SEARCH · PubMed Health

Results for “Spatial Distribution”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 199 records · Page 11Linked to original sources

PubMed1994

Cartographic system for spatial distribution analysis of corneal endothelial cells.

A combined cartographic and morphometric endothelium analyser has been developed by integrating the HISTO 2000 histological imaging and analysis system with a prototype human corneal endothelium analyser. The complete system allows the elaboration and analysis of cartographies of corneal endothelial tissue, and hence the in vitro study of the spatial distribution of corneal endothelial cells, according to their regional morphometric characteristics (cell size and polygonality). The global cartographic reconstruction is obtained by sequential integration of the data analysed for each microscopic field. Subsequently, the location of each microscopically analysed field is referred to its real position on the histologic preparation by means of X-Y co-ordinates; both are provided by micrometric optoelectronic sensors installed on the optical microscope stage. Some cartographies of an excised human corneal keratoconus button in vitro are also presented. These cartographic images allow a macroscopic view of endothelial cells analysed microscopically. Parametric colour images show the spatial distribution of endothelial cells, according to their specific morphometric parameters, and exhibit the variability in size and cellular shape which depend on the analysed area.

Biomedical Engineering↗

PubMed1987

The spatial distribution of neurons and glia in human cortex based on the poisson distribution.

A method was devised that employs deviations from the Poisson distribution to analyze the spatial arrangement of neurons and glia in human cerebral cortex. A field of randomly distributed points equal in number of a sample field of neuronal or glial cells is generated by computer, and the proportion of cells in the sample field that are closer to the nearest neighboring cells than to the nearest randomly distributed point is determined. We call this proportion the "Poisson ratio." When the cells are randomly distributed, the Poisson ratio is equal to 0.5. If the Poisson ratio is less than 0.5, the cells are farther away from one another than a random distribution would predict (exclusionary pattern); if the Poisson ratio is greater than 0.5, the cells are closer to one another than a random distribution would predict (clustering). A simple nonparametric statistical test is used to determine the significance of differences in the ratios. This method was applied to samples of human cerebral cortex in order to test the hypothesis that patients with schizophrenic psychosis may have an altered pattern of neuronal clustering. The analysis revealed that there is no difference in the nearest-neighbor distribution of either neurons or glia between psychotic patients and controls. It was found, however, that there is a highly significant difference in the spatial distribution of neurons versus glia in human cerebral cortex. Neurons of layers II to VI in the human cortex show greater-than-expected distances among them and are distributed according to an exclusionary pattern, while neurons in layer I show a clustering pattern.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebral Cortex↗

PubMed1999

Spatial distribution of deoxymyoglobin in human muscle: an index of local tissue oxygenation.

The proximal histidyl NdeltaH signal of myoglobin is detectable in 1H NMR spectra of myocardial and skeletal muscle, and its intensity reflects the intracellular oxygenation. At 1.5 Tesla (T), the typical field strength of clinical magnetic resonance imaging (MRI) magnets, the paramagnetic relaxation contribution decreases sufficiently to permit the implementation of chemical shift imaging technique to map the spatial distribution of the deoxy Mb NdeltaH signal from human gastrocnemius muscle. One and two-dimensional chemical shift imaging experiments reveal clearly the localized deoxy Mb signal in muscle and consequently the spatial distribution of the cellular oxygenation. The results indicate the feasibility to assess the pO2 in tissue regions and to directly study the regulation of oxidative metabolism in human tissue.

Humans↗

PubMed2005

The concentration, gene expression, and spatial distribution of aggrecan in canine articular cartilage, meniscus, and anterior and posterior cruciate ligaments: a new molecular distinction between hyaline cartilage and fibrocartilage in the knee joint.

