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PubMed2000

Difference spatial distribution function analysis of aqueous solutions. IV. Hydration structure changes of ethylene glycol solutions throughout conformational change process from gGg' to tGg' conformers.

Monte Carlo (MC) simulations were carried out for an infinitely dilute aqueous solution of two stable conformers (gGg' and tGg') and of three conformations between gGg' and tGg' conformers of ethylene glycol (EG) at 298K. Based on the spatial distribution function (SDF) goo(x,y,z), obtained from the MC simulation in the above conformations in liquid water, the high distribution of hydration water molecules could be divided into hydrogen acceptor (HA), hydrogen donor (HD), MIX (overlapped distribution of HA and HD), and hydrophobic hydration (HH) regions. The spatial orientations of hydrogen-bonded water molecules were found to be of a linear type with a triple-layer structure in the HA region and HA part (in the MIX region), and double-layer structures in the HD region and HD part (in the MIX region). In addition, it was apparent that the spatial orientations of these water molecules were of the linear type throughout the conformational change process from gGg' to tGg' conformers in liquid water. From the difference SDF (DSDF), deltagoo(x,y, z), between the SDFs of two conformations, we concluded that the distribution of hydration water molecules in the HA and HD parts of the MIX region are governed by the competition of internal hydrogen bonds between the hydrogen atom and two lone-pair electrons on the oxygen atom of an EG molecule.

Algorithms↗
PubMed1991

Spatial distribution of "tissue-specific" antigens in the developing human heart and skeletal muscle. II. An immunohistochemical analysis of myosin heavy chain isoform expression patterns in the embryonic heart.

The spatial distribution of alpha- and beta-myosin heavy chain isoforms (MHCs) was investigated immunohistochemically in the embryonic human heart between the 4th and the 8th week of development. The development of the overall MHC isoform expression pattern can be outlined as follows: (1) In all stages examined, beta-MHC is the predominant isoform in the ventricles and outflow tract (OFT), while alpha-MHC is the main isoform in the atria. In addition, alpha-MHC is also expressed in the ventricles at stage 14 and in the OFT from stage 14 to stage 19. This expression pattern is very reminiscent of that found in chicken and rat. (2) In the early embryonic stages the entire atrioventricular canal (AVC) wall expresses alpha-MHC whereas only the lower part expresses beta-MHC. The separation of atria and ventricles by the fibrous annulus takes place at the ventricular margin of the AVC wall. Hence, the beta-MHC expressing part of the AVC wall, including the right atrioventricular ring bundle, is eventually incorporated in the atria. (3) In the late embryonic stages (approx. 8 weeks of development) areas of alpha-MHC reappear in the ventricular myocardium, in particular in the subendocardial region at the top of the interventricular septum. These coexpressing cells are topographically related to the developing ventricular conduction system. (4) In the sinoatrial junction of all hearts examined alpha- and beta-MHC coexpressing cells are observed. In the older stages these cells are characteristically localized at the periphery of the SA node.

Adult↗
PubMed2002

Spatial distribution patterns of interphase centromeres during retinoic acid-induced differentiation of promyelocytic leukemia cells.

BACKGROUND: The pericentromeric heterochromatin is an important element for the regulation of gene silencing. Its spatial distribution during interphase appears to be cell-type specific. This study analyzes three-dimensional (3D) centromere distribution patterns during cellular differentiation along the neutrophil pathway. METHODS: Differentiation of the promyelocytic leukemia cell line NB4 was induced by retinoic acid. Centromeres in interphase nuclei were visualized by immunofluorescence staining of centromere-associated proteins with CREST serum. 3D images of nuclei were obtained by confocal microscopy. Automated methods for the segmentation of point-like objects in 3D images were implemented to detect the position of centromeres. Features of centromere localization patterns were determined by constructing the minimal spanning tree of the centromere distribution. RESULTS: In differentiated NB4 cells, the number of centromere conglomerates (chromocenters) was decreased and the distance between chromocenters was increased as compared with untreated controls. The nuclear volume did not differ between the two groups. CONCLUSIONS: The measured rearrangement of centromeres indicates a progressive clustering of heterochromatin and a global remodeling of interphase chromosome territories during differentiation of NB4 cells. The developed methods for the analysis of 3D centromere distribution patterns provide the opportunity for a fast and objective analysis of heterochromatin remodeling.

