Increase of a Caribbean leatherback turtle Dermochelys coriacea nesting population linked to long-term nest protection

The leatherback turtle Dermochelys coriacea is considered to be at serious risk of global extinction, despite ongoing conservation efforts. Intensive long-term monitoring of a leatherback nesting population on Sandy Point (St. Croix, US Virgin Islands) offers a unique opportunity to quantify basic population parameters and evaluate effectiveness of nesting beach conservation practices. We report a significant increase in the number of females nesting annually from ca. 18-30 in the 1980s to 186 in 2001, with a corresponding increase in annual hatchling production from ca. 2000 to over 49,000. We then analyzed resighting data from 1991 to 2001 with an open robust-design capture-mark-recapture model to estimate annual nester survival and adult abundance for this population. The expected annual survival probability was estimated at ca. 0.893 (95% CL 0.87-0.92) and the population was estimated to be increasing ca. 13% pa since the early 1990s. Taken together with DNA fingerprinting that identify mother-daughter relations, our findings suggest that the increase in the size of the nesting population since 1991 was probably due to an aggressive program of beach protection and egg relocation initiated more than 20 years ago. Beach protection and egg relocation provide a simple and effective conservation strategy for this Northern Caribbean nesting population as long as adult survival at sea remains relatively high. (c) 2005 Elsevier Ltd. All rights reserved.

Long-term loading inhibits ERK1/2 phosphorylation and increases FGFR3 expression in MC3T3-E1 osteoblast cells

Bone tissue homeostasis relies upon the ability of cells to detect and interpret extracellular signals that direct changes in tissue architecture. This study utilized a four-point bending model to create both fluid shear and strain forces (loading) during the time-dependent progression of MC3T3-E1 preosteoblasts along the osteogenic lineage. Loading was shown to increase cell number, alkaline phosphatase (ALP) activity, collagen synthesis, and the mRNA expression levels of Runx2, osteocalcin (OC), osteopontin, and cyclo-oxygenase-2. However, mineralization in these cultures was inhibited, despite an increase in calcium accumulation, suggesting that loading may inhibit mineralization in order to increase matrix deposition. Loading also increased fibroblast growth factor receptor-3 (FGFR3) expression coincident with an inhibition of FGFR1, FGFR4, FGF1, and extracellular signal-related kinase (ERK)1/2 phosphorylation. To examine whether these loading-induced changes in cell phenotype and FGFR expression could be attributed to the inhibition of ERK1/2 phosphorylation, cells were grown for 25 days in the presence of the MEK1/2 inhibitor, U0126. Significant increases in the expression of FGFR3, ALP, and OC were observed, as well as the inhibition of FGFR1, FGFR4, and FGF1. However, U0126 also increased matrix mineralization, demonstrating that inhibition of ERK1/2 phosphorylation cannot fully account for the changes observed in response to loading. in conclusion, this study demonstrates that preosteoblasts are mechanoresponsive, and that long-term loading, whilst increasing proliferation and differentiation of preosteoblasts, inhibits matrix mineralization. In addition, the increase in FGFR3 expression suggests that it may have a role in osteoblast differentiation.