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PubMed2006

Radiolytic hydrogen yields in aqueous suspensions of gold particles.

The effect of high concentrations of large gold particles, in the hundreds of nanometer size regime, on the yields of molecular hydrogen, G(H(2)), produced in the radiolysis of several aqueous solutions was determined. In particular we look for direct effect of radiation absorbed by the solid particles on the yield of water products. These particles, however, are catalytically active in the conversion of reducing radicals to molecular hydrogen as well. A very small increase in G(H(2)) observed in bromide solutions upon addition of 50 wt % of gold particles indicates that the radiolysis of the solid particles does not affect the yields in the aqueous phase. Very little exchange of charge carriers or energy between the two phases occurs in these large particle suspensions. On the other hand, efficient catalytic conversion of (CH(3))(2)C(*)OH radicals to H(2) is shown to occur. The efficiency of the presently studied suspensions in the redox-catalytic process is similar to that of suspensions of small particles of similar total surface area. In the presence of radicals from hydrogen atom abstraction from tert-butyl alcohol the yield decreases significantly, again similar to the behavior in suspensions of small particles. We conclude that the redox catalysis does not depend on the size of the particles when their size exceeds a few nanometers.

Journal Article↗
PubMed2004

Flow electrification in nonaqueous colloidal suspensions, studied with video microscopy.

Flow electrification in nonaqueous suspensions has been scarcely reported in the literature but can significantly affect colloidal stability and (phase) behavior, perhaps even without being recognized. We have observed it in shear flow experiments on concentrated binary suspensions of hydrophobized silica particles in chloroform. In this low-polarity solvent, electrical charges on the large-particles' surfaces manifest themselves via long-ranged forces, because hardly any screening can take place through counterions. By shearing the suspension for a prolonged time, we could demonstrate that the effective interactions between the large particles change from weakly attractive (due to the small particles) to strongly repulsive (due to acquired Coulomb interactions). One of the conditions required for flow electrification was the presence of a glass surface in the shear cell. A spectacular manifestation of the phenomenon was observed with confocal video microscopy. First, the formation of large-particle aggregates was seen, while subsequently (over a long shearing time) the aggregates disintegrated into small entities, mostly primary particles. The spatial distribution of these entities in the quiescent state after stopping the flow showed evidence for acquired long-range repulsion. The occurrence of flow electrification was further corroborated by control experiments, where no flow was imposed, antistatic agent was added, or the glass bottom was coated with a conducting (indium tin oxide, ITO) layer: here, the aggregates kept growing until they became very large. To further diagnose the phenomenon, we have also done experiments in which an external electric field was applied (via the ITO layer) to an aggregated suspension. When the lower electrode was given the lowest potential, the aggregates were found to move away from the bottom and disintegrate. The qualitative similarity hereof with the flow electrification experiment suggests that in the latter, the glass acquired negative charges. After prolonged application of an external electric field, we observed segregation into regions enriched in large particles and regions completely depleted of them. In the quiescent fluid these regions exist as isolated units, but in shear flow they merge into bands, a behavior which resembles shear banding.

Journal Article↗
PubMed2006

Lignans from cell suspension cultures of Phyllanthus niruri, an Indonesian medicinal plant.

Cell suspension cultures of Phyllanthus niruri were used to study the lignan profiles and biosynthesis. Suspension cultures yielded two lignans: the new cubebin dimethyl ether (1) and urinatetralin (2), a new lignan from P. niruri, but reported earlier from P. urinaria. This is the first report of cell suspension cultures of P. niruri that successfully produce lignans. Feeding 0.5 mM ferulic acid or 0.5 mM caffeic acid, being early precursors of lignan biosynthesis, resulted in an increase up to 0.7 mg g(-1) DW of 1 (control value 0.1 mg g(-1) DW) and up to 0.3 mg g(-1) DW of 2 (control value 0.2 mg g(-1) DW). Comparison of the lignan profiles of cell suspensions, callus cultures, aerial plant parts, roots, and seeds showed significant differences.

