• Cell biologist, MBL Director and CEO and Cellular Dynamics Program (CDP) member Gary Borisy has been elected to the National Acadamy of Sciences, an honorific society of distinguished scholars engaged in scientific and engineering research. Dr. Borisy discovered the protein tubulin in 1965 and has been instrumental in descriptions of the cytoskeleton, chromosome movement and various processes and structures related to cell division. More >>.

NEW MBL CELLULAR DYNAMICS PROGRAM
CDP website >> 

The MBL is in the process of creating a new Cellular Dynamics Program (CDP) which will combine the advanced imaging technologies of the Architectural Dynamics in Living Cells (ADLC) program with the Self-Referencing Technologies of the BioCurrents Research Center. The BRC and ADLC Programs will become part of the new CDP and the current Molecular Physiology Program will dissipate. BRC director Peter Smith is also the director of the CDP.

"The MBL's distinguished history of cell studies, nucleus of outstanding expertise on instrumentation and its application to direct studies on living cells, and the tradition of interdisciplinary collaboration makes the institution an ideal home for the Program in Cellular Dynamics." - Shinya Inoue'

Dielectriphoretic assembly of insulinoma cells and fluorescent nanosensors into three-dimensional 'pseudo-islet' constructs

Dielectrophoretic forces, generated by radio-frequency voltages applied to micromachined, transparent, indium tin oxide electrodes, have been used to condense suspensions of insulinoma cells (BETA-TC-6 and INS-1) into a 10×10 array of three-dimensional cell constructs. Some of these constructs, measuring ~150 µm in diameter, 120 µm in height and containing around 1000 cells, were of the same size and cell density as a typical islet of Langerhans. With the dielectrophoretic force maintained, these engineered cell constructs were able to withstand mechanical shock and fluid flow forces. Reproducibility of the process required knowledge of cellular dielectric properties, in terms of membrane capacitance and membrane conductance, which were obtained by electrorotation measurements. The ability to incorporate fluorescent nanosensors, as probes of cellular oxygen and pH levels, into these `pseudo-islets' was also demonstrated. The footprint of the 10×10 array of cell constructs was compatible with that of a 1536 microtitre plate, and thus amenable to optical interrogation using automated plate reading equipment.

Pethig, R., Menachery, A., Heart, E., Sanger R.H and. Smith, P.J.S. 2008. Dielectrophoretic assembly of insulinoma cells and fluorescent nanosensors into three-dimensional 'pseudo-islet' constructs. IET Nanobiotechnology. 2(2): 31-38.

FEATURED PUBLICATIONS

Transepithelial projections from basal cells are luminal sensors in pseudostratified epithelia. Basal cells are by definition located on the basolateral side of several epithelia, and they have never been observed reaching the lumen. Using high-resolution 3D confocal imaging, we report that basal cells extend long and slender cytoplasmic projections that not only reach toward the lumen but can cross the tight junction barrier in some epithelia of the male reproductive and respiratory tracts. In this way, the basal cell plasma membrane is exposed to the luminal environment. In the epididymis, in which luminal acidification is crucial for sperm maturation and storage, these projections contain the angiotensin II type 2 receptor (AGTR2). Activation of AGTR2 by luminal angiotensin II, increases proton secretion by adjacent clear cells, which are devoid of AGTR2. We propose a paradigm in which basal cells scan and sense the luminal environment of pseudostratified epithelia and modulate epithelial function by a mechanism involving crosstalk with other epithelial cells.

Shum, W.W, Da Silva, N., McKee, M, Smith, P.J, Brown, D., Breton, S. 2008. Transepithelial projections from basal cells are luminal sensors in pseudostratified epithelia. Cell. Dec 12;135(6):1108-17.

Ion trapping with fast response, ion-selective microelectrodes enhances detection of extracellular ion channel gradients Previously, functional mapping of channels has been achieved by measuring the passage of net charge and of specific ions with electrophysiological and intracellular fluorescence imaging techniques. However, functional mapping of ion channels using extracellular ion-selective microelectrodes has distinct advantages over the former methods. We have developed this method through measurement of extracellular K+ gradients caused by efflux through Ca2+-activated K+ channels expressed in Chinese hamster ovary cells. We report that electrodes constructed with short columns of a mechanically stable K+-selective liquid membrane respond quickly and measure changes in local [K+] consistent with a diffusion model. When used in close proximity to the plasma membrane (<4 mm), the ISMs pose a barrier to simple diffusion, creating an ion trap. The ion trap amplifies the local change in [K+] without dramatically changing the rise or fall time of the [K+] profile. Measurement of extracellular Kþ gradients from activated rSlo channels shows that rapid events, 10–55 ms, can be characterized. This method provides a noninvasive means for functional mapping of channel location and density as well as for characterizing the properties of ion channels in the plasma membrane.

