Polychlorinated dibenzodioxins/furans and dioxin-like polychlorinated biphenyls in fish and crustaceans of a recreationally fished estuary, following targeted remediation

Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (dl-PCBs) are a suite of harmful chemicals (hereafter collectively referred to as 'dioxins'), and their emission into aquatic habitats leads to persistent contamination of sediments, aquatic food-webs, and seafoods. Quantifying contaminant levels in seafood species is important for the ongoing management of exposure risk by fishers, particularly after any remediation actions. We present dioxin concentrations in four seafood species (Yellowfin Bream Acanthopagrus australis, Sea Mullet Mugil cephalus, Eastern School Prawn Metapenaeus macleayi, and Eastern King Prawn Penaeus plebejus) in a recreationally fished estuary, in relation to a contaminated site that has undergone a remediation process, partially removing contaminated sediments (Homebush Bay, Port Jackson, New South Wales, Australia). Dioxin concentrations in these species were measured before (2005/6) and after (2015/16) remediation at a range of locations in and around the remediated site. Dioxin concentrations and congener profiles differed substantially among taxa, and concentrations were frequently higher than Australian screening criteria. The two prawn species showed evidence of a decline in dioxin concentrations after remediation, but the fish species only showed a declining dioxin concentration with distance from the contaminated site (not between periods). There were some minor changes in the congener profile for some species following remediation. While there was evidence for greatly reduced dioxin concentrations in prawn species following remediation, the complex patterns for fish were likely affected by environmental changes, species-specific and temporal changes in lipid content, and animal movement patterns. Future monitoring may aid interpretation of the patterns and modelling of exposure risk associated with seafood consumption into the future.

Per- and polyfluoroalkyl substances (PFAS) in little penguins and associations with urbanisation and health parameters

Per- and Polyfluoroalkyl substances (PFAS) are increasingly detected in wildlife and present concerning and unknown health risks. While there is a growing body of literature describing PFAS in seabird species, knowledge from temperate Southern Hemisphere regions is lacking. Little penguins (Eudyptula minor) can nest and forage within heavily urbanised coastal environments and hence may be at risk of exposure to pollutants. We analysed scat contaminated nesting soils (n = 50) from 17 colonies in lutruwita/Tasmania for 16 PFAS, plasma samples (n = 45) from nine colonies, and three eggs for 49 PFAS. We detected 14 PFAS across the sample types, with perfluorooctanesulfonic acid (PFOS) and perfluorohexanesulfonic acid (PFHxS) most commonly detected. Mean concentration of PFOS in plasma was 2.56 ± 4.3 ng/mL ( Collapse

Key Words

• Ecotoxicology
• Genotoxicity
• Human impacts
• Seabird sentinels
• Wildlife health

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MESH Headings

• Male
• Female
• Animals
• Spheniscidae
• Urbanization
• Alkanesulfonic Acids/analysis
• Environmental Pollutants/analysis
• Fluorocarbons/analysis
• Soil
• Sulfonic Acids

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Grants Collapse

Application of in-source fragmentation to the identification of perfluoropentanoic acid and perfluorobutanoic acid in environmental matrices and human serum by isotope dilution liquid chromatography coupled with tandem mass spectrometry

Liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) is the most common analytical technique for per- and polyfluoroalkyl substances (PFASs) research and monitoring. The PFAS identification requires a minimum of two multiple reaction monitoring (MRM) transition ions as quantifier transition ion and qualifier transition ion, respectively. The second transition ion abundance for perfluoropentanoic acid (PFPeA) and perfluobutanoic acid (PFBA) is too low for practical use. A method using the in-source fragment ions as the precursor ion for MRM or pseudo-MRM has been developed and evaluated for PFPeA and PFBA identification in various environmental abiotic and biotic samples including water, soil, sediment, WWTP sludge, fruits, vegetables, egg, macrophytes, fish, dolphin liver and human serum. The PFPeA qualifier MRM transition ion (m/z = 219 > 69) has been successfully applied in all the matrices with spike recoveries (90-125%), signal to noise ratios (>10) and transition ions ratio variation (80-120%). The PFBA qualifier pseudo-MRM transition ion (m/z = 169 > 169) works well in all the matrices except dolphin liver sample. The interpretation of pseudo-MRM results should be with cautions due to lower specificity compared to MRM. In addition, this project indicated under typical chromatographic conditions the MRM isobaric interference does happen frequently to PFPeA quantifier transition ion (m/z = 263 > 219) in serum and fish composite samples, and to PFBA quantifier transition ion (m/z = 213 > 169) in macrophytes, fish composite and dolphin liver samples.

Laboratory batch representation of PFAS leaching from aged field soils: Intercomparison across new and standard approaches

Relating laboratory leaching methods to partitioning and transport of per- and poly-fluoroalkyl substances (PFAS) in field soils is challenging, making estimation of fluxes to groundwater and surface water uncertain. Existing laboratory leaching methods have limitations when assessing field leaching. For 37 aged field soils from five sites historically contaminated with PFAS over decades, we assess PFAS leaching using new and existing laboratory leaching methods to provide alternative methods better reflecting PFAS risks posed by its leaching and movement. Dominant PFAS in the soils were perfluorooctane sulfonic acid, perfluorohexane sulfonic acid, and perfluorohexanoic acid and to a lesser extent perfluorooctanoic acid. Leaching from intact soil cores (Exp 1) was taken to reflect field conditions. These were compared to two new laboratory batch tests, saturate-spin (Exp 2) and saturate-tumble-spin (Exp 3), and two standard approaches; Australian Standard Leaching Procedure (ASLP, Exp 4) and the Leaching Environmental Assessment Framework (LEAF, Exp 5). The tests varied in terms of liquid:soil ratio, tumbling time and pH of the starting solution, with LEAF-1313 conducted across seven pHs (2-12). Correlations between leachate and soil concentrations were highest for Exp 4 and Exp 5 (R² = 0.72-0.98) and lowest for Exp 3 (R² = 0.53). The PFAS mass leached as a fraction of the total increased such that: soil core leaching (27 %) < saturate-spin (30 %) < saturate-tumble-spin (65 %) ≤ LEAF-1313 (65 to 88 % at pH 5-9) < ASLP (90 %). As a fraction of individual PFAS compounds in leachate compared with soil, the shorter chain PFAS (e.g., perfluorobutanoic acid) were higher in the leachate in all tests. Across all tests, the saturate-spin batch test most closely represented intact soil core leaching and therefore potentially provides a measure more analogous of in situ soil leaching at field sites. Other methods would apply to broader applications such as landfill disposal.

