Exploring protein-protein interactions and oligomerization state of pulmonary surfactant protein C (SP-C) through FRET and fluorescence self-quenching

Pulmonary surfactant (PS) is a lipid-protein complex that forms films reducing surface tension at the alveolar air-liquid interface. Surfactant protein C (SP-C) plays a key role in rearranging the lipids at the PS surface layers during breathing. The N-terminal segment of SP-C, a lipopeptide of 35 amino acids, contains two palmitoylated cysteines, which affect the stability and structure of the molecule. The C-terminal region comprises a transmembrane α-helix that contains a ALLMG motif, supposedly analogous to a well-studied dimerization motif in glycophorin A. Previous studies have demonstrated the potential interaction between SP-C molecules using approaches such as Bimolecular Complementation assays or computational simulations. In this work, the oligomerization state of SP-C in membrane systems has been studied using fluorescence spectroscopy techniques. We have performed self-quenching and FRET assays to analyze dimerization of native palmitoylated SP-C and a non-palmitoylated recombinant version of SP-C (rSP-C) using fluorescently labeled versions of either protein reconstituted in different lipid systems mimicking pulmonary surfactant environments. Our results reveal that doubly palmitoylated native SP-C remains primarily monomeric. In contrast, non-palmitoylated recombinant SP-C exhibits dimerization, potentiated at high concentrations, especially in membranes with lipid phase separation. Therefore, palmitoylation could play a crucial role in stabilizing the monomeric α-helical conformation of SP-C. Depalmitoylation, high protein densities as a consequence of membrane compartmentalization, and other factors may all lead to the formation of protein dimers and higher-order oligomers, which could have functional implications under certain pathological conditions and contribute to membrane transformations associated with surfactant metabolism and alveolar homeostasis.

Attitudes scale toward cancer-related cognitive changes - an initial Colombian validation

OBJECTIVE

The aim of this study was to develop an initial valid tool to measure attitudes toward cancer-related cognitive changes.

SUBJECTS AND METHODS

After revising the literature, three main dimensions were hypothesized. Eight judges were contacted to obtain content validity evidence. A robust Exploratory Factor Analysis (EFA) was performed via a parallel analysis with an Unweighted Least Squares (ULS) estimator and polychoric correlations. The results were crossed with sociodemographic variables to find possible statistical differences and estimate the size effect. Analysis was performed in the software Factor and the statistical package R.

RESULTS

A sample of 374 participants was obtained, involving oncology patients, their caregivers, and people from the general community. A statistical fit was found in two dimensions: Awareness and Judgments [root mean squared error of approximation (RMSEA) = 0.042, standardized root mean square residual (SRMR) = 0.02, comparative fit index (CFI) = 0.99, Tucker-Lewis index (TLI) = 0.98] with a moderate correlation between them (r = 0.612). Optimal reliability indices were obtained for the total scale and its dimensions. No real statistical difference was found between sociodemographic variables; the interpretation norms were established via the quartiles.

CONCLUSIONS

The first attempt to measure the construct of interest was developed with two primary validity evidence based on the content and its internal structure. This instrument could help strengthen the prevention of cancer-related cognitive changes. More research is needed to adhere more valid evidence to the scale.

Cell lipid droplet heterogeneity and altered biophysical properties induced by cell stress and metabolic imbalance

Lipid droplets (LD) are important regulators of lipid metabolism and are implicated in several diseases. However, the mechanisms underlying the roles of LD in cell pathophysiology remain elusive. Hence, new approaches that enable better characterization of LD are essential. This study establishes that Laurdan, a widely used fluorescent probe, can be used to label, quantify, and characterize changes in cell LD properties. Using lipid mixtures containing artificial LD we show that Laurdan GP depends on LD composition. Accordingly, enrichment in cholesterol esters (CE) shifts Laurdan GP from ~0.60 to ~0.70. Moreover, live-cell confocal microscopy shows that cells present multiple LD populations with distinctive biophysical features. The hydrophobicity and fraction of each LD population are cell type dependent and change differently in response to nutrient imbalance, cell density, and upon inhibition of LD biogenesis. The results show that cellular stress caused by increased cell density and nutrient overload increased the number of LD and their hydrophobicity and contributed to the formation of LD with very high GP values, likely enriched in CE. In contrast, nutrient deprivation was accompanied by decreased LD hydrophobicity and alterations in cell plasma membrane properties. In addition, we show that cancer cells present highly hydrophobic LD, compatible with a CE enrichment of these organelles. The distinct biophysical properties of LD contribute to the diversity of these organelles, suggesting that the specific alterations in their properties might be one of the mechanisms triggering LD pathophysiological actions and/or be related to the different mechanisms underlying LD metabolism.