Caffeic Acids↗
PubMed2006

Comparison of ovalbumin quantification using forward-phase protein microarrays and suspension arrays.

We employed ovalbumin (a simulant used for ricin and botulism toxins in biodefense applications) and its high affinity polyclonal antibody as a model system to examine the sensitivity, dynamic range, linearity, and reproducibility of forward-phase array results in comparison to suspension arrays. It was found that protein microarrays had a dynamic range of 4 orders of magnitude and a sensitivity of less than 1 pg/mL, respectively. The dynamic range and sensitivity of suspension arrays were close to 2 orders of magnitude and 0.25 ng/mL, respectively. The sensitivity we observed for the suspension arrays is comparable to that reported for enzyme-linked immunosorbent assays (ELISAs) in the literature. We used ovalbumin samples with two different purities, 38.0% and 76.0% (w/w), as determined by polyacrylamide gel electrophoresis (PAGE). These samples were used to evaluate the effect of impure samples on detection. The data obtained from the forward-phase protein arrays gave values that were consistent with the PAGE data. The data from the suspension arrays were not as consistent and may indicate that this format may not give as reliable data with impure samples. Knowledge of the advantages and disadvantages of the two proteomic methods would allow their more rational use in clinical diagnosis.

Animals↗
PubMed1999

Influence of crystal habit on trimethoprim suspension formulation.

PURPOSE: The role of crystal habit in influencing the physical stability and pharmacokinetics of trimethoprim suspensions was examined. METHODS: Different habits for trimethoprim (TMP) were obtained by recrystallizing the commercial sample (PD) utilizing solvent-change precipitation method. Four distinct habits (microscopic observation) belonging to the same polymorphic state (DSC studies) were selected for studies. Preformulation and formulation studies were carried out on suspension dosage forms containing these crystals. The freshly prepared suspensions were also evaluated for their pharmacokinetic behaviour on healthy human volunteers using a cross over study. RESULTS: Variation of crystallization conditions produces different habits of TMP. Among the different crystal habits exhibiting same polymorphic state, the most anisometric crystal showed best physical stability in terms of sedimentation volume and redispersibility. However, habit did not significantly affect the extent of TMP excreted in urine. CONCLUSIONS: Modification of surface morphology without significantly altering the polymorphic state can be utilized for improving physical stability of TMP suspensions. However, the pharmacokinetic profile remains unaltered.

Adult↗
PubMed2002

Lignification related enzymes in Picea abies suspension cultures.

Activity of a number of enzymes related to lignin formation was measured in a Picea abies (L) Karsten suspension culture that is able to produce native-like lignin into the nutrient medium. This cell culture is an attractive model for studying lignin formation, as the process takes place independently of the complex macromolecular matrix of the native apoplast. Suspension culture proteins were fractionated into soluble cellular proteins, ionically and covalently bound cell wall proteins and nutrient medium proteins. The nutrient medium contained up to 5.3% of total coniferyl alcohol peroxidase (EC 1.11.1.7) activity and a significant NADH oxidase activity that is suggested to be responsible for hydrogen peroxide (H2O2) production. There also existed some malate dehydrogenase (EC 1.1.1.37) activity in the apoplast of suspension culture cells (in ionically and covalently bound cell wall protein fractions), possibly for the regeneration of NADH that is needed for peroxidase-catalysed H2O2 production. However, there is no proof of the existence of NADH in the apoplast. Nutrient medium peroxidases could be classified into acidic, slightly basic and highly basic isoenzyme groups by isoelectric focusing. Only acidic peroxidases were found in the covalently bound cell wall protein fraction. Several peroxidase isoenzymes across the whole pI range were detected in the protein fraction ionically bound to cell walls and in the soluble cellular protein fraction. One laccase-like isoenzyme with pI of approximately 8.5 was found in the nutrient medium that was able to form dehydrogenation polymer from coniferyl alcohol in the absence of H2O2. The total activity of this oxidase towards coniferyl alcohol was, however, several orders of magnitude smaller than that of peroxidases in vitro. According to 2D 1H-13C correlation NMR spectra, most of the abundant structural units of native lignin and released suspension culture lignin are present in the oxidase produced dehydrogenation polymer but in somewhat different amounts compared to peroxidase derived synthetic lignin preparations. A coniferin beta-glucosidase (EC 3.2.1.21) was observed to be secreted into the culture medium.

