Time-dependent effects of lead on rat reproductive functions

The effects of exposure to lead on endocrine function and the reproductive parameters were studied in pubertal rats treated with 1.0 g l(-1) lead acetate in drinking water for 20 days (subacute group) or 9 months (chronic group) in addition to i.v. injections of lead acetate (0.1 mg 100 g(-1) body wt.) every 10 (subacute group) or 15 days (chronic group). Although basal levels of testosterone were higher both in plasma and in testes of acutely intoxicated animals, the circulating levels of luteinizing hormone (LH) were not affected in either group, nor was the LH-releasing hormone content of the median eminence. The density of [I-125]LH/human chorionic gonadotrophin (hCG) binding sites in testicular homogenates was reduced by saturnism in both groups, concomitant with a significantly increased apparent affinity constant of the hormone-receptor complex. These data can be viewed as the result of a mixture of specific lead toxicity (e.g. at the enzyme level) with other more general actions (e.g. at the level of the hypothalamus-pituitary-testicular axis).

Synthesis and thermal study of the barium complexes with 8-hydroxyquinolinate derivatives

In this present work, barium ion was reacted with different ligands which are 5,7-dibromo, 5,7-dichloro, 7-iodo and 5-chloro-7-iodo-8-hydroxyquinoline, in acetone/ammonium hydroxide medium under constant stirring and the obtained compounds were as follows: (I) Ba[(C9H4ONBr2)(2)].1.5H(2)O; (II) Ba[(C9H4ONCl2)(OH)]. 1H(2)O; (III) Ba[(C9H5ONI)(2)]. 1H(2)O and (IV) Ba[(C9H4ONICl)(2)]. 5H(2)O, respectively. The compounds were characterized by elemental analysis, infrared absorption spectrum (IR), inductively coupled plasma spectrometry (ICP), simultaneous thermogravimetry-differential thermal analysis (TG-DTA) and differential scanning calorimeter (DSC).The final residue of the thermal decomposition was characterized as orthorhombic BaBr2 from (I); the intermediate residue, as a mixture of orthorhombic BaCO3 and BaCl2 and cubic BaO and the final residue, as a mixture of cubic and tetragonal BaO and orthorhombic BaCl2 (II); the intermediate residue, as orthorhombic BaCO3 and as a final residue, a mixture of cubic and tetragonal BaO from (III); and the intermediate residue, as a mixture of orthorhombic BaCO3 and BaCl2 and as a final residue, a mixture of cubic and tetragonal BaO and orthorhombic BaCl2 from (IV).

Characterization and catalytic activity of iron(III) mono(4-N-methyl pyridyl)-tris(halophenyl) porphyrins in homogeneous and heterogeneous systems

The synthesis, characterization and catalytic activity of the cationic iron porphyrins Fe[M(4-N-MePy)TDCPP]Cl-2 and Fe[M(4-N-MePy)TFPP]Cl-2 in the epoxidation of (Z)-cyclooctene by PhIO in homogeneous solution and supported on silica gel (SG), imidazole propyl gel (IPG) or SG modified with 2-(4-sulfonatophenyl)ethyl groups (SiSO3) have been accomplished. When supported on IPG, both cationic FeP bind to the support via Fe-imidazole coordination. Fe[M(4-N-MePy)TDCPP]IPG contains a mixture of low-spin bis-coordinated (FeP)-P-III and high-spin mono-coordinated (FeP)-P-III species, whereas Fe[M(4-N-MePy)TFPP]IPG only contains high-spin mono-coordinated (FeP)-P-III. These FePIPG catalysts also contain (FeP)-P-II species, whose presence was confirmed by EPR spectroscopy using NO as a paramagnetic probe. Both cationic FePs coordinate to SG through Fe-O ligation and they are present as high-spin (FeP)-P-III species. The cationic FePs supported on SiSO3- are also high-spin (FeP)-P-III species and they bind to the support via electrostatic interaction between the 4-N-methylpyridyl groups and the SO3- groups present on the matrix. In homogeneous solution, both Fe[M(4-N-MePy)TDCPP]Cl-2 and Fe[M(4-N-MePy)TFPP]Cl-2 have similar catalytic activity to Fe(TDCPP)Cl and Fe(TFPP)Cl, leading to cis-epoxycyclooctane yields of 92%. When supported on inorganic matrices,both FePs lead to epoxide yields comparable to their homogeneous analogues and their anchoring enables catalyst recovery and re-use. Recycling of Fe[M(4-N-MePy)TDCPP]SiSO3- shows that this FeP maintains its activity in a second reaction. (C) 1999 Elsevier B.V. B.V. All rights reserved.

