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PubMedDate not supplied

[Effect of ultrafiltrates in plasma from patients with chronic uremia on platelet aggregation].

An effect of 20 ultrafiltrates from patients with chronic renal failure on ADP-, epinephrine-, and arachidonic acid-induced platelet aggregation. Ultrafiltrates were collected at the beginning and the end of dialysis. It was found that ultrafiltrates collected at the beginning of dialysis decrease ADP-induced platelet aggregation whereas ultrafiltrates collected at the and of dialysis exert reverse effect. No effect on epinephrine- and arachidonic acid-induced platelet aggregation was seen. Removal of substances inhibiting platelet aggregation produced by ADP hemodialysis may reveal increased platelet aggregation in patients with uremia.

Adolescent↗
PubMed1976

Anti-beta adrenoreceptor blockade activity of plasma ultrafiltrate in two uraemic patients: effect of parathyroidectomy.

A possible interaction between d-1 propranolol and hyperparathyroid plasma ultrafiltrate on guinea pig auricles has been studied in "in vitro" experiments. Plasma ultrafiltrates have been samples in two patients on chronci haemodialysis before (pre-PTx) and after (post-PTx) parathyroidectomy. A significant inhibition of propranolol depressant activity on cardiac contractile strength has been observed in the presence of pre-PTx plasma ultrafiltrates. On the contrary, no such inhibition was noted in the presence of post-PTx plasma ultrafiltrates.

Animals↗
PubMedDate not supplied

[Methodologic aspects of isolated ultrafiltration of the blood in nonspecialized units].

14 isolated ultrafiltration procedures have been performed in 7 patients, using AT-196 device and renal dialyzer DIP-02-02. Volumetric blood flow was 100-120 ml/min; 1.0-1.2 l of ultrafiltrate were removed during 1 h. The patients' conditions gradually improved in the course of ultrafiltration procedure. A simple method of isolated ultrafiltration that can be used in any medical institution is described.

Acute Kidney Injury↗
PubMed1989

[Treatment of persistent cardiac failure by ultrafiltration].

Ultrafiltration, a method of extra renal filtering, which accomplishes an iso-osmotic removal of water an sodium from the plasma, was used in twelve patients. It is reserved for terminal persistent heart failures. In one case, it preceded a heart transplant. Simple to carry out, this technique is well tolerated when the pulmonary pressure is elevated, respecting an ultrafiltration output inferior or equal to 500 ml/h. Immediate improvement of the patients is spectacular. A new treatment failure may impose long-term ultrafiltration sessions. Failure of the medical treatment, impossibility of heart transplant, must be an indication for ultrafiltration which improves the comfort, and most likely the life expectancy of patients with persistent heart failure.

Adult↗
PubMed1993

[Changes in the physical characteristics of the lung can account for the improvement observed after ultrafiltration in patients with moderate heart failure].

Ultrafiltration improves the clinical condition of patients with moderate congestive heart failure. Ultrafiltration (1895 +/- 120 ml of plasma water, rate 600 ml/h, veno-venous bypass) was performed in 30 patients with moderate congestive heart failure in stable clinical conditions. The effects of ultrafiltration were assessed through pulmonary function and cardiopulmonary exercise tests performed before and 30 days after the procedure. Vital capacity, forced expiratory volume (1 s) and maximal voluntary ventilation improved as improved exercise performance (increase in oxygen consumption at peak exercise and at anaerobic threshold). Tidal volume at anaerobic threshold and at peak exercise increased by 10% with no changes in respiratory rate. This suggests that ultrafiltration induces changes at the physical characteristics of the lungs probably related to changes in lung water content.

Aged↗
PubMed1999

Non-absorption of ingested lipophilic and amphiphilic allelochemicals by generalist grasshoppers: the role of extractive ultrafiltration by the peritrophic envelope.

