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At least 1,153 records · Page 64Linked to original sources
PubMed1975

Spatial distribution of effects of negative poins on cultured human cells.

Cultured human kidney T-1 cells were irradiated in flasks or on coverslips at different depths in a water phantom using the Los Alamos Meson Physics Facility Biomedical negative pion beam. Postirradiation colony formation and cell multiplication were assayed. Maximum cell inactivation occurred in the vicinity of maximum pion dose. Comparison of dose-survival curves with those found following x irradiation indicated RBE = 1.4 plus or minus 0.3 for colony formation and approximately 1.5 for growth delay. Delivery of 400 pion rads in four fractions resulted in higher survival than did delivery of 400 rads in a single fraction.

Cell Division↗
PubMed1983

Colon and rectal carcinoma: spatial distribution and detection.

Recent studies have challenged the concept that 50% of colon cancers are detectable by digital examination and two-thirds are within reach of the rigid sigmoidoscope. This is an important consideration because of the potential for failure of an otherwise appropriate screening method when evaluating a patient for carcinoma of the colon. An analysis of 2,298 cases of colorectal carcinoma diagnosed over 20 years showed that the most common sites were the rectum (34%) and sigmoid (25%). Over the 20 years, the incidence of cancer in the cecum increased and that in the rectum decreased. Cecal, ascending, and transverse colon cancers accounted for 34% of lesions - all beyond the range of the flexible sigmoidoscope. The changing site distribution emphasizes the need for an accurate and inexpensive technique to evaluate the entire colon. These data suggest that the barium pneumocolon examination should be included in the screening of high-risk patients.

Barium Sulfate↗
PubMed2001

Function and spatial distribution of ion channels and transporters in cell migration.

Cell migration plays a central role in many physiological and pathophysiological processes, such as embryogenesis, immune defense, wound healing, or the formation of tumor metastases. Detailed models have been developed that describe cytoskeletal mechanisms of cell migration. However, evidence is emerging that ion channels and transporters also play an important role in cell migration. The purpose of this review is to examine the function and subcellular distribution of ion channels and transporters in cell migration. Topics covered will be a brief overview of cytoskeletal mechanisms of migration, the role of ion channels and transporters involved in cell migration, and ways by which a polarized distribution of ion channels and transporters can be achieved in migrating cells. Moreover, a model is proposed that combines ion transport with cytoskeletal mechanisms of migration.

Animals↗
PubMed1988

Effect of body posture on spatial distribution of pulmonary blood flow.

Single-photon emission-computed tomography (SPECT) on intact dogs and humans suggests that one aspect of regional blood flow in the lung (Qr) is independent of gravity, e.g., the gradient in Qr between the core and the periphery. To further evaluate these findings, six anesthetized healthy dogs (approximately 30 kg), two in the supine posture, two in the prone posture, and two suspended in the upright posture, breathing spontaneously, were injected (iv) at end expiration with 20 mCi99mTc-labeled albumin macroaggregates. The animals were killed, their chests were opened, their lungs were removed and dissected free of other tissue, and the blood was drained. The lungs were dried by blowing warm air (50 degrees C) while they were inflated to full capacity for about 18 h. The fully inflated and dry lungs were placed in the supine position and SPECT was performed to determine the three-dimensional distribution of activity. One hundred and twenty projections of the activity in the entire lungs were obtained at 3 degrees steps with a rotating gamma camera and stored in computer memory. Once SPECT was completed, either a coronal slice or a sagittal slice (1 cm thick) was cut and imaged directly by placing it against the gamma camera collimator for 6 min. The tomographic-reconstructed slices revealed that at isogravity, in all body postures, Qr in the central region of the lungs was up to 10 times that in the periphery. Furthermore, the central-peripheral gradient was discernible within the individual lobes. The direct images of slices also confirmed these findings. Although flow inequalities independent of gravity were present, the central region with the highest flow often was closer to the dependent regions of the lungs, suggesting that gravity had some influence on the final distribution. The results suggest that factors other than gravity also play an important role in the distribution of pulmonary blood flow. These factors may be related to the conductance of the vascular pathways that lead to different regions in the lungs.