Efficient adsorption of bulky reactive dyes from water using sustainably-derived mesoporous carbons

Hazardous reactive dyes can cause serious environmental problems, as they are difficult to remove from water using conventional adsorbents due to their large molecular sizes and bulky structures. Sustainable mesoporous carbons derived from alginic acid demonstrated promising adsorbent capacity for several representative industrial bulky reactive dye molecules that account for almost 30% of the global textile dye market: Procion Yellow H-XEL (PY), Remazol Black (RB), Procion Crimson H-XEL (PC) and Procion Navy H-XEL (PN). These new adsorbents showed high mesoporosity (>90%) and large pore diameters (>20 nm) facilitating more straightforward and efficient adsorption and desorption processes when compared with predominately microporous activated carbon (AC), Norit, of similar surface chemistry, or with Silica gel (Sgel) that shows good mesoporosity but is hydrophilic. Their adsorption capacity was also significantly higher than that of both AC and Sgel, verifying suitability for bulky dye elimination from wastewater. Adsorption kinetic studies showed a best fit with the Elovich model, indicating a heterogeneous surface adsorption process. The adsorption isotherm data was best represented via the Toth model for almost all adsorbent/dye systems (R² ≥ 0.98), validating the results of the Elovich model whereby the adsorbent is structurally heterogenous with multilayer dye coverage. From thermodynamic analysis, the derived parameters of ΔG (-11.6 ∼ -6.2 kJ/mol), ΔH and ΔS demonstrate a spontaneous, enthalpy controlled adsorption process that was exothermic for RB (-10.0 kJ/mol) and PC (-23.9 kJ/mol) and endothermic for PY (3.9 kJ/mol) and PN (13.2 kJ/mol). Overall these alginic acid based mesoporous carbons are cost-effective, sustainable and efficient alternatives to current predominantly microporous adsorbent systems.

Effect of Cisplatin and Its Cationic Analogues in the Phase Behavior and Permeability of Model Lipid Bilayers

Increasing evidence suggests a critical role of lipids in both the mechanisms of toxicity and resistance of cells to platinum(II) complexes. In particular, cisplatin and other analogues were reported to interact with lipids and transiently promote lipid phase changes both in the bulk membranes and in specific membrane domains. However, these processes are complex and not fully understood. In this work, cisplatin and its cationic species formed at pH 7.4 in low chloride concentrations were tested for their ability to induce phase changes in model membranes with different lipid compositions. Fluorescent probes that partition to different lipid phases were used to report on the fluidity of the membrane, and a leakage assay was performed to evaluate the effect of cisplatin in the permeability of these vesicles. The results showed that platinum(II) complex effects on membrane fluidity depend on membrane lipid composition and properties, promoting a stronger decrease in the fluidity of membranes containing gel phase. Moreover, at high concentration, these complexes were prone to alter the permeability of lipid membranes without inducing their collapse or aggregation.

Data on accumulative allocation of water rights in the Atacama Desert (Antofagasta Region, northern Chile), 1905–2018

This article presents a dataset on the accumulated water flow (L/s) granted in the Antofagasta Region for each year between 1905 and 2018. We produced the dataset starting from the official public records on water rights (Registro Público de Derechos de Aprovechamiento de Aguas, RPDAA), which are free to access and available at the National Water Agency's website (Dirección General de Aguas, DGA). The initial data described 1047 individual water rights granted in the Antofagasta Region according to 65 criteria. In order to find errors in the data, inconsistencies between the data, or/and the absence of relevant information, we revised and validated the data through different methods, including a literature review and interviews to public officials. Then, we calculated the accumulated water flow (L/s) from the annual flow granted each year (1905–2018) in the two main basins of the region: the Loa River Basin, and the Salar de Atacama Basin. In doing so, we differentiated the type of water (ground or surface water) and the use of water. Thus, the data show and compare temporal variations in the allocation of ground and surface water to different water uses in the two basins. The data are useful to researchers, decision makers and to the general population interested in the processes of water distribution within the Chilean context.

Clinical Correlates of Cardiac Conduction in Bipolar Disorder

Introduction

Patients with bipolar disorder (BD) have an increased risk for cardiovascular morbimortality. Clinical risk factors, specifically for arrhythmias and sudden cardiac death remain understudied.

Objectives

This study was conducted to assess differences in cardiac conduction among BD patients.

