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PubMed1986

Efferent projections of nucleus locus coeruleus: topographic organization of cells of origin demonstrated by three-dimensional reconstruction.

The present study examines the spatial distribution within rat locus coeruleus of neurons projecting to particular brain regions. In order to accurately recreate, in digital and pictorial formats, the spatial distribution of neurons for the entire nucleus locus coeruleus, three-dimensional reconstructions were created which specified the location of each individual Nissl-stained locus coeruleus cell in each of five nuclei. Dynamic computerized displays were visually analyzed and statistically compared. The nuclei from different brains were found to be strikingly similar in density and distribution of cells. In order to determine whether the cells of origin for particular locus coeruleus projections were clustered within the nucleus, reconstructions were created of the distributions of cells labeled by injections of a retrograde tracer, horseradish peroxidase, into particular terminal regions. Groups consisting of animals with injections into the same target areas were visually and statistically compared. The cells of origin of most efferent projections were found to be spatially organized within locus coeruleus. Specifically, projections to both the dorsal and ventral hippocampus originated solely from the dorsal segment of the nucleus, while spinal cord projections originated from ventral-posterior locus coeruleus. Cells of origin of cerebral and cerebellar cortical efferents, as well as hypothalamic efferents, exhibited less clustering, although reliable differences in distribution were observed. The most striking example of clustered cells of origin was exhibited by the large norepinephrine-containing cells constituting the anterior pole of locus coeruleus which were labeled only by hypothalamic injections. This analysis of spatial organization within locus coeruleus is unique in its utilization of a defined control group, experimental groups consisting of strictly defined replications, accurate three-dimensional reconstruction, and statistical comparisons. The demonstrated spatial heterogeneity of locus coeruleus neurons with respect to efferent projections can now be compared to the spatial distributions of other cellular characteristics such as soma morphology, colocalized transmitters and physiological properties. Presumably, such spatial segregation reflects the operation of functionally important organizing principles within the nucleus.

Animals↗
PubMed2004

The effects of land use change on mercury distribution in soils of Alta Floresta, Southern Amazon.

This study presents the spatial distribution, degree of contamination and storage capacity of Hg in surface forest and pasture soils from Alta Floresta, Southern Amazon, a significant gold mining site from 1980 to 1996. During that period, average annual gold production was about 6.5 tons, with an estimated Hg annual emission to the environment of about 8.8 tons, 60-80% of it being emitted to the atmosphere. Mercury sources to the region are mining sites and gold-dealer shops at the city of Alta Floresta, where gold is smelted and commercialized. Mercury concentrations in forest soils (15-248 ng g(-1), average=61.9 ng g(-1)) were 1.5-3.0 times higher than in pasture soils (10-74 ng g(-1), average=33.8 ng g(-1)), suggesting strong re-mobilization after deforestation. Highest Hg concentrations were found within a distance of 20-30 km from mining sites in both soil types. The influence of the refining operations within the city of Alta Floresta, however, was less clear. Somewhat higher concentrations were observed only within a 5 km radius from the city center where gold-dealer shops are located. Wind direction controls the spatial distribution of Hg. Background concentrations (15-50 ng g(-1)) were generally found at the outer perimeter of the sampling grid, about 40 km from sources. This suggests that Hg released from mining and refining activities undergoes rapid deposition. Estimated cumulative Hg burdens for the first 10 cm of soil averaged 8.3 mg m(-2) and 4.9 mg m(-2), for forest and pasture soils respectively and compare well with ultisols and hydromorphic oxisols, but were lower than those found in yellow-red and yellow latosols and podsols from other Amazonian areas. Our results show that changing land use in the Amazon is a strong re-mobilizing agent of Hg deposited on soils from the atmosphere.

Animals↗
PubMed2006

[Application and verification of distributed model in simulating watershed evapotranspiration].

Based on the conventional observed meteorological data during 1989 approximately 2000, a distributed model was employed to simulate the temporal and spatial distribution of the potential and actual evapotranspiration in the upper Zagunao watershed of Sichuan Province. Grids of 500 m and step of 1 d were used to describe the spatial and temporal heterogeneity and variability in the study area. The potential evapotranspiration was simulated by a deformation form of Penman-Monteith Equation, and a method for calculating actual evapotranspiration was proposed, with the underlying conditions considered. The results showed that the relative error of the normal annual evapotranspiration in the 12 years between the simulation and the calculation was 3.47%, with a reasonable temporal and spatial distribution. The research results provided an effective method for the distributed rainfall-runoff model in simulating actual evapotranspiration.

Mathematics↗
PubMed1990

Gastrin-releasing peptide: neuronal distribution and spatial relation to endocrine cells in the human upper gut.

