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PubMed2005

Compressed representations of macromolecular structures and properties.

We introduce a new and unified, compressed volumetric representation for macromolecular structures at varying feature resolutions, as well as for many computed associated properties. Important caveats of this compressed representation are fast random data access and decompression operations. Many computational tasks for manipulating large structures, including those requiring interactivity such as real-time visualization, are greatly enhanced by utilizing this compact representation. The compression scheme is obtained by using a custom designed hierarchical wavelet basis construction. Due to the continuity offered by these wavelets, we retain very good accuracy of molecular surfaces, at very high compression ratios, for macromolecular structures at multiple resolutions.

Computational Biology↗
PubMed2000

Oral pentoxifylline for treatment of venous leg ulcers.

BACKGROUND: Healing of venous leg ulcers is improved by the use of compression bandaging but some venous ulcers do not respond to compression therapy. Pentoxifylline, a drug which helps blood flow, has been used to treat venous leg ulcers but to date there has been no systematic review. OBJECTIVES: To assess the effects of pentoxifylline ('Trental 400') for treating venous leg ulcers, when compared with placebo, or in comparison with other therapies, in the presence or absence of compression therapy. SEARCH STRATEGY: We searched the Cochrane Peripheral Vascular Diseases and Wounds Groups specialised registers (date of search August 1999), and reference lists of relevant articles. We hand searched relevant journals and conference proceedings, and contacted Hoechst (the manufacturer of the drug) and experts in the field. SELECTION CRITERIA: Randomised trials comparing pentoxifylline with placebo or other therapy in the presence or absence of compression, in patients with venous leg ulcers. DATA COLLECTION AND ANALYSIS: Details from eligible trials were extracted and summarised by one reviewer using a coding sheet. Data extraction was independently verified by one other reviewer. MAIN RESULTS: Nine trials involving 572 adults were included. The quality of trials was variable. Eight trials compared pentoxifylline with placebo; in five of these trials patients received compression therapy. In one trial pentoxifylline was compared with defibrotide in patients who also received compression. By pooling eight trials that compared pentoxifylline with placebo (with or without compression) it was found pentoxifylline was more effective than placebo in terms of complete healing or significant improvement (relative risk for healing with pentoxifylline compared with placebo 1.41, 95% confidence interval 1.19 -1.66). Pentoxifylline and compression was more effective than placebo and compression (relative risk for healing with pentoxifylline 1.30, 95% confidence interval 1.10-1.54). Combination of similar trials using compression obtained a number needed to treat (NNT) of 7 (95%confidence interval 4-17). A comparison between pentoxifylline and defibrotide found no difference in healing rates. More adverse effects were reported in the pentoxifylline group, although this was not statistically significant (relative risk for adverse effects with pentoxifylline 1. 25, 95% confidence interval 0.87-1.80). Nearly half of the adverse effects were reported to be gastro-intestinal. REVIEWER'S CONCLUSIONS: Pentoxifylline appears to be an effective adjunct to compression bandaging for treating venous ulcers. There was no cost effectiveness data available and healthcare commissioners may therefore conclude that it not be considered a routine adjunct. Pentoxifylline in the absence of compression may be effective for treating venous ulcers in the absence of compression, although the evidence should be cautiously interpreted. The majority of adverse effects are likely to be tolerated by patients, and gastrointestinal disturbances (indigestion, diarrhoea and nausea) are the most frequent adverse effect.

Administration, Oral↗
PubMed2004

Improving the prediction of exceptionally poor tableting performance: an investigation into Hiestand's "special case".

The mechanical and flow properties of selected pharmaceutical powdered excipients and drug substances were evaluated to investigate their behavior as extremely poor tableting, or "special case," materials. The compaction stress, dynamic indentation hardness, and tensile strength of compacts compressed to 15% porosity and their powder's effective angle of internal friction were measured using the tableting indices technology and a simple shear cell, respectively. It has been previously demonstrated that compacts of special case materials exhibit a dynamic indentation hardness greater than the stress required to form the compact under slow compression conditions. In addition, new data suggest that special case materials also exhibit low compact dynamic indentation hardness, low compact tensile strength, and low powder effective angle of internal friction. These findings support the theory that the particles of such materials preferentially rearrange rather than deform under compressive conditions because bonding between them is weak. The added special case indicator measurements can be used to clearly identify exceptionally poor tableting powders during the selection of components for solid dosage formulations. Careful consideration of the data will provide guidance to the proper use of the bonding indices equations.

