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Biomedical subjects

J E Andrews

Publications and source records attributed to J E Andrews.

At least 19 recordsLinked to original sources
PubMed2006

Biogeochemical value of managed realignment, Humber estuary, UK.

We outline a plausible, albeit extreme, managed realignment scenario ('Extended Deep Green' scenario) for a large UK estuary to demonstrate the maximum possible biogeochemical effects and economic outcomes of estuarine management decisions. Our interdisciplinary approach aims to better inform the policy process, by combining biogeochemical and socioeconomic components of managed realignment schemes. Adding 7494 ha of new intertidal area to the UK Humber estuary through managed realignment leads to the annual accumulation of a 1.2 x 10(5) t of 'new' sediment and increases the current annual sink of organic C and N, and particle reactive P in the estuary by 150%, 83% and 50%, respectively. The increase in intertidal area should also increase denitrification. However, this positive outcome is offset by the negative effect of enhanced greenhouse gas emissions in new marshes in the low salinity region of the estuary. Short-term microbial reactions decrease the potential benefits of CO(2) sequestration through gross organic carbon burial by at least 50%. Net carbon storage is thus most effective where oxidation and denitrification reactions are reduced. In the Humber this translates to wet, saline marshes at the seaward end of estuaries. Cost-benefit analysis (CBA) was used to determine the economic efficiency of the Extended Deep Green managed realignment. When compared to a 'Hold-the-Line' future scenario, i.e. the present state/extent of sea defences in the estuary, the CBA shows that managed realignment is cost effective when viewed on >25 year timescales. This is because capital costs are incurred in the first years, whereas the benefits from habitat creation, carbon sequestration and reduced maintenance costs build up over time. Over 50- and 100-year timescales, the Extended Deep Green managed realignment scenario is superior in efficiency terms. The increased sediment accumulation is also likely to enhance storage of contaminant metals. In the case of Cu, a metal that currently causes significant water quality issues, Cu removal due to burial of suspended sediment in realigned areas translates to a value of approximately pounds sterling 1000 a(-1) (avoided clean up costs). Although this is not formally included in the CBA it illustrates another likely positive economic outcome of managed realignment. Although we focus on the Humber, the history of reclamation and its biogeochemistry is common to many estuaries in northern Europe.

Conservation of Natural Resources↗
PubMed2005

Copper and zinc removal from aqueous solution by mixed mineral systems II. The role of solution composition and aging.

This study investigates Cu and Zn removal onto binary mixed mineral sorbents from simulated wastewater, relevant to streams impacted by acid mine drainage and effluents. Mixed suspensions of kaolinite/montmorillonite and kaolinite/goethite exhibited different sorption behavior from the single mineral components, reducing Cu and Zn removal (except Cu sorbed on montmorillonite/goethite) over the range of pH investigated. Cu and Zn removal by the electrolyzed systems showed a complex response to increased ionic strength, which increased solid concentration, leading to lower Cu and Zn sorption. Enhanced Cu sorption on the montmorillonite/goethite as age increased may be attributed to increased hydroxylation of the mineral surface resulting in the formation of new reactive sites.

Journal Article↗
PubMed2005

Copper and zinc removal from aqueous solution by mixed mineral systems I. Reactivity and removal kinetics.

This study investigates the reactivity and removal kinetics of Cu and Zn onto mixed mineral systems from aqueous solution related to acid mine drainage impacted areas. The sorbents used were kaolinite, Al-montmorillonite, goethite, and their mixtures. The effects of surface charge, proton coefficient, and sorption kinetics were studied at room temperature (23+/-2 degrees C). Using an empirical model, mineral mixing reduced the exchange of protons for sorbing ions and the acidity of the reactive sites, thus impeding Cu and Zn removal by proton exchange. Based on the amount of Cu and Zn sorbed on the mixed mineral suspensions at ionic strength 0.01 to 0.1 M and pH 4, it is suggested that Cu and Zn removal from aqueous solution was by both inner and outer sphere complexation. Mineral mixing reduced the transfer rate of Cu relative to the single mineral suspensions in both slow and fast reaction phases. The behavior of the mixed suspensions in Cu and Zn sorption suggest that different reactive sites were involved at the onset of sorption, becoming similar to those of the single mineral components over time.