Animals↗
PubMed2005

Spatial distribution of gravity-dependent gain changes in the vestibuloocular reflex.

This study determined whether dependence of angular vestibuloocular reflex (aVOR) gain adaptation on gravity is a fundamental property in three dimensions. Horizontal aVOR gains were adaptively increased or decreased in two cynomolgus monkeys in upright, side down, prone, and supine positions, and aVOR gains were tested in darkness by yaw rotation with the head in a wide variety of orientations. Horizontal aVOR gain changes peaked at the head position in which the adaptation took place and gradually decreased as the head moved away from this position in any direction. The gain changes were plotted as a function of head tilt and fit with a sinusoid plus a bias to obtain the gravity-dependent (amplitude) and gravity-independent (bias) components. Peak-to-peak gravity-dependent gain changes in planes containing the position of adaptation and the magnitude of the gravity-independent components were both approximately 25%. We assumed that gain changes over three-dimensional space could be described by a sinusoid the amplitude of which also varied sinusoidally. Using gain changes obtained from the head position in which the gains were adapted, a three-dimensional surface was generated that was qualitatively similar to a surface obtained from the experimental data. This extends previous findings on vertical aVOR gain adaptation in one plane and introduces a conceptual framework for understanding plasticity in three dimensions: aVOR gain changes are composed of two components, one of which depends on head position relative to gravity. It is likely that this gravitational dependence optimizes the stability of retinal images during movement in three-dimensional space.

Adaptation, Physiological↗
PubMed1999

Textural analysis of nuclear mitotic apparatus antigen (NuMA) spatial distribution in interphase nuclei from human drug-resistant CEM lymphoblasts.

In tumour cell lines, the resistance of cancer cells to a variety of structurally unrelated chemotherapeutic drugs is termed multidrug-resistance or MDR. We reported previously [6] that MDR leukemic cells displayed nuclear texture changes, as assessed by image cytometry. The nature of these changes remained uncertain but they could be associated with alterations of the nuclear matrix which could serve an important role in DNA organization and chromatin structure. Therefore, we have compared the textural features observed in G0/G1 nuclei from human leukemic CEM cells and their MDR variant CEM-VLB, after staining of either DNA by Feulgen method or nuclear matrix by immunodetection of NuMA antigen on DNase treated samples. Chromatin or NuMA distributions within the nucleus were evaluated by image cytometry. Changes in textural parameters indicate that modifications of NuMA distribution observed in MDR cells are parallel to those observed at the whole chromatin level (i.e., a more decondensed and coarse texture with increase of Energy and Long-run sections and decrease of Contrast and Short-run sections). Moreover, Optical Densities measurements indicate that MDR cells seem to contain less NuMA, a datum confirmed by immunoblotting of nuclear proteins. In conclusion, chromatin changes observed by image cytometry in drug-resistant human leukemic CEM cells appear associated with modifications of the nuclear matrix structure.

Antigens, Nuclear↗
PubMedDate not supplied

Knowledge of stimulus repetition affects the magnitude and spatial distribution of low-frequency event-related brain potentials.

Rate effects are defined as a reduction in amplitude of an evoked brain response with increasing stimulus frequency. In auditory paired-stimulus paradigms, a smaller amplitude evoked response to the second stimulus at a latency of 50 ms has been proposed to index a preattentive sensory gating mechanism. The present study investigated the possibility that expectancy and/or attentional biases could alter evoked potentials associated with rate effects. EEG data were recorded from 30 channels while subjects received 240 trials of 1, 2 or 3 click stimuli (with successive stimuli being separated by 500-ms intervals). Half of the subjects knew (blocked condition) and half of the subjects did not know (mixed condition) how many stimuli they would receive on a given trial. Subjects in the blocked condition had a significantly larger rate effect than subjects in the mixed condition. This effect was present only for low-frequency components of the event-related brain potential (ERP; below 10 Hz) and occurred from 30 to 60, 90 to 160 and 190 to 260 ms after stimulus presentation (P(1)-N(1)-P(2) complex). Mixed condition subjects also had larger contributions to their ERPs from temporal channels. These results suggest that the rate effect can be significantly altered by expectancy, and they are inconsistent with the thesis that ERPs near 50 ms in a paired-stimulus paradigm solely index a preattentive sensory gating mechanism.

