Evasion of CO2 from streams – The dominant component of the carbon export through the aquatic conduit in a boreal landscape

Evasion of gaseous carbon (C) from streams is often poorly quantified in landscape C budgets. Even though the potential importance of the capillary network of streams as C conduits across the land–water–atmosphere interfaces is sometimes mentioned, low‐order streams are often left out of budget estimates due to being poorly characterized in terms of gas exchange and even areal surface coverage. We show that evasion of C is greater than all the total dissolved C (both organic and inorganic) exported downstream in the waters of a boreal landscape. In this study evasion of carbon dioxide (CO₂) from running waters within a 67 km² boreal catchment was studied. During a 4 year period (2006–2009) 13 streams were sampled on 104 different occasions for dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC). From a locally determined model of gas exchange properties, we estimated the daily CO₂ evasion with a high‐resolution (5 × 5 m) grid‐based stream evasion model comprising the entire ~100 km stream network. Despite the low areal coverage of stream surface, the evasion of CO₂ from the stream network constituted 53% (5.0 (±1.8) g C m^?2 yr^?1) of the entire stream C flux (9.6 (±2.4) g C m^?2 yr^?1) (lateral as DIC, DOC, and vertical as CO₂). In addition, 72% of the total CO₂ loss took place already in the first‐ and second‐order streams. This study demonstrates the importance of including CO₂ evasion from low‐order boreal streams into landscape C budgets as it more than doubled the magnitude of the aquatic conduit for C from this landscape. Neglecting this term will consequently result in an overestimation of the terrestrial C sink strength in the boreal landscape.     

Repeated inhalations of diesel exhaust particles and oxidatively damaged DNA in young oxoguanine DNA glycosylase (OGG1) deficient mice

DNA repair may prevent increased levels of oxidatively damaged DNA from prolonged oxidative stress induced by, e.g. exposure to diesel exhaust particles (DEP). We studied oxidative damage to DNA in broncho-alveolar lavage cells, lungs, and liver after 4 × 1.5 h inhalations of DEP (20 mg/m³) in Ogg1^{? / ?} and wild type (WT) mice with similar extent of inflammation. DEP exposure increased lung levels of 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxodG) in Ogg1^{? / ?} mice, whereas no effect on 8-oxodG or oxidized purines in terms of formamidopyrimidine DNA glycosylase (FPG) sites was observed in WT mice. In both unexposed and exposed Ogg1^{? / ?} mice the level of FPG sites in the lungs was 3-fold higher than in WT mice. The high basal level of FPG sites in Ogg1^{? / ?} mice probably saturated the assay and prevented detection of DEP-generated damage. In conclusion, Ogg1^{? / ?} mice have elevated pulmonary levels of FPG sites and accumulate genomic 8-oxodG after repeated inhalations of DEP.     

ATP Impedes the Inhibitory Effect of Hsp90 on Aβ40 Fibrillation

Heat shock protein 90 (Hsp90) is a molecular chaperone that assists protein folding in an Adenosine triphosphate (ATP)-dependent way. Hsp90 has been reported to interact with Alzheime?s disease associated amyloid-β (Aβ) peptides and to suppress toxic oligomer- and fibril formation. However, the mechanism remains largely unclear. Here we use a combination of atomic force microscopy (AFM) imaging, circular dichroism (CD) spectroscopy and biochemical analysis to quantify this interaction and put forward a microscopic picture including rate constants for the different transitions towards fibrillation. We show that Hsp90 binds to Aβ₄₀ monomers weakly but inhibits Aβ₄₀ from growing into fibrils at substoichiometric concentrations. ATP impedes this interaction, presumably by modulating Hsp90’s conformational dynamics and reducing its hydrophobic surface. Altogether, these results might indicate alternative ways to prevent Aβ₄₀ fibrillation by manipulating chaperones that are already abundant in the brain.     

