Mitochondrial Redox Metabolism in Trypanosomatids Is Independent of Tryparedoxin Activity

Tryparedoxins (TXNs) are oxidoreductases unique to trypanosomatids (including Leishmania and Trypanosoma parasites) that transfer reducing equivalents from trypanothione, the major thiol in these organisms, to sulfur-dependent peroxidases and other dithiol proteins. The existence of a TXN within the mitochondrion of trypanosomatids, capable of driving crucial redox pathways, is considered a requisite for normal parasite metabolism. Here this concept is shown not to apply to Leishmania. First, removal of the Leishmania infantum mitochondrial TXN (LiTXN2) by gene-targeting, had no significant effect on parasite survival, even in the context of an animal infection. Second, evidence is presented that no other TXN is capable of replacing LiTXN2. In fact, although a candidate substitute for LiTXN2 (LiTXN3) was found in the genome of L. infantum, this was shown in biochemical assays to be poorly reduced by trypanothione and to be unable to reduce sulfur-containing peroxidases. Definitive conclusion that LiTXN3 cannot directly reduce proteins located within inner mitochondrial compartments was provided by analysis of its subcellular localization and membrane topology, which revealed that LiTXN3 is a tail-anchored (TA) mitochondrial outer membrane protein presenting, as characteristic of TA proteins, its N-terminal end (containing the redox-active domain) exposed to the cytosol. This manuscript further proposes the separation of trypanosomatid TXN sequences into two classes and this is supported by phylogenetic analysis: i) class I, encoding active TXNs, and ii) class II, coding for TA proteins unlikely to function as TXNs. Trypanosoma possess only two TXNs, one belonging to class I (which is cytosolic) and the other to class II. Thus, as demonstrated for Leishmania, the mitochondrial redox metabolism in Trypanosoma may also be independent of TXN activity. The major implication of these findings is that mitochondrial functions previously thought to depend on the provision of electrons by a TXN enzyme must proceed differently

The Beaker phenomenon and the genomic transformation of northwest Europe

From around 2750 to 2500 bc, Bell Beaker pottery became widespread across western and central Europe, before it disappeared between 2200 and 1800 bc. The forces that propelled its expansion are a matter of long-standing debate, and there is support for both cultural diffusion and migration having a role in this process. Here we present genome-wide data from 400 Neolithic, Copper Age and Bronze Age Europeans, including 226 individuals associated with Beaker-complex artefacts. We detected limited genetic affinity between Beaker-complex-associated individuals from Iberia and central Europe, and thus exclude migration as an important mechanism of spread between these two regions. However, migration had a key role in the further dissemination of the Beaker complex. We document this phenomenon most clearly in Britain, where the spread of the Beaker complex introduced high levels of steppe-related ancestry and was associated with the replacement of approximately 90% of Britain’s gene pool within a few hundred years, continuing the east-to-west expansion that had brought steppe-related ancestry into central and northern Europe over the previous centuries

Uma análise da influência da estocasticidade das informações sobre um modelo de programação linear

Neste trabalho foi discutido o impacto de perturbações estocásticas em um modelo de planejamento florestal. Foi desenvolvido um modelo de programação linear e uma abordagem, através de simulações estocásticas, para analisar e quantificar a variabilidade que ocorre nos valores da função objetivo, perante a natureza estocástica dos dados que alimentam o modelo. Um programa para efetuar tais simulações foi desenvolvido. O conceito de razão de variabilidade objeto-sistema foi introduzido para medir a suscetibilidade do sistema em relação às variações ocorridas no objeto.<br>The impact of stochastic perturbations in a forest planning model was discussed in this work. It was developed a linear programming and an approach, through stochastic simulations, to analyse and quantify the variability that occurs in the values of the objective function, because of the nature of the data that are used in the model. A program to do such simulations was developed. A new concept was introduced, called object-system ratio of variability, in order to measure the sensitivity of the response of the system when variations occur in the object

Uma proposta de solução para o problema da construção de escalas de motoristas e cobradores de ônibus por meio do algoritmo do matching de peso máximo A proposed solution for bus driver and fare collector scheduling problems using the maximum weight matching algorithm

