Probing dry-weight improves left ventricular mass index.

BACKGROUND: Although probing dry-weight improves blood pressure control, its effect on echocardiographic left ventricular mass index (LVMI) is unknown. METHODS: Shortly following dialysis, 292 echocardiograms in 150 patients participating in the DRIP trial were obtained at baseline and longitudinally every 4 weeks on 2 occasions. RESULTS: At baseline, LVMI was 136.3 g/m(2) in the control group and 138.7 g/m(2) in the ultrafiltration group (p > 0.2 for difference). The change from baseline in LVMI in the control group was +3.5 g/m(2) at 4 weeks and +0.3 g/m(2) at 8 weeks (p > 0.2 for both changes). The change from baseline in LVMI in the ultrafiltration group was -7.4 g/m(2) at 4 weeks (p = 0.005) and -6.3 g/m(2) at 8 weeks (p = 0.045). With ultrafiltration, the change in LVMI diameter was -10.9 g/m(2) more compared to the control group at 4 weeks (p = 0.012) and -6.6 g/m(2) more compared to the control group at 8 weeks (p = 0.21). The reduction in interdialytic ambulatory blood pressure was also greater in response to probing dry-weight in those in the top half of LVMI at baseline (p = 0.02 for interaction effect at week 8). CONCLUSION: LVMI, an important determinant of prognosis among long-term dialysis patients, is responsive to probing dry-weight.

Inferior vena cava diameter and left atrial diameter measure volume but not dry weight.

BACKGROUND AND OBJECTIVES: Hypervolemia is an important and modifiable cause of hypertension. Hypertension improves with probing dry weight, but its effect on echocardiographic measures of volume is unknown. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Shortly after dialysis, echocardiograms were obtained at baseline and longitudinally every 4 weeks on two occasions. Among 100 patients in the additional ultrafiltration group, 198 echocardiograms were performed; among 50 patients in the control group, 104 echocardiograms were performed. RESULTS: Baseline inferior vena cava (IVC)(insp) diameter was approximately 5.1 mm/m(2); with ultrafiltration, change in IVC(insp) diameter was -0.95 mm/m(2) more compared with the control group at 4 weeks and -1.18 mm/m(2) more compared with the control group at 8 weeks. From baseline IVC(exp) diameter of approximately 8.2 mm/m(2), ultrafiltration-induced change at 4 weeks was -1.06 mm/m(2) more and at 8 weeks was -1.07 mm/m(2) more (P=0.044). From a baseline left atrial diameter of 2.1 cm/m(2), ultrafiltration-induced change at 4 weeks was -0.14 cm/m(2) more and at 8 weeks was -0.15 cm/m(2) more. At baseline, there was no relationship between interdialytic ambulatory BP and echocardiographic parameters of volume. The reduction in interdialytic ambulatory BP was also independent of change in the echocardiographic volume parameters. CONCLUSIONS: The inferior vena cava and left atrial diameters are echocardiographic parameters that are responsive to probing dry weight; thus, they reflect excess volume. However, echocardiographic volume parameters are poor determinants of interdialytic BP, and their change does not predict the BP response to probing dry weight.

Differential carbon source utilization by Campylobacter jejuni 11168 in response to growth temperature variation.

Campylobacter spp. readily colonize the intestinal tracts of both human and avian species. While most often commensal organisms in birds, campylobacters remain the leading cause of bacterial gastroenteritis in humans. The association of campylobacters with poultry is well established as a primary route for human exposure. The difference in normal core body temperature between chickens (42 degrees C) and humans (37 degrees C) has been suggested to trigger potential colonization or virulence factors and investigators have demonstrated differential gene expression at the two temperatures. Campylobacter spp. exhibit unique nutritional requirements and have been thought to only utilize amino acids and Kreb cycle intermediates as carbon sources for growth. We evaluated the ability of the genome-sequenced strain of Campylobacter jejuni 11168 (GS) to oxidize 190 different substrates as sole carbon sources at 37 degrees C and 42 degrees C using phenotype microarray (PM) technology. Results indicate that the expected amino acids, l-serine, l-aspartic acid, l-asparagine, and l-glutamic acid were utilized in addition to a number of organic acids. In general, oxidation of the substrates was greater at 42 degrees C than at 37 degrees C with a few exceptions. By employing the PM method, we observed a number of potential false-positive reactions for substrates including the triose, dihydroxyacetone; and the pentose sugars, d-xylose, d-ribose, l-lyxose, and d- and l-arabinose. The presence of genes possibly responsible for utilization of pentose sugars is supported by the genomic sequence data, but actual utilization as sole carbon sources for active respiration has not been observed. A better understanding of the metabolic pathways and nutritional requirements of campylobacters could lead to improvements in culture media for detection and isolation of the pathogen and to future intervention methods to reduce human exposure.