Algorithms↗
PubMed1992

Spatial distribution of the Sm antigen in Drosophila early embryos.

Anti-Sm antibodies recognize the major small nuclear RNA-protein particles (snRNPs) involved in pre-mRNA processing. The spatial distribution of the snRNPs has been investigated in Drosophila embryos up to the cellularization stage (cycle 14), using the Y12 anti-Sm antibody. Our results show that: 1) all or most of the Sm antigen is localized in the cytoplasm of the syncytial blastoderm until the 12th cycle of division, in both the nuclear and cytoplasmic compartments at cycle 13, and then in the nuclei at cycle 14 and later. This relocalization takes place when zygotic transcriptional activation occurs; 2) at the subcellular level, the Sm antigen localizes in a speckled pattern and in foci-like structures within the nucleus of Drosophila blastoderm embryos; 3) strikingly, some nuclei of embryos at the 14th cycle appear to contain more snRNPs than others. The position of these nuclei differs from one embryo to another, and their distribution does not resemble any known developmental pattern of Drosophila embryogenesis. We propose that random differences in snRNP concentration may serve as an epigenetic signal for stochastic events occurring during development.

Animals↗
PubMed2003

Temporal and spatial distribution of paramoebae in the water column--a pilot study.

Amoebic gill disease is the main disease affecting the salmonid industry in Tasmania, but no information on the distribution of the causative pathogen, Neoparamoeba pemaquidensis, in the aquatic environment is available. This pilot study aimed to determine temporal and spatial distributions of paramoebae species in the water column, using an immuno-dot blot technique. Water samples were collected from inside fish cages at various depths (0.5, 5.5 and 11.0 m) in both summer and winter, as well as various distances (0, 0.5, 240, 280, 750 and 1100 m) away from the sea cage and farming site. Paramoebae densities were estimated using the most probable number technique (MPN). Temperature, salinity, dissolved oxygen, turbidity, nitrite and nitrates, and bacterial counts were measured for each water sample. Data were analysed using a residual maximum likelihood test and significant associations between paramoebae densities and environmental factors were analysed. Results showed that densities were significantly higher in summer (P = 0.017), at 5.5 m depth (P = 0.029), and reduced to the lowest density at 1100 m away from the cage sites (P = 0.008). Bacterial counts, turbidity and temperature were found to be significantly associated with paramoebae densities.

Amoebida↗
PubMed2002

Is the spatial distribution of brain lesions associated with closed-head injury in children predictive of subsequent development of posttraumatic stress disorder?

PURPOSE: To determine whether there is an association between the spatial distributions of lesions detected at magnetic resonance (MR) imaging of the brain in children, adolescents, and young adults after closed-head injury (CHI) and development of the reexperiencing symptoms of posttraumatic stress disorder (PTSD). MATERIALS AND METHODS: Data obtained in 94 subjects without a history of PTSD as determined by parental interview were analyzed. MR images were obtained 3 months after CHI. Lesions were manually delineated and registered to the Talairach coordinate system. Mann-Whitney analysis of lesion distribution and PTSD status at 1 year (again, as determined by parental interview) was performed, consisting of an analysis of lesion distribution versus the major symptoms of PTSD: reexperiencing, hyperarousal, and avoidance. RESULTS: Of the 94 subjects, 41 met the PTSD reexperiencing criterion and nine met all three PTSD criteria. Subjects who met the reexperiencing criterion had fewer lesions in limbic system structures (eg, the cingulum) on the right than did subjects who did not meet this criterion (Mann-Whitney, P =.003). CONCLUSION: Lesions induced by CHI in the limbic system on the right may inhibit subsequent manifestation of PTSD reexperiencing symptoms in children, adolescents, and young adults.

Adolescent↗
PubMed2005

Spatial distribution of lead in enamel and coronal dentine of wistar rats.

Lead is one of the most hazardous environmental toxins known. The assessment of lead in dental hard tissues is important in the understanding of its toxic effects on oral tissues and in estimating exposure and body burden in individuals exposed to lead from the environment. However, current information on the uptake and distribution of lead in enamel and dentine is limited. The aim of this project was to study, at high resolution, the spatial distribution of lead in enamel and coronal dentine using an experimental rat model. A dose of 40 mg/L of lead nitrate was administered to pregnant female rats during the periods of gestation and lactation through drinking water. First mandibular molar teeth were removed from their 15-d-old pups and the distribution of lead was studied using a nuclear microprobe (NMP). The distribution of lead in enamel and coronal dentine showed four distinct zones with significantly different mean lead concentrations (p<0.05). High levels of lead were observed in the superficial regions of enamel and in the dentine directly adjacent to the pulp. Additionally, the results confirmed that the NMP is capable of mapping the distribution of lead in teeth at micron resolutions with a detection limit of approx 1 microg/g.

