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PubMed1976

Recovery from unilateral visuo-spatial neglect?

Patients who had demonstrated unilateral visuo-spatial neglect on a simple drawing and copying task three to four weeks after a right hemisphere stroke were reassessed five months later. Although the incidence of neglect as defined had dropped markedly in that period, they remained impaired on tests of spatial analysis and visual perception relative to a group of right hemisphere patients without neglect. The measurement of neglect is discussed in the light of both these results and the stability of the neglect group's abnormal position preference on one of the tests administered.

Cerebrovascular Disorders↗
PubMed2003

Development of a rod photoreceptor mosaic revealed in transgenic zebrafish.

The number and distribution of neurons within the vertebrate retina are tightly regulated. This is particularly apparent in the highly ordered, crystalline-like arrangement of the cone photoreceptors in the teleost. In this report, using a transgenic line of zebrafish, a novel and developmentally regulated mosaic pattern of the rod photoreceptors is described. The spatial and temporal expression of EGFP, under the control of the Xenopus rhodopsin gene promoter, was nearly identical to the endogenous rhodopsin. EGFP was first detected in the ventral nasal retinal in an area of precocious neurogenesis referred to as the "ventral patch". Subsequent expression of EGFP was observed in isolated cells sporadically distributed across the dorsal and central retina. However, confocal microscopy and spatial analysis of larval eyes or retinal explants from adults revealed a precise arrangement to the rod photoreceptors. The rod terminals were arranged in regularly spaced rows with clearly identifiable telodendria linking neighboring cells. The rod inner segments projected through the cone mosaic in a predictable pattern. In the adult, the rod mosaic originated near the retinal margin where clusters of rods differentiated around the immature short single cone. In the embryo, the sporadic differentiation of the rods led to the gradual formation of the mosaic pattern. With the growing interest in neuronal stem cells, revisiting this model of neurogenesis provides an avenue to uncover mechanisms underlying the precise integration of new neuronal elements into a preexisting neural network.

Animals↗
PubMed2002

Coastal freshwater runoff is a risk factor for Toxoplasma gondii infection of southern sea otters (Enhydra lutris nereis).

The association among anthropogenic environmental disturbance, pathogen pollution and the emergence of infectious diseases in wildlife has been postulated, but not always well supported by epidemiologic data. Specific evidence of coastal contamination of the marine ecosystem with the zoonotic protozoan parasite, Toxoplasma gondii, and extensive infection of southern sea otters (Enhydra lutris nereis) along the California coast was documented by this study. To investigate the extent of exposure and factors contributing to the apparent emergence of T. gondii in southern sea otters, we compiled environmental, demographic and serological data from 223 live and dead sea otters examined between 1997 and 2001. The T. gondii seroprevalence was 42% (49/116) for live otters, and 62% (66/107) for dead otters. Demographic and environmental data were examined for associations with T. gondii seropositivity, with the ultimate goal of identifying spatial clusters and demographic and environmental risk factors for T. gondii infection. Spatial analysis revealed clusters of T. gondii-seropositive sea otters at two locations along the coast, and one site with lower than expected T. gondii seroprevalence. Risk factors that were positively associated with T. gondii seropositivity in logistic regression analysis included male gender, older age and otters sampled from the Morro Bay region of California. Most importantly, otters sampled near areas of maximal freshwater runoff were approximately three times more likely to be seropositive to T. gondii than otters sampled in areas of low flow. No association was found between seropositivity to T. gondii and human population density or exposure to sewage. This study provides evidence implicating land-based surface runoff as a source of T. gondii infection for marine mammals, specifically sea otters, and provides a convincing illustration of pathogen pollution in the marine ecosystem.

Aging↗
PubMed2001

Electrophysiological assessment of impulsive behavior in healthy subjects.

