Publications

2015

• Multiphoton light-sheet microscopy using wavelength mixing: fast multicolor imaging of the beating Zebrafish heart with low photobleaching.
  
  • Mahou Pierre
  • Vermot Julien
  • Beaurepaire Emmanuel
  • Supatto Willy
  , 2015, 9329. Two-photon laser scanning microscopy has become a standard to map thick and live tissues. However, its application for fast and multicolor imaging remains challenging. To address this issue, we report on the implementation of mixed wavelength excitation in a two-photon light-sheet microscope. We illustrate the potential of the technique by recording sustained multicolor two-photon movies of the beating heart in zebrafish embryos with negligible photobleaching at 28 million pixels/second. In particular, 3D reconstructions of the heart periodic motion are obtained with sufficient spatiotemporal resolution to track the fast movements of individual cells during a cardiac cycle. © (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only. (10.1117/12.2079176)
  DOI : 10.1117/12.2079176
• ROS Detection and Quantification with Lanthanide-Based Nanosensors
  
  • Abdesselem Mouna
  • Gacoin Thierry
  • Boilot Jean-Pierre
  • Tharaux Pierre-Louis
  • Alexandrou Antigoni
  • Bouzigues Cedric I.
  , 2015, 108 (2), pp.483a. Reactive oxygen species (ROS), in particular hydrogen peroxide (H2O2), are produced as secondary cellular messengers involved in a variety of signaling pathways. Detecting ROS concentration in cells and in living organisms is particularly important because ROS oxidative stress plays a complex role in multiple pathologies: inflammatory processes, neurodegenerative diseases, and cancer. We first report on an europium-based H2O2 sensor (Y0.6Eu0.4VO4) that shows red, oxidant-dependant, reversible luminescence modulation used in cells in culture. (10.1016/j.bpj.2014.11.2640)
  DOI : 10.1016/j.bpj.2014.11.2640
• Time-resolved circular dichroism: What can we learn on conformational changes ?
  
  • Hache François
  , 2015. Time-resolved circular dichroism (CD) measurements can yield relevant information on the dynamics of conformational changes in molecules on the condition that some a priori knowledge is obtained. This can be the use of simple models such as the excitonic coupling or the octant rule or the phenomenological relationship between far-UV CD and secondary structures in proteins for example. This article describes such experiments where CD has brought relevant conformational information. (10.1117/12.2075705)
  DOI : 10.1117/12.2075705
• Long-term consequences of invasive deer on songbird communities: Going from bad to worse?
  
  • Chollet Simon
  • Bergman Carita
  • Gaston Anthony
  • Martin Jean-Louis
  Biological Invasions, Springer Verlag, 2015, 17 (2), pp.777-790. Although we understand many initial effects of invasive deer on songbirds, we do not yet understand how their longer-term effects unfold. We looked for such potential long-term effects on songbirds in the context of an archipelago where deer were introduced over a century ago. Initial data consist of vegetation plots and songbird point-counts on 57 islands in Haida Gwaii (British Columbia, Canada) taken in 1989 when the impacts of introduced deer lacking predators had already developed for [50 years. Twenty years later, we surveyed these islands using the same methods. To isolate the effects of deer, we compare results to nearby islands never colonized by deer and assess how canopy birds have fared relative to understory birds. We also compare responses between islands of ‘‘moderate deer impact’’ where the understory vegetation was only moderately depleted by deer in 1989 and those with ‘‘severe deer impact’’ where understory vegetation was strongly depleted even in 1989. In 1989 all islands with deer were impoverished in songbirds that depend on understory vegetation, but the moderate impact islandsstill had richer and more abundant understory forestbird communities than found on severe impact islands.Islands with the fewest deer impacts in 1989 were small and isolated from sources of deer colonization.By 2009, severe deer impacts extended to islands that were initially less affected by deer. The severity ofimpacts also increased even on islands that had been dramatically affected by 1989. Declines in bird abundance occurred before declines in bird diversity. These results support the need for actions by wildlife managers to curtail deer impacts as soon as these become evident, especially in reserves and protected areas that lack hunters and other deer predators. (10.1007/s10530-014-0768-0)
  DOI : 10.1007/s10530-014-0768-0
• Time-resolved circular dichroism : what can we learn on conformational changes ?
  
