Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Spatial Distribution--changes”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

373 records · Page 21Linked to original sources
PubMed2006

Natural selection and climate change: temperature-linked spatial and temporal trends in gene frequency in Fagus sylvatica.

Rapid increases in global temperature are likely to impose strong directional selection on many plant populations, which must therefore adapt if they are to survive. Within populations, microgeographic genetic differentiation of individuals with respect to climate suggests that some populations may adapt to changing temperatures in the short-term through rapid changes in gene frequency. We used a genome scan to identify temperature-related adaptive differentiation of individuals of the tree species Fagus sylvatica. By combining molecular marker and dendrochronological data we assessed spatial and temporal variation in gene frequency at the locus identified as being under selection. We show that gene frequency at this locus varies predictably with temperature. The probability of the presence of the dominant marker allele shows a declining trend over the latter half of the 20th century, in parallel with rising temperatures in the region. Our results show that F. sylvatica populations may show some capacity for an in situ adaptive response to climate change. However as reported ongoing distributional changes demonstrate, this response is not enough to allow all populations of this species to persist in all of their current locations.

Alleles↗
PubMed2006

EMG amplitude distribution changes over the upper trapezius muscle are similar in sustained and ramp contractions.

AIM: To investigate whether global motor unit recruitment to compensate for muscle fatigue during sustained contraction and to regulate force increase during ramp contraction are controlled in similar manners in the upper trapezius muscle. METHODS: Fourteen subjects performed a 10-s ramp contraction from 0% to 90% of maximal voluntary contraction (MVC) and a 3-min sustained contraction at 25% MVC. Both contractions involved isometric shoulder elevation with a multi-channel surface electromyographical grid placed on the skin above the muscle. To evaluate the global muscle activation pattern, the changes in spatial amplitude distribution of the sustained and the ramp contraction were examined and compared. RESULTS: In both contraction types, the upper part of the trapezius muscle was spatially non-uniform (inhomogeneous) activated. Throughout the sustained contraction, the amplitude distribution of the upper trapezius muscle became more similar to the amplitude distribution at higher force levels. CONCLUSION: These findings support the hypothesis that global motor unit recruitment to compensate for muscle fatigue during a sustained contraction, and to regulate force increase during a ramp contraction is controlled in a similar manner. Consequently, they confirm fundamental principles of motor unit activation based on recordings of limited motor unit samples.

Adult↗
PubMed1988

Assessment of lung water distribution by nuclear magnetic resonance. A new method for quantifying and monitoring experimental lung injury.

We have developed a new analytical method that uses nuclear magnetic resonance (NMR) imaging data to quantify lung water content and distribution. This new method generates a distribution of lung water density in which the fraction of voxels corresponding to a given water density is plotted on the vertical axis as a function of water density on the horizontal axis, thereby complementing the spatial information provided by the NMR image. We obtained reproducible lung water distribution data at comparable lung volumes in normal excised lungs and in intact living rats. In normal excised unperfused rat lungs, the distribution varied with the degree of inflation, but the changes were small compared with those associated with lung edema. The lung water density distribution changed markedly after induction of lung edema by intrabronchial saline instillation, intravenous oleic acid injection, and rapid intravenous saline infusion. Lung water density distribution data were well correlated (correlation coefficient = 0.948 for the excised lungs and 0.823 for the intact living rats) with gravimetric lung water measurements. The new analytical method is noninvasive, provides easily repeatable measurements, and is as sensitive as the gravimetric technique to lung water changes.

Animals↗
PubMed1999

Regulated expression and subcellular localization of syndecan heparan sulfate proteoglycans and the syndecan-binding protein CASK/LIN-2 during rat brain development.

