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PubMed2005

Spatial attention: more than intrinsic alerting?

It has been proposed that the right hemisphere alerting network co-activates, either directly or via the brainstem, the attention system in the parietal cortex involved in spatial attention. The observation that impaired alertness and sustained attention can predict the outcome of neglect might suggest such a relationship, too. In the present fMRI study, we intended to analyse and compare the functional anatomy of two attentional conditions both involving intrinsic (endogenous) alerting and fixation but differing with respect to the degree of spatially distributed attention by using the same paradigm under two different attentional conditions. In a group of ten participants, both a focused and a distributed visuospatial attention condition evoked similar patterns of activation in dorsolateral prefrontal regions, in the anterior cingulate gyrus, in the superior and inferior parietal cortex as well as in the superior temporal gyrus and in the thalamus. These activation foci were stronger in the right hemisphere under both conditions. After subtraction of the alertness condition with focused spatial attention, distributed spatial attention with stimuli appearing at unpredictable locations within both visual fields induced additional bilateral activations only in the left and right superior parietal cortex and in the right precuneus suggesting that these regions are specific for a more widespread dispersion of spatial attention.

Adult↗
PubMed2004

Mechanical environment alters tissue formation patterns during fracture repair.

Fracture repair has previously been shown to be sensitive to mechanical environment, yet the specific relationship between strain character, magnitude and frequency, as well as other mechanical parameters, and tissue formation is not well understood. This study aimed to correlate strain distribution within the healing fracture gap with patterns of tissue formation using a rat model of a healing osteotomy subject to mechanical stimulation in bending. Finite element models based on realistic tissue distributions were used to estimate both the magnitude and spatial distribution of strains within the fracture gap. The spatial distribution of regenerating tissue was determined by microcomputed tomography and histology, and was confirmed using reverse transcription-polymerase chain reaction (RT-PCR). Results suggest that tensile strains suppress chondrogenesis during the mechanical stimulation period. After stimulation ends, however, tensile strains increased chondrogenesis followed by rapid bone formation. In contrast, in compressive environments, bone is formed primarily via intramembranous ossification. Taken together, these results suggest that intermittent tensile strains during fracture repair stimulate endochondral ossification and promote eventual bone healing compared to intermittent compressive strains and unstimulated fractures. Further understanding of these relationships may allow proposal of optimal therapeutic strategies for improvement of the fracture repair process.

Animals↗
PubMed2006

Interactive effects of natural and human disturbances on vegetation dynamics across landscapes.

Accurate measures of human effects on landscape processes require consideration of both the direct impacts from human activities and the indirect consequences of the interactions between humans and the landscape. This is particularly evident in systems experiencing regular natural disturbances such as in the mountainous areas of southwestern China, where the remaining population of giant pandas (Ailuropoda melanoleuca) is supported. Here the spatiotemporal patterns of human impacts, forests, and bamboo episodic die-offs combine to determine the distribution of panda habitat. To study the complex interactions of humans and landscapes, we developed an integrated spatiotemporally explicit model of household activities, natural vegetation dynamics, and their impacts on panda habitat. Using this model we examined the direct consequences of local fuelwood collection and household creation on areas of critical giant panda habitat and the indirect impacts when coupled with vegetation dynamics. Through simulations, we found that over the next 30 years household impacts would result in the loss of up to 30% of the habitat relied on by pandas during past bamboo die-offs. The accumulation and spatial distribution of household impacts would also have a considerable indirect influence on the spatial distribution of understory bamboo. While human impacts influence both bamboo die-off and regeneration, over 19% of pre-existing low-elevation bamboo habitat may be lost following an episodic die-off depending on the severity of the impacts and timing of the die-offs. Our study showed not only the importance of the spatial distribution of direct household impacts on habitat, but also the far-reaching effects of the indirect interactions between humans and the landscapes they are modifying.

Animals↗
PubMed2003

[Regional differences of mortality from malignancies in Hungary].