Journal Article↗
PubMed1991

Effects of graded oxygen tension on adenosine release by renal medullary and thick ascending limb suspensions.

Adenosine is released from renal cells, and extracellular adenosine may influence the effects of ischemia on medullary tubule segments by altering ion transport or renal hemodynamics. While adenosine release and excretion are enhanced during renal ischemia, the specific sites of renal adenosine production have not been completely elucidated. In the present study, extracellular adenosine concentrations in suspensions of renal outer medulla and thick ascending limb segments were quantitated by reversed-phase high performance liquid chromatography. Media from other medullary (OM) suspensions incubated for 8 and 15 minutes at 0% oxygen contained significantly greater amounts of adenosine (1.404 +/- 0.21 and 2.034 +/- 0.27 ng/micrograms protein, respectively), when compared to values obtained from media of suspensions incubated for equivalent periods under non-hypoxic conditions (8, 20, and 95% oxygen), 0.78 +/- 0.05 (8 min) and 1.37 +/- 0.21 ng/micrograms protein (15 min). Similarly, adenosine release was greater in medullary thick ascending limb (mTAL) suspensions incubated for 8 minutes at 0% versus 8% oxygen (0.81 +/- 0.17 vs. 0.20 +/- 0.12 ng/micrograms protein, respectively). Moreover, the observed increase in adenosine release by thick ascending limbs at 0% oxygen could be inhibited completely by either furosemide or ouabain. These studies demonstrate that: 1) the renal medulla and medullary thick ascending limb are sites of adenosine release; 2) adenosine release by the mTAL is enhanced significantly during hypoxic conditions; and 3) the increased release of adenosine during hypoxia appears to be related to ion transport and oxidative metabolism, as the increased release was prevented by two disparate inhibitors of transport in this segment.

Adenosine↗
PubMed1994

Expansion of hematopoietic progenitor cell populations in stirred suspension bioreactors of normal human bone marrow cells.

We have investigated the potential of stirred suspension cultures to support hematopoiesis from starting innocula of normal human bone marrow cells. Initial studies showed that the short-term maintenance of both colony-forming cell (CFC) numbers and their precursors, detected as long-term culture-initiating cells (LTC-IC), could be achieved as well in stirred suspension cultures as in static cultures. Neither of these progenitor cell populations was affected in either type of culture when porous microcarriers were added to provide an increased surface for adherent cell attachment. Supplementation of the medium with 10 ng/ml of Steel factor (SF) and 2 ng/ml of interleukin-3 (IL-3) resulted in a significant expansion of LTC-IC, CFC and total cell numbers in stirred cultures. Both the duration and ultimate magnitude of these expansions were correlated with the initial cell density and after 4 weeks the number of LTC-IC and CFC present in stirred cultures initiated with the highest starting cell concentration tested reflected average increases of 7- and 22-fold, respectively, above input values. Stirred suspension cultures offer the combined advantages of homogeneity and lack of dependence on the formation and maintenance of an adherent cell layer. Our results suggest their applicability to the development of scaled-up bioreactor systems for clinical procedures requiring the production of primitive hematopoietic cell populations. In addition, stirred suspension cultures may offer a new tool for the analysis of hematopoietic regulatory mechanisms.

Biotechnology↗
PubMed1965

Effect of chloramphenicol on ribonucleic acid synthesis in liver cells in suspension.

