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 145 records · Page 8Linked to original sources

PubMed1997

Microbial production of surfactants and their commercial potential.

Many microorganisms, especially bacteria, produce biosurfactants when grown on water-immiscible substrates. Biosurfactants are more effective, selective, environmentally friendly, and stable than many synthetic surfactants. Most common biosurfactants are glycolipids in which carbohydrates are attached to a long-chain aliphatic acid, while others, like lipopeptides, lipoproteins, and heteropolysaccharides, are more complex. Rapid and reliable methods for screening and selection of biosurfactant-producing microorganisms and evaluation of their activity have been developed. Genes involved in rhamnolipid synthesis (rhlAB) and regulation (rhlI and rhlR) in Pseudomonas aeruginosa are characterized, and expression of rhlAB in heterologous hosts is discussed. Genes for surfactin production (sfp, srfA, and comA) in Bacillus spp. are also characterized. Fermentative production of biosurfactants depends primarily on the microbial strain, source of carbon and nitrogen, pH, temperature, and concentration of oxygen and metal ions. Addition of water-immiscible substrates to media and nitrogen and iron limitations in the media result in an overproduction of some biosurfactants. Other important advances are the use of water-soluble substrates and agroindustrial wastes for production, development of continuous recovery processes, and production through biotransformation. Commercialization of biosurfactants in the cosmetic, food, health care, pulp- and paper-processing, coal, ceramic, and metal industries has been proposed. However, the most promising applications are cleaning of oil-contaminated tankers, oil spill management, transportation of heavy crude oil, enhanced oil recovery, recovery of crude oil from sludge, and bioremediation of sites contaminated with hydrocarbons, heavy metals, and other pollutants. Perspectives for future research and applications are also discussed.

Bacteria↗

PubMed1998

Determination of physiological levels of volatile organic compounds in blood using static headspace capillary gas chromatography with serial triple detection.

A static capillary gas chromatographic method using three different detectors [photoionization detector (PID), electron capture detector (ECD) and flame ionization detector (FID)] switched in series is presented for the determination of volatile organic compounds (VOCs) in sub microgram l-1 levels. The method was applied for the analysis of selected environmentally and occupationally relevant non-halogenated and chlorinated aromatic hydrocarbons (e.g., benzene, toluene, xylenes, dichlorobenzenes) as well as chlorinated aliphatic hydrocarbons (e.g., trichloroethene, tetrachloroethene) in blood samples. Detailed investigations, in respect to the figures of merit were carried out. For most of the selected VOCs detection limits (calculated as the three-fold standard deviation of low level calibration standards) in the range from 26 (benzene) to 67 ng l-1 (m/p-xylene) were achieved which are comparable with those reported for dynamic headspace techniques in combination with mass spectrometric detection. For the individual VOCs the within-series precision varied from 4 to 19% and the day-to-day precision from 11 to 28%. Regarding PID as well as FID the calibration graphs for all substances were linear up to at least 10 micrograms l-1 while the ECD response was linear up to concentrations of about 0.6 microgram l-1 for the halogenated compounds. Our method is applicable for the quantitative determination of VOCs in blood in the occupationally as well as in the physiologically relevant (normal) concentration range.

Air Pollutants↗

PubMed1979

Consideration and implications of tumor antigenic expression.

This review is an attempt to simplify the myriad descriptions of tumor antigens, by considering such antigens in the perspective of their mechanisms of formation. We believe that most and possibly all tumor antigens previously described and currently under study will ultimately fit into one of the categories discussed in this article, since there are only a finite number of biochemical mechanisms for producing new antigens in any cell--cancerous or otherwise. Pragmatically, we view the vagaries of expression of tumor antigens as among their most important properties, and the search for tumor antigens has in fact opened a Pandora's box of molecular variability. Large tumor masses consisting of multiple subclones with different karyotypes, chromosomal anomalies and mutations would appear to be capable of expressing a motley group of tumor antigens. To the best of our knowledge, no tumor antigen has been shown to be necessary and causal in transformation, except in virally-induced tumors. The presence of tumor antigens appears to be coincidental and reflects dedifferentiation and karyotypic, metabolic and nutritional variations occurring in tumors. Undoubtedly, some antigens may give a tumor a selective advantage of growth, metabolism or metastatic potential, but many antigens may simply reflect the vagaries of the tumor cell. The intratumor and intertumor variations of tumor antigens, their mechanisms of origin and their rather uncanny capabilities to change their phenotype--antigen expression--secondary to environmental selection during tumor expansion or following therapy should be kept in mind when tumor antigens and immunotherapy are considered.

