Ultrabright Fluorescent Polymeric Nanoparticles with a Stealth Pluronic Shell for Live Tracking in the Mouse Brain

Visualizing single organic nanoparticles (NPs) in vivo remains a challenge, which could greatly improve our understanding of the bottlenecks in the field of nanomedicine. To achieve high single-particle fluorescence brightness, we loaded polymer poly(methyl methacrylate)-sulfonate (PMMA-SO3H) NPs with octadecyl rhodamine B together with a bulky hydrophobic counterion (perfluorinated tetraphenylborate) as a fluorophore insulator to prevent aggregation-caused quenching. To create NPs with stealth properties, we used the amphiphilic block copolymers pluronic F-127 and F-68. Fluorescence correlation spectroscopy and Förster resonance energy transfer (FRET) revealed that pluronics remained at the NP surface after dialysis (at one amphiphile per 5.5 nm2) and prevented NPs from nonspecific interactions with serum proteins and surfactants. In primary cultured neurons, pluronics stabilized the NPs, preventing their prompt aggregation and binding to neurons. By increasing dye loading to 20 wt % and optimizing particle size, we obtained 74 nm NPs showing 150-fold higher single-particle brightness with two-photon excitation than commercial Nile Red-loaded FluoSpheres of 39 nm hydrodynamic diameter. The obtained ultrabright pluronic-coated NPs enabled direct single-particle tracking in vessels of mice brains by two-photon intravital microscopy for at least 1 h, whereas noncoated NPs were rapidly eliminated from the circulation. Following brain injury or neuroinflammation, which can open the blood–brain barrier, extravasation of NPs was successfully monitored. Moreover, we demonstrated tracking of individual NPs from meningeal vessels until their uptake by meningeal macrophages. Thus, single NPs can be tracked in animals in real time in vivo in different brain compartments and their dynamics visualized with subcellular resolution

Structural changes of CA1 pyramidal neurons after stroke in the contralesional hippocampus

Significant progress has been made with regard to understanding how the adult brain responds after a stroke. However, a large number of patients continue to suffer lifelong disabilities without adequate treatment. In the present study, we have analyzed possible microanatomical alterations in the contralesional hippocampus from the ischemic stroke mouse model tMCAo 12-14 weeks after transient middle cerebral artery occlusion. After individually injecting Lucifer yellow into pyramidal neurons from the CA1 field of the hippocampus, we performed a detailed three-dimensional analysis of the neuronal complexity, dendritic spine density, and morphology. We found that, in both apical (stratum radiatum) and basal (stratum oriens) arbors, CA1 pyramidal neurons in the contralesional hippocampus of tMCAo mice have a significantly higher neuronal complexity, as well as reduced spine density and alterations in spine volume and spine length. Our results show that when the ipsilateral hippocampus is dramatically damaged, the contralesional hippocampus exhibits several statistically significant selective alterations. However, these alterations are not as significant as expected, which may help to explain the recovery of hippocampal function after stroke. Further anatomical and physiological studies are necessary to better understand the modifications in the intact contralesional lesioned brain regions, which are probably fundamental to recover functions after stroke

RIPK1 or RIPK3 deletion prevents progressive neuronal cell death and improves memory function after traumatic brain injury

Traumatic brain injury (TBI) causes acute and subacute tissue damage, but is also associated with chronic inflammation and progressive loss of brain tissue months and years after the initial event. The trigger and the subsequent molecular mechanisms causing chronic brain injury after TBI are not well understood. The aim of the current study was therefore to investigate the hypothesis that necroptosis, a form a programmed cell death mediated by the interaction of Receptor Interacting Protein Kinases (RIPK) 1 and 3, is involved in this process. Neuron-specific RIPK1- or RIPK3-deficient mice and their wild-type littermates were subjected to experimental TBI by controlled cortical impact. Posttraumatic brain damage and functional outcome were assessed longitudinally by repetitive magnetic resonance imaging (MRI) and behavioral tests (beam walk, Barnes maze, and tail suspension), respectively, for up to three months after injury. Thereafter, brains were investigated by immunohistochemistry for the necroptotic marker phosphorylated mixed lineage kinase like protein(pMLKL) and activation of astrocytes and microglia. WT mice showed progressive chronic brain damage in cortex and hippocampus and increased levels of pMLKL after TBI. Chronic brain damage occurred almost exclusively in areas with iron deposits and was significantly reduced in RIPK1- or RIPK3-deficient mice by up to 80%. Neuroprotection was accompanied by a reduction of astrocyte and microglia activation and improved memory function. The data of the current study suggest that progressive chronic brain damage and cognitive decline after TBI depend on the expression of RIPK1/3 in neurons. Hence, inhibition of necroptosis signaling may represent a novel therapeutic target for the prevention of chronic post-traumatic brain damage

