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PubMed1999

The dynamics of glomerular filtration after Caesarean section.

The objective of this study was to determine whether the glomerular hyperfiltration of pregnancy is maintained even after Caesarean section and, if so, to define the responsible hemodynamics. The dynamics of glomerular filtration were evaluated in 12 healthy women who had just completed an uncomplicated pregnancy and were delivered by Caesarean section. Age-matched but non-gravid female volunteers (n = 22) served as control subjects. GFR in postpartum women was elevated above control values by 41%; 149+/-10 versus 106+/-3 ml/min per 1.73 m2, respectively (P < 0.001). In contrast, corresponding renal plasma flow was the same in the two groups, such that the postpartum filtration fraction was significantly elevated by 20%. Computation of glomerular intracapillary oncotic pressure (piGC) from knowledge of plasma oncotic pressure and the filtration fraction revealed this quantity to be significantly reduced in postpartum women, 20.6+/-1.7 versus 26.1+/-2.0 mmHg in control subjects (P < 0.001). A theoretical analysis of glomerular ultrafiltration suggests that depression of piGC, the force opposing the formation of filtrate, is predominantly or uniquely responsible for the observed postpartum hyperfiltration.

Adult↗
PubMed2006

Membrane filtration coupled with chemical precipitation to treat recirculating aquaculture system effluents.

Effluents from recirculating aquaculture systems (RAS) contain high concentrations of nitrogen and phosphorous wastes and thus often require proper treatment to prevent potential detrimental impacts on receiving water bodies. The purpose of this study was to evaluate the feasibility of membrane filtration coupled with chemical precipitation as a pretreatment step with emphasis on phosphorus removal from RAS effluents. Chemical precipitation tests were conducted by adding magnesium chloride and alum at different chemical concentrations and pH values, respectively. Crossflow, flat-sheet membrane filtration modules were used to examine the effects of transmembrane pressure and crossflow velocity in terms of solid/liquid separation efficiency and permeate flux decline. The results showed that membrane filtration can effectively separate the phosphorus precipitates after chemical precipitation. The total phosphorus in the treated effluent was reduced to less than 0.05 mg L(-1) with a removal efficiency of more than 90%. However, much lower removal efficiencies were obtained for total organic carbon (TOC), total nitrogen, and turbidity. It was concluded that membrane filtration coupled with chemical precipitation can become an effective, compact treatment technology to meet the stringent regulatory requirements for RAS effluent discharge.

Alum Compounds↗
PubMed2006

Filter clogging in coarse pore filtration activated sludge process under high MLSS concentration.

Coarse pore filtration activated sludge process is a type of hybrid process in which the secondary settling tank of the conventional activated sludge process is replaced by non- woven and coarse pore filter modules. The filter has pores, which are irregular in shape, and much bigger than micro-filtration membrane pores in size. The objective of the study is to find out the effect of the microbial community structure on filter clogging in the coarse pore filtration activated sludge process under high MLSS concentration in aerobic and anoxic/aerobic (A/A) conditions. Filter clogging started from day 65 and 70 in the A/A and aerobic process, respectively, but it was more severe in the A/A process compared to that in the aerobic process. EPS contents of sludge did not change significantly during the operation in both processes, and did not have a crucial effect on the observed filter clogging. There was no strong evidence for direct effect of the type and number of metazoa on filter clogging. The main difference between aerobic sludge and A/A sludge during the filter clogging period was the relative abundance of filamentous bacteria. According to the obtained results, it can be concluded that a higher presence of filamentous bacteria could reduce the severity of filter clogging in a coarse pore filtration activated sludge process.

Bacteria, Aerobic↗
PubMed1989

The acute effect of acetazolamide on glomerular filtration rate and proximal tubular reabsorption of sodium and water in normal man.

