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H Stolte

Publications and source records attributed to H Stolte.

At least 37 records · Page 2Linked to original sources
PubMed1994

Isolated glomeruli of the Atlantic hagfish Myxine glutinosa as an alternative in vitro model to study glomerular protein metabolism in pharmaco-toxicology of anticancer drugs.

This study was designed to validate an alternative in vitro system with isolated glomeruli of the Atlantic hagfish Myxine glutinosa as a model to study alterations in glomerular protein metabolisms in pharmaco-toxicology of anticancer drugs. A morphometric characterization of the glomeruli of Myxine glutinosa reveals a calculated glomerular volume of 180 nl/glomerulus. The glomerular extracellular volume, measured as inulin space, is 38.5 nl/glomerulus. Total glomerular protein content of Myxine glutinosa amounts to 3.56 micrograms/glomerulus and total DNA content to 0.44 microgram/glomerulus. Metabolic properties, estimated as glomerular protein synthesis, are comparable with mammalian glomeruli. The glomeruli of Myxine glutinosa are viable in a tissue culture for up to 12 hr. The incorporation rate of radiolabeled amino acids into glomerular, acid-precipitable proteins is almost identical to that of rats (e.g. Myxine glutinosa 1091 +/- 98 DPM/micrograms DNA vs. rat 1340 +/- 84 DPM/micrograms DNA after 4 hr incubation). To evaluate how nephrotoxic substances affect glomerular metabolism in this model, the anticancer drug Adriamycin (ADR) was used to experimentally induce a glomerular lesion. ADR caused an increase in glomerular protein synthesis in isolated glomeruli of Myxine glutinosa, which is in accordance with data found in rats. Cisplatin, in contrast, known to mainly interfere with tubular integrity, had no effect on glomerular protein synthesis, confirming the specificity of the model. The isolated glomeruli of Myxine glutinosa are suggested as a valid alternative multicellular in vitro system for studying alterations in glomerular metabolism under pharmaco-toxicological conditions and for the evaluation of specific target-cell toxicity of selected nephrotoxins.

Animals↗
PubMed1993

Urinary proteins and enzymes as early indicators of renal dysfunction in chronic exposure to cadmium.

We tested the diagnostic sensitivity of various urinary analytes for detecting cadmium-induced nephropathy at an early stage. We investigated 73 healthy persons (control group 1) and individuals exposed to cadmium, either environmentally (n = 36, risk group 2) or occupationally (n = 62, exposed group 3). All data were related to limits of the central 95% reference intervals of the control group. The serum creatinine and ribonuclease values, indicators of the glomerular filtration rate, were not different in the three groups. In the exposed persons (group 3), proximal tubular indicators (low-M(r) proteins lysozyme, ribonuclease, retinol-binding protein, and alpha 1-microglobulin) were more often increased than the glomerular indices (higher-M(r) proteins transferrin, IgG, and albumin). Both the low-M(r) proteins and tubular enzymes were differently altered in their excretion rates. Alanine aminopeptidase, alkaline phosphatase, and N-acetyl-beta-D-glucosaminidase increased even in the risk group 2. alpha 1-Microglobulin was increased in the exposed persons whose cadmium excretion was < 5 mumol/mol creatinine. The combined determination of alpha 1-microglobulin and N-acetyl-beta-D-glucosaminidase exceeded the corresponding upper reference limits in 30% of group 2 and 39% of group 3. We recommend screening for these two analytes to detect cadmium-induced renal dysfunction at an early stage.

Acetylglucosaminidase↗
PubMed1993

Origin of urinary fibronectin.

BACKGROUND: Fibronectin (FN) is a major component of the glomerular extracellular matrix and it is also abundant in plasma. In physiologic conditions, FN fragments are excreted into urine. Increased urinary FN excretion has been observed in renal diseases raising the question whether urinary FN could reflect changes in the renal extracellular matrix. This study examines whether urinary FN is filtered from plasma or derived from the kidney and it attempts to specify the potential renal source of urinary FN. EXPERIMENTAL DESIGN: (a) To investigate whether urinary FN is filtered from plasma, labeled, biotinylated FN (b-FN) was injected into rats and urine samples were specifically analyzed for b-FN by an immunoblot procedure. (b) To specify the renal source of urinary FN and to evaluate possible alterations of this protein during passage into final urine, tubular fluid was collected from distinct localizations of the nephron by micropuncture techniques. The samples were analyzed for endogenous FN by a highly sensitive immunoblot system, and the pattern was compared with that normally found in final urine. RESULTS: (a) Urine samples collected over a period of 5 days after injection of b-FN contained no labeled FN. Control experiments in rats with highly elevated glomerular permeability confirmed that the plasma levels of injected b-FN were sufficiently high since b-FN was detected in urine in this condition. (b) The FN fragment pattern, with two protein bands at 75 and 45 kilodaltons, that is normally found in final urine, was already present in samples taken from the early proximal tubule and the distal tubule. CONCLUSIONS: The fibronectin fragments normally found in urine originate from the kidney and are not derived from plasma. Since these fragments are already observed in early proximal tubular fluid, the glomerulus is the probable source of urinary FN. The FN fragment pattern of early proximal tubular fluid is not substantially altered during passage into final urine, thus reflecting glomerular FN release in urine. It is suggested that examination of urinary FN excretion could be helpful in the assessment of altered glomerular extracellular matrix in pathologic conditions.

