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PubMed1985

Spatial distribution of immature Culicoides variipennis (Coq.).

Circadian fluctuation in the spatial distribution of immature Culicoides variipennis (Coq.) was studied in Saltville, Virginia, USA during the summer of 1983. Pupae and early instar larvae (1st and 2nd) were localized above the shoreline in the top cm of mud and displayed little migration from this region during the 24 hr sampling period, however, later instar larvae (3rd and 4th) showed marked migration patterns. Most larval movement was horizontal rather than vertical and was confined to the top cm of mud. Late instar larvae moved towards the water during the day but migrated up above shoreline during the night. Seasonal fluctuation in larval spatial distribution was also studied. Larvae appeared to move progressively downward into the mud during the autumn. However, when the site became frozen the majority of larvae occupied a narrow liquid interface between the ice cover and the frozen mud beneath.

Animals↗
PubMed2001

Spatial distribution analysis on climatic variables in northeast China.

Information ecology is a new research area of modern ecology. Here describes the spatial distribution analysis methods of four sorts of climatic variables, i.e. temperature, precipitation, relative humidity and sunshine fraction in Northeast China. First, digital terrain models was built with large-scale maps and vector data. Then trend surface analysis and interpolation method were used to analyze the spatial distribution of these four kinds of climatic variables at three temporal scale: (1) monthly data; (2) mean monthly data of thirty years, and (3) mean annual data of thirty years. Ecological information system were used for graphics analysis on the spatial distribution of these climatic variables.

Algorithms↗
PubMed1995

Spatial distributions of genotypes under isolation by distance.

The spatial distributions of single-locus diploid genotypes, produced within populations of sexually reproducing individuals under isolation by distance, are measured and characterized in detail by quantifying the join-counts for simulated model populations. The models more realistically reflect spatially explicit distributions of genotypes in populations, because unlike the classical theory, they include the stochasticity inherent in the process of matings between genotypes. This stochasticity causes the formation of large areas or patches containing mostly one homozygous genotype, which is not predicted by the classical theory. A number of previously uncharacterized features of the spatial structures produced under isolation by distance are revealed. Spatial autocorrelation measures based on counts of pairs of homozygotes are highly consistent quantifications of the concentrations of homozygotes in patchy genotypic distributions for a given level of dispersal. Most strikingly, the degree of intermixing of homozygotes with heterozygotes over small spatial scales is much higher than previously thought, unless dispersal is extremely limited (e.g., Wright's neighborhood size less than approximately 5.0). Among implications for studies of spatial structure of real populations, one is that the results provide a basis for using join-counts as estimators of gene dispersal based solely on genetic data.

Diploidy↗
PubMed1994

The spatial distribution and geographic analysis of endodontic office locations at the national scale.

The major purpose of this article was to quantify and describe the spatial distribution of endodontic office locations at the national scale. This study consisted of 2858 US American Association of Endodontists member endodontists as subjects. Three research questions were developed and explored. The location quotient technique, the spatial autocorrelation approach, and the multiple-regression procedure were the major analytical methods. Major results were as follows: the highest concentration (2.09 to 2.62) of endodontic offices per 100,000 US population was located in just two states, Massachusetts and Connecticut; the spatial distribution of endodontic office locations did exhibit significant (p < or = 0.05, two-tailed test) spatial autocorrelation. Therefore, the spatial distribution of endodontic office locations was nonrandom. Individually, the most significant predictor of endodontic office locations was the location of general practice dentists (its beta coefficient was 0.960606, significant at p < or = 0.0001).

Adult↗
PubMed1984

Spatial distribution of messenger RNA in the cytoskeletal framework of ascidian eggs.

