Oswaldo Ramos - Academia.edu (original) (raw)

Papers by Oswaldo Ramos

Drugs, 1988

Data collected from various geographical areas show that hypertension is a major public health pr... more Data collected from various geographical areas show that hypertension is a major public health problem in Brazil. Hypertension is estimated to occur in over 8 million Brazilians and cardiovascular disease-related mortality figures, to which hypertension is a major contributor, increased from 11.8% of the total mortality rate in 1930 to 30.8% in 1980. Costs involved in the treatment of hypertensive patients are very high since hypertension was among the 3 most frequent clinical diagnoses in outpatient visits in 1985. Hypertension is also a major cause of temporary or permanent work incapacitation among Brazilians and data from São Paulo show that hypertension is very common among workers. Finally, demographic tendencies in São Paulo indicate that older age groups have increased in the general population during the past 2 decades. These data, when taken altogether, indicate that hypertension is a major public health problem in Brazil.

American Journal of The Medical Sciences, 1973

Clinical Pharmacology & Therapeutics, 1984

Metoclopramide (MCP), a dopaminergic antagonist, is effective in postural hypotension, but the me... more Metoclopramide (MCP), a dopaminergic antagonist, is effective in postural hypotension, but the mechanisms of action have not been well defined. We studied responses of mean arterial pressure (MAP), heart rate, cardiac output (CO), and total peripheral resistance (TPR) after 5 min of increasing degrees of head tilt (15° to 90°) before and after MCP (20 mg IV) in seven subjects with diabetic postural hypotension. Plasma renin activity (PRA) and plasma aldosterone levels (PA) were determined at each degree of tilt; responses to the cold pressor test were also assessed before and after MCP. Before MCP, the maximal degree of tilt tolerated was 75°, while after MCP four subjects were able to support 90° tilt. At 45° tilt, the decreases in MAP were smaller after than before MCP (−7.6 ± 3.3 and −28.1 ± 8.5 mm Hg; X ± SE). This was associated with responses of TPR to tilt after (from 18.6 ± 2.6 to 24.0 ± 3.9 arbitrary units [AU]) but not before (from 22.9 ± 4.0 to 25.6 ± 4.5 AU) MCP. Reductions in CO were of the same order before and after MCP. PRA responded to tilt better after than before MCP. Supine PA levels increased with MCP (Δ PA = 5.4 ± 0.7 ng/dl), but its response to tilt was unaltered. There were significant rises in MAP and HR during the cold pressor test after but not before MCP. Our data suggest that vasoconstriction is the main mechanism of MCP improvement in blood pressure response to an orthostatic stimulus in diabetic postural hypotension, possibly because of its antidopaminergic property.Clinical Pharmacology and Therapeutics (1984) 36, 738–744; doi:10.1038/clpt.1984.251

Nephron, 1996

The absorptive or renal origin of hypercalciuria can be discriminated using an acute oral calcium... more 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 hypercalciuric (HCa) and 58 (67%) normocalciuric (NCa) on their customary free diet, containing 542 +/- 29 mg/day (mean +/- SE) of calcium. Since the apparently normal 24-hour calcium excretion of many calcium stone formers (CSF) may be due to a combination of high calcium absorption with moderately low calcium intake, all patients were investigated by ACLT. Of 28 HCa patients, 13 (46%) were classified as absorptive (AH) and 15 (54%) as renal hypercalciuria (RH). Of the 58 NCa patients, 38 (65%) presented features of intestinal hyperabsorption and were therefore designated as AH-like, and 20 (35%) as RH-like. To further elucidate the role of dietary calcium in these CSF, a chronic calcium load test (CCLT), consisting of 1 g/day of oral Ca for 7 days, was designed. A positive response to the CCLT was considered to occur when urinary calcium (uCa) was > or = 4 mg/ kg/24 h on the 7th day. Among NCa patients, 29% of AH-like subjects responded to the CCLT and 71% did not; 50% of RH-like subjects also responded and 50% did not. In HCa patients, 85% of AH and 67% of RH subjects maintained uCa > or = 4 mg/kg/24 h after the CCLT and 15% of AH and 23% of RH subjects did not. However, a significant additional increase in mean uCa was not observed among HCa patients. All patients were submitted to a second evaluation of fasting calciuria (Ca/Cr). A modification of this parameter was noticed in 89% of RH-like and 78% of RH patients. In conclusion, these data suggest the presence of subpopulations of patients sensitive or not to calcium intake, regardless of whether the acute response to a calcium overload test suggested AH or RH. The CCLT disclosed dietary hypercalciuria in 21/58 (36%) of previously NCa patients. In these NCa patients, the ACLT may be replaced by the CCLT. The distinction between AH and RH initially evidenced by the ACLT was not further confirmed. These data suggest that either fasting Ca/Cr is not adequate for subclassification of HCa or that AH and RH represent a different spectrum of the same disease, and that a primary resorptive component should also be considered.

