C. Niederstadt

Population analysis of mesothelium in situ and in vivo exposed to bicarbonate-buffered peritoneal dialysis fluid.

Population analysis of mesothelium (PAM) done using the in vivo and almost in situ technique of mesothelial cell imprints revealed that lactate-buffered solutions had detrimental effects upon cell viability, that high glucose concentration affected cytokinesis, whereas the association of both components led to a decreased density population of cells showing a larger surface area. In the present study, PAM was done on mesothelium of mice exposed to bicarbonate-buffered peritoneal dialysis fluid (BBF) with glucose concentrations of 1.5 and 4.25%, for periods of time of 2 h, 15 and 30 days, as well as after recovery intervals of 7 and 30 days, BBF did not affect mesothelial cell viability. However, the increased incidence of multinucleated cells observed with both glucose concentrations, more marked with the 4.25% solution, suggests a detrimental effect upon the mechanism of cytokinesis. Furthermore, the higher the glucose concentration, the higher the mean-cell cytoplasmic surface area and the proportion of large cells, both resulting most probably from the regulatory volume increase developed by cells continuously exposed to hyperosmolar fluids. So far, evidence presented in this study suggests once more that BBF is remarkably more compatible with a higher quality of adaptation and survival of the exposed mesothelium than the lactated fluid. The question of whether the alterations induced by the high concentration of glucose result from a specific effect of glucose, by the coincidental hyperosmolarity, or by both still remains unanswered.

Hypothesis : Is accumulation of a furan dicarboxylic acid (3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid) related to the neurological abnormalities in patients with renal failure ?

The plasma concentrations of a lipophilic furan dicarboxylic acid (3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid; 5-propyl FPA), which is highly bound to albumin and not removed by haemodialysis,

Relevance of resistive index ultrasonographic measurement in renal transplantation

The usefulness of the ultrasonographic measurement of resistive index (RI) is not yet fully understood. To obtain a better definition of its relevance in renal disease we studied this parameter in a group of 212 renal transplant patients, aged between 15 and 55 years: 81 first grafts with an excellent renal function, 44 hypertensive patients, 30 type II diabetics, 29 cases of chronic graft dysfunction, 28 cases during an episode of acute rejection. RI was measured in three different renal vascular areas: prerenal, interlobar and cortical. A two-way analysis of variance showed a statistical significance for the site of RI sampling and the type of pathology. There was no interaction between the two variables studied (p = 0.30). Plasma creatinine levels, analyzed as covariate, showed a high statistical correlation with RI values (p = 0.0001). The mean RI of the 80 transplanted patients with normal creatinine plasma levels showed a remarkable homogeneity and a statistically significant progressive reduction of the values from the main renal artery to the interlobar and cortical vessels (p = 0.00001). In the other groups a greater dispersion of data was present. RI values significantly increased in hypertensive and diabetic patients (p = 0.05) but more in acute rejection (p = 0.0001) or chronic graft dysfunction (p = 0.01). In acute rejection and in chronic graft dysfunction the curve of RI values tended to become flat, while in hypertensive and diabetic patients the aspect of the curve became steeper. In conclusion, RI is a hemodynamic index that reflects the vascular status of the explored area and is not only the simple expression of reduction of the kidney functional units. The differences observed in the various kidney areas stress the importance of measuring this parameter at more than one vascular site. The increase in RI values on the kidney cortex vessels is likely to be an index of glomerular hyperfiltration. If this hypothesis is true the measure of RI might be a reliable method for diagnosing in the kidney vascular damage, glomerular hypertension and hypertrophy.

Human trehalase : Characterization, localization, and its increase in urine by renal proximal tubular damage

By using polymerase chain reaction, cDNA encoding human renal trehalase has been isolated. The partial amino acid sequence deduced by the cDNA showed homologies in rabbit, Tenebrio molitor and silkworm trehalase. Northern blots showed renal trehalase mRNA to be about 2.0 kb. To examine the properties of renal and urinary human trehalase, the trehalase cDNA was inserted in the pMAL-cRI vector downstream from the malE gene, which encodes maltose-binding protein. Transfection of the recombinant pMAL-cRI in Escherichia coli provided high levels of expression of the maltose binding protein-trehalase fusion protein. A rabbit was immunized with purified fusion protein, and antihuman trehalase antibodies were obtained. Immunoblot analysis disclosed that renal and urinary trehalase exhibited a molecular mass of about 75 kDa. Analysis by indirect fluorescent microscopy demonstrated that the enzyme located in only proximal tubular cells. Urinary trehalase activity was low in the healthy infants and elevated in patients with asphyxia. Markedly high activity was observed in a patient with Lowe syndrome. The immunoreactive urinary trehalase with 75 kDa was increased dependent on the elevation of the activity. On the basis of these findings, we conclude that the increase of urinary trehalase reflects the extent of renal tubular damage, and we propose that urinary trehalase can be a specific marker of renal tubular damage.

