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At least 559 records · Page 31Linked to original sources
PubMedDate not supplied

Orientation and two-dimensional organization of proteins at chelator lipid interfaces.

The analysis how proteins interact or assemble with each other in time and space is of central interest. Biofunctionalized interfaces can be applied to study protein-protein interactions in solution or elementary biological processes at membranes. Chelator lipid layers are well suited for these applications as they specifically bind histidine-tagged fusion proteins and further mimic the two-dimensional world of biological membranes. Here, we used green fluorescent protein (GFP) as a model to study its reversible, functional, and oriented immobilization via histidine-tag at chelator lipid interfaces by various surface sensitive techniques. Taking advantage of the self-organizing properties of chelator lipids, the association and dissociation kinetics, the surface density as well as the organization of the protein in two-dimensional arrays can be controlled. The chelator lipid system can be used for bioanalytical and structural studies as well as to examine recognition processes at membranes.

Chelating Agents↗
PubMed1990

The effects of microgravity on the skeletal system--a review.

Exposure of astronauts to microgravity leads to the loss of calcium from weightbearing bones. Prolonged exposure, e.g., during a journey to Mars, may present problems on return to Earth, with increased risk of fractures and premature osteoporosis in later life. The precise mechanisms of calcium loss have yet to be determined although a key feature is the absence of mechanical loading. Countermeasures aimed at reducing calcium loss to acceptable levels include the use of exercise, drugs, dietary modifications and inertia suits such as the Soviet "Penguin" suit. Missions of a number of years may, however, require the development of artificial gravity on a spacecraft. The country that first solves the physiological problems of man in space and, in particular, skeletal calcium loss, will almost certainly be the first to be able to put a man on Mars.

Adaptation, Physiological↗
PubMed1992

[Treatment of vesicovaginal fistulas].

The authors evaluated in a retrospective analysis their experience with treatment of vesicovaginal fistulae in 36 patients. Most frequently--almost in 90%--the fistulae developed after a gynaecological operation, in particular surgery on account of benign, but also malignant disease. The authors used for surgical correction of the fistulae a transvaginal approach in 28 (77.8%) patients, a transvesical approach in 5 (13.9%) patients and a transvesical and transperitoneal approach in two (5.5%) patients. One fistula receded spontaneously during drainage of the urinary bladder. Primary correction of the fistula was successful in 34 (94.4%) patients. In two patients further surgical treatment was necessary. With regard to their favourable experience the authors recommend a transvaginal approach which is in their opinion suited for the majority of non- complicated vesicovaginal fistulae. In corrections of extensive fistulae after radiotherapy a combined transvesical and transperitoneal approach with fixation of the omentum in the space between the vagina and urinary bladder proved useful.

Adult↗
PubMed1977

[Contribution to the problem of color reproduction in photomicrography with color films (author's transl)].

In order to define clearly the possibilities and conformities in reproducing stained microscopic specimens we need an exact system of formal co-ordination and conception. Therefore, an assay was made to find practical criterions allowing the choice of the most suited color films for the photomicrography of stained preparations. This was done by splitting up the transfer of information by adequate reproducible colors of the slides with the color space. Examples are given for Eosin bluish, for the mixture of Light green and Xylidin Ponceau and for the colors of Fujichrome R 100.

Histological Techniques↗
PubMed1993

[Possibilities of quality assurance in ambulatory rehabilitation].

Formal, structurally determined quality requirements (for medical and non-medical staff, space and equipment, respectively) are supplemented by guidelines that are able to inform about the actual course of rehabilitation. Not only externally controlled medical reports on the treatment are suited for this, but also inquiries of patients comparisons between sickness insurances (for example on duration of inability to work, need for hospital measures of rehabilitation) and the comparison with patients who did not take part in ambulant rehabilitation. A report system has to be built up that pictures the clientele of the "reha"-institution, measures changes and documents results a long-term basis. The proposed periodical tests and final test serve not only for the control of patient progress in each single case with information for the practitioner, but also give financial committees hints on the efficiency of the work of the institutions for rehabilitation. Continuous attendance is proposed with a report system and scientific evaluation, whose results are sent concisely but anonymous by to the contract partners on a quarterly basis. A committee for quality assurance discusses new developments and improves ambulant rehabilitation.

