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Biomedical subjects

J F Wetzels

Publications and source records attributed to J F Wetzels.

At least 37 records · Page 2Linked to original sources
PubMed1999

Recurrent focal glomerulosclerosis: natural course and treatment with plasma exchange.

BACKGROUND: Focal glomerulosclerosis (FGS) can recur after renal transplantation and prognosis is poor in untreated patients. A circulating plasma factor has been implicated in the pathogenesis of a recurrent FGS and treatment with plasma exchange has proven effective in decreasing proteinuria in some patients. METHODS: We retrospectively studied the course of disease in patients with recurrent FGS, transplanted in our centre. Seven patients transplanted between 1991 and 1997, received treatment with plasma exchange, whereas 10 patients, transplanted between 1973 and 1991, were left untreated and served as historical controls. RESULTS: The time of onset of proteinuria (>3.5 g/day) was comparable in the untreated and treated patients (9 and 10 days respectively), as was the average proteinuria at that time (5.5 and 5.8 g/day respectively). In the untreated patients, proteinuria persisted and eventually all grafts were lost, on average 43 months after the diagnosis of a recurrence. In five cases (50%) the recurrence was the single cause of graft loss. The clinical course was different in the seven patients who were treated with plasma exchange. In five of these patients, the recurrence occurred within 3 weeks after transplantation. Plasma exchange was started 1-14 days after onset of proteinuria in these patients. Two lost their grafts after 0.7 and 1.0 months because of untreatable rejection. In the remaining three patients the plasma exchange resulted in abrupt disappearance of the proteinuria, and the response has been lasting for 2-3.2 years. In these patients the only histological abnormality was foot effacement on electron-microscopy. In two patients the recurrence became manifest at 9 weeks and 5.8 years after transplantation respectively. These two patients relapsed after the initial course of plasma exchange, but responded to repeated session, and are currently being treated once a month. They have been followed for 1. 7 and 1.4 years after the onset of proteinuria and their urinary protein levels are 0.23 and 1.2 g/10 mmol creatinine. CONCLUSIONS: The prognosis of untreated recurrent FGS is poor. Treatment with plasma exchange can lead to complete remission of proteinuria and relapsing patients may respond to repeated sessions. Best results are obtained when plasma exchange is started early, when there are no visible lesions on light-microscopy.

Adolescent↗
PubMed1999

Renal transplantation in patients with dense deposit disease: morphological characteristics of recurrent disease and clinical outcome.

BACKGROUND: Dense deposit disease (DDD) is an uncommon cause of end-stage renal disease (ESRD). As a consequence, information on the outcome of renal transplantation in patients with DDD comes from series with a limited number of patients. METHODS: We present the histological and clinical data of 13 adult patients with DDD, who received their first allograft in our centre in the period between 1983 and 1994. RESULTS: Renal transplant biopsies were performed in 11 patients, at 2.9 months after transplantation (median; range 0.4-13.8 months). The indication for taking the biopsy was in all instances a raised serum creatinine level. Five patients also had a significant proteinuria. In only one patient, light microscopy showed alterations in the capillary walls suggestive of a recurrence of DDD. However, by immunofluorescence or electron microscopy, we found glomerular deposits compatible with a recurrence of DDD in all 11 patients. Three patterns of glomerular C3 deposition were found: globular depositions only in the mesangium; mesangial accumulation with linear deposits in the capillary wall; and prominent linear presence in the capillary wall with only a few mesangial granules. The findings by electron microscopy matched the immunofluorescence results. The linear C3 accumulation in the capillary wall was visible ultrastructurally as electron-dense ribbon-like transformation of the glomerular basement membrane. Mesangial C3 deposits were seen ultrastructurally as local electron-dense deposits in the mesangium. Four patients showed a pronounced glomerular influx of neutrophils, accompanied by crescents in three patients. In these three latter patients, the recurrence of DDD was the only histological lesion. In the other patients, the recurrence was merely a coincidence, the biopsy demonstrating an additional histological lesion (three chronic vascular rejection, two acute rejection, one ischaemic necrosis and two cyclosporin A toxicity). Eight patients with a recurrence of DDD have progressed to ESRD at an average of 14 months (range 0.2-38 months) after transplantation. The recurrence was the sole cause of graft loss in the three patients with crescents. The patients in whom the C3 deposits were confined to the mesangium appeared to have a better prognosis. CONCLUSIONS: The histological recurrence rate of DDD is high. The histological picture is quite diverse, and in most patients abnormalities are only found by immunofluorescence and electron microscopy. Up to one-quarter of the patients with DDD lost their grafts because of a recurrence.

