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PubMed2002

Reducing environmental bias when measuring natural selection.

Crucial to understanding the process of natural selection is characterizing phenotypic selection. Measures of phenotypic selection can be biased by environmental variation among individuals that causes a spurious correlation between a trait and fitness. One solution is analyzing genotypic data, rather than phenotypic data. Genotypic data, however, are difficult to gather, can be gathered from few species, and typically have low statistical power. Environmental correlations may act through traits other than through fitness itself. A path analytic framework, which includes measures of such traits, may reduce environmental bias in estimates of selection coefficients. We tested the efficacy of path analysis to reduce bias by re-analyzing three experiments where both phenotypic and genotypic data were available. All three consisted of plant species (Impatiens capensis, Arabidopsis thaliana, and Raphanus sativus) grown in experimental plots or the greenhouse. We found that selection coefficients estimated by path analysis using phenotypic data were highly correlated with those based on genotypic data with little systematic bias in estimating the strength of selection. Although not a panacea, using path analysis can substantially reduce environmental biases in estimates of selection coefficients. Such confidence in phenotypic selection estimates is critical for progress in the study of natural selection.

Arabidopsis↗
PubMedDate not supplied

A new selective enrichment procedure for isolating Pasteurella multocida from avian and environmental samples.

A selective enrichment procedure, using two new selective media, was developed to isolate Pasteurella multocida from wild birds and environmental samples. These media were developed by testing 15 selective agents with six isolates of P. multocida from wild avian origin and seven other bacteria representing genera frequently found in environmental and avian samples. The resulting media--Pasteurella multocida selective enrichment broth and Pasteurella multocida selective agar--consisted of a blood agar medium at pH 10 containing gentamicin, potassium tellurite, and amphotericin B. Media were tested to determine: 1) selectivity when attempting isolation from pond water and avian carcasses, 2) sensitivity for detection of low numbers of P. multocida from pure and mixed cultures, 3) host range specificity of the media, and 4) performance compared with standard blood agar. With the new selective enrichment procedure, P. multocida was isolated from inoculated (60 organisms/ml) pond water 84% of the time, whereas when standard blood agar was used, the recovery rate was 0%.

Animals↗
PubMed1999

Nature, nurture and first sexual intercourse in the USA: fitting behavioural genetic models to NLSY kinship data.

Fisher (1930) presented both theoretical and empirical results concerning genetic influences on fertility. Since then, only sparse research has been done on the genetics of fertility, although more sophisticated methodogy and data now exist than were available to Fisher. This paper presents a behavioural genetic analysis of age at first intercourse, accounting for genetic, shared environmental, and selected non-shared environmental influences. The data came from the nationally representative National Longitudinal Survey of Youth (NLSY). A newly developed kinship linking procedure was used that identifies links for cousins, half-siblings, full-siblings and twins in the NLSY. The results suggest a genetic influence in the overall dataset, and also among whites and in male-male and opposite-sex pairs. Genetic influences were extremely small or non-existent for blacks and for female-female pairs. Shared environmental influences were small for most subsets of the data, but moderate for female-female pairs. Two specific non-shared environmental influences--self-esteem and locus of control--were ruled out as accounting for any meaningful variance, although other general sources of non-shared environmental influence appear potentially important. Analysis of selected samples from upper and lower tails suggested that genetic influences are important in accounting for both early and late non-virginity. These findings are consistent with work reported by Miller et al. (1999), who used molecular genetic methods. Generally, these findings support the existence of genetic influences and implicate non-shared environmental influences as being important determinants of the timing of loss of virginity among US adolescents and young adults.

Adolescent↗
PubMedDate not supplied

Treating selective mutism in a paediatric rehabilitation patient by altering environmental reinforcement contingencies.

