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PubMed1994

Migration in variable environments: exploring life-history evolution using structured population models.

In this paper, we explore the hypothesis that environmental variability favors the evolution of migration. Using the single-locus invasion condition for a novel allele in a variable environment, we derive conditions where increased migration rates between two sites are favored. We find that while there is a strong advantage to migrants entering a resident population with no migration, there is little advantage to migrants entering a population where the residents migrate at a different rate. Instead of an optimal rate of migration, there is a range of favored migration rates. Negative spatial correlation and a population structure including more than two sites accentuate the advantage of migration. Extending this model to include the effects of developmental delay (e.g. seed dormancy or diapause) on the evolution of migration, we find that higher levels of such delay reduce the advantage to migrants.

Animals↗
PubMed2001

Litterfall and organic matter decomposition in a seasonal forest of the eastern Chaco (Argentina).

Amazonia and the Gran Chaco are the largest phytogeographic units of the Neotropical Region. The Forest Wedge of the Santa Fe province of Argentina is the southernmost part of the Eastern Chaco, and there are three main types of forest, 1) the mixed dense forests, 2) the Schinopsis balansae "quebrachal" and 3) the Prosopis nigra var. ragonesei forests, distributed along an environmental gradient correlated with topographic elevation. In this paper litterfall and organic matter decomposition of four species were studied in two different microsites in a Schinopsis balansae forest during three years. Litter fall varied along the year following seasonal environmental variation but litterfall variations between years were not significant. Litterfall was not uniform over the whole surface, under close canopy monthly average litterfall amounts 32.67 g/m2, in open gaps 4.47 g/m2 and 15.07 g/m2 under medium density canopy. Organic matter decomposition, like in other forests, was a negative exponential function of time, and the decomposition rate is independent from the microsites where it falls, 0.15 and 0.12 in sunny and shadow microsites respectively for Maytenus vitis-idaea, 0.10 and 0.11 in sunny and shadow microsites respectively for Achatocarpus praecox, 0.04 and 0.03 for Acacia praecox, 0.04 and 0.06 for Schinopsis balansae in sunny and shadow microsites respectively. Shurbs litter was decomposed faster than the tree litter, and the shurbs litter nutrientes level was also higher. Therefore the rate of organic matter decomposition is more correlated with leaf characteristics than with environmental variables.

Argentina↗
PubMed2005

Genetic and environmental correlations between bone phenotypes and anthropometric indices in Chinese.

Height, weight, bone mineral density (BMD), and bone size are all influenced by genetic and environmental factors as well as interactions between them. Height and weight are often used in population studies to adjust the bone phenotypes. However, it is still unknown what proportion of genetic and environmental variability is shared between these anthropometric characteristics and the bone phenotypes. The genetic and environmental correlations between the bone phenotypes and anthropometric indices in Chinese subjects were studied by bivariate quantitative genetic analysis on a sample of 931 healthy subjects from 292 Chinese nuclear families aged from 19 to 79 years. BMD and bone size at the lumbar spine (L1-L4) and the hip of all subjects were measured by dual-energy X-ray absorptiometry. We found significant genetic correlations between weight and spine BMD, hip BMD, spine bone size and hip bone size, which were 0.50 (P<0.01), 0.45 (P<0.01), 0.36 (P=0.02), and 0.38 (P<0.01), respectively. Likewise, significant genetic correlations between height and spine BMD, spine bone size, and hip bone size were 0.30 (P=0.02), 0.54 (P<0.01), and 0.58 (P<0.01), respectively. The environmental correlations were found to be significant only between height and spine bone size (P<0.001) and weight and hip BMD (P=0.02). These results suggest the probability that the same genetic and environmental factors contribute to these different phenotypes. Moreover, when a candidate gene or genomic region is responsible for the variation of both bone phenotypes and anthropometric indices, its true genetic effect on the bone phenotypes may be lost after one has adjusted the phenotypic values with weight and height as random environmental factors. It may have implications for population studies of candidate genes that underlie the complex bone phenotypes and for the development of strategies for therapeutic application.

Absorptiometry, Photon↗
PubMed1974

Interaction between radiation effects, gravity and other environmental factors in Tribolium confusum.

