4,140 research outputs found

    Cells use molecular working memory to navigate inchanging chemoattractant fields

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    In order to migrate over large distances, cells within tissues and organisms rely on sensing local gradient cues which are irregular, conflicting, and changing over time and space. The mechanism how they generate persistent directional migration when signals are disrupted, while still remaining adaptive to signal's localization changes remain unknown. Here we find that single cells utilize a molecular mechanism akin to a working memory to satisfy these two opposing demands. We derive theoretically that this is characteristic for receptor networks maintained away from steady states. Time-resolved live-cell imaging of Epidermal growth factor receptor (EGFR) phosphorylation dynamics shows that cells transiently memorize position of encountered signals via slow-escaping remnant of the polarized signaling state, a dynamical 'ghost', driving memory-guided persistent directional migration. The metastability of this state further enables migrational adaptation when encountering new signals. We thus identify basic mechanism of real-time computations underlying cellular navigation in changing chemoattractant fields

    Multiple Dens Invaginatus - A case report and review of literature

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    Dens invaginatus is a developmental variation of a tooth resulting from an alteration in the normal growth pattern of the dental papilla. It is clinically characterized by a palatine furrow that can be limited to the coronal pulp or may extend to the radicular apex. The commonly affected tooth is maxillary lateral incisor. The occurrence of multiple dens invaginatus is extremely rare. Although a clinical examination may reveal a deep pit or fissure on the lingual surfaces of maxillary anterior teeth, the radiographic examination is the choice for diagnosis of dens invaginatus. Familiarity with the radiographic appearance of this anomaly is essential for the dental practitioner. The purpose of this paper is to present a clinical case of multiple dens invaginatus involving maxillary anterior teeth which was diagnosed during routine radiographic evaluation

    Effect of Inorganic Fertilizer and Crop Residue on Carbohydrate and Fat Content in Basmati Rice (Oryza sativa L.)

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    A field experiment was conducted during Kharif season of July 2013 & 2014at crop research farm SHIATS Allahabad to study the effect of inorganic fertilizer and wheat residue on carbohydrate and fat content in basmati rice. Treatments were arranged using (4x3) factorial R.B.D with three replications. Increasing level of NPK fertilizer significantly increases carbohydrate content in grain in 100% RDF ha-1over control. Among incorporation/ retention of wheat residue also increase the carbohydrate content with increasing level from 0 to 5 tone ha-1. It was lower in control and higher in highest level of wheat residue, which was at par with 2.5 t ha-1 wheat residues in the year of experiment 2013-2014. In the fat content maximum increased in 100% RDF (NPK) over control. Among the fat content maximum increased in incorporation of 5 t ha-1 wheat residue was found better than the rest of the treatment both the years of experiment 2013,14 respectively

    Unusual mass shoreward movement of bivalve (Mollusca) Donax scortum Linnaeus along the coastal waters off Calicut - South Eastern Arabian Sea

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    67-72Eutrophication and oxygen depletion are the major factors influencing the responses of benthic organisms in coastal ecosystems. Along the coastal waters of South Eastern Arabian Sea a mass shoreward movement of bivalve Donax scortum (locally referred as “eranthu”) occurred during end phase of summer monsoon upwelling. Possible reasons for this shoreward movement points to the low dissolved oxygen (0.25 ml L-1) in the bottom waters. Intense blooms of large dinoflagellate species, Noctiluca scintillans were observed a week prior to this event along these coastal waters and the crashing related decaying might have resulted in lower DO values in the region. The study discuss on the deleterious effects of hypoxic conditions caused by summer monsoon algal blooms on benthic fauna of South Eastern Arabian Sea

    Resonant inelastic X-ray scattering in a Mott insulator

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    We calculate the resonant inelastic X-ray scattering (RIXS) response in a Mott insulator which is described by the Falicov-Kimball model. The model can be solved exactly within the single site dynamical mean-field theory (DMFT) approximation and the calculated RIXS response is accurate up to a local background correction. We find that on resonance the RIXS response is greatly enhanced over various other non-resonant background effects and the response systematically evolves from a single peak structure, arising due to relaxation processes within the lower Hubbard band, to a two peak structure, arising due to relaxation processes within the upper Hubbard band as well as across the Mott gap into the lower Hubbard band, as we vary the incident photon frequency to access states from the bottom of the lower Hubbard band to the top of the upper Hubbard band. The charge transfer excitations are found to disperse monotonically outwards (as a function of transfered energy) as we go from the center of the Brillouin zone towards the zone corner. These correlation induced features have been observed by Hasan {\it et. al.} (Science {\bf 288}, 1811 (2000)) and many other experimentalists in RIXS measurements over various transition metal oxide compounds and are found to be robust and survive even for large Auger lifetime broadening effects. As a comparison, we also calculate the dynamic structure factor for this model, which is proportional to the nonresonant part of the response, and does not show these specific signatures.Comment: 14 pages, 14 figures, submitted to Physical Review

    A self-organized synthetic morphogenic liposome responds with shape changes to local light cues

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    Reconstituting artificial proto-cells capable of transducing extracellular signals into cytoskeletal changes can reveal fundamental principles of how non-equilibrium phenomena in cellular signal transduction affect morphogenesis. Here, we generated a Synthetic Morphogenic Membrane System (SynMMS) by encapsulating a dynamic microtubule (MT) aster and a light-inducible signaling system driven by GTP/ATP chemical potential into cell-sized liposomes. Responding to light cues in analogy to morphogens, this biomimetic design embodies basic principles of localized Rho-GTPase signal transduction that generate an intracellular MT-regulator signaling gradient. Light-induced signaling promotes membrane-deforming growth of MT-filaments by dynamically elevating the membrane-proximal tubulin concentration. The resulting membrane deformations enable recursive coupling of the MT-aster with the signaling system, which generates global self-organized morphologies that reorganize towards local external cues in dependence on prior shape. SynMMS thereby signifies a step towards bio-inspired engineering of self-organized cellular morphogenesis

    Unilateral pulmonary agenesis

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