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At least 469 records · Page 26Linked to original sources

PubMedDate not supplied

Video-capture virtual reality system for patients with paraplegic spinal cord injury.

This article presents results from a feasibility study of a video-capture virtual reality (VR) system used with patients who have paraplegic spinal cord injury (SCI) and who need balance training. The advantages of the VR system include providing the user with natural control of movements, the ability to use as many parts of the body as are deemed suitable within the context of therapeutic goals, and flexibility in the way the system can be adapted to suit specific therapeutic objectives. Thirteen participants with SCI experienced three virtual environments (VEs). Their responses to a Short Feedback Questionnaire showed high levels of presence. We compared performance in the environments with a group of 12 nondisabled participants. Response times for the patient group were significantly higher and percentage of success was significantly lower than that for the nondisabled group. In addition, significant moderate correlations were found between performance within a VE and static balance ability as measured by the Functional Reach Test. This study is a first step toward future studies aimed at determining the potential of using this VR system during the rehabilitation of patients with SCI.

Activities of Daily Living↗

PubMed1993

The cytosolic chloride concentration in macula densa and cortical thick ascending limb cells.

It is believed that chloride transport through the macula densa (MD) cells is a factor involved in the tubuloglomerular feedback (TGF) mechanism and in MD-mediated renin release. In this study isolated and perfused rabbit kidney cortical thick ascending limb (cTAL) segments containing MD plaques and attached glomeruli were loaded with chloride (CL-sensitive) 6 methoxy-1-fluorophore (sulphanate-propyl) quinolinium (SPQ). MD and cTAL intracellular chloride concentration ([Cl-]i) was determined by using image-intensified video microscopy and digital image-processing for measuring the intensity of the emitted SPQ fluorescence. With 150 mM NaCl in lumen and bath the [Cl-]i in MD and cTAL cells was 58.8 +/- 7.2 mM (n = 20) and 68.7 +/- 9.8 mM (n = 14), respectively. When the presumed luminal Na(+)-2Cl(-)-K+ co-transporter was blocked by adding 10(-4)M furosemide, the [Cl-]i was reduced in both, MD and cTAL cells from 55.5 +/- 11.9 to 28.6 +/- 10.0 mM (n = 10) and from 43.8 +/- 2.6 to 13.1 +/- 4.5 mM (n = 5), respectively. A reduction in luminal NaCl from 150 to 30 mM also decreased both, MD and cTAL [Cl-]i from 69.4 +/- 9.1 to 36.5 +/- 5.1 mM (n = 9) and from 82.9 +/- 14.5 to 49.4 +/- 8.0 mM (n = 8), respectively. Basolateral addition of the Cl(-)-channel blocker NPPB increased MD [Cl-]i from 31.1 +/- 2.0 to 100.7 +/- 17.0 mM (n = 5) and cTAL [Cl-]i from 44.4 +/- 12.9 to 89.7 +/- 11.7 mM (n = 5).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2004

Copulation in the cricket is performed by chain reaction.

The male and female genitalia are finely designed to match each other for copulation in the cricket Gryllus bimaculatus. Copulatory acts of the male, stereotyped and time-fixed, are elicited by stimulation of mechanoreceptors on particular regions of the abdomen, cerci and genitalia. Sequential execution of each motor act proceeds as a chain reaction in which one act stimulates some receptors which in turn elicits another act and so on, while the female remains immobile on the male's back. Each key stimulus for a motor act appears as a result of the male's own act, except for copulatory papilla protrusion by the female. The final sequence of spermatophore extrusion and transfer are irreversible fixed motor actions which are triggered when the female copulatory papilla stimulates the epiphallic hairs. They proceed without continual central drive from the brain, and apparently without sensory feedback. In addition, they are well coordinated with movement and posture in the entire body. Some neural mechanisms of controlling mating behavior and switching the reproductive cycle are discussed.

Animals↗

PubMed1995

Automated instrument tracking in robotically assisted laparoscopic surgery.