Multicellular organisms possess homeostatic control systems, which, in responding to changes of the external environment, modify the internal milieu of the organism accordingly, in order to make survival and normal physiological processes possible. This group has studied effects on physiological processes of single and combined environmental factors in the flour beetle, Tribolium confusum. Studies included low- and high-LET radiation, gravity compensation, near-weightlessness in space flight, ambient temperature, atmospheric composition, and magnetic field effects on the growth and development of Tribolium. For somatic effects, there appears to be a "normal physiological range" for each of these environmental variables; moreover, their effects seem independent of each other. When one of the listed environmental factors is near the limits of normal physiological tolerance, however, marked synergism has been observed between the effects of this factor and other environmental stresses. Fertilized Tribolium eggs showed a differential radiosensitivity to external irradiation, and a linear, dose-effect relationship was obtained, as accelerated heavy nitrogen and oxygen ions were used. Synergism was found when Tribolium were irradiated with ionizing radiation and subsequently exposed to temperature either below or above their normal physiological range. Gravity compensation or near-weightlessness in space flight have adverse effects on the development of Tribolium when an ambient temperature is near the higher or lower limit of tolerance. Similar results were observed when pupae were exposed to a combination of oxygen, temperature and magnetic field stresses.

Animals↗
PubMed1989

Multidimensional gas chromatographic determination of cotinine as a marker compound for particulate-phase environmental tobacco smoke.

Multidimensional gas chromatographic analysis of air particles for the tobacco alkaloid cotinine is described. The analytical procedure requires little sample preparation. Unambiguous identification of cotinine and nicotine in cigarette smoke and indoor air samples was achieved by precise, reproducible retention times observed with two parallel analytical columns of different polarities and a nitrogen-specific detector. Further investigation of smoking and environmental variables is needed to validate the use of cotinine as a marker compound for environmental tobacco smoke particulate matter.

Chromatography, Gas↗
PubMed2000

The relation between risk factors for binge eating and bulimia nervosa: a population-based female twin study.

This study investigated the differential risk factors for the initiation of binge eating and the transition from binge eating to bulimia nervosa. Women from a population-based twin registry (850 complete pairs) were assessed with respect to specific measured variables (including demographics, religiosity, lifetime psychopathology, current symptomatology, and personality) and latent genetic and environmental variables. Because of the relative rarity of bulimia nervosa, statistical power was low, but findings suggested considerable overlap between the genetic risk factors for the development of binge eating and the genetic risk factors for the transition from binge eating to bulimia nervosa. Genetic risk factors for binge eating and bulimia nervosa may be largely similar, whereas nonshared environment may be important in influencing the risk for bulimia nervosa once binge eating is initiated.

Adult↗
PubMed1983

Field study of ventilation in volunteer scuba divers during head-out immersion.

Seven subjects had spirometric studies during head-out immersion before and after working at depth in coral research. Under the variable environmental conditions of a field study the seven subjects demonstrated changes in the spirometric variables consistent with those found in wet laboratories. Exercise at depth did not change the variables from preexercise levels. This suggests either that the body reestablishes preexercise head-out immersion equilibrium rapidly or that subtle changes were beyond the sensitivity of the instrument. On head-out immersion, one subject with abnormal control values of FEV1/FVC% and FEF25-75 had a rise rather than a fall in these values, which was the opposite of that of the other six subjects and the expected result.

Adolescent↗
PubMed2002

Evaluating a model of the historical behavior of two hexachlorocyclohexanes in the Baltic Sea environment.

The POPCYCLING-Baltic model, a non-steady-state multicompartmental mass balance model of long-term chemical fate in the Baltic Sea environment, is evaluated for its capability to simulate the behavior of alpha- and gamma-hexachlorocyclohexane isomers from 1970 to 2000. The model predicts HCH concentrations in air, seawater, marine sediments, and needles well within an order of magnitude, often within a factor of 2, and reproduces major features of the observed differences in space and time. The spatial and temporal patterns of HCHs in the Baltic Sea environment are found to be controlled mostly by chemical input, both through direct emissions within the drainage basin and through advective inflow from adjacent areas, but variable environmental conditions can significantly modify the spatial distribution patterns. Simulations with different boundary conditions, i.e., variable assumptions concerning advective atmospheric inflow, suggest that sources within the drainage basin alone are not capable of explaining the observed HCH levels and that significant transport into the region must occur. Deviations between predicted and measured HCH concentrations can often be explained by uncertain estimates of usage and advective import, illustrating the usefulness of the model for evaluating the reasonability of emission estimates and boundary conditions.

Baltic States↗
PubMedDate not supplied

Sibling correlations for growth status in schoolchildren from a rural community in Oaxaca, Mexico.

Sibling similarities in several anthropometric dimensions were examined in schoolchildren from a rural, agrarian Zapotec community in the Valley of Oaxaca in southern Mexico. The sample consisted of 44 brother, 44 sister, and 110 unlike-sex sibling pairs. Anthropometric dimensions included weight, height, limb circumferences, triceps skinfold, skeletal lengths, and craniofacial, trunk, and extremity breadths. Environmental effects were controlled using data from a household survey, and were summarized in composite variables. Environmental covariance was suggested in partial correlations of the sibling z-scores. The base 10 log of environmental data and sibling z-scores produced slightly different results. Partial correlations of the log-transformed data resulted in a slight overall decrease in sibling correlations for all pairings. This suggests a genetic-environment interaction, and may offer an explanation for the generally higher sibling correlations observed in non-European populations than in European-derived ones.

