Elaboration de complexes hétérobinucléaires par approche chimie Click pour une application en imagerie bimodale

L'imagerie biomédicale s'est beaucoup développée au XXème siècle, avec les techniques comme l'IRM, la scintigraphie ou l'imagerie optique. Des améliorations de ces techniques ont conduit au principe de multimodalité : combiner en une analyse unique plusieurs modalités, afin de tirer avantage des points forts de chacune et d'en limiter les lacunes. Suivant cette approche, des agents de contraste multimodaux sont actuellement développés. Dans cette optique, nous avons synthétisé et évalué des complexes hétérobimétalliques pouvant répondre à différentes combinaisons d'imagerie bimodale, grâce à la chimie Click. La première structure est une optimisation de précédents travaux : elle se compose d'un complexe de Re(I)-pyridine-triazole pyta bidente, sur lequel est greffée une pince iminodiacétate tridente complexant le 99mTc(I). Les études photophysiques ont montré de bonnes propriétés optiques. Les stabilités, ainsi que les premiers résultats de cytotoxicité et de pénétration cellulaire, ont révélé une potentielle application en tant que sonde bimodale fluorescence/scintigraphie. Dans la deuxième famille de structures, un dérivé du cyclène, le DO3A, est lié à un motif pyta ou son équivalent tétrazole pytz, pour complexer resp. un ion Ln(III) et un Re(I). Les motifs pyta et pytz servent aussi de chromophore pour sensibiliser les ions Ln(III) luminescents. La synthèse des complexes monométalliques à base de lanthanides (Eu et Tb) a été réalisée et les évaluations photophysiques ont révélé d'excellentes propriétés optiques. Dans un second temps, les premiers essais de complexation de Re(I) ont montré la possibilité d'obtenir les complexes hétérobinucléaires souhaités.Biomedical imaging has been successfully developed during the last century, with efficient technics as MRI, nuclear or optical imaging. Constant improvements lead to "multimodality", i.e. combining different imaging modalities to add strengths and limit weaknesses of each one. Following this new philosophy, multimodal contrast agents have been developed. We aimed to prepare new bimodal ones: we synthesized new heterobimetallic complexes thanks to Click chemistry reactions, and evaluated their properties as bimodal probes. The first structure is an optimization of our previous work: a Re(I)-pyridine-triazole (Re-pyta) is bound to an iminodiacetate, which chelates radioactive 99mTc(I). This heterobimetallic complex has shown good photophysical properties and an excellent stability in biological media. This results and the first biological studies, cytotoxicity and cellular uptake, are compatible with a potential application as a fluorescent/nuclear probes. After a bioconjugation of this compound, in vivo studies should be the next step of the validation of such a probe. The second structure type contains a DO3A pattern linked to a pyta moiety or a tetrazole equivalent, pytz, to resp. chelate a Ln(III) ion and a Re(I) ion. Pyta and pytz moieties are used as Ln-sensitizers. We synthesized Ln monometallic complexes (Ln = Eu, Tb): they revealed excellent photophysical properties. Then, through the complexation of a second ion, Re(I), we showed it is possible to get the wanted heterobinuclear complexes

Radiation and soil temperature interactions on the growth and physiology of eastern white pine (Pinus strobus L.) seedlings

A greenhouse experiment was set up during one growing season to test the hypothesis that soil temperature controls a significant part of the light response of eastern white pine (Pinus strobus L.) seedlings that is observed in the field. The experimental design was a three by three factorial split-plot design, with three levels of light availability: 10%, 40% and 80% of full light; and three levels of soil temperature: 16 °C, 21 °C, and 26 °C in the soil at midday. The results show significant interactions between light and soil temperature factors on several variables (gas exchange, root growth, leaf-mass ratio and leaf–mass per unit area), but not on shoot dry mass. These interactions indicate that, in the field, a significant proportion of the light response of young eastern white pine could result from changes in soil temperature, especially under conditions of limiting water availability. Our results suggest that soil temperature must be taken explicitly into account as a driving variable when relating the growth of young eastern white pine to photosynthetic radiation

Ternary Rhenium(I) Complexes: from Fluorescent Reporters to Interesting Scaffolds for Dual-Imaging Heterobimetallic Probes

Five ternary tricarbonylrhenium(I) complexes based on a pyridinetriazole moiety, so called pyta, were synthesized and spectroscopically characterized. The photophysical properties of these cationic complexes of general formula, [Re(CO)3(pyta-COOMe)L] (L = substituted pyridine derivatives) have been investigated, as well. Three of them are fluorescent and could be considered as interesting scaffolds for the preparation of dual-imaging heterobimetallic species

