Main Menu (Mobile)- Block

Main Menu - Block

custom | custom

Search Results

filters_region_cap | custom

Filter

facetapi-Q2b17qCsTdECvJIqZJgYMaGsr8vANl1n | block

Associated Lab

facetapi-W9JlIB1X0bjs93n1Alu3wHJQTTgDCBGe | block
facetapi-61yz1V0li8B1bixrCWxdAe2aYiEXdhd0 | block
facetapi-PV5lg7xuz68EAY8eakJzrcmwtdGEnxR0 | block
facetapi-aK0bSsPXQOqhYQEgonL2xGNrv4SPvFLb | block

Tool Types

general_search_page-panel_pane_1 | views_panes

1832 Janelia Publications

Showing 1771-1780 of 1832 results
12/23/08 | Multilayer three-dimensional super resolution imaging of thick biological samples.
Vaziri A, Tang J, Shroff H, Shank CV
Proceedings of the National Academy of Sciences of the United States of America. 2008 Dec 23;105(51):20221-6. doi: 10.1073/pnas.0810636105

Recent advances in optical microscopy have enabled biological imaging beyond the diffraction limit at nanometer resolution. A general feature of most of the techniques based on photoactivated localization microscopy (PALM) or stochastic optical reconstruction microscopy (STORM) has been the use of thin biological samples in combination with total internal reflection, thus limiting the imaging depth to a fraction of an optical wavelength. However, to study whole cells or organelles that are typically up to 15 microm deep into the cell, the extension of these methods to a three-dimensional (3D) super resolution technique is required. Here, we report an advance in optical microscopy that enables imaging of protein distributions in cells with a lateral localization precision better than 50 nm at multiple imaging planes deep in biological samples. The approach is based on combining the lateral super resolution provided by PALM with two-photon temporal focusing that provides optical sectioning. We have generated super-resolution images over an axial range of approximately 10 microm in both mitochondrially labeled fixed cells, and in the membranes of living S2 Drosophila cells.

View Publication Page
12/11/08 | Unfolding warping for object recognition.
Xie J, Hu M, Shah M
19TH International Conference on Pattern Recognition. 2008 December 11:. doi: 10.1109/ICPR.2008.4761188

In practice, understanding the spatial relationships between the surfaces of an object, can significantly improve the performance of object recognition systems. In this paper we propose a novel framework to recognize objects in pictures taken from arbitrary viewpoints. The idea is to maintain the frontal views of the major faces of objects in a global flat map. Then an unfolding warping technique is used to change the pose of the query object in the test view so that all visible surfaces of the object can be observed from a frontal viewpoint, improving the handling of serious occlusions and large viewpoint changes. We demonstrate the effectiveness of our approach through analysis of recognition trials of complex objects with comparison to popular methods.

View Publication Page
12/09/08 | A genetically encoded fluorescent sensor of ERK activity.
Harvey CD, Ehrhardt AG, Cellurale C, Zhong H, Yasuda R, Davis RJ, Svoboda K
Proceedings of the National Academy of Sciences of the United States of America. 2008 Dec 9;105(49):19264-9. doi: 10.1073/pnas.0804598105

The activity of the ERK has complex spatial and temporal dynamics that are important for the specificity of downstream effects. However, current biochemical techniques do not allow for the measurement of ERK signaling with fine spatiotemporal resolution. We developed a genetically encoded, FRET-based sensor of ERK activity (the extracellular signal-regulated kinase activity reporter, EKAR), optimized for signal-to-noise ratio and fluorescence lifetime imaging. EKAR selectively and reversibly reported ERK activation in HEK293 cells after epidermal growth factor stimulation. EKAR signals were correlated with ERK phosphorylation, required ERK activity, and did not report the activities of JNK or p38. EKAR reported ERK activation in the dendrites and nucleus of hippocampal pyramidal neurons in brain slices after theta-burst stimuli or trains of back-propagating action potentials. EKAR therefore permits the measurement of spatiotemporal ERK signaling dynamics in living cells, including in neuronal compartments in intact tissues.

