Mechanisms by which selected flavonoids, terpenes and nitrate esters of heterocyclic compounds exert activity towards Candida albicans strains isolated from the human oral cavity

Vrsta Candida albicans jedan je od najčešćih uzročnika gljivičnih infekcija ljudi. U okviru ove doktorske disertacije ispitivani su mehanizmi antifungalnog delovanja 9 flavonoida (apigenin, apigetrin, astragalin, kvercetin, kvercitrin, izokvercitrin, rutin, luteolin i viteksin), 2 terpena (kamfor i eukaliptol) i 4 nitratna estra heterocikličnih jedinjenja (N-(2-nitrooksietil)-1Η-indol-2-karboksamid (MK55), Ν-(2-nitroksietil)-hinolin-2-karboksamid (MK56), Ν-(2-nitroksietil)-6-(piperidin-1-il)-9H-purin acetamid (MK94), 5΄-Ο-nitro adenozin (MK129)). Najbolju antifungalnu aktivnost ispoljili su nitratni estri heterocikličnih jedinjenja. U smanjenju razvoja virulentnosti ove gljive, nastanku biofilma i formiranju hifalnih ćelija, istakla se aktivnost flavonoida, posebno apigetrina, apigenina i izokvercitrina. Razvoj antifungalne rezistencije C. albicans povezan je sa povećanjem aktivnosti efluks pumpi kodiranih genima MDR1, CDR1 i CDR2. Promene u ekspresiji ovih gena zabeležene su nakon tretmana astragalinom i apigeninom (smanjenje ekspresije CDR1), kamforom (povećanje ekspresije CDR1, smanjenje ekspresije CDR2) i eukaliptolom (povećanje ekspresije CDR1 i CDR2), ukazujući na potencijalna korisna svojstva flavonoida, ali i moguće neželjene posledice primene testiranih terpena. Rezistencija je povezana i sa povećanom ekspresijom ERG11, gena koji kodira protein lanosterol 14α-demetilazu (CYP51), ciljno mesto azolnih lekova. Izokvercitrin i MK94 izazivaju neželjeno povećanje, dok MK55 redukuje nivo ekspresije ovog gena. Mehanizam antifungalnog delovanja MK55 obuhvata i inhibiciju fungalnog proteina CYP51. Narušavanje integriteta ćelijske membrane, kao potencijalnog mehanizma delovanja, potvrđeno je za apigenin, apigetrin i astragalin. Upotreba MK55, MK94, apigenina, apigetrina, rutina, kvercetina, kvercitrina, izokvercitrina, luteolina i kamfora može se smatrati bezbednom, dok se eukaliptol zbog svog citotoksičnog efekta prema ćelijama jetre ne preporučuje za potencijalnu primenu u antifungalnoj terapiji.Candida albicans is among the most common human fungal pathogens. Mode of antifungal action has been tested for 9 flavonoids (apigenin, apigetrin, astragalin, quercetin, quercitrin, isoquercitrin, rutin, luteolin and vitexin), 2 terpens (camphor and eucalyptol) and 4 nitrate esters of heterocyclic compounds (N-(2-nitooxyethyl)-1Η-indol-2-carboxamide (MK55), Ν-(2-nitrooxyethyl)-quinoline-2-carboxamide (MK56), Ν-(2-nitrooxyethyl)-6-(piperidin-1-yl)-9H-purine acetamide (MK94), 5΄-Ο-nitroadenosine (MK129)). The most prominent anticandidal activity has been proven for nitrate esters of heterocyclic compounds. Significant activity of flavonoids, especially apigetrin, apigenin and isoquercitrin, could be noticed in reducing fungal virulence, biofilm formation and hyphal growth. Resistance to antifungal therapy is linked to increased activity of C. albicans efflux pumps encoded by MDR1, CDR1 and CDR2. Disturbance in expression levels of these genes has been observed after treatment with astragalin and apigenin (decreased CDR1 expression), camphor (increased CDR1 and decreased CDR2 expression) and eucalyptol (increased CDR1 and CDR2 expression levels), suggesting possible beneficial antimicrobial effects of flavonoids as well as potential harmful consequences of selected terpenes application. Antifungal resistance is also linked to increased expression of ERG11, gene encoding for lanosterol 14α-demethylase (CYP51), target protein for azole antifungals. Treatment with isoquercitrin and MK94 led to increased expression of this gene, while treatment with MK55 reduced it. Mode of action for MK55 involves inhibition of CYP51 enzyme. Damage of fungal cell membrane as a potential mechanism of antifungal activity has been observed for apigenin, apigetrin and astragalin. Application of MK55, MK94, apigenin, apigetrin, rutin, quercetin, quercitrin, isoquercitrin, luteolin and camphor could be considered safe, based on the results of their cytotoxicity towards the liver cell line, while eucalyptol should be used with serious precaution

