Bioactive glass sol-gel foam scaffolds:evolution of nanoporosity during processing and in situ monitoring of apatite layer formation using small- and wide-angle X-ray scattering

Recent work has highlighted the potential of sol-gel-derived calcium silicate glasses for the regeneration or replacement of damaged bone tissue. The work presented herein provides new insight into the processing of bioactive calcia-silica sol-gel foams, and the reaction mechanisms associated with them when immersed in vitro in a simulated body fluid (SBF). Small-angle X-ray scattering and wide-angle X-ray scattering (diffraction) have been used to study the stabilization of these foams via heat treatment, with analogous in situ time-resolved data being gathered for a foam immersed in SBF. During thermal processing, pore sizes have been identified in the range of 16.5-62.0 nm and are only present once foams have been heated to 400 degrees C and above. Calcium nitrate crystallites were present until foams were heated to 600 degrees C; the crystallite size varied from 75 to 145 nm and increased in size with heat treatment up to 300 degrees C, then decreased in size down to 95 rim at 400 degrees C. The in situ time-resolved data show that the average pore diameter decreases as a function of immersion time in SBF, as calcium phosphates grow on the glass surfaces. Over the same time, Bragg peaks indicative of tricalcium phosphate were evident after only 1-h immersion time, and later, hydroxycarbonate apatite was also seen. The hydroxycarbonate apatite appears to have preferred orientation in the (h,k,0) direction.

Identification of the HLA-DM/HLA-DR interface

Human leukocyte antigen (HLA)-DM is a critical participant in antigen presentation that catalyzes the dissociation of the Class II-associated Invariant chain-derived Peptide (CLIP) from the major histocompatibility complex (MHC) Class II molecules. There is competition amongst peptides for access to an MHC Class II groove and it has been hypothesised that DM functions as a 'peptide editor' that catalyzes the replacement of one peptide for another within the groove. It is established that the DM catalyst interacts directly with the MHC Class II but the precise location of the interface is unknown. Here, we combine previously described mutational data with molecular docking and energy minimisation simulations to identify a putative interaction site of >4000A2 which agrees with known point mutational data for both the DR and DM molecule. The docked structure is validated by comparison with experimental data and previously determined properties of protein-protein interfaces. A possible dissociation mechanism is suggested by the presence of an acidic cluster near the N terminus of the bound peptide.

Decellularization of bovine corneas for tissue engineering applications

Scaffolds derived from processed tissues offer viable alternatives to synthetic polymers as biological scaffolds for regenerative medicine. Tissue-derived scaffolds provide an extracellular matrix (ECM) as the starting material for wound healing and the functional reconstruction of tissues, offering a potentially valuable approach for the replacement of damaged or missing tissues. Additionally, acellular tissue may provide a natural microenvironment for host-cell migration and the induction of stem cell differentiation to contribute to tissue regeneration. There are a number of processing methods that aim to stabilize and provide an immunologically inert tissue scaffold. Furthermore, these tissue-processing methods can often be applied to xenogenic transplants because the essential components of the ECM are often maintained between species. In this study, we applied several tissue-processing protocols to the cornea in order to obtain a decellularized cornea matrix that maintained the clarity and mechanical properties of the native tissue. Histology, mechanical testing and electron microscopy techniques were used to assess the cell extraction process and the organization of the remaining ECM. In vitro cell seeding experiments confirmed the processed corneas’ biocompatibility.

Pharmacokinetics of melatonin in preterm infants

Aims - Preterm infants are deprived of the normal intra-uterine exposure to maternal melatonin and may benefit from replacement therapy. We conducted a pharmacokinetic study to guide potential therapeutic trials. Methods - Melatonin was administered to 18 preterm infants in doses ranging from 0.04–0.6 μg kg−1 over 0.5–6 h. Pharmacokinetic profiles were analyzed individually and by population methods. Results - Baseline melatonin was largely undetectable. Infants receiving melatonin at 0.1 μg kg−1 h−1 for 2 h showed a median half-life of 15.82 h and median maximum plasma concentration of 203.3 pg ml−1. On population pharmacokinetics, clearance was 0.045 l h−1, volume of distribution 1.098 l and elimination half-life 16.91 h with gender (P = 0.047) and race (P < 0.0001) as significant covariates. Conclusions - A 2 h infusion of 0.1 μg kg−1 h−1 increased blood melatonin from undetectable to approximately peak adult concentrations. Slow clearance makes replacement of a typical maternal circadian rhythm problematic. The pharmacokinetic profile of melatonin in preterm infants differs from that of adults so dosage of melatonin for preterm infants cannot be extrapolated from adult studies. Data from this study can be used to guide therapeutic clinical trials of melatonin in preterm infants.