Excipients↗
PubMed1979

Multiplicative effects on sentence comprehension for combined acoustic distortions.

This study was designed to explore the effect on speech comprehension of combining two types of signal distortion. A tape of clearly-enunciated sentences in quiet was distorted in each of four ways: low-pass (LP) filtering, time compression, interruption, and noise masking. Data are reported on a population of normal-hearing young men for multiple-choice answer tests of colloquial sentences of either LP filtered at 1, 2, 3, or 4 kHz, time compressed by computer at 250 words/min, interrupted (50 msec on--50 msec off), masked by speech-spectrum noise at +2 dB S/N, or given each of the 12 possible combinations of LP filtering plus the other three distortions. Individual distortion conditions were adjusted to reduce speech comprehension performance to about 90% accuracy, Low-pass filtering above 1 kHz reduced comprehension by no more than five to 10 percentage points, but when LP filtering was added to the other distortions in turn, latent effects were uncovered. The reduction in comprehension with the combined distortions was much greater than the simple additive effects of the distortion and LP filtering by themselves. For example, LP filtering above 2 kHz produced no measurable effect on sentence comprehension but this same distortion in combination with noise masking reduced performance from 89.4 to 59.7% correct (where 25% was chance). This study further validates the multiply-compounded nature of simultaneous types of distortion. The use of LP filtering extends the multiplicative principle to the simulated case of high-frequency hearing losses.

Adult↗
PubMed2006

Improvement in the reproducibility and accuracy of DNA microarray quantification by optimizing hybridization conditions.

BACKGROUND: DNA microarrays, which have been increasingly used to monitor mRNA transcripts at a global level, can provide detailed insight into cellular processes involved in response to drugs and toxins. This is leading to new understandings of signaling networks that operate in the cell, and the molecular basis of diseases. Custom printed oligonucleotide arrays have proven to be an effective way to facilitate the applications of DNA microarray technology. A successful microarray experiment, however, involves many steps: well-designed oligonucleotide probes, printing, RNA extraction and labeling, hybridization, and imaging. Optimization is essential to generate reliable microarray data. RESULTS: Hybridization and washing steps are crucial for a successful microarray experiment. By following the hybridization and washing conditions recommended by an oligonucleotide provider, it was found that the expression ratios were compressed greater than expected and data analysis revealed a high degree of non-specific binding. A series of experiments was conducted using rat mixed tissue RNA reference material (MTRRM) and other RNA samples to optimize the hybridization and washing conditions. The optimized hybridization and washing conditions greatly reduced the non-specific binding and improved the accuracy of spot intensity measurements. CONCLUSION: The results from the optimized hybridization and washing conditions greatly improved the reproducibility and accuracy of expression ratios. These experiments also suggested the importance of probe designs using better bioinformatics approaches and the need for common reference RNA samples for platform performance evaluation in order to fulfill the potential of DNA microarray technology.

Animals↗
PubMed2005

Effect of mechanical compression on the lumbar nerve root: localization and changes of intraradicular inflammatory cytokines, nitric oxide, and cyclooxygenase.

