Mortality Rates Across 25-Hydroxyvitamin D (25[OH]D) Levels among Adults with and without Estimated Glomerular Filtration Rate <60 ml/min/1.73 m2: The Third National Health and Nutrition Examination Survey

Background

Previous studies exploring the association between 25[OH]D levels and mortality in adults with and without kidney disease utilized 25[OH]D thresholds that have recently been scrutinized by the Institute of Medicine Committee to Review Dietary References Intakes for Vitamin D and Calcium.

Objective

We explored all-cause mortality rates across the spectrum of 25[OH]D levels over an eighteen-year follow-up among adults with and without an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m².

Design

The study included 1,097 U.S. adults with eGFR <60 ml/min/1.73 m² and 14, 002 adults with eGFR ≥60 ml/min/1.73 m². Mortality rates and rate ratios (RR) across 25[OH]D groups were calculated with Poisson regression and restricted cubic splines while adjusting for covariates.

Results

Prevalence of 25[OH]D levels <30 and <20 ng/ml among adults with eGFR <60 ml/min/1.73 m² was 76.5% (population estimate 6.2 million) and 35.4% (population estimate 2.9 million), respectively. Among adults with eGFR ≥60 ml/min/1.73 m², 70.5% had 25[OH]D levels <30 ng/ml (population estimate 132.2 million) while 30.3% had 25[OH]D levels <20 ng/ml (population estimate 56.8 million). Significantly higher mortality rates were noted among individuals with 25[OH]D levels <12 ng/ml compared to referent group (24 to <30 ng/ml): RR1.41 (95% CI 1.17, 1.71) among individuals with eGFR <60 ml/min/1.73 m² and RR 1.32 (95% CI 1.13, 1.56) among individuals with eGFR ≥60 ml/min/1.73 m² after adjustment for covariates including co-morbid conditions. Mortality rates were fairly similar across all 25[OH]D groups with levels >20 ng/ml after adjustment for all covariates.

Conclusions

Regardless of presence of eGFR <60 ml/min/1.73 m², mortality rates across groups with 25[OH]D levels 20–40 ng/ml are similar.     

Invasive fungal infections in solid organ transplant recipients

Invasive fungal infections are a major problem in solid organ transplant (SOT) recipients. Overall, the most common fungal infection in SOT is candidiasis, followed by aspergillosis and cryptococcosis, except in lung transplant recipients, where aspergillosis is most common. Development of invasive disease hinges on the interplay between host factors (e.g., integrity of anatomical barriers, innate and acquired immunity) and fungal factors (e.g., exposure, virulence and resistance to prophylaxis). In this article, we describe the epidemiology and clinical features of the most common fungal infections in organ transplantation. Within this context, we review recent advances in diagnostic modalities and antifungal chemotherapy, and their impact on evolving prophylaxis and treatment paradigms.     

Two active forms of Zymomonas mobilis levansucrase. An ordered microfibril structure of the enzyme promotes levan polymerization

Fructansucrases, members of glycoside hydrolase family 68, catalyze both sucrose hydrolysis and the polymerization of fructose to beta-d-fructofuranose polymers. The resulting fructan polymers are distinguished by the nature of the glycosidic bond: inulin (beta-(2-1)-fructofuranose) and levan (beta-(2-6)-fructofuranose). In this study we demonstrate that Zymomonas mobilis levansucrase exists in two active forms, depending on the pH and ionic strength. At pH values above 7.0, the enzyme is mainly a dimer, whereas at pH values below 6.0, the protein forms well ordered microfibrils that precipitate out of the solution. These two forms are readily interchangeable simply by changing the pH. Surprisingly the manner in which the enzyme is arranged strongly affects its product specificity and kinetic properties. At pH values above 7.0, the activity of the enzyme as a dimer is mainly sucrose hydrolysis and the synthesis of short fructosaccharides (degree of polymerization, 3). At pH values below 6.0, in its microfibril form, the enzyme catalyzes almost exclusively the synthesis of levan (a degree of polymerization greater than 20,000). This difference in product specificity appears to depend on the form of the enzyme, dimer versus microfibril, and not directly on the pH. Images made by negative stain transmission electron microscopy reveal that the enzyme forms a very ordered structure of long fibrils that appear to be composed of repeating rings of six to eight protein units. A single amino acid replacement of H296R abolished the ability of the enzyme to form microfibrils with organized fibril networks and to synthesize levan at pH 6.0.     

Crystal structure of colicin E3 immunity protein: an inhibitor of a ribosome-inactivating RNase

BACKGROUND: Colicins are antibiotic-like proteins of Escherichia coli that kill related strains. Colicin E3 acts as an RNase that specifically cleaves 16S rRNA, thereby inactivating the ribosomes in the infected cell. The producing organism is protected against colicin E3 by a specific inhibitor, the immunity protein Im3, which forms a tight 1:1 complex with colicin E3 and renders it inactive. Crystallographic studies on colicin E3 and Im3 have been undertaken to unravel the structural basis for the ribonucleolytic activity and its inhibition. RESULTS: The crystal structure of Im3 has been determined to a resolution of 1.8 A. The structure consists of a four-standard antiparallel beta sheet flanked by three alpha helices on one side of the sheet. Thr7, Phe9, Phe16 and Phe74 form a hydrophobic cluster on the surface of the protein in the vicinity of Cys47. This cluster is part of a putative binding pocket which also includes nine polar residues. CONCLUSIONS: The putative binding pocket of Im3 is the probable site of interaction with colicin E3. The six acidic residues in the pocket may interact with some of the numerous basic residues of colicin E3. The involvement of hydrophobic moieties in the binding is consistent with the observation that the tight complex can only be dissociated by denaturation. The structure of Im3 resembles those of certain nucleic acid binding proteins, in particular domain II of topoisomerase I and RNA-binding proteins that contain the ribonucleoprotein (RNP) sequence motif. This observation suggests that Im3 has a nucleic acid binding function in addition to binding colicin E3.     