Ambulatory Care↗
PubMed2000

Acoustic field variability induced by time evolving internal wave fields

A space- and time-dependent internal wave model was developed for a shallow water area on the New Jersey continental shelf and combined with a propagation algorithm to perform numerical simulations of acoustic field variability. This data-constrained environmental model links the oceanographic field, dominated by internal waves, to the random sound speed distribution that drives acoustic field fluctuations in this region. Working with a suite of environmental measurements along a 42-km track, a parameter set was developed that characterized the influence of the internal wave field on sound speed perturbations in the water column. The acoustic propagation environment was reconstructed from this set in conjunction with bottom parameters extracted by use of acoustic inversion techniques. The resulting space- and time-varying sound speed field was synthesized from an internal wave field composed of both a spatially diffuse (linear) contribution and a spatially localized (nonlinear) component, the latter consisting of solitary waves propagating with the internal tide. Acoustic simulation results at 224 and 400 Hz were obtained from a solution to an elastic parabolic equation and are presented as examples of propagation through this evolving environment. Modal decomposition of the acoustic field received at a vertical line array was used to clarify the effects of both internal wave contributions to the complex structure of the received signals.

Journal Article↗
PubMed1991

A slim needle-shaped multiwire microelectrode for intracerebral recording.

The construction of a needle-shaped multiwire microelectrode is described. It can be made with simple mechanical tools. The presented electrode assembly consists of 12 insulated nichrome wires (core diameter 25 microns) which are embedded in epoxylite resin. The straight-cut wire tips are aligned lengthwise and have a relative spacing of 150 microns. Outer dimensions vary from 100 x 180 microns at the level of the 1st electrode channel, to 100 x 100 microns at the level of the 12th channel at the tip. The configuration of this electrode was determined by its application: the laminar analysis of evoked potentials in the cortex of the rat. However, the number of channels, the diameter of the (nichrome) wire which determines the surface area of these channels, and the channel spacing can be easily adjusted during construction to meet other experimental requirements, such as the recording of single-unit activity. The electrode which is composed of biocompatible materials is suited for the study of field potentials and multiple-unit activity, in both acute and chronic experiments, and can be used repeatedly. To demonstrate the performance of the electrode assembly, a depth profile of field potentials is presented, accompanied by the corresponding current source density distribution. The potentials were recorded in the somatosensory cortex of the rat following stimulation of the median nerve under ketamine anesthesia.

Animals↗
PubMed2000

Vestibular and visual contribution to fish behavior under microgravity.

Vestibular and visual information are two major factors fish use for controlling their posture under 1 G conditions. Parabolic flight experiments were carried out to observe the fish behavior under microgravity for several different strains of Medaka fish (Oryzias latipes). There existed a clear strain-difference in the behavioral response of the fish under microgravity: Some strains looped, while other strains did not loop at all. However, even the latter strains looped under microgravity conditions when kept in complete darkness, suggesting the contribution of visual information to the posture control under microgravity. In the laboratory, eyesight (visual acuity) was checked for each strain, using a rotating striped-drum apparatus. The results also showed a strain-difference, which gave a clue to the different degree of adaptability to microgravity among different strains. Beside loopings, some fish exhibited rolling movement around their body axis. Tracing each fish during and between parabolas, it was shown that to which side each fish rolls was determined specifically to each individual fish, and not to each strain. Thus, rolling direction is not genetically determined. This may support the otolith asymmetry hypothesis. Fish of a mutant strain (ha strain, having homozygous recessive of one gene ha) have some malfunction in otolith-vestibular system, and their behavior showed they are not dependent on gravity. Morphological abnormalities of their ear vesicles during the embryonic and baby stages were noted. Their eyesight and dorsal light responses were also studied. Progress in the project of establishing a new strain which has good eyesight and, at the same time, being deficient in otolith-vestibular system was reported. Crosses between the strain of good eyesight and ha strain were made, and to some extent, F2 fish have already shown such characteristics suited for living under microgravity conditions.

Animals↗
PubMed1997

[Approaches for a systemic modelling of health programs].

The aim of this paper is to achieve a systemic model to describe a health programme taking into account the influence of the actors. The data were collected via interviews with 15 people collaborating on two programmes: screening of colorectal cancer using the Hémoccult II test in France, and restructuring health services in a district in Guinea. The results stress that a public and community health programme can be described as a self-organizing, dynamic, observing and observed system. With a systemic approach, a programme can be modelled according to three steps. First, preliminaries: although initially motivated by the wish to improve the system, the intervention on it meets with resistance to any change. This stage proposes to open an "intervention space" including the definition of an appropriate framework, and the modelling of the problematic situation. Second, change: this stage brings new standards in the system. The more useful, the more suited to the mind of the collaborators and the more integrated into the existing social networks, the more easily the changes are welcomed. Finally, autonomization: the regulations of the system contribute to maintain the new standards, and thus to strengthen the changes. In conclusion, in the initial purpose to improve its operational capabilities, an intervention on a local part of the social and health system may, on the contrary, cause troubles. The systemic approach proposes a scenario in order to deal with this complexity. It also gives new insights for planning, implementing, and assessing health programmes.

