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PubMed2000

Difference spatial distribution function analysis of aqueous solutions. III. Hydration structures of alcohol and ether solutions having straight chain and branched alkyl groups.

Spatial distribution functions (SDFs), gOO(x,y,z) and gOH(x,y,z), obtained from Monte Carlo simulations at 298 K were applied to characterize the anisotropic structure of infinitely dilute aqueous solutions of alcohols and ethers having straight chain and branched alkyl groups. In spite of the different size and shape of the hydrophobic groups, the spatial orientation of the hydrogen-bonded water molecules was found to be of linear type with a triple layer structure in the hydrogen acceptor (HA) region and a double layer structure in the hydrogen donor (HD) region. The volumes and the coordination number (CN) in the HA region were essentially identical for all alcohol and ether solutions, but the volumes for the isopropyl alcohol (IPA) and isopropyl methyl ether (IPE) solutions were greater than those for the other solutions. In the hydrophobic hydration (HH) region, these values increased with increasing size and shape of hydrophobic groups, except in the case of IPA and IPE solutions. These results indicated that the hydration structures around the isopropyl group in alcohol and ether solutions differed from those in other solutions. From the results of the difference SDF (DSDF), AgOO(x,y,z), between SDFs gOO(x,y,z) for the two states, it was apparent that the distribution of hydration water molecules in the HA region for ether solution was characterized by the increase of the distribution in the direction of lone pair electrons on the oxygen atom of the solute molecule with increasing hydrophobicity.

Alcohols↗
PubMed2002

DNA spatial distribution in unfertilized human oocytes by confocal laser scanning microscope.

The aim of this study is to investigate the DNA spatial distribution in unfertilized human oocytes by confocal laser scanning microscope (CLSM). One hundred and forty unfertilized oocytes after conventional in vitro fertilization (IVF) and one hundred and three after intracytoplasmic sperm injection (ICSI) were studied. The chromatin was stained with chromomycin A3 (CA3) initially and at a second step with propidium iodide, allowing the observation of the deprotaminated sperm heads in the ooplasm. CLSM offered the opportunity for studying the three-dimensional position of the spermatozoon in the oocyte and the description of the status of the maternal and paternal chromatin. For each of the IVF and ICSI group of unfertilized oocytes, subgroups were performed according to the status of the maternal and paternal chromatin. The maternal chromosomes were either aligned at metaphase II or disarrayed at metaphase II, and the sperm head was either condensed or swollen/decondensed. Few oocytes were activated and formed a pronucleus. The spatial approaching between paternal and maternal chromatin was calculated for all subgroups of unfertilized oocytes and the distances were compared among them. There was no statistical difference in the distance between the spermatozoon and the maternal chromatin among subgroups of the IVF group, while statistical differences occurred among subgroups of the ICSI group. The spermatozoa in the IVF group approached maternal chromatin more than those in the ICSI group. Movement of the spermatozoon into the oocyte and chromatin remodeling for the formation of pronucleus seem to occur independently and are possibly directed by different mechanisms.

Chromatin↗
PubMed1998

Temporal-spatial distribution of hepatocyte nuclear factor-3beta in developing human lung and other foregut derivatives.

We assessed the temporal-spatial distribution of hepatocyte nuclear factor-3beta (HNF-3beta) in developing human lung and other foregut derivatives. Tissue from 31 fetuses (10-40 weeks) and 24 infants with hyaline membrane disease (HMD) or bronchopulmonary dysplasia (BPD) (2 days to 7 months) was studied. HNF-3beta was detected in nuclei of epithelial cells of trachea and of conducting and terminal airways at 10 weeks. Thereafter, epithelial nuclei were immunolabeled more widely in peripheral than proximal airways. HNF-3beta was confined to bronchiolo-alveolar portals and Type II cells in nonfetal lung. In infants with BPD, HNF-3beta was expressed abundantly in regenerating epithelial cells at the periphery of lung lobules. HNF-3beta was also detected in fetal esophagus, pancreas, duodenum, stomach, and gallbladder, suggesting that it is a marker for progenitor cells in foregut derivatives. The pattern of expression of HNF-3beta in the lung was similar to that of thyroid transcription factor-1 (TTF-1) at all ages. The temporal-spatial patterns of HNF-3beta and TTF-1 in the developing and regenerating lung are consistent with their proposed role in epithelial cell differentiation, regeneration, and surfactant protein gene expression. (J Histochem Cytochem 46:955-962, 1998)

Bronchi↗
PubMed2000

Spatial distribution of contextual interactions in primary visual cortex and in visual perception.