1. Chloramphenicol has a stimulatory effect on the incorporation of radioactive phosphate into the RNA of perfused rat-liver slices, whole liver homogenates or the liver-cell suspensions, and no effect on the incorporation of [(14)C]adenine and [(14)C]uracil into the RNA of the tissue slices. 2. Chloramphenicol completely inhibits the incorporation of labelled adenine and uracil into the RNA of the cell suspensions, or into the RNA of homogenates derived from the whole liver tissues. 3. Chloramphenicol has at most a slight inhibitory effect on the transport of labelled adenine or uracil in the hepatic cells in suspension; in the slices, the transport of these bases is not inhibited at all. 4. The above observations indicate that: (a) unlike the tissue slices, hepatic cells in suspension are permeable to chloramphenicol; (b) in the presence of chloramphenicol, for reasons that are not clear, the conversion of the base into the appropriate nucleotide does not proceed.

Journal Article↗
PubMed1996

Enhanced eradication of Helicobacter pylori by pre- versus post-prandial amoxycillin suspension with omeprazole: implications for antibiotic delivery.

BACKGROUND: Strategies to improve antibiotic treatment of Helicobacter pylori infection are hampered by lack of knowledge about the route of antibiotic delivery. Post-prandial dosing with antibiotics prolongs their gastric residence time and improves their intragastric distribution, leading to improved local delivery compared with pre-prandial dosing. We aimed to assess whether pre- or post-prandial dosing. with amoxycillin suspension was more effective for H. pylori eradication in an amoxycillin/omeprazole regimen. METHODS: Seventy-nine patients with H. pylori infection were treated with omeprazole 40 mg o.m. for 28 days and amoxycillin suspension 500 mg q.d.s. for days 15-28, the amoxycillin being randomized to either 1 h before or immediately after food. RESULTS: The H. pylori eradication rate, for those completing the trial, was 67% (22/33) when amoxycillin suspension was given pre-prandially, compared with 39% (15/38) when it was given post-prandially (P < 0.05). Good compliance was achieved, with H. pylori eradication in 59% (28/46) of good compliers compared with 36% (9/25) of others completing the protocol (P < 0.05). CONCLUSION: When given with omeprazole, pre-prandial dosing with amoxycillin suspension is more effective for H. pylori eradication than post-prandial dosing. This is consistent with the hypothesis that systemic rather than local delivery of amoxycillin is important for H. pylori eradication.

Adult↗
PubMed1998

Clarification of small volume microbial suspensions in an ultrasonic standing wave.

The removal of Saccharomyces cerevisiae and Escherichia coli from 2.5 ml suspensions in ultrasonic standing wave formed at 1 or 3 MHz has been characterized. The standing wave was set up by a plane transducer and reflector mounted in the vertical plane. Cells in the ultrasonic field first concentrated in vertical planes at half wavelength separations. The ultrasound was then pulsed to allow clumps of concentrated cells to sediment in a controlled way during the short 'off' intervals. Yeast removal from suspension at a concentration of 3 x 10(9) ml-1 (14% volume v/v) was 99.5% in a total time of 4.5 min. Almost total (99.5%) clarification of prokaryote (E. coli) suspension was achieved here for the first time in a standing wave field. The clarification of a 1.3 x 10(11) ml-1 (16% v/v) E. coli suspension occurred over 11.5 min. The period decreased to 7 min in the presence of a polycationic flocculant, polyethyleneimine. The implications of the results for design of systems to further reduce clarification times are discussed. Removal efficiency for both S. cerevisiae and E. coli decreased with decrease in cell concentration. This concentration dependence is shown not to be simply a consequence of acoustic interaction between single cells. Flow cytometry of stained cells detected no loss of cell viability arising from the ultrasonic procedure.

Bacteriological Techniques↗
PubMed2000

Bactericidal action of high-power Nd:YAG laser light on Escherichia coli in saline suspension.

