Melectin MAPs: the influence of dendrimerization on antimicrobial and hemolytic activity

The recently described antimicrobial peptide melectin (MEP, GFLSILKKVLPKVMAHMK-NH₂) exhibits high antimicrobial activity against Gram-positive and Gram-negative bacteria. Here we describe the synthesis and biological activities of 23 new analogues of MEP. We studied the influence of dimerization and tetramerization (MAP-constructs of MEP) on the antimicrobial and hemolytic activities, as well as the role of Met in positions 14 and 17 of the peptide chain. Oxidation of the Met to Met(O) and Met(O₂) decreases antimicrobial activity of all tested bacteria if the peptide is in the monomeric form, however, only to Staphylococcus aureus if in the form of dimer or tetramer. Dimerization and tetramerization increase the undesirable hemolytic activity of the peptides. Interestingly, substitution of Leu for Val in position 6 leads to the decrease of hemolytic activity. Introduction of the isosteric amino acid Nle into positions 14 or 17 or both leads to slight increase of hemolytic activity under preservation of high antimicrobial activities. Unfortunately, dimerization again leads to an increase of hemolytic activity.     

Novel antimicrobial peptides from the venom of the eusocial bee Halictus sexcinctus (Hymenoptera: Halictidae) and their analogs

Two novel antimicrobial peptides, named halictines, were isolated from the venom of the eusocial bee Halictus sexcinctus. Their primary sequences were established by ESI-QTOF mass spectrometry, Edman degradation and enzymatic digestion as Gly-Met-Trp-Ser-Lys-Ile-Leu-Gly-His-Leu-Ile-Arg-NH₂ (HAL-1), and Gly-Lys-Trp-Met-Ser-Leu-Leu-Lys–His-Ile-Leu-Lys-NH₂ (HAL-2). Both peptides exhibited potent antimicrobial activity against Gram-positive and Gram-negative bacteria but also noticeable hemolytic activity. The CD spectra of HAL-1 and HAL-2 measured in the presence of trifluoroethanol or SDS showed ability to form an amphipathic α-helical secondary structure in an anisotropic environment such as bacterial cell membrane. NMR spectra of HAL-1 and HAL-2 measured in trifluoroethanol/water confirmed formation of helical conformation in both peptides with a slightly higher helical propensity in HAL-1. Altogether, we prepared 51 of HAL-1 and HAL-2 analogs to study the effect of such structural parameters as cationicity, hydrophobicity, α-helicity, amphipathicity, and truncation on antimicrobial and hemolytic activities. The potentially most promising analogs in both series are those with increased net positive charge, in which the suitable amino acid residues were replaced by Lys. This improvement basically relates to the increase of antimicrobial activity against pathogenic Pseudomonas aeruginosa and to the mitigation of hemolytic activity.     

Effect of functional electrical stimulation on the effort and walking speed,surface electromyography activity,and metabolic responses in stroke subjects

ObjectiveTo investigate the effects of functional electrical stimulation (FES) combined with conventional rehabilitation program on the effort and speed of walking, the surface electromyographic (sEMG) activity and metabolic responses in the management of drop foot in stroke subjects.MethodsFifteen patients with a drop foot resulting from stroke at least 3 months prior to the start of the trial took part in this study. All subjects were treated 1 h a day, 5 days a week, for 12 weeks, including conventional stroke rehabilitation program and received 30 min of FES to the tibialis anterior (TA) muscle of the paretic leg in clinical settings. Baseline and post-treatment measurements were made for temporal and spectral EMG parameters of TA muscle, walking speed, the effort of walking as measured by physiological cost index (PCI) and metabolic responses.ResultsThe experimental results showed a significant improvement in mean-absolute-value (21.7%), root-mean-square (66.3%) and median frequency (10.6%) of TA muscle EMG signal, which reflects increased muscle strength. Mean increase in walking speed was 38.7%, and a reduction in PCI of 34.6% between the beginning and at end of the trial. Improvements were also found in cardiorespiratory responses with reduction in oxygen consumption (24.3%), carbon dioxide production (19.9%), heart rate (7.8%) and energy cost (22.5%) while walking with FES device.ConclusionsThe results indicate that the FES may be a useful therapeutic tool combined with conventional rehabilitation program to improve the muscle strength, walking ability and metabolic responses in the management of drop foot with stroke patients.     