Methods

We included patients with BD in a cross-sectional design, confirmed by structured interview, age 18 through 80. Clinical characteristics were obtained using a structured questionnaire or medical records review. ECG intervals duration and morphology were manually assessed by cardiologists and compared among clinical subgroups using Chi-square, Mann-Whitney, and Kruskall-Wallis tests. Exploratory multivariable linear and logistic regression models were fitted to adjust for potential confounders.

Results

We included 117 patients (60.7% women, 76.9% bipolar I, 50% history of psychosis, 22.6% suicide attempts). We found a significantly longer QTc interval in BD patients with hypertension (difference: 9.5 ms, p=0.006), obesity (difference: 25 ms, p=0.001), and metabolic syndrome (difference: 13 ms, p=0.007). Hypertension remained a significant predictor of longer QTc after adjusting for age, gender, and antipsychotic use (estimate 17.718, p=0.018). We observed a significantly shorter PR interval in women (difference: 6 ms, p=0.029), early age of onset (difference 6 ms, p=0.025), non-users of lithium (difference 4 ms, p=0.002), and early trauma (difference 4 ms, p=0.038). Finally, we identified significant correlations between symptom severity, blood glucose and PR interval (r=0.298, p=0.001; r=0.278, p=0.003; respectively).

Conclusions

Patients with BD and hypertension may have an increased risk for QTc prolongation. Careful cardiovascular monitoring may be warranted.

Disclosure

No significant relationships.

On the foundations of fluorescence: The work of Robert W. Cowgill

This note on the work of Robert W. Cowgill in 1963 (Archives Biochemistry and Biophysics 100, 36-44), addressing the effect of substituents in indole and phenol compounds as models for tryptophan and tyrosine, intends to frame it within the foundations of protein fluorescence and its applications, considering its relevance and impact.

Laurdan in live cell imaging: Effect of acquisition settings, cell culture conditions and data analysis on generalized polarization measurements

Cell function is highly dependent on membrane structure, organization, and fluidity. Therefore, methods to probe the biophysical properties of biological membranes are required. Determination of generalized polarization (GP) values using Laurdan in fluorescence microscopy studies is one of the most widely-used methods to investigate changes in membrane fluidity in vitro and in vivo. In the last couple of decades, there has been a major increase in the number of studies using Laurdan GP, where several different methodological approaches are used. Such differences interfere with data interpretation inasmuch as it is difficult to validate if Laurdan GP variations actually reflect changes in membrane organization or arise from biased experimental approaches. To address this, we evaluated the influence of different methodological details of experimental data acquisition and analysis on Laurdan GP. Our results showed that absolute GP values are highly dependent on several of the parameters analyzed, showing that incorrect data can result from technical and methodological inconsistencies. Considering these differences, we further analyzed the impact of cell variability on GP determination, focusing on basic cell culture conditions, such as cell confluency, number of passages and media composition. Our results show that GP values can report alterations in the biophysical properties of cell membranes caused by cellular adaptation to the culture conditions. In summary, this study provides thorough analysis of the factors that can lead to Laurdan GP variability and suggests approaches to improve data quality, which would generate more precise interpretation and comparison within individual studies and among the literature on Laurdan GP.

Probing the Structural Dynamics of the Activation Gate of KcsA Using Homo-FRET Measurements

The allosteric coupling between activation and inactivation processes is a common feature observed in K⁺ channels. Particularly, in the prokaryotic KcsA channel the K⁺ conduction process is controlled by the inner gate, which is activated by acidic pH, and by the selectivity filter (SF) or outer gate, which can adopt non-conductive or conductive states. In a previous study, a single tryptophan mutant channel (W67 KcsA) enabled us to investigate the SF dynamics using time-resolved homo-Förster Resonance Energy Transfer (homo-FRET) measurements. Here, the conformational changes of both gates were simultaneously monitored after labelling the G116C position with tetramethylrhodamine (TMR) within a W67 KcsA background. At a high degree of protein labeling, fluorescence anisotropy measurements showed that the pH-induced KcsA gating elicited a variation in the homo-FRET efficiency among the conjugated TMR dyes (TMR homo-FRET), while the conformation of the SF was simultaneously tracked (W67 homo-FRET). The dependence of the activation pK_a of the inner gate with the ion occupancy of the SF unequivocally confirmed the allosteric communication between the two gates of KcsA. This simple TMR homo-FRET based ratiometric assay can be easily extended to study the conformational dynamics associated with the gating of other ion channels and their modulation.

