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At least 19 recordsLinked to original sources
PubMed1979

Concentration of poliovirus from tap water using positively charged microporous filters.

Microporous filters that are more electropositive than the negatively charged filters currently used for virus concentrations from water by filter adsorption-elution methods were evaluated for poliovirus recovery from tap water. Zeta Plus filters composed of diatomaceous earth-cellulose-"charge-modified" resin mixtures and having a net positive charge of up to pH 5 to 6 efficiently adsorbed poliovirus from tap water at ambient pH levels 7.0 to 7.5 without added multivalent cation salts. The adsorbed virus were eluted with glycine-NaOH, pH 9.5 to 11.5. Electropositive asbestos-cellulose filters efficiently adsorbed poliovirus from tap water without added multivalent cation salts between pH 3.5 and 9.0, and the absorbed viruses could be eluted with 3% beef extract, pH 9, but not with pH 9.5 to 11.5 glycine-NaOH. Under water quality conditions in which poliovirus recoveries from large volumes of water were less than 5% with conventional negatively charged filters and standard methods, recoveries with Zeta Plus filters averaged 64 and 22.5% for one- and two-stage concentration procedures, respectively. Electropositive filters appear to offer distinct advantages over conventional negatively charged filters for concentrating enteric viruses from water, and their behavior tends to confirm the importance of electrostatic forces in virus recovery from water by microporous filter adsorption-elution methods.

Adsorption↗
PubMed1980

Rapid concentration of bacteriophages from large volumes of freshwater: evaluation of positively charged, microporous filters.

Microporous, positively charged Zeta Plus 60 S filters were evaluated for bacteriophage recovery from large volumes of natural water. A variety of phages adsorbed efficiently to the filter medium at water pH levels below neutrality, but adsorption was reduced above pH 7. Adsorbed phages were easily eluted with an arginine/1% beef extract solution, pH 9.0. A concentration procedure suitable for the field isolation of bacteriophages from large volumes of river water was devised. The procedure involves, (1) prefiltration through 10" cartridge depth filters, (2) adjustment of water pH to pH 5.5--6.0, (3) adsorption of the phages on to Zeta Plus 60 S filters, (4) elution of bound phage in a small volume of eluent, (5) secondary concentration by ultrafiltration of the resulting eluates. Using this procedure, bacteriophages in 65 1 of river water was concentrated to 35 ml with recoveries in the range 50--60%.

Adsorption↗
PubMed1983

Simplified micropore filter assay of neutrophil migration using whole blood.

A new method of micropore filter assay of neutrophil migration requiring only 0.1 ml of whole blood is described and compared with the standard separated polymorphonuclear neutrophil micropore filter assay. Whole blood was added to the upper compartment of a modified Boyden chemotactic chamber, and the neutrophils were allowed to migrate into a cellulose nitrate micropore filter. Acetic acid was used to remove erythrocytes and hemoglobin from the filter. Neutrophil chemotaxis was performed with cells from 19 neonates and 34 adults. The mean neonatal PMN migration was 40% of the adult value (48.1 +/- 12.6 vs 96.8 +/- 16.8 micron) with the whole blood assay and 39% of the adult value (44.7 +/- 10.1 vs 72.9 +/- 22.2 micron) with the separated polymorphonuclear neutrophil assay. The whole blood micropore filter assay, a simple and reliable method of determining neutrophil migration, is especially useful in studying patients when there are difficulties in obtaining large blood samples, such as with neonates and young children.

Cells, Cultured↗
PubMed1988

Novel approach for modifying microporous filters for virus concentration from water.

