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Bengt Rippe

Publications and source records attributed to Bengt Rippe.

26 records · Page 2Linked to original sources
PubMedDate not supplied

Ambulatory blood pressure in type 2 diabetic patients with albuminuria: relation to the renal function and structural lesions.

BACKGROUND/AIMS: To investigate possible relationships between ambulatory blood pressure (BP) and renal structure and function in type 2 diabetic patients. METHODS: Renal biopsies were performed on 39 patients with urine albumin concentrations above 100 mg/l. BP was investigated with a 24-h, automated, portable BP device. RESULTS: None of the patients in the study had signs of other renal disease than nephrosclerosis or diabetic nephropathy. Ten patients had slight, 13 intermediate, and 6 severe diabetic nephropathy on the renal biopsy. Among the remaining patients, 4 had normal microscopy findings and 6 had nephrosclerosis. The degree of albuminuria correlated to the systolic BP during the day (r = .43; P < .01) and night (r = .49; P < .01). The glomerular filtration rate (GFR) was associated with the systolic BP daytime (r = -.32; P < .05) and nighttime (r = -.47; P < .01). Neither degree of albuminuria nor GFR was associated with the diastolic BP levels. The degree of the glomerular pathology correlated to the systolic BP during daytime (P < .05), whereas the degree of interstitial fibrosis did not correlate to the BP levels. CONCLUSIONS: We have demonstrated that degree of albuminuria and GFR was significantly associated with daytime and nocturnal BP and glomerular structure with daytime BP. Furthermore, no renal disease other than diabetic nephropathy was found.

Adult↗
PubMedDate not supplied

Transendothelial transport of low-density lipoprotein and albumin across the rat peritoneum in vivo: effects of the transcytosis inhibitors NEM and filipin.

This study was performed to investigate the mechanisms responsible for the transport of albumin and low-density lipoprotein (LDL) across capillary walls in vivo. To separate transcytosis from passive, 'porous' transport, we tested the effects of the transcytosis inhibitors N-ethylmaleimide (NEM) and filipin given intraperitoneally on the peritoneal capillary clearance of LDL and albumin in anesthetized rats undergoing peritoneal dialysis. Radiolabeled human albumin or LDL was given intra-arterially, and (51)Cr-EDTA was infused intravenously. A 2-hour peritoneal dialysis dwell was performed using 16 ml of conventional 1.36% glucose-based dialysis fluid. The clearance of LDL and albumin to the dialysate and the peritoneal mass transfer coefficient for (51)Cr-EDTA were assessed. Following intraperitoneal NEM incubations (0.5-5 mM), there were marked increases in the peritoneal transport of albumin and LDL for NEM doses exceeding 1 mM. For lower NEM doses, there were no reductions in clearance. Filipin incubations (0.2-4 microg/ml) did not affect the clearance of either macromolecule. In conclusion, neither NEM nor filipin caused reductions in albumin or LDL clearance across the peritoneal capillaries. The present data clearly show that NEM and filipin are unsuitable as transcytosis inhibitors in vivo.

Albumins↗
PubMedDate not supplied

Transendothelial transport: the vesicle controversy.

The relative contribution of transcytosis vs. large pore transport to the passage of macromolecules across microvascular endothelia has been a controversial issue for nearly half a century. To separate transcytosis from 'porous' transport, the transcytosis inhibitors N-ethylmaleimide (NEM) and filipin have been tested in in situ or ex vivo perfused organs with highly conflicting results. In continually weighed isolated perfused organs, where measurements of pre- and post-capillary resistances, capillary pressure and capillary filtration coefficients can be repeatedly performed, high doses of NEM and filipin increased the bulk transport of macromolecules from blood to tissue, despite producing vasoconstriction. By contrast, in in situ perfused organs, marked reductions in the tissue uptake of albumin tracer have been observed after NEM and filipin. When tissue cooling has been employed as a means of inhibiting (active) transcytosis, results have invariably shown a low cooling sensitivity of albumin transport, compatible with passive transendothelial passage of albumin. This observation is further strengthened by the commonly observed dependence of albumin transport upon the capillary pressure and the rate of transcapillary convection. For low-density lipoprotein (LDL), a cooling-sensitive, non-selective transport component has been discovered, which may be represented by filtration through paracellular gaps, lateral diffusion through transendothelial channels formed by fused vesicles, or by transcytosis. From a physiological standpoint there is little evidence supporting active transendothelial transport of most plasma macromolecules. This seems to be supported by studies on caveolin-1-deficient mice lacking plasmalemmal vesicles (caveolae), in which there are no obvious abnormalities in the transendothelial transport of albumin, immunoglobulins or lipoproteins. Nevertheless, specific transport in peripheral capillaries of several hormones and other specific substances, similar to that existing across the blood-brain barrier, still remains as a possibility.

