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PubMed2001

On-line particle concentrator with upstream ultrafiltration in continuous SPLITT fractionation.

An upstream ultrafiltration (UU) method is employed for the on-line concentration of collected particle fraction and for the convenient regulation of flow rates in split-flow thin (SPLITT) fractionation. Concentration of the collected particle fraction is necessary to fractionate particles by smaller cutoff diameters in SPLITT fractionation. By introducing a simple device utilizing upstream ultrafiltration with tangential flow, particle solution collected at each SP

Journal Article↗
PubMed2001

Use of ultrafiltration on the analysis of low molecular weight complexing molecules. Analysis of iminodiacetic acid at constant ionic strength.

Low molecular weight complexing molecules may be indirectly analyzed by ultrafiltration with the aid of a water-soluble polymer. The theory concerned is developed and the analysis of iminodiacetic acid (IDAA) is performed by ultrafiltration of aqueous solutions containing poly(sodium-4-styrenesulfonate) (PSS), Cu(NO3)2, and IDAA in variable concentrations. The technique allows measuring IDAA in a range of concentrations between 10(-4) M and 10(-5) M when a 1.6 x 10(-4) M Cu2+ solution is ultrafiltered in the presence of PSS and IDAA.

Journal Article↗
PubMed1999

Recovery of thuringiensin with cetylpyridinium chloride using micellar-enhanced ultrafiltration process

A cationic cetylpyridinium chloride (CPC) surfactant-based micellar-enhanced ultrafiltration (MEUF) process was used to recover thuringiensin from the supernatant of Bacillus thuringeinsis fermentation broth. Several different strategies of manipulating process variables, such as ionic strength, pH, CPC concentration, micelle formation temperature, and membrane pore size, were investigated. It was found that CPC concentration and membrane pore size were two major factors to the increase of thuringiensin recovery, while the ionic strength and pH adjustments were not necessary and micelle formation temperature was not important within the temperature range studied. Finally, a novel two-step MEUF processing scheme was developed which includes microfiltration and two-step ultrafiltration (UF) processes. The thuringiensin recovery up to 94.6% was attained when an initial CPC concentration of 4% (w/v) and UF membrane of molecular weight cutoff (MWCO) of 3000 was used in conjunction with the previous UF process using a MWCO 30 000 membrane. The bioassay results showed that the spray-dried thuringiensin with CPC was more toxic to fly larvae than without CPC. This research demonstrated that CPC not only facilitated thuringiensin recovery but also improved the insecticidal effect.

Journal Article↗
PubMed2002

On-site classification of humic-rich hydrocolloids and their metal species by means of online multistage ultrafiltration.

Humic-rich hydrocolloids and their metal species (e.g., Al, Fe, Ca, Cu, Fe, Mg, Mn, Pb, Zn) in selected bogwaters of German origin (Black Forest (HO), Muensterland (VM), Arnsberger Wald (AW)) were size classified in the subparticulate and macromolecular range by on-site multistage ultrafiltration (MST-UF). For this purpose two MST-UF cascades, equipped with up to eight conventional flat membranes (0.45, 0.22, 0.1 micron (Millipore); 100, 50, 10, 5, 3, and/or 1 kDa (Gelman PallFiltron OMEGA), were coupled and used for an online fractionation of hydrocolloidal matter immediately after water sample collection. Quantification of dissolved organic carbon (DOC) and metals was carried out off-site by conventional laboratory methods (carbon analyzer, atomic spectrometry). The size distribution of some humic-rich hydrocolloids (e.g. in HO) was exhibited to be surprisingly stable even over storage periods of 1-4 weeks. On the other side, their size distribution (e.g. in VM) considerably varied during the collection period. The natural metal loadings (e.g. Al, Fe, Mn, Zn) of hydrocolloids showed characteristic size distributions and, mostly, strong metal enrichment in subparticulate and macromolecular fractions. Further results of on-site classification of hydrocolloids, obtained by parallel single-stage ultrafiltration (P-UF) with the same membranes, were only comparable to those of MST-UF in the case of low DOC concentration.

Colloids↗
PubMedDate not supplied

Identification of proteins in slow continuous ultrafiltrate by reversed-phase chromatography and proteomics.