Diabetes Research and Clinical Practice, 1995

The renin-aldosterone axis was evaluated by captopril test in 22 normotensive normoalbuminuric in... more The renin-aldosterone axis was evaluated by captopril test in 22 normotensive normoalbuminuric insulin-dependent diabetes mellitus (IDDM) patients with and without glomerular hyperfiltration. Patients were divided into those with glomerular hyperfiltration (Hf-IDDM) and with normal glomerular filtration rate (GFR; Nf-IDDM) according to the upper limit of GFR (134.7 ml/min per 1.73 m2). Sixteen normal individuals were also studied. GFR was measured by the 51Cr-EDTA single injection method, extracellular fluid volume as the distribution volume of 51Cr-EDTA, and blood volume using 51Cr-sodium chromate-labelled red blood cells. Twenty-five mg of captopril were administered per os and plasma renin activity (PRA; RIA), plasma aldosterone (RIA) and blood pressure were measured at 0 and 120 min post-captopril. PRA at time zero (Hf-IDDM = 2.4 ± 1.7; Nf-IDDM = 2.5 ± 1.9; controls = 1.0 ± 0.6 ng/ml/h) and at 120 min (Hf-IDDM = 9.9 ± 8.3; Nf-IDDM = 11.2 ± 8.9; controls = 5.4 ± 5.7 ng/ml/h) was higher in IDDM patients than in controls (P = 0.01). The increase of PRA was similar in patients (Hf-IDDM = 7.5 ± 7.3, and Nf-IDDM = 8.7 ± 7.2 ng/ml/h) and controls (4.4 ± 5.3 ng/ml/h). There was no difference in PRA levels between Hf-IDDM and Nf-IDDM patients. PRA did not correlate with GFR, aldosterone, blood pressure, blood volume, duration of diabetes, 24-h urinary sodium and metabolic control indexes. Plasma aldosterone and the magnitude of its decrease after captopril was similar among patients and controls. Captopril induced a greater reduction of systolic blood pressure in patients (Hf-IDDM = 12.3 ± 6.9 mmHg; Nf-IDDM = 11.1 ± 7.3 mmHg) than in controls (5.4 ± 5.2 mmHg) (P = 0.01). No difference was found between Hf-IDDM and Nf-IDDM patients. In conclusion, normoalbuminuric IDDM patients, irrespective of glomerular hyperfiltration, presented increased levels of PRA and larger blood pressure response to captopril as compared to normal individuals.

