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At least 127 records · Page 7Linked to original sources
PubMed1995

Efficacy of portable filtration units in reducing aerosolized particles in the size range of Mycobacterium tuberculosis.

OBJECTIVE: To evaluate engineering control measures to prevent nosocomial transmission of diseases such as tuberculosis, we studied four portable high-efficiency air filtration units, including three high-efficiency particulate air (HEPA) filtration units, for their ability to remove aerosolized particles. DESIGN: Studies were conducted in either a nonventilated aerosol chamber or in a hospital isolation room that met CDC guidelines for TB control (negative pressure, > or = 6 air changes per hour, air exhausted directly to the outside). The rooms were challenged with aerosolized mineral oil in the size range of 0.3 to 5.0 microns at levels 10 to 20 times the normal airborne particle load in the room at baseline. Airborne particles were counted with a laser counter capable of simultaneously measuring sizes > or = 0.3, > or = 0.5, > or = 1.0, and > or = 5.0 microns. Experimental runs were conducted with the filtration units in the center or corner of the chamber or room, and the particle counter in the center of the room or at the exhaust vent. RESULTS: Portable filtration units were effective in accelerating the removal of aerosolized submicron particles. In the nonventilated room, time required by the various portable filtration units for removal of 90% of aerosolized particles (> or = 0.3 microns) ranged from a low of 5 to 6 minutes to a high of 18 to 31 minutes, compared to the control (no filtration unit), > 171 minutes. In the hospital room, individual filtration units removed 90% of aerosolized particles (> or = 0.3 microns) in times ranging from 5 to 8 minutes to 9 to 12 minutes, compared to the control (no filtration unit), 12 to 16 minutes. The location of the portable filtration unit (center versus corner) did not affect the clearance rate of airborne particles. CONCLUSION: Our data indicate that portable filtration units can rapidly reduce levels of airborne particles similar in size to infectious droplet nuclei and, therefore, may aid in reducing the risk of tuberculosis exposure.

Aerosols↗
PubMed1971

The relative contributions of reabsorptive rate and redistributed nephron filtration rate to changes in proximal tubular fractional reabsorption during acute saline infusion and aortic constriction in the rat.

The absolute rate of reabsorption by superficial rat proximal tubules was measured by the in situ microperfusion technique under conditions of hydropenia, infusion of saline, and infusion of saline plus aortic constriction sufficient to decrease whole kidney filtration rate below hydropenic levels. Fractional reabsorption was measured in adjacent filtering nephrons by collecting and recollecting tubular fluid from late proximal convolutions during each experimental condition. During hydropenia, the absolute rate of proximal tubular reabsorption averaged 3.56 +/-0.60 nl/min per mm and late proximal tubular fractional reabsorption averaged 0.56 +/-0.10. From these two measurements and measurements of tubule length to the site of micropuncture, a value for filtration rate was calculated for filtering nephrons. During hydropenia this value averaged 32.9 +/-7.1 nl/min. Saline infusion increased sodium excretion to 5.5% of the filtered load as the absolute rate of proximal tubular reabsorption decreased 38% and fractional reabsorption decreased 45%. Calculated superficial nephron filtration rate increased 21% which on the average was identical with the simultaneously measured increase in whole kidney filtration rate. Similar results were obtained in a separate group of animals by the technique of total collection of late proximal tubular fluid. Aortic constriction during saline infusion decreased whole kidney and calculated nephron filtration rate to the same degree and to values lower than those during hydropenia. Fractional reabsorption increased but not to hydropenic values. The persistent natriuresis during aortic constriction was associated with a continued depression of the absolute rate of proximal tubular reabsorption which was sufficient to maintain an increased delivery of filtrate out of the proximal tubule despite the fall in nephron filtration rate. These results indicate that depressed fractional reabsorption in the proximal tubule during acute saline infusion is due predominantly to a decrease in absolute reabsorptive rate and to a lesser extent to an increase in superficial nephron filtration rate which is proportional to the increase in whole kidney filtration. Continued natriuresis when filtration rate is decreased during saline infusion can be accounted for entirely by the persistent large reduction in the absolute rate of proximal tubular reabsorption.

Aminohippuric Acids↗
PubMed2000

Hemolysis during leukocyte-reduction filtration of stored red blood cells.

