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PubMed2003

Specificity in the settlement -- modifying response of bacterial biofilms towards zoospores of the marine alga Enteromorpha.

Previous studies have shown that the rate of settlement of zoospores of the green alga Enteromorpha is stimulated by mixed microbial biofilms and that the number of zoospores settling is positively correlated with the number of bacteria in the biofilm. In the present study the specificity of this relationship has been investigated. Ninety-nine strains of marine bacteria were isolated from natural biofilms on rocks and the surface of Enteromorpha plants. Isolates were screened by denaturing gradient gel electrophoresis (DGGE) to eliminate replicates and 16S rDNA sequencing identified a total of 37 unique strains. Phylogenetic analysis revealed that the isolated bacterial strains belonged to three groups gamma-Proteobacteria (28 strains), Cytophaga-Flavobacteria-Bacteroid (CFB) group (six strains) and alpha-Proteobacteria (one strain). Two strains were unassigned, showing < 93% sequence similarity with the CFB group. The main genera of gamma-Proteobacteria were Pseudoalteromonas (14 strains), Vibrio (five strains), Shewanella (five strains), Halomonas (three strains) and Pseudomonas (one strain). Spore settlement experiments were conducted on single-species biofilms, developed for different times on glass slides. The effect of correcting spore settlement values for biofilm density was evaluated. Results showed that the effect of bacterial strains on spore settlement was strain- but not taxon-specific and activity varied with the age of the biofilm. However, most of the strains belonging to genera Vibrio and Shewanella showed stimulation. Pseudoalteromonas strains showed a range of effects including settlement-inhibiting, paralysing and lysing activities. Spatial analysis of bacterial density in the presence and absence of spores revealed a range of different types of association between spores and bacteria. Overall, the spatial association between spores and bacteria appears to be independent of the overall quantitative influence of bacterial cells on spore settlement.

Animals↗
PubMed1980

Dental health and the application of geographical methodology.

Reorganisation of dental services in Britain gives new opportunities for planning. Geographical methodology provides new techniques. An elementary spatial analysis of variations in dental health in Newcastle Area Health Authority (Teaching) shows that dental health varies with availability and access to treatment facilities. Opposite types of geographical distribution of community (School) and general dental services are illustrated showing location biases for each type of service. The evaluation of the spatial distribution of dental services is shown to be basic to planning and a key to improved dental health.

Catchment Area, Health↗
PubMed2005

Significant genetic differentiation between Poland and Germany follows present-day political borders, as revealed by Y-chromosome analysis.

To test for human population substructure and to investigate human population history we have analysed Y-chromosome diversity using seven microsatellites (Y-STRs) and ten binary markers (Y-SNPs) in samples from eight regionally distributed populations from Poland (n = 913) and 11 from Germany (n = 1,215). Based on data from both Y-chromosome marker systems, which we found to be highly correlated (r = 0.96), and using spatial analysis of the molecular variance (SAMOVA), we revealed statistically significant support for two groups of populations: (1) all Polish populations and (2) all German populations. By means of analysis of the molecular variance (AMOVA) we observed a large and statistically significant proportion of 14% (for Y-SNPs) and 15% (for Y-STRs) of the respective total genetic variation being explained between both countries. The same population differentiation was detected using Monmonier's algorithm, with a resulting genetic border between Poland and Germany that closely resembles the course of the political border between both countries. The observed genetic differentiation was mainly, but not exclusively, due to the frequency distribution of two Y-SNP haplogroups and their associated Y-STR haplotypes: R1a1*, most frequent in Poland, and R1*(xR1a1), most frequent in Germany. We suggest here that the pronounced population differentiation between the two geographically neighbouring countries, Poland and Germany, is the consequence of very recent events in human population history, namely the forced human resettlement of many millions of Germans and Poles during and, especially, shortly after World War II. In addition, our findings have consequences for the forensic application of Y-chromosome markers, strongly supporting the implementation of population substructure into forensic Y chromosome databases, and also for genetic association studies.

Chromosomes, Human, Y↗
PubMed2001

Characterization of enzootic foci of Venezuelan equine encephalitis virus in western Venezuela.

