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PubMed2002

The rat glomerular filtration barrier does not show negative charge selectivity.

OBJECTIVE: To characterize the effects of size, shape, and negative charge on the transport of macromolecules across the glomerular capillary wall by using the sieving curves (fractional clearance vs. solute molecular radii) of fluorescent polydispersed polysaccharide tracers. METHODS: Glomerular fractional clearances (FC) were measured with fluorescent neutral [isoelectric point (pI) = 7.3 +/- 0.2] and negatively charged (pI = 3.5 +/- 0.4) dextrans (DEX) in comparison with negatively charged (pI = 4.8 +/- 0.3) hydroxy ethyl starch (HES) and (pI = 4.6 +/- 0.1) bovine serum albumin (BSA) in Sprague-Dawley and Fischer 344/Brown Norway rats. FCs (n = 53) were measured by using the urinary clearance of (14)C-inulin to determine the glomerular filtration rate. The relative uptake of each fluorescent probe by endothelial and renal proximal tubule epithelial (LLC-PK(1)) cells, in vitro, was measured microscopically by using a cooled (-25 degrees C) CCD camera. RESULTS: The sieving curves for randomly coiled neutral and negatively charged DEX probes were identical. These FC values were 6-fold greater than those for HES and 200-fold above similarly sized fluorescent BSA. The polysaccharide probes did not show significant binding to serum proteins. The uptake of BSA by LLC-PK(1) cells was 20- to 100-fold greater than that for neutral or negatively charged macromolecules. CONCLUSIONS: These findings indicate that the rat glomerular filtration barrier restricts the transport of polysaccharide macromolecules as a function of their size and configuration but not negative charge.

Animals↗
PubMed2005

Hydrodynamic filtration for on-chip particle concentration and classification utilizing microfluidics.

We propose here a new method for continuous concentration and classification of particles in microfluidic devices, named hydrodynamic filtration. When a particle is flowing in a microchannel, the center position of the particle cannot be present in a certain distance from sidewalls, which is equal to the particle radius. The proposed method utilizes this fact, and is performed using a microchannel having multiple side branch channels. By withdrawing a small amount of liquid repeatedly from the main stream through the side channels, particles are concentrated and aligned onto the sidewalls. Then the concentrated and aligned particles can be collected according to size through other side channels (selection channels) in the downstream of the microchannel. Therefore, continuous introduction of a particle suspension into the microchannel enables both particle concentration and classification at the same time. In this method, the flow profile inside a precisely fabricated microchannel determines the size limit of the filtered substances. So the filtration can be performed even when the channel widths are much larger than the particle size, without the problem of channel clogging. In this study, concentrations of polymer microspheres with diameters of 1-3 microm were increased 20-50-fold, and they were collected independently according to size. In addition, selective enrichment of leukocytes from blood was successfully performed.

Cell Separation↗
PubMed1965

GEL FILTRATION APPLIED TO THE STUDY OF LIPASES AND OTHER ESTERASES.

1. Sephadex G-100 and G-200 gel-filtration columns were calibrated for molecular-weight estimation with proteins of known molecular weights, and used to study the composition of several lipase or esterase preparations. 2. Enzymes from cow's milk, rat adipose tissue and pig pancreas were detected in the column effluents by their ability to liberate free acid from emulsified tributyrin at pH 8.5. 3. Four tributyrinases were detected in preparations from individual cow's milks. Molecular weights 62000, 75000 and 112000 were estimated for three of them, but although the fourth may be of unusually low molecular weight an estimate was not possible. 4. Extracts of rat adipose tissue apparently contained six tributyrinases (molecular weights 39000, 47000, 55000, 68000, 75000 and 200000) but the relative amounts of these enzymes varied widely from rat to rat. 5. Tributyrinase activity in juice expressed from pig pancreatic tissue was due mainly to one enzyme (molecular weight 42000). On the other hand, activity in extracts of acetone-dried pancreas was confined to material of molecular weight > 10(6), which may be an aggregated form of the lower-molecular-weight enzyme. 6. Activity in fractionated wheat-germ extracts was assayed with emulsified triacetin substrate, and was evidently due to one enzyme (molecular weight 51000). 7. Some problems arising in the application of gel filtration to the study of lipase-esterase systems were indicated.

Adipose Tissue↗
PubMed1970

A filtration method for the separation of cell sap from the large-particle fraction of rat liver suspensions, enabling the rapid measurement of nucleotide distributions.

