Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “FILTRATION”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 307 records · Page 17Linked to original sources
PubMed1998

Identification and characterization of a 29-kilodalton protein from Mycobacterium tuberculosis culture filtrate recognized by mouse memory effector cells.

Culture filtrate proteins from Mycobacterium tuberculosis induce protective immunity in various animal models of tuberculosis. Two molecular mass regions (6 to 10 kDa and 24 to 36 kDa) of short-term culture filtrate are preferentially recognized by Th1 cells in animal models as well as by patients with minimal disease. In the present study, the 24- to 36-kDa region has been studied, and the T-cell reactivity has been mapped in detail. Monoclonal antibodies were generated, and one monoclonal antibody, HYB 71-2, with reactivity against a 29-kDa antigen located in the highly reactive region below the antigen 85 complex was selected. The 29-kDa antigen (CFP29) was purified from M. tuberculosis short-term culture filtrate by thiophilic adsorption chromatography, anion-exchange chromatography, and gel filtration. In its native form, CFP29 forms a polymer with a high molecular mass. CFP29 was mapped in two-dimensional electrophoresis gels as three distinct spots just below the antigen 85 complex component MPT59. CFP29 is present in both culture filtrate and the membrane fraction from M. tuberculosis, suggesting that this antigen is released from the envelope to culture filtrate during growth. Determination of the N-terminal amino acid sequence allowed cloning and sequencing of the cfp29 gene. The nucleotide sequence showed 62% identity to the bacteriocin Linocin from Brevibacterium linens. Purified recombinant histidine-tagged CFP29 and native CFP29 had similar T-cell stimulatory properties, and they both elicited the release of high levels of gamma interferon from mouse memory effector cells isolated during the recall of protective immunity to tuberculosis. Interspecies analysis by immunoblotting and PCR demonstrated that CFP29 is widely distributed in mycobacterial species.

Amino Acid Sequence↗
PubMed2002

Characterization of a cytotoxic factor in culture filtrates of Serratia marcescens.

Serratia marcescens culture filtrates have been reported to be cytotoxic to mammalian cells. Using biochemical and genetic approaches, we have identified a major source of this cytotoxic activity. Both heat and protease treatments abrogated the cytotoxicity of S. marcescens culture filtrates towards HeLa cells, suggesting the involvement of one or more protein factors. A screen for in vitro cytotoxic activity revealed that S. marcescens mutant strains that are deficient in production of a 56-kDa metalloprotease are significantly less cytotoxic to mammalian cells. Cytotoxicity was significantly reduced when culture filtrates prepared from wild-type strains were pretreated with either EDTA or 1,10-phenanthroline, which are potent inhibitors of the 56-kDa metalloprotease. Furthermore, cytotoxic activity was restored when the same culture filtrates were incubated with zinc divalent cations, which are essential for enzymatic activity of the 56-kDa metalloprotease. Finally, recombinant expression of the S. marcescens 56-kDa metalloprotease conferred a cytotoxic phenotype on the culture filtrates of a nonpathogenic Escherichia coli strain. Collectively, these data suggest that the 56-kDa metalloprotease contributes significantly to the in vitro cytotoxic activity commonly observed in S. marcescens culture filtrates.

Bacterial Toxins↗
PubMed2006

Sex-related effects on venous compliance and capillary filtration in the lower limb.

Recent studies in humans have suggested sex differences in venous compliance of the lower limb, with lower compliance in women. Capillary fluid filtration could, however, be a confounder in the evaluation of venous compliance. The venous capacitance and capillary filtration response in the calves of 12 women (23.2 +/- 0.5 years) and 16 men (22.9 +/- 0.5 years) were studied during 8 min lower body negative pressure (LBNP) of 11, 22, and 44 mmHg. Calf venous compliance is dependent on pressure and was determined using the first derivative of a quadratic regression equation that described the capacitance-pressure relationship [compliance = beta1 + (2 x beta2 x transmural pressure)]. We found a lower venous compliance in women at low transmural pressures, and the venous capacitance in men was increased (P < 0.05). However, the difference in compliance between sexes was reduced and not seen at higher transmural pressures. Net capillary fluid filtration and capillary filtration coefficient (CFC) were greater in women than in men during LBNP (P < 0.05). Furthermore, calf volume increase (capacitance response + total capillary filtration) during LBNP was equivalent in both sexes. When total capillary filtration was not subtracted from the calf capacitance response in the calculation of venous compliance, the sex differences disappeared, emphasizing that venous compliance measurement should be corrected for the contribution of CFC.

