1,354,714 research outputs found
MOBILITY, MICROSTRUCTURE AND MRI. DTI WITHOUT A DTI BLACK BOX: THE ART OF MAKING DO.
No full textBecause of its non invasive nature, NMR is a unique tool for studying the
microstrusture of biological and material samples. This is usually done by monitoring
the diffusion coefficients and relaxation times, whose behavior is related to the
translational and rotational random molecular motion of the system components. These
parameters report on motion on very different time scales, thus providing structural
information at a microscopic scale well beyond the usual image resolution. However,
while relaxation-weighted images are relatively straightforward to record and analyze,
the study of diffusion through MRI calls for an higher level of complexity from both a
theoretical and instrumental point of view and it is nowadays well established in the
form of diffusion tensor imaging (DTI), a technique introduced by Basser et al. in 1994
[1]. Although software modules exist that alleviate the tedious task of setting all the
parameters for the DTI sequence in newer instruments or medical scanners, our old
spectrometer - a 4.7 Tesla Bruker AM WB equipped with a PFG drive unit for
microimaging - did not offer the "turnkey” DT-MRI Bruker acquisition interface. We
got round this by implementing a DTI acquisition module and analyzing the raw data
with an open source DTI reconstruction software [2]. Our experience led us to elaborate
some of the theoretical and methodological basic concepts of DTI, summarized in the
following steps: i) Theoretical basis and assumptions of the equations that lead to the
true and apparent calculation of the diffusion coefficient(s) [3]; ii) Acquisition scheme:
a diffusion-weighted preparation module based on stimulated echo (STEAM) to provide
long diffusion times with minimal T2 relaxation [4] prior to and independent of the
imaging scheme; iii) DTI scheme: the amount of diffusion weighting and at least six not
collinear PFG orientations (icosahedral geometry) to estimate the six independent
elements of the symmetric diffusion tensor; iv) the corrections for cross-terms
interactions [5]; v) reduction of eddy currents that generate image artifacts; vi) diffusion
tensor reconstruction from DTI raw data, providing information on sample
microstructure and architecture for each voxel: mean diffusivity; anisotropy indices and
fiber orientation mapping; vii) Phantoms to test and validate the whole procedure:
isotropic (water, BSA) and anisotropic (fibers and celery) at different anisotropy degre
Guerrerostrongylus zetta
No full text<i>Guerrerostrongylus zetta</i> (Travassos 1937) <p> <b>Site of infection.</b> small intestine</p> <p> <b>Collection number.</b> MLP-He7350</p> <p> <b>Host species.</b> <i>Oligoryzomys nigripes</i>. CG190</p> <p> <b>Localities.</b> CAMB, RVSU and PPU</p> <p> <b>Comments.</b> The morphological characters observed in the specimens agree with the original description and subsequent redescriptions given by Travassos (1937) and e.g. Digiani <i>et al</i>. (2012), i.e. synlophe with numerous (ca. 40) subequal ridges, ellipsoidal caudal bursa with hypertrophied and divided at mid-length dorsal ray, very long rays 6, well-sclerotized and usually strongly twisted thin spicules and SpL/BL of 9.8–21.6%.</p> <p> <i>Guerrerostrongylus zetta</i> was originally described by Travassos (1937) as <i>Longistriata zetta</i> from the small intestine of a “rato rapé” (no specific name) in Angra dos Reis, RJ, Brazil. Afterward it was transferred to <i>Hassalstrongylus</i> and then to <i>Guerrerostrongylus</i> (Durette-Desset; 1971; Sutton & Durette-Desset, 1991). The host list in Brazil comprises <i>Nectomys squamipes</i>, <i>Cerradomys subflavus</i> (Wagner, 1842), <i>O. nigripes</i> and <i>Galea spixii</i> (Wagler, 1831), <i>Akodon cursor</i> and <i>E. russatus</i> (Pinto <i>et al.</i> 1982; Gomes <i>et al</i>. 2003). Its geographical range was extended to Rio de Janeiro by Simões <i>et al</i>. (2011, 2012b) (in <i>A. cursor</i> and <i>O. nigripes</i>) and to Rio Grande do Sul by de Werk <i>et al</i>. (2016) (in <i>O. nigripes</i>).