The distribution of the sylvatic subtype ID Venezuelan equine encephalitis (VEE) viruses in the lowland tropical forests of western Venezuela was investigated using remote sensing and geographic information system technologies. Landsat 5 Thematic Mapper satellite imagery was used to study the reflectance patterns of VEE endemic foci and to identify other locations with similar reflectance patterns. Enzootic VEE virus variants isolated during this study are the closest genetic relatives of the epizootic viruses that emerged in western Venezuela during 1992-1993. VEE virus surveillance was conducted by exposing sentinel hamsters to mosquito bites and trapping wild vertebrates in seven forests identified and located by means of the satellite image. We isolated VEE viruses from 48 of a total of 1,363 sentinel hamsters in two of the forests on six occasions, in both dry and wet seasons. None of the 12 small vertebrates captured in 8,190 trap-nights showed signs of previous VEE virus infection. The satellite image was classified into 13 validated classes of land use/vegetation using unsupervised and supervised techniques. Data derived from the image consisted of the raw digital values of near- and mid-infrared bands 4, 5, and 7, derived Tasseled Cap indices of wetness, greenness, and brightness, and the Normalized Difference Vegetation Index. Digitized maps provided ancillary data of elevation and soil geomorphology. Image enhancement was applied using Principal Component Analysis. A digital layer of roads together with georeferenced images was used to locate the study sites. A cluster analysis using the above data revealed two main groups of dense forests separated by spectral properties, altitude, and soil geomorphology. Virus was isolated more frequently from the forest type identified on flat flood plains of main rivers rather than the forest type found on the rolling hills of the study area. The spatial analysis suggests that mosquitoes carrying the enzootic viruses would reach 82-97% of the total land area by flying only 1-3 km from forests. We hypothesize that humans within that area are at risk of severe disease caused by enzootic ID VEE viruses. By contrast, equines could actually become naturally vaccinated, thus preventing the local emergence of epizootic IC VEE virus strains and protecting humans indirectly.

Animals↗
PubMed2005

Geographic bias related to geocoding in epidemiologic studies.

BACKGROUND: This article describes geographic bias in GIS analyses with unrepresentative data owing to missing geocodes, using as an example a spatial analysis of prostate cancer incidence among whites and African Americans in Virginia, 1990-1999. Statistical tests for clustering were performed and such clusters mapped. The patterns of missing census tract identifiers for the cases were examined by generalized linear regression models. RESULTS: The county of residency for all cases was known, and 26,338 (74%) of these cases were geocoded successfully to census tracts. Cluster maps showed patterns that appeared markedly different, depending upon whether one used all cases or those geocoded to the census tract. Multivariate regression analysis showed that, in the most rural counties (where the missing data were concentrated), the percent of a county's population over age 64 and with less than a high school education were both independently associated with a higher percent of missing geocodes. CONCLUSION: We found statistically significant pattern differences resulting from spatially non-random differences in geocoding completeness across Virginia. Appropriate interpretation of maps, therefore, requires an understanding of this phenomenon, which we call "cartographic confounding."

Journal Article↗
PubMedDate not supplied

Local-scale variation in malaria infection amongst rural Gambian children estimated by satellite remote sensing.

We investigated local-scale variation in malaria transmission and infection in children within a continuous landscape by retrospective spatial analysis of entomological and clinical data collected during 1988 and 1989 in The Gambia, West Africa. Parasite prevalence was negatively correlated with vector abundance and exposure to malaria parasites in 10 villages where entomological surveillance had been carried out. Variation in bednet use did not explain this finding. Mosquito-breeding habitat was retrospectively mapped using 20-m spatial resolution multispectral SPOT satellite imagery from 1988. From these data we estimated by linear regression the risk of exposure to malaria parasites in 26 villages where clinical surveys of children had been made. As exposure increased, so did parasite prevalence; but at higher levels of exposure, parasite prevalence declined. Our findings demonstrate marked differences in exposure to malaria in villages over distances of less than 2 km from mosquito breeding sites and suggest that there are also large differences in immunity between neighbouring settlements.

Animals↗
PubMed2003

A new method for analysis of motion of carotid plaques from RF ultrasound images.

Motion of carotid artery plaques during the cardiac cycle may contribute to plaque disruption and embolism. We have developed a computerized method that objectively analyzes such motion from a sequence of ultrasound (US) radiofrequency (RF) images. A displacement vector map is obtained by 2-D correlation of local areas in consecutive images. From this map, motion dynamics can be quantified and presented as function of time, spatial (image) coordinates or as single numbers. Correct functionality has been verified on laboratory data. Applied to patient data, the method gives temporal results that correlate well with ECG data and the calculated peak systolic velocities of typically 10 mm/s agree well with values reported in the literature. The spatial analysis demonstrates that different plaque regions may exhibit different motion patterns that may cause internal stress, leading to fissures and plaque disruption. Thus, the motion analysis method may provide new and important information about the plaque characteristics and the prospective risk of cerebrovascular events.