Adult↗
PubMed2005

Determining the subunit structure of phosphodiesterases using gel filtration and sucrose density gradient centrifugation.

Size-exclusion chromatography (gel filtration) is a widely used method to determine the molecular weight of a protein. Often, the elution volume of several standard proteins is plotted against their known molecular weight to generate a standard curve, which is then used to determine the molecular weight of the protein of interest by its elution volume. However, gel filtration does not measure the mass of a particle as such, but the Stokes radius (Rs), a property dependent on mass, shape, and hydration of a protein. Thus, this method works well only if the protein of interest has a spherical symmetrical shape and an average hydration level. For all other proteins, the use of gel filtration as the sole means to determine the molecular weight will be misleading. The molecular weight of any given protein can be calculated, however, using the method of Siegel and Monty. This method combines Stokes radii obtained from gel filtrations and sedimentation coefficients derived from density gradient centrifugations to calculate the mass of a protein independently of its shape or hydration. It has been shown previously that PDE4D3, a representative of the long PDE4 splice forms, behaves as a dimer, whereas PDE4D2, a prototype of the short PDE4 splice forms, is a monomer. Both proteins exhibit an anomalous behavior on gel filtration columns. For this reason, they are used in this study to demonstrate the necessity of performing both gel filtration and density gradient centrifugation to determine the molecular weight of a protein.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1990

The effect of whole ejaculate filtration on the morphology and the fertility of bovine semen.

A Sephadex G-15 filtration method was developed to remove abnormal and nonmotile bull sperm from an entire ejaculate. The efficiency of filtration was determined by adding freeze-killed sperm to the ejaculate or using ejaculates with elevated numbers of abnormal cells induced by scrotal insulation. A fertility trial, using split ejaculates, compared fertility of filtered and unfiltered semen. After filtration, samples with 0, 25, and 50% killed cells added contained 77 to 81% motile cells. Addition of 75% killed sperm resulted in significant decrease (52%) of motile cells following filtration. Morphologic examination of semen with elevated numbers of abnormal cells revealed higher percentages of sperm with normal shaped heads and normal or swollen acrosomes after filtration than in unfiltered samples. Percentage of pear-shaped heads, lifted acrosomes, and bent tails decreased after filtration. Six high fertility and six low fertility bulls were used to evaluate fertility of filtered semen. Filtering increased motile sperm from 51 to 57% and from 36 to 50% for the high and low fertility bulls, respectively. The 60- to 90-d nonreturn rates for high fertility bulls were not increased by filtering (73 vs. 72%). However, filtering significantly improved the nonreturn rates for the low fertility bulls (61 vs. 67%).

Animals↗
PubMed2005

[Response to laser iridotomy in Hispanic and Caucasian patients with narrow, occludable filtration angles].

PURPOSE: Laser iridotomy (LI) is the standard procedure to relieve relative pupillary block in patients with narrow occludable filtration angles. We have observed a difference in response to this procedure in declared Hispanic and Caucasian patients. In this study an attempt is made to compare the effectiveness of an LI in this two ethnic groups. MATERIAL AND METHODS: In a prospective study an LI was performed in 21 (42 eyes) Hispanic and 14 (23 eyes) Caucasian patients with narrow, occludable filtration angles. A standard clinical examination along with evaluation of the filtration angles (goniscopy and/or ultrasound biomicroscopy) was performed in each patient before and after the LI. RESULTS: Age range for Hispanic patients was 47 to 83 (mean 66) years, 37 to 76 (mean 57) years in Caucasians. Non-occludable filtration angles following LI were observed and documented in 17/36 eyes (47.2%) of Hispanic and 17/23 eyes (73.9%) of Caucasian patients. Those with plasteau iris syndrome were similarly compared: 2/4 eyes (50.0%) in Hispanics and 9/12 eyes (75.0%) in Caucasians were non-occludable after LI. The remaining patients with occludable filtration angles form causes other than plateau iris, responded positively to LI in 15/32 eyes (46.9%) in the Hispanic cohort, and 8/11 eyes (72.7%) in the Caucasian. CONCLUSIONS: Non-occludable filtration angles following LI are achieved more frequently in Caucasians when compared with Hispanics.

Adult↗
PubMed2005

[Observation on effect of double filtration plasmapheresis on patients with active rheumatoid arthritis in active stage].

