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Results for “environmental variability”

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PubMed1996

The influence of genotype and environment on the physiological and metabolic diversity of Fusarium compactum.

Fungal species produce a large variety of secondary metabolites which are of considerable interest to the pharmaceutical industry. It is clear that the secondary metabolite production of a species varies significantly in strains from different geographic locations and from different habitats. The influence of genotype and environment on metabolite production is, however, poorly understood. In this study we examined the influence of genotypic variability, physiological variability, environmental location, and habitat on metabolite production by Fusarium compactum. Isolates of the fungus from two geographic locations and two distinct habitat types were examined for growth on 95 different carbon sources, and genotypic variability was determined using RAPDs and rDNA-RFLP analysis. In a blind test secondary metabolite production was assessed using HPLC profiles of methanolic cell extracts. A number of correlations were observed between genotypic groupings, as determined using parsimony, and specific metabolic production. Similar correlations were also observed with physiological groups although genotypic analysis proved to be a more sensitive predictor of metabolite variability. The data suggest a complex relationship between environment, genotype, and metabolite production but highlight the use of genetic screening as a means of optimizing the changes of identifying a wide range of metabolites from a given species.

Base Sequence↗
PubMed2003

Interpreting results from field deployments of semipermeable membrane devices.

Three canisters of semipermeable membrane devices (SPMDs), each containing five SPMDs, were deployed at three different locations on a transect across a small river removed from the impact of near-field point sources. Following a 62-day deployment, the masses of various polynuclear aromatic hydrocarbons (PAH) sequestered by each SPMD in each canister were determined. The compound-specific mean residues (ng/SPMD) obtained for the PAHs with pK(ow) values >4.4 showed statistically significant (alpha = 0.10) differences between the three deployment locations (canisters) ranging from approximately 10 to 160 ng/SPMD, corresponding to relative percent differences (RPDs) ranging from 10% to 54%. There were no statistically significant differences between the same three locations for the single PAH with a pK(ow) <4.4. A detailed discussion of how different (uncontrollable) environmental variables may have impacted the experimental results is provided to illustrate the uncertainties associated with interpreting the results from SPMD field deployments and highlight the need for some means of correcting for these impacts. The results from this work also illustrate the need to account for spatial variability in water column concentrations (i.e., sample heterogeneity) as part of any interpretation.

Environmental Monitoring↗
PubMed2026

Phylogenetic Constraints and Environmental Filtering Jointly Drive Adaptive Evolution in Phragmites australis: From Genetic Structure to Trait Decoupling on the Mongolian Plateau.

The Mongolian Plateau, a typical arid and semi-arid zone in Eurasia, is characterized by highly heterogeneous and fragmented wetland habitats. Phragmites australis, a common wetland species in this region, exhibits remarkable adaptability. Unraveling the coordination between phylogenetic history and local environmental filtering is crucial for elucidating its adaptive mechanisms. Integrating landscape genomics and trait-based phylogenetic analyses, we analyzed transcriptome-wide SNPs, multidimensional functional traits, and environmental variables across 90 individuals from 30 natural P. australis populations. This study aims to reveal the genetic and phenotypic variation patterns underlying population genetic structure and trait variation, specifically distinguishing the roles of geographic isolation, environmental filtering, and phylogenetic history. Results reveal a significant drainage-dependent pattern in genetic structure. Populations in hydrologically connected basins show extensive admixture, whereas those in isolated endorheic basins form distinct lineages. While geographic isolation underpins genetic differentiation, environmental filtering independently explains ~33.84% of the genetic variation, driven primarily by moisture heterogeneity (precipitation seasonality and soil moisture). Crucially, we observed differentiated evolutionary trajectories across functional traits. Structural traits (e.g., plant height, leaf thickness) are phylogenetically conserved; in contrast, physiological traits (e.g., water use efficiency) are decoupled from phylogeny, showing patterns consistent with high plasticity regulated by local environments. This evolutionary decoupling strategy enables P. australis to flexibly adapt to heterogeneous habitats while maintaining structural stability. This study uncovers the synergistic mechanisms by which geographic isolation and environmental filtering jointly shape the genetic patterns of this cosmopolitan species at a regional scale, clarifies that its evolutionary responses may depend heavily on the differentiated plasticity of trait types, and provides valuable regional insights into how widespread wetland species adapt to heterogeneous environments under global change.

Mongolia Plateau↗
PubMed1980

The interaction of a fixed time food delivery schedule and body weight on self-administration of narcotic analgesics.

