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At least 253 records · Page 14Linked to original sources
PubMed2003

A flow-injection ultrafiltration sampling chemiluminescence system for on-line determination of drug-protein interaction.

A flow-injection ultrafiltration sampling chemiluminescence system for on-line determination of cimetidine-bovine serum albumin (BSA) interaction is proposed in this paper. Cimetidine can be oxidized by N-bromosuccinimide (NBS) and sensitized by fluorescein to produce high chemiluminescence emission in basic media. The concentration of cimetidine is linear with the CL intensity in the range 3 x 10(-7) - 1 x 10(-4) mol L(-1) with a detection limit of 1 x 10(-7) mol L(-1) (3 sigma). The drug and protein were mixed in different molar ratios in 0.067 mol L(-1) phosphate buffer, pH 7.4, and incubated at 37 degrees C in a water bath. The ultrafiltration probe was utilized to sample the mixed solution at a flow rate of 5 micro L min(-1). The data obtained by the proposed ultrafiltration flow-injection chemiluminescence method was analyzed with Scrathard analysis and a Klotz plot. The estimated association constant ( K) and the number of the binding site ( n) on one molecule of BSA by Scrathard analysis and Klotz plot were 3.15 x 10(4) L mol(-1) and 0.95, 3.25 x 10(4) L mol(-1) and 0.92, respectively. The proposed system proved that flow-injection chemiluminescence analysis coupled with on-line ultrafiltration sampling is a simple and reliable technique for the study of drug-protein interaction.

Binding Sites↗
PubMed1996

Comparison of ethanol plasma-protein precipitation with plasma ultrafiltration and trichloroacetic acid protein precipitation for the measurement of unbound platinum concentrations.

Sample preparation for the measurement of non-protein-bound platinum was evaluated by precipitation of plasma proteins with cold ethanol. The method was compared with the routinely used plasma ultrafiltration and with trichloroacetic acid (TCA) protein precipitation. After incubation of human plasma samples with cisplatin or carboplatin, unbound platinum concentrations were determined applying Amicon Diaflo ultrafiltration membranes and Millipore ultrafree-MC filters. For protein precipitation, 1 ml of cold (-20 degrees C) pure ethanol was added to 0.5 ml of human plasma and the supernatant was collected after 2 h, or 0.5 ml of cold 20% TCA was added to 0.5 ml of plasma. Platinum was analyzed by atomic absorption spectrophotometry (AAS). There was no significant difference between the ethanol and ultrafiltration methods in the unbound platinum concentration. The protein content in the supernatant (1.00 +/- 0.20%) was slightly higher than that in the Amicon (0.58 +/- 0.05%) and Millipore (0.55 +/- 0.04%) ultrafiltrates. On average, the TCA and ethanol method seemed to be equally appropriate. The ethanol precipitation method is concluded to be simple, convenient, and reproducible and has negligible costs.

Blood Proteins↗
PubMed1984

A high-performance liquid chromatographic assay with improved selectivity for cisplatin and active platinum (II) complexes in plasma ultrafiltrate.

cis-Diamminedichloroplatinum(II) (DDP) was measured in plasma ultrafiltrate following derivatization with sodium diethyldithiocarbamate (DDTC) by quantitation against a nickel chloride internal standard. A chloroform extract containing the Pt(DDTC)2 and Ni(DDTC)2 complexes was separated by reversed-phase high-performance liquid chromatography on a C18 radial compression column. The complex was eluted with methanol/water, 4/1, at a flow rate of 1.5 ml/min, and was detected at 254 nm. The limit of sensitivity was 0.1 microgram/ml DDP in the ultrafiltrate. This analytical approach was validated by comparison to graphite furnace atomic absorption spectrophotometric determinations of duplicate samples. There was clearly a component of the ultrafiltrable platinum present that was resistant to derivatization by DDTC. Evidence is presented that this component, presumably Pt(II) complexed with endogenous small molecules, is non cytotoxic and, hence, that this method may be selective for "active Pt(II)." This method offers an advantage over atomic absorption determination of total platinum in ultrafiltrate which does not discriminate between active and inactive forms, and over off-line FAA detection of parent DDP in HPLC eluates which ignores other active forms. Using this technique we have measured the pharmacokinetics of DDTC-reactive Pt(II) in humans after either i.v. infusion or infusion of DDP into the peritoneal cavity of patients with ovarian carcinoma.

