A network approach to the geometric structure of shallow cloud fields

NASA Astrophysics Data System (ADS)

Glassmeier, F.; Feingold, G.

2017-12-01

The representation of shallow clouds and their radiative impact is one of the largest challenges for global climate models. While the bulk properties of cloud fields, including effects of organization, are a very active area of research, the potential of the geometric arrangement of cloud fields for the development of new parameterizations has hardly been explored. Self-organized patterns are particularly evident in the cellular structure of Stratocumulus (Sc) clouds so readily visible in satellite imagery. Inspired by similar patterns in biology and physics, we approach pattern formation in Sc fields from the perspective of natural cellular networks. Our network analysis is based on large-eddy simulations of open- and closed-cell Sc cases. We find the network structure to be neither random nor characteristic to natural convection. It is independent of macroscopic cloud fields properties like the Sc regime (open vs closed) and its typical length scale (boundary layer height). The latter is a consequence of entropy maximization (Lewis's Law with parameter 0.16). The cellular pattern is on average hexagonal, where non-6 sided cells occur according to a neighbor-number distribution variance of about 2. Reflecting the continuously renewing dynamics of Sc fields, large (many-sided) cells tend to neighbor small (few-sided) cells (Aboav-Weaire Law with parameter 0.9). These macroscopic network properties emerge independent of the Sc regime because the different processes governing the evolution of closed as compared to open cells correspond to topologically equivalent network dynamics. By developing a heuristic model, we show that open and closed cell dynamics can both be mimicked by versions of cell division and cell disappearance and are biased towards the expansion of smaller cells. This model offers for the first time a fundamental and universal explanation for the geometric pattern of Sc clouds. It may contribute to the development of advanced Sc parameterizations. As an outlook, we discuss how a similar network approach can be applied to describe and quantify the geometric structure of shallow cumulus cloud fields.

Hydrodynamics of stratified epithelium: Steady state and linearized dynamics

NASA Astrophysics Data System (ADS)

Yeh, Wei-Ting; Chen, Hsuan-Yi

2016-05-01

A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.

Repertoire comparison of the B-cell receptor encoding loci in humans and rhesus macaques by next generation sequencing

USDA-ARS?s Scientific Manuscript database

Rhesus macaques are a widely used model system for the study of vaccines, infectious diseases, and microbial pathogenesis. Their value as a model lies in their close evolutionary relationship to humans, which, in theory, allows them to serve as a close approximation of the human immune system. Howev...

Porous Media Approach for Modeling Closed Cell Foam

NASA Technical Reports Server (NTRS)

Ghosn, Louis J.; Sullivan, Roy M.

2006-01-01

In order to minimize boil off of the liquid oxygen and liquid hydrogen and to prevent the formation of ice on its exterior surface, the Space Shuttle External Tank (ET) is insulated using various low-density, closed-cell polymeric foams. Improved analysis methods for these foam materials are needed to predict the foam structural response and to help identify the foam fracture behavior in order to help minimize foam shedding occurrences. This presentation describes a continuum based approach to modeling the foam thermo-mechanical behavior that accounts for the cellular nature of the material and explicitly addresses the effect of the internal cell gas pressure. A porous media approach is implemented in a finite element frame work to model the mechanical behavior of the closed cell foam. The ABAQUS general purpose finite element program is used to simulate the continuum behavior of the foam. The soil mechanics element is implemented to account for the cell internal pressure and its effect on the stress and strain fields. The pressure variation inside the closed cells is calculated using the ideal gas laws. The soil mechanics element is compatible with an orthotropic materials model to capture the different behavior between the rise and in-plane directions of the foam. The porous media approach is applied to model the foam thermal strain and calculate the foam effective coefficient of thermal expansion. The calculated foam coefficients of thermal expansion were able to simulate the measured thermal strain during heat up from cryogenic temperature to room temperature in vacuum. The porous media approach was applied to an insulated substrate with one inch foam and compared to a simple elastic solution without pore pressure. The porous media approach is also applied to model the foam mechanical behavior during subscale laboratory experiments. In this test, a foam layer sprayed on a metal substrate is subjected to a temperature variation while the metal substrate is stretched to simulate the structural response of the tank during operation. The thermal expansion mismatch between the foam and the metal substrate and the thermal gradient in the foam layer causes high tensile stresses near the metal/foam interface that can lead to delamination.

A Magnetohydrodynamic Modeling of the Interchange Cycle for Oblique Northward Interplanetary Magnetic Field

NASA Astrophysics Data System (ADS)

Watanabe, Masakazu; Fujita, Shigeru; Tanaka, Takashi; Kubota, Yasubumi; Shinagawa, Hiroyuki; Murata, Ken T.

2018-01-01

We perform numerical modeling of the interchange cycle in the magnetosphere-ionosphere convection system for oblique northward interplanetary magnetic field (IMF). The interchange cycle results from the coupling of IMF-to-lobe reconnection and lobe-to-closed reconnection. Using a global magnetohydrodynamic simulation code, for an IMF clock angle of 20° (measured from due north), we successfully reproduced the following features of the interchange cycle. (1) In the ionosphere, for each hemisphere, there appears a reverse cell circulating exclusively in the closed field line region (the reciprocal cell). (2) The topology transition of the magnetic field along a streamline near the equatorial plane precisely represents the magnetic flux reciprocation during the interchange cycle. (3) Field-aligned electric fields on the interplanetary-open separatrix and on the open-closed separatrix are those that are consistent with IMF-to-lobe reconnection and lobe-to-closed reconnection, respectively. These three features prove the existence of the interchange cycle in the simulated magnetosphere-ionosphere system. We conclude that the interchange cycle does exist in the real solar wind-magnetosphere-ionosphere system. In addition, the simulation revealed that the reciprocal cell described above is not a direct projection of the diffusion region as predicted by the "vacuum" model in which diffusion is added a priori to the vacuum magnetic topology. Instead, the reciprocal cell is a consequence of the plasma convection system coupled to the so-called NBZ ("northward Bz") field-aligned current system.

A model to determine open or closed cellular convection

NASA Technical Reports Server (NTRS)

Helfand, H. M.; Kalnay, E.

1981-01-01

A simple mechanism is proposed to explain the observed presence in the atmosphere of open or closed cellular convection. If convection is produced by cooling concentrated near the top of the cloud layer, as in radiative cooling of stratus clouds, it develops strong descending currents which are compensated by weak ascent over most of the horizontal area, and closed cells result. Conversely, heating concentrated near the bottom of a layer, as when an air mass is heated by warm water, results in strong ascending currents compensated by weak descent over most of the area, or open cells. This mechanism is similar to the one suggested by Stommel (1962) to explain the smallness of the oceans' sinking regions. The mechanism is studied numerically by means of a two-dimensional, nonlinear Boussinesq model.

Kinetic model of continuous ethanol fermentation in closed-circulating process with pervaporation membrane bioreactor by Saccharomyces cerevisiae.

PubMed

Fan, Senqing; Chen, Shiping; Tang, Xiaoyu; Xiao, Zeyi; Deng, Qing; Yao, Peina; Sun, Zhaopeng; Zhang, Yan; Chen, Chunyan

2015-02-01

Unstructured kinetic models were proposed to describe the principal kinetics involved in ethanol fermentation in a continuous and closed-circulating fermentation (CCCF) process with a pervaporation membrane bioreactor. After ethanol was removed in situ from the broth by the membrane pervaporation, the secondary metabolites accumulated in the broth became the inhibitors to cell growth. The cell death rate related to the deterioration of the culture environment was described as a function of the cell concentration and fermentation time. In CCCF process, 609.8 g L(-1) and 750.1 g L(-1) of ethanol production were obtained in the first run and second run, respectively. The modified Gompertz model, correlating the ethanol production with the fermentation period, could be used to describe the ethanol production during CCCF process. The fitting results by the models showed good agreement with the experimental data. These models could be employed for the CCCF process technology development for ethanol fermentation. Copyright © 2014 Elsevier Ltd. All rights reserved.

Animal Model of Fatal Human Monocytotropic Ehrlichiosis

PubMed Central

Sotomayor, Edgar A.; Popov, Vsevolod L.; Feng, Hui-Min; Walker, David H.; Olano, Juan P.

2001-01-01

Human monocytotropic ehrlichiosis caused by Ehrlichia chaffeensis is a life-threatening, tick-borne, emerging infectious disease for which no satisfactory animal model has been developed. Strain HF565, an ehrlichial organism closely related to E. chaffeensis isolated from Ixodes ovatus ticks in Japan, causes fatal infection of mice. C57BL/6 mice became ill on day 7 after inoculation and died on day 9. The liver revealed confluent necrosis, ballooning cell injury, apoptosis, poorly formed granulomas, Kupffer cell hyperplasia, erythrophagocytosis, and microvesicular fatty metamorphosis. The other significant histological findings consisted of marked expansion of the marginal zone and infiltration of the red pulp of the spleen by macrophages, interstitial pneumonitis, and increased numbers of immature myeloid cells and areas of necrosis in the bone marrow. Ehrlichiae were detected by immunohistology and electron microscopy in the liver, lungs, and spleen. The main target cells were macrophages, including Kupffer cells, hepatocytes, and endothelial cells. Apoptosis was detected in Kupffer cells, hepatocytes, and macrophages in the lungs and spleen. This tropism for macrophages and the pathological lesions closely resemble those of human monocytotropic ehrlichiosis for which it is a promising model for investigation of immunity and pathogenesis. PMID:11159213

Authentication of Primordial Characteristics of the CLBL-1 Cell Line Prove the Integrity of a Canine B-Cell Lymphoma in a Murine In Vivo Model

PubMed Central

Reimann-Berg, Nicola; Walter, Ingrid; Fuchs-Baumgartinger, Andrea; Wagner, Siegfried; Kovacic, Boris; Essler, Sabine E.; Schwendenwein, Ilse; Nolte, Ingo; Saalmüller, Armin; Escobar, Hugo Murua

2012-01-01

Cell lines are key tools in cancer research allowing the generation of neoplasias in animal models resembling the initial tumours able to mimic the original neoplasias closely in vivo. Canine lymphoma is the major hematopoietic malignancy in dogs and considered as a valuable spontaneous large animal model for human Non-Hodgkin's Lymphoma (NHL). Herein we describe the establishment and characterisation of an in vivo model using the canine B-cell lymphoma cell line CLBL-1 analysing the stability of the induced tumours and the ability to resemble the original material. CLBL-1 was injected into Rag2−/−γc −/− mice. The generated tumor material was analysed by immunophenotyping and histopathology and used to establish the cell line CLBL-1M. Both cell lines were karyotyped for detection of chromosomal aberrations. Additionally, CLBL-1 was stimulated with IL-2 and DSP30 as described for primary canine B-cell lymphomas and NHL to examine the stimulatory effect on cell proliferation. CLBL-1 in vivo application resulted in lymphoma-like disease and tumor formation. Immunophenotypic analysis of tumorous material showed expression of CD45+, MHCII+, CD11a+ and CD79αcy+. PARR analysis showed positivity for IgH indicating a monoclonal character. These cytogenetic, molecular, immunophenotypical and histological characterisations of the in vivo model reveal that the induced tumours and thereof generated cell line resemble closely the original material. After DSP30 and IL-2 stimulation, CLBL-1 showed to respond in the same way as primary material. The herein described CLBL-1 in vivo model provides a highly stable tool for B-cell lymphoma research in veterinary and human medicine allowing various further in vivo studies. PMID:22761949

Authentication of primordial characteristics of the CLBL-1 cell line prove the integrity of a canine B-cell lymphoma in a murine in vivo model.

PubMed

Rütgen, Barbara C; Willenbrock, Saskia; Reimann-Berg, Nicola; Walter, Ingrid; Fuchs-Baumgartinger, Andrea; Wagner, Siegfried; Kovacic, Boris; Essler, Sabine E; Schwendenwein, Ilse; Nolte, Ingo; Saalmüller, Armin; Murua Escobar, Hugo

2012-01-01

Cell lines are key tools in cancer research allowing the generation of neoplasias in animal models resembling the initial tumours able to mimic the original neoplasias closely in vivo. Canine lymphoma is the major hematopoietic malignancy in dogs and considered as a valuable spontaneous large animal model for human Non-Hodgkin's Lymphoma (NHL). Herein we describe the establishment and characterisation of an in vivo model using the canine B-cell lymphoma cell line CLBL-1 analysing the stability of the induced tumours and the ability to resemble the original material. CLBL-1 was injected into Rag2(-/-)γ(c) (-/-) mice. The generated tumor material was analysed by immunophenotyping and histopathology and used to establish the cell line CLBL-1M. Both cell lines were karyotyped for detection of chromosomal aberrations. Additionally, CLBL-1 was stimulated with IL-2 and DSP30 as described for primary canine B-cell lymphomas and NHL to examine the stimulatory effect on cell proliferation. CLBL-1 in vivo application resulted in lymphoma-like disease and tumor formation. Immunophenotypic analysis of tumorous material showed expression of CD45(+), MHCII(+), CD11a(+) and CD79αcy(+). PARR analysis showed positivity for IgH indicating a monoclonal character. These cytogenetic, molecular, immunophenotypical and histological characterisations of the in vivo model reveal that the induced tumours and thereof generated cell line resemble closely the original material. After DSP30 and IL-2 stimulation, CLBL-1 showed to respond in the same way as primary material. The herein described CLBL-1 in vivo model provides a highly stable tool for B-cell lymphoma research in veterinary and human medicine allowing various further in vivo studies.

Closed-Loop Control and Advisory Mode Evaluation of an Artificial Pancreatic β Cell: Use of Proportional–Integral–Derivative Equivalent Model-Based Controllers

PubMed Central

Percival, Matthew W.; Zisser, Howard; Jovanovič, Lois; Doyle, Francis J.

2008-01-01

Background Using currently available technology, it is possible to apply modern control theory to produce a closed-loop artificial β cell. Novel use of established control techniques would improve glycemic control, thereby reducing the complications of diabetes. Two popular controller structures, proportional–integral–derivative (PID) and model predictive control (MPC), are compared first in a theoretical sense and then in two applications. Methods The Bergman model is transformed for use in a PID equivalent model-based controller. The internal model control (IMC) structure, which makes explicit use of the model, is compared with the PID controller structure in the transfer function domain. An MPC controller is then developed as an optimization problem with restrictions on its tuning parameters and is shown to be equivalent to an IMC controller. The controllers are tuned for equivalent performance and evaluated in a simulation study as a closed-loop controller and in an advisory mode scenario on retrospective clinical data. Results Theoretical development shows conditions under which PID and MPC controllers produce equivalent output via IMC. The simulation study showed that the single tuning parameter for the equivalent controllers relates directly to the closed-loop speed of response and robustness, an important result considering system uncertainty. The risk metric allowed easy identification of instances of inadequate control. Results of the advisory mode simulation showed that suitable tuning produces consistently appropriate delivery recommendations. Conclusion The conditions under which PID and MPC are equivalent have been derived. The MPC framework is more suitable given the extensions necessary for a fully closed-loop artificial β cell, such as consideration of controller constraints. Formulation of the control problem in risk space is attractive, as it explicitly addresses the asymmetry of the problem; this is done easily with MPC. PMID:19885240

Design and Optimization of Copper Indium Gallium Selenide Thin Film Solar Cells

DTIC Science & Technology

2015-09-01

determined by the intensity of the illumination that the solar cell is exposed to. The diffusion lengths L can be further defined by n n nL D τ...absorbers with graded Ga concentrations. (3) Back Contact Model Models for back contact silicon solar cells have been created with results that closely...Radiation. New York, NY: Academic Press, 2012. [12] B. Richards, “Enhancing the performance of silicon solar cells via the application of passive

Geometric modeling of Plateau borders using the orthographic projection method for closed cell rigid polyurethane foam thermal conductivity prediction

NASA Astrophysics Data System (ADS)

Xu, Jie; Wu, Tao; Peng, Chuang; Adegbite, Stephen

2017-09-01

The geometric Plateau border model for closed cell polyurethane foam was developed based on volume integrations of approximated 3D four-cusp hypocycloid structure. The tetrahedral structure of convex struts was orthogonally projected into 2D three-cusp deltoid with three central cylinders. The idealized single unit strut was modeled by superposition. The volume of each component was calculated by geometric analyses. The strut solid fraction f s and foam porosity coefficient δ were calculated based on representative elementary volume of Kelvin and Weaire-Phelan structures. The specific surface area Sv derived respectively from packing structures and deltoid approximation model were put into contrast against strut dimensional ratio ɛ. The characteristic foam parameters obtained from this semi-empirical model were further employed to predict foam thermal conductivity.

Mechanism of Tacrine Block at Adult Human Muscle Nicotinic Acetylcholine Receptors

PubMed Central

Prince, Richard J.; Pennington, Richard A.; Sine, Steven M.

2002-01-01

We used single-channel kinetic analysis to study the inhibitory effects of tacrine on human adult nicotinic receptors (nAChRs) transiently expressed in HEK 293 cells. Single channel recording from cell-attached patches revealed concentration- and voltage-dependent decreases in mean channel open probability produced by tacrine (IC50 4.6 μM at −70 mV, 1.6 μM at −150 mV). Two main effects of tacrine were apparent in the open- and closed-time distributions. First, the mean channel open time decreased with increasing tacrine concentration in a voltage-dependent manner, strongly suggesting that tacrine acts as an open-channel blocker. Second, tacrine produced a new class of closings whose duration increased with increasing tacrine concentration. Concentration dependence of closed-times is not predicted by sequential models of channel block, suggesting that tacrine blocks the nAChR by an unusual mechanism. To probe tacrine's mechanism of action we fitted a series of kinetic models to our data using maximum likelihood techniques. Models incorporating two tacrine binding sites in the open receptor channel gave dramatically improved fits to our data compared with the classic sequential model, which contains one site. Improved fits relative to the sequential model were also obtained with schemes incorporating a binding site in the closed channel, but only if it is assumed that the channel cannot gate with tacrine bound. Overall, the best description of our data was obtained with a model that combined two binding sites in the open channel with a single site in the closed state of the receptor. PMID:12198092

High-efficiency AlGaAs-GaAs Cassegrainian concentrator cells

NASA Technical Reports Server (NTRS)

Werthen, J. G.; Hamaker, H. C.; Virshup, G. F.; Lewis, C. R.; Ford, C. W.

1985-01-01

AlGaAs-GaAs heteroface space concentrator solar cells have been fabricated by metalorganic chemical vapor deposition. AMO efficiencies as high as 21.1% have been observed both for p-n and np structures under concentration (90 to 100X) at 25 C. Both cell structures are characterized by high quantum efficiencies and their performances are close to those predicted by a realistic computer model. In agreement with the computer model, the n-p cell exhibits a higher short-circuit current density.

Distribution of serotonergic and dopaminergic nerve fibers in the salivary gland complex of the cockroach Periplaneta americana

PubMed Central

Baumann, Otto; Dames, Petra; Kühnel, Dana; Walz, Bernd

2002-01-01

Background The cockroach salivary gland consists of secretory acini with peripheral ion-transporting cells and central protein-producing cells, an extensive duct system, and a pair of reservoirs. Salivation is controled by serotonergic and dopaminergic innervation. Serotonin stimulates the secretion of a protein-rich saliva, dopamine causes the production of a saliva without proteins. These findings suggest a model in which serotonin acts on the central cells and possibly other cell types, and dopamine acts selectively on the ion-transporting cells. To examine this model, we have analyzed the spatial relationship of dopaminergic and serotonergic nerve fibers to the various cell types. Results The acinar tissue is entangled in a meshwork of serotonergic and dopaminergic varicose fibers. Dopaminergic fibers reside only at the surface of the acini next to the peripheral cells. Serotonergic fibers invade the acini and form a dense network between central cells. Salivary duct segments close to the acini are locally associated with dopaminergic and serotonergic fibers, whereas duct segments further downstream have only dopaminergic fibers on their surface and within the epithelium. In addition, the reservoirs have both a dopaminergic and a serotonergic innervation. Conclusion Our results suggest that dopamine is released on the acinar surface, close to peripheral cells, and along the entire duct system. Serotonin is probably released close to peripheral and central cells, and at initial segments of the duct system. Moreover, the presence of serotonergic and dopaminergic fiber terminals on the reservoir indicates that the functions of this structure are also regulated by dopamine and serotonin. PMID:12095424

Distribution of serotonergic and dopaminergic nerve fibers in the salivary gland complex of the cockroach Periplaneta americana.

PubMed

Baumann, Otto; Dames, Petra; Kühnel, Dana; Walz, Bernd

2002-06-24

The cockroach salivary gland consists of secretory acini with peripheral ion-transporting cells and central protein-producing cells, an extensive duct system, and a pair of reservoirs. Salivation is controlled by serotonergic and dopaminergic innervation. Serotonin stimulates the secretion of a protein-rich saliva, dopamine causes the production of a saliva without proteins. These findings suggest a model in which serotonin acts on the central cells and possibly other cell types, and dopamine acts selectively on the ion-transporting cells. To examine this model, we have analyzed the spatial relationship of dopaminergic and serotonergic nerve fibers to the various cell types. The acinar tissue is entangled in a meshwork of serotonergic and dopaminergic varicose fibers. Dopaminergic fibers reside only at the surface of the acini next to the peripheral cells. Serotonergic fibers invade the acini and form a dense network between central cells. Salivary duct segments close to the acini are locally associated with dopaminergic and serotonergic fibers, whereas duct segments further downstream have only dopaminergic fibers on their surface and within the epithelium. In addition, the reservoirs have both a dopaminergic and a serotonergic innervation. Our results suggest that dopamine is released on the acinar surface, close to peripheral cells, and along the entire duct system. Serotonin is probably released close to peripheral and central cells, and at initial segments of the duct system. Moreover, the presence of serotonergic and dopaminergic fiber terminals on the reservoir indicates that the functions of this structure are also regulated by dopamine and serotonin.

Testing the Role of p21-Activated Kinases in Schwannoma Formation Using a Novel Genetically Engineered Murine Model that Closely Phenocopies Human NF2 Disease

DTIC Science & Technology

2015-06-01

preclinical models of NF1? Can whole kinome analysis predict pathways for drug resistance in treated mice? Procuring Contracting/Grants Officer: Emily...cells. b) Evaluate transduction of hydroxyethyl starch (HES)-processed hematopoietic cells. c) Monitor gene transfer in primary FANCC-/- progenitors

Myogenic progenitors contribute to open but not closed fracture repair.

PubMed

Liu, Renjing; Birke, Oliver; Morse, Alyson; Peacock, Lauren; Mikulec, Kathy; Little, David G; Schindeler, Aaron

2011-12-22

Bone repair is dependent on the presence of osteocompetent progenitors that are able to differentiate and generate new bone. Muscle is found in close association with orthopaedic injury, however its capacity to make a cellular contribution to bone repair remains ambiguous. We hypothesized that myogenic cells of the MyoD-lineage are able to contribute to bone repair. We employed a MyoD-Cre+:Z/AP+ conditional reporter mouse in which all cells of the MyoD-lineage are permanently labeled with a human alkaline phosphatase (hAP) reporter. We tracked the contribution of MyoD-lineage cells in mouse models of tibial bone healing. In the absence of musculoskeletal trauma, MyoD-expressing cells are limited to skeletal muscle and the presence of reporter-positive cells in non-muscle tissues is negligible. In a closed tibial fracture model, there was no significant contribution of hAP+ cells to the healing callus. In contrast, open tibial fractures featuring periosteal stripping and muscle fenestration had up to 50% of hAP+ cells detected in the open fracture callus. At early stages of repair, many hAP+ cells exhibited a chondrocyte morphology, with lesser numbers of osteoblast-like hAP+ cells present at the later stages. Serial sections stained for hAP and type II and type I collagen showed that MyoD-lineage cells were surrounded by cartilaginous or bony matrix, suggestive of a functional role in the repair process. To exclude the prospect that osteoprogenitors spontaneously express MyoD during bone repair, we created a metaphyseal drill hole defect in the tibia. No hAP+ staining was observed in this model suggesting that the expression of MyoD is not a normal event for endogenous osteoprogenitors. These data document for the first time that muscle cells can play a significant secondary role in bone repair and this knowledge may lead to important translational applications in orthopaedic surgery. Please see related article: http://www.biomedcentral.com/1741-7015/9/136.

Thermal Expansion of Polyurethane Foam

NASA Technical Reports Server (NTRS)

Lerch, Bradley A.; Sullivan, Roy M.

2006-01-01

Closed cell foams are often used for thermal insulation. In the case of the Space Shuttle, the External Tank uses several thermal protection systems to maintain the temperature of the cryogenic fuels. A few of these systems are polyurethane, closed cell foams. In an attempt to better understand the foam behavior on the tank, we are in the process of developing and improving thermal-mechanical models for the foams. These models will start at the microstructural level and progress to the overall structural behavior of the foams on the tank. One of the key properties for model characterization and verification is thermal expansion. Since the foam is not a material, but a structure, the modeling of the expansion is complex. It is also exacerbated by the anisoptropy of the material. During the spraying and foaming process, the cells become elongated in the rise direction and this imparts different properties in the rise direction than in the transverse directions. Our approach is to treat the foam as a two part structure consisting of the polymeric cell structure and the gas inside the cells. The polymeric skeleton has a thermal expansion of its own which is derived from the basic polymer chemistry. However, a major contributor to the thermal expansion is the volume change associated with the gas inside of the closed cells. As this gas expands it exerts pressure on the cell walls and changes the shape and size of the cells. The amount that this occurs depends on the elastic and viscoplastic properties of the polymer skeleton. The more compliant the polymeric skeleton, the more influence the gas pressure has on the expansion. An additional influence on the expansion process is that the polymeric skeleton begins to breakdown at elevated temperatures and releases additional gas species into the cell interiors, adding to the gas pressure. The fact that this is such a complex process makes thermal expansion ideal for testing the models. This report focuses on the thermal expansion tests and the response of the microstructure. A novel optical method is described which is appropriate for measuring thermal expansion at high temperatures without influencing the thermal expansion measurement. Detailed microstructural investigations will also be described which show cell expansion as a function of temperature. Finally, a phenomenological model on thermal expansion will be described.

Simple equations to simulate closed-loop recycling liquid-liquid chromatography: Ideal and non-ideal recycling models.

PubMed

Kostanyan, Artak E

2015-12-04

The ideal (the column outlet is directly connected to the column inlet) and non-ideal (includes the effects of extra-column dispersion) recycling equilibrium-cell models are used to simulate closed-loop recycling counter-current chromatography (CLR CCC). Simple chromatogram equations for the individual cycles and equations describing the transport and broadening of single peaks and complex chromatograms inside the recycling closed-loop column for ideal and non-ideal recycling models are presented. The extra-column dispersion is included in the theoretical analysis, by replacing the recycling system (connecting lines, pump and valving) by a cascade of Nec perfectly mixed cells. To evaluate extra-column contribution to band broadening, two limiting regimes of recycling are analyzed: plug-flow, Nec→∞, and maximum extra-column dispersion, Nec=1. Comparative analysis of ideal and non-ideal models has shown that when the volume of the recycling system is less than one percent of the column volume, the influence of the extra-column processes on the CLR CCC separation may be neglected. Copyright © 2015 Elsevier B.V. All rights reserved.

Architecture of GnRH-Gonadotrope-Vasculature Reveals a Dual Mode of Gonadotropin Regulation in Fish.

PubMed

Golan, Matan; Zelinger, Einat; Zohar, Yonathan; Levavi-Sivan, Berta

2015-11-01

The function and components of the hypothalamic-pituitary axis are conserved among vertebrates; however, in fish, a neuroglandular mode of delivery (direct contact between axons and endocrine cells) was considered dominant, whereas in tetrapods hypothalamic signals are relayed to their targets via the hypophysial portal blood system (neurovascular delivery mode). By using a transgenic zebrafish model we studied the functional and anatomical aspects of gonadotrope regulation thus revisiting the existing model. FSH cells were found to be situated close to the vasculature whereas the compact organization of LH cells prevented direct contact of all cells with the circulation. GnRH3 fibers formed multiple boutons upon reaching the pituitary, but most of these structures were located in the neurohypophysis rather than adjacent to gonadotropes. A close association was observed between FSH cells and GnRH3 boutons, but only a fifth of the LH cells were in direct contact with GnRH3 axons, suggesting that FSH cells are more directly regulated than LH cells. GnRH3 fibers closely followed the vasculature in the neurohypophysis and formed numerous boutons along these tracts. These vessels were found to be permeable to relatively large molecules, suggesting the uptake of GnRH3 peptides. Our findings have important implications regarding the differential regulation of LH and FSH and contradict the accepted notion that fish pituitary cells are mostly regulated directly by hypothalamic fibers. Instead, we provide evidence that zebrafish apply a dual mode of gonadotrope regulation by GnRH3 that combines both neuroglandular and neurovascular components.

Computational analysis of the human sinus node action potential: model development and effects of mutations

PubMed Central

Fabbri, Alan; Fantini, Matteo; Wilders, Ronald

2017-01-01

Key points We constructed a comprehensive mathematical model of the spontaneous electrical activity of a human sinoatrial node (SAN) pacemaker cell, starting from the recent Severi–DiFrancesco model of rabbit SAN cells.Our model is based on electrophysiological data from isolated human SAN pacemaker cells and closely matches the action potentials and calcium transient that were recorded experimentally.Simulated ion channelopathies explain the clinically observed changes in heart rate in corresponding mutation carriers, providing an independent qualitative validation of the model.The model shows that the modulatory role of the ‘funny current’ (I f) in the pacing rate of human SAN pacemaker cells is highly similar to that of rabbit SAN cells, despite its considerably lower amplitude.The model may prove useful in the design of experiments and the development of heart‐rate modulating drugs. Abstract The sinoatrial node (SAN) is the normal pacemaker of the mammalian heart.  Over several decades, a large amount of data on the ionic mechanisms underlying the spontaneous electrical activity of SAN pacemaker cells has been obtained, mostly in experiments on single cells isolated from rabbit SAN. This wealth of data has allowed the development of mathematical models of the electrical activity of rabbit SAN pacemaker cells. The present study aimed to construct a comprehensive model of the electrical activity of a human SAN pacemaker cell using recently obtained electrophysiological data from human SAN pacemaker cells.  We based our model on the recent Severi–DiFrancesco model of a rabbit SAN pacemaker cell. The action potential and calcium transient of the resulting model are close to the experimentally recorded values. The model has a much smaller ‘funny current’ (I f) than do rabbit cells, although its modulatory role is highly similar. Changes in pacing rate upon the implementation of mutations associated with sinus node dysfunction agree with the clinical observations. This agreement holds for both loss‐of‐function and gain‐of‐function mutations in the HCN4, SCN5A and KCNQ1 genes, underlying ion channelopathies in I f, fast sodium current and slow delayed rectifier potassium current, respectively. We conclude that our human SAN cell model can be a useful tool in the design of experiments and the development of drugs that aim to modulate heart rate. PMID:28185290

The actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations

NASA Astrophysics Data System (ADS)

Westendorf, Christian; Negrete, Jose, Jr.; Bae, Albert; Sandmann, Rabea; Bodenschatz, Eberhard; Beta, Carsten

2013-03-01

We report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. The averaged F-actin response of many cells to a short-time pulse of cAMP is reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. We systematically exposed a large number of cells to periodic pulse trains. The results indicate a resonance peak at periodic inputs of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the actin regulatory network. To quantitatively test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and Aip1. These served as markers of the F-actin disassembly process and thus allow us to estimate the delay time. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed experimentally. Financial support by the Max-Planck Society and the DFG (SFB 937).

Xenobiotic-metabolizing enzymes in the skin of rat, mouse, pig, guinea pig, man, and in human skin models.

PubMed

Oesch, F; Fabian, E; Guth, K; Landsiedel, R

2014-12-01

The exposure of the skin to medical drugs, skin care products, cosmetics, and other chemicals renders information on xenobiotic-metabolizing enzymes (XME) in the skin highly interesting. Since the use of freshly excised human skin for experimental investigations meets with ethical and practical limitations, information on XME in models comes in the focus including non-human mammalian species and in vitro skin models. This review attempts to summarize the information available in the open scientific literature on XME in the skin of human, rat, mouse, guinea pig, and pig as well as human primary skin cells, human cell lines, and reconstructed human skin models. The most salient outcome is that much more research on cutaneous XME is needed for solid metabolism-dependent efficacy and safety predictions, and the cutaneous metabolism comparisons have to be viewed with caution. Keeping this fully in mind at least with respect to some cutaneous XME, some models may tentatively be considered to approximate reasonable closeness to human skin. For dermal absorption and for skin irritation among many contributing XME, esterase activity is of special importance, which in pig skin, some human cell lines, and reconstructed skin models appears reasonably close to human skin. With respect to genotoxicity and sensitization, activating XME are not yet judgeable, but reactive metabolite-reducing XME in primary human keratinocytes and several reconstructed human skin models appear reasonably close to human skin. For a more detailed delineation and discussion of the severe limitations see the "Overview and Conclusions" section in the end of this review.

Morphology of retinal ganglion cells in the ferret (Mustela putorius furo).

PubMed

Isayama, Tomoki; O'Brien, Brendan J; Ugalde, Irma; Muller, Jay F; Frenz, Aaron; Aurora, Vikas; Tsiaras, William; Berson, David M

2009-12-01

The ferret is the premiere mammalian model of retinal and visual system development, but the spectrum and properties of its retinal ganglion cells are less well understood than in another member of the Carnivora, the domestic cat. Here, we have extensively surveyed the dendritic architecture of ferret ganglion cells and report that the classification scheme previously developed for cat ganglion cells can be applied with few modifications to the ferret retina. We confirm the presence of alpha and beta cells in ferret retina, which are very similar to those in cat retina. Both cell types exhibited an increase in dendritic field size with distance from the area centralis (eccentricity) and with distance from the visual streak. Both alpha and beta cell populations existed as two subtypes whose dendrites stratified mainly in sublamina a or b of the inner plexiform layer. Six additional morphological types of ganglion cells were identified: four monostratified cell types (delta, epsilon, zeta, and eta) and two bistratified types (theta and iota). These types closely resembled their counterparts in the cat in terms of form, relative field size, and stratification. Our data indicate that, among carnivore species, the retinal ganglion cells resemble one another closely and that the ferret is a useful model for studies of the ontogenetic differentiation of ganglion cell types.

Rheological behavior of mammalian cells.

PubMed

Stamenović, D

2008-11-01

Rheological properties of living cells determine how cells interact with their mechanical microenvironment and influence their physiological functions. Numerous experimental studies have show that mechanical contractile stress borne by the cytoskeleton and weak power-law viscoelasticity are governing principles of cell rheology, and that the controlling physics is at the level of integrative cytoskeletal lattice properties. Based on these observations, two concepts have emerged as leading models of cytoskeletal mechanics. One is the tensegrity model, which explains the role of the contractile stress in cytoskeletal mechanics, and the other is the soft glass rheology model, which explains the weak power-law viscoelasticity of cells. While these two models are conceptually disparate, the phenomena that they describe are often closely associated in living cells for reasons that are largely unknown. In this review, we discuss current understanding of cell rheology by emphasizing the underlying biophysical mechanism and critically evaluating the existing rheological models.

Respiration in heterotrophic unicellular eukaryotic organisms.

PubMed

Fenchel, Tom

2014-08-01

Surface:volume quotient, mitochondrial volume fraction, and their distribution within cells were investigated and oxygen gradients within and outside cells were modelled. Cell surface increases allometrically with cell size. Mitochondrial volume fraction is invariant with cell size and constitutes about 10% and mitochondria are predominantly found close to the outer membrane. The results predict that for small and medium sized protozoa maximum respiration rates should be proportional to cell volume (scaling exponent ≈1) and access to intracellular O2 is not limiting except at very low ambient O2-tensions. Available data do not contradict this and some evidence supports this interpretation. Cell size is ultimately limited because an increasing fraction of the mitochondria becomes exposed to near anoxic conditions with increasing cell size. The fact that mitochondria cluster close to the cell surface and the allometric change in cell shape with increasing cell size alleviates the limitation of aerobic life at low ambient O2-tension and for large cell size. Copyright © 2014 Elsevier GmbH. All rights reserved.

Molecular conformation of the full-length tumor suppressor NF2/Merlin—a small angle neutron scattering study

PubMed Central

Khajeh, Jahan Ali; Ju, Jeong Ho; Atchiba, Moussoubaou; Allaire, Marc; Stanley, Christopher; Heller, William T.; Callaway, David J.E.; Bu, Zimei

2014-01-01

Summary The tumor suppressor protein Merlin inhibits cell proliferation upon establishing cell-cell contacts. Because Merlin has high sequence similarity to the Ezrin-Radixin-Moesin (ERM) family of proteins, the structural model of ERM protein autoinhibition and cycling between closed/resting and open/active conformational states is often employed to explain Merlin function. However, recent biochemical studies suggest alternative molecular models of Merlin function. Here, we have determined the low resolution molecular structure and binding activity of Merlin and a Merlin(S518D) mutant that mimics the inactivating phosphorylation at S518 using small angle neutron scattering (SANS) and binding experiments. SANS shows that in solution both Merlin and Merlin(S518D) adopt a closed conformation, but binding experiments indicate that a significant fraction of either Merlin or Merlin(S518D) is capable of binding to the target protein NHERF1. Upon binding to the phosphatidylinositol 4,5-bisphosphate lipid, the wild-type Merlin adopts a more open conformation than in solution, but Merlin(S518D) remains in a closed conformation. This study supports a rheostat model of Merlin in NHERF1 binding, and contributes to resolve a controversy about the molecular conformation and binding activity of Merlin. PMID:24882693

Incorporating photon recycling into the analytical drift-diffusion model of high efficiency solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lumb, Matthew P.; Naval Research Laboratory, Washington, DC 20375; Steiner, Myles A.

The analytical drift-diffusion formalism is able to accurately simulate a wide range of solar cell architectures and was recently extended to include those with back surface reflectors. However, as solar cells approach the limits of material quality, photon recycling effects become increasingly important in predicting the behavior of these cells. In particular, the minority carrier diffusion length is significantly affected by the photon recycling, with consequences for the solar cell performance. In this paper, we outline an approach to account for photon recycling in the analytical Hovel model and compare analytical model predictions to GaAs-based experimental devices operating close tomore » the fundamental efficiency limit.« less

Mathematical estimation of the level of microbial contamination on spacecraft surfaces by volumetric air sampling

NASA Technical Reports Server (NTRS)

Oxborrow, G. S.; Roark, A. L.; Fields, N. D.; Puleo, J. R.

1974-01-01

Microbiological sampling methods presently used for enumeration of microorganisms on spacecraft surfaces require contact with easily damaged components. Estimation of viable particles on surfaces using air sampling methods in conjunction with a mathematical model would be desirable. Parameters necessary for the mathematical model are the effect of angled surfaces on viable particle collection and the number of viable cells per viable particle. Deposition of viable particles on angled surfaces closely followed a cosine function, and the number of viable cells per viable particle was consistent with a Poisson distribution. Other parameters considered by the mathematical model included deposition rate and fractional removal per unit time. A close nonlinear correlation between volumetric air sampling and airborne fallout on surfaces was established with all fallout data points falling within the 95% confidence limits as determined by the mathematical model.

A grey box model of glucose fermentation and syntrophic oxidation in microbial fuel cells.

PubMed

de Los Ángeles Fernandez, Maria; de Los Ángeles Sanromán, Maria; Marks, Stanislaw; Makinia, Jacek; Gonzalez Del Campo, Araceli; Rodrigo, Manuel; Fernandez, Francisco Jesus

2016-01-01

In this work, the fermentative and oxidative processes taking place in a microbial fuel cell (MFC) fed with glucose were studied and modeled. The model accounting for the bioelectrochemical processes was based on ordinary, Monod-type differential equations. The model parameters were estimated using experimental results obtained from three H-type MFCs operated at open or closed circuits and fed with glucose or ethanol. The experimental results demonstrate that similar fermentation processes were carried out under open and closed circuit operation, with the most important fermentation products being ethanol (with a yield of 1.81molmol(-1) glucose) and lactic acid (with a yield of 1.36molmol(-1) glucose). A peak in the electricity generation was obtained when glucose and fermentation products coexisted in the liquid bulk. However, almost 90% of the electricity produced came from the oxidation of ethanol. Copyright © 2015 Elsevier Ltd. All rights reserved.

Numerical Field Model Simulation of Full Scale Fire Tests in a Closed Spherical/Cylindrical Vessel.

DTIC Science & Technology

1987-12-01

the behavior of an actual fire on board a ship. The computer model will be verified by the experimental data obtained in Fire-l. It is important to... behavior in simulations where convection is important. The upwind differencing scheme takes into account the unsymmetrical phenomenon of convection by using...TANK CELL ON THE NORTH SIDE) FOR A * * PARTICULAR FIRE CELL * * COSUMS (I,J) = THE ARRAY TO STORE THE SIMILIAR VALUE FOR THE FIRE * * CELL TO THE SOUTH

Dynamic Modeling, Model-Based Control, and Optimization of Solid Oxide Fuel Cells

NASA Astrophysics Data System (ADS)

Spivey, Benjamin James

2011-07-01

Solid oxide fuel cells are a promising option for distributed stationary power generation that offers efficiencies ranging from 50% in stand-alone applications to greater than 80% in cogeneration. To advance SOFC technology for widespread market penetration, the SOFC should demonstrate improved cell lifetime and load-following capability. This work seeks to improve lifetime through dynamic analysis of critical lifetime variables and advanced control algorithms that permit load-following while remaining in a safe operating zone based on stress analysis. Control algorithms typically have addressed SOFC lifetime operability objectives using unconstrained, single-input-single-output control algorithms that minimize thermal transients. Existing SOFC controls research has not considered maximum radial thermal gradients or limits on absolute temperatures in the SOFC. In particular, as stress analysis demonstrates, the minimum cell temperature is the primary thermal stress driver in tubular SOFCs. This dissertation presents a dynamic, quasi-two-dimensional model for a high-temperature tubular SOFC combined with ejector and prereformer models. The model captures dynamics of critical thermal stress drivers and is used as the physical plant for closed-loop control simulations. A constrained, MIMO model predictive control algorithm is developed and applied to control the SOFC. Closed-loop control simulation results demonstrate effective load-following, constraint satisfaction for critical lifetime variables, and disturbance rejection. Nonlinear programming is applied to find the optimal SOFC size and steady-state operating conditions to minimize total system costs.

Evaluating cell lines as tumour models by comparison of genomic profiles

PubMed Central

Domcke, Silvia; Sinha, Rileen; Levine, Douglas A.; Sander, Chris; Schultz, Nikolaus

2013-01-01

Cancer cell lines are frequently used as in vitro tumour models. Recent molecular profiles of hundreds of cell lines from The Cancer Cell Line Encyclopedia and thousands of tumour samples from the Cancer Genome Atlas now allow a systematic genomic comparison of cell lines and tumours. Here we analyse a panel of 47 ovarian cancer cell lines and identify those that have the highest genetic similarity to ovarian tumours. Our comparison of copy-number changes, mutations and mRNA expression profiles reveals pronounced differences in molecular profiles between commonly used ovarian cancer cell lines and high-grade serous ovarian cancer tumour samples. We identify several rarely used cell lines that more closely resemble cognate tumour profiles than commonly used cell lines, and we propose these lines as the most suitable models of ovarian cancer. Our results indicate that the gap between cell lines and tumours can be bridged by genomically informed choices of cell line models for all tumour types. PMID:23839242

Cloud regimes as phase transitions

NASA Astrophysics Data System (ADS)

Stechmann, Samuel; Hottovy, Scott

2017-11-01

Clouds are repeatedly identified as a leading source of uncertainty in future climate predictions. Of particular importance are stratocumulus clouds, which can appear as either (i) closed cells that reflect solar radiation back to space or (ii) open cells that allow solar radiation to reach the Earth's surface. Here we show that these clouds regimes - open versus closed cells - fit the paradigm of a phase transition. In addition, this paradigm characterizes pockets of open cells (POCs) as the interface between the open- and closed-cell regimes, and it identifies shallow cumulus clouds as a regime of higher variability. This behavior can be understood using an idealized model for the dynamics of atmospheric water as a stochastic diffusion process. Similar viewpoints of deep convection and self-organized criticality will also be discussed. With these new conceptual viewpoints, ideas from statistical mechanics could potentially be used for understanding uncertainties related to clouds in the climate system and climate predictions. The research of S.N.S. is partially supported by a Sloan Research Fellowship, ONR Young Investigator Award N00014-12-1-0744, and ONR MURI Grant N00014-12-1-0912.

Effect of Microstructural Parameters on the Relative Densities of Metal Foams

NASA Technical Reports Server (NTRS)

Raj, S. V.; Kerr, Jacob A.

2010-01-01

A detailed quantitative microstructural analyses of primarily open cell FeCrAlY and 314 stainless steel metal foams with different relative densities and pores per inch (p.p.i.) were undertaken in the present investigation to determine the effect of microstructural parameters on the relative densities of metal foams. Several elements of the microstructure, such as longitudinal and transverse cell sizes, cell areas and perimeters, ligament dimensions, cell shapes and volume fractions of closed and open cells, were measured. The cross-sections of the foam ligaments showed a large number of shrinkage cavities, and their circularity factors and average sizes were determined. The volume fractions of closed cells increased linearly with increasing relative density. In contrast, the volume fractions of the open cells and ligaments decreased with increasing relative density. The relative densities and p.p.i. were not significantly dependent on cell size, cell perimeter and ligament dimensions within the limits of experimental scatter. A phenomenological model is proposed to rationalize the present microstructural observations.

Mimicking Metastases Including Tumor Stroma: A New Technique to Generate a Three-Dimensional Colorectal Cancer Model Based on a Biological Decellularized Intestinal Scaffold.

PubMed

Nietzer, Sarah; Baur, Florentin; Sieber, Stefan; Hansmann, Jan; Schwarz, Thomas; Stoffer, Carolin; Häfner, Heide; Gasser, Martin; Waaga-Gasser, Ana Maria; Walles, Heike; Dandekar, Gudrun

2016-07-01

Tumor models based on cancer cell lines cultured two-dimensionally (2D) on plastic lack histological complexity and functionality compared to the native microenvironment. Xenogenic mouse tumor models display higher complexity but often do not predict human drug responses accurately due to species-specific differences. We present here a three-dimensional (3D) in vitro colon cancer model based on a biological scaffold derived from decellularized porcine jejunum (small intestine submucosa+mucosa, SISmuc). Two different cell lines were used in monoculture or in coculture with primary fibroblasts. After 14 days of culture, we demonstrated a close contact of human Caco2 colon cancer cells with the preserved basement membrane on an ultrastructural level as well as morphological characteristics of a well-differentiated epithelium. To generate a tissue-engineered tumor model, we chose human SW480 colon cancer cells, a reportedly malignant cell line. Malignant characteristics were confirmed in 2D cell culture: SW480 cells showed higher vimentin and lower E-cadherin expression than Caco2 cells. In contrast to Caco2, SW480 cells displayed cancerous characteristics such as delocalized E-cadherin and nuclear location of β-catenin in a subset of cells. One central drawback of 2D cultures-especially in consideration of drug testing-is their artificially high proliferation. In our 3D tissue-engineered tumor model, both cell lines showed decreased numbers of proliferating cells, thus correlating more precisely with observations of primary colon cancer in all stages (UICC I-IV). Moreover, vimentin decreased in SW480 colon cancer cells, indicating a mesenchymal to epithelial transition process, attributed to metastasis formation. Only SW480 cells cocultured with fibroblasts induced the formation of tumor-like aggregates surrounded by fibroblasts, whereas in Caco2 cocultures, a separate Caco2 cell layer was formed separated from the fibroblast compartment beneath. To foster tissue generation, a bioreactor was constructed for dynamic culture approaches. This induced a close tissue-like association of cultured tumor cells with fibroblasts reflecting tumor biopsies. Therapy with 5-fluorouracil (5-FU) was effective only in 3D coculture. In conclusion, our 3D tumor model reflects human tissue-related tumor characteristics, including lower tumor cell proliferation. It is now available for drug testing in metastatic context-especially for substances targeting tumor-stroma interactions.

Noisy Oscillations in the Actin Cytoskeleton of Chemotactic Amoeba.

PubMed

Negrete, Jose; Pumir, Alain; Hsu, Hsin-Fang; Westendorf, Christian; Tarantola, Marco; Beta, Carsten; Bodenschatz, Eberhard

2016-09-30

Biological systems with their complex biochemical networks are known to be intrinsically noisy. Here we investigate the dynamics of actin polymerization of amoeboid cells, which are close to the onset of oscillations. We show that the large phenotypic variability in the polymerization dynamics can be accurately captured by a generic nonlinear oscillator model in the presence of noise. We determine the relative role of the noise with a single dimensionless, experimentally accessible parameter, thus providing a quantitative description of the variability in a population of cells. Our approach, which rests on a generic description of a system close to a Hopf bifurcation and includes the effect of noise, can characterize the dynamics of a large class of noisy systems close to an oscillatory instability.

Noisy Oscillations in the Actin Cytoskeleton of Chemotactic Amoeba

NASA Astrophysics Data System (ADS)

Negrete, Jose; Pumir, Alain; Hsu, Hsin-Fang; Westendorf, Christian; Tarantola, Marco; Beta, Carsten; Bodenschatz, Eberhard

2016-09-01

Biological systems with their complex biochemical networks are known to be intrinsically noisy. Here we investigate the dynamics of actin polymerization of amoeboid cells, which are close to the onset of oscillations. We show that the large phenotypic variability in the polymerization dynamics can be accurately captured by a generic nonlinear oscillator model in the presence of noise. We determine the relative role of the noise with a single dimensionless, experimentally accessible parameter, thus providing a quantitative description of the variability in a population of cells. Our approach, which rests on a generic description of a system close to a Hopf bifurcation and includes the effect of noise, can characterize the dynamics of a large class of noisy systems close to an oscillatory instability.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Podoskin, A. A., E-mail: podoskin@mail.ioffe.ru; Shashkin, I. S.; Slipchenko, S. O.

A model describing the operation of a completely optical cell, based on the competition of lasing of Fabry-Perot cavity modes and the high-Q closed mode in high-power semiconductor lasers is proposed. Based on rate equations, the conditions of lasing switching between Fabry-Perot modes for ground and excited lasing levels and the closed mode are considered in the case of increasing internal optical loss under conditions of high current pump levels. The optical-cell operation conditions in the mode of a high-power laser radiation switch (reversible mode-structure switching) and in the mode of a memory cell with bistable irreversible lasing switching betweenmore » mode structures with various Q-factors are considered.« less

Genetically engineered mouse models in oncology research and cancer medicine.

PubMed

Kersten, Kelly; de Visser, Karin E; van Miltenburg, Martine H; Jonkers, Jos

2017-02-01

Genetically engineered mouse models (GEMMs) have contributed significantly to the field of cancer research. In contrast to cancer cell inoculation models, GEMMs develop de novo tumors in a natural immune-proficient microenvironment. Tumors arising in advanced GEMMs closely mimic the histopathological and molecular features of their human counterparts, display genetic heterogeneity, and are able to spontaneously progress toward metastatic disease. As such, GEMMs are generally superior to cancer cell inoculation models, which show no or limited heterogeneity and are often metastatic from the start. Given that GEMMs capture both tumor cell-intrinsic and cell-extrinsic factors that drive de novo tumor initiation and progression toward metastatic disease, these models are indispensable for preclinical research. GEMMs have successfully been used to validate candidate cancer genes and drug targets, assess therapy efficacy, dissect the impact of the tumor microenvironment, and evaluate mechanisms of drug resistance. In vivo validation of candidate cancer genes and therapeutic targets is further accelerated by recent advances in genetic engineering that enable fast-track generation and fine-tuning of GEMMs to more closely resemble human patients. In addition, aligning preclinical tumor intervention studies in advanced GEMMs with clinical studies in patients is expected to accelerate the development of novel therapeutic strategies and their translation into the clinic. © 2016 The Authors. Published under the terms of the CC BY 4.0 license.

Domain model for Ca2(+)-inactivation of Ca2+ channels at low channel density.

PubMed Central

Sherman, A; Keizer, J; Rinzel, J

1990-01-01

The "shell" model for Ca2(+)-inactivation of Ca2+ channels is based on the accumulation of Ca2+ in a macroscopic shell beneath the plasma membrane. The shell is filled by Ca2+ entering through open channels, with the elevated Ca2+ concentration inactivating both open and closed channels at a rate determined by how fast the shell is filled. In cells with low channel density, the high concentration Ca2+ "shell" degenerates into a collection of nonoverlapping "domains" localized near open channels. These domains form rapidly when channels open and disappear rapidly when channels close. We use this idea to develop a "domain" model for Ca2(+)-inactivation of Ca2+ channels. In this model the kinetics of formation of an inactivated state resulting from Ca2+ binding to open channels determines the inactivation rate, a mechanism identical with that which explains single-channel recordings on rabbit-mesenteric artery Ca2+ channels (Huang Y., J. M. Quayle, J. F. Worley, N. B. Standen, and M. T. Nelson. 1989. Biophys. J. 56:1023-1028). We show that the model correctly predicts five important features of the whole-cell Ca2(+)-inactivation for mouse pancreatic beta-cells (Plants, T. D. 1988. J. Physiol. 404:731-747) and that Ca2(+)-inactivation has only minor effects on the bursting electrical activity of these cells. PMID:2174274

Modeling and simulation of viscoelastic biological particles' 3D manipulation using atomic force microscopy

NASA Astrophysics Data System (ADS)

Korayem, M. H.; Habibi Sooha, Y.; Rastegar, Z.

2018-05-01

Manipulation of the biological particles by atomic force microscopy is used to transfer these particles inside body's cells, diagnosis and destruction of the cancer cells and drug delivery to damaged cells. According to the impossibility of simultaneous observation of this process, the importance of modeling and simulation can be realized. The contact of the tip with biological particle is important during manipulation, therefore, the first step of the modeling is choosing appropriate contact model. Most of the studies about contact between atomic force microscopy and biological particles, consider the biological particle as an elastic material. This is not an appropriate assumption because biological cells are basically soft and this assumption ignores loading history. In this paper, elastic and viscoelastic JKR theories were used in modeling and simulation of the 3D manipulation for three modes of tip-particle sliding, particle-substrate sliding and particle-substrate rolling. Results showed that critical force and time in motion modes (sliding and rolling) for two elastic and viscoelastic states are very close but these magnitudes were lower in the viscoelastic state. Then, three friction models, Coulomb, LuGre and HK, were used for tip-particle sliding mode in the first phase of manipulation to make results closer to reality. In both Coulomb and LuGre models, critical force and time are very close for elastic and viscoelastic states but in general critical force and time prediction of HK model was higher than LuGre and the LuGre model itself had higher prediction than Coulomb.

Models of non-Newtonian Hele-Shaw flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kondic, L.; Palffy-Muhoray, P.; Shelley, M.J.

1996-11-01

We study the Saffman-Taylor instability of a non-Newtonian fluid in a Hele-Shaw cell. Using a fluid model with shear-rate dependent viscosity, we derive a Darcy{close_quote}s law whose viscosity depends upon the squared pressure gradient. This yields a natural, nonlinear boundary value problem for the pressure. A model proposed recently by Bonn {ital et} {ital al}. [Phys. Rev. Lett. {bold 75}, 2132 (1995)] follows from this modified law. For a shear-thinning liquid, our derivation shows strong constraints upon the fluid viscosity{emdash} strong shear-thinning does not allow the construction of a unique Darcy{close_quote}s law, and is related to the appearance of slipmore » layers in the flow. For a weakly shear-thinning liquid, we calculate corrections to the Newtonian instability of an expanding bubble in a radial cell. {copyright} {ital 1996 The American Physical Society.}« less

Closed-cell crystalline foams: self-assembling, resonant metamaterials.

PubMed

Spadoni, Alessandro; Höhler, Reinhard; Cohen-Addad, Sylvie; Dorodnitsyn, Vladimir

2014-04-01

Internal degrees of freedom and periodic structure are critical requirements in the design of acoustic/elastic metamaterials since they can give rise to extraordinary properties like negative effective mass and stiffness. However, they are challenging to realize in three dimensions. Closed-cell, crystalline foams are a particularly advantageous basis to develop metamaterials as they intrinsically have a complex microstructure, exhibiting internal resonances. Recently self-assembly techniques have been implemented to produce such foams: a Kelvin (body centered cubic) foam, a face centered cubic foam, and a Weaire-Phelan structure. Numerical models are employed to demonstrate that such foams are superanisotropic, selectively behaving as a fluid or a solid, pentamode solids as a result of fluid-structure interaction, in addition to having regimes characterized by film resonances and high density of states. Microstructural deformations obtained from numerical models allow the derivation of equivalent mechanical models.

The functional role of xylem parenchyma cells and aquaporins during recovery from severe water stress.

PubMed

Secchi, Francesca; Pagliarani, Chiara; Zwieniecki, Maciej A

2017-06-01

Xylem parenchyma cells [vessel associated cells (VACs)] constitute a significant fraction of the xylem in woody plants. These cells are often closely connected with xylem vessels or tracheids via simple pores (remnants of plasmodesmata fields). The close contact and biological activity of VACs during times of severe water stress and recovery from stress suggest that they are involved in the maintenance of xylem transport capacity and responsible for the restoration of vessel/tracheid functionality following embolism events. As recovery from embolism requires the transport of water across xylem parenchyma cell membranes, an understanding of stem-specific aquaporin expression patterns, localization and activity is a crucial part of any biological model dealing with embolism recovery processes in woody plants. In this review, we provide a short overview of xylem parenchyma cell biology with a special focus on aquaporins. In particular we address their distributions and activity during the development of drought stress, during the formation of embolism and the subsequent recovery from stress that may result in refilling. Complemented by the current biological model of parenchyma cell function during recovery from stress, this overview highlights recent breakthroughs on the unique ability of long-lived perennial plants to undergo cycles of embolism-recovery related to drought/rewetting or freeze/thaw events. © 2016 John Wiley & Sons Ltd.

In vitro model for Campylobacter pylori adherence properties.

PubMed Central

Neman-Simha, V; Mégraud, F

1988-01-01

The adherence of 12 strains of Campylobacter pylori was studied on four cell lines. Immunofluorescence and scanning and transmission electron microscopy were used to visualize the bacteria. A heavy adherence to the epithelial cell line HEp-2 and to the intestinal cell line Int-407 was noted. By transmission electron microscopy, a close association between bacteria and cells in the form of cup-like structures was observed, but pedestals were not present. Images PMID:3182085

Design and test hardware for a solar array switching unit

NASA Technical Reports Server (NTRS)

Patil, A. R.; Cho, B. H.; Sable, D.; Lee, F. C.

1992-01-01

This paper describes the control of a pulse width modulated (PWM) type sequential shunt switching unit (SSU) for spacecraft applications. It is found that the solar cell output capacitance has a significant impact on SSU design. Shorting of this cell capacitance by the PWM switch causes input current surges. These surges are minimized by the use of a series filter inductor. The system with a filter is analyzed for ripple and the control to output-voltage transfer function. Stable closed loop design considerations are discussed. The results are supported by modeling and measurements of loop gain and of closed-loop bus impedance on test hardware for NASA's 120 V Earth Observation System (EOS). The analysis and modeling are also applicable to NASA's 160 V Space Station power system.

A hybrid mathematical model of solid tumour invasion: the importance of cell adhesion.

PubMed

Anderson, Alexander R A

2005-06-01

In this paper we present a hybrid mathematical model of the invasion of healthy tissue by a solid tumour. In particular we consider early vascular growth, just after angiogenesis has occurred. We examine how the geometry of the growing tumour is affected by tumour cell heterogeneity caused by genetic mutations. As the tumour grows, mutations occur leading to a heterogeneous tumour cell population with some cells having a greater ability to migrate, proliferate or degrade the surrounding tissue. All of these cell properties are closely controlled by cell-cell and cell-matrix interactions and as such the physical geometry of the whole tumour will be dependent on these individual cell interactions. The hybrid model we develop focuses on four key variables implicated in the invasion process: tumour cells, host tissue (extracellular matrix), matrix-degradative enzymes and oxygen. The model is considered to be hybrid since the latter three variables are continuous (i.e. concentrations) and the tumour cells are discrete (i.e. individuals). With this hybrid model we examine how individual-based cell interactions (with one another and the matrix) can affect the tumour shape and discuss which of these interactions is perhaps most crucial in influencing the tumour's final structure.

Diffused junction p(+)-n solar cells in bulk GaAs. II - Device characterization and modelling

NASA Technical Reports Server (NTRS)

Keeney, R.; Sundaram, L. M. G.; Rode, H.; Bhat, I.; Ghandhi, S. K.; Borrego, J. M.

1984-01-01

The photovoltaic characteristics of p(+)-n junction solar cells fabricated on bulk GaAs by an open tube diffusion technique are presented in detail. Quantum efficiency measurements were analyzed and compared to computer simulations of the cell structure in order to determine material parameters such as diffusion length, surface recombination velocity and junction depth. From the results obtained it is projected that proper optimization of the cell parameters can increase the efficiency of the cells to close to 20 percent.

Spatial Pattern of Cell Damage in Tissue from Heavy Ions

NASA Technical Reports Server (NTRS)

Ponomarev, Artem L.; Huff, Janice L.; Cucinotta, Francis A.

2007-01-01

A new Monte Carlo algorithm was developed that can model passage of heavy ions in a tissue, and their action on the cellular matrix for 2- or 3-dimensional cases. The build-up of secondaries such as projectile fragments, target fragments, other light fragments, and delta-rays was simulated. Cells were modeled as a cell culture monolayer in one example, where the data were taken directly from microscopy (2-d cell matrix). A simple model of tissue was given as abstract spheres with close approximation to real cell geometries (3-d cell matrix), as well as a realistic model of tissue was proposed based on microscopy images. Image segmentation was used to identify cells in an irradiated cell culture monolayer, or slices of tissue. The cells were then inserted into the model box pixel by pixel. In the case of cell monolayers (2-d), the image size may exceed the modeled box size. Such image was is moved with respect to the box in order to sample as many cells as possible. In the case of the simple tissue (3-d), the tissue box is modeled with periodic boundary conditions, which extrapolate the technique to macroscopic volumes of tissue. For real tissue, specific spatial patterns for cell apoptosis and necrosis are expected. The cell patterns were modeled based on action cross sections for apoptosis and necrosis estimated based on BNL data, and other experimental data.

Gene Expression Profiles of Human Dendritic Cells Interacting with Aspergillus fumigatus in a Bilayer Model of the Alveolar Epithelium/Endothelium Interface

PubMed Central

Morton, Charles Oliver; Fliesser, Mirjam; Dittrich, Marcus; Mueller, Tobias; Bauer, Ruth; Kneitz, Susanne; Hope, William; Rogers, Thomas Richard; Einsele, Hermann; Loeffler, Juergen

2014-01-01

The initial stages of the interaction between the host and Aspergillus fumigatus at the alveolar surface of the human lung are critical in the establishment of aspergillosis. Using an in vitro bilayer model of the alveolus, including both the epithelium (human lung adenocarcinoma epithelial cell line, A549) and endothelium (human pulmonary artery epithelial cells, HPAEC) on transwell membranes, it was possible to closely replicate the in vivo conditions. Two distinct sub-groups of dendritic cells (DC), monocyte-derived DC (moDC) and myeloid DC (mDC), were included in the model to examine immune responses to fungal infection at the alveolar surface. RNA in high quantity and quality was extracted from the cell layers on the transwell membrane to allow gene expression analysis using tailored custom-made microarrays, containing probes for 117 immune-relevant genes. This microarray data indicated minimal induction of immune gene expression in A549 alveolar epithelial cells in response to germ tubes of A. fumigatus. In contrast, the addition of DC to the system greatly increased the number of differentially expressed immune genes. moDC exhibited increased expression of genes including CLEC7A, CD209 and CCL18 in the absence of A. fumigatus compared to mDC. In the presence of A. fumigatus, both DC subgroups exhibited up-regulation of genes identified in previous studies as being associated with the exposure of DC to A. fumigatus and exhibiting chemotactic properties for neutrophils, including CXCL2, CXCL5, CCL20, and IL1B. This model closely approximated the human alveolus allowing for an analysis of the host pathogen interface that complements existing animal models of IA. PMID:24870357

Targeted gene knockin in porcine somatic cells using CRISPR/Cas ribonucleoproteins

USDA-ARS?s Scientific Manuscript database

The domestic pig is an ideal large animal model for genetic engineering applications. A relatively short gestation interval and large litter size makes the pig a conducive model for generating and propagating genetic modifications. The domestic pig also shares close similarity in anatomy, physiolo...

Architecture and inherent robustness of a bacterial cell-cycle control system.

PubMed

Shen, Xiling; Collier, Justine; Dill, David; Shapiro, Lucy; Horowitz, Mark; McAdams, Harley H

2008-08-12

A closed-loop control system drives progression of the coupled stalked and swarmer cell cycles of the bacterium Caulobacter crescentus in a near-mechanical step-like fashion. The cell-cycle control has a cyclical genetic circuit composed of four regulatory proteins with tight coupling to processive chromosome replication and cell division subsystems. We report a hybrid simulation of the coupled cell-cycle control system, including asymmetric cell division and responses to external starvation signals, that replicates mRNA and protein concentration patterns and is consistent with observed mutant phenotypes. An asynchronous sequential digital circuit model equivalent to the validated simulation model was created. Formal model-checking analysis of the digital circuit showed that the cell-cycle control is robust to intrinsic stochastic variations in reaction rates and nutrient supply, and that it reliably stops and restarts to accommodate nutrient starvation. Model checking also showed that mechanisms involving methylation-state changes in regulatory promoter regions during DNA replication increase the robustness of the cell-cycle control. The hybrid cell-cycle simulation implementation is inherently extensible and provides a promising approach for development of whole-cell behavioral models that can replicate the observed functionality of the cell and its responses to changing environmental conditions.

Dysregulated hepatic bile acids collaboratively promote liver carcinogenesis

PubMed Central

Xie, Guoxiang; Wang, Xiaoning; Huang, Fengjie; Zhao, Aihua; Chen, Wenlian; Yan, Jingyu; Zhang, Yunjing; Lei, Sha; Ge, Kun; Zheng, Xiaojiao; Liu, Jiajian; Su, Mingming; Liu, Ping; Jia, Wei

2017-01-01

Dysregulated bile acids (BAs) are closely associated with liver diseases and attributed to altered gut microbiota. Here, we show that the intrahepatic retention of hydrophobic BAs including deoxycholate (DCA), taurocholate (TCA), taurochenodeoxycholate (TCDCA), and taurolithocholate (TLCA) were substantially increased in a streptozotocin and high fat diet (HFD) induced nonalcoholic steatohepatitis-hepatocellular carcinoma (NASH-HCC) mouse model. Additionally chronic HFD-fed mice spontaneously developed liver tumors with significantly increased hepatic BA levels. Enhancing intestinal excretion of hydrophobic BAs in the NASH-HCC model mice by a 2% cholestyramine feeding significantly prevented HCC development. The gut microbiota alterations were closely correlated with altered BA levels in liver and feces. HFD-induced inflammation inhibited key BA transporters, resulting in sustained increases in intrahepatic BA concentrations. Our study also showed a significantly increased cell proliferation in BA treated normal human hepatic cell lines and a down-regulated expression of tumor suppressor gene CEBPα in TCDCA treated HepG2 cell line, suggesting that several hydrophobic BAs may collaboratively promote liver carcinogenesis. PMID:27273788

On the Interaction between Marine Boundary Layer Cellular Cloudiness and Surface Heat Fluxes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kazil, J.; Feingold, G.; Wang, Hailong

2014-01-02

The interaction between marine boundary layer cellular cloudiness and surface uxes of sensible and latent heat is investigated. The investigation focuses on the non-precipitating closed-cell state and the precipitating open-cell state at low geostrophic wind speed. The Advanced Research WRF model is used to conduct cloud-system-resolving simulations with interactive surface fluxes of sensible heat, latent heat, and of sea salt aerosol, and with a detailed representation of the interaction between aerosol particles and clouds. The mechanisms responsible for the temporal evolution and spatial distribution of the surface heat fluxes in the closed- and open-cell state are investigated and explained. Itmore » is found that the horizontal spatial structure of the closed-cell state determines, by entrainment of dry free tropospheric air, the spatial distribution of surface air temperature and water vapor, and, to a lesser degree, of the surface sensible and latent heat flux. The synchronized dynamics of the the open-cell state drives oscillations in surface air temperature, water vapor, and in the surface fluxes of sensible and latent heat, and of sea salt aerosol. Open-cell cloud formation, cloud optical depth and liquid water path, and cloud and rain water path are identified as good predictors of the spatial distribution of surface air temperature and sensible heat flux, but not of surface water vapor and latent heat flux. It is shown that by enhancing the surface sensible heat flux, the open-cell state creates conditions by which it is maintained. While the open-cell state under consideration is not depleted in aerosol, and is insensitive to variations in sea-salt fluxes, it also enhances the sea-salt flux relative to the closed-cell state. In aerosol-depleted conditions, this enhancement may replenish the aerosol needed for cloud formation, and hence contribute to the perpetuation of the open-cell state as well. Spatial homogenization of the surface fluxes is found to have only a small effect on cloud properties in the investigated cases. This indicates that sub-grid scale spatial variability in the surface flux of sensible and latent heat and of sea salt aerosol may not be required in large scale and global models to describe marine boundary layer cellular cloudiness.« less

In Vivo Imaging of Branched Chain Amino Acid Metabolism in Prostate Cancer

DTIC Science & Technology

2013-08-01

model more closely mimicking human metabolism by assessing four prostate cancer cell lines: PC-3, DU-145, LNCaP and LAPC-4. The PC-3 cells had...Although the xenograph BCAT activity was 2.5 fold higher than cells alone (approaching human levels), the tumors grew very poorly (volumes ≤ 0.2 cc...assessment of prostate cancer (see Appendix 1: Revised Statement of Work). Specifically, as part of these cell - culture and xenograph experiments we

Three-Dimensional Organotypic Co-Culture Model of Intestinal Epithelial Cells and Macrophages to Study "Salmonella Enterica" Colonization Patterns

NASA Technical Reports Server (NTRS)

Ott, Mark; Yang, J; Barilla, J.; Crabbe, A.; Sarker, S. F.; Liu, Y.

2017-01-01

Three-dimensional/3-D organotypic models of human intestinal epithelium mimic the differentiated form and function of parental tissues often not exhibited by 2-D monolayers and respond to Salmonella in ways that reflect in vivo infections. To further enhance the physiological relevance of 3-D models to more closely approximate in vivo intestinal microenvironments during infection, we developed and validated a novel 3-D intestinal co-culture model containing multiple epithelial cell types and phagocytic macrophages, and applied to study enteric infection by different Salmonella pathovars.

AlgiMatrix™-Based 3D Cell Culture System as an In Vitro Tumor Model: An Important Tool in Cancer Research.

PubMed

Godugu, Chandraiah; Singh, Mandip

2016-01-01

Routinely used two-dimensional cell culture-based models often fail while translating the observations into in vivo models. This setback is more common in cancer research, due to several reasons. The extracellular matrix and cell-to-cell interactions are not present in two-dimensional (2D) cell culture models. Diffusion of drug molecules into cancer cells is hindered by barriers of extracellular components in in vivo conditions, these barriers are absent in 2D cell culture models. To better mimic or simulate the in vivo conditions present in tumors, the current study used the alginate based three-dimensional cell culture (AlgiMatrix™) model, which resembles close to the in vivo tumor models. The current study explains the detailed protocols involved in AlgiMatrix™ based in vitro non-small-cell lung cancer (NSCLC) models. The suitability of this model was studied by evaluating, cytotoxicity, apoptosis, and penetration of nanoparticles into the in vitro tumor spheroids. This study also demonstrated the effect of EphA2 receptor targeted docetaxel-loaded nanoparticles on MDA-MB-468 TNBC cell lines. The methods section is subdivided into three subsections such as (1) preparation of AlgiMatrix™-based 3D in vitro tumor models and cytotoxicity assays, (2) free drug and nanoparticle uptake into spheroid studies, and (3) western blot, IHC, and RT-PCR studies.

Entropy, Ergodicity, and Stem Cell Multipotency

NASA Astrophysics Data System (ADS)

Ridden, Sonya J.; Chang, Hannah H.; Zygalakis, Konstantinos C.; MacArthur, Ben D.

2015-11-01

Populations of mammalian stem cells commonly exhibit considerable cell-cell variability. However, the functional role of this diversity is unclear. Here, we analyze expression fluctuations of the stem cell surface marker Sca1 in mouse hematopoietic progenitor cells using a simple stochastic model and find that the observed dynamics naturally lie close to a critical state, thereby producing a diverse population that is able to respond rapidly to environmental changes. We propose an information-theoretic interpretation of these results that views cellular multipotency as an instance of maximum entropy statistical inference.

Biological insights into the expression of translation initiation factors from recombinant CHOK1SV cell lines and their relationship to enhanced productivity.

PubMed

Mead, Emma J; Masterton, Rosalyn J; Feary, Marc; Obrezanova, Olga; Zhang, Lin; Young, Robert; Smales, C Mark

2015-12-15

Translation initiation is on the critical pathway for the production of monoclonal antibodies (mAbs) by mammalian cells. Formation of a closed loop structure comprised of mRNA, a number of eukaryotic initiation factors (eIFs) and ribosomal proteins has been proposed to aid re-initiation of translation and therefore increase global translational efficiency. We have determined mRNA and protein levels of the key components of the closed loop, eIFs (eIF3a, eIF3b, eIF3c, eIF3h, eIF3i and eIF4G1), poly(A)-binding protein (PABP) 1 and PABP-interacting protein 1 (PAIP1), across a panel of 30 recombinant mAb-producing GS-CHOK1SV cell lines with a broad range of growth characteristics and production levels of a model recombinant mAb. We have used a multi-level statistical approach to investigate the relationship between key performance indicators (cell growth and recombinant antibody productivity) and the intracellular amounts of target translation initiation factor proteins and the mRNAs encoding them. We show that high-producing cell lines maintain amounts of the translation initiation factors involved in the formation of the closed loop mRNA, maintaining these proteins at appropriate levels to deliver enhanced recombinant protein production. We then utilize knowledge of the amounts of these factors to build predictive models for and use cluster analysis to identify, high-producing cell lines. The present study therefore defines the translation initiation factor amounts that are associated with highly productive recombinant GS-CHOK1SV cell lines that may be targets for screening highly productive cell lines or to engineer new host cell lines with the potential for enhanced recombinant antibody productivity. © 2015 Authors; published by Portland Press Limited.

Voronoi Cell Patterns: theoretical model and application to submonolayer growth

NASA Astrophysics Data System (ADS)

González, Diego Luis; Einstein, T. L.

