Detection of toxins involved in foodborne diseases caused by Gram‐positive bacteria

Bacterial toxins are food safety hazards causing about 10% of all reported foodborne outbreaks in Europe. Pertinent to Gram‐positive pathogens, the most relevant toxins are emetic toxin and diarrheal enterotoxins of Bacillus cereus, neurotoxins of Clostridium botulinum, enterotoxin of Clostridium perfringens, and a family of enterotoxins produced by Staphylococcus aureus and some other staphylococci. These toxins are the most important virulence factors of respective foodborne pathogens and a primary cause of the related foodborne diseases. They are proteins or peptides that differ from each other in their size, structure, toxicity, toxicological end points, solubility, and stability, types of food matrix to which they are mostly related to. These differences influence the characteristics of required detection methods. Therefore, detection of these toxins in food samples, or detection of toxin production capacity in the bacterial isolate, remains one of the cornerstones of microbial food analysis and an essential tool in understanding the relevant properties of these toxins. Advanced research has led into new insights of the incidence of toxins, mechanisms of their production, their physicochemical properties, and their toxicological mode of action and dose‐response profile. This review focuses on biological, immunological, mass spectrometry, and molecular assays as the most commonly used detection and quantification methods for toxins of B. cereus, C. botulinum, C. perfringens, and S. aureus. Gathered and analyzed information provides a comprehensive blueprint of the existing knowledge on the principles of these assays, their application in food safety, limits of detection and quantification, matrices in which they are applicable, and type of information they provide to the user.     

Evaluation of corrosion inhibition performance of silica sol–gel layers deposited on galvanised steel

The present work reports a comparative investigation of the electrochemical behaviour of some new types of silica sol–gel coatings with enhanced corrosion resistance deposited on electrolytically or thermally (hot-dip) zinc-coated steel. The coatings were rendered hydrophobic by silylation. Dichlorodimethylsilane or trimethylchlorosilane were used as silylating agents and cetyltrimethylammonium bromide or Pluronic PE 10300, as templating agents. The morpho-structural and optical properties of compact and mesoporous silica coatings were characterised with different methods. The corrosion behaviour of the coatings was evaluated by open circuit potential measurements, Tafel interpretation of the polarisation curves and electrochemical impedance spectroscopy. Both silylating agents improve significantly the corrosion resistance of both porous and compact coatings by reducing the corrosion current density with at least one order of magnitude. The possibility to use the porous structure of the coatings as corrosion inhibitor carriers was explored by loading of mesoporous silica layers with 1H-benzotriazole.     

Properties of coatings on the basis of carbon,tungsten, boron,and titanium obtained by the pulsed vacuum-arc method

Results of an investigation of the properties of coatings on the basis of carbon, tungsten, boron, and titanium obtained by the pulsed vacuum-arc method are presented. It has been found that the adhesion characteristics of coatings based on boron and titanium may be improved using a composite carbon-based coating, doped with tungsten, boron, and titanium, which, moreover, has a microhardness greater than those of a coating based on titanium and boron.     

Three-dimensional analysis of mesoscale deformation phenomena in welded low-carbon steel

A three-dimensional numerical analysis of the mesoscale deformation behavior of welded low-carbon steel specimens is performed. A weld-affected polycrystalline microstructure is designed to reproduce gradual changes of the grain size throughout the base metal and heat-affected zone regions. A mathematical model based on a double-limit yield criterion is used to describe Lüders band propagation characteristic of this type of steel. The effects of the free surface, grain boundaries and interfaces between the fusion zone and the heat-affected zone, and between the heat-affected zone and the base metal are discussed.     

Patterning as a signature of human epidermal stem cell regulation

Understanding how stem cells are regulated in adult tissues is a major challenge in cell biology. In the basal layer of human epidermis, clusters of almost quiescent stem cells are interspersed with proliferating and differentiating cells. Previous studies have shown that the proliferating cells follow a pattern of balanced stochastic cell fate. This behaviour enables them to maintain homeostasis, while stem cells remain confined to their quiescent clusters. Intriguingly, these clusters reappear spontaneously in culture, suggesting that they may play a functional role in stem cell auto-regulation. We propose a model of pattern formation that explains how clustering could regulate stem cell activity in homeostatic tissue through contact inhibition and stem cell aggregation.     

Cytoprotective Activity of Polyamines Is Associated with the Alternative Splicing of RAD51A Pre-mRNA in Normal Human CD4+ T Lymphocytes

Physiological polyamines are ubiquitous polycations with pleiotropic biochemical activities, including regulation of gene expression and cell proliferation as well as modulation of cell signaling. They can also decrease DNA damage and promote cell survival. In the present study, we demonstrated that polyamines have cytoprotective effects on normal human CD4⁺ T lymphocytes but not on cancer Jurkat or K562 cells. Pretreatment of lymphocytes with polyamines resulted in a significant reduction in cells with DNA damage induced by doxorubicin, cisplatin, or irinotecan, leading to an increase in cell survival and viability. The induction of RAD51A expression was in response to DNA damage in both cancer and normal cells. However, in normal cells, putrescin pretreatment resulted in alternative splicing of RAD51A and the switch of the predominant expression from the splice variant with the deletion of exon 4 to the full-length variant. Induction of RAD51A alternative splicing by splice-switching oligonucleotides resulted in a decrease in DNA damage and cell protection against cisplatin-induced apoptosis. The results of this study suggest that the cytoprotective activity of polyamines is associated with the alternative splicing of RAD51A pre-mRNA in normal human CD4⁺ T lymphocytes. The difference in the sensitivity of normal and cancer cells to polyamines may become the basis for the use of these compounds to protect normal lymphocytes during lymphoblastic chemotherapy.     

Properties of Coatings Based on Carbon and Nitrogen-Doped Carbon Obtained Using a Pulsed Vacuum Arc Method

Diamond-like carbon coatings on hard-alloy substrates, including coatings doped with nitrogen about 1.0 μm thick have been obtained using a pulse vacuum-arc method. Three types of coatings have been investigated: a carbon diamond-like coating (C), a carbon coating doped with nitrogen (C: N), and a composite coating based on (C: N + C) layers. The coatings have been annealed in atmospheric air at a temperature of 400°C. The tribological characteristics (wear resistance and friction coefficient change dynamics), the adhesion strength, and the microhardness of coatings in the initial state and after annealing have been studied. The composite coating consisting of C: N + C layers surpasses the constituent coatings in properties, both in the initial state and after annealing at a temperature of 400°C.