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PubMed1993

Removal of cytomegalovirus DNA from donor blood by filtration.

Blood from five donors, previously shown to be positive for cytomegalovirus (CMV) DNA following polymerase chain reaction (PCR) amplification, was filtered through commercially available leucocyte filters. Analysis of pre- and post-filtration samples by PCR with ethidium bromide staining has shown that filtration was successful in removing CMV DNA from all samples. This is evidence that leucocyte filtration of red cell concentrates may greatly decrease the risk of CMV disease following transfusion to susceptible patients.

Base Sequence↗
PubMed2004

Preparation of milk samples for PCR analysis using a rapid filtration technique.

AIMS: To investigate the usefulness of a straightforward filtration method for the isolation of Escherichia coli O157:H7 contaminants from milk for PCR detection. METHODS AND RESULTS: Escherichia coli O157:H7 is grown in milk and enriched in Luria-Bertani (LB) medium. Samples are filtered through a 0.45-microm pore membrane. The membrane is immersed in 200-microl lysis buffer and incubated at 95 degrees C for 10 min to release bacterial DNA for subsequent PCR detection. Under current conditions, the overall duration from filtration to PCR-ready DNA generation is <20 min, and the detection level for PCR was as low as 10 CFU of bacteria in 1 ml of milk. CONCLUSION: Bacterial contaminants of milk can be concentrated and isolated by a simple, one-step filtration and their DNA can be released for subsequent PCR detection by heating the filter membrane at 95 degrees C for 10 min. SIGNIFICANCE AND IMPACT OF THE STUDY: The simplicity of this method allows inexpensive, high throughput automation that meets the demands of modern food hygiene monitoring.

Animals↗
PubMed1983

Perturbations of granulocyte counts induced by procedural, chemical and physiological events occurring during filtration leukapheresis in rats.

During filtration leukapheresis a factor(s) is produced, released or extracted into rat blood which causes a transient granulocytosis in pheresed animals and in recipients of homologous plasma from these animals. To identify which factors contribute to this granulocytosis, the procedural steps involved in filtration leukapheresis as well as a number of chemical agents which are potentially extracted from of produced by the procedure, were tested for their ability to stimulate granulocytosis. Procedural steps tested included the depth of anesthesia, effect of the anticoagulant and possible interactions of blood cells with the plastic tubing in the system (sham-pheresis). Chemical agents tested included common mediators of inflammation and proteinases released by polymorphonuclear leukocytes (PMNs), extracts of nylon fibers and Tygon tubing, nylon monomers and solvents used in the manufacture of nylon, oxidized and decomplemented plasma and lysates of PMNs or microorganisms. Our findings demonstrate that several of these agents contribute to the granulocytosis seen during filtration leukapheresis of rats.

Anesthetics↗
PubMed1976

Proteins of axonal transport: investigation of solubility characteristics and behaviour in gel filtration.

Rapid axonal transport of proteins in retinal ganglion cells of the rabbit was studied following intraocular injections of labelled amino acids. Approximately 10% of the transported radioactivity was found in the supernatant following homogenization and high-speed centrifugation of the nerve terminal region. Relatively simple manipulations with ionic strength, pH and the presence of a chelating agent could solubilize an equivalent amount of radioactivity from the pellet. Lithium diiodosalicylate solubilized most rapidly transported membrane proteins. Gel filtration of readily soluble rapidly transported radioactivity gave a main macromolecular radioactive peak with an approximate mol. wt. of 500,000 dalton as determined on Sephadex G-200. However, gel filtration on Sepharose CL-6B gave a mol. wt. of about 160,000 for the same radioactive peak. SDS polyacrylamide gel electrophoresis of rapidly transported soluble proteins and fractions derived from these proteins via gel filtration and ion exchange chromatography revealed in all cases a very complex picture of labelled polypeptides. Thus rapid axonal transport of soluble proteins in this system seems to involve many different macromolecules.

Animals↗
PubMed1984

Forefoot capillary filtration rate measured during lowering in normal subjects and in patients with occlusive arterial disease before and after arterial reconstruction.