Adolescent↗
PubMed1999

Transcapillary escape rate of albumin is increased and related to haemodynamic changes in normo-albuminuric type 1 diabetic patients.

OBJECTIVE: An increase in urinary albumin excretion (UAE) in type 1 diabetic patients might reflect changes in vascular permeability and/or local haemodynamic factors. Indeed, transcapillary escape of albumin (TERalb), a measure of systemic capillary efflux, is increased in diabetic patients, even in those with a modest increase of albuminuria. In normo-albuminuric type 1 diabetic patients, systemic capillary and glomerular flow is increased. We hypothesized that these haemodynamic changes contribute to an elevated TERalb, even in the phase preceding micro-albuminuria. METHODS: We measured TERalb in 39 normo-albuminuric type 1 diabetic patients and 46 healthy controls. TERalb was calculated from the disappearance curve of 125I-albumin. Renal and systemic haemodynamics were measured by standard techniques. Forearm blood flow (FBF) was measured by plethysmography. Endothelial function was assessed by intra-arterial infusion of acetylcholine. The structural integrity of the vessel wall was determined by the post-occlusive reactive hyperaemia test. RESULTS: TERalb was increased in diabetic patients (5.53+/-0.40 versus 4.39+/-0.21 %/h, P = 0.01). Patients were divided into tertiles with respect to their TERalb. There were no differences in UAE, blood pressure, metabolic parameters, endothelial function or maximal vasodilatation after occlusion between the groups. However, filtration fraction and FBF were significantly increased in the group of diabetic patients with the highest levels of TERalb. Overall, in diabetic patients, FBF was significantly correlated with TERalb. CONCLUSIONS: TERalb is increased in normo-albuminuric type 1 diabetic patients. In these patients with an increased capillary permeability, there is no evidence of endothelial dysfunction or vessel wall damage. However, both FBF and filtration fraction are increased. Therefore, the increased vascular permeability in the early phase of type 1 diabetes is associated with general haemodynamic alterations. Notably, such an increase in vascular permeability is not necessarily reflected by abnormal UAE. This could be due to either a lack of change in glomerular permeability or due to the fact that the threshold for tubular reabsorption of albumin has not been exceeded.

Adult↗
PubMed1999

Influence of albumin infusion on the urinary excretion of beta2-microglobulin in patients with proteinuria.

UNLABELLED: Most filtered proteins are reabsorbed by the renal proximal tubule by a mechanism that involves binding to the brush border membrane and endocytosis. Under normal conditions the low-molecular-weight protein beta2-microglobulin (beta2M), which is used to detect tubular injury, is reabsorbed almost completely. However, in proteinuric patients an increased urinary excretion of beta2M may not simply reflect tubular damage but might also result from a decreased tubular reabsorption due to competitive mechanisms. To examine the magnitude of such an effect we have studied the renal effects of albumin infusion (40 g in 2 h of a 20% solution) in 10 patients with a glomerular disease and proteinuria >3.5 g/24 h. Before, during and after albumin infusion the GFR (inulin clearance), RPF (PAH clearance), blood pressure and the urinary excretion of albumin, IgG, transferrin and beta2M were measured. Albumin infusion resulted in a slight decrease of the GFR (72 +/- 11 ml/min before and 67 +/- 10 ml/min after infusion), an increase of the RPF (379 +/- 66 ml/min before and 445 +/- 83 ml/min after), a decrease of the filtration fraction (0.20 before and 0.17 after), and hemodilution. After infusion the urinary excretion of albumin increased from 4.5 +/- 0.7 to 8.4 +/- 1.6 mg/min (p < 0.05). The urinary excretion of IgG and transferrin increased, probably reflecting a change in glomerular size-selectivity. In contrast, the urinary excretion of beta2M did not change significantly (baseline 12 +/- 5 microg/min, end 13 +/- 6 microg/min, percentage change 16.8 +/- 11%). To correct for changes in tubular load we calculated the fractional reabsorption of beta2M. The initial rise in albuminuria during infusion did not affect fractional tubular reabsorption (Delta%: 0. 72 +/- 0.52%, median 0.005%). In the period after infusion a slight decrease was noted (median -0.33%, p < 0.01). A decrease in the fractional reabsorption was particularly observed in patients with pre-existing tubular damage. IN CONCLUSION: infusion of albumin in proteinuric patients has no clinically relevant effect on the tubular reabsorption of beta2M. Therefore, beta2M is useful as a parameter to detect tubular injury and alterations in tubular handling of proteins in patients with proteinuria and glomerular diseases.

