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PubMed1997

Spatial distribution of corticospinal potentials following transcranial electric and magnetic stimulation in human spinal cord.

To investigate the spatial distribution of the human corticospinal tract in the spinal cord, evoked spinal cord potentials (ESCPs) following transcranial electrical and magnetic stimulation were recorded simultaneously from both the anterior and posterior epidural space in five anesthetized patients. One ESCP component following transcranial electrical stimulation (D-wave) and at least two ESCP components (initially D-wave and later I-wave) following transcranial magnetic stimulation were recorded in all subjects. The negative peak latency of all the potentials recorded from the posterior epidural space was the same as that recorded anteriorly. The amplitude ratio of the ESCP following electrical stimulation (posterior/anterior) was 1.10+/-0.12, while that of ESCPs following magnetic stimulation was 1.08+/-0.12 (N1) and 1.15+/-0.16 (N2). These results suggest that lateral corticospinal tract descending dorsolateral fasciculus in the spinal cord is main corticospinal pathway and spatial distribution of D and I-waves are similar in the human cervical cord.

Cerebral Cortex↗

PubMed2003

Infrared microspectroscopic imaging maps the spatial distribution of exogenous molecules in skin.

Infrared (IR) microscopic imaging is used, in a series of proof-of-principle experiments to map the spatial distribution of two penetration enhancers, dimethylsulphoxide (DMSO) and propylene glycol, in skin. The current instrumentation utilizes a 64 x 64 array of IR detectors imaged at the focal plane of an IR microscope, each collecting a complete mid-infrared spectrum of the skin section on each pass of the interferometer. The spatial area sampled by each element in the array is approximately 6.3 x 6.3 microm. Any spectral parameter (e.g., arising from lipid or protein vibrational modes of the endogenous tissue or the exogenous component) may be quantitatively analyzed across the entire array of 4096 spectra, thereby generating an IR spectroscopic image of that particular parameter throughout the sample. The images directly reveal the spatial heterogeneity of the protein and lipid distributions. In transverse slices of skin, the depth dependencies of the spatial distribution of triglyceride and protein have been monitored, and compared to those of the exogenous penetration enhancers. Images of both DMSO and propylene glycol suggest that each penetrates the skin to a depth of at least 1 mm (under our experimental protocols), and reveals a spatial distribution that is essentially coincident with the protein constituents of the skin. These results demonstrate that IR microscopic imaging has great potential for mechanistic studies of topical, dermal, and transdermal delivery.

Animals↗

PubMed1992

Cyclic GMP-activated channels of salamander retinal rods: spatial distribution and variation of responsiveness.

1. Patch-clamp methods were used to investigate the areal density and spatial location of cyclic GMP-activated channels in the surface membrane of salamander rod outer segments. 2. The density of active channels (i.e. channels able to respond to cyclic GMP) in patches excised from outer segments was determined from the number of active channels, N, and the membrane area, A. N was estimated from the current induced by a saturating concentration of cyclic GMP, while A was estimated from the electrical capacitance of the patch. 3. In patches excised from forty-one isolated outer segments prepared in the light the active channel density varied over a remarkable range: 0.34-629 microns-2, with a mean of 166 microns-2. Density was not correlated with patch area in this or any of the conditions studied. 4. The spatial distribution of open channels on the outer segment of a transducing rod was measured by recording the local dark current at various positions with a loose-patch electrode. The apparent density of open channels varied by only about +/- 50% around the circumference of the outer segment and up and down its length. This indicates that the wide range of densities in excised patches did not result from sampling a non-uniform spatial distribution of channels. 5. Patches excised from sixteen dark-adapted whole cells with healthy appearances and saturating light responses of normal size had active channel densities of 1.1-200 microns-2, with a mean of 60 microns-2. Patches from twenty light-adapted whole cells had similar densities. Many densities from the whole cells were much lower than expected. This, and the wide variation in densities, suggests that obtaining a patch often lowered the density of active channels. The number of channels in a patch was quite stable from 1 s to 30 min after excision, ruling out progressive denaturation or adsorption of channels to the glass as a cause for this effect. 6. The mean active channel density in patches excised from whole cells was lower with calcium present in the external solution than with calcium absent (80 vs. 152 microns-2, n = 36 and 30 respectively). 7. We conclude that copies of the channel protein were present at a density of at least 650 microns-2 in the surface membrane of the outer segment and that the distribution of channels was fairly uniform on a 1 micron scale.(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Ocular↗