Capillary filtration rate (CFR) was measured by a mercury-in-silastic strain-gauge around the forefoot when the forefoot was lowered 40 cm below heart level. In seven normal limbs, CFR was 0.061 (0.049-0.086) ml (100 g min)-1 against 0.049 (0.016-0.071) ml (100 g min)-1 in 24 limbs with occlusive arterial disease (P = 0.01). About 8 days after arterial reconstruction CFR decreased to 0.039 (0.018-0.071) ml (100 g min)-1, but before 3 months after reconstruction CFR increased to normal values 0.061 (0.037-0.071) ml (100 g min)-1. The explanation offered for the reduced CFR before and immediately after arterial reconstruction is temporary thrombosis in the smallest distributing arteries and in the arterioles resulting in heterogeneous flow distribution and decreased fluid filtration in poorly perfused segments of the capillary bed. The results speak against increased capillary filtration as the aetiology of the post-reconstructive oedema.

Adult↗
PubMed1984

Analytical comparison of single-pass and dead-end operation in cascade filtration plasmapheresis.

Derived mathematical models are employed to compare cascade filtration plasmapheresis in the dead-end and single-pass formats. The high filtration fraction and low sieving coefficients associated with single-pass cascade filtration are shown to require treatment of the retentate concentration profile in an integrated rather than a length-averaged fashion. The models are best applied to specific simulations, but in general predict that (a) for a given membrane, the dead-end format will yield a higher albumin recovery but a lower macroglobulin rejection than single pass; (b) the single-pass format is more suited to loose membranes and the dead-end to tight membranes; and (c) in the single-pass but not the dead-end format, solute recovery is conveniently independent of the quantity filtered. Agreement between predicted and measured performance is good, although a larger data base would be required for complete validation of the models.

Models, Theoretical↗
PubMed2005

Impact of inverse plasma filtration on complement activation in porcine blood.

During extracorporeal circulation, activation of the complement system as a bioincompatibility reaction upon contact with artificial surfaces is well known. This may induce adverse effects for the patient as well as for the bioreactor when using a hybrid liver support system. At present, the achievable clearance rates in hybrid liver support systems are restricted by the limitations of blood flow through the capillaries of the plasma filter. In order to enhance clearance rates it is desirable to develop a high-flow plasma separation unit in which the activation of the complement system is as low as possible. Conventional plasma filters operating in normal and in inverse (blood flow around the capillaries and the capillary lumen serving as plasma compartment) modes were investigated applying an in vitro circuit (n = 4 in each group). For this purpose heparinized porcine blood was used. Complement activation was measured as generation of the soluble membrane attack complex, SC5b-9. With a normal flow mode the maximum achievable filtration rates varied from 25 to 40 mL/min, whereas the maximal filtration rates with an inverse flow mode varied from 40 to 100 mL/min. While these values were significantly higher than those with regularly operating plasma filters, there was no significant difference between normal and inverse mode in the production of SC5b-9. We conclude that the outer surface of the investigated conventional plasma filtration membranes is suitable for an inverse mode and does not lead to an excessive activation of the complement system upon dynamic blood contact. Thus, the inversion of the blood and the plasma compartments may be a possible way forward in the development of a high-flow plasma separation filter.

Animals↗
PubMed1984

Comparison of gel filtration and ammonium sulphate precipitation in the purification of diphtheria toxin and toxoid.

Crude diphtheria toxin and toxoid were subjected to purification by gel filtration and stepwise ammonium sulphate precipitation. The various fractions obtained by the purification procedures were studied by immunological methods. A high molecular weight fraction of glycoprotein nature was present in all of the crude preparations studied. The fraction was antigenically non-identical with the real toxin or toxoid and did not have its origin in the culture medium. It showed a long flocculation time when tested against equine diphtheria toxoid antiserum. The fraction could be removed from the crude preparations by gel filtration or by precipitation with 21% (w/v) ammonium sulphate. When comparing toxoids purified by each of these methods, the method of gel filtration resulted in a somewhat higher degree of purity, suggesting that this method would be more suitable than the AS precipitation method for the purification of diphtheria toxoid.