Hemolysis has been reported in red blood cells (RBCs) that have undergone leukocyte-reduction filtration. This study investigated whether the age of RBCs or the filter type affected hemolysis. One hundred eighty units of RBCs (adenine-saline added) were leukocyte-reduced by filtration. At each of the 6 weeks of shelf life, 10 units were filtered with the "BPF4" filter, 10 units with the "Purecell RCQ" filter, and 10 units with the "Sepacell" filter. Filtration was performed with strict adherence to the manufacturers' directions. Pre- and post-filtration samples were assayed for plasma hemoglobin by measuring the plasma absorbances at 578 nm and 562 nm. The increase of plasma hemoglobin concentration following filtration was significantly greater (p < 0.05) in older units, compared to fresher units, when the Sepacell and BPF4 filters were used. For example, the increase of plasma hemoglobin at week 6 (83.47 mg/dl:Sepacell, 128.93 mg/dl BPF4) was significantly greater than at week 1 (7.07 mg/dl Sepacell, 4.77 mg/dl BPF4) (Sepacell: p=0.008; BPF4: p=0.006). For units stored 1, 2, 4, 5, or 6 weeks, the increase of plasma hemoglobin concentration post-filtration was significantly greater with the BPF4 filter, compared to the Purecell RCQ filter (p <0.045); for units stored 5 weeks, the increase in plasma hemoglobin concentration post-filtration was significantly greater with the BPF4 filter compared to the Sepacell filter (p = 0.009). Mean filtration times were significantly longer in older units compared to fresh units. This study shows that increased storage duration of RBCs (adenine-saline added) is attended by greater hemolysis during leukocyte-reduction filtration and by prolongation of the filtration time. In addition, the amount of hemolysis may be influenced by the type of filter.

Blood Preservation↗
PubMedDate not supplied

Rotation-induced Taylor vortex enhances filtrate flux in plasma separation.

Techniques of plasma filtration with rotating flat membranes are capable of producing a Taylor vortex and concomitantly reducing concentration polarization by formed elements. The present study describes filtration characteristics of a small-sized rotating filter that is superior to a capillary filter in terms of filtrate flux. The rotating filter with a surface area of 60 cm2 was composed of two concentric cylinders, with the inner cylinder mobile, with a flat polycarbonate membrane (pore diameter: 0.8 micron), and the outer cylinder fixed. Filtration experiments were performed using bovine blood to determine filtrate flux at rotational speeds from 600 to 4,500 rpm. Photographic observations using aluminum powder revealed that many Taylor vortices were present in the radial gap (0.6 mm). Filtrate flux increased with transmembrane pressure until a maximum filtrate flux of 0.02 cm/min at 600 rpm, 0.42 cm/min at 1,800 rpm, 0.60 cm/min at 3,600 rpm, and 0.69 cm/min at 4,500 rpm were reached at a blood flow rate of 100 ml/min. Based on the filtration resistance model, values for fractional filtration resistance of the red blood cell polarization layer ranged from 0.25 to 0.80 at a rotational speed of 3,600 rpm, whereas those of a capillary filter range from 0.80 to 0.90. This indicates that Taylor vortices promote back diffusion of red blood cells accumulated on membrane surfaces. Thus, the filtrate flux of a rotating filter is two orders of magnitude higher than that of a capillary filter because of the back diffusion of red blood cells facilitated by Taylor vortices.

Animals↗
PubMedDate not supplied

Analysis of flow acceleration during erythrocyte filtration: dependence of hematocrit and cell rigidity.

At flow onset the blood filtration rate accelerates to a steady state, this may affect the interpretation of red blood cell (RBC) filterability. We studied the acceleration of flow while the pressure is built up across the filter to analyse effects of various hematocrits and RBC rigidity by glutaraldehyde (GA) hardening. This was analysed by a new filtration system with high time resolution and unlimited filtration volume. The system uses a digital balance that samples the accumulated weight (e.g., filtration rate through 5 microns Nucleopore membranes) with on-line computer communication. The filtration is computer controlled via a pneumatic valve. White blood cells (WBC) were removed prior to filtration by a WBC-eliminating filter to avoid clogging artifacts. When flow is initiated a steady state is reached at 0.3-0.4 s. This timing was also tested and confirmed by a video monitoring technique of filtration flow into a horizontal pipette. The digital balance has a mathematical function to reduce the effects of vibration noise; when this function was activated the apparent acceleration was retarded to 1.2 s. With any of these techniques the steady state timing did not vary with the hematocrit, however, the volume of filtered suspension during acceleration varied with both the hematocrit and the GA hardening (p < 0.001). Extrapolation to yield the initial filtration rate from the relative flow curve (RBC suspension divided by buffer flow) varied depending on if the acceleration phase was included or not. In the most unfavourable situation, with GA-hardened RBC, this difference was 340% (p < 0.01). The slope to calculate clogging rate was affected in a similar way. Moreover, with the most GA-hardened RBC a delay in flow onset was observed with this technique. The acceleration phenomenon may cause artifacts in systems employing volume-derived filtration kinetics because of fixed volumes of filtrated medium.

