Atomistic simulations of calcium aluminosilicate interfaced with liquid water

The dissolution behavior of calcium aluminosilicate based glass fibers, such as stone wool fibers, is an important consideration in mineral wool applications for both the longevity of the mineral wool products in humid environments and limiting the health impacts of released and inhaled fibers from the mineral wool product. Balancing these factors requires a molecular-level understanding of calcium aluminosilicate glass dissolution mechanisms, details that are challenging to resolve with experiment alone. Molecular dynamics simulations are a powerful tool capable of providing complementary atomistic insights regarding dissolution; however, they require force fields capable of describing not-only the calcium aluminosilicate surface structure but also the interactions relevant to dissolution phenomena. Here, a new force field capable of describing amorphous calcium aluminosilicate surfaces interfaced with liquid water is developed by fitting parameters to experimental and first principles simulation data of the relevant oxide-water interfaces, including ab initio molecular dynamics simulations performed for this work for the wüstite and periclase interfaces. Simulations of a calcium aluminosilicate surface interfaced with liquid water were used to test this new force field, suggesting moderate ingress of water into the porous glass interface. This design of the force field opens a new avenue for the further study of calcium and network-modifier dissolution phenomena in calcium aluminosilicate glasses and stone wool fibers at liquid water interfaces.

Circulating exosomes deliver free fatty acids from the bloodstream to cardiac cells: Possible role of CD36

Regulation of circulating free fatty acid (FFA) levels and delivery is crucial to maintain tissue homeostasis. Exosomes are nanomembranous vesicles that are released from diverse cell types and mediate intercellular communication by delivering bioactive molecules. Here, we sought to investigate the uptake of FFAs by circulating exosomes, the delivery of FFA-loaded exosomes to cardiac cells and the possible role of the FFA transporter CD36 in these processes. Circulating exosomes were purified from the serum of healthy donors after an overnight fast (F) or 20 minutes after a high caloric breakfast (postprandial, PP). Western blotting, Immunogold Electron Microscopy and FACS analysis of circulating exosomes showed that CD36 was expressed under both states, but was higher in postprandial-derived exosomes. Flow cytometry analysis showed that circulating exosomes were able to take-up FFA directly from serum. Importantly, preincubation of exosomes with a blocking CD36 antibody significantly impeded uptake of the FFA analogue BODIPY, pointing to the role of CD36 in FFA exosomal uptake. Finally, we found that circulating exosomes could delivery FFA analogue BODIPY into cardiac cells ex vivo and in vivo in a mice model. Overall, our results suggest a novel mechanism in which circulating exosomes can delivery FFAs from the bloodstream to cardiac tissue. Further studies will be necessary to understand this mechanism and, in particular, its potential involvement in metabolic pathologies such as obesity, diabetes and atherosclerosis.

Corynebacterium striatum peritoneal dialysis catheter exit site infection

BACKGROUND

Regarded as normal flora of the human skin and mucus membranes, non-diphtheria corynebacteria are frequently dismissed as contaminants or harmless colonizers. Recently, the pathogenic potential of C. striatum has been realized in immunocompromised patients with indwelling medical devices and previous antibiotic exposure.

OBJECTIVE

We report here the diagnosis, treatment and clinical outcome of a peritoneal dialysis patient with a C. striatum infection of the catheter exit site. The aim is to present important features to assist in identifying clinically significant infections and provide guidelines for treatment.

RESULTS

An immunocompromised patient with previous antimicrobial exposure developed an acute dialysis catheter exit site infection. C. striatum was isolated in pure growth. After initial treatment failure with oral antibiotics and intensified wound care, a satisfactory outcome was ultimately achieved without relapse or loss of the catheter with a 1-month course of vancomycin, 1 g intravenously, administered at 5-day intervals.

CONCLUSIONS

The virulent capacity of Corynebacterium species should not be underestimated, particularly in high-risk patients. The presence of clinical signs of infection with isolation of the organism in pure culture and the presence of Gram-positive rods on direct Gram stain, especially in association with a leukocyte reaction, supports a cause and effect relationship. Because corynebacteria may be multiresistant, susceptibility testing should be performed on clinically significant isolates. Initial antibiotic selection is influenced by the severity of the infection, however, current experience favors vancomycin in significant infections.

Singlet molecular oxygen-mediated photo-oxidation of tetracyclines: kinetics, mechanism and microbiological implications

Members of the biologically active series tetracyclines (TCs) suffer visible light-promoted photodynamic degradation to different extents, depending on their respective chemical structures and reaction conditions (solvent polarity and pH). The photo-oxidation is accompanied by a partial loss of the antimicrobial power. The photodamage is very fast in the alkaline pH range and less aggressive. although not negligible in kinetic terms, in the physiological pH region. Photo-oxidation quantum efficiencies, evaluated for eight TC derivatives, through singlet molecular oxygen [O2(1Delta(g))] phosphorescence detection, spectrophotometric and polarographic methods, range from 0.12 to 0.65 as upper limits in alkaline medium. The photo-oxidation essentially proceeds via a O2(1Delta(g)) mediated process, with rose bengal or eosine as dye-sensitizers, Nevertheless, as a minor reactive pathway,the excited triplet state of the dye sensitizers interacts with TCS in a competitive process with O2(1Delta(g) generation. The O2(1Delta(g)-mediated photo-oxidation of TCs appears to be a plausible mechanism to account for their phototransformations in biological media, in the presence of visible-absorbing pigments. In both highly and moderately polar media, the quenching of the excited oxygen species is mainly represented by a reactive interaction. It is exerted by the TC molecule through a cooperative effect from the different contributions of several nuclear and extranuclear O2(1Delta(g)-sensitive substituents, as discussed in detail in this paper. The TC lower than 0.03 in the most favourable cases. Nevertheless, the TC photoproduct, formed through direct irradiation, efficiently generates O2(1Delta(g) with Phi(Delta)=0.24. This important finding constitutes the first direct evidence of Type II sensitization by TC photoproducts, and could contribute to the elucidation of the mechanism of TC phototoxicity.

[Stents for bifurcational coronary lesion]

We describe two cases of coronary angioplasty with stents implantation in bifurcational lesion of the left anterior descending artery and the diagonal branch using new techniques successfully performed. Angiographic reestenosis was not present after seven months in one case and the patient was asymptomatic after six months of clinical follow-up in the other.