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%.

Effect of hypoxia on the calcium and magnesium content, lipid peroxidation level, and Ca²âº-ATPase activity of syncytiotrophoblast plasma membranes from placental explants.

In the current study the possible relationship between the Ca(2+)/Mg(2+) ratio of human syncytiotrophoblast plasma membranes and their lipid peroxidation and Ca(2+)-ATPase activity was determined. Syncytiotrophoblast plasma membranes of placental explants cultured under hypoxia increased their lipid peroxidation and Ca(2+) content, diminished their Ca(2+)-ATPase activity, and kept their Mg(2+) content unchanged. Membranes preincubated with different concentrations of Ca(2+) increased their Ca(2+) content without changes in their Mg(2+) content. There is a direct relationship between Ca(2+) content and lipid peroxidation of the membranes, as well as an inverse relationship between their Ca(2+) content and Ca(2+)-ATPase activity. On the contrary, preincubation of membranes with different concentrations of Mg(2+) showed a higher Mg(2+) content without changing their lipid peroxidation and Ca(2+)-ATPase activity. Explants cultured under hypoxia in the presence of 4 mM MgSO4 showed similar values of lipid peroxidation and Ca(2+)-ATPase activity of their membranes compared to those of explants cultured under normoxia. Increased Ca(2+) content of the membranes by interacting with negatively charged phospholipids could result in destabilizing effects of the membrane structure, exposing hydrocarbon chains of fatty acids to the action of free radicals. Mg(2+) might exert a stabilizing effect of the membranes, avoiding their exposure to free radicals.

Lead exposure in day care centres in the Caracas Valley--Venezuela.

Lead has been used as an additive to improve the anti-knock quality of gasoline. However, the combustion of lead gasoline produces particles rich in this element. These kinds of particles impact the alveoli and move into the bloodstream, causing serious health problems. The objective of this study is to determine the granulometric distribution, mineralogy, and lead levels in samples such as settled dust and soil, as well as lead concentration in drinking water, in different day care centers located in the metropolitan area of Caracas, which have been previously studied and classified, according to the Total Suspended Particles (TSP) levels by the national environmental office, as high (80 microg m(-3)) and low (50 microg m(-3)) polluted areas. The chemical analysis was performed by atomic absorption spectroscopy and atomic emission spectroscopy-inductively coupled plasma. The mineralogy was determined using X-ray differentiation. Results show that all samples are enriched by small particles (<44 microm). Lead concentrations in day care centres located in areas of high vehicular density were higher than those in areas of low vehicular traffic. Lead concentration for drinking water samples was below the standard value reported by the Environmental Protection Agency (EPA) (15 microg Pb/l).

Hipozinquemia en la anemia drepanocitica: efecto de la suplementación con zinc / Hypozinquemia in the anemia sickle cell: effect of the zinc supplementation

El Zinc es un elemento traza esencial, componente de diversas enzimas importantes, entre ellas las que participan en la síntesis de ADN y ARN y de la forma activa de la hormaona tímica. Su deficiencia se acompaña de atrofia tímica, linfopenia, disminución de niveles de hormona tímica e inmunodepresión. Debido a competencia por los sitios de unión a las proteinas de transporte, existe una relación inversa entre los niveles séricos de zinc y cobre. Los pacientes con anemia depranocitica presentan hipozinquemia asociada asociada a hipercupremia. Niveles bajos de zinc también se observan en sus eritrocitos y neutrófilos. El déficit de zinc puedecontribuir al aumento de la susceptibilidad a las infecciones que se observa en los pacientes con hemoglobinopatía SS, así como al retardo de su crecimiento y signos de deficiencia gonodal. La suplementación con zinc ha probado ser beneficiosa en individuos con hemoglobinopatía SS, ya que promueve el desarrollo pondoestatural y puberal, aumenta la filterabilidad de los glóbulos rojos y disminuye el porcentaje de depranocitos irreversibles reduciendo el riesgo de vasooclusión y los signos de hemólisis. El zinc, prevendría la polimerización de la hemoglobina S al aumentar su afinidad por el O2 y disminuiría el número de drepanocitos irreversibles al reducir la formación de tactoides, pero especialmente por su antagonismo con el Ca y su acción expansora de la membrana del glóbulo rojo. Esto permitiría un mejor control del flujo de iones, evitando la pérdida de K+ el ingreso excesivo de Na+ y Ca2+, la deshidratación de los glóbulos rojos y el aumento en la concentración de hemoglobina intracorpuscular

Análisis de azúcares por HPLC en mieles venezolanas / Sugar analyses by HPLC in venezuelan honey

El análisis de azúcares es un parámetro de calidad en el control de calidad de las mieles. En las normas nacionales para miél de abejas (COVENIN 2136-84 y COVENIN 2191-84) se seleccionaron métodos volumétricos y gravimétricos para determinar azúcares reductores y sacarosa; sin embargo, el análisis de azúcares por HPLC ofrece otras posibilidades para el estudio de las mieles. En el presente trabajo se analizaron 41 muestras de mieles comerciales procedentes de distintas regiones de Venezuela. Se empleó una columna ubondapack/Carbohydrate y un detector de índice de refracción para determinar el contenido de fructosa, glucosa, sacarosa y también la presencia de melecitosa. Las mieles genuinas presentaron rangos de 27-53 por ciento para la fructosa, 25-45 por ciento para la glucosa y 0,5-5 por ciento para la sacarosa, mientras que en las mieles fraudulentas los rangos de variación de esos azúcares fueron de 17-34 por ciento, 23-37 por ciento y 12-39 por ciento, respectivamente