2012-02-01

We use a simple fragmentation model to describe the statistical behavior of the Voronoi cell patterns generated by a homogeneous and isotropic set of points in 1D and in 2D. In particular, we are interested in the distribution of sizes of these Voronoi cells. Our model is completely defined by two probability distributions in 1D and again in 2D, the probability to add a new point inside an existing cell and the probability that this new point is at a particular position relative to the preexisting point inside this cell. In 1D the first distribution depends on a single parameter while the second distribution is defined through a fragmentation kernel; in 2D both distributions depend on a single parameter. The fragmentation kernel and the control parameters are closely related to the physical properties of the specific system under study. We apply our model to describe the Voronoi cell patterns of island nucleation for critical island sizes i=0,1,2,3. Experimental results for the Voronoi cells of InAs/GaAs quantum dots are also described by our model.

Identifying mechanisms for superdiffusive dynamics in cell trajectories

NASA Astrophysics Data System (ADS)

Passucci, Giuseppe; Brasch, Megan; Henderson, James; Manning, M. Lisa

Self-propelled particle (SPP) models have been used to explore features of active matter such as motility-induced phase separation, jamming, and flocking, and are often used to model biological cells. However, many cells exhibit super-diffusive trajectories, where displacements scale faster than t 1 / 2 in all directions, and these are not captured by traditional SPP models. We extract cell trajectories from image stacks of mouse fibroblast cells moving on 2D substrates and find super-diffusive mean-squared displacements in all directions across varying densities. Two SPP model modifications have been proposed to capture super-diffusive dynamics: Levy walks and heterogeneous motility parameters. In mouse fibroblast cells displacement probability distributions collapse when time is rescaled by a power greater than 1/2, which is consistent with Levy walks. We show that a simple SPP model with heterogeneous rotational noise can also generate a similar collapse. Furthermore, a close examination of statistics extracted directly from cell trajectories is consistent with a heterogeneous mobility SPP model and inconsistent with a Levy walk model. Our work demonstrates that a simple set of analyses can distinguish between mechanisms for anomalous diffusion in active matter.

A systems biology approach to the analysis of subset-specific responses to lipopolysaccharide in dendritic cells.

PubMed

Hancock, David G; Shklovskaya, Elena; Guy, Thomas V; Falsafi, Reza; Fjell, Chris D; Ritchie, William; Hancock, Robert E W; Fazekas de St Groth, Barbara

2014-01-01

Dendritic cells (DCs) are critical for regulating CD4 and CD8 T cell immunity, controlling Th1, Th2, and Th17 commitment, generating inducible Tregs, and mediating tolerance. It is believed that distinct DC subsets have evolved to control these different immune outcomes. However, how DC subsets mount different responses to inflammatory and/or tolerogenic signals in order to accomplish their divergent functions remains unclear. Lipopolysaccharide (LPS) provides an excellent model for investigating responses in closely related splenic DC subsets, as all subsets express the LPS receptor TLR4 and respond to LPS in vitro. However, previous studies of the LPS-induced DC transcriptome have been performed only on mixed DC populations. Moreover, comparisons of the in vivo response of two closely related DC subsets to LPS stimulation have not been reported in the literature to date. We compared the transcriptomes of murine splenic CD8 and CD11b DC subsets after in vivo LPS stimulation, using RNA-Seq and systems biology approaches. We identified subset-specific gene signatures, which included multiple functional immune mediators unique to each subset. To explain the observed subset-specific differences, we used a network analysis approach. While both DC subsets used a conserved set of transcription factors and major signalling pathways, the subsets showed differential regulation of sets of genes that 'fine-tune' the network Hubs expressed in common. We propose a model in which signalling through common pathway components is 'fine-tuned' by transcriptional control of subset-specific modulators, thus allowing for distinct functional outcomes in closely related DC subsets. We extend this analysis to comparable datasets from the literature and confirm that our model can account for cell subset-specific responses to LPS stimulation in multiple subpopulations in mouse and man.

Actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations

PubMed Central

Westendorf, Christian; Negrete, Jose; Bae, Albert J.; Sandmann, Rabea; Bodenschatz, Eberhard; Beta, Carsten

2013-01-01

The rapid reorganization of the actin cytoskeleton in response to external stimuli is an essential property of many motile eukaryotic cells. Here, we report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. When averaging the actin response of many cells to a short pulse of the chemoattractant cAMP, we observed a transient accumulation of cortical actin reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. To substantiate that an oscillatory mechanism governs the actin dynamics in these cells, we systematically exposed a large number of cells to periodic pulse trains of different frequencies. Our results indicate a resonance peak at a stimulation period of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the regulatory network of the actin system. To test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and actin-interacting protein 1, as well as knockout mutants that lack Coronin and actin-interacting protein 1. These actin-binding proteins enhance the disassembly of actin filaments and thus allow us to estimate the delay time in the regulatory feedback loop. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed in our periodic stimulation experiments. PMID:23431176

Accelerated tumor invasion under non-isotropic cell dispersal in glioblastomas

NASA Astrophysics Data System (ADS)

Fort, Joaquim; Solé, Ricard V.

2013-05-01

Glioblastomas are highly diffuse, malignant tumors that have so far evaded clinical treatment. The strongly invasive behavior of cells in these tumors makes them very resistant to treatment, and for this reason both experimental and theoretical efforts have been directed toward understanding the spatiotemporal pattern of tumor spreading. Although usual models assume a standard diffusion behavior, recent experiments with cell cultures indicate that cells tend to move in directions close to that of glioblastoma invasion, thus indicating that a biased random walk model may be much more appropriate. Here we show analytically that, for realistic parameter values, the speeds predicted by biased dispersal are consistent with experimentally measured data. We also find that models beyond reaction-diffusion-advection equations are necessary to capture this substantial effect of biased dispersal on glioblastoma spread.

Correlated receptor transport processes buffer single-cell heterogeneity

PubMed Central

Kallenberger, Stefan M.; Unger, Anne L.; Legewie, Stefan; Lymperopoulos, Konstantinos; Eils, Roland

2017-01-01

Cells typically vary in their response to extracellular ligands. Receptor transport processes modulate ligand-receptor induced signal transduction and impact the variability in cellular responses. Here, we quantitatively characterized cellular variability in erythropoietin receptor (EpoR) trafficking at the single-cell level based on live-cell imaging and mathematical modeling. Using ensembles of single-cell mathematical models reduced parameter uncertainties and showed that rapid EpoR turnover, transport of internalized EpoR back to the plasma membrane, and degradation of Epo-EpoR complexes were essential for receptor trafficking. EpoR trafficking dynamics in adherent H838 lung cancer cells closely resembled the dynamics previously characterized by mathematical modeling in suspension cells, indicating that dynamic properties of the EpoR system are widely conserved. Receptor transport processes differed by one order of magnitude between individual cells. However, the concentration of activated Epo-EpoR complexes was less variable due to the correlated kinetics of opposing transport processes acting as a buffering system. PMID:28945754

Equivalent circuit-based analysis of CMUT cell dynamics in arrays.

PubMed

Oguz, H K; Atalar, Abdullah; Köymen, Hayrettin

2013-05-01

Capacitive micromachined ultrasonic transducers (CMUTs) are usually composed of large arrays of closely packed cells. In this work, we use an equivalent circuit model to analyze CMUT arrays with multiple cells. We study the effects of mutual acoustic interactions through the immersion medium caused by the pressure field generated by each cell acting upon the others. To do this, all the cells in the array are coupled through a radiation impedance matrix at their acoustic terminals. An accurate approximation for the mutual radiation impedance is defined between two circular cells, which can be used in large arrays to reduce computational complexity. Hence, a performance analysis of CMUT arrays can be accurately done with a circuit simulator. By using the proposed model, one can very rapidly obtain the linear frequency and nonlinear transient responses of arrays with an arbitrary number of CMUT cells. We performed several finite element method (FEM) simulations for arrays with small numbers of cells and showed that the results are very similar to those obtained by the equivalent circuit model.

On the robustness of SAC silencing in closed mitosis

NASA Astrophysics Data System (ADS)

Ruth, Donovan; Liu, Jian

Mitosis equally partitions sister chromatids to two daughter cells. This is achieved by properly attaching these chromatids via their kinetochores to microtubules that emanate from the spindle poles. Once the last kinetochore is properly attached, the spindle microtubules pull the sister chromatids apart. Due to the dynamic nature of microtubules, however, kinetochore-microtubule attachment often goes wrong. When this erroneous attachment occurs, it locally activates an ensemble of proteins, called the spindle assembly checkpoint proteins (SAC), which halts the mitotic progression until all the kinetochores are properly attached by spindle microtubules. The timing of SAC silencing thus determines the fidelity of chromosome segregation. We previously established a spatiotemporal model that addresses the robustness of SAC silencing in open mitosis for the first time. Here, we focus on closed mitosis by examining yeast mitosis as a model system. Though much experimental work has been done to study the SAC in cells undergoing closed mitosis, the processes responsible are not well understood. We leverage and extend our previous model to study SAC silencing mechanism in closed mitosis. We show that a robust signal of the SAC protein accumulation at the spindle pole body can be achieved. This signal is a nonlinear increasing function of number of kinetochore-microtubule attachments, and can thus serve as a robust trigger to time the SAC silencing. Together, our mechanism provides a unified framework across species that ensures robust SAC silencing and fidelity of chromosome segregation in mitosis. Intramural research program in NHLBI at NIH.

Glass shell manufacturing in space

NASA Technical Reports Server (NTRS)

Downs, R. L.; Ebner, M. A.; Nolen, R. L., Jr.

1981-01-01

Highly-uniform, hollow glass spheres (shells), which are used for inertial confinement fusion targets, were formed from metal-organic gel powder feedstock in a vertical furnace. As a result of the rapid pyrolysis caused by the furnace, the gel is transformed to a shell in five distinct stages: (a) surface closure of the porous gel; (b) generation of a closed-cell foam structure in the gel; (c) spheridization of the gel and further expansion of the foam; (d) coalescence of the closed-cell foam to a single-void shell; and (e) fining of the glass shell. The heat transfer from the furnace to the falling gel particle was modeled to determine the effective heating rate of the gel. The model predicts the temperature history for a particle as a function of mass, dimensions, specific heat, and absorptance as well as furnace temperature profile and thermal conductivity of the furnace gas. A model was developed that predicts the gravity-induced degradation of shell concentricity in falling molten shells as a function of shell characteristics and time.

Mesohysteresis model for ferromagnetic materials by minimization of the micromagnetic free energy

NASA Astrophysics Data System (ADS)

van den Berg, A.; Dupré, L.; Van de Wiele, B.; Crevecoeur, G.

2009-04-01

To study the connection between macroscopic hysteretic behavior and the microstructural properties, this paper presents and validates a new material dependent three-dimensional mesoscopic magnetic hysteresis model. In the presented mesoscopic description, the different micromagnetic energy terms are reformulated on the space scale of the magnetic domains. The sample is discretized in cubic cells, each with a local stress state, local bcc crystallographic axes, etc. The magnetization is assumed to align with one of the three crystallographic axes, in positive or negative sense, defining six volume fractions within each cell. The micromagnetic Gibbs free energy is described in terms of these volume fractions. Hysteresis loops are computed by minimizing the mesoscopic Gibbs free energy using a modified gradient search for a sequence of external applied fields. To validate the mesohysteresis model, we studied the magnetic memory properties. Numerical experiments reveal that (1) minor hysteresis loops are indeed closed and (2) the closed minor loops are erased from the memory.

Involvement of cell surface TG2 in the aggregation of K562 cells triggered by gluten.

PubMed

Feriotto, G; Calza, R; Bergamini, C M; Griffin, M; Wang, Z; Beninati, S; Ferretti, V; Marzola, E; Guerrini, R; Pagnoni, A; Cavazzini, A; Casciano, F; Mischiati, C

2017-03-01

Gluten-induced aggregation of K562 cells represents an in vitro model reproducing the early steps occurring in the small bowel of celiac patients exposed to gliadin. Despite the clear involvement of TG2 in the activation of the antigen-presenting cells, it is not yet clear in which compartment it occurs. Herein we study the calcium-dependent aggregation of these cells, using either cell-permeable or cell-impermeable TG2 inhibitors. Gluten induces efficient aggregation when calcium is absent in the extracellular environment, while TG2 inhibitors do not restore the full aggregating potential of gluten in the presence of calcium. These findings suggest that TG2 activity is not essential in the cellular aggregation mechanism. We demonstrate that gluten contacts the cells and provokes their aggregation through a mechanism involving the A-gliadin peptide 31-43. This peptide also activates the cell surface associated extracellular TG2 in the absence of calcium. Using a bioinformatics approach, we identify the possible docking sites of this peptide on the open and closed TG2 structures. Peptide docks with the closed TG2 structure near to the GTP/GDP site, by establishing molecular interactions with the same amino acids involved in stabilization of GTP binding. We suggest that it may occur through the displacement of GTP, switching the TG2 structure from the closed to the active open conformation. Furthermore, docking analysis shows peptide binding with the β-sandwich domain of the closed TG2 structure, suggesting that this region could be responsible for the different aggregating effects of gluten shown in the presence or absence of calcium. We deduce from these data a possible mechanism of action by which gluten makes contact with the cell surface, which could have possible implications in the celiac disease onset.

40 CFR 98.433 - Calculating GHG contained in pre-charged equipment or closed-cell foams.

Code of Federal Regulations, 2014 CFR

2014-07-01

...-charged equipment or closed-cell foams. 98.433 Section 98.433 Protection of Environment ENVIRONMENTAL... Exporters of Fluorinated Greenhouse Gases Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.433 Calculating GHG contained in pre-charged equipment or closed-cell foams. (a) The total mass of each...

40 CFR 98.433 - Calculating GHG contained in pre-charged equipment or closed-cell foams.

Code of Federal Regulations, 2013 CFR

2013-07-01

...-charged equipment or closed-cell foams. 98.433 Section 98.433 Protection of Environment ENVIRONMENTAL... Exporters of Fluorinated Greenhouse Gases Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.433 Calculating GHG contained in pre-charged equipment or closed-cell foams. (a) The total mass of each...

40 CFR 98.433 - Calculating GHG contained in pre-charged equipment or closed-cell foams.

Code of Federal Regulations, 2011 CFR

2011-07-01

...-charged equipment or closed-cell foams. 98.433 Section 98.433 Protection of Environment ENVIRONMENTAL... Exporters of Fluorinated Greenhouse Gases Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.433 Calculating GHG contained in pre-charged equipment or closed-cell foams. (a) The total mass of each...

40 CFR 98.433 - Calculating GHG contained in pre-charged equipment or closed-cell foams.

Code of Federal Regulations, 2012 CFR

2012-07-01

...-charged equipment or closed-cell foams. 98.433 Section 98.433 Protection of Environment ENVIRONMENTAL... Exporters of Fluorinated Greenhouse Gases Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.433 Calculating GHG contained in pre-charged equipment or closed-cell foams. (a) The total mass of each...

Characterization of small microfluidic valves for studies of mechanical properties of bacteria

DOE PAGES

Yang, Da; Greer, Clayton M.; Jones, Branndon P.; ...

2015-09-02

Lab-on-a-chip platforms present many new opportunities to study bacterial cells and cellular assemblies. Here, the authors describe a new platform that allows us to apply uniaxial stress to individual bacterial cells while observing the cell and its subcellular assemblies using a high resolution optical microscope. The microfluidic chip consists of arrays of miniature pressure actuated valves. By placing a bacterium under one of such valves and partially closing the valve by externally applied pressure, the cell can be deformed. Although large pressure actuated valves used in integrated fluidic circuits have been extensively studied previously, here the authors downsize those microfluidicmore » valves and use flow channels with rectangular cross-sections to maintain the bacteria in contact with cell culture medium during the experiments. The closure of these valves has not been characterized before. First, these valves are modeled using finite element analysis, and then compared the modeling results with the actual closing profiles of the valves, which is determined from absorption measurements. The measurements and modeling show with good agreement that the deflection of valves is a linear function of externally applied pressure and the deflection scales proportionally to the width of the flow channel. In addition to characterizing the valve, the authors show at a proof-of-principle level that it can be used to deform a bacterial cell at considerable magnitude. They found the largest deformations in 5 μm wide channels where the bacterial width and length increase by 1.6 and 1.25 times, respectively. Narrower and broader channels are less optimal for these studies. Finally, the platform presents a promising approach to probe, in a quantitative and systematic way, the mechanical properties of not only bacterial cells but possibly also yeast and other single-celled organisms.« less

Establishment of a translational endothelial cell model using directed differentiation of induced pluripotent stem cells from Cynomolgus monkey.

PubMed

Thoma, Eva C; Heckel, Tobias; Keller, David; Giroud, Nicolas; Leonard, Brian; Christensen, Klaus; Roth, Adrian; Bertinetti-Lapatki, Cristina; Graf, Martin; Patsch, Christoph

2016-10-25

Due to their broad differentiation potential, pluripotent stem cells (PSCs) offer a promising approach for generating relevant cellular models for various applications. While human PSC-based cellular models are already advanced, similar systems for non-human primates (NHPs) are still lacking. However, as NHPs are the most appropriate animals for evaluating the safety of many novel pharmaceuticals, the availability of in vitro systems would be extremely useful to bridge the gap between cellular and animal models. Here, we present a NHP in vitro endothelial cell system using induced pluripotent stem cells (IPSCs) from Cynomolgus monkey (Macaca fascicularis). Based on an adapted protocol for human IPSCs, we directly differentiated macaque IPSCs into endothelial cells under chemically defined conditions. The resulting endothelial cells can be enriched using immuno-magnetic cell sorting and display endothelial marker expression and function. RNA sequencing revealed that the differentiation process closely resembled vasculogenesis. Moreover, we showed that endothelial cells derived from macaque and human IPSCs are highly similar with respect to gene expression patterns and key endothelial functions, such as inflammatory responses. These data demonstrate the power of IPSC differentiation technology to generate defined cell types for use as translational in vitro models to compare cell type-specific responses across species.

A coupled diffusion-fluid pressure model to predict cell density distribution for cells encapsulated in a porous hydrogel scaffold under mechanical loading.

PubMed

Zhao, Feihu; Vaughan, Ted J; Mc Garrigle, Myles J; McNamara, Laoise M

2017-10-01

Tissue formation within tissue engineering (TE) scaffolds is preceded by growth of the cells throughout the scaffold volume and attachment of cells to the scaffold substrate. It is known that mechanical stimulation, in the form of fluid perfusion or mechanical strain, enhances cell differentiation and overall tissue formation. However, due to the complex multi-physics environment of cells within TE scaffolds, cell transport under mechanical stimulation is not fully understood. Therefore, in this study, we have developed a coupled multiphysics model to predict cell density distribution in a TE scaffold. In this model, cell transport is modelled as a thermal conduction process, which is driven by the pore fluid pressure under applied loading. As a case study, the model is investigated to predict the cell density patterns of pre-osteoblasts MC3T3-e1 cells under a range of different loading regimes, to obtain an understanding of desirable mechanical stimulation that will enhance cell density distribution within TE scaffolds. The results of this study have demonstrated that fluid perfusion can result in a higher cell density in the scaffold region closed to the outlet, while cell density distribution under mechanical compression was similar with static condition. More importantly, the study provides a novel computational approach to predict cell distribution in TE scaffolds under mechanical loading. Copyright © 2017 Elsevier Ltd. All rights reserved.

Experimental and theoretical investigation of deformation and fracture of subcutaneous fat under compression

NASA Astrophysics Data System (ADS)

Sapozhnikov, S. B.; Ignatova, A. V.

2013-01-01

The subcutaneous fat is considered as a structural material undergoing large inelastic deformations and failure under uniform compression. In calculation, the fat is replaced with a set of cells operating in parallel and suffering failure independently of one another. An elementary cell is considered as a closed thin-wall cylindrical shell filled with an incompressible liquid. All cells in the model are of the same size, and their material is hyperelastic, whose stiffness grows in tension. By comparing experimental data with the mathematical shell model, three parameters are determined to describe the hyperelastic behavior of the cells in transverse compression. A mathematical model with seven constants is presented for describing the deformation of subcutaneous fat under compression. The results obtained are used in a model of human thorax subjected to a local pulse action corresponding to the loading of human body under the impact of a bullet on an armor vest.

Using Shock Waves to Improve the Acoustic Properties of Closed-Cell Foams

NASA Astrophysics Data System (ADS)

Brouillette, M.; Hébert, C.; Atalla, N.; Doutres, O.

Foam microstructure can be seen as a collection of interlinked struts forming a packing of cells interconnected to others through pores. Materials with a totality of pores closed by thin membranes are called closed-cell foams. The filtration and acoustic efficiency of closed-cell foams is poor compared to open-cell foams since it is very difficult for the fluid or the acoustic waves to penetrate inside the material.

Mathematical models of tumor heterogeneity and drug resistance

NASA Astrophysics Data System (ADS)

Greene, James

In this dissertation we develop mathematical models of tumor heterogeneity and drug resistance in cancer chemotherapy. Resistance to chemotherapy is one of the major causes of the failure of cancer treatment. Furthermore, recent experimental evidence suggests that drug resistance is a complex biological phenomena, with many influences that interact nonlinearly. Here we study the influence of such heterogeneity on treatment outcomes, both in general frameworks and under specific mechanisms. We begin by developing a mathematical framework for describing multi-drug resistance to cancer. Heterogeneity is reflected by a continuous parameter, which can either describe a single resistance mechanism (such as the expression of P-gp in the cellular membrane) or can account for the cumulative effect of several mechanisms and factors. The model is written as a system of integro-differential equations, structured by the continuous "trait," and includes density effects as well as mutations. We study the limiting behavior of the model, both analytically and numerically, and apply it to study treatment protocols. We next study a specific mechanism of tumor heterogeneity and its influence on cell growth: the cell-cycle. We derive two novel mathematical models, a stochastic agent-based model and an integro-differential equation model, each of which describes the growth of cancer cells as a dynamic transition between proliferative and quiescent states. By examining the role all parameters play in the evolution of intrinsic tumor heterogeneity, and the sensitivity of the population growth to parameter values, we show that the cell-cycle length has the most significant effect on the growth dynamics. In addition, we demonstrate that the agent-based model can be approximated well by the more computationally efficient integro-differential equations, when the number of cells is large. The model is closely tied to experimental data of cell growth, and includes a novel implementation of transition rates as a function of global density. Finally, we extend the model of cell-cycle heterogeneity to include spatial variables. Cells are modeled as soft spheres and exhibit attraction/repulsion/random forces. A fundamental hypothesis is that cell-cycle length increases with local density, thus producing a distribution of observed division lengths. Apoptosis occurs primarily through an extended period of unsuccessful proliferation, and the explicit mechanism of the drug (Paclitaxel) is modeled as an increase in cell-cycle duration. We show that the distribution of cell-cycle lengths is highly time-dependent, with close time-averaged agreement with the distribution used in the previous work. Furthermore, survival curves are calculated and shown to qualitatively agree with experimental data in different densities and geometries, thus relating the cellular microenvironment to drug resistance.

A minimal physical model for crawling cells

NASA Astrophysics Data System (ADS)

Tiribocchi, Adriano; Tjhung, Elsen; Marenduzzo, Davide; Cates, Michael E.

Cell motility in higher organisms (eukaryotes) is fundamental to biological functions such as wound healing or immune response, and is also implicated in diseases such as cancer. For cells crawling on solid surfaces, considerable insights into motility have been gained from experiments replicating such motion in vitro. Such experiments show that crawling uses a combination of actin treadmilling (polymerization), which pushes the front of a cell forward, and myosin-induced stress (contractility), which retracts the rear. We present a simplified physical model of a crawling cell, consisting of a droplet of active polar fluid with contractility throughout, but treadmilling connected to a thin layer near the supporting wall. The model shows a variety of shapes and/or motility regimes, some closely resembling cases seen experimentally. Our work supports the view that cellular motility exploits autonomous physical mechanisms whose operation does not need continuous regulatory effort.

A minimal physical model captures the shapes of crawling cells

NASA Astrophysics Data System (ADS)

Tjhung, E.; Tiribocchi, A.; Marenduzzo, D.; Cates, M. E.

2015-01-01

Cell motility in higher organisms (eukaryotes) is crucial to biological functions ranging from wound healing to immune response, and also implicated in diseases such as cancer. For cells crawling on hard surfaces, significant insights into motility have been gained from experiments replicating such motion in vitro. Such experiments show that crawling uses a combination of actin treadmilling (polymerization), which pushes the front of a cell forward, and myosin-induced stress (contractility), which retracts the rear. Here we present a simplified physical model of a crawling cell, consisting of a droplet of active polar fluid with contractility throughout, but treadmilling connected to a thin layer near the supporting wall. The model shows a variety of shapes and/or motility regimes, some closely resembling cases seen experimentally. Our work strongly supports the view that cellular motility exploits autonomous physical mechanisms whose operation does not need continuous regulatory effort.

Neural Differentiation of Human Pluripotent Stem Cells for Nontherapeutic Applications: Toxicology, Pharmacology, and In Vitro Disease Modeling.

PubMed

Yap, May Shin; Nathan, Kavitha R; Yeo, Yin; Lim, Lee Wei; Poh, Chit Laa; Richards, Mark; Lim, Wei Ling; Othman, Iekhsan; Heng, Boon Chin

2015-01-01

Human pluripotent stem cells (hPSCs) derived from either blastocyst stage embryos (hESCs) or reprogrammed somatic cells (iPSCs) can provide an abundant source of human neuronal lineages that were previously sourced from human cadavers, abortuses, and discarded surgical waste. In addition to the well-known potential therapeutic application of these cells in regenerative medicine, these are also various promising nontherapeutic applications in toxicological and pharmacological screening of neuroactive compounds, as well as for in vitro modeling of neurodegenerative and neurodevelopmental disorders. Compared to alternative research models based on laboratory animals and immortalized cancer-derived human neural cell lines, neuronal cells differentiated from hPSCs possess the advantages of species specificity together with genetic and physiological normality, which could more closely recapitulate in vivo conditions within the human central nervous system. This review critically examines the various potential nontherapeutic applications of hPSC-derived neuronal lineages and gives a brief overview of differentiation protocols utilized to generate these cells from hESCs and iPSCs.

Entrainment and Control of Bacterial Populations: An in Silico Study over a Spatially Extended Agent Based Model.

PubMed

Mina, Petros; Tsaneva-Atanasova, Krasimira; Bernardo, Mario di

2016-07-15

We extend a spatially explicit agent based model (ABM) developed previously to investigate entrainment and control of the emergent behavior of a population of synchronized oscillating cells in a microfluidic chamber. Unlike most of the work in models of control of cellular systems which focus on temporal changes, we model individual cells with spatial dependencies which may contribute to certain behavioral responses. We use the model to investigate the response of both open loop and closed loop strategies, such as proportional control (P-control), proportional-integral control (PI-control) and proportional-integral-derivative control (PID-control), to heterogeinities and growth in the cell population, variations of the control parameters and spatial effects such as diffusion in the spatially explicit setting of a microfluidic chamber setup. We show that, as expected from the theory of phase locking in dynamical systems, open loop control can only entrain the cell population in a subset of forcing periods, with a wide variety of dynamical behaviors obtained outside these regions of entrainment. Closed-loop control is shown instead to guarantee entrainment in a much wider region of control parameter space although presenting limitations when the population size increases over a certain threshold. In silico tracking experiments are also performed to validate the ability of classical control approaches to achieve other reference behaviors such as a desired constant output or a linearly varying one. All simulations are carried out in BSim, an advanced agent-based simulator of microbial population which is here extended ad hoc to include the effects of control strategies acting onto the population.

Mechanical design of an intracranial stent for treating cerebral aneurysms.

PubMed

Shobayashi, Yasuhiro; Tanoue, Tetsuya; Tateshima, Satoshi; Tanishita, Kazuo

2010-11-01

Endovascular treatment of cerebral aneurysms using stents has advanced markedly in recent years. Mechanically, a cerebrovascular stent must be very flexible longitudinally and have low radial stiffness. However, no study has examined the stress distribution and deformation of cerebrovascular stents using the finite element method (FEM) and experiments. Stents can have open- and closed-cell structures, and open-cell stents are used clinically in the cerebrovasculature because of their high flexibility. However, the open-cell structure confers a risk of in-stent stenosis due to protrusion of stent struts into the normal parent artery. Therefore, a flexible stent with a closed-cell structure is required. To design a clinically useful, highly flexible, closed-cell stent, one must examine the mechanical properties of the closed-cell structure. In this study, we investigated the relationship between mesh patterns and the mechanical properties of closed-cell stents. Several mesh patterns were designed and their characteristics were studied using numerical simulation. The results showed that the bending stiffness of a closed-cell stent depends on the geometric configuration of the stent cell. It decreases when the stent cell is stretched in the circumferential direction. Mechanical flexibility equal to an open-cell structure was obtained in a closed-cell structure by varying the geometric configuration of the stent cell. Copyright © 2010 IPEM. Published by Elsevier Ltd. All rights reserved.

Short-term spheroid culture of primary colorectal cancer cells as an in vitro model for personalizing cancer medicine

PubMed Central

Jeppesen, Maria; Hagel, Grith; Glenthoj, Anders; Vainer, Ben; Ibsen, Per; Harling, Henrik; Thastrup, Ole; Jørgensen, Lars N.

2017-01-01

Chemotherapy treatment of cancer remains a challenge due to the molecular and functional heterogeneity displayed by tumours originating from the same cell type. The pronounced heterogeneity makes it difficult for oncologists to devise an effective therapeutic strategy for the patient. One approach for increasing treatment efficacy is to test the chemosensitivity of cancer cells obtained from the patient’s tumour. 3D culture represents a promising method for modelling patient tumours in vitro. The aim of this study was therefore to evaluate how closely short-term spheroid cultures of primary colorectal cancer cells resemble the original tumour. Colorectal cancer cells were isolated from human tumour tissue and cultured as spheroids. Spheroid cultures were established with a high success rate and remained viable for at least 10 days. The spheroids exhibited significant growth over a period of 7 days and no difference in growth rate was observed for spheroids of different sizes. Comparison of spheroids with the original tumour revealed that spheroid culture generally preserved adenocarcinoma histology and expression patterns of cytokeratin 20 and carcinoembryonic antigen. Interestingly, spheroids had a tendency to resemble tumour protein expression more closely after 10 days of culture compared to 3 days. Chemosensitivity screening using spheroids from five patients demonstrated individual response profiles. This indicates that the spheroids maintained patient-to-patient differences in sensitivity towards the drugs and combinations most commonly used for treatment of colorectal cancer. In summary, short-term spheroid culture of primary colorectal adenocarcinoma cells represents a promising in vitro model for use in personalized medicine. PMID:28877221

A Closed Parameterization of DNA–Damage by Charged Particles, as a Function of Energy — A Geometrical Approach

PubMed Central

Van den Heuvel, Frank

2014-01-01

Purpose To present a closed formalism calculating charged particle radiation damage induced in DNA. The formalism is valid for all types of charged particles and due to its closed nature is suited to provide fast conversion of dose to DNA-damage. Methods The induction of double strand breaks in DNA–strings residing in irradiated cells is quantified using a single particle model. This leads to a proposal to use the cumulative Cauchy distribution to express the mix of high and low LET type damage probability generated by a single particle. A microscopic phenomenological Monte Carlo code is used to fit the parameters of the model as a function of kinetic energy related to the damage to a DNA molecule embedded in a cell. The model is applied for four particles: electrons, protons, alpha–particles, and carbon ions. A geometric interpretation of this observation using the impact ionization mean free path as a quantifier, allows extension of the model to very low energies. Results The mathematical expression describes the model adequately using a chi–square test (). This applies to all particle types with an almost perfect fit for protons, while the other particles seem to result in some discrepancies at very low energies. The implementation calculating a strict version of the RBE based on complex damage alone is corroborated by experimental data from the measured RBE. The geometric interpretation generates a unique dimensionless parameter for each type of charged particle. In addition, it predicts a distribution of DNA damage which is different from the current models. PMID:25340636

Characterization of biomechanical properties of cells through dielectrophoresis-based cell stretching and actin cytoskeleton modeling.

PubMed

Bai, Guohua; Li, Ying; Chu, Henry K; Wang, Kaiqun; Tan, Qiulin; Xiong, Jijun; Sun, Dong

2017-04-04

Cytoskeleton is a highly dynamic network that helps to maintain the rigidity of a cell, and the mechanical properties of a cell are closely related to many cellular functions. This paper presents a new method to probe and characterize cell mechanical properties through dielectrophoresis (DEP)-based cell stretching manipulation and actin cytoskeleton modeling. Leukemia NB4 cells were used as cell line, and changes in their biological properties were examined after chemotherapy treatment with doxorubicin (DOX). DEP-integrated microfluidic chip was utilized as a low-cost and efficient tool to study the deformability of cells. DEP forces used in cell stretching were first evaluated through computer simulation, and the results were compared with modeling equations and with the results of optical stretching (OT) experiments. Structural parameters were then extracted by fitting the experimental data into the actin cytoskeleton model, and the underlying mechanical properties of the cells were subsequently characterized. The DEP forces generated under different voltage inputs were calculated and the results from different approaches demonstrate good approximations to the force estimation. Both DEP and OT stretching experiments confirmed that DOX-treated NB4 cells were stiffer than the untreated cells. The structural parameters extracted from the model and the confocal images indicated significant change in actin network after DOX treatment. The proposed DEP method combined with actin cytoskeleton modeling is a simple engineering tool to characterize the mechanical properties of cells.

Experimental investigations, modeling, and analyses of high-temperature devices for space applications: Part 1. Final report, June 1996--December 1998

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tournier, J.; El-Genk, M.S.; Huang, L.

1999-01-01

The Institute of Space and Nuclear Power Studies at the University of New Mexico has developed a computer simulation of cylindrical geometry alkali metal thermal-to-electric converter cells using a standard Fortran 77 computer code. The objective and use of this code was to compare the experimental measurements with computer simulations, upgrade the model as appropriate, and conduct investigations of various methods to improve the design and performance of the devices for improved efficiency, durability, and longer operational lifetime. The Institute of Space and Nuclear Power Studies participated in vacuum testing of PX series alkali metal thermal-to-electric converter cells and developedmore » the alkali metal thermal-to-electric converter Performance Evaluation and Analysis Model. This computer model consisted of a sodium pressure loss model, a cell electrochemical and electric model, and a radiation/conduction heat transfer model. The code closely predicted the operation and performance of a wide variety of PX series cells which led to suggestions for improvements to both lifetime and performance. The code provides valuable insight into the operation of the cell, predicts parameters of components within the cell, and is a useful tool for predicting both the transient and steady state performance of systems of cells.« less

Experimental investigations, modeling, and analyses of high-temperature devices for space applications: Part 2. Final report, June 1996--December 1998

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tournier, J.; El-Genk, M.S.; Huang, L.

1999-01-01

The Institute of Space and Nuclear Power Studies at the University of New Mexico has developed a computer simulation of cylindrical geometry alkali metal thermal-to-electric converter cells using a standard Fortran 77 computer code. The objective and use of this code was to compare the experimental measurements with computer simulations, upgrade the model as appropriate, and conduct investigations of various methods to improve the design and performance of the devices for improved efficiency, durability, and longer operational lifetime. The Institute of Space and Nuclear Power Studies participated in vacuum testing of PX series alkali metal thermal-to-electric converter cells and developedmore » the alkali metal thermal-to-electric converter Performance Evaluation and Analysis Model. This computer model consisted of a sodium pressure loss model, a cell electrochemical and electric model, and a radiation/conduction heat transfer model. The code closely predicted the operation and performance of a wide variety of PX series cells which led to suggestions for improvements to both lifetime and performance. The code provides valuable insight into the operation of the cell, predicts parameters of components within the cell, and is a useful tool for predicting both the transient and steady state performance of systems of cells.« less

Light scattering of a Bessel beam by a nucleated biological cell: An eccentric sphere model

NASA Astrophysics Data System (ADS)

Wang, Jia Jie; Han, Yi Ping; Chang, Jiao Yong; Chen, Zhu Yang

2018-02-01

Within the framework of generalized Lorenz-Mie theory (GLMT), an eccentrically stratified dielectric sphere model illuminated by an arbitrarily incident Bessel beam is applied to investigate the scattering characteristics of a single nucleated biological cell. The Bessel beam propagating in an arbitrary direction is expanded in terms of vector spherical wave functions (VSWFs), where the beam shape coefficients (BSCs) are calculated rigorously in a closed analytical form. The effects of the half-cone angle of Bessel beam, the location of the particle in the beam, the size ratio of nucleus to cell, and the location of the nucleus inside the cell on the scattering properties of a nucleated cell are analyzed. The results provide useful references for optical diagnostic and imaging of particle having nucleated structure.

Isolation of Oct4-Expressing Extraembryonic Endoderm Precursor Cell Lines

PubMed Central

Debeb, Bisrat G.; Galat, Vasiliy; Epple-Farmer, Jessica; Iannaccone, Steve; Woodward, Wendy A.; Bader, Michael; Iannaccone, Philip; Binas, Bert

2009-01-01

Background The extraembryonic endoderm (ExEn) defines the yolk sac, a set of membranes that provide essential support for mammalian embryos. Recent findings suggest that the committed ExEn precursor is present already in the embryonic Inner Cell Mass (ICM) as a group of cells that intermingles with the closely related epiblast precursor. All ICM cells contain Oct4, a key transcription factor that is first expressed at the morula stage. In vitro, the epiblast precursor is most closely represented by the well-characterized embryonic stem (ES) cell lines that maintain the expression of Oct4, but analogous ExEn precursor cell lines are not known and it is unclear if they would express Oct4. Methodology/Principal Findings Here we report the isolation and characterization of permanently proliferating Oct4-expressing rat cell lines (“XEN-P cell lines”), which closely resemble the ExEn precursor. We isolated the XEN-P cell lines from blastocysts and characterized them by plating and gene expression assays as well as by injection into embryos. Like ES cells, the XEN-P cells express Oct4 and SSEA1 at high levels and their growth is stimulated by leukemia inhibitory factor, but instead of the epiblast determinant Nanog, they express the ExEn determinants Gata6 and Gata4. Further, they lack markers characteristic of the more differentiated primitive/visceral and parietal ExEn stages, but exclusively differentiate into these stages in vitro and contribute to them in vivo. Conclusions/Significance Our findings (i) suggest strongly that the ExEn precursor is a self-renewable entity, (ii) indicate that active Oct4 gene expression (transcription plus translation) is part of its molecular identity, and (iii) provide an in vitro model of early ExEn differentiation. PMID:19784378

Modelling the formation of necrotic regions in avascular tumours.

PubMed

Tindall, M J; Please, C P; Peddie, M J

2008-01-01

The mechanisms underlying the formation of necrotic regions within avascular tumours are not well understood. In this paper, we examine the relative roles of nutrient deprivation and of cell death, from both the proliferating phase of the cell cycle via apoptosis and from the quiescent phase via necrosis, in changing the structure within multicellular tumour spheroids and particularly the accumulation of dead cell material in the centre. A mathematical model is presented and studied that accounts for nutrient diffusion, changes in cell cycling rates, the two different routes to cell death as well as active motion of cells and passive motion of the dead cell material. In studying the accumulation of dead cell matter we do not distinguish between the route by which each was formed. The resulting mathematical model is examined for a number of scenarios. Results show that in many cases the size of the necrotic core is closely correlated with low levels in nutrient concentration. However, in certain cases, particularly where the rate of necrosis is large, the resulting necrotic core can lead to regions of non-negligible nutrient concentration-dependent upon the mode of cell death.

Compositional control of continuously graded anode functional layer

NASA Astrophysics Data System (ADS)

McCoppin, J.; Barney, I.; Mukhopadhyay, S.; Miller, R.; Reitz, T.; Young, D.

2012-10-01

In this work, solid oxide fuel cells (SOFC's) are fabricated with linear-compositionally graded anode functional layers (CGAFL) using a computer-controlled compound aerosol deposition (CCAD) system. Cells with different CGAFL thicknesses (30 um and 50 um) are prepared with a continuous compositionally graded interface deposited between the electrolyte and anode support current collecting regions. The compositional profile was characterized using energy dispersive X-ray spectroscopic mapping. An analytical model of the compound aerosol deposition was developed. The model predicted compositional profiles for both samples that closely matched the measured profiles, suggesting that aerosol-based deposition methods are capable of creating functional gradation on length scales suitable for solid oxide fuel cell structures. The electrochemical performances of the two cells are analyzed using electrochemical impedance spectroscopy (EIS).

Deformation and relaxation of an incompressible viscoelastic body with surface viscoelasticity

NASA Astrophysics Data System (ADS)

Liu, Liping; Yu, Miao; Lin, Hao; Foty, Ramsey

2017-01-01

Measuring mechanical properties of cells or cell aggregates has proven to be an involved process due to their geometrical and structural complexity. Past measurements are based on material models that completely neglect the elasticity of either the surface membrane or the interior bulk. In this work, we consider general material models to account for both surface and bulk viscoelasticity. The boundary value problems are formulated for deformations and relaxations of a closed viscoelastic surface coupled with viscoelastic media inside and outside of the surface. The linearized surface elasticity models are derived for the constant surface tension model and the Helfrich-Canham bending model for coupling with the bulk viscoelasticity. For quasi-spherical surfaces, explicit solutions are obtained for the deformation, stress-strain and relaxation behaviors under a variety of loading conditions. These solutions can be applied to extract the intrinsic surface and bulk viscoelastic properties of biological cells or cell aggregates in the indentation, electro-deformation and relaxation experiments.

Recent advances in lineage differentiation from stem cells: hurdles and opportunities?

PubMed Central

Terryn, Joke; Tricot, Tine; Gajjar, Madhavsai; Verfaillie, Catherine

2018-01-01

Pluripotent stem cells have the property of long-term self-renewal and the potential to give rise to descendants of the three germ layers and hence all mature cells in the human body. Therefore, they hold the promise of offering insight not only into human development but also for human disease modeling and regenerative medicine. However, the generation of mature differentiated cells that closely resemble their in vivo counterparts remains challenging. Recent advances in single-cell transcriptomics and computational modeling of gene regulatory networks are revealing a better understanding of lineage commitment and are driving modern genome editing approaches. Additional modification of the chemical microenvironment, as well as the use of bioengineering tools to recreate the cellular, extracellular matrix, and physical characteristics of the niche wherein progenitors and mature cells reside, is now being used to further improve the maturation and functionality of stem cell progeny. PMID:29552337

Predictive lethal proarrhythmic risk evaluation using a closed-loop-circuit cell network with human induced pluripotent stem cells derived cardiomyocytes

NASA Astrophysics Data System (ADS)

Nomura, Fumimasa; Hattori, Akihiro; Terazono, Hideyuki; Kim, Hyonchol; Odaka, Masao; Sugio, Yoshihiro; Yasuda, Kenji

2016-06-01

For the prediction of lethal arrhythmia occurrence caused by abnormality of cell-to-cell conduction, we have developed a next-generation in vitro cell-to-cell conduction assay, i.e., a quasi in vivo assay, in which the change in spatial cell-to-cell conduction is quantitatively evaluated from the change in waveforms of the convoluted electrophysiological signals from lined-up cardiomyocytes on a single closed loop of a microelectrode of 1 mm diameter and 20 µm width in a cultivation chip. To evaluate the importance of the closed-loop arrangement of cardiomyocytes for prediction, we compared the change in waveforms of convoluted signals of the responses in the closed-loop circuit arrangement with that of the response of cardiomyocyte clusters using a typical human ether a go-go related gene (hERG) ion channel blocker, E-4031. The results showed that (1) waveform prolongation and fluctuation both in the closed loops and clusters increased depending on the E-4031 concentration increase. However, (2) only the waveform signals in closed loops showed an apparent temporal change in waveforms from ventricular tachycardia (VT) to ventricular fibrillation (VF), which is similar to the most typical cell-to-cell conductance abnormality. The results indicated the usefulness of convoluted waveform signals of a closed-loop cell network for acquiring reproducible results acquisition and more detailed temporal information on cell-to-cell conduction.

Voronoi cell patterns: Theoretical model and applications

NASA Astrophysics Data System (ADS)

González, Diego Luis; Einstein, T. L.

2011-11-01

We use a simple fragmentation model to describe the statistical behavior of the Voronoi cell patterns generated by a homogeneous and isotropic set of points in 1D and in 2D. In particular, we are interested in the distribution of sizes of these Voronoi cells. Our model is completely defined by two probability distributions in 1D and again in 2D, the probability to add a new point inside an existing cell and the probability that this new point is at a particular position relative to the preexisting point inside this cell. In 1D the first distribution depends on a single parameter while the second distribution is defined through a fragmentation kernel; in 2D both distributions depend on a single parameter. The fragmentation kernel and the control parameters are closely related to the physical properties of the specific system under study. We use our model to describe the Voronoi cell patterns of several systems. Specifically, we study the island nucleation with irreversible attachment, the 1D car-parking problem, the formation of second-level administrative divisions, and the pattern formed by the Paris Métro stations.

Fuel cell tubes and method of making same

DOEpatents

Borglum, Brian P.

1999-11-30

A method of manufacturing porous ceramic tubes for fuel cells with improved properties and higher manufacturing yield is disclosed. The method involves extruding a closed end fuel cell tube, such as an air electrode of a solid oxide fuel cell, in which the closed end also functions as the sintering support. The resultant fuel cell tube has a superior porosity distribution which allows improved diffusion of oxygen at the closed end of the tube during operation of the fuel cell. Because this region has the highest current density, performance enhancement and improved reliability of the fuel cell tube result. Furthermore, the higher manufacturing yield associated with the present method decreases the overall fuel cell cost. A method of manufacturing porous ceramic tubes for fuel cells with improved properties and higher manufacturing yield is disclosed. The method involves extruding a closed end fuel cell tube, such as an air electrode of a solid oxide fuel cell, in which the closed end also functions as the sintering support. The resultant fuel cell tube has a superior porosity distribution which allows improved diffusion of oxygen at the closed end of the tube during operation of the fuel cell. Because this region has the highest current density, performance enhancement and improved reliability of the fuel cell tube result. Furthermore, the higher manufacturing yield associated with the present method decreases the overall fuel cell cost.

Residential Proximity to Major Roadways Is Associated With Increased Levels of AC133+ Circulating Angiogenic Cells.

PubMed

DeJarnett, Natasha; Yeager, Ray; Conklin, Daniel J; Lee, Jongmin; O'Toole, Timothy E; McCracken, James; Abplanalp, Wes; Srivastava, Sanjay; Riggs, Daniel W; Hamzeh, Ihab; Wagner, Stephen; Chugh, Atul; DeFilippis, Andrew; Ciszewski, Tiffany; Wyatt, Brad; Becher, Carrie; Higdon, Deirdre; Ramos, Kenneth S; Tollerud, David J; Myers, John A; Rai, Shesh N; Shah, Jasmit; Zafar, Nagma; Krishnasamy, Sathya S; Prabhu, Sumanth D; Bhatnagar, Aruni

2015-11-01

Previous studies have shown that residential proximity to a roadway is associated with increased cardiovascular disease risk. Yet, the nature of this association remains unclear, and its effect on individual cardiovascular disease risk factors has not been assessed. The objective of this study was to determine whether residential proximity to roadways influences systemic inflammation and the levels of circulating angiogenic cells. In a cross-sectional study, cardiovascular disease risk factors, blood levels of C-reactive protein, and 15 antigenically defined circulating angiogenic cell populations were measured in participants (n=316) with moderate-to-high cardiovascular disease risk. Attributes of roadways surrounding residential locations were assessed using geographic information systems. Associations between road proximity and cardiovascular indices were analyzed using generalized linear models. Close proximity (<50 m) to a major roadway was associated with lower income and higher rates of smoking but not C-reactive protein levels. After adjustment for potential confounders, the levels of circulating angiogenic cells in peripheral blood were significantly elevated in people living in close proximity to a major roadway (CD31(+)/AC133(+), AC133(+), CD34(+)/AC133(+), and CD34(+)/45(dim)/AC133(+) cells) and positively associated with road segment distance (CD31(+)/AC133(+), AC133(+), and CD34(+)/AC133(+) cells), traffic intensity (CD31(+)/AC133(+) and AC133(+) cells), and distance-weighted traffic intensity (CD31(+)/34(+)/45(+)/AC133(+) cells). Living close to a major roadway is associated with elevated levels of circulating cells positive for the early stem marker AC133(+). This may reflect an increased need for vascular repair. Levels of these cells in peripheral blood may be a sensitive index of cardiovascular injury because of residential proximity to roadways. © 2015 American Heart Association, Inc.

Design of a Novel MEMS Microgripper with Rotatory Electrostatic Comb-Drive Actuators for Biomedical Applications.

PubMed

Velosa-Moncada, Luis A; Aguilera-Cortés, Luz Antonio; González-Palacios, Max A; Raskin, Jean-Pierre; Herrera-May, Agustin L

2018-05-22

Primary tumors of patients can release circulating tumor cells (CTCs) to flow inside of their blood. The CTCs have different mechanical properties in comparison with red and white blood cells, and their detection may be employed to study the efficiency of medical treatments against cancer. We present the design of a novel MEMS microgripper with rotatory electrostatic comb-drive actuators for mechanical properties characterization of cells. The microgripper has a compact structural configuration of four polysilicon layers and a simple performance that control the opening and closing displacements of the microgripper tips. The microgripper has a mobile arm, a fixed arm, two different actuators and two serpentine springs, which are designed based on the SUMMiT V surface micromachining process from Sandia National Laboratories. The proposed microgripper operates at its first rotational resonant frequency and its mobile arm has a controlled displacement of 40 µm at both opening and closing directions using dc and ac bias voltages. Analytical models are developed to predict the stiffness, damping forces and first torsional resonant frequency of the microgripper. In addition, finite element method (FEM) models are obtained to estimate the mechanical behavior of the microgripper. The results of the analytical models agree very well respect to FEM simulations. The microgripper has a first rotational resonant frequency of 463.8 Hz without gripped cell and it can operate up to with maximum dc and ac voltages of 23.4 V and 129.2 V, respectively. Based on the results of the analytical and FEM models about the performance of the proposed microgripper, it could be used as a dispositive for mechanical properties characterization of circulating tumor cells (CTCs).

Design of a Novel MEMS Microgripper with Rotatory Electrostatic Comb-Drive Actuators for Biomedical Applications

PubMed Central

Velosa-Moncada, Luis A.; Aguilera-Cortés, Luz Antonio; Raskin, Jean-Pierre

2018-01-01

Primary tumors of patients can release circulating tumor cells (CTCs) to flow inside of their blood. The CTCs have different mechanical properties in comparison with red and white blood cells, and their detection may be employed to study the efficiency of medical treatments against cancer. We present the design of a novel MEMS microgripper with rotatory electrostatic comb-drive actuators for mechanical properties characterization of cells. The microgripper has a compact structural configuration of four polysilicon layers and a simple performance that control the opening and closing displacements of the microgripper tips. The microgripper has a mobile arm, a fixed arm, two different actuators and two serpentine springs, which are designed based on the SUMMiT V surface micromachining process from Sandia National Laboratories. The proposed microgripper operates at its first rotational resonant frequency and its mobile arm has a controlled displacement of 40 µm at both opening and closing directions using dc and ac bias voltages. Analytical models are developed to predict the stiffness, damping forces and first torsional resonant frequency of the microgripper. In addition, finite element method (FEM) models are obtained to estimate the mechanical behavior of the microgripper. The results of the analytical models agree very well respect to FEM simulations. The microgripper has a first rotational resonant frequency of 463.8 Hz without gripped cell and it can operate up to with maximum dc and ac voltages of 23.4 V and 129.2 V, respectively. Based on the results of the analytical and FEM models about the performance of the proposed microgripper, it could be used as a dispositive for mechanical properties characterization of circulating tumor cells (CTCs). PMID:29789474

Simple theoretical models for composite rotor blades

NASA Technical Reports Server (NTRS)

Valisetty, R. R.; Rehfield, L. W.

1984-01-01

The development of theoretical rotor blade structural models for designs based upon composite construction is discussed. Care was exercised to include a member of nonclassical effects that previous experience indicated would be potentially important to account for. A model, representative of the size of a main rotor blade, is analyzed in order to assess the importance of various influences. The findings of this model study suggest that for the slenderness and closed cell construction considered, the refinements are of little importance and a classical type theory is adequate. The potential of elastic tailoring is dramatically demonstrated, so the generality of arbitrary ply layup in the cell wall is needed to exploit this opportunity.

Microfluidic devices for cell culture and handling in organ-on-a-chip applications

NASA Astrophysics Data System (ADS)

Becker, Holger; Schulz, Ingo; Mosig, Alexander; Jahn, Tobias; Gärtner, Claudia

2014-03-01

For many problems in system biology or pharmacology, in-vivo-like models of cell-cell interactions or organ functions are highly sought after. Conventional stationary cell culture in 2D plates quickly reaches its limitations with respect to an in-vivo like expression and function of individual cell types. Microfabrication technologies and microfluidics offer an attractive solution to these problems. The ability to generate flow as well as geometrical conditions for cell culture and manipulation close to the in-vivo situation allows for an improved design of experiments and the modeling of organ-like functionalities. Furthermore, reduced internal volumes lead to a reduction in reagent volumes necessary as well as an increased assay sensitivity. In this paper we present a range of microfluidic devices designed for the co-culturing of a variety of cells. The influence of substrate materials and surface chemistry on the cell morphology and viability for long-term cell culture has been investigated as well as strategies and medium supply for on-chip cell cultivation.

Development of advanced fuel cell system, phase 2

NASA Technical Reports Server (NTRS)

Handley, L. M.; Meyer, A. P.; Bell, W. F.

1973-01-01

A multiple task research and development program was performed to improve the weight, life, and performance characteristics of hydrogen-oxygen alkaline fuel cells for advanced power systems. Development and characterization of a very stable gold alloy catalyst was continued from Phase I of the program. A polymer material for fabrication of cell structural components was identified and its long term compatibility with the fuel cell environment was demonstrated in cell tests. Full scale partial cell stacks, with advanced design closed cycle evaporative coolers, were tested. The characteristics demonstrated in these tests verified the feasibility of developing the engineering model system concept into an advanced lightweight long life powerplant.

Application of an Elongated Kelvin Model to Space Shuttle Foams

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.; Ghosn, Louis J.; Lerch, Bradley A.

2009-01-01

The space shuttle foams are rigid closed-cell polyurethane foams. The two foams used most-extensively oil space shuttle external tank are BX-265 and NCFL4-124. Because of the foaming and rising process, the foam microstructures are elongated in the rise direction. As a result, these two foams exhibit a nonisotropic mechanical behavior. A detailed microstructural characterization of the two foams is presented. Key features of the foam cells are described and the average cell dimensions in the two foams are summarized. Experimental studies are also conducted to measure the room temperature mechanical response of the two foams in the two principal material directions (parallel to the rise and perpendicular to the rise). The measured elastic modulus, proportional limit stress, ultimate tensile strength, and Poisson's ratios are reported. The generalized elongated Kelvin foam model previously developed by the authors is reviewed and the equations which result from this model are summarized. Using the measured microstructural dimensions and the measured stiffness ratio, the foam tensile strength ratio and Poisson's ratios are predicted for both foams and are compared with the experimental data. The predicted tensile strength ratio is in close agreement with the measured strength ratio for both BX-265 and NCFI24-124. The comparison between the predicted Poisson's ratios and the measured values is not as favorable.

Eotaxin-rich Proangiogenic Hematopoietic Progenitor Cells and CCR3+ Endothelium in the Atopic Asthmatic Response

PubMed Central

Asosingh, Kewal; Vasanji, Amit; Tipton, Aaron; Queisser, Kimberly; Wanner, Nicholas; Janocha, Allison; Grandon, Deepa; Anand-Apte, Bela; Rothenberg, Marc. E.; Dweik, Raed; Erzurum, Serpil C.

2016-01-01

Angiogenesis is closely linked to and precedes eosinophilic infiltration in asthma. Eosinophils are recruited into the airway by chemoattractant eotaxins, which are expressed by endothelial cells, smooth muscles cells, epithelial cells, and hematopoietic cells. We hypothesized that bone marrow-derived proangiogenic progenitor cells that contain eotaxins contribute to the initiation of angiogenesis and inflammation in asthma. Whole lung allergen challenge of atopic asthma patients revealed vascular activation occurs within hours of challenge, and prior to airway inflammation. The eotaxin receptor CCR3 was expressed at high levels on submucosal endothelial cells in patients and murine model of asthma. Exvivo exposure of murine endothelial cells to eotaxins induced migration and angiogenesis. In mechanistic studies, wildtype mice transplanted with eotaxin-1/2 deficient bone marrow had markedly less angiogenesis and inflammation in an atopic asthma model, while adoptive transfer of proangiogenic progenitor cells from wildtype mice in an atopic asthma model into the eotaxin-1/2 deficient mice led to angiogenesis and airway inflammation. The findings indicate that TH2-promoting hematopoietic progenitor cells are rapidly recruited to the lung upon allergen exposure and release eotaxins that coordinately activate endothelial cells, angiogenesis, and airway inflammation. PMID:26810221

A spatial hazard model for cluster detection on continuous indicators of disease: application to somatic cell score.

PubMed

Gay, Emilie; Senoussi, Rachid; Barnouin, Jacques

2007-01-01

Methods for spatial cluster detection dealing with diseases quantified by continuous variables are few, whereas several diseases are better approached by continuous indicators. For example, subclinical mastitis of the dairy cow is evaluated using a continuous marker of udder inflammation, the somatic cell score (SCS). Consequently, this study proposed to analyze spatialized risk and cluster components of herd SCS through a new method based on a spatial hazard model. The dataset included annual SCS for 34 142 French dairy herds for the year 2000, and important SCS risk factors: mean parity, percentage of winter and spring calvings, and herd size. The model allowed the simultaneous estimation of the effects of known risk factors and of potential spatial clusters on SCS, and the mapping of the estimated clusters and their range. Mean parity and winter and spring calvings were significantly associated with subclinical mastitis risk. The model with the presence of 3 clusters was highly significant, and the 3 clusters were attractive, i.e. closeness to cluster center increased the occurrence of high SCS. The three localizations were the following: close to the city of Troyes in the northeast of France; around the city of Limoges in the center-west; and in the southwest close to the city of Tarbes. The semi-parametric method based on spatial hazard modeling applies to continuous variables, and takes account of both risk factors and potential heterogeneity of the background population. This tool allows a quantitative detection but assumes a spatially specified form for clusters.

Mapping local and global variability in plant trait distributions.

PubMed

Butler, Ethan E; Datta, Abhirup; Flores-Moreno, Habacuc; Chen, Ming; Wythers, Kirk R; Fazayeli, Farideh; Banerjee, Arindam; Atkin, Owen K; Kattge, Jens; Amiaud, Bernard; Blonder, Benjamin; Boenisch, Gerhard; Bond-Lamberty, Ben; Brown, Kerry A; Byun, Chaeho; Campetella, Giandiego; Cerabolini, Bruno E L; Cornelissen, Johannes H C; Craine, Joseph M; Craven, Dylan; de Vries, Franciska T; Díaz, Sandra; Domingues, Tomas F; Forey, Estelle; González-Melo, Andrés; Gross, Nicolas; Han, Wenxuan; Hattingh, Wesley N; Hickler, Thomas; Jansen, Steven; Kramer, Koen; Kraft, Nathan J B; Kurokawa, Hiroko; Laughlin, Daniel C; Meir, Patrick; Minden, Vanessa; Niinemets, Ülo; Onoda, Yusuke; Peñuelas, Josep; Read, Quentin; Sack, Lawren; Schamp, Brandon; Soudzilovskaia, Nadejda A; Spasojevic, Marko J; Sosinski, Enio; Thornton, Peter E; Valladares, Fernando; van Bodegom, Peter M; Williams, Mathew; Wirth, Christian; Reich, Peter B

2017-12-19

Our ability to understand and predict the response of ecosystems to a changing environment depends on quantifying vegetation functional diversity. However, representing this diversity at the global scale is challenging. Typically, in Earth system models, characterization of plant diversity has been limited to grouping related species into plant functional types (PFTs), with all trait variation in a PFT collapsed into a single mean value that is applied globally. Using the largest global plant trait database and state of the art Bayesian modeling, we created fine-grained global maps of plant trait distributions that can be applied to Earth system models. Focusing on a set of plant traits closely coupled to photosynthesis and foliar respiration-specific leaf area (SLA) and dry mass-based concentrations of leaf nitrogen ([Formula: see text]) and phosphorus ([Formula: see text]), we characterize how traits vary within and among over 50,000 [Formula: see text]-km cells across the entire vegetated land surface. We do this in several ways-without defining the PFT of each grid cell and using 4 or 14 PFTs; each model's predictions are evaluated against out-of-sample data. This endeavor advances prior trait mapping by generating global maps that preserve variability across scales by using modern Bayesian spatial statistical modeling in combination with a database over three times larger than that in previous analyses. Our maps reveal that the most diverse grid cells possess trait variability close to the range of global PFT means.

Multistep Model of Cervical Cancer: Participation of miRNAs and Coding Genes

PubMed Central

López, Angelica Judith Granados; López, Jesús Adrián

2014-01-01

Aberrant miRNA expression is well recognized as an important step in the development of cancer. Close to 70 microRNAs (miRNAs) have been implicated in cervical cancer up to now, nevertheless it is unknown if aberrant miRNA expression causes the onset of cervical cancer. One of the best ways to address this issue is through a multistep model of carcinogenesis. In the progression of cervical cancer there are three well-established steps to reach cancer that we used in the model proposed here. The first step of the model comprises the gene changes that occur in normal cells to be transformed into immortal cells (CIN 1), the second comprises immortal cell changes to tumorigenic cells (CIN 2), the third step includes cell changes to increase tumorigenic capacity (CIN 3), and the final step covers tumorigenic changes to carcinogenic cells. Altered miRNAs and their target genes are located in each one of the four steps of the multistep model of carcinogenesis. miRNA expression has shown discrepancies in different works; therefore, in this model we include miRNAs recording similar results in at least two studies. The present model is a useful insight into studying potential prognostic, diagnostic, and therapeutic miRNAs. PMID:25192291

Interstitial diffusion and the relationship between compartment modelling and multi-scale spatial-temporal modelling of (18)F-FLT tumour uptake dynamics.

PubMed

Liu, Dan; Chalkidou, Anastasia; Landau, David B; Marsden, Paul K; Fenwick, John D

2014-09-07

Tumour cell proliferation can be imaged via positron emission tomography of the radiotracer 3'-deoxy-3'-18F-fluorothymidine (18F-FLT). Conceptually, the number of proliferating cells might be expected to correlate more closely with the kinetics of 18F-FLT uptake than with uptake at a fixed time. Radiotracer uptake kinetics are standardly visualized using parametric maps of compartment model fits to time-activity-curves (TACs) of individual voxels. However the relationship between the underlying spatiotemporal accumulation of FLT and the kinetics described by compartment models has not yet been explored. In this work tumour tracer uptake is simulated using a mechanistic spatial-temporal model based on a convection-diffusion-reaction equation solved via the finite difference method. The model describes a chain of processes: the flow of FLT between the spatially heterogeneous tumour vasculature and interstitium; diffusion and convection of FLT within the interstitium; transport of FLT into cells; and intracellular phosphorylation. Using values of model parameters estimated from the biological literature, simulated FLT TACs are generated with shapes and magnitudes similar to those seen clinically. Results show that the kinetics of the spatial-temporal model can be recovered accurately by fitting a 3-tissue compartment model to FLT TACs simulated for those tumours or tumour sub-volumes that can be viewed as approximately closed, for which tracer diffusion throughout the interstitium makes only a small fractional change to the quantity of FLT they contain. For a single PET voxel of width 2.5-5 mm we show that this condition is roughly equivalent to requiring that the relative difference in tracer uptake between the voxel and its neighbours is much less than one.

Interpretable dimensionality reduction of single cell transcriptome data with deep generative models.

PubMed

Ding, Jiarui; Condon, Anne; Shah, Sohrab P

2018-05-21

Single-cell RNA-sequencing has great potential to discover cell types, identify cell states, trace development lineages, and reconstruct the spatial organization of cells. However, dimension reduction to interpret structure in single-cell sequencing data remains a challenge. Existing algorithms are either not able to uncover the clustering structures in the data or lose global information such as groups of clusters that are close to each other. We present a robust statistical model, scvis, to capture and visualize the low-dimensional structures in single-cell gene expression data. Simulation results demonstrate that low-dimensional representations learned by scvis preserve both the local and global neighbor structures in the data. In addition, scvis is robust to the number of data points and learns a probabilistic parametric mapping function to add new data points to an existing embedding. We then use scvis to analyze four single-cell RNA-sequencing datasets, exemplifying interpretable two-dimensional representations of the high-dimensional single-cell RNA-sequencing data.

A quantitative systems approach to identify paracrine mechanisms that locally suppress immune response to Interleukin-12 in the B16 melanoma model

PubMed Central

Kulkarni, Yogesh M.; Chambers, Emily; McGray, A. J. Robert; Ware, Jason S.; Bramson, Jonathan L.

2012-01-01

Interleukin-12 (IL12) enhances anti-tumor immunity when delivered to the tumor microenvironment. However, local immunoregulatory elements dampen the efficacy of IL12. The identity of these local mechanisms used by tumors to suppress immunosurveillance represents a key knowledge gap for improving tumor immunotherapy. From a systems perspective, local suppression of anti-tumor immunity is a closed-loop system - where system response is determined by an unknown combination of external inputs and local cellular cross-talk. Here, we recreated this closed-loop system in vitro and combined quantitative high content assays, in silico model-based inference, and a proteomic workflow to identify the biochemical cues responsible for immunosuppression. Following an induction period, the B16 melanoma cell model, a transplantable model for spontaneous malignant melanoma, inhibited the response of a T helper cell model to IL12. This paracrine effect was not explained by induction of apoptosis or creation of a cytokine sink, despite both mechanisms present within the co-culture assay. Tumor-derived Wnt-inducible signaling protein-1 (WISP-1) was identified to exert paracrine action on immune cells by inhibiting their response to IL12. Moreover, WISP-1 was expressed in vivo following intradermal challenge with B16F10 cells and was inferred to be expressed at the tumor periphery. Collectively, the data suggest that (1) biochemical cues associated with epithelial-to-mesenchymal transition can shape anti-tumor immunity through paracrine action and (2) remnants of the immunoselective pressure associated with evolution in cancer include both sculpting of tumor antigens and expression of proteins that proactively shape anti-tumor immunity. PMID:22777646

A neural network based computational model to predict the output power of different types of photovoltaic cells.

PubMed

Xiao, WenBo; Nazario, Gina; Wu, HuaMing; Zhang, HuaMing; Cheng, Feng

2017-01-01

In this article, we introduced an artificial neural network (ANN) based computational model to predict the output power of three types of photovoltaic cells, mono-crystalline (mono-), multi-crystalline (multi-), and amorphous (amor-) crystalline. The prediction results are very close to the experimental data, and were also influenced by numbers of hidden neurons. The order of the solar generation power output influenced by the external conditions from smallest to biggest is: multi-, mono-, and amor- crystalline silicon cells. In addition, the dependences of power prediction on the number of hidden neurons were studied. For multi- and amorphous crystalline cell, three or four hidden layer units resulted in the high correlation coefficient and low MSEs. For mono-crystalline cell, the best results were achieved at the hidden layer unit of 8.

Rectified directional sensing in long-range cell migration

PubMed Central

Nakajima, Akihiko; Ishihara, Shuji; Imoto, Daisuke; Sawai, Satoshi

2014-01-01

How spatial and temporal information are integrated to determine the direction of cell migration remains poorly understood. Here, by precise microfluidics emulation of dynamic chemoattractant waves, we demonstrate that, in Dictyostelium, directional movement as well as activation of small guanosine triphosphatase Ras at the leading edge is suppressed when the chemoattractant concentration is decreasing over time. This ‘rectification’ of directional sensing occurs only at an intermediate range of wave speed and does not require phosphoinositide-3-kinase or F-actin. From modelling analysis, we show that rectification arises naturally in a single-layered incoherent feedforward circuit with zero-order ultrasensitivity. The required stimulus time-window predicts ~5 s transient for directional sensing response close to Ras activation and inhibitor diffusion typical for protein in the cytosol. We suggest that the ability of Dictyostelium cells to move only in the wavefront is closely associated with rectification of adaptive response combined with local activation and global inhibition. PMID:25373620

Aberrant AKT activation drives well-differentiated liposarcoma

PubMed Central

Gutierrez, Alejandro; Snyder, Eric L.; Marino-Enriquez, Adrian; Zhang, Yi-Xiang; Sioletic, Stefano; Kozakewich, Elena; Grebliunaite, Ruta; Ou, Wen-bin; Sicinska, Ewa; Raut, Chandrajit P.; Demetri, George D.; Perez-Atayde, Antonio R.; Wagner, Andrew J.; Fletcher, Jonathan A.; Fletcher, Christopher D. M.; Look, A. Thomas

2011-01-01

Well-differentiated liposarcoma (WDLPS), one of the most common human sarcomas, is poorly responsive to radiation and chemotherapy, and the lack of animal models suitable for experimental analysis has seriously impeded functional investigation of its pathobiology and development of effective targeted therapies. Here, we show that zebrafish expressing constitutively active Akt2 in mesenchymal progenitors develop WDLPS that closely resembles the human disease. Tumor incidence rates were 8% in p53 wild-type zebrafish, 6% in p53 heterozygotes, and 29% in p53-homozygous mutant zebrafish (P = 0.013), indicating that aberrant Akt activation collaborates with p53 mutation in WDLPS pathogenesis. Analysis of primary clinical specimens of WDLPS, and of the closely related dedifferentiated liposarcoma (DDLPS) subtype, revealed immunohistochemical evidence of AKT activation in 27% of cases. Western blot analysis of a panel of cell lines derived from patients with WDLPS or DDLPS revealed robust AKT phosphorylation in all cell lines examined, even when these cells were cultured in serum-free media. Moreover, BEZ235, a small molecule inhibitor of PI3K and mammalian target of rapamycin that effectively inhibits AKT activation in these cells, impaired viability at nanomolar concentrations. Our findings are unique in providing an animal model to decipher the molecular pathogenesis of WDLPS, and implicate AKT as a previously unexplored therapeutic target in this chemoresistant sarcoma. PMID:21930930

Neural Differentiation of Human Pluripotent Stem Cells for Nontherapeutic Applications: Toxicology, Pharmacology, and In Vitro Disease Modeling

PubMed Central

Yap, May Shin; Nathan, Kavitha R.; Yeo, Yin; Poh, Chit Laa; Richards, Mark; Lim, Wei Ling; Othman, Iekhsan; Heng, Boon Chin

2015-01-01

Human pluripotent stem cells (hPSCs) derived from either blastocyst stage embryos (hESCs) or reprogrammed somatic cells (iPSCs) can provide an abundant source of human neuronal lineages that were previously sourced from human cadavers, abortuses, and discarded surgical waste. In addition to the well-known potential therapeutic application of these cells in regenerative medicine, these are also various promising nontherapeutic applications in toxicological and pharmacological screening of neuroactive compounds, as well as for in vitro modeling of neurodegenerative and neurodevelopmental disorders. Compared to alternative research models based on laboratory animals and immortalized cancer-derived human neural cell lines, neuronal cells differentiated from hPSCs possess the advantages of species specificity together with genetic and physiological normality, which could more closely recapitulate in vivo conditions within the human central nervous system. This review critically examines the various potential nontherapeutic applications of hPSC-derived neuronal lineages and gives a brief overview of differentiation protocols utilized to generate these cells from hESCs and iPSCs. PMID:26089911

Wnt-Responsive Cancer Stem Cells Are Located Close to Distorted Blood Vessels and Not in Hypoxic Regions in a p53-Null Mouse Model of Human Breast Cancer

PubMed Central

Landua, John D.; Bu, Wen; Wei, Wei; Li, Fuhai; Wong, Stephen T.C.; Dickinson, Mary E.; Rosen, Jeffrey M.; Lewis, Michael T.

2014-01-01

Cancer stem cells (CSCs, or tumor-initiating cells) may be responsible for tumor formation in many types of cancer, including breast cancer. Using high-resolution imaging techniques, we analyzed the relationship between a Wnt-responsive, CSC-enriched population and the tumor vasculature using p53-null mouse mammary tumors transduced with a lentiviral Wnt signaling reporter. Consistent with their localization in the normal mammary gland, Wnt-responsive cells in tumors were enriched in the basal/myoepithelial population and generally located in close proximity to blood vessels. The Wnt-responsive CSCs did not colocalize with the hypoxia-inducible factor 1α-positive cells in these p53-null basal-like tumors. Average vessel diameter and vessel tortuosity were increased in p53-null mouse tumors, as well as in a human tumor xenograft as compared with the normal mammary gland. The combined strategy of monitoring the fluorescently labeled CSCs and vasculature using high-resolution imaging techniques provides a unique opportunity to study the CSC and its surrounding vasculature. PMID:24797826

Efficiency of bulk-heterojunction organic solar cells

PubMed Central

Scharber, M.C.; Sariciftci, N.S.

2013-01-01

During the last years the performance of bulk heterojunction solar cells has been improved significantly. For a large-scale application of this technology further improvements are required. This article reviews the basic working principles and the state of the art device design of bulk heterojunction solar cells. The importance of high power conversion efficiencies for the commercial exploitation is outlined and different efficiency models for bulk heterojunction solar cells are discussed. Assuming state of the art materials and device architectures several models predict power conversion efficiencies in the range of 10–15%. A more general approach assuming device operation close to the Shockley–Queisser-limit leads to even higher efficiencies. Bulk heterojunction devices exhibiting only radiative recombination of charge carriers could be as efficient as ideal inorganic photovoltaic devices. PMID:24302787

PV cells electrical parameters measurement

NASA Astrophysics Data System (ADS)

Cibira, Gabriel

2017-12-01

When measuring optical parameters of a photovoltaic silicon cell, precise results bring good electrical parameters estimation, applying well-known physical-mathematical models. Nevertheless, considerable re-combination phenomena might occur in both surface and intrinsic thin layers within novel materials. Moreover, rear contact surface parameters may influence close-area re-combination phenomena, too. Therefore, the only precise electrical measurement approach is to prove assumed cell electrical parameters. Based on theoretical approach with respect to experiments, this paper analyses problems within measurement procedures and equipment used for electrical parameters acquisition within a photovoltaic silicon cell, as a case study. Statistical appraisal quality is contributed.