Use of a carbon paste electrode modified with spinel-type manganese oxide as a potentiometric sensor for lithium ions in flow injection analysis

A potentiometric sensor constructed from a mixture of 25% (m/m) spinel-type manganese oxide (lambda-MnO2), 50% (m/m) graphite powder and 25% (m/m) mineral oil is used for the determination of lithium ions in a flow injection analysis system. Experimental parameters, such as pH of the carrier solution, flow rate, injection sample volume, and selectivity for Li+ against other alkali and alkaline-earth ions and the response time of this sensor were investigated. The sensor response to lithium ions was linear in the concentration range 8.6 x 10(-5) - 1.0 x 10(-2) mol L-1 with a slope 78.9 +/- 0.3 mV dec(-1) over a wide pH range 7 - 10 (Tris buffer), without interference of other alkali and alkaline-earth metals. For a flow rate of 5.0 mL min(-1) and a injection sample volume of 408.6 muL, the relative standard deviation for repeated injections of a 5.0 x 10(-4) mol L-1 lithium ions was 0.3%.

Calcium bioavailability from the kale (Brassica-oleracea) consumed as a complement of a basal rice and bean diet

The bioavailability of calcium from the kale (Brassica oleracea var. acephala) consumed as a complement of a basal rice and bean diet was studied. Three groups of diets, two controls and one experimental were fed to Wistar female rats. The protein source of the first control was casein and of the second, a mixture of bean and rice. To both groups, graded levels of CaCO3 were added. The experimental diet was similar to the second control, except that CaCO3 was substituted for kale supplying the same amount of calcio. At 35 days of experimental period, they were killed and the calcium and phosphorus were determined in the right femur. The results indicated that the calcium from the kale is better utilized than that of the CaCO3. There was no significant difference in the concentration of calcium in the soft tissues studied among three dietary groups. Considering the high concentration and availability of calcium from the kale its consumption as a complement of the basal rice and bean diet may be recommended as a cheap and good source of this mineral.

Catalysis and temperature dependence on the formation of ZnO nanoparticles and of zinc acetate derivatives prepared by the sol-gel route

The chemical and structural nature of powders prepared from the zinc acetate-derived precursor using the sol-gel route is discussed. The influence of the synthesis temperature and of the hydrolytic catalyst on the structural features of the powder is focused on the basis of X-ray powder diffraction (XRPD) and extended X-ray absorption fine structure (EXAFS) measurements and complemented with density and thermoanalysis (TG-DTA) results. EXAFS and XRPD results show that no-washed nanoparticulate powders are composed of a mixture of ZnO (wurtzite), zinc acetate, and zinc hydroxyacetate. The latter has a layered structure typical of hydroxy double salts (HDS). The main component of no-washed powders is always unreacted zinc acetate solid but the relative amount of the zinc-based compounds depends on the nature of the hydrolytic catalyst, hydrolysis ratio, and of synthesis temperature. According to the proportion of the three zinc-based compounds, three families of powders could be distinguished. The amount of ZnO nanoparticles (1.6 +/- 0.6 nm) decreases as the synthesis temperature increases, as the hydrolysis ratio decreases, or by changing from basic to acid catalysis. This finding suggests that the formation of zinc compounds is controlled by the equilibrium between hydrolysis-condensation and complexation-reprecipitation reactions.

Sealing evaluation of the cervical base in intracoronal bleaching

Discoloration of non-vital teeth is an esthetic deficiency frequently requiring bleaching treatment. The purpose of this study was to evaluate in vitro the cervical base efficacy in order to prevent or to minimize the leakage along the root canal filling and into the dentinal tubules. Thirty-eight extracted single-root human teeth were used, which were biomechanically prepared, filled, and divided into three experimental groups: G1, a cervical base was applied (3 mm of thickness) below the cemento-enamel junction, with resin-modified glass-ionomer cement (Vitremer); G2, the base was done with glass-ionomer cement (Vidrion R); and G3 (Control), did not receive any material as base. A mixture of sodium perborate and hydrogen peroxide 30% was placed inside the pulp chamber for 3 days, and the access opening was sealed with Cimpat. This procedure was repeated thrice. Soon after this, a paste of calcium hydroxide was inserted into the pulp chamber for 14 days. All teeth were covered with two layers of sticky wax, except the access opening, and immersed in blue India Ink for 5 days. The results did not show statistically significant differences between the three groups concerning the leakage inside the dentinal tubules. Regarding the apical direction, a statistical difference (ANOVA P < 0.05) was observed among the experimental group G1 and control group G3. No statistically significant difference was observed between G2 and G3 groups. Therefore, the placement of a cervical base before internal bleaching procedures is still recommended.