Erythrocyte Aggregation↗
PubMed2004

Differential effects of human atrial natriuretic peptide and furosemide on glomerular filtration rate and renal oxygen consumption in humans.

OBJECTIVE: Imbalance in the renal medullary oxygen supply/demand relationship can cause hypoxic medullary damage and ischemic acute renal failure. Human atrial natriuretic peptide (h-ANP) increases glomerular filtration rate in clinical acute renal failure. This would increase renal oxygen consumption due to increased tubular load of sodium. Loop diuretics are commonly used in acute renal failure. Data on the effects of loop diuretics on glomerular filtration rate and renal oxygen consumption in humans are, however, controversial. We evaluated the effects of h-ANP and furosemide on renal oxygen consumption, glomerular filtration rate, and renal hemodynamics in humans. DESIGN AND SETTING: Prospective two-agent interventional study in a university hospital cardiothoracic ICU. PATIENTS: Nineteen uncomplicated, mechanically ventilated postcardiac surgery patients with normal renal function. INTERVENTIONS: h-ANP (25 and 50 ng/kg per minute, n=10) or furosemide (0.5 mg/kg per hour, n=9). MEASUREMENTS AND RESULTS: Renal plasma flow and glomerular filtration rate were measured using the infusion clearance technique for (51)Cr-labeled EDTA and paraaminohippurate, corrected for by renal extraction of PAH. h-ANP increased glomerular filtration rate, renal filtration fraction, fractional excretion of sodium, and urine flow. This was accompanied by an increase in tubular sodium reabsorption (9%) and renal oxygen consumption (26%). Furosemide infusion caused a 10- and 15-fold increase in urine flow and fractional excretion of sodium, respectively, accompanied by a decrease in tubular sodium reabsorption (-28%), renal oxygen consumption (-23%), glomerular filtration rate and filtration fraction (-12% and -7%, respectively). CONCLUSIONS: The filtered load of sodium is an important determinant of renal oxygen consumption. h-ANP improves glomerular filtration rate but does not have energy-conserving tubular effects. In contrast, furosemide decreases tubular sodium reabsorption and renal oxygen consumption and thus has the potential to improve the oxygen supply/demand relationship in clinical ischemic acute renal failure.

Acute Kidney Injury↗
PubMedDate not supplied

Capture of bacteria from fermentation broth by body feed filtration: a solved problem?

The direct capture of bacteria produced in high cell density fermentation by filtration is not possible once the milliliter-scale has been surpassed. Filtration in the presence of a filter aid (body feed filtration) constitutes a putative and scalable alternative, but only if conditions proposed by industry for large-scale filtration processes, namely, flow rates (for aqueous solutions) in the range of 500-1,500 L/(m(2) x h) and a filter aid concentration of <or=20 g/L, can be met. To this end several filter aids (grades of cellulose, diatomaceous earth, mixes thereof) were tested, albeit with no success. Capture and retention of bacteria was low (not possible in the case of cellulose), and the produced filter cakes were unstable and of low permeability. In the case of the diatomaceous earth close to 100% bacterial capture was possible, but only with filter aid concentrations that were 1 order of magnitude above the proposed limit. By using flocculating agents (Fe(3+)/Al(3+), PEI) either alone or in combination with diatomaceous earth and also the use of positively charged cellulose, bacteria capture could be achieved from several liters of cell suspension (OD(600) <or= 15) in filtration experiments adhering to the industrial recommendations. However, the bacteria were only weakly retained in such cakes and easily released by sudden pressure pulses. Satisfactory results were only obtained by filtration of the bacteria suspension at slightly alkaline pH (8.0, 50 mM Tris buffer) after treatment with sodium-activated bentonite (5 g/L) and PEI (50 mg/L) in the presence of 250 mM NaCl. In such cases 100% of the bacteria could reproducibly be captured in a filtration using 20 g/L of diatomaceous earth as filter aid. The thus produced filter cakes strongly retained the bacteria and showed good filtration performance. The procedure is at present limited to E. coli culture with biomass contents of OD(600) <or= 15. Cultures with higher OD(600) have to be diluted prior to filtration.