Journal Article↗
PubMed2004

Developmental toxicity of mixtures: the water disinfection by-products dichloro-, dibromo- and bromochloro acetic acid in rat embryo culture.

The chlorination of drinking water results in production of numerous disinfection by-products (DBPs). One of the important classes of DBPs is the haloacetic acids. We have previously shown that the haloacetic acids (HAs), dichloro (DCA), dibromo (DBA) and bromochloro (BCA) acetic acid are developmentally toxic in mouse whole embryo culture. Human exposure to these contaminants in drinking water would involve simultaneous exposure to all three HAs. This study explores the question of developmental toxicity interactions between these compounds. Gestational day (GD) 9.5 rat embryos were exposed to various concentrations of the three HAs (singly or in combination) for 48 h and then evaluated for dysmorphology. The embryonic effects from exposure to the single compounds and mixtures were evaluated using developmental score (DEVSC) as the parameter of comparison. Concentrations of individual compounds and mixtures were chosen (based on a dose-additivity model) which were predicted to produce scores 10 or 20% lower than control levels. Evaluations were performed on all possible combinations of the three HAs. The HAs were dysmorphogenic and resulted in primarily rotation and heart defects and to a lesser extent prosencephalic, visceral arch, and eye defects. The percent anomalies in the rat were comparable to those previously published for the mouse at comparable toxicant concentration. There was a low incidence of neural tube defects in the rat following exposure to the HAs. The rat neural tube appeared less sensitive to the HAs than did the mouse resulting in a higher rate of neural tube dysmorphology in the mouse. Following exposures to BCA and DBA, alone and in combination, there was a significant incidence of delayed embryonic caudal development with apparent normal development anterior to the second visceral arch. The developmental scores for embryos exposed to combinations of the three compounds, when compared to scores for embryos exposed to the single compounds, indicated that the dose-additivity model adequately predicted the observed toxicity and that the developmental toxicity of these water disinfection by-products appears to be additive in whole embryo culture (WEC).

Abnormalities, Drug-Induced↗
PubMed2003

The Humber catchment and its coastal area: from UK to European perspectives.

The present water quality of the Humber rivers and coastal zone depends on a complex interplay of factors, including physical ones, such as the underlying geology, which influences soil type, climatic ones, such as the rainfall, which influences runoff, socio-economic ones, which influence present-day human activities in the catchment, and the legacy of former activities, such as contaminated sediments from mining. All of these factors affect the fluxes of nutrients and other contaminants to the rivers and coastal zone. The Water Framework Directive (WFD) requires the production of a river basin management plan intended to lead to the achievement of good chemical and ecological status for all water bodies in the catchment over the next two decades. This paper provides an overview of the current environmental and socio-economic state of the Humber catchment and coastal zone, and broadly examines how socio-economic drivers affect the fluxes of nutrients and contaminants to the coastal zone, using the driver-pressure-state-impact-response (DPSIR) approach. This is followed by an overview of future research, describing the use of scenarios to simulate future fluxes and provide a consistent framework to evaluate potential policies to improve water quality in the estuary. The Humber catchment is one of eight case studies within a European research project, EUROCAT (EVK1-CT-2000-00044), which aims to achieve integrated catchment and coastal zone management by analysing the response of the coastal sea to changes in fluxes of nutrients and contaminants from the catchments. For the Humber case study, the research focuses on the fluxes of two nutrient elements, N and P, and four metal contaminants, As, Cu, Pb and Zn. The project requires the integration of scientific and socio-economic approaches, bringing together quantitative environmental data garnered for individual river catchments and coastal zones in previous research programmes, and local and regional socio-economic data, to aid decision-makers in their search for integrated and sustainable coastal zone management strategies.

Animals↗
PubMed2001

Size-fractionated plutonium isotopes in a coastal environment.

