Blood lead analysis - precision and stability.
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Computational analysis of the thermal stability in thioredoxins: a molecular dynamics approach.
The knowledge of the relationship between the three-dimensional structure of a protein and its biological and stability is one of the most challenging problem in protein chemistry, since offers the possibility of changing both the specific action of a protein and its stability. In this work, we have approached the problem with studies on a protein family, the thioredoxins, using homology procedures, molecular dynamics simulations in vacuo at 300 K and 500 K and in water solution at 300 K, to determine the relationship between the three-dimensional structure of these proteins and their thermal stability. A comparative analysis, using computational approach, was performed between two thioredoxins with different resistance to temperature. Results obtained using the molecular dynamics techniques and minimization procedures give explanations of the experimental data, underlining that these techniques are able to correlate the increase in protein stabilization with the conformational and structural changes caused by single amino acid replacement. In addition, we report the factors that can be used as a guide in protein engineering and in site-directed mutagenesis to increase or decrease thermal stabilization for this protein family.
Amino Acid Sequence↗
Qualitative analysis of lumbar stabilization using point light and normal video displays.
Professionals in many fields use qualitative analysis to improve human movement. In previous research examining the reliability of physical therapists' qualitative assessments of lumbar stabilization, three experienced observers showed substantial agreement when viewing point light displays, but only moderate agreement when observing normal video displays. Replication of these findings in a larger group of less experienced observers would strengthen the notion that point light displays enhance qualitative analysis. The present study examined the reliability of qualitative assessments of lumbar stabilization when novice observers made judgments from two types of video displays. 50 fourth-year physical therapy students viewed either normal or point light video displays to judge lumbar stabilization of individuals performing a floor to waist lift. Multirater kappa coefficients for assessments made from normal displays and point light displays were .30 and .46, indicating fair and moderate agreement, respectively. These results suggest that point light displays may enhance observers' visual perception of human movement.
Adult↗
Analysis of karyotypic stability of homoeologous-pairing (ph) mutants in allopolyploid wheats.
Karyotypic analysis of wheat lines with different genotypes for the homoeologous-pairing loci Ph1 and Ph2 was carried out by means of a genomic in situ hybridization method that allowed unequivocal identification of the A, B and D genomes. Chromosomal rearrangements mainly affecting the A and D genomes were found in all plants of allohexaploid wheat (AABBDD) lacking Ph1 activity. The frequency of intergenomic exchanges per plant in ph1b mutant and nulli-5B lines was 4.31 and 3.40, respectively. In addition, an unbalanced genomic constitution was found in a few plants, some even showing a euploid chromosomal number. By contrast, rearranged karyotypes were detected neither in the ph1 mutant line (ph1c) of allotetraploid wheat (AABB) nor in the allohexaploid wheat lines lacking Ph2 activity, namely ph2b mutant and nulli-3D lines. These results were compared with the chromosomal pairing behaviour displayed by mutant lines ph1c, ph1b and ph2b at first meiotic metaphase. Despite the finding of standard, nonrearranged karyotypes in the phlc tetraploid mutant, the frequency of A-B homoeologous metaphase I association was similar to that observed in the ph1b hexaploid mutant. The results presented clearly demonstrate that inactivity of the Ph1 locus induces karyotypic instability in wheat. Intergenomic exchanges have probably been accumulating since the original ph1 mutant and aneuploid lines were obtained, which should be taken into account when it is planned to use these lines for basic research on Ph1 function or in applied wheat breeding programmes.
Chromosome Pairing↗
Development and validation of a high-performance liquid chromatographic stability-indicating method for the analysis of Synercid in quality control, stability and compatibility studies.
A gradient high-performance liquid chromatographic (HPLC) method was developed for the analysis of Synercid freeze-dried powder in routine quality control, stability and compatibility studies. This method is suited for a simultaneous assay of drug substances and impurities. The method was validated for precision, reproducibility, linearity, accuracy and limits of detection. The robustness study that was performed according to an experimental design is described.
Anti-Bacterial Agents↗
Stability and accuracy of metamemory in adulthood and aging: a longitudinal analysis.