The different concepts of impulsivity cover a wide range of divergent behaviors. In clinical terms, aspects of impulsivity are both an important feature in several psychiatric conditions related to a low central serotonergic neurotransmission like aggressive behavior and suicidality, and a core symptom of frontal lobe syndromes of various etiologies. Assessment of the different forms of impulsivity so far relies on clinical observations and self-rating questionnaires. Measurements of a distinct brain function associated with impulsive behavior are not available yet, however, electrophysiological parameters of cognitive response control elicited with the execution (Go-condition) and the inhibition (NoGo-condition) of a prepared motor response within the Continuous Performance Test (CPT) might be suitable candidates. By means of a spatial analysis method the centers of gravity (centroids) of the brain electrical fields evoked with Go- and NoGo-responses can be localized and quantified. In the present study, the Go- and NoGo-centroids and the impulsivity score in Eysenck's I(7)-scale were determined in 22 healthy subjects (10 women, 12 men, mean age 42.0+/-10.1 years). Impulsivity was correlated with both, a more anterior location of the Go- (r=0.58, P<0.01) and the NoGo-centroid (r=0.53, P=0.01). These results indicate, that in healthy subjects the amount of I(7)-impulsivity is associated with differences in the prefrontal brain activation pattern during cognitive response control. However, a replication study with a larger sample and an investigation of psychiatric patients with pathological levels of impulsivity are necessary to qualify these topographical ERP-parameters of cognitive response control as valid measures of the brain electrical basis of impulsive behavior.

Adult↗
PubMedDate not supplied

The use of grid sampling methodology for rapid assessment of the distribution of bancroftian filariasis.

The recent World Health Assembly Resolution to eliminate lymphatic filariasis as a public health problem once more brings to the fore the need for reliable data for the effective planning of disease control programmes. Most countries do not have data on the distribution of lymphatic filariasis and are therefore not in the position to initiate control programmes based on sound baseline data. We tested in Ghana in 1998-99 a method for the Rapid Assessment of the Geographical Distribution of Bancroftian Filariasis (RAGFIL) that uses a spatial sampling grid with 50 km between sampled villages, rapid assessment surveys for filariasis prevalence in the sampled villages and spatial analysis to estimate the geographical distribution of filariasis throughout the study area. The prevalence contours obtained with the 50 x 50-km sampling grid were operationally similar to those obtained with a 25 x 25-km grid. The predicted prevalence was not statistically different from the sample survey prevalence in 57 independent villages and the 50 x 50-km grid appears adequate for rapid mapping of filariasis. For the purpose of filariasis mapping, the antigen test would seem a better diagnostic test than clinical examination for hydrocoele. We recommend that a regional approach to mapping be used because of the importance of cross-border foci as demonstrated by our findings from the north of Ghana. Application of the method will provide the minimal information required for effective planning of treatment programmes, and will facilitate estimation of the number of people to be treated. It will also help improve estimates of the number of people at risk and affected, and of the burden of disease due to lymphatic filariasis in Africa.

Adolescent↗
PubMed2001

Radon risk mapping in southern Belgium: an application of geostatistical and GIS techniques.

A data set of long-term radon measurements in approximately 2200 houses in southern Belgium has been collected in an on-going national radon survey. The spatial variation of indoor Rn concentrations is modelled by variograms. A radon distribution map is produced using the log-normal kriging technique. A GIS is used to digitise, process and integrate a variety of data, including geological maps, Rn concentrations associated with house locations and an administrative map, etc. It also allows evaluation of the relationships between various spatial data sets with the goal of producing radon risk maps. Based on geostatistical mapping and spatial analysis, we define three categories of risk areas: high risk, medium risk and low risk area. The correlation between radon concentrations and geological features is proved in this study. High and medium Rn risk zones are dominantly situated in bedrock from the Cambrian to Lower Devonian, although a few medium risk zones are within the Jurassic. It is evident that high-risk zones are related to a strongly folded and fractured context.

Air Pollutants, Radioactive↗
PubMed1999

The NoGo-anteriorization as a neurophysiological standard-index for cognitive response control.

Event related potentials (ERPs) during the Go- and the NoGo-condition of the Continuous Performance Test (CPT) were applied to investigate the neurophysiological basis of cognitive response control. These conditions of the test represent the execution and the inhibition of an anticipated motor response. In a previous study, the comprehensive spatial analysis of the ERPs allowed to define a parameter which robustly reflected the anteriorization of the positive P300 field area during the NoGo- compared to the Go-condition (NoGo-anteriorisation, NGA). The result was found consistently in all investigated subjects. The present study replicated the finding in 27 healthy subjects without any exception. Moreover, the latencies were longer and the amplitudes showed a trend to be higher in the NoGo- compared to the Go-ERP. This is interpreted as a sign of higher processing demands in the NoGo-condition. In conclusion, the ability of the NGA to express reliably the differences of brain activity leading to execution or suppression of a prepared motor response qualifies this parameter as a topographical standard-index for cognitive response control.

Adult↗
PubMed1998

Three-dimensional tomography of event-related potentials during response inhibition: evidence for phasic frontal lobe activation.