Animals↗

PubMed1992

Prevention of ischemia-induced cerebral hypothermia by controlling the environmental temperature.

Regulation of brain temperature during and after cerebral ischemia plays an important role in the evolution of neuronal damage. Therefore, it is essential to maintain brain temperature at 37 degrees C during and after the ischemic insult. To get information about brain temperature during the experimental procedure, researchers in previous works have made various attempts to correlate between brain and body temperature during and after ischemia. In the present study, brain temperature was measured when ischemia was performed either at 30 degrees C or at 20 degrees C environmental temperature. For this purpose a stainless-steel guide of a temperature probe was introduced through the bregma and implanted between both hemispheres of the rat. Rats were then subjected to a 10-min period of forebrain ischemia. Cerebral temperature was measured during ischemia and up to 90 min; in some experiments up to 4 hr after ischemia. In another group of experiments, ischemia was performed also at either 30 degrees C or 20 degrees C environmental temperature, and histological assessment of the rat hippocampus was carried out. In addition, the influence of chlorpromazine as a hypothermic agent on the cerebral temperature and the neuronal loss was also tested at both of the experimental conditions. Recording the brain temperature at both of the selected environmental temperatures suggests that it is possible to preserve cerebral normothermia during and after ischemia by working at 30 degrees C environmental temperature. On the other hand, brain temperature dropped sharply immediately after ischemia when working under 20 degrees C environmental temperature, and brain tissue was thereby protected against ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1983

Gastrointestinal cancer mortality in New Jersey counties, and the relationship with environmental variables.

The State of New Jersey (NJ) USA has been thought to have an unusually high cancer mortality rate; this assumption has been based on 1950-1969 mortality data for its 21 counties. This paper presents an analysis of gastrointestinal (GI) cancer mortality rates in New Jersey counties during 1968-1977, a comparison with the 1950-1969 rates, and associations between current GI cancer mortality rates and selected environmental variables. Age-adjusted mortality rates for GI cancers were calculated for the 21 NJ counties during the period 1968-1977, and were compared with the period 1950-1969, with the Surveillance, Epidemiology and End Results (SEER) survey and with cancer mortality in the US, 1973-1977. The county rates were also correlated with: the distribution of chemical toxic waste disposal sites; annual per capita income; the rates of low birth weight, birth defects, and infant mortality; chemical industry distribution; percentage of the population employed in chemical industries; the density of population; and the urbanization index for each of the counties. Some of the major findings are: Age-adjusted GI cancer mortality rates (all sites combined) were higher than national rates in 20 of 21 NJ counties. In comparison with national trends, NJ stomach cancer rates have declined less, oesophageal cancer rates have declined more, and pancreatic cancer mortality rates have followed similar patterns. Cancer mortality rates in NJ during the period 1968-1977 significantly (p less than 0.0001) exceeded national rates for cancer of the oesophagus (white male, non-white male), stomach (men and women), colon (white male, white female, non-white female), and rectum (whites only). In 18 of the 21 NJ counties, the observed number of cancer deaths for at least one GI cancer site was significantly greater than expected at the 0.0001 level for at least one population subgroup. Among white men, a significant (p less than 0.0001) excess of observed over expected cancer deaths was observed for three or more GI cancer sites in seven counties. The environmental variables that were most frequently associated with GI cancer mortality rates (except pancreatic cancer) were degree of urbanization, population density, and chemical toxic waste disposal sites. Some of the implications of the study findings are discussed and recommendations made for future investigations.

Adult↗

PubMed2006

Development of AFLP-derived, functionally specific markers for environmental persistence studies of fungal strains.

