Vanadium Alkylidyne Initiated Cyclic Polymer Synthesis: The Importance of a Deprotiovanadacyclobutadiene Moiety.

Reported is the catalytic cyclic polymer synthesis by a 3d transition metal complex: a V(V) alkylidyne, [(dBDI)V≡CtBu(OEt2)] (1-OEt2), supported by the deprotonated ß-diketiminate dBDI2- (dBDI2- = ArNC(CH3)CHC(CH2)NAr, Ar = 2,6-iPr2C6H3). Complex 1-OEt2 is a precatalyst for the polymerization of phenylacetylene (PhCCH) to give cyclic poly(phenylacetylene) (c-PPA), whereas its precursor, complex [(BDI)V≡CtBu(OTf)] (2-OTf; BDI- = [ArNC(CH3)]2CH, Ar = 2,6-iPr2C6H3, OTf = OSO2CF3), and the zwitterion [((C6F5)3B-dBDI)V≡CtBu(OEt2)] (3-OEt2) exhibit low catalytic activity despite having a neopentylidyne ligand. Cyclic polymer topologies were verified by size-exclusion chromatography (SEC) and intrinsic viscosity studies. A component of the mechanism of the cyclic polymerization reaction was probed by isolation and full characterization of 4- and 6-membered metallacycles as model intermediates. Metallacyclobutadiene (MCBD) and deprotiometallacyclobutadiene (dMCBD) complexes (dBDI)V[C(tBu)C(H)C(tBu)] (4-tBu) and (BDI)V[C(tBu)CC(Mes)] (5-Mes), respectively, were synthesized upon reaction with bulkier alkynes, tBu- (tBuCCH) and Mes-acetylene (MesCCH), with 1-OEt2. Furthermore, the reaction of the conjugate acid of 1-OEt2, [(BDI)V≡CtBu(OTf)] (2-OTf), with the conjugated base of phenylacetylene, lithium phenylacetylide (LiCCPh), yields the doubly deprotio-metallacycle complex, [Li(THF)4]{(BDI)V[C(Ph)CC(tBu)CC(Ph)]} (6). Protonation of the doubly deprotio-metallacycle complex 6 yields 6-H+, a catalytically active species toward the polymerization of PhCCH, for which the polymers were also confirmed to be cyclic by SEC studies. Computational mechanistic studies complement the experimental observations and provide insight into the mechanism of cyclic polymer growth. The noninnocence of the supporting dBDI2- ligand and its role in proton shuttling to generate deprotiometallacyclobutadiene (dMCBD) complexes that proposedly culminate in the formation of catalytically active V(III) species are also discussed. This work demonstrates how a dMCBD moiety can react with terminal alkynes to form cyclic polyalkynes.

Solid pseudopapillary neoplasm: Report of a case of primary ovarian origin and review of the literature.

Background: Solid pseudopapillary neoplasms (SPNs) are uncommon tumors of low malignancy with a generally favorable prognosis, mostly originating from the pancreas. To date, 12 cases of SPNs with a primary ovarian origin (SPN-Os) have been reported globally, and their detailed characteristics have not been fully elucidated. Case description: We reported the 13th SPN-O case, which occurred in a 52-year-old woman with an 18.5 cm left ovarian mass. Four imaging methods, including ultrasound, computed tomography, magnetic resonance imaging and positron emission tomography, were utilized before surgery. An elevated level of serum cancer antigen 125 was detected and a total hysterectomy plus bilateral salpingo-oophorectomy was performed. Microscopic examination revealed a typical solid pseudopapillary structure. The tumor cells were stained focally for pan-cytokeratin, synaptophysin, CD99 and CD10, while ß-catenin, vimentin and CD56 were diffusely expressed. The Ki-67 proliferation index was 3%, and immunohistochemical (IHC) staining for chromogranin-A, inhibin-a, and E-cadherin was negative. No evidence of recurrence or metastasis was observed by clinical and imaging data during a 5-month postoperative follow-up. Conclusion: This is a report of an unusual case of a primary ovarian SPN with an up-to-date review of SPN-Os. A minimum combination of imaging methods and IHC stains was proposed for SPN-Os, which may prove beneficial in clinical practice.

