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Managed realignment (MR) is a ‘soft’ engineering technique that involves the deliberate landwards retreat of the existing line of coastal defence and subsequent tidal inundation of land. Managed realignment has been established worldwide for over 30 years and its goals may include habitat restoration, recovery of biodiversity and sustainable coastal defence. In southeast England in particular, an increasing number of MR sites (20–110 ha) have been commissioned in the last decade in response to increasing coastal habitat loss and sea-level rise. Following initial sea wall breaching and site flooding, monitoring of these sites is usually carried out for a period of 5 years and during this time changes in ecosystem structure can be easily observed. However, there is a poor understanding of the long-term effects of flooding on soil physicochemical parameters including sediment geochemistry and geochemical cycling, nutrient fluxes and soil maturation processes. Such physical and chemical changes may continue to take place over time-scales exceeding 5 years and therefore current monitoring practices may not be sufficient. This paper examines the changes in the physicochemical parameters of sediments in vertical core sections at the Orplands Farm MR site, Blackwater Estuary, Essex, 8 years after its flooding in 1995. Post-breach sediment accumulation rates at the site have been determined and a multi-proxy approach has been used to identify a pre-breach land surface. Soil development and the vertical distribution of saltmarsh plants following breaching have also been examined. The species saturation index approach has been used to provide an indication of the success of MR at this site. The pre-breach land surface was identified at 4–6 cm depth indicating a sediment accumulation rate ca. 0.75 cm a?1 since the site was breached in 1995. This sedimentation rate exceeds the regional sea-level rise of 0.1–0.3 cm a?1 and hence marsh development at the site is expected to continue in the short term. The examination of physicochemical parameters with depth indicates that the pre-breach land surface forms a barrier that may inhibit vertical tidal flushing, nutrient transfer and contaminant removal. The vegetation was mostly a pioneer and low-mid marsh assemblage typical of the area, although the species saturation index is low compared to other European sites and this may be attributed to a range of factors including poor drainage at the site and reduced seed availability.

On exposure to carbon dioxide (CO2) at a pressure of 3 bars, compacts formed from pressed ground slag, and 12.5 weight percent water, were found to react with approximately 18% of their own weight of CO2. The reaction product formed was calcium carbonate causing the slag to self-cement. Unconfined compressive strengths of 9MPa were recorded in carbonated compacts whereas strengths of1 MPa were recorded in non-carbonated slag compacts. As molten stainless steel slag containing dicalcium silicate (C2S) cools it can undergo several phase transitions. The final transformation from the beta-polymorph to gamma-C2S is accompanied by a volume change that causes the slag to self-pulverise or 'dust'. As a consequence of this the fine grained portion of the slag contains more of this phase whilst the coarser particles of the slag contain more of the calcium magnesium silicates that contribute the bulk of the waste. The fine fraction (125 microm) of the slag when ground is found to react to the same extent as the ground bulk slag and produces compacts with equivalent strength. A coarser fraction (4-8 mm) when ground to a similar grading does not react as extensively and produces a weaker product. Additions of ordinary Portland cement (OPC) at 5 and 10 percent by weight did not alter the degree of reaction during carbonation of the bulk slag or ground fine fraction, however the strength of the 4-8 mm fraction was increased by this change.

The acid neutralisation capacity test is widely used to assess the long‐term performance of waste materials prior to disposal. Samples of fixed mass are exposed to increasing additions of nitric acid in sealed containers and the resultant pH is plotted as a titration curve. In this work, the acid neutralisation capacity test was used in the assessment of an accelerated carbonated stainless steel slag. Difficulties arose in applying the test procedure to this material. This was largely because of the raised pressure from significant volumes of released carbon dioxide trapped in the sealed sample containers, causing an alteration to leachate pH values. Consequently, the acid neutralisation capacity test was modified to enable testing of samples in equilibrium with the atmosphere. No adverse effects on the results from testing of a carbonate free material were recorded