PubMedDate not supplied

Geography of surnames in the Azores: specificity and spatial distribution analysis.

In order to obtain a better understanding of the genetic structure of the Azorean population, a specificity and spatial distribution analysis was performed, based on 2,454 different surnames present in the Azorean telephone directory (2002). We considered as specific surnames those with an absolute frequency ratio equal to or higher than 50%. The results revealed 51 specific surnames in the whole archipelago. The smallest island presents the only surname with 100% specificity (Pedras). In addition, São Miguel island, which contains 54% of the Azorean population, has the highest number of specific surnames (25 specific surnames). The spatial distribution analysis was used to detect genetic similarity between municipalities through the calculation of spatial autocorrelation (Moran's I coefficient). Of 240 surnames included in the analysis, 113 showed statistically significant patterns. Five different patterns were obtained, of which the most relevant was isolation by distance and depression (41.6%). However, 43.4% had no defined pattern. The overall correlogram shows a majority of positive values for distances lower than 49 km and between 269-309 km, indicating high similarity between closer municipalities and between distant municipalities whose populations show historic and sociocultural affinities. In conclusion, our data are in agreement with the historical background of the Azorean population.

Azores↗

PubMed1978

Time course and spatial distribution of phenylalanine ammonia-lyase and peroxidase activity in wounded potato tuber tissue.

The time course and spatial distribution of wound-induced activities of phenylalanine ammonia-lyase and peroxidase were determined to establish correlations between molecular and cellular aspects of the wound-induced pattern of cell differentiation in potato (Solanum tuberosum L.) tissue. A high correlation between peroxidase activity and suberization was observed. Peroxidase activity increased for several days after wounding. Peroxidase content of suberizing cells was more than 10 times higher than that of the immediately adjacent dividing cells. Suberizing and dividing cells contained different isoperoxidases. Neither time course nor spatial distribution of the wound-induced activity of phenylalanine ammonia-lyase was directly correlated with the wound-induced pattern of cell differentiation.

Journal Article↗

PubMed1999

Spatial distribution of QT dispersion measured by magnetocardiography under stress in coronary artery disease.

This study investigated changes in spatial distribution of QT duration in patients with and without coronary artery disease (CAD) using magnetocardiography. Thirty-six-channel magnetocardiograms (MCGs) were registered at rest and under stress in 15 patients with chest pain, seven of whom had significant coronary stenosis. QT dispersion (QTd) was calculated for MCG and 12-lead electrocardiogram (ECG) under both conditions. For MCG, homogeneity of repolarization was measured using a smoothness index (SI). Also, at each registration site, the intraindividual difference between QT at rest and under stress was determined (deltaQT). QTd values as determined by standard 12-lead configurations were not significantly different between groups. MCG QTd values were significantly higher in the CAD group at rest only when all available channels were taken into consideration (P < .05); SI values differed significantly between groups under both conditions (rest, P < .005; stress, P < .01). Good separation between groups was possible using the range of deltaQT (P < .05) and SI (deltaQT) (P < .005). Consideration of the spatial distribution of QTd increases its sensitivity in the detection of CAD, suggesting that CAD involves complex changes in repolarization, not apparent in limited lead sets such as standard 12-lead configurations.

Adrenergic beta-Agonists↗

PubMedDate not supplied

Spatial distribution of PAHs in a contaminated valley in Southeast China.

