Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “spatial spread”

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.

At least 1,153 records · Page 64Linked to original sources
PubMed1995

Landscape ecology of arboviruses in southern California: temporal and spatial patterns of vector and virus activity in Coachella Valley, 1990-1992.

Consistent temporal and spatial patterns in the activity of Culex tarsalis Coquillett and western equine encephalomyelitis (WEE) and St. Louis encephalitis (SLE) viruses were delineated that were useful in developing a stratified surveillance program. Vernal increases in Cx. tarsalis abundance typically were associated with flooding of saline marshes along the north shore of the Salton Sea and were followed 6-8 wk later by the onset of WEE and SLE virus activity. Viruses then spread to managed marsh (duck club) and agricultural habitats in the Whitewater Channel flood plain and, depending upon the intensity of amplification, to agricultural and residential areas in the more elevated northwestern portion of the valley. Mean annual Cx. tarsalis abundance was correlated inversely with elevation and distance from the Salton Sea. Abundance was greatest at managed marsh habitats. Although spatially correlated with vector abundance among sites, virus transmission rates to sentinel chickens were asynchronous temporally with vector abundance. Seroconversion rates were related to flock location but not flock size (10 versus 20 chickens). Human cases were not detected during the study period, despite elevated transmission rates of both WEE and SLE viruses to sentinel chickens positioned in peridomestic habitats.

Animals↗
PubMedDate not supplied

The effects of misregistration of the projections on spatial resolution of CT scanners.

Misregistration of the projections in 360 degrees computed tomographic (CT) scanners has been found to blur the image without generating artifacts. The effects of this error were investigated by analytical methods and by reconstruction of real and simulated data. The point-spread function which results from shifting each projection by a constant distance epsilon consists of a two-dimensional impulse function surrounding a region of negative density. The locus of the impulse function is a circle for parallel-beam geometry and a sixth-order curve for fanbeam geometry. The anisotropy and position dependence of the point-spread function in fanbeam geometry have been characterized. The line-spread function due to the error in parallel-beam geometry consists of two delta functions located at +/- epsilon. In fanbeam geometry, the line-spread function consists of two delta functions separated by approximately 2 epsilon, with the locations of the impulses dependent on the position and orientation of the line. This error, combined with other sources of blurring, results in a system edge-response function which contains a flat region at one-half the maximum density.

Technology, Radiologic↗
PubMed1996

Immunohistochemical localization of urokinase-type plasminogen activator, type-1 plasminogen-activator inhibitor, urokinase receptor and alpha(2)-macroglobulin receptor in human breast carcinomas.

We have investigated the localization of urokinase-type plasminogen activator (u-PA), type-1 plasminogen-activator inhibitor (PAI-1), u-PA receptor (u-PAR) and alpha(2)-macroglobulin- receptor/low-density-lipoprotein-receptor-related protein (alpha(2)MR/LRP) in human breast tumors by immunohistochemical methods. Frozen sections of 133 primary breast carcinomas, 6 ductal carcinomas in situ and 33 lymph-node metastases were stained with monoclonal antibodies. Formalin-fixed sections of 15 primary tumors and 2 lymph-node metastases were stained with polyclonal antibodies. In primary tumors, u-PA and PAI-1 immunoreactivities were intense in macrophages and mast cells, and moderate in benign and malignant epithelial cells as well as in myofibroblasts and endothelial cells. A sub-group of poorly differentiated tumors showed particularly strong staining of stromal fibroblasts. u-PA immunoreactivity was also present in lymphocytes. alpha(2)MR/LRP and u-PAR immunoreactivities were intense in macrophages, but apart from these cells, alpha(2)MR/LRP was found only in fibroblasts, and u-PAR only in tumor cells located peripherally in tumor-cell clusters and glands and some myofibroblasts in the adjacent stroma. Lymph-node metastases showed staining for u-PA and PAI-1 both of cancer cells and of stromal fibroblasts, also staining for u-PA of lymphocytes. Similarly to some of the poorly differentiated primary tumors, approximately half of the metastases showed very strong staining of stromal fibroblasts, and extracts of these metastases had higher u-PA and PAI-1 levels, as determined by ELISA, than extracts of metastases without this staining pattern. alpha(2)MR/LRP was present only in fibroblasts and u-PAR only in some tumor cells. The presence of u-PA, PAI-1, alpha(2)MR/LRP and u-PAR was controlled biochemically by immunoblotting analyses, ligand-blotting analyses, and direct and reverse zymography. The spatial distribution and the variation in concentration of the various components of the plasminogen-activation system point to a complex, multifunctional role for the 4 proteins in and/or during the development and spread of breast cancer.