Infra-red light (1064 nm) from a high-power Nd:YAG laser caused more than 90% loss of viability of Escherichia coli during exposures that raised the temperature of PBS suspensions of the bacteria to 50 C in a thermocouple-equipped cuvette. In contrast, there was minimal loss of viability after heating the same suspensions to 50 degrees C in a water-bath, or in a PCR thermal cycler. The mechanism of laser killing at 50 degrees C was explored by differential scanning calorimetry, by laser treatment of transparent and turbid bacterial suspensions, and by optical absorbency studies of E. coli suspensions at 1064 nm. Taken together, the data suggested that the bactericidal action of Nd:YAG laser light at 50 degrees C was due partly to thermal heating and partly to an additional, as yet undefined, mechanism. Scanning electron microscopy revealed localized areas of surface damage on laser-exposed E. coli cells.

Colony Count, Microbial↗
PubMed2004

Cryopreservation of transformed and wild-type Arabidopsis and tobacco cell suspension cultures.

We have recently described Arabidopsis cell suspension cultures that can be effectively synchronised. Here, we describe procedures that allow clonal-transformed cell suspension lines to be produced using Agrobacterium-mediated transformation, and an optimised and straightforward procedure for the cryopreservation and recovery of both parental and transformed lines. Frozen cultures show 90% viability and rapid re-growth after recovery. We show that the cryopreservation procedure is equally applicable to the frequently used tobacco bright yellow (BY)2 cell suspension culture, and that cell cycle synchronisation capacity of parental lines is maintained after both transformation and recovery from cryopreservation. The techniques require no specialised equipment, and are suitable for routine laboratory use, greatly facilitating the handling and maintenance of cell cultures and providing security against both contamination and cumulative somaclonal variation. Finally, the ability to store easily large numbers of transformed lines opens the possibility of using Arabidopsis cell suspension cultures for high-throughput analysis.

Arabidopsis↗
PubMed1999

Urinary continence and erectile function after bladder neck sling suspension in male patients with spinal dysraphism.

OBJECTIVE: To assess the outcome of using sling suspensions combined with clean intermittent catheterization (CIC) in patients with spina bifida, of whom a third are incontinent through pelvic floor paralysis. PATIENTS AND METHODS: Between March 1992 and April 1997, 14 male patients (mean age at surgery 11.7 years, range 6.5-15.2) with spina bifida and neurogenic sphincter incontinence underwent a puboprostatic sling suspension as a primary treatment. The procedure, via an abdominoperineal approach, consists of suspending the bladder neck by placing a simple U-shaped rectus abdominus fascial sling. The perineal approach is used to develop the plane between the rectum and Denonvillier's fascia, and to prepare the passage of the sling alongside the prostate. Apart from the sling procedure, eight of the 14 patients underwent autoaugmentation of the bladder and two underwent ileocystoplasty during the same operation. All patients used CIC daily. Erectile function was assessed by reports from the patients and their parents, and continence by report and urodynamic studies. RESULTS: Of the 14 patients, 13 achieved urinary continence with no additional procedures; one required a subsequent submucosal injection at the suspension site with silicone particles in povidone (Macroplastique(R)) to become continent. Two patients reported slight leakage at night. Before surgery, all but one patient reported having spontaneous or mechanically manipulated erections; none had erections on psychological stimulation. After surgery, erectile function was preserved in 13 of the 14 patients; in one there were problems establishing the right dissection plane between the rectum and prostate, but spontaneous erections returned a year after surgery. CONCLUSION: In males, the abdominoperineal puboprostatic sling suspension using rectus abdominis fascia appears to be a successful treatment for sphincter incontinence in patients with spina bifida, and safely maintains erectile function.

Adolescent↗
PubMed1999

Test controller design, implementation, and performance for a magnetic suspension continuous flow ventricular assist device.

