Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “stability”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources
PubMed2004

Influence of free protein on flocculation stability of beta-lactoglobulin stabilized oil-in-water emulsions at neutral pH and ambient temperature.

The influence of protein concentration and order of addition relative to homogenization (before or after) on the extent of droplet flocculation in oil-in-water emulsions stabilized by a globular protein was examined using laser diffraction. n-Hexadecane (10 wt%) oil-in-water emulsions (pH 7, 150 mM NaCl) stabilized by beta-lactoglobulin (beta-Lg) were prepared by three methods: (1) 4 mg/mL beta-Lg added before homogenization; (2)10 mg/mL beta-Lg added before homogenization; (3) 4 mg/mL beta-Lg added before homogenization and 6 mg/mL beta-Lg added after homogenization. Emulsion 1 contained little nonadsorbed protein (<3%) and underwent extremely rapid and extensive droplet flocculation immediately after homogenization. Emulsion 2 contained a significant fraction of nonadsorbed beta-Lg and exhibited relatively slow droplet flocculation for some hours after homogenization. Measurements on Emulsion 3 showed that the extremely rapid particle growth observed in Emulsion 1 could be arrested by adding native beta-Lg immediately after homogenization. The extent of particle growth in the three types of emulsions was highly dependent on the time that the salt was added to the emulsions, i.e., after 0 or 24 h aging. We postulate that the observed differences are due to changes in droplet surface hydrophobicity caused by differences in the packing or conformation of adsorbed proteins. Our data suggest that history effects have a strong influence on the flocculation stability of protein-stabilized emulsions, which has important implications for the formulation and production of protein stabilized oil-in-water emulsions.

Adsorption↗
PubMed2000

Stabilization of oral anticoagulant therapy in hospitalized patients and characteristics associated with lack of stabilization.

The initiation and stabilization of oral anticoagulant therapy in hospitalized patients in a setting without specialized medical or pharmaceutical advice, was studied. In addition, potential risk factors for lack of stabilization were studied. All patients from three wards (orthopaedic surgery, general surgery and internal medicine) in two Dutch hospitals, who were started on oral anticoagulant therapy and who gave informed consent, were included in this three months prospective follow-up study. When a patient had two consecutive INR's within the range 2-3 during hospitalization (on day 6 or later), he was defined as stable. Stable and unstable patients were compared with respect to age, gender, quetelet index, length of hospital stay, indication for oral anticoagulant therapy, induction dosing schedule of oral anticoagulant therapy, prescribing physician, type of hospital (teaching or non-teaching), concurrently used drugs, concurrently used drugs known to potentially interact with oral anticoagulant therapy (drug-drug interactions that influence INR) and (co)morbidity. A total of 125 patients, who all used acenocoumarol as oral anticoagulant, were recruited in the study. The study population mainly comprised orthopaedic discharges on prophylactic oral anticoagulants. The mean length of hospital stay was 14.5 days (median 11.0, standard deviation (SD) 10.2) for the patients included in the study (patients with a short length of stay < 6 days were excluded from the study, because of the definition of stability). 43 patients (34%) became stable during hospitalization. The second INR within the range was reached after on average 11.1 days (median 10.0, SD 4.5). 18 different induction dosing schedules were used. Differences in apparent risk of INR instability were statistically associated with length of hospital stay (odds ratio (OR) 0.85, 95% confidence interval (CI) 0.78-0.92), concurrent use of musculoskeletal drugs, mainly NSAIDs, (OR 1.68, 95% CI 1.04-2.72) and two individual prescribing physicians (OR 6.61, 95% CI 1.47-29.82 for one physician and OR 0.23, 95% CI 0.06-0.99 for the other physician). This population has a high percentage of instability and reaches stability relatively late. The instability was associated with length of hospital stay, the concurrent use of musculoskeletal drugs (mostly NSAID's) and physician. Most of the unstable patients had INR's below therapeutic range, suggesting a conservative dosing habit. Part of the instability may also be due to the many different physicians who dose their own patients. Interventions to improve dosing may aid in better stabilization in hospitalized patients and thus in reduced length of hospital stay.

