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PubMed2005

Human archival tissues provide a valuable source for the analysis of spatial genome organization.

Sections from archival formalin-fixed, paraffin wax-embedded human tissues are a valuable source for the study of the nuclear architecture of specific tissue types in terms of the three-dimensional spatial positioning and architecture of chromosome territories and sub-chromosomal domains. Chromosome painting, centromeric, and locus-specific probes were hybridized to tissue microarrays prepared from formalin-fixed paraffin wax-embedded samples of pancreas and breast. The cell nuclei were analyzed using quantitative three-dimensional image microscopy. The results obtained from non-neoplastic pancreatic cells of randomly selected individuals indicated that the radial arrangement of the chromosome 8 territories as well as their shape (roundness) did not significantly differ between the individuals and were in accordance with assumptions of a probabilistic model for computer simulations. There were considerable differences between pancreatic tumor and non-neoplastic cells. In non-neoplastic ductal epithelium of the breast there was a larger, but insignificant, variability in the three-dimensional positioning of the centromere 17 and HER2 domains between individuals. In neoplastic epithelial breast cells, however, the distances between centromere and gene domains were, on average, smaller than in non-neoplastic cells. In conclusion, our results demonstrate the feasibility of studying the genome architecture in archival, formalin-fixed, paraffin wax-embedded human tissues, opening new directions in tumor research and cell classification.

Breast↗
PubMed1984

Functional analysis of spatially discriminative neurons in prefrontal cortex of rhesus monkey.

The present study addresses the question of whether prefrontal neurons that exhibit spatially selective patterns of discharge during the delay period in spatial delayed-response tasks code a mnemonic event. To examine this question, rhesus monkeys were trained to perform two variants of the classical spatial delayed-response task in both of which a delay intervened between cue presentation and response and the discriminative stimulus had to be recalled at the moment of response. They were also trained to perform two control tasks in which memory was not required since cues present throughout the delay informed the monkey of the correct response. Extracellular recordings were obtained from 192 neurons located in and around the principal sulcus of the frontal lobe during performance of both control and delay tasks. Comparison of the same neuron's activity across the 4 task conditions revealed a class of neuron that displayed spatially discriminative activity in the delay period only during delayed-response tasks and not during the same period of the control tasks. These neurons are candidates for units engaged in a central mnemonic process. Other neurons either exhibited similar activity in the delay period of control and delayed-response tasks or stronger discriminative behavior during this period in control tasks than in delayed response tasks. We conclude that delay-related spatially discriminative neurons found in the prefrontal association cortex are diversified and that certain of them play a specific role in mnemonic coding.

Animals↗
PubMed1994

An analysis of spatial navigation in prenatally protein malnourished rats.

Developing rats were either malnourished or adequately nourished during the prenatal period by feeding their dams diets of low (6% casein) or adequate (25% casein) protein content 5 weeks prior to mating and throughout pregnancy. All pups received adequate nutrition from the day of birth onwards. Male offspring were tested in one of two spatial navigation tests in the Morris water tank. In proximal-cue tests (postnatal days 16-20), the position of a platform, which provided a means to escape from swimming, was denoted by an obvious visual cue located directly on the platform. In distal-cue tests (postnatal days 20-27 and adult ages, days 70-71 and days 220-221), the escape platform was submerged below the surface of the water so that the rats were required to use extramaze visual cues to guide them to the platform. Neither proximal-cue nor distal-cue navigation was significantly impaired in the prenatally malnourished rats relative to controls, at any of the ages tested.

Animals↗
PubMed1989

A choice reaction time analysis of spatial frequency discrimination.

