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PubMed1996

Use of the modified technique of ultrafiltration in pediatric open-heart surgery: a prospective study.

The use of cardiopulmonary bypass (CPB) in children is associated with significant morbidity due to the accumulation of an excessive amount of water. This can be decreased by massive diuresis, peritoneal dialysis, or conventional ultrafiltration technique (CUF) during bypass. However, we were dissatisfied with their effect on the outcome of our young patients, and recently began to use the modified technique of ultrafiltration (MUF) with good results. MUF was carried out for 15 min after completion of CPB to a hematocrit of 40%. Eighty patients were equally divided into two groups--MUF (group A) and control (group B)--and prospectively studied. There was one death in group A and two deaths in group B. The chest was left open in one patient in group A and in three patients in group B. At the end of MUF, the cardiac size was smaller, performance was better, and systemic blood pressure was higher in group A. Hematocrit levels in the two groups were similar during preoperative and CPB time, but post-CPB hematocrit in group A was significantly higher, 39.4% mean (range 35-50) vs. 28.5 (range 22-38) in group B (P <0.05). Blood loss was 10.56 ml/kg per 24 h (2-48.7) in group A vs. 20.8 (4.5-105.6) in group B (P <0.05). Blood transfused was 7.2 ml/kg per 24 h (0-29) in group A vs. 17.3 (3.1-49) in group B (P <0.05). Colloids transfused were 16.7 ml/kg per 24 h (0-64) in group A vs. 27.5 (0-58.6) in group B (P <0.05). No significant difference was found in urine output or the use of diuretics between the two groups. MUF results in better hemodynamic status in children, with the added advantage of less transfused blood and blood products. We believe that the use of accepted surgical techniques in combination with MUF will further improve the outcome of complex cardiac malformations.

Blood Loss, Surgical↗
PubMedDate not supplied

[Veno-venous hemofiltration with controlled ultrafiltration].

We haven't been using continuous veno-venous hemodiafiltration in our unit as an extrarenal depuration technique since 1991. With this work we want to provide our experience in what we call controlled ultrafiltration, technique which we have been using more frequently in the last two years and which consists on using the venous bomb of double head for ultrafiltration (UF) extraction, managing to obtain a more accurate control of it. The development of this technique has allowed us to obtain a higher control of the patient, reduce the risk of hypothermia and reduce the nursing burden. We show the procedure of priming, connection, disconnection and the necessary material, as well as the advantages and specific care we perform in our unit.

Anticoagulants↗
PubMedDate not supplied

[Blood ultrafiltration in postoperative brain edema-swelling in neuro-oncology patients].

A hundred and sixteen postoperative patients after removal of various brain tumors in whom brain edema developed were treated with 1-3 courses of blood ultrafiltration (BUF). 0.5-9.0 liters of ultrafiltrate was removed. BUF does not lead to blood concentration due to the movement of the fluid from intracellular to intravascular space. BUF allows to decrease the amount of toxic medium-sized peptides and osmolarity discriminant. Seldom the minor complications were observed because of usage of the plate shaped dialyzers. When the capillary dialyzers were used, no complications were noted. BUF may be recommended in patients with brain tumors in early postoperative period when traditional medical management does not seem to be effective enough. The technique helps to reduce the duration of brain edema in treated patients by 8-10 days vs. controls treated traditionally.

Adolescent↗
PubMedDate not supplied

[The use of modified ultrafiltration in correcting complex congenital heart defects in newborn and nursing infants].

Modified ultrafiltration (MUF) was used in radical correction of complex congenital heart disease in 61 newborns and infants. The children were divided into 2 groups: group 1, 46 patients subjected to MUF, and group 2, 15 children operated on without MUF. Hemodynamic, hematological, biochemical, and immunological parameters were monitored. MUF in the newborns and infants helped adequately correct the hemohydrobalance due to ultrafiltration in the patient and hemoconcentration of the remaining volume in artificial ventilation device; it normalized the hematocrit values without additional infusion of donor blood. Elimination of inflammation mediators and cytokines recommends MUF for the treatment of newborns and infants.

Anesthesia, General↗
PubMedDate not supplied

Analysis of the prevalence and causes of ultrafiltration failure during long-term peritoneal dialysis: a cross-sectional study.