Messerli MA, Collis LP & Smith PJS. 2009. Ion trapping with fast response, ion-selective microelectrodes enhances detection of extracellular ion channel gradients . Biophys. Journal. Vol 96:1-9

Imaging electric fields We have developed a noninvasive instrument called the bioelectric field imager (BFI) for mapping the electric field between the epidermis and the stratum corneum near wounds in both mouse and human skin. Rather than touching the skin, the BFI vibrates a small metal probe with a displacement of 180 μm in air above the skin to detect the surface potential of the epidermis through capacitative coupling. Here we describe our first application of the BFI measuring the electric field between the stratum corneum and epidermis at the margin of skin wounds in mice.

Nuccitelli, R. Nuccitelli, P. , Ramlatchan, S., Sanger, R. and Smith, P.J.S. 2008. Imaging the electric field associated with mouse and human skin wounds. Wound Repair and Regeneration. 16 (3): 432-441.

Na+ and Cl- liquid membranes and self-referencing microelectrodes Self-referencing with ion-selective microelectrodes (ISMs) is a useful approach for monitoring near-real-time ion flux near single cells and across epithelia. While ISMs for H+, Ca2+, and K+ have been optimized for use with self-referencing, ISMs for two other primary inorganic ions, Na+ and Cl−, have not. In this study, we have characterized ISMs based on three Na+ ionophores (I, VI, and X) and one Cl− ionophore to assess their suitability for use with self-referencing. ISMs constructed with Na+ ionophore VI have short response times (≈100 ms) but possess nearly an order of magnitude less selectivity for Na+ over K+ than ISMs constructed with Na+ ionophore X.

Messerli, M.A., Kurtz, I. and Smith, P.J.S. 2008. Characterization of Optimized Na+ and Cl- liquid membranes for use with extracellular, self-referencing microelectrodes. Anal. Bioanal. Chem. 390(5): 1355-9.

Depolarized mitochondria and diabetes Accumulation of depolarized mitochondria within beta-cells has been associated with oxidative damage and development of diabetes. To determine the source and fate of depolarized mitochondria, individual mitochondria were photolabeled and tracked through fusion and fission. Mitochondria were found to go through frequent cycles of fusion and fission in a 'kiss and run' pattern. .

Li, H., Chen, Y., Jones, A.F., Sanger, R.H., Collis, L.P., Flannery, R., McNay, E.C., Schwartzenbacher, R., Bossy, B., Bossy-Wetzel, E., Bennett, M.V.L., Pypaert, M., Hickman, J.A., Smith, P.J.S., Hardwick, J.M. and Jonas, E.A. 2008. The anti-apoptotic protein BCL-xL controls synapse formation. PNAS. 105(6): 2169-2174

SPECIAL PUBLICATION NOTES We would like to remind our readers of three recent reviews: Smith, P.J.S., Sanger, R.S. and Messerli, M.A. 2007. Principles, development and applications of self-referencing electrochemical microelectrodes to the determination of fluxes at cell membranes. In: Methods and New Frontiers in Neuroscience. Ed. Adrian C. Michael. CRC Press. Ch. 18: 373-405. Messerli, M.A., Robinson, K.R. and Smith, P.J.S. 2006. Electrochemical sensor applications to the study of molecular physiology and analyte flux in plants. In: Plant electrophysiology - Theory and Methods. (PDF: 1,955 Kb) Ed. Alexander G. Volkov.  Springer Sections 4.1–4.5. Smith, P.J.S. and Remsen, D. 2006. Using Pharmabase to Perform Pharmacological Analyses of Cell Function. In Current Protocols in Bioinformatics: Cheminformatics. Eds. Baxevanis, A., Davison,.D., Page, R., Petsko, G., Stormo, G. and Stein. L. John Wiley and Sons. Supplement 13, Section 14.2, 14.2.1 - 14.2.17. __________________________________________________________ We would like to thank Sutter Instruments for including BRC techniques in their P-97 Pipette Cookbook. Download cookbook (8,999 Kb)