Evaluation of a polyacrylamide soil additive to reduce agricultural-associated contamination.

Polyacrylamide is an effective water treatment product used to reduce suspended sediment and associated contaminants. An anionic polyacrylamide-containing product was tested for sediment and associated contaminant reduction and potential toxicity in agricultural irrigation and rainfall runoff. The product effectively reduced turbidity, total suspended solids, and phosphate concentrations in the field when compared to the untreated runoff waters. Acute survival of Ceriodaphnia dubia and Pimephales promelas was not decreased compared to laboratory controls. No significant increases in toxicity were measured in 10-d sediment toxicity tests with Chironomus dilutus. Product applications were effective in controlling sediment and nutrient contamination without increasing measured toxicity.

Considerations for assessments of wadable drainage systems in the agriculturally dominated deltas of Arkansas and Mississippi.

The watershed approach, currently used to assess regional streams in the United States, emphasizes least-disturbed reference conditions. Consideration of extensive wadable drainage systems found in Arkansas and Mississippi deltas challenges concepts of disturbance within a landscape of historic agricultural land use. Seventeen wadable drainage ditch sites in Arkansas and Mississippi deltas were characterized using water quality parameters and rapid bioassessment protocols. In all, 19 fish and 105 macroinvertebrate taxa were identified. Macroinvertebrate assemblages were dominated by coleopteran, dipteran, and hemipteran taxa at most drainage sites. Predominance of mobile, early colonists in ditches limits applicability of some metrics for assessment of stream integrity beyond prevalent conditions of ephemeral water quantity and habitat maintenance. This study provides evidence of considerable variability of physical characteristics, water quality, and fish and invertebrate metrics in wadable drainage systems. It indicates a disparity in usefulness of the watershed approach, emphasizing least-disturbed reference conditions, in assessing ecological integrity for a region with ditches as dominant landscape features.

In vitro penetration of egg yolks by Salmonella Enteritidis and Salmonella Heidelberg strains during thirty-six-hour ambient temperature storage.

Although Salmonella deposition inside yolks is uncommon in naturally contaminated eggs, migration through the vitelline membrane into the nutrient-rich yolk contents could enable rapid bacterial multiplication. Egg refrigeration restricts both penetration and growth, but a recently proposed national Salmonella Enteritidis control program would allow unrefrigerated ambient temperature storage of eggs on farms for up to 36 h. The present study used an in vitro egg contamination model to assess the ability of small numbers of 4 Salmonella Enteritidis strains and 4 Salmonella Heidelberg strains to penetrate the vitelline membrane and multiply inside yolks during 36 h of storage at either 20 or 30 degrees C. After inoculation onto the exterior surface of the vitelline membrane, all 8 Salmonella strains penetrated to the yolk contents (at a mean frequency of 45.1%), and most strains grew to significantly higher levels (with a mean (log)10 bacterial concentration of 2.2 cfu/mL) during incubation at 30 degrees C. Significant differences in penetration frequency and yolk multiplication were observed between individual strains and between serotypes (Salmonella Enteritidis > Salmonella Heidelberg for both parameters). Penetration and multiplication were significantly less frequent during incubation at 20 degrees C. These results demonstrate that controlling ambient temperatures during prerefrigeration storage may be an important adjunct to prompt refrigeration for limiting Salmonella growth in eggs and thereby for preventing egg-transmitted human illness.

Assessment of diazinon toxicity in sediment and water of constructed wetlands using deployed Corbicula fluminea and laboratory testing.