Experiment 1 reported the effects of the interaction of a fixed 1 min delivery schedule and body weight, using schedule-induced self-injection paradigm, in the rate of acquisition of methadone and heroin. Eighty-one rats were assigned to 100% and 80% reduced body weight conditions with and without a schedule. The findings show that: (a) voluntary heroin and methadone intake was enhanced when a schedule was introduced to animals at 80% but not at 100% body weight; (b) high intake of heroin and methadone was accompanied by increased levels of plasma 11-OHCS. Experiment 2 showed that the high rate of self-injection was due to the interaction of pharmacological properties of opiates and environmental variables rather than to a general increase in activity arising from the deprivation state or the effects of the schedule. The results are discussed in terms of a stress factor arising from an interaction between environmental and pharmacological factors.

Analgesics, Opioid↗
PubMed1988

Cultural and cognitive considerations in the prevention of American Indian adolescent suicide.

A description of cultural considerations associated with American Indian adolescent coping is presented within a transactional, cognitive-phenomenological framework. Select cultural values and cultural beliefs of American Indians associated with death are discussed in terms of person variables and situational demand characteristics that interplay in the transactional coping process. Three situational demand characteristics (ambiguity of identity, frequency of loss, and pervasiveness of hardships) are then presented to illustrate the reciprocal relationship between environmental contingencies and American Indian individual and community efforts at coping. The dynamic interdependence between person and environmental variables is emphasized and considered essential for inclusion in the design of interventions to prevent suicide. Existing intervention efforts with American Indian adolescent suicide attempters are reviewed and a school-wide cognitive behavioural approach based on the transactional model of coping with suicide is described. It is suggested that on-going cognitive restructuring, social skills training, and peer counselling training activities be culturally adapted and integrated into relevant areas of the school curricula in order that coping be enhanced and suicide ameliorated.

Adaptation, Psychological↗
PubMed2000

Population variability in space and time.

One of the most ubiquitous phenomena of all natural populations is their variability in numbers in space and time. However, there are notable differences among populations in the way the population size fluctuates. One of the major challenges in population and community ecology is to explain and understand this variety and to find possible underlying rules that might be modified from case-to-case. Population variability also has a spatial component because fluctuations are often synchronized over relatively large distances. Recently, this has led to growing interest in how 'internal' (density-dependent) processes interact with 'external' factors such as environmental variability.

Journal Article↗
PubMed2006

Risk factors associated with clinical signs of lower urinary tract disease in indoor-housed cats.

OBJECTIVE: To determine associations between environmental and cat-related factors and lower urinary tract signs in indoor-housed domestic cats. DESIGN: Case-control study. Animals-238 healthy cats, 157 cats with clinical signs of lower urinary tract disease, and 70 cats with other diseases. PROCEDURE: Data collected from owners of the cats were analyzed. Descriptive statistics, environmental variables, and physical and behavioral signs were analyzed by use of ANOVA and logistic regression analysis to assess which factors were associated with clinical signs of lower urinary tract disease. RESULTS: The only demographic or environmental factors associated with lower urinary tract signs were older age and months owned. In contrast, cats with clinical signs of lower urinary tract disease had significantly greater owner-observed gastrointestinal tract signs and scratching, fearful, nervous, and aggressive behaviors. CONCLUSIONS AND CLINICAL RELEVANCE: Lower urinary tract signs in indoor-housed cats may be more closely associated with cat-related factors than with demographic or environmental factors.

Age Factors↗
PubMed1988

Low temperature and the growth of plants.

The growth responses of plants at low temperature are discussed, with particular reference to the reversible effects of low positive temperatures upon the growth of obligately chilling-resistant species. Techniques for the measurement of growth and the control of meristem temperature are described, and evidence concerning the sites of temperature perception and transduction in the developing monocot leaf is reviewed. The rapidity and reversibility of such responses, and their apparent independence of changes in carbon supply or meristem cell turgor are held to support the hypothesis that chilling alters the physical properties of the walls of extending cells within the meristematic zone. The existence of marked genetic variability in these responses facilitates agricultural exploitation of low-temperature growth. The effects of longer-term chilling upon growth, cell extension and cell division are described, with particular reference to interactions with other environmental variables and with developmental factors which can alter the nature of the temperature response. The relationship between growth reduction and the development of freezing tolerance during chilling is discussed in relation to programmes of crop improvement which will maximize productivity at low temperatures without adversely affecting survival.

