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PubMed1981

The Worthington "ultrafree" device evaluated for determination of ultrafiltrable calcium in serum.

We evaluated a commercially-available disposable device ("Ultrafree," Worthington Diagnostics) for the anaerobic preparation of protein-free ultrafiltrates from serum for measurement of ultrafiltrable calcium. Sufficient filtrate for the analysis is obtained with 10 min from 0.2 to 0.4 mL of serum at room temperature. We assessed these ultrafilters with regard to permeability of calcium citrate, exclusion of proteins, frequency of leakage, and effect of temperature on results. Within-run and day-to-day coefficients of variation for human serum pools were 1.2 and 1.5%, respectively. Reference intervals (in mmol/L) for total (2.16-2.58), ultrafiltrable (1.44-1.67), dialyzable (1.25-1.41), and ionized (1.04-1.25) calcium have been determined for a healthy population of 69 women and 81 men, ages to 18 to 65 years. The device appears to be the most practicable yet available for use in making this measurement.

Adolescent↗
PubMed1994

Erythrocyte, plasma total, ultrafiltrable and platelet magnesium in type 2 (non-insulin dependent) diabetes mellitus.

We studied plasma magnesium, plasma ultrafiltrable magnesium, erythrocyte and platelet magnesium in 28 non-insulin dependent (NIDDM) patients and 28 age and sex matched non-diabetic control subjects. The plasma magnesium concentration was significantly lower in the diabetic subjects as compared with the control subjects (0.67 +/- 0.09 mmol/l versus 0.72 +/- 0.07 mmol/l, P < 0.05) as was plasma ultrafiltrable magnesium (0.43 +/- 0.06 mmol/l versus 0.47 +/- 0.05 mmol/l, P < 0.01. Similarly, erythrocyte magnesium was lower in the diabetic subjects than the non diabetic controls, (0.17 +/- 0.03 nmol/10(6) cells versus 0.19 +/- 0.02 nmol/10(6) cells, P < 0.01. Platelet magnesium was higher in the diabetic subjects (48.3 +/- 19.1 umol/g platelet protein versus 36.6 +/- 22.2 umol/g platelet protein, P < 0.01). There was no significant difference between the % plasma ultrafiltrable magnesium with respect to total plasma levels between the diabetic and normal subjects (64.7 +/- 4.7% versus 65.8 +/- 3.2% respectively). There was no significant correlation between any of these parameters and systolic or diastolic blood pressure of HbA1C in the diabetics. Nor were there any significant differences in these magnesium parameters in patients with or without diabetic complications.

Age Factors↗
PubMed1995

Fractionation of BSA and myoglobin with modified and unmodified ultrafiltration membranes.

Fractionation of the model proteins, bovine serum albumin and myoglobin, was studied with modified and unmodified polysulfone ultrafiltration membranes. A commercial polysulfone ultrafiltration membrane with a nominal cut-off value of 50,000 g mol-1 was used as the reference membrane, and it was modified with ultraviolet irradiation in different protein solutions. The permeate fluxes and the streaming potentials of the membranes were measured simultaneously. Ultrafiltration experiments were carried out at the isoelectric points of the proteins. The results show that the fractionation can best be carried out at the isoelectric point of myoglobin. Modification of the membranes with bovine serum albumin resulted in smaller adsorption and flux reduction, while membranes modified with myoglobin were more selective for myoglobin.

Animals↗
PubMed1995

Determination of the relation between alterations of total body water and thoracic fluid content during ultrafiltration by bioelectrical impedance analysis.