Total metal concentrations in surface sediments and historically contaminated sediments were determined in sediment cores collected from three estuaries (Thames, Medway and Blackwater) in south-east England. The partitioning behaviour of metals in these sediments was also determined using a sequential extraction scheme. These data were then compared with sediment quality values (SQVs) to determine the potential ecotoxicological risk to sediment dwelling organisms. When total metal concentrations in surface sediments are examined, no risk to biota in any of the estuaries is indicated. However, when historically contaminated sediments at depth are also considered, risks to biota are apparent and are greatest for the Thames, followed by the Medway and then the Blackwater. This suggests that regulatory authorities should examine vertical metal profiles, particularly in estuaries that are experiencing low sediment accumulation rates where historically contaminated sediments are in the shallow sub-surface zone and where erosion or dredging activities may take place. When metal partitioning characteristics are also considered, the risk to biota is comparable for the Medway and the Blackwater with the potentially bioavailable fraction presenting no ecotoxicological risk. Conversely, over 70% of metals are labile in the Thames Estuary sediments and toxic effects are probable. This suggests that the application of SQVs using total sediment metal concentrations may over- or under-estimate the risk to biota in geochemically dissimilar estuarine sediments. Keywords: sediment quality values, estuarine sediments, metal contamination, partitioning, sequential extraction

Recent changes in the UK's coastal defence strategy have resulted in the introduction of Managed Realignment (MR), a technique which attempts to establish salt marshes on low-lying coastal farmland. This work investigates the impact of MR, in particular on the interactions between sediment movement, changes in heavy metal concentrations and salt marsh development. Pre- and post-inundation samples were collected and analysed between 1995 and 1997. Sediment transport patterns (1996) demonstrated that sediment particles were distributed by tides around the site, resulting in a change in the spatial distribution of the metals which was related to the sediment particle size distribution. Despite the presence of some metal contaminants found within the MR site, vegetated salt marsh has developed since 1997. However, heavy metals such as Cu, Mn, Ni, Pb and Zn exhibited relative depletion in the sediment developing with salt marsh in 1997, which is in agreement with data indicating that concentrations of metals within sediments is related to frequency of tidal inundation. During initial development of the site, sediment transport was the main factor controlling metal distribution, however, subsequently the frequency of tidal inundation became the most significant factor. Further work may allow for prediction of how future MR sites will develop with respect to redistribution of sediments and subsequent transport of contaminants in the dissolved phase.

The aggregation behaviour of two ethylene oxide–propylene oxide–ethylene oxide block copolymers [PE182:(EO) 6 (PO) 34 (EO) 6 and PE333:(EO) 17 (PO) 60 (EO) 17 ] has been investigated using high sensitivity differential scanning calorimetry. The thermal data obtained was examined using previously outlined procedures [I. Patterson, J. Armstrong, B. Chowdhry, S. Leharne, Langmuir 13 (1997) 2219; B.Z. Chowdhry, M.J. Snowden, S.A. Leharne, J. Phys. Chem. 101 (1997) 10226]. These data analysis routines have revealed the existence of a small dissociation transition within the thermal envelope of the overall aggregation transition. The transition appears to be associated with the thermally induced break-up of large aggregates and occurs simultaneously with or slightly before the micellar aggregation of the block copolymers. A reasonable linear relationship exists between the van’t Hoff enthalpy and T 1/2 (the temperature at which the transition is half completed) using the data obtained for both copolymers, which suggests that the origin of the dissociation transitions in both copolymers is the same.

Salt marshes have recently been considered to be a major part of the coastal system and have played a key role in the development of the UK coastal management strategy. Managed Retreat (MR) is a process aimed to restore salt marshes by realignment of the seawalls allowing tidal inundation of low value agricultural land. The resultant marshes are expected to function both as an integral part of the flood defence system and as an ecological conservation area. We report on the effects of salt marsh restoration on metal and nutrient loading of the sediment at the Orplands Farm MR site, Essex, UK. Surficial grab and sediment cores were collected from the two fields that comprise the site. The heavy metals, Cd, Cr, Cu, Hg, Pb, Ni and Zn were analysed to determine changes in anthropogenic inputs to sediments. The major ions, Al, Ca, Fe, K, Mg, Mn and Na were also monitored to identify changes in sediment geochemistry. Analysis of the cored sediments after inundation for Na and Sr demonstrated that penetration of estuarine water had, within 2 yr of exposure, reached an average depth of 20 cm. The study observed that input of heavy metals had occurred to the sediments with the most significant being that of Pb, however increases were also observed for Cr and Cu. However, concentrations of Cd in the MR sediments decreased from 1995 to 1997. For the major metals within both fields it was found that the dominant changes were those of enrichment of marine associated metals, Ca, K, Mg and Na via inputs from tidal inundation. The concentration of Ca in the sediments was further enriched by the deposition of carbonates to the sediments. One field demonstrated a significant loss of Fe from sediments which corresponded to changes in redox potential of the sediments. Differences observed in geochemical profiles between the two fields of the site were attributed to differences in land use prior to flooding.

