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At least 793 records · Page 44Linked to original sources
PubMed2006

Use of steady-state laurdan fluorescence to detect changes in liquid ordered phases in human erythrocyte membranes.

In artificial phospholipid bilayers, dual measurements of laurdan steady-state anisotropy and emission spectra can be used to identify the presence of liquid ordered phases. Human erythrocytes were used as a model to test whether similar measurements could be applied to biological samples. Specifically, laurdan anisotropy and emission spectra were obtained from native erythrocytes before and after treatment with calcium ionophore and from the microvesicles (known to be enriched in liquid ordered domains) shed from the cells during calcium entry. Spectral and anisotropy data were consistent with an increased order and reduced fluidity of erythrocyte membrane lipids upon ionophore treatment. Microvesicle membranes appeared more ordered than native erythrocytes and similar to ionophore-treated cells based on laurdan emission. In contrast, the anisotropy value was lower in microvesicles compared to ionophore-treated cells, suggesting greater probe mobility. Parallel measurements of diphenylhexatriene anisotropy corroborated the laurdan data. These results were consistent with the liquid ordered property of microvesicle membranes based on comparisons to behavior in artificial membranes. Two-photon microscopy was used to examine the distribution of laurdan fluorescence along the surface of erythrocyte membranes before and after ionophore treatment. A dual spatial analysis of laurdan anisotropy, as revealed by the distribution of laurdan emission spectra, and intensity excited by polarized light suggested that the plasma membranes of ionophore-treated erythrocytes may also exhibit elevated numbers of liquid ordered domains.

2-Naphthylamine↗
PubMed2002

A GIS-based approach for assessing the regional conservation status of genetic diversity: an example from the southern Appalachians.

Conserving genetic diversity requires an assessment of the distribution of genetic variants in relation to patterns of land use and environmental variation at a regional scale. This assessment requires a novel approach to integrating and analyzing the genetic and environmental data across spatial scales. To explore the integration of genetic data with other geospatial data sets, we developed a GIS-based approach for examining patterns of genetic diversity for several species of salamanders in southern Appalachians. The genetic data, from allozyme surveys in the genetics literature, were integrated into a GIS database along with related attributes including population identifications and spatial locations. Using existing geospatial data, we classified sample locations as being either protected from anthropogenic disturbance (e.g., National Parks, Wilderness Areas) or as unprotected (e.g., private lands, multiple-use lands in National Forests). We used multidimensional scaling of allelic frequencies and contributions of populations to interpopulation differences in allelic richness to determine which populations had genetic characteristics most different from other populations in the sample. Measures of genetic differentiation were integrated into the GIS database to facilitate spatial analysis and visualization of the indices in relation to land use. This approach was useful for both identification of populations with components of genetic variation that were not well represented at protected sites and for identifying areas of species distributions where more genetic sampling would be necessary to make informed management decisions. Our approach could be readily adapted for use by managers and geneticists working with other species and types of genetic markers.

Animals↗
PubMed2005

Rapid assessment of soil erosion in the Rio Lempa Basin, Central America, using the universal soil loss equation and geographic information systems.

Soil erosion is a severe problem for many developing regions that lack adequate infrastructure to combat the problem. The authors established a first-order method for prioritizing areas to be examined and remediated using preexisting data and expert knowledge where data are lacking. The Universal Soil Loss Equation was applied to the Rio Lempa Basin in Central America using geographic information systems and remote sensing technologies, and the estimated erosion rates were compared with sediment delivery ratios. Spatial analysis indicates that agriculture on very steep slopes contributes only a small fraction to the total estimated soil erosion, whereas agriculture on gentle and moderately steep slopes contributes a large fraction of the erosion. Although much of the basin is in El Salvador, the greatest estimated amount of erosion is from Honduras. Data quality and availability were impaired by a lack of coordination among agencies and across countries. Several avenues for improving the authors' methods are described.

