The role of air relative humidity on the wettability of Pseudomonas fluorescens AR11 biofilms

Biofilms are complex porous materials formed by microorganisms, polysaccharides, proteins, eDNA, inorganic matter, and water. They are ubiquitous in various environmental niches and are known to grow at solid-liquid, solid-air and air-liquid interfaces, often causing problems in several industrial and sanitary fields. Their removal is a challenge in many applications and numerous studies have been conducted to identify promising chemical species as cleaning agents. While these substances target specific components of biofilm structure, the role of water content in biofilm, and how it can influence wettability and detergent absorption have been quite neglected in the literature. Estimating water content in biofilm is a challenging task due to its heterogeneity in morphology and chemical composition. In this study, we controlled water content in Pseudomonas fluorescens AR 11 biofilms grown on submerged glass slides by regulating environmental relative humidity after drying. Interfacial properties of biofilm were investigated by measuring wetting of water and soybean oil. The morphology of biofilm structure was evaluated using Confocal Laser Scanning Microscopy and Scanning Electron Microscopy. The results showed that biofilm water content has a significant and measurable effect on its wettability, leading to the hypothesis that a preliminary control of water content can play a crucial role in biofilm removal process.

Forced Wetting Properties of Bacteria-Laden Droplets Experiencing Initial Evaporation

Microbial adhesion and spreading on surfaces are crucial aspects in environmental and industrial settings being also the early stage of complex surface-attached microbial communities known as biofilms. In this work, Pseudomonas fluorescens-laden droplets on hydrophilic substrates (glass coupons) are allowed to partially evaporate before running wetting measurements, to study the effect of evaporation on their interfacial behavior during spillover or splashing. Forced wetting is investigated by imposing controlled centrifugal forces, using a novel rotatory device (Kerberos). At a defined evaporation time, results for the critical tangential force required for the inception of sliding are presented. Microbe-laden droplets exhibit different wetting/spreading properties as a function of the imposed evaporation times. It is found that evaporation is slowed down in bacterial droplets with respect to nutrient medium ones. After sufficient drying times, bacteria accumulate at droplet edges, affecting the droplet shape and thus depinning during forced wetting tests. Droplet rear part does not pin during the rotation test, while only the front part advances and spreads along the force direction. Quantitative results obtained from the well-known Furmidge's equation reveal that force for sliding inception increases as evaporation time increases. This study can be of support for control of biofilm contamination and removal and possible design of antimicrobial/antibiofouling surfaces.

Impact of the first wave of the COVID-19 pandemic on French Health students

Context

In France, care workers and health students have been intensely mobilized during the first wave of the COVID-19 pandemic. But few studies have evaluated psychological distress on non-medical health students, in addition to the challenges posed by pedagogical continuity while universities are closed following health and safety regulations.

Objectives

This study aims to assess COVID-19's impact on health students in France on different levels: psychological, educational and social.

Methods

An online national cross-sectional study, from April 11 to May 30 2020, included sociodemographic, work conditions and numeric scales.

Results

A total of 4411 students answered. Regarding the K6 scale, 39% of students had moderate distress, and 21% had a high level of distress. Risk factors of psychological distress included being a woman (P < 0.001), being between 19 and 21 years old (P < 0.001), living alone (P = 0.008), and not having the ability to isolate (P < 0.001). Students on the frontline had less psychological distress (57 vs 62%, P = 0.003), better quality of sleep (34% vs 28% high quality, P < 0.001) but a higher consumption of medical (8.5% vs 6.5%, P = 0.044) and non-medical (18% vs 10%, P < 0.001) psychotropic drugs. Nurse and medical students had more distress and used more non-medical psychotropic substances than other health students (15% vs 9.2%).

Discussion

COVID-19’ crisis had an important impact on health students’ mental health, social life and training with discrepancies regarding the speciality whether they were on the frontline or not. There is an urgent need for psychological and pedagogical support for students, and even more so regarding the prolongation of the COVID-19 epidemic.

