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At least 991 records · Page 55Linked to original sources
PubMed2003

Reduction of TMD pain by high-frequency vibration: a spatial and temporal analysis.

Under some conditions, vibration delivered to the skin can reduce pain (vibratory analgesia). Previous studies of this phenomenon in a clinical context have been somewhat variable in terms of stimulus control, and have not examined the way in which the spatial distribution of pain is affected. In the present study, we used rigorously controlled conditions to examine vibratory analgesia in participants (N=17) with painful temporomandibular disorders (TMD). Results of 20- and 100-Hz vibration were compared with data from a no-vibration control condition. The results document for the first time that vibratory analgesia occurs in TMD chronic pain conditions. We measured its time course using continuous visual analog scale (VAS) recording, and its spatial aspects by asking subjects to indicate painful regions on standardized drawings. VAS ratings and drawings both showed that pain is reduced by 100-Hz, but not by 20-Hz, vibration. The effectiveness of the high-frequency vibration cannot be attributed to a mechanism involving Pacinian corpuscles, since these receptors are lacking in the skin of the orofacial region. Spatial analyses revealed that ipsilateral and contralateral effects of vibration were statistically equivalent, suggesting that vibratory analgesia relies at least in part on central nervous system processes rather than local mechanisms.

Adolescent↗
PubMed2003

[Spatial diversity index analysis on wildlife habitat pattern change in the Liaohe Delta].

Based on the study of land cover change in the Liaohe Delta with GIS and RS, the wildlife habitat pattern was described quantitatively, and the pattern change between 1988 and 1998 was analyzed with spatial diversity index. The results showed that the wildlife habitat pattern had an obvious change during the ten years caused by natural and human disturbance. The area of suitable habitat(Sd > or = 0.35) was becoming smaller and more fragmented, with a deteriorated quality. It was proved that spatial diversity index could reflect the habitat suitability of wildlife, and describe the habitat spatial pattern explicitly. This study would provide a scientific basis for protecting wild animals and their habitats.

Animals↗
PubMed1984

A quantitative analysis of the spatial organization of the vestibulo-ocular reflexes in lateral- and frontal-eyed animals--I. Orientation of semicircular canals and extraocular muscles.

The spatial relationship between extraocular muscles and semicircular canals was evaluated in cat (frontal-eyed animal) and rabbit (lateral-eyed animal). Semicircular canal orientations in the rabbit were determined by a principal components analysis of data points obtained from the exposed osseous canals using a three-axis micromanipulator. Canal orientations were presented in terms of unit sensitivity vectors. Orientation of extraocular muscles in rabbits and cats was derived from measurements of the insertion and origin of each muscle with respect to a reference point on the skull and a calculated estimate of the center of the eye. Muscle orientations were presented in terms of unit action vectors. Semicircular canal planes of the rabbit labyrinth were not orthogonal, having deviations up to 14 degrees. Pairs of antagonistically acting vertical semicircular canals, left (right) anterior-right (left) posterior deviated from coplanarity by 16 degrees, while the deviation for the horizontal canals was 9 degrees. In both animals, muscles of an antagonistic pair were coplanar to within 8 degrees, with the exception of the oblique muscles in the rabbit for which the deviation was 19 degrees. The three pairs of antagonistic muscles were almost orthogonal to each other, the maximum deviation between any of the pairs being 8 degrees in the cat and 18 degrees in the rabbit. Comparing extraocular muscle planes and semicircular canal planes reveals that they are roughly aligned. However, there were slight but consistent differences between a given semicircular canal plane and the planes of the muscles to which this canal is connected by the classical three-neuron-arc (principal vestibulo-ocular reflex circuits).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

Isthmus and ligament interrelationships: a computerized analysis of the spatial relationships of the hinge structures in unionid mussels.

A study of the isthmus and ligament in unionid mussels was undertaken employing methods specifically designed to preserve the in vivo relationships of these interrelated structures. Serial sections of the hard and soft tissues were used for two-dimensional analysis. From these, a tridimensional computerized reconstruction was developed. Special dissections of the undisturbed isthmus were also utilized. By using such methodologies, a new description of the ligament has been developed employing such terminology as the foliated ligament and the posterior folding laminae. Similarly, for the isthmus, an anterior lyre, a pallial crest, a pallial peduncle, and a posterior lyre are described. Such entities are both morphologically and physiologically related to the shell and ligament.