Agriculture↗
PubMed1995

Natural history and determinants of clinical severity of sickle cell disease.

Some of the factors determining the extremely variable clinical course of homozygous sickle cell disease are being identified. Genetic factors include alpha-thalassemia, beta-globin gene haplotypes, heterocellular hereditary persistence of fetal hemoglobin, and high total hemoglobin. Other factors include a variety of environmental variables and socioeconomic status. These risk factors, when occurring in conjunction with apparently random precipitating events, produce features of the disease. Many complications--which are age specific, with highest morbidity and mortality in the first 5 years--may be prevented by specific education and prophylaxis. Current median survival in individuals with sickle cell disease in the United States is approximately 40 to 50 years, at which age the major determinants of mortality are chronic end organ damage of the lungs and kidneys.

Anemia, Sickle Cell↗
PubMed2006

Identifying environmental determinants of diurnal distribution in marine birds and mammals.

Marine birds and mammals move between various habitats during the day as they engage in behaviors related to resting, sleeping, preening, feeding, and breeding. The per capita rates of movement between these habitats, and hence the habitat occupancy dynamics, often are functions of environmental variables such as tide height, solar elevation, wind speed, and temperature. If the system recovers rapidly after disturbance, differential equation models of occupancy dynamics can be reduced to algebraic equations on two time scales. Identification of environmental factors that influence movement between habitats requires time series census data collected in both the absence and presence of disturbance.

Algorithms↗
PubMed2005

Genetic association studies of complex traits: design and analysis issues.

Most common diseases and many important quantitative traits are complex genetic traits, with multiple genetic and environmental variables contributing to the observed phenotype. Because of the multi-factorial nature of complex traits, each individual genetic variant generally has only a modest effect, and the interaction of genetic variants with each other or with environmental factors can potentially be quite important in determining the observed phenotype. It remains largely unknown what sort of genetic variants explain inherited variation in complex traits, but recent evidence suggests that common genetic variants will explain at least some of the inherited variation in susceptibility to common disease. Genetic association studies, in which the allele or genotype frequencies at markers are determined in affected individuals and compared with those of controls (either population- or family-based), may be an effective approach to detecting the effects of common variants with modest effects. With the explosion in single nucleotide polymorphism (SNP) discovery and genotyping technologies, large-scale association studies have become feasible, and small-scale association studies have become plentiful. We review the different types of association studies and discuss issues that are important to consider when performing and interpreting association studies of complex genetic traits. Heritable and accurately measured phenotypes, carefully matched large samples, well-chosen genetic markers, and adequate standards in genotyping, analysis, and interpretation are all integral parts of a high-quality association study.

Gene Frequency↗
PubMed2007

Factors affecting hearing in mice, rats, and other laboratory animals.

The auditory system of rodents and other animals is affected by numerous genetic and environmental variables. These include genes that cause hearing loss, exposure to noise that induces hearing loss, ameliorative effects of an augmented acoustic environment on hearing loss, and effects of background noise on arousal. An understanding of genetic and environmental influences on hearing and auditory behavior is important for those who provide, use, and care for laboratory animals.

Animals↗
PubMed1987

Computational model for insensible water loss from the newborn.

A mathematical model for predicting insensible water loss from the newborn infant has been developed, and its adjustable parameters have been evaluated using existing data for respiratory and transepidermal water loss components. Subsequently, the model was verified by using an independent set of available data on total insensible loss from naked infants who were not mechanically ventilated and who did not sweat. Under these conditions, the model was capable of correctly predicting the influence of ambient humidity, gestational age, and postnatal age, and in general, the predictions had a precision of +/- 14%, but they tended to underestimate insensible water loss by -16%. The straightforward algebraic form of the model makes it suitable for computerized calculations, which can be readily available at the bedside and quickly updated to account for changes in infant or environmental variables. The model is useful both for anticipating the abnormally large insensible water loss of the premature infant early in life and for computing expected changes in insensible water loss as a result of intentional manipulation of environmental factors, such as incubator temperature or supplemental humidification.

Computer Simulation↗
PubMed2002

Biological and chemical factors influencing shallow lake eutrophication: a long-term study.