Constructed wetlands for mitigation of nonpoint agricultural runoff have been assessed for their ability to decrease potential toxicity from associated contaminants. After a simulated runoff event, constructed wetlands positioned in series were used to measure the effects of the organophosphate insecticide diazinon. Water, sediment, and plant samples from five sites were analyzed for diazinon concentrations from 0.5 hours to 26 days; peak concentrations were measured in sediment after 0.5 hours (268.7 microg/kg) and in water and plant tissue after 3 hours (121.71 microg/L and 300.7 microg/kg, respectively). Cholinesterase activity and changes in shell growth were measured from Corbicula fluminea deployed at corresponding sites. Water collected after 9 hours from all wetland sites contained diazinon concentrations sufficient to cause toxicity to Ceriodaphnia dubia, but not to Pimephales promelas. C. dubia survival was decreased in water sampled through 7 days from the site nearest runoff introduction, whereas C. fluminea deployed at this same site experienced 100% mortality after 26 days. Clams from lower sites survived wetland conditions, but growth and ChE activity were significantly decreased lower than that of clams from a control site. C. dubia exposed to water from these sites continued to have decreased survival throughout the 26-day sampling. Sediment sampled from 48 hours through 14 days at the lowest wetland site decreased the laboratory survival of Chironomus dilutus, and sediment from upper sites elicited an effect only on day 26. Although wetland concentrations of aqueous diazinon were decreased lower than toxic thresholds after 26 days, decreased ChE activity in deployed clams provided evidence of residual diazinon effects to deployed organisms.

Pathotyping of Salmonella enterica by analysis of single-nucleotide polymorphisms in cyaA and flanking 23S ribosomal sequences.

The egg-contaminating phenotype of Salmonella enterica serotype Enteritidis was linked to single-nucleotide polymorphisms (SNPs) occurring in cyaA, which encodes adenylate cyclase that produces cAMP and pyrophosphate from ATP. Ribotyping indicated that SNPs in cyaA were linked to polymorphisms occurring in the rrlC and rrlA 23S ribosomal subunits. Phylogenetic analysis of cyaA discriminated between Salmonella enterica serotypes and within serotype Enteritidis. Serotypes Typhimurium, Heidelberg and Enteritidis produced one, three and six cyaA allelic variants, respectively, among the set of 56 isolates examined. Asparagine(702) of CyaA was converted to serine in a biofilm-producing isolate. Statistical analysis was applied to 42 other genes encoding proteins between 800 and 1000 amino acids (aa). Results show that the 848 aa CyaA of serovar Enteritidis evolved by nucleotide substitutions that did not significantly alter the purine-to-pyrimidine nucleotide substitution ratio, which was a characteristic of large genes that was positively correlated with increasing gene size. In summary, these analyses link SNPs occurring in the rrlC-rrlA genomic fragment of S. enterica to genetic drift within S. Enteritidis that is associated with egg contamination.

Hydroponic uptake of atrazine and lambda-cyhalothrin in Juncus effusus and Ludwigia peploides.

Phytoremediation encompasses an array of plant-associated processes known to mitigate contaminants from soil, sediment, and water. Modification of pesticides associated with agricultural runoff includes processes directly associated with aquatic macrophytes in addition to changes in soil geochemistry and associated rhizospheric degradation. Remediation attributes of two vegetative species common to agricultural drainages in the Mississippi Delta, USA, were assessed using atrazine and lambda-cyhalothrin. Concentrations used in 8-d hydroponic exposures were calculated using recommended field applications and a 5% runoff model from a 0.65-cm rainfall event on a 2.02-ha field. While greater atrazine uptake was measured in Juncus effusus, greater lambda-cyhalothrin uptake occurred in Ludwigia peploides. Maximum pesticide uptake was reached within 48h for each exposure and subsequent translocation of pesticides to upper plant biomass occurred in macrophytes exposed to atrazine. Sequestration of 98.2% of lambda-cyhalothrin in roots of L. peploides was measured after 8d. Translocation of lambda-cyhalothrin in J. effusus resulted in 25.4% of pesticide uptake partitioned to upper plant biomass. These individual macrophyte remediation studies measured species- and pesticide-specific uptake rates, indicating that seasonality of pesticide applications and macrophyte emergence might interact strongly to enhance mitigation capabilities in edge-of-field conveyance structures.