Agriculture↗
PubMed2001

Impacts of urbanization on stream habitat and fish across multiple spatial scales.

We analyzed the relation of the amount and spatial pattern of land cover with stream fish communities, in-stream habitat, and baseflow in 47 small southeastern Wisconsin, USA, watersheds encompassing a gradient of predominantly agricultural to predominantly urban land uses. The amount of connected impervious surface in the watershed was the best measure of urbanization for predicting fish density, species richness, diversity, and index of biotic integrity (IBI) score; bank erosion; and base flow. However, connected imperviousness was not significantly correlated with overall habitat quality for fish. Nonlinear models were developed using quantile regression to predict the maximum possible number of fish species, IBI score, and base flow for a given level of imperviousness. At watershed connected imperviousness levels less than about 8%, all three variables could have high values, whereas at connected imperviousness levels greater than 12% their values were inevitably low. Connected imperviousness levels between 8 and 12% represented a threshold region where minor changes in urbanization could result in major changes in stream condition. In a spatial analysis, connected imperviousness within a 50-m buffer along the stream or within a 1.6-km radius upstream of the sampling site had more influence on stream fish and base flow than did comparable amounts of imperviousness further away. Our results suggest that urban development that minimizes amount of connected impervious surface and establishes undeveloped buffer areas along streams should have less impact than conventional types of development.

Agriculture↗
PubMed2000

Locational Probability for a Dammed, Urbanizing Stream: Salt River, Arizona, USA.

/ Data from historical aerial photographs analyzed with a GIS show that river channel change on the Salt River in the Phoenix metropolitan area of central Arizona has been driven by large-scale regional flood events and local human activities. Mapping of functional surfaces such as low-flow channels, high-flow channels, islands, bars attached to channel banks, and engineered surfaces shows that during the period from 1935 to 1997, the relative areal coverage of these surfaces has changed. Flood events have caused general changes in sinuosity of the low-flow channel, but islands have remained remarkably consistent in location and size, while channel-side bars have waxed and waned. The most important determinant of local channel form and process is sand and gravel mining, which in some reaches occupies more than 70% of the active channel area. The general location of mining is closely related to the location of the moving urban fringe, which serves as a market for sand and gravel during construction. Quantitative spatial analysis of imagery supplemented by field mapping shows that for each location within the general channel area, it is possible to specify a probability of encountering a low-flow channel or other fluvial features. Maps showing the distribution of these probabilities of occurrence reveal the most probable location and configuration of the channel as it occurred in the past. Some reaches have the low-flow channel located persistently within a limited area as a result of bedrock or sinuosity controls, but other reaches dominated by flow separation or shallow gradient have almost no persistence in channel location from one flood to another.

Journal Article↗
PubMed1997

Intracellular Ca2+ distribution in migrating transformed epithelial cells.

Migration of transformed Madin-Darby canine kidney (MDCK-F) cells depends on the polarized activity of a Ca2+-sensitive K+ channel. We tested whether a gradient of intracellular Ca2+-concentration ([Ca2+]i) underlies the horizontal polarization of K+ channel activity. [Ca2+]i was measured with the fluorescent dye fura-2/AM. Spatial analysis of [Ca2+]i indicated that a horizontal gradient exists, with [Ca2+]i being higher in the cell body than in the lamellipodium. Resting and maximal levels during oscillations of [Ca2+]i in the cell body were found to be 135 +/- 34 and 405 +/- 59 nml/l, respectively, whereas they were 79 +/- 18 and 307 +/- 102 nmol/l in the lamellipodium. This gradient can partially explain the preferential activation of K+ channels in the plasma membrane of the cell body. We applied a local superfusion technique during migration experiments and measurements of [Ca2+]i to test whether its maintenance is due to an uneven distribution of Ca2+ influx into migrating MDCK-F cells. Locally superfusing the cell body of migrating MDCK-F cells with La3+ alone or together with charybdotoxin, a specific blocker of Ca2+-sensitive K+ channels, slowed migration to 47 +/- 10% and 9 +/- 5% of control, respectively. Local blockade of Ca2+ influx into the cell body and the lamellipodium with la3+ was followed by a decrease of [Ca2+]i at both cell poles. This points to Ca2+ influx occurring over the entire cell surface. This conclusion was confirmed by locally superfusing Mn2+ over the cell body and the lamellipodium. Fura-2 fluorescence was quenched in both areas, the decrease of fluorescence being two to three times faster in the cell body than in the lamellipodium. However, this difference is insufficient to account for the observed gradient of [Ca2+]i. We hypothesize that the polarized distribution of intracellular Ca2+ stores contributes significantly to the generation of a gradient of [Ca2+]i.