Lipid Hydroperoxide Compromises the Membrane Structure Organization and Softens Bending Rigidity

Lipid hydroperoxides are key mediators of diseases and cell death. In this work, the structural and dynamic perturbations induced by the hydroperoxidized POPC lipid (POPC-OOH) in fluid POPC membranes, at both 23 and 37 °C, were addressed using advanced small-angle X-ray scattering (SAXS) and fluorescence methodologies. Notably, SAXS reveals that the hydroperoxide group decreases the lipid bilayer bending rigidity. This alteration disfavors the bilayer stacking and increases the swelling in-between stacked bilayers. We further investigated the changes in the apolar/polar interface of hydroperoxide-containing membranes through time-resolved fluorescence/anisotropy experiments of the probe TMA-DPH and time-dependent fluorescence shifts of Laurdan. A shorter mean fluorescence lifetime for TMA-DPH was obtained in enriched POPC-OOH membranes, revealing a higher degree of hydration near the membrane interface. Moreover, a higher microviscosity near TMA-DPH and lower order are predicted for these oxidized membranes, at variance with the usual trend of variation of these two parameters. Finally, the complex relaxation process of Laurdan in pure POPC-OOH membranes also indicates a higher membrane hydration and viscosity in the close vicinity of the -OOH moiety. Altogether, our combined approach reveals that the hydroperoxide group promotes alterations in the membrane structure organization, namely, at the level of membrane order, viscosity, and bending rigidity.

The long chain base unsaturation has a stronger impact on 1-deoxy(methyl)-sphingolipids biophysical properties than the structure of its C1 functional group

1-deoxy-sphingolipids, also known as atypical sphingolipids, are directly implicated in the development and progression of hereditary sensory and autonomic neuropathy type 1 and diabetes type 2. The mechanisms underlying their patho-physiological actions are yet to be elucidated. Accumulating evidence suggests that the biological actions of canonical sphingolipids are triggered by changes promoted on membrane organization and biophysical properties. However, little is known regarding the biophysical implications of atypical sphingolipids. In this study, we performed a comprehensive characterization of the effects of the naturally occurring 1-deoxy-dihydroceramide, 1-deoxy-ceramide^Δ14Z and 1-deoxymethyl-ceramide^Δ3E in the properties of a fluid membrane. In addition, to better define which structural features determine sphingolipid ability to form ordered domains, the synthetic 1-O-methyl-ceramide^Δ4E and 1-deoxy-ceramide^Δ4E were also studied. Our results show that natural and synthetic 1-deoxy(methyl)-sphingolipids fail to laterally segregate into ordered domains as efficiently as the canonical C16-ceramide. The impaired ability of atypical sphingolipids to form ordered domains was more dependent on the presence, position, and configuration of the sphingoid base double bond than on the structure of its C1 functional group, due to packing constraints introduced by an unsaturated backbone. Nonetheless, absence of a hydrogen bond donor and acceptor group at the C1 position strongly reduced the capacity of atypical sphingolipids to form gel domains. Altogether, the results showed that 1-deoxy(methyl)-sphingolipids induce unique changes on the biophysical properties of the membranes, suggesting that these alterations might, in part, trigger the patho-biological actions of these lipids.

Interface-Mediated Mechanism of Action-The Root of the Cytoprotective Effect of Immediate-Release Omeprazole

Omeprazole is usually administered under an enteric coating. However, there is a Food and Drug Administration-approved strategy that enables its release in the stomach. When locally absorbed, omeprazole shows a higher efficacy and a cytoprotective effect, whose mechanism was still unknown. Therefore, we aimed to assess the effect of the absorption route on the gastric mucosa. 2D and 3D models of dipalmitoylphosphatidylcholine (DPPC) at different pH values (5.0 and 7.4) were used to mimic different absorption conditions. Several experimental techniques, namely, fluorescence studies, X-ray scattering methodologies, and Langmuir monolayers coupled with microscopy, X-ray diffraction, and infrared spectroscopy techniques, were combined with molecular dynamics simulations. The results showed that electrostatic and hydrophobic interactions between omeprazole and DPPC rearranged the conformational state of DPPC. Omeprazole intercalates among DPPC molecules, promoting domain formation with untilted phospholipids. Hence, the local release of omeprazole enables its action as a phospholipid-like drug, which can reinforce and protect the gastric mucosa.

Limnological response from high-altitude wetlands to the water supply in the Andean Altiplano

The Andean Altiplano-Puna is located at an elevation of approximately 4000 m.a.s.l. and is delineated by the Western and the Eastern Andes Cordillera. The high-altitude wetlands (HAWs) in the Central Andes are unique ecosystems located in the Altiplano that provide many ecosystem services. The objective of this study was to characterize the spatial heterogeneity of the environmental conditions associated with varying hydrology of the HAW, Salar de Tara, in the Andean Altiplano. Sediment samples of up to 20 cm in depth were obtained from various salt flat sub-environments. The samples were analyzed using proxies for mineralogical and chemical composition, thermal analysis, and magnetic susceptibility. Diatom and ostracod communities were also identified and analyzed. The results reflected changes in the geochemistry, carbon content, mineralogy, and magnetic properties of the sediments that can be explained by variations in the sources of water input to the Salar de Tara. The sub-environments depend on the supply of water via the groundwater recharge of springs adjacent to the streamflow from the Zapaleri River, which promotes greater diversity and richness of genera. Our results suggest that water extraction at industrial levels greatly impacts the persistence of hydrologically connected HAWs, which concentrate a worldwide interest in brine mining.