Concentrations of total mercury (T-Hg) were measured in eel and roach from five selected rivers in East Anglia, U.K, to determine Hg bioaccumulation in fish throughout the region. Levels of T-Hg in sediment and river water were also analysed to assess their potential as pathways to the fish. Accumulated Hg levels in River Yare eel and roach continue to exhibit a strong positive relationship with surface sediment Hg levels, which are declining with time. Mercury in muscle from all sampled fish were below the limit set by the EU Directive (93/351/EEC). Analysis of muscle:liver (M:L) ratios confirm that eel from all sites are in equilibrium with their environment. Various statistical methods (single factor analysis of variance, Spearman's correlation coefficients) were performed on the experimentally derived data on mercury concentrations in fish flesh. Significant correlations were noted for accumulated Hg in fish flesh with length and weight in eel, and length, weight and age in roach.

Bulk deposition and soils were analysed for total mercury (T-Hg) from five sites in East Anglia, U.K., in order to evaluate atmospheric deposition as a source of Hg to the region, and to determine whether Hg in soils constitutes a source of Hg to fish. Levels of Cr, Cu, Ni, Pb and Zn were also measured in soils to determine the strength of association with Hg. Average mercury concentrations in soils were 0.135 mg kg−1 and were above the previously reported UK average of 0.098 mg kg−1. All sites revealed an increasing north to south gradient of anthropogenic heavy metal loading to surface soils with enhanced loading for Hg, Cu, Pb, and Zn at the River Yare location. Levels of T-Hg in bulk deposition displayed a similar gradient, averaging 89 ng l−1 for the region, suggesting atmospheric deposition as a likely source of Hg to soils and biota (fish) in East Anglia.

Phosphorus trends in the Thames Catchment have been investigated, and the relation between phosphorus, flow and phytoplankton blooms evaluated. Temporal and spatial trends in phosphorus concentrations were examined in three rivers, the Thames, Blackwater and Kennet, which have a diverse range of surrounding land use. Phosphorus levels were generally found to be high, averaging 0.99 mg/l PO4-P with a maximum of 6.70 mg/l PO4-P, particularly in relation to urban areas where effluent discharge was a significant source. A strong seasonal component relating to flow was evident. The relation between phosphorus, flow and chlorophyll-a (used as the measure of algal abundance) was analysed by regression analysis. Neither phosphorus nor flow appeared to be limiting phytoplankton growth, probably because phosphorus concentrations were much greater than levels likely to be limiting. There was a clear relation between phosphorus and phytoplankton growth, with peak values of phosphorus occurring after the phytoplankton maxima. Cycles of algal assimilation and decomposition readily explain this relationship.

The muscle tissue total mercury (THg) and organomercury (OrHg) concentrations of eel (Anguilla anguilla) and roach (Rutilus rutilis) from the Hg-contaminated River Yare and the uncontaminated Ormesby Broad were compared to their respective bed sediment THg and OrHg concentrations in order to determine if fish in the River Yare had begun to approach 'background' levels. While eel from the Yare had higher flesh concentrations (260 μg kg-1) than those from Ormesby Broad (102 μg kg- 1), roach were found to have similar concentrations regardless of location (55 and 54 μg kg-1 for Yare and Ormesby respectively). However, roach in the Yare had significantly higher body burdens of Hg and organomercury, which when analysed over time (1985–95) showed a decreasing trend approaching the levels observed in fish from Ormesby Broad, suggesting that roach are an overall better biomonitor of contamination then eel. This said, the elevated levels of Hg found in fish from Ormesby Broad indicate the existence of a diffuse source such as atmospheric deposition to the surface waters of East Anglia.