The syndecan family of cell surface heparan sulfate proteoglycans interacts via their cytoplasmic C-terminal tail with the PDZ domain of CASK/LIN-2, a membrane-associated guanylate kinase homolog. The syndecan-CASK interaction may be involved in intercellular signaling and/or cell adhesion. Here we show that syndecan-1 to syndecan-4 have distinctive mRNA distributions in adult rat brain by in situ hybridization, with syndecan-2 and -3 being the major syndecans expressed in neurons of the forebrain. At the protein level, syndecan-2 and -3 are differentially localized within neurons; syndecan-3 is concentrated in axons, whereas syndecan-2 is localized in synapses. The synaptic accumulation of syndecan-2 occurs late in synapse development. CASK is a cytoplasmic-binding partner for syndecans, and its subcellular distribution changes strikingly during development, shifting from a primarily axonal distribution in the first 2 postnatal weeks to a somatodendritic distribution in adult brain. This change in CASK distribution correlates temporally and spatially with the expression patterns of syndecan-3 and -2, consistent with the association of both of these syndecans with CASK in vivo. In support of this, we were able to coimmunoprecipitate a complex of CASK and syndecan-3 from brain extracts. Our results indicate that specific syndecans are differentially expressed in various cell types of the brain and are targeted to distinct subcellular compartments in neurons, where they may serve specialized functions. Moreover, CASK is appropriately expressed and localized to interact with both syndecan-2 and -3 in different compartments of the neuron throughout postnatal development.

Aging↗
PubMed1991

Changes in the distribution of extracellular matrix components accompany early morphogenetic events of mammalian cortical development.

As a step in defining the molecular environment for development of the mammalian cerebral cortex, we have used immunohistochemistry to analyze the distribution and remodeling of three major extracellular matrix (ECM) components, fibronectin, chondroitin sulfate proteoglycan (CSPG), and tenascin, during embryonic and early postnatal stages in the mouse. Fibronectin and CSPG are distributed throughout the proliferative zone that initially comprises the thin wall of the telencephalic vesicle, but their distribution changes as newly generated cells form the preplate just beneath the pia. Immunolabeling for CSPG becomes most prominent in the preplate, and fibronectin becomes restricted to that layer. Just after this change occurs, processes of preplate neurons, visualized with antibodies to neurofilaments, become evident within the matrix-rich preplate zone. The association of fibronectin and CSPG with preplate cells persists as cortical plate neurons divide the preplate; both ECM components are now most prominent in the marginal zone and subplate, the layers above and below the cortical plate that are preplate derived. Within the preplate and its derivatives, immunolabeling of fibronectin is punctate and closely associated with radial glial processes, while labeling of CSPG is more intense and diffuse. Labeling of fibronectin and CSPG declines rapidly as the cortical plate begins to differentiate into cortex; labeling for tenascin first appears at this stage in the most mature layers, the marginal zone and subplate, then gradually becomes widespread throughout all of cortex and subcortical white matter. In early postnatal life, tenascin is eliminated from the hollows of the vibrissal barrels in the somatosensory region; it then declines rapidly throughout cortex. The association of both fibronectin and CSPG with preplate cells and the distribution of fibronectin along radial glia during early cortical development suggest that one or both of these transient cell types might produce specific ECM components or induce their local deposition. The spatial and temporal distribution of fibronectin and CSPG suggests a role in defining a destination for migrating neurons that form the cortical plate and in delineating the pathway for early axonal extension. In contrast, the relatively late appearance of tenascin correlates best with the formation of astrocytes and their processes rather than with the establishment of cortical layers or major axonal pathways. These events are well underway before labeling of tenascin is evident.

Animals↗
PubMed1986

Cell distribution during mouse secondary palate closure. II. Mesenchymal cells.

The patterns of distribution of both total mesenchymal cells and the ratios of [3H]thymidine-labelled to total cells were mapped during secondary palatal shelf reorientation in vivo and in vitro. Smoothed spatial averaging, a computer-assisted method which takes into account the positions of all cells across an entire histological section of the shelf, was employed. Changes in shelf cross-sectional area and cell size were also measured. Three shelf regions, anterior and posterior presumptive hard and presumptive soft palate, were studied at developmental stages which were 30, 24 and 18 h prior to expected in vivo elevation, after in vivo reorientation and during the course of in vitro reorientation. Region-specific patterns of cell distribution change with shelf reorientation. These changes were observable within 6 h. Increases in cell number by cell division may enhance some high local cell densities, but cannot account for decreases in cell density. Increase in cell size is not a factor in decreasing cell density, nor is cell death. Displacement of cells by expansion of the extracellular matrix may be involved.

Animals↗