Cyclic polyacetylene.

Here we demonstrate the synthesis of cyclic polyacetylene (c-PA), or [∞]annulene, via homogeneous tungsten-catalysed polymerization of acetylene. Unique to the cyclic structure and evidence for its topology, the c-PA contains >99% trans double bonds, even when synthesized at -94 °C. High activity with low catalyst loadings allows for the synthesis of temporarily soluble c-PA, thus opening the opportunity to derivatize the polymer in solution. Absolute evidence for the cyclic topology comes from atomic force microscopy images of bottlebrush derivatives generated from soluble c-PA. Now available in its cyclic form, initial characterization studies are presented to elucidate the topological differences compared with traditionally synthesized linear polyacetylene. One advantage to the synthesis of c-PA is the direct synthesis of the trans-transoid isomer. Low defect concentrations, low soliton concentration, and relatively high conjugation lengths are characteristics of c-PA. Efficient catalysis permits the rapid synthesis of lustrous flexible thin films of c-PA, and when doped with I2, they are highly conductive (398 (±76) Ω-1 cm-1).

The involvement of FoxO in cell survival and chemosensitivity mediated by Mirk/Dyrk1B in ovarian cancer.

Minibrain-related kinase (Mirk) is a serine/threonine kinase which is also known as the dual specificity tyrosine-phosphorylation-regulated kinase 1B (Dyrk1B). It is known that Dyrk1A, the closest family member to Mirk/Dyrk1B can mediate cellular localization of mammalian forkhead subclass O (FoxO1), a transcription factor, although the effect of Mirk/Dyrk1B on FoxO factors remains to be defined. In this study, we showed that Mirk/Dyrk1B protein was overexpressed in 5 of 8 ovarian cancer cell lines and negatively correlated with the protein level of FoxO factors (FoxO1+FoxO3A). Knockdown of Mirk by small interfering RNA (siRNA) resulted in cell apoptosis and sensitized cells to cisplatin accompanied by nuclear translocation of FoxO1 and/or FoxO3A as well as increased Bim, TRADD, cleaved caspase-3 and PARP. Furthermore, combined siRNAs of Mirk with FoxO1 and/or FoxO3A led to fewer apoptotic cells and cisplatin sensitivity compared to Mirk siRNA alone, suggesting that FoxO is involved in Mirk-mediated cell survival and chemosensitivity of ovarian cancer. Taken together, Mirk/Dyrk1B plays an important role in ovarian cancer cell survival through modulating FoxO translocation and may be a novel therapeutic target for ovarian cancer.

[The effect of vitamin E on renal ischemia/reperfusion injury in young and aged rats].

OBJECTIVE: To investigate the effect of vitamin E on renal ischemia/reperfusion injury (RI/RI) in young and aged rats. METHODS: The model of (RI/RI) was induced by bilateral clamping the renal artery and vein for 45 min followed by reperfusion. The contents of BUN, Scr, MDA, SOD, NO and iNOS were measured. Proteins of HSP70 were observed by immunohistochemistry. Flow cytometer was used to estimate the apoptosis rate of renal cortex cells. RESULTS: After ischemia/reperfusion injury, the contents of BUN, Scr and iNOS were increased. Compared with young ischemia/reperfusion group, the contents of MDA were higher and the contents of SOD were lower in aged ischemia/reperfusion group. The expression of HSP70, the contents of NO and the apoptosis rate of renal cortex cells were higher in aged ischemia/reperfusion group than that in control group. Vitamin E significantly decreased the contents of BUN, Scr, MDA and iNOS, and increased the contents of NO and SOD after RI/RI. The expression of HSP70 was increased in both VE groups than that in both I/R groups. The apoptosis rate of renal cortex cells was less in both VE groups than that in both I/R groups. CONCLUSION: Vitamins E may up-regulate the expression of HSP70, increase the contents of SOD and NO, and enhance an ability of clear free radicals, which may contributes to decreasing renal ischemia/reperfusion injury in young and aged rats.