To examine the role of primary visual cortex in visuospatial integration, we studied the spatial arrangement of contextual interactions in the response properties of neurons in primary visual cortex of alert monkeys and in human perception. We found a spatial segregation of opposing contextual interactions. At the level of cortical neurons, excitatory interactions were located along the ends of receptive fields, while inhibitory interactions were strongest along the orthogonal axis. Parallel psychophysical studies in human observers showed opposing contextual interactions surrounding a target line with a similar spatial distribution. The results suggest that V1 neurons can participate in multiple perceptual processes via spatially segregated and functionally distinct components of their receptive fields.

Animals↗
PubMed1990

Spatial distribution of the capacity to initiate a secondary embryo in the 32-cell embryo of Xenopus laevis.

To examine the spatial distribution of dorsal determinants in the early embryos of Xenopus laevis, individual cells from the 32-cell embryo were transplanted into the same tier of the ventral side of a synchronous recipient. Their abilities to initiate a secondary embryo were measured by the incidence of secondary embryos and by the length of the secondary axis relative to the primary embryo. The ability was found to be localized in all cells (A1, B1, C1, and D1) of the dorsal most column and in the vegetal cells (C2 and D2) of the dorsolateral column. Transplanted C1 (subequatorial) cells caused the highest incidence of a secondary embryo and the average relative length of the secondary embryo was also greatest. Effectiveness decreased in the order: D1, B1, D2, C2, and A1. When these results were compared with Dale and Slack's fate map of the 32-cell embryo, it was concluded that the distribution of dorsal determinants is unique and does not coincide with the prospective regions for any tissues, though it is somewhat similar to the prospective region of dorsal endoderm or notochord. From these results it seems that dorsal determinants do not determine a particular tissue in an embryo but rather the "dorsal" region of an embryo.

Animals↗
PubMed2006

Comparative analysis of (239)Pu, (137)Cs, (210)Pb and (40)K spatial distributions in the top soil layer at the Baltic coast.

This paper presents the results of an investigation into the spatial distribution of radionuclides of artificial ((239,240)Pu, (137)Cs) and natural ((210)Pb, (40)K) origins in the upper (0-5 cm) soil layers on the Baltic coastline of Lithuania ( approximately 5 km(2) area). The samples were analysed by gamma ray spectrometry and combined radiochemical procedures. The highest (210)Pb, (239,240)Pu and (137)Cs activity concentrations were determined in the forest samples, whereas (40)K activity was rather homogeneous across the study area. Relatively high (239,240)Pu and (40)K activity concentrations were determined along the surf zone. The (210)Pb and (137)Cs activity concentrations showed a gradual increase from the surf zone to the forest. The average activity concentrations of (239,240)Pu, (137)Cs, (210)Pb and (40)K in the beach and forest samples, respectively, were as follows: 0.32+/-0.08 and 0.74+/-0.14; 50+/-4 and 1190+/-50; 4.7+/-2.0 and 48+/-6; 186+/-15 and 216+/-17 Bq/kg.

Baltic States↗
PubMed2001

Social democratic government and spatial distribution of health care facilities. The case of hospital beds in Germany.

BACKGROUND: In this paper, the hypothesis that the spatial distribution of hospital beds is more even in countries with socialist or social democratic governments than in countries with conservative or Christian democratic governments was tested. To avoid the confounding influences of historical and institutional differences between countries, we used the Federal Republic of Germany as a case study. The German federal states have their own governments who play an important role in creating structures for the planning of hospital facilities. METHODS: The test of the hypothesis was largely quantitative. At the level of federal states the rank correlation was computed between the weighted number of years of left-wing government participation and the coefficient of variation in the number of hospital beds per 1000 inhabitants. In addition to this, the hospital plans of two federal states were studied. RESULTS: The hypothesis was supported by the data, showing a positive association between the number of years of left-wing government participation and regional variation in the number of hospital beds. A comparison of the hospital plans of two contrasting federal states showed less government interference in hospital planning in the state with a tradition of right-wing government. CONCLUSION: There seems to be a relation between left-wing government participation in West German states and a more equal distribution of the number of hospital beds per 1,000 inhabitants.