Per and polyfluoroalkyl substances (PFAS) at high concentrations in neonatal Australian pinnipeds

Per and polyfluorinated substances (PFAS) exposure was investigated in Australian pinnipeds. Concentrations of 16 PFAS were measured in the livers of Australian sea lion (Neophoca cinerea), Australian fur seal (Arctocephalus pusillus doriferus) and a long-nosed Fur Seal (Arctocephalus forsteri) pup sampled between 2017 and 2020 from colonies in South Australia and Victoria. Findings reported in this study are the first documented PFAS concentrations in Australian pinnipeds. Median and observed range of values in ng/g wet weight were highest for perfluorooctane sulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorononanoic acid (PFNA) in the liver of N. cinerea (PFOS = 7.14, 1.00-16.9; PFOA = 2.73, 0.32-11.2; PFNA = 2.96, 0.61-8.22; n = 28), A. forsteri (PFOS = 15.98, PFOA = 2.02, PFNA = 7.86; n = 1) and A. p. doriferus (PFOS = 27.4, 10.5-2119; PFOA = 0.98, 0.32-52.2; PFNA = 2.50, 0.91-44.2; n = 20). PFAS concentrations in A. p. doriferus pups were significantly greater (p < 0.05) than in N. cinerea pups for all PFAS except PFOA and were of similar magnitude to those reported in northern hemisphere marine animals. These results demonstrate exposure differences in both magnitude and PFAS profiles for N. cinerea in South Australia and A. p. doriferus in Victoria. This study reports detectable PFAS concentrations in Australian pinniped pups indicating the importance of maternal transfer of these toxicants. As N. cinerea are endangered and recent declines in pup production has been reported for A. p. doriferus at the colony sampled, investigation of potential health impacts of these toxicants on Australian pinnipeds is recommended.

Biological and behavioral responses of European honey bee (Apis mellifera) colonies to perfluorooctane sulfonate exposure

Bees provide pollination services to managed and wild ecosystems but are threatened globally due to multiple stressors, including exposure to contaminants. Perfluorooctane sulfonate (PFOS) is a widely detected and persistent contaminant that accumulates and biomagnifies in food chains. In this exposure effect study, small whole colonies of Apis mellifera (1000 bees) were exposed to PFOS using a purpose-built cage system over a 4-week period. The PFOS exposure concentrations were provided to bees in sugar syrup at concentrations detected in the environment, ranging from 0 to 1.6 mg L^-1 . A range of biological and behavioral responses were monitored. Bee tissue, honey, and fecal matter were analyzed using isotope dilution combined with liquid chromatography-tandem mass spectrometry adapted for bee and honey matrix analysis. Bee mortality increased significantly with PFOS exposure at 0.8 mg L^-1  or greater, and brood development ceased entirely at 0.02 mg L^-1  or greater. Colony activity, temperament, hive maintenance, and defense were adversely affected in all PFOS exposure treatments compared with the control, even at the lowest PFOS exposure of 0.02 mg L^-1 . Perfluorooctane sulfonate was detected in bee tissue with a mean bioaccumulation factor of 0.3, and it was also identified in honey and in feces collected from the hive cages. These findings provide the first evidence that PFOS exposure adversely affects honey bee colonies and may transfer to honey. With PFOS contaminating thousands of sites worldwide, our study has implications for exposed bee populations under natural conditions, pollination services, the honey industry, and human health. Integr Environ Assess Manag 2021;17:673-683. © 2021 SETAC.

Evaluation of Residues in Hen Eggs After Exposure of Laying Hens to Water Containing Per- and Polyfluoroalkyl Substances

Per- and polyfluoroalkyl substances (PFAS) have been used in aqueous film-forming foams used in firefighting, resulting in soil and groundwater contamination and leading to human exposure via animal products grown in contaminated areas. The present study reports the relationship between PFAS intake by hens and the PFAS concentrations in the edible parts of eggs. Laying hens were exposed via drinking water to different concentrations of 4 PFAS compounds (perfluorooctane sulfonate [PFOS], perfluorohexane sulfonate [PFHxS], perfluorooctanoic acid [PFOA], and perfluorohexanoic acid) over 61 d. Egg PFAS residues were assessed for a further 30 d after exposure ceased. The target concentrations of PFAS were 0, 0.3, 3, 30, and 300 µg/L for the treatment groups T1-T5, respectively; and PFAS residues were determined from the eggs collected every second day. There was a linear correlation between the PFAS concentrations in the drinking water of hens and those detected in the egg, which could be useful in estimating PFAS concentrations in the egg by measuring water concentrations. Exposure of hens to drinking water with PFAS concentrations below the Australian Government Department of Health limits (PFOS and PFHxS, 0.07 µg/L; PFOA, 0.56 µg/L), and with no other sources of PFAS exposure, is unlikely to result in egg PFAS concentrations that would exceed the 10% limit set by Food Standards Australia New Zealand for human consumption. Environ Toxicol Chem 2021;40:735-743. © 2020 SETAC.

GAPS-megacities: A new global platform for investigating persistent organic pollutants and chemicals of emerging concern in urban air

A pilot study was initiated in 2018 under the Global Atmospheric Passive Sampling (GAPS) Network named GAPS-Megacities. This study included 20 megacities/major cities across the globe with the goal of better understanding and comparing ambient air levels of persistent organic pollutants and other chemicals of emerging concern, to which humans residing in large cities are exposed. The first results from the initial period of sampling are reported for 19 cities for several classes of flame retardants (FRs) including organophosphate esters (OPEs), polybrominated diphenyl ethers (PBDEs), and halogenated flame retardants (HFRs) including new flame retardants (NFRs), tetrabromobisphenol A (TBBPA) and hexabromocyclododecane (HBCDD). The two cities, New York (USA) and London (UK) stood out with ∼3.5 to 30 times higher total FR concentrations as compared to other major cities, with total concentrations of OPEs of 15,100 and 14,100 pg/m³, respectively. Atmospheric concentrations of OPEs significantly dominated the FR profile at all sites, with total concentrations in air that were 2-5 orders of magnitude higher compared to other targeted chemical classes. A moderately strong and significant correlation (r = 0.625, p < 0.001) was observed for Gross Domestic Product index of the cities with total OPEs levels. Although large differences in FR levels were observed between some cities, when averaged across the five United Nations regions, the FR classes were more evenly distributed and varied by less than a factor of five. Results for Toronto, which is a 'reference city' for this study, agreed well with a more in-depth investigation of the level of FRs over different seasons and across eight sites representing different urban source sectors (e.g. traffic, industrial, residential and background). Future sampling periods under this project will investigate trace metals and other contaminant classes, linkages to toxicology, non-targeted analysis, and eventually temporal trends. The study provides a unique urban platform for evaluating global exposome.

