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PubMed1991

Automated cytometry of muscle fibre sections: size and spatial distribution of the four fibre types in young and adult rats.

An automated cytometry program was applied to the extensor digitorum longus muscle of young and adult rats. Lesser diameter and spatial distribution of about 4000 fibres were measured in digital images from ATPase-stained muscle sections. All fibre types grow thicker with age, but the coefficient of variation of the diameter is age-independent. At both ages, 2B fibres have the largest mean diameter and are most frequent. 2A fibres in young rats present a diameter smaller or equal to type 1 but then show a faster increase in size; their relative number increases from 20 to 28%. Consequently type 2A displays the most important change with age. The spatial distribution of fibres is mathematically expressed; most images show a random distribution of type 1 and type 2 fibres. Taking into account the variation of fibre size of each type, the number of fibres which should be measured in order to reach a specified precision was calculated.

Analysis of Variance↗
PubMed2001

Life history and spatial distribution of the enchytraeid worm Cognettia sphagnetorum (Oligochaeta) in metal-polluted soil: below-ground sink-source population dynamics?

We studied the life history, metal-avoidance behavior, spatial distribution, and population growth of enchytraeid worms (Cognettia sphagnetorum [Oligochaeta]) originating from two sites: one uncontaminated, and another patchily polluted by heavy metals. Effects of patchy soil contamination on populations were studied in microcosms. In uncontaminated soil, worms from the polluted site had lower viability and reduced growth rate as juveniles but higher growth rate as adults compared to worms from the unpolluted site. They were also smaller in size at fragmentation (reproduction). Worms from the polluted site reached a larger population size than worms from the unpolluted site. Hence, worms from the polluted site seemed to allocate more energy to reproduction, because such a strategy can be highly adaptive when living in a less-polluted patch (the source) in, on average, a highly polluted environment. The C. sphagnetorum actively avoided Cu-contaminated soil, with the response being stronger in individuals from the contaminated site. When an unpolluted patch (the source) was surrounded by a toxic environment (the sink), worms were found in the sink, either because intraspecific competition overrode the avoidance behavior or because of random walk migration. As a result, total population size in these microcosms were as high as those in totally uncontaminated microcosms. Our results indicate that avoidance behavior and increased allocation to reproduction, together with the observed dispersal pattern, can be an adaptive strategy for C. sphagnetorum in the presence of small, less-polluted patches in, on average, a hostile environment. Hence, sink-source population regulation can explain spatial distribution and survival of C. sphagnetorum in patchily polluted field soils. When such population dynamics occur, this pattern should be taken into account when population densities in the field are monitored for ecological risk-assessment procedures concerning toxicants.

Adaptation, Physiological↗
PubMed1997

Spatial distribution of cytoskeleton intermediate filaments during fetal rat hepatocyte differentiation.

The construction of the liver parenchyma throughout fetal development depends on the elaboration of intercellular contacts between epithelial cells and between epithelial and mesenchymal cells. During this time, the spatial distribution of cytokeratins in hepatocytes shows a striking evolution as demonstrated by confocal microscopy and image analysis. In the early stages of fetal rat development, the liver is mainly a hematopoietic organ and hepatocytes represent fewer than 40% of all liver cells. At this time, cytokeratin filaments are scarce and are randomly distributed inside the cytoplasm. A coexpression of desmin and cytokeratin is found in some cells. Intercellular contacts between epithelial and mesenchymal cells are more numerous than between epithelial cells. Later in development, hepatocytes are arranged in a "muralium duplex" architecture (two-cell-thick sheets). Contacts between hepatocytes become more numerous and bile canaliculi become well developed. The density of cytokeratin filaments increases and appears to be very high near the bile canaliculi. In adult liver, hepatocytes are arranged in a "muralium simplex" architecture. Cytokeratin filaments show a symmetrical distribution in relation to the nuclear region. The highest density of filaments is found near the cytoplasmic membrane. Variations of the spatial distribution of intermediate filaments throughout hepatocyte differentiation were investigated in a pilot study using computerized image analysis. We found significant differences between the filament networks in fetal and adult hepatocytes.