This paper describes a practical and reliable image analysis and tracking algorithm to achieve automated instrument localization and scope maneuvering in robotically assisted laparoscopic surgery. Laparoscopy is a minimally invasive surgical procedure that utilizes multiple small incisions on the patient's body through which the surgeon inserts tools and a videoscope in order to conduct an operation. The scope relays images of internal organs to a camera, and the images are displayed on a video screen. The surgeon performs the operation by viewing the scope images rather than performing the traditional "open" procedure, where a large incision is made on the patient's body for direct viewing. The current mode of laparoscopy employs an assistant to hold the scope and position it in response to the surgeon's verbal commands. However, this results in suboptimal visual feedback, because the scope is often aimed incorrectly and vibrates due to hand trembling. We have developed a robotic laparoscope positioner to replace the assistant. The surgeon commands the robotic positioner through a hand/foot controller interface. To further simplify the human-machine interface that controls the robotic scope positioner, we report here a novel scope-positioning scheme using automated image analysis and robotic visual servoing. The scheme enables the surgeon to control visual feedback and to perform surgery more efficiently without requiring additional use of the hands.

Algorithms↗

PubMed1995

Project youth inform--a school-based sexually transmitted disease/acquired immune deficiency syndrome education programme.

A pilot project, ¿Youth Inform¿ endorsed by the Ministry of Health and Ministry of Education, Singapore, was undertaken in 1992 for 2 years. It aims to enhance sexually transmitted disease (STDs)/human immunodeficiency virus (HIV) control in Singapore by providing structured information for young people between the ages of 16 to 20 years in Polytechnics, Junior Colleges, Centralised Institutes and Pre-University Centres. Project Youth Inform comprises 8 components. They include a focus group discussion, a training seminar for teachers, a lecture/slide presentation cum question-and-answer session, an educational booklet/bookmark, exhibitions, a video, provisions for anonymous questions, and an evaluation. The programme is conducted during school hours at the premises of the institutions and the attendance per session is between 150 to 350 students. A total of 152 sessions have been completed for all the schools. It is ongoing and is currently administered by the School Health Service and Training and Health Education Department. Feedback from principals, teachers and students was gathered formally through surveys and informally through interviews and observations. One thousand students were randomly selected for the survey to assess their responses towards the programme. Eighty-six percent reported that they found it educational and informative. Indicators found to have an influence on the effectiveness of the programme were timing, vocabulary used (medical terms) and integration of the programme into the school's curriculum. In conclusion, Project Youth Inform was on the whole positively received. However, it is essential to constantly accommodate and adapt to new facts and methods of teaching and maintain close coordination with the Ministries and the schools. An effective STD/acquired immune deficiency syndrome programme is an important step towards the prevention, management and control of the epidemic.

Acquired Immunodeficiency Syndrome↗

PubMed2006

Transparent polymeric cell culture chip with integrated temperature control and uniform media perfusion.

Modern microfabrication and microfluidic technologies offer new opportunities in the design and fabrication of miniaturized cell culture systems for online monitoring of living cells. We used laser micromachining and thermal bonding to fabricate an optically transparent, low-cost polymeric chip for long-term online cell culture observation under controlled conditions. The chip incorporated a microfluidic flow equalization system, assuring uniform perfusion of the cell culture media throughout the cell culture chamber. The integrated indium-tin-oxide heater and miniature temperature probe linked to an electronic feedback system created steady and spatially uniform thermal conditions with minimal interference to the optical transparency of the chip. The fluidic and thermal performance of the chip was verified by finite element modeling and by operation tests under fluctuating ambient temperature conditions. HeLa cells were cultured for up to 2 weeks within the cell culture chip and monitored using a time-lapse video recording microscopy setup. Cell attachment and spreading was observed during the first 10-20 h (lag phase). After approximately 20 h, cell growth gained exponential character with an estimated doubling time of about 32 h, which is identical to the observed doubling time of cells grown in standard cell culture flasks in a CO2 incubator.

Cell Culture Techniques↗

PubMed1998

Volumetric object modeling for surgical simulation.

Surgical simulation has many applications in medical education, surgical training, surgical planning and intra-operative assistance. However, extending current surface-based computer graphics methods to model phenomena such as the deformation, cutting, tearing or repairing of soft tissues poses significant challenges for real-time interactions. This paper discusses the use of volumetric methods for modeling complex anatomy and tissue interactions. New techniques are introduced that use volumetric methods for modeling soft-tissue deformation and tissue cutting at interactive rates. An initial prototype for simulating arthroscopic knee surgery is described which uses volumetric models of the knee derived from 3-D magnetic resonance imaging, visual feedback via real-time volume and polygon rendering, and haptic feedback provided by a force-feedback device.

