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Results for “Environmental selection”

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PubMed2000

Heteroduplex mobility assay as a tool for predicting phylogenetic affiliation of environmental ribosomal RNA clones.

Heteroduplex mobility assay (HMA) of partial 16S rRNA gene fragments was tested as a tool for predicting bacterial phylogenetic relationships. Approximately 400-bp fragments were amplified from a selection of cloned environmental DNAs representing a range of sequence identities and phylogenetic relationships. Heteroduplexes between pairs of sequences were formed by mixing equal amounts of PCR products, denaturing and annealing. Annealed mixes were separated on 8% polyacrylamide gels and silver stained. Heteroduplexes were readily distinguished from reannealed homoduplex and unannealed fragments in all sequences where percentage identity was less than 95%. The heteroduplexes showed retarded electrophoretic migration with respect to homoduplexes. The relative retardation was strongly correlated to the percentage sequence identity between the two strands. The HMA is a useful tool for screening environmental clone libraries to systematically select clones representative of the phylogenetic diversity within the sample, or to selectively retrieve members of a particular phylogenetic group for more detailed study.

Bacteria↗

PubMed2006

Immobilized methyltrioxo rhenium (MTO)/H2O2 systems for the oxidation of lignin and lignin model compounds.

A convenient and efficient application of heterogeneous methylrhenium trioxide (MTO) systems for the selective oxidation of lignin model compounds and lignins is reported. Environmental friendly and low-cost H2O2 was used as the oxygen atom donor. Overall, the data presented and discussed in this paper point toward the conclusion that the immobilized heterogeneous catalytic systems based on H2O2/and MTO catalysts are able to extensively oxidize both phenolic and non-phenolic, monomeric, and dimeric, lignin model compounds. Condensed diphenylmethane models were found also extensively oxidized. Technical lignins, such as hydrolytic sugar cane lignin (SCL) and red spruce kraft lignin (RSL), displayed oxidative activity with immobilized MTO catalytic systems. After oxidation, these lignins displayed the formation of more soluble lignin fragments with a high degree of degradation as indicated by the lower contents of aliphatic and condensed OH groups, and the higher amounts of carboxylic acid moieties. Our data indicate that immobilized MTO catalytic systems are significant potential candidates for the development of alternative totally chlorine-free delignification processes and environmental sustainable lignin selective modification reactions.

Catalysis↗

PubMed2002

[Studies on efficient methods for detection of Legionella species from environmental water by use of its selective media].

To examine the optimal pH range for growth on media, growth of Legionella spp. on its selective media, BCYE alpha, WYO alpha and MWY agar media, in a pH range of 6.0-8.0 (at 0.5 intervals) was compared. The growth of two strains of L. pneumophila and one strain of L. micdadei on a WYO alpha agar supplemented with some selecting antimicrobial agents was markedly inhibited at all pH range except 6.0 and 7.0, suggesting a narrow optimal pH range for growth of these species compared to the BCYE alpha without selecting antimicrobioal agents. Vancomycin (VCM) added to the selective agar suppressed the growth of some Legionella spp. depending on the concentration. However, the extent of suppression was different among species and/or strains of Legionella spp. The selectivity for species other than Legionella spp. was also affected similarly by VCM concentration added to their media, suggesting that it is important to use proper amounts of the selecting antimicrobial agent depending on the species and/or strains of Legionella spp. or the other species in water samples. Amphothericin B (AMPH-B) added to a selective medium, MWY agar, in the concentration of 80 micrograms/ml hardly affected the growth of Legionella spp. examined, but effectively inhibited the growth of fungal strains identified as Aspergillus sp., Trichoderma sp., Scolecobasidium sp. and Mucor sp. which were isolated from cooling-tower water samples together with Legionella spp. Furthermore, the growth of a combination culture of one each of the 4 strains of isolated fungi and one each of the 3 strains of Legionella spp. was examined at various concentration of AMPH-B. Addition of AMPH-B to the selective medium at the concentration of 80 micrograms/ml suppressed the growth of spreading fungi, permitting the growth of Legionella spp. to allow efficient detection of the species.

Bacteriological Techniques↗

PubMed2004

Total ranking models by the genetic algorithm variable subset selection (GA-VSS) approach for environmental priority settings.

