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Results for “Spatial Distribution”

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At least 145 records · Page 8Linked to original sources

PubMed1995

Semi-automatic data acquisition for quantitative neuroanatomy. MicroTrace--computer programme for recording of the spatial distribution of neuronal populations.

We present a computer programme, MicroTrace, designed for user-guided digitisation of objects in biological sections. The programme is optimised for recording the spatial distribution of neuronal structures, such as large populations of tracer-labelled cell bodies or axonal plexuses, regional borders, and surfaces. System requirements are a PC running Microsoft Windows, a microscope equipped with stepping motors, and a drawing tube. A computer generated drawing area, surrounded by menus and icons, is projected into the microscope field of view via the drawing tube. Different 'object' icons are assigned to individual object categories (cell types, surfaces, etc.). Digitisation is performed by pointing the cursor at objects in the section. Computer graphical symbols are superimposed on the digitised objects. All object categories are digitised, before moving the stage to other fields of view by manipulating the joystick or scroll bars. Movement of the microscope stage is accompanied by a translation of the graphical image, so that continuous feedback on the progress of the digitisation is provided. MicroTrace can readily be adapted to the specific needs of the user. We show its use in different experimental neuroanatomical techniques. Two-dimensional images and three-dimensional reconstructions of neuronal distribution and surfaces are demonstrated.

Animals↗

PubMed1976

Quantitation of the spatial distribution of 'prespore vacuoles' in pseudoplasmodia of Dictyostelium discoideum.

The axial distribution of an organelle, the prespore vacuole (PV), previously reported absent from the prestalk region, was determined in pseudoplasmodia of varying sizes, under differing conditions of photostimulation of migration. The distribution of these organelles, determined quantitatively by electron microscopy of sections from known axial locations, was found to have a spatial pattern which varied with pseudoplasmodial size. The total complement of these organelles appeared constant for any size of pseudoplasmodium under similar conditions of illumination. Increased illumination decreased the total number of the organelles. The spatial distribution of PV varies with total cell number, and the size of the region with no PV bears no relationship to the proportion of the cell mass which would form stalk cells. Similarly, the number of cells containing PV bears no fixed relationship to the number of cells which will form spores. On these grounds, the reported role of PV, that of directing or reflecting spore differentiation, appears unlikely.

Cell Differentiation↗

PubMed1986

Studies of the temporal and spatial distribution of aerosols in multi-tiered inhalation exposure chambers.

Two multi-tiered whole body inhalation exposure chambers with nominal volumes of 1 m3 (H-1000) and 2 m3 (H-2000) were evaluated for their performance in terms of the temporal and spatial distribution of test aerosols within the chamber. Parameters investigated included chamber type, single-chamber-single-aerosol generator versus two-chamber-single-aerosol generator systems, chamber air supply and exhaust systems, particle size, and aerosol diluter type. Results indicated that: 1) particle size has an effect on chamber aerosol concentration distribution, with the larger particle resulting in a higher variation; 2) the single-chamber-single-generator system is more stable than the two-chamber-single-generator system; 3) the H-2000 chamber has a lower aerosol spatial variability than the H-1000 chamber; and 4) the aerosol distribution within the chamber could be improved with the use of a newly designed diluter.

Aerosols↗

PubMed1997

Spatial distribution of postotic crest cells defines the head/trunk interface of the vertebrate body: embryological interpretation of peripheral nerve morphology and evolution of the vertebrate head.

