Search PubMed⌕ Search

Biomedical subjects

J A Arruda

Publications and source records attributed to J A Arruda.

At least 19 recordsLinked to original sources
PubMed2001

Relaxin decreases renal interstitial fibrosis and slows progression of renal disease.

BACKGROUND: Relaxin, a hormone of the insulin-growth factor family, promotes collagen remodeling. In rodent models of pulmonary and dermal fibrosis, relaxin reduced interstitial fibrosis. To study relaxin's effect in renal disease, we used the experimental bromoethylamine (BEA) model that leads to severe renal interstitial fibrosis, a decrease in glomerular filtration rate, and albuminuria at one month. METHODS: Rats were injected with BEA one week prior to implantation of an osmotic pump delivering relaxin (2 microg/hour) or vehicle continuously for 28 days. RESULTS: BEA caused a significant decrease in creatinine clearance, which was partially prevented by relaxin. In the relaxin-treated BEA rats, serum creatinine was normal, and albumin excretion was slightly decreased. By morphometric measurement, relaxin administration was associated with a significant decrease in interstitial fibrosis at the corticomedullary junction. This was accompanied by a decrease in the number of ED-1 positive cells (an index of macrophage infiltration) and in the intensity of immunohistochemical staining for transforming growth factor-beta. This antifibrotic effect of relaxin did not appear to be mediated by systemic hemodynamic changes since the mean arterial pressure was not significantly different among the groups. CONCLUSIONS: Relaxin may have a useful application in decreasing interstitial fibrosis and thereby slowing the progression of renal disease.

Animals↗
PubMed2001

SFKs, Ras, and the classic MAPK pathway couple muscarinic receptor activation to increased Na-HCO(3) cotransport activity in renal epithelial cells.

Cholinergic agents are known to affect the epithelial transport of H2O and electrolytes in the kidney. In proximal tubule cells, cholinergic agonists increase basolateral Na-HCO(3) cotransport activity via M(1) muscarinic receptor activation. The signaling intermediates that couple these G protein-coupled receptors to cotransporter activation, however, are not well defined. We therefore sought to identify distal effectors of muscarinic receptor activation that contribute to increased NBC activity in cultured proximal tubule cells. As demonstrated previously for acute CO2-regulated cotransport activity, we found that inhibitors of Src family kinases (SFKs) or the classic mitogen-activated protein kinase (MAPK) pathway prevented the stimulation of NBC activity by carbachol. The ability of carbachol to activate Src, as well as the proximal (Raf) and distal [extracellular signal-regulated kinases 1 and 2 (ERK1/2)] elements of the classic MAPK module, was compatible with these findings. Cholinergic stimulation of ERK1/2 activity was also completely prevented by overexpression of a dominant negative mutant of Ras (N17-Ras). Taken together, these findings suggest a requirement for the sequential activation of SFKs, Ras, and the classic MAPK pathway [Raf-->MAPK/ERK kinase (MEK)-->ERK]. These findings provide important insights into the molecular mechanisms underlying cholinergic regulation of NBC activity in renal epithelial cells. They also suggest a specific mechanism whereby cholinergic stimulation of the kidney can contribute to pH homeostasis.

Animals↗
PubMed2001

Differential effects of enalapril and irbesartan in experimental papillary necrosis.

This study was undertaken to determine whether angiotensin receptor blockers are as renoprotective as angiotensin-converting enzyme inhibitors in an experimental model of chronic interstitial renal disease. Groups of rats received one of the following treatments for 1 week: (1) enalapril, (2) diltiazem, (3) a cocktail of hydralazine, reserpine, and hydrochlorothiazide, or (4) irbesartan (an AT1 antagonist). The animals were injected with bromoethylamine (200 mg/kg), and antihypertensive treatment continued for 1 month. All drugs were effective in lowering the mean arterial pressure. The bromoethylamine-treated rats developed albuminuria and sustained a 40-50% decrease in creatinine clearance. Enalapril and irbesartan reduced albuminuria, but only enalapril partially prevented the decline in creatinine clearance and lowered the number of ED-1-positive cells. Diltiazem and cocktail had no effect on proteinuria, creatinine clearance, or ED-1 cells. In this experimental model, the effects of enalapril and irbesartan were not identical. Both drugs reduced proteinuria, but enalapril was more effective in protecting the renal function. The fact that the AT1 antagonist protected against albuminuria but did not affect the clearance of creatinine implies that the results seen with angiotensin-converting enzyme inhibition may be in part due to an effect on angiotensin II via AT2 receptor blockade or through an effect on bradykinin.

