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Biomedical subjects

R Rocha

Publications and source records attributed to R Rocha.

At least 19 recordsLinked to original sources
PubMed2006

Mercury contents in aquatic macrophytes from two reservoirs in the Paraíba do Sul: Guandú river system, SE Brazil.

This paper reports on a study to determine the Hg content in the five most abundant aquatic macrophyte species (Elodea densa, Sagittaria montevidensis, Salvinia auriculata, Pistia stratiotes and Eichhornia crassipes) in two artificial reservoirs flooded by water diverted from the Paraíba do Sul river, SE Brazil. The potential of these species for Hg accumulation and their role in Hg transport along the river system due to macrophyte management were evaluated. Mercury concentrations were higher in free-floating than in rooted species. Roots were also richer in Hg than were leaves. Dry weight Hg concentrations in leaves and roots from all species varied from 46-246 ng.g(-1) to 37-314 ng.g(-1), respectively. These values are higher than those reported for uncontaminated lakes in Brazil and in other tropical areas and similar to those reported for moderately contaminated sites. Mercury concentrations can be attributed to fluvial transport from the heavily industrialized Paraíba do Sul river basin. Intensive sampling of Pistia stratiotes from two sites in the Vigário reservoir was performed to evaluate the capacity of Hg incorporation in short periods of time. The results showed a significant negative correlation between Hg content and size class of individual plants, demonstrating the importance of juveniles, fast growing plants in absorbing Hg. The foremost impact related to Hg contents in the studied area concerns the periodic removal of macrophytes for reservoir management, followed by disposal in nearby areas. This results in the mobilization of 0.52 to 1.3 Kg of Hg per year, a significant fraction of the Hg burden present in reservoir waters. Disposal of such material may result in Hg leaching to river systems, affecting the Hg transfer throughout the basin.

Brazil↗
PubMed2005

Body mass index and waist circumference in non-alcoholic fatty liver disease.

OBJECTIVE: To evaluate the association of anthropometric indexes (body mass index and waist circumference) in patients with non-alcoholic fatty liver disease (NAFLD), and its association with insulin resistance (IR), metabolic syndrome (MS) and histological findings. METHODS: From August 2003 to July 2004 a case series of 81 outpatients with clinic and/or histological diagnosis of NAFLD were selected at the Bahia University Gastro-Hepatology Clinic, Brazil. Liver function tests, lipid profile, glucose and insulin were performed in all patients. Body mass index (BMI) and waist circumference (WC) were determined according to WHO criteria. IR was measured by means of the homeostasis model assessment (HOMA) and IR was considered with HOMA > or =3. MS was defined according to the Adult Treatment Panel III (ATP III). Liver biopsy was performed in 37 cases. RESULTS: Body mass index > or = 30 kg m(-2) (obesity) was found in 39% of the cases and BMI > or = 25-29.9 kg m(-2) (overweight) in 53%. BMI was correlated with IR (r = 0.29; P = 0.02) and WC with ALT (r = 0.02; P = 0.03). Increased WC also was related to IR and to MS. The presence of steatohepatitis with fibrosis on liver biopsy was associated with overweight (68%) and increase of WC (41%). CONCLUSIONS: Body mass index and WC are frequent associated with MS, IR and histological findings (steatohepatitis and fibrosis) in patients with NAFLD.

Adult↗
PubMed2004

Distinguishing the antihypertensive and electrolyte effects of eplerenone.

In two clinical trials on the antihypertensive effects of the mineralocorticoid receptor antagonist eplerenone 397 essential hypertensives were dose titrated (50, 100, and 200 mg/d) over successive 4-wk periods until they reached target blood pressure levels. Of the total, 44% reached target on 50 mg/d, 17% on 100 mg/d, and 19% on 200 mg/d, with 20% failing to do so despite stepwise dose increases. At each dose level, those who reached target (responders) were compared with those who did not (nonresponders), with three major findings. First, at each dose level, the blood pressure fall in responders (systolic, 16-20 mm Hg; diastolic, approximately 15 mm Hg) was markedly more than mean values in nonresponders (systolic, 2-5 mm Hg; diastolic, 1-3 mm Hg). Second, sensitivity to eplerenone varied widely across the population studied in terms of blood pressure reduction. Third, there was no difference in plasma [K+] levels between responders and nonresponders at any dose level. We interpret these data as evidence for the major antihypertensive effect of eplerenone being via mechanisms other than those involving epithelial electrolyte and fluid transport. The modest (< or =0.2 mEq/liter at 200 mg/d) mean elevation in plasma [K+] suggests that titration to effect rather than forced titration may minimize the risk of hyperkalemia, even where relatively high (100-200 mg/d) doses of the specific mineralocorticoid receptor antagonist eplerenone may ultimately be required.