The ability to rapidly identify and quantify a microbial strain in a complex environmental sample has widespread applications in ecology, epidemiology, and industry. In this study, we describe a rapid method to obtain functionally specific genetic markers that can be used in conjunction with standard or real-time polymerase chain reaction (PCR) to determine the abundance of target fungal strains in selected environmental samples. The method involves sequencing of randomly cloned AFLP (amplified fragment length polymorphism) products from the target organism and the design of PCR primers internal to the AFLP fragments. The strain-specific markers were used to determine the fate of three industrially relevant fungi, Aspergillus niger, Aspergillus oryzae, and Chaetomium globosum, during a 4 month soil microcosm experiment. The persistence of each of the three fungal strains inoculated separately into intact soil microcosms was determined by PCR analyses of DNA directly extracted from soil. Presence and absence data based on standard PCR and quantification of the target DNA by real-time PCR showed that all three strains declined after inoculation (approximately 14-, 32-, and 4-fold for A. niger, A. oryzae, and C. globosum, respectively) but remained detectable at the end of the experiment, suggesting that these strains would survive for extended periods if released into nature.

Aspergillus niger↗

PubMedDate not supplied

Mothers of chronically ill children and perceptions of environmental variables.

Environment plays a critical role in supporting families, but the influence of the environment on families with a chronically ill child has remained relatively unexplored. This paper presents a study that examined the role of the environment in families with a chronically ill child. This study, using a secondary analysis of two existing data bases (Holaday & Turner-Henson, 1991; U.S. Bureau of the Census, 1980), examined the influence of selected environmental factors on mothers' perceptions of the environment as supportive, resourceful, safe, and accessible. A presentation of the study findings, as well as implications for nursing practice, is presented.

Adult↗

PubMed2006

Genetic and phenotypic diversity of quorum-sensing systems in clinical and environmental isolates of Vibrio cholerae.

Vibrio cholerae is the causative agent of cholera, a severe and devastating diarrheal disease. V. cholerae lives naturally in various aquatic habitats during interepidemic periods. Recent studies reveal that quorum-sensing systems, which exist in many bacteria and help them monitor their population densities and regulate various cellular functions, control V. cholerae pathogenesis, biofilm formation, and protease production. In this study we surveyed quorum-sensing systems in 16 geographically diverse V. cholerae strains from epidemic-causing O1 and O139 strains as well as non-O1/non-O139 and environmental isolates and discovered an unexpectedly high rate of dysfunctional components. We also found that a functional quorum-sensing system conferred a survival advantage on bacteria in biofilms when the bacteria were exposed to seawater, though quorum sensing was less important to survival in a planktonic state under the same conditions. These findings suggest that variations in quorum-sensing systems are due to environmental selective pressures and might be beneficial to V. cholerae's fitness under certain conditions found in its natural reservoirs.

Amino Acid Sequence↗

PubMed1998

Isolation of carbon- and nitrogen-deprivation-induced loci of Sinorhizobium meliloti 1021 by Tn5-luxAB mutagenesis.

Soil bacteria, such as Sinorhizobium meliloti, are subject to variation in environmental conditions, including carbon- and nitrogen-deprivation. The ability of bacteria to sense changes in their environment and respond accordingly is of vital importance to their survival and persistence in the soil and rhizosphere. A derivative of Tn5 which creates transcriptional fusions to the promoterless luxAB genes was used to mutagenize S. meliloti 1021 and 5000 insertion mutants were subsequently screened for gene fusions induced by selected environmental stresses. The isolation of 21 gene fusions induced by nitrogen-deprivation and 12 induced by carbon-deprivation is described. Cloning and partial DNA sequence analysis of the transposon-tagged loci revealed a variety of novel genes, as well as S. meliloti genes with significant similarity to known bacterial loci. In addition, nodule occupancy studies were carried out with selected Tn5-luxAB insertion mutants to examine the role of the tagged genes in competition.

Amino Acid Sequence↗

PubMed2003

'Ready made' virulence and 'dual use' virulence factors in pathogenic environmental fungi--the Cryptococcus neoformans paradigm.

Environmental pathogenic fungi present a paradox in that they are virulent in animals without requiring animal hosts for replication or survival, a phenomenon we call 'ready-made' virulence. In the human pathogenic fungus Cryptococcus neoformans, the capacity for virulence in animals may originate from environmental selective pressures imposed by such organisms as amoeboid and nematode predators. Many C. neoformans virulence factors appear to have 'dual use' capabilities that confer survival advantages in both animal hosts and in the environment. The findings with C. neoformans may provide a paradigm for understanding the origin and maintenance of virulence in other pathogenic environmental fungi.

