Solution structure of the cytohesin-1 (B2–1) Sec7 domain and its interaction with the GTPase ADP ribosylation factor 1

Cytohesin-1 (B2–1) is a guanine nucleotide exchange factor for human ADP ribosylation factor (Arf) GTPases, which are important for vesicular protein trafficking and coatamer assembly in the cell. Cytohesin-1 also has been reported to promote cellular adhesion via binding to the β2 integrin cytoplasmic domain. The solution structure of the Sec7 domain of cytohesin-1, which is responsible for both the protein’s guanine nucleotide exchange factor function and β2 integrin binding, was determined by NMR spectroscopy. The structure consists of 10 α-helices that form a unique tertiary fold. The binding between the Sec7 domain and a soluble, truncated version of human Arf-1 was investigated by examining ¹H-¹⁵N and ¹H-¹³C chemical shift changes between the native protein and the Sec7/Arf-1 complex. We show that the binding to Arf-1 occurs through a large surface on the C-terminal subdomain that is composed of both hydrophobic and polar residues. Structure-based mutational analysis of the cytohesin-1 Sec7 domain has been used to identify residues important for binding to Arf and for mediating nucleotide exchange. Investigations into the interaction between the Sec7 domain and the β2 integrin cytoplasmic domain suggest that the two proteins do not interact in the solution phase.     

Female genital schistosomiasis – a differential diagnosis to sexually transmitted disease: genital itch and vaginal discharge as indicators of genital Schistosoma haematobium morbidity in a cross‐sectional study in endemic rural Zimbabwe

Objective To examine the association between schistosomiasis and reproductive tract symptoms. Method A cross‐sectional study was conducted in a Schistosoma haematobium‐endemic area of rural Zimbabwe. A total of 483 permanently resident adult women of Mupfure Ward aged 20–49 were interviewed and examined clinically, each providing three consecutive urine samples. Logistic regression analysis was used to control for sexually transmitted diseases (STDs). Results Women with genital sandy patches had significantly more genital itch (P = 0.009) and perceived their discharge as abnormal (P = 0.003). Eighty percent of the women who had genital itch, yellow discharge, and childhood or current waterbody contact had sandy patches. Fifty‐two percent of the women with genital sandy patches did not have detectable S. haematobium ova in urine. Genital schistosomiasis was associated with stress incontinence and pollakisuria, but not with menstrual irregularities, current or previous ulcers, or tumours. Conclusion Genital schistosomiasis may be a differential diagnosis to the STDs in women who have been exposed to fresh water in endemic areas. Because of the chronic nature of the disease in adults, we suggest to pay special attention to the prevention of morbidity.     

Molecular Genetics of Type 2 von Willebrand Disease

Type 2 von Willebrand disease (VWD) is characterized by a wide heterogeneity of functional and structural defects. These abnormalities' cause either defective von Willebrand factor (VWF)-dependent platelet function in subtypes 2A, 2B, and 2M or defective VWF-factor VIII (FVIII) binding in subtype 2N. The diagnoses of types 2A, 2B, and 2M VWD may be guided by the observation of disproportionately low levels of ristocetin cofactor activity or collagen-binding capacity relative to VWF antigen. The abnormal platelet-dependent function is often associated with the absence of high molecular weight (HMW) multimers (type 2A, type 2B), but the HMW multimers may also be present (type 2M, some type 2B), and supranormal multimers may exist ("Vicenza" variant). The observation of a low FVIII-to-VWF:Ag ratio is a hallmark of type 2N VWD. in which the FVIII levels depend on the severity of the FVIII-binding defect. Today, the identification of mutations in particular domains of the pre-pro-VWF is helpful in classifying these variants and providing further insight into the structure-function relationship and the biosynthesis of VWF. Thus, mutations in the D2 domain, involved in the multimerization process, are found in patients with type 2A, formerly named IIC VWD. Mutations located in the D' domain or in the N terminus of the D3 domain define type 2N VWD. Mutations in the D3 domain characterize Vicenza and IIE patients. Mutations in the A1 domain may modify the binding of VWF multimers to platelets, either increasing (type 2B) or decreasing (type 2M, 2A/2M) the affinity of VWF for platelets. In type 2A VWD, molecular abnormalities identified in the A2 domain, which contains a specific proteolytic site, are associated with alterations in folding, impairing VWF secretion or increasing its susceptibility to proteolysis. Finally, a mutation localized in the carboxy-terminus CK domain, which is crucial for the dimerization of the VWF subunit, has been identified in a rare subtype 2A, formerly named IID.     

Functional impact of vibratory proprioceptive assistance in patients with facioscapulohumeral muscular dystrophy

Introduction: In this study we analyzed the effects of a rehabilitation method based on the use of vibratory proprioceptive assistance (VPA) in subjects with facioscapulohumeral muscular dystrophy. Methods: Eight subjects were given 1 month of mechanical vibratory treatment that consisted of 8 sessions of 40‐min stimulation on the more affected side. During each session, illusory movements were induced as follows: sensations of extension or flexion of the forearm or elevation of the arm via vibration applied to the distal tendon of the biceps brachialis (BB), triceps brachialis (TB), or pectoralis major muscles (PM), respectively, and of elevation of the arm with extension or flexion of the forearm via vibration of PM+BB or PM+TB, respectively. Results: Treatment led to a significant increase in the amplitude of voluntary shoulder flexion, constant score, and self‐rated health. Conclusion: VPA may serve as a rehabilitation method for reducing the deleterious effects of decline in motor activities. Muscle Nerve 52 : 780–787, 2015     