Ammonium Sulfate↗
PubMed1981

Effect of orthostatic blood pressure changes upon capillary filtration-absorption rate in the human calf.

The effect of postural changes upon fluid filtration rate in the calf was studied in 3 healthy subjects placed in supine position. Volume changes in the calf were measured by a water plethysmograph. Relative changes in blood flow in subcutaneous tissue and anterior tibial muscle were measured by the local 133Xe washout technique. Lowering the calf from 5-25 cm caused a linear increase in filtration rate whereas blood flow in subcutaneous tissue of the segment studied and anterior tibial muscle remained constant. Based on this average CFC was about 0.0012 ml X min-1 X 100 g-1 X mmHg-1. Further lowering of the calf caused a decrease in blood flow in subcutaneous tissue and skeletal muscle by about 50% corresponding to an increase in total vascular resistance by about 100%. During these circumstances the increase in infiltration rate was reduced by about 33%. The resulted indicate that the local veno-anterior reflex responsible for the observed vasoconstriction in the tissue under study together with intrinsic vascular mechanisms reduces transcapillary fluid filtration in the lower position. The mechanism appears to be mainly due to a reduction of the increase in mean capillary pressure whereas CFC seems to remain almost constant.

Axons↗
PubMed2006

Effect of endurance training on muscle microvascular filtration capacity and vascular bed morphometry in the elderly.

AIM: Exercise training is a strong stimulus for vascular remodelling and could restore age-induced vascular alterations. The purpose of the study was to test the hypothesis that an increase in vascular bed filtration capacity would corroborate microvascular adaptation with training. METHODS: We quantified (1) microvascularization from vastus lateralis muscle biopsy to measure the capillary to fibre interface (LC/PF) and (2) the microvascular filtration capacity (K(f)) in lower limbs through a venous congestion plethysmography procedure. Twelve healthy older subjects (74 +/- 4 years) were submitted to a 14-week training programme during which lower-limbs were trained for endurance exercise. RESULTS: The training programme induced a significant increase in the aerobic exercise capacity of lower limbs (+11% V(O2peak); P < 0.05; +28% Citrate Synthase Activity; P < 0.01). K(f) was largely increased (4.3 +/- 0.9 10(-3) mL min(-1) mmHg(-1) 100 mL(-1) post-training vs. 2.4 +/- 0.8 pre-training, mean +/- SD; P < 0.05) and microvascularization developed as shown by the rise in LC/PF (0.29 +/- 0.06 post- vs. 0.23 +/- 0.06 pre-training; P < 0.05). Furthermore, K(f) and LC/PF were correlated (r = 0.65, P < 0.05). CONCLUSION: These results demonstrated the microvascular adaptation to endurance training in the elderly. The increase in K(f) with endurance training was probably related to a greater surface of exchange with an increased microvessel/fibre interface area. We conclude that measurement of the microvascular filtration rate reflects the change in the muscle exchange area and is influenced by exercise training.

Aged↗
PubMed1979

The ultrastructure of frog mesenteric capillaries of known filtration coefficient.

The capillaries of the frog mesentery were investigated by transmission electronmicroscopy. The mean diameter of these vessels was 20 micrometers and a single layer of five to six endothelial cells (on average) contributed to each circumference. Their ultrastructure was very similar to that of mammalian capillaries of the continuous type [Bennett, Luft and Hampton, 1959]. The endotherlial cells, which contained many vesicles, were joined by specialized junctions and surrounded by a continuous basement membrane. Eleven capillaries were examined after the filtration coefficient of their walls had been investigated by the microperfusion micro-occlusion technique of Michel, Mason, Curry and Tooke [1974]. No abnormal appearances were observed even after the vessels had been perfused with protein free solutions which have been shown to increase filtration coefficient five fold. No morphological differences between capillaries were seen to accompany large differences in the filtration coefficients.

