Effect of Ca/P ratio and milling material on the mechanochemical preparation of hydroxyapaptite.

The mechanochemical transformation of Ca(OH)(2)-(NH(4))(2)HPO(4) with different Ca/P ratios 1; 1.5; 1.67 and 1.75 was carried out for different periods of time from 10 min to 24 h in a horizontal vibration mill using steel and agate vials and balls. The phase transformations obtained at each milling stage were characterized by X-ray diffraction, infrared spectroscopy and transmission electron microscopy. Complete transformation to hydroxyapatite took place during the first 5 h of milling, for Ca/P ratios 1.5 to 1.7, when milling was carried out with steel vials and balls. The contamination was not significant for the periods of milling studied for both milling media.

Simultaneous determination of nickel, iron, and copper in margarine by inductively coupled plasma-atomic emission spectroscopy after sample emulsification.

Nickel, iron, and copper were determined in margarine samples by using emulsification followed by inductively coupled plasma-atomic emission spectroscopy. Sample treatment and instrumental conditions were optimized, and the results were compared with those obtained by a pseudodigestion method in order to evaluate the compatibility of both methodologies. The optimum amount of margarine in the emulsion was 35% when the surfactant Tween 80 was added as the emulsifier. Copper was below the detection limits of both methodologies, i.e., digestion and emulsion; iron and nickel concentrations found by both methodologies were similar. The detection limits of the emulsion method were 0.002, 0.015, and 0.092 mg/kg for copper, iron, and nickel, respectively. A benefit of the emulsion method is that laborious and lengthy sample digestion procedures are avoided. In addition, accurate and precise results are obtained. Recoveries with the emulsion method ranged from 101 to 104%, with relative standard deviations of < or = 6%.

Blood pressure, magnesium and other mineral balance in two rat models of salt-sensitive, induced hypertension: effects of a non-peptide angiotensin II receptor type 1 antagonist.

The renin-angiotensin system is critically involved in regulating arterial blood pressure (BP). Inappropriate angiotensin type-1 receptor activation by angiotensin-II (Ang-II) is related to increased arterial BP. Mg has a role in BP; it can affect cardiac electrical activity, myocardial contractility, and vascular tone. To evaluate the relationship between high BP induced by a high sodium (Na) diet and Mg, and other mineral balances, two experimental rat models of salt-sensitive, induced-hypertension were used: Ang-II infused and Dahl salt-sensitive (SS) rats. We found that: 1) Ang-II infusion progressively increased BP, which was accompanied by hypomagnesuria and signs of secondary hyperaldosteronism; 2) an additive effect between Ang-II and a high Na load may have an effect on strontium (Sr), zinc (Zn) and copper (Cu) balances; 3) Dahl SS rats fed a high Na diet had a slow pressor response, accompanied by altered Mg, Na, potassium (K), and phosphate (P) balances; and 4) losartan prevented BP increases induced by Ang II-NaCl, but did not modify mineral balances. In Dahl SS rats, losartan attenuated high BP and ameliorated magnesemia, Na and K balances. Mg metabolism maybe considered a possible defect in this strain of rat that may contribute to hypertension.

Temporal distribution of heavy metal concentrations in oysters Crassostrea rhizophorae from the central Venezuelan coast.

The oyster Crassostrea rhizophorae is a bivalve abundant in Venezuelan estuaries and consumed by local populations. No known values have been reported on trace metals in oysters from the central Venezuelan coast. We report the concentrations of Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sr, V and Zn in the soft parts of C. rhizophorae, which were collected bimonthly between March 2008 and March 2009, at two sampling areas from the Central Venezuelan Coast: Buche estuary and Mochima estuary. Our results show that for each metal there is a similar temporal variation pattern. The concentrations of the heavy metals reported in this work are useful as reliable baselines and can be used for comparison in future environment studies. Concentrations in C. rhizophorae from the Buche estuary can be interpreted to be high on a global scale for Cd, Cu, Ni and Mn, indicating atypically raised bioavailabilities.

High levels of Mercury and Lead detected by hair analysis in two Venezuelan environments / Altos níveis de Mercúrio e Chumbo detectados pela análise de cabelo em dois ambientes venezuelanos

Mercury and Lead concentrations obtained by ICP-OAS analysis of human hair from riverside communities along the Orinoco river in the Amazon state (Venezuela) were compared with those from Caracas, Venezuela. Taking into account the characteristics of these two environments and the values of the average concentrations of Mercury and Lead, baselines were established suggesting that gold mining activity near the Orinoco river is responsible for the high levels of Mercury in hair from the Amazon state, whereas automobile activity is responsible for high levels of Lead in hair in Caracas.

Concentrações de mercúrio e chumbo obtidas pela análise ICP-OAS de amostras de cabelo humano de comunidades ribeirinhas ao longo do rio Orinoco no estado de Amazonas (Venezuela) foram comparadas com outras de Caracas, Venezuela. Levando em consideração as características desses dois ambientes e os valores das concentrações médias de mercúrio e chumbo, foram estabelecidas linhas basais que sugerem que as atividades de minério de ouro próximo ao rio Orinoco são responsáveis pelos altos conteúdos de mercúrio em cabelo no estado de Amazonas. Entretanto, a indústria automotriz é responsável pelo alto conteúdo de chumbo em cabelo em Caracas.