Can drug safety be predicted and animal experiments reduced by using isolated mitochondrial fractions?

Mitochondrial toxicity has resulted in the withdrawal of several drugs from the market. One particular example is nefazodone, an anti-depressant withdrawn in the USA due to hepatoxicity caused by drug-induced mitochondrial dysfunction. Drug development and safety testing can involve the use of large numbers of laboratory animals, which, without a decisive pre-screening for mitochondrial toxicity, are often unable to pre-empt higher mortality rates in some patient groups. The use of isolated mitochondria as a screening tool for drug safety can decrease the number of laboratory animals used in pre-clinical studies, thus improving animal welfare and healthcare outcomes and costs. Novel techniques involving high-throughput methods can be used to investigate whether a molecule is a mitochondrial toxicant. Moreover, these screens are mechanistically-based, since the effects of the drug on oxidative phosphorylation, calcium homeostasis and mitochondrial genetics can be assessed. This review is intended to demonstrate that isolated mitochondrial fractions are suitable for predicting drug and general chemical safety in toxicological screenings, thus contributing to the refinement and reduction of animal use in laboratory research

Psoriasis

Pretende-se nestas Recomendações Terapêuticas dar uma visão global dos conhecimentos actuais sobre a patogenia, clínica e tratamento da psoríase. A educação dos doentes deve incidir na evicção dos factores desencadeantes (medicamentos, trauma, álcool, infecções, stress) e enfa tizar a acção benéfica da exposição solar controlada na psoríase. A terapêutica tópica emolientes, queratolíticos, derivados do alcatrão, antralina, corticosteróides tópicos, calcipotriol — é essencial no controlo da psoríase vulgar em placas e é importante como adjuvante nos casos mais graves; chama-se a atenção para os graus de potência e para os potenciais efeitos indesejáveis da corticoterapia tópica. A radiação UV isolada (fototerapia) ou em associação a fotos sensibilizantes (fotoquimioterapia) está indicada nalgumas formas de psoríase (gutata, em placas, palmo-plantar) refractárias aos tópicos. A terapêutica sistémica — retinóides, metotrexato, ciclosporina está reservada para as formas mais graves, extensas e refractárias de psoríase, sendo indispensável na psoríase eritrodérmica, pustulosa ou artropática. A estratégia actual visa obter o melhor índice terapêutico e dá particular importância às terapêuticas combinadas e/ou rotativas. Para finalizar, incluem-se alguns fluxogramas, com o objectivo de ordenar os passos a dar na abordagem do doente com psorfase e salientar a validade científica das diferentes terapêuticas disponíveis

Modelling economic impacts of deficit irrigated maize in Brazil with consideration of different rainfall regimes

Deficit irrigation is often required to cope with droughts and limited water availability. However, to select an appropriate irrigation management, it is necessary to assess when economic impacts of deficit irrigation are acceptable. Thus, the main goal of this study was to evaluate economic water productivity for maize submitted to various levels of water deficits and different irrigation systems. The study was based on two different experiments conducted in Southern Brazil, one using sprinkler irrigation to supplement rainfall and the other using drip irrigation with precipitation excluded by a rainfall shelter to simulate cultivation under dry conditions. Water productivity indicators were calculated referring to: a) actual field collected data, including yields, commodity prices and production costs; and b) a sensitivity analysis to commodity prices and production costs. Alternative centrepivot irrigation scenarios were also developed to assess their feasibility in terms of water use and productivity when irrigation is used to supplement rainfall or when rainfall is scarce. Results show that the feasibility of deficit irrigation is highly influenced by commodity prices and by the irrigation (and water) costs when the irrigation costs are a large part of the production costs. Results also show that deficit irrigation applied when rainfall is abundant is easier to implement than deficit irrigation where rainfall is very scarce, when only a mild stress is economically viable. For well-designed and managed centrepivot systems, results confirm that adopting deficit irrigation when rainfall is scarce is less attractive than under conditions of irrigation to supplement rainfall. It could be concluded that farmers are unlikely to choose a deficit irrigation strategy unless they are facing reduced water availability for irrigatio

Towards a molecular mechanism underlying mitochondrial protein import through the TOM and TIM23 complexes

Nearly all mitochondrial proteins need to be targeted for import from the cytosol. For the majority, the first port of call is the translocase of the outer membrane (TOM complex), followed by a procession of alternative molecular machines, conducting transport to their final destination. The pre-sequence translocase of the inner membrane (TIM23-complex) imports proteins with cleavable pre-sequences. Progress in understanding these transport mechanisms has been hampered by the poor sensitivity and time resolution of import assays. However, with the development of an assay based on split NanoLuc luciferase, we can now explore this process in greater detail. Here, we apply this new methodology to understand how ∆ψ and ATP hydrolysis, the two main driving forces for import into the matrix, contribute to the transport of pre-sequence-containing precursors (PCPs) with varying properties. Notably, we found that two major rate-limiting steps define PCP import time: passage of PCP across the outer membrane and initiation of inner membrane transport by the pre-sequence – the rates of which are influenced by PCP size and net charge. The apparent distinction between transport through the two membranes (passage through TOM is substantially complete before PCP-TIM engagement) is in contrast with the current view that import occurs through TOM and TIM in a single continuous step. Our results also indicate that PCPs spend very little time in the TIM23 channel – presumably rapid success or failure of import is critical for maintenance of mitochondrial fitness

Interplay between Mitochondrial Protein Import and Respiratory Complexes Assembly in Neuronal Health and Degeneration.

