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Results for “Environmental selection”

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PubMed2001

Potentiometric polymeric membrane electrodes for measurement of environmental samples at trace levels: new requirements for selectivities and measuring protocols, and comparison with ICPMS.

It is here established that potentiometric polymeric membrane electrodes based on electrically neutral ionophores are useful analytical tools for heavy metal ion determinations in drinking water at nanomolar total concentrations. This means that they can compete with the most sophisticated techniques of instrumental analysis. With optimized ion-selective membranes based on the lead-selective ionophore 4-tert-butylcalix[4]arenetetrakis(thioacetic acid dimethylamide) as model example, a number of native and spiked drinking water samples are potentiometrically assessed for lead, and the results compared with ICPMS measurements. The goal of this work is to demonstrate that detection limits in real world samples are routinely achieved that are, with 1.5 ppb, at least 10-fold lower than the lead action limit imposed by the U.S. Environmental Protection Agency (15 ppb). In contrast to earlier reports, different conditioning and measuring protocols are followed, and membranes and inner filling solution of optimized composition are used. The sensors are shown to be useful for the speciation analysis of lead in water as well. Typical water samples are acidified to pH 4 to assess total lead rather than free, uncomplexed lead. For lead concentrations above 2 ppb, the values compare very well with ICPMS. Main interferences are found to be H+ and Cu2+, although Cu2+ only shows significant interference at levels around or above its own action limit (1.3 ppm), in which case the water sample would anyway show quality problems. An explicit, simplified flux model targeted to the practical use of these sensors explains the extent of expected interference. Sensors are shown to require a higher selectivity than predicted by models not considering ion fluxes, since in dilute samples, the counterdiffusion flux of lead from the membrane into the sample becomes potential determining. The model and experiments shown here are a foundation for future trace level applications of potentiometric polymeric membrane electrodes.

Algorithms↗

PubMed2006

Myopia as a latent phenotype of a pleiotropic gene positively selected for facilitating neurocognitive development, and the effects of environmental factors in its expression.

Myopia has become an almost pandemic problem in many populations. There are compelling evidence to suggest that myopia is a hereditary condition. However, myopia would constitute a definite selection disadvantage during most stages of human evolution, which is incompatible with its moderate to high prevalence in most modern populations. The rapid upsurge of myopia over just a few decades also implies that its inheritance does not follow any of the usual patterns, and environmental factors may have an important role in precipitating its occurrence in those who are genetically predisposed. Previous studies showed that myopes were, on average, more intelligent than non-myopes, and this association had been attributed to a biological link between eye growth and brain development. We propose a pleiotropic genetic model to explain the atypical epidemiologic and inheritance pattern of myopia and its relationship with neurocognitive development. This pleiotropic gene was positively selected for its facilitation of human intelligence. The myopic component is a latent phenotype; myopia will not be expressed unless some novel external factors are encountered (i.e. a "quirk" phenomenon). Therefore, the myopic component was selectively neutral in our ancestral environment. The net gain in Darwinian fitness enables the pleiotropic gene to attain a high frequency in the human population, as reflected by our current prevalence of myopia.

Animals↗

PubMed1997

Transcriptional analysis of the Streptococcus mutans hrcA, grpE and dnaK genes and regulation of expression in response to heat shock and environmental acidification.

