Doron Kaplan

Low Energy Visible Light Induces Reactive Oxygen Species Generation and Stimulates an Increase of Intracellular Calcium Concentration in Cardiac Cells

Low energy visible light (LEVL) irradiation has been shown to exert some beneficial effects on various cell cultures. For example, it increases the fertilizing capability of sperm cells, promotes cell proliferation, induces sprouting of neurons, and more. To learn about the mechanism of photobiostimulation, we studied the relationship between increased intracellular calcium ([Ca2+]i) and reactive oxygen species production following LEVL illumination of cardiomyocytes. We found that visible light causes the production of \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \(\mathrm{O}_{2}^{{\bar{{\cdot}}}}\) \end{document} and H2O2 and that exogenously added H2O2 (12 μm) can mimic the effect of LEVL (3.6 J/cm2) to induce a slow and transient increase in [Ca2+]i. This [Ca2+]i elevation can be reduced by verapamil, a voltage-dependent calcium channel inhibitor. The kinetics of [Ca2+]i elevation and morphologic damage following light or addition of H2O2 were found to be dosedependent. For example, LEVL, 3.6 J/cm2, which induced a transient increase in [Ca2+]i, did not cause any cell damage, whereas visible light at 12 J/cm2 induced a linear increase in [Ca2+]i and damaged the cells. The linear increase in [Ca2+]i resulting from high energy doses of light could be attenuated into a non-linear small rise in [Ca2+]i by the presence of extracellular catalase during illumination. We suggest that the different kinetics of [Ca2+]i elevation following various light irradiation or H2O2 treatment represents correspondingly different adaptation levels to oxidative stress. The adaptive response of the cells to LEVL represented by the transient increase in [Ca2+]i can explain LEVL beneficial effects.

Propagating Waves of Directionality and Coordination Orchestrate Collective Cell Migration

The ability of cells to coordinately migrate in groups is crucial to enable them to travel long distances during embryonic development, wound healing and tumorigenesis, but the fundamental mechanisms underlying intercellular coordination during collective cell migration remain elusive despite considerable research efforts. A novel analytical framework is introduced here to explicitly detect and quantify cell clusters that move coordinately in a monolayer. The analysis combines and associates vast amount of spatiotemporal data across multiple experiments into transparent quantitative measures to report the emergence of new modes of organized behavior during collective migration of tumor and epithelial cells in wound healing assays. First, we discovered the emergence of a wave of coordinated migration propagating backward from the wound front, which reflects formation of clusters of coordinately migrating cells that are generated further away from the wound edge and disintegrate close to the advancing front. This wave emerges in both normal and tumor cells, and is amplified by Met activation with hepatocyte growth factor/scatter factor. Second, Met activation was found to induce coinciding waves of cellular acceleration and stretching, which in turn trigger the emergence of a backward propagating wave of directional migration with about an hour phase lag. Assessments of the relations between the waves revealed that amplified coordinated migration is associated with the emergence of directional migration. Taken together, our data and simplified modeling-based assessments suggest that increased velocity leads to enhanced coordination: higher motility arises due to acceleration and stretching that seems to increase directionality by temporarily diminishing the velocity components orthogonal to the direction defined by the monolayer geometry. Spatial and temporal accumulation of directionality thus defines coordination. The findings offer new insight and suggest a basic cellular mechanism for long-term cell guidance and intercellular communication during collective cell migration.

The effect of airflow pattern on filter breakthrough in physical adsorption

Abstract The Wheeler–Jonas (WJ) model for prediction of the protection capacity of organic vapor filters under a fixed airflow was extended to breathing-simulation, pulsating flow. Breakthrough curves of dimethyl-methyl phosphonate (DMMP) and decane were measured under fixed flow and sinusoidal flow. A linear dependence of ln( C X / C 0 ) on the breakthrough time ( t B ) was observed in all the experiments, indicating that the concepts of critical bed weight ( W C ) and dynamic adsorption capacity ( W E ) as defined by the WJ model are applicable to pulsating flow as well. W E was found to be almost unchanged by the flow pattern, whereas W C was considerably larger (by 7–44%) at pulsating flow compared to fixed flow with the same average rate. Thus, shifting from fixed flow to pulsating flow may shorten t B significantly. The effect of the flow type on t B increases with the ratio of the critical weight to the total bed weight. For a high protection level ( C 0 / C X =60 000), the protection capacity of personal NBC canisters was reduced by up to 15% upon shifting from fixed to pulsating flow.

The protective effect of class III antiarrhythmic agents against calcium overload in cultured myocytes

Calcium ions have been implicated in the mechanisms of ventricular arrhythmias. Impairment of intercellular coupling by calcium overload is considered to facilitate ventricular fibrillation (VF) and to sup-press its self termination. According to our hypothesis, any compound that decreases intracellular calcium concentration [Ca2+]i during VF can serve as defibrillating drug. In this study, we examined the effect of d-sotalol and tedisamil on calcium overload in cultured, spontaneously beating rat cardiomyocytes. The changes of [Ca2+]i were measured by indo-1 method and the intercellular synchronization by image analysis. The results showed that increase in [Ca2+]o from 1.9 mM to 3.9 mM increased [Ca2+]i from 100 nM to 320 nM and transformed the synchronized cell movement to an asynchronous one. Administration of 5 x 10(-6) M d-sotalol or 10(-6) M tedisamil, decreased the [Ca2+]i to its basic level and restored the synchronized activity. In summary: Our results showed that increase in [Ca2+]i known to cause inhibition of intercellular coupling, that could lead to arrhythmia and fibrillation while d-sotalol or tedisamil prevented this effect. These results support our hypothesis, that class III antiarrhythmic compounds with positive inotropic effect, increase intercellular synchronization, by decreasing free [Ca2+]i, most probably by increasing the Ca2+ uptake by the sarcoplasmic reticulum, and therefore act as a defibrillating compound.