Blotting, Western↗
PubMed1994

Vitread proliferation of filamentous processes in avian Müller cells and its putative functional correlates.

In order to examine to what extent the neuronal and metabolic activities of avascular vertebrate retinae are reflected in the morphology of their Müller cells we have studied (by using several monoclonal antibodies) the morphology of Müller cells in two species of diurnal birds (chicken, Gallus domesticus, and pigeon, Columba livia) and one species of nocturnal saltwater crocodiles (Crocodylus porosi). In all three species, the outer nuclear layer is relatively thin and the Müller cell trunks divide into rootlets that wrap around the photoreceptors. In both diurnal birds studied, the trunks of Müller cells in the inner plexiform layers invariably divide into numerous fine filamentous processes that terminate in small expansions covering most of the vitreal surface of the retina. Furthermore, the networks of filamentous processes of birds' Müller cells exhibit conspicuous horizontal lamination in the inner plexiform layer. In contrast, the filamentous processes arising from the individual Müller cell trunks of the crocodile, if present, are much less numerous and less widely spread than those of diurnal birds. It is proposed that the splitting of the Müller cell trunks into numerous filamentous processes terminating in small vitreal expansions represents a morphological adaptation for: 1) effective spatial buffering of K+ ions in thick and presumably metabolically highly active, yet avascular, avian retinae, and 2) effective absorption and distribution of nutrients leaking from the vitreally located supplemental nutritive organ, the pecten.

Alligators and Crocodiles↗
PubMed2003

Active dendritic properties constrain input-output relationships in neurons of the central olfactory pathway in the crayfish forebrain.

Parasol cells are multimodal sensory interneurons of the hemi-ellipsoid body in the decapod forebrain. In reptant crustaceans, the hemi-ellipsoid body resides in the base of the eyecup, as an appendage to the terminal medulla. Parasol cells exhibit periodic depolarizations at a frequency of 0.5-1.0 Hz. I have investigated the role of these periodic depolarizations and their superimposed impulse bursts in affecting the input/output properties of these neurons. Parasol cells receive input from photic, olfactory, and mechanosensory pathways. Strong stimulation over any one of these pathways can lead to the generation of one or more impulse bursts in a subset of parasol cells, timed to occur at the peak of successive periodic depolarizations. A role for the periodic depolarizations in the function of the parasol cells has yet to be established. I suggest the possibility that they may act as a nonlinear amplifier that boosts spatially-summated excitatory synaptic potentials from strong or appropriate stimuli above threshold for burst generation. Another possibility includes modification of voltage-sensitive ion channels in the dendritic membrane, permitting a more effective spread of excitatory synaptic currents to impulse or burst initiating zones. Impulse bursts may be a highly effective mode of output for these neurons, especially so as they occur synchronously in a subset of cells in response to strong sensory input. Furthermore, backfiring of bursts into the dendritic tree has a brief (2-3 second) but effective suppressive action upon weak sensory input, which can thereby be masked by stronger, burst-generating input. This masking phenomenon is seen in other arthropod sensory interneurons, where its physiological basis appears to be a transient accumulation of intracellular Ca(++) ions that open calcium-sensitive potassium channels.

Animals↗
PubMed1997

Three-dimensional endoscopic ultrasound of the esophagus. Preliminary experience.

