Zinc supplementation does not inhibit basal and metoclopramide-stimulated prolactinemia secretion in healthy men.

Dopamine (DA) and zinc (Zn++) share common mechanisms in their inhibition of prolactin (PRL) secretion. Both substances are present in the same brain areas, where Zn++ is released together with DA, suggesting a modulatory effect of Zn++ on dopaminergic receptors. The aim of the present study was to evaluate the effect of Zn++ supplementation on basal and PRL secretion stimulated by metoclopramide (MCP), a dopaminergic antagonist. Seven healthy men were evaluated in controlled study, where MCP (5 mg) was given intravenously, before and after 3 months of oral Zn++ (25 mg) administration. Our results indicate that chronic Zn++ administration does not change basal or MCP-stimulated plasma PRL secretion suggesting that, in humans, Zn++ does not interfere on PRL secretion mediated through dopaminergic receptors.

Iron derivatives from casein hydrolysates as a potential source in the treatment of iron deficiency.

The properties of an Fe(3+)-peptide complex containing 5.6% Fe, obtained by the reaction of ferric chloride with an enzymatic hydrolysate of casein, are described. The major site of iron binding corresponds primarily to the carboxylate groups and to a lesser extent to the peptide bonds. The Fe(3+)-peptide complex is insoluble at acid pH and completely soluble at neutral to alkaline pH. When soluble, the Fe(3+) is tightly bound to the complex peptide mixture but can be displaced and complexed by a low molecular weight ligand such as cysteine. Its efficacy in relation to iron sulfate was compared in rats. Both iron sources were administrated in Milli-Q water by gastric gavage to male Wistar rats (180-200 g) after an 18 h fast with water ad libitum. Fe(3+) from the Fe(3+)-peptide complex was transferred to the blood in a dose-dependent manner (1-8 mg of Fe/kg), and the serum iron levels were significantly higher (p < 0.001) than in a similar group of rats treated with iron sulfate. In the comparative kinetics experiments, the rats received 4 mg of Fe/kg. Both iron sources presented maximum absorption, as indicated by the elevation of serum iron levels, 30 min after administration, and the AUC(0)(-->2h) of the Fe(3+)-peptide complex was significantly higher (p < 0.05) than that observed with iron sulfate. The simultaneous administration of free peptides (0-192 mg) with the Fe(3+)-peptide complex or iron sulfate did not modify the extent of absorption of iron from both sources, suggesting that the absorption is due to the complex formed and probably not to exchange reactions in the gastrointestinal tract. In the hemoglobin repletion experiments carried out on newly weaned rats with anemia induced by a low-iron diet, supplementation of the diet with the the Fe(3+)-peptide complex was as efficient as supplementation with iron sulfate in the conversion from diet to hemoglobin iron. These results, taken together, suggest that the Fe(3+)-peptide complex is a potential compound for use as an iron source in biological situations.

Amálgama dental: estudo da emissao de vapor de mercúrio, efeito de tempo, brunidura e verniz / Dental amalgam: study of mercury emission, effect of time, burnishing and varnish

Os autores estudaram a emissao de vapor de mercúrio de amálgamas, convencional e com maior conteúdo de cobre com o objetivo de verificar os efeitos produzidos pela brunidura, pela aplicaçao de verniz e tempo. As dosagens de mercúrio foram realizadas, após a condensaçao do amálgama, com um espectrofotômetro de absorçao atômica, com câmara de captaçaode vapor de mercúrio. Nas condiçoes experimentais estudadas podemos afirmar que a emissao é mais intensa nos primeiros tempos com características de decrescer em funçao do tempo e se estabiliza a partir de 60 minutos. Os resultados obtidos mostram que a liga com maior conteúdo de cobre emite maior quantidade de vapor de mercúrio nos períodos iniciais quando comparada com os amálgamas obtidos das ligas convencionsis que tem médias semelhantes entre si. Os amálgamas apenas esculpidos emitem maior quantidade de mercúrio quando comparadas aqueles que foram brunidos com ou sem aplicaçao de verniz cavitário, ou com aqueles que foram apenas esculpidos, tendo sido condensados após a aplicaçao de verniz cavitário

Ligas alternativas à base de cobre: a importância de sua composiçäo e micro-estrutura / Alternatives copper alliage composition and structure importancy

Duas ligas comerciais à base de cobre e suas respectivas soldas foram analisadas com a finalidade de identificar seus elementos constituintes, quantificando-os sempre que possível. Comparou-se os resultados a outros citados na literatura e houve alguns casos de divergências na quantificaçäo e até na composiçäo das ligas. As ligas foram classificadas como latöes, com uma fase Beta: segundo os resultados da difraçäo de Raios X, o que é confirmado comparando os resultados com o diagrama de equilíbrio do sistema Cu/Ai