Tetraoctylammonium, a Long Chain Quaternary Ammonium Blocker, Promotes a Noncollapsed, Resting-Like Inactivated State in KcsA

Alkylammonium salts have been used extensively to study the structure and function of potassium channels. Here, we use the hydrophobic tetraoctylammonium (TOA⁺) to shed light on the structure of the inactivated state of KcsA, a tetrameric prokaryotic potassium channel that serves as a model to its homologous eukaryotic counterparts. By the combined use of a thermal denaturation assay and the analysis of homo-Förster resonance energy transfer in a mutant channel containing a single tryptophan (W67) per subunit, we found that TOA⁺ binds the channel cavity with high affinity, either with the inner gate open or closed. Moreover, TOA⁺ bound at the cavity allosterically shifts the equilibrium of the channel's selectivity filter conformation from conductive to an inactivated-like form. The inactivated TOA⁺-KcsA complex exhibits a loss in the affinity towards permeant K⁺ at pH 7.0, when the channel is in its closed state, but maintains the two sets of K⁺ binding sites and the W67-W67 intersubunit distances characteristic of the selectivity filter in the channel resting state. Thus, the TOA⁺-bound state differs clearly from the collapsed channel state described by X-ray crystallography and claimed to represent the inactivated form of KcsA.

The mechanism of action of pepR, a viral-derived peptide, against Staphylococcus aureus biofilms

OBJECTIVES

To investigate the mechanism of action at the molecular level of pepR, a multifunctional peptide derived from the Dengue virus capsid protein, against Staphylococcus aureus biofilms.

METHODS

Biofilm mass, metabolic activity and viability were quantified using conventional microbiology techniques, while fluorescence imaging methods, including a real-time calcein release assay, were employed to investigate the kinetics of pepR activity at different biofilm depths.

RESULTS

Using flow cytometry-based assays, we showed that pepR is able to prevent staphylococcal biofilm formation due to a fast killing of planktonic bacteria, which in turn resulted from a peptide-induced increase in the permeability of the bacterial membranes. The activity of pepR against pre-formed biofilms was evaluated through the application of a quantitative live/dead confocal laser scanning microscopy (CLSM) assay. The results show that the bactericidal activity of pepR on pre-formed biofilms is dose and depth dependent. A CLSM-based assay of calcein release from biofilm-embedded bacteria was further developed to indirectly assess the diffusion and membrane permeabilization properties of pepR throughout the biofilm. A slower diffusion and delayed activity of the peptide at deeper layers of the biofilm were quantified.

CONCLUSIONS

Overall, our results show that the activity of pepR on pre-formed biofilms is controlled by its diffusion along the biofilm layers, an effect that can be counteracted by an additional administration of peptide. Our study sheds new light on the antibiofilm mechanism of action of antimicrobial peptides, particularly the importance of their diffusion properties through the biofilm matrix on their activity.

Canonical and 1-Deoxy(methyl) Sphingoid Bases: Tackling the Effect of the Lipid Structure on Membrane Biophysical Properties

Compared to the canonical sphingoid backbone of sphingolipids (SLs), atypical long-chain bases (LCBs) lack C1-OH (1-deoxy-LCBs) or C1-CH₂OH (1-deoxymethyl-LCBs). In addition, when unsaturated, they present a cis-double bond instead of the canonical  Δ4-5 trans-double bond. These atypical LCBs are directly correlated with the development and progression of hereditary sensory and autonomic neuropathy type 1 and diabetes type II through yet unknown mechanisms. Changes in membrane properties have been linked to the biological actions of SLs. However, little is known about the influence of the LCB structure, particularly 1-deoxy(methyl)-LCB, on lipid-lipid interactions and their effect on membrane properties. To address this question, we used complementary fluorescence-based methodologies to study membrane model systems containing POPC and the different LCBs of interest. Our results show that 1-deoxymethyl-LCBs have the highest ability to reduce the fluidity of the membrane, while the intermolecular interactions of 1-deoxy-LCBs were found to be weaker, leading to the formation of less-ordered domains compared to their canonical counterparts-sphinganine and sphingosine. Furthermore, while the presence of a trans-double bond at the Δ4-5 position of the LCB increased the fluidity of the membrane compared to a saturated LCB, a cis-double bond completely disrupted the ability of the LCB to segregate into ordered domains. In conclusion, even small changes on the structure of the LCB, as seen in 1-deoxy(methyl)-LCBs, strongly affects lipid-lipid interactions and membrane fluidity. These results provide evidence that altered balance between species with different LCBs affect membrane properties and may contribute to the pathobiological role of these lipids.