Adult↗
PubMed2003

The lactate minimum test protocol provides valid measures of cycle ergometer VO(2)peak.

AIM: The aim of the present study was to investigate the validity of the Lactate Minimum Test (LMT) for the determination of peak VO(2) on a cycle ergometer and to determine the submaximal oxygen uptake (VO(2)) and pulmonary ventilation (VE) responses in an incremental exercise test when it is preceded by high intensity exercise (i.e., during a LMT). METHODS: Ten trained male athletes (triathletes and cyclists) performed 2 exercise tests in random order on an electromagnetic cycle ergometer: 1). Control Test (CT): an incremental test with an initial work rate of 100 W, and with 25 W increments at 3-min intervals, until voluntary exhaustion; 2). LMT: an incremental test identical to the CT, except that it was preceded by 2 supramaximal bouts of 30-sec (approximately 120% VO(2)peak) with a 30-sec rest to induce lactic acidosis. This test started 8 min after the induction of acidosis. RESULTS: There was no significant difference in peak VO(2) (65.6+/-7.4 ml x kg(-1) x min(-1); 63.8 +/- 7.5 ml x kg(-1) x min(-1) to CT and LMT, respectively). However, the maximal power output (POmax) reached was significantly higher in CT (300.6+/-15.7 W) than in the LMT (283.2+/-16.0 W). VO(2) and VE were significantly increased at initial power outputs in LMT. CONCLUSION: Although the LMT alters the submaximal physiological responses during the incremental phase (greater initial metabolic cost), this protocol is valid to evaluate peak VO(2), although the POmax reached is also reduced.

Analysis of Variance↗
PubMed2001

Pathophysiological effects of aldosterone in cardiovascular tissues.

The advent of antihypertensive therapy has resulted in a significant decrease in cardiovascular morbidity and mortality. Nevertheless, the incidence of heart failure, stroke and end-stage renal failure continues to increase. This trend suggests that a mechanism, independent of hypertension, is responsible for end-organ damage. Genetic and experimental models of hypertension have demonstrated that excess aldosterone induces severe injury in the heart, brain and kidneys, and that pharmacological antagonism of aldosterone or adrenalectomy markedly reduces myocardial injury, cerebral hemorrhage and renal vascular disease. In clinical studies, plasma aldosterone levels have been shown to correlate with left ventricular hypertrophy, stroke and renal dysfunction. Moreover, aldosterone antagonism has been shown to reduce morbidity and mortality in patients with heart failure. Thus, an increasing body of evidence now indicates that aldosterone is an independent risk factor for cardiovascular disease.

Adrenalectomy↗
PubMed2001

Frequency and determinants of microalbuminuria in mild hypertension: a primary-care-based study.

OBJECTIVE: To evaluate the frequency of microalbuminuria and its relationship with several risk factors and left ventricular mass in a population of mildly hypertensive subjects attended in a primary-care setting. DESIGN: Cross-sectional study. SETTING: Eight primary-care centres. PATIENTS: Two hundred and twenty-three non-diabetic patients recently diagnosed with mild hypertension were included in the study. None of them had clinical evidence of target-organ damage or had received prior antihypertensive treatment. INTERVENTIONS: Subjects included in the study underwent clinical interview, measurement of blood pressure (BP) on three visits, blood analysis, measurement of albumin by immunonephelometry in three overnight urine collections, 24 h BP monitoring and M-mode and Doppler echocardiography. MAIN OUTCOME MEASURES: Tobacco habit, clinic BP, body mass index, serum lipids and uric acid, glycaemia, urinary albumin excretion (UAE), ambulatory BP and left ventricular mass index. RESULTS: The frequency of microalbuminuria was 7.2%. Microalbuminuric patients were more likely to be men and to be characterized by higher ambulatory BP, body mass index and uric acid levels. Regression analysis demonstrated that male sex and 24 h systolic BP were determinants of UAE. Patients with white-coat hypertension showed lower UAE than did subjects with sustained hypertension. Although a certain relationship between UAE and left ventricular mass index was found, these variables were not significantly correlated. CONCLUSIONS: A low proportion of mildly hypertensive patients attended in a primary care setting are microalbuminuric. In this population, UAE is an expression of BP values over 24 h and correlates with several risk factors.