Adolescent↗
PubMed2005

Quantitative aspects of the spatial distribution and morphological characteristics of the sea bass (Dicentrarchus labrax L.; Teleostei, Serranidae) trunk lateral line neuromasts.

The results presented herein report quantitative data relative to the distribution and morphological characteristics of both types of neuromasts encountered on the trunk lateral line of the sea bass (Dicentrarchus labrax, L.). These data were obtained from scanning electron micrographs. They indicate that, as expected, each modified scale of the sea bass possessed a single canal neuromast with long axis oriented parallel to the fish's long axis. In contrast to several fish species, two thirds of superficial neuromasts observed herein were oriented perpendicular to the fish's long axis. However, whatever the main orientation of superficial neuromasts, two thirds of their hair bundles were oriented parallel to the long axis of the animal with approximately half of them in the direction of the head. Similar ratios were observed for canal neuromasts whatever the area of the maculae: central or peripheral. For both types of neuromasts it was not possible to clearly distinguish a paired organization of hair bundles with opposing polarities. Superficial neuromasts on each trunk canal scale were located on either the dorsal or ventral side of the canal and appeared to be distributed along the trunk lateral line with a higher probability to be encountered closer to the operculum. The frequency of presence and the average number of superficial neuromasts per scale increased with fish size. We observed a size gradient for canal neuromasts between the operculum and caudal peduncle. This gradation was correlated with a reduction of the width of the central area of the canal segment. Canal neuromasts were always localized in the larger portions of the canal segments. Taken together, these results point out some specific features associated with the sea bass trunk lateral line. With the previous report, they establish the first full description of the trunk lateral line of sea bass and will be useful for upcoming experiments regarding the function of the two types of neuromasts.

Animals↗
PubMed2005

Spatial distribution of osteocyte lacunae in equine radii and third metacarpals: considerations for cellular communication, microdamage detection and metabolism.

Osteocytes, which are embedded in bone matrix, are the most abundant cells in bone. Despite the ideal location of osteocytes to sense the local environment and influence bone remodeling, their functions, and the relative importance of these functions, remain controversial. In this study, we tested several hypotheses that address the possibilities that population densities of osteocyte lacunae (Ot.Lc.N/B.Ar) correlate with strain-, remodeling- or metabolism-related aspects of the local biomechanical environments of mid-third diaphyseal equine radii and third metacarpals from skeletally mature animals. Ot.Lc.N/B.Ar data, quantified in multiple cortical locations, were analyzed for possible correlations with (1) structural and material characteristics (e.g., cortical thickness, percent ash, secondary osteon population density, mean osteon cross-sectional area, and predominant collagen fiber orientation), (2) strain characteristics, including prevalent/predominant strain magnitude and mode (tension, compression, shear), (3) hypothesized strain-mode-related microdamage characteristics, which might be perceived by osteocyte 'operational' networks, and (4) variations in remodeling dynamics and/or metabolism (i.e. presumably higher in endocortical regions than in other transcortical locations). Results showed relatively uniform Ot.Lc.N/B.Ar between regions with highly non-uniform strain and strain-related environments and markedly heterogeneous structural and material organization. These results suggest that population densities of these cells are poorly correlated with mechanobiological characteristics, including local variations in metabolic rate and strain magnitude/mode. Although osteocytes hypothetically evolved both as strain sensors and fatigue damage sensors able to direct the removal of damage as needed, the mechanisms that govern the distribution of these cells remain unclear. The results of this study provide little or no evidence that the number of osteocyte lacunae has a functional role in mechanotransduction pathways that are typically considered in bone adaptation.

Animals↗
PubMed1990

Spatial distribution of mRNAs for myelin proteins in primary cultures of mouse brain.

