102 research outputs found
"Wet-to-Dry" Conformational Transition of Polymer Layers Grafted to Nanoparticles in Nanocomposite
The present communication reports the first direct measurement of the
conformation of a polymer corona grafted around silica nano-particles dispersed
inside a nanocomposite, a matrix of the same polymer. This measurement
constitutes an experimental breakthrough based on a refined combination of
chemical synthesis, which permits to match the contribution of the neutron
silica signal inside the composite, and the use of complementary scattering
methods SANS and SAXS to extract the grafted polymer layer form factor from the
inter-particles silica structure factor. The modelization of the signal of the
grafted polymer on nanoparticles inside the matrix and the direct comparison
with the form factor of the same particles in solution show a clear-cut change
of the polymer conformation from bulk to the nanocomposite: a transition from a
stretched and swollen form in solution to a Gaussian conformation in the matrix
followed with a compression of a factor two of the grafted corona. In the
probed range, increasing the interactions between the grafted particles (by
increasing the particle volume fraction) or between the grafted and the free
matrix chains (decreasing the grafted-free chain length ratio) does not
influence the amplitude of the grafted brush compression. This is the first
direct observation of the wet-to-dry conformational transition theoretically
expected to minimize the free energy of swelling of grafted chains in
interaction with free matrix chains, illustrating the competition between the
mixing entropy of grafted and free chains, and the elastic deformation of the
grafted chains. In addition to the experimental validation of the theoretical
prediction, this result constitutes a new insight for the nderstanding of the
general problem of dispersion of nanoparticles inside a polymer matrix for the
design of new nanocomposites materials
Histopathological and biochemical findings of congenital copper deficiency: are these similar to those of caprine arthritis-encephalitis?
This study was done after identifying animals with a twisted carpal joint in goat herd. These included a kid goat walking on its articulus carpii and a newborn goat with a stiff leg. Necropsies of the diseased goats revealed swollen carpal joints that were twisted backwards. Arthritis was observed during microscopic examination of the carpal joints. Very low levels of eosinophil, leucocyte, and lymphocyte cell infiltration were found in the central nervous system and meninges. Serum copper levels were significantly decreased in most of the animals. All of these results led us to diagnose the animals with swayback disease
The role of CSF1R-dependent macrophages in control of the intestinal stem cell niche
Colony-stimulating factor 1 (CSF1) controls the growth and differentiation of macrophages.CSF1R signaling has been implicated in the maintenance of the intestinal stem cell niche and differentiation of Paneth cells, but evidence of expression of CSF1R within the crypt is equivocal. Here we show that CSF1R-dependent macrophages influence intestinal epithelial differentiation and homeostasis. In the intestinal lamina propria CSF1R mRNA expression is restricted to macrophages which are intimately associated with the crypt epithelium, and is undetectable in Paneth cells. Macrophage ablation following CSF1R blockade affects Paneth cell differentiation and leads to a reduction of Lgr5 intestinal stem cells. The disturbances to the crypt caused by macrophage depletion adversely affect the subsequent differentiation of intestinal epithelial cell lineages. Goblet cell density is enhanced, whereas the development of M cells in Peyer's patches is impeded. We suggest that modification of the phenotype or abundance of macrophages in the gut wall alters the development of the intestinal epithelium and the ability to sample gut antigens
Deletion of a Csf1r enhancer selectively impacts CSF1R expression and development of tissue macrophage populations.
The proliferation, differentiation and survival of mononuclear phagocytes depend on signals from the receptor for macrophage colony-stimulating factor, CSF1R. The mammalian Csf1r locus contains a highly conserved super-enhancer, the fms-intronic regulatory element (FIRE). Here we show that genomic deletion of FIRE in mice selectively impacts CSF1R expression and tissue macrophage development in specific tissues. Deletion of FIRE ablates macrophage development from murine embryonic stem cells. Csf1r mice lack macrophages in the embryo, brain microglia and resident macrophages in the skin, kidney, heart and peritoneum. The homeostasis of other macrophage populations and monocytes is unaffected, but monocytes and their progenitors in bone marrow lack surface CSF1R. Finally, Csf1r mice are healthy and fertile without the growth, neurological or developmental abnormalities reported in Csf1r rodents. Csf1r mice thus provide a model to explore the homeostatic, physiological and immunological functions of tissue-specific macrophage populations in adult animals
Evaluation of effects of magnesium sulphate in reducing intraoperative anaesthetic requirements
Background. The present randomized, placebo-controlled, double-blind study was designed to assess the effect of peroperatively administered i.v. magnesium sulphate on anaesthetic and analgesic requirements during total i.v. anaesthesia
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