Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Suspensions”

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 793 records · Page 44Linked to original sources
PubMed2006

Behavior of yeast cells in aqueous suspension affected by pulsed electric field.

This work discusses pulsed electric fields (PEF) induced effects in treatment of aqueous suspensions of concentrated yeast cells (S. cerevisiae). The PEF treatment was done using pulses of near-rectangular shape, electric field strength was within E=2-5 kV/cm and the total time of treatment was t(PEF)=10(-4)-0.1 s. The concentration of aqueous yeast suspensions was in the interval of C(Y)=0-22 (wt%), where 1% concentration corresponds to the cellular density of 2x10(8) cells/mL. Triton X-100 was used for studying non-ionic surfactant additive effects. The electric current peak value I was measured during each pulse application, and from these data the electrical conductivity sigma was estimated. The PEF-induced damage results in increase of sigma with t(PEF) increasing and attains its saturation level sigma approximately sigma(max) at long time of PEF treatment. The value of sigma(max) reflects the efficiency of damage. The reduced efficiency of damage at suspension volume concentration higher than phi(Y) approximately 32 vol% is explained by the percolation phenomenon in the randomly packed suspension of near-spherical cells. The higher cytoplasmic ions leakage was observed in presence of surfactant. Experiments were carried out in the static and continuous flow treatment chambers in order to reveal the effects of mixing in PEF-treatment efficiency. A noticeable aggregation of the yeast cells was observed in the static flow chamber during the PEF treatment, while aggregation was not so pronounced in the continuous flow chamber. The nature of the enhanced aggregation under the PEF treatment was revealed by the zeta-potential measurements: these data demonstrate different zeta-potential signs for alive and dead cells. The effect of the electric field strength on the PEF-induced extraction of the intracellular components of S. cerevisiae is discussed.

Chemistry, Physical↗
PubMed2006

Effect of surface interaction of silica nanoparticles modified by silane coupling agents on viscosity of methylethylketone suspension.

In order to control the viscosity of a dense silica methylethylketone (MEK) suspension, the surfaces of silica nanoparticles were modified by 3-glycidoxypropyltrimethoxysilane (GPS) or hexyltrimethoxysilane (C6S) in MEK with the addition of a small amount of pH-controlled water. First, the effect of water addition on the amount of chemisorbed coupling agent was investigated. pH-controlled water enhanced the reactivity of the coupling agent in MEK. The amount of chemisorbed coupling agent increased slightly with the addition of pH 3 water and increased remarkably with the addition of pH 12 water. Next, the effect of the organic functional groups of the coupling agent, pH of the additive water, and additive amount of coupling agent on surface interaction were determined by colloid probe AFM. The steric repulsive force between the silica nanoparticles increased due to water addition, particularly when the pH was maintained at 3. The viscosity of the silica MEK suspension reduced effectively when this repulsive force appeared; however, the optimum condition for reducing the suspension viscosity was dependent on the coupling agent species. The viscosity of the dense silica MEK suspension can be controlled by the addition of small amounts of pH-controlled water and the functional groups of the coupling agent.

Butanones↗
PubMed2005

Antibacterial action of photoactivated disinfection {PAD} used on endodontic bacteria in planktonic suspension and in artificial and human root canals.

OBJECTIVES: To measure antibacterial action of photoactivated disinfection (PAD) on endodontic bacteria in planktonic suspension and root canals. METHODS: Four bacteria, Fusobacterium nucleatum,Peptostreptococcus micros, Prevotella intermedia and Streptococcus intermedius, were tested in suspension. After mixing equal volumes of Tolonium chloride and bacterial suspension for 60s, each 200 microL of concentration (>10(6)cfu mL(-1)) was irradiated with light at 633+/-2 nm. Each energy dose/Tolonium chloride concentration combination was tested eight times, with controls. Prepared root canals in Training Blocs and extracted human teeth were inoculated with S. intermedius followed by 10 mg L(-1) Tolonium chloride or saline. Bacteria in canals were sampled before and after light irradiation. Student t-test assessed significance of changes in viable bacteria produced by treatment of either light or Tolonium chloride alone and light/Tolonium chloride combinations. RESULTS: In suspension, reductions in bacteria were highly significant (P<0.01) for light/Tolonium chloride combinations compared to light or Tolonium chloride alone. Maximum mean log reductions of 1.14 (P. intermedia), 2.48 (P. micros), 2.81 (F. nucleatum) and 6.73 (S. intermedius) were at 4.8 J/20 mg L(-1). Antibacterial action was increased by energy dose increase (not always significantly), but not by Tolonium chloride concentration. In control canals mean log reductions of 0.42 (Blocs) and 0.38 (teeth) from initial levels were not significant. PAD mean log reductions of 2.40 (Blocs) and 2.01 (teeth) were highly significant. Changes for PAD/energy dose combinations were not significant. CONCLUSION: PAD killed endodontic bacteria at statistically significant levels compared to controls. Kills varied with bacterial species.

