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PubMed2006

Eye movement assessment of selective attentional capture by emotional pictures.

The eye-tracking method was used to assess attentional orienting to and engagement on emotional visual scenes. In Experiment 1, unpleasant, neutral, or pleasant target pictures were presented simultaneously with neutral control pictures in peripheral vision under instruction to compare pleasantness of the pictures. The probability of first fixating an emotional picture, and the frequency of subsequent fixations, were greater than those for neutral pictures. In Experiment 2, participants were instructed to avoid looking at the emotional pictures, but these were still more likely to be fixated first and gazed longer during the first-pass viewing than neutral pictures. Low-level visual features cannot explain the results. It is concluded that overt visual attention is captured by both unpleasant and pleasant emotional content.

Adult↗

PubMed2002

Biocatalytic precipitation induced by an affinity reaction on dendrimer-activated surfaces for the electrochemical signaling from immunosensors.

We have developed a strategy of signal generation for immunosensors that transduces biospecific affinity recognition reactions into electrochemical signals. The cyclic voltammetric method, tracking the precipitation of insoluble products onto the sensing surface and the subsequent decrement in the electrode area, was chosen for signal registration. Precipitation of insolubilities was induced by the catalytic reaction of enzymes, which were labeled to the biospecifically attached protein or antibody molecules. As a model system for affinity recognition, we have investigated the functionalization of biotin groups to the sensing monolayer and their biospecific interactions with anti-biotin antibody molecules. The immunosensing interface was developed onto the dendrimer-activated self-assembled monolayers (SAMs), as the base template for the functionalization of the antigen moiety and signal generation. The advantages of using dendrimer-activated SAMs in comparison to the plain modified thiolate SAMs for the sensing surface were shown in terms of sensing performances, and the analytical characteristics of the resulting immunosensor were examined. Additionally, the sensing system was applied for biotin/(strept)avidin couples, extending the applicability of the developed strategy.

Anti-Bacterial Agents↗

PubMed2005

Opposite changes in carotid versus aortic stiffness during healthy human pregnancy.

Systemic arterial compliance has been known to increase during healthy pregnancy, whereas, recently, the carotid artery has been reported to stiffen. To clarify this controversy, we simultaneously measured aortic PWV (pulse wave velocity) and carotid artery elastic parameters in a cohort of pregnant women. Twelve normotensive pregnant women were studied longitudinally during the three trimesters of pregnancy (T1, T2 and T3 respectively) and 12 weeks PP (postpartum). Carotid artery diastolic diameter and pulsatile distension was measured by an echo-wall tracking method and carotid pulse pressure by applanation tonometry. Carotid strain, compliance, distensibility coefficient, stiffness index beta, Einc (incremental elastic modulus) and augmentation index were calculated. Aortic PWV was determined to estimate aortic distensibility. All carotid artery elastic parameters indicated significant stiffening from T1 to T3 (1.8+/-0.2 versus 2.9+/-0.3 mmHg for Einc), which was reversed after delivery (2.3+/-0.2 mmHg). Aortic PWV decreased during pregnancy (6.2+/-0.2 versus 5.4+/-0.2 m/s) and increased in the PP period (6.7+/-0.2 m/s). No correlation was found between changes in carotid artery elastic parameters and changes in aortic PWV either from T1 to T3 or from T3 to PP. The carotid artery exhibits regionally specific stiffening during pregnancy, which appears to represent a qualitatively different change in arterial elastic behaviour.

Adult↗

PubMed1980

Loudness discomfort levels: a clinical procedure for hearing aid evaluations.

Before any amplification system is evaluated, prescribed, or recommended, the audiologist must determine that the limits of its output across frequency are not greater than the levels at which clients experience discomfort, that is, their Loudness Discomfort Levels (LDL). After reviewing terminology, reasons for obtaining LDLs, and several sources of variability in LDL measurements, a new clinical LDL measurement procedure for hearing aid evaluations is suggested. The main aspects of this procedure are the instructions (from Morgan, Wilson and Dirks, 1974), the stimuli (sweep-frequency pulsed pure tones), the psychophysical method (tracking procedure), the calibration of the stimuli (by a hearing aid receiver attached to a 2 cm3 coupler), and the presentation of the stimuli (through the hearing aid receiver coupled to the client's earmold). This technique is suggested as clinically feasible and as a defensible procedure for obtaining LDLs for the purpose of more closely specifying an appropriate SSPL90 curve.