Direct determination of arsenic in sugar by GFAAS with transversely heated graphite atomizer and longitudinal Zeeman-effect background correction

A method has been developed for the direct determination of As in sugar by graphite furnace atomic absorption spectrometry with a transversely heated graphite atomizer (end-capped THGA) and longitudinal Zeeman-effect background correction. The thermal behavior of As during the pyrolysis and atomization steps was investigated in sugar solutions containing 0.2% (v/v) HNO3 using Pd, Ni, and a mixture of Pd + Mg as the chemical modifiers. For a 60-muL sugar solution, an aliquot of 8% (m/v) in 0.2% (v/v)HNO3 was dispensed into a pre-heated graphite tube at 70 degreesC. Linear analytical curves were obtained in the 0.25 - 1.50-mug L-1 As range. Using 5 mug Pd and a first pyrolysis step at 600 degreesC assisted by air during 40 s, the formation of a large amount of carbonaceous residue inside the atomizer was avoided. The characteristic mass was calculated as 24 pg As and the lifetime of the graphite tube was around 280 firings. The limit of detection (L.O.D.) based on integrated absorbance was 0.08 mug L-1 (4.8 pg As) and the typical relative standard deviation (n = 12) was 7% for a sugar solution containing 0.5 mug L-1. Recoveries of As added to sugar samples varied from 86 to 98%. The accuracy was checked in the direct analysis of eight sugar samples. A paired t-test showed that the results were in agreement at the 95% confidence level with those obtained for acid-digested sugar samples by GFAAS.

Spectrophotometric determination of formaldehyde with chromotropic acid in phosphoric acid medium assisted by microwave oven

In the present study. a spectrophotometric method for the determination of formaldehyde by using chromotropic acid was devised. in which the use of potentially hazardous and corrosive concentrated sulfuric acid was eliminated and advantageously C replaced by a mixture of H, concentrated H3PO4 and H2O2. The reaction between formaldehyde and chromotropic acid (CA) in a cone phosphoric acid medium was accelerate by irradiating the mixture with microwave energy for 35 s (1100 W), producing a violetred compound (lambda(max)=570 nm). Beer's Law is obeyed in a concentration range of 0.8-4.8 mg 1(-1) of formaldehyde with a good correlation coefficient (r = 0.9968). The proposed method was applied in the analysis of formaldehyde in commercial disinfectants. Recoveries were within 98.0-100.4%, with standard deviations ranging from 0.03 to 0.13%. (C) 2003 Elsevier B.V All rights reserved.

An investigation of the thermal behavior of heterobimetallic species containing copper(II) and tetracyanopalladate(II)

Synthesis, characterization and thermal behavior of four compounds that have the general formula [Cu{Pd(CN)(4)}(L)(x)](n), in which en = 1,2-diaminoethane and pn = 1,3-diaminopropane (L = en, x = 1 (I); L = pn, x = 1 (II); L = en, x = 2 (III); L = pn, x = 2 (IV)) were described in this work. The complexes were studied by elemental analysis, infrared spectroscopy (IR), differential thermal analysis (DTA) and thermogravimetry (TG) and the residues of the thermal decomposition were characterized by X-ray powder diffraction and found as a mixture of CuO and PdO. The stoichiometry of the compounds was established via thermogravimetric and elemental analyses and their structures were proposed as coordination polymers based on their infrared spectra. The following thermal stability sequence was found: IV < I=II < III.

In situ UV-vis and EXAFS studies of ZnO quantum-sized nanocrystals and Zn-HDS formations from sol-gel route

We have pointed Out that. zinc-based particles obtained from zinc acetate sol-gel route is a mixture of quantum-sized ZnO nanoparticles, zinc acetate, and zinc hydroxide double salt (Zn-HDS). Aiming the knowledge of the mechanisms involved in the formation of ZnO and Zn-HDS phases, the thermohydrolysis of ethanolic zinc acetate solutions induced by lithium hydroxide ([LiOH]/[Zn2+] = 0.1) or water ([H2O]/[Zn2+] = 0.05) addition was investigated at different isothermal temperatures (40, 50, 60 and 70 degrees C) by in situ measurements of turbidity, UV-vis absorption spectra and extended X-ray absorption fine structures (EXAFS). Only the growth of ZnO nanoparticles was observed in sol prepared with LiOH, while a two-step process was observed in that prepared with water addition, leading the fast growth of Zn-HDS and the formation of ZnO nanoparticles at advanced stage. A mechanism of dissolution/reprecipitation governed by the water/ethanol proportion is proposed to account for relative amount of ZnO. (c) 2007 Elsevier Ltd. All rights reserved.

