Metagenomic Analysis Reveals Previously Undescribed Bat Coronavirus Strains in Eswatini

EcoHealth - We investigated the prevalence of coronaviruses in 44 bats from four families in northeastern Eswatini using high-throughput sequencing of fecal samples. We found evidence of...     

Seasonal dynamics and bioavailability of dissolved organic matter in two contrasting temperate estuaries

Production and bioavailability of dissolved organic matter (DOM) were followed during a year in the nutrient-rich estuary, Roskilde Fjord (RF), and the more oligotrophic strait, Great Belt (GB), in Denmark. Bioavailability of dissolved organic carbon (DOC), nitrogen (DON), and phosphorous (DOP) was determined during incubations over six months. Overall, RF had three to five times larger pools of total nitrogen (TN) and total phosphorous (TP) and five to eight times higher concentrations of inorganic nutrients compared to GB. However, the allocation of carbon, nitrogen, and phosphorous into different pools were remarkably similar between the two systems. DON and DOP contributed with about equal relative fractions in the two systems: 72 ± 13% of total nitrogen and 21 ± 12% of total phosphorous. The average bioavailability of DOM was 25 ± 15, 17 ± 5.5, and 49 ± 29% for carbon, nitrogen, and phosphorous, respectively. The observed release of DIN from degradation of DON amounted to between 0.1 (RF winter) and 14 times (GB summer) the loadings from land and contributed with half of the total input of bioavailable nitrogen during summer. Hence, this study shows that nitrogen in DOM is important for the nitrogen cycling, especially during summer. The sum of inorganic nutrients, particulate organic matter, and bioavailable DOM (the dynamic pools of nutrients) accounted for 42 and 92% of nitrogen, and phosphorous, respectively, and was remarkably similar between the two systems compared to the difference in nutrient richness. It is hypothesized that the pelagic metabolism of nutrients in marine systems dictates a rather uniform distribution of the different fractions of nitrogen and phosphorous containing compounds regardless of eutrophication level.     

Kinetics of Sulfur Oxidation at Suboptimal Temperatures

Chemolithoautotrophic bacteria were enriched from mine water at incubation temperatures ranging from 4 to 46°C, using elemental sulfur as a substrate in acid mineral salts media. Thiobacillus-type bacteria were successfully enriched for at all test temperatures except 46°C. Changes in pH (−dpH/dt) were used to estimate the rate constants for the enrichment cultures. The rate constants yielded a linear Arrhenius plot, an activation energy of 65 kJ/mol, and a temperature coefficient (Q₁₀) of 2.1 for the 4 to 37°C temperature interval.     

Localization of catecholamines and acetylcholinesterase in the terminal nerve fibres of the rabbit myometrium

Summary The autonomic nerves of the myometrium of the rabbit were studied in order to demonstrate simultaneously the adrenergic nature of an axon and the localization of acetylcholinesterase (AChE) in the same axons. The synaptic vesicles of the adrenergic axons and nerve terminals remained partially filled with the electron dense material typical for them after formaldehyde fixation and short incubation time for AChE. AChE stain was localized regularly on the axons which contained agranular synaptic vesicles and also on axons which contained dense cored synaptic vesicles beeing probably adrenergic. The role of AChE on the adrenergic axons is discussed.     

The structure of bovine complement component 3 reveals the basis for thioester function

The third component of complement (C3) is a 190 kDa glycoprotein essential for eliciting the complement response. The protein consists of two polypeptide chains (alpha and beta) held together with a single disulfide bridge. The beta-chain is composed of six MG domains, one of which is shared with the alpha-chain. The disulfide bridge connecting the chains is positioned in the shared MG domain. The alpha-chain consists of the anaphylatoxin domain, three MG domains, a CUB domain, an alpha(6)/alpha(6)-barrel domain and the C-terminal C345c domain. An internal thioester in the alpha-chain of C3 (present in C4 but not in C5) is cleaved during complement activation. This mediates covalent attachment of the activated C3b to immune complexes and invading microorganisms, thereby opsonizing the target. We present the structure of bovine C3 determined at 3 Angstroms resolution. The structure shows that the ester is buried deeply between the thioester domain and the properdin binding domain, in agreement with the human structure. This domain interface is broken upon activation, allowing nucleophile access. The structure of bovine C3 clearly demonstrates that the main chain around the thioester undergoes a helical transition upon activation. This rearrangement is proposed to be the basis for the high level of reactivity of the thioester group. A strictly conserved glutamate residue is suggested to function catalytically in thioester proteins. Structure-based design of inhibitors of C3 activation may target a conserved pocket between the alpha-chain and the beta-chain of C3, which appears essential for conformational changes in C3.     