Concentrations of some legacy pollutants have increased in South Australian bottlenose dolphins from 1989 to 2014

Information about pollution and its potential impact in Australian marine wildlife is scarce. To fill this knowledge gap, our study investigated concentrations of legacy pollutants as well as naturally produced methoxylated polybrominated diphenyl ethers (MeO-PBDEs) in blubber, liver, kidney and muscle of Indo-Pacific bottlenose dolphins (Tursiops aduncus) from two large inverse estuaries in South Australia from 1989 to 1995 and 2009-2014. Our results show that concentrations of most pollutant classes are relatively low compared to the literature but at the higher end of the ranges reported for marine mammals in Australia. Results for some individuals exceed toxicity thresholds indicative of immunotoxicity in marine mammals. It is important to note that concentrations of some compound classes, particularly PBDEs and polychlorinated biphenyls (PCBs), increased over a time interval of 20 years thereby placing more individuals at risk in recent years. Some of the highest concentrations of persistent organic pollutants (POPs) were measured in juveniles, which may jeopardize their development and the success of future generations. These results indicate that legacy pollutants may play a role in the long-term health of T. aduncus and should be included in biomonitoring efforts.

Emerging and legacy contaminants across land-use gradients and the risk to aquatic ecosystems

Information on potentially harmful emerging and legacy chemicals is essential to understand the risks to the environment and inform regulatory actions. The objective of this study was to assess the occurrence, concentration, and distribution of emerging and legacy contaminants across a gradient of land-use intensity and determine the risk posed to aquatic ecosystems. The land-use intensity gradient considered was: background/undeveloped < low-intensity agriculture < high-intensity agriculture < urban residential < urban industrial. Twenty-five sites were sampled for surface water, sediment, and soil. A total of 218 chemicals were analyzed: pesticides, per- and poly-fluoroalkyl substances (PFAS), polybrominated biphenyls and polybrominated diphenyl ethers (PBDEs), phthalates, and short-chain chlorinated paraffins (SCCPs). The risk posed by the analyzed chemicals to the aquatic environment was measured using hazard quotients (HQs), which were calculated by dividing the maximum measured environmental concentration by a predicted no-effect concentration for each chemical. A HQ > 1 was considered to indicate a high risk of adverse effects from the given chemical. A total of 68 chemicals were detected: 19 pesticides, 18 PFAS, 28 PBDEs, two phthalates, and SCCPs (as total SCCPs). There were no significant differences in the overall chemical composition between land uses. However, the insecticide bifenthrin, PFAS, PBDEs, and phthalates were more frequently found in samples from residential and/or industrial sites, suggesting urban land uses are hotspots and potential large-scale sources of these chemicals. Nineteen chemicals had a HQ > 1; most had a restricted spatial distribution limited to high-intensity agriculture and industrial sites in Melbourne. Bifenthrin and the perfluorooctanesulfonic acid (PFOS) had the highest HQs in residential and industrial sites, suggesting an increased risk to aquatic ecosystems in urban settings. The results of this study will enhance future research, predictive methods, and effective targeting of monitoring, and will help guide regulatory management actions and mitigation solutions.

First observations of perfluorooctane sulfonate occurrence and depuration from Sydney Rock Oysters, Saccostrea glomerata, in Port Stephens NSW Australia

Following the discovery of potential chronic perfluoroalkyl substances (PFAS) contamination of Tilligerry Creek, Port Stephens (New South Wales Australia), sampling was undertaken to confirm the presence, extent and levels of contamination in commercial oyster crops of Sydney Rock Oyster (Saccostrea glomerata) and Pacific Oyster (Crassostrea gigas) grown within the estuary. Among a range of PFAS tested, only perfluorooctane sulfonate (PFOS) was detected. Concentrations of PFOS in oyster tissues for S. glomerata ranged from 1.6μgkg^-1 ww (wet weight) to below the limit of reporting of 0.3μgkg^-1 ww, with concentrations generally decreasing toward the lower reaches of the estuary. The sample of C. gigas tested had a PFOS concentration of 0.71μgkg^-1 ww that was consistent with concentrations observed in nearby S. glomerata. For harvest size (50-60g) S. glomerata, both holding contaminated oysters in a depuration system, and relocation to a non-contaminated area, saw significant reductions in the tissue PFOS concentrations. For oysters held in a depuration system, PFOS depurated at a rate of 0.008h^-1 (0.004-0.019h^-1; 90% CI), which corresponded with a depuration half-life of 87h (35-155h; 90%). A more conservative model (fitted to data that assumed concentrations<LOR were equal 0.5·LOR) predicted a depuration half-life of 131h. PFOS concentrations had fallen to below detectable limits within 162h. Similar decreases were observed in relocated oysters.

Utility of fur as a biomarker for persistent organic pollutants in Australian fur seals (Arctocephalus pusillus doriferus)

Persistent Organic Pollutants (POPs) can cause toxic effects in many species which include endocrine dysfunction, immunotoxicity, developmental defects and neoplasia. Species dominating the upper trophic level are vulnerable to these effects due to bioaccumulation. In Bass Strait, the Australian fur seal (Arctocephalus pusillus doriferus) is an important top order predator and sentinel species for ecosystem health. An alopecia syndrome is seen at high prevalence in juvenile, female Australian fur seals at Lady Julia Percy Island, Victoria, Australia. Previous investigations suggest causality could be due to an endocrine-like toxicant. The alopecia syndrome has significance for thermoregulation and is a likely risk factor for mortality. Fur collected from case (alopecic) and control (unaffected) seals sampled at Lady Julia Percy Island were analysed for POPs. To investigate the utility of fur for monitoring POPs concentrations in pinnipeds, a comparison of POPs concentrations in the fur and blubber of Australian fur seals stranded along the Victorian coast was undertaken. The concentration of selected POPs including polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), dioxin-like polychlorinated biphenyls (dl-PCBs), polybrominated diphenyl ethers (PBDEs) and perfluorooctane sulfonate/perfluorooctanoic acid (PFOS/PFOA) were determined in fur using either High Resolution Gas Chromatography-Mass Spectrometry or Liquid Chromatography-Mass Spectrometry. Results indicate detectable, and in some individuals, elevated levels of dl-PCBs, PCDD/Fs and PBDEs in juvenile fur seals sampled on Lady Julia Percy Island, with significantly higher levels of dl-PCBs in case compared to control seals. Elevated levels of dl-PCBs and PCDD/Fs were found in blubber samples collected from stranded fur seals with significant correlations between blubber and fur concentrations seen, particularly for dl-PCBs. This study discusses the significance of POPs concentrations in relation to the causality of an alopecia syndrome in the Australian fur seal, and assesses the utility of fur as a non-invasive biomarker to monitor POPs exposure in this sentinel species.

