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5 Publications

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    12/04/16 | Sensitive enhancement of vessel wall imaging with an endoesophageal Wireless Amplified NMR Detector (WAND).
    Zeng X, Barbic M, Chen L, Qian C
    Magnetic Resonance in Medicine. 2016 Dec 04;78(5):2048-54. doi: 10.1002/mrm.26562

    PURPOSE: To improve the imaging quality of vessel walls with an endoesophageal Wireless Amplified NMR Detector (WAND).

    METHODS: A cylindrically shaped double-frequency resonator has been constructed with a single metal wire that is self-connected by a pair of nonlinear capacitors. The double-frequency resonator can convert wirelessly provided pumping power into amplified MR signals. This compact design makes the detector easily insertable into a rodent esophagus.

    RESULTS: The detector has good longitudinal and axial symmetry. Compared to an external surface coil, the WAND can enhance detection sensitivity by at least 5 times, even when the distance separation between the region of interest and the detector's cylindrical surface is twice the detector's own radius. Such detection capability enables us to observe vessel walls near the aortic arch and carotid bifurcation with elevated sensitivity.

    CONCLUSION: A cylindrical MRI detector integrated with a wireless-powered amplifier has been developed as an endoesophageal detector to enhance detection sensitivity of vessel walls. This detector can greatly improve the imaging quality for vessel regions that are susceptible to atherosclerotic lesions. Magn Reson Med, 2016. © 2016 International Society for Magnetic Resonance in Medicine.

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    09/14/16 | Effect of magnetic nanoparticle shape on flux amplification in inductive coil magnetic resonance detection.
    Barbic M, El Bidweihy H
    Journal of Applied Physics. 2016 Sep 14:104506-1-7. doi: 10.1063/1.4962451

    We model and analyze the effect of particle shape on the signal amplification in inductive coil magnetic resonance detection using the reversible transverse magnetic susceptibility of oriented magnetic nanostructures. Utilizing the single magnetic domain Stoner-Wohlfarth model of uniform magnetization rotation, we reveal that different ellipsoidal particle shapes can have a pronounced effect on the magnetic flux enhancement in detection configurations typical of magnetic resonance settings. We compare and contrast the prolate ellipsoids, oblate ellipsoids, and exchange-biased spheres and show that the oblate ellipsoids and exchange-biased spheres have a significantly higher flux amplification effect than the prolate ellipsoids considered previously. In addition, oblate ellipsoids have a much broader polarizing magnetic fieldrange over which their transverse flux amplification is significant. We show the dependence of transverse flux amplification on magnetic resonance bias field and discuss the resulting signal-to-noise ratio of inductive magnetic resonance detection due to the magnetic nanoparticle-filled core of the magnetic resonance detection coil.

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    05/30/16 | A bright cyan-excitable orange fluorescent protein facilitates dual-emission microscopy and enhances bioluminescence imaging in vivo.
    Chu J, Oh Y, Sens A, Ataie N, Dana H, Macklin JJ, Laviv T, Welf ES, Dean KM, Zhang F, Kim BB, Tang CT, Hu M, Baird MA, Davidson MW, Kay MA, Fiolka R, Yasuda R, Kim DS, Ng H, Lin MZ
    Nature Biotechnology. 2016 May 30;34(7):760-7. doi: 10.1038/nbt.3550

    Orange-red fluorescent proteins (FPs) are widely used in biomedical research for multiplexed epifluorescence microscopy with GFP-based probes, but their different excitation requirements make multiplexing with new advanced microscopy methods difficult. Separately, orange-red FPs are useful for deep-tissue imaging in mammals owing to the relative tissue transmissibility of orange-red light, but their dependence on illumination limits their sensitivity as reporters in deep tissues. Here we describe CyOFP1, a bright, engineered, orange-red FP that is excitable by cyan light. We show that CyOFP1 enables single-excitation multiplexed imaging with GFP-based probes in single-photon and two-photon microscopy, including time-lapse imaging in light-sheet systems. CyOFP1 also serves as an efficient acceptor for resonance energy transfer from the highly catalytic blue-emitting luciferase NanoLuc. An optimized fusion of CyOFP1 and NanoLuc, called Antares, functions as a highly sensitive bioluminescent reporter in vivo, producing substantially brighter signals from deep tissues than firefly luciferase and other bioluminescent proteins.

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    03/24/16 | Sensitive red protein calcium indicators for imaging neural activity.
    Dana H, Mohar B, Sun Y, Narayan S, Gordus A, Hasseman JP, Tsegaye G, Holt GT, Hu A, Walpita D, Patel R, Macklin JJ, Bargmann CI, Ahrens MB, Schreiter ER, Jayaraman V, Looger LL, Svoboda K, Kim DS
    eLife. 2016 Mar 24;5:. doi: 10.7554/eLife.12727

    Genetically encoded calcium indicators (GECIs) allow measurement of activity in large populations of neurons and in small neuronal compartments, over times of milliseconds to months. Although GFP-based GECIs are widely used for in vivo neurophysiology, GECIs with red-shifted excitation and emission spectra have advantages for in vivo imaging because of reduced scattering and absorption in tissue, and a consequent reduction in phototoxicity. However, current red GECIs are inferior to the state-of-the-art GFP-based GCaMP6 indicators for detecting and quantifying neural activity. Here we present improved red GECIs based on mRuby (jRCaMP1a, b) and mApple (jRGECO1a), with sensitivity comparable to GCaMP6. We characterized the performance of the new red GECIs in cultured neurons and in mouse, Drosophila, zebrafish and C. elegans in vivo. Red GECIs facilitate deep-tissue imaging, dual-color imaging together with GFP-based reporters, and the use of optogenetics in combination with calcium imaging.

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    02/18/16 | Structured dendritic inhibition supports branch-selective integration in CA1 pyramidal cells.
    Bloss EB, Cembrowski MS, Karsh B, Colonell J, Fetter RD, Spruston N
    Neuron. 2016 Feb 18:. doi: 10.1016/j.neuron.2016.01.029

    Neuronal circuit function is governed by precise patterns of connectivity between specialized groups of neurons. The diversity of GABAergic interneurons is a hallmark of cortical circuits, yet little is known about their targeting to individual postsynaptic dendrites. We examined synaptic connectivity between molecularly defined inhibitory interneurons and CA1 pyramidal cell dendrites using correlative light-electron microscopy and large-volume array tomography. We show that interneurons can be highly selective in their connectivity to specific dendritic branch types and, furthermore, exhibit precisely targeted connectivity to the origin or end of individual branches. Computational simulations indicate that the observed subcellular targeting enables control over the nonlinear integration of synaptic input or the initiation and backpropagation of action potentials in a branch-selective manner. Our results demonstrate that connectivity between interneurons and pyramidal cell dendrites is more precise and spatially segregated than previously appreciated, which may be a critical determinant of how inhibition shapes dendritic computation.

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