BACKGROUND: The aim of this study was to develop a technique for three-dimensional endoscopic ultrasound of the esophagus based on standard ultrasonic images. METHODS: Endoscopic ultrasound was performed in five esophageal cancer patients using a high-resolution miniprobe (360 degrees, 12.5 MHz). For acquisition of three-dimensional data sets, the miniprobe was attached to a stepping motor that enabled ECG-triggered withdrawal of the transducer. Three-dimensional images were reconstructed from serial transverse sections on a PC-based 3D work station. RESULTS: Twelve volume scans were obtained in five patients with esophageal cancer. The system enabled the acquisition of accurate three-dimensional ultrasound data within 30-50 s. Computed image processing allowed us to display the data in transverse, longitudinal, and oblique sections, or as a 3D reconstruction. Three-dimensional imaging provided accurate visualization of the tumor and surrounding structures in all cases. The tumor stage was determined correctly in four of five patients. Longitudinal scan planes and 3D views improved the assessment of longitudinal tumor infiltration and the spatial relation of the tumor to relevant mediastinal structures. CONCLUSION: This study shows that three-dimensional endoscopic ultrasound of the esophagus is technically feasible. The technique allows the assessment of local tumor spread in previously unattainable scan planes and 3D views. This promising preliminary experience should encourage further exploration of this method.

Endosonography↗
PubMed2005

Investigations of cattle herd breakdowns with bovine tuberculosis in four counties of England and Wales using VETNET data.

Cattle herd breakdown (HBR) with bovine tuberculosis (BTB) was investigated for farms in four counties of England and Wales outside southwest England from 1986 to early 2000. Data from the national database of TB testing history (VETNET) were used. Factors that influenced HBR included calendar time, herd size, number of cattle tested, the test type, the inter-test interval and spatial grouping of farms. Herd tests other than routine herd tests had an increased risk of HBR in all four counties. In all counties, the risk of HBR increased with calendar time and in Shropshire a test interval of 3 years was associated with an increased risk of HBR compared with a 1-year test interval. In Staffordshire and Sussex, a 4-year test interval was associated with a lower risk of HBR compared with a 1-year test interval. There was no evidence of spatial clustering of HBR in West Glamorgan (equal spatial risk in a 15-30 km radius) and weak evidence of spatial clustering in Shropshire (7-15 km) and Sussex (5-10 km). In Staffordshire, there was evidence of spatial (2-4 km) and time (3-4 years) clustering of HBR. The locally increased rate of testing following a confirmed HBR increased the detection of infected herds but did not prevent local spread in two of the four counties (Shropshire and Staffordshire) since the rate of HBR increased linearly from 1988 to 2000. The main conclusion is that there were both local and distant components of spread.

Animals↗
PubMed2000

Three-dimensional spectral imaging by hadamard transform spectroscopy in a programmable array microscope.

We report the acquisition and deconvolution of three-dimensional spectrally resolved images in a programmable array microscope implementing a Hadamard transform fluorescence spectroscopy system with adjustable spectral resolution. A stack of 16 two-dimensional spectral images was collected at 400 nm intervals along the optical axis. The specimen consisted of a polytene chromosome spread from Drosophila melanogaster doubly labelled for the Polyhomeotic protein by indirect immunofluorescence labelling with Alexa594 and for DNA with YOYO-1. The resulting four-dimensional data set consisted of the xyz spatial dimensions (898 x 255 x 16) with a 26-point spectrum at each spatial location. The total exposure time to the sample was 34 min. The system requires the acquisition of multiple images, and thus works best with fluorophores that are resistant to photobleaching. Image deconvolution reduced the amount of out-of-focus blur by up to a factor of 8, resulting in a dramatic improvement in the visualization of the chromosome backbone and localization of the specific Polyhomeotic domains.

Animals↗
PubMed2003

Interaction of sensory responses with spontaneous depolarization in layer 2/3 barrel cortex.