Combining 3D human in vitro methods for a 3Rs evaluation of novel titanium surfaces in orthopaedic applications

In this study, we report on a group of complementary human osteoblast in vitro test methods for the preclinical evaluation of 3D porous titanium surfaces. The surfaces were prepared by additive manufacturing (electron beam melting [EBM]) and plasma spraying, allowing the creation of complex lattice surface geometries. Physical properties of the surfaces were characterized by SEM and profilometry and 3D in vitro cell culture using human osteoblasts. Primary human osteoblast cells were found to elicit greater differences between titanium sample surfaces than an MG63 osteoblast-like cell line, particularly in terms of cell survival. Surface morphology was associated with higher osteoblast metabolic activity and mineralization on rougher titanium plasma spray coated surfaces than smoother surfaces. Differences in osteoblast survival and metabolic activity on titanium lattice structures were also found, despite analogous surface morphology at the cellular level. 3D confocal microscopy identified osteoblast organization within complex titanium surface geometries, adhesion, spreading, and alignment to the biomaterial strut geometries. Mineralized nodule formation throughout the lattice structures was also observed, and indicative of early markers of bone in-growth on such materials. Testing methods such as those presented are not traditionally considered by medical device manufacturers, but we suggest have value as an increasingly vital tool in efficiently translating pre-clinical studies, especially in balance with current regulatory practice, commercial demands, the 3Rs, and the relative merits of in vitro and in vivo studies. Biotechnol. Bioeng. 2016;113: 1586-1599. © 2015 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

Isomer-specific investigation of PCDD/F mobility and other fate processes in deep soil cores

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) are highly hydrophobic compounds with low migration potential in soil-water. Nevertheless, they have been occasionally reported in subsurface soils hypothesised as the result of facilitated transport processes with colloids or surfactants, or yet unidentified in-situ formation processes. To date, however, the prevalence of deep soil contamination, involved processes and their kinetics remain poorly understood. This study investigated PCDD/F concentrations and isomer profiles through deep soil cores (to 20 m) from agricultural, industrial and urban sites in Queensland, Australia. Based on isomer profiles, a unique source common to all core soils (regardless of depth) was identified, dominated by octachlorodibenzo-p-dioxin (OCDD). The source was consistent with contamination resulting from pesticide impurities. Elevated PCDD concentrations (μg/kg range) to depths up to ∼4-17 m and a continuous increase of peri-chlorinated (1,4,6,9-substituted) isomers through the cores suggested that vertical transport and lateral dechlorination were key post-depositional processes at these sites. The mobility of PCDDs in the present study is far greater than previously reported in soils in general. High estimated mass transport rates for OCDD in four agricultural cores (3.0-6.2% year(-1)) likely reflect significant levels of facilitating species, including surfactants, and intensive rainfall at these sites. The implications of such extensive subsurface transport of PCDD/Fs for groundwater contamination and load estimates may be significant. If the cores of the present study are assumed representative of the region, a total PCDD/F load in the order of 800 tonnes (1.6 tonnes TEQ) could be present in subsurface Queensland coastal soils.

Polychlorinated biphenyl (PCB) and dioxin concentrations in residential dust of pregnant women

Polychlorinated biphenyls (PCBs) and dioxins are well known for their persistence in the environment. PCBs can be found in the residential environment long after the use of these chemicals in domestic products and industrial processes has ceased. Dioxins have been assessed in Australia as being of very low concentrations. Despite concerns about residential dust as a source of human exposure to persistent chemicals, there has been limited testing of PCBs and dioxins in dust in Australia. As part of an assessment of maternal exposure to a variety of persistent toxic substances, we analysed 30 residential dust samples from a variety of geographical settings for their dioxin and PCB concentrations. PCBs were found in most samples, the median and range concentrations (pg g(-1)) of dominant congeners of PCB were as follows: PCB118 (315; <35.0-29 000), PCB105 (130; 14.0-16 000) and PCB156 (440; <5.00-2800). Dioxin concentrations were generally low with median concentrations for the total sum of dioxin-like polychlorinated dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) of 3.75 pg g(-1) each. There was a very high percentage of non-detects. Concentrations of both PCBs and dioxins were low compared with most studies reporting residential dust concentrations internationally. Age of dwelling was the only factor observed to influence both PCB congener concentrations and dioxin isomers in multivariate regression analyses. No other housing or sociodemographic variables, including proximity to industry, were important predictors in multivariate linear regression models.

Polycyclic aromatic hydrocarbons in road-deposited sediments, water sediments, and soils in Sydney, Australia: Comparisons of concentration distribution, sources and potential toxicity

Sixteen polycyclic aromatic hydrocarbons (PAHs) considered as priority environmental pollutants were analysed in surface natural soils (NS), road-deposited sediments (RDS), and water sediments (WS) at Kogarah in Sydney, Australia. Comparisons were made of their concentration distributions, likely sources and potential toxicities. The concentrations (mg/kg) in NS, RDS, and WS ranged from 0.40 to 7.49 (mean 2.80), 1.65 to 4.00 (mean 2.91), and 0.49 to 5.19 (mean 1.76), respectively. PAHs were dominated by relatively high molecular weight compounds with more than three fused benzene rings, indicating that high temperature combustion processes were their predominant sources. The proportions of high molecular weight PAHs with five or six fused benzene rings were higher in NS than in RDS, whereas the low molecular weight PAHs were higher in RDS. Concentrations of all PAHs compounds were observed to be the lowest in WS. The concentrations of most of the high molecular weight PAHs significantly correlated with each other in RDS and WS. All PAHs (except naphthalene) were significantly correlated in NS suggesting a common PAH source. Ratios for individual diagnostic PAHs demonstrated that the primary source of PAHs in WS and NS was of pyrogenic origin (combustion of petroleum (vehicle exhaust), grass, and wood) while in RDS it was petrogenic (i.e. unburned or leaked fuel and oil, road asphalt, and tyre particles) as well as pyrogenic. The potential toxicities of PAHs calculated using a toxicity equivalent quotient (TEQ) were all low but higher for NS compared to WS and RDS.