The stability and accuracy of memory perceptions in 2 longitudinal samples was examined. Sample 1 consisted of 231 adults (22-78 years) tested twice over 2 years. Sample 2 consisted of 234 adults (55-86 years) tested 3 times over 6 years. Measures of perceived and actual memory change were obtained. A primary focus was whether perceptions of memory change stem from application of an implicit theory about aging and memory or from accurate monitoring of actual changes in performance. Individual differences in metamemory were highly stable over time. Results suggested at least some accurate monitoring of memory in Sample 2, in which actual change was greatest. However the overall pattern of results is largely consistent with predictions derived from an implicit theory hypothesis.
Adult↗
[Calculations of stability of A and B forms of dA6.dT6 and dG6.dC6 duplexes by molecular mechanics method in an aqueous solution and approximation of the statistical model. Analysis of unusual stability of the dA6.dT6 B form].
The statistical model of the environment for estimating the influence of the aqueous electrolyte solution on the macromolecule has been developed. The energy of the water-fasteners between macromolecule atoms has been calculated. The calculations of A and B form dA6.dT6 and dG6.dC6 duplexes have been made. The unusual stability of B form in dA6.dT6 and their unstability in dG6.dC6 have been analysed. B form duplexes have optimal energy of Van-der-Waals interactions, but a more strained ribose-phosphate backbone, the latter being the reason of its high conformational lability. The aqueous solution stabilizes B form duplexes. The main types of sequence-dependent B form stabilizing interactions are: electrostatic interactions between phosphate groups and bases, the effect of the solvent molecular structure and energy of water fasteners between nucleic bases and ribose-phosphate backbone.
DNA↗
Analysis of the stability of cytochrome c(6) with an improved stopped-flow protocol.
This work presents an improved stopped-flow protocol for the simultaneous measurement of thermodynamic and kinetic protein stability data from a single experiment, along with a formalism for the global analysis of the data. The method was applied to the comparison of the stabilities of cytochrome c(6) from Anabaena sp. PCC 7119 and one of its mutants (D72K). Compared to the wild type the mutant was found to have a significantly reduced thermodynamic (deltadeltaG(U0)=2.7 kJ mol(-1)) and kinetic stability, as well as a more pronounced shift in transition state structure upon destabilization.
Circular Dichroism↗
Insights into the molecular basis of thermal stability from the analysis of ion-pair networks in the glutamate dehydrogenase family.
The recent structure determination of glutamate dehydrogenase from the hyperthermophile Pyrococcus furiosus and the comparison of this structure with its counterparts from the mesophiles Clostridium symbiosum and Escherichia coli has highlighted the formation of extended networks of ion-pairs as a possible explanation for the superior thermal stability of the hyperthermostable enzyme. In the light of this, we have carried out a homology-based modelling study using sequences of a range of glutamate dehydrogenases drawn from species which span a wide spectrum of optimal growth temperatures. We have attempted to analyse the extent of the formation of ion-pair networks in these different enzymes and tried to correlate this with the observed thermal stability. The results of this analysis indicate that the ion-pair networks become more fragmented as the temperature stability of the enzyme decreases and are consistent with a role for the involvement of such networks in the adaptation of enzymes to extreme temperatures.
Amino Acid Sequence↗
[Analysis of the stability of some properties of tick-borne encephalitis virus (strain 205) upon passaging in mice].
Comparative analysis of the characteristics of tick-borne encephalitis (TBE) strain 205 used for the production of vaccine against TBE and of its variants obtained by passages in mouse brain showed the stability of such properties as infective activity, neurovirulence, sensitivity to physical (heating to 50 C) and chemical (sodium deoxycholate treatment) factors. At the same time increased neurovirulence of variants 205/M10 and 205/M20, which undergone through 10 and 20 passages in white mouse brain, for low-sensitive Syrian hamsters was revealed. Use of a panel of 5 monoclonal antibodies to protein E and of 4 monoclonal antibodies to protein E and of 4 monoclonal antibodies to protein NS3 helped differentiate between not only strains 205 and Sofyin, but between variants of strain 205 as well.
Animals↗
[Maxillary prosthesis for better QOL--analysis of maxillary prosthesis stability].
