Made available in DSpace on 2016-06-02T19:22:10Z (GMT). No. of bitstreams: 1 5474.pdf: 2975915 bytes, checksum: e9d30ed81c2e8431af179d83ebf62b96 (MD5) Previous issue date: 2013-05-10 / Universidade Federal de Sao Carlos / Lead acetate (Pb) is a nonessential and highly toxic heavy metal which is released to the environment by several routes, mainly by industrial and mining activities. Recent studies have suggested that lead caused a decrease in femur strength of adult rats. A wide range of chelating has been evaluated as possible protective agents against lead acetate toxicity. Dissodium ethylenediaminetetraacetate (Na2EDTA) is the chelating agent most widely used in the treatment of Pb poisoning. The chelating therapy with EDTA might induce Pb mobilization from inert deposition organs toward such critical tissues as the brain. But, it is questioned the safety of the use of this compound in the management of Pb poisoning. The lack of safety and efficacy demonstrated by conventional chelating has encouraged the search for new ways to remove heavy metals from the body. Recently, a supplementation of Chlorella vulgaris extract (CV) was shown to alleviate the heavy metals toxicity in rats. The aim of this study was to evaluate possible protective influence of Chlorella and Na2EDTA supplementation on bone physical and biomechanical properties of rats exposed to lead acetate. For this purpose, male Wistar rats were distributed into eight groups (n=8): Control (0.9% saline 0.1 ml/100g body weight- BW), EDTA (150 mg/Kg BW), CV 50 (50 mg/Kg BW), CV 250 (250 mg/Kg BW), Pb (250 mg/Kg BW), Pb (250 mg/Kg BW) plus EDTA (150 mg/Kg BW), Pb (250 mg/Kg BW) plus CV 50 (50 mg/Kg BW) and Pb (250 mg/Kg BW) plus CV 250 (250 mg/Kg BW). The treatment was done once a week, for 8 weeks by gastric gavage. Bone volume, bone mineral density (BMD) and biomechanical properties (maximum load, resilience and stiffness) of the femoral diaphysis and 5th lumbar vertebra were examined. The biomechanical properties of femurs were obtained by the three-points bending test and compression test for vertebrae, using a universal test machine Instron, model 4444. Bone MMP-2 activitie was measured by gelatin zymography. Concentrations of lead and zinc in whole blood and lead, zinc, calcium and magnesium in the left femur and 4th lumbar vertebra were determined by ICP-MS (Inductively Coupled Plasma Mass Spectrometry). Exposure to 250 mg/kg BW of Pb caused significant reduction of maximum load, stiffness and resilience indicating the ability of this element to damage the quality of bone tissue. In the 5th lumbar vertebrae, exposure to Pb caused significant reduction of bone mineral density. The treatment with Chlorella vulgaris (50 mg/kg BW and 250 mg/Kg BW) and EDTA (150 mg/Kg BW) during Pb exposure prevented the weakening of the bone strength. In the 5th lumbar vertebrae, the CV and EDTA prevented the reduction of bone mineral density due to Pb. The pro, intermediate and active MMP-2 activity in bone of animals exposed to lead showed a significant increase compared to control. The CV 50 administration in animals exposed to lead reduced the activity of MMP-2 isoforms in their pro, intermediate and active levels compared to control group. The exposure to Pb resulted in an increase of the blood concentration of this heavy metal and its accumulation in the liver, kidney, brain and bone concentration. The CV and EDTA reduced blood lead concentrations, leading to reduction of lead concentration in liver, kidney, brain and bone. These findings seem to indicate that treatment with Chlorella vulgaris and EDTA during exposure to Pb may be beneficial for the skeleton of subjects chronically exposed to Pb. / O chumbo, um metal não-essencial e altamente tóxico, é liberado no ambiente por diversas vias, principalmente através da atividade industrial e mineração. Estudos recentes sugerem que o acetato de chumbo causa redução da resistência óssea em ratos. Uma grande variedade de quelantes tem sido usada como possíveis agentes protetores contra a toxicidade provocada pelo acetato de chumbo. Etilenodiaminotetraacetato Cálcico Dissódico (EDTA) é o agente quelante mais usado no tratamento do envenenamento por chumbo. A terapia quelante com EDTA pode induzir redistribuição do chumbo endógeno e sua deposição em órgãos críticos, tal como o cérebro. Entretanto, é questionada a segurança do uso deste composto no tratamento do envenamento com chumbo. A falta de segurança e eficácia demonstrada pelos quelantes convencionais tem encorajado pesquisas por novas maneiras de remover metais tóxicos do organismo. Recentemente, uma suplementação com Extrato de Chlorella vulgaris (CV) mostrou aliviar a toxicidade de metais tóxicos em ratos. O objetivo deste estudo foi avaliar a possível influência protetora da suplementação com Chlorella e Na2EDTA sobre as propriedades físicas e biomecânicas ósseas de ratos expostos ao acetato de chumbo. Para este propósito, ratos