Animals↗
PubMedDate not supplied

Fluid and electrolyte transport across the peritoneal membrane during CAPD according to the three-pore model.

In the present review, we summarize the principles governing the transport of fluid and electrolytes across the peritoneum during continuous ambulatory peritoneal dialysis (CAPD) in "average" patients and during ultrafiltration failure (UFF), according to the three-pore model of peritoneal transport. The UF volume curves as a function of dwell time [V(t)] are determined in their early phase by the glucose osmotic conductance [product of the UF coefficient (LpS) and the glucose reflection coefficient (sigmag)] of the peritoneum; in their middle portion by intraperitoneal volume and glucose diffusivity; and in their late portion by the LpS, Starling forces, and lymph flow. The most common cause of UFF is increased transport of small solutes (glucose) across the peritoneum, whereas the LpS is only moderately affected. Concerning peritoneal ion transport, ions that are already more or less fully equilibrated across the membrane at the start of the dwell, such as Na+ (Cl-), Ca2+, and Mg2+, have a convection-dominated transport. The removal of these ions is proportional to UF volume (approximately 10 mmol/L Na+ and 0.12 mmol/L Ca2+ removed per deciliter UF in 4 hours). The present article examines the impact on fluid and solute transport of varying concentrations of Ca2+ and Na+ in peritoneal dialysis solutions. Particularly, the effect of "ultralow" sodium solutions on transport and UF is simulated and discussed. Ions with high initial concentration gradients across the peritoneum, such as K+, phosphate, and bicarbonate, display a diffusion-dominated transport. The transport of these ions can be adequately described by non-electrolyte equations. However, for ions that are in (or near) their diffusion equilibrium over the peritoneum (Na+, Ca2+, Mg2+), more complex ion transport equations need to be used. Due to the complexity of these equations, however, non-electrolyte transport formalism is commonly employed, which leads to a marked underestimation of mass transfer area coefficients (PS). This can be avoided by determining the PS when transperitoneal ion concentration gradients are steep.

Bicarbonates↗
PubMedDate not supplied

Biocompatibility of peritoneal dialysis fluids: long-term exposure of nonuremic rats.

OBJECTIVES: Long-term peritoneal dialysis (PD) leads to structural and functional changes in the peritoneum. The aim of the present study was to investigate the long-term effects of PD fluid components, glucose and glucose degradation products (GDP), and lactate-buffered solution on morphology and transport characteristics in a nonuremic rat model. METHODS: Rats were subjected to two daily intraperitoneal injections (20 mL/day) during 12 weeks of one of the following: commercial PD fluid (Gambrosol, 4%; Gambro AB, Lund, Sweden), commercial PD fluid with low GDP levels (Gambrosol trio, 4%; Gambro AB), sterile-filtered PD fluid (4%) without GDP, or a glucose-free lactate-buffered PD fluid. Punctured and untreated controls were used. Following exposure, the rats underwent a single 4-hour PD dwell (30 mL, 4% glucose) to determine peritoneal function. Additionally, submesothelial tissue thickness, percentage of high mesothelial cells (perpendicular diameter > 2 microm), vascular density, vascular endothelial growth factor (VEGF), and transforming growth factor (TGF) beta1 mRNA expression were determined. Submesothelial collagen concentration was estimated by van Gieson staining. RESULTS: Submesothelial tissue thickness and vascular density, mediated by VEGF and TGFbeta production, in the diaphragmatic peritoneum increased significantly in rats exposed to any PD fluid. Gambrosol induced a marked increased fibrosis of the hepatic peritoneum. A significant increase in high mesothelial cells was observed in the Gambrosol group only. Net ultrafiltration was reduced in the Gambrosol and in the glucose-free groups compared to untreated controls. Small solute transport was unchanged, but all groups exposed to fluids showed significantly increased lymph flow. CONCLUSIONS: Our results show that long-term exposure to different components of PD fluids leads to mesothelial cell damage, submesothelial fibrosis, and neoangiogenesis. Mesothelial cell damage could be connected to the presence of GDP; the other changes were similar for all fluids. Peritoneal transport characteristics did not change in any consistent way and the neoangiogenesis observed was not paralleled by increased solute transport.

Animals↗
PubMedDate not supplied

Validation by computer simulation of two indirect methods for quantification of free water transport in peritoneal dialysis.

