Tissue engineering a ligamentous construct

Tendon and ligament damage causes extreme pain and decreased joint functionality. Current repair methods cannot restore original joint biomechanics nor promote regeneration of native tissue. Recent advances in tendon and ligament repair have involved engineering tissue using cell-seeded scaffolds. Self-aligned cellular structures, similar to those in ligaments and tendons, have been successfully formed, albeit with weak attachment between construct and bone. Calcium phosphates form an intimate bond with both soft and hard tissues and have successfully been used in tissue engineering bone, whilst hydrogels have often been used as cellular scaffolds. This thesis explores agarose, gelatin, carrageenan and fibrin hydrogels as potential soft tissue scaffolds. Fibrin gel exhibited high cellular compatibility with highest metabolic activity on day 14. Although the cellular gel contracted significantly, it was found that the dry weight remained stable in both the acellular and cellular forms. 3D powder printed calcium phosphate scaffolds remained structurally stable after immersion in cell culture media with immersion in protein-rich sera promoting tenocyte attachment. Bracket designs were developed to enhance grip of the cell-seeded fibrin. Ligament constructs were selfsupporting and exhibited structural characteristics similar to native connective tissue. Tenocyte density peaked on day 14, with added L-proline and ascorbic acid inducing a constant level of glycosaminoglycans and 7.4 ± 1.5 % w/w collagen. This research may significantly enhance the clinical application of tissue engineered ligaments and tendons

3D bioprinting for tissue engineering: Stem cells in hydrogels

Surgical limitations require alternative methods of repairing and replacing diseased and damaged tissue. Regenerative medicine is a growing area of research with engineered tissues already being used successfully in patients. However, the demand for such tissues greatly outweighs the supply and a fast and accurate method of production is still required. 3D bioprinting offers precision control as well as the ability to incorporate biological cues and cells directly into the material as it is being fabricated. Having precise control over scaffold morphology and chemistry is a significant step towards controlling cellular behaviour, particularly where undifferentiated cells, i.e., stem cells, are used. This level of control in the early stages of tissue development is crucial in building more complex systems that morphologically and functionally mimic in vivo tissue. Here we review 3D printing hydrogel materials for tissue engineering purposes and the incorporation of cells within them. Hydrogels are ideal materials for cell culture. They are structurally similar to native extracellular matrix, have a high nutrient retention capacity, allow cells to migrate and can be formed under mild conditions. The techniques used to produce these materials, as well as their benefits and limitations, are outlined

Zero Flow Global Ischemia-Induced Injuries in Rat Heart Are Attenuated by Natural Honey

Purpose: In the present study, effects of preischemic administration of natural honey on cardiac arrhythmias and myocardial infarction size during zero flow global ischemia were investigated in isolated rat heart. Methods:The isolated hearts were subjected to 30 min zero flow global ischemia followed by 120 min reperfusion then perfused by a modified drug free Krebs-Henseleit solution throughout the experiment (control) or the solution containing 0.25, 0.5, 1 and 2% of natural honey for 15 min before induction of global ischemia (treated groups), respectively. Cardiac arrhythmias were determined based on the Lambeth conventions and the infarct size was measured by computerized planimetry. Results: Myocardial infarction size was 55.8±7.8% in the control group, while preischemic perfusion of honey (0.25, 0.5, 1 and 2%) reduced it to 39.3±11, 30.6±5.5 (P<0.01), 17.9±5.6 (P<0.001) and 8.7±1.1% (P<0.001), respectively. A direct linear correlation between honey concentrations and infarction size reduction was observed (R2=0.9948). In addition, total number of ventricular ectopic beats were significantly decreased by all used concentrations of honey (P<0.05) during reperfusion time. Honey (0.25, 0.5 and 1 %) also lowered incidence of irreversible ventricular fibrillation (P<0.05). Moreover, number and duration of ventricular tachycardia were reduced in all honey treated groups. Conclusion: Preischemic administration of natural honey before zero flow global ischemia can protect isolated rat heart against ischemia/reperfusion injuries as reduction of infarction size and arrhythmias. Maybe, antioxidant and free radical scavenging activities of honey, reduction of necrotized tissue and providing energy sources may involve in these cardioprotective effects of honey

To What Extent is the Motivation of Western Teachers Understood by School Leaders in a Boys' Elementary School in Saudi Arabia?