Administration, Oral↗
PubMed1996

[Effectiveness of outer stability aids on rotational stability of the ankle joints].

The main goal in nonoperative treatment of lateral ankle ligament injuries is the reduction of the possible supination at the ankle joint complex. Complete ligament healing can only be achieved when protected from overstress. There is general agreement that talar tilt should be avoided. Recent reports, however, have shown that instability of the ankle joint is at least in one form an axial rotational one. Therefore, the reduction of tibial rotation should also be taken into consideration. The purpose of this study was to determine the effect of three commonly used ankle braces and ankle taping on rotational stability of the ankle joint complex. The Künzli stabilizing shoe was the only orthosis that stabilized sufficiently the ankle joint complex when the foot was in slight plantarflexion. The reduction of external tibial rotation was in foot flexion of 20 degrees: Künzli stabilizing shoe, 58%; Aircast, 23%; Mikros, 12%; and taping, 10%. This becomes more relevant as this foot position is the most dangerous one where most of the ligament injuries does occur. It could be that the insufficient effect of various ankle braces on rotational stability may be the reason for residual problems after ankle sprain.

Adult↗
PubMed1995

Specificity of ligand-dependent androgen receptor stabilization: receptor domain interactions influence ligand dissociation and receptor stability.

The molecular basis for the different physiological effects of testosterone (T) and dihydrotestosterone (DHT) was investigated using recombinantly expressed wild-type and mutant androgen receptor (AR). Rates of androgen dissociation from nuclear and cytoplasmic AR were compared with hormone- and concentration-dependent receptor degradation rates. T dissociates from AR 3 times faster than DHT or methyltrienolone (R1881) and is less effective in stabilizing the receptor. Analysis of AR deletion mutants and AR/glucocorticoid receptor chimeras indicates that the AR NH2-terminal domain has a specific role in stabilizing the receptor by slowing the rate of ligand dissociation and AR degradation. Amino acid mutations that abolish receptor dimerization, nuclear localization, or DNA-binding activity have no significant effect on androgen dissociation or AR degradation. A naturally occurring steroid-binding domain mutation (Val889 to Met) that causes androgen insensitivity, but does not alter equilibrium androgen binding affinity, lowered the androgen-binding capacity as a result of increased rates of androgen dissociation and AR degradation. Thus, AR stabilization and function require prolonged receptor occupancy with androgen, with a similar extent of stabilization observed at higher concentrations of faster dissociating androgens and lower concentrations of slower dissociating androgens. Retention of receptor-bound androgen is enhanced by an interaction between the AR NH2-terminal and steroid-binding domains. The ligand specificity and concentration dependence of receptor stabilization provide an explanation for physiological differences in the actions of T and DHT.

Animals↗
PubMed1986

What is psychophysically perfect image stabilization? Do perfectly stabilized images always disappear?

High-contrast luminance gratings stabilized on the retina with a Purkinje image eyetracker do not disappear completely. This could be due to small errors of stabilization, or the visual system could include mechanisms capable of responding to temporally constant images. We examined the visual system's sensitivity to small movements of gratings. We (1) replicated previous measurements of contrast sensitivity for gratings with controlled retinal-drift velocities, (2) developed a method for calculating sensitivity to small oscillations of gratings using thresholds for flickering stabilized gratings, and (3) examined the calculations empirically. We calculated that movements of only 8 sec of arc peak to peak produce detectable temporal changes. Since existent stabilization systems cannot eliminate movements this small, residual stabilized-grating detectability does not require detectors sensitive to temporally constant images.

Humans↗
PubMedDate not supplied

Postural stability index is a more valid measure of stability than equilibrium score.