Continuous modes of renal replacement therapy (CRRT) are increasingly being utilized in the intensive care unit. The removal of cytokines and other inflammatory proteins during ultrafiltration may be responsible for some of the beneficial effects of CRRT. We used proteomic tools to identify proteins found in the ultrafiltrate from a patient with acute renal failure. Identification of these proteins could help elucidate the mechanism(s) of improved outcome with continuous renal replacement therapy. Protein was loaded on a reversed-phase C4 column and eluted with stepwise isocratic flows starting with 0%, 5%, 10%, 25%, and 50% of acetonitrile. Effluent was collected, pooled, desalted, and separated by two-dimensional gel electrophoresis (2DE). Reversed-phase separation improved the resolution and the number of spots seen on the gels. Protein spots were digested with trypsin and spotted onto MALDI plates. Proteins were identified by either peptide mass fingerprinting using a MALDI-TOF mass spectrometer or by peptide sequencing using a MALDI-TOF/TOF tandem mass spectrometer. From 196 spots cut, 47 were identified, representing multiple charge forms of 10 different proteins. Proteins identified were albumin, apolipoprotein A-IV, beta-2-microglobulin, lithostathine, mannose-binding lectin associated serine protease 2 associated protein, plasma retinol-binding protein, transferrin, transthyretin, vitamin D-binding protein and Zn alpha-2 glycoprotein. Continuous renal replacement therapy is frequently used in acutely ill patients with renal failure. Removal of proteins occurs during this process. The physiological significance of this protein removal is unclear. Identification of these proteins will lead to better understanding of the role of protein removal in continuous renal replacement therapy.

Chromatography, High Pressure Liquid↗
PubMed1977

Mechanisms of the defect in glomerular ultrafiltration associated with gentamicin administration.

Micropuncture studies were performed in three groups of Munich-Wistar rats: eight normal hydropenic controls (group I) and two groups (eight rats each) which were treated with gentamicin in doses of either 4 or 40 mg/kg/day for ten days (groups II and III, respectively). Following gentamicin administration, values for single nephron (SN) GFR were reduced markedly, from the control mean of 31 +/- 0.7 (SEM) nl/min to 22.4 +/- 1.5 and 20.5 +/- 0.9 for groups II and III, respectively. Declines in whole kidney GFR paralleled these falls in SNGFR. The primary cause of the reduction in SNGFR was a marked decline in glomerular capillary ultrafiltration coefficient, Kf, in both gentamicin treatment groups. None of the other determinants of glomerular ultrafiltration were significantly affected in the low dose group (group II). In the high dose group (group III), however, mean values for initial glomerular plasma flow rate and mean transglomerular hydraulic pressure difference were significantly lower than in the control group, accounting for the somewhat greater decline in SNGFR observed in group III. Electron microscopic examination of kidney tissue from rats treated with both doses of gentamicin revealed no obvious abnormalities of the glomerular capillary wall, whereas the previously described morphologic aberrations of proximal convoluted tubule cells were readily demonstrable.

Animals↗
PubMed1987

Maximum ultrafiltration rates during peritoneal dialysis in rats.

It has been suggested that filtration pressure equilibrium could occur in peritoneal capillaries during peritoneal dialysis with very hypertonic exchanges. Rats were exposed to peritoneal dialysis solutions using 16 ml instillations, 30 minute cycles, and dextrose concentrations from 1.4 to 20 g%. There was a plateau in ultrafiltration per exchange at mean osmotic gradients above 360 mOsm/kg H2O near 12.5 ml/ex (0.42 ml/min). The findings are also compatible with filtration pressure equilibrium predictions at an effective capillary plasma flow of 0.84 ml/min and a filtration fraction near 50%. Studies with cardiovascular drugs (norepinephrine i.v., nitroprusside i.p., and dobutamine i.v.) showed no effects on the maximum ultrafiltration rates. This might indicate that flow is rather fixed because of known microcirculatory effects of solutions themselves.

Animals↗
PubMed1996

Action of endothelin-1 on glomerular haemodynamics in the dog: lack of direct effects on glomerular ultrafiltration coefficient.

