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At least 1,027 records · Page 57Linked to original sources
PubMed1992

Urokinase activity in the developing avian heart: a spatial and temporal analysis.

Early events in cardiac morphogenesis are characterized by cell migrations and extensive tissue remodeling. This study was undertaken to determine the levels of urokinase in specific regions of the avian heart during early stages of development. Urokinase has previously been shown to be involved in both cell migration and matrix turnover. Elevated urokinase activity and mRNA levels were associated with the onset of ventricular trabeculation and mesenchymal cell migration in the endocardial cushion tissues. Urokinase was localized by immunostaining to the endocardial and mesenchymal cells of the developing atrioventricular canal (AVC) and outflow tract (OFT) as well as with evaginating ventricular endocardium. No immunoreactivity was seen associated directly with the matrix, suggesting that the enzyme remained mostly cell associated, a finding which was confirmed in isolated endocardial cells. Results from this study suggest a role for urokinase in the tissue remodeling and cell migration that occurs during the early stages of cardiac morphogenesis.

Animals↗
PubMed2002

Analysis of the spatial characteristics of metabolic abnormalities in newly diagnosed glioma patients.

PURPOSE: To evaluate the role of 3D MR spectroscopic imaging (MRSI) as a tool for characterizing heterogeneity within a lesion in glioma patients. MATERIALS AND METHODS: Forty-nine patients with newly diagnosed glioma were studied with 3D water-suppressed proton (1-H) MRSI. Signal intensities from choline (Cho), creatine (Cr), N-acytel aspartate (NAA), and lactate/lipid (LL) were estimated from the spectra. Regions of interest (ROIs) corresponding to the metabolic abnormalities were defined and compared with the anatomic lesions. RESULTS: This study showed that the tumor burden measured with either the volumes of the metabolic abnormalities or the metabolic levels in the most abnormal voxels was correlated with the degree of malignancy of the tumor. The volumes of elevated Cho and decreased NAA were useful for distinguishing low-grade from high-grade lesions. The volume of abnormal LL was correlated with the existence of necrosis and with the volume of contrast-enhancing lesions in high-grade lesions. The differences in the volume of abnormal LL were also statistically significant between patients in each grade. CONCLUSION: These 3D-MRSI data provide important additional information to conventional MRI for evaluating and characterizing gliomas.

Brain↗
PubMed1994

Eye-head-hand coordination in pointing at visual targets: spatial and temporal analysis.

This study investigated whether the execution of an accurate pointing response depends on a prior saccade orientation towards the target, independent of the vision of the limb. A comparison was made between the accuracy of sequential responses (in which the starting position of the hand is known and the eye centred on the target prior to the onset of the hand pointing movement) and synergetic responses (where both hand and gaze motions are simultaneously initiated on the basis of unique peripheral retinal information). The experiments were conducted in visual closed-loop (hand visible during the pointing movement) and in visual open-loop conditions (vision of hand interrupted as the hand started to move). The latter condition eliminated the possibility of a direct visual evaluation of the error between hand and target during pointing. Three main observations were derived from the present work: (a) the timing of coordinated eye-head-hand pointing at visual targets can be modified, depending on the executed task, without a deterioration in the accuracy of hand pointing; (b) mechanical constraints or instructions such as preventing eye, head or trunk motion, which limit the redundancy of degrees of freedom, lead to a decrease in accuracy; (c) the synergetic movement of eye, head and hand for pointing at a visible target is not trivially the superposition of eye and head shifts added to hand pointing. Indeed, the strategy of such a coordinated action can modify the kinematics of the head in order to make the movements of both head and hand terminate at approximately the same time. The main conclusion is that eye-head coordination is carried out optimally by a parallel processing in which both gaze and hand motor responses are initiated on the basis of a poorly defined retinal signal. The accuracy in hand pointing is not conditioned by head movement per se and does not depend on the relative timing of eye, head and hand movements (synergetic vs sequential responses). However, a decrease in the accuracy of hand pointing was observed in the synergetic condition, when target fixation was not stabilised before the target was extinguished. This suggests that when the orienting saccade reaches the target before hand movement onset, visual updating of the hand motor control signal may occur. A rapid processing of this final input allows a sharper redefinition of the hand landing point.