By using immunocytochemical techniques, we have studied the distribution of gastrin releasing peptide (GRP)-containing neurons as well as the spatial relationship between these neurons and the endocrine cells in the human stomach and duodenum. Moderate numbers of immunoreactive fibers were distributed in the smooth muscle and submucosa of the stomach; they were more rare in the duodenal wall. Numerous GRP-containing nerve fibers were found in the oxyntic mucosa, the antral mucosa harboured only few GRP immunoreactive nerve fibers. The mucosa of the proximal duodenum was found to be virtually devoid of such fibers. Only occasionally did we observe signs of a direct contact between GRP-containing nerve fibers and gastrin and somatostatin cells in the antral mucosa. In the oxyntic mucosa GRP-containing nerve fibers sometimes seemed to contact endocrine cells, including somatostatin cells as well as individual parietal cells. In conclusion, although GRP-containing nerve fibers were quite numerous in the wall of the human upper gastro-intestinal (GI)-tract, we observed a lack of intimate spatial relationship between these fibers and endocrine cells in the antral mucosa, suggesting additive mechanisms to a direct innervation of gastrin cells and somatostatin cells by GRP nerve fibers explaining the physiological effects on hormonal release.

Adult↗
PubMed2005

Distribution and speciation of metals in annual rings of black willow.

Information on the spatial distribution and speciation of metals in nonhyperaccumulator plants is lacking. This study used synchrotron X-ray fluorescence (SXRF) compositional imaging to investigate the spatial distribution of Ni, Mn, Cu, Zn, and Fe in annual rings of black willow (Salix nigra L.) collected from a metal-contaminated area, and used X-ray absorption spectroscopy (XAS) to investigate Ni and Mn speciation in regions of the annual rings with elevated Ni concentrations. Annual rings were recollected in early 2003 from an individual known to be enriched with Ni from previous studies. Compositional imaging showed Ni and associated co-contaminants conservatively located in an annual ring. When compared with a corresponding photomicrograph, SXRF compositional images showed that metals were sharply constrained by the boundaries of the annual ring, indicating a sudden onset and cessation of uptake, and a lack of post-growth mobility of the metals. There was a particularly strong correlation between Ni and Mn in the metal-enriched annual ring (r = 0.8822), which suggested similar transport and binding behavior of these elements. X-ray absorption spectroscopy showed Ni and Mn to be present in the 2+ oxidation state. X-ray absorption near edge structure spectroscopy (XANES) fingerprinting of localized, highly Ni-enriched regions within the lumen of willow xylem vessels found similarities with Ni-pectic acid complexes, Ni-histidine, and NiSO4.

Environmental Monitoring↗
PubMed1996

The neurotopography of vowels as mirrored by evoked magnetic field measurements.

The auditory evoked neuromagnetic field elicited by synthetic specimens of the vowels [a], [ae], [u], and [i] was recorded over the left and the right hemisphere of 11 subjects. The N100m and the SF deflection of the recorded signal was submitted to equivalent current source analysis using the model of a single dipole in a spherical volume conductor. Vowel processing was hypothesized to occur in a multistage process rendering a sequence of representations of the acoustic input. Vowel representations were considered to differ among each other in the features they make salient, thus, in the kind of dissimilarity relationship they establish, and, by implication, in terms of the vowel space defined by the respective set of dissimilarities. It was investigated whether a mapping exists between at least one of a number of hypothetical vowel spaces and the cortical response space spanned by the spatial distribution of vowel evoked equivalent current dipoles. Although the spatial configuration of vowel evoked sources proved to be highly variable across subjects, the ordering of distances between N100m and SF equivalent current dipole locations turned out to correspond to the ordering of distances between the corners of a vowel trapezium. There were some, albeit weak, indications of hemispheric differences in vowel processing. The results suggest that the spatial distribution of the equivalent current dipole sources of both the N100m and the SF deflection of the neuromagnetic field elicited by vowels reflect a processing stage transitional between auditory and phonetic representation.

Acoustic Stimulation↗
PubMedDate not supplied

[Functional organization of the vestibulospinal system in amphibians].

