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PubMedDate not supplied

Assessment of myocardial fatty acid metabolism with 1-11C-palmitate.

The myocardium has the capacity to utilize a variety of metabolic substrates, including long-chain fatty acids, ketone bodies, glucose, lactate, and amino acids. Under most conditions long-chain fatty acids constitute the major myocardial energy source. Imaging of long-chain fatty acids can be accomplished with carbon 11-labeled palmitate (1-11C-palmitate) and positron emission tomography. Imaging can be performed in either static or dynamic modes. In normal subjects accumulation of the tracer is homogeneous throughout the heart. In patients with myocardial infarction, distinct defects in accumulation are seen. In dilated cardiomyopathy, uptake is spatially heterogeneous. Clearance of 1-11C-palmitate in normal myocardium is biexponential and homogeneous throughout the heart. Administration of glucose, or feeding, decreases uptake of the tracer into the early rapid turnover pool and decreases clearance of the tracer from that pool. In normal myocardium atrial pacing increases the rate of clearance; in ischemic myocardium the degree of increased clearance is attenuated. In patients with cardiomyopathy caused by long-chain fatty acid coenzyme A dehydrogenase deficiency, 1-11C-palmitate clearance is diminished compared with total myocardial oxygen consumption traced with carbon 11-labeled acetate. Thus positron emission tomography with 1-11C-palmitate permits assessment of patients with ischemic heart disease and cardiomyopathy of diverse causes, providing insights into both pathophysiologic mechanisms and the effectiveness of various therapeutic interventions.

Carbon Radioisotopes↗

PubMed2001

BETR North America: a regionally segmented multimedia contaminant fate model for North America.

We present the Berkeley-Trent North American contaminant fate model (BETR North America), a regionally segmented multimedia contaminant fate model based on the fugacity concept. The model is built on a framework that links contaminant fate models of individual regions, and is generally applicable to large, spatially heterogeneous areas. The North American environment is modeled as 24 ecological regions, within each region contaminant fate is described using a 7 compartment multimedia fugacity model including a vertically segmented atmosphere, freshwater, freshwater sediment, soil, coastal water and vegetation compartments. Inter-regional transport of contaminants in the atmosphere, freshwater and coastal water is described using a database of hydrological and meteorological data compiled with Geographical Information Systems (GIS) techniques. Steady-state and dynamic solutions to the 168 mass balance equations that make up the linked model for North America are discussed, and an illustrative case study of toxaphene transport from the southern United States to the Great Lakes Basin is presented. Regionally segmented models such as BETR North America can provide a critical link between evaluative models of long-range transport potential and contaminant concentrations observed in remote regions. The continent-scale mass balance calculated by the model provides a sound basis for evaluating long-range transport potential of organic pollutants, and formulation of continent-scale management and regulatory strategies for chemicals.

Air Movements↗

PubMed2004

Increasing terrestrial vegetation activity in China, 1982-1999.

Variations in vegetation activity during the past 18 years in China were investigated using the normalized difference vegetation index (NDVI) derived from the 3rd generation time series dataset of NOAA-AVHRR from 1982 to 1999. In order to eliminate the effects of non-vegetation factors, we characterized areas with NDVI < 0.1 as "sparsely vegetated areas" and areas with NDVI > or = 0.1 as "vegetated areas". The results showed that increasing NDVI trends were evident, to varying extents, in almost all regions in China in the 18 years, indicating that vegetation activity has been rising in recent years in these regions. Compared to the early 1980s, the vegetated area increased by 3.5% by the late 1990s, while the sparsely vegetated area declined by 18.1% in the same period. The national total mean annual NDVI increased by 7.4% during the study period. Extended growing seasons and increased plant growth rates accounted for the bulk of these increases, while increases in temperature and summer rainfall, and strengthening agricultural activity were also likely important factors. NDVI changes in China exhibited relatively large spatial heterogeneity; the eastern coastal regions experienced declining or indiscernibly rising trends, while agricultural regions and western China experienced marked increases. Such a pattern was due primarily to urbanization, agricultural activity, regional climate characteristics, and different vegetation responses to regional climate changes.