Adult↗
PubMed1990

Unobserved heterogeneity and the analysis of longitudinal spatial choice data.

"This paper tackles the problem of handling uncontrolled heterogeneity due to unobserved influences on the decision process of spatial choice. It concentrates upon a discrete-time/'random-effects' approach to the problem of unobserved heterogeneity and documents parametric and non-parametric methods of specifying and estimating models which can cope with unobserved heterogeneity." The model is applied to data from Wales. (SUMMARY IN FRE)

Behavior↗
PubMed2006

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

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

Journal Article↗
PubMed2006

Integration of flowering dates in phenology and pollen counts in aerobiology: analysis of their spatial and temporal coherence in Germany (1992-1999).

We studied the possibility of integrating flowering dates in phenology and pollen counts in aerobiology in Germany. Data were analyzed for three pollen types (Betula, Poaceae, Artemisia) at 51 stations with pollen traps, and corresponding phenological flowering dates for 400 adjacent stations (< 25 km) for the years 1992-1993 and 1997-1999. The spatial and temporal coherence of these data sets was investigated by comparing start and peak of the pollen season with local minima and means of plant flowering. Our study revealed that start of birch pollen season occurred on average 5.7 days earlier than local birch flowering. For mugwort and grass, the pollen season started on average after local flowering was observed; mugwort pollen was found 4.8 days later and grass pollen season started almost on the same day (0.6 days later) as local flowering. Whereas the peak of the birch pollen season coincided with the mean flowering dates (0.4 days later), the pollen peaks of the other two species took place much later. On average, the peak of mugwort pollen occurred 15.4 days later than mean local flowering, the peak of grass pollen catches followed 22.6 days after local flowering. The study revealed a great temporal divergence between pollen and flowering dates with an irregular spatial pattern across Germany. Not all pollen catches could be explained by local vegetation flowering. Possible reasons include long-distance transport, pollen contributions of other than phenologically observed species and methodological constraints. The results suggest that further research is needed before using flowering dates in phenology to extrapolate pollen counts.

Artemisia↗
PubMed1988

A spatial and temporal analysis of dorsal root and sympathetic ganglion formation in the avian embryo.

The present study explores the formation of the dorsal root and sympathetic ganglia in the trunk of the avian embryo. Particular emphasis was given to the timing of gangliogenesis and the relative positions of the neural crest-derived ganglia with respect to the somites. Neural crest cells and their derivatives were recognized by the HNK-1 antibody. The time at which neural crest cell coalesced to form ganglia was assessed by the state of cellular aggregation. The state of ganglionic differentiation was assessed by the expression of neurofilament proteins and the neural cell adhesion molecule (N-CAM). At the level of the 15th somite, neural crest cells were observed in the rostral half of the somite at stage 15, during active neural crest migration, and occupied the rostral two-thirds of the somite at progressive stages. HNK-1 positive cells appeared to be organized in three to four streams of cells oriented mediolaterally and dorsoventrally. The dorsal root ganglia and sympathetic ganglia were first detectable at stages 20 and 21, respectively. Both ganglionic rudiments were aligned with the rostral portion of the somite. The dorsal root ganglia occupied the rostral two-thirds of each somite, whereas cells in the sympathetic ganglia occupied a region corresponding to approximately one-third of each somite. At the time of condensation of the dorsal root ganglia, abundant neurofilament staining was observed within the ganglia. However, no N-CAM immunoreactivity was detected until three stages later at stage 23. In contrast, the sympathetic ganglia demonstrated both neurofilament and N-CAM immunoreactivity at the time of condensation. The observation that both dorsal root and sympathetic ganglia form in register with the rostral portion of somite suggests that cues localized at these axial levels, perhaps within the rostral somite, may influence the position where neural crest cells condense to form ganglia. In sensory ganglia, N-CAM expression does not correlate with the onset of gangliogenesis, suggesting that molecules other than N-CAM may play an important role in the aggregation of some neuronal populations.

Animals↗
PubMed1989

The cortical actin-membrane cytoskeleton of unfertilized sea urchin eggs: analysis of the spatial organization and relationship of filamentous actin, nonfilamentous actin, and egg spectrin.