Maternal poly(A)+RNA, histone mRNA, and actin mRNA exhibit unique spatial distributions in the different ooplasmic regions of ascidian eggs. These RNAs also appear to migrate with their respective ooplasms during the episode of extensive cytoplasmic rearrangement that occurs after fertilization, suggesting they are associated with a structural framework. The role of the cytoskeletal framework (CF) in determining the spatial distribution of maternal mRNA was tested by subjecting Triton X-100 extracted (Styela plicata) eggs and early embryos to in situ hybridization with poly(U) and cloned DNA probes. Grain counts indicated that substantial proportions of the egg poly(A)+RNA, histone mRNA, and actin mRNA were present in the CF and that there was no alteration in the extent of mRNA-CF interactions during the period between fertilization and the two-cell stage. Analysis of grain distributions indicated that poly(A)+RNA, histone mRNA, and actin mRNA were concentrated in the same regions of detergent-extracted eggs as they are in intact eggs. The proportions and spatial distribution of these RNAs in the CF were not affected when the actin cytoskeleton was destabilized by cytochalasin B or DNase I. The data suggest that maternal mRNA is associated with the CF, that this association is responsible for mRNA rearrangement during ooplasmic segregation, and that mRNA-CF interactions are not dependent on the integrity of the actin cytoskeleton.

Actins↗
PubMed1995

[Spatial distribution of cancer incidence by anatomic site in Quebec].

Knowledge of the spatial distribution of diseases provides useful information in etiologic research and in implementation of preventive activities in community health. Spatial autocorrelation analysis is one of the various methods that enables to determine spatial clustering of diseases. This method has not been applied to lung, stomach and colon cancer in Québec. These cancers are frequent and are associated with environmental factors. The objectives of the study are to determine spatial distribution of incidence rates of these cancer sites by sex and to help generate etiologic hypotheses. Community health departments (CHDs) of residence are considered as risk markers since their population and environment may be related to the selected cancer sites. Data were obtained from Québec Cancer Registry. Rates were standardized by the direct method. Autocorrelation analysis was done through BW coefficient and Moran's coefficient I for correlograms. Results of standardized rates were compared to those of non standardized rates. Rates yielded the same results for the BW coefficient. Conversely, results were quite different for the correlograms. This implies that results from standardized rates should be kept since the age structure of CHD populations are different. Important variation in the level of spatial autocorrelation was found among the six sex-specific cancer sites. For male lung cancer and male stomach cancer first-order neighbouring CHDs showed similar incidence rates according to a geographic gradient. Female lung cancer exhibited spatial autocorrelation. Absence of spatial autocorrelation for colon cancer suggests that CHD is not the appropriate scale for study of this cancer and allows use of conventional epidemiologic methods. These results are discussed in relation to current etiologic hypotheses.(ABSTRACT TRUNCATED AT 250 WORDS)

Cluster Analysis↗
PubMed1993

The spatial distribution of immunotoxins in solid tumors: assessment by quantitative autoradiography.

The spatial distribution of i.v. administered immunotoxins in s.c. human rhabdomyosarcoma RD2 xenografts was studied. The toxin and immunotoxins were: (a) diphtheria toxin (DT); (b) a binding-deficient form of DT (CRM107) linked to a monoclonal IgG1 antibody (454A12) directed against the human transferrin receptor (454A12-107); (c) the binding-deficient form of DT linked to the Fab' fragment of 454A12 (Fab'-107); and (d) the binding-deficient form of DT coupled to MOPC21, a monoclonal IgG1 with no significant binding to RD2 cells. DT and the immunotoxins were radiolabeled with 125I and injected via the tail vein into tumor-bearing athymic mice (median tumor weight, 0.25 g). Tumors were removed 2, 6, and 24 h after injection of DT or immunotoxin. Film images of 20-microns frozen sections were digitized by video microscopy, and gray levels were converted to tissue concentrations based upon the film response to radioactivity standards and the specific activity of the radiolabeled toxins. Images of the tumors were characterized quantitatively by the kurtosis and the area above threshold; the kurtosis is a measure of the spatial heterogeneity of the radiolabeled immunotoxins, and the area above threshold is defined here as the fractional tumor area that reaches or exceeds 1.5% of the initial plasma concentration. The spatial distribution of DT in the tumors was extremely uniform, characterized by low kurtosis values. In contrast, the autoradiograms of 454A12-107 were punctate in appearance and were characterized by very high kurtosis values. Fab'-107, which has approximately one-half the molecular weight of the intact immunotoxin and binds only monovalently, also produced punctate images with kurtosis values similar to those for 454A12-107. The nonbinding immunotoxin distributed somewhat less uniformly than DT but much more homogeneously than either of the binding immunotoxins. DT, 454A12-107, and Fab'-107 have similar affinities for their respective receptors, but the concentration of binding sites for DT on RD2 cells (<3,000 receptors/cell) is much lower than the concentration of transferrin receptor (60,000 receptors/cell). Thus, the heterogeneous distribution of 454A12-107 and Fab'-107 probably reflects retarded penetration due to binding to the tumor cells. The area above threshold was greatest for DT and lowest for 454A12-107; the fragment and nonbinding immunotoxins had intermediate values. The lower area above threshold for the nonbinding immunotoxin as compared with DT may be due to the considerably large molecular weight and hence the lower capillary permeability and diffusion coefficient of the immunotoxin.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1996