Preparation and characterization of spherical silica-porphyrin catalysts obtained by the sol-gel methodology

This work describes the synthesis of a first-generation iron porphyrin catalyst entrapped in a silica matrix by the sol-gel route, leading to spherical particles. The catalyst was synthesized by the method of Stober, through hydrolysis and condensation of the alkoxysilane TEOS in a mixture of alcohol, water and ammonia, in the presence of the iron porphyrin Fe(TPP)Cl. The relation between particle morphology and catalytic activity of the different Fe(TPP)-SiO2, obtained using different H2O/silane molar ratios and ammonia concentrations in the xerogel syntheses, was studied.The obtained catalysts were characterized by UV-vis spectroscopy, NMR Si-29. thermogravimetric analysis and transmission electron microscopy. Their ability to catalyze (Z)-cyclooctene epoxidation and cyclohexane oxidation was tested using iodosylbenzene as oxygen donor; the oxidation products were analyzed by gas chromatography and the catalysts obtained in a form of particles spherical and monodispersed showed to be a promising catalytic system for selective oxidation. (c) 2005 Elsevier B.V. All rights reserved.

Small angle X-ray scattering study of surface modified tin oxide nanoparticles prepared by sol-gel route

The surface properties of SnO2 nanoparticles were modified by grafting ionic (Tiron (R). (OH)(2)C6H2(SO3Na)(2)(H2O)-H-.) or non-ionic (Catechol (R). C6H4-1,2-(OH)(2)) capping Molecules during aqueous sol-gel processing to improve the redispersibility of powdered xerogel. The effect of the amount of grafted organic molecules on the redispersibility of powders in aqueous solution at several basic pH values was Studied. The nanostructural features of the colloidal suspensions were analyzed by small angle X-ray scattering (SAXS) measurements. Irrespective of the nature and amount of grafted molecules, complete redispersion was obtained in aqueous solution at pH = 13. The redispersion at pH = 11 results in a mixture of dispersed primary particles and aggregates. The proportion of well dispersed nanoparticles and aggregates (and their average size) can be tuned by the quantity of grafted ionic molecules.

Dynamical study of ZnO nanocrystal and Zn-HDS layered basic zinc acetate formation from sol-gel route

We have pointed out that zinc based particles obtained from ethanolic solution of a zinc acetate derivative (zinc oxy-acetate, Zn4O(Ac)(6)) are a mixture of nanometer sized ZnO, zinc oxy-acetate, and zinc hydroxide double salt (Zn-HDS). The knowledge of the mechanisms involved in the formation of ZnO and Zn-HDS phases, and the evolution of Zn species in reaction medium was monitored in situ during 14 h by simultaneous measurements of UV-vis absorption and extended X-ray absorption fine structures (EXAFS) spectra. This spectroscopic monitoring was initialized just after the addition of an ethanolic lithium hydroxide solution ([LiOH]/[Zn] = 0. 1) to the reaction medium kept under controlled temperature (40 degrees C). This study points out the first direct evidence of the reaction between ZnO nanoparticles and unreacted zinc oxy-acetate to form a Zn-HDS phase. The dissolution of ZnO and the reprecipitation of Zn-HDS are induced by the gradual release of water mainly produced by ethanol esterification well evidenced by gas chromatography coupled to mass spectroscopy and FT-IR measurements.

Integrated assessment of multilevel biomarker responses and chemical analysis in Mussels from Sao Sebastiao, São Paulo, Brazil

The aim of the present study was to investigate the presence of contaminants in the mussel Perna perna from Sao Sebastiao Channel, São Paulo, Brazil, and to evaluate the effects of these contaminants on these organisms at biochemical (catalase [CAT], glutathione-S-transferase [GST], and cholinesterase [ChE]), cellular (neutral red retention time [NRRT] assay), and physiological (cardiac monitoring) levels. Two sampling surveys were performed (winter of 2001 and summer of 2002) at six stations along the channel: Cigarras, station 1; late Clube de Ilhabela, station 2; Oil Terminal, station 3; Toque Toque, station 4; Ponta da Sela, station 5 (reference station); and Taubate, station 6. Differences in CAT activity were observed between mussels from stations 3 and 5 during the winter, but no differences were detected in the summer. No differences in GST activity were found among stations during the winter, although animals from station 3 showed higher activity during the summer. The ChE activity was significantly higher in the mussels from stations I and 2 during the winter and from stations I and 3 during the summer. Organisms from stations I through 4 showed statistically lower NRRT in both seasons. Similar heart rates were observed in the mussels from all stations. Hydrocarbons were detected in organisms from all the stations in both seasons. During the winter, higher polycyclic aromatic hydrocarbon (PAH) levels were observed in organisms from station 3, whereas during the summer, higher levels of metals were found in organisms from stations 1, 3, and 4. The multivariate analyses showed a strong influence of PAHs on the winter biological results, but metals showed higher influence on these responses in the summer, indicating multiple contaminant sources.