A novel chimeric MOMP antigen expressed in Escherichia coli, Arabidopsis thaliana, and Daucus carota as a potential Chlamydia trachomatis vaccine candidate

The major outer membrane protein (MOMP) of Chlamydia trachomatis is a highly antigenic and hydrophobic transmembrane protein. Our attempts to express the full-length protein in a soluble form in Escherichia coli and in transgenic plants failed. A chimeric gene construct of C. trachomatis serovar E MOMP was designed in order to increase solubility of the MOMP protein but with retained antigenicity. The designed construct was successfully expressed in E. coli, in Arabidopsis thaliana, and in Daucus carota. The chimeric MOMP expressed in and purified from E. coli was used as antigen for production of antibodies in rabbits. The anti-chimeric MOMP antibodies recognized the corresponding protein in both E. coli and in transgenic plants, as well as in inactivated C. trachomatis elementary bodies. Transgenic Arabidopsis and carrots were characterized for the number of MOMP chimeric genetic inserts and for protein expression. Stable integration of the transgene and the corresponding protein expression were demonstrated in Arabidopsis plants over at least six generations. Transgenic carrots showed a high level of expression of the chimeric MOMP – up to 3% of TSP.     

Binding free energy landscape of domain-peptide interactions

Peptide recognition domains (PRDs) are ubiquitous protein domains which mediate large numbers of protein interactions in the cell. How these PRDs are able to recognize peptide sequences in a rapid and specific manner is incompletely understood. We explore the peptide binding process of PDZ domains, a large PRD family, from an equilibrium perspective using an all-atom Monte Carlo (MC) approach. Our focus is two different PDZ domains representing two major PDZ classes, I and II. For both domains, a binding free energy surface with a strong bias toward the native bound state is found. Moreover, both domains exhibit a binding process in which the peptides are mostly either bound at the PDZ binding pocket or else interact little with the domain surface. Consistent with this, various binding observables show a temperature dependence well described by a simple two-state model. We also find important differences in the details between the two domains. While both domains exhibit well-defined binding free energy barriers, the class I barrier is significantly weaker than the one for class II. To probe this issue further, we apply our method to a PDZ domain with dual specificity for class I and II peptides, and find an analogous difference in their binding free energy barriers. Lastly, we perform a large number of fixed-temperature MC kinetics trajectories under binding conditions. These trajectories reveal significantly slower binding dynamics for the class II domain relative to class I. Our combined results are consistent with a binding mechanism in which the peptide C terminal residue binds in an initial, rate-limiting step.     

A systematic review of the psychometric properties of self-report research utilization measures used in healthcare

Background

In healthcare, a gap exists between what is known from research and what is practiced. Understanding this gap depends upon our ability to robustly measure research utilization.

Objectives

The objectives of this systematic review were: to identify self-report measures of research utilization used in healthcare, and to assess the psychometric properties (acceptability, reliability, and validity) of these measures.

Methods

We conducted a systematic review of literature reporting use or development of self-report research utilization measures. Our search included: multiple databases, ancestry searches, and a hand search. Acceptability was assessed by examining time to complete the measure and missing data rates. Our approach to reliability and validity assessment followed that outlined in the Standards for Educational and Psychological Testing.

Results

Of 42,770 titles screened, 97 original studies (108 articles) were included in this review. The 97 studies reported on the use or development of 60 unique self-report research utilization measures. Seven of the measures were assessed in more than one study. Study samples consisted of healthcare providers (92 studies) and healthcare decision makers (5 studies). No studies reported data on acceptability of the measures. Reliability was reported in 32 (33%) of the studies, representing 13 of the 60 measures. Internal consistency (Cronbach's Alpha) reliability was reported in 31 studies; values exceeded 0.70 in 29 studies. Test-retest reliability was reported in 3 studies with Pearson's r coefficients > 0.80. No validity information was reported for 12 of the 60 measures. The remaining 48 measures were classified into a three-level validity hierarchy according to the number of validity sources reported in 50% or more of the studies using the measure. Level one measures (n = 6) reported evidence from any three (out of four possible) Standards validity sources (which, in the case of single item measures, was all applicable validity sources). Level two measures (n = 16) had evidence from any two validity sources, and level three measures (n = 26) from only one validity source.

Conclusions

This review reveals significant underdevelopment in the measurement of research utilization. Substantial methodological advances with respect to construct clarity, use of research utilization and related theory, use of measurement theory, and psychometric assessment are required. Also needed are improved reporting practices and the adoption of a more contemporary view of validity (i.e., the Standards) in future research utilization measurement studies.     

Cerebrospinal Fluid (CSF) 25-Hydroxyvitamin D Concentration and CSF Acetylcholinesterase Activity Are Reduced in Patients with Alzheimer's Disease

Background

Little is known of vitamin D concentration in cerebrospinal fluid (CSF) in Alzheimer´s disease (AD) and its relation with CSF acetylcholinesterase (AChE) activity, a marker of cholinergic function.

