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PubMed2006

Spiropyran-based photochromic polymer nanoparticles with optically switchable luminescence.

Polymer nanoparticles of 40-400 nm diameter with spiropyran-merocyanine dyes incorporated into their hydrophobic cavities have been prepared; in contrast to their virtually nonfluorescent character in most environments, the merocyanine forms of the encapsulated dyes are highly fluorescent. Spiro-mero photoisomerization is reversible, allowing the fluorescence to be switched "on" and "off" by alternating UV and visible light. Immobilizing the dye inside hydrophobic pockets of nanoparticles also improves its photostability, rendering it more resistant than the same dyes in solution to fatigue effects arising from photochemical switching. The photophysical characteristics of the encapsulated fluorophores differ dramatically from those of the same species in solution, making nanoparticle-protected hydrophobic fluorophores attractive materials for potential applications such as optical data storage and switching and biological fluorescent labeling. To evaluate the potential for biological tagging, these optically addressable nanoparticles have been delivered into living cells and imaged with a liquid nitrogen-cooled CCD.

Acrylamides↗

PubMed2007

A broad view of arsenic.

In the mind of the general public, the words "arsenic" and "poison" have become almost synonymous. Yet, As is a natural metallic element found in low concentrations in virtually every part of the environment, including foods. Mining and smelting activities are closely associated with As, and the largest occurrence of As contamination in the United States is near the gold mines of northern Nevada. Inhabitants of Bangladesh and surrounding areas have been exposed to water that is naturally and heavily contaminated with As, causing what the World Health Organization has described as the worst mass poisoning in history. Although readily absorbed by humans, most inorganic As (>90%) is rapidly cleared from the blood with a half-life of 1 to 2 h, and 40 to 70% of the As intake is absorbed, metabolized, and excreted within 48 h. Arsenic does not appreciably bioaccumulate, nor does it biomagnify in the food chain. The United States has for some time purchased more As than any other country in the world, but As usage is waning, and further reductions appear likely. Arsenic is used in a wide variety of industrial applications, from computers to fireworks. All feed additives used in US poultry feeds must meet the strict requirements of the US Food and Drug Administration Center for Veterinary Medicine (Rockville, MD) before use. Although some public health investigators have identified poultry products as a potentially significant source of total As exposure for Americans, studies consistently demonstrate that <1% of samples tested are above the 0.5 ppm limit established by the US Food and Drug Administration Center for Veterinary Medicine. Although laboratory studies have demonstrated the possibility that As in poultry litter could pollute ground waters, million of tons of litter have been applied to the land, and no link has been established between litter application and As contamination of ground water. Yet, the fact that <2% of the United States population is involved in production agriculture and the overtones associated with the word "arsenic" could mean the matter becomes a perception issue.

Animal Feed↗

PubMed1994

Migraine diagnosis and clinical symptomatology.

Migraine is a very common phenomenon. Eighteen percent of women in this country and 6% of men have migraine. The old classification for headaches and diagnostic criteria were published in 1962, more than a quarter of a century ago. In 1988, the International Headache Society published a new classification and diagnostic criteria for all headache disorders, cranial neuralgias, and facial pain. The International Headache Society classification divides migraine, as it had been divided in the past, into two major categories: migraine without aura (formerly called common migraine) and migraine with aura (formerly called classical migraine). These criteria are rather complex and simpler criteria are proposed for clinical practice. The typical patient with migraine is a woman whose headaches began in adolescence or young adult life. There usually is a family history of migraine. Migraine is almost always more than just a headache. Virtually anything in the external environment and many things in the internal milieu may provoke migraine in a susceptible individual. There are many potential manifestations of the aura of migraine, but 90% are visual phenomena. Migraine in children is a little different than in adults. When the onset is below the age of puberty, the ratio of females to males is equal, but after puberty there is a striking predominance of women over men in a ratio of 3:1. Whenever the history of migraine is not typical or if something unexpected is found on examination, imaging studies are warranted.

Child↗

PubMed1976

Marine oscillatoria (Trichodesmium): explanation for aerobic nitrogen fixation without heterocysts.