Total order ranking (TOR) strategies, which are mathematically based on elementary methods of discrete mathematics, seem to be attractive and simple tools for performing data analysis. Moreover order-ranking strategies seem to be a very useful tool not only to perform data exploration but also to develop order ranking models, a possible alternative to conventional quantitative structure-activity relationship (QSAR) methods. In fact, when data material is characterised by uncertainties, order methods can be used as alternative to statistical methods such as multilinear regression (MLR), because they do not require specific functional relationships between the independent and dependent variables (responses). A ranking model is a relationship between a set of dependent attributes, experimentally investigated, and a set of independent attributes, i.e. model attributes, which are calculated attributes. As in regression and classification models, the variable selection model is one of the main steps in finding predictive models. In this work the genetic algorithm-variable subset selection (GA-VSS) approach is proposed as the variable selection method for searching for the best ranking models within a wide set of variables. The models based on the selected subsets of variables are compared with the experimental ranking and evaluated by the Spearman's rank index. A case study application is presented on a TOR model developed for polychlorinated biphenyl (PCB) compounds, which have been analysed according to some of their physicochemical properties which play an important role in their environmental impact.

Journal Article↗

PubMed2006

A new perspective on developmental plasticity and the principles of adaptive morph determination.

Organisms can have divergent paths of development leading to alternative phenotypes, or morphs. The choice of developmental path may be set by environmental cues, the individual's genotype, or a combination of the two. Using individual-based simulation and analytical investigation, we explore the idea that from the viewpoint of a developmental switch, genetic morph determination can sometimes be regarded as adaptive developmental plasticity. We compare the possibilities for the evolution of environmental and genetic morph determination and combinations of the two in situations with spatial variation in conditions. We find that the accuracy of environmental cues in predicting coming selective conditions is important for environmental morph determination, in accordance with previous results, and that genetic morph determination is favored in a similar way by the accuracy of genetic cues, in the form of selectively maintained gene frequency differences between local populations. Restricted gene flow and strong selection acting on the phenotypic alternatives produce clearer gene frequency differences and lead to greater accuracy of genetic cues. For combined environmental and genetic morph determination, we show that the developmental machinery can evolve toward efficiently combining information in environmental and genetic cues for the purpose of predicting coming selective conditions.

Adaptation, Biological↗

PubMedDate not supplied

Environmental lead-210 and bismuth-210 accrue selectively in the brain proteins in Alzheimer disease and brain lipids in Parkinson disease.

We studied the occurrence of the environmental radon daughters, 210Po (alpha particles), and 210Bi (beta particles), in the protein and lipid fractions of cortical gray and subcortical white matter from the frontal and temporal lobes of human brains of persons with Alzheimer disease (AD), persons with Parkinson disease (PD), smokers, or persons with no previous evidence of clinical neurologic disease (controls). We found a 10-fold increase in 210Po and 210Pb radioactivity in the protein fraction from both the cortical gray and subcortical white matter in AD and smokers, and a similar increase in the lipid fraction in PD. The pathognomonic distribution of the radon daughters to the lipids in PD and to the proteins in AD was inferred to reflect the increase of local chlorine availability to which radon daughters bound selectively. Cigarette smoking strongly increases radon daughter retention in the central nervous system.

Aged↗

PubMed2005

The selection of mixed microbial inocula in environmental biotechnology: example using petroleum contaminated tropical soils.

The impact of inorganic N and P additions on a tropical soil contaminated with petroleum hydrocarbons was investigated using molecular and culture techniques. Microcosms were incubated for 42 days and sampled at 0, 1, 7, 28 and 42 days. Changes in bacterial community structure were determined using denaturing gradient gel electrophoresis (DGGE) of the rRNA following reverse transcription PCR using primers specific to the V3 region of the 16S rRNA gene. To identify which components of the microbial community were changing during incubation, PCR amplicons were resolved using DGGE and the banding patterns analyzed using stepwise discriminant function analysis (SDA). SDA showed that the number of bands needed to recover the differences between samples over time could be reduced from the initial 11 bands for the 16S rRNA transcript to 3 bands. Sequences originating from the rRNA gels (16S rRNA transcripts) were recovered in clades containing known cultured isolates of Bacillus marisflavi, Microbacterium oxydans and Pseudomonas oleovorans. Isolation studies on these soils using lubricant oil as a carbon source yielded 317 bacterial isolates, 3 of which showed high sequence similarity (>96%) with the 16S rRNA transcripts identified using SDA as being important in differentiating between bacterial communities over time. These isolates were then tested singly and in combination for their ability to degrade lubricant oil. These analyses demonstrated that the consortium selected using the combined molecular-SDA approach was more effective at degrading the lubricant in both liquid media and in contaminated sand than the single isolates.