STUDY DESIGN: Investigation of intraradicular inflammation induced by mechanical compression. OBJECTIVE: To investigate the mechanism of nerve root pain, this study used a lumbar nerve root compression model. SUMMARY OF BACKGROUND DATA: The manifestation of pain at sites of inflammation has a close relationship with the release of mediators from macrophages. However, the mediators involved in inflammation of nerve roots as a result of mechanical compression remain almost unknown. METHODS: In this study, the seventh lumbar nerve root of dogs was compressed with a clip for 3 weeks to observe the changes caused by compression. Immunohistochemistry was performed using the avidin-biotin-peroxidase complex method to observe the changes of T cells (CD45) and macrophages (Mac-1) after compression. Antibodies against as interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-alpha), inducible nitric oxide synthase (i-NOS), and cyclooxygenase (COX)-1 and 2 were used to examine the localization and changes of these mediators caused by nerve root compression. RESULTS: In control animals, resident T cells were detected, but there were no macrophages. IL-1beta and COX-2 were positive in the Schwann cells and vascular endothelial cells, while COX-1 was detected in the vascular endothelial cells. However, no cells showed TNF-alpha or i-NOS positively. After nerve root compression, numerous T cells and macrophages appeared among the demyelinized nerve fibers. The macrophages were positive for IL-1beta, TNF-alpha, i-NOS, and COX-2. CONCLUSION: Inflammatory cytokines, NO, and COX-2 may be deeply involved in radiculitis caused by mechanical compression, and these mediators seem to be important in the manifestation of root pain.

Animals↗
PubMed1987

Ordinal discrimination of ECG orthogonal features.

A rigorous mathematical analysis of Electrocardiogram (ECG) data is presented in this paper, as a decision support system for ECG interpretation. The mathematical analysis: provides a new insight to the ECG data, provides flexibility for future understanding of the heart system or the ECG, and avoids the need of measurements of parameters and the disagreement concerning the standard criteria of those parameters. The system enables compressed storage of the ECG data and an easy and accurate retrieval ability. An "ordinal straight line" method is presented for simple description of the ECG features as a combination of straight lines. A new developed discrimination method--the bisector method--is used for discrimination and classification between the normal and pathological groups. The physician's decision is based on both the physician's heuristic approach and the system's classification.

Data Collection↗
PubMed2000

Testing the impact attenuation of loose-fill playground surfaces.

OBJECTIVES: Our objective was to measure the impact attenuation performance of five types of loose-fill playground surfaces at a variety of drop heights, material depths, and conditions. METHODS: In a laboratory setting, an instrumented head form was dropped on varying depths of loose-fill materials at one foot height increments until critical deceleration values were exceeded. The effects of test box size, material temperature, and compression were also studied. RESULTS: Data suggest that a larger test box size influences test results. Uncompressed materials performed quite unexpectedly, that is, resilience did not necessarily increase with increasing depth of material and temperature did not have uniform effects. Compression before testing improved consistency of results. CONCLUSION: The current standard test procedure (ASTM F1292) appears problematic for loose-fill materials. Our results indicate that (1) shredded rubber was the best performer; (2) there was little difference between sand, wood fibers, and wood chips; and (3) pea gravel had the worst performance, making it a poor choice for playground surfacing.

Accidental Falls↗
PubMed2004

Peripheral vasculature: whole-body MR angiography with midfemoral venous compression--initial experience.

Five volunteers and 10 patients suspected of having peripheral vascular disease underwent multistation contrast material-enhanced three-dimensional whole-body magnetic resonance (MR) angiography. The first examination, based on standard protocol, lasted 72 seconds, while the following two examinations, performed with a high-spatial-resolution T1-weighted gradient-recalled-echo sequence for the last two stations (lower extremities) lasted 170 seconds. In the second high-resolution examination, midfemoral venous compression was used. Intraindividual comparison showed the high-resolution protocol with venous compression resulted in the best qualitative and quantitative image quality through higher signal-to-noise and contrast-to-noise ratios in the calf arteries. Despite prolonged acquisition times, there was no venous contamination. The data suggest that midfemoral venous compression should be incorporated in multistation protocols of the lower extremities to improve depiction of calf arteries without disturbing venous overlap.

Adult↗
PubMed2005

Comparison of two intermittent pneumatic compression systems. A hemodynamic study.