We have examined the distribution of individual Pu isotopes (239Pu, 240Pu, and 241Pu) in seawater from the Gulf of Maine (GOM). Samples were size-fractionated with a 1 kD cross-flow ultrafiltration (CFF) membrane. Subfractioned samples were radiochemically purified and Pu isotopes were analyzed using a three-stage thermal ionization mass spectrometer (TIMS). To our knowledge, this is the first time that both size class and Pu isotopic data have been obtained for seawater samples. Within measurement uncertainties a single 240Pu/239Pu atom ratio of 0.18 was found for all sample collection depths and sample size fractions. This signifies a current, single Pu source in GOM waters, namely global fallout, and suggests that no measurable isotopic fractionation occurred during CFF processing. The majority of Pu was found in the low molecular weight fraction (< 1 kD). Colloidal Pu varied from 8% of the total in surface waters to < 1% in the deepest (250 m) seawater sample. Evidence suggests that the vertical distribution of Pu in GOM is primarily controlled by conservative mixing processes. The high Pu fraction found in the low molecular size fraction implies that most of the Pu is in the non-particle-reactive oxidized fraction, and is consistent with the conservative Pu behavior. The activity levels are in agreement with other studies which show a slow decrease in Pu with time due to continued mixing and relatively slow particle removal.

Atlantic Ocean↗
PubMed2000

Isolation and expression of a novel member of the CITED family.

Chicken CITED3 (cCITED3) is a novel gene, which is expressed in the pre-somitic mesoderm, the mesonephric tubules, the Wolffian ducts and collecting tubules of the developing urogenital system and in the cranial sensory ganglia. Sequence analysis revealed that cCITED3 encodes a protein which contains two conserved domains that have been described for members of the CITED family.

Amino Acid Sequence↗
PubMed2000

Creating local bibliographic databases: new tools for evidence-based health care.

The Internet has created new opportunities for librarians to present literature search results to clinicians. In order to take full advantage of these opportunities, libraries need to create locally maintained bibliographic databases. A simple method of creating a local bibliographic database and publishing it on the Web is described. The method uses off-the-shelf software and requires minimal programming. A hedge search strategy for outcome studies of clinical process interventions is created, and Ovid is used to search MEDLINE. The search results are saved and imported into EndNote libraries. The citations are modified, exported to a Microsoft Access database, and published on the Web. Clinicians can use a Web browser to search the database. The bibliographic database contains 13,803 MEDLINE citations of outcome studies. Most searches take between four and ten seconds and retrieve between ten and 100 citations. The entire cost of the software is under $900. Locally maintained bibliographic databases can be created easily and inexpensively. They significantly extend the evidence-based health care services that libraries can offer to clinicians.

Costs and Cost Analysis↗
PubMed2000

Data discretization for novel resource discovery in large medical data sets.

This paper is motivated by the problems of dealing with large data sets in information retrieval. The authors suggest an information retrieval framework based on mathematical principles to organize and permit end-user manipulation of a retrieval set. By adjusting through the interface the weights and types of relationships between query and set members, it is possible to expose unanticipated, novel relationships between the query/document pair. The retrieval set as a whole is parsed into discrete concept-oriented subsets (based on within-set similarity measures) and displayed on screen as interactive "graphic nodes" in an information space, distributed at first based on the vector model (similarity measure of set to query). The result is a visualized map wherein it is possible to identify main concept regions and multiple sub-regions as dimensions of the same data. Users may examine the membership within sub-regions. Based on this framework, a data visualization user interface was designed to encourage users to work with the data on multiple levels to find novel relationships between the query and retrieval set members. Space constraints prohibit addressing all aspects of this project.

Computer Graphics↗
PubMed1998

Effects of combinations of methanol and formic acid on rat embryos in culture.

