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PubMed1990

Spatial and temporal analysis of calcium-dependent electrical activity in guinea pig Purkinje cell dendrites.

We have used the calcium indicator dye arsenazo III, together with a photodiode array, to record intracellular calcium changes simultaneously from all regions of individual guinea pig cerebellar Purkinje cells in slices. The optical signals, recorded with millisecond time resolution, are good indicators of calcium-dependent electrical events. For many cells the sensitivity of the recordings was high enough to detect signals from each array element without averaging. Consequently, it was possible to use these signals to follow the complex spatial and temporal patterns of plateau and spike potentials. Calcium entry corresponding to action potentials was detected from all parts of the dendritic field including the fine spiny branchlets, demonstrating that calcium action potentials spread over the entire arbor. Usually, the entire dendritic tree fired at once. But sometimes only restricted areas had signals at any one moment with transients detected in different regions at other times. In one cell, six separate zones were distinguished. These results show that calcium action potentials could be regenerative in some dendrites and could fail to propagate into others. Signals from plateau potentials were also detected from extensive areas in the dendritic field but were always smaller than those caused by a burst of action potentials.

Action Potentials↗

PubMed1978

[Analysis of the spatial organization of the endothelium of several major vessels].

The aim of the investigation was to appreciate quantitatively the degree of endothelial heteromorphy and its spatial organization according to some indices allowing morphofunctional interpretation of their importance. Endothelium of the rabbit protal and jugular veins was studied in the flat film preparations along the length of 16--20 mm continuously. To elucidate changeability in tissue state, autocorrelative function was calculated with the following determination of spectral density. The latter makes it possible to reveal the presence of a monotonous trend and rhythmicity in vessel structure. Spectral analysis demonstrated that in different parts of endothelium the indices involved varied in their character. The parameters reflecting cell histophysiology are characterized by a marked monotonous trend. The parameters influenced by hemodynamic conditions change rhythmically. Nearly all the indices in the portal vein, evidently because of its peculiar physiological conditions, distinguish themselves by their more complex spectral composition than those of the jugular vein. The quantitative data obtained support heteromorphic character of endothelium and demonstrate that physiology and hemodynamics of the vessel are responsible for its degree of significance as there is a constant interrelation between the vessel and blood.

Animals↗

PubMed1997

[Laser Raman spectral analysis of superhelical spatial conformation on plasmid DNA].

The pBR322 recombinant plasmids DNA products, which purified by phenol-extract and equilibrium centrifugation in CsCl-ethidium bromide gradients, have been shown as mainly spatial conformation of covalently closed circular DNA (i.e. cccDNA) by agarose gel electrophoresis for homogeneity detection. Laser Raman spectra in the region 450-1750 cm-1 have been obtained for the circular double-stranded plasmids DNA molecule in an aqueous solution, indicating not only contain those marker peaks of secondary structure as in conventional B-form of DNA, but also present both 854 and 1083 cm-1 diagnostic bands of reflecting the vibration state of deoxyribosyl phosphodiester backbone. The present analysis have demonstrated relationship between the superhelical state for cccDNA and the two conformational marker bands that can be considered as the tertiary structure marker on plasmids DNA. Because of markedly Raman hypochromicity of charecter band 1378cm-1 of dT in contrast to liear DNA molecule, as well as the carbonyl double bond vibration line of dT have shifted to higher wave number position, the base stacking analysis represent occurrence of both increase in staking reaction activity of dT, and injury of a number of the Hoogsteen hydrogen bond between dA and dT with exist supercoil structure in cccDNA.

DNA, Circular↗

PubMed1993

Trace elemental analysis at nanometer spatial resolution by parallel-detection electron energy loss spectroscopy.

Parallel-detection electron energy loss spectroscopy (EELS) combined with scanning transmission electron microscopy (STEM) and a field emission source provides an unprecedented sensitivity for elemental microanalysis. By deflecting the energy loss spectrum across a parallel detector and computing the difference spectrum from sequentially collected energy-shifted spectra, the effects due to detector pattern noise are nearly eliminated so that signals less than 0.1% of the background can be readily detected. Measurements on a series of glass standard reference materials show that EELS provides both high spatial resolution and trace sensitivity at the 10 atomic ppm level for a wide range of elements including the alkaline earths, 3-d transition metals, and the lanthanides. For analytical volumes with dimensions of the order of 10 nm, this translates into near-single atom detectability.

