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PubMed1990

Responses in the diagonal band of Broca, adjacent septal nuclei and the islands of Calleja of cats to stimulation of the subcallosal fornix, medial basal hypothalamus and medial forebrain bundle.

The projection of neurons in the septal nuclei and the insula magna of the islands of Callaja (IC) was explored together with their response to stimulation of the fornix. The septal nuclei all contained neurons projecting in the medial forebrain bundle (MFB). Only the diagonal band of Broca (DBB) and the lateral septal nucleus (LS) contained many neurons projecting toward the medial basal hypothalamus (MBH). The spatial distribution of neurons excited by stimulation of the fornix in the DBB was almost identical with the distribution of neurons projecting toward the MBH and there was considerable overlap (10/28 cells). In the medial septal nucleus the spatial distribution of neurons excited by stimulation of the fornix and neurons projecting in the MFB was similar and there was considerable overlap (6/21 cells). The connectivity of the IC resembled that of the MS but there was little overlap between the neurons excited by fornix stimulation and those projecting in the MFB (1/27 cells). In the LS there were almost equal numbers of neurons projecting in the MFB and toward the MBH but there was very little input from the fornix. Neurons were significantly more often excited by stimulation of the lateral fornix, carrying axons from the subiculum, than they were by medial stimulation exciting axons from Ammon's horn. Axons projecting toward the MBH or in the MFB had conduction velocities less than 1 m/s.

Animals↗

PubMed2001

Baylisascaris procyonis (Nematoda: Ascaridae) in raccoons (Procyon lotor) in Orange County, California.

Baylisascaris procyonis is one of the common nematodes of the raccoon (Procyon lotor), being well recognized as a cause of visceral, ocular, and neural larval migrans in many species of wild and domestic birds and mammals, including humana. Between January 15 and December 31, 2000 in Orange County, CA, 640 raccoons (P. lotor) were live-trapped in four spatial distributions zones, and B. procyonis egg shedding prevalence and fecal egg per gram (EPG) counts were determined in relation to spatial distribution zones, season of the year, age, and sex. Egg shedding prevalence rates were not statistically different between zones, but the EPG count in the primarily residential Zone D differed significantly from other zones. Egg shedding prevalence and EPG counts exhibited a significant rise in the fall and decline in the winter and were significantly higher in juvenile and male raccoons than in adult and female raccoons. The overall fecal egg shedding prevalence was 72.0 +/- 1.8% (461/640), and the overall EPG count was 27,982 +/- 1,006.

Animals↗

PubMed2004

Induced radioactivity in CU targets produced by high-energy heavy ions and the corresponding estimated photon dose rates.

Irradiation experiments were performed at the Heavy Ion Medical Accelerator in Chiba (HIMAC) facility, National Institute of Radiological Sciences. The radioactive spallation products in a thick Cu target were obtained for Ar(230, 400 MeV per nucleon), Si(800 MeV per nucleon), Ne(100, 230, 400 MeV per nucleon), C(100, 230, 400 MeV per nucleon), He(100, 230 MeV per nucleon), p(100, 230 MeV) ions. The gamma-ray spectra from irradiated Cu samples inserted into the composite Cu target were measured with a high-purity germanium (HPGe) detector. From the gamma-ray spectra, we obtained the spatial distribution of radioactive yields of spallation products of 40 nuclides in the Cu sample in the Cu target. From the spatial distribution of radioactive yields, we estimated the residual activity and photon dose induced in the Cu target. The residual activity and photon dose become larger with the increase in projectile energy per nucleon and the range of the projectile beam for the same projectile energy per nucleon.

Copper↗

PubMed2001

Phasic and tonic coupling between EEG and EMG demonstrated with independent component analysis.

The authors describe a method for demonstrating the tonic and phasic couplings between suitably time-aligned surface eletromyographs (sEMGs) and the simultaneously recorded EEGs. The method, based on independent component analysis, was applied to data recorded from two normal subjects performing sustained submaximal contractions or continual repetitive movements of the arm. Augmented datasets, consisting of the EEG and either the sEMG from a single muscle (subject 1) or a combination of sEMGs from several muscles (subject 2), were analyzed with independent component analysis to determine the EEG/sEMG coupling. Each derived coupling consisted of a spatial distribution on the scalp and a waveform representing an EEG channel combination coactivating with the sEMG. The combinations of sEMGs, derived by applying independent component analysis to the simultaneous sEMG recordings from several muscles to create sEMG independent components (ICs), were either tonic or phasic with differing periods of activation. The topographic distributions on the scalp of the couplings between the EEG and sEMG ICs were different for each sEMG IC. The spatial distributions of the couplings between tonic sEMG ICs or single-muscle sEMGs and the EEG followed topographic patterns in sensorimotor regions. Phasic couplings were bifrontal, lateral, and bioccipital. Calculation of coherence between the sEMG ICs and calculated EEG combinations agreed well with the frequency spectra of the independent component analysis-derived coupling waveforms. These preliminary results demonstrate that detection of both the tonic and phasic coupling between the sEMG and the EEG is possible when monitoring unpaced proximal arm movement. This may thus be a practical means of exploring the dynamic cortical/muscle relationships in subjects unable to perform fine finger movements, such as patients recovering from stroke.

