PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Environmental selection”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 901 records · Page 50Linked to original sources
PubMed1999

A double-selective tissue culture system for isolation of wild-type poliovirus from sewage applied in a long-term environmental surveillance.

We describe a simple, cost-efficient, double-selective method for isolation of wild-type poliovirus from sewage samples containing vaccine polioviruses and other enteroviruses, with a detection limit of 18 to 50 PFU per 1 to 2 liters of sewage. By this method we were able to process 1,700 sewage samples collected between 1991 and 1996, from which 10,472 plaques were isolated, 41 of them being identified as wild-type polioviruses.

Animals↗
PubMed2002

Criteria for chemical selection for programs on human milk surveillance and research for environmental chemicals.

The people of the United States is exposed to a large number of chemicals in their daily lives. In order to prioritize chemicals that should be considered for surveillance of and/or research in human milk, criteria were developed at the Technical Workshop on Human Milk Surveillance and Research on Environmental Chemicals in the United States. The criteria include (1) lipid solubility and/or persistence in the environment; (2) extensive exposure (e.g., high-production-volume chemicals and chemicals in personal care products); (3) known or suspected toxicity in a biological system; (4) historical interest, trend information; (5) chemicals of emerging concern; and (6) chemicals for medicinal use and chemicals in occupational settings. A working list of chemicals was developed for each of the criteria. It should be noted that more than one criterion may be applicable to a selected chemical, but the selected chemical should possess at least one of these designated criteria. It is hoped that by following a cohort of nursing women through their lactational cycle for a group of these chemicals, data generated will indicate the extent of infant exposure and may suggest methods for risk management to decrease inadvertent exposure for breast-feeding mothers and infants. While not the focus of this article, certain endogenous chemicals in human milk beneficial to the health of the infant warrant study as well.

Adult↗
PubMed2002

Analytic considerations for measuring environmental chemicals in breast milk.

The presence of environmental chemicals in human breast milk is of general concern because of the potential health consequence of these chemicals to the breast-fed infant and the mother. In addition to the mother's exposure, several features determine the presence of environmental chemicals in breast milk and their ability to be determined analytically. These include maternal factors and properties of the environmental chemical--both physical and chemical--such as its lipid solubility, degree of ionization, and molecular weight. Environmental chemicals with high lipid solubility are likely to be found in breast milk; they include polyhalogenated compounds such as polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, organochlorine insecticides, and polybrominated diphenylethers. These fat-soluble chemicals are incorporated into the milk as it is synthesized, and they must be measured in accordance with the fat content of the milk to allow for meaningful comparisons within an individual and among populations. Although the analytic approach selected to measure the environmental chemical is predominantly determined by the characteristics of the chemical, the concentration of the chemical in the milk sample and the existence of structurally similar chemicals (e.g., congeners) must be considered as well. In general, the analytic approach for measuring environmental chemicals in breast milk is similar to the approach for measuring the same chemicals in other matrices, except special considerations must be given for the relatively high fat content of milk. The continued efforts of environmental scientists to measure environmental chemicals in breast milk is important for defining the true contribution of these chemicals to public health, especially to the health of the newborn. Work is needed for identifying and quantifying additional environmental chemicals in breast milk from the general population and for developing analytic methods that have increased sensitivity and the ability to speciate various chemicals.

Adult↗
PubMed2007

Depressive behavior and selective down-regulation of serotonin receptor expression after early-life seizures: reversal by environmental enrichment.

Depression is the most common psychiatric comorbidity in epilepsy. To better understand the contribution of seizures versus environment to depression in epilepsy, we investigated differential gene expression using microarray and quantitative RT-PCR, and depressive behavior, in the Porsolt forced swim test in juvenile rats reared in different environments after kainic acid (KA)-induced seizures. We selected for genes significantly down-regulated by KA seizures and upregulated by environmental enrichment. This common gene selection process yielded one known gene involved in mood and affect: serotonin receptor 5B. The changes in serotonin receptor gene expression were paralleled by decreased mobility in the forced swim tests; depressive behavior exhibited after seizures was no longer evident in rats reared in environmental enrichment. Our results suggest that seizures lead to increased susceptibility to depression through transcriptional regulation while environment, in turn, can interact with gene expression to influence the behavioral outcome of epilepsy.