Researchers, therapists, and physicians often use equilibrium score (ES) from the Sensory Organization Test, a key test in the NeuroCom EquiTest System (a dynamic posturography system) to assess stability. ES reflects the overall coordination of the visual, proprioceptive, and vestibular systems for maintaining standing posture. In our earlier article, we proposed a new measure of anterior-posterior (A-P) postural stability called the Postural Stability Index (PSI), which accounts for more biomechanical aspects than ES. This article showed that PSI provides a clinically important adjunct to ES. In the present article, we show that PSI can provide an acceptable index even if a person falls during the trial, whereas ES assigns a zero score for any fall. We also show that PSI decreases as ankle stiffness increases, which is intuitive, while ES exhibits the opposite behavior. Ankle stiffness is generally recognized as an indicator of postural stability. These results suggest that PSI is a more valid measure of A-P stability than ES.

Adult↗
PubMed1997

VEGF mRNA is stabilized by ras and tyrosine kinase oncogenes, as well as by UV radiation--evidence for divergent stabilization pathways.

Vascular Endothelial Growth Factor (VEGF) is a pivotal endothelial cell mitogen that mediates both normal and pathological angiogenesis. Although expressed at very low levels in cells not undergoing vascularization, VEGF mRNA is transiently upregulated and stabilized by a variety of extracellular stimuli, and is persistently upregulated and stabilized in many human tumor cell lines (White et al., 1995). Here we demonstrate that oncogenic activation of tyrosine protein kinases and Ras proteins induce a 6- to 16-fold increase in the abundance of VEGF mRNA and a 3- to 5-fold increase in the stability of VEGF mRNA, suggesting that persistent activation of signaling pathways induced by these oncoproteins accounts for overexpression of VEGF in a significant fraction of human tumors. In addition to these oncoproteins, ultraviolet (UV) radiation upregulated and stabilized VEGF mRNA 15- and 5-fold, respectively. While the tyrosine kinase inhibitor, genistein, blocked VEGF upregulation by activated tyrosine protein kinases, and the Ras inhibitor, N-Acetyl-S-trans-farnesyl-L-cysteine (AFC), eliminated VEGF expression in cells transformed by v-Ras, neither agent blocked upregulation by hypoxia or UV radiation. These data argue that multiple divergent pathways upregulate and stabilize VEGF mRNA.

3T3 Cells↗
PubMedDate not supplied

A new force-plate technology measure of dynamic postural stability: the dynamic postural stability index.

CONTEXT: New measures of dynamic postural stability are needed to address weaknesses of previous measures. OBJECTIVE: To assess the feasibility, reliability, and precision of a new measure of dynamic postural stability. DESIGN: A single within-subjects design was used to determine optimal sampling interval as well as intersession reliability. SETTING: Biomechanics laboratory. PATIENTS OR OTHER PARTICIPANTS: Eighteen subjects (7 men [age = 22 +/- 3 years, height = 175 +/- 5 cm, mass = 75 +/- 16 kg] and 11 women [age = 23 +/- 2 years, height = 163 +/- 6 cm, mass = 68 +/- 13 kg]) without lower extremity impairment. INTERVENTION(S): A jump protocol that required subjects to perform a 2-legged jump to a height equivalent to 50% of their maximum vertical leap and land on a single leg. MAIN OUTCOME MEASURE(S): The Dynamic Postural Stability Index (DPSI) and the directional components (medial-lateral, anterior-posterior, and vertical) after a jump landing. RESULTS: We observed a significant sampling-interval main effect (F(2,51) = 26.88, P < .01) for the DPSI; the 10-second trial duration produced significantly smaller means than the 5- and 3-second trial durations, whereas the 5-second trial result was also significantly smaller than that of the 3-second trial. The DPSI was highly reliable between test sessions (intraclass correlation coefficient = .96) and very precise (SEM = .03). CONCLUSIONS: These results suggest that the DPSI can be used in conjunction with a functional single-leg hop stabilization test and is a reliable and precise measure of dynamic postural stability. We believe the shortest sampling interval (3 seconds) is the best choice for studying and mimicking athletic performance as closely as possible.

Journal Article↗
PubMed1991

Cervical spine stabilization. A three-dimensional, biomechanical evaluation of rotational stability, strength, and failure mechanisms.