Angiotensin Receptor Antagonists↗
PubMed2000

Evaluation of a new fluorescent dye method to measure urinary albumin in lieu of urinary total protein.

Urinary total protein (UTP) determinations are notoriously inaccurate, poorly reproducible, and difficult to interpret in early renal disease, causing many investigators to measure urinary albumin instead. In this study, we compare a new nonimmunologic fluorescent dye (AB-dye) for measuring albumin with the more expensive and cumbersome radioimmunoassay. We tested 207 urine specimens from patients with variable protein concentrations and divided the results into five arbitrary ranges (0 to 20, 21 to 50, 51 to 100, 101 to 200, and 201 to 400) for chi-square analysis. There was a high degree of correlation between the two methods (chi-square = 260. 8 with 16 degrees of freedom; P < 0.001). The correlation was also high when analyzed by linear regression (R = 0.86; F < 0.01). Based on our comparison of total protein and albumin concentration in the same urine samples, we hypothesized that patients with mild proteinuria may not necessarily have microalbuminuria. Urine samples with UTP between 150 and 400 microg/mL were tested for albumin by the AB-dye. Of 41 samples in this range, 18 (44%) had normal albumin levels. We conclude that measuring urinary albumin with the AB-dye is comparable in performance to radioimmunoassay and could replace UTP determinations, especially for patients with borderline elevations of UTP, many of whom do not have microalbuminuria.

Albuminuria↗
PubMed2000

A simple method to detect an albumin permeability factor in the idiopathic nephrotic syndrome.

BACKGROUND: Several investigators have detected an albumin permeability factor in the serum of patients with the idiopathic nephrotic syndrome (INS), that is, minimal change disease (MCD) or focal segmental glomerulosclerosis (FSGS), but the methods used have been complex. METHODS: We describe here a simpler method using cultured rat glomerular epithelial cell monolayers grown to confluence on Millicell filters, which allow sampling of apical and basolateral media. 125I-labeled human serum albumin (125I-HSA) was added to the basolateral compartment, and its leakage across the epithelial cell monolayer into the apical compartment was measured. RESULTS: In untreated cells (negative control), the albumin leakage reached 5.3% at 18 hours. Cell monolayers fixed with 95% ethanol (positive control) showed 62% leakage. Sera from three out of four patients with MCD and three out of four with FSGS resulted in considerable albumin leakage, whereas sera from nine patients with other types of nephrotic renal disease and five normal subjects caused no leakage. CONCLUSION: This study shows that the Millicell system provides a simple and useful method to screen for permeability factors in the INS.

Adult↗
PubMed2000

Motor neuron diseases in the university hospital of Fortaleza (Northeastern Brazil): a clinico-demographic analysis of 87 cases.

In this retrospective (1980-1998) study, we have analyzed clinico-demographically, from the records of the University Hospital of Fortaleza (Brazil), a group of 87 patients showing signs and symptoms of motor neuron diseases (MNDs). Their diagnosis was determined clinically and laboratorially. The WFN criteria were used for amyotrophic lateral sclerosis (ALS) diagnosis. The clinico-demographic analysis of the 87 cases of MNDs showed that 4 were diagnosed as spinal muscular atrophy (SMA), 5 cases as ALS subsets: 2 as progressive bulbar paralysis (PBP), 2 as progressive muscular atrophy (PMA) and 1 as monomelic amyotrophy (MA), and 78 cases of ALS. The latter comprised 51 males and 27 females, with a mean age of 42.02 years. They were sub-divided into 4 groups according to age: from 15 to 29 years (n= 17), 30 to 39 years (n= 18), 40 to 69 years (n= 39) and 70 to 78 years (n= 4). From the 78 ALS patients, 76 were of the classic sporadic form whilst only 2 were of the familial form. The analysis of the 87 patients with MNDs from the University Hospital of Fortaleza showed a predominance of ALS patients, with a high number of cases of juvenile and early onset adult sporadic ALS.