Evidence against a role for insulin-signaling proteins PI 3-kinase and Akt in insulin resistance in human skeletal muscle induced by short-term GH infusion

Prolonged growth hormone (GH) excess is known to be associated with insulin resistance, but the underlying mechanisms remain unknown. The aim of this study was to assess the impact of GH on insulin-stimulated glucose metabolism and insulin signaling in human skeletal muscle. In a cross-over design, eight healthy male subjects (age 26.0 +/- 0.8 yr and body mass index 24.1 +/- 0.5 kg/m2) were infused for 360 min with either GH (Norditropin, 45 ng.kg(-1).min(-1)) or saline. During the final 180 min of the infusion, a hyperinsulinemic euglycemic clamp was performed (insulin infusion rate: 1.2 mU.kg(-1).min(-1)). Muscle biopsies from vastus lateralis were taken before GH/saline administration and after 60 min of hyperinsulinemia. GLUT4 content and insulin signaling, as assessed by insulin receptor substrate (IRS)-1-associated phosphatidylinositol 3-kinase and Akt activity were determined. GH levels increased to a mean (+/-SE) level of 20.0 +/- 2.3 vs. 0.5 +/- 0.2 microg/l after saline infusion (P < 0.01). During GH infusion, the glucose infusion rate during hyperinsulinemia was reduced by 38% (P < 0.01). In both conditions, free fatty acids were markedly suppressed during hyperinsulinemia. Despite skeletal muscle insulin resistance, insulin still induced a similar approximately 3-fold rise in IRS-1-associated PI 3-kinase activity (269 +/- 105 and 311 +/- 71% compared with baseline, GH vs. saline). GH infusion did not change Akt protein expression, and insulin caused an approximately 13-fold increase in Akt activity (1,309 +/- 327 and 1,287 +/- 173%) after both GH and saline infusion. No difference in total GLUT4 content was noted (114.7 +/- 7.4 and 107.6 +/- 16.7 arbitrary units, GH vs. saline, compared with baseline). In conclusion, insulin resistance in skeletal muscle induced by short-term GH administration is not associated with detectable changes in the upstream insulin-signaling cascade or reduction in total GLUT4. Yet unknown mechanisms in insulin signaling downstream of Akt may be responsible.     

Nonlinear Cross-Bridge Elasticity and Post-Power-Stroke Events in Fast Skeletal Muscle Actomyosin

Generation of force and movement by actomyosin cross-bridges is the molecular basis of muscle contraction, but generally accepted ideas about cross-bridge properties have recently been questioned. Of the utmost significance, evidence for nonlinear cross-bridge elasticity has been presented. We here investigate how this and other newly discovered or postulated phenomena would modify cross-bridge operation, with focus on post-power-stroke events. First, as an experimental basis, we present evidence for a hyperbolic [MgATP]-velocity relationship of heavy-meromyosin-propelled actin filaments in the in vitro motility assay using fast rabbit skeletal muscle myosin (28–29°C). As the hyperbolic [MgATP]-velocity relationship was not consistent with interhead cooperativity, we developed a cross-bridge model with independent myosin heads and strain-dependent interstate transition rates. The model, implemented with inclusion of MgATP-independent detachment from the rigor state, as suggested by previous single-molecule mechanics experiments, accounts well for the [MgATP]-velocity relationship if nonlinear cross-bridge elasticity is assumed, but not if linear cross-bridge elasticity is assumed. In addition, a better fit is obtained with load-independent than with load-dependent MgATP-induced detachment rate. We discuss our results in relation to previous data showing a nonhyperbolic [MgATP]-velocity relationship when actin filaments are propelled by myosin subfragment 1 or full-length myosin. We also consider the implications of our results for characterization of the cross-bridge elasticity in the filament lattice of muscle.     

The Role of Convictions and Trust for Public Protest Potential in the Case of Carbon Dioxide Capture and Storage (CCS)

For the public to accept new technologies, trust and convictions play an important role. In the present research, we used structural equation modeling to examine an extensive causal model of the role of convictions and trust for the public's protest potential against carbon dioxide capture and storage (CCS) among a large sample of the general population (N = 769). Trust, convictions, perceived benefits, and risks were included in the model. Our model fitted the data well. Convictions regarding emission reduction, decentralization of energy production, and tampering with natural structures in the deep subsurface influenced the perception of benefits and risks. Trust, in contrast, was barely influential. Perceived benefits were more prominent for public protest potential than perceived risks. However, perceived benefits did not dominate perceived risks as much as earlier studies found for acceptance. We argue that trust can become fully effective as a determinant of perceived risks and benefits only when the public perceives the distinct positioning of the stakeholders involved. Until then, laypeople are likely to draw on their own convictions and intuitive mental concepts for making decisions about accepting a new technology or protesting it.