The role of the peritrophic envelope in the non-absorption of three allelochemicals ingested by generalist grasshoppers was examined. This study tested the hypothesis that the association of lipophilic and amphiphilic allelochemicals with lipid aggregates (mixed micelles) reduces their permeability through the peritrophic envelope, a process similar to extractive ultrafiltration. Each of three allelochemicals (digitoxin, ouabain, and xanthotoxin) were solubilized in a lysolecithin suspension and injected separately into the midgut lumens of adult Melanoplus sanguinipes (Orthoptera: Acrididae). The low permeability of digitoxin through the peritrophic envelope was consistent with the extractive ultrafiltration of this compound. By comparison, ouabain and xanthotoxin permeability coefficients were 7- and 12-fold higher, respectively, than those of digitoxin. The results of extractive ultrafiltration assays confirmed that digitoxin is effectively extracted in lysolecithin micelles, but that neither ouabain nor xanthotoxin aggregates efficiently with these micelles.

Animals↗
PubMed2004

Highly selective membranes in protein ultrafiltration.

A new ultrafiltration technique based on a multimembrane stack has been developed to fractionate solutes closer in size than conventionally possible. The technique is illustrated here by obtaining a pure protein product from a binary protein mixture. By employing membranes in series without any gaskets or spacers in-between, ultrafiltration is carried out to separate two proteins relatively close in molecular weight or size. Flat YM30 regenerated cellulose membranes, all of the same molecular weight cut-off (MWCO) 30,000, are stacked together in the desired number, and ultrafiltration takes place. The membrane rejection of a protein is amplified with each additional membrane, ultimately resulting in a completely rejected species. Complete purification of the more permeable protein may be achieved regardless of the physicochemical condition that may be optimal or suboptimal for selective separation by a single membrane. Two systems, myoglobin and beta-lactoglobulin, as well as myoglobin and alpha-lactalbumin were studied, under various operating conditions. The solvent flux reduction encountered when each membrane is added may also be avoided, by operating at increased pressure, while still achieving the desired purification. Cleaning in situ is achievable with reproducible experimental results before and after on-line cleaning. The results clearly demonstrate that multimembrane stacks can be used for fractionation of proteins that are quite close in molecular weight/size.

Biotechnology↗
PubMed2005

Separation of monoclonal antibody alemtuzumab monomer and dimers using ultrafiltration.

This article examines the feasibility of using ultrafiltration to separate the monomer of the monoclonal antibody alemtuzumab (Campath or Campath-1H) from a mixture of dimer and higher-order oligomers (collectively called "dimers" here). Using parameter scanning ultrafiltration, we initially assessed the suitability of the following membranes: 100 kDa and 300 kDa polyethersulfone (PES) membranes, and a 100 kDa polyvinylidene fluoride (PVDF) membrane. A detailed study was then carried out to examine the effects of operating conditions (such as solution pH, ionic strength, stirring speed, and permeate flux) on the separation of the monomer from the dimers using 300 kDa PES and 100 kDa PVDF membranes. Results of the experiments carried out in the carrier phase ultrafiltration (CPUF) mode indicate that the size-based protein-protein separation critically depends on the membrane used as well as the system hydrodynamics. The separation of the monoclonal antibody monomer and dimers using 100 kDa PVDF membranes in the diafiltration mode was also examined. Experimental results demonstrate that under suitable conditions, it is feasible to obtain the alemtuzumab monomer with a purity of more than 93% and a yield of more than 85% (from a mixture of 75% monomer and 25% dimers, which is the typical composition obtained after affinity chromatography). Simulation study indicates that this could be further improved to a purity of more than 96% and a monomer yield of more than 96% by increasing the selectivity of separation or by employing a two-stage diafiltration process.

Alemtuzumab↗
PubMed1988

Ultrafiltration in the treatment of refractory congestive heart failure.

