Página 7 dos resultados de 6914 itens digitais encontrados em 0.018 segundos

‣ Processing and characterization of dual phase steel foam

Gruttadauria,A.; Mombelli,Davide; Castrodeza,E. M.; Mapelli,C.
Fonte: Rede Latino-Americana de Materiais Publicador: Rede Latino-Americana de Materiais
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2010 Português
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Porous materials featuring cellular structures are known to have many interesting combinations of physical and mechanical properties. Some of them have been extensively used in the transportation field (i.e. balsa wood). Steel foams presented promising theoretical properties for both functional and structural applications in transportation, but processing of such a kind of foams is complex due to their high melting point. Recently a technique for processing Cu-based alloys open-cell foams through the molten metal infiltration of a leachable bed of amorphous SiO2 particles was proposed. A variation of the proposed technique that uses SiC particles as space holder is now presented and was recently successfully applied for dual phase steel foam processing. Results from a processing of dual phase DP500 steel foams, including some morphological, micro-structural and mechanical characterization, are here presented.

‣ Alphaherpesvirus Proteins Related to Herpes Simplex Virus Type 1 ICP0 Affect Cellular Structures and Proteins

Parkinson, Jane; Everett, Roger D.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /11/2000 Português
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The herpes simplex virus type 1 (HSV-1) immediate-early protein ICP0 interacts with several cellular proteins and induces the proteasome-dependent degradation of others during infection. In this study we show that ICP0 is required for the proteasome-dependent degradation of the ND10 protein Sp100 and, as with the other target proteins, the ICP0 RING finger domain is essential. Further, comparison of the kinetics and ICP0 domain requirements for the degradation of PMI and Sp100 suggests that a common mechanism is involved. Homologues of ICP0 are encoded by other members of the alphaherpesvirus family. These proteins show strong sequence homology to ICP0 within the RING finger domain but limited similarity elsewhere. Using transfection assays, we have shown that all the ICP0 homologues that we tested have significant effects on the immunofluorescence staining character of at least one of the proteins destabilized by ICP0, and by using a recombinant virus, we found that the equine herpesvirus ICP0 homologue induced the proteasome-dependent degradation of endogenous CENP-C and modified forms of PML and Sp100. However, in contrast to ICP0, the homologue proteins had no effect on the distribution of the ubiquitin-specific protease USP7 within the cell...

‣ Effects of diffusible products of peroxidation of rat liver microsomal lipids

Benedetti, Angelo; Casini, Alessandro F.; Ferrali, Marco; Comporti, Mario
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/05/1979 Português
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The effects on cellular structures of products of peroxidation of rat liver microsomal lipids were investigated. A system containing actively peroxidizing liver microsomal fraction was separated from a revealing or target system by a dialysis membrane. The target system, contained in the dialysis tube, consisted of either intact cells (erythrocytes) or subcellular fractions (liver microsomal fraction). When liver microsomal fractions were incubated with NADPH (or an NADPH-generating system), lipid peroxidation, as measured by the amount of malonaldehyde formed, occurred very rapidly. The malon-aldehyde concentration tended to equilibrate across the dialysis membrane. When the target system consisted of erythrocytes, haemolysis occurred abruptly after a lag phase. The lysis was greatly accelerated when erythrocytes from vitamin E-deficient rats were used, but no haemolysis was observed when erythrocytes from vitamin E-treated rats were used. When, in the same system, freshly prepared liver microsomal fractions were exposed to diffusible factors produced by lipid peroxidation, the glucose 6-phosphatase activity markedly decreased. A similar decrease in glucose 6-phosphatase activity, as well as a smaller but significant decrease in cytochrome P-450...