Різнолігандні комплекси ренію(i): від флуоресцентних міток до гетеробіметалічних зон- дів з цікавою топологією для подвійної візуалізації

In this paper, five new ternary tricarbonylrhenium(I) complexes based on a pyridinetriazole moiety, the so-called pyta, have been investigated. These cationic complexes of the general formula [Re(CO)3(pyta-COOMe)L] (L = substituted pyridine derivatives) combine a carboxylate functionalization, for further biomolecule conjugation, with a metal chelating site – a pyta-based tricarbonylrhenium moiety – which can act as a fluorescent reporter. The complexes have been prepared using a two-steps pathway involved the activation of [Re(CO)3Cl(bipy)] with triflate silver salts in the presence of acetonitrile followed by the thermally activated substitution of the acetonitrile adduct by commercially available substituted pyridine derivatives. They have been prepared from modest to good yields, fully characterized by means of NMR, IR and mass spectrometry, and their photophysical properties have been investigated. Upon excitation into the MLCT band of each complex (absorption band at ca. 300 nm), three of them exhibit a bright green luminescence centered at c.a. 494 nm, with a quantum yield of 0.60% in acetonitrile. These interesting photophysical features make them potential fluorescent cellular imaging agents. Moreover, thank to their ancillary ligand, they could be also considered as interesting scaffolds for the preparation of dual-imaging heterobimetallic species.В данной работе представлены результаты исследований пяти новых разнолигандных трис-карбонильных комплексов рения(I) на основе пиридинтриазольных производных, так называемых pyta. Такие катионные комплексы общей формулы [Re(CO)3(pyta-COOMe)L] (L = производные пиридина) сочетают в себе карбоксилатную функциональную группу для дальнейшего биомолекулярного связывания с хелатированным металлсодержащим фрагментом – на основе pyta-трискарбонильных комплексных частиц, которые могут выступать в качестве флуоресцентного центра. Комплексы были получены двухстадийной реакцией, основанной на активации [Re(CO)3Cl(bipy)] трифлатом серебра в присутствии ацетонитрила с дальнейшим взаимодействием термически активированного ацетонитрильного аддукта с коммерчески доступными замещенными пиридинпроизводными. Координационные соединения были получены с разными выходами, исследованы методами ЯМР-, ИК- и масс-спектроскопии и изучены их фотофизические свойства. При использовании длины волны возбуждения, соответствующей центру полосы переноса заряда металл-лиганд (MLCT) для каждого комплекса (полоса поглощения ~ 300 нм), три из них проявляют ярко-зеленую люминесценцию в ацетонитриле с центром ~ 494 нм и квантовым выходом 0,60%. Такие фотофизические особенности делают их потенциальными флуоресцентными биовизуализирующими агентами. Кроме того, благодаря дополнительным лигандам они могут быть использованы как основа для получения гетеробиметаллических частиц для двойственной визуализации.В даній публікації представлені результати досліджень п’яти нових різнолігандних трис-карбонільних комплексів ренію(I) на основі піридинтриазольних похідних, так званих pyta. Такі катіонні комплекси загальної формули [Re(CO)3(pyta-COOMe)L] (L = похідні піридину) поєднують карбоксилатну функціональну групу, яка може бути використана для подальшого біомолекулярного зв’язування з хелатованим металовмісним фрагментом на основі pyta-трис-карбонільних комплексних часточок, які можуть виступати в якості флуоресцентного центру. Комплекси були отримані двостадійною реакцією, заснованою на активації [Re(CO)3Cl(bipy)] трифлатом срібла в присутності ацетонітрилу з подальшою взаємодією термічно активованого ацетонітрильного аддукту з комерційно доступними заміщеними піридинпохідними. Координаційні сполуки були отримані з різними виходами, охарактеризовані методами ЯМР-, ІЧ- та мас-спектроскопії і досліджені їх фотофізичні властивості. При використанні довжини хвилі збудження, яка відповідає центру смуги переносу заряду метал-ліганд (MLCT) для кожного комплексу (смуга поглинання ~300 нм), три з них виявляють яскраво-червону люмінесценцію в ацетонітрилі з центром ~494 нм та квантовим виходом 0,60%. Такі фотофізичні особливості роблять їх потенційними флуоресцентними біовізуалізуючими агентами. До того ж, завдяки додатковим лігандам вони можуть бути використані як основа для створення гетеробіметалічних часточок для подвійної візуалізації

Managing Understory Vegetation for Maintaining Productivity in Black Spruce Forests: A Synthesis within a Multi-Scale Research Model