Chromatography, High Pressure Liquid↗
PubMed1977

Human transfer factor prepared by dialysis, ultrafiltration and gel chromatography: biological activity in local transfer of skin sensitivity.

Human transfer factor (TF) was prepared by a variety of methods including dialysis using cellophane tubing, ultrafiltration through a membrane of known pore size. Sephadex G25 chromatography or combinations of some of these methods. In general the various preparations when injected locally into human skin gave greater delayed-type responses than antigen (PPD or Candida) alone. The combination of either vacuum dialysis, or ultrafiltration, with G-25 chromatography gave as good or better TF activity when compared with unchromatographed materials. Since ultrafiltration and concentration is rapid procedure and eliminates the need for freeze-drying, in contrast to vacuum dialysis against water, these results indicate that ultrafiltration and G-25 chromatography provide a convenient method for preparing large batches of relatively pure TF from leucocyte extracts.

Antigens, Fungal↗
PubMed1982

Determination of unbound fraction of disopyramide in plasma: a comparison of equilibrium dialysis, ultrafiltration through dialysis membranes and ultrafree anticonvulsant drug filters.

A simple, rapid ultrafiltration technique for determination of free drug concentration in plasma is described and compared with equilibrium dialysis and ultrafiltration through dialysis membranes. When used for disopyramide protein binding studies, this method requires only 1 ml of plasma and up to 20 samples may be filtered simultaneously in 20-40 min. Commercially available Ultrafree anticonvulsant drug filters are used, these are attached to 2 ml leur tip syringes, which provide the pressure gradient for filtration. Compared to equilibrium dialysis this technique is far quicker and permits protein binding to be measured at the drug concentration in the original plasma. Ultrafiltration through dialysis membranes was found to be more tedious and time-consuming than it was through Ultrafree filters. Adsorption of disopyramide from the plasma sample and protein leakage were also problems with this method. Leakage of protein did not occur with either Ultrafree filters or equilibrium dialysis. With the Ultrafree method, recovery of 14C-labeled disopyramide in buffer at 1.1 micrograms/ml and 8.4 micrograms/ml was 87% and 89% respectively. In carefully controlled experiments, a comparison of the Ultrafree method with equilibrium dialysis and ultrafiltration gave comparable values for the free fraction of the drug for total concentrations from 0.3-8 microgram/ml disopyramide.

Blood Proteins↗
PubMed1993

Pharmacokinetic studies using micellar electrokinetic capillary chromatography with in vivo capillary ultrafiltration probes.

Micellar electrokinetic capillary chromatography (MECC) is shown to be a quantitative method for the determination of theophylline in capillary ultrafiltrates of biological systems. MECC exhibits reproducibility in migration times of 1.3% relative standard deviation (R.S.D.) (n = 31) and peak heights of 3.0% R.S.D. (n = 28). MECC and reversed-phase liquid chromatography (LC) are shown to be complementary techniques for the determination of theophylline in ultrafiltrate samples. In vivo sampling of awake, freely moving rats is achieved using capillary ultrafiltration probes implanted in subcutaneous tissue. The ability of MECC coupled with in vivo capillary ultrafiltration to determine theophylline pharmacokinetics is demonstrated. The half-life of elimination for a 15 mg/kg intraperitoneal dose of theophylline was determined to be 3.1 +/- 0.4 h for MECC and 3.2 +/- 0.4 h for LC (n = 4, mean +/- standard error of the mean). Concurrent results for derived pharmacokinetic parameters (area under the curve, volume of distribution, concentration at time zero and clearance) were obtained for MECC and LC.

Animals↗
PubMed2006

Determination of the extent of protein binding of antibiotics by means of an automated continuous ultrafiltration method.

The extent of the protein binding of a drug is an important pharmacokinetic parameter. In this study, the determination of the protein binding of the antibiotics gatifloxacin, moxifloxacin, linezolid and telithromycin to bovine serum albumin (BSA) and human serum albumin (HSA) was performed by means of an automated continuous ultrafiltration method. The continuous ultrafiltration has several advantages compared to classical methods like equilibrium dialysis or discontinuous ultrafiltration. The method is appropriate for a fast determination of the extent of the protein binding of a drug. In one single experiment the calculation of the protein binding over a wide range of different drug/protein ratios is possible. Comparing the results obtained with the continuous ultrafiltration with binding data reported in literature shows good correlation and proves the reliability of the method.

