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PubMed1985

The development of basic mechanisms of pattern vision: spatial frequency channels.

The mature visual system possesses mechanisms that analyze visual inputs into bands of spatial frequency. This analysis appears to be important to several visual capabilities. We have investigated the development of these spatial-frequency channels in young infants. Experiment 1 used a masking paradigm to test 6-week-olds, 12-week-olds, and adults. The detectability of sine wave gratings of different spatial frequencies was measured in the presence and the absence of a narrowband noise masker. The 12-week data showed that at least two spatial-frequency channels with adultlike specificity are present at 12 weeks. The 6-week data did not reveal the presence of narrowband spatial-frequency channels. Experiment 2 used a different paradigm to investigate the same issue. The detectability of gratings composed of two sine wave components was measured in 6-week-olds and adults. The results were entirely consistent with those of experiment 1. The 12-week and adult data indicated the presence of narrowband spatial-frequency channels. The 6-week data did not. The results of these experiments suggest that the manner in which pattern information is processed changes fundamentally between 6 and 12 weeks of age.

Adult↗
PubMed2003

Cluster analysis of Delhi's ambient air quality data.

The purpose of this study was to study the spatial patterns of ambient air quality in Delhi in the absence of extensive datasets needed for space-time modeling. A spatial classification was attempted on the basis of ambient air quality data of nine years (1998 is latest year for which published data were available) for three criteria pollutants--nitrogen dioxide, sulfur dioxide, and suspended particulate matter. Monitoring stations take 24-hour samples twice a week. Published monthly average concentration data were used in this study. A hierarchical agglomerative algorithm using the average linkage between groups method and the Euclidean distance metric was used. Cluster analysis indicated that till 1998, by and large, two distinct classes existed. The results of cluster analysis prompted an investigation of systematic biases in the monitored data. No statistically significant differences in the mean concentration of all pollutants were observed between stations belonging to different land-use types (residential and industrial). This fact would be useful, if and when the authorities consider modifying the network or expanding it in Delhi. The results also support the recommendation that Delhi have a uniform standard across all areas. This study has provided a methodology for Indian researchers and practitioners to do an exploratory study of spatial patterns of air pollution and data quality issues in Indian cities using the National Ambient Air Quality Monitoring System data.

Air Pollutants↗
PubMed2001

The regulation of ornithine decarboxylase gene expression by sucrose and small upstream open reading frame in tomato (Lycopersicon esculentum Mill).

We identified a near-full-length cDNA clone encoding ornithine decarboxylase (ODC) from tomato (Lycopersicon esculentum Mill). It contained a small upstream open reading frame (uORF) within its 5' untranslated region. An in vitro translation assay demonstrated that the uORF repressed expression of downstream ORF. Neither nucleotide nor predicted peptide sequence of the uORF was responsible for the repression. The presence of upstream AUG codon was shown to be responsible. ODC expression appeared to be organ specific. The ODC gene was expressed in roots, hypocotyls and sink leaves but not in source leaves. ODC transcripts were observed in apical meristem of primary roots, and were distributed in cells of cortex layer preferentially. ODC expression responded immediately to sucrose availability via the sucrose-specific pathway independent of hexokinase. Sucrose induction of ODC gene was seen in roots, hypocotyls and flowers but not in mature leaves. Moreover, only the root apical meristem responded to sucrose availability. These observations indicate that the spatial pattern of ODC expression is closely associated with cell proliferation and that sucrose sensing plays a major role in the spatial pattern of ODC expression. Also, the differential regulation of ODC and arginine decarboxylase gene expression by factors modulating plant growth suggests that they would have different physiological roles in plant development.

5' Untranslated Regions↗
PubMed1989

Genetic interactions underlying flower color patterns in Antirrhinum majus.

Diverse spatial patterns of flower color in Antirrhinum can be produced by a series of alleles of pallida, a gene encoding an enzyme required for pigment biosynthesis. The alleles arose by imprecise excision of a transposable element, Tam3, and we show that they carry a series of deletions involving progressive removal of sequences adjacent to the excision site. This has enabled us to define three cis-acting upstream regions, A, B, and C, which differentially affect the level of pallida expression in distinct areas of the flower. We show further that an unlinked locus, delila, regulates the spatial distribution of pallida transcript. Deletion of regions ABC at the pallida locus uncouples pallida from regulation by delila, whereas deletion of A or AB brings pallida under regulation by delila in a new area of the flower. These results suggest that diverse patterns of pallida expression reflect the different ways in which alleles interact with a prepattern of both common and spatially specific genetic signals in the flower.