Bentonite↗
PubMed2001

Pathogen filtration, heterogeneity, and the potable reuse of wastewater.

Filtration is commonly employed in water and wastewater treatment to remove particles and reduce the concentration of microbial pathogens. All physical models of packed-bed filtration are based on a proportional relationship between particle removal per unit depth of bed and the local particle concentration, dC/dz = -C/l, where l is the filtration length scale. Although l is known to vary with time and filter depth for heterogeneous suspensions or "dirty" beds, this paper demonstrates that the filtration rates of even seemingly monodisperse particle suspensions under clean-bed filtration conditions cannot be described with a single filtration length scale. A new model is derived for particle filtration that accounts for heterogeneity at two different spatial scales. Heterogeneity at the scale of the pathogen and/or collector (microscale heterogeneity) leads to a slow power-law decay of contaminant concentration with distance, instead of the fast exponential decay predicted by the standard model. Heterogeneity at the filter scale (macroscale heterogeneity) provides another level of complexity that can be evaluated once microscale heterogeneity effects are characterized. This model for microscale and macroscale heterogeneous particle filtration is verified by filtration experiments on a recombinant analogue of the waterborne pathogen Norwalk virus.

Filtration↗
PubMed1992

Increased glomerular filtration rate as a predictor of diabetic nephropathy--an 8-year prospective study.

The objective was to study the natural history and the predictive value of glomerular filtration rate, albumin excretion rate, blood pressure, and hemoglobin A1c for diabetic nephropathy. A cohort of 75 type-1 diabetic adolescents with a diabetes duration of 8 years was studied. Thirty-one females, 33 males, mean age 16.9 +/- 0.3 (SEM) participated in the follow-up study. Glomerular filtration rate, albumin excretion rate, blood pressure, and hemoglobin A1c were measured every second year during 8 years to determine the predictive value of glomerular filtration rate for future nephropathy. Initial differences and patterns of changes in glomerular filtration rate, albumin excretion rate, and hemoglobin A1c were examined in patients who did (group 1) and did not (group 2) develop incipient or overt nephropathy. Five of 64 patients developed overt nephropathy. They had an initial glomerular filtration rate of greater than 125 ml/min/1.73 m2. Fifteen of 53 initially normoalbuminuric patients developed incipient and three of 53 overt nephropathy. Age, age at onset, diabetes duration, initial albumin excretion rate, initial blood pressure, and hemoglobin A1c were similar in groups 1 and 2. Glomerular filtration rate was initially higher in group 1 than in group 2 (P = 0.01). The positive predictive value for combined incipient and overt nephropathy of an initial glomerular filtration rate greater than 125 ml/min was 53%. The negative predictive value of glomerular filtration rate less than 125 ml/min was 95%. In initially normoalbuminuric patients multiple regression revealed initial glomerular filtration rate as the only significant independent predictor for nephropathy when also corrected for hemoglobin A1c (P = 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Albuminuria↗
PubMed2003

Evaluation of depth filtration to remove prion challenge from an immune globulin preparation.

BACKGROUND AND OBJECTIVES: Plasma-derived therapeutic proteins have the potential to contain transmissible spongiform encephalopathy (TSE) infectivity. This study evaluated the effectiveness and characterized the mechanism of abnormal prion protein removal during a depth-filtration step used in the manufacture of an immunoglobulin preparation. MATERIALS AND METHODS: Scrapie brain homogenate was treated with lysolecithin, sonicated and sequentially filtered through 0.45-, 0.22- and 0.1-microm membrane filters. The scrapie brain homogenate was then added (at a 1:51 dilution) to the Supernatant III fraction used in the manufacture of Rho(D) immune globulin (human). The spiked immunoglobulin preparation was then filtered through a depth filter under the same conditions used in full-scale production. After filtration, the depth filter was washed with hypertonic NaCl solutions to elute the abnormal prion protein (PrPSc) from the filter. A Western blot assay for PrPSc was used to quantify removal from the filtrate and recovery from the filter washes. A second run was performed whereby the PrPSc-spiked Supernatant III was filtered through a 0.22-microm membrane filter prior to depth filtration. A third run evaluated depth filtration of PrPSc in Tris-buffered saline (TBS). RESULTS: The depth filter removed greater than four logs of PrPSc from the Supernatant III filtrate. A significant portion of the PrPSc could be recovered from the depth filter by elution with high-molarity NaCl solutions. Prefiltration (through a 0.22-microm membrane filter) of the spiked Supernatant III prior to depth filtration removed all detectable PrPSc. Depth filtration removed less than one log of PrPSc from TBS. CONCLUSIONS: Depth filtration appears to remove PrPSc from the immunoglobulin preparation by mechanical straining rather than by adsorption to the filter matrix. The immunoglobulin preparation caused the PrPSc to aggregate from particles <0.1 microm in size to particles of >0.22 microm, probably as a result of the presence of methanol in the preparation. The depth filter failed to remove PrPSc from a purely aqueous environment.