We report here an analysis of 100 cases of maxillary prosthesis, experienced from July, 1981 through June, 1989, with special reference to stability. Sixty-four percent of prostheses were partial denture type and complete denture type comprised thirty-two percent. Eighty-six percent of cases were estimated to have defects exceeding 2/6 and 3/6 of the surface width of the palate. Ninety percent of prostheses weighed less than 15 gm. The stability of these prostheses was estimated to be good in 85% of cases, the stability of the denture type being good in 95% of partial denture type cases, and 62% of complete denture type cases. According to type distinctions among maxillary defects as a whole, in the smaller 1/6 and 2/6 defect cases, good stability can be expected, and in 3/6 and 4/6 defect cases, 80% achieve good stability. According to prosthesis weight, 80% of those weighing less than 15 gm were considered to have shown good stability. Thus, these maxillary prostheses can remain in place and functional ameliorating disability and contributing to the patient's quality of life.
Adult↗
Randomized algorithms for stability and robustness analysis of high-speed communication networks.
This paper initiates a study toward developing and applying randomized algorithms for stability of high-speed communication networks. The focus is on congestion and delay-based flow controllers for sources, which are "utility maximizers" for individual users. First, we introduce a nonlinear algorithm for such source flow controllers, which uses as feedback aggregate congestion and delay information from bottleneck nodes of the network, and depends on a number of parameters, among which are link capacities, user preference for utility, and pricing. We then linearize this nonlinear model around its unique equilibrium point and perform a robustness analysis for a special symmetric case with a single bottleneck node. The "symmetry" here captures the scenario when certain utility and pricing parameters are the same across all active users, for which we derive closed-form necessary and sufficient conditions for stability and robustness under parameter variations. In addition, the ranges of values for the utility and pricing parameters for which stability is guaranteed are computed exactly. These results also admit counterparts for the case when the pricing parameters vary across users, but the utility parameter values are still the same. In the general nonsymmetric case, when closed-form derivation is not possible, we construct specific randomized algorithms which provide a probabilistic estimate of the local stability of the network. In particular, we use Monte Carlo as well as quasi-Monte Carlo techniques for the linearized model. The results obtained provide a complete analysis of congestion control algorithms for internet style networks with a single bottleneck node as well as for networks with general random topologies.
Algorithms↗
Triple arthrodesis stabilization: a quantitative analysis of screw versus staple fixation in fresh cadaveric matched-pair specimens.
Qualitative analyses of midfoot stabilization in triple arthrodeses utilizing bone staple versus 4.5-mm cannulated cancellous screw fixation, with and without washers, were performed in fresh cadaveric specimens. Twenty-two trials (11 matched-pair feet) were used for direct comparison. Stiffness, defined as force/displacement, was determined at each talonavicular and calcaneocuboid joint. Ultimate load failure points of each specimen were also calculated. Trial results showed no statistically significant difference in stiffness or ultimate failure between these two forms of midfoot fixation for triple arthrodeses.
Arthrodesis↗
The determinants of marital stability: a comparative analysis of first and higher-order marriages.
"This study examines similarities and differences in the determinants of stability for first marriages and remarriages. Focusing primarily on the role of investments in marriage-specific human capital, the paper develops several hypotheses about the effects of children from the current marriage, children from previous unions, and home-production skills. The empirical results, based on white and black respondents from the 1982 [U.S.] National Survey of Family Growth, are generally consistent with the hypotheses and underscore the importance of marriage-specific human capital as a determinant of union stability."
Adolescent↗
Cognitive influence on postural stability: a neuromuscular analysis in young and older adults.
