Propionic acid side chain hydrogen bonding in the malaria pigment beta-hematin

Malaria pigment, or beta-hematin, the insoluble heme detoxification product resulting from the intraerythrocitic digestion of hemoglobin by young malaria trophozoites has been structurally characterized by X-ray powder diffraction and shown to contain chains of propionic acid linked dimers. Although there is considerable spectroscopic evidence for a monodentate propionate-iron interaction in this crystalline material, the spectroscopic characterization of the propionic acid dimer is limited. Herein we demonstrate the presence of the propionic acid dimer unit by H/D isotope substitution in carboxylic acid dimer. In the Raman spectrum of the deuterium substituted compound there is a circa 12 cm(-1) shift, H: 1629 cm(-1) vs. D: 1617 cm(-1) in the symmetric ring breathing mode for the propionic acid dimer. On the other hand, the IR active asymmetric stretch has a very small shift, <3 cm(-1), upon deuteration. These, and other vibrational data, are consistent with the presence of a planar carboxylic acid dimer in the structure of beta-hematin.     

Cross-contamination with Salmonella on a broiler slaughterhouse line demonstrated by use of epidemiological markers

AIMS: To investigate contamination of surfaces on a poultry slaughter line from infected poultry and subsequent cross-contamination of non-infected poultry. METHODS AND RESULTS: A broiler slaughterhouse was investigated for the presence of Salmonella on 17 defined points over two 1-week periods. Flocks supplied to slaughter and neck skin samples from processed chicken were likewise investigated. Salmonella was detected in 10 out of 18 flocks at ante-mortem inspection, while seven flocks tested positive in the finished products. Equipment at all but one control point at the slaughter line tested positive at least once during the study. The chicken receiving area was the most contaminated. By comparison of typing results from serotyping, plasmid profile typing and phage typing, direct evidence for cross-contamination with Salm. serotype Typhimurium, Salm. Serotype 4.12:b:- and Salm. serotype Virchow on the slaughter line was obtained for four of the flocks. The cleaning procedure in place did not remove all Salmonella from the contaminated areas. CONCLUSIONS: Evidence for contamination of equipment on a slaughter line and subsequent cross-contamination to non-infected chicken was provided by typing methods. SIGNIFICANCE AND IMPACT OF THE STUDY: This study has provided detailed information on cross-contamination on a slaughter line by the use of phage typing and plasmid profiling. The study stresses the importance of controlling Salmonella in the primary production, as contamination of the equipment on the slaughter line will act as a vehicle to contaminate finished products. Cleaning procedures on slaughter lines cannot be expected to control this problem with the current equipment.     

Chromosome location, genomic organization of the porcine COL10A1 gene and model structure of the NC1 domain

The porcine COL10A1 gene, encoding the alpha1(X) chain of type X collagen, has been sequenced. The gene structure is evolutionarily conserved, consisting of three exons and two introns spanning 7100 bp. Linkage mapping localized the gene to chromosome 1, which is in agreement with human-pig homology maps. Furthermore, protein structure comparison of the functionally important carboxyl domain between species revealed that amino acid changes were few and mainly situated in loop regions.     

NAGase activity in airborne biomass dust and relationship between NAGase concentrations and fungal spores

Inhalation of airborne fungal spores or fungalenzymes may cause adverse pulmonary healtheffects. The enzyme NAGase(N-acetyl--D-glucosaminidase) is achitinase presumed to be secreted by all fungi. In this study, NAGase activities andconcentrations of fungi are estimated inairborne biomass dust to acquire knowledgeabout the level of NAGase activity and therelationship between NAGase activity andconcentrations of airborne fungal spores.NAGase was sampled on both teflon andpolycarbonate filters, and polycarbonatefilters proved to be better for extraction ofNAGase than teflon filters. NAGase was foundin airborne dust at a biofuel plant and in dustgenerated from biomass. At a biofuel plant, themedian level of exposure to NAGase was 21 pmols^–1 m^–3. Significant correlationswere found between NAGase activities, totalnumber of fungal spores and CFU of fungi, withthe highest degree of correlation being betweenthe total number of fungal spores and theNAGase activity (r = 0.802, n = 76). Furthermore,when dust was stored for different periods, theculturability of fungal spores was stronglyreduced and the NAGase activity was not or onlyslightly reduced after up to 40 days ofstorage. Accordingly, NAGase activity may beused as a rapid method to get an estimate ofthe exposure level to airborne fungal spores.Whether pure NAGase or the NAGaseconcentrations observed here cause any healtheffects is not known, although it has beenshown that other fungal enzymes can causerespiratory disorders and a chitinase isdescribed as an allergen.     