Spatial distribution of QT intervals: an alternative approach to QT dispersion.

QT dispersion (QTd) describes the heterogeneity of ventricular repolarization on the basis of the temporal range of QT intervals as measured in the 12-lead ECG. We examined the spatial distribution of QTd using multichannel magnetocardiograms (MCGs), which noninvasively register changes in magnetic field strength at 37 sites over the heart. As in ECG, the MCG signal in each channel may be used to measure QT interval. By calculating QT deviation from QTmin at each site, one can reconstruct the spatial distribution of QTd. Analysis of spatial QTd in ten healthy subjects and ten patients after acute myocardial infarction (MI) showed clear differences in spatial distribution. The healthy subjects generally displayed shorter QT intervals along a line corresponding to the approximate position of the septum with longer intervals in plateaus in the upper right and lower left. Spatial QTd of the post-MI patients deviated from this pattern, often displaying a sharp rise in QT duration over specific areas, which could be related to functional and morphological disturbances. The quantification of local irregularities as well as the overall pattern on the basis of a smoothness index allowed better discrimination between healthy subjects and post-MI patients than QTd. Distribution patterns of QTd which reflect local repolarization alterations may thus represent a more differentiated marker for pathology and risk.

Adult↗
PubMed2026

Impact of spatial distribution of M2 macrophages on prognosis and neoadjuvant chemotherapy resistance in gastric cancer.

BACKGROUND: Neoadjuvant chemotherapy (NAC) is a crucial treatment for locally advanced gastric cancer; however, approximately 30-40% of patients experience primary resistance, the mechanisms of which urgently require elucidation. The tumor microenvironment exhibits a high degree of spatial heterogeneity. M2 macrophages, as critical immune cells within this environment, are typically associated with poor prognosis. Yet, whether their spatial distribution impacts chemotherapy efficacy remains unclear. This study aims to investigate the relationship between the in situ spatial distribution characteristics of M2 macrophages and chemoresistance in gastric cancer. METHODS: Based on The Cancer Genome Atlas Stomach Adenocarcinoma (TCGA-STAD) cohort, the association between M2 markers (CD163, MRC1) and histological grade as well as overall survival (OS) was evaluated. Spearman correlation and functional enrichment analyses were conducted to explore the mechanistic link between M2 macrophages and stromal barrier construction. Multiplex immunofluorescence (mIF) and digital pathology image analysis were utilized to calculate the areal density of M2 macrophages in the intratumoral core and the peritumoral stroma, respectively. The tumor-to-peritumoral ratio (TPR) was constructed, followed by a rank correlation analysis between TPR and the tumor regression grade (TRG). RESULTS: TCGA-STAD results confirmed that patients with high expression of M2 markers had worse OS (P=0.03), and the expression levels of M2 markers increased with histological grade. MRC1 was highly significantly and positively correlated with the pro-fibrotic factor TGFB1 (rho=0.447, P<0.001), with the gene set significantly enriched in pathways such as positive regulation of cytokine production and myeloid leukocyte activation. Histological examination revealed that in chemoresistant patients (TRG 3), M2 macrophages were primarily retained in the peritumoral stroma, with a median TPR of 0.50; in chemosensitive patients (TRG 1-2), a massive influx of M2 macrophages into the tumor core was observed, with a median TPR of 6.67. TPR was negatively correlated with TRG (rs=-0.65, P=0.043). CONCLUSIONS: The clinical impact of M2 macrophages in the gastric cancer microenvironment is highly dependent on their spatial distribution. The peritumoral-enriched pattern (TPR <1) mediates primary chemoresistance, whereas high infiltration in the core objectively reflects the pathological footprint following effective chemotherapy. The TPR serves as a novel tool for assessing neoadjuvant chemosensitivity in gastric cancer.

