Functional Relationship between Skull Form and Feeding Mechanics in Sphenodon, and Implications for Diapsid Skull Development

The vertebrate skull evolved to protect the brain and sense organs, but with the appearance of jaws and associated forces there was a remarkable structural diversification. This suggests that the evolution of skull form may be linked to these forces, but an important area of debate is whether bone in the skull is minimised with respect to these forces, or whether skulls are mechanically “over-designed” and constrained by phylogeny and development. Mechanical analysis of diapsid reptile skulls could shed light on this longstanding debate. Compared to those of mammals, the skulls of many extant and extinct diapsids comprise an open framework of fenestrae (window-like openings) separated by bony struts (e.g., lizards, tuatara, dinosaurs and crocodiles), a cranial form thought to be strongly linked to feeding forces. We investigated this link by utilising the powerful engineering approach of multibody dynamics analysis to predict the physiological forces acting on the skull of the diapsid reptile Sphenodon. We then ran a series of structural finite element analyses to assess the correlation between bone strain and skull form. With comprehensive loading we found that the distribution of peak von Mises strains was particularly uniform throughout the skull, although specific regions were dominated by tensile strains while others were dominated by compressive strains. Our analyses suggest that the frame-like skulls of diapsid reptiles are probably optimally formed (mechanically ideal: sufficient strength with the minimal amount of bone) with respect to functional forces; they are efficient in terms of having minimal bone volume, minimal weight, and also minimal energy demands in maintenance

The impact of natural resource use on bird and reptile communities within multiple-use protected areas: evidence from sub-arid southern Madagascar

Multiple-use protected areas, in which sustainable levels of extractive livelihood activities are permitted, play an increasingly important role in the global protected area estate, and are expected to rise in prevalence. However, we know little about their effectiveness at conserving biodiversity. We surveyed bird and reptile communities in three areas across a forest disturbance gradient resulting from charcoal production and shifting cultivation within a multiple-use protected area in Madagascar’s sub-arid spiny forest. We scored individual species using a Conservation Value Index (CVI; a simple metric based on rarity, threat and distinctiveness), and estimated the total conservation value of each treatment by calculating the sum of frequency-weighted CVI scores across all present species. Bird and reptile community responses to forest disturbance were idiosyncratic. Bird richness was greatest in the moderate-disturbance treatment, but the low-disturbance treatment had the superior conservation value due to higher frequencies of locally-endemic species. Reptile richness was the same in low- and moderate-disturbance treatments, but the conservation value of the latter was greater. The high-disturbance areas had lowest richness and conservation value for both groups. For birds, increasing disturbance levels were accompanied by community turnover from high-value to low-value species, a pattern highlighted by CVI that is masked by assessing species richness alone. Although some endemic species appear to be resilient to degradation, multiple-use protected areas in Madagascar may lose biodiversity since most endemic species are forest-dependent. Stricter protected area models may be more appropriate in areas where much of the high-value biodiversity is sensitive to habitat degradation

A comparison of mandibular and maxillary alveolar osteogenesis over six weeks: a radiological examination

INTRODUCTION : Insufficient information exists on comparing radiological differences in bone density of the regeneration rate in the alveolar bone of the maxilla and mandible following the creation of similar defects in both. METHODS : Alveolar bone defects were created from five healthy Chacma baboons. Standardized x-ray images were acquired over time and the densities of the selected defect areas were measured pre-operatively, directly post-operatively and at three- and six weeks post-operatively. Differences in densities were statistically tested using ANOVA. RESULTS : The maxilla was significantly more radiologically dense (p = 0.026) than the mandible pre- operatively. No differences were obtained between the maxilla and mandible directly postoperatively and three- and six weeks post-operatively respectively; i.e. densities were not significantly different at the different time points after the defects had been created (three weeks: t = 1.08, p = 0.30; six weeks: t = 1.35, p = 0.19; three to six weeks: t = 1.20, p =0.25). The increase in density in the mandible was 106% (8.9±7.6%/time versus 4.3 ± 2.7%/time) over three weeks, 28% (15.0 ± 8.1%/time versus 11.7 ± 8.0%/time) over six weeks and 56% (12.5 ± 9.7%/time versus 8.0 ± 6.9%/time) over three-to-six weeks and was higher than in the maxilla over the same intervals. CONCLUSIONS : Radiological examination with its standardized gray-scale analysis can be used to determine the difference in bone density of the maxilla and mandible. Although not statistically significant, the mandible healed at a faster rate than the maxilla, especially observed during the first three weeks after the defects were created.http://www.head-face-med.com/hb201

Tumour-targeted delivery of TRAIL using Salmonella typhimurium enhances breast cancer survival in mice

BACKGROUND: An effective cancer therapeutic must selectively target tumours with minimal systemic toxicity. Expression of a cytotoxic protein using Salmonella typhimurium would enable spatial and temporal control of delivery because these bacteria preferentially target tumours over normal tissue. METHODS: We engineered non-pathogenic S. typhimurium to secrete murine TNF-related apoptosis-inducing ligand (TRAIL) under the control of the prokaryotic radiation-inducible RecA promoter. The response of the RecA promoter to radiation was measured using fluorometry and immunoblotting. TRAIL toxicity was determined using flow cytometry and by measuring caspase-3 activation. A syngeneic murine tumour model was used to determine bacterial accumulation and the response to expressed TRAIL. RESULTS: After irradiation, engineered S. typhimurium secreted TRAIL, which caused caspase-3-mediated apoptosis and death in 4T1 mammary carcinoma cells in culture. Systemic injection of Salmonella and induction of TRAIL expression using 2 Gy γ-irradiation caused a significant delay in mammary tumour growth and reduced the risk of death by 76% when compared with irradiated controls. Repeated dosing with TRAIL-bearing Salmonella in conjunction with radiation improved the 30-day survival from 0 to 100%. CONCLUSION: These results show the pre-clinical utility of S. typhimurium as a TRAIL expression vector that effectively reduces tumour growth and extends host survival