Analysis of Variance↗
PubMed2006

Prediction of genotoxicity of various environmental pollutants by artificial neural network simulation.

In order to evaluate human carcinogenic risks, genotoxicity data such as animal cancer bioassay are often not available. In this study, to assess the relevance of indicator of carcinogenic risks, we used the "molecular diversity approach" to estimate the genotoxicity based upon Salmonella genotoxicity test using the umu test and systemic toxicity data of the 82 environmental chemicals predicted by neural network simulation. The 82 environmental chemicals were randomly selected for this study according to the production and usage in Japan. Even in this challenging trial for QSTR (Quantitative Structure Toxicity Relationship) study, approaches using artificial neural networks can account for about 94% of the variation in the genotoxicity results derived by the umu-test.

Computer Simulation↗
PubMed2002

Relationships among severity and duration of clinical mastitis and sire transmitting abilities for somatic cell score, udder type traits, productive life, and protein yield.

The objective of this study was to determine the relationships among severity and duration of clinical mastitis during first and second lactation and sire transmitting abilities for somatic cell score, udder type traits, productive life, and protein yield. Recording of clinical episodes began at first parturition for 1704 Holstein cows (in six Pennsylvania herds and one Nebraska herd) and continued into second lactation for 1055 of these cows. A total of 456 cows (sired by 168 bulls) had at least one clinical episode during first lactation, and 230 cows (sired by 100 bulls) had at least one clinical episode during second lactation. A severity code from 1 (normal milk) to 5 (acute systemic mastitis) was assigned daily (for up to 30 d after detection) to all quarters that had clinical mastitis. Only the severity codes for the first clinical episode to occur during first and second lactation are considered here. The initial and maximum severity codes, as well as the natural logarithms of both the sum of severity codes that were above normal (> 1) and the total days severity codes were above normal were regressed on herd (a classification variable), age at first calving, days in milk at clinical detection, and sire transmitting abilities taken one at a time. Linear and nonlinear effects were estimated for sire transmitting abilities. Separate analyses were conducted on dependent variables that considered severity and duration of clinical mastitis from: all organisms, coagulase-negative staphylococci, coliform species, streptococci other than Streptococcus agalactiae, and the most common environmental organisms (coliform species and streptococci other than Streptococcus agalactiae). Daughters of sires that transmit the lowest somatic cell score had the least severe and shortest clinical episodes from environmental organisms during first lactation. Selection for lower somatic cell score may reduce the severity and duration of clinical episodes from environmental organisms during first lactation.

Animals↗
PubMedDate not supplied

Behavior problems among children from different family structures: the influence of genetic self-selection.

To examine both genetic and environmental influences on children's behavior problems in households defined by marital status and sibling relatedness, this study applied behavioral genetic methodology to four groups totalling 1524 sibling pairs drawn from 796 households: (1) two-parent full siblings, (2) two-parent half siblings, (3) mother-only full siblings, and (4) mother-only half siblings. Model-fitting procedures found that within-group variation on four subscales from the Behavior Problems Index was best explained by a model including both genetic and shared environmental factors. This model was then fit to the behavior problems means of the four groups. Its successful fit to these mean structures suggested that mean-level differences between groups were explained with the same influences that accounted for within-group variation. Genetic influences accounted for 81% to 94% of the mean-level difference in behavior problems between the two-parent, full sibling and the mother-only, half sibling groups. In contrast, shared environmental influences accounted for 67% to 88% of the mean-level difference in behavior problems between the two-parent, full sibling and mother-only, full sibling groups. The genetic influences are interpreted in terms of genetic self-selection into family structures.

Adolescent↗
PubMed2006

Application of heuristic optimization techniques and algorithm tuning to multilayered sorptive barrier design.

