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PubMed1997

Configural processing in memory retrieval: multiple cues and ensemble representations.

When retrieving information from memory, a number of contextual cues may interact to determine which ideas will be easily accessible. Even the simplest case in which joint cue action obtains (two cues) is very revealing of the principles of memory access and representation of compounds. Mechanisms by which dual cues interact to constrain retrieval from episodic memory are considered. A holistic mechanism of cue integration is contrasted with two nonholistic mechanisms: a multiplicative or intersection mechanism and an independent-contributions mechanism. Holistic- and intersection-cuing mechanisms are consistent with different variants of compound cue models of priming. The independent cuing mechanism is consistent with spreading activation models of priming. Data from four experiments which examined dual-cued recognition of items from (newly learned) triples demonstrated strongly configural, holistic, action of dual cues. The two cues and test item must form an encoded compound to yield cuing advantages. Two independent cues to the test item are ineffective if the two cues and test were not learned together as a triple; one valid and one invalid cue are also ineffective. This is so despite the availability of pairwise information for each cue-test relation, and despite the fact that these cues are effective when operating alone. A compound cue model which predicts precisely this surprising pattern of priming is developed. The compound cue model also predicts previously obtained configural priming of associative judgments, as well as the bias priming generally observed in item recognition and similar paradigms.

Analysis of Variance↗

PubMed1997

Actin filament bundles in cortical fiber cells of the rat lens.

The distribution and organization of actin filament bundles were studied in cortical fiber cells of rat lenses at various ages (3 days to 2.5 months old), using thin-section electron microscopy, immunocytochemistry and immunoblotting. Electron microscopy showed that actin bundles were regularly found along cortical fiber cell membranes of the lens at all ages studied. The actin bundles were commonly arranged in three distinct units, one bundle in each fiber cell, located at the intersections where three hexagonal fiber cells meet as seen in cross sections. These actin bundles were approximately 150 nm in diameter and were composed of 7-nm small filaments. They were aligned parallel to the long axis of fiber cells as judged by both cross and longitudinal sections. The outside border of each bundle was always surrounded by a zone of 10-nm intermediate filaments which have the same orientation as that of the actin bundles. In longitudinal sections, elongated actin bundles were always parallel to the cell membranes. A number of individual actin bundles sometimes were found to form a chain with periodic short intervals. In addition, actin bundles were frequently associated with adherens junctions near the intersections and other regions of fiber cell membranes. By immunoelectron microscopy, we demonstrated that these filament bundles indeed contained actins. By rhodamine-phalloidin labelling, we found that labeled actin bundles appeared as large, distinct dots at the corners of hexagonal fiber cells in all ages studied. In addition, non-bundle F-actins were labeled preferentially along the cell membranes of the short sides of hexagonal fiber cells. This resulted in a unique zigzag pattern of actin labeling commonly seen in the cortical fiber cells of a mature rat lens. Finally, we showed that alpha-actinin was associated with the actin bundles in the fiber cells by immunofluorescent double labeling and immunoblotting. It is suggested that this unique arrangement of actin bundles in fiber cells may provide a stabilizing structure for forming a sharp angle at each corner of fiber cells, thereby the hexagonal shape of the cells can be maintained.

Actinin↗

PubMed1999

Numerical Model of Electrokinetic Flow for Capillary Electrophoresis.

A numerical study is presented for the steady electrokinetic flow in intersecting channels in a T-shaped configuration. The electric potential and space charge density distribution along the capillary are obtained numerically by solving the nonlinear Poisson-Boltzmann equation for arbitrary electrokinetic radius and arbitrary surface potential. The velocity and pressure profiles are obtained by solving a modified Navier-Stokes equation using a primitive variable algorithm. A systematic study of flow in T-shaped intersecting channels showed that the hydrodynamic effect is an important factor that influences fluid leakage out of a channel where the electric potential is left floating. It was found that the flow in each channel can be controlled by applying a potential at each reservoir connected to the end of a channel. Copyright 1999 Academic Press.