Correction of Hearing Impairment↗

PubMed1978

Effects of stimulus duration and stimulus off time on the auditory and acoustic reflex thresholds.

The effects of stimulus duration and stimulus off time on the thresholds of hearing and the acoustic reflex were investigated in 10 normal-hearing subjects and 10 subjects with sensorineural hearing loss. A 1000-Hz stimulus with on-off times of 500-500 msec and 30-30 msec was used to obtain hearing sensitivity and acoustic reflex thresholds via a tracking method. Auditory threshold was poorer for the 30-30 msec tone than the 500-500 msec stimulus in both groups. Using the different stimuli, no significant difference in acoustic reflex threshold was observed in either group. These results suggest that the addition of a short off time modifies the previously observed effects of both duration and off time on the acoustic reflex and auditory threshold.

Adult↗

PubMed2002

Effect of the selective serotonin reuptake inhibitor sertraline on gastric sensitivity and compliance in healthy humans.

Abstract Visceral hypersensitivity may contribute to symptoms in functional dyspepsia. Selective serotonin reuptake inhibitors (SSRIs) may be beneficial in functional gastrointestinal disorders. The aim of this study was to determine whether the SSRI sertraline affects gastric sensitivity and compliance in healthy humans. Ten healthy humans completed a 6-week randomized, double-blind, crossover trial of sertraline (50 mg day(-1)) vs. placebo. After each 2-week treatment, fullness, pain and nausea were rated at increasing gastric barostat distending pressures. Sensation thresholds above minimal distending pressure (MDP) were determined with a tracking method. Somatic sensory testing was performed by hand immersion in ice water. No differences were found between sertraline and placebo for symptoms as a function of distending pressure (fullness, P = 0.72; pain, P = 0.79; nausea, P = 0.41), gastric compliance (P = 0.15), median and interquartile range thresholds for first sensation [4.1 (3.5-5.7) vs. 6.2 (3.3-10.0) mmHg above MDP, P = 0.19] and pain [15.2 (8.3-21.0) vs. 15.3 (10.3-19.8) mmHg above MDP, P = 0.85], and median tolerance times for hand ice water immersion [27 (19-99) vs. 29 (20-180) s, P = 0.73]. In conclusion, sertraline had no effect on gastric sensitivity or compliance, or somatic pain tolerance in healthy humans. Studies are needed to assess the effects of SSRIs on visceral sensation and clinical symptoms in patients with functional dyspepsia.

Adult↗

PubMed2002

Numerical investigation of the effect of blade geometry on blood trauma in a centrifugal blood pump.

Fluid dynamic forces in centrifugal blood pump impellers are of key importance in destruction of red blood cells (RBCs) because high rotational speed leads to strong interaction between the impeller and the RBCs. In this paper, three-dimensional models of five different blade geometries are investigated numerically using the commercial software CFX-TASCflow, and the streaklines of RBCs are obtained using the Lagrangian particle tracking method. In reality, RBCs pass through the pump along complicated paths resulting in a highly irregular loading condition for each RBC. In order to enable the prediction of blood damage under the action of these complex-loading conditions, a cumulative damage model for RBCs was adopted in this paper. The numerically simulated percent hemoglobin (%HB) released as RBCs traversed the impeller and volute was examined. It was observed that the residence time of particles in the blade passage is a critical factor in determining hemolytic effects. This, in turn, is a function of the blade geometry. In addition, it was observed that the volute profile is an important influence on the computed HB% released.

Computer Simulation↗

PubMed2003

[Schooling, living conditions and study motivation of students partaking in the traditional or reformed course of instruction at the Charité (Hospital)].