INTRODUCTION: The mortality of the Hungarian population is very unfavourable in relation to other European countries. Mortality from malignant diseases is the second most frequent cause of death in both sexes. The most frequent localisation of cancer is that of the bronchi and the lungs, followed by colorectal, breast and oral cavity cancers. AIM: Of the publication was to demonstrate the spatial distribution of mortality from malignant diseases of all sites, bronchi and the lungs, as well as mortality from cancer of the thyroid gland and leukaemias, and to evaluate the possible impact of the Chernobyl nuclear accident on the frequency of cancer mortality. METHOD: The spatial distribution of mortality in the country is evaluated by computing standardized mortality ratio on settlement level, using geographical information system. In case of frequent mortality events a region analysis was carried out, in the opposite case--a cluster analysis. RESULTS: Regarding the spatial distribution of mortality from all malignant diseases of 0-64 year-old males there are regions with excess mortality in almost each county. In case of women of this age group, there is a significantly higher mortality in Budapest, in three counties in the Eastern part of the country, and in some settlements in Transdanubia. Mortality from the cancer of the bronchi and the lungs significantly accumulates in both sexes in four counties in Eastern Hungary. Mortality from cancer of the thyroid gland and leukaemias does not show typical spatial accumulation as well. CONCLUSIONS: The premature mortality from all malignant diseases and of cancer of the bronchi and lungs of the Hungarian male and female population shows an increasing tendency. Mortality from the latter cause shows a typical spatial accumulation, which causes should be investigated in analytical epidemiological studies. The potential causative role of the Chernobyl accident could not be proven in any case.

Adolescent↗
PubMed2005

Mark-release-recapture experiments with Anopheles saperoi (Diptera: Culicidae) in the Yona Forest, northern Okinawa, Japan.

Six mark-release-recapture experiments with Anopheles saperoi Bohart and Ingram were performed in the Yona Forest, northern Okinawa, Japan from June 1998 - November 1999, in order to estimate the gonotrophic cycle, survival, spatial distribution, flight range, and population size of An. saperoi. Adults and immature An. saperoi were collected from the Yona Forest area, taken to the laboratory and maintained under a controlled temperature and humidity in order to get a lager number of mosquitos for the mark-release-recapture experiments. Cohorts of An. saperoi females and males, numbering 3,016, 4,728, 327, and 2,603 for experiments I, II, III, and IV, respectively, were released. Cohorts of An. saperoi females only, numbering 709 and 586 for experiments V and VI, respectively, were also released. At the release site, the An. saperoi were marked with 0.5% fluorescent dye Rhodamine B and released. The recapture rates were 14 (0.93%), 33 (1.40%), 3 (1.83%), 32 (2.46%), 14 (1.97%), and 22 (3.75%) for experiments 1, II, III, IV, V, and VI, respectively. The length of the gonotrophic cycle of the recaptured An. saperoi females was estimated to be about 4 days, through the dissection method. The daily survival rate was estimated to be 0.73 by regression coefficient. The spatial distribution of marked, recaptured An. saperoi was similar to that of unmarked captured An. saperoi. The spatial distribution of the marked, recaptured An. saperoi among the collection site categories was significantly different. The observed differences in the frequency distribution of marked recaptured An. saperoi were considered to be due to the spatial variation of the habitats between the collection sites. The maximum flight range of the recaptured An. saperoi recorded in this study was 0.93 km. The population size of An. saperoi females in the study area was estimated by the Seber method to be 23,841, 1,182, 3,514, 5,679, and 9,238 for experiments I, II, IV, V, and VI, respectively. The estimated population size has a low standard of error using the Seber method, therefore we estimated our population size reasonably well. The population attributes and ecology of An. saperoi in the Yona Forest, in northern Okinawa are discussed.

Animals↗
PubMed1997

Fundus autofluorescence in age-related macular disease imaged with a laser scanning ophthalmoscope.