A survey was conducted on the accumulation and spatial distribution of PAHs in surface soils under different land use patterns in a valley in the Yangtze Delta region with an area of 10 km(2) containing 15 small copper- and zinc-smelting furnaces. Sixty-five topsoil (0-20 cm) samples were collected and 16 PAHs were determined. The average amount of all the 16 PAHs ranged from 0 to 530 microg kg(-1) (oven dry basis), with a mean concentration of 33.2 microg kg(-1). Benzo[a]pyrene and indeno[1, 2, 3, -cd]pyrene were the two main PAHs present at high concentrations, while pyrene and fluorene had very low concentrations. PAH concentrations were higher in uncultivated than in cultivated soils, and areas of woods and shrubbery had the lowest soil PAH contents. The average PAH-homologue concentrations ranked as follows: 5-rings >> 3-rings, 4-rings > 6-rings >2-rings. Much higher concentrations of PAHs were found in the southern part of the sampling area, perhaps due to deposition of airborne particles by the southeasterly winds in winter and spring. We conclude that the small smelting furnaces were the dominant source of PAHs that accumulated in the soils and the southeasterly winds led to the spatial distribution of PAHs in the topsoils. Land vegetation cover and soil utilization patterns also affected the accumulation and distribution of soil PAHs.

China↗

PubMed1991

Spatial distribution of connexin43, the major cardiac gap junction protein, in the developing and adult rat heart.

The developmental appearance and spatial distribution pattern of gap junctions were studied in prenatal and adult rat hearts. Gap junctions were visualized immunohistochemically with an antibody raised against a unique cytoplasmic epitope of connexin43, and the spatial distribution pattern was determined by three-dimensional reconstruction. The results demonstrate that from embryonic day 13 onward, connexin43 becomes detectable immunohistochemically in the myocardium of atria and ventricles. No expression is initially detectable in the myocardium of the sinus venosus, the sinoatrial node, the posterior wall of the atrium and pulmonary veins, the interatrial septum, the atrioventricular canal, including atrioventricular node and bundle, the interventricular septum, and the outflow tract. The developmental increase in the density of gap junctions in atria and ventricles of prenatal hearts correlates well with the reported developmental increase in conduction velocity. Whereas connexin43 becomes expressed in the derivatives of the sinus venosus (except for the sinoatrial node) and in the subepicardial layer of the ventricular free wall shortly before birth, it remains undetectable in the atrioventricular node and bundle and the proximal part of the ventricular conduction tissue, even in the adult heart. The apparent absence of an abundant expression of connexin43 at a location with a supposedly high conduction velocity (i.e., the atrioventricular bundle and bundle branches) is unexpected. These observations were confirmed in studies of the adult mouse heart, which showed, in addition, that connexin32 is not expressed in any part of the heart.

Aging↗

PubMed2003

Validation of the novel indices of nuclear pleomorphism, polarity and spatial distribution in the grading of urothelial carcinoma.

