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PubMed1996

CD-ROM multimedia. The step before virtual reality.

Applications developed using key multimedia elements are finding their way into a number of training and information exchange environments including the laparoscopy training market. Emerging multimedia-based applications range from procedural information for patients to interactive CD-ROM-based applications used to train highly skilled surgeons. These products are designed with a high level of interactivity that allows the surgeon to plan a surgical procedure, review detailed patient information and then merge that information into the surgical planning process. Using this new technology, a surgeon now has the ability to review CD-ROM-based course materials and efficiently meet continuing education requirements. The factor found most limiting in the development of multimedia-based applications for laparoscopy training is generally not the technology, but the limits placed on the technology because of one's reluctance to think beyond what is accepted as the norm. Properly implemented, multimedia applications developed for laparoscopy training reduce the cost and time associated with learning new materials, assist a user in retaining more of the information reviewed, and in many cases make the learning experience much more enjoyable.

Audiovisual Aids↗

PubMed2004

Congener-specific accumulation and food chain transfer of polybrominated diphenyl ethers in two arctic food chains.

Congener-specific accumulation and prey to predator transfer of 22 polybrominated diphenyl ethers (PBDEs) were assessed in polar cod, ringed seal, polar bear, and beluga whale. Although the concentrations found were relatively low, these results show that PBDEs have reached the Arctic. PBDE congeners 47, 99, and 100 were dominant in all species studied. The pattern in ringed seal was somewhat simpler than in polar cod, with PBDE 47 accounting for more than 90% of the total PBDEs. In contrast, beluga whales, feeding on prey similar to that of ringed seals, showed higher PBDE levels and a more complex PBDE pattern than ringed seals. In contrast, polar bears contained only PBDE 47 in relatively small amounts. These differences in levels and patterns are likely due to species-specific differences in PBDE metabolism and accumulation. The metabolic index suggested that PBDEs 47 and 99 accumulate to the same magnitude as PCB 153 (PCB = polychlorinated biphenyl) in ringed seals and beluga whales. In contrast to beluga whales, ringed seals can metabolize PBDE 100 to some extent. Polar bears are seemingly capable of metabolizing virtually all PBDEs and are therefore unsuitable as indicators for PBDE contamination in the environment.

Animals↗

PubMed2004

Palaeogeography: Devonian tetrapod from western Europe.

Several discoveries of Late Devonian tetrapods (limbed vertebrates) have been made during the past two decades, but each has been confined to one locality. Here we describe a tetrapod jaw of about 365 million years (Myr) old from the Famennian of Belgium, which is the first from western continental Europe. The jaw closely resembles that of Ichthyostega, a Famennian tetrapod hitherto known only from Greenland. The environment of this fossil provides information about the conditions that prevailed just before the virtual disappearance of tetrapods from the fossil record for 20 Myr.

Animals↗

PubMed1991

Biosynthesis of membrane lipids in rat axons.

Compartmented cultures of sympathetic neurons from newborn rats were employed to test the hypothesis that the lipids required for maintenance and growth of axonal membranes must be synthesized in the cell body and transported to the axons. In compartmented cultures the distal axons grow into a compartment separate from that containing the cell bodies and proximal axons, in an environment free from other contaminating cells such as glial cells and fibroblasts. There is virtually no bulk flow of culture medium or small molecules between the cell body and axonal compartments. When [methyl-3H]choline was added to the cell body-containing compartment the biosynthesis of [3H]-labeled phosphatidylcholine and sphingomyelin occurred in that compartment, with a gradual transfer of lipids (less than 5% after 16 h) into the axonal compartment. Surprisingly, addition of [methyl-3H]choline to the compartment containing only the distal axons resulted in the rapid incorporation of label into phosphatidylcholine and sphingomyelin in that compartment. Little retrograde transport of labeled phosphatidylcholine and sphingomyelin (less than 15%) into the cell body compartment occurred. Moreover, there was minimal transport of the aqueous precursors of these phospholipids (e.g., choline, phosphocholine and CDP-choline) between cell compartments. Similarly, when [3H]ethanolamine was used as a phospholipid precursor, the biosynthesis of phosphatidylethanolamine occurred in the pure axons, and approximately 10% of the phosphatidylethanolamine was converted into phosphatidylcholine. Experiments with [35S]methionine demonstrated that proteins were made in the cell bodies, but not in the axons. We conclude that axons of rat sympathetic neurons have the capacity to synthesize membrane phospholipids. Thus, a significant fraction of the phospholipids supplied to the membrane during axonal growth may be synthesized locally within the growing axon.