The acute effects on kidney function of acetazolamide (250 mg) given intravenously were evaluated in seven healthy subjects. Glomerular filtration rate was measured as the renal clearance of 51Cr-EDTA, and fluid flow rate out of the proximal tubules was assessed by measurement of the renal lithium clearance. An 18% decline in glomerular filtration rate (ml/min) was observed after acetazolamide administration (109 +/- 16 vs 89 +/- 14, p less than 0.02), while lithium clearance (ml/min) increased by 35% (30 +/- 5 vs 38 +/- 8, p less than 0.02). Absolute proximal tubular reabsorption of water (ml/min) was reduced by about one third (79 +/- 12 vs 51 +/- 9, p less than 0.02), and fractional proximal reabsorption of water and sodium (%) declined (73 +/- 2 vs 58 +/- 6, p less than 0.02). Renal sodium clearance and absolute distal reabsorption of sodium increased, while fractional distal reabsorption of sodium declined. Acetazolamide reduces absolute and fractional proximal tubular reabsorption of sodium and water, and glomerular filtration rate. Primarily, this induces an increase in the output of fluid from the proximal tubules accounting for the diuretic effect of the drug. The acute fall in glomerular filtration rate is probably mediated by a temporary increase in proximal intratubular pressure and activation of the tubuloglomerular feedback mechanism.

Acetazolamide↗
PubMed1978

Determination of glomerular filtration rate in advanced renal insufficiency.

The glomerular filtration rate (GFR) has been determined in 17 patients with advanced renal insufficiency (GFR less than 15 ml/min) by different clearance techniques using creatinine, inulin and 51Cr-EDTA as filtration markers. With renal inulin clearance as reference method for GFR, endogenous renal creatinine clearance overestimated GFR by an average of 30%. Renal clearance of 51Cr-EDTA and inulin were closely correlated and thus 51Cr-EDTA is a suitable GFR marker even at low filtration rates. However, it was found that the plasma clearance of 51Cr-EDTA overestimated the GFR often by more than 100% in the range 2.6--11.2 ml/min. Renal clearance measured during 24 h was lower than 4 h renal clearance with the patient well hydrated and resting in bed. It is concluded that the precise measurement of low glomerular filtration rates requires the use of renal clearance techniques. Four-hour 51Cr-EDTA renal clearance is a suitable method for measuring and following the development of renal function in advanced renal insufficiency.

Adult↗
PubMed2001

Particle size analysis as a tool for performance measurements in high rate effluent filtration.

In the Netherlands almost all wastewater treatment plants have been redesigned and adapted in order to remove nitrogen, phosphorus and suspended solids to a very low level. The improved effluent quality leads to a growing interest in the reuse of effluent of the modernised wastewater treatment plants. This again results in investigations on filtration techniques as deep bed filtration and membrane filtration. At the wastewater treatment plant Ede research was done on deep bed filtration in order to develop relations between particle removal and filter performance and to explore ways of optimization. The results of the experiments are rather typical for effluent of modern Dutch wastewater treatment plants. The very low concentrations of suspended solids and precipitable substances result in poor flocculating properties. From turbidity measurements it may be concluded that the best results were obtained with a dosage of flocculant. However, the particle size measurements indicated the opposite. Suspended solids calculations, based on the particle volume distributions, showed a better removal without a dosage of flocculant. From this it is concluded that a dosage of coagulant (Fe3+ or Al3+) has an adverse effect on the removal efficiencies even at low dosages (1 mg/l).

Conservation of Natural Resources↗
PubMed2002

A prospective evaluation of the glomerular filtration rate in older adults with frequent nighttime urination.

PURPOSE: We assessed the association of renal function with frequent nighttime urination in older adults. MATERIALS AND METHODS: We recruited a convenience sample of 48 adults 65 years old and older, and admitted them to a general clinical research center. Of the 48 participants 45 completed a 7-day voiding record, ate a research diet for 4 days and finished a 3-day stay with 3 glomerular filtration rate measurements, including an estimation of serum creatinine using the Cockcroft-Gault formula, a calculation using 24-hour urine volume and a determination by 131iodine iothalamate clearance. RESULTS: Subjects with frequent nighttime voiding, defined as a mean of 2 or more voiding episodes from 11 p.m. to 7 a.m., had slightly lower but statistically similar glomerular filtration rate measurements than those with a mean of less than 2 nighttime voids. The glomerular filtration rate did not correlate with the number of nighttime voids (Pearson correlation coefficient -0.006, p = 0.971). Mean 24-hour urine output was similar in the 2 groups and the correlation of the number of nighttime voids with 24-hour urine output was insignificant (Pearson correlation coefficient -0.06, p = 0.683). A greater number of nighttime voids was associated with producing more urine at night and smaller mean voided volume. CONCLUSIONS: As determined by a gold standard glomerular filtration rate measurement, renal function was not associated with the number of nighttime voids in our study population. Total 24-hour urine output was also not associated with the number of nighttime voids. Our findings confirmed the positive association of a greater number of nighttime voids with greater nighttime urine production and lower bladder voided volume.