Animals↗
PubMed2000

Difference spatial distribution function analysis of aqueous solutions. II. Hydration structures of dimethyl ether, 180 degrees ethyl methyl ether and 0 degree ethyl methyl ether solutions.

Monte Carlo simulations are systematically presented to demonstrate the influence of the hydrophobic group's steric bulk on hydration structure. We have simulated a dimethyl ether (DME), two conformations for ethyl methyl ether (0 degree EME and 180 degrees EME), and 0 degree ethanol solutions. Spatial distribution function (SDF), goo(x,y,z) and difference SDF (DSDF), delta goo(x,y,z), obtained from MC simulation in an infinitely dilute aqueous solution of ether show the three-dimensional probability of an atom-atom pair distribution between solute and solvent atoms. Based on the results of SDF in an infinitely dilute aqueous solution of ether, the distribution of hydration water molecules can be divided into hydrogen acceptor (HA) and hydrophobic hydration (HH), regions, and the spatial orientation of the hydrogen-bonded water in the HA region is found to form a triple-layer structure, as it does in alcohol solutions. From the results of an analysis of the DSDF delta goo(x,y,z) between the SDFs of EME and DME, it is apparent that the distribution changes of hydration water molecules in ether solutions are essentially similar to those in the alcohol solutions. Further, we show that the hydration water molecules are distributed mainly in the stable area in the binding energy's (BE) contour maps for each region.

Algorithms↗
PubMed2000

Difference spatial distribution function analysis of aqueous solutions. IV. Hydration structure changes of ethylene glycol solutions throughout conformational change process from gGg' to tGg' conformers.

Monte Carlo (MC) simulations were carried out for an infinitely dilute aqueous solution of two stable conformers (gGg' and tGg') and of three conformations between gGg' and tGg' conformers of ethylene glycol (EG) at 298K. Based on the spatial distribution function (SDF) goo(x,y,z), obtained from the MC simulation in the above conformations in liquid water, the high distribution of hydration water molecules could be divided into hydrogen acceptor (HA), hydrogen donor (HD), MIX (overlapped distribution of HA and HD), and hydrophobic hydration (HH) regions. The spatial orientations of hydrogen-bonded water molecules were found to be of a linear type with a triple-layer structure in the HA region and HA part (in the MIX region), and double-layer structures in the HD region and HD part (in the MIX region). In addition, it was apparent that the spatial orientations of these water molecules were of the linear type throughout the conformational change process from gGg' to tGg' conformers in liquid water. From the difference SDF (DSDF), deltagoo(x,y, z), between the SDFs of two conformations, we concluded that the distribution of hydration water molecules in the HA and HD parts of the MIX region are governed by the competition of internal hydrogen bonds between the hydrogen atom and two lone-pair electrons on the oxygen atom of an EG molecule.

Algorithms↗
PubMed1995

A generalized estimating equations approach for spatially correlated binary data: applications to the analysis of neuroimaging data.

This paper proposes a generalized estimating equations approach for the analysis of spatially correlated binary data when there are large numbers of spatially correlated observations on a moderate number of subjects. This approach is useful when the scientific focus is on modeling the marginal mean structure. Proper modeling of the spatial correlation structure is shown to provide large efficiency gains along with precise standard error estimates for inference on mean structure parameters. Generalized estimating equations for estimating the parameters of both the mean and spatial correlation structure are proposed. The use of semivariogram models for parameterizing the correlation structure is discussed, and estimation of the sample semivariogram is proposed as a technique for choosing parametric models and starting values for generalized estimating equations estimation. The methodology is illustrated with neuroimaging data collected as part of the National Institute of Neurological Disorders and Stroke (NINDS) Stroke Data Bank. A simulation study demonstrates the importance of accurate modeling of the spatial correlation structure in data with large numbers of spatially correlated observations such as those found in neuroimaging studies.

Brain↗
PubMed2004

Examining localized patterns of air quality perception in Texas: a spatial and statistical analysis.