Sustainable management of boreal ecosystems involves the establishment of vigorous tree regeneration after harvest. However, two groups of understory plants influence regeneration success in eastern boreal Canada. Ericaceous shrubs are recognized to rapidly dominate susceptible boreal sites after harvest. Such dominance reduces recruitment and causes stagnant conifer growth, lasting decades on some sites. Additionally, peat accumulation due to Sphagnum growth after harvest forces the roots of regenerating conifers out of the relatively nutrient rich and warm mineral soil into the relatively nutrient poor and cool organic layer, with drastic effects on growth. Shifts from once productive black spruce forests to ericaceous heaths or paludified forests affect forest productivity and biodiversity. Under natural disturbance dynamics, fires severe enough to substantially reduce the organic layer thickness and affect ground cover species are required to establish a productive regeneration layer on such sites. We succinctly review how understory vegetation influences black spruce ecosystem dynamics in eastern boreal Canada, and present a multi-scale research model to understand, limit the loss and restore productive and diverse ecosystems in this region. Our model integrates knowledge of plant-level mechanisms in the development of silvicultural tools to sustain productivity. Fundamental knowledge is integrated at stand, landscape, regional and provincial levels to understand the distribution and dynamics of ericaceous shrubs and paludification processes and to support tactical and strategic forest management. The model can be adapted and applied to other natural resource management problems, in other biomes

Safety of meglumine gadoterate (Gd-DOTA)-enhanced MRI compared to unenhanced MRI in patients with chronic kidney disease (RESCUE study)

OBJECTIVE: To prospectively compare the renal safety of meglumine gadoterate (Gd-DOTA)-enhanced magnetic resonance imaging (MRI) to a control group (unenhanced MRI) in high-risk patients. METHODS: Patients with chronic kidney disease (CKD) scheduled for MRI procedures were screened. The primary endpoint was the percentage of patients with an elevation of serum creatinine levels, measured 72 ± 24 h after the MRI procedure, by at least 25 % or 44.2 μmol/l (0.5 mg/dl) from baseline. A non-inferiority margin of the between-group difference was set at −15 % for statistical analysis of the primary endpoint. Main secondary endpoints were the variation in serum creatinine and eGFR values between baseline and 72 ± 24 h after MRI and the percentage of patients with a decrease in eGFR of at least 25 % from baseline. Patients were screened for signs of nephrogenic systemic fibrosis (NSF) at 3-month follow-up. RESULTS: Among the 114 evaluable patients, one (1.4 %) in the Gd-DOTA-MRI group and none in the control group met the criteria of the primary endpoint [Δ = −1.4 %, 95%CI = (−7.9 %; 6.7 %)]. Non-inferiority was therefore demonstrated (P = 0.001). No clinically significant differences were observed between groups for the secondary endpoints. No serious safety events (including NSF) were noted. CONCLUSION: Meglumine gadoterate did not affect renal function and was a safe contrast agent in patients with CKD. KEY POINTS: • Contrast-induced nephropathy (CIN) is a potential problem following gadolinium administration for MRI. • Meglumine gadoterate (Gd-DOTA) appears safe, even in patients with chronic kidney disease. • Gd-DOTA only caused a temporary creatinine level increase in 1/70 such patients. • No case or sign of NSF was detected at 3-month follow-up

Population-level emergence of bedaquiline and clofazimine resistance-associated variants among patients with drug-resistant tuberculosis in southern Africa: a phenotypic and phylogenetic analysis.