Human induced pluripotent stem cell-derived hepatic cell lines as a new model for host interaction with hepatitis B virus

PubMed Central

Kaneko, Shun; Kakinuma, Sei; Asahina, Yasuhiro; Kamiya, Akihide; Miyoshi, Masato; Tsunoda, Tomoyuki; Nitta, Sayuri; Asano, Yu; Nagata, Hiroko; Otani, Satoshi; Kawai-Kitahata, Fukiko; Murakawa, Miyako; Itsui, Yasuhiro; Nakagawa, Mina; Azuma, Seishin; Nakauchi, Hiromitsu; Nishitsuji, Hironori; Ujino, Saneyuki; Shimotohno, Kunitada; Iwamoto, Masashi; Watashi, Koichi; Wakita, Takaji; Watanabe, Mamoru

2016-01-01

Hepatitis B virus (HBV) is not eradicated by current antiviral therapies due to persistence of HBV covalently closed circular DNA (cccDNA) in host cells, and thus development of novel culture models for productive HBV infection is urgently needed, which will allow the study of HBV cccDNA eradication. To meet this need, we developed culture models of HBV infection using human induced pluripotent stem cell-derived hepatocyte lineages, including immature proliferating hepatic progenitor-like cell lines (iPS-HPCs) and differentiated hepatocyte-like cells (iPS-Heps). These cells were susceptible to HBV infection, produced HBV particles, and maintained innate immune responses. The infection efficiency of HBV in iPS-HPCs predominantly depended on the expression levels of sodium taurocholate cotransporting polypeptide (NTCP), and was low relative to iPS-Heps: however, long-term culture of iPS-Heps was difficult. To provide a model for HBV persistence, iPS-HPCs overexpressing NTCP were established. The long-term persistence of HBV cccDNA was detected in iPS-HPCs overexpressing NTCP, and depended on the inhibition of the Janus-kinase signaling pathway. In conclusion, this study provides evidence that iPS-derived hepatic cell lines can be utilized for novel HBV culture models with genetic variation to investigate the interactions between HBV and host cells and the development of anti-HBV strategies. PMID:27386799

Generals die in friendly fire, or modeling immune response to HIV

NASA Astrophysics Data System (ADS)

Rouzine, Igor M.; Murali-Krishna, Kaja; Ahmed, Rafi

2005-12-01

We develop a kinetic model for CD8 T lymphocytes (CTL) whose purpose is to kill cells infected with viruses and intracellular parasites. Using a set of first-order nonlinear differential equations, the model predicts how numbers of different cell types involved in CTL response depend on time. The model postulates that CTL response requires continuous presence of professional antigen-presenting cells (APC) comprised of macrophages and dendritic cells. It assumes that any virus present in excess of a threshold level activates APC that, in turn, activate CTL that expand in number and become armed "effector" cells. In the end, APC are deactivated after virus is cleared. The lack of signal from APC causes effector cells to differentiate, by default, into "transitory cells" that either die, or, in a small part, become long-lived memory cells. Viruses capable of infecting APC will cause premature retirement of effector CTL. If transitory cells encounter virus, which takes place after the premature depletion, CTL become anergic (unresponsive to external stimuli). The model is designed to fit recent experiments on primary CTL response to simian immunodeficiency virus closely related to HIV and lymphocytic choriomeningitis virus. The two viruses are known to infect APC and make them targets for CTL they are supposed to control. Both viruses cause premature depletion and anergy of CTL and persist in the host for life.

How do generalized jamming transitions affect collective migration in confluent tissues?

NASA Astrophysics Data System (ADS)

Manning, M. Lisa

Recent experiments have demonstrated that tissues involved in embryonic development, lung function, wound healing, and cancer progression are close to fluid-to-solid, or ``jamming'' transitions. Theoretical models for confluent 2D tissues have also been shown to exhibit continuous rigidity transitions. However, in vivobiological systems can differ in significant ways from the simple 2D models. For example, many tissues are three-dimensional, mechanically heterogeneous, and/or composed of mechanosensitive cells interspersed with extracellular matrix. We have extended existing models for confluent tissues to capture these features, and we find interesting predictions for collective cell motion that are ultimately related to an underlying generalized jamming transition. For example, in 2D, we find that heterogeneous mixtures of cells spontaneously self-organize into rigid regions of stiffer cells interspersed with string-like groups of soft cells, reminiscent of cellular streaming seen in cancer. We also find that alignment interactions (of the sort often explored in self-propelled particle models) alter the transition and generate interesting flocked liquid and flocked solid collective migration patterns. Our model predicts that 3D tissues also exhibit a jamming transition governed by cell shape, as well as history-dependent aging, and we are currently exploring whether ECM-like interactions in 3D models might help explain compressional stiffening seen in experiments on human tissue.

T Cells Are Not Required for Pathogenesis in the Syrian Hamster Model of Hantavirus Pulmonary Syndrome ▿

PubMed Central

Hammerbeck, Christopher D.; Hooper, Jay W.

2011-01-01

Andes virus (ANDV) is associated with a lethal vascular leak syndrome in humans termed hantavirus pulmonary syndrome (HPS). In hamsters, ANDV causes a respiratory distress syndrome closely resembling human HPS. The mechanism for the massive vascular leakage associated with HPS is poorly understood; however, T cell immunopathology has been implicated on the basis of circumstantial and corollary evidence. Here, we show that following ANDV challenge, hamster T cell activation corresponds with the onset of disease. However, treatment with cyclophosphamide or specific T cell depletion does not impact the course of disease or alter the number of surviving animals, despite significant reductions in T cell number. These data demonstrate, for the first time, that T cells are not required for hantavirus pathogenesis in the hamster model of human HPS. Depletion of T cells from Syrian hamsters did not significantly influence early events in disease progression. Moreover, these data argue for a mechanism of hantavirus-induced vascular permeability that does not involve T cell immunopathology. PMID:21775442

T cells are not required for pathogenesis in the Syrian hamster model of hantavirus pulmonary syndrome.

PubMed

Hammerbeck, Christopher D; Hooper, Jay W

2011-10-01

Andes virus (ANDV) is associated with a lethal vascular leak syndrome in humans termed hantavirus pulmonary syndrome (HPS). In hamsters, ANDV causes a respiratory distress syndrome closely resembling human HPS. The mechanism for the massive vascular leakage associated with HPS is poorly understood; however, T cell immunopathology has been implicated on the basis of circumstantial and corollary evidence. Here, we show that following ANDV challenge, hamster T cell activation corresponds with the onset of disease. However, treatment with cyclophosphamide or specific T cell depletion does not impact the course of disease or alter the number of surviving animals, despite significant reductions in T cell number. These data demonstrate, for the first time, that T cells are not required for hantavirus pathogenesis in the hamster model of human HPS. Depletion of T cells from Syrian hamsters did not significantly influence early events in disease progression. Moreover, these data argue for a mechanism of hantavirus-induced vascular permeability that does not involve T cell immunopathology.

Comparison of closed-cell and hybrid-cell stent designs in carotid artery stenting: clinical and procedural outcomes

PubMed Central

Tatli, Ersan; Vatan, Mehmet Bulent; Agac, Mustafa Tarik; Gunduz, Huseyin; Akdemir, Ramazan; Kilic, Harun

2017-01-01

Introduction Carotid artery stenting (CAS) is a promising alternative to surgery in high-risk patients. However, the impact of stent cell design on outcomes in CAS is a matter of continued debate. Aim To compare the periprocedural and clinical outcomes of different stent designs for CAS with distal protection devices. Material and methods All CAS procedures with both closed- and hybrid-cell stents performed at our institution between February 2010 and December 2015 were analyzed retrospectively. Adverse events were defined as death, major stroke, minor stroke, transient ischemic attack and myocardial infarction. Periprocedural and 30-day adverse events and internal carotid artery (ICA) vasospasm rates were compared between the closed-cell and hybrid-cell stent groups. Results The study included 234 patients comprising 146 patients with a closed-cell stent (Xact stent, Abbott Vascular) (mean age: 68.5 ±8.6; 67.1% male) and 88 patients with a hybrid-cell stent (Cristallo Ideale, Medtronic) (mean age: 67.2 ±12.8; 68.2% male). There was no significant difference between the groups with respect to periprocedural or 30-day adverse event rates. While there was no difference in terms of tortuosity index between the groups, there was a higher procedural ICA vasospasm rate in the closed-cell stent group (35 patients, 23%) compared with the hybrid-cell stent group (10 patients, 11%) (p = 0.017). Conclusions The results of this study showed no significant difference in the clinical adverse event rates after CAS between the closed-cell stent group and the hybrid-cell stent group. However, procedural ICA vasospasm was more common in the closed-cell stent group. PMID:28798784

SPH simulations of WBC adhesion to the endothelium: the role of haemodynamics and endothelial binding kinetics.

PubMed

Gholami, Babak; Comerford, Andrew; Ellero, Marco

2015-11-01

A multiscale Lagrangian particle solver introduced in our previous work is extended to model physiologically realistic near-wall cell dynamics. Three-dimensional simulation of particle trajectories is combined with realistic receptor-ligand adhesion behaviour to cover full cell interactions in the vicinity of the endothelium. The selected stochastic adhesion model, which is based on a Monte Carlo acceptance-rejection method, fits in our Lagrangian framework and does not compromise performance. Additionally, appropriate inflow/outflow boundary conditions are implemented for our SPH solver to enable realistic pulsatile flow simulation. The model is tested against in-vitro data from a 3D geometry with a stenosis and sudden expansion. In both steady and pulsatile flow conditions, results show close agreement with the experimental ones. Furthermore we demonstrate, in agreement with experimental observations, that haemodynamics alone does not account for adhesion of white blood cells, in this case U937 monocytic human cells. Our findings suggest that the current framework is fully capable of modelling cell dynamics in large arteries in a realistic and efficient manner.

Closed-form solution of the Ogden-Hill's compressible hyperelastic model for ramp loading

NASA Astrophysics Data System (ADS)

Berezvai, Szabolcs; Kossa, Attila

2017-05-01

This article deals with the visco-hyperelastic modelling approach for compressible polymer foam materials. Polymer foams can exhibit large elastic strains and displacements in case of volumetric compression. In addition, they often show significant rate-dependent properties. This material behaviour can be accurately modelled using the visco-hyperelastic approach, in which the large strain viscoelastic description is combined with the rate-independent hyperelastic material model. In case of polymer foams, the most widely used compressible hyperelastic material model, the so-called Ogden-Hill's model, was applied, which is implemented in the commercial finite element (FE) software Abaqus. The visco-hyperelastic model is defined in hereditary integral form, therefore, obtaining a closed-form solution for the stress is not a trivial task. However, the parameter-fitting procedure could be much faster and accurate if closed-form solution exists. In this contribution, exact stress solutions are derived in case of uniaxial, biaxial and volumetric compression loading cases using ramp-loading history. The analytical stress solutions are compared with the stress results in Abaqus using FE analysis. In order to highlight the benefits of the analytical closed-form solution during the parameter-fitting process experimental work has been carried out on a particular open-cell memory foam material. The results of the material identification process shows significant accuracy improvement in the fitting procedure by applying the derived analytical solutions compared to the so-called separated approach applied in the engineering practice.

Modelling wound closure in an epithelial cell sheet using the cellular Potts model.

PubMed

Noppe, Adrian R; Roberts, Anthony P; Yap, Alpha S; Gomez, Guillermo A; Neufeld, Zoltan

2015-10-01

We use a two-dimensional cellular Potts model to represent the behavior of an epithelial cell layer and describe its dynamics in response to a microscopic wound. Using an energy function to describe properties of the cells, we found that the interaction between contractile tension along cell-cell junctions and cell-cell adhesion plays an important role not only in determining the dynamics and morphology of cells in the monolayer, but also in influencing whether or not a wound in the monolayer will close. Our results suggest that, depending on the balance between cell-cell adhesion and junctional tension, mechanics of the monolayer can either correspond to a hard or a soft regime that determines cell morphology and polygonal organization in the monolayer. Moreover, the presence of a wound in a hard regime, where junctional tension is significant, can lead to two results: (1) wound closure or (2) an initial increase and expansion of the wound area towards an equilibrium value. Theoretical approximations and simulations allowed us to determine the thresholds in the values of cell-cell adhesion and initial wound size that allow the system to lead to wound closure. Overall, our results suggest that around the site of injury, changes in the balance between contraction and adhesion determine whether or not non-monotonous wound closure occurs.

Use of HyperCard to Simulate a Tissue Culture Laboratory.

ERIC Educational Resources Information Center

Nester, Bradley S.; Turney, Tully H.

1992-01-01

Describes the use of a Macintosh computer and HyperCard software to create an introduction to cell culture techniques that closely approximates a hands-on laboratory experiment. Highlights include data acquisition, data analysis, the generation of growth curves, and electronic modeling. (LRW)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alparslan, Burcu, E-mail: burcu.alparslan@gmail.com; Nas, Omer Fatih, E-mail: omerfatihnas@gmail.com; Eritmen, Ulku Turpcu, E-mail: drulkutur@hotmail.com.tr

PurposeThe aim of this study was to investigate the effect of stent cell geometry on midterm results of carotid artery stenting (CAS).Materials and MethodOne hundred fifty-five patients underwent CAS between February 2010 and December 2012. Ninety-one open- and 84 closed-cell stents were used in this non-randomized, retrospective study. Periprocedural complications were defined as the ones happened during the procedure or within 30 days afterwards. Starting from the 6th month after the procedure, in-stent restenosis was detected with multidetector computed tomography angiography and classified into four groups from focal restenosis to occlusion.ResultsEleven complications were encountered in the periprocedural period (four on themore » open- and seven on the closed-cell group). Total complication rate was 6.3 % (11/175). No significant difference was detected in terms of periprocedural complications between two groups (p = 0.643). There was statistically significant difference between stent design groups in regard to radiological findings (p = 0.002). Sixteen of open-cell stents and three of closed-cell stents had focal restenosis. One closed-cell stent had diffuse proliferative restenosis and one open-cell stent had total occlusion.ConclusionIn-stent restenosis was more common in open-cell stent group, which have larger free cell area than closed-cell stents. Although our radiologic findings promote us to use closed-cell design if ‘possible’, no difference was detected in terms of clinical outcomes.« less

Design and testing of botanical thermotropic actuator mechanisms in thermally adaptive building coverings

NASA Astrophysics Data System (ADS)

Barrett, Ronald M.; Barrett, Ronald P.; Barrett, Cassandra M.

2017-09-01

This paper lays out the inspiration, operational principles, analytical modeling and coupon testing of a new class of thermally adaptive building coverings. The fundamental driving concepts for these coverings are derived from various families of thermotropic plant structures. Certain plant cellular structures like those in Mimosa pudica (Sensitive Plant), Rhododendron leaves or Albizia julibrissin (Mimosa Tree), exhibit actuation physiology which depends on changes in cellular turgor pressures to generate motion. This form of cellular action via turgor pressure manipulation is an inspiration for a new field of thermally adaptive building coverings which use various forms of cellular foam to aid or enable actuation much like plant cells are used to move leaves. When exposed to high solar loading, the structures use the inherent actuation capability of pockets of air trapped in closed cell foam as actuators to curve plates upwards and outwards. When cold, these same structures curve back towards the building forming large convex pockets of dead air to insulate the building. This paper describes basic classical laminated plate theory models comparing theory and experiment of such coupons containing closed-cell foam actuators. The study concludes with a global description of the effectiveness of this class of thermally adaptive building coverings.

Biofabricated constructs as tissue models: a short review.

PubMed

Costa, Pedro F

2015-04-01

Biofabrication is currently able to provide reliable models for studying the development of cells and tissues into multiple environments. As the complexity of biofabricated constructs is becoming increasingly higher their ability to closely mimic native tissues and organs is also increasing. Various biofabrication technologies currently allow to precisely build cell/tissue constructs at multiple dimension ranges with great accuracy. Such technologies are also able to assemble together multiple types of cells and/or materials and generate constructs closely mimicking various types of tissues. Furthermore, the high degree of automation involved in these technologies enables the study of large arrays of testing conditions within increasingly smaller and automated devices both in vitro and in vivo. Despite not yet being able to generate constructs similar to complex tissues and organs, biofabrication is rapidly evolving in that direction. One major hurdle to be overcome in order for such level of complex detail to be achieved is the ability to generate complex vascular structures within biofabricated constructs. This review describes several of the most relevant technologies and methodologies currently utilized within biofabrication and provides as well a brief overview of their current and future potential applications.

Evaluating the feasibility of global climate models to simulate cloud cover effect controlled by Marine Stratocumulus regime transitions

NASA Astrophysics Data System (ADS)

Goren, Tom; Muelmenstaedt, Johannes; Rosenfeld, Daniel; Quaas, Johannes

2017-04-01

Marine stratocumulus clouds (MSC) occur in two main cloud regimes of open and closed cells that differ significantly by their cloud cover. Closed cells gradually get cleansed of high CCN concentrations in a process that involves initiation of drizzle that breaks the full cloud cover into open cells. The drizzle creates downdrafts that organize the convection along converging gust fronts, which in turn produce stronger updrafts that can sustain more cloud water that compensates the depletion of the cloud water by the rain. In addition, having stronger updrafts allow the clouds to grow relatively deep before rain starts to deplete its cloud water. Therefore, lower droplet concentrations and stronger rain would lead to lower cloud fraction, but not necessary also to lower liquid water path (LWP). The fundamental relationships between these key variables derived from global climate model (GCM) simulations are analyzed with respect to observations in order to determine whether the GCM parameterizations can represent well the governing physical mechanisms upon MSC regime transitions. The results are used to evaluate the feasibility of GCM's for estimating aerosol cloud-mediated radiative forcing upon MSC regime transitions, which are responsible for the largest aerosol cloud-mediated radiative forcing.

Closed Large Cell Clouds

Atmospheric Science Data Center

2013-04-19

article title:  Closed Large Cell Clouds in the South Pacific ... the Multi-angle Imaging SpectroRadiometer (MISR) provide an example of very large scale closed cells, and can be contrasted with the  ... MD. The MISR data were obtained from the NASA Langley Research Center Atmospheric Science Data Center in Hampton, VA. Image ...

40 CFR 98.436 - Data reporting requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.436 Data reporting requirements. (a) Each importer of fluorinated GHGs contained in pre-charged equipment or closed-cell foams must submit an annual...) Total mass in metric tons of each fluorinated GHG imported in pre-charged equipment or closed-cell foams...

40 CFR 98.436 - Data reporting requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.436 Data reporting requirements. (a) Each importer of fluorinated GHGs contained in pre-charged equipment or closed-cell foams must submit an annual...) Total mass in metric tons of each fluorinated GHG imported in pre-charged equipment or closed-cell foams...

40 CFR 98.436 - Data reporting requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.436 Data reporting requirements. (a) Each importer of fluorinated GHGs contained in pre-charged equipment or closed-cell foams must submit an annual...) Total mass in metric tons of each fluorinated GHG imported in pre-charged equipment or closed-cell foams...

Fabrication and Compressive Properties of Low to Medium Porosity Closed-Cell Porous Aluminum Using PMMA Space Holder Technique

PubMed Central

Jamal, Nur Ayuni; Tan, Ai Wen; Yusof, Farazila; Katsuyoshi, Kondoh; Hisashi, Imai; Singh, S.; Anuar, Hazleen

2016-01-01

In recent years, closed-cell porous Aluminum (Al) has drawn increasing attention, particularly in the applications requiring reduced weight and energy absorption capability such as in the automotive and aerospace industries. In the present work, porous Al with closed-cell structure was successfully fabricated by powder metallurgy technique using PMMA as a space holder. The effects of the amount of PMMA powder on the porosity, density, microstructure and compressive behaviors of the porous specimens were systematically evaluated. The results showed that closed-cell porous Al having different porosities (12%–32%) and densities (1.6478 g/cm3, 1.5125 g/cm3 and 1.305 g/cm3) could be produced by varying the amount of PMMA (20–30 wt %). Meanwhile, the compressive behavior results demonstrated that the plateau stress decreased and the energy absorption capacity increased with increasing amount of PMMA. However, the maximum energy absorption capacity was achieved in the closed-cell porous Al with the addition of 25 wt % PMMA. Therefore, fabrication of closed-cell porous Al using 25 wt % PMMA is considered as the optimal condition in the present study since the resultant closed-cell porous Al possessed good combinations of porosity, density and plateau stress, as well as energy absorption capacity. PMID:28773377

Mutation that blocks ATP binding creates a pseudokinase stabilizing the scaffolding function of kinase suppressor of Ras, CRAF and BRAF.

PubMed

Hu, Jiancheng; Yu, Haiyang; Kornev, Alexandr P; Zhao, Jianping; Filbert, Erin L; Taylor, Susan S; Shaw, Andrey S

2011-04-12

Because mutations in RAS and BRAF represent the most common mutations found in human tumors, identification of inhibitors has been a major goal. Surprisingly, new oncogenic BRAF specific inhibitors inhibit cells transformed with mutated BRAF but paradoxically stimulate the growth of cells transformed with RAS. Here, we show that the mechanism for activation is via drug-induced dimer formation between CRAF and kinase suppressor of Ras (KSR)1. To understand the function of KSR1, we generated a KSR1 mutant that cannot bind ATP but stabilizes the closed, active conformation of KSR1. Molecular modeling suggested that the mutant stabilizes the two hydrophobic spines critical for the closed active conformation. We, therefore, could use the mutant to discriminate between the scaffold versus kinase functions of KSR1. The KSR1 mutant bound constitutively to RAF and mitogen-activated protein kinase kinase (MEK) but could not reconstitute activity suggesting that the catalytic activity of KSR1 is required for its function. Analogous mutations in BRAF and CRAF allowed us to test the generality of the model. The mutation induced changes consistent with the active, closed conformation of both kinases and confirmed that BRAF functions distinctly from CRAF in the MAP kinase pathway. Not only does this work suggest that KSR1 may function as a kinase, we anticipate that the mutation that we generated may be broadly applicable to stabilize the closed conformation of other kinases many of which may also form dimers.

Detailed Multi-dimensional Modeling of Direct Internal Reforming Solid Oxide Fuel Cells.

PubMed

Tseronis, K; Fragkopoulos, I S; Bonis, I; Theodoropoulos, C

2016-06-01

Fuel flexibility is a significant advantage of solid oxide fuel cells (SOFCs) and can be attributed to their high operating temperature. Here we consider a direct internal reforming solid oxide fuel cell setup in which a separate fuel reformer is not required. We construct a multidimensional, detailed model of a planar solid oxide fuel cell, where mass transport in the fuel channel is modeled using the Stefan-Maxwell model, whereas the mass transport within the porous electrodes is simulated using the Dusty-Gas model. The resulting highly nonlinear model is built into COMSOL Multiphysics, a commercial computational fluid dynamics software, and is validated against experimental data from the literature. A number of parametric studies is performed to obtain insights on the direct internal reforming solid oxide fuel cell system behavior and efficiency, to aid the design procedure. It is shown that internal reforming results in temperature drop close to the inlet and that the direct internal reforming solid oxide fuel cell performance can be enhanced by increasing the operating temperature. It is also observed that decreases in the inlet temperature result in smoother temperature profiles and in the formation of reduced thermal gradients. Furthermore, the direct internal reforming solid oxide fuel cell performance was found to be affected by the thickness of the electrochemically-active anode catalyst layer, although not always substantially, due to the counter-balancing behavior of the activation and ohmic overpotentials.

Numerical Simulation of Multiphase Magnetohydrodynamic Flow and Deformation of Electrolyte-Metal Interface in Aluminum Electrolysis Cells

NASA Astrophysics Data System (ADS)

Hua, Jinsong; Rudshaug, Magne; Droste, Christian; Jorgensen, Robert; Giskeodegard, Nils-Haavard

2018-06-01

A computational fluid dynamics based multiphase magnetohydrodynamic (MHD) flow model for simulating the melt flow and bath-metal interface deformation in realistic aluminum reduction cells is presented. The model accounts for the complex physics of the MHD problem in aluminum reduction cells by coupling two immiscible fluids, electromagnetic field, Lorentz force, flow turbulence, and complex cell geometry with large length scale. Especially, the deformation of bath-metal interface is tracked directly in the simulation, and the condition of constant anode-cathode distance (ACD) is maintained by moving anode bottom dynamically with the deforming bath-metal interface. The metal pad deformation and melt flow predicted by the current model are compared to the predictions using a simplified model where the bath-metal interface is assumed flat. The effects of the induced electric current due to fluid flow and the magnetic field due to the interior cell current on the metal pad deformation and melt flow are investigated. The presented model extends the conventional simplified box model by including detailed cell geometry such as the ledge profile and all channels (side, central, and cross-channels). The simulations show the model sensitivity to different side ledge profiles and the cross-channel width by comparing the predicted melt flow and metal pad heaving. In addition, the model dependencies upon the reduction cell operation conditions such as ACD, current distribution on cathode surface and open/closed channel top, are discussed.

Detecting cell division of Pseudomonas aeruginosa bacteria from bright-field microscopy images with hidden conditional random fields.

PubMed

Ong, Lee-Ling S; Xinghua Zhang; Kundukad, Binu; Dauwels, Justin; Doyle, Patrick; Asada, H Harry

2016-08-01

An approach to automatically detect bacteria division with temporal models is presented. To understand how bacteria migrate and proliferate to form complex multicellular behaviours such as biofilms, it is desirable to track individual bacteria and detect cell division events. Unlike eukaryotic cells, prokaryotic cells such as bacteria lack distinctive features, causing bacteria division difficult to detect in a single image frame. Furthermore, bacteria may detach, migrate close to other bacteria and may orientate themselves at an angle to the horizontal plane. Our system trains a hidden conditional random field (HCRF) model from tracked and aligned bacteria division sequences. The HCRF model classifies a set of image frames as division or otherwise. The performance of our HCRF model is compared with a Hidden Markov Model (HMM). The results show that a HCRF classifier outperforms a HMM classifier. From 2D bright field microscopy data, it is a challenge to separate individual bacteria and associate observations to tracks. Automatic detection of sequences with bacteria division will improve tracking accuracy.

Glassy dynamics in three-dimensional embryonic tissues

PubMed Central

Schötz, Eva-Maria; Lanio, Marcos; Talbot, Jared A.; Manning, M. Lisa

2013-01-01

Many biological tissues are viscoelastic, behaving as elastic solids on short timescales and fluids on long timescales. This collective mechanical behaviour enables and helps to guide pattern formation and tissue layering. Here, we investigate the mechanical properties of three-dimensional tissue explants from zebrafish embryos by analysing individual cell tracks and macroscopic mechanical response. We find that the cell dynamics inside the tissue exhibit features of supercooled fluids, including subdiffusive trajectories and signatures of caging behaviour. We develop a minimal, three-parameter mechanical model for these dynamics, which we calibrate using only information about cell tracks. This model generates predictions about the macroscopic bulk response of the tissue (with no fit parameters) that are verified experimentally, providing a strong validation of the model. The best-fit model parameters indicate that although the tissue is fluid-like, it is close to a glass transition, suggesting that small changes to single-cell parameters could generate a significant change in the viscoelastic properties of the tissue. These results provide a robust framework for quantifying and modelling mechanically driven pattern formation in tissues. PMID:24068179

Stochastic modeling and experimental analysis of phenotypic switching and survival of cancer cells under stress

NASA Astrophysics Data System (ADS)

Zamani Dahaj, Seyed Alireza; Kumar, Niraj; Sundaram, Bala; Celli, Jonathan; Kulkarni, Rahul

The phenotypic heterogeneity of cancer cells is critical to their survival under stress. A significant contribution to heterogeneity of cancer calls derives from the epithelial-mesenchymal transition (EMT), a conserved cellular program that is crucial for embryonic development. Several studies have investigated the role of EMT in growth of early stage tumors into invasive malignancies. Also, EMT has been closely associated with the acquisition of chemoresistance properties in cancer cells. Motivated by these studies, we analyze multi-phenotype stochastic models of the evolution of cancers cell populations under stress. We derive analytical results for time-dependent probability distributions that provide insights into the competing rates underlying phenotypic switching (e.g. during EMT) and the corresponding survival of cancer cells. Experimentally, we evaluate these model-based predictions by imaging human pancreatic cancer cell lines grown with and without cytotoxic agents and measure growth kinetics, survival, morphological changes and (terminal evaluation of) biomarkers with associated epithelial and mesenchymal phenotypes. The results derived suggest approaches for distinguishing between adaptation and selection scenarios for survival in the presence of external stresses.

Toward a CRISPR Picture: Use of CRISPR/Cas9 to Model Diseases in Human Stem Cells In Vitro.

PubMed

Freiermuth, Jamie L; Powell-Castilla, Ian J; Gallicano, G Ian

2018-01-01

Human induced pluripotent stem cells (iPSCs) can be differentiated into any cell in the body unlocking enormous research potential. Combined with the recent discovery of CRISPR/Cas9 endonucleases in bacteria and their modification for use in biomedical research, these methods have the potential to revolutionize the field of genetic engineering and open the door to generating in vitro models that more closely resemble the in vivo system than ever before. Use of CRISPR/Cas9 has created a whirlwind within the scientific community in the last few years, as the race to move beyond just disease analysis and toward the goal of gene and cell therapy moves further. This review will detail the CRISPR/Cas9 method and its use in stem cells as well as highlight recent studies that demonstrate its use in creating robust disease models. Finally, recent results and current controversies in the field are reviewed and lingering challenges to further development are explored. J. Cell. Biochem. 119: 62-68, 2018. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

Non-linear Min protein interactions generate harmonics that signal mid-cell division in Escherichia coli

PubMed Central

Walsh, James C.; Angstmann, Christopher N.; Duggin, Iain G.

2017-01-01

The Min protein system creates a dynamic spatial pattern in Escherichia coli cells where the proteins MinD and MinE oscillate from pole to pole. MinD positions MinC, an inhibitor of FtsZ ring formation, contributing to the mid-cell localization of cell division. In this paper, Fourier analysis is used to decompose experimental and model MinD spatial distributions into time-dependent harmonic components. In both experiment and model, the second harmonic component is responsible for producing a mid-cell minimum in MinD concentration. The features of this harmonic are robust in both experiment and model. Fourier analysis reveals a close correspondence between the time-dependent behaviour of the harmonic components in the experimental data and model. Given this, each molecular species in the model was analysed individually. This analysis revealed that membrane-bound MinD dimer shows the mid-cell minimum with the highest contrast when averaged over time, carrying the strongest signal for positioning the cell division ring. This concurs with previous data showing that the MinD dimer binds to MinC inhibiting FtsZ ring formation. These results show that non-linear interactions of Min proteins are essential for producing the mid-cell positioning signal via the generation of second-order harmonic components in the time-dependent spatial protein distribution. PMID:29040283

Shape Transformation of the Nuclear Envelope during Closed Mitosis.

PubMed

Zhu, Qian; Zheng, Fan; Liu, Allen P; Qian, Jin; Fu, Chuanhai; Lin, Yuan

2016-11-15

The nuclear envelope (NE) in lower eukaryotes such as Schizosaccharomyces pombe undergoes large morphology changes during closed mitosis. However, which physical parameters are important in governing the shape evolution of the NE, and how defects in the dividing chromosomes/microtubules are reflected in those parameters, are fundamental questions that remain unresolved. In this study, we show that improper separation of chromosomes in genetically deficient cells leads to membrane tethering or asymmetric division in contrast to the formation of two equal-sized daughter nuclei in wild-type cells. We hypothesize that the poleward force is transmitted to the nuclear membrane through its physical contact with the separated sister chromatids at the two spindle poles. A theoretical model is developed to predict the morphology evolution of the NE where key factors such as the work done by the poleward force and bending and surface energies stored in the membrane have been taken into account. Interestingly, the predicted phase diagram, summarizing the dependence of nuclear shape on the size of the load transmission regions, and the pole-to-pole distance versus surface area relationship all quantitatively agree well with our experimental observations, suggesting that this model captures the essential physics involved in closed mitosis. Copyright © 2016 Biophysical Society. Published by Elsevier Inc. All rights reserved.

Mapping local and global variability in plant trait distributions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Butler, Ethan E.; Datta, Abhirup; Flores-Moreno, Habacuc

2017-12-01

Our ability to understand and predict the response of ecosystems to a changing environment depends on quantifying vegetation functional diversity. However, representing this diversity at the global scale is challenging. Typically, in Earth system models, characterization of plant diversity has been limited to grouping related species into plant functional types (PFTs), with all trait variation in a PFT collapsed into a single mean value that is applied globally. Using the largest global plant trait database and state of the art Bayesian modeling, we created fine-grained global maps of plant trait distributions that can be applied to Earth system models. Focusingmore » on a set of plant traits closely coupled to photosynthesis and foliar respiration—specific leaf area (SLA) and dry mass-based concentrations of leaf nitrogen (N m) and phosphorus (P m), we characterize how traits vary within and among over 50,000 ~50×50-km cells across the entire vegetated land surface. We do this in several ways—without defining the PFT of each grid cell and using 4 or 14 PFTs; each model’s predictions are evaluated against out-of-sample data. This endeavor advances prior trait mapping by generating global maps that preserve variability across scales by using modern Bayesian spatial statistical modeling in combination with a database over three times larger than that in previous analyses. Our maps further reveal that the most diverse grid cells possess trait variability close to the range of global PFT means.« less

Single cell isolation process with laser induced forward transfer.

PubMed

Deng, Yu; Renaud, Philippe; Guo, Zhongning; Huang, Zhigang; Chen, Ying

2017-01-01

A viable single cell is crucial for studies of single cell biology. In this paper, laser-induced forward transfer (LIFT) was used to isolate individual cell with a closed chamber designed to avoid contamination and maintain humidity. Hela cells were used to study the impact of laser pulse energy, laser spot size, sacrificed layer thickness and working distance. The size distribution, number and proliferation ratio of separated cells were statistically evaluated. Glycerol was used to increase the viscosity of the medium and alginate were introduced to soften the landing process. The role of laser pulse energy, the spot size and the thickness of titanium in energy absorption in LIFT process was theoretically analyzed with Lambert-Beer and a thermal conductive model. After comprehensive analysis, mechanical damage was found to be the dominant factor affecting the size and proliferation ratio of the isolated cells. An orthogonal experiment was conducted, and the optimal conditions were determined as: laser pulse energy, 9 μJ; spot size, 60 μm; thickness of titanium, 12 nm; working distance, 700 μm;, glycerol, 2% and alginate depth, greater than 1 μm. With these conditions, along with continuous incubation, a single cell could be transferred by the LIFT with one shot, with limited effect on cell size and viability. LIFT conducted in a closed chamber under optimized condition is a promising method for reliably isolating single cells.

Polarity, cell division, and out-of-equilibrium dynamics control the growth of epithelial structures

PubMed Central

Cerruti, Benedetta; Puliafito, Alberto; Shewan, Annette M.; Yu, Wei; Combes, Alexander N.; Little, Melissa H.; Chianale, Federica; Primo, Luca; Serini, Guido; Mostov, Keith E.; Celani, Antonio

2013-01-01

The growth of a well-formed epithelial structure is governed by mechanical constraints, cellular apico-basal polarity, and spatially controlled cell division. Here we compared the predictions of a mathematical model of epithelial growth with the morphological analysis of 3D epithelial structures. In both in vitro cyst models and in developing epithelial structures in vivo, epithelial growth could take place close to or far from mechanical equilibrium, and was determined by the hierarchy of time-scales of cell division, cell–cell rearrangements, and lumen dynamics. Equilibrium properties could be inferred by the analysis of cell–cell contact topologies, and the nonequilibrium phenotype was altered by inhibiting ROCK activity. The occurrence of an aberrant multilumen phenotype was linked to fast nonequilibrium growth, even when geometric control of cell division was correctly enforced. We predicted and verified experimentally that slowing down cell division partially rescued a multilumen phenotype induced by altered polarity. These results improve our understanding of the development of epithelial organs and, ultimately, of carcinogenesis. PMID:24145168

Eotaxin-Rich Proangiogenic Hematopoietic Progenitor Cells and CCR3+ Endothelium in the Atopic Asthmatic Response.

PubMed

Asosingh, Kewal; Vasanji, Amit; Tipton, Aaron; Queisser, Kimberly; Wanner, Nicholas; Janocha, Allison; Grandon, Deepa; Anand-Apte, Bela; Rothenberg, Marc E; Dweik, Raed; Erzurum, Serpil C

2016-03-01

Angiogenesis is closely linked to and precedes eosinophilic infiltration in asthma. Eosinophils are recruited into the airway by chemoattractant eotaxins, which are expressed by endothelial cells, smooth muscles cells, epithelial cells, and hematopoietic cells. We hypothesized that bone marrow-derived proangiogenic progenitor cells that contain eotaxins contribute to the initiation of angiogenesis and inflammation in asthma. Whole-lung allergen challenge of atopic asthma patients revealed vascular activation occurs within hours of challenge and before airway inflammation. The eotaxin receptor CCR3 was expressed at high levels on submucosal endothelial cells in patients and a murine model of asthma. Ex vivo exposure of murine endothelial cells to eotaxins induced migration and angiogenesis. In mechanistic studies, wild-type mice transplanted with eotaxin-1/2-deficient bone marrow had markedly less angiogenesis and inflammation in an atopic asthma model, whereas adoptive transfer of proangiogenic progenitor cells from wild-type mice in an atopic asthma model into the eotaxin-1/2-deficient mice led to angiogenesis and airway inflammation. The findings indicate that Th2-promoting hematopoietic progenitor cells are rapidly recruited to the lung upon allergen exposure and release eotaxins that coordinately activate endothelial cells, angiogenesis, and airway inflammation. Copyright © 2016 by The American Association of Immunologists, Inc.

Mechanisms governing the visco-elastic responses of living cells assessed by foam and tensegrity models.

PubMed

Cañadas, P; Laurent, V M; Chabrand, P; Isabey, D; Wendling-Mansuy, S

2003-11-01

The visco-elastic properties of living cells, measured to date by various authors, vary considerably, depending on the experimental methods and/or on the theoretical models used. In the present study, two mechanisms thought to be involved in cellular visco-elastic responses were analysed, based on the idea that the cytoskeleton plays a fundamental role in cellular mechanical responses. For this purpose, the predictions of an open unit-cell model and a 30-element visco-elastic tensegrity model were tested, taking into consideration similar properties of the constitutive F-actin. The quantitative predictions of the time constant and viscosity modulus obtained by both models were compared with previously published experimental data obtained from living cells. The small viscosity modulus values (10(0)-10(3) Pa x s) predicted by the tensegrity model may reflect the combined contributions of the spatially rearranged constitutive filaments and the internal tension to the overall cytoskeleton response to external loading. In contrast, the high viscosity modulus values (10(3)-10(5) Pa x s) predicted by the unit-cell model may rather reflect the mechanical response of the cytoskeleton to the bending of the constitutive filaments and/or to the deformation of internal components. The present results suggest the existence of a close link between the overall visco-elastic response of micromanipulated cells and the underlying architecture.

Drug scheduling of cancer chemotherapy based on natural actor-critic approach.

PubMed

Ahn, Inkyung; Park, Jooyoung

2011-11-01

Recently, reinforcement learning methods have drawn significant interests in the area of artificial intelligence, and have been successfully applied to various decision-making problems. In this paper, we study the applicability of the NAC (natural actor-critic) approach, a state-of-the-art reinforcement learning method, to the drug scheduling of cancer chemotherapy for an ODE (ordinary differential equation)-based tumor growth model. ODE-based cancer dynamics modeling is an active research area, and many different mathematical models have been proposed. Among these, we use the model proposed by de Pillis and Radunskaya (2003), which considers the growth of tumor cells and their interaction with normal cells and immune cells. The NAC approach is applied to this ODE model with the goal of minimizing the tumor cell population and the drug amount while maintaining the adequate population levels of normal cells and immune cells. In the framework of the NAC approach, the drug dose is regarded as the control input, and the reward signal is defined as a function of the control input and the cell populations of tumor cells, normal cells, and immune cells. According to the control policy found by the NAC approach, effective drug scheduling in cancer chemotherapy for the considered scenarios has turned out to be close to the strategy of continuing drug injection from the beginning until an appropriate time. Also, simulation results showed that the NAC approach can yield better performance than conventional pulsed chemotherapy. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

40 CFR 98.437 - Records that must be retained.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.437 Records that must be retained. (a) In... closed-cell foams must retain the following records substantiating each of the imports that they report... entry form. (4) Ports of entry through which the pre-charged equipment or closed-cell foams passed. (5...

40 CFR 98.437 - Records that must be retained.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.437 Records that must be retained. (a) In... closed-cell foams must retain the following records substantiating each of the imports that they report... entry form. (4) Ports of entry through which the pre-charged equipment or closed-cell foams passed. (5...

40 CFR 98.437 - Records that must be retained.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.437 Records that must be retained. (a) In... closed-cell foams must retain the following records substantiating each of the imports that they report... entry form. (4) Ports of entry through which the pre-charged equipment or closed-cell foams passed. (5...

A new interpretation of the Keller-Segel model based on multiphase modelling.

PubMed

Byrne, Helen M; Owen, Markus R

2004-12-01

In this paper an alternative derivation and interpretation are presented of the classical Keller-Segel model of cell migration due to random motion and chemotaxis. A multiphase modelling approach is used to describe how a population of cells moves through a fluid containing a diffusible chemical to which the cells are attracted. The cells and fluid are viewed as distinct components of a two-phase mixture. The principles of mass and momentum balance are applied to each phase, and appropriate constitutive laws imposed to close the resulting equations. A key assumption here is that the stress in the cell phase is influenced by the concentration of the diffusible chemical. By restricting attention to one-dimensional cartesian geometry we show how the model reduces to a pair of nonlinear coupled partial differential equations for the cell density and the chemical concentration. These equations may be written in the form of the Patlak-Keller-Segel model, naturally including density-dependent nonlinearities in the cell motility coefficients. There is a direct relationship between the random motility and chemotaxis coefficients, both depending in an inter-related manner on the chemical concentration. We suggest that this may explain why many chemicals appear to stimulate both chemotactic and chemokinetic responses in cell populations. After specialising our model to describe slime mold we then show how the functional form of the chemical potential that drives cell locomotion influences the ability of the system to generate spatial patterns. The paper concludes with a summary of the key results and a discussion of avenues for future research.

Compressive Deformation Behavior of Closed-Cell Micro-Pore Magnesium Composite Foam.

PubMed

Wang, Jing; Wang, Nannan; Liu, Xin; Ding, Jian; Xia, Xingchuan; Chen, Xueguang; Zhao, Weimin

2018-05-04

The closed-cell micro-pore magnesium composite foam with hollow ceramic microspheres (CMs) was fabricated by a modified melt foaming method. The effect of CMs on the compressive deformation behavior of CM-containing magnesium composite foam was investigated. Optical microscopy and scanning electron microscopy were used for observation of the microstructure. Finite element modeling of the magnesium composite foam was established to predict localized stress, fracture of CMs, and the compressive deformation behavior of the foam. The results showed that CMs and pores directly affected the compressive deformation behavior of the magnesium composite foam by sharing a part of load applied on the foam. Meanwhile, the presence of Mg₂Si phase influenced the mechanical properties of the foam by acting as the crack source during the compression process.

Compressive Deformation Behavior of Closed-Cell Micro-Pore Magnesium Composite Foam

PubMed Central

Wang, Jing; Wang, Nannan; Liu, Xin; Ding, Jian; Xia, Xingchuan; Chen, Xueguang; Zhao, Weimin

2018-01-01

The closed-cell micro-pore magnesium composite foam with hollow ceramic microspheres (CMs) was fabricated by a modified melt foaming method. The effect of CMs on the compressive deformation behavior of CM-containing magnesium composite foam was investigated. Optical microscopy and scanning electron microscopy were used for observation of the microstructure. Finite element modeling of the magnesium composite foam was established to predict localized stress, fracture of CMs, and the compressive deformation behavior of the foam. The results showed that CMs and pores directly affected the compressive deformation behavior of the magnesium composite foam by sharing a part of load applied on the foam. Meanwhile, the presence of Mg2Si phase influenced the mechanical properties of the foam by acting as the crack source during the compression process. PMID:29734700

Modeling the instability behavior of thin film devices: Fermi Level Pinning

NASA Astrophysics Data System (ADS)

Moeini, Iman; Ahmadpour, Mohammad; Gorji, Nima E.

2018-05-01

We investigate the underlying physics of degradation/recovery of a metal/n-CdTe Schottcky junction under reverse or forward bias stressing conditions. We used Sah-Noyce-Shockley (SNS) theory to investigate if the swept of Fermi level pinning at different levels (under forward/reverse bias) is the origin of change in current-voltage characteristics of the device. This theory is based on Shockley-Read-Hall recombination within the depletion width and takes into account the interface defect levels. Fermi Level Pinning theory was primarily introduced by Ponpon and developed to thin film solar cells by Dharmadasa's group in Sheffield University-UK. The theory suggests that Fermi level pinning at multiple levels occurs due to high concentration of electron-traps or acceptor-like defects at the interface of a Schottky or pn junction and this re-arranges the recombination rate and charage collection. Shift of these levels under stress conditions determines the change in current-voltage characteristics of the cell. This theory was suggested for several device such as metal/n-CdTe, CdS/CdTe, CIGS/CdS or even GaAs solar cells without a modeling approach to clearly explain it's physics. We have applied the strong SNS modeling approach to shed light on Fermi Level Pinning theory. The modeling confirms that change in position of Fermi Level and it's pining in a lower level close to Valence band increases the recombination and reduces the open-circuit voltage. In contrast, Fermi Level pinning close to conduction band strengthens the electric field at the junction which amplifies the carrier collection and boosts the open-circuit voltage. This theory can well explain the stress effect on device characteristics of various solar cells or Schottky junctions by simply finding the right Fermi level pinning position at every specific stress condition.

Brain tumor modeling: glioma growth and interaction with chemotherapy

NASA Astrophysics Data System (ADS)

Banaem, Hossein Y.; Ahmadian, Alireza; Saberi, Hooshangh; Daneshmehr, Alireza; Khodadad, Davood

2011-10-01

In last decade increasingly mathematical models of tumor growths have been studied, particularly on solid tumors which growth mainly caused by cellular proliferation. In this paper we propose a modified model to simulate the growth of gliomas in different stages. Glioma growth is modeled by a reaction-advection-diffusion. We begin with a model of untreated gliomas and continue with models of polyclonal glioma following chemotherapy. From relatively simple assumptions involving homogeneous brain tissue bounded by a few gross anatomical landmarks (ventricles and skull) the models have been expanded to include heterogeneous brain tissue with different motilities of glioma cells in grey and white matter. Tumor growth is characterized by a dangerous change in the control mechanisms, which normally maintain a balance between the rate of proliferation and the rate of apoptosis (controlled cell death). Result shows that this model closes to clinical finding and can simulate brain tumor behavior properly.

A mathematical model of cancer stem cell driven tumor initiation: implications of niche size and loss of homeostatic regulatory mechanisms.

PubMed

Gentry, Sara N; Jackson, Trachette L

2013-01-01

Hierarchical organized tissue structures, with stem cell driven cell differentiation, are critical to the homeostatic maintenance of most tissues, and this underlying cellular architecture is potentially a critical player in the development of a many cancers. Here, we develop a mathematical model of mutation acquisition to investigate how deregulation of the mechanisms preserving stem cell homeostasis contributes to tumor initiation. A novel feature of the model is the inclusion of both extrinsic and intrinsic chemical signaling and interaction with the niche to control stem cell self-renewal. We use the model to simulate the effects of a variety of types and sequences of mutations and then compare and contrast all mutation pathways in order to determine which ones generate cancer cells fastest. The model predicts that the sequence in which mutations occur significantly affects the pace of tumorigenesis. In addition, tumor composition varies for different mutation pathways, so that some sequences generate tumors that are dominated by cancerous cells with all possible mutations, while others are primarily comprised of cells that more closely resemble normal cells with only one or two mutations. We are also able to show that, under certain circumstances, healthy stem cells diminish due to the displacement by mutated cells that have a competitive advantage in the niche. Finally, in the event that all homeostatic regulation is lost, exponential growth of the cancer population occurs in addition to the depletion of normal cells. This model helps to advance our understanding of how mutation acquisition affects mechanisms that influence cell-fate decisions and leads to the initiation of cancers.

A 3D Poly(ethylene glycol)-based Tumor Angiogenesis Model to Study the Influence of Vascular Cells on Lung Tumor Cell Behavior

PubMed Central

Roudsari, Laila C.; Jeffs, Sydney E.; Witt, Amber S.; Gill, Bartley J.; West, Jennifer L.

2016-01-01

Tumor angiogenesis is critical to tumor growth and metastasis, yet much is unknown about the role vascular cells play in the tumor microenvironment. In vitro models that mimic in vivo tumor neovascularization facilitate exploration of this role. Here we investigated lung adenocarcinoma cancer cells (344SQ) and endothelial and pericyte vascular cells encapsulated in cell-adhesive, proteolytically-degradable poly(ethylene) glycol-based hydrogels. 344SQ in hydrogels formed spheroids and secreted proangiogenic growth factors that significantly increased with exposure to transforming growth factor beta 1 (TGF-β1), a potent tumor progression-promoting factor. Vascular cells in hydrogels formed tubule networks with localized activated TGF-β1. To study cancer cell-vascular cell interactions, we engineered a 2-layer hydrogel with 344SQ and vascular cell layers. Large, invasive 344SQ clusters (area > 5,000 μm2, circularity < 0.25) developed at the interface between the layers, and were not evident further from the interface or in control hydrogels without vascular cells. A modified model with spatially restricted 344SQ and vascular cell layers confirmed that observed cluster morphological changes required close proximity to vascular cells. Additionally, TGF-β1 inhibition blocked endothelial cell-driven 344SQ migration. Our findings suggest vascular cells contribute to tumor progression and establish this culture system as a platform for studying tumor vascularization. PMID:27596933

A 3D Poly(ethylene glycol)-based Tumor Angiogenesis Model to Study the Influence of Vascular Cells on Lung Tumor Cell Behavior

NASA Astrophysics Data System (ADS)

Roudsari, Laila C.; Jeffs, Sydney E.; Witt, Amber S.; Gill, Bartley J.; West, Jennifer L.

2016-09-01

Tumor angiogenesis is critical to tumor growth and metastasis, yet much is unknown about the role vascular cells play in the tumor microenvironment. In vitro models that mimic in vivo tumor neovascularization facilitate exploration of this role. Here we investigated lung adenocarcinoma cancer cells (344SQ) and endothelial and pericyte vascular cells encapsulated in cell-adhesive, proteolytically-degradable poly(ethylene) glycol-based hydrogels. 344SQ in hydrogels formed spheroids and secreted proangiogenic growth factors that significantly increased with exposure to transforming growth factor beta 1 (TGF-β1), a potent tumor progression-promoting factor. Vascular cells in hydrogels formed tubule networks with localized activated TGF-β1. To study cancer cell-vascular cell interactions, we engineered a 2-layer hydrogel with 344SQ and vascular cell layers. Large, invasive 344SQ clusters (area > 5,000 μm2, circularity < 0.25) developed at the interface between the layers, and were not evident further from the interface or in control hydrogels without vascular cells. A modified model with spatially restricted 344SQ and vascular cell layers confirmed that observed cluster morphological changes required close proximity to vascular cells. Additionally, TGF-β1 inhibition blocked endothelial cell-driven 344SQ migration. Our findings suggest vascular cells contribute to tumor progression and establish this culture system as a platform for studying tumor vascularization.

A model for chromosome organization during the cell cycle in live E. coli.

PubMed

Liu, Yuru; Xie, Ping; Wang, Pengye; Li, Ming; Li, Hui; Li, Wei; Dou, Shuoxing

2015-11-24

Bacterial chromosomal DNA is a highly compact nucleoid. The organization of this nucleoid is poorly understood due to limitations in the methods used to monitor the complexities of DNA organization in live bacteria. Here, we report that circular plasmid DNA is auto-packaged into a uniform dual-toroidal-spool conformation in response to mechanical stress stemming from sharp bending and un-winding by atomic force microscopic analysis. The mechanism underlying this phenomenon was deduced with basic physical principles to explain the auto-packaging behaviour of circular DNA. Based on our observations and previous studies, we propose a dynamic model of how chromosomal DNA in E. coli may be organized during a cell division cycle. Next, we test the model by monitoring the development of HNS clusters in live E. coli during a cell cycle. The results were in close agreement with the model. Furthermore, the model accommodates a majority of the thus-far-discovered remarkable features of nucleoids in vivo.

A model for chromosome organization during the cell cycle in live E. coli

PubMed Central

Liu, Yuru; Xie, Ping; Wang, Pengye; Li, Ming; Li, Hui; Li, Wei; Dou, Shuoxing

2015-01-01

Bacterial chromosomal DNA is a highly compact nucleoid. The organization of this nucleoid is poorly understood due to limitations in the methods used to monitor the complexities of DNA organization in live bacteria. Here, we report that circular plasmid DNA is auto-packaged into a uniform dual-toroidal-spool conformation in response to mechanical stress stemming from sharp bending and un-winding by atomic force microscopic analysis. The mechanism underlying this phenomenon was deduced with basic physical principles to explain the auto-packaging behaviour of circular DNA. Based on our observations and previous studies, we propose a dynamic model of how chromosomal DNA in E. coli may be organized during a cell division cycle. Next, we test the model by monitoring the development of HNS clusters in live E. coli during a cell cycle. The results were in close agreement with the model. Furthermore, the model accommodates a majority of the thus-far-discovered remarkable features of nucleoids in vivo. PMID:26597953

Proportional Insulin Infusion in Closed-Loop Control of Blood Glucose

PubMed Central

Grasman, Johan

2017-01-01

A differential equation model is formulated that describes the dynamics of glucose concentration in blood circulation. The model accounts for the intake of food, expenditure of calories and the control of glucose levels by insulin and glucagon. These and other hormones affect the blood glucose level in various ways. In this study only main effects are taken into consideration. Moreover, by making a quasi-steady state approximation the model is reduced to a single nonlinear differential equation of which parameters are fit to data from healthy subjects. Feedback provided by insulin plays a key role in the control of the blood glucose level. Reduced β-cell function and insulin resistance may hamper this process. With the present model it is shown how by closed-loop control these defects, in an organic way, can be compensated with continuous infusion of exogenous insulin. PMID:28060898

Structural determinants of hydration, mechanics and fluid flow in freeze-dried collagen scaffolds.

PubMed

Offeddu, G S; Ashworth, J C; Cameron, R E; Oyen, M L

2016-09-01

Freeze-dried scaffolds provide regeneration templates for a wide range of tissues, due to their flexibility in physical and biological properties. Control of structure is crucial for tuning such properties, and therefore scaffold functionality. However, the common approach of modeling these scaffolds as open-cell foams does not fully account for their structural complexity. Here, the validity of the open-cell model is examined across a range of physical characteristics, rigorously linking morphology to hydration and mechanical properties. Collagen scaffolds with systematic changes in relative density were characterized using Scanning Electron Microscopy, X-ray Micro-Computed Tomography and spherical indentation analyzed in a time-dependent poroelastic framework. Morphologically, all scaffolds were mid-way between the open- and closed-cell models, approaching the closed-cell model as relative density increased. Although pore size remained constant, transport pathway diameter decreased. Larger collagen fractions also produced greater volume swelling on hydration, although the change in pore diameter was constant, and relatively small at ∼6%. Mechanically, the dry and hydrated scaffold moduli varied quadratically with relative density, as expected of open-cell materials. However, the increasing pore wall closure was found to determine the time-dependent nature of the hydrated scaffold response, with a decrease in permeability producing increasingly elastic rather than viscoelastic behavior. These results demonstrate that characterizing the deviation from the open-cell model is vital to gain a full understanding of scaffold biophysical properties, and provide a template for structural studies of other freeze-dried biomaterials. Freeze-dried collagen sponges are three-dimensional microporous scaffolds that have been used for a number of exploratory tissue engineering applications. The characterization of the structure-properties relationships of these scaffolds is necessary to understand their biophysical behavior in vivo. In this work, the relationship between morphology and physical properties in the dry and hydrated states was investigated across a range of solid concentrations in the scaffolds. The quantitative results provided can aid the design of scaffolds with a target trade-off between mechanical properties and structural features important for their biological activity. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Study of the model of hole superconductivity in multiple band cases and its application to transition metals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hong, X.Q.

1992-01-01

The authors have studied a simple model consisting of a chain of atoms with two atoms per unit cell. This model develops two bands when the inter-cell and intra-cell hopping amplitudes are different. They have found that superconductivity predominantly occurs when the Fermi level is close to the top of the upper band where the wavefunction has antibonding feature both inside the unit cell and between unit cells. Superconductivity occurs only in a restricted parameter range when the Fermi level is close to the top of the lower band because of the repulsive interaction within the unit cell. They findmore » that pair expectation values that 'mix' carriers of both bands can exist when interband interactions other than V12 of Suhl et al are present. But the magnitude of the 'mixed pairs' order parameters is much smaller than that of the intra-band pairs. The V12 of Suhl et al is the most important interband interaction that gives rise to the main features of a two-band model: a single transition temperature and two different gaps. They have used the model of hole superconductivity to study the variation of T(sub c) among transition metal series--the Matthias rules. They have found that the observed T(sub c)'s are consistent with superconductivity of a metal with multiple bands at the Fermi level being caused by the single band with strongest antibonding character at the Fermi level. When the Fermi level is the lower part of a band, there is no T(sub c). As the band is gradually filled, T(sub c) rises, passes through a maximum, then drops to zero when the band is full. This characteristic feature is independent of any fine structure of the band. The position of the peak and the width of the peak are correlated. Quantitative agreement with the experimental results is obtained by choosing parameters of onsite Coulomb interaction U, modulated hopping term Delta-t, and nearest neighbor repulsion V to fit the magnitude of T(sub c) and the positions of experimental peaks.« less

Immortalization of T-cells is accompanied by gradual changes in CpG methylation resulting in a profile resembling a subset of T-cell leukemias.

PubMed

Degerman, Sofie; Landfors, Mattias; Siwicki, Jan Konrad; Revie, John; Borssén, Magnus; Evelönn, Emma; Forestier, Erik; Chrzanowska, Krystyna H; Rydén, Patrik; Keith, W Nicol; Roos, Göran

2014-07-01

We have previously described gene expression changes during spontaneous immortalization of T-cells, thereby identifying cellular processes important for cell growth crisis escape and unlimited proliferation. Here, we analyze the same model to investigate the role of genome-wide methylation in the immortalization process at different time points pre-crisis and post-crisis using high-resolution arrays. We show that over time in culture there is an overall accumulation of methylation alterations, with preferential increased methylation close to transcription start sites (TSSs), islands, and shore regions. Methylation and gene expression alterations did not correlate for the majority of genes, but for the fraction that correlated, gain of methylation close to TSS was associated with decreased gene expression. Interestingly, the pattern of CpG site methylation observed in immortal T-cell cultures was similar to clinical T-cell acute lymphoblastic leukemia (T-ALL) samples classified as CpG island methylator phenotype positive. These sites were highly overrepresented by polycomb target genes and involved in developmental, cell adhesion, and cell signaling processes. The presence of non-random methylation events in in vitro immortalized T-cell cultures and diagnostic T-ALL samples indicates altered methylation of CpG sites with a possible role in malignant hematopoiesis. Copyright © 2014 Neoplasia Press, Inc. Published by Elsevier Inc. All rights reserved.

A model of type 2 diabetes in the guinea pig using sequential diet-induced glucose intolerance and streptozotocin treatment

PubMed Central

Ackart, David F.; Richardson, Michael A.; DiLisio, James E.; Pulford, Bruce; Basaraba, Randall J.

2017-01-01

ABSTRACT Type 2 diabetes is a leading cause of morbidity and mortality among noncommunicable diseases, and additional animal models that more closely replicate the pathogenesis of human type 2 diabetes are needed. The goal of this study was to develop a model of type 2 diabetes in guinea pigs, in which diet-induced glucose intolerance precedes β-cell cytotoxicity, two processes that are crucial to the development of human type 2 diabetes. Guinea pigs developed impaired glucose tolerance after 8 weeks of feeding on a high-fat, high-carbohydrate diet, as determined by oral glucose challenge. Diet-induced glucose intolerance was accompanied by β-cell hyperplasia, compensatory hyperinsulinemia, and dyslipidemia with hepatocellular steatosis. Streptozotocin (STZ) treatment alone was ineffective at inducing diabetic hyperglycemia in guinea pigs, which failed to develop sustained glucose intolerance or fasting hyperglycemia and returned to euglycemia within 21 days after treatment. However, when high-fat, high-carbohydrate diet-fed guinea pigs were treated with STZ, glucose intolerance and fasting hyperglycemia persisted beyond 21 days post-STZ treatment. Guinea pigs with diet-induced glucose intolerance subsequently treated with STZ demonstrated an insulin-secretory capacity consistent with insulin-independent diabetes. This insulin-independent state was confirmed by response to oral antihyperglycemic drugs, metformin and glipizide, which resolved glucose intolerance and extended survival compared with guinea pigs with uncontrolled diabetes. In this study, we have developed a model of sequential glucose intolerance and β-cell loss, through high-fat, high-carbohydrate diet and extensive optimization of STZ treatment in the guinea pig, which closely resembles human type 2 diabetes. This model will prove useful in the study of insulin-independent diabetes pathogenesis with or without comorbidities, where the guinea pig serves as a relevant model species. PMID:28093504

Survival signals and targets for therapy in breast implant-associated ALK--anaplastic large cell lymphoma.

PubMed

Lechner, Melissa G; Megiel, Carolina; Church, Connor H; Angell, Trevor E; Russell, Sarah M; Sevell, Rikki B; Jang, Julie K; Brody, Garry S; Epstein, Alan L

2012-09-01

Anaplastic lymphoma kinase (ALK)-negative, T-cell, anaplastic, non-Hodgkin lymphoma (T-ALCL) in patients with textured saline and silicone breast implants is a recently recognized clinical entity for which the etiology and optimal treatment remain unknown. Using three newly established model cell lines from patient biopsy specimens, designated T-cell breast lymphoma (TLBR)-1 to -3, we characterized the phenotype and function of these tumors to identify mechanisms of cell survival and potential therapeutic targets. Cytogenetics revealed chromosomal atypia with partial or complete trisomy and absence of the NPM-ALK (2;5) translocation. Phenotypic characterization showed strong positivity for CD30, CD71, T-cell CD2/5/7, and antigen presentation (HLA-DR, CD80, CD86) markers, and interleukin (IL)-2 (CD25, CD122) and IL-6 receptors. Studies of these model cell lines showed strong activation of STAT3 signaling, likely related to autocrine production of IL-6 and decreased SHP-1. STAT3 inhibition, directly or by recovery of SHP-1, and cyclophosphamide-Adriamycin-vincristine-prednisone (CHOP) chemotherapy reagents, effectively kill cells of all three TLBR models in vitro and may be pursued as therapies for patients with breast implant-associated T-ALCLs. The TLBR cell lines closely resemble the primary breast implant-associated lymphomas from which they were derived and as such provide valuable preclinical models to study their unique biology. ©2012 AACR.

40 CFR 98.432 - GHGs to report.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Equipment or Closed-Cell Foams § 98.432 GHGs to report. You must report the mass of each fluorinated GHG contained in pre-charged equipment or closed-cell foams that you import or export during the calendar year. For imports and exports of closed-cell foams where you do not know the identity and mass of the...

40 CFR 98.432 - GHGs to report.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Equipment or Closed-Cell Foams § 98.432 GHGs to report. You must report the mass of each fluorinated GHG contained in pre-charged equipment or closed-cell foams that you import or export during the calendar year. For imports and exports of closed-cell foams where you do not know the identity and mass of the...

40 CFR 98.432 - GHGs to report.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Equipment or Closed-Cell Foams § 98.432 GHGs to report. You must report the mass of each fluorinated GHG contained in pre-charged equipment or closed-cell foams that you import or export during the calendar year. For imports and exports of closed-cell foams where you do not know the identity and mass of the...

40 CFR 98.432 - GHGs to report.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Equipment or Closed-Cell Foams § 98.432 GHGs to report. You must report the mass of each fluorinated GHG contained in pre-charged equipment or closed-cell foams that you import or export during the calendar year. For imports and exports of closed-cell foams where you do not know the identity and mass of the...

Specialised sympathetic neuroeffector associations in rat iris arterioles

PubMed Central

SANDOW, SHAUN L.; WHITEHOUSE, DREW; HILL, CARYL E.

1998-01-01

Vascular sympathetic neuroeffector associations have been examined in rat iris arterioles using serial section electron microscopy and reconstruction techniques. Examination of random sections showed that, of all profiles of varicosities (199) seen to lie closer than 4 μm to vascular smooth muscle cells, only a small proportion (29/199) were found in close association with vascular smooth muscle cells, where adjacent membranes were separated by less than 100 nm. However, serial section examination, from intervaricose region to intervaricose region, of 79 varicosities similarly observed lying within 4 μm of vascular smooth muscle cells showed that 54 formed close associations with vascular smooth muscle cells. In serial sections, all these varicosities were also closely associated with melanocytes and of the 25 remaining varicosities, 22 formed close associations with melanocytes alone, whilst 3 did not come into close association with any effector cell. The increased observation of close associations with vascular smooth muscle cells in serial sections, compared with random sections, is consistent with the demonstration that the area of contact only occupies, on average, a small percentage (5%) of the total surface area of the varicosity as seen in the 3-dimensional reconstructions. In both random and serial sections, close associations were observed between varicosities and vascular smooth muscle cells or melanocytes irrespective of whether fibres were present singly or in small nerve bundles. Three-dimensional reconstruction of associations of varicosities and vascular smooth muscle cells demonstrated several common features, such as accumulations of synaptic vesicles and loss of Schwann cell covering at the region of membrane facing the effector cell. The similarity in the appearance of the neuroeffector association seen in this study and those described in previous studies provides evidence for the existence of a common sympathetic neuroeffector association, irrespective of the receptor subtype involved in neurotransmission. PMID:9568560

Lysophosphatidic acid enhances collagen deposition and matrix thickening in engineered tissue.

PubMed

Chabaud, Stéphane; Marcoux, Thomas-Louis; Deschênes-Rompré, Marie-Pier; Rousseau, Alexandre; Morissette, Amélie; Bouhout, Sara; Bernard, Geneviève; Bolduc, Stéphane

2015-11-01

The time needed to produce engineered tissue is critical. A self-assembly approach provided excellent results regarding biological functions and cell differentiation because it closely respected the microenvironment of cells. Nevertheless, the technique was time consuming for producing tissue equivalents with enough extracellular matrix to allow manipulations. Unlike L-arginine supplementation that only increased accumulation of collagen in cell culture supernatant in our model, addition of lysophosphatidic acid, a natural bioactive lipid, did not modify the amount of accumulated collagen in the cell culture supernatant; however, it enhanced the matrix deposition rate without inducing fibroblast hyperproliferation and tissue fibrosis. Copyright © 2013 John Wiley & Sons, Ltd.

Microgravity

NASA Image and Video Library

1996-01-01

Close-up view of the interior of a NASA Bioreactor shows the plastic plumbing and valves (cylinders at right center) to control fluid flow. The rotating wall vessel is at top center. The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. The Bioreactor is rotated to provide gentle mixing of fresh and spent nutrient without inducing shear forces that would damage the cells. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. The work is sponsored by NASA's Office of Biological and Physical Research. The bioreactor is managed by the Biotechnology Cell Science Program at NASA's Johnson Space Center (JSC). NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues being cultured in rotating bioreactors by investigators.

The passive cable properties of hair cell stereocilia and their contribution to somatic capacitance measurements.

PubMed

Breneman, Kathryn D; Highstein, Stephen M; Boyle, Richard D; Rabbitt, Richard D

2009-01-01

Somatic measurements of whole-cell capacitance are routinely used to understand physiologic events occurring in remote portions of cells. These studies often assume the intracellular space is voltage-clamped. We questioned this assumption in auditory and vestibular hair cells with respect to their stereocilia based on earlier studies showing that neurons, with radial dimensions similar to stereocilia, are not always isopotential under voltage-clamp. To explore this, we modeled the stereocilia as passive cables with transduction channels located at their tips. We found that the input capacitance measured at the soma changes when the transduction channels at the tips of the stereocilia are open compared to when the channels are closed. The maximum capacitance is felt with the transducer closed but will decrease as the transducer opens due to a length-dependent voltage drop along the stereocilium length. This potential drop is proportional to the intracellular resistance and stereocilium tip conductance and can produce a maximum capacitance error on the order of fF for single stereocilia and pF for the bundle.

Experimental Human Cell and Tissue Models of Pemphigus

PubMed Central

van der Wier, Gerda; Pas, Hendri H.; Jonkman, Marcel F.

2010-01-01

Pemphigus is a chronic mucocutaneous autoimmune bullous disease that is characterized by loss of cell-cell contact in skin and/or mucous membranes. Past research has successfully identified desmosomes as immunological targets and has demonstrated that acantholysis is initiated through direct binding of IgG. The exact mechanisms of acantholysis, however, are still missing. Experimental model systems have contributed considerably to today's knowledge and are still a favourite tool of research. In this paper we will describe to what extent human cell and tissue models represent the in vivo situation, for example, organ cultures of human skin, keratinocyte cultures, and human skin grafted on mice and, furthermore, how suitable they are to study the pathogenesis of pemphigus. Organ cultures closely mimic the architecture of the epidermis but are less suitable to answer posed biochemical questions. Cultured keratinocyte monolayers are convenient in this respect, but their desmosomal make-up in terms of adhesion molecules does not exactly reflect the in vivo situation. Reconstituted skin is a relatively new model that approaches organ culture. In models of human skin grafted on mice, acantholysis can be studied in actual human skin but now with all the advantages of an animal model. PMID:20585596

Engineering cancer microenvironments for in vitro 3-D tumor models

PubMed Central

Asghar, Waseem; El Assal, Rami; Shafiee, Hadi; Pitteri, Sharon; Paulmurugan, Ramasamy; Demirci, Utkan

2017-01-01

The natural microenvironment of tumors is composed of extracellular matrix (ECM), blood vasculature, and supporting stromal cells. The physical characteristics of ECM as well as the cellular components play a vital role in controlling cancer cell proliferation, apoptosis, metabolism, and differentiation. To mimic the tumor microenvironment outside the human body for drug testing, two-dimensional (2-D) and murine tumor models are routinely used. Although these conventional approaches are employed in preclinical studies, they still present challenges. For example, murine tumor models are expensive and difficult to adopt for routine drug screening. On the other hand, 2-D in vitro models are simple to perform, but they do not recapitulate natural tumor microenvironment, because they do not capture important three-dimensional (3-D) cell–cell, cell–matrix signaling pathways, and multi-cellular heterogeneous components of the tumor microenvironment such as stromal and immune cells. The three-dimensional (3-D) in vitro tumor models aim to closely mimic cancer microenvironments and have emerged as an alternative to routinely used methods for drug screening. Herein, we review recent advances in 3-D tumor model generation and highlight directions for future applications in drug testing. PMID:28458612

Apoptosis generates mechanical forces that close the lens vesicle in the chick embryo

NASA Astrophysics Data System (ADS)

Oltean, Alina; Taber, Larry A.

2018-03-01

During the initial stages of eye development, optic vesicles grow laterally outward from both sides of the forebrain and come into contact with the surrounding surface ectoderm (SE). Within the region of contact, these layers then thicken locally to create placodes and invaginate to form the optic cup (primitive retina) and lens vesicle (LV), respectively. This paper examines the biophysical mechanisms involved in LV formation, which consists of three phases: (1) lens placode formation; (2) invagination to create the lens pit (LP); and (3) closure to form a complete ellipsoidally shaped LV. Previous studies have suggested that extracellular matrix deposited between the SE and optic vesicle causes the lens placode to form by locally constraining expansion of the SE as it grows, while actomyosin contraction causes this structure to invaginate. Here, using computational modeling and experiments on chick embryos, we confirm that these mechanisms for Phases 1 and 2 are physically plausible. Our results also suggest, however, that they are not sufficient to close the LP during Phase 3. We postulate that apoptosis provides an additional mechanism by removing cells near the LP opening, thereby decreasing its circumference and generating tension that closes the LP. This hypothesis is supported by staining that shows a ring of cell death located around the LP opening during closure. Inhibiting apoptosis in cultured embryos using caspase inhibitors significantly reduced LP closure, and results from a finite-element model indicate that closure driven by cell death is plausible. Taken together, our results suggest an important mechanical role for apoptosis in lens development.

Mycoplasma pneumoniae, an Underutilized Model for Bacterial Cell Biology

PubMed Central

2014-01-01

In recent decades, bacterial cell biology has seen great advances, and numerous model systems have been developed to study a wide variety of cellular processes, including cell division, motility, assembly of macromolecular structures, and biogenesis of cell polarity. Considerable attention has been given to these model organisms, which include Escherichia coli, Bacillus subtilis, Caulobacter crescentus, and Myxococcus xanthus. Studies of these processes in the pathogenic bacterium Mycoplasma pneumoniae and its close relatives have also been carried out on a smaller scale, but this work is often overlooked, in part due to this organism's reputation as minimalistic and simple. In this minireview, I discuss recent work on the role of the M. pneumoniae attachment organelle (AO), a structure required for adherence to host cells, in these processes. The AO is constructed from proteins that generally lack homology to those found in other organisms, and this construction occurs in coordination with cell cycle events. The proteins of the M. pneumoniae AO share compositional features with proteins with related roles in model organisms. Once constructed, the AO becomes activated for its role in a form of gliding motility whose underlying mechanism appears to be distinct from that of other gliding bacteria, including Mycoplasma mobile. Together with the FtsZ cytoskeletal protein, motility participates in the cell division process. My intention is to bring this deceptively complex organism into alignment with the better-known model systems. PMID:25157081

Research in Optical Sciences

DTIC Science & Technology

1990-03-12

where this is not so (see, e.g., the Jaynes - Cummings problem). This is why this model , and the closely related micromaser, remain exceedingly important...55 one calculates the plane- wave spectrum ( without 7.), one must arbitrarily impose nearly zero phase mismatch to obtain a similar spectrum.3" 2.7...taking approximately 3 CPU minutes. To model the intentionally introduced astigmatism, a phase term was added to the input wavefront at the cell entrance

Novel Model of Frontal Impact Closed Head Injury in the Rat

PubMed Central

Kilbourne, Michael; Kuehn, Reed; Tosun, Cigdem; Caridi, John; Keledjian, Kaspar; Bochicchio, Grant; Scalea, Thomas; Gerzanich, Volodymyr

2009-01-01

Abstract Frontal impact, closed head trauma is a frequent cause of traumatic brain injury (TBI) in motor vehicle and sports accidents. Diffuse axonal injury (DAI) is common in humans and experimental animals, and results from shearing forces that develop within the anisotropic brain. Because the specific anisotropic properties of the brain are axis-dependent, the anatomical site where force is applied as well as the resultant acceleration, be it linear, rotational, or some combination, are important determinants of the resulting pattern of brain injury. Available rodent models of closed head injury do not reproduce the frontal impact commonly encountered in humans. Here we describe a new rat model of closed head injury that is a modification of the impact-acceleration model of Marmarou. In our model (the Maryland model), the impact force is applied to the anterior part of the cranium and produces TBI by causing anterior-posterior plus sagittal rotational acceleration of the brain inside the intact cranium. Skull fractures, prolonged apnea, and mortality were absent. The animals exhibited petechial hemorrhages, DAI marked by a bead-like pattern of β-amyloid precursor protein (β-APP) in damaged axons, and widespread upregulation of β-APP in neurons, with regions affected including the orbitofrontal cortex (coup), corpus callosum, caudate, putamen, thalamus, cerebellum, and brainstem. Activated caspase-3 was prominent in hippocampal neurons and Purkinje cells at the grey-white matter junction of the cerebellum. Neurobehavioral dysfunction, manifesting as reduced spontaneous exploration, lasted more than 1 week. We conclude that the Maryland model produces diffuse injuries that may be relevant to human brain injury. PMID:19929375

An analytical model with flexible accuracy for deep submicron DCVSL cells

NASA Astrophysics Data System (ADS)

Valiollahi, Sepideh; Ardeshir, Gholamreza

2018-07-01

Differential cascoded voltage switch logic (DCVSL) cells are among the best candidates of circuit designers for a wide range of applications due to advantages such as low input capacitance, high switching speed, small area and noise-immunity; nevertheless, a proper model has not yet been developed to analyse them. This paper analyses deep submicron DCVSL cells based on a flexible accuracy-simplicity trade-off including the following key features: (1) the model is capable of producing closed-form expressions with an acceptable accuracy; (2) model equations can be solved numerically to offer higher accuracy; (3) the short-circuit currents occurring in high-low/low-high transitions are accounted in analysis and (4) the changes in the operating modes of transistors during transitions together with an efficient submicron I-V model, which incorporates the most important non-ideal short-channel effects, are considered. The accuracy of the proposed model is validated in IBM 0.13 µm CMOS technology through comparisons with the accurate physically based BSIM3 model. The maximum error caused by analytical solutions is below 10%, while this amount is below 7% for numerical solutions.