Environmental and human health issues associated with outdoor air pollution, such as ozone, sulfur dioxide, and other pollutants in metropolitan regions, are an area of growing concern for both policy officials and the general public. Increasing attention from the news media, new health data, and public debate over the effectiveness of clean air regulations have raised the importance of air quality in the public consciousness. While public perceptions of air quality have been studied thoroughly dating back to the 1960s, little empirical research has been conducted to explain the spatial aspects of these perceptions, particularly at the local level. Although recent studies suggest characteristics of local setting are important in shaping perceptions of air quality, the roles of proximity, neighborhood characteristics, and location have not been clarified. This study seeks to improve understanding of the major factors shaping public perceptions of air quality by examining the spatial pattern of local risk perception, the role of socioeconomic characteristics in forming these perceptions, and the relationship between perceived and scientifically measured air pollution. First, we map the spatial pattern of local air quality perceptions using Geographic Information Systems (GIS) across the Dallas and Houston metropolitan areas. Next, we explain these perceptions through local contextual factors using both bivariate correlations and multivariate regression analysis. Results indicate that perceptions of air quality in the study areas are not significantly correlated with air quality based on readings of air monitoring stations. Instead, perceptions appear to be influenced by setting (urban vs. rural), state identification, access to information, and socioeconomic characteristics such as age, race, and political identification. We discuss the implications of the findings and provide direction on how further research can provide a deeper understanding of the local contextual factors influencing public perceptions.

Air Pollutants↗
PubMed2002

Spatial independent component analysis of functional MRI time-series: to what extent do results depend on the algorithm used?

Independent component analysis (ICA) has been successfully employed to decompose functional MRI (fMRI) time-series into sets of activation maps and associated time-courses. Several ICA algorithms have been proposed in the neural network literature. Applied to fMRI, these algorithms might lead to different spatial or temporal readouts of brain activation. We compared the two ICA algorithms that have been used so far for spatial ICA (sICA) of fMRI time-series: the Infomax (Bell and Sejnowski [1995]: Neural Comput 7:1004-1034) and the Fixed-Point (Hyvärinen [1999]: Adv Neural Inf Proc Syst 10:273-279) algorithms. We evaluated the Infomax- and Fixed Point-based sICA decompositions of simulated motor, and real motor and visual activation fMRI time-series using an ensemble of measures. Log-likelihood (McKeown et al. [1998]: Hum Brain Mapp 6:160-188) was used as a measure of how significantly the estimated independent sources fit the statistical structure of the data; receiver operating characteristics (ROC) and linear correlation analyses were used to evaluate the algorithms' accuracy of estimating the spatial layout and the temporal dynamics of simulated and real activations; cluster sizing calculations and an estimation of a residual gaussian noise term within the components were used to examine the anatomic structure of ICA components and for the assessment of noise reduction capabilities. Whereas both algorithms produced highly accurate results, the Fixed-Point outperformed the Infomax in terms of spatial and temporal accuracy as long as inferential statistics were employed as benchmarks. Conversely, the Infomax sICA was superior in terms of global estimation of the ICA model and noise reduction capabilities. Because of its adaptive nature, the Infomax approach appears to be better suited to investigate activation phenomena that are not predictable or adequately modelled by inferential techniques.

Adult↗
PubMed1993

[Standardized analysis of visual spatial perception. Construction of the procedure and applications].

Assessment of visuo-spatial perception (VS) in brain-damaged patients. So far, no comprehensive methods for reliable assessment of visuo-spatial deficits after brain damage have been described. The tests usually applied are subtests of intelligence tests, paper-pencil tests or visual-constructive tests which also require motor and planning abilities. Almost all these methods are unsuitable for measuring therapeutic changes and do not reveal specific impairments. The computational method presented here (VS) is suitable for the quantitative assessment of visuo-spatial functions, e.g. subjective visual vertical and horizontal; orientation, length, distance, form and position discrimination as well as line bisection. It can easily be installed on an IBM compatible PC. A clinical standard examination can be performed within 20-30 minutes including numerical and graphical analysis of the results. The method is sensitive for measuring therapeutic changes. Moreover, it offers a wide range of experimental task manipulations for more sophisticated experimental tests.

Attention↗
PubMed1990

Spatial and temporal analysis by neurons in the representation of the central visual field in the cat's lateral suprasylvian visual cortex.