The concentration, spatial distribution, and gene expression of aggrecan in meniscus, articular cartilage, and the anterior and posterior cruciate ligaments (ACL and PCL) was determined in the knee joints of five mature dogs. An anti-serum against peptide sequences specific to the G1 domain of aggrecan was employed in competitive-inhibition ELISA of guanidine HCl extracts and immunofluorescence microscopy. Gene expression was determined by Taqman real-time PCR. The concentration of aggrecan in articular cartilage (240.1 +/- 32 nMol/g dry weight) was higher than that in meniscus (medial meniscus: 33.4 +/- 4.3 nMol/g) and ligaments (ACL: 6.8 +/- 0.9 nMol/g). Aggrecan was more concentrated in the inner than the outer zone of the meniscus. Aggrecan in meniscus showed an organized, spatial network, in contrast to its diffuse distribution in articular cartilage. Thus, differences in the concentration, gene expression, and spatial distribution of aggrecan constitute another molecular distinction between hyaline cartilage and fibrocartilage of the knee.

Aggrecans↗

PubMed2006

Phlebotominae spatial distribution asssociated with a focus of tegumentary leishmaniasis in Las Lomitas, Formosa, Argentina, 2002.

Las Lomitas, Formosa, Argentina, reported 96 cases of tegumentary leishmaniasis during 2002. The urban transmission was suggested although previous outbreaks were related with floods of the Bermejo river (BR) 50 km from the village. Phlebotomine collections were performed during March 2002 to define the spatial distribution of risk, together with satellite imaginery. The phlebotomine/trap obtained was 1679.5 in the southern BR shore, 1.1 in the periruban-rural environment and 2.3 in the northern Pilcomayo river marshes. Lutzomyia neivai was the prevalent species (91.1%) among the 2393 phlebotomine captured, and it was only found in the BR traps. The other species were L. migonei (7.9%), L. cortelezzii (0.9%), and Brumptomyia guimaraesi (0.1%). The satellite images analysis indicates that the fishing spots at the BR were significantly overflowed during the transmission peak, consistent with fishermen recollections. This spatial restricted flood might concentrate vectors, reservoirs, and humans in high places. Therefore, both the spatial distribution of vectors and the sensor remoting data suggests that in Las Lomitas area the higher transmission risk it is still related with the gallery forest of the BR, despite of the urban residence of the cases. The surveillance and control implications of these results are discussed.

Animals↗

PubMed1982

Polarizing microscopy of Picrosirius stained bone sections as a method for analysis of spatial distribution of collagen fibers by optical diffractometry.

Cross sections of femur diaphysis obtained from control and osteopetrotic rats were stained with hematoxylin-eosin (HE) and Picrosirius (SR). Analogous selected areas of bone sections photographed under a polarizing microscope were analysed by optical diffractometry. Since the collagen fibers are a good marker for the structure of bone tissue, their spatial distribution evaluated by optical diffractometry provides information on the tissue architecture. The Picrosirius staining technique enhances the natural birefringency of collagen fibers. Therefore, in the polarizing microscope, pictures of high contrast are obtained. This procedure, by increasing the amount of information in the image, increases the quantity of the data obtained by optical diffractometry in comparison with the HE staining method. The results obtained prove that SR staining combined with polarizing microscopy might be useful for optical diffractometry in analysis of the spatial distribution of collagen fibers in all connective tissues, where they could serve as markers of tissue architecture.

Animals↗

PubMed2004

Spatial distribution of bluetongue virus and its Culicoides vectors in Sicily.

