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At least 433 records · Page 24Linked to original sources
PubMed1998

PCR analysis and spatial repartition of trypanosomes infecting tsetse flies in Sidéradougou area of Burkina Faso.

A parasitological and entomological survey was conducted in the Sideradougou area (south of Bobo Dioulasso, Burkina Faso) in order to identify transmission factors of African trypanosomosis. A total of 3600 tsetse flies (Glossina tachinoides, Glossina palpalis gambiensis) were captured along 120 km of linear gallery forest and half of them were dissected. PCR analysis was undertaken on parasitologically positive flies (161 G. tachinoides, 92 G. palpalis gambiensis) to characterize the different trypanosomes. All the results were integrated in a GIS (Geographical Information System). Spatial repartition of the characterized trypanosomes enabled to recognize different areas with specific patterns of infection. Relations with environmental factors are discussed.

Animals↗
PubMed2006

Inferring population history from fine-scale spatial genetic analysis in Oryza rufipogon (Poaceae).

Determining the genetic structure of an in situ conserved population can provide insight into the dynamics of population genetic processes associated with successful plant conservation. We used 21 microsatellite loci to analyse the genetic relationships among individuals (n = 813) collected from a small Oryza rufipogon population conserved since 1993 in Hunan Province of China. The analysis revealed four distinct genetic subpopulations (F(ST) = 0.145) without geographic isolation. One subpopulation was composed of possible introgressed individuals, two subpopulations were composed of seed recruits and their descendants, and the fourth subpopulation consisted of reintroduced individuals, seed recruits and their descendants. Positive spatial genetic structures were detected by spatial autocorrelation statistics at the population (c. 63 m) and subpopulation levels (11-30 m), but the degree of autocorrelation was stronger at the population level. These results showed that prejudging the cryptic structure is important before autocorrelation analysis for the entire population. Our study suggests that population history can be a significant determinant on population structure for plant restoration projects.

China↗
PubMed1991

Temporal analysis and spatial mapping of Lymantria dispar nuclear polyhedrosis virus transcripts and in vitro translation polypeptides.

Genomic expression of the Lymantria dispar multinucleocapsid nuclear polyhedrosis virus (LdMNPV) was studied. Viral specific transcripts expressed in cell culture at various times from 2 through 72 h postinfection were identified and their genomic origins mapped through Northern analysis. Sixty-five distinct transcripts were identified in this analysis. Most viral transcripts were expressed late in infection, and originated from throughout the viral genome. Viral polypeptides expressed in infected 652Y cells were labeled with [35S]methionine and identified by autoradiography after separation by SDS polyacrylamide gel electrophoresis. Viral protein synthesis was found to occur in a sequential manner. Four proteins were identified in the early phase of viral replication (4-12 h p.i.), 24 proteins in the intermediate phase (12-24 h p.i.), and 5 proteins during the late phase (greater than 24 h p.i.). Cytoplasmic RNAs were isolated from LdMNPV infected cells at 16, 24, and 48 h p.i., and used for hybrid selections with overlapping DNA fragments that covered the entire LdMNPV genome. The selected RNAs were translated in vitro, and 61 distinct viral polypeptides were identified and their genomic origins mapped. Temporal and spatial transcription and translation maps of the LdMNPV genome were generated with these data, and the expression pattern of the LdMNPV genome was compared to that of the Autographa californica nuclear polyhedrosis virus.

Animals↗
PubMed2004

The geographic distribution of breast cancer incidence in Massachusetts 1988 to 1997, adjusted for covariates.

BACKGROUND: The aims of this study were to determine whether observed geographic variations in breast cancer incidence are random or statistically significant, whether statistically significant excesses are temporary or time-persistent, and whether they can be explained by covariates such as socioeconomic status (SES) or urban/rural status? RESULTS: A purely spatial analysis found fourteen geographic areas that deviated significantly from randomness: ten with higher incidence rates than expected, four lower than expected. After covariate adjustment, three of the ten high areas remained statistically significant and one new high area emerged. The space-time analysis identified eleven geographic areas as statistically significant, seven high and four low. After covariate adjustment, four of the seven high areas remained statistically significant and a fifth high area also identified in the purely spatial analysis emerged. CONCLUSIONS: These analyses identify geographic areas with invasive breast cancer incidence higher or lower than expected, the times of their excess, and whether or not their status is affected when the model is adjusted for risk factors. These surveillance findings can be a sound starting point for the epidemiologist and has the potential of monitoring time trends for cancer control activities.

