Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “environmental variability”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29Linked to original sources
PubMed1985

Genetic variation in North Amerindian populations: covariance with climate.

Allelic frequencies at seven polymorphic loci in 74 North Amerindian populations are examined relative to patterns of climatic variation. Canonical correlation analysis reveals strong and significant associations of heterozygosity at the ABO, Ss, Duffy, and P loci with climatic variability. Principal component analysis demonstrates that these loci tend to form correlated ensembles. Moreover, canonical correlation analysis of component scores provides support for an association between polymorphism at these loci and environmental variability. The results are concordant with two previous investigations which suggested a relationship between polymorphism for the ABO, Duffy, and Diego systems and climate. It is suggested that the examination of broad geographic patterns of genetic variation at multiple loci is a valuable, but underutilized, method of screening for the effects of long-term systematic pressures.

Climate↗
PubMedDate not supplied

Correlates of sleep quality in persons with HIV disease.

This study used the Symptom Experience dimension of the revised UCSF Symptom Management Conceptual model to examine correlates of sleep quality in HIV-infected persons. According to this model, person, health/illness, and environment categories influence perception of a symptom. The average person in the sample (N = 58) reported being HIV-infected for 8.5 years and was 46 years old, not working, and a person of color. Depending on the level of data, either chi square or Pearson correlations were computed between the person, health/illness, and environment categories and the dependent variable, sleep quality, as measured by the Pittsburgh Sleep Quality Index. Person variables significantly related to sleep quality were employment status, trait anxiety, and general well-being. Health/illness variables significantly related to sleep quality were length of time living with HIV disease and five health status measures (depressive symptoms, state anxiety, symptom severity, daytime sleepiness, and functional status). The environmental variables associated with sleep quality were sleeping alone, having a separate bedroom, and sleeping in a noisy room. Correlates of better sleep quality are positive general well-being, less anxious personality trait and emotional state, less daytime sleepiness, less depressive symptoms, and less symptom severity. Correlates of worse sleep quality are impaired functional status and longer duration of living with HIV disease.

Adult↗
PubMed2003

Modelling the combined effects of pH, temperature and sodium chloride stresses on the thermal inactivation of Bacillus subtilis spores in a buffer system.

AIMS: The inactivation of Bacillus subtilis 168 spores subjected to the combined stress of pH, temperature and sodium chloride in a buffer system was modelled. METHODS AND RESULTS: Bacillus subtilis 168 spore suspension in 50 mmol l-1 potassium phosphate buffer was heated in an open system using a block heater. A second order polynomial equation was used to describe the relationship between pH, temperature, sodium chloride concentration and the logarithm of the decimal reduction time (D-value) of the spores. Response surface graphs were constructed to predict the inactivation within the experimental domain. The data obtained were also compared with those reported for B. subtilis in different media and foods included in a large reference-based database of thermal inactivation (ThermoKill Database, TKDB R9100), which was constructed in the laboratory. CONCLUSIONS: All the variables studied seemed to have a significant effect on the inactivation of B. subtilis 168 spores in potassium phosphate buffer. The coefficient of determination, r2, and an analysis of the residuals from the model indicated the adequacy of the model to predict the inactivation of B. subtilis spores within the range of the experimental variables studied. SIGNIFICANCE AND IMPACT OF THE STUDY: The findings of this study will enable a better understanding of the inactivation of B. subtilis spores under the influence of the studied environmental variables. The model can be used by food industries to assess and monitor the shelf life of food products in the event of a chance contamination by B. subtilis spores.

Bacillus subtilis↗
PubMed2006

Ecological and developmental context of natural selection: maternal effects and thermally induced plasticity in the frog Bombina orientalis.

Variation in fitness generated by differences in functional performance can often be traced to morphological variation among individuals within natural populations. However, morphological variation itself is strongly influenced by environmental factors (e.g., temperature) and maternal effects (e.g., variation in egg size). Understanding the full ecological context of individual variation and natural selection therefore requires an integrated view of how the interaction between the environment and development structures differences in morphology, performance, and fitness. Here we use naturally occurring environmental and maternal variation in the frog Bombina orientalis in South Korea to show that ovum size, average temperature, and variance in temperature during the early developmental period affect body sizes, shapes, locomotor performance, and ultimately the probability of an individual surviving interspecific predation in predictable but nonadditive ways. Specifically, environmental variability can significantly change the relationship between maternal investment in offspring and offspring fitness so that increased maternal investment can actually negatively affect offspring over a broad range of environments. Integrating environmental variation and developmental processes into traditional approaches of studying phenotypic variation and natural selection is likely to provide a more complete picture of the ecological context of evolutionary change.

