Short‐chain fatty acids affect cell‐association and invasion of HEp‐2 cells by Salmonella typhimurium

Abstract

This study demonstrates that the growth of S. typhimurium in Luria Bertani broth supplemented with acetate, propionate, butyrate, or a mixture of the three SCFA, affected cell‐association and the ability to invade cultured HEp‐2 cells. Cell‐association and invasion was determined after growth for 4 h of growth in the presence of the SCFA at pH 6 and 7. The results suggest that the growth rate of the culture may have affected cell‐association and invasion since accompanying the significant decrease in growth rate in the presence of SCFA at pH 6 was a decrease in cell‐association and invasion. However, the results also suggest that the individual SCFA may play a role in modulating cell‐association and the invasion phenotype and the regulation of cell‐association and invasion by the SCFA was dependent on the concentration and the pH of the medium. Although the growth rates were similar for S. typhimurium in the SCFA mixture, butyrate (100 mM) and propionate (50 mM) at pH 6, differences in cell‐association and invasion were observed among these cultures. Also, at pH 7, differences were observed among the SCFA treatments even though the growth rates were similar.     

Note On A Preliminary Study of the Effects of Roof Tar Evaporate on Oxidant Levels Measured by Iodide Colorimetry

Some evidence exists to relate elevated oxidant levels, as measured by iodine colorimetry or coulometry, to the presence of roof tar evaporates or the oxidation products produced from such evaporates in the presence of sunlight.     

Depositional flux of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans in an urban setting

Dry and wet deposition fluxes of the PCDD/F substituted congeners were measured at two different sites (Clinton Drive and Lang Road) in Houston, TX between December 2003 and April 2004. Average total dry deposition fluxes of 351 and 125pgm(-2)d(-1) were found at Clinton Drive and Lang Road, respectively. A wet deposition flux of 2.873pgm(-2)d(-1) was measured at the Clinton Drive site. The results indicated that the dry deposition process exhibited spatial variability. In addition, the results also demonstrated that precipitation, although intermittent, is the most important mechanism for the removal of dioxins from atmosphere in the area of study. Combining the contributions of the dry and wet deposition processes at Clinton Drive resulted in a total bulk deposition flux of 527pg m(-2)d(-1). The total dry and wet deposition fluxes were dominated by OCDD followed by 1,2,3,4,6,7,8-HpCDD at both sites. Overall average dry deposition velocities of 0.35 and 0.15cms(-1) were calculated at Clinton Drive and Lang Road sites, respectively. While these velocities were similar to velocities observed in other geographical areas, the contribution of OCDD to the total deposition flux in Houston was significantly higher, probably reflecting the unique nature and character of Houston dioxin sources. The results also showed that lower chlorinated congeners, primarily present in the gas phase, are more likely to be removed from the atmosphere by precipitation. Relationships between the detected congeners in the dry deposition samples and other routinely measured air pollutants/meteorological parameters were found. The results showed that in general, the dry deposition of these congeners was consistently negatively correlated with SO(2) and NO(x) concentrations in the air and positively correlated with relative humidity. However, more research is needed to ascertain those correlations.     

Freezing and drying effects on potential plant contributions to phosphorus in runoff

Phosphorus (P) in runoff from landscapes can promote eutrophication of natural waters. Soluble P released from plant material can contribute significant amounts of P to runoff particularly after plant freezing or drying. This study was conducted to evaluate P losses from alfalfa or grass after freezing or drying as potential contributors to runoff P. Alfalfa (Medicago sativa L.) and grass (principally, Agropyron repens L.) plant samples were subjected to freezing and drying treatments to determine P release. Simulated rainfall runoff and natural runoff from established alfalfa fields and a grass waterway were collected to study P contributions from plant tissue to runoff. The effects of freezing and drying on P released from plant tissue were simulated by a herbicide treatment in selected experiments. Soluble reactive P (SP) extracted from alfalfa and grass samples was markedly increased by freezing or drying. In general, SP extracted from plant samples increased in the order fresh < frozen < frozen/thawed < dried, and averaged 1, 8, 14, and 26% of total P in alfalfa, respectively. Soluble reactive P extracted from alfalfa after freezing or drying increased with increasing soil test P (r(2) = 0.64 to 0.68), suggesting that excessive soil P levels increased the risk of plant P contributions to runoff losses. In simulated rainfall studies, paraquat (1,1'-dimethyl-4, 4'-bipyridinium ion) treatment of alfalfa increased P losses in runoff, and results suggested that this treatment simulated the effects of drying on plant P loss. In contrast to the simulated rainfall results, natural runoff studies over 2 yr did not show higher runoff P losses that could be attributed to P from alfalfa. Actual P losses likely depend on the timing and extent of plant freezing and drying and of precipitation events after freezing.     