Anti-Bacterial Agents↗
PubMed2006

Degradation of pentachlorophenol in contaminated soil suspensions by potassium monopersulfate catalyzed oxidation by a supramolecular complex between tetra(p-sulfophenyl)porphineiron(III) and hydroxypropyl-beta-cyclodextrin.

To enhance the catalytic oxidation of pentachlorophenol (PCP) in contaminated soil suspensions using tetra(p-sulfophenyl)porphineiron(III) (Fe(III)-TPPS) as a catalyst and potassium monopersulfate (KHSO(5)) as the single-oxygen donor, the effect of added hydroxypropyl-beta-cyclodextrin (HP-beta-CD) was examined. At pH 4 and 6, the percentage of PCP disappearance increased substantially in the presence of HP-beta-CD. In addition, the self-degradation of Fe(III)-TPPS was significantly retarded in the presence of HP-beta-CD. This retarded self-degradation can be attributed to the stabilization of Fe(III)-TPPS via the formation of a supramolecular complex with HP-beta-CD. The kinetic constant for the self-degradation of Fe(III)-TPPS in the presence of HP-beta-CD at pH 6 was much smaller than that at pH 4, indicating that Fe(III)-TPPS is more stable at pH 6. Thus, the amount of Fe(III)-TPPS, KHSO(5) and HP-beta-CD required to degrade PCP in contaminated soil suspensions was optimal at pH 6. When PCP-contaminated soil suspensions were treated under the optimized conditions, 12-18% and 24-28% of the PCP was mineralized to CO(2) in the absence and presence of HP-beta-CD, respectively. These results show that the presence of HP-beta-CD in the Fe(III)-TPPS/KHSO(5) catalytic system is effective in enhancing the degradation of PCP in contaminated soil suspensions.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed2004

Aminoglutethimide included in nanocapsules suspension: comparison of GC-MS and HPLC methods for control.

Gas chromatography-mass spectrometry (GC-MS) and high performance liquid chromatography (HPLC) offer highly efficient and potentially sensitive separation and detection techniques. This work describes the quantification of aminoglutethimide (AG) in nanocapsules suspension with both techniques. The analysis of different lots containing known concentrations of drug (1, 2, 3 and 4 mg ml(-1)) were used to investigate the quantitative capabilities of both chromatographic techniques. Both chromatographic methods were successful and on an analytical point of view the validations of aminoglutethimide dosing were suitable in both cases. In routine, the determination of the quality of nanocapsules suspension could be preferentially evaluated by difference between total AG concentration in suspension (evaluated by direct HPLC measure of the suspension diluted in acetonitrile) and free AG concentration (evaluated by direct HPLC measure of simple dilution of the supernatant).

Aminoglutethimide↗
PubMed2006

A simple viability-maintaining method produces homogenic cell suspensions of autoaggregating wild-type Actinobacillus actinomycetemcomitans.

Tenacious adherence and autoaggregation of wild-type Actinobacillus actinomycetemcomitans strains jeopardize reliability of determined cell concentrations, e.g. for studies on bacteria-host interactions. We first compared the efficacy of two methods, an indirect and a direct method, for homogenizing cell suspensions of a wild-type, autoaggregating (SA269) strain and of a non-autoaggregating laboratory variant (ATCC 43718) used as a reference. Since the direct method left visible clumps in SA269 suspension, only the indirect method was further tested. In serial dilutions of the homogenized cell suspensions of strains SA269 and ATCC 43718, the OD600 values (R2=0.99, R2=0.99, respectively) and protein concentrations (R2=0.93, R2=0.95, respectively) correlated significantly (all P<0.002) with the dilution factor. There were no differences (P>0.05) in the bacterial viable counts between the two strains or between suspending solutions, i.e., PBS and water, the cell concentrations demonstrating 1x10(9) cells/ml at OD600=1. Repeated microscopic cell counts did not differ (P>0.05) from each other. Large aggregates occurred as 1% of cell units counted. Dispersing bacterial mass indirectly to solution leads to homogeneous cell suspensions with repeatable cell concentrations. Viability of A. actinomycetemcomitans was also maintained when cells were suspended in water.

Aggregatibacter actinomycetemcomitans↗
PubMed2005

Tongue base suspension combined with UPPP in severe OSA patients.