Adolescent↗
PubMed1999

Cocaine-induced hypertension: role of the peripheral sympathetic system.

Cocaine causes hypertension at least in part by stimulating the sympathetic nervous system, but it is not clear if this effect is centrally or peripherally mediated. To address this issue we studied the vasoconstrictive effect of cocaine in vivo and in isolated artery segments. In vivo cocaine increased mean arterial blood pressure (MAP) by 40 mmHg within 1 min of administration. Pretreatment with prazosin blocked this response by 62%. With clonidine the pre-cocaine MAP was lower and the hypertensive effect of cocaine was blocked by 50%, indicating an important role for central alpha-adrenergic mechanisms. In isolated rat carotid arteries cocaine-induced vasoconstriction was completely blocked by prazosin, phentolamine, and 6-hydroxydopamine, indicating a clear role for a peripheral effect. However, the relative contribution of the central alpha-adrenergic mechanism to the total vasoconstrictive response of cocaine was not clarified. 1999 Academic Press.

Adrenergic Agents↗
PubMed1999

Carbamylated proteins activate glomerular mesangial cells and stimulate collagen deposition.

Carbamylated proteins formed in renal insufficiency from the spontaneous decomposition of urea exert a variety of metabolic effects. Here we examined the effects of carbamylated proteins on glomerular mesangial cells to determine whether urea retention in early renal insufficiency may itself promote glomerular sclerosis and hasten the progression to kidney failure. To this effect we carbamylated fetal bovine serum proteins in vitro and tested their effect on mesangial cell proliferation (by tritiated thymidine uptake), de novo protein synthesis (by tritiated leucine uptake), collagen I and collagen IV accumulation (by avidin-biotin enzyme immunoassay), and gelatinase levels in the medium (by zymography and quantitative fluorescence assay). Carbamylated fetal bovine serum at concentrations present in uremia increased tritiated thymidine incorporation by 50% without altering tritiated leucine incorporation, and it increased collagens I and IV in the monolayer by 150% to 300%. Gelatinase activity was unchanged. We conclude that carbamylated proteins can activate mesangial cells to a profibrogenic phenotype. From a clinical perspective, the carbamylation of proteins by elevated urea levels may accelerate the progression to kidney failure and thus set up a vicious cycle in which the nitrogen retention itself would cause further progression of fibrosis and deterioration of kidney function.

Animals↗
PubMed1999

Evolution of experimentally induced papillary necrosis to focal segmental glomerulosclerosis and nephrotic proteinuria.

Bromoethylamine (BEA)-induced papillary necrosis is a reproducible model for analgesic nephropathy. We induced this lesion in groups of male Sprague-Dawley rats and followed the functional and histological changes for 1 year. We found that by 1 month, necrosis of the papilla was complete, glomerular filtration rate was depressed, and urine albumin excretion was increased. There was an extensive interstitial fibrosis characterized by a mononuclear cell infiltrate and patchy tubular atrophy. By 6 months, there was re-epithelialization of the papillary stump accompanied by a marked increase in albuminuria and an improvement in concentrating ability. Changes seen at 9 months were more advanced. There was extensive cortical fibrosis manifested by pitting of the surface of the kidney. At 1 year, renal function remained impaired (creatinine clearance reduced by 65% to 0.26 mL/min/100 g), and the animals were now markedly nephrotic, with albuminuria of 254 mg of albumin/24 h. In the BEA rats, there was selective destruction of the deep nephrons leading to an increase in the volume-ratio of superficial to deep nephrons. Glomerular changes, affecting approximately 60% of the glomeruli, were characteristic of focal segmental glomerular sclerosis. This model of papillary necrosis/interstitial fibrosis is associated with chronic renal insufficiency and leads to the development of focal glomerular sclerosis and nephrotic proteinuria by 6 to 12 months after its induction.

