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PubMed2003

Spatial and temporal distribution of "curvina" larvae (Plagioscion squamosissimus Heckel, 1840) and its relationship to some environmental variables in the Upper Paraná River floodplain, Brazil.

With the objective of studying the spatial and temporal distribution of "curvina" Plagioscion squamosissimus larvae and verifying respective spawning sites, monthly sampling was carried out from March 1993 to February 1994 on the Upper Paraná River floodplain. Using a conical-cylindrical plankton net (0.5 mm mesh), samples were taken from the surface of the water bodies, and in the marginal vegetation a strainer and a dragnet ("picaré") were used. Water samples were collected for environmental variable analysis (temperature, dissolved oxygen, water pH, and electrical conductivity). Water level data were obtained from hydrometric stations. High average density of larvae was found from December 1993 to February 1994 due to high temperature and water level. The Baía sub-area was shown to be the most important in the larvae catch, probably due to its semi-lotic characteristics. Larvae size distribution was shown to be more frequent in the 4.0 mm standard length class, indicating that the sampling stations were next to the spawning sites.

Animals↗
PubMed1986

Risk factors for malnutrition in Brazilian children: the role of social and environmental variables.

The article reports the effects of several socioeconomic and environmental indicators on the nutritional status (stunting, underweight, and wasting) of a sample of 802 children aged 12-35.9 months in urban and rural areas of southern Brazil. Of the social variables studied, family income and father's education level were the two risk factors that showed the strongest associations with nutritional status. The mother's education level, employment status of the head of the family, number of siblings, and family's ethnic background also showed some degree of association, but these were less significant when family income was included in the analysis. Environmental variables, particularly the type of housing, degree of crowding, and type of sewage disposal, were also strongly associated with malnutrition. The effects of having access to piped or treated water were only apparent on stunting and wasting.

Anthropometry↗
PubMed1987

Environmental variables and releasing-valence transfer in stimulus-directed pecking of chicks.

Releasing valence transfer occurs when the power or valence to release responses is transferred from a primary releasing stimulus to a second, initially neutral, stimulus. In the exemplar, pecking responses by neonatal chicks are released and directed by a pointed object operated to make pecking movements. Stimuli attached to or pecked by the arrow thereby acquire enhanced releasing valence. Chicks peck at matching stimuli in preference to comparable but unenhanced stimuli. Research reported here shows that primary and transferred releasing valences are differentially affected by environmental variables. Specific findings were Pecking by chicks occurs only within a narrow range of ambient temperature. Outside of this range, pecking is low in frequency and insensitive to valence-enhanced release. Pecking by chicks appears to be finely tuned to arrow peck rates between 120 and 180 pecks per minute. Within this range, frequency of pecks by chicks is low whereas the percentage of pecks to the valence-enhanced stimulus is maximal. The maternal food call was a weak releaser of pecking by chicks with no valence-enhancing properties.

Animals↗
PubMed2002

Environmental variability and semelparity vs. iteroparity as life histories.

Research on the evolution of life histories addresses the topic of fitness trade-offs between semelparity (reproducing once in a lifetime) and iteroparity (repeated reproductive bouts per lifetime). Bulmer (1994) derived the relationship v+P(A)<1 (P(A) is the adult survival;vb(S) and b(S) are the offspring numbers for iteroparous and semelparous breeding strategies, respectively), under which a resident semelparous population cannot be invaded by an iteroparous mutant when the underlying population dynamics are stable. We took Bulmer's population dynamics, and added noise in juvenile and adult survival and in offspring numbers. Long-term coexistence of the two strategies is possible in much of the parameter region ofv +P(A)<1 when noise occurs simultaneously in all three components, or (more restricted) when it affects juvenile and adult survival or adult survival and offspring numbers. Iteroparity cannot persist when the environmental variability involves juvenile survival and offspring numbers, or when the noise acts on the three components separately.

Animals↗
PubMed2003

Talkin' 'bout my generation: environmental variability and cohort effects.

In variable environments, it is probable that environmental conditions in the past can influence demographic performance now. Cohort effects occur when these delayed life-history effects are synchronized among groups of individuals in a population. Here we show how plasticity in density-dependent demographic traits throughout the life cycle can lead to cohort effects and that there can be substantial population dynamic consequences of these effects. We show experimentally that density and food conditions early in development can influence subsequent juvenile life-history traits. We also show that conditions early in development can interact with conditions at maturity to shape future adult performance. In fact, conditions such as food availability and density at maturity, like conditions early in development, can generate cohort effects in mature stages. Based on these data, and on current theory about the effects of plasticity generated by historical environments, we make predictions about the consequences of such changes on density-dependent demography and on mite population dynamics. We use a stochastic cohort effects model to generate a range of population dynamics. In accordance with the theory, we find the predicted changes in the strength of density dependence and associated changes in population dynamics and population variability.