The fact that >99% of mitochondrial proteins are encoded by the nuclear genome and synthesised in the cytosol renders the process of mitochondrial protein import fundamental for normal organelle physiology. In addition to this, the nuclear genome comprises most of the proteins required for respiratory complex assembly and function. This means that without fully functional protein import, mitochondrial respiration will be defective, and the major cellular ATP source depleted. When mitochondrial protein import is impaired, a number of stress response pathways are activated in order to overcome the dysfunction and restore mitochondrial and cellular proteostasis. However, prolonged impaired mitochondrial protein import and subsequent defective respiratory chain function contributes to a number of diseases including primary mitochondrial diseases and neurodegeneration. This review focuses on how the processes of mitochondrial protein translocation and respiratory complex assembly and function are interlinked, how they are regulated, and their importance in health and disease

Additive techniques to refurbish Ni based components

The attractiveness of additive techniques to refurbish worn components requires the availability of data from different process. This study correlates two additive techniques, Plasma Transferred Arc (PTA – AM) and Direct Laser Deposition (DLD), using IN 625 wire. Specific features of each technique are discussed regarding their potential use to recover geometry and properties of worn components. Multilayers were processed with each technique on a section of a blade and the interaction between materials together with the effect of post deposition heat treatment were characterized. Results show that there are differences in the final microstructure and in the interaction with the part being refurbished imposed by the additive technique used. Competitive changes can be made by changing the feedstock. PTA-AM using powder material exhibits a microstructure that approaches that obtained in DLD using wire

Influência do efeito de exposições ambientais no comportamento pós-fissurado de um BAC reforçado com fibras de aço

Neste trabalho apresentam-se os principais resultados do estudo da influência de certo tipo de exposições ambientais no comportamento pós-fissurado de betão auto-compactável reforçado com fibras de aço, BACRFA. Para o devido efeito foram produzidos diversos provetes prismáticos de BACRFA. Inicialmente os provetes foram sujeitos a ensaios cíclicos de flexão em três pontos, com o objetivo de se induzir dois níveis de pré-fissuração distintos, respetivamente, com uma abertura de fenda de 0.3 e 1.0 mm. Posteriormente, os provetes pré-fissurados foram submetidos a três tipos de exposição ambiental durante um período de dezoito meses. Por fim caracterizou-se o desempenho mecânico dos provetes após exposição ambiental

Essential role of the czc determinant for cadmium, cobalt and zinc resistance in Gluconacetobacter diazotrophicus PAl 5

The mechanisms of cadmium, cobalt and zinc resistance were characterized in the plant-growth-promoting bacterium Gluconacetobacter diazotrophicus PAl 5. The resistance level of the wild-type strain was evaluated through the establishment of minimum inhibitory concentrations (MIC) of the soluble compounds CdCl2·H2O, CoCl2·6H2O and ZnCl2. Gluconacetobacter diazotrophicus PAl 5 was resistant to high concentrations of Cd, Co and Zn, with MICs of 1.2, 20 and 20 mM, respectively. Screening of an insertion library from transposon EZ-Tn5<R6Kyori/KAN-2> in the presence of ZnO revealed that the mutant GDP30H3 was unable to grow in the presence of the compound. This mutant was also highly sensitive to CdCl2·H2O, CoCl2·6H2O and ZnCl2. Molecular characterization established that the mutation affected the czcA gene, which encodes a protein involved in metal efflux. In silico analysis showed that czcA is a component of the czcCBARS operon together with four other genes. This work provides evidence of the high tolerance of G. diazotrophicus PAl 5 to heavy metalsand that czc is a determinant for metal resistance in this bacterium. [Int Microbiol 2012; 15(2):69-78

The protist Trichomonas vaginalis harbors multiple lineages of transcriptionally active Mutator-like elements

<p>Abstract</p> <p>Background</p> <p>For three decades the <it>Mutator </it>system was thought to be exclusive of plants, until the first homolog representatives were characterized in fungi and in early-diverging amoebas earlier in this decade.</p> <p>Results</p> <p>Here, we describe and characterize four families of <it>Mutator</it>-like elements in a new eukaryotic group, the Parabasalids. These <b><it>T</it></b><it>richomonas </it><b><it>v</it></b><it>aginalis </it><it><b>Mu</b>tator- <b>l</b>ike </it><it><b>e</b>lements</it>, or <it>TvMULEs</it>, are active in <it>T. vaginalis </it>and patchily distributed among 12 trichomonad species and isolates. Despite their relatively distinctive amino acid composition, the inclusion of the repeats <it>TvMULE1</it>, <it>TvMULE2</it>, <it>TvMULE3 </it>and <it>TvMULE4 </it>into the <it>Mutator </it>superfamily is justified by sequence, structural and phylogenetic analyses. In addition, we identified three new <it>TvMULE</it>-related sequences in the genome sequence of <it>Candida albicans</it>. While <it>TvMULE1 </it>is a member of the <it>MuDR </it>clade, predominantly from plants, the other three <it>TvMULEs</it>, together with the <it>C. albicans </it>elements, represent a new and quite distinct <it>Mutator </it>lineage, which we named <it>TvCaMULEs</it>. The finding of <it>TvMULE1 </it>sequence inserted into other putative repeat suggests the occurrence a novel TE family not yet described.</p> <p>Conclusion</p> <p>These findings expand the taxonomic distribution and the range of functional motif of <it>MULEs </it>among eukaryotes. The characterization of the dynamics of <it>TvMULEs </it>and other transposons in this organism is of particular interest because it is atypical for an asexual species to have such an extreme level of TE activity; this genetic landscape makes an interesting case study for causes and consequences of such activity. Finally, the extreme repetitiveness of the <it>T. vaginalis </it>genome and the remarkable degree of sequence identity within its repeat families highlights this species as an ideal system to characterize new transposable elements.</p