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PubMedDate not supplied

[Spatial distribution of sharks captures in the Pacific of Nicaragua and its relationship with several oceanographic variables].

Between August 1995 and August 1997 long line fishing techniques and a bathythermograph were used to correlate some physical variables with the spatial distribution of four shark species in 26 fishing cruises off the Nicaraguan Pacific Coast. They were the thresher (Alopias vulpinus), blue (Prionace glaucea), gray (Carcharhinus falciformis) and hammer (Sphyra lewini). All species concentrated in the southeastern Nicaraguan Pacific, at the seasonal upwelling area of Papagayo Gulf. The range of sea surface temperatures in which the sharks were captured was 25-28 degrees C. We could clearly associate this physical parameter with shark availability. The vertical distribution of the captured sharks suggests that they occupy termocline levels above the 15 degrees C isotherm. Although these species are oceanic, the blue shark was captured in ocean waters over the 1800 m isobar, while the grey and thresher sharks where close to the continental shelf. Body length in decreasing order are: thresher (210-290 cm, SN = 21), blue (60-240 cm, SN = 13) and gray (80-200 cm, SN = 17).

Animals↗
PubMed2001

Spatial distribution and subunit composition of GABA(A) receptors in the inferior olivary nucleus.

GABAergic inhibitory feedback from the cerebellum onto the inferior olivary (IO) nucleus plays an important role in olivo-cerebellar function. In this study we characterized the physiology, subunit composition, and spatial distribution of gamma-aminobutyric acid-A (GABA(A)) receptors in the IO nucleus. Using brain stem slices, we identified two types of IO neuron response to local pressure application of GABA, depending on the site of application: a slow desensitizing response at the soma and a fast desensitizing response at the dendrites. The dendritic response had a more negative reversal potential than did the somatic response, which confirmed their spatial origin. Both responses showed voltage dependence characterized by an abrupt decrease in conductance at negative potentials. Interestingly, this change in conductance occurred in the range of potentials wherein subthreshold membrane potential oscillations usually occur in IO neurons. Immunostaining IO sections with antibodies for GABA(A) receptor subunits alpha 1, alpha 2, alpha 3, alpha 5, beta 2/3, and gamma 2 and against the postsynaptic anchoring protein gephyrin complemented the electrophysiological observation by showing a differential distribution of GABA(A) receptor subtypes in IO neurons. A receptor complex containing alpha 2 beta 2/3 gamma 2 subunits is clustered with gephyrin at presumptive synaptic sites, predominantly on distal dendrites. In addition, diffuse alpha 3, beta 2/3, and gamma 2 subunit staining on somata and in the neuropil presumably represents extrasynaptic receptors. Combining electrophysiology with immunocytochemistry, we concluded that alpha 2 beta 2/3 gamma 2 synaptic receptors generated the fast desensitizing (dendritic) response at synaptic sites whereas the slow desensitizing (somatic) response was generated by extrasynaptic alpha 3 beta 2/3 gamma 2 receptors.

Animals↗
PubMed1988

[Spatial distribution and activity of excited neurons after penicillin administration to the nucleus gigantocellularis].

The central part of the nucleus reticularis gigantocellularis was examined in experiments on white anesthetized rats by microelectrodes in the constant stereotaxic coordinates before and after penicillin microinjection. It has been established that normal spatial distribution of gigantocellular neurons was characterized by irregular disposition of the active neurons, i.e. most of them were observed in caudo-medial and central regions. Penicillin microinjection produced enhancement of the number of excited neurons and spatial redistribution of the density of active neurons in caudo-lateral and ventral regions. Correlation changes between three main types of neurons were found in nonsequential interval histograms (unimodal, bimodal and exponential).

Animals↗
PubMed2006

Spatial distribution and orientation of dermatan sulfate in human medial collateral ligament.

