1,721,009 research outputs found
Thermogravimetric technique for volatiles detection in planetary and space environments
Full text linkIntroduction. The PhD work has been performed at Institute of Astrophysics and Space Planetology (IAPS-INAF) in the framework of the two projects VISTA (Volatile In-Situ Thermogravimeter Analyser) and CAM (Contamination Assessment Microbalance), funded by Italian Space Agency and European Space Agency, respectively, both aiming at developing a microbalance sensor for space mission applications, i.e. to study the minor bodies of Solar System (i.e., ESA-M5 Missions Call, MarcoPolo-M5, Akon, JEM and Castalia) by measuring in-situ volatiles material of scientific interest (VISTA project) and to assess the contamination issue (CAM project).
VISTA is a miniaturized thermogravimeter (composed by Piezoelectric Crystal Microbalance and the related Proximity Electronics), based on Thermogravimetric Analysis (TGA), i.e. a widely used technique to monitor the processes involving compounds, i.e. absorption/desorption and evaporation/sublimation. Thanks to the variation in the microbalance oscillation frequency it is possible to estimate the sample mass loss/deposited from thermal cycles. VISTA is composed of two sensor heads, i.e. the Sensor Head 1 (SH1) for in-orbit contamination measurements from outgassing processes and Sensor Head 2 (SH2) for planetary in-situ measurements, respectively. The breadboard and the Engineering Model of VISTA SH1 have been developed for ESA Project, i.e. CAM, an Invitation to Tender of European Space Agency (EMITS-ESA) aiming at developing a thermogravimeter for contamination measurements in space, leaded by IAPS-INAF and developed by a consortium of three Italian institutes and one Industry. The VISTA SH2 breadboard has been developed in the framework of MarcoPolo-R Mission, where VISTA was part of the scientific payload.
Objectives. In this work, the VISTA capability to monitor the contamination processes in space environment and for the study of planetary surfaces and atmospheres has been demonstrated as well as the good capability of sensor heads to monitoring and to characterizing a contaminant source and organic compounds by realizing TGA cycles and Effusion Method (EM) to obtain the vapor pressures and enthalpy of sublimation.
Material and Method. The first phase of the work was based on the study of Volatile Organic Compounds (VOCs): 1) in planetary atmospheres including their physical-chemical properties and their connections with the atmospheric aerosol sources (biogenic and anthropogenic); 2) in space, coming from outgassing processes of materials exposed to space environment, and the related instrumentation issues. Thus, organic compounds (found in Carbonaceous Chondrite meteorites and in Earth's VOCs) have been selected to perform deposition processes and TGA cycles obtaining a complete characterization with SH1 and SH2. The vapor pressures and enthalpy of sublimation were identified as those thermochemical parameters able to characterize a kinetics process regarding VOCs in planetary atmosphere and in space. Thus, a laboratory activity was planned and divided in a first design and development phase of two laboratory setup and in a second calibration phase of VISTA sensor heads. A third phase was devoted at performing different tests for contamination study in space (using a contaminant source and SH1 breadboard) and for VOCs characterization in atmosphere (using five dicarboxylic acids and SH2 breadboard). Results. The breadboards of VISTA instrument SH1 and SH2 have been developed to monitor the contamination in space (SH1) and to characterize organic compounds (SH2). The main results reached in the PhD work with VISTA SH1 have been: 1) to monitor contamination processes in vacuum chamber simulating the space environment (between 5x10-9 to 7x10-4 g/cm2); 2) the contaminant source characterization by means of TGA cycles (ΔTmax~60°C) and