Decontamination of adsorbed chemical warfare agents on activated carbon using hydrogen peroxide solutions.

Mild treatment with hydrogen peroxide solutions (3-30%) efficiently decomposes adsorbed chemical warfare agents (CWAs) on microporous activated carbons used in protective garments and air filters. Better than 95% decomposition of adsorbed sulfur mustard (HD), sarin, and VX was achieved at ambient temperatures within 1-24 h, depending on the H2O2 concentration. HD was oxidized to the nontoxic HD-sulfoxide. The nerve agents were perhydrolyzed to the respective nontoxic methylphosphonic acids. The relative rapidity of the oxidation and perhydrolysis under these conditions is attributed to the microenvironment of the micropores. Apparently, the reactions are favored due to basic sites on the carbon surface. Our findings suggest a potential environmentally friendly route for decontamination of adsorbed CWAs, using H2O2 without the need of cosolvents or activators.

Octreotide ameliorates glucose intolerance following acute experimental pancreatitis.

The long-term effects of octreotide, thesynthetic analog of the hormone somatostatin, on acuteexperimental pancreatitis were studied. Acutepancreatitis was induced in rats by intraparenchymalinjections of 0.5 ml 5% or 10% sodium taurocholate.Octreotide (10 mg/kg/day, subcutaneously), or salineinjections as controls, were started four hours later,and their effects were assessed 30, 60, and 90 daysafter the induction of pancreatitis. Neitherintrapancreatic saline injections nor octreotideadministration without the induction of pancreatitiscaused any biochemical or histological abnormalities.Taurocholate-induced pancreatitis was followed by remarkablehyperglycemia, which was ameliorated by octreotide.Thirty days after induction of pancreatitis, glucoselevels were 269 ± 21 mg/100 ml and 153 ±17 mg/100 ml in the control and octreotide treated animals,respectively (P < 0.02). Octreotide administrationwas associated with increased pH values after 60 and 90days (P < 0.05 for the 90 days group). The levels ofhematocrit, calcium, and amylase were already within thenormal ranges after 30 days and were unaffected byoctreotide. There were no signs of chronic exocrineinsufficiency and all the surviving rats gained weight during the follow-up. However, the relativeweights of the pancreases of the octreotide-treatedanimals were higher than those of the controls 30 daysafter IOP. Histopathological evaluation demonstrated regeneration of the pancreatic tissue, andincreased number and hypertrophy of the islets ofLangherhans. There were no significant differenceswhether the octreotide treatment was given for only 48or 96 hr. Survival was significantly improved byoctreotide; only one octreotide-treated rat (2.5%) with10% taurocholate-induced pancreatitis died, while six(15%) of the control animals succumbed (P < 0.05). These studies provided data on the sequelae ofacute pancreatitis and showed that octreotide may havelong-term beneficial effects in this disease.

The Effects of Aging on the Dynamic Adsorption of Hazardous Organic Vapors on Impregnated Activated Carbon

The effects of an eight-year natural aging of ASC impregnated activated carbon on the adsorption capacity and breakthrough times of model organic vapors and of the nerve agent sarin were investigated. Aging delayed methanol breakthrough from dry air on pre-dried carbon, but shortened the breakthrough time of both methanol and hexane under relative humidity (RH) of 30–85% on pre-humidified carbon. Aging also shortened the breakthrough time of the less volatile model compound 2-methoxyethanol, especially under RH of 60–85%. Aging significantly reduced the protection capacity against sarin at RH of 85%. The effects of aging on physisorption are attributed to enhanced hydrogen-bonding capability and strength of the interaction between water and adsorption sites on the carbon surface.

Live time-lapse dataset of in vitro wound healing experiments

BackgroundThe wound healing assay is the common method to study collective cell migration in vitro. Computational analyses of live imaging exploit the rich temporal information and significantly improve understanding of complex phenomena that emerge during this mode of collective motility. Publicly available experimental data can allow application of new analyses to promote new discoveries, and assess algorithms’ capabilities to distinguish between different experimental conditions.FindingsA freely-available dataset of 31 time-lapse in vitro wound healing experiments of two cell lines is presented. It consists of six different experimental conditions with 4–6 replicates each, gathered to study the effects of a growth factor on collective cell migration. The raw data is available at ‘The Cell: an Image Library’ repository. This Data Note provides detailed description of the data, intermediately processed data, scripts and experimental validations that have not been reported before and are currently available at GigaDB. This is the first publicly available repository of live collective cell migration data that includes independent replicates for each set of conditions.ConclusionsThis dataset has the potential for extensive reuse. Some aspects in the data remain unexplored and can be exploited extensively to reveal new insight. The dataset could also be used to assess the performance of available and new quantification methods by demonstrating phenotypic discriminatory capabilities between the different experimental conditions. It may allow faster and more elaborated, reproducible and effective analyses, which will likely lead to new biological and biophysical discoveries.