Simple reaction time to the onset of sinewave gratings was measured as a function of spatial frequency in two observers. These results are compared to the choice reaction time required for the observer to correctly discriminate the spatial frequency of two gratings flashed sequentially. Grating contrast was either 0.75 or 1.5 logarithmic units above the detection threshold for each spatial frequency tested. The spatial phase and contrast of the reference and test gratings were varied from trial to trial by small random amounts to eliminate fixed cues other than the difference frequency. The spatial frequency difference between the reference and test grating was either 0.125, 0.25 or 0.5 octave. As has been earlier reported, simple reaction time increases with increasing spatial frequency. Contrary to this, choice reaction time first increases (up to 4 c/deg) and then decreases. We derived the time required by the observer to make a spatial frequency judgment by subtracting the simple reaction time from the choice reaction time for a given spatial frequency and contrast. The maximum decision time occurs in the medium spatial frequency range (between 1 and 4 c/deg), at which frequencies we are most sensitive. The time required to make a correct spatial-frequency discrimination decreases with increasing spatial-frequency difference. The decision time is, however, fairly invariant over a large range of suprathreshold contrast levels. The findings suggest that the decision time for spatial frequency discrimination increases with the number of mechanisms involved.

Contrast Sensitivity↗
PubMed1990

Nonlinear analysis of spatial vision using first-and-second-order Volterra transfer functions measurement.

The harmonic input method of nonlinear system identification is modified to allow the Volterra series approach to be used for psychophysical investigation of various aspects of human pattern vision in the spatial frequency domain. While it is well known that only one modulation transfer function provides a complete characterization of a linear system, a number of multidimensional transfer functions are needed to identify a nonlinear system. We have shown, that so far as the contrast sensitivity to sine-wave gratings may be used for an empirical estimate of the first-order modulation transfer function of the human visual system, the contrast sensitivity to difference harmonics may be used as an empirical estimate of the second-order modulation transfer function. A difference harmonic arises from a mixture of two sine-wave gratings resulting from the nonlinearity of the visual system. Difference harmonic, experienced as some periodic beatlike structure, may still be observed if frequencies of the component gratings are higher than the maximum visual acuity. The visibility of the low-frequency beatlike pattern produced by pairs of sine-wave gratings, which themselves are of spatial frequencies too high to be resolved, could be accounted for either by a difference frequency distortion product (Burton, 1973) or by a special beat detector (Derrington & Badcock, 1985). We found that increasing the contrast of one component grating may be compensated for by reducing the contrast of the other component grating, the beatlike pattern being at threshold. This is exactly what would be expected if the beatlike pattern is detected because of the difference harmonics produced by nonlinearity of the visual system. We have determined contrast thresholds for the difference harmonics which occur between two unresolved different spatial frequencies. The contrast sensitivity function for difference harmonics was found to have a marked similarity both in the shape and position of peak sensitivity to the contrast sensitivity function for single sine-wave gratings. Another important characteristic of the contrast sensitivity function for difference harmonics is that it depends only on the frequency difference, delta f = f1 - f2, rather than on the value of either f1 or f2. All this indicates that a difference harmonic arises from local nonlinearities in the visual system. More specifically, the visual system may be represented as a cascade system, composed of a linear system with transfer function O (f) followed by a nonlinear element, r(.), without spatial spread in cascade with another linear system with transfer function P (f).(ABSTRACT TRUNCATED AT 400 WORDS)

Contrast Sensitivity↗
PubMed1983

A behavioural analysis of spatial localization following electrolytic, kainate- or colchicine-induced damage to the hippocampal formation in the rat.

This experiment examines the notion that in the rat the hippocampal formation is an essential structure in the neurological representation of spatial abilities. Spatial localization by rats with different types of hippocampal damage, including bilateral electrolytic lesions, unilateral and bilateral kainic acid-induced CA3-CA4 lesions, and unilateral and bilateral colchicine-induced dentate gyrus lesions, was compared with vehicle-injected and normal control groups in the Morris water task. The task required the rats to escape from cold water by finding a submerged and hidden platform located at a fixed place within the room. The start point was varied randomly from trial to trial and there were no local cues available to indicate the position of the hidden platform. After training, the platform was moved. Escape latencies and the initial swimming headings revealed that all lesion groups, except the unilateral CA3-damaged group, were impaired at finding the platform: the dentate-damaged rats exhibited the greatest deficit. When the platform was moved the control rats swam mainly in the part of the pool that had previously contained the platform and, on finding it in the new location, they showed a marked dishabituation of rearing. None of the bilateral lesion groups showed these effects.

