Kinetics and mechanism of complex formation reactions in the Iron(III)-phosphate ion system at large iron(III) excess. Formation of a tetranuclear complex.

The kinetics and mechanism of the iron(III)-phosphate ion reaction were studied at large iron(III) excess using the stopped-flow method at 10.0 degrees C in 1.0 M NaClO4. In the first few hundred milliseconds of the reaction, the formation of a novel tetranuclear complex was confirmed. The following composition is proposed for the new species: Fe4(PO4)(OH)2(H2O)16(7+). According to detailed kinetic studies, the formation of this species is first order with respect to Fe2(OH)2(H2O)8(4+) and H2PO4- and presumably proceeds via a dinuclear intermediate species. At longer reaction times slow dissociation of the tetranuclear complex controls the formation of the thermodynamically favored Fe(PO4)(H2O)5 complex. The overall reaction was interpreted in terms of the following reactions: Fe2(OH)2(H2O)8(4+) [symbol: see text] 2Fe3+ mn; Fe2(OH)2(H2O)8(4+) + P(V) [symbol: see text] Fe2PV; Fe2PV + Fe2(OH)2(H2O)8(4+) [symbol: see text] Fe4PV; Fe3+ mn + P(V) [symbol: see text] Fe(PO4)(H2O)5. (Fe3+ mn = Fe(H2O)6(3+) + Fe(OH)(H2O)5(2+); P(V) = H3PO4 + H2PO4-; Fe2PV = Fe2(HPO4)(OH)(H2O)8(3+); Fe4PV = Fe4(PO4)(OH)2(H2O)16(7+).) The pH dependence and relevant rate and equilibrium constants are reported for the individual reaction steps.

Early blood pressure level as a mark of familial aggregation of metabolic cardiovascular risk factors--the Rio de Janeiro Study.

OBJECTIVE: To investigate the familial aggregation of metabolic risk factors (RF) according to blood pressure (BP) percentile of children and adolescents. DESIGN AND METHODS: Normal BP was established in 3906 children and adolescents in 1987. From this population two groups of target individuals were separated: group A (n = 327) with systolic and/or diastolic BP percentile > 95 and group B (n = 327) with systolic and diastolic BP percentile < or = 50. Ten years later, familial aggregation of metabolic RF was evaluated using clinical and laboratorial data from 785 individuals, divided into two groups: group 1 with 135 target individuals (BP percentile > 95), 181 parents, 100 siblings and 16 grandparents; and group 2: 106 target individuals (BP percentile < or = 50), 145 parents, 84 siblings and 18 grandparents. RESULTS: (1) The longitudinal study 10 years later (tracking effect) showed that 34.8% of target individuals of group 1 and 90.5% of group 2 remained at the same BP percentile. (2) Comparing the two groups of target individuals, group 1 had higher weight and body mass index (BMI), systolic BP (SBP), diastolic BP (DBP), and heart rate (HR) (P < 0.001) and lower HDL (P < 0.003). (3) Comparing target individuals' and their relatives' measurements together, group 1 had higher BMI, HR, SBP, DBP (P < 0.03) and lower HDL (P < 0.001). (4) SBP and DBP showed significant correlation with all metabolic variables even when BMI was controlled in a multiple regression analysis (P < 0.04). CONCLUSION: BP level in children and adolescents was a good marker for familial aggregation of metabolic RF, suggesting an interaction of genetic and environmental factors. Primary intervention should be carried out in early stages of life.

[Coronary fistula associated with severe pulmonary stenosis and cianosis]. / Fístula coronariana associada à estenose pulmonar grave e cianose.

A 17 year old male adolescent was admitted to the hospital due to dyspnea and cyanosis, since the age of 6 years. On physical examination, it was found a continuous murmur over the left esternal border at the 4th and 5th intercostal spaces suggesting a coronary fistula. A color-echocardiogram associated with an angiography confirmed the diagnosis of coronary fistula and severe pulmonary stenosis. The functional consequence was a right to left shunt with cyanosis. A surgical repair was performed with closure of the fistula at the point where it drained into the right ventricle plus a pulmonary commissurotomy. The patient had an uneventful recovery.