Although heuristic optimization techniques are increasingly applied in environmental engineering applications, algorithm selection and configuration are often approached in an ad hoc fashion. In this study, the design of a multilayer sorptive barrier system served as a benchmark problem for evaluating several algorithm-tuning procedures, as applied to three global optimization techniques (genetic algorithms, simulated annealing, and particle swarm optimization). Each design problem was configured as a combinatorial optimization in which sorptive materials were selected for inclusion in a landfill liner to minimize the transport of three common organic contaminants. Relative to multilayer sorptive barrier design, study results indicate (i) the binary-coded genetic algorithm is highly efficient and requires minimal tuning, (ii) constraint violations must be carefully integrated to avoid poor algorithm convergence, and (iii) search algorithm performance is strongly influenced by the physical-chemical properties of the organic contaminants of concern. More generally, the results suggest that formal algorithm tuning, which has not been widely applied to environmental engineering optimization, can significantly improve algorithm performance and provide insight into the physical processes that control environmental systems.

Algorithms↗
PubMed1995

Extreme fitness differences in mammalian and insect hosts after continuous replication of vesicular stomatitis virus in sandfly cells.

Continuous, persistent replication of a wild-type strain of vesicular stomatitis virus in cultured sandfly cells for 10 months profoundly decreased virus replicative fitness in mammalian cells and greatly increased fitness in sandfly cells. After persistent infection of sandfly cells, fitness was over 2,000,000-fold greater than that in mammalian cells, indicating extreme selective differences in the environmental conditions provided by insect and mammalian cells. The sandfly-adapted virus also showed extremely low fitness in mouse brain cells (comparable to that in mammalian cell cultures). It also showed an attenuated phenotype, requiring a nearly millionfold higher intracranial dose than that of its parent clone to kill mice. A single passage of this adapted virus in BHK-21 cells at 37 degrees C restored fitness to near neutrality and also restored mouse neurovirulence. These results clearly illustrate the enormous capacity of RNA viruses to adapt to changing selective environments.

Animals↗
PubMed2006

Delimitation of lymphatic filariasis transmission risk areas: a geo-environmental approach.

BACKGROUND: The Global Programme to Eliminate Lymphatic Filariasis (GPELF) depends upon Mass Drug Administration (MDA) to interrupt transmission. Therefore, delimitation of transmission risk areas is an important step, and hence we attempted to define a geo-environmental risk model (GERM) for determining the areas of potential transmission of lymphatic filariasis. METHODS: A range of geo-environmental variables has been selected, and customized on GIS platform to develop GERM for identifying the areas of filariasis transmission in terms of "risk" and "non-risk". The model was validated through a 'ground truth study' following standard procedure using GIS tools for sampling and Immuno-chromotographic Test (ICT) for screening the individuals. RESULTS: A map for filariasis transmission was created and stratified into different spatial entities, "risk' and "non-risk", depending on Filariasis Transmission Risk Index (FTRI). The model estimation corroborated well with the ground (observed) data. CONCLUSION: The geo-environmental risk model developed on GIS platform is useful for spatial delimitation purpose on a macro scale.

Journal Article↗
PubMed1996

Risk factors for essential thrombocythemia: A case-control study. Italian Leukemia Study Group.

BACKGROUND: Very little information is presently available regarding risk factors for essential thrombocythemia (ET). METHODS: A case-control study was performed to study the possible association between ET and selected behavioral, occupational, and environmental exposures. RESULTS: Thirty-nine patients aged 20 years or older and 156 controls were enrolled in 2 Italian Hematology Departments located in Rome and Pavia. Controls were recruited among outpatients seen in the same hospitals and matched 4:1 to the patients after stratification by age and sex. Odds ratio (OR) estimates suggest an association between ET and hair dye use (in particular the use of dark hair dye for periods longer than 10 years: OR - 5.3; 95% confidence interval [CI], 1.4-19.9), living in houses built with tuff (a material with a high concentration of gamma-emitting radionuclides and radon) for longer than 9 years (OR = 5.1; 95% CI, 1.2-22.1), and selected occupations (electrical worker and shoemaker, OR +infinity and 2.7; 95% CI, 0.5-16 respectively). CONCLUSION: Behavioral exposures such as hair dyes, living in a tuff house, and working as an electrician are significantly associated with ET development. The data are consistent with those observed in acute leukemias.

Adult↗
PubMed2006

Developing methods for assessing neurotoxic effects in Hispanic non-English speaking children.