Agriculture↗

PubMed2026

From family trials to genomic mate allocation: statistical and genomic strategies to accelerate sugarcane genetic improvement.

Sugarcane (Saccharum spp.) underpins global sugar and bioenergy supply and is increasingly valued as a renewable biomass feedstock. Sustained improvement in commercial traits and resilience is constrained by long breeding cycles, clonal propagation, multi-stage testing, and a highly polyploid, heterozygous, and frequently aneuploid genome with substantial non-additive genetic variation. Genomic selection has demonstrated value for predicting elite-clone performance, yet its operational use remains limited at earlier decision points, including family selection, parent evaluation, and cross design. This review examines the biological, statistical, and genomic factors that shape these decisions, with emphasis on the Australian breeding context based on progeny assessment trials (PATs), clonal assessment trials (CATs), and final assessment trials (FATs). We evaluate challenges arising from family plot means, the use of different full-sib samples as nominal family replicates, spatial heterogeneity, competition, genotype-by-environment interaction, and the partitioning of additive and non-additive effects. We also assess the integration of pedigree and genomic relationship, genotype representation, allele-dosage estimation, aneuploidy, genomic prediction models, and training-population design. We then consider genomic prediction of cross performance and constrained mate allocation as approaches for improving expected family performance, accounting for cross-specific non-additive effects and managing relatedness. We propose a decision-centred framework that links family and clonal data across breeding stages, tracks the propagation of information and uncertainty, and supports parent recycling and cross allocation. We conclude with a practical research agenda for stage-integrated mixed-model and single-step analyses that connect early family evaluation with genomic prediction and cross-level decision support in sugarcane breeding.

Saccharum↗

PubMed2000

Spatial distribution of in-patient service use of psychiatric patients: somatic departments versus psychiatric units.

BACKGROUND: It has long been recognized that a high proportion of psychiatric patients are admitted to emergency, medical and surgical wards. However, until now no assessment has been made of which urban general hospitals would be most appropriate for the establishment of specific psychiatric facilities. METHOD: Our study concerned Germany's second largest city, Hamburg (population 1.7 million), and involved an evaluation of psychiatric principal diagnoses in general and psychiatric hospitals. The research was based on data collected between 1988 and 1994 embracing approximately 77% of all psychiatric patients (n = 64,000) in 41 hospitals. The evaluation was carried out using the statistics programs SPSS and DismapWin. RESULTS: We established that the proportion of male patients discharged from somatic wards, mainly internal medicine, with alcohol and drug abuse as well as with neuroses and personality disorders or illegal drug abuse was surprisingly high (70%, 34% and 24% respectively). For female patients the figures were 67%, 40% and 35% respectively. A geographical analysis of spatial heterogeneity of hospitalization risks showed that general hospitals admit a disproportionately high number of patients from areas of lower social status - both male and female from the above-mentioned diagnostic categories. A rank correlation between the classification of areas based on the heterogeneity model and the social status of the areas supports this hypothesis, at least for males. CONCLUSION: Our findings lead us to the conclusion that the establishment of new psychiatric services should focus on internal wards in hospitals located in areas of low social status.

Adult↗

PubMed2000

Assessing the contribution of natural sources to the global mercury cycle: the importance of intercomparing dynamic flux measurements.

In order to constrain the contribution of natural sources of mercury to the global atmospheric cycle we need to: 1. assess the methods used to measure mercury flux, 2. characterize those factors most important in controlling emissions, 3. develop a database of emissions from representative locations, and 4. develop a means of scaling up measured emissions to estimate fluxes on a regional basis. This paper describes how an international multi-collaborator project, the Nevada SToRMS Project, held September 1997 in Reno, Nevada, USA, contributed to our ability to constrain natural source mercury emissions. This study entailed a field intercomparison of those methods typically applied to measure mercury flux from substrate combined with evening workshops and round-table discussions. The project was unique in that it focused on assessing our ability to measure the flux of an environmental contaminant. This is more difficult than measurement of the concentration of a contaminant because of the number and nature of the variables which influence the field flux measurements, including experimental design, spatial heterogeneity, and temporally changing environmental conditions. As a result of the Nevada SToRMS Project, rapid and significant advances in our understanding of how to constrain emission fluxes from large areas of mercury enrichment were realized. Because this intercomparison was a multi-investigator project, the results and implications of the project have been broadly circulated. The sincere scientific collaboration that evolved amongst those working on the study has led to significant advancements in our understanding of the fate and transport of mercury in the environment.

