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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
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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
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