A nonradioactive in situ hybridization procedure was employed to study the distribution of mRNAs for myelin basic protein (MBP), proteolipid protein (PLP), myelin-associated glycoprotein (MAG) and 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNP) in oligodendrocytes in primary cultures of mouse brain. This procedure provided good cellular localization and allowed rapid detection of the mRNAs with low backgrounds. Gradual movement of MBP mRNAs from oligodendrocyte somas into processes was observed with time in culture. The MBP mRNAs were observed to be distributed in an asymmetric fashion within the somas and cell processes. Antigalactocerebroside staining indicated the presence of oligodendrocyte processes prior to movement of MBP mRNA, suggesting that the presence of processes alone was insufficient for translocation of MBP mRNAs. The mRNAs for PLP and MAG remained confined to the oligodendrocyte somas at all times in culture at least up to 28 days. While most of the CNP mRNAs were observed to be associated with the perikarya of oligodendrocytes, in less than 1% of these cells the presence of CNP mRNA in the processes was evident. This suggests that there may exist a subset of oligodendrocytes in which the translocation of these messages occurs.

2',3'-Cyclic-Nucleotide Phosphodiesterases↗
PubMed1996

Spatial distribution of sex chromosomes and ribosomal genes: a study on human lymphocytes and testicular cells.

The location of the sex chromosomes in relation to the rRNA genes in the nuclei of human lymphocytes and testicular cells was examined. Sex chromosomes were found to be located closer to ribosomal genes than would be expected assuming a random arrangement of these chromosomes with respect to rRNA genes. This proximity could be observed irrespective of the transcriptional activity of ribosomal genes indicating that the chromosomal material and not transcriptional activity is responsible for the intranuclear order of these chromosomes.

Adult↗
PubMed1986

Characterization of the spatial distribution of late ventricular potentials by body surface mapping in patients with ventricular tachycardia.

Low-level activity at the end of the QRS complex was analyzed from 63 thoracic leads in 15 normal subjects and in 21 patients with ventricular tachycardia (VT). The latter had old myocardial infarction and no conduction disturbances and had not been receiving antiarrhythmic drugs. In both normal subjects and patients with VT, isopotential maps of the time-averaged and filtered (25 Hz high-pass) electrocardiograms during the terminal portion of the QRS were dipolar, i.e., they showed single positive and negative regions. For patients with VT, the extrema were either distant, with one over the precordial area and the other over the back, or close together in the precordial region. In 10 patients, maps recorded after administration of antiarrhythmic drugs remained the same while QRS duration was prolonged. In six patients, maps recorded before antiarrhythmic surgery showed distant extrema for septal or posterobasal VT sites of origin and close extrema for anterior or posteroapical sites. Generally, QRS duration was reduced and maps were modified after surgery. Late potentials can be well detected with only three orthogonal leads because their distributions are dipolar, but maps provide additional information about their distribution, which may be related to conduction delay sites and possibly to VT sites of origin. Sources near the torso surface would produce close extrema, whereas deeper sources would produce distant extrema.

Adult↗
PubMed1987

Spatial distribution and prognostic significance of ST segment potential determined by body surface mapping in patients with acute inferior myocardial infarction.

We investigated the mechanism and significance of ST segment changes in inferior infarction by studying 100 patients with acute inferior infarction in whom body surface maps were recorded on admission. The magnitude of the maximum ST segment elevation (denoted Vmax) and magnitude of the maximum ST segment depression (denoted Vmin), as well as the ST depression on the standard 12-lead electrocardiogram were analyzed against morbidity and mortality (at a median follow-up time of 14 months). A value obtained by subtracting Vmax from Vmin correlated (p less than .0002) with outcome. Correlations were also found between Vmin and complications, Vmin and mortality, and between increasing levels of ST depression on the 12-lead electrocardiogram and mortality. The maps were also studied by grouping the 100 ST segment map patterns into five groups by cluster analysis techniques. One group showed marked anterior negativity and had 37% mortality compared with an overall 5% mortality for the remaining groups. The limited arteriographic and autopsy data available indicated that the findings of a diseased artery or arteries corresponded with the results of mapping. The mean map patterns of the five groups showed that, in most patients with inferior infarction, the standard chest leads V1 to V6 are over a region of steep voltage gradient. Small changes in the position of the standard chest lead can cause large changes in the displayed potentials. This study indicates that patients at high risk after acute inferior infarction can be identified by surface mapping on admission to the coronary care unit.

Electrocardiography↗