5,156 research outputs found
Differential Midgut Attachment of Leishmania (Viannia) braziliensis in the Sand Flies Lutzomyia (Nyssomyia) whitmani and Lutzomyia (Nyssomyia) intermedia
The interaction between Leishmania and sand flies has been demonstrated in many Old and New World species. Besides the morphological differentiation from procyclic to infective metacyclic promastigotes, the parasite undergoes biochemical transformations in its major surface lipophosphoglycan (LPG). An upregulation of β-glucose residues was previously shown in the LPG repeat units from procyclic to metacyclic phase in Leishmania (Viannia) braziliensis, which has not been reported in any Leishmania species. LPG has been implicated as an adhesion molecule that mediates the interaction with the midgut epithelium of the sand fly in the Subgenus Leishmania. These adaptations were explored for the first time in a species from the Subgenus Viannia, L. (V.) braziliensis with its natural vectors Lutzomyia (Nyssomyia) intermedia and Lutzomyia (Nyssomyia) whitmani. Using two in vitro binding techniques, phosphoglycans (PGs) derived from procyclic and metacyclic parasites were able to bind to the insect midgut and inhibit L. braziliensis attachment. Interestingly, L. braziliensis procyclic parasite attachment was ∼11-fold greater in the midgut of L. whitmani than in L. intermedia. The epidemiological relevance of L. whitmani as a vector of American Cutaneous Leishmaniasis (ACL) in Brazil is discussed
O PÊNDULO DEFASADO: um exemplo de sistema caótico para estudantes do ciclo inicial do curso de graduação em Física
Neste trabalho é apresentado um estudo realizado por estudantes ingressantes do curso de Física da Universidade Federal do Pará com o objetivo de se analisar os estados de estabilidade de um pêndulo cujo pivô está em movimento circular uniforme (MCU). O modelo teórico foi desenvolvido utilizando-se a descrição de Lagrange da Mecânica Clássica. Após a modelagem, comparou-se as previsões teóricas com um aparato experimental, afim de se observar os casos de estabilidade. O projeto foi desenvolvido em uma disciplina piloto que se utilizou de uma metodologia ativa, baseada na indagação, em particular com o uso de problemas em aberto, para desenvolver nos estudantes habilidades e competências ligadas ao processo investigativo em ciências exatas, contribuindo também indiretamente para o entendimento da natureza da ciências
Fabrication and characterization of Eri silk fibers-based sponges for biomedical application
Cocoon-derived semi-domesticated Eri silk fibers still lack exploitation for tissue engineering applications due to their poor solubility using conventional methods. The present work explores the ability to process cocoon fibers of non-mulberry Eri silk (Samia/Philosamia ricini) into sponges through a green approach using ionic liquid (IL) â 1-buthyl-imidazolium acetate as a solvent. The formation of β-sheet structures during Eri silk/IL gelation was acquired by exposing the Eri silk/IL gels to a saturated atmosphere composed of two different solvents: (i) isopropanol/ethanol (physical stabilization) and (ii) genipin, a natural crosslinker, dissolved in ethanol (chemical crosslinking). The sponges were then obtained by freeze-drying. This approach promotes the formation of both stable and ordered non-crosslinked Eri silk fibroin matrices. Moreover, genipin-crosslinked silk fibroin sponges presenting high height recovery capacity after compression, high swelling degree and suitable mechanical properties for tissue engineering applications were produced. The incorporation of a model drug â ibuprofen â and the corresponding release study from the loaded sponges demonstrated the potential of using these matrices as effective drug delivery systems. The assessment of the biological performance of ATDC5 chondrocyte-like cells in contact with the developed sponges showed the promotion of cell adhesion and proliferation, as well as extracellular matrix production within two weeks of culture. Spongesâ intrinsic properties and biological findings open up their potential use for biomedical applications.The authors SSS, DSC, MBO, NMO acknowledge financial support
from Portuguese Foundation for Science and Technology –
FCT (Grants SFRH/BPD/45307/2008, SFRH/BPD/85790/2012,
SFRH/BD/71396/2010 and SFRH/BD/73172/2010, respectively),
‘‘Fundo Social Europeu” – FSE, and ‘‘Programa Diferencial de Potencial
Humano POPH”. This work is also financially supported by the European Union Seventh Framework Programme (FP7/2007-2013)
under grant agreement n REGPOT-CT2012-316331-POLARIS and
from Fundação para a Ciência e Tecnologia (FCT) through the project
ENIGMA – PTDC/EQU-EPR/121491/2010. The laboratory work