The dental pathogen Streptococcus mutans persists and causes diseases in highly dynamic environments and gains a selective ecological advantage in environmental conditions that frequently exceed the limits for growth of the organism, particularly with regard to environmental pH. The goal of this study was to begin a molecular genetic analysis of a major stress protein, DnaK/Hsp70, to begin to understand how stress responses are regulated in this lactic acid bacterium and to establish a relationship between dnaK gene expression and exposure to acidic environments. Cloning and nucleotide sequence analysis revealed that the dnaK gene is preceded by, and is in an operon-like arrangement with, the hrcA and grpE genes, although intergenic spacing was unlike that described in other bacteria. An inverted repeat (a CIRCE element) was identified by sequence analysis and, using primer extensions, a heat shock-responsive, sigmaA-type promoter, P1, 5' to the hrcA gene, and a sigmaB-type promoter, 5' to the grpE translational start site, were identified. No promoters were detected between grpE and dnaK. A strain carrying a strongly polar insertion in the hrcA gene had markedly diminished levels of dnaK mRNA, indicating that dnaK was transcribed as part of an operon from P1, and to a lesser extent from P2. Results from physiological manipulation of S. mutans in continuous chemostat culture demonstrated that steadystate levels of S. mutans dnaK mRNA and DnaK protein were (i) increased in response to acid shock; (ii) elevated in acid 'adapted' cells; and (iii) induced in response to alkali shock of acid 'adapted' cells. In all cases, increased amounts of dnaK mRNA could be correlated with enhanced transcription from P1. This study provides the first detailed analysis of the expression of a heat shock gene from an oral isolate, and the evidence provided suggests that sigmaB-like promoters may also be involved in class I heat shock gene expression in some Gram-positive organisms.

Amino Acid Sequence↗

PubMed2003

Ontogenies in mice selected for high voluntary wheel-running activity. I. Mean ontogenies.

The evolutionary importance of postnatal ontogenies has long been recognized, but most studies of ontogenetic trajectories have focused exclusively on morphological traits. For animals, this represents a major omission because behavioral traits and their ontogenies often have relatively direct relationships to fitness. Here four replicate lines of house mice artificially selected for high early-age wheel running and their four replicate control lines were used to evaluate the effects of early-age directional selection, genetic drift, and activity environment (presence or absence of a running wheel) on variation in the ontogenies of three traits known to be genetically correlated: voluntary wheel running, body mass, and food consumption. Early-age selection significantly changed both the shape and position of the wheel-running and food-consumption ontogenies while influencing the position, but not the shape, of the body mass ontogeny. Genetic drift (as indicated by variation among replicate lines) produced significant changes in both the position and shape of all three ontogenies; however, its effect differed between the selection and control groups. For wheel running and food consumption, genetic drift only influenced the control ontogenies, whereas for body mass, genetic drift had a significant effect in both selection groups. Both body-mass and food-consumption ontogenies were significantly altered by activity environment, with the environment causing significant changes in the shape and position of both ontogenies. Overall the results demonstrate strong effects of early-age selection, genetic drift, and environmental variation on the evolution and expression of behavioral and morphological ontogenies, with selection changing only the position of the morphological ontogeny but both the position and shape of the behavioral ontogenies.

Analysis of Variance↗

PubMed2002

The inheritance of mating songs in two cryptic, sibling lacewing species (Neuroptera: Chrysopidae: Chrysoperla).

Speciation often involves incremental responses to natural selection and results in large scale genomic changes, but it may also occur abruptly and with little genetic imprint, as seen in some complexes of cryptic species. Recent attention has focused on sexual selection in rapid speciation, because it can disrupt premating signals that mediate reproductive isolation. Some models require that environmental adaptation assist sexual selection during speciation, while others show that populations can diverge through mate choice alone. We propose that speciation involving environmental adaptation in premating signals is likely to have a polygenic basis, while speciation due to arbitrary changes in premating signals could be accompanied by changes at just a few loci. The sibling species Chrysoperla plorabunda and Chrysoperla johnsoni belong to a large complex of cryptic species of green lacewings, and meet all criteria for speciation via sexual selection. We perform a genetic analysis of line crosses between them, focusing on their substrate-borne premating songs. Measurements of seven song features and their principal components are compared among parentals, F1 and F2 hybrids, and backcrosses. The distributions of phenotypes are consistent with a model of more than one, but not many, genes. Sex linkage and/or maternal effects are negligible. C. plorabunda is dominant for most traits affecting mate choice. Bayesian analyses of segregation variance show significant additive and epistatic effects on line means. A Bayesian Castle-Wright estimate suggests that relatively few effective factors are responsible for variation in volley period (x = two factors), number of volleys per song (x = 1), and PC-1 (x = 4). Our results are consistent with simple genetic architecture of songs, supporting a role for major genes in premating isolation and strengthening the notion that mate choice alone, without significant environmental adaptation, has been responsible for generating new lacewing species.

