983 resultados para Nd3 spectroscopic properties


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In this work we have studied the modifications in the biological properties of Trypanosoma cruzi when the parasite is maintained for a long time in axenic culture. The studies were done with a clone from an avirulent strain (Dm30L) and a non-cloned virulent strain (EP) of T. cruzi. Both parasiteswere maintained, for at least three years, by successive triatomine/mouse alternate passage (control condition), or by serial passage in axenic medium (culture condition), or only in the mouse (mouse condition). The comparison between parasites of culture and control condition showed that metacyclogenesis capacity was reduced in the former and that the resulting metacyclics displayed an attenuatedvirulence. In order to compare the virulence of metacyclics from the urine of the insect vector, Rhodnius prolixus were infected by artificial feeding with parasites of the control or culture condition. After three triatomine/triatomine passages, there was observed an almost identical biological behavior for these parasites, hence indicating that the maintenance of T. cruzi for a long time in axenic culture affects the differentiation capacity and the virulence of the parasite. Additionally, it was demonstrated that it is possible to maintain T. cruzi exclusively through passages in the invertebrate host.

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RDM1 (RAD52 Motif 1) is a vertebrate protein involved in the cellular response to the anti-cancer drug cisplatin. In addition to an RNA recognition motif, RDM1 contains a small amino acid motif, named RD motif, which it shares with the recombination and repair protein, RAD52. RDM1 binds to single- and double-stranded DNA, and recognizes DNA distortions induced by cisplatin adducts in vitro. Here, we have performed an in-depth analysis of the nucleic acid-binding properties of RDM1 using gel-shift assays and electron microscopy. We show that RDM1 possesses acidic pH-dependent DNA-binding activity and that it binds RNA as well as DNA, and we present evidence from competition gel-shift experiments that RDM1 may be capable of discrimination between the two nucleic acids. Based on reported studies of RAD52, we have generated an RDM1 variant mutated in its RD motif. We find that the L119GF --> AAA mutation affects the mode of RDM1 binding to single-stranded DNA.

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Measuring tissue oxygenation in vivo is of interest in fundamental biological as well as medical applications. One minimally invasive approach to assess the oxygen partial pressure in tissue (pO2) is to measure the oxygen-dependent luminescence lifetime of molecular probes. The relation between tissue pO2 and the probes' luminescence lifetime is governed by the Stern-Volmer equation. Unfortunately, virtually all oxygen-sensitive probes based on this principle induce some degree of phototoxicity. For that reason, we studied the oxygen sensitivity and phototoxicity of dichlorotris(1, 10-phenanthroline)-ruthenium(II) hydrate [Ru(Phen)] using a dedicated optical fiber-based, time-resolved spectrometer in the chicken embryo chorioallantoic membrane. We demonstrated that, after intravenous injection, Ru(Phen)'s luminescence lifetime presents an easily detectable pO2 dependence at a low drug dose (1 mg∕kg) and low fluence (120 mJ∕cm2 at 470 nm). The phototoxic threshold was found to be at 10 J∕cm2 with the same wavelength and drug dose, i.e., about two orders of magnitude larger than the fluence necessary to perform a pO2 measurement. Finally, an illustrative application of this pO2 measurement approach in a hypoxic tumor environment is presented.

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For several decades mechanical properties of shallow formations (soil) obtained by sonic to ultrasonic wave testing were reported to be greater than those based on mechanical tests. The present article relying on a statistical analysis of more than 300 tests shows that elastic moduli of the soil can indeed be obtained from (ultra)sonic tests and that they are identical to those resulting from mechanical tests.

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This instrumental study was designed to investigate the psychometric properties of the French version and the cross-language replicability of the Zuckerman-Kuhlman Personality Questionnaire (ZKPQ) at the factor- and at the facet-level. The ZKPQ is an instrument aimed at assessing the five basic factors of Zuckerman's Alternative Five-Factor Model (AFFM). Subjects were 843 French-speaking Swiss, mainly students. At the factor-level, the reliability ranged from .73 to .87 and at the facet level, the reliability ranged from .57 to .77. Differences between genders are congruent with those found in the American sample. Women scored higher on N-Anx, and lower on ImpSS, and Act. A series of exploratory factor analyses supported the overall five-factor structure and the structure at the facet-level. The correlations among the scales support that the five basic factors of the AFFM are orthogonal. Targeted factor analyses and congruence coefficients show high cross-language replicability at the factor- and at the facet-level. The adequacy of the model at the factor- and facet-level was tested using confirmatory factor analyses. The results show that the French version of the ZKPQ is a reliable and valid instrument and has a high cross-language replicability.