OBJECTIVES: Spatial analysis of the evoked brain electrical fields during a cued continuous performance test (CPT) revealed an extremely robust anteriorization of the positivity of a P300 microstate in the NoGo compared to the Go condition (NoGo-anteriorization in a previous study). To allow a neuroanatomical interpretation the NoGo-anteriorization was investigated with a new three-dimensional source tomography method (LORETA) was applied. METHODS: The CPT contains subsets of stimuli requiring the execution (Go) or the inhibition (NoGo) of a cued motor response which can be considered as mutual control conditions for the event-related potential (ERP) study of inhibitory brain functions 21-channel ERPs were obtained from 10 healthy subjects during a cued CPT, and analyzed with LORETA. RESULTS: Topographic analyses revealed significantly different scalp distributions between the Go and the NoGo conditions in both P100 and P300 microstates, indicating that already at an early stage different neural assemblies are activated. LORETA disclosed a significant hyperactivity located in the right frontal lobe during the NoGo condition in the P300 microstate. CONCLUSIONS: The results indicate that right frontal sources are responsible for the NoGo-anteriorization of the scalp P300 which is consistent with animal and human lesion studies of inhibitory brain functions. Furthermore, it demonstrates that frontal activation is confined to a brief microstate and time-locked to phasic inhibitory motor control. This adds important functional and chronometric specificity to findings of frontal activation obtained with PET and Near-Infrared-Spectroscopy studies during the cued CPT, and suggests that these metabolic results are not due to general task demands.

Adult↗
PubMed1997

The effect of spatial definition on the allocation of clients to screening clinics.

We compared four strategies for inviting 91,456 women aged 50-69 years to one of six clinics for mammography screening and 40,142 men aged 60-79 years to one of 10 clinics for abdominal aortic aneurysm (AAA) screening. The strategies were invitation to the clinic nearest to the client and invitation to the clinic nearest to the client's area of residence defined by census small area, postcode and local government area. For each strategy we calculated the expected demand at each clinic and the travel distances for clients. We found that when women were allocated to mammography clinics on the basis of the local government area instead of their individual address, expected demand at one clinic increased by 60%, and 19% of clients were invited to attend a more remote clinic, entailing 99,000 km of additional travel. Similar results were obtained for men allocated to AAA clinics by their postcode of residence instead of their individual address: 55% difference in expected demand, 13% to a more remote clinic and 60,000 km of extra travel. Allocation on the basis of small areas did not show such great differences, except for travel distance, which was about 5% higher for each clinic type. We recommend that allocation of clients to screening clinics be made according to residential address, that assessment of the location of clinics be based on distances between residences and nearest clinic, but that planning new locations for clinics be aided with spatial analysis tools using small area demographic and social data.

Aged↗
PubMed1998

Putting risk in its place: methodological considerations for investigating extreme event health risk.

Health is affected by the places in which people live, work and interact, yet many epidemiological studies overlook the characteristics of places and instead focus solely on the people who inhabit them. Place-based investigations of disparities in health outcomes are concerned with the healthiness of places and not merely the healthiness of the populations in these places. A place-based approach has been used within medical geography and medical sociology, typically in the study of health differentials associated with long-term, cumulative exposures to a wide range of environmental variables. This approach has rarely been extended, however, to health research that looks at the effects of extreme events (such as industrial accidents or hurricanes). The purpose of this paper is to incorporate a place-based framework into extreme event health research. The paper first discusses methodological considerations for a place-based approach and then illustrates the use of spatial analysis techniques as the first step in identifying place-based risk factors in mortality associated with heat waves. The study centers on St. Louis, Missouri, a city where heat waves are frequent and heat-related mortality is high. The results show that heat-related mortality rates during the most severe heat waves were generally higher in the warmer, less stable and more disadvantaged areas of St. Louis and lower in the cooler and more affluent parts of the city. During the milder years analyzed, there was little evidence of a relationship between place-based characteristics and the distribution of heat-related mortality. These findings about extreme event mortality risk would not have been evident from a population-based analysis. Ongoing dialog between epidemiologists and social scientists can help to bring place into the arena of extreme event research and to increase understanding of the role of place in risk.

Health Status Indicators↗
PubMed2003

Adjusting irrigation abstraction to minimise the impact on stream flow in the East of Scotland.