Acoustic Stimulation↗

PubMed2004

Evolvability is a selectable trait.

Concomitant with the evolution of biological diversity must have been the evolution of mechanisms that facilitate evolution, because of the essentially infinite complexity of protein sequence space. We describe how evolvability can be an object of Darwinian selection, emphasizing the collective nature of the process. We quantify our theory with computer simulations of protein evolution. These simulations demonstrate that rapid or dramatic environmental change leads to selection for greater evolvability. The selective pressure for large-scale genetic moves such as DNA exchange becomes increasingly strong as the environmental conditions become more uncertain. Our results demonstrate that evolvability is a selectable trait and allow for the explanation of a large body of experimental results.

Computer Simulation↗

PubMed2006

Selective solid-phase extraction of tebuconazole in biological and environmental samples using molecularly imprinted polymers.

Molecularly imprinted polymers (MIPs) were prepared by precipitation polymerization using tebuconazole (TBZ) as a template. Frontal chromatography and selectivity experiments were used to determine the binding capabilities and binding specificities of different MIPs. The polymer that had the highest binding selectivity and capability was used as the solid-phase extraction (SPE) sorbent for the direct extraction of TBZ from different biological and environmental samples (cabbage, pannage, shrimp, orange juice and tap water). The extraction protocol was optimized and the optimum conditions were: conditioning with 5 mL methanol:acetic acid (9:1), 5 mL methanol and 5 mL water respectively, loading with 5 mL aqueous samples, washing with 1.2 mL acetonitrile (ACN):phosphate buffer (5:5, pH3), and eluting with 3 mL methanol. The MIPs were able to selectively recognize, effectively trap and preconcentrate TBZ over a concentration range of 0.5-15 micromol/L. The intraday and interday RSDs were less than 9.7% and 8.6%, respectively. The limit of quantification was 0.1 micromol/L. Under optimum conditions, the MISPE recoveries of spiked cabbage, pannage, shrimp, orange juice and tap water were 62.3%, 75.8%, 71.6%, 89% and 93.9%, respectively. MISPE gave better HPLC separation efficiencies and higher recoveries than C18 SPE and strong cation exchange (SCX) SPE.

Acetic Acid↗

PubMed2026

Soil erosion and landscape elevation as unnoticed determinants of environmental antibiotic resistance distribution.

Climate change is reshaping the global antibiotic resistance gene (ARG) landscape through geomorphological processes that remain largely overlooked in the One Health framework. This critical review synthesises evidence on how soil erosion and landscape elevation gradients redistribute, select for, and disseminate ARGs across terrestrial and aquatic ecosystems. Erosion physically removes and transports ARG-bearing microbes, depletes nutrients, and co-selects for resistance via heavy metal exposure and horizontal gene transfer, creating source-sink dynamics that connect eroding hillslopes to downstream water bodies and food systems. Elevation gradients impose abiotic stressors-declining temperature, elevated UV radiation, and shifting pH-that drive microbial community reassembly through environmental selection and dispersal limitation, with emerging evidence linking bacterial competition at high altitude to enhanced multidrug efflux and resistome complexity. The review identifies critical knowledge gaps, including unquantified ARG mass fluxes across erosion-deposition gradients, unresolved dispersal-versus-selection mechanisms along elevation transects, and the absence of integrated One Health surveillance linking environmental ARG reservoirs to clinical outcomes. A synthesis of global case studies illustrates how these processes converge across diverse landscapes. The review concludes with a mechanistic research agenda-including reciprocal transplant experiments, landscape connectivity modelling, and cross-sectoral surveillance-needed to translate these emerging drivers into actionable climate-AMR mitigation policy.

