Aline Silva

17β-estradiol decreases methylmercury-induced neurotoxicity in male mice

There is increasing evidence that health effects of toxic metals, including methylmercury (MeHg), differ in prevalence or are manifested differently in men and women. The present study was aimed at investigating the potential differential susceptibility of male and female Swiss mice against MeHg-induced neurotoxicity, which was evaluated by biochemical (cerebellar oxidative stress-related parameters) and behavioral (locomotor activity and motor performance) variables. We also aimed to evaluate the potential protective effects of 17β-estradiol against such toxicity in MeHg-exposed male animals. MeHg exposure (40mg/L, diluted in tap water, during 2 weeks) decreased locomotor activity and motor performance in both male and female animals, but such phenomena were higher in males. 17β-estradiol co-treatment (10μg/animal, in alternate days) prevented MeHg-induced locomotor deficits in males. MeHg exposure caused a significant increase (60%) in cerebellar lipid peroxidation in male mice, but did not in females. In close agreement, MeHg exposure decreased (43%) cerebellar glutathione peroxidase activity in males, but did not in females. These events were prevented by 17β-estradiol administration. Cerebellar GR activity was increased (25%) in MeHg-exposed males and such event was partially prevented by 17β-estradiol administration. These results indicate that the low susceptibility of female mice to the neurotoxicity elicited by MeHg is linked to neuroprotective effects of sex steroids, which appear to modulate the activities of glutathione-related enzymes. Our experimental observation corroborates previous epidemiological studies showing the greater developmental effects in male than in female humans exposed to MeHg.

Synergistic neurotoxicity induced by methylmercury and quercetin in mice

Methylmercury (MeHg) is a highly neurotoxic pollutant, whose mechanisms of toxicity are related to its pro-oxidative properties. A previous report showed under in vivo conditions the neuroprotective effects of plants of the genus Polygala against MeHg-induced neurotoxicity. Moreover, the flavonoid quercetin, isolated from Polygala sabulosa, displayed beneficial effects against MeHg-induced oxidative damage under in vitro conditions. In this study, we sought for potential beneficial effects of quercetin against the neurotoxicity induced by MeHg in Swiss female mice. Animals were divided into six experimental groups: control, quercetin low dose (5 mg/kg), quercetin high dose (50 mg/kg), MeHg (40 mg/L, in tap water), MeHg+quercetin low dose, and MeHg+quercetin high dose. After the treatment (21 days), a significant motor deficit was observed in MeHg+quercetin groups. Biochemical parameters related to oxidative stress showed that the simultaneous treatment with quercetin and MeHg caused a higher cerebellar oxidative damage when compared to the individual exposures. MeHg plus quercetin elicited a higher cerebellar lipid peroxidation than MeHg or quercetin alone. The present results indicate that under in vivo conditions quercetin and MeHg cause additive pro-oxidative effects toward the mice cerebellum and that such phenomenon is associated with the observed motor deficit.

Study of Soft Magnetic Nickel-Iron Based Alloys Processed by Powder Injection Molding

Ni-Fe based soft-magnetic alloys, processed via Metal Injection Molding (MIM), were investigated regarding the influence of processing route on final magnetic properties and compared to fully dense cast materials. The process variations included high and low temperature debinding, different sintering routes and the application of hot isostatic pressing (HIP). The different densities resulting from the process variations were related to maximum magnetic permeability. Results have shown that density, in the range between 7,5g/cm³ and 8,0g/cm³, does not have significant influence on the maximum permeability, allowing cost-effective process routes. It was also verified that fullydense cast alloys still exhibits superior properties, with lower coercive fields and higher permeability, but results achieved after HIP process overcame even the values of these commercial grade alloys.

Magnetic Properties Obtained for Fe-50Co Alloy Produced by MIM with Elemental Powders

In order to obtain specific magnetic properties, it is of paramount importance to increase the alloy density of components fabricated by powder metallurgy. An alternative to increase the density of alloys such as Fe-49Co-2V would be the use of elemental Fe and Co instead of the prealloyed powder. Trying to give some insight on the industrial application of this strategy, this paper investigates the replacement of more conventional pre-alloyed Fe-49Co-2V powders with elemental Fe and Co. A previous analysis shows that it is possible to achieve higher densities using elemental Fe and Co powders sintered at the same temperature than Fe-49Co-2V. It is also shown that this leads to a noticeable improvement in some important magnetic properties such as permeability and magnetic induction.

Processing of the Fe3Si Alloy from Prealloyed Powder Fe45Si by Metal Injection Molding

The known process as Metal Injection Molding is derived from the conventional powder metallurgy (M/P) being an alternative for production of parts with complex geometry, great dimensional precision and freedom of chemical composition. The present work has the objective to evaluate the processing of the Fe3Si alloy sintering in the vacuum furnace using as raw materials iron powder carbonyl and prealloyed powder Fe45Si with D90<10-m. Properties of microhardness, density, coercivity, magnetic permeability, and chemical composition was evaluated. The obtained results were compared with what is presented in the literature for parts processed by conventional ways and with parts processed by M/P. A density of 7,620 kg/m3, a coercive field (Hc) of 101.14 A/m, a relative maximum permeability of 5,484 and a residual induction of 1.1 T was achieved by MIM. Comparing with conventional processes (where 100% of densification is reached), the MIM process results were worse, however they were better than P/M.

On the Use of Elemental Powders to Process Fe-50Co Alloys by Powder Injection Molding

Aiming to obtain components with higher density, this work evaluated the technical and economical viabilities to replace the pre-alloyed Fe49Co2V by an elemental powder alloy of iron and cobalt (Fe-50Co). Using an elemental alloy could increase the density of the final material due to the driving force created by the chemical gradient between the powders. The results showed that is possible to achieve higher densities in an elemental powder Fe-50Co alloy sinterized at the same temperature and in shorter times than the Fe49Co2V alloy. The analysis of economical viability showed that the replacement of the alloys have advantages as the pre-alloyed powder price is higher than the elemental.