The three-dimensional rotational biomechanical properties of several different types of posterior stabilizing procedures are reported. A severe ligamentous and bony injury was simulated with three vertebral body human cervical spine segments. Good stabilization was noted for all of the repairs in flexion loading. Without polymethylmethacrylate supplementation, none of the repairs was stable in extension. All of the repairs provided reasonable stabilization for lateral bending except for the posterior wiring without methacrylate, and all but the posterior wiring and facet fusion provided reasonable stabilization against axial rotation loading. The supplementation of all of these repairs with polymethylmethacrylate added considerably to the stability of all the constraints. These findings may be useful in clinical decision-making for determining the kind of repairs and postoperative brace protection to use.

Biomechanical Phenomena↗
PubMed1990

Erythrocyte nucleotide stability and plasma hypoxanthine concentrations: improved ATP stability with short-term storage at room temperature.

We have measured erythrocyte nucleotide concentrations at timed intervals over 24 h in heparinised blood stored at 4 degrees C, room temperature, or 37 degrees C. The objective was to determine whether the grossly altered NAD concentrations found in the erythrocytes of patients with two different inherited purine disorders could be related to altered stability or turnover rates. An unexpected finding was the improved stability of all erythrocyte nucleotides in blood stored at room temperature compared with 4 degrees C. Not only was the breakdown of ATP greater at 4 degrees C compared with room temperature, higher hypoxanthine concentrations were present in the plasma associated with a fictitious increment in inosine. NAD and NADP, by contrast, showed remarkable stability in both control and patient erythrocytes, irrespective of their original value. Although these studies failed to establish an explanation for the altered NAD levels in the patients, the superior ATP stability in blood stored at room temperature in the erythrocytes from both patients and controls suggests that current practices of storing blood on ice for short-term studies require re-evaluation.

Adenosine Triphosphate↗
PubMed2001

A combination of weakly stabilizing mutations with a disulfide bridge in the alpha-helix region of Trichoderma reesei endo-1,4-beta-xylanase II increases the thermal stability through synergism.

Thermal stability and other functional properties of Trichoderma reesei endo-1,4-beta-xylanase II (XYNII; family 11) were studied by designed mutations. Mutations at three positions were introduced to the XYNII mutant containing a disulfide bridge (S110C-N154C) in the alpha-helix. The disulfide bridge increased the half-life of XYNII from less than 1 min to 14 min at 65 degrees C. An additional mutation at the C-terminus of the alpha-helix (Q162H or Q162Y) increased the half-life to 63 min. Mutations Q162H and Q162Y alone had a stabilizing effect at 55 degrees C but not at 65 degrees C. The mutations N11D and N38E increased the half-life to about 100 min. Due to the stabilizing mutations the pH stability increased in a wide pH range, but at the same time the activity decreased both in acidic and neutral-alkaline pH, the pH optimum being at pH region 5-6. There was no essential difference between the specific activities of the mutants and the wild-type XYNII.

Catalytic Domain↗
PubMed2000

On the stabilizing action of protein denaturants: acetonitrile effect on stability of lysozyme in aqueous solutions.

Stability of hen lysozyme in the presence of acetonitrile (MeCN) at different pH values of the medium was studied by scanning microcalorimetry with a special emphasis on determination of reliable values of the denaturational heat capacity change. It was found that the temperature of denaturation decreases on addition of MeCN. However, the free energy extrapolation showed that below room temperature the thermodynamic stability increases at low concentrations of MeCN in spite of the general destabilizing effect at higher concentrations and temperatures. Charge-induced contribution to this stabilization was shown to be negligible (no pH-dependence was found); therefore, the most probable cause for the phenomenon is an increase of hydrophobic interactions at low temperatures in aqueous solutions containing small amounts of the organic additive. The difference in preferential solvation of native and denatured states of lysozyme was calculated from the stabilization free energy data. It was found that the change in preferential solvation strongly depends on the temperature in the water-rich region. At the higher MeCN content this dependence decreases until, at 0.06 mole fractions of MeCN, the difference in the preferential solvation between native and denatured lysozyme becomes independent of the temperature over a range of 60 K. The importance of taking into account non-ideality of a mixed solution, when analyzing preferential solvation phenomena was emphasized.