Animals↗
PubMed2004

Nitric oxide spatial distribution in single cultured hippocampus neurons: investigation by projection of reconstructed 3-D image and visualization technique.

Recent studies have revealed a non-homogeneous distribution of nitric oxide synthase (NOS) in neurons. However, it is not yet clear whether the intracellular distribution of NOS represents the intracellular nitric oxide (NO) distribution. In the present study, software developed in our laboratory was applied to the reconstructed image obtained from confocal slice images in order to project the 3-D reconstructed images in any direction and to cut the neuron in different sections. This enabled the spatial distribution of NO to be visualized in any direction and section. In single neurons, NO distribution was seen to be heterogeneous. After stimulation with glutamate, the spatial changes in different areas of the neuron were different. These findings are consistent with immunocytochemical data on the intracellular localization of nNOS in hippocampus neurons, and will help to elucidate the specificity of nitric oxide signaling. Finally, the administration of SNAP and L-NAME was used to examine DAF-2 distribution in the neurons. The results showed this distribution to be homogenous; therefore, it did not account for the NO distribution results.

Animals↗
PubMed1996

The spatial distribution of phospholipids and glycolipids in the membrane of the bacterium Micrococcus luteus varies during the cell cycle.

Recently, we have developed a photocrosslinking approach which uses anthracene as a photoactivatable group and which allows us to determine the lateral distribution of lipids in membranes quantitatively. In synchronous cultures of the gram-positive bacterium Micrococcus luteus, this approach shows that the spatial distribution of phosphatidylglycerol and dimannosyldiacylglycerol, the two major lipids in the bacterial membrane, varies greatly during the cell cycle. Minimum heterogeneity was observed during cell growth while maximum heterogeneity was detected during cell division.

Cell Cycle↗
PubMed2002

Spatial distribution and yield of DNA double-strand breaks induced by 3-7 MeV helium ions in human fibroblasts.

Accelerated helium ions with mean energies at the target location of 3-7 MeV were used to simulate alpha-particle radiation from radon daughters. The experimental setup and calibration procedure allowed determination of the helium-ion energy distribution and dose in the nuclei of irradiated cells. Using this system, the induction of DNA double-strand breaks and their spatial distributions along DNA were studied in irradiated human fibroblasts. It was found that the apparent number of double-strand breaks as measured by a standard pulsed-field gel assay (FAR assay) decreased with increasing LET in the range 67-120 keV/microm (corresponding to the energy of 7-3 MeV). On the other hand, the generation of small and intermediate-size DNA fragments (0.1-100 kbp) increased with LET, indicating an increased intratrack long-range clustering of breaks. The fragment size distribution was measured in several size classes down to the smallest class of 0.1-2 kbp. When the clustering was taken into account, the actual number of DNA double-strand breaks (separated by at least 0.1 kbp) could be calculated and was found to be in the range 0.010-0.012 breaks/Mbp Gy(-1). This is two- to threefold higher than the apparent yield obtained by the FAR assay. The measured yield of double-strand breaks as a function of LET is compared with theoretical Monte Carlo calculations that simulate the track structure of energy depositions from helium ions as they interact with the 30-nm chromatin fiber. When the calculation is performed to include fragments larger than 0.1 kbp (to correspond to the experimental measurements), there is good agreement between experiment and theory.

Cells, Cultured↗
PubMed2005

Spatial distribution of cold antihydrogen formation.

Antihydrogen is formed when antiprotons are mixed with cold positrons in a nested Penning trap. We present experimental evidence, obtained using our antihydrogen annihilation detector, that the spatial distribution of the emerging antihydrogen atoms is independent of the positron temperature and axially enhanced. This indicates that antihydrogen is formed before the antiprotons are in thermal equilibrium with the positron plasma. This result has important implications for the trapping and spectroscopy of antihydrogen.

