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PubMed2002

Temporal variability of bioavailable Cd, Hg, Zn, Mn and Al in an upwelling regime.

Monthly variability of Cd, Hg, Zn, Mn and Al concentrations in mussels (Mytilus californianus) soft tissue and brown seaweed (Macrocystis pyrifera) was studied at a pristine rocky shore off San Quintin Bay, Baja California, México. The results were related to climatic and hydrographic conditions and to the physiological state of the mussels (condition index) by correlation analysis and principal component analysis (PCA). A "normalization" to account for the variability induced by the physiological state of the mussel was performed. The PCA was performed in two ways to relate the environmental variables and the condition index to: (1) the metal concentrations in mussels, and (2) the "normalized" mussel concentrations. The association of the variability of Cd with the upwelling season was revealed in both PCAs. The temporal variability of this metal in mussels was highly correlated to that in seaweed, suggesting that the dissolved phase determined the variability of Cd in mussels. However, for Hg, Zn, Mn and Al the results from both PCAs were different. The first PCA showed the relationship of these metals to pluvial precipitation and to the condition index. The PCA for the normalized mussel concentrations showed that, after eliminating the effect of the condition index, only Al was related to pluvial precipitation. Manganese, and to a less degree Zn, were related to these metals in seaweed. Because zinc is an essential element in mussels, some regulation of their internal concentrations is likely. Mercury was not detected in seaweed, but because of its reactive nature, it is not expected that the dissolved fraction could be a significant pathway; therefore, it can be concluded that its temporal variability was determined by the variability in the condition index only.

Aluminum↗
PubMed1997

[Leptospira interrogans in a canine population of Greater Buenos Aires: variables associated with seropositivity].

We determined the seroprevalence of leptospirosis in a suburban canine population for the purpose of analyzing the association between different individual and environmental variables and seropositivity for leptospirosis. The study, which was cross-sectional, was performed in July 1992 in a neighborhood of Greater Buenos Aires with approximately 9,500 inhabitants and a canine population of around 2,000 animals. We studied a random sample of 223 dogs and obtained a blood sample from each. Each animal's epidemiologic history was obtained by interviewing the housewife. Serologic measurements were performed by the microagglutination technique with the use of 10 different serotypes of Leptospira interrogans. Of the 223 dogs that were tested, 57% showed seropositivity; 82% of the positive sera coagglutinated with two or more serotypes. The most frequently detected serotypes were canicola and pyrogenes. Seroprevalence in females was less common than in males (P < 0.05) and in puppies less than 1 year old it was less common than in older animals (P < 0.01). Street behavior in the dog and the presence of stagnant water in front of the owner's dwelling were the most important of the risk factors examined. The associations between seropositivity on the one hand and contact with trash deposits, hunting behavior and the presence of rodents inside the dwelling on the other were not statistically significant. Different control measures are discussed.

Age Factors↗
PubMed1980

Predicting adaptive functioning of mentally retarded persons in community settings.

The impact of a variety of individual, residential, and community variables on adaptive functioning of retarded persons was examined using a multiple-regression analysis. Individual characteristics (especially IQ) accounted for 21 percent of the variance, while environmental variables, primarily those related to normalization, accounted for 35 percent. The data suggest that environmental normalization may be an effective technology for the promotion of independent functioning of retarded people as well as an ideology.

Adolescent↗
PubMed2000

Iron and copper in human milk.

The reported concentrations of iron and copper in breast milk show a wide variation. Research published over the past 50 y has reported median values of 0.47 and 0.32 mg/L for iron and copper, respectively. The levels of both metals decrease with the progress of lactation. The calculated iron-to-copper ratio of reported means differs from 0.25 to 6.29 (median = 1.18). Maternal constitutional variables such as undernutrition, iron and copper body reserves, stage of lactation, adolescent motherhood, gestation length, and infection and environmental variables such as iron and copper dietary intake, in addition to supplementation, smoking, vegetarianism, and prolonged use of hormonal contraceptives before and during lactation did not consistently affect the concentrations of iron and copper in breast milk. Extreme cases of either low or high levels of body metal availability or altered metabolism due to chelating therapy or illnesses such as Wilson's disease and infections did not affect metal transfer from blood serum to breast milk. There is no clinical or scientific support for the need of extra iron or copper, besides the quantities provided by milk in the full-term breast-fed infant, at least during the first 6 mo.