OBJECTIVE: To evaluate the role of the novel histomorphometric variables of pleomorphism, orientation and variability of spatial cytologic organization to objectively quantify histopathologic grade in urothelial carcinoma. STUDY DESIGN: As a validation model, we chose 51 papillary urothelial carcinomas. Thirty-six (70%) were low and 15 (29%) high grade tumors (World Health Organization grading system). Thirty-one cases (61%) were noninvasive, 12 (23%) exhibited lamina propria invasion, and 8 (16%) invaded the deep smooth muscle. Histomorphometric measurements were performed on noninvasive areas only. Pleomorphism was characterized by the anisokaryosis index (AIX), based on the autocorrelation function applied to classic nuclear shape descriptors. Additional indices of pleomorphism included standard deviations (sd) and coefficients of variation of these shape descriptors. Loss of polarity was assessed by the orientation index (ORX), based on Fourier transformation. Intraepithelial nuclear spatial distribution index (NSDX) was also computed. RESULTS: Low grade tumors exhibited less pleomorphism, higher orientation indices and a more homogeneous spatial distribution than did high grade tumors (area-AIX: P = .004, ORX: P < .0001, NSDX: P = .001). Multivariate analysis revealed the significant discriminators of grade to be nuclear size and orientation (size: max-diam, P < .0001; width: P < .0001; orientation: ORX: P < .0001). A discriminant score combining these independent variables distinguished between low and high grades in 98% of cases. The method was successfully validated using a testing sample of 40 new patients (accuracy, 94%). Lamina propria invasion was independently predicted by nuclear pleomorphism (width-sd: P = .0001, sensitivity = 64%, specificity = 91%). Muscle invasion was independently predicted by nuclear area (P < .0001) and pleomorphism (area-sd: P < .0001, max-diam-sd: P < .0001, width-AIX: P < .0001, sensitivity = 87%, specificity = 100%). CONCLUSION: These novel morphometric methods may serve as more objective methods of histopathologic grading and may contribute to the development of automated systems for quantitative grading of stratified and transitional epithelial neoplasms.

Aged↗

PubMed2001

Spatial distribution and polarization dependence of the optical near-field in a silicon microfabricated probe.

This paper reports on the spatial distribution and polarization behaviour of the optical near-field at the aperture of a Si micromachined probe. A sub-100 nm aperture at the apex of a SiO2 tip on a Si cantilever was successfully fabricated by selective etching of the SiO2 tip in a buffered-HF solution using a thin Cr film as a mask. The aperture, 10-100 nm in size, can be reproducibly fabricated by optimizing the etching time. The optical throughput of several apertures was measured. For a 100 nm aperture, a throughput of 1% was approved. The probe shows a very high optical throughput owing to the geometrical structure of the tip. The spatial distribution of the near-field light is measured and simulated using a finite difference-time domain method. The polarization behaviour of apertures with different shapes was analysed using a photon counting camera system.

Journal Article↗

PubMed1997

Estimation of the spatial distribution of target cells for radiation pneumonitis in mouse lung.

PURPOSE: Recent studies of Liao et al. and Travis et al. have demonstrated that irradiation of cross-sectional partial volumes contiguous to the base of mouse lung produces a higher incidence of pneumonitis than irradiation of equally sized subvolumes contiguous to the apex. One interpretation of this finding is that the critical target cells for pneumonitis are not distributed uniformly throughout the lung. The purpose of the present study was to test this interpretation by obtaining an estimate of the spatial distribution of the critical target cells for pneumonitis in mouse lung, based on the partial-volume data. METHODS AND MATERIALS: A mathematical model was derived describing the probability of radiation pneumonitis as a function of dose, volume of lung irradiated, and location in the lung of the irradiated subvolume. The model includes a nonparametric description of the spatial target-cell distribution in lung, to be estimated from data. The model was fitted to the lethality data of Liao et al. and Travis et al. to obtain estimates of the proportion of target cells contained in each of various subvolumes of the lung. RESULTS: The results indicate that the critical target cells in mouse lung are concentrated in the base and, to a somewhat lesser extent, in the apex of the lung, with fewer cells in the middle region. The estimated spatial distribution of target cells in mouse lung agrees well with the distribution of alveoli, whose concentration in the midlung is limited by the presence of the major conducting airways. CONCLUSION: Heterogeneity in the spatial distribution of critical target cells in normal tissue implies that the complication probability (NTCP) depends on the location in the organ of the irradiated subvolume, as well as on radiation dose and subvolume size. Calculations using an NTCP model for mouse lung indicate that irradiation of equal subvolumes of lung with the same dose can lead to complication probabilities covering the full range from 0 to 100%, depending only on the location in the lung of the irradiated subvolume.

Animals↗

PubMed2006

Spatial distribution and vertical variation of arsenic in Guangdong soil profiles, China.