Nitrogen fixation in marine Oscillatoria appears to be associated with differentiated cells located in the center of the colony. These central cells exhibit reduced pigmentation relative to peripherally located cells and do not incorporate 14CO2 in photosynthesis. Central cells apparently do not produce O2 which would deactivate nitrogenase. When central cells are exposed to O2 via disruption of the colonies, N2 fixation (acetylene reduction) decreases sharply even though individual trichomes remain intact. Disruption of colonies in the absence of O2 does not cause reduced nitrogenase activity. In the sea, turbulence from wave action apparently separates trichomes allowing O2 to enter thus decreasing nitrogenase activity. These observations explain how Oscillatoria is able to fix N2 without heterocysts in an aerobic environment and why it blooms virtually always occur in calm seas.

Eukaryota↗

PubMed1983

Fetal rat lung maturation: initiation and modulation.

The purpose of this study was to determine whether a rise in the level of circulating hormones is responsible for initiating fetal lung maturation. Explants of 13- to 20-day fetal rat lung were cultured in a constant chemically defined medium containing 0 or 1% serum. Growth, morphological maturation, and two biochemical markers of lung development, disaturated phosphatidylcholine (DSPC) synthesis and specific nuclear glucocorticoid binding, showed evidence of continuing development in culture. There is normally a marked increase in DSPC content and in the rate of choline incorporation into DSPC after 20 days gestation. Regardless of the gestational age of the fetal lungs used, there was a similar increase in culture at an equivalent gestational age of 20 days (e.g., 14-day lung after 6 days, 16-day lung after 4 days). Removal of 50 or 75% of the lung mesenchymal tissue at the initiation of the culture period did not prevent the increase in choline incorporation. Since the culture environment was constant and contained virtually no hormones, we conclude that the stimulus for the initiation of fetal lung maturation is most likely located in the lung tissue itself. The role of circulating hormones is probably later modulation of the maturational process.

Animals↗

PubMed2005

Internal model of gravity for hand interception: parametric adaptation to zero-gravity visual targets on Earth.

Internal model is a neural mechanism that mimics the dynamics of an object for sensory motor or cognitive functions. Recent research focuses on the issue of whether multiple internal models are learned and switched to cope with a variety of conditions, or single general models are adapted by tuning the parameters. Here we addressed this issue by investigating how the manual interception of a moving target changes with changes of the visual environment. In our paradigm, a virtual target moves vertically downward on a screen with different laws of motion. Subjects are asked to punch a hidden ball that arrives in synchrony with the visual target. By using several different protocols, we systematically found that subjects do not develop a new internal model appropriate for constant speed targets, but they use the default gravity model and reduce the central processing time. The results imply that adaptation to zero-gravity targets involves a compression of temporal processing through the cortical and subcortical regions interconnected with the vestibular cortex, which has previously been shown to be the site of storage of the internal model of gravity.

Adaptation, Physiological↗

PubMed2006

The listening in spatialized noise test: an auditory processing disorder study.

The Listening in Spatialized Noise test (LISN) produces a virtual three-dimensional auditory environment under headphones. Various measures assess the extent to which either spatial, vocal, or spatial and vocal cues combined increase a listener's ability to comprehend a target story in the presence of distracter sentences, without being affected by differences between participants in variables such as linguistic skills. Ten children at risk for auditory processing disorder (APD group) were assessed on the LISN, as well as a traditional APD test battery. The APD group performed significantly more poorly on all LISN measures than 48 age-matched controls. On the spatial advantage measure, the APD group achieved a mean advantage of only 3.7 dB when the distracters were spatially separated from the target by +/-90 degrees, compared to 10.0 dB for the controls-the 6.3 dB difference significant at p < 0.000001, with nine children scoring outside the normal range. The LISN was considered a promising addition to an APD test battery.

Acoustic Stimulation↗

PubMedDate not supplied

Psychosocial support: a crucial component for the successful management of AIDS volunteers.

A multidisciplinary approach in the support of AIDS volunteers is discussed employing three dimensions: educational, social and psychological. This approach was developed by the Foundation for Interfaith Research and Ministry (FIRM) in Houston, Texas, to combat volunteer burnout and attrition often exhibited by volunteers when serving clients with AIDS and other chronic, debilitating diseases. An examination of the specific goals and tasks required of volunteer managers/coordinators to utilize this approach are outlined. Although these three components of support were implemented for AIDS volunteers, they can easily be modified to suit virtually any type of volunteer environment and are appropriate tools to enhance a variety of volunteer settings. Ideas and suggestions as to how this psychosocial model of support can be adapted for an organization's use are included.

Acquired Immunodeficiency Syndrome↗

PubMed1992

Physician extenders increase healthcare access.

