INTRODUCTION: We used a functional MRI paradigm involving conventional vs. unconventional views of objects to assess bottom-up vs. top-down visual processing in Parkinson's disease (PD) with normal cognition, PD with mild cognitive impairment (MCI), and MCI due to Alzheimer's disease (AD) as compared to healthy controls. We particularly aimed at determining whether the task discriminated between PD with and without MCI and between two MCI groups due to distinct pathologies (AD and PD). METHODS: 116 right-handed subjects (21 MCI due to AD; 16 PD with normal cognition; 24 PD with MCI; 55 healthy controls) performed a visual object-matching task in a T MR scanner. T statistic maps were computed to contrast task-based activation during unconventional vs. conventional view conditions. One-way ANOVAs and post hoc tests were performed to assess differences across and between groups. RESULTS: Both MCI groups performed worse than controls in the unconventional views condition and showed reduced activation of right anterior cingulate cortex and right superior parietal lobule (PD with MCI), and right middle and inferior frontal gyri (MCI due to AD). Neural responses in cortical areas within the ventral and dorsal visual pathway appeared to be preserved in both MCI groups. Receiver operating characteristic analysis of MRI contrast in the right superior parietal lobule distinguished PD with and without MCI with 87.50% sensitivity and 86.98% specificity. CONCLUSIONS: Impaired recognition of objects presented in unconventional orientations in MCI due to PD and AD was associated with decreased activation of frontoparietal regions, consistent with defective top-down regulation of visual processing. Aberrant activation of superior parietal cortex may serve as an early imaging biomarker of impending cognitive impairment in PD.

• Klíčová slova
• Alzheimer's disease, Mild cognitive impairment, Parkinson's disease, Top-down visual processing, fMRI,
• MeSH
• Alzheimerova nemoc patofyziologie   psychologie   MeSH
• kognitivní dysfunkce patofyziologie   psychologie   MeSH
• lidé středního věku MeSH
• lidé MeSH
• magnetická rezonanční tomografie MeSH
• mapování mozku MeSH
• mozek patofyziologie   MeSH
• Parkinsonova nemoc patofyziologie   psychologie   MeSH
• rozpoznávání (psychologie) MeSH
• rozpoznávání obrazu fyziologie   MeSH
• senioři MeSH
• světelná stimulace MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH

The oxygen reduction reaction (ORR) is of great interest for future sustainable energy conversion and storage, especially concerning fuel cell applications. The preparation of active, affordable, and scalable electrocatalysts and their application in fuel cell engines of hydrogen cars is a prominent step toward the reduction of air pollution, especially in urban areas. Alloying nanostructured Pt with lanthanides is a promising approach to enhance its catalytic ORR activity, whereby the development of a simple synthetic route turned out to be a nontrivial endeavor. Herein, for the first time, we present a successful single-step, scalable top-down synthetic route for Pt-lanthanide alloy nanoparticles, as witnessed by the example of Pr-alloyed Pt nanoparticles. The catalyst was characterized by high-resolution transmission electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and photoelectron spectroscopy, and its electrocatalytic oxygen reduction activity was investigated using a rotating disk electrode technique. Pt xPr/C showed ∼3.5 times higher [1.96 mA/cm2Pt, 0.9 V vs reversible hydrogen electrode (RHE)] specific activity and ∼1.7 times higher (0.7 A/mgPt, 0.9 V vs RHE) mass activity compared to commercial Pt/C catalysts. On the basis of previous findings and characterization of the Pt xPr/C catalyst, the activity improvement over commercial Pt/C originates from a lattice strain introduced by the alloying process.

• Klíčová slova
• cathodic corrosion, electrocatalysis, fuel cell, lanthanides, oxygen reduction, platinum alloys, top-down synthesis,
• Publikační typ
• časopisecké články MeSH

Two-dimensional mass spectrometry (2D MS) is a multiplexed tandem mass spectrometry method that does not rely on ion isolation to correlate the precursor and fragment ions. On a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS), 2D MS instead uses the modulation of precursor ion radii inside the ICR cell before fragmentation and yields 2D mass spectra that show the fragmentation patterns of all the analytes. In this study, we perform 2D MS for the first time with quadrupolar detection in a dynamically harmonized ICR cell. We discuss the advantages of quadrupolar detection in 2D MS and how we adapted existing data processing techniques for accurate frequency-to-mass conversion. We apply 2D MS with quadrupolar detection to the top-down analysis of covalently labeled ubiquitin with ECD fragmentation, and we develop a workflow for label-free relative quantification of biomolecule isoforms in 2D MS.