Age Factors↗
PubMedDate not supplied

Antioxidant responses of the Mediterranean mussel, Mytilus galloprovincialis, to environmental variability of dissolved oxygen.

Physiological responses of Mytilus galloprovincialis against environmental dissolved oxygen partial pressure (pO(2)) variation were studied in terms of the modulated induction of the main antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT) and selenium-dependent glutathione peroxidase (GPX). Field in vivo studies were performed at two sites of the Lagoon of Venice, characterized by different aquatic environmental conditions implying different pO(2). SOD and GPX are more active in gills, and their complementary role is discussed. CAT is more active in the digestive gland, where the enzyme dismutates H(2)O(2) derived from divalent reduction of O(2) performed by various oxidases in peroxisomes. Antioxidant enzyme activities are correlated with water dissolved oxygen (DO), especially in the gills. This tissue, because of its anatomical localization and its physiological role, responds to DO variations modulating the induction of the antioxidant enzymes as a protection mechanism against potential toxicity due to increases in ROS formation.

Animals↗
PubMed1995

Effect of environmental variables in turkey confinement houses on airborne Aspergillus and mycoflora composition.

Environmental conditions and airborne mycoflora were measured concurrently in 10 turkey confinement houses during warm and cold weather. The following variables in the environment were measured: numbers of feed- and litter-associated yeast and mold fungi, temperature, relative humidity, airspeed, carbon dioxide and ammonia concentration, airborne bacteria, and airborne particulate mass, particle number, and particle size distribution. Winter air in turkey confinement houses contained significantly higher concentrations of Aspergillus, Scopulariopsis, and Mucor sp. and significantly lower concentrations of Cladosporium, Fusarium, and Alternaria sp. when compared with summer air. Significantly greater numbers of Mucor sp. were recovered per cubic meter of air where the current turkey flock was present less than 100 d when compared to houses where the current flock resided 100 d or more. Management decisions regarding control of the internal environment of turkey confinement houses apparently influence airborne mycoflora composition.

Air Microbiology↗
PubMedDate not supplied

Adjusting for temporal variation in the analysis of parallel time series of health and environmental variables.

Time series of daily administrative cardio-respiratory health and environmental information have been extensively used to assess the potential public health impact of ambient air pollution. Both series are subject to strong but unrelated temporal cycles. These cycles must be removed from the time series prior to examining the role air pollution plays in exacerbating cardio-respiratory disease. In this paper, we examine a number of methods of temporal filtering that have been proposed to eliminate such temporal effects. The techniques are illustrated by linking the number of daily admissions to hospital for respiratory diseases in Toronto, Canada for the 11 year period 1981 to 1991 with daily concentrations of ambient ozone. The ozone-hospitalization relationship was found to be highly sensitive to the length of temporal cycle removed from the admission time series, and to day of the week effects, ranging from a relative risk of 0.874 if long wave cycles were not removed at all to 1.020 for models which removed at least cycles greater than or equal to one month based on the interquartile pollutant range. The specific statistical method of adjustment was not a critical factor. The association was not as sensitive to removal of cycles less than one month, except that negative autocorrelation increased for series in which cycles of one week or less were removed. We recommend three criteria in selecting the degree of smoothing in the outcome: removal of temporal cycles, minimizing autocorrelation and optimizing goodness of fit. The association between ambient ozone levels and hospital admissions for respiratory diseases was also sensitive to the season of examination, with weaker associations observed outside the summer months.

Air Pollution↗
PubMed2004

The effect of autocorrelation in environmental variability on the persistence of populations: an experimental test.

Despite its significance regarding the conservation and management of biological resources, the body of theory predicting that the correlation between successive environmental states can profoundly influence extinction has not been empirically validated. Identical clonal populations from a model experimental system based on the collembolan Folsomia candida were used in the present study to investigate the effect of environmental autocorrelation on time to extinction. Environmental variation was imposed by variable implementation (present/absent) of a culling procedure according to treatments that represented six patterns of environmental autocorrelation. The average number of culling events was held constant across treatments but, as environmental autocorrelation increased, longer runs of both favourable and unfavourable culling tended to occur. While no difference was found among the survival functions for the various treatments, the time taken for 50% of the component populations to become extinct decreased significantly with increasing environmental autocorrelation. Similarly, analysis of all extinct populations demonstrated that time to extinction was shortened as environmental autocorrelation increased. However, this acceleration of extinction can be fully offset if sequential introduction is used in place of simultaneous introduction when founding the populations.