To ensure rural residents access to primary care services, Saint Vincent Hospital and Health Center, Billings, MT, operates five physician-operated clinics, located between 8 and 81 miles from Billings. Two of the clinics are in communities that are not large enough to sustain a physician practice, so they are staffed by certified physician assistants (PA-Cs). Licensed and practicing with supervision of a physician, PAs provide a variety of patient care services in virtually every medical specialty and environment. One-third of the nation's PAs work in primary care health professional shortage areas, providing services comparable to those of a family practitioner. National studies reveal a high degree of satisfaction among both consumers and supervising physicians regarding the level of care provided by PAs. Professional liability claims against PAs are fewer than those against physicians, probably because of the higher degree of communication and attention patients receive as a result of the team approach. PAs can increase patient contact hours, decrease waiting times, and improve access to care overall. In addition, PA utilization is a cost-effective approach to healthcare delivery.

Community Health Centers↗

PubMed2004

A 3D interactive multimodal viewer as data mining tool for the Visible Human Dataset color image histograms.

An on-line virtual three-dimensional immersive environment to navigate through colorimetric characterization of the Visible Human Dataset (VHD) cryosectional cross-section color images is introduced. Real-time analysis of color component characteristics of a user defined set of VHD images is now possible. This is a potentially useful resource to many developers working on the VHD raw data, however it could be used in medical education.

Female↗

PubMed2005

Control of laparoscopic instrument motion in an inanimate bench model: implications for the training and evaluation of technical skills.

Laparoscopic surgery requires new methods of technical competency evaluation, as well as training. The first purpose was to assess the differences in motion characteristics between the tip of the instrument and the wrist. The second purpose was to determine whether similar control strategies are used to move instruments in virtual reality and bench model environments. Surgically naive participants were required to tap a laparoscopic instrument between two targets that differed in size and separation distance. Large amplitude movements were controlled with the movements of the wrist and small amplitude with the wrist and the fingers (p<.001). Participants utilized the flexibility of the skin of the laparoscopic trainer to facilitate their movements. These results suggest that monitoring the motions of the instrument tip is a more precise indication of its motions than are motions of the wrist when movements of small amplitudes are produced. Moreover, in order to increase fidelity, VR trainers should simulate the flexibility of the real structures around the insertion of the instrument.

Canada↗

PubMed1994

The crystal structure of adamalysin II, a zinc-endopeptidase from the snake venom of the eastern diamondback rattlesnake Crotalus adamanteus.

1. Adamalysin II, alias proteinase II, a 24-kDa zinc-endopeptidase from the snake venom of Crotalus adamanteus, is a member of a large family of metalloproteinases isolated as small proteinases or proteolytic domains of mosaic hemorrhagic proteins from various snake venoms. Homologous domains have been recently detected in multimodular mammalian reproductive tract proteins and in mammalian gene products, somatic rearrangements of which seem to be linked to primary breast cancers. 2. The 2.0 A X-ray crystal structure of adamalysin II reveals an ellipsoidal molecule with a shallow active-site cleft separating a relatively irregularly folded sub-domain from the main molecular body composed of a 5-stranded beta-sheet and four alpha-helices. Opposite to this active-site cleft is an integrated calcium ion liganded by carbonyl and strongly conserved carboxylate/carboxamide residues. The folding of the peptide fragment containing the zinc-binding motif HExxHxxGxxH bears only a distant resemblance to thermolysin; it is identical to that found in astacin, in collagenases, and in serralysins, with the three histidines (His142, His146, His152) and a water molecule (linked to the glutamic acid Glu143) likewise constituting the zinc ligand; similar to collagenases, but in contrast to astacin, adamalysin II lacks a fifth (tyrosine) zinc ligand, leaving its zinc-ion tetrahedrally coordinated. Furthermore, adamalysin II shares an identical active-site basement formed by a common Met-turn. 3. Due to their virtually identical active-site environment and similar folding topology, the snake venom metalloproteinases (hitherto called adamalysins) and the three other proteinases might be grouped into a common superfamily called metzincins with distinct differences from the thermolysin family.

Amino Acid Sequence↗

PubMed2006

Performance and ergonomic characteristics of expert surgeons using a face-mounted display during virtual reality-simulated laparoscopic surgery: an electromyographically based study.