Disease modeling using human induced pluripotent stem cells: lessons from the liver.

PubMed

Gieseck, Richard L; Colquhoun, Jennifer; Hannan, Nicholas R F

2015-01-01

Human pluripotent stem cells (hPSCs) have the capacity to differentiate into any of the hundreds of distinct cell types that comprise the human body. This unique characteristic has resulted in considerable interest in the field of regenerative medicine, given the potential for these cells to be used to protect, repair, or replace diseased, injured, and aged cells within the human body. In addition to their potential in therapeutics, hPSCs can be used to study the earliest stages of human development and to provide a platform for both drug screening and disease modeling using human cells. Recently, the description of human induced pluripotent stem cells (hIPSCs) has allowed the field of disease modeling to become far more accessible and physiologically relevant, as pluripotent cells can be generated from patients of any genetic background. Disease models derived from hIPSCs that manifest cellular disease phenotypes have been established to study several monogenic diseases; furthermore, hIPSCs can be used for phenotype-based drug screens to investigate complex diseases for which the underlying genetic mechanism is unknown. As a result, the use of stem cells as research tools has seen an unprecedented growth within the last decade as researchers look for in vitro disease models which closely mimic in vivo responses in humans. Here, we discuss the beginnings of hPSCs, starting with isolation of human embryonic stem cells, moving into the development and optimization of hIPSC technology, and ending with the application of hIPSCs towards disease modeling and drug screening applications, with specific examples highlighting the modeling of inherited metabolic disorders of the liver. This article is part of a Special Issue entitled Linking transcription to physiology in lipodomics. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

Transforming growth factor-β signalling controls human breast cancer metastasis in a zebrafish xenograft model.

PubMed

Drabsch, Yvette; He, Shuning; Zhang, Long; Snaar-Jagalska, B Ewa; ten Dijke, Peter

2013-11-07

The transforming growth factor beta (TGF-β) signalling pathway is known to control human breast cancer invasion and metastasis. We demonstrate that the zebrafish xenograft assay is a robust and dependable animal model for examining the role of pharmacological modulators and genetic perturbation of TGF-β signalling in human breast tumour cells. We injected cancer cells into the embryonic circulation (duct of cuvier) and examined their invasion and metastasis into the avascular collagenous tail. Various aspects of the TGF-β signalling pathway were blocked by chemical inhibition, small interfering RNA (siRNA), or small hairpin RNA (shRNA). Analysis was conducted using fluorescent microscopy. Breast cancer cells with different levels of malignancy, according to in vitro and in vivo mouse studies, demonstrated invasive and metastatic properties within the embryonic zebrafish model that nicely correlated with their differential tumourigenicity in mouse models. Interestingly, MCF10A M2 and M4 cells invaded into the caudal hematopoietic tissue and were visible as a cluster of cells, whereas MDA MB 231 cells invaded into the tail fin and were visible as individual cells. Pharmacological inhibition with TGF-β receptor kinase inhibitors or tumour specific Smad4 knockdown disturbed invasion and metastasis in the zebrafish xenograft model and closely mimicked the results we obtained with these cells in a mouse metastasis model. Inhibition of matrix metallo proteinases, which are induced by TGF-β in breast cancer cells, blocked invasion and metastasis of breast cancer cells. The zebrafish-embryonic breast cancer xenograft model is applicable for the mechanistic understanding, screening and development of anti-TGF-β drugs for the treatment of metastatic breast cancer in a timely and cost-effective manner.

Dynamical mechanism of circadian singularity behavior in Neurospora

NASA Astrophysics Data System (ADS)

Sun, Maorong; Wang, Yi; Xu, Xin; Yang, Ling

2016-09-01

Many organisms have oscillators with a period of about 24 hours, called "circadian clocks". They employ negative biochemical feedback loops that are self-contained within a single cell (requiring no cell-to-cell interaction). Circadian singularity behavior is a phenomenon of the abolishment of circadian rhythmicities by a critical stimulus. These behaviors have been found experimentally in Neurospora, human and hamster, by temperature step-up or light pulse. Two alternative models have been proposed to explain this phenomenon: desynchronization of cell populations, and loss of oscillations in all cells by resetting each cell close to a steady state. In this work, we use a mathematical model to investigate the dynamical mechanism of circadian singularity behavior in Neurospora. Our findings suggest that the arrhythmic behavior after the critical stimulus is caused by the collaboration of the desynchronization and the loss of oscillation amplitude. More importantly, we found that the stable manifold of the unstable equilibrium point, instead of the steady state itself, plays a crucial role in circadian singularity behavior.

Wounding coordinately induces cell wall protein, cell cycle and pectin methyl esterase genes involved in tuber closing layer and wound periderm development.

PubMed

Neubauer, Jonathan D; Lulai, Edward C; Thompson, Asunta L; Suttle, Jeffrey C; Bolton, Melvin D

2012-04-15

Little is known about the coordinate induction of genes that may be involved in agriculturally important wound-healing events. In this study, wound-healing events were determined together with wound-induced expression profiles of selected cell cycle, cell wall protein, and pectin methyl esterase genes using two diverse potato genotypes and two harvests (NDTX4271-5R and Russet Burbank tubers; 2008 and 2009 harvests). By 5 d after wounding, the closing layer and a nascent phellogen had formed. Phellogen cell divisions generated phellem layers until cessation of cell division at 28 d after wounding for both genotypes and harvests. Cell cycle genes encoding epidermal growth factor binding protein (StEBP), cyclin-dependent kinase B (StCDKB) and cyclin-dependent kinase regulatory subunit (StCKS1At) were induced by 1 d after wounding; these expressions coordinated with related phellogen formation and the induction and cessation of phellem cell formation. Genes encoding the structural cell wall proteins extensin (StExt1) and extensin-like (StExtlk) were dramatically up-regulated by 1-5 d after wounding, suggesting involvement with closing layer and later phellem cell layer formation. Wounding up-regulated pectin methyl esterase genes (StPME and StPrePME); StPME expression increased during closing layer and phellem cell formation, whereas maximum expression of StPrePME occurred at 5-14 d after wounding, implicating involvement in later modifications for closing layer and phellem cell formation. The coordinate induction and expression profile of StTLRP, a gene encoding a cell wall strengthening "tyrosine-and lysine-rich protein," suggested a role in the formation of the closing layer followed by phellem cell generation and maturation. Collectively, the genes monitored were wound-inducible and their expression profiles markedly coordinated with closing layer formation and the index for phellogen layer meristematic activity during wound periderm development; results were more influenced by harvest than genotype. Importantly, StTLRP was the only gene examined that may be involved in phellogen cell wall thickening after cessation of phellogen cell division. Published by Elsevier GmbH.

Open-cell vs. Closed-cell Stent Design Differences in Blood Flow Velocities after Carotid Stenting

PubMed Central

Pierce, Damon S.; Rosero, Eric B; Modrall, J Gregory; Adams-Huet, Beverley; Valentine, R James; Clagett, G Patrick; Timaran, Carlos H

2009-01-01

Objective The differential effect of stent design, i.e. open-cell vs. closed-cell configuration, on carotid velocities detected by duplex ultrasonography (DUS) has not been established. To identify possible stent design differences in carotid velocities, we analyzed our experience with DUS obtained before and immediately after CAS. Methods In a series of 141 CAS procedures performed over a 3 year period, data from the first postinterventional DUS and carotid angiograms were evaluated for each patient. Peak systolic velocities (PSV), end-diastolic velocities (EDV), and internal carotid artery-to-common carotid artery (ICA-CCA) PSV ratios were compared according to stent design. Differences in carotid velocities were analyzed using nonparametric statistical tests. Results Completion angiogram revealed successful revascularization and less that 30% residual stenosis in each case. The 30-day stroke-death rate in this series was 1.6% and was unrelated to stent type. Postintervention DUS was obtained a median of 5 days after CAS (interquartile range [IQR], 1–25 days). Closed-cell stents were used in 41 cases (29%) and open-cell stents in 100 cases (71%). The median PSV was significantly higher for closed-cell stents (122cm/s; IQR, 89–143cm/s) than for open-cell stents (95.9cm/s; IQR, 77.–123) (P=.007). Median EDV (36 vs. 29 cm/s; P=.006) and median ICA-CCA PSV ratio (1.6 vs. 1.1; P=.017) were also significantly higher for closed-cell stents. 45% of closed-cell stents had carotid velocities that exceeded the threshold of 50% stenosis by DUS criteria for a nonstented artery compared to 26% of open-cell stents (P=.04). In fact, closed cell-stents had a 2.2-fold increased risk of yielding abnormally elevated carotid velocities after CAS compared with open-cell stents (odds ratio, 2.2; 95% confidence interval, 1.02–4.9). Conclusions Carotid velocities are disproportionately elevated after CAS with closed-cell stents compared with open-cell stents, which suggests that velocity criteria for quantifying stenosis may require modification according to stent design. The importance of these differences in carotid velocities related to stent design and the potential relationship with recurrent stenosis remains to be established. PMID:19268763

Glial cell migration in the eye disc.

PubMed

Silies, Marion; Yuva, Yeliz; Engelen, Daniel; Aho, Annukka; Stork, Tobias; Klämbt, Christian

2007-11-28

Any complex nervous system is made out of two major cell types, neurons and glial cells. A hallmark of glial cells is their pronounced ability to migrate. En route to their final destinations, glial cells are generally guided by neuronal signals. Here we show that in the developing visual system of Drosophila glial cell migration is largely controlled by glial-glial interactions and occurs independently of axonal contact. Differentiation into wrapping glia is initiated close to the morphogenetic furrow. Using single cell labeling experiments we identified six distinct glial cell types in the eye disc. The migratory glial population is separated from the wrapping glial cells by the so-called carpet cells, extraordinary large glial cells, each covering a surface area of approximately 10,000 epithelial cells. Subsequent cell ablation experiments demonstrate that the carpet glia regulates glial migration in the eye disc epithelium and suggest a new model underlying glial migration and differentiation in the developing visual system.

Coaction of intercellular adhesion and cortical tension specifies tissue surface tension

PubMed Central

Manning, M. Lisa; Foty, Ramsey A.; Steinberg, Malcolm S.; Schoetz, Eva-Maria

2010-01-01

In the course of animal morphogenesis, large-scale cell movements occur, which involve the rearrangement, mutual spreading, and compartmentalization of cell populations in specific configurations. Morphogenetic cell rearrangements such as cell sorting and mutual tissue spreading have been compared with the behaviors of immiscible liquids, which they closely resemble. Based on this similarity, it has been proposed that tissues behave as liquids and possess a characteristic surface tension, which arises as a collective, macroscopic property of groups of mobile, cohering cells. But how are tissue surface tensions generated? Different theories have been proposed to explain how mesoscopic cell properties such as cell–cell adhesion and contractility of cell interfaces may underlie tissue surface tensions. Although recent work suggests that both may be contributors, an explicit model for the dependence of tissue surface tension on these mesoscopic parameters has been missing. Here we show explicitly that the ratio of adhesion to cortical tension determines tissue surface tension. Our minimal model successfully explains the available experimental data and makes predictions, based on the feedback between mechanical energy and geometry, about the shapes of aggregate surface cells, which we verify experimentally. This model indicates that there is a crossover from adhesion dominated to cortical-tension dominated behavior as a function of the ratio between these two quantities. PMID:20616053

Starch Biosynthesis in Guard Cells But Not in Mesophyll Cells Is Involved in CO2-Induced Stomatal Closing1[OPEN

PubMed Central

Stephan, Aaron B.; Schroeder, Julian I.

2016-01-01

Starch metabolism is involved in stomatal movement regulation. However, it remains unknown whether starch-deficient mutants affect CO2-induced stomatal closing and whether starch biosynthesis in guard cells and/or mesophyll cells is rate limiting for high CO2-induced stomatal closing. Stomatal responses to [CO2] shifts and CO2 assimilation rates were compared in Arabidopsis (Arabidopsis thaliana) mutants that were either starch deficient in all plant tissues (ADP-Glc-pyrophosphorylase [ADGase]) or retain starch accumulation in guard cells but are starch deficient in mesophyll cells (plastidial phosphoglucose isomerase [pPGI]). ADGase mutants exhibited impaired CO2-induced stomatal closure, but pPGI mutants did not, showing that starch biosynthesis in guard cells but not mesophyll functions in CO2-induced stomatal closing. Nevertheless, starch-deficient ADGase mutant alleles exhibited partial CO2 responses, pointing toward a starch biosynthesis-independent component of the response that is likely mediated by anion channels. Furthermore, whole-leaf CO2 assimilation rates of both ADGase and pPGI mutants were lower upon shifts to high [CO2], but only ADGase mutants caused impairments in CO2-induced stomatal closing. These genetic analyses determine the roles of starch biosynthesis for high CO2-induced stomatal closing. PMID:27208296

Improving Soldier Recovery from Catastrophic Bone Injuries: Developing an Animal Model for Standarizing the Bone Reparative Potential of Emerging Progenitor Cell Therapies

DTIC Science & Technology

2008-08-01

To better understand the cellular basis of a long bone defect, we have utilized the GFP reporters in the closed tibial fracture. The surprise finding...callus. In the coming year we will apply the information learned from the calvarial defect to a non-union extension of the tibial fracture model...initiated a comprehensive examination of the tibial fracture model in mice bearing GFP reporters of lineage progression. This project has been assumed

8th Annual Glycoscience Symposium: Integrating Models of Plant Cell Wall Structure, Biosynthesis and Assembly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Azadi, Paratoo

2015-09-24

The Complex Carbohydrate Research Center (CCRC) of the University of Georgia holds a symposium yearly that highlights a broad range of carbohydrate research topics. The 8th Annual Georgia Glycoscience Symposium entitled “Integrating Models of Plant Cell Wall Structure, Biosynthesis and Assembly” was held on April 7, 2014 at the CCRC. The focus of symposium was on the role of glycans in plant cell wall structure and synthesis. The goal was to have world leaders in conjunction with graduate students, postdoctoral fellows and research scientists to propose the newest plant cell wall models. The symposium program closely followed the DOE’s missionmore » and was specifically designed to highlight chemical and biochemical structures and processes important for the formation and modification of renewable plant cell walls which serve as the basis for biomaterial and biofuels. The symposium was attended by both senior investigators in the field as well as students including a total attendance of 103, which included 80 faculty/research scientists, 11 graduate students and 12 Postdoctoral students.« less

Computational Analysis of AMPK-Mediated Neuroprotection Suggests Acute Excitotoxic Bioenergetics and Glucose Dynamics Are Regulated by a Minimal Set of Critical Reactions.

PubMed

Connolly, Niamh M C; D'Orsi, Beatrice; Monsefi, Naser; Huber, Heinrich J; Prehn, Jochen H M

2016-01-01

Loss of ionic homeostasis during excitotoxic stress depletes ATP levels and activates the AMP-activated protein kinase (AMPK), re-establishing energy production by increased expression of glucose transporters on the plasma membrane. Here, we develop a computational model to test whether this AMPK-mediated glucose import can rapidly restore ATP levels following a transient excitotoxic insult. We demonstrate that a highly compact model, comprising a minimal set of critical reactions, can closely resemble the rapid dynamics and cell-to-cell heterogeneity of ATP levels and AMPK activity, as confirmed by single-cell fluorescence microscopy in rat primary cerebellar neurons exposed to glutamate excitotoxicity. The model further correctly predicted an excitotoxicity-induced elevation of intracellular glucose, and well resembled the delayed recovery and cell-to-cell heterogeneity of experimentally measured glucose dynamics. The model also predicted necrotic bioenergetic collapse and altered calcium dynamics following more severe excitotoxic insults. In conclusion, our data suggest that a minimal set of critical reactions may determine the acute bioenergetic response to transient excitotoxicity and that an AMPK-mediated increase in intracellular glucose may be sufficient to rapidly recover ATP levels following an excitotoxic insult.

Computational Analysis of AMPK-Mediated Neuroprotection Suggests Acute Excitotoxic Bioenergetics and Glucose Dynamics Are Regulated by a Minimal Set of Critical Reactions

PubMed Central

Connolly, Niamh M. C.; D’Orsi, Beatrice; Monsefi, Naser; Huber, Heinrich J.; Prehn, Jochen H. M.

2016-01-01

Loss of ionic homeostasis during excitotoxic stress depletes ATP levels and activates the AMP-activated protein kinase (AMPK), re-establishing energy production by increased expression of glucose transporters on the plasma membrane. Here, we develop a computational model to test whether this AMPK-mediated glucose import can rapidly restore ATP levels following a transient excitotoxic insult. We demonstrate that a highly compact model, comprising a minimal set of critical reactions, can closely resemble the rapid dynamics and cell-to-cell heterogeneity of ATP levels and AMPK activity, as confirmed by single-cell fluorescence microscopy in rat primary cerebellar neurons exposed to glutamate excitotoxicity. The model further correctly predicted an excitotoxicity-induced elevation of intracellular glucose, and well resembled the delayed recovery and cell-to-cell heterogeneity of experimentally measured glucose dynamics. The model also predicted necrotic bioenergetic collapse and altered calcium dynamics following more severe excitotoxic insults. In conclusion, our data suggest that a minimal set of critical reactions may determine the acute bioenergetic response to transient excitotoxicity and that an AMPK-mediated increase in intracellular glucose may be sufficient to rapidly recover ATP levels following an excitotoxic insult. PMID:26840769

A study of cryogenic tissue-engineered liver slices in calcium alginate gel for drug testing.

PubMed

Chen, Ruomeng; Wang, Bo; Liu, Yaxiong; Lin, Rong; He, Jiankang; Li, Dichen

2018-06-01

To address issues such as transportation and the time-consuming nature of tissue-engineered liver for use as an effective drug metabolism and toxicity testing model, "ready-to-use" cryogenic tissue-engineered liver needs to be studied. The research developed a cryogenic tissue-engineered liver slice (TELS), which comprised of HepG2 cells and calcium alginate gel. Cell viability and liver-specific functions were examined after different cryopreservation and recovery culture times. Then, cryogenic TELSs were used as a drug-testing model and treated with Gefitinib. Cryogenic TELSs were stored at -80 °C to ensure high cell viability. During recovery in culture, the cells in the cryogenic TELS were evenly distributed, massively proliferated, and then formed spheroid-like aggregates from day 1 to day 13. The liver-specific functions in the cryogenic TELS were closely related to cryopreservation time and cell proliferation. As a reproducible drug-testing model, the cryogenic TELS showed an obvious drug reaction after treatment with the Gefitinib. The present study shows that the cryopreservation techniques can be used in drug-testing models. Copyright © 2018 Elsevier Inc. All rights reserved.

The pivotal role of angiogenesis in a multi-scale modeling of tumor growth exhibiting the avascular and vascular phases.

PubMed

Salavati, Hooman; Soltani, M; Amanpour, Saeid

2018-05-06

The mechanisms involved in tumor growth mainly occur at the microenvironment, where the interactions between the intracellular, intercellular and extracellular scales mediate the dynamics of tumor. In this work, we present a multi-scale model of solid tumor dynamics to simulate the avascular and vascular growth as well as tumor-induced angiogenesis. The extracellular and intercellular scales are modeled using partial differential equations and cellular Potts model, respectively. Also, few biochemical and biophysical rules control the dynamics of intracellular level. On the other hand, the growth of melanoma tumors is modeled in an animal in-vivo study to evaluate the simulation. The simulation shows that the model successfully reproduces a completed image of processes involved in tumor growth such as avascular and vascular growth as well as angiogenesis. The model incorporates the phenotypes of cancerous cells including proliferating, quiescent and necrotic cells, as well as endothelial cells during angiogenesis. The results clearly demonstrate the pivotal effect of angiogenesis on the progression of cancerous cells. Also, the model exhibits important events in tumor-induced angiogenesis like anastomosis. Moreover, the computational trend of tumor growth closely follows the observations in the experimental study. Copyright © 2018 Elsevier Inc. All rights reserved.

Detailed Multi‐dimensional Modeling of Direct Internal Reforming Solid Oxide Fuel Cells

PubMed Central

Tseronis, K.; Fragkopoulos, I.S.; Bonis, I.

2016-01-01

Abstract Fuel flexibility is a significant advantage of solid oxide fuel cells (SOFCs) and can be attributed to their high operating temperature. Here we consider a direct internal reforming solid oxide fuel cell setup in which a separate fuel reformer is not required. We construct a multidimensional, detailed model of a planar solid oxide fuel cell, where mass transport in the fuel channel is modeled using the Stefan‐Maxwell model, whereas the mass transport within the porous electrodes is simulated using the Dusty‐Gas model. The resulting highly nonlinear model is built into COMSOL Multiphysics, a commercial computational fluid dynamics software, and is validated against experimental data from the literature. A number of parametric studies is performed to obtain insights on the direct internal reforming solid oxide fuel cell system behavior and efficiency, to aid the design procedure. It is shown that internal reforming results in temperature drop close to the inlet and that the direct internal reforming solid oxide fuel cell performance can be enhanced by increasing the operating temperature. It is also observed that decreases in the inlet temperature result in smoother temperature profiles and in the formation of reduced thermal gradients. Furthermore, the direct internal reforming solid oxide fuel cell performance was found to be affected by the thickness of the electrochemically‐active anode catalyst layer, although not always substantially, due to the counter‐balancing behavior of the activation and ohmic overpotentials. PMID:27570502

Zipf's Law in Gene Expression

NASA Astrophysics Data System (ADS)

Furusawa, Chikara; Kaneko, Kunihiko

2003-02-01

Using data from gene expression databases on various organisms and tissues, including yeast, nematodes, human normal and cancer tissues, and embryonic stem cells, we found that the abundances of expressed genes exhibit a power-law distribution with an exponent close to -1; i.e., they obey Zipf’s law. Furthermore, by simulations of a simple model with an intracellular reaction network, we found that Zipf’s law of chemical abundance is a universal feature of cells where such a network optimizes the efficiency and faithfulness of self-reproduction. These findings provide novel insights into the nature of the organization of reaction dynamics in living cells.

The role and mechanics of dendritic cells in tumor antigen acquisition and presentation following laser immunotherapy

NASA Astrophysics Data System (ADS)

Laverty, Sean M.; Dawkins, Bryan A.; Chen, Wei R.

2018-02-01

We extend our model of the antitumor immune response initiated by laser-immunotherapy treatment to more closely examine key steps in the immune response 1) tumor antigen acquisition by antigen-presenting dendritic cells (DCs) and 2) cytotoxic T cell (CTL) priming by lymphatic DCs. Specifically we explore the formation of DC-CTL complexes that lead to CTL priming. We find that the bias in the dissociation rate of the complex influences the outcome of treatment. In particular, a bias towards priming favors a rapid activated CTL response and the clearance of tumors.

A computational model of amoeboid cell swimming

NASA Astrophysics Data System (ADS)

Campbell, Eric J.; Bagchi, Prosenjit

2017-10-01

Amoeboid cells propel by generating pseudopods that are finger-like protrusions of the cell body that continually grow, bifurcate, and retract. Pseudopod-driven motility of amoeboid cells represents a complex and multiscale process that involves bio-molecular reactions, cell deformation, and cytoplasmic and extracellular fluid motion. Here we present a 3D model of pseudopod-driven swimming of an amoeba suspended in a fluid without any adhesion and in the absence of any chemoattractant. Our model is based on front-tracking/immersed-boundary methods, and it combines large deformation of the cell, a coarse-grain model for molecular reactions, and cytoplasmic and extracellular fluid flow. The predicted shapes of the swimming cell from our model show similarity with experimental observations. We predict that the swimming behavior changes from random-like to persistent unidirectional motion, and that the swimming speed increases, with increasing cell deformability and protein diffusivity. The unidirectionality in cell swimming is observed without any external cues and as a direct result of a change in pseudopod dynamics. We find that pseudopods become preferentially focused near the front of the cell and appear in greater numbers with increasing cell deformability and protein diffusivity, thereby increasing the swimming speed and making the cell shape more elongated. We find that the swimming speed is minimum when the cytoplasm viscosity is close to the extracellular fluid viscosity. We further find that the speed increases significantly as the cytoplasm becomes less viscous compared with the extracellular fluid, resembling the viscous fingering phenomenon observed in interfacial flows. While these results support the notion that softer cells migrate more aggressively, they also suggest a strong coupling between membrane elasticity, membrane protein diffusivity, and fluid viscosity.

Nucleocytoplasmic protein translocation during mitosis in the social amoebozoan Dictyostelium discoideum.

PubMed

O'Day, Danton H; Budniak, Aldona

2015-02-01

Mitosis is a fundamental and essential life process. It underlies the duplication and survival of all cells and, as a result, all eukaryotic organisms. Since uncontrolled mitosis is a dreaded component of many cancers, a full understanding of the process is critical. Evolution has led to the existence of three types of mitosis: closed, open, and semi-open. The significance of these different mitotic species, how they can lead to a full understanding of the critical events that underlie the asexual duplication of all cells, and how they may generate new insights into controlling unregulated cell division remains to be determined. The eukaryotic microbe Dictyostelium discoideum has proved to be a valuable biomedical model organism. While it appears to utilize closed mitosis, a review of the literature suggests that it possesses a form of mitosis that lies in the middle between truly open and fully closed mitosis-it utilizes a form of semi-open mitosis. Here, the nucleocytoplasmic translocation patterns of the proteins that have been studied during mitosis in the social amoebozoan D. discoideum are detailed followed by a discussion of how some of them provide support for the hypothesis of semi-open mitosis. © 2014 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.

Prediction of traction forces of motile cells.

PubMed

Roux, Clément; Duperray, Alain; Laurent, Valérie M; Michel, Richard; Peschetola, Valentina; Verdier, Claude; Étienne, Jocelyn

2016-10-06

When crawling on a flat substrate, living cells exert forces on it via adhesive contacts, enabling them to build up tension within their cytoskeleton and to change shape. The measurement of these forces has been made possible by traction force microscopy (TFM), a technique which has allowed us to obtain time-resolved traction force maps during cell migration. This cell 'footprint' is, however, not sufficient to understand the details of the mechanics of migration, that is how cytoskeletal elements (respectively, adhesion complexes) are put under tension and reinforce or deform (respectively, mature and/or unbind) as a result. In a recent paper, we have validated a rheological model of actomyosin linking tension, deformation and myosin activity. Here, we complement this model with tentative models of the mechanics of adhesion and explore how closely these models can predict the traction forces that we recover from experimental measurements during cell migration. The resulting mathematical problem is a PDE set on the experimentally observed domain, which we solve using a finite-element approach. The four parameters of the model can then be adjusted by comparison with experimental results on a single frame of an experiment, and then used to test the predictive power of the model for following frames and other experiments. It is found that the basic pattern of traction forces is robustly predicted by the model and fixed parameters as a function of current geometry only.

Active Solute Transport across Frog Skin and Epithelial Cell Systems According to the Association-Induction Hypothesis,

DTIC Science & Technology

1980-01-01

indicated in insect Malpighian tubules, insect midgut , choroid plexus and gastric mucosa. 9.2.5 Conciliation of the Conflict Between Models of "Homocellular...SeApeinaebility is therefore under close I Ling (P;. 14) control by hormones or drugs that react with receptor sites on these protelns and so...bears remembering that in active transport across bifacial cells the key cation is not always No% Thus in MalPighian tubules of insects the key Lon

Retinal Remodeling in the Tg P347L Rabbit, a Large-Eye Model of Retinal Degeneration

PubMed Central

Jones, Bryan William; Kondo, Mineo; Terasaki, Hiroko; Watt, Carl Brock; Rapp, Kevin; Anderson, James; Lin, Yanhua; Shaw, Marguerite Victoria; Yang, Jia-Hui; Marc, Robert Edward

2013-01-01

Retinitis pigmentosa (RP) is an inherited blinding disease characterized by progressive loss of retinal photo-receptors. There are numerous rodent models of retinal degeneration, but most are poor platforms for interventions that will translate into clinical practice. The rabbit possesses a number of desirable qualities for a model of retinal disease including a large eye and an existing and substantial knowledge base in retinal circuitry, anatomy, and ophthalmology. We have analyzed degeneration, remodeling, and reprogramming in a rabbit model of retinal degeneration, expressing a rhodopsin proline 347 to leucine transgene in a TgP347L rabbit as a powerful model to study the pathophysiology and treatment of retinal degeneration. We show that disease progression in the TgP347L rabbit closely tracks human cone-sparing RP, including the cone-associated preservation of bipolar cell signaling and triggering of reprogramming. The relatively fast disease progression makes the TgP347L rabbit an excellent model for gene therapy, cell biological intervention, progenitor cell transplantation, surgical interventions, and bionic prosthetic studies. PMID:21681749

Reticulation of low density shape memory polymer foam with an in vivo demonstration of vascular occlusion

PubMed Central

Rodriguez, Jennifer N.; Miller, Matthew W.; Boyle, Anthony; Horn, John; Yang, Cheng-Kang; Wilson, Thomas S.; Ortega, Jason M.; Small, Ward; Nash, Landon; Skoog, Hunter; Maitland, Duncan J.

2014-01-01

Predominantly closed-cell low density shape memory polymer (SMP) foam was recently reported to be an effective aneurysm filling device in a porcine model (Rodriguez et al., Journal of Biomedical Materials Research Part A 2013: (http://dx.doi.org/10.1002/jbm.a.34782)). Because healing involves blood clotting and cell migration throughout the foam volume, a more open-cell structure may further enhance the healing response. This research sought to develop a non-destructive reticulation process for this SMP foam to disrupt the membranes between pore cells. Non-destructive mechanical reticulation was achieved using a gravity-driven floating nitinol pin array coupled with vibratory agitation of the foam and supplemental chemical etching. Reticulation resulted in a reduced elastic modulus and increased permeability, but did not impede shape memory behavior. Reticulated foams were capable of achieving rapid vascular occlusion in an in vivo porcine model. PMID:25222869

Loss of phase-locking in non-weakly coupled inhibitory networks of type-I model neurons.

PubMed

Oh, Myongkeun; Matveev, Victor

2009-04-01

Synchronization of excitable cells coupled by reciprocal inhibition is a topic of significant interest due to the important role that inhibitory synaptic interaction plays in the generation and regulation of coherent rhythmic activity in a variety of neural systems. While recent work revealed the synchronizing influence of inhibitory coupling on the dynamics of many networks, it is known that strong coupling can destabilize phase-locked firing. Here we examine the loss of synchrony caused by an increase in inhibitory coupling in networks of type-I Morris-Lecar model oscillators, which is characterized by a period-doubling cascade and leads to mode-locked states with alternation in the firing order of the two cells, as reported recently by Maran and Canavier (J Comput Nerosci, 2008) for a network of Wang-Buzsáki model neurons. Although alternating-order firing has been previously reported as a near-synchronous state, we show that the stable phase difference between the spikes of the two Morris-Lecar cells can constitute as much as 70% of the unperturbed oscillation period. Further, we examine the generality of this phenomenon for a class of type-I oscillators that are close to their excitation thresholds, and provide an intuitive geometric description of such "leap-frog" dynamics. In the Morris-Lecar model network, the alternation in the firing order arises under the condition of fast closing of K( + ) channels at hyperpolarized potentials, which leads to slow dynamics of membrane potential upon synaptic inhibition, allowing the presynaptic cell to advance past the postsynaptic cell in each cycle of the oscillation. Further, we show that non-zero synaptic decay time is crucial for the existence of leap-frog firing in networks of phase oscillators. However, we demonstrate that leap-frog spiking can also be obtained in pulse-coupled inhibitory networks of one-dimensional oscillators with a multi-branched phase domain, for instance in a network of quadratic integrate-and-fire model cells. Finally, for the case of a homogeneous network, we establish quantitative conditions on the phase resetting properties of each cell necessary for stable alternating-order spiking, complementing the analysis of Goel and Ermentrout (Physica D 163:191-216, 2002) of the order-preserving phase transition map.

A pressure relaxation closure model for one-dimensional, two-material Lagrangian hydrodynamics based on the Riemann problem

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kamm, James R; Shashkov, Mikhail J

2009-01-01

Despite decades of development, Lagrangian hydrodynamics of strengthfree materials presents numerous open issues, even in one dimension. We focus on the problem of closing a system of equations for a two-material cell under the assumption of a single velocity model. There are several existing models and approaches, each possessing different levels of fidelity to the underlying physics and each exhibiting unique features in the computed solutions. We consider the case in which the change in heat in the constituent materials in the mixed cell is assumed equal. An instantaneous pressure equilibration model for a mixed cell can be cast asmore » four equations in four unknowns, comprised of the updated values of the specific internal energy and the specific volume for each of the two materials in the mixed cell. The unique contribution of our approach is a physics-inspired, geometry-based model in which the updated values of the sub-cell, relaxing-toward-equilibrium constituent pressures are related to a local Riemann problem through an optimization principle. This approach couples the modeling problem of assigning sub-cell pressures to the physics associated with the local, dynamic evolution. We package our approach in the framework of a standard predictor-corrector time integration scheme. We evaluate our model using idealized, two material problems using either ideal-gas or stiffened-gas equations of state and compare these results to those computed with the method of Tipton and with corresponding pure-material calculations.« less

Hematopoiesis and hematopoietic organs in arthropods.

PubMed

Grigorian, Melina; Hartenstein, Volker

2013-03-01

Hemocytes (blood cells) are motile cells that move throughout the extracellular space and that exist in all clades of the animal kingdom. Hemocytes play an important role in shaping the extracellular environment and in the immune response. Developmentally, hemocytes are closely related to the epithelial cells lining the vascular system (endothelia) and the body cavity (mesothelia). In vertebrates and insects, common progenitors, called hemangioblasts, give rise to the endothelia and blood cells. In the adult animal, many differentiated hemocytes seem to retain the ability to proliferate; however, in most cases investigated closely, the bulk of hemocyte proliferation takes place in specialized hematopoietic organs. Hematopoietic organs provide an environment where undifferentiated blood stem cells are able to self-renew, and at the same time generate offspring that differentiate into different blood cell types. Hematopoiesis in vertebrates, taking place in the bone marrow, has been subject to intensive research by immunologists and stem cell biologists. Much less is known about blood cell formation in invertebrate animals. In this review, we will survey structural and functional properties of invertebrate hematopoietic organs, with a main focus on insects and other arthropod taxa. We will then discuss similarities, at the molecular and structural level, that are apparent when comparing the development of blood cells in hematopoietic organs of vertebrates and arthropods. Our comparative review is intended to elucidate aspects of the biology of blood stem cells that are more easily missed when focusing on one or a few model species.

Induced Pluripotent Stem Cells for Disease Modeling and Drug Discovery in Neurodegenerative Diseases.

PubMed

Cao, Lei; Tan, Lan; Jiang, Teng; Zhu, Xi-Chen; Yu, Jin-Tai

2015-08-01

Although most neurodegenerative diseases have been closely related to aberrant accumulation of aggregation-prone proteins in neurons, understanding their pathogenesis remains incomplete, and there is no treatment to delay the onset or slow the progression of many neurodegenerative diseases. The availability of induced pluripotent stem cells (iPSCs) in recapitulating the phenotypes of several late-onset neurodegenerative diseases marks the new era in in vitro modeling. The iPSC collection represents a unique and well-characterized resource to elucidate disease mechanisms in these diseases and provides a novel human stem cell platform for screening new candidate therapeutics. Modeling human diseases using iPSCs has created novel opportunities for both mechanistic studies as well as for the discovery of new disease therapies. In this review, we introduce iPSC-based disease modeling in neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. In addition, we discuss the implementation of iPSCs in drug discovery associated with some new techniques.

Structural model of the open–closed–inactivated cycle of prokaryotic voltage-gated sodium channels

PubMed Central

Bagnéris, Claire; Naylor, Claire E.; McCusker, Emily C.

2015-01-01

In excitable cells, the initiation of the action potential results from the opening of voltage-gated sodium channels. These channels undergo a series of conformational changes between open, closed, and inactivated states. Many models have been proposed for the structural transitions that result in these different functional states. Here, we compare the crystal structures of prokaryotic sodium channels captured in the different conformational forms and use them as the basis for examining molecular models for the activation, slow inactivation, and recovery processes. We compare structural similarities and differences in the pore domains, specifically in the transmembrane helices, the constrictions within the pore cavity, the activation gate at the cytoplasmic end of the last transmembrane helix, the C-terminal domain, and the selectivity filter. We discuss the observed differences in the context of previous models for opening, closing, and inactivation, and present a new structure-based model for the functional transitions. Our proposed prokaryotic channel activation mechanism is then compared with the activation transition in eukaryotic sodium channels. PMID:25512599

Aligned fibers direct collective cell migration to engineer closing and nonclosing wound gaps

PubMed Central

Sharma, Puja; Ng, Colin; Jana, Aniket; Padhi, Abinash; Szymanski, Paige; Lee, Jerry S. H.; Behkam, Bahareh; Nain, Amrinder S.

2017-01-01

Cell emergence onto damaged or organized fibrous extracellular matrix (ECM) is a crucial precursor to collective cell migration in wound closure and cancer metastasis, respectively. However, there is a fundamental gap in our quantitative understanding of the role of local ECM size and arrangement in cell emergence–based migration and local gap closure. Here, using ECM-mimicking nanofibers bridging cell monolayers, we describe a method to recapitulate and quantitatively describe these in vivo behaviors over multispatial (single cell to cell sheets) and temporal (minutes to weeks) scales. On fiber arrays with large interfiber spacing, cells emerge (invade) either singularly by breaking cell–cell junctions analogous to release of a stretched rubber band (recoil), or in groups of few cells (chains), whereas on closely spaced fibers, multiple chains emerge collectively. Advancing cells on fibers form cell streams, which support suspended cell sheets (SCS) of various sizes and curvatures. SCS converge to form local gaps that close based on both the gap size and shape. We document that cell stream spacing of 375 µm and larger hinders SCS advancement, thus providing abilities to engineer closing and nonclosing gaps. Altogether we highlight the importance of studying cell-fiber interactions and matrix structural remodeling in fundamental and translational cell biology. PMID:28747440

Nonlinear Dynamic Theory of Acute Cell Injuries and Brain Ischemia

NASA Astrophysics Data System (ADS)

Taha, Doaa; Anggraini, Fika; Degracia, Donald; Huang, Zhi-Feng

2015-03-01

Cerebral ischemia in the form of stroke and cardiac arrest brain damage affect over 1 million people per year in the USA alone. In spite of close to 200 clinical trials and decades of research, there are no treatments to stop post-ischemic neuron death. We have argued that a major weakness of current brain ischemia research is lack of a deductive theoretical framework of acute cell injury to guide empirical studies. A previously published autonomous model based on the concept of nonlinear dynamic network was shown to capture important facets of cell injury, linking the concept of therapeutic to bistable dynamics. Here we present an improved, non-autonomous formulation of the nonlinear dynamic model of cell injury that allows multiple acute injuries over time, thereby allowing simulations of both therapeutic treatment and preconditioning. Our results are connected to the experimental data of gene expression and proteomics of neuron cells. Importantly, this new model may be construed as a novel approach to pharmacodynamics of acute cell injury. The model makes explicit that any pro-survival therapy is always a form of sub-lethal injury. This insight is expected to widely influence treatment of acute injury conditions that have defied successful treatment to date. This work is supported by NIH NINDS (NS081347) and Wayne State University President's Research Enhancement Award.

Causes and correlations in cambium phenology: towards an integrated framework of xylogenesis.

PubMed

Rossi, Sergio; Morin, Hubert; Deslauriers, Annie

2012-03-01

Although habitually considered as a whole, xylogenesis is a complex process of division and maturation of a pool of cells where the relationship between the phenological phases generating such a growth pattern remains essentially unknown. This study investigated the causal relationships in cambium phenology of black spruce [Picea mariana (Mill.) BSP] monitored for 8 years on four sites of the boreal forest of Quebec, Canada. The dependency links connecting the timing of xylem cell differentiation and cell production were defined and the resulting causal model was analysed with d-sep tests and generalized mixed models with repeated measurements, and tested with Fisher's C statistics to determine whether and how causality propagates through the measured variables. The higher correlations were observed between the dates of emergence of the first developing cells and between the ending of the differentiation phases, while the number of cells was significantly correlated with all phenological phases. The model with eight dependency links was statistically valid for explaining the causes and correlations between the dynamics of cambium phenology. Causal modelling suggested that the phenological phases involved in xylogenesis are closely interconnected by complex relationships of cause and effect, with the onset of cell differentiation being the main factor directly or indirectly triggering all successive phases of xylem maturation.

Causes and correlations in cambium phenology: towards an integrated framework of xylogenesis

PubMed Central

Rossi, Sergio; Morin, Hubert; Deslauriers, Annie

2012-01-01

Although habitually considered as a whole, xylogenesis is a complex process of division and maturation of a pool of cells where the relationship between the phenological phases generating such a growth pattern remains essentially unknown. This study investigated the causal relationships in cambium phenology of black spruce [Picea mariana (Mill.) BSP] monitored for 8 years on four sites of the boreal forest of Quebec, Canada. The dependency links connecting the timing of xylem cell differentiation and cell production were defined and the resulting causal model was analysed with d-sep tests and generalized mixed models with repeated measurements, and tested with Fisher’s C statistics to determine whether and how causality propagates through the measured variables. The higher correlations were observed between the dates of emergence of the first developing cells and between the ending of the differentiation phases, while the number of cells was significantly correlated with all phenological phases. The model with eight dependency links was statistically valid for explaining the causes and correlations between the dynamics of cambium phenology. Causal modelling suggested that the phenological phases involved in xylogenesis are closely interconnected by complex relationships of cause and effect, with the onset of cell differentiation being the main factor directly or indirectly triggering all successive phases of xylem maturation. PMID:22174441

Chromatin conformation in living cells: support for a zig-zag model of the 30 nm chromatin fiber

NASA Technical Reports Server (NTRS)

Rydberg, B.; Holley, W. R.; Mian, I. S.; Chatterjee, A.

1998-01-01

A new method was used to probe the conformation of chromatin in living mammalian cells. The method employs ionizing radiation and is based on the concept that such radiation induces correlated breaks in DNA strands that are in spatial proximity. Human dermal fibroblasts in G0 phase of the cell cycle and Chinese hamster ovary cells in mitosis were irradiated by X-rays or accelerated ions. Following lysis of the cells, DNA fragments induced by correlated breaks were end-labeled and separated according to size on denaturing polyacrylamide gels. A characteristic peak was obtained for a fragment size of 78 bases, which is the size that corresponds to one turn of DNA around the nucleosome. Additional peaks between 175 and 450 bases reflect the relative position of nearest-neighbor nucleosomes. Theoretical calculations that simulate the indirect and direct effect of radiation on DNA demonstrate that the fragment size distributions are closely related to the chromatin structure model used. Comparison of the experimental data with theoretical results support a zig-zag model of the chromatin fiber rather than a simple helical model. Thus, radiation-induced damage analysis can provide information on chromatin structure in the living cell. Copyright 1998 Academic Press.

Modeling of steady-state convective cooling of cylindrical Li-ion cells

NASA Astrophysics Data System (ADS)

Shah, K.; Drake, S. J.; Wetz, D. A.; Ostanek, J. K.; Miller, S. P.; Heinzel, J. M.; Jain, A.

2014-07-01

While Lithium-ion batteries have the potential to serve as an excellent means of energy storage, they suffer from several operational safety concerns. Temperature excursion beyond a specified limit for a Lithium-ion battery triggers a sequence of decomposition and release, which can preclude thermal runaway events and catastrophic failure. To optimize liquid or air-based convective cooling approaches, it is important to accurately model the thermal response of Lithium-ion cells to convective cooling, particularly in high-rate discharge applications where significant heat generation is expected. This paper presents closed-form analytical solutions for the steady-state temperature profile in a convectively cooled cylindrical Lithium-ion cell. These models account for the strongly anisotropic thermal conductivity of cylindrical Lithium-ion batteries due to the spirally wound electrode assembly. Model results are in excellent agreement with experimentally measured temperature rise in a thermal test cell. Results indicate that improvements in radial thermal conductivity and axial convective heat transfer coefficient may result in significant peak temperature reduction. Battery sizing optimization using the analytical model is discussed, indicating the dependence of thermal performance of the cell on its size and aspect ratio. Results presented in this paper may aid in accurate thermal design and thermal management of Lithium-ion batteries.

A Multistate Toggle Switch Defines Fungal Cell Fates and Is Regulated by Synergistic Genetic Cues

PubMed Central

Anderson, Matthew Z.; Porman, Allison M.; Wang, Na; Mancera, Eugenio; Bennett, Richard J.

2016-01-01

Heritable epigenetic changes underlie the ability of cells to differentiate into distinct cell types. Here, we demonstrate that the fungal pathogen Candida tropicalis exhibits multipotency, undergoing stochastic and reversible switching between three cellular states. The three cell states exhibit unique cellular morphologies, growth rates, and global gene expression profiles. Genetic analysis identified six transcription factors that play key roles in regulating cell differentiation. In particular, we show that forced expression of Wor1 or Efg1 transcription factors can be used to manipulate transitions between all three cell states. A model for tristability is proposed in which Wor1 and Efg1 are self-activating but mutually antagonistic transcription factors, thereby forming a symmetrical self-activating toggle switch. We explicitly test this model and show that ectopic expression of WOR1 can induce white-to-hybrid-to-opaque switching, whereas ectopic expression of EFG1 drives switching in the opposite direction, from opaque-to-hybrid-to-white cell states. We also address the stability of induced cell states and demonstrate that stable differentiation events require ectopic gene expression in combination with chromatin-based cues. These studies therefore experimentally test a model of multistate stability and demonstrate that transcriptional circuits act synergistically with chromatin-based changes to drive cell state transitions. We also establish close mechanistic parallels between phenotypic switching in unicellular fungi and cell fate decisions during stem cell reprogramming. PMID:27711197

G-protein-mediated inhibition of the Trp channel TRPM1 requires the Gβγ dimer.

PubMed

Shen, Yin; Rampino, Melissa Ann F; Carroll, Reed C; Nawy, Scott

2012-05-29

ON bipolar cells are critical for the function of the ON pathway in the visual system. They express a metabotropic glutamate receptor (mGluR6) that, when activated, couples to the G(o) class of G protein. The channel that is primarily responsible for the synaptic response has been recently identified as the transient receptor potential cation channel subfamily M member 1 (TRPM1); TRPM1 is negatively coupled to the mGluR6/Go cascade such that activation of the cascade results in closure of the channel. Light indirectly opens TRPM1 by reducing transmitter release from presynaptic photoreceptors, resulting in a decrease in mGluR6 activation. Conversely, in the dark, binding of synaptic glutamate to mGluR6 inhibits TRPM1 current. Closure of TRPM1 by G-protein activation in the dark is a critical step in the process of ON bipolar cell signal transduction, but the precise pathway linking these two events is not understood. To address this question, we measured TRPM1 activity in retinal bipolar cells, in human ependymal melanocytes (HEMs) that endogenously express TRPM1, and in HEK293 cells transfected with TRPM1. Dialysis of the Gβγ subunit dimer, but not Gα(o), closed TRPM1 channels in every cell type that we tested. In addition, activation of an endogenous G-protein-coupled receptor pathway in HEK293 cells that releases Gβγ without activating Go protein also closed TRPM1 channels. These results suggest a model in which the Gβγ dimer that is released as a result of the dissociation from Gα(o) upon activation of mGluR6 closes the TRPM1 channel, perhaps via a direct interaction.

Stretch Injury of Human Induced Pluripotent Stem Cell Derived Neurons in a 96 Well Format

PubMed Central

Sherman, Sydney A.; Phillips, Jack K.; Costa, J. Tighe; Cho, Frances S.; Oungoulian, Sevan R.; Finan, John D.

2016-01-01

Traumatic brain injury (TBI) is a major cause of mortality and morbidity with limited therapeutic options. Traumatic axonal injury (TAI) is an important component of TBI pathology. It is difficult to reproduce TAI in animal models of closed head injury, but in vitro stretch injury models reproduce clinical TAI pathology. Existing in vitro models employ primary rodent neurons or human cancer cell line cells in low throughput formats. This in vitro neuronal stretch injury model employs human induced pluripotent stem cell-derived neurons (hiPSCNs) in a 96 well format. Silicone membranes were attached to 96 well plate tops to create stretchable, culture substrates. A custom-built device was designed and validated to apply repeatable, biofidelic strains and strain rates to these plates. A high content approach was used to measure injury in a hypothesis-free manner. These measurements are shown to provide a sensitive, dose-dependent, multi-modal description of the response to mechanical insult. hiPSCNs transition from healthy to injured phenotype at approximately 35% Lagrangian strain. Continued development of this model may create novel opportunities for drug discovery and exploration of the role of human genotype in TAI pathology. PMID:27671211

The self-organization of grid cells in 3D

PubMed Central

Stella, Federico; Treves, Alessandro

2015-01-01

Do we expect periodic grid cells to emerge in bats, or perhaps dolphins, exploring a three-dimensional environment? How long will it take? Our self-organizing model, based on ring-rate adaptation, points at a complex answer. The mathematical analysis leads to asymptotic states resembling face centered cubic (FCC) and hexagonal close packed (HCP) crystal structures, which are calculated to be very close to each other in terms of cost function. The simulation of the full model, however, shows that the approach to such asymptotic states involves several sub-processes over distinct time scales. The smoothing of the initially irregular multiple fields of individual units and their arrangement into hexagonal grids over certain best planes are observed to occur relatively quickly, even in large 3D volumes. The correct mutual orientation of the planes, though, and the coordinated arrangement of different units, take a longer time, with the network showing no sign of convergence towards either a pure FCC or HCP ordering. DOI: http://dx.doi.org/10.7554/eLife.05913.001 PMID:25821989

Gap-junction coupling and ATP-sensitive potassium channels in human β -cell clusters: Effects on emergent dynamics

NASA Astrophysics Data System (ADS)

Loppini, A.; Pedersen, M. G.; Braun, M.; Filippi, S.

2017-09-01

The importance of gap-junction coupling between β cells in pancreatic islets is well established in mouse. Such ultrastructural connections synchronize cellular activity, confine biological heterogeneity, and enhance insulin pulsatility. Dysfunction of coupling has been associated with diabetes and altered β -cell function. However, the role of gap junctions between human β cells is still largely unexplored. By using patch-clamp recordings of β cells from human donors, we previously estimated electrical properties of these channels by mathematical modeling of pairs of human β cells. In this work we revise our estimate by modeling triplet configurations and larger heterogeneous clusters. We find that a coupling conductance in the range 0.005 -0.020 nS/pF can reproduce experiments in almost all the simulated arrangements. We finally explore the consequence of gap-junction coupling of this magnitude between β cells with mutant variants of the ATP-sensitive potassium channels involved in some metabolic disorders and diabetic conditions, translating studies performed on rodents to the human case. Our results are finally discussed from the perspective of therapeutic strategies. In summary, modeling of more realistic clusters with more than two β cells slightly lowers our previous estimate of gap-junction conductance and gives rise to patterns that more closely resemble experimental traces.

Transient Macroscopic Chemistry in the DSMC Method

NASA Astrophysics Data System (ADS)

Goldsworthy, M. J.; Macrossan, M. N.; Abdel-Jawad, M.

2008-12-01

In the Direct Simulation Monte Carlo method, a combination of statistical and deterministic procedures applied to a finite number of `simulator' particles are used to model rarefied gas-kinetic processes. Traditionally, chemical reactions are modelled using information from specific colliding particle pairs. In the Macroscopic Chemistry Method (MCM), the reactions are decoupled from the specific particle pairs selected for collisions. Information from all of the particles within a cell is used to determine a reaction rate coefficient for that cell. MCM has previously been applied to steady flow DSMC simulations. Here we show how MCM can be used to model chemical kinetics in DSMC simulations of unsteady flow. Results are compared with a collision-based chemistry procedure for two binary reactions in a 1-D unsteady shock-expansion tube simulation and during the unsteady development of 2-D flow through a cavity. For the shock tube simulation, close agreement is demonstrated between the two methods for instantaneous, ensemble-averaged profiles of temperature and species mole fractions. For the cavity flow, a high degree of thermal non-equilibrium is present and non-equilibrium reaction rate correction factors are employed in MCM. Very close agreement is demonstrated for ensemble averaged mole fraction contours predicted by the particle and macroscopic methods at three different flow-times. A comparison of the accumulated number of net reactions per cell shows that both methods compute identical numbers of reaction events. For the 2-D flow, MCM required similar CPU and memory resources to the particle chemistry method. The Macroscopic Chemistry Method is applicable to any general DSMC code using any viscosity or non-reacting collision models and any non-reacting energy exchange models. MCM can be used to implement any reaction rate formulations, whether these be from experimental or theoretical studies.

Enhanced clinical-scale manufacturing of TCR transduced T-cells using closed culture system modules.

PubMed

Jin, Jianjian; Gkitsas, Nikolaos; Fellowes, Vicki S; Ren, Jiaqiang; Feldman, Steven A; Hinrichs, Christian S; Stroncek, David F; Highfill, Steven L

2018-01-24

Genetic engineering of T-cells to express specific T cell receptors (TCR) has emerged as a novel strategy to treat various malignancies. More widespread utilization of these types of therapies has been somewhat constrained by the lack of closed culture processes capable of expanding sufficient numbers of T-cells for clinical application. Here, we evaluate a process for robust clinical grade manufacturing of TCR gene engineered T-cells. TCRs that target human papillomavirus E6 and E7 were independently tested. A 21 day process was divided into a transduction phase (7 days) and a rapid expansion phase (14 days). This process was evaluated using two healthy donor samples and four samples obtained from patients with epithelial cancers. The process resulted in ~ 2000-fold increase in viable nucleated cells and high transduction efficiencies (64-92%). At the end of culture, functional assays demonstrated that these cells were potent and specific in their ability to kill tumor cells bearing target and secrete large quantities of interferon and tumor necrosis factor. Both phases of culture were contained within closed or semi-closed modules, which include automated density gradient separation and cell culture bags for the first phase and closed GREX culture devices and wash/concentrate systems for the second phase. Large-scale manufacturing using modular systems and semi-automated devices resulted in highly functional clinical-grade TCR transduced T-cells. This process is now in use in actively accruing clinical trials and the NIH Clinical Center and can be utilized at other cell therapy manufacturing sites that wish to scale-up and optimize their processing using closed systems.

Recapitulation of spinal motor neuron-specific disease phenotypes in a human cell model of spinal muscular atrophy

PubMed Central

Wang, Zhi-Bo; Zhang, Xiaoqing; Li, Xue-Jun

2013-01-01

Establishing human cell models of spinal muscular atrophy (SMA) to mimic motor neuron-specific phenotypes holds the key to understanding the pathogenesis of this devastating disease. Here, we developed a closely representative cell model of SMA by knocking down the disease-determining gene, survival motor neuron (SMN), in human embryonic stem cells (hESCs). Our study with this cell model demonstrated that knocking down of SMN does not interfere with neural induction or the initial specification of spinal motor neurons. Notably, the axonal outgrowth of spinal motor neurons was significantly impaired and these disease-mimicking neurons subsequently degenerated. Furthermore, these disease phenotypes were caused by SMN-full length (SMN-FL) but not SMN-Δ7 (lacking exon 7) knockdown, and were specific to spinal motor neurons. Restoring the expression of SMN-FL completely ameliorated all of the disease phenotypes, including specific axonal defects and motor neuron loss. Finally, knockdown of SMN-FL led to excessive mitochondrial oxidative stress in human motor neuron progenitors. The involvement of oxidative stress in the degeneration of spinal motor neurons in the SMA cell model was further confirmed by the administration of N-acetylcysteine, a potent antioxidant, which prevented disease-related apoptosis and subsequent motor neuron death. Thus, we report here the successful establishment of an hESC-based SMA model, which exhibits disease gene isoform specificity, cell type specificity, and phenotype reversibility. Our model provides a unique paradigm for studying how motor neurons specifically degenerate and highlights the potential importance of antioxidants for the treatment of SMA. PMID:23208423

Analytical approximations of the firing rate of an adaptive exponential integrate-and-fire neuron in the presence of synaptic noise.

PubMed

Hertäg, Loreen; Durstewitz, Daniel; Brunel, Nicolas

2014-01-01

Computational models offer a unique tool for understanding the network-dynamical mechanisms which mediate between physiological and biophysical properties, and behavioral function. A traditional challenge in computational neuroscience is, however, that simple neuronal models which can be studied analytically fail to reproduce the diversity of electrophysiological behaviors seen in real neurons, while detailed neuronal models which do reproduce such diversity are intractable analytically and computationally expensive. A number of intermediate models have been proposed whose aim is to capture the diversity of firing behaviors and spike times of real neurons while entailing the simplest possible mathematical description. One such model is the exponential integrate-and-fire neuron with spike rate adaptation (aEIF) which consists of two differential equations for the membrane potential (V) and an adaptation current (w). Despite its simplicity, it can reproduce a wide variety of physiologically observed spiking patterns, can be fit to physiological recordings quantitatively, and, once done so, is able to predict spike times on traces not used for model fitting. Here we compute the steady-state firing rate of aEIF in the presence of Gaussian synaptic noise, using two approaches. The first approach is based on the 2-dimensional Fokker-Planck equation that describes the (V,w)-probability distribution, which is solved using an expansion in the ratio between the time constants of the two variables. The second is based on the firing rate of the EIF model, which is averaged over the distribution of the w variable. These analytically derived closed-form expressions were tested on simulations from a large variety of model cells quantitatively fitted to in vitro electrophysiological recordings from pyramidal cells and interneurons. Theoretical predictions closely agreed with the firing rate of the simulated cells fed with in-vivo-like synaptic noise.

Open-cell and closed-cell clouds off Peru

NASA Image and Video Library

2010-04-27

2010/107 - 04/17 at 21 :05 UTC. Open-cell and closed-cell clouds off Peru, Pacific Ocean Resembling a frosted window on a cold winter's day, this lacy pattern of marine clouds was captured off the coast of Peru in the Pacific Ocean by the MODIS on the Aqua satellite on April 19, 2010. The image reveals both open- and closed-cell cumulus cloud patterns. These cells, or parcels of air, often occur in roughly hexagonal arrays in a layer of fluid (the atmosphere often behaves like a fluid) that begins to "boil," or convect, due to heating at the base or cooling at the top of the layer. In "closed" cells warm air is rising in the center, and sinking around the edges, so clouds appear in cell centers, but evaporate around cell edges. This produces cloud formations like those that dominate the lower left. The reverse flow can also occur: air can sink in the center of the cell and rise at the edge. This process is called "open cell" convection, and clouds form at cell edges around open centers, which creates a lacy, hollow-looking pattern like the clouds in the upper right. Closed and open cell convection represent two stable atmospheric configurations — two sides of the convection coin. But what determines which path the "boiling" atmosphere will take? Apparently the process is highly chaotic, and there appears to be no way to predict whether convection will result in open or closed cells. Indeed, the atmosphere may sometimes flip between one mode and another in no predictable pattern. Satellite: Aqua NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team To learn more about MODIS go to: rapidfire.sci.gsfc.nasa.gov/gallery/?latest NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

A Novel Method for Preparing Auxetic Foam from Closed-cell Polymer Foam Based on Steam Penetration and Condensation (SPC) Process.

PubMed

Fan, Donglei; Li, Minggang; Qiu, Jian; Xing, Haiping; Jiang, Zhiwei; Tang, Tao

2018-05-31

Auxetic materials are a class of materials possessing negative Poisson's ratio. Here we establish a novel method for preparing auxetic foam from closed-cell polymer foam based on steam penetration and condensation (SPC) process. Using polyethylene (PE) closed-cell foam as an example, the resultant foams treated by SPC process present negative Poisson's ratio during stretching and compression testing. The effect of steam-treated temperature and time on the conversion efficiency of negative Poisson's ratio foam is investigated, and the mechanism of SPC method for forming re-entrant structure is discussed. The results indicate that the presence of enough steam within the cells is a critical factor for the negative Poisson's ratio conversion in the SPC process. The pressure difference caused by steam condensation is the driving force for the conversion from conventional closed-cell foam to the negative Poisson's ratio foam. Furthermore, the applicability of SPC process for fabricating auxetic foam is studied by replacing PE foam by polyvinyl chloride (PVC) foam with closed-cell structure or replacing water steam by ethanol steam. The results verify the universality of SPC process for fabricating auxetic foams from conventional foams with closed-cell structure. In addition, we explored potential application of the obtained auxetic foams by SPC process in the fabrication of shape memory polymer materials.

Influenza Vaccination Accelerates Recovery of Ferrets from Lymphopenia

PubMed Central

Music, Nedzad; Reber, Adrian J.; Kamal, Ram P.; Blanchfield, Kristy; Wilson, Jason R.; Donis, Ruben O.; Katz, Jacqueline M.; York, Ian A.

2014-01-01

Ferrets are a useful animal model for human influenza virus infections, since they closely mimic the pathogenesis of influenza viruses observed in humans. However, a lack of reagents, especially for flow cytometry of immune cell subsets, has limited research in this model. Here we use a panel of primarily species cross-reactive antibodies to identify ferret T cells, cytotoxic T lymphocytes (CTL), B cells, and granulocytes in peripheral blood. Following infection with seasonal H3N2 or H1N1pdm09 influenza viruses, these cell types showed rapid and dramatic changes in frequency, even though clinically the infections were mild. The loss of B cells and CD4 and CD8 T cells, and the increase in neutrophils, were especially marked 1–2 days after infection, when about 90% of CD8+ T cells disappeared from the peripheral blood. The different virus strains led to different kinetics of leukocyte subset alterations. Vaccination with homologous vaccine reduced clinical symptoms slightly, but led to a much more rapid return to normal leukocyte parameters. Assessment of clinical symptoms may underestimate the effectiveness of influenza vaccine in restoring homeostasis. PMID:24968319

Influenza vaccination accelerates recovery of ferrets from lymphopenia.

PubMed

Music, Nedzad; Reber, Adrian J; Lipatov, Aleksandr S; Kamal, Ram P; Blanchfield, Kristy; Wilson, Jason R; Donis, Ruben O; Katz, Jacqueline M; York, Ian A

2014-01-01

Ferrets are a useful animal model for human influenza virus infections, since they closely mimic the pathogenesis of influenza viruses observed in humans. However, a lack of reagents, especially for flow cytometry of immune cell subsets, has limited research in this model. Here we use a panel of primarily species cross-reactive antibodies to identify ferret T cells, cytotoxic T lymphocytes (CTL), B cells, and granulocytes in peripheral blood. Following infection with seasonal H3N2 or H1N1pdm09 influenza viruses, these cell types showed rapid and dramatic changes in frequency, even though clinically the infections were mild. The loss of B cells and CD4 and CD8 T cells, and the increase in neutrophils, were especially marked 1-2 days after infection, when about 90% of CD8+ T cells disappeared from the peripheral blood. The different virus strains led to different kinetics of leukocyte subset alterations. Vaccination with homologous vaccine reduced clinical symptoms slightly, but led to a much more rapid return to normal leukocyte parameters. Assessment of clinical symptoms may underestimate the effectiveness of influenza vaccine in restoring homeostasis.

Quantifying the contribution of chromatin dynamics to stochastic gene expression reveals long, locus-dependent periods between transcriptional bursts.

PubMed

Viñuelas, José; Kaneko, Gaël; Coulon, Antoine; Vallin, Elodie; Morin, Valérie; Mejia-Pous, Camila; Kupiec, Jean-Jacques; Beslon, Guillaume; Gandrillon, Olivier

2013-02-25

A number of studies have established that stochasticity in gene expression may play an important role in many biological phenomena. This therefore calls for further investigations to identify the molecular mechanisms at stake, in order to understand and manipulate cell-to-cell variability. In this work, we explored the role played by chromatin dynamics in the regulation of stochastic gene expression in higher eukaryotic cells. For this purpose, we generated isogenic chicken-cell populations expressing a fluorescent reporter integrated in one copy per clone. Although the clones differed only in the genetic locus at which the reporter was inserted, they showed markedly different fluorescence distributions, revealing different levels of stochastic gene expression. Use of chromatin-modifying agents showed that direct manipulation of chromatin dynamics had a marked effect on the extent of stochastic gene expression. To better understand the molecular mechanism involved in these phenomena, we fitted these data to a two-state model describing the opening/closing process of the chromatin. We found that the differences between clones seemed to be due mainly to the duration of the closed state, and that the agents we used mainly seem to act on the opening probability. In this study, we report biological experiments combined with computational modeling, highlighting the importance of chromatin dynamics in stochastic gene expression. This work sheds a new light on the mechanisms of gene expression in higher eukaryotic cells, and argues in favor of relatively slow dynamics with long (hours to days) periods of quiet state.

Newly-derived neuroblastoma cell lines propagated in serum-free media recapitulate the genotype and phenotype of primary neuroblastoma tumours.

PubMed

Bate-Eya, Laurel T; Ebus, Marli E; Koster, Jan; den Hartog, Ilona J M; Zwijnenburg, Danny A; Schild, Linda; van der Ploeg, Ida; Dolman, M Emmy M; Caron, Huib N; Versteeg, Rogier; Molenaar, Jan J

2014-02-01

Recently protocols have been devised for the culturing of cell lines from fresh tumours under serum-free conditions in defined neural stem cell medium. These cells, frequently called tumour initiating cells (TICs) closely retained characteristics of the tumours of origin. We report the isolation of eight newly-derived neuroblastoma TICs from six primary neuroblastoma tumours and two bone marrow metastases. The primary tumours from which these TICs were generated have previously been fully typed by whole genome sequencing (WGS). Array comparative genomic hybridisation (aCGH) analysis showed that TIC lines retained essential characteristics of the primary tumours and exhibited typical neuroblastoma chromosomal aberrations such as MYCN amplification, gain of chromosome 17q and deletion of 1p36. Protein analysis showed expression for neuroblastoma markers MYCN, NCAM, CHGA, DBH and TH while haematopoietic markers CD19 and CD11b were absent. We analysed the growth characteristics and confirmed tumour-forming potential using sphere-forming assays, subcutaneous and orthotopic injection of these cells into immune-compromised mice. Affymetrix mRNA expression profiling of TIC line xenografts showed an expression pattern more closely mimicking primary tumours compared to xenografts from classical cell lines. This establishes that these neuroblastoma TICs cultured under serum-free conditions are relevant and useful neuroblastoma tumour models. Copyright © 2013 Elsevier Ltd. All rights reserved.

A+-Helix of Protein C Inhibitor (PCI) Is a Cell-penetrating Peptide That Mediates Cell Membrane Permeation of PCI*

PubMed Central

Yang, Hanjiang; Wahlmüller, Felix Christof; Sarg, Bettina; Furtmüller, Margareta; Geiger, Margarethe

2015-01-01

Protein C inhibitor (PCI) is a serpin with broad protease reactivity. It binds glycosaminoglycans and certain phospholipids that can modulate its inhibitory activity. PCI can penetrate through cellular membranes via binding to phosphatidylethanolamine. The exact mechanism of PCI internalization and the intracellular role of the serpin are not well understood. Here we showed that testisin, a glycosylphosphatidylinositol-anchored serine protease, cleaved human PCI and mouse PCI (mPCI) at their reactive sites as well as at sites close to their N terminus. This cleavage was observed not only with testisin in solution but also with cell membrane-anchored testisin on U937 cells. The cleavage close to the N terminus released peptides rich in basic amino acids. Synthetic peptides corresponding to the released peptides of human PCI (His1–Arg11) and mPCI (Arg1–Ala18) functioned as cell-penetrating peptides. Because intact mPCI but not testisin-cleaved mPCI was internalized by Jurkat T cells, a truncated mPCI mimicking testisin-cleaved mPCI was created. The truncated mPCI lacking 18 amino acids at the N terminus was not taken up by Jurkat T cells. Therefore our model suggests that testisin or other proteases could regulate the internalization of PCI by removing its N terminus. This may represent one of the mechanisms regulating the intracellular functions of PCI. PMID:25488662

Manipulation of morphology and structure of the top of GaAs nanowires grown by molecular-beam epitaxy

NASA Astrophysics Data System (ADS)

Li, Lixia; Pan, Dong; Yu, Xuezhe; So, Hyok; Zhao, Jianhua

2017-10-01

Self-catalyzed GaAs nanowires (NWs) are grown on Si (111) substrates by molecular-beam epitaxy. The effect of different closing sequences of the Ga and As cell shutters on the morphology and structural phase of GaAs NWs is investigated. For the sequences of closing the Ga and As cell shutters simultaneously or closing the As cell shutter 1 min after closing the Ga cell shutter, the NWs grow vertically to the substrate surface. In contrast, when the As cell shutter is closed first, maintaining the Ga flux is found to be critical for the following growth of GaAs NWs, which can change the growth direction from [111] to < 11\\bar{1}> . The evolution of the morphology and structural phase transition at the tips of these GaAs NWs confirm that the triple-phase-line shift mode is at work even for the growth with different cell shutter closing sequences. Our work will provide new insights for better understanding of the growth mechanism and realizing of the morphology and structure control of the GaAs NWs. Project supported partly by the MOST of China (No. 2015CB921503), the National Natural Science Foundation of China (Nos. 61504133, 61334006, 61404127), and Youth Innovation Promotion Association, CAS (No. 2017156).

Presence of closely spaced protein thiols on the surface of mammalian cells.

PubMed Central

Donoghue, N.; Yam, P. T.; Jiang, X. M.; Hogg, P. J.

2000-01-01

It has been proposed that certain cell-surface proteins undergo redox reactions, that is, transfer of hydrogens and electrons between closely spaced cysteine thiols that can lead to reduction, formation, or interchange of disulfide bonds. This concept was tested using a membrane-impermeable trivalent arsenical to identify closely spaced thiols in cell-surface proteins. We attached the trivalent arsenical, phenylarsenoxide, to the thiol of reduced glutathione to produce 4-(N-(S-glutathionylacetyl)amino)phenylarsenoxide (GSAO). GSAO bound tightly to synthetic, peptide, and protein dithiols like thioredoxin, but not to monothiols. To identify cell-surface proteins that contain closely spaced thiols, we attached a biotin moiety through a spacer arm to the primary amino group of the gamma-glutamyl residue of GSAO (GSAO-B). Incorporation of GSAO-B into proteins was assessed by measuring the biotin using streptavidin-peroxidase. Up to 12 distinct proteins were labeled with GSAO-B on the surface of endothelial and fibrosarcoma cells. The pattern of labeled proteins differed between the different cell types. Protein disulfide isomerase was one of the proteins on the endothelial and fibrosarcoma cell surface that incorporated GSAO-B. These findings demonstrate that the cell-surface environment can support the existence of closely spaced protein thiols and suggest that at least some of these thiols are redox active. PMID:11206065

Preferential effects of leptin on CD4 T cells in central and peripheral immune system are critically linked to the expression of leptin receptor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, So Yong; Lim, Ju Hyun; Choi, Sung Won

2010-04-09

Leptin can enhance thymopoiesis and modulate the T-cell immune response. However, it remains controversial whether these effects correlate with the expression of leptin receptor, ObR. We herein addressed this issue by using in vivo animal models and in vitro culture systems. Leptin treatment in both ob/ob mice and normal young mice induced increases of CD4 SP thymocytes in thymus and CD4 T cells in the periphery. Interestingly, expression of the long form ObR was significantly restricted to DN, DP and CD4 SP, but not CD8 SP thymocytes. Moreover, in the reaggregated DP thymocyte cultures with leptin plus TSCs, leptin profoundlymore » induced differentiation of CD4 SP but not CD8 SP thymocytes, suggesting that the effects of leptin on thymocyte differentiation might be closely related to the expression of leptin receptor in developing thymocytes. Surprisingly, ObR expression was markedly higher in peripheral CD4 T cells than that in CD8 T cells. Furthermore, leptin treatment with or without IL-2 and PHA had preferential effects on cell proliferation of CD4 T cells compared to that of CD8 T cells. Collectively, these data provide evidence that the effects of leptin on differentiation and proliferation of CD4 T cells might be closely related to the expression of leptin receptor.« less

A new insight into the three-dimensional architecture of the Golgi complex: Characterization of unusual structures in epididymal principal cells

PubMed Central

Martínez-Martínez, Narcisa; Martínez-Alonso, Emma; Tomás, Mónica; Neumüller, Josef; Pavelka, Margit

2017-01-01

Principal epididymal cells have one of the largest and more developed Golgi complex of mammalian cells. In the present study, we have used this cell as model for the study of the three-dimensional architecture of the Golgi complex of highly secretory and endocytic cells. Electron tomography demonstrated the presence in this cell type of some unknown or very unusual Golgi structures such as branched cisternae, pocket-like cisternal invaginations or tubular connections. In addition, we have used this methodology and immunoelectron microscopy to analyze the close relationship between this organelle and both the endoplasmic reticulum and microtubules, and to describe in detail how these elements interact with compact and non-compact regions of the ribbon. PMID:28957389

Bursts of activity in collective cell migration

PubMed Central

Chepizhko, Oleksandr; Giampietro, Costanza; Mastrapasqua, Eleonora; Nourazar, Mehdi; Ascagni, Miriam; Sugni, Michela; Fascio, Umberto; Leggio, Livio; Malinverno, Chiara; Scita, Giorgio; Santucci, Stéphane; Alava, Mikko J.; Zapperi, Stefano; La Porta, Caterina A. M.