View Publication Page
12/01/08 | Advances in the speed and resolution of light microscopy.
Ji N, Shroff H, Zhong H, Betzig E
Current Opinion in Neurobiology. 2008 Dec;18(6):605-16. doi: 10.1016/j.conb.2009.03.009

Neurobiological processes occur on spatiotemporal scales spanning many orders of magnitude. Greater understanding of these processes therefore demands improvements in the tools used in their study. Here we review recent efforts to enhance the speed and resolution of one such tool, fluorescence microscopy, with an eye toward its application to neurobiological problems. On the speed front, improvements in beam scanning technology, signal generation rates, and photodamage mediation are bringing us closer to the goal of real-time functional imaging of extended neural networks. With regard to resolution, emerging methods of adaptive optics may lead to diffraction-limited imaging or much deeper imaging in optically inhomogeneous tissues, and super-resolution techniques may prove a powerful adjunct to electron microscopic methods for nanometric neural circuit reconstruction.

View Publication Page
12/01/08 | Advances in the speed and resolution of light microscopy. (With commentary)
Ji N, Shroff H, Zhong H, Betzig E
Current Opinion in Neurobiology. 2008 Dec;18(6):605-16. doi: 10.1016/j.conb.2009.03.009

Neurobiological processes occur on spatiotemporal scales spanning many orders of magnitude. Greater understanding of these processes therefore demands improvements in the tools used in their study. Here we review recent efforts to enhance the speed and resolution of one such tool, fluorescence microscopy, with an eye toward its application to neurobiological problems. On the speed front, improvements in beam scanning technology, signal generation rates, and photodamage mediation are bringing us closer to the goal of real-time functional imaging of extended neural networks. With regard to resolution, emerging methods of adaptive optics may lead to diffraction-limited imaging or much deeper imaging in optically inhomogeneous tissues, and super-resolution techniques may prove a powerful adjunct to electron microscopic methods for nanometric neural circuit reconstruction.

Commentary: A brief review of recent trends in microscopy. The section “Caveats regarding the application of superresolution microscopy” was written in an effort to inject a dose of reality and caution into the unquestioning enthusiasm in the academic community for all things superresolution, covering the topics of labeling density and specificity, sample preparation artifacts, speed vs. resolution vs. photodamage, and the implications of signal-to-background for Nyquist vs. Rayleigh definitions of resolution.

View Publication Page
12/01/08 | Photoactivated localization microscopy (PALM) of adhesion complexes. (With commentary)
Shroff H, White H, Betzig E
Current Protocols in Cell Biology. 2008 Dec;Chapter 4(Unit 4):21. doi: 10.1002/0471143030.cb0421s41

Key to understanding a protein’s biological function is the accurate determination of its spatial distribution inside a cell. Although fluorescent protein markers allow the targeting of specific proteins with molecular precision, much of this information is lost when the resultant fusion proteins are imaged with conventional, diffraction-limited optics. In response, several imaging modalities that are capable of resolution below the diffraction limit (approximately 200 nm) have emerged. Here, both single- and dual-color superresolution imaging of biological structures using photoactivated localization microscopy (PALM) are described. The examples discussed focus on adhesion complexes: dense, protein-filled assemblies that form at the interface between cells and their substrata. A particular emphasis is placed on the instrumentation and photoactivatable fluorescent protein (PA-FP) tags necessary to achieve PALM images at approximately 20 nm resolution in 5 to 30 min in fixed cells.

Commentary: A paper spearheaded by Hari which gives a thorough description of the methods and hardware needed to successfully practice PALM, including cover slip preparation, cell transfection and fixation, drift correction with fiducials, characterization of on/off contrast ratios for different photoactivted fluorescent proteins, identifying PALM-suitable cells, and mechanical and optical components of a PALM system.