In vivo measurement, in vitro estimation and fugacity prediction of PAH bioavailability in post-remediated creosote-contaminated soil

In this study, PAH bioavailability was assessed in creosote-contaminated soil following bioremediation in order to determine potential human health exposure to residual PAHs from incidental soil ingestion. Following 1,000 days of enhanced natural attenuation (ENA), a residual PAH concentration of 871 ± 8 mg kg(-1) (∑16 USEPA priority PAHs in the <250 μm soil particle size fraction) was present in the soil. However, when bioavailability was assessed to elucidate potential human exposure using an in vivo mouse model, the upper-bound estimates of PAH absolute bioavailability were in excess of 65% irrespective of the molecular weight of the PAH. These results indicate that a significant proportion of the residual PAH fraction following ENA may be available for absorption following soil ingestion. In contrast, when PAH bioavailability was estimated/predicted using an in vitro surrogate assay (FOREhST assay) and fugacity modelling, PAH bioavailability was up to 2000 times lower compared to measured in vivo values depending on the methodology used.

Concentrations of polybrominated diphenyl ethers (PBDEs) in residential dust samples from Western Australia

Polybrominated diphenyl ethers (PBDEs) are one of the most common types of brominated flame retardants applied to foams, plastics and textiles to prevent fires. These flame retardants are now regulated and are either banned or being voluntarily phased. However, as these chemicals are persistent humans continue to be exposed. Dust has been identified as an important source of exposure and hence residential concentrations are of interest. The aim of this paper was to determine the concentrations of PBDEs in samples of residential dust from the homes of pregnant women in Western Australia. Thirty residential dust samples were analysed for concentrations of 32 PBDE congeners. Samples were collected from urban and rural areas. PBDEs were detected in all residential dust samples with the sum of the most common PBDEs (Σ(7) of BDEs 47, 99, 100, 153, 154, 183 and 209) ranging from 60.4 to 82400 ng g(-1) (median 571 ng g(-1)). DecaBDE makes up the highest proportion of PBDEs in residential dust, on average 66% of Σ(32)PBDEs. We did not find a relationship between housing characteristics nor the presence of appliances and PBDE concentrations. Dust from urban areas had significantly higher concentrations of BDE-209 and Σ(32)PBDEs than dust from rural areas of Western Australia (p values 0.01 and 0.03 respectively). PBDEs were present in residential dust in Western Australia at concentrations higher than reported previously in Australia. Further investigation of sources with a larger sample size is required to determine associations between PBDE concentrations and potential exposure sources and geographical regions.

Formation of dioxins during exposure of pesticide formulations to sunlight

Chlorinated pesticides can contain impurities of dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), and their precursors, as a result of various manufacturing processes and conditions. As precursor formation of PCDD/Fs can also be mediated by ultraviolet light (UV), this study investigated whether PCDD/Fs are formed when currently used pesticides are exposed to natural sunlight. Formulations containing pentachloronitrobenzene (PCNB; n=2) and 2,4-dichlorophenoxyacetic acid (2,4-D; n=1) were exposed to sunlight in quartz tubes, and the concentration of 93 PCDD/F congeners were monitored over time. Considerable formation of PCDD/Fs was observed in both PCNB formulations (by up to 5600%, to a maximum concentration of 57000 μg ∑PCDD/F kg(-1)) as well as the 2,4-D formulation (by 3000%, to 140 μg ∑PCDD/F kg(-1)). TEQ also increased by up to 980%, to a maximum concentration of 28 μg kg(-1) in PCNB, but did not change in the 2,4-D formulation. Assuming similar yields as observed in the present study as a worst case scenario the use of PCNB in Australia may result in the formation of 155 g TEQ annum(-1), contributed primarily by OCDD formation. This warrants detailed evaluations on the contemporary release of PCDD/Fs to the environment after the use of pesticides. Changes in congener profiles (including the ratio of PCDDs to PCDFs (DF ratio)) suggest that pesticide sources of PCDD/Fs after sunlight exposure may not be recognized based on matching source fingerprints established from manufacturing impurities. These changes also provide preliminary insights into the possible formation routes and types of precursors involved.

Facilitated transport of dioxins in soil following unintentional release of pesticide-surfactant formulations

Colloids such as surfactant micelles can act as transport facilitators for highly lipophilic, generally immobile contaminants in soil. Following a fire at a pesticide facility, this study investigated vertical and lateral migration of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in heterogeneous soil beneath bunded ponds, where contaminated wastewater containing high surfactant loads was stored until remediation. Initially, surface and subsurface soil was obtained during excavation, and subsequently intact cores to 5.7 m were collected. ΣPCDD/F concentrations were elevated in the wastewater (15-81 ng/L) and correspondingly in pond surface soils (6.1-61 ng/g). Maximum ΣPCDD/F concentrations were, however, observed at 2-2.5 m depth (68-130 ng/g), far below their expected mobility range based on physicochemical properties. Congener specific analysis further indicated that PCDD/F mobility was reversed, with the least water-soluble congener migrating to the greatest extent. The presence of higher chlorinated PCDD/Fs throughout a core collected in the direction of groundwater flow indicated subsequent lateral transport. These results provide field evidence for rapid vertical migration (2.4 m in <4 months) of highly lipophilic PCDD/Fs and suggest surfactant facilitated transport as the dominant transport mechanism. Quantification and evaluation of such fundamental changes in contaminant transport and fate in the presence of surfactants is required to identify areas at risk of groundwater contamination.

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) impurities in pesticides: a neglected source of contemporary relevance

Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) may be formed during the manufacture of chlorinated pesticides, and can remain in the products as impurities. However, the contemporary release of PCDD/Fs to the environment from pesticide use is poorly understood. For this study, 27 pesticide formulations were analyzed for PCDD/Fs (n = 23 registered for use in Australia). PCDD/F impurities were present in all samples, ranging from 0.020 to 2100 ng SigmaPCDD/F g(-1) active ingredient (AI). Among current use pesticides, pentachloronitrobenzene (PCNB) contained the highest impurity levels (up to 2000 ng SigmaPCDD/F g(-1) AI and 5.6 ng TEQ g(-1) AI). The quantity of pesticide used in Australia and associated release of PCDD/Fs was estimated for PCNB and phenoxy herbicides (2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenoxybutyric acid (2,4-DB)) using a probabilistic approach. Input parameters to model pesticide use contributed the highest proportions to the variability of the estimated PCDD/F release, and were considered to have the highest uncertainty. Preliminary estimates of PCDD/F release suggest that contaminated pesticides represent an important ongoing PCDD/F source to the Australian environment (10th-90th percentiles for PCNB = 14-42 and 2,4-D/2,4-DB = 0.35-1.6 g TEQ annum(-1)). These results may have global relevance given that many of the pesticides analyzed were imported into Australia, and are used in high volumes in other countries.

