Using sensitivity analysis to identify keystone species and keystone links in size‐based food webs

Human‐induced alterations in the birth and mortality rates of species and in the strength of interactions within and between species can lead to changes in the structure and resilience of ecological communities. Recent research points to the importance of considering the distribution of body sizes of species when exploring the response of communities to such perturbations. Here, we present a new size‐based approach for assessing the sensitivity and elasticity of community structure (species equilibrium abundances) and resilience (rate of return to equilibrium) to changes in the intrinsic growth rate of species and in the strengths of species interactions. We apply this approach on two natural systems, the pelagic communities of the Baltic Sea and Lake Vättern, to illustrate how it can be used to identify potential keystone species and keystone links. We find that the keystone status of a species is closely linked to its body size. The analysis also suggests that communities are structurally and dynamically more sensitive to changes in the effects of prey on their consumers than in the effects of consumers on their prey. Moreover, we discuss how community sensitivity analysis can be used to study and compare the fragility of communities with different body size distributions by measuring the mean sensitivity or elasticity over all species or all interaction links in a community. We believe that the community sensitivity analysis developed here holds some promise for identifying species and links that are critical for the structural and dynamic robustness of ecological communities.     

Reactive oxygen species play a role in P2X7 receptor-mediated IL-6 production in spinal astrocytes

Purinergic Signalling - Astrocytes mediate a remarkable variety of cellular functions, including gliotransmitter release. Under pathological conditions, high concentrations of the purinergic...     

Extracellular vesicle‐mediated crosstalk between NPCE cells and TM cells result in modulation of Wnt signalling pathway and ECM remodelling

Primary open‐angle glaucoma is a leading cause of irreversible blindness, often associated with increased intraocular pressure. Extracellular vesicles (EVs) carry a specific composition of proteins, lipids and nucleotides have been considered as essential mediators of cell‐cell communication. Their potential impact for crosstalk between tissues responsible for aqueous humour production and out‐flow is largely unknown. The study objective was to investigate the effects of EVs derived from non‐pigmented ciliary epithelium (NPCE) primary cells on the expression of Wnt proteins in a human primary trabecular meshwork (TM) cells and define the mechanism underlying exosome‐mediated regulation that signalling pathway. Consistent with the results in TM cell line, EVs released by both primary NPCE cells and NPCE cell line showed diminished pGSK3β phosphorylation and decreased cytosolic levels of β‐catenin in primary TM cells. At the molecular level, we showed that NPCE exosome treatment downregulated the expression of positive GSKβ regulator‐AKT protein but increased the levels of GSKβ negative regulator‐PP2A protein in TM cells. NPCE exosome protein analysis revealed 584 miRNAs and 182 proteins involved in the regulation of TM cellular processes, including WNT/β‐catenin signalling pathway, cell adhesion and extracellular matrix deposition. We found that negative modulator of Wnt signalling miR‐29b was abundant in NPCE exosomal samples and treatment of TM cells with NPCE EVs significantly decreased COL3A1 expression. Suggesting that miR‐29b can be responsible for decreased levels of WNT/β‐catenin pathway. Overall, this study highlights a potential role of EVs derived from NPCE cells in modulating ECM proteins and TM canonical Wnt signalling.     

Rosuvastatin protects isolated hearts against ischemia-reperfusion injury: role of Akt-GSK-3β, metabolic environment,and mitochondrial permeability transition pore

Journal of Physiology and Biochemistry - The cardioprotective activity of rosuvastatin (R) is yet to be known. The objective of this study was to research whether R perfusion before global ischemia...     