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Following the positive results obtained regarding the molluscicidal properties of the latex of Euphorbia splendens that were corroborated in laboratory and field tests under restricted conditions, a field study was conducted in experimental streams located in an endemic area. After recording the average annual fluctuations of vectors in three streams, a solution of E. splendens latex at 12 ppm was applied in stream A, a solution of niclosamide at 3 ppm that was applied in stream B and a third stream (C) remained untreated for negative control. Applications of E. splendens and niclosamide resulted in a mortality of 100% among the snails collected in the streams A and B. No dead snails were found in the negative control stream. A monthly follow-up survey conducted during three consecutive months confirmed the return of vectors to both experimental streams treated with latex and niclosamide. This fact has called for a need to repeat application in order to reach the snails that remained buried in the mud substrate or escaped to the water edge, as well as, newly hatched snails that did not respond to the concentration of these molluscicides. Adults snails collected a month following treatment led us to believe that they had migrate from untreated areas of the streams to those previously treated

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In the investigation of thin films of transition metal nitrides, an essential role is played by the accurate determination of their chemical composition. Actually the chemical composition depends on the deposition parameters and influences the optical properties. These relations are illustrated in thin films of TiNx and (Ti1-yVy)N-x deposited by reactive magnetron sputtering from composite targets of the elements. By variation of the nitrogen partial pressure and the target composition, different samples have been obtained. The chemical composition has been measured by electron probe microanalysis at low irradiation voltages. The optical properties are evaluated by ex-situ ellipsometry. Using the screened Drude model, they are correlated with the differences in composition. Adding vanadium or nitrogen in Ti-N is shown to have the same effect on the optical properties.

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In the context of resource allocation on the basis of priorities, Ergin (2002) identifies a necessary and sufficient condition on the priority structure such that the student-optimal stable mechanism satisfies a consistency principle. Ergin (2002) formulates consistency as a local property based on a fixed population of agents and fixed resources -- we refer to this condition as local consistency and to his condition on the priority structure as local acyclicity. We identify a related but stronger necessary and sufficient condition (unit acyclicity) on the priority structure such that the student-optimal stable mechanism satisfies a more standard global consistency property. Next, we provide necessary and sufficient conditions for the student-optimal stable mechanism to satisfy converse consistency principles. We identify a necessary and sufficient condition (local shift-freeness) on the priority structure such that the student-optimal stable mechanism satisfies local converse consistency. Interestingly, local acyclicity implies local shift-freeness and hence the student-optimal stable mechanism more frequently satisfies local converse consistency than local consistency. Finally, in order for the student-optimal stable mechanism to be globally conversely consistent, one again has to impose unit acyclicity on the priority structure. Hence, unit acyclicity is a necessary and sufficient condition on the priority structure for the student-optimal stable mechanism to satisfy global consistency or global converse consistency.

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-lactamase activity was studied in Neisseria gonorrhoeae strains. Optimum temperature was found to be 37C. The enzyme was inactivated at temperatures higher than 60C, but remained active during storage at low temperatures (4C, -30C and -70C) for two months. Enzyme activity was observed within a pH range of 5.8-8.0, while the optimum pH was 7.0-7.2. Addition of Ni2+, Fe2+, Fe3+, Mn2+ and p-chloromercurybenzoate to the reaction buffer exerted a negative effect upon the activity, whereas Hg2+ and ethylene diamine tetra-acetic acid produced complete inhibition. These results would indicate the presence of -SH groups at the catalytic site of the enzyme.

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The electrostatic surface charge and surface tension of mononuclear cells/monocytes obtained from young and adult marsupials (Didelphis marsupialis) were investigated by using cationized ferritin and colloidal iron hydroxyde, whole cell electrophoresis, and measurements of contact angles. Anionic sites were found distributed throughout the entire investigated cell surfaces. The results revealed that the anionic character of the cells is given by electrostatic charges corresponding to -18.8 mV (cells from young animals) and -29.3 mV (cells from adult animals). The surface electrostatic charge decreased from 10 to 65.2% after treatment of the cells with each one of trypsin, neuraminidase and phospholipase C. The hydrophobic nature of the mononuclear cell surfaces studied by using the contact angle method revealed that both young and adult cells possess cell surfaces of high hidrofilicity since the angles formed with drops of saline water were 42.5and 40.8, respectively. Treatment of the cells with trypsin or neuraminidase rendered their surfaces more hydrophobic, suggesting that sialic acid-containing glycoproteins are responsible for most of the hydrophilicity observed in the mononuclear cell surfaces from D. marsupialis.

