Matrix condition mitigates the effects of habitat fragmentation on species extinction risk

Habitat loss is the leading cause of global biodiversity decline, but the influence of human pressure within the matrix surrounding habitat fragments remains poorly understood. Here we measure the relationship between fragmentation, matrix condition (measured as the extent of high human footprint levels), and the change in extinction risk of 4,327 terrestrial mammals. We find that the matrix condition and the fragmentation of habitat are strongly associated with changes in species extinction risk. Importantly, we discover that fragmentation is a stronger predictor of risk than species life-history traits, habitat loss, and habitat amount. Moreover, the importance of fragmentation increases with an increasing deterioration of the matrix condition, highlighting the critical influence matrix quality plays on the effects of fragmentation. These findings suggest that restoration measures in habitat matrices may be an important conservation action for mitigating the effects of fragmentation relative to extinction risk of terrestrial mammals.

Uniaxially fixed mechanical boundary condition elicits cellular alignment in collagen matrix with induction of osteogenesis

Osteocytes differentiated from osteoblasts play significant roles as mechanosensors in modulating the bone remodeling process. While the well-aligned osteocyte network along the trabeculae with slender cell processes perpendicular to the trabeculae surface is known to facilitate the sensing of mechanical stimuli by cells and the intracellular communication in the bone matrix, the mechanisms underlying osteocyte network formation remains unclear. Here, we developed a novel in vitro collagen matrix system exerting a uniaxially-fixed mechanical boundary condition on which mouse osteoblast-like MC3T3-E1 cells were subcultured, evoking cellular alignment along the uniaxial boundary condition. Using a myosin II inhibitor, blebbistatin, we showed that the intracellular tension via contraction of actin fibers contributed to the cellular alignment under the influence of isometric matrix condition along the uniaxially-fixed mechanical boundary condition. Furthermore, the cells actively migrated inside the collagen matrix and promoted the expression of osteoblast and osteocyte genes with their orientations aligned along the uniaxially-fixed boundary condition. Collectively, our results suggest that the intracellular tension of osteoblasts under a uniaxially-fixed mechanical boundary condition is one of the factors that determines the osteocyte alignment inside the bone matrix.

The effectivity of Difructose Anhydride III to increase absorption of calcium in the femur bone of calcium deficient rats

Background: Dried yogurt enriched by Difructose Anhydride III when used as a functional food has been observed to increase calcium absorption, making it useful in osteoporosis prevention. The objective of this study was to analyze the effectiveness of Difructose Anhydride III in increasing the absorption of calcium in female rat models, strain Sprague Dawley, in the pre-menopausal age during which they’re calcium deficient.Methods: The effectiveness test of Difructose Anhydride III to increase absorption of calcium in pre-menopausal Sprague Dawley rats was performed in calcium-deficient conditions. A completely randomized experimental design was used with 4 treatments for 6 weeks and 4 replications: normal rats fed with purified diet (C), calcium-deficient rats fed with calcium-deficient diet (CD), calcium-deficient rats fed with calcium-deficient diet and DFA III (dahlia tubers) fortified in dry yogurt (CD+DFA III dahlia), and calcium-deficient rats fed with a calcium-deficient diet and DFA III (chicory roots) fortified in dry yogurt (CD+DFA III chicory). The parameters measured were serum calcium concentration, femur bone calcium concentration, femur bone matrix condition, and femur bone strength.Results: DFA III (dahlia tubers and chicory roots) fortified in dry yogurt contained 0.334% and 0.322% of calcium concentration. The provision of a calcium-deficient diet for 12 weeks was shown to reduce the serum calcium concentration of the deficient calcium rat to 7.72±1.08 mg dL-1 and the control rat to 11.60±0.85 mg dL-1. CD+DFA III chicory treatments also showed a high calcium concentration in the femur bone (34.94±3.21%), a relatively higher bone strength (9.34±3.61 kg cm-2), and a denser femur bone matrix condition than the control. The femur bone calcium level of rats treated with CD+DFA III dahlia and chicory tubers was 28.95±1.95% and 34.94±3.21%, respectively. These results were significantly different than the CD treatment (17.49±4.38%).Conclusion: The evidence from this study suggests that sufficient calcium intake could provide high calcium deposits in the bones. Diets containing 3.60% w/w DFA III fortified in dry yogurt have been shown to enhance calcium absorption in calcium-deficient rats. Additionally, the effectiveness of dried yogurt enriched by DFA III from chicory tubers was higher than that of the dried yogurt enriched by DFA III from dahlia tubers.Preclinical Trial Registration: Animal Ethics Committee at IPB University No. 12-2013Keywords: Bone femur; calcium deficiency; effectivity of Difructose Anhydride III

On the Matrix Condition of Phylogenetic Tree

Phylogenetic comparative analyses use trees of evolutionary relationships between species to understand their evolution and ecology. A phylogenetic tree of n taxa can be algebraically transformed into an n by n squared symmetric phylogenetic covariance matrix C where each element [Formula: see text] in C represents the affinity between extant species i and extant species j. This matrix C is used internally in several comparative methods: for example, it is often inverted to compute the likelihood of the data under a model. However, if the matrix is ill-conditioned (ie, if [Formula: see text], defined by the ratio of the maximum eigenvalue of C to the minimum eigenvalue of C, is too high), this inversion may not be stable, and thus neither will be the calculation of the likelihood or parameter estimates that are based on optimizing the likelihood. We investigate this potential issue and propose several methods to attempt to remedy this issue.