Gastric cancer (GC)↗
PubMed1988

Perforant path activation of the hippocampus: spatial distribution, effects of urethane and atropine.

Spatial distribution of field responses evoked by perforant path stimulation were studied in the hippocampus of both anaesthetized and drug-free rats. Simultaneous recordings with an array of 4 electrodes allowed us to construct a 2-dimensional map of the evoked field potentials. In addition, we examined the effects of atropine-SO4 and urethane on the amplitude of the dentate response. Trisynaptic activation of the CA1 region occurred regularly in the drug-free rat while CA1 population spikes were rarely seen in the anaesthetized animal. The latency of the CA1 population spike was shortest at the fimbrial side and increased gradually towards the subicular side. In the dentate gyrus atropine increased the amplitude of the population spike. We suggest that atropine may interfere with the septo-hippocampal feed-forward inhibition, and urethane may decrease the effectiveness of the perforant path-granule cell synapse, as well as the intrahippocampal excitatory circuit.

Animals↗
PubMed1999

The spatial distribution of larvae of Culicoides impunctatus biting midges.

The spatial distribution of Culicoides impunctatus Goetghebuer (Diptera: Ceratopogonidae) larvae was sampled at a site in western Scotland, and geostatistical analyses were used to quantify spatial dependencies. Nested sampling and analysis indicated that most of the spatial variance occurred within distances of 160-640 cm, levelling off at distances >640 cm. Semivariograms for transformed data from three 100 m x 100 m grids showed similar, isotropic patterns for larval counts, soil organic content, soil water content and the distribution of Juncus spp. rushes, with the variance increasing with separation distance. High levels of significance were associated with power models used to describe the semivariograms, which was indicative of the absence of a plateau (or 'sill') in the respective data. Correlation analysis of transformed data revealed significantly positive relationships between larval counts and soil pH, soil percentage organic content, soil percentage water content and also the distribution of Sphagnum spp., Juncus spp. and Myrica gale. There were also significantly negative relationships between larval counts and the distribution of Pteridium aquilinum and all mosses other than Sphagnum spp. The results suggest a far more structured and predictable pattern of C. impunctatus larval sites than previous studies and are discussed in relation to their application in localized Culicoides control and to studies of the mechanisms determining the spatial distribution of C. impunctatus larvae.

Animals↗
PubMed1996

Spatial distribution of visual attention: perceptual sensitivity and response latency.

Studies of the spatial distribution of visual attention have shown that attentional facilitation monotonically decreases in a graded fashion with increasing distance from an attended location. However, reaction time (RT) measures have typically shown broader gradients than have signal detection (SD) measures of perceptual sensitivity. It is not clear whether these differences have arisen because the stages of information processing indexed by RT measures are different from those indexed by SD measures, or whether these differences are due to methodological confounds in the SD studies. In the present set of experiments, the spatial distribution of attention was studied by using a luminance detection task in an endogenous cuing paradigm that was designed to permit accurate calculations of SD and RT measures for targets at cued and uncued locations. Subjects made target-present/absent decisions at one of six possible cued or uncued upper visual hemifield locations on each trial. The results from three experiments suggest that the differences between broad and focal attentional distributions are not the result of different stages of information processing indexed by RT measures as opposed to SD measures. Rather, the differing distributions appear to reflect variations in attentional allocation strategies induced by the perceptual requirements typical of RT paradigms as opposed to SD paradigms. These findings support numerous prior studies showing that spatial attention affects perceptual sensitivity and that the strategic allocation of attention is a highly flexible process.