Animals↗
PubMed2000

New phenotypes associated with the swallow gene of Drosophila: evidence for a general role in oocyte cytoskeletal organization.

During oogenesis in Drosophila, several mRNAs and proteins are localized to discrete regions of the developing oocyte, resulting in a mature oocyte with a well-defined anterior-posterior axis. The product of the swallow (sww) gene is required for the localization of two different mRNAs during oogenesis, bicoid (bcd) and Adducin-like/hu-li tai shao (hts). We initiated a detailed characterization of the phenotypes associated with each of eight sww alleles as a means of investigating the role of sww in oogenic patterning. RNA localization defects in various sww mutants were examined by radioactive in situ hybridization to paraffin sections. Using this technique, several previously unreported RNA localization defects have been observed. Although bcd RNA localization is often lost completely in sww oocytes, in a high proportion of cases, bcd RNA is localized inappropriately along the periphery of the mature oocyte. In several sww mutants, a portion of the bcd mRNA population becomes concentrated at the posterior pole of the oocyte during late oogenesis. Several sww mutations also result in oskar RNA localization defects, consistent with a global role for sww in cytoskeletal regulation or organization. A detailed temporal and spatial analysis of hts RNA localization in sww mutants and in drug-treated ovaries reveals many similarities to bcd RNA localization, and implies the two independent localization events are accomplished by the same mechanism.

Animals↗
PubMed2005

Spatial distribution of ectomycorrhizal Basidiomycete Russula subsect. Foetentinae populations in a primary dipterocarp rainforest.

The spatial distribution of basidiocarps of the ectomycorrhizal Basidiomycete Russula subsect. Foetentinae was assessed in a primary forest in the Western Ghâts (India) dominated by the ectomycorrhizal tree species Vateria indica and Dipterocarpus indicus. Over a 7,700-m(2) sampling area, both trees and basidiocarps of Russula subsect. Foetentinae were mapped during the first month of the 2002 rainy season. First-order spatial analysis revealed that the distribution of the 45 collected carpophores was highly aggregated, with 60% of all basidiocarps located at a distance lower than 1 m from the nearest one. The genetic structure of the Russula subsect. Foetentinae population was studied by inter-simple sequence repeat polymorphism analysis using three primers. Eighteen of the 45 genotypes were represented by single basidiocarps. Twenty-seven basidiocarps were identified as belonging to 11 genets or separated ramets. Five genets were small, with diameters ranging from 0.5 to 5 m. The six others were large, with a diameter ranging from 31 m to a maximum measured distance of 70 m. In spite of the lack of data concerning the reproductive biology of this species, the presence of large genets suggests that mature stands may shelter well-spread underground mycelium, crucial for durable interaction with plant partner.

Basidiomycota↗
PubMed2003

A prospective randomized evaluation of negative-pressure wound dressings for diabetic foot wounds.

