Highly Robust Nickel Catalysts Containing Anilinonaphthoquinone Ligand for Copolymerization of Ethylene and Polar Monomers

Copolymerizations of ethylene with polar monomers such as 5-hexene-1-yl acetate and allyl acetate are explored using nickel complexes bearing a class of anilino­naphthoquinone ligands. High tolerability of this complex toward polar comonomer is achieved by the installation of sterically bulky substituent on the aniline ligand. Moreover, the heterogenization of the nickel complexes using silica-supported modified methylaluminoxane enhances the copolymerization performances. The catalyst is highly active and thermally stabile to give semicrystalline ester-functionalized high molecular weight polyethylenes

α-MSH inhibited the up-regulation of <i>Foxo4</i> in the retina of diabetic rats.

<p>The relative expression of <i>Foxo1</i>, <i>Foxo3</i>, <i>Foxo4</i>, and <i>Foxo6</i> at the transcript level in the diabetic and normal retinas were examined by real-time RT-PCR and normalized to those of <i>GAPDH</i>. The expression of <i>Foxo4</i>, but not the other <i>Foxo</i> genes, was significantly up-regulated in diabetic retinas compared with the normal controls, and α-MSH treatments inhibited the up-regulation. n = 5–7/group, * p<0.05, ** p<0.01.</p

<i>Foxo4</i> overexpression abrogated anti-apoptotic effects of α-MSH in retinal vascular endothelial cells.

<p>Following various treatments, the cell groups were stained with Alexa 488-annexin V and analyzed by flow cytometry. The dot plot (A) shows the gate selection based on the forward scatter (abscissa) and side scatter (ordinate) of the RF/6A cells, so that the dead cells and cell debris were excluded. The histograms (B) are representative images of the flow cytometry analyses. The abscissa and ordinate represent the fluorescence intensity of Alexa 488-annexin V and cell counts, respectively. The distribution of the non-stained RF/6A cells cultured under the complete culture media was included as a negative control (red line) and used to set the marker M1. The distributions of the treated and stained cells are also shown (black line). The cell populations inside M1 were considered positive for Alexa 488-annexin V staining. The number above M1 indicates the percentage of the cells positive for the Alexa 488-annexin V staining in each representative picture. The Alexa 488-annexin V staining positivity in each treatment group was compared in (C). n = 6/group, ** p<0.01, *** p<0.001.</p

Intravitreal injections of α-MSH corrected aberrant gene expression in the diabetic retina.

<p>The relative mRNA expression levels of <i>eNOS</i> (A), <i>iNOS</i> (B), <i>nNOS</i> (C), <i>ICAM-1</i> (D), and <i>TNF-α</i> (E) in the retinal samples were examined by real-time RT-PCR and normalized to those of <i>GAPDH</i>. n = 5–7/group, * p<0.05, ** p<0.01, *** p<0.001.</p

<i>Foxo4</i> overexpression abolished anti-oxidative effects of α-MSH in retinal vascular endothelial cells.

<p>In the CM-H2DCFDA assay, the fluorescence intensities of cell groups was measured and cell images were captured under a fluorescence microscope. Representative images are shown in (A). The fluorescence intensity was normalized to the total protein concentration of each sample (B). n = 5–10/group, * p<0.05, ** p<0.01, *** p<0.001.</p

Intravitreal injections of α-MSH normalized the ROS levels and the total anti-oxidative abilities in early diabetic retinas.

<p>The levels of H₂O₂ (A) and ROS (B), and the total anti-oxidative abilities (C) were measured and normalized to total protein concentrations in the retina samples from experimental groups. n = 5–10/group, * p<0.05, ** p<0.01.</p

PCR Primers used in this study.

<p>PCR Primers used in this study.</p

α-MSH inhibited <i>Foxo4</i> up-regulation in retinal vascular endothelial cells.

<p>The RF/6A cells, a monkey retinal microvessel endothelial cell line, were treated with HG (25 mM) alone or with different concentrations of α-MSH 30 min before and during the HG stimulation. Eight hours following treatment, HG stimulation induced a reduced cell viability that was moderately but significantly boosted by α-MSH at 0.1 μM (A). Then, the cells were exposed to 25 mM HG for 8 h, the mRNA level of <i>Foxo4</i>, but not <i>Foxo1</i> and <i>3</i>, was significantly up-regulated, and this up-regulation was inhibited by incubating the cells with 0.1 μM α-MSH 30 min before and during HG stimulation (B). n = 6/group, * p<0.05, ** p<0.01, *** p<0.001.</p

α-MSH significantly reduced the number of apoptotic cells in the neuroretina of diabetic rats.

<p>Retinal cryosections were subjected to TUNEL staining. The merged images of TUNEL staining and DAPI counterstaining are shown in (A). The positive and negative controls for TUNEL staining are shown in the upper panel of (A). Representative images for normal, DM and α-MSH+DM groups are shown in the lower panel of (A). The apoptotic cells are indicated by white arrows. The estimated representation of the number of apoptotic cells per section is shown in (B). n = 5–6/group, *** p<0.001. Scale bar, 50 μm.</p

α-MSH administration substantially reduced the number of apoptotic cells in the trypsin-digested diabetic retina preparation.

<p>TUNEL staining images were merged with those of DAPI counterstaining. The positive and negative controls for TUNEL staining are shown in (A). The TUNEL staining images of normal control (normal), diabetes (DM), and diabetes with α-MSH intervention (α-MSH+DM) are shown in (B); the insets are the amplified portion of the images for better visualization. n = 8/group, scale bar, 20 μm.</p