Adolescent↗
PubMed2001

Spatial distribution and behaviour of laying hens housed in an alternative system.

The spatial distribution and behaviour of perchery housed laying hens were compared at a constant stocking density (18.5 birds/m(2)) in eight pens with colonies of five different sizes (323 birds (N=1), 374 birds (N=2), 431 birds (N=2), 572 birds (N=1) and 912 birds (N=2)). The birds were placed in the perchery when they were 12 weeks old. Observations began when they were 26 weeks old and continued at 8 week intervals until 61 weeks of age. Colony size did not appear to affect the spatial distribution of birds, but more standing behaviour and less feeding behaviour were observed in the smallest and largest colony sizes. Older birds spent more time on the floor areas and less time on perches. Young birds (26-28 weeks) spent more time feeding, foraging, drinking and preening, and less time standing idle than older birds. In the afternoons, there were fewer birds on the perches and more on the floor levels, corresponding with less time spent resting and more time spent performing active behaviours. Birds did not distribute themselves evenly throughout their pens: within specific areas of pens densities varied between 9 and 41 birds/m(2). This variation, which reflects the flux of birds from one part of the pen to another, was greatest for the larger colony sizes, and may have adverse implications for welfare in terms of crowding and hysteria.

Journal Article↗
PubMed1999

Time trends, cohort effect and spatial distribution of cerebrovascular disease mortality in Spain.

STUDY OBJECTIVE: This study describes mortality due to cerebrovascular disease (CVD) in Spain, based on time-series analysis in the period 1951-1995 by age, sex, and cohort of birth; spatial distribution observed for the five-year period 1991 1995, and time-spatial analysis in the period 1992-1995 vs. 1988-1991. Special attention is paid to risk of medium aged population. DESIGN: Longitudinal and cross-sectional observational study. SETTING AND PARTICIPANTS: Spanish population. All mortality data used were taken from official statistics. Time trends and spatial distribution were analyzed using log-linear Poisson regression models. MAIN RESULTS: CVD mortality declined over the last two decades of the study period (1974-1995) by an annual average of 4.16% (95% CI: 3.95-4.36) and 4.00% (95% CI: 3.77-4.24) in men and women, respectively. The downward trends were accelerated in last decade. An excess of male mortality was in evidence. For all age groups mortality declined with more recent cohorts, but the decline was less marked among ages 35 64. Spatial distribution of CVD mortality revealed a north-south pattern, but this is being difuminated by increasing rates in the lower risk provinces. Internationally, Spain ranks midway to low in terms of its overall CVD mortality. CONCLUSIONS: Efforts to reduce CVD incidence and case fatality are the essential prerequisite for any long-term improvement in mortality. Accordingly, further research is called for into current disease morbidity and the risk factors to be targeted at a general population level, nationwide.

Adult↗
PubMed1987

Spatial distribution of twitch and tonic fibres in a snake muscle one myofibre thick.

The spatial distribution of twitch and tonic fibres in a snake muscle one myofibre thick (ventral costocutaneous) has been investigated. It was found that small groups of like fibres were favoured at the expense of larger groups when compared with sequences generated by a computer in which fibres were distributed randomly. The number of times that like fibres occurred next to one another was used as another measure of their spatial distribution. The number of adjacencies of like fibres was less than the expected number of adjacencies determined both by random sequences and by probability theory. The expected number of adjacencies determined by means of random sequences and a priori probability theory were almost identical. This dispersion of like fibres may reflect processes that occur during muscle development and may have functional implications.

Animals↗
PubMed1975

Spatial distribution of rat fungiform papillae.

