Extensive search for new endosymbiotic systems in ciliates occasionally reverts us to the endosymbiotic bacteria described in the pre-molecular biology era and, hence, lacking molecular characterization. A pool of these endosymbionts has been referred to as a hidden bacterial biodiversity from the past. Here, we provide a description of one of such endosymbionts, retrieved from the ciliate Paramecium nephridiatum. This curve-shaped endosymbiont (CS), which shared the host cytoplasm with recently described “Candidatus Megaira venefica”, was found in the same host and in the same geographic location as one of the formerly reported endosymbiotic bacteria and demonstrated similar morphology. Based on morphological data obtained with DIC, TEM and AFM and molecular characterization by means of sequencing 16S rRNA gene, we propose a novel genus, “Candidatus Mystax”, with a single species “Ca. Mystax nordicus”. Phylogenetic analysis placed this species in Holosporales, among Holospora-like bacteria. Contrary to all Holospora species and many other Holospora-like bacteria, such as “Candidatus Gortzia”, “Candidatus Paraholospora” or “Candidatus Hafkinia”, “Ca. Mystax nordicus” was never observed inside the host nucleus. “Ca. Mystax nordicus” lacked infectivity and killer effect. The striking peculiarity of this endosymbiont was its ability to form aggregates with the host mitochondria, which distinguishes it from Holospora and Holospora-like bacteria inhabiting paramecia.

Aim. Is the morphometric analysis of the working surfaces of endodontic rotating nickel-titanium instruments.Materials and methods. The chemical composition and physical properties of the three types of endodontic rotating nickel-titanium F2 instruments have been analyzed: proptaper Universal (PTu, Dentsply, Maillefer, Ballaigues, Switzeland), Ultrataper (Eurofile, China) and Superfile (Eurofile, China) protapers. The evaluation of endodontic treatment of 75 endoblocks was also carried out.Results. The research work shows that endodontic rotary instruments have both different chemical composition and heterogeneity of the alloy. The average comparable percentage of titanium and nickel in the studied alloy samples has been revealed. The quality of endodontic treatment of the endoblocks’ channels with various rotating nickel-titanium instruments is also comparable and meets the specified criteria.Conclusion. The morphometric analysis has revealed a difference in the structure of the metal alloy of the F2 protapers, with a comparable content of nickel (46-52%) and titanium (38-41%). The content of pure nickel-titanium alloy along the periphery of the endodontic instrument in Universal protapers ensures high cutting ability of the faces. The obtained data on different resistance to cyclic loads should be taken into account in the endodontic treatment of multi-root teeth. The analysis of the structure of the nickel-titanium alloy indicates the predetermination of the development of the tool’s fracture with prolonged use and the need to take into account the cycles of the endodontic rotary tool.

Here, we report a comprehensive description of the stable associations between two Paramecium species (P. nephridiatum and P. caudatum) and their cytoplasmic bacterial endosymbiont Pseudolyticum multiflagellatum. These spindle-like, rod-shaped, non-motile peritrichous bacteria demonstrate significant phenotypic polymorphism. Considering the differences in bacterial morphology and host species, several scientific groups have previously described these endosymbionts as distinct species. Our study provides brand-new molecular data, which allows us to unify earlier descriptions and determine the phylogenetic position of this endosymbiont as a member of the family “Ca. Midichloriaceae” (Rickettsiales). The distinguishing feature of this bacterium is the presence of a highly refractive granule in its cytoplasm, well detectable with differential interference contrast (DIC) microscopy. The protein nature of these peculiar inclusion bodies is considered. The other endosymbiont, “Ca. Megaira venefica”, co-inhabiting the cytoplasm of the studied P. nephridiatum strains, also displayed polymorphism, rounded forms being infected with phages.

The aim of the study. To study the trace element composition of various areas of hard tooth tissues in caries, pathological attrition and periodontal diseases on the archaeological material of dental remains of the X—XX centuries. Materials and methods. The microelement composition of hard dental tissues of X—XX centuries’ teeth was analyzed using the TM 3000 electronic microanalyzer (Hitachi, Japan). Results. The patterns of microelement composition in diseases of hard dental tissues and periodontal disease have been revealed. The results of two-factor analysis of variance confirmed a statistically significant dependence of the average values of O and C content in enamel over the centuries (p<0.0001), the average values of P, Zn, O and Mg in dentin (p<0.0001), the average values of O and C content in cement (p<0.0001). High correlation between Ca and Sr in enamel (Pearson’s r=0.847; t-criterion=7.98; statistical significance p<0.01; n=27) and a noticeable correlation in dentin (Pearson’s r=0.512; t-criterion=2.46; p<0.05). Conclusion. The results indicate that with the relative constancy of anatomical and morphological characteristics, the variability of the mineral composition is observed, as well as its pronounced dependence on exogenous factors.

A new method combining atomic force (AFM) and confocal laser scanning microscopy (CLSM) and permitting not only to obtain information about the surface topography of nanostructures in the cell nucleus, but to simultaneously identify their molecular composition by using fluorescent dyes and treatment with specific enzymes, is proposed. The content of the vegetative nuclei of the ciliate Paramecium caudatum stained with DAPI for revealing DNA and fluorescently labeled phalloidin specifically binding fibrillar actin was been sequentially studied using CLSM and AFM and by successive analysis with AFM after RNAse and Proteinase K treatments. The proposed method allows one to characterize the surface topography of chromatin and RNP-complexes and reveal nanostructures containing nuclear actin which cannot be visualized using CLSM only.

Background Neuronal cell death during Alzheimer disease (AD) causes the release of cytosolic proteins, particularly glyceraldehyde-3-phosphate dehydrogenase (GAPDH), which forms highly cytotoxic detergent-insoluble complexes with amyloid-β (Aβ) and promotes neurodegeneration. Methods We detected and quantified the complex formation between Aβ and GAPDH released from brain tissue of patients with AD using ultrafiltration, and fluorescence resonance energy transfer (FRET). To explore the biochemical and structural features of Aβ-GAPDH complexes we employed novel immunoenzyme assays and atomic force microscopy. Lentiviral infection in situ was used to elevate GAPDH in brain tissue of rat and mouse models of AD. The Morris maize water test, MRI, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL), and lactate dehydrogenase (LDH)-activity assays were used to characterize the effects of Aβ-GAPDH complexes in animal and cellular models of AD. Results Here we report that GAPDH forms stable aggregates with extracellular Aβ. We detected these aggregates in cerebrospinal fluid (CSF) from AD patients at levels directly proportional to the progressive stages of AD. We found that GAPDH forms a covalent bond with Q15 of Aβ that is mediated by transglutaminase (tTG). The Q15A substitution weakens the interaction between Aβ and GAPDH and reduces Aβ-GAPDH cytotoxicity. Lentivirus-driven GAPDH overexpression in two AD animal models increased the level of apoptosis of hippocampal neurons, neuronal degeneration, and cognitive dysfunction. In contrast, in vivo knockdown of GAPDH reversed these pathogenic abnormalities suggesting a pivotal role of GAPDH in Aβ-stimulated neurodegeneration. CSF obtained from animals with enhanced GAPDH expression demonstrated increased cytotoxicity in vitro . Furthermore, RX-624, a specific GAPDH small molecular ligand reduced accumulation of Aβ aggregates and reversed memory deficit in AD transgenic mice. Conclusions Extracellular GAPDH compromises Aβ clearance and accelerates neurodegeneration, thus representing a promising pharmacological target for AD.