Attempts to identify Cassava Brown Streak Virus in western Democratic Republic of Congo

Open Access ArticleRoot necrosis similar to those of the cassava brown streak disease (CBSD) were observed on cassava in western provinces of the Democratic Republic of Congo (DR.Congo) in the early 2000’s. However molecular laboratory diagnosis were not able to detect any causative agent responsible for the attacks, hence, the disease related to these symptoms was named CBSD-like disease. In order to assess the distribution and the incidence of the CBSD-like disease, surveys were carried out in four western provinces, comprising, Kwango and Kwilu, Sud Ubangi, Kinshasa and Kongo Central. CBSD-like disease was observed in all surveyed provinces on the basis of root symptoms because foliar symptoms were different to those of the documented cases of CBSD in other parts of east Africa. CBSD-like disease incidence was high in Kongo Central and Sud Ubangi, exceeding an average of 50 %, but low in Kwango and Kwilu (32.8%) and in Kinshasa (19.1%). During the surveys, cassava leaf samples were collected for lab identification of the causal agent. PCR diagnosis was done on these samples using primers specific for the two known CBSVs. All samples tested negative with no amplification of DNA fragments of the correct size. Thus, further analysis on the causative organism is needed using Next Generation Sequencing (NGS) approaches. NGS approaches will help also to identify the causative organism in other Central Africa countries (Angola, Congo-Brazzaville and Gabon) where such cassava root necrosis have been reported or are suspected

Synthesis of Mycobacterial Ergothioneine biosynthetic pathway metabolites

Many gram positive bacteria, such as Mycobacterium tuberculosis, lack the redox protective molecule, glutathione and produce mycothiol (MSH) and ergothioneine (ESH) as their principal low molecular mass thiol instead. Ergothioneine has been known for a while as an anti-oxidant; however its role as a protective thiol in Mycobacterium tuberculosis is still undefined. Present knowledge indicates that ergothioneine may play a critical role in the in vivo and in vitro survival of Mycobacteria, hence enzymes involved in ESH synthesis can be considered as potential drug targets. Ergothioneine is synthesized by the sequential action of five enzymes, encoded by the genes egtA, egtB, egtC, egtD and egtE. Three of these enzymes implicated in the ergothioneine synthesis have been expressed and purified. The last step catalyzed by EgtE, a pyridoxal 5-phosphate (PLP)-dependent β-lyase convert the S-(β-amino-β-carboxyethyl) ergothioneine sulfoxide to ergothioneine. This thesis describes the synthesis of ESH pathway enzyme substrates, with the main focus on the synthesis of the EgtE enzyme substrate, ESH biosynthetic precursor, R- and S-(β-amino-β-carboxyethyl) ergothioneine sulfoxide. In order to prove that synthesized compounds are indeed mycobacterium ESH pathway enzyme substrates, crude M. smeg cell free lysate enzyme was used to convert substrates to ESH. Enzymatic transformation was followed by LCMS analysis. One of two synthetic routes studied, required sufficient quantities of ESH and were therefore thoroughly reviewed. An improved synthetic procedure for ESH was obtained. Deuterated hercynine and ESH was prepared, which will serve as a valuable internal standards and probes for ergothioneine metabolic studies. Enantioselective sulfoxidation of EgtE enzyme substrate precursor, hercynyl cysteine sulfide gave the required hercynyl cysteine sulfoxide derivative and in same cases the hercynyl cysteine sulfone. Crude enzyme mediated transformation of substrates indicated that the hercynyl cysteine sulfide undergoes efficient conversion to ESH

The Effects of IMF\u27s Lending and Conditionalities on Economic Growth: Case of SADC Countries

I examine the impact of IMF credit use and its conditions on economic growth performance in 12 South African countries over a period of 1999-2019. The work adopts an empirical and quantitative approach to analyzing the relationship between the GDP per Capita, the use of IMF Credit, Government Final Consumption Expenditure, Net Domestic Credit and Current Account balance. These variables are the most recommended in the IMF conditionalities during the lending arrangements with SADC members. The study uses Fixed-effect approach to evaluate how the use of IMF program and the conditions imposed directly affects economic growth. A dummy variable is included to evaluate GDP growth if a country met or not the imposed condition. The result from the analyses concludes that overall, the use of IMF credit has no statistical significance on the economic growth. But when some conditions are met, the GDP responds positively. Other variables current account, government expenditure, and net domestic shows significant and positive change on the GDP growth of SADC countries

Synthesis of thiohistidines and its metabolic pathway precursors

Natural thiohistidines such as ergothioneine and ovothiols are biosynthesized by actinomycetes, fungi and many parasitic protozoa, respectively. Actinomycetes such as Mycobacterium tuberculosis produce mycothiol and ergothioneine as their principal low molecular mass thiols. It is only very recently that the link between ergothioneine and tuberculosis disease has started to emerge, these studies suggested that ergothioneine is essential for the survival of Mycobacterium tuberculosis, the causal agent of tuberculosis. The biosynthesis of ergothioneine involved five enzymes encoded by the genes egtA, egtB, egtC, egtD and egtE. Because of the essentiality of these enzymes, in particular EgtD, could be considered as a potential tuberculosis drug target. Ergothioneine is a newly discovered vitamin and is widely used in cosmetics as an antioxidant, whereas ovothiol biosynthesis has received interest for the synthetic design of potential trypanosomal drugs. However, the commercial availability of these thiohistidines is limited, mainly due to multiple challenges associated to their synthesis or isolation from natural sources. This study describes the improved total synthesis of the super-antioxidant, ergothioneine and all its biosynthetic pathway intermediates, including deuterated versions thereof. A simple, short and high yielding novel process of the synthesis of ergothioneine was developed. Additionally, enzymatic methods were also considered for the desulfurisation step. The C-S lyase experiments mediated by Mycobacterium smegmatis cell-free lysate provided small scale transformations by the C-S lyase, EgtE, acting on its substrate, hercynylcysteine sulfoxide. Overoxidation of the latter substrate provided a sulfone that inhibited ergothioneine biosynthesis. While hercynylcysteine sulfoxide is known to be the substrate in Neurospora crassa, the EgtC enzyme in mycobacteria prefer γ-glutamyl hercynylcysteinesulfoxide as its precursor to ergothioneine. Hence, the need for sufficient quantity of this important metabolite has motivated the development of the first total synthesis of EgtC enzyme substrate, γ-glutamylhercynylcysteine sulfoxide. Finally, interesting synthetic challenges toward the synthesis of the most powerful natural related ovothiol, completes this study

