Anionic polymers amplify electrokinetic perfusion through extracellular matrices.

Electrical stimulation (ES) promotes healing of chronic epidermal wounds and delays degeneration of articular cartilage. Despite electrotherapeutic treatment of these non-excitable tissues, the mechanisms by which ES promotes repair are unknown. We hypothesize that a beneficial role of ES is dependent on electrokinetic perfusion in the extracellular space and that it mimics the effects of interstitial flow.

Electrokinetic Perfusion Through Three-Dimensional Culture Reduces Cell Mortality.

Cell proliferation and survival are dependent on mass transfer. , fluid flow promotes mass transfer through the vasculature and interstitial space, providing a continuous supply of nutrients and removal of cellular waste products. In the absence of sufficient flow, mass transfer is limited by diffusion and poses significant challenges to cell survival during tissue engineering, tissue transplantation, and treatment of degenerative diseases.

Linear polysaccharides reduce production of inflammatory cytokines by LPS-stimulated bovine fibroblasts.

Chronic lesions in the limbs of farm animals cause lameness due to chronic infection and inflammation. Exploratory treatments for chronic wounds in humans may be suitable for adaptation into the field of animal care. Specifically, antimicrobial linear polysaccharides like oxidized regenerated cellulose (ORC) and chitin/chitosan are biodegradable hemostats that are being explored to promote healing of chronic wounds but have not been directly compared using the same biological specimen.

Genetic and Genomic Advances in Developmental Models: Applications for Nutrition Research.

There is increasing appreciation that dietary components influence and interact with genes important to metabolism. How such influences impact developmental regulation and programming or risks of chronic diseases remains unclear. Nutrition is recognized to affect development and chronic diseases, but our understanding about how genes essential to nutrient metabolism regulate development and impact risks of these diseases remains unclear.

Construction and Composition of the Squid Pen from .

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.

Electromigration of cell surface macromolecules in DC electric fields during cell polarization and galvanotaxis.

DC electric fields (EFs) can often induce cellular polarity, and direct migration of cells toward one of the electrical poles. The mechanism(s) by which cells sense weak EFs is not established. We present here a molecular flux model to describe electromigration of plasma membrane macromolecules and compare its predictions to electromigration of a lipid-anchored surface protein, tdTomato-GPI, under different experimental conditions.

Advances in Electrochemistry for Monitoring Cellular Chemical Flux.

The transport of molecules and inorganic ions across the plasma membrane results in chemical fluxes that reflect cellular function in healthy and diseased states. Measurement of these chemical fluxes enables the characterization of protein function and transporter stoichiometry, characterization of the viability of single cells and embryos prior to implantation, and screening of pharmaceutical agents. Electrochemical sensors are sensitive and noninvasive tools for measuring chemical fluxes immediately outside the cells in the boundary layer, that are capable of monitoring a diverse range of transported analytes including inorganic ions, gases, neurotransmitters, hormones, and pharmaceutical agents.

Reversing the direction of galvanotaxis with controlled increases in boundary layer viscosity.

Weak external electric fields (EFs) polarize cellular structure and direct most migrating cells (galvanotaxis) toward the cathode, making it a useful tool during tissue engineering and for healing epidermal wounds. However, the biophysical mechanisms for sensing weak EFs remain elusive. We have reinvestigated the mechanism of cathode-directed water flow (electro-osmosis) in the boundary layer of cells, by reducing it with neutral, viscous polymers.

Cisplatin Resistant Spheroids Model Clinically Relevant Survival Mechanisms in Ovarian Tumors.

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.

Metabolic oxygen consumption measurement with a single-cell biosensor after particle microbeam irradiation.

A noninvasive, self-referencing biosensor/probe system has been integrated into the Columbia University Radiological Research Accelerator Facility Microbeam II end station. A single-cell oxygen consumption measurement has been conducted with this type of oxygen probe in 37° C Krebs-Ringer Bicarbonate buffer immediately before and after a single-cell microbeam irradiation. It is the first such measurement made for a microbeam irradiation, and a six fold increment of oxygen flux induced during a 15-s period of time has been observed following radiation exposure.

A zinc transporter gene required for development of the nervous system.