Journal Article↗

PubMed2004

Relationship between DDE concentrations and laying sequence in eggs of two passerine species.

Passerine eggs make useful biomonitors of environmental pollutants. Among passerines, it is not known whether organochlorine contaminants in eggs within the same clutch are independent observations or follow a laying order effect. Intraclutch variation of DDE (1,1-dichloro-2,2-bis[(p-chlorophenyl)]ethylene) concentrations was studied in eggs collected from prothonotary warblers (Protonotaria citrea) and European starlings (Sturnus vulgaris) nesting on National Priority List sites in lower Alabama and central Colorado, respectively. All 209 eggs collected for this study contained detectable levels of DDE. Mean concentration of DDE across all prothonotary warbler eggs (mean 8.71 microg/g +/- 1.19, n = 20) was almost two orders of magnitude greater than mean concentrations of DDE in all starling eggs (mean 0.70 microg/g +/- 0.06, n = 189). In both species, there was a large amount of variability among individual eggs of the same clutch and no significant relationship between laying order and DDE concentration. Variation among eggs laid in the same sequential order was high and effectively masked any potential trends in laying order effect. We hypothesized that the variability was caused by the spatial heterogeneity of DDE on our study sites, the nature of egg development within a female passerine, or a combination of these factors. Investigators focusing on lipophilic contaminants should exercise caution when making inferences about contaminant concentrations in an entire clutch of passerine eggs after the collection and analysis of a single egg because our data show that DDE levels in a single egg collected for analysis do not consistently reflect DDE levels in the eggs remaining in the nest.

Animals↗

PubMed2003

Shifts in diversity and microscale distribution of the adapted bacterial phenotypes due to Hg(II) spiking in soil.

In a previous experiment [Ranjard et al. (2000) FEMS Microbiol Ecol 31:107-115], the spatial heterogeneity of a mercury impact on soil bacterial community was revealed by an increase of mercury-resistant (HgR) bacterial numbers in the outer fraction and the sand fractions when compared to those in the silt fractions. The objectives of the present study were (i) to investigate whether mercury exposure affects the diversity and the distribution within the various fractions of the HgR populations and (ii) to evaluate the contribution of the HgR populations to the overall community adaptation. A total of 236 strains isolated before (104 isolates) and 30 days (132 isolates) after spiking were characterized by an amplified ribosomal DNA restriction analysis (ARDRA) and grouped into 30 different genotypes. Whereas almost the same numbers of different genotypes were observed at both sampling times when considering all microenvironments, important changes in their evenness were observed. At the microscale level, we also noticed a heterogeneous distribution of the genotypes. Partial 16S rDNA sequences of each genotype were determined to permit phylogenetic affiliation. Whereas Pseudomonas-like species were dominant in all microenvironments at T = 0, genotypes not detected before spiking such as genotypes closely related to Xanthomonas, Pseudoaminobacter, and Sphingomonas-like species became dominant at T = 30. Similarly, several genotypes close to Bacillus, Streptomyces, and Rhodococcus species were only detected in the sand fractions at T = 0 and could not be detected in these fractions at T = 30. Probes defined within the intergenic spacer between the rrs and rrl genes were designed for the dominant genotypes and were hybridized toward the RISA (Ribosomal Intergenic Spacer Analysis) profiles derived from the T = 0 and T = 30 bacterial communities associated to the unfractionated soil. Results showed that the culturable dominant HgR genotypes partially contributed to the adaptation of the whole bacterial community.

