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PubMed1989

The molluscicidal properties of Ambrosia maritima L. (Compositae). 4. Temporal and spatial distribution of Biomphalaria alexandrina in Egyptian village irrigation systems with reference to schistosomiasis transmission control.

Data on the temporal and spatial distribution of Biomphalaria alexandrina were collected throughout one year in two village irrigation systems near Alexandria, Egypt. Snails bearing Schistosoma mansoni cercariae were found from May to December but about 80% of annual transmission potential was confined from June to August. Although snail infection rates were generally 0-2%, higher rates were recorded and tended to be associated with smaller number snail collections. Infected snails were found in most canal and drain types and were judged to be present across most of the irrigated area of each village. In view of the dispersed nature of both infected snails and human-water contact in the area, it is suggested that schistosomiasis transmission is more widespread than focal. Effective transmission control using molluscicides should therefore require application to all village irrigation water-courses. The difficulties these various findings might impose on the use of commercial molluscicides are discussed and some possible advantages of the alternative plant molluscicide, Ambrosia maritima are noted.

Animals↗
PubMed1993

The spatial distribution of calcium signals in squid presynaptic terminals.

1. The fluorescent Ca2+ indicator dye, fura-2, was used to examine the spatial distribution of intracellular Ca2+ signals in giant presynaptic terminals of squid. Brief trains of presynaptic action potentials were evoked to open Ca2+ channels within the giant presynaptic terminals and elevate presynaptic Ca2+ concentration. 2. Electrical stimulation produced pronounced rises in presynaptic Ca2+ concentration. These rises were much larger in the terminal region than in the adjacent axonal region of the presynaptic neuron, suggesting that Ca2+ channels are most abundant in the terminal. 3. Stimulation also produced gradients in Ca2+ concentration across the width of the presynaptic terminal. During stimulation, Ca2+ concentration was highest in the compartment of the presynaptic terminal closest to the postsynaptic neuron. This suggests that the Ca2+ channels are localized to this region of the presynaptic terminal. 4. Following the end of action potential trains, the rises in Ca2+ concentration became uniform across the width of the terminal. The redistribution of Ca2+ presumably is due to diffusion of Ca2+ throughout the presynaptic cytoplasm. Stimulus-evoked rises in Ca2+ declined slowly over several tens of seconds. 5. Histological examination of a giant presynaptic terminal used for imaging experiments revealed that the spatial compartments where stimulus-induced rises in Ca2+ concentration were highest were also enriched in active zones, the presynaptic sites of transmitter secretion. The co-localization of Ca2+ transients and active zones strongly suggests that neurons cluster Ca2+ channels selectively at active zones and that they do so to enhance the magnitude of Ca2+ signals in the vicinity of the active zone. 6. Longitudinal gradients in Ca2+ concentration also occur within presynaptic terminals and can be quantitatively accounted for by gradients in surface/volume ratio and density of active zones along the length of the presynaptic terminal.

Action Potentials↗
PubMed1993

Spatial distribution of nerve injury after occlusion of individual major vessels in rat sciatic nerves.

In an attempt to better understand the spatial distribution of ischemic injury secondary to occlusion of major arteries, we measured nerve blood flow (NBF) and studied morphologic changes at various levels distal to the ligature site. Arterial ligation of the femoral, internal iliac, or superior gluteal artery was preceded and followed by measurement of NBF using laser Doppler flowmetry which helped identify "watershed areas" and guided the sampling process as nerves were examined pathologically and areas of injury were identified. Femoral artery ligation produced the most severe ischemia, focally reducing NBF by 80% in the tibial nerve at a level just below the knee. Within these ischemic nerve segments there were degenerative changes of nerve fibers seen mainly in the subperineurial region. Ligation of the internal iliac artery caused an approximately 60% reduction in NBF at the upper and mid-thigh levels of the sciatic nerve which resulted only in endoneurial edema in tissue taken at this level. Following superior gluteal artery ligation. NBF was reduced by only 20% at the pelvic level of the sciatic nerve and there was neither endoneurial edema nor fiber abnormalities. This study demonstrates the watershed pattern of ischemic injury associated with single vessel ligation by correlating neuropathologic change with quantitative measures of local nerve blood flow. The data further support the concept that mild levels of ischemia cause endoneurial edema, while moderate levels of ischemia produce demyelination and severe ischemia produces Wallerian degeneration.

Animals↗
PubMed1996

PML-containing nuclear bodies: their spatial distribution in relation to other nuclear components.

