Contaminação por mercúrio na Odontologia: a utilidade da análise quantitativa em ambiente de prática restauradora com amálgama / Mercury contamination in Dentistry: the utility of quantitative analysis in environment with amalgam restorative practice

Objetivo - Verificar o uso e aplicação de um medidor portátil de análise quantitativa de vapores de mercúrio. Os locais de escolha foram a Clínica Odontológica e o Laboratório Multidisciplinar 104 da Faculdade de Odontologia das Faculdades São José, Rio de Janeiro-RJ, Brasil. Nesses locais ocorrem muitas atividades restauradoras com amálgama dentário realizadas por alunos, tornando-se importante a verificação da possível contaminação por vapores tóxicos de mercúrio existente naqueles ambientes. Métodos - Para a medição foi utilizado um aparelho analisador Zeeman quantitativo avançado de mercúrio portátil da marca Lumex modelo RA-915+. O aparelho foi acionado no final da tubulação de rejeito das cuspideiras das cadeiras A, C, D, E, F, J, H e ar do amalgamador recém-acionado. No Laboratório Multidisciplinar 104 foram inspecionados: ar/ambiente e em manequim usado para treino. Foram feitas também inspeções no ar em ambiente onde não se usa amálgama a fim de verificação do teor zero. Resultados - Na Clínica Odontológica as cadeiras C, E, F e H foram as que apresentaram os maiores índices de contaminação, dentre estas a cadeira H destacou-se com 26.140 ngHg/m³. Os locais onde não se manipula amálgama o índice foi 0ngHg/m³. Conclusões - Os altos índices de vapores de mercúrio nas tubulações das cadeiras indicam que as medidas seguras de descartes de resíduos não estão sendo realizadas adequadamente. Este sistema de medição quantitativa direta mostrou-se simples no manuseio e extremamente útil no monitoramento de ambientes sujeitos à contaminação por vapores tóxicos de mercúrio.

Objective - To examine the use and application of a portable meter for quantitative analysis of mercury vapors. The places of choice were the Dental Clinic and Laboratory Training 104 of the School of Dentistry of São José College, Rio de Janeiro-RJ, Brazil. In these places many activities occur restorative dental amalgam made by students, making it important to check the possible contamination by toxics vapors mercury existing in those environments. Methods - For the measurement we used an advanced device analyzer Zeeman quantitative mercury brand laptop Lumex model RA-915+. The device was fired at the end of the waste pipe spitting chairs A, C, D, E, F, J, H and air amalgamator newly activated. In the Laboratory Training 104 were inspected: air/environment and dummy used for training. Inspections were performed also on air at ambient where amalgam is not used to check content zero. Results - In Dental Clinic chairs C, E, F and H were the ones that showed the highest levels of contamination, among these the seat H stood out with 26.140 ngHg / m³. Places where no handles amalgam index was 0ngHg/m³. Conclusions - The high levels of mercury vapor in the pipes of the chairs indicate that measures of safe waste disposal are not being carried out properly. This direct quantitative measurement system proved simple in handling and extremely useful in monitoring environments subject to contamination by toxic mercury vapors.

Effect of mercury ion on the stability of the lipid-protein complex of isolated chloroplasts.

Mercury is known to interact with different parts of living systems causing serious biochemical and physiological disorder. In order to know the effect of mercury (Hg2+) ion on chloroplasts, the cell free organelle are incubated in an isotonic buffer medium in presence of mercury ion. The metal ion is found to induce membrane lipid peroxidation, loss of photosynthetic pigments and degradation of proteins. Such degradation brings about a drastic modification of lipid-protein organization of chloroplasts as reflected from a blue shift of absorption peaks and lowering of chlorophyll-a fluorescence intensity. The detrimental effect of Hg2+ ion has been explained in terms of direct binding with lipid-protein complex of photosynthetic membrane. Such a binding of metal ion exposes the lipid-protein complex for an easier entry and attack of reactive oxygen species (ROS) generated during incubation of chloroplasts in light and dark, thereby resulting in higher disorganization, which is evident from cation- induced changes in absorption and emission characteristics of the organelle.

Increase in NADH-glutamate dehydrogenase activity by mercury in excised bean leaf segments.