Adolescent↗
PubMed2001

Resolving problems associated with alcohol and drug misuse: understanding relations between addictive behavior change and the use of services.

"Natural resolutions" highlight how influences on addictive behavior change may differ from and interact with influences on the use of substance-related services. These distinct literatures are summarized and implicate extra-therapeutic environmental variables in both processes. Whether assisted by interventions or not, stable resolutions are surrounded by environmental contexts characterized by improved circumstances across several years that bracket cessation of substance misuse. Psychosocial problems associated with substance use increase help-seeking, and interventions enhance improvements that typically follow initial resolution. Implications for promoting help-seeking and behavior change and necessary revisions in conventional views about relations between the processes are discussed.

Behavior, Addictive↗
PubMed1985

Family and school influences on behavioural development.

Research findings are reviewed with respect to possible family and school influences on behavioural development, but with special reference to socially disapproved conduct. The hypothesis that statistical associations between environmental variables and children's disorders represent causal connections is considered in terms of the three main alternatives--hereditary influences, the effect of children on their parents, and the operation of some third variable. It is concluded that each has some validity but that nevertheless there are true environmental effects. The mechanisms underlying their operation are discussed with respect to parental criminality, family discord, weak family relationships, ineffective discipline, and peer group influences. Individual differences in response to adversity are discussed in terms of age, sex, temperament, genetic factors, coping processes, patterning of stressors, compensatory good experiences and catalytic factors. The various ways in which environmental effects may persist over time are considered in terms of linkages within the environment as well as within the child. It is concluded that long-term effects are far from independent from intervening circumstances.

Child↗
PubMed2003

Environmental influences on healthcare expenditures: an exploratory analysis from Ontario, Canada.

STUDY OBJECTIVE: This paper explores the relation between healthcare expenditures (HCEs) and environmental variables in Ontario, Canada. DESIGN: The authors used a sequential two stage regression model to control for variables that may influence HCEs and for the possibility of endogenous relations. The analysis relies on cross sectional ecological data from the 49 counties of Ontario. MAIN RESULTS: The results show that, after control for other variables that may influence health expenditures, both total toxic pollution output and per capita municipal environmental expenditures have significant associations with health expenditures. Counties with higher pollution output tend to have higher per capita HCEs, while those that spend more on defending environmental quality have lower expenditures on health care. CONCLUSIONS: The implications of our findings are twofold. Firstly, sound investments in public health and environmental protection have external benefits in the form of reduced HCEs. Combined with the other benefits such as recreational values, investments in environmental protection probably yield net social benefits. Secondly, health policy that excludes consideration of environmental quality may eventually result in increased expenditures. These results suggest a need to broaden the cost containment debate to ensure environmental determinants of health receive attention as potential complements to conventional cost control policies.

Air Pollution↗
PubMed1983

Delta-9-tetrahydrocannabinol in cancer chemotherapy: research problems and issues.

A critical review of the literature assessing the antiemetic efficacy of delta-9-tetrahydrocannabinol (THC) in patients receiving cancer chemotherapy showed considerable inconsistency in results. The equivocal nature of these results partly reflects the difficulty of doing research on antiemetic therapies, but also can be attributed to differences in the adequacy and nature of the research designs, procedures, and assessment instruments that have been used. Several factors were also identified that are seldom studied but may be important in determining whether THC will be effective: patient variables, such as chemotherapy regimen and age; pharmacologic variables, such as drug tolerance, dose, schedule, toxicity, route of administration, and drug interactions; and environmental variables associated with administration setting. The need to differentiate pharmacologically induced from conditioned nausea and vomiting was also pointed out. We believe that THC does have antiemetic efficacy, but the lack of controlled research does not allow precise knowledge of its true effectiveness and toxicity. Well-controlled trials are needed to help answer some of these questions.

Antiemetics↗
PubMed2004

Workers' compensation for psychological injury: personal and environmental correlates.

The aim of this study was to determine the personal and environmental factors that contribute to the lodging of a workers' compensation claim for psychological injury. Four groups were compared: individuals who had lodged a workers' compensation claim, people who had sought psychological assistance for the management of work-related stress reactions but who had not lodged a workers' compensation claim; people who had experienced stress symptoms but who had not lodged a claim or sought help; and people who experienced stressful work events but who had not developed symptoms. Examination was made of cognitive distortion, irrational beliefs and coping resources as individual factors, and stressful life events, daily hassles and work environment factors as environmental variables. The Compensation group was distinguished from other groups only on the basis of work environmental factors. The implications of these results in the understanding of the decision to lodge a workers' compensation claim are considered.