Whole mounts, cryosections, and isolated cortices of unfertilized sea urchin eggs were probed with fluorescent phalloidin, anti-actin and anti-egg spectrin antibodies to investigate the organizational state of the cortically associated actin-membrane cytoskeleton. Filamentous actin and egg spectrin were localized to the plasma membrane, within microvillar and nonmicrovillar domains. The nonmicrovillar filamentous actin was located immediately subjacent to the microvilli forming an extensive interconnecting network along the inner surface of the plasma membrane. The organization of this filamentous actin network precisely correlated with the positioning of the underlying cortical granules. The cortical cytoplasm did not contain any detectable filamentous actin, but instead contained a sequestered domain of nonfilamentous actin. Spectrin was localized to the cytoplasmic surface of the plasma membrane with concentrated foci co-localized with the filamentous actin present in microvilli. Spectrin was also observed to coat the surfaces of cortical granules as well as other populations of intracellular vesicles. On the basis of light microscopic morphology, intracellular distribution, and co-isolation with the egg cortex, some of these spectrin-coated organelles represent acidic vesicles. Identification of an elaborate organization of inter-related domains of actin (filamentous and nonfilamentous) and spectrin forming the cortical membrane cytoskeleton provides insight into the fundamental mechanisms for early membrane restructuring during embryogenesis. Additionally, the localization of spectrin to the surface of intracellular vesicles is indicative of its newly identified functional roles in membrane trafficking, membrane biogenesis and cellular differentiation.

Actins↗
PubMed1983

The use of ligament efficiency to model fenestrations in the internal elastic lamina of cerebral arteries. II--analysis of the spatial geometry.

During uniaxial extension of the latex model, the holes (both marked on the sheet and perforated) demonstrated a distinctive change in their shape, from circular to elliptical. Measurements of the axial and transverse diameters of a consistent row of holes, along with the width of the sample at distinct elongations were converted into an area, ligament efficiency (transverse and axial) and shape factor (eccentricity). Values for the expansion ratio of the holes and necking of the latex sheet were also computed. The perforations expanded more rapidly than with the holes only marked on the solid material, which translated into a more rapid increase for the axial diameter, area and eccentricity, while the axial ligament efficiency decreased more rapidly. The transverse diameter and transverse ligament efficiency remained essentially constant. Necking of the latex sheet was consistent for all of the specimens (both solid and perforated). The relative expansion ratios paralleled the relative changes for the standardized stresses presented in Part I.

Biomechanical Phenomena↗
PubMed1995

Spatial and temporal analysis of the Drosophila FMRFamide neuropeptide gene product SDNFMRFamide: evidence for a restricted expression pattern.

The expression of SDNFMRFamide, one of five different FMRFamide-containing peptides encoded by the Drosophila melanogaster FMRFamide gene, has been determined. To study expression, we generated antisera to the N-terminus of SDNFMRFamide to avoid crossreactivity with FMRFamide-containing peptides. The antisera were purified and the specificity characterized. SDNFMRFamide immunoreactive material is present in the central nervous system throughout development. Immunoreactivity is first observed in embryonic neural tissue in a cluster of cells in the subesophageal ganglion and immunoreactive fibers projecting from these cells to the brain and ventral ganglion. This pattern of expression is also observed in neural tissue dissected from larva, pupa, and adult. Double-labelling experiments indicate that cells recognized by SDNFM-antisera are also stained with FMRFamide antisera. Based on position, SDNFMRFamide immunoreactive material is expressed in a limited number of cells that contain the FMRFamide polypeptide precursor. This finding suggests that the Drosophila FMRFamide precursor undergoes differential post-translational processing.

Amino Acid Sequence↗
PubMed1993

The cortical actin cytoskeleton in a Dipteran embryo: analysis of the spatial reorganization of F-actin aggregates during the early nuclear division cycles.

Rhodamine phalloidin-staining was used to study the organization of the cortical actin cytoskeleton of the early Ceratitis capitata embryo. The dynamics of the actin aggregates and their changes in distribution during the formation of the syncytial blastoderm, were followed in detail. It was found that these aggregates formed a shell-like cluster around the interphase nuclei, and concentrated toward the poles of the mitotic apparatus when the nuclei divided. Laser scanning confocal microscopy revealed that aggregates not clustered at the poles of the mitotic apparatus were closely associated with fine fibers of a dense cytoplasmic network of actin filaments.