Aged↗
PubMed2001

[The expression of red blood cell deformability in micropore filtration tests].

For the purpose of evaluating and comparing RBC deformability quantitatively with micropore filtration method, the precise meanings and applicability of physical parameters and defined indices expressing RBC deformability are discussed and analyzed in detail. The mean transit time (or the relative transit resistance) and the proportion of pore-clogging cells are found to be appropriate for representing the average deformability and the clogging characteristic of RBCs respectively. To eliminate the effects of clogging on filtration, previous studies were conducted filtration with as less clogging as possible. Investigations on experimental results from various filtration methods, however, reveal that the clogging property of RBCs contains important information on the RBC deformability. It reflects a different aspect of the RBC deformability besides the average deformability and is more sensitive to the abnormal deformability induced by physical, chemical, especially pathological factors.

Erythrocyte Deformability↗
PubMed1998

[Effects of homoharringtonine liposomes and homoharringtonine solution on glaucoma filtration surgery in rabbits].

OBJECTIVE: Homoharringtonine (HHT), a Chinese herbal drug, was used in the form of liposome or solution as an adjunct to glaucoma filtration surgery in rabbits to determine its effect in preventing closure of sclerostomy. METHODS: Forty rabbits that underwent a standard posterior-lip sclerectomy in both eyes were divided into 5 post-operative groups. Group 1 received subconjunctival HHT liposomes (0.025%). Group 2 received subconjunctival blank liposomes and served as control. Group 3 and 5 received subconjunctival HHT solution at low (0.025%) and high (0.1%) doses respectively. Group 4 received subconjunctival normal saline and served as control. Intraocular pressure, interval between operation and bleb failure, rate of scleral fistula occlusion and ocular toxicity were determined in each group. RESULTS: Subconjunctival treatment with HHT solution at a high dose transiently prolongs the survival of filtration surgery, but the subconjunctival use with HHT liposomes or HHT solution at a low dose does not significantly prolong the survival of filtration surgery in rabbits. Significant corneal haze and corneal neovascularization resulted from using HHT at a high dose. CONCLUSIONS: The success rate of rabbit filtration surgery can not be markedly increased by the postoperative use of HHT liposomes or its low dose solution. When the high dosage of HHT solution is used, transient elevation of the success rate can be obtained, however the side-effect is also significantly increased.

Animals↗
PubMed2003

Glomerular filtration: an overview.

The formation of urine is a process that begins with glomerular filtration and is greatly influenced by changes in renal hemodynamics. Selective filtration of the blood is possible because of the unique characteristics of the glomerulus and renal circulation. Many factors interact to maintain a consistent blood flow allowing filtration and urine formation to continue despite systemic changes in blood pressure. Factors that impact on renal hemodynamics include the autoregulatory mechanism, the renin-angiotensin mechanism, eicosanoids, kinins, the sympathetic nervous system (SNS), catecholamines, antidiuretic hormone, endothelin, nitric oxide, atrial natriuretic peptide, and dopamine. Knowledge of the effects of these factors will allow the nephrology nurse to predict, identify, and assist in the treatment of clinical conditions that can alter renal hemodynamics and glomerular filtration.

Creatinine↗
PubMed2003

[Particle entrapment mechanism in deep bed filtration].