Drug Resistance, Microbial↗

PubMed2006

Potential self-selection bias in a nested case-control study on indoor environmental factors and their association with asthma and allergic symptoms among pre-school children.

Selection bias means a systematic difference between the characteristics of selected and non-selected individuals in epidemiological studies. Such bias may be introduced if participants select themselves for a study. The present study aims at identifying differences in family characteristics, including health, building characteristics of the home, and socioeconomic factors between participating and non-participating families in a nested case-control study on asthma and allergy among children. Information was collected in a baseline questionnaire to the parents of 14,077 children aged 1-6 years in a first step. In a second step 2,156 of the children were invited to participate in a case-control study. Of these, 198 cases and 202 controls were finally selected. For identifying potential selection bias, information concerning all invited families in the case-control study was obtained from the baseline questionnaire. Results show that there are several possible biases due to self-selection involved in an extensive study on the impact of the home environment on asthma and allergy among children. Factors associated with participating were high socioeconomic status of the family, more health problems in the case families, and health-related lifestyle factors, such as non-smoking parents. The overall conclusion of this study is that there are selection biases involved in studies that need close cooperation with the families involved. One solution to this problem is stratification, i.e. investigating associations between exposures and health in the same socioeconomic strata.

Air Pollution, Indoor↗

PubMed2004

Sensitivity of the immature rat uterotrophic assay to mixtures of estrogens.

We have evaluated whether mixtures of estrogens, present in the mix at doses that are individually inactive in the immature rat uterotrophic assay, can give a uterotrophic response. Seven chemicals were evaluated: nonylphenol, bisphenol A (BPA), methoxychlor, genistein (GEN), estradiol, diethylstilbestrol, and ethinyl estradiol. Dose responses in the uterotrophic assay were constructed for each chemical. The first series of experiments involved evaluating binary mixtures of BPA and GEN at dose levels that gave moderate uterotrophic responses when tested individually. The mixtures generally showed an intermediate or reduced uterotrophic effect compared with when the components of the mixture were tested alone at the dose used in the mixture. The next series of experiments used a multicomponent (complex) mixture of all seven chemicals evaluated at doses that gave either weakly positive or inactive uterotrophic responses when tested individually in the assay. Doses that were nominally equi-uterotrophic ranged over approximately six orders of magnitude for the seven chemicals. Doses of agents that gave a weak uterotrophic response when tested individually gave a marginally enhanced positive response in the assay when tested combined as a mixture. Doses of agents that gave a negative uterotrophic response when tested individually gave a positive response when tested as a mixture. These data indicate that a variety of different estrogen receptor (ER) agonists, present individually at subeffective doses, can act simultaneously to evoke an ER-regulated response. However, translating these findings into the process of environmental hazard assessment will be difficult. The simple addition of the observed, or predicted, activities for the components of a mixture is confirmed here to be inappropriate and to overestimate the actual effect induced by the mixture. Equally, isobole analysis is only suitable for two- or three-component mixtures, and concentration addition requires access to dose-response data and EC50 values (concentration giving 50% of the maximum response) for the individual components of the mixture--requirements that will rarely be fulfilled for complex environmental samples. Given these uncertainties, we conclude that it may be most expedient to select and bioassay whole environmental mixtures of potential concern.

Animals↗

PubMed2001

[Epidemiological study of genetic and environmental factors in asthma, bronchial hyperresponsiveness and atopy. Protocol and potential selection bias].

BACKGROUND: The EGEA study combines a case-control study and a family study to assess genetic and environmental risk factors and their interactions for asthma, bronchial hyperresponsiveness and atopy. Information is scanty regarding potential selection biases, in particular regarding familial ressemblance in epidemiological surveys of this kind. METHODS: Asthmatic probands (adult and paediatric) were recruited in chest clinics of six clinical centres. Controls were mostly population-based (electoral rolls) for adults and recruited in surgery departments for children. RESULTS: The population examined includes 348 nuclear families ascertained by one asthmatic and 416 controls, totalling 1847 subjects (EGEA I) and an additional sample of 40 families ascertained by two asthmatic siblings (EGEA II). Potential biases for the various types of analyses have been studied. Quantification of the consequences of the greater participation of probands with a parental history of asthma shows it does not introduce a major bias in the estimates of familial resemblance. Cases and controls showed a good comparability regarding sex, age, area of residence and familial geographical origin, allowing proper associations studies for environmental and candidate genetic factors. CONCLUSIONS: The case-control component of the study will allow to perform studies on environmental factors and association studies for various genetic polymorphisms. Using the family base collected, segregation and genetic linkage/association analyses with DNA markers may be performed.