O objetivo deste trabalho é mostrar a aplicação do Algoritmo do Matching de peso máximo, na elaboração de jornadas de trabalho para motoristas e cobradores de ônibus. Este problema deve ser resolvido levando-se em consideração o maior aproveitamento possível das tabelas de horários, com o objetivo de minimizar o número de funcionários, de horas extras e de horas ociosas. Desta forma, os custos das companhias de transporte público são minimizados. Na primeira fase do trabalho, supondo-se que as tabelas de horários já estejam divididas em escalas de curta e de longa duração, as escalas de curta duração são combinadas para a formação da jornada diária de trabalho de um funcionário. Esta combinação é feita com o Algoritmo do Matching de peso máximo, no qual as escalas são representadas por vértices de um grafo, e o peso máximo é atribuído às combinações de escalas que não formam horas extras e horas ociosas. Na segunda fase, uma jornada de final de semana é designada para cada jornada semanal de dias úteis. Por meio destas duas fases, as jornadas semanais de trabalho para motoristas e cobradores de ônibus podem ser construídas com custo mínimo. A terceira e última fase deste trabalho consiste na designação das jornadas semanais de trabalho para cada motorista e cobrador de ônibus, considerando-se suas preferências. O Algoritmo do Matching de peso máximo é utilizado para esta fase também. Este trabalho foi aplicado em três empresas de transporte público da cidade de Curitiba - PR, nas quais os algoritmos utilizados anteriormente eram heurísticos, baseados apenas na experiência do encarregado por esta tarefa.<br>The purpose of this paper is to discuss how the maximum weight Matching Algorithm can be applied to schedule the workdays of bus drivers and bus fare collectors. This scheduling should be based on the best possible use of timetables in order to minimize the number of employees, overtime and idle hours, thereby minimizing the operational costs of public transportation companies. In the first phase of this study, assuming that the timetables are already divided into long and short duration schedules, the short schedules can be combined to make up an employee's workday. This combination is done by the maximum weight Matching Algorithm, in which the scales are represented by vertices on a graph and the maximum weight is attributed to combinations of scales that do not lead to overtime or idle hours. In the second phase, a weekend schedule is assigned for every weekly work schedule. Based on these two phases, the weekly work schedules of bus drivers and bus fare collectors can be arranged at a minimal cost. The third and final phase of this study consisted of assigning a weekly work schedule to each bus driver and collector, considering his/her preferences. The maximum weight Matching Algorithm was also used in this phase. This method was applied in three public transportation companies in Curitiba, state of Paraná, which had until then used old heuristic algorithms based solely on managerial experience

Técnicas da pesquisa operacional no problema de horários de atendentes em centrais telefônicas Operations research techniques in the call center schedule problem

Este trabalho propõe uma solução para a elaboração e a designação de jornadas de trabalho em uma central telefônica de atendimento 24 horas. O trabalho foi desenvolvido em três fases: na primeira, determina-se o número de atendentes necessários a cada meia hora do dia por meio de um simulador da central telefônica, visando ao pronto atendimento ao cliente. Na segunda, é determinado o conjunto de jornadas de trabalho que atendem à demanda, minimizando os gastos da empresa com salários; para isso, foram utilizados os resultados da primeira fase e as jornadas disponíveis para, então, construir um modelo de Programação Inteira, o qual foi resolvido com o software LINDO. Finalmente, na terceira fase são designados os atendentes aos horários de acordo com suas preferências, utilizando o algoritmo do Matching de peso máximo. Os resultados encontrados foram analisados em termos de economia para a empresa, melhor atendimento ao usuário e satisfação dos atendentes.<br>This work deals with the call center attendants' assignment and schedule problem. It proposes a solution for a night and day continuous operation in a call center. The work is developed into three phases. Firstly, it was determined the number of necessary attendants for every 30 minutes in a day by simulating the arriving calls to the center, in order to satisfy the clients demand. Secondly, it was determined the set of journeys of work by solving an Integer Programming Model using the software LINDO, in order to satisfy the client demand minimizing the company's costs; the results obtained in the first phase and the available journeys by the company were used for it. Finally, in the third phase, the attendants are assigned to the work according with their preferences using the Maximum Weigh Matching Algorithm. The results obtained in this work were analyzed in terms of savings to the company, better clients' service and attendants' satisfaction

The level of ascorbate peroxidase is enhanced in benznidazole-resistant populations of Trypanosoma cruzi and its expression is modulated by stress generated by hydrogen peroxide

Ascorbate peroxidases (APX) are class I heme-containing enzymes that convert hydrogen peroxide into water molecules. The gene encoding APX has been characterized in 11 strains of Trypanosoma cruzi that are sensitive or resistant to benznidazole (BZ). Bioinformatic analysis revealed the presence of two complete copies of the T. cruzi APX (TcAPX) gene in the genome of the parasite, while karyotype analysis showed that the gene was present in the 2.000-kb chromosome of all of the strains analyzed. The sequence of TcAPX exhibited greater levels of similarity to those of orthologous enzymes from Leishmania spp than to APXs from the higher plant Arabidopsis thaliana. Northern blot and real-time reverse transcriptase polymerase chain reaction (RT-PCR) analyses revealed no significant differences in TcAPX mRNA levels between the T. cruzi strains analyzed. On the other hand, Western blots showed that the expression levels of TcAPX protein were, respectively, two and three-fold higher in T. cruzi populations with in vitro induced (17 LER) and in vivo selected (BZR) resistance to BZ, in comparison with their corresponding susceptible counterparts. Moreover, the two BZ-resistant populations exhibited higher tolerances to exogenous hydrogen peroxide than their susceptible counterparts and showed TcAPX levels that increased in a dose-dependent manner following exposure to 100 and 200 µM hydrogen peroxide