The rodent primary somatosensory cortex is spontaneously active in the form of locally synchronous membrane depolarizations (UP states) separated by quiescent hyperpolarized periods (DOWN states) both under anesthesia and during quiet wakefulness. In vivo whole-cell recordings and tetrode unit recordings were combined with voltage-sensitive dye imaging to analyze the relationship of the activity of individual pyramidal neurons in layer 2/3 to the ensemble spatiotemporal dynamics of the spontaneous depolarizations. These were either brief and localized to an area of a barrel column or occurred as propagating waves dependent on local glutamatergic synaptic transmission in layer 2/3. Spontaneous activity inhibited the sensory responses evoked by whisker deflection, accounting almost entirely for the large trial-to-trial variability of sensory-evoked postsynaptic potentials and action potentials. Subthreshold sensory synaptic responses evoked while a cortical area was spontaneously depolarized were smaller, briefer and spatially more confined. Surprisingly, whisker deflections evoked fewer action potentials during the spontaneous depolarizations despite neurons being closer to threshold. The ongoing spontaneous activity thus regulates the amplitude and the time-dependent spread of the sensory response in layer 2/3 barrel cortex.

Action Potentials↗
PubMed2001

The neural cell recognition molecule neurofascin interacts with syntenin-1 but not with syntenin-2, both of which reveal self-associating activity.

Neurofascin belongs to the L1 subgroup of the immunoglobulin superfamily of cell adhesion molecules and is implicated in axonal growth and fasciculation. We used yeast two-hybrid screening to identify proteins that interact with neurofascin intracellularly and therefore might link it to trafficking, spatial targeting, or signaling pathways. Here, we demonstrate that rat syntenin-1, previously published as syntenin, mda-9, or TACIP18 in human, is a neurofascin-binding protein that exhibits a wide-spread tissue expression pattern with a relative maximum in brain. Syntenin-1 was found not to interact with other vertebrate members of the L1 subgroup such as L1 itself or NrCAM. We confirmed the specificity of the neurofascin-syntenin-1 interaction by ligand-overlay assay, surface plasmon resonance analysis, and colocalization of both proteins in heterologous cells. The COOH terminus of neurofascin was mapped to interact with the second PDZ domain of syntenin-1. Furthermore, we isolated syntenin-2 that may be expressed in two isoforms. Despite their high sequence similarity to syntenin-1, syntenin-2alpha, which interacts with neurexin I, and syntenin-2beta do not bind to neurofascin or several other transmembrane proteins that are binding partners of syntenin-1. Finally, we report that syntenin-1 and -2 both form homodimers and can interact with each other.

Amino Acid Sequence↗
PubMed2004

Spatial and temporal distribution of cholera in Ecuador between 1991 and 1996.

BACKGROUND: The seventh pandemic of cholera affected South America in 1991 after a century of absence. Favoured by local conditions, the epidemic of cholera in Ecuador had a rapid impact. The epidemic of cholera evolved with temporal and geographical variations. METHODS: The temporal and geographical variations of cholera in Ecuador between 1991 and 1996 have been analysed. The Ecuadorian epidemiological surveillance system is a semi-active one based on obligatory weekly declarations. A geographical representation of annual impact rate has been made. Using a smoothing technique by cross-validation, time curves were identified and spatial diffusion was studied by cartography. RESULTS: In 1991 and 1992, cholera in Ecuador evolved in an epidemic mode with two explosive epidemic peaks. Cholera then entered a phase of regression. The disease spread from two main epicentres, one in the South (El Oro, Guayas, Los Rios) and the other in the North (Esmeraldas and Imbabura). These focal outbreaks spread to neighbouring provinces during the peak outbreaks between 1991 and 1993. CONCLUSION: This study demonstrated that the epidemic spread from the affected provinces in the South and the North of the country.

Cholera↗
PubMed1992

Communication compartments in hair follicles and their implication in differentiative control.