A Mental Health Assessment and Support Team for Community Elders in Fife (EAST)

Background

The aging population combined with the increased recognition of the need to assess elderly patients with mental health difficulties in their own environment encouraged service redesign in Fife with the focus on community assessment of older people with mental health needs.

Aims

To establish and assess the functioning of a joint Health and Social Services enhanced assessment and support team (EAST) for community-dwelling elders with significant mental health needs living in a Scottish health region, and to determine the impact of this team on the requirement for acute psychogeriatric hospital services.

Methods

Prospective three-year data collection of service activity involving EAST and the local psychogeriatric acute inpatient and day hospital facilities.

Results

EAST assessed 111 patients during the study, 83% with a diagnosis of dementia. The mean duration of assessment was six weeks with 9% of patients receiving an overnight home assessment and 6% requiring hospital admission. Overall there was a substantial reduction in utilization of both acute psychogeriatric admission beds and day hospital placements.

Conclusions

Multi-agency community assessment of elders with mental health problems can be addressed effectively without recourse to hospital admission, which may allow resource release for further service developments.

Polybrominated diphenyl ethers and polybrominated biphenyls in Australian sewage sludge

This paper presents a brief review of the international scientific literature of polybrominated diphenyl ethers (PBDEs) and polybrominated biphenyls (PBBs) in sewage sludge and a survey of these compounds in sewage sludge from 16 Australian wastewater treatment plants (WWTPs). The SigmaPBDE mean concentration in the Australian study was 1137microgkg(-1) dry weight (d.w.) (s.d. 1116) and ranged between 5 and 4 230microgkg(-1)d.w. The urban mean of 1308microgkg(-1) (s.d. 1320) and the rural mean of 911microgkg(-1) (s.d. 831) are not statistically different and are similar to levels in European sludges. Principal components analysis was performed on the data set and revealed that 76% of the data variation could be explained by two components that corresponded to overall concentration of the pentaBDE and the decaBDE commercial formulations. An analysis of variance was performed comparing PBDEs levels at three WWTPs over the years 2005 and 2006, finding differences between treatment plants (BDE-47) but no significant difference in PBDE levels in the years 2005 and 2006. Low levels of BB-153 were detected in all samples of this survey (n=16); mean 0.6microgkg(-1)d.w. (s.d. 0.5). This compound has rarely been reported in any other study of sewage sludges undertaken outside Australia. This work highlights the need for a risk assessment of PBDEs in sewage sludge when used for land application, taking into account typical levels found in Australian sludges and soils.

Treatment of post-transplant lymphomas with anti-B-cell monoclonal antibodies

The treatment of post-transplant lymphomas still needs major improvements in order to put the patient in remission and to retain graft function. Chemotherapy is far too toxic in these patients. A more specific treatment such as anti-B-cell monoclonal antibody is very promising. The cytotoxic effect of antibody relies mainly on complement-induced and antibody-dependent cellular cytotoxicity; apoptosis may also induce tumor cell death. B-cell antigens expressed on the cell surface are the targets of antibody attack; some specificities may be chosen because of their level of expression or because of signaling induced within the cell. Anti-B-cell antibodies can be produced by genetic engineering in order to be humanized or to carry bispecific Fabs. The efficacy and safety of anti-B-cell monoclonal antibodies (mAbs) in transplant patients have been proven with different antibodies such as anti-CD21/CD24 mAb, anti-CD38 mAb and anti-CD20 mAb. In a retrospective analysis of different centers in France, rituximab (anti-CD20 mAb, Roche Products) achieved an overall 69% remission rate in 34 organ and bone-marrow transplant patients. But the conditions of use of antibody must be better defined, particularly with regard to the immunosuppressive therapy, the type of tumor and the dose of antibody. We must also improve our understanding of the in vivo mechanisms of action of antibody to develop more efficient antibody constructs.

Tomographic Small-Animal Imaging Using a High-Resolution Semiconductor Camera

We have developed a high-resolution, compact semiconductor camera for nuclear medicine applications. The modular unit has been used to obtain tomographic images of phantoms and mice. The system consists of a 64 x 64 CdZnTe detector array and a parallel-hole tungsten collimator mounted inside a 17 cm x 5.3 cm x 3.7 cm tungsten-aluminum housing. The detector is a 2.5 cm x 2.5 cm x 0.15 cm slab of CdZnTe connected to a 64 x 64 multiplexer readout via indium-bump bonding. The collimator is 7 mm thick, with a 0.38 mm pitch that matches the detector pixel pitch. We obtained a series of projections by rotating the object in front of the camera. The axis of rotation was vertical and about 1.5 cm away from the collimator face. Mouse holders were made out of acrylic plastic tubing to facilitate rotation and the administration of gas anesthetic. Acquisition times were varied from 60 sec to 90 sec per image for a total of 60 projections at an equal spacing of 6 degrees between projections. We present tomographic images of a line phantom and mouse bone scan and assess the properties of the system. The reconstructed images demonstrate spatial resolution on the order of 1-2 mm.

Health and housing: a historical examination of alternative perspectives

The deleterious effect of low-quality housing and related environmental factors on the physical and mental health of its residents is a widely accepted phenomenon. Yet low-quality housing continues to exist, partly because of the nature of housing as a commodity in a capitalist system. This paper defines three political-analytic perspectives within which the housing-health relationship can be seen: individualistic, reformist, and dialectical-materialist. These approaches incorporate perspectives on the nature of the relationship as well as strategic implications arising from them. In this context, the housing-health relationship is examined in fact and interpretation from the 1840s to the present. All three perspectives are illustrated by various popular analyses of changes in urban form and housing as well as the housing-health relationship. The dependence of housing quality on the mode of production is shown, demonstrating the weaknesses of the individualistic and reformist perspectives, which assume housing quality to be independent of the mode of production. The different strategic implications of the three perspectives are illustrated in the conclusion in a discussion of the case of lead paint poisoning.

A survey of methohexitone use by anesthetists in the clinical practice of ECT in Edinburgh

The dosage of methohexitone (methohexital) administered by anesthetic staff was surveyed in a consecutive series of 52 patients referred for electroconvulsive therapy (ECT) in routine clinical practice in Edinburgh. Patients were weighed before the first treatment, and the ratio of administered dose to weight in kilograms calculated. Anesthesia was administered by three consultant staff and six nonconsultant staff. In only one patient (2%) was the administered dose within the range recommended by the Royal College of Psychiatrists (0.75-0.9 mg/kg), and in only four patients (8%) were the doses within the range recommended by the American Psychiatric Association (0.75-1.0 mg/kg). In all other patients the dose exceeded these recommended ranges; the average dose was 1.5 (+/- 0.3) mg/kg. The possible implications of these findings are discussed.