Arthroscopy↗

PubMed2006

Spontaneous behavior of a rhesus monkey (Macaca mulatta) during memory tests suggests memory awareness.

Humans can predict with some accuracy whether or not they know the correct answer to a question before responding. In some cases the capacity to make such predictions depends on memory awareness, the ability to introspectively discriminate between knowing and not knowing. In this unplanned retrospective analysis of video taped behavior we asked whether a rhesus monkey's apparent frustration predicted his accuracy in a matching-to-sample task on a trial-by-trial basis. The monkey was likely to aggressively strike the computer touchscreen when committing errors, whereas he generally touched the screen more gently when selecting the correct stimulus. This difference in behavior, which occurred before the monkey received feedback on the accuracy of his choice, suggests that he knew whether or not he remembered the correct response.

Aggression↗

PubMed2004

Visual and motor constraints on trajectory planning in pointing movements.

The aim of the present study was to show that planning and controlling the trajectory of a pointing movement is influenced not solely by physical constraints but also by visual constraints. Subjects were required to point towards different targets located at 20 degrees , 40 degrees , 60 degrees and 80 degrees of eccentricity. Movements were either constrained (i.e. two-dimensional movements) or unconstrained (i.e. three-dimensional movements). Furthermore, movements were carried out either under a direct or a remote visual control (use of a video system). Results revealed that trajectories of constrained movements were nearly straight whatever the eccentricity of the target and the type of visual control. A different pattern was revealed for unconstrained movements. Indeed, under direct vision the trajectory curvature increased as the eccentricity augmented, whereas under indirect vision, trajectories remained nearly straight whatever the eccentricity of the target. Thus, movements controlled through a remote visual feedback appear to be planned in extrinsic space as constrained movements.

Adolescent↗

PubMed1996

Bridging the gap between theory and practice: a multimedia tutorial for students of voice therapy.

A computer-based tutorial for speech and language therapy students is described in which a digitized video-recording of a diagnostic interview with a voice-disordered client was dynamically linked to an on-screen transcript window. A student-centered tutorial package, which provided guidance through questions, assessment tasks, and commentary from an experienced speech and language pathologist as well as the lecturer in voice disorder, was constructed. Evaluation of the tutorial as an aid to active learning, including feedback from students and supervising clinicians, is reported and the role of this type of program as a preparation for clinical practice is discussed.

Adult↗

PubMedDate not supplied

Statistical quality assurance in cytology. Use of the Pathfinder to continuously assess screener process control in real time.

OBJECTIVE: To evaluate the suitability of the Pathfinder (CompuCyte Corp., Cambridge, Massachusetts, U.S.A.), an innovative instrument for monitoring the mechanical aspects of cytology screening, as a training aid and workstation component for cytotechnologists for daily work flow in a large cytology laboratory. STUDY DESIGN: The impact of the implementation of the Pathfinder was assessed by comparing the performance of a group of senior cytotechnologists with the Pathfinder features enabled (displayed) and disabled (not displayed). When enabled, statistical parameters, including the percentage of screenable slide surface viewed, the amount of time spent viewing the slide and the percentage of overlap of the fields of view, were continuously displayed to the cytotechnologist on a small, dedicated video display terminal. Areas of the slide requiring additional review by the pathologist were indicated by a series of electronic icons placed by the cytotechnologists. RESULTS: The Pathfinder was found to provide critical insight into the variability that exists among cytotechnologists in their approach to screening. By establishing laboratory performance criteria for the aforementioned parameters, variability in performance could be reduced immediately. CONCLUSION: The continuous feedback provided by the Pathfinder to the cytotechnologist during the actual screening process could help to diminish false negative cervical cytologic smear evaluations due to correctable unsuspected errors in the practice of screening.

Evaluation Studies as Topic↗

PubMed2006

The impact of experiential learning on NUS medical students: our experience with task trainers and human-patient simulation.