Self-rated residual symptoms do not predict 1-year recurrence of depression

Background

Residual depressive symptoms are generally documented as a risk factor for recurrence. In the absence of a specific instrument for the assessment of residual symptoms, a new 25-item Depression Residual Symptom Scale (DRSS) was elaborated and tested for recurrence prediction over a 1-year follow-up.

Sampling and methods

Fifty-nine patients in remission after a major depressive episode (MDE) were recruited in two centres. They were assessed with the DRSS and the Montgomery-Asberg Depression Rating Scale (MADRS) at inclusion and followed for 1 year according to a seminaturalistic design. The DRSS included specific depressive symptoms and subjective symptoms of vulnerability, lack of return to usual self and premorbid level of functioning.

Results

Severity of residual symptoms was not significantly associated with increased risk of recurrence. However, DRSS score was significantly higher among patients with three or more episodes than one to two episodes. Number of previous episodes and treatment interruption were not identified as significant predictors of recurrence.

Conclusion

The proposed instrument is not predictive of depressive recurrence, but is sensitive to increased perception of vulnerability associated with consecutive episodes. Limitations include small sample size, seminaturalistic design (no standardisation of treatment) and content of the instrument.

Network integration of data and analysis of oncology interest

The Human Genome Project has deeply transformed biology and the field has since then expanded to the management, processing, analysis and visualization of large quantities of data from genomics, proteomics, medicinal chemistry and drug screening. This huge amount of data and the heterogeneity of software tools that are used implies the adoption on a very large scale of new, flexible tools that can enable researchers to integrate data and analysis on the network. ICT technology standards and tools, like Web Services and related languages, and workflow management systems, can support the creation and deployment of such systems. While a number of Web Services are appearing and personal workflow management systems are also being more and more offered to researchers, a reference portal enabling the vast majority of unskilled researchers to take profit from these new technologies is still lacking. In this paper, we introduce the rationale for the creation of such a portal and present the architecture and some preliminary results for the development of a portal for the enactment of workflows of interest in oncology.

Psychological stress and cortisol secretion in anhedonic alcoholic men

We investigated plasma cortisol in a psychological stress paradigm in seven weaned anhedonic alcoholics in comparison with seven age-matched healthy controls. Alcoholics had significantly higher mean plasma cortisol at baseline and no increase following a psychological stress paradigm. Anhedonic alcoholics judged the experimental situation less agreeable than controls. Anhedonic alcoholics may have blunted cortisol response to psychological stress.

The frequency of conjugative transposition of Tn916 is not determined by the frequency of excision

Excision and formation of a covalently closed circular transposon molecule are required for conjugative transposition of Tn916 but are not the only factors that limit the frequency of conjugative transposition from one host to another. We found that in gram-positive bacteria, an increase in the frequency of excision and circularization of Tn916 caused by expression of integrase (Int) and excisionase (Xis) from a xylose-inducible promoter does not lead to an increase in the frequency of conjugative transposition. We also found that the concentration of Int and Xis in the recipient cell does not limit the frequency of conjugative transposition and that increased excision does not result in increased expression of transfer functions required to mobilize a plasmid containing the Tn916 origin of transfer. We conclude that in gram-positive hosts in which the Tn916 functions Int and Xis are overexpressed, the frequency of conjugative transposition is limited by the availability of transfer functions.

3-Hydroxy-3-methylglutaryl-CoA reductase inhibitors attenuate vascular smooth muscle proliferation by preventing rho GTPase-induced down-regulation of p27(Kip1)