• MeSH
• cyklotrony MeSH
• Fourierova analýza MeSH
• proteomika * metody   MeSH
• tandemová hmotnostní spektrometrie * metody   MeSH
• ubikvitin MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• ubikvitin MeSH

The relative contribution of top-down and bottom-up processes regulating primary decomposers can influence the strength of the link between the soil animal community and ecosystem functioning. Although soil bacterial communities are regulated by bottom-up and top-down processes, the latter are considered to be less important in structuring the diversity and functioning of fungal-dominated ecosystems. Despite the huge diversity of mycophagous (fungal-feeding) soil fauna, and their potential to reverse the outcomes of competitive fungal interactions, top-down grazing effects have never been found to translate to community-level changes. We constructed soil mesocosms to investigate the potential of isopods grazing on cord-forming basidiomycete fungi to influence the community composition and functioning of a complex woodland soil microbial community. Using metagenomic sequencing we provide conclusive evidence of direct top-down control at the community scale in fungal-dominated woodland soil. By suppressing the dominant cord-forming basidiomycete fungi, isopods prevented the competitive exclusion of surrounding litter fungi, increasing diversity in a community containing several hundred fungal species. This isopod-induced modification of community composition drove a shift in the soil enzyme profile, and led to a restructuring of the wider mycophagous invertebrate community. We highlight characteristics of different soil ecosystems that will give rise to such top-down control. Given the ubiquity of isopods and basidiomycete fungi in temperate and boreal woodland ecosystems, such top-down community control could be of widespread significance for global carbon and nutrient cycling.

• MeSH
• fungální proteiny genetika   metabolismus   MeSH
• houby klasifikace   enzymologie   fyziologie   MeSH
• Isopoda fyziologie   MeSH
• půda chemie   MeSH
• půdní mikrobiologie * MeSH
• regulace genové exprese enzymů MeSH
• regulace genové exprese u hub MeSH
• zvířata MeSH
• Check Tag
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fungální proteiny MeSH
• půda MeSH

Nanostructured palladium (Pd) is a universal catalyst that is widely used in applications ranging from catalytic converters of combustion engine cars to hydrogenation catalysts in industrial processes. Standard protocols for synthesizing such nanoparticles (NPs) typically use bottom-up approaches. They utilize special and often expensive physical techniques or wet-chemical methods requiring organic surfactants. These surfactants should often be removed before catalytic applications. In this article, the synthesis of Pd NPs immobilized on carbon support by electrochemical erosion without using any surfactants or toxic materials is reported. The Pd NPs synthesis essentially relies on a Pd bulk pretreatment, which causes material embrittlement and allows the erosion process to evolve more efficiently, producing homogeneously distributed NPs on the support. Moreover, the synthesized catalyst is tested for hydrogen evolution reaction. The activity evaluations identify optimal synthesis parameters related to the erosion procedure. The electrocatalytic properties of the Pd NPs produced with sizes down to 6.4 ± 2.9 nm are compared with a commercially available Pd/C catalyst. The synthesized catalyst outperforms the commercial catalyst within all properties, like specific surface area, geometric activity, mass activity, specific activity, and durability.

• Klíčová slova
• electrochemical erosion, hydrogen embrittlement, hydrogen evolution reaction, nanoparticles, palladium,
• Publikační typ
• časopisecké články MeSH

