Anisotropic pH-Responsive Hydrogels Containing Soft or Hard Rod-Like Particles Assembled Using Low Shear

A simple and versatile low-shear approach for assembling hydrogels containing aligned rod-like particles (RLPs) that are birefringent and exhibit pH-triggered anisotropic swelling is developed. Anisotropic composite hydrogels are prepared by applying low shear (0.1 s–1) to mixtures of pH-responsive nanogels (NGs) and RLPs. The NGs, which contained high methacrylic acid contents, acted as both shear transfer vehicles and macro-cross-linkers for anisotropic gel formation. Three model RLP systems are investigated: (i) soft triblock copolymer worms, (ii) stiff self-assembled β-sheet peptide fibers, and (iii) ultrahigh modulus nanocrystalline cellulose fibers. RLP alignment was confirmed using polarized light imaging, atomic force microscopy, and small-angle X-ray scattering as well as modulus and anisotropic swelling experiments. Unexpectedly, the composite gel containing the soft copolymer worms showed the most pronounced anisotropy swelling. The copolymer worms enabled higher RLP loadings than was possible for the stiffer RLPs. For fixed RLP loading, the extent of anisotropic swelling increased with intra-RLP bonding strength. The facile and versatile approach to anisotropic gel construction demonstrated herein is expected to enable new applications for strain sensing or biomaterials for soft tissue repair

Tumor Suppressor Protein p53 Recruits Human Sin3B/HDAC1 Complex for Down-Regulation of Its Target Promoters in Response to Genotoxic Stress

Master regulator protein p53, popularly known as the “guardian of genome” is the hub for regulation of diverse cellular pathways. Depending on the cell type and severity of DNA damage, p53 protein mediates cell cycle arrest or apoptosis, besides activating DNA repair, which is apparently achieved by regulation of its target genes, as well as direct interaction with other proteins. p53 is known to repress target genes via multiple mechanisms one of which is via recruitment of chromatin remodelling Sin3/HDAC1/2 complex. Sin3 proteins (Sin3A and Sin3B) regulate gene expression at the chromatin-level by serving as an anchor onto which the core Sin3/HDAC complex is assembled. The Sin3/HDAC co-repressor complex can be recruited by a large number of DNA-binding transcription factors. Sin3A has been closely linked to p53 while Sin3B is considered to be a close associate of E2Fs. The theme of this study was to establish the role of Sin3B in p53-mediated gene repression. We demonstrate a direct protein-protein interaction between human p53 and Sin3B (hSin3B). Amino acids 1–399 of hSin3B protein are involved in its interaction with N-terminal region (amino acids 1–108) of p53. Genotoxic stress induced by Adriamycin treatment increases the levels of hSin3B that is recruited to the promoters of p53-target genes (HSPA8, MAD1 and CRYZ). More importantly recruitment of hSin3B and repression of the three p53-target promoters upon Adriamycin treatment were observed only in p53+/+ cell lines. Additionally an increased tri-methylation of the H3K9 residue at the promoters of HSPA8 and CRYZ was also observed following Adriamycin treatment. The present study highlights for the first time the essential role of Sin3B as an important associate of p53 in mediating the cellular responses to stress and in the transcriptional repression of genes encoding for heat shock proteins or proteins involved in regulation of cell cycle and apoptosis

Real-time shadow casting using fake soft shadow volume

Shadows are essential to realistic and visually appealing images, but they are difficult to compute in most display environments especially in computer games. Since the introduction of shadow volume by Crow (1977), shadow map by William (1978) and then fake shadows by Blinn (1988, 1996), a lot of development has been done to improve shadow algorithm in real-time graphic application. Current issues about shadow are on real-time dynamic soft shadows and hardware improvement that improvised real- time shadow generation

The effect of hyperoxia on inflammation and platelet responses in an ex vivo extracorporeal membrane oxygenation circuit

Use of extracorporeal membrane oxygenation (ECMO) is expanding, however, it is still associated with significant morbidity and mortality. Activation of inflammatory and innate immune responses and hemostatic alterations contribute to complications. Hyperoxia may play a role in exacerbating these responses. Nine ex vivo ECMO circuits were tested using fresh healthy human whole blood, with two oxygen levels: 21% inspired fraction of oxygen (FiO(2); mild hyperoxia; n = 5) and 100% FiO(2)(severe hyperoxia; n = 4). Serial blood samples were taken for analysis of platelet aggregometry, leukocyte activation, inflammatory, and oxidative stress markers. ECMO resulted in reduced adenosine diphosphate- (P < .05) and thrombin receptor activating peptide-induced (P < .05) platelet aggregation, as well as increasing levels of the neutrophil activation marker, neutrophil elastase (P = .013). Additionally, levels of the inflammatory chemokine interleukin-8 were elevated (P < .05) and the activity of superoxide dismutase, a marker of oxidative stress, was increased (P = .002). Hyperoxia did not augment these responses, with no significant differences detected between mild and severe hyperoxia. Our ex vivo model of ECMO revealed that the circuit itself triggers a pro-inflammatory and oxidative stress response, however, exposure to supra-physiologic oxygen does not amplify that response. Extended-duration studies and inclusion of an endothelial component could be beneficial in characterizing longer term changes

Repeat Expansion Affects Both Transcription Initiation and Elongation in Friedreich Ataxia Cells*

Expansion of a GAA·TTC repeat in the first intron of the frataxin (FXN) gene causes an mRNA deficit that results in Friedreich ataxia (FRDA). The region flanking the repeat on FRDA alleles is associated with more extensive DNA methylation than is seen on normal alleles and histone modifications typical of repressed genes. However, whether these changes are responsible for the mRNA deficit is controversial. Using chromatin immunoprecipitation and cell lines from affected and unaffected individuals, we show that certain marks of active chromatin are also reduced in the promoter region of the FXN gene in patient cells. Thus, the promoter chromatin may be less permissive for transcription initiation than it is on normal alleles. Furthermore, we show that the initiating form of RNA polymerase II and histone H3 trimethylated on lysine 4, a chromatin mark tightly linked to transcription initiation, are both present at lower levels on FRDA alleles. In addition, a mark of transcription elongation, trimethylated H3K36, shows a reduced rate of accumulation downstream of the repeat. Our data thus suggest that repeat expansion reduces both transcription initiation and elongation in FRDA cells. Our findings may have implications for understanding the mechanism responsible for FRDA as well as for therapeutic approaches to reverse the transcription deficit