The colanic acid gene cluster of Salmonella enterica has a complex history

The colanic acid gene cluster of Salmonella enterica LT2 was sequenced and compared with that of Escherichia coli K-12. The two clusters are similar with divergence slightly higher than average for genes of the two species. The cluster was divided into four blocks by GC content and seems likely to have transferred from a higher GC content species to the ancestor of E. coli and S. enterica. All 19 genes of K-12 and 13 genes of LT2 appear to have undergone random genetic drift with amelioration of the GC content. However, in the case of S. enterica, we believe that the six genes of the GDP-fucose pathway group were replaced relatively recently by genes closely related to those of the original donor species. Two repetitive elements were observed: a bacterial interspersed mosaic element in the intergenic region between wzx and wcaK in K-12 only and a RSA (repetitive sequence element) sequence between wcaJ and wzx in LT2 only.

L-685,458, an aspartyl protease transition state mimic, is a potent inhibitor of amyloid beta-protein precursor gamma-secretase activity

Progressive cerebral amyloid beta-protein (A beta) deposition is believed to play a central role in the pathogenesis of Alzheimer's disease (AD). Elevated levels of A beta(42) peptide formation have been linked to early-onset familial AD-causing gene mutations in the amyloid beta-protein precursor (A beta PP) and the presenilins. Sequential cleavage of A beta PP by the beta- and gamma-secretases generates the N- and C-termini of the A beta peptide, making both the beta- and gamma-secretase enzymes potential therapeutic targets for AD. The identity of the A beta PP gamma-secretase and the mechanism by which the C-termini of A beta are formed remain uncertain, although it has been suggested that the presenilins themselves are novel intramembrane-cleaving gamma-secretases of the aspartyl protease class [Wolfe, M. S., Xia, W., Ostaszewski, B. L., Diehl, T. S., Kimberly, W. T., and Selkoe, D. J. (1999) Nature 398, 513-517]. In this study we report the identification of L-685,458 as a structurally novel inhibitor of A beta PP gamma-secretase activity, with a similar potency for inhibition of A beta(42) and A beta(40) peptides. This compound contains an hydroxyethylene dipeptide isostere which suggests that it could function as a transition state analogue mimic of an aspartyl protease. The preferred stereochemistry of the hydroxyethylene dipeptide isostere was found to be the opposite to that required for inhibition of the HIV-1 aspartyl protease, a factor which may contribute to the observed specificity of this compound. Specific and potent inhibitors of A beta PP gamma-secretase activity such as L-685,458 will enable important advances toward the identification and elucidation of the mechanism of action of this enigmatic protease.

Effects of storage conditions and hemolysis on vitamin E concentrations in porcine serum and liver

Vitamin E (alpha-tocopherol) is an antioxidant vitamin important in protecting unsaturated fatty acids in lipid membranes from peroxidation. Variation in collection, storage, and shipping conditions of samples can potentially lead to breakdown of vitamin E prior to analysis. Therefore, the purposes of this project were 1) to determine the stability of vitamin E in refrigerated and frozen porcine liver and serum and 2) to evaluate the effects of red blood cell (RBC) hemolysis on porcine serum vitamin E concentrations. Porcine liver and nonhemolyzed serum were collected and stored refrigerated or frozen. Samples were analyzed for vitamin E immediately or on days 2, 3, 7, or 14. In addition, porcine RBCs were added to normal serum at concentrations from 1 x 10(6) to 1 X 10(9) RBC/ml and hemolyzed by freeze-thaw prior to analysis for vitamin E or products of lipid peroxidation.

Polycyclic aromatic hydrocarbons in fuel-oil contaminated soils, Antarctica

Where fuel oil spills have occurred on Antarctic soils polycyclic aromatic hydrocarbons (PAH) may accumulate. Surface and subsurface soil samples were collected from fuel spill sites up to 30 years old, and from nearby control sites, and analysed for the 16 PAHs on the USEPA priority pollutants list, as well as for two methyl substituted naphthalenes, 1-methylnaphthalene and 2-methylnaphthalene. PAH levels ranged from 41-8105 ng g-1 of dried soil in the samples from contaminated sites and were below detection limits in control site samples. PAH were detected in surface soils and had migrated to lower depths in the contaminated soil. The predominant PAH detected were naphthalene and its methyl derivatives.

Nursing implications of a vancomycin resistant enterococcus outbreak in a renal unit

Vancomycin Resistant Enterococcus is a difficult organism to treat and is becoming more prevalent world-wide. When it was identified in a busy renal unit, radical and expensive measures were taken to try and control the outbreak. Although these had costs to both patients and staff, the organism was eradicated from the unit.

Towards filmless and distance radiology

To many people radiology is synonymous with films. For 20 years or so, however, it has been possible to capture digitally data traditionally displayed on film, and that was true from the beginning of computed tomography and magnetic resonance imaging too. There is more to picture archiving and communication systems (PACS) than the economies of filmlessness and the ability to modify images. To realise the full potential of PACS requires huge and expensively equipped networks linking the radiology department, hospital wards, outpatient clinics, laboratories, family doctors' clinics, and so on, permitting simultaneous consultations on different sites and almost instant reporting from specialist radiologists at a distance. The data sets that need to be transferred are huge but some of the technical obstacles are now being overcome and the past few years have seen some hospitals move to a filmless state. The more common pattern, though, will be a piecemeal approach. PACS and teleradiology certainly provide a quicker imaging service. How soon a total PACS will save money for a hospital operating budget is less clear.

Outcome of patients discharged from a coronary care unit with a diagnosis of "chest pain not yet diagnosed"

OBJECTIVE

To determine the outcome and 3-year mortality rate among patients discharged from a coronary care unit (CCU) with a diagnosis of "chest pain not yet diagnosed."

DESIGN

Prospective observational cohort study.

SETTING

CCU in a university teaching hospital.

PATIENTS

All 158 eligible patients discharged from the CCU between August 1986 and December 1988. Of them, 27 refused to participate and 31 did not meet the inclusion criteria because of significant co-morbidity or transportation difficulties.

INTERVENTIONS

Evaluation with maximal and thallium exercise stress testing and four major gastrointestinal (GI) investigations: 24-hour intraesophageal pH monitoring, upper GI endoscopy with biopsy, esophageal motility studies and an upper GI barium series.

