1,720,970 research outputs found
Phosphatidylcholine (PC) biosynthesis within the nuclear matrix of human IMR-32 neuroblastoma cells
No full textExpression of cell-surface activation markers on human CD15<sup>+</sup> cells after selected non esterified fatty acid supplementations
No full textBackground: Cell surface marker (CD) expressions and membrane lipid changes characterise circulating neutrophil transmigration into inflammation sites. Specific CD expressions mandate neutrophil activation. Lipid changes alter membrane fluidity, deformability, cell spreading and transmigration. Circulating neutrophil, predominantly CD15 positive (CD15+), recruitment to the lungs and activation is a crucial innate immune response in Acute Respiratory Distress Syndrome (ARDS) pathology. During transmigration, their membrane lipids rapidly acquire significant whole cell arachidonic acid enrichment. The source of arachidonate is unclear but neutrophils incorporate non-esterified fatty acids (NEFA) from their microenvironment, adjusting cellular fatty acyl-CoA pools. We hypothesised that inflammation-associated, specific NEFA incorporation(s) into neutrophil membrane lipids mandate activation. We evaluated patterns of synthesis, composition and turnover of phosphatidylcholine (PC), alongside transmigration markers, following NEFA supplementations of freshly isolated human CD15+ cells. Methods: CD15+ cells were collected from venous blood samples of 5 healthy volunteers using the autoMACS system with CD15+ microbeads. Isolated CD15+ cells were incubated for 3 h with methyl-D9-choline chloride. NEFA supplements were added separately or in combination. Modified Bligh and Dyer lipid extracts were analysed by mass spectrometry. Unlabelled PC composition was determined by precursor scans of the m/z + 184 and the deuteriated m/z + 193 fragment was used to report newly synthesised methyl-D9-choline labelled PC. Results: Four NEFAs were chosen, oleic acid, linoleic acid, palmitic acid and arachidonic acid. All supplementations downregulated CD62L expression and increased expressions of CD11a and CD11b, hallmarks of activation. Membrane PC composition consisted of di-acyl species (59%) and alkylacyl PC species (41%), primary PC being PC34:1. Incorporation of methyl-D9-into polyunsaturated PC species was consistently elevated compared with endogenous composition. NEFA supplementations did not change bulk endogenous PC composition. There was lower fractional methyl-D9 enrichment with oleic acid compared to other NEFAs and the fractional enrichment varied between individual species. Conclusions: CD15+ microenvironmental exposure to every NEFA investigated resulted in expression of cellular activation markers. NEFA-defined changes in synthesis patterns of individual molecular species of membrane PC were consistent with membrane fluidity changes facilitating recruitment of activation markers and transmigration. Data suggest that altered neutrophil exposure to NEFA in vivo may potentially regulate their immune response.</p
Lipidome analysis of Symbiodiniaceae reveals possible mechanisms of heat stress tolerance in reef coral symbionts
No full textClimate change-induced global warming threatens the survival of key ecosystems including shallow water coral reefs. Elevated temperatures can disrupt the normal physiological functioning of photosynthetic organisms by altering the fluidity and permeability of chloroplast membranes that is defined and regulated by their lipid composition. Since the habitat-forming reef corals rely on the obligatory symbiosis with dinoflagellates of the family Symbiodiniaceae, their heat stress response can be expected to be strongly influenced by the symbiont's lipid metabolism. However, in contrast to the steady increase in the knowledge of the functioning of coral symbionts at the genomic and transcriptomic level, the understanding of their membrane lipid composition and regulation in response to temperature stress is lagging behind. We have utilised mass spectrometry-based lipidomic analyses to identify the key polar lipids that form the biological membranes of reef coral symbionts, comparing the thermotolerant species Durusdinium trenchii with the thermosensitive taxon Cladocopium C3, both hosted by Acropora valida. Our results indicate that the superior thermotolerance D. trenchii inside the host corals could be achieved through (1) the amount and saturation of sulfoquinovosyldiacylglycerols, in particular through putative photosystem II interactions, (2) the increased digalactosyldiacylglycerol to monogalactosyldiacylglycerol ratio with the potential to stabilise thylakoid membranes and integrated proteins, and (3) the chaperone-like function of lyso-lipids. Thereby, our study provides novel insights into the heat tolerance of coral symbionts, contributing to the understanding of the potential of coral reef ecosystems to respond and adjust to heat stress events that are becoming more frequent due to climate change. Finally, our identification of multiple mechanisms of heat tolerance in Symbiodiniaceae furthers the knowledge of the general stress physiology of photosynthetic organisms
Surfactant phospholipid kinetics in patients with Acute Respiratory Distress Syndrome (ARDS)
No full textIntroduction and Aims ARDS is a significant health burden. Mortality still remains high between 30–50%. Surfactant is a mixture of phospholipids and proteins. Phosphatidylcholines (PC) account for 80% of total phospholipids. PC16:0/16:0 is the main PC with surface tension reducing characteristics. Surfactant abnormalities are well recognised in patients with ARDS However, replacement strategies remain unhelpful in improving mortality. Existing diagnostic definitions fail to identify a homogeneous population and this lack of phenotyping of patients according to surfactant biology may in part explain the absence of therapeutic benefit. The aims of this study are to assess surfactant PC kinetics by the incorporation of methyl-D9-choline in patients with ARDS.