PURPOSE: To image and quantify the spatial distribution of fundus autofluorescence in normal subjects, to determine its age dependence, and to document the deviation from normal in patients with age-related macular disease. METHODS: Using a confocal laser scanning ophthalmoscope (cLSO), the intensity and spatial distribution of fundus autofluorescence was studied in 33 normal subjects, 97 eyes with drusen only, and 111 eyes with visual loss caused by age-related macular disease. RESULTS: Fundus autofluorescence intensity in normal subjects was highest at the posterior pole and dipped at the fovea. Autofluorescence increased with age at the posterior pole. Fundus in eyes with age-related maculopathy showed localized high autofluorescence that did not correspond with drusen. Linear pigmentation at the level of the retinal pigment epithelium (RPE), whether detached or flat, fluoresced brightly, whereas plaques of melanin did not. Areas of low and high levels of autofluorescence were seen in lesions containing choroidal new vessels. In areas of geographic atrophy, autofluorescence was low. CONCLUSIONS: The spatial distribution of background fundus autofluorescence and the correlation of autofluorescence with age in normal subjects imply that autofluorescence is derived from lipofuscin at the level of the RPE. Focal accumulation of autofluorescent material occurs at the level of the RPE in patients with drusen, but the drusen do not show marked increases in autofluorescence. It is likely that melanolipofuscin accounts for the high levels of autofluorescence, corresponding to linear pigmentation at the level of the RPE. Low-intensity autofluorescence occurs in the presence of retinal photoreceptor loss, and variable levels over disciform lesions probably relate to variations in metabolic activity of the RPE.

Adolescent↗
PubMed1988

Abnormal patterns of embryogenesis in Dirofilaria immitis treated with ivermectin.

The percentage composition and spatial distribution of embryogenic stages in the uteri of female Dirofilaria immitis were examined at various times after treatment with a microfilaricidal dose of ivermectin and compared to nontreated parasites. Worms sampled 42 days post-treatment (PT) exhibited an increased proportion of stretched microfilariae in the distal portion of the uterus. A decreased proportion of developed embryos was noted in the mid body region of worms sampled 42 days PT, and these forms were completely absent from the proximal area of the uterus. Relative numbers and spatial distribution of other stages remained virtually identical to controls. Radical changes in the composition and spatial distribution of embryogenic forms were noted in the uteri of a single worm sampled 80 days PT. Unlike nontreated parasites and worms sampled 42 days PT, stretched microfilariae constituted the predominant form in the distal uterus of this worm, and these stages were found in decreasing numbers throughout the proximal segments. Also, the intermediate embryogenic stages were either rare or absent.

Animals↗
PubMed1992

Functional topography of cat primary auditory cortex: representation of tone intensity.

The neuronal response to tones as a function of intensity was topographically studied with multiple-unit recordings in the primary auditory cortex (AI) of barbiturate-anesthetized cats. The spatial distribution of the characteristics of rate/level functions was determined in each of three intensely studied cases and their relationship to the distribution of spectral parameters (sharpness of tuning and responses to broadband transients) in the same animals was determined. The growth of the high-intensity portion of rate/level functions was estimated by linear regression. Locations with monotonically growing high-intensity portions were spatially segregated from locations with nonmonotonic rate/level functions. Two noncontiguous areas with a high degree of nonmonotonicity were observed. One was located at the dorsoventral center of AI, and a second in the dorsal third of AI. The more ventral aggregate of high nonmonotonicity coincided with the region of sharp frequency tuning. The stimulus levels that produced the highest firing rate (strongest response level, SRL) at any sampled location ranged from 10 to 80 dB sound pressure level (SPL). Several spatial aggregates with either high or low SRLs were observed in AI. The region of sharpest tuning was always associated with a region of low SRLs. The response threshold to contralateral tones at the characteristic frequency (CF) ranged from -10 dB SPL to 85 dB SPL with the majority between 0 and 40 dB SPL. The spatial distribution of response thresholds indicated several segregated areas containing clusters with either higher or lower response thresholds. The correlation of response threshold with integrated bandwidth and transient responses was only weak. Low- and high-intensity tones of the same frequency are represented at different locations in AI as judged by the amount of evoked neuronal activity and are largely independent of the frequency organization. The spatial distribution of locations with high monotonicity and low strongest response levels were aligned with the organization of the integrated excitatory bandwidth and covaried with the response strength to broadband stimuli.

Acoustic Stimulation↗
PubMed1979

Myocardial hypertrophy: the distribution of cell growth within the layers of the myocardium.

The spatial distribution of radioactively labeled microspheres was studied in normal and in experimentally hypertrophied hearts of adult pigs. The hearts had been "tagged" with microspheres when the pigs were young. When the adult animal was killed, the spatial distribution of the microspheres was identical in the normal and in the hypertrophied hearts. This demonstrates that hypertrophic growth had occurred evenly throughout all layers of the myocardium.