retrieval of vapour pressure of compounds (Pi) and the enthalpy of sublimation (ΔHsub) by using the Langmuir and Clausius-Clapeyron relations; 3) the sensor regeneration by means of thermal cycles by using the integrated heaters on crystal surface (with an accuracy within 0.1°C). On the other hand, the main scientific objectives reached with VISTA SH2 have been: 1) the volatiles material measurement deposited on the sensor surface at different temperatures by using the Effusion Method simulating the asteroidal/cometary environment; 2) the characterization of VOCs, i.e. dicarboxylic acids, by calculating the enthalpy of sublimation (ΔHsub) with Van't Hoff relation. Conclusion. In this work, the VISTA SH1 and SH2 Breadboards have been designed and developed as well as two different laboratory set-up to verify the capability of SH1 and SH2 to monitor a contamination process and to characterize a pure organic compound, respectively, using TGA cycles and EM. The enthalpies of sublimation results obtained with SH1 from one contaminant source (adipic acid) using TGA and EM, are in agreement within 3.5% while the enthalpies of sublimation obtained for five dicarboxylic acids and using EM, are in agreement within 6% (oxalic, succinic and adipic acids) and 11% (azelaic and suberic acids) with previous works. These results demonstrate the capability of SH1 and SH2 Breadboards to detect organic contaminant and to characterize different organic compounds presents in VOCs terrestrial atmosphere obtaining a good characterization for a pure compound
THE PATHOGENESIS OF MALARIA ACUTE RESPIRATORY DISTRESS SYNDROME (MA-ARDS): MODIFICATION OF THE LIPID PROFILE, ANTIOXIDANT DEFENCES AND CYTOKINE CONTENT IN DIFFERENT TISSUES OF MALARIA INFECTED MICE
Full text linkINTRODUCTION Malaria is a major health problem, with more than 650.000 deaths and 200 million clinical cases each year. Respiratory distress as malaria associated acute respiratory distress syndrome (MA-ARDS) is a common complication. The pathogenesis of MA-ARDS is mainly inflammatory and one of the main observation is the presence of abundant monocytes and macrophages inside the blood capillaries, in the interstitium and also in alveolar spaces. Malaria pigment or haemozoin (Hz) is often seen in these cells reflecting active phagocytosis and leads to the production of cytokines and other inflammatory mediators. Multiple organ dysfunctions are described in MA-ARDS, including liver damages. ARDS in non malarious patients is often associated with disorders of the lung surfactant, which can lead to the increase in surface tension, alveolar collapse and loss of the liquid balance in the lungs. Surfactant is known to reduce the surface tension at the air–liquid interface of lung epithelia and to regulate the local host immune response. It can be separated into a surface active Large Aggregate fractions (LA), representing a reservoir for the surface film located at the air-liquid interface of the alveoli and a less surface active, Small Aggregate fraction (SA). It is not known at present if alterations of the surfactant also exist in MA-ARDS and how they may contribute to the pathology and the development of the inflammatory response.
AIM The aim of our studies was to perform a comprehensive analysis of the local and systemic inflammatory response present in MA-ARDS and to analyse the lipid profile of the pulmonary surfactant, the lung and liver tissues and plasma using two different models of murine malaria of similar gravity, but different involvement of lungs or liver. In particular, we studied C57BL/6J mice infected with two different species of Plasmodium: Plasmodium berghei NK65 strain which induces MA-ARDS and Plasmodium chabaudi (PcAS), which does not. The two models allowed us to directly compare the different pathological manifestation of the same infection in order to identify peculiarities which could be exploited for novel therapeutic interventions.