UNLABELLED: Total body impedance (TBI) is used to monitor alterations in total body water (TBW), e.g. during haemodialysis. However, 80% of the TBI signal is due to the resistance in extremities. Therefore TBI measurements give little information about alterations in thoracic fluid content (TF). Measuring both total body impedance and thoracic impedance (THI) can be a useful method to monitor TBW and TF changes during haemodialysis. In this study TBI and THI measurements were performed during 30 dialysis sessions and also in one group of 24 control subjects with normal tissue hydration. During haemodialysis TBI and THI significantly increased, demonstrating a decrease of TBW and TF. The ratio THI/TBI did not differ significantly during haemodialysis, indicating a similar effect of ultrafiltration on TBW and TF. The finding that TF decreased during haemodialysis was rather surprising, whereas pulmonary oedema is not an evident clinical problem in patients on maintenance haemodialysis treatment. THI measurements after dialysis proved to be significantly higher in comparison to the control subjects. This finding supports the hypothesis that the decrease in TF during dialysis is partly due to the sudden ultrafiltration-induced hypovolaemia leading to a fall in thoracic blood volume. ABBREVIATIONS: UF volume, ultrafiltration volume; TBI, total body impedance; THI, thorax impedance; TBW, total body water; TF, thoracic fluid.

Aged↗
PubMedDate not supplied

[Concentration of bacteria in water using the ultrafiltration method (author's transl)].

Four ultrafiltration units have been tested in order to concentrate bacteria in water. The experiments run with Escherichia coli allows the selection of an ultrafiltration apparatus which concentrates bacteria with high recovery efficiencies. The use of this concentrator is simple and fast. Its filtration power is very stable and its little capacity allows the continuous ultrafiltration of large volumes of water.

Adenosine Triphosphate↗
PubMed1993

Peritoneal resting is beneficial in peritoneal hyperpermeability and ultrafiltration failure.

Ultrafiltration failure (UFF) is one of the most frequent causes of continuous ambulatory peritoneal dialysis (CAPD) dropout and is a common consequence of peritoneal hyperpermeability secondary to inappropriate regeneration of mesothelial cells. In this paper we present the results of 25 peritoneal resting periods of 4 weeks in 16 patients who showed UFF. The mean duration of CAPD was 44 +/- 22 months. All patients had been free of peritonitis for at least 3 months when included in the peritoneal resting trial. UFF was always defined as a long-lasting decrease of UF capacity such that dry weight could no longer be achieved by CAPD. The former incidence of peritonitis was 3.9 +/- 2.3 episodes. Results compared to the preresting data: urea MTC (mass transfer coefficient) decreased from 24.9 +/- 6.8 to 21.0 +/- 6.1 (p < 0.05), creatinine MTC from 16.5 +/- 6.0 to 13.8 +/- 4.0 (p < 0.05), and UF increased from 493.8 +/- 278.0 to 881.3 +/- 388.1 (p < 0.001). The response in terms of UF in patients with low permeability ultrafiltration (creat MTC less than 13) was heterogeneous and lower than in patients with criteria of hyperpermeability (greater than 13): 720 +/- 396 to 1150 +/- 533 (NS) versus 491 +/- 310 to 808 +/- 205, respectively. Simultaneously, creatinine MTC did not change in the former group (10.2), while hyperpermeability patients showed a remarkable decrease (19 +/- 5 to 15 +/- 2, p < 0.05). In conclusion, peritoneal resting is a useful tool in the management of ultrafiltration failure in CAPD patients, primarily in those with peritoneal hyperpermeability.

Adult↗
PubMed1993

Free cortisol in serum assayed by temperature-controlled ultrafiltration before fluorescence polarization immunoassay.

A method is described for a temperature-controlled ultrafiltration procedure to measure free cortisol in serum. A special thermometer with a sensor was developed, measuring the temperature directly in the ultrafiltration device. The sensor is screwed on the axis of the centrifuge rotor, and the centrifuge is placed in a temperature-controlled box so that the temperature of the sample is kept at 37 degrees C +/- 0.1 degrees C. The overall CV of the free cortisol assay ranges from 2.2% to 11.4%, of which the ultrafiltration contributes only 2.2-3.6%. Increasing amounts of cortisol-binding protein, as found in women using estrogen-containing oral contraceptives, have minor but significant effects on the free cortisol concentrations in serum. Serum free cortisol concentrations in a reference population (n = 114; central 95 percentiles) were 12-43 nmol/L (4-9.5% of total cortisol); in the group of the oral-contraceptive users (n = 27), the reference interval was 11-53 nmol/L (1.5-4.5%).