Research on dance interventions (DIs) in the elderly has shown promising benefits to physical and cognitive outcomes. The effect of DIs on resting-state functional connectivity (rs-FC) varies, which is possibly due to individual variability. In this study, we assessed the moderation effects of residual cognitive reserve (CR) on DI-induced changes in dynamic rs-FC and their association on cognitive outcomes. Dynamic rs-FC (rs-dFC) and cognitive functions were evaluated in non-demented elderly subjects before and after a 6-month DI (n = 36) and a control group, referred to as the life-as-usual (LAU) group (n = 32). Using linear mixed models and moderation, we examined the interaction effect of DIs and CR on changes in the dwell time and coverage of rs-dFC. Cognitive reserve was calculated as the residual difference between the observed memory performance and the performance predicted by brain state. Partial correlations accounting for CR evaluated the unique association between changes in rs-dFC and cognition in the DI group. In subjects with lower residual CR, we observed DI-induced increases in dwell time [t(58) = -2.14, p = 0.036] and coverage [t(58) = -2.22, p = 0.030] of a rs-dFC state, which was implicated in bottom-up information processing. Increased dwell time was also correlated with a DI-induced improvement in Symbol Search (r = 0.42, p = 0.02). In subjects with higher residual CR, we observed a DI-induced increase in coverage [t(58) = 2.11, p = 0.039] of another rs-dFC state, which was implicated in top-down information processing. The study showed that DIs have a differential and behaviorally relevant effect on dynamic rs-dFC, but these benefits depend on the current CR level.

• Klíčová slova
• attention, bottom-up processing, cognitive reserve, coverage, dance intervention, dwell time, dynamic resting-state functional connectivity, top-down processing,
• Publikační typ
• časopisecké články MeSH

The objective is to study the involvement of the posterior medial cortex (PMC) in encoding and retrieval by visual and auditory memory processing. Intracerebral recordings were studied in two epilepsy-surgery candidates with depth electrodes implanted in the retrosplenial cingulate, precuneus, cuneus, lingual gyrus and hippocampus. We recorded the event-related potentials (ERP) evoked by visual and auditory memory encoding-retrieval tasks. In the hippocampus, ERP were elicited in the encoding and retrieval phases in the two modalities. In the PMC, ERP were recorded in both the encoding and the retrieval visual tasks; in the auditory modality, they were recorded in the retrieval task, but not in the encoding task. In conclusion, the PMC is modality dependent in memory processing. ERP is elicited by memory retrieval, but it is not elicited by auditory encoding memory processing in the PMC. The PMC appears to be involved not only in higher-order top-down cognitive activities but also in more basic, rather than bottom-up activities.

• MeSH
• akustická stimulace MeSH
• dospělí MeSH
• elektroencefalografie metody   MeSH
• epilepsie patofyziologie   MeSH
• implantované elektrody MeSH
• lidé MeSH
• mozek fyziologie   MeSH
• paměť fyziologie   MeSH
• počítačové zpracování signálu MeSH
• sluchové evokované potenciály fyziologie   MeSH
• světelná stimulace MeSH
• zrakové evokované potenciály fyziologie   MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: The default mode network (DMN) decreases its activity when switching from a resting state to a cognitive task condition, while activity of the network engaged in the given task increases. Visual processing is typically disturbed in Parkinson's disease dementia (PDD). OBJECTIVE: Using functional MRI, we studied the DMN effective connectivity patterns in PDD as compared with cognitively normal patients with Parkinson's disease (PD) and healthy controls (HC) when switching from baseline to a visual cognitive task condition. METHODS: In all, 14 PDD, 18 PD, and 18 age-matched healthy controls participated in this functional MRI study. We used a psychophysiological interaction analysis with the precuneus (PCu) as a seed. The threshold was set at p(FWE) <0.05. RESULTS: The healthy controls showed greater PCu connectivity with the bilateral middle temporal/middle occipital gyri at baseline than during the task condition. The correlation direction changed from positive to negative. Both PD and PDD showed disturbed DMN connectivity with the brain regions that are involved in bottom-up visual processing. In PD, we also found impaired integration of the areas engaged in the ventral attentional network, which might reflect specific attentional deficits observed during the early course of PD. In mild PDD, we detected increased engagement of areas involved in the dorsal attentional network, which corresponds to increased top-down control in this patient group as compared to the healthy controls. CONCLUSION: Our results show impaired dynamic interplay between large scale brain networks in PD that spread far beyond the motor system.

