Effects of sodium caseinate concentration and storage conditions on the oxidative stability of oil-in-water emulsions.

The oxidative stability of various oils (sunflower, camelina and fish) and 20% oil-in-water (O/W) emulsions, were examined. The mean particle size decreased from 1179 to 325 nm as sodium caseinate (emulsifier) concentration was increased from 0.25% to 3% in O/W emulsions (P<0.05). Increasing the microfluidisation pressure from 21 to 138 MPa, resulted in a particle size decrease from 289 to 194 nm (P<0.05). Emulsified oils had lower detectable lipid hydroperoxide and p-Anisidine values than their corresponding bulk oils (P<0.05). The lipid hydroperoxide and p-Anisidine values of emulsions generally decreased as sodium caseinate concentration increased, and similarly decreased as microfluidisation pressure increased (P<0.05). Increasing storage temperature of the emulsions from 5 to 60°C, resulted in lower detectable lipid oxidation products during storage (P<0.05).

Effects of emulsification and microencapsulation on the oxidative stability of camelina and sunflower oils.

Oil-in-water (O/W) emulsions were prepared using different concentrations of camelina or sunflower oil. Sodium caseinate was used as the emulsifier and dried glucose syrup as the wall material. Emulsions were subsequently spray dried to yield high-fat powders (71.7-85.0%). Emulsification and microencapsulation of bulk oils decreased their level of lipid oxidation (lipid hydroperoxide and p-Anisidine values, p-Avs). Sunflower oil, O/W emulsions and reconstituted powders generally had lower oxidation products than corresponding camelina oil-based products throughout storage at 15°C. p-Avs of bulk oils remained constant, whereas p-Avs of O/W emulsions and reconstituted powders decreased early in storage, and remained low thereafter. Microencapsulated omega (ω)-3 rich powders were produced, easily reconstituted and showed no signs of deterioration throughout storage. These powders provided functional properties with potential for incorporation into various food systems as a source of beneficial ω-3 fatty acids.

Helicobacter pylori extract induces nuclear factor-kappa B, activator protein-1, and cyclooxygenase-2 in esophageal epithelial cells.

Helicobacter pylori infection is recognized as the major cause of gastritis and gastric cancer; however, its role in the development of gastroesophageal reflux disease and Barrett's adenocarcinoma is unclear. The expression of NF-kappaB, AP-1, and COX-2 may be important in inflammation and tumorigenesis in the esophagus. The aim of this study was to examine the effect of live H pylori or H pylori extract (HPE) on these factors in the esophageal epithelial cell lines SKGT-4 and OE33. NF-kappaB and AP-1 activity were assessed by gel shift assay and COX-2 by Western blotting. Coculture of SKGT-4 and OE33 with live H pylori and HPE induced NF-kappaB and AP-1 DNA-binding activity, and also decreased IkappaB-alpha levels. Treatment with the specific MEK1/2 MAPK inhibitor PD98059, but not the p38 MAPK inhibitor SB203580, inhibited NF-kappaB and AP-1 activity. The antioxidant vitamin C inhibited H pylori-induced NF-kappaB activation, but increased AP-1 expression. Moreover, HPE induced COX-2 expression and IL-8 production, and PD98059 inhibited COX-2 expression, ERK1/2 phosphorylation, and IL-8 production. These data demonstrate that both live H pylori and HPE induce NF-kappaB and AP-1 expression in esophageal epithelial cells. The induction of such transcription factors may play a role in the specific immune response within Barrett's mucosa and may indirectly cause inflammation of the gastric cardia and the distal esophagus.

The serine-aspartate repeat (Sdr) protein family in Staphylococcus epidermidis.

Staphylococcus epidermidis can express three different cell-surface-associated proteins, designated SdrF, SdrG and SdrH, that contain serine-aspartate dipeptide repeats. Proteins SdrF and SdrG are similar in sequence and structural organization to the Sdr proteins of Staphylococcus aureus and comprise unique 625- and 548-residue A regions at their N termini, respectively, followed by 110-119-residue B-repeat regions and SD-repeat regions. The C termini contain LPXTG motifs and hydrophobic amino acid segments characteristic of surface proteins covalently anchored to peptidoglycan. In contrast, SdrH has a short 60-residue A region at its N terminus followed by a SD-repeat region, a unique 277-residue C region and a C-terminal hydrophobic segment. SdrH lacks a LPXTG motif. Recombinant proteins representing the A regions of SdrF, SdrG and SdrH were expressed and purified from Escherichia coli. Antisera specific to these proteins were raised in rabbits and used to identify Sdr proteins expressed by S. epidermidis. Only SdrF was released from lysostaphin-generated protoplasts of cells grown to late-exponential phase. SdrG and SdrH remained associated with the protoplast fraction and thus appear to be ineffectively sorted along the conventional pathway used for cell-wall-anchored proteins. In Southern hybridization analyses, the sdrG and sdrH genes were present in all 16 strains tested, whilst sdrF was present in 12 strains. Antisera from 16 patients who had recovered from S. epidermidis infections contained antibodies that reacted with recombinant A regions of SdrG and SdrH, suggesting that these proteins can be expressed during infection.

Three new members of the serine-aspartate repeat protein multigene family of Staphylococcus aureus.

Three new genes encoding the serine-aspartate (SD) repeat-containing proteins SdrC, SdrD and SdrE were found in Staphylococcus aureus strain Newman. The SD repeats had earlier been found in the S. aureus fibrinogen-binding clumping factors ClfA and ClfB. The clfA and clfB genes encode high-molecular-mass fibrinogen-binding proteins that are anchored to the cell surface of S. aureus. The sdr genes now reported are closely linked and tandemly arrayed. The putative Sdr proteins have both organizational and sequence similarity to ClfA and ClfB. At the N-terminus, putative secretory signal sequences precede approximately 500 residue A regions. The A regions of the Sdr and Clf proteins exhibit only 20-30% residue identity when aligned with any other member of the family. The only conserved sequence is the consensus motif TYTFTDYVD. The Sdr proteins differ from ClfA and ClfB by having two to five additional 110-113 residue repeated sequences (B-motifs) located between region A and the R-region. Each B-motif contains a consensus Ca2+-binding EF-hand loop normally found in eukaryotic proteins. The structural integrity of recombinant SdrD(B1-B5) protein comprising the five B-repeats of SdrD was shown by bisANS fluorescence analysis to be Ca2+-dependent, suggesting that the EF-hands are functional. When Ca2+ was removed the structure collapsed to an unfolded conformation. The original structure was restored by addition of Ca2+. The C-terminal R-domains of the Sdr proteins contain 132-170 SD residues. These are followed by conserved wall-anchoring regions characteristic of many surface proteins of Gram-positive bacteria. The sdr locus was present in all 31 S. aureus strains from human and bovine sources tested by Southern hybridization, although in a few strains it contained two rather than three genes.