1. Although numerous studies have demonstrated the potent vasoconstrictor effect of endothelin-1 on the renal vasculature, it is difficult to differentiate in vivo between indirect and direct actions of endothelin. 2. In the present study we therefore performed micropuncture experiments in 14 anaesthetized dogs after the administration of endothelin-1 into the renal artery (i.r.a.) for 15 min at a dose of 2.78 ng min-1 kg-1 which did not affect blood pressure or contralateral kidney function. 3. In seven dogs on a 'normal' sodium diet (3.5 mmol of NaCl day-1 kg-1) endothelin-1 resulted in decreases in renal blood flow and glomerular filtration rate with a rise in filtration fraction from 0.24 +/- 0.01 to 0.35 +/- 0.01. Similar changes were seen at the single-nephron level. An increase from 0.11 +/- 0.01 to 0.23 +/- 0.02 (+109 +/- 11%) in efferent, and from 0.15 +/- 0.01 to 0.24 +/- 0.02 mmHg min-1 microliter-1 (+58 +/- 4%) in afferent arteriolar resistance was observed. The ultrafiltration coefficient, Kf, decreased from 4.75 +/- 0.14 to 3.67 +/- 0.14 microliter min-1 mmHg-1 (P < 0.01). 4. In another group of seven dogs, the same endothelin-1 infusion was given after an administration into the renal artery of a 'cocktail' designed to block the receptors of alpha- and beta-adrenergic agonists, thromboxane A2, leukotrienes and angiotensin II together with intravenous cyclo-oxygenase inhibition. Under these conditions, the vasoconstrictor action of endothelin-1 was reduced by more than 30%. The increase in vascular resistance was now relatively similar in both arterioles, i.e. +44 +/- 5% in the afferent and 66 +/- 6% in the efferent arterioles (no significant difference). No change in Kf was seen after the 'cocktail'-blockade (9.4 +/- 0.4 versus 10.1 +/- 0.1 microliter min-1 mmHg-1). 5. In conclusion, in anaesthetized dogs on a 'normal' salt diet, the vasoconstrictor effect of endothelin-1 is more pronounced on the efferent than on the afferent arteriole. This is accompanied by decreases in glomerular filtration rate and water, urea and electrolyte excretion. Part of the vasoconstrictor action of endothelin seems to be mediated by other autacoids. Endothelin-1 itself contributes only partly to pre- and post-glomerular vasoconstriction and has no direct effect on the glomerular ultrafiltration coefficient Kf.

Adrenergic alpha-Antagonists↗
PubMed2003

A practical method for the detection of macroprolactinaemia using ultrafiltration.

OBJECTIVE: The aim of this study was to evaluate a method for the estimation of the percentage of big-big prolactin (bb-PRL) in serum, based on centrifugal ultrafiltration (UF) and to be used for the detection of macroprolactinaemia. DESIGN: Serum samples were submitted to gel filtration chromatography (GFC), UF and precipitation with polyethylene glycol (PEG). PATIENTS: Serum samples obtained from 13 patients with macroprolactinaemia (Group 1) and from 15 hyperprolactinaemic patients without macroprolactinaemia (Group 2) were studied by the three methods. MEASUREMENTS: PRL was measured in serum, fractions from GFC, filtrate and retentate obtained after UF (this last measurement was used only to study the 'recovery' of PRL after UF and was not necessary for clinical purposes), and supernatant obtained after PEG precipitation. The calculation of the percentage of bb-PRL, by UF, was made using a simple algorithm. RESULTS: In Group 1 the percentages (mean and SD) of bb-PRL as determined by GFC, UF and PEG were, respectively, 73 +/- 16, 83 +/- 5.3 and 78 +/- 7.0. In Group 2, the percentages of bb-PRL were, in the same order as above, 4.3 +/- 8.2, 16 +/- 19 and 3.7 +/- 11. The difference of the means between Groups 1 and 2 was highly significant (P << 0.001) for all the three methods. In Group 1 the percentages of bb-PRL were widely scattered when measured by GFC but closely clustered when measured by either UF or PEG. The opposite occurred in Group 2. CONCLUSIONS: The centrifugal ultrafiltration method for the detection of macroprolactinaemia is simple, inexpensive, requires only two prolactin assays and yields the same results as the polyethylene glycol precipitation method.

Adenoma↗
PubMed2003

On-line mixed hemodiafiltration with a feedback for ultrafiltration control: effect on middle-molecule removal.