Journal Article↗
PubMed2005

The role of geographic analysis in locating, understanding, and using plant genetic diversity.

The genetic structure of an organism is shaped by various factors, many of which vary significantly over space. In this chapter, we provide insight on how studying geographic patterns may contribute to an improved understanding of variability in genetic structure. We first review the theoretical background on how differences in genetic structure may be generated through processes that are inherently variable over space. We then present novices with some basics on how geographic information systems (GIS) may be adopted to study this variation, including advice on software, data, and the type of research questions that might be addressed. The chapter finishes with a brief review of how spatial analysis has contributed to the conservation and use of plant genetic resources, through an understanding of spatial patterns in species distribution and genetic structure. We conclude that spatial variation is a factor often overlooked in genetic studies and one that merits greater consideration. With the advent of functional genomics and improved quantification of adaptive traits, spatial analysis may be key in understanding variation in genetic structure through careful analysis of genotype-environment interactions.

Algorithms↗
PubMed2005

Confocal microscopy and biochemical analysis reveal spatial and functional separation between anandamide uptake and hydrolysis in human keratinocytes.

The signaling activity of anandamide (AEA) is terminated by its uptake across the cellular membrane and subsequent intracellular hydrolysis by the fatty acid amide hydrolase (FAAH). To date, the existence of an AEA membrane transporter (AMT) independent of FAAH activity remains questionable, although it has been recently corroborated by pharmacological and genetic data. We performed confocal microscopy and biochemical analysis in human HaCaT keratinocytes, in order to study the cellular distribution of AMT and FAAH. We found that FAAH is intracellularly localized as a punctate staining partially overlapping with the endoplasmic reticulum. Consistently, subcellular fractionation and reconstitution of vesicles from membranes of different compartments demonstrated that FAAH activity was localized mainly in microsomal fractions, whereas AMT activity was almost exclusively in plasma membranes. These results provide the first morphological and biochemical evidence to support the view that transport and hydrolysis are two spatially and functionally distinct processes in AEA degradation.

Amidohydrolases↗
PubMed1996

GenomeInspector: basic software tools for analysis of spatial correlations between genomic structures within megabase sequences.

The speed of acquisition of genomic sequence data exceeds the evaluation of function of the sequences by a vast margin. Most software available for the prediction of individual features does not assess the correlation of different motifs (level 1 methods). Here, we present a second-level software package called GenomeInspector (GI) for further analysis of results obtained with level 1 methods. Our approach does not require any a priori knowledge about motif organization and was designed as a modular package with a graphical user interface. Three examples for GI application are presented.

Genome↗
PubMed2002

Binding and transport in norepinephrine transporters. Real-time, spatially resolved analysis in single cells using a fluorescent substrate.

Monoamine transporters, the molecular targets for drugs of abuse and antidepressants, clear norepinephrine, dopamine, or serotonin from the synaptic cleft. Neurotransmitters, amphetamines, and neurotoxins bind before being transported, whereas cocaine and antidepressants bind to block transport. Although binding is crucial to transport, few assays separate binding from transport, nor do they provide adequate temporal or spatial resolution to describe real-time kinetics or localize sites of active uptake. Here, we report a new method that distinguishes substrate binding from substrate transport using single-cell, space-resolved, real-time fluorescence microscopy. For these studies we use a fluorescent analogue of 1-methyl-4-phenylpyridinium, a neurotoxic metabolite and known substrate of monoamine transporters, to assess binding and transport with 50-ms, sub-micron resolution. We show that ASP(+) (4-(4-(dimethylamino)styrl)-N-methylpyridinium) has micromolar potency for the human norepinephrine transporter, that ASP(+) accumulation is Na(+)-, Cl(-)-, cocaine-, and desipramine-sensitive and temperature-dependent, and that ASP(+) competes with norepinephrine uptake. Using this method we demonstrate that norepinephrine transporters are efficient buffers for substrate, with binding rates exceeding transport rates by 100-fold. Furthermore, substrates bind deep within the transporter, isolated from both the bath and the lipid bilayer. Although transport per se depends on Na(+) and Cl(-), binding is independent of Na(+) and actually increases in low Cl(-). We further demonstrate that ASP(+) interacts with transporters not only in transfected cells but in cultured neurons. ASP(+) is also a substrate for dopamine and serotonin transporters and therefore represents a powerful new technique for studying the biophysical properties of monoamine transporters, an approach also amenable to high throughput assays for drug discovery.