Kidney International, 1992

Glomerular hemodynamics and hormonal evaluation during starvation in rats. The effects of total f... more Glomerular hemodynamics and hormonal evaluation during starvation in rats. The effects of total food deprivation on renal function were evaluated in normal Munich-Wistar rats submitted to starvation (S) periods of two to eight days (Groups S2 to S3). A prompt and sustained decrease in renal plasma flow (RPF) and an increase in total renal vascular resistance (TRVR) were observed after the second day, together with a gradual decrease in glomerular filtration rate (GFR) until the fourth day (40% in the S4 group, P < 0.05). After this period, a spontaneous and progressive increase in GFR occurred in spite of continuing low RPF and high TRVR. Glomerular hemodynamics were evaluated in additional animals from groups S4 and S7. As observed for whole kidney GFR, mean single nephron (SN) GFR was reduced in group S4. but not in group S7. The decline in SNGFR in S4 was the result of a decline (-40%) in glomerular plasma flow rate (QA) and glomerular capillary hydraulic pressure (P0), due to a predominant increase (-60%) in afferent arteriolar resistance. In S7, SNGFR and its determinants did not differ from the control. Angiotensin II (Ang II), prostanglandin (but not thromboxane A2, TxA2) inhibition blunted the alterations in whole kidney function observed in S4. Conversely in S7, the inhibition of vasoconstrictor agents (Ang II and TxA2) did not normalize GFR, suggesting that the intrarenal vasoconstriction could be an important factor to maintain GFR after a prolonged period of starvation. Thus, prolonged starvation induces a biphasic profile of renal function in rats: a first phase characterized by a decline in GFR and SNGFR followed by an adaptative phase with normalization of GFR and superficial glomerular function. Results suggest that these physiological alterations are dependent on a complex hormonal relationship involving hormones such as Ang II and prostaglandins. Important metabolic, hormonal and functional alterations are induced by starvation . This abrupt form of food restriction can induce adaptive mechanisms which permit survival for prolonged periods of starvation. Indeed, human beings can endure several months of fasting . The renal functional responses to starvation are a reduction in glomerular filtration rate [4], natriuresis and polyuria . However, the physiological mechanisms present in the kidney during progressive and prolonged periods of starvation are not fully understood, nor is it known whether renal function can adapt to total food deprivation. Thus, the objectives of the present investigation were to study the effects of progressive periods of starvation (S) during two to eight days (Groups S2 to S8) on renal function in rats, and to evaluate the glomerular hemodynamics and renal microcir-culation during medium (S4) and prolonged (S7) periods of starvation. The role of hormones such as angiotensin II, prostaglandins and thromboxane A2 in the alterations of whole kidney function induced by four and seven days of starvation was also evaluated. The results of the present study showed a biphasic profile of whole GFR and SNGFR with reduction during the first phase (4 days) followed by a spontaneous normalization in the late phase. The physiological alterations in the whole kidney function were dependent, at least in part, on angiotensin II and prostaglandins.

Retinol-binding protein (RBP) is a low-molecular-mass protein (21 kDa), easily filtered in renal ... more Retinol-binding protein (RBP) is a low-molecular-mass protein (21 kDa), easily filtered in renal glomeruli and very efficiently reabsorbed by the proximal convolutedtubules (PCTs). In PCT dysfunction, high concentrations of RBP are found in urine. Several methods have been used to determine RBP in serum or urine. We describe the production, selection, labeling, and utilizationof anti-RBP monoclonal antibodies in two-or one-step immunoenzymometnc assays for the determination of RBP. The one-step assay has good precision, with within-run and between-run CVs <6.6% and 5.9%, respectively. Comparison with radial immunodiffusion (x) showed good

International Journal of Technology Assessment in Health Care, 1990

Cost-effectiveness analysis compared four treatments of end-stage renal disease in Brazil: contin... more Cost-effectiveness analysis compared four treatments of end-stage renal disease in Brazil: continuous ambulatory peritoneal dialysis (CAPD), in-center hemodialysis (HD), cadaver donor transplantation (CD-Tx), and living related donor transplantation (LR-Tx). After 2 years, the costs per year of survival were CAPD, 12,134;HD,12,134; HD, 12,134;HD,10,065; CD-Tx, 6,978;andLR−Tx,6,978; and LR-Tx, 6,978;andLR−Tx,3,022. The HD cost was lower than CAPD partially because of the reuse of hemodialyzers in Brazil. Although less cost-effective, both dialysis treatments yielded more years of survival after 2 years. This analysis reveals a trade-off between cost per year of survival and years of survival.

Journal of Cardiovascular Pharmacology, 1991

In order to complement earlier short-term observations, we studied the effects of isradipine (1.2... more In order to complement earlier short-term observations, we studied the effects of isradipine (1.25 or 2.5 mg twice daily) on blood pressure as well as its action in reversing cardiac hypertrophy in 25 moderately hypertensive patients. We observed that the treatment produced short-term (3 month) and longer-term (9 month) control of blood pressure [decreases in mean arterial pressure (MAP) from 128 +/- 2.3 to 112 +/- 2.7 mm Hg and to 105.5 +/- 2.9 mm Hg; p less than 0.001] while heart rate remained constant throughout the study (from 76.6 +/- 2.3 to 74.7 +/- 2.4 beats/min; NS). Reversal of left ventricular hypertrophy (LVH) obtained after 3 months of treatment (LV mass index from 173.7 +/- 8.8 to 135.7 +/- 4.5 g/m2; p less than 0.001) was accentuated with continued therapy (to 131.0 +/- 4.0 and 124.4 +/- 3.1 g/m2 at 6 and 9 months, respectively; p less than 0.01). These results indicate that significant regression of LVH can be obtained with short-term treatment of hypertension with isradipine and that this effect will be fully obtained with longer-term (9 month) therapy.