Electronegative microporous filters composed of epoxyfiberglass (Filterite) were treated with cationic polymers to enhance their virus-adsorbing properties. This novel and inexpensive approach to microporous filter modification entails soaking filters in an aqueous solution of a cationic polymer such as polyethyleneimine (PEI) for 2 h at room temperature and then allowing the filters to air dry overnight on absorbent paper towels. PEI-treated filters were evaluated for coliphage (MS2, T2, and phi X174) and enterovirus (poliovirus type 1 and coxsackievirus type B5) adsorption from buffer at pH 3.5 to 9.0 and for indigenous coliphages from unchlorinated secondary effluent at ambient pH. Adsorbed viruses were recovered with 3% beef extract (pH 9). Several other cationic polymers were used to modify epoxyfiberglass filters and were evaluated for their ability to concentrate viruses from water. Zeta potentials of disrupted filter material indicated that electronegative epoxyfiberglass filters were made more electropositive when treated with cationic polymers. In general, epoxyfiberglass filters treated with cationic polymers were found to adsorb a greater percentage of coliphages and enteroviruses than were untreated filters.

Coliphages↗
PubMed1987

Characterization of retinal pigment epithelial cells cultured on microporous filters.

Retinal pigment epithelium (RPE) cultured on microporous filter supports was compared to RPE cultured on plastic and evaluated for features characteristic of RPE in vivo. RPE cells grown on filters were cuboidal, formed junctional complex structures between cells, and had elaborate microvilli and basal infoldings similar to RPE in vivo, while RPE grown on plastic also formed intercellular junctions but appeared squamous and had few microvilli and basal infoldings. RPE grown on filters or plastic secreted an extracellular matrix at the basal surface and ingested isolated rat rod outer segments at the apical surface. RPE grown on filters coated with laminin or fibronectin became confluent more rapidly than RPE grown on uncoated filters, while RPE grown at the same density on filters coated with collagen type I did not become confluent. The laminin and fibronectin coatings did not alter the RPE cell morphology; however, cells seeded on collagen-coated filters grew in large disorganized clusters. RPE grown on laminin-coated filters formed functional tight junctions as evidenced by the capacity of RPE monolayers to prevent the bulk flow of medium and the passage of trypan blue across the filter. Radiolabeled sucrose and inulin were used to measure the paracellular flux through the tight junctions between cells. The passage of these tracers was linear over time, with the lower molecular weight tracer, sucrose, passing through the monolayer more readily than inulin. Values for the flux of radiolabeled bovine serum albumin across RPE monolayers fell between values for sucrose and inulin. The results from these studies show that RPE monolayers cultured on laminin-coated filters maintain a morphology similar to that of RPE in vivo, are capable of ingesting rod outer segments, and form a selectively permeable barrier to various tracers. This culture system should be useful for studies of transepithelial transport, secretion, endocytosis and exocytosis that require independent control of the extracellular environment at the apical and basolateral cell surfaces.

Animals↗
PubMed1985

Effects of bentonite clay solids on poliovirus concentration from water by microporous filter methods.

To determine whether suspended solids interfere with enteric virus recovery from water by microporous filter methods, the effects of bentonite clay solids at a concentration of 10 nephelometric turbidity units on the recovery of poliovirus type 1 from seeded, activated carbon-treated, filtered tap water were studied. Volumes (500 ml) of virus-laden water at pH 5.5 or 7.5, with and without 50 mM MgCl2, were filtered through 47-mm-diameter, electropositive (Virosorb 1MDS) and electronegative (Filterite) filters that had been pretreated with Tween 80 to minimize direct virus adsorption to filter surfaces. Bentonite solids enhanced virus retention on both types of filters, even under conditions in which viruses were not solids associated. However, bentonite solids also interfered with elution of retained viruses when eluting with 0.3% beef extract-50 mM glycine (pH 9.5). Under some conditions, overall virus recoveries were lower from water with bentonite solids than from solids-free control water. The results of this study indicate that clay turbidity can interfere somewhat with virus recovery by current microporous filter methods.

Adsorption↗
PubMed1981

Neutrophil-endothelial cell interactions on endothelial monolayers grown on micropore filters.