Electrons↗

PubMed1990

Direct observations of cooperative effects in oral streptococcal adhesion to glass by analysis of the spatial arrangement of adhering bacteria.

The spatial arrangement of two strains of oral bacteria adhering on glass was studied in order to investigate cooperative effects in their adhesion mechanisms. Streptococcus salivarius HB was a strain which possessed several classes of fibrillar surface appendages, whereas on the cell surface of S. mutants NS no surface appendages could be identified. The bacteria were deposited from a flowing suspension with various buffer concentrations on the bottom glass plate of a parallel plate flow cell and were observed directly with a video camera mounted on a phase contrast microscope. The positions of all adhering bacteria were determined by means of automated real time image analysis and subsequently employed for calculating radial and angular pair distribution functions. Pair distribution functions indicate the average relative number density of bacteria around one deposited bacterium as a function of the radial distance or the angular orientation relative to the flow direction. From the calculated pair distribution functions of both bacterial strains it was concluded that cooperative effects contributed to the adhesion of S. salivarius HB, but not to adhesion of S. mutants NS. It was suggested that these cooperative effects originate from the surface appendages of S. salivarius HB.

Bacterial Adhesion↗

PubMed1994

In vitro analysis of the spatial organization of chondrogenic regions of avian mandibular mesenchyme.

The mechanism(s) which control patterning in the face remain elusive, due in large part to the absence of morphologically identifiable controlling regions such as the AER of the limb bud. In order to identify the controlling region(s) and timing of patterning in the face, an investigation was launched to determine the spatial organization of tissues within this region, beginning with the chondrogenic zones of the avian (chick and quail) mandible. The mandibles from HH stage 23/24 chick and equivalent stage quail embryos were initially bisected in three planes giving rostral or caudal, proximal or distal, and medial or lateral halves. The mesenchyme from these various regions was isolated, plated out in high density micromass cultures, and grown for 4 days. Additionally, further cultures were grown, consisting of mandibular mesenchyme subdivided into quarters along the long axis of the mandible (e.g., rostro-proximal quarter) as well as the bisecting of medial or lateral halves (e.g., medial-rostral quarter). Nodule number and area were determined by morphometric analysis for each culture as well as whole mandible controls. The demarcation between chondrogenic and non-chondrogenic regions was dramatic. Of the bisected halves, proximal and lateral were the most chondrogenic with the lateral subdivision displaying much more cartilage than whole mandible. The nodules of the lateral cultures fused into a sheet of cartilage. In contrast mesenchyme from the medial half was virtually non-chondrogenic. When ranked by the amount of chondrogenesis, the order was, lateral > proximal = whole = core > distal > caudal > rostral > periphery >> medial. Interestingly, when subdivided further an altered pattern appeared.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2000

Shifting visual attention in space: an electrophysiological analysis using high spatial resolution mapping.

OBJECTIVES: Evidence from cortical electrophysiology and functional imaging converges on the view that visual spatial selective attention results in a facilitation of early sensory processing in visual cortical structures. Little is known, however, about the neural control processes that lead to this facilitation. The present study was aimed at further investigating these control processes and their neural correlates by analyzing high spatial resolution maps of brain activity that were evoked by attention-directing cues, but occurred prior to presentation of the target stimulus. METHODS: Subjects (n=14) were presented with central arrow cues that instructed them to attend covertly to either a left or right field location in order to compare two subsequent target stimuli simultaneously presented to the location. On half of the trials, targets were presented to the cued location, while in the other half, targets were presented to the opposite visual field location. Subjects had to respond via button press on 16% of the trials when target stimuli were identical. Event-related potentials (ERPs) were recorded from 92 scalp electrodes which allowed a sufficiently finegrained analysis of the regional specificity of the ERP components. RESULTS: In response to the cues, an initial component over occipital-parietal electrode sites was consistent with an early involvement of the posterior-parietal cortex, perhaps in the initial step of attentional orienting. A second component over the lateral-prefrontal cortex is consistent with the voluntary control and maintenance of attention, a function known to be subserved by frontal cortical structures. A late component narrowly focussed over occipital-temporal electrode sites is most plausibly related to activation of parts of the ventral extrastriate cortex. CONCLUSIONS: The data support the current view that voluntarily orienting visual attention in space leads to top-down modulations in cortical excitability of ventral extrastriate regions initiated by posterior-parietal and mediated by lateral-prefrontal cortical structures.