Abstractions of surface and groundwater for irrigation in Scotland are currently subject to control in only two small catchments. Under the terms of the EU Water Framework Directive, it will be necessary to introduce new legislation to control abstractions elsewhere. To help in the development of appropriate policy for Scotland a study has been carried out to examine the significance of irrigation and the effectiveness of different types of control strategies in terms of the economics of potato cropping and stream hydrology in Scotland. This paper presents the findings of the hydrological study and highlights some of the spatial and temporal issues that need to be considered in the selection of control mechanisms, if they are to be successful in achieving objectives for environmental improvement. The study was focussed on two catchments in the east of Scotland, the Tyne and West Peffer. The effectiveness of several different abstraction control strategies was examined to see how stream flows in the catchment would be modified by their implementation. The results of the study demonstrated that the West Peffer catchment in particular is significantly affected by irrigation abstractions. Control mechanisms based on allowable monthly abstraction volumes and flow-based abstraction bans would be of considerable help in restoring stream flows to their natural levels, but would modify the hydrological regime in slightly different ways. A spatial analysis of stream flows demonstrated that implementation of controls based on a single monitoring point may be ineffective at maintaining acceptable levels of flow throughout the catchment and that this may require a tighter control at the monitoring point.

Agriculture↗
PubMed2003

Tracking of multiple sound sources defined by interaural time differences: brain potential evidence in humans.

Among other cues, interaural time differences (ITD) can be used to compute the location of a sound. To investigate whether ITD can be used for the preattentive detection of sounds coming from a different location than standard sounds (P=0.7, no ITD), left and right 'far' (900 micros ITD, 80 degrees excentricity) and 'near ' (300 micros ITD, 30 degrees ) deviant stimuli (each deviant P=0.075) were presented via headphones. While 15 young healthy subjects passively listened to these sequences, the mismatch negativity (MMN) of the event-related potential was obtained for the deviant sounds. MMN was reliable for all four deviants but larger for the far-lateralized sounds. Moreover, MMN was larger contralateral to the location of the deviant. This indicates a role of preattentive mechanisms in the spatial analysis of auditory scenes.

Adult↗
PubMed2002

Serological cross-sectional survey of psoroptic sheep scab in Switzerland.

Sheep scab, caused by the mite Psoroptes ovis, is a notifiable disease in Switzerland. Mandatory prophylactic treatments are carried out in spring for all sheep grazing on common alpine pastures. Despite these strict control measures the number of outbreaks has been increasing in recent years, raising questions on the spread of this epizootic disease. To improve the traditional microscopic diagnosis, we developed an ELISA for the specific determination of antibodies against psoroptic antigens with sensitivity and specificity of 93.7 and 96.5%, respectively. Using this test, a serum bank, representative of the sheep population in Switzerland (approximately 15% of registered sheep flocks, randomly chosen, collected between February and May 1998), was screened. The prevalence using 16,404 sera was 10.4, and 11.9% of the 2083 flocks were diagnosed as positive. Additionally, there was a significant increase found for mean seropositivity relative to the flock size (P<0.001, linear regression). Therefore, larger flocks had a higher risk of sheep scab, which may be caused by more frequent animal movement. Spatial analysis of the results revealed a region with significantly higher risk (relative risk = 3.5, P<0.001) of seropositivity, where no cases have officially been notified in the period between 1997 and 1999. The next goal is to establish an efficient control strategy based on serological monitoring of the total sheep population.

Animals↗
PubMed2002

Tracking the mind's image in the brain I: time-resolved fMRI during visuospatial mental imagery.

Mental imagery, the generation and manipulation of mental representations in the absence of sensory stimulation, is a core element of numerous cognitive processes. We investigate the cortical mechanisms underlying imagery and spatial analysis in the visual domain using event-related functional magnetic resonance imaging during the mental clock task. The time-resolved analysis of cortical activation from auditory perception to motor response reveals a sequential activation of the left and right posterior parietal cortex, suggesting that these regions perform distinct functions in this imagery task. This is confirmed by a trial-by-trial analysis of correlations between reaction time and onset, width, and amplitude of the hemodynamic response. These findings pose neurophysiological constraints on cognitive models of mental imagery.

Acoustic Stimulation↗
PubMed2002

Interactions between MHC molecules and co-receptors of the TCR.