Bacteria↗

PubMed1996

Differential mRNA transport and the regulation of protein synthesis: selective sensitivity of Purkinje cell dendritic mRNAs to translational inhibition.

Although the majority of mRNAs expressed in neurons are confined to the perikaryon, a growing number appear to be transported into dendrites. It is likely that this allows for the local regulation of protein synthesis within discrete subcellular compartments. Here, three different subcellular distribution patterns are demonstrated for four mRNAs that encode proteins highly expressed in Purkinje cells and their dendrites; mRNAs are found in the perikaryon only, perikaryon and proximal dendrite, or perikaryon and proximal plus distal dendrites. Further, it is shown that transport of an mRNA into the dendrites increases its sensitivity to translational inhibition by diphtheria toxin. These data suggest a simple model whereby the transport machinery can regulate the translation of selected mRNAs. Thus, environmental signals that generally affect translational efficiency in concert with the selectivity provided by the transport machinery could provide a means to locally regulate the synthesis of a restricted pool of proteins.

Animals↗

PubMed1992

Narrowing the zone of uncertainty between research and development in biological warfare defense.

Although "research" is not prohibited by the Biological Weapons Convention, States Parties to the Convention have maintained the spirit of the Convention in actions relating to research. The confidence-building measures agreed to at RC2 refer to research facilities, publication of research results, and promotion of contacts between scientists engaged in research related to the Convention. However, assessment of basic research on biological agents is not a productive way to distinguish an offensive from a defensive program. Additionally, if a country were to initiate a biological weapons program, basic research on biological agents may not be necessary. For example, the extensive published research on Bacillus anthracis, both as a cause of anthrax in cattle and other species and as a biological-warfare agent, would enable any motivated group or nation to initiate a biological weapons program that could immediately advance to the development and scale-up stages. Research on biological agents for offensive purposes would be characterized by activities such as selection for growth, virulence, and toxin production; improving stability under varying environmental conditions; and selection of strains that might overcome existing means of prophylaxis and treatment. A biological program with an offensive intent would in most cases be characterized by evidence of development efforts in mass production and dissemination, which are often agent-specific. Thus, an assessment of development may distinguish offensive from defensive programs. If a country were to initiate a biological weapons research program, and were willing to risk worldwide condemnation should existence of such a program become known, it is likely that such a program would include development and production capabilities. If a country were not committed to production capability, there would be no rationale for an offensive biological research that would bring worldwide condemnation. Critics of the U.S. Biological Defense Research Program have suggested that the program could easily and quickly be turned into an offensive effort. To accomplish this, however, we have to assume that all military personnel, including the civilians employed by the Department of the Army, are unethical and willing to break the law and run the risk of placing the U.S. in a noncompliance status. The Army is under constant scrutiny by governmental agencies, by visiting scientists, by audiences at scientific meetings, by scientists who review manuscripts for publications, by news media, and by private citizens.(ABSTRACT TRUNCATED AT 400 WORDS)

Biological Warfare↗

PubMed2001

[Biological risk factors for differentiated thyroid cancer].

UNLABELLED: Apart from the two relatively well documented risk factors for thyroid cancer i.e. iodine deficiency and ionising radiation, the mechanism of carcinogenesis involves a number of biological and environmental factors. The aim of the study was to analyse the selected biological and environmental risk factors in patients with differentiated thyroid cancer in comparison with a reference group in a case-control study. METHODS: Both the group of 188 women and 30 men with thyroid cancer including 92 with follicular carcinoma and 126 with papillary carcinoma and the control group of 287 women and 58 men were subjected to the examination. All the study participants were given a standard questionnaire and underwent physical examination including thyroid USG, blood hormone levels and urine iodine concentration. The following risk factors were included in the analysis: family history, sex, age, thyroid morbidity, employment, body weight, hormone replacement therapy in women, cigarette smoking. In both groups with thyroid cancer women predominant with the female to male ratio 6.7 in follicular carcinoma and 6.0 in the papillary variant. In both groups of diagnoses the mean age was high--above 50, higher in men than in women. Over 70% of the patients with thyroid cancer had nodular goitre before the detection of cancer. In the control group the proportion of diagnosed goitre was slightly above 10%. A significantly more frequent hormone replacement therapy and contraception and more frequent miscarriages in women with thyroid cancer were noteworthy. One may assume that initiation, promotion and progression of the neoplastic process in the thyroid is triggered by a number of factors, both biological and environmental, and only multifactorial analysis may provide an insight into the mechanisms of carcinogenesis followed by initiation of preventives measures in appropriate cases.

