University of California, Davis

About: University of California, Davis is a education organization based out in Davis, California, United States. It is known for research contribution in the topics: Population & Poison control. The organization has 78770 authors who have published 180033 publications receiving 8064158 citations. The organization is also known as: UC Davis & UCD.

A phylogeny-driven genomic encyclopaedia of Bacteria and Archaea.

Abstract: Sequencing of bacterial and archaeal genomes has revolutionized our understanding of the many roles played by microorganisms. There are now nearly 1,000 completed bacterial and archaeal genomes available, most of which were chosen for sequencing on the basis of their physiology. As a result, the perspective provided by the currently available genomes is limited by a highly biased phylogenetic distribution. To explore the value added by choosing microbial genomes for sequencing on the basis of their evolutionary relationships, we have sequenced and analysed the genomes of 56 culturable species of Bacteria and Archaea selected to maximize phylogenetic coverage. Analysis of these genomes demonstrated pronounced benefits (compared to an equivalent set of genomes randomly selected from the existing database) in diverse areas including the reconstruction of phylogenetic history, the discovery of new protein families and biological properties, and the prediction of functions for known genes from other organisms. Our results strongly support the need for systematic phylogenomic efforts to compile a phylogeny-driven Genomic Encyclopedia of Bacteria and Archaea in order to derive maximum knowledge from existing microbial genome data as well as from genome sequences to come. © 2009 Macmillan Publishers Limited. All rights reserved.

Multimodality Imaging Probes: Design and Challenges

Abstract: The conundrum of modality selection in clinical diagnostic imaging is that modalities with the highest sensitivity have relatively poor resolution, while those with high resolution have relatively poor sensitivity In recent years, the idea of using multiple modalities in conjunction has gained in popularity and researchers have come to realize that the complementary abilities of different imaging modalities could be harnessed to great effect by using them in tandem The idea of combining imaging technologies moved to the mainstream with the advent of the first successful commercial fused instruments The first fused PET/CT instrument, developed in 1998 by Townsend and colleagues in collaboration with Siemens Medical, was available commercially in 2001 The “Biograph” was named as one of the “Inventions of the Year” in 2000 by Time magazine, and its success was such that by 2003 fused PET/CT instruments were available from all of the major clinical instrument manufacturers, GE, Philips, CTI, and Siemens1 Over the ensuing years, PET/CT sales increased with such vigor that by the year 2006 there were virtually no sales of standalone PET instruments; all PET sales were as part of multimodality systems2–4 The next wave of innovation has been in PET/MRI-fused instruments, which have generated much hope for improved patient safety and imaging capability over PET/CT Although research on PET/MRI instruments was initiated around the same time as PET/CT, the economic and engineering challenges of merging the two modalities slowed development, and the first commercial PET/MRI prototype for a human scale hybrid scanner was not unveiled until 20075,6 With hybrid technology clearly on the rise, the excitement over these new instruments has triggered a tumult of activity in probe design and development as investigators seek to boost the clinical benefits of hybrid instrument technology As the preponderance of recent reviews and increase in attention at scientific meetings will attest, there has been a surge in research on multimodal contrast agent development over the past few years5,7–17 For molecular imaging, particularly, the rise in multimodal instrumentation has sparked hopes for new ways to track multiple molecular targets simultaneously, or to use different imaging methods in combination to more clearly delineate localization and expression of biochemical markers In the best of situations, the combined imaging methods and probes work synergistically to allow high-resolution, high-sensitivity investigation of biological activity For example, with dual function probes for PET/MRI, the high sensitivity of PET can be used as a whole body screen to identify regions of interest, thereby reducing the volume of tissue that needs to be scanned; this reduces scan time required for high-resolution imaging by MRI5,18 However, probe design and development has sometimes preceded the identification of clear applications that merit use of the multimodal principle There are many literature examples of probes that are “all dressed up with nowhere to go”; they possess unique physical properties that have yet to find a clear province in medicine or biology Nonetheless, it is not unusual for technology to sometimes presage the need, and it is these advances that can spur imaginative solutions to problems that had been intractable with the previously existing technology The goal of multimodal functionality has already reaped benefits by driving innovation in many areas of chemical synthesis, most notably in nanotechnology While combining multimodal detectability in the same probe is not necessitated by all applications, there can be advantages to this arrangement A single probe helps to ensure the same pharmacokinetics and colocalization of signal for each modality if that is a concern It also can avoid putting the additional stress on the body’s blood clearance mechanisms that can accompany administration of multiple doses of agents The caveat is that because the sensitivities of different imaging modalities can vary by 3 orders of magnitude, it may not be practical to simply add all functionalities to one molecule, although we will see that is a common design, because the requirements for contrast agent concentrations can be vastly different between modalities In this review, we provide an overview of the many strategies that have been applied to achieve multimodal functionality in a single probe unit These span the range from small molecule to nanoparticulate systems and vary in complexity from facile encapsulation or conjugation of commercially available probes to de novo synthesis This review is limited to reports from the last approximately 5 years that deal with agents that carry two or more species of contrast enhancers Tables summarizing the physical properties from cited articles are included with each major category of probe to facilitate “browsing” by the reader