Alleles↗
PubMedDate not supplied

Facilitation and suppression of single striate-cell activity by spatially discrete pattern stimuli presented beyond the receptive field.

Visual stimulation of a region outside the receptive field of single cells in visual cortex often results in the modulation of their responses. The modulatory effects are thought to be mediated through lateral connections within visual cortex. Research on lateral interactions commonly shows suppression. There has been no systematic study of the optimal conditions for facilitation. Here we have studied the nature of the modulation using a new type of compound stimulus: contrast reversal of pattern stimuli made of three discrete grating patches. The middle patch, optimally fitted to the receptive field in orientation, size, and spatial as well as temporal frequencies, was flanked by two similar patches presented well outside the receptive field. We found that (1) both facilitation and suppression occurred often in the same cells, when orientations of the target and flankers matched the receptive-field's optimal orientation; (2) facilitation with collinear flankers occurred most frequently at target contrasts just above the cell's firing threshold and suppression prevailed at high contrasts; (3) facilitative or suppressive modulation was obtained with target-flankers separation of up to 12 deg or more; (4) collinear facilitation was lost when flankers' orientation was rotated by 90 deg, while keeping all other parameters the same; and (5) neither the modulation mode nor the proportion of modulated cells was related to the cell types (simple vs. complex cells) and cells' laminar locations. Here we have provided physiological evidence for contrast-dependent, collinear facilitation probably underlying perceptual grouping in humans.

Animals↗
PubMed1975

Effects of posterior parietal and frontal neocortical lesions in the squirrel monkey.

Brightness discrimination, three forms of a spatial pattern discrimination in which the essential cue and site of reinforcement were separated (SSP), delayed response, form discrimination, and three forms of a spatial pattern discrimination in which the essential cue and site of reinforcement were identical (ISP) were given, in the order mentioned, to two groups of squirrel monkeys with frontal lesions were impaired on delayed response, and those with parietal lesions were impaired on form and SSP discriminations. Neither group was impaired on brightness discrimination. The results confirm and extend previous findings by other investigators that the posterior parietal cortex of nonhuman primates is critically involved in visually guided spatial discriminations when the primary cue and the site of reinforcement are separated.

Animals↗
PubMed1995

Spatial and temporal pattern of Purkinje cell degeneration in shaker mutant rats with hereditary cerebellar ataxia.

Temporal-spatial patterns of surviving Purkinje cells were studied quantitatively in a rat mutant (shaker) with differential hereditary cerebellar ataxia and Purkinje cell degeneration. Shaker rat mutants are characterized behaviorally as mild if they are ataxic or as strong if they have ataxia and tremor. Purkinje cells degenerate in both mild and strong shaker mutants, but the temporal and spatial patterns of cell death are strikingly different. In mild shaker mutants, Purkinje cell death is temporally restricted, with 31-46% of the Purkinje cells in lobules I-IX dying by 3 months of age. Very few Purkinje cells degenerate after this age. Purkinje cell death is spatially random. In lobules I-IX, every second, third, or fourth Purkinje cell degenerates. Purkinje cells in lobule X do not degenerate. In strong shaker mutants, Purkinje cell degeneration is temporally protracted and spatially restricted. By 3 months of age, most Purkinje cells in lobules I-VIa, -b, and -d have degenerated. Numerous Purkinje cells in the paravermis of lobules VIIb-VIII have also degenerated. Surviving Purkinje cells in the vermis and lateral hemisphere of lobules VIIb-VIII are aligned in parasagittally oriented stripes or transversely oriented bands. Purkinje cells continue to degenerate in localized areas of the posterior lobe such that, by 18 months of age, surviving Purkinje cells are limited primarily to lobules VIc, VIIa, IXd, and X. Quantitative analysis indicates that none of the Purkinje cells in these lobules degenerate.

Animals↗
PubMed1991

Optical mapping of the early development of the response pattern to vagal stimulation in embryonic chick brain stem.