The photochemical transformation of the chlorophenoxy herbicide MCPA was investigated under a variety of reaction conditions using distilled water, Thames river water and solutions of naturally occurring photosensitizers. Under low intensity UV (300–450 nm), MCPA was transformed in river water with a pseudo first-order k exp of 0.029 h −1 and a t 1/2 of 23.8 h. In contrast, transformation in distilled water was insignificant, with a first-order experimental rate constant k exp of 0.002 h −1 and an experimental half-life ( t 1/2 ) of 309 h. Under sunlight (late September to early October, 51°N), MCPA was transformed in river water with a pseudo first-order k exp of 0.009 h −1 and an experimental t 1/2 of 7 days. (However, as experiments were conducted in test-tubes, this experimental t 1/2 needs to be multiplied by a factor of 2 to provide an estimate of t 1/2 for the flat surface of a natural water body.) MCPA was also degraded under low intensity UV in the presence of nitrate, nitrite and humates tested singly and in combination in distilled water. Thus, MCPA is photo-oxidized in the presence of hydroxyl radicals, which are generated by nitrate and nitrite following absorption of UV light and also by photo-oxidants generated by humates. In tests where combinations of sensitizers were varied over environmental concentrations, the pseudo first-order k exp ranged from 0.03 h −1 (s.e. 0.0008) to 0.048 h −1 (s.e. 0.0022). The results indicate that although hydroxyl radicals produced by nitrate and nitrite appear to enhance rates of photo-oxidation, their relative importance is significantly diminished in mixtures of sensitizers due to scavenging of hydroxyl radicals by humates. Thus, photo-oxidants generated by humates appear to be of greater environmental significance than hydroxyl radicals in the phototransformation of MCPA.

The contaminants Hg and Cu, as well as Fe, Mn and K were sequentially extracted from upland disposed dredge spoil using DTPA and 10% nitric acid. Concentrations of these metals in aerial plant tissue and roots of Urtica dioica growing on the dredge spoil were also determined and used to correlate the biological absorption coefficients (BACs) and mobile element absorption coefficients (MACs) with soil extractable metals. DTPA extractions were most suitable for prediction of aerial plant tissue uptake of Cu, Mn and K whilst total Hg and Fe soil concentrations were correlated with plant root BACs and MACs. A laboratory bioassay using Eisenia fetida was also used to assess the potential biological uptake of the contaminants. Both Hg and Cu were accumulated by the worms, but interpretation of the results was hampered by the inherent difficulties of such active biomonitoring.

Increases in industrial mercury (Hg) emissions in recent years have led many researchers to believe that Hg from the atmosphere constitutes a main source of Hg to aquatic biota in the absence of point source discharges. Established background levels for fish (0.2–1.0 mg kg-1) now exceed the pre industrial level of 0.15 mg kg-1, suggesting an anthropogenic origin. This review of recent literature illustrates how levels of mercury (Hg) species in the atmosphere are effectively transported into the aquatic arena, where chemical parameters combine to determine bioaccumulation rates in fish. Limited studies on methyl mercury (MeHg) in precipitation shown that concentrations average from 5% of total-Hg (T-Hg), to 1% in industrial regions. Observations of increased Hg is snow and precipitation from the Arctic Circle, related to poleward atmospheric circulation patterns, also demonstrate a spring maximum accompanying ozone depletion. Increases in oxidants and soil derived Hg in the atmosphere during the summer best explain summer Hg maximums observed in precipitation, while increased temperatures raise fish metabolism increasing Hg uptake through respiration and ingestion rate. The major route of entry for MeHg to fish appears to be biomagnification, after input from precipitation, runoff and inlake methylation. Regions buffered against acid precipitation maintain low fish-Hg levels by reduced MeHg production and maintaining gill function. When considering the bioaccumulation of Hg in fish this study shows that there are many variables to consider, not all of which originate from inside the aquatic arena. Both catchment and atmospheric processes combine with aquatic variables to dictate the overall levels of MeHg observed in fish tissue. There now appears to be sufficient knowledge to develop an axiom for the identification of aquatic systems likely to be susceptible to bioaccumulation from atmospheric derived Hg.

The Blackwater Estuary, Essex, UK is the primary site for the investigation of Managed Retreat: a coastal management technique aimed at the restoration of salt marshes. The success of Managed Retreat trials will be judged by the development of healthy salt marsh communities. Accretion of sediments is a key part of this development. The metal content of accreting sediments may be significant in salt marsh development and has environmental importance. Therefore, information on estuarine sediment geochemistry in the Blackwater Estuary will be valuable in interpretation of the geochemical development of Managed Retreat sites. The spatial distribution of 15 metals in the sediments of the estuary has been assessed by the use of the multivariate statistical techniques: cluster analysis; multidimensional scaling; principal component analysis; and canonical variate discriminant analysis. The assessment indicated a general landward to seaward decrease in heavy metal concentrations in the estuary. This was the effect of elevated concentrations of heavy metals, particularly Pb, Zn, Cd and Cu, at the head of the estuary resulting from specific discharges associated with the congregation of anthropogenic activity in this zone. In comparison, sediments in the lower estuary, where Managed Retreat schemes have been instigated, were less contaminated. However, heavy metal concentrations were elevated in the lower estuary at a site of enhanced deposition, which was proximal to a localized source of metals. This has implications for concentrations of metals incorporated into sediments at Managed Retreat sites in the lower estuary where accretion is being actively promoted. A depletion of calcium was observed in salt marshes as compared to mudflats throughout the estuary.