The PML protein is a human growth suppressor concentrated in 10 to 20 nuclear bodies per nucleus (PML bodies). Disruption of the PML gene has been shown to be related to acute promyelocytic leukaemia (APL). To obtain information about the function of PML bodies we have investigated the 3D-distribution of PML bodies in the nucleus of T24 cells and compared it with the spatial distribution of a variety of other nuclear components, using fluorescence dual-labeling immunocytochemistry and confocal microscopy. Results show that PML bodies are not enriched in nascent RNA, the splicing component U2-snRNP, or transcription factors (glucocorticoid receptor, TFIIH, and E2F). These results show that PML bodies are not prominent sites of RNA synthesis or RNA splicing. We found that a large fraction of PML bodies (50 to 80%) is closely associated with DNA replication domains during exclusively middle-late S-phase. Furthermore, in most cells that we analysed we found at least one PML body was tightly associated with a coiled body. In the APL cell line NB4, the PML gene is fused with the RAR alpha gene due to a chromosomal rearrangement. PML bodies have disappeared and the PML antigen, i.e., PML and the PML-RAR fusion protein, is dispersed in a punctated pattern throughout the nucleoplasm. We showed that in NB4 cells the sites that are rich in PML antigen significantly colocalize with sites at which nascent RNA accumulates. This suggests that, in contrast to non-APL cells, in NB4 cells the PML antigen is associated with sites of transcription. The implications of these findings for the function of PML bodies are consistent with the idea that PML bodies are associated with specific genomic loci.

Cell Nucleus↗
PubMed2001

Spatial distribution and histogenesis of colorectal Paneth cell metaplasia in idiopathic inflammatory bowel disease.

BACKGROUND AND AIM: Colorectal Paneth cell metaplasia (PCM) is known to be a sign of idiopathic inflammatory bowel disease (IBD), although its distribution and histogenesis are not fully understood. Objectives of this research were to investigate the spatial distribution of PCM in IBD and other forms of colitis (non-IBD), and to find stimuli causing PCM. METHODS: We studied multiple biopsy specimens from 181 patients with ulcerative colitis (UC), 159 with Crohn's disease (CD), 448 with non-IBD, and 78 normal controls. Paneth cell metaplasia frequency, at each colorectal site, was evaluated to find possible differences among diseases, phases of activity, and extents of disease. RESULTS: In non-IBD and controls, PCM was rarely (0-1.9%) seen at distal sites, but frequently (up to 48.7%) found at the ascending colon and cecum (P < 0.001). Paneth cell metaplasia frequency was significantly higher in IBD than in non-IBD patients and controls at distal sites (P < 0.001), but did not differ significantly between UC and CD, or among active, resolving, and quiescent phases. In UC, proctitis and left-sided colitis rarely displayed PCM at unaffected sites. Multiple logistic regression analysis revealed that PCM was positively associated with crypt distortion and mononuclear cell infiltration (P < 0.005), but negatively or not significantly associated with crypt atrophy, mucin depletion, acute inflammation, or phase of activity. CONCLUSIONS: Paneth cell metaplasia is a non-specific phenomenon in the proximal colon, but distal PCM, which occurs exclusively in affected mucosa, is a useful marker indicating IBD, even in the inactive phase. Regression analysis suggests that repair and regeneration may be the most potent stimuli causing PCM.

Adult↗
PubMed1990

The spatial distribution of attention during covert visual orienting.

Many studies of covert orienting of visual attention in response to informative pre-cues have focused on the spatial distribution of improved or impaired performance. One can find at least four different models in the literature, each describing a different distribution: the fixed gradient spotlight; the zoom lens spotlight; the hemifield activation hypothesis; and the flexible allocation of resources model. In previous work examining procedural details that might have led to the formulation of the hemifield activation hypothesis, it was postulated (Klein and McCormick 1989) that under conditions of uncertainty about which of two locations to attend, an observer may focus attention on a visual channel (i.e., midlocation placement of a fixed gradient spotlight) that is spatially intermediate. The present experiment was designed to distinguish among the four models of attentional distribution, and to test the midlocation placement strategy. Our findings show support for midlocation placement, demonstrate evidence against flexible allocation and hemifield activation, but could not differentiate between fixed gradient and zoom lens variants of the spotlight model.

Attention↗
PubMed2003

Raman spectroscopic study of spatial distribution of propolis in comb of Apis mellifera carnica (Pollm.).