Acetonitriles↗
PubMed2003

Influence of environmental conditions on the stability of oil in water emulsions containing droplets stabilized by lecithin-chitosan membranes.

Oil-in-water emulsions containing cationic droplets stabilized by lecithin-chitosan membranes were produced using a two-stage process. A primary emulsion containing anionic lecithin-coated droplets was prepared by homogenizing oil and emulsifier solution using a high-pressure valve homogenizer (5 wt % corn oil, 1 wt % lecithin, 100 mM acetic acid, pH 3.0). A secondary emulsion containing cationic lecithin-chitosan-coated droplets was formed by diluting the primary emulsion with an aqueous chitosan solution (1 wt % corn oil, 0.2 wt % lecithin, 100 mM acetic acid, and 0.036 wt % chitosan). The stabilities of the primary and secondary emulsions with the same oil concentration to thermal processing, freeze-thaw cycling, high calcium chloride concentrations, and lipid oxidation were determined. The results showed that the secondary emulsions had better stability to droplet aggregation during thermal processing (30-90 degrees C for 30 min), freeze-thaw cycling (-10 degrees C for 22 h/30 degrees C for 2 h), and high calcium chloride contents (</=500 mM CaCl(2)) and exhibited less lipid oxidation (peroxide formation) than primary emulsions. The interfacial engineering technology used in this study could lead to the creation of food emulsions with improved stability to environmental stresses.

Calcium Chloride↗
PubMed2004

Influence of pH and iota-carrageenan concentration on physicochemical properties and stability of beta-lactoglobulin-stabilized oil-in-water emulsions.

The influence of pH and iota-carrageenan concentration on the properties of beta-lactoglobulin (beta-Lg)-stabilized oil-in-water emulsions was investigated by measuring the particle charge, particle size distribution, and creaming stability. Emulsions containing droplets stabilized by beta-Lg were produced by homogenization, and then, iota-carrageenan was added. At pH 3, the droplet charge did not change for iota-carrageenan concentrations <or=0.1 wt % but decreased rapidly at high concentrations, while the mean particle diameter increased slightly as the iota-carrageenan concentration was increased. These results suggest that the interaction between iota-carrageenan and beta-Lg was weak at pH 3 probably because some sulfate groups were protonated (pK(a) = 2). At pH 4 and pH 5, the droplet charge decreased dramatically as the iota-carrageenan concentration was increased from 0 to 0.15 wt %, but droplet aggregation and creaming occurred in the emulsions, indicating that interfacial complexes between iota-carrageenan and beta-Lg could not stabilize the emulsions, probably due to bridging flocculation. At pH 6, the droplet charge in the primary emulsions was negative and became more negative as the iota-carrageenan concentration was increased. The mean particle diameter was relatively small at all iota-carrageenan concentrations, and emulsions were stable to creaming after 1 week of storage. We propose that carrageenan adsorbed to the droplet surfaces and increased the electrostatic repulsion between droplets. At pH 7 and pH 8, the droplet charge did not change as the iota-carrageenan concentration was increased, but these emulsions became unstable to creaming above a critical carrageenan concentration, which was attributed to depletion flocculation.

Carrageenan↗
PubMed2002

Lysozyme stability in primary emulsion for PLGA microsphere preparation: effect of recovery methods and stabilizing excipients.