BACKGROUND: Ultrafiltration failure (UFF) is a major complication of peritoneal dialysis (PD). It can occur at any stage of PD, but develops in time and is, therefore, especially important in long-term treatment. To investigate its prevalence and to identify possible causes, we performed a multicenter study in The Netherlands, where patients treated with PD for more than 4 years were studied using a peritoneal function test (standard peritoneal permeability analysis) with 3.86% glucose. UFF was defined as net UF < 400 mL after a 4-hour dwell. RESULTS: 55 patients unselected for the presence or absence of UFF were analyzed. Mean age was 48 years (range 18 - 74 years); duration of PD ranged from 48 to 144 months (median 61 months); UFF was present in 20 patients (36%). Patients with and without UFF did not differ in age or duration of PD. Median values for patients with normal UF compared to patients with UFF were, for net UF 659 mL versus 120 mL (p < 0.01), transcapillary UF rate 3.8 versus 2.1 mL/ minute (p < 0.01), effective lymphatic absorption 1.0 versus 1.6 mL/min (p < 0.05), mass transfer area coefficient (MTAC) for creatinine 9.0 versus 12.9 mL/min (p< 0.01), dialysate-to-plasma ratio (D/P) for creatinine 0.71 versus 0.86 (p < 0.01), glucose absorption 60% versus 73% (p < 0.01), maximum dip in D/P sodium (as a measure of free water transport) 0.109 versus 0.032 (p < 0.01), and osmotic conductance to glucose 3.0 versus 2.1 microL/min/mmHg (p < 0.05). As causes for UFF, high MTAC creatinine, defined as > 12.5 mL/min, or a glucose absorption > 72%, both reflecting a large vascular surface, a lymphatic absorption rate (LAR) of > 2.14 mL/min, and a decreased dip in D/P sodium of < 0.046 were identified. Most patients had a combination of causes (12 patients), whereas there was only a decreased dip in D/P sodium in 3 patients, only high MTAC creatinine in 1 patient, and only high LAR in 2 patients. We could not identify a cause in 2 patients. Both groups had similar clearances of serum proteins and peritoneal restriction coefficients. However, dialysate cancer antigen 125 concentrations, reflecting mesothelial cell mass, were lower in the UFF patients (2.79 vs 5.38 U/L). CONCLUSION: The prevalence of UFF is high in long-term PD. It is caused mainly by a large vascular surface area and by impaired channel-mediated water transport. In addition, these patients also had signs of a reduced mesothelial cell mass, indicating damage of the peritoneum on both vascular and mesothelial sites.

Biological Transport↗
PubMed2000

Separation of amino acid enantiomers by micelle-enhanced ultrafiltration.

A Micelle-enhanced ultrafiltration (MEUF) separation process was investigated that can potentially be used for large-scale enantioseparations. Copper(II)-amino acid derivatives dissolved in nonionic surfactant micelles were used as chiral selectors for the separation of dilute racemic amino acids solutions. For the alpha-amino acids phenylalanine, phenylglycine, O-methyltyrosine, isoleucine, and leucine good separation was obtained using cholesteryl L-glutamate and Cu(II) ions as chiral selector with an operational enantioselectivity (alpha(op)) up to 14.5 for phenylglycine. From a wide set of substrates, including four beta-amino acids, it was concluded that the performance of this system is determined by two factors: the hydrophobicity of the racemic amino acid, which results in a partitioning of the racemic amino acid over micelle and aqueous solution, and the stability of the diastereomeric complex formed upon binding of the amino acid with the chiral selector. The chiral hydrophobic cholesteryl anchor of the chiral selector also plays an active role in the recognition process, since inversion of the chirality of the glutamate does not yield the reciprocal enantioselectivities. However, if the cholesteryl group is replaced by a nonchiral alkyl chain, reciprocal operational enantioselectivities are found with enantiomeric glutamate selectors.

Amino Acids↗
PubMed2003

Microfiltration and ultrafiltration of polysaccharides produced by fermentation using a rotating disk dynamic filtration system.