Adrenergic Uptake Inhibitors↗
PubMed2004

Spatial statistical analysis of adult mosquito (Diptera: Culicidae) counts: an example using light trap data, in Redland Shire, Southeastern Queensland, Australia.

Many mosquito control agencies use carbon dioxide-baited traps as surveillance tools for adult vector populations. However, decisions regarding the number and location of trap sites and the frequency of collections are often based on logistical issues, and not on the bionomics or spatial distribution of the target species. Therefore, with the aim of providing practical information for adult mosquito surveillance programs, we used an array of 81 carbon dioxide- and octenol-baited lights traps to obtain weekly samples of adult mosquitoes in Redland Shire in southeastern Queensland, Australia. The spatial patterns of four different mosquito species were examined, and positive spatial autocorrelation in trap counts was evident for Ochlerotatus vigilax (Skuse), Coquillettidia linealis (Skuse), and Culex annulirostris Skuse, but not for the container species Ochlerotatus notoscriptus (Skuse). Of the three species that exhibited spatially correlated trap counts, the autocorrelation was greatest in Oc. vigilax at a lag distance of 0-1.5 km, with Moran's I values of 0.30-0.64. Moran's I indices were also positive and statistically significant (P < 0.05) at lag distances of 1.5-3.0 and 3.0-4.5 km on each of the 15 sampling occasions. However, at 3.0-4.5 km the Moran's I values were low, which indicated only weak spatial autocorrelation in trap counts. Universal kriging was used to estimate the numbers of each species at unsampled locations throughout the study area, and leave-one-out cross validation analyses indicated that this was a robust method for Cq. linealis and Oc. vigilax. In contrast, trap counts for the container-breeding species Oc. notoscriptus were randomly distributed and the interpolated counts were not reliable. Comparisons of weekly contour maps of adult mosquito counts indicated a consistent spatial pattern for Oc. vigilax and Cq. linealis. Particular geographic areas had consistently high or low numbers of vectors, and these patterns were stable from year to year. Definition of geographic areas with consistently high or low numbers of vectors may allow control activities to be focused in areas with the greatest risk of arbovirus transmission.

Animals↗
PubMed1997

Analysis of spatial patterns in histological sections of brain tissue.

A method is described which enables the spatial pattern of discrete objects in histological sections of brain tissue to be determined. The method can be applied to cell bodies, sections of blood vessels or the characteristic lesions which develop in the brain of patients with neurodegenerative disorders. The density of the histological feature under study is measured in a series of contiguous sample fields arranged in a grid or transect. Data from adjacent sample fields are added together to provide density data for larger field sizes. A plot of the variance/mean ratio (V/M) of the data versus field size reveals whether the objects are distributed randomly, uniformly or in clusters. If the objects are clustered, the analysis determines whether the clusters are randomly or regularly distributed and the mean size of the clusters. In addition, if two different histological features are clustered, the analysis can determine whether their clusters are in phase, out of phase or unrelated to each other. To illustrate the method, the spatial patterns of senile plaques and neurofibrillary tangles were studied in histological sections of brain tissue from patients with Alzheimer's disease.

Alzheimer Disease↗
PubMed1989

Binocular interactions in the cat's dorsal lateral geniculate nucleus. I. Spatial-frequency analysis of responses of X, Y, and W cells to nondominant-eye stimulation.