Theoretical analysis was carried out in this paper to study the interaction in the bed filtration process, and the physico-chemical forces between the filter media and suspended particles in water were presented. Pilot study of the micro-flocculation deep bed filtration was carried out in the No. 9 Potable Water Treatment Plant of Beijing, the interception of particles of 1-10 microns diameter in the 500 cm deep filter bed was analyzed, and the head loss variation during 65 h was monitored. The shear force of 1-10 microns diameter-particle under 24 m/h filtration velocity was calculated. The theoretical physico-chemical forces between the filter bed and suspended particle of 1-10 microns diameter under the condition of -25 mV and -125 mV surface potential was also presented. The theoretical results are reasonably consistent with the experimental data, from which it can be concluded that the operation principles of micro-flocculation deep bed filtration could be analyzed by the physico-chemical interaction between the particles and filter media.

Filtration↗
PubMed1992

Rapid measurement of protein kinase and phosphatase activities by slot-filtration.

A slot-filtration method has been developed for the detection and quantitation of protein kinase and phosphatase activities. In this technique, after kinase-dependent phosphorylation or phosphatase-dependent dephosphorylation of different substrates, samples are transferred under vacuum onto nitrocellulose using a slot-blotting apparatus. Non-incorporated or released radioactivity is then removed by filtration and washing under vacuum. Quantitation is performed by scintillation or Cerenkov counting of the excised membrane slots. Application of the method to the assay of four different protein kinases (protein kinase N, cyclic AMP-dependent protein kinase and calcium/calmodulin-dependent protein kinases type I and type III) and one phosphatase is presented. A number of protein substrates with varying molecular masses and isoelectric points were found suitable for the slot-filtration technique. The method is applicable to impure as well as purified kinase and phosphatase preparations, can be used over a wide range of concentrations of substrates, has a very low background of nonspecific ATP binding and provides highly reproducible data. The slot-filtration method can also be adapted for use with ion-exchange paper, particularly for assays using peptides as substrates. The technique, with either nitrocellulose or ion-exchange paper, can be used to rapidly process large numbers of samples and can be simultaneously applied to direct comparison of different kinases, phosphatases and/or substrates in the same experiment.

Animals↗
PubMed2004

[The Hanssen method for measurement of single glomerular filtration rate].

The human renal function is usually obtained as the sum of filtration of 2 million glomeruli in both kidneys. Different glomerular size in the deep and superficial renal cortex led physiologists to suspect differences in both filtration rates and regulation. From 1955 to 1963, a young Norwegian physician, Odd E. Hanssen (1917-64) in the department of pathological anatomy at Rikshospitalet University hospital in Oslo developed a method for estimating single glomerular filtration rate in all layers of the renal cortex of experimental animals by determining tubular content of filtered ferrocyanide. When testing the method he also made several new observations on tubular functions. After a delay of several years, the "Hanssen method" was adopted in 17 laboratories around the world. In about 50 publications the filtration distribution was described in many species under control conditions, during varying salt intake, and during exposure to various nervous and humoral stimuli. Odd Hanssen did not live to see the widespread use of his method; he died from cerebral haemorrhage in 1964 at the age of 47.

Ferrocyanides↗
PubMed1992

Platelet concentrates stored in synthetic medium after filtration.

Platelet concentrates prepared from pooled buffy coats (BCPC) were stored in Plasma-Lyte A, a glucose-free synthetic medium, after leukocyte depletion by filtration through Pall PL 50, and compared to paired unfiltered BCPC stored in the same medium. Each pair of BCPC units was prepared from a pool of 10 buffy coats split into two identical units. Platelet and leukocyte counts per unit of BCPC were 2.70 +/- 0.19 x 10(11) and 3.8 +/- 2.8 x 10(6) (filtered BCPC), 2.59 +/- 0.27 x 10(11) and 79 +/- 56 x 10(6) (control BCPC), respectively. Filtration procedures did not affect in vitro parameters of platelet quality and function such as osmotic reversal, ATP release and aggregation in response to collagen and ADP during 15-day storage. A similar decrease of platelet membrane glycoprotein Ib and a similar rise of activation markers GMP-140, gp 53 and platelet-bound fibrinogen were observed during storage of filtered and control BCPC. Our study indicates that storage of BCPC after filtration is feasible and that a reduction in leukocyte content by filtration to mean cell counts of less than five millions per unit has probably no effect on platelet storage lesion.