‣ The isolation and subfractionation of plasma membrane from the cellular slime mould Dictyostelium discoideum

Green, Anita A.; Newell, Peter C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /05/1974 Português
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A procedure for the isolation and separation of three different subfractions of plasma membrane from the cellular slime mould Dictyostelium discoideum is described. The cells were disrupted by freeze-thawing in liquid N2 and plasma membranes were purified by equilibrium centrifugation in a sucrose gradient. The cell surface was labelled with radioactive iodide by using the lactoperoxidase iodination method. Alkaline phosphatase was identified as a plasma-membrane marker by its co-distribution with [125I]iodide. 5′-Nucleotidase, which has been widely described as a plasma-membrane marker enzyme in mammalian tissues, was not localized to any marked extent in D. discoideum plasma membrane. The isolated plasma membranes showed a 24-fold enrichment of alkaline phosphatase specific activity relative to the homogenate and a yield of 50% of the total plasma membranes. Determination of succinate dehydrogenase and NADPH–cytochrome c reductase activities indicated that the preparation contained 2% of the total mitochondria and 3% of the endoplasmic reticulum. When the plasma-membrane preparation was further disrupted in a tight-fitting homogenizer, three plasma-membrane subfractions of different densities were obtained by isopycnic centrifugation. The enrichment of alkaline phosphatase was greatest in the subfraction with the lowest density. This fraction was enriched 36-fold relative to the homogenate and contained 19% of the total alkaline phosphatase activity but only 0.08% of the succinate dehydrogenase activity and 0.34% of the NADPH–cytochrome c reductase activity. Electron microscopy of this fraction showed it to consist of smooth membrane vesicles with no recognizable contaminants.

‣ Voltage-dependent activation of potassium current in Helix neurones by endogenous cellular calcium.

Akaike, N; Brown, A M; Dahl, G; Higashi, H; Isenberg, G; Tsuda, Y; Yatani, A
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /01/1983 Português
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1. The effect of endogenous Ca on potential-dependent K current IKD, was examined in identifiable neurones of Helix aspersa. The suction pipette method of internal perfusion was used along with a combined voltage-clamp method in which the membrane potential was measured by a separate glass micro-electrode and the current was passed by the suction pipette. Activation of the potential-dependent A current, IA, was prevented by using holding potentials of -40 mV where IA is inactivated and by the addition of the A-current blocker 4-aminopyridine. Activation of K currents by transmembrane Ca current, IKCa, was suppressed by Co substitution for Ca ion extracellularly. 2. Under these conditions, IKD rose to a peak value and then subsided to a steady level. The current-voltage (I-V) relationship for peak IKD had an upward bump at about +50 mV that gave it an S-shape. The I-V curve for steady IKD rose continuously. Peak and steady IKD were reduced by perfusing with EGTA or F ions intracellularly. The EGTA effect occurred at intracellular Ca activity levels below 10(-7) M. Increases in the concentration of EGTAi at constant Cai had no additional effect; however, recovery experiments do not allow us to rule out some direct action of EGTA on IKD. 3. Prolonged extracellular perfusion with Co-substituted solutions also reduced IKD and the effects occurred more quickly when the solutions were made hypertonic or caffeine was added to them. The peak transient was abolished...

‣ Interactions between glycolytic enzymes and components of the cytomatrix

Masters, C.
Fonte: The Rockefeller University Press Publicador: The Rockefeller University Press
Tipo: Artigo de Revista Científica
Publicado em 01/07/1984 Português
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Evidence is provided that enzymes absorb to cellular structures in a wide range of tissues. In particular, the interactions between glycolytic enzymes and the microfilaments of the cytoplasm are described. The relevance of these interactions to the compartmentation of carbohydrate metabolism is discussed. Examples are given of the variations in degree of binding during alteration of tissue metabolism and, for individual glycolytic enzymes, during fetal development and differentiation. Overall, these data support the concept that metabolic activities in the cytoplasm have an organized structure. Just as the structural elements of the cytosolic compartment have evolved with the capacity to assemble and disassemble in response to the changing requirements of the organism, so the metabolic elements appear to have evolved a parallel system that provides for the appropriate positioning of an energy-producing sequence in relation to the specific, dynamic requirements of the cytoskeleton.