RESULTS AND DISCUSSION
Macroscopic and functional analysis of lung tissues in the two strains. The lungs of PbNK65 infected mice were swollen, increased in weight and with a dark brown aspect due to micro haemorrhages and to the deposition of Hz clusters in concentrations significantly higher compared to the lungs of mice infected with PcAS. The expression of TNF-α and IFN- was increased only in PbNK65 mice, indicating that these cytokines are induced specifically during MA-ARDS and are not a consequence of malaria infection. This hypothesis was confirmed by the decrease of lung weight and of the CD8+ cells infiltrate, and the reduction /delay in mortality rates seen in PbNK65 mice treated with DEX without a concomitant reduction in parasitaemia. Therefore, DEX seems to ameliorate MA-ARDS, not by inhibiting parasite growth but rather by modulating the immunopathology and the inflammatory response. A significant increase of the total phospholipid (PL) content and cholesterol esters (ChoE) was observed in PbNK65 lungs and was reverted by DEX. Moreover, compared to the control mice (CTR), the fatty acid distribution of lung ChoE was characterized by higher levels of the polyunsaturated fatty acid and an high linoleic/oleic ratio typical of plasma ChoE. All these features confirm a strict correlation between the interstitial oedema and the infiltration of plasma lipoproteins during MA-ARDS. Protein and lipid composition of surfactant and plasma of infected mice. The total bronchoalveolar lavage (BAL) of PbNK65 mice showed a significant increase in the protein levels compared to CTR or PcAS mice, probably due to plasma derived proteins being incorporated into or associated with microstructures in the alveolar hypophase. This event is known to decrease the intrinsic surface activity of surfactant. The total content of PL was not different from CTR, whereas the PL profile of the LA and SA fractions in PbNK65 infected mice showed a significant increase in the amounts of sphingomyelin and a decrease in phosphatidylglycerol. These changes were absent in PcAS mice and may be related to the altered re-uptake and synthesis of PL by injured cells or to PL contamination due to inflammatory cells. The plasma levels of PL and triacylglycerol (TG) were significantly higher in PbNK65 mice than in CTR or PcAS mice. Compared to PcAS or CTR mice in PbNK65 group all the PL classes were significantly increased with the exception of lisophosphatidilcholine (LisoPC) that was decreased. These plasma alterations may be related to an impaired activity of the enzymes involved in the lipoprotein metabolism during infections or inflammatory diseases. The most important observation, both in PbNK65 and PcAS mice, was the significant increase of docosahexahenoic acid (C22:6 n-3, DHA) compared to CTR, which was only partially reverted by DEX treatment, suggesting that the increase of DHA is not related to lung pathology but rather to the malaria infection. Analysis of the liver tissue of infected mice. The hypothesis that the higher PL and TG content of PbNK65 plasma might be due to an enhanced hepatic lipogenesis was confirmed by the higher TG and ChoE content of the liver of PbNK65 mice compared to PcAS and CTR. An increased ratio linoleic (LA)/arachidonic acid (AA) was also present possibly due to the impairment of the elongation/desaturation pathway from LA to AA acid. Higher levels of Hz, compared to PcAS, were present in PbNK65 mice and, in agreement with the Hz capability of stimulating Kupffer cells, we found higher levels of TNF-α. Both Hz and TNF-α can induce lipoperoxidation as confirmed by the elevated levels of malondialdehyde (MDA) in the liver of PbNK65 mice. This finding was paralleled by the lower content of glutathione and of antioxidant enzymes particularly in the late stage of the pathology.
CONCLUSIONS This is the first time that a comprehensive analysis of the lipid content and inflammatory response of different organs in a model of murine MA-ARDS has been performed. All together the data suggest that in MA-ARDS as in other severe non infectious pathologies, a pulmonary-liver metabolic interplay exist which may contribute to the pathology. In PbNK65 mice, Hz and the derived inflammation play an important role in the lung pathology inducing changes in the lipid composition of lung and surfactant, cellular infiltration and cytokine production. Lung pathology is associated with liver disorders and alterations in the lipoprotein profile. Hz accumulation may induce macrophages to produce TNF-α and ROS that can interfere with liver functions by inducing lipogenesis and affecting the lipid profile of liver and plasma, which in turn contribute to the altered lipid composition of the lung tissue. These results confirm that severe malaria is a multi-organ dysfunction in which inflammation has an important role in different organs and thus, in addition to antimalarial treatment, adjunct therapies with anti-inflammatory drugs can be envisaged
Modulation of L-Arginine metabolism and bioavailability by free plasma heme
No full textSevere falciparum malaria is associated with high levels of free heme [Fe(III)-protoporphyrin IX, FP], hypoargininemia and low nitric oxide (NO). Hypoargininemia can be partially explained by the increased level of plasma arginase due to the disease-induced hemolysis, but its precise cause is unknown.
The aim of this work was to investigate whether FP can affect the membrane transport of arginine (ARG) and/or the activity of plasma and red blood cell (RBC) arginase, therefore limiting ARG bioavailability for NO production.
Design and Methods. ARG transport was evaluated in human RBC by measurement of influx of radiolabeled ARG and resolved into the saturable transport components y+ and y+L by selective inhibition of the two systems with 2 mM N-ethylmaleimide or 1 mM leucine. respectively. Arginase activity was evaluated after pre-treatment of RBC or cell-free extract with FP in different experimental conditions and expressed as mol urea produced/gr Hb.