BACKGROUND: There are two different tracks in undergraduate medical education at the Charité, a traditional (TT) one and a reformed one (RT) which was implemented in 1999. We report a survey reflecting on possible differences between students joining the two tracks. METHODS: During the winter term 2001/02 a questionnaire was sent to all 223 newly enrolled medical students. Three groups were distinguished: those following either the traditional or the reformed course (TT or RT), or those who followed the TT, although they had applied for it, because there were not enough vacancies in the RT. PARTICIPANTS: 150 (63% female; average age: 21.5 years) of 223 first year medical students. RESULTS: Applicants for the RT did not differ significantly from those of the other groups with respect to school-leaving grades, their choice of main courses at school an their motivation to study medicine. But they differed in the demands that they placed on their instruction. The wish for a good practical medical training, advancing their individual potential and the ability to select for themselves any instructional priorities were of greater importance for those choosing the RT than those who preferred the TT. More students of the RT than the TT would again have chosen to study medicine and less often stated that they had considered giving up their medical course. CONCLUSION: Students have different expectations concerning medical curricula. The possibility to choose between different ways of studying may help to meet different expectations.

Adult↗

PubMed1993

[Fundus-controlled microperimetry with the scanning laser ophthalmoscope in macular diseases].

BACKGROUND: Scanning laser microperimetry allows focal sensitivity testing of any localization of the retina under direct visual control. Physiological or involuntary fixation shifts can be corrected by manual fundus-tracking. METHODS: For static fundus-controlled microperimetry we used a confocal scanning laser ophthalmoscope equipped with a helium-neon laser as light source for background illumination and for generating the stimuli by acousto-optic modulation. Fundus imaging was achieved by an infrared diode laser scanning synchronous with the helium-neon laser. In comparison computerized static projection perimetry was performed using the Humphrey Field Analyser, program 10-2. RESULTS: On the basis of four exemplary cases (macular hole, juxtafoveal pigment epithelium atrophy, subretinal neovascularization secondary to age-related macular degeneration) it is shown that extension and depth of scotomas can be recorded more precisely with scanning laser microperimetry than with conventional projection perimetry. Microscotomas can be detected. By using infrared laser for fundus imaging choroidal structures such as subretinal neovascular membranes can be visualized, even when moderate intra- or subretinal hemorrhages secondary to age-related macular degeneration are present. Thus focal sensitivity testing of the retina overlying neovascular membranes is possible. Simultaneous registration of fixation allows precise localization of the fixation point and its relationship to neovascular membranes. CONCLUSION: The advantage of fundus-controlled microperimetry is a precise examination of the impact of morphological changes on psychophysical functions of the macula. Due to its simultaneous registration of fixation fundus-oriented microperimetry is a very informative aid in the indication of laser therapy and the selection of different laser procedures in the treatment of subretinal neovascularizations.

Adult↗

PubMed2004

Absence of charge inversion on rodlike polyelectrolytes with excess divalent counterions.

Filamentous viruses such as fd and M13 are highly charged rodlike polyelectrolytes. In this study, we employ fd virus to test the recent prediction of charge inversion [Nguyen, Rouzina, and Shklovskii, J. Chem. Phys. 112, 2562 (2000)]. Light scattering measurements show bundle formation and resolubilization of fd viruses when MgCl(2) was added from 0 to 600 mM. The effective charge of fd was studied by measuring their electrophoretic mobility using a filament tracking method uniquely suited for the system. Monte Carlo simulations were performed under canonical ensemble to predict the charge distribution around the rodlike virus. Charge inversion, which has been suggested theoretically to accompany with bundle resolubilization, was not observed in either experiments or simulations. A modified analysis of force balance is called upon to account for these new findings.

Bacteriophage M13↗

PubMed2004

Correlations among within-channel and between-channel auditory gap-detection thresholds in normal listeners.

We obtained data on within-channel and between-channel auditory temporal gap-detection acuity in the normal population. Ninety-five normal listeners were tested for gap-detection thresholds, for conditions in which the gap was bounded by spectrally identical, and by spectrally different, acoustic markers. Separate thresholds were obtained with the use of an adaptive tracking method, for gaps delimited by narrowband noise bursts centred on 1.0 kHz, noise bursts centred on 4.0 kHz, and for gaps bounded by a leading marker of 4.0 kHz noise and a trailing marker of 1.0 kHz noise. Gap thresholds were lowest for silent periods bounded by identical markers--'within-channel' stimuli. Gap thresholds were significantly longer for the between-channel stimulus--silent periods bounded by unidentical markers (p < 0.0001). Thresholds for the two within-channel tasks were highly correlated (R = 0.76). Thresholds for the between-channel stimulus were weakly correlated with thresholds for the within-channel stimuli (1.0 kHz, R = 0.39; and 4.0 kHz, R = 0.46). The relatively poor predictability of between-channel thresholds from the within-channel thresholds is new evidence on the separability of the mechanisms that mediate performance of the two tasks. The data confirm that the acuity difference for the tasks, which has previously been demonstrated in only small numbers of highly trained listeners, extends to a population of untrained listeners. The acuity of the between-channel mechanism may be relevant to the formation of voice-onset time-category boundaries in speech perception.