The proteoglycan decorin and its associated glycosaminoglycan (GAG), dermatan sulfate (DS), regulate collagen fibril formation, control fibril diameter, and have been suggested to contribute to the mechanical stability and material properties of connective tissues. The spatial distribution and orientation of DS within the tissue are relevant to these mechanical roles, but measurements of length and orientation from 2D transmission electron microscopy (TEM) are prone to errors from projection. The objectives of this study were to construct a 3D geometric model of DS GAGs and collagen fibrils, and to use the model to interpret TEM measurements of the spatial orientation and length of DS GAGs in the medial collateral ligament of the human knee. DS was distinguished from other sulfated GAGs by treating tissue with chondroitinase B, an enzyme that selectively degrades DS. An image processing pipeline was developed to analyze the TEM micrographs. The 3D model of collagen and GAGs quantified the projection error in the 2D TEM measurements. Model predictions of 3D GAG orientation were highly sensitive to the assumed GAG length distribution, with the baseline input distribution of 69+/-23 nm providing the best predictions of the angle measurements from TEM micrographs. The corresponding orientation distribution for DS GAGs was maximal at orientations orthogonal to the collagen fibrils, tapering to near zero with axial alignment. Sulfated GAGs that remained after chondroitinase B treatment were preferentially aligned along the collagen fibril. DS therefore appears more likely to bridge the interfibrillar gap than non-DS GAGs. In addition to providing quantitative data for DS GAG length and orientation in the human MCL, this study demonstrates how a 3D geometric model can be used to provide a priori information for interpretation of geometric measurements from 2D micrographs.

Chondroitinases and Chondroitin Lyases↗
PubMed2005

Factors controlling spatial distribution of soil acidification and Al forms in forest soils.

Soil acidification and Al release in forest soils is controlled by a number of factors, like acid deposition, forest type, parent rock, altitude, etc. This paper studies the principal stand factors affecting spatial distribution of the content of KCl-extractable Al (Al(KCl), mainly exchangeable), Na4P2O7-extractable Al (Al(Na4P2O7), mainly organically bound), and other soil characteristics related to acidification in surface organic (O) and subsurface mineral (B) horizons in the Jizera Mountains region. Geostatistical methods were exploited. The highest Al(KCl) contents in the O horizons were related to high S and N content, low pH and low Ca and Mg content in soil. Liming decreased Al(KCl) contents in the O horizons. Al(Na4P2O7) in the O horizons was more abundant under spruce than under beech; in both horizons it was increased on the immission clear-cut areas populated by grass. Surface horizons are more sensitive to external influence (acid deposition, liming) and their spatial variation is stronger. In the mineral horizons, the effect of pedogenetic processes is more important. The effect of stand factors on Al behaviour is complex and often indirect, mediated for example by organic matter or soil reaction. It is difficult to clearly distinguish the effects of the particular factors.

Journal Article↗
PubMed2000

Difference spatial distribution function analysis of aqueous solutions. II. Hydration structures of dimethyl ether, 180 degrees ethyl methyl ether and 0 degree ethyl methyl ether solutions.

Monte Carlo simulations are systematically presented to demonstrate the influence of the hydrophobic group's steric bulk on hydration structure. We have simulated a dimethyl ether (DME), two conformations for ethyl methyl ether (0 degree EME and 180 degrees EME), and 0 degree ethanol solutions. Spatial distribution function (SDF), goo(x,y,z) and difference SDF (DSDF), delta goo(x,y,z), obtained from MC simulation in an infinitely dilute aqueous solution of ether show the three-dimensional probability of an atom-atom pair distribution between solute and solvent atoms. Based on the results of SDF in an infinitely dilute aqueous solution of ether, the distribution of hydration water molecules can be divided into hydrogen acceptor (HA) and hydrophobic hydration (HH), regions, and the spatial orientation of the hydrogen-bonded water in the HA region is found to form a triple-layer structure, as it does in alcohol solutions. From the results of an analysis of the DSDF delta goo(x,y,z) between the SDFs of EME and DME, it is apparent that the distribution changes of hydration water molecules in ether solutions are essentially similar to those in the alcohol solutions. Further, we show that the hydration water molecules are distributed mainly in the stable area in the binding energy's (BE) contour maps for each region.

Algorithms↗
PubMed2005

[Spatial distribution of Anopheles pseudopunctipennis in the Yungas de Salta rainforest, Argentina].

OBJECTIVE: To compare the abundance of Anopheles pseudopunctipennis and other anopheline mosquitoes in three different wild areas, modified by human activities, and to verify how environmental differences affect the spatial distribution of these mosquitoes. METHODS: Samples were collected monthly from December 2001 to December 2002 in Yungas de Salta, Argentina. CO2 -baited CDC light traps were placed at each sample site (forest, transition area and peridomiciliary area). In the peridomiciliary area, two agents also suctioned mosquitoes from house walls. Species diversity and abundance indices were estimated and the study sample sites were compared by ANOVA, cosine calculations and cluster analyses. RESULTS: Anopheles pseudopunctipennis was the most abundant species. An. argyritarsis, An. nuneztovari, An. rangeli and An. strodei were also collected. Except for An. nuneztovari that was not captured in the peridomiciliary area, the other species were collected in the three different environments. There were no differences in the diversity indices and between sample sites. However, the cluster analysis showed the transition area to be more abundant for all species. CONCLUSIONS: The highest abundance of species was found in the transition area, which, besides the peridomiciliary area, is the main area of risk for malarial transmission.