Adult↗

PubMed1992

DNA double labelling with IdUrd and CldUrd for spatial and temporal analysis of cell proliferation and DNA replication.

A procedure was developed that very effectively distinguishes between IdUrd and CldUrd incorporated in the DNA of cell nuclei and chromosomes. For double staining we used the rat anti-BrdUrd monoclonal antibody from Sera-lab that binds specifically to CldUrd and BrdUrd but not to IdUrd, in combination with the mouse anti-BrdUrd monoclonal antibody from Becton Dickinson. This antibody binds to all three halogenated deoxyuridines, but when the nuclei are washed in TRIS buffer with a high salt concentration the antibodies linked to CldUrd-labelled DNA are removed. When analysing the effect of the deoxyuridines on the cell cycle we found that the growth kinetics of Chinese hamster cells were not changed by adding IdUrd or CldUrd for 30 min at a concentration of 10 microM, whereas adequate double labelling required only 2 min pulses. The effectiveness of the technique was demonstrated in two model experiments. The first test concerned the assessment of cell recruitment in the central areas of slow-growing clones, after addition of fresh medium. The second experiment focussed on the spatial resolution of the method. Double-labelled metaphase chromosomes showed interspersed green and red replication bands with a spacing corresponding with medium resolution Giemsa banding patterns.

Animals↗

PubMed2005

Spatially resolved stress analysis in Al2O3/3Y-TZP multilayered composite using confocal fluorescence spectroscopy.

Fluorescence piezo-spectroscopy (PS) was applied to evaluate the residual stress fields stored in a multilayered Al(2)O(3)/3Y-TZP (3 mol% Y(2)O(3)-stabilized ZrO(2)) composite using the chromophoric fluorescence spectra of Al(2)O(3). The PS results were compared with a theoretical stress distribution in the laminate, calculated according to a repeating unit cell model. However, in practical fluorescence spectroscopy, each measurement point corresponded to a finite volume of material, within which the scattered light experienced fluorescence wavelengths characteristic of the local (weight-average) stress fields. Because of the finite volume of material probed in PS measurements, a comparison between the experimental and calculated values requires that the calculated stresses be convoluted according to the depth-response function of the probe. A pinhole aperture incorporated in the Raman microprobe was used to control the collection probe depth and to modulate the portion of the whole fluorescence emission reaching the detector. According to calibrations of the probe depth and probe response function, probe-convoluted stresses were obtained and a spatially resolved mapping of residual stresses could be obtained.

Journal Article↗

PubMed2002

Spatial and temporal analysis of Rac activation during live neutrophil chemotaxis.

The ability of cells to recognize and respond with directed motility to chemoattractant agents is critical to normal physiological function. Neutrophils represent the prototypic chemotactic cell in that they respond to signals initiated through the binding of bacterial peptides and other chemokines to G protein-coupled receptors with speeds of up to 30 microm/min. It has been hypothesized that localized regulation of cytoskeletal dynamics by Rho GTPases is critical to orchestrating cell movement. Using a FRET-based biosensor approach, we investigated the dynamics of Rac GTPase activation during chemotaxis of live primary human neutrophils. Rac has been implicated in establishing and maintaining the leading edge of motile cells, and we show that Rac is dynamically activated at specific locations in the extending leading edge. However, we also demonstrate activated Rac in the retracting tail of motile neutrophils. Rac activation is both stimulus and adhesion dependent. Expression of a dominant-negative Rac mutant confirms that Rac is functionally required both for tail retraction and for formation of the leading edge during chemotaxis. These data establish that Rac GTPase is spatially and temporally regulated to coordinate leading-edge extension and tail retraction during a complex motile response, the chemotaxis of human neutrophils.

Chemotaxis, Leukocyte↗

PubMed2004

Factor analysis in both spatial and temporal domains of color blooming artifacts in ultrasound investigations utilizing contrast agents.

Color blooming artifacts can cause misinterpretations of normal and pathological structures during color Doppler flow imaging with ultrasound contrast agents (USCAs). These artifacts are characterized in both the spatial and temporal domains: in the spatial domain, artifacts result from wave propagation and the ultrasound system; and in the temporal domain, the color blooming time (CBT) is used to denote the duration of artifacts. In our experiments, CBT decreased from 86.7 to 46.8 s when the transmitting pressure was decreased from 370 to 180 kPa. From this, we conclude that an adaptive mechanical index can significantly shorten the CBT, which may in turn prolong the optimal viewing time during in vivo ultrasound investigations utilizing USCAs.

