Modulation of the proteolytic activity of matrix metalloproteinase-2 (gelatinase A) on fibrinogen

The proteolytic processing of bovine fibrinogen by MMP-2 (gelatinase A), which brings about the formation of a product unable to form fibrin clots, has been studied at 37 degrees C. Catalytic parameters, although showing a somewhat lower catalytic efficiency with respect to thrombin and plasmin, indeed display values indicating a pathophysiological significance of this process. A parallel molecular modelling study predicts preferential binding of MMP-2 to the beta-chain of fibrinogen through its haemopexin-like domain, which has been directly demonstrated by the inhibitory effect in the presence of the exogenous haemopexin-like domain. However, the removal of this domain does not impair the interaction between MMP-2 and fibrinogen, but it dramatically alters the proteolytic mechanism, producing different fragmentation intermediates. The investigation at various pH values between 6.0 and 9.3 indicates a proton-linked behaviour, which is relevant for interpreting the influence on the process by environmental conditions occurring at the site of an injury. Furthermore, the action of MMP-2 on peroxynitrite-treated fibrinogen has been investigated, a situation possibly occurring under oxidative stress. The chemical alteration of fibrinogen, which has been shown to abolish its clotting activity, brings about only limited modifications of the catalytic parameters without altering the main enzymatic mechanism.     

Phytosterols, but not pectin, added to a high-saturated-fat diet modify saturated fatty acid excretion in relation to chain length

The main objective of this article was to study how the excretion of saturated fatty acids (SFA) is modified after the consumption of a high-saturated-fat diet that was supplemented with phytosterol and pectin. We present the results of a longitudinal 4-week study on guinea pigs. Diets were supplemented with 0.33% of cholesterol and differed in the content of pectin (three levels) and of phytosterols (three levels). Seventy-two female Dunkin Hartley guinea pigs were randomly assigned to the treatment groups (8 animals/group). Addition of phytosterol resulted in a decrease of lauric (12:0) and myristic (14:0) excretions and in an increase of arachidic (20:0) and behenic (22:0) excretions. Palmitic (16:0) and stearic (18:0) acids did not show a clear change after phytosterol supplementation. Addition of pectin resulted in a decreased excretion of all SFA, although this was not significant. These results suggest that phytosterols added to a high-saturated-fat diet enhance the absorption of the most atherogenic fatty acids (lauric and myristic) after 1 week of treatment, as compared with the high-saturated-fat diet alone.     

Studies on bacterioplankton and inhibitory strains of aquatic actinomycetes in Lake Bardawil,Egypt

Lake Bardawil represents a hyper-saline shallow (50–600 cm deep) water basin lying along the northern shore of Sinai. Surface water samples were collected monthly from this lake for physico-chemical and microbiological analysis. Seasonal variations in the averages of temperature, pH and transparency of the tested water samples were determined. Seasonal averages of the total bacterial counts at 22 and 37°C, biovolumes of cells and bacterial biomass of the lake’s water at different regions were also determined. In addition to the gram-negative pathogen, Edwardsiella tarda, faecal contamination indicators, total coliforms, faecal coliforms and faecal streptococci were counted in the lake’s water samples from various regions during different seasons. The number of actinomycetes per milliliter of the lake’s water samples were determined. Fifteen actinomycetes were isolated and screened for their antibacterial activity against E. coli and pathogenic E. tarda isolated from the same water samples. Five isolates of these actinomycetes showed antibacterial activities and nine of them were identified as Streptomyces. The most antibacterially active isolate was subjected to morphological, physiological and biochemical studies and identified as Streptomyces viridiviolaceus. The identified organism exhibited antimicrobial activities against the main indicator of water pollution, E. coli, pathogenic E. tarda, Corynebacterium michiganese B-33, Pseudomonas solanacearum B-3212 and Staphylococcus. No antimicrobial activities were recorded against Bacillus cereus, Micrococcus, Mycobacterium, Aspergillus niger, Candida albicans, C. tropicalis or Rhizopus nigricans.     