Animals↗
PubMed2004

Base line prevalence and spatial distribution of Echinococcus multilocularis in a newly recognized endemic area in the Netherlands.

The base line prevalence of Echinococcus multilocularis in foxes was determined in the eastern part of the province of Groningen in the Netherlands adjacent to the German border. This region has been identified in a previous study in 1998 as one of the westernmost border areas of E. multilocularis. Base line prevalence data are important for a better insight in the possible spread of the parasite and its changes in time. As fox feces containing E. multilocularis eggs are an important source for human exposure this base line prevalence is also an indicator for the potential risk for public health. The base line prevalence was estimated at 9.4% (95% CI: 5.2-16.5%). These results confirm previous findings of E. multilocularis in the same region. The spatial distribution of the infected foxes has been analyzed as a spatial gradient using a logistic model. The prevalence appeared to change strongest in east-western direction and was highest near the German border, adjacent to a German endemic area. These results suggest that the border areas in the Netherlands are the most margin of E. multilocularis territory.

Animals↗
PubMed2005

Statistical modelling of the spatial distribution of prevalence of Calicophoron daubneyi infection in sheep from central Italy.

Statistical modelling for Disease Mapping and Ecological Analysis is of particular importance in veterinary parasitology because environmental characteristics can affect parasite distribution. However, the main difficulties relate to the concentration of animal populations within farms, which contrasts to the study of wild animal populations. In the present paper we report the results of a cross-sectional coprological survey designed to study the presence and distribution of the rumen fluke Calicophoron daubneyi--which causes paramphistomosis, a snail borne disease--in pastured sheep living in the Latina province of central Italy. We show how techniques derived from human epidemiology can be used to study the spatial distribution of parasite infection in animals. We proposed a hierarchical Bayesian model with random terms for unstructured variability (heterogeneity) to account for local farm characteristics and spatially structure terms (clustering) to cope with medium-large scale environmental characteristics.

Animal Husbandry↗
PubMed1996

Persistence of multispecies host-parasitoid interactions in spatially distributed models with local dispersal.

Recent theoretical studies have shown that dispersal between neighbouring local populations can promote the persistence of interacting metapopulations, even when the local dynamics are unstable and the environment is uniform. This persistence is associated with striking and self-organized spatial patterns in the densities of the local populations. Here we extend previous work on spatially distributed host-parasitoid interactions to wider questions of community structure, by considering various three-species systems: two parasitoid species attacking a common host species; two host species attacked by a single parasitoid species; or a host-parasitoid-hyperparasitoid interaction. In each of these cases, multispecies coexistence of the total populations can occur, even though the local population dynamics are unstable. Furthermore, co-existence tends to be accompanied by some degree of persistent spatial segregation of the competing species, despite the completely uniform environment. At its most extreme, this results in one species being confined to small, relatively static, "islands" within the habitat, giving the appearance of isolated pockets of favourable habitat. That dynamics can impose and maintain such "self-organizing" spatial segregation of competing species, has interesting implications for understanding the local abundance of natural populations.

Animals↗
PubMed1990

Temporal and spatial distribution of type XII collagen in high cell density culture of periosteal-derived cells.

Periosteal-derived cells of young chicks have been reported to possess the potential to undergo terminal differentiation into osteogenic or chondrogenic phenotypes under high cell density culture conditions. In this culture, the temporal and spatial distribution of type XII collagen was immunocytochemically assessed using a monoclonal antibody. These high-density plated cells first formed a multilayer of fibroblast-like cells, in which type I and XII collagen were evenly distributed throughout the full thickness of the culture. With time, the top portion of the culture differentiated into bone tissue, while cells below this top layer differentiated into hypertrophic chondrocytes. In this transition, type XII collagen was temporally and spatially colocalized primarily with type I collagen: the top portion of bone layer was positive for both type I and XII collagens, whereas their staining intensity in the bottom portion decreased with time in culture. Using this antibody, type XII collagen was also found in developing embryonic chick tibiotarsus. These observations, taken together, suggest that type XII collagen production is a characteristic property of bone-forming cells.