‘Managed retreat’ is a salt-marsh restoration technique which is under experimental implementation in the UK. The technique involves the engineered tidal inundation of coastal land in front of re-aligned flood defences. Salt marshes developed by this method are intended to act as hydraulic buffers in front of coastal defences and to provide zones of environmental enhancement. Two managed retreat trials were instigated in 1995 on the Blackwater Estuary, Essex, UK. In June 1995, two months after breaching the seawalls, the initial environmental impact and geochemical development of the Orplands managed retreat site were investigated by surveys of tidal exchanges. Tidal stage curves and quantities of exchange were determined by four hydrological surveys at the extremes of a neap-spring tidal cycle, and the chemistry of exchanges was investigated by water sampling during these surveys.

Partitioning of metals between dissolved and particulate sedimentary phases provides useful information which can be used to assess their mobility and sources. Bioavailability and toxicity has also been found in many cases to be related to metal partitioning. Sediment cores were taken from salt marsh areas in the Thames Estuary and along the Essex and North Norfolk coasts, and porewaters were separated by centrifugation and filtration. Concentrations of Cd, Cu, Fe, Mn, Ni and Pb in the porewaters, and in HCl/HNO3 digests of the total sediment, were determined by AAS. The order of metal mobility showed inter-site differences, indicating that the partitioning characteristics were influenced by physico-chemical and hydrodynamic controls. These inter-site differences were reflected in the partitioning distribution of Mn and the sediment redox potentials. Cadmium showed the strongest tendency to partition towards dissolved phases, and porewater concentrations decreased in the Essex salt marshes with increasing...

The session on Membrane Transport was a lively, interactive one with substantial audience participation in the discussion periods. Progress in this area of amino acid science is rapid as the genes encoding the transporter proteins are being cloned and characterized. The contributors to the platform session represented institutions from several countries giving the meeting a truly international flavor. Most of the participants contributed articles to this volume. The platform speakers were Dr. John McGivan (United Kingdom), Dr. Marcal Pastor-Anglada (Spain), Dr. Bruce Stephens (USA), Dr. G. Gazzola and Dr. V. Dall'Asta (Italy), Dr. Carol MacLeod (USA), Miss Maria Rivera-Correa (Puerto Rico), Dr. Ellen Closs (Germany), Dr. Manuel Palacin (Spain), Dr. Ovidio Bussolati (Italy), Dr. Suresh Tate (USA), Dr. S. Nakamura (Japan).

The majority of mammalian cationic amino acid transport is mediated by the transport system y(+) which facilitates Na(+) independent cationic amino acid (arginine, lysine,ornithine) transport and Na(+) dependent zwitterionic amino acid (glutaminehomoserine) transport. Other transport systems y(+)L, b(0,+) and B(0,+) also mediate cationic amino acid transport. Their broad substrate specificities and overlapping expression patterns confound biochemical analysis. The isolation of cDNA clones has permitted an analysis of their regulation and opens the opportunity to define the role of each protein in specific cell types. Two genes,Cat1 andCat2 encode transporters with properties similar to the y(+) transport system. Thecat2 gene from the mouse encodes two distinct proteins. mCAT2, and mCAT2A via alternate splicing; each protein has distinctly different transport properties. The regulation of mCAT1, mCAT2 and mCAT2A proteins are reviewed here. The implications of this gene specific regulation on cationic amino acid transport is discussed.