Biodiversity,biogeography, and connectivity of polychaetes in the world's largest marine minerals exploration frontier

Aim

The abyssal Clarion-Clipperton Zone (CCZ), Pacific Ocean, is an area of commercial importance owing to the growing interest in mining high-grade polymetallic nodules at the seafloor for battery metals. Research into the spatial patterns of faunal diversity, composition, and population connectivity is needed to better understand the ecological impacts of potential resource extraction. Here, a DNA taxonomy approach is used to investigate regional-scale patterns of taxonomic and phylogenetic alpha and beta diversity, and genetic connectivity, of the dominant macrofaunal group (annelids) across a 6 million km² region of the abyssal seafloor.

Location

The abyssal seafloor (3932–5055 m depth) of the Clarion-Clipperton Zone, equatorial Pacific Ocean.

Methods

We used a combination of new and published barcode data to study 1866 polychaete specimens using molecular species delimitation. Both phylogenetic and taxonomic alpha and beta diversity metrics were used to analyse spatial patterns of biodiversity. Connectivity analyses were based on haplotype distributions for a subset of the studied taxa.

Results

DNA taxonomy identified 291–314 polychaete species from the COI and 16S datasets respectively. Taxonomic and phylogenetic beta diversity between sites were relatively high and mostly explained by lineage turnover. Over half of pairwise comparisons were more phylogenetically distinct than expected based on their taxonomic diversity. Connectivity analyses in abundant, broadly distributed taxa suggest an absence of genetic structuring driven by geographical location.

Main Conclusions

Species diversity in abyssal Pacific polychaetes is high relative to other deep-sea regions. Results suggest that environmental filtering, where the environment selects against certain species, may play a significant role in regulating spatial patterns of biodiversity in the CCZ. A core group of widespread species have diverse haplotypes but are well connected over broad distances. Our data suggest that the high environmental and faunal heterogeneity of the CCZ should be considered in future policy decisions.     

What is a suitable management for Typha latifolia control in wet meadows?

Aim

Typha latifolia causes serious problems in wet meadows by overgrowing and suppressing other native plants. To determine suitable management for T. latifolia control, we addressed the following question: What are the effects of long-term cutting at different frequencies (once or twice per year and no management) and biomass removal on cover and other characteristics of T. latifolia, and on sward productivity and plant species composition?

Location

Malá Strana nature reserve, Jizerské hory Mountains, Czechia.

Methods

A long-term experiment arranged in a randomised block design with three blocks was established in 2005. Data were collected from five treatments: unmanaged control; cutting once a year in June without biomass removal and with biomass removal; cutting twice per year in June and August without biomass removal and with biomass removal. Percentage cover of T. latifolia and other vascular plant species was visually estimated and T. latifolia characteristics (tiller density, height, dry-matter biomass [DMB] yield and litter), sward height and DMB yield were measured during 2005–2018 at the end of June.

Results and Discussion

Regular cutting once or twice per year regardless of cut biomass removal led to reductions in tiller density, height, litter and DMB yield of T. latifolia. Biomass removal had only a slight tendency to affect T. latifolia characteristics. The higher frequency of cutting significantly decreased the mean T. latifolia cover, litter and DMB yield. Cutting once or twice per year regardless of biomass removal led to successive changes in plant species composition but had no effect on the species richness and evenness.

Conclusions

Cutting at least once per year without biomass removal seems to be sufficient to achieve a decrease in DMB yield and litter of T. latifolia plants, and thereby maintain the wet-meadow vegetation without loss of species richness and also preventing the overgrowth of shrubs and trees.     

Adenosine modulates LPS-induced cytokine production in porcine monocytes

Adenosine plays an important role during inflammation, particularly through modulation of monocyte function. The objective of the present study was to evaluate the effect of synthetic adenosine analogs on cytokine production by porcine monocytes. The LPS-stimulated cytokine production was measured by flow cytometry and quantitative real-time PCR. Adenosine receptor expression was measured by quantitative real-time PCR. The present study demonstrates that adenosine analog N-ethylcarboxyamidoadenosine (NECA) down-regulates TNF-α production and up-regulates IL-8 production by LPS-stimulated porcine monocytes. The effect was more pronounced in CD163^? subset of monocytes compared to the CD163⁺ subset. Although both monocyte subsets express mRNA for A1, A2A, A2B and A3 adenosine receptors, the treatment of monocytes with various adenosine receptor agonists and antagonists proved that the effect of adenosine is mediated preferentially via A2A adenosine receptor. Moreover, the study suggests that the effect of NECA on porcine monocytes alters the levels of the cytokines which could play a role in the differentiation of naive T cells into Th17 cells. The results suggest that adenosine plays an important role in modulation of cytokine production by porcine monocytes.