Animals↗
PubMed2003

Effects of a PPARgamma agonist, GI262570, on renal filtration fraction and nitric oxide level in conscious rats.

PPARgamma agonists ameliorate insulin resistance and lower blood pressure. Volume expansion/edema has been observed in susceptible patients treated with these agents. Alterations of renal hemodynamics affect renal tubular reabsorption, and thus may contribute to volume expansion. This study seeks to determine whether volume expansion caused by a PPARgamma agonist, GI262570, is related to changes in glomerular filtration rate, effective renal plasma flow, or renal filtration fraction. Chronically catheter-implanted conscious rats were studied to determine the effects on glomerular filtration rate, effective renal plasma flow, and renal filtration fraction after 1, 4, and 10 days of GI262570 treatment (8 mg/kg, p.o., B.I.D.). Elevated adipose mRNA of PPARgamma target genes confirmed PPARgamma activation in GI262570-treated rats. GI262570 treatment for 10 days decreased hematocrit, hemoglobin, and serum albumin (all P < 0.05), indicating volume expansion, but did not alter glomerular filtration rate, effective renal plasma flow, or renal filtration fraction. However, nitrate + nitrite was significantly higher in plasma and hind limb muscle of GI262570-treated rats (both P < 0.05). This study demonstrated that treatment with PPARgamma agonist GI262570 resulted in volume expansion and increased nitric oxide, but did not affect glomerular filtration rate, effective renal plasma flow, or renal filtration fraction, indicating PPARgamma agonist-induced volume expansion is not related to changes in renal filtration fraction, and increased nitric oxide may contribute to the PPARgamma agonist-induced blood-pressure lowering.

Animals↗
PubMed1996

Glomerular filtration rate and kidney size after six years disease duration in non-insulin-dependent diabetic subjects.

The objective of the present study was to estimate how glomerular filtration rate and kidney size change after six years of diabetes in subjects with non-insulin-dependent disease. It is a population-based prospective study of a cohort of non-insulin diabetic patients (n = 150) diagnosed 1985-1988. The baseline studies utilized a non-diabetic control group, whose basic characteristics were equal to the study group. The setting was a primary health care center in an urban area. Main outcome measures were the glomerular filtration rate and its relation to renal area, mean blood pressure, hemoglobin A1c, serum insulin and cholesterol. Seventeen patients had died and 109 were eligible for evaluation at follow-up. The mean (standard deviation) of the glomerular filtration rate (ml/min/1.73 m2) remained elevated at follow-up, 118 (28), just as it was at baseline, 118 (28) in the diabetic subjects compared to matched non-diabetic subjects, 103 (24) (p = 0.0000). Kidney size (cm2) was larger in diabetic subjects at follow-up, 114 (19) than at baseline, 109 (18) (p = 0.0000) and in non-diabetic subjects 98 (14) (p < 0.0000). This resulted in a decline in glomerular filtration rate per unit renal area in the diabetic subjects at follow-up, 1.0 (0.23) compared to at baseline, 1.09 (0.23) (p = 0.002) and to non-diabetic subjects, 1.07 (0.23). The renal area at baseline was directly and significantly related to the glomerular filtration rate at follow-up (p < 0.001). The relation of baseline serum cholesterol, hemoglobin A 1c and mean arterial blood pressure to the glomerular filtration rate at follow-up was inverse and reached significance in those diabetic subjects having had high filtration rates at baseline but displaying a faster decline than on average i.e. in those patients who were at increased risk of renal insufficiency. We conclude that after the first six years of non-insulin-dependent diabetes the glomerular filtration rate remains high. Kidney size increases further from the attained increase at diagnosis and is an important determinant of continuing hyperfiltration. The deleterious effect of serum cholesterol and high blood glucose on the glomerular filtration rate at this early stage of diabetic kidney disease is suggestive.