Journal of Cardiovascular Pharmacology, 1991

Advances in Experimental Medicine and Biology, 1986

Plasma levels of low and high molecular weight kininogens, prokallikrein and active kallikrein we... more Plasma levels of low and high molecular weight kininogens, prokallikrein and active kallikrein were determined in four models of experimental hypertension and in genetically hypertensive rats. The high molecular weight kininogen remained essentially unaltered in all groups, whereas the low molecular weight kininogen was decreased in the renovascular groups. In the glucocorticoid hypertensive rats low molecular weight kininogen increased, but rats with hypertension induced both by renovascular and glucocorticoid mechanisms had normal kininogen. Genetically hypertensive rats had levels of low molecular weight kininogen similar to the ones observed in control group. The data presented reinforce the hypothesis of a participation of the kallikrein-kinin system in the etiopathogenesis of hypertension, indicating an implication of the low molecular weight kininogen in some types of severe experimental hypertension.

Pediatric Nephrology, 1993

... In: Holliday MA, Ban'att TM, Vernier RL (eds) Pediatric nephrology. Williams and Wilkins... more ... In: Holliday MA, Ban'att TM, Vernier RL (eds) Pediatric nephrology. Williams and Wilkins, Baltimore, pp 384-404 6. Gupta SK, Venkataseshan VS, Churg J (1991) Mesangiocapillary glomerulonephritis in Down's syndrome. ... Carvalhaes, Horacio Ajzen, Oswaldo L, Ramos, ...

Kidney International, 1989

Renal function and glomerular hemodynamics in male endotoxemic rats. The renal effects of a singl... more Renal function and glomerular hemodynamics in male endotoxemic rats. The renal effects of a single intravenous dose of two different E. coli lipopolysaccharides (LPS 0111 :B4 and LPS 0127:B8), at the same dose of 100 pg/kg, were evaluated in euvolemic Munich-Wistar (MW) rats by whole kidney clearance techniques and micropuncture studies. Following LPS infusion, a significant decrease (8%) in mean BP was observed only in the LPS 0127:B8 treated group. Inulin clearance fell 57% (LPS Olll:B4), P < 0.01, and 38% (LPS 0127:B8), P < 0.01.

Transplantation, 1995

Page 1. 914 TRANSPLANTATION Vol. 59, No. 6 INCREASED PRODUCTION OF BETA-2 MICROGLOBULIN IN STABLE... more Page 1. 914 TRANSPLANTATION Vol. 59, No. 6 INCREASED PRODUCTION OF BETA-2 MICROGLOBULIN IN STABLE RENAL TRANSPLANT PATIENTS12 Alvaro Pacheco-Silva,3 Sonia К. Nishida, Marcelo Souza Silva, Oswaldo L. Ramos, Horacio Ajzen, Jose О. ...

Pediatric Nephrology, 1992

In order to determine metabolic disorders in children with urolithiasis, 50 patients with urinary... more In order to determine metabolic disorders in children with urolithiasis, 50 patients with urinary calculi were studied. Abdominal pain and/or haematuria were the most predominant symptoms. Surgical procedures were required in 22% of these children and urinary tract infection was observed in 34% of this group. Only 2 children had anatomical malformations of the urinary tract. Absorptive hypercalciuria (32%), renal hypercalciuria (34%) and uric acid hyperexcretion (24%) were the most common metabolic abnormalities in these children. We were unable to find an underlying metabolic abnormality in only 14% of the patients. These data suggest that appropriate metabolic study will allow rational management of children with urinary stones.

Transplantation, 1995

Drugs, 1988

American Journal of The Medical Sciences, 1973

Clinical Pharmacology & Therapeutics, 1984

Nephron, 1996

Diabetes Research and Clinical Practice, 1995

Kidney International, 1992

International Journal of Technology Assessment in Health Care, 1990

Journal of Cardiovascular Pharmacology, 1991

Advances in Experimental Medicine and Biology, 1986

Pediatric Nephrology, 1993

Kidney International, 1989

Transplantation, 1995

Pediatric Nephrology, 1992

Transplantation, 1995