Biomedical subjects

M Noris

Publications and source records attributed to M Noris.

49 records · Page 3Linked to original sources

PubMed1993

Enhanced nitric oxide synthesis in uremia: implications for platelet dysfunction and dialysis hypotension.

Nitric oxide (NO), a potent vasodilator which also inhibits platelet adhesion and aggregation, is generated by endothelial cells and platelets from its precursor L-arginine. Since N-monomethyl-L-arginine (L-NMMA), an inhibitor of NO synthesis, normalizes the prolonged bleeding time of uremic rats, it has been suggested that bleeding associated with uremia was due to an excessive NO formation. With the present study we sought to evaluate whether in patients with chronic renal failure--like in uremic rats--defective platelet aggregation were associated with excessive formation of NO and whether uremic plasma promotes NO synthesis by cultured vascular endothelium. Data indicated that plasma L-arginine was higher in uremics than in controls, uremic platelets generated more NO than control platelets, and intraplatelet levels of cGMP (the NO second messenger) were also higher in uremic than in control platelets. Moreover, uremic plasma potently induced NO synthesis by cultured endothelial cells, a phenomenon which was further amplified by adding to uremic plasma endotoxin and interferon gamma. Increased NO biosynthesis may contribute to platelet dysfunction and possibly other manifestations of uremic syndrome, including hemodialysis hypotension.

Adult↗

PubMed1993

Defective glomerular [3H]lysoPAF metabolism in the autologous phase of rabbit nephrotoxic nephritis.

Glomerular infiltration of blood-derived mononuclear cells contributes to the glomerular injury in the autologous phase of nephrotoxic nephritis (NTN). LysoPAF has recently been shown to be chemotactic for human monocytes, thus its accumulation might account for monocyte recruitment. We investigated [3H]lysoPAF metabolism in isolated glomeruli from normal and NTN rabbits studied both in the heterologous and in the autologous phases of the disease. [3H]lysoPAF was converted to [3H]1-O-alkyl-glycerol and [3H]1-O-alkyl-2-acyl-GPC by phospholipase C and acyltransferase, respectively, both in normal and NTN glomeruli. Glomerular metabolism of [3H]lysoPAF was normal during the heterologous phase of NTN. By contrast, in isolated glomeruli from NTN rabbits studied in the autologous phase of the disease, a significantly lower [3H]lysoPAF degradation occurred with respect to normal ones. This defective degradation resulted in a significantly reduced formation of [3H]1-O-alkyl-glycerol. The apparent Km for enzymatic conversion of [3H]lysoPAF to [3H]1-O-alkyl-glycerol, determined at 15 minutes as a function of [3H]lysoPAF concentration, was doubled in glomeruli from rabbits studied in the autologous phase of NTN as compared to normal ones, while Vmax values were similar in the two groups. These results show a defective glomerular lysoPAF degradation in the autologous phase of NTN, likely due to a decreased affinity of phospholipase C to lysoPAF. Altered lysoPAF metabolism results in glomerular accumulation of lysoPAF in the autologous phase of NTN, as shown by significantly higher levels of lysoPAF measured in nephritic glomeruli as compared to normal ones.

Animals↗

PubMed1993

Urinary excretion of platelet activating factor in patients with immune-mediated glomerulonephritis.

We have investigated whether human immune-mediated glomerulonephritis is associated with changes in platelet activating factor (PAF) biosynthesis. Urinary PAF, taken as a marker of its renal synthesis, was significantly higher in patients with membranous nephropathy (N = 9) than in healthy controls (N = 8). This was not due to a lower degradation of PAF since urinary acetylhydrolase activity was comparable in patients and controls. A significant positive correlation between urinary excretion of PAF and proteinuria was observed. PAF generation was comparable in polymorphonuclear cells isolated from patients with membranous nephropathy and controls. PAF levels in blood from patients with membranous nephropathy were significantly lower than in controls, suggesting that the excessive generation of PAF is confined to the kidney. The results document that signs of renal disease activity in human membranous nephropathy are associated with an excessive renal synthesis of PAF.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗

PubMed1992

Urinary excretion of platelet-activating factor in haemolytic uraemic syndrome.

Since some of the features of haemolytic uraemic syndrome (HUS), such as platelet activation and glomerular injury, could be brought about by platelet-activating factor (PAF), we have studied the urinary excretion of PAF in 10 children with HUS and in 10 healthy age-matched controls. Urinary PAF concentrations, measured by radioimmunoassay, were significantly higher in acute-phase HUS patients than in controls (mean 2.04 [SD 1.66] vs 0.72 [0.43] ng/mg creatinine, p less than 0.05) but were similar to those in controls in samples taken after recovery. High PAF concentrations during the acute phase of HUS may reflect platelet activation and glomerular injury; the lower values after recovery suggest that urinary PAF may be a marker of disease activity.