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DNA in bacterial chromosomes and bacterial plasmids is supercoiled. DNA supercoiling is essential for DNA replication and gene regulation. However, the density of supercoiling in vivo is circa twice smaller than in deproteinized DNA molecules isolated from bacteria. What are then the specific advantages of reduced supercoiling density that is maintained in vivo? Using Brownian dynamics simulations and atomic force microscopy we show here that thanks to physiological DNA-DNA crowding DNA molecules with reduced supercoiling density are still sufficiently supercoiled to stimulate interaction between cis-regulatory elements. On the other hand, weak supercoiling permits DNA molecules to modulate their overall shape in response to physiological changes in DNA crowding. This plasticity of DNA shapes may have regulatory role and be important for the postreplicative spontaneous segregation of bacterial chromosomes.

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Lipopolysaccharides (LPS, endotoxins) are main constituents of the outer membranes of Gram-negative bacteria, with the 'endotoxic principle' lipid A anchoring LPS into the membrane. When LPS is removed from the bacteria by the action of the immune system or simply by cell dividing, it may interact strongly with immunocompetent cells such as mononuclear cells. This interaction may lead, depending on the LPS concentration, to beneficial (at low) or pathophysiological (at high concentrations) reactions, the latter frequently causing the septic shock syndrome. There is a variety of endogenous LPS-binding proteins. To this class belong lactoferrin (LF) and hemoglobin (Hb), which have been shown to suppress and enhance the LPS-induced cytokine secretion in mononuclear cells, respectively. To elucidate the interaction mechanisms of endotoxins with these proteins, we have investigated in an infrared reflection-absorption spectroscopy (IRRAS) study the interaction of LPS or lipid A monolayers at the air/water interface with LF and Hb proteins, injected into the aqueous subphase. The data are clearly indicative of completely different interaction mechanisms of the endotoxins with the proteins, with the LF acting only at the LPS backbone, whereas Hb incorporates into the lipid monolayer. These data allow an understanding of the different reactivities in the biomedicinal systems.