Endozoochory of a dry‐fruited tree aids quarry passive restoration and seed soaking further increases seedling emergence

As practitioners promote passive restoration as a complementary approach to technical reclamation, it is imperative to know its drivers. Although the consequences of endozoochory can be crucial to passive restoration success, few experimental studies assess the use of heavily disturbed sites by seed dispersers such as carnivores and how the seeds they bring in emerge and survive. Using an indoor sowing experiment conducted in a quarry located within a natural park in Portugal, we examined for the first time how carnivore endozoochorous seeds collected in the quarry potentially influence its passive restoration, through effects on plant emergence and survival. Also, we tested whether sowing date and water soaking, relevant factors when sowings are to be carried out, would affect seedling emergence and mortality rates when compared with the effect of endozoochory. Our target species were included in the revegetation plan of the quarry, of which endozoochorous seeds of Carob tree (Ceratonia siliqua) were collected in sufficient number for analysis. Irrespective of the carnivore species, endozoochorous carob seeds performed similarly to untreated seeds regarding emergence rates. Endozoochorous carob seedlings showed greater mortality rates but the net result for the plant can still be the colonization of recently vacant habitats by a large proportion of viable seeds. Concerning sowing date, the later carob seeds were sown over the fruit‐ripening season the faster seedlings emerged. Water soaking increased emergence rate by 6.5 times. Broadly, sowings with previous soaking and carnivore‐mediated seed dispersal of this dry‐fruited tree can jointly enhance quarry restoration.     

Stimulation of Bovicin HC5 Production and Selection of Improved Bacteriocin-Producing Streptococcus equinus HC5 Variants

Probiotics and Antimicrobial Proteins - Bovicin HC5 is a peptide that has inhibitory activity against various pathogenic microorganisms and food spoilage bacteria. Aiming to improve the...     

rDNA analysis of the Red Sea seagrass,Halophila, reveals vicariant evolutionary diversification

The effects of opening the Suez Canal as a connection between the Red Sea and the Mediterranean Sea were reported for a number of marine species. However, the evolutionary origin of the seagrasses in the Red Sea and the linking population genetics of seagrasses between the Arabian Sea, the Gulf of Aden, the Red Sea and the Mediterranean Sea have not yet been investigated in detail. The invasion of Halophila stipulacea Asch. from the Red Sea into the Mediterranean Sea after the opening of the Suez Canal was already recorded. We hypothesize that Halophila ovalis populations in the Red Sea developed through long-term historical processes such as vicariant evolutionary diversification. Seagrass samples were collected along the Egyptian coastline of the Red Sea and analysed by the molecular marker ITS. The sequences were compared with published ITS sequences from seagrasses collected in the whole area of interest. In this study, we reveal the linking population genetics, phylogeography and phylogenetics of two dominant seagrass species, Halophila stipulacea and Halophila ovalis, among species collected in the Red Sea and worldwide. The results indicate that the Red Sea Halophila ovalis populations do not group to Halophila ovalis worldwide, and Halophila major, Halophila ovalis collected worldwide and Halophila ovalis collected at the Red Sea are sister clades. Hence, vicariant evolutionary diversification for Halophila ovalis may occur in the Red Sea.     

Photodegradation and Stabilization of Betamethasone-17 Valerate in Aqueous/Organic Solvents and Topical Formulations

The effects of solvent [acetonitrile, methanol, and acetonitrile/water mixture (20:80, v/v)], buffer concentration (phosphate buffer, pH 7.5), ionic strength and commonly employed adjuvants on the photodegradation of betamethasone-17 valerate in cream and gel formulations have been studied on exposure to UV light (300–400 nm). A validated high-performance liquid chromatography method has been used to determine the parent compound and its photodegraded products. The photodegradation data in the studied solvents showed greater decomposition of the drug in solvents with a lower dielectric constant. A comparatively higher rate of photodegradation was observed in the cream formulation compared to that for the gel formulation. The kinetic treatment of the photodegradation data revealed that the degradation of the drug follows first-order kinetics and the apparent first-order rate constants for the photodegradation reactions, in the media studied, range from 1.62 to 11.30 × 10⁻³ min⁻¹. The values of the rate constants decrease with increasing phosphate concentration and ionic strength which could be due to the deactivation of the excited state and radical quenching. The second-order rate constant (k′) for the phosphate ion-inhibited reactions at pH 7.5 has been found to be 5.22 × 10⁻² M⁻¹ s⁻¹. An effective photostabilization of the drug has been achieved in cream and gel formulations with titanium dioxide (33.5–42.5%), vanillin (21.6–28.7%), and butyl hydroxytoluene (18.2–21.6%).Key words: betamethasone-17 valerate, creams and gels, kinetics, photodegradation, photostabilization