Dibasic inhibitors of human mast cell tryptase. Part 3: identification of a series of potent and selective inhibitors containing the benzamidine functionality.

A survey of charged groups and linkers for a series of symmetrical and unsymmetrical dibasic inhibitors is described, leading to several classes of potent and selective inhibitors. In particular, the benzamidine functionality was identified as the most potent charged group investigated.     

Ocean acidification bends the mermaid's wineglass

Ocean acidification lowers the saturation state of calcium carbonate, decreasing net calcification and compromising the skeletons of organisms such as corals, molluscs and algae. These calcified structures can protect organisms from predation and improve access to light, nutrients and dispersive currents. While some species (such as urchins, corals and mussels) survive with decreased calcification, they can suffer from inferior mechanical performance. Here, we used cantilever beam theory to test the hypothesis that decreased calcification would impair the mechanical performance of the green alga Acetabularia acetabulum along a CO₂ gradient created by volcanic seeps off Vulcano, Italy. Calcification and mechanical properties declined as calcium carbonate saturation fell; algae at 2283 µatm CO₂ were 32% less calcified, 40% less stiff and 40% droopier. Moreover, calcification was not a linear proxy for mechanical performance; stem stiffness decreased exponentially with reduced calcification. Although calcifying organisms can tolerate high CO₂ conditions, even subtle changes in calcification can cause dramatic changes in skeletal performance, which may in turn affect key biotic and abiotic interactions.     

A Conserved Aspartic Acid Is Important for Agonist (VUAA1) and Odorant/Tuning Receptor-Dependent Activation of the Insect Odorant Co-Receptor (Orco)

Insect odorant receptors function as heteromeric odorant-gated cation channels comprising a conventional odorant-sensitive tuning receptor, and a conserved co-receptor (Orco). An Orco agonist, VUAA1, is able to activate both heteromeric and homomeric Orco-containing channels. Very little is known about specific residues in Orco that contribute to cation permeability and gating. We investigated the importance of two conserved Asp residues, one in each of transmembrane domains 5 and 7, for channel function by mutagenesis. Drosophila melanogaster Orco and its substitution mutants were expressed in HEK cells and VUAA1-stimulated channel activity was determined by Ca²⁺ influx and whole-cell patch clamp electrophysiology. Substitution of D466 in transmembrane 7 with amino acids other than glutamic acid resulted in a substantial reduction in channel activity. The D466E Orco substitution mutant was ∼2 times more sensitive to VUAA1. The permeability of the D466E Orco mutant to cations was unchanged relative to wild-type Orco. When D466E Orco is co-expressed with a conventional tuning odorant receptor, the heteromeric complex also shows increased sensitivity to an odorant. Thus, the effect of the D466E mutation is not specific to VUAA1 agonism or dependent on homomeric Orco assembly. We suggest the gain-of-activation characteristic of the D466E mutant identifies an amino acid that is likely to be important for activation of both heteromeric and homomeric insect odorant receptor channels.     

Effect of screw position on load transfer in lumbar pedicle screws: a non-idealized finite element analysis

Angled screw insertion has been advocated to enhance fixation strength during posterior spine fixation. Stresses on a pedicle screw and surrounding vertebral bone with different screw angles were studied by finite element analysis during simulated multidirectional loading. Correlations between screw-specific vertebral geometric parameters and stresses were studied. Angulations in both the sagittal and axial planes affected stresses on the cortical and cancellous bones and the screw. Pedicle screws pointing laterally (vs. straight or medially) in the axial plane during superior screw angulation may be advantageous in terms of reducing the risk of both screw loosening and screw breakage.     