Journal Article↗
PubMed1994

Spatial distribution of Escherichia coli in the mouse large intestine inferred from rRNA in situ hybridization.

Fluorescent oligonucleotide probes targeting rRNA were used to develop an in situ hybridization technique by which the spatial distribution of Escherichia coli in the large intestines of streptomycin-treated mice was determined. Single E. coli cells were identified in thin frozen sections from the large intestines by the use of a probe specific for E. coli 23S rRNA. Furthermore, the total bacterial population was visualized with an rRNA probe targeting the domain Bacteria. By this technique, all E. coli cells were seen embedded in the mucosal material overlying the epithelial cells of the large intestine, and no direct attachment to the epithelium was observed.

Animals↗
PubMed1995

A distributed-parameter model of the myelinated human motor nerve fibre: temporal and spatial distributions of action potentials and ionic currents.

A double cable model of the myelinated human motor nerve fibre is presented. The model is based on the nodal and internodal channels in a previous, two-component model of human motor axons (Bostock et al. 1991), added to a complex extended cable structure of nodal, paranodal and internodal segments. The model assumes a high-resistance myelin sheath and a leakage pathway to the internodal axolemma via the paranodal seal resistance and periaxonal space. The parameter values of the model were adjusted to match the recordings of threshold electrotonus in human motor fibres from Bostock et al. (1991). Kirchoff's current law was used to derive a system of partial differential equations for the electrical equivalent circuit, and numerical integration was performed with a fixed time increment and non-uniform spatial step sizes, in accordance with the complex structure of the fibre. The model calculations provide estimates of the spatial and temporal distributions of action potentials and their transaxonal and transmyelin components, both in different segments of the fibre and at different moments during action potential propagation. The distribution of transaxonal and transmyelin currents along the fibre and their contributions from different ionic channels are also explored.

Action Potentials↗
PubMed2002

Modeling and spatially distributing forest net primary production at the regional scale.

Forest, agricultural, rangeland, wetland, and urban landscapes have different rates of carbon sequestration and total carbon sequestration potential under alternative management options. Changes in the proportion and spatial distribution of land use could enhance or degrade that area's ability to sequester carbon in terrestrial ecosystems. As the ecosystems within a landscape change due to natural or anthropogenic processes, they may go from being a carbon sink to a carbon source or vice versa. Satellite image analysis has been tested for timely and accurate measurement of spatially explicit land use change and is well suited for use in inventory and monitoring of terrestrial carbon. The coupling of Landsat Thematic Mapper (TM) data with a physiologically based forest productivity model (PnET-II) and historic climatic data provides an opportunity to enhance field plot-based forest inventory and monitoring methodologies. We use periodic forest inventory data from the U.S. Department of Agriculture (USDA) Forest Service's Forest Inventory and Analysis (FIA) Program to obtain estimates of forest area and type and to generate estimates of carbon storage for evergreen, deciduous, and mixed-forest classes. The area information is used in an accuracy assessment of remotely sensed forest cover at the regional scale. The map display of modeled net primary production (NPP) shows a range of forest carbon storage potentials and their spatial relationship to other landscape features across the southern United States. This methodology addresses the potential for measuring and projecting forest carbon sequestration in the terrestrial biosphere of the southern United States.

Ecosystem↗
PubMed2002

Characterization and spatial distribution of heavy metals in sediment from Cedar and Ortega rivers subbasin.

The Cedar and Ortega rivers subbasin is a complex environment where both natural and anthropogenic processes influence the characteristics and distributions of sediments and contaminants, which in turn is of importance for maintenance, dredging and pollution control. This study investigated the characteristics and spatial distribution of heavy metals, including lead (Pb), copper (Cu), zinc (Zn) and cadmium (Cd), from sediments in the subbasin using field measurements and three-dimensional kriging estimates. Sediment samples collected from three sampling depth intervals (i.e., 0-0.10, 0.11-0.56 and 0.57-1.88 m) in 58 locations showed that concentrations of Pb ranged from 4.47 to 420.00 mg/kg dry weight, Cu from 2.30 to 107.00 mg/kg dry weight, Zn from 9.75 to 2,050.00 mg/kg dry weight and Cd from 0.07 to 3.83 mg/kg dry weight. Kriging estimates showed that Pb, Cu and Cd concentrations decreased significantly from the sediment depth of 0.10 to 1.5 m, whereas Zn concentrations were still enriched at 1.5 m. It further revealed that the Cedar River area was a potential source area since it was more contaminated than the rest of the subbasin. Comparison of aluminum (Al)-normalized metal concentrations indicated that most of the metals within the top two intervals (0-0.56 m) had concentrations exceeding the background levels by factors of 2-10. A three-dimensional view of the metal contamination plumes showed that all of the heavy metals, with concentrations exceeding the threshold effect level (TEL) that could pose a threat to the health of aquatic organisms, were primarily located above the sediment depth of 1.5 m.