Democracy↗
PubMed2005

Randomised controlled trials in Africa of HIV and AIDS: descriptive study and spatial distribution.

OBJECTIVES: To identify and describe randomised controlled trials on HIV and AIDS conducted in Africa and to map their spatial distribution using exact geographic coordinates. DESIGN: Construction and analysis of a database of trials conducted wholly or partly in Africa and reported before 2004. DATA SOURCES: CENTRAL, Medline, Embase, and LILACS. RESULTS: Our comprehensive search yielded 284 distinct records that were potentially eligible for inclusion in the database. Of these, 150 articles reported on 77 eligible trials published or reported from 1987 to 2003. Seven trials were identified exclusively from the CENTRAL database. Trials were conducted in 18 of 48 countries in sub-Saharan Africa. None were conducted in north Africa. Only 19 had a principal investigator located in an African country. Forty two trials assessed prevention and 35 assessed treatment. Most studies were funded by government agencies outside Africa (n = 43), with the pharmaceutical industry providing partial support to 16 of these. The pharmaceutical industry provided full or partial support to a further 18 trials. Only 43 trials reported conducting a power calculation for determining sample size. There was no mention of ethical approval or informed consent in 19 and 17 trials, respectively. CONCLUSION: The relatively small number of HIV/AIDS trials conducted in Africa is not commensurate with the burden of disease. Geographical mapping as an adjunct to prospective trial registration is a useful tool for researchers and decision makers to track existing and future trials.

Africa↗
PubMed2003

A framework to contain a spatially distributed model of the degradation of solid waste in landfills.

This paper describes the concept and development of a generic spatially distributed numerical model that can contain and link sub-models of landfill processes in order to simulate solid waste degradation and gas generation in landfills. The model has been designed to simulate anaerobic degradation of solid waste saturated in leachate, and to reflect the effect on degradation of the control of both the flow and chemistry of the leachate in the pore space of the solids. The model can accommodate different profiles of waste constituents and therefore has the potential to simulate the effects of pre-treatment techniques such as shredding and inoculation. Components of the model simulate the transport of leachate and gases, and the consolidation of the solid waste. The results of some prototype calculations are presented.

Environmental Pollutants↗
PubMed2002

[The spatial distribution of asymmetry coefficients of the brain bioelectric activity while experiencing negative emotions].

Statistically significant differences were revealed in the spatial distribution of the asymmetry coefficients in the brain bioelectrical activity for different negative emotions. In case of the asthenic emotion (anger) the asymmetry coefficients in the beta-2 band were positive and greater in the frontal part of the brain as compared to the background. When the subjects experienced (imagined) the asthenic emotion (grief), the asymmetry coefficients were negative in the beta-1 band and a generalized growth of slow-wave activity was observed.

Adult↗
PubMed2003

[Spatial distribution characteristics and ecological effects of carbon and nitrogen of soil in Huolin River catchment wetland].

This paper studied the spatial distribution characteristics and ecological effects of organic carbon and nitrogen in soils of Huolin River catchment wetland in horizontal and vertical levels. The results showed that the differences of horizontal and vertical distribution of organic carbon and nitrogen were very obvious, and of all the factors such as the period of wetting and drying cycles, leaching, plant and flood etc., the period of wetting and drying cycles was contents the critical one, which caused the differences. Soil organic carbon was significantly correlated with soil nitrogen (r = 0.977). The ratio of carbon and nitrogen (C/N) changed along with the humidity gradient, and soil pH values obviously influenced the concentration of organic carbon and nitrogen. The correlation of C/N values and organic carbon and nitrogen contents in wetland soil and in grassland soil were remarkably different, and the ecological effects mainly included production effect and clarification effect.

Carbon↗
PubMed1989

The molluscicidal properties of Ambrosia maritima L. (Compositae). 4. Temporal and spatial distribution of Biomphalaria alexandrina in Egyptian village irrigation systems with reference to schistosomiasis transmission control.

Data on the temporal and spatial distribution of Biomphalaria alexandrina were collected throughout one year in two village irrigation systems near Alexandria, Egypt. Snails bearing Schistosoma mansoni cercariae were found from May to December but about 80% of annual transmission potential was confined from June to August. Although snail infection rates were generally 0-2%, higher rates were recorded and tended to be associated with smaller number snail collections. Infected snails were found in most canal and drain types and were judged to be present across most of the irrigated area of each village. In view of the dispersed nature of both infected snails and human-water contact in the area, it is suggested that schistosomiasis transmission is more widespread than focal. Effective transmission control using molluscicides should therefore require application to all village irrigation water-courses. The difficulties these various findings might impose on the use of commercial molluscicides are discussed and some possible advantages of the alternative plant molluscicide, Ambrosia maritima are noted.