Journal Article↗

PubMed1998

Automated Processing of Two-Dimensional Correlation Spectra

An automated scheme is described which locates the centers of cross peaks in two-dimensional correlation spectra, even under conditions of severe overlap. Double-quantum-filtered correlation (DQ-COSY) spectra have been investigated, but the method is also applicable to TOCSY and NOESY spectra. The search criterion is the intrinsic symmetry (or antisymmetry) of cross-peak multiplets. An initial global search provides the preliminary information to build up a two-dimensional "chemical shift grid." All genuine cross peaks must be centered at intersections of this grid, a fact that reduces the extent of the subsequent search program enormously. The program recognizes cross peaks by examining the symmetry of signals in a test zone centered at a grid intersection. This "symmetry filter" employs a "lowest value algorithm" to discriminate against overlapping responses from adjacent multiplets. A progressive multiplet subtraction scheme provides further suppression of overlap effects. The processed two-dimensional correlation spectrum represents cross peaks as points at the chemical shift coordinates, with some indication of their relative intensities. Alternatively, the information is presented in the form of a correlation table. The authenticity of a given cross peak is judged by a set of "confidence criteria" expressed as numerical parameters. Experimental results are presented for the 400-MHz double-quantum-filtered COSY spectrum of 4-androsten-3,17-dione, a case where there is severe overlap. Copyright 1998 Academic Press.

Journal Article↗

PubMed1995

A computerized method for determination of microvascular density.

Currently accepted stereological methods for vascular density measurements involve manual counting of labeled vessels with a grid image overlay and determination of vessel-grid intersections. This method both is tedious and may be prone to error; therefore, our laboratory has developed a method for computer-automated determination of microvascular density using digital image processing techniques. An image of the microvasculature is acquired using computer videomicroscopy. The image is processed in three general steps, involving (1) background correction, (2) thresholding of the gray level image to create a binary image, and (3) processing of the binary image using erosion, dilation, and skeletonization algorithms. Testing of this procedure was performed on 328 typical images of skeletal muscle tissue sections taken from the hindlimb of Sprague-Dawley rats and quantitated by both traditional measures and our new computer method. Results from this comparison reveal that the automated vessel counting is highly correlated (r2 = 0.71) and decreased analysis time from 15 min/image to 30 sec/image when compared with manual counting methods. Our computer-based method also appears to be superior to the traditional method due to the unbiased and nonsubjective nature of determining vessel-grid intersections.

Animals↗

PubMed1995

Validation of collagenous protein synthesis as an index for angiogenesis with the use of morphological methods.

A method providing a biochemical index for the evaluation of promoters or inhibitors of angiogenesis in the chick chorioallantoic membrane (CAM) is here described and validated. This method is based on the determination of collagenous protein synthesis which takes place during new vessel formation. Validation was done by comparing collagenous protein synthesis to morphological methods of determining vascular density either by counting the number of vessels intersecting three concentric rings or by computer-assisted image analysis. Five compounds which promote or inhibit angiogenesis in the CAM were used for this purpose. The protein kinase C activator 4-beta-phorbol 12-myristate 13-acetate and alpha-thrombin increased collagenous protein synthesis and these results correlated with those obtained by using the two morphological methods mentioned above. Similarly, the inhibitors of angiogenesis, Ro318220, tricyclodecan-9-yl xanthate (D609), and 8,9-dihydroxy-7-methyl-benzo[b]quinolizinium bromide (GPA1734), reduced collagenous protein synthesis and vascular density (determined by image analysis or by counting the number of vessels intersecting three concentric rings) to a comparable degree. These results indicate that collagenous protein synthesis can be used as a reliable, reproducible, and unbiased index of angiogenesis in the chick chorioallantoic membrane.

2H-Benzo(a)quinolizin-2-ol, 2-Ethyl-1,3,4,6,7,11b-↗

PubMed1999

Second order components of moving plaids activate extrastriate cortex: a positron emission tomography study.

A moving plaid is a composite pattern produced by superimposing two sinusoidal gratings which differ in orientation and motion direction. The perceived drift direction of a plaid appears to be determined partly by a binocular mechanism, which follows intersection of constraint rules (Burke and Wenderoth, 1993b), and partly by a monocular mechanism, which tracks the dark and bright intersects of the plaid, the contrast envelopes. The first neurones that respond to plaids as patterns rather than component gratings are found in area V5, also known as MT, which is exclusively binocular. Therefore, the psychophysical evidence suggesting that the contrast envelope tracking mechanism is monocular is surprising but has been obtained consistently. We aimed to localize the contrast envelope tracking mechanism by undertaking a positron emission tomography (PET) activation experiment in which the subjects were presented with alternating plaid components during the control scan and with the moving plaid resulting from the superposition of these components as the activation scan. The results showed differential activation in area V3. Recent results from macaque single cell recordings have also demonstrated increased sensitivity to moving plaid stimuli compared to the plaid component gratings in V3 neurones.

Adult↗

PubMed2002

Automated anatomical labeling of activations in SPM using a macroscopic anatomical parcellation of the MNI MRI single-subject brain.