BACKGROUND: Increased middle-molecular uremic toxin removal seems to favorably influence survival in dialysis patients. The aim of this study was to verify if, in on-line mixed hemodiafiltration, solute removal by convection may be enhanced by forcing the ultrafiltration rate (QUF) and optimizing the infusion technique in order to achieve the highest possible filtration fraction (FF). METHODS: Removal of beta2-microglobulin (beta2-m), urea, creatinine, and phosphate were compared in 20 patients randomly submitted to one dialysis session (A), one postdilution hemodiafiltration session (B), and three sessions of mixed hemodiafiltration (C, D, and E) at different infusion rates (QS). In mixed hemodiafiltration, a newly developed feedback system automatically maintained the transmembrane pressure (TMP) within its highest range of safety (250 to 300 mm Hg) at constant QUF, while ensuring the maximum FF by splitting infusion between pre- and postdilution. RESULTS: A mean QS of 134 +/- 20 mL/min (mean FF = 0.65) was attained in post-HDF, and up to 307 +/- 41 mL/min (mean FF = 0.69) in mixed hemodiafiltration. The mean dialysate clearances (KDQ) for all tested solutes and urea eKt/V were significantly higher in all hemodiafiltration sessions than in dialysis. Only in the case of urea did the infusion mode have no significant effect. KDQ for beta2-m was maximal in session D and significantly higher than in session B (90.2 +/- 11 mL/min vs. 77.5 +/- 11 mL/min; P = 0.02). KDQ for beta2-m significantly correlated with QS and the plasma water flow rate (QPW). The highest KDQ for beta2-m was found at values of QS approximately QPW. Beyond this value KDQ decreased. CONCLUSION: The mixed infusion mode in hemodiafiltration, controlled by the TMP-ultrafiltration feedback, seems to improve the efficiency of hemodiafiltration by fully exploiting the convective mechanism of solute removal. The feedback automatically adjusted the infusion rate and site to the maximum FF taking into account flow conditions, internal pressures, and hydraulic permeability of the dialyzer and their complex interactions.

Aged↗
PubMed2001

Urea reduction ratio that considers effects of ultrafiltration and intradialytic urea generation.

We modified the urea reduction ratio (URR) equation to correct the effects of ultrafiltration and intradialytic urea generation on the delivered dose of hemodialysis: mURR = [1 - (R/1 + 2*UF/BW) + 0.01*t] x 100% where mURR is modified URR, R is postdialysis plasma urea nitrogen (PUN) to predialysis PUN ratio, UF is ultrafiltrate volume in liters, BW is postdialysis body weight in kilograms, and t is dialysis session length in hours. The equation was validated against 145 hemodialysis treatments on 33 stable maintenance dialysis patients. The mURR values obtained closely predicted single-pool Kt/V (spKt/V) values. In contrast to conventional URR, the range of spKt/V values at each mURR value is narrow over a wide range of UF, t, and R values. Based on the mURR equation, mURR values of 64%, 70%, and 76% are mathematically equivalent to spKt/V levels of 1.0, 1.2, and 1.4, respectively. This equation can be a useful bedside tool to quantify hemodialysis dose.

Blood Urea Nitrogen↗
PubMed2006

Does the additional use of heparin-coated extracorporeal circuits (ECC) optimize the effect of modified ultrafiltration (MUF) in pediatric perfusion?