A simple method is described that allows a rapid separation of a cell-sap fraction from the large-particle fraction of rat liver suspensions. The method is based on the filtration under suction of liver suspensions through Millipore filters that retain nuclei, mitochondria and some of the endoplasmic-reticulum fraction, but allow quantitative passage of cell sap into a collecting tube. The cell sap may be separated in this manner within 2min of the death of the rat. The method was applied to study the intracellular distribution of ATP and of the nicotinamide-adenine dinucleotides and the results obtained were compared with those obtained after separating the cell sap by a rapid centrifuging procedure. The percentage of total liver ATP in the cell sap was found to be 46% by the filtration method and more than 70% by the centrifuging procedure. Corresponding figures found for the distribution of NADP(+)+NADPH were 40 and 49% respectively.

Adenosine Triphosphate↗
PubMed1988

Dependence of mitochondrial and cytosolic adenine nucleotides on oxygen partial pressure in isolated hepatocytes. Application of a new rapid high pressure filtration technique for fractionation.

By using a new rapid high pressure filtration technique, mitochondrial and cytosolic ATP and ADP contents were determined in isolated hepatocytes at different oxygen partial pressures. At 670 mmHg, subcellular adenine nucleotide contents and ATP/ADP ratios were comparable with values obtained with the digitonin fractionation technique. However at lower oxygen partial pressure ADP appears to be rephosphorylated during digitonin fractionation whereas with high pressure filtration fractionation rephosphorylation of ADP is avoided due to shorter fractionation times. Cytosolic and mitochondrial ATP/ADP ratios decrease if oxygen partial pressure is lowered. However the absolute values of ATP/ADP ratios depend critically on the incubation conditions. Thus incubation of hepatocytes in an oxystat system, where oxygen partial pressure is maintained constant by infusing oxygen-saturated medium and the hepatocyte suspension is continuously stirred, yields much higher subcellular and overall ATP/ADP ratios than incubation in Erlenmeyer flasks gassed with different gas mixtures and shaken in a water bath. This is ascribed to limited diffusion of oxygen from the medium into the cell if the suspension is not mixed thoroughly by stirring. The strong dependence of subcellular ATP/ADP ratios on incubation conditions indicates that oxygen may be one rate-controlling factor for oxidative phosphorylation in the intact cell.

Adenine Nucleotides↗
PubMed1976

Inter-relationship between autoregulation of glomerular filtration rate, tubuloglomerular feedback and juxtaglomerular renin activity in normotensive and hypertensive rats.

1. Reduction of renal perfusion pressure from 133 mmHg to 117 mmHg in control rats did not induce a significant change of kidney glomerular filtration rate (GFR) or nephron GFR determined in distal tubules. In contrast, nephron GFR measured in proximal tubular segments (NGFR-P) fell significantly. 2. Qualitatively the same response of filtration rate to changes of arterial blood pressure was found in the chronically clipped kidneys of Goldblatt hypertensive rats after acute removal of the clip. 3. In contrast, autoregulation of kidney GFR, NGFR-D and NGFR-P was abolished in the contralateral kidneys of Goldblatt hypertensive rats. 4. Microperfusion studies showed that tubuloglomerular feedback regulation of NGFR was present in the renin-rich ischaemic kidneys of Goldblatt rats after removal of the constricting clip, but greatly attenuated in the renin-depleted contralateral kidneys. 5. These data indicate that tubuloglomerular feedback participates in establishing renal autoregulation, possibly by mediation of the renin-angiotensin system.

Animals↗
PubMed1977

Lack of dependence of urine PCO2 upon reduction of glomerular filtration rate in alkalotic dogs.

1. The PCO2 gradient between alkaline urine and arterial blood (U-B PCO2) is thought to depend primarily on distal hydrogen ion secretion. However, other variables affecting the U-B PCO2 include the urine flow rate, the urinary bicarbonate and phosphate excretion rates and the glomerular filtration rate. 2. In order to evaluate the effects of acute changes in these factors on the U-B PCO2, bicarbonate-loaded dogs with maximal U-B PCO2 values were subjected to either acute unilateral elevations of ureteral pressure or hypotension caused by nitroprusside infusion. The results demonstrate that acute reduction in the glomerular filtration rate does not cause a decrease in the U-B PCO2 as long as the urinary concentrations of phosphate and bicarbonate do not decline. 3. Urinary concentrations of phosphate and bicarbonate appeared more important than their excretion rates in the maintenance of elevated U-B PCO2 values.

Alkalosis↗
PubMed1982

A biochemical and immunological investigation into the physiological basis of the increased albumin filtration induced in hyperalbuminaemic female Wistar rats.