Total of 260 soil profiles were reported to investigate the arsenic spatial distribution and vertical variation in Guangdong province. The arsenic concentration followed an approximately lognormal distribution. The arsenic geometric mean concentration of 10.4 mg/kg is higher than that of China. An upper baseline concentration of 23.4 mg/kg was estimated for surface soils. The influence of soil properties on arsenic concentration was not important. Arsenic spatial distributions presented similar patterns that high arsenic concentration mainly located in limestone, and sandshale areas, indicating that soil arsenic distribution was dependent on bedrock properties than anthropogenic inputs. Moreover, from A- to C-horizon arsenic geometric mean concentrations had an increasing tendency of 10.4, 10.7 to 11.3 mg/kg. This vertical variation may be related to the lower soil organic matter and soil degradation and erosion. Consequently, the soil arsenic export into surface and groundwaters would reach 1040 t year-1 in the study area.

Arsenic↗

PubMed1994

Spatial distribution of bremsstrahlung in a dual electron beam used in total skin electron treatments: errors due to ionization chamber cable irradiation.

The spatial distribution of the bremsstrahlung dose in total skin electron therapy and large electron fields has been assumed to be symmetric along the match line; however, the measured data in the entire plane have not been available. Das et al. ["Spatial distribution of bremsstrahlung in total skin electron irradiation," Med. Phys. 19, 810 (1992)] reported the ion-chamber measured bremsstrahlung data in the Stanford six-field technique and found that the bremsstrahlung dose profile was 2.5 times greater in the caudal plane (beam facing toward floor) as compared to the cephalic plane. This observation was recently quoted by Klevenhagen [Physics and Dosimetry of Therapy Electron Beams (Medical Physics, Madison, WI, 1993)]. Further study using thermoluminescent dosimeters and careful measurements using ion chambers showed that the bremsstrahlung radiation was indeed symmetric at the match line as theoretically predicted and was not a function of the beam angle or the type of floor. The earlier observations of Das et al. were found to be due to cable effects. Ionization chamber cable response in a large electron field and the associated errors in the bremsstrahlung distribution are presented. It is suggested that a cable-free dosimeter should be used for measuring low levels of bremsstrahlung radiation in large electron fields and at extended distances.

Biophysical Phenomena↗

PubMed2004

The spatial distribution of attention in perceptual latency priming.

The spatial distribution of visual attention is a yet unresolved question. One of the main topics is whether attention is distributed in a graded fashion around an attended location (e.g., Downing, 1988; Zimba & Hughes, 1987). The present experiments explore whether, and on which conditions, gradients of attention arise and contribute to perceptual facilitation. A masked or unmasked prime precedes one of two targets whose temporal order has to be judged. The prime captures attention, which shortens the perceptual latency of the primed target (perceptual latency priming; Scharlau & Neumann, 2003a; Shore, Spence, & Klein, 2001). No strong evidence for an attentional gradient was found. (1) Accuracy of temporal order judgements was independent of the distance between the two targets that were judged. That is, facilitation of the second target by the first target was spatially invariant. (2) With targets of short duration, facilitation was independent of prime-target distance. (3) With targets of long duration, gradients were found: Facilitation declined continuously with distance. Thus, long duration of stimuli may be a sufficient precondition for an attentional gradient. A control experiment showed that object-based attention contributes only marginally to perceptual latency priming.

Adult↗

PubMed1991

Spatial distribution of nociceptive processing in the rat spinal cord.