Observations on hair follicles presented in this paper show that boundaries to junctional communication are formed between groups of cells following different pathways of differentiation. The patterns of junctional communication in the bulbs of rat vibrissa follicles and human hair follicles were studied by microinjection of the fluorescent tracer dye Lucifer Yellow CH. Dye spread was extensive between undifferentiated cells of the hair bulb matrix but communication boundaries were found between groups of morphologically distinct cells. For example, boundaries to dye spread were observed between undifferentiated matrix cells and cells in the early stage of differentiation into the inner root sheath, between Huxley's and Henle's layers in the early inner root sheath and between cells of the cuticle and cortex of the hair. Dye did not spread between epithelial cells of the hair bulb and mesenchymal cells of the connective tissue sheath or dermal papilla. The patterns of dye spread became more complex (increased boundary formation and subcompartmentation) as differentiation progressed in higher regions of the hair bulb. The observed communication can be related to previous ultrastructural studies by others on the distribution of gap junctions in the wool follicle. These results show that junctional communication, with its consequent intercellular spread of small ions and molecules, is associated with uniformity of expression and behaviour within cell populations and that interruption of communication through the formation of boundaries and communication compartments is temporally and spatially related to the production of subpopulations of cells committed to the expression of different phenotypes.

Animals↗
PubMed2003

Mode analysis of spreading of partially coherent beams propagating through atmospheric turbulence.

The spreading of partially coherent beams propagating through atmospheric turbulence is studied by use of the coherent-mode representation of the beams. Specifically, we consider partially coherent Gaussian Schell-model beams entering the atmosphere, and we examine the spreading of each coherent mode, represented by a Hermite-Gaussian function, on propagation. We find that in atmospheric turbulence the relative spreading of higher-order modes is smaller than that of lower-order modes, whereas the relative spreading of all order modes is the same as in free space. This modal behavior successfully explains why under certain circumstances partially coherent beams are less affected by atmospheric turbulence than are fully spatially coherent laser beams.

Journal Article↗
PubMed2003

Spatial patterns of the pathological changes in the cerebellar cortex in sporadic Creutzfeldt-Jakob disease (sCJD).

The spatial patterns of the vacuolation ("spongiform change"), surviving cells, and prion protein (PrP) deposition were studied in the various cell laminae of the cerebellar cortex in 11 cases of sporadic Creutzfeldt-Jakob disease (sCJD). Clustering of the histological features, with the clusters regularly distributed along the folia, was evident in all cell laminae. In the molecular layer, clusters of vacuoles coincided with the surviving Purkinje cells. In the granule cell layer, however, the spatial relationship between the vacuoles and surviving cells was more complex and varied between cases. PrP deposition was not spatially correlated with either the vacuoles or the surviving cells in any of the cerebellar laminae in the majority of cases. In some cases, there were spatial relationships between the histological features in the molecular and granule cell layers. The data suggest that degeneration of the cerebellar cortex in sCJD may occur in a topographic pattern consistent with the spread of prion pathology along anatomical pathways. The development of the vacuolation may be an early stage of the pathology in the cerebellum preceding the appearance of the PrP deposits. In addition, there is evidence that the pathological changes may spread across the different laminae of the cerebellar cortex.

Aged↗
PubMed1981

Intracortical spread of exogenous catecholamines: effective concentration for modifying cortical plasticity.

The present study is aimed to clarify the question of maximal intracortical spread of locally perfused 6-hydroxydopamine (6-OHDA) and norepinephrine (NE) through a continuous microperfusion system. The following analyses were performed: 1) catecholamine (CA) fluorescence histochemistry in 6-OHDA-perfused cortex, 2) spatial distribution of tritium counts in the visual cortex perfused either with [3H]-6-OHDA or with [3H]N# and 3) chemical assay of endogenous CAs in 6-OHDA-perfused cortex. 4) High voltage paper electrophoresis was also used to separate unchanged NE from NE metabolites in cortex samples perfused with [3H]NE. Taking the present results together with those in previous physiological assays of cortical synaptic plasticity, we calculated the lowest effective concentration of 6-OHDA for depletion and of NE for restoration of synaptic plasticity in kitten visual cortex: it was approximately 3 microM for 6-OHDA and 0.3 microM for NE, respectively. This concentration of 6-OHDA seems to be low enough for its specific uptake by CA-containing nerve terminals in the visual cortex. The effective concentration of NE appears to be close to or less than the endogenous level of NE per unit of volume of the normal cortical tissue. In addition, by comparing the size of chemical lesions placed by 6-OHDA perfusion in the visual cortex and the spatial distribution of endogenous NE in cortical tissues which had been treated similarly with 6-OHDA, we evaluated the lower limit of sensitivity of a modified glyoxylic acid-perfusion histofluorescence method for visualizing CA (mostly NE)-containing fibers and terminals. The threshold of sensitivity seemed to be 20% of the control.