1. In both intact and slice preparations of vagus-brain stem isolated from 3- to 8-day-old chick embryos, the spatial pattern of neural responses to vagal stimulation and its development were assessed by means of multiple-site optical recording of electrical activity, using a voltage-sensitive merocyanine-rhodanine dye (NK2761) and a 12 x 12-element photodiode array. 2. The first neural responses, viz. fast optical signals (related to the action potential), were recorded in the 4-day-old brain stem preparation, and slow optical signals (related to excitatory postsynaptic potentials) were detected from late 7- and 8-day-old brain stem preparations. 3. The evoked optical signals appeared to be concentrated longitudinally in the central region of the stimulated side of the intact brain stem preparation and in a limited dorsal area in the slice preparation. The signal size gradually increased and the response area expanded as development proceeded. 4. Based on the above results, we have constructed developmental maps of the spatial patterns of the fast and slow optical responses. In the maps, the positions of the peak-size regions of the fast and slow signals were assessed and we have found that there were differences in the location of these areas for the fast vs. the slow signals in the late 7- and 8-day-old embryonic brain stem preparations. 5. In the maps for the late 7- and 8-day-old embryonic brain stems, the fast signal response area seems to correspond to the dorsal motor nucleus of the vagus nerve and the slow response area to the nucleus tractus solitarii.

Action Potentials↗
PubMed2003

Clustering of neuronal inclusions in "dementia with neurofilament inclusions".

Dementia with neurofilament inclusions (DNI) is a new disorder characterized clinically by early-onset dementia and histologically by the presence of intraneural inclusions immunopositive for neurofilament antigens but lacking tau and alpha-synuclein reactivity. We studied the clustering patterns of the neurofilament inclusions (NI) in regions of the temporal lobe in three cases of DNI to determine whether they have the same spatial patterns as inclusions in the tauopathies and alpha-synucleinopathies. The NI exhibited a clustered distribution (mean size of clusters 400 microm, range 50-800 microm, SD 687.8) in 24/28 of the areas studied. In 22 of these areas, the clusters exhibited a regular distribution along the tissue parallel to the pia mater or alveus. In 3 cortical areas, there was evidence of a more complex pattern in which the NI clusters were aggregated into larger superclusters. In 6 cortical areas, the size of the clusters approximated to those of the cells of origin of the cortico-cortical pathways but in the remaining areas cluster size was smaller than 400 microm. Despite the unique molecular profile of the NI, their spatial patterns are similar to those shown by filamentous neuronal inclusions in the tauopathies and alpha-synucleinopathies.

Adult↗
PubMed2004

Spatial effects in discrete generation population models.

A framework is developed for constructing a large class of discrete generation, continuous space models of evolving single species populations and finding their bifurcating patterned spatial distributions. Our models involve, in separate stages, the spatial redistribution (through movement laws) and local regulation of the population; and the fundamental properties of these events in a homogeneous environment are found. Emphasis is placed on the interaction of migrating individuals with the existing population through conspecific attraction (or repulsion), as well as on random dispersion. The nature of the competition of these two effects in a linearized scenario is clarified. The bifurcation of stationary spatially patterned population distributions is studied, with special attention given to the role played by that competition.

Animals↗
PubMed1989

A novel spatial transcription pattern associated with the segmentation gene, giant, of Drosophila.

The segmentation gene, giant, is located in 3A1 within a cloned chromosome region surrounding the zeste locus. Rearrangement breakpoints associated with giant mutations were localized on the genomic clone map, and nearby transcription units were identified. One transcription unit is active during early embryogenesis and its transcripts are spatially localized from blastoderm into extended germband stages, consistent with expected expression patterns predicted by the 'gap' phenotype of giant mutants. Germ line transformation experiments using a 10-kb DNA fragment containing this transcription unit gave complete rescue of the abdominal giant defect but only partial correction of the head defect. The effect of mutations in three other gap loci, Kr, kni and hb, were also analyzed.

Alleles↗
PubMed2003

Traveling stripes on the skin of a mutant mouse.

In the course of animal development, complex structures form autonomously from the apparently shapeless egg. How cells can produce spatial patterns that are much larger than each cell is one of the key issues in developmental biology. It has been suggested that spatial patterns in animals form through the same principles by which dispatched structures are formed in the nonbiological system. However, because of the complexity of biological systems, molecular details of such phenomena have been rarely clarified. In this article, we introduce an example of a pattern-forming phenomenon that occurs in the skin of mutant mice. The mutant mouse has a defect in splicing of the Foxn1 (Whn or nude) gene, which terminates hair follicle development just after pigment begins to accumulate in the follicle. The immature follicles are rapidly discharged, and a new hair cycle resumes. Eventually, the skin color of the mouse appears to oscillate. The color oscillation is synchronous in juvenile mice, but the phase gradually shifts among skin regions to eventually form traveling, evenly spaced stripes. Although the time scale is quite different, the pattern change in the mutant mouse shares characteristics with the nonlinear waves generated on excitable media, such as the Belousov-Zhabotinskii reaction, suggesting that a common principle underlies the wave pattern formation. Molecular details that underlie the phenomenon can be conjectured from recent molecular studies.