‣ Cellular Proteins PML and Daxx Mediate an Innate Antiviral Defense Antagonized by the Adenovirus E4 ORF3 Protein▿

Ullman, Amanda J.; Hearing, Patrick
Fonte: American Society for Microbiology (ASM) Publicador: American Society for Microbiology (ASM)
Tipo: Artigo de Revista Científica
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The adenovirus (Ad) E4 ORF3 protein is both necessary and sufficient to reorganize a nuclear subdomain, the PML nuclear body (PML-NB), from punctate structures into elongated nuclear tracks. PML-NB disruption is recapitulated by a variety of DNA viruses that encode proteins responsible for compromising PML-NB integrity through different mechanisms. PML-NB disruption has been correlated with the antagonism of both innate and intrinsic immune responses. The E4 ORF3 protein is required for adenoviral DNA replication in the interferon (IFN)-induced antiviral state. This may reflect the fact that PML itself, in addition to several other PML-NB proteins, is encoded by an interferon-stimulated gene. Here, we demonstrate that reorganization of the PML-NB by E4 ORF3 antagonizes an innate antiviral response mediated by both PML and Daxx. Reduction of either of these proteins is sufficient to restore the replicative capacity of virus with the E4 ORF3 protein deleted in the IFN-induced antiviral state. Further, we provide evidence that both the HSV1 ICP0 and HCMV IE1 proteins, which disrupt PML-NBs by mechanistically distinct strategies, behave in a manner functionally analogous to E4 ORF3 with respect to antagonizing the IFN-induced antiviral state. In addition...

‣ A Novel Arabidopsis Vacuolar Glucose Exporter Is Involved in Cellular Sugar Homeostasis and Affects the Composition of Seed Storage Compounds1[W][OA]

Poschet, Gernot; Hannich, Barbara; Raab, Sabine; Jungkunz, Isabel; Klemens, Patrick A.W.; Krueger, Stephan; Wic, Stefan; Neuhaus, H. Ekkehard; Büttner, Michael
Fonte: American Society of Plant Biologists Publicador: American Society of Plant Biologists
Tipo: Artigo de Revista Científica
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Subcellular sugar partitioning in plants is strongly regulated in response to developmental cues and changes in external conditions. Besides transitory starch, the vacuolar sugars represent a highly dynamic pool of instantly accessible metabolites that serve as energy source and osmoprotectant. Here, we present the molecular identification and functional characterization of the vacuolar glucose (Glc) exporter Arabidopsis (Arabidopsis thaliana) Early Responsive to Dehydration-Like6 (AtERDL6). We demonstrate tonoplast localization of AtERDL6 in plants. In Arabidopsis, AtERDL6 expression is induced in response to factors that activate vacuolar Glc pools, like darkness, heat stress, and wounding. On the other hand, AtERDL6 transcript levels drop during conditions that trigger Glc accumulation in the vacuole, like cold stress and external sugar supply. Accordingly, sugar analyses revealed that Aterdl6 mutants have elevated vacuolar Glc levels and that Glc flux across the tonoplast is impaired under stress conditions. Interestingly, overexpressor lines indicated a very similar function for the ERDL6 ortholog Integral Membrane Protein from sugar beet (Beta vulgaris). Aterdl6 mutant plants display increased sensitivity against external Glc...

‣ Formin’ cellular structures: Physiological roles of Diaphanous (Dia) in actin dynamics

Bogdan, Sven; Schultz, Jörg; Grosshans, Jörg
Fonte: Landes Bioscience Publicador: Landes Bioscience
Tipo: Artigo de Revista Científica
Publicado em 08/01/2014 Português
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Members of the Diaphanous (Dia) protein family are key regulators of fundamental actin driven cellular processes, which are conserved from yeast to humans. Researchers have uncovered diverse physiological roles in cell morphology, cell motility, cell polarity, and cell division, which are involved in shaping cells into tissues and organs. The identification of numerous binding partners led to substantial progress in our understanding of the differential functions of Dia proteins. Genetic approaches and new microscopy techniques allow important new insights into their localization, activity, and molecular principles of regulation.