INTRODUCTION: Experiential learning is one of the key methods for effective teaching of medical students. The use of simulation is ideal to achieve this goal. Simulation training allows the learner to be actively involved, and provides realism, self-direction, feedback and practice. We present 2 pilot projects in which the efficacy of experiential learning with simulation is demonstrated. MATERIALS AND METHODS: In the first project, groups of 4 to 6 fourth-year medical students were exposed to common crisis scenarios. Each student took turns to individually handle the situation (in the hot seat), while the rest of the group watched "live" via video-link. A group debrief was done after the completion of all scenarios and learning points were emphasized. A test was conducted shortly after, and the student who managed the same scenario in the hot seat earlier was compared to the rest of the group with respect to crisis recognition, management and diagnosis. In the second project, 36 fourth-year medical students were assigned to learn endotracheal intubation through a directed or experiential method. Students were recalled after 3 months and tested on 4 major categories: preparation, technique, success and ventilation. RESULTS: Students in the hot seat tended to perform better (72% vs. 64%), and were more likely to be the highest scoring student within their group; although this did not reach statistical significance. For the intubation study, students in the experiential group had a higher success rate at 3 months (78% vs. 41%). CONCLUSIONS: Experiential teaching methods with simulation result in better learning of crisis management and endotracheal intubation.

Clinical Competence↗

PubMed1991

Intracellular cytosolic free calcium concentration in the macula densa and in ascending limb cells at different luminal concentrations of sodium chloride and with added furosemide.

The juxtaglomerular apparatus fulfils several important regulatory functions in the kidney, such as tubuloglomerular feedback (TGF) control and control of renin release. The macula densa (MD) cells sense the fluid load by perceiving the distal NaCl concentration via a Na-K-2Cl cotransport system in the luminal cell membrane. It has been proposed that macula densa cell activation may involve changes in intracellular cytosolic free calcium concentration ([Ca2+]i), as one link in the chain of events activating TGF or releasing renin. We therefore investigated the changes in the intracellular calcium concentrations with fura-2, using a video system, in macula densa cells, and compared them with the changes in the corresponding concentrations in the ascending limb of the loop of Henle (c-TAL). The results show that our technique for analysing intracellular cytosolic free calcium in isolated perfused tubules is valid for this purpose, and the Kd value obtained was similar to that found by Grynkiewicz et al. (1985). The intracellular cytosolic free calcium concentration was about 90 nM both in the macula densa and c-TAL cells, and the macula densa cell intracellular cytosolic free calcium concentration increased by about 20 nM when the tubular lumen was perfused with Na and Cl at low concentrations. No significant changes were noted when furosemide was added to the perfusion solutions. We consider it hardly likely that this small change in intracellular cytosolic free calcium concentration can be entirely responsible for full activation of renin release or full inactivation of the TGF control mechanism. It would seem that the signal transmission from the macula densa cells could occur by other routes than through activation of intracellular cytosolic free calcium concentration.

Animals↗

PubMed2002

Complex metabolic oscillations in plants forced by harmonic irradiance.

Plants exposed to harmonically modulated irradiance, approximately 1 + cos(omegat), exhibit a complex periodic pattern of chlorophyll fluorescence emission that can be deconvoluted into a steady-state component, a component that is modulated with the frequency of the irradiance (omega), and into at least two upper harmonic components (2omega and 3omega). A model is proposed that accounts for the upper harmonics in fluorescence emission by nonlinear negative feedback regulation of photosynthesis. In contrast to simpler linear models, the model predicts that the steady-state fluorescence component will depend on the frequency of light modulation, and that amplitudes of all fluorescence components will exhibit resonance peak(s) when the irradiance frequency is tuned to an internal frequency of a regulatory component. The experiments confirmed that the upper harmonic components appear and exhibit distinct resonant peaks. The frequency of autonomous oscillations observed earlier upon an abrupt increase in CO(2) concentration corresponds to the sharpest of the resonant peaks of the forced oscillations. We propose that the underlying principles are general for a wide spectrum of negative-feedback regulatory mechanisms. The analysis by forced harmonic oscillations will enable us to examine internal dynamics of regulatory processes that have not been accessible to noninvasive fluorescence monitoring to date.