Adaptation, Biological↗

PubMed2005

Fungal epiphytes and endophytes of coffee leaves (Coffea arabica).

Plants harbor diverse communities of fungi and other microorganisms. Fungi are known to occur both on plant surfaces (epiphytes) and inside plant tissues (endophytes), but the two communities have rarely been compared. We compared epiphytic and endophytic fungal communities associated with leaves of coffee (Coffea arabica) in Puerto Rico. We asked whether the dominant fungi are the same in both communities, whether endophyte and epiphyte communities are equally diverse, and whether epiphytes and endophytes exhibit similar patterns of spatial heterogeneity among sites. Leaves of naturalized coffee plants were collected from six sites in Puerto Rico. Epiphytic and endophytic fungi were isolated by placing leaf pieces on potato dextrose agar without and with surface sterilization, respectively. A total of 821 colonies were isolated and grouped into 131 morphospecies. The taxonomic affinities of the four most common nonsporulating fungi were determined by sequencing the nuclear ribosomal internal transcribed spacer (ITS) region: two grouped with Xylaria and one each with Botryosphaeria and Guignardia. Of the most common genera, Pestalotia and Botryosphaeria were significantly more common as epiphytes; Colletotrichum, Xylaria, and Guignardia were significantly more common as endophytes. Suprisingly, more morphospecies occurred as endophytes than as epiphytes. Differences among sites in number of fungi per plant were significant. Thus epiphytic and endophytic communities differed greatly on a single leaf, despite living only millimeters apart, and both communities differed from site to site. Significant correlations between occurrence of fungal morphospecies suggested that fungi may have positive or negative effects on their neighbors. This is the first quantitative comparison of epiphytic and endophytic fungal floras in any plant, and the first to examine endophytic fungi or epiphytic fungi in leaves of coffee, one of the world's most valuable crops.

Classification↗

PubMed2002

Integrating fuzzy logic, optimization, and GIS for ecological impact assessments.

Appraisal of ecological impacts has been problematic because of the behavior of ecological system and the responses of these systems to human intervention are far from fully understood. While it has been relatively easy to itemize the potential ecological impacts, it has been difficult to arrive at accurate predictions of how these impacts affect populations, communities, or ecosystems. Furthermore, the spatial heterogeneity of ecological systems has been overlooked because its examination is practically impossible through matrix techniques, the most commonly used impact assessment approach. Besides, the public has become increasingly aware of the importance of the EIA in decision-making and thus the interpretation of impact significance is complicated further by the different value judgments of stakeholders. Moreover, impact assessments are carried out with a minimum of data, high uncertainty, and poor conceptual understanding. Hence, the evaluation of ecological impacts entails the integration of subjective and often conflicting judgments from a variety of experts and stakeholders. The purpose of this paper is to present an environmental impact assessment approach based on the integration fuzzy logic, geographical information systems and optimization techniques. This approach enables environmental analysts to deal with the intrinsic imprecision and ambiguity associated with the judgments of experts and stakeholders, the description of ecological systems, and the prediction of ecological impacts. The application of this approach is illustrated through an example, which shows how consensus about impact mitigation can be attained within a conflict resolution framework.

Decision Making↗

PubMed2002

Setting priorities for research on pollution reduction functions of agricultural buffers.

The success of buffer installation initiatives and programs to reduce nonpoint source pollution of streams on agricultural lands will depend the ability of local planners to locate and design buffers for specific circumstances with substantial and predictable results. Current predictive capabilities are inadequate, and major sources of uncertainty remain. An assessment of these uncertainties cautions that there is greater risk of overestimating buffer impact than underestimating it. Priorities for future research are proposed that will lead more quickly to major advances in predictive capabilities. Highest priority is given for work on the surface runoff filtration function, which is almost universally important to the amount of pollution reduction expected from buffer installation and for which there remain major sources of uncertainty for predicting level of impact. Foremost uncertainties surround the extent and consequences of runoff flow concentration and pollutant accumulation. Other buffer functions, including filtration of groundwater nitrate and stabilization of channel erosion sources of sediments, may be important in some regions. However, uncertainty surrounds our ability to identify and quantify the extent of site conditions where buffer installation can substantially reduce stream pollution in these ways. Deficiencies in predictive models reflect gaps in experimental information as well as technology to account for spatial heterogeneity of pollutant sources, pathways, and buffer capabilities across watersheds. Since completion of a comprehensive watershed-scale buffer model is probably far off, immediate needs call for simpler techniques to gage the probable impacts of buffer installation at local scales.