OBJECTIVE: To investigate the effect of filtration plasmapheresis (DFPP) on blood contents of rheumatoid factor (RF), C reactive protein (CRP), and erythrocyte sedimentation rate (ESR) in patients with rheumatoid arthritis (RA) in active stage, and to appraise the therapeutic effect of DFPP on RA. METHODS: The changes in contents of blood RF, CRP, ESR before and after DFPP were compared. The treatment was given for 2-3 times, and the activity of RA and the appearance of filtrate plasma were compared before and after the treatment. RESULTS: There were dramatic reductions of the levels of RF, CRP, ESR after single DFPP by 22.55%, 57.08% and 50.48%, respectively, compared with those before the treatment (all P<0.001). The color of the filtrate was green in RA in active stage. The cases with dark green filtrate had higher active indexes (pain, tenderness, swelling) and blood contents of CRP and ESR than those with green or yellow-green ones (all P<0.001). CONCLUSION: DFPP can remarkably reduce the level of RF, CRP, ESR of blood. The filtrate of RA in active stage appeared green. There is a relationship between the activity of RA and the color of filtrates.

Adult↗
PubMed1988

[Comparative characterization of the morphologic changes induced by the cytotoxic action of a filtrate of Clostridium difficile strain B in cell cultures].

Investigations carried out by the authors have demonstrated the possibility of the simultaneous evaluation of the results of the quantitative and qualitative characterization of the cytotoxic action of the filtrate of C. difficile strain B in the cultures of diploid human cells and cells Fl. The action of the filtrate used in the same dilution (1:1,000) over equal incubation periods (15 minutes) has resulted in the appearance of different morphological changes in each of these cultures. The degree of the manifestation of the cytotoxic action of the filtrate and the consequences of this action depend not only on the dose of the filtrate and the duration of the contact, but also on the kind of cell cultures used in the experiment. The 15-minute contact of human diploid cell culture with the filtrate leads to irreversible lesions of the cells. The rounding of cells Fl, observed during the first 15 minutes of the action of the filtrate, is not fatal for them; in the overwhelming majority of these cells the capacity for proliferation restores at the expiration of a certain period (about 3 weeks), and their adhesive properties increase.

Cell Survival↗
PubMed1977

[Comparative characteristics of cell-free filtrates of Shigella flexneri of different virulence].

It was shown for the first time that the virulent Sh. flexneri strain grown on Luria broth differed from the avirulent one by the yield of readily released surface-located complexes--lipopolysaccharide (determined by rhamnose) and protein into the filtrate. There was no distinct correlation between the strain virulence and the content of rhamnose-determined lipopolysaccharide in the filtrate; growing bacteria in the presence of Ca and Mg ions had no significant influence on the lipopolysaccharide release into the filtrate. Protein release into the cell-free filtrate was thrice that in the virulent shigella strain than in the avirulent one. When bacteria were grown in the presence of Ca ions protein release from the virulent strain increased 1.5-fold and changed but little in the avirulent culture. Cell-free filtrates of the virulent strain produced toxic action on L tissue culture cells; in conjunctival infection of guinea pigs they caused some reduction of the LD50 of the virulent strain and sharply aggravated the course of the infectious process. Heating of the filtrate at 100 degrees C for 15 min decreased their toxic action on L cells. The data obtained indicated that the active biological factor revealed in the virulent strain of Sh. flexneri was protein or its derivative.

Animals↗
PubMed1987

Transmembrane pressures generated by filtrate line suction maneuvers and predilution fluid replacement during in vitro continuous arteriovenous hemofiltration.

A recirculating in vitro CAVH system was designed which generated pulsatile blood and filtrate flows. Monitors recorded hydrostatic pressures simultaneously in the arterial, venous and filtrate lines during varying plasma or blood flow rates and predilution (vs postdilution) replacement fluid flow rates. Similar hydrostatic pressure monitoring was carried out during multiple maneuvers to generate suction on the filtrate side of the hemofilter (Amicon D-20's and Renaflo's). With a plasma flow (Qp) of 100 cc/min and predilution replacement fluid infusion rate of 500 cc/hr, the arterial pressure was 5% greater than during postdilution (p less than 0.05). With a blood flow (Qb) of 50 cc/min, predilution fluid replacement rates of 500 and 1000 cc/hr, and vacuum suction applied to the filtrate compartment, the arterial pressure was 33% lower than during postdilution fluid replacement (p less than 0.03). Nonetheless, the ultrafiltration rate (UFR) was 10 to 30% higher (p less than 0.03). At many other combinations of Qp, Qb and replacement rates and modes, there were no significant changes in arterial pressure. Despite these arterial pressure changes, greater than 70% of the transmembrane hydrostatic pressure (TMP) was due to the negative pressure induced by filtrate suction (gravity, Gomco, wall suction, IMED). The actual pressure in the filtrate compartment measured during Gomco or wall suction was 3/4 of that stated by their gauges, presumably due to leakage. Maximum wall suction never generated TMP's greater than 150 mmHg.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood↗
PubMed1983

[Evaluation of age-related changes of erythrocyte filtration].

