Perinatal lead exposure affects nitric oxide and cyclooxygenase pathways in aorta of weaned rats

Perinatal Pb exposure may modulate arterial tone through nitric oxide (NO) and cyclooxygenase products. To investigate this, Wistar dams received 1000 ppm of Pb or sodium acetate (control) in drinking water during pregnancy and lactation. Curves were constructed in phenylephrine-precontracted intact and/or denuded rings of thoracic aortas of weaned (23-day-old) male pups from their responses to N-omega-nitro-L-arginine methyl ester (L-NAME, NO synthase inhibitor) and ACh in the absence or presence of indomethacin (10(-5)M, cyclooxygenase inhibitor) or L-NAME (3 x 10(-7)M and 3 x 10(-4)M). Blood lead concentration and systolic blood pressure (SBP) were higher in intoxicated than control pups (blood lead mu g/dl: control < 3.0, Pb 58.7 +/- 6.5*; SBP mmHg: control 111.4 +/- 2.3, Pb 135.5 +/- 2.4*). In L-NAME-treated rings maximal responses increased in Pb-exposed rats, and were higher in intact than in denuded aortas (contraction [% of phenylephrine] intact: control 184.3 +/- 23.7, Pb 289.1 +/- 18.3*; denuded: control 125.1 +/- 4.5, Pb 154.8 +/- 13.3*). ACh-induced relaxation in intact aortas from Pb-exposed rats presented rightward shift in L-NAME presence (EC50 x 10(-7)M: control 1.32 [0.33-5.18], Pb 4.88 [3.56-6.69]*) but moved left under indomethacin (EC50 x 10(-7)M: control 8.95 [3.47-23.07], Pb 0.97 [0.38-2.43]*). *p < 0.05 significant relative to the respective control; N = 7-9. Endothelium removal abolished ACh-induced relaxation. Perinatal Pb exposure caused hypertension associated with alterations in the production and/or release of basal and stimulated endothelium-derived relaxing factors-NO and constricting cyclooxygenase products. These findings may help explain the contribution of NO and cyclooxygenase products to the etiology and/or maintenance of Pb-induced hypertension and could ultimately lead to therapeutic advantages in plumbism.

Determination of lead in the absence of supporting electrolyte using carbon fiber ultramicroelectrode without mercury film

The determination of lead ions directly in water, for application in analysis of samples of environmental interest, was studied by electroanalytical techniques. Linear sweep anodic stripping voltammetry with a carbon fiber disk ultramicroelectrode (7.0 mu m in diameter), without mercury film, has been used for lead determination, by standard addition, in purified water in the absence of supporting electrolyte. The response was linear in the range from 10.0 to 50.0 mu g L-1, with a detection limit of 0.8 mu g L-1, for 300 s preconcentration time, at -1.2 V and 1.0 V s(-1) scan rate. The reliability of the analytical procedure was evaluated by precision using relative standard deviations (5.6%, for three repetitive stripping current measurements of solution with 10.0 mu g L-1 lead ions) and by the accuracy with recovery experiments (mean of 110.8%) for the same concentration.

At the interface: Crystal structures of phospholipases A(2)

The protein content of many snake venoms often includes one or more phospholipases A(2) (PLA(2)). In recent years a growing number of venoms from snakes of Agkistrodon, Bothrops and Trimeresurus species have been shown to contain a catalytically inactive PLA(2)-homologue in which the highly conserved aspartic acid at position 49 (Asp49) is substituted by lysine (Lys49). Although demonstrating little or no catalytic activity, these Lys49-PLA(2)s disrupt membranes by a Ca2+-independent mechanism of action. In addition, this family of PLA(2)s demonstrates myotoxic and cytolytic pharmacological activities, however the structural bases underlying these functional properties are poorly understood. Through the application of X-ray crystallography in combination with biophysical and bioinformatics techniques, we are studying structure/function relationships of Lys49-PLA(2)s. We here present results of a systematic X-ray crystallographic and amino acid sequence analysis study of Lys49-PLA(2)s and propose a model to explain the Ca2+ independent membrane damaging activity. (C) 1998 Elsevier B.V. Ltd. All rights reserved.

Light-front zero-mode contribution to the Ward Identity

In a covariant gauge we implicitly assume that the Green's function propagates information from one point of the space-time to another, so that the Green's function is responsible for the dynamics of the relativistic particle. In the light front form one would naively expect, that this feature would be preserved. In this manner, the fermionic field propagator can be split into a propagating piece and a non-propagating (contact) term. Since the latter (contact) one does not propagate information; and therefore, supposedly can be discarded with no harm to the field dynamics we wanted to know what would be the impact of dropping it off. To do that, we investigated its role in the Ward identity in the light front. Here we use the terminology Ward identity to identify the limiting case of photon's zero momentum transfer in the vertex from the more general Ward-Takahashi identity with nonzero momentum transfer.