Animals↗
PubMed1992

The physiological and pathophysiological basis of glomerular permeability for plasma proteins and erythrocytes.

The barrier function of glomerular capillaries in vivo, which prevents the leakage of plasma proteins and cellular elements, depends on the basic morphological and electro-chemical fine structure of the glomerular capillary wall, and on a functional barrier maintained by components obtained from blood, which effect the definitive barrier against the leakage of plasma proteins and cellular elements. The functional component of the barrier may explain the variability and some of the phenomena known as functional proteinuria. A certain size and number of morphological "defects" are thought to represent the normal condition, but under pathological conditions they may increase in size and number, resulting in a shift to an increasing permeability for higher molecular mass proteins; also an increase of the size and number of larger defects may enable more red cells to pass the barrier compared with the normal condition. These defects are different from the minimal glomerular lesions which are due to charge defects in the glomerular capillary membrane, primarily the lamina rara interna and the lamina rara externa of the basement membrane.

Animals↗
PubMed1992

Glycation of serum albumin and its role in renal protein excretion and the development of diabetic nephropathy.

The present study was designed to investigate whether microalbuminuria at the onset of diabetic nephropathy might be partially due to the glycation of serum albumin. It is postulated elsewhere (Ghiggeri et al., Proc. Eur. Dial. Transplant. Assoc. 21 (1984) 633-636) that the glycation of serum albumin and the subsequent cationization may induce microalbuminuria. To investigate whether a relationship exists between the amount of glycated albumin in its cationized form and the development, and progression of diabetic nephropathy, the urinary excretion of glycated albumin was studied in diabetic patients. The diabetic patients (type I and II diabetes) were divided into groups according to their albumin excretion rates: group I diabetics had a normal albumin excretion (n = 30, x = 4.2 mg/12 h); group II diabetes displayed microalbuminuria (n = 17, x = 38.6 mg/12 h); group III diabetics displayed macroalbuminuria (n = 21, x = 582.5 mg/12 h). The fraction of glycated albumin in serum (Glyco Gel Test Kit) was 0.032 in group I, 0.042 in group II, and 0.038 in group III, all these values were significantly higher than the value for the controls (0.014%; n = 17, 2 alpha = 0.001) as measured with the Glyco Gel Test Kit. The concentration of glycated albumin in the urine of the controls and group I was below the detection limit. Urine in group II contained only a glycated albumin fraction of 0.0002 of total albumin, and the fraction for group III was 0.0008. Isoelectric focussing (IEF) and chromato-focussing revealed native albumin with an isoelectric point of 4.7-4.9, and anionic glycated albumin with a pI of 3.0-4.2.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Metabolic heterogeneity of isolated cortical and juxtamedullary glomeruli in adriamycin nephrotoxicity.

The anticancer drug adriamycin (ADR) is selectively toxic to glomerular cells when administered intravenously (5 mg/kg b.w.) to female MWF/Ztm rats. Recent data have shown that the proteinuria associated with the lesion does not occur in cortical glomeruli, suggesting the selective injury of juxtamedullary glomeruli. In the present study, the effect of ADR on glomerular metabolism was studied with special reference to possible differences between cortical and juxtamedullary glomeruli. On day 7 after ADR treatment, cortical and juxtamedullary glomeruli were separately isolated by the sieving method and 14C glucose oxidation to 14CO2 and the incorporation of 3H proline into macromolecules were measured in vitro and used to study target selective injury in ADR-treated rats compared to control rats. The investigations revealed differences in the response of cortical and juxtamedullary glomeruli to ADR. ADR treatment increased proline incorporation over a 4-hour incubation period in both glomerular populations compared to controls, but the effect was significantly (p less than 0.05) more pronounced in juxtamedullary glomeruli (juxtamedullary: 187 +/- 8% of control; cortical: 167 +/- 4% of control). Glucose oxidation was enhanced after 4 h only in juxtamedullary glomeruli (juxtamedullary: 132 +/- 3% of control; cortical: 82 +/- 10% of control). These data show that glomerular damage caused by ADR is associated with a stimulating effect on glomerular metabolism which is more marked in juxtamedullary than in cortical glomeruli, thus indicating a heterogenous response of different glomerular populations and supporting the concept that the selective damage of juxtamedullary glomeruli accounts for the proteinuria.