Evidence of influenza a virus RNA in siberian lake ice

Influenza A virus infects a large proportion of the human population annually, sometimes leading to the deaths of millions. The biotic cycles of infection are well characterized in the literature, including in studies of populations of humans, poultry, swine, and migratory waterfowl. However, there are few studies of abiotic reservoirs for this virus. Here, we report the preservation of influenza A virus genes in ice and water from high-latitude lakes that are visited by large numbers of migratory birds. The lakes are along the migratory flight paths of birds flying into Asia, North America, Europe, and Africa. The data suggest that influenza A virus, deposited as the birds begin their autumn migration, can be preserved in lake ice. As birds return in the spring, the ice melts, releasing the viruses. Therefore, temporal gene flow is facilitated between the viruses shed during the previous year and the viruses newly acquired by birds during winter months spent in the south. Above the Arctic Circle, the cycles of entrapment in the ice and release by melting can be variable in length, because some ice persists for several years, decades, or longer. This type of temporal gene flow might be a feature common to viruses that can survive entrapment in environmental ice and snow.     

Matrix-assisted refolding of single-chain Fv- cellulose binding domain fusion proteins.

We describe a method for the isolation of recombinant single-chain antibodies in a biologically active form. The single-chain antibodies are fused to a cellulose binding domain as a single-chain protein that accumulates as insoluble inclusion bodies upon expression in Escherichia coli. The inclusion bodies are then solubilized and denatured by an appropriate chaotropic solvent, then reversibly immobilized onto a cellulose matrix via specific interaction of the matrix with the cellulose binding domain (CBD) moiety. The efficient immobilization that minimizes the contact between folding protein molecules, thus preventing their aggregation, is facilitated by the robustness of the Clostridium thermocellum CBD we use. This CBD is unique in retaining its specific cellulose binding capability when solubilized in up to 6 M urea, while the proteins fused to it are fully denatured. Refolding of the fusion proteins is induced by reducing with time the concentration of the denaturing solvent while in contact with the cellulose matrix. The refolded single-chain antibodies in their native state are then recovered by releasing them from the cellulose matrix in high yield of 60% or better, which is threefold or higher than the yield obtained by using published refolding protocols to recover the same scFvs. The described method should have general applicability for the production of many protein-CBD fusions in which the fusion partner is insoluble upon expression.     

Characterization and delignification activity of a thermostable α-l-arabinofuranosidase from Bacillus stearothermophilus

Bacillus stearothermophilus L1 was isolated by enrichment culture using an alkaline extract of pulp as the carbon source at 65°C and pH 9.0. The bacterium produced extracellular xylanase and -l-arabinofuranosidase (EC 3.2.1.55). The xylanase activity was high when the cells were grown in the presence of d-xylose, whereas the arabinofuranosidase activity was high when grown in media containing l-arabinose. The arabinofuranosidase was purified 59-fold with an 80% yield by DEAE Sephacel and Sephadex G-100 chromatography. The purified enzyme had an apparent molecular mass of 110 000 kDa and consisted of two subunits of 52 500 kDa and 57 500 kDa. Using p-nitrophenyl--l-arabinofuranosidase as the substrate, the enzyme had a Michaelis constant (K _m) of 2.2 × 10^–4 m, maximum reaction velocity (V_max) of 11o mol min^–1 mg^–1, temperature optimum of 70°C and pH optimum of 7.0 (50% activity at pH 8.0). The enzyme was specific for the furanoside configuration. The purified enzyme partially delignified softwood Kraft pulp. Treatment of the pulp with 38 units ml^–1 of -l-arabinofuranosidase at 65°C for 2 h at pH 8.0 and 9.0 led to lignin releases of 2.3% and 2.1%, respectively. The enzyme acted synergistically with a thermophilic xylanase in the delignification process, yielding a 19.2% release of lignin. Correspondence to: Eugene Rosenberg     

Bacterial degradation of emulsan.

Emulsan is a polyanionic heteropolysaccharide bioemulsifier produced by Acinetobacter calcoaceticus RAG-1. A mixed bacterial population was obtained by enrichment culture that was capable of degrading emulsan and using it as a carbon source. From this mixed culture, an emulsan-degrading bacterium, termed YUV-1, was isolated. Strain YUV-1 is an aerobic, gram-negative, non-spore-forming, rod-shaped bacterium which grows best in media containing yeast extract. When placed on preformed lawns of A. calcoaceticus RAG-1, strain YUV-1 produced translucent plaques which grew in size until the entire plate was covered. Plaque formation was due to solubilization of the emulsan capsule of RAG-1. Plaque formation was not observed on emulsan-negative mutants of RAG-1. As a consequence of the solubilization of the emulsan capsule, RAG-1 cells became more hydrophobic, as determined by adherence to hexadecane. Growth of YUV-1 on a medium containing yeast extract and emulsan was biphasic. During the initial 24 h, cell concentration increased 10-fold, but emulsan was not degraded; during the lag in growth (24 to 48 h), emulsan was inactivated and depolymerized but not consumed; during the second growth phase (48 to 70 h) the depolymerized emulsan products were consumed.