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At least 19 recordsLinked to original sources

PubMed1995

Effect of antibodies to membrane skeletal proteins on the shape of erythrocytes and their ability to respond to shape-modulating agents. Important role of 4.1 protein in the determination/maintenance of the discoid shape of erythrocytes.

Monospecific anti-spectrin, anti-4.1 protein, anti-ankyrin, and anti-band 3 cytoplasmic domain antibodies were individually internalized in human erythrocytes by hypotonic lysis in the presence of 2 mM Mg-ATP. The concentrations of the polyclonal antibodies, or their Fab fragments, varied from 0.5 to 4.0 mg/ml. After resealing and glutaraldehyde fixation, the shape of the erythrocytes was examined by phase-contrast or scanning electron microscopy. The antibody-internalized cells were also treated, prior to fixation, with dinitrophenol, chlorpromazine (membrane-penetrable crenation- and cup-forming agents, respectively), or serum albumin (membrane nonpenetrating cup-forming agent). Anti-spectrin antibodies produced a cup shape in the cells at low concentrations (0.5 mg/ml), with a few cells showing multiple cavities. The proportion of the latter increased with increasing concentration of the antibody. The Fab fragments of the antibody were without any effect on the shape. At lower concentrations of anti-4.1 antibodies (0.5 and 1 mg/ml), crenations were observed in antibody-internalized cells. At higher antibody concentrations, the cells underwent sphering. These looked dense under the phase-contrast microscope and often were found to project vesicles from their surface via long stalks. These were generally absent on cells when viewed under the electron microscope, probably due to their breakage during processing. The Fab fragments of the anti-4.1, at equimolar concentrations, were as effective as the intact antibody in altering the cell shape. Anti-ankyrin antibodies or the Fab fragments produced no effect on the shape of the cell. The intact anti-band 3 cytoplasmic domain antibodies, but not their Fab fragments, produced cups at low concentrations and multiple cavities at higher concentrations and multiple cavities at higher concentrations. The anti-spectrin- and anti-band 3 cytoplasmic domain-internalized cells resisted the shape-modulating actions of dinitrophenol, chlorpromazine, and serum albumin. The anti-4.1 antibody-internalized cells also did not respond to dinitrophenol and serum albumin; however, they were converted to contracted cups in the presence of high concentration of chlorpromazine. The cells in which anti-ankyrin antibodies were internalized responded to the actions of the shape-changing agents similarly to normal cells. The results show that the 4.1 protein plays an important role in the determination or maintenance of the normal shape of the erythrocyte and that the cells possessing antibody-modified membrane skeleton do not respond to amphiphilic ions in the manner that normal cells do.

Anion Exchange Protein 1, Erythrocyte↗

PubMed2005

Generalization of convex shapes by bees: what are shapes made of?

For about 70 years, bees were assumed not to possess the capacity to discriminate among convex shapes, such as a disc, a square or a triangle, based on results of early studies conducted by presenting shapes on horizontal planes. Using shapes presented on a vertical plane, we recently demonstrated that bees do discriminate among a variety of convex shapes. Several findings, summarized here, provide indirect evidence that discrimination is based on a cue located at the shapes' boundaries. In the present study, we test this hypothesis directly in two different ways. (1) Three groups of bees are each trained with a different pair of convex shapes, one positive (rewarding), the other not (negative), producing colour contrast, luminance contrast or motion contrast against the background. The trained bees are then offered a choice between pairs of stimuli whose shapes are identical to those of the training shapes, but whose contrast against the background is varied by changing the pattern, the colour or the luminance of the areas. The results show that bees discriminate between the pairs of novel shapes, i.e. they generalize the shapes among the different types of contrast, revealing that they use a particular cue extracted from the positive shape. The bees' choices between a stimulus that produces the correct contrast but has the wrong shape and one that possesses the correct shape but the wrong contrast show, in addition, that the relevant cue is not located within the area of the shape. (2) Bees trained with pairs of convex shapes are tested with the same pairs of shapes, but which lack the inner area, i.e. only the contours or fragments of the contours are presented in the tests. Bees are found to prefer the stimulus whose contours (or fragments of contours) agree with those of the positive training shape. Taken together, the results suggest that convex shapes are not represented by the form of their areas but rather by some cue located at their boundaries.