BACKGROUND: Display positions for laparoscopy in current operating rooms may not be optimal for surgeon comfort or task performance, and face-mounted displays (FMDs) have been forwarded as a potential ergonomic solution. Little is known concerning expert use characteristics of these devices that might help define their role in future surgical care. The authors report the performance and ergonomic characterization of an FMD using virtual reality simulation technology to recreate the surgical environment. METHODS: An FMD was studied in short- and long-duration trials of validated virtual reality-simulated surgical tasks. For the short-duration phase 7, expert surgeons were familiarized with a task on a conventional monitor, then returned on two separate occasions to repeat the task with the FMD while digital photos were taken during task performance and at the end in a standardized fashion. For the long-duration phase 5, expert surgeons performed two separate trials with repetitive groups of validated tasks for a minimum of 30 min while electromyelogram and performance data were measured. Photos of their gaze angle during and at the end of the trial were taken. RESULTS: All the participants consistently assumed a gaze angle slightly below horizontal during task performance. Performance scores on the FMD did not differ from those obtained with a conventional display, and remained stable with repetitive task performance. No participant had electromyelogram signals that exceeded the established thresholds for fatigue, but some had values within the threshold range. CONCLUSION: The natural gaze angle during simulated surgery was consistently a bit below horizontal during rigorous virtual reality-simulated tasks. Performance was not compromised during expert surgeons' use of an FMD, nor did muscle fatigue characteristics arise under these conditions. The findings suggest that these devices may represent a viable alternative to conventional displays for minimally invasive surgery, but definition of specific roles requires further investigation.

Biomedical Research↗

PubMed2003

Use of the evoked potential P3 component for control in a virtual apartment.

Virtual reality (VR) may prove useful for training individuals to use a brain-computer interface (BCI). It could provide complex and controllable experimental environments during BCI research and development as well as increase user motivation. In the study reported here, we examined the robustness of the evoked potential P3 component in virtual and nonvirtual environments. We asked subjects to control several objects or commands in a virtual apartment. Our results indicate that there are no significant differences in the P3 signal between subjects performing a task while immersed in VR versus subjects looking at a computer monitor. This indicates the robustness of the P3 signal over different environments. For an online control task, the performance in a VR environment was not significantly different from performance when looking at a computer monitor. There was, however, a more significant result when the subject's head view of the virtual world was fixed (p < 0.05) when compared with looking at a computer monitor. We also found that subjects' self-reported qualitative experiences did not necessarily match their objective performance. Six out of nine subjects liked the VR environment better, but only one of these subjects performed the best in this environment. The possible ramifications of this, as well as plans for future work, are discussed.

Activities of Daily Living↗

PubMed2003

Evolution was chemically constrained.

The objective of this paper is to present a systems view of the major features of biological evolution based upon changes in internal chemistry and uses of cellular space, both of which it will be stated were dependent on the changing chemical environment. The account concerns the major developments from prokaryotes to eukaryotes, to multi-cellular organisms, to animals with nervous systems and a brain, and finally to human beings and their uses of chemical elements in space outside themselves. It will be stated that the changes were in an inevitable progression, and were not just due to blind chance, so that "random searching" by a coded system to give species had a fixed overall route. The chemical sequence is from a reducing to an ever-increasingly oxidizing environment, while organisms retained reduced chemicals. The process was furthered recently by human beings who have also increased the range of reduced products trapped on Earth in novel forms. All the developments are brought about from the nature of the chemicals which organisms accumulate using the environment and its changes. The relationship to the manner in which particular species (gene sequences) were coincidentally changed, the molecular view of evolution, is left for additional examination. There is a further issue in that the changes of the chemistry of the environment developed largely at equilibrium due to the relatively fast reactions there of the available inorganic chemicals. Inside cells, some of these same chemicals also came to equilibrium within compounds. All such equilibria reduced the variance (degrees of freedom) of the total environmental/biological system and its possible development. However, the more sophisticated organic chemistry, almost totally inside cells until humans evolved, is kinetically controlled and limited by the demands of cellular reduction necessary to produce essential chemicals and by the availability of certain elements and energy. Hence the variability of reductive cellular organic chemistry and its limitations in cells have to be considered separately. While as a whole they drive the oxidation of the environment, they also allow speciation within the major changes of organisms. Human beings have introduced recently new, virtually irreversible, inorganic and organic chemistry in the environment, much of it new modes of irreversible storage of reduced chemicals, and this is, we state, the last possible step of chemical evolution. We must attempt to evaluate its effect on organisms generally. It must be clear that all the changes and the original life forms are dependent upon energy as well as material capture and flow. We shall have to consider in which forms energy was available over the period of evolution, how it was usefully transformed, and the ways in which its sources changed.