Malignant Hypertension and Antiphospholipid Syndrome

Dr. A.E. Sirvent, Avda Orihuela 4, 6 D, E-03006 Alicante (Spain) Dear Sir, The kidney is now recognized as another target organ in the antiphospholipid syndrome (AS) [1]. Renal involvement is consistent with thrombosis of the major renal vessels and noninflammatory microvascular disease [2-4]. In the clinical findings renal failure has been emphasized over systemic hypertension. We report here on a patient with systemic malignant hypertension and throm-botic microangiopathy (TM) with no other occlusive complications. A 29-year-old man was hospitalized with acute renal failure during a malignant hypertensive episode, after developing hypertension in the 3 months prior to admission. Thrombocytopenia was also detected. Physical examination showed: blood pressure 230/ 130 mm Hg, grade IV retinal changes, no abdominal bruits were heard; the signs were compatible with congestive heart failure. The most significant laboratory findings were: hemoglobin lOg/dl, WBC 14,000/μl (normal differential count), platelets 47,000/μl, normal coagulation tests, fíbrinogen 490 mg/dl and schistocytes on a peripheral blood smear. Urea was 35 mmol/l, creatinine 884 μmol/l, LDH 971 U/l, haptoglobin 11 mg/dl, and urine contained proteinuria 2.1 g/day, 10-15 erythrocytes/hpf. Chest X-ray revealed pulmonary edema and cardiomegaly, and echo-cardiography indicated left ventricular hypertrophy, normal ejection fraction and mild mitral regurgitation. The abdominal ultrasound showed a right kidney of 11.9 cm and a left kidney of 8.7 cm. No evidence of kidney infarction was seen in the renal CT scan. The magnetic resonance angiogram disclosed normal aorta and renal arteries. The following laboratory data were negative or normal: urine cultures, urine catecholamines and VMA, HBsAg, serology for HCV, cryoglobulins, rheumatoid factor, ANCA, anti-GBM, ANA, anti-DNA, anti-SSA (Ro), anti-SSB (La), anti-Sm, anti-RNP antibodies, C3, C4, VDRL, brain CT, cystography, lupus anticoagulant; anticardiolipin antibodies (aCL) IgG 63.3 GPL/ml (n.v. < 23), IgM 3.1 MPL/ml (n.v. < 11), and repeated after 8 weeks, IgG 40 GPL/ml (ELISA). Antiplatelet antibodies were positive. The kidney biopsy showed TM; no deposits were noted in the immunofluores-cence study. Blood pressure was controlled. An increase in platelets and normalization of LDH was achieved following plasma exchange with FFP as the replacement fluid; upon withdrawal of the plasma exchange, thrombocytopenia recurred. After receiving the aCL determination

Sensitivity to Calcium Intake in Calcium Stone Forming Patients

The absorptive or renal origin of hypercalciuria can be discriminated using an acute oral calcium load test (ACLT). Of 86 patients with calcium oxalate kidney stones, 28 (23%) were found to be hyperca

Prospective case control study to determine the effect of lovastatin on serum testosterone and cortisol concentrations in hyperlipidemic nephrotic patients with chronic renal failure.

In order to investigate the effects of lovastatin on adrenal and gonadal function, we prospectively determined the basal and gonadorelin-stimulated concentrations of testosterone, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and the cortisol response to adrenocorticotropic hormone (ACTH) in a sample of 25 male patients with advanced chronic renal failure, hypercholesterolemia and proteinuria. Hormone studies were done prior to and after lovastatin treatment. The values of these patients were compared with those of a matched healthy control group. Before starting treatment with lovastatin, the patients showed significantly lower testosterone concentration and higher LH concentration than the control group. After stimulation with gonadorelin, they also showed a lower increase in testosterone and LH. After 12 months of lovastatin treatment, a significant decrease in the concentration of cholesterol, LDL C, VLDL C and apo B was observed, but neither the basal testosterone concentration nor the response to gonadorelin stimulation was modified. Before treatment, basal and ACTH-stimulated serum cortisol levels did not differ from those of the control group. After lovastatin treatment, neither the basal serum cortisol levels nor the response to ACTH was modified. We conclude that in the patients studied, although the decrease in testosterone concentration may be partially attributable to a decrease in its synthesis, lovastatin treatment does not increase testosterone deficit. This is either because this drug does not inhibit gonadal hydroxymethylglutaryl CoA reductase at the does given or because the cholesterol which LDL C provides the cell with is enough to maintain testosterone synthesis.