</p> <p> In Argentina, Digiani <i>et al</i>. (2012) found <i>G. zetta</i> parasitizing <i>O. nigripes</i> from Reserva UNLP, Valle del Arroyo Cuña Pirú, Aristóbulo del Valle, and Reserva Privada de Vida Silvestre Urugua-í, Misiones province, Argentina. Based on this material and on the type specimens housed in the Helminthological Collection of the Instituto Oswaldo Cruz (CHIOC), these authors emended the description of the species taking into account the description of the synlophe, and assigned <i>N. squamipes</i> as the type host.</p>Published as part of <i>Guillermo Panisse, María Del Rosario Robles, María Celina Digiani, Juliana Notarnicola, Carlos Galliari & Graciela Teresa Navone, 2017, Description of the helminth communities of sympatric rodents (Muroidea: Cricetidae) from the Atlantic Forest in northeastern Argentina, pp. 243-262 in Zootaxa 4337 (2)</i> on page 251, DOI: 10.11646/zootaxa.4337.2.4, <a href="http://zenodo.org/record/1018756">http://zenodo.org/record/1018756</a>
Probing Protein Structure by Solvent Perturbation of NMR Spectra. I. A comparison with photo-CIDNP techniques applied to native a-lactalbumin
No full textWe have suggested elsewhere the use of surface mapping by spin label probes (Esposito et al., 1992). According to this approach, soluble nitroxides are added to a protein solution. Resonances of protons that are accessible to the nitroxide are broadened and bleached out of the spectrum, while resonances in the protein interior remain unaffected. This approach is, in principle, complementary to another technique, photochemically induced dynamic nuclear polarization, which maps the position of aromatic protons on the protein surface. A detailed comparison between the two techniques is necessary for a confident use of the more recent suggested nitroxide perturbation approach. In the present study, we show that the results obtained by the two techniques for the native state of bovine alpha-lactalbumin are fully consistent and may therefore be combined for the study of protein surfaces
Nuclear Magnetic Resonance of 129Xe and 1H as a probe for the characterization of void space in human myoglobin isoforms in solution
No full textMagnetic Resonance Imaging of molecular transport in living Morning Glory stems.
No full textMRI was applied to investigate the transport pathways in Morning Glory plant stems. The study was carried out on living plants without affecting their integrity. The architecture of a dicotyledonous plant was deeply characterized: the root system structure and the vascular bundle location were identified, the presence of central voids caused by cell maturation and loss were observed in the stem. Molecular transport components were recognized, by observing the concentration profile of a tracer, which changed with time after its absorption by the plant roots. MRI analysis revealed the presence of an axial transport as the progress of the tracer front through the vascular bundles and a radial molecular transport from the vascular bundles toward the surface of the stem. As a result, the tracer molecular transport formed the parabolic tracer front (PTF). A model was built up through the analysis of the PTF that consisted of an axial front at the peak position and a radial front at the width of the parabolic tail. PTF analysis revealed differences between the tracer transport velocities in the axial and the radial directions in the plant stem. The model revealed that the width of the parabolic tail reflected the magnitudes of diffusion and permeation of the tracer in the plant stem
Temperature and pH dependence of energy balance by 31P- and 1H-MRS in anaerobic frog muscle
No full textAbstractThe temperature (T)-dependence of energy consumption of resting anaerobic frog gastrocnemii exposed to different, changing electrochemical gradients was assessed. To this aim, the rate of ATP resynthesis (Δ∼P/Δt) was determined by 31P- and 1H-MRS as the sum of the rates of PCr hydrolysis (Δ[PCr]/Δt) and of anaerobic glycolysis (Δ[La]/ Δt, based on a ∼P/La ratio of 1.5). The investigated T levels were 15, 20 and 25 °C, whereas initial extracellular pH (pHe) values were 7.9, 7.3 and 7.0, i.e. higher, equal or lower, respectively, than intracellular pH (pHi). The latter was changing with T according to the neutrality point (dpH/dT=−0.0165 pH units/°C).Both rates of PCr hydrolysis and of lactate accumulation and that of their