SEARCH · PubMed Health

Results for “Spatial Distribution”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources

PubMed2005

Spatial distribution of di- and tri-methyl lysine 36 of histone H3 at active genes.

Methylation of lysine 4 of histone H3 (K4/H3) is linked to transcriptional activity, whereas methylation of K9/H3 is tightly associated with gene inactivity. These are well characterized sites of methylation within histones, but there are numerous other, less characterized, sites of modification. In Saccharomyces cerevisiae, methylation of K36/H3 has been linked to active genes, but little is known about this methylation in higher eukaryotes. Here we analyzed for the first time the levels and spatial distribution of di- and tri-methyl (di- and tri-Me) K36/H3 in metazoan genes. We analyzed chicken genes that are developmentally regulated, constitutively active, or inactive. We found that active genes contain high levels of these modifications compared with inactive genes. Furthermore, in actively transcribed regions the levels of di- and tri-Me K36/H3 peak toward the 3' end of the gene. This is in striking contrast to the distributions of di- and tri-Me K4/H3, which peak early in actively transcribed regions. Thus, di/tri-Me K4/H3 and di/tri-Me K36/H3 are both useful markers of active genes, but their genic distribution indicates differing roles. Our data suggest that the unique spatial distribution of di- and tri-Me K36/H3 plays a role in transcriptional termination and/or early RNA processing.

Animals↗

PubMed2002

Spatially distributed alternative splice variants of the renal Na-K-Cl cotransporter exhibit dramatically different affinities for the transported ions.

Three splice variants of the renal Na-K-Cl cotransporter (NKCC2 F, A, and B) are spatially distributed along the thick ascending limb of the mammalian kidney. To test whether NKCC2 splice variants differ in ion transport characteristics we expressed cDNAs encoding rabbit NKCC2 F, A, and B in Xenopus oocytes and determined the ion dependence of bumetanide-sensitive (86)Rb influx. The three splice variants of NKCC2 showed dramatic differences in their kinetic behavior. The medullary variant F exhibited 3-4-fold lower affinity than variants A and B for Na(+) and K(+). Chloride affinities also markedly distinguish the three variants (K(m)F = 111.3, K(m)A = 44.7, and K(m)B = 8.9 mm Cl(-)). Thus, the kinetic properties of the NKCC2 splice variants are consistent with the spatial distribution of the variants along the thick ascending limb as they are involved in reabsorbing Na(+), K(+), and Cl(-) from a progressively diluted fluid in the tubule lumen. Variant B also showed an anomalous inhibition of rubidium influx at high extracellular Na(+) concentrations, possibly important in its highly specialized role in the macula densa. The adaptation of the kinetic characteristics of the NKCC2 variants to the luminal concentrations of substrate represents an excellent example of functional specialization and diversity that can be achieved through alternative mRNA splicing.

Alternative Splicing↗

PubMed2003

Spatial distribution analysis of AT- and GC-rich regions in nuclei using corrected fluorescence resonance energy transfer.

We employed microscopic intensity-based fluorescence resonance energy transfer (FRET) images with correction by donor and acceptor concentrations to obtain unbiased maps of spatial distribution of the AT- and GC-rich DNA regions in nuclei. FRET images of 137 bovine aortic endothelial cells stained by the AT-specific donor Hoechst 33258 and the GC-specific acceptor 7-aminoactinomycin D were acquired and corrected for the donor and acceptor concentrations by the Gordon's method based on the three fluorescence filter sets. The corrected FRET images were quantitatively analyzed by texture analysis to correlate the spatial distribution of the AT- and GC-rich DNA regions with different phases of the cell cycle. Both visual observation and quantitative texture analysis revealed an increased number and size of the low FRET efficiency centers for cells in the G(2)/M-phases, compared to the G(1)-phase cells. We have detected cell cycle-dependent changes of the spatial organization and separation of the AT- and GC-rich DNA regions. Using the corrected FRET (cFRET) technique, we were able to detect early DNA separation stages in late interphase nuclei.

AT Rich Sequence↗

PubMed2006

Laser ablation inductively coupled plasma mass spectrometry for direct analysis of the spatial distribution of trace elements in metallurgical-grade silicon.