Long-term erythropoietin in rats with reduced renal mass

Hematocrit increase with recombinant erythropoietin (rEPO) has been associated with increased progression of renal insufficiency in experimental models of renal mass reduction. The aim of the present study was to assess the effects of therapy with rEPO and various antihypertensives on the progression of chronic renal insufficiency and on arterial hypertension in an experimental model of renal mass reduction. Rats subjected to a two-thirds nephrectomy were randomly assigned to an untreated control group or to therapy with rEPO (subcutaneously, at an initial dose of 40 U/kg thrice weekly), rEPO plus verapamil (subcutaneously, 0.5 mg/kg/day), or rEPO plus enalapril (orally, 50 mg/l in the drinking water). Combining enalapril and rEPO therapy controlled systemic blood pressure (BP) and the increase in proteinuria. Glomerular injury, as assessed 16 weeks after renal ablation, was more marked in the animals treated with rEPO with or without either antihypertensive. The morphometric analyses showed greater glomerular tuft areas in the three groups receiving rEPO than in the controls. The glomerular tuft area was directly correlated with the rate of glomerulosclerosis. In about 11% of the rEPO-treated hypertensive rats, the lesions showed severe hypertensive vasculopathy; in the animals treated with rEPO plus enalapril, the lesions were less severe. We conclude that therapy with rEPO was associated to renal damage which could not be attenuated by enalapril despite controlling BP and proteinuria, and may have a nonhemodynamic cause. Therapy with rEPO might trigger lesions usually associated with severe arterial hypertension; concomitant therapy with enalapril attenuates hypertensive vasculopathy.

Ovariectomy Attenuates Proteinuria and Glomerular Injury in Unilaterally Nephrectomized Female Sprague-Dawley Rats

To determine the contribution of the ovary to the development of glomerulosclerosis, we investigated the effect of ovariectomy on glomerulosclerosis, using the unilaterally nephrectomized (Nx) female Sprague-Dawley rat. At 6 weeks of age, groups 2 and 3 underwent unilateral right nephrectomy and group 3 was simultaneously ovariectomized, while group 1 underwent a sham operation. Body weight, blood pressure, urinary protein, serum albumin, cholesterol, blood urea nitrogen and serum creatinine were checked every 2 months from 2 to 12 months after right nephrectomy. Control group 1, the Nx group 2 and the ovariectomized (Nx + ovariectomized) group 3 were studied morphologically at 6 and 12 months after nephrectomy. Body weight significantly increased in ovariectomized rats as compared with control and Nx rats. Nx rats became proteinuric with age. Ovariectomy significantly reduced proteinuria to the same levels in the controls. The glomerulosclerosis index was significantly higher in Nx rats than in either controls or ovariectomized rats. Ovariectomy attenuated glomerular injury in Nx rats, though not to the same levels in the control rats. Three groups showed no significant differences in either blood pressure or plasma somatomedin C. Growth hormone (GH) was significantly decreased by ovariectomy. The severity of glomerular injury and the glomerular tuft volume correlated with GH levels. Our results suggested that a decrease in plasma GH may contribute to the attenuating effect of ovariectomy on the development of glomerular injury in aging unilaterally Nx female Sprague-Dawley rats.

Urinary excretion of glycosaminoglycans in patients with early diabetic nephropathy.

F. Pérez-Blanco, PO Box 752, E-18080 Granada (Spain) Table 1. Urinary excretion of GAG in patients with diabetes mellitus Group B C D n 52 63 37 29 Mean ± SD 16.8 ± 0.8 40.1 + 27.5 90.1 ± 62.0 193.3 + 83.9 p < O.Ol < 0.05 < O.Ol Dear Sir, The kidney undergoes structural and functional alterations throughout the course of diabetes, microalbuminuria being the first manifestation of nephropathy [1]. Albumin excretion depends mainly on glomerular hy-perfiltration and changes in charge selectivity and pore size in the glomerular basement membrane (GBM) [2]. Although the structural basis of diabetic nephropathy is unknown, it is related with expansion of the mesangium and thickening of the GBM. This membrane, which represents a selective barrier to glomerular filtration, is formed of a dense network of collagen filaments, poly-peptides of different chain structures, and glycosaminoglycans (GAG), heparan sulfate proteoglycan being the major type. The GAG play an important role as a selective filter in the GBM, ensuring that a negative charge is maintained. In diabetes mellitus, the negative charge on the GBM is reduced because of a decrease in heparan sulfate proteoglycan [3]. As a result, albuminuria and pore size are both increased. The early phase of nephropathy is characterized by an increase in the activity of the enzymes responsible for glycoprotein (n-ace-tylglucosaminidase) and mucopolysaccha-ride metabolism (ß-glucuronidase). These enzymes break down complex intracellular macromolecules and degrade glycoconju-gates on the endothelial membrane [4], leading to structural alterations in the GBM, and the abnormal excretion of GAG [5]. We investigated the urinary excretion of GAG in 129 patients in different stages of nephropathy caused by insulin-dependent diabetes: 63 patients without hypertension or microalbuminuria (group B), 37 patients without hypertension but with microalbuminuria (group C), and 29 patients with both (group D). As a control group we studied 52 healthy control subjects (group A).