Animals↗

PubMed2002

Enzymatic manganese(II) oxidation by metabolically dormant spores of diverse Bacillus species.

Bacterial spores are renowned for their longevity, ubiquity, and resistance to environmental insults, but virtually nothing is known regarding whether these metabolically dormant structures impact their surrounding chemical environments. In the present study, a number of spore-forming bacteria that produce dormant spores which enzymatically oxidize soluble Mn(II) to insoluble Mn(IV) oxides were isolated from coastal marine sediments. The highly charged and reactive surfaces of biogenic metal oxides dramatically influence the oxidation and sorption of both trace metals and organics in the environment. Prior to this study, the only known Mn(II)-oxidizing sporeformer was the marine Bacillus sp. strain SG-1, an extensively studied bacterium in which Mn(II) oxidation is believed to be catalyzed by a multicopper oxidase, MnxG. Phylogenetic analysis based on 16S rRNA and mnxG sequences obtained from 15 different Mn(II)-oxidizing sporeformers (including SG-1) revealed extensive diversity within the genus Bacillus, with organisms falling into several distinct clusters and lineages. In addition, active Mn(II)-oxidizing proteins of various sizes, as observed in sodium dodecyl sulfate-polyacrylamide electrophoresis gels, were recovered from the outer layers of purified dormant spores of the isolates. These are the first active Mn(II)-oxidizing enzymes identified in spores or gram-positive bacteria. Although extremely resistant to denaturation, the activities of these enzymes were inhibited by azide and o-phenanthroline, consistent with the involvement of multicopper oxidases. Overall, these studies suggest that the commonly held view that bacterial spores are merely inactive structures in the environment should be revised.

Bacillus↗

PubMed2004

Saramago's All the Names and the epidemiological dream.

Language is crucial for all established scientific disciplines in contemporary society, particularly epidemiology. Portuguese writer Saramago wrote All the Names, a book about the Conservatória, a gigantic registry that stores the whole life of an entire population. A parallel is made with the first social observatories that used entire populations for systematic observation, permitting the development of epidemiological methodology. Such "epidemiological dream" almost became true in virtual form with the introduction of electronic data processing. The central thesis of this paper is that Saramago's Conservatória allegory might be interpreted as akin to the virtual world construed by epidemiological science. Specifically, it is about abstract realities (or theoretical environments) that by definition are necessary for the process of scientific inquiry, particularly when oriented by knowledge production through observational strategies. Reading Saramago, the epidemiological virtualscape may be envisaged, more imaginary than it is usual to imagine and more real than it is usual to realise.

Epidemiologic Methods↗

PubMed1992

The cell cycle of glial cells grown in vitro: an immunocytochemical method of analysis.

Studies of cell cycles have traditionally employed [3H]- and [14C]-thymidine to label the DNA of proliferating cells and autoradiography to reveal the thymidine label. The development of antibodies to the thymidine analogue 5-bromodeoxyuridine (BrdU) has allowed the development of an immunocytochemical method analogous to the thymidine autoradiographic technique. In direct comparisons, we found that the immunocytochemical method consistently detected a larger number of proliferating cells. This suggests that it may be a more sensitive index of proliferation than thymidine autoradiography in some systems. We used the BrdU method to analyze the cycle of astroglia cultured from neonatal mouse cerebral cortex. Cells were exposed to BrdU for 1 hr to label a discrete subpopulation of proliferating cells. At 2-36 hr after the pulse, a combination of anti-BrdU immunocytochemistry and counterstaining with propidium iodide was used to identify proliferating cells. The length of the cell cycle was determined by charting the percent of BrdU-labeled mitotic cells vs time after the pulse. We found the average length of the cell cycle of astrocytes grown in vitro to be 20.5 hr. The combined G2 + M phases were 2-3 hr. These values are virtually identical with those found for glial cells in vivo, suggesting that the culture environment does not interfere with the normal control of cell cycle length.