OUTCOME MEASURES

Results of investigations and incidence of recurrent chest pain, CCU readmission, coronary angiography, coronary artery bypass surgery, myocardial infarction and death at 6, 12, 24 and 36 months after the index visit.

RESULTS

Of the patients enrolled in the study 79% (79/100) had a normal exercise thallium stress test result, 74% (68/92) had an abnormal result from the 24-hour pH monitoring, 87% (82/94) had abnormal endoscopic results, 90% (84/93) had abnormal manometric results, and 89% (83/93) had signs of reflux with the barium series. At 3 years 50 patients had recurrent chest pain and 3 underwent coronary artery bypass surgery. Three patients died over the 3 years, all of noncardiac causes.

CONCLUSION

Many patients discharged from the CCU with a diagnosis of chest pain not yet diagnosed have a high incidence of esophageal disorders and a very low 3-year mortality rate. More research into the early and effective identification and management of patients with such a diagnosis is needed.

Organization of the Escherichia coli K-12 gene cluster responsible for production of the extracellular polysaccharide colanic acid

Colanic acid (CA) is an extracellular polysaccharide produced by most Escherichia coli strains as well as by other species of the family Enterobacteriaceae. We have determined the sequence of a 23-kb segment of the E. coli K-12 chromosome which includes the cluster of genes necessary for production of CA. The CA cluster comprises 19 genes. Two other sequenced genes (orf1.3 and galF), which are situated between the CA cluster and the O-antigen cluster, were shown to be unnecessary for CA production. The CA cluster includes genes for synthesis of GDP-L-fucose, one of the precursors of CA, and the gene for one of the enzymes in this pathway (GDP-D-mannose 4,6-dehydratase) was identified by biochemical assay. Six of the inferred proteins show sequence similarity to glycosyl transferases, and two others have sequence similarity to acetyl transferases. Another gene (wzx) is predicted to encode a protein with multiple transmembrane segments and may function in export of the CA repeat unit from the cytoplasm into the periplasm in a process analogous to O-unit export. The first three genes of the cluster are predicted to encode an outer membrane lipoprotein, a phosphatase, and an inner membrane protein with an ATP-binding domain. Since homologs of these genes are found in other extracellular polysaccharide gene clusters, they may have a common function, such as export of polysaccharide from the cell.

Radiology in the detection and prevention of colorectal cancer

Imaging techniques available for detection of colorectal cancer include barium enema, endoscopy, computed tomography (CT), ultrasound, magnetic resonance (MR) and immunoscintigraphy. Technical advances continue rapidly and prompt frequent re-evaluation of the optimal approach to management of these patients. Barium enema and colonoscopy are the main techniques for evaluation of symptomatic patients, although CT may well assume the predominant role within a few years. Variation in quality of barium enemas and colonoscopy poses a challenge for continuing medical education (CME) activities. Screening of asymptomatic individuals has to be considered separately for high, moderate and low risk population. Recommendations have to be made at present in the absence of evidence of effectiveness. Staging of disease pre-operatively is of limited value. Follow-up after surgery should be primarily clinical although endoscopy, CT, MR, ultrasound and immunoscintigraphy all have specific roles in the evaluation of patients suspected of harbouring recurrent disease.

Radiology in screening for colorectal cancer

This paper is in two sections. The first reports our own experience at McMaster University with screening for colorectal cancer (CRC), and the second discusses some general aspects of screening, and problems with the methods that are available.

A plasmid-borne O-antigen chain length determinant and its relationship to other chain length determinants

We identify a function-controlling O antigen chain length for a plasmid-borne gene, cldpHS-2, harboured by Flexneri strains of Escherichia coli known to cause reactive arthritis. The predicted amino acid sequence of the gene product is very similar to those of other cld genes and that of fepE, thought to be part of the enterobactin iron uptake system of E. coli. The predicted proteins are compared with rfb-associated chain length determinants as a family of related genes.

Structure of the O antigen of Escherichia coli K-12 and the sequence of its rfb gene cluster

Escherichia coli K-12 has long been known not to produce an O antigen. We recently identified two independent mutations in different lineages of K-12 which had led to loss of O antigen synthesis (D. Liu and P. R. Reeves, Microbiology 140:49-57, 1994) and constructed a strain with all rfb (O antigen) genes intact which synthesized a variant of O antigen O16, giving cross-reaction with anti-O17 antibody. We determined the structure of this O antigen to be -->2)-beta-D-Galf-(1-->6)-alpha-D-Glcp- (1-->3)-alpha-L-Rhap-(1-->3)-alpha-D-GlcpNAc-(1-->, with an O-acetyl group on C-2 of the rhamnose and a side chain alpha-D-Glcp on C-6 of GlcNAc. O antigen synthesis is rfe dependent, and D-GlcpNAc is the first sugar of the biological repeat unit. We sequenced the rfb (O antigen) gene cluster and found 11 open reading frames. Four rhamnose pathway genes are identified by similarity to those of other strains, the rhamnose transferase gene is identified by assay of its product, and the identities of other genes are predicted with various degrees of confidence. We interpret earlier observations on interaction between the rfb region of Escherichia coli K-12 and those of E. coli O4 and E. coli Flexneri. All K-12 rfb genes were of low G+C content for E. coli. The rhamnose pathway genes were similar in sequence to those of (Shigella) Dysenteriae 1 and Flexneri, but the other genes showed distant or no similarity. We suggest that the K-12 gene cluster is a member of a family of rfb gene clusters, including those of Dysenteriae 1 and Flexneri, which evolved outside E. coli and was acquired by lateral gene transfer.

Identification of L-tryptophan derivatives with potent and selective antagonist activity at the NK1 receptor

As part of a program of screening the Merck sample collection, N-ethyl-L-tryptophan benzyl ester was identified as a weak antagonist at the substance P (NK1) receptor. Structure-activity studies showed that the indole ring system could be replaced by 3,4-dichlorophenyl, alpha- or beta-naphthyl, or benzthiophene with retention or only small loss of affinity. It was found that acylation of the tryptophan nitrogen gave compounds with higher affinity than N-ethyl or other basic amines. Optimization of substitution on the benzyl ester led to the identification of the 3,5-bis-(trifluoromethyl)benzyl ester of N-acetyl-L-tryptophan 26 as a potent and selective substance P receptor antagonist. Compound 26 blocked substance P induced dermal extravasation in vivo and was the most potent compound from this structurally novel class of antagonists which further adds to the diversity of small molecules that bind to the (NK1) receptor.