Analysis of Variance↗
PubMed2003

Immunosuppressive substances in Aspergillus fumigatus culture filtrate.

Invasive aspergillosis has become a serious problem in clinical practice, but the actual factor that confers virulence on the fungus has not been thoroughly elucidated. To identify and isolate the immunosuppressive substances produced by the fungus, the bioactivity of culture filtrates was assessed, and analyses of the culture filtrates were carried out. Culture filtrates from different strains of Aspergillus fumigatus were assessed for their effect on human polymorphonuclear leukocytes and murine macrophages. To assess their activities in vivo, their effect on the survival of mice infected by the fungus was also studied. Subsequently, the composition of the culture filtrates was analyzed by gas chromatography-mass spectrometry. The analyses revealed that the culture filtrates contained gliotoxin at concentrations of 3 to 4 microgram/ml, and some other unidentified compounds. The bioactivities of the culture filtrates were similar to those of gliotoxin. The fungal culture filtrate reduced the survival of infected mice, but the filtrate itself did not cause the death of mice. However, all the bioactivities could not be accounted for by gliotoxin itself. These results indicate that gliotoxin in the culture filtrates may be responsible for part of the immunosuppressive activity, but some other components produced by A. fumigatus contribute, in an additive or synergistic manner, to the virulence of the fungus.

Animals↗
PubMed2005

Effects of pulsation frequency and endothelial integrity on enhanced arterial transmural filtration produced by pulsatile pressure.

The role of the endothelium in regulating transmural fluid filtration into the artery wall under pulsatile pressure and the effects of changes in pulsatile frequency on filtration have received little attention. Previous experiments (Alberding JP, Baldwin AL, Barton JK, and Wiley E. Am J Physiol Heart Circ Physiol 286: H1827-H1835, 2004) demonstrated significantly increased filtration after initial onset of pulsatile pressure compared with that predicted by using parameters measured under steady pressure. To determine the role of the endothelium in this phenomenon, the following experiments were performed on five New Zealand White rabbits (anesthetized with 30 mg/kg pentobarbital sodium). One of each pair of carotid arteries was deendothelialized, and filtration measurements under steady and pulsatile pressure were compared with those made in intact vessels (Alberding JP, Baldwin AL, Barton JK, and Wiley E. Am J Physiol Heart Circ Physiol 286: H1827-H1835, 2004). To determine the effect of increasing pulsatile frequency on arterial filtration, transmural filtration was measured by using pulsatile pressure frequencies of 1 Hz, followed by 2 Hz, in another set of intact arteries (6 arteries and 3 animals). For deendothelialized vessels, the initial increase in filtration after onset of pulsatility was similar to that observed in intact vessels, but the subsequent reduction in filtration was less abrupt. When pulsatile frequency was increased from 1 to 2 Hz in intact arteries, an initial increase in filtration was observed, similar to that obtained after onset of pulsatile pressure subsequent to a steady pressure. The observed responses of arteries to pulsatile pressure, with and without endothelium, or undergoing a frequency change, suggest a dynamic role for the endothelium in regulating transvascular transport in vivo.

Animals↗
PubMed1995

Glomerular epithelial foot processes and filtration slits in IDDM patients.

Diabetic nephropathy is associated with functional changes in the glomerular filtration barrier but the structural counterpart remains unknown. Width of glomerular epithelial cell foot processes and of filtration slits were determined by morphometric methods in 11 non-diabetic kidney donors and in 28 diabetic patients with albumin excretion rates ranging from normal to proteinuria. Foot process width was estimated from the ratio of tuft surface density to length density of slits. At high magnification independently sampled, perpendicularly cut slits were classified. Foot process width on peripheral basement membrane was increased in microalbuminuric compared to normoalbuminuric diabetic patients (p<0.05) but showed no significant correlation with the level of albumin excretion when patients with increased barrier permeability were considered. Width of filtration slits in normo- and microalbuminuric diabetic patients exceeded that in non-diabetic control subjects (p<0.05). Filtration slits were narrower in patients with overt proteinuria than in patients with microalbuminuria (p<0.05) and correlated with glomerular filtration rate in all of the diabetic patients (r=0.65, p<0.005). The results show that insulin-dependent diabetic patients with nephropathy present changes of epithelial cells and filtration slits, demonstrable already in the stage of microalbuminuria. The mechanism of albumin leakage is not achieved by these measures. The dimension of filtration slits may play a contributing role in the level of glomerular filtration rate in diabetic patients.