  • Hache François
  Display and Imaging, 2015, 1 (3-4), pp.197-209. Time-resolved circular dichroism (CD) measurements can yield relevant information on the dynamics of conformational changes in molecules on the condition that some a priori knowledge is obtained. This can be the use of simple models such as the excitonic coupling or the octant rule or the phenomenological relationship between far-UV CD and secondary structures in proteins for example. This article describes such experiments where CD has brought relevant conformational information.
• Ex vivo multiscale quantitation of skin biomechanics in wild-type and genetically-modified mice using multiphoton microscopy
  
  • Bancelin Stéphane
  • Lynch Barbara
  • Bonod-Bidaud Christelle
  • Ducourthial Guillaume
  • Psilodimitrakopoulos Sotiris
  • Dokládal Petr
  • Allain Jean-Marc
  • Schanne-Klein Marie-Claire
  • Ruggiero, Florence
  Scientific Reports, Nature Publishing Group, 2015, 5, pp.17635. Soft connective tissues such as skin, tendon or cornea are made of about 90% of extracellular matrix proteins, fibrillar collagens being the major components. Decreased or aberrant collagen synthesis generally results in defective tissue mechanical properties as the classic form of Elhers-Danlos syndrome (cEDS). This connective tissue disorder is caused by mutations in collagen V genes and is mainly characterized by skin hyperextensibility. To investigate the relationship between the microstructure of normal and diseased skins and their macroscopic mechanical properties, we imaged and quantified the microstructure of dermis of ex vivo murine skin biopsies during uniaxial mechanical assay using multiphoton microscopy. We used two genetically-modified mouse lines for collagen V: a mouse model for cEDS harboring a Col5a2 deletion (a.k.a. pN allele) and the transgenic K14-COL5A1 mice which overexpress the human COL5A1 gene in skin. We showed that in normal skin, the collagen fibers continuously align with stretch, generating the observed increase in mechanical stress. Moreover, dermis from both transgenic lines exhibited altered collagen reorganization upon traction, which could be linked to microstructural modifications. These findings show that our multiscale approach provides new crucial information on the biomechanics of dermis that can be extended to all collagen-rich soft tissues. (10.1038/srep17635)
  DOI : 10.1038/srep17635
• Quantitative measurement of permeabilization of living cells by terahertz attenuated total reflection
  
  • Grognot Marianne
  • Gallot Guilhem
  Applied Physics Letters, American Institute of Physics, 2015, 107 (10), pp.103702. Using Attenuated Total Reflection imaging technique in the terahertz domain, we demonstrate non-invasive, non-staining real time measurements of cytoplasm leakage during permeabilization of epithelial cells by saponin. The terahertz signal is mostly sensitive to the intracellular protein concentration in the cells, in a very good agreement with standard bicinchoninic acid protein measurements. It opens the way to in situ real time dynamics of protein content and permeabilization in live cells. (10.1063/1.4930168)
  DOI : 10.1063/1.4930168
• In Vivo Single-Cell Detection of Metabolic Oscillations in Stem Cells
  
  • Stringari Chiara
  • Wang Hong
  • Geyfman Mikhail
  • Crosignani Viera
  • Kumar Vivek
  • Takahashi Joseph s.
  • Andersen Bogi
  • Gratton Enrico
  Cell Reports, Elsevier Inc, 2015, 10 (1), pp.1-7. Through the use of bulk measurements in metabolic organs, the circadian clock was shown to play roles in organismal energy homeostasis. However, the relationship between metabolic and circadian oscillations has not been studied in vivo at a single-cell level. Also, it is unknown whether the circadian clock controls metabolism in stem cells. We used a sensitive, noninvasive method to detect metabolic oscillations and circadian phase within epidermal stem cells in live mice at the single-cell level. We observe a higher NADH/NAD+ ratio, reflecting an increased glycolysis/oxidative phosphorylation ratio during the night compared to the day. Furthermore, we demonstrate that single-cell metabolic heterogeneity within the basal cell layer correlates with the circadian clock and that diurnal fluctuations in NADH/NAD+ ratio are Bmal1 dependent. Our data show that, in proliferating stem cells, the circadian clock coordinates activities of oxidative phosphorylation and glycolysis with DNA synthesis, perhaps as a protective mechanism against genotoxicity. (10.1016/j.celrep.2014.12.007)
  DOI : 10.1016/j.celrep.2014.12.007
• Time-resolved infrared spectroscopic studies of ligand dynamics in the active site from cytochrome c oxidase
  
  • Vos Marten H.
  • Liebl Ursula
  Biochimica et Biophysica Acta (BBA) - Reviews on Bioenergetics, Elsevier, 2015, 1847 (1), pp.79–85. The catalytic site of heme–copper oxidases encompasses two close-lying ligand binding sites: the heme, where oxygen is bound and reduced and the CuB atom, which acts as ligand entry and release port. Diatomic gaseous ligands with a dipole moment, such as the signaling molecules carbon monoxide (CO) and nitric oxide (NO), carry clear infrared spectroscopic signatures in the different states that allow characterization of the dynamics of ligand transfer within, into and out of the active site using time-resolved infrared spectroscopy. We review the nature and diversity of these processes that have in particular been characterized with CO as ligand and which take place on time scales ranging from femtoseconds to milliseconds. These studies have advanced our understanding of the functional ligand pathways and reactivity in enzymes and more globally represent intriguing model systems for mechanisms of ligand motion in a confined protein environment. This article is part of a Special Issue entitled: Vibrational spectroscopies and bioenergetic systems. (10.1016/j.bbabio.2014.07.018)
  DOI : 10.1016/j.bbabio.2014.07.018