The migration pathways and spatial distribution of neural crest cells largely depend on the embryonic architecture. At the preotic level in the chick embryo, cephalic crest adhere to even-numbered rhombomeres proximally, and populate each pharyngeal arch distally, thus prefiguring the morphology of the branchiomeric nerves. This distribution pattern is possible because of the absence of somites in the head. In the postotic region, however, somites and pharyngeal arches coexist at the same axial level. The caudalmost cephalic crest cell population, the circumpharyngeal crest cells, are derived from the postotic crest and their distribution covers the entire innervation areas of cranial nerves IX and X. In their proximal migration pathway, circumpharyngeal crest cells can exist along the dorsolateral pathway only where somites are absent. They divert around the occipital somites rostrally, making an arc that represents the caudal limit of the dorsolateral pathway of cephalic crest cells, or the head/trunk interface at the paraxial level. Ventrally, the circumpharyngeal crest cells localize in postotic pharyngeal arches as well as in an arc-shaped ridge, called the circumpharyngeal ridge. Since the circumpharyngeal ridge represents the caudal limit of the pharynx, it indicates the head/trunk interface at the level of the lateral body wall. These two interfaces of reverse orientation make an S-shaped, head/trunk interface together. Several structures unique to this region develop in this interface. Since the rhombomeric compartmentalization is distinct only in higher vertebrates, the rhombomere-dependent segregation of cephalic crest cells is more likely to be a secondary feature of the vertebrate head. The topographical configuration of the vertebrate crest cell distribution pattern does not support the idea that the vertebrate head evolved as a specialized trunk. but rather supports the idea that two distinct methods of segmental patterning have evolved in rostral and caudal parts of the vertebrate body, which resulted in the head and trunk, respectively. Postotic crest is located at the intermediate level between the trunk and the head, giving rise to both the cephalic and trunk crest cells. Its cephalic components circumpharyngeal crest cells, are distributed only rostral to the S-shaped interface.

Animals↗

PubMed1971

Prediction of the spatial distribution of cell survival in heavy ion beams.

The possible use of heavy ion beams for biomedical applications was examined through calculations of the physical beam properties and the spatial distribution of cell survival. Range straggling, creation of secondary particles, electron pickup, and the effects of inhomogeneous absorbers were analyzed in terms of cell survival. Depth-survival plots for typical irradiations provide substantial encouragement for the investigation of these beams for biomedical applications in which localized tissue destruction is desired.

Cell Survival↗

PubMed1991

Spatial distribution of "tissue-specific" antigens in the developing human heart and skeletal muscle. II. An immunohistochemical analysis of myosin heavy chain isoform expression patterns in the embryonic heart.

The spatial distribution of alpha- and beta-myosin heavy chain isoforms (MHCs) was investigated immunohistochemically in the embryonic human heart between the 4th and the 8th week of development. The development of the overall MHC isoform expression pattern can be outlined as follows: (1) In all stages examined, beta-MHC is the predominant isoform in the ventricles and outflow tract (OFT), while alpha-MHC is the main isoform in the atria. In addition, alpha-MHC is also expressed in the ventricles at stage 14 and in the OFT from stage 14 to stage 19. This expression pattern is very reminiscent of that found in chicken and rat. (2) In the early embryonic stages the entire atrioventricular canal (AVC) wall expresses alpha-MHC whereas only the lower part expresses beta-MHC. The separation of atria and ventricles by the fibrous annulus takes place at the ventricular margin of the AVC wall. Hence, the beta-MHC expressing part of the AVC wall, including the right atrioventricular ring bundle, is eventually incorporated in the atria. (3) In the late embryonic stages (approx. 8 weeks of development) areas of alpha-MHC reappear in the ventricular myocardium, in particular in the subendocardial region at the top of the interventricular septum. These coexpressing cells are topographically related to the developing ventricular conduction system. (4) In the sinoatrial junction of all hearts examined alpha- and beta-MHC coexpressing cells are observed. In the older stages these cells are characteristically localized at the periphery of the SA node.

Adult↗

PubMed1992

Spatial distribution of the Sm antigen in Drosophila early embryos.

Anti-Sm antibodies recognize the major small nuclear RNA-protein particles (snRNPs) involved in pre-mRNA processing. The spatial distribution of the snRNPs has been investigated in Drosophila embryos up to the cellularization stage (cycle 14), using the Y12 anti-Sm antibody. Our results show that: 1) all or most of the Sm antigen is localized in the cytoplasm of the syncytial blastoderm until the 12th cycle of division, in both the nuclear and cytoplasmic compartments at cycle 13, and then in the nuclei at cycle 14 and later. This relocalization takes place when zygotic transcriptional activation occurs; 2) at the subcellular level, the Sm antigen localizes in a speckled pattern and in foci-like structures within the nucleus of Drosophila blastoderm embryos; 3) strikingly, some nuclei of embryos at the 14th cycle appear to contain more snRNPs than others. The position of these nuclei differs from one embryo to another, and their distribution does not resemble any known developmental pattern of Drosophila embryogenesis. We propose that random differences in snRNP concentration may serve as an epigenetic signal for stochastic events occurring during development.