Bridging the digital divide in African post-conflict countries : a case study of the DRC cities of Kinshasa and Kananga

Includes bibliographical references (leaves 34-37).The digital divide is largely seen as the main problem that developing economies and societies must overcome to gain economic productivity and social welfare. In this document we state that modern western perception of the digital divide lured advancement of lCT into developing countries especially in Africa. lCT must not be seen as a goal in itself but as a means to service human needs. This study attempts to analyze the willingness of people to adopt existing lCT infrastructures and the factors impeding its use in the DRC's cities of Kinshasa and Kananga

Fungos agaricoides de Portugal Continental. Situação atual e novas perspetivas

O conhecimento da diversidade micológica de Portugal Continental ainda é incompleto e fragmentado, não permitindo definir áreas de distribuição, nem estatutos de conservação para as diferentes espécies. Após uma listagem preliminar, publicada em 2002, não foi efetuada até à presente data nenhuma atualização dessa listagem. Contudo, esta situação não se verifica por falta de informação mais atual, pois o conhecimento sobre a diversidade de fungos agaricoides tem aumentado nas últimas décadas, bem como a profusão de bases de dados digitais reconhecidas internacionalmente. Porém, a atualização dos registos de fungos agaricoides é uma tarefa exigente a vários níveis: disponibilidade, acessibilidade e acima de tudo, o recrutamento de recursos humanos especializados. O presente trabalho pretende contribuir para o conhecimento da diversidade dos fungos agaricoides e a sua distribuição regional ao nível das antigas províncias de Portugal Continental, através da compilação de dados e análise da informação recolhida em duas fontes acreditadas; Agaricoid fungi of Continental Portugal. Current Situation and New Perspectives. Abstract: The information about the mycological diversity of Portugal still fragmented and incomplete, and it is not possible to define distribution areas, nor conservation statutes for various species. After a preliminary listing, published in 2002, no update has been made. This circumstance do not drift from the lack of information, since in the last decades the information about the agaricoid fungi diversity has increased, as well as the profusion of internationally recognized digital databases. However, updating the records of agaricoid fungi is a demanding task at several levels: availability, accessibility and, above all, the recruitment of specialized human resources. The present work aims to contribute to the knowledge of Portugal agaricoid fungi diversity and its regional distribution, at old province level, through the data compilation and analysis, assembled from two recognized sources

Impacto do anúncio de pagamento de dividendos no preço das ações: estudo comparativo do sector financeiro entre a África do Sul e Nigéria

O presente estudo tem como foco a análise do impacto do anúncio do pagamento de dividendos sobre o preço das ações do sector financeiro de dois dos maiores mercados financeiros de África nomeadamente, Nigéria e África do Sul. Para o efeito, são abordadas teorias financeiras relacionadas com a hipótese de eficiência dos mercados e teorias relacionadas com a política de dividendos que representam a componente bibliográfica do trabalho. A componente empírica é baseada na metodologia de estudos de eventos (MacKinlay 1997). Foram estudadas empresas do setor financeiro cotadas nas duas bolsas enunciadas, e que anunciaram o pagamento de dividendos durante o período de janeiro 2014 a janeiro 2017. Com vista a avaliar a hipótese de eficiência dos mercados na sua forma semiforte foram analisadas as rentabilidades posteriores ao anúncio de pagamento de dividendos com intuito de verificar se sofrem alterações significativas face as rentabilidades esperadas. De forma global em ambos os mercados os resultados apontam para existência de rentabilidades médias anormais estatisticamente não significantes; Abstract: Impact of dividend payment announcement on stock prices: Nigerian and South African financial sector comparative study. The present study focuses on the analysis of the influence of the announcement of dividend payments on the financial sector stock price of two of Africa's largest financial markets, namely, Nigeria and South Africa. the hypothesis of market efficiency and the dividend policy that represent the bibliographic component of the work. The empirical component is based on the event study methodology (MacKinlay 1997). Financial sector companies listed on the two listed exchanges, which announced the payment of dividends during the period from January 2014 to January 2017, will be studied. In order to evaluate the hypothesis of market efficiency in its semi-strong form, post-announcement returns will be analyzed. payment of dividends and to verify whether they undergo significant changes in relation to expected returns. Overall in both markets the results point to the existence of statistically non-significant abnormal returns

Rhodium-Catalyzed Asymmetric Intramolecular Hydroamination of Unactivated Alkenes

One for the Rh(oad): The first rhodium-catalyzed asymmetric intramolecular hydroamination of unactivated olefins was developed by using dialkylbiaryl phosphine ligands (see scheme; cod=1,5-cyclooctadiene, Cy=cyclohexyl). A variety of 2-methylpyrrolidines have been synthesized with high enantioselectivities.National Institutes of Health (U.S.) (Grant GM46059)Merck & Co.Boehringer Ingelheim PharmaceuticalsNational Institutes of Health (U.S.) (GM 1S10RR13886-01