Animals↗
PubMed2003

Spatial distribution of heavy metals in urban soils of Naples city (Italy).

Concentrations of surface and sub-surface soil Cu, Cr, Pb and Zn in the Naples city urban area were measured in 1999. Contourmaps were constructed to describe the metals spatial distribution. In the most contaminated soil samples, metals were speciated by means of the European Commission sequential extraction procedure. At twelve sites, Cu, Pb and Zn levels in soil were compared with those from a 1974 sampling. Many surface soils from the urban area as well as from the eastern industrial district contained levels of Cu, Pb and Zn that largely exceeded the limits (120, 100 and 150 mg kg(-l) for Cu, Pb and Zn, respectively) set for soils of public, residential and private areas by the Italian Ministry of Environment. Chromium values were never above regulatory limits(120 mg kg(-1)). Copper apparently accumulates in soils contiguous to railway lines and tramway. Cu and Cr existed in soil mainly inorganic forms (-68%), whereas Pb occurs essentially as residual mineral phases (77%). The considerable presence of Zn in the soluble, exchangeable and carbonate bound fraction (23%) suggests this element has high potential bioavailability and leachability through the soil. Concentrations of Cu, Pb and Zn have greatly increased since the 1974 sampling, with higher accumulation in soils from roadside fields.

Chemical Fractionation↗
PubMed2005

[Spatial distribution pattern of Larix chinensis population in Taibai Mt].

Larix chinensis is an endangered species only distributed in Qinling Mountains of China. It has a concentrated distribution in Taibai Mt., and plays an important role in environmental protection in the high altitude. After an investigation on fifteen 400 m2 plots, a comparative study on the spatial distribution pattern of L. chinensis population and its dynamics was made by the tests of discrete distribution pattern and aggregation intensity. The results showed that at different sampling areas, L. chinensis populations all performed the pattern of clustering distribution. As the sampling area increased, the congregating intensity of L. chinensis population appeared the pattern of high-->low-->high, but the highest congregation occurred in the areas of 100 m2 and 25 m2. The clustering intensity went down from low to high altitude, and the area with the highest clustering intensity occurred on that of 25 m2 in low altitude, 150 m2 in middle altitude, and 100 m2 in higher altitude. The clustering intensity in shade slope was higher than that in sunny slope, and the area with the highest clustering intensity was 100 m2 on shade slope, and 150 m2 on sunny slope. With the population age increased, the distribution pattern had a trend from clustering to random, the clustering intensity decreased somewhat, and the area with the highest clustering intensity was 150 m2 in young or old stages, and 100 m2 in middle stage. The distribution pattern of L. chinensis population was related to its ecological characteristics, community composition, and environmental factors. In situ conservation should be strengthened in the future. In lower altitude or on shade slope, the measurements of thinning no-aim in tree and shrub species should be taken; while in higher altitude area or sunny slope, thinning shrub species in patch form would be better for L. chinensis populations block renovating. The fostering area for L. chinensis populations should be suit to the area with the highest clustering intensity of populations.

China↗
PubMed2003

Spatial distribution of repolarization times in patients with coronary artery disease.

The potential clinical value of QT dispersion (QTd), a measure of the interlead range of QT interval duration in the surface 12-lead ECG, remains ambiguous. The aim of the study was the temporal and spatial analysis of the QT interval in healthy subjects and in patients with coronary artery disease (CAD) using magnetocardiography (MCG) and surface ECG. Standard 12-lead ECG and 37-channel MCG were performed in 20 healthy subjects, 23 patients with CAD without prior myocardial infarction (MI), 31 MI patients and 11 MI patients with ventricular tachycardia (VT). QTd was increased in CAD without MI compared to normals (ECG 46.1 +/- 6.0 vs 42.8 +/- 5.0, P < 0.05; MCG 66.8 +/- 20.3 vs 49.7 +/- 10.8, P < 0.01) and in VT compared to MI (ECG 66.8 +/- 16.5 vs 51.9 +/- 16.6, P < 0.05; MCG 93.6 +/- 29.6 vs 66.8 +/- 20.8, P < 0.005). In MCG, spatial distribution of QT intervals in patient groups differed from those in healthy subjects in three ways: (1) greater dispersion, (2) greater local variability, and (3) a change in overall pattern. This was quantified on the basis of smoothness indexes (SI). Normalized SI was higher in CAD without MI compared to normals (3.8 +/- 1.1 vs 2.7 +/- 0.6, P < 0.001) and in VT compared to MI (6.4 +/- 1.6 vs 4.2 +/- 1.4, P < 0.0005). For the normal-CAD comparison a sensitivity of 74% and a specificity of 80% was obtained, for MI-VT, 100% and 77%, respectively. The results suggest that examining the spatial interlead variability in multichannel MCG may aid in the initial identification of CAD patients with unimpaired left ventricular function and the identification of post-MI patients with augmented risk for VT.