Evaluation of eggshell quality of hens infected with Salmonella enteritidis by application of compression.

Eggs collected from hens of different ages and that differed in infection status with Salmonella enteritidis were evaluated for the ability to resist cracking following application of maximum compression load from an Instron materials testing machine. Orally infected 24-wk-old hens that were prepeak produced eggs with significantly lower hardness units (HU) of shells compared with a paired control group (P < or = 0.01). However, 1 of 3 additional infection trials in hens at peak (29 wk) and older hens postpeak (58 wk) showed an increase in HU in one trial and no difference in the other 2 trials. Thus, Salmonella enteritidis may be able to alter HU in a manner that is influenced by multiple factors, which include the age of the hen and the strain used for infection. Hardness was overall a sensitive physiological barometer of age, because readings correlated positively (all R > 0.50) with hens entering peak production, regardless of infection status. Detection of a very low HU reading (<1.0) was indicative of a hairline crack in the egg, which increased in incidence from 0.01% preinfection to 0.08% postinfection. Two other clinical signs noted postinfection in hens were that i) daily egg production significantly increased in older hens, and ii) emaciation was evident in a few hens that were infected by contact. These results suggest that there may be supportive approaches to achieve reduction of S. enteritidis in table eggs that do not rely on culturing.

Evaluated fate and effects of atrazine and lambda-cyhalothrin in vegetated and unvegetated microcosms.

Contaminants such as nutrients, metals, and pesticides can interact with constructed wetlands and existing drainage ditches used as agricultural best-management practices. Our research has shown that the presence of macrophytes and a hydrologic regime aid in the transfer and transformation of pesticides associated with agricultural runoff. This study consisted of application of both atrazine (triazine herbicide) and lambda-cyhalothrin (pyrethroid insecticide) to vegetated and unvegetated microcosms in order to measure the fate and effects of pesticides applied at suggested field application rates. Exposures focused on monocultures of Ludwigia peploides (water primrose) and Juncus effusus (soft rush). Pesticide sorption was evident through concentrations of atrazine and lambda-cyhalothrin in plant tissue as high as 2461.4 and 86.50 microg/kg, respectively. Toxicity was measured in water from unvegetated microcosms for 28 days and in Chironomus tentans (midge larvae) exposed to sediment collected from 3 h to 56 days in microcosms receiving the pesticide combination. The comparative survival of test organisms in this study suggests that effective mitigation of pesticides from runoff can depend on the macrophyte contact and vegetative attributes associated with ditches.

Evaluating acute toxicity of methyl parathion application in constructed wetland mesocosms.

Wetland ecosystems have reduced ambient levels of various organic and metallic compounds, although their effectiveness on agricultural pesticides is not well documented. Five stations within each of two 10 x 50 m constructed wetlands (two vegetated, two nonvegetated) were selected to measure the fate and effects of methyl parathion (MeP). Following a simulated storm event (0.64 cm of rainfall), aqueous, sediment, and plant samples were collected and analyzed spatially (5, 10, 20, and 40 m from the inlet) and temporally (after 3-10 days) for MeP concentrations and for the impact of those concentrations on the aquatic fauna. Aqueous toxicity to fish decreased spatially and temporally in the vegetated mesocosm. Pimephales promelas survival was significantly reduced, to 68%, at the 10-m station of the nonvegetated wetlands (3 h postapplication), with pesticide concentrations averaging 9.6 microg MeP/L. Ceriodaphnia in both the vegetated and nonvegetated wetlands was sensitive (i.e., a significant acute response to MeP occurred) to pesticide concentrations through 10 days postapplication. Mean MeP concentrations in water ranged from 0.5 to 15.4 microg/L and from 0.1 to 27.0 microg/L in the vegetated and nonvegetated wetlands, respectively. Hyalella azteca aqueous tests resulted in significant mortality in the 5-m vegetated segment 10 days after exposure to MeP (2.2 microg/L). Solid-phase (10-day) sediment toxicity tests showed no significant reduction in Chironomus tentans survival or growth, except for the sediments sampled 3 h postapplication in the nonvegetated wetland (65% survival). Thereafter, midge survival averaged >87% in sediments sampled from both wetlands. These data suggest that wetlands play a significant role in mitigating the effect of MeP exposure in sensitive aquatic biota.