BACKGROUND: In peritoneal dialysis, approximately 40% of the total osmotic ultrafiltration (UF) induced by glucose can be predicted to be due to "free" water transport across aquaporin-1 (APQ-1). Theoretically, it would be possible to assess the fraction of free water transport in the early phase of a hypertonic dwell, when UF rate is high and the relative contribution of Na+ diffusion is low. La Milia et al. [La Milia V. et al. Fast-fast peritoneal equilibration test (FAST-FAST-PET): a simple method for peritoneal hydraulic permeability study [Abstract]. Nephrol Dial Transplant 2002; 17 (Suppl 1):17-18] suggested a technique to assess sodium-associated water transport based on sodium removal (Na+R) divided by the plasma Na+ concentration during a "fast-fast" (60 minute) peritoneal equilibration test (PET) for 3.86% glucose, yielding an estimate of the UF passing through the small pores (UFSP). Free water transport (UF through ultrasmall pores; UFUSP) was obtained by subtracting UFSP from total UF. Although peritoneal Na+ transport is almost totally convective, this technique will slightly overestimate small-pore UF due to the presence of some small-pore Na+ diffusion from the circulation during the dwell. A way of dealing with this problem was presented recently by Smit (Smit W. et al. Quantification of free water transport in peritoneal dialysis. Kidney Int 2004; 66:849-854). METHODS: In the present study we used the three-pore model of peritoneal transport to predict the degree of overestimation of UFSP for the technique presented by La Milia et al., and any potential deviations from theory for the technique presented by Smit et at. Simulations were performed under ordinary conditions and during simulated UF failure for 3.86% glucose. The fractional UF coefficient accounted for by APQ-1 was set at 2%. RESULTS: Estimating the UFSP from the sodium-associated water transport according to the method by La Milia et al. consistently overestimated UFSP and underestimated UFUSP. These errors were, however, minimal for dwells lasting between 30 and 80 minutes. The technique by Smit et al. to calculate aquaporin-mediated water flow (UFUSP), using an elaborate correction for Na+ diffusion from the circulation during the dwell, seemed accurate in most situations but, in general, tended to moderately overestimate UFUSP at early dwell times (<30 minutes) and underestimate UFUSP at long dwell times (4 hours). CONCLUSIONS: The technique presented by La Milia et at. to calculate free water transport during a fast-fast PET was found to be surprisingly accurate, although the procedure would further improve by the introduction of a correction algorithm. The technique by Smit is even more accurate for dwells up to 4 hours' duration. However, since the Smit technique is elaborate, it is less practical for routine determinations of aquaporin-mediated water transport in peritoneal dialysis.

Algorithms↗
PubMedDate not supplied

Improvement of peritoneal ultrafiltration with peritoneal dialysis solution buffered with bicarbonate/lactate mixture.

BACKGROUND: In computer simulations, according to the three-pore model of peritoneal transport, neutralization of conventional acidic peritoneal dialysis fluids is predicted to produce an improved ultrafiLtration (UF). However, in a previous study, a two-compartment peritoneal dialysis system with a minimum of glucose degradation products (GDP), PD-Bio, having a pH of 6.3 and being conventionalLy lactate buffered, did not produce an increased UF. SETTING: We tested a newly formulated, glucose-based, GDP-reduced solution, denoted "N" for "neutral," containing a mixture of lactate (30 mmol/L) and bicarbonate (10 mmol/L) as buffer system, and having a pH of 7.2. This new formulation was compared with Gambrosol trio (GT) (identical in composition to PD-Bio, but delivered in a three-compartment system; both by Gambro Lundia AB, Lund, Sweden) in an open, prospective controlled study of 13 patients. MATERIAL AND METHODS: Each of the 13 patients used GT for 14 days, followed by 14 days of N. All bags were weighed on a digital scale before instillation and after drainage to assess the UF in each dwell (and during 24 hours). Glucose concentration in each bag was noted. In the morning and night dwells, dialysis fluid glucose concentration was standardized to 2.5%. Body weight was measured every morning (empty abdomen). In the middle of each 14-day period, a 4-hour standardized ("study day") dwell was performed, using 125I-albumin (RISA) as volume marker, during which blood and dialysate samples were taken repeatedly and anaLyzed for RISA, creatinine, urea, phosphate, glucose, standard bicarbonate, lactate, and pH. The permeability surface area product (PS) for small solutes (and A0/deltaX; "area parameter") was calculated. Clearance (Cl) of RISA to plasma (P) (C-->P), "direct lymphatic absorption," and total Cl of RISA out of the peritoneal cavity (Cl(out)) were also determined. RESULTS: The 13 patients using N, compared to GT, displayed an increased daily UF, the difference being 233 mL (p < 0.05). The pH values of N were higher during the first 90 minutes of the 4-hour dwell compared to the pH values of GT. Neither the small solute PS values nor RISA determined UF, nor did body weight differ significantly between the GT and the N periods. CONCLUSIONS: A new bicarbonate/lactate-buffered solution, N, with neutral pH (of 7.2) and low in GDP seems to produce an improved UF compared to a lactate-buffered solution with a pH of 6.3, equally low in GDP, partly in agreement with our earlier predictions. A dialysis solution with a neutral pH combined with a reduced lactate concentration, partially replaced by bicarbonate, evidently increases UF, conceivably by causing less peritoneal vasodilatation than solutions buffered by lactate or high concentrations of bicarbonate alone.

Adult↗