Animals↗
PubMed2003

Delivery modes and neonatal EEG: spatial pattern analysis.

BACKGROUND: Animal studies indicate that postnatal adaptation and development of neonates could be different due to the birth method and that these effects may last throughout adulthood. STUDY DESIGN: We applied a spatio-temporal analysis to EEG recordings of a group of neonates to investigate the influence of a cesarean section on maturation and extrauterine adaptation of the brain. EEG were recorded at 2 h and at 24 h after delivery. SUBJECTS: A spectral analysis technique, the so-called Karhunen-Loeve (KL) method, was applied to EEG of 10 neonates from vaginal delivery and 17 from C-section to obtain the spatio-temporal eigenpatterns. RESULTS: Spatio-temporal analysis showed noticeable pattern differences between the two groups. Compared to the C-section, the vaginal delivered neonate's EEG recordings showed a significant increase of amplitude at Fp1 in the pattern 24 h after the delivery, but not 2 h after delivery. Dynamics in this spectral analyses were not significantly different between both groups 2 h after delivery, but the regional differences increased during the next day between both groups. CONCLUSIONS: This could come from the early insufficient complexity in C-section neonates. Global EEG complexity in C-section neonates fell short of that of vaginal delivered neonates 2 h after delivery. Many aspects of pattern change in C-section neonates followed the nature of vaginal delivered neonates. These could be considered as parts of a retarded transition of C-section neonates in the early adaptation, but some of the differences in global EEG pattern could not be explained in this way. Pattern analysis suggests that the neuronal activities of the neonatal brain are changing regionally concurrent with bi-hemispheric global dynamics. Moreover, the delivery modes could have an influence on the early postneonatal adaptation of the physiological activity in brain.

Adult↗
PubMed2005

Cobalt sorption onto anaerobic granular sludge: isotherm and spatial localization analysis.

This study investigated the effect of different feeding regimes on the cobalt sorption capacity of anaerobic granular sludge from a full-scale bioreactor treating paper mill wastewater. Adsorption experiments were done with non-fed granules in monometal (only Co) and competitive conditions (Co and Ni in equimolar concentrations). In order to modify the extracellular polymeric substances and sulfides content of the granules, the sludge was fed for 30 days with glucose (pH 7, 30 degrees C, organic loading rate=1.2 g glucose l(-1) day-1) in the presence (COD/SO4(2-)=1) or absence of sulfate. The partitioning of the sorbed cobalt between the exchangeable, carbonates, organic matter/sulfides and residual fractions was determined using a sequential extraction procedure (modified Tessier). Experimental equilibrium sorption data for cobalt were analysed by the Langmuir, Freundlich and Redlich-Peterson isotherm equations. The total Langmuir maximal sorption capacity of the sludge fed with glucose and sulfate loaded with cobalt alone displayed a significantly higher maximal cobalt sorption (Qmax =18.76 mg g-1 TSS) than the sludge fed with glucose alone (Qmax =13.21 mg g-1 TSS), essentially due to an increased sorption capacity of the exchangeable (30-107%) and organic/sulfides fractions (70-30%). Environmental scanning electron microscopy coupled with an energy dispersive X-ray analysis of granular cross-sections showed that mainly iron minerals (i.e. iron sulfides) were involved in the cobalt accumulation. Moreover, the sorbed cobalt was mainly located at the edge of the granules. The sorption characteristics of the exchangeable and carbonates fractions fitted well to the Redlich-Peterson model (intermediate multi-layer sorption behaviour), whereas the sorption characteristics of the organic matter/sulfides and residual fractions fitted well to the Langmuir model (monolayer sorption behaviour). The organic matter/sulfides fraction displayed the highest affinity for cobalt for the three sludge types investigated.

Adsorption↗
PubMed2005

In-depth analysis of spatial cognition in Williams syndrome: A critical assessment of the role of the LIMK1 gene.