Algorithms↗

PubMed1983

Timing of dispersal in juvenile jewel fish during development is unaffected by available space.

The spatial distributions of 2 groups of sibling juvenile jewel fish were examined between 58 and 99 days of age to determine the effects of spatial experience on the timing of dispersal from a more aggregative behavioral mode. One group was provided a seminatural 1000-liter aquarium, the other with 70% less space per fish, but both groups were able to observe the same number of fish. Using a computer and digitizing tablet, distances between 1st-6th nearest neighbors were measured from time-sampled video recordings of spatial distributions in either overhead or underneath plan views. Both groups exhibited changes in aggregative behavior that were remarkably similar. Between 65 and 92 days of age, both groups showed gradual dispersal, which accelerated abruptly at 93-99 days of age. These results suggest that the timing of dispersal is regulated by developmental processes operating independently of spatial experience.

Animals↗

PubMed2005

Risk factors and spatial patterns of hookworm infection among schoolchildren in a rural area of western Côte d'Ivoire.

This study is aimed at investigating the risk factors for hookworm infection among schoolchildren in a rural area of western Côte d'Ivoire and predicting and mapping the spatial distribution of infection. We used demographic and socio-economic data from a cross-sectional survey of 6-16-year-old schoolchildren from 56 schools. Infection with hookworm was determined by microscopic examination of stool samples employing the Kato-Katz technique and an ether-concentration method. Environmental data were derived from satellite images and digitised maps. Bayesian variogram models were applied to investigate the variation of hookworm infection in relation to demographic, socio-economic and environmental factors. The overall hookworm infection prevalence, based on the pooled microscopic diagnoses, was 43.3% and ranged from 5.4 to 79.1% in the schools surveyed. Bivariate analyses showed that sex, age, socio-economic status, elevation, rainfall and land cover were significantly associated with the spatial distribution of hookworm infection. The final multivariate spatial model consisted of the covariates age, sex, socio-economic status, elevation and land cover. When assuming non-stationary underlying spatial dependency, the results of the model suggested that spatial correlation depended on the location only marginally. We conclude that, at the current resolution, it seems more reasonable to target interventions based on well-established epidemiologic risk factors, rather than on spatial factors.

Adolescent↗

PubMed2003

Stochastic model of autocrine and paracrine signals in cell culture assays.

Autocrine signaling systems are commonly studied under cell culture conditions. In a typical cell culture assay, a layer of liquid medium covers a random two-dimensional dispersion of cells, which secrete ligands. In a growing number of experiments, it is important to characterize the spatial range of autocrine and paracrine cell communication. Currently, the spatial distribution of diffusing signals can be analyzed only indirectly, from their effects on the intracellular signaling or physiological responses of autocrine cells. To directly characterize the spatial range of secreted ligands, we propose a stochastic model for autocrine cell cultures and analyze it using a combination of analytical and computational tools. The two main results derived within the framework of this model are 1), an expression for the fraction of autocrine trajectories, i.e., the probability for a ligand to be trapped by the same cell from which it has been secreted; and 2), an expression for the spatial distribution of trapping points of paracrine trajectories. We test these analytical results by stochastic simulations with efficient Brownian dynamics code and apply our model to analyze the spatial operation of autocrine epidermal growth factor receptor systems.

Algorithms↗

PubMed1991

Imaging Jupiter's aurorae from H3+ emissions in the 3-4 micrometers band.

Since H3+ was first spectroscopically detected on Jupiter, there has been considerable interest in using this simple molecular ion to probe conditions existing in the planet's auroral regions. Here we present a series of images of Jupiter recorded at wavelengths sensitive to emission by H3+, which reveal the spatial distribution of excited H3+ molecular ions in the jovian ionosphere, as seen from Earth. We believe that they provide high-spatial-resolution images of polar aurorae on Jupiter. They suggest that the intensity of the auroral emission can vary on a timescale of an hour, a shorter period than had previously been noted. We also find that the spatial distribution of H3+ emissions correlates only partially with the loci of auroral activity inferred from ultraviolet and longer-wavelength infrared observations. The H3+ emission may therefore be controlled by auroral processes that are different from those responsible for the ultraviolet and infrared emissions.