In experiments on the preparation of a frog perfused brain, using recording of intracellular potentials the vestibulospinal neurons were identified on the basis of excitatory postsynaptic potentials evoked by the stimulation of the ipsilateral vestibular nerve and antidromic activation from the stimulation of the cervical and lumbar enlargements of the spinal cord. The average conduction velocity determined for axons of C neurons was 10.67 m/s and for L neurons 15.84 m/s. The ratio of C and L neurons over the vestibular nuclear complex was very stimular to each other: 52% C neurons and 48% L neurons. The majority of both types of neurons were localized in the lateral vestibular nucleus (58.6%), to the lesser extent in the descending vestibular nucleus (30.7%) and very little in the medial vestibular nucleus (10.6%). Fast and slow cells were detected among the vestibulospinal neurons. The fast neurons of L cells did not prevail greatly over the slow ones, whereas the slow neurons of C cells prevailed comparatively largely over the fast neurons. Thus, it became possible to reconstruct spatial distribution of the identified vestibulospinal neurons. The results of spatial distribution of C and L vestibulospinal neurons in the frogs failed to conform to definite somatotopy, which is characteristic for mammalian vestibular nuclei. C and L neurons in the frog's vestibular nuclei as a source of vestibulospinal fibres, are scattered separately or more frequently in groups, so that they establish a "patch-like" somatotopy and do not form a distinctly designed fields as in mammals.

Amphibians↗
PubMed2006

Large organic aerosols in a dynamic and continuous whole-body exposure chamber tested on humans and on a heated mannequin.

Exposure to large airborne organic aerosols may cause respiratory and skin symptoms. The use of human exposure chambers permits safe mechanistic studies of the effect of inhalation or dermal deposition of such particles. The performance of a dynamic and continuous whole-body human exposure chamber using turbulent air mixing during exposure to these organic aerosols of humans and of a new heated mannequin was evaluated. Variability of temporal and spatial distribution of the airborne particle concentration, and aerodynamic aerosol size distribution of the inhalable fraction, were evaluated. The temporal and spatial distribution of these aerosols close to the breathing zone during an exposure session was typically < or = 10%, which is low for airborne particles of this size. In a larger section around a human, only slightly higher spatial variation was found. Variability between exposure sessions was also low (< 10%). Only limited effect of relative humidity for the organic aerosols was observed. The aerodynamic particle size distribution curves differed slightly, but some were comparable to those in occupational environments. The outcome of the performance tests as measured with the heated mannequin was almost the same as with humans, indicating that the mannequin could be used in preparatory tests in this type of chamber.

Aerosols↗
PubMed2003

Connectivity distribution of spatial networks.

We study spatial networks constructed by randomly placing nodes on a manifold and joining two nodes with an edge whenever their distance is less than a certain cutoff. We derive the general expression for the connectivity distribution of such networks as a functional of the distribution of the nodes. We show that for regular spatial densities, the corresponding spatial network has a connectivity distribution decreasing faster than an exponential. In contrast, we also show that scale-free networks with a power law decreasing connectivity distribution are obtained when a certain information measure of the node distribution (integral of higher powers of the distribution) diverges. We illustrate our results on a simple example for which we present simulation results. Finally, we speculate on the role played by the limiting case P(k) proportional, variant k(-1) which appears empirically to be relevant to spatial networks of biological origin such as the ones constructed from gene expression data.

Journal Article↗
PubMed2001

Texture analysis of fluorescence lifetime images of nuclear DNA with effect of fluorescence resonance energy transfer.

BACKGROUND: Fluorescence lifetime imaging microscopy (FLIM) is becoming an important tool in cellular imaging. In FLIM, the image contrast is concentration insensitive, whereas it is sensitive to the local environment and interactions of fluorophores such as fluorescence resonance energy transfer (RET). METHODS: Fluorescence microscopy, lifetime imaging, and texture analysis were used to study the spatial distribution of fluorophores bound to nuclear DNA. 3T3-Swiss albino mice fibroblast nuclei were labeled with Hoechst 33258 (Ho), an AT-specific dye, and 7-aminoactinomycin D (7-AAD), a GC-specific dye. Ho is a RET donor to the 7-AAD acceptor. RESULTS: Texture analysis of 50 alcohol-fixed nuclei quantitatively showed changes of spatial distribution of apparent donor lifetimes. RET increased the spatial heterogeneity in the phase and modulation lifetime images. In most of the doubly stained cells (about 80%), the phase and modulation lifetime distributions were spatially homogeneous. In about 20% of the cells, we noticed that lower phase and modulation lifetimes caused by RET were correlated with regions of high Ho intensity in the nuclei. CONCLUSIONS: The spatial lifetime heterogeneity of Ho in presence of 7-AAD seems to be caused by RET between closely spaced strands in the three dimensionally condensed regions of DNA.

3T3 Cells↗
PubMed1997

Responses of Picea, Pinus and Pseudotsuga roots to heterogeneous nutrient distribution in soil.

