Feb 13, 2013 - Comment on âIvory-billed Woodpecker (Campephilus principalis) Persists in ... billed woodpecker eliminate a normal pileated woodpecker ...
LETTERS
Letters to the Editor Letters (~300 words) discuss material published in Science in the previous 6 months or issues of general interest. They can be submitted through the Web (www.submit2science.org) or by regular mail (1200 New York Ave., NW, Washington, DC 20005, USA). Letters are not acknowledged upon receipt, nor are authors generally consulted before publication. Whether published in full or in part, letters are subject to editing for clarity and space.
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food-consumption levels, which turned out to be very similar despite the smaller size of the KO mice. The KO mice showed less weight loss on the CR diet most likely because they were smaller and leaner than wild type, even though they ate comparable levels of food ad libitum. Previous studies establish the precedent that leaner mice can exhibit less weight loss on a CR diet (1). However, we concluded then and now that the KO mice were as calorie restricted as the wild type, first, because they were food-restricted to the same degree of their ad libitum levels as wild type and second, because they underwent similar changes in the physiological parameters mentioned above. Although a comprehensive study of the Sirt1 KO mice is clearly important, we believe that the data in our Brevia do indicate important defects in the ability of the Sirt1 KO mice to respond normally to CR. DANICA CHEN,1 ANDREW STEELE,2 SUSAN LINDQUIST,2 LEONARD GUARENTE1 1Department
of Biology, Massachusetts Institute of Technology, Cambridge, MA 02139, USA. 2Whitehead Institute for Biomedical Research, Nine Cambridge Center, Cambridge, MA 02142, USA.
Reference 1. J. G. Vander Tuig, D. R. Romsos, G. A. Leveille, Int. J. Obes. 4 (no. 1), 79 (1980).
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Sea Urchins as Crystallographers IN THEIR PERSPECTIVE “CHOOSING THE CRYSTALlization path less traveled” (12 Aug. 2005, p. 1027), S. Weiner et al. emphasize the significance of a disordered amorphous precursor phase in a biological strategy for making “beautifully sculpted carbonate minerals.” Size and sculpted shape are only part of the problem because most organisms form minerals that also have a precisely oriented crystallography (1–3). Thus, the finished product may be a large c-axis–oriented single crystal derived from an amorphous precursor within an organic compartment, as in sea urchin plates, or small caxis–oriented crystals derived from epitactic growth on an ordered amelogenin microribbon, as in dental enamel (4). Yet the more fundamental problem remains unsolved: What orients the “small crystal seed,” the “nucleation substrate,” or the long axes of the microribbons? In 1972 (1), I wrote, “The single most important feature of almost all mineralized tissues … is not so much the shape or even the mineralogy of the inorganic phase but rather its crystallography. The crystallographic preferred orientation, the ordered arrangement of crystallographic axes, is of paramount concern.” This precise orienta-
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in wild-type but not in Sirt1 knockout (KO) mice, demonstrating the first example in which a mammalian sirtuin is required for any phenotype induced by this dietary regimen. Pani et al. suggest that our KO mice might not have been as calorie restricted and energy limited as the wildtype (WT) mice. However, both wildtype and KO mice showed comparable physiological changes in response to CR, namely similar reductions in blood glucose, triglycerides, and IGF-1. As we stated, “body weights were also reduced by calorie restriction” in both strains, but as Pani et al. correctly point out, the KO mice did not lose as high a percentage of their body weight on the regimen. Food intake for both wild-type and KO mice was restricted to 60% of their ad libitum
LETTERS
KENNETH M. TOWE Senior Scientist Emeritus, Department of Paleobiology, Smithsonian Institution, 230 West Adams Street, Tennille, GA 31089, USA.
that the road less traveled is still long. STEPHEN WEINER AND LIA ADDADI Department of Structural Biology, Weizmann Institute of Science, Rehovot 76100, Israel.
References 1. L. Addadi, S. Weiner, Proc. Natl. Acad. Sci. U.S.A. 82,
References 1. K. M. Towe, Biomineralization Res. Rep. 4, 1 (1972). 2. H. A. Lowenstam, S. Weiner, On Biomineralization (Oxford Univ. Press, Oxford, 1989). 3. K. M. Towe, W. U. Berthold, D. E. Appleman, J. Foraminiferal Res. 7, 58 (1977). 4. C. Du et al., Science 307, 1450 (2005).
Response TOWE’S LETTER HIGHLIGHTS AN IMPORTANT aspect of biological crystal formation, namely control over crystal orientation. Progress on this issue has been made over the last few decades using both proteins and designed nucleation substrates (1–4). Progress has also been made on polymorph selection by proteins extracted from the organic matrix of mollusk shells, which involves nucleation (5, 6), although more remains to be learned. The Perspective, however, highlighted another unusual feature of biomineralization—the role of an amorphous precursor phase. Eventually these different aspects will need to be integrated, and perhaps the conclusion at this stage should be
4110 (1985). 2. J. Aizenberg, A. J. Black, G. M. Whitesides, Nature 397, 4500 (1999). 3. A. Berman et al., Science 269, 515 (1995). 4. S. Mann et al., Science 261, 1286 (1993). 5. A. M. Belcher et al., Nature 381, 56 (1996). 6. G. Falini, S. Albeck, S. Weiner, L. Addadi, Science 271, 67 (1996).
TECHNICAL COMMENT ABSTRACTS
Comment on “Ivory-billed Woodpecker (Campephilus principalis) Persists in Continental North America” David A. Sibley, Louis R. Bevier, Michael A. Patten, Chris S. Elphick We reanalyzed the video presented as confirmation that an ivory-billed woodpecker (Campephilus principalis) persists in Arkansas (Fitzpatrick et al., Reports, 3 June 2005, p. 1460). None of the features described as diagnostic of the ivorybilled woodpecker eliminate a normal pileated woodpecker (Dryocopus pileatus). Although we support efforts to find and protect ivory-billed woodpeckers, the video evidence does not demonstrate that the species persists in the United States. Full text at www.sciencemag.org/cgi/content/full/311/5767/1555a
Response to Comment on “Ivory-billed Woodpecker (Campephilus principalis) Persists in Continental North America” John W. Fitzpatrick, Martjan Lammertink, M. David Luneau Jr., Tim W. Gallagher, Kenneth V. Rosenberg Claims that the bird in the Luneau video is a normal pileated woodpecker are based on misrepresentations of a pileated’s underwing pattern, interpretation of video artifacts as plumage pattern, and inaccurate models of takeoff and flight behavior. These claims are contradicted by experimental data and fail to explain evidence in the Luneau video of white dorsal plumage, distinctive flight behavior, and a perched woodpecker with white upper parts. Full text at www.sciencemag.org/cgi/content/full/311/5767/1555b
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tion remains the big mystery of biomineralization. Organisms know how to do it; we do not yet know how they know.
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