Artificial subtraction of fluids and solutes was evaluated in the course of acute and chronic heart failure when it became refractory to standard intensive medical treatment. A group of 19 patients (mean age 57 years), 9 with ischemic, 2 amyloidotic, 4 valvular, and 4 idiopathic cardiomyopathy, were treated. In 17 patients extracorporeal ultrafiltration (UF) by means of a polysulfonate ultrafilter was adopted along 125 sessions (105 assisted by a roller pump and 20 as a slow continuous ultrafiltrate). In two patients continuous peritoneal dialysis was adopted. In every case UF was well tolerated. Ultrafiltrate volumes ranged from 1680 to 3500 ml for every session with corresponding Na losses ranging from 194 to 434 mEq/session. Improved clinical and functional status with reduction of edema was observed in 17 of 19 patients. In 12 patients UF could be discontinued due to restored response to diuretics; 5 of these patients could subsequently undergo heart surgery (1 transplant, 3 valve replacement, 1 coronary bypass). The remaining 7 patients survived on medical therapy alone for an average of 228 days. In 7 of 19 cases, UF could not be discontinued, and these patients died after an average of 23 days of treatment. In conclusion, UF proved to be effective in eliminating salt-fluid overload and restoring response to medical treatment. Patients who are potential surgical candidates seem to be the most suitable for UF.

Adult↗
PubMed1997

Measurement of prebeta-1 HDL in human plasma by an ultrafiltration-isotope dilution technique.

Prebeta-1 HDL is a 67-kDa species of plasma high-density lipoproteins (HDL) that contains two copies of apolipoprotein A-I. It functions in a metabolic cycle of cholesterol retrieval and may be formed during lipolysis in plasma. We have found that centrifugal ultrafiltration using a membrane with a permeability limit of 100 kDa discriminates categorically between the 67-kDa species and larger HDL particle species. Thus, the ultrafiltrate samples the pool of prebeta-1 HDL in plasma. We have developed a technique using the dispersal of purified prebeta-1 HDL, labeled covalently with tritium, in plasma samples, to label the prebeta-1 HDL pool. Subsequent determination of the specific activity of prebeta-1 HDL in the ultrafiltrate provides a means of calculating the content of prebeta-1 HDL in plasma by the isotope dilution principle. We employ a modification of an enzyme-linked immunosorbent assay technique for apolipoprotein A-I that allows the equal detection of that protein in prebeta-1 HDL and in other HDL particle species for determination of the fraction of total apolipoprotein A-I that is present in the prebeta-1 HDL particle species. The mean level of prebeta-1 HDL-associated apolipoprotein A-I in plasma samples from 86 normolipidemic adults was 74 +/- 43 microg/ml (+/-SD), representing an average of 6.6% of the total apolipoprotein A-I in plasma.

Adult↗
PubMed1998

Pulsed ultrafiltration characterization of binding.

We describe a new method for measuring binding constants, pulsed ultrafiltration. In this technique, a single injection or "pulse" of ligand is passed through a cell containing macromolecules confined by a conventional ultrafiltration membrane. Any binding of the ligand to the macromolecule alters the elution profile of the ligand. We describe this interaction by a set of coupled differential equations whose solution allows us to extract the binding density as a function of free ligand concentration eluting from the cell. A method of comparing elution profile areas which leads to values for both binding affinity and stoichiometry is also presented. We show that the pulsed ultrafiltration method can generate an extensive binding isotherm with a dense set of data points over a wide range of binding densities. We apply the method to several model ligand-macromolecule binding systems to demonstrate the measurement of equilibrium association constants and binding stoichiometry, the accuracy and precision of the method, and temperature dependence of binding. In general, our results agree with those from the literature, and they show that the approach is a fast and flexible method for characterizing ligand-macromolecule binding.

Chromatography, High Pressure Liquid↗
PubMed1998

Ligand binding to macromolecules or micelles: use of centrifugal ultrafiltration to measure low-affinity binding.