Adult↗
PubMed1999

Elevated skeletal muscle blood flow in noncomplicated type 1 diabetes mellitus: role of nitric oxide and sympathetic tone.

Capillary hyperperfusion precedes and contributes to the occurrence of diabetic microangiopathy. Vascular tone is regulated by the balance of vasodilating and vasoconstricting factors, of which nitric oxide (NO; an endothelium dependent vasodilator) and norepinephrine (NE; a potent vasoconstrictor), respectively, are of primary importance. To investigate the role of these factors in hyperperfusion, we measured forearm blood flow (FBF) in 50 patients with noncomplicated type 1 diabetes (DP) and 50 healthy control subjects (CS) under baseline conditions and during intrabrachial infusion of N(G)-monomethyl-L-arginine (L-NMMA), an endothelium-dependent vasoconstrictor, and acetylcholine (ACh), an endothelium-dependent vasodilator. Furthermore, we determined arterial plasma NE concentration at baseline and then determined alpha-adrenergic receptor sensitivity by measuring FBF response to intra-arterially infused NE. We found that basal FBF was increased in DP (2.9+/-0.1 versus 2.0+/-0.1 mL. min(-1). dL(-1) in CS; P<0.01). L-NMMA caused a similar vasoconstriction in both groups (28.5+/-1. 7% in DP versus 31.2+/-2.2% in CS; P=NS). Maximum blood flow during infusion of ACh was not different (23.3+/-1.9 mL. min(-1). dL(-1) in DP versus 20.1+/-1.6 in CS). Arterial plasma NE concentrations were significantly decreased in DP (0.57+/-0.03 versus 0.81+/-0.05 nmol/L in CS; P<0.01). The vasoconstrictive effect of NE was increased in DP (slope log dose-response curve, 31.3+/-1.5 versus 24.3+/-1.8 in CS; P<0.01). We conclude that basal FBF is increased in noncomplicated type 1 diabetes. We found no evidence of a disturbance of basal or stimulated NO production. Arterial plasma NE concentrations are decreased in noncomplicated type 1 diabetes. This may explain the vasodilatation at baseline and the increased vascular response to intra-arterially NE.

Acetylcholine↗
PubMed1999

In vivo antibody-mediated modulation of aminopeptidase A in mouse proximal tubular epithelial cells.