Blood Preservation↗
PubMed1993

Rapid determination by centrifugal ultrafiltration of inter-mixed micellar/vesicular (non-lecithin-associated) bile salt concentrations in model bile: influence of Donnan equilibrium effects.

We have developed the technique of rapid (< 2 h) centrifugal ultrafiltration to measure the inter-mixed micellar/vesicular (non-lecithin-associated) bile salt (BS) concentrations (IMC) of individual BS in model biles. This methodology uses a centrifugal concentrator with a reinforced membrane, through which a small fraction (< 15% total volume) of model biles was ultrafiltered by low centrifugal forces (1500 g 5-60 min). Total and individual BS concentrations in the filtrate were measured by high performance liquid chromatography. However, non-filterable anions, in this case BS/lecithin/cholesterol mixed micelles and unilamellar vesicles, induce an asymmetric distribution of ions across the membrane. Therefore, BS concentrations in the filtrate exceeded the true IMC, which was estimated taking into account Donnan equilibrium effects. To confirm the hypothesis that a correction for Donnan forces was necessary, distributions of BS and another filterable anion, chloride, were measured in systems containing the non-filterable polyanion dextran sulfate as an analogue for non-filterable polyanionic mixed micelles and vesicles. An asymmetric distribution of the monovalent anions chloride and BS monomers as well as polyvalent simple BS micelles was indeed present during centrifugal ultrafiltration. This new methodology was validated by comparing IMC values with those obtained by modified equilibrium dialysis also corrected for Donnan equilibrium effects (Donovan, J.M., et al. 1991. J. Lipid Res. 32: 1501-1512). Centrifugal ultrafiltration, which utilizes < 1 ml of bile, determines the composition in the IMC necessary to separate micelles and vesicles of native biles by techniques that involve dilution of bile such as gel filtration chromatography.

Bile↗
PubMed1995

Use of bethanechol chloride to increase available ultrafiltration in CAPD.

Reabsorption of peritoneal dialysis fluid during the prolonged dwell time of continuous ambulatory peritoneal dialysis (CAPD) reduces the efficiency of ultrafiltration and sacrifices effective dialysis adequacy. Studies by Nolph indicate a predominant role of lymphatics in this fluid loss. Khanna has reported that lymphatic flow may be influenced by acetylcholine. This study was designed to determine if bethanechol chloride (BC) would increase the availability of drained volume during CAPD. Nine patients were studied, including 7 patients who exhibited inadequate ultrafiltration. During a 5-day control period, total dialysate drained volume was collected and a standard peritoneal equilibration test (PET) performed. This was followed by a corresponding 5-day test period in which BC (mean dose 0.27 +/- 0.13 mg/kg/day) was administered orally. Drained volume during the control standard 4-hr PET was 1996.68 +/- 279.87 mL. The result for the test period was 2363.33 +/- 321.13 mL (p < 0.05), indicating an 18.4% increase using BC. The PET indicated no change in transport of urea, creatinine, and glucose. In conclusion, the total drained volume can be effectively increased with a subsequent increase in metabolite clearance using BC. Patients exhibiting inadequate ultrafiltration were able to be maintained on CAPD using this cholinergic drug.

Absorption↗
PubMed1977

Binding of dye to albumin, as studied by ultrafiltration.

We describe a procedure for measuring the binding of small molecules to proteins by means of a dynamic ultrafiltration system. A continuous binding curve is obtained by continuously monitoring the absorbance of ultrafiltrate as a function of ultrafiltrate volume, and corrections are made for the retention of the small molecule by the membrane and the leakage of the protein through the membrane. The method is applied to the binding of bromcresol green to human albumin. Some major sources of uncertainties in the method are discussed.

Albumins↗
PubMed1977

[Studies on the ultrafiltration in coil-type dialysers for recirculation].

Ultrafiltration in recirculating coil dialysers is discussed. The difficulty of determining the exact transmembrane pressure is stressed. The data normally available are insufficient and take no account of the direction of recirculation, which may be a determining factor. Input and output dialysing fluid pressure were measured in vitro and the respective ultrafiltration values were compared with those observed clinically. Calculation of the mean blood pressure in the dialyser circuit is examined. If determined from the simple arithmetical mean between the input and output pressure, this does not reflect the real situation inside the filter. It is thus unreliable when used to calculate the real transmembrane pressure, and hence the ultrafiltration.