OBJECTIVE: Tongue base surgery in the severe OSA patients may improve the success of uvulopalatopharyngoplasty (UPPP) as the collapse is multilevel. The aim of this study was to evaluate the long-term objective and subjective effectiveness of the minimally invasive tongue base suspension combined with UPPP in severe OSA patients. STUDY DESIGN AND SETTING: We conducted a retrospective analysis of 22 OSA patients undergoing UPPP and the tongue base suspension for the treatment of severe OSA. RESULTS: Twenty-two men who had their preoperative and postoperative polysomnography had a 54% reduction in the preoperative Respiratory Disturbance Index (RDI), from 47.50 +/- 15.74 to a level of 17.31 +/- 14.17. The standard surgical cure rate which is a >50% reduction in the RDI and a postoperative RDI of <20 events/hour was 81.81%. All patients had some degree of subjective improvement in their snoring, daytime sleepiness, and the Epworth sleepiness scale. CONCLUSIONS: The tongue base suspension combined with UPPP has been shown to reduce RDI better than UPPP alone. This minimally invasive technique is highly successful at 81.81% when combined with UPPP in the severe OSA patients with multilevel airway collapse. SIGNIFICANCE: This study shows the benefits of minimally invasive tongue base suspension combined with UPPP in severe obstructive sleep apnea syndrome.

Adult↗
PubMed2005

Anatomic changes after hyoid suspension for obstructive sleep apnea: an MRI study.

OBJECTIVE: To assess the effects of isolated hyoid suspension on subjective and objective parameters of obstructive sleep apnea and to evaluate changes in upper airway anatomy with the help of standardized magnetic resonance imaging. STUDY DESIGN AND SETTING: Fifteen patients received isolated hyoid suspension. Changes in respiratory disturbance index were assessed with polysomnography, and anatomical changes with standardized magnetic resonance imaging. Snoring, daytime sleepiness, and functional parameters were assessed with questionnaires. Lateral x-ray cephalometry was performed preoperatively. RESULTS: Mean respiratory disturbance index was reduced from 35.2 +/- 19.1 to 27.4 +/- 26.2. Forty percent of the patients were classified as responders. Daytime sleepiness improved significantly. Relevant changes in upper airway anatomy could not be detected. There were no remarkable differences between responders and nonresponders in regard to imaging. CONCLUSIONS: Hyoid suspension is effective only in a subgroup of patients and does not lead to relevant changes in airway diameters in the awake patient. Magnetic resonance imaging and x-ray cephalometry do not add additional information for patient selection. SIGNIFICANCE: The reported clinical effects of hyoid suspension are more likely due to functional changes in airway collapsibility than to an enlargement of the upper airway.

Adult↗
PubMed2005

Responses of antioxidant system in Arabidopsis thaliana suspension cells to the toxicity of microcystin-RR.

Microcystins are cyclic heptapeptide hepatoxins produced by many species of cyanobacteria. The toxic effects and mechanism of microcystins on animals have been well studied both in vivo and in vitro. It was also reported that microcystins had adverse effects on plants. However, to our knowledge, there is no information about the toxic effects and mechanism of microcystins on plant suspension cells. In this study, Arabidopsis thaliana suspension cells were exposed to a range dose of microcystin-RR. Lipid peroxidation, a main manifestation of oxidative damage, was studied and a time- and dose-dependent increase in malondiadehyde was observed. In contrast, glutathione (GSH) levels in the cells decreased after 48 h treatment with 1 and 5mg/L of microcystin-RR. The activities of superoxide dismutase (SOD) and catalase (CAT) increased significantly after 48 h exposure to 1 and 5mg/L of microcystin-RR, but glutathione S-transferase (GST) activity showed no difference compared with the control. These results clearly indicate that microcystin-RR is able to cause oxidative damage in A. thaliana suspension cells. Decrease of GSH content and increases of SOD and CAT activities reveal that the antioxidant system may play an important role in eliminating or alleviating the toxicity of microcystin-RR. The possible toxicity mechanism of microcystin-RR on the A. thaliana suspension cells is also discussed in this paper.

Analysis of Variance↗
PubMed2001

Alternating ptosis after bilateral frontalis muscle suspension for congenital ptosis.

PURPOSE: To report an unusual response to bilateral frontalis suspension surgery for congenital ptosis. METHODS: Case report. RESULTS: A 6-year-old child with infantile esotropia and bilateral congenital ptosis received a homologous fascia lata frontalis suspension. After surgery, the patient exhibited an alternating ptosis, caused by alternating unilateral frontalis muscle contraction, which has persisted throughout 3 years of postoperative observation. CONCLUSION: Symmetric frontalis muscle activation may not always occur after bilateral frontalis muscle suspension surgery for congenital ptosis. Amblyopia, strabismus, or fixation preference may predispose patients to use unilateral brow elevation, despite bilateral frontalis muscle suspension surgery.