The objective of this study was to determine the spatial distribution of fungiform papillae on the rat's tongue. Since each fungiform papilla in the rat has a single taste bud, the spatial distribution of fungiform papillae is equivalent to the location of taste buds on the anterior tongue. A mean total number of 187 fungiform papillae per tongue were found which were about equally divided between the two lateral halves of the tongue. Over 50% of the total number of fungiform papillae were located on the tongue tip for an average density of 3.4 papillae/mm2,while the dorsal surface of the tongue had an average density of 1.3 papillae/mm2 of tongue surface. Papillae were absent on the dorsal midline, but a paracentral line of papillae running from anterior to posterior was a consistent finding. Though not identical, the distribution of papillae was essentially the same on different tongues. The functional significance of the papilla distribution is not understood, but electrophysiological experiments show evidence of neural interaction of papillae which are clustered together. The distribution of papillae and the distribution of nerve fibers which innervate them must be evaluated together in order to appreciate the significance of the distribution of fungiform papillae and their associated taste buds.

Animals↗
PubMed1994

[Hyperintensive intramedullary lesions in psychiatric patients. Spatial distribution and psychopathologic symptoms].

In a sample of 130 patients who had undergone MRI (transverse T2-weighted SE sequence) patchy white matter lesions (WML) were documented according to number and spatial distribution in the brain. Ventricle-to-Brain Ratio (VBR) was determined. Configural frequency analysis led to delineation of four patient groups on the basis of WML location: 1. no WML (n = 35), 2. right frontal-temporal WML (n = 23), 3. bifrontal WML (n = 12), 4. WML in all/all but one brain region (n = 16). Psychopathological symptoms reported in the course of a maximum of 3 years were documented by chart review. In the 'pervasive WML' group psychopathological items characteristic of organic brain syndromes prevailed, mean VBR exceeded values in all other groups (ANOVA, p < 0.001). WML spatial distribution accounted for 10.2% of total psychopathological variance. Patient age, but not VBR, had a significant impact on symptom profile (MANCO-VA). When the 'pervasive WML' group was excluded, the finding of a significant effect of WML location on psychopathological symptom profiles was robust. Bifrontal WML were associated with thought incoherence, right frontal-temporal WML with affective symptoms. Findings support an impact of spatial distribution of unspecific WML on psychopathological symptoms in psychiatric patients.

Adult↗
PubMed2001

Infrared microscopic imaging of bone: spatial distribution of CO3(2-).

This article describes a novel technology for quantitative determination of the spatial distribution of CO3(2-) substitution in bone mineral using infrared (IR) imaging at approximately 6 microm spatial resolution. This novel technology consists of an IR array detector of 64 x 64 elements mapped to a 400 microm x 400 microm spot at the focal plane of an IR microscope. During each scan, a complete IR spectrum is acquired from each element in the array. The variation of any IR parameter across the array may be mapped. In the current study, a linear relationship was observed between the band area or the peak height ratio of the CO3(2-) v3 contour at 1415 cm(-1) to the PO4(3-) v1,v3 contour in a series of synthetic carbonated apatites. The correlation coefficient between the spectroscopically and analytically determined ratios (R2 = 0.989) attests to the practical utility of this IR area ratio for determination of bone CO3(2-) levels. The relationship forms the basis for the determination of CO3(2-) in tissue sections using IR imaging. In four images of trabecular bone the average CO3(2-) levels were 5.95 wt% (2298 data points), 6.67% (2040 data points), 6.66% (1176 data points), and 6.73% (2256 data points) with an overall average of 6.38+/-0.14% (7770 data points). The highest levels of CO3(2-) were found at the edge of the trabeculae and immediately adjacent to the Haversian canal. Examination of parameters derived from the phosphate v1,v3 contour of the synthetic apatites revealed that the crystallinity/perfection of the hydroxyapatite (HA) crystals was diminished as CO3(2-) levels increased. The methodology described will permit evaluation of the spatial distribution of CO3(2-) levels in diseased and normal mineralized tissues.

Bone and Bones↗