Animals↗
PubMed1991

Altered renal fibronectin excretion in early adriamycin nephrosis of rats.

The anticancer drug adriamycin (ADR) induces severe nonselective glomerular proteinuria in rats. The proliferation of the glomerular mesangium in chronic ADR nephrosis suggests a disturbed metabolism of extracellular matrix proteins. In the present study the structural protein fibronectin was analyzed by immunological methods in urine and plasma in two rat strains after a single injection of 5 mg of ADR/kg b.wt. After ADR administration the excretion of 220 kd-plasma fibronectin, identified by its electrophoretic mobility and Western blotting, increased. This was confirmed by quantitative measurement (ELISA) of total urinary fibronectin (ADR-treated Munich Wistar Frömter rats: 85.4 +/- 49.5 ng/hr, N = 31; controls: 1.7 +/- 0.7 ng/hr, N = 26; day 7 after ADR injection). Control urines contained distinct fragments of fibronectin with a molecular weight range of 40 to 60 kd. It is suggested that these fragments did not originate from plasma inasmuch as only little correspondence between the fibronectin patterns of urine and plasma was found, and also because in ADR-treated rats the excretion of the fibronectin fragments decreased from day 4 of ADR administration. The data suggest that the urinary fibronectin fragments are released from cellular fibronectin during the normal catabolism of the glomerular extracellular matrices, and that ADR interferes in the metabolism of matrix components. Only as a consequence of an enhanced glomerular permeability is plasma fibronectin excreted in ADR-treated rats.

Animals↗
PubMed1990

Uncoupling of glomerular and tubular regulations of urea excretion in rat.

Renal adjustments to diets varying in protein and sodium content were studied in young anesthetized Munich-Wistar rats. Diets were as follows: high (50%) protein (HP), normal (24%) protein (NP), reduced (8%) protein without extra salt (RPNS), and RP with extra salt (RPWS, 2.8% extra salt). Rats grew at the same rate on all diets. Glomerular filtration rate (GFR), urea, sodium, and osmolar clearances were measured. In series 1, groups of rats were maintained for 4 wk on the four diets and one group on changed diet (CP2d, RPWS diet for 4 wk changed to NP diet for 2 days). GFR was reduced compared with NP rats by 12% in RPNS and RPWS, and by 16% in CP2d rats, but the differences were not statistically significant. Fractional excretion of urea (FEurea) was significantly changed compared with NP. It was 40% higher in HP rats, and 50 and 56% lower in RPNS and RPWS, respectively. In the CP2d group it had increased to the NP value. In series 2, groups of rats were maintained on the RPNS diet for 1, 2, 3, and 4 wk, respectively. GFR decreased 21.6% after only 1 wk but after 4 wk it was not significantly lower than in the NP group. In contrast, no significant reduction was found in FEurea after 1 wk, whereas it decreased by 40% during the 2nd wk, with no further decrease after 3 and 4 wk. GFR was not directly related to protein or salt intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1990

Urinary IgA, secretory IgA and secretory component in women with recurrent urinary tract infections.

Urinary secretory IgA (sIgA), consisting of free secretory component (FSC) and dimeric IgA, is involved in the defense against urinary tract infections (UTI). Recurrent UTIs (rUTI) have been suggested to be associated with a defective excretion of sIgA. Therefore urinary sIgA, FSC and serum-type IgA concentrations were measured by ELISA in 68 normal women, 10 asymptomatic women with rUTIs and no urological abnormality (group A), 8 asymptomatic women with rUTIs and a urological abnormality (B), 4 women with acute UTI (C) and 5 women with a selective serum IgA deficiency (D). Annual UTI rates were increased in groups A, B and C, but normal in group D. In no patient group urinary FSC concentration was different from the normals, while sIgA concentrations were increased in group C, markedly reduced in group D, but normal in groups A and B. Urinary serum-type IgA concentrations were significantly increased in group A and C, markedly reduced in group D and normal in group B. These results demonstrate that the urinary sIgA system participates in the immune response to bacterial infections, but that even a complete failure of the sIgA system does not lead to an increased UTI rate. Furthermore, no association of recurrent UTIs with disturbances of the urinary sIgA excretion could be demonstrated.

Adolescent↗
PubMed1989

Study on the renal handling of sex dependent proteins in male rats studied by micropuncture techniques and by the isolated perfused rat kidney.