Animals↗
PubMed2005

Spatial distribution of Escherichia coli O157-positive farms in Scotland.

Using a sample of 949 Scottish farms with finishing cattle, the spatial distribution of Escherichia coli O157-positive farms was investigated using disease mapping models. The overall prevalence of E. coli O157-positive farms was estimated as 22%. The regions used in this study were the 16 postcode areas of Scotland. For each region, the posterior relative risk (RR) was estimated as a model-based alternative to the saturated standardized morbidity ratio (SMR), i.e., the ratio between observed and expected cases in a region. Three Bayesian hierarchical models with generalized linear modeling of the area-specific risks were used to estimate the posterior relative risk of E. coli O157-positive farms in the postcode areas: a random-effects model incorporating only spatially uncorrelated heterogeneity; a model incorporating both spatially correlated and uncorrelated heterogeneity; and a pseudo-mixture model with unstructured correlation and a weighted mix of two variance components representing the spatial correlation and a jump structure. None of the models identified any areas with a significant increase or decrease in risk. The deviance information criteria slightly favored the simplest model (RR range: 0.92--1.09). However, this model appeared to smooth out more of the variation in the RR compared to the pseudo-mixture model, which gave a more informative pattern of the posterior relative risks (range: 0.81--1.22).

Animals↗
PubMed1993

The spatial distribution of calcium signals in squid presynaptic terminals.

1. The fluorescent Ca2+ indicator dye, fura-2, was used to examine the spatial distribution of intracellular Ca2+ signals in giant presynaptic terminals of squid. Brief trains of presynaptic action potentials were evoked to open Ca2+ channels within the giant presynaptic terminals and elevate presynaptic Ca2+ concentration. 2. Electrical stimulation produced pronounced rises in presynaptic Ca2+ concentration. These rises were much larger in the terminal region than in the adjacent axonal region of the presynaptic neuron, suggesting that Ca2+ channels are most abundant in the terminal. 3. Stimulation also produced gradients in Ca2+ concentration across the width of the presynaptic terminal. During stimulation, Ca2+ concentration was highest in the compartment of the presynaptic terminal closest to the postsynaptic neuron. This suggests that the Ca2+ channels are localized to this region of the presynaptic terminal. 4. Following the end of action potential trains, the rises in Ca2+ concentration became uniform across the width of the terminal. The redistribution of Ca2+ presumably is due to diffusion of Ca2+ throughout the presynaptic cytoplasm. Stimulus-evoked rises in Ca2+ declined slowly over several tens of seconds. 5. Histological examination of a giant presynaptic terminal used for imaging experiments revealed that the spatial compartments where stimulus-induced rises in Ca2+ concentration were highest were also enriched in active zones, the presynaptic sites of transmitter secretion. The co-localization of Ca2+ transients and active zones strongly suggests that neurons cluster Ca2+ channels selectively at active zones and that they do so to enhance the magnitude of Ca2+ signals in the vicinity of the active zone. 6. Longitudinal gradients in Ca2+ concentration also occur within presynaptic terminals and can be quantitatively accounted for by gradients in surface/volume ratio and density of active zones along the length of the presynaptic terminal.

Action Potentials↗
PubMed2005

Weed seedbank evaluating method to generate spatial distribution maps.

The objective of this work was to develop a fast and practical method of weed seedbank evaluation to generate spatially distributed maps for use in site-specific weed management. Soil cores were collected at 0.20 m depth, air-dried, and then submitted to seedling growth in greenhouse. The sampling grid of 20 by 20 m was georeferenced by Global Positioning System, obtaining 73 soil cores with three replicates. During the greenhouse trial, there were two peaks of weed seedling growth: one in 119 days after water irrigation and another after KNO3 application. Weeds seedbank maps were obtained at different stages of seedling growth. The Pearson correlation was 0.99 for Brachiaria plantaginea seedbank map, 0.95 for Commelina benghalensis, and 0.85 for Cyperus rotudus generated at 119 days compared with 392 days after seedling growth in the greenhouse. The Brachiaria plantaginea seedbank map evaluated at 35 days presented correlation of 0.97 with 392 days. It was concluded that, for site-specific weed seedbank management, the evaluation of seedling growth in greenhouse until the first emergence peak is enough to generate weed seedbank maps.