Agriculture↗

PubMed2004

Uncertainty assessment for management of soil contaminants with sparse data.

In order for soil resources to be sustainably managed, it is necessary to have reliable, valid data on the spatial distribution of their environmental impact. However, in practice, one often has to cope with spatial interpolation achieved from few data that show a skewed distribution and uncertain information about soil contamination. We present a case study with 76 soil samples taken from a site of 15 square km in order to assess the usability of information gleaned from sparse data. The soil was contaminated with cadmium predominantly as a result of airborne emissions from a metal smelter. The spatial interpolation applies lognormal anisotropic kriging and conditional simulation for log-transformed data. The uncertainty of cadmium concentration acquired through data sampling, sample preparation, analytical measurement, and interpolation is factor 2 within 68.3 % confidence. Uncertainty predominantly results from the spatial interpolation necessitated by low sampling density and spatial heterogeneity. The interpolation data are shown in maps presenting likelihoods of exceeding threshold values as a result of a lognormal probability distribution. Although the results are not deterministic, this procedure yields a quantified and transparent estimation of the contamination, which can be used to delineate areas for soil improvement, remediation, or restricted area use, based on the decision-makers' probability safety requirement.

Data Collection↗

PubMed2000

RESEARCH: Conceptualizing Environmental Stress: A Stress-Response Model of Coastal Sandy Barriers.

/ The purpose of this paper is to develop and apply a conceptual framework of environmental stress-response for a geomorphic system. Constructs and methods generated from the literature were applied in the development of an integrative stress-response framework using existing environmental assessment techniques: interaction matrices and a systems diagram. Emphasis is on the interaction between environmental stress and the geomorphic environment of a sandy barrier system. The model illustrates a number of stress concepts pertinent to modeling environmental stress-response, including those related to stress-dependency, frequency-recovery relationships, environmental heterogeneity, spatial hierarchies and linkages, and temporal change. Sandy barrier stress-response and recovery are greatly impacted by fluctuating water levels, stress intensity and frequency, as well as environmental gradients such as differences in sediment storage and supply. Aspects of these stress-response variables are articulated in terms of three main challenges to management: dynamic stability, spatial integrity, and temporal variability. These in turn form the framework for evaluative principles that may be applied to assess how policies and management practices reflect key biophysical processes and human stresses identified by the model.

Journal Article↗

PubMed2003

The evolution of dispersal.

A non-local model for dispersal with continuous time and space is carefully justified and discussed. The necessary mathematical background is developed and we point out some interesting and challenging problems. While the basic model is not new, a 'spread' parameter (effectively the width of the dispersal kernel) has been introduced along with a conventional rate paramter, and we compare their competitive advantages and disadvantages in a spatially heterogeneous environment. We show that, as in the case of reaction-diffusion models, for fixed spread slower rates of diffusion are always optimal. However, fixing the dispersal rate and varying the spread while assuming a constant cost of dispersal leads to more complicated results. For example, in a fairly general setting given two phenotypes with different, but small spread, the smaller spread is selected while in the case of large spread the larger spread is selected.

Animals↗

PubMed2001

Inverse bifurcation problem, singular Wiener-Hopf equations, and mathematical models in ecology.