Fracture prevention in COPD patients; a clinical 5-step approach

Although osteoporosis and its related fractures are common in patients with COPD, patients at high risk of fracture are poorly identified, and consequently, undertreated. Since there are no fracture prevention guidelines available that focus on COPD patients, we developed a clinical approach to improve the identification and treatment of COPD patients at high risk of fracture. We organised a round-table discussion with 8 clinical experts in the field of COPD and fracture prevention in the Netherlands in December 2013. The clinical experts presented a review of the literature on COPD, osteoporosis and fracture prevention. Based on the Dutch fracture prevention guideline, they developed a 5-step clinical approach for fracture prevention in COPD. Thereby, they took into account both classical risk factors for fracture (low body mass index, older age, personal and family history of fracture, immobility, smoking, alcohol intake, use of glucocorticoids and increased fall risk) and COPD-specific risk factors for fracture (severe airflow obstruction, pulmonary exacerbations and oxygen therapy). Severe COPD (defined as postbronchodilator FEV₁ < 50% predicted) was added as COPD-specific risk factor to the list of classical risk factors for fracture. The 5-step clinical approach starts with case finding using clinical risk factors, followed by risk evaluation (dual energy X-ray absorptiometry and imaging of the spine), differential diagnosis, treatment and follow-up. This systematic clinical approach, which is evidence-based and easy-to-use in daily practice by pulmonologists, should contribute to optimise fracture prevention in COPD patients at high risk of fracture.     

Comparative effects of trichothecene mycotoxins on bovine platelet function: Acetyl T-2 toxin,a more potent inhibitor than T-2 toxin

The effects of the trichothecene mycotoxins (acetyl T-2 toxin, T-2 toxin, HT-2 toxin, palmityl T-2 toxin, diacetoxyscirpenol (DAS), deoxynivalenol (DON), and T-2 tetraol) on bovine platelet function were examined in homologous plasma stimulated with platelet activating factor (PAF). The mycotoxins inhibited platelet function with the following order of potency: acetyl T-2 toxin > palmityl T-2 toxin = DAS > HT-2 toxin = T-2 toxin. While T-2 tetraol was completely ineffective as an inhibitor, DON exhibited minimal inhibitory activity at concentrations above 10×10^?4M. The stability of the platelet aggregates formed was significantly reduced in all mycotoxin treated platelets compared to that of the untreated PAF controls. It is suggested that the increased sensitivity of PAF stimulated bovine platelets to the more lipophilic mycotoxins may be related to their more efficient partitioning into the platelet membrane compared to the more hydrophilic compounds.     

Ultrastructure and distribution of microbodies in leaves of grasses with and without CO2-photorespiration

Summary A comparative study was made of the ultrastructure, distribution and abundance of leaf microbodies in four species of temperate grasses with high and four tropical grasses with low CO₂-photorespiration. The temperate grasses were all festucoid; the tropical grasses included two panicoid species and two chloridoid. Comparisons of relative abundance were made by computing the average numbers of microbody profiles per cell section.Although microbodies were present in the green parenchymatous leaf cells in all grasses examined, their average number per cell was in general severalfold greater in the grasses with high CO₂-photorespiration than in those with low. Furthermore, whereas in the grasses with high CO₂-photorespiration the microbodies were distributed through the mesophyll, in those with low CO₂-photorespiration they were concentrated in the vascular-bundle-sheath cells and were smaller and relatively scarce in the mesophyll cells. The leaf microbodies of the eight grass species resembled one another in general morphology, but differed to some extent in regard to size and type of inclusion. Microbodies of all four festucoid species contained numerous fibrils with a discernible substructure. Those of the two panicoid species contained clusters of round bodies with transparent cores. The equivalence of the microbodies to peroxisomes as biochemically defined was shown cytochemically by employing 3,3-diaminobenzidine for the localization of catalase, a marker enzyme for the peroxisome. This reaction was blocked by the catalase inhibitor, aminotriazole.The observations on the relative abundance and distribution of peroxisomes in leaves of grasses with high CO₂-photorespiration versus those with low are consistent with the published biochemical data on the levels and distribution of peroxisomal enzymes in representatives of plants with high and low CO₂-photorespiration, and may help explain the differences in apparent photorespiratory levels between these two groups of plants.