Adult↗
PubMed2001

Eplerenone: a selective aldosterone receptor antagonist (SARA).

Aldosterone, the final product of the renin-angiotensin-aldosterone system (RAAS), is a mineralocorticoid hormone that classically acts, via the mineralocorticoid (aldosterone) receptor, on epithelia of the kidneys, colon, and sweat glands to maintain electrolyte homeostasis. Aldosterone has also been shown to act at nonepithelial sites where it can contribute to cardiovascular disease such as hypertension, stroke, malignant nephrosclerosis, cardiac fibrosis, ventricular hypertrophy, and myocardial necrosis. Although angiotensin-converting enzyme (ACE) inhibitors and angiotensin type 1 (AT(1)) receptor antagonists act to suppress the RAAS, these agents do not adequately control plasma aldosterone levels--a phenomenon termed "aldosterone synthesis escape." Spironolactone, a nonselective aldosterone receptor antagonist, is an effective agent to suppress the actions of aldosterone; its use is, however, associated with progestational and antiandrogenic side effects due to its promiscuous binding to other steroid receptors. For these reasons, eplerenone--the first agent of a new class of drugs known as the selective aldosterone receptor antagonists (SARAs)--is under development. In rodent models, eplerenone provides marked protection against vascular injury in the kidney and heart. In phase II clinical trials, eplerenone demonstrates 24-h control of blood pressure with once or twice daily dosing, and is safe and well tolerated in patients with heart failure when given with standard of care agents. Pharmacokinetic studies reveal that eplerenone has good bioavailability with low protein binding, good plasma exposure, and is highly metabolized to inactive metabolites and excreted principally in the bile. Eplerenone is well tolerated in acute and chronic safety pharmacology studies. Ongoing phase III trials of eplerenone in the treatment of hypertension and heart failure are underway. These studies will extend our understanding of selective aldosterone receptor antagonism in the treatment of chronic cardiovascular disease.

Animals↗
PubMed2000

Antioxidants in medicinal plant extracts. A research study of the antioxidant capacity of Crataegus, Hamamelis and Hydrastis.

The antioxidant capacity of extracts of Crataegus oxyacantha, Hamamelis virginiana, Hydrastis canadensis, plants native to Europe and North America which have long been used in herbal medicine for the treatment of cardiac and circulatory functions, has been investigated. The total antioxidant potential conferred by all hydrogen donating antioxidants present in these extracts has been assessed by the ABTS assay and the relative order of antioxidant potential has been established. Gas chromatography coupled to mass spectrometry (GC-MS) has been used for the chemical identification of the antioxidant volatile compounds present in the extracts. The GC-MS data were related to the results obtained using the ABTS assay.

Antioxidants↗
PubMed2000

Aldosterone: a mediator of myocardial necrosis and renal arteriopathy.

To determine the role of aldosterone in mediating cardiovascular damage, we performed ablation/replacement experiments with aldosterone in a rat model of cardiac injury. Administration of angiotensin II and Nomega-nitro-L-arginine methyl ester (L-NAME; nitric oxide synthesis inhibitor) to male rats drinking 1% saline caused hypertension, severe biventricular myocardial necrosis, proteinuria, and fibrinoid necrosis of renal and cardiac vessels. Removal of aldosterone by adrenalectomy or through administration of the selective aldosterone antagonist eplerenone markedly reduced the cardiac and renal damage without significantly altering blood pressure. Aldosterone infusion in adrenalectomized, glucocorticoid-replaced L-NAME/angiotensin II-treated animals restored damage. Thus, we identified aldosterone as a critical mediator of L-NAME/angiotensin II induced vascular damage through mechanisms apparently independent of its effects on systolic blood pressure.

