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PubMed2002

Spatial analysis of plant metabolism: sucrose imaging within Vicia faba cotyledons reveals specific developmental patterns.

During legume embryogenesis the differentiation of the cotyledons proceeds gradually in a wave-like manner. The process is metabolically and genetically controlled and regulated by sugars. In order to perform a spatial and temporal analysis of the sugar distribution pattern a new method was developed to specifically measure sucrose directly in tissues via bioluminescence and single photon counting. This enabled a quantitative sucrose imaging with a resolution close to the single cell level. The procedure was applied on sections of Vicia faba cotyledons covering the main stages of histodifferentiation. Young embryos before the storage phase contained moderate levels of sucrose, which were evenly distributed. At the onset of maturation high concentrations were present within a tissue layer covering the outward half of the coytledons. This layer was directly underneath the epidermis expressing a sucrose transporter gene indicating that epidermal transporters caused the high sucrose accumulation in the underlying tissue. At that stage the sucrose gradient was inversely oriented compared with cell size and the starch content. Cells within the interior were larger, contained starch but low sucrose. Thus, the sucrose pattern is controlled by uptake activity and permeability within the parenchyma. However, during the main storage phase actively elongating and starch accumulating cells contain highest sucrose concentrations indicating that differences in growth and starch accumulation also affect intracotyledonary sugar distribution. High sucrose concentrations were correlated with transcript levels of sucrose synthase and ADP-Glc pyrophosphorylase indicating a signaling function for sucrose to induce starch biosynthesis on the gene expression level. Carbon flux through the sucrose synthase pathway towards starch increased when hexoses levels decreased.

Carbohydrate Metabolism↗
PubMed1998

Distribution and abundance of Ixodes scapularis (Acari: Ixodidae) in North America: ecological processes and spatial analysis.

Conditions influencing the distribution and abundance of Ixodes scapularis Say in North America have been the object of considerable study during the past 2 decades, resulting in new information about its expanding range, population structure, host associations, and environmental constraints. Variation in the methods, timing, or extent of sampling, the type of population estimate developed, and the spatial scale of analysis makes comparisons of results difficult. This report summarizes research on I. scapularis habitat, including the diversity of hosts and physical conditions in the environment where they are abundant, and how this may influence dispersal and range expansion. Recent efforts to analytically address spatial distributions are considered. Approaches that may be useful in clarifying and resolving unanswered questions are suggested, and a conceptual framework for analyzing this vector's expanding abundance and distribution is offered.

Animals↗
PubMed2005

Temporal and spatial analysis of the 1999 outbreak of acute clinical infectious bursal disease in broiler flocks in Denmark.

The objective of this study was to describe the spatial and temporal dynamics of the 1999 outbreak of acute clinical infectious bursal disease (IBD) in broiler chicken farms in Denmark. The analysis was performed using data from all broiler farms located in the Jutland peninsula and the island of Funen (168 municipalities). The Moran's index I, K-functions and scan statistics were used to describe the dynamics of the epidemic. In addition, spatially correlated survival analyses were performed and the posterior frailties were mapped to identify areas with high or low survival times. From January to October 1999, a total of 43 farms (81 flocks) out of a total of 299 farms (2970 flocks) in 110 municipalities were infected with IBD. The outbreak developed more or less simultaneously in two regions, one in the north and the other in the center of the study area. The space-time descriptive methods suggested that the cases were more likely to occur during a short period of time and over relatively short distances, indicating that local factors facilitated the spread of the virus. For instance, the highest risk, as estimated by the K-function, was within 20 km and 20 days. The risk of transmission peaked in July and remained high until the end of the study. The spatially correlated survival analysis identified municipalities with low survival times that roughly corresponded to the clusters found using scan statistics. The analysis for the full hierarchical structure of the dataset identified variation (i.e. clustering) at the farm and municipality levels.

Animals↗
PubMedDate not supplied

Spatial analysis of the air pollution-mortality relationship in the context of ecologic confounders.