of SCK is supported by Department of Biotechnology and Indian
Council of Medical Research, Govt of India. SCK and RLR acknowledge
their short visits either Institutes. SCK is also grateful to 3B´ s
Research Group- Biomaterials, Biodegradables and Biomimetics,
University of Minho, Portugal for providing facilities during his
short visit
Polymeric glabrescione B nanocapsules for passive targeting of Hedgehog-dependent tumor therapy in vitro
Aim: With the purpose of delivering high doses of glabrescione B (GlaB) to solid tumors after systemic administration, long-circulating GlaB-loaded oil-cored polymeric nanocapsules (NC-GlaB) were formulated. Materials & methods: Synthesis of GlaB and its encapsulation in nanocapsules (NCs) was performed. Empty and GlaB- loaded NCs were assessed for their physico-chemical properties, in vitro cytotoxicity and in vivo biodistribution. Results: GlaB was ef ciently loaded into NCs (~90%), which were small (~160 nm), homogeneous and stable upon storage. Further, GlaB and NC-GlaB demonstrated speci c activities against the cancer stem cells. Preliminary studies in tumor-bearing mice supported the ability of NC to accumulate in pancreatic tumors. Conclusion: This study provides early evidence that NC-GlaB has the potential to be utilized in a preclinical setting and justi es the need to perform therapeutic experiments in mice
Study of Leading Hadrons in Gluon and Quark Fragmentation
The study of quark jets in e+e- reactions at LEP has demonstrated that the
hadronisation process is reproduced well by the Lund string model. However, our
understanding of gluon fragmentation is less complete. In this study enriched
quark and gluon jet samples of different purities are selected in three-jet
events from hadronic decays of the Z collected by the DELPHI experiment in the
LEP runs during 1994 and 1995. The leading systems of the two kinds of jets are
defined by requiring a rapidity gap and their sum of charges is studied. An
excess of leading systems with total charge zero is found for gluon jets in all
cases, when compared to Monte Carlo Simulations with JETSET (with and without
Bose-Einstein correlations included) and ARIADNE. The corresponding leading
systems of quark jets do not exhibit such an excess. The influence of the gap
size and of the gluon purity on the effect is studied and a concentration of
the excess of neutral leading systems at low invariant masses (<~ 2 GeV/c^2) is
observed, indicating that gluon jets might have an additional hitherto
undetected fragmentation mode via a two-gluon system. This could be an
indication of a possible production of gluonic states as predicted by QCD.Comment: 19 pages, 6 figures, Accepted by Phys. Lett.
Measurement and Interpretation of Fermion-Pair Production at LEP energies above the Z Resonance
This paper presents DELPHI measurements and interpretations of
cross-sections, forward-backward asymmetries, and angular distributions, for
the e+e- -> ffbar process for centre-of-mass energies above the Z resonance,
from sqrt(s) ~ 130 - 207 GeV at the LEP collider. The measurements are
consistent with the predictions of the Standard Model and are used to study a
variety of models including the S-Matrix ansatz for e+e- -> ffbar scattering
and several models which include physics beyond the Standard Model: the
exchange of Z' bosons, contact interactions between fermions, the exchange of
gravitons in large extra dimensions and the exchange of sneutrino in R-parity
violating supersymmetry.Comment: 79 pages, 16 figures, Accepted by Eur. Phys. J.
A Determination of the Centre-of-Mass Energy at LEP2 using Radiative 2-fermion Events
Using e+e- -> mu+mu-(gamma) and e+e- -> qqbar(gamma) events radiative to the
Z pole, DELPHI has determined the centre-of-mass energy, sqrt{s}, using energy
and momentum constraint methods. The results are expressed as deviations from
the nominal LEP centre-of-mass energy, measured using other techniques. The
results are found to be compatible with the LEP Energy Working Group estimates
for a combination of the 1997 to 2000 data sets.Comment: 20 pages, 6 figures, Accepted by Eur. Phys. J.
Study of Tau-pair Production in Photon-Photon Collisions at LEP and Limits on the Anomalous Electromagnetic Moments of the Tau Lepton
Tau-pair production in the process e+e- -> e+e-tau+tau- was studied using
data collected by the DELPHI experiment at LEP2 during the years 1997 - 2000.
The corresponding integrated luminosity is 650 pb^{-1}. The values of the
cross-section obtained are found to be in agreement with QED predictions.
Limits on the anomalous magnetic and electric dipole moments of the tau lepton
are deduced.Comment: 20 pages, 9 figures, Accepted by Eur. Phys. J.
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