Adult↗

PubMed2005

Evaluating the application of a decision support system in identifying adequate wastewater treatment for small communities. A case study: the Fluvia River Basin.

The identification of adequate wastewater treatment for small communities is a complex problem since it demands a combination of data from different sources, such as aspects of the community and landscape, the receiving environment and the available wastewater treatment technologies. The Catalan Water Agency (Agència Catalana de l'Aigua) considered using an EDSS (Environmental Decision Support System) as a tool to help water managers select the most adequate treatment for the urban wastewater of nearly 3,500 small communities in Catalonia (Spain). From that moment, EDSS was applied to all the river basins in Catalonia. In this paper the authors present the results obtained for the 76 small communities located in one of these river basins: the Fluvia River Basin. The characteristics of the community used in the reasoning process of the EDSS, the list of selected wastewater treatment alternatives, the technical environmental justification for the selected treatments and the reasons for discarding, favouring or disadvantaging them are presented. Finally, some results for the Fluvia River Basin are compared with those obtained in other Catalan river basins with different characteristics in order to evaluate which are the significant features in identifying adequate wastewater treatments.

Cities↗

PubMed2005

Predictive adaptive responses and human evolution.

The importance of a single genotype being able to produce different phenotypes in different environments (phenotypic plasticity) is widely recognized in evolutionary theory and its adaptive significance is clear. In most cases, the developing organism responds to an environmental cue by producing a selectively and immediately appropriate phenotype. One subset of phenotypic responses to environmental stimuli, however, does not necessarily provide an immediate selective advantage. Rather, these kinds of responses, which we call 'predictive adaptive responses' (PARs), act primarily to improve fitness at a later stage of development. We argue that PARs have had an important role in human evolution, and that their recognition and interpretation has major significance for public health.

Journal Article↗

PubMed2003

Quadrupole time-of-flight versus triple-quadrupole mass spectrometry for the determination of non-steroidal antiinflammatory drugs in surface water by liquid chromatography/tandem mass spectrometry.

A triple-quadrupole instrument and a hybrid quadrupole/time-of-flight (TOF) mass spectrometer were compared for the determination of pharmaceutical compounds in water samples. The drugs investigated were the analgesics Ibuprofen, Fenoprofen, Ketoprofen, Naproxen, and Diclofenac. The recently introduced Q2-pulsing function, which enhances the transmission of fragment ions of a selected m/z window from the collision cell into the TOF analyzer, improved the sensitivity of product ion scans on the quadrupole/TOF instrument. The selectivity is much better on quadrupole/TOF systems than on triple quadrupoles because the high resolving power of the reflectron-TOF mass analyzer permits high-accuracy fragment ion selection. This minimizes interferences from environmental matrices and allows acquisition of full spectra for selected analytes with better signal-to-noise characteristics than comparable spectra obtained with a scanned quadrupole. The qualitative information obtained (mass accuracy, resolution and full-scan spectra) by hybrid quadrupole/TOF mass spectrometry allows a more certain identification of analytes in environmental matrices at trace levels. Sample enrichment of water samples was achieved by a solid-phase extraction procedure. Average recoveries for loading 1 L of samples varied from 88 to 110%, and the quantification limits were less than 1.2 ng/L for the triple-quadrupole instrument (in MRM mode) and less than 3 ng/L for the quadrupole/TOF instrument.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2000

Comparison of the Rodac imprint method to selective enrichment broth for recovery of vancomycin-resistant enterococci and drug-resistant Enterobacteriaceae from environmental surfaces.