Animals↗

PubMed2004

Therapeutic potential of hammerhead ribozymes in the treatment of hyper-proliferative diseases.

The limited efficacy of current therapeutic approaches for a number of socially relevant human diseases such as cancer and cardiovascular pathologies, has required the exploration of alternative and more effective therapeutic strategies. In the last two decades, nucleic acid based drugs have emerged as an attractive and novel alternative with great therapeutic potential. Among these molecules, hammerhead ribozymes were the first to be extensively studied and predicted to be of potential practical utility. Hammerhead ribozymes are catalytic RNA molecules capable of inducing the site-specific cleavage of a phosphodiester bond within an RNA molecule. Thus, they can be used to reduce the intracellular level of a specific mRNA coding for a protein which affects cellular metabolism or environment, causing disease. As hammerhead ribozymes can be engineered to reduce the level of virtually any mRNA, they have a very broad applicability. Among the several pathological conditions amenable for a hammerhead ribozyme based therapeutic approach, we focused our attention on pathologies sustained by a dis-regulated and excessive cellular proliferation, being sure to properly demonstrate their usefulness. Trying to be as objective as possible in regard to the feasibility of hammerhead ribozyme employment as therapeutics, a technical section, describing some of the unresolved problems in this field, has been also included. Although some aspects of hammerhead ribozymes as therapeutics can and should be optimized, the encouraging results displayed so far fully justifies further efforts, economic and scientific, to bring them closer to the clinical practice.

Animals↗

PubMed2000

Perception of facial features and face-to-face communications in space.

This paper examines how human face-to-face communications may be compromised by exposure to the microgravity environment of space. Although efficient face-to-face communications are acknowledged to be essential for astronauts to work safely and effectively, the space environment causes facial edema, and allows speakers and listeners to confront one another in multiple orientations that can potentially interfere with many important non-linguistic communication cues. In addition, high background noises in space shuttles and stations can mask auditory messages. Currently, the effects of spaceflight on the ability to identify facial features, to read lips, to integrate visual and auditory sensory information, and to interpret spoken messages in noisy environments while the speakers are at various orientations with respect to the listeners, are virtually unknown. Ground-based experiments conducted in our laboratory with computer-displayed facial images presented at various orientations have suggested how non-linguistic cues may be degraded by changes in the retinal orientations of facial images. The results of our ground-based studies illustrating impaired recognition of facial features in non-erect images are described, their implications for effective face-to-face communications among astronauts in space are discussed, and two experiments that can quantify the effects of microgravity on face-to-face communications in space are outlined.

Adult↗

PubMed2001

Identification and initial characterization of spore-like cells in adult mammals.

We describe the identification and initial characterization of a novel cell type that seems to be present in all tissues. To date we have isolated what we term "spore-like cells" based on the characteristics described below. They are extremely small, in the range of less than 5 microm, and appear to lie dormant and to be dispersed throughout the parenchyma of virtually every tissue in the body. Being dormant, they survive in extremely low oxygen environments, as evidenced by their viability in tissues (even in metabolically very active tissues such as the brain or spinal cord) for several days after sacrifice of an animal without delivery of oxygen or nutrients. The spore-like cells described in this report have an exceptional ability to survive in hostile conditions, known to be detrimental to mammalian cells, including extremes of temperature. Spore-like cells remain viable in unprepared tissue, frozen at -86 degrees C (using no special preservation techniques) and then thawed, or heated to 85 degrees C for more than 30 min. Preliminary characterization of these cells utilizing basic and special stains, as well as scanning and transmission electron microscopy reveal very small undifferentiated cells, which contain predominantly nucleus within a small amount of cytoplasm and a few mitochondria. Focal periodic acid-Schiff and mucicarmine stains suggest a coating of glycolipid and mucopolysaccharide. In vitro, these structures have the capacity to enlarge, develop, and differentiate into cell types expressing characteristics appropriate to the tissue environment from which they were initially isolated. We believe that these unique cells lie dormant until activated by injury or disease, and that they have the potential to regenerate tissues lost to disease or damage.

Animals↗

PubMed2002

Speed-accuracy trade-off of grasping movements during microgravity.