Acute human exposure to methanol (MeOH) results in elevated serum concentrations of both MeOH and formic acid. In order to better assess the risk of adverse developmental effects of MeOH exposure in humans, the effects of the combination of formate and MeOH, in addition to the individual toxicity profiles for MeOH and formate, need to be established. Gestational day 9 rat embryos were exposed to various concentrations of MeOH and formate in whole embryo culture (WEC) for 48 hr and the degree of embryotoxicity was evaluated using developmental score (DEVSC) as the parameter of comparison across exposure combinations. After establishing embryo toxicity of the individual compounds in previous studies, concentrations of MeOH and formate were chosen which would produce similar DEVSCs, and isoboles were plotted joining the equivalently toxic doses. These mixtures would be expected to have similar toxicity to the MeOH or formate concentrations according to a dose-addition model. The responses of embryos to the selected concentrations along each isobole were measured and tested for linearity to determine the nature of any interaction between the two agents. The concentrations of MeOH and formate used separately and in combination ranged from 0 to 8.75 mg/ml MeOH and 0 to 1.51 mg/ml formate. Increasing concentrations of either MeOH or formate resulted in significant decreases in DEVSC. Exposure to combinations of MeOH and formate had less effect on DEVSC than would be expected based on simple toxicity additivity. This observation was also true for embryonic crown-rump length, head length, and somite number. These results suggest that the embryotoxicity observed following low level exposure to MeOH is mechanistically different from that observed following exposure to formate.

Abnormalities, Drug-Induced↗
PubMed1998

Chlorpyrifos elicits mitotic abnormalities and apoptosis in neuroepithelium of cultured rat embryos.

Chlorpyrifos is used increasingly as a pesticide in place of more toxic alternatives such as parathion. Although chlorpyrifos is not a potent dysmorphogen, recent reports that fetal or infant exposures may exceed acceptable limits have raised concern about the potentially more subtle effects on brain development. In the current study, whole rat embryo culture was used to study the effects of chlorpyrifos at the neural tube stage of development. On embryonic day 9.5, embryos were exposed to 0.5, 5, or 50 micrograms/ml of chlorpyrifos. After 48 hr (embryonic day 11.5), embryos were examined for dysmorphogenesis and were then processed for light microscopic examination of the neuroepithelium. Examination of 1-micron-thick toluidine blue-stained sections of the forebrain and hindbrain region revealed reduced and altered mitotic figures, with dispersion and disorientation of the mitotic layer. In addition, cytotoxicity was evidenced by cytoplasmic vacuolation, enlargement of intercellular spaces, and the presence of a significant number of apoptotic cells. These alterations were evident even at the lowest concentration of chlorpyrifos, which produced no dysmorphogenesis. The effects were intensified at higher concentrations, which were just at the threshold for dysmorphogenesis; the neuroepithelial abnormalities, however, were still present in embryos that were not dysmorphogenic. Our results in rat embryo culture support the idea that chlorpyrifos specifically targets brain development at low concentrations, indicating the need to reevaluate the safety of this compound for exposure in vivo.

Abnormalities, Drug-Induced↗
PubMed1998

Effects of boric acid on axial skeletal development in rats.

Prenatal exposure to elevated levels of boric acid (BA) causes reduced incidences of supernumerary ribs and shortening/absence of the 13th rib in multiple laboratory species. To explore this further, Sprague-Dawley rats received 500 mg/kg b.i.d. on gestation days (gd) 5-9, 6-9, 6-10, or on single days between gd 6 and 11 (plug day = gd 0); gd-21 fetuses were stained for skeletal examination. Following multiday exposures, malformations of the axial skeleton involved the head, sternum, ribs, and vertebrae. Shortening/absence of the 13th rib was seen particularly in the gd 5-9 and 6-10 exposure groups. Although most groups exposed on single days were generally unaffected, about 90% of the gd-9 exposed fetuses had only six cervical vertebrae; the deficient region was usually C3-C5. In contrast, gd-10 treatment caused agenesis of a thoracic/lumbar vertebra in over 60% of the fetuses; the deficient region was usually T11. For 13-ribbed fetuses, the length of rib 13 was shortened compared to controls. Postnatal assessment suggested increased mortality for gd-10 exposed pups. Embryos in culture showed reduced development when exposed to BA for 48 h. These findings demonstrate the critical periods for axial development in the rat and provide an experimental model for the study of homeotic shifts.