Animals↗

PubMed2006

Environmental and dietary risk factors for infantile atopic eczema among a Slovak birth cohort.

Infantile atopic eczema (AE) is a risk marker for future asthma. This study assesses the contribution of modifiable exposures to infantile AE. If modifiable exposures contribute substantially to infantile AE, its prevention might be a sensible approach to asthma prevention. Pregnant women (n = 1978) were systematically recruited from maternity hospitals of the Slovak Republic; their birthed cohort of 1990 children were prospectively followed for 1 yr. Children's exposures to selected environmental and dietary factors were assessed via maternal questionnaires administered at delivery and 1 yr of age. A child was considered to have AE, based on physical examination (SCORAD index >2) or mother's report of a previous physician diagnosis. Multivariate logistic regression was used to calculate adjusted odds ratios and percent total regression scores (TRS) for each variable. At 1 yr of age 1326 (67%) of the children remained in the cohort and 207 (15.6%) developed AE. Various modifiable environmental and dietary exposures increased the likelihood of AE (ownership of cats; consumption of infant formula, eggs, and fish) while others decreased the likelihood of AE (ownership of livestock; exclusive breast feeding for > or =4 months). Overall, modifiable exposures contributed less to the TRS than did non-modifiable exposures (38% vs. 62%, respectively). The modifiable exposure category that contributed most to the TRS was infant feeding practices (27.5% TRS). Modifiable exposures -- especially those related to infant feeding practices -- significantly contribute to infantile AE, although modifiable factors contribute less overall than do non-modifiable exposures.

Adult↗

PubMed1996

A pragmatic primer ... lessons from natural science for the profession of dentistry.

Artificially supplementing our community water supplies with optimal amounts of fluoride to gain the benefits of a significant reduction in dental caries is a lesson we have learned from natural science, a lesson from nature we have appropriated for culture- and a very pragmatic lesson. Today, we have discovered through science additional principles of nature that can be instructive and that can be appropriated for the profession of dentistry's benefit. This paper reviews five principles of natural science and derives lessons for the profession from these principles. The principles include natural selection, environmental change, form follows function, symbiosis, and entropy. Lessons derived from these principles of natural science are, respectively: survival and thriving of the profession are dependent upon the environment; the status quo will not be maintained-the profession must acknowledge, encourage, and celebrate change; the form the profession assumes must be consistent with its function of serving society; the profession must acknowledge the interdependence and reciprocity existing in its relationship with society; and the profession must continuously, energetically, and creatively reconstruct and renew itself. The challenge before us is to transform dentistry into a profession that continuously anticipates environmental changes by energetically creating new forms or structures that will result in more effective fulfillment of our function: gaining the benefits of oral health for society.

Community-Institutional Relations↗

PubMed1992

Environmental health risks of toxic waste site exposures--an epidemiological perspective.

A general account is given of the problems of assessing the impact of human exposure to toxic waste sites, including the identification of truly exposed populations and of exposure pathways. Epidemiological studies of populations at risk are briefly reviewed and methodological problems summarised. These include the use of relatively weak study designs, inadequate exposure assessment and recall biases associated with symptom reporting among anxious residents living in the vicinity of waste sites. In South Africa, health risks associated with exposure to toxic waste sites need to be viewed in the context of current community health concerns, competing causes of disease and ill-health, and the relative lack of knowledge about environmental contamination and associated health effects. A nonspecific deterioration of health and well-being is more likely to result from waste site exposures than is overt clinical disease. Socially acceptable policies and controls may have to be based on criteria other than demonstrable ill-health. Detailed inventories and registries of the nature of disposed materials need to be maintained, sites of poorly controlled disposal in the past identified and selective environmental monitoring conducted. Epidemiological studies may be justified in situations where exposures well in excess of acceptable norms are demonstrated. An integrated national waste management policy for the country is urgently needed.

Environmental Exposure↗

PubMed2003

Use of audit tools to evaluate the efficacy of cleaning systems in hospitals.