Selective mutism is a disorder which can cause severe social and academic impairment, and for which a wide variety of treatment approaches have been used, with varying degrees of success. Selective mutism can be conceptualized as the lack of generalization of a class of operant responses (e.g. audible and comprehensible verbalizations) across environmental contexts. The rehabilitation hospital setting, in which the patient is seen daily by multiple people in multiple settings, is particularly well-suited for implementing a systematic behavioural intervention to establish verbal behaviour and simultaneously reinforce its generalization. Data are presented on a 7-year-old female admitted to a rehabilitation hospital following orthopaedic surgery, who met the DSM-IV diagnostic criterion for selective mutism. Additional medical diagnoses included cerebral palsy, microcephaly, and mild mental retardation. A behavioural programme was developed and implemented to reinforce differentially first any communication, then verbal communication across staff and settings. Results were evaluated using a modified multiple baseline across settings design, and demonstrate that verbal, written, and tangible reinforcement effectively increased verbal behaviour where it previously rarely occurred. Results are discussed in terms of the relationship between selective mutism, social phobia and related disorders. The theoretical roles of behavioural phenomena (discriminative stimuli, stimulus generalization) in the development and treatment of these disorders are discussed.

Behavior Therapy↗
PubMed2000

Environmental heterogeneity and balancing selection in the acorn barnacle Semibalanus balanoides.

The northern acorn barnacle Semibalans banlanoides occupies several intertidal microhabitats which vary greatly in their degree of physical stress. This environmental heterogeneity creates distinct selection regimes which can maintain genetic variation in natural populations. Despite considerable attention placed on the link between spatial variation in fitness and balancing selection at specific loci, experimental manipulations and fitness estimates for molecular polymorphisms have rarely been conducted in the wild. The aim of this transplant experiment was to manipulate the level of physical stress experienced by a cohort of barnacles in the field and then investigate the spatial variation in fitness for genotypes at three loci: two candidate allozymes and the mitochondrial DNA control region. The viability of mannose-6-phosphate isomerase (Mpi) genotypes was dependent on the level of physical stress experienced in the various treatments; alternative homozygotes were favoured in alternative high stress-low stress environments. In contrast, the fitness of genotypes at other loci was equivalent among treatments and unaffected by the manipulation. Evaluated in the light of balancing selection models, these data indicate that the presence of multiple environmental niches is sufficient to promote a stable Mpi polymorphism in barnacle populations and that allelic variation at this locus reflects the process of adaptation to the heterogeneous intertidal landscape.

Alleles↗
PubMed1999

Thermal preference behavior following clonidine, norepinephrine, isoproterenol, and ephedrine.

A thermal gradient (temperature range 7-45 degrees C) was used to assess ambient temperature (Ta) preferences of rats following treatment with clonidine (25 microg/kg), norepinephrine (NE, 250 microg/kg), isoproterenol (ISO, 50 microg/kg), and ephedrine (EPH, 10 mg/kg). Clonidine produced a preference for a temperature (31.5 degrees C) slightly warmer than that preferred after saline (28.3 degrees C), but this resulted in no significant change in posttest colonic temperature (Tc). NE, ISO and EPH produced a preference for a colder region of the gradient (20-22 degrees C) compared to saline (24.5-28.9 degrees C). Posttest Tc was reduced significantly from 37.7-37.9 degrees C after saline to 37.2 degrees C (NE), 37.3 degrees C (ISO), and 36.8 degrees C (EPH). Thus, given the opportunity to select an environmental temperature, the animals selected a Ta that resulted in significantly lower body temperatures after NE, ISO, and EPH. This suggests that paradoxical thermoregulatory effects of these thermogenic adrenergic agonists are due, at least in part, to a preference for a lower body temperature.

Adrenergic Agonists↗
PubMedDate not supplied

[Physiological model of the stabilizing form of natural selection at the cellular level].

By means of directional elimination of the parental gametes in frogs, the effects of two basic forms (i.e. normalizing and canalizing ones) of natural selection on the heat resistance level of muscle fibers in the progeny have been reproduced. Experimental evidence is presented that both male and female gametes account for hereditary transformation of cellular heat resistance as a quantitative physiological parameter. Polymodal pattern of regulation of this parameter is suggested which includes indispensable participation of both thermal and non-thermal factors of selection. The environmental temperature, as a selective factor, accounts for the formation of cellular heat resistance directly, whereas non-thermal factors exert their control on this parameter indirectly, associatively. It is suggested that the polymodal pattern of regulation of physiological functions presents the main mode of realization of canalizing form of natural selection.

