Bioactive composites for bone tissue engineering

One of the major challenges of bone tissue engineering is the production of a suitable scaffold material. In this review the current composite materials options available are considered covering both the methods of both production and assessing the scaffolds. A range of production routes have been investigated ranging from the use of porogens to produce the porosity through to controlled deposition methods. The testing regimes have included mechanical testing of the materials produced through to in vivo testing of the scaffolds. While the ideal scaffold material has not yet been produced, progress is being made

Germline mutations of the STK11 gene in Korean Peutz–Jeghers syndrome patients

Peutz–Jeghers syndrome (PJS) is an autosomal dominantly inherited disease characterized by hamartomatous gastrointestinal polyps and mucocutaneous pigmentation, with an increased risk for various neoplasms, including gastrointestinal cancer. Recently, the PJS gene encoding the serine/threonine kinase STK11 (also named LKB1) was mapped to chromosome 19p13.3, and germline mutations were identified in PJS patients. We screened a total of ten Korean PJS patients (nine sporadic cases and one familial case including two patients) to investigate the germline mutations of the STK11 gene. By polymerase chain reaction–single-strand conformation polymorphism and DNA sequencing analysis, three kinds of mis-sense mutation and a frame-shift mutation were identified: codon 232 (TCC to CCC) in exon 5, codon 256 (GAA to GCA) in exon 6, codon 324 (CCG to CTG) in exon 8, and a guanine insertion at codon 342 resulting in a premature stop codon in exon 8. These mis-sense variants were not detected in 100 control DNA samples. Furthermore, we found an intronic mutation at the dinucleotide sequence of a splice-acceptor site: a one base substitution from AG to CG in intron 1, which may cause aberrant splicing. Most reported germline mutations of the STK11 gene in PJS patients were frame-shift or non-sense mutations resulting in truncated proteins. Together, these findings indicate that germline mis-sense mutations of the STK11 gene are found in PJS patients in addition to truncating mutations. The effects of these mutations on protein function require further examination. In summary, we found germline mutations of the STK11 gene in five out of ten Korean PJS patients. © 2000 Cancer Research Campaig

Elastic properties and apparent density of human edentulous maxilla and mandible

The aim of this study aim was to determine whether elastic properties and apparent density of bone differ in different anatomical regions of the maxilla and mandible. Additional analyses assessed how elastic properties and apparent density were related. Four pairs of edentulous maxilla and mandibles were retrieved from fresh human cadavers. Bone samples from four anatomical regions (maxillary anterior, maxillary posterior, mandibular anterior, mandibular posterior) were obtained. Elastic modulus (EM) and hardness (H) were measured using the nano-indentation technique. Bone samples containing cortical and trabecular bone were used to measure composite apparent density (cAD) using Archimedes’ principle. Statistical analyses used repeated measures ANOVA and Pearson correlations. Bone physical properties differed between regions of the maxilla and mandible. Generally, mandible had higher physical property measurements than maxilla. EM and H were higher in posterior than in anterior regions; the reverse was true for cAD. Posterior maxillary cAD was significantly lower than that in the three other regions

Band gap opening by two-dimensional manifestation of Peierls instability in graphene

Using first-principles calculations of graphene having high-symmetry distortion or defects, we investigate band gap opening by chiral symmetry breaking, or intervalley mixing, in graphene and show an intuitive picture of understanding the gap opening in terms of local bonding and antibonding hybridizations. We identify that the gap opening by chiral symmetry breaking in honeycomb lattices is an ideal two-dimensional (2D) extension of the Peierls metal-insulator transition in 1D linear lattices. We show that the spontaneous Kekule distortion, a 2D version of the Peierls distortion, takes place in biaxially strained graphene, leading to structural failure. We also show that the gap opening in graphene antidots and armchair nanoribbons, which has been attributed usually to quantum confinement effects, can be understood with the chiral symmetry breaking

Bioethanol Production from Ulva pertusa Kjellman by High-temperature Liquefaction

This work was investigated to improve hydrolysis yields of macro alga, Ulva pertusa Kjellman by high-temperature liquefaction process (HTLP). We hydrolyzed this alga to produce bioethanol. U. pertusa Kjellman contains approximately w = 32 % glucose, comprising w = 6 % cellulose and 20 % starch, along with w = 5.9 % xylose. Among 32 % of total carbohydrates, ca. 26 % of glucose was hydrolyzed from starch (20 %) and cellulose (6 %), respectively, which tells that a more efficient process might be considered to completely hydrolyze the polymers containing fermentable sugars such as glucose and galctose, etc. Optimal hydrolysis conditions for the high-temperature liquefaction process (HTLP) were determined to be 15 MPa and 150 °C for 15 min, with water as the solvent. We found that the process temperature and time were the most important factors in the operation. Under these conditions, the conversion yields of glucose and xylose were 9.08 and 21.14 %, respectively. After cellulase and amyloglucosidase treatment, 61.1 % glucose (based on w = 32.1 %, dry basis) was converted into glucose without further conversion into xylose. The present process provided 3.1 to 12.6 % higher overall hydrolysis yields from U. pertusa Kjellman than those from other agricultural biomass. The HTLP process generated only about 40 mg L–1 of HMF (5-hydroxymethylfurfural). This concentration was much less than those from other pretreatment processes and resulted in approximately 90 % of the maximum theoretical ethanol yield. In addition, the hydrolysis pattern of U. pertusa Kjellman was much different from those of agricultural biomass materials due to different starch compositions and polymer structures