2016-01-01

Dense monolayers of living cells display intriguing relaxation dynamics, reminiscent of soft and glassy materials close to the jamming transition, and migrate collectively when space is available, as in wound healing or in cancer invasion. Here we show that collective cell migration occurs in bursts that are similar to those recorded in the propagation of cracks, fluid fronts in porous media, and ferromagnetic domain walls. In analogy with these systems, the distribution of activity bursts displays scaling laws that are universal in different cell types and for cells moving on different substrates. The main features of the invasion dynamics are quantitatively captured by a model of interacting active particles moving in a disordered landscape. Our results illustrate that collective motion of living cells is analogous to the corresponding dynamics in driven, but inanimate, systems. PMID:27681632

[The effect of 18β-glycyrrhetinic acid on tight junctions of the nasal mucosa epithelial cells in rat models with allergic rhinitis].

PubMed

Ma, Yi; Gui, Yan; Wang, Youhu; Xi, Kehu; Chen, Xiaowan; Zhang, Fuhong; Ma, Chunxia; Hong, Hao; Liu, Xiangyi; Jiang, Ying; Dong, Ming; Yang, Guijun; Zhang, Xiaobing

2014-10-01

To observe 18β-glycyrrhetinic acid (GA) impact on ultrastructure of tight junctions (TJs) of nasal mucosa epithelial cells in rats models of allergic rhinitis (AR). Ninety-six Wistar rats were randomly divided into control group, model group, loratadine group, and 18β-glycyrrhetinic acid group, and each group had 24 rats. Ovalbumin was used to establish a rat AR model. The behavioral changes and the tight junctions of nasal epithelial were observed and compared in different groups after 2,4,6 and 10 weeks intervention. The length of TJs in allergic rhinitis model became shorter, electron-high-density plasma membrane became thicker, number of the integration loci reduced and gap of TJs widened or even ruptured. With the consistent effect of allergens,the changes of TJs in the model group aggravated gradually,and the changes of ultrastructure of TJs in 18β-glycyrrhetinic acid group was relieved apparently compared to model group and even were close to the control model with time. 18β-glycyrrhetinic acid can recover the ultrastructure of the tight junctions of AR rat nasal epithelial cells.

Triple point temperature of neon isotopes: Dependence on nitrogen impurity and sealed-cell model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavese, F.; Steur, P. P. M.; Giraudi, D.

2013-09-11

This paper illustrates a study conducted at INRIM, to further check how some quantities influence the value of the triple point temperature of the neon high-purity isotopes {sup 20}Ne and {sup 22}Ne. The influence of nitrogen as a chemical impurity in neon is critical with regard to the present best total uncertainty achieved in the measurement of these triple points, but only one determination is available in the literature. Checks are reported, performed on two different samples of {sup 22}Ne known to contain a N{sub 2} amount of 157⋅10{sup −6}, using two different models of sealed cells. The model ofmore » the cell can, in principle, have some effects on the shape of the melting plateau or on the triple point temperature observed for the sample sealed in it. This can be due to cell thermal parameters, or because the INRIM cell element mod. c contains many copper wires closely packed, which can, in principle, constrain the interface and induce a premelting-like effect. The reported results on a cell mod. Bter show no evident effect from the cell model and provide a value for the effect of N{sub 2} in Ne liquidus point of 8.6(1.9) μK ppm N{sub 2}{sup −1}, only slightly different from the literature datum.« less

Use of a chemical equilibrium model to describe surface properties and uptake of cadmium, strontium, and lead by Chlorella (UTEX 252)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hassett, J.M.

1988-01-01

Metal-aquatic biota interactions are important in both natural and engineered systems. In this study, the uptake of cadmium, strontium and lead by the unicellular green alga Chlorella (UTEX 252) was investigated. Variables included metal concentration, pH, and ionic strength. Data gathered included dry weights (mg/l), cell counts (cells/ml), electrophoretic mobilities (EPMs, {mu}m/sec/V/cm) of metal-free and metal-exposed cells, and metal uptake - difference in concentration in filtrate of cell-metal and cell-free metal solutions. Derived data included cell volumes and surface area, uptake on a {mu}M/m{sup 2} basis, {zeta}-potentials, diffuse layer potentials and charge densities. Typical uptake values were 1.1, 5.2, andmore » 6 {mu}M/m{sup 2} for Cd, Pb, and Sr, respectively, from solutions of pH 6, ionic strength 0.02M, and metal concentration 10{sup {minus}4} M. Cell EPMs were insensitive to metal; under certain conditions, however, (pM > 4, pH > 8), cadmium exposed cells exhibited a reversal in surface charge from negative to positive. The chemical equilibrium model MINEQL1 + STANFORD was used to model algal surface properties and metal uptake. Input data included site pK, density, and {Delta}pK, estimated from EPM-pH data. The model described surface properties of Chlorella (UTEX 252) as judged by a close fit of {zeta}-potentials and model-derived diffuse layer potentials. Metal uptake was modelled by adjusting site density and/or metal-surface site equilibrium constants. Attempts to model surface properties and metal uptake simultaneously were not successful.« less

A Novel Three-Dimensional Immune Oncology Model for High-Throughput Testing of Tumoricidal Activity.

PubMed

Sherman, Hilary; Gitschier, Hannah J; Rossi, Ann E

2018-01-01

The latest advancements in oncology research are focused on autologous immune cell therapy. However, the effectiveness of this type of immunotherapy for cancer remediation is not equivalent for all patients or cancer types. This suggests the need for better preclinical screening models that more closely recapitulate in vivo tumor biology. The established method for investigating tumoricidal activity of immunotherapies has been study of two-dimensional (2D) monolayer cultures of immortalized cancer cell lines or primary tumor cells in standard tissue culture vessels. Indeed, a proven means to examine immune cell migration and invasion are 2D chemotaxis assays in permeabilized supports or Boyden chambers. Nevertheless, the more in vivo -like three-dimensional (3D) multicellular tumor spheroids are quickly becoming the favored model to examine immune cell invasion and tumor cell cytotoxicity. Accordingly, we have developed a 3D immune oncology model by combining 96-well permeable support systems and 96-well low-attachment microplates. The use of the permeable support system enables assessment of immune cell migration, which was tested in this study as chemotactic response of natural killer NK-92MI cells to human stromal-cell derived factor-1 (SDF-1α). Immune invasion was assessed by measuring NK-92MI infiltration into lung carcinoma A549 cell spheroids that were formed in low-attachment microplates. The novel pairing of the permeable support system with low-attachment microplates permitted simultaneous investigation of immune cell homing, immune invasion of tumor spheroids, and spheroid cytotoxicity. In effect, the system represents a more comprehensive and in vivo -like immune oncology model that can be utilized for high-throughput study of tumoricidal activity.

NiAl Oxidation Reaction Processes Studied In Situ Using MEMS-Based Closed-Cell Gas Reaction Transmission Electron Microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Unocic, Kinga A.; Shin, Dongwon; Unocic, Raymond R.

The nanoscale oxidation mechanisms and kinetics of a model β-NiAl system were investigated using in situ closed-cell gas reaction scanning transmission electron microscopy (STEM). Here, we directly visualize the dynamic structural and chemical changes that occur during high-temperature oxidation at a high spatial resolution of 50.3Ni–49.7Al (at.%) nanoparticles under static air conditions at 730 Torr with heating up to 750 °C at 5 °C/s. A MEMS-based gas cell system, with microfabricated heater devices and a gas delivery system, was used to reveal site-specific oxidation initiation sites. Through time-resolved annular dark-field STEM imaging, we tracked the nanoscale oxidation kinetics of Almore » 2O 3. After oxidation at 750 °C, nucleation of voids at the Ni/Al 2O 3 interface was observed along a NiAl grain boundary, followed by the formation of faceted NiO crystals. Small faceted cubic crystals of NiO were formed at the initial stage of oxidation at high PO 2 due to the outward self-diffusion of Ni 2+ ions, followed by the formation of a mixture of metastable and stable α-Al 2O 3 at the oxide/metal interface that is attributed to a PO 2 decrease with oxidation time, which agreed with thermodynamic modeling calculations. Furthermore, the results from these in situ oxidation experiments in the β-NiAl system are in agreement with the established oxidation mechanisms; however, with in situ closed-cell gas microscopy it is now feasible to investigate nanoscale oxidation mechanisms and kinetics in real time and at high spatial resolution and can be broadly applied to understand the basic high-temperature oxidation mechanisms for a wide range of alloy compositions.« less

NiAl Oxidation Reaction Processes Studied In Situ Using MEMS-Based Closed-Cell Gas Reaction Transmission Electron Microscopy

DOE PAGES

Unocic, Kinga A.; Shin, Dongwon; Unocic, Raymond R.; ...

2017-02-07

The nanoscale oxidation mechanisms and kinetics of a model β-NiAl system were investigated using in situ closed-cell gas reaction scanning transmission electron microscopy (STEM). Here, we directly visualize the dynamic structural and chemical changes that occur during high-temperature oxidation at a high spatial resolution of 50.3Ni–49.7Al (at.%) nanoparticles under static air conditions at 730 Torr with heating up to 750 °C at 5 °C/s. A MEMS-based gas cell system, with microfabricated heater devices and a gas delivery system, was used to reveal site-specific oxidation initiation sites. Through time-resolved annular dark-field STEM imaging, we tracked the nanoscale oxidation kinetics of Almore » 2O 3. After oxidation at 750 °C, nucleation of voids at the Ni/Al 2O 3 interface was observed along a NiAl grain boundary, followed by the formation of faceted NiO crystals. Small faceted cubic crystals of NiO were formed at the initial stage of oxidation at high PO 2 due to the outward self-diffusion of Ni 2+ ions, followed by the formation of a mixture of metastable and stable α-Al 2O 3 at the oxide/metal interface that is attributed to a PO 2 decrease with oxidation time, which agreed with thermodynamic modeling calculations. Furthermore, the results from these in situ oxidation experiments in the β-NiAl system are in agreement with the established oxidation mechanisms; however, with in situ closed-cell gas microscopy it is now feasible to investigate nanoscale oxidation mechanisms and kinetics in real time and at high spatial resolution and can be broadly applied to understand the basic high-temperature oxidation mechanisms for a wide range of alloy compositions.« less

Therapeutic manipulation of natural killer (NK) T cells in autoimmunity: are we close to reality?

PubMed Central

Simoni, Y; Diana, J; Ghazarian, L; Beaudoin, L; Lehuen, A

2013-01-01

T cells reactive to lipids and restricted by major histocompatibility complex (MHC) class I-like molecules represent more than 15% of all lymphocytes in human blood. This heterogeneous population of innate cells includes the invariant natural killer T cells (iNK T), type II NK T cells, CD1a,b,c-restricted T cells and mucosal-associated invariant T (MAIT) cells. These populations are implicated in cancer, infection and autoimmunity. In this review, we focus on the role of these cells in autoimmunity. We summarize data obtained in humans and preclinical models of autoimmune diseases such as primary biliary cirrhosis, type 1 diabetes, multiple sclerosis, systemic lupus erythematosus, rheumatoid arthritis, psoriasis and atherosclerosis. We also discuss the promise of NK T cell manipulations: restoration of function, specific activation, depletion and the relevance of these treatments to human autoimmune diseases. PMID:23199318

Thyroid receptor ligands. Part 8: Thyromimetics derived from N-acylated-alpha-amino acid derivatives displaying modulated pharmacological selectivity compared with KB-141.

PubMed

Garg, Neeraj; Li, Yi-Lin; Garcia Collazo, Ana Maria; Litten, Chris; Ryono, Denis E; Zhang, Minsheng; Caringal, Yolanda; Brigance, Robert P; Meng, Wei; Washburn, William N; Agback, Peter; Mellström, Karin; Rehnmark, Stefan; Rahimi-Ghadim, Mahmoud; Norin, Thomas; Grynfarb, Marlena; Sandberg, Johnny; Grover, Gary; Malm, Johan

2007-08-01

Based on the scaffold of the pharmacologically selective thyromimetic 2b, structurally a close analog to KB-141 (2a), a number of novel N-acylated-alpha-amino acid derivatives were synthesized and tested in a TR radioligand binding assay as well as in a reporter cell assay. On the basis of TRbeta(1)-isoform selectivity and affinity, as well as affinity to the reporter cell assay, 3d was selected for further studies in the cholesterol-fed rat model. In this model 3d revealed an improved therapeutic window between cholesterol and TSH lowering but decreased margins versus tachycardia compared with 2a.

Comparative Investigation on Thermal Insulation of Polyurethane Composites Filled with Silica Aerogel and Hollow Silica Microsphere.

PubMed

Liu, Chunyuan; Kim, Jin Seuk; Kwon, Younghwan

2016-02-01

This paper presents a comparative study on thermal conductivity of PU composites containing open-cell nano-porous silica aerogel and closed-cell hollow silica microsphere, respectively. The thermal conductivity of PU composites is measured at 30 degrees C with transient hot bridge method. The insertion of polymer in pores of silica aerogel creates mixed interfaces, increasing the thermal conductivity of resulting composites. The measured thermal conductivity of PU composites filled with hollow silica microspheres is estimated using theoretical models, and is in good agreement with Felske model. It appears that the thermal conductivity of composites decreases with increasing the volume fraction (phi) when hollow silica microsphere (eta = 0.916) is used.

Multi-layer membrane model for mass transport in a direct ethanol fuel cell using an alkaline anion exchange membrane

NASA Astrophysics Data System (ADS)

Bahrami, Hafez; Faghri, Amir

2012-11-01

A one-dimensional, isothermal, single-phase model is presented to investigate the mass transport in a direct ethanol fuel cell incorporating an alkaline anion exchange membrane. The electrochemistry is analytically solved and the closed-form solution is provided for two limiting cases assuming Tafel expressions for both oxygen reduction and ethanol oxidation. A multi-layer membrane model is proposed to properly account for the diffusive and electroosmotic transport of ethanol through the membrane. The fundamental differences in fuel crossover for positive and negative electroosmotic drag coefficients are discussed. It is found that ethanol crossover is significantly reduced upon using an alkaline anion exchange membrane instead of a proton exchange membrane, especially at current densities higher than 500 A m

Continuous Release of Tumor-Derived Factors Improves the Modeling of Cachexia in Muscle Cell Culture.

PubMed

Jackman, Robert W; Floro, Jess; Yoshimine, Rei; Zitin, Brian; Eiampikul, Maythita; El-Jack, Kahlid; Seto, Danielle N; Kandarian, Susan C

2017-01-01

Cachexia is strongly associated with a poor prognosis in cancer patients but the biological trigger is unknown and therefore no therapeutics exist. The loss of skeletal muscle is the most deleterious aspect of cachexia and it appears to depend on secretions from tumor cells. Models for studying wasting in cell culture consist of experiments where skeletal muscle cells are incubated with medium conditioned by tumor cells. This has led to candidates for cachectic factors but some of the features of cachexia in vivo are not yet well-modeled in cell culture experiments. Mouse myotube atrophy measured by myotube diameter in response to medium conditioned by mouse colon carcinoma cells (C26) is consistently less than what is seen in muscles of mice bearing C26 tumors with moderate to severe cachexia. One possible reason for this discrepancy is that in vivo the C26 tumor and skeletal muscle share a circulatory system exposing the muscle to tumor factors in a constant and increasing way. We have applied Transwell®-adapted cell culture conditions to more closely simulate conditions found in vivo where muscle is exposed to the ongoing kinetics of constant tumor secretion of active factors. C26 cells were incubated on a microporous membrane (a Transwell® insert) that constitutes the upper compartment of wells containing plated myotubes. In this model, myotubes are exposed to a constant supply of cancer cell secretions in the medium but without direct contact with the cancer cells, analogous to a shared circulation of muscle and cancer cells in tumor-bearing animals. The results for myotube diameter support the idea that the use of Transwell® inserts serves as a more physiological model of the muscle wasting associated with cancer cachexia than the bolus addition of cancer cell conditioned medium. The Transwell® model supports the notion that the dose and kinetics of cachectic factor delivery to muscle play a significant role in the extent of pathology.

Modeling the cost and benefit of proteome regulation in a growing bacterial cell

NASA Astrophysics Data System (ADS)

Sharma, Pooja; Pratim Pandey, Parth; Jain, Sanjay

2018-07-01

Escherichia coli cells differentially regulate the production of metabolic and ribosomal proteins in order to stay close to an optimal growth rate in different environments, and exhibit the bacterial growth laws as a consequence. We present a simple mathematical model of a growing-dividing cell in which an internal dynamical mechanism regulates the allocation of proteomic resources between different protein sectors. The model allows an endogenous determination of the growth rate of the cell as a function of cellular and environmental parameters, and reproduces the bacterial growth laws. We use the model and its variants to study the balance between the cost and benefit of regulation. A cost is incurred because cellular resources are diverted to produce the regulatory apparatus. We show that there is a window of environments or a ‘niche’ in which the unregulated cell has a higher fitness than the regulated cell. Outside this niche there is a large space of constant and time varying environments in which regulation is an advantage. A knowledge of the ‘niche boundaries’ allows one to gain an intuitive understanding of the class of environments in which regulation is an advantage for the organism and which would therefore favour the evolution of regulation. The model allows us to determine the ‘niche boundaries’ as a function of cellular parameters such as the size of the burden of the regulatory apparatus. This class of models may be useful in elucidating various tradeoffs in cells and in making in-silico predictions relevant for synthetic biology.

Bayesian Networks Predict Neuronal Transdifferentiation.

PubMed

Ainsworth, Richard I; Ai, Rizi; Ding, Bo; Li, Nan; Zhang, Kai; Wang, Wei

2018-05-30

We employ the language of Bayesian networks to systematically construct gene-regulation topologies from deep-sequencing single-nucleus RNA-Seq data for human neurons. From the perspective of the cell-state potential landscape, we identify attractors that correspond closely to different neuron subtypes. Attractors are also recovered for cell states from an independent data set confirming our models accurate description of global genetic regulations across differing cell types of the neocortex (not included in the training data). Our model recovers experimentally confirmed genetic regulations and community analysis reveals genetic associations in common pathways. Via a comprehensive scan of all theoretical three-gene perturbations of gene knockout and overexpression, we discover novel neuronal trans-differrentiation recipes (including perturbations of SATB2, GAD1, POU6F2 and ADARB2) for excitatory projection neuron and inhibitory interneuron subtypes. Copyright © 2018, G3: Genes, Genomes, Genetics.

Rodent models of glaucoma and their applicability for drug discovery.

PubMed

Agarwal, Renu; Agarwal, Puneet

2017-03-01

Rodents have widely been used to represent glaucomatous changes both in the presence and absence of elevated intraocular pressure (IOP) as they offer clear advantages over other animal species. IOP elevation is commonly achieved by creating an obstruction in the aqueous outflow pathways, consequently leading to retinal ganglion cell and optic nerve (ON) damage, the hallmark of glaucoma. These changes may also be achieved in the absence of elevated IOP by directly inflicting injury to retina or ON. Areas covered: This paper presents a summary of currently used rodent models of glaucoma. The characteristics of these models from several studies are summarized. The benefits and shortcomings of these models are also discussed. Expert opinion: The choice of animal model that closely represents human disease is key for successful translational of preclinical research to clinical practice. Rodent models of rapid IOP elevation are likely to be least representative, whereas models such as steroid-induced glaucoma models more closely resemble the trabecular meshwork changes seen in glaucomatous human eyes. However, this model needs further characterization. Rodent models based on direct retinal and ON injury are also useful tools to investigate molecular mechanisms involved at the site of final common pathology and neuroprotective strategies.

A novel closed cell culture device for fabrication of corneal epithelial cell sheets.

PubMed

Nakajima, Ryota; Kobayashi, Toyoshige; Moriya, Noboru; Mizutani, Manabu; Kan, Kazutoshi; Nozaki, Takayuki; Saitoh, Kazuo; Yamato, Masayuki; Okano, Teruo; Takeda, Shizu

2015-11-01

Automation technology for cell sheet-based tissue engineering would need to optimize the cell sheet fabrication process, stabilize cell sheet quality and reduce biological contamination risks. Biological contamination must be avoided in clinical settings. A closed culture system provides a solution for this. In the present study, we developed a closed culture device called a cell cartridge, to be used in a closed cell culture system for fabricating corneal epithelial cell sheets. Rabbit limbal epithelial cells were cultured on the surface of a porous membrane with 3T3 feeder cells, which are separate from the epithelial cells in the cell cartridges and in the cell-culture inserts as a control. To fabricate the stratified cell sheets, five different thicknesses of the membranes which were welded to the cell cartridge, were examined. Multilayered corneal epithelial cell sheets were fabricated in cell cartridges that were welded to a 25 µm-thick gas-permeable membrane, which was similar to the results with the cell-culture inserts. However, stratification of corneal epithelial cell sheets did not occur with cell cartridges that were welded to 100-300 µm-thick gas-permeable membranes. The fabricated cell sheets were evaluated by histological analyses to examine the expression of corneal epithelial-specific markers. Immunohistochemical analyses showed that a putative stem cell marker, p63, a corneal epithelial differentiation maker, CK3, and a barrier function marker, Claudin-1, were expressed in the appropriate position in the cell sheets. These results suggest that the cell cartridge is effective for fabricating corneal epithelial cell sheets. Copyright © 2012 John Wiley & Sons, Ltd.

NASA Bioreactor

NASA Technical Reports Server (NTRS)

1996-01-01

Close-up view of the interior of a NASA Bioreactor shows the plastic plumbing and valves (cylinders at right center) to control fluid flow. The rotating wall vessel is at top center. The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. The Bioreactor is rotated to provide gentle mixing of fresh and spent nutrient without inducing shear forces that would damage the cells. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. The work is sponsored by NASA's Office of Biological and Physical Research. The bioreactor is managed by the Biotechnology Cell Science Program at NASA's Johnson Space Center (JSC). NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues being cultured in rotating bioreactors by investigators.

Verification of a 2 kWe Closed-Brayton-Cycle Power Conversion System Mechanical Dynamics Model

NASA Technical Reports Server (NTRS)

Ludwiczak, Damian R.; Le, Dzu K.; McNelis, Anne M.; Yu, Albert C.; Samorezov, Sergey; Hervol, Dave S.

2005-01-01

Vibration test data from an operating 2 kWe closed-Brayton-cycle (CBC) power conversion system (PCS) located at the NASA Glenn Research Center was used for a comparison with a dynamic disturbance model of the same unit. This effort was performed to show that a dynamic disturbance model of a CBC PCS can be developed that can accurately predict the torque and vibration disturbance fields of such class of rotating machinery. The ability to accurately predict these disturbance fields is required before such hardware can be confidently integrated onto a spacecraft mission. Accurate predictions of CBC disturbance fields will be used for spacecraft control/structure interaction analyses and for understanding the vibration disturbances affecting the scientific instrumentation onboard. This paper discusses how test cell data measurements for the 2 kWe CBC PCS were obtained, the development of a dynamic disturbance model used to predict the transient torque and steady state vibration fields of the same unit, and a comparison of the two sets of data.

Tissue engineered tumor models.

PubMed

Ingram, M; Techy, G B; Ward, B R; Imam, S A; Atkinson, R; Ho, H; Taylor, C R

2010-08-01

Many research programs use well-characterized tumor cell lines as tumor models for in vitro studies. Because tumor cells grown as three-dimensional (3-D) structures have been shown to behave more like tumors in vivo than do cells growing in monolayer culture, a growing number of investigators now use tumor cell spheroids as models. Single cell type spheroids, however, do not model the stromal-epithelial interactions that have an important role in controlling tumor growth and development in vivo. We describe here a method for generating, reproducibly, more realistic 3-D tumor models that contain both stromal and malignant epithelial cells with an architecture that closely resembles that of tumor microlesions in vivo. Because they are so tissue-like we refer to them as tumor histoids. They can be generated reproducibly in substantial quantities. The bioreactor developed to generate histoid constructs is described and illustrated. It accommodates disposable culture chambers that have filled volumes of either 10 or 64 ml, each culture yielding on the order of 100 or 600 histoid particles, respectively. Each particle is a few tenths of a millimeter in diameter. Examples of histological sections of tumor histoids representing cancers of breast, prostate, colon, pancreas and urinary bladder are presented. Potential applications of tumor histoids include, but are not limited to, use as surrogate tumors for pre-screening anti-solid tumor pharmaceutical agents, as reference specimens for immunostaining in the surgical pathology laboratory and use in studies of invasive properties of cells or other aspects of tumor development and progression. Histoids containing nonmalignant cells also may have potential as "seeds" in tissue engineering. For drug testing, histoids probably will have to meet certain criteria of size and tumor cell content. Using a COPAS Plus flow cytometer, histoids containing fluorescent tumor cells were analyzed successfully and sorted using such criteria.

Tissue grown in space in NASA Bioreactor

NASA Technical Reports Server (NTRS)

1998-01-01

For 5 days on the STS-70 mission, a bioreactor cultivated human colon cancer cells, such as the culture section shown here, which grew to 30 times the volume of control specimens grown on Earth. This significant result was reproduced on STS-85 which grew mature structures that more closely match what are found in tumors in humans. The two white circles within the tumor are part of a plastic lattice that helped the cells associate. The work is sponsored by NASA's Office of Biological and Physical Research. The bioreactor is managed by the Biotechnology Cell Science Program at NASA's Johnson Space Center (JSC). The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues being cultured in rotating bioreactors by investigators.

Short-term differential adaptation to anaerobic stress via genomic mutations by Escherichia coli strains K-12 and B lacking alcohol dehydrogenase.

PubMed

Kim, Hyun Ju; Jeong, Haeyoung; Hwang, Seungwoo; Lee, Moo-Seung; Lee, Yong-Jik; Lee, Dong-Woo; Lee, Sang Jun

2014-01-01

Microbial adaptations often occur via genomic mutations under adverse environmental conditions. This study used Escherichia coli ΔadhE cells as a model system to investigate adaptation to anaerobic conditions, which we then compared with the adaptive mechanisms of two closely related E. coli strains, K-12 and B. In contrast to K-12 ΔadhE cells, the E. coli B ΔadhE cells exhibited significantly delayed adaptive growth under anaerobic conditions. Adaptation by the K-12 and B strains mainly employed anaerobic lactate fermentation to restore cellular growth. Several mutations were identified in the pta or pflB genes of adapted K-12 cells, but mostly in the pta gene of the B strains. However, the types of mutation in the adapted K-12 and B strains were similar. Cellular viability was affected directly by severe redox imbalance in B ΔadhE cells, which also impaired their ability to adapt to anaerobic conditions. This study demonstrates that closely related microorganisms may undergo different adaptations under the same set of adverse conditions, which might be associated with the specific metabolic characteristics of each strain. This study provides new insights into short-term microbial adaptation to stressful conditions, which may reflect dynamic microbial population changes in nature.

Assessment of electrochemical properties of a biogalvanic system for tissue characterisation

PubMed Central

Chandler, J.H.; Culmer, P.R.; Jayne, D.G.; Neville, A.

2015-01-01

Biogalvanic characterisation is a promising method for obtaining health-specific tissue information. However, there is a dearth of understanding in the literature regarding the underlying galvanic cell, electrode reactions and their controlling factors which limits the application of the technique. This work presents a parametric electrochemical investigation into a zinc–copper galvanic system using salt (NaCl) solution analogues at physiologically-relevant concentrations (1.71, 17.1 & 154 mM). The potential difference at open cell, closed cell maximum current and the internal resistance (based on published characterisation methods) were measured. Additionally, independent and relative polarisation scans of the electrodes were performed to improve understanding of the system. Our findings suggest that the prominent reaction at the cathode is that of oxygen-reduction, not hydrogen-evolution. Results indicate that cell potentials are influenced by the concentration of dissolved oxygen at low currents and maximum closed cell currents are limited by the rate of oxygen diffusion to the cathode. Characterised internal resistance values for the salt solutions did not correspond to theoretical values at the extremes of concentration (1.71 and 154 mM) due to electrode resistance and current limitation. Existing biogalvanic models do not consider these phenomena and should be improved to advance the technique and its practical application. PMID:25460609

Structural Continuum Modeling of Space Shuttle External Tank Foam Insulation

NASA Technical Reports Server (NTRS)

Steeve, Brian; Ayala, Sam; Purlee, T. Eric; Shaw, Phillip

2006-01-01

This document is a viewgraph presentation reporting on work in modeling the foam insulation of the Space Shuttle External Tank. An analytical understanding of foam mechanics is required to design against structural failure. The Space Shuttle External Tank is covered primarily with closed cell foam to: Prevent ice, Protect structure from ascent aerodynamic and engine plume heating, and Delay break-up during re-entry. It is important that the foam does not shed unacceptable debris during ascent environment. Therefore a modeling of the foam insulation was undertaken.

A simple hanging drop cell culture protocol for generation of 3D spheroids.

PubMed

Foty, Ramsey

2011-05-06

Studies of cell-cell cohesion and cell-substratum adhesion have historically been performed on monolayer cultures adherent to rigid substrates. Cells within a tissue, however, are typically encased within a closely packed tissue mass in which cells establish intimate connections with many near-neighbors and with extracellular matrix components. Accordingly, the chemical milieu and physical forces experienced by cells within a 3D tissue are fundamentally different than those experienced by cells grown in monolayer culture. This has been shown to markedly impact cellular morphology and signaling. Several methods have been devised to generate 3D cell cultures including encapsulation of cells in collagen gels or in biomaterial scaffolds. Such methods, while useful, do not recapitulate the intimate direct cell-cell adhesion architecture found in normal tissues. Rather, they more closely approximate culture systems in which single cells are loosely dispersed within a 3D meshwork of ECM products. Here, we describe a simple method in which cells are placed in hanging drop culture and incubated under physiological conditions until they form true 3D spheroids in which cells are in direct contact with each other and with extracellular matrix components. The method requires no specialized equipment and can be adapted to include addition of any biological agent in very small quantities that may be of interest in elucidating effects on cell-cell or cell-ECM interaction. The method can also be used to co-culture two (or more) different cell populations so as to elucidate the role of cell-cell or cell-ECM interactions in specifying spatial relationships between cells. Cell-cell cohesion and cell-ECM adhesion are the cornerstones of studies of embryonic development, tumor-stromal cell interaction in malignant invasion, wound healing, and for applications to tissue engineering. This simple method will provide a means of generating tissue-like cellular aggregates for measurement of biomechanical properties or for molecular and biochemical analysis in a physiologically relevant model. Copyright © 2011 Journal of Visualized Experiments

Effect of foaming temperature on the mechanical properties of produced closed-cell A356Aluminum foams with melting method

NASA Astrophysics Data System (ADS)

Movahedi, N.; Mirbagheri, S. M. H.; Hoseini, S. R.

2014-07-01

In this study an attempt was carried out to determine the effect of production temperature on the mechanical properties and energy absorption behavior of closed-cell A356 alloy foams under uniaxial compression test. For this purpose, three different A356 alloy closed-cell foams were synthesized at three different casting temperatures, 650 °C, 675 °C and 700 °C by adding the same amounts of granulated calcium as thickening and TiH2 as blowing agent. The samples were characterized by SEM to study the pore morphology at different foaming temperatures. Compression tests of the A356 foams were carried out to assess their mechanical properties and energy absorption behavior. The results indicated that increasing the foaming temperature from 650 °C to 675 °C and 700 °C reduces the relative density of closed cell A356 alloys by 18.3% and 38% respectively and consequently affects the compressive strength and energy absorption of cellular structures by changing them from equiaxed polyhedral closed cells to distorted cells. Also at 700 °C foaming temperature, growth of micro-pores and coalescence with other surrounding pores leads to several big voids.

Holographic intravital microscopy for 2-D and 3-D imaging intact circulating blood cells in microcapillaries of live mice

NASA Astrophysics Data System (ADS)

Kim, Kyoohyun; Choe, Kibaek; Park, Inwon; Kim, Pilhan; Park, Yongkeun

2016-09-01

Intravital microscopy is an essential tool that reveals behaviours of live cells under conditions close to natural physiological states. So far, although various approaches for imaging cells in vivo have been proposed, most require the use of labelling and also provide only qualitative imaging information. Holographic imaging approach based on measuring the refractive index distributions of cells, however, circumvent these problems and offer quantitative and label-free imaging capability. Here, we demonstrate in vivo two- and three-dimensional holographic imaging of circulating blood cells in intact microcapillaries of live mice. The measured refractive index distributions of blood cells provide morphological and biochemical properties including three-dimensional cell shape, haemoglobin concentration, and haemoglobin contents at the individual cell level. With the present method, alterations in blood flow dynamics in live healthy and sepsis-model mice were also investigated.

Identification and functional characterization of muscle satellite cells in Drosophila

PubMed Central

Reichert, Heinrich

2017-01-01

Work on genetic model systems such as Drosophila and mouse has shown that the fundamental mechanisms of myogenesis are remarkably similar in vertebrates and invertebrates. Strikingly, however, satellite cells, the adult muscle stem cells that are essential for the regeneration of damaged muscles in vertebrates, have not been reported in invertebrates. In this study, we show that lineal descendants of muscle stem cells are present in adult muscle of Drosophila as small, unfused cells observed at the surface and in close proximity to the mature muscle fibers. Normally quiescent, following muscle fiber injury, we show that these cells express Zfh1 and engage in Notch-Delta-dependent proliferative activity and generate lineal descendant populations, which fuse with the injured muscle fiber. In view of strikingly similar morphological and functional features, we consider these novel cells to be the Drosophila equivalent of vertebrate muscle satellite cells. PMID:29072161

A two-step mechanism for stem cell activation during hair regeneration.

PubMed

Greco, Valentina; Chen, Ting; Rendl, Michael; Schober, Markus; Pasolli, H Amalia; Stokes, Nicole; Dela Cruz-Racelis, June; Fuchs, Elaine

2009-02-06

Hair follicles (HFs) undergo cyclic bouts of degeneration, rest, and regeneration. During rest (telogen), the hair germ (HG) appears as a small cell cluster between the slow-cycling bulge and dermal papilla (DP). Here we show that HG cells are derived from bulge stem cells (SCs) but become responsive quicker to DP-promoting signals. In vitro, HG cells also proliferate sooner but display shorter-lived potential than bulge cells. Molecularly, they more closely resemble activated bulge rather than transit-amplifying (matrix) cells. Transcriptional profiling reveals precocious activity of both HG and DP in late telogen, accompanied by Wnt signaling in HG and elevated FGFs and BMP inhibitors in DP. FGFs and BMP inhibitors participate with Wnts in exerting selective and potent stimuli to the HG both in vivo and in vitro. Our findings suggest a model where HG cells fuel initial steps in hair regeneration, while the bulge is the engine maintaining the process.

On the biological plausibility of grandmother cells: implications for neural network theories in psychology and neuroscience.

PubMed

Bowers, Jeffrey S

2009-01-01

A fundamental claim associated with parallel distributed processing (PDP) theories of cognition is that knowledge is coded in a distributed manner in mind and brain. This approach rejects the claim that knowledge is coded in a localist fashion, with words, objects, and simple concepts (e.g. "dog"), that is, coded with their own dedicated representations. One of the putative advantages of this approach is that the theories are biologically plausible. Indeed, advocates of the PDP approach often highlight the close parallels between distributed representations learned in connectionist models and neural coding in brain and often dismiss localist (grandmother cell) theories as biologically implausible. The author reviews a range a data that strongly challenge this claim and shows that localist models provide a better account of single-cell recording studies. The author also contrast local and alternative distributed coding schemes (sparse and coarse coding) and argues that common rejection of grandmother cell theories in neuroscience is due to a misunderstanding about how localist models behave. The author concludes that the localist representations embedded in theories of perception and cognition are consistent with neuroscience; biology only calls into question the distributed representations often learned in PDP models.

Closed-channel culture system for efficient and reproducible differentiation of human pluripotent stem cells into islet cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hirano, Kunio; Konagaya, Shuhei; Turner, Alexander

Human pluripotent stem cells (hPSCs) are thought to be a promising cell-source solution for regenerative medicine due to their indefinite proliferative potential and ability to differentiate to functional somatic cells. However, issues remain with regard to achieving reproducible differentiation of cells with the required functionality for realizing human transplantation therapies and with regard to reducing the potential for bacterial or fungal contamination. To meet these needs, we have developed a closed-channel culture device and corresponding control system. Uniformly-sized spheroidal hPSCs aggregates were formed inside wells within a closed-channel and maintained continuously throughout the culture process. Functional islet-like endocrine cell aggregatesmore » were reproducibly induced following a 30-day differentiation protocol. Our system shows an easily scalable, novel method for inducing PSC differentiation with both purity and functionality. - Highlights: • A simple, closed-channel-based, semi-automatic culture system is proposed. • Uniform cell aggregate formation and culture is realized in microwell structure. • Functional islet cells are successfully induced following 30-plus-day protocol. • System requires no daily medium replacement and reduces contamination risk.« less

Expression patterns of tight junction components induced by CD24 in an oral epithelial cell-culture model correlated to affected periodontal tissues.

PubMed

Ye, P; Yu, H; Simonian, M; Hunter, N

2014-04-01

Previously we demonstrated uniformly strong expression of CD24 in the epithelial attachment to the tooth and in the migrating epithelium of the periodontitis lesion. Titers of serum antibodies autoreactive with CD24 peptide correlated with reduced severity of periodontal disease. Ligation of CD24 expressed by oral epithelial cells induced formation of tight junctions that limited paracellular diffusion. In this study, we aimed to reveal that the lack of uniform expression of tight junction components in the pocket epithelium of periodontitis lesions is likely to contribute to increased paracellular permeability to bacterial products. This is proposed as a potential driver of the immunopathology of periodontitis. An epithelial culture model with close correspondence for expression patterns for tight junction components in periodontal epithelia was used. Immunohistochemical staining and confocal laser scanning microscopy were used to analyse patterns of expression of gingival epithelial tight junction components. The minimally inflamed gingival attachment was characterized by uniformly strong staining at cell contacts for the tight junction components zona occludens-1, zona occludens-2, occludin, junction adhesion molecule-A, claudin-4 and claudin-15. In contrast, the pocket epithelium of the periodontal lesion showed scattered, uneven staining for these components. This pattern correlated closely with that of unstimulated oral epithelial cells in culture. Following ligation of CD24 expressed by these cells, the pattern of tight junction component expression of the minimally inflamed gingival attachment developed rapidly. There was evidence for non-uniform and focal expression only of tight junction components in the pocket epithelium. In the cell-culture model, ligation of CD24 induced a tight junction expression profile equivalent to that observed for the minimally inflamed gingival attachment. Ligation of CD24 expressed by gingival epithelial cells by lectin-like receptors of commensal oral streptococci could mediate the phenotype of health, whereas pathogenic organisms associated with periodontal disease might not signal effectively through CD24. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Dll1 maintains quiescence of adult neural stem cells and segregates asymmetrically during mitosis.

PubMed

Kawaguchi, Daichi; Furutachi, Shohei; Kawai, Hiroki; Hozumi, Katsuto; Gotoh, Yukiko

2013-01-01

Stem cells often divide asymmetrically to produce one stem cell and one differentiating cell, thus maintaining the stem cell pool. Although neural stem cells (NSCs) in the adult mouse subventricular zone have been suggested to divide asymmetrically, intrinsic cell fate determinants for asymmetric NSC division are largely unknown. Stem cell niches are important for stem cell maintenance, but the niche for the maintenance of adult quiescent NSCs has remained obscure. Here we show that the Notch ligand Delta-like 1 (Dll1) is required to maintain quiescent NSCs in the adult mouse subventricular zone. Dll1 protein is induced in activated NSCs and segregates to one daughter cell during mitosis. Dll1-expressing cells reside in close proximity to quiescent NSCs, suggesting a feedback signal for NSC maintenance by their sister cells and progeny. Our data suggest a model in which NSCs produce their own niche cells for their maintenance through asymmetric Dll1 inheritance at mitosis.

Dll1 maintains quiescence of adult neural stem cells and segregates asymmetrically during mitosis

PubMed Central

Kawaguchi, Daichi; Furutachi, Shohei; Kawai, Hiroki; Hozumi, Katsuto; Gotoh, Yukiko

2013-01-01

Stem cells often divide asymmetrically to produce one stem cell and one differentiating cell, thus maintaining the stem cell pool. Although neural stem cells (NSCs) in the adult mouse subventricular zone have been suggested to divide asymmetrically, intrinsic cell fate determinants for asymmetric NSC division are largely unknown. Stem cell niches are important for stem cell maintenance, but the niche for the maintenance of adult quiescent NSCs has remained obscure. Here we show that the Notch ligand Delta-like 1 (Dll1) is required to maintain quiescent NSCs in the adult mouse subventricular zone. Dll1 protein is induced in activated NSCs and segregates to one daughter cell during mitosis. Dll1-expressing cells reside in close proximity to quiescent NSCs, suggesting a feedback signal for NSC maintenance by their sister cells and progeny. Our data suggest a model in which NSCs produce their own niche cells for their maintenance through asymmetric Dll1 inheritance at mitosis. PMID:23695674

Long-term exposure of immortalized keratinocytes to arsenic induces EMT, impairs differentiation in organotypic skin models and mimics aspects of human skin derangements.

PubMed

Weinmuellner, R; Kryeziu, K; Zbiral, B; Tav, K; Schoenhacker-Alte, B; Groza, D; Wimmer, L; Schosserer, M; Nagelreiter, F; Rösinger, S; Mildner, M; Tschachler, E; Grusch, M; Grillari, J; Heffeter, P

2018-01-01

Arsenic is one of the most important human carcinogens and environmental pollutants. However, the evaluation of the underlying carcinogenic mechanisms is challenging due to the lack of suitable in vivo and in vitro models, as distinct interspecies differences in arsenic metabolism exist. Thus, it is of high interest to develop new experimental models of arsenic-induced skin tumorigenesis in humans. Consequently, aim of this study was to establish an advanced 3D model for the investigation of arsenic-induced skin derangements, namely skin equivalents, built from immortalized human keratinocytes (NHEK/SVTERT3-5). In contrast to spontaneously immortalized HACAT cells, NHEK/SVTERT3-5 cells more closely resembled the differentiation pattern of primary keratinocytes. With regard to arsenic, our results showed that while our new cell model was widely unaffected by short-time treatment (72 h) with low, non-toxic doses of ATO (0.05-0.25 µM), chronic exposure (6 months) resulted in distinct changes of several cell characteristics. Thus, we observed an increase in the G2 fraction of the cell cycle accompanied by increased nucleus size and uneven tubulin distribution. Moreover, cells showed strong signs of de-differentiation and upregulation of several epithelial-to-mesenchymal transition markers. In line with these effects, chronic contact to arsenic resulted in impaired skin-forming capacities as well as localization of ki67-positive (proliferating) cells at the upper layers of the epidermis; a condition termed Bowen's disease. Finally, chronically arsenic-exposed cells were characterized by an increased tumorigenicity in SCID mice. Taken together, our study presents a new model system for the investigation of mechanisms underlying the tumor-promoting effects of chronic arsenic exposure.

A biophysical model of kiwifruit (Actinidia deliciosa) berry development

PubMed Central

Hall, Alistair J.

2013-01-01

A model of kiwifruit berry development is presented, building on the model of Fishman and Génard used for peach fruit. That model has been extended to incorporate a number of important features of kiwifruit growth. First, the kiwifruit berry is attached to the stem through a pedicel/receptacle complex which contributes significantly to the hydraulic resistance between the stem and the fruit, and this resistance changes considerably during the season. Second, much of the carbohydrate in kiwifruit berries is stored as starch until the fruit matures late in the season, when the starch hydrolyses to soluble sugars. This starch storage has a major effect on the osmotic potential of the fruit, so an existing model of kiwifruit starch dynamics was included in the model. Using previously published approaches, we also included elasticity and extended the modelling period to cover both the cell division and cell expansion phases of growth. The resulting model showed close simulation of field observations of fresh weight, dry matter, starch, and soluble solids in kiwifruit. Comparison with continuous measurements of fruit diameter confirmed that elasticity was needed to adequately simulate observed diurnal variation in fruit size. Sensitivity analyses suggested that the model is particularly sensitive to variation in inputs relating to water (stem water potential and the humidity of the air), and to parameters controlling cell expansion (cell wall extensibility). Some limitations in the model structure were identified, suggesting that a revised model including current apoplastic/symplastic concepts needs to be developed. PMID:24123250

A biophysical model of kiwifruit (Actinidia deliciosa) berry development.

PubMed

Hall, Alistair J; Minchin, Peter E H; Clearwater, Michael J; Génard, Michel

2013-12-01

A model of kiwifruit berry development is presented, building on the model of Fishman and Génard used for peach fruit. That model has been extended to incorporate a number of important features of kiwifruit growth. First, the kiwifruit berry is attached to the stem through a pedicel/receptacle complex which contributes significantly to the hydraulic resistance between the stem and the fruit, and this resistance changes considerably during the season. Second, much of the carbohydrate in kiwifruit berries is stored as starch until the fruit matures late in the season, when the starch hydrolyses to soluble sugars. This starch storage has a major effect on the osmotic potential of the fruit, so an existing model of kiwifruit starch dynamics was included in the model. Using previously published approaches, we also included elasticity and extended the modelling period to cover both the cell division and cell expansion phases of growth. The resulting model showed close simulation of field observations of fresh weight, dry matter, starch, and soluble solids in kiwifruit. Comparison with continuous measurements of fruit diameter confirmed that elasticity was needed to adequately simulate observed diurnal variation in fruit size. Sensitivity analyses suggested that the model is particularly sensitive to variation in inputs relating to water (stem water potential and the humidity of the air), and to parameters controlling cell expansion (cell wall extensibility). Some limitations in the model structure were identified, suggesting that a revised model including current apoplastic/symplastic concepts needs to be developed.

Cholesterol Alters the Dynamics of Release in Protein Independent Cell Models for Exocytosis

NASA Astrophysics Data System (ADS)

Najafinobar, Neda; Mellander, Lisa J.; Kurczy, Michael E.; Dunevall, Johan; Angerer, Tina B.; Fletcher, John S.; Cans, Ann-Sofie

2016-09-01

Neurons communicate via an essential process called exocytosis. Cholesterol, an abundant lipid in both secretory vesicles and cell plasma membrane can affect this process. In this study, amperometric recordings of vesicular dopamine release from two different artificial cell models created from a giant unilamellar liposome and a bleb cell plasma membrane, show that with higher membrane cholesterol the kinetics for vesicular release are decelerated in a concentration dependent manner. This reduction in exocytotic speed was consistent for two observed modes of exocytosis, full and partial release. Partial release events, which only occurred in the bleb cell model due to the higher tension in the system, exhibited amperometric spikes with three distinct shapes. In addition to the classic transient, some spikes displayed a current ramp or plateau following the maximum peak current. These post spike features represent neurotransmitter release from a dilated pore before constriction and show that enhancing membrane rigidity via cholesterol adds resistance to a dilated pore to re-close. This implies that the cholesterol dependent biophysical properties of the membrane directly affect the exocytosis kinetics and that membrane tension along with membrane rigidity can influence the fusion pore dynamics and stabilization which is central to regulation of neurochemical release.

Peptide immunotherapy in allergic asthma generates IL-10–dependent immunological tolerance associated with linked epitope suppression

PubMed Central

Campbell, John D.; Buckland, Karen F.; McMillan, Sarah J.; Kearley, Jennifer; Oldfield, William L.G.; Stern, Lawrence J.; Grönlund, Hans; van Hage, Marianne; Reynolds, Catherine J.; Boyton, Rosemary J.; Cobbold, Stephen P.; Kay, A. Barry; Altmann, Daniel M.; Larché, Mark

2009-01-01

Treatment of patients with allergic asthma using low doses of peptides containing T cell epitopes from Fel d 1, the major cat allergen, reduces allergic sensitization and improves surrogate markers of disease. Here, we demonstrate a key immunological mechanism, linked epitope suppression, associated with this therapeutic effect. Treatment with selected epitopes from a single allergen resulted in suppression of responses to other (“linked”) epitopes within the same molecule. This phenomenon was induced after peptide immunotherapy in human asthmatic subjects and in a novel HLA-DR1 transgenic mouse model of asthma. Tracking of allergen-specific T cells using DR1 tetramers determined that suppression was associated with the induction of interleukin (IL)-10+ T cells that were more abundant than T cells specific for the single-treatment peptide and was reversed by anti–IL-10 receptor administration. Resolution of airway pathophysiology in this model was associated with reduced recruitment, proliferation, and effector function of allergen-specific Th2 cells. Our results provide, for the first time, in vivo evidence of linked epitope suppression and IL-10 induction in both human allergic disease and a mouse model designed to closely mimic peptide therapy in humans. PMID:19528258

Bifurcation and Spike Adding Transition in Chay-Keizer Model

NASA Astrophysics Data System (ADS)

Lu, Bo; Liu, Shenquan; Liu, Xuanliang; Jiang, Xiaofang; Wang, Xiaohui

Electrical bursting is an activity which is universal in excitable cells such as neurons and various endocrine cells, and it encodes rich physiological information. As burst delay identifies that the signal integration has reached the threshold at which it can generate an action potential, the number of spikes in a burst may have essential physiological implications, and the transition of bursting in excitable cells is associated with the bifurcation phenomenon closely. In this paper, we focus on the transition of the spike count per burst of the pancreatic β-cells within a mathematical model and bifurcation phenomenon in the Chay-Keizer model, which is utilized to simulate the pancreatic β-cells. By the fast-slow dynamical bifurcation analysis and the bi-parameter bifurcation analysis, the local dynamics of the Chay-Keizer system around the Bogdanov-Takens bifurcation is illustrated. Then the variety of the number of spikes per burst is discussed by changing the settings of a single parameter and bi-parameter. Moreover, results on the number of spikes within a burst are summarized in ISIs (interspike intervals) sequence diagrams, maximum and minimum, and the number of spikes under bi-parameter value changes.

Towards immunotherapy with redirected T cells in a large animal model: Ex vivo activation, expansion, and genetic modification of canine T cells

PubMed Central

Mata, Melinda; Vera, Juan; Gerken, Claudia; Rooney, Cliona M.; Miller, Tasha; Pfent, Catherine; Wang, Lisa L.; Wilson-Robles, Heather M.; Gottschalk, Stephen

2014-01-01

Adoptive transfer of T cells expressing chimeric antigen receptors (CARs) has shown promising anti-tumor activity in early phase clinical studies, especially for hematological malignancies. However, most preclinical models do not reliably mimic human disease. We reasoned that developing an adoptive T-cell therapy approach for spontaneous osteosarcoma (OS) occurring in dogs would more closely reproduce the condition in human cancer. To generate CAR-expressing canine T cells we developed expansion and transduction protocols that allow for the generation of sufficient numbers of CAR-expressing canine T cells for future clinical studies in dogs within 2 weeks of ex vivo culture. To evaluate the functionality of CAR-expressing canine T cells we targeted HER2-positive OS. We demonstrate that canine OS is positive for HER2, and that canine T cells expressing a HER2-specific CAR with human-derived transmembrane and CD28.ζ signaling domains recognize and kill HER2-positive canine OS cell lines in an antigen-dependent manner. To reduce the potential immunogenicity of the CAR we evaluated a CAR with canine-derived transmembrane and signaling domains, and found no functional difference between human and canine CARs. Hence, we have successfully developed a strategy to generate CAR-expressing canine T cells for future preclinical studies in dogs. Testing T-cell therapies in an immunocompetent, outbred animal model may improve our ability to predict their safety and efficacy prior to conducting studies in humans. PMID:25198528

A plant cell division algorithm based on cell biomechanics and ellipse-fitting.

PubMed

Abera, Metadel K; Verboven, Pieter; Defraeye, Thijs; Fanta, Solomon Workneh; Hertog, Maarten L A T M; Carmeliet, Jan; Nicolai, Bart M

2014-09-01

The importance of cell division models in cellular pattern studies has been acknowledged since the 19th century. Most of the available models developed to date are limited to symmetric cell division with isotropic growth. Often, the actual growth of the cell wall is either not considered or is updated intermittently on a separate time scale to the mechanics. This study presents a generic algorithm that accounts for both symmetrically and asymmetrically dividing cells with isotropic and anisotropic growth. Actual growth of the cell wall is simulated simultaneously with the mechanics. The cell is considered as a closed, thin-walled structure, maintained in tension by turgor pressure. The cell walls are represented as linear elastic elements that obey Hooke's law. Cell expansion is induced by turgor pressure acting on the yielding cell-wall material. A system of differential equations for the positions and velocities of the cell vertices as well as for the actual growth of the cell wall is established. Readiness to divide is determined based on cell size. An ellipse-fitting algorithm is used to determine the position and orientation of the dividing wall. The cell vertices, walls and cell connectivity are then updated and cell expansion resumes. Comparisons are made with experimental data from the literature. The generic plant cell division algorithm has been implemented successfully. It can handle both symmetrically and asymmetrically dividing cells coupled with isotropic and anisotropic growth modes. Development of the algorithm highlighted the importance of ellipse-fitting to produce randomness (biological variability) even in symmetrically dividing cells. Unlike previous models, a differential equation is formulated for the resting length of the cell wall to simulate actual biological growth and is solved simultaneously with the position and velocity of the vertices. The algorithm presented can produce different tissues varying in topological and geometrical properties. This flexibility to produce different tissue types gives the model great potential for use in investigations of plant cell division and growth in silico.

Arborvitae (Thuja plicata) essential oil significantly inhibited critical inflammation- and tissue remodeling-related proteins and genes in human dermal fibroblasts.

PubMed

Han, Xuesheng; Parker, Tory L

2017-06-01

Arborvitae ( Thuja plicata ) essential oil (AEO) is becoming increasingly popular in skincare, although its biological activity in human skin cells has not been investigated. Therefore, we sought to study AEO's effect on 17 important protein biomarkers that are closely related to inflammation and tissue remodeling by using a pre-inflamed human dermal fibroblast culture model. AEO significantly inhibited the expression of vascular cell adhesion molecule 1 (VCAM-1), intracellular cell adhesion molecule 1 (ICAM-1), interferon gamma-induced protein 10 (IP-10), interferon-inducible T-cell chemoattractant (I-TAC), monokine induced by interferon gamma (MIG), and macrophage colony-stimulating factor (M-CSF). It also showed significant antiproliferative activity and robustly inhibited collagen-I, collagen-III, plasminogen activator inhibitor-1 (PAI-1), and tissue inhibitor of metalloproteinase 1 and 2 (TIMP-1 and TIMP-2). The inhibitory effect of AEO on increased production of these protein biomarkers suggests it has anti-inflammatory property. We then studied the effect of AEO on the genome-wide expression of 21,224 genes in the same cell culture. AEO significantly and diversely modulated global gene expression. Ingenuity pathway analysis (IPA) showed that AEO robustly affected numerous critical genes and signaling pathways closely involved in inflammatory and tissue remodeling processes. The findings of this study provide the first evidence of the biological activity and beneficial action of AEO in human skin cells.

Flow-driven waves and sink-driven oscillations during aggregation of Dictyostelium discoideum

NASA Astrophysics Data System (ADS)

Gholami, Azam; Zykov, Vladimir; Steinbock, Oliver; Bodenschatz, Eberhard

The slime mold Dictyostelium discoideum (D.d) is a well-known model system for the study of biological pattern formation. Under starvation, D.d. cells aggregate chemotactically towards cAMP signals emitted periodically from an aggregation center. In the natural environment, D.d cells may experience fluid flows that can profoundly change the underlying wave generation process. We investigate spatial-temporal dynamics of a uniformly distributed population of D.d. cells in a flow-through narrow microfluidic channel with a cell-free inlet area. We show that flow can significantly influence the dynamics of the system and lead to a flow- driven instability that initiate downstream traveling cAMP waves. We also show that cell-free boundary regions have a significant effect on the observed patterns and can lead to a new kind of instability. Since there are no cells in the inlet to produce cAMP, the points in the vicinity of the inlet lose cAMP due to advection or diffusion and gain only a little from the upstream of the channel (inlet). In other words, there is a large negative flux of cAMP in the neighborhood close to the inlet, which can be considered as a sink. This negative flux close to the inlet drives a new kind of instability called sink-driven oscillations. Financial support of the MaxSynBio Consortium is acknowledged.

Comprehensive Computational Pathological Image Analysis Predicts Lung Cancer Prognosis.

PubMed

Luo, Xin; Zang, Xiao; Yang, Lin; Huang, Junzhou; Liang, Faming; Rodriguez-Canales, Jaime; Wistuba, Ignacio I; Gazdar, Adi; Xie, Yang; Xiao, Guanghua

2017-03-01

Pathological examination of histopathological slides is a routine clinical procedure for lung cancer diagnosis and prognosis. Although the classification of lung cancer has been updated to become more specific, only a small subset of the total morphological features are taken into consideration. The vast majority of the detailed morphological features of tumor tissues, particularly tumor cells' surrounding microenvironment, are not fully analyzed. The heterogeneity of tumor cells and close interactions between tumor cells and their microenvironments are closely related to tumor development and progression. The goal of this study is to develop morphological feature-based prediction models for the prognosis of patients with lung cancer. We developed objective and quantitative computational approaches to analyze the morphological features of pathological images for patients with NSCLC. Tissue pathological images were analyzed for 523 patients with adenocarcinoma (ADC) and 511 patients with squamous cell carcinoma (SCC) from The Cancer Genome Atlas lung cancer cohorts. The features extracted from the pathological images were used to develop statistical models that predict patients' survival outcomes in ADC and SCC, respectively. We extracted 943 morphological features from pathological images of hematoxylin and eosin-stained tissue and identified morphological features that are significantly associated with prognosis in ADC and SCC, respectively. Statistical models based on these extracted features stratified NSCLC patients into high-risk and low-risk groups. The models were developed from training sets and validated in independent testing sets: a predicted high-risk group versus a predicted low-risk group (for patients with ADC: hazard ratio = 2.34, 95% confidence interval: 1.12-4.91, p = 0.024; for patients with SCC: hazard ratio = 2.22, 95% confidence interval: 1.15-4.27, p = 0.017) after adjustment for age, sex, smoking status, and pathologic tumor stage. The results suggest that the quantitative morphological features of tumor pathological images predict prognosis in patients with lung cancer. Copyright © 2016 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.

Reflectance model of a plant leaf

NASA Technical Reports Server (NTRS)

Kumar, R.; Silva, L.

1973-01-01

A light ray, incident at 5 deg to the normal, is geometrically plotted through the drawing of the cross section of a soybean leaf using Fresnel's Equations and Snell's Law. The optical mediums of the leaf considered for ray tracing are: air, cell sap, chloroplast, and cell wall. The above ray is also drawn through the same leaf cross section considering cell wall and air as the only optical mediums. The values of the reflection and transmission found from ray tracing agree closely with the experimental results obtained using a Beckman DK-2A Spectroreflectometer. Similarly a light ray, incident at about 60 deg to the normal, is drawn through the palisade cells of a soybean leaf to illustrate the pathway of light, incident at an oblique angle, through the palisade cells.

Statistical Properties of Cell Topology and Geometry in a Tissue-Growth Model

NASA Astrophysics Data System (ADS)

Sahlin, Patrik; Hamant, Olivier; Jönsson, Henrik

Statistical properties of cell topologies in two-dimensional tissues have recently been suggested to be a consequence of cell divisions. Different rules for the positioning of new walls in plants have been proposed, where e.g. Errara’s rule state that new walls are added with the shortest possible path dividing the mother cell’s volume into two equal parts. Here, we show that for an isotropically growing tissue Errara’s rule results in the correct distributions of number of cell neighbors as well as cellular geometries, in contrast to a random division rule. Further we show that wall mechanics constrain the isotropic growth such that the resulting cell shape distributions more closely agree with experimental data extracted from the shoot apex of Arabidopsis thaliana.

Dynamic subcellular imaging of cancer cell mitosis in the brain of live mice.

PubMed

Momiyama, Masashi; Suetsugu, Atsushi; Kimura, Hiroaki; Chishima, Takashi; Bouvet, Michael; Endo, Itaru; Hoffman, Robert M

2013-04-01

The ability to visualize cancer cell mitosis and apoptosis in the brain in real time would be of great utility in testing novel therapies. In order to achieve this goal, the cancer cells were labeled with green fluorescent protein (GFP) in the nucleus and red fluorescent protein (RFP) in the cytoplasm, such that mitosis and apoptosis could be clearly imaged. A craniotomy open window was made in athymic nude mice for real-time fluorescence imaging of implanted cancer cells growing in the brain. The craniotomy window was reversibly closed with a skin flap. Mitosis of the individual cancer cells were imaged dynamically in real time through the craniotomy-open window. This model can be used to evaluate brain metastasis and brain cancer at the subcellular level.

Processing and Modeling of Porous Copper Using Sintering Dissolution Process

NASA Astrophysics Data System (ADS)

Salih, Mustafa Abualgasim Abdalhakam

The growth of porous metal has produced materials with improved properties as compared to non-metals and solid metals. Porous metal can be classified as either open cell or closed cell. Open cell allows a fluid media to pass through it. Closed cell is made up of adjacent sealed pores with shared cell walls. Metal foams offer higher strength to weight ratios, increased impact energy absorption, and a greater tolerance to high temperatures and adverse environmental conditions when compared to bulk materials. Copper and its alloys are examples of these, well known for high strength and good mechanical, thermal and electrical properties. In the present study, the porous Cu was made by a powder metallurgy process, using three different space holders, sodium chloride, sodium carbonate and potassium carbonate. Several different samples have been produced, using different ratios of volume fraction. The densities of the porous metals have been measured and compared to the theoretical density calculated using an equation developed for these foams. The porous structure was determined with the removal of spacer materials through sintering process. The sintering process of each spacer material depends on the melting point of the spacer material. Processing, characterization, and mechanical properties were completed. These tests include density measurements, compression tests, computed tomography (CT) and scanning electron microscopy (SEM). The captured morphological images are utilized to generate the object-oriented finite element (OOF) analysis for the porous copper. Porous copper was formed with porosities in the range of 40-66% with density ranges from 3 to 5.2 g/cm3. A study of two different methods to measure porosity was completed. OOF (Object Oriented Finite Elements) is a desktop software application for studying the relationship between the microstructure of a material and its overall mechanical, dielectric, or thermal properties using finite element models based on real or simulated micrographs. OOF provides methods for segmenting images, creating meshes and solving of complex geometries using finite element models, and visualizing 2D results.

Colony Expansion of Socially Motile Myxococcus xanthus Cells Is Driven by Growth, Motility, and Exopolysaccharide Production

PubMed Central

Patra, Pintu; Kissoon, Kimberley; Cornejo, Isabel; Kaplan, Heidi B.; Igoshin, Oleg A.

2016-01-01

Myxococcus xanthus, a model organism for studies of multicellular behavior in bacteria, moves exclusively on solid surfaces using two distinct but coordinated motility mechanisms. One of these, social (S) motility is powered by the extension and retraction of type IV pili and requires the presence of exopolysaccharides (EPS) produced by neighboring cells. As a result, S motility requires close cell-to-cell proximity and isolated cells do not translocate. Previous studies measuring S motility by observing the colony expansion of cells deposited on agar have shown that the expansion rate increases with initial cell density, but the biophysical mechanisms involved remain largely unknown. To understand the dynamics of S motility-driven colony expansion, we developed a reaction-diffusion model describing the effects of cell density, EPS deposition and nutrient exposure on the expansion rate. Our results show that at steady state the population expands as a traveling wave with a speed determined by the interplay of cell motility and growth, a well-known characteristic of Fisher’s equation. The model explains the density-dependence of the colony expansion by demonstrating the presence of a lag phase–a transient period of very slow expansion with a duration dependent on the initial cell density. We propose that at a low initial density, more time is required for the cells to accumulate enough EPS to activate S-motility resulting in a longer lag period. Furthermore, our model makes the novel prediction that following the lag phase the population expands at a constant rate independent of the cell density. These predictions were confirmed by S motility experiments capturing long-term expansion dynamics. PMID:27362260

Therapeutic Effect of Human Adipose Tissue-Derived Mesenchymal Stem Cells in Experimental Corneal Failure Due to Limbal Stem Cell Niche Damage.

PubMed

Galindo, Sara; Herreras, José M; López-Paniagua, Marina; Rey, Esther; de la Mata, Ana; Plata-Cordero, María; Calonge, Margarita; Nieto-Miguel, Teresa

2017-10-01

Limbal stem cells are responsible for the continuous renewal of the corneal epithelium. The destruction or dysfunction of these stem cells or their niche induces limbal stem cell deficiency (LSCD) leading to visual loss, chronic pain, and inflammation of the ocular surface. To restore the ocular surface in cases of bilateral LSCD, an extraocular source of stem cells is needed to avoid dependence on allogeneic limbal stem cells that are difficult to obtain, isolate, and culture. The aim of this work was to test the tolerance and the efficacy of human adipose tissue-derived mesenchymal stem cells (hAT-MSCs) to regenerate the ocular surface in two experimental models of LSCD that closely resemble different severity grades of the human pathology. hAT-MSCs transplanted to the ocular surface of the partial and total LSCD models developed in rabbits were well tolerated, migrated to inflamed tissues, reduced inflammation, and restrained the evolution of corneal neovascularization and corneal opacity. The expression profile of the corneal epithelial cell markers CK3 and E-cadherin, and the limbal epithelial cell markers CK15 and p63 was lost in the LSCD models, but was partially recovered after hAT-MSC transplantation. For the first time, we demonstrated that hAT-MSCs improve corneal and limbal epithelial phenotypes in animal LSCD models. These results support the potential use of hAT-MSCs as a novel treatment of ocular surface failure due to LSCD. hAT-MSCs represent an available, non-immunogenic source of stem cells that may provide therapeutic benefits in addition to reduce health care expenses. Stem Cells 2017;35:2160-2174. © 2017 AlphaMed Press.

Colony Expansion of Socially Motile Myxococcus xanthus Cells Is Driven by Growth, Motility, and Exopolysaccharide Production.

PubMed

Patra, Pintu; Kissoon, Kimberley; Cornejo, Isabel; Kaplan, Heidi B; Igoshin, Oleg A

2016-06-01

Myxococcus xanthus, a model organism for studies of multicellular behavior in bacteria, moves exclusively on solid surfaces using two distinct but coordinated motility mechanisms. One of these, social (S) motility is powered by the extension and retraction of type IV pili and requires the presence of exopolysaccharides (EPS) produced by neighboring cells. As a result, S motility requires close cell-to-cell proximity and isolated cells do not translocate. Previous studies measuring S motility by observing the colony expansion of cells deposited on agar have shown that the expansion rate increases with initial cell density, but the biophysical mechanisms involved remain largely unknown. To understand the dynamics of S motility-driven colony expansion, we developed a reaction-diffusion model describing the effects of cell density, EPS deposition and nutrient exposure on the expansion rate. Our results show that at steady state the population expands as a traveling wave with a speed determined by the interplay of cell motility and growth, a well-known characteristic of Fisher's equation. The model explains the density-dependence of the colony expansion by demonstrating the presence of a lag phase-a transient period of very slow expansion with a duration dependent on the initial cell density. We propose that at a low initial density, more time is required for the cells to accumulate enough EPS to activate S-motility resulting in a longer lag period. Furthermore, our model makes the novel prediction that following the lag phase the population expands at a constant rate independent of the cell density. These predictions were confirmed by S motility experiments capturing long-term expansion dynamics.

A theoretical framework for jamming in confluent biological tissues

NASA Astrophysics Data System (ADS)

Manning, M. Lisa

2015-03-01

For important biological functions such as wound healing, embryonic development, and cancer tumorogenesis, cells must initially rearrange and move over relatively large distances, like a liquid. Subsequently, these same tissues must undergo buckling and support shear stresses, like a solid. Our work suggests that biological tissues can accommodate these disparate requirements because the tissues are close to glass or jamming transition. While recent self propelled particle models generically predict a glass/jamming transition that is driven by packing density φ and happens at some critical φc less than unity, many biological tissues that are confluent with no gaps between cells appear to undergo a jamming transition at a constant density (φ = 1). I will discuss a new theoretical framework for predicting energy barriers and rates of cell migration in 2D tissue monolayers, and show that this model predicts a novel type of rigidity transition, which takes place at constant φ = 1 and depends only on single cell properties such as cell-cell adhesion, cortical tension and cell elasticity. This model additionally predicts that an experimentally observable parameter, the ratio between a cell's perimeter and the square root of its cross-sectional area, attains a specific, critical value at the jamming transition. We show that this prediction is precisely realized in primary epithelial cultures from human patients, with implications for asthma pathology.

Open-cell and closed-cell clouds off Peru [detail

NASA Image and Video Library

2017-12-08

2010/107 - 04/17 at 21 :05 UTC. Open-cell and closed-cell clouds off Peru, Pacific Ocean. To view the full fame of this image to go: www.flickr.com/photos/gsfc/4557497219/ Resembling a frosted window on a cold winter's day, this lacy pattern of marine clouds was captured off the coast of Peru in the Pacific Ocean by the MODIS on the Aqua satellite on April 19, 2010. The image reveals both open- and closed-cell cumulus cloud patterns. These cells, or parcels of air, often occur in roughly hexagonal arrays in a layer of fluid (the atmosphere often behaves like a fluid) that begins to "boil," or convect, due to heating at the base or cooling at the top of the layer. In "closed" cells warm air is rising in the center, and sinking around the edges, so clouds appear in cell centers, but evaporate around cell edges. This produces cloud formations like those that dominate the lower left. The reverse flow can also occur: air can sink in the center of the cell and rise at the edge. This process is called "open cell" convection, and clouds form at cell edges around open centers, which creates a lacy, hollow-looking pattern like the clouds in the upper right. Closed and open cell convection represent two stable atmospheric configurations — two sides of the convection coin. But what determines which path the "boiling" atmosphere will take? Apparently the process is highly chaotic, and there appears to be no way to predict whether convection will result in open or closed cells. Indeed, the atmosphere may sometimes flip between one mode and another in no predictable pattern. Satellite: Aqua NASA/GSFC/Jeff Schmaltz/MODIS Land Rapid Response Team To learn more about MODIS go to: rapidfire.sci.gsfc.nasa.gov/gallery/?latest NASA Goddard Space Flight Center is home to the nation's largest organization of combined scientists, engineers and technologists that build spacecraft, instruments and new technology to study the Earth, the sun, our solar system, and the universe.

Mixed oligomers and monomeric amyloid-β disrupts endothelial cells integrity and reduces monomeric amyloid-β transport across hCMEC/D3 cell line as an in vitro blood-brain barrier model.

PubMed

Qosa, Hisham; LeVine, Harry; Keller, Jeffrey N; Kaddoumi, Amal

2014-09-01

Senile amyloid plaques are one of the diagnostic hallmarks of Alzheimer's disease (AD). However, the severity of clinical symptoms of AD is weakly correlated with the plaque load. AD symptoms severity is reported to be more strongly correlated with the level of soluble amyloid-β (Aβ) assemblies. Formation of soluble Aβ assemblies is stimulated by monomeric Aβ accumulation in the brain, which has been related to its faulty cerebral clearance. Studies tend to focus on the neurotoxicity of specific Aβ species. There are relatively few studies investigating toxic effects of Aβ on the endothelial cells of the blood-brain barrier (BBB). We hypothesized that a soluble Aβ pool more closely resembling the in vivo situation composed of a mixture of Aβ40 monomer and Aβ42 oligomer would exert higher toxicity against hCMEC/D3 cells as an in vitro BBB model than either component alone. We observed that, in addition to a disruptive effect on the endothelial cells integrity due to enhancement of the paracellular permeability of the hCMEC/D3 monolayer, the Aβ mixture significantly decreased monomeric Aβ transport across the cell culture model. Consistent with its effect on Aβ transport, Aβ mixture treatment for 24h resulted in LRP1 down-regulation and RAGE up-regulation in hCMEC/D3 cells. The individual Aβ species separately failed to alter Aβ clearance or the cell-based BBB model integrity. Our study offers, for the first time, evidence that a mixture of soluble Aβ species, at nanomolar concentrations, disrupts endothelial cells integrity and its own transport across an in vitro model of the BBB. Copyright © 2014 Elsevier B.V. All rights reserved.

Exact solutions to model surface and volume charge distributions

NASA Astrophysics Data System (ADS)

Mukhopadhyay, S.; Majumdar, N.; Bhattacharya, P.; Jash, A.; Bhattacharya, D. S.

2016-10-01

Many important problems in several branches of science and technology deal with charges distributed along a line, over a surface and within a volume. Recently, we have made use of new exact analytic solutions of surface charge distributions to develop the nearly exact Boundary Element Method (neBEM) toolkit. This 3D solver has been successful in removing some of the major drawbacks of the otherwise elegant Green's function approach and has been found to be very accurate throughout the computational domain, including near- and far-field regions. Use of truly distributed singularities (in contrast to nodally concentrated ones) on rectangular and right-triangular elements used for discretizing any three-dimensional geometry has essentially removed many of the numerical and physical singularities associated with the conventional BEM. In this work, we will present this toolkit and the development of several numerical models of space charge based on exact closed-form expressions. In one of the models, Particles on Surface (ParSur), the space charge inside a small elemental volume of any arbitrary shape is represented as being smeared on several surfaces representing the volume. From the studies, it can be concluded that the ParSur model is successful in getting the estimates close to those obtained using the first-principles, especially close to and within the cell. In the paper, we will show initial applications of ParSur and other models in problems related to high energy physics.

Towards a commercial process for the manufacture of genetically modified T cells for therapy

PubMed Central

Kaiser, A D; Assenmacher, M; Schröder, B; Meyer, M; Orentas, R; Bethke, U; Dropulic, B

2015-01-01

The recent successes of adoptive T-cell immunotherapy for the treatment of hematologic malignancies have highlighted the need for manufacturing processes that are robust and scalable for product commercialization. Here we review some of the more outstanding issues surrounding commercial scale manufacturing of personalized-adoptive T-cell medicinal products. These include closed system operations, improving process robustness and simplifying work flows, reducing labor intensity by implementing process automation, scalability and cost, as well as appropriate testing and tracking of products, all while maintaining strict adherence to Current Good Manufacturing Practices and regulatory guidelines. A decentralized manufacturing model is proposed, where in the future patients' cells could be processed at the point-of-care in the hospital. PMID:25613483

Molecular regulation of the mitosis/meiosis decision in multicellular organisms.

PubMed

Kimble, Judith

2011-08-01

A major step in the journey from germline stem cell to differentiated gamete is the decision to leave the mitotic cell cycle and begin progression through the meiotic cell cycle. Over the past decade, molecular regulators of the mitosis/meiosis decision have been discovered in most of the major model multicellular organisms. Historically, the mitosis/meiosis decision has been closely linked with controls of germline self-renewal and the sperm/egg decision, especially in nematodes and mice. Molecular explanations of those linkages clarify our understanding of this fundamental germ cell decision, and unifying themes have begun to emerge. Although the complete circuitry of the decision is not known in any organism, the recent advances promise to impact key issues in human reproduction and agriculture.