Lack of control for confounding by ecological covariates that may relate to sulfate air pollution and mortality was a key criticism of the two studies that were the focus of the Particle Reanalysis Project. To assess the validity of this criticism, we address the question: "Does sulfate air pollution exert health effects when the impact of other individual and ecologic variables thought to influence health is taken into account?" A related question arises from the possibility of autocorrelation in the mortality risks and ecologic covariates. Failure to control for autocorrelation can lead to false positive significance tests and may indicate bias resulting from a missing variable or group of variables. We control for more than 25 individual risk factors and for 20 ecologic variables representing environmental, socioeconomic, demographic, health- care, and lifestyle determinants of health in a two-stage multilevel analysis. Four modeling strategies are used to control for spatial autocorrelation. Of the 20 ecologic variables tested, only sulfate and sulfur dioxide are significant in models that incorporate spatial autocorrelation. Accounting for autocorrelation also reduces the size and certainty of the sulfate effect on mortality when compared to results generated from Cox models where independent observations are assumed. Confidence limits for the sulfate relative risk include unity in models that simultaneously control for sulfur dioxide and autocorrelation.

Air Pollution↗
PubMed1986

Two simple methods of spatial analysis and their applications in location-oriented health services research.

This paper illustrates the usefulness of cartographic and centrographic methods in examining the locational characteristics of health care resources, such as specialist physicians' offices. Cartographic analysis involving map comparisons not only describes the nature of particular spatial patterns, but it also suggests relevant hypotheses on the basis of observed locational relationships among the mapped phenomena. Centrographic analysis generally substantiates the findings of simple map analysis by providing certain objective quantitative measures regarding the basic characteristics of a point distribution; additionally, it generates a graphic summary, the Standard Deviational Ellipse (SDE), which offers a convenient means for direct comparison of multiple spatial patterns. The essentially complementary nature of the two methods is highlighted, and it is concluded that they are most useful when used in conjunction with one another.

Catchment Area, Health↗
PubMed2006

Spatial analysis of American Visceral Leishmaniasis in Mato Grosso do Sul State, Central Brazil.

OBJECTIVES: To map American Visceral Leishmaniasis (AVL) in Mato Grosso do Sul State (Central Brazil). METHODS: The distribution of AVL was mapped, using the Geographic Information System. RESULTS: The disease was endemic to the Corumbá Region from 1913 to 1998. Spatial and temporal analysis indicated that the expansion route and dissemination through the State of the disease has been from west to east, coinciding with three different human interventions; two of them, a federal highway and a rail-road, were constructed in the early twentieth century, from east to west, from Bauru city, in São Paulo State, to Corumbá city, in Mato Grosso do Sul State. The third anthropogenic intervention was the construction of a gas pipeline that started in 1998, and attracted thousands of workers. This construction route has the same direction, west to east, and timescale as the observed expansion and dissemination of AVL. CONCLUSIONS: The results relate the expansion of the disease to intense human traffic along the route of spread.

Animals↗
PubMed2005

Estimation of leaf water potential by thermal imagery and spatial analysis.

Canopy temperature has long been recognized as an indicator of plant water status and as a potential tool for irrigation scheduling. In the present study, the potential of using thermal images for an in-field estimation of the water status of cotton under a range of irrigation regimes was investigated. Thermal images were taken with a radiometric infrared video camera. Specific leaves that appeared in the camera field of view were sampled, their LWP was measured and their temperature was calculated from the images. Regression models were built in order to predict LWP according to the crop canopy temperature and to the empirical formulation of the crop water stress index (CWSI). Statistical analysis revealed that the relationship between CWSI and LWP was more stable and had slightly higher correlation coefficients than that between canopy temperature and LWP. The regression models of LWP against CWSI and against leaf temperatures were used to create LWP maps. The classified LWP maps showed that there was spatial variability in each treatment, some of which may be attributed to the difference between sunlit and shaded leaves. The distribution of LWP in the maps showed that irrigation treatments were better distinguished from each other when the maps were calculated from CWSI than from leaf temperature alone. Furthermore, the inclusion of the spatial pattern in the classification enhanced the differences between the treatments and was better matched to irrigation amounts. Optimal determination of the water status from thermal images should be based on an overall view of the physical status as well as on the analysis of the spatial structure. Future study will involve investigating the robustness of the models and the potential of using water status maps, derived from aerial thermal images, for irrigation scheduling and variable management in commercial fields.

Agriculture↗
PubMed2005

Temporal-spatial analysis of severe acute respiratory syndrome among hospital inpatients.