Differential Maternal Feeding Practices, Eating Self-Regulation, and Adiposity in Young Twins

Restrictive feeding is associated with childhood obesity; however, this could be due to other factors that drive children to overeat and parents to restrict (eg, child genetics). Using a twin design to better control for confounders, we tested differences in restrictive feeding within families in relation to differences in twins’ self-regulatory eating and weight status

CRISPR-Cas9 interrogation of a putative fetal globin repressor in human erythroid cells

Sickle Cell Disease and beta-thalassemia, which are caused by defective or deficient adult beta-globin (HBB) respectively, are the most common serious genetic blood diseases in the world. Persistent expression of the fetal beta-like globin, also known gamma-globin, can ameliorate both disorders by serving in place of the adult beta-globin as a part of the fetal hemoglobin tetramer (HbF). Here we use CRISPR-Cas9 gene editing to explore a potential gamma-globin silencer region upstream of the delta-globin gene identified by comparison of naturally-occurring deletion mutations associated with up-regulated gamma-globin. We find that deletion of a 1.7 kb consensus element or select 350 bp sub-regions from bulk populations of cells increases levels of HbF. Screening of individual sgRNAs in one sub-region revealed three single guides that caused increases gamma-globin expression. Deletion of the 1.7 kb region in HUDEP-2 clonal sublines, and in colonies derived from CD34+ hematopoietic stem/progenitor cells (HSPCs), does not cause significant up-regulation of gamma-globin. These data suggest that the 1.7 kb region is not an autonomous gamma-globin silencer, and thus by itself is not a suitable therapeutic target for gene editing treatment of beta-hemoglobinopathies.Peer reviewe

Investigation of MC1R SNPs and Their Relationships with Plumage Colors in Korean Native Chicken

The melanocortin 1 receptor (MC1R) gene is related to the plumage color variations in chicken. Initially, the MC1R gene from 30 individuals was sequenced and nine polymorphisms were obtained. Of these, three and six single nucleotide polymorphisms (SNPs) were confirmed as synonymous and nonsynonymous mutations, respectively. Among these, three selected SNPs were genotyped using the restriction fragment length polymorphism (RFLP) method in 150 individuals from five chicken breeds, which identified the plumage color responding alleles. The neighbor-joining phylogenetic tree using MC1R gene sequences indicated three well-differentiated different plumage pigmentations (eumelanin, pheomelanin and albino). Also, the genotype analyses indicated that the TT, AA and GG genotypes corresponded to the eumelanin, pheomelanin and albino plumage pigmentations at nucleotide positions 69, 376 and 427, respectively. In contrast, high allele frequencies with T, A and G alleles corresponded to black, red/yellow and white plumage color in 69, 376 and 427 nucleotide positions, respectively. Also, amino acids changes at position Asn23Asn, Val126Ile and Thr143Ala were observed in melanin synthesis with identified possible alleles, respectively. In addition, high haplotype frequencies in TGA, CGG and CAA haplotypes were well discriminated based on the plumage pigmentation in chicken breeds. The results obtained in this study can be used for designing proper breeding and conservation strategies for the Korean native chicken breeds, as well as for the developing breed identification markers in chicken

Spectrum of confining strings in SU(N) gauge theories

We study the spectrum of the confining strings in four-dimensional SU(N) gauge theories. We compute, for the SU(4) and SU(6) gauge theories formulated on a lattice, the string tensions sigma_k related to sources with Z_N charge k, using Monte Carlo simulations. Our results are consistent with the sine formula sigma_k/sigma = sin k pi/N / sin pi/N for the ratio between sigma_k and the standard string tension sigma. For the SU(4) and SU(6) cases the accuracy is approximately 1% and 2%, respectively. The sine formula is known to emerge in various realizations of supersymmetric SU(N) gauge theories. On the other hand, our results show deviations from Casimir scaling. We also discuss an analogous behavior exhibited by two-dimensional SU(N) x SU(N) chiral models.Comment: Latex, 34 pages, 10 figures. Results of new SU(4) simulations added. The new data are included in the analysis, leading to improved final estimates for SU(4). Conclusions unchange