During the recent Mediterranean epizootic of bluetongue, an extensive programme of serological and vector (Culicoides biting midges (Diptera: Ceratopogonidae)) surveillance was carried out across Sicily. This paper presents the analysis of 911 light trap catches collected at the times of peak Culicoides abundance (summer to autumn 2000-2002) in 269 sites, in order to produce detailed maps of the spatial distribution of the main European vector, Culicoides imicola Kieffer and that of potential novel vectors. Whereas C. imicola was found at only 12% of sites, potential novel vectors, Culicoides obsoletus group Meigen, Culicoides pulicaris Linnaeus and Culicoides newsteadi Austen were present at over 50% of sites. However, the spatial distribution of C. imicola showed the closest correspondence to that of the 2000 and 2001 bluetongue (BT) outbreaks and its presence and abundance were significant predictors of the probability of an outbreak, suggesting that it was the main vector during these years. Although C. imicola may have played a role in transmission in several sites near Paternó, it was absent from the majority of sites at which outbreaks occurred in 2002 and from all sites in the province of Messina. All three potential novel vectors were widespread across sites at which outbreaks occurred during 2002. Of these, C. newsteadi was an unlikely candidate, as it was significantly less prevalent in outbreak vs. non-outbreak sites in Messina. It is hypothesized that the yearly distribution and intensity of outbreaks is directly attributable to the distribution and abundance of the vectors involved in transmission during each year. When C. imicola operated as the main vector in 2000 and 2001, outbreaks were few in number and were restricted to coastal regions due to low abundance and prevalence of this species. In 2002, it is hypothesized that BTV transmission was handed over to more prevalent and abundant novel vector species, leading to numerous and widespread outbreaks and probably to overwintering of the virus between 2001 and 2002. Based on catch ranges in outbreak vs. non-outbreak sites, it is tentatively suggested that nightly catches of 400 or more C. obsoletus and 150 or more C. pulicaris allow BTV transmission at a site, and provide a strategy for a fuller examination of the relationship between BTV transmission and the abundance and distribution of different vector species.

Animals↗

PubMed2003

A climate-based model predicts the spatial distribution of the Lyme disease vector Ixodes scapularis in the United States.

An understanding of the spatial distribution of the black-legged tick, Ixodes scapularis, is a fundamental component in assessing human risk for Lyme disease in much of the United States. Although a county-level vector distribution map exists for the United States, its accuracy is limited by arbitrary categories of its reported presence. It is unknown whether reported positive areas can support established populations and whether negative areas are suitable for established populations. The steadily increasing range of I. scapularis in the United States suggests that all suitable habitats are not currently occupied. Therefore, we developed a spatially predictive logistic model for I. scapularis in the 48 conterminous states to improve the previous vector distribution map. We used ground-observed environmental data to predict the probability of established I. scapularis populations. The autologistic analysis showed that maximum, minimum, and mean temperatures as well as vapor pressure significantly contribute to population maintenance with an accuracy of 95% (p < 0.0001). A cutoff probability for habitat suitability was assessed by sensitivity analysis and was used to reclassify the previous distribution map. The spatially modeled relationship between I. scapularis presence and large-scale environmental data provides a robust suitability model that reveals essential environmental determinants of habitat suitability, predicts emerging areas of Lyme disease risk, and generates the future pattern of I. scapularis across the United States.

Animals↗

PubMed1998

Spatial distribution of nerve processes and beta-adrenoreceptors in the rat atrioventricular node.

Atrioventricular (AV) nodal conduction time is known to be modulated by the autonomic nervous system. The presence of numerous parasympathetic and sympathetic nerve fibres in association with conduction tissue in the heart is well authenticated. In this study, confocal microscopy was used to image the distribution of antibodies directed against the general neuronal marker PGP 9.5, tyrosine hydroxylase (TH), vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP) and beta1 and beta2-adrenoreceptors. Serial 12 microm sections of fresh frozen tissue taken from the frontal plane of the rat atrioventricular node, His bundle and bundle branches were processed for histology, acetylcholinesterase (AChE) activity and immunohistochemistry. It was found that the AV and ventricular conduction systems were more densely innervated than the atrial and ventricular myocardium as revealed by PGP 9.5 immunoreactivity. Furthermore, the transitional cell region was more densely innervated than the midnodal cell region, while spatial distribution of total innervation was uniform throughout all AV nodal regions. AChE-reactive nerve processes were found throughout the AV and ventricular conduction systems, the spatial distribution of which was nonuniform exhibiting a paucity of AChE-reactive nerve processes in the central midnodal cell region and a preponderance in the circumferential transitional cell region. TH-immunoreactivity was uniformly distributed throughout the AV and ventricular conduction systems including the central midnodal and circumferential transitional cell regions. Beta1-adrenoreceptors were found throughout the AV and ventricular conduction systems with a preponderance in the circumferential transitional cell region. Beta2-adrenoreceptors were localised predominantly in AV and ventricular conduction systems with a paucity of expression in the circumferential transitional cell region. These results demonstrate that the overall uniform distribution of total nerve processes is comprised of nonuniformly distributed subpopulations of parasympathetic and sympathetic nerve processes. The observation that the midnodal cell region exhibits a differential spatial pattern of parasympathetic and sympathetic innervation suggests multiple sites for modulation of impulse conduction within this region. Moreover, the localisation of beta2-ARs in the AV conduction system, with an absence of expression in the circumferential transitional cell layer, suggests that subtype-specific pharmacological agents may have distinct effects upon AV nodal conduction.