Animals↗
PubMedDate not supplied

Indicators in environmental health: identifying and selecting common sets.

In association with the proposed goals of the conference, this paper is presented to support the conference discussions on environmental health indicators by providing background on indicators for environmental health and their identification, selection, organization and use. This paper discusses the purpose of indicator use, frameworks used to organize indicators and the common types of indicators in use in monitoring programs today. It proposes a process for the identification and selection of indicators within the different environments, stressing the importance of clear goal definition and scientific and use-based criteria selection to support decisions. Finally, the paper suggests methods by which to organize and limit the number of indicators retained within a program, and the development of a potential "core" of indicators common to many environments and geographical scales.

Ecosystem↗
PubMed2006

Environmental analysis in the selection of alternative corridors in a long-distance linear project: a methodological proposal.

A linear engineering project--i.e. a pipeline--has a potential long- and short-term impact on the environment and on the inhabitants therein. We must find better, less expensive, and less time-consuming ways to obtain information on the environment and on any modifications resulting from anthropic activity. We need scientifically sound, rapid and affordable assessment and monitoring methods. Construction companies, industries and the regulating government organisms lack the resources needed to conduct long-term basic studies of the environment. Thus there is a need to make the necessary adjustments and improvements in the environmental data considered useful for this development project. More effective and less costly methods are generally needed. We characterized the landscape of the study area, situated in the center and north-east of Argentina. Little is known of the ecology of this region and substantial research is required in order to develop sustainable uses and, at the same time, to develop methods for reducing impacts, both primary and secondary, resulting from anthropic activity in this area. Furthermore, we made an assessment of the environmental impact of the planned linear project, applying an ad hoc impact index, and we analyzed the different alternatives for a corridor, each one of these involving different sections of the territory. Among the alternative corridors considered, this study locates the most suitable ones in accordance with a selection criterion based on different environmental and conservation aspects. We selected the corridor that we considered to be the most compatible--i.e. with the least potential environmental impact--for the possible construction and operation of the linear project. This information, along with suitable measures for mitigating possible impacts, should be the basis of an environmental management plan for the design process and location of the project. We pointed out the objectivity and efficiency of this methodological approach, along with the possibility of integrating the information in order to allow for the application thereof in this type of study.

Argentina↗
PubMed2002

Scientific and societal considerations in selecting assessment endpoints for environmental decision making.

It is sometimes argued that, from an ecological point of view, population-, community-, and ecosystem-level endpoints are more relevant than individual-level endpoints for assessing the risks posed by human activities to the sustainability of natural resources. Yet society values amenities provided by natural resources that are not necessarily evaluated or protected by assessment tools that focus on higher levels of biological organization. For example, human-caused stressors can adversely affect recreational opportunities that are valued by society even in the absence of detectable population-level reductions in biota. If protective measures are not initiated until effects at higher levels of biological organization are apparent, natural resources that are ecologically important or highly valued by the public may not be adequately protected. Thus, environmental decision makers should consider both scientific and societal factors in selecting endpoints for ecological risk assessments. At the same time, it is important to clearly distinguish the role of scientists, which is to evaluate ecological effects, from the role of policy makers, which is to determine how to address the uncertainty in scientific assessment in making environmental decisions and to judge what effects are adverse based on societal values and policy goals.

Animals↗
PubMed2005

A facile, catalytic, and environmentally benign method for selective deprotection of tert-butyldimethylsilyl ether mediated by phosphomolybdic acid supported on silica gel.

An environmentally benign PMA supported on SiO(2) is found to be an efficient catalyst for the chemoselective deprotection of TBDMS ethers under very mild conditions. Various labile functional groups such as isopropylidene acetal, OTBDPS, OTHP, Oallyl, OBn, alkene, alkyne, OAc, OBz, N-Boc, N-Cbz, N-Fmoc, mesylate, and azide are found to be stable under the reaction conditions. This "truly catalytic" heterogeneous reaction does not require aqueous workup, and the supported catalyst and the solvent can be readily recovered and recycled.