Animals↗

PubMed1996

The spatial distribution of phospholipids and glycolipids in the membrane of the bacterium Micrococcus luteus varies during the cell cycle.

Recently, we have developed a photocrosslinking approach which uses anthracene as a photoactivatable group and which allows us to determine the lateral distribution of lipids in membranes quantitatively. In synchronous cultures of the gram-positive bacterium Micrococcus luteus, this approach shows that the spatial distribution of phosphatidylglycerol and dimannosyldiacylglycerol, the two major lipids in the bacterial membrane, varies greatly during the cell cycle. Minimum heterogeneity was observed during cell growth while maximum heterogeneity was detected during cell division.

Cell Cycle↗

PubMed1994

Spatial distribution of Escherichia coli in the mouse large intestine inferred from rRNA in situ hybridization.

Fluorescent oligonucleotide probes targeting rRNA were used to develop an in situ hybridization technique by which the spatial distribution of Escherichia coli in the large intestines of streptomycin-treated mice was determined. Single E. coli cells were identified in thin frozen sections from the large intestines by the use of a probe specific for E. coli 23S rRNA. Furthermore, the total bacterial population was visualized with an rRNA probe targeting the domain Bacteria. By this technique, all E. coli cells were seen embedded in the mucosal material overlying the epithelial cells of the large intestine, and no direct attachment to the epithelium was observed.

Animals↗

PubMed1995

A distributed-parameter model of the myelinated human motor nerve fibre: temporal and spatial distributions of action potentials and ionic currents.

A double cable model of the myelinated human motor nerve fibre is presented. The model is based on the nodal and internodal channels in a previous, two-component model of human motor axons (Bostock et al. 1991), added to a complex extended cable structure of nodal, paranodal and internodal segments. The model assumes a high-resistance myelin sheath and a leakage pathway to the internodal axolemma via the paranodal seal resistance and periaxonal space. The parameter values of the model were adjusted to match the recordings of threshold electrotonus in human motor fibres from Bostock et al. (1991). Kirchoff's current law was used to derive a system of partial differential equations for the electrical equivalent circuit, and numerical integration was performed with a fixed time increment and non-uniform spatial step sizes, in accordance with the complex structure of the fibre. The model calculations provide estimates of the spatial and temporal distributions of action potentials and their transaxonal and transmyelin components, both in different segments of the fibre and at different moments during action potential propagation. The distribution of transaxonal and transmyelin currents along the fibre and their contributions from different ionic channels are also explored.

Action Potentials↗

PubMed1994

Spatial distribution of naturally occurring 210Po and 226Ra in children's teeth.

Deciduous and permanent teeth extracted from juveniles for orthodontic purposes have been analysed using alpha-sensitive plastic track detectors for the spatial distribution of total alpha-activity and naturally occurring 210Pb-supported 210Po and 226Ra. The distribution of these radionuclides is non-uniform, with 210Po being primarily associated with outer enamel and 226Ra with the pulp. The observations suggest that 210Pb/210Po concentrates at the interface of enamel with saliva or blood, by means of unidirectional ionic exchange with calcium. In contrast, 226Ra concentrates in the predentine band at the interface with pulp and with systemic blood circulation, where its uptake is permitted by the incomplete calcification in this band. Activity concentration was measured in 900 teeth. Total concentration on the outer enamel surface of deciduous teeth, permanent teeth from children < or = 10 years and permanent teeth from children > 10 years give respective mean values of 8.63 +/- 0.26, 5.76 +/- 0.48 and 7.00 +/- 0.15 Bq kg-1. 226Ra concentration on the corresponding longitudinal sections comprising pulp, dentine and annular enamel give respective mean values of 0.715 +/- 0.055, 0.418 +/- 0.083 and 0.514 +/- 0.029 Bq kg-1. Mean activity concentration in 32 foetal teeth was 2.05 +/- 0.31 Bq kg-1. The results form the basis of more detailed studies of (1) age-dependent uptake of alpha-radionuclides in teeth and their microdistribution, and (2) the geographical variation in activity concentration with respect to environmental factors such as domestic radon exposure.