sum, expressed as Δ∼P/Δt, were highly T-dependent. By contrast, the pHe-dependence of the muscle energy balance was nil or extremely limited at 15 and 20 °C, respectively, but remarkable at 25 °C (with a depression of the ATP resynthesis rate up to 25% with a decrease of pHe from 7.9 to 7.0). The pHe-dependent reduction of metabolic rate was associated with a down-regulation of anaerobic glycolysis due to reduced activity of ion-transporters controlling acid–base balance and/or to a shift from Na+/H+ to a more efficient Na+-dependent Cl−/HCO3− exchanger. Uncoupling of glycogenolysis from P-metabolite concentrations, both as function of T (≥20 °C) and of pHe (≤7.3), was also shown, attributable to a T-dependence of glycolytic enzyme activity and/or H+ ion transport systems.The described metabolic slowdown observed in isolated muscle preparations subjected to the combined regimes of anoxia/acidosis implies that the mechanism determining survival time at the cellular level is mediated by exchange transport systems. A similar mechanism might affect muscle metabolism of homeotherms during chronic hypoxia and/or ischemia
Solution structure of a Bowman Birk Inhibitor isolated from snail medic seeds (Medicago Scutellata) showing anticarcinogenic activity and analysis of self-association behaviour
No full textRelatório de estágio - Desenvolvimento de sistema web para manejo florestal na agência Zetta
No full textAtualmente, boa parte do sistema de manejo florestal realizado pelo Estado de Mato Grosso do Sul consiste em processos manuais burocráticos e lentos. No intuito de facilitar e agilizar tais processos, o sistema web Licenciamento Ambiental, mantido pela Agência Zetta, permite que o usuário faça o cadastro da sua solicitação de licenças ambientais online. O presente relatório apresenta o estágio supervisionado na Agência Zetta, onde o discente atuou desenvolvendo este sistema. O discente atuou em atividades frontend e backend utilizando tecnologias como Play Framework, AngularJS e PostgreSQL. Com esse sistema, espera-se que a emissão de licenças ambientais ocorra de forma mais eficiente no Estado de Mato Grosso do Sul
Effects of temperature and extracellular pH on metabolites: kinetics of anaerobic metabolism in resting muscle by 31P and 1H MRS
No full textEnvironmental stress, such as low temperature, extracellular acidosis and anoxia, is known to play a key role in metabolic regulation. The aim of the present study was to gain insight into the combined temperature-pH regulation of metabolic rate in frog muscle, i.e. an anoxia-tolerant tissue. The rate of exergonic metabolic processes occurring in resting isolated muscles was determined at 15°C and 25°C as well as at extracellular pH values higher (7.9), similar (7.3) and lower (7.0) than the physiological intracellular pH. 31P and 1H nuclear magnetic resonance spectroscopy high-resolution measurements were carried out at 4.7 T in isolated frog (Rana esculenta) gastrocnemius muscle during anoxia to assess, by means of reference compounds, the concentration of all phosphate metabolites and lactate. Intra- and extracellular pH was also determined. In the range of examined temperatures (15-25°C), the temperature dependence of anaerobic glycolysis was found to be higher than that of PCr depletion (Q10=2.3). High-energy phosphate metabolism was confirmed to be the initial and preferential energy source. The rate of phosphocreatine hydrolysis did not appear to be affected by extracellular pH changes. By contrast, independent of the intracellular pH value, at the higher temperature (25°C) a lowering of the extracellular pH from 7.9 to 7.0 caused a depression in lactate accumulation. This mechanism was ascribed to the transmembrane proton concentration gradient. This parameter was demonstrated to regulate glycolysis, probably through a reduced lactate efflux, depending on the activity of the lactate-H+ co-transporter. The calculated intracellular buffer capacity was related to intra- and extracellular pH and temperature. At the experimental extracellular pH of 7.9 and at a temperature of 15°C and 25°C, calculated intracellular buffering capacity was 29.50 μmol g -1 pH unit-1 and 69.98 μmol g-1 pH unit -1, respectively
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