In two groups of subjects (young and elderly), the red blood cell (RBC) deformability was examined determining the filtration time by means of two different methods (filtration of whole blood and filtration of RBC suspension with hematocrit adjusted at 20%, respectively). In addition, the DFE (Debit de filtration erythrocytaire), an indirect index of capillary blood flow, was mathematically derived. Since the filtration times appear to be positively correlated with age, it is conceivable that in the elderly, erythrocytes are less deformable than in the young, and that this change may impair both capillary blood flow and tissue oxygen delivery; this alteration is further emphasized when the relationship between whole blood filtration time and hematocrit is taken into account.

Adult↗
PubMedDate not supplied

Viscous filtration of red blood cell suspensions.

Filtration experiments on red blood cell suspensions are usually conducted in a saline buffer solution. As a result, the flow of a particle in a pore is largely dominated by viscous effects, and it is not possible to distinguish between normal and membrane altered cells. A new approach to red cell filtration is proposed here, whereby the cells are suspended in a Dextran solution that has roughly the same viscosity as the internal hemoglobin solution. It is thus aimed to detect alterations of the membrane properties. In order to prove this point, filtration measurements are conducted with a hemorheometer on dilute (hematocrit 8%) suspensions of normal and membrane hardened (diamide treatment) cells, suspended either in a 8 mPa.s Dextran solution or in a 1 mPa.s buffer solution. As expected when the cells are suspended in buffer, there is no detectable difference in the filtration index for normal and treated cells. However, when they are suspended in the 8 mPa.s solution, the filtration index is significantly larger for treated than for normal cells. This shows that filtration in a viscous liquid can be used to measure changes in cell deformability due to membrane modifications.

Blood Viscosity↗
PubMed1965

FACTORS IN THE MEMBRANE FILTRATION OF ENTEROVIRUSES.

The filtration of two species of enteroviruses through membranes of porosity ranging from 50 to 220 mmu was studied. It was shown that extensive or total losses of virus may attend filtration at these porosities, apparently owing to adsorption of the virus to the membrane matrix. This could be minimized by the incorporation of serum into the virus suspension at the time of filtration, or by pretreating the membrane with serum or with a gelatin solution. It was also found that the first few drops of filtrate, even under optimal conditions, were likely to be virus-free, so that the filtration of too small a volume of virus suspension would result in a relatively great loss of titer. The degree to which these factors were critical was found to decrease with increasing pore diameter.

Adsorption↗
PubMed1976

A filtration model for study of leukocyte transit in the microcirculation.

In order to study characteristics of leukocytes which would be important determinants of their flow in the microcirculation, a model system was tested which utilizes in vitro filtration of leukocytes. Normal human peripheral blood leukocytes (85-90% granulocytes) were studied with filters with uniform 8 mum pore size. Studies were performed to determine the effects of EDTA, temperature, hydrostatic pressure, pH, and osmolarity on filtration. Filterability was optimal at 0.2% EDTA, 10 cm hydrostatic pressure, neutral pH, isotonicity, and at room temperature. Filtration was slowed greatly at leukocyte concentrations exceeding 25 X 10(9)/liter. When leukocyte membranes were altered by formalin fixation, filtration slowed greatly, indicating that deformability is an important determinant of flow through small orifices. When mixtures of erythrocytes and leukocytes were filtered, there was a paradoxically enhanced transit of leukocytes compared to filtration of leukocytes alone, indicating interactions between these cells which alter flow. These studies serve to characterize this model system which can be used to study the contribution to flow in the microcirculation of both normal and pathological leukocytes.

Adult↗
PubMed1993

Evaluation of amniotic fluid cell filtration: an experimental approach to early amniocentesis.