Child↗

PubMed1979

Spatial distribution of pulmonary blood flow in the dog with PEEP ventilation.

The effects of mechanical ventilation without and with a positive end-expiratory pressure (PEEP) of 20 cmH2O and, after hemorrhage, on the spatial distribution of lobar lung blood flow were studied by means of iv injections of radioactive microspheres in supine dogs. The lungs were excised and dried at an inflation pressure of 30 cmH2O. Each lobe was cut into slices. In five slices from each lobe, 30--60 samples were punched out. The activity was measured in a gamma counter. By this means distribution of lobar blood flow could be described three-dimensionally. In dogs awake and spontaneously breathing or anesthetized and mechanically ventilated, blood flow distribution was rather even, except for a vertical gradient. PEEP caused a) a two- to threefold reduction in total lung blood flow, b) a redistribution from the right to the left lung, and c) a redistribution from the core to the periphery of the lung. This pattern of redistribution could not be reproduced by reducing cardiac output by hemorrhage during mechanical ventilation without PEEP.

Animals↗

PubMed1975

The number, size and spatial distribution of neurons in lamina IV of the mouse SmI neocortex.

We located the corresponding barrel in Layer IV of the mouse SmI cortex in eleven cerebral hemispheres sectioned in a plane tangential to the pia overlying SmI and in one sectioned and prepared by a combined Golgi-Nissl method. In the section in which barrel C-1 could be optimally visualized each neuronal soma was outlined with a camera lucida and the cross-sectional area measured with the aid of a small computer. In all, nearly 7,000 neurons were measured. We estimate that on average barrel C-1 contains about 2,000 neurons. The mean cross-sectional area of the perikarya is 62.51 mu2 (S.D. plus or minus 14.51 mu2) and the size distribution of the neurons is unimodal and positively skewed. There is no segregation of cells within the barrel on the basis of size. The spatial distribution of cells in the barrel is fairly constant, from specimen to specimen, and the charactieristic cytoarchitectonic appearance of the barrel can be related to regional neuronal packing density since there are at least 1.6 as many neurons in the sides of the barrel as the hollow. The constancy of the cellular composition of the barrels indicates that the mechanisms responsible for the development of the mouse SmI cortex are fairly rigidly determined, and that the barrel field should lend itself well to further quantitative, developmental and physiological analysis.

Animals↗

PubMed1994

Spatial distribution of sound pressure and energy flow in the ear canals of cats.

Spatial pressure distributions have been measured in the ear canals of ten cats and analyzed to obtain the energy reflection properties of the middle ear over a 10- to 25-kHz range of frequencies. Considerable intersubject variability is observed, much of which can be correlated with the condition of the tympanic membrane. For ears judged to be in good condition, reflection coefficients typically take values of about 0.2 between 15 and 25 kHz, indicating good matching of the dynamical properties of the auditory system to the ear canal sound field. At lower frequencies, the reflection coefficients tend to be somewhat higher and at higher frequencies the reflection coefficients increase quite rapidly with frequency. For ears judged to be in poorer condition, energy reflection coefficients of 0.5 and 0.9 were determined for the 15- to 25-kHz range. The variations of sound pressure along the canal (about 10 dB, even in well-coupled systems) confirm that single point pressure measurements may be inappropriate for defining the acoustical input at higher frequencies and new measures for specifying the input should be investigated. The net flow of acoustic energy into the auditory system, the sound power, is one possibility. Some initial measurements of sound power, obtained from analysis of the spatial pressure distributions, are presented.

