Browsing by Author "Villarroel, L"
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- ItemGenetic variation in P450c11AS in Chilean patients with low renin hypertension(ENDOCRINE SOC, 1996) Fardella, CE; Rodriguez, H; Montero, J; Zhang, GR; Vignolo, P; Rojas, A; Villarroel, L; Miller, WLLow renin hypertension (LRH), which accounts for 10-20% of patients with idiopathic ''essential'' hypertension, bears hormonal similarities to mineralocorticoid-induced hypertension, but elevated mineralocorticoid concentrations have not been found. Some patients with LRH have normal, rather than suppressed, plasma aldosterone concentrations, so that the ratio of aldosterone concentration to PRA (Aldo/PRA) is high, suggesting inappropriately increased aldosterone biosynthesis. We characterized the CYP11B2 gene that encodes the aldosterone synthase, P450c11AS, in hypertensive and control populations in a single clinic in Santiago, Chile. We directly sequenced the entire CYP11B2 gene in 12 patients with LRH, 2 high renin hypertensive controls, and 2 normotensive controls. All sequences were identical, except that 8 of 24 LRH alleles encoded arginine rather than lysine at position 173. The Arg(173) and Lys(173) variants were expressed in transfected MA-10 cells, and their ability to convert deoxycorticosterone to aldosterone was measured; the apparent Michaelis constant (K-m) for Lys(173) was 2.73 mu mol/L; the K-m for Arg(173) was 2.53 mu mol/L. The apparent maximal velocity (V-max) for Lys(173) was 6.5x10(-3) mu g/mL . 24 h; the V-max for Arg(173) was 7.8x10(-3) mu g/mL . 24 h. The first order rate constant, V-max/K-m was 2.38 for Lys(173) and 3.08 for Arg(173). As these values were not significantly different, we sought to determine whether Arg(173) is a polymorphism linked to LRH. We examined position 173 in 52 unselected patients with idiopathic hypertension and 55 normotensive controls by PCR amplification of CYP11B2 exons 3-5 followed by digestion with Bsu36I, which digests the Arg(173) sequence, but not the Lys(173) sequence. More of the hypertensive alleles (39 of 104, 37.5%) than normotensive alleles (25 of 110, 22.5%) carried Arg(173) (chi(2)=5.57; P <0.02). Most of the Arg(173) alleles (31 of 72, 43.1%) were from hypertensive patients with Aldo/PRA below 30, whereas only 5 of 24 (20.8%) Arg(173) alleles were found in patients with Aldo/PRA greater than 30 (chi(2)=3.79; P=0.05) Thus, the Arg(173) variant of CYP11B2 may be linked to LRH in Chilean patients.
- ItemMaternal body composition near term and birth weight(LIPPINCOTT WILLIAMS & WILKINS, 1998) Mardones Santander, F; Salazar, G; Rosso, P; Villarroel, LObjective: To assess the relative influence of maternal body composition at late gestation on birth weight.
- ItemMicrosatellite instability and loss of heterozygosity have distinct prognostic value for testicular germ cell tumor recurrence(TAYLOR & FRANCIS INC, 2004) Velasco, A; Riquelme, E; Schultz, M; Wistuba, II; Villarroel, L; Koh, MS; Leach, FSGerm cell tumor (GCT) is the most common genitourinary malignancy of men between the ages of 18 and 35 years. Therapy is ultimately successful in over 90% of patients, however significant morbidity and mortality can be associated with adjuvant treatment and relapse. Molecular markers that predict treatment response and/or poor outcome would have immediate clinical benefit since adjuvant treatment could be selectively reserved for patients at higher risk for relapse and those patients most likely to respond to treatment. In order to identify potential prognostic molecular markers, we evaluated 118 GCT for microsatellite instability (MSI), loss of heterozygosity (LOH) and MSH2 immunostaining to identify tumors associated with relapse and/or poor outcome following initial surgical, medical and/or radiation therapy.
- ItemMismatch repair gene expression and genetic instability in testicular germ cell tumor(2004) Velasco, A; Riquelme, E; Schultz, M; Wistuba, II; Villarroel, L; Pizarro, J; Berlin, A; Ittmann, M; Koh, MS; Leach, FSHuman mismatch repair (MMR) genes encode highly conserved interacting proteins that correct replication errors predisposing to hereditary gastrointestinal and genitourinary malignancies. A subset of sporadic genitourinary tumors also exhibits MMR deficiency and can be identified by measuring the frequency of microsatellite instability (MSI) in cancer cell DNA. We investigated expression of the two most commonly mutated MMR genes, MSH2 and MLH1, in sporadic testicular germ cell tumor (GCT) in order to: (1) determine the expression pattern of MSH2 and MLH1 proteins in normal seminiferous tubules and histologically distinct GCT subtypes, (2) correlate MMR gene expression with genetic instability in GCT and (3) develop a panel of molecular markers that can identify genetically distinct subsets of GCT for prognostic assessment.
- ItemPrevalence of Epstein Barr virus infection in healthy individuals in Santiago, Chile(SOC MEDICA SANTIAGO, 1995) Ferres, M; Prado, P; Ovalle, J; Fuentes, R; Villarroel, L; Ferreccio, C; Vial, PTo study the rate of infection by Epstein Barr virus (EBV) in Santiago, Chile, the prevalence of antibody to the viral capsid antigen (VCA-lgG) was determined in a group of 663 healthy individuals grouped by age and socioeconomic level (SEL). In addition, several risk factors for infection were studied. VCA-lgG was determined by ELISA. The total prevalence was 76,7%. When grouped by age and SEL, 50% of the children from low and medium SEL had been already infected by the age two, compared to 5,9% in the high SEL (p<0.01). However, by age twenty, 90% of the total sample had already specific antibodies to EBV. Age and number of household members were positively associated with the infection. High socioeconomic level represented a delay factor in the acquisition of the virus, (p<0.01). These results show that EBV infection is frequent in Santiago, occurring early in childhood among medium and low SEL. Hence, the classical infectious mononucleosis should be recognized more frequently among adolescents and young adults belonging to high SEL, while the clinical spectrum of associated manifestations different from the typical mononucleosis syndrome should be investigated among these exposed in early age.
- ItemT235 Variant of the angiotensinogen gene and blood pressure in the Chilean population(LIPPINCOTT WILLIAMS & WILKINS, 1998) Fardella, CE; Claverie, X; Vignolo, P; Montero, J; Villarroel, LBackground The angiotensinogen gene has recently been linked to essential hypertension, A variant within this gene, encoding threonine rather than methionine at amino acid position 235, was associated with essential hypertension, However, results of new studies have not confirmed this association, suggesting that ethnic differences may explain the different results.
- ItemUrinary kallikrein excretion in the human menstrual cycle, normal pregnancy and lactation(PARTHENON PUBLISHING GROUP, 1998) Valdes, G; Corthorn, J; Oyarzun, E; Berrios, C; Foradori, A; Germain, AM; Villarroel, LObjectives To evaluate the temporal pattern of active and total urinary kallikrein excretion during the menstrual cycle, pregnancy and lactation, and to associate changes in kallikrein excretion with those of ovarian and placental hormones.