Teaching and learning in ecology: a horizon scan of emerging challenges and solutions

We currently face significant, anthropogenic, global environmental challenges and the role of ecologists in mitigating these challenges is arguably more important than ever. Consequently there is an urgent need to recruit and train future generations of ecologists, both those whose main area is ecology, but also those involved in the geological, biological and environmental sciences. Here we present the results of a horizon scanning exercise that identified current and future challenges facing the teaching of ecology, through surveys of teachers, students and employers of ecologists. Key challenges identified were grouped in terms of the perspectives of three groups: students, for example the increasing disconnect between people and nature; teachers, for example the challenges associated with teaching the quantitative skills that are inherent to the study of ecology; and society, for example poor societal perceptions of the field of ecology. In addition to the challenges identified, we propose a number of solutions developed at a workshop by a team of ecology teaching experts, with supporting evidence of their potential to address many of the problems raised. These proposed solutions include developing living labs, teaching students to be ecological entrepreneurs and influencers, embedding skills-based learning and coding in the curriculum, an increased role for learned societies in teaching and learning, and using new technology to enhance fieldwork studies including virtual reality, artificial intelligence and real-time spoken language translation. Our findings are focused towards UK higher education, but they should be informative for students and teachers of a wide range of educational levels, policy makers and professional ecologists worldwide.     

Agent-based models to investigate sound impact on marine animals: bridging the gap between effects on individual behaviour and population level consequences

Marine ambient sound levels have risen due to noisy human activities, such as shipping, fishing, seismic surveys and piling for windfarms. Marine mammals and fishes are two prominent taxonomic groups that are exposed to this noise pollution, which may experience detrimental effects at the population level. Acoustic effects on individual behaviour such as deterrence, disturbance, distraction and masking of biologically relevant sounds, can be translated energetically to changes in vital rates (growth, maturation, reproduction and survival) in a population consequences of acoustic disturbance (PCAD) approach. However, we typically neglect spatial variation in species distributions and noise pollution, while abiotic factors like temperature, bathymetry and currents, as well as habitat quality in terms of feeding or hiding opportunities, will also have a geographically variable impact on potential consequences. We here address the conceptual integration of agent based models (ABM) into the PCAD framework, as a suitable theoretical tool with high potential for the exploration of these spatial factors and their modifying role in noise impact assessment studies. We review five ABM case studies, including investigations into: 1) effects of movement strategy on the impact of explosions in harbour porpoise; 2) effects of disturbance sensitivity on pile driving impact on migrating cod; 3) impact of seismic survey sounds on Atlantic mackerel distribution and movement; 4) population-level impact of mitigation of harbour porpoise bycatch with pingers; and 5) population effects of alternative windfarm construction scenarios in harbour porpoise. We discuss similarities and differences among these studies in sound and species mapping approaches and we evaluate model realism and pattern validation. We believe that ABMs are a valuable tool for integrating spatial information into ecological impact studies that investigate acoustic disturbance, for any type of sound source, and for both marine mammals and fish.     

SdrC induces staphylococcal biofilm formation through a homophilic interaction

The molecular pathogenesis of many Staphylococcus aureus infections involves growth of bacteria as biofilm. In addition to polysaccharide intercellular adhesin (PIA) and extracellular DNA, surface proteins appear to mediate the transition of bacteria from planktonic growth to sessile lifestyle as well as biofilm growth, and can enable these processes even in the absence of PIA expression. However, the molecular mechanisms by which surface proteins contribute to biofilm formation are incompletely understood. Here we demonstrate that self‐association of the serine‐aspartate repeat protein SdrC promotes both bacterial adherence to surfaces and biofilm formation. However, this homophilic interaction is not required for the attachment of bacteria to abiotic surfaces. We identified the subdomain that mediates SdrC dimerization and subsequent cell‐cell interactions. In addition, we determined that two adjacently located amino acid sequences within this subdomain are required for the SdrC homophilic interaction. Comparative amino acid sequence analysis indicated that these binding sites are conserved. In summary, our study identifies SdrC as a novel molecular determinant in staphylococcal biofilm formation and describes the mechanism responsible for intercellular interactions. Furthermore, these findings contribute to a growing body of evidence suggesting that homophilic interactions between surface proteins present on neighbouring bacteria induce biofilm growth.     