We studied quantitatively the receptive-field properties of 74 units recorded from the representation of the central visual fields in the cat's lateral suprasylvian (LS) visual cortex. In agreement with previous workers, we found that LS receptive fields tended to be large and to lack discernible spatial structure. They resembled the complex receptive fields of areas 17 and 18 in their general organization. We examined the responses of these neurons to moving optimally oriented sinusoidal gratings that varied in spatial and temporal frequency of drift. Most LS neurons were selective for the spatial frequency of sinusoidal gratings; 7% responded to all spatial frequencies below a cutoff value. In agreement with previous reports, the optimal spatial frequencies for LS neurons covered a wider range than is seen in either area 17 or 18 alone (0.05-1 cycle/deg), but are certainly included in the range covered by both these afferent areas. Individual neurons in LS responded to a range of spatial frequencies broader than is typical for neurons in areas 17 and 18. The effect of varying the drift rate of otherwise optimal gratings was similar in LS to that reported for areas 17 and 18. Most neurons were optimally responsive to drift rates between 0.5 and 4 Hz, and resolved frequencies as high as 10-30 Hz. A few neurons had optima higher than 6 Hz and resolved frequencies in excess of 30 Hz. We conclude that the receptive fields of LS neurons reflect rather closely the properties of their afferents from areas 17 and 18.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Analysis of a spatially regulated phosphotyrosine phosphatase identifies tyrosine phosphorylation as a key regulatory pathway in Dictyostelium.

We have cloned a Dictyostelium phosphotyrosine phosphatase (PTP1) with a catalytic domain showing approximately 38%-50% amino acid identity to those of other PTPs. PTP1 contains an approximately 99 amino acid insert and bacterially produced PTP1 possesses PTP activity. PTP1 is expressed at a very low level in vegetative cells, induced by 4 hr, and maximally expressed at the tight aggregate stage. PTP1-lacZ studies indicate that PTP1 is spatially localized to prestalk and anterior-like cell types. PTP1 gene disruptants show accelerated development, whereas strains overexpressing PTP1 to a high level fail to aggregate. Strains overexpressing moderate levels exhibit severe morphological defects following aggregation, including multiply tipped aggregates and morphologically aberrant fruiting bodies. Western blot analysis using anti-phosphotyrosine antibodies shows specific changes in the mutant strains when compared with wild-type cells. The results indicate that reversible protein-tyrosine phosphorylation and PTP1 play important regulatory roles during Dictyostelium development.

Amino Acid Sequence↗
PubMed2003

Caenorhabditis elegans DAF-21 (HSP90) is characteristically and predominantly expressed in germline cells: spatial and temporal analysis.

Three monoclonal antibodies against antigens that exist in the Caenorhabditis elegans germ line have previously been described. In the present study, a full-length mRNA for one of these antigens was isolated, and by sequencing its corresponding cDNA, it was predicted that the protein would show a high homology with the 90 kDa heat shock protein (HSP90) in other species, and with the protein of daf-21, a previously identified hsp90 homologue. The spatial and temporal distribution of the antigen (DAF-21) was analyzed in C. elegans, and the localization of daf-21 mRNA, as detected by in situ hybridization, agreed with that detected by the monoclonal antibody. Under normal conditions, daf-21 mRNA is characteristically distributed in postembryonic germ cells derived from Z2 and Z3 cells in both hermaphrodites and males. Under heat stress conditions, however, daf-21 mRNA was not only detected in germ cells, but also apparently expressed all over the body. In addition, the DAF-21 protein seemed to be localized in the perinuclear region of somatic cells.

Amino Acid Sequence↗
PubMed2004

A spatial and temporal analysis of safety-belt usage and safety-belt laws.

Safety-belt usage has increased significantly in the US since the introduction of mandatory safety-belt usage laws in the 1980s. This paper analyzes the impact of these laws on increasing safety-belt usage while controlling for other state-specific variables. A fixed effects cross-sectional time-series analyses shows the relative significance of various state-level attributes in explaining safety-belt usage, including whether or not primary or secondary safety-belt laws have been passed. To further explore these relationships we employ spatial analyses techniques and find spatial autocorrelation in the data. Spatial correlation also exhibits a clear east-west direction. When the analyses is further corrected for temporal autocorrelation we find that the spatial autocorrelation is greatly diminished and that many variables lose their statistical significance, though safety-belt laws are still statistically significant. Results suggest that for this data, it is critical to control for temporal autocorrelation while spatial autocorrelation is less important. We also find that our spatial analyses does provide interesting information on similarities between various regions on the effectiveness of safety-belt laws.