1. The level of proteinuria induced in female Wistar rats after bovine albumin injection intraperitoneally was highly dose dependent. 2. The proteinuria remained highly selective, with albumin constituting approximately 90% of the total protein excreted, even in the most severely affected rats. 3. Calculations relating the amount of bovine albumin available in the serum for filtration to the amount excreted in the urine indicated that complete saturation of the reticuloendothelial and tubular protein reabsorption systems may have occurred during the course of the 5 day injection period in rats given more than 3.5 mg of bovine albumin day-1 g-1 body wt. 4. When this situation was attained there appeared to be no further increase in glomerular permeability to either rat or bovine albumin and an equilibrium state seemed to exist where, when serum albumin levels were raised above the normal level, all the excess albumin passed across the glomerular filter to be excreted in the urine. 5. The passage of these large quantities of albumin across the glomerular filter may have resulted not from ultrastructural damage to the filter itself but rather from the generation of vastly increased concentration gradients across the glomerular basement membrane, which were sufficiently large to overcome the electrostatic repulsive forces which normally severely restrict albumin filtration.

Albumins↗
PubMed1987

Interaction between renal prostaglandins and angiotensin II in controlling glomerular filtration in the dog.

Although previous studies suggest that the renal vasoconstrictor effects of angiotensin II (ANG II) are normally confined to the efferent arterioles, the mechanisms that prevent ANG II from constricting preglomerular vessels are still unclear. In the present study, the role of prostaglandins (PG) in protecting preglomerular vessels from ANG II constriction was examined in dogs with normal or non-filtering kidneys in which ANG II formation was blocked with captopril and renal artery pressure was servo-controlled at 75-80 mmHg. Before PG blockade (n = 6), ANG II infusion (20 ng min-1 kg-1) decreased renal blood flow (RBF) by 54 +/- 4%, but did not change glomerular filtration rate (GFR) significantly. After PG blockade (n = 6), ANG II infusion decreased GFR by 37 +/- 7% and RBF by 56 +/- 6%, while increasing calculated preglomerular resistance much more than before PG blockade. In another group of dogs, secondary changes in renal resistances, due to tubuloglomerular feedback, were prevented by occluding the ureter during mannitol diuresis until glomerular filtration ceased. After inhibition of tubuloglomerular feedback in non-filtering kidneys (n = 7), ANG II decreased RBF by 40 +/- 3% and increased glomerular hydrostatic pressure, estimated from stop-flow ureteral pressure and plasma colloid osmotic pressure, by 8.7 +/- 1.7 mmHg. Postglomerular resistance increased by 91 +/- 12% while preglomerular resistance was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗
PubMed1988

Relationship between glomerular filtration rate and renal blood flow at different levels of protein-induced hyperfiltration in man.

1. We studied the relationship between changes in glomerular filtration rate (GFR) determined as inulin clearance (CIn), and changes in renal blood flow (RBF), determined as p-aminohippurate clearance (CPAH), after the ingestion of a large (1.35 +/- SEM 0.04 g/kg, n = 9), moderate (1.08 +/- 0.03 g/kg, n = 10) or mild (0.55 +/- 0.02 g/kg, n = 8) protein load given as a meat meal. Control subjects (n = 10) received a carbohydrate meal. 2. CIn and CPAH increased after a protein meal. Two hours after eating the test meal, GFR levels were (mean +/- SEM) 160.0 +/- 13.8 (P less than 0.05), 141 +/- 7.69 and 127.8 +/- 9.07 ml/min in the groups that received a large, moderate and mild protein load, respectively. Peak CIn values after the meal were 211.6 +/- SEM 14.92 (P less than 0.001), 177.5 +/- 10.88 (P less than 0.01) and 129.0 +/- 8.72 ml/min after a large, moderate and mild protein load, respectively. 3. At peak GFR levels after the meal, filtration fraction (FF) (CIn X 100/CPAH) increased significantly (P less than 0.02) with the large and with the moderate protein load, but not with the mild protein load. 4. There was a significant (P less than 0.001) positive relationship between increments of FF and increments of CIn, but not CPAH, whether the values were expressed as post-meal/pre-meal ratios or as absolute changes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Changes in glomerular filtration rate, lithium clearance and plasma protein clearances in the early phase after unilateral nephrectomy in living healthy renal transplant donors.