Journal Article↗
PubMed2003

Time-resolved fluorescence allows selective monitoring of Trp30 environmental changes in the seven-Trp-containing human pancreatic lipase.

Human pancreatic lipase (HPL, triacylglycerol acylhydrolase, EC 3.1.1.3) is a carboxyl esterase which hydrolyzes insoluble emulsified triglycerides and is essential for the efficient digestion of dietary fats. Though the three-dimensional structure of this enzyme has been determined, monitoring the conformational changes that may accompany the binding of various substrates and inhibitors is still of interest. Because of its sensitivity and ease of use, fluorescence spectroscopy of the intrinsic Trp residues is ideally suited for this purpose. However, the presence of seven Trp residues spread all over the HPL structure renders the interpretation of the fluorescence changes difficult with respect to the identification and location of the conformational or environmental changes taking place at the various Trp residues. In this context, the aim of this work was to investigate the contribution of the individual Trp residues to the fluorescence properties of HPL. To this end, we analyzed the steady-state and time-resolved fluorescence parameters of five single-point mutants in which one Trp residue was substituted with a weakly fluorescent Phe residue. In addition to the Trp residues at positions 30, 86, and 252, strategically located with respect to the active site, we also mutated Trp residues at positions 17 and 402, as representative residues of the HPL N- and C-terminal domains, respectively. Taken together, our data suggested that the solvent-exposed Trp30 residue contributed to at least 44% of the overall fluorescence of wild-type HPL. Moreover, we found that the long-lived fluorescence lifetime (6.77 ns) of wild-type HPL could be specifically attributed to Trp30, a feature that enables selective monitoring of its environmental changes. Additionally, Trp residues at positions 17 and 402 strongly contributed to the 1.61 ns lifetime of HPL, while Trp residues at positions 86 and 252 contributed to the 0.29 ns lifetime.

Base Sequence↗
PubMed1999

A comparison of multilocus clines maintained by environmental adaptation or by selection against hybrids.

There has recently been considerable debate over the relative importance of selection against hybrids ("endogenous" selection) vs. adaptation to different environments ("exogenous") in maintaining stable hybrid zones and hence in speciation. Single-locus models of endogenous and exogenous viability selection generate clines of similar shape, but the comparison has not been extended to multilocus systems, which are both quantitatively and qualitatively very different from the single-locus case. Here we develop an analytical multilocus model of differential adaptation across an environmental transition and compare it to previous heterozygote disadvantage models. We show that the shape of clines generated by exogenous selection is indistinguishable from that generated by endogenous selection. A stochastic simulation model is used to test the robustness of the analytical description to the effects of drift and strong selection, and confirms the prediction that pairwise linkage disequilibria are predominantly generated by migration. However, although analytical predictions for the width of clines maintained by heterozygote disadvantage fit well with the simulation results, those for environmental adaptation are consistently too narrow; reasons for the discrepancy are discussed. There is a smooth transition between a system in which a set of loci effectively act independently of each other and one in which they act as a single nonrecombining unit.

Adaptation, Physiological↗
PubMed1983

Practical limitations of epidemiologic methods.

Epidemiologic methods can be categorized into demographic studies of mortality and morbidity and observational studies that are either retrospective or prospective. Some of the limitations of demographic studies are illustrated by a review of one specific mortality study showing possible relationship of nuclear fallout to leukemia. Problems of accuracy of diagnosis or causes of death on death certificates, estimates of population, migration from areas of study, and the issue of "ecological fallacy" are discussed. Retrospective studies have such problems as recall of previous environmental exposure, selection bias and survivor bias. In environmental epidemiology, prospective studies have been used. The problems associated with these studies are illustrated by reviewing some of the details of the study of effects of microwave radiation on embassy employees in Moscow. The study population had to be reconstructed, individuals had to be located and information on exposure status had to be obtained by questionnaire. The relatively small size of the exposed group permitted the detection of only fairly large relative risks. Despite these limitations, epidemiologic studies have been remarkably productive in elucidating etiological factors. They are necessary since "the proper study of man is man."

Demography↗
PubMed2000

[Medium selection and compounding of environmental eco-engineering through making use of life rubbish to produce carpet turf].