Mercury mobilization off of aquifer sediments by acid rain, road salt runoff and fertilizer solutions is investigated using column and batch equilibria experiments. Sediments from the Kirkwood Cohansey aquifer System, New Jersey are used to determine the mobilization potential of mercury due to changing infiltration water chemistry. In a series of batch equilibria and column experiments mercury contaminated sediments were treated with a dilute nitric acid solutions, 20-20-20 fertilizer, super phosphate fertilizer and dilute sodium chloride solutions. Mercury mobilization is enhanced by solutions containing sodium chloride and 20-20-20 fertilizer. These solutions can remove up to 90% of the mercury sorbed to the sediments. Mercury mobilization by phosphate fertilizer and acid rain proceeds at a slower rate and only 30% of the mercury is removed. It was found that irrigation of the sediments following treatment with 20-20-20 fertilizer or sodium chloride increased mercury mobilization associated with the de...

Because a water sample collected from a well is an integration of water from different depths along the well screen, measured concentrations can be biased if analyte concentrations are not uniform along the length of the well screen. The resulting concentration in the sample, therefore, is a function of variations in well-screen inflow rate and analyte concentration with depth. A multiport sampler with seven short screened intervals was designed and used to investigate small-scale vertical variations in water chemistry and aquifer hydraulic conductivity in ground water contaminated by leaded gasoline at Galloway Township, Atlantic County, New Jersey. The multiport samplers were used to collect independent samples from seven intervals within the screened zone that were flow-rate weighted and integrated to simulate a 5-foot-long, 2.375-inch-outside-diameter conventional wire-wound screen. The integrations of the results of analyses of samples collected from two multiport samplers showed that a conventional 5-foot-long well screen would integrate contaminant concentrations over its length and resulted in an apparent contaminant concentration that was as little as 28 percent of the maximum concentration observed in the multiport sampler.

A new method of collecting samples of unsaturated-zone water for quantitative analysis for a volatile organic compound, trichloroethene (TCE), was compared to three other, previously described sampling methodologies in the laboratory and in the field. In the laboratory, prepared water samples containing TCE in a known concentration (20 μg/L) were sampled repeatedly by using each of the four methods to quantify method precision and accuracy.

Cisplatin (DDP) is the most effective drug for the treatment of human ovarian cancer, but the mechanisms that determine sensitivity to the cytotoxic action of DDP are not well understood. Treatment of two human ovarian carcinoma cell lines with epidermal growth factor (EGF) simultaneously increased sensitivity to DDP and caused a persistent change in morphology in the absence of any mitogenic effect. Sensitization to DDP was shown to be dependent on both EGF concentration and EGF receptor number in C127 mouse fibroblasts expressing the human EGF receptor after transfection with a pBPV plasmid construct containing the human EGF receptor gene under control of the transferrin receptor 3'-inducible regulator. Sensitization of human ovarian carcinoma cells to DDP was not blocked by inhibition of protein synthesis. EGF did not enhance sensitivity to DDP or alter morphology in DDP-resistant human ovarian carcinoma cells despite the presence of functional EGF receptors on these cells. These results showed that elements of the signal transduction pathway activated by EGF determined cellular sensitivity to DDP, and that a DDP-resistant phenotype is associated with a defect in this signal transduction pathway.

Quicklime mixing is an established solidification/stabilization technique to improve mechanical properties and immobilise contaminants in soils. This study examined the effects of quicklime mixing on the concentrations and leachability of petroleum hydrocarbon compounds, in two natural soils and on a number of artificial sand/kaolinite mixtures. Several independent variables, such as clay content, moisture content and quicklime content were considered in the study. After mixing the soils with the quicklime, pH, temperature, moisture content, Atterberg limits and concentrations of petroleum hydrocarbon compounds were determined on soil and leachate samples extracted from the treated soils. Significant decreases in concentrations of petroleum hydrocarbon compounds were measured in soils and leachates upon quicklime mixing, which may be explained by a number of mechanisms such as volatilization, degradation and encapsulation of the hydrocarbon compounds promoted by the quicklime mixing. The increase in temperature due to the exothermic hydration reaction of quicklime when in contact with porewater helps to volatilize the light compounds but may not be entirely responsible for their concentration decreases and for the decrease of heavy aliphatics and aromatics concentrations.

The Cat family of genes have revealed unexpected complexity and regulation. The first 5 years of research have been productive, yet many important questions remain to be addressed. A major problem for the field of amino acid transport is a severe paucity of data on the structure of these proteins and their arrangement in membranes. There is a need for epitope-specific antisera to distinguish the mCAT2/2A proteins and reagents that will specifically block transport to each of these proteins. The question of gene redundancy will be answered by using genetic approaches such as targeted gene ablation, tissue-specific gene knockout and transgenic overexpression. From this information and more physiological analysis, it will be possible to determine the role and significance of these transport proteins.

