Search

Abstract Bacterial spores owe their incredible resistance capacities to molecular structures that protect the cell content from external aggressions. Among the determinants of resistance are the quaternary structure of the chromosome and an extracellular shell made of proteinaceous layers (the coat), the assembly of which remains poorly understood. Here, in situ cryo-electron tomography on lamellae generated by cryo-focused ion beam micromachining provides insights into the ultrastructural organization of Bacillus subtilis sporangia. The reconstructed tomograms reveal that early during sporulation, the chromosome in the forespore adopts a toroidal structure harboring 5.5-nm thick fibers. At the same stage, coat proteins at the surface of the forespore form a stack of amorphous or structured layers with distinct electron density, dimensions and organization. By analyzing mutant strains using cryo-electron tomography and transmission electron microscopy on resin sections, we distinguish seven nascent coat regions with different molecular properties, and propose a model for the contribution of coat morphogenetic proteins.

Pancreatic cancer is associated with a poor prognosis despite multimodal treatments. To improve the efficacy of radiotherapy, the use of nanoscintillators is emerging. Made of high‐Z elements, they absorb X‐rays more efficiently than tissues and can locally enhance the radiation dose provided they have accumulated near tumor cells. This study focuses on the role of the coating, a key parameter that controls both in vitro and in vivo properties of nanoparticles, including their internalization, biocompatibility, and therapeutic efficacy. Polyethylene glycol and tripolyphosphate molecules are used to coat lanthanum fluoride nanoscintillators, and their properties are evaluated on pancreatic cancer models. The experiments demonstrate a higher internalization of the nanoparticles when coated with tripolyphosphate, in both 2D and 3D culture models, correlating with greater efficacy under X‐rays, which may be associated with higher radiation dose‐enhancement. The nanoparticles are also injected intravenously in healthy or tumor‐bearing mice in order to study their toxicity, pharmacokinetics, and biodistribution. Despite a strong liver and spleen accumulation, especially for the tripolyphosphate‐coated nanoparticles, no toxicity is observed for either coating. Because they show promising radiation dose‐enhancement in vitro in both culture models and a limited toxicity in vivo, polyethylene glycol‐coated nanoparticles are good candidates for biomedical applications.

Heart failure with preserved ejection fraction (HFpEF) is associated with exercise intolerance due to alterations in the skeletal muscle (SKM). Leucine supplementation is known to alter the anabolic/catabolic balance and to improve mitochondrial function. Thus, we investigated the effect of leucine supplementation in both a primary and a secondary prevention approach on SKM function and factors modulating muscle function in an established HFpEF rat model. Female ZSF1 obese rats were randomized to an untreated, a primary prevention, and a secondary prevention group. For primary prevention, leucine supplementation was started before the onset of HFpEF (8 weeks of age) and for secondary prevention, leucine supplementation was started after the onset of HFpEF (20 weeks of age). SKM function was assessed at an age of 32 weeks, and SKM tissue was collected for the assessment of mitochondrial function and histological and molecular analyses. Leucine supplementation prevented the development of SKM dysfunction whereas it could not reverse it. In the primary prevention group, mitochondrial function improved and higher expressions of mitofilin, Mfn-2, Fis1, and miCK were evident in SKM. The expression of UCP3 was reduced whereas the mitochondrial content and markers for catabolism (MuRF1, MAFBx), muscle cross-sectional area, and SKM mass did not change. Our data show that leucine supplementation prevented the development of skeletal muscle dysfunction in a rat model of HFpEF, which may be mediated by improving mitochondrial function through modulating energy transfer.