Recovery of silver residues from dental amalgam

Dental amalgam residues are probably the most important chemical residues generated from clinical dental practice because of the presence of heavy metals among its constituents, mainly mercury and silver. OBJECTIVE: The purpose of this study was to develop an alternative method for the recovery of silver residues from dental amalgam. MATERIAL AND METHODS: The residue generated after vacuum distillation of dental amalgam for the separation of mercury was initially diluted with 32.5% HNO3, followed by precipitation with 20% NaCl. Sequentially, under constant heating and agitation with NaOH and sucrose, the sample was reduced to metallic silver. However, the processing time was too long, which turned this procedure not viable. In another sequence of experiments, the dilution was accomplished with concentrated HNO3 at 90ºC, followed by precipitation with 20% NaCl. After washing, the pellet was diluted with concentrated NH4OH, water and more NaCl in order to facilitate the reaction with the reducer. RESULTS: Ascorbic acid was efficiently used as reducer, allowing a fast reduction, thus making the procedure viable. CONCLUSIONS: The proposed methodology is of easy application and does not require sophisticated equipment or expensive reagents.FAPESPODONTOPRE

Proteomic analysis of gastrocnemius muscle in rats with streptozotocin-induced diabetes and chronically exposed to fluoride

Administration of high doses of fluoride (F) can alter glucose homeostasis and lead to insulin resistance (IR). This study determined the profile of protein expression in the gastrocnemius muscle of rats with streptozotocin- induced diabetes that were chronically exposed to F. Male Wistar rats (60 days old) were randomly distributed into two groups of 18 animals. In one group, diabetes was induced through the administration of streptozotocin. Each group (D-diabetic and ND-non-diabetic) was further divided into 3 subgroups each of which was exposed to a different F concentration via drinking water (0 ppm, 10 ppm or 50 ppm F, as NaF). After 22 days of treatment, the gastrocnemius muscle was collected and submitted to proteomic analysis (2D-PAGE followed by LC-MS/MS). Protein functions were classified by the GO biological process (ClueGO v2.0.7+Clupedia v1.0.8) and protein-protein interaction networks were constructed (PSICQUIC, Cytoscape). Quantitative intensity analysis of the proteomic data revealed differential expression of 75 spots for ND0 vs. D0, 76 for ND10 vs. D10, 58 spots for ND50 vs. D50, 52 spots for D0 vs. D10 and 38 spots for D0 vs. D50. The GO annotations with the most significant terms in the comparisons of ND0 vs. D0, ND10 vs. D10, ND50 vs. D50, D0 vs. D10 and D0 vs. D50, were muscle contraction, carbohydrate catabolic processes, generation of precursor metabolites and energy, NAD metabolic processes and gluconeogenesis, respectively. Analysis of subnetworks revealed that, in all comparisons, proteins with fold changes interacted with GLUT4. GLUT4 interacting proteins, such as MDH and the stress proteins HSPB8 and GRP78, exhibited decreased expression when D animals were exposed to F. The presence of the two stress proteins indicates an increase in IR, which might worsen diabetes. Future studies should evaluate whether diabetic animals treated with F have increased IR, as well as which molecular mechanisms are involved.Fil: Lima Leite, Aline. Universidade Federal do São Carlos; Brasil. Universidade de Sao Paulo; BrasilFil: Lobo, Janete Gualiume Vaz Madureira. Universidade de Sao Paulo; BrasilFil: Pereira, Heloísa Aparecida Barbosa Da Silva. Universidade Federal do São Carlos; BrasilFil: Fernandes, Mileni Silva. Universidade Federal do São Carlos; BrasilFil: Martini, Tatiani. Universidade de Sao Paulo; BrasilFil: Zucki, Fernanda. Universidade de Sao Paulo; BrasilFil: Hissako Sumida, Dóris. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Rigalli, Alfredo. Universidad Nacional de Rosario; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario; ArgentinaFil: Rabelo Buzalaf, Marilia Afonso. Universidade de Sao Paulo; Brasi

Liver proteome of mice with different genetic susceptibilities to the effects of fluoride

A/J and 129P3/J mice strains have been widely studied over the last few years because they respond quite differently to fluoride (F) exposure. 129P3/J mice are remarkably resistant to the development of dental fluorosis, despite excreting less F in urine and having higher circulating F levels. These two strains also present different characteristics regardless of F exposure. Objective In this study, we investigated the differential pattern of protein expression in the liver of these mice to provide insights on why they have different responses to F. Material and Methods Weanling male A/J and 129P3/J mice (n=10 from each strain) were pared and housed in metabolic cages with ad libitum access to low-F food and deionized water for 42 days. Liver proteome profiles were examined using nLC-MS/MS. Protein function was classified by GO biological process (Cluego v2.0.7 + Clupedia v1.0.8) and protein-protein interaction network was constructed (PSICQUIC, Cytoscape). Results Most proteins with fold change were increased in A/J mice. The functional category with the highest percentage of altered genes was oxidation-reduction process (20%). Subnetwork analysis revealed that proteins with fold change interacted with Disks large homolog 4 and Calcium-activated potassium channel subunit alpha-1. A/J mice had an increase in proteins related to energy flux and oxidative stress. Conclusion This could be a possible explanation for the high susceptibility of these mice to the effects of F, since the exposure also induces oxidative stress