Wistar foram distribuídos em oito grupos (=8): Controle (0,9% salina 0,1 ml/100g massa corporal - MC), EDTA (150 mg/Kg MC), CV 50 (50 mg/Kg MC), CV 250 (250 mg/Kg MC), Pb (250 mg/Kg MC), Pb (250 mg/Kg MC) mais EDTA (150 mg/Kg MC), Pb (250 mg/Kg MC) mais CV 50 (50 mg/Kg MC) e Pb (250 mg/Kg MC) mais CV 250 (250 mg/Kg MC). O tratamento foi realizado uma vez por semana, durante 8 semanas por gavagem gástrica. Volume ósseo, densidade mineral óssea (DMO) e densidade óssea (DO) e propriedades biomecânicas (força máxima, rigidez e resiliência) da diáfise femoral e das quintas vértebras lombares foram examinados. As propriedades biomecânicas dos fêmures foram obtidas pelo teste de flexão a três pontos e das vértebras pelo teste de compressão, usando uma máquina universal Instron 4444. A atividade de MMP-2 óssea foi mensurada por zimografia de gelatina. Foram também realizadas as análises das concentrações de Pb e Zn no sangue, fígado, rim, cérebro e ossos e das concentrações de Ca e Mg nos fêmures e vértebras determinadas por Espectometria de Emissão Atômica. A exposição ao Pb, na dose de 250 mg/Kg MC causou redução significativa da força máxima, rigidez e resiliência dos fêmures, indicando a habilidade deste elemento em prejudicar a qualidade do tecido ósseo. Nas vértebras, a exposição ao chumbo causou redução da densidade mineral óssea. O tratamento com Chlorella vulgaris (50 mg/kg MC e 250 mg/Kg MC) ou EDTA (150 mg/Kg MC) durante exposição ao chumbo, preveniu o enfraquecimento da resistência óssea dos fêmures. Na vértebra, o tratamento com Chlorella vulgaris (50 mg/kg MC e 250 mg/Kg MC) ou EDTA (150 mg/Kg MC) preveniu a redução da densidade mineral óssea. A atividade da MMP-2 pro, intermediária e ativa aumentaram nos ossos de animais expostos ao chumbo quando comparada ao controle. A administração de CV 50 aos animais expostos a este metal reduziu a atividade da MMP-2 nas suas isoformas pro, intermediária e ativa a níveis comparados ao controle. A exposição ao chumbo resulta em aumento da concentração de chumbo sanguínea e sua acumulação no fígado, rim, cérebro e ossos. O tratamento com CV ou EDTA reduziu as concentrações sanguíneas de chumbo, levando à redução da concentração de chumbo nos diversos órgãos estudados (fígado, rim, cérebro e ossos). Os resultados indicam que o tratamento com Chlorella vulgaris e EDTA durante a exposição ao chumbo pode ser benéfico ao osso de indivíduos expostos cronicamente ao acetato de chumbo.

<p>   </p> <p>Mechanical loading models are used to study adaptive skeletal mechanobiology mechanisms. However, most studies have used mammal models, leaving a knowledge gap regarding how these mechanisms differ among vertebrate groups. To address this gap, we evaluated the <em>in vivo</em> bone strain environment of the left tibia in green iguanas during locomotion, axial compressive loading, and with finite element analysis (FEA). Our study involved examining subadult green iguanas (n=7) over a range of speeds (0.4 - 1.3 m/s) and axial load magnitudes (-25 to -100 N) to determine peak strains. Bone strains were measured using single-element strain gauges (n=18) and rosette strain gauges (n=3), surgically attached to the tibial anterior, posterior, and medial surfaces. At a speed of 1.3 m/s, peak strains ± standard deviation observed were 645 ± 699 µε, -448 ± 464 µε, and 206 ± 168 µε at the anterior, posterior, and medial surfaces, respectively. Peak principal tensile and compressive strains on the medial surface were 199 ± 113 µε and -153 ± 98 µε at 1.3 m/s. During -100 N compressive loading, peak strains were 403 ± 277 µε, -506 ± 460 µε, and -52 ± 177 µε at the anterior, posterior, and medial surfaces, respectively. Our FEA model demonstrated a close correlation with experimentally measured strain values at the gauge sites (slope = 1.07, R2=0.7). Using these foundational <em>in vivo</em> strain results and a daily strain stimulus formula, our objective was to develop a novel noninvasive axial compressive tibial loading model to induce a cortical bone adaptive response in the green iguana tibia. However, following three weeks of daily applied compressive loading, no significant difference was detected in critical bone parameters at 37% and 50% (midshaft) volumes of interests from the proximal tibia (P<0.05).  While this study did not yield significant differences in critical bone parameters following the application of daily compressive loading, it provided new knowledge regarding the bone strain environment and the potential for inducing adaptive responses in the green iguana tibia. Further research may refine our understanding of skeletal mechanobiology mechanisms across vertebrate groups and develop more effective loading models for studying bone adaptation. Overall, the findings of this study contribute to the broader field of musculoskeletal mechanobiology, giving insights that may inform bone health and adaptation in diverse species, including humans. </p> <p>  </p>