P. P. B. Santana

Effect of triiodothyronine on developmental competence of bovine oocytes

Developmental competence of in vitro-matured bovine oocytes is a limiting factor in production of embryos in vitro. Several studies have suggested a potential positive effect of thyroid hormones on cultured oocytes and/or their supporting cells. Therefore, the aim of the present study was to ascertain whether medium supplementation with triiodothyronine (T3) improved subsequent developmental competence of in vitro-matured bovine oocytes. For this purpose, we first documented (using reverse transcription PCR) that whereas bovine cumulus cells expressed both thyroid hormone receptor (TR)-α and TRβ, immature bovine oocytes expressed TRα only. Thereafter, to test the effects of TH on developmental competence, abattoir-derived oocytes were matured in vitro in a medium containing 0, 25, 50, or 100 nM T3 and subjected to in vitro fertilization. Embryo quality was evaluated by assessing cleavage and blastocyst rates, morphological quality, development kinetics, and total cell number on Day 8 of culture. Notably, addition of 50 or 100 nM T3 to the in vitro maturation medium increased (P < 0.05) the rate of hatched blastocysts on the eighth day of culture, as compared with other groups (62.4 ± 11.7, 53.1 ± 16.3, and 32.4 ± 5.3, respectively). Next, the relative expression levels of genes related to embryo quality POU-domain transcription factor (POU5F1) and glucose transporter-1 (GLUT 1) were compared between in vivo- and in vitro-produced blastocysts. On the basis of the previous experiments, IVP embryos originating from oocytes that were matured in vitro in the presence or absence of 50 nM T3 were evaluated. The treatment had no effect (P > 0.05) on gene expression. We concluded that supplementation of bovine oocyte in vitro maturation medium with T3 may have a beneficial effect on the kinetics of embryo development.

In vitro evaluation of the genotoxic and cytotoxic effects of artesunate, an antimalarial drug, in human lymphocytes

Artesunate is one of the main antimalarial drugs used in several countries. It is a semisynthetic compound derived from artemisinin, a substance extracted from the Chinese plant, Artemisia annua L. Despite the widespread use of artesunate as an antimalarial drug, there is a lack of data regarding its genotoxic effects in human lymphocytes. Therefore, in this study, we used the comet assay and micronucleus test to evaluate the possible genotoxic effects of artesunate in cultured human lymphocytes. In addition, cell death by necrosis and apoptosis was also assessed. Cells exposed to different concentrations of artesunate showed a significant concentration‐dependent increase (P < 0.05) in DNA damage index and micronuclei frequency. A significant increase in the frequency of apoptotic and necrotic cells was also observed. Our results showed that artesunate is a genotoxic and cytotoxic compound in cultured human lymphocytes. Environ. Mol. Mutagen., 2011.

Diversity and three-dimensional structures of the alpha Mcr of the methanogenic Archaea from the anoxic region of Tucuruí Lake, in Eastern Brazilian Amazonia

Methanogenic archaeans are organisms of considerable ecological and biotechnological interest that produce methane through a restricted metabolic pathway, which culminates in the reaction catalyzed by the Methyl-coenzyme M reductase (Mcr) enzyme, and results in the release of methane. Using a metagenomic approach, the gene of the α subunit of mcr (mcrα) was isolated from sediment sample from an anoxic zone, rich in decomposing organic material, obtained from the Tucuruí hydroelectric dam reservoir in eastern Brazilian Amazonia. The partial nucleotide sequences obtained were 83 to 95% similar to those available in databases, indicating a low diversity of archaeans in the reservoir. Two orders were identified - the Methanomicrobiales, and a unique Operational Taxonomic Unit (OTU) forming a clade with the Methanosarcinales according to low bootstrap values. Homology modeling was used to determine the three-dimensional (3D) structures, for this the partial nucleotide sequence of the mcrα were isolated and translated on their partial amino acid sequences. The 3D structures of the archaean Mcrα observed in the present study varied little, and presented approximately 70% identity in comparison with the Mcrα of Methanopyrus klanderi. The results demonstrated that the community of methanogenic archaeans of the anoxic C1 region of the Tucurui reservoir is relatively homogeneous.