Animals↗

PubMed2002

Amygdala-hippocampal shape differences in schizophrenia: the application of 3D shape models to volumetric MR data.

Evidence suggests that some structural brain abnormalities in schizophrenia are neurodevelopmental in origin. There is also growing evidence to suggest that shape deformations in brain structure may reflect abnormalities in neurodevelopment. While many magnetic resonance (MR) imaging studies have investigated brain area and volume measures in schizophrenia, fewer have focused on shape deformations. In this MR study we used a 3D shape representation technique, based on spherical harmonic functions, to analyze left and right amygdala-hippocampus shapes in each of 15 patients with schizophrenia and 15 healthy controls matched for age, gender, handedness and parental socioeconomic status. Left/right asymmetry was also measured for both shape and volume differences. Additionally, shape and volume measurements were combined in a composite analysis. There were no differences between groups in overall volume or shape. Left/right amygdala-hippocampal asymmetry, however, was significantly larger in patients than controls for both relative volume and shape. The local brain regions responsible for the left/right asymmetry differences in patients with schizophrenia were in the tail of the hippocampus (including both the inferior aspect adjacent to parahippocampal gyrus and the superior aspect adjacent to the lateral geniculate nucleus and more anteriorly to the cerebral peduncles) and in portions of the amygdala body (including the anterior-superior aspect adjacent to the basal nucleus). Also, in patients, increased volumetric asymmetry tended to be correlated with increased left/right shape asymmetry. Furthermore, a combined analysis of volume and shape asymmetry resulted in improved differentiation between groups. Classification function analyses correctly classified 70% of cases using volume, 73.3% using shape, and 87% using combined volume and shape measures. These findings suggest that shape provides important new information toward characterizing the pathophysiology of schizophrenia, and that combining volume and shape measures provides improved group discrimination in studies investigating brain abnormalities in schizophrenia. An evaluation of shape deformations also suggests local abnormalities in the amygdala-hippocampal complex in schizophrenia.

Adult↗

PubMed2006

Bruch's membrane abnormalities in dome-shaped and mushroom-shaped choroidal melanomas.

INTRODUCTION: Mushroom-shaped choroidal melanoma is known to be associated with breaks in Bruch's membrane and is more likely to develop when Bruch's membrane is diseased. The study's goal is to determine if diseases causing breaks in Bruch's membrane predispose a choroidal melanoma to develop into a mushroom-shaped melanoma. MATERIALS AND METHODS: A retrospective review of cases of choroidal melanoma seen at our institution was carried out to determine if mushroom-shaped melanomas are more common than dome-shaped tumours in patients with macular abnormalities involving a loss of Bruch's membrane integrity. Forty-nine eyes of 48 patients were included in this retrospective study. A dome-shaped or mushroom-shaped configuration was assigned to each tumour. Macular degeneration, macular drusen, retinal pigment epithelial (RPE) stippling, macular oedema, choroidal neovascularisation (CNV), angioid streaks, disciform scars, lacquer cracks, and myopia greater than -3.00 D, were considered to constitute evidence of potential Bruch's membrane breaks and were determined in both eyes. A chi-square evaluation was used to compare the proportion of eyes with macular abnormalities in the 2 tumour configuration groups. RESULTS: The tumour was dome-shaped in 40 eyes (82%) and mushroom-shaped in 9 eyes (18%). Macular abnormalities, indicative of loss of Bruch's membrane integrity, were seen in 21 (53%) of 40 eyes with dome-shaped melanomas and 5 (56%) of 9 eyes with mushroom-shaped melanomas. The proportion of eyes with macular abnormalities was not statistically different between the dome-shaped and mushroom-shaped tumours, as assessed by chi-square analysis (P = 0.87). CONCLUSIONS: Bruch's membrane disease does not influence the differentiation of choroidal melanoma into mushroom-shaped or dome-shaped tumour growth patterns.