PURPOSE: To investigate the conformational stability of a model protein, lysozyme, in the primary emulsion phase of the microsphere preparation process. METHODS: The conformational stability of lysozyme during primary emulsification was assessed by differential scanning calorimetry (DSC) and enzymatic activity assay. PEG 400 was used to separate lysozyme from water-in-oil (w/o) emulsion containing poly(lactideco-glycolide) (PLGA). RESULTS: No significant changes in the recovery of lysozyme were observed due to increasing sonication time from 20 to 60 s at 40 W or increasing intensity from 40 to 60 W for 20 s. By using the method involving PEG 400, lysozyme recovery in the presence of PLGA was increased from 11.8% to 709%. Hydroxypropyl-beta-cyclodextrin (HP-beta-CD) increased lysozyme recovery from 35% to 70% at low lysozyme concentration (20 mg/ml), and from 70% to 77% at high lysozyme concentration (100 mg/ml) in the presence of PLGA. Sugars such as trehalose and mannitol failed to increase lysozyme recovery. DSC results suggested the retention of the conformational structure of the recovered lysozyme, which was supported by an enzymatic activity assay. CONCLUSIONS: HP-beta-CD was found to be a promising stabilizer that protected lysozyme during the primary emulsification. Protein recovery method with the help of PEG 400 allowed the study of protein stability in w/o emulsions in the presence of PLGA. DSC provided supplementary information on the conformational changes of lysozyme during emulsification.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2001

A new scale for side-chain contribution to protein stability based on the empirical stability analysis of mutant proteins.

The hydrophobicity scales for amino acid side chains based on the transfer Gibbs energy (DeltaG(trans)) of amino acids from non-aqueous phases to water have been widely used to estimate the contribution of buried side chains to the conformational stability of proteins. In this paper, we propose a new scale for the side-chain contribution to protein stability, which is derived from data on protein denaturation experiments using systematic and comprehensive mutant proteins. In the experiments, the contribution of some physical properties were quantitatively determined as parameters in a unique equation representing the stability change (DeltaDeltaG) of mutant proteins as a function of the structural changes due to the mutations. These parameters are able conveniently to provide a scale for the side-chain contribution to protein stability. This new scale also has the advantage over the previously reported hydrophobicity scales of residues with the contributions of hydrogen bonds or secondary structural propensity. It may find practical application in algorithms for the prediction of protein structures.

Amino Acids↗
PubMed1998

Polyethyleneglycol-stabilized manganese-substituted hydroxylapatite as a potential contrast agent for magnetic resonance imaging: particle stability in biologic fluids.

RATIONALE AND OBJECTIVES: Polymer-stabilized manganese(II)-substituted hydroxylapatite (MnHA) has been investigated as a particulate contrast agent for magnetic resonance imaging. The MnHA core requires a polymer coating to retard opsonization, thereby prolonging its systemic persistence. Therefore, the aim of this study was to assess the stability of various formulations in biologic media in vitro. METHODS: Polyethyleneglycol-coated manganese(II)-substituted hydroxylapatite particles were studied in bovine plasma as a function of the concentration of polymer in the formulation. Particle sizing techniques and nuclear magnetic resonance proton relaxometry were used to evaluate both in vitro and in vivo stability. RESULTS: A small-sized particle (approximately 10 nm diameter) that is stable in bovine plasma and rabbit whole blood was formed in formulations with high amounts of polymer concentration. In formulations with low amounts of polymer concentration, larger-sized particles (approximately 100 nm diameter) were present along with the small-sized population. The larger particles de-aggregated into the small-size particle distribution on dispersion in bovine plasma and rabbit whole blood. CONCLUSIONS: Ultrasmall particles with high surface coat were stable in plasma, whereas larger aggregates de-aggregated. Unlike Mn2+, the interaction of polyethyleneglycol-stabilized manganese(II)-substituted hydroxylapatite with plasma proteins was weak.

Animals↗
PubMed2003

Stabilizing effect of artificial stabilizers for binding activity of QCM immunosensors.

We compare stabilizing effects of artificial and natural stabilizers for maintenance of binding activity of immobilized antibody on the gold surface of quartz crystal microbalance (QCM). Binding activity between immobilizing antibody and specific antigen was measured and considered as a calculated frequency shift with QCM-immunosensor after temperature increasing and long-term storage. According to the experimental results, one stabilizer among eight samples shows the best stabilizing effect for QCM-immunosensor.

Adsorption↗