Animals↗
PubMed1994

X-ray tube potential, filtration, and detector considerations in dual-energy chest radiography.

The effect of x-ray tube potential and prepatient and interdetector filtration in single exposure dual energy chest imaging has been studied employing a carefully benchmarked model. The analysis utilized published methodology. Noise in simulated lung and mediastinum fields of the aluminum (bone) and Lucite (soft tissue) images were studied at fixed entrance skin exposure (ESE) for commonly employed sandwich detector and sandwich imaging plate configurations. Our results indicate noise in the lung increases slowly with tube potential above 120 kVp, while noise in the mediastinum decreases rapidly. Also, at high tube potential (> or = 120 kVp) adding moderate amounts of prepatient K-edge filtration (approximately equal to 100 mg/cm2) while optimizing imaging conditions for the lung tends to decrease noise in the lungs by approximately equal to 30% while increasing noise in the mediastinum by a similar amount. Without K-edge prepatient filtration, noise in the lung is minimized with Cu interdetector filter weights near 400 mg/cm2. In the mediastinum noise is minimized with heavier interdetector filter and prepatient K-edge filter weights. Prepatient K-edge filter weights that minimize image noise in either field can increase the tube loading by factors ranging from 10 to 10(10). Systems designed with sandwich detectors using commercially available phosphors and coating weights can produce contrast-to-noise ratios (CNRs) as high as 50% of the theoretical limit (defined as an optimized system with a totally absorbing rear detector).

Humans↗
PubMed1977

Confirmation of the single-step membrane filtration procedure for estimating Pseudomonas aeruginosa densities in water.

The efficiency of two procedures, membrane filtration and most probable number, to resuscitate and enumerate Pseudomonas aeruginosa have been compared at two temperatures and varying incubation periods. Data indicate that the membrane filtration procedure using mPA or mPA medium B is more efficient than the most-probable-number procedure in estimating P. aeruginosa populations. It was also found that the specificity of the membrane filtration procedure was such that 92 to 99% of the colonies counted as P. aeruginosa were confirmed, whereas only 2.7 to 10% of the nontypical colonies were confirmed as P. aeruginosa. Furthermore, the data indicate that mPA medium B combined with a 3- to 4-day incubation period at 4.15 degrees C is slightly more specific than mPA medium and is a valid single-step procedure for the resuscitation and enumeration of P. aeruginosa from water or sewage effluent.

Culture Media↗
PubMed1979

Comparison of m-Endo LES, MacConkey, and Teepol media for membrane filtration counting of total coliform bacteria in water.

Total coliform counts obtained by means of standard membrane filtration techniques, using MacConkey agar, m-Endo LES agar, Teepol agar, and pads saturated with Teepol broth as growth media, were compared. Various combinations of these media were used in tests on 490 samples of river water and city wastewater after different stages of conventional purification and reclamation processes including lime treatment, and filtration, active carbon treatment, ozonation, and chlorination. Endo agar yielded the highest average counts for all these samples. Teepol agar generally had higher counts then Teepol broth, whereas MacConkey agar had the lowest average counts. Identification of 871 positive isolates showed that Aeromonas hydrophila was the species most commonly detected. Species of Escherichia, Citrobacter, Klebsiella, and Enterobacter represented 55% of isolates which conformed to the definition of total coliforms on Endo agar, 54% on Teepol agar, and 45% on MacConkey agar. Selection for species on the media differed considerably. Evaluation of these data and literature on alternative tests, including most probable number methods, indicated that the technique of choice for routine analysis of total coliform bacteria in drinking water is membrane filtration using m-Endo LES agar as growth medium without enrichment procedures or a cytochrome oxidase restriction.

Culture Media↗
PubMed1981

High Production of beta-Glucosidase in Schizophyllum commune: Isolation of the Enzyme and Effect of the Culture Filtrate on Cellulose Hydrolysis.