Human importin α3 and its N-terminal truncated form, without the importin-β-binding domain, are oligomeric species with a low conformational stability in solution

BACKGROUND

Eukaryotic cells have a continuous transit of macromolecules between the cytoplasm and the nucleus. Several carrier proteins are involved in this transport. One of them is importin α, which must form a complex with importin β to accomplish its function, by domain-swapping its 60-residue-long N terminus. There are several human isoforms of importin α; among them, importin α3 has a particularly high flexibility.

METHODS

We studied the conformational stability of intact importin α3 (Impα3) and its truncated form, where the 64-residue-long, N-terminal importin-β-binding domain (IBB) has been removed (ΔImpα3), in a wide pH range, with several spectroscopic, biophysical, biochemical methods and with molecular dynamics (MD).

RESULTS

Both species acquired native-like structure between pH 7 and 10.0, where Impα3 was a dimer (with an apparent self-association constant of ~10 μM) and ΔImpα3 had a higher tendency to self-associate than the intact species. The acquisition of secondary, tertiary and quaternary structure, and the burial of hydrophobic patches, occurred concomitantly. Both proteins unfolded irreversibly at physiological pH, by using either temperature or chemical denaturants, through several partially folded intermediates. The MD simulations support the presence of these intermediates.

CONCLUSIONS

The thermal stability of Impα3 at physiological pH was very low, but was higher than that of ΔImpα3. Both proteins were stable in a narrow pH range, and they unfolded at physiological pH populating several intermediate species.

GENERAL SIGNIFICANCE

The low conformational stability explains the flexibility of Impα3, which is needed to carry out its recognition of complex cargo sequences.

Introspective and Neurophysiological Measures of Mind Wandering in Schizophrenia

Patients with schizophrenia have often been considered to be “in their own world”. However, this casual observation has not been proven by scientific evidence so far. This can be explained because scientific research has usually addressed cognition related to the processing of external stimuli, but only recently have efforts been made to explain thoughts, images and feelings not directly related to the external environment. This internally directed cognition has been called mind wandering. In this paper, we have explored mind wandering in schizophrenia under the hypothesis that a predominance of mind wandering would be a core dysfunction in this disorder. To this end, we collected verbal reports and measured electrophysiological signals from patients with schizophrenia spectrum disorders and matched healthy controls while they were presented with segments of films. The results showed that mind wandering was more frequent in patients than in controls. This higher frequency of mind wandering did not correlate with deficits in attentional, memory or executive functioning. In addition, mind wandering in patients was characterized by a different pattern of Electroencephalography (EEG) complexity in patients than in controls, leading to the suggestion that mind wandering in schizophrenia could be of a different nature. These findings could have relevant implications for the conceptualization of this severe mental disorder.

Disentangling functional trait variation and covariation in epiphytic lichens along a continent-wide latitudinal gradient

Characterizing functional trait variation and covariation, and its drivers, is critical to understand the response of species to changing environmental conditions. Evolutionary and environmental factors determine how traits vary among and within species at multiple scales. However, disentangling their relative contribution is challenging and a comprehensive trait-environment framework addressing such questions is missing in lichens. We investigated the variation in nine traits related to photosynthetic performance, water use and nutrient acquisition applying phylogenetic comparative analyses in lichen epiphytic communities on beech across Europe. These poikilohydric organisms offer a valuable model owing to their inherent limitations to buffer contrasting environmental conditions. Photobiont type and growth form captured differences in certain physiological traits whose variation was largely determined by evolutionary processes (i.e. phylogenetic history), although the intraspecific component was non-negligible. Seasonal temperature fluctuations also had an impact on trait variation, while nitrogen content depended on photobiont type rather than nitrogen deposition. The inconsistency of trait covariation among and within species prevented establishing major resource use strategies in lichens. However, we did identify a general pattern related to the water-use strategy. Thus, to robustly unveil lichen responses under different climatic scenarios, it is necessary to incorporate both among and within-species trait variation and covariation.