Acoustic Stimulation↗

PubMed2004

Nuclear body movement is determined by chromatin accessibility and dynamics.

Promyelocytic leukemia (PML) and Cajal bodies are mobile subnuclear organelles, which are involved in activities like RNA processing, transcriptional regulation, and antiviral defense. A key parameter in understanding their biological functions is their mobility. The diffusion properties of PML and Cajal bodies were compared with a biochemically inactive body formed by aggregates of murine Mx1 by using single-particle tracking methods. The artificial Mx1-yellow fluorescent protein body showed a very similar mobility compared with PML and Cajal bodies. The data are described quantitatively by a mechanism of nuclear body movement consisting of two components: diffusion of the body within a chromatin corral and its translocation resulting from chromatin diffusion. This finding suggests that the body mobility reflects the dynamics and accessibility of the chromatin environment, which might target bodies to specific nuclear subcompartments where they exert their biological function.

Adenosine Triphosphate↗

PubMed2005

Force mapping in epithelial cell migration.

We measure dynamic traction forces exerted by epithelial cells on a substrate. The force sensor is a high-density array of elastomeric microfabricated pillars that support the cells. Traction forces induced by cell migration are deduced from the measurement of the bending of these pillars and are correlated with actin localization by fluorescence microscopy. We use a multiple-particle tracking method to estimate the mechanical activity of cells in real time with a high-spatial resolution (down to 2 microm) imposed by the periodicity of the post array. For these experiments, we use differentiated Madin-Darby canine kidney (MDCK) epithelial cells. Our data provide definite information on mechanical forces exerted by a cellular assembly. The maximum intensity of the forces is localized on the edge of the epithelia. Hepatocyte growth factor promotes cell motility and induces strong scattering activity of MDCK cells. Thus, we compare forces generated by MDCK cells in subconfluent epithelia versus isolated cells after hepatocyte growth factor treatment. Maximal-traction stresses at the edge of a monolayer correspond to higher values than those measured for a single cell and may be due to a collective behavior.

Actins↗

PubMed2006

Thermal fluctuations of grafted microtubules provide evidence of a length-dependent persistence length.

Microtubules are hollow cylindrical structures that constitute one of the three major classes of cytoskeletal filaments. On the mesoscopic length scale of a cell, their material properties are characterized by a single stiffness parameter, the persistence length l(p). Its value, in general, depends on the microscopic interactions between the constituent tubulin dimers and the architecture of the microtubule. Here, we use single-particle tracking methods combined with a fluctuation analysis to systematically study the dependence of l(p) on the total filament length L. Microtubules are grafted to a substrate with one end free to fluctuate in three dimensions. A fluorescent bead is attached proximally to the free tip and is used to record the thermal fluctuations of the microtubule's end. The position distribution functions obtained with this assay allow the precise measurement of l(p) for microtubules of different contour length L. Upon varying L between 2.6 and 47.5 mum, we find a systematic increase of l(p) from 110 to 5,035 mum. At the same time we verify that, for a given filament length, the persistence length is constant over the filament within the experimental accuracy. We interpret this length dependence as a consequence of a nonnegligible shear deflection determined by subnanometer relative displacement of adjacent protofilaments. Our results may shine new light on the function of microtubules as sophisticated nanometer-sized molecular machines and give a unified explanation of seemingly uncorrelated spreading of microtubules' stiffness previously reported in literature.

Animals↗

PubMed1999

Time-resolved analysis and visualization of dynamic processes in living cells.