Dynamic energy budget approach to evaluate antibiotic effects on biofilms

NASA Astrophysics Data System (ADS)

Birnir, Bjorn; Carpio, Ana; Cebrián, Elena; Vidal, Perfecto

2018-01-01

Quantifying the action of antibiotics on biofilms is essential to devise therapies against chronic infections. Biofilms are bacterial communities attached to moist surfaces, sheltered from external aggressions by a polymeric matrix. Coupling a dynamic energy budget based description of cell metabolism to surrounding concentration fields, we are able to approximate survival curves measured for different antibiotics. We reproduce numerically stratified distributions of cell types within the biofilm and introduce ways to incorporate different resistance mechanisms. Qualitative predictions follow that are in agreement with experimental observations, such as higher survival rates of cells close to the substratum when employing antibiotics targeting active cells or enhanced polymer production when antibiotics are administered. The current computational model enables validation and hypothesis testing when developing therapies.

Analysis of intracerebral EEG recordings of epileptic spikes: insights from a neural network model

PubMed Central

Demont-Guignard, Sophie; Benquet, Pascal; Gerber, Urs; Wendling, Fabrice

2009-01-01

The pathophysiological interpretation of EEG signals recorded with depth electrodes (i.e. local field potentials, LFPs) during interictal (between seizures) or ictal (during seizures) periods is fundamental in the pre-surgical evaluation of patients with drug-resistant epilepsy. Our objective was to explain specific shape features of interictal spikes in the hippocampus (observed in LFPs) in terms of cell and network-related parameters of neuronal circuits that generate these events. We developed a neural network model based on “minimal” but biologically-relevant neuron models interconnected through GABAergic and glutamatergic synapses that reproduces the main physiological features of the CA1 subfield. Simulated LFPs were obtained by solving the forward problem (dipole theory) from networks including a large number (~3000) of cells. Insertion of appropriate parameters allowed the model to simulate events that closely resemble actual epileptic spikes. Moreover, the shape of the early fast component (‘spike’) and the late slow component (‘negative wave’) was linked to the relative contribution of glutamatergic and GABAergic synaptic currents in pyramidal cells. In addition, the model provides insights about the sensitivity of electrode localization with respect to recorded tissue volume and about the relationship between the LFP and the intracellular activity of principal cells and interneurons represented in the network. PMID:19651549

Three-Dimensional Imaging of the Mouse Organ of Corti Cytoarchitecture for Mechanical Modeling

NASA Astrophysics Data System (ADS)

Puria, Sunil; Hartman, Byron; Kim, Jichul; Oghalai, John S.; Ricci, Anthony J.; Liberman, M. Charles

2011-11-01

Cochlear models typically use continuous anatomical descriptions and homogenized parameters based on two-dimensional images for describing the organ of Corti. To produce refined models based more closely on the actual cochlear cytoarchitecture, three-dimensional morphometric parameters of key mechanical structures are required. Towards this goal, we developed and compared three different imaging methods: (1) A fixed cochlear whole-mount preparation using the fluorescent dye Cellmask®, which is a molecule taken up by cell membranes and clearly delineates Deiters' cells, outer hair cells, and the phalangeal process, imaged using confocal microscopy; (2) An in situ fixed preparation with hair cells labeled using anti-prestin and supporting structures labeled using phalloidin, imaged using two-photon microscopy; and (3) A membrane-tomato (mT) mouse with fluorescent proteins expressed in all cell membranes, which enables two-photon imaging of an in situ live preparation with excellent visualization of the organ of Corti. Morphometric parameters including lengths, diameters, and angles, were extracted from 3D cellular surface reconstructions of the resulting images. Preliminary results indicate that the length of the phalangeal processes decreases from the first (inner most) to third (outer most) row of outer hair cells, and that their length also likely varies from base to apex and across species.

Distributed Cerebellar Motor Learning: A Spike-Timing-Dependent Plasticity Model

PubMed Central

Luque, Niceto R.; Garrido, Jesús A.; Naveros, Francisco; Carrillo, Richard R.; D'Angelo, Egidio; Ros, Eduardo

2016-01-01

Deep cerebellar nuclei neurons receive both inhibitory (GABAergic) synaptic currents from Purkinje cells (within the cerebellar cortex) and excitatory (glutamatergic) synaptic currents from mossy fibers. Those two deep cerebellar nucleus inputs are thought to be also adaptive, embedding interesting properties in the framework of accurate movements. We show that distributed spike-timing-dependent plasticity mechanisms (STDP) located at different cerebellar sites (parallel fibers to Purkinje cells, mossy fibers to deep cerebellar nucleus cells, and Purkinje cells to deep cerebellar nucleus cells) in close-loop simulations provide an explanation for the complex learning properties of the cerebellum in motor learning. Concretely, we propose a new mechanistic cerebellar spiking model. In this new model, deep cerebellar nuclei embed a dual functionality: deep cerebellar nuclei acting as a gain adaptation mechanism and as a facilitator for the slow memory consolidation at mossy fibers to deep cerebellar nucleus synapses. Equipping the cerebellum with excitatory (e-STDP) and inhibitory (i-STDP) mechanisms at deep cerebellar nuclei afferents allows the accommodation of synaptic memories that were formed at parallel fibers to Purkinje cells synapses and then transferred to mossy fibers to deep cerebellar nucleus synapses. These adaptive mechanisms also contribute to modulate the deep-cerebellar-nucleus-output firing rate (output gain modulation toward optimizing its working range). PMID:26973504

Good manufacturing practice-compliant expansion of marrow-derived stem and progenitor cells for cell therapy.

PubMed

Gastens, Martin H; Goltry, Kristin; Prohaska, Wolfgang; Tschöpe, Diethelm; Stratmann, Bernd; Lammers, Dirk; Kirana, Stanley; Götting, Christian; Kleesiek, Knut

2007-01-01

Ex vivo expansion is being used to increase the number of stem and progenitor cells for autologous cell therapy. Initiation of pivotal clinical trials testing the efficacy of these cells for tissue repair has been hampered by the challenge of assuring safe and high-quality cell production. A strategy is described here for clinical-scale expansion of bone marrow (BM)-derived stem cells within a mixed cell population in a completely closed process from cell collection through postculture processing using sterile connectable devices. Human BM mononuclear cells (BMMNC) were isolated, cultured for 12 days, and washed postharvest using either standard open procedures in laminar flow hoods or using automated closed systems. Conditions for these studies were similar to long-term BM cultures in which hematopoietic and stromal components are cultured together. Expansion of marrow-derived stem and progenitor cells was then assessed. Cell yield, number of colony forming units (CFU), phenotype, stability, and multilineage differentiation capacity were compared from the single pass perfusion bioreactor and standard flask cultures. Purification of BMMNC using a closed Ficoll gradient process led to depletion of 98% erythrocytes and 87% granulocytes, compared to 100% and 70%, respectively, for manual processing. After closed system culture, mesenchymal progenitors, measured as CD105+CD166+CD14-CD45- and fibroblastic CFU, expanded 317- and 364-fold, respectively, while CD34+ hematopoietic progenitors were depleted 10-fold compared to starting BMMNC. Cultured cells exhibited multilineage differentiation by displaying adipogenic, osteogenic, and endothelial characteristics in vitro. No significant difference was observed between manual and bioreactor cultures. Automated culture and washing of the cell product resulted in 181 x 10(6) total cells that were viable and contained fibroblastic CFU for at least 24 h of storage. A combination of closed, automated technologies enabled production of good manufacturing practice (GMP)-compliant cell therapeutics, ready for use within a clinical setting, with minimal risk of microbial contamination.

Infrared Spectroscopic Imaging for Prostate Pathology Practice

DTIC Science & Technology

2010-03-01

lassification a lgorithm u ses mo rphological f eatures – geometric pr operties of epithelial cells/nuclei and lumens – that are quantified based on H&E stained...images as well as FT-IR images of the samples. By restricting the features used to geometric measures, we sought to m imic t he pa ttern r...be modeled as small elliptical areas in the stained images. This geometrical model is often confounded as multiple nuclei can be so close as to ap

Random Wiring, Ganglion Cell Mosaics, and the Functional Architecture of the Visual Cortex

PubMed Central

Coppola, David; White, Leonard E.; Wolf, Fred

2015-01-01

The architecture of iso-orientation domains in the primary visual cortex (V1) of placental carnivores and primates apparently follows species invariant quantitative laws. Dynamical optimization models assuming that neurons coordinate their stimulus preferences throughout cortical circuits linking millions of cells specifically predict these invariants. This might indicate that V1’s intrinsic connectome and its functional architecture adhere to a single optimization principle with high precision and robustness. To validate this hypothesis, it is critical to closely examine the quantitative predictions of alternative candidate theories. Random feedforward wiring within the retino-cortical pathway represents a conceptually appealing alternative to dynamical circuit optimization because random dimension-expanding projections are believed to generically exhibit computationally favorable properties for stimulus representations. Here, we ask whether the quantitative invariants of V1 architecture can be explained as a generic emergent property of random wiring. We generalize and examine the stochastic wiring model proposed by Ringach and coworkers, in which iso-orientation domains in the visual cortex arise through random feedforward connections between semi-regular mosaics of retinal ganglion cells (RGCs) and visual cortical neurons. We derive closed-form expressions for cortical receptive fields and domain layouts predicted by the model for perfectly hexagonal RGC mosaics. Including spatial disorder in the RGC positions considerably changes the domain layout properties as a function of disorder parameters such as position scatter and its correlations across the retina. However, independent of parameter choice, we find that the model predictions substantially deviate from the layout laws of iso-orientation domains observed experimentally. Considering random wiring with the currently most realistic model of RGC mosaic layouts, a pairwise interacting point process, the predicted layouts remain distinct from experimental observations and resemble Gaussian random fields. We conclude that V1 layout invariants are specific quantitative signatures of visual cortical optimization, which cannot be explained by generic random feedforward-wiring models. PMID:26575467

A model of type 2 diabetes in the guinea pig using sequential diet-induced glucose intolerance and streptozotocin treatment.

PubMed

Podell, Brendan K; Ackart, David F; Richardson, Michael A; DiLisio, James E; Pulford, Bruce; Basaraba, Randall J

2017-02-01

Type 2 diabetes is a leading cause of morbidity and mortality among noncommunicable diseases, and additional animal models that more closely replicate the pathogenesis of human type 2 diabetes are needed. The goal of this study was to develop a model of type 2 diabetes in guinea pigs, in which diet-induced glucose intolerance precedes β-cell cytotoxicity, two processes that are crucial to the development of human type 2 diabetes. Guinea pigs developed impaired glucose tolerance after 8 weeks of feeding on a high-fat, high-carbohydrate diet, as determined by oral glucose challenge. Diet-induced glucose intolerance was accompanied by β-cell hyperplasia, compensatory hyperinsulinemia, and dyslipidemia with hepatocellular steatosis. Streptozotocin (STZ) treatment alone was ineffective at inducing diabetic hyperglycemia in guinea pigs, which failed to develop sustained glucose intolerance or fasting hyperglycemia and returned to euglycemia within 21 days after treatment. However, when high-fat, high-carbohydrate diet-fed guinea pigs were treated with STZ, glucose intolerance and fasting hyperglycemia persisted beyond 21 days post-STZ treatment. Guinea pigs with diet-induced glucose intolerance subsequently treated with STZ demonstrated an insulin-secretory capacity consistent with insulin-independent diabetes. This insulin-independent state was confirmed by response to oral antihyperglycemic drugs, metformin and glipizide, which resolved glucose intolerance and extended survival compared with guinea pigs with uncontrolled diabetes. In this study, we have developed a model of sequential glucose intolerance and β-cell loss, through high-fat, high-carbohydrate diet and extensive optimization of STZ treatment in the guinea pig, which closely resembles human type 2 diabetes. This model will prove useful in the study of insulin-independent diabetes pathogenesis with or without comorbidities, where the guinea pig serves as a relevant model species. © 2017. Published by The Company of Biologists Ltd.

Interactions of water with roasted and ground coffee in the wetting process investigated by a combination of physical determinations.

PubMed

Mateus, Maria-L; Rouvet, Martine; Gumy, Jean-C; Liardon, Rémy

2007-04-18

Three complementary techniques were used in this study to investigate the physical changes during wetting of roasted and ground coffee. Scanning electron microscopy (SEM) was found to provide indirect evidence of the presence of liquid water in the coffee particles. The effect of wetting on coffee closed porosity was studied by helium pycnometry, and finally, particle sizing was used to determine the swelling kinetics of coffee after wetting. Due to the solubilization of compounds, the presence of liquid water could be detected in the coffee cells by SEM. The technique was then used to investigate different water contents; for example, for roasted and ground coffee containing 1 g of water per gram of coffee on a dry basis, liquid water was present in cells only at the periphery of approximately 1.0 mm diameter particles. Coffee closed porosity decreased with increasing water content, as evidenced by pycnometry. For roasted and ground coffee containing 1 g of water per gram of coffee, results showed a closed porosity lower that 0.1 cm3/g ( approximately 20% of the closed porosity measured in dry particles). The decrease of closed porosity may be attributed to both (1) water filling cells' lumen and (2) plasticization of cell wall polymers, resulting in the matrix relaxation and increase of helium accessibility to the pores. Water binding to the matrix polymers was further investigated by calorimetric measurements. The integration of the endothermic peak of freezing water showed that approximately 0.15 g of water/g of coffee is nonfreezable water, that is, water bound to the matrix polymers. Finally, the use of particle sizing showed that the average volume of the coffee particles with 1 g of water/g of coffee increased by up to 20-23% at 10-15 min following wetting. Moisture diffusion coefficients in coffee particles [( approximately 2-3) x 10(-11) m2 s(-1)] were approximated by fitting the swelling curves with a model of diffusion. The observed results may give information about homogeneity and the physical state of water in wetted roasted coffee and thus increase the understanding of the mechanisms of molecular mass transfer during extraction.

PreImplantation Factor in endometriosis: A potential role in inducing immune privilege for ectopic endometrium

PubMed Central

Scarpellini, Fabio; Marconi, Daniela; Rossi, Gabriele; Simmilion, Cedric; Mueller, Michael D.; Barnea, Eytan R.

2017-01-01

Endometriosis is a chronic inflammatory condition characterised by the growth of endometrial epithelial and stromal cells outside the uterine cavity. In addition to Sampson’s theory of retrograde menstruation, endometriosis pathogenesis is facilitated by a privileged inflammatory microenvironment, with T regulatory FoxP3+ expressing T cells (Tregs) being a significant factor. PreImplantation Factor (PIF) is a peptide essential for pregnancy recognition and development. An immune modulatory function of the synthetic PIF analog (sPIF) has been successfully confirmed in multiple animal models. We report that PIF is expressed in the epithelial ectopic cells in close proximity to FoxP3+ stromal cells. We provide evidence that PIF interacts with FoxP3+ cells and modulates cell viability, dependent on cell source and presence of inflammatory mediators. Our finding represent a novel PIF-based mechanism in endometriosis that has potential for novel therapeutics. PMID:28902871

Abnormal gastrointestinal endocrine cells in patients with diabetes type 1: relationship to gastric emptying and myoelectrical activity.

PubMed

El-Salhy, M; Sitohy, B

2001-11-01

Gastrointestinal symptoms in patients with diabetes are believed to be caused by gastrointestinal dysmotility and secretion/absorption disturbances, and the gut endocrine cells play an important part in regulating these two functions. Studies on animal models of human diabetes type I revealed abnormality in these cells, but it is unknown whether abnormality also occurs in patients with diabetes. Eleven patients with long duration of diabetes type I and organ complications, as well as gastrointestinal symptoms, were studied. Endocrine cells in different segments of the gastrointestinal tract were detected by immunocytochemistry and quantified by computerized image analysis. Gastric emptying was measured by scintigraphy and gastric myoelectric activity was determined by electrogastrography. An abnormal density of gastrointestinal endocrine cells was found in patients with diabetes. This abnormality occurred in all segments of the upper and lower gastrointestinal tract investigated, and included most of the endocrine cell types. The patients showed delayed gastric emptying, which correlated closely with the acute glucose level, but did not correlate with HbA1c. Gastric emptying also correlated closely with the density of duodenal serotonin and secretin cells. The patients exhibited bradygastrias and tachygastrias. These dysrhythmias, however, did not differ significantly from controls. The endocrine cells are the anatomical units responsible for the production of gut hormones, and the change in their density would reflect a change in the capacity of producing these hormones. The abnormality in density of the gastrointestinal endocrine cells may contribute to the development of gastrointestinal dysmotility and the symptoms encountered in patients with diabetes.

New aspects of vascular remodelling: the involvement of all vascular cell types.

PubMed

McGrath, John C; Deighan, Clare; Briones, Ana M; Shafaroudi, Majid Malekzadeh; McBride, Melissa; Adler, Jeremy; Arribas, Silvia M; Vila, Elisabet; Daly, Craig J

2005-07-01

Conventionally, the architecture of arteries is based around the close-packed smooth muscle cells and extracellular matrix. However, the adventitia and endothelium are now viewed as key players in vascular growth and repair. A new dynamic picture has emerged of blood vessels in a constant state of self-maintenance. Recent work raises fundamental questions about the cellular heterogeneity of arteries and the time course and triggering of normal and pathological remodelling. A common denominator emerging in hypertensive remodelling is an early increase in adventitial cell density suggesting that adventitial cells drive remodelling and may initiate subsequent changes such as re-arrangement of smooth muscle cells and extracellular matrix. The organization of vascular smooth muscle cells follows regular arrangements that can be modelled mathematically. In hypertension, new patterns can be quantified in these terms and give insights to how structure affects function. As with smooth muscle, little is known about the organization of the vascular endothelium, or its role in vascular remodelling. Current observations suggest that there may be a close relationship between the helical organization of smooth muscle cells and the underlying pattern of endothelial cells. The function of myoendothelial connections is a topic of great current interest and may relate to the structure of the internal elastic lamina through which the connections must pass. In hypertensive remodelling this must present an organizational challenge. The objective of this paper is to show how the functions of blood vessels depend on their architecture and a continuous interaction of different cell types and extracellular proteins.

Chimeric Antigen Receptor-Redirected Regulatory T Cells Suppress Experimental Allergic Airway Inflammation, a Model of Asthma.

PubMed

Skuljec, Jelena; Chmielewski, Markus; Happle, Christine; Habener, Anika; Busse, Mandy; Abken, Hinrich; Hansen, Gesine

2017-01-01

Cellular therapy with chimeric antigen receptor (CAR)-redirected cytotoxic T cells has shown impressive efficacy in the treatment of hematologic malignancies. We explored a regulatory T cell (Treg)-based therapy in the treatment of allergic airway inflammation, a model for asthma, which is characterized by an airway hyper-reactivity (AHR) and a chronic, T helper-2 (Th2) cell-dominated immune response to allergen. To restore the immune balance in the lung, we redirected Tregs by a CAR toward lung epithelia in mice upon experimentally induced allergic asthma, closely mimicking the clinical situation. Adoptively transferred CAR Tregs accumulated in the lung and in tracheobronchial lymph nodes, reduced AHR and diminished eosinophilic airway inflammation, indicated by lower cell numbers in the bronchoalveolar lavage fluid and decreased cell infiltrates in the lung. CAR Treg cells furthermore prevented excessive pulmonary mucus production as well as increase in allergen-specific IgE and Th2 cytokine levels in exposed animals. CAR Tregs were more efficient in controlling asthma than non-modified Tregs, indicating the pivotal role of specific Treg cell activation in the affected organ. Data demonstrate that lung targeting CAR Treg cells ameliorate key features of experimental airway inflammation, paving the way for cell therapy of severe allergic asthma.

Optimization of micro-fabricated porous membranes for intestinal epithelial cell culture and in vitro modeling of the human intestinal barrier

NASA Astrophysics Data System (ADS)

Nair Gourikutty Sajay, Bhuvanendran; Yin, Chiam Su; Ramadan, Qasem

2017-12-01

In vitro modeling of organs could provide a controlled platform for studying physiological events and has great potential in the field of pharmaceutical development. Here, we describe the characterization of in vitro modeling of the human intestinal barrier mimicked using silicon porous membranes as a substrate. To mimic an intestinal in vivo setup as closely as possible, a porous substrate is required in a dynamic environment for the cells to grow rather than a static setup with an impermeable surface such as a petri dish. In this study, we focus on the detailed characterization of Caco-2 cells cultured on a silicon membrane with different pore sizes as well as the effect of dynamic fluid flow on the model. The porous silicon membrane together with continuous perfusion of liquid applying shear stress on the cells enhances the differentiation of polarized cells by providing access to the both their basal and apical surfaces. Membranes with pore sizes of 0.5-3 µm were used and a shear stress of ~0.03 dyne cm-2 was created by applying a low flow rate of 20 nl s-1. By providing these optimized conditions, cells were able to differentiate with columnar morphology, which developed microvilli structures on their apical side and tight junctions between adjacent cells like those in a healthy human intestinal barrier. In this setup, it is possible to study the important cellular functions of the intestine such as transport, absorption and secretion, and thus this model has great potential in drug screening.

Microgravity

NASA Image and Video Library

1998-01-01

For 5 days on the STS-70 mission, a bioreactor cultivated human colon cancer cells, which grew to 30 times the volume of control specimens grown on Earth. This significant result was reproduced on STS-85 which grew mature structures that more closely match what are found in tumors in humans. Shown here, clusters of cells slowly spin inside a bioreactor. On Earth, the cells continually fall through the buffer medium and never hit bottom. In space, they are naturally suspended. Rotation ensures gentle stirring so waste is removed and fresh nutrient and oxygen are supplied. The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. The Bioreactor is rotated to provide gentle mixing of fresh and spent nutrient without inducing shear forces that would damage the cells. The work is sponsored by NASA's Office of Biological and Physical Research. The bioreactor is managed by the Biotechnology Cell Science Program at NASA's Johnson Space Center (JSC). NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues being cultured in rotating bioreactors by investigators.

Targeting breast to brain metastatic tumours with death receptor ligand expressing therapeutic stem cells

PubMed Central

Bagci-Onder, Tugba; Du, Wanlu; Figueiredo, Jose-Luiz; Martinez-Quintanilla, Jordi

2015-01-01

Characterizing clinically relevant brain metastasis models and assessing the therapeutic efficacy in such models are fundamental for the development of novel therapies for metastatic brain cancers. In this study, we have developed an in vivo imageable breast-to-brain metastasis mouse model. Using real time in vivo imaging and subsequent composite fluorescence imaging, we show a widespread distribution of micro- and macro-metastasis in different stages of metastatic progression. We also show extravasation of tumour cells and the close association of tumour cells with blood vessels in the brain thus mimicking the multi-foci metastases observed in the clinics. Next, we explored the ability of engineered adult stem cells to track metastatic deposits in this model and show that engineered stem cells either implanted or injected via circulation efficiently home to metastatic tumour deposits in the brain. Based on the recent findings that metastatic tumour cells adopt unique mechanisms of evading apoptosis to successfully colonize in the brain, we reasoned that TNF receptor superfamily member 10A/10B apoptosis-inducing ligand (TRAIL) based pro-apoptotic therapies that induce death receptor signalling within the metastatic tumour cells might be a favourable therapeutic approach. We engineered stem cells to express a tumour selective, potent and secretable variant of a TRAIL, S-TRAIL, and show that these cells significantly suppressed metastatic tumour growth and prolonged the survival of mice bearing metastatic breast tumours. Furthermore, the incorporation of pro-drug converting enzyme, herpes simplex virus thymidine kinase, into therapeutic S-TRAIL secreting stem cells allowed their eradication post-tumour treatment. These studies are the first of their kind that provide insight into targeting brain metastasis with stem-cell mediated delivery of pro-apoptotic ligands and have important clinical implications. PMID:25910782

A murine model of neurofibromatosis type 1 tibial pseudarthrosis featuring proliferative fibrous tissue and osteoclast-like cells.

PubMed

El-Hoss, Jad; Sullivan, Kate; Cheng, Tegan; Yu, Nicole Y C; Bobyn, Justin D; Peacock, Lauren; Mikulec, Kathy; Baldock, Paul; Alexander, Ian E; Schindeler, Aaron; Little, David G

2012-01-01

Neurofibromatosis type 1 (NF1) is a common genetic condition caused by mutations in the NF1 gene. Patients often suffer from tissue-specific lesions associated with local double-inactivation of NF1. In this study, we generated a novel fracture model to investigate the mechanism underlying congenital pseudarthrosis of the tibia (CPT) associated with NF1. We used a Cre-expressing adenovirus (AdCre) to inactivate Nf1 in vitro in cultured osteoprogenitors and osteoblasts, and in vivo in the fracture callus of Nf1(flox/flox) and Nf1(flox/-) mice. The effects of the presence of Nf1(null) cells were extensively examined. Cultured Nf1(null)-committed osteoprogenitors from neonatal calvaria failed to differentiate and express mature osteoblastic markers, even with recombinant bone morphogenetic protein-2 (rhBMP-2) treatment. Similarly, Nf1(null)-inducible osteoprogenitors obtained from Nf1 MyoDnull mouse muscle were also unresponsive to rhBMP-2. In both closed and open fracture models in Nf1(flox/flox) and Nf1(flox/-) mice, local AdCre injection significantly impaired bone healing, with fracture union being <50% that of wild type controls. No significant difference was seen between Nf1(flox/flox) and Nf1(flox/-) mice. Histological analyses showed invasion of the Nf1(null) fractures by fibrous and highly proliferative tissue. Mean amounts of fibrous tissue were increased upward of 10-fold in Nf1(null) fractures and bromodeoxyuridine (BrdU) staining in closed fractures showed increased numbers of proliferating cells. In Nf1(null) fractures, tartrate-resistant acid phosphatase-positive (TRAP+) cells were frequently observed within the fibrous tissue, not lining a bone surface. In summary, we report that local Nf1 deletion in a fracture callus is sufficient to impair bony union and recapitulate histological features of clinical CPT. Cell culture findings support the concept that Nf1 double inactivation impairs early osteoblastic differentiation. This model provides valuable insight into the pathobiology of the disease, and will be helpful for trialing therapeutic compounds. Copyright © 2012 American Society for Bone and Mineral Research.

Reticulation of low density shape memory polymer foam with an in vivo demonstration of vascular occlusion

DOE PAGES

Rodriguez, Jennifer N.; Miller, Matthew W.; Boyle, Anthony; ...

2014-08-11

Recently, predominantly closed-cell low density shape memory polymer (SMP) foam was reported to be an effective aneurysm filling device in a porcine model (Rodriguez et al., Journal of Biomedical Materials Research Part A 2013: (http://dx.doi.org/10.1002/jbm.a.34782)). Because healing involves blood clotting and cell migration throughout the foam volume, a more open-cell structure may further enhance the healing response. This research sought to develop a non-destructive reticulation process for this SMP foam to disrupt the membranes between pore cells. Non-destructive mechanical reticulation was achieved using a gravity-driven floating nitinol pin array coupled with vibratory agitation of the foam and supplemental chemical etching.more » Lastly, reticulation resulted in a reduced elastic modulus and increased permeability, but did not impede the shape memory behavior. Reticulated foams were capable of achieving rapid vascular occlusion in an in vivo porcine model.« less

How the IMF By induces a By-component on closed field lines during northward IMF Bz

NASA Astrophysics Data System (ADS)

Tenfjord, Paul; Østgaard, Nikolai; Strangeway, Robert J.; Reistad, Jone; Magnus Laundal, Karl; Haaland, Stein; Hesse, Michael; Snekvik, Kristian; Milan, Stephen E.

2017-04-01

We describe how the IMF By-component induces a local By-component on closed field lines during northward IMF Bz. The mechanism is the result of high-latitude reconnection on the dayside when IMF By is non-zero. We describe the dynamical process, in which tension on newly reconnected field lines redistribute the open flux asymmetrically between the two hemispheres, which leads to asymmetric energy flow into the lobes. The resulting shear flows change the magnetic field, thereby inducing a By-component on closed field lines. We use a global magnetohydrodynamics model to illustrate the mechanism. The magnetosphere imposes asymmetric forces on the ionosphere, and the effects on the ionospheric flows are characterized by a departure from a symmetric two-cell configuration to the growth of one of the lobe cells, while the other will contract. We also present the associated timescales of the local By-component to a change in the IMF By, by both theoretical arguments and by a superposed epoch analysis between magnetic field measurements from GOES and a list of IMF By reversals. We find that the magnetosphere responds within 10 minutes and reconfigures within 40 minutes.

Analysis of close associations of uropod-associated proteins in human T-cells using the proximity ligation assay

PubMed Central

Baumann, Tommy; Affentranger, Sarah

2013-01-01

We have shown previously that the raft-associated proteins flotillin-1 and -2 are rapidly recruited to the uropods of chemoattractant-stimulated human neutrophils and T-cells and are involved in cell polarization. Other proteins such as the adhesion receptor PSGL-1, the actin-membrane linker proteins ezrin/radixin/moesin (ERM) and the signaling enzyme phosphatidylinositol-4-phosphate 5-kinase type Iγ90 (PIPKIγ90) also accumulate in the T-cell uropod. Using the in situ proximity ligation assay (PLA) we now have investigated putative close associations of these proteins in human freshly isolated T-cells before and after chemokine addition. The PLA allows in situ subcellular localization of close proximity of endogenous proteins at single-molecule resolution in fixed cells. It allows detection also of weaker and transient complexes that would not be revealed with co-immunoprecipitation approaches. We previously provided evidence for heterodimer formation of tagged flotillin-1 and -2 in T-cells before and after chemokine addition using fluorescence resonance energy transfer (FRET). We now confirm these findings using PLA for the endogenous flotillins in fixed human T-cells. Moreover, in agreement with the literature, our PLA findings confirm a close association of endogenous PSGL-1 and ERM proteins both in resting and chemokine-activated human T-cells. In addition, we provide novel evidence using the PLA for close associations of endogenous activated ERM proteins with PIPKIγ90 and of endogenous flotillins with PSGL-1 in human T-cells, before and after chemokine addition. Our findings suggest that preformed clusters of these proteins coalesce in the uropod upon cell stimulation. PMID:24167781

Characterization of Planctomyces limnophilus and development of genetic tools for its manipulation establish it as a model species for the phylum Planctomycetes.

PubMed

Jogler, Christian; Glöckner, Frank Oliver; Kolter, Roberto

2011-08-15

Planctomycetes represent a remarkable clade in the domain Bacteria because they play crucial roles in global carbon and nitrogen cycles and display cellular structures that closely parallel those of eukaryotic cells. Studies on Planctomycetes have been hampered by the lack of genetic tools, which we developed for Planctomyces limnophilus.

Modeling of Oxygen Transport Across Tumor Multicellular Layers

PubMed Central

Braun, Rod D.; Beatty, Alexis L.

2007-01-01

Purpose Tumor oxygen level plays a major role in the response of tumors to different treatments. The purpose of this study was to develop a method of determining oxygen transport properties in a recently developed 3-D model of tumor parenchyma, the multicellular layer (MCL). Methods OCM-1 human choroidal melanoma cells were grown as 3-D MCL on collagen-coated culture plate inserts. A recessed-cathode oxygen microelectrode was used to measure oxygen tension (PO2) profiles across 8 different MCL from the free surface to the insert membrane. The profiles were fitted to four different one-dimensional diffusion models: 1-, 2-, and 3-region models with uniform oxygen consumption (q) in each region and a modified 3-region model with a central region where q=0 and PO2=0. Results Depending upon the presence of a central region of anoxia, the PO2 profiles were fitted best by either the two-region model or the modified 3-region model. Consumption of tumor cells near the insert membrane was higher than that of cells close to the free surface (33.1 ± 13.6 x 10−4 vs. 11.8 ± 6.7 x 10−4 mm Hg/μm2, respectively). Conclusions The model is useful for determining oxygenation and consumption in MCL, especially for cell lines that cannot be grown as spheroids. In the future, this model will permit the study of parameters important in tumor oxygenation in vitro. PMID:17196225

Interpretation of mutation induction by accelerated heavy ions in bacteria

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kozubek, S.; Ryznar, L.; Horneck, G.

In this report, a quantitative interpretation of mutation induction cross sections by heavy charged particles in bacterial cells is presented. The approach is based on the calculation of the fraction of energy deposited by indirect hits in the sensitive structure. In these events the particle does not pass through the sensitive volume, but this region is hit by {delta} rays. Four track structure models, developed by Katz, Chatterjee et al, Kiefer and Straaten and Kudryashov et al., respectively, were used for the calculations. With the latter two models, very good agreement of the calculations with experimental results on mutagenesis inmore » bacteria was obtained. Depending on the linear energy transfer (LET{infinity}) of the particles, two different modes of mutagenic action of heavy ions are distinguished: {open_quotes}{delta}-ray mutagenesis,{close_quotes} which is related to those radiation qualities that preferentially kill the cells in direct hits (LET{infinity} {ge} 100 keV/{mu}m), and {open_quotes}track core mutagenesis,{close_quotes} which arises from direct hits and is observed for lighter ions or ions with high energy (LET{infinity} {le} 100 keV/{mu}m). 37 refs., 6 figs., 1 tab.« less

The shape and motion of gas bubbles in a liquid flowing through a thin annulus

NASA Astrophysics Data System (ADS)

Lei, Qinghua; Xie, Zhihua; Pavlidis, Dimitrios; Salinas, Pablo; Veltin, Jeremy; Muggeridge, Ann; Pain, Christopher C.; Matar, Omar K.; Jackson, Matthew; Arland, Kristine; Gyllensten, Atle

2017-11-01

We study the shape and motion of gas bubbles in a liquid flowing through a horizontal or slightly-inclined thin annulus. Experimental data show that in the horizontal annulus, bubbles develop a unique ``tadpole'' shape with an elliptical cap and a highly-stretched tail, due to the confinement between the closely-spaced channel walls. As the annulus is inclined, the bubble tail tends to decrease in length, while the geometry of the cap remains almost invariant. To model the bubble evolution, the thin annulus is conceptualised as a ``Hele-Shaw'' cell in a curvilinear space. The three-dimensional flow within the cell is represented by a gap-averaged, two-dimensional model constrained by the same dimensionless quantities. The complex bubble dynamics are solved using a mixed control-volume finite-element method combined with interface-capturing and mesh adaptation techniques. A close match to the experimental data is achieved, both qualitatively and quantitatively, by the numerical simulations. The mechanism for the elliptical cap formation is interpreted based on an analogous irrotational flow field around a circular cylinder. The shape regimes of bubbles flowing through the thin annulus are further explored based on the simulation results. Funding from STATOIL gratefully acknowledged.

Duplication and Nuclear Envelope Insertion of the Yeast Microtubule Organizing Centre, the Spindle Pole Body.

PubMed

Rüthnick, Diana; Schiebel, Elmar

2018-05-10

The main microtubule organizing centre in the unicellular model organisms Saccharomyces cerevisiae and Schizosaccharomyces pompe is the spindle pole body (SPB). The SPB is a multilayer structure, which duplicates exactly once per cell cycle. Unlike higher eukaryotic cells, both yeast model organisms undergo mitosis without breakdown of the nuclear envelope (NE), a so-called closed mitosis. Therefore, in order to simultaneously nucleate nuclear and cytoplasmic MTs, it is vital to embed the SPB into the NE at least during mitosis, similarly to the nuclear pore complex (NPC). This review aims to embrace the current knowledge of the SPB duplication cycle with special emphasis on the critical step of the insertion of the new SPB into the NE.

Intrinsic curvature in wool fibres is determined by the relative length of orthocortical and paracortical cells.

PubMed

Harland, Duane P; Vernon, James A; Woods, Joy L; Nagase, Shinobu; Itou, Takashi; Koike, Kenzo; Scobie, David A; Grosvenor, Anita J; Dyer, Jolon M; Clerens, Stefan

2018-03-22

Hair curvature underpins structural diversity and function in mammalian coats, but what causes curl in keratin hair fibres? To obtain structural data to determine one aspect of this question, we used confocal microscopy to provide in situ measurements of the two cell types that make up the cortex of merino wool fibres, which was chosen as a well-characterised model system representative of narrow diameter hairs, such as underhairs. We measured orthocortical and paracortical cross-sectional areas, and cortical cell lengths, within individual fibre snippets of defined uniplanar curvature. This allowed a direct test of two long-standing theories of the mechanism of curvature in hairs. We found evidence contradicting the theory that curvature results from there being more cells on the side of the fibre closest to the outside, or convex edge, of curvature. In all cases, the orthocortical cells close to the outside of curvature were longer than paracortical cells close to the inside of the curvature, which supports the theory that curvature is underpinned by differences in cell type length. However, the latter theory also implies that, for all fibres, curvature should correlate with the proportions of orthocortical and paracortical cells, and we found no evidence for this. In merino wool, it appears that the absolute length of cells of each type and proportion of cells varies from fibre to fibre, and only the difference between the length of the two cell types is important. Implications for curvature in higher diameter hairs, such as guard hairs and those on the human scalp, are discussed. © 2018. Published by The Company of Biologists Ltd.

Style morphology and pollen tube pathway.

PubMed

Gotelli, M M; Lattar, E C; Zini, L M; Galati, B G

2017-12-01

The style morphology and anatomy vary among different species. Three basic types are: open, closed, and semi-closed. Cells involved in the pollen tube pathway in the different types of styles present abundant endoplasmic reticulum, dictyosomes, mitochondria, and ribosomes. These secretory characteristics are related to the secretion where pollen tube grows. This secretion can be represented by the substances either in the canal or in the intercellular matrix or in the cell wall. Most studies suggest that pollen tubes only grow through the secretion of the canal in open styles. However, some species present pollen tubes that penetrate the epithelial cells of the canal, or grow through the middle lamella between these cells and subepithelial cells. In species with a closed style, a pathway is provided by the presence of an extracellular matrix, or by the thickened cell walls of the stylar transmitting tissue. There are reports in some species where pollen tubes can also penetrate the transmitting tissue cells and continue their growth through the cell lumen. In this review, we define subtypes of styles according to the path of the pollen tube. Style types were mapped on an angiosperm phylogenetic tree following the maximum parsimony principle. In line with this, it could be hypothesized that: the open style appeared in the early divergent angiosperms; the closed type of style originated in Asparagales, Poales, and Eudicots; and the semi-closed style appeared in Rosids, Ericales, and Gentianales. The open style seems to have been lost in core Eudicots, with reversions in some Rosids and Asterids.

Experimental study on nonlinear vibrating of aluminum foam using electronic speckle pattern interferometry

NASA Astrophysics Data System (ADS)

Yang, Fujun; Ma, Yinhang; Tao, Nan; He, Xiaoyuan

2017-06-01

Due to its multi properties, including excellent stiffness-to-weight and strength-to-weight ratios, closed-cell aluminum and its alloy foams become candidate materials for use in many high-technology industries, such as the automotive and aerospace industries. For the efficient use of closed-cell foams in structural applications, it is necessary and important to detailly understand their mechanical characteristics. In this paper, the nonlinear vibration responses of the cantilever beams of closed-cell aluminum foams were investigated by use of electronic speckle pattern interferometry (ESPI). The nonlinear resonant mode shapes of testing specimens under harmonic excitation were measured. It is first time to obtain from the experimental results that there exist super-harmonic responses when the cantilever beams of closed-cell aluminum foam were forced to vibrate, which was caused by its specific cellular structures.

Regularity of beating of small clusters of embryonic chick ventricular heart-cells: experiment vs. stochastic single-channel population model

NASA Astrophysics Data System (ADS)

Krogh-Madsen, Trine; Kold Taylor, Louise; Skriver, Anne D.; Schaffer, Peter; Guevara, Michael R.

2017-09-01

The transmembrane potential is recorded from small isopotential clusters of 2-4 embryonic chick ventricular cells spontaneously generating action potentials. We analyze the cycle-to-cycle fluctuations in the time between successive action potentials (the interbeat interval or IBI). We also convert an existing model of electrical activity in the cluster, which is formulated as a Hodgkin-Huxley-like deterministic system of nonlinear ordinary differential equations describing five individual ionic currents, into a stochastic model consisting of a population of ˜20 000 independently and randomly gating ionic channels, with the randomness being set by a real physical stochastic process (radio static). This stochastic model, implemented using the Clay-DeFelice algorithm, reproduces the fluctuations seen experimentally: e.g., the coefficient of variation (standard deviation/mean) of IBI is 4.3% in the model vs. the 3.9% average value of the 17 clusters studied. The model also replicates all but one of several other quantitative measures of the experimental results, including the power spectrum and correlation integral of the voltage, as well as the histogram, Poincaré plot, serial correlation coefficients, power spectrum, detrended fluctuation analysis, approximate entropy, and sample entropy of IBI. The channel noise from one particular ionic current (IKs), which has channel kinetics that are relatively slow compared to that of the other currents, makes the major contribution to the fluctuations in IBI. Reproduction of the experimental coefficient of variation of IBI by adding a Gaussian white noise-current into the deterministic model necessitates using an unrealistically high noise-current amplitude. Indeed, a major implication of the modelling results is that, given the wide range of time-scales over which the various species of channels open and close, only a cell-specific stochastic model that is formulated taking into consideration the widely different ranges in the frequency content of the channel-noise produced by the opening and closing of several different types of channels will be able to reproduce precisely the various effects due to membrane noise seen in a particular electrophysiological preparation.

Signatures of nonlinearity in single cell noise-induced oscillations.

PubMed

Thomas, Philipp; Straube, Arthur V; Timmer, Jens; Fleck, Christian; Grima, Ramon

2013-10-21

A class of theoretical models seeks to explain rhythmic single cell data by postulating that they are generated by intrinsic noise in biochemical systems whose deterministic models exhibit only damped oscillations. The main features of such noise-induced oscillations are quantified by the power spectrum which measures the dependence of the oscillatory signal's power with frequency. In this paper we derive an approximate closed-form expression for the power spectrum of any monostable biochemical system close to a Hopf bifurcation, where noise-induced oscillations are most pronounced. Unlike the commonly used linear noise approximation which is valid in the macroscopic limit of large volumes, our theory is valid over a wide range of volumes and hence affords a more suitable description of single cell noise-induced oscillations. Our theory predicts that the spectra have three universal features: (i) a dominant peak at some frequency, (ii) a smaller peak at twice the frequency of the dominant peak and (iii) a peak at zero frequency. Of these, the linear noise approximation predicts only the first feature while the remaining two stem from the combination of intrinsic noise and nonlinearity in the law of mass action. The theoretical expressions are shown to accurately match the power spectra determined from stochastic simulations of mitotic and circadian oscillators. Furthermore it is shown how recently acquired single cell rhythmic fibroblast data displays all the features predicted by our theory and that the experimental spectrum is well described by our theory but not by the conventional linear noise approximation. © 2013 Elsevier Ltd. All rights reserved.

Characterization of the host factors required for hepadnavirus covalently closed circular (ccc) DNA formation.

PubMed

Guo, Haitao; Xu, Chunxiao; Zhou, Tianlun; Block, Timothy M; Guo, Ju-Tao

2012-01-01

Synthesis of the covalently closed circular (ccc) DNA is a critical, but not well-understood step in the life cycle of hepadnaviruses. Our previous studies favor a model that removal of genome-linked viral DNA polymerase occurs in the cytoplasm and the resulting deproteinized relaxed circular DNA (DP-rcDNA) is subsequently transported into the nucleus and converted into cccDNA. In support of this model, our current study showed that deproteinization of viral double-stranded linear (dsl) DNA also took place in the cytoplasm. Furthermore, we demonstrated that Ku80, a component of non-homologous end joining DNA repair pathway, was essential for synthesis of cccDNA from dslDNA, but not rcDNA. In an attempt to identify additional host factors regulating cccDNA biosynthesis, we found that the DP-rcDNA was produced in all tested cell lines that supported DHBV DNA replication, but cccDNA was only synthesized in the cell lines that accumulated high levels of DP-rcDNA, except for NCI-H322M and MDBK cells, which failed to synthesize cccDNA despite of the existence of nuclear DP-rcDNA. The results thus imply that while removal of the genome-linked viral DNA polymerase is most likely catalyzed by viral or ubiquitous host function(s), nuclear factors required for the conversion of DP-rcDNA into cccDNA and/or its maintenance are deficient in the above two cell lines, which could be useful tools for identification of the elusive host factors essential for cccDNA biosynthesis or maintenance.

Fibroblasts Protect Melanoma Cells from the Cytotoxic Effects of Doxorubicin

PubMed Central

Tiago, Manoela; de Oliveira, Edson Mendes; Brohem, Carla Abdo; Pennacchi, Paula Comune; Paes, Rafael Duarte; Haga, Raquel Brandão; Campa, Ana; de Moraes Barros, Silvia Berlanga; Smalley, Keiran S.

2014-01-01

Melanoma is the most aggressive form of skin cancer and until recently, it was extremely resistant to radio-, immuno-, and chemotherapy. Despite the latest success of BRAF V600E-targeted therapies, responses are typically short lived and relapse is all but certain. Furthermore, a percentage (40%) of melanoma cells is BRAF wild type. Emerging evidence suggests a role for normal host cells in the occurrence of drug resistance. In the current study, we compared a variety of cell culture models with an organotypic incomplete skin culture model (the “dermal equivalent”) to investigate the role of the tissue microenvironment in the response of melanoma cells to the chemotherapeutic agent doxorubicin (Dox). In the dermal equivalent model, consisting of fibroblasts embedded in type I collagen matrix, melanoma cells showed a decreased cytotoxic response when compared with less complex culture conditions, such as seeding on plastic cell culture plate (as monolayers cultures) or on collagen gel. We further investigated the role of the microenvironment in p53 induction and caspase 3 and 9 cleavage. Melanoma cell lines cultured on dermal equivalent showed decreased expression of p53 after Dox treatment, and this outcome was accompanied by induction of interleukin IL-6, IL-8, and matrix metalloproteinases 2 and 9. Here, we show that the growth of melanoma cells in the dermal equivalent model inflects drug responses by recapitulating important pro-survival features of the tumor microenvironment. These studies indicate that the presence of stroma enhances the drug resistance of melanoma in vitro, more closely mirroring the in vivo phenotype. Our data, thus, demonstrate the utility of organotypic cell culture models in providing essential context-dependent information critical for the development of new therapeutic strategies for melanoma. We believe that the organotypic model represents an improved screening platform to investigate novel anti-cancer agents, as it provides important insights into tumor-stromal interactions, thus assisting in the elucidation of chemoresistance mechanisms. PMID:24548268

Cell-matrix adhesion characterization using multiple shear stress zones in single stepwise microchannel

NASA Astrophysics Data System (ADS)

Kim, Min-Ji; Doh, Il; Bae, Gab-Yong; Cha, Hyuk-Jin; Cho, Young-Ho

2014-08-01

This paper presents a cell chip capable to characterize cell-matrix adhesion by monitoring cell detachment rate. The proposed cell chip can supply multiple levels of shear stress in single stepwise microchannel. As epithelial-mesenchymal transition (EMT), one of hallmarks of cancer metastasis is closely associated to the interaction with extracelluar matrix (ECM), we took advantage of two lung cancer cell models with different adhesion properties to ECM depending their epithelial or mesenchymal properties, including the pair of lung cancer cells with (A549sh) or without E-cadherin expression (A549sh-Ecad), which would be optimal model to examine the alteration of adhesion properties after EMT induction. The cell-matrix adhesion resisting to shear stress appeared to be remarkably differed between lung cancer cells. The detachment rate of epithelial-like H358 and mesenchymal-like H460 cells was 53%-80% and 25%-66% in the shear stress range of 34-60 dyn/cm2, respectively. A549sh-Ecad cells exhibits lower detachment rate (5%-9%) compared to A549sh cells (14%-40%). By direct comparison of adhesion between A549sh and A549sh-Ecad, we demonstrated that A549shE-cad to mimic EMT were more favorable to the ECM attachment under the various levels of shear stress. The present method can be applied to quantitative analysis of tumor cell-ECM adhesion.

A gastric acid secretion model.

PubMed Central

de Beus, A M; Fabry, T L; Lacker, H M

1993-01-01

A theory of gastric acid production and self-protection is formulated mathematically and examined for clinical and experimental correlations, implications, and predictions using analytic and numerical techniques. In our model, gastric acid secretion in the stomach, as represented by an archetypal gastron, consists of two chambers, circulatory and luminal, connected by two different regions of ion exchange. The capillary circulation of the gastric mucosa is arranged in arterial-venous arcades which pass from the gastric glands up to the surface epithelial lining of the lumen; therefore the upstream region of the capillary chamber communicates with oxyntic cells, while the downstream region communicates with epithelial cells. Both cell types abut the gastric lumen. Ion currents across the upstream region are calculated from a steady-state oxyntic cell model with active ion transport, while the downstream ion fluxes are (facilitated) diffusion driven or secondarily active. Water transport is considered iso-osmotic. The steady-state model is solved in closed form for low gastric lumen pH. A wide variety of previously performed static and dynamic experiments on ion and CO2 transport in the gastric lumen and gastric blood supply are for the first time correlated with each other for an (at least) semiquantitative test of current concepts of gastric acid secretion and for the purpose of model verification. Agreement with the data is reported with a few outstanding and instructive exceptions. Model predictions and implications are also discussed. Images FIGURE 1 PMID:8396457

Modeling high-frequency electromotility of cochlear outer hair cell in microchamber experiment.

PubMed

Liao, Zhijie; Popel, Aleksander S; Brownell, William E; Spector, Alexander A

2005-04-01

Cochlear outer hair cells (OHC) are critically important for the amplification and sharp frequency selectivity of the mammalian ear. The microchamber experiment has been an effective tool to analyze the OHC high-frequency performance. In this study, the OHC electrical stimulation in the microchamber is simulated. The model takes into account the inertial and viscous properties of fluids inside and outside the cell as well as the viscoelastic and piezoelectric properties of the cell composite membrane (wall). The closed ends of the cylindrical cell were considered as oscillatory rigid plates. The final solution was obtained in terms of Fourier series, and it was checked against the available results of the microchamber experiment. The conditions of the interaction between the cell and pipette was analyzed, and it was found that the amount of slip along the contact surface has a significant effect on the cell electromotile response. The cell's length changes were computed as a function of frequency, and their dependence on the viscosities of both fluids and the cell wall was analyzed. The distribution of the viscous losses inside the fluids was also estimated. The proposed approach can help in a better understanding of the high-frequency OHC electromotility under experimental and physiological conditions.

40 CFR 98.430 - Definition of the source category.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.430 Definition of the source category. (a) The...-cell foams, consists of any entity that imports or exports pre-charged equipment that contains a fluorinated GHG, and any entity that imports or exports closed-cell foams that contain a fluorinated GHG. ...

40 CFR 98.430 - Definition of the source category.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.430 Definition of the source category. (a) The...-cell foams, consists of any entity that imports or exports pre-charged equipment that contains a fluorinated GHG, and any entity that imports or exports closed-cell foams that contain a fluorinated GHG. ...

40 CFR 98.430 - Definition of the source category.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.430 Definition of the source category. (a) The...-cell foams, consists of any entity that imports or exports pre-charged equipment that contains a fluorinated GHG, and any entity that imports or exports closed-cell foams that contain a fluorinated GHG. ...

40 CFR 98.430 - Definition of the source category.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.430 Definition of the source category. (a) The...-cell foams, consists of any entity that imports or exports pre-charged equipment that contains a fluorinated GHG, and any entity that imports or exports closed-cell foams that contain a fluorinated GHG. ...

Cells growing in NASA Bioreactor

NASA Technical Reports Server (NTRS)

1998-01-01

For 5 days on the STS-70 mission, a bioreactor cultivated human colon cancer cells, which grew to 30 times the volume of control specimens grown on Earth. This significant result was reproduced on STS-85 which grew mature structures that more closely match what are found in tumors in humans. Shown here, clusters of cells slowly spin inside a bioreactor. On Earth, the cells continually fall through the buffer medium and never hit bottom. In space, they are naturally suspended. Rotation ensures gentle stirring so waste is removed and fresh nutrient and oxygen are supplied. The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. The Bioreactor is rotated to provide gentle mixing of fresh and spent nutrient without inducing shear forces that would damage the cells. The work is sponsored by NASA's Office of Biological and Physical Research. The bioreactor is managed by the Biotechnology Cell Science Program at NASA's Johnson Space Center (JSC). NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues being cultured in rotating bioreactors by investigators.

Evaluating maturation and genetic modification of human dendritic cells in a new polyolefin cell culture bag system.

PubMed

Macke, Lars; Garritsen, Henk S P; Meyring, Wilhelm; Hannig, Horst; Pägelow, Ute; Wörmann, Bernhard; Piechaczek, Christoph; Geffers, Robert; Rohde, Manfred; Lindenmaier, Werner; Dittmar, Kurt E J

2010-04-01

Dendritic cells (DCs) are applied worldwide in several clinical studies of immune therapy of malignancies, autoimmune diseases, and transplantations. Most legislative bodies are demanding high standards for cultivation and transduction of cells. Closed-cell cultivating systems like cell culture bags would simplify and greatly improve the ability to reach these cultivation standards. We investigated if a new polyolefin cell culture bag enables maturation and adenoviral modification of human DCs in a closed system and compare the results with standard polystyrene flasks. Mononuclear cells were isolated from HLA-A*0201-positive blood donors by leukapheresis. A commercially available separation system (CliniMACS, Miltenyi Biotec) was used to isolate monocytes by positive selection using CD14-specific immunomagnetic beads. The essentially homogenous starting cell population was cultivated in the presence of granulocyte-macrophage-colony-stimulating factor and interleukin-4 in a closed-bag system in parallel to the standard flask cultivation system. Genetic modification was performed on Day 4. After induction of maturation on Day 5, mature DCs could be harvested and cryopreserved on Day 7. During the cultivation period comparative quality control was performed using flow cytometry, gene expression profiling, and functional assays. Both flasks and bags generated mature genetically modified DCs in similar yields. Surface membrane markers, expression profiles, and functional testing results were comparable. The use of a closed-bag system facilitated clinical applicability of genetically modified DCs. The polyolefin bag-based culture system yields DCs qualitatively and quantitatively comparable to the standard flask preparation. All steps including cryopreservation can be performed in a closed system facilitating standardized, safe, and reproducible preparation of therapeutic cells.

Modeling Tight Junction Dynamics and Oscillations

PubMed Central

Kassab, Fuad; Marques, Ricardo Paulino; Lacaz-Vieira, Francisco

2002-01-01

Tight junction (TJ) permeability responds to changes of extracellular Ca2+ concentration. This can be gauged through changes of the transepithelial electrical conductance (G) determined in the absence of apical Na+. The early events of TJ dynamics were evaluated by the fast Ca2+ switch assay (FCSA) (Lacaz-Vieira, 2000), which consists of opening the TJs by removing basal calcium (Ca2+ bl) and closing by returning Ca2+ bl to normal values. Oscillations of TJ permeability were observed when Ca2+ bl is removed in the presence of apical calcium (Ca2+ ap) and were interpreted as resulting from oscillations of a feedback control loop which involves: (a) a sensor (the Ca2+ binding sites of zonula adhaerens), (b) a control unit (the cell signaling machinery), and (c) an effector (the TJs). A mathematical model to explain the dynamical behavior of the TJs and oscillations was developed. The extracellular route (ER), which comprises the paracellular space in series with the submucosal interstitial fluid, was modeled as a continuous aqueous medium having the TJ as a controlled barrier located at its apical end. The ER was approximated as a linear array of cells. The most apical cell is separated from the apical solution by the TJ and this cell bears the Ca2+ binding sites of zonula adhaerens that control the TJs. According to the model, the control unit receives information from the Ca2+ binding sites and delivers a signal that regulates the TJ barrier. Ca2+ moves along the ER according to one-dimensional diffusion following Fick's second law. Across the TJ, Ca2+ diffusion follows Fick's first law. Our first approach was to simulate the experimental results in a semiquantitative way. The model tested against experiment results performed in the frog urinary bladder adequately predicts the responses obtained in different experimental conditions, such as: (a) TJ opening and closing in a FCSA, (b) opening by the presence of apical Ca2+ and attainment of a new steady-state, (c) the escape phase which follows the halt of TJ opening induced by apical Ca2+, (d) the oscillations of TJ permeability, and (e) the effect of Ca2+ ap concentration on the frequency of oscillations. PMID:12149284

Method Of Making Closed End Ceramic Fuel Cell Tubes

DOEpatents

Borglum, Brian P.

2002-04-30

A method of manufacturing closed end ceramic fuel cell tubes with improved properties and higher manufacturing yield is disclosed. The method involves bonding an unfired cap to a hollow unfired tube to form a compound joint. The assembly is then fired to net shape without subsequent machining. The resultant closed end tube is superior in that it provides a leak-tight seal and its porosity is substantially identical to that of the tube wall. The higher manufacturing yield associated with the present method decreases overall fuel cell cost significantly.

Effects of recombinant human bone morphogenetic protein 7 (rhBMP-7) on the behaviour of oral squamous cell carcinoma: a preliminary in vitro study.

PubMed

Lappin, D F; Abu-Serriah, M; Hunter, K D

2015-02-01

We investigated the effects of recombinant human bone morphogenetic protein-7 (rhBMP-7) on the behaviour of oral keratinocytes and head and neck squamous cell carcinoma (SCC) cells in vitro. Expression of all three BMP receptors was high (p<0.01), and rhBMP-7 exhibited significant dose-related inhibitory effects on the doubling time and viability of cancer cells (p<0.01), but not on the proliferation or viability of oral keratinocytes. It elicited no significant effect on the invasion of Matrigel in SCC of the head and neck. Results indicate that in cell culture, rhBMP-7 exerts antineoplastic effects. This should be tested in an orthotopic animal model to more closely replicate in vivo effects. Copyright © 2014. Published by Elsevier Ltd.

A neuro-computational model of economic decisions.

PubMed

Rustichini, Aldo; Padoa-Schioppa, Camillo

2015-09-01

Neuronal recordings and lesion studies indicate that key aspects of economic decisions take place in the orbitofrontal cortex (OFC). Previous work identified in this area three groups of neurons encoding the offer value, the chosen value, and the identity of the chosen good. An important and open question is whether and how decisions could emerge from a neural circuit formed by these three populations. Here we adapted a biophysically realistic neural network previously proposed for perceptual decisions (Wang XJ. Neuron 36: 955-968, 2002; Wong KF, Wang XJ. J Neurosci 26: 1314-1328, 2006). The domain of economic decisions is significantly broader than that for which the model was originally designed, yet the model performed remarkably well. The input and output nodes of the network were naturally mapped onto two groups of cells in OFC. Surprisingly, the activity of interneurons in the network closely resembled that of the third group of cells, namely, chosen value cells. The model reproduced several phenomena related to the neuronal origins of choice variability. It also generated testable predictions on the excitatory/inhibitory nature of different neuronal populations and on their connectivity. Some aspects of the empirical data were not reproduced, but simple extensions of the model could overcome these limitations. These results render a biologically credible model for the neuronal mechanisms of economic decisions. They demonstrate that choices could emerge from the activity of cells in the OFC, suggesting that chosen value cells directly participate in the decision process. Importantly, Wang's model provides a platform to investigate the implications of neuroscience results for economic theory. Copyright © 2015 the American Physiological Society.

Human Hemato-Lymphoid System Mice: Current Use and Future Potential for Medicine

PubMed Central

Rongvaux, Anthony; Takizawa, Hitoshi; Strowig, Till; Willinger, Tim; Eynon, Elizabeth E.

2014-01-01

To directly study complex human hemato-lymphoid system physiology and respective system-associated diseases in vivo, human-to-mouse xenotransplantation models for human blood and blood-forming cells and organs have been developed over the past three decades. We here review the fundamental requirements and the remarkable progress made over the past few years in improving these systems, the current major achievements reached by use of these models, and the future challenges to more closely model and study human health and disease and to achieve predictive preclinical testing of both prevention measures and potential new therapies. PMID:23330956

Single Neuron Optimization as a Basis for Accurate Biophysical Modeling: The Case of Cerebellar Granule Cells.

PubMed

Masoli, Stefano; Rizza, Martina F; Sgritta, Martina; Van Geit, Werner; Schürmann, Felix; D'Angelo, Egidio

2017-01-01

In realistic neuronal modeling, once the ionic channel complement has been defined, the maximum ionic conductance (G i-max ) values need to be tuned in order to match the firing pattern revealed by electrophysiological recordings. Recently, selection/mutation genetic algorithms have been proposed to efficiently and automatically tune these parameters. Nonetheless, since similar firing patterns can be achieved through different combinations of G i-max values, it is not clear how well these algorithms approximate the corresponding properties of real cells. Here we have evaluated the issue by exploiting a unique opportunity offered by the cerebellar granule cell (GrC), which is electrotonically compact and has therefore allowed the direct experimental measurement of ionic currents. Previous models were constructed using empirical tuning of G i-max values to match the original data set. Here, by using repetitive discharge patterns as a template, the optimization procedure yielded models that closely approximated the experimental G i-max values. These models, in addition to repetitive firing, captured additional features, including inward rectification, near-threshold oscillations, and resonance, which were not used as features. Thus, parameter optimization using genetic algorithms provided an efficient modeling strategy for reconstructing the biophysical properties of neurons and for the subsequent reconstruction of large-scale neuronal network models.

Reprogramming mediated radio-resistance of 3D-grown cancer cells.

PubMed

Xue, Gang; Ren, Zhenxin; Grabham, Peter W; Chen, Yaxiong; Zhu, Jiayun; Du, Yarong; Pan, Dong; Li, Xiaoman; Hu, Burong

2015-07-01

In vitro 3D growth of tumors is a new cell culture model that more closely mimics the features of the in vivo environment and is being used increasingly in the field of biological and medical research. It has been demonstrated that cancer cells cultured in 3D matrices are more radio-resistant compared with cells in monolayers. However, the mechanisms causing this difference remain unclear. Here we show that cancer cells cultured in a 3D microenvironment demonstrated an increase in cells with stem cell properties. This was confirmed by the finding that cells in 3D cultures upregulated the gene and protein expression of the stem cell reprogramming factors such as OCT4, SOX2, NANOG, LIN28 and miR-302a, compared with cells in monolayers. Moreover, the expression of β-catenin, a regulating molecule of reprogramming factors, also increased in 3D-grown cancer cells. These findings suggest that cancer cells were reprogrammed to become stem cell-like cancer cells in a 3D growth culture microenvironment. Since cancer stem cell-like cells demonstrate an increased radio-resistance and chemo-resistance, our results offer a new perspective as to why. Our findings shed new light on understanding the features of the 3D growth cell model and its application in basic research into clinical radiotherapy and medicine. © The Author 2015. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

Short-term differential adaptation to anaerobic stress via genomic mutations by Escherichia coli strains K-12 and B lacking alcohol dehydrogenase

PubMed Central

Kim, Hyun Ju; Jeong, Haeyoung; Hwang, Seungwoo; Lee, Moo-Seung; Lee, Yong-Jik; Lee, Dong-Woo; Lee, Sang Jun

2014-01-01

Microbial adaptations often occur via genomic mutations under adverse environmental conditions. This study used Escherichia coli ΔadhE cells as a model system to investigate adaptation to anaerobic conditions, which we then compared with the adaptive mechanisms of two closely related E. coli strains, K-12 and B. In contrast to K-12 ΔadhE cells, the E. coli B ΔadhE cells exhibited significantly delayed adaptive growth under anaerobic conditions. Adaptation by the K-12 and B strains mainly employed anaerobic lactate fermentation to restore cellular growth. Several mutations were identified in the pta or pflB genes of adapted K-12 cells, but mostly in the pta gene of the B strains. However, the types of mutation in the adapted K-12 and B strains were similar. Cellular viability was affected directly by severe redox imbalance in B ΔadhE cells, which also impaired their ability to adapt to anaerobic conditions. This study demonstrates that closely related microorganisms may undergo different adaptations under the same set of adverse conditions, which might be associated with the specific metabolic characteristics of each strain. This study provides new insights into short-term microbial adaptation to stressful conditions, which may reflect dynamic microbial population changes in nature. PMID:25250024

Packaging Considerations for Biopreservation

PubMed Central

Woods, Erik J.; Thirumala, Sreedhar

2011-01-01

Summary The packaging system chosen for biopreservation is critical for many reasons. An ideal biopreservation container system must provide for closure integrity, sample stability and ready access to the preserved material. This means the system needs to be hermetically sealed to ensure integrity of the specimen is maintained throughout processing, storage and distribution; the system must remain stable over long periods of time as many biobanked samples may be stored indefinitely; and functionally closed access systems must be used to avoid contamination upon sample withdraw. This study reviews the suitability of a new commercially available vial configuration container utilizing blood bag style closure and access systems that can be hermetically sealed and remain stable through cryopreservation and biobanking procedures. This vial based systems allow for current good manufacturing/tissue practice (cGTP) requirements during processing of samples and may provide the benefit of ease of delivery by a care giver. In this study, the CellSeal® closed system cryovial was evaluated and compared to standard screw cap vials. The CellSeal system was evaluated for durability, closure integrity through transportation and maintenance of functional viability of a cryopreserved mesenchymal stem cell model. The results of this initial proof-of-concept study indicated that the CellSeal vials are highly suitable for biopreservation and biobanking, and provide a suitable container system for clinical and commercial cell therapy products frozen in small volumes. PMID:21566715

Two Closely Related Ubiquitin C-Terminal Hydrolase Isozymes Function as Reciprocal Modulators of Germ Cell Apoptosis in Cryptorchid Testis

PubMed Central

Kwon, Jungkee; Wang, Yu-Lai; Setsuie, Rieko; Sekiguchi, Satoshi; Sato, Yae; Sakurai, Mikako; Noda, Mami; Aoki, Shunsuke; Yoshikawa, Yasuhiro; Wada, Keiji

2004-01-01

The experimentally induced cryptorchid mouse model is useful for elucidating the in vivo molecular mechanism of germ cell apoptosis. Apoptosis, in general, is thought to be partly regulated by the ubiquitin-proteasome system. Here, we analyzed the function of two closely related members of the ubiquitin C-terminal hydrolase (UCH) family in testicular germ cell apoptosis experimentally induced by cryptorchidism. The two enzymes, UCH-L1 and UCH-L3, deubiquitinate ubiquitin-protein conjugates and control the cellular balance of ubiquitin. The testes of gracile axonal dystrophy (gad) mice, which lack UCH-L1, were resistant to cryptorchid stress-related injury and had reduced ubiquitin levels. The level of both anti-apoptotic (Bcl-2 family and XIAP) and prosurvival (pCREB and BDNF) proteins was significantly higher in gad mice after cryptorchid stress. In contrast, Uchl3 knockout mice showed profound testicular atrophy and apoptotic germ cell loss after cryptorchid injury. Ubiquitin level was not significantly different between wild-type and Uchl3 knockout mice, whereas the levels of Nedd8 and the apoptotic proteins p53, Bax, and caspase3 were elevated in Uchl3 knockout mice. These results demonstrate that UCH-L1 and UCH-L3 function differentially to regulate the cellular levels of anti-apoptotic, prosurvival, and apoptotic proteins during testicular germ cell apoptosis. PMID:15466400

Steps Towards Industrialization of Cu–III–VI2Thin‐Film Solar Cells:Linking Materials/Device Designs to Process Design For Non‐stoichiometric Photovoltaic Materials

PubMed Central

Chang, Hsueh‐Hsin; Sharma, Poonam; Letha, Arya Jagadhamma; Shao, Lexi; Zhang, Yafei; Tseng, Bae‐Heng

2016-01-01

The concept of in‐line sputtering and selenization become industrial standard for Cu–III–VI2 solar cell fabrication, but still it's very difficult to control and predict the optical and electrical parameters, which are closely related to the chemical composition distribution of the thin film. The present review article addresses onto the material design, device design and process design using parameters closely related to the chemical compositions. Its variation leads to change in the Poisson equation, current equation, and continuity equation governing the device design. To make the device design much realistic and meaningful, we need to build a model that relates the opto‐electrical properties to the chemical composition. The material parameters as well as device structural parameters are loaded into the process simulation to give a complete set of process control parameters. The neutral defect concentrations of non‐stoichiometric CuMSe2 (M = In and Ga) have been calculated under the specific atomic chemical potential conditions using this methodology. The optical and electrical properties have also been investigated for the development of a full‐function analytical solar cell simulator. The future prospects regarding the development of copper–indium–gallium–selenide thin film solar cells have also been discussed. PMID:27840790

Steps Towards Industrialization of Cu-III-VI2Thin-Film Solar Cells:Linking Materials/Device Designs to Process Design For Non-stoichiometric Photovoltaic Materials.

PubMed

Hwang, Huey-Liang; Chang, Hsueh-Hsin; Sharma, Poonam; Letha, Arya Jagadhamma; Shao, Lexi; Zhang, Yafei; Tseng, Bae-Heng

2016-10-01

The concept of in-line sputtering and selenization become industrial standard for Cu-III-VI 2 solar cell fabrication, but still it's very difficult to control and predict the optical and electrical parameters, which are closely related to the chemical composition distribution of the thin film. The present review article addresses onto the material design, device design and process design using parameters closely related to the chemical compositions. Its variation leads to change in the Poisson equation, current equation, and continuity equation governing the device design. To make the device design much realistic and meaningful, we need to build a model that relates the opto-electrical properties to the chemical composition. The material parameters as well as device structural parameters are loaded into the process simulation to give a complete set of process control parameters. The neutral defect concentrations of non-stoichiometric CuMSe 2 (M = In and Ga) have been calculated under the specific atomic chemical potential conditions using this methodology. The optical and electrical properties have also been investigated for the development of a full-function analytical solar cell simulator. The future prospects regarding the development of copper-indium-gallium-selenide thin film solar cells have also been discussed.

One-to-one neuron-electrode interfacing.

PubMed

Greenbaum, Alon; Anava, Sarit; Ayali, Amir; Shein, Mark; David-Pur, Moshe; Ben-Jacob, Eshel; Hanein, Yael

2009-09-15

The question of neuronal network development and organization is a principle one, which is closely related to aspects of neuronal and network form-function interactions. In-vitro two-dimensional neuronal cultures have proved to be an attractive and successful model for the study of these questions. Research is constraint however by the search for techniques aimed at culturing stable networks, whose electrical activity can be reliably and consistently monitored. A simple approach to form small interconnected neuronal circuits while achieving one-to-one neuron-electrode interfacing is presented. Locust neurons were cultured on a novel bio-chip consisting of carbon-nanotube multi-electrode-arrays. The cells self-organized to position themselves in close proximity to the bio-chip electrodes. The organization of the cells on the electrodes was analyzed using time lapse microscopy, fluorescence imaging and scanning electron microscopy. Electrical recordings from well identified cells is presented and discussed. The unique properties of the bio-chip and the specific neuron-nanotube interactions, together with the use of relatively large insect ganglion cells, allowed long-term stabilization (as long as 10 days) of predefined neural network topology as well as high fidelity electrical recording of individual neuron firing. This novel preparation opens ample opportunity for future investigation into key neurobiological questions and principles.

Advances in 3D cell culture technologies enabling tissue-like structures to be created in vitro.

PubMed

Knight, Eleanor; Przyborski, Stefan

2015-12-01

Research in mammalian cell biology often relies on developing in vitro models to enable the growth of cells in the laboratory to investigate a specific biological mechanism or process under different test conditions. The quality of such models and how they represent the behavior of cells in real tissues plays a critical role in the value of the data produced and how it is used. It is particularly important to recognize how the structure of a cell influences its function and how co-culture models can be used to more closely represent the structure of real tissue. In recent years, technologies have been developed to enhance the way in which researchers can grow cells and more readily create tissue-like structures. Here we identify the limitations of culturing mammalian cells by conventional methods on two-dimensional (2D) substrates and review the popular approaches currently available that enable the development of three-dimensional (3D) tissue models in vitro. There are now many ways in which the growth environment for cultured cells can be altered to encourage 3D cell growth. Approaches to 3D culture can be broadly categorized into scaffold-free or scaffold-based culture systems, with scaffolds made from either natural or synthetic materials. There is no one particular solution that currently satisfies all requirements and researchers must select the appropriate method in line with their needs. Using such technology in conjunction with other modern resources in cell biology (e.g. human stem cells) will provide new opportunities to create robust human tissue mimetics for use in basic research and drug discovery. Application of such models will contribute to advancing basic research, increasing the predictive accuracy of compounds, and reducing animal usage in biomedical science. © 2014 The Authors. Journal of Anatomy published by John Wiley & Sons Ltd on behalf of Anatomical Society.

Rigid closed-cell polyimide foams for aircraft applications and foam-in-place technology

NASA Technical Reports Server (NTRS)

Gagliani, J.; Straub, P.; Gagliani, J., Jr.

1983-01-01

Significant accomplishments generated are summarized. Testing of closed cell foams, which has resulted in the characterization of compositions which produce rigid foams for use in galley structure applications is reported. It is shown that the density, compressive strength and shear strength of the foams are directly related to the concentrations of the microballoons. The same properties are also directly related to the resin loading. Prototype samples of rigid closed cell foams meeting the requirements of the program were submitted. Investigation of the apparatus to produce polyimide foams using foam in place techniques, resulted in the selection of a spray gun apparatus, capable to deliver a mixture of microballoons and resin binder on substrates which cures to yield a closed cell foam. It is found that the adhesion of the foam on aluminum, titanium and steel substrates is satisfactory. It is concluded that the material meets the mechanical and thermal requirements of the program.

Interactions of Entamoeba Histolytica with Host Cells in the Gut Mucosa,

DTIC Science & Technology

1977-01-01

amebae were observed close to the cecal epithelium, the apposing epithelial cell was found to have protruded in the lumen and making contact with the... amebae . Such cells often had become detached from their basal lamina and intercellular tight junctions, affording spaces through which amebae invaded the...mucosa. Other epithelial cells in close proximity to amebae showed degenerative changes characterized by swelling of mitochondria and endoplasmic

Micromechanics of Spray-On Foam Insulation

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Aboudi, Jacob; Arnold, Steven M.; Sullivan, Roy M.

2007-01-01

Understanding the thermo-mechanical response of the Space Shuttle External Tank spray-on foam insulation (SOFI) material is critical, to NASA's Return to Flight effort. This closed-cell rigid polymeric foam is used to insulate the metallic Space Shuttle External Tank, which is at cryogenic temperatures immediately prior to and during lift off. The shedding of the SOFI during ascent led to the loss of the Columbia, and eliminating/minimizing foam lass from the tank has become a priority for NASA as it seeks to resume scheduled space shuttle missions. Determining the nature of the SOFI material behavior in response to both thermal and mechanical loading plays an important role as any structural modeling of the shedding phenomenon k predicated on knowledge of the constitutive behavior of the foam. In this paper, the SOFI material has been analyzed using the High-Fidelity Generalized Method of Cells (HFGMC) micromechanics model, which has recently been extended to admit a triply-periodic 3-D repeating unit cell (RUC). Additional theoretical extensions that mere made in order to enable modeling of the closed-cell-foam material include the ability to represent internal boundaries within the RUC (to simulated internal pores) and the ability to impose an internal pressure within the simulated pores. This latter extension is crucial as two sources contribute to significant internal pressure changes within the SOFI pores. First, gas trapped in the pores during the spray process will expand or contract due to temperature changes. Second, the pore pressure will increase due to outgassing of water and other species present in the foam skeleton polymer material. With HFGMC's new pore pressure modeling capabilities, a nonlinear pressure change within the simulated pore can be imposed that accounts for both of these sources, in addition to stmdar&-thermal and mechanical loading; The triply-periodic HFGMC micromechanics model described above was implemented within NASA GRC's MAC/GMC software package, giving the model access to a range of nonlinear constitutive models for the polymeric foam skeleton material. A repeating unit cell architecture was constructed that, while relatively simple, still accounts for the geometric anisotropy of the porous foam microstructure and its thin walls and thicker edges. With the lack of reliable polymeric foam skeleton materia1 properties, many simulations were executed aimed at backing out these material properties. Then, using these properties, predictions of the thermo-mechanical behavior of the foam, including calculated internal applied pressure profiles, were performed and compared with appropriate experimental data.