Genetic experiments indicate similarity between binding sites on MHC class I (MHCI) for CD8 and on MHCII for CD4, but the crystal structures of CD8/MHCI and CD4/MHCII complexes suggest critical differences between the interfaces in the two complexes. Biophysical analyses using ectodomains of co-receptors and MHC molecules demonstrate extremely fast kinetics and low-affinity interactions. Experiments with soluble multimeric MHC ligands suggest that CD4 and CD8 may differ in the mechanisms by which they promote the formation of ternary TCR/MHC/co-receptor complexes. Co-receptor-influenced duration of TCR signaling controls thymocyte selection. In naïve T cells, CD4/MHCII interactions may promote T-cell survival. Temporal and spatial analysis of TCR and CD4 co-clustering in the immunological synapse suggests that CD4 recruitment is regulated by the half-life of the initial TCR/MHCII complex. Diverse experimental systems have yielded conflicting data that have helped to formulate revised mechanistic models of co-receptor function.

Animals↗
PubMedDate not supplied

[The descriptive epidemiology of suicide in Tuscany, 1988-2002].

AIMS: To describe the epidemiology of Suicide in Tuscany according to the triad of time, place and person. METHODS: The 4,764 cases of suicide, defined according to categories E950-E959 of ICD-9 in Tuscany over the period 1988-2002, were obtained from the Tuscan Mortality Register. Mortality indicators were calculated and analyzed. The spatial analysis was carried out by deriving Empirical Bayes Estimates for the 287 municipalities. RESULTS: The crude mortality rate in the 2000-2002 is 7.8 per 100000 population (male: 12.4; female: 3.5). The age-standardized rate in the 2000-2002 is 5.8 per 100,000 population (male: 9.6; female: 2.6). The highest risk for suicide, especially in the case of males, are concentrated in the southern hinterland Tuscany, in a cluster of rural municipalities that represent the old mining district of Tuscany. The SMRs according to residential municipality (population per square kilometre), confirm a greater risk of suicide for males residing in rural communities. CONCLUSIONS: The cluster of excessive mortality from suicide in Southern Tuscany could be the consequence of social determinants, related to the urban and social crisis following agriculture decline and mine closure.

Bayes Theorem↗
PubMed2001

Effects of land use and municipal wastewater treatment changes on stream water quality.

This study was undertaken to analyze the quantitative impact of a municipal wastewater treatment operation on the long-term water quality changes in a tributary of the Han-river, Korea from 1994 to 1999. Changes of land use pattern in the study watershed are quantitatively analyzed on the basis of land use maps that were created by classifying Landsat TM images acquired in April 1994 and March 1999. During this period, the average increase of land use area in terms of residence, cultivation, and barren was 5.89, 0.13, and 0.12%, respectively, and the corresponding decrease in water and forest area was 0.21 and 0.16%. The annual average reductions of BOD, T-N, and T-P by the municipal wastewater treatment operation were about 89, 11 and 27%, respectively. Spatial analysis of the pollution discharge from watershed was undertaken using a geographic information system (GIS) based model. A clear reciprocal relationship was found between the basin-wide self-purification coefficient and the watershed form ratio excepting a catchment area with water drain facilities. Due to land use changes over the five year study period, water quality change in terms of BOD, T-N, and T-P were (+)1.04 mg l(-1) (corresponding to a 13.7% increase of pollution), (+)0.58 mgl(-1) (10.0% increase), and (-)0.01 mg l(-1) (1.6% decrease). On the other hand, the effect of water quality restoration assessed by outward appearance during the same period was about 67.6, 39, and 36.5%, respectively. Consequently, it is understood that total stream water quality recovery in terms of BOD, T-N, and T-P were 81.3, 49.0, and 38.1% respectively, and that this included a negative contribution resulting from increased land use and a positive contribution due to the wastewater treatment operation at Inchon.

Agriculture↗
PubMedDate not supplied

Sharing the geo-referenced results of climate change impact research.

The Prairie Adaptation Research Collaborative (PARC) has implemented an Internet Map Server (IMS) at the PARC web site (www.parc.ca) to 1) disseminate the geo-referenced results of PARC sponsored research on climate change impacts and adaptation, and 2) address data, information and knowledge management within the PARC network of researchers and partners. PARC facilitates interdisciplinary research on adaptation to the impacts of climate change in the Canadian Prairie Provinces. The web site is intended as a platform for sharing information and encouraging discussion of climate change impacts and adaptation. The IMS enables scientists and stakeholders to apply simple climate change scenarios to geo-referenced biophysical and social data, and dynamically create maps that display the geographic distribution of potential impacts of climate change. With a limited capacity for spatial analysis, most geo-processing and the climate impact modeling is done offline within a GIS environment. The IMS will serve the output from climate impact models, such that the model results can be customized by the web site user and be most readily applied to the planning and analysis of adaptation strategies.

Climate↗