Microbial denitrification dominates nitrate losses from forest ecosystems

Denitrification removes fixed nitrogen (N) from the biosphere, thereby restricting the availability of this key limiting nutrient for terrestrial plant productivity. This microbially driven process has been exceedingly difficult to measure, however, given the large background of nitrogen gas (N₂) in the atmosphere and vexing scaling issues associated with heterogeneous soil systems. Here, we use natural abundance of N and oxygen isotopes in nitrate (NO₃⁻) to examine dentrification rates across six forest sites in southern China and central Japan, which span temperate to tropical climates, as well as various stand ages and N deposition regimes. Our multiple stable isotope approach across soil to watershed scales shows that traditional techniques underestimate terrestrial denitrification fluxes by up to 98%, with annual losses of 5.6–30.1 kg of N per hectare via this gaseous pathway. These N export fluxes are up to sixfold higher than NO₃⁻ leaching, pointing to widespread dominance of denitrification in removing NO₃⁻ from forest ecosystems across a range of conditions. Further, we report that the loss of NO₃⁻ to denitrification decreased in comparison to leaching pathways in sites with the highest rates of anthropogenic N deposition.Nitrogen (N) is an essential, although ecologically limiting, nutrient in many terrestrial ecosystems (1). Anthropogenic emissions of reactive forms of N due to fossil fuel combustion and modern agriculture practices have drastically increased N deposition inputs to forests globally (2). Atmospherically deposited N represents a new N input to terrestrial ecosystems and may enhance carbon dioxide sequestration, potentially reducing some global climate impacts (3). On the other hand, long-term N deposition could result in N saturation and increased nitrate (NO₃⁻) losses to leaching and denitrification (4, 5), pathways that have different consequences for the Earth system, including consequences on climate, biodiversity, and water and air quality for human health (6). Thus, in the context of global climate and other biogeochemical changes, it is critically important to understand terrestrial N balances and their responses to anthropogenic N inputs.Denitrification is considered the most poorly resolved pathway of N removal from the soil, owing to difficulties in quantifying denitrification rates using standard methods (7). Conventional approaches used to estimate denitrification rates are largely intrusive and challenged by issues of pattern and scale. Acetylene block, ¹⁵N tracer applications, and direct nitrogen gas (N₂) quantification are examples of approaches that have deepened our understanding of denitrification; however, they are inherently disruptive and cannot be applied at scales larger than individual soil cores without a high degree of extrapolation (7). Whereas watershed mass balance techniques are nonintrusive and can provide larger scale insights into gaseous N losses, this approach relies on difficult-to-measure N input fluxes and assumptions therein, and is geographically constrained to environments that lack ground water seepage (7).As an alternative, natural composition of N and oxygen (O) isotopes in NO₃⁻ provides nonintrusive, quantitative, and integrative constraints on denitrification across a myriad of space-time scales (8, 9). This approach takes advantage of the biological imprint of soil denitrification on the N cycle and the tendency for kinetic isotope effects to elevate ¹⁵N/¹⁴N and ¹⁸O/¹⁶O of NO₃⁻ systematically in forests (8). Here, we extend on this approach by developing a new way to estimate NO₃⁻ supply rates to denitrification, which involves a combined Δ¹⁷O, δ¹⁵N, and δ¹⁸O analysis. We hypothesize that denitrification rates examined via our multiple-isotope approach will be larger than denitrification rates based on conventional soil techniques because they are generally applicable to the upper part of soil [e.g., the upper 50 cm (9)] and are challenged by spatial and temporal complexities in the soil denitrification process. We examine this hypothesis across an array of sites spanning tropical (southern China) to temperate (central Japan) regions, as well as various stand ages and N input levels, including moderate (6.1 kg of N ha⁻¹⋅y⁻¹) to high (33.5 kg of N ha⁻¹⋅y⁻¹;

Fatigue assessment and its impact in the quality of life of patients with ankylosing spondylitis

Clinical Rheumatology - The most frequently reported symptoms by patients with ankylosing spondylitis (AS) are pain, stiffness, and fatigue. Previous studies have estimated a 63 %...     

Antimicrobial dressing efficacy against mature Pseudomonas aeruginosa biofilm on porcine skin explants

An ex vivo porcine skin explant biofilm model that preserves key properties of biofilm attached to skin at different levels of maturity (0–3 days) was used to assess the efficacy of commercially available antimicrobial dressings and topical treatments. Assays were also performed on the subpopulation of antibiotic tolerant biofilm generated by 24 hours of pre‐treatment with gentamicin (120× minimal inhibitory concentration) prior to agent exposure. Five types of antimicrobial agents (iodine, silver, polyhexamethylene biguanide, honey and ethanol) and four types of moisture dressings (cotton gauze, sodium carboxymethylcellulose fibre, calcium alginate fibre and cadexomer beads) were assessed. Time‐release silver gel and cadexomer iodine dressings were the most effective in reducing mature biofilm [between 5 and 7 logarithmic (log) of 7‐log total], whereas all other dressing formulations reduced biofilm between 0·3 and 2 log in 24 or 72 hours with a single exposure. Similar results were found after 24‐hour exposure to silver release dressings using an in vivo pig burn wound model, demonstrating correlation between the ex vivo and in vivo models. Results of this study indicate that commonly used microbicidal wound dressings vary widely in their ability to kill mature biofilm and the efficacy is influenced by time of exposure, number of applications, moisture level and agent formulation (sustained release).