Optimization experiments with response surface statistical analysis were performed with Schizophyllum commune to obtain high beta-glucosidase yields. The factors in the optimization experiment were the concentrations of cellulose, peptone, and KH(2)PO(4). Their optimal values were 3.2, 3.0, and 0.2 g/100 ml, respectively. Enzyme assays revealed very high beta-glucosidase (22.2 U/ml) and cellobiase (68.9 U/ml) yields. The avicelase yield was low as compared with that from Trichoderma reesei. Mixtures of S. commune and T. reesei culture filtrates caused faster and more extensive saccharification of Avicel than could be achieved by either filtrate alone. A beta-glucosidase was isolated and purified from the optimized culture filtrate of S. commune. The electrophoretic mobility of the purified beta-glucosidase indicated a molecular weight of 97,000. The amino acid composition was similar to that of beta-glucosidase from T. reesei. The acidic (aspartate and glutamate) residues or their amides or both made up approximately 20% of the protein. The NH(2)-terminal amino acid of the enzyme was histidine.

Journal Article↗
PubMed1984

Response of marine bacterioplankton to differential filtration and confinement.

The bacterioplankton community of confined seawater at 25 degrees C changed significantly within 16 h of collection. Confinement increased CFU, total cell number (by epifluorescence microscopy), and average cell volume of bacterioplankton and increased the turnover rate of amino acids in seawater sampled at Frying Pan Shoals, N.C. The bacterioplankton community was characterized by two components: differential doubling times during confinement shifted dominance from bacteria which were nonculturable to bacteria which were culturable on a complex nutrient medium. Culturable cells (especially those of the genera Pseudomonas, Alcaligenes, and Acinetobacter) increased from 0.08% of the total cell number in the seawater immediately after collection to 13% at 16 h and 41% at 32 h of confinement. Differential filtration before confinement indicated that particles passing through a 3.9-microns-, but retained by a 0.2-micron-, pore-size Nuclepore filter may be a major source of primary amines to the confined population. The 3.0-microns filtration increased growth rate and ultimate numbers of culturable cells through the removal of bacterial predators or the release of primary amines from cells damaged during filtration or both.

Amines↗
PubMed1965

Filtration method for bacteriophage detection.

A filtration method has been developed which can be used to detect and enumerate phage in low concentrations directly from solution without the need for prior concentration. In this method, a known volume of the phage solution is mixed with a suitable host solution. Samples are filtered through membrane filters; the filter is removed and incubated, and after 24 hr the resultant plaques are counted and the titer is calculated. Escherichia coli B and the coliphage T2 were used in these studies. Host cultures less than 12 hr old produced the best results. Approximately 10(10) host organisms must be present in the sample taken for filtration. To avoid phage reproduction, all steps prior to filtration must be done in less than 45 min. The method was compared with the soft-agar technique and was shown to be less precise but able to measure phage in lower concentrations.

Bacteriophages↗
PubMed1976

Isolation of skin permeability factors from culture filtrates of Salmonella typhimurium.

Engerotoxins isolated from Vibrio cholerae and toxigenic Escherichia coli cause permeability alterations in rabbit skin. Firm induration and erythema are observed within 18 to 24 h, and visualization of the reaction may be enhanced by intravenous injection of Pontamine sky blue dye. Two skin permeability factors (PF) have been found in culture filtrates of Salmonella typhimurium. A rapid acting factor, produced optimally in brain heart infusion broth at 37 degrees C by numerous Salmonella species, has a critical bluing time of 1 h after completion of skin testing. This rapid PF is heat stable at 100 degrees C for at least 4 h and has no associated induration. The delayed factor is heat labile, being completly destroyed within 30 min at 75 degrees C and causes marked duration of the rabbit skin within 18 h that is indistinguishable from the permeability reactions of V. cholerae and E. coli enterotoxins. Induration produced by the delayed PF is observed only after chromatography of the culture filtrate on a Sephadex G-100 column. Thus, the effects of the delayed PF appear to be masked or blocked by an inhibitor-like substance present in crude culture filtrates. Both early and delayed factors are estimated to have a molecular weight of at least 90,000. It is postulated that one or both of these factors may participate in the pathogenesis of Salmonella infections.

Animals↗