The recovery of exopolysaccharides (EPS) produced by Sinorhizobium meliloti bacteria by dynamic microfiltration was investigated using a rotating disk device designed in our laboratory, equipped with a 0.2 microm nylon membrane. This system differs from commercially available systems by the presence of vanes on the disk which produce a very important increase in permeate flux while yielding excellent EPS transmission. For polymers produced under standard fermentation conditions (70 h at 30 degrees C), the mass flux rose to 650 g h(-1) m(-2) using a disk equipped with 2 mm vanes rotating at 2000 rpm against 380 g h(-1) m(-2) with a smooth disk at the same speed. The maximum flux observed was 1560 g h(-1) m(-2) with a 6-mm vanes disk rotating at 3000 rpm and a 36 degrees C broth. An interesting finding was that the permeate flux J(f) for various disks can be correlated by the same function of the mean shear stress at the membrane tau(wm) according to J(f) = 4.6 tau(wm) (0.717) for a 30 degrees C broth, showing that the effect of vanes is merely to increase the shear stress by raising the fluid core velocity between the membrane and the disk. With 6-mm vanes the core angular velocity was found to be 84% of disk velocity vs. 45% for a smooth disk. When the fermentation temperature was increased to 36 degrees C to produce a lower molecular weight polymer, the permeate flux rose by about 250%, much more than what could be expected from the reduction in permeate viscosity and followed the same power law with membrane shear stress as for 30 degrees C. The same device was equipped with a PES 50 kDa membrane to concentrate EPS by ultrafiltration. Permeate fluxes were of the order of 160 L h(-1) m(-2) at 2000 rpm and 30 degrees C with nearly complete EPS rejection. Finally, the net electrical power consumed by the disk was measured by subtracting the power consumed without fluid from the power during filtration at the same speed. This power increases with speed and with the presence of vanes, but since the gain provided by the vanes is very high, the specific energy per m(3) of permeate is minimal with the highest vanes tested (6 mm) and maximal for smooth disks.

Cell Division↗
PubMed2004

Use of protein charge ladders to study electrostatic interactions during protein ultrafiltration.

Recent studies have demonstrated the importance of electrostatic interactions in membrane systems, but there is still controversy about the underlying phenomena. Protein charge ladders, consisting of a set of chemical derivatives of a given protein that differ by single charge groups, were used to quantify the electrostatic interactions during protein ultrafiltration. Myoglobin charge ladders were generated by acylation, with the different derivatives analyzed simultaneously by capillary electrophoresis. Filtration experiments were performed using polyethersulfone and composite regenerated cellulose membranes, with the membrane charge determined from the streaming potential. As expected, the rejection increased as the protein became more heavily charged due to the increase in electrostatic repulsion. However, the transmission of the weakly charged myoglobin species increased dramatically at very low ionic strength. This increase in transmission was attributed to a shift in pH within the pore caused by hydrogen ion partitioning into the charged membrane. The sieving data were in good agreement with theoretical calculations accounting for the effects of this pH shift on the electrostatic interactions.

Computer Simulation↗
PubMed2005

Controlling protein transport in ultrafiltration using small charged ligands.

Previous studies have demonstrated that protein transport during ultrafiltration can be strongly influenced by solution pH and ionic strength. The objective of this study was to examine the possibility of controlling protein transmission using a small, highly charged ligand that selectively binds to the protein of interest. Experiments were performed using bovine serum albumin and the dye Cibacron Blue. Protein sieving data were obtained with essentially neutral and negatively charged versions of a composite regenerated cellulose membrane to examine the effects of electrostatic interactions. The addition of only 1 g/L of Cibacron Blue to an 8 g/L BSA solution reduced the BSA sieving coefficient through the negatively-charged membrane by more than two orders of magnitude, with this effect being largely eliminated at high salt and with the neutral membrane. Protein sieving data were in good agreement with model calculations based on the partitioning of a charged sphere in a charged pore accounting for the change in net protein charge due to ligand binding and the increase in solution ionic strength due to the free ligand in solution.

Cellulose↗
PubMed2005

Effects of protein-protein interaction in ultrafiltration based fractionation processes.

This paper discusses the use of pulsed sample injection ultrafiltration (UF) for investigating protein-protein interaction, particularly its effect on protein transmission through UF membranes. Several binary protein mixtures were investigated; the proteins in each mixture being selected such that one of the proteins in the pair would be preferentially transmitted while the other would be either totally or substantially retained. The "retained" protein either decreased or increased or did not affect the sieving coefficient of the "transmitted" protein, this depending the type of protein-protein interaction, that is, associative, repulsive, or neutral. The type of protein-protein interaction depended on the particular protein pair under investigation as well as on the operating conditions used (pH and salt concentration). The magnitude of either decrease or increase in transmission of a preferentially transmitted protein due to the presence of a retained protein was found to be independent of the manner in which the proteins were injected into the system, that is, simultaneous or sequential. These magnitudes however correlated well with the ratio of the two proteins present in the feed.