Animals↗

PubMed1999

Sex and adaptation in a changing environment.

In this study we consider a mathematical model of a sexual population that lives in a changing environment. We find that a low rate of environmental change can produce a very large increase in genetic variability. This may help to explain the high levels of heritability observed in many natural populations. We also study asexuality and find that a modest rate of environmental change can be very damaging to an asexual population, while leaving a sexual population virtually unscathed. Furthermore, in a changing environment, the advantages of sexuality over asexuality can be much greater than suggested by most previous studies. Our analysis applies in the case of very large populations, where stochastic forces may be neglected.

Adaptation, Physiological↗

PubMed2001

Principles of computer-assisted arthroscopy of the temporomandibular joint with optoelectronic tracking technology.

PURPOSE: This preliminary clinical study evaluated the applicability, accuracy, and benefits of computer-assisted arthroscopy of the temporomandibular joint (TMJ) with optoelectronic tracking technology. MATERIALS AND METHODS: A hybrid of reality and virtual reality is built as a composite-reality environment by extracting 3-dimensional anatomical structures through use of computed tomography, magnetic resonance imaging, radiography, and other types of imaging procedures commonly used in clinical praxis. These various independent sources of imaging data of a particular patient can be combined with and complemented by complex graphic simulations. Intraoperatively they are merged with online position data of surgical instruments inside the patient's TMJ. This hybrid model of detailed anatomical structures, guidelines, and real-time instrument positions allows the surgeon to accurately plan the arthroscopic intervention as well as to navigate effectively intraoperatively. RESULTS: In the first 10 cases of computer-assisted TMJ arthroscopy, composite reality environment technology permitted the online visualization of TMJ structures, puncture sites, instrument positions, and virtual pathways in relation to anatomical landmarks with high spatial accuracy (minimum, 0.0 mm; maximum, 2.5 mm; mean, 1.4 mm; SD, 0.6 mm) and high temporal resolution (100 ms). Past, present, and possible future instrument positions can be displayed. The application of computer-assisted arthroscopy caused little immobility for either surgeon or patient. CONCLUSION: Even experienced surgeons profit from improved precision in the handling of the arthroscope; thus this technology was found to be particularly useful in degenerative temporomandibular disorders and for triangulation procedures.

Arthroscopes↗

PubMed1992

High-performance computing, high-speed networks, and configurable computing environments: progress toward fully distributed computing.

The next several years will see the maturing of a collection of technologies that will enable fully and transparently distributed computing environments. Networks will be used to configure independent computing, storage, and I/O elements into "virtual systems" that are optimal for solving a particular problem. This environment will make the most powerful computing systems those that are logically assembled from network-based components and will also make those systems available to a widespread audience. Anticipating that the necessary technology and communications infrastructure will be available in the next 3 to 5 years, we are developing and demonstrating prototype applications that test and exercise the currently available elements of this configurable environment. The Lawrence Berkeley Laboratory (LBL) Information and Computing Sciences and Research Medicine Divisions have collaborated with the Pittsburgh Supercomputer Center to demonstrate one distributed application that illuminates the issues and potential of using networks to configure virtual systems. This application allows the interactive visualization of large three-dimensional (3D) scalar fields (voxel data sets) by using a network-based configuration of heterogeneous supercomputers and workstations. The specific test case is visualization of 3D magnetic resonance imaging (MRI) data. The virtual system architecture consists of a Connection Machine-2 (CM-2) that performs surface reconstruction from the voxel data, a Cray Y-MP that renders the resulting geometric data into an image, and a workstation that provides the display of the image and the user interface for specifying the parameters for the geometry generation and 3D viewing. These three elements are configured into a virtual system by using several different network technologies. This paper reviews the current status of the software, hardware, and communications technologies that are needed to enable this configurable environment. These interdependent technologies include: (1) user interface and application program construction methodologies, (2) the interprocess communication (IPC) mechanisms used to connect the software modules of the application, (3) the network protocols and interface hardware used by the IPC for communicating between modules running on separate and independent computing system elements, (4) the telecommunications infrastructure that provides the low-level data transfer functions for the networks that connect the geographically distributed elements used by the application, and (5) the nature of the functional elements that will be connected to form virtual systems.

Computer Communication Networks↗