When reporting Nocardia spp is not enough. Brain abscess caused by Nocardia farcinica

Abscesses caused by the genus Nocardia spp are relatively rare, accounting for approximately 2 % of all brain abscesses, but with a significantly higher mortality. Special stains of brain abscess material from a 60-year-old man showed Gram-positive branching bacilli and the presence of long, acid-fast branching filamentous bacilli suggesting Nocardia infection. Presented here is a case of multidisciplinary management of a patient who developed cerebral abscesses by Nocardia farcinica, confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), that was susceptible to trimethoprim/sulfamethoxazole, linezolid, imipenem and not susceptible to minocycline. This case highlights the importance of performing subtyping and antimicrobial testing in order to improve clinical and treatment outcomes due to patterns of antibiotics resistance among Nocardia species.

A case study on the re-establishment of the cyanolichen symbiosis: where do the compatible photobionts come from?

BACKGROUND AND AIMS

In order to re-establish lichen symbiosis, fungal spores must first germinate and then associate with a compatible photobiont. To detect possible establishment limitations in a sexually reproducing cyanolichen species, we studied ascospore germination, photobiont growth and photobiont association patterns in Pectenia plumbea.

METHODS

Germination tests were made with ascospores from 500 apothecia under different treatments, and photobiont growth was analysed in 192 isolates obtained from 24 thalli. We determined the genotype identity [tRNALeu (UAA) intron] of the Nostoc cyanobionts from 30 P. plumbea thalli from one population. We also sequenced cyanobionts of 41 specimens of other cyanolichen species and 58 Nostoc free-living colonies cultured from the bark substrate.

KEY RESULTS

Not a single fungal ascospore germinated and none of the photobiont isolates produced motile hormogonia. Genetic analyses revealed that P. plumbea shares Nostoc genotypes with two other cyanolichen species of the same habitat, but these photobionts were hardly present in the bark substrate.

CONCLUSIONS

Due to the inability of both symbionts to thrive independently, the establishment of P. plumbea seems to depend on Dendriscocaulon umhausense, the only cyanolichen species in the same habitat that reproduces asexually and acts as a source of appropriate cyanobionts. This provides support to the hypothesis about facilitation among lichens.

Lipid profile is associated with treatment regimen in a large cohort of children and adolescents with Type 1 diabetes mellitus: a study from the international SWEET database

AIMS

To examine the effect of pump vs injection therapy on the lipid profile of children with Type 1 diabetes mellitus.

METHODS

A cross-sectional analysis of the lipid profile of children aged ≤ 18 years with Type 1 diabetes mellitus from SWEET, an international diabetes registry, was conducted with a focus on the effect of treatment regimen. Dyslipidaemia was defined as LDL cholesterol ≥2.6 mmol/l or non-HDL cholesterol ≥3.1 mmol/l. LDL and non-HDL cholesterol values among 14 290 children (52% boys, 51% receiving pump therapy) from 60 SWEET centres were analysed by linear and logistic regression analysis adjusted for sex, age, diabetes duration, HbA_1c and BMI-standard deviation score group, region, and common interactions between age, sex, HbA_1c and BMI.

RESULTS

This study confirmed the established associations of increased lipids with female sex, age, diabetes duration, HbA_1c and BMI. LDL and non-HDL cholesterol levels were lower in the pump therapy group compared to the injection therapy group [LDL cholesterol: injection therapy 2.44 mmol/l (95% CI 2.42 to 2.46) vs pump therapy 2.39 mmol/l (95% CI 2.37-2.41), P<0.001; non-HDL cholesterol: injection therapy 2.88 mmol/l (95% CI 2.86 to 2.90) vs pump therapy 2.80 mmol/l (95% CI 2.78-2.82), both P<0.0001]. Similarly, the odds ratios for LDL cholesterol ≥2.6 mmol/l [0.89 (95% CI 0.82-0.97)] and non-HDL cholesterol ≥3.1 mmol/l [0.85 (0.78 to 0.93)] were significantly lower in the pump therapy group, even after all adjustments.

CONCLUSIONS

Our results indicate that pump therapy is associated with a better lipid profile.

Insights into gold nanoparticles as a mucoadhesive system

A large number of drugs are administered on different mucosal surfaces. However, due to the poor mucoadhesion of the current formulations, their bioavailability is often very low. The development of efficient mucoadhesive drug delivery systems is thus crucial for improving the performance of these drugs. The mucoadhesive properties of gold nanoparticles were investigated. First, two types of gold nanoparticles were synthesized: AuNP1 and AuNP2. AuNP1 only contain internal thiol groups on their metallic core, and AuNP2 contain both internal and peripheral thiol groups. Different protocols based on an adapted quantitative colorimetric method, UV-visible and fluorescence spectroscopies were then developed to gather information on their mucoadhesive properties. Moreover, a global correction factor for the inner filter effect in spectrofluorimetry was proposed, and the data obtained were compared to those commonly used in the literature. Mucins deeply interact with AuNP1, perturbing their core, whereas they remain at the periphery of AuNP2. The quantitative method suggests that a larger number of mucins interact with AuNP2. The establishment of this protocol could be applied to assess the mucoadhesive properties of other stable molecules. This mucoadhesive property of gold nanoparticles could be combined with their drug delivery ability in order to improve the medication administered on mucosa.