Coronary Disease↗
PubMed2004

Modelling the spatial distribution of Echinococcus multilocularis infection in foxes.

Alveolar echinococcosis is a rare but fatal disease in humans and is caused by the fox tapeworm Echinococcus multilocularis. The densities of fox and grassland rodent populations and the interactions between them influence E. multilocularis transmission rates in Europe. Successful rabies control has caused fox populations and E. multilocularis prevalence rates to increase in many European countries. The potential increase of the infection pressure on the human population motivates the monitoring of the infection status of foxes over space and time. Detection of E. multilocularis antigen levels in fox faecal samples collected in the field might provide a pragmatic methodology for epidemiological surveillance of the infection status in wildlife hosts across large areas, as well as providing an indication of the spatial distribution of infected faeces contaminating the environment. In this paper, a spatial analysis of antigen levels detected in faeces collected in the Franche-Comté region of eastern France is presented. In Franche-Comté, rodent outbreaks have been observed to originate in areas rich in grassland. Spatial trends in fox infection levels were modelled here as a function of the composition ratio of grassland in the landscape derived from the CORINE land-cover map. Kriging models incorporating the grassland trend term were compared to a variety of models in which five alternative trend expressions were used: the alternative trend expressions included linear and quadratic polynomials on the x and y coordinates with and without a grassland term, and a constant mean model. Leave-one-out cross-validation indicated that the estimation errors of kriging with a trend models were significantly lower when the trend expression contained the grassland index term only. The relationship between observed and predicted antigen levels was strongest when the estimated range of autocorrelation was within the home range size of a single fox. The over-dispersion of E. multilocularis in foxes may therefore account for the majority of spatial autocorrelation locally, while regional trends can be successfully modelled as a function of habitat availability for intermediate hosts.

Animals↗
PubMed2004

[Statistical methods to analyze risk with spatial distribution patterns].

The development of the geographic information systems has improved the interest in analyzing the characteristics of the population, taking into account the place where they live. The health of the population, measured as the risk of morbidity or mortality, is conditioned by the variety of risk factors characteristic of the region which cannot be measured. Analysis of spatial models considers the dependence of the health indicators between close regions. This dependence is due to the existence of the risk factors that are not measured but are shared by the region. Thus, the spatial distribution of these indicators depends on the geographic pattern of these risk factors. In this study, some limitations of the standardized methods and the Poisson regression used to model the spatiality are discussed and the advantages of the spatial models are shown. The methodology is illustrated by the insulin-dependent diabetes type 1 data from Catalonia during 1989 and 1998.

Demography↗
PubMed1999

Development of an agar lift-DNA/DNA hybridization technique for use in visualization of the spatial distribution of Eubacteria on soil surfaces.

While microbial growth is well-understood in pure culture systems, less is known about growth in intact soil systems. The objective of this work was to develop a technique to allow visualization of the two-dimensional spatial distribution of bacterial growth on a homogenous soil surface. This technique is a two-step process wherein an agar lift is taken and analyzed using a universal gene probe. An agar lift is comprised of a thin layer of soil that is removed from a soil surface using an agar slab. The agar is incubated to allow for microbial growth, after which, colonies are transferred to a membrane for conventional bacterial colony DNA/DNA hybridization analysis. In this study, a eubacterial specific probe was used to demonstrate that growing bacterial populations on soil surfaces could be visualized. Results show that microbial growth and distribution was nonuniform across the soil surface. Spot supplementation of the soil with benzoate or glucose resulted in a localized microbial growth response. Since only growing colonies are detected, this technique should facilitate a greater understanding of the microbial distribution and its response to substrate addition in more heterogenous soil systems.

Agar↗