We describe a method for estimating ligand binding to a macromolecular sample under conditions where this binding is of low affinity and must be measured under equilibrium conditions, without removal of the unbound ligand. The method is based on centrifugal ultrafiltration through a membrane with a molecular mass cut-off intermediate between that of the ligand and that of the target, and the amount of bound ligand is calculated from the difference between the (total) ligand in the concentrated sample and the (free) ligand in the ultrafiltrate. Centrifugal ultrafiltration makes it possible to separate free ligand from bound ligand (without changing its concentration) and to simultaneously concentrate the target (such that the proportion of bound ligand becomes significant, even under low-affinity binding conditions). We applied this technique, using Centricon 10 (Amicon) devices, to several cases (soluble proteins, intact membranes, detergent-solubilized proteins, and pure detergent micelles) and assessed its value with respect to the common artifacts that occur in other protocols involving protein retention on nitrocellulose filters (nonspecific ligand adsorption and protein denaturation).

Adenosine Triphosphate↗
PubMed1990

Stroma-free hemoglobin solutions prepared by crystallization and ultrafiltration methods; comparison of composition and coronary vasoconstrictor potency.

Stroma-free hemoglobin solutions (SFHS) were prepared by the crystallization and ultrafiltration methodologies. The preparations were partially characterized with respect to their effects upon the isolated perfused rat heart. SFHS prepared by ultrafiltration is characterized by a substantially lower content of residual membrane phospholipid and a more restricted protein composition. This preparation is also essentially free of vasoconstrictor and contractility-depressant actions on the ex vivo perfused heart. In contrast, crystallization-produced SFHS is less well purified of both phospholipid and protein constituents, is likely to generate denatured protein aggregates during storage and exhibits vasoconstrictor and contractility-depressant activity which may vary significantly, from batch to batch. These findings indicate that preparative methodology based on ultrafiltration and size-exclusion, yields SFHS which is superior in these respect to that produced by a crystallization method.

Animals↗
PubMed1994

Nutritional characteristics of cassava (Manihot esculenta Crantz) leaf protein concentrates obtained by ultrafiltration and acidic thermocoagulation.

Some nutritional characteristics of cassava (Manihot esculenta) leaf protein concentrates obtained by ultrafiltration were compared with that obtained by acidic thermocoagulation. Protein concentrates did not show noticeable differences in their proximal composition and amino acids content. However, higher values of total carotene, available lysine, and in vitro digestibility were found, in contrast with less content of total cyanide in protein concentrates obtained by ultrafiltration. Protein efficiency ratio (PER) values of the leaf protein concentrates obtained by ultrafiltration were higher than those obtained by thermocoagulation, 1.81 and 1.60 respectively. These values increased to 2.30 and 1.90 when the concentrates were mixed with sesame flour, in proportion according to the chemical score of their proteins.

Amino Acids↗
PubMed1986

High and low sodium acetate haemodialysis and ultrafiltration. I. Comparison of haemodynamic effects.

This study was undertaken to evaluate the effect of increasing the dialysate sodium concentration on haemodynamic effects, arterial blood gases and chemistries during haemodialysis and ultrafiltration. Significant changes in mean blood pressure (MBP) and heart rate (HR) were not noted; but significant differences in sodium, potassium, total protein concentration, haematocrit and plasma osmolality during dialysis and ultrafiltration were found with both dialysates. Significant differences were also noted in pCO2 during dialysis and ultrafiltration with both dialysates and increase of pH during dialysis with low sodium dialysate. Significant changes in kind and frequency of unpleasant symptoms were found with both dialysates.

Acetates↗
PubMed1982

Equilibrium dialysis and ultrafiltration studies of calcium and phosphate binding by human salivary proteins. Implications for salivary supersaturation with respect to calcium phosphate salts.