Acetamides↗
PubMed2006

Monitoring of lopinavir and ritonavir in peripheral blood mononuclear cells, plasma, and ultrafiltrate using a selective and highly sensitive LC/MS/MS assay.

For the determination of the HIV protease inhibitors lopinavir and ritonavir in human plasma, plasma ultrafiltrate, and peripheral blood mononuclear cells (PBMCs) a highly sensitive and selective method has been developed, validated, and applied to samples of a healthy volunteer. BD Vacutainer CPT and Amicon Centriplus centrifugal filter devices were used for separation of PBMCs and for ultrafiltrate generation, respectively. After liquid/liquid-extraction extracts were chromatographed isocratically within 6 min on a Jupiter Proteo column. The drugs were quantified using 2H5-saquinavir as internal standard and electrospray tandem mass spectrometry in the selected reaction monitoring mode. Limits of quantification for both analytes were 4.0 ng/mL in plasma, 0.2 ng/mL in ultrafiltrate, and 0.1 ng/cell pellet (approximately 3 x 10(6) cells) in PBMCs. The calibration ranges were linear over more than three logs with an over-all accuracy varying between 98.7% and 111.5% and an over-all precision ranging from 6.2% to 14.0% (SD batch-to-batch). After a regular oral dose of Kaletra (400 mg lopinavir, 100 mg ritonavir) analyte concentrations were detectable over a full dosing interval in plasma, ultrafiltrate, and PBMCs. The method is well suited for monitoring of free and total plasma, and intracellular lopinavir/ritonavir concentrations in samples from clinical trials.

HIV Protease Inhibitors↗
PubMed1984

Ultrafiltration during cardiopulmonary bypass: laboratory evaluation and initial clinical experience.

Ultrafiltration during crystalloid hemodilution cardiopulmonary bypass (CPB) was evaluated in two groups of mongrel dogs: in one group during 2 hours of CPB with the heart empty and beating and in the other during 90 minutes of cold cardioplegic arrest followed by 30 minutes of recovery. In both groups, the accumulation of extravascular lung water was less in the dogs undergoing ultrafiltration than in control animals. In 10 patients with clinical evidence of severe fluid overload, ultrafiltration was employed during CPB. The amount of fluid removed ranged from 1,700 to 6,100 ml (mean, 3,240 +/- 1,481 ml [standard deviation]) and resulted in an average intraoperative fluid balance of -901 +/- 2,537 ml, a weight gain of 1.9 +/- 2.5 kg, and a decrease in extravascular lung water from 1,132 +/- 183 ml to 919 +/- 267 ml (p = 0.209). Ultrafiltration is a safe, effective means of removing body water and of preventing further accumulation of such water during hemodilution CPB.

Animals↗
PubMed1987

Ultrafiltration with an isosmotic solution during long peritoneal dialysis exchanges.

The potential of a starch-derived glucose polymer (molecular weight 16,800) as an osmotic agent for peritoneal dialysis was evaluated. A dialysate isosmotic to uraemic serum (302 [SEM 1.3] mOsm/kg) containing 5% glucose polymer (9.4 mmol/l) was compared with hypertonic (332 [1.0] mOsm/kg) 1.36% glucose (76 mmol/l) solution for ultrafiltration, solute transport, and carbohydrate absorption over 6 h and 12 h peritoneal dialysis exchanges. Glucose polymer solution produced substantially greater net ultrafiltration than glucose, while maintaining stable dialysate osmolality throughout the exchanges. At 6 h and 12 h, 14.4% and 28.1% of glucose polymer had been absorbed, compared with 61.5% and 83.0% of glucose; thus, glucose polymer provided less than 50% of the calorie load of the glucose dialysate per unit volume of ultrafiltrate. There was a 7-9-fold increase in serum maltose with glucose polymer. This high-molecular-weight glucose polymer produced sustained ultrafiltration even when dialysate osmolality remained within the physiological range, by a mechanism resembling "colloid" osmosis. It is a safe and effective osmotic agent but its long-term effects need further study.

Adult↗
PubMed1987

Ultrafiltration failure in continuous ambulatory peritoneal dialysis due to excessive peritoneal cavity lymphatic absorption.