Artifacts↗

PubMed1975

An analysis of the spatial distribution of ciliary units in a ciliate, Euplotes minuta.

Six to eleven longitudinal ciliary rows are arrayed over the dorsal surface of the ciliate Euplotes minuta. Forty-two to 129 ciliary units are distributed among these rows. The number of rows depends on genotype, clonal age, and vegetative ancestry, while the total number of units is controlled partly by the number of rows and also by the separate action of genetic and environmental factors. 2. The pattern of distribution of units among different rows of non-dividing cells can be analysed on the basis of the percentage of the total unit complement of the cell that is found in each individual row. If the assumption is made that ciliary rows are uniformly spaced over a dorsal field whose width is independent of the number of rows, then it can be shown that units are distributed among rows according to a relatively invariant spatial pattern. The form of this pattern remains the same in the face of variation in the absolute number of rows and of units. 3. Prior to cell division new units develop anterior and posterior to old units situated within the equatorial zone of each row. About one-half of the original units are included within this zone. The cell fission line develops within this zone such that the total number of units passed to the anterior and posterior division products are about equal. 4. The pattern according to which units of different zones (proliferating and non-proliferating) are distributed among different rows has been mapped in cells that have completed the process of proliferation of units but have not yet completed cell division. The results of this mapping show that the pattern of distribution of units in the equatorial zone at the conclusion of proliferation is not the same as the overall pattern in non-dividing cells. Further analysis indicates that the geometry of proliferation can be most simply represented as a result of two superimposed processes, one of which is the recruitment of old units into the zone of proliferation, while the other is the intensity of proliferation, i.e. the number of new units formed adjacent to each old unit. Both recruitment and intensity have constant values in the central region of the dorsal field, while recruitment is higher and intensity lower near both margins. The recruitment and intensity distributions are mutually nearly reciprocal, with slight asymmetries that formally account for the more dramatic asymmetry of the pattern of non-dividing cells. 5. A dualistic hypothesis is formulated for the control of the formation of new ciliary units within ciliary rows. The position of each new unit is largely controlled locally in relation to pre-existing units, while the decision of whether or not new units will develop at all, and how many will be formed, depends on superimposed positional systems operating within the context of the entire dorsal surface.

Cell Division↗

PubMed2003

The event-related optical signal (EROS) in visual cortex: replicability, consistency, localization, and resolution.

We previously reported a fast and localized noninvasive event-related optical signal (EROS) elicited by visual field quadrant stimulation in occipital brain areas (Gratton, Corballis, Cho, Fabiani, & Hood, 1995). We now present a replication and extension of that experiment. In addition, we propose a new method for estimating the cross-validity of the results based on intersubject correlations, report further data on the localization of EROS, and present an analysis of its spatial resolution. The results replicate our original findings. The intersubject correlation is generally quite high (r = .6-.8). The spatial resolution analysis indicates that activities from cortical areas located approximately 1.5 cm apart are measurable independently without cross talk. This study provides further support for the idea that noninvasive optical imaging can be used to derive images of brain activity combining good spatial and temporal resolution.

Adult↗

PubMed2004

Spatial carrier-fringe pattern analysis by means of wavelet transform: wavelet transform profilometry.

We present an analysis of a spatial carrier-fringe pattern in three-dimensional (3-D) shape measurement by using the wavelet transform, a tool excelling for its multiresolution in the time- and space-frequency domains. To overcome the limitation of the Fourier transform, we introduce the Gabor wavelet to analyze the phase distributions of the spatial carrier-fringe pattern. The theory of wavelet transform profilometry, an accuracy check by means of a simulation, and an example of 3-D shape measurement are shown.

Algorithms↗

PubMed2006

An analysis of the spatial arrangement of the myocardial aggregates making up the wall of the left ventricle.