BACKGROUND: Earthbound studies have shown that for pointing movements there is a specific relationship between movement speed, amplitude, and accuracy that is known as Fitts' law. We investigated the validity of Fitts' law for grasping movements in normal and microgravity. METHOD: Subjects performed grasping movements toward virtual targets under three different time constraint conditions before and during exposure to microgravity in parabolic flights. RESULTS: The "speed-accuracy trade-off" phenomenon was observed for the grasp component of prehension movements. The results were quantitatively similar in normal and microgravity such that increasing the speed resulted in a diminished accuracy. CONCLUSIONS: Fitts' law is partially valid for grasping movements toward virtual targets without visual feedback of the hand in normal gravity. In a microgravity environment, performance of grasping movements also follows some of the predictions of Fitts' law.

Adult↗

PubMed1990

Inhibition of positively rewarding behavior by the heightened aggressive state evoked either by pain-inducing stimulus or septal lesion.

Using a footshock elicited aggression paradigm, aggressive responses were scored in normal and in septal-lesioned adult male Wistar rats. Septal lesions were made electrolytically to include the medial and lateral septal nuclei. The lesion was confirmed by behavioral criteria (septal aggression) and post-mortem histology. The aggressive response types (threat, attack) of the septal animals were compared with their corresponding age and weight matched controls. Results showed a statistically significant increase (P = 0.05) in the number of attack responses but not the threat responses in septal animals. The modulatory role of the aggressive experience on responsiveness to positively rewarding or hedonic stimuli was assessed by quantifying the intracranial self-stimulation (SS) rates that were obtained before and after an aggression schedule. For testing the SS behavior bipolar electrodes were implanted in the ventral tegmental area--substantia nigra (VTA-SN). Results showed a decrease in SS pedal press rates in post-aggression schedule as compared to the pre-aggression period in the normal subjects. This depressing effect lasted for over a week. In septal lesioned rats the SS rates were virtually abolished even without having an aggressive schedule. These experiments revealed the effect of environment and of a brain area in provoking aggressive mood and its inhibitory consequence on responding for positive experience.

Aggression↗

PubMed2026

Exploring Immersive Virtual Reality as an Approach to Improve School Participation-Related Constructs in Children With ADHD.

BACKGROUND: School participation is frequency and involvement from person-environment transactions, not diagnosis, per the International Classification of Functioning, Disability and Health (ICF) and the family of participation-related constructs (fPRC). In this framework, the environmental and child determinants of school participation (e.g., school routines and peer/teacher context; self-regulation, activity competence and preferences) interact bidirectionally to shape everyday participation. However, many interventions still target isolated impairments, overlooking coordinated changes in capacities and context. Grounded in this contemporary view, this study aimed to investigate the impact of an immersive virtual reality (IVR) intervention on school participation-related constructs in children with ADHD. METHODS: The study included 92 children aged between 7 and 12 years diagnosed with ADHD. Participants were randomly assigned into intervention (n = 46) and control (n = 46) groups. Both groups completed the School Participation Questionnaire (SPQ) and Bruininks-Oseretsky Test of Motor Proficiency Test 2 Brief Form (BOT2-BF) assessment prior to the intervention. The intervention group received an IVR intervention program twice a week for 8 weeks. During this period, the control group did not receive additional therapy. At the end of the 8 weeks, the SPQ was readministered to both groups. RESULTS: Baseline characteristics showed no significant differences in SPQ and BOT2-BF results between groups, confirming homogeneity prior to intervention. Following the intervention, the study group demonstrated significant improvements across all domains of the SPQ (doing, being, symptoms and environment), with large effect sizes for SPQ total score (d = 0.978) and subdomains (d = 0.452-0.910). In contrast, the control group showed no improvements and even declines in subdomains. Post-intervention, between-group comparisons revealed significant differences favouring the study group across all domains (p < 0.001), with large effect sizes (d = 0.878-1.165). CONCLUSIONS: Findings suggest that the IVR program was associated with improvements in teacher-rated environmental and child determinants of school participation (SPQ domains) in children with ADHD.

Humans↗

PubMed2002

Assessing auditory distance perception using virtual acoustics.

