Reversal of selenium and zinc deficiencies in chronic hemodialysis patients by intravenous sodium selenite and zinc gluconate supplementation

In six chronic dialyzed uremic patients, an intravenous sodium selenite (Se 50 μg during 5 wk and then 100 μg) and zinc gluconate (Zn 5 mg) supplementation was performed during 20 wk at each dialysis session three times weekly. Before supplementation, plasma Se and Zn, plasma and erythrocytes (RBC) antioxidant metalloenzymes glutathione peroxidase (GPX), and superoxide dismutase (SOD) were significantly decreased, whereas lipid peroxidation (as thiobarbituric acid reactants TBARs) was increased. To obtain a significative change in plasma selenium, we had to use an Se dose of 100 μg/dialysis session. Then, treatment-increased plasma Se (from 0.58 ±0.09 to 0.89±0.16 μmol/L) led to a repletion of RBC-GPX (from 29.6±6 to 43±5.8 U/g Hb) and increased plasma GPX levels (from 62±13 to 151±43 U/L). Plasma Zn and RBC-SOD did not vary significantly. The change of TBARs was not observed between wk 1 and 4. They decreased significantly between wk 4 (4.80±0.21μmol/L) and wk 20 (4.16±0.26 μmol/L). We noted a low correlation between TBARs and plasma GPX. A strong correlation was observed between Se and plasma GPX. The reversal of Se deficiencies should reduce oxidative damage observed in these patients.     

Analysis of the role of the COL1 domain and its adjacent cysteine-containing sequence in the chain assembly of type IX collagen

The mechanisms of chain selection and assembly of type IX collagen, a heterotrimer 1(IX)2(IX)3(IX), must differ from that of fibrillar collagens since it lacks the characteristic C-propeptide of these latter molecules. We have tested the hypothesis that the information required for this process is contained within the C-terminal triple helical disulfide-bonded region (LMW). The reassociations of the purified LMW fragments of pepsinized bovine type IX collagen were followed by the formation of disulfide-bonded multimers. Our data demonstrate that only three triple helical assemblies form readily, (1)₃, (2)₃, and 123. The information required for chain selection and assembly is thus, at least in part, contained in the studied fragments. Molecular stoichiometries different from the classical heterotrimer may thus also form under certain conditions.     

Group I introns in the liverwort mitochondrial genome: the gene coding for subunit 1 of cytochrome oxidase shares five intron positions with its fungal counterparts.

The complete nucleotide sequence of the mitochondrial DNA (mtDNA) from a liverwort, Marchantia polymorpha, contains thirty-two introns. Twenty-five of these introns possess the characteristic secondary structures and consensus sequences of group II introns. The remaining seven are group I introns, six of which happen to interrupt the gene coding for subunit 1 of cytochrome oxidase (cox1). Interestingly, the insertion sites of one group II and four group I introns in the cox1 gene coincide with those of the respective fungal mitochondrial interns. Moreover, comparison of the four group I introns with their fungal counterparts shows that group I introns inserted at identical genomic sites in different organisms are indeed related to one another, in terms of the peptide sequences generated from the complete or fragmental ORFs encoded by these introns. At the same time, the liverwort introns turned out to be more divergent from their fungal cognates than the latter are from one another. We therefore conclude that vertical transmission from a common ancestor organism is the simplest explanation for the presence of cognate introns in liverwort and fungal mitochondrial genomes.     

Growth and respiratory oxidation of reduced sulfur compounds by intact cells ofThiobacillus novellus (type strain) grown on thiosulfate

Thiobacillus novellus (type strain) was grown chemolithoautrophically on thiosulfate in batch cultures under microaerophilic conditions. Under these conditions,T. novellus grew exponentially (=0.05–0.06 h^–1). The respiratory oxidation rates of tetrathionate, thiosulfate, elemental sulfur (S^o), and sulfite were measured respirometrically with an oxygen electrode, with exponentially growing cells. Cells growing on thiosulfate as the unique energy source retain thiosulfate-oxidizing activity, S^o-oxidizing activity (SOA), and very high sulfite-oxidizing activity, but lack respiratory tetrathionate-oxidizing activity. HQNO (50 m), an inhibitor of the quinone-cytochrome b region, strongly inhibited the SOA (70%), moderately the sulfite-oxidizing activity (45%), and poorly the thiosulfate-oxidizing activity (15%), 1mm KCN totally inhibited (>89%) all respiratory activities. This study confirms that inThiobacillus novellus, as well as in otherThiobacilli, SOA is present in cells grown with thiosulfate as sole electron donor. SOA appears not to be an oxygenase; it is linked to the respiratory chain, and the electrons are probably released in the quinone-cytochrome b region.     