The spatial distribution of plant-available mineral nutrients in forest soils is often highly heterogeneous. To test the hypothesis that local nutrient enrichment of soil leads to increased root proliferation in the nutrient-rich soil zone, we studied the effects of nutrient enrichment on the growth and nutrient concentrations of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst.) roots. Three-year-old seedlings were grown for 9 months in split-root containers filled with nutrient-poor forest mineral soil, with one side supplemented with additional mineral nutrients. Root dry weight and root length in Scots pine and Norway spruce were increased in the nutrient-supplemented soil compared with the nonsupplemented side, whereas root growth in Douglas-fir was unaffected by nutrient enrichment. Of the three species examined, Norway spruce exhibited the highest root and shoot growth and the highest nutrient demand. Specific root length (m g(-1)) and the number of root tips per unit root length were not affected by local nutrient addition in any of the species. Despite increased root growth in Norway spruce and Scots pine in nutrient-supplemented soil, their root systems contained similar nutrient concentrations on both sides of the split-root container. Thus, coniferous trees may respond to local nutrient supply by increased root proliferation, but the response varies depending on the species, and may only occur when trees are nutrient deficient. As a response to local nutrient enrichment, increases in root dry matter or root length may be better indicators of pre-existing nutrient deficiencies in conifers than increases in root nutrient concentrations.

Journal Article↗
PubMed1988

Glucose uptake, lactate release, ketone body turnover, metabolic micromilieu, and pH distributions in human breast cancer xenografts in nude rats.

Glucose uptake, lactate release, ketone body utilization, spatial distribution of glucose, lactate, and ATP concentrations as well as tissue pH distributions were systematically investigated in s.c. and/or "tissue-isolated" human breast cancer xenografts in T-cell-deficient rnu/rnu rats. Large variations in all parameters were detected within and between tumors indicating a very nonuniform substrate turnover. Glucose was taken up by all xenografts. Glucose consumption rates increased with increasing glucose availabilities, implying that the glucose uptake is mainly determined by the efficiency of nutritive tumor blood flow. The average glucose uptake was 0.37 mumol/g/min in medullary and 0.26 mumol/g/min in squamous cell carcinomas of the breast. At wet weights below 5 g, medullary breast cancers consumed more glucose than squamous cell carcinomas (2P less than 0.05). Most tumors (97%) released lactate in an amount linearly related to glucose consumption. The lactate production of medullary (0.33 mumol/g/min) and squamous cell (0.31 mumol/g/min) breast cancers was similar. In general, the xenografts utilized ketone bodies. beta-Hydroxybutyrate was consumed by 82% and acetoacetate by 73% of the tumors, the uptake rates being linearly related to the respective availabilities. The mean uptake of beta-hydroxybutyrate was 3.48 nmol/g/min and that of acetoacetate 2.56 nmol/g/min. No significant differences were seen between medullary and squamous cell breast cancers. The beta-hydroxybutyrate/acetoacetate ratio in the tumor-venous blood rose with decreasing tumor blood flow indicating the development of hypoxia at advanced growth stages. Glucose, lactate, and ATP levels were all very heterogeneously distributed in medullary and squamous cell tumors as compared with normal tissue. No relationship was evident between the spatial distribution of concentrations of these three substrates. The xenografts were acidotic compared with pH values in normal subcutis. The mean tissue pH in medullary breast cancers was 6.81 +/- 0.25 (SD). Compared with these values, the tissue pH distribution in squamous cell breast cancers was shifted to significantly higher values. The mean pH of the latter tumors was 7.04 +/- 0.19 (2P less than 0.001). From the experimental data presented there is clear indication that the metabolism of the xenografts investigated was mainly determined by the efficiency of nutritive blood flow, i.e., by substrate availability, and not by the metabolic demand of the cancer cells.

Animals↗
PubMed1986

Tuberculosis in West Bengal.

Inspite of the various curative and preventive measures the control of tuberculosis has not been effective. Today it persists as an endemic disease in many parts of India. The present study aims to map the spatial distribution of tuberculosis in West Bengal and to evaluate the spatial change over time between 1960 to 1980. The mortality data for the 16 districts of West Bengal have been used to map spatial distribution of tuberculosis for 1980 and the expected deaths have been calculated based on the mid-year population. The rural and urban sectors have been treated separately. Similarly a time space change in tuberculosis mortality has been calculated for the districts based on the quinquinneal population change between 1960, 1965, 1970, and 1980. In all cases the probability has been tested by Poissons Probability model at the significance levels of p less than 0.01 and p less than 0.05. The principal zones of tuberculosis endemicity are the Nn.Hill region and the adjoining plains, the central plains of Bankura district, and Calcutta. A wide rural urban difference is perceptible in spatial context as well as in time scale. Though tuberculosis is principally a disease of the male population, it is more prevalent among females of the lower age group. The declining trend of tuberculosis though observable from 1965 is not uniform for all districts. An increasing trend in Purulia is apparent in the present decade while in Calcutta the trend of decline is very gradual.