BACKGROUND: We report the temporal-spatial spread of severe acute respiratory syndrome (SARS) among inpatients in a hospital ward during a major nosocomial outbreak and discuss possible mechanisms for the outbreak. METHODS: All inpatients who had stayed in the same ward as the initial index case patient for any duration before isolation were recruited into a cohort and followed up to document the occurrence of SARS. The normalized concentration of virus-laden aerosols at different locations of the ward was estimated by use of computational fluid dynamics modeling. The attack rates in the various subgroups stratified by bed location were calculated. Multivariate Cox proportional hazards regression was used to document important risk factors. RESULTS: The overall attack rate of SARS was 41% (30 of 74 subjects). It was 65%, 52%, and 18% in the same bay, adjacent bay, and distant bays, respectively (P = .001). Computation fluid dynamics modeling indicated that the normalized concentration of virus-laden aerosols was highest in the same bay and lowest in the distant bays. Cox regression indicated that staying in the ward on 6 or 10 March entailed higher risk, as well as staying in the same or adjacent bays. The epidemic curve showed 2 peaks, and stratified analyses by bed location suggested >1 generation of spread. CONCLUSIONS: The temporal-spatial spread of SARS in the ward was consistent with airborne transmission, as modeled by use of computational fluid dynamics. Infected health care workers likely acted as secondary sources in the latter phase of the outbreak.

Cohort Studies↗
PubMed2006

Descriptive spatial analysis of scrapie-affected flocks in Great Britain between January 1993 and December 2002.

The spatial distribution of sheep flocks in Great Britain with confirmed clinical scrapie between January 1993 and December 2002 inclusive was investigated by using kernel density estimation and a cluster scan test statistic. Six statistically significant clusters were identified: three were lower risk, and were centred on the north-western coast of Scotland, the north-western coast of Wales and the South Yorkshire/Pennine region; three were of higher risk, and were centred in the central south, North Yorkshire and north Cumbria. General knowledge and the results of previous epidemiological studies were used to generate biologically plausible hypotheses that might explain these findings. They included aspects of flock management and disease transmission, and factors associated with the identification of cases, including their detection, recognition and, in particular, reporting levels, as well as diagnosis and animal movements.

Animals↗
PubMed1996

Spatial analysis of seroconversion of sentinel cattle to bluetongue viruses in Queensland.

OBJECTIVE: To assess quantitatively the spatial distribution of seroconversion of Queensland cattle to bluetongue viruses. DESIGN: A sentinel herd study. SAMPLE POPULATION: Sixty-nine sentinel herds at 30 locations. PROCEDURE: Spatial clustering of seroconversion to bluetongue viruses was investigated during the period from 1990 to 1994. RESULTS: Seroconversion to only two bluetongue virus serotypes, 1 and 21, was observed. The 14 herds, in which seroconversion to bluetongue virus serotype 1 was detected, were located only along the eastern coastal and subcoastal region of Queensland, and were significantly (P < 0.05) clustered. Locations at which seroconversion to serotype 21 was detected, were not significantly clustered. The results generally agree with field observations, except for the failure to detect seroconversion to bluetongue viruses in north-western Queensland. CONCLUSION: Bluetongue infection of cattle in north-western Queensland may be temporally sporadic. The dominance of serotype 1 in the Queensland cattle population may be the result of differential transmission by potential vector species. Long-term surveillance programs are important for defining disease status of animal populations.

Animals↗
PubMed1995

Spatial analysis of nuclear and mitochondrial RFLP genotypes in populations of the chestnut blight fungus, Cryphonectria parasitica.

Spatial structure of both nuclear and mitochondrial RFLPs were studied in several populations of the chestnut blight fungus, Cryphonectria parasitica, using a variety of spatial autocorrelation tests designed to detect nonrandom patterns. Fungal individuals were sampled from cankers on infected chestnut trees, and the location of each tree was mapped. Single-locus nuclear RFLPs, nuclear fingerprints, and mitochondrial DNA haplotypes were determined for each individual. Individuals with the same DNA fingerprint genotypes occurred closer together than would be expected at random in four of the five plots, while mitochondrial DNA haplotypes were aggregated in all five plots. Genetic distances between individuals, expressed as one minus the proportion of shared restriction fragment size classes for fingerprints and mitochondrial haplotypes, were significantly correlated with Euclidean distances between individuals in four of the five populations, but these correlations were very weak (r < 0.18). The same DNA fingerprint and single-copy nuclear RFLP alleles occurred on the same trees or immediately neighbouring trees more often than would be expected at random. Most of the aggregation for all three genetic markers occurred among individuals within the same cluster of chestnut stems or on neighbouring trees. Lack of spatial autocorrelation in one population was probably due to sampling on a larger scale that was too coarse to detect any patterns. Significant aggregation of genotypes in C. parasitica is most likely caused by some degree of restricted dispersal within populations. The implications of restricted dispersal are discussed in relation to the breeding system and isolation by distance in populations of C. parasitica.