The mechanism by which platelet-derived growth factor (PDGF) regulates vascular smooth muscle cell (SMC) DNA synthesis is unknown, but may involve isoprenoid intermediates of the cholesterol biosynthetic pathway. Inhibition of isoprenoid synthesis with the 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor, simvastatin (Sim, 1-10 microM), inhibited PDGF-induced SMC DNA synthesis by >95%, retinoblastoma gene product hyperphosphorylation by 90%, and cyclin-dependent kinases (cdk)-2, -4, and -6 activity by 80 +/- 5, 50 +/- 3, and 48 +/- 3%, respectively. This correlated with a 20-fold increase in p27(Kip1) without changes in p16, p21(Waf1), or p53 levels compared with PDGF alone. Since Ras and Rho require isoprenoid modification for membrane localization and are implicated in cell cycle regulation, we investigated the effects of Sim on Ras and Rho. Up-regulation of p27(Kip1) and inhibition of Rho but not Ras membrane translocation by Sim were reversed by geranylgeranylpyrophosphate, but not farnesylpyrophosphate. Indeed, inhibition of Rho by Clostridium botulinum C3 transferase or overexpression of dominant-negative N19RhoA mutant increased p27(Kip1) and inhibited retinoblastoma hyperphosphorylation. In contrast, activation of Rho by Escherichia coli cytotoxic necrotizing factor-1 decreased p27(Kip1) and increased SMC DNA synthesis. These findings indicate that the down-regulation of p27(Kip1) by Rho GTPase mediates PDGF-induced SMC DNA synthesis and suggest a novel direct effect of 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors on the vascular wall.

Excision of the conjugative transposon Tn916 in Lactococcus lactis

In Lactococcus lactis excision of Tn916 is limited by the concentration of integrase and is increased by providing more excisionase. However, even with increased excision of Tn916 in L. lactis, no conjugative transfer is detectable. This suggests that L. lactis is deficient in a host factor(s) required for conjugative transposition.

Regulation of excision of the conjugative transposon Tn916

Excision from the donor DNA molecule is the first step in conjugative transposition of Tn916 and is followed by circularization of the transposon and its transfer to a new host. We have demonstrated that, in Gram-positive hosts, the Xis protein, as well as the site-specific recombinase Int, is required for the excision of Tn916. Using assays for closure of the excised covalently closed transposon and for repair of the donor DNA molecule, we found that neither protein alone is rate limiting for excision, but overexpression of Int and Xis together results in increased excision. After excision, the frequency of Tn916 circle formation was found to be the same as the frequency of repair of the donor DNA molecule. This suggests that a single reaction results in the closure of both molecules. We have also identified two transcripts that encode Int, one of which also encodes Xis and one of which does not, suggesting that there are steps in conjugative transposition of Tn916 that require Int without Xis.

Anhedonia and relapse in alcoholism

The aim of this study was to determine the role of anhedonia among other psychopathological dimensions in the relapse of alcoholics 6 months after withdrawal. Psychometric assessments included: the Social and Physical Anhedonia Scales, the Sensation Seeking Scale, the Pleasure-Displeasure Scale (including Fawcett-Clark's Pleasure Scale), the Depressive Mood Scale, the Thymasthenic Syndrome Rating Scale and the Comprehensive Psychopathological Rating Scale. Forty-four alcoholics participated in the study. The baseline values recorded during the second week of treatment showed that the more anhedonic the alcoholics were, the less they sought sensations. Type 2 alcoholics (Cloninger's classification) scored higher on the Thrill and Adventure Seeking Subscale. Relapsed alcoholics had higher baseline values on the Thrill and Adventure Seeking Subscale. This was in agreement with the step-wise discriminant analysis which showed that this subscale was the main variable that differentiated abstinent alcoholics from those who relapsed. Our results indicate that anhedonia does not predict relapse.

Use of the lactococcal nisA promoter to regulate gene expression in gram-positive bacteria: comparison of induction level and promoter strength

We characterized the regulated activity of the lactococcal nisA promoter in strains of the gram-positive species Streptococcus pyogenes, Streptococcus agalactiae, Streptococcus pneumoniae, Enterococcus faecalis, and Bacillus subtilis. nisA promoter activity was dependent on the proteins NisR and NisK, which constitute a two-component signal transduction system that responds to the extracellular inducer nisin. The nisin sensitivity and inducer concentration required for maximal induction varied among the strains. Significant induction of the nisA promoter (10- to 60-fold induction) was obtained in all of the species studied at a nisin concentration just below the concentration at which growth is inhibited. The efficiency of the nisA promoter was compared to the efficiencies of the Spac, xylA, and lacA promoters in B. subtilis and in S. pyogenes. Because nisA promoter-driven expression is regulated in many gram-positive bacteria, we expect it to be useful for genetic studies, especially studies with pathogenic streptococci in which no other regulated promoters have been described.

