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At least 325 records · Page 18Linked to original sources
PubMed2002

Toxicity of tetracyclines and tetracycline degradation products to environmentally relevant bacteria, including selected tetracycline-resistant bacteria.

Tetracyclines used in veterinary therapy invariably will find their way as parent compound and degradation products to the agricultural field. Major degradation products formed due to the limited stability of parent tetracyclines (tetracycline, chlortetracycline, and oxytetracycline) in aqueous solution were theoretically identified at various environmental conditions, such as pH, presence of chelating metals, and light. Their potency was assessed on sludge bacteria, tetracycline-sensitive soil bacteria, and tetracycline-resistant strains. Several of the degradation products had potency at the same concentration level as tetracycline, chlortetracycline, and oxytetracycline on both the sludge and the tetracycline-sensitive soil bacteria. Further, both 5a,6-anhydrotetracycline and 5a,6-anhydrochlortetracycline had potency on tetracycline-resistant bacteria supporting a mode of action different from that of the parent compounds.

Bacteria↗
PubMed1999

Birth outcome, the social environment and child health.

OBJECTIVES: This article examines the effects of birth outcome and selected social environmental factors on the health of young children. DATA SOURCE: The data are from the 1994/95 National Longitudinal Survey of Children and Youth. Information provided by the biological mothers of 5,888 children younger than age 3 is analyzed. ANALYTICAL TECHNIQUES: The analysis focuses on two measures of child health: the mother's perception of the child's general health and a diagnosis of asthma. Logistic regression was used to estimate the effects of birth outcome and selected social environmental factors on these measures. Birth outcome refers to gestational age and birthweight. Social environmental factors include maternal education, maternal smoking, maternal age at birth of child, family status and household income. MAIN RESULTS: Preterm low birthweight was associated with a higher risk of poor health and asthma among children when all the other selected risk factors were controlled. Poor maternal health and maternal smoking were important risk factors for poor child health. Maternal asthma and low maternal education were significantly associated with childhood asthma.

Asthma↗
PubMed2005

Poly(ethylene glycol) micro-patterns as environmentally sensitive template for selective or non-selective adsorption.

Poly(ethylene glycol) (PEG), a hydrophilic and repulsive polymer to non-specific adsorption, was stamped onto carboxylic acid-enriched polymer surfaces using the micro-contact printing technique. The patterns are stabilized via hydrogen bonds. Areas printed with PEG were then shown to be non-adsorbed with fluorescein isothiocyanate (FITC)-labeled dextran, while the poly(methacrylic acid) (PMAA) regions could via hydrogen bonding. Due to this contrast, well defined dextran patterns were obtained. Tuned with pH and temperature, the PEG molecules could be detached from the surfaces, erasing the template. Moreover, ionization of PMAA at higher pH induced an abrupt transition to an extended conformation, weakening the interactions between PMAA and dextran. Not only the dextran patterns lose their spatial selectivity, but also the overall adsorption amount is much lower. The pH sensitivity was in a quite narrow range, i.e. around pH 5. As the hydrogen bonds are also temperature sensitive, the attach points of PEG molecules on the surfaces disappeared at higher temperature. For poly(acrylic acid) (PAA) photografted surfaces, the pH sensitivity was more complicated due to the formation of the compact complexes of PEG and PAA molecules.

Adsorption↗
PubMed2003

Raman spectroscopy of selected lead minerals of environmental significance.

The Raman spectra of the minerals cerrusite (PbCO(3)), hydrocerrusite (Pb(2)(OH)(2)CO(3)), phosgenite (Pb(2)CO(3)Cl(2)) and laurionite (Pb(OH)Cl) have been used to qualitatively determine their presence. Laurionite and hydrocerrusite have characteristic hydroxyl stretching bands at 3506 and 3576 cm(-1). Laurionite is also characterised by broad low intensity bands centred at 730 and 595 cm(-1) attributed to hydroxyl deformation vibrations. The minerals cerrusite, hydrocerrusite and phosgenite have characteristic CO (nu(1)) symmetric stretching bands observed at 1061, 1054 and 1053 cm(-1). Phosgenite displays complexity in the CO (nu(3)) antisymmetric stretching region with bands observed at 1384, 1327 and 1304 cm(-1). Cerrusite shows bands at 1477, 1424, 1376 and 1360 cm(-1). The hydrocerrusite Raman spectrum has bands at slightly different positions from cerrusite, with bands at 1479, 1420, 1378 and 1365 cm(-1). The complexity of the nu(3) region is also reflected in the nu(2) and nu(4) regions with the observation of multiple bands. Laurionite is characterised by two intense bands at 328 and 272 cm(-1) attributed to PbO and PbCl stretching bands. Importantly, all four minerals are characterized by their Raman spectra, enabling the mineral identification in leachates and contaminants of environmental significance.