Adolescent↗
PubMed2006

Reduction in MRSA environmental contamination with a portable HEPA-filtration unit.

There is renewed interest in the hospital environment as a potentially important factor for cross-infection with methicillin-resistant Staphylococcus aureus (MRSA) and other nosocomial pathogens. The aim of this study was to evaluate the effectiveness of a portable high-efficiency particulate air (HEPA)-filtration unit (IQAir Cleanroom H13, Incen AG, Goldach, Switzerland) at reducing MRSA environmental surface contamination within a clinical setting. The MRSA contamination rate on horizontal surfaces was assessed with agar settle plates in ward side-rooms of three patients who were heavy MRSA dispersers. Contamination rates were measured at different air filtration rates (60-235 m(3)/h) and compared with no air filtration using Poisson regression. Without air filtration, between 80% and 100% of settle plates were positive for MRSA, with the mean number of MRSA colony-forming units (cfu)/10-h exposure/plate ranging from 4.1 to 27.7. Air filtration at a rate of 140 m(3)/h (one patient) and 235 m(3)/h (two patients), resulted in a highly significant decrease in contamination rates compared with no air filtration (adjusted rate ratios 0.037, 0.099 and 0.248, respectively; P < 0.001 for each). A strong association was demonstrated between the rate of air filtration and the mean number of MRSA cfu/10-h exposure/plate (P for trend < 0.001). In conclusion, this portable HEPA-filtration unit can significantly reduce MRSA environmental contamination within patient isolation rooms, and this may prove to be a useful addition to existing MRSA infection control measures.

Adult↗
PubMed2006

Development of a vacuum filtration system for the conventional microplate washer.

INTRODUCTION: Filter plates are available from many vendors reflecting the growth of their scientific applications in various fields, however, the heterogeneous nature of those applications are the major factor to block the expansion of various filter plate options in a research scale operation. The development of an automatic vacuum filtration system for a conventional plate washer was presented as a possible solution for the filtration process in filter plate applications, especially in the melanin concentrating hormone receptor subtype 1 (MCH1) receptor binding assay with the time resolved fluorescence technology. METHODS: The pilot modification was done in the Embla 96/384 well washer by replacing the original plate carriage with a new carriage mimicking the conventional vacuum manifold to add the function of flow-through vacuum filtration for filter plates. The performance of new vacuum filtration system was evaluated with MCH1 receptor binding assay and ligand washout experiments. RESULTS: The mean background values from ligand washout experiments in AcroWell filter plates were 6406+/-502.9 with a manual vacuum manifold and 5563+/-585.8 with the vacuum filtration system. Z' factors were calculated as 0.6101+/-0.095 for the MCH1 receptor binding assay with the vacuum filtration system. DISCUSSION: The new plate carriage for a conventional plate washer was developed for filter plate applications to enable its use in a flow-through vacuum filtration application in addition to the conventional plate washing by an aspiration. The results from ligand washout and receptor binding assay suggest that the vacuum filtration system can provide a cost-effective solution for filter plate applications and may alleviate the most common problems of those heterogeneous assays to develop as high throughput operations without major investments for the professional workstations.

Animals↗
PubMed1985

A combined recycling affinity column-filtration technique.

A new preparative purification technique for biological macromolecules is developed by combining the affinity column chromatography and the membrane filtration technique. A unique feature of the affinity column-filtration apparatus is that the filtrate from the filtration unit is recycled back to the inlet of the affinity column, thus decreasing considerably the total amount of ligands required for the affinity column. A second important feature is that the pump which connects the affinity column and the filtration unit is monitored by an infrared sensor device on the filtration cell; consequently, the flow of the column eluent into the filtration unit is controlled automatically by the solution height in the filtration cell. Highly homogeneous regulatory subunits of type I cAMP-dependent protein kinase from rabbit skeletal muscle are demonstrated to be obtainable by the new purification technique. Thus, this apparatus could have important applications in the purification of a wide range of biological macromolecules. A test for estimating affinity bound proteins is also discussed.

Animals↗