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188 Publications

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    05/18/11 | Synaptosomes as a platform for loading nanoparticles into synaptic vesicles.
    Budzinski KL, Sgro AE, Fujimoto BS, Gadd JC, Shuart NG, Gonen T, Bajjaleih SM, Chiu DT
    ACS Chemical Neuroscience. 2011 May 18;2(5):236-241. doi: 10.1021/cn200009n

    Synaptosomes are intact, isolated nerve terminals that contain the necessary machinery to recycle synaptic vesicles via endocytosis and exocytosis upon stimulation. Here we use this property of synaptosomes to load quantum dots into synaptic vesicles. Vesicles are then isolated from the synaptosomes, providing a method to probe isolated, individual synaptic vesicles where each vesicle contains a single, encapsulated nanoparticle. This technique provided an encapsulation efficiency of  16%, that is,  16% of the vesicles contained a single quantum dot while the remaining vesicles were empty. The ability to load single nanoparticles into synaptic vesicles opens new opportunity for employing various nanoparticle-based sensors to study the dynamics of vesicular transporters.

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    Riddiford Lab
    05/15/11 | When is weight critical?
    Riddiford LM
    The Journal of Experimental Biology. 2011 May 15;214(Pt 10):1613-5. doi: 10.1242/jeb.049098
    05/09/11 | Electro-optical pockels scattering from a single nanocrystal.
    Hajj B, Perruchas S, Lautru J, Dantelle G, Gacoin T, Zyss J, Chauvat D
    Optics Express. 2011 May 9;19(10):9000-7. doi: 10.1364/OE.19.009000

    The electro-optical Pockels response from a single non-centrosymmetric nanocrystal is reported. High sensitivity to the weak electric-field dependent nonlinear scattering is achieved through a dedicated imaging interferometric microscope and the linear dependence of electro-optical signal upon the applied field is checked. Using different incident light polarization states, a priori random spatial orientation of the crystal can be inferred. The electro-optical response from a nanocrystal provides local subwavelength sensor of quasi-static electric fields with potential applications in physics and biology. It also leads to a new sub-wavelength microscopy towards the nanoscale investigation of interesting phenomena such as nanoferroelectricity.

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    05/06/11 | Automated reconstruction of neuronal morphology based on local geometrical and global structural models.
    Zhao T, Xie J, Amat F, Clack N, Ahammad P, Peng H, Long F, Myers E
    Neuroinformatics. 2011 May 6;9(2-3):247-61. doi: 10.1007/s12021-011-9120-3

    Digital reconstruction of neurons from microscope images is an important and challenging problem in neuroscience. In this paper, we propose a model-based method to tackle this problem. We first formulate a model structure, then develop an algorithm for computing it by carefully taking into account morphological characteristics of neurons, as well as the image properties under typical imaging protocols. The method has been tested on the data sets used in the DIADEM competition and produced promising results for four out of the five data sets.

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    05/03/11 | Robo-3--mediated repulsive interactions guide R8 axons during Drosophila visual system development.
    Pappu KS, Morey M, Nern A, Spitzweck B, Dickson BJ, Zipursky SL
    Proc Natl Acad Sci U S A. 2011 May 03;108(18):7571-6. doi: 10.1073/pnas.1103419108

    The formation of neuronal connections requires the precise guidance of developing axons toward their targets. In the Drosophila visual system, photoreceptor neurons (R cells) project from the eye into the brain. These cells are grouped into some 750 clusters comprised of eight photoreceptors or R cells each. R cells fall into three classes: R1 to R6, R7, and R8. Posterior R8 cells are the first to project axons into the brain. How these axons select a specific pathway is not known. Here, we used a microarray-based approach to identify genes expressed in R8 neurons as they extend into the brain. We found that Roundabout-3 (Robo3), an axon-guidance receptor, is expressed specifically and transiently in R8 growth cones. In wild-type animals, posterior-most R8 axons extend along a border of glial cells demarcated by the expression of Slit, the secreted ligand of Robo3. In contrast, robo3 mutant R8 axons extend across this border and fasciculate inappropriately with other axon tracts. We demonstrate that either Robo1 or Robo2 rescues the robo3 mutant phenotype when each is knocked into the endogenous robo3 locus separately, indicating that R8 does not require a function unique to the Robo3 paralog. However, persistent expression of Robo3 in R8 disrupts the layer-specific targeting of R8 growth cones. Thus, the transient cell-specific expression of Robo3 plays a crucial role in establishing neural circuits in the Drosophila visual system by selectively regulating pathway choice for posterior-most R8 growth cones.

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    05/01/11 | A Drosophila model for alcohol reward.
    Kaun KR, Azanchi R, Maung Z, Hirsh J, Heberlein U
    Nature Neuroscience. 2011 May;14(5):612-9. doi: 10.1038/nn.2805

    The rewarding properties of drugs contribute to the development of abuse and addiction. We developed a new assay for investigating the motivational properties of ethanol in the genetically tractable model Drosophila melanogaster. Flies learned to associate cues with ethanol intoxication and, although transiently aversive, the experience led to a long-lasting attraction for the ethanol-paired cue, implying that intoxication is rewarding. Temporally blocking transmission in dopaminergic neurons revealed that flies require activation of these neurons to express, but not develop, conditioned preference for ethanol-associated cues. Moreover, flies acquired, consolidated and retrieved these rewarding memories using distinct sets of neurons in the mushroom body. Finally, mutations in scabrous, encoding a fibrinogen-related peptide that regulates Notch signaling, disrupted the formation of memories for ethanol reward. Our results thus establish that Drosophila can be useful for understanding the molecular, genetic and neural mechanisms underling the rewarding properties of ethanol.