Micro-Raman spectroscopy and Raman mapping are applied to investigate the spatial distribution and chemical composition of wax and propolis in the comb of Apis mellifera carnica (Pollm). A thick layer of propolis at the rim of some cells is identified by Raman spectroscopy. Raman mapping is applied to resolve the distribution of propolis and wax on a micron scale. Both components are connected at the rim of the cell with a mixture of wax and propolis. A layer of almost pure propolis is found on top of the mixture. It appears that even in the mixture, where both components come into close contact, the propolis and the wax remain separated and keep their chemical identity.

Animals↗
PubMed1993

The spatial distribution of cavitation induced acoustic emission, sonoluminescence and cell lysis in the field of a shock wave lithotripter.

This study examines the spatial distribution of various properties attributed to the cavitation field generated by a shock wave lithotripter. These properties include acoustic emission and sonoluminescence, which result from violent bubble collapse, and the degree of cell lysis in vitro, which appears to be related to cavitation. The acoustic emission detected with a 1 MHz, 12 cm diameter focused hydrophone occurs in two distinct bursts. The immediate signal is emitted from a small region contained within the 4 MPa peak negative pressure contour. A second, delayed, burst is emitted from a region extending further along the beam axis. The delay between these two bursts has also been mapped, and the longest delay occurs at positions close to the regions of maximum peak negative pressure. Sonoluminescence from both single and multiple shocks occurs in a broader region than the acoustic emission but the measurement technique does not allow time resolution of the signal. Cell lysis occurs in a relatively small region that correlates closely with the immediate acoustic emission for a shock propagating in a gelatine solution.

Acoustics↗
PubMed2002

Species composition and spatial distribution of a stream fish assemblage in the east coast of Brazil: comparison of two field study methodologies.

The species composition and spatial distribution of a fish assemblage were studied in three reaches of a river in the east coast of Brazil: a section of rapids (upper), another of water flowing on plain terrain (lowland) and the other of a mangrove environment. Two methods were employed with the purpose of estimating their effectiveness in naturalistic studies of tropical fish assemblages. One method consisted of underwater observations and the other was characterized by catches using gears such as fish traps, sieves and fishing rods. Both methods showed that their effectiveness is dependent upon the characteristics of the environment and the biology of the species. In areas of high water transparency and flow speed rocky substrate and no submerged marginal vegetation (upper reach), the employment of the traditional gears was quite inefficient, despite the excellent conditions for underwater observations. In areas of clear water and high flow speed with abundant submerged marginal vegetation (lowland and mangrove), the gears were rather efficient yielding excellent results when coupled with direct observation methods. Since the abiotic characteristics of a stream change longitudinally, it is appropriate to employ different methods in the study of the ichthyofauna composition and distribution in order to reduce the constraints imposed by sampling methods in running waters.

Analysis of Variance↗
PubMed2000

Dose dependency of canthaxanthin crystals in monkey retina and spatial distribution of its metabolites.

PURPOSE: To establish the threshold level of canthaxanthin crystals in the retina of cynomolgus monkeys. To correlate the spatial distribution of all-trans canthaxanthin and its metabolites with the grade of crystals. METHODS: Monkeys were orally administered 0, 0.2, 0.6, 1.8, 5.4, 16.2, and 48.6 mg/kg body wt canthaxanthin daily for 2.5 to 3 years. A second group of monkeys were administered 200 and 500 mg/kg body wt/d for 5 years. Ophthalmoscopy, electroretinography (ERG), retina and carotenoid analysis were performed as previously reported. RESULTS: Crystals in the retina periphery were observed by ophthalmoscopy preterminally only in the extreme high doses of 200 to 500 mg/kg body wt/d. There were no adverse effects on visual functions as measured by ERG. Crystals in the peripheral retina, and/or in the macula, were detected microscopically in all canthaxanthin treated groups except at the lowest dose of 0.2 mg/kg body wt/d. The grade of crystals increased up to a dose of 16.2 mg/kg body wt/d. Dose-dependent increases in canthaxanthin content also were noted in the retina, the liver, and in plasma. All-trans canthaxanthin was the major compound in the peripheral and paracentral retina of very highly dosed animals, where its concentration correlated largely with the grade of inclusions. In the macula, 4'-OH-echinenone was the dominant canthaxanthin metabolite. CONCLUSIONS: The grade of crystals in monkey retinas was dose dependent with a threshold level at 0.6 mg canthaxanthin/kg body wt/d. It correlated in the retinal periphery with the concentrations of all-trans-canthaxanthin and in the macula with its metabolites.

Administration, Oral↗
PubMed1987

Spatial distribution of disease: three case studies.