Animals↗
PubMed1999

The disappearance of cyclin B at the end of mitosis is regulated spatially in Drosophila cells.

We have followed the behaviour of a cyclin B-green fluorescent protein (GFP) fusion protein in living Drosophila embryos in order to study how the localization and destruction of cyclin B is regulated in space and time. We show that the fusion protein accumulates at centrosomes in interphase, in the nucleus in prophase, on the mitotic spindle in prometaphase and on the microtubules that overlap in the middle of the spindle in metaphase. In cellularized embryos, toward the end of metaphase, the spindle-associated cyclin B-GFP disappears from the spindle in a wave that starts at the spindle poles and spreads to the spindle equator; when the cyclin B-GFP on the spindle is almost undetectable, the chromosomes enter anaphase, and any remaining cytoplasmic cyclin B-GFP then disappears over the next few minutes. The endogenous cyclin B protein appears to behave in a similar manner. These findings suggest that the inactivation of cyclin B is regulated spatially in Drosophila cells. We show that the anaphase-promoting complex/cyclosome (APC/C) specifically interacts with microtubules in embryo extracts, but it is not confined to the spindle in mitosis, suggesting that the spatially regulated disappearance of cyclin B may reflect the spatially regulated activation of the APC/C.

Animals↗
PubMed1989

Model study of the spread of electrotonic potential in cardiac tissue.

This model study describes the electrotonic response of a cable model of cardiac tissue stimulated at one point. The stimulus is applied intracellularly in the form of a 2 ms pulse of current of near threshold amplitude. The attenuation of the electrotonic potential with distance and its mode of propagation along the cable are compared for equivalent passive, continuous and discontinuous cables. The three structures have the same basic physical and electrical characteristic and they differ either with respect to being active or passive or to the presence or absence of intercellular gap junctions. In the continuous cable a just subthreshold stimulus produces a local active response which propagates more slowly and is attenuated less rapidly with distance than in a passive cable. The spatial decrement of the local response in a discontinuous cable is faster than in a continuous cable of equal average resistivity. It is suggested that the larger time constant of the foot of the action potential observed in the longitudinal direction in cardiac muscle could be due in part to the electrotonic spread of the local response from the site of stimulation.

Action Potentials↗
PubMed2001

Linear and nonlinear information flow in spatially extended systems.

Infinitesimal and finite amplitude error propagation in spatially extended systems are numerically and theoretically investigated. The information transport in these systems can be characterized in terms of the propagation velocity of perturbations Vp. A linear stability analysis is sufficient to capture all the relevant aspects associated to propagation of infinitesimal disturbances. In particular, this analysis gives the propagation velocity VL of infinitesimal errors. If linear mechanisms prevail on the nonlinear ones Vp=VL. On the contrary, if nonlinear effects are predominant finite amplitude disturbances can eventually propagate faster than infinitesimal ones (i.e., Vp>VL). The finite size Lyapunov exponent can be successfully employed to discriminate the linear or nonlinear origin of information flow. A generalization of the finite size Lyapunov exponent to a comoving reference frame allows us to state a marginal stability criterion able to provide Vp both in the linear and in the nonlinear case. Strong analogies are found between information spreading and propagation of fronts connecting steady states in reaction-diffusion systems. The analysis of the common characteristics of these two phenomena leads to a better understanding of the role played by linear and nonlinear mechanisms for the flow of information in spatially extended systems.

Journal Article↗