OBJECTIVE: We used the technique of peeling of myocardial aggregates, usually described as 'fibres', to determine the spatial arrangement of the myocytes in the left ventricular wall of a healthy autopsied human heart. METHODS: We digitised the left ventricular outer and inner boundaries, as well as the pathways in space, of almost 3000 aggregates harvested from the left ventricular myocardium. During the process of gradual peeling, we sought to identify the myocardial aggregates as uniformly as possible. Despite this, interpolation was necessary to complete the pattern so as to construct a unit vector field that represented the preferred direction of the myocardial aggregates throughout the entirety of the walls of the left ventricle of this individual human heart. RESULTS: Apart from the overall systematic arrangement of the aggregates necessary to achieve physiologic ventricular contraction, we documented substantial local heterogeneities in the orientation of the myocardial aggregates. In particular, a significant proportion of aggregates was found to intrude obliquely with respect to the ventricular boundaries, with markedly heterogeneous distribution. Moreover, the distribution of the helical angle of the aggregates relative to the ventricular base varied notably throughout the left ventricular free walls and the septum. Within the generally quite uniform and continuous structure of the ventricular mass, we were, however, unable to identify any organised tracts or functional subunits such as a 'helical ventricular band', nor did we find radial fibrous lamellas coursing across the ventricular wall. CONCLUSION: We suggest that the impact of local anatomical inhomogeneities, associated with gradients in regional contractile function on global ventricular dynamics, has been systematically underestimated in the past. Our analysis confirms furthermore the continuous nature of the myocardium associated with an overall gross organisation of the fibre direction field; however, there is no evidence of substructures compartmentalising the ventricles.

Endocardium↗

PubMed2003

Psorophora columbiae and Psorophora toltecum (Diptera: Culicidae) Colombian populations cannot be differentiated by isoenzymes.

Two populations of the mosquito Psorophora columbiae from the central Andean area of Colombia and one population of Ps. toltecum from the Atlantic coast of Colombia were analyzed for 11 isoenzyme markers. Psorophora columbiae and Ps. toltecum are two of the main vectors of Venezuelan equine encephalitis. We found no conspicuous genetic differences between the two species. The relatively high gene flow levels among these populations indicate that these are not two different species or that there has been recent divergence between these taxa. In addition, no global differential selection among the loci was detected, although the alpha-GDH locus showed significantly less genetic heterogeneity than the remaining loci, which could mean that homogenizing natural selection acts at this locus. No isolation by distance was detected among the populations, and a spatial population analysis showed opposite spatial trends among the 31 alleles analyzed. Multiregression analyses showed that both expected heterozygosity and the average number of alleles per locus were totally determined by three variables: altitude, temperature and size of the human population at the locality. Individually, the expected heterozygosity is more related to these three variables than to the average number of alleles.

Animals↗

PubMed1995

VS--a new computer program for detailed offline analysis of visual-spatial perception.

A new IBM-AT-compatible software program, VS, for the analysis of visual-spatial (VS) perception in humans, especially brain-damaged patients, is described. VS is suitable for analysis of the following visual-spatial tests: (1) subjective visual vertical (SVV), (2) subjective visual horizontal (SVH), and (3) orientation, length, distance, form and position discrimination, as well as line/bar bisection. The program allows manipulation of a wide range of experimental tasks by varying relevant parameters, e.g., length, width, color, movement direction, step width, and position on screen of the stimuli. Psychophysical parameters are computed (methods of limits) and stored in dBASE files which can be retrieved for further data analysis with commercial statistics or graphics software. VS has a versatile text editor, with two macro languages which enables the user to define their own experimental configurations and realize individual graphic plots on screen or laser printer. VS incorporates two standard examinations together with normative data of control subjects and standard plots of the subject's performance. The results of separate investigations show highly stable results in normal control subjects in repeated examinations as well as good retest-reliability of these standard examinations in brain-damaged patients (rtt = 0.77). Representative case reports of a patient with left-sided visual neglect, a patient with Balint's syndrome as well as a patient with visual-spatial deficits subsequent to a left parietal brain lesion demonstrate the sensitivity and specificity of the program.

Adult↗

PubMed1999

An analysis of the spatial distribution of surnames in the Lecco area (Lombardy, Italy).

The internal mobility of the population of the province of Lecco (Lombardy, Italy) was evaluated on the basis of the frequency of characteristic surnames in three territorial areas as a function of their geographical distance. Nearly three fourths of the patterns are statistically significant in one of the three areas, where the process of diffusion of surnames could be interpreted as due to socioeconomic factors. On the contrary, a similar distribution is less evident in the other two areas of the same territory. Am. J. Hum. Biol. 11:305-315, 1999. Copyright 1999 Wiley-Liss, Inc.

Journal Article↗