Maps transformed so as to have constant density of residential population were used to analyze the spatial distribution of disease in three specific areas. Each area had received recent attention because of suspected environmental pollution. The area adjacent to the Rocky Flats Facility (CO) was examined to identify any association between possible plutonium releases and increases in lung cancer or leukemia incidence. The industrial area of northern Contra Costa County (CA) was studied to explore a relationship between petrochemical industrial emissions and histologic-specific lung cancers. Finally, a suspected increase in the risk of congenital cardiac defects possibly related to pollution of the Santa Clara County (CA) water supply was investigated. No evidence of elevated risk of disease was found to be associated with either the Rocky Flats Facility or the polluted water of Santa Clara County. An increase in lung cancer, found by other investigators in earlier years, was shown to persist in association with industrial emissions in Contra Costa County.

Adult↗
PubMed1972

Spatial distribution of potential in a flat cell. Application to the catfish horizontal cell layers.

An analytical solution is obtained for the three-dimensional spatial distribution of potential inside a flat cell, such as the layer of horizontal cells, as a function of its geometry and resistivity characteristics. It was found that, within a very large range of parameter values, the potential is given by [Formula: see text] where r = rho/rho(0), z = z/rho(0), rho = (R(i)/R(m)).rho(0), delta = h/rho(0); K is a constant; J is the assumed synaptic current; rho, z are cylindrical coordinates; rho(0) is the radius of the synaptic area of excitation; h is the cell thickness; and R(i), R(m) are the intracellular and membrane resistivities, respectively. Formula A closely fits data for the spatial decay of potential which were obtained from the catfish internal and external horizontal cells. It predicts a decay which is exponential down to about 40% of the maximum potential but is much slower than exponential below that level, a characteristic also exhibited by the data. Such a feature in the decay mode allows signal integration over the large retinal areas which have been observed experimentally both at the horizontal and ganglion cell stages. The behavior of the potential distribution as a function of the flat cell parameters is investigated, and it is found that for the range of the horizontal cell thicknesses (10-50 mu) the decay rate depends solely on the ratio R(m)/R(i). Data obtained from both types of horizontal cells by varying the diameter of the stimulating spot and for three widely different intensity levels were closely fitted by equation A. In the case of the external horizontal cell, the fit for different intensities was obtained by varying the ratio R(m)/R(i); in the case of the internal horizontal cell it was found necessary, in order to fit the data for different intensities, to vary the assumed synaptic current J.

Animals↗
PubMed1992

Spatial distribution of sperm-derived chromatin in zygotes determined by fluorescence in situ hybridization.

Fluorescence in situ hybridization was used to determine the spatial distribution of chromatin in zygote pronuclei. A hybrid system involving golden hamster eggs and individual human sperm permitted use of DNA probes specific for the entire human chromosome 4, for the heterochromatic region on the long arm of the human Y chromosome and for unique DNA sequences on human chromosome 19. Chromosome 4 occupied a circumscribed domain in the pronuclei, similar to findings in somatic interphases. Unlike the situation in somatic interphases, the Y heterochromatin was extended throughout the first cell cycle. Pronuclear chromatin was extended 3- to 4-fold compared to somatic interphase chromatin. The extended pronuclear chromatin conformation is likely to affect a zygote's susceptibility to environmental hazards.

Animals↗
PubMed1993

Temporal and spatial distribution of Ixodes pacificus and Dermacentor occidentalis (Acari: Ixodidae) and prevalence of Borrelia burgdorferi in Contra Costa County, California.

The seasonal activity and spatial distribution of adult and immature Ixodes pacificus Cooley & Kohls and Dermacentor occidentalis Marx were determined along trails and on hillsides in two parks in Contra Costa County, CA. I. pacificus and D. occidentalis adults were most numerous in January and May, respectively. Adult ticks were significantly more abundant along heavily vegetated trails than on open grassy hillsides, and on the uphill versus the downhill side of trails. Five species of rodents were captured, and numbers of I. pacificus and D. occidentalis larvae per rodent were highest in May-June and July, respectively. Few nymphs were recovered either by flagging or from captured rodents. An average of 2.2 and 2.8% of the I. pacificus adults collected from the two parks were infected with the Lyme disease spirochete, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner. The greatest risk of contracting Lyme disease from adult I. pacificus in these two Contra Costa County parks is during the winter months, especially while hiking near the uphill side of trails.

Acari↗
PubMed2001

Spatial distribution of nutritive and nonnutritive vascular routes in perfused rat hindlimb muscle using microspheres.

