Organization and Regulation of Mitochondrial Protein Synthesis

Mitochondria are essential organelles of endosymbiotic origin that are responsible for oxidative phosphorylation within eukaryotic cells. Independent evolution between species has generated mitochondrial genomes that are extremely diverse, with the composition of the vestigial genome determining their translational requirements. Typically, translation within mitochondria is restricted to a few key subunits of the oxidative phosphorylation complexes that are synthesized by dedicated ribosomes (mitoribosomes). The dramatically rearranged mitochondrial genomes, the limited set of transcripts, and the need for the synthesized proteins to coassemble with nuclear-encoded subunits have had substantial consequences for the translation machinery. Recent high-resolution cryo-electron microscopy has revealed the effect of coevolution on the mitoribosome with the mitochondrial genome. In this review, we place the new structural information in the context of the molecular mechanisms of mitochondrial translation and focus on the novel ways protein synthesis is organized and regulated in mitochondria.</p

Electrophysiological and auditory behavioral evaluation of individuals with left temporal lobe epilepsy Avaliação eletrofisiológica e comportamental da audição em individuos com epilepsia em lobo temporal esquerdo

The purpose of this study was to determine the repercussions of left temporal lobe epilepsy (TLE) for subjects with left mesial temporal sclerosis (LMTS) in relation to the behavioral test-Dichotic Digits Test (DDT), event-related potential (P300), and to compare the two temporal lobes in terms of P300 latency and amplitude. We studied 12 subjects with LMTS and 12 control subjects without LMTS. Relationships between P300 latency and P300 amplitude at sites C3A1,C3A2,C4A1, and C4A2, together with DDT results, were studied in inter-and intra-group analyses. On the DDT, subjects with LMTS performed poorly in comparison to controls. This difference was statistically significant for both ears. The P300 was absent in 6 individuals with LMTS. Regarding P300 latency and amplitude, as a group, LMTS subjects presented trend toward greater P300 latency and lower P300 amplitude at all positions in relation to controls, difference being statistically significant for C3A1 and C4A2. However, it was not possible to determine laterality effect of P300 between affected and unaffected hemispheres.<br>O objetivo deste estudo foi determinar a repercussão da epilepsia de lobo temporal esquerdo (LTE) em indivíduos com esclerose mesial temporal esquerda (EMTE) em relação à avaliação auditiva comportamental-Teste Dicótico de Dígitos (TDD), ao Potencial Evocado Auditivo de Longa Latência (P300) e comparar o P300 do lobo temporal esquerdo e direito. Estudamos 12 indivíduos com EMTE (grupo estudo) e 12 indivíduos controle com desenvolvimento típico. Analisamos as relações entre a latência e amplitude do P300, obtidos nas posições C3A1,C3A2,C4A1 e C4A2 e os resultados obtidos no TDD. No TDD, o grupo estudo apresentou pior desempenho em relação ao grupo controle, sendo esta diferença estatisticamente significante em ambas as orelhas. Para o P300, observamos que em seis indivíduos com EMTE o potencial foi ausente. Para a latência e amplitude, verificamos que estes indivíduos apresentaram uma tendência ao aumento da latência e redução da amplitude para todas as posições em relação ao grupo controle, sendo estatisticamente significante em C3A1 e C4A2. Contudo, não foi possível determinar efeito de lateralidade do P300 entre o hemisfério afetado e não-afetado