The LIM kinase1 protein (LIMK1) is thought to be involved in neuronal development and brain function. However, its role in spatial cognition in individuals with Williams syndrome (WS) is currently ambiguous, with conflicting reports on the cognitive phenotypes of individuals who do not have classic WS but harbour partial deletions including LIMK1. Two families with partial WS deletions have been described with deficits in visuospatial cognition (Frangiskakis, J. M., Ewart, A. K., Morris, C. A., Mervis, C. B., Bertrand, & J., Robinson, et al. (1996). LIM-kinase 1 hemizygosity implicated in impaired visuospatial constructive cognition. Cell, 86, 59-69), in contrast to others with similar partial deletions who did not display spatial impairments (Tassabehji, M., Metcalfe, K., Karmiloff-Smith, A., Carette, M. J., Grant, J., & Dennis, N., et al. (1999). Williams syndrome: Use of chromosomal microdeletions as a tool to dissect cognitive and physical phenotypes. American Journal of Human Genetics, 64, 118-125). To determine the role of LIMK1 in the highly penetrant visuospatial deficits associated with classic WS, it is essential to investigate the discrepancies between the two studies. Previous research used a standardised task to measure spatial cognition, which may not pick up subtle impairments. We therefore undertook more extensive testing of the spatial cognition of two adults with partial genetic deletions in the WS critical region (LIMK1 and ELN only), who had not displayed spatial impairments in the previous study, and compared them to two high-functioning adults with WS matched on verbal ability. All participants completed a broad battery of 16 perceptual and constructive spatial tests, and the clear-cut spatial difficulties observed in the WS group were not found in the partial deletion group. These findings rule out the claim that the deletion of one copy of LIMK1 is alone sufficient to result in spatial impairment, but leave open the possibility that LIMK1 contributes to the WS cognitive deficits if deleted in combination with other genes within the WS deletion. We conclude that a deeper assessment of WS at the genetic level is required before the contribution of specific genes to phenotypic outcomes can be fully understood.

Adult↗
PubMedDate not supplied

Immuocytochemical analysis of spatial organization of photoreceptors and amacrine and ganglion cells in the tiger salamander retina.

In the present study, using double- or triple-label immunocytochemistry in conjunction with confocal microscopy, we aimed to examine the population and distribution of photoreceptors, GABAergic and glycinergic amacrine cells, and ganglion cells, which are basic but important parameters for studying the structure-function relationship of the salamander retina. We found that the outer nuclear layer (ONL) contained 82,019 +/- 3203 photoreceptors, of which 52% were rods and 48% were cones. The density of photoreceptors peaked at approximately 8000 cells/mm2 in the ventral and dropped to approximately 4000 cells/mm2 in the dorsal retina. In addition, the rod/cone ratio was less than 1 in the central retina but larger than I in the periphery. Moreover, in the proximal region of the inner nuclear layer (INL3), the total number of cells was 50,576 +/- 8400. GABAergic and glycinergic amacrine cells made up approximately 78% of all cells in this layer, including 43% GABAergic, 32% glycinergic, and 3% GABA/glycine colocalized amacrine cells. The density of these amacrine cells was approximately 6500 cells/mm2 in the ventral and approximately 3200 cells/mm2 in the dorsal area. The ratio of GABAergic to glycinergic amacrine cells was larger than 1. Furthermore, in the ganglion cell layer (GCL), among a total of 36,007 +/- 2010 cells, ganglion cells accounted for 65.7 +/- 1.5% of the total cells, whereas displaced GABAergic and glycinergic amacrine cells comprised about 4% of the cells in this layer. The ganglion cell density was approximately 1800 cells/mm2 in the ventral and approximately 600 cells/mm2 in the dorsal retina. Our data demonstrate that all three major cell types are not uniformly distributed across the salamander retina. Instead, they exhibit a higher density in the ventral than in the dorsal retina and their spatial arrangement is associated with the retinal topography. These findings provide a basic anatomical reference for the electrophysiological study of this species.

Amacrine Cells↗