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Biomedical subjects

J P Rolland

Publications and source records attributed to J P Rolland.

At least 19 recordsLinked to original sources
PubMed2006

Human Experience Modeler: context-driven cognitive retraining to facilitate transfer of learning.

We describe a cognitive rehabilitation mixed-reality system that allows therapists to explore natural cuing, contextualization, and theoretical aspects of cognitive retraining, including transfer of training. The Human Experience Modeler (HEM) mixed-reality environment allows for a contextualized learning experience with the advantages of controlled stimuli, experience capture and feedback that would not be feasible in a traditional rehabilitation setting. A pilot study for testing the integrated components of the HEM is discussed where the participant presents with working memory impairments due to an aneurysm.

Activities of Daily Living↗
PubMed2000

Assessing adolescents' personality with the NEO PI-R.

The suitability of the Revised NEO Personality Inventory (NEO PI-R) to assess adolescents' personality traits was investigated in an unselected heterogeneous sample of 469 adolescents aged 12 to 17 years. They were further administered the Hierarchical Personality Inventory for Children (HiPIC) to allow an examination of convergent and discriminant validity. The adult NEO PI-R factor structure proved to be highly replicable in the sample of adolescents, with all facet scales primarily loading on the expected factors, independent of the age group. Domain and facet internal consistency coefficients were comparable to those obtained in adult samples, with less than 12% of the items showing corrected item-facet correlations below absolute value .20. Although, in general, adolescents reported few difficulties with the comprehensibility of the items, they tend to report more problems with the Openness to Ideas (05) and Openness to Values (06) items. Correlations between NEO PI-R and HiPIC scales underscored the convergent and discriminant validity of the NEO facets and HiPIC scales. It was concluded that the NEO PI-R in its present form is useful for assessing adolescents' traits at the primary level, but additional research is necessary to infer the most appropriate facet level structure.

Adolescent↗
PubMed1999

Oligomerization state of MIP proteins expressed in Xenopus oocytes as revealed by freeze-fracture electron-microscopy analysis.

The MIP (major intrinsic protein) family is a widespread family of membrane proteins exhibiting two major types of channel properties: aquaporins and solute facilitators. In the present study, freeze-fracture electron microscopy was used to investigate the oligomerization state of two MIP proteins heterologously expressed in the plasma membrane of Xenopus laevis oocytes: AQPcic, an aquaporin from the insect Cicadella viridis, and GlpF, a glycerol facilitator from Escherichia coli. Swelling assays performed on oocytes 48 and 72 h following cRNA microinjections showed that these proteins were functionally expressed. Particle density determinations indicated that expression of proteins is related to an increase in particle density on the P fracture face of oocyte plasma membranes. Statistical analysis of particle sizes was performed on protoplasmic fracture faces of the plasma membrane of oocytes expressing AQPcic and GlpF 72 h after cRNA microinjections. Compared to control oocytes, AQPcic-expressing oocytes exhibited a specific population of particles with a mean diameter of 8.7 +/- 0.1 nm. This value is consistent with the previously reported tetrameric organization of AQPcic. In addition, AQPcic particles aggregate and form orthogonal arrays similar to those observed in native membranes of C. viridis, consisting of homotetramers of AQPcic. On the protoplasmic fracture face of oocytes expressing GlpF, the particle density is increased by 4.1-fold and the mean diameter of specifically added particles is 5.8 +/- 0.1 nm. This value fits with a monomer of the 28-kDa GlpF protein plus the platinum-carbon layer. These results clearly demonstrate that GlpF is a monomer when functionally expressed in plasma membranes of Xenopus oocytes and therefore emphasize the key role of the oligomerization state of MIP proteins with respect to their function.

Animals↗
PubMed1999

Phase behavior of fluorocarbon and hydrocarbon double-chain hydroxylated and galactosylated amphiphiles and bolaamphiphiles. Long-term shelf-stability of their liposomes.

