84 research outputs found
Quantitative model for efficient temporal targeting of tumor cells and neovasculature
The combination of cytotoxic therapies and anti-angiogenic agents is emerging
as a most promising strategy in the treatment of malignant tumors. However, the
timing and sequencing of these treatments seem to play essential roles in
achieving a synergic outcome. Using a mathematical modeling approach that is
grounded on available experimental data, we investigate the spatial and
temporal targeting of tumor cells and neovasculature with a nanoscale delivery
system. Our model suggests that the experimental success of the nanoscale
delivery system depends crucially on the trapping of chemotherapeutic agents
within the tumor tissue. The numerical results also indicate that substantial
further improvements in the efficiency of the nanoscale delivery system can be
achieved through an adjustment of the temporal targeting mechanism.Comment: 17 pages, 5 figure
Invasive Plant Suppresses the Growth of Native Tree Seedlings by Disrupting Belowground Mutualisms
The impact of exotic species on native organisms is widely acknowledged, but poorly understood. Very few studies have empirically investigated how invading plants may alter delicate ecological interactions among resident species in the invaded range. We present novel evidence that antifungal phytochemistry of the invasive plant, Alliaria petiolata, a European invader of North American forests, suppresses native plant growth by disrupting mutualistic associations between native canopy tree seedlings and belowground arbuscular mycorrhizal fungi. Our results elucidate an indirect mechanism by which invasive plants can impact native flora, and may help explain how this plant successfully invades relatively undisturbed forest habitat
Fungal root endophyte associations of plants endemic to the Pamir Alay Mountains of Central Asia
The fungal root endophyte associations of 16 species from 12 families of plants endemic to the Pamir Alay Mountains of Central Asia are presented. The plants and soil samples were collected in Zeravshan and Hissar ranges within the central Pamir Alay mountain system. Colonization by arbuscular mycorrhizal fungi (AMF) was found in 15 plant species; in 8 species it was of the Arum type and in 4 of the Paris type, while 3 taxa revealed intermediate arbuscular mycorrhiza (AM) morphology. AMF colonization was found to be absent only in Matthiola integrifolia, the representative of the Brassicaceae family. The AM status and morphology are reported for the first time for all the species analyzed and for the genera Asyneuma, Clementsia, and Eremostachys. Mycelia of dark septate endophytes (DSE) accompanied the AMF colonization in ten plant species. The frequency of DSE occurrence in the roots was low in all the plants, with the exception of Spiraea baldschuanica. However, in the case of both low and higher occurrence, the percentage of DSE root colonization was low. Moreover, the sporangia of Olpidium spp. were sporadically found inside the root epidermal cells of three plant species. Seven AMF species (Glomeromycota) found in the trap cultures established with soils surrounding roots of the plants being studied were reported for the first time from this region of Asia. Our results provide information that might well be of use to the conservation and restoration programmes of these valuable plant species. The potential application of beneficial root-inhabiting fungi in active plant protection projects of rare, endemic and endangered plants is discussed
Membrane-mediated interactions
Interactions mediated by the cell membrane between inclusions, such as
membrane proteins or antimicrobial peptides, play important roles in their
biological activity. They also constitute a fascinating challenge for
physicists, since they test the boundaries of our understanding of
self-assembled lipid membranes, which are remarkable examples of
two-dimensional complex fluids. Inclusions can couple to various degrees of
freedom of the membrane, resulting in different types of interactions. In this
chapter, we review the membrane-mediated interactions that arise from direct
constraints imposed by inclusions on the shape of the membrane. These effects
are generic and do not depend on specific chemical interactions. Hence, they
can be studied using coarse-grained soft matter descriptions. We deal with
long-range membrane-mediated interactions due to the constraints imposed by
inclusions on membrane curvature and on its fluctuations. We also discuss the
shorter-range interactions that arise from the constraints on membrane
thickness imposed by inclusions presenting a hydrophobic mismatch with the
membrane.Comment: 38 pages, 10 figures, pre-submission version. In: Bassereau P., Sens
P. (eds) Physics of Biological Membranes. Springer, Cha
Fluctuation regimes of driven epitaxial surfaces
We derive the Langevin equation for the random deposition and diffusion of surface particles during homoepitaxial growth. The coefficients in this equation are determined directly by the growth parameters (temperature and flux) and provide initial conditions for renormalization-group transformations that reveal a hierarchy of continuum equations along the trajectory of coarse-grained length and time scales. Excellent agreement with previous kinetic Monte Carlo simulations of the atomistic model is obtained for all length and time scales and values of the growth parameters, but our analytic method also allows the systematic study of the interplay between deposition and diffusion for general experimental input parameters
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