Liver proteome of mice with different genetic susceptibilities to the effects of fluoride

ABSTRACT A/J and 129P3/J mice strains have been widely studied over the last few years because they respond quite differently to fluoride (F) exposure. 129P3/J mice are remarkably resistant to the development of dental fluorosis, despite excreting less F in urine and having higher circulating F levels. These two strains also present different characteristics regardless of F exposure. Objective In this study, we investigated the differential pattern of protein expression in the liver of these mice to provide insights on why they have different responses to F. Material and Methods Weanling male A/J and 129P3/J mice (n=10 from each strain) were pared and housed in metabolic cages with ad libitum access to low-F food and deionized water for 42 days. Liver proteome profiles were examined using nLC-MS/MS. Protein function was classified by GO biological process (Cluego v2.0.7 + Clupedia v1.0.8) and protein-protein interaction network was constructed (PSICQUIC, Cytoscape). Results Most proteins with fold change were increased in A/J mice. The functional category with the highest percentage of altered genes was oxidation-reduction process (20%). Subnetwork analysis revealed that proteins with fold change interacted with Disks large homolog 4 and Calcium-activated potassium channel subunit alpha-1. A/J mice had an increase in proteins related to energy flux and oxidative stress. Conclusion This could be a possible explanation for the high susceptibility of these mice to the effects of F, since the exposure also induces oxidative stress

Proteomic Analysis of Liver in Rats Chronically Exposed to Fluoride

<div><p>Fluoride (F) is a potent anti-cariogenic element, but when ingestion is excessive, systemic toxicity may be observed. This can occur as acute or chronic responses, depending on both the amount of F and the time of exposure. The present study identified the profile of protein expression possibly associated with F-induced chronic hepatotoxicity. Weanling male <i>Wistar</i> rats (three-weeks old) were divided into three groups and treated with drinking water containing 0, 5 or 50 mg/L F for 60 days (n=6/group). At this time point, serum and livers were collected for F analysis, which was done using the ion-sensitive electrode, after hexamethyldisiloxane-facilitated diffusion. Livers were also submitted to histological and proteomic analyses (2D-PAGE followed by LC-MS/MS). Western blotting was done for confirmation of the proteomic data A dose-response was observed in serum F levels. In the livers, F levels were significantly increased in the 50 mg/L F group compared to groups treated with 0 and 5 mg/L F. Liver morphometric analysis did not reveal alterations in the cellular structures and lipid droplets were present in all groups. Proteomic quantitative intensity analysis detected 33, 44, and 29 spots differentially expressed in the comparisons between control <i>vs.</i> 5 mg/L F, control <i>vs.</i> 50 mg/L F, and 5 mg/L <i>vs.</i> 50 mg/L F, respectively. From these, 92 proteins were successfully identified. In addition, 18, 1, and 5 protein spots were shown to be exclusive in control, 5, and 50 mg/L F, respectively. Most of proteins were related to metabolic process and pronounced alterations were seen for the high-F level group. In F-treated rats, changes in the apolipoprotein E (ApoE) and GRP-78 expression may account for the F-induced toxicity in the liver. This can contribute to understanding the molecular mechanisms underlying hepatoxicity induced by F, by indicating key-proteins that should be better addressed in future studies.</p> </div

Functional distribution of proteins identified with differential expression in the liver of rats chronically treated with F or not.

<p>Category of protein based on its primary biological function according to Rison et al. (2000).</p

Effect of chronic treatment with F on the expression of protein Apo-E in the liver of rats chronically treated with F or not.

<p>(A) Representative blotting of Apo-E (~36 kDa) and constitutive β-tubulin (~50 kDa) in samples of individual animals from each group (n=2 or 3). Samples are identified as indicated. Gels were performed in duplicate, each containing 3 different samples per respective group. (B) Densitometric analysis was done using mage J software. The average of arbitrary values obtained for control group (n=6) was considered 1 and the averages of the other groups (n=6) were calculated in respect to control. Distinct letters indicate statistical significance (p<0.05).</p

Photomicrographs of liver of rats showing macrovesicular lipid droplets (LD) in all groups.

<p>(A) control, (B) 5 mg/L F and (C) 50 mg/L F. In the left images, the regions bounded by the square are shown in greater increase in right images.</p

Simplified scheme of F-induced alterations in the expression of proteins related to energetic metabolism pathways in liver.

<p>F^- (fluoride ion); red arrows indicate increased expression and green arrows indicate decreased expression; P (phosphate); Fructose-bisP-AldoB (Fructose-bisphosphate aldolase B); L-PK (R-type isoform of piruvate kinase isozymes R/L); PDHE1-B (Pyruvate dehydrogenase E1 component subunit beta, mitochondrial); LDH-A (L-lactate dehydrogenase A chain); Mdh2 (Malate dehydrogenase); OAA (oxaloacetate); VLCAD (Very long-chain specific acyl-CoA dehydrogenase, mitochondrial); 3-Ketoacyl-CoA thiolase – m.(3-Ketoacyl-CoA thiolase, mitochondrial). </p