Child↗

PubMed1992

Renal prostacyclin biosynthesis is reduced in children with hemolytic-uremic syndrome in the context of systemic platelet activation.

Previous studies have reported various abnormalities in prostacyclin (PGI2) synthesis and metabolism in hemolytic-uremic syndrome (HUS). However, the conclusions of most of these studies are based on in vitro or ex vivo experiments that only give an indirect estimate of the actual biosynthesis in vivo. We studied the urinary excretion of PGI2 metabolites, taken as a marker of the actual biosynthesis, in six children with HUS during the acute phase of the disease and again when remission was achieved. Eight age- and sex-matched healthy children were studied as controls. Since HUS is also associated with platelet activation and consumption, we also studied the urinary excretion of thromboxane A2 (TxA2) metabolites. Urinary PGI2 and TxA2 metabolites were assessed by radioimmunoassay after high-performance liquid chromatography (HPLC) purification. Urinary excretion of the PGI2 hydrolysis product, 6-keto-PGF1 alpha, was significantly reduced in children with acute HUS as compared with controls, indicating a defective renal synthesis of PGI2. A significant inverse correlation was found between urinary 6-keto-PGF1 alpha and blood urea nitrogen (BUN), as well as plasma creatinine. At remission, urinary 6-keto-PGF1 alpha levels increased to values higher than those of controls. By contrast, the urinary excretion of the major PGI2 beta-oxidation product, 2,3-dinor-6-keto-PGF1 alpha, was comparable to controls, indicating normal systemic PGI2 biosynthesis. The urinary excretion of both TxA2 hydrolysis product, TxB2, and the major beta-oxidation metabolite, 2,3-dinor-TxB2, were lower than normal in the acute phase of HUS if expressed as absolute values.(ABSTRACT TRUNCATED AT 250 WORDS)

Child↗

PubMed1992

Methylprednisolone dosage effects on peripheral lymphocyte subpopulations and eicosanoid synthesis.

Glucocorticoids have a major role in the treatment of glomerular diseases. Despite recent advances in understanding of their mechanism of action, very few studies have addressed the relative advantage of the wide range of different dose regimens employed in clinical practice. We studied the effects of methylprednisolone given intravenously for three consecutive days at the doses of 1 mg/kg (group 1, N = 7; group 2, N = 5), 5 mg/kg (group 3, N = 5) or 15 mg/kg (group 4, N = 6) on total blood peripheral leukocytes and on lymphocyte subsets in patients with glomerular diseases, and investigated whether such effects were a function of the drug concentration in the blood. Since glucocorticoids have an inhibitory effect on the formation of eicosanoids in different cells, we also investigated in the same patients the effect of 1 and 15 mg/kg methylprednisolone on systemic and renal eicosanoid synthesis. Results of pharmacokinetic study showed that the three different doses of methylprednisolone we used resulted in major differences in patient's exposure to the drug, and within the same dose there was a great individual variability. By contrast the three different doses of methylprednisolone induced a comparable drop in the absolute number of lymphocytes six hours after the first injection of methylprednisolone, while 24 hours later blood lymphocyte counts returned to the pre-injection values in all patients. Analysis of lymphocyte subsets showed a selective decrease in the number of circulating CD4+ and CD8+ cells six hours after methylprednisolone which was comparable in the four groups of patients studied. As for the effect of methylprednisolone on systemic and renal eicosanoid synthesis in patients with glomerular diseases, 1 and 15 mg/kg were equally unable to reduce thromboxane A2 (TxA2) and prostaglandin E2 (PGE2) release by circulating polimorphonuclear cells (PMNs). By contrast, methylprednisolone partially inhibited eicosanoid synthesis by PMNs in vitro. Consistent with the data on PMNs, urinary excretion of TxA2 and prostacyclin (PGI2) metabolites were unaltered by the different doses of methylprednisolone. By contrast urinary PGE2 was markedly and significantly reduced in patients given 15 but not 1 mg/kg. We conclude that 1 mg/kg methylprednisolone given to patients with glomerular diseases has the same effect on peripheral total blood leukocyte count and lymphocyte subsets than 5 and 15 mg/kg. The same is true for eicosanoid synthesis by PMNs. Renal synthesis of PGE2 is inhibited by 15 mg/kg but not by 1 mg/kg.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗

PubMed1991

Increased urinary excretion of platelet activating factor in mice with lupus nephritis.