Aged↗
PubMed2004

Geographic information systems (GIS) analysis of under five mortality in Alexandria.

The aim of this study is to analyze under five mortality in Alexandria using GIS. A retrospective study is conducted to collect recorded data about under-5 deaths and live births from 1996 to 2001 from Health Information Center and CAPMAS in Alexandria. Data used include sociodemographic and environmental conditions in Alexandria sub-districts digitized maps of Alexandria districts and sub-districts (scale 1 50 0000). The spatial analysis of the geographical database revealed that there is regional variations of U5MR. GIS overlay analysis indicates that there is no association between low sociodemographic and environmental indicators and deaths caused by perinatal conditions and congenital malformations. The cause of death most associated with low sociodemographic and environmental indicators are found to be ARI and external causes of mortality. This is quietly evident in Amria and Borg Al Arab sub-districts.

Cause of Death↗
PubMed1995

[The analysis of the spatial aggregation of health events using risk surface density estimation methods].

Methods for the analysis of the spatial aggregation of health events has received growing attention under the pressure of public opinion concern and as tools for the identification of potential risk sources, for monitoring relevant geographical areas and, finally, for public health decisions. The development of statistical methods for the detection and localization of spatial clusters has mainly concerned individual data. This paper is aimed at describing one of the methods proposed for the identification of clusters in the case of information at individual level and at presenting its extension to grouped data. This method, the surface density estimation method using the Kernel approach, offers remarkable advantages in terms of simplicity of implementation and flexibility, this latter being an extremely important characteristic in the case of exploratory analyses. For exemplification purposes, the density estimation method has been applied to individual data concerning the spatial distribution of cerebral tumors in Campi Bisenzio (FI) and to the distribution of gastric cancer mortality in the municipalities around Arezzo and Pesaro.

Brain Neoplasms↗
PubMed2005

Responses of V1 neurons to two-dimensional hermite functions.

Neurons in primary visual cortex are widely considered to be oriented filters or energy detectors that perform one-dimensional feature analysis. The main deviations from this picture are generally thought to include gain controls and modulatory influences. Here we investigate receptive field (RF) properties of single neurons with localized two-dimensional stimuli, the two-dimensional Hermite functions (TDHs). TDHs can be grouped into distinct complete orthonormal bases that are matched in contrast energy, spatial extent, and spatial frequency content but differ in two-dimensional form, and thus can be used to probe spatially specific nonlinearities. Here we use two such bases: Cartesian TDHs, which resemble vignetted gratings and checkerboards, and polar TDHs, which resemble vignetted annuli and dartboards. Of 63 isolated units, 51 responded to TDH stimuli. In 37/51 units, we found significant differences in overall response size (21/51) or apparent RF shape (28/51) that depended on which basis set was used. Because of the properties of the TDH stimuli, these findings are inconsistent with simple feedforward nonlinearities and with many variants of energy models. Rather, they imply the presence of nonlinearities that are not local in either space or spatial frequency. Units showing these differences were present to a similar degree in cat and monkey, in simple and complex cells, and in supragranular, infragranular, and granular layers. We thus find a widely distributed neurophysiological substrate for two-dimensional spatial analysis at the earliest stages of cortical processing. Moreover, the population pattern of tuning to TDH functions suggests that V1 neurons sample not only orientations, but a larger space of two-dimensional form, in an even-handed manner.

Action Potentials↗
PubMed2004

Participation of primary motor cortical neurons in a distributed network during maze solution: representation of spatial parameters and time-course comparison with parietal area 7a.

Traditionally, primary motor cortex (M1) has been thought to be involved solely in planning and generating movements. Recent evidence suggests that the arm area of M1 plays a role in other functions, such as the representation of serial order (Pellizzer et al. 1995, Science 269:702-705; Carpenter et al. 1999, Science 283:1752-1757) and spatial processing (Georgopoulos et al. 1989, Science 243:234-236). Previous studies of such cognitive processes have used tasks in which a directed arm movement was required, raising a question as to whether this brain area is involved in cognitive processing per se, or whether such cognitive signals may be gated into the arm area of M1 only when arm movements are required. To study this question, we developed a task that required a spatial analysis of a complex visual stimulus, but required no arm movement as a response. In this task, monkeys were shown an octagonal maze. After an imposed delay of 2 to 2.5 s, they indicated whether a path that emanated from the center of the maze exited at the perimeter (exit maze) or terminated within the maze (no-exit maze) by pressing a pedal with their left or right foot, respectively. We recorded from 785 cells from the arm area of M1 from two monkeys during the delay period of the maze task. We found that cell activity was influenced by both the exit status and the direction of the path, beginning soon after the maze was displayed. This activity was not related to the activation of arm muscles, suggesting that the directional signals observed represented abstract spatial aspects of maze processing. Finally, we compared maze-related activity of M1 neurons with those recorded from posterior parietal area 7a, reported previously (Crowe et al. 2004). Interestingly, cells from each area exhibited similar properties. Both the exit status and path direction were encoded by cells in M1 and 7a, although to different extents. An analysis of the time-course of the neural representation of these factors revealed that area 7a and M1 begin to encode these factors at the same time, suggesting these brain areas are part of a distributed system performing the spatial computations involved in maze solution.