Humans↗
PubMed1996

Determination of individual ultrafiltration time (APEX) and purification phosphate time by peritoneal equilibration test: application to individual peritoneal dialysis modality prescription in children.

Efficiency of peritoneal dialysis (PD) is dependent on adequate ultrafiltration (UF) and purification (solute clearance). These two goals apparently seem to conflict in terms of duration of dwells: short dwell time enhances UF capacity and, conversely, long dwell time enhances solute clearance. Peritoneal equilibration test (PET) allows an approach to the ultrafiltration time: the point at which the over time dialysate urea saturation and glucose desaturation curves cross, call APEX time. PET also allows an approach to the purification time: the point at which dialysate-to-plasma (D/P) concentration ratios over time are high. Because of the value of phosphate as a uremic factor of morbidity, we have chosen the time at which D/P phosphate is equal to 0.6 as a purification phosphate dwell time (PPT). A total of 17 patients were studied, over a five-year period, allowing 142 determinations. APEX times (range 18-71 min) and PPT (range 105-238 min) were spread over a wide distribution. PPT and APEX times were significantly shorter in children younger than three years of age than in children older than ten years of age. PPT were nearly four times longer than APEX times. Knowledge of these conflicting ultrafiltration and purification times should help, in our view, in the individual choice of the PD modality: if UF is the major goal, short dwell times should be used (automated PD); if purification is the major goal, long dwell times should be used, as in continuous ambulatory peritoneal dialysis; if both are the target goal, tidal PD should be discussed.

Adolescent↗
PubMed2000

Post-column reaction detection of biotin in human plasma ultrafiltrate based on laser-induced fluorescence energy transfer in the far-red spectral region.

High performance liquid chromatography followed by post-column reaction detection in the far-red spectral region provides added sensitivity and selectivity. A homogeneous fluorescence energy transfer assay in the competitive mode based on the binding of biotin and streptavidin was developed as an on-line post-column reaction detection system. The labels used for energy transfer were R-Phycoerythrin conjugated to biotin and Cyanine 5 labeled with streptavidin. The energy transfer peak was measured at 670 nm and excitation was achieved using the 488 nm line of an argon ion laser. The biotin concentration in plasma ultrafiltrate ranged from 0.024 to 6.12 ng/mL (n = 6). The precision of the two controls, 0.24 and 2. 44 ng/mL, was found to be 18.70% and 9.92% relative standard deviation respectively. Accuracy was 10.47% and 1.95% difference from spiked, respectively (n = 6). The limit of detection was 21.70 pg/mL (8.90 x 10(-11)M) calculated based on a factor of 2x the standard deviation of the blank (n = 6). The correlation coefficient for the calibration curve was found to be 0.9995. Recovery from plasma ultrafiltrate at 2.44 ng/mL was 103.40% (n = 6). Detection selectivity was indicated by the absence of background fluorescence in six different plasma samples collected from six individual donors. Endogenous levels were detected in two of the six pools of plasma ultrafiltrates.

Biotin↗
PubMed1996

Ultrafiltration of Micellar Solutions in the Presence of Electrolytes

Micellar extraction coupled with ultrafiltration techniques represents a potentially attractive tool for the removal of different kinds of contaminants from waste waters. Even though most industrial streams to be treated contain large amounts of electrolytes, very little is known about the behavior of micellar solutions in ultrafiltration when large amounts of salts are present. This paper is concerned with an investigation of two cationic surfactants (cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC)) and one anionic surfactant (sodium dodecylsulfate (SDS)) in the presence of several salts occurring in specific industrial processes (carbonates and hydrogenocarbonates, nitrites, nitrates). The ultrafiltration behavior of these systems, with individual salt concentrations up to 0.9 M, is studied from the viewpoint of the fluxes obtained, the amount of surfactant leakage and of the membrane "gel point." Two types of polymeric membranes with molecular weight cutoff of 10,000 Da are considered (cellulose and polysulfone), which show significantly different behaviors.