Many factors affect the growth and development of children, including chemicals in the environment. Children have greater exposure to toxicants than adults due to both behavior and their increased food: body-mass ratio. Furthermore, the developing brain and organ systems of infants and children and their immature metabolism also make them more vulnerable to environmental toxins. Children from all cultures and backgrounds are at risk. However, minorities may be at greatest risk. In order to evaluate the impact of environmental exposures on neurodevelopment it is necessary to have effective methods that will allow accurate conclusions to be drawn. We have developed a battery to assess neurobehavioral performance in non-English speaking Hispanic children ages 4 years and older. This paper will examine the associations between age and performance and present test-retest correlations. Two hundred and forty one Hispanic children between the ages of 4 and 9 years completed a neurobehavioral test battery twice, approximately 1 month apart. The battery consists of computerized tests from the Behavioral Assessment and Research System, tests selected from the Pediatric Environmental Neurobehavioral Test Battery, and the Object Memory Test. Multiple regression was used to examine the association between age, gender and mother's education on performance. All of the tests, except for Continuous Performance, showed that performance improved as the child gets older. Gender differences were found on several tests with females generally performing worse than males. Correlation coefficients on performance retest measures ranged from .51 to .88. This study has demonstrated the utility of using this test battery to assess cognitive and motor performance in non-English speaking Hispanic children. Tests in the battery assess a range of functions and the measures are sensitive to differences in ages. Test-retest correlations show the reliability of the battery. These support the use of this battery in both cross-sectional and longitudinal studies.

Child↗
PubMed2003

Differential and special properties of the major human UGT1-encoded gastrointestinal UDP-glucuronosyltransferases enhance potential to control chemical uptake.

UDP-glucuronosyltransferase (UGT) isozymes detoxify metabolites, drugs, toxins, and environmental chemicals via conjugation to glucuronic acid. Based on the extended UGT1 locus combined with Northern blot analysis and in situ hybridization, we determined the distribution of UGT1A1 and UGT1A7 through UGT1A10 mRNAs and found them for the first time segmentally distributed in the mucosal epithelia layer of the gastrointestinal tract. Biochemically, recombinant isozymes exhibited pH optima of 5.5, 6.4, 7.6, 8.5, and/or a broad pH range, and activities were found to be unaffected or progressively inhibited by increasing substrate concentrations after attaining Vmax for certain chemicals. Under different optimal conditions, all exhibited wide substrate selections for dietary and environmentally associated chemicals. Evidence also suggests tandem effects of isozymes in the time for completion of reactions when comparing short- and long-term incubations. Moreover, treatment of colon cells with certain diet-associated constituents, curcumin and nordihydroguaiaretic acid, reversibly targets UGTs causing inhibition without affecting protein levels; there is no direct inhibition of control UGT using curcumin as substrate in the in vitro assay. In summary, we demonstrate that UGTs are located in gastrointestinal mucosa, have vast overlapping activities under differential optimal conditions, and exhibit marked sensitivity to certain dietary substrates/constituents, representing a first comprehensive study of critical properties concerning glucuronidating isozymes in alimentary tissues. Additionally, the highly dynamic, complex, and variable properties necessarily impact absorption of ingested chemicals and therapeutic drugs.

Animals↗
PubMedDate not supplied

How does arthropod segment number evolve?--Some clues from centipedes.

Studies of intraspecific variation in the number of trunk segments of geophilomorph centipedes provide clues as to how different species of arthropods, and whole clades in some cases, come to be characterized by different segment numbers. However, although previous work in this area has revealed an interesting geographical pattern-a latitudinal cline in which segment number decreases with increasing latitude-the causality of the cline remains obscure. Is it because of selection on genetically based variation, or is it a result of a form of phenotypic plasticity in which the segmentation process is directly affected by a latitude-correlated factor such as temperature? Here, we provide some indirect evidence for plasticity. If the cline is indeed a plastic one, a paradox arises, because the cline mirrors interspecific variation-geophilomorph species with more northern ranges typically have fewer segments than those from further south-but interspecific differences cannot arise from nonheritable variation. We propose a resolution of this apparent paradox via a model in which genetic and environmental factors interact through selection acting on developmental reaction norms.

Animals↗
PubMed2005

Seasonal trends in usnic acid concentrations of Arctic, alpine and Patagonian populations of the lichen Flavocetraria nivalis.