A new continuous flow ventricular assist device using full magnetic suspension has been designed, constructed, and tested. The magnetic suspension centers the centrifugal pump impeller within the clearance passages in the pump, thus avoiding any form of contact. The noncontact operation is designed to give very high expected mechanical reliability, large clearances, low hemolysis, and a relatively small size compared to current pulsatile devices. A unique configuration of magnetic actuators on the inlet side and exit sides of the impeller provides full 5 axis control and suspension of the impeller. The bearing system is divided into segments which allow for 3 displacement axes and 2 angular control axes. The controller chosen for the first suspension tests consists of a decentralized set of 5 proportional integral derivative (PID) controllers. This document describes both the controller and an overview of some results pertaining to the magnetic bearing performance. The pump has been successfully operated in both water and blood under design conditions suitable for use as a ventricular assist device.

Equipment Design↗
PubMed1997

[Frontalis suspension with "expanded polytetrafluoroethylene (ePTFE) strips" in congenital ptosis].

BACKGROUND: The Frontalis Suspension Technique is indicated in cases with minimal or no levator function. At the beginning sutures were used as sling material and after further modifications suture material was replaced by autologous or homologous fascia lata. In the last years ePTFE has proved to be a very suitable sling material. PATIENTS AND METHODS: Since ePTFE is very biocompatible, it was used for this modified frontalis suspension technique. The anterior tarsal surface is exposed and a small tunnel is created between the skin incision and the second incision superior to the brow. An 0.3 mm thin ePTFE strip is induced into the tunnel and connects the upper lid with the frontalis muscle. The ePTFE Soft Tissue Patch must be exactly adapted to the tarsus and has to be deeply sutured to the frontalis muscle below the brow incision. Since 1994 17 modified frontalis suspension procedures have been performed on 14 patients. RESULTS: The functional and cosmetic result were good in nearly all patients. No implant had to be removed during the follow up period. DISCUSSION: The new technique of frontalis suspension using a ePTFE strip guarantees a regular upper lid lifting by the axial and direct connection of the anterior tarsal surface with the frontalis muscle.

Blepharoptosis↗
PubMed1980

[Results of the operative treatment of stress incontinence in women with urethro-vesical suspension according to Pereyra (author's transl)].

From 1971-1979, 380 women with marked stress incontinence had urethro-vesical suspensions according to Pereyra. In the majority of the cases this urethrovesical suspension was done as an additional operation to vaginal hysterectomy and anterior and posterior colporrhaphy. The follow-up examination of 189 patients 6 to 60 months after the operation included as for the pre-operative examination the history, the gynaecological findings, the Bonney test, the residual urine determination, chromocystoscopy, urinalysis with culture and sensitivity and a lateral cysto-urethrogram. 86.2% of the patients were objectively and subjectively cured. In 13.8% no improvement of the stress incontinence was found. The Pereyra urethro-vesical suspension is a valuable addition to the operative treatment of urinary stress incontinence. The complication rate is as low as for other methods and the results are at least the same. The Pereyra urethro-vesical suspension is recommended.

Adult↗
PubMed2005

A coarse-grained explicit solvent simulation of rheology of colloidal suspensions.

We use a simple extension of the dissipative particle dynamics (DPD) model to address the dynamical properties of macrosolutes immersed in complex fluid solvents. In this approach, the solvent particles are still represented as DPD particles, thereby retaining the time and length scale advantages offered by the DPD approach. In contrast, the solute particles are represented as hard particles of the appropriate size. We examine the applicability of this simulation approach to reproduce the correct hydrodynamical characteristics of the mixture. Our results focus on the equilibrium dynamics and the steady-state shear rheological behaviors for a range of volume fractions of the suspension, and demonstrate excellent agreement with many published experimental and theoretical results. Moreover, we are also able to track the glass transition of our suspension and the associated dynamical signatures in both the diffusivities and the rheological properties of our suspension. Our results suggest that the simulation approach can be used as a one-parameter model to examine quantitatively the rheological properties of colloidal suspensions in complex fluid solvents such as polymeric melts and solutions, as well as allied dynamical phenomena such as phase ordering in mixtures of block copolymers and particles.

Journal Article↗