‣ Incisive Imaging and Computation for Cellular Mysteries: Lessons from Abscission

Elia, Natalie; Ott, Carolyn; Lippincott-Schwartz, Jennifer
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 05/12/2013 Português
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The final cleavage event that terminates cell division, abscission of the small, dense intercellular bridge, has been particularly challenging to resolve. Here, we describe imaging innovations that helped answer long-standing questions about the mechanism of abscission. We further explain how computational modeling of high-resolution data was employed to test hypotheses and generate additional insights. We present the model that emerges from application of these complimentary approaches. Similar experimental strategies will undoubtedly reveal exciting details about other underresolved cellular structures.

‣ Live Imaging of Mitosomes and Hydrogenosomes by HaloTag Technology

Martincová, Eva; Voleman, Luboš; Najdrová, Vladimíra; De Napoli, Maximiliano; Eshar, Shiri; Gualdron, Melisa; Hopp, Christine S.; Sanin, David E.; Tembo, Dumizulu L.; Walker, Dawn; Marcinčiková, Michaela; Tachezy, Jan; Doležal, Pavel; Van Tyne, Dar
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
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Hydrogenosomes and mitosomes represent remarkable mitochondrial adaptations in the anaerobic parasitic protists such as Trichomonas vaginalis and Giardia intestinalis, respectively. In order to provide a tool to study these organelles in the live cells, the HaloTag was fused to G. intestinalis IscU and T. vaginalis frataxin and expressed in the mitosomes and hydrogenosomes, respectively. The incubation of the parasites with the fluorescent Halo-ligand resulted in highly specific organellar labeling, allowing live imaging of the organelles. With the array of available ligands the HaloTag technology offers a new tool to study the dynamics of mitochondria-related compartments as well as other cellular components in these intriguing unicellular eukaryotes.

‣ Gas2l3, a Novel Constriction Site-Associated Protein Whose Regulation Is Mediated by the (APC/C^{Cdh1}) Complex

Pe’er, Tal; Lahmi, Roxane; Sharaby, Yaara; Chorni, Evelin; Noach, Meirav; Vecsler, Manuela; Zlotorynski, Eitan; Steen, Hanno; Steen, Judith A.; Tzur, Amit
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
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Growth arrest-specific 2-like protein 3 (Gas2l3) was recently identified as an Actin/Tubulin cross-linker protein that regulates cytokinesis. Using cell-free systems from both frog eggs and human cells, we show that the Gas2l3 protein is targeted for ubiquitin-mediated proteolysis by the (APC/C^{Cdh1}) complex, but not by the (APC/C^{Cdc20}) complex, and is phosphorylated by Cdk1 in mitosis. Moreover, late in cytokinesis, Gas2l3 is exclusively localized to the constriction sites, which are the narrowest parts of the intercellular bridge connecting the two daughter cells. Overexpression of Gas2l3 specifically interferes with cell abscission, which is the final stage of cell division, when the cutting of the intercellular bridge at the constriction sites occurs. We therefore suggest that Gas2l3 is part of the cellular mechanism that terminates cell division.

‣ Cellular building components : investigation into parametric modeling and production logics

Austin, Charles B., M. Arch. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 86 p.; 5399114 bytes; 5403031 bytes; application/pdf; application/pdf
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Recent advances in digital fabrication technologies have sparked a renewed interest in topology and biological form. The ability to design and prototype structural forms inspired by nature has challenged architects preconceived notions of space and form. With the assistance of parametric modeling and rapid prototyping we now not only have the ability to physically generate complex forms, but also the ability to create a seemingly infinite number of formal variations. As a result, this has caused architects to push toward new spatial concepts. Among these new spatial concepts are those that seek to create entire building systems out of a single material solution. Inspiration for such systems can be found by studying organic cellular structures. Unlike the component based design processes of most architects, in which multiple problems are solved through multiple material solutions, natural systems tend to create solutions that solve multiple problems through one material solution. This thesis is interested in answering the question, "Is it possible to create a building system (both structure and enclosure) out of a single adaptable building unit?" Furthermore, can the building unit also be capable of transforming from being either permeable to impermeable? If so...