BACKGROUND: Bedaquiline and clofazimine are important drugs in the treatment of drug-resistant tuberculosis and are commonly used across southern Africa, although drug susceptibility testing is not routinely performed. In this study, we did a genotypic and phenotypic analysis of drug-resistant Mycobacterium tuberculosis isolates from cohort studies in hospitals in KwaZulu-Natal, South Africa, to identify resistance-associated variants (RAVs) and assess the extent of clofazimine and bedaquiline cross-resistance. We also used a comprehensive dataset of whole-genome sequences to investigate the phylogenetic and geographical distribution of bedaquiline and clofazimine RAVs in southern Africa. METHODS: In this study, we included M tuberculosis isolates reported from the PRAXIS study of patients with drug-resistant tuberculosis treated with bedaquiline (King Dinuzulu Hospital, Durban) and three other cohort studies of drug-resistant tuberculosis in other KwaZulu-Natal hospitals, and sequential isolates from six persistently culture-positive patients with extensively drug-resistant tuberculosis at the KwaZulu-Natal provincial referral laboratory. Samples were collected between 2013 and 2019. Microbiological cultures were done as part of all parent studies. We sequenced whole genomes of included isolates and measured bedaquiline and clofazimine minimum inhibitory concentrations (MICs) for isolates identified as carrying any Rv0678 variant or previously published atpE, pepQ, and Rv1979c RAVs, which were the subject of the phenotypic study. We combined all whole-genome sequences of M tuberculosis obtained in this study with publicly available sequence data from other tuberculosis studies in southern Africa (defined as the countries of the Southern African Development Community), including isolates with Rv0678 variants identified by screening public genomic databases. We used this extended dataset to reconstruct phylogenetic relationships across lineage 2 and 4 M tuberculosis isolates. FINDINGS: We sequenced the whole genome of 648 isolates from 385 patients with drug-resistant tuberculosis recruited into cohort studies in KwaZulu-Natal, and 28 isolates from six patients from the KwaZulu-Natal referral laboratory. We identified 30 isolates with Rv0678 RAVs from 16 (4%) of 391 patients. We did not identify any atpE, pepQ, or Rv1979c RAVs. MICs were measured for 21 isolates with Rv0678 RAVs. MICs were above the critical concentration for bedaquiline resistance in nine (43%) of 21 isolates, in the intermediate category in nine (43%) isolates, and within the wild-type range in three (14%) isolates. Clofazimine MICs in genetically wild-type isolates ranged from 0·12-0·5 μg/mL, and in isolates with RAVs from 0·25-4·0 μg/mL. Phylogenetic analysis of the extended dataset including M tuberculosis isolates from southern Africa resolved multiple emergences of Rv0678 variants in lineages 2 and 4, documented two likely nosocomial transmission events, and identified the spread of a possibly bedaquiline and clofazimine cross-resistant clone in eSwatini. We also identified four patients with pepQ frameshift mutations that may confer resistance. INTERPRETATION: Bedaquiline and clofazimine cross-resistance in southern Africa is emerging repeatedly, with evidence of onward transmission largely due to Rv0678 mutations in M tuberculosis. Roll-out of bedaquiline and clofazimine treatment in the setting of limited drug susceptibility testing could allow further spread of resistance. Designing strong regimens would help reduce the emergence of resistance. Drug susceptibility testing is required to identify where resistance does emerge. FUNDING: Wellcome Trust, National Institute of Allergy and Infectious Diseases and National Center for Advancing Translational Sciences of the National Institutes of Health

Consensus Clustering of temporal profiles for the identification of metabolic markers of pre-diabetes in childhood (EarlyBird 73)

In longitudinal clinical studies, methodologies available for the analysis of multivariate data with multivariate methods are relatively limited. Here, we present Consensus Clustering (CClust) a new computational method based on clustering of time pro les and posterior identi cation of correlation between clusters and predictors. Subjects are rst clustered in groups according to a response variable temporal pro le, using a robust consensus-based strategy. To discover which of the remaining variables are associated with the resulting groups, a non-parametric hypothesis test is performed between groups at every time point, and then the results are aggregated according to the Fisher method. Our approach is tested through its application to the EarlyBird cohort database, which contains temporal variations of clinical, metabolic, and anthropometric pro les in a population of 150 children followed-up annually from age 5 to age 16. Our results show that our consensus-based method is able to overcome the problem of the approach-dependent results produced by current clustering algorithms, producing groups de ned according to Insulin Resistance (IR) and biological age (Tanner Score). Moreover, it provides meaningful biological results con rmed by hypothesis testing with most of the main clinical variables. These results position CClust as a valid alternative for the analysis of multivariate longitudinal data

Detection of a reservoir of bedaquiline / clofazimine resistance associated variants in Mycobacterium tuberculosis predating the antibiotic era

Drug resistance in tuberculosis (TB) poses a major ongoing challenge to public health. The recent inclusion of bedaquiline into TB drug regimens has improved treatment outcomes, but this advance is threatened by the emergence of strains of Mycobacterium tuberculosis (Mtb) resistant to bedaquiline. Clinical bedaquiline resistance is most frequently conferred by resistance-associated variants (RAVs) in the Rv0678 gene which can also confer cross-resistance to clofazimine, another TB drug. We compiled a dataset of 3,682 Mtb genomes, including 223 carrying Rv0678 bedaquiline RAVs. We identified at least 15 cases where RAVs were present in the genomes of strains collected prior to the use of bedaquiline in TB treatment regimes. Phylogenetic analyses point to multiple emergence events and circulation of RAVs in Rv0678, often prior to the introduction of bedaquiline or clofazimine. We also identify one case where the RAV Ile67fs is estimated to have emerged prior to the antibiotic era. The presence of a pre-existing reservoir of bedaquiline-resistant Mtb strains augments the need for rapid drug susceptibility testing and individualised regimen selection to safeguard the use of bedaquiline in TB care and control