Improved reporting of DNA methylation data derived from studies of the human placenta

Epigenetic variation is increasingly hypothesized as a mechanism underlying the effect of the in utero environment on long-term postnatal health; however, there is currently little clear data to support this in humans. A number of biological and technical factors provide challenges for the design of clinical epigenetic studies: from the type of cells or tissues that are available to the large range of predicted confounders that may impact findings. The human placenta, in addition to other neonatal tissues and whole blood, is commonly sampled for the study of epigenetic modifications. However there is little conformity for the most appropriate methods for study design, data analysis, and importantly, data interpretation. Here we present general recommendations for the reporting of DNA methylation in biological samples, with specific focus on the placenta. We outline key guidelines for: (1) placental sampling, (2) data analysis and presentation, and (3) interpretation of DNA methylation data. We emphasize the need to consider methodological noise, increase statistical power and to ensure appropriate adjustment for biological covariates. Finally, we highlight that epigenetic changes may be non-pathological and not necessarily translate into disease-associated changes. Improved reporting of DNA methylation data will be critical to identify epigenetic-based effects and to better understand the full phenotypic impact of these widely-reported epigenomic changes.     

Direct observation of microtubule pushing by cortical dynein in living cells

Microtubules are under the influence of forces mediated by cytoplasmic dynein motors associated with the cell cortex. If such microtubules are free to move, they are rapidly transported inside cells. Here we directly observe fluorescent protein–labeled cortical dynein speckles and motile microtubules. We find that several dynein complex subunits, including the heavy chain, the intermediate chain, and the associated dynactin subunit Dctn1 (also known as p150glued) form spatially resolved, dynamic speckles at the cell cortex, which are preferentially associated with microtubules. Measurements of bleaching and dissociation kinetics at the cell cortex reveal that these speckles often contain multiple labeled dynein heavy-chain molecules and turn over rapidly within seconds. The dynamic behavior of microtubules, such as directional movement, bending, or rotation, is influenced by association with dynein speckles, suggesting a direct physical and functional interaction. Our results support a model in which rapid turnover of cell cortex–associated dynein complexes facilitates their search to efficiently capture and push microtubules directionally with leading plus ends.     

TLR4 single nucleotide polymorphisms (SNPs) associated with Salmonella shedding in pigs

Toll-like receptor 4 (TLR4) is a key factor in the innate immune recognition of lipopolysaccharide (LPS) from Gram-negative bacteria. Previous studies from our group identified differences in the expression profile of TLR4 and genes affected by the TLR4 signaling pathway among pigs that shed varying levels of Salmonella, a Gram-negative bacterium. Therefore, genetic variation in this gene may be involved with the host’s immune response to bacterial infections. The current study screened for single nucleotide polymorphisms (SNPs) in the TLR4 gene and tested their association with Salmonella fecal shedding. Pigs (n?=?117) were intranasally challenged at 7 weeks of age with 1?×?10⁹ CFU of S. Typhimurium χ4232 and were classified as low or persistent Salmonella shedders based on the levels of Salmonella being excreted in fecal material. Salmonella fecal shedding was determined by quantitative bacteriology on days 2, 7, 14, and 20/21 post exposure, and the cumulative levels of Salmonella were calculated to identify the low (n?=?20) and persistent (n?=?20) Salmonella shedder pigs. From those 40 animals, the TLR4 region was sequenced, and 18 single nucleotide polymorphisms (SNPs) in TLR4 were identified. Twelve SNPs have been previously described and six are novel SNPs of which five are in the 5′ untranslated region and one is in intron 2. Single marker association test identified 13 SNPs associated with the qualitative trait of Salmonella fecal shedding, and seven of those SNPs were also associated with a quantitative measurement of fecal shedding (P?<?0.05). Using a stepwise regression process, a haplotype composed of SNPs rs80787918 and rs80907449 (P?≤?4.0?×?10^?3) spanning a region of 4.9 Kb was identified, thereby providing additional information of the influence of those SNPs on Salmonella fecal shedding in pigs.