Through making use of life rubbish as medium and choosing several materials with high feasibility as compound materials to produce carpet turf, the medium selection and compounding were carried out, and the growth effect of several kinds of turfgrass on each compound medium, its pH value and water stress function were also studied. Sawdust could raise the drought-resistant capacity of turfgrass by strengthening the water-retaining capacity of medium, and promote turfgrass growth. Plant ash showed a strong basicity, and when it made up 25% of medium, the pH value of the medium could be over 9. Fine river sand could improve the ventilating capacity of medium, but if mixed too much, it would decrease its nutritional level. It is suggested that the performance of compound mediums differed greatly with compound materials. Synthesizing each index studied showed that among all compounding mediums sawdust had a significantly positive effect, and had a broad application value.

Ecosystem↗
PubMed1999

Environmental lighting has a selective influence on ethanol intake in rats.

The effect of lighting condition on levels of absolute ethanol intake were systematically examined in the present study. Wistar rats were exposed to one of three lighting conditions: constant light, constant dark, and a standard 12/12 light/dark cycle. The animals were acclimatized to lighting conditions for 2 weeks prior to ethanol (EtOH) acquisition with water and food available ad lib. EtOH was then presented in increasing concentrations from 2% (v/v; 95% with tap water) to 10% on alternate days in free choice with water. Immediately following the acquisition phase, a maintenance period was initiated that began with everyday presentations of 10% EtOH solution in free choice with water. After 10 days, lighting conditions for the constant light and dark groups were switched to normal lighting (12/12 light/ dark). EtOH and water intake were recorded for an additional 10 days. Rats exposed to constant light during EtOH acquisition and maintenance consumed less EtOH during the maintenance period than rats exposed to normal lighting conditions. When lighting conditions were switched to a normal cycle, water consumption increased significantly but EtOH intake did not change. Rats living in constant dark during EtOH acquisition and maintenance consumed less EtOH during the acquisition period when compared with rats living in normal lighting conditions. Unlike animals trained under constant lighting, switching to normal lighting conditions had no effect on EtOH or water intake. There were no differences in water consumption levels among the groups during acquisition and maintenance, suggesting a specificity of the effects of lighting condition on EtOH intake. The present study, therefore, has attempted to show that an environmental variable such as lighting may exert a selective influence on EtOH self-selection in rats.

Alcohol Drinking↗
PubMed2005

Environmental origins of sexually selected variation and a critique of the fluctuating asymmetry-sexual selection hypothesis.

Identifying sources of phenotypic variability in secondary sexual traits is critical for understanding their signaling properties, role in sexual selection, and for predicting their evolutionary dynamics. The present study tests for the effects of genotype, developmental temperature, and their interaction, on size and fluctuating asymmetry of the male sex comb, a secondary sexual character, in Drosophila bipectinata Duda. Both the size and symmetry of elements of the sex comb have been shown previously to be under sexual selection in a natural population in northeastern Australia. Two independent reciprocal crosses were conducted at 25 degrees and 29 degrees C between genetic lines extracted from this population that differed in the size of the first (TC1) and third (TC3) comb segments. These temperatures are within the documented range experienced by the species in nature. Additive and dominance genetic effects were detected for TC1, whereas additive genetic, and Y-chromosomal effects were detected for TC3. TC2 and TC3 decreased sharply with increasing temperature, by 10% and 22%, respectively. In contrast, positional fluctuating asymmetry (PFA) significantly increased with temperature, by up to 38%. The results (1) document an important source of environmental variance in a sexual ornament expected to reduce trait heritability in field populations, and thus act to attenuate response to sexual selection, (2) suggest that variation in ornament size reflects differences in male condition; and (3) support the general hypothesis that asymmetry in a sexual ornament is indicative of developmental instability arising from environmental stress. The "environmental heterogeneity" (EH) hypothesis is proposed, and supportive evidence for it presented, to explain negative size-FA correlations in natural populations. Data and theory challenge the use of negative size-FA correlations observed in nature to support the FA-sexual selection hypothesis, which posits that such correlations are driven by differences in genetic quality among individuals.

Analysis of Variance↗