Aminopeptidase A (APA) is one of the many renal hydrolases. In mouse kidney, APA is predominantly expressed on the brush borders and sparsely on the basolateral membranes of proximal tubular epithelial cells. However, when large amounts of monoclonal antibodies (MAbs) against APA were injected into mice, we observed strong binding of the MAbs to the basolateral membranes, whereas the MAbs bound only transiently to the brush borders of the proximal tubular epithelial cells. In parallel, APA itself disappeared from the brush borders by both endocytosis and shedding, whereas it was increasingly expressed on the basolateral sides. Using ultrastructural immunohistology, we found no evidence for transcellular transport of endocytosed APA to the basolateral side of the proximal tubular epithelial cells. The absence of transcellular transport was confirmed by experiments in which we used a low dose of the MAbs. Such a low dose did not result in binding of the MAbs to the brush borders and had no effect on the presence of APA in the brush borders of the proximal tubular epithelial cells. In these experiments we still could observe binding of the MAbs to the basolateral membranes in parallel with the local appearance of APA. In addition, treatment of mice with chlorpromazine, a calmodulin antagonist that interferes with cytoskeletal function, largely inhibited the MAb-induced modulation of APA. Our studies suggest that injection of MAbs to APA specifically interrupts the normal intracellular traffic of this enzyme in proximal tubular epithelial cells. This intracellular transport is dependent on the action of cytoskeletal proteins.

Aminopeptidases↗
PubMed1999

Prevalence of "syndrome X" features in parents of type 1 diabetic patients with or without nephropathy.

OBJECTIVE: To compare the prevalence of "syndrome X"-related parameters in parents of type 1 diabetic patients with diabetic nephropathy (DNP) to those in parents of diabetic patients without DNP. RESEARCH DESIGN AND METHODS: In this cross-sectional study, we included 50 parents of type 1 diabetic patients with DNP and 50 parents of diabetic patients without DNP. All parents were investigated in a fasting state for serum lipids including nonesterified fatty acids (NEFAs), glucose, HbA1c, plasma uric acid, fasting insulin levels, and albuminuria. Blood pressure was recorded in the supine position using an automatic device; ankle/brachial index was measured with Doppler ultrasound. Presence of cardiovascular disease was determined by a standardized questionnaire and electrocardiogram registration. Subjects without known diabetes underwent a 2-h oral glucose tolerance test. Anthropometric parameters such as BMI, waist-to-hip ratio, and percentage of body fat were measured. In addition to univariate analysis, a syndrome X score (SXS) was formulated, comprising a number of syndrome X-related biochemical, physiological, and/or anthropometric parameters. RESULTS: Univariate analysis revealed no significant differences in syndrome X parameters between parents of type 1 diabetic patients with or without DNP. Also, the composite SXS was similar in both groups. CONCLUSIONS: In this study, no differences were found in the prevalence of syndrome X features between parents of type 1 diabetic patients with DNP and parents of patients without DNP.

Adult↗
PubMed1999

Fibrillary-immunotactoid glomerulopathy with renal deposits of IgAlambda: a rare cause of glomerulonephritis.

We describe a 24-year-old patient who presented with a nephrotic syndrome. His renal biopsy revealed a diffuse mesangioproliferative glomerulonephritis with eosinophilic deposits. Electron microscopy showed organized, Congo-red negative deposits, forming microtubules of about 20 nm width in the capillary walls and in the mesangium, establishing a diagnosis of fibrillary-immunotactoid glomerulopathy. Fibrillary-immunotactoid glomerulopathy is a rare cause of glomerulonephritis, characterized by Congo-red-negative glomerular deposits of fibrils, sometimes organized in microtubules, predominantly containing IgG and C3. Patients clinically present with the nephrotic syndrome, hematuria and hypertension. The pathogenesis of this glomerulopathy has not been elucidated yet. In our patient, the renal deposits contained IgAlambda. This peculiar feature is suggestive of an underlying paraproteinemia. However, in the serum no paraproteins or cryoglobulins were found, and also microscopical examination and immunophenotyping of the bone marrow did not point to the presence of a monoclonal plasma cell dyscrasia. Our patient was not treated with immunosuppressive drugs and he is currently progressing to end-stage renal disease.

Adult↗
PubMed1998

[Immunosuppressive treatment of patients with a nephrotic syndrome due to minimal change glomerulopathy].

Prednisone monotherapy is the treatment of choice for patients with a nephrotic syndrome due to minimal change glomerulopathy. In adult patients treatment should be continued for at least 24 weeks. Within this period a remission of proteinuria will occur in 75 to 90% of the patients. Patients who do not respond satisfactorily to prednisone treatment can be treated with alkylating agents. Cyclophosphamide is the drug used most commonly. Prolonged treatment (> 12 weeks) is associated with a high risk of infertility. If alkylating agents cannot be used, prolonged treatment with ciclosporine is an option.