Results. FP impairs the influx of ARG into RBC in a dose dependent manner with a more pronounced effect on the transport system y+L. FP-treated RBC show an enhancement of the arginase activity. Experiments performed in different experimental conditions have shown that arginase activation is not simply related to oxidative modifications induced by the porphyrin
Conclusions: impairment of ARG influx and activation of arginase could limit ARG availability for NO production by RBC NOS. Additionally, release of a more active arginase by damaged RBC during intravascular hemolysis could worsen hypoargininemia, reducing ARG availability for NO production also in endothelial cells
Involvement of NOD2 in macrophage response to leishmania tropica infection
No full textBACKGROUND-AIM Leishmaniasis is a protozoan disease caused by parasites belonging to the genus Leishmania. In the human host, these parasites invade macrophages where they develop into intracellular amastigotes and multiply within phagolysosomes. Host cells can control the infection initially through the triggering of innate immune responses. NOD-like receptors (NLRs) are a family of innate immune cytosolic receptors able to recognize pathogen-associated molecular patterns. NOD1 and NOD2 detect pathogens that are able to invade and multiply intracellularly. Once stimulated, these receptors induce the activation of NF-κB and MAPKs, which lead to the transcription of genes involved in inflammation and immune responses. The aim of this work was to evaluate the role of NOD2 in some innate immune responses of macrophages infected with L. tropica. In particular, the production of TNF-a, or nitric oxide (NO), and the expression of inducible NO synthase (iNOS) were evaluated METHODS Immortalized bone marrow-derived macrophages (BMDM) from wild type (WT) C57Bl/6 or knockout (KO) mice for NOD2 were used. The levels of TNF-a released into the supernatants of BMDM-WT or -NOD2-KO treated with L. tropica were measured by ELISA. Also, the presence of nitrite was evaluated, through the Griess test, as an indication of nitric oxide (NO) production. Finally, protein and gene expression levels of iNOS were retrieved by Western blot analysis and realtime PCR, respectively. RESULTS The involvement of NOD2 in BMDM treated with L. tropica was elucidated as the levels of TNF-a or NO released from BMDM-WT infected with L. tropica were significantly higher compared to the BMDM-NOD2-KO. On the other side, the expression of iNOS (RNA and protein) was higher in BMDM-WT treated with L. tropica than in BMDM-NOD2-KO. CONCLUSIONS Altogether, these data indicated a crucial role of NOD2 for these innate immune responses of BMDM infected with L.tropica
Effect of circulating free heme on plasma arginase activity and L-arginine cellular influx
No full textSevere falciparum malaria is associated with high levels of free heme [Fe(III)-protoporphyrin IX, FP], hypoargininemia and low nitric oxide (NO). Hypoargininemia can be partially explained by the increased level of plasma arginase due to the disease-induced hemolysis, but its precise cause is unknown.
Objectives. Investigate whether FP can affect the membrane transport of arginine (ARG) and/or the activity of plasma or red blood cell (RBC) arginase, therefore limiting ARG bioavailability for NO production.
Design and Methods. ARG transport was evaluated in RBC by measurement of influx of radiolabeled ARG and resolved into the saturable transport components y+ and y+L by selective inhibition with 2 mM N-ethylmaleimide or 1 mM leucine. respectively. Arginase activity was evaluated after pre-treatment of RBC or cell-free extract with FP in different experimental conditions and expressed as mol urea produced/gr Hb.
Results. FP impairs the influx of ARG into RBC in a dose dependent manner with a more pronounced effect on the transport system y+L. FP-treated RBC show an enhancement of the arginase activity but experiments performed in different experimental conditions have shown that arginase activation is not simply related to oxidative modifications induced by the porphyrin
Conclusions: impairment of ARG influx and activation of arginase could limit ARG availability for NO production by RBC NOS. Additionally, release of a more active arginase by damaged RBC during intravascular hemolysis could worsen hypoargininemia, reducing ARG availability for NO production also in endothelial cells
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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