The spatial distribution and concentration of impurities in metallurgical-grade silicon (MG-Si) samples (97-99% w/w Si) were investigated by use of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The spatial resolution (120 mum) and low limits of detection (mg kg(-1)) for quality assurance of such materials were studied in detail. The volume-dependent precision and accuracy of non-matrix-matched calibration for quantification of minor elements, using NIST SRM 610 (silicate standard), indicates that LA-ICP-MS is well suited to rapid process control of such materials. Quantitative results from LA-ICP-MS were compared with previously reported literature data obtained by use of ICP-OES and rf-GD-OES. In particular, the distribution of element impurities and their relationship to their different segregation coefficients in silicon is demonstrated.

Journal Article↗

PubMed2001

Spatial distribution of tropospheric ozone in national parks of California: interpretation of passive-sampler data.

The National Park Service (NPS) has tested and used passive ozone samplers for several years to get baseline values for parks and to determine the spatial variability within parks. Experience has shown that the Ogawa passive samplers can provide +/-10% accuracy when used with a quality assurance program consisting of blanks, duplicates, collocated instrumentation, and a standard operating procedure that carefully guides site operators. Although the passive device does not meet EPA criteria as a certified method (mainly, that hourly values be measured), it does provide seasonal summed values of ozone. The seasonal ozone concentrations from the passive devices can be compared to other monitoring to determine baseline values, trends, and spatial variations. This point is illustrated with some kriged interpolation maps of ozone statistics. Passive ozone samplers were used to get elevational gradients and spatial distributions of ozone within a park. This was done in varying degrees at Mount Rainier, Olympic, Sequoia-Kings Canyon, Yosemite, Joshua Tree, Rocky Mountain, and Great Smoky Mountains national parks. The ozone has been found to vary by factors of 2 and 3 within a park when average ozone is compared between locations. Specific examples of the spatial distributions of ozone in three parks within California are given using interpolation maps. Positive aspects and limitations of the passive sampling approach are presented.

Air Pollution↗

PubMed2001

Three-dimensional computerised atlas of the rat brain stem precerebellar system: approaches for mapping, visualization, and comparison of spatial distribution data.

Comparisons of microscopical neuroanatomic data from different experiments and investigators are typically hampered by the use of different section planes and dissimilar techniques for data documentation. We have developed a framework for visualization and comparison of section-based, spatial distribution data, in brain stem nuclei. This framework provides opportunities for harmonized data presentation in neuroinformatics databases. Three-dimensional computerized reconstructions of the rat brain stem and precerebellar nuclei served as a basis for establishing internal coordinate systems for the pontine nuclei and the precerebellar divisions of the sensory trigeminal nuclei. Coordinate based diagrams were used for presentation of experimental data (spatial distribution of labelled neurons and axonal plexuses) from standard angles of view. Each nuclear coordinate system was based on a cuboid bounding box with a defined orientation. The bounding box was size-adjusted to touch cyto- and myeloarchitectonically defined boundaries of the individual nuclei, or easily identifiable nearby landmarks. We exemplify the use of these internal coordinate systems with dual retrograde neural tracing data from pontocerebellar and trigeminocerebellar systems. The new experimental data were combined, in the same coordinate based diagrams, with previously published data made available via a neuroinformatics data repository (www.nesys.uio.no/Database, see also www.cerebellum.org). Three-dimensional atlasing, internal nuclear coordinate systems, and consistent formats for presentation of neuroanatomic data in web-based data repositories, offer new opportunities for efficient analysis and re-analysis of neuroanatomic data.

Animals↗

PubMed2002

Spatial distribution of fiber types within skeletal muscle fascicles from Standardbred horses.

Skeletal muscle fascicles from superficial and deep portions of semitendinosus (ST) and gluteus medius (GM) muscles from Standardbred trotters were analyzed with regard to muscle fiber type proportion (types I, IIA, and IIB) and spatial distribution. Muscle fibers within a fascicle were divided into four layers (L(1-4)) from the fascicle periphery toward the center. The observed proportions of fiber types among layers were found to be statistically significantly different from a random distribution of fiber types. Type IIB fibers predominated in the peripheral layer, type I fibers prevailed in the layer underneath, and proportions close to the mean of the whole fascicles were observed in the central layer. This pattern of spatial distribution of fiber types within the layers of the fascicles was observed at all four muscle sampling sites. The functional significance of the common pattern is unknown, but possible functional roles are discussed.

Animals↗

PubMed1985

The relative spatial distribution of CFU-S in the mouse spleen.