Acoustic Stimulation↗

PubMed1996

Performance differences as a function of stimulus-response compatibility with rapid serial visual presentation and spatially distributed presentation styles.

A means of presenting information temporally has been developed from the basic research on reading. Temporal displays allowed for faster processing speeds by reducing the number of saccades normally required to process spatially distributed information; however, a potential disadvantage to using temporal displays was an increased rate of error. Payne and Lang reported that a tradeoff between speed and accuracy is sometimes the result of using temporally distributed displays. As they used an alphabetic coding scheme which may not have facilitated the most optimal stimulus-response mapping, the current experiment tested the effects of a directional coding scheme on a temporally distributed display with 24 subjects. Analysis indicated the coding scheme did improve processing speed on the temporal display, but the error rate for the temporal display was higher than with the alphabetic coding scheme. Therefore, the limitation of temporal displays in a tradeoff between speed and accuracy persisted using the directional coding scheme.

Adult↗

PubMed1987

[Spatial distribution of hippocampal responses to dental pulp stimulation and acoustic clicks].

Evoked potentials and unitary discharges in responses to tooth pulp and acoustic click stimuli were recorded from the hippocampus of freely moving rats. The spatial distribution of evoked field responses to tooth pulp stimulation and acoustic clicks were identical. Averaged evoked potentials consisted of a large negative deflection (N1) preceded by a small positive potential (P1). The shortest latency N1 was recorded from the middle third of the dentate molecular layer and the outer portion of apical dendrites of Ca3 (27 ms). The peak latency of N1 was significantly longer (34 ms) in the stratum radiatum of CA1. Laminar profiles of N1 in the dentate gyrus and CA3 were similar to that evoked by electrical stimulation of the perforant path and in CA1 similar to the response profile evoked by the Schaffer collaterals. The largest amplitude P1 was observed above the pyramidal layer of CA1 and the hilus. Both sensory modalities were able to modify the discharge rate of neurons in all hippocampal regions. A conclusion is made that information about sensory stimuli can reach the hippocampus by two distinctive pathways: a short-latency inhibitory input via the fimbrial fornix and a longer-latency path via the entorhinal cortex.

Afferent Pathways↗

PubMed1984

Temporal sequence and spatial distribution of early events of fertilization in single sea urchin eggs.

Measurements and observations of five early events of fertilization, singly and in pairs, from single sea urchin eggs have revealed the precise temporal sequence and spatial distribution of these events. In the Arbacia punctulata egg, a wave of surface contraction occurs coincident with membrane depolarization (t = 0). These two earliest events are followed by the onset of a rapid, propagated increase in cytoplasmic-free calcium at approximately 23 s as measured by calcium-aequorin luminescence. The luminescence reaches its peak value by 40 s after the membrane depolarization. The luminescence remains uniformly elevated for some time before its decay over several minutes. The onset of an increase in the pyridine nucleotide (NAD(P)H) fluorescence follows the membrane depolarization at approximately 51 s. The fertilization membrane begins its elevation in a wave-like fashion coincidentally with the increase in NAD(P)H fluorescence. Similar results are observed in the Lytechinus variegatus egg. The results suggest that while the increase in cytoplasmic-free calcium may be important for many changes occurring in the egg, the elevated-free calcium is not directly responsible for the propagated wave of cortical granule exocytosis.

Animals↗

PubMed1975

The spatial distribution of urban pharmacies.

Pharmacists are thought to play a central role in providing information and advice on health to lower income and other socially disadvantaged groups. However, recent evidence suggests that social biases exist in the spatial distribution of urban pharmacies. Such biases would severely limit the accessibility of the poor and the nonwhite to pharmacy services. To test the general nature of this evidence, we used multiple regression techniques to assess the simultaneous influence of several ecological and socioeconomic variables on the location of pharmacies in Pittsburgh and Omaha. After controlling for the influence of physicians, hospitals, commercial activity, population, and other variables thought to affect pharmacy location, we were unable to detect any evidence of a direct association between pharmacy location and the socioeconomic or demographic (other than total population) characteristics of areas in either city.

Delivery of Health Care↗