A single-species population dynamics with dispersal in a spatially heterogeneous environment is modeled by a nonlinear reaction-diffusion equation with a potential term. To each nonlinear kinetics there corresponds a bifurcation curve that describes the relation between the growth rate and the central density of a steady-state population distribution. Our main concern is an inverse problem for this correspondence. The existence of nonlinear kinetics realizing a prescribed bifurcation curve is established. It is shown that the freedom of such kinetics is of degree finite and even, depending only on the heterogeneity of the environment, and conversely that any nonnegative even integer occurs as the degree of freedom in some environments. A discussion is also made on under what kind of environment the degree is equal to zero or is positive. The mathematical analysis involves the development of a general theory for singular multiplicative Wiener-Hopf integral equations.

Bioreactors↗

PubMed2005

Gene expression in human skeletal muscle: alternative normalization method and effect of repeated biopsies.

The reverse transcriptase-polymerase chain reaction (RT-PCR) method has lately become widely used to determine transcription and mRNA content in rodent and human muscle samples. However, the common use of endogenous controls for correcting for variance in cDNA between samples is not optimal. Specifically, we investigated (1) a new normalization method based on determining the cDNA content by the flourophores PicoGreen and OliGreen, (2) effect of repeated muscle biopsies on mRNA gene expression, and (3) the spatial heterogeneity in mRNA expression across the muscle. Standard curves using oligo standards revealed a high degree of sensitivity and linearity (2.5-45 ng; R2>0.99) with OliGreen reagent, as was the case for OliGreen analyses with standard curves constructed from serial dilutions of representative RT samples (R2 >0.99 for a ten times dilution range of a representative reversed transcribed (RT) sample). Likewise, PicoGreen reagent detected the RNA:DNA hybrid content in RT samples with great sensitivity. Standard curves constructed from both double-stranded lambda DNA (1-10 ng) and from serial dilutions of representative RT samples consistently resulted in linearity with R2 >0.99. The present determination of cDNA content in reversed transcribed human skeletal muscle RNA samples by both PicoGreen and OliGreen analyses suggests that these fluorophores provide a potential alternative normalization procedure for human gene expression studies. In addition, the present study shows that multiple muscle biopsies obtained from the same muscle do not influence the mRNA response induced by an acute exercise bout for any of the genes examined.

Adaptation, Physiological↗

PubMed2001

Local photolysis using tapered quartz fibres.

We describe a versatile, low-cost photolysis system in which sub-millisecond flashes generated by a xenon flash lamp are conveyed through a silica fibre directly onto a cell. The fibre, which is tapered to a sub-micrometre diameter and sputtered with chromium and aluminium, illuminates an area of about 1 microm2. Site and timing of photolysis can be chosen independently from other experimental parameters. As an application example we show the spatially heterogeneous distribution of Ca2+-dependent Cl- channels in olfactory receptor neurons.

Acetates↗

PubMed2003

Spatio-temporal patterns of photosystem II activity and plasma-membrane proton flows in Chara corallina cells exposed to overall and local illumination.

Pulse-amplitude modulated microfluorometry and an extracellular pH microprobe were used to examine light-induced spatial heterogeneity of photosynthetic and H(+)-transporting activities in cells of Chara corallina Klein ex Willd. Subcellular domains featuring different PSII photochemical activities were found to conform to alternate alkaline and acid zones produced near the cell surface, with peaks of PSII activity correlating with the position of acid zones. Buffers eliminated pH variations near the cell surface but did not destroy the variations in PSII photochemical yield (deltaF/Fm'). When a dark-adapted cell was exposed to actinic light, the PSII effective yield decreased within 5-15 min in the alkaline regions but rose after the initial decline in the acid regions. The light-induced decrease in deltaF/Fm' in the alkaline regions occurred prior to or synchronously with the steep rise in local pH. The kinetics of deltaF/Fm', Fm', and F observed in alkaline regions under overall illumination of Chara cells were replaced by those typical of acid regions, when the illumination area size was restricted to 1.5-2 mm. The data show that photoinduced patterns in photosynthetic activity are not predetermined by the particular structural organization of alkaline and acid cell regions but are subject to dynamic changes.

Cell Membrane↗