Biophysical Phenomena↗

PubMed2004

Adaptively quadratic (AQua) image interpolation.

Image interpolation is a key aspect of digital image processing. This paper presents a novel interpolation method based on optimal recovery and adaptively determining the quadratic signal class from the local image behavior. The advantages of the new interpolation method are the ability to interpolate directly by any factor and to model properties of the data acquisition system into the algorithm itself. Through comparisons with other algorithms it is shown that the new interpolation is not only mathematically optimal with respect to the underlying image model, but visually it is very efficient at reducing jagged edges, a place where most other interpolation algorithms fail.

Algorithms↗

PubMed2005

Enhancement of excitatory synaptic integration by GABAergic inhibition in the subthalamic nucleus.

The activity patterns of subthalamic nucleus (STN) neurons, which are intimately related to normal movement and abnormal movement in Parkinson's disease (PD), are sculpted by feedback GABAergic inhibition from the reciprocally connected globus pallidus (GP). To understand the principles underlying the integration of GABAergic inputs, we used gramicidin-based patch-clamp recording of STN neurons in rat brain slices. Voltage-dependent Na+ (Nav) channels actively truncated synthetic IPSPs and were required for autonomous activity. In contrast, hyperpolarization-activated cyclic nucleotide-gated and class 3 voltage-dependent Ca2+ channels contributed minimally to the integration of single or low-frequency trains of IPSPs and autonomous activity. Interestingly, IPSPs modified action potentials (APs) in a manner that suggested IPSPs enhanced postsynaptic Nav channel availability. This possibility was confirmed in acutely isolated STN neurons using current-clamp recordings containing IPSPs as voltage-clamp waveforms. Tetrodotoxin-sensitive subthreshold and spike-associated Na+ currents declined during autonomous spiking but were indeed transiently boosted after IPSPs. A functional consequence of inhibition-dependent augmentation of postsynaptic excitability was that EPSP-AP coupling was dramatically improved when IPSPs preceded EPSPs. Because STN neuronal activity exhibits coherence with cortical beta-oscillations in PD, we tested how rhythmic sequences of cortical EPSPs were integrated in the absence and presence of feedback inhibition. STN neuronal activity was consistently entrained by EPSPs only in the presence of feedback inhibition. These observations suggest that feedback inhibition from the GP is critical for the emergence of coherent beta-oscillations between the cortex and STN in PD.

Animals↗

PubMed1998

Innovative informatics education: aligning theory and practice through strategic partnership.

The University of Victoria School of Health Information Science (HINF) and The Toronto Hospital (TTH) have formed a strategic partnership to align current information management theory with practical experience. The fourth year undergraduate course in Information Management and Technology was redesigned to include a joint research project with TTH. Staff from TTH were paired with groups of 2-3 students to explore current information management issues. Technology such as electronic mail and conference calls enabled timely communication. Final results were presented via video conference at the end of the term and jointly graded by the professor and hospital staff. Over the three years, a variety of projects have been undertaken and the approach has been refined. Each year offered new insight to both students and staff. Findings include several key success factors: senior level support, early planning, timely communication, access to technology, and opportunity for staff and student feedback. This partnership offers strategic advantages to both organizations in innovation, mutual learning, recruiting, and partnership. Next steps include expansion of the project to a regional model and seminars on current information management topics for TTH staff.

Canada↗

PubMed2002

Spring: a general framework for collaborative, real-time surgical simulation.

We describe the implementation details of a real-time surgical simulation system with soft-tissue modeling and multi-user, multi-instrument, networked haptics. The simulator is cross-platform and runs on various Unix and Windows platforms. It is written in C++ with OpenGL for graphics; GLUT, GLUI, and MUI for user interface; and supports parallel processing. It allows for the relatively easy introduction of patient-specific anatomy and supports many common file formats. It performs soft-tissue modeling, some limited rigid-body dynamics, and suture modeling. The simulator interfaces to many different interaction devices and provides for multi-user, multi-instrument collaboration over the Internet. Many virtual tools have been created and their interactions with tissue have been implemented. In addition, a number of extra features, such as voice input/output, real-time texture-mapped video input, stereo and head-mounted display support, and replicated display facilities are presented.

Computer Communication Networks↗