Elemental sulfur production during mixotrophic growth on hydrogen and thiosulfate of thermophilic hydrogen-oxidizing bacteria

In this study we measured the exogenous production and the intracellular content of elemental sulfur (S⁰) in the thermophilic sulfur-oxidizing bacteriaHydrogenobacter spp. andBacillus schlegelii during mixolithoautotrophic growth on hydrogen and thiosulfate. Under these conditions, all strains produced and released white-yellow hydrophilic S⁰ particles into the growth medium. Hydrophilic S⁰ was separated from cells by a differential low-speed centrifugation procedure. The S⁰ pellets were dried, and the S⁰ was purified by column chromatography and by thin-layer chromatography (TLC). The S⁰ TLC-band could be stained with triphenyltetrazolium chloride and piperidine procedure. Determination of intracellular S⁰ content was performed from fresh cells absolutely free of exogenous S⁰ particles. quantitation of S⁰ was performed by high-performance liquid chromatography, colorimetric thiocyanate procedure, and by UV-spectra analyses. All the strains studied, in particularB. schlegelii strains, released significant quantities of S⁰ into the growth media. In contrast, the intracellular S⁰ content was very low. Significant rhodanese activity in the presence of thiosulfate was measured with toluenepermeabilized cells and cell-free extracts ofB. schlegelii (type strain) andHydrogenobacter spp. (strain T3).     

In vitro study of the proteolytic activity of rumen anaerobic fungi

Abstract To better define the antigenic structure of the outer cell membranes of Legionellae, a panel of 6 monoclonal antibodies was raised against partially purified outer membranes of Legionella pneumophila serogroup 1, Corby strain. This study describes the purification and characterization of one of these monoclonal antibodies reacting with a 135-kDa protein, which was shown to be common to all 14 serogroups of Legionella pneumophila . It shows no cross-reactivity with 20 other Legionella species, or 9 other Gram-negative species tested by SDS-PAGE and Western blotting procedures. The epitope would appear to be predominantly surface exposed and, from preliminary detergent extraction studies, not peptidoglycan-associated.     

Identification of a UDP-glucosyltransferase conferring deoxynivalenol resistance in Aegilops tauschii and wheat

Aegilops tauschii is the diploid progenitor of the wheat D subgenome and a valuable resource for wheat breeding, yet, genetic analysis of resistance against Fusarium head blight (FHB) and the major Fusarium mycotoxin deoxynivalenol (DON) is lacking. We treated a panel of 147 Ae. tauschii accessions with either Fusarium graminearum spores or DON solution and recorded the associated disease spread or toxin-induced bleaching. A k-mer-based association mapping pipeline dissected the genetic basis of resistance and identified candidate genes. After DON infiltration nine accessions revealed severe bleaching symptoms concomitant with lower conversion rates of DON into the non-toxic DON-3-O-glucoside. We identified the gene AET5Gv20385300 on chromosome 5D encoding a uridine diphosphate (UDP)-glucosyltransferase (UGT) as the causal variant and the mutant allele resulting in a truncated protein was only found in the nine susceptible accessions. This UGT is also polymorphic in hexaploid wheat and when expressed in Saccharomyces cerevisiae only the full-length gene conferred resistance against DON. Analysing the D subgenome helped to elucidate the genetic control of FHB resistance and identified a UGT involved in DON detoxification in Ae. tauschii and hexaploid wheat. This resistance mechanism is highly conserved since the UGT is orthologous to the barley UGT HvUGT13248 indicating descent from a common ancestor of wheat and barley.     

Induction of phagocytic behaviour in human epithelial cells by Escherichia coli cytotoxic necrotizing factor type1

Cytotoxic necrotizing factor type 1 (CNF1) from strains of pathogenic Escherichia coli induces in human epithelial HEp-2 cells, a profound reorganization of the actin cytoskeleton into prominent stress fibres and membrane ruffles. We report here that this process is associated with induction of phagocytic-like activity. CNF1-treated cells acquired the ability to ingest latex beads as well as non-invasive bacteria such as Listeria innocua, which were taken as a model system. Uptake of bacteria was similar to pathogen-induced phagocytosis, since L. innocua transformed with DNA coding for the pore-forming toxin listeriolysln O behaved, with respect to intracellular growth, like the invasive, pathogenic species L. monocytogenes. Our results raise the possibility that, in vivo, pathogenic CNF1 -producing E. coli may invade epithelia by this novel induced phagocytic-like mechanism.     

PCR-mediated screening and labeling of DNA from clones

A simplified and economical protocol for DNA library screening and nonradioactive labeling is described. Bacterial clones are lysed in 1% of Triton X-100 and subjected to polymerase chain reaction in the presence of digoxigenin-11-dUTP to screen and simultaneously to label the DNA inserts. Bacteriallysates are stable in storage at −20°C and can be used repeatedly for PCR-mediated labeling. In this protocol, very low concentrations of dNTP, digoxigenin-dUTP, and primers are used in combination with a reduced reaction volume. This will considerably reduce the expense of screening and labeling bacterial clones and facilitate the exchange of DNA probes among laboratories.