We describe a continuous ambulatory peritoneal dialysis (CAPD) patient who developed failure of ultrafiltration for no apparent cause during the first year of treatment. Further investigation showed that peritoneal cavity lymphatic reabsorption during the dwell time exceeded cumulative transcapillary ultrafiltration and so caused negative net ultrafiltration. Peritoneal lymphatic drainage should be added to the list of causes that, either singly or in combination, lead to loss of ultrafiltration in CAPD.

Absorption↗
PubMed1988

Prolonged intraperitoneal dwell decreases ultrafiltration coefficient in rabbits.

In rabbits undergoing peritoneal dialysis, hypertonic (6% dextrose) dialysis solution increased the net ultrafiltration rate (UF) from 233 to 462 microL/kg/min, which was not proportional to the increment in the osmotic gradient, so the ultrafiltration coefficient decreased. As intraperitoneal dwell of hypertonic dialysate was prolonged, the gross and net UFs and ultrafiltration coefficients decreased, and the UF per dextrose absorption declined. The decrement in UF was multifactorial, including a component of fluid and solute stagnation, increasing the distance over which osmotic forces must exert their effects. Excessively hypertonic dialysis fluid should be used only briefly to achieve ultrafiltration efficiently and to avoid the high dextrose loading.

Absorption↗
PubMed1992

Capillary ultrafiltration: in vivo sampling probes for small molecules.

Capillary ultrafiltration is a novel sampling method convenient for low molecular weight substances in living biological systems. By application of a negative pressure across a hydrophilic membrane capillary, small molecules are actively "pulled" across the membrane and collected. By elimination of large molecules and cellular matter, the ultrafiltrate collected is well suited for further analysis by liquid chromatography, capillary electrophoresis, or mass spectrometry. Ultrafiltration probes (UF probes) provide a simple means to obtain a small-volume sample from subcutaneous tissue, blood, saliva, or any other biological fluid in vivo. The dependence of recovery on flow rate, temperature, membrane dimensions, and vacuum magnitude are considered. The relative merits of capillary ultrafiltration probes and microdialysis probes are considered. UF probe applications presented include in vivo monitoring of drug disposition in human saliva and in the subcutaneous space of awake, freely moving rats.

Acetaminophen↗
PubMed1997

Pulsed ultrafiltration mass spectrometry: a new method for screening combinatorial libraries.

In response to the need for rapid screening of combinatorial libraries to identify new lead compounds during drug discovery, we have developed an on-line combination of ultrafiltration and electrospray mass spectrometry, called pulsed ultrafiltration mass spectrometry, which facilitates the identification of solution-phase ligands in library mixtures that bind to solution-phase receptors. After ligands contained in a library mixture were bound to a macromolecular receptor, e.g., human serum albumin or calf intestine adenosine deaminase, the ligand-receptor complexes were purified by ultrafiltration and then dissociated using methanol to elute the ligands into the electrospray mass spectrometer for detection. Ligands with dissociation constants in the micromolar to nanomolar range were successfully bound, released, and detected using this method, including warfarin, salicylate, furosemide, and thyroxine binding to human serum albumin, and erythro-9-(2-hydroxy-3-nonyl)adenine binding to calf intestine adenosine deaminase. Repetitive bind- and-release experiments demonstrated that the receptor could be reused. Thus, pulsed ultrafiltration mass spectrometry was shown to provide a simple and powerful new method for the screening of combinatorial libraries in support of new drug discovery.

Adenine↗
PubMed2006

Trace metal speciation in brackish water using diffusive gradients in thin films and ultrafiltration: comparison of techniques.

Diffusive gradients in thin films (DGT) and ultrafiltration were used to measure trace metal concentrations in the Baltic Sea. The results provide the first comparison of these two fundamentally different speciation methods for trace metals. Cd, Cu, Mn, Ni, and Zn were measured at two sites with different total trace metal concentrations. DGT units prepared with APA-gel as diffusive layer and Chelex 100 resin as binding agent were used throughout the study. The ultrafiltration was performed with Millipore Prep/Scale modules with cutoffs of 1 and 10 kDa. Concentration levels of Mn, Zn, and Cd measured by DGT agreed with the concentrations measured in 1 kDa ultrafiltered samples. For Cu and Ni the ultrafiltered concentrations exceeded the DGT-labile concentrations. The ability of DGT to preconcentrate metals was found to be an analytical advantage compared with ultrafiltration. DGT appears to be a good alternative to 1 kDa ultrafiltration for measurement of truly dissolved Mn, Cd, and Zn in the Baltic Sea.