Animals↗
PubMed1999

Changes in collagenases and TGF-beta precede structural alterations in a model of chronic renal fibrosis.

BACKGROUND: To study the role of collagenases and transforming growth factor-beta (TGF-beta) in the genesis of interstitial fibrosis, we used the model of bromoethylamine (BEA)-induced papillary necrosis, which is known to lead over a period of 1 to 12 months to interstitial fibrosis and renal insufficiency. METHODS: Rats were injected with BEA, and urine and kidney tissue (cortex and medulla) were collected after 1, 2, 3, 7, and 30 days. One kidney was perfused and fixed for morphological studies and immunostained for collagen type I, III, and IV. The other kidney was used to prepare cortex and medulla extracts for gelatinases (by fluorometric and zymographic techniques), tissue inhibitors of metalloproteinase-1 (TIMP-1), and TIMP-2 (by enzyme-linked immunosorbent assay, ELISA) and TGF-beta1 (by ELISA). RESULTS: Albuminuria and interstitial fibrosis were present in BEA rats by day 7, which continued until day 30. Immunocytochemical staining for collagen types showed that collagen III and IV increased in the interstitium by day 30, but collagen I remained unchanged. Gelatinase activity in the medulla decreased by 57% compared with control by day 2 and remained low until day 30. In the cortex, gelatinase activity remained unchanged between 0 and 7 days after BEA but decreased by 72% by day 30. TIMP-1 and TIMP-2 were decreased by 80% compared with day 0 in both the medulla (by day 1) and cortex (by day 2) and remained low up to day 30. TGF-beta1 immunoreactivity increased progressively until day 2 in the medulla (16-fold higher than control) and day 3 in the cortex (8-fold higher than control) and returned to control level by day 3 in the medulla and by day 30 in the cortex. Two days after BEA injection, the mRNA for TGF-beta1 was increased eightfold in the cortex and 12-fold in the medulla, and it remained high for up to 30 days. CONCLUSIONS: The fibrosis that follows papillary necrosis is associated with both high TGF-beta1 expression and depressed gelatinolytic activity.

Animals↗
PubMed1999

Regulation of the renal Na-HCO(3) cotransporter. XI. Signal transduction underlying CO(2) stimulation.

We have previously shown that CO(2) stimulation of the renal Na-HCO(3) cotransporter (NBC) activity is abrogated by general inhibitors of protein tyrosine kinases. The more selective inhibitor herbimycin also blocked this effect at concentrations known to preferentially inhibit Src family kinases (SFKs). We therefore examined a role for SFKs in CO(2)-stimulated NBC activity. To this end, we engineered OK cells to express the COOH-terminal Src kinase (Csk), a negative regulator of SFKs. CO(2) stimulated NBC activity normally in beta-galactosidase-expressing and untransfected control cells. In contrast, Csk-expressing cells had normal baseline NBC activity that was not stimulated by CO(2). CO(2) stimulation increased both total SFK activity and specific tyrosine phosphorylation of Src. The specific MEK1/2 inhibitor PD-98059 completely inhibited the CO(2) stimulation of NBC activity as well as the accompanying phosphorylation and activation of ERK1/2. Our data suggest the involvement of both SFKs, probably Src, and the "classic" MAPK pathway in mediating CO(2)-stimulated NBC activity in renal epithelial cells.

Animals↗
PubMed1998

Regulation of the renal Na-HCO3 cotransporter: IX. Modulation by insulin, epidermal growth factor and carbachol.