Action Potentials↗
PubMed2004

Gene expression of periostin in the early stage of fracture healing detected by cDNA microarray analysis.

To comprehensively evaluate gene expression in the early stage of fracture healing, we used a cDNA microarray with 2304 cDNA clones derived from an oligo-capped mouse embryo library. Closed mid-diaphyseal fractures were created in mouse tibiae and expression profiles were analyzed 3 days after fracture. Six genes were up-regulated in comparison to those in unfractured bones and these included three genes previously identified but never shown to be present in fractures, periostin, calumenin, and FHL-1. Cloning of these genes has been completed but their expression pattern and function during fracture healing and bone formation remain to be elucidated. Up-regulation of the six genes was reconfirmed by semi-quantitative RT-PCR analysis. Spatial and temporal expression of one of the newly identified fracture-induced genes, periostin, was analyzed using in situ hybridization, because it displayed the highest up-regulation ratio. A signal for periostin was detected in undifferentiated mesenchymal cells and immature preosteoblastic cells in the periosteal tissues between days 3 and 14 after fracture. Northern analysis showed that periostin gene expression rapidly increased by day 3, reached a peak on day 7, and declined by day 14. These findings suggest that periostin is a specific marker for preosteoblasts and may play an important role in periosteal callus formation during the early stage of fracture healing.

Animals↗
PubMed2002

[Application of multifactor spatial composite model to predict transmission tendency of malaria at national level].

OBJECTIVE: To predict the transmission tendency of malaria at national level by application of geographic information system(GIS) technique. METHODS: With the assistance of ArcView 3.0 a software and its spatial analyst extension, the surface spatial analysis on three natural factors, namely, total growing degree days(TGDD), precipitation and relative humidity, were conducted individually. The map calculation was preformed based on the three factors' ratio of 5:3:2 resulted from the Delphi investigation. RESULTS: The individual maps and composition map of TGDD, precipitation and relative humidity were created, respectively, based on the spatial composite model, which were used to predict the transmission tendency of malaria at national level. CONCLUSION: The high risk areas for malaria transmission, predicted by the spatial composite model based on the multilayers of environmental factors, are correlated with the previous reports. This will, therefore, provide information for predicting malaria transmission by multiple factors in a larger area.

China↗
PubMed1995

Visual information processing: topography of brain electrical activity.

Multichannel recordings allow the non-invasive assessment of the electrical fields of the brain. Topographical analysis of EEG and EPs should not be restricted to the qualitative graphical display of maps at many time points instead of time series at many recording points. It is mandatory that quantitative methods are applied to EEG and evoked potential data in order to extract relevant information from such series of maps. For spontaneous EEG data the spatial analysis of frequency bands is of major interest while evoked potential fields are analyzed in terms of latencies and amplitudes of individual components. The computation of global field power, global dissimilarity as well as the location of potential maxima, minima or centroids enable a meaningful data reduction and the statistical evaluation of the effects of different experimental conditions and the comparison of various clinical populations. In a similar way multivariate statistical techniques may be employed in order to detect characteristic potential field configurations. Topographical methods to analyze brain electrical activity are illustrated with multichannel data evoked by localized visual stimuli and by stereoscopic stimulation as well as with evoked potential data obtained during perceptual learning experiments.

Brain↗
PubMed2003

Functional topography of the secondary somatosensory cortex for nonpainful and painful stimuli: an fMRI study.

The regional activity of the contralateral primary (SI) and the bilateral secondary (SII) somatosensory areas during median nerve stimulations at five intensity levels (ranging from nonpainful motor threshold to moderate pain) was studied by means of functional magnetic resonance imaging (fMRI). The aim was to characterize the functional topography of SII compared to SI as a function of the stimulus intensity. Results showed that the galvanic stimulation of the median nerve activated the contralateral SI at all stimulus intensities. When considered as a single region, SII was more strongly activated in the contralateral than in the ipsilateral hemisphere. When a finer spatial analysis of the SII responses was performed, the activity for the painful stimulation was localized more posteriorly compared to that for the nonpainful stimulation. This is the first report on such a SII segregation for transient galvanic stimulations. The activity (relative signal intensity) of this posterior area increased with the increase of the stimulus intensity. These results suggest a spatial segregation of the neural populations that process signals conveyed by dorsal column-medial lemniscus (nonpainful signals) and neospinothalamic (painful signals) pathways. Further fMRI experiments should evaluate the functional properties of these two SII subregions during tasks involving sensorimotor integration, learning, and memory demands.