Environmental Pollutants↗
PubMed2006

Maintenance of environmental homeostasis by biota, selected nonlocally by circulation and fluctuation mechanisms.

A simple abstract model is presented to show that a species with a favorable global effect on the whole biota (for example, by generating a moderate temperature range) can be selected through evolution. In the model, fluctuation in the growth rate among species leads to selection. The accompanying fluctuations in the quantity of resources, which return by circulation with a certain time lag, are likely to cause this selection. Different functions and various parameters are applied to the equations to monitor their effects on the whole system. In nature, producers satisfy the theoretical conditions of the model, implying the reality of the selection described by the mechanism presented here, during the history of the biota.

Biodiversity↗
PubMed1986

Hexachlorobenzene in selected marine samples: an environmental perspective.

Hexachlorobenzene (HCB) has been designated by the US Environmental Protection Agency as a chemical of interest. Re-examination of previously analysed gas chromatograms and archived samples revealed peaks that co-eluted with the authentic HCB standard. Levels of HCB were less than 1 ng/g in all samples re-examined, and were at least three to four orders of magnitude lower than those of poly-chlorinated biphenyls, two orders of magnitude lower than those of pyrene and one to two orders of magnitude lower than levels of either phenanthrene or benzo[a]-pyrene found in the same mussel samples. Chromatograms of sea water (dissolved and particulate phases) and sediments also revealed very low levels of HCB. Because gas chromatography-mass spectrometry results indicated that levels of HCB were below the level of detection it was not possible to verify its presence. The environmental data on HCB provided by the US Mussel Watch programme demonstrate that HCB levels in mussels are minor compared with other organic compounds such as polychlorinated biphenyls and polycyclic aromatic hydrocarbons (phenanthrene, pyrene and benzo[a]pyrene). Mussels were transplanted to areas affected by industrial activity and by disposal of sewage sludge and dredged materials, and in relatively clean reference sites. Transplanted mussels were used to monitor the marine food chain, as surrogates for other biota in the same areas and as sentinel organisms to monitor localized differences in biologically available chemical compounds. The degree of environmental threat posed by HCB in the marine environment, as indicated by the US Mussel Watch data, is relatively low. It is therefore recommended that a decision be made not to pursue an expanded HCB monitoring programme in the marine environment solely to collect more HCB data.

Animals↗
PubMed1993

Effects of environmental changes on natural selection active on human polygenic traits.

During the last century, industrialized countries experienced such an improvement in socioeconomic conditions and in sanitation that it is likely that the selective forces active on human metric traits have been modified. Perinatal mortality as a function of birth weight is one of the clearest examples of natural selection in humans. Here, trends over time of stabilizing and directional selection associated with birth weight have been analyzed in Japan from 1969 to 1989. The population of newborns has been subdivided according to gestational age, which is one of the main covariates of birth weight. The results show that in full-term babies both stabilizing and directional selection are coming to an end, whereas in babies born after 8 months of gestation these selective forces are still active, even if at much lower levels than in the past. The peculiar results found in the 7-month-gestation population are probably due to grossly abnormal cases of immaturity.

Birth Weight↗
PubMed2000

Is the Prunella (Lamiaceae) hybrid zone structured by an environmental gradient? Evidence from a reciprocaltransplant experiment.

Hybrid zones may be structured by environmentally independent selection against intrinsically unfit hybrids (tension zone models), or by environmentally dependent fitness differences among parental species and hybrids (ecological selection-gradient models). A 30-m slope in a mountain grassland harbors a hybrid zone of the clonal perennials, Prunella grandiflora and P. vulgaris (Lamiaceae), with P. grandiflora in the upper, P. vulgaris in the lower, and both parental species and P. grandiflora × P. vulgaris Hybrids in a narrow middle part. We found gradients for soil depth and water content, and vegetation height and biomass along the slope. A reciprocal transplant experiment yielded crossing reaction norms for vegetative reproduction. Parental species were locally adapted to their home sites, while the three taxa did not differ in vegetative reproduction in the Hybrid transplant site. Local adaptation for vegetative reproduction of P. grandiflora was mediated through higher survival and that of P. vulgaris through higher ramet number, indicating adaptation of their clonal growth strategies (phalanx vs. guerrilla) to the different habitats. Hybrid performance was intermediate between that of the parental species in all three sites, although Hybrids flowered more often than the parental species in the Hybrid site. Our results support ecological selection-gradient rather than tension zone models.

Journal Article↗