Adrenalectomy↗
PubMed1999

Role of aldosterone in renal vascular injury in stroke-prone hypertensive rats.

Stroke-prone spontaneously hypertensive rats (SHRSP) on 1% NaCl drinking solution and Stroke-Prone Rodent Diet develop severe hypertension and glomerular and vascular lesions characteristic of thrombotic microangiopathy seen in malignant nephrosclerosis. We recently reported that spironolactone, a mineralocorticoid receptor antagonist, markedly reduced proteinuria and malignant nephrosclerotic lesions in these animals. This observation, together with our previous findings that angiotensin-converting enzyme inhibitors prevent the development of vascular damage, suggests that mineralocorticoids, as part of the renin-angiotensin-aldosterone system, play a pathophysiological role in this model. In the present study, we examined whether chronic (2-week) infusion of aldosterone can reverse the renal vascular protective effects of captopril in SHRSP. SHRSP received vehicle (n=8); captopril alone (50 mg. kg-1. d-1, orally) (n=10); aldosterone infusion alone (40 microg. kg-1. d-1, SC) (n=7); or captopril and aldosterone at 20 (n=6) or 40 (n=7) microg. kg-1. d-1. Systolic blood pressure was markedly elevated in all groups. Vehicle- and aldosterone-infused SHRSP developed severe proteinuria and comparable degrees of renal injury (21+/-3% and 29+/-3%, respectively) manifested as thrombotic and proliferative lesions in the arterioles and glomeruli. Captopril treatment reduced plasma aldosterone levels concomitant with marked reductions in proteinuria and the absence of histologic lesions of malignant nephrosclerosis. Aldosterone substitution at 20 or 40 microg. kg-1. d-1 in captopril-treated SHRSP resulted in the development of severe renal lesions (16+/-3% and 21+/-2%, respectively) and proteinuria comparable with that observed in SHRSP given either aldosterone or vehicle alone. These findings support a major role for aldosterone in the development of malignant nephrosclerosis in saline-drinking SHRSP, independent of the effects of blood pressure.

Aldosterone↗
PubMed1999

Measurement of relative antioxidant activity of compounds: a methodological note.

The relative activities of some hydrogen-donating antioxidants were assessed by comparing their activities with that of Trolox (Trolox equivalent antioxidant capacity, TEAC) for scavenging the ABTS radical cation (ABTS.+) generated in the aqueous phase. We have verified, however, that TEAC values may change with the concentration of compounds and with the measuring times used. Not withstanding, TEAC values do not differ significantly if the compounds have kinetic curves of ABTS.+ formation similar to that of Trolox. This is the case with ascorbic acid, whose TEAC values, determined by using five concentrations at three different measuring times, are very close. For the flavonoids studied (catechin, rutin, naringenin and silibinin) which have kinetic curves of ABTS.+ formation different from that of Trolox, the TEAC values decrease with increasing concentrations of the compounds for each measuring time, and increase with increasing measuring times for each concentration. In the present study, we conclude that, in order to evaluate relative antioxidant activities of compounds by the ABTS assay, it is essential to perform kinetic studies to assess scavenging of ABTS.+ by these compounds. Therefore, when the TEAC values of compounds are determined for more than one measuring time, we may be sure that all the antioxidant potential of compounds is being considered and whether or not it is possible to establish a hierarchy for their antioxidant activities.

Antioxidants↗
PubMed1998

Mineralocorticoid blockade reduces vascular injury in stroke-prone hypertensive rats.