Contraceptives, Oral↗
PubMed1985

Infant temperament and noncompliant behavior at four years: a longitudinal study.

Noncompliant behavior in early childhood (i.e., exaggerated, but age-appropriate negativism) has been inadequately studied. This longitudinal study explores preschool temperament and maternal behavior as current correlates of negativistic behavior at age 4, and early maternal characteristics and infant temperament as etiological variables in the production of negativism. Longitudinal evidence was collected from 62 mother-child dyads, representative of all social classes. This evidence included home observations of maternal and child behavior at 4 years, a temperament questionnaire at 4 years, a questionnaire about infant temperament, and observational and interview measures at various stages from birth to 3 years, of infant behavior and maternal characteristics. The findings suggest that infant and childhood temperament (especially the degree of infant fussiness) are highly predictive of physical noncompliance, and that physical noncompliance is unrelated to maternal or demographic variables. A combination of maternal variables including warmth, closeness, and verbal directiveness, both positive and negative, as well as child variables, predict verbal noncompliance. Demographic variables, temperament, and maternal attitudes predict passive noncompliance. Noncompliance is viewed as a complex phenomenon in which constitutional and environmental variables interact.

Child Behavior Disorders↗
PubMed2003

Assessing anchor damage on coral reefs: a case study in selection of environmental indicators.

Because environmental conservation can remove scarce natural resources from competing uses, it is important to gain support for conservation programs by demonstrating that management actions have been effective in achieving their goals. One way to do this is to show that selected significant environmental variables (indicators) vary between managed and unmanaged areas or change over time following implementation of a management regime. However, identifying indicators that reflect environmental conditions relevant to management practices has proven difficult. This paper focuses on developing a framework for choosing indicators in a coral reef habitat. The framework consisted of three phases: (1) information gathering to identify candidate variables; (2) field-testing candidate variables at sites that differ in intensity of human activity, thus identifying potential indicators; and (3) evaluating potential indicators against a set of feasibility criteria to identify the most useful indicators. To identify indicators suitable to measure the success of a management strategy to reduce anchor damage to a coral reef, 24 candidate variables were identified and evaluated at sites with different intensities of anchoring. In this study, measures that reflected injuries to coral colonies were generally more efficient than traditional measures of coral cover in describing the effects of anchoring. The number of overturned colonies was identified as the single most useful indicator of coral reef condition associated with anchoring intensities. The indicator selection framework developed here has the advantages of being transparent, cost efficient, and readily transferable to other types of human activities and management strategies.

Animals↗
PubMed1996

An epidemiological study of roadway fatalities related to farm vehicles: United States, 1988 to 1993.

Compared with the estimated injury fatality rate for workers in all occupations (nine in 100,000 in 1988) the farm fatality rate (48 in 100,000) was among the highest in the nation; in 1993, these rates were eight and 35 in 100,000, respectively. On-road farm-vehicle fatalities have been identified as a significant problem, yet these events apparently have not been investigated in a comprehensive manner. The purpose of this study was to investigate the circumstances surrounding all on-road, non-truck, farm-vehicle crash fatalities in the United States form 1988 through 1993. The National Highway Traffic Safety Administration's Fatal Accident Reporting System, which includes data for all US fatal on-road motor vehicle crashes, was the source of data. Driver-related variables were compared among farm vehicles, vehicles in collisions with farm vehicles, and all other vehicles in rural, fatal crashes; environmental variables were compared between rural farm-vehicle and non-farm-vehicle crashes. During 1988 to 1993, in rural areas, 444 farm-vehicle occupants were killed; in addition, 238 occupants of other vehicles or pedestrians were killed in collisions with the farm vehicles. The farm vehicles were disproportionately involved in overturns, rear-end collisions, and incidents in which the injured person fell from the vehicle, when compared with all other non-farm vehicles involved in rural-area fatal crashes. Of the farm vehicles involved in fatal crashes at night, dawn, or dusk, 65% were struck in the rear, compared with 4% of vehicles involved in fatal non-farm-vehicle crashes. Compared with drivers in all other rural crashes, farm-vehicle operators were more likely to be male, have a greater proportion of convictions for driving while intoxicated, and a lower proportion of previous speeding convictions. From this initial investigation, it appears that the fatal-crash involvement of farm vehicles are related to vehicle and environmental factors that are changeable. Given the proportion of overturns associated with farm-vehicle crashes (21%) compared with non-farm vehicles (9%), there is a need to investigate design characteristics of the farm vehicles. The large proportion of farm vehicles struck in the rear during daylight (24%) as well as night, dawn, or dusk hours (65%), compared with non-farm vehicles (4% and 4%, respectively), suggest factors related to visibility and perception of the farm vehicles' speed that provide a basis for further study.