Adult↗

PubMed1977

Recognition of random shapes followed at varying delays by attended or unattended shapes, digits, and line grids.

Three experiments evaluated the effect of poststimulus distractor characteristics in altering recognition of random shapes. Experiment 1 demonstrated that when 150 msec or 300 msec were allowed for processing the initial shape stimulus, recognition was lowered only when it was followed by an attended shape or digit distractor. Unattended shapes, digits, and line grids and attended line grids left recognition essentially perfect. Attended shapes lowered recognition more than attended digits. Experiment 2 found that attended shapes, digits, and line grids all masked random shapes when presented immediately upon offset of a random shape displayed for 50 msec. As processing time increased, digit distractors became less effective than shape distractors, while line grids lost all effect. The shape distractors lowered recognition up to 1,200 msec. Experiment 3 showed that the larger recognition loss produced by the shape distractor than by the digit distractor could not be attributed to differences in response procedure. It was suggested that memory for random shapes moves from brief visual storage to a limited capacity visual short-term memory. Attended shape distractors may eliminate the stimulus shape from visual short-term memory thus preventing long-term storage.

Attention↗

PubMed1997

Dynamics of pear-shaped dimensions and volume of intracavitary brachytherapy in cancer of the cervix: a desirable pear shape in the era of three-dimensional treatment planning.

PURPOSE: To evaluate the dynamics of pear-shaped dimensions and volume of the intracavitary brachytherapy, and to define a desirable pear-shape in the era of three-dimensional (3D) treatment planning. METHODS AND MATERIALS: Since Point A has been used for the dose specification, the pear shape defined the surface enclosed by Point A. This study utilized a new method of evaluating pear-shaped dimensions and its configuration. The pear shape was artificially divided into tandem and colpostat portions for evaluation of its changes. Width, height, and thickness at the tandem portion (Wt, Ht, and Tt) and at the colpostat portion (Wc, Hc, and Tc) were defined, respectively, on the frontal and sagittal plane. To evaluate the dynamics of the pear-shape configuration, 12 variations of applicator geometry and source loading were applied to generate the pear-shape isodose line and dose-volume histogram. RESULTS: When the source strengths in the colpostats were reduced for optimization with the same dose to Point A dose, Wc, Hc, and Tc were decreased, whereas Wt, Ht, and Tt were increased without a change in the overall pear-shaped volume. When the separation of the colpostats was increased without a change in the source strength, Wc was increased, whereas Hc and Tc were reduced without a change in Wt, Ht, Tt and overall pear-shape volume. When the separation of colpostats and distal tandem source were increased, these changes at the colpostat portion were magnified. However, when both colpostat separation and its source strength were increased proportionally, Wc, Hc, and Tc were increased proportionally as well as its volume. CONCLUSION: The dose specification at Point A is less meaningful without a desirable pear shape encompassing the tumor around the cervix. In the era of 3D treatment planning, understanding the dynamics of the pear shape should improve the individualized dosimetry according to tumor size and location. The relationships between a desirable pear shape and its tumor coverage should establish a more reliable dose specification for cancer of the cervix.

Brachytherapy↗

PubMed1986

The human erythrocyte membrane skeleton may be an ionic gel. II. Numerical analyses of cell shapes and shape transformations.

In the first paper in this series (Stokke et al. Eur Biophys J 1986, 13:203-218) we developed the general theory of the mechanochemical properties and the elastic free energy of the protein gel--lipid bilayer membrane model. Here we report on an extensive numerical analysis of the human erythrocyte shapes and shape transformations predicted by this new cell membrane model. We have calculated the total elastic free energy of deformation of four different cell shape classes: disc-shaped cells, cup-shaped cells, crenated cells, and cells with membrane invaginations. We find that which of these shape classes is favoured depends strongly on the spectrin gel osmotic tension, IIGu, and the surface tensions, IIEu and IIPu, of the extracellular and protoplasmic halves of the membrane lipid bilayer, respectively. For constant ratio IIEu/IIPu greater than O large negative or positive values of IIGu favour respectively the crenated and invaginated cell shape classes. For small absolute values of IIGu, IIEu, and IIPu, biconcave or cup-shaped cells are the stable ones. Our numerical analysis shows that the higher the membrane skeleton compressibility is, the smaller are the values of IIGu needed to induce cell shape transformation. We find that the stable and metastable shapes of discocytes and stomatocytes generally depend both on the shape of the stressfree membrane skeleton and the membrane skeleton compressibility.

