Mechanism of insulin resistance in a rat model of kidney disease and the risk of developing type 2 diabetes.

International audienceChronic kidney disease is associated with homeostatic imbalances such as insulin resistance. However, the underlying mechanisms leading to these imbalances and whether they promote the development of type 2 diabetes is unknown. The effect of chronic kidney disease on insulin resistance was studied on two different rat strains. First, in a 5/6th nephrectomised Sprague-Dawley rat model of chronic kidney disease, we observed a correlation between the severity of chronic kidney disease and hyperglycemia as evaluated by serum fructosamine levels (p<0.0001). Further, glucose tolerance tests indicated an increase of 25% in glycemia in chronic kidney disease rats (p<0.0001) as compared to controls whereas insulin levels remained unchanged. We also observed modulation of glucose transporters expression in several tissues such as the liver (decrease of ≈40%, p≤0.01) and muscles (decrease of ≈29%, p≤0.05). Despite a significant reduction of ≈37% in insulin-dependent glucose uptake in the muscles of chronic kidney disease rats (p<0.0001), the development of type 2 diabetes was never observed. Second, in a rat model of metabolic syndrome (Zucker Leprfa/fa), chronic kidney disease caused a 50% increased fasting hyperglycemia (p<0.0001) and an exacerbated glycemic response (p<0.0001) during glucose challenge. Similar modulations of glucose transporters expression and glucose uptake were observed in the two models. However, 30% (p<0.05) of chronic kidney disease Zucker rats developed characteristics of type 2 diabetes. Thus, our results suggest that downregulation of GLUT4 in skeletal muscle may be associated with insulin resistance in chronic kidney disease and could lead to type 2 diabetes in predisposed animals

Spatially resolved variations in reflectivity across iron oxide thin films

The spin polarising properties of the iron oxide magnetite (Fe3O4) make it attractive for use in spintronic devices, but its sensitivity to compositional and structural variations make it challenging to prepare reli- ably. Infrared microspectroscopy and modelling are used to determine the spatial variation in the chem- ical composition of three thin films of iron oxide; one prepared by pulsed laser deposition (PLD), one by molecular beam epitaxy (MBE) deposition of iron whilst simultaneously flowing oxygen into the chamber and one by flowing oxygen only once deposition is complete. The technique is easily able to distinguish between films which contain metallic iron and different iron oxide phases as well as spatial variations in composition across the films. The film grown by post-oxidising iron is spatially uniform but not fully oxi- dised, the film grown by simultaneously oxidising iron showed spatial variation in oxide composition while the film grown by PLD was spatially uniform magnetite

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Electroanalysis at a single giant vesicle generating enzymatically a reactive oxygen species

International audienceIn the framework of artificial or synthetic cell development, giant liposomes are common basic structures. Their enclosed membrane permits to encapsulate proteins, DNA, reactants, etc while its phospholipid nature allows some exchanges with the surrounding medium. Biochemical reactions induced inside giant liposomes or vesicles are often monitored or imaged by fluorescence microscopy techniques. Here, we show that electrochemistry performed with ultramicroelectrodes is perfectly suitable to monitor an enzymatic reaction occurring in a single giant unilamellar vesicle. Glucose oxidase (GOx) was micro-injected inside individual vesicles containing 1 mM glucose. H2O2 was thus generated in the vesicle and progressively diffused across the membrane toward the surrounding environment. An ultramicroelectrode sensitive to H2O2 (black platinum-modified carbon surface) was placed next to the membrane and provided a direct detection of the hydrogen peroxide flux generated by the enzyme activity. Electrochemistry offered a highly sensitive (in situ detection), selective (potential applied at the electrode), time-resolved analysis (chronoamperometry) of the GOx activity over an hour duration, without modifying the internal GUV medium. These results demonstrate that electroanalysis with microsensors is well adapted and complementary to fluorescence microscopy to sense enzymatic activities, for instance generating Reactive Oxygen Species, at single vesicles further used to develop artificial cells

Dynamic monitoring of a bi-enzymatic reaction at a single biomimetic giant vesicle

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Biopsy of brain tumors by stereotaxy assisted by tomodensimetry: setting of a new protocol and first clinicat applications in dog

Le diagnostic précis des lésions de l’encéphale ne peut être obtenu qu’après examen histopathologique d’une biopsie. Nous décrivons la conception d’un prototype permettant la réalisation d’une biopsie par stéréotaxie assistée par tomodensitométrie dont le but est d’obtenir le prélèvement de cibles d’un diamètre supérieur à 1 cm chez le chien. La précision de la procédure fut tout d’abord mesurée en injectant 1 ml d’un produit pâteux radio-opaque en une cible préalablement déterminée (coordonnées xl yl, zl) au sein de 10 cerveaux frais de chiens. Un nouveau scanner permettait de déterminer le centre de la masse ainsi créée et de calculer la différence entre les coordonnées de la cible et de la biopsie réelle selon les axes X, Y et Z. La technique fut alors appliquée chez 8 chiens présentant des tumeurs cérébrales. La procédure a démontré sa grande précision dans les deux essais. La précision fut calculée à 2,9 mm. La biopsie fut diagnostiquée dans les 8 cas et deux complications furent observées. La biopsie stéréotaxique assistée par tomodensitométrie est une technique rapide, aisée et reproductible, indiquée en présence de toute lésion cérébrale mal caractérisée par la seule imagerie chez le chien.Accurate diagnosis of brain lesions can only be reached by obtaining a tissue sample for histopathologic examination. We describe the design of a prototype device for CT-guided stereotaxic biopsy (CTGSB) of the canine brain which can perform biopsy procedure in 1 cm-lesions. The procedure was initially ascertained in 10 dog cadaver heads in wich 1 ml of a radiolucent paste was injected in a point chosen on the CT images (coordinates : xl, ol, zl). ACT scan was performed again and the center of the injected mass was measured (coordinates : x2, y2, z2). Means and standard deviations (Dx, Dy and Dz) were calculated. Eight dogs demons trating intracranial tumours were submitted to CTGSB. The procedure has proved to be highly accurate on our trials. Accuracy was 2,9 mm. CTGSB yielded diagnostic samples in the eight dogs. Two complications was observed. CTGSB appears to be a quick, easy and reliable procedure indicated for all unknown brain lesions in the dog

Challenges underlying the in situ analysis of single bacterial cells by synchrotron FTIR spectromicroscopy

Challenges underlying the in situ analysis of single bacterial cells by synchrotron FTIR spectromicroscopy. European Conference on the Spectroscopy of Biological Molecules (ECSBM 16