Molecular Probe Data Base (MPDB)

In this paper, the current status of the Molecular Probe Data Base (http://www.biotech.ist.unige.it/interlab/ mpdb.html ) is briefly presented together with a short analysis of its activity during 1997. This has been performed by statistically evaluating the 'logs' of the Internet servers that are used for its distribution with reference to the geographical origin of the requests, the words that were utilized to carry out of the searches and the oligonucleotides that were retrieved. Planned enhancements of this database are also described. They include a revision of its data structure and, even more relevant, of its data management procedures.

[Addictive potential in man: methodological aspects]

Different methods have been developed in clinical abuse liability testing in man. Tolerance, psychic and/or physical dependence must be investigated through clinical studies during drug development of a new substance. Adequate methodology is needed using double-blind, time-blind evaluations, comparisons of different dose levels and duration of treatment for a given drug, abrupt and gradual interruption of treatment, appropriate period of observation after treatment cessation ... The optimal scale to evaluate properly the symptoms occurring after drug discontinuation is still under investigation. These studies will or should permit the differentiation of rebound, withdrawal and recurrence. Methods developed to study reinforcing effects in post-addicts and healthy subjects are self-administration and choice procedures. In addition, the more traditional approach has been through assessing self-reported effects in which standardized questionnaires are used (Addiction Research Center Inventory or A.R.C.I.; Single Dose Questionnaire or S.D.Q.). A third focus of measurement has been discrimination studies performed in individuals with histories of drug abuse as well as healthy subjects. Abuse-liability testing of a new compound needs a multidimensional assessment to optimize the predictivity in defining the relative risk.

Conjugative transposition of Tn916: preferred targets and evidence for conjugative transfer of a single strand and for a double-stranded circular intermediate

Transposition of conjugative transposons proceeds by excision and formation of a covalently closed circular intermediate that includes at its joint the six flanking bases from its previous host (coupling sequences). To elucidate the role of the coupling sequences in this process and to determine the sequence of targets used by Tn916, we studied its insertion into a plasmid following conjugation. The results differ from those previously observed when Tn916 was introduced by transformation. They suggest that only one specific strand of the transposon molecule is transferred during the conjugation event and that complementary strand synthesis produces a double-stranded transposon circle with no mismatches which serves as the reaction intermediate. Tn916 inserts preferentially at specific sites and the same targets are used when Tn916 comes from donors with different coupling sequences. An analysis of the sequences of preferred targets is presented.

Effect of glutaraldehyde fixation and valve constraint conditions on porcine aortic valve leaflet coaptation

In an investigation of the influence of glutaraldehyde fixation pressure and subsequent valve constraint on the coaptive characteristics of porcine aortic valves, 14 valves were examined, eight having been fixed at low pressure (congruent to 1 mm Hg) and six at high pressure (80 mm Hg). The coaptive ratios of the left and right coronary leaflets in the low-pressure-fixed valves showed a significant improvement over those of the same leaflets in the high-pressure-fixed valves. Inflation to 80 mm Hg results in a variable "peeling back" of the coaptive margins of the low-pressure-fixed valves but not of the high-pressure-fixed valves. Comparable coaptive ratios are therefore expected during full inflation of the unconstrained valves fixed both at low pressure and at high pressure. Constraining the low-pressure-fixed valves during inflation to simulate the effect of mounting on a rigid stent produced either a reduction or virtual elimination of this "peeling back" motion or in some instances a slight reversal of the effect, thus increasing the width of the coaptive margin. Hence it is expected that the stented low-pressure-fixed valve will manifest better coaptation than the high-pressure-fixed valve. Finally, the experimental findings of this study, combined with the improved mechanical function of the leaflet tissue already known to occur in the low-pressure-treated valves, provide a convincing case for valve fixation to be carried out under lower pressures.