This paper describes the morphological characterization, by freeze-fracture electron microscopy, and the thermotropic phase behavior, by differential scanning calorimetry and/or X-ray scattering, of aqueous dispersions of various hydroxylated and galactosylated double-chain amphiphiles and bolaamphiphiles, several of them containing one or two hydrophobic fluorocarbon chains. Colloidal systems are observed in water with the hydroxylated hydrocarbon or fluorocarbon bolaamphiphiles only when they are dispersed with a co-amphiphile such as rac-1,2-dimyristoylphosphatidylcholine (DMPC) or rac-1,2-distearoylphosphatidylcholine (DSPC). Liposomes are formed providing the relative content of bolaamphiphiles does not exceed 20% mol. Most of these liposomes can be thermally sterilized and stored at room temperature for several months without any significant modification of their size and size distribution. The hydrocarbon galactosylated bolaamphiphile HO[C24][C12]Gal forms in water a lamellar phase (the gel to liquid-crystal phase transition is complete at 45 degrees C) and a Im3m cubic phase above 47 degrees C. The fluorocarbon HO[C24][F6C5]Gal analog displays a more complex and metastable phase behavior. The fluorinated non-bolaform galactosylated [F8C7][C16]AEGal and SerGal amphiphiles form lamellar phases in water. Low amounts (10% molar ratio) of the HO[C24][F6C5]Gal or HO[C24][C12]Gal bolaamphiphiles or of the single-headed [F8C7][C16]AEGal improve substantially the shelf-stability of reference phospholipon/cholesterol 2/1 liposomes. These liposomes when co-formulated with a single-headed amphiphile from the SerGal series are by far less stable.

Calorimetry, Differential Scanning↗
PubMed1999

Visualization of AqpZ-mediated water permeability in Escherichia coli by cryoelectron microscopy.

Transport of water across the plasma membrane is a fundamental process occurring in all living organisms. In bacteria, osmotic movement of water across the cytoplasmic membrane is needed to maintain cellular turgor; however, the molecular mechanisms of this process are poorly defined. Involvement of aquaporin water channels in bacterial water permeability was suggested by the recent discovery of the aquaporin gene, aqpZ, in Escherichia coli. By employing cryoelectron microscopy to compare E. coli cells containing (AqpZ+) and lacking (AqpZ-) aquaporin, we show that the AqpZ water channel rapidly mediates large water fluxes in response to sudden changes in extracellular osmolarity. These findings (i) demonstrate for the first time functional expression of a prokaryotic water channel, (ii) evidence the bidirectional water channel feature of AqpZ, (iii) document a role for AqpZ in bacterial osmoregulation, and (iv) define a suitable model for studying the physiology of prokaryotic water transport.

Aquaporins↗
PubMed1999

Automatic modeling of knee joint motion for the virtual reality dynamic anatomy (VRDA) tool.

A system for automatic modeling of anatomical joint motion for use in the Virtual Reality Dynamic Anatomic (VRDA) tool is described. The modeling method described in this article relies on collision detection. An original incremental algorithm use this information to achieve stable positions and orientations of the tibia on the femur for each angle considered between these two components on the range of motion. The stable states then become the basis for a look-up table employed in the animation of the motion of the joint. The strength of the method lies in its robustness to animate any "normal" anatomical joint, given a set of kinematic constraints for the joint type as well as an accurate 3D geometric model of the joint. The demonstration could be patient specific (based on a person's real anatomical data from an imaging procedure such as CT scanning) or scaled from a generic joint based on external patient measurements. The modeling method has been implemented on a generic knee model for use in the VRDA tool.

Algorithms↗
PubMed1998

Modification of Unicryl composition for rapid polymerization at low temperature without alteration of immunocytochemical sensitivity.

We introduced a slight modification of Unicryl for fast polymerization at low temperature (in the range-20 degree C to-35 degree C) without modification of both physical properties and immunocytochemical yield. An UV initiator benzoin ethyl ether (BEE) is added at 0.05% concentration in neat resin during infiltration and final polymerization at-35 degree C. Immunogold labeling of amylase of mouse pancreas embedded in standard conditions recommended by the manufacturer or with our modification were compared by counting colloidal gold particles over zymogen granules using MACS, a specialized software dedicated to this operation. We noticed that addition of 0.05% BEE in Unicryl reduces the curing time to 16 h, which can be extended up to a maximum of 48 h at-35 degree C without noticeable modification of ultrastructural morphology, physical properties and immunocytochemical yield.