1. X, Y, and W cells in the A and C layers of the cat's dorsal lateral geniculate nucleus (LGN) were tested for responses to stimulation of the nondominant eye. The main purpose was to determine the incidence of nondominant-eye excitation and inhibition among different classes of cells and to examine the spatial-frequency tuning of responses to the nondominant eye. 2. Of 198 cells that were tested with drifting sine-wave gratings presented to the nondominant eye, 109 (55%) showed statistically significant responses. Four types of responses were observed: an increase in the mean discharge rate (F0 excitation), a decrease in the mean discharge rate (F0 inhibition), an increased modulation at the fundamental frequency of the grating (F1 excitation), and a decreased modulation at the fundamental frequency of the grating (F1 inhibition). Overall, 29% of the cells responded with inhibition, 24% responded with excitation, and 2% showed both excitation and inhibition, depending upon the spatial frequency and/or the harmonic response component. The relative incidence of excitation and inhibition was similar for X, Y, and W cells, for cells with on-center and off-center receptive fields, for cells with different receptive-field eccentricities, and for cells in each LGN layer. In addition, within layers A and A1, responses were similar for cells at different distances from the laminar borders. 3. Spatial-frequency response functions indicated that cells could have band-pass or low-pass spatial-frequency tuning through the nondominant eye. Band-pass cells tended to be narrowly tuned (less than or equal to 1 octave), and low-pass cells responded to a broader range of spatial frequencies. These properties were similar for X, Y, and W cells. Spatial resolution tended to be low (less than or equal to 0.8 c/deg for most cells), although a few cells responded to the highest spatial frequency tested (5.4 c/deg). Likewise, optimal spatial frequency was low (less than or equal to 0.2 c/deg) for most cells. These properties were similar for X and Y cells, and there was a weak tendency for X and Y cells to have higher optimal spatial frequencies and spatial resolutions than W cells. 4. In terms of absolute change in activity, responses to drifting gratings were weak. However, cells that were inhibited generally showed 20-60% decreases in activity to the optimal spatial frequency, and cells that were excited generally showed 40-100% increases. Response amplitudes were similar for X, Y, and W cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1978

Stiffness gradient along the basilar membrane as a basis for spatial frequency analysis within the cochlea.

Stiffness z of the basilar membrane of the house mouse against a displacement by sound was calculated from data on width and thickness of the membrane. Three functions of the kind log10z = ax + b were obtained which equally express the stiffness change in dependence on the locus x on the basilar membrane. These functions were compared with the one for frequency representation. The result is that the spatial distribution of displacement maxima for frequencies and of stiffness follows the same kind of place-dependent functions over a large portion of the basilar membrane. From this it can be concluded empirically that the frequency and stiffness (calculated from width and thickness of the basilar membrane) scales along the cochlea are generally proportional to each other and that stiffness is a dominant factor for the determination of the locus of the displacement maximum for a given frequency.

Acoustic Stimulation↗
PubMed1992

Application of three-dimensional molecular hydrophobicity potential to the analysis of spatial organization of membrane domains in proteins: I. Hydrophobic properties of transmembrane segments of Na+, K(+)-ATPase.

A new computer-aided molecular modeling approach based on the concept of three-dimensional (3D) molecular hydrophobicity potential has been developed to calculate the spatial organization of intramembrane domains in proteins. The method has been tested by calculating the arrangement of membrane-spanning segments in the photoreaction center of Rhodopseudomonas viridis and comparing the results obtained with those derived from the X-ray data. We have applied this computational procedure to the analysis of interhelical packing in membrane moiety of Na+, K(+)-ATPase. The work consists of three parts. In Part I, 3D distributions of electrostatic and molecular hydrophobicity potentials on the surfaces of transmembrane helical peptides were computed and visualized. The hydrophobic and electrostatic properties of helices are discussed from the point of view of their possible arrangement within the protein molecule. Interlocation of helical segments connected with short extramembrane loops found by means of optimization of their hydrophobic/hydrophilic contacts is considered in Part II. The most probable 3D model of packing of helical peptides in the membrane domain of Na+, K(+)-ATPase is discussed in the final part of the work.

Amino Acid Sequence↗
PubMed2004

Quantitative analysis of spatial sampling error in the infant and adult electroencephalogram.

The purpose of this report was to determine the required number of electrodes to record the infant and adult electroencephalogram (EEG) with a specified amount of spatial sampling error. We first developed mathematical theory that governs the spatial sampling of EEG data distributed on a spherical approximation to the scalp. We then used a concentric sphere model of current flow in the head to simulate realistic EEG data. Quantitative spatial sampling error was calculated for the simulated EEG, with additive measurement noise, for 64, 128, and 256 electrodes equally spaced over the surface of the sphere corresponding to the coverage of the human scalp by commercially available "geodesic" electrode arrays. We found the sampling error for the infant to be larger than that for the adult. For example, a sampling error of less than 10% for the adult was obtained with a 64-electrode array but a 256-electrode array was needed for the infant to achieve the same level of error. With the addition of measurement noise, with power 10 times less than that of the EEG, the sampling error increased to 25% for both the infant and adult, for these numbers of electrodes. These results show that accurate measurement of the spatial properties of the infant EEG requires more electrodes than for the adult.