Mouse spleens were separated into white and red pulp fractions and into axial and marginal fractions for analysis of the relative concentration of hemopoietic stem cells (CFU-S) with respect to their spatial distribution in the spleen. Of the total splenic CFU-S population, 80% was in the red pulp fraction. The CFU-S concentration in this fraction was 11 times higher than in the white pulp fraction, which contained lymphoid follicles, periarteriolar sheaths, surrounding marginal zones, and occasional fragments of red pulp areas. Within the red pulp, CFU-S were spatially distributed with high concentrations in the subcapsular regions and decreasing frequency toward the median intersept of the spleen, where the CFU-S frequency was about one-fifth that found in the subcapsular area. The data suggest that marginal zones contain relatively more CFU-S than the follicles themselves.

Animals↗

PubMed1994

Automated cytometry of fibre size and spatial distribution in the superficial masseter muscle of the rat at three ages.

An image cytometry program was applied to sections of the superficial masseter muscle of female and male 21-, 42- and 105-day-old rats. Lesser diameter and spatial distribution of more than 6000 muscle fibres were automatically measured in digital images from muscle sections stained for myofibrillar ATPase activity. In this muscle, only type 2A, 2B and 2C fibres were observed. At the three ages and in both sexes, 2A fibres were found to have the largest diameter and were the most frequent (> 54%). In the 21-day-old animals, females presented larger diameters than did males; in contrast, in the 105-day-old animals, the three fibre types were larger in males than in females. At all ages and in both sexes, type 2A occupied 32 to 80% more cross-sectional area than type 2B. Most images (98%) showed a random spatial distribution of their fibre types. All fibre types grew in diameter with age. The coefficient of variation of the diameter was age-independent and remained under 23%. The finding of an age-independent variable could have a practical application: an increase of the coefficient of variation (> 25%) can be considered as pathological, even without a perfect age-matched control.

Aging↗

PubMedDate not supplied

Spatial distribution of the Human T-Lymphotropic Virus types I and II (HTLV-I/II) infection among blood donors of Hemominas Foundation, Belo Horizonte, Minas Gerais State, Brazil, 1994-1996.

We conducted a cross-sectional study of the spatial distribution of HTLV-I/II infection among blood donors of Hemominas Foundation, living in Belo Horizonte, from 1994 to 1996. Study population (1,022) was composed by 533 cases (positive Western Blot (WB), indeterminate WB and ELISA positive without WB result) and a random sample of 489 non-cases (HTLV-I/II serum negative). Cases and non-cases were georeferenced using the exact or an approximation of the household address reported at the blood donation interview. Using multivariate analysis, cases with WB result are less likely to be reposition blood donors compared to voluntary ones (OR = 0.70; CI 95%: 0.50-0.99). Using the difference between univariate K functions, we found no evidence that cases and non-cases differ in their spatial distribution. We found no evidence that cases with and without WB result differ in the distance between their residence and Hemominas Foundation. No donors without WB result were georeferenced by the exact address. These donors could not have received the Hemominas letter inviting them to return to collect the second blood sample.

Blood Donors↗

PubMed1985

Spatial distribution of retinol-binding protein and retinyl palmitate hydrolase activity in normal and vitamin A-deficient rat liver.

A study was conducted to explore the spatial distribution within rat liver of two proteins importantly involved in retinoid metabolism in liver, namely, retinol-binding protein (RBP) and the enzyme retinyl palmitate hydrolase (RPH). The study was conducted with both vitamin A-sufficient (control) and vitamin A-deficient rats. Livers were carefully and reproducibly dissected into 11 sections each, and RBP levels and RPH activities were measured for each section homogenate. Both RBP and RPH activity displayed highly significant spatial heterogeneity in their distributions in liver. For control rats, the mean level of RBP was 39.0 micrograms/g wet weight, with a section-to-section variation of 14.5. For deficient rats, the corresponding RBP mean and variation values were 283 and 56 micrograms/g wet weight. For RPH, the mean level was 136 pmol free fatty acids (FFA) formed/(min X mg) with a section-to-section variation of 178. Both inspection of the data and analysis of variance indicated that this significant section-to-section variation (spatial heterogeneity) did not follow a consistent anatomic pattern from rat to rat. Thus, no one specific anatomic location in the liver was consistently high or low with regard to either RBP or RPH. Since the spatial distributions of both RBP and RPH activity did not follow a consistent anatomic pattern, it is not possible to obtain an accurate measure of the total liver levels for either parameter in a homogenate made from a small section. Finally, the patterns of distribution of RBP and RPH activity observed in the liver sections from both vitamin A-sufficient and deficient rats were not significantly correlated, either directly or inversely, as determined by chi-square analysis. Thus, RBP and RPH activity levels vary independently of each other in their heterogeneous anatomic distributions in rat liver.