Application of Hg to excised bean leaf segments increased the glutamate dehydrogenase (NADH-GDH) activity substantially. However, specific activity of the enzyme decreased at lower concentration of Hg, and increased to lesser extent at higher concentration of Hg. Mercury supply increased the glutamate synthase (NADH-GOGAT) activity also. Mercury supply increased the NADH-GDH activity in the presence of NH4NO3, but to a lesser extent than in the absence of NH4NO3. The specific activity of the enzyme decreased considerably at lower concentration of Hg, but increased significantly at higher concentration of Hg. An increase in NADH-GOGAT activity was observed in the presence of NH4NO3, but specific activity of the enzyme decreased marginally. Increase in GDH activity due to Hg remained unaffected by the supply of sucrose, but was reduced by glutamine and glutathione and enhanced by Al. The glutamate dehydrogenase (+Hg enzyme) from mercury treated leaf segments had higher value of S0.5 for NADH than the enzyme (-Hg enzyme) from material not treated with mercury indicating that Hg binding to enzyme prevented NADH binding to the enzyme possibly at thiol groups. However, + Hg enzyme has more reactivity, as apparent Vmax value was higher for it. It has been suggested that Hg activates the NADH-GDH enzyme in the bean leaf segments by binding to thiol groups of protein and pronounced increase in activity by Hg suggests a possible role of enzyme under Hg-stress.

Mercury induced modifications in the stereochemistry of the active site through Cys-73 in a serine protease--crystal structure of the complex of a partially modified proteinase K with mercury at 1.8 A resolution.

Proteinese K (PK) isolated from Tritirachium album Limber was crystallized with HgCl2 in excess, under microgravity conditions. The intensity data were collected at 4 degrees C to 1.8 A resolution and the final R-factor after refinement for all the reflections was 0.164. Mercury has been found at two sites with partial occupancies (0.4 and 0.6) which are at distances of 2.48 A and 2.58 A respectively from Cys-73 Sgamma. The Cys-73 in the enzyme structure is located close to the active site residue, His-69. This region is completely buried and is not accessible to the solvent. It is rather tightly packed. Therefore, the binding of mercury distorts the stereochemistry of the neighbouring residues including those belonging to the catalytic triad. As a result of this, the Ogamma of Ser-224 is displaced by 0.6 A which causes the inactivation of proteinase K by increasing the H-bond distance to 3.7 A between Ser-224 Ogamma and His-69 Nepsilon2.

Effects of mercury on the arterial blood pressure of anesthetized rats

The available data suggests that hypotension caused by Hg2+ administration may be produced by a reduction of cardiac contractility or by cholinergic mechanisms. The hemodynamic effects of an intravenous injection of HgCl2 (5 mg/kg) were studied in anesthetized rats (N = 12) by monitoring left and right ventricular (LV and RV) systolic and diastolic pressures for 120 min. After HgCl2 administration the LV systolic pressure decreased only after 40 min (99 +or - 3.3 to 85 + or - 8.8 mmHg at 80 min). However, RV systolic pressure increased, initially slowly but faster after 30 min (25 + or - 1.8 to 42 + or - 1.6 mmHg at 80 min). Both right and left diastolic pressures increased after HgCl2 treatment, suggesting the development of diastolic ventricular dysfunction. Since HgCl2 could be increasing pulmonary vascular resistance, isolated lungs (N = 10) were perfused for 80 min with Krebs solution (continuous flow of 10 ml/min) containing or not 5 µM HgCl2. A continuous increase in pulmonary vascular resistance was observed, suggesting the direct effect of Hg2+ on the pulmonary vessels (12 + or - 0.4 to 29 + or - 3.2 mmHg at 30 min). To examine the interactions of Hg2+ and changes in cholinergic activity we analyzed the effects of acetylcholine (Ach) on mean arterial blood pressure (ABP) in anesthetized rats (N = 9) before and after Hg2+ treatment (5 mg/kg). Using the same amount and route used to study the hemodynamic effects we also examined the effects of Hg2+ administration on heart and plasma cholinesterase activity (N = 10). The in vivo hypotensive response to Ach (0.035 to 10.5 µg) was reduced after Hg2+ treatment. Cholinesterase activity (µM h-1 mg protein-1) increased in heart and plasma (32 and 65 percent, respectively) after Hg2+ treatment. In conclusion, the reduction in ABP produced by Hg2+ is not dependent on a putative increase in cholinergic activity. HgCl2 mainly affects cardiac function. The increased pulmonary vascular resistance and cardiac failure due to diastolic dysfunction of both ventricles are factors that might contribute to the reduction of cardiac output and the fall in arterial pressure

Resistência de enterobactérias, estafilococos, streptococus mutans e lactobacillus spp., isolados da cavidade bucal, e o uso de antimicrobianos, clorexidina e mercúrio nas práticas médica e odontológica / Resistance of enterobacteriaceae, staphylococcus, streptococcus mutans and lactobacillus spp., isolated from the oral cavity and the use of antimicrobials, chlorhexidine and mercury in medical and odontological practice