The focus of eutrophication research has tended to be upon short-term and experimental studies. However, given the range of factors that can influence eutrophication dynamics, and that these matter over a range of time scales, some discrete, some continuous, eutrophication dynamics may only be fully investigated when long-term, time-series data are available. The present study aims to evaluate the interacting effects of abiotic processes and biotic dynamics in explaining variations of phytoplankton biomass in a eutrophic shallow lake, Barton Broad (Norfolk, UK) using a long-term data set. Multivariate statistical analysis shows that the inter-relationships between phytoplankton variability, nutrient and grazing factors were highly sensitive to seasonal periodicity. In spring phytoplankton biomass was related to phosphorus, nitrogen and silicon. In summer phytoplankton biomass was associated with phosphorus, nitrogen and zooplankton. In autumn phytoplankton was related to phosphorus, nitrogen, silicon and zooplankton. In winter, no significant relationship could be established between phytoplankton and environmental variables. This paper improves our understanding of the governing role of nitrogen, phosphorus, silicon and zooplankton upon phytoplankton variability, and hence, improves management methods for eutrophic lakes.

Animals↗
PubMed1981

Modelling determinants of health.

The linear regression procedure of stepwise elimination has been used to examine the association between a range of environmental variables and infant mortality rates (IMR) in Sri Lanka. The nature of the water supply was found to be significantly associated with IMR. Latrines were significantly associated with IMR once qualitative differences between districts were allowed for. Other 'environmental determinants of health', 3 indices of housing quality and the presence of electricity supplies, were not significant. The cost of effecting changes in IMR by extending subsidies to water supply improvements is estimated.

Developing Countries↗
PubMed2001

Pervasive influence of large-scale climate in the dynamics of a terrestrial vertebrate community.

BACKGROUND: Large-scale climatic variability has been implicated in the population dynamics of many vertebrates throughout the Northern Hemisphere, but has not been demonstrated to directly influence dynamics at multiple trophic levels of any single system. Using data from Isle Royale, USA, comprising time series on the long-term dynamics at three trophic levels (wolves, moose, and balsam fir), we analyzed the relative contributions of density dependence, inter-specific interactions, and climate to the dynamics of each level of the community. RESULTS: Despite differences in dynamic complexity among the predator, herbivore, and vegetation levels, large-scale climatic variability influenced dynamics directly at all three levels. The strength of the climatic influence on dynamics was, however, strongest at the top and bottom trophic levels, where density dependence was weakest. CONCLUSIONS: Because of the conflicting influences of environmental variability and intrinsic processes on population stability, a direct influence of climate on the dynamics at all three levels suggests that climate change may alter stability of this community. Theoretical considerations suggest that if it does, such alteration is most likely to result from changes in stability at the top or bottom trophic levels, where the influence of climate was strongest.

Abies↗
PubMed2000

Evaluation of dietary and environmental risk factors for hyperthyroidism in cats.

OBJECTIVE: To identify dietary and environmental risk factors for hyperthyroidism in cats. DESIGN: Case-control study. ANIMALS: 100 cats with hyperthyroidism and 163 control cats. PROCEDURE: Medical records were examined, and owners completed a mailed questionnaire. Data collected included information regarding demographic variables, environmental exposures, and diet, including preferred flavors of canned cat food. RESULTS: Case cats were significantly less likely to have been born recently than control cats. Housing; exposure to fertilizers, herbicides, or plant pesticides; regular use of flea products; and presence of a smoker in the home were not significantly associated with an increased risk of disease, but cats that preferred fish or liver and giblets flavors of canned cat food had an increased risk. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggest that cats that prefer to eat certain flavors of canned cat food may have a significantly increased risk of hyperthyroidism.

Age Factors↗
PubMed1988

[Assessment of risk in occupational tasks with exposure to environmental noise of variable duration and intensity].

The discontinuous exposure to environmental working noise often brings about risk situations hardly assessable by means of phonometric measurements and studying the exposure time, even if accurate. The use of the personal dosimetry can simplify the measurements and give a time-weighted value (Leq) comparable to a fixed limit value. Such a measurement is effective only for the considered time (usually a work shift); nevertheless it is assumed to be representative of the usual exposure to the job even though the variability of the working conditions constitute a limiting factor. In this work we tried to verify the possible use of the measurements of environmental sound pressure levels given by the dosimeter every 0.25 sec. The first aim being the study of the type of distribution of these values (during 5 consecutive shifts) and the estimate of mean and standard deviation values. The mean and the standard deviation values were used to get a OTL (one sided tolerance limits) usually employed for assessing the working chemical pollution. The second aim being the compliance control and the possible need of more measurements.

Environmental Monitoring↗