BACKGROUND: Recent publicity has highlighted both the inadequacies of hospital cleaning and high levels of methicillin-resistant Staphylococcus aureus infections in UK hospitals. "Standards for Environmental Cleanliness" (SEC) was a checklist developed in April 1999 by the Infection Control Nurses Association and the Association of Domestic Managers to evaluate cleaning services regardless of who is the provider. More recently, the National Health Service plan (July 2000) was an attempt to generate a rapid improvement in the cleanliness and tidiness of hospitals via a National Health Service patient environment audit (PEA). On the basis of models used in the food industry to manage cleaning practices cost-effectively, a risk-based audit checklist incorporating rapid hygiene monitoring was developed to assess the adequacy of cleaning programs and standards in hospitals. This checklist (Audit for Cleaning Efficacy, or ACE) as well as the SEC and PEA approaches were applied at 4 hospitals, and environmental microbial surface counts were compared. SEC and PEA rely on visual assessment, whereas the ACE approach is more comprehensive and included more specific questions relating to the management and monitoring of cleaning as well as standards on the basis of rapid hygiene monitoring. METHODS: Two wards in each of the 4 hospitals were visited on 3 separate occasions immediately after cleaning was completed. Visual assessment, adenosine triphosphate bioluminescence, and microbiologic sampling of selected environmental sites were performed to evaluate the effectiveness of cleaning. The 3 audits were completed during the final hospital visit. RESULTS: Visual assessment indicated that 90% of sites were satisfactory, whereas adenosine triphosphate bioluminescence showed that 100% and microbiologic sampling showed that 90% of sites did not meet benchmark values. There was no significant difference between the SEC and PEA audits (P =.311), which used visual assessment, and the results suggest that they both are similar in passing surfaces that have microbiologic benchmark values that are too high. However, the ACE audit showed a significant difference (P = <.001) in results compared with the SEC and the PEA audits and did not pass surfaces with microbiologic benchmark values that were too high. The ACE audit, which incorporates rapid hygiene testing, showed a much stronger association with the microbial counts; this was not apparent with the SEC and the PEA audits. CONCLUSION: The data suggest that visual assessment is a poor indicator of cleaning efficacy and that the ACE audit gives a better assessment of cleaning programs compared with the other 2 audit methods in relation to microbial surface counts. It is recommended that hospital cleaning regimes be designed to ensure that surfaces are cleaned adequately and that efficacy is assessed with use of internal auditing and rapid hygiene testing.

Adenosine Triphosphate↗

PubMed1998

Hemophilia growth and development study: relationships between neuropsychological, neurological, and MRI findings at baseline.

OBJECTIVE: To determine the effects of human immunodeficiency virus (HIV) infection on children's development by identifying neurological and environmental variables associated with neuropsychological measures of cognitive development in HIV-seronegative (HIV-) and HIV-seropositive (HIV+)children and adolescents with hemophilia. METHODS: Participants (N = 298; 60% HIV+) were males ages 7-19 years enrolled in the Hemophilia Growth and Development Study (HGDS). Least squares modeling was used to determine whether there was a difference at baseline in mean neuropsychological test scores by HIV status, age, and neurological baseline findings, adjusting for selected environmental and medical history variables. RESULTS: The participants were within age expectations for general intelligence. Variables associated with lowered neuropsychological performance included academic problems, coordination and/or gait abnormalities, parents' education, and previous head trauma. CONCLUSIONS: Hemophilia-related morbidity has a subtle adverse influence on cognitive performance. HIV infection was not associated with neuropsychological dysfunction in this group even when MRI abnormalities were present.

Adolescent↗

PubMed1997

Environmental factors and aryl hydrocarbon hydroxylase activity (CYP1A1 phenotype) in human lymphocytes.