Astronomical Phenomena↗

PubMed2003

Distribution of inspiratory drive to the external intercostal muscles in humans.

The external intercostal muscles in humans show marked regional differences in respiratory effect, and this implies that their action on the lung during breathing is primarily determined by the spatial distribution of neural drive among them. To assess this distribution, monopolar electrodes were implanted under ultrasound guidance in different muscle areas in six healthy individuals and electromyographic recordings were made during resting breathing. The muscles in the dorsal portion of the third and fifth interspace showed phasic inspiratory activity with each breath in every subject. However, the muscle in the ventral portion of the third interspace showed inspiratory activity in only three subjects, and the muscle in the dorsal portion of the seventh interspace was almost invariably silent. Also, activity in the ventral portion of the third interspace, when present, and activity in the dorsal portion of the fifth interspace were delayed relative to the onset of activity in the dorsal portion of the third interspace. In addition, the discharge frequency of the motor units identified in the dorsal portion of the third interspace averaged (mean +/- S.E.M.) 11.9 +/- 0.3 Hz and was significantly greater than the discharge frequency of the motor units in both the ventral portion of the third interspace (6.0 +/- 0.5 Hz) and the dorsal portion of the fifth interspace (6.7 +/- 0.4 Hz). The muscle in the dorsal portion of the third interspace started firing simultaneously with the parasternal intercostal in the same interspace, and the discharge frequency of its motor units was even significantly greater (11.4 +/- 0.3 vs. 8.9 +/- 0.2 Hz). These observations indicate that the distribution of neural inspiratory drive to the external intercostals in humans takes place along dorsoventral and rostrocaudal gradients and mirrors the spatial distribution of inspiratory mechanical advantage.

Adult↗

PubMed2003

Simultaneous reconstruction of absorption and scattering maps with ultrasound localization: feasibility study using transmission geometry.

We report the experimental results of the simultaneous reconstruction of absorption and scattering coefficient maps with ultrasound localization. Near-infrared (NIR) data were obtained from frequency domain and dc systems with source and detector fibers configured in transmission geometry. High- or low-contrast targets located close to either the boundary or the center of the turbid medium were reconstructed by using NIR data only and NIR data with ultrasound localization. Results show that the mean reconstructed absorption coefficient and the spatial distribution of the absorption map have been improved significantly with ultrasound localization. The improvements in the mean scattering coefficient and the spatial distribution of the scattering coefficient are moderate. When both the absorption and the scattering coefficients are reconstructed the performance of the frequency-domain systemis much better than that of the dc system.

Algorithms↗

PubMedDate not supplied

Straining, attachment, and detachment of cryptosporidium oocysts in saturated porous media.

Accurate knowledge of the transport and deposition behavior for pathogenic Cryptosporidium parvum oocysts is needed to assess contamination and protect water resources. Experimental and modeling studies were undertaken to examine the roles of attachment, detachment, and straining on oocyst transport and retention. Saturated column studies were conducted using Ottawa aquifer sands (U.S. Silica, Ottawa, IL) with median grain sizes of 710, 360, and 150 microm. Decreasing the median sand size tended to produce lower effluent concentrations, greater oocyst retention in the sand near the column inlet, and breakthrough of oocysts at later times. Oocyst transport data also exhibited concentration tailing. Mathematical modeling of the oocyst transport data using fitted first-order attachment and detachment coefficients provided a satisfactory description of the observed effluent concentration curves, but a poor characterization of the oocyst spatial distribution. Modeling of these data using an irreversible straining term that is depth dependent provided a better description of the oocyst spatial distribution, but could not account for the observed effluent concentration tailing or late breakthrough times. A more physically realistic description of the data was obtained by modeling attachment, detachment, and straining. The percentage of total oocysts retained by straining was estimated from effluent mass balance considerations to be 68% for 710-microm sand, 79% for 360-microm sand, and 87% for 150-microm sand. Straining coefficients were then selected to achieve these percentages of total oocyst retention, and attachment and detachment coefficients were fitted to the effluent concentration curves. Dramatic differences in the predicted oocyst breakthrough curves were observed at greater transport distances for the various model formulations (inclusion or exclusion of straining). Justification for oocyst straining was provided by trends in the transport data, simulation results, pore size distribution information, and published literature.