Animals↗
PubMed2001

Electron paramagnetic resonance for small animal imaging applications.

Magnetic resonance imaging (MRI) provides high-resolution morphological images useful in diagnostic radiology to differentiate between normal and abnormal/pathological states in tissues. More recently, emerging developments in MRI have added a functional/physiological dimension to anatomical images. Electron paramagnetic resonance (EPR), a magnetic resonance technique similar to nuclear magnetic resonance, detects paramagnetic species such as free radicals. Like MRI, EPR can be implemented as an imaging technique for small animals and potentially human applications. Because of the low abundance of naturally occurring paramagnetic species, exogenous paramagnetic species are needed for in vivo EPR imaging (EPRI). The image data from EPRI contain both spatial distribution of paramagnetic species and spectral information. Hence, spatially encoded functional information such as tissue oxygen status and redox status can be extracted and coregistered with the spatial distribution of the spin probe, to the anatomy, or both by suitable means. Ultimately, the images obtained from EPRI may be used to overlay the functional information (containing spatial tissue physiology information) onto detailed anatomical maps. With its ability to enable whole animal imaging in mice, EPRI will be a useful imaging technique that complements other techniques such as MRI and positron emission tomography in obtaining valuable functional/physiological images.

Anatomy, Cross-Sectional↗
PubMed2001

Two-generation analysis of pollen flow across a landscape. I. Male gamete heterogeneity among females.

Gene flow is a key factor in the spatial genetic structure in spatially distributed species. Evolutionary biologists interested in microevolutionary processess and conservation biologists interested in the impact of landscape change require a method that measures the real time process of gene movement. We present a novel two-generation (parent-offspring) approach to the study of genetic structure (TwoGener) that allows us to quantify heterogeneity among the male gamete pools sampled by maternal trees scattered across the landscape and to estimate mean pollination distance and effective neighborhood size. First, we describe the model's elements: genetic distance matrices to estimate intergametic distances, molecular analysis of variance to determine whether pollen profiles differ among mothers, and optimal sampling considerations. Second, we evaluate the model's effectiveness by simulating spatially distributed populations. Spatial heterogeneity in male gametes can be estimated by phiFT, a male gametic analogue of Wright's F(ST) and an inverse function of mean pollination distance. We illustrate TwoGener in cases where the male gamete can be categorically or ambiguously determined. This approach does not require the high level of genetic resolution needed by parentage analysis, but the ambiguous case is vulnerable to bias in the absence of adequate genetic resolution. Finally, we apply TwoGener to an empirical study of Quercus alba in Missouri Ozark forests. We find that phiFT = 0.06, translating into about eight effective pollen donors per female and an effective pollination neighborhood as a circle of radius about 17 m. Effective pollen movement in Q. alba is more restricted than previously realized, even though pollen is capable of moving large distances. This case study illustrates that, with a modest investment in field survey and laboratory analysis, the TwoGener approach permits inferences about landscape-level gene movements.

Genetic Variation↗
PubMedDate not supplied

Method for three-dimensional visualization of neurodegeneration in cupric-silver stained serial rat brain slices.

The spatial distribution of neurodegeneration in brains is difficult to visualize when working from 2-D serial slices. In studies where repetitive operant behavior measurements are made over several weeks following organic solvent exposure, definitive evidence of degeneration in brain structures may have been significantly cleared by the time the tissue is prepared histologically. The only remaining evidence that injury has occurred may be nothing more than neuronal and cellular debris. By choosing stains that are specific for this type of residual and/or indicative of specific pathology, a 3-D representation of the spatial distribution of the neuronal and cellular debris fields within the organ can be highlighted and displayed. We present a method for visualizing the spatial distribution of neuronal degeneration that can result from low-level organic solvent exposure scenarios. A cupric-silver stain highly specific for neuronal degeneration is used to identify neuronal debris fields in 73 serial slices of brains of rodents that were exposed to toluene vapors. Serial brain sections stained with cupric-silver are scanned at 600 dpi using a gray-scale protocol. Using commercially available software, scans are assembled into 3-D images showing both topographical and internal anatomical details. The reassembled images are further processed into stereo pairs. Gray-scale scans are compared to the original sections to establish gray-scale ranges for healthy and damaged tissue and artifact staining.