Elasticity↗

PubMed2001

Retinal vascular alterations associated with dome-shaped and mushroom-shaped choroidal melanomas.

PURPOSE: Retinal vascular abnormalities are associated with choroidal melanoma. Although tumor ischemia, resulting in soluble angiogenic factor production, is a proposed etiology of these abnormalities, other sources of ischemia may also contribute. Mushroom-shaped choroidal melanomas have increased loss of the overlying choriocapillaris and increased subretinal fluid when compared to dome-shaped tumors; factors that may result in outer retinal ischemia, angiogenic factor production and resultant retinal vascular abnormalities. The differing amounts of retinal vascular abnormalities overlying dome-shaped compared to mushroom-shaped melanomas were determined to evaluate this hypothesis. METHODS: Retinal vascular abnormalities observed on fluorescein angiograms of eyes with choroidal melanoma were compared to the tumor configuration and presence of subretinal fluid. RESULTS: 23 eyes of 22 patients were included in the study. Retinal vascular abnormalities observed included dilated capillaries, telangiectatic capillaries, capillary nonperfusion, microaneurysms, neovascularization, lipid exudation and late staining of dye within the retina. Retinal vascular abnormalities were present in 4 of 14 eyes with dome-shaped tumors (29%) and in 8 of 9 eyes with mushroom-shaped tumors (89%). (Fisher's Exact Test, p = 0.009). Retinal vascular abnormalities were present in 2 of 10 eyes without subretinal fluid (20%) and in 10 of 13 eyes with subretinal fluid (77%). (Fisher's Exact Test, p = 0.012). CONCLUSIONS: Retinal vascular abnormalities are associated with mushroom-shaped choroidal melanomas more commonly than dome-shaped tumors. Outer retinal ischemia may result from choriocapillaris loss or the presence of subretinal fluid, contributing to soluble angiogenic factor production and resultant retinal vascular abnormalities in these eyes. SUMMARY STATEMENT: Retinal vascular abnormalities are associated with mushroom-shaped choroidal melanomas more commonly than dome-shaped tumors. These retinal vascular abnormalities may be related to an increase in outer retinal ischemia associated with mushroom-shaped tumors.

Adult↗

PubMed2004

The influence of object size and surface shape on shape constancy from stereo.

The failure of shape constancy from stereoscopic information is widely reported in the literature. In this study we investigate how shape constancy is influenced by the size of the object and by the shape of the object's surface. Participants performed a shape-judgment task on objects of five sizes with three different surface shapes. The shapes used were: a frontoparallel rectangle, a triangular ridge surface, and a cylindrical surface, all of which contained the same maximum depth information, but different variations in depth across the surface. The results showed that, generally, small objects appear stretched and large objects appear squashed along the depth dimension. We also found a larger variance in shape judgments for rectangular stimuli than for cylindrical and ridge-shaped stimuli, suggesting that, when performing shape judgments with cylindrical and ridge-shaped stimuli, observers rely on a higher-order shape representation.

Depth Perception↗

PubMed2003

Processing shape, motion and three-dimensional shape-from-motion in the human cortex.