We have developed a technique for growing endothelial monolayers on micropore filters. These monolayers demonstrate confluence by phase and electron microscopy and provide a functional barrier to passage of radiolabeled albumin. Neutrophils readily penetrate the monolayer in response to chemotaxin, whereas there is little movement in the absence of chemotaxin. This system offers unique advantages over available chemotaxis assays and may have wider applications in the study of endothelial function.

Blood Vessels↗
PubMed1985

Micropore filters for sterile filtration may leach toxic compounds affecting cell cultures (HL 60).

Reduction in HL-60 cell growth could be traced unexpectedly to sterile filtration procedures. To circumvent this problem, 11 available brands of micropore filters (five prepacked and six to be packed and autoclaved) were investigated with the aim of finding the least toxic product. Samples of 10 ml of RPMI 1640 medium with 10% fetal calf serum added were filtered through four filters of each brand to detect even small amounts of leached toxic compounds. HL-60 cells were cultured in these filtered media for three days and the results compared with cultures using unfiltered medium. A large variation in growth inhibition was found between the filters investigated, ranging from 0% to about 90%. The growth inhibition was due to leaching of toxic compounds, as revealed by viability test, reseeding, and direct microscopy. Adsorption of essential proteins to the micropore filters was found for only one of the filters investigated in this study.

Cell Survival↗
PubMed1989

Further studies on the flow of aqueous humor through microporous filters.

It has recently been shown that aqueous humor is able to obstruct flow through Nuclepore polycarbonate filters having flow dimensions similar to those found in the juxtacanalicular tissue (JCT). We undertook studies designed to identify the component(s) of aqueous humor responsible for this obstruction and to determine the mechanism of blockage. We conclude that aqueous humor contains two components (one of which is specific to aqueous) which, when simultaneously present, hydrophobically bind to microporous filters and lead to filter blockage. Some implications for aqueous humor flow through the JCT are briefly discussed.

Animals↗
PubMed1974

Recovery of poliovirus from turbid estuarine water on microporous filters by the use of celite.

The application of a new step for recovering poliovirus from moderately to highly turbid estuarine water by the filter virus-adsorption technique was investigated. The experiments were conducted under both (i) laboratory-based conditions (200-ml volumes) where the turbidity was controlled and (ii) simulated field conditions (15- to 100-gal volumes) where the turbidity varied depending upon the hydrology of the raw estuarine water. The new step consisted of adding Celite to the turbid water prior to sampling for virus. In the experiments, the pH of the water was first adjusted to 3.5 and then AlCl(3) was added to 0.0005 M. Celite was added to a concentration of 0.01% and mixed thoroughly. Either an HE Cox M-780 microfilter (Cox Instrument, Div. of Lynch Corp., Detroit, Mich.) or an MF-membrane filter (Millipore Corp., Bedford, Mass.) was used as the virus adsorbent. Virus was eluted from the Celite-filter complex in situ at pH 9 with 5x nutrient broth. In the laboratory-based experiments, when turbidity ranged from 5.0 to 30.0 Jackson turbidity units (JTU), virus recovery ranged from 66 to 89%. In the simulated field experiments, when the turbidity ranged from 8.5 to 80.0 JTU, virus recovery ranged from <1 to 74%, depending upon the multiplicity of virus input and the level of turbidity. The new step greatly improved the filtration-flux of turbid water and significantly reduced the premature clogging problem usually observed with microporous filters.

Adsorption↗
PubMed1979

A rapid, semi-automated procedure for the evaluation of leukocyte locomotion in the micropore filter assay.

A commerically available bacterial colony counter has been modified to allow rapid, accurate, semi-automated evaluation of cell numbers in the micropore filter assay for chemotaxis. The method is valuable for objective, rapid evaluation of cell counts at various levels through the filter, as well as counts on the distal surface of the filter. Coupled with a programmable calculator, this instrument had made feasible a new method of assessing random migration by the regression line analysis, which discriminates between migration rate and mass migration of cells. This combination of equipment may thus serve as a considerable time saving accessory to laboratories engaged in cell locomotion research, but also will allow more rigorous assessment of differences among specific populations of cells.

