High lactic acid levels in the brain contribute to the generation of focal slowing on the electroencephalogram.

Focal slowing on the EEG is often associated with structural pathology of the brain. Despite the clinical significance of focal slowing, the actual electrochemical mechanisms underlying this EEG phenomenon are still poorly understood. This paper briefly reviews the role of lactate in the pathogenesis of brain disorders that are primarily related to focal EEG slowing. An attempt is made to trace the hypothetical link between this EEG pattern and focal cerebral tissue lactacidosis.

Phenotypic and genomic characteristics of oxacillin-susceptible mecA-positive Staphylococcus aureus, rapid selection of high-level resistance to beta-lactams.

The aim of this study is to describe the phenotypic and genetic properties of oxacillin-susceptible methicillin-resistant Staphylococcus aureus (OS-MRSA) isolates and their beta-lactam resistant derivatives obtained after selection with oxacillin. A collection of hospital- (HA-) and community-acquired (CA-) MRSA was screened for oxacillin susceptibility. Antibiotic susceptibility testing, population analysis profile (PAP), mecA expression analysis, and whole genome sequencing (WGS) were performed for 60 mecA-positive OS-MRSA isolates. Twelve high-level beta-lactam resistant derivatives selected during PAP were also subjected to WGS. OS-MRSA were more prevalent among CA-MRSA (49/205, 24%) than among HA-MRSA (11/575, 2%). OS-MRSA isolates belonged to twelve sequence types (ST), with a predominance of ST22-t223-SCCmec IVc and ST59-t1950-SCCmec V lineages. OS-MRSA were characterized by mecA promoter mutations at - 33 (C→T) or - 7 (G→T/A) along with PBP2a substitutions (S225R or E246G). The basal and oxacillin-induced levels of mecA expression in OS-MRSA isolates were significantly lower than those in control ST8-HA-MRSA isolates. Most of the OS-MRSA isolates were heteroresistant to oxacillin. High-level beta-lactam resistant OS-MRSA derivatives selected with oxacillin carried mutations in mecA auxiliary factors: relA (metabolism of purines), tyrS, cysS (metabolism of tRNAs), aroK, cysE (metabolism of amino acids and glycolysis). Cefoxitin-based tests demonstrated high specificity for OS-MRSA detection. The highest positive predictive values (PPV > 0.95) were observed for broth microdilution, the VITEK® 2 automatic system, and chromogenic media. Susceptibility testing of CA-MRSA requires special attention due to the high prevalence of difficult-to-detect OS-MRSA among them. Mis-prescription of beta-lactams for the treatment of OS-MRSA may lead to selection of high-level resistance and treatment failures.

Comparative Analysis of Library Preparation Approaches for SARS-CoV-2 Genome Sequencing on the Illumina MiSeq Platform.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been responsible for over two years of the COVID-19 pandemic and a global health emergency. Genomic surveillance plays a key role in overcoming the ongoing COVID-19 pandemic despite its relative successive waves and the continuous emergence of new variants. Many technological approaches are currently applied for the whole genome sequencing (WGS) of SARS-CoV-2. They differ in key stages of the process, and they feature some differences in genomic coverage, sequencing depth, and in the accuracy of variant-calling options. In this study, three different protocols for SARS-CoV-2 WGS library construction are compared: an amplicon-based protocol with a commercial primer panel; an amplicon-based protocol with a custom panel; and a hybridization capture protocol. Specific differences in sequencing depth and genomic coverage as well as differences in SNP number were found. The custom panel showed suitable results and a predictable output applicable for the epidemiological surveillance of SARS-CoV-2 variants.

More than just immaturity: evidence supporting the hypothesis that sleep spindle characteristics reflect GABAergic depolarization in infancy.

Sleep spindles are thalamocortical oscillations with waxing-waning morphology, which comprise the key electroencephalographic (EEG) hallmark of stage 2 non-rapid eye movement sleep. The functional role of sleep spindles is not sufficiently clear, but there is a large body of literature that indicates the relationship between spindle activity and neural plasticity. Many of the spindle parameters (frequency, configuration, duration, density, and topography) vary significantly throughout life. However, the long duration, asynchrony and sharp morphology are the most distinctive characteristics of sleep spindles in infants. This unique infantile phenotype of sleep spindles typically changes after approximately one year of postnatal life in humans. Considering that EEG reflects brain electrochemical activity, there is evidence to suggest that substantial neurochemical events underlie these changes. In this paper, we hypothesize that the GABA (gamma-aminobutyric acid) shift is a key event influencing the sleep spindle phenotype during infancy. We briefly review evidence for the relation between infantile sleep spindles and depolarizing GABA transmission occurring in the developing brain.