To examine the role of tyrosine kinase (TK) on basolateral membrane (BLM) transport, we looked for the presence of TK activity in these membranes and showed that the synthetic substrate for TK, poly [Glu80 Na, Tyr20] caused a three-fold increase in tyrosine phosphorylation. This effect was completely blocked by the TK inhibitors, 2-hydroxy-5(2,5-dihydroxybenzyl) aminobenzoic acid (HAC), 1 microM, and methyl 2,5-dihydroxycinnamate (DHC), 5 microM. We then examined the effect of agents that cause TK stimulation on tyrosine kinase immunocontent and on the Na-HCO3 cotransporter activity in BLM and in primary cultures of the proximal tubule. We utilized the cholinergic agent, carbachol (10(-4) M), epidermal growth factor (EGF 10(-8) M), and insulin (10(-8) M), well known activators of TK. Carbachol, insulin, and EGF caused a significant increase in TK immunoreactive protein content which was blocked by HAC and DHC. In BLM, carbachol significantly stimulated HCO3-dependent 22Na uptake and this effect was totally prevented by the monoclonal antibody against TK. In cultured proximal tubule cells, carbachol, EGF and insulin at physiologic concentration caused a significant stimulation of the cotransporter activity and this effect was completely blocked by the TK inhibitor, HAC. Increasing the dose of insulin 100-fold did not cause further stimulation of the cotransporter indicating that insulin plays a permissive role on the cotransporter. These results demonstrate the presence of TK in renal proximal tubule cells and show that activation of this kinase by dissimilar agents enhance the activity of the Na-HCO3 cotransporter.

Aminobenzoates↗
PubMed1998

pH-dependent fluorescence of a heterologously expressed Aequorea green fluorescent protein mutant: in situ spectral characteristics and applicability to intracellular pH estimation.

The green fluorescent protein of Aequorea victoria (GFP) is a natural peptide chromophore without substrate or cofactor requirements for fluorescence. In vitro, a recombinant F64L/S65T GFP mutant (GFPmut1) exhibited pH sensitive fluorescence within the physiologic range. When heterologously expressed in BS-C-1 cells or rabbit proximal tubule cells, uniform cytosolic and nuclear fluorescence was observed. Cytosolic fluorescence constituted over 80% of the total. Excitation scanning of transfected cells revealed two GFPmut1-specific regions that were pH-sensitive over the physiologic range, and each region exhibited a unique pH "bias" in fluorescence emission. Excitation at or near the expected maximum of 488 nm (region II) uniformly resulted in fluorescence that was preferentially altered at acidic pH. In contrast, a novel "wild-type" excitation peak at 400 nm (region I) resulted in alkaline-biased fluorescence similar to that described for the wild-type chromophore in vitro, suggesting that wild-type spectral features disrupted in vitro by mutagenesis may be recovered in intact cells. Calibration of intracellular pH (pHi) with in situ fluorescence following excitation in either region revealed a semilogarithmic relationship between fluorescence intensity and pH within the physiologic range. We therefore measured pHi changes attributable to altered Na/HCO3 cotransport (NBC) activity both in GFPmut1-expressing cells and in paired untransfected cells loaded with BCECF. Basal NBC activity was the same in each group, as was the stimulation of activity by 10% CO2, thus validating the utility of GFPmut1 as a fluorescent probe for pHi and establishing a novel, useful, and practical application for GFPmut1 in monitoring pHi in real time.

Animals↗
PubMed1998

Regulation of renal Na-HCO3 cotransporter: VIII. Mechanism Of stimulatory effect of respiratory acidosis.

We examined the effect of respiratory acidosis on the Na-HCO3 cotransporter activity in primary cultures of the proximal tubule of the rabbit exposed to 10% CO2 for 5 min, 2, 4, 24 and 48 hr. Cells exposed to 10% CO2 showed a significant increase in Na-HCO3 cotransporter activity (expressed as % of control levels, 5 min: 142 +/- 6, 2 hr: 144 +/- 13, 4 hr: 145 +/- 11, 24 hr: 150 +/- 15, 48 hr: 162 +/- 24). The increase in activity was reversible after 48 hr. The role of protein kinase C (PKC) on the stimulatory effect of respiratory acidosis on the cotransporter was examined in presence of PKC inhibitor calphostin C or in presence of PKC depletion. Both calphostin C and PKC depletion prevented the effect of 10% CO2 for 5 min or 4 hr to increase the activity of the cotransporter. 10% CO2 for 5 min or 4 hr increased total and particulate fraction PKC activity. To examine the role of phosphotyrosine kinase (PTK) on the increase in cotransporter activity we studied the effect of two different inhibitors, 2-hydroxy-5-(2,5-dihydroxylbenzyl) aminobenzoic acid (HAC) and methyl 2,5-dihydroxycinnamate (DHC) which inhibit phosphotyrosine kinase in basolateral membranes. Cells were pretreated either with vehicle or HAC or DHC and then exposed to 10% CO2 for 5 min or 4 hr. In cells treated with vehicle, 10% CO2 significantly increased cotransporter activity as compared to control cells exposed to 5% CO2. This stimulation by 10% CO2 was completely prevented by HAC or DHC at 5 min (5% CO2: 1.8 +/- 0.2, 10% CO2: 2.6 +/- 0.2, 10% CO2 + HAC: 1.6 +/- 0.2, 10% CO2: +DHC: 2.0 +/- 0.3 pH unit/min) and also at 4 hr. The protein synthesis inhibitors actinomycin D and cycloheximide appear to prevent the effect of 10% CO2 for 4 hr on the cotransporter. Our results show that early respiratory acidosis stimulates the Na-HCO3 cotransporter through PKC and PTK-dependent mechanisms and the late effect appears to be mediated through protein synthesis.