Prior to a prospective application of amniotic fluid (AF) cell filtration to early amniocentesis, we tested the technique on a surplus from mid-trimester samples. By using the same sample size of 5 ml in experiments with a filter and in routine diagnostic procedures (control), we evaluated an optimal filter system. The prolonged culture time of filtered cells and the reduced number of clones are most probably due to mechanical stress (filtration pressure), whereas loss of the cells by adhesion to the filter system, and an AF-free culture medium (growth factors) are suggested to be less important. The AF cells are very sensitive to mechanical stress. Slow filtration (< or = ml AF/min) through filters with a high porosity and the largest possible pore size should be preferred. A mixed cellulose ester filter membrane with a pore size of 5.0 microns proved to be the most efficient, allowing harvest of the filtered cells after only a slight prolongation of the culture time (+2.4 days) compared with unfiltered aliquots. A filter set with a bypass connected by three-way taps allows cell filtration during either aspiration or reinjection of the AF. Cell filtration after amniocentesis and consecutive reverse flushing of the membrane with the appropriate amount of culture medium proved to be the best with regard to easy handling and reducing the risk of bacterial contamination.

Amniocentesis↗
PubMed1984

Impaired autoregulation of glomerular filtration rate in type 1 (insulin-dependent) diabetic patients with nephropathy.

The effect of acute lowering of arterial blood pressure upon kidney function in nephropathy was studied in 13 patients with long-term Type 1 (insulin-dependent) diabetes. Ten normal subjects (six normotensive and four hypertensive) and five short-term Type 1 diabetic patients without nephropathy served as controls. Renal function was assessed by glomerular filtration rate (single bolus 51Cr-EDTA technique) and urinary albumin excretion rate (radial immunodiffusion). The study was performed twice within 2 weeks, with the subjects receiving an intravenous injection of either clonidine (225 micrograms) or saline (0.154 mmol/l). The arterial blood pressure was similar in the diabetic patients with nephropathy (mean 136 +/- 11 divided by 88 +/- mmHg) and in the non-diabetic control subjects (mean 140 +/- 25 divided by 92 +/- 15 mmHg). The clonidine injection induced similar reductions in mean arterial blood pressure in all three groups (16-18 mmHg). While glomerular filtration rate and urinary albumin excretion rate remained unchanged in both control groups after clonidine injection, glomerular filtration rate diminished from 78 to 71 ml/min per 1.73 m2 (p les than 0.01), and urinary albumin excretion declined from 1707 to 938 micrograms/min (p less than 0.01) in the patients with diabetic nephropathy. Our results suggest that an intrinsic vascular (arteriolar) mechanism underlying the normal autoregulation of glomerular filtration rate, i.e. the relative constancy of glomerular filtration rate that occurs in response to rather wide variations in perfusion pressure, is defective in diabetic nephropathy.

Adult↗
PubMed1983

Comparison of the filtration and centrifugation methods for assaying [3H](D-ala2, D-leu5)enkephalin binding to mouse brain membranes.

The binding of [3H](D-ala2, D-leu5)enkephalin (DADLE) to mouse brain membranes was studied via rapid filtration with GF/C filters and via the centrifugation method. The amount of specific binding determined by filtration was found to be dependent on the length of time between the initiation of vacuum and the actual time of filtration. Vacuum strength alone also significantly affected the amount of specifically bound [3H]DADLE measured by filtration. The centrifugation method increased the number of experimentally determined binding sites when compared to the filtration method. The difference in the number of binding sites was only partially attributable to passage of binding material through the GF/C filter. The ability of morphine to displace [3H]DADLE was also found to differ slightly between the two methods. These data indicate that centrifugation is a better method of determining the binding parameters of [3H]DADLE in mouse brain membrane preparations.

Animals↗
PubMed1999

Changing glomerular filtration with progression from impaired glucose tolerance to Type II diabetes mellitus.

Glomerular filtration rate (iothalamate clearance) was measured serially for 48 months in 26 Pima Indians with impaired glucose tolerance and 27 with normal glucose tolerance. At baseline, the mean glomerular filtration rate (SEM) was 133+/-8 ml/min in subjects with impaired glucose tolerance and 123+/-5 ml/min in those with normal glucose tolerance (p = 0.12). In the 12 subjects with impaired glucose tolerance who progressed to Type II (non-insulin-dependent) diabetes during follow-up, mean glomerular filtration rate increased by 30% (p = 0.011). Among the remaining 14 subjects with impaired glucose tolerance, 12 reverted to normoglycaemia. The glomerular filtration rate both at baseline and after 48 months in this subgroup exceeded the values of subjects with normal glucose tolerance by 20 % (p = 0.008) and 14% (p=0.013), respectively. A pronounced rise in the glomerular filtration rate occurs at the onset of Type II diabetes but a trend to hyperfiltration is also present in those with impaired glucose tolerance.

Analysis of Variance↗