Accidents, Occupational↗
PubMed1994

The evolution of a concept: aggression and violence in psychiatric settings.

In a series of studies examining aggression and violence by persons with a mental illness, a coercive interactional style emerged as an important predictive variable in hospital settings. This interactive style addresses one issue noted in the literature, the relative effect of personal versus environmental variables, by describing how violent individuals interact with their environment in purposeful ways. The findings from three specific studies are summarized to describe how this interactive style was identified, quantified and documented as a predictor of aggression and violence. It is hoped that this synthesis of research findings will facilitate the application of research to practice settings.

Aggression↗
PubMed2006

Modeling individual and physical environmental factors with adolescent physical activity.

BACKGROUND: Recent calls have been made to consider both environmental factors and individual-level factors in the explanation of physical activity (PA). The present study tested a conceptual model that integrated past PA, relevant environmental-level and individual-level factors and their associations with adolescent PA, using the tenets of the Theory of Planned Behavior (TPB). METHODS: Data were gathered in an adolescent sample (n=221; 60% girls) using questionnaires. PA was assessed in May 2003 and November 2003. Theory of Planned Behavior cognitions regarding PA and the environmental factors under study were assessed in November 2003. Confirmatory factor analyses and path analyses were performed using AMOS software. RESULTS: The initial structural model did not provide an acceptable fit to the data. Including a direct path from past PA to current PA significantly improved model fit to an acceptable fit. Including a direct path from past PA to environmental perceptions did not significantly improve model fit. Including a direct path from the environmental variables to current PA did not significantly improve model fit. Current PA was most strongly influenced by past PA, while environmental aesthetics and distance to PA opportunities were indirectly related to adolescents' intention to be physically active. Significant standardized path coefficients ranged from 0.14 to 0.34 and explained 17% variance in current PA. CONCLUSIONS: Combining past PA, Theory of Planned Behavior cognitions, and environmental factors increased our understanding of their relative influences on adolescent PA. Implications for future research on physical activity are discussed.

Adolescent↗
PubMed2005

Air-soil exchange of mercury from background soils in the United States.

The air-surface exchange of mercury (Hg) was measured, using a dynamic polycarbonate flux chamber, for soils with low or "background" Hg concentrations (<0.1 mg/kg) at eleven locations across the contiguous United States. Sampling locations included agricultural, desert, grassland, mixed and pine forest ecosystems (n=1326 soil flux measurements at 46 individual sites). An overall soil Hg flux of 0.9+/-0.2 ng/m2/h for these background soils was obtained by averaging the means for the different locations. Soil Hg fluxes were significantly lower in dark conditions than in the light for all but the grassland sites. Mean inlet air Hg concentrations were 1.0+/-0.1 ng/m3 in the dark and 1.3+/-0.2 ng/m3 in the light. Soil temperature inside and outside of the chamber, air temperature, relative humidity, and irradiance were measured concurrently with soil Hg flux. Soil-air Hg exchange was weakly predicted by environmental variables (R2 from 0.07 to 0.52). For a single location, flux was better correlated with soil moisture than other measured environmental parameters, suggesting that soil moisture might be an important driver for Hg emissions from background soils. In addition, based on data collected we suggest some quality control measures for use of Tekran 2537A analyzers when measuring low mercury fluxes. Using basic scaling procedures, we roughly estimate that natural emissions from soils in the contiguous U.S. release approximately 100 Mg/yr of Hg to the atmosphere.

Agriculture↗
PubMed1993

Polyparasitism on the Kenya coast. 2. Spatial heterogeneity in parasite distributions.

In a parasitological survey of people living in 20 clusters of homes within 50 km of Kilifi, Coast Province, Kenya, internally age-standardized prevalences showed considerable variation. While this was correlated, in part, with the steep gradients of environmental variables related to distance from the coast, considerable residual variation remained. Indeed, isopleths for parasite prevalence frequently transected those for environmental parameters. It is concluded that broad environmental parameters are limited in their predictive value for determining parasite presence or prevalence; a study of the causes of major differences between villages in the same environment might indicate relatively simple control measures.