Saltcedar control and water salvage on the Pecos river, Texas, 1999–2003

A large scale ecosystem restoration program was initiated in 1997 on the Pecos River in Western Texas. Saltcedar (Tamarix spp.), a non-native invasive tree, had created a near monoculture along the banks of the river by replacing most native vegetation. Local irrigation districts, private landowners, federal and state agencies, and private industry worked together to formulate and implement a restoration plan, with a goal of reducing the effects of saltcedar and restoring the native ecosystem of the river. An initial management phase utilizing state-of-the-art aerial application of herbicide began in 1999 and continued through 2003. Initial mortality of saltcedar averaged about 85–90%. Monitoring efforts were initiated at the onset of the project to include evaluating the effects of saltcedar control on salinity of the river water, efficiency of water delivery down the river as an irrigation water source, and estimates of water salvage. To date, no effect on salinity can be measured and irrigation delivery was suspended in 2002–2003 due to drought conditions. Water salvage estimates show a significant reduction in system water loss after saltcedar treatment. However, a flow increase in the river is not yet evident. Monitoring efforts will continue in subsequent years.     

Evaluating the “Catch‐Can” Test for Measuring Lawn Sprinkler Application Rates1

Abstract: The effectiveness of measuring lawn sprinkler application rates using the catch‐can test was evaluated. A survey of sources recommending the catch‐can test for measuring application rates show that catch‐can test procedures differ in the collector type, collector placement, number of collectors, and test duration. Analyses of catch‐can tests were performed to address these procedural differences, with emphasis on the type and number of collectors required to provide a reasonable level of confidence in test results. The accuracy of the catch‐can test generally improves as the number of randomly placed collectors increases. In order to achieve an accuracy of ±25% for 90 out of 100 catch‐can tests, the number of randomly placed collectors required ranged from 6 to over 50 for hand‐move systems, while for in‐ground systems, the number of randomly placed collectors required ranged from 2 to 8, depending on the pressure and percent overlap of the water distribution pattern. As long as a reasonable number of collectors were used when performing a catch‐can test, no consistent differences were observed in catch‐can test results due to type of collectors when using tuna fish cans, soup cans, or coffee mugs.     

Packaging waste measurement—A key element in digital's total quality program

Measurement of packaging waste is a key element of the Total Quality Management program at Digital Equipment Corporation. This case study shows how the company uses measurement techniques to set priorities for which areas of packaging waste should be addressed first and to track improvements over time. To date, an 1,800-ton annual reduction in packaging waste has been achieved, with associated annual savings of $2.7 million.     

The use of isotope dilution mass spectrometry for the certification of standard reference materials

Isotope dilution mass spectrometry (IDMS) has been used extensively at the U.S. National Bureau of Standards as an accurate method to determine trace element concentrations in natural materials. Thermal ionization mass spectrometry is a single element technique capable of high accuracy and precision, and has been used for “definitive” measurements of trace elements in sera with 95% confidence limits less than 0.25%. Spark source mass spectrometry is a complementary multielement, high-sensitivity technique that has been used to determine up to 20 elements in a sample, with typical accuracies of 2%–5%. Together with appropriate chemical separations, such as anion and cation exchange, chelate resins, electrodeposition, and chemical extraction, IDMS has been applied to elemental concentration measurements ranging over eight orders of magnitude, from decigrams/gram to picograms/gram. Many of these applications have been used for the certification of a broad spectrum of biological and environmental Standard Reference Materials, including lead in Trace Elements in Water (SRM 1643), 15 elements in Coal Fly Ash (SRM 1633a), uranium in Bovine Liver (SRM 1577a), and mercury in water (SRM 1642).     

The formation of chlorodibenzo-p-dioxins by air oxidation and chlorination of bituminous coal

A well characterized bituminous coal was subjected to high temperature air oxidation and chlorination. After an extensive cleanup procedure, the reaction products were analyzed for chlorinated dibenzo-p-dioxins by gas chromatography-mass spectrometry. Substantial quantities of chlorodibenzo-p-dioxins, some of which are known to be highly toxic, were observed with chlorination by hydrogen chloride and chlorine gas.