O objetivo dessa investigação foi realizar um estudo caso-controle do impacto do uso de antimicrobianos, clorexidina e mercúrio, na resistência dos microrganismos (enterobactérias, estafilococos, Streptococus mutans e Lactobacillus spp) presentes na cavidade bucal. Foram testados quatro grupos, com dez voluntários cada, a saber: A - com múltiplas restaurações à amálgama, B- em uso de antimicrobianos, C- em uso de digluconato de clorexidina a 0,12 por cento em bochechos diários e, D- sem história de cárie dentária (controle). A resistência foi determinada, in vitro, pelas técnicas de diluição em agar e E test. Uma colonização importante por enterobactérias (50 por cento) foi detectada no grupo em uso de antimicrobianos. Todos os isolados foram resistentes à clorexidina e cloreto de mercúrio, independente de grupo. A colonização por Staphylococcus aureus no grupo B também foi de 50 por cento, contra 30 por cento no grupo controle, onde os isolados desse microrganismo, e os Staphylococcus spp., mostraram-se resistentes à oxacilina (CIM s90 >512mg/L); esses microrganismos, independente do grupo, foram suscetíveis à clorexidina e resistentes ao cloreto de mercúrio, mas com CIM s para o mercúrio, três vezes mais elevadas para aquelas dos grupos com restaurações ou em uso de antimicrobianos. No grupo de voluntários em uso regular de clorexidina, os isolados de Streptococcus mutans do grupo B (8/10) apresentam CIM 90 > 512mg/L para ampicilina e suscetibilidade à clorexidina e mercúrio em todos os grupos de voluntários.

Respiratory responses and blood sugar level of the crab, Barytelphusa cunicularis (Westwood), exposed to mercury, copper and zinc.

Barytelphusa cunicularis (Westwood), a freshwater crab was exposed to mercuric chloride, copper sulphate and zinc sulphate from 0 to 12 hr and the oxygen consumption of the animal was measured in order to study the stress caused by these heavy metals. Normal oxygen consumption was affected by the three heavy metals. Similarly, crabs exposed to sublethal concentrations of the same pollutants for 24, 48, 72 and 96 hr showed an elevation in the blood sugar level with a maximum increase at 48 hr. The results indicate a switch towards glycolysis in order to overcome the anaerobic stress caused by the heavy metals.

A PMA degrading constitutive organomercurial lyase in a broad-spectrum mercury resistant Bacillus pasteurii strain DR2.

A broad-spectrum Hg-resistant strain of B. pasteurii DR2 utilized phenylmercuric acetate (PMA) as sole source of carbon. This bacterial strain contained a constitutive organomercurial lyase which specifically degraded PMA but not other organo-mercurials. This PMA-lyase activity was also stimulated to different extents when this bacterial strain was grown in presence of different organic compounds as sole source of carbon.

Alterations in plasma sodium and potassium levels following chronic oral ingestion of lead, mercury and cadmium in male albino rats.

Adult male albino rats were orally administered 0, 25, 50 and 100 ppm of lead nitrate, mercuric chloride and cadmium chloride for 60, 120 and 180 days. The plasma sodium levels were decreased in rats exposed to varying doses of lead and mercury up to 180 days, while animals which consumed cadmium chloride showed an increase in sodium levels. In lead and mercury treated animals, plasma potassium levels were increased up to 180 days. The levels were decreased in cadmium exposed rats. These observations suggest that chronic exposure to these heavy metals considerably influences plasma sodium and potassium levels depending on the dose and duration of exposure.

Heavy metal and disinfectant resistance in clinical isolates of gram-negative rods.

Ninety-five clinical strains of Gram-negative bacteria were examined for resistance to mercury, silver and disinfectants. 41% of the strains possessed resistance to mercury, 21% to silver and 7.3% of the strains were resistant to chlorhexidine. Mercury resistance was shown to be plasmid-mediated in 17 strains and silver resistance in 10 strains. Chlorhexidine resistance was not shown to be transferable.

Toxic effect of mercury on testes in different animal species.

Testicular changes following the administration of mercuric chloride, (HgCl2, ip in various dosages) over one month were studied in rats, mice, guinea pigs and hamsters. HgCl2 (5 mg/kg) caused a testicular degeneration and cellular deformation was observed in both the seminiferous tubules and the Leydig cells in all species: a significant decrease of testicular weight also resulted. There was no cellular deformation at the dose of 2 mg/kg: only spermatogenic inhibition and Leydig cell atrophy were observed in the animals. At the dose of 1 mg/kg, testicular degeneration was observed only in the hamster, only partial degeneration was recorded in the rat and the mouse and no change was noted in the guinea pig.