Animals↗

PubMed1990

Spatial distribution of modalities and receptive fields in sensorimotor cortex of awake cats.

A sample of 504 single neurons isolated in three curvilinear arrays of 10 closely spaced tracks in primary somatosensory and in pericruciate sensorimotor cortex was studied in two awake, restrained domestic cats. Modality sensitivity and receptive field size and location were assessed for each neuron, along with response adaptation rate and state of arousal at the time of recording. Reconstruction of the spatial distribution of these response properties failed to show any simple organization, beyond general somatotopy. The spatial distribution of modality sensitivities was quantitatively tested in relation to a strict columnar model and to a random model; the data could not be clearly distinguished from the random model, in any of the three recording arrays. Observations made on two or more neurons isolated simultaneously at the same recording site revealed that few shared both modality and receptive field (RF) in common. Among the simultaneously recorded neurons, five-ninths showed disparate modality sensitivities and two-thirds showed limited or no RF overlap. Many pairs of neurons showing the same modality sensitivity showed limited or no RF overlap, and many pairs showing partial or complete RF overlap showed disparate modality sensitivities. Hence, the data failed to support any model of cerebral organization that features local, bounded regions within which all neuron response properties are the same and, in particular, the model of columnar organization. On the other hand, models that feature intermingled local clusters of neurons (a cluster consists of neurons that share the same response properties) are not excluded by the data.

Adaptation, Physiological↗

PubMed1988

Spatial distribution of trabeculae in iliac bone from 145 osteoporotic females.

145 women showing clinical and radiological signs of involutional osteoporosis of the spine were biopsed at the ilium for histomorphometric analysis of bone mass including trabecular bone volume and parameters reflecting the spatial distribution of bony elements (mean trabecular plate thickness, density and separation). Results were compared with an age-matched population of 22 healthy females. Postmenopausal osteoporotics (i.e. younger than 75 years) were characterized by a significant reduction in trabecular bone volume, plate density and thickness, while senile osteoporotics (i.e. older than 75 years) did not exhibit any difference with controls. 51% of the osteoporotic patients had a trabecular bone volume higher than the spontaneous vertebral crush threshold defined by Meunier. Osteoporotic patients with trabecular bone volume under the vertebral crush threshold had a significant decrease in all trabecular parameters. On the opposite, patients with trabecular bone volume above the vertebral crush threshold had only a significant decrease in the number of trabeculae. A negative correlation was found between age and plate density in both osteoporotic patients and controls. A linear correlation was found between trabecular bone volume and plate density, but thickness and density of trabecular plates were not correlated. This study confirms that involutional osteoporosis is not only a decreased bone mass disorder. A modified spatial distribution of trabeculae or a mechanically less resistant bone matrix could be additional factors.

Aged↗

PubMed2005

Patchiness and spatial distribution of laccase genes of ectomycorrhizal, saprotrophic, and unknown basidiomycetes in the upper horizons of a mixed forest cambisol.

Decomposition of plant litter by the soil microbial community is an important process of controlling nutrient cycling and soil humus formation. Fungal laccases are key players in litter-associated polyphenol degradation, but little is known about the diversity and spatial distribution of fungal species with laccase genes in soils. Diversity of basidiomycete laccase genes was assessed in a cambisolic forest soil, and the spatial distribution of the sequences was mapped in a 100-m(2) plot by using polymerase chain reaction (PCR) on soil DNA extracts. Diversity of laccase sequences was higher in the organic horizon and decreased with the depth. A total of 167 different sequences sharing 44-96% oligonucleotide similarity was found in 13 soil cores harvested in the 100-m(2) plot. Dissimilarity in laccase sequence content was 67% between adjacent cores; 45.5%, 35.5% and 19% of laccase sequences were attributed to ectomycorrhizal, unknown and saprotrophic basidiomycetes, respectively. Most dominant sequences were attributed to the extramatrical hyphae of known ectomycorrhizal taxa (e.g., Russulaceae) and restricted to small patches (<0.77 m(2)) in a specific soil horizon. Soil fungi with laccase genes occupied different niches and showed strikingly variable distribution patterns. The distribution of laccase sequences, and corresponding fungi, likely reflected a part of the oxidative potential in soils.

Base Sequence↗

PubMed2003

Loss and altered spatial distribution of oligodendrocytes in the superior frontal gyrus in schizophrenia.