Since aryl hydrocarbon hydroxylase (AHH) is considered to be responsible for the activation of benzo(a)pyrene (BP) and other polyaromatic hydrocarbons in cigarette smoke to carcinogens, it is important to examine AHH activity in the determination of susceptibility to lung cancer. Lymphocytes from healthy male adults (239) of non-smokers and smokers were cultured in vitro and assayed for non-induced and 3-methylcholanthrene (MC)-induced AHH activity and AHH inducibility (MC-induced AHH activity/non-induced AHH activity). A day-to-day variation in AHH activity was not observed while a seasonal variation was apparent. Very wide differences in non-induced AHH and MC-induced AHH activities were observed. The association of some selected environmental factors and AHH activity was studied. Age was related to non-induced AHH activity (Spearman's rank correlation coefficients (r), r = 0.185, p < 0.005) and AHH inducibility (r = -0.329, p < 0.001). Coffee consumption was associated with non-induced (age-adjusted r = 0.138, p < 0.05) and MC-induced AHH activity (age-adjusted r = 0.173, p < 0.01). Cigarette smoking was correlated with non-induced AHH activity (age-adjusted r = 0.191, p < 0.005) and AHH inducibility (age-adjusted r = -0.191, p < 0.005). No significant association was observed for any other selected factors, including alcohol intake or broiled food consumption. In conclusion, AHH activity might be affected by cigarette smoking and coffee consumption, and was dependent on the age of the donor. Day-to-day and seasonal variation analyses showed that this assay method was reproducible and reliable and AHH inducibility might be a useful biomarker in cancer epidemiology. As those factors may affect the AHH activity, a careful control of those factors to AHH activity is necessary in epidemiological studies on the association between AHH inducibility in human lymphocytes and lung cancer.

Adult↗

PubMed2003

Analysis of environmental Escherichia coli isolates for virulence genes using the TaqMan PCR system.

AIMS: To assess the presence of virulence genes in environmental and foodborne Escherichia coli isolates using the TaqMan PCR system. METHODS AND RESULTS: Three TaqMan pathogen detection kits called O157:H7, StxI and StxII were used to investigate the presence of virulence genes in Escherichia coli isolates. All 54 foodborne E. coli O157:H7 isolates showed expected results using these kits. Ninety (15%) of 604 environmental isolates gave positive amplification with an O157:H7-specific kit. TaqMan PCR amplification products from these 90 isolates were analysed by agarose gel electrophoresis, and 90% (81 of 90) of the environmental samples contained the expected PCR product. Sixty-six of these 90 were chosen for serotyping tests and only 35% (23 of 66) showed agglutination with both anti-O157 and anti-H7 antibodies. Further ribotyping of 16 sero-positive isolates in an automated Riboprinter did not identify these to be O157:H7. Multiplex PCR with primers for eaeA, stxI and stxII genes was used to confirm the TaqMan results in 10 selected environmental isolates. CONCLUSIONS: All three TaqMan pathogen detection kits were useful for virulence gene analysis of prescreened foodborne O157:H7 isolates, while the O157:H7-specific kit may not be suitable for virulence gene analysis of environmental E. coli isolates, because of high false positive identification. SIGNIFICANCE AND IMPACT OF THE STUDY: The ability to rapidly identify the presence of pathogenic E. coli in food or environmental samples is essential to avert outbreaks. These results are of importance to microbiologists seeking to use TaqMan PCR to rapidly identify pathogenic E. coli in environmental samples. Furthermore, serotyping may not be a reliable method for identification of O157:H7 strains.

Bacterial Typing Techniques↗

PubMed1990

Evidence for neutral and selective processes in the recruitment of enzyme-crystallins in avian lenses.

In apparent contrast to most other tissues, the ocular lenses in vertebrates show striking differences in protein composition between taxa, most notably in the recruitment of different enzymes as major structural proteins. This variability appears to be the result of at least partially neutral evolutionary processes, although there is also evidence for selective modification in molecular structure. Here we describe a bird, the chimney swift (Chaetura pelagica), that lacks delta-crystallin/argininosuccinate lyase, usually the major crystallin of avian lenses. Clearly, delta-crystallin is not specifically required for a functionally effective avian lens. Furthermore the lens composition of the swift is more similar to that of the related hummingbirds than to that of the barn swallow (Hirundo rustica), suggesting that phylogeny is more important than environmental selection in the recruitment of crystallins. However differences in epsilon-crystallin/lactate dehydrogenase-B sequence between swift and hummingbird and other avian and reptilian species suggest that selective pressures may also be working at the molecular level. These differences also confirm the close relationship between swifts and hummingbirds.

Amino Acid Sequence↗