Adolescent↗
PubMed1992

Three dimensional vector analysis of the spatial components and voltage magnitudes of the P300 response during different attentional states and stimulus modalities.

The spatial orientation and vector magnitude of the P300 event related potential (ERP) were investigated under both passive and active attentional states using stimuli presented to two sensory modalities. Three orthogonal electrode pairs were used to establish a tri-axial reference frame. By combining the separate single channel data recordings into a Cartisian coordinate system, both the spatial orientation and the vector magnitude of the P300 response could be derived and described as a hypothetical dipole. Results suggested that changes in amplitudes, recorded with individual electrode pairs, can be attributed largely to changes in the spatial orientation of a rotating P300 response dipole, and not simply to the altered magnitude of the response. The combined-axes P300 response occurs in two separate spatial domains, depending on stimulus modality and attentional state.

Acoustic Stimulation↗
PubMed1986

Spatial orientation of the mitotic apparatus and its stability in a polarized epithelial cell. A computer-assisted morphometric analysis.

The spatial and temporal orientation of the mitotic apparatus in reference to the polarized structure of an epithelial cell, as well as the relationship between mitotic spindle positioning and the direction of epithelial cell migration, was investigated. As an experimental model the epithelium of the mouse small intestine was chosen. Computer-assisted morphometric analysis applied in this study disclosed that the position of the mitotic spindle axis is restricted to a plane which is perpendicular to the axis of cell polarity. On this plane the spindle axis may occupy a random position. The latter finding indicates that there exists no correlation between the orientation of the mitotic spindle and the direction of epithelial cell migration. The plane of the spindle axis is established at metaphase, and no repositioning at further stages of mitosis has been observed. It is suggested that cell polarity plays a role in determination and stabilization of the mitotic spindle orientation in epithelial cells.

Animals↗
PubMed1998

Stimulation of tumour angiogenesis by proximal wounds: spatial and temporal analysis by MRI.

We show here, using high-resolution magnetic resonance imaging, that injured tissue provides a favourable milieu for the neovascularization and growth of C6 glioma spheroids, implanted subcutaneously in nude mice. Moreover, the presence of micro-tumours in an injured tissue inhibited the healing process, leaving an open persistent wound. In correlation with the induced angiogenesis of implanted spheroids in the presence of proximal wounds, a shorter lag period was observed for initiation of tumour growth. This effect was restricted spatially and was observed only for wounds within 5 mm from the tumour. In such proximal wounds, angiogenesis was enhanced in the first days after injury, and vessel regression, which normally starts 4 days after injury, did not occur. Injury causing interference to tumour perfusion promoted tumour vascularization and growth even for more remote incisions, possibly by activating stress-induced angiogenesis. The kinetics of vascularization and growth of these wound-tumour systems sheds light on the clinical observations of increased probability of metastatic recurrence and stimulated regrowth of residual tumour in the site of surgical intervention. High-resolution magnetic resonance imaging could detect the aberrant angiogenic activity of these tumour-wound systems as early as 1 week after injury.

Animals↗
PubMed2001

Analysis of the spatial, temporal and tissue-specific transcription of gamma-sarcoglycan gene using a transgenic mouse.

To evaluate the promoter function of the 5'-flanking sequence of mouse gamma-sarcoglycan (gamma-SG) gene in vivo, we generated transgenic mice harboring this sequence fused with enhanced green fluorescent protein reporter gene. The reporter expression was restricted in striated muscles and particularly strong in all myofibers in skeletal muscles. Using these mice, we examine the spatial and temporal transcriptional patterns of the gamma-SG gene during mouse skeletal muscle development. The expression of basic helix loop helix transcriptional factors preceded that of the reporter. Differences between the expression of reporter and endogenous gamma-SG genes in non-muscle tissues suggested the existence of additional promoter elements in the endogenous gene, and the analysis of endogenous mRNAs demonstrated the existence of a novel upstream exon and promoter active in non-muscle tissues.

Animals↗