Animals↗
PubMedDate not supplied

Chemometric investigations on environmental data from Carlo Alberto irrigation canal (Alessandria, Piedmont, Italy).

The Carlo Alberto Canal connects Bormida and Tanaro rivers in Piedmont (ITALY). It was created for irrigation purposes but since its waters are suspected to be polluted, a sampling campaign was performed by the ARPA of Alessandria. The physico-chemical parameters analysed along 3 years (1998-2000) were investigated by multivariate chemometric methods. PCA showed that the waters situation depends heavily on the sampling period. Also a Kohonen self-organising map confirmed the clustering observed, providing insights into the causes of the clusterisation. New samplings are now being performed and a larger set of environmental variables is determined on each sample.

Agriculture↗
PubMed1994

A genetic analysis of senescence in Drosophila.

Two attractive theories for the evolution of senescence are based on the principle that the force of natural selection decreases with age. The theories differ in the type of age-specific gene action that they assume. Antagonistic pleiotropy postulates that pleiotropic genes with positive effects early in life and negative effects of comparable magnitude late in life are favoured by selection, whereas genes with the reverse pattern of action are selected against. Mutation accumulation assumes that deleterious mutant alleles with age-specific effects will equilibrate at a lower frequency if their effects are expressed early rather than late in life. Explicit models demonstrate that both mechanisms can lead to the evolution of senescent life histories under reasonable conditions. Antagonistic pleiotropy has gained considerable empirical support, but the evidence in support of mutation accumulation is more sparse. Here we report that the genetic variability of mortality in male Drosophila melanogaster increases greatly at very late ages, as predicted by the mutation accumulation hypothesis. The rate of increase in mortality with age exhibits substantial genetic and environmental variability. This result provides a possible explanation for recent observations of non-increasing mortality rates in very old flies.

Aging↗
PubMedDate not supplied

State-dependent peculiarities of cocaine-induced behavioral sensitization and their possible reasons.

To study determinants and possible reasons of cocaine-induced behavioral sensitization, locomotor effects of the drug (COC, 15 mg/kg, IP; 5 daily injections followed by a "challenge," four days later) and various stimuli associated (procedure of injection, placement in the test cage) and nonassociated (tail-pinch) with its administration were measured in rats under different experimental conditions. When COC was injected in quite conditions, two hours after animal habituation to the test cages, locomotor response to the first drug injection was only slightly higher compared to one of saline and these responses were relatively stable following repeated treatment (no sensitization). An enhanced locomotor response to the procedure of injection (needle prick) without changes in responsivity to other stimuli used were found in these COC-treated rats. When COC was injected in activated conditions (animal placement in test cages), locomotor response to the first drug administration was significantly higher compared to one of saline and COC used in the quiet state and it was enhanced following repeated treatment (sensitization). More intense locomotion associated with placement in test cages without any changes in responses to other stimuli was found in rats after this procedure of treatment. Thus, locomotor effects of COC and dynamics of its changes following repeated treatment depend upon the organism's functional state accompanying the drug's effect. Reinforcing action of COC determining development of interinfluence of its effects and ones triggered by environmental variables (learning based on conditioning) is considered as a proposed initial cause and a main mechanism both for enhanced reactivity to cocaine administered under conditions of its previous use and to various environmental events associated with previous cocaine effects.

Animals↗
PubMed1979

Familial aggregation of blood pressure and weight in adoptive families. II. Estimation of the relative contributions of genetic and common environmental factors to blood pressure correlations between family members.

An analysis of the familial aggregation of blood pressure (BP) was conducted to provide estimates of the role of genes and household environment in determining the phenotypic resemblance between biologically related family members. The biological model used for this analysis parameterizes the correlations between family members into the contributions of genetic and environmental variability shared within and across generations. Hypothesis testing about different parameters in the model suggests that shared environment explains larger fractions of the parent-natural child and the full sib correlations for diastolic BP than for systolic BP. For diastolic BP, children in a household share the effects of common environment in addition to the effects which they share with their parents. Dependence of the degree of resemblance between household members on the effects of environmental factors shared within and a-ross generations is not explained by the variability of length of cohabitation among individuals.

Adolescent↗
PubMed2001

The relative contribution of diet and genotype to bone development.