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    05/01/11 | A Drosophila model for fetal alcohol syndrome disorders: role for the insulin pathway.
    McClure KD, French RL, Heberlein U
    Disease Models & Mechanisms. 2011 May;4(3):335-46. doi: 10.1242/dmm.006411

    Prenatal exposure to ethanol in humans results in a wide range of developmental abnormalities, including growth deficiency, developmental delay, reduced brain size, permanent neurobehavioral abnormalities and fetal death. Here we describe the use of Drosophila melanogaster as a model for exploring the effects of ethanol exposure on development and behavior. We show that developmental ethanol exposure causes reduced viability, developmental delay and reduced adult body size. We find that flies reared on ethanol-containing food have smaller brains and imaginal discs, which is due to reduced cell division rather than increased apoptosis. Additionally, we show that, as in mammals, flies reared on ethanol have altered responses to ethanol vapor exposure as adults, including increased locomotor activation, resistance to the sedating effects of the drug and reduced tolerance development upon repeated ethanol exposure. We have found that the developmental and behavioral defects are largely due to the effects of ethanol on insulin signaling; specifically, a reduction in Drosophila insulin-like peptide (Dilp) and insulin receptor expression. Transgenic expression of Dilp proteins in the larval brain suppressed both the developmental and behavioral abnormalities displayed by ethanol-reared adult flies. Our results thus establish Drosophila as a useful model system to uncover the complex etiology of fetal alcohol syndrome.

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    05/01/11 | PALM and STORM: unlocking live-cell super-resolution.
    Henriques R, Griffiths C, Hesper Rego E, Mhlanga MM
    Biopolymers. 2011 May;95(5):322-31. doi: 10.1002/bip.21586

    Live-cell fluorescence light microscopy has emerged as an important tool in the study of cellular biology. The development of fluorescent markers in parallel with super-resolution imaging systems has pushed light microscopy into the realm of molecular visualization at the nanometer scale. Resolutions previously only attained with electron microscopes are now within the grasp of light microscopes. However, until recently, live-cell imaging approaches have eluded super-resolution microscopy, hampering it from reaching its full potential for revealing the dynamic interactions in biology occurring at the single molecule level. Here we examine recent advances in the super-resolution imaging of living cells by reviewing recent breakthroughs in single molecule localization microscopy methods such as PALM and STORM to achieve this important goal.

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    Singer Lab
    05/01/11 | Qualification of a new and precise automatic tool for the assessment of hair diameters in phototrichograms.
    Scheede S, Herpens A, Burmeister F, Oltrogge B, Saenger K, Schmidt-Rose T, Schreiner V, Wenck H, Knieps T, Berlage T
    Skin Research & Technology. 2011 May;17(2):186-95. doi: 10.1111/j.1600-0846.2010.00482.x

    BACKGROUND/PURPOSE: To automatically assess hair growth during cosmetic trials, incorporating parameters such as anagen-to-telogen rate, growth rate, and especially hair diameter.

    METHODS: We designed and qualified a new and automatic phototrichogram system based on a high-resolution DSLR camera system (theoretical resolution of 2.557 μm/pixel) and modular macrolens system with fixed focus, combined with a trainable pattern recognition software for automated analysis.

    RESULTS: We improved the standard routine for dermatological phototrichogram technique to overcome inaccuracy in thickness measurements due to hair swelling by using an alternative immersion fluid, and increased the effective resolution for hair size and thickness measurement to <4 μm. After having qualified manual measurements as gold standard for the determination of hair diameters, we established a new trainable automatic picture analysis software able to locate and measure individual hairs in length and thickness even in picture series taken from the same skin area at different time points. Comparisons between manual and automatic measurements of the same hairs showed a >90% correlation, and by comparing the automatic results with manual measurements of the same images without individual hair annotation, we could find a correlation of at least 80%.

    CONCLUSION: According to the results and findings generated in this qualification study, we have a reliable tool now that enables us to test cosmetic products for hair treatment in a highly automated way with a sufficient degree of precision and accuracy to detect even small changes in hair diameter during cosmetic trials.

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    05/01/11 | Rapid three-dimensional isotropic imaging of living cells using Bessel beam plane illumination.
    Planchon TA, Gao L, Milkie DE, Davidson MW, Galbraith JA, Galbraith CG, Betzig E
    Nature Methods. 2011 May;8(5):417-23. doi: 10.1038/nmeth.1586

    A key challenge when imaging living cells is how to noninvasively extract the most spatiotemporal information possible. Unlike popular wide-field and confocal methods, plane-illumination microscopy limits excitation to the information-rich vicinity of the focal plane, providing effective optical sectioning and high speed while minimizing out-of-focus background and premature photobleaching. Here we used scanned Bessel beams in conjunction with structured illumination and/or two-photon excitation to create thinner light sheets (<0.5 μm) better suited to three-dimensional (3D) subcellular imaging. As demonstrated by imaging the dynamics of mitochondria, filopodia, membrane ruffles, intracellular vesicles and mitotic chromosomes in live cells, the microscope currently offers 3D isotropic resolution down to \~{}0.3 μm, speeds up to nearly 200 image planes per second and the ability to noninvasively acquire hundreds of 3D data volumes from single living cells encompassing tens of thousands of image frames.

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