Adolescent↗
PubMed1998

[Immunosuppressive therapy for idiopathic membranous glomerulopathy].

Idiopathic membranous nephropathy is the most frequent cause of nephrotic syndrome in adults. The natural course of idiopathic membranous nephropathy is characterized by a high incidence of spontaneous remissions. Some 50% of the patients reach end-stage renal disease. Treatment with corticosteroids alone is not efficacious; treatment with a combination of immunosuppressive drugs improves renal survival. However, because of the high incidence of spontaneous remissions and the risk of treatment-related toxicity, immunosuppressive treatment should be reserved for patients with proven renal insufficiency. Cyclophosphamide appears to be more efficacious and better tolerated than chlorambucil. Identification of high-risk patients at an early stage of the renal disease may contribute to a more efficient use of immunosuppressive treatment.

Adult↗
PubMed1998

Cold preservation of isolated rabbit proximal tubules induces radical-mediated cell injury.

BACKGROUND: Reactive oxygen species (ROS) are involved in reperfusion injury after preservation. Recent studies in isolated endothelial cells and hepatocytes suggested the occurrence of ROS-mediated injury during the period of cold incubation. In the present study, formation of ROS and subsequent cell injury were studied in freshly isolated rabbit proximal tubules (PTs). METHODS: PTs were incubated in University of Wisconsin (UW) solution, Euro-Collins solution, or a modified Krebs-Henseleit buffer under aerobic conditions for up to 94 hr at 4 degrees C. ROS formation and cell death were assessed as lipid peroxidation (formation of thiobarbituric acid-reactive substances [TBARS]) and release of lactate dehydrogenase, respectively. The involvement of ROS was further investigated in UW solution using compounds that might interfere with ROS formation. In addition, tubules were studied under anaerobic conditions (gassing with 95% N2/5% CO2). RESULTS: Cold preservation of rabbit PTs in any of the solutions under aerobic conditions caused progressive lipid peroxidation and concomitant cell injury. Addition to UW solution of inhibitors of ROS formation, in particular 2,2'-dipyridyl, or removal of oxygen by gassing with 95% N2/5% CO2, prevented lipid peroxidation and protected rabbit PTs against cold injury. Both the nitric oxide (NO) synthase inhibitor L-NAME and dexamethasone, which blocks the inducible NO synthase, were ineffective. The cytoprotectant glycine affected neither TBARS formation nor lactate dehydrogenase release. CONCLUSIONS: Cold preservation of renal PTs under aerobic conditions caused cell injury even in the specially designed preservation solution UW. Cell injury is caused by iron-dependent, NO synthase-independent ROS formation.

Adenosine↗
PubMed1998

Hyponatremia due to sodium valproate.

We describe a 50-year-old male patient with hyponatremia (serum sodium level, 128 mEq/L) discovered during routine follow-up for Henoch-Schönlein nephritis. The patient was known to have a generalized idiopathic epilepsy and was on 2,000 mg/day of sodium valproate. After exclusion of other causes such as hypothyroidism and adrenal insufficiency, we considered sodium valproate as the cause of the hyponatremia. Repeated water loading tests performed at different dosages of this drug confirmed that the ability to excrete water was reduced in a dose dependent manner. We conclude that sodium valproate can cause an SIADH-like syndrome with hyponatremia and that serum sodium levels have to be monitored during treatment with high dosages of this drug.

Anticonvulsants↗
PubMed1998

Effects of renal cytoprotective agents on erythrocyte membrane stability.