The present review addresses the relative contribution of diet and genotype to variability in human bone growth and mineralisation in the context of the aetiology of osteoporosis. Heritability studies indicate that 60-70 % of the variability in bone mineral mass or bone mineral density (BMD) can be accounted for by genetic variation. Cross-trait analyses suggest that a proportion of this variation reflects genetic influences on bone and body size, such as height and lean body mass. Candidate-gene studies have demonstrated associations between several genetic polymorphisms and bone mineral mass but, as yet, genotype determinations have proved unhelpful in identifying individuals at increased risk of osteoporosis. Variations in diet and other environmental factors contribute 30-40 % to total phenotypic variance in bone mineral mass or BMD. Correlations between intakes of individual nutrients and BMD have been reported, but these relationships are subject to confounding due to size. However, no specific dietary factor has been identified from prospective and twin studies as making a significant contribution to environmental variability in BMD or bone loss. This finding may reflect the difficulties in quantifying environmental exposures. both current and over a lifetime. In addition, the influence of diet on bone health may depend on the genotype of the individual. Optimisation of nutrition and lifestyle remains an attractive strategy for the reduction of fracture risk, but more research is required to fully define optimal dietary requirements.

Bone Density↗
PubMed2006

Below-ground bud banks increase along a precipitation gradient of the North American Great Plains: a test of the meristem limitation hypothesis.

In perennial grasslands, the below-ground population of meristems (bud bank) plays a fundamental role in plant population dynamics. Here, we tested the 'meristem limitation hypothesis' prediction - that bud banks increase along an increasing precipitation/productivity gradient in North American grasslands - and assessed the seasonal dynamics of bud banks. We sampled bud and stem populations quarterly at six sites across a 1100 km gradient in central North America. Bud banks increased with average annual precipitation, which explained 80% of the variability between the sites. In addition, seasonal changes in grass bud banks were surprisingly similar across a 2.5-fold range in precipitation and a 4-fold range of productivity: densities peaked in March, decreased in June and increased slightly in September. Increasing meristem limitation may constrain vegetation responses to inter-annual changes in resources. An important consequence of this is that biomes with large bud banks may be the most responsive to environmental change. If meristem limitation represents an important constraint on productivity responses to environmental variability, then bud banks must be considered in developing predictive models for grassland responses to environmental change.

Acclimatization↗
PubMed1999

From individuals to aggregations: the interplay between behavior and physics.

This paper analyses the processes by which organisms form groups and how social forces interact with environmental variability and transport. For aquatic organisms, the latter is especially important-will sheared or turbulent flows disrupt organism groups? To analyse such problems, we use individual-based models to study the environmental and social forces leading to grouping. The models are then embedded in turbulent flow fields to gain an understanding of the interplay between the forces acting on the individuals and the transport induced by the fluid motion. Instead of disruption of groups, we find that flows often enhance grouping by increasing the encounter rate among groups and thereby promoting merger into larger groups; the effect breaks down for strong flows. We discuss the transformation of individual-based models into continuum models for the density of organisms. A number of subtle difficulties arise in this process; however, we find that a direct comparison between the individual model and the continuum model is quite favorable. Finally, we examine the dynamics of group statistics and give an example of building an equation for the spatial and temporal variations of the group-size distribution from the individual-based simulations. These studies lay the groundwork for incorporating the effects of grouping into models of the large scale distributions of organisms as well as for examining the evolutionary consequences of group formation.

Animals↗
PubMed2001

Modelling sustainable development planning: a multicriteria decision conferencing approach.

Development planning is multidimensional in nature. On the one hand, it addresses economic growth, and on the other, it deals with economic development of the whole nation. Sustainable development, on the other hand, emphasizes the need for integration of economics and environment, as well as promoting intra- and intergenerational equity. While the literature deals extensively with the issues of sustainable development, it lacks a prescription of an easy-to-use, yet rigorous, methodology for it. In this paper, we offer a decision conferencing approach to sustainable development planning based on a multicriteria model. The integrated model is presented and applied to a sustainable development planning exercise in a third world country. Sample results are presented and detailed sensitivity analyses show the environmental variables that are of major concern.

Animals↗
PubMed1986

Clinical methods in psychiatric genetics. III. Environmental stratification may simulate a genetic effect in adoption studies.

In adoption studies, the possibility of inadvertent matching between biological and adoptive parents for some environmental variable (known or unknown) correlated with illness must be considered. We examine such bias quantitatively and show how a genetic effect can be simulated. Existence of a genetic effect which is independent of environmental correlation can be accepted, when the frequency of a disease in adoptees who have a biological parent affected and no adoptive parents affected is significantly greater than the frequency of the disease in adoptees who have an adopted parent affected and no biological parents affected. The published data on schizophrenia, alcoholism, and criminality do not exclude the possibility of undetected environmental correlations simulating a genetic effect, according to this direct criterion.