Blepharoptosis↗
PubMed2003

Effective conductivity of a suspension of permeabilized cells: a theoretical analysis.

During the electroporation cell membrane undergoes structural changes, which increase the membrane conductivity and consequently lead to a change in effective conductivity of a cell suspension. To correlate microscopic membrane changes to macroscopic changes in conductivity of a suspension, we analyzed the effective conductivity theoretically, using two different approaches: numerically, using the finite elements method; and analytically, by using the equivalence principle. We derived the equation, which connects membrane conductivity with effective conductivity of the cell suspension. The changes in effective conductivity were analyzed for different parameters: cell volume fraction, membrane and medium conductivity, critical transmembrane potential, and cell orientation. In our analysis we used a tensor form of the effective conductivity, thus taking into account the anisotropic nature of the cell electropermeabilization and rotation of the cells. To determine the effect of cell rotation, as questioned by some authors, the difference between conductivity of a cell suspension with normally distributed orientations and parallel orientation was also calculated, and determined to be <10%. The presented theory provides a theoretical basis for the analysis of measurements of the effective conductivity during electroporation.

Cell Count↗
PubMedDate not supplied

Inertial migration based concentration factors for suspensions of Chlorella microalgae in branched tubes.

When a dilute suspension flows in the laminar regime through a tube, under certain conditions the suspended particles migrate radially to an equilibrium radial position. Branched tubes can use this radial concentration distribution to concentrate dilute suspensions. Suspensions of microalgae, Chlorella vulgaris, were pumped through tubes of various diameters for tube Reynolds number ranging from 47-1839 and photographed. Upstream particle concentration profiles were obtained by image analysis of the photographs. The dividing stream surfaces in branched tubes were obtained from the three-dimensional numerical solutions of the Navier-Stokes equations for steady, laminar, and homogeneous flow through tubes having one and two orthogonal branches. Concentration factors for Chlorella suspensions in branched tubes, predicted by a general method, fall in the range of 1.0-1.3.

Chlorella↗
PubMedDate not supplied

Wall shear stress in backward-facing step flow of a red blood cell suspension.

An experimental investigation of the wall shear stress distribution downstream of a backward-facing step is carried out. The wall shear stress distribution was determined by measuring the deformation of a gel layer, attached to the wall downstream of the step. Speckle pattern interferometry was applied to measure the deformation of the gel layer. The measured deformation, combined with the properties of the gel layer, served as an input for a finite element solid mechanics computation to determine the stress distribution in the gel layer. The wall shear stress, required to generate the measured deformation of the gel layer, was determined from these computations. A Newtonian buffer solution and a non-Newtonian red blood cell suspension were used as measuring fluids. The deformation of the gel layer was determined for a Newtonian buffer solution to evaluate the method and to obtain the properties of the gel layer. Subsequently, the wall shear stress distribution for the non-Newtonian red blood cell suspension was determined for three different flow rates. The inelastic non-Newtonian Carreau-Yasuda model served as constitutive model for the red blood cell suspension. Using this model, the velocity and wall shear stress distribution were computed by means of a finite element fluid mechanics computation. From the comparison between the numerical and the experimental results, it can be concluded that wall shear stresses, induced by the red blood cell suspension, can be modeled accurately by employing a Carreau-Yasuda model.

Blood Vessels↗
PubMed2001

Effects of a short-term suspension of hormone replacement therapy on mammographic density.

OBJECTIVE: To evaluate the effects of hormone replacement therapy (HRT) and of a short-term suspension of HRT on mammographic density. DESIGN: Prospective clinical study. SETTING: Outpatient menopausal clinic of the Second University of Naples. PATIENT(S): Ninety-seven healthy postmenopausal women. INTERVENTION(S): Thirty-nine menopausal women with intact uterus (group A) were treated with continuous transdermal E(2) plus acetate nomegestrolo sequentially added, 37 women in surgical menopause (group B) were treated with transdermal E(2) continuously administered, and 21 menopausal women did not receive any medication (group C). At the entry and after 12 months, a mammography was performed without suspension of HRT (group A1: 19 women; group B1: 19 women) or after a short-term suspension (group A2: 20 women; group B2: 18 women). MAIN OUTCOME MEASURE(S): Mammographic density evaluated according to a quantitative method. RESULT(S): At the second mammography, seven patients in group A1, four patients in group B1, and one patient in both groups A2 and B2 showed an increase in mammographic density, whereas no mammographic density increase was observed in patients in group C. A statistically significant difference in the mammographic density increase was found between group A1 and group A2; no difference was found between group B1 and B2. CONCLUSION(S): Suspension of HRT for about 3 weeks may reverse mammographic density increase associated with its use.