Recent development of in vivo microscopy techniques, including green fluorescent proteins, has allowed the visualization of a wide range of dynamic processes in living cells. For quantitative and visual interpretation of such processes, new concepts for time-resolved image analysis and continuous time-space visualization are required. Here, we describe a versatile and fully automated approach consisting of four techniques, namely highly sensitive object detection, fuzzy logic-based dynamic object tracking, computer graphical visualization, and measurement in time-space. Systematic model simulations were performed to evaluate the reliability of the automated object detection and tracking method. To demonstrate potential applications, the method was applied to the analysis of secretory membrane traffic and the functional dynamics of nuclear compartments enriched in pre-mRNA splicing factors.

Animals↗

PubMed2002

Dynamitin controls Beta 2 integrin avidity by modulating cytoskeletal constraint on integrin molecules.

Dynamitin, a subunit of the microtubule-dependent motor complex, was implicated in cell adhesion by binding to MacMARCKS (Macrophage-enriched myristoylated alanine-rice C kinase substrate). However, how dynamitin is involved in cell adhesion is unclear despite the fact that both MacMARCKS and microtubules regulate beta(2) integrin activation. We report that dynamitin regulates beta(2) integrin avidity toward iC3b by modulating the lateral mobility of beta(2) integrin molecules. Using the single particle tracking method, we found that integrin molecular mobility in cells expressing the fusion protein CFP (cyan fluorescent protein)-dynamitin or CFP-MB (the MacMARCKS binding domain peptide of dynamitin) increased 6-fold over the control cells, suggesting that disturbing dynamitin function dramatically altered the cytoskeletal constraint on beta(2) integrin molecules. Further mechanistic studies revealed that overexpression of dynamitin stimulated the phosphorylation of endogenous MacMARCKS protein, which lead to the enhanced tyrosine phosphorylation of paxillin. This effect of dynamitin correlates with the observation that higher concentration of PKC inhibitor is required to block beta(2) integrin mobility in dynamitin-expressing cells. Although dynamitin acts at the point of MacMARCKS phosphorylation, it is upstream of RhoA, because its effect was blocked by RhoA inhibitor. Thus, we conclude that dynamitin is a part of the cytoskeletal constraint that locks beta(2) integrin in the inactive form.

Animals↗

PubMedDate not supplied

From wired to wireless: a miniature robot for intestinal inspection.

Increasingly more robots are used for various medical purposes, one of which is for intestinal inspection. A prototype robotic endoscope is presented along with a locomotion mechanism and relative experiment. Image, pH, pressure and temperature, etc. can be measured by the robot, which is very helpful in diagnoses. A wired robot will be replaced by a wireless robot because it is not comfortable for subjects and the wired robot cannot advance further into the small intestine because of too many folds and projections in the intestine. Key obstacles of the future wireless robot for intestinal inspection are discussed in detail and a reversed tracking method is provided.

Endoscopy, Gastrointestinal↗

PubMedDate not supplied

Use of genetically engineered microorganisms (GEMs) for the bioremediation of contaminants.

This paper presents a critical review of the literature on the application of genetically engineered microorganisms (GEMs) in bioremediation. The important aspects of using GEMs in bioremediation, such as development of novel strains with desirable properties through pathway construction and the modification of enzyme specificity and affinity, are discussed in detail. Particular attention is given to the genetic engineering of bacteria using bacterial hemoglobin (VHb) for the treatment of aromatic organic compounds under hypoxic conditions. The application of VHb technology may advance treatment of contaminated sites, where oxygen availability limits the growth of aerobic bioremediating bacteria, as well as the functioning of oxygenases required for mineralization of many organic pollutants. Despite the many advantages of GEMs, there are still concerns that their introduction into polluted sites to enhance bioremediation may have adverse environmental effects, such as gene transfer. The extent of horizontal gene transfer from GEMs in the environment, compared to that of native organisms including benefits regarding bacterial bioremediation that may occur as a result of such transfer, is discussed. Recent advances in tracking methods and containment strategies for GEMs, including several biological systems that have been developed to detect the fate of GEMs in the environment, are also summarized in this review. Critical research questions pertaining to the development and implementation of GEMs for enhanced bioremediation have been identified and posed for possible future research.

Bacteria↗