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ABSTRACT Malaria is a major worldwide public health problem, with transmission occurring throughout Africa, Asia, Oceania and Latin America. Over two billion people live in malarious areas of the world and it is estimated that 300-500 million cases and 1.5-2.7 million deaths occur annually. The increase in multi-drug resistant parasites and insecticide-resistant vectors has made the development of malaria vaccine a public health priority. The published genome offers tremendous opportunity for the identification of new antigens that can befast-tracked for vaccine development. We identified potential protein antigens present on the surface of asexual malaria blood stages through bioinformatics and published transcriptome and proteorn analysis. Amongst the proteins identified, we selected those that contain predicted a-helical coiled-coil regions, which are generally short and structurally stable as isolated fragments. Peptides were synthesized and used to immunize mice. Most peptides tested were immunogenic as demonstrated in ELISA assays, and induced antibodies of varying titres. In immunofluorescence assays, anti-sera from immunized mice reacted with native proteins expressed at different intraerythrocytic developmental stages of the parasite's cycle. In parallel in vitro ADCI functional studies, human antibodies affinity purified on some of these peptides inhibited parasite growth in association with monocytes in magnitudes similar to that seen in semiimmune African adults. Siudies using human immune sera taken from different malaria endemic regions, demonstrated that majority of peptides were recognized at high prevalence. 73 peptides were next tested in longitudinal studies in two cohorts separated in space and time in coastal Kenya. In these longitudinal analyses, antibody responses to peptides were sequentially examined in two cohorts of children at risk of clinical malaria in order to characterize the level of peptide recognition by age, and the role of anti-peptide antibodies in protection from clinical malaria. Ten peptides were associated ?with a significantly reduced odds ratio for an episode of clinical malaria in the first cohort of children and two of these peptides (LR146 and S202.11) were associated with a significantly reduced odds ratio in both cohorts. This study has identified proteins PFB0145c and MAL6P1.37 among others as likely targets of protective antibodies. Our findings support further studies to systematically assess immunogenicity of peptides of interest in order to establish clear criteria for optimal design of potential vaccine constructs to be tested in clinical trials. RESUME La malaria est un problme de sant publique mondial principalement en Afrique, en Asie, en Ocanie et en Amrique latine. Plus de 2 milliards de personnes vivent dans des rgions endmiques et le nombre de cas par anne est estim entre 300 et 500 millions. 1.5 2.7 millions de dcs surviennent annuellement dans ces zones. L'augmentation de la rsistance aux mdicaments et aux insecticides fait du dveloppement d'un vaccin une priorit. Le squenage complet du gnome du parasite offre l'opportunit d'identifier de nouveaux antignes qui peuvent rapidement mener au dveloppement d'un vaccin. Des protines antigniques potentielles prsentes la surface des globules rouges infects ont t identifies par bioinformatique et par l'analyse du protome et du transcriptome. Nous avons slectionn, parmi ces protines, celles contenant des motifs dits "a helical coiled-coil" qui sont gnralement courts et structurellement stables. Ces rgions ont t obtenues par synthse peptidique et utilises pour immuniser des souris. La plupart des peptides tests sont immunogniques et induisent un titre variable d'anticorps dtermin par ELISA. Les rsultats de tests d'immunofluorescence indiquent que les sera produits chez la souris reconnaissent les protines natives exprimes aux diffrents stades de dveloppement du parasite. En parallle, des tudes d'ADCI in vitro montrent qu des anticorps humains purifis partir de ces peptides associs des monocytes inhibent la croissance du parasite aussi bien que celle observe chez des adultes africains protgs. Des tudes d'antignicit utilisant des sera de personnes protges de diffrents ges vivant dans des rgions endmiques montrent que la majorit des peptides sont reconnus avec une haute prvalence. 73 peptides ont t tests dans une tude longitudinale avec 2 cohortes de la cte du Kenya. Ces 2 groupes viennent de zones bien distinctes et les prlvements n'ont pas t effectus pendant la mme priode. Dans cette tude, la rponse anticorps contre les peptides synthtiques a t teste dans les 2 cohortes d'enfants risque de dvelopper un pisode de malaria afin de caractriser le niveau de reconnaissance des peptides en fonction de l'ge et de dterminer le rle des anticorps anti-peptides dans la protection contre la malaria. Parmi ces peptides, 10 sont associs une rduction significative des risques de dvelopper un pisode de malaria dans la premire cohorte alors qu'un seul (LR146 et AS202.11) l'est dans les 2 cohortes. Cette tude a identifi, parmi d'autres, les protines PFB0145c et MAL6P1.37 comme pouvant tre la cible d'anticorps. Ces rsultats sont en faveur de futures tudes qui valueraient systmatiquement l'immunognicit des peptides d'intrt dans le but d'tablir des critres de slection clairs pour le dveloppement d'un vaccin. Rsum pour un large public La malaria est un problme de sant publique mondial principalement en Afrique, en Asie, en Ocanie et en Amrique latine. Plus de 2 milliards de personnes vivent dans des rgions endmiques et le nombre de cas par anne est estim entre 300 et 500 millions. 1.5 2.7 millions de dcs surviennent annuellement dans ces zones. La rsistance aux mdicaments et aux insecticides augmente de plus en plus d'o la ncessit de dvelopper un vaccin. Le squenage complet du gnome (ensemble des gnes) de P. falciparum a conduit au dveloppement de nouvelles .tudes large chelle dans le domaine des protines du parasite (protome) ; dans l'utilisation d'algorithmes, de techniques informatiques et statistiques pour l'analyse de donnes biologiques (bioinformatique) et dans les technologies de transcription et de profiles d'expression (transcriptome). Nous avons identifi, en utilisant les outils ci-dessus, des nouvelles protines antigniques qui sont prsentes au stade sanguin de la malaria. Nous avons slectionn, parmi ces protines, celles contenant un motif dit "a-helical coiled-coil" qui sont des domaines impliqus dans un large ventail de fonctions biologiques. Des peptides reprsentant ces rgions structurellement stables ont t synthtiss et utiliss pour immuniser des souris. La plupart des peptides tests sont immunogniques et induisent un titre variable d'anticorps dtermin par ELISA. Les rsultats de tests d'immunofluorescence indiquent que plusieurs sera de souris immunises avec ces peptides reconnaissent les protines natives exprimes la surface des globules rouges infects. En parallle, des tudes d'ADCI in vitro montrent que des anticorps humains purifis partir de ces peptides en prsence de monocytes inhibent la croissance du parasite de manire similaire celle observe chez des adultes africains protgs. Des tudes d'antignicit utilisant des sera de personnes immunes de diffrents ges (adultes et enfants) vivant dans des rgions endmiques montrent que la majorit des peptides sont reconnus avec une haute prvalence. 73 peptides ont t tests dans des tudes pidmiologiques dans 2 villages ctiers du Kenya Ces 2 groupes vivent dans des zones bien distinctes et les prlvements n'ont pas t effectus pendant la mme priode. Dans ces tudes, la rponse anticorps dirige contre les peptides synthtiques a t teste en utilisant 467 chantillons sanguins d'enfants risque de dvelopper un pisode de malaria afin de caractriser le niveau de reconnaissance des peptides en fonction de l'ge et de dterminer le rle des anticorps anti-peptides dans la protection contre la malaria crbrale. Parmi ces peptides, 10 sont associs une protection contre un pisode de malaria dans le premier village alors qu'un seul l'est dans les 2 villages. Ces rsultats sont en faveur de futures tudes qui valueraient systmatiquement l'immunognicit des peptides intressants dans le but d'tablir des critres de slection clairs pour le dveloppement d'un vaccin.