In most naturally occurring situations, multiple acoustic properties of the sound reaching a listener's ears change as sound source distance changes. Because many of these acoustic properties, or cues, can be confounded with variation in the acoustic properties of the source and the environment, the perceptual processes subserving distance localization likely combine and weight multiple cues in order to produce stable estimates of sound source distance. Here, this cue-weighting process is examined psychophysically, using a method of virtual acoustics that allows precise measurement and control of the acoustic cues thought to be salient for distance perception in a representative large-room environment. Though listeners' judgments of sound source distance are found to consistently and exponentially underestimate true distance, the perceptual weight assigned to two primary distance cues (intensity and direct-to-reverberant energy ratio) varies substantially as a function of both sound source type (noise and speech) and angular position (0 degrees and 90 degrees relative to the median plane). These results suggest that the cue-weighting process is flexible, and able to adapt to individual distance cues that vary as a result of source properties and environmental conditions.

Adult↗

PubMed1991

The portable virtual simulator.

The Virtual Simulator is a software tool for support and management of the geometric component of 3-dimensional radiotherapy treatment design. The Virtual Simulator is a software implementation of a physical simulator with additional functionality not currently available on physical simulators. Treatment of a virtual patient, derived from CT or other source, is simulated using the Virtual Simulator in the same way a physical simulator would be used. The intent of this approach is to provide the user with a familiar working environment for radiotherapy treatment design. Key features include an effective and efficient user interface, and the use of computing techniques and software standards which enhance portability to a variety of computer workstations. The Virtual Simulator is implemented in the C programming language using the X Window System, and has been written with the generic UNIX workstation in mind. It has been demonstrated that it can be installed and run without modification on workstations from a number of vendors.

Computer Simulation↗

PubMed2006

One-dimensional and multi-dimensional studies of the exocentric distance estimates in frontoparallel plane, virtual space, and outdoor open field.

The aim of this study is twofold: on the one hand, to determine how visual space, as assessed by exocentric distance estimates, is related to physical space. On the other hand, to determine the structure of visual space as assessed by exocentric distance estimates. Visual space was measured in three environments: (a) points located in a 2-D frontoparallel plane, covering a range of distances of 20 cm; (b) stakes placed in a 3-D virtual space (range = 330 mm); and (c) stakes in a 3-D outdoors open field (range = 45 m). Observers made matching judgments of distances between all possible pairs of stimuli, obtained from 16 stimuli (in a regular squared 4 x 4 matrix). Two parameters from Stevens' power law informed us about the distortion of visual space: its exponent and its coefficient of determination (R2). The results showed a ranking of the magnitude of the distortions found in each experimental environment, and also provided information about the efficacy of available visual cues of spatial layout. Furthermore, our data are in agreement with previous findings showing systematic perceptual errors, such as the further the stimuli, the larger the distortion of the area subtended by perceived distances between stimuli. Additionally, we measured the magnitude of distortion of visual space relative to physical space by a parameter of multidimensional scaling analyses, the RMSE. From these results, the magnitude of such distortions can be ranked, and the utility or efficacy of the available visual cues informing about the space layout can also be inferred.

Adult↗

PubMed1976

Abolition of direction selectivity in the visual cortex of the cat.

Cats were reared in a stroboscopically illuminated environment, which deprived them of expereience with visual movement but allowed them form vision. In these cats, neurons of the visual cortex displayed normal orientation selectivity, but direction selectivity was virtually abolished. The effect remained unaltered by long periods of normal visual exposure.

Animals↗

PubMed2006

New tools for sculpting cranial implants in a shared haptic augmented reality environment.

New volumetric tools were developed for the design and fabrication of high quality cranial implants from patient CT data. These virtual tools replace time consuming physical sculpting, mold making and casting steps. The implant is designed by medical professionals in tele-immersive collaboration. Virtual clay is added in the virtual defect area on the CT data using the adding tool. With force feedback the modeler can feel the edge of the defect and fill only the space where no bone is present. A carving tool and a smoothing tool are then used to sculpt and refine the implant. To make a physical evaluation, the skull with simulated defect and the implant are fabricated via stereolithography to allow neurosurgeons to evaluate the quality of the implant. Initial tests demonstrate a very high quality fit. These new haptic volumetric sculpting tools are a critical component of a comprehensive tele-immersive system.

Computer-Aided Design↗