AIM: Sequential leg compression has been previously shown to be superior to uniform compression. The aim of our study was to compare the hemodynamic effectiveness of the portable sequential compression device (SCD Express Compression System, Tyco Healthcare Group LP, Mansfield, MA, USA) with a rapid inflation device (VenaFlow, Aircast, Inc, Summit, NJ, USA). The former, by sensing venous refill time, commences compression when the calf veins are refilled. METHODS: The two devices were tested in 12 normal volunteers in the semirecumbent position using duplex ultrasound. Baseline and augmented flow velocity and volume flow were measured at the level of the common femoral vein, above the saphenofemoral junction. Refilling time was determined from velocity recordings of the common femoral vein. Total and peak volume of blood expelled per hour during compression were calculated using flow data and the individual cycling rate. RESULTS: Both devices increased venous flow velocity, up to 3.8 times the baseline (all P<0.001). Refill time of the rapid inflation device was shorter in comparison with the sequential compression device (15+/-2.2 vs 25+/-4 s; P<0.001), suggesting incomplete vein evacuation. The sequential compression device, by augmenting flow throughout a significantly longer compression period per cycle (10.9 s vs 6.3 s), expelled significantly more venous blood (121+/-68 vs 81+/-63 mL; P<0.001). Similarly, the total volume of blood expelled per hour with the sequential compression device was 100% higher than the rapid inflation device (9685+/-5426 vs 4853+/-3658 mL; P<0.001). Although peak velocity enhancement was higher with the rapid inflation device, flow augmentation (a product of average blood flow velocity) was comparable (669+/-367 vs 771+/-574 cm/s; P=0.223) with the sequential compression device, mainly because the rapid inflation device failed to maintain flow enhancement beyond the initial flow surge. CONCLUSIONS: Sequential compression showed hemodynamic superiority compared to a rapid inflation device. This was enhanced further by the sensing of refill time, which resulted in more compression cycles over time. The relative efficacy of the two devices in deep vein thrombosis prevention should be tested in future studies.

Blood Flow Velocity↗
PubMed1985

Force response to rapid and slow small amplitude length releases in isometrically contracting normal width and radially compressed trabeculae from rat heart.

The early transient force response to small amplitude ramp length release, applied at the plateau of calcium activated force development, was studied in normal width and radially compressed trabeculae from rat right ventricle. Force recovery immediately following "rapid" (5 ms ramp duration) release was less in compressed than in normal width muscle. Force recovery immediately following "slow" (ramp duration greater than 160 ms) release was virtually absent in both compressed and normal width muscle. The difference in force levels between the beginning and end of slow releases was small in normal width muscle; in compressed muscle a noticeable difference in force levels was seen. The rate of force recovery immediately following "rapid" release, as given by the rate constant obtained by fitting a single exponential equation to the force recovery vs time data, was not altered by compression. These results suggest that radial compression divides crossbridges into two distinct populations: one which cycles normally and another which cycles very slowly, if at all.

Animals↗
PubMed1998

An implantable mechanical urinary sphincter: a new nonhydraulic design concept.

OBJECTIVES: We present data concerning an artificial implantable mechanical urinary sphincter that was designed to eliminate the inherent problems of the current hydraulic artificial urinary sphincter (American Medical System [AMS] 800). Our goal was to design a sphincter that creates urethral compression similar to the AMS 800 but creates the force without the use of fluid, thereby eliminating as much as 50% of the reoperations seen with the AMS 800, which occur because of fluid-related malfunctions. METHODS: An implantable artificial mechanical sphincter consisting of a compressive coil encompassed in a polytetrafluoroethylene sheath was devised and tested in 6 live mongrel dogs to establish compressive force versus bladder pressure data, so as to provide data to create a mechanical sphincter for use in humans. RESULTS: A direct relationship between bladder leakage pressure and cable tension force was demonstrated in all 6 experimental animals, thereby creating a mathematical equation that can be used by mechanical engineers to design a mechanical sphincter for use in humans. CONCLUSIONS: This study demonstrated that a mechanical urinary sphincter can be created that will provide continence and eliminate the problems associated with the hydraulic aspect of the AMS 800. In doing so, nearly 50% of the reoperations seen with the current AMS 800 can be eliminated, thereby improving the quality of life of patients for whom an artificial urinary sphincter is indicated.