An anatomical parcellation of the spatially normalized single-subject high-resolution T1 volume provided by the Montreal Neurological Institute (MNI) (D. L. Collins et al., 1998, Trans. Med. Imag. 17, 463-468) was performed. The MNI single-subject main sulci were first delineated and further used as landmarks for the 3D definition of 45 anatomical volumes of interest (AVOI) in each hemisphere. This procedure was performed using a dedicated software which allowed a 3D following of the sulci course on the edited brain. Regions of interest were then drawn manually with the same software every 2 mm on the axial slices of the high-resolution MNI single subject. The 90 AVOI were reconstructed and assigned a label. Using this parcellation method, three procedures to perform the automated anatomical labeling of functional studies are proposed: (1) labeling of an extremum defined by a set of coordinates, (2) percentage of voxels belonging to each of the AVOI intersected by a sphere centered by a set of coordinates, and (3) percentage of voxels belonging to each of the AVOI intersected by an activated cluster. An interface with the Statistical Parametric Mapping package (SPM, J. Ashburner and K. J. Friston, 1999, Hum. Brain Mapp. 7, 254-266) is provided as a freeware to researchers of the neuroimaging community. We believe that this tool is an improvement for the macroscopical labeling of activated area compared to labeling assessed using the Talairach atlas brain in which deformations are well known. However, this tool does not alleviate the need for more sophisticated labeling strategies based on anatomical or cytoarchitectonic probabilistic maps.

Brain↗

PubMed2005

A novel phantom-less spatial and temporal ultrasound calibration method.

This paper introduces a novel method for ultrasound calibration for both spatial and temporal parameters. The main advantage of this method is that it does not require a phantom, which is usually expensive to fabricate. Furthermore, the method does not require extensive image processing. For spatial calibration, we solve an optimization problem established by a set of equations that relate the orientations of a line (i.e., calibration pointer) to the intersection points appearing in the ultrasound image. The line orientation is provided through calibration of both ends of the calibration pointer. Temporal calibration is achieved by processing of the captured pointer orientations and the corresponding image positions of intersection along with the timing information. The effectiveness of the unified method for both spatial and temporal calibration is apparent from the quality of the 3D reconstructions of a known object.

Algorithms↗

PubMed1991

Coverage and the design of striate cortex.

Hubel and Wiesel (1977) suggested that ocular dominance and orientation columns in the macaque monkey striate cortex might be bands of uniform width that intersected orthogonally. They pointed out that if this were the case, there would be an equal allocation of cells of different orientation preference to each eye and to each point in visual space. However, orientation and ocular dominance columns have a more complex structural organization than is implied by this model: for example, iso-orientation domains do not intersect ocular dominance stripes at right angles and the two columnar systems have different periodicities. This raises the question as to how well the striate cortex manages to allocate equal numbers of neurons of different orientation preference to each eye and to each region of visual space, a factor referred to here as coverage. This paper defines a measure of uniformity of coverage, c', and investigates its dependence on several different parameters of columnar organisation. Calculations were done first using a simplified one-dimensional model of orientation and ocular dominance columns and were then repeated using more realistic two-dimensional models, generated with the algorithms described in the preceding paper (Swindale 1991). Factors investigated include the relative periodicities of the two columnar systems, the size of the cortical point image, the width of orientation tuning curves, whether columns are spatially anisotropic or not, and the role of the structural relationships between columns described by Blasdel and Salama (1986). The results demonstrate that coverage is most uniform when orientation hypercolumns are about half the size of ocular dominance hypercolumns. Coverage is most uneven when the hypercolumns are the same size, unless they are related in the way described by Blasdel and Salama, in which case coverage gets only slightly worse as the size ratio (ori/od) increases above 0.5. The minimum diameter of cortical point image that ensures reasonably uniform coverage is about twice the size of an ocular dominance hypercolumn i.e. about 1.5-2.0 mm.

Animals↗

PubMed1988

Adherens junctions in the ocular lens of various species: ultrastructural analysis with an improved fixation.

The ultrastructure and distribution of adherens junctions in the intact adult lens of human, chicken, dove, rat, and rainbow trout were studied with thin-section electron microscopy, using an improved fixation containing a mixture of glutaraldehyde, lysine, and tannic acid. The nature of adherens junctions in the fiber-cells of the lens was also verified by immunofluorescence and rhodamine-phalloidin labelings for vinculin and actin. Electron microscopy revealed that adherens junctions of the lens were different ultrastructurally from the desmosomes found only between the lateral epithelial cells of the lens. The adherens junctions had the same structural characteristics as the zonulae adherentes, except that they were macular contacts, not belts. However, cross bridges were evident within the interspace of the junctions. Adherens junctions were located between the fiber-cells, between the epithelial cells and fiber-cells, and between the epithelial cells. They had a characteristic distribution in the "intersections" where three hexagonal fiber-cells met, as seen in cross-sections in all species studied. In addition, adherens junctions and associated actin were found distributed randomly along the entire cell membranes of both wide and narrow sides of cortical fiber-cells in the human, chicken, and dove lenses which have good accomodating capability. However, in the poorly-accomodating lenses of rat and fish, these junctions were seen predominantly on the narrow sides and at the regions of the wide sides that were very close to the "intersections". It is suggested that adherens junctions and associated actin microfilaments are involved in stabilizing the structural integrity of lens cells during accomodation and in preserving a specific lens shape.

