Reconfigurable terahertz metamaterials

We demonstrate reconfigurable anisotropic metamaterials at terahertz frequencies where artificial "atoms" reorient within unit cells in response to an external stimulus. This is accomplished by fabricating planar arrays of split ring resonators on bimaterial cantilevers designed to bend out of plane in response to a thermal stimulus. We observe a marked tunability of the electric and magnetic response as the split ring resonators reorient within their unit cells. Our results demonstrate that adaptive metamaterials offer significant potential to realize novel electromagnetic functionality ranging from thermal detection to reconfigurable cloaks or absorbers.

Osteopontin induces angiogenesis through activation of PI3K/AKT and ERK1/2 in endothelial cells

Angiogenesis is a key step in tumor growth and metastasis. The mechanism by which osteopontin (OPN) induces the angiogenesis of endothelial cells remains unclear. Here, we show that OPN confers cytoprotection through the activation of the PI3K/Akt pathway with subsequent upregulation of Bcl-xL and activation of nuclear factor-kappaB. OPN enhances the expression of vascular endothelial growth factor (VEGF) through the phosphorylation of AKT and extracellular signal-regulated kinase (ERK). In turn, OPN-induced VEGF activates PI3K/AKT and the ERK1/2 pathway as a positive feedback signal. Blocking the feedback signal by anti-VEGF antibody, PI3-kinase inhibitor or ERK inhibitor can partially inhibit the OPN-induced human umbilical vein endothelial cell (HUVEC) motility, proliferation and tube formation, while blocking the signal by anti-OPN or anti-alphavbeta3 antibody completely abrogates the biological effects of OPN on HUVECs. In addition, blood vessel formation is also investigated in vivo. The antiangiogenesis efficacy of anti-OPN antibody in vivo is more effective than that of anti-VEGF antibody, which only blocks the feedback signals. These data show that OPN enhances angiogenesis directly through PI3K/AKT- and ERK-mediated pathways with VEGF acting as a positive feedback signal. The results suggest that OPN might be a valuable target for developing novel antiangiogenesis therapy for treatment of cancer.

Tumor progression in Apc(1638N) mice with Exo1 and Fen1 deficiencies

Flap endonuclease 1 (Fen1) and exonuclease 1 (Exo1) have sequence homology and similar nuclease capabilities. Both function in multiple pathways of DNA metabolism, but appear to have distinct in vivo nucleic acid substrates, and therefore distinct metabolic roles. When combined with Apc(1638N), Fen1 promotes tumor progression. Because of functional similarity to Fen1, and because Exo1 is involved in DNA mismatch repair (MMR) by interaction with Msh2 and Mlh1, genes that cause hereditary nonpolyposis colorectal cancer (HNPCC), we investigated the possibility that Exo1 might also act as a modifier to Apc(1638N). We present evidence that mice with combined mutations in Apc(1638N) and Exo1 and Apc(1638N), Exo1 and Fen1 genes show moderate increased tumor incidence and multiplicity in comparison to Apc(1638N) siblings, implying a low penetrance role for Exo1 in early gastrointestinal (GI) tumorigenesis. Despite a decrease in median survival (10 months) in Apc(1638N) Exo1 mice, their tumors do not progress any more rapidly than those of Apc(1638N). Instead these animals die from infections that are the result of impaired immune response. Apc(1638N) Exo1 Fen1 mice survive longer (18 months), and therefore appear relatively immune competent. They die of invasive GI tumors that display microsatellite instability (MSI). Our results show that Exo1 has a modest tumor suppressor function.

A mechanism for anomalous decline in radon precursory to an earthquake

Mechanisms for interpreting anomalous decreases in radon in ground water prior to earthquakes are examined with the help of a case study to show that radon potentially is a sensitive tracer of strain changes in the crust preceding an earthquake. The 2003 Chengkung earthquake of magnitude (M) 6.8 on December 10, 2003, was the strongest earthquake near the Chengkung area in eastern Taiwan since 1951. The Antung radon-monitoring station was located 20 km from the epicenter. Approximately 65 d prior to the 2003 Chengkung earthquake, precursory changes in radon concentration in ground water were observed. Specifically, radon decreased from a background level of 780 pCi/L to a minimum of 330 pCi/L. The Antung hot spring is situated in a fractured block of tuffaceous sandstone surrounded by ductile mudstone. Given these geological conditions, we hypothesized that the dilation of brittle rock mass occurred at a rate faster than the recharge of pore water and gas saturation developed in newly created cracks preceding the earthquake. Radon partitioning into the gas phase may explain the anomalous decrease of radon precursory to the 2003 Chengkung earthquake. To support the hypothesis, vapor-liquid, two-phase radon-partitioning experiments were conducted at formation temperature (60 degrees C) using formation brine from the Antung hot spring. Experimental data indicated that the decrease in radon required a gas saturation of 10% developed in rock cracks. The observed decline in radon can be correlated with the increase in gas saturation and then with the volumetric strain change for a given fracture porosity.

Activation of human peripheral blood immune cells in vitro by sodium stibogluconate (SSG) and SSG/IL-2 combination

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Background: SSG, an inhibitor of SHP-1 and SHP2 which are negative regulatory signaling tyrosine phosphatases, suppressed the growth of murine renal carcinoma (Renca) in combination with IL-2 via an interferon (IFN)-γ+ T cell-dependent mechanism (J Immunol 175:7003–8, 2005). Activation of primary human immune cells by SSG or SSG/IL-2 would provide additional supporting evidence for SSG clinical evaluation in combination with IL-2. Methods: Peripheral blood of healthy and melanoma donors were treated in vitro with SSG or SSG/IL-2 and then subjected to ELISPOT assays and FACS analysis for quantification of TH1 (IFN-γ+) and TH2 (IL-5+) cells. Results: Characterization by ELISPOT assays of peripheral blood identified IFN-γ+ cells with marked increase (9.1x) following SSG/IL-2 treatment in contrast to the modest increases induced by SSG alone (2.1x) at its clinically achievable dose (20 μg/ml) or by IL-2 (3.1x) at its Cmax of low-dose schedule (30 IU/ml). SSG at an even higher dose (100 μg/ml) was less effective alone (1.5x) or in combination with IL-2 (7.8x). IL-5+ cells were not induced by the agents individually or in combination. Induction of peripheral IFN-γ+ cells by SSG/IL-2 was detectable after 4 and 16 h. Increased effectiveness of the SSG/IL-2 combination vs. the individual agents in inducing IFN-γ+ cells in vitro was detected by ELISPOT assays in the peripheral blood from 7 healthy donors and 6 melanoma patients. FACS analysis showed that the combination induced IFN-γ+ cells in the CD4+ and CD8+ lymphocytes and also increased lymphocytes expressing the activation marker CD69 in both CD4+ (2–5x) and CD4− populations (∼ 3x). Conclusion: SSG, a compound used clinically for treatment of leishmaniasis, can interact with IL-2 in vitro to activate immune cells in peripheral blood of healthy and melanoma donors. Results provide further rationale, in addition to the mouse tumor data, for proof of concept clinical trials for effecting augmentation of IL-2 through inhibition of negative regulatory signaling phosphatases.

No significant financial relationships to disclose.