A psychometric study of the Russian-language version of the "Bayley Scales of Infant and Toddler Development-third edition": An assessment of reliability and validity.

Introduction: The Bayley Scales of Infant and Toddler Development-third edition (Bayley-III) is one of the most widely used tools for assessing child development, and adapted versions of this instrument have been successfully used in many countries. No comprehensive psychometric studies of the Bayley-III have yet been performed in Russia. Materials and methods: This psychometric study was part of the longitudinal study conducted by the Ural Federal University in 2016-2020. Within the project, the original Bayley-III manual was translated into Russian and then used in a cohort of 333 infants to assess cognition, expressive/receptive communication, and fine/gross motor skills. For the purpose of psychometric analysis, we selected the data for four age groups of children from the longitudinal study database: 4-6 months (N = 149), 10 months (N = 138), 15 months (N = 151), and 24 months (N = 124). The development scores of the sample children were compared with the original Bayley-III norms in each age strata separately. Reliability and validity of the translated instrument were examined using correlation analysis, tests of internal consistency, and confirmatory factor analysis (CFA). Results: The average scaled scores of the examined children were generally comparable with the original (US) Bayley-III norms, with the exception of those older than 1 year, who demonstrated 1.2-1.9 points better performance in cognitive development and gross motor skills and 0.9-2.6 points lower performance in expressive communication. The correlation of both raw and scaled scores between different scales was low to moderate in all age groups (Spearman's ρ mostly within the range of 0.3-0.6; p < 0.001 for all pairwise correlations). Internal consistency tests confirmed high reliability of the translated instrument (Cronbach's α = 0.74-0.87, McDonald's ω = 0.79-0.89). CFA demonstrated a good fit of the three-factor model (cognitive, communicative, and motor components) in all age strata. Conclusion: The Russian version of the Bayley-III proved to be a psychometrically valid and reliable tool for assessing child development, at least in a research context. The development of the examined children was close to the original US norms, with some deviation in cognitive, gross motor, and expressive communication scores mostly in older children, which could be attributed to the biased sample.

Linking ecology, morphology, and metabolism: Niche differentiation in sympatric populations of closely related species of the genus Littorina (Neritrema).

Divergence of ecological niches in phylogenetically closely related species indicates the importance of ecology in speciation, especially for sympatric species are considered. Such ecological diversification provides an advantage of alleviating interspecies competition and promotes more efficient exploitation of environmental resources, thus being a basis for ecological speciation. We analyzed a group of closely related species from the subgenus Neritrema (genus Littorina, Caenogastropoda) from the gravel-bouldery shores. In two distant sites at the Barents and Norwegian Sea, we examined the patterns of snail distribution during low tide (quantitative sampling stratified by intertidal level, presence of macrophytes, macrophyte species, and position on them), shell shape and its variability (geometric morphometrics), and metabolic characteristics (metabolomic profiling). The studied species diversified microbiotopes, which imply an important role of ecological specification in the recent evolution of this group. The only exception to this trend was the species pair L. arcana / L. saxatilis, which is specifically discussed. The ecological divergence was accompanied by differences in shell shape and metabolomic characteristics. Significant differences were found between L. obtusata versus L. fabalis and L. saxatilis / L. arcana versus L. compressa both in shell morphology and in metabolomes. L. saxatilis demonstrated a clear variability depending on intertidal level which corresponds to a shift in conditions within the occupied microhabitat. Interestingly, the differences between L. arcana (inhabiting the upper intertidal level) and L. compressa (inhabiting the lower one) were analogous to those between the upper and lower fractions of L. saxatilis. No significant level-dependent changes were found between the upper and lower fractions of L. obtusata, most probably due to habitat amelioration by fucoid macroalgae. All these results are discussed in the contexts of the role of ecology in speciation, ecological niche dynamics and conservatism, and evolutionary history of the Neritrema species.

LPDs - «Linked to penumbra¼ discharges or EEG correlate of excitotoxicity: A review based hypothesis.

Periodic lateralized epileptiform discharges (PLEDs) or lateralized periodic discharges (LPDs) are a well-known variant of pathological EEG activity. However, the mechanisms underpinning the appearance of this pattern are not completely understood. The heterogeneity of the features derived from LPDs patterns, and the wide range of pathological conditions in which they occur, raise a question about the unifying mechanisms underlying these phenomena. This paper reassesses the current opinion surrounding LPDs which considers glutamate excitotoxicity to be the primary pathophysiological basis, and the penumbral region to be the main morphological substrate. Arguments in favour of this hypothesis are presented, with interpretations supported by evidence from recent literature involving clinical and experimental data. Presently, no single hypothesis places considerable emphasis on the pathochemical properties of LPDs, which are implicitly meaningful towards better understanding of the clinical significance of this pattern.