We compared the Rodac imprint technique to selective enrichment broth for detecting vancomycin-resistant enterococci (VRE) and multidrug-resistant Enterobacteriaceae (MDRE) on surfaces. Rodac plates contained tryptic soy agar with 5% sheep blood, vancomycin (6 microg/ml), ceftazidime (2 microg/ml), amphotericin B (2 microg/ml), and clindamycin (1 microg/ml). Two types of broth were used: brain heart infusion (BHI) and BHI plus vancomycin (6 microg/ml) and ceftazidime (2 microg/ml) (BHIVC). Of the 46 surfaces cultured for VRE, 12 (26%) were positive. Of the 12 VRE-positive surfaces, 11 (92%) grew from Rodac, 8 (67%) grew from BHIVC, and 7 (58%) grew from BHI. A larger study is needed for MDRE, as only 4 of 43 surfaces were MDRE positive. The Rodac imprint technique successfully recovered VRE from environmental surfaces.

Culture Media↗

PubMed2002

Selection of subjects for human milk surveillance and research studies.

Subject selection for studies investigating environmental chemicals in human milk requires thoughtful consideration of multiple factors. Studies often need to produce generalizable and representative data that can be compared to other similar studies. Goals of the study determine the selection of subjects. Exposure is only one factor that influences the levels of environmental chemicals in human milk. Many maternal and infant characteristics should be considered in subject selection. Collection procedures of human milk samples also affect subject selection, as subject burden may be enough to reduce compliance with the collection protocols. Decisions must be made about pooling of samples both within subjects and within populations. Guidelines for subject selection are provided by the World Health Organization for human milk monitoring, but distinct differences in the lactational practices, geography, and ethnic and racial diversity of the U.S. population require somewhat different approaches.

Adult↗

PubMed2004

Environmental risk assessment of medicinal products for human use according to European Commission recommendations.

Presented here, based on new recommendations of the European Commission, is an environmental risk assessment (ERA) of a selected group of pharmaceuticals for Phase I, environmental exposure assessment, and Phase II Tier A, initial environmental fate and effect analysis. This pharmaceutical group is composed of the 111 highest-selling human drug substances that have annual sales in Germany of more than 5,000 kg. The data required for this ERA came from analyzing: (1) sales annually (in kg or IU) of the 2671 active pharmaceutical drug substances (2001) on the German market in all medicinal products sold by pharmacies (with and without prescriptions) and used in hospitals in 1996-2001; (2) the use pattern of drug substances as categorized according to Anatomical Therapeutic Chemical (ATC) classification indexes ATC3 and ATC7; (3) data for excretion, toxicity, and metabolites of the 111 selected human drug substances; (4) the physicochemical properties of these substances; and (5) the degradability of selected drug substances in sewage treatment plants (STPs) by using a validated and accredited liquid chromatography-electrospray ionization tandem mass spectrometry method. A correction factor for the pharmaceutical therapeutic (PT) activity of metabolites, the PT(Index) (excretion rate/100) for drug substances and PT active metabolites was established to refine the predicted environmental concentration (PEC(SURFACEWATER)). A refinement of the PEC(SURFACEWATER) was carried out with the market penetration factor of the human drug substances in Germany. In addition, for effect analysis the predicted no-effects concentration (PNEC) was calculated using assessment factors. The estimated PEC results were validated with the exposure results of effluents of the STPs. All results on ERA of drug substances have been documented in a Microsoft Access 2000 database.

Advisory Committees↗

PubMedDate not supplied

Environmental chemicals and nervous system dysfunction.

Selected examples of associations between nervous system diseases and exposures to occupational and environmental chemicals have been reviewed. Recent outbreaks of human neurotoxicity from both wellknown and previously unknown toxicants reemphasize the need for the medical community to give increased attention to chemical causes of nervous system dysfunction.

Animals↗