Animals↗
PubMed1998

Changes in fatty acid composition of lipids from birds, rodents, and preschool children exposed to lead.

Chronic treatment with inorganic lead (Pb) has been shown to increase the proportion of arachidonic acid (ArA), as well as the arachidonate/linoleate (ArA/LA) ratio, in the fatty acids of lipids from a variety of avian tissues. Changes in two fatty acid-mediated phenomena, peroxidation of membrane lipids and synthesis of eicosanoid cytokines, are associated with this enhanced ArA content. The authors are not aware of any reports in the literature in which these effects of Pb have been described for any animals other than birds. In the current study, the authors investigated the effect of Pb on lipid metabolism in three species: avian, rodent, and human. The group of children identified as suffering environmental Pb exposure were from a Pb-surveillance program and had blood Pb concentrations (PbB) averaging 23 microg/dL. Turkey poults fed 100 ppm dietary Pb as Pb acetate-trihydrate for 19 d had a PbB of 46 microg/dL. Gastric intubation of rats with 80 mg Pb/kg/d for 10 d resulted in a PbB of 74 microg/dL. We analyzed fatty acid composition of whole blood from children, poults, and virgin rats. Low-dose (nongrowth inhibitory) Pb exposure resulted in significantly increased ArA concentration and ArA/LA ratio in blood from all species. Also analyzed were plasma and liver of poults, virgin rats, and pregnant rats and their fetuses. In plasma and liver from Pb-treated poults and virgin rats, ArA and the ArA/LA ratio were again enhanced. Pb intoxication also affected omega3 composition, increasing the concentrations of all long-chain omega3 fatty acids of fetuses from Pb-treated pregnant dams. The authors propose that altered fatty acid metabolism may be responsible for some indications of Pb poisoning. Possible consequences mediated through lipid peroxidation and production of ArA-derivative eicosanoids are considered.

Animals↗
PubMed1998

Nicotine evokes cell death in embryonic rat brain during neurulation.

Maternal cigarette smoking during pregnancy represents the most prevalent exposure to a suspected neuroteratogen, nicotine. Although animal models have demonstrated brain cell loss and synaptic abnormalities after prenatal nicotine exposure, the multiple effects of nicotine on the maternal-fetal unit make it difficult to prove that nicotine itself is a neuroteratogen. In the current study, whole rat embryo culture was used to study the effects of nicotine at the neural tube stage of development. Beginning on embryonic day 9.5, embryos were exposed to 1, 10 or 100 microM nicotine. After 48 hr, embryos were examined for dysmorphogenesis and were then processed for light microscopic examination of the neuroepithelium. Examination of the forebrain, midbrain and hindbrain regions revealed extensive cytotoxicity, evidenced by cytoplasmic vacuolation, enlargement of intercellular spaces and a sharply increased incidence of pyknotic/apoptotic cells. These alterations were evident in the absence of generalized dysmorphogenesis and were detectable even at the lowest concentration of nicotine. At the highest concentration, abnormalities were present in the majority of cells. Superimposed on cell damage, we found an increase in mitotic figures. Although enhanced mitosis could represent partial compensation for cell loss, the regional selectivity and concentration dependence of the mitogenic effect differed significantly from that of cell death, suggesting separable mechanisms. The present results support the view that nicotine is a neuroteratogen, specifically targeting brain development at concentrations below the threshold for dysmorphogenesis.

Animals↗
PubMed1997

Stereoselective dysmorphogenicity of the enantiomers of the valproic acid analogue 2-N-propyl-4-pentynoic acid (4-yn-VPA): cross-species evaluation in whole embryo culture.