Vegetative and structural characteristics of agricultural drainages in the Mississippi Delta landscapes.

Agricultural drainage ditches in the Mississippi Alluvial Delta landscape vary from edge-of-field waterways to sizeable drainages. Ditch attributes vary with size, location and maintenance and may aid in mitigation of contaminants from agricultural fields. The goal of this study was to better understand how vegetative characteristics affect water quality in conveyance structures in the context of ditch class and surrounding land use. Characterization of 36 agricultural ditches included presence of riparian buffer strips, water depth, surrounding land use, vegetative cover, and associated aqueous physicochemical parameters. Vegetation was assessed quantitatively, obtaining stem counts in a sub-sample of ditch sites, using random quadrat method. Physical features varied with ditch size and vegetative diversity was higher in larger structures. Polygonum sp. was the dominant bed vegetation and was ubiquitous among site sizes. Macrophytes varied from aquatic to upland species, and included Leersia sp. and upland grasses (Poaceae family) in all drainage size classes. Percent cover of bed and bank varied from 0 to 100% and 70 to 100%, respectively, and highest nutrient values were measured in sites with no buffer strips. These conveyance structures and surrounding buffer zones are being ranked for their ability to reduce excess nutrients, suspended solids, and pesticides associated with runoff.

Evaluating toxicity of Asana XL (esfenvalerate) amendments in agricultural ditch mesocosms.

Agricultural ditches primarily serve to remove and store excess water associated with irrigation and storm events. The ability of these ecosystems to mitigate potential contaminants is not well understood. Five sites along a 650-m agricultural ditch located in the Mississippi Delta Management Systems Evaluation Area (MDMSEA) were used to measure fate and effects of an esfenvalerate (insecticide) exposure. Following a 0.64-cm simulated storm event, samples were collected from water and sediments and analyzed spatially from five sites and temporally from 0.5 h to 56 d. Results of aqueous toxicity bioassays indicated that lethality progressed downstream throughout all sampling intervals, while sediment toxicity bioassays only elicited biological responses at the point of pesticide application to the ditch (0 m). Significant reductions in survival of Ceriodaphnia dubia and Pimephales promelas in water were measured at the 0-, 20-, and 80-m sites following application. Ten-day solid phase sediment testing of Chironomus tentans indicated persistent toxicity only at the point of application (0 m) and throughout 56 d (mean=14.4% survival). No lethality or significant reduction in midge growth was measured for remaining downstream sites. These measurements were used to evaluate the potential of agricultural ditches to reduce potential deleterious effects of contaminants in agricultural drainage systems that precede receiving streams.

Acute toxicity of methyl-parathion in wetland mesocosms: assessing the influence of aquatic plants using laboratory testing with Hyalella azteca.

Methyl-parathion (MeP) was introduced into constructed wetlands for the purpose of assessing the importance of distance from the source of contamination and the role of emergent vegetation on the acute toxicity to Hyalella azteca (Crustacea: Amphipoda). A vegetated (90% cover: mainly Juncus effuses) and a nonvegetated wetland (each with a water body of 50 x 5.5 x 0.2 m) were each exposed to a simulated MeP storm runoff event. H. azteca was exposed for 48 h in the laboratory to water samples taken from the wetlands at a distance of 5, 10, 20, and 40 m from the pesticide inlet 3 h, 24 h, 96 h, and 10 days following application. Methyl-parathion was detected throughout the nonvegetated wetland, whereas the pesticide was only transported halfway through the vegetated wetland. A repeated-measure three-way analysis of variance (ANOVA) using time, location, and vegetation indicated significantly lower toxicity in the vegetated wetland. Furthermore, the mortality decreased significantly with both increasing distance from the inlet and time (48-h LC50 +/- 95% CI: 9.0 +/- 0.3 microg/L). A significant three-way interaction of time x vegetation x location confirmed higher toxicity at the inlet area of the nonvegetated wetland immediately after contamination. Significant linear regressions of maximum mortality (independent of time) versus distance from the pesticide inlet indicated that 44 m of vegetated and 111 m of nonvegetated wetland would reduce H. azteca mortality to < or = 5%. These results suggest that vegetation contributes to reduced MeP effects in constructed wetlands.