6 research outputs found
Age-Related Adaptation of Bone-PDL-Tooth Complex: Rattus-Norvegicus as a Model System
Get PDFFunctional loads on an organ induce tissue adaptations by converting mechanical energy into chemical energy at a cell-level. The transducing capacity of cells alters physico-chemical properties of tissues, developing a positive feedback commonly recognized as the form-function relationship. In this study, organ and tissue adaptations were mapped in the bone-tooth complex by identifying and correlating biomolecular expressions to physico-chemical properties in rats from 1.5 to 15 months. However, future research using hard and soft chow over relevant age groups would decouple the function related effects from aging affects. Progressive curvature in the distal root with increased root resorption was observed using micro X-ray computed tomography. Resorption was correlated to the increased activity of multinucleated osteoclasts on the distal side of the molars until 6 months using tartrate resistant acid phosphatase (TRAP). Interestingly, mononucleated TRAP positive cells within PDL vasculature were observed in older rats. Higher levels of glycosaminoglycans were identified at PDL-bone and PDL-cementum entheses using alcian blue stain. Decreasing biochemical gradients from coronal to apical zones, specifically biomolecules that can induce osteogenic (biglycan) and fibrogenic (fibromodulin, decorin) phenotypes, and PDL-specific negative regulator of mineralization (asporin) were observed using immunohistochemistry. Heterogeneous distribution of Ca and P in alveolar bone, and relatively lower contents at the entheses, were observed using energy dispersive X-ray analysis. No correlation between age and microhardness of alveolar bone (0.7±0.1 to 0.9±0.2 GPa) and cementum (0.6±0.1 to 0.8±0.3 GPa) was observed using a microindenter. However, hardness of cementum and alveolar bone at any given age were significantly different (P<0.05). These observations should be taken into account as baseline parameters, during development (1.5 to 4 months), growth (4 to 10 months), followed by a senescent phase (10 to 15 months), from which deviations due to experimentally induced perturbations can be effectively investigated
The Shifting Structure of Agricultural R&D : Worldwide Investment Patterns and Payoffs
No full textThe future path and pace of agricultural productivity growth areinextricably intertwined with investments in food and agricultural research and development (R&D). Looking back over half a century of evidence, we find that the lay of the global food and agricultural R&D land is changing, with indications that we are in the midst of an historic transition. The more notable trends are as follows: (1) for the first time in modern history (in purchasing power parity, PPP, terms), the middle-income countries now outspend the rich countries in terms of public-sector investments in food and agricultural R&D; (2) the shifting public shares reflect a continuing decline in the rate of growth of food and agricultural R&D spending by the rich countries, along with a generally sustained and substantial growth in spending by the middle-income countries (especially China, India, and Brazil); (3) in PPP terms, China now spends more than the United States on both public- and private-sector food and agricultural R&D; (4) the global share of food and agricultural R&D being conducted by the private sector has increased, especially in the high- and rapidly growing middle-income countries; and (5) the low-income countries are losing ground and account for an exceptionally small share of global spending. The mean and median values of the reported rates of return to food and agricultural R&D based on the IRR are high and remain so, with no signs of a diminution in the payoffs to more recent (compared with earlier) investments in R&D. But the available evidence on the returns to food and agricultural R&D is not fully representative of the institutional (i.e., public versus private), locational, or commodity orientation of the research and the agricultural sector itself. The Shifting Structure of Agricultural R&D: Worldwide.... Available from: https://www.researchgate.net/publication/321253196_The_Shifting_Structure_of_Agricultural_RD_Worldwide_Investment_Patterns_and_Payoffs [accessed May 15 2018]