BACKGROUND: Brain imaging, molecular genetic, and ultrastructural evidence indicate the existence of pathologic alterations in the cortical and subcortical white matter of schizophrenic patients. METHODS: We performed a stereologic analysis of numbers, densities, and spatial distribution of oligodendrocytes in layer III and in the gyral white matter of Brodmann's area 9 in the superior frontal gyrus to assess whether these cells are affected in schizophrenia. Counts were obtained on Nissl-stained materials and on sections immunolabeled for the oligodendrocyte marker 2',3'-cyclic nucleotide-3'-phosphodiesterase (CNPase) in seven schizophrenic and seven age-matched control cases. RESULTS: A 28% decrease in total numbers (or densities) of cortical layer III oligodendrocytes and a 27% decrease in the white matter were detected in schizophrenic compared with control cases based on CNPase immunostaining. Nissl and CNPase immunohistochemistry yielded comparable results. The spatial distribution of oligodendrocytes in area 9 white matter exhibited a less clustered arrangement in schizophrenic cases. CONCLUSIONS: These results suggest a severe pathology of oligodendrocytes in schizophrenia and provide a quantitative cellular correlate of the white matter changes observed by brain imaging in vivo, showing reduced fractional anisotropy in schizophrenia. The data support recent evidence that several genes encoding myelin-related proteins consistently exhibit reduced expression in schizophrenia.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗

PubMed2001

Non-independence of individuals in a population of Drosophila melanogaster: effects on spatial distribution and dispersal.

We used a simple quadrat analysis to globally categorise the spatial distribution of Drosophila melanogaster individuals. Individuals were spatially aggregated and this was not only due to sexual attraction. This aggregation seemed to be maintained during dispersal, hence explaining the great variability of this behaviour observed in our work and by other authors. Thus, individuals are expected to arrive as small groups into a new patch. This may induce costs through competition and benefits by ensuring the presence of reproductive mates and/or if there is a phenomenon of local resource enhancement by the presence of conspecifics, hence influencing the evolution of dispersal.

Animals↗

PubMed1991

Spatial distribution of fiber degeneration in acute hypoglycemic neuropathy in rat.

Hypoglycemia may cause axonal nerve fiber degeneration, but to do so it must be severe (less than 1.5 mmol/L) and of long duration (greater than or equal to 12 hours). Since in our previous study, systemic PO2, PCO2, pH, blood pressure, temperature, and hematocrit were maintained within physiologic limits, fiber degeneration cannot be attributed to systemic hypoxia. In this study the spatial distribution of axonal degeneration was assessed in transverse epoxy sections and teased fibers from different proximal-to-distal levels of nerves of the lower limb of the rats. Reactions in lumbar spinal motor neurons, spinal ganglia, and fasciculus gracilis were also studied. Axonal degeneration was the characteristic fiber alteration and it predominated in central fascicular distributions of distal sciatic, proximal tibial, and proximal peroneal nerves. This proximal-to-distal and central fascicular spatial distribution is not typical of distal polyneuropathy or of neuronal degeneration, but it is characteristic of a focal or multifocal nerve trunk neuropathy. Although local hypoxic-ischemic injury, possibly mediated by enhanced sympathetic tone, has not been excluded, we postulate a generalized deficiency of energy substrate manifesting itself by fiber degeneration at watershed zones of poorest perfusion.

Animals↗

PubMed2006

Total fluoride in Guangdong soil profiles, China: spatial distribution and vertical variation.

A total of 260 soil profiles were reported to investigate the fluoride distribution and vertical variation in Guangdong province. The soil fluoride contents followed an approximately lognormal distribution. Although the soil fluoride geometric mean concentration of 407 mg/kg is lower than that of China, its content varied from 87 to 2860 mg/kg. An upper baseline concentration of 688 mg/kg was estimated for surface soils. In A-, B-, and C-horizon soil fluoride spatial distribution presented similar patterns that high fluoride concentration mainly located in limestone, purple shale, and sandshale areas, indicated that soil fluoride spatial distribution was primarily dependent on the regional bedrock properties rather than anthropogenic inputs. From A- to C- horizon soil fluoride geometric mean concentration had an increasing tendency of 407, 448, and 465 mg/kg. This vertical variation was the result of the intensive eluviation under the subtropical hydrothermal condition, and had closely related with soil properties, such as lower organic matters and clay content variations. Moreover, the soil degradation and erosion was also an important pathway of soil fluoride movement, as a result the soil fluoride exported into surface and groundwaters would reach about 4.1x10(4) t year-1 in the study area.

China↗