA sequencing 1S a mighty big hammer, which means that most biologieal questions look a whole lot like nails to many molecular biologists. Many other biologists know, however, that the genome project era is only the bt-gi"lning to a fuller understanding of biology. Somewhere on the other side will he a return to biochemistry, particularly comparative biochemistry. Avian Biochemistry and Molecular Biology 1S now and will continue to be a valuable reference for biologists wanting to understand and research avian biology at a molecular level. GARYOXFORD Department oi Natural Sciences Longwood College Farmville, VA 23909 fune 1998 BEYOND REDUCTIONISM Integrative Approaches to Molecular Biology. Julio CoUado-Vides, Boris Magasanik, and Temple F. Smith, eds. MIT Press, Cambridge, MA, 1996. 345 pp., iUus. $50.00 (ISBN 0-262-032391 cloth). "Molecular biology must show that it works in the real world of the organism," state Jack Cohen and Sean Riee, the authors of chapter 12 of Integrative Approaches to Molecu/ar Bi%gy (p. 251). Despite the incredible success of molecular biology in the past half-century, its reductionistic approach has been criticized by evolutionary biologists. ecologists, developmental biologists, and feminists from its earliest days. A denouement of the systemic and molecular approaches has been sought not only by those workers in these fields who have welcomed the power of moleeular tools, but also by theoretical and mathematical bi~ ologists, who have long realized that differentiation goes hand in hand with integration. Furthermore, re~ cent advances in nonlinear dynam~ ics, fractal geometry, nonequilibrium thermodynamics, and computational complexity have introduced funda~ mentally new tools to study complex systems. But molecular biologists themselves have also recognized the need for integrative approaches. The colleetion of massive amounts of sequence data, three-dimensional structures of many macromolecules, kinetie eonstants of numerous multienzyme complexes, steps in metabolic pathways, and so on has given rise to databases that are so enormous that workers need new tools for sorting, searching, retrieving, and displaying complex phenomena. Molecular biologists have learned that certain problems have computational complexity that taxes even the fastest supercomputers, with the largest memory storage. Nevertheless. few molecular biologists have argued for an entirely new philosophical and theoretical foundation; thus, the freshness of this collection fills an important vacuum. The power of Integrative Approaches to Molecular Biology is that it draws on five different integrative, historically important approaches: evolutionary (Michael Savageau's biochemical systems theory and fractal kinetics), thermodynamic (Michael Mavrovouniotis's metabolie control theory, and the eonstructton of novel pathways), kinetic (Rene Thomas's Boolean kinetic logical approach), linguistic (Julio ColladoVides's grammar for syntax of regula tory domains), and genomic (perhaps best represented theoretieaUy here by Robert ]. Robbins's "Comparative Genomics" and pragmatieaUy by Temple F. Smith, Riehard Lathrop, and Fred Cohen). The excellent bibliography allows readers to trace the growth of these five approaches over the past 30 years; the integrative approaehes have the benefit of having been applied to numerous examples and massive amounts of data. Savageau criticizes most of en~ zyme kinetie practiee because experiments are designed to maintain the Michaelis-Menten formalism and to do so under unrealistic cellular conditions: dilute solutions that are spatially homogeneous (i.e., that lack compartments and membranes) and at far-from-equilihrium conditions. He emphasizes that "elementary chemical kinetics are very different when reactions are diffusion-limited, are dimensionally restricted, or occur on fractal surfaces" (p. 124). Through biochemical systems theory, Savageau predicts evolutionary successful strategies that are qualitatively robust, in part due to their dependence on power laws, whieh intrinsically work across wide scales. His multivariate approach uses stability, robustness, decisiveness, efficiency, responsiveness, and selectivity to evaluate which gain-and-coupling strategy is best for positively and negatively inducible and repressible systems. A strength of this approach is that it is qualitative, dependent only on the topology of circuitry, and, hence, easier than standard kinetic models to evaluate experimentally in vivo. Similarly, Mavrovouniotis stresses other kinetic aspects that are not covered in standard experimental practice. His "qualitative analysis ... relies on bioreaetion stoichiometries, thermodynamic feasibility study of pathways, and idealized kinetic 479