Animals↗
PubMed1996

Imaging of the spatial density distribution on the capsule of the lens with Scheimpflug photography.

The density characteristics of the anterior and posterior surfaces of the lens, although of primary importance for its optical quality, are difficult to determine. Scheimpflug photography, however, allows distinct density measurements from the optical axis towards the periphery with the only limitation of a sufficient mydriasis, so that a 3-dimensional scatter profile of both capsular surfaces can be calculated via multilinear densitometric evaluation of a sufficient number of meridians. On this methodical basis, we analysed Scheimpflug images recorded with the Topcon SL-45 on Kodak T-Max 400 film from 25 patients in an age range between 19 and 63 years. Images from the 0 degree + 45 degree meridians were scanned with multilinear microdensitometry and the data computed to get a density profile. In general, most scattering profiles show a marked interindividual variability. Nevertheless, a general trend can be established between the periphery and the center of the anterior and posterior capsules: (a) the anterior capsule generally has a higher density than the posterior; (b) in most cases, the center of the posterior capsule has a higher density than the periphery; (c) the anterior capsule has a more uniform spatial density distribution in all cases. From the cases evaluated, it can be concluded that the density of the peripheral posterior capsule is more importantly influenced by shading effects of the iris, so that geometrical correction is needed.

Adult↗
PubMed1998

Possible Ca2+-dependent mechanism of apical outer hair cell modulation within the cochlea of the guinea pig.

Calcium ions were precipitated with potassium antimonate after injection of the inorganic calcium channel blocker MnCl2 or the inorganic potassium channel blockers BaCl2 or CsCl into the perilymph of the scala vestibuli of the guinea pig. The spatial distribution of the formed histochemical reaction products within the organ of Corti was studied by energy-filtering transmission-electron microscopy. Compared with untreated control ears, the number of the formed precipitates drastically increased at the extracellular side of the lamina reticularis after application of the various inorganic channel blockers. The apical side of the outer hair cells and the intervening Deiter cells were covered by a thick layer of calcium precipitates, whereas the number of histochemical reaction products was clearly reduced in the nearby acellular tectorial membrane. The high calcium content within the formed reaction products at the lamina reticularis could be demonstrated by elemental mapping and by electron energy-loss spectroscopy. To ascertain the alterations in the amounts of the calcium precipitates within the tectorial membrane after application of the various inorganic channel blockers, the precipitate densities were determined semiquantitatively by an image processing system and the values obtained compared with those of untreated control specimens. The observed histochemical results are in good agreement with published electrophysiological findings concerning the spatial distribution of ion channels located at the apical outer hair cell membrane. The detected alterations in the spatial distribution of calcium precipitates might correspond to calcium-dependent processes involved in outer hair cell modulation.

Animals↗
PubMed2001

Clinal differentiation and putative hybridization in a contact zone of Pinus ponderosa and P. arizonica (Pinaceae).

The widely distributed Pinus subsection Ponderosae is a species complex that has a transition zone among taxa in the southwestern United States. In southern Arizona and New Mexico at least two recognized taxa, Pinus ponderosa var. scopulorum and Pinus arizonica or P. ponderosa var. arizonica, are known to coexist in close proximity. In this study, we report the existence of populations where the taxa are sympatric. One of the key characteristics distinguishing taxa is the number of needles per fascicle; P. ponderosa typically has three, P. arizonica has five. We examined the spatial distribution of needle-number types in a belt transect that covers a transition zone from nearly pure three-needle types at the top of Mount Lemmon to five-needle types downslope, in the Santa Catalina Mountains, Arizona. The spatial distribution is inconsistent with there being both free interbreeding among types and selective neutrality of types. Trees with intermediate types, having combinations of three, four, and five needles and/or mean numbers of needles between 3.0 and 5.0, are spatially concentrated in the middle of the transition zone. The spatial distribution supports the occurrence of hybridization and introgression, and this is consistent with reported crossabilities of the types. The results suggest that selection is acting, either on needle number per se or on other traits of the ecotype with which it may be in linkage disequilibrium, to maintain the observed steep clinal differentiation.