We previously reported the in vitro differential stereoselective dysmorphogenic potential of the R(+) and S(-) enantiomers of 2n-propyl-4-pentynoic acid (4-yn-VPA) in mice. To determine whether this stereoselectivity is species specific, we evaluated the dysmorphogenic potential of these isomers as well as valproic acid (VPA) to gestational day 9 rat embryos using whole embryo culture (WEC). Aqueous solutions of the sodium salts of R-4-yn-VPA, S-4-yn-VPA, 50%R/ 50%S-4-yn-VPA or VPA were added to the culture medium to give 0, 0.075, 0.15, 0.3, 0.6, or 1.2 mmol/L and embryos were evaluated 48 hr later. The S-4-yn-VPA enantiomer gave clear concentration-dependent dysmorphology as well as effects on developmental score, somite number, crown rump length, and head length. Effects on rotation and defects of the neural tube, somites and heart were observed. Embryolethality was observed only at 1.2 mmol/L concentration. The R-4-yn-VPA enantiomer was neither embryo toxic nor dysmorphogenic at any concentration. VPA significantly reduced all parameters and was dysmorphogenic at the highest concentration but was not embryo lethal. The 50/50 mixture of R- and S-isomers appeared to elicit a degree of embryolethality and dysmorphology similar to VPA. The potency order for the four chemicals was S(-) > S(-)/R(+) = VPA > > > R(+), comparable to that observed in mice by either in vivo or in vitro exposure. These data demonstrate that the stereoselective dysmorphology for these enantiomers can be observed across species and is not related to maternal metabolism.

Abnormalities, Drug-Induced↗
PubMed1997

Sites of estrogen receptor and aromatase expression in the chicken embryo.

Estrogens have been implicated in sexual differentiation of both the gonads and the genitalia of birds. In chicken embryos, the gonads are steroidogenically active from an early age, and the aromatase gene, (cAROM), necessary for estrogen synthesis, is expressed only in females at the time of gonadal sex differentiation. However, no studies have directly demonstrated the distribution of estrogen receptor (cER) transcripts or proteins in the embryonic avian reproductive system. Whole-mount in situ hybridization and immunohistochemistry were used here to identify sites of estrogen receptor expression in the embryonic chicken urogenital system. Estrogen receptor mRNA was observed in both male and female gonads prior to morphological differentiation, at Stage 26 (4.5 days of incubation), and continued until after sexual dimorphism at Stage 32 (7.5 days). Transcripts of cER were also detected in the Müllerian ducts and developing external genitalia of both sexes. Estrogen receptor protein was analysed in the embryonic gonads by immunohistochemistry and found to be most abundant in the cortex of the left ovary, although it was also present in the medulla of both female gonads. No significant cER protein expression was detected in the male gonad by immunohistochemistry. In contrast, the aromatase gene was expressed in the gonads of female embryos from the onset of sexual dimorphism but was not detectable in male gonads at any stage examined. These findings suggest that estrogen involvement in both gonadogenesis and genital development in chickens is mediated by the estrogen receptor.

Animals↗
PubMed1997

Gonadal sex differentiation in chicken embryos: expression of estrogen receptor and aromatase genes.

Estrogen is implicated in sexual differentiation of the avian gonad. Expression of the estrogen receptor and aromatase genes was therefore examined at the time of gonadal sex differentiation in chicken embryos, using reverse transcription and the polymerase chain reaction (RT-PCR). Estrogen receptor (cER) transcripts were detected in the gonads of both presumptive sexes at embryonic days 4.5, 5.5 and 6.5, and in female but not male urogenital tissues at day 3.5. Aromatase (cAROM) transcripts were detected in female but not male gonads from day 6.5 of embryogenesis, and in adult gonads of both sexes. Both female and male embryos thus express cER mRNA before morphological differentiation of the gonads, which begins on day 5, whereas cAROM expression begins at or shortly after the onset of differentiation and is female-specific. Examination of other tissues showed that, in 5.5-day-old embryos, cER expression was limited to the gonads; no transcripts were detected in the mesonephric kidney, liver, brain, hindlimb or heart of either sex. In 9.5-day-old female embryos, cER and cAROM transcripts were present in both the left (ovarian) and the right (regressing) gonads. Altogether, these observations imply that the gonads of both sexes develop the capacity to respond to estrogens early in embryogenesis, before morphological differentiation, whereas the capacity to synthesize estrogens is female-specific and occurs later, at the time of differentiation. These observations are consistent with estrogens having a key role in ovarian development.

Animals↗