Colorectal Neoplasms↗
PubMed1999

A mathematical model for the analysis of cross-sectional brain glucose metabolism data in children.

1. The authors present here a 5-parameter developmental function designed to describe quantitatively the time-course of changes in glucose metabolism with age. This function consists of a plateau phase which is described by the rate of increase with age and the height of the plateau, followed by a decline phase characterized by the rate of decrease to adult levels. These two phases are separated by a distinct point in time, at which the transition between the two phases occurs. 2. The model is designed to fit published data showing that glucose metabolic rate in frontal cortex at birth is about 60% of adult values (mean adult value is 24 mumol/100 g/min) and increases to slightly less than triple adult value by age 3. The metabolic rate remains at this level until the age of approximately 8 years when it starts the decline to adult values. 3. A procedure is presented which allows the approximate computation of the 98% confidence contours in data space for the developmental function. The computation is based on the joint probability function obtained from the model covariance matrix. 4. The newly designed 5-parameter developmental function is well suited to describe maturational changes of glucose metabolism. Due to its excellent model identifiability and the interpretability of individual parameters, this function is better suited for description of maturational changes than the gamma-function. Furthermore, this function may provide a useful framework for interpretation of other data sets during development.

Adolescent↗
PubMed1999

Crystal structure retrieval by maximum entropy analysis of atomic resolution incoherent images

In this paper, we discuss the application of the maximum entropy method to atomic resolution Z-contrast images acquired in a scanning transmission electron microscope. Z-contrast is an incoherent imaging technique, and can be described as a convolution between an object function (the real-space map of the columnar scattering cross-section to high angles) and a point spread function (the effective electron probe). As such, we show that the technique is ideally suited to maximum entropy analysis which can, given an electron probe distribution, retrieve the 'most likely' Z-contrast object function. Using both simulated and experimentally acquired data, we explore the capabilities of maximum entropy analysis when applied to atomic resolution Z-contrast images, drawing conclusions on both the range of applicability of the technique and the nature of the retrieved crystal structures. Ultimately, we show the way in which the combination of Z-contrast imaging with maximum entropy analysis can be used to yield important information on unexpected atomic structures.

Journal Article↗
PubMed2005

Deliberate perioperative systems design improves operating room throughput.

BACKGROUND: New operating room (OR) design focuses more on the surgical environment than on the process of care. The authors sought to improve OR throughput and reduce time per case by goal-directed design of a demonstration OR and the perioperative processes occurring within and around it. METHODS: The authors constructed a three-room suite including an OR, an induction room, and an early recovery area. Traditionally sequential activities were run in parallel, and nonsurgical activities were moved from the OR to the supporting spaces. The new workflow was supported by additional anesthesia and nursing personnel. The authors used a retrospective, case- and surgeon-matched design to compare the throughput, cost, and revenue performance of the new OR to traditional ORs. RESULTS: For surgeons performing the same case mix in both environments, the new OR processed more cases per day than traditional ORs and used less time per case. Throughput improvement came from superior nonoperative performance. Nonoperative Time was reduced from 67 min (95% confidence interval, 64-70 min) to 38 min (95% confidence interval, 35-40 min) in the new OR. All components of Nonoperative Time were meaningfully reduced. Operative Time decreased by approximately 5%. Hospital and anesthesia costs per case increased, but the increased throughput offset costs and the global net margin was unchanged. CONCLUSIONS: Deliberate OR and perioperative process redesign improved throughput. Performance improvement derived from relocating and reorganizing nonoperative activities. Better OR throughput entailed additional costs but allowed additional patients to be accommodated in the OR while generating revenue that balanced these additional costs.

Anesthesia↗
PubMed1992

Temporoparietal fascial flap for orbital and eyelid reconstruction.

The temporoparietal fascial flap is a recognized technique for the transfer of vascularized tissue in the craniofacial region. The flap has a predictable axial vessel, provides thin vascularized tissue, and can be harvested with minimal donor-site morbidity. The temporoparietal fascial flap is well suited for orbital or eyelid reconstruction because of its proximity to the orbit. The flap is useful for reconstruction of anatomic barriers between the orbit, intracranial cavity, and paranasal sinus spaces. We present four patients in whom the temporoparietal fascial flap was used for orbital reconstruction following extirpative surgery for orbital neoplasm and two patients in whom the flap was used for lower eyelid and malar reconstruction.