Cell Nucleus↗
PubMed1997

Telomeres cluster de novo before the initiation of synapsis: a three-dimensional spatial analysis of telomere positions before and during meiotic prophase.

We have analyzed the progressive changes in the spatial distribution of telomeres during meiosis using three-dimensional, high resolution fluorescence microscopy. Fixed meiotic cells of maize (Zea mays L.) were subjected to in situ hybridization under conditions that preserved chromosome structure, allowing identification of stage-dependent changes in telomere arrangements. We found that nuclei at the last somatic prophase before meiosis exhibit a nonrandom, polarized chromosome organization resulting in a loose grouping of telomeres. Quantitative measurements on the spatial arrangements of telomeres revealed that, as cells passed through premeiotic interphase and into leptotene, there was an increase in the frequency of large telomere-to-telomere distances and a decrease in the bias toward peripheral localization of telomeres. By leptotene, there was no obvious evidence of telomere grouping, and the large, singular nucleolus was internally located, nearly concentric with the nucleus. At the end of leptotene, telomeres clustered de novo at the nuclear periphery, coincident with a displacement of the nucleolus to one side. The telomere cluster persisted throughout zygotene and into early pachytene. The nucleolus was adjacent to the cluster at zygotene. At the pachytene stage, telomeres rearranged again by dispersing throughout the nuclear periphery. The stage-dependent changes in telomere arrangements are suggestive of specific, active telomere-associated motility processes with meiotic functions. Thus, the formation of the cluster itself is an early event in the nuclear reorganizations associated with meiosis and may reflect a control point in the initiation of synapsis or crossing over.

Cell Nucleus↗
PubMed1982

A spatial analysis of voting on health care issues. United States House of Representatives, 86th Congress, First Session.

This study examines the spatial patterns of congressional voting on health issues. Thirteen roll call votes on health care issues occurring during the 1st Session of the 96th Congress are factor analyzed. This analysis shows that health care questions cluster around two major issues: health care regulation and health care spending. The factor scores for each Representative are mapped, and a regression model is developed relating health care voting to characteristics of the Representative, the Congressional district, and the hospitals in that district. The most important findings were: (1) support for both health care spending and regulation is strongest in the Northeast and upper Midwest. (2) Although Representatives from most of the Southern states are opposed to health care regulation, they generally favor health care spending. (3) Representatives from a few of the Southern states, however, do not fit this generalization. (4) Although Representatives from the Pacific Coast states are the strongest proponents of regulation, they are opposed to spending (5) Opposition to health care spending is particularly strong among Representatives from suburban districts.

Cost Control↗
PubMed1992

Spatial analysis of the distribution of Ixodes dammini (Acari: Ixodidae) on white-tailed deer in Ogle County, Illinois.

The pattern of infestations of Ixodes dammini on white-tailed deer in Ogle County in Illinois was studied through examinations of hunted deer from 1988 to 1990. The Illinois Geographic Information System mapped the spatial distribution of tick infestations on deer and related it to a known endemic focus for I. dammini and Borrelia burgdorferi (Castle Rock State Park), and to a major waterway (Rock River). Second-order neighborhood analysis was used to analyze the spatial distribution of deer around Castle Rock State Park. More than 25% of deer were infested. All deer were clustered around CRSP, but the clustering resulted mostly from clustering of infested deer around CRSP. CRSP is apparently the only important source of tick infestations in Ogle County. Clustering of infested deer did not change during the 3-yr study period. The dispersion pattern of ticks on deer was aggregated, with twice and three times as many ticks collected from bucks as from does and from fawns, respectively. More male ticks than female ticks were collected from infested deer. Of 59 ticks removed from harvested deer in 1990, 5.1% tested positive for B. burgdorferi.