Child, Preschool↗
PubMedDate not supplied

Involuntary exposure to tobacco smoke in adolescents: urinary cotinine and environmental factors.

The relationship between environmental tobacco smoke exposure and urinary cotinine was studied in 434 14-y-old schoolchildren. To estimate the independent contribution of physiological and environmental variables to cotinine concentrations, we conducted a multiple regression analysis of log-transformed cotinine (R(2) = .21, p < .0001). Environmental tobacco smoke exposure was associated with sharing a household with members who smoked. The most profound associations were linked to (a) the smoking habits of the mother (beta = 5.135, p = .0397); (b) the combined smoking habits of the mother and other family members (beta = 8.201, p = .0020); and (c) the total number cigarettes smoked each day by family members in the household (beta = 0.217, p = .0008). Passive smoke exposure of adolescents is a preventable risk that could be reduced by improving ventilation and by increasing the living space available to each family member. Parents should avoid smoking at home in the presence of their children.

Adolescent↗
PubMedDate not supplied

Analysis of aberrant behaviour associated with Rett syndrome.

PURPOSE: The purpose of this study was to identify the variables involved in the maintenance of aberrant behaviours associated with Rett syndrome. The occurrence of aberrant behaviours associated with Rett syndrome is typically attributed to biological variables associated with the disorder. In some cases. however, these behaviours have been shown to be sensitive to manipulations of environmental variables (i.e. operant contingencies). However, little research exists regarding the variables involved in the maintenance of these behaviours and the manner in which these variables can be manipulated to effectively reduce the occurrence of these behaviours. METHOD: We conducted functional analyses of the aberrant behaviours exhibited by two females diagnosed with Rett syndrome. Following the functional analyses, treatments were developed to disrupt the relationship between the aberrant response and the reinforcer maintaining it. RESULTS: Results from the functional analysis suggested that in both cases the aberrant behaviours (i.e. hand wringing and hand mouthing) were maintained by automatic reinforcement. Treatment, which included interrupting hand wringing for one individual and preventing hand mouthing for the other participant, resulted in dramatic changes in the levels of aberrant behaviour for both participants. These changes suggested that preventing reinforcement delivery reduced the motivation to engage in aberrant behaviour. CONCLUSIONS: These results suggest that operant variables can be manipulated to influence the occurrence of aberrant behaviour associated with Rett syndrome.

Adolescent↗
PubMed1995

The limits of the possible: models of power supply and demand in cycling.

This paper outlines a general strategy for mathematical modeling of cycling performance. This strategy involves formulating one expression describing the power available for external work from physiological sources. The variables used in this expression include maximal aerobic power (VO2max), fractional utilisation of VO2max, mechanical efficiency, maximal accumulated oxygen deficit, and the time constants relating to the expression of aerobic and anaerobic capacities. A second expression describing the power demand of cycling is then constructed. The variables used in this expression include the mass, projected frontal area and drag characteristics of the system, the coefficient of rolling resistance, environmental variables such as temperature, barometric pressure, relative humidity, wind speed and direction and the slope of the course. The two expressions are equated and solved using an iterative procedure. Two series of trials were used to assess the predictive accuracy of the model, one using track endurance performances and the other a 26 km road time-trial. The correlations between actual and predicted times have been excellent (0.92-0.95, p < or = 0.0001), with small mean differences (0-1.83% of mean performance time) and mean absolute differences (1.07-3.24%). The model allows us to make predictions about the effect of equipment changes and environmental factors, to compare performances under very different conditions, and to predict the limits of the possible in cycling performance. A range of options designed to improve cycling performance is described.

Bicycling↗
PubMed1999

ENVIRONMENTAL AUDITING: Integrating Environmental Characteristics and Fisheries Management in Northern Finland River Impoundments.

