The authors thank Drs. Nadeem Dhanani, Marie McHenry, Ben McHone, and Peter Pinto for their surgical assistance during the experiments. This effort was supported (in part) by the Department of Defense (work unit no. 602227D.0483.01.A0518, Medical Free Electron Laser Program). We also acknowledge support from the intramural program of the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health. The experiments reported herein were conducted in compliance with the Animal Welfare Act and in accordance with the principles set forth in the “Guide for the Care and Use of Laboratory Animals,” Institute of Laboratory Animals Resources, National Research Council, National Academy Press, 1996. The views expressed in this manuscript are those of the authors and do not reflect the official policy of the Department of the Army, Department of the Navy, the Department of Defense, or the U.S. government. This work was prepared as part of official government duties. Title 17 U.S.C. 105 provides that “Copyright protection under this title is not available for any work of the United States government.” Title 17 U.S.C. 101 defines a U.S. government work as a work prepared by a military service member or employee of the U.S. government as part of that person’s official duties. We certify that all individuals who qualify as authors have been listed; each has participated in the conception and design of this work, the analysis of data (when applicable), the writing of the document, and the approval of the submission of this version; that the document represents valid work; that if we used information derived from another source, we obtained all necessary approvals to use it and made appropriate acknowledgements in the document; and that each author takes public responsibility for it.