Actins↗

PubMed1992

Senile plaques, amyloid beta-protein, and acetylcholinesterase fibres: laminar distributions in Alzheimer's disease striate cortex.

The laminar distributions of senile plaques and amyloid beta-protein (A beta P) within the striate cortex of patients with Alzheimer's disease (AD) were studied with enhanced Bielschowsky (roughly equivalent to the Campbell technique) and immunohistochemical methods. The laminar distribution of acetylcholinesterase (AChE) fibres within the striate cortex of both AD patients and control patients was studied with an enzyme histochemical method. Quantification of Bielschowsky-stained plaque numbers along intersect lines drawn parallel to laminar boundaries revealed a significant aggregation of plaques at the interface of layers IVc and V. Lines drawn through layer VI intersected significantly fewer plaques than lines through other laminae. Immunoperoxidase staining for A beta P revealed a similar distribution of senile plaques, and addition, prominent, diffuse deposits of A beta P within layers I and IVc. AChE fibres were markedly depleted in the striate cortex of AD cases. In control cases, AChE fibres were, like A beta P immunoreactivity, concentrated within layer I and IVc. The results indicate that enhanced silver methods may not reveal the complete distribution of A beta P. The codistribution of A beta P-immunoreactive diffuse amyloid deposits and AChE fibres to the same cortical laminae is consistent with the possibility that these deposits may be formed from degenerating cholinergic elements. The formation of a line of senile plaques at the interface of two cortical laminae within the striate cortex, in an anatomically analogous situation to a similar line of plaques within the dentate gyrus, suggests that formation of well-defined plaques may be accelerated by the interaction of specific neuronal systems.

Acetylcholinesterase↗

PubMed1991

Freeze-fracture observations on normal and abnormal human perineurial tight junctions: alterations in diabetic polyneuropathy.

Perineurial cells in the human sural nerve possess tight junctions which in freeze-fracture replicas are seen to be composed of networks of branching and anastomosing P face strands and E face grooves. Isolated circular tight junctions (maculae occludentes) may represent attachment devices between adjacent perineurial lamellae. At the overlapping margins of the cells, a belt-like tight junction (zonula occludens) encircles the cells and is believed to comprise a paracellular diffusion barrier. As the permeability of the perineurium has been found to be altered in diabetic polyneuropathy, the zonulae occludentes have been studied. In freeze-fracture replicas from cases of diabetic polyneuropathy a mixed population of structurally normal and abnormal junctions was observed. In some, the strands were abnormally curved with reduced numbers of intersections, the intervening plasma membrane displaying prominent P face concavities and E face convexities. At other sites, the junctions were severely disorganized and represented by fragmented and isolated strands with few intersections and numerous free ends. These abnormalities resemble changes that have been produced experimentally in epithelial tight junctions by osmotic damage. The possibility is considered that similar mechanisms could result in the alterations of the perineurial tight junctions in diabetic polyneuropathy and account for its impaired permeability barrier properties.

Adult↗

PubMed1996

Modification of the stapled functional end-to-end anastomosis for ileostomy closure.

The use of stapling devices simplifies ileostomy closure; however, the original functional end-to-end anastomotic technique creates intersecting staple lines, generally causing disruption of the anastomosis at the intersections. Therefore, we modified the stapling technique to prevent the two staple lines from crossing. After the everted ileostomy spout is turned back, a stapled side-to-side anastomosis is made. Everting traction sutures are then placed around the ileostomy orifice prior to closure with a linear stapler, thus ensuring that this staple line does not cross the V-shaped staple line of the intestinal anastomosis. This modified technique was employed in the treatment of 20 patients, none of whom developed any signs of anastomotic leakage or intestinal obstruction.

Anastomosis, Surgical↗

PubMed1988

Prescheduling graphic displays for optimal cancer therapies to reveal possible tumor regression or stabilization.