Skeletal muscle appears to have two vascular flow routes, nutritive and nonnutritive, where the balance of flow is controlled by vasoconstrictors. In the present study, spatial distributions of the two flow routes in muscles of the perfused rat hindlimb were attempted using fluorescent microspheres (15 microm in diameter). Microspheres were injected during steady-state perfusion with norepinephrine (proposed recruiter of nutritive flow), serotonin (proposed recruiter of nonnutritive flow), or vehicle. The three-dimensional location of individual microspheres in representative muscles was determined using a Fluorescent Imaging CryoMicrotome. Norepinephrine and serotonin each increased perfusion pressure (P < 0.05) but stimulated and inhibited oxygen consumption (P < 0.05), respectively. The distribution of microspheres lodged in muscle was independent of the agent used. Spatial perfusion indices for norepinephrine, serotonin, and vehicle did not differ from each other. Similarly, there was no difference in these indices for a theoretical distribution where microspheres were deliberately positioned in muscle bundle capillaries or interfibrillar connective tissue vessels. We conclude that the nutritive and nonnutritive flow routes are distributed throughout muscle sections consistent with their locations in muscle bundle capillaries and interfibrillar connective tissue, respectively.

Animals↗
PubMed2000

Relation between spatial distribution of late potentials and location of origin of premature ventricular complexes on body surface map in patients with postinfarction ventricular tachycardia.

We studied the relationship between the spatial distribution of late potentials (LPs) and the origin of premature ventricular complexes (PVCs) using body surface maps in 55 patients with postinfarction sustained ventricular tachycardia (VT). Body surface maps were recorded from 87 leads to construct departure maps during sinus rhythm and signal-averaged ECGs were recorded from 32 unipolar leads to construct a LP map. The root-mean-square values during 40 ms intervals behind the QRS end were computed as LPs. The PVC map was recorded simultaneously in 14 patients presenting PVC with similar morphology to VT during LP detection. The origin of PVC was localized at the site of isopotential minimum when the potential exceeded -0.5 mV during the early QRS period. The LP area and the departure area showed a similar distribution. However, the PVC origin was closer to the site of LP maximum than the departure minimum in 11 (79%) patients, and the spatial correlation between the LP maximum and the PVC origin was good in 12 (86%) patients. LP and PVC mapping from the body surface is feasible and of worth to predict noninvasively the site of origin of ventricular arrhythmias in patients with remote myocardial infarction and sustained VT.

Adult↗
PubMed2003

The spatial distribution of attentional selectivity in touch: evidence from somatosensory ERP components.

OBJECTIVE: Somatosensory event-related brain potentials (ERPs) were measured to investigate the spatial distribution of selective attention in touch, and whether the focus of tactile attention can be split between non-contiguous areas of the body surface. METHODS: On each trial, vibratory tactile stimuli were delivered to one of 4 possible locations of the right hand. Participants had to attend to either one or two locations in order to detect infrequently presented target stimuli there. ERPs were recorded to tactile non-targets at attended and unattended locations. RESULTS: Attention directed to one finger versus another was reflected by amplitude modulations of the sensory-specific P100 component and a subsequent attentional negativity (Nd). These effects were smaller for within-finger as compared to between-finger selection. When attention was directed simultaneously to non-adjacent fingers, ERPs in response to stimuli delivered to spatially and anatomically intervening fingers showed no attentional modulations whatsoever. CONCLUSIONS: Allocating tactile-spatial attention to one finger versus another affects early modality-specific somatosensory processing stages, and these effects of within-hand attentional selectivity decrease gradually with increasing distance from the current attentional focus. Unlike vision, the focus of tactile attention can be split, and directed simultaneously to non-adjacent areas, thus excluding spatially and anatomically intermediate regions from attentional processing.

Adult↗
PubMed1987

Spin-echo fluorine magnetic resonance imaging at 2 T: in vivo spatial distribution of halothane in the rabbit head.

Spin-echo 19F magnetic resonance imaging was performed at 2.0 T to explore the in vivo spatial distribution of halothane in the rabbit head. Because the halothane concentration is low in vivo, and because the measured relaxation times of the 19F resonance peak for halothane were T1 approximately equal to 1.0 sec and T2 approximately equal to 3.5-65 msec, 1-3-h imaging times were required (TR = 1 sec, TE = 9 msec) in order to obtain adequate images with a 64 X 256 raw data matrix and a 20-mm slice thickness. With this technique, halothane was primarily detected in lipophilic regions of the rabbit head, but little or no halothane was observed in brain tissue. Because T2 was shorter in brain tissue than in surrounding fat, a shorter TE than we could obtain is needed for optimal spin-echo imaging of brain halothane.

Animals↗