This dissertation investigates the motivation of Western teachers in the Saudi Arabian education system. Qualitative data collection methods are used to understand the different realities experienced by teachers and leaders. The transformative aspect to this project recognises the stark power inequality between Western teachers and school leaders in Saudi Arabia. Documentary evidence, reflective journal entries, group and individual interviews, as well as questionnaires are all used to understand the state and management of teacher motivation in a Riyadh school. The results indicate that the only way school leaders effectively motivated teachers in the school studied, was through the provision of material rewards. A top-down culture of compliance and a lack of autonomy for teachers were serious demotivators, as was the lack of professional development (PD) provided without caveats. It is argued that the school would benefit by moving away from the unsustainable model of motivating teachers with material rewards. It is recommended that school leaders ought to involve and inspire teachers with a vision and boost intrinsic motivation by developing autonomous teachers. To raise morale, performance and motivation, the prevailing top-down culture should be reformed into a more democratic one, where teachers reciprocate the trust shown in them by leaders

Genetic parameters and correlations of related feed efficiency, growth, and carcass traits in Hanwoo beef cattle

[EN] Objective: This study aimed to estimate the genetic parameters and genetic correlations for related feed efficiency, growth, and carcass traits in Hanwoo cattle. Methods: Phenotypic data from 15,279 animals born between 1989 and 2015 were con & shy; sidered. The related feed efficiency traits considered were Kleiber ratio (KR) and relative growth rate (RGR). Carcass traits analyzed were backfat thickness (BT), carcass weight, eye muscle area, and marbling score. Growth traits were assessed by the average daily gain (ADG), metabolic body weight (MBW) at mid & shy;test age from 6 to 24 months, and yearling weight (YW). Variance and covariance components were estimated using res & shy; tricted maximum likelihood using nine multi & shy;trait animal models. Results: The heritability estimates for related feed efficiency (0.28 +/- 0.04 for KR and RGR) and growth traits (0.26 +/- 0.02 to 0.33 +/- 0.04) were moderate, but the carcass traits tended to be higher (0.38 +/- 0.04 to 0.61 +/- 0.06). The related feed efficiency traits were positively gene & shy; tically correlated with all the carcass traits (0.37 +/- 0.09 to 0.47 +/- 0.07 for KR, and 0.14 +/- 0.09 to 0.37 +/- 0.09 for RGR), except for BT, which showed null to weak correlation. Conversely, the genetic correlations of RGR with MBW (-0.36 +/- 0.08) and YW (-0.30 +/- 0.08) were negative, and those of KR with MBW and YW were close to zero, whereas the genetic correlations of ADG with RGR (0.40 +/- 0.08) and KR (0.70 +/- 0.05) were positive and relatively moderate to high. The genetic (0.92 +/- 0.02) correlations between KR and RGR were very high. Conclusion: Sufficient genetic variability and heritability were observed for traits of interest. Moreover, the inclusion of KR and/or RGR in Hanwoo cattle breeding programs could improve the feed efficiency without producing any unfavorable effects on the carcass traits.We are grateful to all the staff of the Korean Hanwoo Improvement Center of the National Agricultural Cooperative Federation for supplying the Hanwoo cattle data. This study was supported by grants from the IPET Program (No. 20093068) , Ministry of Agriculture, Food and Rural Affairs, Republic of Korea, and Hankyong National UniversityMehrban, H.; Naserkheil, M.; Lee, DH.; Ibáñez-Escriche, N. (2021). Genetic parameters and correlations of related feed efficiency, growth, and carcass traits in Hanwoo beef cattle. Animal Bioscience (Online). 34(5):824-832. https://doi.org/10.5713/ajas.20.0135S82483234

Chemistry of Platinum and Palladium Metal Complexes in Homogeneous and Heterogeneous Catalysis: A Mini Review

Transition metal complexes of platinum and palladium are most widely used in catalysis. Many synthetic reactions have been carried out with such complexes (used as a catalyst) which have specifically polymer ligands, through hydrosilylation, acetoxylation, hydrogenation, hydro-formylation, oligo-merisation and polymerization. Almost many platinum and palladium catalysts are heterogeneous in nature i.e. the reaction taking place on a solid surface. Now from few years homogeneous catalysts which are completely soluble in the liquid phase reactant, has acknowledged too much attention, yet having small industrial applications, mainly due to the striving of platinum and palladium complexes separation from the catalytic products. More recently a transitional type of platinum and palladium catalysts have been synthesized through attachment of the activated transition metal complexes on the surface of polymer support particularly insoluble which has been establish to offe

Active screen plasma nitriding enhances cell attachment to polymer surfaces

Active screen plasma nitriding (ASPN) is a well-established technique used for the surface modification of materials, the result of which is often a product with enhanced functional performance. Here we report the modification of the chemical and mechanical properties of ultra-high molecular weight poly(ethylene) (UHMWPE) using 80:20 (v/v) N2/H2 ASPN, followed by growth of 3T3 fibroblasts on the treated and untreated polymer surfaces. ASPN-treated UHMWPE showed extensive fibroblast attachment within 3 h of seeding, whereas fibroblasts did not successfully attach to untreated UHMWPE. Fibroblast coated surfaces were maintained for up to 28 days, monitoring their metabolic activity and morphology throughout. The chemical properties of the ASPN-treated UHMWPE surface were studied using X-ray photoelectron spectroscopy, revealing the presence of C N, C N, and C N chemical bonds. The elastic modulus, surface topography, and adhesion properties of the ASPN-treated UHMWPE surface were studied over 28 days during sample storage under ambient conditions and during immersion in two commonly used cell culture media