BACKGROUND: Modified ultrafiltration (MUF) has been shown to exert beneficial effects on the coagulation system and the capillary leak after pediatric cardiac surgery using extracorporeal circulation (ECC). The aim of this study was to investigate whether the additional use of heparin-coated circuits is a useful option for improving biocompatibility. METHODS: We randomized 28 children, using heparin-coated ECC circuits in group A (n = 14) and an uncoated equivalent set in group B (n = 14). After congenital heart surgery, MUF was performed post ECC in a standardized fashion. Blood samples were analyzed preoperatively, 10 min, 30 min, 1 h, and 48 h after ECC by flow cytometric analysis (FACSort) using surface antigens CD62/CD41b (platelets) and CD45/CD14 (monocytes). RESULTS: No significant difference was found with respect to mean age (20.6 months vs. 21.6 months), mean body weight (9.2 kg vs. 8.4 kg), mean ultrafiltration rate (9.1 ml/kg vs. 11.4 ml/kg), chest tube drainage, blood products, ICU stay, and 30-d survival. The percentage of CD62/CD41-positive platelets in group A (vs. B) increased up to 118 % at 60 min vs. 130 % ( P < 0.05) and declined to 98 % at 48 h postop. vs. 99 % (n. s.). The percentage of CD45/CD14-positive monocytes in group A (vs. B) increased up to 158 % at 60 min vs. 155 % (n. s.) and declined to 122 % (A) at 48 h postop. vs. 61 % (B) ( P > 0.05). CONCLUSIONS: Heparin coating of ECC in addition to MUF leads to a lower platelet activation. Monocyte surface markers CD45 and CD14 indicated a marked activation during ECC in both groups but additional heparin coating showed a better postoperative regeneration of monocyte markers in the late course indicating a beneficial additive effect.

Antigens, Surface↗
PubMed2003

Coupling ultrafiltration with an activated carbon cloth for the treatment of highly coloured wastewaters: a techno-economic study.

This work investigates the coupling of a membrane technique, ultrafiltration, with a recent adsorbent, activated carbon cloth for the treatment of industrial highly coloured wastewaters. A first experimental part shows the high treatment ability of this process for fountain-pen inks effluents arising from the rinsing of vats in which inks were produced. Whereas ultrafiltration enables more than 97% of colour removal, COD and DOC are not completely retained and a residual value of 1,700 mg l(-1) of DOC is obtained in the permeate. The second step of the process, activated carbon cloth, allows residual organic matter to be removed and a complete discolouring of the permeate. Adsorption capacities of COD and DOC are high, equal to 500 and 250 mg g(-1) respectively. Furthermore, this adsorbent induces a complete removal of glycol compounds (acting as antifreeze) which were not retined by a nanofiltration technique. A second part is an evaluation of the economic feasibility of such an integrated process. Only direct costs are considered at this phase of the study, and are divided into fixed costs (equipment, depreciation, maintenance), variable costs (electricity and consumption) and labour costs. The technical-economic study is carried out for two configurations: a low capacity unit (the UF membrane area is 2.4 m2) and an industrial capacity unit (with a 100 m2 UF membrane). Costs per treated m3 are respectively 111 and 32 euros, with costs partitioning which are dependent on the unit capacity.

Absorption↗
PubMed2005

Characterization and ultrafiltration of semiconductor indium phosphide (InP) wastewater for recycling.

This research work investigated the physical and chemical properties of a new type of wastewater produced from the semiconductor industry. The wastewater generated from indium phosphide (InP) wafer backgrinding and sawing processes was characterized in term of its particle size distribution (PSD), zeta potential, suspended and dissolved solids, total organic carbon, and turbidity. The wastewater contained high concentration of fine InP dusts with a size ranging from 0.07 - 1.44 mm. In spite of its high concentration of suspended solids resulting in high turbidity up to 371 NTU, the wastewater contained very low organic matters (TOC < 2.2 mg l(-1)) and other inorganic impurities (SO4(2-) < 0.21 mg l(-1) and Na+ < 0.16 mg l(-1)). Based on the experimental data collected, the treatment technologies using chemical precipitation and ultrafiltration were applied to the wastewater. Both processes could effectively remove InP particles from the wastewater, however the coagulants in chemical precipitation introduced other ionic contents into the process resulting in difficulties of water recycling in the later stage. In comparison, ultrafiltration was more promising for InP wastewater treatment and recycling. Based on the results of this study, a full-scale UF system was built in a local semiconductor plant and it has successfully reclaimed water from the InP wastes for the past six months without any quality issue being raised.

Conservation of Natural Resources↗
PubMed2003

The effect of metal ions on humic acid removal and permeation properties in an ultrafiltration system.

With a view to improving the removal of humic acid from aqueous solution, the effect of metal ion addition on the separation of humic acid from water in an utrafiltration (UF) system was investigated. The valence of the metal ion and the molar ratio of humic acid to metal ion strongly affected the permeation flux during ultrafiltration. It was found that the ionic strength, dissociation constant and operating pressure were not major factors affecting the separation performance of the ultrafiltration process. As well as indicating that a suitable ratio of humic acid to metal ion and valence of metal ion were the key factors in improving separation efficiency. The results also showed that separation of humic acid depended on the level of formation of humic acid-metal ion complexes, and on the degree of fouling on the membrane surface.