Adult↗
PubMed2004

Analysis of spatial and temporal evolution of vegetation cover in the Spanish Central Pyrenees: role of human management.

A vegetation cover increase has been identified at global scales using satellite images and vegetation indices. This fact is usually explained by global climatic change processes such as CO(2) and temperature increases. Nevertheless, although these causes can be important, the role of socioeconomic transformations must be considered in some places, since in several areas of Northern Hemisphere an important change in management practices has been detected. Rural depopulation and land abandonment have reactivated the natural vegetation regeneration processes. This work analyses the vegetation evolution in the central Spanish Pyrenees from 1982 to 2000. The analysis has been done by using calibrated-NDVI temporal series from NOAA-AVHRR images. A positive and significant trend in NDVI data has been identified from 1982 to 2000 coinciding with a temperature increase in the study area. However, the spatial differences in magnitude and the sign of NDVI trends are significant. The role of land management changes in the 20th century is considered as a hypothesis to explain the spatial differences in NDVI trends. The role of land-cover and human land-uses on this process has been analyzed. The highest increment of NDVI is detected in lands affected by abandonment and human extensification. The importance of management changes in vegetation growth is discussed, and we indicate that although climate has great importance in vegetal evolution, land-management changes can not be neglected in our study area.

Altitude↗
PubMed2004

Genome-wide analysis of spatial gene expression in Arabidopsis flowers.

We have compared the gene expression profiles of inflorescences of the floral homeotic mutants apetala1, apetala2, apetala3, pistillata, and agamous with that of wild-type plants using a flower-specific cDNA microarray and a whole genome oligonucleotide array. By combining the data sets from the individual mutant/wild type comparisons, we were able to identify a large number of genes that are, within flowers, predicted to be specifically or at least predominantly expressed in one type of floral organ. We have analyzed the expression patterns of several of these genes by in situ hybridization and found that they match the predictions that were made based on the microarray experiments. Moreover, genes with known floral organ-specific expression patterns were correctly assigned by our analysis. The vast majority of the identified transcripts are found in stamens or carpels, whereas few genes are predicted to be expressed specifically or predominantly in sepals or petals. These findings indicate that spatially limited expression of a large number of genes is part of flower development and that its extent differs significantly between the reproductive organs and the organs of the perianth.

Arabidopsis↗
PubMed2000

Analysis of spatial patterns in histological sections of brain tissue using a method based on regression.

A method of determining the spatial pattern of any histological feature in sections of brain tissue which can be measured quantitatively is described and compared with a previously described method. A measurement of a histological feature such as density, area, amount or load is obtained for a series of contiguous sample fields. The regression coefficient (beta) is calculated from the measurements taken in pairs, first in pairs of adjacent samples and then in pairs of samples taken at increasing degrees of separation between them, i.e. separated by 2, 3, 4,..., n units. A plot of beta versus the degree of separation between the pairs of sample fields reveals whether the histological feature is distributed randomly, uniformly or in clusters. If the feature is clustered, the analysis determines whether the clusters are randomly or regularly distributed, the mean size of the clusters and the spacing of the clusters. The method is simple to apply and interpret and is illustrated using simulated data and studies of the spatial patterns of blood vessels in the cerebral cortex of normal brain, the degree of vacuolation of the cortex in patients with Creutzfeldt-Jacob disease (CJD) and the characteristic lesions present in Alzheimer's disease (AD).

Alzheimer Disease↗
PubMed1978

[Electrophysiological methods of assessing myocardial hypoxia].

The potentialitis of the standard electrocardiogram, precordial cartogram and spatial analysis are confronted in 38 patients with extensive anterior or anteroseptal myocardial infarction, acute phase, in order to determine the extent and propagation of the myocardial hypoxia. The determination is performed on the base of the correlation dependence as regards the creatinine-phosphokinase level in blood. The best degree of correlation dependence has the spatial analysis of the changes in the segment ST - Vmax ST sp. r=0.69, as well as the changes in the segment ST reflected in the precordial electrocardiography - nST-0.1 mv. r=0.67. Close is the degree of correlation dependence in the standard electrocardiogram - STv r=0.59. The difference in the correlation coefficients are not statistically significant, allowing their application in the routine work of the three methods.

Acute Disease↗