Age Factors↗
PubMed1996

Monitoring the temporal and spatial activation pattern of astrocytes in focal cerebral ischemia using in situ hybridization to GFAP mRNA: comparison with sgp-2 and hsp70 mRNA and the effect of glutamate receptor antagonists.

We investigated the temporo-spatial expression of astrocyte glial fibrillary acidic protein (gfap) and sulfated glycoprotein 2 (sgp-2) mRNAs in comparison to 70-kDa heat shock protein (hsp70) mRNA by in situ hybridisation in rats subjected to permanent occlusion of the middle cerebral artery (MCA). Gfap mRNA started to increase in the cingulate cortex of the lesioned hemisphere 6 h after MCA occlusion and gradually spread over the lateral part of the ipsilateral cortex and the striatum from 12 h to 3 days, peaking at 3 days after MCA occlusion. Gfap mRNA also increased in the contralateral cingulate cortex and corpus callosum at 12 and 24 h. Hsp70 mRNA increased markedly in the ipsilateral cortex adjacent to the ischemic lesion, and slightly within the lesion area from 3 to 24 h and disappeared after 3 days. By 7 days, gfap and sgp-2 mRNAs were increased markedly in the peri-infarct area, and in the ipsilateral thalamus parallel with the delayed neuronal damage, whereas the widespread increase of gfap mRNA in the ipsilateral hemisphere declined. Post-occlusion treatment with the glutamate receptor antagonists MK-801 and NBQX slightly attenuate the induction of gfap but did not qualitatively affect the topical expression pattern. Within the cingulate cortex MK-801 treatment resulted in a significant decrease of the signal intensity at all survival times, reflecting most likely an attenuation of lesion-induced spreading depression like depolarization waves by MK-801. The area of hsp70 expression was reduced by both MK-801 and NBQX, most likely reflecting the decrease of the lesion area by both treatment regimens. Our study thus revealed an early and widespread increase of gfap mRNA in the non-ischemic area including the contralateral hemisphere starting between 3 and 6 h, and a delayed circumscribed expression in the peri-infarct border zone after 1 week. Comparison with the expression of hsp70 mRNA suggests that the absence of an early gfap mRNA induction in the peri-lesion zone reflects an impairment of astrocytic function which may be of importance for infarct growth during the early evolution of the pathological process.

Animals↗
PubMed2003

Stereologic characterization and spatial distribution patterns of Betz cells in the human primary motor cortex.

Betz cells are giant motoneurons located in layer Vb of the primate primary motor cortex. We conducted stereological analyses of Betz cells and neighboring pyramidal cells from the brains of six neurologically normal elderly humans to determine their volume, total number, and spatial distribution, and to relate these data to functional localization. The distribution of cellular volumes exhibits a bimodal pattern, delineating two different subpopulations. Betz cell volumes follow a mediolateral gradient, the largest Betz cells being located on the most medial part of the motor cortex. Additionally, the shape of Betz cells varies between the rostral and caudal parts of the primary motor cortex, supporting the notion that there are anatomically distinct zones in primary motor cortex. The total number of Betz cells per hemisphere accounts for about one-tenth of the total number of pyramidal cells in layer Vb. Analysis of spatial distribution using Voronoi tessellation revealed maximal clustering of Betz cells in a zone situated two-thirds from the midline along the mediolateral axis of the primary motor cortex. These data suggest that Betz cells have a discrete subregional distribution that may correspond to certain aspects of the functional parcellation of area 4. These results may offer a histological correlate of functional imaging studies and are relevant in the context of neurodegenerative diseases such as amyotrophic lateral sclerosis, progressive supranuclear palsy, and Guamanian amyotrophic lateral sclerosis/Parkinsonism-dementia, and in studies of normal brain aging.

Aged↗
PubMed1987

The organization of mesodermal pattern in Xenopus laevis: experiments using a Xenopus mesoderm-inducing factor.