Acrylic Resins↗
PubMed1998

Sucrose is a nonaccumulated osmoprotectant in Sinorhizobium meliloti.

Intracellular accumulation of sucrose in response to lowered water activity seems to occur only in photosynthetic organisms. Here we demonstrate, for the first time, the potent ability of this common sugar, supplied exogenously, to reduce growth inhibition of Sinorhizobium meliloti cells in media of inhibitory osmolarity. Independently of the nature of the growth substrates and the osmotic agent, sucrose appears particularly efficient in promoting the recovery of cytoplasmic volume after plasmolysis. Surprisingly, sucrose is not accumulated by the bacteria at an osmotically efficient level. Instead, it strongly stimulates the accumulation of the main endogenous osmolytes glutamate and N-acetylglutaminylglutamine amide (NAGGN). Examining cell volume changes during the hyperosmotic treatment, we found a close correlation between the enhancement of the osmotically active solute pool and the increase in cell volume. Sucrose shares several features with ectoine, another nonaccumulated osmoprotectant for S. meliloti. Overall, osmoregulation in S. meliloti appears to be strongly divergent from that in most bacteria.

Betaine↗
PubMed1998

A non-intrusive display technique for providing real-time data within a surgeons critical area of interest.

Modern surgeons have at their disposal a vast array of advanced technological data dissemination devices. The ring of high resolution monitors circling the typical operating area to display pre-operative and real-time patient data is esteemly supportive. The drawback, however, is that such displays require the surgeons to frequently shift their head and gaze away from the principle field of interest. We describe a new display technique that provides surgeons with a lightweight, wearable display surface that permits localization of medical data of main interest near the field of operation with minimal head and gaze movements.

Data Display↗
PubMed1998

Modeling of a knee joint for the VRDA tool.

We propose in this paper a novel method for the modeling of the motion of anatomical joints. The method is based on collision detection and knowledge of biomedical experimental data.

Computer-Assisted Instruction↗
PubMed1997

Towards a novel augmented-reality tool to visualize dynamic 3-D anatomy.

Using augmented reality (AR) to teach dynamic 3-D anatomy may impart better understanding of bone dynamics during body movement. We are currently developing an AR tool that will allow superimposition and registration of bone structures on real anatomical counterparts of a human subject. This article describes the application, the problems to be solved, and reports on preliminary developmental studies of a first prototype of the tool. Specifically, studies test approaches to simulating real-time dynamic anatomy, and the feasibility in achieving registration of 3-D anatomical bones on their real counterparts. Such a tool will offer several unique advantages over traditional teaching methods and overcome many of their current limitations.

Anatomy↗
PubMed1996

Molecular packing of highly fluorinated phosphatidylcholines in monolayers.

Surface pressure-area isotherms of a series of fluorinated DFnCmPC phosphatidylcholines bearing two acyl chains ended by a perfluoroalkyl Fn tail of variable lengths were recorded at the air-water interface. The limiting molecular areas (Ax), the collapse pressures (pi c), the pressures of the liquid-expanded to liquid-condensed phase transition (pi t) and their associated Ac and At areas were deduced from these experiments and compared to those of their hydrocarbon DMPC, DPPC and DSPC analogs. The impact of the fluorinated tails on the characteristics of phosphatidylcholine monolayers, as well as the dependence of the observed effects on the length of these tails and their relative weight with respect to the whole hydrophobic chain length, i.e. the degree of 'fluorination' of the monolayer, is interpreted in terms of steric hindrance, hydrophobicity and chain-chain interaction balance.

Chemical Phenomena↗
PubMed1996

Linking object boundaries at scale: a common mechanism for size and shape judgments.