Administration, Cutaneous↗
PubMedDate not supplied

Histopathological study of frontalis suspension materials.

PURPOSE: This study is designed to find the most suitable frontalis suspension material by comparing the histopathologic findings of frequently used suspension materials in vivo. METHODS: Three kinds of suspension materials-autologous fascia lata, 1-0 Prolene suture material, and Silicone Band-were implanted in the white rabbit. Histopathologic study was done sequentially 1 week, 2 weeks, 4 weeks, and 8 weeks after implantation. RESULTS: Histologically, autologous fascia lata showed less inflammatory reaction and better incorporation with surrounding structures than the Silicone Band and suture material. Suture material and Silicone Band showed marked inflammatory reaction and did not incorporate or tightly bond with surrounding tissue in any of the samples. CONCLUSIONS: Fresh autologous fascia lata appears to be the most suitable material for frontalis suspension after histopathological testing.

Animals↗
PubMed2003

High-performance liquid chromatographic determination of polysorbate 80 in pharmaceutical suspensions.

A quick HPLC method is reported for the analysis of polysorbate 80 in pharmaceutical suspensions. A typical pharmaceutical suspension was mixed with dilute potassium hydroxide, and heated at 40 degrees C for 6 h. This procedure resulted in quantitative hydrolysis of polysorbate 80 to release oleic acid. A quick HPLC procedure was used to analyze the hydrolyzed samples without further sample treatment. Polysorbate 80 USP, treated in the same way as the pharmaceutical suspensions, was used as standard. Full validation tests were carried out and the validation studies demonstrated that this method is suitable for accurate and reproducible analysis of polysorbate 80 in pharmaceutical suspensions.

Chromatography, High Pressure Liquid↗
PubMed2003

PAA/PEO comb polymer effects on rheological properties and inter-particle forces in aqueous silica suspensions.

The effects of a poly(acrylic acid) (PAA)-poly(ethylene) (PEO) comb polymer dispersant on the rheological properties and inter-particle forces in aqueous silica suspensions have been studied under varying pH conditions. The comb polymer was found to adsorb more strongly under acidic than basic conditions, indicating that the PAA backbone of the copolymer preferentially adsorbs onto silica surfaces with the PEO "teeth" extending out from the surface into the solution. In the presence of low concentrations of copolymer, the silica suspensions were stable due to electrostatic repulsions between the silica surfaces. At higher copolymer concentrations and under neutral and basic conditions, where the copolymer interacted only weakly with silica, the suspensions showed a transition from a dispersed to weakly flocculated state and attractive forces were measured between silica surfaces. Under acidic conditions, the silica dispersion also destabilized at intermediate copolymer adsorbed density and then was re-stabilized at higher adsorbed coverage. The silica suspensions were stable at high copolymer coverage due to steric repulsions between the particles. The destabilization at intermediate coverage is thought to be due to polymer bridging between particles or possibly depletion forces.

Journal Article↗
PubMed2003

Interfacial and rheological properties of humic acid/hematite suspensions.

This work deals with the effect of humic acid (HA) adsorption on the interfacial properties, the stability, and the rheology of aqueous iron oxide (hematite) suspensions. It is first of all demonstrated that HA effectively adsorbs onto hematite, mainly at acid pH. Since the charge of the HA chains is negative, it will be electrostatically attracted to the hematite surface below the point of zero charge of the particles, when they are positively charged. Electrophoresis measurements of hematite suspensions as a function of pH in the presence and absence of HA clearly demonstrate the adsorption of negatively charged entities on the oxide. Since the HA-covered particles can be thought of as "soft" colloids, Ohshima's theory was used to gain information on the surface potential and the charge density of the HA layer (H. Ohshima, in: A.V. Delgado (Ed.), Interfacial Electrokinetics and Electrophoresis, Dekker, New York, 2002, p. 123). A different procedure was also used to ascertain the degree of modification experienced by the hematite surface when placed in contact with HA solutions. The contact angles of selected liquids on pretreated hematite layers lead to the conclusion that the humic acid molecules impart to the particles a significant electron-donor character, in turn increasing their hydrophilicity. All this amount of information is used in the work for the interpretation of the rheological properties of hematite suspensions; the results are consistent with a stabilizing effect of HA adsorption on the suspensions, mainly as a consequence of the increased electrostatic repulsion between particles.

Journal Article↗