Methods ARDS patients were identified according to American European Consensus Conference (AECC) criteria. Patients were infused with 3.6mg/kg methyl-D9-choline. Small volume bronchoalveolar lavages were performed via a fibre optic bronchoscope at serial time points. Healthy volunteers were used as controls. The phospholipid fraction was extracted and analysed by triple quadrupole electrospray ionisation mass spectrometry.
Results Ten patients and nine healthy controls were recruited. The endogenous PC composition consisted primarily of PC16:0/16:0, PC16:0/18:1 and PC18:0/18:2. There was significant reduction in the relative proportion of endogenous PC16:0/16:0 in patients. Compared to healthy controls, newly synthesised deuteriated PC16:0/16:0 was much lower in patients (26%) than controls (47%).
Total surfactant PC D9-incorporation was linear until 48 hours (0.019%/h, r2=0.9734, P<0.05) and reached its maximum at 48 hours (0.93±0.15%). Steady state of incorporation was achieved between 48–96 hours. There was ∼80% increase in the fractional D9 labelling in patients at 48 hours compared to healthy controls.
Total plasma PC D9-incorporation was linear until 24 hours (0.032%/h, r2=0.9825, P<0.05) and reached its maximum (0.755±0.056%) at 24 hours. Linear decline in enrichment was noted after 24 hours at a rate of 0.003% per hour (r2=0.9915, P<0.05). The total surfactant PC D9-incorporation was much higher for patients at 24 hours and 48 hours reflecting increased synthetic rate.
Conclusions By labelling surfactant PC precursors, it is possible to study surfactant kinetics in patients with ARDS. The methodology may be utilised to phenotype patients according to alveolar surfactant kinetics prior to replacement strategies
Bronchoalveolar lavage, tracheal wash and induced sputum surfactant phospholipid kinetics from healthy volunteers
No full textIntroduction and Aims: Pulmonary surfactant is a complex mixture of lipoproteins synthesised and secreted by alveolar type II cells. The assessment of surfactant synthetic function and metabolism may provide essential information in disease states characterised by surfactant dysfunction. Airway surfactant is thought to be of alveolar origin. However, surfactant kinetics from airway secretions may vary from alveolar surfactant. Stable isotope labelling of surfactant precursors enables dynamic mapping of surfactant PC molecular species. This study aimed to compare three surfactant recovery methods [bronchoalveolar lavage (BAL), tracheal wash (TW) and induced sputum (IS)] to assess surfactant PC kinetics in healthy adults. Surfactant phosphatidylcholine (PC) is synthesised de novo from choline via CDP-choline pathway. By labelling choline with deuterium, a naturally occurring isotope of hydrogen, it is possible to assess surfactant PC synthesis and metabolism in humans.
Methods: Healthy human volunteers had an infusion of methyl-D9-choline-chloride [3.6mg/kg] for 3 hours. BAL and TW specimens were taken at 24 and 48 hours and induced sputum samples were taken at 0, 8, 24, 48 and 96 hours after choline infusion. The lipid fraction was extracted with chloroform and methanol. The samples were analysed by triple quadrupole electro spray ionisation mass spectrometer (ESI/MS). The results are expressed in mean (+/–standard error of mean).
Results: Ten healthy volunteers were recruited. The endogenous PC composition from BAL and TW were similar. The newly synthesised PC fraction mirrored the endogenous composition at 48 hours for both BAL and TW IS PC composition and D9 labelled PC fraction was variable. The total PC D9-incorporation at 48 hours was higher than 24 hours for BAL (0.55±0.04%), TW (0.56±0.04%) and IS (0.58±0.06). PC16:0/16:0 D9-incorporation had significant correlation for BAL and TW (r2=0.8201, P<0.05).
Conclusions: Isotope labelling of choline using ESI/MS analytical method, it is possible to assess surfactant PC metabolism. The tracheal aspirate is an alternative technique to assess surfactant metabolism in patients otherwise unable to tolerate invasive bronchoscopy. This methodology may be utilised to assess surfactant synthetic function in patients with acute lung injury
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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