Animals↗

PubMed1998

[Comparison of atrial premature depolarization topography during vagal stimulation and humoral acetylcholine administration].

Epicardial atrial mapping in open-chest dogs during different cholinergic influences has shown that, in acetylcholine administration and vagal stimulation, spatial distribution of atrial premature depolarisation (APDs) seems to be similar to prevalence of ectopic sources from both atria and atrial septum. Spatial distribution of the APDs in acetylcholine administration in the sinus node artery was limited to the region of this artery so that the APDs mainly arise from intercaval area of the right atrium and from atrial septum, but never from the left atrium. The latent pacemakers spread over both atria and atrial septum, could participate in initiation of cholinergically-induced APDs and atrial fibrillation. A direct effect of acetylcholine seems to be necessary for development of arrhythmic activity of the latent pacemakers.

Acetylcholine↗

PubMed2002

Expression of Na(+)/Ca(2+) exchanger isoforms (NCX1 and NCX3) and plasma membrane Ca(2+) ATPase during osteoblast differentiation.

The ability to deliver calcium to the osteoid is critical to osteoblast function as a regulator of bone calcification. There are two known transmembrane proteins capable of translocating calcium out of the osteoblast, the Na(+)/Ca(2+) exchanger (NCX) and the plasma membrane Ca(2+)-ATPase (PMCA). In this study, we reveal the presence of the NCX3 isoform in primary osteoblasts and examine the expression of NCX1, NCX3, and PMCA1 during osteoblast differentiation. The predominant NCX isoform expressed by osteoblasts is NCX3. NCX1 also is expressed, but at low levels. Both NCX isoforms are expressed at nearly static levels throughout differentiation. In contrast, PMCA expression peaks at 8 days of culture, early in osteoblast differentiation, but declines thereafter. Immunocytochemical co-detection of NCX and PMCA reveal that NCX is positioned along surfaces of the osteoblast adjacent to osteoid, while PMCA is localized to plasma membrane sites distal to the osteoid. The expression pattern and spatial distribution of NCX support a role as a regulator of calcium efflux from osteoblasts required for calcification. The expression pattern and spatial distribution of PMCA makes its role in the mineralization process unlikely and suggests a role in calcium homeostasis following signaling events.

Animals↗

PubMed1992

[Diffuse infiltrative lung diseases: histological support of elementary lesions observed on tomodensitometry].

High resolution computed tomography (TDM-HR) is now the technique of choice in the diagnosis and management of diffuse infiltrative lung disease (PID). After a brief review of the technique the authors describe the normal appearance; anatomical observations and the in vivo findings have shown that TDM-HR allow for the exploration of details of structure down to the second pulmonary lobule. Thus, through the alterations that are transmitted in the lobular area, and from its contents and its limits, PID has led to the elaboration of a new semeiology. The authors review the basic computed tomographic images and correlate these in each case with the histological evidence. The spatial distribution and the time sequence of the elementary images are the two other terms in the diagnostic equation of PID. The spatial distribution of several elementary images presents in TDM-HR a superior aetiological pointer to that which is furnished by thoracic radiographs; and the time sequence may furnish a useful indication as to the progress of the treated disease. Sarcoidosis, histiocytosis X, idiopathic interstitial fibrosis and lymphangitis carcinomatosis would serve as examples. Nevertheless, the authors point out that it would be dangerous during the period of evaluation to prematurely extend to all cases of PID conclusions which are only possible to make at present in a restricted number of disorders.

Histiocytosis, Langerhans-Cell↗

PubMed1994

Translating stochastic density-dependent individual behavior with sensory constraints to an Eulerian model of animal swarming.

Density-dependent social behaviors such as swarming and schooling determine spatial distribution and patterns of resource use in many species. Lagrangian (individual-based) models have been used to investigate social groups arising from hypothetical algorithms for behavioral interactions, but the Lagrangian approach is limited by computational and analytical constraints to relatively small numbers of individuals and relatively short times. The dynamics of "group properties", such as population density, are often more ecologically useful descriptions of aggregated spatial distributions than individual movements and positions. Eulerian (partial differential equation) models directly predict these group properties; however, such models have been inadequately tied to specific individual behaviors. In this paper, I present an Eulerian model of density-dependent swarming which is derived directly from a Lagrangian model in which individuals with limited sensing distances seek a target density of neighbors. The essential step in the derivation is the interpretation of the density distribution as governing the occurrence of animals as Poisson points; thus the number of individuals observed in any spatial interval is a Poisson-distributed random variable. This interpretation appears to be appropriate whenever a high degree of randomness in individual positions is present. The Eulerian model takes the form of a nonlinear partial integro-differential equation (PIDE); this equation accurately predicts statistically stationary swarm characteristics, such as expected expected density distribution. Stability analysis of the PIDE correctly predicts transients in the stochastic form of the aggregation model. The model is presented in one-dimensional form; however, it illustrates an approach that can be equally well applied in higher dimensions, and for more sophisticated behavioral algorithms.