Abortion, Spontaneous↗

PubMedDate not supplied

An advantage of sexual reproduction in a rapidly changing environment.

When an environmental change imposes strong directional selection, there are two advantages of sexual reproduction. First, an asexual population is limited to the most extreme individual in the population, and progress under directional selection can go no farther without mutation; no such limitation applies to a sexual population. Second, more quantitatively, directional selection in an asexual population monotonically decreases the variance, whereas the variance of a sexual population quickly reaches a steady value; this difference remains even if the direction of selection occasionally changes. With realistic environmental changes small alterations in any particular measurement or trait are usually sufficient to keep up with the changes, but fitness, since it depends on a large number of traits, will be selected with greater intensity, which may be enough to confer a distinct advantage on sexual reproduction. This applies particularly to a large or rapid environmental change. Eventually mutation will enhance the variance, but by then it may be too late to prevent extinction of asexual strains.

Environment↗

PubMed1998

Selection of very small differences in bacterial evolution.

As the Science of Biology is constantly changing due to new discoveries and advanced techniques it is essential that a systematic study of the environmental causes of natural selection on microorganisms be conducted. Very small phenotypic differences among individuals within bacterial populations arise as a result of spontaneous genetic variation, but the evolutionary importance of these small changes is frequently considered to be non-significant. Recent in vitro experiments indicate that efficient selection of these very small differences may take place in environmental compartments where a particular intensity of the selective agent is exerted. Model studies based on competition between bacterial populations only differing in one or two amino acid changes of a detoxifying antibiotic enzyme (e.g. beta-lactamase) have shown that at a narrow range of antibiotic concentrations the variant population is strongly selected over the original type, despite the extremely low phenotypic differences in antibiotic susceptibility. These selective concentrations are expected to occur in precise environmental compartments (selective compartments). Due to the high frequency of structured habitats in natural environments, the intensity of selective agents is commonly exerted along certain gradients. Each one of the points forming these gradients (or intersection among gradients) may have a particular selective ability for a specific genetic variant. Considering the environment as a composition of an extremely high number of specific selective compartments may help to understand the existence of high levels of genetic variability in natural bacterial populations. This may be one of the clues towards the unraveling of bacterial evolution.

Bacteria↗

PubMed1983

Employee-related environmental information systems.

Most industrial organizations must collect various types of employee-related environmental exposure information to satisfy governmental regulations and to provide managers with the information which is required to control employee exposures to adverse environmental conditions. The three basic elements of systems which are designed to collect and store employee-related environmental information are examined and the characteristics of 21 different systems which can be constructed from these basic elements are discussed. Some techniques which are useful for the selection of the best environmental information system for a specific plant or group of employees are discussed and illustrated by examples. Some problems which require further investigation to improve the design and selection of environmental information systems are also identified and discussed.

Environmental Exposure↗

PubMed1997

Developments in the application of impact assessment methodologies for pollution prevention.

Pollution prevention requires the assessment of various multimedia environmental impacts to ensure that the alternative selected most closely represents the environmental goals and priorities of the facility. While some facility's environmental policies are easy to assess (e.g., reduce TRI emissions), others require a more sophisticated assessment methodology (e.g., select the most environmentally-friendly manufacturing process). Chemical environmental impact assessment for pollution prevention can be very effective, but can only provide a scientifically defensible decision point if the methodologies, analytical tools, and data quality are consistent with the environmental goals and priorities expressed. In many assessments completed in the past, the assessment methodologies have been overly simplistic when compared to the environmental goals projected. More sophisticated chemical impact assessment methodologies have not been used in the past for a variety of reasons, including: poor study design, poor data quality, inadequate funding, inadequate computer systems and databases, and practitioner's lack of understanding. This paper will describe a broad range of assessment methodologies, the steps involved in various evaluations, various resources available to conduct pollution prevention impact assessments, and on-going methodology development.