Previous ultrafiltration studies indicated that up to one-half of the calcium and two-thirds of the phosphate in human salivary secretions may be bound by salivary proteins. Since this binding is an important variable in determining the extent of salivary supersaturation with respect to calcium phosphate salts, and since the amount of binding reported is surprisingly large, calcium and phosphate ion-binding by salivary macromolecules has been reexamined. From experiments using equilibrium dialysis, it was found that (1) the fraction of salivary calcium involved in macromolecular complexes ranges from a few percent for unstimulated secretions, to no more than about 10% for stimulated glandular salivas, and (2) salivary proteins do not bind phosphate ions to any significant extent. These findings, and experiments using an improved ultrafiltration membrane, indicate that the earlier results were artifacts of the ultrafiltration technique. Fractionation of salivary proteins, followed by equilibrium dialysis measurements, showed that the anionic proline-rich proteins and a basic proline-rich glycoprotein are responsible for most of the calcium binding now observed. The finding that macromolecular complexes of salivary calcium and phosphate have been overestimated in the past, leads to the conclusion that salivary calcium and phosphate ion activities in stimulated salivary secretions may be up to 50 to 100% higher than previously thought. Revised values were therefore used to recalculate the degree of salivary supersaturation with respect to calcium phosphate salts. The results indicate that stimulated salivary secretions are supersaturated with respect to dicalcium phosphate dihydrate; this is a substantially greater degree of supersaturation than previously reported.

Calcium Phosphates↗
PubMed2005

Ultrafiltration behavior of selected pharmaceuticals on natural and synthetic membranes in the presence of humic-rich hydrocolloids.

The separation behavior of the frequently administered pharmaceuticals sulfamethoxazol (Sulfa), carbamazepine (Carba), diclofenac (Diclo), and ibuprofen (Ibu) on different natural and synthetic ultrafiltration membranes was studied. Commercially available cattle intestine natural membranes (NM), polyethersulfone (PES), and regenerated cellulose-based (RC) flat membranes (nominal cut-off 1 kDa) have been investigated as ultrafiltration membranes in a small tangential-flow ultrafiltration unit (TF-UF). First, the nominal cut-off of the NM membranes under study was assessed at approximately 5 kDa, by using polystyrenesulfonate standards for pore-size classification at low TF-UF pressure (0.25 x 10(5) Pa). Working pressures of >1.5 x 10(5) Pa strongly increased the cut-off of NM, in contrast with that of PES and RC membranes. Sulfa, Carba, Diclo and Ibu (1 mg L(-1) each) in colloid-free aqueous solutions (400 mg L(-1) NaCl) completely permeated through NM membranes, but less through PES and RC, which had particular sorption capability towards Diclo. The drugs were routinely determined by using high-performance liquid chromatography (HPLC). Detailed TF-UF investigation of drug retention on NM in the presence of humic hydrocolloids revealed strong interactions between aquatic humic substances (HS) and Diclo and Ibu (but not with Sulfa and Carba) causing retention of up to 80% of Diclo and Ibu, probably because of their binding to macromolecular HS. The standard deviation (SD) of both drug and HS permeation through a single NM was between 2.5 (Sulfa) and 4.0% (Diclo), in contrast with the SD of permeation through separate membranes taken from different lots [SD up to 14.0% (Diclo)], presumably caused by natural variation of the studied NM. Accordingly, membrane filtration of drug-containing water samples on cattle intestines enables both analyte/matrix separations for Carba and Sulfa in the presence of humic colloids and analytical discrimination between free and colloid-bound Diclo and Ibu fractions.

Animals↗
PubMed2005

Ultrafiltration in decompensated heart failure.

Fluid congestion is the hallmark of decompensated heart failure. As heart failure progresses, reduced response to diuretics is common. In these patients, ultrafiltration has been found to alleviate excess volume and improve diuretic sensitivity. Compared with diuretics, ultrafiltration provides a more predictable and safer way to achieve euvolemia with minimal electrolyte abnormalities and neurohormonal activation. The emerging familiarity and ease of use of ultrafiltration suggests that in the future this will be an important therapy for the treatment of acute and chronic volume overload associated with decompensated heart failure.

Heart Failure↗