Adenosine Diphosphate↗
PubMed2004

Contribution of the colmation layer to the elimination of coliphages by slow sand filtration.

River bank or slow sand filtration is a major procedure for processing surface water to drinking water in central europe. In order to model the performance of river bank and slow sand filtration plants, we are studying the different mechanisms by which the elimination of pathogens is realized. An important question concerning the mode of action of slow sand filters and river bank filtration units is the role of the colmation layer or "schmutzdecke" on the elimination of human pathogens. The schmutzdecke is an organic layer which develops at the surface of the sand filter short after the onset of operation. We have inoculated a pilot plant for slow sand filtration with coliphages and determined their rate of breakthrough and their final elimination. In the first experiment, with a colmation layer still missing, the breakthrough of the coliphages in the 80 cm mighty sandy bed amounted to ca. 40 %. In contrast, less than 1 % of coliphages escaped from the filter as the same experiment was repeated two months later, when a substantial colmation layer had developed. Our preliminary conclusions are that the colmation layer is extremely efficient in eliminating of viruses.

Coliphages↗
PubMed1992

Renal physiology series: Part 2 of 8. Glomerular filtration and renal hemodynamics.

The formation of urine is a process that begins with glomerular filtration and is greatly influenced by changes in renal hemodynamics. Selective filtration of the blood is possible because of the unique characteristics of the glomerulus and renal circulation. Many factors interact to maintain a consistent blood flow, allowing filtration and urine formation to continue despite systemic changes in blood pressure. Factors that impact on renal hemodynamics include the autoregulatory mechanism, the renin-angiotensin mechanism, eicosanoids, kinins, the sympathetic nervous system, catecholamines, antidiuretic hormone, dopamine, histamine, endothelin, endothelium-derived relaxing factor, and atrial natriuretic peptide. Knowledge of the effects of these factors will allow the nephrology nurse to predict, identify, and assist in the treatment of clinical conditions that can alter renal hemodynamics and glomerular filtration.

Glomerular Filtration Rate↗
PubMed1992

Peroxidase activity loss after filtration and centrifugation of whole saliva. Influence of citrate.

Filtration or centrifugation are two methods frequently used to clarify human whole saliva. This study compares both the drop in peroxidase activity following filtration (49.3% +/- 16.4%; N = 12) or centrifugation (33.6% +/- 15.9%; N = 6) and the drop in total protein concentration after filtration (33.9% +/- 13.4%) and centrifugation (23.6% +/- 8.7%). After filtration, the loss was not only due to retention of the large particle-bound fraction but also to adsorption on the filter membranes. This adsorption could be inhibited by a previous dilution of saliva in a citrate buffer, which also gave rise to active subunits with a molecular weight less than or equal to 100 kDa.

Adsorption↗
PubMed2006

A study of the efficacy of various home filtration substrates in the removal of microcystin-LR from drinking water.

This study was conducted to determine whether common water filtration and purification systems bought by consumers and used in the home would remove cyanotoxins from water. Commonly used universal filter housings and filter sizes were utilized to identify filter media that may be effective in the removal of microcystin-LR in deionized water. Results suggest that the efficacy of home filtration devices in removing microcystin-LR varies considerably with the type of device being used. Carbon filters successfully removed microcystin-LR allowing only 0.05-0.3% of the toxin load to pass through the filter. On the other hand, pleated paper and string wound filters allowed > 90% of microcystin-LR present in the sample to pass through the filters. Theoretically, the use of carbon home filtration devices tested in this study may provide protection against human exposure to cyanotoxin in addition to protection provided by water treatment methodologies utilized in water treatment facilities. Further studies need to be done to assess the efficacy of home filtration devices for various cyanotoxins and for other filtering conditions such as increased toxin load, the presence of other contaminants in drinking water, and the repetitive use of the same filter over longer time intervals.

Bacterial Toxins↗