Chemical Fractionation↗
PubMed2006

Purification of monoclonal antibodies derived from transgenic goat milk by ultrafiltration.

With the goal of recovering heterologous immunoglobulin (IgG), which comprises 10-15% of the total proteins, from transgenic goat milk at 80% yield and 80% purity, we have developed and tested a two-step membrane isolation and purification process. In the first step, reported earlier by Baruah and Belfort, microfiltration was used to fractionate the milk proteins and recover > 90% of the original IgG at a purity of about 15-20% in the permeate stream. Here, we focus on ultrafiltration (UF) to increase the purity of the target protein to 80%, while maintaining a relatively high IgG yield (80%). Tangential flow UF experiments in diafiltration mode were conducted with 100 kDa cellulosic membranes to evaluate the optimal pH, ionic strength, and uniform transmembrane pressure (TMP). The TMP was kept uniform by permeate circulation in co-flow mode. The traditional approach of conducting the UF process close to the pI of the predominant whey proteins (15-40 kDa, pI 5.2), to transmit these proteins while retaining heterologous IgG (155 kDa), could not be applied here because of precipitation of residual casein at pH values lower than 8.5. Instead, the packing characteristics of the cake layer on the membrane wall, as elucidated in the Aggregate Transport Model presented by Baruah et al. was utilized to achieve a selectivity of > 15, which was sufficient to meet the stated goals of purity and yield for this difficult separation. This combined process is expected to reduce the load on subsequent purification and polishing steps for eventual therapeutic use.

Animals↗
PubMed2006

Ultrafiltration characteristics of pegylated proteins.

There is growing clinical interest in the use of pegylated recombinant proteins with enhanced stability, half-life, and bioavailability. The objective of this study was to develop a quantitative understanding of the ultrafiltration characteristics of a series of pegylated proteins with different degrees of pegylation. Sieving data were compared with available theoretical models and with corresponding results for the partition coefficient in size exclusion chromatography (SEC). The sieving coefficients of the pegylated proteins depended not only on the protein size and the total molecular weight of the polyethylene glycol (PEG) but also on the number of PEG chains. This is in sharp contrast to the partition coefficient in SEC, which was uniquely determined by the total molecular weight of the PEG and protein. This difference is due to the deformation and/or elongation of the PEG chains caused by the convective flow into the membrane pores, an effect that is not present in SEC. These results provide important insights into the transport and separation characteristics of pegylated proteins.

Chromatography, Gel↗
PubMed1976

Immobilization of a cephalosporin acetylesterase by containment within an ultrafiltration device.

A cephalosporin acetylesterase produced by Bacillus subtilis catalyzes the deacetylation of 7-aminocephalosporanic acid (7-ACA). Previous reports from our laboratory described the kinetic constants that characterize the reaction: Km = 2.8 X 10(-3)M, Kia acetate = 5 X 10(-2)M, and Kid deacetyl-7-ACA = 3.6 X 10(-2)M. These constants were used to predict the time course of the reaction using the following equation for dual competitive product inhibition. (see article) where St =mg/ml 7-ACA, At =mg/ml acetate, Dt =mg/ml deacetyl-7-ACA. The predicted time course closely matched the time course measured experimentally. The equation also was solved without the inhibition terms and the solution indicated that product inhibition caused about a 30% increase in the time required for complete (greater than 97%) hydrolysis of a 24 mg/ml 7-ACA solution. The esterase was immobilized by containment within an ultrafiltration device. With this technique the enzyme was reused 20 times over an 11 day span to deacetylate 7-ACA solutions containing 4 to 24 mg/ml 7-ACA. The specific activity after the 20th use was the same as the activity prior to the first use, indicating little enzyme inactiviation occurred.

Acetylesterase↗
PubMed1980

Concentration of baboon endogenous virus in large-scale production by use of hollow-fiber ultrafiltration technology.

A process is described in which the baboon endogenous virus (BaEV) is produced under optimum conditions in cell culture, and concentrated by hollow-fiber ultrafiltration technology under conditions of large-scale production. This system has advantages over conventional systems in that the flow rate is increased 2.5-fold during concentration. Thermal inactivation of BaEV was retarded by the addition of lactose glutamate to the harvested tissue culture fluid. After concentration, at least 91% of the virus RNA-directed DNA polymerase is recovered with a concomitant increase in infectious virus. Materials needed for modifying described systems may be obtained from commercial sources.