Fluvial transport of lead, zinc and copper contents in polluted mining regions

Ore mines installed in the lower-middle portion of Ribeira de Iguape River (São Paulo State, southeastern Brazil), together with the Panelas Plant are responsible for the contamination of the Iguape-Cananeia-Paranagua lagoon-estuarine complex. The lower-middle portion of Grande Creek Basin, located in the district of Adrianopolis (Parana State, southern Brazil) is under environmental impact because of mining activities. The mines of Perau, at Perau Creek, Canoas at Canoas Creek, and Barrinha at Barrinha Creek and Laranjal Creek have been paralyzed. The transport of lead in fluvial sediments is mainly associated with organic matter, carbonates, the residual fraction, and adsorbables, whereas the transport of zinc is associated with the organic and residual fraction, oxides and hydroxides of iron and manganese, carbonate, and adsorbables. The transport of copper is associated with the residual fraction and oxides and hydroxides of iron and manganese, organic matter, carbonate, and adsorbables.

Nanosized lead lanthanum titanate (PLT) ceramic powders synthesized by the oxidant peroxo method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Study on the K3Li2Nb5O15 formation during the production of (Na0.5K0.5)((1-x))LixNbO3 lead-free piezoceramics at the morphotropic phase boundary

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Structural and dielectric characterization of praseodymium-modified lead titanate ceramics synthesized by the OPM route

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and characterization of lead zirconate titanate powders obtained by the oxidant peroxo method

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Contribution of structural order-disorder to the room-temperature photoluminescence of lead zirconate titanate powders

Intense and broad visible photoluminescent (PL) band was observed at room temperature in structurally disordered PbZr0.53Ti0.47O3 powders. The lead zirconate titanate PbZr0.53Ti0.47O3 powders prepared by the polymeric precursor method and heat treated at different temperatures were structurally characterized at long range by means of X-ray diffraction. The PL was measured at room temperature samples heat treated at different temperatures. Experimental measurements and quantum-mechanical calculations showed that the high structural order and the high structural disorder in PbZr0.53Ti0.47O3 lattice are not favorable to the intense PL emission. Only samples containing simultaneous structural order and disorder in their lattice present the intense visible PL emission at room temperature. (C) 2007 Published by Elsevier B.V.

Mathematical equation correction to spectral and transport interferences in high-resolution continuum source flame atomic absorption spectrometry: determination of lead in phosphoric acid

Um método de correção de interferência espectral e de transporte é proposto, e foi aplicado para minimizar interferências por moléculas de PO produzidas em chama ar-acetileno e de transporte causada pela variação da concentração de ácido fosfórico. Átomos de Pb e moléculas de PO absorvem a 217,0005 nm, então Atotal217,0005 nm = A Pb217,0005 nm + A PO217,0005 nm. Monitorando o comprimento de onda alternativo de PO em 217,0458 nm, é possível calcular a contribuição relativa de PO na absorbância total a 217,0005 nm: A Pb217,0005 nm = Atotal217,0005 nm - A PO217,0005 nm = Atotal217,0005 nm - k (A PO217,0458 nm). O fator de correção k é a razão entre os coeficientes angulares de duas curvas analíticas para P obtidas a 217,0005 e 217,0458 nm (k = b217,0005 nm/b217,0458 nm). Fixando-se a taxa de aspiração da amostra em 5,0 ml min-1, e integrando-se a absorbância no comprimento de onda a 3 pixels, curvas analíticas para Pb (0,1 - 1,0 mg L-1) foram obtidas com coeficientes de correlação típicos > 0,9990. As correlações lineares entre absorbância e concentração de P nos comprimentos de onda 217,0005 e 217,0458 foram > 0,998. O limite de detecção de Pb foi 10 µg L-1. O método de correção proposto forneceu desvios padrão relativos (n=12) de 2,0 a 6,0%, ligeiramente menores que os obtidos sem correção (1,4-4,3%). As recuperações de Pb adicionado às amostras de ácido fosfórico variaram de 97,5 a 100% (com correção pelo método proposto) e de 105 a 230% (sem correção).

Simultaneous Determination of Cadmium and Lead in Medicinal Plants Using Graphite Furnace Atomic Absorption Spectrometry and Direct Slurry Sampling

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Determination of lead in medicinal plants by high-resolution continuum source graphite furnace atomic absorption spectrometry using direct solid sampling

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Anodic Stripping Voltammetric Determination of Lead (II) and Cadmium (II) by Using a Carbon Nanotubes Paste Electrode Modified with Ion Exchange Synthetic Resin

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Thermal behaviour study of solid state compounds of manganese (II), zinc (II) and lead (II) with cinnamic acid

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)