Search results for "Biophysic"
showing 10 items of 3565 documents
Critical behavior of a tumor growth model: directed percolation with a mean-field flavor.
2012
We examine the critical behaviour of a lattice model of tumor growth where supplied nutrients are correlated with the distribution of tumor cells. Our results support the previous report (Ferreira et al., Phys. Rev. E 85, 010901 (2012)), which suggested that the critical behaviour of the model differs from the expected Directed Percolation (DP) universality class. Surprisingly, only some of the critical exponents (beta, alpha, nu_perp, and z) take non-DP values while some others (beta', nu_||, and spreading-dynamics exponents Theta, delta, z') remain very close to their DP counterparts. The obtained exponents satisfy the scaling relations beta=alpha*nu_||, beta'=delta*nu_||, and the general…
Fluctuation Methods To Study Protein Aggregation in Live Cells: Concanavalin A Oligomers Formation
2011
Prefibrillar oligomers of proteins are suspected to be the primary pathogenic agents in several neurodegenerative diseases. A key approach for elucidating the pathogenic mechanisms is to probe the existence of oligomers directly in living cells. In this work, we were able to monitor the process of aggregation of Concanavalin A in live cells. We used number and brightness analysis, two-color cross number and brightness analysis, and Raster image correlation spectroscopy to obtain the number of molecules, aggregation state, and diffusion coefficient as a function of time and cell location. We observed that binding of Concanavalin A to the membrane and the formation of small aggregates paralle…
pRb suppresses camptothecin-induced apoptosis in human osteosarcoma Saos-2 cells by inhibiting c-Jun N-terminal kinase
2001
AbstractThis paper studies the cytotoxic effect induced by the topoisomerase I inhibitor camptothecin in human osteosarcoma Saos-2 cells, which lack p53 and contain a non-functional form of the product of the retinoblastoma gene, pRb. Cytotoxicity induced by camptothecin was dose- and time-dependent; the treatment with 100 nM camptothecin reduced cell viability by 50% at 32 h and by 75% at 72 h of exposure. The cytotoxic effect was caused by apoptosis, as ascertained by morphological evidence, acridine orange-ethidium bromide staining and flow cytometric analysis. Apoptosis was accompanied by both the activation of caspase-3 and the fragmentation of poly(ADP-ribose) polymerase. Treatment wi…
Species-specific aggregation factor in sponges V. Influence on programmed syntheses
1976
Isolated cells from the siliceous sponge Geodia cydonium as well as small primary aggregates (diameter: 70 mum) consisting of them show no increase in rates of programmed syntheses and mitotic activity with time. After addition of a highly purified aggregation factor to a culture with primary aggregates which subsequently form secondary aggregates (diameter: larger than 1000 mum), a dramatic increase of DNA, RNA and protein synthesis occurs. Together with this increase, the cells show a high mitotic activity. The values for the mitotic coefficient reach a first maximum 8 h after the beginning of the secondary aggregation process. The stimulation of the mitotic activity of cells during the a…
Promotion of osteogenic cell response using quasicovalent immobilized fibronectin on titanium surfaces: introduction of a novel biomimetic layer syst…
2012
Purpose Despite the undeniable potential of cell adhesion molecules such as fibronectin to support osteogenic cell responses and consecutive dental implant healing, the most beneficial mode of application onto titanium implant surfaces still requires investigation. Unspecific fibronectin adsorption on titanium dioxide (TiO2) surfaces can result in low-loading, high-desorption rates and protein–metal interactions with impaired biologic activity. The aim of the present study was to monitor the osteogenic cell responses (cell adhesion, proliferation, and differentiation) specifically to fibronectin biofunctionalized TiO2. Materials and Methods An innovative biomimetic streptavidin-biotin layer…
72/74As-labeling of HPMA based polymers for long-term in vivo PET imaging
2010
Abstract In the context of molecular imaging, various polymers based on the clinically approved N-(2-hydroxypropyl)-methacrylamide (HPMA) have been radio-labeled using longer-living positron emitters 72As t1/2 = 26 h or 74As t1/2 = 17.8 d. This approach may lead to non-invasive determination of the long-term in vivo fate of polymers by PET (positron emission tomography). Presumably, the radio label itself will not strongly influence the polymer structure due to the fact that the used nuclide binds to already existing thiol moieties within the polymer structure. Thus, the use of additional charges or bulky groups can be avoided.
Inter-Model Consistency and Complementarity: Learning from ex-vivo Imaging and Electrophysiological Data towards an Integrated Understanding of Cardi…
2011
International audience; Computational models of the heart at various scales and levels of complexity have been independently developed, parameterised and validated using a wide range of experimental data for over four decades. However, despite remarkable progress, the lack of coordinated efforts to compare and combine these computational models has limited their impact on the numerous open questions in cardiac physiology. To address this issue, a comprehensive dataset has previously been made available to the community that contains the cardiac anatomy and fibre orientations from magnetic resonance imaging as well as epicardial transmembrane potentials from optical mapping measured on a per…
Concurrent fast and slow synchronized efferent phrenic activities in time and frequency domain.
1990
Abstract In urethane-anesthetized or decerebrated vagotomized rabbits efferent multifiber activity of the phrenic nerve was investigated for synchronized activities both in time and frequency domains. When respiratory drive was steadily increased by either an elevation of end-tidal CO2 concentration or i.v. administration of 4-aminopyridine, medium-frequency oscillations (MFO) first increased, then decreased and finally became absent. The power of high-frequency oscillations (HFO) steadily rose with increasing respiratory drive. In contrast to HFO which revealed a unimodal spectral peak of mostly small bandwidth, the MFO spectrum in most cases consisted of a broad complex. This complex in s…
Constitutive hsp70 is essential to mitosis during early cleavage of Paracentrotus lividus embryos: The blockage of constitutive hsp70 impairs mitosis
1999
Localization of constitutive hsp70 in eggs and early embryos of sea urchin Paracentrotus lividus is shown by means of in situ immunostaining. An accumulation of this protein is shown in the mitotic structures (asters, spindles and centrosomes). Microinjection of anti-hsp70 antibodies into eggs causes impairment of formation of mitotic structures and of cell division. This impairment goes from a complete mitotic block, to irregular mitotic apparatus formation with irregular cleavage, depending upon the antibody concentration. The localization of hsp70 after antibody microinjection is also described. Blockage of mitotic apparatus formation by nocodazole also blocks the concentration of hsp70 …
The effect of long-chain bases on polysialic acid-mediated membrane interactions
2011
AbstractNegatively-charged polysialic acid (polySia) chains are usually membrane-bound and are often expressed on the surface of neuroinvasive bacterial cells, neural cells, and tumor cells. PolySia can mediate both repulsive and attractive cis interactions between membrane components, and trans interactions between membranes. Positively-charged long-chain bases are widely present in cells, are often localized in membranes and can function as bioactive lipids. Here we use Langmuir monolayer technique, fluorescence spectroscopy and electron microscopy of lipid vesicles to study the role of a simple long-chain base, octadecylamine (ODA), in both cis and trans interactions mediated by polySia …