Adoption↗
PubMedDate not supplied

Environmental influences on relapse in substance use disorders.

Characteristics of the posttreatment environment have been implicated in relapse and recovery in substance use disorders. We summarize these findings and describe how different models of relapse interpret the data and diverge in their representations and measurement operations of environmental variables. The advantages and limitations of common measures of the posttreatment environment are discussed using research on life events and relapse as an example. An alternative approach to representing covariation over time between environmental characteristics and substance use that is derived from an application of behavioral theories of choice to relapse is presented.

Adaptation, Psychological↗
PubMed1991

Humor in therapy for the mentally ill.

There are many benefits of humor as a planned intervention for CMI patients. In addition to physiological, psychological, social, and communicative benefits for the patient are the benefits of humor for the nurse therapist. According to Keller (1984), another legitimate function of humor in therapy is as a source of rejuvenation for the therapist. Working with a population of clients whose progress is sometimes difficult to ascertain can sometimes be draining and may result in burnout if nurses are not periodically rejuvenated. Humor can act as an energizer for both clients and nurses, and can help nurses maintain their equilibrium. Areas for Further Research. Sullivan and Deane (1988) posed five potential areas for study in gerontological-oriented humor, but all of these areas are also applicable in the study of humor among the chronically mentally ill: Identification of any functional level changes and cognitive flexibility resulting from increased humor experiences. Development of humor assessment tools. Identification of environmental variables and barriers that affect the spontaneous occurrence of humor, especially in institutional settings. Exploration of differences in the effects of group and dyadic humor on mental health. Exploration of favorable and unfavorable environmental contexts and outcomes for using therapeutic humor.

Chronic Disease↗
PubMed1993

Environmental and health problems of developing countries.

Environmental variables largely determine the disease pattern in developing countries. Infections and malnutrition predominate, due to the effects of both poverty (a summary of many aspects of material deprivation) and a high ambient temperature. Environmental changes may be intended to improve health--examples include improved domestic water supplies and sanitation--or they may be due to socio-economic developments, which often have favourable or unfavourable health consequences. These are explored for water resource developments, where the health effects are complex, and for deforestation and urbanization. Although environmental impact assessment has been of value in reducing the adverse health impacts of socio-economic development projects, the use of health opportunity assessment is proposed as a more positive approach to optimizing the consequences of development to human health.

Developing Countries↗
PubMed2003

GIS-based prediction of malaria risk in Egypt.

Environmental variables in a malaria geographic information system (GIS) database were analysed to discriminate between governorates at high and low risk of malaria. Only Fayoum governorate was categorized as a high risk area for malaria during the last 2 decades. Discriminant models correctly classified 96.3% of the risk categories and indicated that the most important predictor of risk is hydrogeology. Further GIS spatial analysis indicated that the high malaria risk in Fayoum is associated with a unique environmental envelope of biotic (presence of both efficient malaria vectors) and abiotic (hydrogeology and soil) variables. Recommendations for surveillance and control are discussed.

Agriculture↗
PubMed2004

Constraints on spatial variability in soft-sediment communities affected by contamination from an Antarctic waste disposal site.

A small-scale (<500 m length) transect-based survey was conducted in December 1998 to examine the spatial distribution of soft-sediment communities and of concentrations of heavy metals and hydrocarbons in sediments in Brown Bay, adjacent to an abandoned waste dump, at Casey Station, Antarctica. Samples were taken along three transects at increasing distances (nine stations) from the shore-line waste dump. A gradient of contamination was detected, but concentrations of contaminants were very variable with "hotspots" or high levels of contaminants at some stations. Multivariate analysis revealed that the distribution of soft-sediment communities was distinctly different between the inner, middle and outer stations. Abundances of most taxa were very variable with few patterns apparent, but some fauna displayed an abundance gradient from the inner to the outer part of the bay. Many taxa had maximum abundances at outer stations and minimum at inner stations. Multivariate correlations between environmental variables and soft-sediment communities indicated that combinations of some metals (Cd, Cu, Sn, Pb) and grain size (mainly finer fractions, fine sands and coarse silts) were the variables that best "matched" the community patterns within Brown Bay. This study indicated that there were significant correlations between the presence of contaminants and the distribution and composition of soft-sediment communities over very small spatial scales.

Animals↗