1. Glomerular and tubular function was studied before and 2 months after unilateral nephrectomy in 14 healthy kidney donors by measurement of the clearances of 51Cr-labelled ethylenediaminetetra-acetate, lithium, beta 2-microglobulin, albumin and immunoglobulin G. 2. The glomerular filtration rate (GFR) of the kidney that remained in the donor rose from 45 +/- 10 (mean +/- SD) to 59 +/- 10 ml/min (P less than 0.01) 5 days after contralateral nephrectomy and remained at this level through the observation period. 3. The lithium clearance (CLi) of the remaining kidney rose from 11.6 +/- 3.7 to 20.5 +/- 8.2 ml/min (P less than 0.01) and remained significantly elevated throughout the observation period. 4. Absolute proximal fluid reabsorption rate (APR), which was estimated as GFR minus CLi, was unchanged 5 days after contralateral nephrectomy, but then rose gradually to reach significantly elevated levels after 4 weeks. 5. Fractional proximal reabsorption (FPR; APR/GFR) fell from 0.75 +/- 0.06 to 0.66 +/- 0.11 (P less than 0.01) but subsequently rose to levels not significantly decreased from normal. 6. Twenty-four hour fractional clearances of beta 2-microglobulin, albumin and immunoglobulin G rose markedly on the day of nephrectomy, peaked at 2-3 days and subsequently fell to moderately elevated levels. 7. Both the CLi and the plasma protein clearance studies demonstrate that the early response of the remaining kidney to contralateral nephrectomy in man is an increase in GFR, an unchanged APR and a fall in FPR. The proximal tubules thus initially handle the increased filtrate load by passing it on to more distal nephron segments.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Circadian rhythm of glomerular filtration rate in normal individuals.

1. In a group of 11 normal individuals we measured glomerular filtration rate (GFR) by inulin clearances and effective renal plasma flow (ERPF) by p-aminohippurate clearances during a period of 24 h and a regimen of bedrest, identical food intake per 3 h and normal sleep/wake and light/dark cycles. 2. All subjects had a circadian rhythm for GFR with a maximum of 122 ml/min (SD 22) in the daytime, a minimum of 86 ml/min (SD 12) at night and with a relative amplitude of 33% (SD 15). 3. ERPF had a circadian rhythm with a similar relative amplitude as the GFR rhythm, but with a different phase. Because of this difference in phase, the calculated filtration fraction (GFR/ERPF) followed a circadian rhythm as well. 4. The circadian rhythms of urine volume and sodium excretion were in phase with the GFR rhythm, but the potassium rhythm had a different phase, probably because urinary potassium is largely derived from tubular secretion. 5. Urinary albumin and beta 2-microglobulin excretion had a circadian rhythm in phase with the GFR rhythm. 6. The highest quantity of sodium, water and beta 2-microglobulin was reabsorbed in the daytime; tubular reabsorption, expressed as percentage of the filtered load (fractional reabsorption), had a rhythm with a reversed phase.

Adult↗
PubMed1990

Role of atrial natriuretic peptide in the increase in glomerular filtration rate induced by a protein meal.

1. The increase in glomerular filtration rate after a protein meal is believed to be mediated by hormonal factors. Since natriuresis is often observed after a protein meal, it was postulated that the increase in glomerular filtration rate after a protein meal might be mediated by atrial natriuretic peptide. 2. Subjects were given a low, medium or high protein meal. Fluid intake was controlled so as to avoid significant extracellular fluid volume expansion. It was found that the creatinine clearance, the urea excretion, the fractional sodium excretion and the potassium excretion were elevated in all subjects after protein meals (P less than 0.05). These effects were not observed in subjects given a carbohydrate control meal. 3. The plasma atrial natriuretic peptide concentrations remained unchanged in all subjects except those given a high protein meal (P less than 0.05). There was no significant relationship between plasma atrial natriuretic peptide concentrations and creatinine clearance before or after a protein meal. 4. The data suggest that a high protein meal induces a minor increase in plasma atrial natriuretic peptide concentration, whereas a low or medium protein meal does not. It is unlikely that the change in creatinine clearance after a protein meal can be explained by a change in plasma atrial natriuretic peptide levels.

Adult↗
PubMed2002

Measuring the filtration performance of breathing system filters using sodium chloride particles.

The filtration performance of 33 breathing system filters (nine pleated hydrophobic and 24 electrostatic filters) was measured using sodium chloride particles. The particles had a size distribution with a count median diameter of 0.07 microm and a geometric standard deviation not exceeding 1.83. The geometric mean penetration values ranged from 0.002 to 0.67% for the nine pleated hydrophobic filters and from 0.25 to 35% for the 24 electrostatic filters (p < 0.0001 for the difference between the two filter types). The filtration performance obtained when filters are challenged with either sodium chloride particles or microbes is compared and discussed.

Anesthesia, Inhalation↗
PubMed2003

The effect of loading on the filtration performance of breathing system filters.