Acetylcholinesterase↗

PubMed1989

Spatial distribution of exercise-induced ST-segment depression and U-wave inversion in identifying the ischemic site in patients with coronary artery disease.

Eighty-seven unipolar electrocardiograms were simultaneously recorded before and after symptom-limited treadmill exercise in 75 patients with coronary artery narrowing (greater than equal to 70%) and without previous myocardial infarction. Body surface distributions of ST segment depression were divided into 3 types; upper, lower, and diffuse types. Body surface distributions of U-wave inversion were divided into 2 types; upper, and lower types. These distribution patterns were compared with the location of ischemia determined by T1-201 exercise myocardial perfusion imaging. For ST-segment depression, a considerable number of patients had diffuse-type ST depression, whether the site of ischemia was anterior (22/32, 69%), inferior (18/27, 67%) or both (5/5, 100%). However, upper-type ST depression was associated with anterior ischemia, and lower-type ST depression, with inferior ischemia. The sensitivity and specificity of the spatial distribution of ST depression in identifying the myocardial ischemic site were 27% and 95% for anterior ischemia. The sensitivity and specificity of the spatial distribution of St depression in identifying the myocardial ischemic site were 27% and 95% for anterior ischemia respectively, and 28% and 88% for inferior ischemia, respectively. The incidence of U-wave inversion was moderate (29/75, 39%), but the distribution pattern was specific for the site of ischemia; upper-type U inversion associated with anterior ischemia, and lower type with inferior ischemia. The sensitivity and specificity were 59% and 100% for anterior ischemia respectively, and 22% and 100% for inferior ischemia respectively. By a combination of ST-depression and U-inversion, the sensitivity and specificity were 78% and 95% for anterior ischemia, and 44% and 88% for inferior ischemia. Body surface electrocardiographic mapping provided important information in the non-invasive diagnosis of the site of myocardial ischemia.

Adult↗

PubMed1989

The spatial distribution of different elements in and on the foliage of Norway spruce growing in Switzerland.

This study centres around the question of how far the analysis of spruce needles (Picea abies L.) provides a suitable tool for detecting and describing large-scale air pollution, primarily by heavy metals, in Switzerland. For that reason 1637 spruce shoots from 833 sites were analysed, relationships between the different elements were calculated and maps of their spatial distribution drawn. The results show that needle analysis is a valid instrument for the identification of various air pollutants in Switzerland. The element best suited is Pb, followed by some others like Mo, Fe, Cd or S. The most heavily polluted areas in Switzerland are the midlands, and in the north and north-west. Their spatial distribution suggests that in these areas the indicator elements are derived from local sources.

Journal Article↗

PubMed2003

[Structures and spatial distribution patterns of dominant populations in Sycopsis sinensis community in Houhe Nature Reserve].

