Bacteriophages mediating somatic antigenic conversion in Salmonella cholerae-suis: their isolation from sewage and other Salmonella serotypes possessing the somatic 6 antigen

Bacteriophages which mediate the conversion of the O somatic antigen of Salmonella cholerae-suis from the 6(2)7 to the 6(1)7 phenotype have been isolated from two strains of S. newport and one of S. muenchen, and also from sewage collected from two areas where there have been no reports of S. cholerae-suis infection for several years. The phages differed from each other by cross-resistance tests.     

A Simple 96-Well Microplate Method for Estimation of Total Polyphenol Content in Seaweeds

Seaweed polyphenols are potent antioxidants and have also been shown to have α-glucosidase inhibiting activity. In our continuous efforts to develop new marine-based nutraceuticals and functional food ingredients, we have investigated many algal species collected on the Atlantic coast of Canada. A simple method for estimating the total polyphenol content in seaweeds and their extracts was developed based on the classic Folin-Ciocalteau colorimetric reaction. By using the 96-well microplate and a microplate reader, this new method saves experimental time, significantly reduces the amount of sample required, handles large number of samples in one experiment, and also improves the repeatability of the results.A number of algal samples collected on the seashore of Nova Scotia, Canada, were analyzed for their levels of polyphenol content using this microplate-based method. The antioxidant activity of these samples was also assessed by using DPPH (2, 2-diphenyl-1-picrylhydrazyl) radical scavenging assay. The results showed that there is a strong correlation between the total polyphenol content and the potency of antioxidant effect.     

NMR studies of amyloid beta-peptides: proton assignments, secondary structure, and mechanism of an alpha-helix----beta-sheet conversion for a homologous, 28-residue, N-terminal fragment.

Beta-peptide is a major component of amyloid deposits in Alzheimer's disease. We report here a proton nuclear magnetic resonance (NMR) spectroscopic investigation of a synthetic peptide that is homologous to residues 1-28 of beta-peptide [abbreviated as beta-(1-28)]. The beta-(1-28) peptide produces insoluble beta-pleated sheet structures in vitro, similar to the beta-pleated sheet structures of beta-peptide in amyloid deposits in vivo. For peptide solutions in the millimolar range, in aqueous solution at pH 1-4 the beta-(1-28) peptide adopts a monomeric random coil structure, and at pH 4-7 the peptide rapidly precipitates from solution as an oligomeric beta-sheet structure, analogous to amyloid deposition in vivo. The NMR work shown here demonstrates that the beta-(1-28) peptide can adopt a monomeric alpha-helical conformation in aqueous trifluoroethanol solution at pH 1-4. Assignment of the complete proton NMR spectrum and the determination of the secondary structure were arrived at from interpretation of two-dimensional (2D) NMR data, primarily (1) nuclear Overhauser enhancement (NOE), (2) vicinal coupling constants between the amide (NH) and alpha H protons, and (3) temperature coefficients of the NH chemical shifts. The results show that at pH 1.0 and 10 degrees C the beta-(1-28) peptide adopts an alpha-helical structure that spans the entire primary sequence. With increasing temperature and pH, the alpha-helix unfolds to produce two alpha-helical segments from Ala2 to Asp7 and Tyr10 to Asn27. Further increases in temperature to 35 degrees C cause the Ala2-Asp7 section to become random coil, while the His13-Phe20 section stays alpha-helical. A mechanism involving unfavorable interactions between charged groups and the alpha-helix macrodipole is proposed for the alpha-helix----beta-sheet conversion observed at midrange pH.     

Preliminary studies on eicosanoid production by fish leucocytes, using GC-mass spectrometry

Culture supernatants from dogfish leucocytes, exposed to the Ca²⁺ ionophore A23187, were analyzed for eicosanoid production by gas chromatography-electron capture mass spectrometry. Consistently high levels of the prostaglandins (PG) D₂, F_2α and E₂ were produced, while thromboxane B₂ and leukotriene B₄ were found in smaller amounts. No 6-oxo PGF_1α, a degradation product of prostacyclin, or 13,14-dihydro-15-oxo-PGF_2α, a metabolite of PGE₂ and PGF_2α, were detected. The results are compared with similar experiments using mammalian leucocytes.