Animals↗
PubMed1997

Imaging of axonal damage in multiple sclerosis: spatial distribution of magnetic resonance imaging lesions.

We performed magnetic resonance imaging and magnetic resonance spectroscopic imaging on 28 patients with multiple sclerosis stratified for disability and clinical course (relapsing with at least partial remissions or secondary progressive disease). Lesions were segmented on the conventional proton density and T2-weighted magnetic resonance images, and lesion distribution images were generated for, each patient. The conventional magnetic resonance and spectroscopic images were transformed into a standard brain-based stereotaxic coordinate space, allowing comparison of images from different patients on a voxel-by-voxel basis. The spatial distribution of lesions in the transformed magnetic resonance images did not differ significantly between the relapsing and the progressive disease groups. We then generated from the individual data sets, group lesion probability distribution images for the relapsing and the progressive disease groups. The spatial distribution of metabolites was characterized with respect to lesion distribution using the magnetic resonance spectroscopic images transformed into stereotaxic space and averaged. The neuronal marker N-acetylaspartate was diffusely lower in the multiple sclerosis patients than in normal control subjects. Comparison of the averaged metabolite and T2-weighted lesion probability images confirmed loss of N-acetylaspartate in regions of both high and low lesion probability. This suggests that diffuse axonal volume loss or dysfunction extends beyond the inflammatory lesions of multiple sclerosis, perhaps due to microscopic disease or wallerian degeneration along projection pathways of axons traversing the lesions.

Adult↗
PubMed1993

The spatial distribution of spindle microtubules in anaphase 3Y1 cells.

The spatial distribution of the microtubules (MT) in the rat 3Y1 cells in mitosis was investigated by immunoelectron microscopy and computer-graphic reconstruction of serial thin sections. In anaphase the interzone-MT increased in number gradually with advancing phase, while the kinetochore-MT in half-spindles decreased. The interzone-MT overlapped with each other at the equatorial region of the cell, and they formed a specific structure called the 'stem bodies'. The ends of the interzone-MT opposite to the stem bodies often attached to chromosomes but not to the poles. The stem bodies were not labeled with immunogold particles of anti-alpha tubulin. Some of the stem bodies or MT which originate from stem bodies were found just beneath the plasma membrane in the equatorial region where abundant actin filaments appear showing the formation of the contractile ring and subsequently the cleavage furrow begins. On the basis of these observations it is assumed that the interzone-MT is involved both in the separation of chromosomes in anaphase and in the formation of the cleavage furrow in telophase.

Anaphase↗
PubMed2001

Modelling the spatial distribution of SO2 and NOx emissions in Ireland.

The spatial distributions of sulphur dioxide (SO2) and nitrogen oxides (NOx) emissions are essential inputs to models of atmospheric transport and deposition. Information of this type is required for international negotiations on emission reduction through the critical load approach. High-resolution emission maps for the Republic of Ireland have been created using emission totals and a geographical information system, supported by surrogate statistics and landcover information. Data have been subsequently allocated to the EMEP 50 x 50-km grid, used in long-range transport models for the investigation of transboundary air pollution. Approximately two-thirds of SO2 emissions in Ireland emanate from two grid-squares. Over 50% of total SO2 emissions originate from one grid-square in the west of Ireland, where the largest point sources of SO2 are located. Approximately 15% of the total SO2 emissions originate from the grid-square containing Dublin. SO2 emission densities for the remaining areas are very low, < 1 t km-2 year-1 for most grid-squares. NOx emissions show a very similar distribution pattern. However, NOx emissions are more evenly spread over the country, as about 40% of total NOx emissions originate from road transport.

Air Movements↗
PubMed2002

[Sensitivity and parameters of the otolith as a spatially distributed system].