Adolescent↗
PubMed1988

Experimental demonstration of lateral cohesion in a layer of adsorbed protein and in layers of gold-antibody complexes bound to surface immobilised antigen.

The spatial distribution of ferritin molecules adsorbed on quartz surfaces and the spatial distribution of antibody-coated colloidal gold particles over an antigen-coated surface was studied by electron microscopy. Ferritin molecules were found to initially adsorb in small clusters at 2.5 X 10(9) sites/cm2. The initial nucleation was followed by growth of the clusters. Gold antibody complexes were initially bound to the antigen-coated surface as single particles, and formation of clusters was a secondary event at higher particle densities. The results indicate that lateral cohesion between macromolecules may play a role in the stability of adsorbed layers of protein and surface immobilised antigen-antibody complexes.

Animals↗
PubMed1993

Structure-activity relationships for mitomycins. Application of the distance and charge analysis method.

Molecular orbital calculations based on coordinates from X-ray analysis have been performed for a set of 24 mitomycins, of which eight compounds have not been isolated so far. To prioritize the order of synthesis of these missing compounds, a new method named DISCA (distance and charge analysis) has been developed. DISCA screens correlations between spatial distribution of charge in molecules and their biological activity. The spatial distribution of charge is represented by several indexes in DISCA. LD50 and ED50 were used as measures of biological activity. DISCA has successfully extracted indexes which have significantly high correlation coefficients. The indexes with the highest correlation coefficient were common to both LD50 and ED50. By use of the correlation functions with high correlation coefficients DISCA has predicted that 9-epi-1a-N-demethylmitomycin D should have the best ED50 and a modest LD50 among the missing mitomycins.

Mitomycins↗
PubMed1966

Receptive fields of opponent color units in the optic nerve of the ground squirrel.

When mapped with white light, each receptive field consisted either of an excitatory ("on") center and a concentric inhibitory ("off") surround, or of the reverse arrangement. Monochromatic stimuli revealed that each receptive field was composed of two mutually antagonistic components (one excitatory, one inhibitory) which had different spectral sensitivities and different spatial distributions. For some units the two chromatic components had identical spatial distributions.

Animals↗
PubMed1988

Primary and Bacterial Secondary Production in a Southwestern Reservoir.

Rates of primary and bacterial secondary production in Lake Arlington, Texas, were determined. The lake is a warm (annual temperature range, 7 to 32 degrees C), shallow, monomictic reservoir with limited macrophyte development in the littoral zone. Samples were collected from six depths within the photic zone from a site located over the deepest portion of the lake. Primary production and bacterial production were calculated from NaHCO(3) and [methyl-H]thymidine incorporation, respectively. Peak instantaneous production ranged between 14.8 and 220.5 mug of C liter h. There were two distinct periods of high rates of production. From May through July, production near the metalimnion exceeded 100 mug of C liter h. During holomixis, production throughout the water column was in excess of 100 mug of C liter h and above 150 mug of C liter h near the surface. Annual areal primary production was 588 g of C m. Bacterial production was markedly seasonal. Growth rates during late fall through spring were typically around 0.002 h, and production rates were typically 5 mug of C liter h. Growth rates were higher during warmer parts of the year and reached 0.03 h by August. The maximum instantaneous rate of bacterial production was approximately 45 mug of C liter h. Annual areal bacterial production was 125 g of C m. Temporal and spatial distributions of bacterial numbers and activities coincided with temporal and spatial distributions of primary production. Areal primary and bacterial secondary production were highly correlated (r = 0.77, n = 15, P < 0.002).

Journal Article↗
PubMed1995

Order and disorder in auditory cortical maps.

Recent physiological experiments suggest that several basic receptive field properties of neurons show non-uniform spatial distributions in the primary auditory cortex of cats and primates. The spatial distribution patterns of some of these receptive field parameters are suggestive of a parallel coding scheme for processing sound information onto several superimposed cortical 'maps'. The representations of these parameters in the auditory cortex are compatible with general features of self-organizing mapping algorithms, as the spatial representations exhibit global parameter gradients with overlaid functional patchiness. Recent studies have also revealed that within a 'representational' map, the degree of local coherence varies over a wide range and that the map can contain a substantial degree of disorder in its parametric representation of sounds. Although the causes and consequences of this representational disorder are not known, it may reflect yet unresolved organizational principles in the auditory cortex.

Acoustic Stimulation↗