Platelet activating factor (PAF) is present in urine from humans and experimental animals in normal conditions. Very little is known about changes in PAF urinary excretion under pathologic conditions and no data are available about the origin of PAF in the urine. In the present study we explored the possibility that immunologic renal disease is associated with an increase in PAF urinary excretion using gas chromatography-mass spectrometry technique. To clarify the renal or extrarenal origin of urinary PAF we evaluated whether exogenously administered PAF (1-[1', 2'-3H]alkyl) is filtered through the glomerulus and excreted in the urine. The results show that: 1) urine from mice with lupus nephritis in the early phase of the disease contained amounts of PAF comparable to those excreted in normal mouse urine, 2) PAF levels increased when animals started to develop high grade proteinuria, 3) after intravenous injection of [3H] PAF in nephritic mice, a negligible amount of [3H] ether lipid, corresponding to [3H]1-alkyl -2-acyl-3-phosphocholine (alkyl-2-acyl-GPC), was recovered from the 24 h urine extract.

Animals↗

PubMed1991

L-arginine, the precursor of nitric oxide, abolishes the effect of estrogens on bleeding time in experimental uremia.

We have reported previously that conjugated estrogens that are effective in shortening the prolonged bleeding time in uremic patients are also effective on bleeding time in a rat model of uremia. Using such a rat model we have recently demonstrated that nitric oxide (NO), an endothelium-derived vasodilator, is involved in mediating the bleeding tendency of uremia. With the present study we wanted to investigate whether conjugated estrogen mixture or its active component, 17 beta-estradiol, reduce uremic bleeding by interfering with the NO pathway. Our results showed that the shortening effect of conjugated estrogen and 17 beta-estradiol on bleeding time of uremic rats was completely reversed by giving the animals the NO precursor L-arginine, but not D-arginine, which is not a precursor of NO. Dexamethasone which at variance to progesterone inhibits the process of induction of NO-forming enzyme, shortened the prolonged bleeding time of uremic rats within 4 hours from injection. This effect was eliminated by L-arginine but not D-arginine administration. The glucocorticoid receptor antagonist cortexolone prevented the shortening of bleeding time induced by dexamethasone, suggesting that a receptor-mediated mechanism is involved in the hemostatic effect of dexamethasone as previously reported for estrogens. Unlike conjugated estrogens and dexamethasone, progesterone had no effect on bleeding time. All these findings would indicate that the effect of estrogens and dexamethasone on primary hemostasis in uremia might be mediated by changes in NO synthetic pathway.

Animals↗

PubMed1990

Renal metabolism and urinary excretion of platelet-activating factor in the rat.

The origin of platelet-activating factor (PAF) in the urine remains ill defined. The present study documents that [3H]PAF (3.5 mu Ci) injected into the renal artery of isolated control rat kidney preparations perfused at constant pressure with a cell-free medium containing 1% bovine serum albumin (BSA) was excreted in negligible amounts (0.034%) in the urine, whereas 6% was retained by the kidney. When kidneys were perfused with a BSA-free medium, 0.029 and 71% of the total radioactivity added to the perfusate was recovered in the urine and in the renal tissue, respectively. [3H]PAF urine excretion in proteinuric kidneys from adriamycin-treated rats was still negligible (0.015%). Analysis of the renal tissue-retained radioactivity in control and proteinuric kidneys perfused with 1% BSA indicated metabolism into long chain acyl-sn-glycero-3-phosphorylcholine species, lyso-PAF, glycerols, and intact PAF. Thin layer chromatography analysis of [3H]glycerol fraction in these renal extracts showed two major components comigrating with 1-O-alkylglycerol and 1-O-alkyl-2-fatty acylglycerol. Isolated proximal tubules, but not glomeruli from nephrotic rats exposed to increasing concentrations of BSA (0-4%), had a higher PAF uptake than control tubules for BSA concentrations ranging from 0 to 0.1%. Our findings in the isolated perfused kidneys indicate that, in normal conditions, circulating PAF is excreted in the urine in negligible amounts and that the altered glomerular permeability to proteins does not affect this excretion rate. Moreover, analysis of renal tissue radioactivity documented that the renal metabolism of PAF is comparable in control and nephrotic kidneys.

Animals↗

PubMed1989

Development of a mass spectrometric method to quantitate platelet activating factor in mouse urine.