Based on the investigation data of 2 quadrats (1,600 m2 and 2,400 m2) in Houhe Nature Reserve, tree size class method was applied to analyze the structures of the dominant populations, and t-test of v/m ratio, mean crowing index, negative binomial parameter, patchiness index and Morisita index were applied to analyze the spatial distribution patterns of two dominant populations. The clumping degrees were also evaluated according to their size classes in different quadrats. The results showed that Sycopsis sinensis population was a declining population, dominated by IV trees and difficult to regenerate. In the population, the individual percentage of IV trees accounted for 79.4% in Q1 and 87.4% in Q2, and those of I trees and II trees were few. However, the population of Cyclobalanopsis axyodon was an growing one, and the individual percentages declined with the increasing size classes. The spatial distribution patterns of the two dominant populations distributed in clumps, but the clumping degrees existed diversity. With the increase of the size classes, the clumping degree of the population of Sycopsis sinensis intensified from random to clumping distribution, while that of the population of Cyclobalanopsis axyodon weakened from clumping to random distribution.

Conservation of Natural Resources↗

PubMed2005

[Spatial distribution pattern and space dependence of Contarinia sp. and Erigonidium graminicola in jujube orchard].

With the principles and methodologies of geostatistics, this paper studied the spatial structure and space dependence of Contarinia sp. and its natural enemy Erigonidium graminicola in a jujube orchard at different date. The results indicated that the semivariogram of Contarinia sp. on 8 June, 27 August and 19 October could be described by spherical model, showing an aggregated spatial distribution with the ranges of spatial dependence being 26.3, 7.8 and 22.0 m, and the degrees of spatial dependence being 88.05%, 85.77% and 87.58%, respectively. The semivariogram of Erigonidium graminicola could be also described by spherical model, showing an aggregated distribution with the ranges of spatial dependence being 28.3, 22.5 and 22.2 m, and the degrees of spatial dependence being 90.09%, 87.96% and 85.72%, respectively. It is suggested that Erigonidium graminicola is the dominant natural enemy against Contarinia sp. population in the examined jujube orchard.

Animals↗

PubMed1993

The spatial distribution and relative abundance of gap-junctional connexin40 and connexin43 correlate to functional properties of components of the cardiac atrioventricular conduction system.

Electrical coupling between heart muscle cells is mediated by specialised regions of sarcolemmal interaction termed gap junctions. In previous work, we have demonstrated that connexin42, a recently identified gap-junctional protein, is present in the specialised conduction tissues of the avian heart. In the present study, the spatial distribution of the mammalian homologue of this protein, connexin40, was examined using immunofluorescence, confocal scanning laser microscopy and quantitative digital image analysis in order to determine whether a parallel distribution occurs in rat. Connexin40 was detected by immunofluorescence in all main components of the atrioventricular conduction system including the atrioventricular node, atrioventricular bundle, and Purkinje fibres. Quantitation revealed that levels of connexin40 immunofluorescence increased along the axis of atrioventricular conduction, rising over 10-fold between atrioventricular node and atrioventricular bundle and a further 10-fold between atrioventricular bundle and Purkinje fibres. Connexin40 and connexin43, the principal gap-junctional protein of the mammalian heart, were co-localised within atrioventricular nodal tissues and Purkinje fibres. By applying a novel photobleach/double-labelling protocol, it was demonstrated that connexin40 and connexin43 are co-localised in precisely the same Purkinje fibre myocytes. A model, integrating data on the spatial distribution and relative abundance of connexin40 and connexin43 in the heart, proposes how myocyte-type-specific patterns of connexin isform expression account for the electrical continuity of cardiac atrioventricular conduction.

Animals↗

PubMed2004

Seasonal and spatial distributions of adult screwworms (Diptera: Calliphoridae) in the Panama Canal area, Republic of Panama.