• Klíčová slova
• Default mode network, Parkinson's disease, dementia, functional MRI, precuneus, visual processing,
• MeSH
• atrofie etiologie   patologie   MeSH
• hyperkinetická porucha etiologie   MeSH
• kognitivní poruchy etiologie   patologie   MeSH
• kyslík krev   MeSH
• lidé středního věku MeSH
• lidé MeSH
• magnetická rezonanční tomografie MeSH
• mapování mozku MeSH
• modely neurologické MeSH
• nervové dráhy krevní zásobení   patologie   MeSH
• neuropsychologické testy MeSH
• Parkinsonova nemoc komplikace   patologie   MeSH
• počítačové zpracování obrazu MeSH
• poruchy zraku etiologie   patologie   MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• studie případů a kontrol MeSH
• světelná stimulace MeSH
• temenní lalok krevní zásobení   patologie   MeSH
• Check Tag
• lidé středního věku MeSH
• lidé MeSH
• mužské pohlaví MeSH
• senioři nad 80 let MeSH
• senioři MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyslík MeSH

Posttranslational modifications (PTMs) of proteins represent fascinating extensions of the dynamic complexity of living cells' proteomes. The results of enzymatically catalyzed or spontaneous chemical reactions, PTMs form a fourth tier in the gene - transcript - protein cascade, and contribute not only to proteins' biological functions, but also to challenges in their analysis. There have been tremendous advances in proteomics during the last decade. Identification and mapping of PTMs in proteins have improved dramatically, mainly due to constant increases in the sensitivity, speed, accuracy and resolution of mass spectrometry (MS). However, it is also becoming increasingly evident that simple gel-free shotgun MS profiling is unlikely to suffice for comprehensive detection and characterization of proteins and/or protein modifications present in low amounts. Here, we review current approaches for enriching and separating posttranslationally modified proteins, and their MS-independent detection. First, we discuss general approaches for proteome separation, fractionation and enrichment. We then consider the commonest forms of PTMs (phosphorylation, glycosylation and glycation, lipidation, methylation, acetylation, deamidation, ubiquitination and various redox modifications), and the best available methods for detecting and purifying proteins carrying these PTMs. This article is part of a Special Issue entitled: Posttranslational Protein modifications in biology and Medicine.

• Klíčová slova
• PTM, PTM detection, Posttranslational modification, Protein enrichment, Proteome, Top-down proteomics,
• MeSH
• lidé MeSH
• posttranslační úpravy proteinů * MeSH
• proteom chemie   izolace a purifikace   metabolismus   MeSH
• proteomika metody   MeSH
• zvířata MeSH
• Check Tag
• lidé MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• proteom MeSH

Cryoconite holes (water reservoirs) significantly contribute to biodiversity and biogeochemical processes on glacier surfaces. However, the lack of seasonal observations of cryoconite biota limits our knowledge of glacial ecosystem functioning. We studied photoautotrophs, consumers and sediment characteristics (community structure, biomass, elemental composition, organic matter content, δ13C, δ15N) from cryoconite holes in the upper and lower parts of the Forni Glacier ablation zone (Italy) throughout the ablation season. Dominant cyanobacteria were Oscillatoriaceae and Leptolyngbyaceae, while dominant green algae were Zygnemataceae and Chlorellaceae. Tardigrades (Cryobiotus klebelsbergi) were the dominant consumers. The biomass of consumers negatively correlated with the biomass of green algae, indicating that grazing likely controls algal communities in the upper part. Green algae dominated the upper part, while a shift from green algae- to cyanobacteria-dominated communities was observed in the lower part during the season. The increase in δ13C of cryoconite organic matter (OM) in the lower part followed the trend of the community shift of photoautotrophs potentially affected by precipitation. Also, δ13C of tardigrades positively correlated with δ13C of cryoconite OM in the upper part, indicating some cryoconite OM as their food. Some photoautotrophic taxa appeared only on specific dates, and no spatio-temporal changes in the cryoconite general elemental composition were found. Our data indicate that changes in the community structure and biomass of cryoconite biota on the Forni Glacier likely depend on the interplay between phenology, stochastic events (e.g., rainfall) and top-down or bottom-up controls. We demonstrate that multiple observations are essential for understanding the ecology of biota inhabiting cryoconite holes throughout the ablation season.

• Klíčová slova
• Forni glacier, Tardigrada, phenology, stable isotopes, supraglacial habitats, top‐down control,
• Publikační typ
• časopisecké články MeSH