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At least 37 records · Page 2Linked to original sources
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↗
PubMedDate not supplied

Evaluation of an immunoisolation membrane formed by incorporating a polyvinyl alcohol hydrogel within a microporous filter support.

An immunoisolation membrane formed by incorporating a high water content polyvinyl alcohol (PVA) hydrogel into a microporous polyether sulfone (PES) filter has been investigated in this study. The PVA hydrogel is formed in situ within the filter pores via glutaraldehyde (GA) crosslinking under acidic conditions. The tortuous nature of the microporous filter pores securely anchors the embedded hydrogel to provide excellent structural integrity. The high void fraction of the PES filter support (>80%) and high water content of the PVA hydrogel (>85% water by weight) allow excellent solute transport rates, while an appropriate level of glutaraldehyde crosslinking supplies the required molecular size selectivity. In vitro permeability measurements made with solutes covering a wide range of molecular sizes demonstrate high transport rates for small nutrient molecules with rapidly diminishing permeabilities above a molecular weight of approximately 1,000 Dalton. Implantation experiments show that the membrane properties are not deleteriously affected by prolonged in vivo exposure or common sterilization techniques. Thus, this hybrid hydrogel/filter membrane system offers a promising approach to the immunoisolation of implanted cells.

Animals↗
PubMed1996

Use of fluorochromes in the determination of chemotaxis and haptotaxis of granulocytes by micropore filter assays.

Most conventional assays for the in vitro measurement of polymorphonuclear leukocyte (PMN) migration are modifications of the Boyden chamber technique, which requires quantification of migrated cells on micropore filters. This quantification is accompanied by several disadvantages, comprising errors in direct cell counting, low sensitivity of turbidimetric methods, the loss of marker enzymes by activation of PMNs, or the use of radioactive isotopes. We set up an improved fluorometric method to measure chemotactic and haptotactic migration of PMNs using polycarbonate filter-bearing Transwell culture plate inserts. This improved fluorometric method allows the evaluation of effects of fluorescent-dye labeling on chemotaxis and haptotaxis - defined as cell migration due to cell surface- or matrix-bound gradients of chemoattractants - by collecting data in an automated system. Results were compared with data obtained from direct microscopic cell counting in Transwell experiments as well as in conventional 48-multiwell Boyden chamber assays. Calcein-AM and BCECF-AM proved to be fluorochromes with minimal effect on both types of PMN migration. We conclude that the fluorochromes are powerful tools for the analysis of PMN migration and allow modifications of chemotaxis/haptotaxis assays for automated quantification.

Chemotaxis↗
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↗
PubMed1984

Comparison of microporous filters for concentration of viruses from wastewater.

The 1-MDS Virosorb filter and the 50S and 30S Zeta-plus filters, all with a net positive charge, were compared with the negatively charged Filterite filter for concentration of naturally occurring coliphages and animal viruses from sewage effluent. When Filterite filters were used, the effluent was adjusted to pH 3.5 and AlCl3 was added before filtration to facilitate virus adsorption. No adjustment was required with the positively charged filters. Sets of each filter type were eluted with 3% beef extract (pH 9.5) or eluted with 0.05 M glycine (pH 11.5). A maximum volume of 19 liters could be passed through 142-mm diameter Filterite filters before clogging, whereas only 11, 11, and 15 liters could be passed through the 1-MDS, 50S, and 30S filters, respectively. For equal volumes passed through the filters, coliphage recoveries were 14, 15, 18, and 37% in primary effluent and 40, 97, 50, and 46% in secondary effluent for the Filterite , 1-MDS, 50S, and 30S filters, respectively. No statistically significant difference was observed in the recovery of animal viruses among the filters from secondary effluent, whereas in the Filterite and 50S filters, higher numbers of viruses from primary effluent were recovered than in the 1-MDS and 30S filters in two of three collections. Glycine was found to be a less-efficient eluent than beef extract in the recovery of naturally occurring viruses.

Animals↗
PubMed1988

Effects of preparative procedures and of cell activation on flow of white cells through micropore filters.

Using newly developed filtration techniques to analyse the flow resistance of white blood cells (WBC), the effects of preparative procedures and of various treatments (including activation) have been tested. Flow rates of WBC were measured using both 5 and 8 micron pore filters. It was found that EDTA was the anticoagulant of choice over heparin and sodium citrate, and that calcium-containing media should be avoided because they promoted cell-cell aggregation. Exposure to density separation media did not significantly alter filtration rates, but storage of prepared WBC for even 1 h caused deterioration in flow. Storage of whole blood before preparation of the WBC had a much lesser effect. Storage appeared to be linked to cell activation, and use of the activating agents phorbol ester (PE, 4.5 x 10(6) M/l) and f-methyl-leucyl-phenylalanine (FMPL, 10(-7) and 10(-9) M/l) also increased WBC resistance to pore transit. The effect of PE was greater, causing rapid pore blockage, but was non-specific, while the lesser effect of FMLP was restricted to granulocytes and was concentration dependent. Cell volume was increased by these agents, but measurement of the filterability of hypotonically swollen granulocytes showed that volume changes alone only partly explained the activation effects. These results suggest that activation in vivo would have a significant rheological effect, detectable by filtration methods.