Whole-body cellular mapping in mouse using standard IgG antibodies

Whole-body imaging techniques play a vital role in exploring the interplay of physiological systems in maintaining health and driving disease. We introduce wildDISCO, a new approach for whole-body immunolabeling, optical clearing and imaging in mice, circumventing the need for transgenic reporter animals or nanobody labeling and so overcoming existing technical limitations. We identified heptakis(2,6-di-O-methyl)-beta-cyclodextrin as a potent enhancer of cholesterol extraction and membrane permeabilization, enabling deep, homogeneous penetration of standard antibodies without aggregation. WildDISCO facilitates imaging of peripheral nervous systems, lymphatic vessels and immune cells in whole mice at cellular resolution by labeling diverse endogenous proteins. Additionally, we examined rare proliferating cells and the effects of biological perturbations, as demonstrated in germ-free mice. We applied wildDISCO to map tertiary lymphoid structures in the context of breast cancer, considering both primary tumor and metastases throughout the mouse body. An atlas of high-resolution images showcasing mouse nervous, lymphatic and vascular systems is accessible at

Emerson's knowledge and use of Islamic literature

The purpose of this study is to show the extent of Emerson's knowledge of Islamic literature, specifically Arabic and Persian, and to demonstrate its impact on his thinking and writing. Preliminary to a discussion of Emerson's personal involvement with Islamic literature, a survey is made of the scope and quality of Near Eastern materials--translations and scholarly works--available to Emerson and his contemporaries both in New England and Great Britain. After a long period of misunderstanding of Islam and prejudice against it in the West, fresh efforts were made in Emerson's time to approach and present Islamic culture objectively. Emerson's own attitude toward Arabic and Persian literature and culture reflects this more liberal interpretation. [...]English, Department o

Ambition in Marlowe's drama

This thesis is intended to emphasize Christopher Marlowe's interest in the theme of ambition and to point out the dichotomy that characterized this attitude. A survey of the Elizabethan conceptions of ambition shows that the playwright's contemporaries were also strongly interested in the theme of ambition and would regard it as a sin which threatened the order embodied in the great chain of being and which diverted man from his concern with the after life whose value was acknowledged as paramount. [...]English, Department o

Récepteur B2 de la bradykinine (une nouvelle cible thérapeutique pour le traitement du traumatisme cérébral diffus?)

PARIS-BIUP (751062107) / SudocSudocFranceF

Microglia in action: how aging and injury can change the brain’s guardians

Neuroinflammation, the inflammatory response in the CNS, is a major determinant of neuronal function and survival during ageing and disease progression. Microglia, as the resident tissue-macrophages of the brain, provide constant support to surrounding neurons in healthy brain. Upon any stress signal (such as trauma, ischemia, inflammation) they are one of the first cells to react. Local and/or peripheral signals determine microglia stress response, which can vary within a continuum of states from beneficial to detrimental for neuronal survival, and can be shaped by ageing and previous insults. In this review, we discuss the roles of microglia upon an ischemic or traumatic injury, and give our perspective how ageing may contribute to microglia behavior in the injured brain. We speculate that a deeper understanding of specific microglia identities will pave the way to develop more potent therapeutics to treat the diseases of ageing brain

Inadequate food and water intake determine mortality following stroke in mice

Experimental stroke models producing clinically relevant functional deficits are often associated with high mortality. Because the mechanisms that underlie post-stroke mortality are largely unknown, results obtained using these models are often difficult to interpret, thereby limiting their translational potential. Given that specific forms of post-stroke care reduce mortality in patients, we hypothesized that inadequate food and water intake may underlie mortality following experimental stroke. C57BL/6 mice were subjected to 1h of intraluminal filament middle cerebral artery occlusion. Nutritional support beginning on the second day after filament middle cerebral artery occlusion reduced the 14-day mortality rate from 59% to 15%. The surviving mice in the post-stroke support group had the same infarct size as non-surviving control mice, suggesting that post-stroke care was not neuroprotective and that inadequate food and/or water intake are the main reasons for filament middle cerebral artery occlusion-induced mortality. This notion was supported by the presence of significant hypoglycemia, ketonemia, and dehydration in control mice. Taken together, these data suggest that post-filament middle cerebral artery occlusion mortality in mice is not primarily caused by ischemic brain damage, but secondarily by inadequate food and/or water intake. Thus, providing nutritional support following filament middle cerebral artery occlusion greatly minimizes mortality bias and allows the study of long-term morphological and functional sequelae of stroke in mice