The area over which boundary information contributes to the determination of the center of an extended object was inferred from results of a bisection task. The object to be bisected was a rectangle with two long sinusoidally modulated sides, i.e. a wiggly rectangle. The spatial frequency and amplitude of the edge modulation were varied. Two object widths were tested. The modulation of the perceived center approximately equaled that of the edges at very low edge modulation frequencies and decreased in amplitude with increasing edge modulation frequency. The edge modulation had a greater modulating effect on the perceived center for the narrower object than for the wider object. This scaling with object width didn't follow perfect zoom invariance but was precisely matched by the scaling of the bisection threshold with width, strongly supporting the idea that the same mechanism determines both the location of the perceived center for these stimuli and its variance. We propose that this mechanism is the linking of object boundaries at a scale determined by the object width.

Form Perception↗
PubMed1996

IBIS version 3: an OSF/Motif-based interface for IBIS--integrated biological imaging system.

IBIS is a set of computer programs dedicated to the processing of electron micrographs, mainly for structural analysis of biological macromolecules. We present IBIS version 3, a UNIX/OSF/Motif 1.2-based package which carries out and provides visual display of the many operations essential to image analysis. To ensure portability, the software is written in FORTRAN 77 for computing mathematical functions and in C for display routines. A description of the IBIS OSF/Motif interface is given with the new functions added to the original version. IBIS v.3 is available free of charge to other laboratories on the internet via anonymous ftp (URL: ftp://ftp.univ-rennes1.fr/pub/ incoming/IBIS.tar.Z).

Computer Communication Networks↗
PubMed1996

Occlusion edge blur: a cue to relative visual depth.

We studied whether the blur/sharpness of an occlusion boundary between a sharply focused surface and a blurred surface is used as a relative depth cue. Observers judged relative depth in pairs of images that differed only in the blurriness of the common boundary between two adjoining texture regions, one blurred and one sharply focused. Two experiments were conducted; in both, observers consistently used the blur of the boundary as a cue to relative depth. However, the strength of the cue, relative to other cues, varied across observers. The occlusion edge blur cue can resolve the near/far ambiguity inherent in depth-from-focus computations.

Depth Perception↗
PubMed1995

Structural analysis of a MIP family protein from the digestive tract of Cicadella viridis.

Homopteran insects, and especially Cicadella viridis, display in their digestive tract a specialized epithelial differentiation, the filter chamber (FC) acting as a water-shunting complex. The main intrinsic membrane protein of the FC is a 25,000-Da polypeptide (P25). In this paper we demonstrate that this P25 polypeptide is a member of the MIP family of membrane channel proteins, and that P25 forms homotetramers in the native membranes. Using polymerase chain reaction, a 360-base pair cDNA, named cic, was isolated from RNA of the FC. cic encodes a 119-amino acid polypeptide (CIC) whose homologies with MIP26, AQP1 (CHIP), AQP2, and gamma-TIP are 38, 38, 34, and 20%, respectively. Using a specific antibody raised against a 15-amino acid peptide from the CIC sequence, we concluded that CIC and P25 are identical entities, and hence that P25 belongs to the MIP family. We investigated the quaternary structure of P25 in the membranes of the FC using biophysical analysis of P25 nondenaturing detergent micelles, scanning transmission electron microscopy, and image processing of conventional transmission electron microscopic images. All those different approaches converged to the conclusion that P25 exists as an homotetramer forming a regular two-dimensional array in the membranes.

Amino Acid Sequence↗
PubMed1995

Introduction to perceptual linearization of video display systems for medical image presentation.

The perceptual linearization of video display systems should play a significant role in medical image presentation. It maximizes the faithfulness of information transfer to the human observer; it provides a method for standardizing the appearance of images across different display devices; and it allows for calculation of the inherent contrast resolution of different display devices. This paper provides insight into the process of perceptual linearization by decomposing it into the digital driving level-to-monitor luminance relationship, the monitor luminance-to-human brightness perception relationship, and the construction of a linearization function derived from these two relationships. A discussion of previous work in these areas is given. We then compare and contrast the results of previous work with recent experiments in our laboratory and related work in vision and computer science. We conclude that (1) sufficiently good visual models exist for agreeing on a standard method of calculating the perceptual linearization function; (2) improvements in the resolution and luminance distribution of the digital-to-analog circuitry in display systems are required for medical imaging; and (3), methods for calculating a linearization remapping from a perceptual linearization function currently have significant error and should be replaced with methods that minimize perceptual error.

Analog-Digital Conversion↗