Journal Article↗
PubMed1999

Glossopharyngeal nerve transection eliminates quinine-stimulated fos-like immunoreactivity in the nucleus of the solitary tract: implications for a functional topography of gustatory nerve input in rats.

The relationship between specific gustatory nerve activity and central patterns of taste-evoked neuronal activation is poorly understood. To address this issue within the first central synaptic relay in the gustatory system, we examined the distribution of neurons in the nucleus of the solitary tract (NST) activated by the intraoral infusion of quinine using Fos immunohistochemistry in rats with bilateral transection of the chorda tympani (CTX), bilateral transection of the glossopharyngeal nerve (GLX), or combined neurotomy (DBLX). Compared with nonstimulated and water-stimulated controls, quinine evoked significantly more Fos-like-immunoreactive (FLI) neurons across the rostrocaudal extent of the gustatory NST (gNST), especially within its dorsomedial portion (subfield 5). Although the somatosensory aspects of fluid stimulation contributed to the observed increase in FLI neurons, the elevated number and spatial distribution of FLI neurons in response to quinine were remarkably distinguishable from those in response to water. GLX and DBLX produced a dramatic attenuation of quinine-evoked FLI neurons and a shift in their spatial distribution such that their number and pattern were indiscernable from those observed in water-stimulated controls. Although CTX had no effect on the number of quinine-evoked FLI neurons within subfield 5 at intermediate levels of the gNST, it produced intermediate effects elsewhere; yet, the spatial distribution of the quinine-evoked FLI neurons was not altered by CTX. These findings suggest that the GL provides input to all FLI neurons responsive to quinine, however, some degree of convergence with CT input apparently occurs in this subpopulation of neurons. Although the role of these FLI neurons in taste-guided behavioral responses to quinine remains speculative, their possible function in oromotor reflex control is considered.

Analysis of Variance↗
PubMed2005

Spatial prediction of corn rootworm (Coleoptera: Chrysomelidae) adult emergence in Iowa cornfields.

The most common management options for corn rootworms are rotating corn with nonhost crops, planting genetically engineered corn resistant to corn rootworms (e.g., Bacillus thuringiensis [Bt] corn), and treating with a soil insecticide at planting time. Because these control tactics are preventive, the decision to apply controls has been made without any knowledge of rootworm density and spatial distribution. This study was conducted to predict the spatial distribution of adult emergence and to generate and test management zones for insecticides and Bt corn. To identify variables that correlated best with adult emergence the following year, plant height, plant stage, soil moisture, altitude, and corn rootworm adults were sampled spatially and temporally. Correlation and regression analyses showed that the best prediction for the adult emergence the following year was adult counts in the ear zone at peak population densities during the present year. Based on the prediction, geostatistics and the geographic information system were used to generate and test prescription maps with management zones for insecticides and Bt corn. Map-overlaying analysis showed that management zones for insecticides based on the economic injury level and Bt corn with 20% refuge had potential failure of 3-15% and 0-12% of field areas, respectively. This study demonstrated the spatial prediction of adult emergence the following year and generation of management zones, which has the potential of preventative, site-specific management of corn rootworms.

Agriculture↗
PubMed1989

Optical imaging of calcium accumulation in hippocampal pyramidal cells during synaptic activation.

The dynamic response of nerve cells to synaptic activation and the spatial distribution of biochemical processes regulated by ion concentration are critically dependent on the cell-surface distribution of ion channels. In the hippocampus, intracellular calcium-ion concentration is thought to influence the biochemical events associated with kindling, excitotoxicity, and long-term potentiation. Computer models of hippocampal pyramidal cells also indicate that calcium-channel location influences dynamic characteristics such as bursting. Here, we have used in situ microfluorometric imaging in brain slices to directly measure the spatial distribution of calcium accumulation in guinea-pig CA1 pyramidal cells during trains of orthodromic synaptic stimulation. Calcium accumulation is substantial throughout the entire proximal section of the apical and basal dendrites. Most of this accumulation results from influx through non-NMDA (N-methyl-D-aspartate) voltage-gated calcium channels, and in the apical dendrite it drops steeply as the dendrite enters stratum moleculare, the termination zone of perforant path afferents. These results demonstrate a marked segregation of calcium-channel activity and directly show a spatial distribution of calcium accumulation during orthodromic synaptic activation.

Animals↗