1. Quantitative 2-deoxyglucose (2-DG) experiments were undertaken to determine the spatial distribution of nociceptive responses in the rat spinal cord. Twenty unanesthetized, paralyzed rats with T2 transected spinal cords were divided into groups (n = 4) and stimulated with non-noxious (35 degrees C) or graded noxious temperatures (45 degrees, 47 degrees, 48 degrees, and 49 degrees C). Stimulation was delivered by cyclical immersion of one hind paw in a temperature-controlled water bath. 2. When stimulation began, 50 microCi of 2-DG was injected into the rat, and timed sequential blood samples were drawn to monitor plasma glucose and 2-DG levels. On termination of stimulation, spinal cords were removed, sectioned, and prepared for autoradiography. Local rates of spinal cord metabolism were obtained by microcomputer analysis of autoradiographs. 3. Nociceptive stimulation produced increases in glucose utilization in some of the grey matter laminae previously implicated in nociceptive processing. Within the nociceptive range, 49 degrees and 48 degrees C intensities elicited significantly greater responses than did 45 degrees C stimulation. 4. The rostrocaudal spatial distribution of nociceptive responses was most extensive within laminae V-VI with stimulus-evoked metabolic activity extending 9 mm from L2-L5. Similarly, metabolic increases occurred over 7 mm within lamina VII. In contrast, metabolic activity within the upper dorsal horn (laminae I-IV) extended only 3 mm and was limited to L4. Metabolic patterns within laminae VIII-IX sharply differed from those within other laminae in that no increases occurred within L4, although regions of L3 and L5 were responsive to stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2005

A new method to reconstruct three-dimensional spatial distribution function from radial distribution function in solvation structure.

Three-dimensional spatial distribution function (SDF) of solvent is a fundamental quantity for analysis of solvation. However, its calculation has been very limited because long computational time is required. We here developed a novel and robust method to construct approximated SDFs of solvent sites from radial distribution functions. In this method, the expansion of SDFs in real solid harmonics around atoms of solute leads to a linear equation, from which SDFs are evaluated with reasonable computational time. This method is applied to the analysis of the solvation structure of liquid water, as an example. The successful results clearly show that this method is very powerful to investigate solvation structure.

Journal Article↗

PubMedDate not supplied

Kriging method evaluation for assessing the spatial distribution of urban soil lead contamination.

Describing contaminant spatial distribution is an integral component of risk assessment. Application of geostatistical techniques for this purpose has been demonstrated previously. These techniques may provide both an estimate of the concentration at a given unsampled location, as well as the probability that the concentration at that location will exceed a critical threshold concentration. This research is a comparative study between multiple indicator kriging and kriging with the cumulative distribution function of order statistics, with both local and global variograms. The aim was to determine which of the four methods is best able to delineate between "contaminated" and "clean" soil. The four methods were validated with a subset of data values that were not used in the prediction. Method performance was assessed by calculating the root mean square error (RMSE), analysis of variance, the proportion of sites misclassified by each method as either "clean" when they were actually "contaminated" or vice versa, and the expected loss for each misclassification type. The data used for the comparison were 807 topsoil Pb concentrations from the inner-Sydney suburbs of Glebe and Camperdown, Australia. While there was very little difference between the four methods, multiple indicator kriging was found to produce the most accurate predictions for delineating "clean" from "contaminated" soil.

Cities↗

PubMed2000

Temporo-spatial distribution of endothelial-monocyte activating polypeptide II, an anti-angiogenic protein, in the mouse embryo.

We describe the temporo-spatial distribution of Endothelial-Monocyte Activating Polypeptide (EMAP) II in order to better understand what role this anti-angiogenic proteins may play in fetal development. In situ hybridization, immunohistochemistry, and Western analysis were performed on fetal, neonatal, and adult tissue. EMAP II was first detected only within the central nervous system on 9 days postcoitum (dpc). Subsequently, at 11 through 18 dpc, EMAP II expression was detected in the respiratory, central nervous, cardiovascular, urogenital systems, sense organs, and digestive tract. EMAP II mRNA and protein was localized to the epithelium, with its highest expression in neurons, blood vessels, and at sites of epithelial-mesenchymal interaction. The temporo-spatial distribution of EMAP II suggests that it could play an important role in morphogenesis of the vertebrate embryo.

Angiogenesis Inhibitors↗