Ice formation in isolated human hepatocytes and human liver tissue.

PubMed

Bischof, J C; Ryan, C M; Tompkins, R G; Yarmush, M L; Toner, M

1997-01-01

Cryopreservation of isolated cells and tissue slices of human liver is required to furnish extracorporeal bioartificial liver devices with a ready supply of hepatocytes, and to create in vitro drug metabolism and toxicity models. Although both the bioartificial liver and many current biotoxicity models are based on reconstructing organ functions from single isolated hepatocytes, tissue slices offer an in vitro system that may more closely resemble the in vivo situation of the cells because of cell-cell and cell-extracellular matrix interactions. However, successful cryopreservation of both cellular and tissue level systems requires an increased understanding of the fundamental mechanisms involved in the response of the liver and its cells to freezing stress. This study investigates the biophysical mechanisms of water transport and intracellular ice formation during freezing in both isolated human hepatocytes and whole liver tissue. The effects of cooling rate on individual cells were measured using a cryomicroscope. Biophysical parameters governing water transport (Lpg = 2.8 microns/min-atm and ELp = 79 kcal/mole) and intracellular heterogeneous ice nucleation (omega het = 1.08 x 10(9) m-2s-1 and kappa het = 1.04 x 10(9) K5) were determined. These parameters were then incorporated into a theoretical Krogh cylinder model developed to simulate water transport and ice formation in intact liver tissue. Model simulations indicated that the cellular compartment of the Krogh model maintained more water than isolated cells under the same freezing conditions. As a result, intracellular ice nucleation occurred at lower cooling rates in the Krogh model than in isolated cells. Furthermore, very rapid cooling rates (1000 degrees C/min) showed a depression of heterogeneous nucleation and a shift toward homogeneous nucleation. The results of this study are in qualitative agreement with the findings of a previous experimental study of the response to freezing of intact human liver.

Efficient coarse simulation of a growing avascular tumor

PubMed Central

Kavousanakis, Michail E.; Liu, Ping; Boudouvis, Andreas G.; Lowengrub, John; Kevrekidis, Ioannis G.

2013-01-01

The subject of this work is the development and implementation of algorithms which accelerate the simulation of early stage tumor growth models. Among the different computational approaches used for the simulation of tumor progression, discrete stochastic models (e.g., cellular automata) have been widely used to describe processes occurring at the cell and subcell scales (e.g., cell-cell interactions and signaling processes). To describe macroscopic characteristics (e.g., morphology) of growing tumors, large numbers of interacting cells must be simulated. However, the high computational demands of stochastic models make the simulation of large-scale systems impractical. Alternatively, continuum models, which can describe behavior at the tumor scale, often rely on phenomenological assumptions in place of rigorous upscaling of microscopic models. This limits their predictive power. In this work, we circumvent the derivation of closed macroscopic equations for the growing cancer cell populations; instead, we construct, based on the so-called “equation-free” framework, a computational superstructure, which wraps around the individual-based cell-level simulator and accelerates the computations required for the study of the long-time behavior of systems involving many interacting cells. The microscopic model, e.g., a cellular automaton, which simulates the evolution of cancer cell populations, is executed for relatively short time intervals, at the end of which coarse-scale information is obtained. These coarse variables evolve on slower time scales than each individual cell in the population, enabling the application of forward projection schemes, which extrapolate their values at later times. This technique is referred to as coarse projective integration. Increasing the ratio of projection times to microscopic simulator execution times enhances the computational savings. Crucial accuracy issues arising for growing tumors with radial symmetry are addressed by applying the coarse projective integration scheme in a cotraveling (cogrowing) frame. As a proof of principle, we demonstrate that the application of this scheme yields highly accurate solutions, while preserving the computational savings of coarse projective integration. PMID:22587128

Encapsulated living choroid plexus cells: potential long-term treatments for central nervous system disease and trauma.

PubMed

Skinner, S J M; Geaney, M S; Lin, H; Muzina, M; Anal, A K; Elliott, R B; Tan, P L J

2009-12-01

In neurodegenerative disease and in acute brain injury, there is often local up-regulation of neurotrophin production close to the site of the lesion. Treatment by direct injection of neurotrophins and growth factors close to these lesion sites has repeatedly been demonstrated to improve recovery. It has therefore been proposed that transplanting viable neurotrophin-producing cells close to the trauma lesion, or site of degenerative disease, might provide a novel means for continuous delivery of these molecules directly to the site of injury or to a degenerative region. The aim of this paper is to summarize recent published information and present new experimental data that indicate that long-lasting therapeutic implants of choroid plexus (CP) neuroepithelium may be used to treat brain disease. CP produces and secretes numerous biologically active neurotrophic factors (NT). New gene microarray and proteomics data presented here indicate that many other anti-oxidant, anti-toxin and neuronal support proteins are also produced and secreted by CP cells. In the healthy brain, these circulate in the cerebrospinal fluid through the brain and spinal cord, maintaining neuronal networks and associated cells. Recent publications describe how transplanted CP cells and tissue, either free or in an immunoprotected encapsulated form, can effectively deliver therapeutic molecules when placed near the lesion or site of degenerative disease in animal models. Using simple techniques, CP neuroepithelial cell clusters in suspension culture were very durable, remaining viable for 6 months or more in vitro. The cell culture conditions had little effect on the wide range and activity of genes expressed and proteins secreted. Recently, completed experiments show that implanting CP within alginate-poly-ornithine capsules effectively protected these xenogeneic cells from the host immune system and allowed their survival for 6 months or more in the brains of rats, causing no adverse effects. Previously reported evidence demonstrated that CP cells support the survival and differentiation of neuronal cells in vitro and effectively treat acute brain injury and disease in rodents and non-human primates in vivo. The accumulated preclinical data together with the long-term survival of implanted encapsulated cells in vivo provide a sound base for the investigation of these treatments for chronic inherited and established neurodegenerative conditions.

Encapsulated living choroid plexus cells: potential long-term treatments for central nervous system disease and trauma

NASA Astrophysics Data System (ADS)

Skinner, S. J. M.; Geaney, M. S.; Lin, H.; Muzina, M.; Anal, A. K.; Elliott, R. B.; Tan, P. L. J.

2009-12-01

In neurodegenerative disease and in acute brain injury, there is often local up-regulation of neurotrophin production close to the site of the lesion. Treatment by direct injection of neurotrophins and growth factors close to these lesion sites has repeatedly been demonstrated to improve recovery. It has therefore been proposed that transplanting viable neurotrophin-producing cells close to the trauma lesion, or site of degenerative disease, might provide a novel means for continuous delivery of these molecules directly to the site of injury or to a degenerative region. The aim of this paper is to summarize recent published information and present new experimental data that indicate that long-lasting therapeutic implants of choroid plexus (CP) neuroepithelium may be used to treat brain disease. CP produces and secretes numerous biologically active neurotrophic factors (NT). New gene microarray and proteomics data presented here indicate that many other anti-oxidant, anti-toxin and neuronal support proteins are also produced and secreted by CP cells. In the healthy brain, these circulate in the cerebrospinal fluid through the brain and spinal cord, maintaining neuronal networks and associated cells. Recent publications describe how transplanted CP cells and tissue, either free or in an immunoprotected encapsulated form, can effectively deliver therapeutic molecules when placed near the lesion or site of degenerative disease in animal models. Using simple techniques, CP neuroepithelial cell clusters in suspension culture were very durable, remaining viable for 6 months or more in vitro. The cell culture conditions had little effect on the wide range and activity of genes expressed and proteins secreted. Recently, completed experiments show that implanting CP within alginate-poly-ornithine capsules effectively protected these xenogeneic cells from the host immune system and allowed their survival for 6 months or more in the brains of rats, causing no adverse effects. Previously reported evidence demonstrated that CP cells support the survival and differentiation of neuronal cells in vitro and effectively treat acute brain injury and disease in rodents and non-human primates in vivo. The accumulated preclinical data together with the long-term survival of implanted encapsulated cells in vivo provide a sound base for the investigation of these treatments for chronic inherited and established neurodegenerative conditions.

Bacillus subtilis extracytoplasmic function (ECF) sigma factors and defense of the cell envelope

PubMed Central

Helmann, John D.

2016-01-01

Summary Bacillus subtilis provides a model for investigation of the bacterial cell envelope, the first line of defense against environmental threats. Extracytoplasmic function (ECF) sigma factors activate genes that confer resistance to agents that threaten the integrity of the envelope. Although their individual regulons overlap, σW is most closely associated with membrane-active agents, σX with cationic antimicrobial peptide resistance, and σV with resistance to lysozyme. Here, I highlight the role of the σM regulon, which is strongly induced by conditions that impair peptidoglycan synthesis and includes the core pathways of envelope synthesis and cell division, as well as stress-inducible alternative enzymes. Studies of these cell envelope stress responses provide insights into how bacteria acclimate to the presence of antibiotics. PMID:26901131

Molecular Regulation of the Mitosis/Meiosis Decision in Multicellular Organisms

PubMed Central

Kimble, Judith

2011-01-01

A major step in the journey from germline stem cell to differentiated gamete is the decision to leave the mitotic cell cycle and begin progression through the meiotic cell cycle. Over the past decade, molecular regulators of the mitosis/meiosis decision have been discovered in most of the major model multicellular organisms. Historically, the mitosis/meiosis decision has been closely linked with controls of germline self-renewal and the sperm/egg decision, especially in nematodes and mice. Molecular explanations of those linkages clarify our understanding of this fundamental germ cell decision, and unifying themes have begun to emerge. Although the complete circuitry of the decision is not known in any organism, the recent advances promise to impact key issues in human reproduction and agriculture. PMID:21646377

High Fill Factors of Si Solar Cells Achieved by Using an Inverse Connection Between MOS and PN Junctions.

PubMed

Wang, Liang-Xing; Zhou, Zhi-Quan; Zhang, Tian-Ning; Chen, Xin; Lu, Ming

2016-12-01

Fill factors (FFs) of ~0.87 have been obtained for crystalline Si (c-Si) solar cells based on Ag front contacts after rapid thermal annealing. The usual single PN junction model fails to explain the high FF result. A metal/oxide/semiconductor (MOS) junction at the emitter is found to be inversely connected to the PN one, and when its barrier height/e is close to the open-circuit voltage of the solar cell, very high FF is obtainable. In this work, although the open-circuit voltage (<580 mV) is not high here, the efficiency of c-Si solar cell still reaches the state-of-the-art value (>20 %) due to the high FF achieved.

Patient-derived xenograft in zebrafish embryos: a new platform for translational research in neuroendocrine tumors.

PubMed

Gaudenzi, Germano; Albertelli, Manuela; Dicitore, Alessandra; Würth, Roberto; Gatto, Federico; Barbieri, Federica; Cotelli, Franco; Florio, Tullio; Ferone, Diego; Persani, Luca; Vitale, Giovanni

2017-08-01

Preclinical research on neuroendocrine tumors usually involves immortalized cell lines and few animal models. In the present study we described an in vivo model based on patient-derived xenografts of neuroendocrine tumor cells in zebrafish (Danio rerio) embryos, allowing a rapid analysis of the angiogenic and invasive potential. Patient-derived neuroendocrine tumor cells were transplanted in 48 hours post-fertilization Tg(fli1a:EGFP) y1 zebrafish embryos that express enhanced green fluorescent protein in the entire vasculature. Neuroendocrine tumor cells, stained with CM-Dil, were injected into the subperidermal (perivitelline) space, close to the developing subintestinal venous plexus. A proper control group, represented by zebrafish injected with only D-PBS, was included in this study. Angiogenic and invasive potentials of each patient-derived xenograft were evaluated by both epifluorescence and confocal microscopes. Six out of eight neuroendocrine tumor samples were successfully transplanted in zebrafish embryos. Although the implanted tumor mass had a limited size (about 100 cells for embryos), patient-derived xenografts showed pro-angiogenic (5 cases) and invasive (6 cases) behaviors within 48 hours post injection. Patient-derived xenograft in zebrafish embryos appears to be a reliable in vivo preclinical model for neuroendocrine tumors, tumors with often limited cell availability. The rapidity of this procedure makes our model a promising platform to perform preclinical drug screening and opens a new scenario for personalized treatment in patients with neuroendocrine tumors.

Epidermal Homeostasis and Radiation Responses in a Multiscale Tissue Modeling Framework

NASA Technical Reports Server (NTRS)

Hu, Shaowen; Cucinotta, Francis A.

2013-01-01

The surface of skin is lined with several thin layers of epithelial cells that are maintained throughout life time by a small population of stem cells. High dose radiation exposures could injure and deplete the underlying proliferative cells and induce cutaneous radiation syndrome. In this work we propose a multiscale computational model for skin epidermal dynamics that links phenomena occurring at the subcellular, cellular, and tissue levels of organization, to simulate the experimental data of the radiation response of swine epidermis, which is closely similar to human epidermis. Incorporating experimentally measured histological and cell kinetic parameters, we obtain results of population kinetics and proliferation indexes comparable to observations in unirradiated and acutely irradiated swine experiments. At the sub-cellular level, several recently published Wnt signaling controlled cell-cycle models are applied and the roles of key components and parameters are analyzed. Based on our simulation results, we demonstrate that a moderate increase of proliferation rate for the survival proliferative cells is sufficient to fully repopulate the area denuded by high dose radiation, as long as the integrity of underlying basement membrane is maintained. Our work highlights the importance of considering proliferation kinetics as well as the spatial organization of tissues when conducting in vivo investigations of radiation responses. This integrated model allow us to test the validity of several basic biological rules at the cellular level and sub-cellular mechanisms by qualitatively comparing simulation results with published research, and enhance our understanding of the pathophysiological effects of ionizing radiation on skin.

The effects of flagellar hook compliance on motility of monotrichous bacteria: A modeling study

NASA Astrophysics Data System (ADS)

Shum, H.; Gaffney, E. A.

2012-06-01

A crucial structure in the motility of flagellated bacteria is the hook, which connects the flagellum filament to the motor in the cell body. Early mathematical models of swimming bacteria assume that the helically shaped flagellum rotates rigidly about its axis, which coincides with the axis of the cell body. Motivated by evidence that the hook is much more flexible than the rest of the flagellum, we develop a new model that allows a naturally straight hook to bend. Hook dynamics are based on the Kirchhoff rod model, which is combined with a boundary element method for solving viscous interactions between the bacterium and the surrounding fluid. For swimming in unbounded fluid, we find good support for using a rigid model since the hook reaches an equilibrium configuration within several revolutions of the motor. However, for effective swimming, there are constraints on the hook stiffness relative to the scale set by the product of the motor torque with the hook length. When the hook is too flexible, its shape cannot be maintained and large deformations and stresses build up. When the hook is too rigid, the flagellum does not align with the cell body axis and the cell "wobbles" with little net forward motion. We also examine the attraction of swimmers to no-slip surfaces and find that the tendency to swim steadily close to a surface can be very sensitive to the combination of the hook rigidity and the precise shape of the cell and flagellum.

The Role of Infected Cell Proliferation in the Clearance of Acute HBV Infection in Humans

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goyal, Ashish; Ribeiro, Ruy Miguel; Perelson, Alan S.

Around 90–95% of hepatitis B virus (HBV) infected adults do not progress to the chronic phase and, instead, recover naturally. The strengths of the cytolytic and non-cytolytic immune responses are key players that decide the fate of acute HBV infection. In addition, it has been hypothesized that proliferation of infected cells resulting in uninfected progeny and/or cytokine-mediated degradation of covalently closed circular DNA (cccDNA) leading to the cure of infected cells are two major mechanisms assisting the adaptive immune response in the clearance of acute HBV infection in humans. We employed fitting of mathematical models to human acute infection datamore » together with physiological constraints to investigate the role of these hypothesized mechanisms in the clearance of infection. Results suggest that cellular proliferation of infected cells resulting in two uninfected cells is required to minimize the destruction of the liver during the clearance of acute HBV infection. In contrast, we find that a cytokine-mediated cure of infected cells alone is insufficient to clear acute HBV infection. Lastly, our modeling indicates that HBV clearance without lethal loss of liver mass is associated with the production of two uninfected cells upon proliferation of an infected cell.« less

The Role of Infected Cell Proliferation in the Clearance of Acute HBV Infection in Humans

DOE PAGES

Goyal, Ashish; Ribeiro, Ruy Miguel; Perelson, Alan S.

2017-11-18

Around 90–95% of hepatitis B virus (HBV) infected adults do not progress to the chronic phase and, instead, recover naturally. The strengths of the cytolytic and non-cytolytic immune responses are key players that decide the fate of acute HBV infection. In addition, it has been hypothesized that proliferation of infected cells resulting in uninfected progeny and/or cytokine-mediated degradation of covalently closed circular DNA (cccDNA) leading to the cure of infected cells are two major mechanisms assisting the adaptive immune response in the clearance of acute HBV infection in humans. We employed fitting of mathematical models to human acute infection datamore » together with physiological constraints to investigate the role of these hypothesized mechanisms in the clearance of infection. Results suggest that cellular proliferation of infected cells resulting in two uninfected cells is required to minimize the destruction of the liver during the clearance of acute HBV infection. In contrast, we find that a cytokine-mediated cure of infected cells alone is insufficient to clear acute HBV infection. Lastly, our modeling indicates that HBV clearance without lethal loss of liver mass is associated with the production of two uninfected cells upon proliferation of an infected cell.« less

A novel murine model of rhinoscleroma identifies Mikulicz cells, the disease signature, as IL-10 dependent derivatives of inflammatory monocytes

PubMed Central

Fevre, Cindy; Almeida, Ana S; Taront, Solenne; Pedron, Thierry; Huerre, Michel; Prevost, Marie-Christine; Kieusseian, Aurélie; Cumano, Ana; Brisse, Sylvain; Sansonetti, Philippe J; Tournebize, Régis

2013-01-01

Rhinoscleroma is a human specific chronic disease characterized by the formation of granuloma in the airways, caused by the bacterium Klebsiella pneumoniae subspecies rhinoscleromatis, a species very closely related to K. pneumoniae subspecies pneumoniae. It is characterized by the appearance of specific foamy macrophages called Mikulicz cells. However, very little is known about the pathophysiological processes underlying rhinoscleroma. Herein, we characterized a murine model recapitulating the formation of Mikulicz cells in lungs and identified them as atypical inflammatory monocytes specifically recruited from the bone marrow upon K. rhinoscleromatis infection in a CCR2-independent manner. While K. pneumoniae and K. rhinoscleromatis infections induced a classical inflammatory reaction, K. rhinoscleromatis infection was characterized by a strong production of IL-10 concomitant to the appearance of Mikulicz cells. Strikingly, in the absence of IL-10, very few Mikulicz cells were observed, confirming a crucial role of IL-10 in the establishment of a proper environment leading to the maturation of these atypical monocytes. This is the first characterization of the environment leading to Mikulicz cells maturation and their identification as inflammatory monocytes. PMID:23554169

A hybrid scanning mode for fast scanning ion conductance microscopy (SICM) imaging

PubMed Central

Zhukov, Alex; Richards, Owen; Ostanin, Victor; Korchev, Yuri; Klenerman, David

2012-01-01

We have developed a new method of controlling the pipette for scanning ion conductance microscopy to obtain high-resolution images faster. The method keeps the pipette close to the surface during a single line scan but does not follow the exact surface topography, which is calculated by using the ion current. Using an FPGA platform we demonstrate this new method on model test samples and then on live cells. This method will be particularly useful to follow changes occurring on relatively flat regions of the cell surface at high spatial and temporal resolutions. PMID:22902298

Evoking prescribed spike times in stochastic neurons

NASA Astrophysics Data System (ADS)

Doose, Jens; Lindner, Benjamin

2017-09-01

Single cell stimulation in vivo is a powerful tool to investigate the properties of single neurons and their functionality in neural networks. We present a method to determine a cell-specific stimulus that reliably evokes a prescribed spike train with high temporal precision of action potentials. We test the performance of this stimulus in simulations for two different stochastic neuron models. For a broad range of parameters and a neuron firing with intermediate firing rates (20-40 Hz) the reliability in evoking the prescribed spike train is close to its theoretical maximum that is mainly determined by the level of intrinsic noise.

Modeling the effects of vorinostat in vivo reveals both transient and delayed HIV transcriptional activation and minimal killing of latently infected cells

DOE PAGES

Ke, Ruian; Lewin, Sharon R.; Elliott, Julian H.; ...

2015-10-23

Recent efforts to cure human immunodeficiency virus type-1 (HIV-1) infection have focused on developing latency reversing agents as a first step to eradicate the latent reservoir. The histone deacetylase inhibitor, vorinostat, has been shown to activate HIV RNA transcription in CD4+ T-cells and alter host cell gene transcription in HIV-infected individuals on antiretroviral therapy. In order to understand how latently infected cells respond dynamically to vorinostat treatment and determine the impact of vorinostat on reservoir size in vivo, we have constructed viral dynamic models of latency that incorporate vorinostat treatment. We fitted these models to data collected from a recentmore » clinical trial in which vorinostat was administered daily for 14 days to HIV-infected individuals on suppressive ART. The results show that HIV transcription is increased transiently during the first few hours or days of treatment and that there is a delay before a sustained increase of HIV transcription, whose duration varies among study participants and may depend on the long term impact of vorinostat on host gene expression. Parameter estimation suggests that in latently infected cells, HIV transcription induced by vorinostat occurs at lower levels than in productively infected cells. Lastly, the estimated loss rate of transcriptionally induced cells remains close to baseline in most study participants, suggesting vorinostat treatment does not induce latently infected cell killing and thus reduce the latent reservoir in vivo.« less

Modeling the effects of vorinostat in vivo reveals both transient and delayed HIV transcriptional activation and minimal killing of latently infected cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ke, Ruian; Lewin, Sharon R.; Elliott, Julian H.

Recent efforts to cure human immunodeficiency virus type-1 (HIV-1) infection have focused on developing latency reversing agents as a first step to eradicate the latent reservoir. The histone deacetylase inhibitor, vorinostat, has been shown to activate HIV RNA transcription in CD4+ T-cells and alter host cell gene transcription in HIV-infected individuals on antiretroviral therapy. In order to understand how latently infected cells respond dynamically to vorinostat treatment and determine the impact of vorinostat on reservoir size in vivo, we have constructed viral dynamic models of latency that incorporate vorinostat treatment. We fitted these models to data collected from a recentmore » clinical trial in which vorinostat was administered daily for 14 days to HIV-infected individuals on suppressive ART. The results show that HIV transcription is increased transiently during the first few hours or days of treatment and that there is a delay before a sustained increase of HIV transcription, whose duration varies among study participants and may depend on the long term impact of vorinostat on host gene expression. Parameter estimation suggests that in latently infected cells, HIV transcription induced by vorinostat occurs at lower levels than in productively infected cells. Lastly, the estimated loss rate of transcriptionally induced cells remains close to baseline in most study participants, suggesting vorinostat treatment does not induce latently infected cell killing and thus reduce the latent reservoir in vivo.« less

Modeling of the Non-Auditory Response to Blast Overpressure. Calculation of the Internal Mechanical Response of Sheep to Blast Loading

DTIC Science & Technology

1990-01-01

through the esophagus into the left lung lobe and fially to the left rib surface. Spinal Process of Sixth Vertebra Seventh Vertebra Scapula Esophagus...for the calculations are as follows: 2.54 cm 12.7 cm 2.64 cm ’ J End Plate + Transducer Plexiglas (hard) or_ Closed-Cell Neoprene (soft) Figure 4

JPRS Report, Science & Technology, USSR: Life Sciences.

DTIC Science & Technology

1988-02-12

polypeptide chain frag- ments inside protein membranes or on their surfaces using bacteriorhodopsin as the test object. Purple membranes, partially...outside the membrane or close to its surface . A model was developed from these data which involved folding of certain regions of bacteriorhodopsin...into hepatic endothelial and Kupffer cells. These findings point to the putative usefulness of the PLP approach in gene therapy. Figures h

Engineering adolescence: maturation of human pluripotent stem cell-derived cardiomyocytes.

PubMed

Yang, Xiulan; Pabon, Lil; Murry, Charles E

2014-01-31

The discovery of human pluripotent stem cells (hPSCs), including both human embryonic stem cells and human-induced pluripotent stem cells, has opened up novel paths for a wide range of scientific studies. The capability to direct the differentiation of hPSCs into functional cardiomyocytes has provided a platform for regenerative medicine, development, tissue engineering, disease modeling, and drug toxicity testing. Despite exciting progress, achieving the optimal benefits has been hampered by the immature nature of these cardiomyocytes. Cardiac maturation has long been studied in vivo using animal models; however, finding ways to mature hPSC cardiomyocytes is only in its initial stages. In this review, we discuss progress in promoting the maturation of the hPSC cardiomyocytes, in the context of our current knowledge of developmental cardiac maturation and in relation to in vitro model systems such as rodent ventricular myocytes. Promising approaches that have begun to be examined in hPSC cardiomyocytes include long-term culturing, 3-dimensional tissue engineering, mechanical loading, electric stimulation, modulation of substrate stiffness, and treatment with neurohormonal factors. Future studies will benefit from the combinatorial use of different approaches that more closely mimic nature's diverse cues, which may result in broader changes in structure, function, and therapeutic applicability.

Scheduling cisplatin and radiotherapy in the treatment of squamous cell carcinomas of the head and neck: a modelling approach

NASA Astrophysics Data System (ADS)

Marcu, L.; Bezak, E.; Olver, I.

2006-08-01

The aim of the present work was to implement the kinetics of cisplatin into a previously developed tumour growth model and to simulate the combined cisplatin-radiotherapy treatment with the emphasis on time sequencing and scheduling of drug and radiation. An investigation into whether the effect of cisplatin-radiation is determined by independent cell kill or by cisplatin-produced radiosensitization was also undertaken. It was shown that cisplatin administered before radiation conferred similar tumour control to the post-radiation sequencing of the drug. The killing effect of the combined modality treatment on tumour increased with the increase in cell recruitment. Furthermore, the individual cell kill produced by the two cytotoxins led to an additive only tumour response when the treatments were given concurrently, suggesting that for a synergistic effect, cisplatin must potentiate the effect of radiation, through the radiosensitizing mechanisms addressed in the literature. It was concluded that the optimal timing of cisplatin should be close to radiation. The model showed that daily administration of cisplatin led to a 35% improvement of tumour control as compared to radiation alone, while weekly cisplatin has improved radiotherapy by only 6%.

Cryopreservation in Closed Bag Systems as an Alternative to Clean Rooms for Preparations of Peripheral Blood Stem Cells.

PubMed

Spoerl, Silvia; Peter, Robert; Krackhardt, Angela M

2016-01-01

Autologous and allogeneic stem cell transplantation (SCT) represents a therapeutic option widely used for hematopoietic malignancies. One important milestone in the development of this treatment strategy was the development of effective cryopreservation technologies resulting in a high quality with respect to cell viability as well as lack of contamination of the graft.Stem cell preparations have been initially performed within standard laboratories as it is routinely still the case in many countries. With the emergence of cleanrooms, manufacturing of stem cell preparations within these facilities has become a new standard mandatory in Europe. However, due to high costs and laborious procedures, novel developments recently emerged using closed bag systems as reliable alternatives to conventional cleanrooms. Several hurdles needed to be overcome including the addition of the cryoprotectant dimethylsulfoxide (DMSO) as a relevant manipulation. As a result of the development, closed bag systems proved to be comparable in terms of product quality and patient outcome to cleanroom products. They also comply with the strict regulations of good manufacturing practice.With closed systems being available, costs and efforts of a cleanroom facility may be substantially reduced in the future. The process can be easily extended for other cell preparations requiring minor modifications as donor lymphocyte preparations. Moreover, novel developments may provide solutions for the production of advanced-therapy medicinal products in closed systems.

Culture of human cells in experimental units for spaceflight impacts on their behavior.

PubMed

Cazzaniga, Alessandra; Moscheni, Claudia; Maier, Jeanette Am; Castiglioni, Sara

2017-05-01

Because space missions produce pathophysiological alterations such as cardiovascular disorders and bone demineralization which are very common on Earth, biomedical research in space is a frontier that holds important promises not only to counterbalance space-associated disorders in astronauts but also to ameliorate the health of Earth-bound population. Experiments in space are complex to design. Cells must be cultured in closed cell culture systems (from now defined experimental units (EUs)), which are biocompatible, functional, safe to minimize any potential hazard to the crew, and with a high degree of automation. Therefore, to perform experiments in orbit, it is relevant to know how closely culture in the EUs reflects cellular behavior under normal growth conditions. We compared the performances in these units of three different human cell types, which were recently space flown, i.e. bone mesenchymal stem cells, micro- and macrovascular endothelial cells. Endothelial cells are only slightly and transiently affected by culture in the EUs, whereas these devices accelerate mesenchymal stem cell reprogramming toward osteogenic differentiation, in part by increasing the amounts of reactive oxygen species. We conclude that cell culture conditions in the EUs do not exactly mimic what happens in a culture dish and that more efforts are necessary to optimize these devices for biomedical experiments in space. Impact statement Cell cultures represent valuable preclinical models to decipher pathogenic circuitries. This is true also for biomedical research in space. A lot has been learnt about cell adaptation and reaction from the experiments performed on many different cell types flown to space. Obviously, cell culture in space has to meet specific requirements for the safety of the crew and to comply with the unique environmental challenges. For these reasons, specific devices for cell culture in space have been developed. It is important to clarify whether these alternative culture systems impact on cell performances to allow a correct interpretation of the data.

Culture of human cells in experimental units for spaceflight impacts on their behavior

PubMed Central

Cazzaniga, Alessandra; Moscheni, Claudia; Maier, Jeanette AM

2016-01-01

Because space missions produce pathophysiological alterations such as cardiovascular disorders and bone demineralization which are very common on Earth, biomedical research in space is a frontier that holds important promises not only to counterbalance space-associated disorders in astronauts but also to ameliorate the health of Earth-bound population. Experiments in space are complex to design. Cells must be cultured in closed cell culture systems (from now defined experimental units (EUs)), which are biocompatible, functional, safe to minimize any potential hazard to the crew, and with a high degree of automation. Therefore, to perform experiments in orbit, it is relevant to know how closely culture in the EUs reflects cellular behavior under normal growth conditions. We compared the performances in these units of three different human cell types, which were recently space flown, i.e. bone mesenchymal stem cells, micro- and macrovascular endothelial cells. Endothelial cells are only slightly and transiently affected by culture in the EUs, whereas these devices accelerate mesenchymal stem cell reprogramming toward osteogenic differentiation, in part by increasing the amounts of reactive oxygen species. We conclude that cell culture conditions in the EUs do not exactly mimic what happens in a culture dish and that more efforts are necessary to optimize these devices for biomedical experiments in space. Impact statement Cell cultures represent valuable preclinical models to decipher pathogenic circuitries. This is true also for biomedical research in space. A lot has been learnt about cell adaptation and reaction from the experiments performed on many different cell types flown to space. Obviously, cell culture in space has to meet specific requirements for the safety of the crew and to comply with the unique environmental challenges. For these reasons, specific devices for cell culture in space have been developed. It is important to clarify whether these alternative culture systems impact on cell performances to allow a correct interpretation of the data. PMID:28492348

40 CFR 98.434 - Monitoring and QA/QC requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.434 Monitoring and QA/QC requirements. (a) For... equipment or closed-cell foam in the correct quantities (metric tons) and units (kg per piece of equipment...

40 CFR 98.434 - Monitoring and QA/QC requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.434 Monitoring and QA/QC requirements. (a) For... equipment or closed-cell foam in the correct quantities (metric tons) and units (kg per piece of equipment...

40 CFR 98.434 - Monitoring and QA/QC requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Contained in Pre-Charged Equipment or Closed-Cell Foams § 98.434 Monitoring and QA/QC requirements. (a) For... equipment or closed-cell foam in the correct quantities and units. [74 FR 56374, Oct. 30, 2009, as amended...

Heterotypic contact reveals a COX-2-mediated suppression of osteoblast differentiation by endothelial cells: A negative modulatory role for prostanoids in VEGF-mediated cell: cell communication?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Clarkin, Claire E.; Garonna, Elena; Pitsillides, Andrew A.

In bone, angiogenesis must be initiated appropriately, but limited once remodelling or repair is complete. Our recent findings have supported a role for prostaglandins (PG), known modulators of osteoblast (OB) and endothelial cell (EC) behaviour, in facilitating VEGF-mediated paracrine communication from OBs to 'remotely located' ECs, but the mechanism(s) regulating OB:EC crosstalk when these cells are closely opposed are undefined. In this study we have examined: (i) the effects of exogenous PGE{sub 2} on VEGF-driven events in ECs, and (ii) the role of endogenous COX-2-derived prostanoids in mediating communication between intimately opposed OBs and ECs in direct contact. Exposure ofmore » ECs to PGE{sub 2} increased ERK1/2 phosphorylation, COX-2 induction, 6-keto-PGF{sub 1{alpha}} release and EC proliferation. In contrast, PGE{sub 2} attenuated VEGF{sub 165}-induced VEGFR2/Flk1 phosphorylation, ERK1/2 activation and proliferation of ECs, suggesting that exogenous PGE{sub 2} restricts the actions of VEGF. However, the COX-2-selective inhibitor, NS398, also attenuated VEGF-induced proliferation, implying a distinct role for endogenous COX-2 activity in regulating EC behaviour. To examine the effect of OB:EC proximity and the role of COX-2 products further, we used a confrontational co-culture model. These studies showed that COX-2 blockade with NS398 enhanced EC-dependent increases in OB differentiation, that this effect was reversed by exogenous PGH{sub 2} (immediate COX-2 product), and that exogenous VEGF did not influence EC-dependent OB differentiation under these conditions. Our findings indicate that locally produced prostanoids may serve distinct roles depending on OB:EC proximity and negatively modulate VEGF-mediated changes in EC behaviour when these cells are closely opposed to control angiogenesis during bone (re)modelling.« less

Inhibition of Tumorigenesis by the Thyroid Hormone Receptor β in Xenograft Models

PubMed Central

Kim, Won Gu; Zhao, Li; Kim, Dong Wook; Willingham, Mark C.

2014-01-01

Background: Previous studies showed a close association between several types of human cancers and somatic mutations of thyroid hormone receptor β (TRβ) and reduced expression of TRβ due to epigenetic inactivation and/or deletion of the THRB gene. These observations suggest that TRβ could act as a tumor suppressor in carcinogenesis. However, the mechanisms by which TRβ could function to inhibit tumorigenesis are less well understood. Methods: We used the human follicular thyroid cancer cell lines (FTC-133 and FTC-236 cells) to elucidate how functional expression of the THRB gene could affect tumorigenesis. We stably expressed the THRB gene in FTC cells and evaluated the effects of the expressed TRβ on cancer cell proliferation, migration, and tumor growth in cell-based studies and xenograft models. Results: Expression of TRβ in FTC-133 cells, as compared with control FTC cells without TRβ, reduced cancer cell proliferation and impeded migration of tumor cells through inhibition of the AKT-mTOR-p70 S6K pathway. TRβ expression in FTC-133 and FTC-236 led to less tumor growth in xenograft models. Importantly, new vessel formation was significantly suppressed in tumors induced by FTC cells expressing TRβ compared with control FTC cells without TRβ. The decrease in vessel formation was mediated by the downregulation of vascular endothelial growth factor in FTC cells expressing TRβ. Conclusions: These findings indicate that TRβ acts as a tumor suppressor through downregulation of the AKT-mTOR-p70 S6K pathway and decreased vascular endothelial growth factor expression in FTC cells. The present results raise the possibility that TRβ could be considered as a potential therapeutic target for thyroid cancer. PMID:23731250

Learning pattern recognition and decision making in the insect brain

NASA Astrophysics Data System (ADS)

Huerta, R.

2013-01-01

We revise the current model of learning pattern recognition in the Mushroom Bodies of the insects using current experimental knowledge about the location of learning, olfactory coding and connectivity. We show that it is possible to have an efficient pattern recognition device based on the architecture of the Mushroom Bodies, sparse code, mutual inhibition and Hebbian leaning only in the connections from the Kenyon cells to the output neurons. We also show that despite the conventional wisdom that believes that artificial neural networks are the bioinspired model of the brain, the Mushroom Bodies actually resemble very closely Support Vector Machines (SVMs). The derived SVM learning rules are situated in the Mushroom Bodies, are nearly identical to standard Hebbian rules, and require inhibition in the output. A very particular prediction of the model is that random elimination of the Kenyon cells in the Mushroom Bodies do not impair the ability to recognize odorants previously learned.

Amnioserosa cell constriction but not epidermal actin cable tension autonomously drives dorsal closure.

PubMed

Pasakarnis, Laurynas; Frei, Erich; Caussinus, Emmanuel; Affolter, Markus; Brunner, Damian

2016-11-01

Tissue morphogenesis requires coordination of multiple force-producing components. During dorsal closure in fly embryogenesis, an epidermis opening closes. A tensioned epidermal actin/MyosinII cable, which surrounds the opening, produces a force that is thought to combine with another MyosinII force mediating apical constriction of the amnioserosa cells that fill the opening. A model proposing that each force could autonomously drive dorsal closure was recently challenged by a model in which the two forces combine in a ratchet mechanism. Acute force elimination via selective MyosinII depletion in one or the other tissue shows that the amnioserosa tissue autonomously drives dorsal closure while the actin/MyosinII cable cannot. These findings exclude both previous models, although a contribution of the ratchet mechanism at dorsal closure onset remains likely. This shifts the current view of dorsal closure being a combinatorial force-component system to a single tissue-driven closure event.

X‐linked retinoschisis: an update

PubMed Central

Sikkink, Stephen K; Biswas, Susmito; Parry, Neil R A; Stanga, Paulo E; Trump, Dorothy

2007-01-01

X‐linked retinoschisis is the leading cause of macular degeneration in males and leads to splitting within the inner retinal layers leading to visual deterioration. Many missense and protein truncating mutations have now been identified in the causative retinoschisis gene (RS1) which encodes a 224 amino acid secreting retinal protein, retinoschisin. Retinoschisin octamerises is implicated in cell–cell interactions and cell adhesion perhaps by interacting with β2 laminin. Mutations cause loss of retinoschisin function by one of the three mechanisms: by interfering with protein secretion, by preventing its octamerisation or by reducing function in the secreted octamerised protein. The development of retinoschisis mouse models have provided a model system that closely resembles the human disease. Recent reports of RS1 gene transfer to these models and the sustained restoration of some retinal function and morphology suggest gene replacement may be a possible future therapy for patients. PMID:17172462

Statistical mechanics of tuned cell signalling: sensitive collective response by synthetic biological circuits

NASA Astrophysics Data System (ADS)

Voliotis, M.; Liverpool, T. B.

2017-03-01

Living cells sense and process environmental cues through noisy biochemical mechanisms. This apparatus limits the scope of engineering cells as viable sensors. Here, we highlight a mechanism that enables robust, population-wide responses to external stimulation based on cellular communication, known as quorum sensing. We propose a synthetic circuit consisting of two mutually repressing quorum sensing modules. At low cell densities the system behaves like a genetic toggle switch, while at higher cell densities the behaviour of nearby cells is coupled via diffusible quorum sensing molecules. We show by systematic coarse graining that at large length and timescales that the system can be described using the Ising model of a ferromagnet. Thus, in analogy with magnetic systems, the sensitivity of the population-wide response, or its ‘susceptibility’ to a change in the external signal, is highly enhanced for a narrow range of cell-cell coupling close to a critical value. We expect that our approach will be used to enhance the sensitivity of synthetic bio-sensing networks.

Spatiotemporal Dynamics of Insulitis in Human Type 1 Diabetes

PubMed Central

Wedgwood, Kyle C. A.; Richardson, Sarah J.; Morgan, Noel G.; Tsaneva-Atanasova, Krasimira

2016-01-01

Type 1 diabetes (T1D) is an auto-immune disease characterized by the selective destruction of the insulin secreting beta cells in the pancreas during an inflammatory phase known as insulitis. Patients with T1D are typically dependent on the administration of externally provided insulin in order to manage blood glucose levels. Whilst technological developments have significantly improved both the life expectancy and quality of life of these patients, an understanding of the mechanisms of the disease remains elusive. Animal models, such as the NOD mouse model, have been widely used to probe the process of insulitis, but there exist very few data from humans studied at disease onset. In this manuscript, we employ data from human pancreases collected close to the onset of T1D and propose a spatio-temporal computational model for the progression of insulitis in human T1D, with particular focus on the mechanisms underlying the development of insulitis in pancreatic islets. This framework allows us to investigate how the time-course of insulitis progression is affected by altering key parameters, such as the number of the CD20+ B cells present in the inflammatory infiltrate, which has recently been proposed to influence the aggressiveness of the disease. Through the analysis of repeated simulations of our stochastic model, which track the number of beta cells within an islet, we find that increased numbers of B cells in the peri-islet space lead to faster destruction of the beta cells. We also find that the balance between the degradation and repair of the basement membrane surrounding the islet is a critical component in governing the overall destruction rate of the beta cells and their remaining number. Our model provides a framework for continued and improved spatio-temporal modeling of human T1D. PMID:28082906

THP-1 monocytes but not macrophages as a potential alternative for CD34{sup +} dendritic cells to identify chemical skin sensitizers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lambrechts, Nathalie; Verstraelen, Sandra; Lodewyckx, Hanne

2009-04-15

Early detection of the sensitizing potential of chemicals is an emerging issue for chemical, pharmaceutical and cosmetic industries. In our institute, an in vitro classification model for prediction of chemical-induced skin sensitization based on gene expression signatures in human CD34{sup +} progenitor-derived dendritic cells (DC) has been developed. This primary cell model is able to closely mimic the induction phase of sensitization by Langerhans cells in the skin, but it has drawbacks, such as the availability of cord blood. The aim of this study was to investigate whether human in vitro cultured THP-1 monocytes or macrophages display a similar expressionmore » profile for 13 predictive gene markers previously identified in DC and whether they also possess a discriminating capacity towards skin sensitizers and non-sensitizers based on these marker genes. To this end, the cell models were exposed to 5 skin sensitizers (ammonium hexachloroplatinate IV, 1-chloro-2,4-dinitrobenzene, eugenol, para-phenylenediamine, and tetramethylthiuram disulfide) and 5 non-sensitizers (L-glutamic acid, methyl salicylate, sodium dodecyl sulfate, tributyltin chloride, and zinc sulfate) for 6, 10, and 24 h, and mRNA expression of the 13 genes was analyzed using real-time RT-PCR. The transcriptional response of 7 out of 13 genes in THP-1 monocytes was significantly correlated with DC, whereas only 2 out of 13 genes in THP-1 macrophages. After a cross-validation of a discriminant analysis of the gene expression profiles in the THP-1 monocytes, this cell model demonstrated to also have a capacity to distinguish skin sensitizers from non-sensitizers. However, the DC model was superior to the monocyte model for discrimination of (non-)sensitizing chemicals.« less

New saliva secretion model based on the expression of Na+-K+ pump and K+ channels in the apical membrane of parotid acinar cells.

PubMed

Almássy, János; Siguenza, Elias; Skaliczki, Marianna; Matesz, Klara; Sneyd, James; Yule, David I; Nánási, Péter P

2018-04-01

The plasma membrane of parotid acinar cells is functionally divided into apical and basolateral regions. According to the current model, fluid secretion is driven by transepithelial ion gradient, which facilitates water movement by osmosis into the acinar lumen from the interstitium. The osmotic gradient is created by the apical Cl - efflux and the subsequent paracellular Na + transport. In this model, the Na + -K + pump is located exclusively in the basolateral membrane and has essential role in salivary secretion, since the driving force for Cl - transport via basolateral Na + -K + -2Cl - cotransport is generated by the Na + -K + pump. In addition, the continuous electrochemical gradient for Cl - flow during acinar cell stimulation is maintained by the basolateral K + efflux. However, using a combination of single-cell electrophysiology and Ca 2+ -imaging, we demonstrate that photolysis of Ca 2+ close to the apical membrane of parotid acinar cells triggered significant K + current, indicating that a substantial amount of K + is secreted into the lumen during stimulation. Nevertheless, the K + content of the primary saliva is relatively low, suggesting that K + might be reabsorbed through the apical membrane. Therefore, we investigated the localization of Na + -K + pumps in acinar cells. We show that the pumps appear evenly distributed throughout the whole plasma membrane, including the apical pole of the cell. Based on these results, a new mathematical model of salivary fluid secretion is presented, where the pump reabsorbs K + from and secretes Na + to the lumen, which can partially supplement the paracellular Na + pathway.

Integrin receptor involvement in actin cable formation in an in vitro model of events associated with wound contraction.

PubMed

Stephens, P; Genever, P G; Wood, E J; Raxworthy, M J

1997-01-01

Actin cables have been reported to act in vivo as contractile 'purse strings' capable of closing embryonic wounds through generation of circumferential tension. Furthermore, their involvement in wounds within in vitro model systems suggests that actin cable contraction may be an important mechanism involved in the process of wound closure. The aim of this study therefore, was to investigate the appearance of actin cables in a contracting fibroblast populated collagen lattice, an in vitro model of events associated with wound contraction. Utilising this in vitro model, the time-course of actin cable production was investigated and the involvement of integrin receptors analysed using immunofluorescent labelling techniques. Over a period of hours distinct cellular cable-like structures developed at the edges of collagen lattices coinciding with the onset of contraction. Cellular organisation within the cable was evident as was polymerisation of actin microfilaments into elongated stress fibres forming a continuous cell-cell 'actin cable' around the circumference of the lattice. Immunolocalisation demonstrated that integrin receptor subunits beta 1 and alpha 2 but not alpha 5 were involved in apparent intimate cell-cell contact between juxtaposed fibroblasts within this actin cable. This study demonstrates the involvement of integrin receptors in actin cable formation within collagen lattice systems undergoing reorganisation. Such integrin involvement may enable participating cells to respond to the tensional status of their surrounding environment and via cell-cell communication, to permit a co-ordinated contraction of the cable. It is concluded that integrin receptor involvement in active actin cable contraction may be involved in the process of wound contraction.

Loss of basal cells precedes bronchiolitis obliterans-like pathological changes in a murine model of chlorine gas inhalation.

PubMed

O'Koren, Emily G; Hogan, Brigid L M; Gunn, Michael Dee

2013-11-01

Bronchiolitis obliterans (BO) is a major cause of chronic airway dysfunction after toxic chemical inhalation. The pathophysiology of BO is not well understood, but epithelial cell injury has been closely associated with the development of fibrotic lesions in human studies and in animal models of both toxin-induced and transplant-induced BO. However, whereas almost all cases and models of BO include epithelial injury, not all instances of epithelial injury result in BO, suggesting that epithelial damage per se is not the critical event leading to the development of BO. Here, we describe a model of chlorine-induced BO in which mice develop tracheal and large airway obliterative lesions within 10 days of exposure to high (350 parts per million [ppm]), but not low (200 ppm), concentrations of chlorine gas. Importantly, these lesions arise only under conditions and in areas in which basal cells, the resident progenitor cells for large airway epithelium, are eliminated by chlorine exposure. In areas of basal cell loss, epithelial regeneration does not occur, resulting in persistent regions of epithelial denudation. Obliterative airway lesions arise specifically from regions of epithelial denudation in a process that includes inflammatory cell infiltration by Day 2 after exposure, fibroblast infiltration and collagen deposition by Day 5, and the ingrowth of blood vessels by Day 7, ultimately leading to lethal airway obstruction by Days 9-12. We conclude that the loss of epithelial progenitor cells constitutes a critical factor leading to the development of obliterative airway lesions after chemical inhalation.

Nascent RNA kinetics: Transient and steady state behavior of models of transcription

NASA Astrophysics Data System (ADS)

Choubey, Sandeep

2018-02-01

Regulation of transcription is a vital process in cells, but mechanistic details of this regulation still remain elusive. The dominant approach to unravel the dynamics of transcriptional regulation is to first develop mathematical models of transcription and then experimentally test the predictions these models make for the distribution of mRNA and protein molecules at the individual cell level. However, these measurements are affected by a multitude of downstream processes which make it difficult to interpret the measurements. Recent experimental advancements allow for counting the nascent mRNA number of a gene as a function of time at the single-inglr cell level. These measurements closely reflect the dynamics of transcription. In this paper, we consider a general mechanism of transcription with stochastic initiation and deterministic elongation and probe its impact on the temporal behavior of nascent RNA levels. Using techniques from queueing theory, we derive exact analytical expressions for the mean and variance of the nascent RNA distribution as functions of time. We apply these analytical results to obtain the mean and variance of nascent RNA distribution for specific models of transcription. These models of initiation exhibit qualitatively distinct transient behaviors for both the mean and variance which further allows us to discriminate between them. Stochastic simulations confirm these results. Overall the analytical results presented here provide the necessary tools to connect mechanisms of transcription initiation to single-cell measurements of nascent RNA.

Metabolomics and cytotoxicity of monomethylhydrazine (MMH) and (E)-1,1,4,4-tetramethyl-2-tetrazene (TMTZ), two liquid propellants.

PubMed

Guyot, Laetitia; Machon, Christelle; Honorat, Myléne; Manship, Brigitte; Bouard, Charlotte; Vigneron, Arnaud; Puisieux, Alain; Labarthe, Emilie; Jacob, Guy; Dhenain, Anne; Guitton, Jérôme; Payen, Léa

2018-06-07

Hydrazine-based liquid propellants are routinely used for space rocket propulsion, in particular monomethylhydrazine (MMH), although such compounds are highly hazardous. For several years, great efforts were devoted to developing a less hazardous molecule. To explore the toxicological effects of an alternative compound, namely (E)-1,1,4,4-tetramethyl-2-tetrazene (TMTZ), we exposed various cellular animal and human models to this compound and to the reference compound MMH. We observed no cytotoxic effects following exposure to TMTZ in animal, as well as human models. However, although the three animal models were unaffected by MMH, exposure of the human hepatic HepaRG cell model revealed that apoptotic cytotoxic effects were only detectable in proliferative human hepatic HepaRG cells and not in differentiated cells, although major biochemical modifications were uncovered in the latter. The present findings indicate that the metabolic mechanisms of MMH toxicity is close to those described for hydrazine with numerous biochemical alterations induced by mitochondrial disruption, production of radical species, and aminotransferase inhibition. The alternative TMTZ molecule had little impact on cellular viability and proliferation of rodent and human dermic and hepatic cell models. TMTZ did not produce any metabolomic effects and appears to be a promising putative industrial alternative to MMH. Copyright © 2018. Published by Elsevier Ltd.

Slow and Steady: Ocean Circulation. The Influence of Sea Surface Height on Ocean Currents

NASA Technical Reports Server (NTRS)

Haekkinen, Sirpa

2000-01-01

The study of ocean circulation is vital to understanding how our climate works. The movement of the ocean is closely linked to the progression of atmospheric motion. Winds close to sea level add momentum to ocean surface currents. At the same time, heat that is stored and transported by the ocean warms the atmosphere above and alters air pressure distribution. Therefore, any attempt to model climate variation accurately must include reliable calculations of ocean circulation. Unlike movement of the atmosphere, movement of the ocean's waters takes place mostly near the surface. The major patterns of surface circulation form gigantic circular cells known as gyres. They are categorized according to their general location-equatorial, subtropical, subpolar, and polar-and may run across an entire ocean. The smaller-scale cell of ocean circulation is known' as an eddy. Eddies are much more common than gyres and much more difficult to track in computer simulations of ocean currents.

Measurement of the transient shielding effectiveness of shielding cabinets

NASA Astrophysics Data System (ADS)

Herlemann, H.; Koch, M.

2008-05-01

Recently, new definitions of shielding effectiveness (SE) for high-frequency and transient electromagnetic fields were introduced by Klinkenbusch (2005). Analytical results were shown for closed as well as for non closed cylindrical shields. In the present work, the shielding performance of different shielding cabinets is investigated by means of numerical simulations and measurements inside a fully anechoic chamber and a GTEM-cell. For the GTEM-cell-measurements, a downscaled model of the shielding cabinet is used. For the simulations, the numerical tools CONCEPT II and COMSOL MULTIPHYSICS were available. The numerical results agree well with the measurements. They can be used to interpret the behaviour of the shielding effectiveness of enclosures as function of frequency. From the measurement of the electric and magnetic fields with and without the enclosure in place, the electric and magnetic shielding effectiveness as well as the transient shielding effectiveness of the enclosure are calculated. The transient SE of four different shielding cabinets is determined and discussed.

Encapsulated Optically Responsive Cell Systems: Toward Smart Implants in Biomedicine.

PubMed

Boss, Christophe; Bouche, Nicolas; De Marchi, Umberto

2018-04-01

Managing increasingly prevalent chronic diseases will require close continuous monitoring of patients. Cell-based biosensors may be used for implantable diagnostic systems to monitor health status. Cells are indeed natural sensors in the body. Functional cellular systems can be maintained in the body for long-term implantation using cell encapsulation technology. By taking advantage of recent progress in miniaturized optoelectronic systems, the genetic engineering of optically responsive cells may be combined with cell encapsulation to generate smart implantable cell-based sensing systems. In biomedical research, cell-based biosensors may be used to study cell signaling, therapeutic effects, and dosing of bioactive molecules in preclinical models. Today, a wide variety of genetically encoded fluorescent sensors have been developed for real-time imaging of living cells. Here, recent developments in genetically encoded sensors, cell encapsulation, and ultrasmall optical systems are highlighted. The integration of these components in a new generation of biosensors is creating innovative smart in vivo cell-based systems, bringing novel perspectives for biomedical research and ultimately allowing unique health monitoring applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Development and matching of binocular orientation preference in mouse V1.

PubMed

Bhaumik, Basabi; Shah, Nishal P

2014-01-01

Eye-specific thalamic inputs converge in the primary visual cortex (V1) and form the basis of binocular vision. For normal binocular perceptions, such as depth and stereopsis, binocularly matched orientation preference between the two eyes is required. A critical period of binocular matching of orientation preference in mice during normal development is reported in literature. Using a reaction diffusion model we present the development of RF and orientation selectivity in mouse V1 and investigate the binocular orientation preference matching during the critical period. At the onset of the critical period the preferred orientations of the modeled cells are mostly mismatched in the two eyes and the mismatch decreases and reaches levels reported in juvenile mouse by the end of the critical period. At the end of critical period 39% of cells in binocular zone in our model cortex is orientation selective. In literature around 40% cortical cells are reported as orientation selective in mouse V1. The starting and the closing time for critical period determine the orientation preference alignment between the two eyes and orientation tuning in cortical cells. The absence of near neighbor interaction among cortical cells during the development of thalamo-cortical wiring causes a salt and pepper organization in the orientation preference map in mice. It also results in much lower % of orientation selective cells in mice as compared to ferrets and cats having organized orientation maps with pinwheels.

A plant cell division algorithm based on cell biomechanics and ellipse-fitting

PubMed Central

Abera, Metadel K.; Verboven, Pieter; Defraeye, Thijs; Fanta, Solomon Workneh; Hertog, Maarten L. A. T. M.; Carmeliet, Jan; Nicolai, Bart M.

2014-01-01

Background and Aims The importance of cell division models in cellular pattern studies has been acknowledged since the 19th century. Most of the available models developed to date are limited to symmetric cell division with isotropic growth. Often, the actual growth of the cell wall is either not considered or is updated intermittently on a separate time scale to the mechanics. This study presents a generic algorithm that accounts for both symmetrically and asymmetrically dividing cells with isotropic and anisotropic growth. Actual growth of the cell wall is simulated simultaneously with the mechanics. Methods The cell is considered as a closed, thin-walled structure, maintained in tension by turgor pressure. The cell walls are represented as linear elastic elements that obey Hooke's law. Cell expansion is induced by turgor pressure acting on the yielding cell-wall material. A system of differential equations for the positions and velocities of the cell vertices as well as for the actual growth of the cell wall is established. Readiness to divide is determined based on cell size. An ellipse-fitting algorithm is used to determine the position and orientation of the dividing wall. The cell vertices, walls and cell connectivity are then updated and cell expansion resumes. Comparisons are made with experimental data from the literature. Key Results The generic plant cell division algorithm has been implemented successfully. It can handle both symmetrically and asymmetrically dividing cells coupled with isotropic and anisotropic growth modes. Development of the algorithm highlighted the importance of ellipse-fitting to produce randomness (biological variability) even in symmetrically dividing cells. Unlike previous models, a differential equation is formulated for the resting length of the cell wall to simulate actual biological growth and is solved simultaneously with the position and velocity of the vertices. Conclusions The algorithm presented can produce different tissues varying in topological and geometrical properties. This flexibility to produce different tissue types gives the model great potential for use in investigations of plant cell division and growth in silico. PMID:24863687

Progression from productive infection to integration and oncogenic transformation in human papillomavirus type 59-immortalized foreskin keratinocytes.

PubMed

Spartz, Helena; Lehr, Elizabeth; Zhang, Benyue; Roman, Ann; Brown, Darron R

2005-05-25

Studies of changes in the virus and host cell upon progression from human papillomavirus (HPV) episomal infection to integration are critical to understanding HPV-related malignant transformation. However, there exist only a few in vitro models of both productive HPV infection and neoplastic progression on the same host background. We recently described a unique foreskin keratinocyte cell line (ERIN 59) that contains HPV 59 (a close relative of HPV 18). Early passages of ERIN 59 cells (passages 9-13) contained approximately 50 copies of episomes/cell, were feeder cell-dependent, and could be induced to differentiate and produce infectious virus in a simple culture system. We now report that late passage cells (passages greater than 50) were morphologically different from early passage cells, were feeder cell independent, and did not differentiate or produce virus. These late passage cells contained HPV in an integrated form. An integration-derived oncogene transcript was expressed in late passage cells. The E2 open reading frame was interrupted in this transcript at nucleotide 3351. Despite a lower viral genome copy number in late passage ERIN 59 cells, expression of E6/E7 oncogene transcripts was similar to early passage cells. We conclude that ERIN 59 cells are a valuable cell line representing a model of progression from HPV 59 episomal infection and virus production to HPV 59 integration and associated oncogenic transformation on the same host background.

Method and apparatus for improving the insulating properties of closed cell foam

DOEpatents

Glicksman, Leon R.; Lanciani, Arlene J.

1991-04-23

A filler of non-metallic, light transparent material is formed into particles or flakes and coated with opaque material and dispersed in closed cell foam to reduce overall thermal conductivity and, specifically, to reduce radiation heat transfer.

Understanding the hypoxic niche of multiple myeloma: therapeutic implications and contributions of mouse models

PubMed Central

Hu, Jinsong; Van Valckenborgh, Els; Menu, Eline; De Bruyne, Elke; Vanderkerken, Karin

2012-01-01

Multiple myeloma (MM) is the second most common hematological malignancy and is characterized by the clonal expansion of plasma cells in the bone marrow. Recently, hypoxia has received increased interest in the context of MM, in both basic and translational research. In this review, we describe the discovery of the hypoxic niche in MM and how it can be targeted therapeutically. We also discuss mouse models that closely mimic human MM, highlighting those that allow preclinical research into new therapies that exploit the hypoxic niche in MM. PMID:23115205

Close-field electroporation gene delivery using the cochlear implant electrode array enhances the bionic ear.

PubMed

Pinyon, Jeremy L; Tadros, Sherif F; Froud, Kristina E; Y Wong, Ann C; Tompson, Isabella T; Crawford, Edward N; Ko, Myungseo; Morris, Renée; Klugmann, Matthias; Housley, Gary D

2014-04-23

The cochlear implant is the most successful bionic prosthesis and has transformed the lives of people with profound hearing loss. However, the performance of the "bionic ear" is still largely constrained by the neural interface itself. Current spread inherent to broad monopolar stimulation of the spiral ganglion neuron somata obviates the intrinsic tonotopic mapping of the cochlear nerve. We show in the guinea pig that neurotrophin gene therapy integrated into the cochlear implant improves its performance by stimulating spiral ganglion neurite regeneration. We used the cochlear implant electrode array for novel "close-field" electroporation to transduce mesenchymal cells lining the cochlear perilymphatic canals with a naked complementary DNA gene construct driving expression of brain-derived neurotrophic factor (BDNF) and a green fluorescent protein (GFP) reporter. The focusing of electric fields by particular cochlear implant electrode configurations led to surprisingly efficient gene delivery to adjacent mesenchymal cells. The resulting BDNF expression stimulated regeneration of spiral ganglion neurites, which had atrophied 2 weeks after ototoxic treatment, in a bilateral sensorineural deafness model. In this model, delivery of a control GFP-only vector failed to restore neuron structure, with atrophied neurons indistinguishable from unimplanted cochleae. With BDNF therapy, the regenerated spiral ganglion neurites extended close to the cochlear implant electrodes, with localized ectopic branching. This neural remodeling enabled bipolar stimulation via the cochlear implant array, with low stimulus thresholds and expanded dynamic range of the cochlear nerve, determined via electrically evoked auditory brainstem responses. This development may broadly improve neural interfaces and extend molecular medicine applications.

Specialised sympathetic neuroeffector associations in immature rat iris arterioles

PubMed Central

SANDOW, SHAUN L.; HILL, CARYL E.

1999-01-01

Sympathetic nerve-mediated vasoconstriction in iris arterioles of mature rats occurs via the activation of α1B-adrenoceptors alone, while in immature rat iris arterioles, vasoconstriction occurs via activation of both α1- and α2-adrenoceptors. In mature rats the vast majority of sympathetic varicosities form close neuroeffector junctions. Serial section electron microscopy of 14 d iris arterioles has been used to determine whether restriction in physiological receptor types with age may result from the establishment of these close neuroeffector junctions. Ninety varicosities which lay within 4 μm of arteriolar smooth muscle were followed for their entire length. Varicosities rarely contained dense cored vesicles even after treatment with 5-hydroxydopamine. 47% of varicosities formed close associations with muscle cells and 88% formed close associations with muscle cells or melanocytes. Varicosities in bundles were as likely as single varicosities to form close associations with vascular smooth muscle cells, although the distribution of synaptic vesicles in single varicosities did not show the asymmetric accumulation towards the smooth muscle cells seen in the varicosities in bundles which were frequently clustered together. We conclude that restriction of physiological receptor types during development does not appear to correlate with the establishment of close neuroeffector junctions, although changes in presynaptic structures may contribute to the refinement of postsynaptic responses. PMID:10529061

Algal culture studies for CELSS

NASA Technical Reports Server (NTRS)

Radmer, R.; Behrens, P.; Arnett, K.; Gladue, R.; Cox, J.; Lieberman, D.

1987-01-01

Microalgae are well-suited as a component of a Closed Environmental Life Support System (CELSS), since they can couple the closely related functions of food production and atmospheric regeneration. The objective was to provide a basis for predicting the response of CELSS algal cultures, and thus the food supply and air regeneration system, to changes in the culture parameters. Scenedesmus growth was measured as a function of light intensity, and the spectral dependence of light absorption by the algae as well as algal respiration in the light were determined as a function of cell concentration. These results were used to test and confirm a mathematical model that describes the productivity of an algal culture in terms of the competing processes of photosynthesis and respiration. The relationship of algal productivity to cell concentration was determined at different carbon dioxide concentrations, temperatures, and light intensities. The maximum productivity achieved by an air-grown culture was found to be within 10% of the computed maximum productivity, indicating that CO2 was very efficiently removed from the gas stream by the algal culture. Measurements of biomass productivity as a function of cell concentration at different light intensities indicated that both the productivity and efficiency of light utilization were greater at higher light intensities.

Structure and mechanical behavior of bird beaks

NASA Astrophysics Data System (ADS)

Seki, Yasuaki

The structure and mechanical behavior of Toco toucan (Ramphastos toco) and Wreathed hornbill (Rhyticeros undulatus) beaks were examined. The structure of Toco toucan and Wreathed hornbill beak was found to be a sandwich composite with an exterior of keratin and a fibrous bony network of closed cells made of trabeculae. A distinctive feature of the hornbill beak is its casque formed from cornified keratin layers. The casque is believed to have an acoustic function due to the complex internal structure. The toucan and hornbill beaks have a hollow region that extends from proximal to mid-section. The rhamphotheca is comprised of super-posed polygonal scales (45 mum diameter and 1 mum thickness) fixed by some organic adhesive. The branched intermediate filaments embedded in keratin matrix were discovered by transmission electron microscopy (TEM). The diameter of intermediate laments was ~10 nm. The orientation of intermediate filaments was examined with TEM tomography and the branched filaments were homogeneously distributed. The closed-cell foam is comprised of the fibrous structure of bony struts with an edge connectivity of three or four and the cells are sealed off by the thin membranes. The volumetric structure of bird beak foam was reproduced by computed tomography for finite element modeling.

Single-cell RNA-seq and computational analysis using temporal mixture modelling resolves Th1/Tfh fate bifurcation in malaria

PubMed Central

Lönnberg, Tapio; Svensson, Valentine; James, Kylie R.; Fernandez-Ruiz, Daniel; Sebina, Ismail; Montandon, Ruddy; Soon, Megan S. F.; Fogg, Lily G.; Nair, Arya Sheela; Liligeto, Urijah; Stubbington, Michael J. T.; Ly, Lam-Ha; Bagger, Frederik Otzen; Zwiessele, Max; Lawrence, Neil D.; Souza-Fonseca-Guimaraes, Fernando; Bunn, Patrick T.; Engwerda, Christian R.; Heath, William R.; Billker, Oliver; Stegle, Oliver; Haque, Ashraful; Teichmann, Sarah A.

2017-01-01

Differentiation of naïve CD4+ T cells into functionally distinct T helper subsets is crucial for the orchestration of immune responses. Due to extensive heterogeneity and multiple overlapping transcriptional programs in differentiating T cell populations, this process has remained a challenge for systematic dissection in vivo. By using single-cell transcriptomics and computational analysis using a temporal mixtures of Gaussian processes model, termed GPfates, we reconstructed the developmental trajectories of Th1 and Tfh cells during blood-stage Plasmodium infection in mice. By tracking clonality using endogenous TCR sequences, we first demonstrated that Th1/Tfh bifurcation had occurred at both population and single-clone levels. Next, we identified genes whose expression was associated with Th1 or Tfh fates, and demonstrated a T-cell intrinsic role for Galectin-1 in supporting a Th1 differentiation. We also revealed the close molecular relationship between Th1 and IL-10-producing Tr1 cells in this infection. Th1 and Tfh fates emerged from a highly proliferative precursor that upregulated aerobic glycolysis and accelerated cell cycling as cytokine expression began. Dynamic gene expression of chemokine receptors around bifurcation predicted roles for cell-cell in driving Th1/Tfh fates. In particular, we found that precursor Th cells were coached towards a Th1 but not a Tfh fate by inflammatory monocytes. Thus, by integrating genomic and computational approaches, our study has provided two unique resources, a database www.PlasmoTH.org, which facilitates discovery of novel factors controlling Th1/Tfh fate commitment, and more generally, GPfates, a modelling framework for characterizing cell differentiation towards multiple fates. PMID:28345074

Human endothelial cells hollow fiber membrane bioreactor as a model of the blood vessel for in vitro studies.

PubMed

Ciechanowska, Anna; Ladyzynski, Piotr; Hoser, Grazyna; Sabalinska, Stanislawa; Kawiak, Jerzy; Foltynski, Piotr; Wojciechowski, Cezary; Chwojnowski, Andrzej

2016-09-01

Human endothelial cells are used in experimental models for studying in vitro pathophysiological mechanisms of different diseases. We developed an original bioreactor, which can simulate human blood vessel, with capillary polysulfone membranes covered with the human umbilical vein endothelial cells (HUVECs) and we characterized its properties. The elaborated cell seeding and culturing procedures ensured formation of a confluent cell monolayer on the inside surface of capillaries within 24 h of culturing under the shear stress of 6.6 dyn/cm(2). The optimal density of cells to be seeded was 60,000 cells/cm(2). Labeling HUVECs with carboxyfluorescein succinimidyl ester (CFSE) did not influence cells' metabolism. Flow cytometry-based analysis of HUVECs stained with CFSE demonstrated that in a presence of the shear stress cells' proliferation was much inhibited (after 72 h proliferation index was equal to 1.9 and 6.2 for cultures with and without shear stress, respectively) and the monolayer was formed mainly due to migration and spreading of cells that were physiologically elongated in a direction of the flow. Monitoring of cells' metabolism showed that HUVECs cultured in a presence of the shear stress preferred anaerobic metabolism and they consumed 1.5 times more glucose and produced 2.3 times more lactate than the cells cultured under static conditions. Daily von Willebrand factor production by HUVECs was near 2 times higher in a presence of the shear stress. The developed model can be used for at least 3 days in target studies under conditions mimicking the in vivo state more closely than the static HUVEC cultures.

Quantitative Analysis of Complex Glioma Cell Migration on Electrospun Polycaprolactone Using Time-Lapse Microscopy

PubMed Central

Johnson, Jed; Nowicki, M. Oskar; Lee, Carol H.; Chiocca, E. Antonio; Viapiano, Mariano S.; Lawler, Sean E.

2009-01-01

Malignant gliomas are the most common tumors originating within the central nervous system and account for over 15,000 deaths annually in the United States. The median survival for glioblastoma, the most common and aggressive of these tumors, is only 14 months. Therapeutic strategies targeting glioma cells migrating away from the tumor core are currently hampered by the difficulty of reproducing migration in the neural parenchyma in vitro. We utilized a tissue engineering approach to develop a physiologically relevant model of glioma cell migration. This revealed that glioma cells display dramatic differences in migration when challenged by random versus aligned electrospun poly-ɛ-caprolactone nanofibers. Cells on aligned fibers migrated at an effective velocity of 4.2 ± 0.39 μm/h compared to 0.8 ± 0.08 μm/h on random fibers, closely matching in vivo models and prior observations of glioma spread in white versus gray matter. Cells on random fibers exhibited extension along multiple fiber axes that prevented net motion; aligned fibers promoted a fusiform morphology better suited to infiltration. Time-lapse microscopy revealed that the motion of individual cells was complex and was influenced by cell cycle and local topography. Glioma stem cell–containing neurospheres seeded on random fibers did not show cell detachment and retained their original shape; on aligned fibers, cells detached and migrated in the fiber direction over a distance sixfold greater than the perpendicular direction. This chemically and physically flexible model allows time-lapse analysis of glioma cell migration while recapitulating in vivo cell morphology, potentially allowing identification of physiological mediators and pharmacological inhibitors of invasion. PMID:19199562

A study of wound repair in Dictyostelium cells by using novel laserporation.

PubMed

Pervin, Mst Shaela; Itoh, Go; Talukder, Md Shahabe Uddin; Fujimoto, Koushiro; Morimoto, Yusuke V; Tanaka, Masamitsu; Ueda, Masahiro; Yumura, Shigehiko

2018-05-22

We examined the mechanism of cell membrane repair in Dictyostelium cells by using a novel laser-based cell poration method. The dynamics of wound pores opening and closing were characterized by live imaging of fluorescent cell membrane proteins, influx of fluorescent dye, and Ca 2+ imaging. The wound closed within 2-4 sec, depending on the wound size. Cells could tolerate a wound size of less than 2.0 µm. In the absence of Ca 2+ in the external medium, the wound pore did not close and cells ruptured. The release of Ca 2+ from intracellular stores also contributed to the elevation of cytoplasmic Ca 2+ but not to wound repair. Annexin C1 immediately accumulated at the wound site depending on the external Ca 2+ concentration, and annexin C1 knockout cells had a defect in wound repair, but it was not essential. Dictyostelium cells were able to respond to multiple repeated wounds with the same time courses, in contrast to previous reports showing that the first wound accelerates the second wound repair in fibroblasts.

The role of satellite cells in muscle hypertrophy.

PubMed

Blaauw, Bert; Reggiani, Carlo

2014-02-01

The role of satellite cells in muscle hypertrophy has long been a debated issue. In the late 1980s it was shown that proteins remain close to the myonucleus responsible for its synthesis, giving rise to the idea of a nuclear domain. This, together with the observation that during various models of muscle hypertrophy there is an activation of the muscle stem cells, i.e. satellite cells, lead to the idea that satellite cell activation is required for muscle hypertrophy. Thus, satellite cells are not only responsible for muscle repair and regeneration, but also for hypertrophic growth. Further support for this line of thinking was obtained after studies showing that irradiation of skeletal muscle, and therefore elimination of all satellite cells, completely prevented overload-induced hypertrophy. Recently however, using different transgenic approaches, it has become clear that muscle hypertrophy can occur without a contribution of satellite cells, even though in most situations of muscle hypertrophy satellite cells are activated. In this review we will discuss the contribution of satellite cells, and other muscle-resident stem cells, to muscle hypertrophy both in mice as well as in humans.

Assessing the role of spatial correlations during collective cell spreading

PubMed Central

Treloar, Katrina K.; Simpson, Matthew J.; Binder, Benjamin J.; McElwain, D. L. Sean; Baker, Ruth E.

2014-01-01

Spreading cell fronts are essential features of development, repair and disease processes. Many mathematical models used to describe the motion of cell fronts, such as Fisher's equation, invoke a mean–field assumption which implies that there is no spatial structure, such as cell clustering, present. Here, we examine the presence of spatial structure using a combination of in vitro circular barrier assays, discrete random walk simulations and pair correlation functions. In particular, we analyse discrete simulation data using pair correlation functions to show that spatial structure can form in a spreading population of cells either through sufficiently strong cell–to–cell adhesion or sufficiently rapid cell proliferation. We analyse images from a circular barrier assay describing the spreading of a population of MM127 melanoma cells using the same pair correlation functions. Our results indicate that the spreading melanoma cell populations remain very close to spatially uniform, suggesting that the strength of cell–to–cell adhesion and the rate of cell proliferation are both sufficiently small so as not to induce any spatial patterning in the spreading populations. PMID:25026987

Tropomodulin1 is required for membrane skeleton organization and hexagonal geometry of fiber cells in the mouse lens

PubMed Central

Nowak, Roberta B.; Fischer, Robert S.; Zoltoski, Rebecca K.; Kuszak, Jerome R.