Multi-objective constrained optimizations of VAWT composite blades based on FEM and PSO

Vetroturbine sa vertikalnom osom obrtanja predstavljaju privlačno oruđe za iskorišćenje energije vetra, naročito pogodno za male potrošače ili nepristupačne terene. Iako su jednostavne geometrije (ovde su pretpostavljene prave lopatice konstantnog aeroprofila), njihova aerodinamička analiza može biti izrazito složena. Metode proračunske mehanike fluida iskorišćene su za procenu aerodinamičkih performansi rotora. Rad daje pregled i ocenu mogućih strategija za izvršenje višekriterijumskih optimizacija tokom projektovanja lopatice vetroturbine sa vertikalnom osom obrtanja laminatne strukture koje se odnose na njene glavne strukturne parametre: redosled ređanja i broj slojeva laminata. Brojni proračuni strukture kompozitnih lopatica vetroturbine izvedeni su metodom konačnih elemenata. Višekriterijumske ograničene optimizacije rojem čestica, evolutivnim metodom, izvršene su u odnosu na: ukupnu masu lopatice, najveće pomeranje strukture lopatice pri statičkom opterećenju, proračunate sopstvene frekvencije i kriterijum loma po lopatici. Kombinacijom različitih ulaznih i izlaznih parametara (ciljnih funkcija i ograničenja) moguće je definisati veliki broj prihvatljivih, poboljšanih rešenja.Vertical-axis wind turbines (VAWTs) are attractive tools for wind energy extraction particularly suitable for small consumers or off-grid areas. Although their geometry is simple (here, rectangular blade of constant airfoil is assumed), aerodynamic analysis may be quite complex. Computational fluid dynamics (CFD) approach is employed for the estimation of rotor aerodynamic performances. This paper provides a review of possible multi-objective optimization strategies for the design of small-scale VAWT laminate blades in terms of its main structural parameters: ply-order and ply-number. Numerous structural analyses of the composite turbine blades were performed by finite element method (FEM). Multi-criteria constrained optimizations, by an evolutionary method - particle swarm optimization (PSO), were performed with respect to blade total mass, maximum blade tip deflection under static loading, computed natural frequencies and failure index along the blade. By combining different input and output parameters (cost functions and constraints) a large variety of feasible solutions can be achieved

Multi-objective constrained optimizations of VAWT composite blades based on FEM and PSO

Vetroturbine sa vertikalnom osom obrtanja predstavljaju privlačno oruđe za iskorišćenje energije vetra, naročito pogodno za male potrošače ili nepristupačne terene. Iako su jednostavne geometrije (ovde su pretpostavljene prave lopatice konstantnog aeroprofila), njihova aerodinamička analiza može biti izrazito složena. Metode proračunske mehanike fluida iskorišćene su za procenu aerodinamičkih performansi rotora. Rad daje pregled i ocenu mogućih strategija za izvršenje višekriterijumskih optimizacija tokom projektovanja lopatice vetroturbine sa vertikalnom osom obrtanja laminatne strukture koje se odnose na njene glavne strukturne parametre: redosled ređanja i broj slojeva laminata. Brojni proračuni strukture kompozitnih lopatica vetroturbine izvedeni su metodom konačnih elemenata. Višekriterijumske ograničene optimizacije rojem čestica, evolutivnim metodom, izvršene su u odnosu na: ukupnu masu lopatice, najveće pomeranje strukture lopatice pri statičkom opterećenju, proračunate sopstvene frekvencije i kriterijum loma po lopatici. Kombinacijom različitih ulaznih i izlaznih parametara (ciljnih funkcija i ograničenja) moguće je definisati veliki broj prihvatljivih, poboljšanih rešenja.Vertical-axis wind turbines (VAWTs) are attractive tools for wind energy extraction particularly suitable for small consumers or off-grid areas. Although their geometry is simple (here, rectangular blade of constant airfoil is assumed), aerodynamic analysis may be quite complex. Computational fluid dynamics (CFD) approach is employed for the estimation of rotor aerodynamic performances. This paper provides a review of possible multi-objective optimization strategies for the design of small-scale VAWT laminate blades in terms of its main structural parameters: ply-order and ply-number. Numerous structural analyses of the composite turbine blades were performed by finite element method (FEM). Multi-criteria constrained optimizations, by an evolutionary method - particle swarm optimization (PSO), were performed with respect to blade total mass, maximum blade tip deflection under static loading, computed natural frequencies and failure index along the blade. By combining different input and output parameters (cost functions and constraints) a large variety of feasible solutions can be achieved