Animals↗
PubMed2006

Bayesian spatial analysis and disease mapping: tools to enhance planning and implementation of a schistosomiasis control programme in Tanzania.

OBJECTIVE: To predict the spatial distributions of Schistosoma haematobium and S. mansoni infections to assist planning the implementation of mass distribution of praziquantel as part of an on-going national control programme in Tanzania. METHODS: Bayesian geostatistical models were developed using parasitological data from 143 schools. RESULTS: In the S. haematobium models, although land surface temperature and rainfall were significant predictors of prevalence, they became non-significant when spatial correlation was taken into account. In the S. mansoni models, distance to water bodies and annual minimum temperature were significant predictors, even when adjusting for spatial correlation. Spatial correlation occurred over greater distances for S. haematobium than for S. mansoni. Uncertainties in predictions were examined to identify areas requiring further data collection before programme implementation. CONCLUSION: Bayesian geostatistical analysis is a powerful and statistically robust tool for identifying high prevalence areas in a heterogeneous and imperfectly known environment.

Adolescent↗
PubMed2006

Spatial analysis of Aedes albopictus (Diptera: Culicidae) oviposition in suburban neighborhoods of a Piedmont community in North Carolina.

Temporal and spatial distribution of egg-laying by Aedes albopictus (Skuse) (Diptera: Culicidae) was investigated in suburban neighborhoods in Raleigh, NC, by using oviposition traps (ovitraps) at fixed sampling stations during the 2002 and 2003 mosquito seasons. Variations in the phenology of oviposition between the two mosquito seasons resulted from differences in the patterns and amounts of rainfall early in the season. Aerial images of each study neighborhood were digitized, and the proportions of specific types of land cover within buffer zones encompassing ovitraps were estimated. Retrospective analyses showed that in some neighborhoods, oviposition intensity was significantly associated with specific types of land cover. However, in general, it seemed that gravid Ae. albopictus searched throughout the landscape for water-filled containers in which to lay eggs. Peridomestic surveys were carried out concurrently with ovitrap collections to estimate production of Ae. albopictus pupae in discarded water-filled containers and the abundance of females in vegetation that made up the resting habitat. Results of linear regression analyses indicated that the mean standing crop of pupae (total and per container) per residence was not a significant predictor of mean egg densities in ovitraps. However, the mean standing crop of adult females was a significant but weak predictor variable, because the magnitude and sign of regression coefficients varied between neighborhoods. Linear spatial regression analyses revealed that oviposition intensity was not spatially dependent on pupal standing crop or the numbers of pupae-positive containers distributed peridomestically. However, a weak spatial dependence on the standing crop of adult females was found in some neighborhoods. Based on spherical variogram models, kriging was carried out to predict the spatial patterns of oviposition in suburban neighborhoods. Focal areas of high and low oviposition intensity were evident in most neighborhoods; however, the spatial patterns of oviposition changed between mosquito seasons. Kriging predictions were evaluated, using cross-validation, by systematically removing each data point from our data set and predicting the removed point by using the remaining points. The root mean square (standardized) error values of best fitting variogram models approximated 1, and plots of standardized PRESS residuals showed no distinct pattern for most neighborhoods, indicating that predictions of the spatial distribution of oviposition intensity were valid. Spherical variogram models are a satisfactory method for describing the spatial distribution of Ae. albopictus oviposition, and kriging can be a useful technique for predicting oviposition intensity at locations that have not been sampled.

Aedes↗
PubMed2002

The urban spread of visceral leishmaniasis: clues from spatial analysis.

BACKGROUND: The pattern of spread of visceral leishmaniasis in Brazilian cities is poorly understood. METHODS: We used geographic information systems and spatial statistics to evaluate the distribution of 1061 cases of visceral leishmaniasis in Teresina, Brazil, in 1993 through 1996. RESULTS: A locally weighted (LOESS) regression model, which was fit as a smoothed function of spatial coordinates, demonstrated large-scale variation, with high incidence rates in peripheral neighborhoods that bordered forest land and pastures. Moran's I indicated small-scale variation and clustering up to 300 m, roughly the flight range of the sand fly vector. CONCLUSIONS: Spatial analytical techniques can identify high-risk areas for targeting control interventions.

Brazil↗