Chronic treatment of saline-drinking stroke-prone spontaneously hypertensive rats (SHRSP) with agents that interfere with the formation or actions of angiotensin II (Ang II) prevents the development of stroke and renal vascular damage. Ang II, in addition to its direct vascular effects, stimulates the synthesis and release of aldosterone. To assess the role of aldosterone in the development of pathologic changes in these rats, we implanted time-release pellets containing 200 mg of the mineralocorticoid receptor antagonist, spironolactone, into 14 SHRSP at 7.5 weeks of age. Eight SHRSP littermates received placebo pellets. Over the period of study (3 to 4 weeks), systolic blood pressure (SBP) was not different between the groups. Spironolactone did not enhance water and electrolyte excretion. All placebo-treated SHRSP developed marked proteinuria (150+/-6 mg/d) whereas in spironolactone-treated SHRSP, urinary protein excretion (UPE) averaged 39+/-9 mg/d (P<.0001). In a second study to assess effects on survival, 6 SHRSP received spironolactone (10 mg/kg/d) and 6 received vehicle. All but one of the control rats displayed signs of stroke and died by 16 weeks of age, while the spironolactone-treated SHRSP remained asymptomatic through 19 weeks of age (P<.03). At 16 weeks of age, spironolactone-treated SHRSP were severely hypertensive (247+/-3 mm Hg), yet UPE remained at baseline levels. In contrast, preterminal UPE averaged 136+/-13 mg/d in control rats (P<.0001). In both studies, histopathologic examination revealed a marked protective effect of spironolactone against the development of malignant nephrosclerotic and cerebrovascular lesions. These observations indicate a vascular and end organ protective effect of spironolactone in the absence of lowered blood pressure in saline-drinking SHRSP and are consistent with a major role for mineralocorticoids as hormonal mediators of vascular injury.

Aging↗
PubMed1995

Experience with a mixed semantic/syntactic parser.

The value of the computerized medical record is derived in part from the availability of medical information in a coded form accessible to manipulation by processes designed for automated decision support, medical research, and computer assistance in the management of health care delivery. To meet these needs medical reports captured and stored as natural language documents must be encoded. Below we discuss an ongoing formative process aimed at developing a natural language understanding system for chest x-ray reports. Comparative data showing the progress of this process is presented.

Hospital Information Systems↗
PubMed1994

Hemophilia A or von Willebrand disease?

Seven members of the same family were studied on several occasions due to a history of hemorrhages. The propositus, a 12-year-old boy, his sister, one brother, and their father all had a low plasma factor VIII (FVIII) level. Von Willebrand factor (vWF) activity, vWF multimeric analysis, and vWF factor domain for binding to FVIII were normal in all seven subjects. The sister had a normal 46XX karyotype. The study of two intragenic restriction fragment length polymorphisms (RFLPs) and two closely linked, highly polymorphic extragenic markers showed a phenotypic expression of mild hemophilia A, which suggests that the sister of the propositus is homozygous or compound heterozygous at the hemophilia A locus. She would have inherited two hemophilic genes: one from her carrier mother and the other from her father, a mild hemophiliac.

Binding Sites↗
PubMed1994

A natural language understanding system combining syntactic and semantic techniques.

A large proportion of the medical record currently available in computerized medical information systems is in the form of free text reports. While the accessibility of this source of data is improved through inclusion in the computerized record, it remains unavailable for automated decision support, medical research, and management of medical delivery systems. Natural language understanding systems (NLUS) designed to encode free text reports represent one approach to making this information available for these uses. Below we describe an experimental NLUS designed to parse the reports of chest radiographs and store the clinical data extracted in a medical data base.

Bayes Theorem↗
PubMed1993

A high-field superferric NMR magnet.

Strong, extensive magnetic fringe fields are a significant problem with magnetic resonance imaging magnets. This is particularly acute with 4-T, whole-body research magnets. To date this problem has been addressed by restricting an extensive zone around the unshielded magnet or by placing external unsaturated iron shielding around the magnet. This paper describes a solution to this problem which uses superconducting coils closely integrated with fully saturated iron elements. A 4-T, 30-cm-bore prototype, based on this design principle, was built and tested. The 5 G fringe field is contained within 1 meter of the magnet bore along the z axis. Homogeneity of the raw magnetic field is 10 ppm over 30% of the magnet's diameter after passive shimming. Compared with an unshielded magnet, 20% less superconductor is required to generate the magnetic field. Images and spectra are presented to demonstrate the magnet's viability for magnetic resonance imaging and spectroscopy.

Magnetic Resonance Spectroscopy↗