Five novel complementary DNA (cDNA) clones which are differentially expressed between two closely related T lymphoma cell clones were isolated using subtraction-enriched differential screening. SL12.4 cells, from which the cDNAs were isolated, have characteristics of thymocytes at an intermediate stage in development and cause prominent extranodal ovarian tumors in syngeneic animals. A sister cell clone, SL12.3, derived from the same tumor, has a distinct phenotype and causes more aggressive, diffuse lymphomas. Four of the five novel genes are expressed in normal thymus, activated spleen cells, or gut-associated lymphoid tissue. The DNA sequence and predicted protein sequence are presented for one of the novel cDNA clones. This novel cDNA clone detects mRNA in normal thymus, gut-associated lymphoid tissue, and ovarian tissue. The predicted protein has four putative transmembrane-spanning regions. The expression of the transcript is repressed in somatic cell hybrids formed from SL12.4 cells fused with three different T lymphoma cell lines which lack detectable mRNA complementary to the novel cDNA clone. This trans-negative regulation suggests that the expression of the gene is regulated by repressional mechanisms.

Sediment cores were collected from the Tilbury Tidal Basin in the Thames Estuary to determine the depositional history of metals in the estuary. Profiles of metals in sediments deposited in the lower Thames Estuary show a 30–50% decrease in concentration for Ag, Cd, Cu, Pb, and Zn, and a 70% decrease for Hg in recent decades. Historic depth soundings data showed the decreases in metal concentrations occurred between 1944 and 1966. The decline in sediment metal concentrations has been attributed to reduced inputs to the estuary, following updating of the major sewage treatment works in 1959 and 1963. This is indicated by the through-core distribution of Mn which implies that prior to 1960 the sediments were deposited in anoxic conditions, which subsequently improved. An increase in Mn concentrations observed in one of the cores has been attributed to increases in the dissolved oxygen of the estuarine waters resulting from the increased efficiency of the sewage treatment works.

A sequential extraction method was employed to extract the metals Al, Ag, Cd, Co, Cr, Cu, Pb, Fe, Li, Mn, Ni, and Zn from a 10-m sediment core taken from the Tilbury Basin on the Thames Estuary. Characteristics of the observed metal partitioning distributions were attributed primarily to the composition of the estuarine waters at the time of deposition. For some metals, a decrease in the bulk sediment metal concentrations from a depth of −6.59 m ODN to the surface was also observed in one of the solid phases. This was the case for Cr, Cu, and Pb extracted from the organic phase and for Zn extracted from the carbonate phase. This decrease in sediment concentrations is thought to reflect reported improvements to water quality in this region of the Thames Estuary in the early 1960s, following updating of major sewage treatment works (STW) approximately 20 km upstream. These findings give an indication of the influence of estuarine inputs from STW on metal partitioning distributions. The order of mobility for the metals of environmental concern was Cd>Ag>Cr>Ni, Zn>Co, Cu, Pb. for Cd and Ag there was a tendency to partition towards the exchangeable phase, both at the surface and at depth, which indicates the potential for long-term leaching of these metals from the sediments.

The cell cycle progression and viability of stimulated and intact lymphocytes from 20 subjects with acquired immune deficiency syndrome (AIDS) was determined by flow cytometry. As compared to controls, 62% less AIDS lymphocytes, cultured for 72 hr in the presence of lectins (Con-A, PHA, PWM), had entered the proliferative phases of the cell cycle, while the respective value for periodic-acid (H5lO6)-stimulated cells was 34%. The helper-suppressor ratios and natural kill cell percentages of the unstimulated and PHA-activated AIDS lymphocytes increased approximately 3-fold after 72 hr in culture. The natural killer (NK) cell fraction of the PHA-stimulated and unstimulated AIDS cultures comprised approximately 20% as compared to 10% in controls. However, no changes in the percentages of T-lymphocytes were detected in the AIDS cell cultures. Throughout the culture period, viability of the unstimulated AIDS lymphocytes exceeded 90%, whereas in stimulated cultures it fluctuated within the 65-90% range. It is concluded that the liability of AIDS lymphocytes to mitogens is probably a direct consequence of the human immunodeficiency virus (HIV) infection.