Animals↗
PubMed1979

[Presentation of continuous electrocardiograms in compressed form. Preliminary note].

The conventional electrocardiogramme is poorly suited to the study of continuous electrocardiographical recordings. The rapid interpretation of recordings obtained by the Holter method is not compatible with the preservation of an analogous record of the whole period under study. The study of continuous electrocardiogrammes by computer uses only part of the data recorded. The technique of compression based on the principle of Contourography is a method of preserving continuous electrocardiographical records in their analogical form. This recording is a useful addition to the Holter method.

Electrocardiography↗
PubMed2001

Relaxation and sleep compression for late-life insomnia: a placebo-controlled trial.

Older adults with insomnia were recruited from the community and randomized to treatments: relaxation, sleep compression, and placebo desensitization. Questionnaire data collected at baseline, posttreatment, and 1-year follow-up and polysomnography data collected at baseline and follow-up yielded the following conclusions: All treatments improved self-reported sleep, but objective sleep was unchanged. Clinical significance analyses yielded the strongest findings supporting the active treatments and suggested that sleep compression was most effective. Results partially supported the conclusion that individuals with high daytime impairment (i.e., fatigue) respond best to treatments that extend sleep, as in relaxation, and individuals with low daytime impairment respond best to treatments that consolidate sleep, as in sleep compression. Strong methodological features including a placebo condition and a treatment implementation scheme elevate the confidence due these findings.

Aged↗
PubMed1988

[A computerized manual for assessing the dosage absorbed by breast tissue in mammography].

The computerized translation of "Handbook of glandular tissue doses in mammography" (HHS publication FDA 85-8239) is presented. It is registered on floppy disk and suitable for use in MS-DOS on IBM personal computer, Olivetti or compatible. The manual collects data published by many authors and suggests a method to estimate the dose released to the glandular tissue (considered at risk for breast cancer) in the most commonly used conditions for mammography. Besides translation manual, the program holds an algorithm developed by the authors, which allows the dose to the glandular tissue to be evaluated, given the following data: projection: craniocaudal or mediolateral; compression level: firm or moderate; breast size: small, medium or large; breast composition: percentage of glandular tissue content (by weight); X-ray beam quality: HVL mm Al. The algorithm is obtained from a bidimensional fit of the original data and is based on the terms contained in the manual. The program flow is guided by menus that make the procedure suitable for inexperienced operators too, both for consulting and printing and for computing program.

Algorithms↗
PubMed1998

Magnetic resonance imaging of experimental subacute spinal cord compression.

STUDY DESIGN: Subacute compression of the spinal cord was applied to rats. The animals were chronologically observed using magnetic resonance imaging for more than 8 weeks after surgery and were killed for histopathologic examination. OBJECTIVES: To investigate the correlation of changes in signal intensity on magnetic resonance images with those observed in histopathologic study and with the degree of spinal cord compression and paralysis. SUMMARY OF BACKGROUND DATA: No consensus has been reached concerning the correlation of magnetic resonance images to clinical symptoms of compressive myelopathy. Few reports are available in which magnetic resonance imaging findings are compared with histopathologic features in chronic or subacute experiments. METHODS: In rats under general anesthesia, the T11 lamina was thinned and a slow increase in volume was applied. Hind limb paralysis appeared 1 week after the procedure and spontaneously subsided thereafter. The degree of spinal compression and signal intensity was observed chronologically using magnetic resonance imaging. The signal intensity on the final MR images was rated on a four-point scale and compared with histopathologic findings. RESULTS: As spinal compression increased, the incidence of high signal intensity on long spin-echo images became higher. Low signal intensities on short spin-echo images were visible in animals in which compression and paralysis were the most severe. In these animals, cavitation and a dilated central canal were visible. High signal intensities on long spin-echo images reflected various pathologic changes. CONCLUSIONS: Changes in signal intensity on MR images are visible after the induction of myelopathy by high-pressure compression. These signal intensities may be useful in predicting the outcome of compressive myelopathy.

Animals↗