Acidosis, Respiratory↗
PubMed1998

Role of nitric oxide in cocaine-induced acute hypertension.

Cocaine causes acute hypertension by blocking catecholamine reuptake. There is evidence that it also impairs the peripheral endothelial nitric oxide system, which is normally vasodilatory. We further explored the role of nitric oxide in cocaine-induced vasoconstriction in anesthetized rats, and in vitro by using isolated carotid artery segments. Cocaine administered intravenously in rats increased mean arterial pressure by 30 to 40 mm Hg within 1 min. This effect was dose dependent and the maximum effect was observed at a dose of 1.25 mg/kg. The prototype catecholamine norepinephrine induced a similar increase in blood pressure. When rats were pretreated with NG-monomethyl-L-arginine (L-NMMA, a blocker of nitric oxide) and challenged with cocaine, the increase in blood pressure was blocked by 80%, whereas pretreatment with L-NMMA did not block norepinephrine-induced vasoconstriction. Both cocaine and norepinephrine also induced an immediate vasoconstriction in isolated carotid artery preparations. The in vitro vasoconstriction induced by cocaine was blocked by pretreatment with L-NMMA, whereas L-NMMA did not block the norepinephrine-induced vasoconstriction in vitro. Furthermore, carotid artery stripped of endothelium responded to norepinephrine but failed to respond to L-NMMA or cocaine. S-nitroso-N-acetyl-D,L-penicillamine (SNAP)-a precursor of nitric oxide- stimulated nitric oxide production in control coronary artery fragments. When these fragments were incubated with cocaine there was a 20% reduction in the production of nitrite oxide. These results suggest that cocaine exerts its peripheral vasoconstriction at least in part by inhibiting local vasodilator nitric oxide.

Animals↗
PubMed1998

Prevalence of hypertension in chronic cocaine users.

The association of cocaine and acute hypertension is well known; however, cocaine use has not generally been linked to chronic hypertension. We hypothesized that chronic use of cocaine over time would increase the prevalence of hypertension and that cocaine induced vasoconstriction would result in urine protein leakage, manifested by microalbuminuria. Therefore, we studied a population of predominantly black male patients admitted for addiction treatment whose drug of dependence was cocaine. A urine toxicology screen was considered positive if cocaine was detected within 24 h prior to or during admission to the hospital. A total of 301 patients with normal renal function were observed over their 2 week hospitalization. The majority (62%) of the patients were normotensive regardless of the status of their initial urine toxicology screen. Twenty percent of the population had acutely elevated blood pressure that normalized within 1 day, whereas 18% had blood pressure chronically >140/90 mm Hg (chronic hypertension). Levels of systolic and diastolic blood pressures were examined at age deciles and compared to the NHANES III (Third National Health and Nutrition Examination Survey) data for a predominantly black population. There was no significant difference in blood pressure with age in the cocaine users compared to the NHANES groups. Random urine samples were screened for the presence of microalbuminuria and no significant elevation was detected in any of the samples tested. We conclude that chronic cocaine use is associated with acute but not chronic hypertension in middle-aged black males. Cocaine use does not cause microalbuminuria.

Adult↗