Messerli Mark A.

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Mark A.

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Now showing 1 - 7 of 7
  • Article
    Extracellular electrical fields direct wound healing and regeneration
    (Marine Biological Laboratory, 2011-08) Messerli, Mark A. ; Graham, David M.
    Endogenous DC electric fields (EFs) are important, fundamental components of development, regeneration, and wound healing. The fields are the result of polarized ion transport and current flow through electrically conductive pathways. Nullification of endogenous EFs with pharmacological agents or applied EFs of opposite polarity disturbs the aforementioned processes, while enhancement increases the rate of wound closure and the extent of regeneration. EFs are applied to humans in the clinic, to provide an overwhelming signal for the enhancement of healing of chronic wounds. Although clinical trials, spanning a course of decades, have shown that applied EFs enhance healing of chronic wounds, the mechanisms by which cells sense and respond to these weak cues remains unknown. EFs are thought to influence many different processes in vivo. However, under more rigorously controlled conditions in vitro, applied EFs induce cellular polarity and direct migration and outgrowth. Here we review the generation of endogenous EFs, the results of their alteration, and the mechanisms by which cells may sense these weak fields. Understanding the mechanisms by which native and applied EFs direct development and repair will enable current and future therapeutic applications to be optimized.
  • Preprint
    Ion trapping with fast-response ion-selective microelectrodes enhances detection of extracellular ion channel gradients
    ( 2008-11) Messerli, Mark A. ; Collis, Leon P. ; Smith, Peter J. S.
    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 μm), 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 K+ 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.
  • Preprint
    Construction, Theory, and Practical Considerations for using Self-referencing of Ca2+-Selective Microelectrodes for Monitoring Extracellular Ca2+ Gradients
    ( 2010-10) Messerli, Mark A. ; Smith, Peter J. S.
    Ca2+ signaling in the extra- and intracellular domains is linked to Ca2+ transport across the plasma membrane. Non-invasive monitoring of these resulting extracellular Ca2+ gradients with self-referencing of Ca2+-selective microelectrodes is used for studying Ca2+ signaling across Kingdoms. The quantitated Ca2+ flux enables comparison with changes to intracellular [Ca2+] measured with other methods and determination of Ca2+ transport stoichiometry. Here we review the construction of Ca2+-selective microelectrodes, their physical characteristics and their use in self-referencing mode to calculate Ca2+ flux. We also discuss potential complications when using them to measure Ca2+ gradients near the boundary layers of single cells and tissues.
  • Article
    Spatial manipulation of cells and organelles using single electrode dielectrophoresis
    (Informa Healthcare USA, 2012-01) Graham, David M. ; Messerli, Mark A. ; Pethig, Ronald
    The selection, isolation, and accurate positioning of single cells in three dimensions are increasingly desirable in many areas of cell biology and tissue engineering. We describe the application of a simple and low cost dielectrophoretic device for picking out and relocating single target cells. The device consists of a single metal electrode and an AC signal generator. It does not require microfabrication technologies or sophisticated electronics. The dielectrophoretic manipulator also discriminates between live and dead cells and is capable of redistributing intracellular organelles.
  • Article
    Construction and composition of the squid pen from Doryteuthis pealeii
    (University of Chicago Press, 2019-07-08) Messerli, Mark A. ; Raihan, M. Jahir ; Kobylkevich, Brian M. ; Benson, Austin C. ; Bruening, Kristi S. ; Shribak, Michael ; Rosenthal, Joshua J. C. ; Sohn, Joel J.
    The pen, or gladius, of the squid is an internalized shell. It serves as a site of attachment for important muscle groups and as a protective barrier for the visceral organs. The pen’s durability and flexibility are derived from its unique composition of chitin and protein. We report the characterization of the structure, development, and composition of pens from Doryteuthis pealeii. The nanofibrils of the polysaccharide β-chitin are arranged in an aligned configuration in only specific regions of the pen. Chitin is secreted early in development, enabling us to characterize the changes in pen morphology prior to hatching. The chitin and proteins are assembled in the shell sac surrounded by fluid that has a significantly different ionic composition from squid plasma. Two groups of proteins are associated with the pen: those on its surface and those embedded within the pen. Only 20 proteins are identified as embedded within the pen. Embedded proteins are classified into six groups, including chitin associated, protease, protease inhibitors, intracellular, extracellular matrix, and those that are unknown. The pen proteins share many conserved domains with proteins from other chitinous structures. We conclude that the pen is one of the least complex, load-bearing, chitin-rich structures currently known and is amenable to further studies to elucidate natural construction mechanisms using chitin and protein.
  • Preprint
    Windows to cell function and dysfunction : signatures written in the boundary layers
    ( 2010-01-26) Smith, Peter J. S. ; Collis, Leon P. ; Messerli, Mark A.
    The medium surrounding cells either in culture or in tissues contains a chemical mix varying with cell state. As solutes move in and out of the cytoplasmic compartment they set up characteristic signatures in the cellular boundary layers. These layers are complex physical and chemical environments whose profiles both reflect cell physiology and provide conduits for intercellular messaging. Here we review some of the most relevant characteristics of the extracellular/intercellular space. Our initial focus is primarily with cultured cells but we extend our consideration to the far more complex environment of tissues and discuss how chemical signatures in the boundary layer can or may affect cell function. Critical to the entire essay are the methods used, or being developed, to monitor chemical profiles in the boundary layers. We review recent developments in ultramicro electrochemical sensors and tailored optical reporters suitable for the task in hand.
  • Article
    Cisplatin resistant spheroids model clinically relevant survival mechanisms in ovarian tumors
    (Public Library of Science, 2016-03-17) Chowanadisai, Winyoo ; Messerli, Shanta M. ; Miller, Daniel H. ; Medina, Jamie E. ; Hamilton, Joshua W. ; Messerli, Mark A. ; Brodsky, Alexander S.
    The majority of ovarian tumors eventually recur in a drug resistant form. Using cisplatin sensitive and resistant cell lines assembled into 3D spheroids we profiled gene expression and identified candidate mechanisms and biological pathways associated with cisplatin resistance. OVCAR-8 human ovarian carcinoma cells were exposed to sub-lethal concentrations of cisplatin to create a matched cisplatin-resistant cell line, OVCAR-8R. Genome-wide gene expression profiling of sensitive and resistant ovarian cancer spheroids identified 3,331 significantly differentially expressed probesets coding for 3,139 distinct protein-coding genes (Fc >2, FDR < 0.05) (S2 Table). Despite significant expression changes in some transporters including MDR1, cisplatin resistance was not associated with differences in intracellular cisplatin concentration. Cisplatin resistant cells were significantly enriched for a mesenchymal gene expression signature. OVCAR-8R resistance derived gene sets were significantly more biased to patients with shorter survival. From the most differentially expressed genes, we derived a 17-gene expression signature that identifies ovarian cancer patients with shorter overall survival in three independent datasets. We propose that the use of cisplatin resistant cell lines in 3D spheroid models is a viable approach to gain insight into resistance mechanisms relevant to ovarian tumors in patients. Our data support the emerging concept that ovarian cancers can acquire drug resistance through an epithelial-to-mesenchymal transition.