The essentiality of zinc for normal brain development is well established. It has been suggested that primary and secondary zinc deficiencies can contribute to the occurrence of numerous human birth defects, including many involving the central nervous system. In a recent study, we searched for zinc transporter genes that were critical for neurodevelopment.

Epidermal keratinocyte polarity and motility require Ca²⁺ influx through TRPV1.

Ca(2+) has long been known to play an important role in cellular polarity and guidance. We studied the role of Ca(2+) signaling during random and directed cell migration to better understand whether Ca(2+) directs cell motility from the leading edge and which ion channels are involved in this function by using primary zebrafish keratinocytes. Rapid line-scan and time-lapse imaging of intracellular Ca(2+) (Ca(2+)i) during migration and automated image alignment enabled us to characterize and map the spatiotemporal changes in Ca(2+)i.

Neurulation and neurite extension require the zinc transporter ZIP12 (slc39a12).

Zn(2+) is required for many aspects of neuronal structure and function. However, the regulation of Zn(2+) in the nervous system remains poorly understood. Systematic analysis of tissue-profiling microarray data showed that the zinc transporter ZIP12 (slc39a12) is highly expressed in the human brain.

Spatial manipulation of cells and organelles using single electrode dielectrophoresis.

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.

Extracellular electrical fields direct wound healing and regeneration.

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.

Construction, theory, and practical considerations for using self-referencing of Ca(2+)-selective microelectrodes for monitoring extracellular Ca(2+) gradients.

Ca(2+) signaling in the extra- and intracellular domains is linked to Ca(2+) transport across the plasma membrane. Noninvasive monitoring of these resulting extracellular Ca(2+) gradients with self-referencing of Ca(2+)-selective microelectrodes is used for studying Ca(2+) signaling across Kingdoms. The quantitated Ca(2+) flux enables comparison with changes to intracellular [Ca(2+)] measured with other methods and determination of Ca(2+) transport stoichiometry.

Windows to cell function and dysfunction: signatures written in the boundary layers.

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 the profiles of which reflect cell physiology and provide conduits for intercellular messaging.

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.

The involvement of Ca2+ and integrins in directional responses of zebrafish keratocytes to electric fields.

Many cells respond directionally to small DC electrical fields (EFs) by an unknown mechanism, but changes in intracellular Ca(2+) are widely assumed to be involved. We have used zebrafish (Danio rerio) keratocytes in an effort to understand the nature of the EF-cell interaction. We find that the adult zebrafish integument drives substantial currents outward through wounds produced by scale removal, establishing that keratocytes near the wound will experience endogenous EFs.

Imaging of the Yellow Cameleon 3.6 indicator reveals that elevations in cytosolic Ca2+ follow oscillating increases in growth in root hairs of Arabidopsis.

In tip-growing cells, the tip-high Ca(2+) gradient is thought to regulate the activity of components of the growth machinery, including the cytoskeleton, Ca(2+)-dependent regulatory proteins, and the secretory apparatus. In pollen tubes, both the Ca(2+) gradient and cell elongation show oscillatory behavior, reinforcing the link between the two. We report that in growing root hairs of Arabidopsis (Arabidopsis thaliana), an oscillating tip-focused Ca(2+) gradient can be resolved through imaging of a cytosolically expressed Yellow Cameleon 3.

Characterization of optimized Na+ and Cl- liquid membranes for use with extracellular, 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.

Measuring extracellular ion gradients from single channels with ion-selective microelectrodes.

Under many different conditions activated plasma membrane ion channels give rise to changes in the extracellular concentration of the permeant ion(s). The magnitude and duration of these changes are dependent on the electrochemical driving force(s) on the permeant ion(s) as well as conductance, open time, and channel density. We have modeled the change in the extracellular [K+] due to efflux through Ca2+-activated K+ channels, mSlo, to determine the range of parameters that would give rise to measurable signals in the surrounding media.

Chloride fluxes in lily pollen tubes: a critical reevaluation.

Microelectrodes, made from a Cl(-)-selective liquid ion exchanger previously used to measure putative Cl- fluxes in Lilium longiflorum pollen tubes, were characterized. The electrodes were poorly selective, possessing only about 10-fold selectivity for Cl- over other anions tested. They had only 2.