Platelet activating factor (PAF) is a lipid mediator of inflammation released by a variety of stimulated inflammatory cells. It may be involved in immune glomerulonephritis. Thus, its measurement in urine could give information on the mechanism of this disease. We present here a method to measure PAF in mouse urine, using gas-liquid chromatography-mass spectrometry (GLC-MS) in the selected ion recording (SIR) mode. Before instrumental analysis, the extracted and purified samples were hydrolyzed and derivatized with pentafluorobenzoyl chloride. Different experimental conditions are presented and discussed to corroborate the analytical findings. PAF levels in mouse urine were 2.08 +/- 0.46 ng/24 h. This procedure might represent a new experimental tool to establish the possible role of PAF as mediator of tissue damage in renal disease.

Animals↗

PubMedDate not supplied

Physiology and pathophysiology of nitric oxide in chronic renal disease.

Nitric oxide (NO), an L-arginine derivative, exerts a variety of renal and extrarenal physiological and pathophysiological effects. NO is generated by three isoforms of nitric oxide synthases (NOS): two acutely responsive, constitutive isoforms, neuronal NOS (nNOS) and endothelial NOS (ecNOS), and the slower, more persistent, inducible NOS (iNOS). NO regulates glomerular ultrafiltration; tubular reabsorption, and intrarenal renin secretion. A number of recent studies, most of them in the experimental model of renal mass reduction (RMR) in rats, have raised the hypothesis that an impaired NO synthetic pathway could have a key role in mediating the complex renal hemodynamic and nonhemodynamic disorders associated with the progression of renal disease. Thus, kidneys from rats with RMR produce less NO than normal rats, and NO generation negatively correlates with markers of renal damage. The abnormality is due to a defect in iNOS in the kidney. Data are also available showing that drugs capable of enhancing renal NO activity may be renoprotective in a variety of experimental renal diseases, particularly those characterized by derangements of glomerular hemodynamics. Fewer studies are available in humans and these have shown less than conclusive results.

Animals↗

PubMedDate not supplied

Nitric oxide/L-arginine in uremia.

Nitric oxide (NO), a gaseous free radical derived from L-arginine, is a potent modulator of vascular tone and platelet functions. A number of recent studies, both in the experimental model of renal mass reduction (RMR) in rats and in uremic patients, have raised the hypothesis that abnormalities of NO synthetic pathway could have a key role in mediating the complex hemodynamic and hemostatic disorders associated to the progression of renal disease. Thus, kidneys from rats with RMR produce less NO than normal rats and NO generation negatively correlates with markers of renal damage. The abnormality is due to a strong defect of inducible NO synthase (iNOS) content in the kidney. Recent in vitro and in vivo data have raised the possibility that excessive renal synthesis of the potent vasoconstrictor and promitogenic peptide endothelin-1 (ET-1) is a major determinant for progressive iNOS loss in the kidney of RMR rats. In contrast, uremia is associated with excessive systemic NO release, both in experimental model and in human beings. In the systemic circulation of uremic rats, as well as uremic patients, NO is formed in excessive amounts. Possible cause of the increased NO levels is higher release from systemic vessels due to the augmented expression of both iNOS and endothelial NOS. A putative cause for excessive NO production in uremia can be guanidinosuccinate, an uremic toxin that accumulates in the circulation of uremic patients and upregulates NO synthesis from cultured endothelial cells. Upregulation of systemic NO synthesis might be a defense mechanism against hypertension of uremia. On the other hand, more NO available to circulating cells may sustain the bleeding tendency, a well-known complication of uremia.

Animals↗

PubMedDate not supplied

Pathogenesis of Takayasu's arteritis.

Takayasu's arteritis is an inflammatory disease of the arteries that involves large vessels. The inflammatory lesions in Takayasu's arteritis originate in the vasa vasorum and are followed by cellular infiltration, mainly composed of T cells (gammadelta lymphocytes, cytotoxic T lymphocytes, T helper cells), but also of natural killer cells, dendritic cells, monocytes and granulocytes, invading the outer layer of the media and/or its neighbouring adventitia. At this stage, positive production of inflammatory cytokines and/or adhesion molecules around these areas is remarkable. According to data available--in Takayasu's arteritis--interleukin-6, interleukin-1 and RANTES are released in large amounts by infiltrating inflammatory cells within damaged tissue, as well as by circulating inflammatory cells, and very likely help maintain the aberrant immune activation, by promoting endothelial cells activation and by inducing lymphocyte infiltration. Although the nature of the antigen that triggers the auto-immune process is still unknown, the infiltrating T lymphocytes may recognize one or a few self-antigens processed and presented in association with HLA. A considerable percentage of patients with Takayasu's arteritis have immune complexes in sera; moreover, on peripheral blood lymphocyte, Fc receptors and antibodies reactive against human endothelial cells (AECA) have been detected. This observation raised the possibility that AECA might have a role in endothelial cell activation and expression of adhesion molecules, which will facilitate leukocyte traffic.

Antibodies↗