BACKGROUND: Previous literature indicates that attentional resources are required for recovery of postural stability. Previous studies have also examined the effect of aging on the performance of a static postural task while a secondary cognitive task is being conducted. This study describes the effect of a cognitive task on the neuromuscular response characteristics underlying reactive balance control in young versus older adults. METHODS: The attentional demand on the neuromuscular system was examined in 14 young and 12 healthy older adults by analysis of the integrated electromyography activity while the adults were performing a dual-task paradigm. The primary task involved standing platform perturbations and the secondary task was a math task that involved subtraction by threes. Integrated electromyography activity was compared between the cognitive (math and balance) task versus control (balance only) task. RESULTS: For both groups of subjects, onset latency of postural muscle responses did not change under dual-task conditions. In contrast, the amplitude of postural muscle activity was significantly affected by performance of a secondary task. When electromyography data were combined for both young and older adults, there was a decrease in muscle response amplitude in both agonist (gastrocnemius) and antagonist (tibialis anterior) muscles when the cognitive math task was performed. This was apparent at 350-500 milliseconds from plate onset for the gastrocnemius and between 150 and 500 for the tibialis anterior. When young and older adults were compared, an age by task interaction effect was seen in muscle response amplitude for the agonist (gastrocnemius) muscle between 350 to 500 milliseconds, with older adults showing a significantly greater reduction than young adults. CONCLUSION: The decline of muscle activity when the secondary task was performed suggests that less attentional processing capacity was available for balance control during the dual-task paradigm. The results also indicate that the dual-task activity has a greater impact on balance control in the older adults than in the young adults.
Adult↗
Stabilization and quantitative analysis of fecapentaenes in human feces, using synthetic fecapentaene-12.
Naturally occurring fecal mutagens, called fecapentaenes, are hypothesized to contribute to large bowel carcinogenesis. To understand health risks it is necessary to relate fecal mutagen concentrations to intestinal pathologies, i.e. colon cancer. However, fast and reliable methods for analysis of stool for fecapentaene levels are not available. This study presents an evaluation of stabilizing effects on synthetic fecapentaene-12 of various antioxidants, indicating tri-ethylamine to give the best results. Furthermore, it describes a fast extraction procedure for human stool and a subsequent HPLC-analysis which produces quantitative data on fecapentaene-12 concentrations within 30 min.
Butylated Hydroxytoluene↗
An improved (99m)Tc-aprotinin kit formulation: quality control analysis of radiotracer stability and cold kit shelf life.
(99m)Tc-aprotinin scintigraphy has been demonstrated to be a useful noninvasive imaging technique for amyloid deposits located in extraabdominal regions of patients. The aim of this study was to develop an improved aprotinin cold kit formulation, to validate the kit for long-term stability, as well as to assess the radiotracer stability by novel quality control methods. The aprotinin cold kit formulation of Trasylol, pyrophosphate (PYP)-chelated stannous reductant and an alkaline buffer, was dispensed into nitrogen-filled vials and aliquots frozen at -20 degrees C. After 0, 1, 2, 3 and 6 months of storage, three samples were reconstituted with 750-850 MBq of (99m)Tc-pertechnetate, followed by quality control analyses by paper chromatography methods at 25, 85 and 265 min postreconstitution (pr). Cation-exchange cartridge quality control methods were also investigated. The cold kits proved to be stable to long-term storage for up to 6 months, and the radiotracer was stable for at least 4 h pr. (99m)Tc-aprotinin was formed at greater than 95% efficiency at all time points tested with (99m)TcO2 present as the major impurity (1-4%) and (99m)Tc-pertechnetate and (99m)Tc-PYP present in trace amounts. An alternative, rapid, safe and reliable method was found in Oasis MCX-BSA-treated cartridges using saline as the eluting solution to assay for (99m)Tc-aprotinin.
Aprotinin↗
Surface analysis of posterior stabilized femoral components used in total knee arthroplasty.
The purpose of this study was to evaluate the preimplantation surface finish of the femoral component used in total knee arthroplasty. Nine femoral components from various manufacturers were obtained for analysis. All were fixed-bearing, posterior-stabilized implants intended for cemented arthroplasty. Surface characterization involved light profilometry over multiple surface points from the condylar surface, trochlear groove, and the posterior stabilizing cam. Results revealed that the condylar surface roughness was not significantly different when comparing designs with a mean roughness average ranging from 43.6 to 116 nm. The trochlear surface was generally similar to that of the condyles in most implants, although significant differences were seen in 2 implants (P <.05). Of note, the articular surface of the stabilizing cam was uniformly rougher than the condylar surface in all implants and significantly rougher (P <.05) in 6 of the 9 components.
Arthroplasty, Replacement, Knee↗