View Publication Page
11/12/08 | Receptors, circuits, and behaviors: new directions in chemical senses.
Katz DB, Matsunami H, Rinberg D, Scott K, Wachowiak M, Wilson RI
The Journal of Neuroscience: The Official Journal of the Society for Neuroscience. 2008 Nov 12;28(46):11802-5. doi: 10.1523/JNEUROSCI.3613-08.2008

The chemical senses, smell and taste, are the most poorly understood sensory modalities. In recent years, however, the field of chemosensation has benefited from new methods and technical innovations that have accelerated the rate of scientific progress. For example, enormous advances have been made in identifying olfactory and gustatory receptor genes and mapping their expression patterns. Genetic tools now permit us to monitor and control neural activity in vivo with unprecedented precision. New imaging techniques allow us to watch neural activity patterns unfold in real time. Finally, improved hardware and software enable multineuron electrophysiological recordings on an expanded scale. These innovations have enabled some fresh approaches to classic problems in chemosensation.

View Publication Page
10/13/08 | Fast monte carlo simulation methods for biological reaction-diffusion systems in solution and on surfaces.
Kerr RA, Bartol TM, Kaminsky B, Dittrich M, Chang JJ, Baden SB, Sejnowski TJ, Stiles JR
SIAM Journal on Scientific Computing: A Publication of the Society for Industrial and Applied Mathematics. 2008 Oct 13;30(6):3126. doi: 10.1137/070692017

Many important physiological processes operate at time and space scales far beyond those accessible to atom-realistic simulations, and yet discrete stochastic rather than continuum methods may best represent finite numbers of molecules interacting in complex cellular spaces. We describe and validate new tools and algorithms developed for a new version of the MCell simulation program (MCell3), which supports generalized Monte Carlo modeling of diffusion and chemical reaction in solution, on surfaces representing membranes, and combinations thereof. A new syntax for describing the spatial directionality of surface reactions is introduced, along with optimizations and algorithms that can substantially reduce computational costs (e.g., event scheduling, variable time and space steps). Examples for simple reactions in simple spaces are validated by comparison to analytic solutions. Thus we show how spatially realistic Monte Carlo simulations of biological systems can be far more cost-effective than often is assumed, and provide a level of accuracy and insight beyond that of continuum methods.

View Publication Page
Eddy/Rivas Lab
09/19/08 | Probabilistic phylogenetic inference with insertions and deletions.
Rivas E, Sean R. Eddy
PLoS Computational Biology. 2008 Sep 19;4(9):e1000172. doi: 10.1371/journal.pcbi.1000172

A fundamental task in sequence analysis is to calculate the probability of a multiple alignment given a phylogenetic tree relating the sequences and an evolutionary model describing how sequences change over time. However, the most widely used phylogenetic models only account for residue substitution events. We describe a probabilistic model of a multiple sequence alignment that accounts for insertion and deletion events in addition to substitutions, given a phylogenetic tree, using a rate matrix augmented by the gap character. Starting from a continuous Markov process, we construct a non-reversible generative (birth-death) evolutionary model for insertions and deletions. The model assumes that insertion and deletion events occur one residue at a time. We apply this model to phylogenetic tree inference by extending the program dnaml in phylip. Using standard benchmarking methods on simulated data and a new "concordance test" benchmark on real ribosomal RNA alignments, we show that the extended program dnamlepsilon improves accuracy relative to the usual approach of ignoring gaps, while retaining the computational efficiency of the Felsenstein peeling algorithm.

View Publication Page
09/01/08 | Bioimage informatics: a new area of engineering biology.
Peng H
Bioinformatics. 2008 Sep 1;24(17):1827-36. doi: 10.1007/s12021-010-9090-x

In recent years, the deluge of complicated molecular and cellular microscopic images creates compelling challenges for the image computing community. There has been an increasing focus on developing novel image processing, data mining, database and visualization techniques to extract, compare, search and manage the biological knowledge in these data-intensive problems. This emerging new area of bioinformatics can be called ’bioimage informatics’. This article reviews the advances of this field from several aspects, including applications, key techniques, available tools and resources. Application examples such as high-throughput/high-content phenotyping and atlas building for model organisms demonstrate the importance of bioimage informatics. The essential techniques to the success of these applications, such as bioimage feature identification, segmentation and tracking, registration, annotation, mining, image data management and visualization, are further summarized, along with a brief overview of the available bioimage databases, analysis tools and other resources.

View Publication Page