Journal Article↗
PubMed1999

Permeate Flux in Crossflow Ultrafiltration under Intermediate Pressures.

The intermediate pressure range stands for an important condition for ultrafiltration operations where permeate flux falls below that predicted from a linear flux-pressure relationship but does not reach the limiting flux. Optimal performance of ultrafiltration might be achieved on the upper end of the intermediate pressure range because the maximum permeate flux will be obtained at the lowest possible pressure. Unlike in the low pressure range or in the high pressure range, little has been known about the behavior of permeate flux in the intermediate pressure range. A general theory of permeate flux in the intermediate pressure range is developed in this study. The theory includes the linear-increasing and limiting fluxes as two special cases and, therefore, can be used to study the behavior of permeate flux in ultrafiltration in the whole pressure range. Copyright 1999 Academic Press.

Journal Article↗
PubMed2001

Obtaining the Osmotic Pressure of Electrostatically Stabilized Colloidal Dispersions from Frontal Ultrafiltration Experiments.

A new method for determining the osmotic pressure of electrostatically stabilized colloidal particles from frontal ultrafiltration experiments has been developed. The method is based on a reverse calculation utilizing a previously developed analysis of frontal ultrafiltration (W. R. Bowen and F. Jenner, Chem. Eng. Sci. 50, 1707, 1995; W. R. Bowen and P. M. Williams, Biotechnol. Bioeng. 50, 125, 1996). The method has the following advantages over conventional membrane osmometer measurements: (i) only very simple apparatus is required, (ii) results are obtained quickly, (iii) only small sample quantities are required, and (iv) only dilute initial samples are needed, as the ultrafiltration process creates a concentrated solution at the membrane, making sample preparation a simple task. A comparison of the osmotic pressure determined by this new method with previously measured osmotic pressure data shows excellent agreement. The approach demonstrates how analysis of process data may provide quantitative information on the interactions of concentrated colloidal systems. Copyright 2001 Academic Press.

Journal Article↗
PubMed2002

Ultrafiltration of surfactant solutions.

The ultrafiltration of colloid solutions containing hexadecyltrimethylammonium bromide (CTAB), sodium dodecyl sulfate (SDS), and alkylpolyglucoside (APG) through hydrophilic membranes with a 10,000 mol wt cut-off from regenerated cellulose was studied. The effects of experimental conditions on the permeate flux and secondary resistance were determined. It was found that both CTAB and APG were convenient surfactants for ultrafiltration, as high permeability of their solutions was observed. The secondary resistance was always significantly lower than the resistance of the membrane. Additionally, electrolytes had a relatively weak negative effect upon ultrafiltration fluxes. SDS was the least convenient surfactant due to formation of a gel layer, susceptibility of its colloid solutions to electrolyte content, and a high secondary resistance. The concentration of the surfactant in the permeate could increase above critical micelle concentration, especially under conditions inducing high polarization. Migration of CTAB on the surface of pores seemed responsible for that transfer.

Journal Article↗
PubMed2002

The role of exopolysaccharides in fouling phenomenon during ultrafiltration of microalgae (Chlorellasp. and Porphyridium purpureum): advantage of a swirling decaying flow.

Ultrafiltration of two microalgae species, Chorellasp. and Porphyridium purpureum, has been performed in two filtration units of different configurations: a module generating a classical tangential-plane flow and another one inducing a swirling decaying flow. The swirling motion is generated by a unique tangential inlet at the bottom of an annulus. Permeation flux obtained in each ultrafiltration unit depends on the filtered species, and specific deposits are associated to each species and module. Enhancement in permeation flux in the swirling configuration compared with that obtained in the plane unit can reach 40% during the ultrafiltration of Porphyridium purpureum and is negligible for the suspensions of Chlorella sp. The experimental data revealed the significant role of the soluble compounds in the medium culture in terms of flux limitation. It seems that the soluble products and their interactions with the microalgal cells are strongly involved in the fouling mechanism.

Journal Article↗