Fístula coronariana associada à estenose pulmonar grave e cianose / Coronary Fistula Associated with Severe Pulmonary Stenosis and Cianosis

Adolescente do sexo masculino, 17 anos, com queixa de dispnéia e cianose desde os 6 anos, apresentava ao exame fisíco sopro contínuo nos quarto e quinto espaços intercostais esquerdos, sugestivo de fístula coronariana. O eco-color e a angiografia confirmaram a hipótese de fístula coronariana associada a estenose pulmonar valvar grave e shunt direito-esquerdo, o que provocava a cianose. Foi submetido a correçäo cirúrgica para fechamento da fístula ao nível do seu sítio de drenagem e realizaçäo de cosurotomia pulmonar, permanecendo assintomático até o momento.

A possible path for mercury in biological systems: the oxidation of metallic mercury by molecular oxygen in aqueous solutions.

Metallic mercury has been assumed by several authors as not very reactive and, as a consequence, with little or no toxicity. The toxicity of this element is usually ascribed to alkyl-mercury ions considered to be formed by some microorganisms. In this work, we describe experiments that clearly show that metallic mercury can be easily oxidized by molecular oxygen in aqueous solution in the presence of species such as chloride, which complex Hg(II). The experiments were carried out using metallic mercury in NaCl aqueous solution under 'open air' (temperature and agitation rate maintained constant) and under more controlled conditions (CO2 rate bubbling, i.e. pH = 4.2; air rate bubbling, i.e., O2 constant concentration, temperature, agitation rate). The reactions were monitored spectrophotometricaly at 230 nm (HgCl2-(4)). Significative values of the concentration of Hg(II) in the form of HgCl2-(4) were soon attained in those solutions. For example, in 'open air' conditions, at 25 degrees C and [NaCl] = 30 g/l (0.51 mol/dm3), the maximal concentration of 13 ppm (6.44 x 10(-5) mol/dm3) of Hg(II) in the form of HgCl2-(4) was reached in 120 min; for [NaCl] = 5 g/l at 25 degrees C, (0.085 mol/dm3) the maximal concentration of 0.3 ppm (1.53 x 10(-6) mol/dm3) of Hg(II) in the form of HgCl2-(4) was reached in 10 min. The rate constants, kobs, of the oxidation of the metallic mercury under the studied conditions are pseudo zero-order at 25 degrees C, and under more controlled conditions have ranged from 1.0 x 10(-7) mol/min ([NaCl] = 5 g/l identical to 0.085 mol/dm3) to 20.0 x 10(-7) mol/min ([NaCl] = 300 g/l identical to 5.12 mol/dm3). The rate constant increases with temperature, up to 25 degrees C, from where kobs remains constant up to 40 degrees C. From the analysis of the experimental results it was possible to propose a mechanism of oxidation of metallic mercury by O2 in aqueous solution containing NaCl. This oxidation is proposed as a possible route for the introduction of mercury into biological systems.

Aneurisma subvalvar mitral em criança pós meningite bacteriana / Subvalvar mitral aneurism in child with bacterial meningitis

Os autores relatam um caso de aneurisma subvalvar mitral pós meningite bacteriana aguda, em crianças de cor branca. O aneurisma ventricular surgiu como complicaçäo de uma miopericardite, três semanas após a relaizaçäo de uma pericardiocentese. Foi realizada a resseçäo cirúrgica do aneurisma e a funçäo do ventrículo esquerdo penaneceu inalterada. Säo discutidas as possíveis causas de aneurisma ventricular.

[Acute myocardial infarct in a patient with dextrorotation]. / Infarto agudo do miocárdio em paciente com dextro-rotção.

A 79-year-old woman developed myocardial infarction associated with acute pulmonary edema. The electrocardiogram recorded QRS complex of QS type in V1 with upper ST extending from V3R to V6R. The polarity of the P wave in bipolar leads was positive, so compatible with dextrorotation complicated by myocardial infarction. The dextrorotation was confirmed with chest roentgenogram and echocardiogram.