Adult↗
PubMedDate not supplied

An approach to the perceptual optimization of complex visualizations.

This paper proposes a new experimental framework within which evidence regarding the perceptual characteristics of a visualization method can be collected, and describes how this evidence can be explored to discover principles and insights to guide the design of perceptually near-optimal visualizations. We make the case that each of the current approaches for evaluating visualizations is limited in what it can tell us about optimal tuning and visual design. We go on to argue that our new approach is better suited to optimizing the kinds of complex visual displays that are commonly created in visualization. Our method uses human-in-the-loop experiments to selectively search through the parameter space of a visualization method, generating large databases of rated visualization solutions. Data mining is then used to extract results from the database, ranging from highly specific exemplar visualizations for a particular data set, to more broadly applicable guidelines for visualization design. We illustrate our approach using a recent study of optimal texturing for layered surfaces viewed in stereo and in motion. We show that a genetic algorithm is a valuable way of guiding the human-in-the-loop search through visualization parameter space. We also demonstrate several useful data mining methods including clustering, principal component analysis, neural networks, and statistical comparisons of functions of parameters.

Algorithms↗
PubMed1994

Estimation of renal interstitial adenosine and purine metabolites by microdialysis.

It has been proposed that adenosine, derived from ATP and released into the renal interstitium, mediates a reduction in renal function in ischemic acute renal failure. Because no direct measurements of interstitial adenosine are available, we evaluated an in vivo microdialysis technique to assess the levels of adenosine and its metabolites in the cortex of the normal rat kidney (n = 6). Microdialysis probe implantation did not alter cortical renal blood flow, glomerular filtration rate, or fractional sodium excretion. The interstitial concentration of adenosine was 199 +/- 53 nM, and relative concentrations of inosine, hypoxanthine, xanthine, and uric acid were 99 +/- 47, 182 +/- 29, and 183 +/- 70 nM and 1.8 +/- 0.4 microM, respectively. Infusion of ATP-MgCl2 (n = 5) resulted in a significant increase in the dialysate levels of adenosine (67 +/- 11 to 378 +/- 97 nM), inosine (230 +/- 102 to 803 +/- 219 nM), and uric acid (3.5 +/- 1.3 to 6.9 +/- 1.7 microM). In conclusion, this study demonstrates that the microdialysis technique is suited to monitor metabolically important substances in the renal interstitium.

Adenosine↗
PubMed1999

Hockey.

Hockey is a game of strength, speed, and skill. It is among the most difficult to master, the costliest to equip, the fastest to watch, and the most dangerous to play. It requires a combination of power, endurance, and flexibility applied within a confined space over a cold, hard, and slippery surface. It is a game of control and lack of control, both of emotions and flying objects. Hopefully, the reader will be better suited to understand the "culture" of hockey, both clinically and functionally, and can better interact with the men and women who play this fantastic sport, the one I hope to be playing for another 25 years, or until I finally get it right!

Adolescent↗
PubMed1969

Intestinal hydrogen and methane of men fed space diet.

Intestinal bacteria form two gases, hydrogen (H2) and methane (CH4), that could constitute a fire hazard in a closed chamber. So H2 and CH4 pass from the anus but these gases are also transported by the blood to the lungs and removed to the atmosphere. Several factors affect gas formation: 1) amount and kind of fermentable substrate; 2) abundance, types, and location of microflora; and 3) psychic and somatic conditions that affect the gut. We evaluated the first factor by studying men fed different diets and have also recorded influences of uncontrollable factors. One group of 6 men ate Gemini-type diet (S) and another received a bland formula (F), for 42 days. Breath and rectal gases were analyzed during the first and final weeks. Flatus gases varied widely within dietary groups but much more gas was generated with diet S than with F. In the first 12-hour collection, subjects fed S passed 3 to 209 ml (ATAP) of rectal H2 (avg 52) and 24 to 156 ml (avg 69) from the lungs (assuming normal pulmonary ventilation). With F, these values were 0 to 3 ml (avg 1) and 6 to 36 ml (avg 20). Subjects were calmer during the second test. Gas production was lower with S than initially; F values were unchanged. Methane differed idiosyncratically, presumably due to differences in flora. Computed from 12-hour values, maximum potential daily H2 and CH4 are per man: for S, 730 ml and 382 ml; for F, 80 and 222 ml. Volumes would be larger at reduced spacecraft and suit pressures.

Bacteria↗