‣ Meriolins (3-(pyrimidin-4-yl)-7-azaindoles): synthesis, kinase inhibitory activity, cellular effects, and structure of a CDK2/cyclin A/Meriolin complex

Echalier, A.; Bettayeb, K.; Ferandin, Y.; Lozach, O.; Clement, M.; Valette, A.; Liger, F.; Marquet, B.; Morris, J.; Endicott, J.; Joseph, B.; Meijer, L.
Fonte: Amer Chemical Soc Publicador: Amer Chemical Soc
Tipo: Artigo de Revista Científica
Publicado em //2008 Português
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We report the synthesis and biological characterization of 3-(pyrimidin-4-yl)-7-azaindoles (meriolins), a chemical hybrid between the natural products meridianins and variolins, derived from marine organisms. Meriolins display potent inhibitory activities toward cyclin-dependent kinases (CDKs) and, to a lesser extent, other kinases (GSK-3, DYRK1A). The crystal structures of 1e (meriolin 5) and variolin B (Bettayeb, K.; Tirado, O. M.; Marionneau-Lambert, S.; Ferandin, Y.; Lozach, O.; Morris, J.; Mateo-Lozano, S.; Drückes, P.; Schächtele, C.; Kubbutat, M.; Liger, F.; Marquet, B.; Joseph, B.; Echalier, A.; Endicott, J.; Notario, V.; Meijer, L. Cancer Res. 2007, 67, 8325−8334) in complex with CDK2/cyclin A reveal that the two inhibitors are orientated in very different ways inside the ATP-binding pocket of the kinase. A structure−activity relationship provides further insight into the molecular mechanism of action of this family of kinase inhibitors. Meriolins are also potent antiproliferative and proapoptotic agents in cells cultured either as monolayers or in spheroids. Proapoptotic efficacy of meriolins correlates best with their CDK2 and CDK9 inhibitory activity. Meriolins thus constitute a promising class of pharmacological agents to be further evaluated against the numerous human diseases that imply abnormal regulation of CDKs including cancers...

‣ Structural Relationships and Cellular Tropism of Staphylococcal Superantigen-Like Proteins

Al-Shangiti, Ali M.; Naylor, Claire E.; Nair, Sean P.; Briggs, David C.; Henderson, Brian; Chain, Benjamin M.
Fonte: American Society for Microbiology Publicador: American Society for Microbiology
Tipo: Artigo de Revista Científica
Publicado em /07/2004 Português
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The staphylococcal superantigen-like proteins (SSLs) are a family of polymorphic paralogs encoded in the Staphylococcus aureus genome whose function is unknown. The crystal structure of SSL7 was determined and compared to that of SSL5 and that of a classical superantigen, streptococcal pyrogenic exotoxin. Although the overall architecture of the superantigen family is retained in both SSL7 and SSL5, there are significant differences in the structures which suggest that the characteristic major histocompatibility complex binding site of superantigens has been lost. To complement these data, the abilities of SSL7 and a closely related paralog, SSL9, to interact with cells of the immune system were investigated. In populations of human white blood cells, both SSLs interacted selectively with monocytes via specific saturable but separate binding sites, which led to rapid uptake of the SSLs. In addition, SSLs were rapidly taken up by dendritic cells, but not by macrophages, into the same endosomal compartment as dextran. The ability of these secreted proteins to target antigen-presenting cells may enhance a misplaced antibody response against the proteins, which may facilitate bacterial colonization rather than contribute to host protection. Like classical superantigens...