Optimisation of tensile stress of poly(lactic acid) 3D printed materials using response surface methodology

Three-dimensional printed plastic products developed through fused deposition modelling (FDM) take long-term mechanical loading in most industrial prototypes. This article focuses on the impact of the 3D printing parameters, type of thermal treatment and variation of characteristic dimensions of standard specimens on the tensile properties of poly(lactic acid) (PLA) material. Two mediums were used for thermal treatment: NaCl powder and plaster. The specimens immersed in NaCl powder were heated to the melting temperature of the filament (200 °C), while the processing of the plastered specimens was performed at a temperature of 100 °C. After treatment, the specimens were cooled at room temperature (25 °C), and the dimensions of the annealed and untreated specimens were controlled. The tensile test of the specimens was performed on the universal test machine. The response surface methodology (RSM) is employed to predict the tensile stress by undertaking input parameters. The analysis of variance (ANOVA) results revealed that the untreated specimens, orientation – 45/45 and layer thickness of 0.1 mm had the highest tensile stress value. Thermal treatment in plaster showed a significant increase in tensile strength, while the best specimens were obtained after treatment in NaCl, and all refer to the –45/45 (0.1 mm) orientation

Sugars and their substitutes increase pathogenicity of Pseudomonas aeruginosa

Introduction: Differentsugars are commonly used in the diet, but little is understood about the various effects of human health that they can affect. Hence, the impact of sugars and their substitutes used in diet on the development of virulence in Pseudomonas aeruginosa PAO1 was investigated. Sugars (fructose, demerara, coconut sugar, and cane sugar) and sugar substitutes (erythritol and stevia) were selected. The genes from three P. aeruginosa QS networks (las - lasI, lasR; rhl - rhlI, rhlR; PQS - pqsA, mvfR) were used for RT-qPCR analysis in order to investigate whether the expression of these genes changes. In this work, the focusis on the expression of genesinvolved in QS and the ability to form biofilms(a type of structured community of microorganisms that is attached to the surface and connected by an exopolysaccharide matrix), as well as determining minimal inhibitory concentration of antibiotics in presence of tested compounds. Methods: Microdiltuion assay, Antibiofilm assay, RT- qPCR Results: In the presence of tested sugars and theirsubstitutes, the minimum inhibitory concentration of commercial antibiotics increased, as well as the percentages of biofilm formation (for instance, the percentage of biofilm formation is 171% in the presence of coconut sugar). Furthermore, exposure of P. aeruginosa to tested compounds caused the greatest increase in expression of virulence associated with the lasI and pvdF genes. Conclusion: More awareness and research is needed to highlight the effectssugars can have on P. aeruginosa and to propose new strategies to reduce this negative aspect

Numerical analysis of screw joint turn table and chassis of low-floor articulated bus IK218N

Rapid growth and development of modern technologies led to increased application of innovative solutions in conceptual design and modelling in all fields of engineering. In order to answer to the increased requirements for more efficient means of transport, it is necessary to pay special attention to public transport (meant for a large number of passengers) which is essential in large cities. Since daily frequency amounts to several thousands of passengers, appropriate maintenance and inspection of the most loaded parts have to be conducted regularly. Low-floor articulated bus IK218N was analysed here. Prototype was completely developed and produced in the Factory of buses and special vehicles – IKARBUS. After years of exploitation in extreme working conditions in Belgrade, a systematic error in the form of screw joint failure at the connecting point between articulated joint and chassis rear part was established. Extreme working conditions imply overloaded vehicles, inadequate, damaged and bumpy roads as well as irregular maintenance. The whole bus was initially modelled in CATIA, which was followed by the numerical simulation of the connecting screw joint by finite element method in ANSYS. The results of structural analysis showed that the screw joints were the most loaded parts which led to their failure. The screws serve to connect the mount and the articulated joint itself. The following conclusion was made: during exploitation, the mount beam lost its initial mechanical characteristics, its deformations reached plasticity which reduced locking forces and led to additional shear load on the screw and its final failure. Consequently, the screw joint had to be redesigned and modified. New solution was applied to low-floor articulated bus IK218N

Polyphenols as Inhibitors of Antibiotic Resistant Bacteria-Mechanisms Underlying Rutin Interference with Bacterial Virulence