The paper describes an adaptive control approach to the problem of the treatment of solid tumors. The evolution with time t of the state of a tumor is modelled by a two-compartment system, governed by two differential equations forming an autonomous system under therapy control u, (formula; see text) where y1 and y2 are the number of proliferating and nonproliferating cells, respectively. The output is analyzed in the phase plane y1y2. The control problem is that of restricting the tumor state to a predetermined region of the plane by selecting a suitable change in therapy control u, e.g., modality and dosage, when the state solution intersects the boundary of this region and the ratio y1/y2 of proliferating to nonproliferating cells is displayed together with an elapsed time scale. Then, consequent selection of a suitable therapeutic sequence may be assisted by the use of a data base as part of an expert system. The process is repeated at each intersection of the prescribed boundary. Such sequences may lead to stabilization of the system through the appearance on a computer display screen of a stable equilibrium point or a limit cycle.

Cell Division↗

PubMed1980

Voltage-current relation and K+ transport in tobacco hornworm (Manduca sexta) midgut.

Voltage-current curves for the isolated midgut of the tobacco hornworm were determined by transient and steady voltage clamping over the range of 200 to -200 mV. Over this range the transient method yields a linear relation while the steady method usually yields a curve consisting of two lines of differing slope which intersect at zero voltage. The difference between the results of the methods is due to a slow decline in total conductance which accompanies steady voltage clamping. Holding the midgut at short circuit increases the total conductance of the tissue in a manner consistent with increasing shunt conductance; this effect was seen in both diet-reared and leaf-reared animals. When potassium transport is inhibited by substitution of choline or sodium for potassium in bathing solution the total conductance decreases and the voltage-current curve intersects the normal curve in the hyperpolarizing region. Applying a simple equivalent circuit analysis to the results from partial or total potassium replacement suggests that the electromotive force of the potassium transport system is of the order of 140-190 mV. The conductance decrease during inhibition of potassium transport by transient anoxia is of similar magnitude, suggesting that a major effect of metabolic inhibition is to decrease the active conductance of the potassium transport pathway.

Animals↗

PubMed1982

Occluding junctions of the Necturus gallbladder.

The paracellular conducting pathway of the Necturus gallbladder was studied with electrophysiological and electromicroscopic methods. The first one consists of the passage of short (5 msec) and small (32 microA cm-2) current pulses associated with a voltage scanning of the plane of the epithelium at the apical surface with a microelectrode to detect the regions where current flows. The procedure shows that (a) the conductance is evenly distributed along the intercellular regions along the intercellular spaces of the cells where occluding junctions are located; (b) the field above the occluding junctions has the shape of a bell, so that the junction can be sensed at 1-2 micron from the region where the intercellular space is visualized by light microscopy; (c) the intersections between three cells, in spite of having 3 half-junctions contributing (instead of two), do not have a higher conductance than the rest of the occluding junction. Scanning electron microscopy shows that (a) cells are densely covered by microvilli which interdigitate above the region of the occluding junctions, and (b) are covered by a surface coat. With transmission electron microscopy, (a) the opening of the occluding junctions at the apical border appears irregular, and most of them oblique; (b) in the last microns the actual mouth of the junction may deviate from the course of the interspace. Freeze-fracture replicas indicate that (a) the occluding junction has a uniform width and little variations in the number of strands around the cell, except (b) at intersections between 3 cells where both, its width and the number of strands, increase toward the basal region.

Animals↗

PubMed2000

"Dog ear" formation after double-stapled low anterior resection as a risk factor for anastomotic disruption.

PURPOSE: The aim of this study was to investigate the possible deleterious effect of the lateral intersecting margins (so-called dog ears) on anastomotic disruption after experimentally performed double-stapled anastomoses. METHODS: Two groups of double-stapled side-to-end anastomoses were performed using pig small intestines. Group A consisted of 35 circular anastomoses and Group B of 32 double-stapled anastomoses with a bilateral dog ear. In both groups bursting pressures were tested using a water-filled, pressure-controlled automatic pumping system (Hamou Endomat), and special attention was paid to the location(s) in the anastomoses were the disruption(s) occurred. RESULTS: In Group A bursting pressures were significantly higher than in Group B (median pressure, 90 vs. 60 mmHg; P < 0.001, Mann-Whitney U test). Remarkably, in Group B in 13 cases (42 percent) the first disruption occurred at the corner of a dog ear. CONCLUSIONS: We conclude that the lateral intersections of double-stapled anastomoses are a structural weak spot and that the currently most often applied double-stapled anastomosis is a less effective type of anastomosis than a complete circular one. Resolving this technical problem might help to reduce the number of anastomotic disruptions after low anterior resections.

Anastomosis, Surgical↗