The distribution of screwworms, Cochliomyia hominivorax, (Coquerel) was studied in a seasonally moist lowland tropical forest in the Republic of Panama using a combination of field collections and satellite imagery. We found that different forest types could be distinguished and mapped using remotely sensed data. To determine the temporal and spatial distribution of flies, we collected flies coming to rotted liver at 82 sites in ten vegetation types (open areas, edge forest, dry scrub forest, forest successional stage 1, forest successional stage 2, forest successional stage 3, forest successional stage 4, forest successional stage 5, mature forests, palm swamp forest, and forest along streams) over three seasons (dry, transitional, wet). Nine of the vegetation types (excluding dry scrub forest) were identified and mapped using SPOT XS and Landsat 5 TM satellite data. Screwworm flies were most abundant during the transition from wet to dry season. Fly numbers were consistently higher in forest habitats, particularly those with trees 20-30 m in height and a fairly open canopy composed of many deciduous species that shed their leaves during the dry season. Screwworm numbers were also high in palm swamp forest, edge forest, and mature growth forest. Traps sampled in open areas had fewer flies and were unrelated to proximity to cattle. Females accounted for 88% of the total fly counts. This study further substantiates the importance of forests in the ecology and behavior of screwworm flies and demonstrates that remotely sensed data can be used to construct the spatial distribution of these flies in a tropical landscape. We discuss implications of this information to the screwworm eradication program.

Animals↗

PubMed1975

Pattern of spatial distribution in Drosophila melanogaster.

The effect of temperature and sex on spatial distribution of Drosophila melanogaster adults was studied in a specially designed apparatus. It was observed that individuals tend to aggregate in sections of the sphere independently of sex and temperature. Nevertheless, decrease in temperature increase aggregation. The mobility of both males and females indicates a negative geotactic tendency.

Animals↗

PubMed1990

Spatial distribution of muscle fibers within the territory of a motor unit.

The spatial distribution of muscle fibers belonging to a motor unit was studied in the soleus (SOL) and tibialis anterior (TA) of adult cats to provide a detailed description of the spatial patterns which exist within the territory of a motor unit. Glycogen depletion of the motor unit was achieved through repetitive stimulation of either the intracellularly identified motoneuron or the functionally isolated motor axon. Muscle fibers belonging to the stimulated unit were identified in serial cross-sections, and in the cross-section which contained the most depleted fibers the centroid of each depleted fiber was determined. Subsequently, three spatial analyses, ie, a quadrat analysis, a point-to nearest neighbor analysis and an interfiber distance analysis, were used to determine if motor unit fibers were distributed randomly throughout the territory of the unit. Motor unit fibers tended to be localized within the muscle cross-section and were not evenly or homogeneously distributed throughout the territory. In general, the analyses suggested that motor unit fibers may be arranged in clusters or subgroups of varying size. The data demonstrate three different quantitative analyses for studying the organization of muscle fibers of normal motor units, which can be used for objective assessment and diagnosis of neuromuscular diseases.

Animals↗

PubMed2006

The spatial distribution and temporal dynamics of brain regions activated during the perception of object and non-object patterns.

Both animal and human studies suggest that the efficiency with which we are able to grasp objects is attributable to a repertoire of motor signals derived directly from vision. This is in general agreement with the long-held belief that the automatic generation of motor signals by the perception of objects is based on the actions they afford. In this study, we used magnetoencephalography (MEG) to determine the spatial distribution and temporal dynamics of brain regions activated during passive viewing of object and non-object targets that varied in the extent to which they afforded a grasping action. Synthetic Aperture Magnetometry (SAM) was used to localize task-related oscillatory power changes within specific frequency bands, and the time course of activity within given regions-of-interest was determined by calculating time-frequency plots using a Morlet wavelet transform. Both single subject and group-averaged data on the spatial distribution of brain activity are presented. We show that: (i) significant reductions in 10-25 Hz activity within extrastriate cortex, occipito-temporal cortex, sensori-motor cortex and cerebellum were evident with passive viewing of both objects and non-objects; and (ii) reductions in oscillatory activity within the posterior part of the superior parietal cortex (area Ba7) were only evident with the perception of objects. Assuming that focal reductions in low-frequency oscillations (<30 Hz) reflect areas of heightened neural activity, we conclude that: (i) activity within a network of brain areas, including the sensori-motor cortex, is not critically dependent on stimulus type and may reflect general changes in visual attention; and (ii) the posterior part of the superior parietal cortex, area Ba7, is activated preferentially by objects and may play a role in computations related to grasping.

Adult↗