Shape and motion are complementary visual features and each appears to be processed in unique cortical areas. However, object motion is a powerful cue for the perception of three-dimensional (3-D) shape, implying that the two types of information--motion and form--are well integrated. We conducted a series of fMRI experiments aimed at identifying the brain regions involved in inferring 3-D shape from motion cues. For each subject, we identified regions in occipital-temporal cortex that were activated when perceiving: (i) motion in unstructured random-dot patterns, (ii) 2-D and 3-D line drawing shapes, and (iii) 3-D shapes defined by motion cues (shape-from-motion, SFM). We found closely adjacent areas in the lateral occipital region activated by random motion and line-drawing shapes. In addition, we found that the SFM stimuli produced a greater MRI signal in only one of the areas identified with the random motion and line-drawing stimuli: the superior lateral occipital (SLO) region. High-resolution analysis showed that SFM objects and line drawings were processed in separate but adjacent sub-regions in SLO, suggesting that SLO codes object shape but retains topographic segregation based on shape cues. Expanding the analysis to the entire cortex identified a parietal area that had overlapping activation for both SFM and line drawings and increased MRI signal for 3-D versus 2-D shapes, suggesting this area is important for processing shape information.

Brain Mapping↗

PubMed2004

View sensitivity increases for same-shape matches if mismatches show pairs of more similar shapes.

Lawson, Bülthoff, and Dumbell (2003) found increased view sensitivity when more similar shapes had to be discriminated. Their sequential picture-picture matching studies showed depth-rotated views of novel, complex, 3-D objects. However, with a similar task and stimuli, Hayward and Williams (2000) found no variation in view sensitivity on same-shape match trials depending on whether similar or dissimilar pairs of shapes were shown on mismatch trials. Thus view sensitivity increases from dissimilar-shape mismatches to similar-shape mismatches to same-shape matches (Lawson et al., 2003). However, view sensitivity may not increase on same-shape matches if those trials are combined with similar-rather than dissimilar-shape mismatches (Hayward & Williams, 2000). The latter result was reexamined here. Matches were view sensitive given even the dissimilar-shape mismatch context. This view sensitivity increased in the medium and especially the hard contexts that showed similar shapes on mismatches. Thus, indirectly increasing shape similarity via mismatch context modulated view-change effects (cf. Hayward & Williams, 2000).

Discrimination, Psychological↗

PubMedDate not supplied

Visual processing of configuration-dependent spatial characteristics of shapes and patterns. A model useful in the study of the role of the departure from circularity or dispersion of shapes in human visual perception.

In this work a theoretical model was used in combination with testings on normal subjects to get more insight in the role of the departure from circularity or dispersion of the shapes in visual perception. The model was inspired by the observation that the intensity of the effect of a given level of contrast of a shape usually increases, for the same area, with the shape being better concentrated around a center. The model introduces as a measurable characteristic the degree of concentration or dispersion of a shape with respect to a center. The measure was based on the maximum of the convolution integral of the characteristic function of the shape with the weighting function 1/2 pi r, r being the distance between the point of convolution and the surface element to be integrated. A program for the calculation of the degree of concentration of figures and other related processing operations was developed in Turbo Pascal language on a 486 PC. The program included the possibility to generate various figures and to operate on them various transformations such as strangulation, fragmentation with separation of fragments. The model introduces a center of the figure, the point best surrounded by the whole figure, with a geometric and visual significance, as resulting from the good concordance between its calculated and perceived positioning in different relatively simple shapes. In symmetrical compact figures subjected to a central separation or narrowing two centres appear entering the two resulting nuclear parts; a good concordance between model and perception was again observed in this transition to two centres and their subsequent positions in the two nuclear parts. In accord to model prediction, testings showed a very pronounced dependence of the summation efficiency over a contrasting area on the degree of dispersion of the area. This is reflected in the drastic decrease upon figure dispersion of the intensity with which a given brightness or colour contrast is perceived. Thus, the model gives a better explanation and a more efficient way to approach the great capacity of the visual system to disclose more compact shapes or agglomeration zones in a complex visual scene. This capacity is to a large extent due to the increase in the intensity with which a given contrast is perceived, occurring in these conditions. This intensity, which strongly depends on the degree of concentration or dispersion of the figure, becomes an important additional signal leading to the accentuation of the difference between compact and rarefied shapes. The model based on the degree of concentration determined around a centre, although useful for finding a centre and applicable satisfactorily to many shapes, do not cover well all aspects of shape dispersions. In shapes without a dominant central part the confrontation model-testing showed an important involvement in global perception of all local concentrations, not only central but also peripheral, the later underestimated in our model. The model can be however improved by taking into account also such local concentrations.