Animals↗
PubMed2006

Determination of human plasma protein binding of baicalin by ultrafiltration and high-performance liquid chromatography.

A simple and selective HPLC assay was developed and utilized for determination of human plasma protein binding of baicalin. The method involved solid-phase extraction and reversed-phase chromatographic separation with a mobile phase of acetonitrile-0.02 mol/L phosphate buffer (pH 2.5; 25:75, v/v) and UV detection at 276 nm. The standard curve for baicalin was linear over the concentration range 0.1-20 microg/mL and the limit of detection was 0.02 microg/mL. The absolute recovery was greater than 76%. The intra-day and inter-day variations were less than 10%. Ultrafiltration technique was applied to determining the plasma protein binding of baicalin in human plasma. Results show the plasma protein binding of baicalin was in the range 86-92% over all the concentrations studied and the protein binding association constant was determined to be 1.21 x 10(5) L/mol at 4 degrees C.

Blood Proteins↗
PubMed1993

Stereoselective distribution of acenocoumarol enantiomers in human plasma: chiral chromatographic analysis of the ultrafiltrates.

Stereoselectivities for the binding of rac-acenocoumarol to human serum albumin (HSA), alpha 1-acid glycoprotein (AGP), and human plasma were determined by chiral HPLC analysis of the ultrafiltrates on a Chiral-AGP column. The results confirmed the previously detected inverse stereoselectivities; for HSA the ratio of the enantiomeric constants was KR/KS approximately 2, while for AGP it was KR/KS approximately 0.3. In plasma the contribution of HSA dominates, although in pathological states, elevated AGP levels may compensate for stereoselective distribution.

Acenocoumarol↗
PubMed2007

Drug release from differently structured monoolein/poloxamer nanodispersions studied with differential pulse polarography and ultrafiltration at low pressure.

Aqueous colloidal monoolein/poloxamer dispersions are under investigation as drug delivery systems. Depending on the composition and preparation procedure these dispersions may either contain predominantly vesicular particles or nanoparticles of cubic inner structure. To study the influence of ultrastructure on drug release, corresponding dispersions loaded with the model drugs diazepam (two different concentrations) and chloramphenicol were prepared by high-pressure homogenization with or without subsequent heat treatment. The dispersions were characterized with regard to particle size and their ultrastructure was confirmed with small angle X-ray diffractometry. Two techniques with high time resolution, differential pulse polarography (DPP) and ultrafiltration at low pressure were compared for their suitability to monitor rapid release from the dispersions. Instantaneous release was found for both drugs independent on the type of particle structure with the amount of released drug being controlled by the partition coefficient. Both release methods were suitable to monitor the rapid appearance of the releasable drug in the release medium.

Chloramphenicol↗
PubMed2005

Polyacrylonitrile enzyme ultrafiltration and polyamide enzyme microfiltration membranes prepared by diffusion and convection.

Glucose oxidase (GOD) and catalase (CAT) were covalently immobilized onto three types of polyacrylonitrile (PAN 1, PAN 2, and PAN 3) ultrafiltration (UF) membranes with different pore sizes and one type of polyamide (PA) microfiltration (MF) membrane by the bifunctional reagent, glutaraldehyde. The initial membranes were pre-modified to generate active amide groups in the PAN membranes and active amino groups in the PA membranes. The PAN 3 membrane contained the highest amount of active groups, and the membrane PA the lowest. The modified membranes were enzyme-loaded by diffusion and convection (UF). The effect of membrane pore size and immobilization methods on enzymatic activity and bound protein were studied. The most effective immobilized system was prepared by diffusion using a PAN 3 membrane as a carrier (bound protein: 0.055 mg/cm(2), relative activity: 87.6%). This membrane had the highest pore size of all the PAN membranes. Despite the highest pore size of PA membrane, the enzyme PA membranes prepared by diffusion showed the lowest amount of bound protein (0.03 mg/cm(2)) and the lowest relative activity (35.38%). This correlates with the lowest amount of active groups found in these membranes. The relative activity was higher for all the enzyme systems loaded by diffusion. The systems prepared by convection of the enzyme solution contained higher amounts of enzymes (0.035-0.13 mg/cm(2) protein), which led to internal substrate diffusion resistance and a decrease in the GOD relative activity (21.55-68.5%) in these systems. The kinetic parameters (V(max) and K(m)) and the glucose conversion of the immobilized systems prepared by diffusion were also studied. [diagram in text].

Acrylic Resins↗