To test the relationship between the concentration of epidermal growth factor (EGF) receptors and tumor growth in vivo, we measured the rate of growth of several independently isolated A431 cell lines in athymic mice. This series of A431 clonal variants with differing extents of EGF receptor gene amplification and protein expression were implanted into athymic mice and the time to solid tumor formation and rate of growth were measured. Results of these experiments indicate that the degree of gene amplification and concentration of EGF receptors are directly correlated with the growth of these cells as solid tumors in host animals. Complementary DNA hybridization analysis revealed no change in the extent of gene amplification and expression in implanted cells versus excised tumors nor any evidence of further gene rearrangement in vivo. A high concentration of EGF receptors appears to facilitate the growth of tumor cells in vivo and in vitro.

It has been observed that subclones from the spontaneous murine AKR/J T-lymphoma cell line SL12 with similar in vitro growth characteristics exhibit stable differences in tumorigenicity. The cell line is composed of at least three distinct cloned cell types that are highly, moderately, or poorly tumorigenic in syngeneic host animals. When healthy, young, syngeneic host animals were given iv injections with the same number of viable growth phase cells, each cloned cell type had a different tumor incidence, latent period, and pattern of tumor spread. The unusual stability of the cloned cell lines is shown by a similar incidence, latency, and spread of the tumors when studied after more than 1 year of continuous in vitro culture. The SL12 clones also differ in several phenotypic characteristics commonly used to classify thymocyte maturation, e.g., a) the expression of three of seven surface antigens examined, b) the cellular response to glucocorticoid hormone, and c) the expression of terminal deoxynucleotidyl transferase.

We have established and characterized a continuous T-cell line derived from the bone marrow of an AKR mouse with disseminated lymphoma. The original tumor cell line is heterogeneous with respect to several markers of thymocyte differentiation. Clones from the line differ in the expression of ThB, Pgp-1, and H-2Kk surface antigens. These clones also differ in their sensitivity to glucocorticoid-induced cell lysis. The quantity, affinity, and nuclear translocation properties of the glucocorticoid receptor are similar in the hormone-sensitive and -resistant clones. Furthermore, dexamethasone-resistant T-cells can be selected in vitro from freshly cloned cells sensitive to hormone-induced lysis at high frequency and without mutagenesis. Of several randomly sampled, spontaneously arising, independently derived dexamethasone resistant clones, all show a coordinate reduction in cell surface Thy-1 and ThB expression with no detectable changes in glucocorticoid receptor properties. Following treatment with the DNA-demethylating agent 5-azacytidine, the original dexamethasone-resistant T-cell line as well as the dexamethasone-resistant derivatives obtained in vitro regain sensitivity to lysis. These results collectively suggest a role of DNA methylation in hormone resistance and are consistent with a model of thymocyte differentiation in which a glucocorticoid-sensitive cell is the progenitor of hormone-resistant T-cells.

Several well characterized murine T-lymphoma cell lines were used in somatic cell hybridization experiments to study the genetic regulation of glucocorticoid-induced lysis. Cell fusions were carried out among the SL12-derived cloned lines and between the W7 and SAK8 lines all of which have functional hormone receptors. These cell lines differ in their sensitivity to glucocorticoid-induced lysis. The resultant hybrids were characterized by their growth response to 1 microM dexamethasone, their hormone receptor content, their chromosome number, and the expression of surface antigens. Fusion of the hormone-sensitive W7 parent to a number of glucocorticoid-resistant cell lines resulted in hybrids which were of the sensitive phenotype. In contrast the fusion of another hormone-sensitive clone, SL12.4, with glucocorticoid-resistant SL12 clones or with SAK8 always resulted in hybrids resistant to glucocorticoid lysis. These results reveal a complex genetic regulation of the hormone response or the requirement for multiple gene activity in the mechanism for glucocorticoid-induced cell lysis.

Flow injection analysis (FIA) involving the on-line oxidation of organomercury species to Hg2+, followed by reduction to Hg0 with acidified tin(II)chloride has been successfully coupled to an atomic fluorescence spectrophotometer (AFS) for determination of total organomercury in environmental samples. The method gave accurate and reproducible results for the certified dogfish samples DORM-1 and DOLT-1. A suitable organomercury extraction procedure for use with the method was established. The FIA-AFS method may also be used for determination of total mercury in environmental samples. The limit of detection (LOD) for organomercury was 200 pg and 2 pg for inorganic mercury using a 100 μ1 injection. The system is dedicated, cost-effective, sensitive and simple to use with a throughput of 17 analyses per hour.