Risk assessment of antimicrobial resistance along the food chain through culture-independent methodologies

Antimicrobial resistance (AMR) represents a major challenge for Public Health and the scientific community, and requires immediate and drastic solutions. Acquired resistance to certain antimicrobials is already widespread to such an extent that their efficacy in the treatment of certain life-threatening infections is already compromised. To date, the emergence and spread of AMR has been attributed to the use, misuse or indiscriminate use of antibiotics as therapeutic drugs in human, animal and plant health, or as growth promoters in veterinary husbandry. In addition, there is growing concern over the possibility of AMR transmission via the food chain. Food processing environments could act as potential hotspots for AMR acquisition and spread. Indeed, biocide use and exposure to food-related stresses and food processing technologies could presumably act as selection pressures for increased microbial resistance against clinically relevant antibiotics. Global AMR surveillance is critical for providing the necessary information to form global strategies and to monitor the effectiveness of public health interventions as well as to detect new trends and emerging threats. Surveillance of AMR is currently based on the isolation of indicator microorganisms and the phenotypic characterisation of the strains isolated. However, this approach provides very limited information on the mechanisms driving AMR or on the presence and spread of AMR genes. Whole genome sequencing (WGS) of bacterial pathogens is a powerful tool that can be used for epidemiological surveillance, outbreak detection and infection control. In addition, whole metagenome sequencing (WMS) allows for the culture-independent analysis of complex microbial communities, providing useful information on the occurrence of AMR genes. Both approaches can be used to provide the information necessary for the implementation of quantitative risk assessment of AMR transmission routes along the food chain.

β-Cyclodextrin as a Precursor to Holey C-Doped g-C3 N4 Nanosheets for Photocatalytic Hydrogen Generation

A green, template-free and easy-to-implement strategy was developed to access holey g-C₃ N₄ (GCN) nanosheets doped with carbon. The protocol involves heating dicyandiamide with β-cyclodextrin (βCD) prior to polymerization. The local symmetry of the GCN skeleton is broken, yielding CxGCN (x corresponds to the initial amount of βCD used) with pores and a distorted structure. The electronic, emission, optical and textural properties of the best-performing material, C2GCN, were significantly modified as compared to bulk GCN. The spectroscopic and luminescent features of C2GCN show the characteristic π-π* electronic transition of GCN, accompanied by much stronger n-π* electronic transitions owing to the porous and distorted network. These new electronic transitions, along with the presence of additional carbon synergistically contributed to enhanced visible light absorption and restrained recombination of electron-hole pairs. Steady-state and time-resolved photoluminescence showed an effective quench of the fluorescence emission, accompanied by a decrease of fluorescence lifetime of C2GCN (2.20 ns) in comparison with GCN (5.85 ns), owing to the delocalization of electron and holes to new recombination centers. The photocatalytic activity of C2GCN was attributed to efficient charge carrier separation and improved visible-light absorbing ability. As result, C2GCN exhibited ∼5 times higher photocatalytic H₂ generation under visible light than bulk GCN.

The combination of block copolymers and phospholipids to form giant hybrid unilamellar vesicles (GHUVs) does not systematically lead to "intermediate" membrane properties

In this work, the elasticity under stretching as well as the fluidity of Giant Hybrid Unilamellar Vesicles (GHUV) has been studied. The membrane structuration of these GHUVs has already been studied at the micro and nanoscale in a previous study of the team. These GHUVs were obtained by the association of a fluid phospholipid (POPC) and a triblock copolymer, poly(ethyleneoxide)-b-poly(dimethylsiloxane)-b-poly(ethyleneoxide). Although the architecture of triblock copolymers can facilitate vesicle formation, they have been scarcely used to generate GHUVs. We show, through micropipette aspiration and FRAP experiments, that the incorporation of a low amount of lipids in the polymer membrane leads to a significant loss of the toughness of the vesicle and subtle modification of the lateral diffusion of polymer chains. We discuss the results within the framework of the conformation of the triblock copolymer chain in the membrane and in the presence of lipid nanodomains.