To elucidate potential mechanisms of ischemic renal injury, investigators often use drugs that interfere with specific pathological pathways and study their protective efficacy in in vitro models of ischemia, such as isolated renal proximal tubules subjected to hypoxia. However, the protective effects of certain drugs may depend on non-specific membrane-stabilizing properties. We have studied the effects of several drugs on membrane integrity using osmotic lysis of erythrocytes as a model system. Freshly isolated rabbit erythrocytes were subjected to a hypotonic shock, and the protective effects of various calcium channel blockers, phospholipase inhibitors, free fatty acids, the NO-synthase inhibitor L-NAME, the amino acid glycine and its receptor-analogue strychnine, and two chloride channel blockers were examined. Most agents protected erythrocytes against hypotonic hemolysis when added to the medium in the same concentration range as used in suspensions of hypoxic proximal tubules. Only the protective agents that proposedly act via a blockade of chloride influx (glycine, strychnine and the chloride channel blockers), did not attenuate hypotonic hemolysis. The erythrocyte hemolysis assay may provide an easy and rapid method to screen for non-specific membrane-stabilizing effects of potentially cytoprotective agents.

Animals↗
PubMed1998

Immunohistological and ultrastructural differences between recurrent type I membranoproliferative glomerulonephritis and chronic transplant glomerulopathy.

In renal transplant recipients with type I membranoproliferative glomerulonephritis (MPGN), the posttransplantation course can be complicated by a recurrence of the original disease. However, it is well known that a recurrence of type I MPGN and chronic transplant glomerulopathy (CTG) cannot easily be distinguished. It has been suggested that the two entities can be differentiated by using electron microscopy (EM) and immunofluorescence (IF) techniques. However, studies are lacking that compare biopsy specimens from patients with either a recurrence of type I MPGN or CTG. We have studied renal biopsy specimens from 10 patients with CTG and compared the ultrastructural and IF findings with biopsy specimens from 12 patients with a possible recurrence of type I MPGN. All the patients with CTG showed an electron-lucent zone of finely flocculent material in the subendothelial space, whereas all patients with a recurrence of type I MPGN showed subendothelial electron-dense deposits on EM. On IF, all patients with CTG showed Immunoglobulin M (IgM) with greater intensity than C3. For the patients with recurrent type I MPGN, the opposite was true. Eleven specimens showed C3 deposits with greater intensity than IgM, and in one patient, C3 and IgM were found in equal intensity. In conclusion, when IF and EM studies are available, CTG and recurrence of type I MPGN can reliably be distinguished.

Chronic Disease↗
PubMed1998

The allopurinol hypersensitivity syndrome.

We describe a 61-year-old male patient who was treated with allopurinol and developed fever, a skin rash, eosinophilia and severe renal and liver dysfunction. We discuss the allopurinol hypersensitivity syndrome as a serious complication of the use of allopurinol, and briefly review the aetiology, prevention and treatment modalities.

Acute Kidney Injury↗
PubMed1998

Hypoxia decreases calcium influx into rat proximal tubules.

Renal ischemia results in adenosine triphosphate (ATP) depletion, particularly in cells of the proximal tubule (PT), which rely heavily on oxidative phosphorylation for energy supply. Lack of ATP leads to a disturbance in intracellular homeostasis of Na+, K+ and Cl-. Also, cytosolic Ca2+ levels in renal PTs may increase during hypoxia [1], presumably by a combination of impaired extrusion and enhanced influx [2]. However, Ca2+ influx was previously measured using radiolabeled Ca2+ and at varying partial oxygen tension [2]. We have now used to Mn2(+)-induced quenching of fura-2 fluorescence to study Ca2+ influx in individual rat PTs during normoxic and hypoxic superfusion. Normoxic Ca2+ influx was indeed reflected by the Mn2+ quenching of fura-2 fluorescence and this influx could be inhibited by the calcium entry blocker methoxyverapamil (D600; inhibition 50 +/- 2% and 35 +/- 3% for 10 and 100 mumol, respectively). La3+ completely blocked normoxic Ca2+ influx. Hypoxic superfusion or rat PTs did not induce an increase in Ca2+ influx, but reduced this influx to 79 +/- 3% of the normoxic control. We hypothesize that reducing Ca2+ influx during hypoxia provides the cell with a means to prevent cellular Ca2+ overload during ATP-depletion, where Ca2+ extrusion is limited.

Adenosine Triphosphate↗