Environmental Monitoring↗
PubMed2006

Seasonal and spatial distribution of nonylphenol in Lanzhou Reach of Yellow River in China.

Nonylphenol (NP) is known as an endocrine disruptor and consequently has drawn much environmental concern. This study focused on seasonal variation and spatial distribution of NP in various matrices including water, suspended particles, and sediment taken from Lanzhou Reach of Yellow River in China. NP was measured in July and November in 2004. Concentrations of NP in water ranged from 34.2 to 599.0 ng/l, in suspended particles from 49.6 to 2835.2 ng/g dry wt, and in sediment from 38.4 to 863.0 ng/g dry wt. In terms of most water and suspended particles samples, concentrations were higher in warmer seasons than in colder seasons. Good linear correlations (R(2)=0.90 in July, R(2)=0.97 in November) were obtained for NP concentrations between water and suspended particles. In terms of sediment samples, concentrations were higher in November than in July, probably due to greater deposition of suspended particles. Reasonable linear correlations (R(2)=0.60 in July, R(2)=0.79 in November) were obtained for NP concentrations between water and sediment.

China↗
PubMed1994

Spatial distribution of naturally occurring 210Po and 226Ra in children's teeth.

Deciduous and permanent teeth extracted from juveniles for orthodontic purposes have been analysed using alpha-sensitive plastic track detectors for the spatial distribution of total alpha-activity and naturally occurring 210Pb-supported 210Po and 226Ra. The distribution of these radionuclides is non-uniform, with 210Po being primarily associated with outer enamel and 226Ra with the pulp. The observations suggest that 210Pb/210Po concentrates at the interface of enamel with saliva or blood, by means of unidirectional ionic exchange with calcium. In contrast, 226Ra concentrates in the predentine band at the interface with pulp and with systemic blood circulation, where its uptake is permitted by the incomplete calcification in this band. Activity concentration was measured in 900 teeth. Total concentration on the outer enamel surface of deciduous teeth, permanent teeth from children < or = 10 years and permanent teeth from children > 10 years give respective mean values of 8.63 +/- 0.26, 5.76 +/- 0.48 and 7.00 +/- 0.15 Bq kg-1. 226Ra concentration on the corresponding longitudinal sections comprising pulp, dentine and annular enamel give respective mean values of 0.715 +/- 0.055, 0.418 +/- 0.083 and 0.514 +/- 0.029 Bq kg-1. Mean activity concentration in 32 foetal teeth was 2.05 +/- 0.31 Bq kg-1. The results form the basis of more detailed studies of (1) age-dependent uptake of alpha-radionuclides in teeth and their microdistribution, and (2) the geographical variation in activity concentration with respect to environmental factors such as domestic radon exposure.

Child↗
PubMed2006

The discrete representation correspondence between quantum and classical spatial distributions of angular momentum vectors.

This work demonstrates that the quantum mechanical moments of a state described by the density matrix correspond to discrete spherical harmonic moments of the classical multipole expansion of the spatial distribution of the angular momentum vectors. For the diagonal density matrix elements, this work exploits the fact that the quantum mechanical vector coupling (Clebsch-Gordan) coefficients become increasingly accurate discrete representations of spherical harmonics as j increases. A Schwinger-type basis accounts for nonaxially symmetric angular distributions, which result in nonzero off-diagonal elements of the density matrix. The resulting discrete minimum uncertainty picture of the classical moments has a stringent equivalence with the quantum mechanical one for all j and provides an unambiguous connection for the classical and quantum moments in the large j limit. The equivalence is numerically tested for simple models, and there is a satisfying equivalence even for small j. Applications, implications, and extensions are indicated, and the relevance of this work for the interpretation of classical mechanical simulations of inelastic and reactive molecular collisions will be documented elsewhere.

Journal Article↗