Form Perception↗

PubMed1988

Abnormalities of dynamic ventricular shape change in patients with aortic and mitral valvular regurgitation: assessment by Fourier shape analysis and global geometric indexes.

The normal cardiac cycle is associated with dynamic changes in left ventricular shape, which can be disturbed in disease states. To assess the influences of diastolic volume, percent ejected volume, and abnormalities of acute or chronic systolic loading on general and detailed chamber geometry, we studied dynamic shape change recorded by x-ray contrast ventriculography in both normal patients and those with aortic (AR) or mitral (MR) valve regurgitation. While both lesions increased diastolic volume, the character of load throughout ejection differed markedly. Detailed cavity geometry was assessed by a Fourier analysis technique and general shape by eccentricity and circularity indexes. Normal hearts, showed increased systolic elongation by all indexes. AR patients displayed a similar rise in eccentricity during ejection; however, the extent of shape change when measured by Fourier and circular indexes was reduced. In contrast, MR patients displayed enhanced systolic shape change, particularly in chamber elongation. Neither simple eccentricity of circular indexes adequately differentiated these shape abnormalities, whereas detailed Fourier geometric analysis precisely characterized the abnormalities of shape change in these two diseases. Relations between the extent of shape change and ejected volume for each patient group revealed significantly more systolic deformation with a different shape versus volume relation for the MR hearts as compared with AR and controls. Thus, while dynamic left ventricular shape is certainly influenced by the extent of volume change, it also varies independently from volume related to the specific nature of loading during ejection.

Algorithms↗

PubMed2005

An active shape model for the reconstruction of scoliotic deformities from back shape data.

OBJECTIVE: The objective of the present study is to improve the accuracy and reliability of the spinal midline reconstructions in scoliosis from back shape data. Design. An active shape model which covers the variety of scoliotic curves with a minimum of adjustable parameters is designed for the reconstruction of the spinal midline based on rasterstereographic back surface measurements. BACKGROUND: To reduce the number of X-rays needed for patients with a scoliosis, an automatic method was developed for the reconstruction of spinal deformities from back shape data. METHODS: 264 digital X-rays of 264 patients with scoliosis were used as a training set. By examining the statistics of the vertebral body centres a point distribution model was derived. The model is used as a basis to reconstruct the spinal midline from back shape data (active shape model). RESULTS: 478 rasterstereographs of 114 scoliotic patients have been evaluated with this new procedure and with an existing procedure. Both procedures deliver a three-dimensional curve of the spinal midline. The frontal projections of these spinal midlines are compared with the vertebral centres of the corresponding 478 X-rays. The active shape model improved the results as compared to the existing procedure from sigma(x)=3.4mm to sigma(x)=3.0mm. CONCLUSION: The use of the active shape model improves the overall accuracy of the spinal midline reconstructions in scoliosis from back shape data.RELEVANCE. Improvements to the accuracy and the reliability of the three-dimensional spinal reconstruction based on back shape data, can lead to an additional reduction of X-rays for patients with a scoliosis.

Artificial Intelligence↗

PubMed1984

Word shape's in poor shape for the race to the lexicon.

Current models of fluent reading often assume that fast and automatic word recognition involves the use of a supraletter feature corresponding to the envelope or shape of the word when it is printed in lowercase. The advantages of mixed case over pure case and of pure lowercase over pure uppercase have often been taken as evidence favoring the word-shape hypothesis. Alternative explanations for these phenomena are offered. Experiment 1 shows that previous demonstrations of word-shape effects during proofreading are better described as individual letter effects. Experiments 2-4 explore the possibility that word shape facilitates lexical access through uncertainty reduction. In all three experiments performance on words with rare shapes is compared to those with common shapes. There were no effects of shape frequency in either tachistoscopic recognition or lexical-decision tasks. This was true regardless of the degree to which the visual shape cue was supplemented by the nonvisual factors of familiarity and expectancy. Possible reasons why fluent readers ignore word shape are discussed within the framework of a model that assumes that automatic word recognition is mediated by the activation of abstract letter identities.