The widespread secondary metabolite usnic acid, a dibenzofuran derivative, is the principal acetone-soluble compound in the lichen Flavocetraria nivalis. Seasonal variation in concentrations were studied in four populations of this lichen, three from Arctic-alpine habitats in the Northern Hemisphere, and one from Patagonian heathland in the Southern Hemisphere. Usnic acid is produced in large amounts, making up between 4% and 8% of thallus dry weight. Large seasonal variation is seen, with a trend towards peak levels in late spring and early summer, and generally low levels during autumn and winter. However, at an Arctic steppe in Central West Greenland, remarkably high levels were also detected during late autumn and early winter. Comparisons with environmental data using model selection procedures show that usnic acid levels of three of the populations are positively correlated with time of season, as measured by the proximity in time to nearest summer solstice, solar radiation levels, and temperature conditions. All these three variables are intercorrelated, thus indicating the same overall trend. For the three driest sites, precipitation rates are included in the models that best explain the variation in usnic acid. However, the explanatory powers of the models are generally low, partly due to high variation between thalli growing together and sampled at the same time. This is the first attempt to compare statistically seasonal variation in usnic acid concentrations and environmental variables, and thus also the first time it is shown that the concentration in various populations of the same lichen species shows different types of correlation with seasonal climatic changes.

Arctic Regions↗
PubMed2006

Analysis of OSPAR priority pharmaceuticals using high-performance liquid chromatography-electrospray ionisation tandem mass spectrometry.

The occurrence and potential adverse effects of pharmaceutical compounds in the aquatic environment have received much scientific interest. Presented are analytical methodologies for the determination of 10 of the pharmaceuticals listed on the Oslo and Paris Commission for the protection of the Marine Environment of the North East Atlantic (OSPAR) hazardous substances website. In addition to these 10 substances, the chemical fluoxetine (Prozac) was also investigated. The performance characteristics of a combined solid phase extraction (SPE) isolation and high-performance liquid chromatography-electrospray ionisation tandem mass spectrometry (HPLC-ESI-MS/MS) procedure have been determined. Extraction efficiencies were obtained for a variety of SPE sorbents, following this initial investigation. Strata-X (Phenomenex, UK) was selected for further development. The extraction method performed satisfactorily for the majority of the 11 compounds analysed, with recoveries of over 60% for most of the compounds and relative standard deviations of between 4 and 13%. The recoveries of chloroquine and closantel were below 50% but the method provides semi-quantitative information regarding the occurrence of these compounds. Separation of the analytes was made using a C18 Luna analytical column (Phenomenex, UK) and mass spectra were obtained using an ion trap mass spectrometer operated in both positive and negative electrospray ionisation modes. Limits of detection for all compounds ranged from 1 to 20 ng/l, making the method suitable for low level environmental analysis. Of the selected surface water and treated sewage effluent samples (n = 6) analysed, chlorpromazine, fluoxetine and miconazole were detected in concentrations ranging from 7 to 34 ng/l. The chemicals determined using this procedure fall into a variety of pharmaceutical classes including antipsychotics and tranquilisers resulting in an analytical method that contains compounds from diverse chemical classes.

Chromatography, High Pressure Liquid↗
PubMed1998

Bioseparation and bioanalytical techniques in environmental monitoring.

The growing use of antibody-based separation methods has paralleled the expansion of immunochemical detection methods in moving beyond the clinical diagnostic field to applications in environmental monitoring. In recent years high-performance immunoaffinity chromatography, which began as a separation technique in biochemical and clinical research, has been adapted for separating and quantifying environmental pollutants. Bioaffinity offers a selective biological basis for separation that can be incorporated into a modular analytical process for more efficient environmental analysis. The use of immunoaffinity chromatography for separation complements the use of immunoassay for detection. A widely used immunochemical detection method for environmental analyses is enzyme immunoassay. The objective of this paper is to review the status of bioaffinity-based analytical procedures for environmental applications and human exposure assessment studies. Environmental methods based on bioaffinity range from mature immunoassays to emerging techniques such as immunosensors and immunoaffinity chromatography procedures for small molecules.

Biosensing Techniques↗