Assay of Salmonella in enrichment cultures of foods, feeds and environmental samples by the polymyxin-cloth enzyme immunoassay

A variety of foods, animal feeds and environmental samples were analyzed for the presence of Salmonella using the polymyxin-cloth enzyme immunoassay (p-CEIA) system. Salmonella lipopolysaccharide (LPS) antigens were captured from test samples on polymyxin-coated polyester cloth, followed by immunoenzymatic detection of bound antigens using a monoclonal antibody recognizing an LPS common core oligosaccharide. Dairy and egg products, animal feeds and environmental samples from food processing plants were pre-enriched for 24 h, followed by selective enrichment for a further 24 h in either tetrathionate brilliant green (TBG), selenite cystine (SC) or brain-heart infusion broth containing 0.5% yeast extract, 0.5% cholate and 0.3% selenite (BYCS). The samples were assayed by the p-CEIA after each stage of enrichment. After selective enrichment, the p-CEIA gave results which were in complete agreement with the standard culture technique in the analysis of all foods examined. On the other hand, a combination of selective enrichment and the p-CEIA out-performed the Modified Semi-Solid Rappaport Vassiliadis (MSRV) method in screening pre-enrichment cultures of feeds and environmental samples. Use of the new selective medium BYCS prior to performing the p-CEIA gave the highest recovery of Salmonella from feeds and environmental samples.     

Cellular mechanisms underlying magnesium sulfate inhibition of phasic myometrial contractions

The neutrophil chemotactic cytokine, IL-8, has been reported to also chemoattract T lymphocytes in vitro and in vivo. Previously we showed that freshly isolated T cells migrated in response to IL-8, but incubation of T cells at 37 degrees C resulted in progressively decreased levels of IL-8 binding sites on T cells in association with reduced chemotactic responses. However, this reduced binding and migration of cultured T cells in response to IL-8 can be prevented by the presence of mononuclear cells in the culture. In order to define the factor(s) responsible for the restoration of T cell binding and migration in response to IL-8, we examined the effects of various cytokines. Addition of IFN-gamma in cultured T cells maintained both the CXC chemokine receptor CXCR1 and CXCR2 binding sites for IL-8 on these cells to the level comparable to that expressed on freshly purified T cells accompanied by an almost complete restoration of their chemotactic response to IL-8. The results suggest that Th1 cytokine, IFN-gamma, produced by mononuclear cells stimulated by proinflammatory signals may play an important role in regulating IL-8 receptor expression on T cells and in sustaining the function of these cells in response to IL-8.     

Influence of the size factor on the thermal shock resistance of ceramic samples

The cracking of brittle samples having suffered thermal shocks may be calculated by using the thermoelastic theory. This theory leads to a size effect, which is not always verified by experiments. The use of acoustic methods of characterization, for samples of various shapes and sizes, shows the size effect, but the experimental T _c values are greater than the calculated ones. This discrepancy must be due both to an overestimation of the A coefficient and an underestimation of the R parameter.     

Sintering and Electrical Properties of Titania- and Zirconia-Containing ln2O3-Sno2(ITO) Ceramics

The deposition rate and film quality of In₂O₃-SnO₂ (ITO) transparent electrodes processed by sputtering are improved when using dense sputtering targets. Unfortunately, ITO ceramics do not sinter easily. It is shown that addition of TiO₂ (<1 wt%) to ITO greatly increases densification without degrading electrical properties of sputtered films. The influence of ZrO₂ and SiO₂ was also investigated.     

Sintering,oxidation and mechanical properties of hot pressed aluminium nitride

Aluminium nitride samples were prepared by hot pressing of fine powder without additives. The sintering process is described. Different porosities were obtained and the ratio total porosity/open porosity was measured. Tests of corrosion in air were performed. The main mechanical properties (hardness, strength, toughness, thermal shock resistance...) were measured and the effects of porosity and temperature studied. The results obtained are compared with the mechanical properties of other structural ceramics.     

Effect of the protein matrix on the digestion of cereal grains by ruminal microorganisms

Experiments were conducted to investigate the role of the protein matrix in the digestion of barley and corn by ruminal microorganisms. Grains, ground and collected on sieves as two particle fractions .25 to .89 mm (small particles) and 2.00 to 3.00 mm (large particles), as well as isolated barley and corn starch granules, were incubated with ruminal inocula. For both grains, digestion of starch in small particles was greater (P < .001) than that of large particles. At 16 and 24 h starch digestion was greater (P < .01) in barley than in corn, for small and large particles. Digestion of barley starch granules did not differ (P > .05) from that of corn starch granules at any incubation time. A 4-h preincubation of small-particle corn and barley with protease increased (P < .001) microbial digestion of starch in corn at 16 h but did not affect digestion of barley. When four ruminally cannulated steers were fed diets containing 80% barley, corn, or wheat or 100% alfalfa hay in a 4 x 4 Latin square experiment, amylolytic activity of ruminal inoculum was higher for steers fed grains than for those fed alfalfa. However, when standardized for total viable counts of bacteria, ruminal amylolytic activity did not differ (P > .05) among diet treatments, but proteolytic activity of ruminal inoculum for steers fed alfalfa was higher (P < .01) than that for steers fed cereal grains. Activity of serine proteases in ruminal inoculum was higher (P < .05) for steers fed alfalfa than for steers fed grains.(ABSTRACT TRUNCATED AT 250 WORDS)     

Antibacterial activity of silver-doped hydroxyapatite nanoparticles against gram-positive and gram-negative bacteria

Ag-doped nanocrystalline hydroxyapatite nanoparticles (Ag:HAp-NPs) (Ca_10-xAg_x(PO₄)₆(OH)₂, x_Ag = 0.05, 0.2, and 0.3) with antibacterial properties are of great interest in the development of new products. Coprecipitation method is a promising route for obtaining nanocrystalline Ag:HAp with antibacterial properties. X-ray diffraction identified HAp as an unique crystalline phase in each sample. The calculated lattice constants of a = b = 9.435 Å, c = 6.876 Å for x_Ag = 0.05, a = b = 9.443 Å, c = 6.875 Å for x_Ag = 0.2, and a = b = 9.445 Å, c = 6.877 Å for x_Ag = 0.3 are in good agreement with the standard of a = b = 9.418 Å, c = 6.884 Å (space group P6₃/m). The Fourier transform infrared and Raman spectra of the sintered HAp show the absorption bands characteristic to hydroxyapatite. The Ag:HAp nanoparticles are evaluated for their antibacterial activity against Staphylococcus aureus, Klebsiella pneumoniae, Providencia stuartii, Citrobacter freundii and Serratia marcescens. The results showed that the antibacterial activity of these materials, regardless of the sample types, was greatest against S. aureus, K. pneumoniae, P. stuartii, and C. freundii. The results of qualitative antibacterial tests revealed that the tested Ag:HAp-NPs had an important inhibitory activity on P. stuartii and C. freundii. The absorbance values measured at 490 nm of the P. stuartii and C. freundii in the presence of Ag:HAp-NPs decreased compared with those of organic solvent used (DMSO) for all the samples (x_Ag = 0.05, 0.2, and 0.3). Antibacterial activity increased with the increase of x_Ag in the samples. The Ag:HAp-NP concentration had little influence on the bacterial growth (P. stuartii).