Agriculture↗
PubMed1993

Spatial distribution of nerve injury after occlusion of individual major vessels in rat sciatic nerves.

In an attempt to better understand the spatial distribution of ischemic injury secondary to occlusion of major arteries, we measured nerve blood flow (NBF) and studied morphologic changes at various levels distal to the ligature site. Arterial ligation of the femoral, internal iliac, or superior gluteal artery was preceded and followed by measurement of NBF using laser Doppler flowmetry which helped identify "watershed areas" and guided the sampling process as nerves were examined pathologically and areas of injury were identified. Femoral artery ligation produced the most severe ischemia, focally reducing NBF by 80% in the tibial nerve at a level just below the knee. Within these ischemic nerve segments there were degenerative changes of nerve fibers seen mainly in the subperineurial region. Ligation of the internal iliac artery caused an approximately 60% reduction in NBF at the upper and mid-thigh levels of the sciatic nerve which resulted only in endoneurial edema in tissue taken at this level. Following superior gluteal artery ligation. NBF was reduced by only 20% at the pelvic level of the sciatic nerve and there was neither endoneurial edema nor fiber abnormalities. This study demonstrates the watershed pattern of ischemic injury associated with single vessel ligation by correlating neuropathologic change with quantitative measures of local nerve blood flow. The data further support the concept that mild levels of ischemia cause endoneurial edema, while moderate levels of ischemia produce demyelination and severe ischemia produces Wallerian degeneration.

Animals↗
PubMed2007

Prevalence and spatial distribution of intestinal parasitic infections in a rural Amazonian settlement, Acre State, Brazil.

A population-based survey of the prevalence and spatial distribution of intestinal parasitism was carried out in an agricultural settlement in the Amazon Basin of Brazil (Granada, Acre State). More than half (53.4%) of the 429 stool specimens from subjects in all age groups, living in 113 households, had cysts, ova, or larvae of intestinal parasites. The most prevalent parasites were Giardia duodenalis (19.6%) and soil-transmitted helminths (12.7%); 105 (24.5%) subjects were infected with more than one species of parasite. Significant age-related differences in prevalence were only found for G. duodenalis (children < 1 year and adults > 30 years were less affected). Six households (5.3%), situated within a radius of 690m, comprised 48.1% of all subjects harboring soil-transmitted helminths in our study area. Households within this cluster were poorer and more crowded than those outside the cluster. The observed spatial clustering of infections with soil-transmitted helminths provides valuable information for the spatial targeting of sanitary interventions in this area.

Adolescent↗
PubMed1996

PML-containing nuclear bodies: their spatial distribution in relation to other nuclear components.

The PML protein is a human growth suppressor concentrated in 10 to 20 nuclear bodies per nucleus (PML bodies). Disruption of the PML gene has been shown to be related to acute promyelocytic leukaemia (APL). To obtain information about the function of PML bodies we have investigated the 3D-distribution of PML bodies in the nucleus of T24 cells and compared it with the spatial distribution of a variety of other nuclear components, using fluorescence dual-labeling immunocytochemistry and confocal microscopy. Results show that PML bodies are not enriched in nascent RNA, the splicing component U2-snRNP, or transcription factors (glucocorticoid receptor, TFIIH, and E2F). These results show that PML bodies are not prominent sites of RNA synthesis or RNA splicing. We found that a large fraction of PML bodies (50 to 80%) is closely associated with DNA replication domains during exclusively middle-late S-phase. Furthermore, in most cells that we analysed we found at least one PML body was tightly associated with a coiled body. In the APL cell line NB4, the PML gene is fused with the RAR alpha gene due to a chromosomal rearrangement. PML bodies have disappeared and the PML antigen, i.e., PML and the PML-RAR fusion protein, is dispersed in a punctated pattern throughout the nucleoplasm. We showed that in NB4 cells the sites that are rich in PML antigen significantly colocalize with sites at which nascent RNA accumulates. This suggests that, in contrast to non-APL cells, in NB4 cells the PML antigen is associated with sites of transcription. The implications of these findings for the function of PML bodies are consistent with the idea that PML bodies are associated with specific genomic loci.

Cell Nucleus↗