‣ Statistical properties and shell analysis in random cellular structures

Aste, T.; Szeto, K. Y.; Tam, W. Y.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/12/1996 Português
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We investigate the statistical properties of two dimensional random cellular systems (froths) in term of their shell structure. The froth is analyzed as a system of concentric layers of cells around a given central cell. We derive exact analytical relations for the topological properties of the sets of cells belonging to these layers. Experimental observations of the shell structure of two-dimensional soap froth are made and compared with the results on two kinds of Voronoi constructions. It is found that there are specific differences between soap froths and purely geometrical constructions. In particular these systems differ in the topological charge of clusters as a function of shell number, in the asymptotic values of defect concentrations, and in the number of cells in a given layer. We derive approximate expressions with no free parameters which correctly explain these different behaviors.; Comment: 23 Pages Postscript, 4 figures

‣ Complexity Measures from Interaction Structures

Kahle, Thomas; Olbrich, Eckehard; Jost, Juergen; Ay, Nihat
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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We evaluate new complexity measures on the symbolic dynamics of coupled tent maps and cellular automata. These measures quantify complexity in terms of $k$-th order statistical dependencies that cannot be reduced to interactions between $k-1$ units. We demonstrate that these measures are able to identify complex dynamical regimes.; Comment: 11 pages, figures improved, minor changes to the text

‣ Magnetic spin imaging under ambient conditions with sub-cellular resolution

Steinert, S.; Ziem, F.; Hall, L.; Zappe, A.; Schweikert, M.; Aird, A.; Balasubramanian, G.; Hollenberg, L.; Wrachtrup, J.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 14/11/2012 Português
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Measuring spins is the corner stone of a variety of analytical techniques including modern magnetic resonance imaging (MRI). The full potential of spin imaging and sensing across length scales is hindered by the achievable signal-to-noise in inductive detection schemes. Here we show that a proximal Nitrogen-Vacancy (NV) ensemble serves as a precision sensing array. Monitoring its quantum relaxation enables sensing of freely diffusing and unperturbed magnetic ions in a microfluidic device. Multiplexed CCD acquisition and an optimized detection scheme enable direct spin noise imaging under ambient conditions with experimental sensitivities down to 1000 statistically polarized spins, of which only 35 ions contribute to a net magnetization, and 20 s acquisition time. We also demonstrate imaging of spin labeled cellular structures with spatial resolutions below 500 nm. Our study marks a major step towards sub-{\mu}m imaging magnetometry and applications in microanalytics, material and life sciences.; Comment: 11 pages, 4 figures

‣ Geometric partition functions of cellular systems: Explicit calculation of the entropy in two and three dimensions

Blumenfeld, Raphael; Edwards, Sam F.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 22/11/2005 Português
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A method is proposed for the characterisation of the entropy of cellular structures, based on the compactivity concept for granular packings. Hamiltonian-like volume functions are constructed both in two and in three dimensions, enabling the identification of a phase space and making it possible to take account of geometrical correlations systematically. Case studies are presented for which explicit calculations of the mean vertex density and porosity fluctuations are given as functions of compactivity. The formalism applies equally well to two- and three-dimensional granular assemblies.; Comment: 14 pages, 4 figures, to appear in The European Physical Journal E - Soft Matter

‣ A local strategy for cleaning expanding cellular domains by simple robots

Klein, Rolf; Kriesel, David; Langetepe, Elmar
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/02/2015 Português
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We present a strategy SEP for finite state machines tasked with cleaning a cellular environment in which a contamination spreads. Initially, the contaminated area is of height $h$ and width $w$. It may be bounded by four monotonic chains, and contain rectangular holes. The robot does not know the initial contamination, sensing only the eight cells in its neighborhood. It moves from cell to cell, $d$ times faster than the contamination spreads, and is able to clean its current cell. A speed of $d<\sqrt{2}(h+w)$ is in general not sufficient to contain the contamination. Our strategy SEP succeeds if $d \geq 3(h+w)$ holds. It ensures that the contaminated cells stay connected. Greedy strategies violating this principle need speed at least $d \geq 4(h+w)$; all bounds are up to small additive constants.