/ Three large rivers in northern Finland, the Kemijoki, Iijoki, and Oulujoki rivers, were dammed for hydropower generation in the 1940s-1960s. Due to differences in environmental conditions, these impoundments require detailed study to produce guidelines for fisheries management.Water quality, hydrology, vegetation, and geomorphology data of 16 impoundments were gathered. Shoreline land-use data were derived from maps, and fish assemblage data were collected by exploratory fishing and from the annual fishery statistics. The relations among environmental variables were studied, and a classification of the impoundments was developed by hierarchical cluster analysis. Consequently, three impoundment groups with different environmental characteristics were formed. Significant differences among impoundment groups were also detected in fish yield. We conclude that the variation in environmental conditions, together with differences in fish communities in the impoundments were important enough to justify the claim that impoundments of different types require different management strategies. KEY WORDS: Impoundments; River regulation; Fish assemblage; Water quality; Aquatic vegetation; Finland

Journal Article↗
PubMed1996

Circadian rest-activity rhythm disturbances in Alzheimer's disease.

Previous studies showed circadian rhythm disturbances in patients with Alzheimer's disease. Rest-activity rhythm disturbances manifest themselves through a fragmentation of the rhythm, a weak coupling with Zeitgebers, and high levels of activity during the night. The aim of the present study was to investigate which factors contribute to the presence of these disturbances. Therefore, several rest-activity rhythm, constitutional, and environmental variables were assessed in a heterogeneous group of 34 patients with Alzheimer's disease, including presenile and senile patients living at home or in a nursing home, as well as in 11 healthy controls. Circadian rest-activity rhythm disturbances were most prominent in institutionalized patients. Regression analyses showed the involvement of the following variables. First stability of the rest-activity rhythm is associated with high levels of daytime activity and high levels of environmental light resulting from seasonal effects as well as from indoor illumination. Presenile onset contributed to instability of the rhythm. Second, fragmentation of periods of activity and rest is associated with low levels of daytime activity, and is most prominent in moderately severe dementia. Third, night-time activity level is higher during the times of the year when the days are getting shorter and lower when the days are growing longer. These findings indicate that rest-activity rhythm disturbances may improve by increasing environmental light and daytime activity, an assumption for which empirical evidence has recently been published.

Aged↗
PubMed2002

Consequences of a freshwater canal discharge on the benthic community and its habitat on an exposed sandy beach.

This paper analyses the spatial and temporal effects of a freshwater discharge (Canal Andreoni) on the macroinfauna community and its habitat in a sandy beach of Uruguay. Bimonthly, we examined 17 environmental variables plus macroinfauna abundance, biomass, richness, evenness and diversity of three sites: Andreoni, at the canal mouth, Coronilla, at 1 km, and Barra, at 13 km from the mouth. Both univariate and multivariate techniques showed an increasing degree of perturbation towards the canal. This was reflected by abiotic and biotic differences between sites and by a consistent two-dimensional ordination of the samples. A clear seasonal pattern was found, specially accentuated at Coronilla, where the effects of the canal were stronger in winter and weaker in summer. Multivariate linking between macroinfauna and its habitat highlighted the role of salinity as explanatory variable of the observed trends.

Animals↗
PubMed1997

Molecular and functional characterization of a novel low-affinity cation transporter (LCT1) in higher plants.

The transport of cations across membranes in higher plants plays an essential role in many physiological processes including mineral nutrition, cell expansion, and the transduction of environmental signals. In higher plants the coordinated expression of transport mechanisms is essential for specialized cellular processes and for adaptation to variable environmental conditions. To understand the molecular basis of cation transport in plant roots, a Triticum aestivum cDNA library was used to complement a yeast mutant deficient in potassium (K+) uptake. Two genes were cloned that complemented the mutant: HKT1 and a novel cDNA described in this report encoding a cation transporter, LCT1 (low-affinity cation transporter). Analysis of the secondary structure of LCT1 suggests that the protein contains 8-10 transmembrane helices and a hydrophilic amino terminus containing sequences enriched in Pro, Ser, Thr, and Glu (PEST). The transporter activity was assayed using radioactive isotopes in yeast cells expressing the cDNA. LCT1 mediated low-affinity uptake of the cations Rb+ and Na+, and possibly allowed Ca2+ but not Zn2+ uptake. LCT1 is expressed in low abundance in wheat roots and leaves. The precise functional role of this cation transporter is not known, although the competitive inhibition of cation uptake by Ca2+ has parallels to whole plant and molecular studies that have shown the important role of Ca2+ in reducing Na+ uptake and ameliorating Na+ toxicity. The structure of this higher plant ion transport protein is unique and contains PEST sequences.

Amino Acid Sequence↗