Optimal treatment for large diabetic foot wounds is ill defined. The purpose of this study was to compare the rate of wound healing with the Vacuum Assisted Closure device trade mark (VAC) to conventional moist dressings in the treatment of large diabetic foot wounds. Diabetics with significant soft tissue defects of the foot were considered for enrollment. Patients were randomized to receive either moist gauze dressings or VAC treatments for 2 weeks, after which they were treated with the alternative dressing for an additional 2 weeks. Wounds were photographed weekly and wound dimensions calculated in a blinded fashion with spatial analysis software. Percent change in wound dimensions were calculated and compared for each weekly assessment and over 2 weeks of therapy with each dressing type. Ten patients were enrolled in the trial, but two were lost to follow-up and two were withdrawn. Complete data were available for analysis on seven wounds in six patients. Average length, width, and depth of the wounds at initiation of the trial was 7.7, 3.5, and 3.1 cm, respectively. Only the wound depth was significantly decreased over the weeks of the trial to 1.2 cm ( p < 0.05). VAC dressings decreased the wound volume and depth significantly more than moist gauze dressings (59% vs. 0% and 49% vs. 8%, respectively). VAC dressings were associated with a decrease in all wound dimensions while wound length and width increased with moist dressings. In summary, over the first several weeks of therapy, VAC dressings decreased wound depth and volume more effectively than moist gauze dressings. Negative-pressure wound treatment may accelerate closure of large foot wounds in the diabetic patient.

Cross-Over Studies↗
PubMed2005

Modeling desertification change in Minqin County, China.

Monitoring environmental processes is becoming increasingly important wherever there is increasing population and economic development pressure placed on fragile environments. Remote sensing, digital image processing, and spatial analysis have proven to be useful technologies in both assessing and monitoring environmental change. In this study, they were used to assess desertification processes and change in Minqin County, China from 1988 to 1997. The results suggest that wind erosion was the dominant cause of desertification in more than half of the study area. Coupled with this were increases in salinization processes, affecting 33.62% of the land area in 1997. Overall, moderate desertification was found to be the dominant desertification grade (43.64% of total area), followed by extreme/severe desertification (26.15% of total area) in 1997. In addition, examination of landscape pattern changes indicated that desertification processes at the landscape level were becoming evident at increasing levels of fragmentation, complexity in shape, and isolation of patches. Major fluctuations in desertification type and grade were found at the fringes of oases, where an ongoing shift was taking place between cultivation, abandonment, and reclamation.

China↗
PubMed2006

Spatial relationships between water quality and pesticide application rates in agricultural watersheds.

Pesticide applications to agricultural lands in California, USA, are reported to a central data base, while data on water and sediment quality are collected by a number of monitoring programs. Data from both sources are geo-referenced, allowing spatial analysis of relationships between pesticide application rates and the chemical and biological condition of water bodies. This study collected data from 12 watersheds, selected to represent a range of pesticide usage. Water quality parameters were measured during six surveys of stream sites receiving runoff from the selected watershed areas. This study had three objectives: to evaluate the usefulness of pesticide application data in selecting regional monitoring sites, to provide information for generating and testing hypotheses about pesticide fate and effects, and to determine whether in-stream nitrate concentration was a useful surrogate indicator for regional monitoring of toxic substances. Significant correlations were observed between pesticide application rates and in-stream pesticide concentrations (p < 0.05) and toxicity (p < 0.10). In-stream nitrate concentrations were not significantly correlated with either the amount of pesticides applied, in-stream pesticide concentrations, or in-stream toxicity (all p > 0.30). Neither total watershed area nor the area in which pesticide usage was reported correlated significantly with the amount of pesticides applied, in-stream pesticide concentrations, or in-stream toxicity (all p > 0.14). In-stream pesticide concentrations and effects were more closely related to the intensity of pesticide use than to the area under cultivation.

Agriculture↗
PubMed2006

Temporal and spatial variation of nutrient levels in the Nemunas River (Lithuania and Belarus).