Adolescent↗

PubMed1997

Early detection of progression in adolescent idiopathic scoliosis by measurement of changes in back shape with the Integrated Shape Imaging System scanner.

STUDY DESIGN: A retrospective study of 78 patients with right thoracic idiopathic scoliosis was done. OBJECTIVES: To evaluate the reliability of the integrated Shape Imaging System scan (Oxford Metrics Ltd, Oxford, UK) in detecting progression of scoliosis and the use of back shape data in predicting scoliosis progression. SUMMARY OF BACKGROUND DATA: At first presentation and every 3-6 months during the follow-up period, all patients underwent integrated Shape Imaging System scans and radiographic examinations, from which the Cobb angle was measured. The follow-up period was 18-49 months (mean = 31.4 months). METHODS: Patients were divided into three groups according to the severity and progression of the Cobb angle. The spinal fusion, brace, and observation groups were compared using analysis of variance and the student's t test to detect significant differences among groups in the progression of deformity as measured by the integrated Shape Imaging System parameters and the Cobb angle. RESULTS: Three of the Integrated Shape Imaging System parameters detected significant progression in the spinal fusion group 1 year earlier than the Cobb angle. Only one of the Integrated Shape Imaging System parameters detected a significant difference in progression between the brace and observation groups. CONCLUSIONS: The Integrated Shape Imaging System technique demonstrated significant changes in this group of patients with progressive scoliosis. Serial measurements of back surface shape, particularly the size of the rib hump, may be predictive of progression. Serial Integrated Shape Imaging System scanning has advantages over serial radiography in the management of idiopathic scoliosis in addition to the avoidance of exposure to ionizing radiation.

Adolescent↗

PubMed1987

Quantitation of nuclear shape in non-Hodgkin's lymphoma. Alternate shape descriptors.

The nuclear contour index (NCI) has been used extensively to quantitate cellular shape in non-Hodgkin's lymphoma (NHL). This disease entity has a mixed cellular component, with nuclei exhibiting a spectrum of shapes; the main disadvantage of conventional shape descriptors, such as NCI, is that similar values are assigned to these widely divergent shapes. In this study, two alternative shape indices, measures of convexity-concavity (C-C) and slimness (SL), were assessed to determine their suitability as shape descriptors. To achieve this, the contours of lymphoid cells in cytologic preparations of NHL were quantitated by means of semiautomated image analysis. C-C was able to identify nuclear clefts, with the values obtained by this index reflecting the number and depth of invaginations present; this index was unaffected by ellipsoid shapes. SL was able to describe ellipsoid profiles, irrespective of the presence of nuclear clefts; the index also characterized indentations, although precise identification of this form of invagination was difficult. This study confirms the usefulness of these indices in the characterization of nuclear shape; utilization of these shape descriptors enhances the accuracy of more-objective approaches to the morphologic classification of lymphoid lesions.

Cell Nucleus↗

PubMed2005

Dynamic changes in the tuning of striate neurons to the shapes of cross-shaped figures.

Time slice analysis was used to study the dynamics of tuning to the shapes of cross-shaped figures flashing in the receptive fields of 83 neurons in the primary visual cortex (field 17) of the cat brain. Tuning was assessed in terms of the numbers of spikes in the overall response and its sequential 20-msec fragments. Only 11.7% of neurons produced reproducibly developing spike responses to a given shape (defined as the angle between the lines), i.e., had a preferred cross-shaped figure. In the remaining cases (88.3%), tuning of neurons to the shape of the cross showed dynamic changes. In 7.2% of cases, changes in the preferred shape of the cross occurred monophasically; changes were biphasic in 27.0% of cases, while in the remaining 54.1% of cases, the dynamics in changes in the preferred cross shape were undulatory. The tuning of receptive field zones is assessed as the cause of these effects and their difference from the previously observed dynamics of preferred orientations of single bars and cross-shaped figures; the functional significance of these effects is also discussed.

Action Potentials↗