The separation of sex dependent urinary proteins of the rat (SDP) by micro-disc electrophoresis results in at least eight well defined protein bands with differing molecular weights. The hepatic origin of a sex dependent urinary protein, named alpha 2u-globulin, has been demonstrated before by other authors applying immunological methods. In the present study, it could been shown that SDP circulate in the plasma at a concentration of 23.8 mg/l. The origin of those protein bands which appear typically upon electrophoresis was still under dispute because they could not been demonstrated in proximal tubular fluid. The present study confirms the extrarenal source of SDP and suggests identity with alpha 2u-globulin. The attempt to track down SDP from plasma to excreted urine demonstrated that, in contrast to proximal fluid, samples from nephron parts distal to the loop of Henle contain large amounts of SDP. An isolated kidney model was used to determine the sieving coefficient and tubular reabsorption of SDP, obtained from male rat urine. We have found a correlation between the sieving coefficient and the molecular weight of SDP. The sieving coefficient ranged from 0.375 to 0.834. The tubular reabsorption which has been determined with an isolated kidney perfused with albumin and erythrocytes also showed variation with regard to molecular weight and was 61.7%, on average.

Alpha-Globulins↗
PubMed1989

Adriamycin affects glomerular renal function: evidence for the involvement of oxygen radicals.

The early nephrotoxic effect of the antitumor drug adriamycin (ADR) is suggested to be related to the generation of oxygen free radicals. Therefore the O2-dependence and the influence of free radical scavengers were studied in the model of the isolated perfused single glomerulus of Myxine glutinosa and by histochemical demonstration of the glomerular ATP-ase. In Myxine, the glomerular ATP-ase activity was decreased after injection of ADR (5 mg/kg, i.v.). Both ADR-treated Myxine and controls were exposed for 48 h to an artificial atmosphere of 20% O2/80% N2 or 80% O2/20% N2, respectively. After 10 days a significant decrease of the hydraulic conductivity (k) was measured in the experimental group exposed to 80% O2 (k-values expressed as nl/s.mm Hg.mm2: controls (7): 0.059 +/- 0.017; ADR (7): 0.033 +/- 0.026). The reduction of k following the administration of ADR (20 mg/kg) could be prevented by the sulphydryl donor N-acetylcysteine (NAC). The sieving coefficient for albumin (phi) was significantly increased in ADR-treated animals, showing no O2-dependence (phi x 10(-2): controls (7) 1.3 +/- 0.2; ADR 20% O2 (8): 8.1 +/- 9.6; ADR 80% O2 (7): 6.9 +/- 6.7). phi was not affected by NAC. The lipid peroxide levels in liver, kidney and heart of Myxine increased after the administration of ADR, peaking by day 2 to 5. The circulation disorders of ADR-treated Myxine were not due to an accumulation of the drug in the heart, but rather to a lack of the intracellular antioxidant glutathione. It is concluded that the early nephrotoxic effect of ADR, as reflected by a decreased glomerular ATP-ase activity, is mediated by free radical formation. Oxidative stress on membrane compounds seems to reduce the water permeability of the glomerular barrier, while the ADR-induced sieving defect may be due to oxygen independent pathological mechanisms.

Adenosine Triphosphatases↗
PubMed1989

Quantification of human urinary free secretory component, secretory and nonsecretory IgA by ELISA.

The specific quantification of human urinary free secretory component (FSC), secretory IgA (SIgA) and total IgA using ELISA has been hampered by mutual interferences of these three molecules. Using affinity chromatographically purified antisera an attempt was therefore made to reduce these interferences without necessitating further assay steps. FSC and total IgA were measured in unprocessed urine by means of anti-FSC and anti-IgA as well as alkaline phosphatase-coupled anti-FSC or anti-IgA antisera. SIgA was determined using anti-IgA as well as alkaline phosphatase-coupled anti-FSC. Nonsecretory urinary IgA was calculated from the measured SIgA and total IgA. The mutual interferences of FSC, SIgA or nonsecretory IgA in the three assay systems were low and not relevant for normal samples. Normal urinary concentrations were: FSC 344 +/- (SD) 208 ng/ml (n = 120), SIgA 1,874 +/- 1,133 ng/ml (n = 123) and nonsecretory IgA, depending on the way of standardization, 712 +/- 699 (n = 56) or 878 +/- 732 ng/ml (n = 51). SIgA excretion increased with age. Lower urinary SIgA as well as total and nonsecretory IgA levels were observed in males as compared to females. No correlation evolved between the hormonal status of women and the excretion of FSC, SIgA or IgA. In IgA-deficient patients virtually no nonsecretory IgA or SIgA was detected in the urine while the FSC concentration was in the normal range.

Adult↗
PubMed1988

Binding sites for atrial natriuretic peptide in the kidney and aorta of the hagfish (Myxine glutinosa).

1. In the atlantic hagfish (Myxine glutinosa) binding sites for atrial natriuretic peptide (ANP) were visualized by autoradiography in contractile structures of the renal system (glomeruli, neck segment, and archinephric duct) and in the aorta. 2. Since the location of binding sites is comparable to that in higher vertebrates including man, these results suggest that ANP may act as a hormone already in cylcostomata.

Animals↗