Actins↗
PubMed1996

Spatial and temporal analysis of evoked neural activity in optical recordings from American cockroach antennal lobes.

The spatio-temporal patterns of neural activity evoked by electrical stimuli to the antennal nerve (AN) in male cockroach antennal lobes (ALs) in vivo were analyzed by optical imaging using a voltage-sensitive dye. The response pattern was initially a depolarization on the AN and subsequently a depolarization followed by a hyperpolarization on the whole area of macroglomerulus (MG) and a part of ordinary glomerulus (OG). It was suggested by the pharmacological results that the depolarizing responses on the AL consist of both a presynaptic response, representing synchronous compound action potentials from the AN, and a postsynaptic response, representing synchronous compound excitatory postsynaptic potentials and action potentials from neurites of AL neurons, and that the inhibitory responses of GABAergic local interneurons in the AN are different in time course from that in the AL.

Action Potentials↗
PubMed2005

Whole-head MEG analysis of cortical spatial organization from unilateral stimulation of median nerve in both hands: no complete hemispheric homology.

We examined the contralateral hemispheric cortical activity in MEG (151 ch) after unilateral median nerve stimulation of the right and left hand in twenty healthy right-handed subjects. The goal was to establish parameters to describe cortical activity of the hemispheric responses and to study the potential ability to assess differences in volunteers and patients. We focused on the within-subject similarity and differences between evoked fields in both hands. Cortical activity was characterized by the overlay display of waveforms (CWP), number of peak stages, loci of focal maxima and minima in each stage, 3D topographic maps and exemplified equivalent current dipole characteristics. The paired-wise test was used to analyze the hemispheric differences. The waveform morphology was unique across the subjects, similar CWPs were noted in both hemispheres of the individual. The contralateral hemispheric responses showed a well defined temporal-spatial activation of six to seven stages in the 500 ms window. Consistently (in over 80% of subjects), the six stages across the subjects were 20M, 30M, 50M, 70M, 90M, and 150M. A 240M was present in the left hemisphere (LH) in 15/20 subjects and in the right hemisphere (RH) in 10/20. Statistics of the latencies and amplitudes of these seven stages were calculated. Our results indicated that the latency was highly consistent and exhibited no statistical mean difference for all stages. Furthermore, no mean amplitude differences between both hemispheres at each stage were found. The patterns of magnetic fields in both hemispheres were consistent in 70% of the subjects. A laterality index (L.I.) was used for defining the magnetic field amplitude differences between two hemispheres for each individual. Overall, the absolute amplitude of the brain responses was larger in the left than in the right hemisphere in the majority of subjects (16/20), yet a significant portion (4/20) exhibited right dominance of the N20m activity. Each individual exhibited a unique CWP, there was reliable consistency of peak latencies and mean amplitudes in median nerve MEG. Nevertheless, this study indicates the limitations of using the intact hemisphere responses to compare with those from the affected (brain) side and suggests caution in assuming full homology in the cortical organization of both hemispheres. This study provides some results to address clinical issues like which parameter describes individual differences best. Whether a genuine difference is found or whether any difference may simply represent the variability encountered in a normal population.

Adult↗
PubMed1983

Computer analysis of the spatial angular parameters of the canine QRSsE loop from necropsy-verified normal dogs.

Vectorcardiograms were recorded by the canine modification of the axial lead system of McFee and Parungao from 38 necropsy-verified normal dogs placed in the recommended position of right lateral recumbency. A digital computer program was used to identify and analyze the spatial characteristics of the QRSsE loop. In order to define the QRSsE loop in more complete terms, a total of 27 angular parameters were evaluated. Time to specified parameters and angular values at specified times were assessed. The smallest angular range for a frontal plane vector was 15.7 degrees which occurred with the maximum leftward vector. In the sagittal plane the most narrow range was 29.8 degrees found with the half-area vector. The most narrow angular range in the transverse plane was 29.7 degrees with the maximum leftward vector. Other characteristics of the normal dog were found, such as the simultaneous occurrence of the following vectors: the peak spatial magnitude vector; frontal plane maximum vector; maximum leftward vector; maximum caudal vector; sagittal plane half-area vector; and transverse plane maximum vector. Also occurring together, but at a different time, were the sagittal plane maximum vector and the transverse plane half-area vector.

Animals↗