There are discordant results on trends in nutrient river water quality from the economical transition countries in Europe. The present study assessed the impact of these economical changes on the load and concentration at 17 monitoring stations along the Nemunas River and its major tributaries (Lithuania and Belarus). Three time periods were evaluated: the Soviet rule command system period 1986-1991, the transfer to market economy period 1992-1996 and the post reform period 1997-2002. The most surprising result in this study, was the increased area-specific load of NO(3)-N from the first to the third period at almost all the sampling sites. The increase was particularly large (43-78%) at the sites in the Lithuanian part of the river. The corresponding load increase in the Belarussian part of the river was only 1-15%. The statistical analyses of concentration data confirm the strong upward NO(3)-N trend at the Nemunas mouth and at 5 of the 6 tributaries in the lower part of Nemunas. Temporal and spatial analysis of nitrates transport in the Nemunas River and its main tributaries revealed that nitrates mainly originate from agricultural areas. The upward trends were most likely an effect of ploughing of pastures and unbalanced crop fertilisation in combination with large storage and accumulation of soil-nitrogen during the Soviet period. On contrary to nitrate-N, the area-specific load of PO(4)-P decreased significantly from the first to the third period at all sites along the Nemunas River (31-86%). Seasonal (SMK) and Partial (PMK) Mann-Kendall tests on PO(4)-P concentrations also showed significant downward trend at 14 of 16 investigated sites. The decrease of PO(4)-P levels was attributed to the reduction of municipal and industrial point source emissions and to the decreased livestock numbers. The NH(4)-N load showed the same pattern as PO(4)-P. At the river mouth the load was 90 kg km(-2) yr(-1) during the first period compared to only 20-30 kg km(-2) yr(-1) in the third period. The trend test on NH(4)-N concentrations detected significant downward trends at 5 out of 16 sites. The declines were explained by decreased emissions from cities and large animal breeding farms. This study showed that trend analysis at multiple sites in a river basin is crucial for the understanding of the variability in time and space. Such analysis is also important for our interpretation of underlying sources and fluxes in a drainage basin over time. This is particularly important for compounds that have different source origin.

Environmental Monitoring↗
PubMed2006

Monitoring of heavy metal pollution of groundwater in a phreatic aquifer in Mersin-Turkey.

In this study, heavy metal contents of groundwater from the Mersin aquifer were determined with photometric methods and used to determine the main factors controlling the pollution of groundwater in the area. Using MapInfo GIS software, spatial analysis and integration were carried out for mapping drinking water quality in the basin. From the photometric heavy metal analysis, it is inferred that the excess concentration of Fe, Ni, Mn, Mo and Cu at some locations is the cause of undesirable quality for drinking purposes. Similarly, the EC thematic map shows that considerable areas in the basin are having high salinity hazards. The reason for excess concentration of various heavy metals is the industrial activities and petroleum pipelines and salinity levels show the sea water intrusion.

Geography↗
PubMed1992

The effect of congenital deafness on cerebral asymmetry in the perception of emotional and non-emotional faces.

Functional hemispheric specialization in recognizing faces expressing emotions was investigated in 18 normal hearing and 18 congenitally deaf children aged 13-14 years. Three kinds of faces were presented: happy, to express positive emotions, sad, to express negative emotions, and neutral. The subjects' task was to recognize the test face exposed for 20 msec in the left or right visual field. The subjects answered by pointing at the exposed stimulus on the response card that contained three different faces. The errors committed in expositions of faces in the left and right visual field were analyzed. In the control group the right hemisphere dominated in case of sad and neutral faces. There were no significant differences in recognition of happy faces. The differentiated hemispheric organization pattern in normal hearing persons supports the hypothesis of different processing of positive and negative emotions expressed by faces. The observed hemispheric asymmetry was a result of two factors: (1) processing of faces as complex patterns requiring visuo-spatial analysis, and (2) processing of emotions contained in them. Functional hemispheric asymmetry was not observed in the group of deaf children for any kind of emotion expressed in the presented faces. The results suggest that lack of auditory experience influences the organization of functional hemispheric specialization. It can be supposed that in deaf children, the analysis of information contained in emotional faces takes place in both hemispheres.