Ecology↗

PubMed2003

The evolution of environmental and genetic sex determination in fluctuating environments.

Twenty years ago, Bulmer and Bull suggested that disruptive selection, produced by environmental fluctuations, can result in an evolutionary transition from environmental sex determination (ESD) to genetic sex determination (GSD). We investigated the feasibility of such a process, using mutation-limited adaptive dynamics and individual-based computer simulations. Our model describes the evolution of a reaction norm for sex determination in a metapopulation setting with partial migration and variation in an environmental variable both within and between local patches. The reaction norm represents the probability of becoming a female as a function of environmental state and was modeled as a sigmoid function with two parameters, one giving the location (i.e., the value of the environmental variable for which an individual has equal chance of becoming either sex) and the other giving the slope of the reaction norm for that environment. The slope can be interpreted as being set by the level of developmental noise in morph determination, with less noise giving a steeper slope and a more switchlike reaction norm. We found convergence stable reaction norms with intermediate to large amounts of developmental noise for conditions characterized by low migration rates, small differential competitive advantages between the sexes over environments, and little variation between individual environments within patches compared to variation between patches. We also considered reaction norms with the slope parameter constrained to a high value, corresponding to little developmental noise. For these we found evolutionary branching in the location parameter and a transition from ESD toward GSD, analogous to the original analysis by Bulmer and Bull. Further evolutionary change, including dominance evolution, produced a polymorphism acting as a GSD system with heterogamety. Our results point to the role of developmental noise in the evolution of sex determination.

Adaptation, Biological↗

PubMedDate not supplied

Selection of a pesticide with low environmental impact.

The conditions were analyzed for evaluation of a mean soil biodegradation of a pesticide within a certain region. Different soils from two Czech and two German regions were used for a highly sensitive analysis based on a laboratory incubation of each isolated active soil strain with a radiolabeled pesticide. It was proved for all analyzed soils that the biodegradation activity of the total biomass was caused by only a small part of the present microbial strains. Not only bacteria, but also fungi and yeast have to be taken into consideration in a pesticide biodegradation. The biodegradation products were quantified by radio high-performance liquid chromatography.

Animals↗

PubMed2001

Immunogenetic heterogeneity of multiple sclerosis in Sardinia.

Multiple sclerosis (MS) predisposition is thought to be influenced by a complex, yet unclear interaction of genetic and environmental factors. Studying ethnically selected populations may reduce genetic and environmental heterogeneities and help clarify the underlying mechanisms of MS susceptibility. Sardinians kept a homogeneous genetic structure and have among the highest MS frequency rates worldwide. Interestingly, MS in Sardinia is linked to otherwise rare HLA alleles. In this light, recent findings from epidemiological and immunogenetic studies of Sardinian MS are presented. Results confirm that, likely due to significant genetic differences at a microgeographic level, even in this homogeneous population MS is immunogenetically heterogeneous and tends to preferentially cluster in some more archaic areas of the island.

Female↗

PubMed2003

Selection of bioindicators for monitoring marine environmental quality in the Bay of Fundy, Atlantic Canada.

Distribution of metals, PAH's and PCB's in lobsters, mussels, and sediments were used to assess marine environmental quality of the Bay of Fundy. This study demonstrates that the lobster (Homarus americanus) is a better bioindicator for monitoring contaminants in the marine environment and has a greater capacity for the uptake and accumulation of contaminants than the mussel (Mytilus edulis) and sediments. A definite pattern in the spatial distribution of lobster Cu, Cd, and Ag was evident. The distribution of organic contaminants for both mussels and lobsters in the Bay of Fundy lacked a spatial trend, and organic contaminants were undetectable in sediments from all sites. The Gulf Watch Programme, which monitors chemicals in mussels in the Bay of Fundy, did not indicate a problem with high levels of Cu, Cd, and Zn in the ecosystem. Analytes below the detection limit, such as in mussels and sediments, increase the difficulties of chemical analysis and detection for environmental monitoring. Deficiencies of mussels in monitoring the Bay of Fundy were discussed.

Animals↗