Animals↗
PubMed2001

Design and analysis of robust total joint replacements: finite element model experiments with environmental variables.

Computer simulation of orthopaedic devices can be prohibitively time consuming, particularly when assessing multiple design and environmental factors. Chang et al. (1999) address these computational challenges using an efficient statistical predictor to optimize a flexible hip implant, defined by a midstem reduction, subjected to multiple environmental conditions. Here, we extend this methodology by: (1) explicitly considering constraint equations in the optimization formulation, (2) showing that the optimal design for one environmental distribution is robust to alternate distributions, and (3) illustrating a sensitivity analysis technique to determine influential design and environmental factors. A thin midstem diameter with a short stabilizing distal tip minimized the bone remodeling signal while maintaining satisfactory stability. Hip joint force orientation was more influential than the effect of the controllable design variables on bone remodeling and the cancellous bone elastic modulus had the most influence on relative motion, both results indicating the importance of including uncontrollable environmental factors. The optimal search indicated that only 16 to 22 computer simulations were necessary to predict the optimal design, a significant savings over traditional search techniques.

Arthroplasty, Replacement, Hip↗
PubMed1996

Control of environmental variables in a field study using a chronobiological protocol.

Field work in chronobiology usually is based on observations which differ from those in laboratory studies which are experimental. Non-invasive protocols are recommended in the field in order not to introduce additional variables. We propose an alternative strategy here. The effect of environmental cycles on biological rhythms can be estimated when the observations are made in more than one area. The areas under study must have at least one characteristic in common which is a guarantee that the limits of oscillation of an environmental cycle will be similar. This proposal has been tested using the biological system consisting of an Onagraceae plant, Ludwigia elegans, and its bee visitors, which is found in two localities at the same latitude, but at different altitudes. Under the same photoperiod, but with the mean temperature ranging within known limits, it was possible to determine temporal characteristics of the system in the field by examining the effects of the light/dark and temperature daily cycles.

Animals↗
PubMedDate not supplied

Life events, environmental variables and child depression.

There is substantial evidence of a significant correlation between life events (LE), socio-environmental factors and the occurrence of psychopathological disorders. This study investigates the possible influence of these variables on depression in children between the ages of 7 and 12 years. We have interviewed parents of 15 depressed and 30 control children, and used the Coddington lists of LE. From a statistical analysis of the response it emerged that what characterises depressed children is a higher number of undesirable and uncontrolled events in the recent past and a lower parent educational level. A few events in particular appear to be strong risk factors. The event 'outstanding personal achievement', much more represented in the control group, seems to be a strengthening event and a stress moderator.

Child↗
PubMed2007

Phenotypic, maximum genetic, and special environmental variability in prehistoric human populations.

The phenotypic variance (V(P)) may be divided into the genetic variance (V(G)), the general environmental variance (V(Eg)), and the special environmental variance (V(Es)). The latter is estimated through repeatability calculation (b). This value is considered the upper limit of heritability and represents maximum genetic variance proportion (V(Gm) = V(G) + V(Eg)) in relation to V(P) (b = (V(G) + V(Eg))/V(P)). This process allows an improved determination of biological relationships among groups from estimators maximizing the genetic information of quantitative characters. Two hundred and thirty-seven individuals inhabiting the northern coast of Chile for 4,000 years were taken as a sample. Measurement was made of six metric characters at both sides of the cranium. Special environmental values (es) were obtained by regression. The difference between these values and the phenotypic values (p) consists in the genetic values plus the general environmental values (g + eg). A mean b value of 0.83 indicated that V(Es) represents 17% of V(P). The results showed: 1) high stability of the maximum genetic variance in time and space, 2) high correlation between the biological relationships model, the phenotypic model, and the maximum genetic model, and 3) random distribution of the nongenetic variation, as expected from the quantitative genetics theory. These results support the use of phenotypic data for the interpretation of the evolution history of prehistoric populations.

Anthropometry↗
PubMed2004

Relationship between macroinvertebrate fauna and environmental variables in small streams of the Dominican Republic.