High internal resistance to CO2 uptake by submerged macrophytes that use HCO3 −: measurements in air,nitrogen and helium

Previous studies have shown that in water the affinity of submerged macrophytes for CO₂ is higher for species restricted to CO₂ than for species with an additional ability to use bicarbonate. We measured slopes of CO₂ uptake versus CO₂ concentration in the gas phase in air, nitrogen and helium for pairs of species, having or lacking the ability to use bicarbonate, but with similar leaf morphology. For species restricted to CO₂, the slope in nitrogen and helium was 1.5 times and 3.2 times greater than in air. The increased slope in nitrogen results from a suppression of photorespiration. The further increase in helium reflects the increased rate of diffusion of CO₂ and shows that, even in gas, external diffusion through the boundary layer is a significant hindrance to CO₂ uptake. In contrast, in species able to use bicarbonate, the uptake slope was not affected by gas composition, suggesting that photorespiration is absent or photorespired CO₂ is efficiently trapped and that internal resistance is high relative to external resistance. Elodea canadensis specimens grown under high concentrations of CO₂ de-regulated their ability to use bicarbonate, and slopes of CO₂ uptake in helium were significantly greater than in air or nitrogen. Overall, these results are consistent with the notion that while a high affinity for CO₂ will maximise carbon uptake in species restricted to CO₂, for species able to use bicarbonate, a high internal resistance would reduce loss of CO₂ and help maintain high concentrations of CO₂ at the site of fixation. This revised version was published online in August 2006 with corrections to the Cover Date.     

Activation of AMP-activated protein kinase reduces cAMP-mediated epithelial chloride secretion

AMP-activated protein kinase (AMPK) is activated in response to fluctuations in cellular energy status caused by oxidative stress. One of its targets is the cystic fibrosis transmembrane conductance regulator (CFTR), which is the predominant Cl- secretory channel in colonic tissue. The aim of this study was to determine the role of AMPK in the modulation of colonic chloride secretion under conditions of oxidative stress and chronic inflammation. Chloride secretion and AMPK activity were examined in colonic tissue from adult IL-10-deficient and wild-type 129 Sv/Ev mice in the presence and absence of pharmacological AMPK inhibitors and activators, respectively. Apical levels of CFTR were measured in brush-border membrane vesicles. Cell culture studies in human colonic T84 monolayers examined the effect of hydrogen peroxide and pharmacological activation of AMPK on forskolin-stimulated chloride secretion. Inflamed colons from IL-10-deficient mice exhibited hyporesponsiveness to forskolin stimulation in association with reductions in surface CFTR expression and increased AMPK activity. Inhibition of AMPK restored tissue responsiveness to forskolin, whereas stimulation of AMPK with 5-aminoimidazole-4-carboxamide-1-beta-d-ribofuranoside (AICAR) induced tissue hyporesponsivness in wild-type mice. T84 cells exposed to hydrogen peroxide demonstrated a time-dependent increase in AMPK activity and reduction of forskolin-stimulated chloride secretion. Inhibition of AMPK prevented the reduction in chloride secretion. Treatment of cells with the AMPK activator, AICAR, resulted in a decreased chloride secretion. In conclusion, AMPK activation is linked with reductions in cAMP-mediated epithelial chloride flux and may be a contributing factor to the hyporesponsiveness seen under conditions of chronic inflammation.     

Vacuolar-type H(+)-ATPase and Na+, K(+)-ATPase expression in gills of Atlantic salmon (Salmo salar) during isolated and combined exposure to hyperoxia and hypercapnia in fresh water

Changes in branchial vacuolar-type H(+)-ATPase B-subunit mRNA and Na+, K(+)-ATPase alpha- and beta-subunit mRNA and ATP hydrolytic activity were examined in smolting Atlantic salmon exposed to hyperoxic and/or hypercapnic fresh water. Pre-smolts, smolts, and post-smolts were exposed for 1 to 4 days to hyperoxia (100% O2) and/or hypercapnia (2% CO2). Exposure to hypercapnic water for 4 days consistently decreased gill vacuolar-type H(+)-ATPase B-subunit mRNA levels. Salmon exposed to hyperoxia had either decreased or unchanged levels of gill B-subunit mRNA. Combined hyperoxia + hypercapnia decreased B-subunit mRNA levels, although not to the same degree as hypercapnic treatment alone. Hyperoxia generally increased Na+, K(+)-ATPase alpha- and beta-subunit mRNA levels, whereas hypercapnia reduced mRNA levels in presmolts (beta) and smolts (alpha and beta). Despite these changes in mRNA levels, whole tissue Na+, K(+)-ATPase activity was generally unaffected by the experimental treatments. We suggest that the reduced expression of branchial vacuolar-type H(+)-ATPase B-subunit mRNA observed during internal hypercapnic acidosis may lead to reduction of functional V-type H(+)-ATPase abundance as a compensatory response in order to minimise intracellular HCO3- formation in epithelial cells.     

Naphthalene and donor cell density influence field conjugation of naphthalene catabolism plasmids

We examined transfer of naphthalene-catabolic genes from donor microorganisms native to a contaminated site to site-derived, rifampin-resistant recipient bacteria unable to grow on naphthalene. Horizontal gene transfer (HGT) was demonstrated in filter matings using groundwater microorganisms as donors. Two distinct but similar plasmid types, closely related to pDTG1, were retrieved. In laboratory-incubated sediment matings, the addition of naphthalene stimulated HGT. However, recipient bacteria deployed in recoverable vessels in the field site (in situ) did not retrieve plasmids from native donors. Only when plasmid-containing donor cells and naphthalene were added to the in situ mating experiments did HGT occur.