In this paper, we study the mechanism by which a Xenopus cell line-derived mesoderm-inducing factor (MIF) might establish the spatial pattern of cellular differentiation in the mesoderm. The effects of the factor on competent animal pole tissue are consistent with it being identical to the natural mesoderm-inducing factor. The signal can only act on those membrane domains of the animal pole that face the blastocoel, but it can be stably recorded there, such that axial mesoderm is formed, after 15 min exposure or less. This exposure can end some hours, or several cell cycles, before the onset of RNA synthesis yet nevertheless be fully effective, although competence to respond also extends well after the onset of transcription. Exposure of the entire blastocoel lining of intact embryos to MIF causes a synchronous and sudden transformation of the behaviour and adhesive properties of all inner animal cap cells. This transformation mimics and is contemporaneous with the involution behaviour of normal mesoderm in the early gastrula marginal zone. Although high concentrations of MIF totally disorganize gastrulation, lower concentrations permit gastrulation to proceed. However, the pattern of mesoderm in these embryos is disrupted and ectopic mesoderm is formed around the blastocoel remnant. When MIF is injected directly into blastomeres, rather than into the blastocoel, it has no effect. This suggests that the molecule is secreted from source cells and affects target cells through an extracellular receptor. Finally, we show that small pieces of animal pole tissue recently exposed to MIF go on to produce morphogenetic signals perhaps distinct from MIF. We discuss the role of these signals in establishing and modifying the spatial pattern of cellular differentiation in the mesoderm of Xenopus.

Animals↗
PubMed2002

Spatial analysis of rabies cases in foxes in Hungary between 1990 and 2001: a preliminary report.

In this paper we present the methodology and some preliminary results of the spatial analysis of rabies positive fox cases diagnosed in Hungary between 1990 and 2001. A database has been built based on the data provided by the Animal Health and Food Control Department of the Ministry of Agriculture, of all registered positive cases, specifying the date, location and affected species. We have developed a Geographical Information System for the spatial analysis. The aim of the study is to analyse the spatial patterns of subsequent rabies cases. Beyond the well-documented seasonality of the cases we want to find out whether they show regular spatial patterns and if yes what is their nature. Another important question is whether clustering of data can be observed and how stable or reoccurring these clusters are at a given location or area. The results might be important in a later stage of the eradication campaign when a strategy for the maintenance of large, rabies free areas should be developed.

Animal Diseases↗
PubMedDate not supplied

Genetic spatial clustering: significant implications for conservation of wild soybean (Glycine soja: Fabaceae).

Knowledge of spatial patterns of genetic variation within populations of wild relative species has significant implications with respect to sampling strategies for ex situ and in situ conservation. To study spatial genetic structure of wild soybean (Glycine soja Sieb. et Zucc.) at the fine scale, three natural populations in northern China were analyzed using inter-simple sequence repeat (ISSR) fingerprints for estimating kinship coefficients. A regression analysis of kinship coefficients against spatial distances revealed that individuals occurring close together tended to be more genetically related. The Sp statistic further indicated a comparable spatial pattern among the three wild soybean populations with similar Sp values (mean = 0.0734, varied from 0.0645 to 0.0943) detected across the three populations. Genetic patches were on average ca. 20 m in size, and the effective neighborhood sizes varied between 10 and 15 m. The spatial genetic structure evident in the wild soybean populations may be attributed to the restricted seed dispersal and predominant inbreeding mating system of this species. The detection of family structure in the populations of wild soybean has a significant implication for the effective conservation of the important genetic resources.

Breeding↗
PubMed2002

Utilization of a particle gun DNA introduction system for the analysis of cis-regulatory elements controlling the spatial expression pattern of the arylsulfatase gene (HpArs) in sea urchin embryos.

We applied a particle gun method to introduce DNA into fertilized sea urchin eggs for the analysis of cis-regulatory elements responsible for spatial gene expression during development. We introduced HpArs (sea urchin arylsulfatase gene) -GFP and HpArs-LacZfusion constructs into the fertilized eggs and obtained high expression levels of the fusion genes. Using this assay system, we demonstrated that a fragment of HpArs (-3,484 to +4,636) is sufficient for aboral ectoderm-specific expression, and that the region in the first intron from +406 to +1,993 contains the control elements responsible for the repression of the HpArs promoter activity in secondary mesenchyme cells.

Animals↗