Field assessment methods for freshwater macroinvertebrates and water quality in tropical small-island states were assessed in the Dominican Republic. Macroinvertebrate samples were collected from 26 river sites within the Dominican Republic's Yaque del Norte river catchment. Environmental data on geographical, physical and chemical variables were also collected from each site. The Biological Monitoring Working Party score and total numbers of Ephemeroptera and Trichoptera were calculated for each site. Physico-chemical and biological data sets were ordinated by principal components analysis and non-parametric multi-dimensional scaling, and the biotic and abiotic data sets were correlated to determine the most influential factors determining site similarities. Macroinvertebrate assemblage structure was correlated with declining water quality: however, a high correlation between water quality and altitude confounded an unqualified interpretation of impairment.

Animals↗
PubMed2005

Sensitivity of cell-based biosensors to environmental variables.

Electrically active living cells cultured on extracellular electrode arrays are utilized to detect biologically active agents. Because cells are highly sensitive to environmental conditions, environmental fluctuations can elicit cellular responses that contribute to the noise in a cell-based biosensor system. Therefore, the characterization and control of environmental factors such as temperature, pH, and osmolarity is critical in such a system. The cell-based biosensor platform described here utilizes the measurement of action potentials from cardiac cells cultured on electrode arrays. A recirculating fluid flow system is presented for use in dose-response experiments that regulates temperature within +/-0.2 degrees C, pH to within +/-0.05 units, and allows no significant change in osmolarity. Using this system, the relationship between the sensor output parameters and environmental variation was quantified. Under typical experimental conditions, beat rate varied approximately 10% per degree change in temperature or per 0.1 unit change in pH. Similar relationships were measured for action potential amplitude, duration, and conduction velocity. For the specific flow system used in this work, the measured environmental sensitivity resulted in an overall beat rate variation of +/-4.7% and an overall amplitude variation of +/-3.3%. The magnitude of the noise due to environmental sensitivity has a large impact on the detection capability of the cell-based system. The significant responses to temperature, pH, and osmolarity have important implications for the use of living cells in detection systems and should be considered in the design and evaluation of such systems.

Biosensing Techniques↗
PubMed1998

Effect of different environmental variables on the synthesis of Hsp70 in Raphidocelis subcapitata.

Heat-shock proteins (Hsp) or stress proteins are strong candidates for biomarkers of environmental pollution since they are activated very early in the cascade of cellular events that follow toxic exposure and at concentrations below the lethal dose. Included in a test battery comprised of different bioassays, Hsp induction could provide a general purpose tier I indicator of pollution. Still, little is known on the induction of Hsp under different environmental conditions. In the present study we have made use of an Enzyme Linked Immunosorbent Assay (ELISA) to detect the synthesis of Hsp70 in Raphidocelis subcapitata in response to changes in pH, temperature, humic acids, nitrates and phosphates. The results show that algae respond to these changes in the environment by a transient increase in Hsp70 levels, the extend of which is dependent on the actual parameter under investigation. Out of these five parameters studied, only temperature and possibly pH were able to induce acquired tolerance, i.e. algae grown at a pH or at a temperature different from control conditions were shown to have acquired resistance to a subsequent challenge with Zn (10(-5) M). Adjustment of the pH and temperature in two physico-chemically different natural surface waters was demonstrated to be sufficient to obtain similar induction patterns of Hsp70 upon exposure to zinc. These results qualify Hsp70 as a good biomonitor for environmental pollution provided essential environmental parameters such as pH and temperature are kept constant.

Environmental Monitoring↗
PubMed1975

Interrelationships among children's environmental variables as related to age, sex, race, and socioeconimic status.

Information concerning their environments was obtained from 127 first and 165 fifth grade children and their patents. These data were examined interactively--to determine whether patterns of relationships among environmental components changed as a function of the general status variables of sex, age, class, and race--and factorially, to obtain groupings of components. Chi square comparison of subgroup intercorrelation matrices revealed no differences among matrices as a function of the status variables. Factor analysis revealed six common factors: Social Class, Interactive Opportunity and Experience, Maturity, Aspiration Level, Family Interaction, and Amount of Income.

Age Factors↗
PubMed1978

Does environmental variability limit niche overlap?

A stochastic theory of limiting similarity is presented that attempts to quantify the relationship between tolerable niche overlap among competing species and the degree of environmental fluctuation. The theory is based on a heuristic analytical approximation that provides conditions under which a rare invading species can increase in the presence of a community of established competitors. The major qualitative conclusion, derived from investigating two symmetric, discrete-time, stochastic analogs of the Lotka-Volterra competition equations, is that weak to moderate stochastic variation does not appear to limit significantly the similarity of competing species. This result is in sharp contrast to the conclusions of May and MacArthur's pioneering study of stochastic limiting similarity. A possible reason for this discrepancy is explored.

Journal Article↗