Algorithms↗

PubMed2001

Simulation and quantitative assessment of homogeneous and inhomogeneous particle distributions in particulate metal matrix composites.

Reinforcement distributions play an important role in various aspects of the processing and final mechanical behaviour of particulate metal matrix composites (PMMCs). Methods for quantifying spatial distribution in such materials are, however, poorly developed, particularly in relation to the range of particle size, shape and orientation that may be present in any one system. The present work investigates via computer simulations the influences of particle morphology, homogeneity and inhomogeneity on spatial distribution measurements obtained by finite-body tessellation. Distribution inhomogeneity was simulated both by the segregation of particles away from specified regions within a microstructure and by generating point density peaks at random locations within a microstructure. Both isotropic and anisotropic inhomogeneous distributions were considered to simulate distribution patterns in PMMCs before and after mechanical working. It was found that the coefficient of variation of the mean near-neighbour distance (COV(dmean)), derived from particle interfaces using finite-body tessellation, was essentially independent of particle shape, size distribution, orientation and area fraction in homogeneous (random) distributions, but showed great sensitivity to inhomogeneity. Increased values of COV(dmean) were seen for both forms of inhomogeneous distributions considered here, with little influence of particle morphology. The COV(dmean) was also seen to be sensitive to anisotropic clustering, the presence of which was identified via nearest-neighbour angles and cell orientations. Although generally formulated for PMMCs, the present results may be generalized to other systems containing low aspect ratio finite bodies of low to moderate area fraction.

Journal Article↗

PubMed2004

Distribution and dispersal behavior of Trogoderma variabile and Plodia interpunctella outside a food processing plant.

The distribution and dispersal distances of insects outside of food processing and storage facilities potentially have an important influence on the population dynamics and spatial distribution of insects inside facilities. In this study, Trogoderma variabile Ballion and Plodia interpunctella (Hübner) sex pheromone-baited trap captures outside and inside a food processing facility were measured, the relationship between trap captures outside and inside the facility was evaluated, and the dispersal ability of the males of these species was assessed using self-mark-recapture stations. T. variabile and P. interpunctella males were captured in high numbers outside the food facility. The two species differed in their spatial distribution around the facility, with T. variabile being more closely associated with the proximity of the building, but most likely originating from sources outside the building. For marked T. variabile, the average recapture distance was 75 m (range 21-508 m) and for marked P. interpunctella the average recapture distance was 135.6 m (range 21-276 m). In an immigration/emigration experiment, three T. variabile marked outside were recaptured inside, but no T. variabile marked inside were recaptured outside and no marked P. interpunctella were recaptured in either location. The potential for outside populations to influence inside populations has implications for the effectiveness of different management and monitoring tools.

Animals↗

PubMedDate not supplied

Localized beta dosimetry of 131I-labeled antibodies in follicular lymphoma.

The purpose of this study is to assess the multicellular dosimetry of 131I-labeled antibody in follicular lymphoma based on histological measurements on human tumor biopsy tissue. Photomicrographs of lymph node specimens were analyzed by first-order treatment to determine the mean values and statistical variations of the radii of follicles (260 +/- 90 microns), interfollicular distances (740 +/- 160 microns), and the number density of follicles [60 +/- 18 in a volume of (2 X 1480 microns)3]. Based on these measurements, two geometrical models were developed for localized beta dosimetry. The first, a regular cubic lattice model, assumes no variation in follicular radius of follicles and interfollicular distance. The second, a randomized distribution model, is a more complicated but more realistic representation of observed histological specimens. In this model, Monte Carlo methods were used to reconstruct the spatial distribution of follicles by simulating the distribution of the radii of follicles, interfollicular distances, and the number density of follicles. Dose calculations were performed using Berger's point kernels for absorbed-dose distribution for beta particles in water, assuming the 131I-labeled antibodies as point sources. It was assumed that the activity concentration of the labeled antibody within the follicles was ten times the activity concentration in the interfollicular spaces. The spatial distribution of localized dose was calculated for a tumor having an average dose of 40 Gy. The localized dose was found to be highly nonuniform, ranging from 20 to 90 Gy, and varying by a factor of about 2 from the average tumor dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