Diffusion↗
PubMed2004

Production of soy protein concentrates using a combination of electroacidification and ultrafiltration.

Soy protein concentrates produced by combining electroacidification and dead-end ultrafiltration with a membrane of 100 kDa (pH 7 and 6) were compared with concentrates produced by ultrafiltration (pH 9) and a traditional acid precipitation procedure at pH 4.5. Mineral removal during ultrafiltration (mainly potassium, phosphorus, and calcium) was enhanced for the pH 6 electroacidified extract, compared to the extract at pH 9. This yielded a concentrate with improved solubility characteristics. The solubility for the concentrate prepared at pH 6 was enhanced by as high as 45% when compared to the concentrate at pH 9. The concentrate produced according to the traditional acid precipitation process showed mineral contents and solubility profile similar to those of the pH 6 concentrate, but required twice as much water during the process. The effect of electroacidification treatments on ultrafiltration permeate flux was quantified through the measurement of the different hydraulic resistances. Cake resistance was the main resistance to the permeate flux, and it was minimum at pH 9, maximum at pH 7, and intermediate at pH 6.

Electrochemistry↗
PubMed1991

Subfractions in uremic plasma ultrafiltrate inhibit calcitriol metabolism.

Previous study from our laboratory has demonstrated that uremic plasma ultrafiltrate suppresses both the production rate (PR) and metabolic clearance rate (MCR) of calcitriol in normal rats. To characterize the the substances responsible for the suppression of the synthesis and degradation of calcitriol, we fractionated 20 ml uremic plasma ultrafiltrates into 13 fractions using high-performance liquid chromatography (HPLC) and studied the effect of each fraction on calcitriol metabolism. We measured the MCR and PR of calcitriol in normal rats after they were infused for 20 hours with each fraction dissolved in 20 ml normal saline. Using a UV absorption and fluorescence emission technique, several known uremic compounds were identified as individual peaks corresponding to the fractions. We found that fractions 4, and 6 to 13 markedly reduced the MCR of calcitriol. The patterns of the MCR suppression by the HPLC fractions suggest that there were at least two groups of chemically distinguishable compounds. Infusion of a solution containing all 13 fractions of the uremic ultrafiltrate also inhibited the calcitriol synthesis. One of the 13 fractions (fraction 4, containing uric acid, xanthine, and hypoxanthine) was further fractionated into eight subfractions. Infusion of subfractions 4 to 7 markedly reduced both the PR and MCR of calcitriol. We conclude that uremic plasma ultrafiltrate contains factors that inhibit calcitriol synthesis and degradation. These substances have molecular weight less than 2,000 Daltons.

Animals↗
PubMed1992

A new scintigraphic method to characterize ultrafiltration in hollow fiber dialyzers.

Ultrafiltration and pressure profiles in hollow fiber dialyzers with different hydraulic permeabilities have been investigated with a new scintigraphic method. Radiolabelled albumin macroaggregates, used as a nondiffusible marker molecule, were added to the blood in an in vitro circuit and circulated through cuprophan and polysulphon dialyzers. Since the marker molecule was too big to cross the dialysis membrane, its changes in concentration were assumed to occur in response to the variation of the blood water content (filtration or back-filtration). These changes in concentration, recorded by a gamma camera, were evaluated to establish the cumulative values of filtration and back-filtration and their relevant profiles along the length of the dialyzer. The achieved data were compared with the experimental values of ultrafiltration empirically measured and with the theoretical values predicted by a classic linear method. Two conditions were analyzed: A) the minimal filtration rate necessary to avoid back-filtration (critical filtration); and B) the condition of zero net filtration in which filtration equals back-filtration. The nuclear method proved to be extremely precise in predicting the ultrafiltration values and significantly more precise than the linear method, especially for the highly permeable dialyzer. The reason for that probably depends on the non-linear pressure and ultrafiltration profile observed with the scintigraphic pattern of the dialyzer. Viscosity changes and local variations in blood flow may in fact interfere with the pressure drop inside the hollow fibers and result in such a complex behavior. The other interesting aspect of this method is the possibility of accurate measurement of the amount of back-filtration that wouldn't be possible with simple calculations. In conclusion, the complex nature of the phenomena regulating the water fluxes in hollow fiber dialyzers requires more complex calculation than a simple linear model to achieve an accurate range of predictability.

Biophysical Phenomena↗