Comparison of the de Vries pendulum and spatially distributed otolith models allowed physical interpretation of the pendulum model parameters and determination of the influence of otolith structure on its mechanical sensitivity when otolith dynamics is represented by a parallel displacement relative to the receptor surface. Proof was obtained that in this case otolith dynamics is independent of total mass, and mechanic sensitivity is not proportional to size of the organ. Possible explanations of the effects of changed dynamics conditions on otolith parameters in the fish are discussed.

Animals↗
PubMed1977

Spatial distribution of the EOG in the rat; a variation with odour quality.

The spatial distribution of olfactory receptors in the rat has been studied by simultaneous recordings of the electroolfactograms (EOGs) from areas of the olfactory mucosa. The potentials were recorded from the dorsal surface of the cribriform plate, leaving the mucosa and the nasal cavities intact. The ratio between the peak amplitude of the EOG potentials served as a measure of the relative sensitivity of one area against the other. The results obtained by stimulating with 31 substances at 38 positions demonstrate a non-homogeneous distribution of different receptors. Each substance gives a spatial pattern of response efficiency. The response distributions are mapped on the cribriform plate for the different odours.

Animals↗
PubMed2001

Lacustrine spatial distribution of landlocked Atlantic salmon populations assessed across generations by multilocus individual assignment and mixed-stock analyses.

The objective of this study was to assess the spatiotemporal distribution of four landlocked Atlantic salmon (Salmo salar) populations during their sympatric feeding phase in lake St-Jean (Québec, Canada). A total of 1100 fish captured over a period of 25 years was genotyped at six microsatellite loci in order to assess the temporal stability of the relative proportion of each population in different lake sectors using both individual-based assignment and mixed-stock analysis. Estimates of relative proportions obtained from both methods were highly correlated. A nonrandom spatial distribution of populations was observed for each period and, despite the fact that the overall proportion of each population varied over time, the pattern of differential distribution remained generally stable over time. Furthermore, there were indications that the extent of horizontal spatial overlap among populations was negatively correlated with that of their genetic differentiation at both microsatellites and a major histocompatibility complex locus, and independent of the geographical distance between the rivers of origin. We discuss the hypothesis that the temporal stability of spatial distribution, the lack of an association between spatial partitioning and geographical distance between rivers of origin, and the apparent negative correlation between spatial overlap and genetic differentiation, reflect the outcome of selective pressures driving behavioural differences for spatial niche partitioning among populations.

Animals↗
PubMed1999

Is the spatial distribution of brain lesions associated with closed-head injury predictive of subsequent development of attention-deficit/hyperactivity disorder? Analysis with brain-image database.

PURPOSE: To determine whether there is an association between the spatial distribution of lesions detected at magnetic resonance (MR) imaging of the brain in children after closed-head injury and the development of secondary attention-deficit/hyperactivity disorder (ADHD). MATERIALS AND METHODS: Data obtained from 76 children without prior history of ADHD were analyzed. MR images were obtained 3 months after closed-head injury. After manual delineation of lesions, images were registered to the Talairach coordinate system. For each subject, registered images and secondary ADHD status were integrated into a brain-image database, which contains depiction (visualization) and statistical analysis software. Using this database, we assessed visually the spatial distributions of lesions and performed statistical analysis of image and clinical variables. RESULTS: Of the 76 children, 15 developed secondary ADHD. Depiction of the data suggested that children who developed secondary ADHD had more lesions in the right putamen than children who did not develop secondary ADHD; this impression was confirmed statistically. After Bonferroni correction, we could not demonstrate significant differences between secondary ADHD status and lesion burdens for the right caudate nucleus or the right globus pallidus. CONCLUSION: Closed-head injury-induced lesions in the right putamen in children are associated with subsequent development of secondary ADHD. Depiction software is useful in guiding statistical analysis of image data.

Adolescent↗
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↗
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↗