Structure of dysprosium and holmium phosphate glasses by the method of isomorphic substitution in neutron diffraction

The relative distribution of rare-earth ions R3+ (Dy3+ or Ho3+) in the phosphate glass RAl0.30P3.05O9.62 was measured by employing the method of isomorphic substitution in neutron diffraction and, by taking the role of Al into explicit account, a self-consistent model of the glass structure was developed. The glass network is found to be made from corner sharing PO4 tetrahedra in which there are, on average, 2.32(9) terminal oxygen atoms, OT, at 1.50(1) Å and 1.68(9) bridging oxygen atoms, OB, at 1.60(1) Å. The network modifying R3+ ions bind to an average of 6.7(1) OT and are distributed such that 7.9(7) R–R nearest neighbours reside at 5.62(6) Å. The Al3+ ion also has a network modifying role in which it helps to strengthen the glass through the formation of OT–Al–OT linkages. The connectivity of the R-centred coordination polyhedra in (M2O3)x(P2O5)1−x glasses, where M3+ denotes a network modifying cation (R3+ or Al3+), is quantified in terms of a parameter fs. Methods for reducing the clustering of rare-earth ions in these materials are then discussed, based on a reduction of fs via the replacement of R3+ by Al3+ at fixed total modifier content or via a change of x to increase the number of OT available per network modifying M3+ cation.

Lys9 for Glu9 substitution in glucagon-like peptide-1(7-36)amide confers dipeptidylpeptidase IV resistance with cellular and metabolic actions similar to those of established antagonists glucagon-like peptide-1(9-36)amide and exendin (9-39)

The incretin hormone glucagon-like peptide-1(7-36)amide (GLP-1) has been deemed of considerable importance in the regulation of blood glucose. Its effects, mediated through the regulation of insulin, glucagon, and somatostatin, are glucose-dependent and contribute to the tight control of glucose levels. Much enthusiasm has been assigned to a possible role of GLP-1 in the treatment of type 2 diabetes. GLIP-l's action unfortunately is limited through enzymatic inactivation caused by dipeptidylpeptidase IV (DPP IV). It is now well established that modifying GLP-1 at the N-terminal amino acids, His7 and Ala8, can greatly improve resistance to this enzyme. Little research has assessed what effect Glu9-substitution has on GLP-1 activity and its degradation by DPP IV. Here, we report that the replacement of Glu9 of GLP-1 with Lys dramatically increased resistance to DPP IV. This analogue (Lys9)GLP-1, exhibited a preserved GLP-1 receptor affinity, but the usual stimulatory effects of GLP-1 were completely eliminated, a trait duplicated by the other established GLP-1-antagonists, exendin (9-39) and GLP-1 (9-36)amide. We investigated the in vivo antagonistic actions of (Lys9)GLP-1 in comparison with GLP-1(9-36)amide and exendin (9-39) and revealed that this novel analogue may serve as a functional antagonist of the GLP-1 receptor.

Nutritional management of blood glucose levels

Background and Objectives: Nutritional management of blood glucose levels is a strategic target in the prevention and management of type 2 diabetes mellitus (T2DM), applicable across the population. To implement a successful strategy it is essential to understand the impact of dietary modulation on the postprandial rise in blood glucose concentrations. Methods: Using the highest quality data, a systematic and comprehensive literature review was undertaken. Included in this review were the major macronutrients (carbohydrate, pro-tein, fat), micronutrient vitamins and minerals, non-nutrient phytochemicals and additional foods such as low-calorie sweeteners, vinegar and alcohol. Results: The strongest corroboration of efficacy for improving glucose homeostasis was for insoluble and moderately fermentable cereal-based fiber and mono-unsaturated fatty acids as replacement of saturated fat. Postprandial glycaemia was decreased by intake of viscous soluble fiber and the predominant mechanism of action was considered to be by delaying absorption of co-ingested carbohydrates. There was weaker but substantial evidence that certain phytochemical-rich foods were likely to be effective. This may be associated with the su-ggestion that the gut microbiota plays an important role in me-tabolic regulation, which includes provision of phytochemical and other metabolites. Conclusions: Based on the evidence, it is clear that dietary components have significant and clinically relevant effects on blood glucose modulation. This suggests that employing a dietary regimen to attenuate the postprandial rise in blood glucose levels along with previously identified targets (reducing excess body weight and an increase in physical activity) will benefit the health of the population and limit the increasing worldwide incidence of T2D.

Using an in vitro human airway model to study the toxic effects of components of e-cigarettes

Cigarette smoke is a complex mixture of more than 4000 hazardous chemicals including the carcinogenic benzopyrenes. Nicotine, the most potent component of tobacco, is responsible for the addictive nature of cigarettes and is a major component of e-cigarette cartridges. Our study aims to investigate the toxicity of nicotine with special emphasis on the replacement of animals. Furthermore, we intend to study the effect of nicotine, cigarette smoke and e-cigarette vapours on human airways. In our current work, the BEAS 2B human bronchial epithelial cell line was used to analyse the effect of nicotine in isolation, on cell viability. Concentrations of nicotine from 1.1µM to 75µM were added to 5x105 cells per well in a 96 well plate and incubated for 24 hours. Cell titre blue results showed that all the nicotine treated cells were more metabolically active than the control wells (cells alone). These data indicate that, under these conditions, nicotine does not affect cell viability and in fact, suggests that there is a stimulatory effect of nicotine on metabolism. We are now furthering this finding by investigating the pro-inflammatory response of these cells to nicotine by measuring cytokine secretion via ELISA. Further work includes analysing nicotine exposure at different time points and on other epithelial cells lines like Calu-3.