Crystalline Assemblies and Densest Packings of a Family of Truncated Tetrahedra and the Role of Directional Entropic Forces

Polyhedra and their arrangements have intrigued humankind since the ancient Greeks and are today important motifs in condensed matter, with application to many classes of liquids and solids. Yet, little is known about the thermodynamically stable phases of polyhedrally-shaped building blocks, such as faceted nanoparticles and colloids. Although hard particles are known to organize due to entropy alone, and some unusual phases are reported in the literature, the role of entropic forces in connection with polyhedral shape is not well understood. Here, we study thermodynamic self-assembly of a family of truncated tetrahedra and report several atomic crystal isostructures, including diamond, {\beta}-tin, and high- pressure lithium, as the polyhedron shape varies from tetrahedral to octahedral. We compare our findings with the densest packings of the truncated tetrahedron family obtained by numerical compression and report a new space filling polyhedron, which has been overlooked in previous searches. Interestingly, the self-assembled structures differ from the densest packings. We show that the self-assembled crystal structures can be understood as a tendency for polyhedra to maximize face-to-face alignment, which can be generalized as directional entropic forces.Comment: Article + supplementary information. 23 pages, 10 figures, 2 table

Microbial Reprogramming Inhibits Western Diet-Associated Obesity

A recent epidemiological study showed that eating ‘fast food’ items such as potato chips increased likelihood of obesity, whereas eating yogurt prevented age-associated weight gain in humans. It was demonstrated previously in animal models of obesity that the immune system plays a critical role in this process. Here we examined human subjects and mouse models consuming Westernized ‘fast food’ diet, and found CD4[superscript +] T helper (Th)17-biased immunity and changes in microbial communities and abdominal fat with obesity after eating the Western chow. In striking contrast, eating probiotic yogurt together with Western chow inhibited age-associated weight gain. We went on to test whether a bacteria found in yogurt may serve to lessen fat pathology by using purified Lactobacillus reuteri ATCC 6475 in drinking water. Surprisingly, we discovered that oral L. reuteri therapy alone was sufficient to change the pro-inflammatory immune cell profile and prevent abdominal fat pathology and age-associated weight gain in mice regardless of their baseline diet. These beneficial microbe effects were transferable into naïve recipient animals by purified CD4[superscript +] T cells alone. Specifically, bacterial effects depended upon active immune tolerance by induction of Foxp3[superscript +] regulatory T cells (Treg) and interleukin (Il)-10, without significantly changing the gut microbial ecology or reducing ad libitum caloric intake. Our finding that microbial targeting restored CD4[superscript +] T cell balance and yielded significantly leaner animals regardless of their dietary ‘fast food’ indiscretions suggests population-based approaches for weight management and enhancing public health in industrialized societies.National Institutes of Health (U.S.) (Grant P30-ES002109)National Institutes of Health (U.S.) (Grant RO1CA108854)National Institutes of Health (U.S.) (Grant P01 AI045757)National Institutes of Health (U.S.) (Grant U19 AI046130)National Institutes of Health (U.S.) (Grant U19 AI070352)National Institutes of Health (U.S.) (Grant P01 AI039671)National Institute of Neurological Disorders and Stroke (U.S.) (Jacob Javits Merit Award NS2427)The Penates FoundationNancy Taylor Foundation for Chronic Diseases, Inc

Receptor Tyrosine Kinases in Osteosarcoma: 2019 Update

The primary conclusions of our 2014 contribution to this series were as follows: Multiple receptor tyrosine kinases (RTKs) likely contribute to aggressive phenotypes in osteosarcoma and, therefore, inhibition of multiple RTKs is likely necessary for successful clinical outcomes. Inhibition of multiple RTKs may also be useful to overcome resistance to inhibitors of individual RTKs as well as resistance to conventional chemotherapies. Different combinations of RTKs are likely important in individual patients. AXL, EPHB2, FGFR2, IGF1R, and RET were identified as promising therapeutic targets by our in vitro phosphoproteomic/siRNA screen of 42 RTKs in the highly metastatic LM7 and 143B human osteosarcoma cell lines. This chapter is intended to provide an update on these topics as well as the large number of osteosarcoma clinical studies of inhibitors of multiple tyrosine kinases (multi-TKIs) that were recently published

Effects of a TAFI-inhibitor combined with a suboptimal dose of rtPA in a murine thromboembolic model of stroke

International audienceBackground: Since thrombolysis is the only approved intervention for ischemic stroke, improving its efficacy and safety is a therapeutic aim of considerable interest. The activated form of thrombin activatable fibrinolysis inhibitor (TAFI) has antifibrinolytic effects, and inhibition of TAFI might thus favor recanalization. The present study compared efficacy between TAFI inhibition alone and TAFI inhibition in combination with rtPA at a suboptimal dose, in a murine model of thromboembolic stroke. Methods: Focal ischemia was induced in mice by thrombin injection in the middle cerebral artery. Animals were placed within the magnet immediately after surgery for baseline MRI (H0). MRI examination comprised diffusion-weighted imaging (DWI), perfusion-weighted imaging (PWI), and T2-weighted imaging (T2-WI). Animals were randomly assigned to 1 of 5 treatment groups: saline, rtPA 5 mg/kg (tPA5: suboptimal or low dose), rtPA 10 mg/kg (tPA10: standard dose), TAFI-I 100 mg/kg (TAFI-I), and rtPA 5 mg/kg + TAFI-I 100 mg/kg (tPA5 + TAFI-I). Treatments were administered inside the magnet, via a catheter placed in the tail vein, using a power injector, as 10% bolus and 90% infusion over a period of 20 min. MRI examination was repeated at 3 h (H3) and 24 h (H24) after surgery. Therapeutic benefit was evaluated by: (1) improvement of reperfusion and (2) reduction in final lesion size. Microhemorrhages were assessed as black spots on T2-WI at H24. Animals were sacrificed after the last MR examination. The surgeon and all investigators were blinded to treatment allocation. Results: A total of 104 mice were operated on. Forty four of these were excluded from the study and 27 from the analysis, according to a priori defined criteria (no lesion or no mismatch), leading to the following distribution: saline (n = 6), tPA5 (n = 8), tPA10 (n = 7), TAFI-I (n = 7), and TAFI-I + tPA5 (n = 5). Standard-dose rtPA treatment (tPA10) significantly improved lesion regression between H0 and H24 compared to saline (-57 ± 18% vs. -36 ± 21%, p = 0.03), which treatment with rtPA5 or TAFI-I alone did not. On the other hand, combined treatment with tPA5 + TAFI-I showed only a trend toward lesion regression (-49 ± 26%), similarly to treatment with tPA10, but not significantly different from saline (p = 0.46). Nine animals showed microhemorrhage on T2-WI at H24. These animals were evenly distributed between groups. Conclusions: The present study showed that the combination of TAFI-I with a suboptimal dose of rtPA is not as effective as the standard dose of rtPA, while TAFI inhibition alone is not effective at all. The thromboembolic model is of particular interest in assessing rtPA association to improve thrombolysis, especially when coupled with longitudinal MRI assessment