Anticoagulants↗
PubMed1984

Influence of water quality on enteric virus concentration by microporous filter methods.

Four enteric viruses, poliovirus type 1, echovirus type 1, reovirus type 3, and simian adenovirus SV-11, were concentrated from seeded 1.3-liter volumes of raw, finished, and granular activated carbon-treated waters by adsorption to 47-mm-diameter (17 cm2), electropositive ( Virosorb 1MDS ) filters at pH 7.5 or electronegative ( Filterite ) filters at pH 3.5 with and without 5 mM added MgCl2, followed by elution with 0.3% beef extract in 50 mM glycine at pH 9.5. Removal of particulates from raw and finished waters by 0.2-micron prefiltration before virus addition and pH adjustment had little effect on virus concentration efficiencies. Soluble organic compounds reduced virus adsorption efficiencies from both raw and finished waters compared with granular activated carbon-treated water, but the extent of interference varied with virus type and adsorption conditions. For electropositive 1MDS filters, organic interference was similar with all virus types. For Filterite filters, organic interference was evident with poliovirus and echovirus, but could be overcome by adding MgCl2. Reovirus and SV-11 were not adversely affected by organics during adsorption to Filterite filters. Elution of reovirus and adenovirus was inefficient compared with that of poliovirus and echovirus. None of the three adsorption schemes ( 1MDS at pH 7.5 and Filterite with and without 5 mM MgCl2 at pH 3.5) could be judged superior for all viruses and water types tested.

Adenoviridae↗
PubMed1999

[Development of air microbe sampler with micropore filter membrane].

Dual head air microbe sampler with a large flow capacity of 100 liters per minute was manufactured. The sampler possesses simple structures, light weight, convenient operation and higher sampling efficiency, equal to 77%-96% of the grade six Anderson sampler. Sampling time is a main factor affecting sampling efficiency. This device is suitable for the determination of degree of biological clean air in clean environment and the detection of the pathogenic microbes in ward and public places and also microbes in ordinary environment.

Air Microbiology↗
PubMed1980

Simple method for the concentration of influenza virus from allantoic fluid on microporous filters.

Membrane filter adsorption-elution is an efficient method for concentration and partial purification of several types of viruses from various aqueous solutions. For efficient virus adsorption to negatively charged filters, the sample is adjusted to pH 3.5 and trivalent salts are added before filtration. Since influenza virus is sensitive to extremes in pH, it cannot be concentrated by ordinary filters. Zeta Plus filters, which have a net positive charge of up to 5 or 6, were evaluated for the concentration of influenza virus from infectious allantoic fluids. Influenza virus efficiently adsorbed to Zeta Plus filters at pH 6, and addition of salts was not necessary. Adsorbed virus was eluted in a small volume of 2% bovine serum albumin plus 1 M NaCl at pH 10. By this procedure, viruses in 100 ml of allantoic fluid were concentrated to a final volume of 8 ml, with an average recovery efficiency of 71.0%.

Adsorption↗
PubMed1988

Methods and theory for analysis of flow of white cell subpopulations through micropore filters.

Methods have been developed for analysing the resistance of WBC to flow, by measuring their transit rates through 5 and 8 microns pore filters at constant pressure. Unfractionated WBC and separated subpopulations have been compared. For either pore size, lymphocytes exhibited least resistance to flow, followed by granulocytes, with monocytes being most resistant. A theoretical model, which represents WBC suspensions as made up of three particle types (a relatively fast and a relatively slow population, plus a pore blocking population) adequately describes the data for flow rate versus volume filtered. For 5 microns pores, this theory indicates that a majority of WBC have transit times approximately less than 0.5 s. Unfractionated and mixed mononuclear samples contained a proportion of particles with transit times an order of magnitude longer, whereas, for granulocytes, no slow flowing population was evident. Removal of monocytes by plating out, reduced the proportion of the slow particles in the mononuclear preparation. Unique values for transit times could not be determined for 8 microns pores, but it could be concluded that the great majority of WBC made a very quick transit, with the flow becoming dominated by a small number of much more resistant cells. Simple flow parameters (initial relative flow rate and slow particle resistance) are described which characterize these two populations. Both 5 and 8 microns pore data indicated that few cells became permanently trapped within pores.

Granulocytes↗