The filtration performance of breathing system filters can be measured by challenging the filter with sodium chloride particles. However, the challenge itself may alter the filtration performance. This effect was determined by repeating a standard challenge test five times on one sample each of 18 different electrostatic filters and seven pleated hydrophobic filters. The penetration of sodium chloride particles through all 18 electrostatic filters increased as the load on the filter increased. In contrast, there was a decrease in penetration through six of the seven pleated hydrophobic filters (p < 0.0001). However, the changes in penetration values were small compared to the large range of penetration values of the filters, and the effect of loading on penetration values using the challenge specified in the European standard is small.

Anesthesia, Inhalation↗
PubMed2003

Increasing oxygen tension improves filtration of sickle trait donor blood.

A major cause of filter failure of red cell (RBC) components from donors with sickle cell trait (HbAS) is the polymerization of haemoglobin. The oxygen saturation (sO2) of blood stored in various plastics and different volumes of air was assessed. Blood from 10 HbAS donors was collected and divided into two bags, one with air added, one without. Bags with added air had increased sO2 levels (from 49 +/- 10% to 76 +/- 6%). Filtration was successful for nine of 10 components with air, and one of 10 without air. Successful filtration of RBC components occurs when sO2 is increased.

Adolescent↗
PubMed2000

Virus-associated haemophagocytic syndrome responsive to steroid pulse therapy and double filtration plasmapheresis.

We present an adult patient with haemophagocytic syndrome (HPS) successfully treated with a combination of steroid pulse therapy and double filtration plasmapheresis (DFPP). A 58-year-old male was admitted with high fever, severe renal dysfunction, liver dysfunction and an increased level of lactate dehydrogenase. A serological test for Epstein-Barr (EB) virus showed an elevation of EBNA-IgM antibody titre. There were increased haemophagocytic histiocytes in the bone marrow in addition to thrombocytopenia and disseminated intravascular coagulation (DIC) accompanied by organ dysfunction. EB virus associated haemophagocytic syndrome was diagnosed. On admission, interferon (IFN)-gamma, interleukin (IL)-6, IL-8, granulocyte colony-stimulating factor (G-CSF) and macrophage (M)-CSF were elevated, and were promptly normalized after steroid pulse therapy was initiated. G-CSF and M-CSF gradually decreased after DFPPs was started. To control hypercytokinaemia until treatment for the underlying disease is initiated, steroid pulse therapy and double filtration plasmapheresis are useful.

Antibodies, Viral↗
PubMed2002

Removal of T and B lymphocytes by in-line filtration: evaluation of the efficiency of a polyester filter type (Pall WBF-2) by flow cytometric counting.

BACKGROUND AND OBJECTIVES: The aim of this study was to investigate whether in-line filtration, using a polyester filter for the preparation of red cell concentrates (RCC) and plasma (PL), leads to an altered proportion of T and B lymphocytes in the fraction of residual white blood cells (WBC). MATERIALS AND METHODS: The capacity of Pall WBF-2 in-line filters to reduce the numbers of T and B lymphocytes from red blood cell concentrates (RCC) and plasma (PL) of 22 donations was investigated by three-colour flow cytometry (FC) using the Tritest-Trucount kit. T and B lymphocytes were identified using monoclonal antibodies (mAbs) against CD3, CD19 and CD45, conjugated with fluorescein isothiocyanate, phycoerythrin or peridinin chlorophyll protein-A, respectively. As the number of B cells was below the detection limit of the FC method, WBC of the respective blood components of healthy donors were concentrated 25-fold by Percoll density-gradient centrifugation. In this fraction the absolute numbers of T and B cells, as well as their ratio, were determined using the Attractor software, which provides a discrimination of rare cell counts from FC in relation to debris. RESULTS: The mean numbers, as well as minima and maxima of T and B lymphocytes per unit, were as follows. T cells in RCC: 4.51 x 10(3) (1.68 x 10(2)-4.09 x 10(4)) and in PL: 1.35 x 10(3) (2.21-1.78 x 10(4)); B cells in RCC: 2.33 x 10(3) (7.10 x 10(1)-9.15 x 10(3)) and in PL: 2.33 x 102 (7.5 x 10(2)-2.8 x 10(3)). T cells were retained, on average, at a higher level than B cells: 3.01 times higher in RCC and 1.01 times higher in PL. CONCLUSION: After filtration, the ratio of T and B lymphocytes changed in RCC (1.95 : 1) compared with unfiltered blood, where it was 5.83 : 1. In PL the ratio did not change notably compared to unfiltered blood. The results of this research show that cell concentration (using gradient centrifugation) in combination with an appropriate FC acquisition and analysis procedure, allows both residual T and B lymphocytes (being under the detection limit without cell concentration) to be determined.

B-Lymphocytes↗