Filtration↗
PubMed1998

Icodextrin use in CCPD patients during peritonitis: ultrafiltration and serum disaccharide concentrations.

BACKGROUND AND METHODS: In a randomized study on the biocompatibility of icodextrin (I) versus glucose (G) in CCPD we used icodextrin or glucose for the long daytime dwell. During the night-time dwells glucose was used in all patients. In case of peritonitis icodextrin was continued. In all patients ultrafiltration (UF) was recorded and serum icodextrin metabolites were determined every 3 months and during peritonitis in I-users when available. RESULTS: Thirty-eight patients ( 19 G, 19 I) entered the study and suffered 30 peritonitis episodes (16 G, 14 I). During peritonitis (P), daytime dwell UF decreased significantly in G (P=0.001), but remained stable in I patients compared to non-peritonitis (NP) episodes. Total 24-h UF decreased in G (P=0.001) and in I patients (P=0.04), as the result of a decreased daytime UF and night-time UF, respectively. There was no difference in the used glucose concentrations during the P versus NP episodes. In five I-patients serum disaccharides increased from 0.05+/-0.01 to 1.26+/-0.23mg/ml during follow up. During peritonitis serum disaccharide concentrations did not increase further (1.47+/-0.24 mg/ml, P= 0.56). In I patients total carbohydrate minus glucose rose to 5.72 +/- 1.2 mg/ml during follow up, and to 6.63 +/- 1.04 mg/ml during peritonitis (P=0.7). These concentrations are comparable to CAPD patients despite the longer dwelltime in CCPD (8-10 versus 14-16 h, respectively). Adverse reactions attributable to icodextrin were not encountered. CONCLUSIONS: In contrast to glucose, icodextrin preserved the daytime dwell ultrafiltration during peritonitis. Serum icodextrin metabolites increased during icodextrin use, but remained stable during peritonitis. Adverse effects were not observed.

Blood Glucose↗
PubMed1991

Fluid balance during haemodialysis and haemofiltration: the effect of dialysate sodium and a variable ultrafiltration rate.

One of the main causes of hypotension during extracorporeal renal replacement therapy is an insufficient substitution of the ultrafiltrated plasma water by tissue water. To investigate the fluid balance and its effects on hypotension in dialysed patients, the following variables were studied: intracellular fluid volume (IFV) and extracellular fluid volume (EFV), blood volume (BV) and blood pressure. IFV and EFV were measured by means of non-invasive electrical conductivity measurements using four electrodes round the leg. Fifteen haemofiltration (HF) and 15 haemodialysis (HD) patients were studied. The latter group was dialysed in three ways: (1) conventionally, i.e. with dialysate sodium of 138 mmol/l (HD) (2) with a variable dialysate sodium (first half: 138 mmol/l; second half: 146 mmol/l) (HDS), and (3) with the same variable dialysate sodium and an ultrafiltration profile (two-thirds was withdrawn during the first half of treatment, the remainder during the second half) (HDSU). Hypotension frequency was less during HDS, HDSU, and HF compared to HD. This was caused by a more stable blood volume due to a better refill. During HD a fluid shift occurred from the EC to the IC compartment. The use of a high sodium dialysate concentration led to a transcellular fluid shift in the opposite direction. This fluid shift increased the refill, thereby stabilising blood volume. HF gave a better refill than HDS and HDSU, probably due to a reduced urea clearance.

Aged↗
PubMed1991

Transcapillary ultrafiltration and lymphatic absorption during childhood continuous ambulatory peritoneal dialysis.

Peritoneal fluid handling depends on a balance between transcapillary ultrafiltration and lymphatic absorption. Lymphatic absorption is reported to be greater in children than in adult continuous ambulatory peritoneal dialysis (CAPD) patients. The present study provides data on peritoneal fluid kinetics in a group of 17 young children (0.4-13 years of age). Net transcapillary ultrafiltration and lymphatic absorption were not dependent on age or duration of treatment. No differences were established from normal values for adult patients reported in the literature.

Absorption↗