The rising incidence of antibiotic resistant microorganisms urges novel antimicrobials development with polyphenols as appealing potential therapeutics. We aimed to reveal the most promising polyphenols among hesperetin, hesperidin, naringenin, naringin, taxifolin, rutin, isoquercitrin, morin, chlorogenic acid, ferulic acid, p-coumaric acid, and gallic acid based on antimicrobial capacity, antibiofilm potential, and lack of cytotoxicity towards HaCaT, and to further test its antivirulence mechanisms. Although the majority of studied polyphenols were able to inhibit bacterial growth and biofilm formation, the most promising activities were observed for rutin. Further investigation proved rutin's ability to prevent/eradicate Pseudomonas aeruginosa and MRSA urinary catheter biofilms. Besides reduction of biofilm biomass, rutin antibiofilm mechanisms included reduction of cell viability, exopolysaccharide, and extracellular DNA levels. Moderate reduction of bacterial adhesion to human keratinocytes upon treatment was observed. Rutin antivirulence mechanisms included an impact on P. aeruginosa protease, pyocyanin, rhamnolipid, and elastase production and the downregulation of the lasI, lasR, rhlI, rhlR, pqsA and mvfR genes. Rutin also interfered with membrane permeability. Polyphenols could repress antibiotic resistant bacteria. Rutin has shown wide antimicrobial and antibiofilm capacity employing a range of mechanisms that might be used for the development of novel antimicrobials

NEW PROBLEMS, OLD SOLUTIONS? A CRITICAL LOOK ON THE REPORT OF THE HIGH LEVEL EXPERT GROUP ON FAKE NEWS AND ON-LINE DISINFORMATION

This article discusses the actual contemporary problems of the spread of fake news, information wars and disinformation campaigns. The authors analyze recent European initiatives in the field of opposing disinformation on the Internet, among which are the report of the High level expert group of the European Commission on fake news and online disinformation (HLEG) and the “Act to improve law enforcement in social networks” (NetzDG). Based on a wide range of political theories and approaches to the problem of fake news, the authors propose to enhance and amend the key principles of HLEG 5

Prunus spinosa L. leaf extracts: polyphenol profile and bioactivities

Prunus spinosa leaf extracts in solvents of different polarity (water, ethanol and acetone), their phenol, flavonoid and anthocyanin contents and biological properties were the object of this study. The richest in phenols as well as in flavonoids was acetone extract with 181.19 mg GAE and 80.10 mg QE per gram of dry extract, respectively. Moreover, the quantity of anthocyanins obtained by HPLC analysis was also the highest in acetone sample. Examined samples possessed antioxidant properties evaluated through four in vitro assays (DPPH, ABTS, FRAP and TRC). The acetone extract was proved to be the best antioxidant among tested samples, which could be ascribed to polyphenols, especially anthocyanins. The aqueous and the ethanol extract exhibited antibacterial effects, being particularly active against B. cereus and E. cloacae. T. viride, P. funiculosum, P. ochrochloron, P. verrucosum var. cyclopium were the most susceptible among fungal microorganisms examined. Both, the aqueous and the ethanol extract expressed inhibitory activity towards enzymes linked to diabetes mellitus type II. Additionally, the ethanol extract showed significantly higher potential in inhibiting α-glucosidase than the drug used as the positive control. Furthermore, the aqueous sample revealed antitumor effects on following malignant cell lines: HeLa, K562 and MDA-MB-453. The results presented herein suggest that P. spinosa leaves should be considered as a natural source of bioactive compounds with potential application in phytopharmacy and food industry

Numerical and experimental modal analysis of aluminium and composite plates

The paper presents the comparative analysis of the dynamic behaviour of two rectangular plates of different material, aluminium and composite. While their global geometric dimensions (length, width and thickness) are identical, their inner structures are quite different. Whereas aluminium plate can be considered isotropic, composite plate is a unidirectional carbon-epoxy laminate. Modal characteristics of the two plates were determined both numerically and experimentally and a comparative analysis of the obtained results was performed. Responses of the plates were documented by an optical, contactless 3D digital image correlation (DIC) system that contains a set of high-speed cameras capable of recording the movement of the white-and-black stochastic pattern applied to the upper surfaces of the plates. Numerical simulations were performed by the finite element method (FEM) in the commercial software package ANSYS. The plates were excited by a modal hammer and allowed to freely oscillate. In order to determine the natural frequencies of the plates the recorded time-domain responses were post-processed, i.e. converted to frequency domain by fast Fourier transform (FFT). The first three natural modes were successfully experimentally established and compared to the corresponding numerical values. Since the differences between the two sets of results are less than 5%, the applied experimental technique can be considered valid and suitable to a wide range of engineering problems involving vibrations