Analysis of Variance↗
PubMed1991

The effect of micropore filters on the aspiration test in epidural analgesia.

Continuous epidural analgesia may be complicated by intravascular or subarachnoid injection of local analgesic, with disastrous consequences. One of the techniques described to prevent these complications is the aspiration test. It is the current standard of practice to employ a micropore bacterial filter for epidural infusions. We present an in vitro study of nine commercially available bacterial filters to determine whether or not the aspiration test could be reliably performed through them. Eight of the nine filters (except the Perifix, Braun) were found to be unreliable if air and liquid were both present in the system (air lock). The role of the aspiration test and the use of micropore filters in epidural analgesia are discussed, as are the implications and possible solutions in practice of this cause of failure of the test.

Analgesia, Epidural↗
PubMed1975

Comparative study of four microporous filters for concentrating viruses from drinking water.

Four microporous virus-absorbent filter media for recovering low levels of virus from 380 liters of drinking water were compared. In addition two of the filter media were compared with 1,900 liters of drinking water. The filter media evaluated were MF nitrocellulose membranes (293 mm), AA Cox M-780 epoxy-fiberglass-asbestos disks (267 mm), K-27 yarn-wound fiberglass cartridges + AA Cox M-780 disks (127 mm), and Balston epoxy-fiberglass tubes (24.5 by 63.5 mm). The filters were used to concentrate seeded poliovirus from 380 liters of finished drinking water. Sodium thiosulfate was added to the drinking water to neutralize chlorine, and hydrochloric acid was added to adjust the pH to 3.5. Virus was eluted from the filters with glycine-NaOH buffer at pH 11.5. In terms of virus recovery efficiency, the filter media ranked Balston greater than Cox 267-mm greater than MF 293-mm congruent to K-27 + Cox 127-mm, but differences were slight. The Balston filters and holders were also superior to the other systems in terms of size, weight, cost, and handling factors. Experiments with 2- and 8-mum porosity Balston filters showed no statistically significant difference in virus recovery. Virus was readily detected by the Balston and the MF 293-mm systems at input levels of 12 to 22 PFU/1,900 liters. Preliminary experiments indicated that an elution pH lower than 11.5 may be satisfactory.

Asbestos↗
PubMed1990

The influence of different flow velocities on tumor cell survival in micropore filters.

Earlier studies have shown a lower degree of lodgement and early survival of tumor cells in muscle than in liver after infusion via the femoral artery and portal vein, respectively. A possible explanation to this difference might be that the tumor cells are mechanically destroyed, and thus die more rapidly in muscle because they enter this capillary network at a much higher flow velocity. In the present study, the effect on early tumor cell (rat fibrosarcoma) survival of a high and a low flow velocity/deformation rate was evaluated in micropore (5 microns) filters, using isotope (Cr51) technique. These experiments were combined with scanning electron microscopic (SEM) analyses. The filter experiments showed no significant differences in the rate of cell death in the filters between tumor cells subjected to high or low deformation rates, and there were no qualitative differences in tumor cell appearance in the SEM study. It is, therefore, concluded that the difference in tumor cell lodgement and survival between muscle and liver is not primarily caused by differences in the rate of cell deformation upon entry of the organ capillary network.

Animals↗
PubMed1990

Embryotoxicity of micropore filters used in liquid sterilization.

Microfiltration is the usual method of sterilization of tissue culture media. The filtrates of eight commercial filters were tested for embryotoxicity using mouse embryo growth. Four of five disk filters tested showed embryo-toxicity in the first 5 ml of filtrate and the three larger-capacity filters showed embryotoxicity for up to the first 10 ml of filtrate. The ethylene oxide-sterilized filters appeared to give poorer results than the gamma-irradiated filters. The importance of discarding the initial filtrate or preflushing such filters before use is emphasized.

Animals↗