Adolescent↗
PubMed1980

Spatial properties of the population of mechanoreceptive units in the glabrous skin of the human hand.

Impulses were recorded in low threshold mechanoreceptive afferents innervating the glabrous skin area of the human hand by means of needle electrodes percutaneously inserted in the median nerve of waking human subjects. In accordance with earlier investigations, the units were separated into 4 groups, mainly on the basis of their adaptation and receptive field properties: RA, PC, SA I and SA II units. The extent of the receptive fields of 255 units were mapped with von Frey hairs. The fields of the RA and SA I units were of similar size with medians of 12.6 sq. mm and 11.0 sq. mm. In contrast, the fields of the SA II and PC units were about 5 and 10 times larger, respectively. A difference in size between fields from different skin regions was found only for the RA fields which were smaller the more distal the skin region. The distributions of the field sizes were positively skewed for all 4 unit types. A model was constructed of the population of RA and SA I fields within the various regions of the hand. The model was based on (i) an estimate of the densities of units reported in a previous study, and (ii) the sizes of the receptive fields. The number and the spatial distribution of the fields which would be stimulated by indentations of simple and defined geometries were deduced from the model. The findings indicate that the RA and SA I units provide the information required for the psychophysical capacity of spatial analysis and discrimination in the glabrous skin of the hand.

Adolescent↗
PubMed1982

Sensitivity to edges of mechanoreceptive afferent units innervating the glabrous skin of the human head.

One type of rapidly adapting (RA) and one type of slowly adapting (SA I) mechanoreceptive unit innervating the glabrous skin area of the human hand have small and well defined receptive fields. Their responses to perpendicular sinusoidal skin displacements were measured when the field was completely covered by a flat contact surface and when the edge of the contact surface was placed over the field. It was found that the majority of the RA and SA I units exhibited stronger responses when the edge of the contactor was placed over the receptive field. This edge sensitivity, which was greatest for the SA I units, may be of particular importance in improving the spatial analysis of the edges of objects in contact with the skin during manual manipulation and exploration.

Adult↗
PubMed1985

Excitation of dorsal column nucleus neurons by air-jet moving across the skin.

Single unit recordings from dorsal column neurons were made during application of mechanical somatic stimuli moving at controlled velocities across the neuron's receptive field. The neurons responded in stereotypic patterns which changed with altered stimulus parameters of velocity, direction and intensity. Spatial analysis of the response patterns indicates that the neurons generate action potentials when the stimulus probe activated particular discrete locations within the receptive field.

Afferent Pathways↗
PubMed1995

Dynamic magnetic resonance imaging of vocal cord closure during deglutition.

BACKGROUND & AIMS: Vocal cord closure is instrumental in airway protection during deglutition. Conventional imaging of vocal cord closure and reopening during deglutition requires invasive and nonphysiological methods. The aim of this study was to characterize the biomechanical properties of normal vocal cord adduction/abduction during deglutition using echoplanar magnetic resonance imaging, a technique that has the capability of imaging soft-tissue motion with real-time temporal resolution. METHODS: The movements of laryngeal and vocal cord structures during swallowing were determined in 11 normal volunteers by single slice and axially reformatted multislice coronal echoplanar images. RESULTS: During swallowing, the larynx ascended to peak elevation, maintained peak elevation for a discrete interval, and descended to its resting position. Vocal cord adduction occurred with a symmetric tent-like configuration at the midpoint of maximal laryngeal elevation, whereas vocal cord abduction occurred at the midpoint of laryngeal descent. Spatial analysis of vocal cord configuration during adduction determined that the vocal cords attained an initial parallel configuration during ascent, followed by closure at peak laryngeal elevation. CONCLUSIONS: These results show that the vocal cords adduct and abduct synchronously with laryngeal ascent and descent, respectively, during deglutition. Echoplanar magnetic resonance imaging constitutes a novel tool used to assess clinical abnormalities of deglutitive laryngeal function.

Adult↗