Adaptation, Psychological↗
PubMed1988

A survey of the occurrence of motion sickness amongst passengers at sea.

A questionnaire survey of motion sickness occurrence on board passenger ferries has been conducted. Data were collected from 20,029 passengers on 114 voyages on 9 vessels: 6 ships, 2 hovercraft, and 1 jetfoil. Information was obtained about feelings of illness, the occurrence of vomiting, the taking of anti-seasickness tablets, the consumption of alcoholic drinks, regularity of travel by sea, age, and sex. Overall, 7% of passengers reported vomiting at some time during the journey, 21% said they felt "slightly unwell," 4% felt "quite ill," and a further 4% felt "absolutely dreadful." Both vomiting incidence and illness rating were greater in females than in males, and there was a slight decrease in sickness occurrence with increasing age. The incidence of vomiting was related to the taking of tablets and the drinking of alcohol; there were also some interaction effects with other variables. Anecdotal information from passengers is reported and consideration is given to the effects of environmental variables.

Adolescent↗
PubMed1980

Population characteristics and environmental factors that influence level and cause of mortality. A review.

Responsible evaluation of energy production effects on human health requires prior accounting for the socioeconomic, cultural, and climatic characteristics known to influence mortality rate and cause. Fifteen population characteristics and environmental variables (education, income, occupation, industrial mix, socioeconomic status, housing quality, climate, urban residence, geographic residence, internal migration, cigarette consumption, alcohol consumption, marital status, foreign birth or stock, and religious affiliation) and three age subgroups are discussed. An initial set of eight variables is indicated for mortality rate standardization, based on the reliability of their relationships with mortality. These eight variables are: education, occupation, industrial mix, urban residence, marital status, ethnic mix, and cigarette and alcohol consumption. Education and occupation are negatively related to mortality. Occupational exposure to toxicants (indicated by industrial mix), cigarette consumption, and alcohol consumption have positive linear relationships with various specific causes of mortality. Urban residence, marital status, and ethnicity have non-linear relationships with mortality and show consistent patterns for certain causes of death. In addition to these characteristics three age subgroups ( less than 1 year, 1-14 years, greater than or equal to 65 years) are discussed because of their relatively high or low rates compared to the rest of the population. A brief review of water and air pollution effects on mortality is included for completeness. Unique to this review is the quantitative summary (presented as an appendix) of the variables influencing adult mortality. It is a compilation of numerical relationships, derived either directly or indirectly from the published data, that support the choice of influencing variables.

Age Factors↗
PubMed1991

Role of genetic variability in neonatal jaundice. A prospective study on full-term, blood group-compatible infants.

A series of genetic, developmental and environmental variables have been analyzed in a prospective sample of full-term newborn babies, compatible with their mothers in the major blood group systems, in order to attempt an evaluation of the effect of these variables on serum bilirubin level during the first few days of life. Three genetic factors (PGM1, ACP1 and ADA) and three non-genetic variables (rise of bilirubin level during the first day of life, a mother with a history of previous abortion, and use of alcoholic beverages by the mother) have a significant predictive value for the separation of newborns with clinically relevant jaundice from other infants.

Acid Phosphatase↗
PubMed2004

A prospective study of management and litter variables associated with cellulitis in California broiler flocks.

Cellulitis has emerged as an economically important disease of broiler chickens. The impact of environmental risk factors on the incidence of cellulitis has not been evaluated in the United States. Escherichia coli (E. coli), the causative agent, is introduced through skin scratches during the grow out. Our previous work suggested that the litter was an important reservoir for cellulitis-associated E. coli. We hypothesized that factors contributing to a positive environment for E. coli growth would increase the opportunity for exposure of a broiler to an infectious dose of E. coli, capable of initiating a cellulitis lesion. This prospective study of 304 flocks on five farms from two integrated broiler companies was conducted to determine the effect of environmental factors on the prevalence of cellulitis in California broiler flocks. Environmental variables included temperature, wind velocity, and relative humidity (RH) at the litter surface. Litter variables measured included E. coli and total gram-negative bacteria load (colony forming units/g dry matter), water activity, and pH. Management variables such as clean out, the number of flocks reared on the same litter (litter run, LR), and downtime (DT) between flocks were also evaluated. Cellulitis ranged from 0.197% to 6.04%. Significant associations were identified using linear regression between farm, LR, DT, ambient temperature during the brooding period, gram-negative bacteria load in the litter during the brooding period, RH mid-grow out, and E. coli load late in the grow out. The significant variation in the rate of cellulitis between farms combined with the strong association of LR and DT with cellulitis demonstrated that management choices were highly influential in this disease syndrome. Based on these data and our previous findings, managers would be advised to increase DT between flocks and perform a total clean out of the house when a flock processes with a high incidence of cellulitis.

Animal Husbandry↗