Fossils, fish and tropical forests: prehistoric human adaptations on the island frontiers of Oceania.

Oceania is a key region for studying human dispersals, adaptations and interactions with other hominin populations. Although archaeological evidence now reveals occupation of the region by approximately 65-45 000 years ago, its human fossil record, which has the best potential to provide direct insights into ecological adaptations and population relationships, has remained much more elusive. Here, we apply radiocarbon dating and stable isotope approaches to the earliest human remains so far excavated on the islands of Near and Remote Oceania to explore the chronology and diets of the first preserved human individuals to step across these Pacific frontiers. We demonstrate that the oldest human (or indeed hominin) fossil outside of the mainland New Guinea-Aru area dates to approximately 11 800 years ago. Furthermore, although these early sea-faring populations have been associated with a specialized coastal adaptation, we show that Late Pleistocene-Holocene humans living on islands in the Bismarck Archipelago and in Vanuatu display a persistent reliance on interior tropical forest resources. We argue that local tropical habitats, rather than purely coasts or, later, arriving domesticates, should be emphasized in discussions of human diets and cultural practices from the onset of our species' arrival in this part of the world. This article is part of the theme issue 'Tropical forests in the deep human past'.

Intracellular calcite and sulfur dynamics of Achromatium cells observed in a lab-based enrichment and aerobic incubation experiment.

We investigated the intracellular dynamics of calcite and sulfur in the large sulfur-oxidizing, calcite-accumulating bacterium Achromatium, with an emphasis on oxygen exposure as a physiological control. For this purpose, morphological changes and possible accretion mechanisms of calcite granules in cells that were freshly collected from natural Achromatium-containing sediment were compared to cells from the same source after prolonged exposure to atmospheric oxygen. Intracellular sulfur is oxidized and removed in response to oxygen exposure. Calcite granules also undergo distinct oxygen-related dynamics; they alternate between tightly packaged, smooth granules with narrow but sharply defined interstitial spaces in atmospheric oxygen-exposed cells, and more loosely packaged granules with irregular, bumpy surface texture and larger interstitial spaces in cells that were not artificially exposed to oxygen. These results suggest that morphological changes of the calcite granules reflect their changing physiological role inside the cell. Sulfur oxidation and calcite dissolution appear to be linked in that proton generation during sulfur oxidation is buffered by gradual calcite erosion, visible in the smooth, rounded surface morphology observed after oxygen exposure. Our results support the hypothesis that calcite dynamics buffer the intracellular pH fluctuations linked to electron acceptor limitation during proton-consuming sulfide oxidation to sulfur, and electron acceptor abundance during proton-generating sulfur oxidation to sulfate.

Synergistic pathogenicity of Porphyromonas gingivalis and Fusobacterium nucleatum in the mouse subcutaneous chamber model.

Porphyromonas gingivalis and Fusobacterium nucleatum are often coisolated from sites of infection, such as suppurative apical periodontitis. The synergistic pathogenicity of mixed infection of P. gingivalis HG 405 with F. nucleatum PK 1594 was studied in the mouse subcutaneous chamber model in groups of seven animals. The minimal dose for P. gingivalis HG 405 that was required to infect 100% of the chambers was reduced by 1,000-fold when animals were inoculated in the same chamber with 1 x 10(9)F. nucleatum PK 1594 (p < 0.001). To benefit from the presence of the fusobacteria, P. gingivalis HG 405 had to be coinoculated; inoculation in separate chambers for the same animal had no such effect (p < 0.001). Subinfective F. nucleatum inocula also benefited from the association with P. gingivalis HG 405 and uniformly established an infection when this partner was present (p < 0.001). These results suggest that the frequent and natural coexistence of P. gingivalis and F. nucleatum in diseased sites may express such a synergism in successful establishment and survival of small inocula.

The effect of hydrofluoric acid treatment of TiO2 grit blasted titanium implants on adherent osteoblast gene expression in vitro and in vivo.

It is widely accepted that implant surface factors affect the quality of the bone-to-implant interface. Recent additional treatments superimposed on moderately rough cpTitanium surface provide further enhancement of bone-to-implant contact. The aim of this study was to compare osteoinductive and bone-specific gene expression in cells adherent to titanium dioxide-grit blasted (TiO2) versus TiO2 grit blasted and HF treated (TiO2/HF) cpTitanium implant surfaces. MC3T3-E1 cells were grown in osteogenic supplements on the titanium disk surfaces for 1-14 days. Real-time PCR was used to measure RUNX-2, Osterix, and bone sialoprotein (BSP) mRNA levels. Implants were placed in rat tibia and, following harvesting at 1-7 days after placement, real-time PCR was used to measure RUNX-2, alkaline phosphatase (ALP), and BSP mRNA levels in implant adherent cells. In cell culture, RUNX-2 and Osterix levels were significantly increased (p<0.05) on the TiO2/HF surfaces as compared to the TiO2 and smooth surfaces through the cultural period, while BSP expression was elevated on both TiO2 and TiO2/HF surfaces when compared to a machined surface control. In cells adherent to implants retrieved from rat tibia, RUNX-2 mRNA levels were 2-fold and 8-fold greater on the TiO2/HF surfaces at 1-3 and 7 days following implantation. This was paralleled by significantly greater levels of ALP at 3 and 7 days and BSP mRNA at 7 days following implantation. As a marker of osteoinduction, the increased levels of RUNX-2 in cells adherent to the TiO2/HF surfaces suggest that the additional HF treatment of the TiO2 grit blasted surface results in surface properties that support adherent cell osteoinduction. In vivo assessments of implant adherent cell phenotypes provide further insight into the mechanisms affecting alloplast-tissue interactions.

The use of flowable composites as filled adhesives.

OBJECTIVE: The effect of filled adhesives on bonding resin composites to dentin has not been fully understood. Due to their filler content, filled adhesives may act as stress breakers. The aim of this in vitro study was to evaluate the use of flowable composites of different viscosities on bonding to enamel and dentin without the use of an intermediate bonding resin. MATERIALS AND METHODS: Enamel and dentin bond strengths of OptiBond FL, Syntac Classic, and EBS Multi combined either with their proprietary bonding agent or a flowable resin composite (Ultraseal XT Plus or Revolution) were measured. The tests were carried out with a microtensile device at a crosshead speed of 1mm/min after 24h of storage at 37 degrees C in water. Mean bond strengths were analyzed using the Wilcoxon test and multiple comparisons according to the Mann-Whitney U-test. The micro-morphology of corresponding resin-dentin interfaces of the same teeth were analyzed using SEM and TEM. RESULTS: The control groups with adhesive systems used as per manufacturers' protocol showed bond strengths of 38.9-41.1 MPa to enamel and 28.8-33.4 MPa to dentin. With respect to bond strength to etched enamel, only Ultraseal XT Plus as bonding resin reached the level of the control groups. When used as bonding agents on dentin, both flowable composites produced lower microtensile bond strengths to etched and primed dentin than did the control groups. Micro-morphological analysis using SEM and TEM resulted in hybrid layer formation for both control and experimental groups. However, many areas of the resin-dentin interface showed insufficient penetration of the flowable composites at the top of the hybrid layer as well as numerous tubules obstructed by filler particles. CONCLUSIONS: The flowable composites tested in this study should not be used to replace bonding agents. Flowable composites of thinner viscosity, such as Ultraseal XT Plus, may bond to enamel adequately without the requirement of an intermediate bonding resin.