Methods

A cross-sectional study of 52 consecutive patients under primary evaluation of cognitive impairment and 17 healthy controls. The patients had AD dementia or mild cognitive impairment (MCI) diagnosed with AD dementia upon follow-up (n = 28), other dementias (n = 12), and stable MCI (SMCI, n = 12). We determined serum and CSF concentrations of calcium, parathyroid hormone (PTH), 25-hydroxyvitamin D (25OHD), and CSF activities of AChE and butyrylcholinesterase (BuChE).

Findings

CSF 25OHD level was reduced in AD patients (P < 0.05), and CSF AChE activity was decreased both in patients with AD (P < 0.05) and other dementias (P < 0.01) compared to healthy controls. None of the measured variables differed between BuChE K-variant genotypes whereas the participants that were homozygous in terms of the apolipoprotein E (APOE) ε4 allele had decreased CSF AChE activity compared to subjects lacking the APOE ε4 allele (P = 0.01). In AD patients (n=28), CSF AChE activity correlated positively with CSF levels of total tau (T-tau) (r = 0.44, P < 0.05) and phosphorylated tau protein (P-tau) (r = 0.50, P < 0.01), but CSF activities of AChE or BuChE did not correlate with serum or CSF levels of 25OHD.

Conclusions

In this pilot study, both CSF 25OHD level and CSF AChE activity were reduced in AD patients. However, the lack of correlations between 25OHD levels and CSF activities of AChE or BuChE might suggest different mechanisms of action, which could have implications for treatment trials.     

Polymorphisms in COX-2, NSAID use and risk of basal cell carcinoma in a prospective study of Danes

We investigated the risk of basal cell carcinoma (BCC) in relation to a number of single nucleotide polymorphisms in genes involved in the inflammatory response. A case-control study including 322 BCC cases and a similar number of controls was nested in a population-based prospective study of 57,053 individuals (aged 50-64 at inclusion) in Denmark. NSAID use was associated with a slightly decreased risk of BCC (IRR=0.85, 95% CI=0.66-1.10). We found that two polymorphisms in COX-2, COX-2 A-1195G and T8473C were associated with risk of BCC. Carriers of the variant allele of COX-2 A-1195G had lower risk of BCC than homozygous wild type carriers (IRR=0.54, 95% CI=0.47-0.89). Homozygous carriers of the variant allele of COX-2 T8473C were at 2.27-fold higher risk of BCC (95% CI=1.31-3.92) than homozygous wild type allele carriers. The polymorphisms IL6 G-174C, IL8 T-251A, PPARgamma2 Pro(12)Ala, IL1beta T-31C, and IL10 C-592A were not associated with risk of BCC. We found no statistically significant interaction between polymorphisms and NSAID use in relation to risk of BCC. While it cannot be ruled out that the present findings are due to chance, the results indicate that high COX-2 expression may increase risk of BCC while NSAID use may be protective.     

A novel branched-chain amino acid metabolon. Protein-protein interactions in a supramolecular complex

The catabolic pathways of branched-chain amino acids have two common steps. The first step is deamination catalyzed by the vitamin B(6)-dependent branched-chain aminotransferase isozymes (BCATs) to produce branched-chain alpha-keto acids (BCKAs). The second step is oxidative decarboxylation of the BCKAs mediated by the branched-chain alpha-keto acid dehydrogenase enzyme complex (BCKD complex). The BCKD complex is organized around a cubic core consisting of 24 lipoate-bearing dihydrolipoyl transacylase (E2) subunits, associated with the branched-chain alpha-keto acid decarboxylase/dehydrogenase (E1), dihydrolipoamide dehydrogenase (E3), BCKD kinase, and BCKD phosphatase. In this study, we provide evidence that human mitochondrial BCAT (hBCATm) associates with the E1 decarboxylase component of the rat or human BCKD complex with a K(D) of 2.8 microM. NADH dissociates the complex. The E2 and E3 components do not interact with hBCATm. In the presence of hBCATm, k(cat) values for E1-catalyzed decarboxylation of the BCKAs are enhanced 12-fold. Mutations of hBCATm proteins in the catalytically important CXXC center or E1 proteins in the phosphorylation loop residues prevent complex formation, indicating that these regions are important for the interaction between hBCATm and E1. Our results provide evidence for substrate channeling between hBCATm and BCKD complex and formation of a metabolic unit (termed branched-chain amino acid metabolon) that can be influenced by the redox state in mitochondria.