2009-01-01

Hexagonal packing geometry is a hallmark of close-packed epithelial cells in metazoans. Here, we used fiber cells of the vertebrate eye lens as a model system to determine how the membrane skeleton controls hexagonal packing of post-mitotic cells. The membrane skeleton consists of spectrin tetramers linked to actin filaments (F-actin), which are capped by tropomodulin1 (Tmod1) and stabilized by tropomyosin (TM). In mouse lenses lacking Tmod1, initial fiber cell morphogenesis is normal, but fiber cell hexagonal shapes and packing geometry are not maintained as fiber cells mature. Absence of Tmod1 leads to decreased γTM levels, loss of F-actin from membranes, and disrupted distribution of β2-spectrin along fiber cell membranes. Regular interlocking membrane protrusions on fiber cells are replaced by irregularly spaced and misshapen protrusions. We conclude that Tmod1 and γTM regulation of F-actin stability on fiber cell membranes is critical for the long-range connectivity of the spectrin–actin network, which functions to maintain regular fiber cell hexagonal morphology and packing geometry. PMID:19752024

Three-dimensional Kinetic Pulsar Magnetosphere Models: Connecting to Gamma-Ray Observations

NASA Astrophysics Data System (ADS)

Kalapotharakos, Constantinos; Brambilla, Gabriele; Timokhin, Andrey; Harding, Alice K.; Kazanas, Demosthenes

2018-04-01

We present three-dimensional (3D) global kinetic pulsar magnetosphere models, where the charged particle trajectories and the corresponding electromagnetic fields are treated self-consistently. For our study, we have developed a Cartesian 3D relativistic particle-in-cell code that incorporates radiation reaction forces. We describe our code and discuss the related technical issues, treatments, and assumptions. Injecting particles up to large distances in the magnetosphere, we apply arbitrarily low to high particle injection rates, and obtain an entire spectrum of solutions from close to the vacuum-retarded dipole to close to the force-free (FF) solution, respectively. For high particle injection rates (close to FF solutions), significant accelerating electric field components are confined only near the equatorial current sheet outside the light cylinder. A judicious interpretation of our models allows the particle emission to be calculated, and consequently, the corresponding realistic high-energy sky maps and spectra to be derived. Using model parameters that cover the entire range of spin-down powers of Fermi young and millisecond pulsars, we compare the corresponding model γ-ray light curves, cutoff energies, and total γ-ray luminosities with those observed by Fermi to discover a dependence of the particle injection rate, { \\mathcal F }, on the spin-down power, \\dot{{ \\mathcal E }}, indicating an increase of { \\mathcal F } with \\dot{{ \\mathcal E }}. Our models, guided by Fermi observations, provide field structures and particle distributions that are not only consistent with each other but also able to reproduce a broad range of the observed γ-ray phenomenologies of both young and millisecond pulsars.

Development of 3D culture models of plexiform neurofibroma and initial application for phenotypic characterization and drug screening.

PubMed

Kraniak, Janice M; Chalasani, Anita; Wallace, Margaret R; Mattingly, Raymond R

2018-01-01

Plexiform neurofibromas (PNs), which may be present at birth in up to half of children with type 1 neurofibromatosis (NF1), can cause serious loss of function, such as quadriparesis, and can undergo malignant transformation. Surgery is the first line treatment although the invasive nature of these tumors often prevents complete resection. Recent clinical trials have shown promising success for some drugs, notably selumetinib, an inhibitor of MAP kinase kinase (MEK). We have developed three-dimensional (3D) cell culture models of immortalized cells from NF1 PNs and of control Schwann cells (SCs) that we believe mimic more closely the in vivo condition than conventional two-dimensional (2D) cell culture. Our goal is to facilitate pre-clinical identification of potential targeted therapeutics for these tumors. Three drugs, selumetinib (a MEK inhibitor), picropodophyllin (an IGF-1R inhibitor) and LDN-193189 (a BMP2 inhibitor) were tested with dose-response design in both 2D and 3D cultures for their abilities to block net cell growth. Cell lines grown in 3D conditions showed varying degrees of resistance to the inhibitory actions of all three drugs. For example, control SCs became resistant to growth inhibition by selumetinib in 3D culture. LDN-193189 was the most effective drug in 3D cultures, with only slightly reduced potency compared to the 2D cultures. Characterization of these models also demonstrated increased proteolysis of collagen IV in the matrix by the PN driver cells as compared to wild-type SCs. The proteolytic capacity of the PN cells in the model may be a clinically significant property that can be used for testing the ability of drugs to inhibit their invasive phenotype. Copyright © 2017 Elsevier Inc. All rights reserved.

Dental Pulp Stem Cells Model Early Life and Imprinted DNA Methylation Patterns.

PubMed

Dunaway, Keith; Goorha, Sarita; Matelski, Lauren; Urraca, Nora; Lein, Pamela J; Korf, Ian; Reiter, Lawrence T; LaSalle, Janine M

2017-04-01

Early embryonic stages of pluripotency are modeled for epigenomic studies primarily with human embryonic stem cells (ESC) or induced pluripotent stem cells (iPSCs). For analysis of DNA methylation however, ESCs and iPSCs do not accurately reflect the DNA methylation levels found in preimplantation embryos. Whole genome bisulfite sequencing (WGBS) approaches have revealed the presence of large partially methylated domains (PMDs) covering 30%-40% of the genome in oocytes, preimplantation embryos, and placenta. In contrast, ESCs and iPSCs show abnormally high levels of DNA methylation compared to inner cell mass (ICM) or placenta. Here we show that dental pulp stem cells (DPSCs), derived from baby teeth and cultured in serum-containing media, have PMDs and mimic the ICM and placental methylome more closely than iPSCs and ESCs. By principal component analysis, DPSC methylation patterns were more similar to two other neural stem cell types of human derivation (EPI-NCSC and LUHMES) and placenta than were iPSCs, ESCs or other human cell lines (SH-SY5Y, B lymphoblast, IMR90). To test the suitability of DPSCs in modeling epigenetic differences associated with disease, we compared methylation patterns of DPSCs derived from children with chromosome 15q11.2-q13.3 maternal duplication (Dup15q) to controls. Differential methylation region (DMR) analyses revealed the expected Dup15q hypermethylation at the imprinting control region, as well as hypomethylation over SNORD116, and novel DMRs over 147 genes, including several autism candidate genes. Together these data suggest that DPSCs are a useful model for epigenomic and functional studies of human neurodevelopmental disorders. Stem Cells 2017;35:981-988. © 2016 AlphaMed Press.

Simulation of unsteady flows by the DSMC macroscopic chemistry method

NASA Astrophysics Data System (ADS)

Goldsworthy, Mark; Macrossan, Michael; Abdel-jawad, Madhat

2009-03-01

In the Direct Simulation Monte-Carlo (DSMC) method, a combination of statistical and deterministic procedures applied to a finite number of 'simulator' particles are used to model rarefied gas-kinetic processes. In the macroscopic chemistry method (MCM) for DSMC, chemical reactions are decoupled from the specific particle pairs selected for collisions. Information from all of the particles within a cell, not just those selected for collisions, is used to determine a reaction rate coefficient for that cell. Unlike collision-based methods, MCM can be used with any viscosity or non-reacting collision models and any non-reacting energy exchange models. It can be used to implement any reaction rate formulations, whether these be from experimental or theoretical studies. MCM has been previously validated for steady flow DSMC simulations. Here we show how MCM can be used to model chemical kinetics in DSMC simulations of unsteady flow. Results are compared with a collision-based chemistry procedure for two binary reactions in a 1-D unsteady shock-expansion tube simulation. Close agreement is demonstrated between the two methods for instantaneous, ensemble-averaged profiles of temperature, density and species mole fractions, as well as for the accumulated number of net reactions per cell.

Three-Dimensional Transport Modeling for Proton Exchange Membrane(PEM) Fuel Cell with Micro Parallel Flow Field

PubMed Central

Lee, Pil Hyong; Han, Sang Seok; Hwang, Sang Soon

2008-01-01

Modeling and simulation for heat and mass transport in micro channel are being used extensively in researches and industrial applications to gain better understanding of the fundamental processes and to optimize fuel cell designs before building a prototype for engineering application. In this study, we used a single-phase, fully three dimensional simulation model for PEMFC that can deal with both anode and cathode flow field for examining the micro flow channel with electrochemical reaction. The results show that hydrogen and oxygen were solely supplied to the membrane by diffusion mechanism rather than convection transport, and the higher pressure drop at cathode side is thought to be caused by higher flow rate of oxygen at cathode. And it is found that the amount of water in cathode channel was determined by water formation due to electrochemical reaction plus electro-osmotic mass flux directing toward the cathode side. And it is very important to model the back diffusion and electro-osmotic mass flux accurately since the two flux was closely correlated each other and greatly influenced for determination of ionic conductivity of the membrane which directly affects the performance of fuel cell. PMID:27879774

Modeled Microgravity Affects Fibroblast Functions Related to Wound Healing

NASA Astrophysics Data System (ADS)

Cialdai, Francesca; Vignali, Leonardo; Morbidelli, Lucia; Colciago, Alessandra; Celotti, Fabio; Santi, Alice; Caselli, Anna; Cirri, Paolo; Monici, Monica

2017-02-01

Wound healing is crucial for the survival of an organism. Therefore, in the perspective of space exploration missions, it is important to understand if and how microgravity conditions affect the behavior of the cell populations involved in wound healing and the evolution of the process. Since fibroblasts are the major players in tissue repair, this study was focused on the behavior of fibroblasts in microgravity conditions, modeled by a RCCS. Cell cytoskeleton was studied by immunofluorescence microscopy, the ability to migrate was assessed by microchemotaxis and scratch assay, and the expression of markers of fibroblast activation, angiogenesis, and inflammation was assessed by western blot. Results revealed that after cell exposure to modeled microgravity conditions, a thorough rearrangement of microtubules occurred and α-SMA bundles were replaced by a tight network of faulty and disorganized filaments. Exposure to modeled microgravity induced a decrease in α-SMA and E-CAD expressions. Also, the expression of the pro-angiogenic protein VEGF decreased, while that of the inflammatory signal COX-2 increased. Fibroblast ability to adhere, migrate, and respond to chemoattractants (PRP), closely related to cytoskeleton integrity and membrane junctions, was significantly impaired. Nevertheless, PRP was able to partially restore fibroblast migration.

Correlations and Functional Connections in a Population of Grid Cells

PubMed Central

Roudi, Yasser

2015-01-01

We study the statistics of spike trains of simultaneously recorded grid cells in freely behaving rats. We evaluate pairwise correlations between these cells and, using a maximum entropy kinetic pairwise model (kinetic Ising model), study their functional connectivity. Even when we account for the covariations in firing rates due to overlapping fields, both the pairwise correlations and functional connections decay as a function of the shortest distance between the vertices of the spatial firing pattern of pairs of grid cells, i.e. their phase difference. They take positive values between cells with nearby phases and approach zero or negative values for larger phase differences. We find similar results also when, in addition to correlations due to overlapping fields, we account for correlations due to theta oscillations and head directional inputs. The inferred connections between neurons in the same module and those from different modules can be both negative and positive, with a mean close to zero, but with the strongest inferred connections found between cells of the same module. Taken together, our results suggest that grid cells in the same module do indeed form a local network of interconnected neurons with a functional connectivity that supports a role for attractor dynamics in the generation of grid pattern. PMID:25714908

Gallic acid inhibits the release of ADAMTS4 in nucleus pulposus cells by inhibiting p65 phosphorylation and acetylation of the NF-κB signaling pathway.

PubMed

Huang, Yao; Chen, Jian; Jiang, Tao; Zhou, Zheng; Lv, Bin; Yin, Guoyong; Fan, Jin

2017-07-18

This study investigated the inhibitory effect of gallic acid (GA) on the release of A Disintegrin and Metalloproteinase with Thrombospondin motifs 4 (ADAMTS4) through the regulation of the NF-κB signaling pathway, which is closely related to the matrix metalloproteinases in nucleus pulposus cells. Different concentrations of GA were added to TNF-α-induced human nucleus pulposus cells (hNPCs) and intervertebral disc degeneration rat model. ADAMTS-4 expression increased both in the TNF-α-induced nucleus pulposus cells and intervertebral disc degeneration rat model. By contrast, the release of ADAMTS-4 was reduced, and the TNF-α-induced apoptosis of nucleus pulposus cells was significantly inhibited after addition of GA at different concentrations. Further study found that the levels of phosphorylated p65 (p-p65) was increased and the classical NF-κB signal pathway was activated after the nucleus pulposus cells were stimulated by TNF-α. Meanwhile, GA suppressed the p65 phosphorylation and inceased p65 deacetylation levels. As a consequence, GA can decrease the expression of ADAMTS-4 in nucleus pulposus cells by regulating the phosphorylation and acetylation of p65 in NF-κB signaling pathways.

Guard cells elongate: relationship of volume and surface area during stomatal movement.

PubMed

Meckel, Tobias; Gall, Lars; Semrau, Stefan; Homann, Ulrike; Thiel, Gerhard

2007-02-01

Stomata in the epidermis of photosynthetically active plant organs are formed by pairs of guard cells, which create a pore, to facilitate CO2 and water exchange with the environment. To control this gas exchange, guard cells actively change their volume and, consequently, surface area to alter the aperture of the stomatal pore. Due to the limited elasticity of the plasma membrane, such changes in surface area require an exocytic addition or endocytic retrieval of membrane during stomatal movement. Using confocal microscopic data, we have reconstructed detailed three-dimensional models of open and closed stomata to precisely quantify the necessary area to be exo- and endocytosed by the guard cells. Images were obtained under a strong emphasis on a precise calibration of the method and by avoiding unphysiological osmotical imbalance, and hence osmocytosis. The data reveal that guard cells of Vicia faba L., whose aperture increases by 111.89+/-22.39%, increase in volume and surface area by 24.82+/-6.26% and 14.99+/-2.62%, respectively. In addition, the precise volume to surface area relationship allows quantitative modeling of the three-dimensional changes. While the major volume change is caused by a slight increase in the cross section of the cells, an elongation of the guard cells achieves the main aperture change.

The effect of the plasma needle on the human keratinocytes related to the wound healing process

NASA Astrophysics Data System (ADS)

Korolov, Ihor; Fazekas, Barbara; Széll, Márta; Kemény, Lajos; Kutasi, Kinga

2016-01-01

In the present study we aim to verify the influence of a non-thermal atmospheric pressure plasma on the wound healing process. In this process the major contributors are the keratinocytes, which migrate to fill in the gap created by the wound. Therefore, we performed the direct treatment of HPV-immortalized human keratinocytes, protected by a layer of phosphate buffered saline (PBS) solution, with the glow discharge generated in flowing helium by a plasma needle. To mimick a wound, a 4 mm scratch was performed on the cell culture (scratch assay). We conducted two types of experiments: (i) cell proliferation and (ii) wound-healing model experiments. The plasma needle configuration, the plasma treatment conditions and the thickness of the protecting PBS layer were set based on viability experiments. The proliferation studies showed that short, 5-10 s, and low power treatments, such as 18 W and 20 W input power, could positively influence the cell proliferation when keratinocytes were protected by PBS. On the other hand, the plasma treatment of cell medium covered keratinocytes resulted in the decrease of proliferation. The wound-healing model (scratch assay) studies showed, that there was a maximum in the wound reduction as a function of the input power and treatment time, namely, at 18 W and 5 s. Furthermore, the wound reduction strongly depended on the treated cell—PBS interaction time. To mimic an infected wound, the scratch assay was covered with a 1× {{10}9} cfu ml-1 Propionibacterium acnes suspension. The plasma treatment of this infected assay resulted in closing of the scratch, while in the non-treated assay the wound did not close at all.

PACAP receptor pharmacology and agonist bias: analysis in primary neurons and glia from the trigeminal ganglia and transfected cells

PubMed Central

Walker, C S; Sundrum, T; Hay, D L

2014-01-01

Background and Purpose A major challenge in the development of new medicines targeting GPCRs is the ability to quantify drug action in physiologically relevant models. Primary cell models that closely resemble the clinically relevant in vivo site of drug action are important translational tools in drug development. However, pharmacological studies in these models are generally very limited due to the methodology used. Experimental Approach We used a neuropeptide system to demonstrate the applicability of using highly sensitive signalling assays in primary cells. We quantified the action of pituitary adenylate cyclase-activating peptide (PACAP)-38, PACAP-27 and vasoactive intestinal polypeptide in primary cultures of neurons and glia derived from rat trigeminal ganglia (TG), comparing our observations to transfected cells. Key Results PACAP-responsive receptors in rat trigeminal neurons, glia and transfected PAC1n receptors were pharmacologically distinct. PACAP-38, but not PACAP-27, activated ERK in glia, while both forms stimulated cellular cAMP production. PACAP(6–38) also displayed cell-type-dependent, agonist-specific, antagonism. Conclusions and Implications The complexity of PACAP pharmacology in the TG may help to direct, more effectively, the development of disease treatments targeting the PACAP receptor. We suggest that these methodologies are broadly applicable to other primary cell types of human or animal origin, and that our approach may allow more thorough characterization of ligand properties in physiologically relevant cell types. PMID:24303997

A question of separation: disentangling tracer bias and gravitational non-linearity with counts-in-cells statistics

NASA Astrophysics Data System (ADS)

Uhlemann, C.; Feix, M.; Codis, S.; Pichon, C.; Bernardeau, F.; L'Huillier, B.; Kim, J.; Hong, S. E.; Laigle, C.; Park, C.; Shin, J.; Pogosyan, D.

2018-02-01

Starting from a very accurate model for density-in-cells statistics of dark matter based on large deviation theory, a bias model for the tracer density in spheres is formulated. It adopts a mean bias relation based on a quadratic bias model to relate the log-densities of dark matter to those of mass-weighted dark haloes in real and redshift space. The validity of the parametrized bias model is established using a parametrization-independent extraction of the bias function. This average bias model is then combined with the dark matter PDF, neglecting any scatter around it: it nevertheless yields an excellent model for densities-in-cells statistics of mass tracers that is parametrized in terms of the underlying dark matter variance and three bias parameters. The procedure is validated on measurements of both the one- and two-point statistics of subhalo densities in the state-of-the-art Horizon Run 4 simulation showing excellent agreement for measured dark matter variance and bias parameters. Finally, it is demonstrated that this formalism allows for a joint estimation of the non-linear dark matter variance and the bias parameters using solely the statistics of subhaloes. Having verified that galaxy counts in hydrodynamical simulations sampled on a scale of 10 Mpc h-1 closely resemble those of subhaloes, this work provides important steps towards making theoretical predictions for density-in-cells statistics applicable to upcoming galaxy surveys like Euclid or WFIRST.

Ulcerative colitis: ultrastructure of interstitial cells in myenteric plexus.

PubMed

Rumessen, J J; Vanderwinden, J-M; Horn, T

2010-10-01

Interstitial cells of Cajal (ICC) are key regulatory cells in the gut. In the colon of patients with severe ulcerative colitis (UC), myenteric ICC had myoid ultrastructural features and were in close contact with nerve terminals. In all patients as opposed to controls, some ICC profiles showed degenerative changes, such as lipid droplets and irregular vacuoles. Nerve terminals often appeared swollen and empty. Glial cells, muscle cells, and fibroblast-like cells (FLC) showed no alterations. FLC enclosed macrophages (MLC), which were in close contact with naked axon terminals. The organization and cytological changes may be of pathophysiological significance in patients with UC.

[Satellite glial cells in sensory ganglia: its role in pain].

PubMed

Costa, Filipa Alexandra Leite; Moreira Neto, Fani Lourença

2015-01-01

Satellite glial cells in sensory ganglia are a recent subject of research in the field of pain and a possible therapeutic target in the future. Therefore, the aim of this study was to summarize some of the important physiological and morphological characteristics of these cells and gather the most relevant scientific evidence about its possible role in the development of chronic pain. In the sensory ganglia, each neuronal body is surrounded by satellite glial cells forming distinct functional units. This close relationship enables bidirectional communication via a paracrine signaling between those two cell types. There is a growing body of evidence that glial satellite cells undergo structural and biochemical changes after nerve injury, which influence neuronal excitability and consequently the development and/or maintenance of pain in different animal models of chronic pain. Satellite glial cells are important in the establishment of physiological pain, in addition to being a potential target for the development of new pain treatments. Copyright © 2014 Sociedade Brasileira de Anestesiologia. Publicado por Elsevier Editora Ltda. All rights reserved.

NIFLUMIC ACID BLOCKS NATIVE AND RECOMBINANT T-TYPE CHANNELS

PubMed Central

Balderas, E; Arteaga-Tlecuitl, R; Rivera, M; Gomora, JC; Darszon, A

2012-01-01

Voltage-dependent calcium channels are widely distributed in animal cells, including spermatozoa. Calcium is fundamental in many sperm functions such as: motility, capacitation and the acrosome reaction, all essential for fertilization. Pharmacological evidence has suggested T-type calcium channels participate in the acrosome reaction. Niflumic acid (NA), a non-steroidal anti-inflammatory drug commonly used as chloride channel blocker, blocks T-currents in mouse spermatogenic cells and Cl− channels in testicular sperm. Here we examine the mechanism of NA blockade and explore if it can be used to separate the contribution of different CaV3 members previously detected in these cells. Electrophysiological patch-clamp recordings were performed in isolated mouse spermatogenic cells and in HEK cells heterologously expressing CaV3 channels. NA blocks mouse spermatogenic cell T-type currents with an IC50 of 73.5 µM, without major voltage-dependent effects. The NA blockade is more potent in the open and in the inactivated state than in the closed state of the T-type channels. Interestingly, we found that heterologously expressed CaV3.1 and CaV3.3 channels were more sensitive to NA than CaV3.2 channels, and this drug substantially slowed the recovery from inactivation of the three isoforms. Molecular docking modeling of drug-channel binding predicts that NA binds preferentially to the extracellular face of CaV3.1 channels. The biophysical characteristics of mouse spermatogenic cell T-type currents more closely resemble those from heterologously expressed CaV3.1 channels, including their sensitivity to NA. As CaV3.1 null mice maintain their spermatogenic cell T-currents, it is likely that a novel CaV3.2 isoform is responsible for them. PMID:21898399

Nanoindentation characterisation of human colorectal cancer cells considering cell geometry, surface roughness and hyperelastic constitutive behaviour

NASA Astrophysics Data System (ADS)

Boccaccio, Antonio; Uva, Antonio E.; Papi, Massimiliano; Fiorentino, Michele; De Spirito, Marco; Monno, Giuseppe

2017-01-01

Characterisation of the mechanical behaviour of cancer cells is an issue of crucial importance as specific cell mechanical properties have been measured and utilized as possible biomarkers of cancer progression. Atomic force microscopy certainly occupies a prominent place in the field of the mechanical characterisation devices. We developed a hybrid approach to characterise different cell lines (SW620 and SW480) of the human colon carcinoma submitted to nanoindentation measurements. An ad hoc algorithm was written that compares the force-indentation curves experimentally retrieved with those predicted by a finite element model that simulates the nanoindentation process and reproduces the cell geometry and the surface roughness. The algorithm perturbs iteratively the values of the cell mechanical properties implemented in the finite element model until the difference between the experimental and numerical force-indentation curves reaches the minimum value. The occurrence of this indicates that the implemented material properties are very close to the real ones. Different hyperelastic constitutive models, such as Arruda-Boyce, Mooney-Rivlin and Neo-Hookean were utilized to describe the structural behaviour of indented cells. The algorithm was capable of separating, for all the cell lines investigated, the mechanical properties of cell cortex and cytoskeleton. Material properties determined via the algorithm were different with respect to those obtained with the Hertzian contact theory. This demonstrates that factors such as: the cell geometry/anatomy and the hyperelastic constitutive behaviour, which are not contemplated in the Hertz’s theory hypotheses, do affect the nanoindentation measurements. The proposed approach represents a powerful tool that, only on the basis of nanoindentation measurements, is capable of characterising material at the subcellular level.

A Good Neighborhood for Cells: Bioreactor Demonstration System (BDS-05)

NASA Technical Reports Server (NTRS)

Chung, Leland W. K.; Goodwin, Thomas J. (Technical Monitor)

2002-01-01

Good neighborhoods help you grow. As with a city, the lives of a cell are governed by its neighborhood connections Connections that do not work are implicated in a range of diseases. One of those connections - between prostate cancer and bone cells - will be studied on STS-107 using the Bioreactor Demonstration System (BDS-05). To improve the prospects for finding novel therapies, and to identify biomarkers that predict disease progression, scientists need tissue models that behave the same as metastatic or spreading cancer. This is one of several NASA-sponsored lines of cell science research that use the microgravity environment of orbit in an attempt to grow lifelike tissue models for health research. As cells replicate, they "self associate" to form a complex matrix of collagens, proteins, fibers, and other structures. This highly evolved microenvironment tells each cell who is next door, how it should grow arid into what shapes, and how to respond to bacteria, wounds, and other stimuli. Studying these mechanisms outside the body is difficult because cells do not easily self-associate outside a natural environment. Most cell cultures produce thin, flat specimens that offer limited insight into how cells work together. Ironically, growing cell cultures in the microgravity of space produces cell assemblies that more closely resemble what is found in bodies on Earth. NASA's Bioreactor comprises a miniature life support system and a rotating vessel containing cell specimens in a nutrient medium. Orbital BDS experiments that cultured colon and prostate cancers have been highly promising.

The relative importance of macrophysical and cloud albedo changes for aerosol-induced radiative effects in closed-cell stratocumulus: insight from the modelling of a case study

NASA Astrophysics Data System (ADS)

Grosvenor, Daniel P.; Field, Paul R.; Hill, Adrian A.; Shipway, Benjamin J.

2017-04-01

Aerosol-cloud interactions are explored using 1 km simulations of a case study of predominantly closed-cell SE Pacific stratocumulus clouds. The simulations include realistic meteorology along with newly implemented cloud microphysics and sub-grid cloud schemes. The model was critically assessed against observations of liquid water path (LWP), broadband fluxes, cloud fraction (fc), droplet number concentrations (Nd), thermodynamic profiles, and radar reflectivities.Aerosol loading sensitivity tests showed that at low aerosol loadings, changes to aerosol affected shortwave fluxes equally through changes to cloud macrophysical characteristics (LWP, fc) and cloud albedo changes due solely to Nd changes. However, at high aerosol loadings, only the Nd albedo change was important. Evidence was also provided to show that a treatment of sub-grid clouds is as important as order of magnitude changes in aerosol loading for the accurate simulation of stratocumulus at this grid resolution.Overall, the control model demonstrated a credible ability to reproduce observations, suggesting that many of the important physical processes for accurately simulating these clouds are represented within the model and giving some confidence in the predictions of the model concerning stratocumulus and the impact of aerosol. For example, the control run was able to reproduce the shape and magnitude of the observed diurnal cycle of domain mean LWP to within ˜ 10 g m-2 for the nighttime, but with an overestimate for the daytime of up to 30 g m-2. The latter was attributed to the uniform aerosol fields imposed on the model, which meant that the model failed to include the low-Nd mode that was observed further offshore, preventing the LWP removal through precipitation that likely occurred in reality. The boundary layer was too low by around 260 m, which was attributed to the driving global model analysis. The shapes and sizes of the observed bands of clouds and open-cell-like regions of low areal cloud cover were qualitatively captured. The daytime fc frequency distribution was reproduced to within Δfc = 0.04 for fc > ˜ 0.7 as was the domain mean nighttime fc (at a single time) to within Δfc = 0.02. Frequency distributions of shortwave top-of-the-atmosphere (TOA) fluxes from the satellite were well represented by the model, with only a slight underestimate of the mean by 15 %; this was attributed to near-shore aerosol concentrations that were too low for the particular times of the satellite overpasses. TOA long-wave flux distributions were close to those from the satellite with agreement of the mean value to within 0.4 %. From comparisons of Nd distributions to those from the satellite, it was found that the Nd mode from the model agreed with the higher of the two observed modes to within ˜ 15 %.

Intracoronary allogeneic cardiosphere-derived stem cells are safe for use in dogs with dilated cardiomyopathy.

PubMed

Hensley, Michael Taylor; Tang, Junnan; Woodruff, Kathleen; Defrancesco, Teresa; Tou, Sandra; Williams, Christina M; Breen, Mathew; Meurs, Kathryn; Keene, Bruce; Cheng, Ke

2017-08-01

Cardiosphere-derived cells (CDCs) have been shown to reduce scar size and increase viable myocardium in human patients with mild/moderate myocardial infarction. Studies in rodent models suggest that CDC therapy may confer therapeutic benefits in patients with non-ischaemic dilated cardiomyopathy (DCM). We sought to determine the safety and efficacy of allogeneic CDC in a large animal (canine) model of spontaneous DCM. Canine CDCs (cCDCs) were grown from a donor dog heart. Similar to human CDCs, cCDCs express CD105 and are slightly positive for c-kit and CD90. Thirty million of allogeneic cCDCs was infused into the coronary vessels of Doberman pinscher dogs with spontaneous DCM. Adverse events were closely monitored, and cardiac functions were measured by echocardiography. No adverse events occurred during and after cell infusion. Histology on dog hearts (after natural death) revealed no sign of immune rejection from the transplanted cells. © 2017 The Authors. Journal of Cellular and Molecular Medicine published by John Wiley & Sons Ltd and Foundation for Cellular and Molecular Medicine.

Dysregulation of Ezrin phosphorylation prevents metastasis and alters cellular metabolism in osteosarcoma

PubMed Central

Ren, Ling; Hong, Sung-Hyeok; Chen, Qing-Rong; Briggs, Joseph; Cassavaugh, Jessica; Srinivasan, Satish; Lizardo, Michael M.; Mendoza, Arnulfo; Xia, Ashley Y.; Avadhani, Narayan; Khan, Javed; Khanna, Chand

2013-01-01

Ezrin links the plasma membrane to the actin cytoskeleton where it plays a pivotal role in the metastatic progression of several human cancers (1, 2), however, the precise mechanistic basis for its role remains unknown. Here we define transitions between active (phosphorylated open) and inactive (dephosphorylated closed) forms of Ezrin that occur during metastatic progression in osteosarcoma. In our evaluation of these conformations we expressed C-terminal mutant forms of Ezrin that are open (phosphomimetic T567D) or closed (phosphodeficient T567A) and compared their biological characteristics to full length wild-type Ezrin in osteosarcoma cells. Unexpectedly, cells expressing open, active Ezrin could form neither primary orthotopic tumors nor lung metastases. In contrast, cells expressing closed, inactive Ezrin were also deficient in metastasis but were unaffected in their capacity for primary tumor growth. By imaging single metastatic cells in the lung, we found that cells expressing either open or closed Ezrin displayed increased levels of apoptosis early after their arrival in the lung. Gene expression analysis suggested dysregulation of genes that are functionally linked to carbohydrate and amino acid metabolism. In particular, cells expressing closed, inactive Ezrin exhibited reduced lactate production and basal or ATP-dependent oxygen consumption. Collectively, our results suggest that dynamic regulation of Ezrin phosphorylation at amino acid T567 that controls structural transitions of this protein plays a pivotal role in tumor progression and metastasis, possibly in part by altering cellular metabolism. PMID:22147261

A closed system for islet isolation and purification using the COBE2991 cell processor may reduce the need of clean room facilities.

PubMed

Klaffschenkel, R A; Biesemeier, A; Waidmann, M; Northoff, H; Steurer, W; Königsrainer, A; Lembert, N

2007-01-01

During the isolation of human islets of Langerhans the digest has repeated direct contact with the ambient atmosphere. In order to fulfill GMP requirements in clinical applications, the entire cell preparation must be performed in clean room facilities. We hypothesized that the use of a closed system, which avoids the direct exposure of tissue to the atmosphere, would significantly ease the preparation procedure. To avoid the direct atmosphere exposure we tested a modification of the isolation and purification process by performing all islet preparation steps in a closed system. In this study we compared the isolation outcome of the traditional open preparation technique with the new closed system. Pancreata from 6-month-old hybrid pigs were procured in the local slaughterhouse. After digestion/filtration the digest was cooled, collected, and concentrated in centrifugation containers and purified thereafter in the COBE2991 by top loading (control). In the control group 502 +/- 253 IEQ per gram pancreas were purified. The total preparation time amounted to 12 h. In the closed system the digest was cooled and directly pumped into the COBE2991 for centrifugation followed by supernatant expelling. Bag filling, centrifugation, and expelling were repeated several times. Islets in pellet form were then purified by adding a gradient (bottom loading). Using this closed system 1098 +/- 489 IEQ per gram pancreas were purified with a total cell viability of 67 +/- 10% and a beta-cell viability of 41 +/- 13%. The total preparation time reduced to 6 h. After 24 h of cell culture the viability of beta-cells was still 56 +/- 10% and was only reduced after the addition of proapoptotic IL-1 and TNF-alpha to 40 +/- 4%, indicating that freshly isolated islets are not apoptotic. In conclusion, the closed system preparation is much faster, more effective, and less expensive than the traditional islet preparation. The closed system may be applicable for human islets preparations to restrict the need of clean room facilities for islet preparations to a minimum and may open the way for islet preparations without clean room demand.

Mechanical properties of palm oil based bio-polyurethane foam of free rise and various densities

NASA Astrophysics Data System (ADS)

Hilmi, Hazmi; Zainuddin, Firuz; Cheng, Teoh Siew; Lan, Du Ngoc Uy

2017-12-01

Bio-foam was produced from palm oil-based polyol (POBP) and methylene diphenyl diisocyanate (MDI) with weight ratio of 1:1. The effect of opened mould (as free rise) and closed mould (control expansion) was investigated. Different densities of bio-polyurethane foam (0.3, 0.4 and 0.5 g.cm-3) were prepared using the closed mould system. The effect of density on morphology and compressive properties of bio-foam was studied. Results showed that bio-foam prepared by closed mould method possessed homogeneous cell structure and cell size compared to bio-foam prepared by opened mould. In addition, bio-foam using closed mould system had higher compression strength (0.47 MPa) than that of bio-foam using opened mould system (0.13 MPa). With higher density and lesser porosity, the compressive modulus and compressive strength of bio foams will be higher. The increase in compressive properties is due to the decrease in the cells size, more homogeneous cell structure and reduction in porosity content.

Bacillus subtilis extracytoplasmic function (ECF) sigma factors and defense of the cell envelope.

PubMed

Helmann, John D

2016-04-01

Bacillus subtilis provides a model for investigation of the bacterial cell envelope, the first line of defense against environmental threats. Extracytoplasmic function (ECF) sigma factors activate genes that confer resistance to agents that threaten the integrity of the envelope. Although their individual regulons overlap, σ(W) is most closely associated with membrane-active agents, σ(X) with cationic antimicrobial peptide resistance, and σ(V) with resistance to lysozyme. Here, I highlight the role of the σ(M) regulon, which is strongly induced by conditions that impair peptidoglycan synthesis and includes the core pathways of envelope synthesis and cell division, as well as stress-inducible alternative enzymes. Studies of these cell envelope stress responses provide insights into how bacteria acclimate to the presence of antibiotics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Genetic Algorithms and Nucleation in VIH-AIDS transition.

NASA Astrophysics Data System (ADS)

Barranon, Armando

2003-03-01

VIH to AIDS transition has been modeled via a genetic algorithm that uses boom-boom principle and where population evolution is simulated with a cellular automaton based on SIR model. VIH to AIDS transition is signed by nucleation of infected cells and low probability of infection are obtained for different mutation rates in agreement with clinical results. A power law is obtained with a critical exponent close to the critical exponent of cubic, spherical percolation, colossal magnetic resonance, Ising Model and liquid-gas phase transition in heavy ion collisions. Computations were carried out at UAM-A Supercomputing Lab and author acknowledges financial support from Division of CBI at UAM-A.

A comparison of mechanical properties of some foams and honeycombs

NASA Technical Reports Server (NTRS)

Bhat, Balakrishna T.; Wang, T. G.

1990-01-01

A comparative study is conducted of the mechanical properties of foam-core and honeycomb-core sandwich panels, using a normalizing procedure based on common properties of cellular solids and related properties of dense solids. Seven different honeycombs and closed-foam cells are discussed; of these, three are commercial Al alloy honeycombs, one is an Al-alloy foam, and two are polymeric foams. It is concluded that ideal, closed-cell foams may furnish compressive strengths which while isotropic can be fully comparable to the compressive strengths of honeycombs in the thickness direction. The shear strength of ideal closed-cell foams may be superior to the shear strength of honeycombs.

In vivo bioluminescence imaging validation of a human biopsy-derived orthotopic mouse model of glioblastoma multiforme.

PubMed

Jarzabek, Monika A; Huszthy, Peter C; Skaftnesmo, Kai O; McCormack, Emmet; Dicker, Patrick; Prehn, Jochen H M; Bjerkvig, Rolf; Byrne, Annette T

2013-05-01

Glioblastoma multiforme (GBM), the most aggressive brain malignancy, is characterized by extensive cellular proliferation, angiogenesis, and single-cell infiltration into the brain. We have previously shown that a xenograft model based on serial xenotransplantation of human biopsy spheroids in immunodeficient rodents maintains the genotype and phenotype of the original patient tumor. The present work further extends this model for optical assessment of tumor engraftment and growth using bioluminescence imaging (BLI). A method for successful lentiviral transduction of the firefly luciferase gene into multicellular spheroids was developed and implemented to generate optically active patient tumor cells. Luciferase-expressing spheroids were injected into the brains of immunodeficient mice. BLI photon counts and tumor volumes from magnetic resonance imaging (MRI) were correlated. Luciferase-expressing tumors recapitulated the histopathologic hallmarks of human GBMs and showed proliferation rates and microvessel density counts similar to those of wild-type xenografts. Moreover, we detected widespread invasion of luciferase-positive tumor cells in the mouse brains. Herein we describe a novel optically active model of GBM that closely mimics human pathology with respect to invasion, angiogenesis, and proliferation indices. The model may thus be routinely used for the assessment of novel anti-GBM therapeutic approaches implementing well-established and cost-effective optical imaging strategies.

Role of immune cells in animal models for inherited neuropathies: facts and visions.

PubMed

Mäurer, Mathias; Kobsar, Igor; Berghoff, Martin; Schmid, Christoph D; Carenini, Stefano; Martini, Rudolf

2002-04-01

Mice heterozygously deficient in the peripheral myelin adhesion molecule P0 (P0+/- mice) are models for some forms of Charcot-Marie-Tooth (CMT) neuropathies. In addition to the characteristic hallmarks of demyelination, elevated numbers of CD8-positive T-lymphocytes and F4/80-positive macrophages are striking features in the nerves of these mice. These immune cells increase in number with age and progress of demyelination, suggesting that they might be functionally related to myelin damage. In order to investigate the pathogenetic role of lymphocytes, the myelin mutants were cross-bred with recombination activating gene 1 (RAG-1)-deficient mice, which lack mature T- and B-lymphocytes. The immunodeficient myelin mutants showed a less severe myelin degeneration. The beneficial effect of lymphocyte-deficiency was reversible, since demyelination worsened in immunodeficient myelin-mutants when reconstituted with bone marrow from wild-type mice. Ultrastructural analysis revealed macrophages in close apposition to myelin and demyelinated axons. We therefore cross-bred the P0+/- mice with spontaneous osteopetrotic (op) mutants deficient in the macrophage colony-stimulating factor (M-CSF), hence displaying impaired macrophage activation. In the corresponding double mutants the numbers of macrophages were not elevated in the peripheral nerves, and the demyelinating phenotype was less severe than in the genuine P0+/- mice, demonstrating that macrophages are also functionally involved in the pathogenesis of genetically mediated demyelination. We also examined other models for inherited neuropathies for a possible involvement of immune cells. We chose mice deficient in the gap junction component connexin 32, a model for the X-linked form of CMT. Similar to P0-deficient mice, T-lymphocytes and macrophages were elevated and macrophages showed a close apposition to degenerating myelin. We conclude that the involvement of T-lymphocytes and macrophages is a common pathogenetic feature in various forms of slowly progressive inherited neuropathies.

Attenuation of endocrine-exocrine pancreatic communication in type 2 diabetes: pancreatic extracellular matrix ultrastructural abnormalities.

PubMed

Hayden, Melvin R; Patel, Kamlesh; Habibi, Javad; Gupta, Deepa; Tekwani, Seema S; Whaley-Connell, Adam; Sowers, James R

2008-01-01

Ultrastructural observations reveal a continuous interstitial matrix connection between the endocrine and exocrine pancreas, which is lost due to fibrosis in rodent models and humans with type 2 diabetes mellitus (T2DM). Widening of the islet-exocrine interface appears to result in loss of desmosomes and adherens junctions between islet and acinar cells and is associated with hypercellularity consisting of pericytes and inflammatory cells in T2DM pancreatic tissue. Organized fibrillar collagen was closely associated with pericytes, which are known to differentiate into myofibroblasts-pancreatic stellate cells. Of importance, some pericyte cellular processes traverse both the connecting islet-exocrine interface and the endoacinar interstitium of the exocrine pancreas. Loss of cellular paracrine communication and extracellular matrix remodeling fibrosis in young animal models and humans may result in a dysfunctional insulino-acinar-ductal-incretin gut hormone axis, resulting in pancreatic insufficiency and glucagon-like peptide deficiency, which are known to exist in prediabetes and overt T2DM in humans.

Attenuation of Endocrine-Exocrine Pancreatic Communication in Type 2 Diabetes: Pancreatic Extracellular Matrix Ultrastructural Abnormalities

PubMed Central

Hayden, Melvin R; Patel, Kamlesh; Habibi, Javad; Gupta, Deepa; Tekwani, Seema S.; Whaley-Connell, Adam; Sowers, James R.

2009-01-01

Ultrastructural observations reveal a continuous interstitial matrix connection between the endocrine and exocrine pancreas, which is lost due to fibrosis in rodent models and humans with type 2 diabetes mellitus (T2DM). Widening of the islet exocrine interface (IEI) appears to result in loss of desmosomes and adherens junctions between islet and acinar cells and is associated with hypercellularity consisting of pericytes and inflammatory cells in T2DM pancreatic tissue. Organized fibrillar collagen was closely associated with pericytes, which are known to differentiate into myofibroblasts – pancreatic stellate cells. Importantly, some pericyte cellular processes traverse both the connecting IEI and the endoacinar interstitium of the exocrine pancreas. Loss of cellular paracrine communication and extracellular matrix remodeling fibrosis in young animal models and humans may result in a dysfunctional insulino-acinar-ductal – incretin gut hormone axis resulting in pancreatic insufficiency and glucagon like peptide deficiency known to exist in prediabetes and overt T2DM in humans. PMID:19040593

Ceroid lipofuscinosis in the border collie dog: retinal lesions in an animal model of juvenile Batten disease.

PubMed

Taylor, R M; Farrow, B R

1992-02-15

Ceroid lipofuscinosis, an inherited disorder of lipopigment accumulation, was identified in a group of Border Collie dogs. The dogs developed mental, motor, and visual signs between age 15 and 22 months and progressed rapidly to severe neurological disease. The principal signs were blindness and gait and behavioural abnormalities with progressive dementia. Lipopigment accumulation was severe in neurones and glial cells of the central nervous system and was present in some visceral cells. Inclusions with variable ultrastructure were common in all cells of the retina, but the pigment accumulation did not damage the retinal architecture. The cytoplasmic inclusions were granular, sudanophilic, eosinophilic, and autofluorescent. Ultrastructural morphology varied, but fingerprint and curvilinear patterns predominated. The retinal lesions in the Border Collies were similar to those in English Setters with ceroid lipofuscinosis, but were much less severe than in juvenile human ceroid lipofuscinosis. This disorder bears a close resemblance to ceroid lipofuscinosis in English Setters and is another useful model for Batten's disease.

Numerical modelling of phase-change material used for PV panels cooling

NASA Astrophysics Data System (ADS)

Sellami, Assia; Elotmani, Rabie; Kandoussi, Khalid; Eljouad, Mohamed; Hajjaji, Abdelowahed; Boutaous, M'Hamed

2017-12-01

Passive cooling of a PV solar panel using phase-change material (PCM) may play an important role in increasing efficiency of PV cells. Because it does not need a maintenance and does not release greenhouses gases, PCM seems to be a good way to decrease the among of overheating of PV cell. The aims of this paper describes a detailed multiphysical issue in order to understand the effect of PCM (RT25) in keeping PV cell temperature close to ambient. The study is focused on modeling the heat and mass transfer in a PCM domain by modifying the buoyancy term in momentum equation. Due to a phase-change and free convection, transient incompressible flow is taken into account to explain the dynamic variations of the velocity profile and viscosity distribution. With standard condition of irradiation and heat flux on both sides of the PV panel, a melt front has been tracked by the energy equation, which gives a good argument for the temperature evolution during phase-change.

Systematic Applications of Metabolomics in Metabolic Engineering

PubMed Central

Dromms, Robert A.; Styczynski, Mark P.

2012-01-01

The goals of metabolic engineering are well-served by the biological information provided by metabolomics: information on how the cell is currently using its biochemical resources is perhaps one of the best ways to inform strategies to engineer a cell to produce a target compound. Using the analysis of extracellular or intracellular levels of the target compound (or a few closely related molecules) to drive metabolic engineering is quite common. However, there is surprisingly little systematic use of metabolomics datasets, which simultaneously measure hundreds of metabolites rather than just a few, for that same purpose. Here, we review the most common systematic approaches to integrating metabolite data with metabolic engineering, with emphasis on existing efforts to use whole-metabolome datasets. We then review some of the most common approaches for computational modeling of cell-wide metabolism, including constraint-based models, and discuss current computational approaches that explicitly use metabolomics data. We conclude with discussion of the broader potential of computational approaches that systematically use metabolomics data to drive metabolic engineering. PMID:24957776

CRISPR-Barcoding for Intratumor Genetic Heterogeneity Modeling and Functional Analysis of Oncogenic Driver Mutations.

PubMed

Guernet, Alexis; Mungamuri, Sathish Kumar; Cartier, Dorthe; Sachidanandam, Ravi; Jayaprakash, Anitha; Adriouch, Sahil; Vezain, Myriam; Charbonnier, Françoise; Rohkin, Guy; Coutant, Sophie; Yao, Shen; Ainani, Hassan; Alexandre, David; Tournier, Isabelle; Boyer, Olivier; Aaronson, Stuart A; Anouar, Youssef; Grumolato, Luca

2016-08-04

Intratumor genetic heterogeneity underlies the ability of tumors to evolve and adapt to different environmental conditions. Using CRISPR/Cas9 technology and specific DNA barcodes, we devised a strategy to recapitulate and trace the emergence of subpopulations of cancer cells containing a mutation of interest. We used this approach to model different mechanisms of lung cancer cell resistance to EGFR inhibitors and to assess effects of combined drug therapies. By overcoming intrinsic limitations of current approaches, CRISPR-barcoding also enables investigation of most types of genetic modifications, including repair of oncogenic driver mutations. Finally, we used highly complex barcodes inserted at a specific genome location as a means of simultaneously tracing the fates of many thousands of genetically labeled cancer cells. CRISPR-barcoding is a straightforward and highly flexible method that should greatly facilitate the functional investigation of specific mutations, in a context that closely mimics the complexity of cancer. Copyright © 2016 Elsevier Inc. All rights reserved.

Immunologic and gene expression profiles of spontaneous canine oligodendrogliomas.

PubMed

Filley, Anna; Henriquez, Mario; Bhowmik, Tanmoy; Tewari, Brij Nath; Rao, Xi; Wan, Jun; Miller, Margaret A; Liu, Yunlong; Bentley, R Timothy; Dey, Mahua

2018-05-01

Malignant glioma (MG), the most common primary brain tumor in adults, is extremely aggressive and uniformly fatal. Several treatment strategies have shown significant preclinical promise in murine models of glioma; however, none have produced meaningful clinical responses in human patients. We hypothesize that introduction of an additional preclinical animal model better approximating the complexity of human MG, particularly in interactions with host immune responses, will bridge the existing gap between these two stages of testing. Here, we characterize the immunologic landscape and gene expression profiles of spontaneous canine glioma and evaluate its potential for serving as such a translational model. RNA in situ hybridization, flowcytometry, and RNA sequencing were used to evaluate immune cell presence and gene expression in healthy and glioma-bearing canines. Similar to human MGs, canine gliomas demonstrated increased intratumoral immune cell infiltration (CD4+, CD8+ and CD4+Foxp3+ T cells). The peripheral blood of glioma-bearing dogs also contained a relatively greater proportion of CD4+Foxp3+ regulatory T cells and plasmacytoid dendritic cells. Tumors were strongly positive for PD-L1 expression and glioma-bearing animals also possessed a greater proportion of immune cells expressing the immune checkpoint receptors CTLA-4 and PD-1. Analysis of differentially expressed genes in our canine populations revealed several genetic changes paralleling those known to occur in human disease. Naturally occurring canine glioma has many characteristics closely resembling human disease, particularly with respect to genetic dysregulation and host immune responses to tumors, supporting its use as a translational model in the preclinical testing of prospective anti-glioma therapies proven successful in murine studies.

40 CFR 82.62 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-07-01

... distributes that product in interstate commerce for export from the United States. Foam Insulation Product, when used to describe a product containing or consisting of plastic foam, means a product containing or consisting of the following types of foam: (1) Closed cell rigid polyurethane foam; (2) Closed cell rigid...

40 CFR 82.62 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... distributes that product in interstate commerce for export from the United States. Foam Insulation Product, when used to describe a product containing or consisting of plastic foam, means a product containing or consisting of the following types of foam: (1) Closed cell rigid polyurethane foam; (2) Closed cell rigid...

40 CFR 82.62 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... distributes that product in interstate commerce for export from the United States. Foam Insulation Product, when used to describe a product containing or consisting of plastic foam, means a product containing or consisting of the following types of foam: (1) Closed cell rigid polyurethane foam; (2) Closed cell rigid...

40 CFR 82.62 - Definitions.

Code of Federal Regulations, 2013 CFR

2013-07-01

... distributes that product in interstate commerce for export from the United States. Foam Insulation Product, when used to describe a product containing or consisting of plastic foam, means a product containing or consisting of the following types of foam: (1) Closed cell rigid polyurethane foam; (2) Closed cell rigid...

Atmospheric pressure reaction cell for operando sum frequency generation spectroscopy of ultrahigh vacuum grown model catalysts

NASA Astrophysics Data System (ADS)

Roiaz, Matteo; Pramhaas, Verena; Li, Xia; Rameshan, Christoph; Rupprechter, Günther

2018-04-01

A new custom-designed ultrahigh vacuum (UHV) chamber coupled to a UHV and atmospheric-pressure-compatible spectroscopic and catalytic reaction cell is described, which allows us to perform IR-vis sum frequency generation (SFG) vibrational spectroscopy during catalytic (kinetic) measurements. SFG spectroscopy is an exceptional tool to study vibrational properties of surface adsorbates under operando conditions, close to those of technical catalysis. This versatile setup allows performing surface science, SFG spectroscopy, catalysis, and electrochemical investigations on model systems, including single crystals, thin films, and deposited metal nanoparticles, under well-controlled conditions of gas composition, pressure, temperature, and potential. The UHV chamber enables us to prepare the model catalysts and to analyze their surface structure and composition by low energy electron diffraction and Auger electron spectroscopy, respectively. Thereafter, a sample transfer mechanism moves samples under UHV to the spectroscopic cell, avoiding air exposure. In the catalytic cell, SFG spectroscopy and catalytic tests (reactant/product analysis by mass spectrometry or gas chromatography) are performed simultaneously. A dedicated sample manipulation stage allows the model catalysts to be examined from LN2 temperature to 1273 K, with gaseous reactants in a pressure range from UHV to atmospheric. For post-reaction analysis, the SFG cell is rapidly evacuated and samples are transferred back to the UHV chamber. The capabilities of this new setup are demonstrated by benchmark results of CO adsorption on Pt and Pd(111) single crystal surfaces and of CO adsorption and oxidation on a ZrO2 supported Pt nanoparticle model catalyst grown by atomic layer deposition.

Investigation of tissue cysts in the retina in a mouse model of ocular toxoplasmosis: distribution and interaction with glial cells.

PubMed

Song, Hyun Beom; Jung, Bong-Kwang; Kim, Jin Hyoung; Lee, Young-Ha; Choi, Min-Ho; Kim, Jeong Hun

2018-06-02

The conversion of tachyzoites into bradyzoites is a way for Toxoplasma gondii to establish a chronic and asymptomatic infection and achieve lifelong persistence in the host. The bradyzoites form tissue cysts in the retina, but not much is known about the horizontal distribution of the cysts or their interactions with glial cells in the retina. A chronic ocular toxoplasmosis model was induced by per oral administration of T. gondii Me49 strain cysts to BALB/c mice. Two months after the infection, retinas were flat-mounted and immunostained to detect cysts, ganglion cells, Müller cells, astrocytes, and microglial cells, followed by observation under fluorescence and confocal microscope. The horizontal distribution showed a rather clustered pattern, but the clusters were not restricted to certain location of the retina. Axial distribution was confined to the inner retina, mostly in ganglion cell layer or the inner plexiform layer. Both ganglion cells, a type of retinal neurons, and Müller cells, predominant retinal glial cells, could harbor cysts. The cysts were spatially separated from astrocytes, the most abundant glial cells in the ganglion cell layer, while close spatial distribution of microglial cells was observed in two thirds of retinal cysts. In this study, we demonstrated that the retinal cysts were not evenly distributed horizontally and were confined to the inner retina axially. Both neurons and one type of glial cells could harbor cysts, and topographic analysis of other glial cells suggests role of microglial cells in chronic ocular toxoplasmosis.

Formation of human hepatocyte-like cells with different cellular phenotypes by human umbilical cord blood-derived cells in the human-rat chimeras

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yan; Xiao, Dong; Zhang, Ruo-Shuang

2007-06-15

We took advantage of the proliferative and permissive environment of the developing pre-immune fetus to develop a noninjury human-rat xenograft small animal model, in which the in utero transplantation of low-density mononuclear cells (MNCs) from human umbilical cord blood (hUCB) into fetal rats at 9-11 days of gestation led to the formation of human hepatocyte-like cells (hHLCs) with different cellular phenotypes, as revealed by positive immunostaining for human-specific alpha-fetoprotein (AFP), cytokeratin 19 (CK19), cytokeratin 8 (CK8), cytokeratin 18 (CK18), and albumin (Alb), and with some animals exhibiting levels as high as 10.7% of donor-derived human cells in the recipient liver.more » More interestingly, donor-derived human cells stained positively for CD34 and CD45 in the liver of 2-month-old rat. Human hepatic differentiation appeared to partially follow the process of hepatic ontogeny, as evidenced by the expression of AFP gene at an early stage and albumin gene at a later stage. Human hepatocytes generated in this model retained functional properties of normal hepatocytes. In this xenogeneic system, the engrafted donor-derived human cells persisted in the recipient liver for at least 6 months after birth. Taken together, these findings suggest that the donor-derived human cells with different cellular phenotypes are found in the recipient liver and hHLCs hold biological activity. This humanized small animal model, which offers an in vivo environment more closely resembling the situations in human, provides an invaluable approach for in vivo investigating human stem cell behaviors, and further in vivo examining fundamental mechanisms controlling human stem cell fates in the future.« less

A discrete element model for the investigation of the geometrically nonlinear behaviour of solids

NASA Astrophysics Data System (ADS)

Ockelmann, Felix; Dinkler, Dieter

2018-07-01

A three-dimensional discrete element model for elastic solids with large deformations is presented. Therefore, an discontinuum approach is made for solids. The properties of elastic material are transferred analytically into the parameters of a discrete element model. A new and improved octahedron gap-filled face-centred cubic close packing of spheres is split into unit cells, to determine the parameters of the discrete element model. The symmetrical unit cells allow a model with equal shear components in each contact plane and fully isotropic behaviour for Poisson's ratio above 0. To validate and show the broad field of applications of the new model, the pin-pin Euler elastica is presented and investigated. The thin and sensitive structure tends to undergo large deformations and rotations with a highly geometrically nonlinear behaviour. This behaviour of the elastica can be modelled and is compared to reference solutions. Afterwards, an improved more realistic simulation of the elastica is presented which softens secondary buckling phenomena. The model is capable of simulating solids with small strains but large deformations and a strongly geometrically nonlinear behaviour, taking the shear stiffness of the material into account correctly.

The First Cell Membranes

NASA Technical Reports Server (NTRS)

Deamer, David; Dworkin, Jason P.; Sandford, Scott A.; Bernstein, Max P.; Allamandola, Louis J.

2004-01-01

Organic compounds are synthesized in the interstellar medium and can be delivered to planetary surfaces such as the early Earth, where they mix with endogenous organic mixtures. Some of these compounds are amphiphilic, having polar and non-polar groups on the same molecule. Amphiphilic compounds spontaneously self-assembly into more complex structures such as bimolecular layers, which in turn form closed membranous vesicles. The first forms of cellular life required self-assembled membranes that were likely to be available on the prebiotic Earth. Laboratory simulations show that such vesicles readily encapsulate functional macromolecules, including nucleic acids and polymerases. A goal of future investigations is to fabricate artificial cells as models of the origin of life.

Microgravity

NASA Image and Video Library

1996-06-01

The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues currently being cultured in rotating bioreactors by investigators

Microgravity

NASA Image and Video Library

1988-07-14

The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues currently being cultured in rotating bioreactors by investigators.

Bioreactor

NASA Technical Reports Server (NTRS)

1996-01-01

The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues currently being cultured in rotating bioreactors by investigators

Rotating Bioreactor

NASA Technical Reports Server (NTRS)

1988-01-01

The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues currently being cultured in rotating bioreactors by investigators.

Functional Na+ Channels in Cell Adhesion probed by Transistor Recording

PubMed Central

Schmidtner, Markus; Fromherz, Peter

2006-01-01

Cell membranes in a tissue are in close contact to each other, embedded in the extracellular matrix. Standard electrophysiological methods are not able to characterize ion channels under these conditions. Here we consider the area of cell adhesion on a solid substrate as a model system. We used HEK 293 cells cultured on fibronectin and studied the activation of NaV1.4 sodium channels in the adherent membrane with field-effect transistors in a silicon substrate. Under voltage clamp, we compared the transistor response with the whole-cell current. We observed that the extracellular voltage in the cell-chip contact was proportional to the total membrane current. The relation was calibrated by alternating-current stimulation. We found that Na+ channels are present in the area of cell adhesion on fibronectin with a functionality and a density that is indistinguishable from the free membrane. The experiment provides a basis for studying selective accumulation and depletion of ion channels in cell adhesion and also for a development of cell-based biosensoric devices and neuroelectronic systems. PMID:16227504

Establishment of a patient-derived orthotopic osteosarcoma mouse model.

PubMed

Blattmann, Claudia; Thiemann, Markus; Stenzinger, Albrecht; Roth, Eva K; Dittmar, Anne; Witt, Hendrik; Lehner, Burkhard; Renker, Eva; Jugold, Manfred; Eichwald, Viktoria; Weichert, Wilko; Huber, Peter E; Kulozik, Andreas E

2015-04-30

Osteosarcoma (OS) is the most common pediatric primary malignant bone tumor. As the prognosis for patients following standard treatment did not improve for almost three decades, functional preclinical models that closely reflect important clinical cancer characteristics are urgently needed to develop and evaluate new treatment strategies. The objective of this study was to establish an orthotopic xenotransplanted mouse model using patient-derived tumor tissue. Fresh tumor tissue from an adolescent female patient with osteosarcoma after relapse was surgically xenografted into the right tibia of 6 immunodeficient BALB/c Nu/Nu mice as well as cultured into medium. Tumor growth was serially assessed by palpation and with magnetic resonance imaging (MRI). In parallel, a primary cell line of the same tumor was established. Histology and high-resolution array-based comparative genomic hybridization (aCGH) were used to investigate both phenotypic and genotypic characteristics of different passages of human xenografts and the cell line compared to the tissue of origin. A primary OS cell line and a primary patient-derived orthotopic xenotranplanted mouse model were established. MRI analyses and histopathology demonstrated an identical architecture in the primary tumor and in the xenografts. Array-CGH analyses of the cell line and all xenografts showed highly comparable patterns of genomic progression. So far, three further primary patient-derived orthotopic xenotranplanted mouse models could be established. We report the first orthotopic OS mouse model generated by transplantation of tumor fragments directly harvested from the patient. This model represents the morphologic and genomic identity of the primary tumor and provides a preclinical platform to evaluate new treatment strategies in OS.

Microgravity

NASA Image and Video Library

1996-01-01

Close-up view of the interior of a NASA Bioreactor shows the plastic plumbing and valves (cylinders at center) to control fluid flow. A fresh nutrient bag is installed at top; a flattened waste bag behind it will fill as the nutrients are consumed during the course of operation. The drive chain and gears for the rotating wall vessel are visible at bottom center center. The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. The Bioreactor is rotated to provide gentle mixing of fresh and spent nutrient without inducing shear forces that would damage the cells. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. The work is sponsored by NASA's Office of Biological and Physical Research. The bioreactor is managed by the Biotechnology Cell Science Program at NASA's Johnson Space Center (JSC). NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues being cultured in rotating bioreactors by investigators.

NASA Bioreactor

NASA Technical Reports Server (NTRS)

1996-01-01

Close-up view of the interior of a NASA Bioreactor shows the plastic plumbing and valves (cylinders at center) to control fluid flow. A fresh nutrient bag is installed at top; a flattened waste bag behind it will fill as the nutrients are consumed during the course of operation. The drive chain and gears for the rotating wall vessel are visible at bottom center center. The NASA Bioreactor provides a low turbulence culture environment which promotes the formation of large, three-dimensional cell clusters. The Bioreactor is rotated to provide gentle mixing of fresh and spent nutrient without inducing shear forces that would damage the cells. Due to their high level of cellular organization and specialization, samples constructed in the bioreactor more closely resemble the original tumor or tissue found in the body. The work is sponsored by NASA's Office of Biological and Physical Research. The bioreactor is managed by the Biotechnology Cell Science Program at NASA's Johnson Space Center (JSC). NASA-sponsored bioreactor research has been instrumental in helping scientists to better understand normal and cancerous tissue development. In cooperation with the medical community, the bioreactor design is being used to prepare better models of human colon, prostate, breast and ovarian tumors. Cartilage, bone marrow, heart muscle, skeletal muscle, pancreatic islet cells, liver and kidney are just a few of the normal tissues being cultured in rotating bioreactors by investigators.

Comparative lipidomic analysis of synovial fluid in human and canine osteoarthritis.

PubMed

Kosinska, M K; Mastbergen, S C; Liebisch, G; Wilhelm, J; Dettmeyer, R B; Ishaque, B; Rickert, M; Schmitz, G; Lafeber, F P; Steinmeyer, J

2016-08-01

The lipid profile of synovial fluid (SF) is related to the health status of joints. The early stages of human osteoarthritis (OA) are poorly understood, which larger animals are expected to be able to model closely. This study examined whether the canine groove model of OA represents early OA in humans based on the changes in the lipid species profile in SF. Furthermore, the SF lipidomes of humans and dogs were compared to determine how closely canine lipid species profiles reflect the human lipidome. Lipids were extracted from cell- and cellular debris-free knee SF from nine donors with healthy joints, 17 patients with early and 13 patients with late osteoarthritic changes, and nine dogs with knee OA and healthy contralateral joints. Lipid species were quantified by electrospray ionization tandem mass spectrometry (ESI-MS/MS). Compared with control canine SF most lipid species were elevated in canine OA SF. Moreover, the lipid species profiles in the canine OA model resembled early OA profiles in humans. The SF lipidomes between dog and human were generally similar, with differences in certain lipid species in the phosphatidylcholine (PC), lysophosphatidylcholine (LPC) and sphingomyelin (SM) classes. Our lipidomic analysis demonstrates that SF in the canine OA model closely mimics the early osteoarthritic changes that occur in humans. Further, the canine SF lipidome often reflects normal human lipid metabolism. Copyright © 2016 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.

[3D evaluation model for drug hepatotoxicity testing on HepG2 cells and its application in drug safety evaluation].

PubMed

Li, Dan-Dan; Tang, Xiang-Lin; Tan, Hong-Ling; Liang, Qian-de; Wang, Yu-Guang; Ma, Zeng-Chun; Xiao, Cheng-Rong; Gao, Yue

2016-04-01

3D in vitro toxicity testing model was developed by magnetic levitation method for culture of the human hepatoma cell line HepG2 and applied to evaluate the drug hepatotoxicity. After formation of stable 3D structure for HepG2 cells, their glycogen storage capacity under 2D and 3D culture conditions were detected by immunohistochemistry technology, and the mRNA expression levels of phase Ⅰ and Ⅱ drug metabolism enzymes, drug transporters, nuclear receptors and liver-specific marker albumin(ALB) were compared between 2D and 3D culture conditions by using RT-PCR method. Immunohistochemistry results showed that HepG2 cells had abundant glycogen storage capacity under 3D culture conditions, which was similar to human liver tissues. The mRNA expression levels of major drug metabolism enzymes, drug transporters, nuclear receptors and ALB in HepG2 cells under 3D culture conditions were up-regulated as compared with 2D culture conditions. For drug hepatotoxicity evaluation, the typical hepatotoxic drug acetaminophen(APAP), and most reported drugs Polygonum multiflorum Thunb.(Chinese name He-shou-wu) and Psoraleae corylifolia L.(Chinese name Bu-gu-zhi) were selected for single dose and repeated dose(7 d) exposure. In the repeated dose exposure test, 3D HepG2 cells showed higher sensitivity. This established 3D HepG2 cells model with magnetic levitation 3D culture techniques was more close to the human liver tissues both in morphology and functions, so it was a better 3D hepatotoxicity evaluation model. Copyright© by the Chinese Pharmaceutical Association.

Surface enhanced Raman spectroscopy (SERS) for the discrimination of Arthrobacter strains based on variations in cell surface composition.

PubMed

Stephen, Kate E; Homrighausen, Darren; DePalma, Glen; Nakatsu, Cindy H; Irudayaraj, Joseph

2012-09-21

Surface enhanced Raman spectroscopy (SERS) is a rapid and highly sensitive spectroscopic technique that has the potential to measure chemical changes in bacterial cell surface in response to environmental changes. The objective of this study was to determine whether SERS had sufficient resolution to differentiate closely related bacteria within a genus grown on solid and liquid medium, and a single Arthrobacter strain grown in multiple chromate concentrations. Fourteen closely related Arthrobacter strains, based on their 16S rRNA gene sequences, were used in this study. After performing principal component analysis in conjunction with Linear Discriminant Analysis, we used a novel, adapted cross-validation method, which more faithfully models the classification of spectra. All fourteen strains could be classified with up to 97% accuracy. The hierarchical trees comparing SERS spectra from the liquid and solid media datasets were different. Additionally, hierarchical trees created from the Raman data were different from those obtained using 16S rRNA gene sequences (a phylogenetic measure). A single bacterial strain grown on solid media culture with three different chromate levels also showed significant spectral distinction at discrete points identified by the new Elastic Net regularized regression method demonstrating the ability of SERS to detect environmentally induced changes in cell surface composition. This study demonstrates that SERS is effective in distinguishing between a large number of very closely related Arthrobacter strains and could be a valuable tool for rapid monitoring and characterization of phenotypic variations in a single population in response to environmental conditions.

Sinusoidal voltage protocols for rapid characterisation of ion channel kinetics.

PubMed

Beattie, Kylie A; Hill, Adam P; Bardenet, Rémi; Cui, Yi; Vandenberg, Jamie I; Gavaghan, David J; de Boer, Teun P; Mirams, Gary R

2018-03-24

Ion current kinetics are commonly represented by current-voltage relationships, time constant-voltage relationships and subsequently mathematical models fitted to these. These experiments take substantial time, which means they are rarely performed in the same cell. Rather than traditional square-wave voltage clamps, we fitted a model to the current evoked by a novel sum-of-sinusoids voltage clamp that was only 8 s long. Short protocols that can be performed multiple times within a single cell will offer many new opportunities to measure how ion current kinetics are affected by changing conditions. The new model predicts the current under traditional square-wave protocols well, with better predictions of underlying currents than literature models. The current under a novel physiologically relevant series of action potential clamps is predicted extremely well. The short sinusoidal protocols allow a model to be fully fitted to individual cells, allowing us to examine cell-cell variability in current kinetics for the first time. Understanding the roles of ion currents is crucial to predict the action of pharmaceuticals and mutations in different scenarios, and thereby to guide clinical interventions in the heart, brain and other electrophysiological systems. Our ability to predict how ion currents contribute to cellular electrophysiology is in turn critically dependent on our characterisation of ion channel kinetics - the voltage-dependent rates of transition between open, closed and inactivated channel states. We present a new method for rapidly exploring and characterising ion channel kinetics, applying it to the hERG potassium channel as an example, with the aim of generating a quantitatively predictive representation of the ion current. We fitted a mathematical model to currents evoked by a novel 8 second sinusoidal voltage clamp in CHO cells overexpressing hERG1a. The model was then used to predict over 5 minutes of recordings in the same cell in response to further protocols: a series of traditional square step voltage clamps, and also a novel voltage clamp comprising a collection of physiologically relevant action potentials. We demonstrate that we can make predictive cell-specific models that outperform the use of averaged data from a number of different cells, and thereby examine which changes in gating are responsible for cell-cell variability in current kinetics. Our technique allows rapid collection of consistent and high quality data, from single cells, and produces more predictive mathematical ion channel models than traditional approaches. © 2018 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society.

40 CFR 82.62 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-07-01

... consisting of the following types of foam: (1) Closed cell rigid polyurethane foam; (2) Closed cell rigid... identification numbers: (1) A federal employer identification number; (2) A state sales tax exemption number; (3... means: (1) The seller of a product to a consumer or another distributor; or (2) A person who sells or...

Genetically modified yeast of the species Issatchenkia orientalis and closely relates species, and fermentation processes using same

DOEpatents

Suominen, Pirkko [Maple Grove, MN; Aristidou, Aristos [Highland Ranch, CO; Pentilla, Merja [Helsinki, FI; Ilmen, Marja [Helsinki, FI; Ruohonen, Laura [Helsinki, FI; Koivuranta, Kari [Vantaa, FI; Roberg-Perez, Kevin [Minneapolis, MN

2012-01-17

Cells of the species Issatchenkia orientalis and closely related yeast species are transformed with a vector to introduce an exogenous lactate dehydrogenase gene. The cells produce lactic acid efficiently and are resistant at low pH, high lactate titer conditions.

Acute exposure of mercury chloride stimulates the tissue regeneration program and reactive oxygen species production in the Drosophila midgut.

PubMed

Chen, Zhi; Wu, Xiaochun; Luo, Hongjie; Zhao, Lingling; Ji, Xin; Qiao, Xianfeng; Jin, Yaping; Liu, Wei

2016-01-01

We used Drosophila as an animal model to study the digestive tract in response to the exposure of inorganic mercury (HgCl2). We found that after oral administration, mercury was mainly sequestered within the midgut. This resulted in increased cell death, which in turn stimulated the tissue regeneration program, including accelerated proliferation and differentiation of the intestinal stem cells (ISCs). We further demonstrated that these injuries correlate closely with the excessive production of the reactive oxygen species (ROS), as vitamin E, an antioxidant reagent, efficiently suppressed the HgCl2-induced phenotypes of midgut and improved the viability. We propose that the Drosophila midgut could serve as a suitable model to study the treatment of acute hydrargyrism on the digestive systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Error catastrophe and phase transition in the empirical fitness landscape of HIV

NASA Astrophysics Data System (ADS)

Hart, Gregory R.; Ferguson, Andrew L.

2015-03-01

We have translated clinical sequence databases of the p6 HIV protein into an empirical fitness landscape quantifying viral replicative capacity as a function of the amino acid sequence. We show that the viral population resides close to a phase transition in sequence space corresponding to an "error catastrophe" beyond which there is lethal accumulation of mutations. Our model predicts that the phase transition may be induced by drug therapies that elevate the mutation rate, or by forcing mutations at particular amino acids. Applying immune pressure to any combination of killer T-cell targets cannot induce the transition, providing a rationale for why the viral protein can exist close to the error catastrophe without sustaining fatal fitness penalties due to adaptive immunity.

The evaporative function of cockroach hygroreceptors.

PubMed

Tichy, Harald; Kallina, Wolfgang

2013-01-01

Insect hygroreceptors associate as antagonistic pairs of a moist cell and a dry cell together with a cold cell in small cuticular sensilla on the antennae. The mechanisms by which the atmospheric humidity stimulates the hygroreceptive cells remain elusive. Three models for humidity transduction have been proposed in which hygroreceptors operate either as mechanical hygrometers, evaporation detectors or psychrometers. Mechanical hygrometers are assumed to respond to the relative humidity, evaporation detectors to the saturation deficit and psychrometers to the temperature depression (the difference between wet-bulb and dry-bulb temperatures). The models refer to different ways of expressing humidity. This also means, however, that at different temperatures these different types of hygroreceptors indicate very different humidity conditions. The present study tested the adequacy of the three models on the cockroach's moist and dry cells by determining whether the specific predictions about the temperature-dependence of the humidity responses are indeed observed. While in previous studies stimulation consisted of rapid step-like humidity changes, here we changed humidity slowly and continuously up and down in a sinusoidal fashion. The low rates of change made it possible to measure instantaneous humidity values based on UV-absorption and to assign these values to the hygroreceptive sensillum. The moist cell fitted neither the mechanical hygrometer nor the evaporation detector model: the temperature dependence of its humidity responses could not be attributed to relative humidity or to saturation deficit, respectively. The psychrometer model, however, was verified by the close relationships of the moist cell's response with the wet-bulb temperature and the dry cell's response with the dry-bulb temperature. Thus, the hygroreceptors respond to evaporation and the resulting cooling due to the wetness or dryness of the air. The drier the ambient air (absolutely) and the higher the temperature, the greater the evaporative temperature depression and the power to desiccate.

In vitro osteogenesis of human stem cells by using a three-dimensional perfusion bioreactor culture system: a review.

PubMed

Ceccarelli, Gabriele; Bloise, Nora; Vercellino, Marco; Battaglia, Rosalia; Morgante, Lucia; De Angelis, Maria Gabriella Cusella; Imbriani, Marcello; Visai, Livia

2013-04-01

Tissue engineering (by culturing cells on appropriate scaffolds, and using bioreactors to drive the correct bone structure formation) is an attractive alternative to bone grafting or implantation of bone substitutes. Osteogenesis is a biological process that involves many molecular intracellular pathways organized to optimize bone modeling. The use of bioreactor systems and especially the perfusion bioreactor, provides both the technological means to reveal fundamental mechanisms of cell function in a 3D environment, and the potential to improve the quality of engineered tissues. In this mini-review all the characteristics for the production of an appropriate bone construct are analyzed: the stem cell source, scaffolds useful for the seeding of pre-osteoblastic cells and the effects of fluid flow on differentiation and proliferation of bone precursor cells. By automating and standardizing tissue manufacture in controlled closed systems, engineered tissues may reduce the gap between the process of bone formation in vitro and subsequent graft of bone substitutes in vivo.