Adult↗
PubMed2004

Functional topography of the secondary somatosensory cortex for nonpainful and painful stimulation of median and tibial nerve: an fMRI study.

Functional magnetic resonance imaging (fMRI) was used to study the cortical activity of the bilateral secondary somatosensory cortex (SII) during nonpainful (motor threshold) and painful electrical stimulation of median and tibial nerves. fMRI recordings were performed in eight normal young adults. The aim was at evaluating the working hypothesis of a spatial segregation of nonpainful and painful populations not only in the "hand" representation of SII [Ferretti, A., Babiloni, C., Del Gratta, C., Caulo, M., Tartaro, A., Bonomo, L., Rossini, P.M., Romani, G.L., 2003. Functional topography of the secondary somatosensory cortex for nonpainful and painful stimuli: an fMRI study. NeuroImage 20, 1625-1638.] but also in its "foot" representation. Results showed that, in both "hand" and "foot" representations of bilateral SII, the activity elicited by the painful stimulation was localized more posteriorly with respect to that elicited by the nonpainful stimulation. A fine spatial analysis of the SII responses revealed a clear somatotopic organization in the bilateral SII subregion especially reactive to the nonpainful stimuli (i.e., segregation of the hand and foot representations). In contrast, it was not possible to disentangle the "hand" and "foot" representations of SII for painful stimuli. These results extended to the SII "foot" representation previous evidence of a spatial segregation in the SII "hand" representation of subregions for the painful and nonpainful stimuli. Furthermore, they suggest that noxious information is not somatotopically represented in human bilateral SII, at least as inferred from fMRI data at 1.5 T.

Adult↗
PubMed2004

Influence of high-pass filtering on noncontact mapping and ablation of atrial tachycardias.

The aim of the study was to define the impact of different high-pass filter settings (HPF) on the accuracy of mapping of ectopic atrial tachycardias (EAT) using a noncontact mapping (NCM) system. In 20 patients with 22 EAT a noncontact probe was deployed in the right (n = 19) or in the left atrium (n = 3). The device enables interpolation and analysis of unipolar electrograms. It provides information on focus localization and signal morphology. These parameters were compared in different HPF of 0.5 Hz, 2 Hz, 8 Hz, and 16 Hz. The NCM signal morphology was preserved at all HPF. An initial negative deflection recorded by NCM system showed a positive predictive value of 93% regarding the ablation success. The deviation (spatial disparity) between visualized focus origin and successful ablation site was 6.9 +/- 5.4 mm. Between two consecutive filter settings, the focus shift was more pronounced between 0.5 and 2 Hz (5.4 +/- 4.5 mm) compared to a setting between 8 and 16 Hz (2.9 +/- 2.9 mm; P < 0.05). Successful ablation was achieved in 15/18 right atrial tachycardias (83%) and in 2/3 left atrial arrhythmias. Different HPF influence NCM spatial analysis of EAT. However, a small variability in foci localization does not impact final ablation results.

Body Surface Potential Mapping↗
PubMed2000

Spatial scale of visual analysis for vernier acuity does not vary over time.

The visual system filters spatial pattern through a range of narrowly tuned spatial mechanisms, but the rules by which the outputs of these mechanisms are combined across time to extract precise geometrical information are not yet clear. One hypothesis is that spatial analysis shifts over time from coarse to finer spatial scales, in order to extract fine spatial information. An alternative hypothesis is that thresholds are determined by the signal-to-noise ratio within an optimal spatial scale. In this study, we measured vernier acuity across exposure duration for equally visible long lines and short lines and found no improvement in spatial precision with time. Using a simultaneous spatial-masking paradigm, we determined the active spatial scales at 100 and 1000 ms. The results show no significant changes in spatial scale, or in the size-range of active scales, for the two exposure durations. Furthermore, whereas vernier thresholds vary markedly with line contrast, we find only modest shifts in spatial scale. Taken together, our results suggest that for vernier acuity, spatial scale is selected very early, and that vernier thresholds are predominantly limited by signal strength within that spatial scale.

Humans↗