Human land use alters soil microbial composition and function in a variety of systems, although few comparable studies have been done in tropical forests and tropical agricultural production areas. Logging and the expansion of oil palm agriculture are two of the most significant drivers of tropical deforestation, and the latter is most prevalent in Southeast Asia. The aim of this study was to compare soil fungal communities from three sites in Malaysia that represent three of the most dominant land-use types in the Southeast Asia tropics: a primary forest, a regenerating forest that had been selectively logged 50 years previously, and a 25-year-old oil palm plantation. Soil cores were collected from three replicate plots at each site, and fungal communities were sequenced using the Illumina platform. Extracellular enzyme assays were assessed as a proxy for soil microbial function. We found that fungal communities were distinct across all sites, although fungal composition in the regenerating forest was more similar to the primary forest than either forest community was to the oil palm site. Ectomycorrhizal fungi, which are important associates of the dominant Dipterocarpaceae tree family in this region, were compositionally distinct across forests, but were nearly absent from oil palm soils. Extracellular enzyme assays indicated that the soil ecosystem in oil palm plantations experienced altered nutrient cycling dynamics, but there were few differences between regenerating and primary forest soils. Together, these results show that logging and the replacement of primary forest with oil palm plantations alter fungal community and function, although forests regenerating from logging had more similarities with primary forests in terms of fungal composition and nutrient cycling potential. Since oil palm agriculture is currently the mostly rapidly expanding equatorial crop and logging is pervasive across tropical ecosystems, these findings may have broad applicability.

Subject-specific three-dimensional finite element models of the knee joint were created and used to study the effect of the frontal plane tibiofemoral angle on the stress and strain distribution in the knee cartilage during the stance phase of the gait cycle. Knee models of three subjects with different tibiofemoral angle and body weight were created based on magnetic resonance imaging of the knee. Loading and boundary conditions were determined from motion analysis and force platform data, in conjunction with the muscle-force reduction method. During the stance phase of walking, all subjects exhibited a valgus-varus-valgus knee moment pattern with the maximum compressive load and varus knee moment occurring at approximately 25% of the stance phase of the gait cycle. Our results demonstrated that the subject with varus alignment had the largest stresses at the medial compartment of the knee compared to the subjects with normal alignment and valgus alignment, suggesting that this subject might be most susceptible to developing medial compartment osteoarthritis (OA). In addition, the magnitude of stress and strain on the lateral cartilage of the subject with valgus alignment were found to be larger compared to subjects with normal alignment and varus alignment, suggesting that this subject might be most susceptible to developing lateral compartment knee OA.

Tiopronin (N-(2-Mercaptopropionyl)glycine) protected gold nanoparticles (TPAu) were crosslinked to collagen via EDC (1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide) coupling. On average, each TPAu forms 8 amide bonds with collagen lysine moieties. The resulting gels were studied with Environmental-SEM, TEM, micro-DSC, and TNBS assay. The porous structure of collagen was significantly altered by crosslinking, resulting in the reduction of the pore size from ca. 140 μm to less than 1μm depending upon the concentration of nanoparticles. The collagenase biodegradation assay showed improved stability of crosslinked material. The cell viability assay, CellTiter 96®, indicates that the gold nanoparticles are not toxic at the concentrations used in gel synthesis. This new material has potential for the delivery of small molecule drugs, as well as Au nanoparticles for photothermal therapies, imaging, and cell targeting.

Cyanobacteria are foundational drivers of global nutrient cycling, with high intracellular iron (Fe) requirements. Fe is found at extremely low concentrations in aquatic systems, however, and the ways in which cyanobacteria take up Fe are largely unknown, especially the initial step in Fe transport across the outer membrane. Here, we identified one TonB protein and four TonB-dependent transporters (TBDTs) of the energy-requiring Fe acquisition system and six porins of the passive diffusion Fe uptake system in the model cyanobacterium sp. strain PCC 6803. The results experimentally demonstrated that TBDTs not only participated in organic ferri-siderophore uptake but also in inorganic free Fe (Fe') acquisition.Fe uptake rate measurements showed that a TBDT quadruple mutant acquired Fe at a lower rate than the wild type and lost nearly all ability to take up ferri-siderophores, indicating that TBDTs are critical for siderophore uptake. However, the mutant retained the ability to take up Fe' at 42% of the wild-type Fe' uptake rate, suggesting additional pathways of Fe' acquisition besides TBDTs, likely by porins. Mutations in four of the six porin-encoding genes produced a low-Fe-sensitive phenotype, while a mutation in all six genes was lethal to cell survival. These diverse outer membrane Fe uptake pathways reflect cyanobacterial evolution and adaptation under a range of Fe regimes across aquatic systems. Cyanobacteria are globally important primary producers and contribute about 25% of global CO fixation. Low Fe bioavailability in surface waters is thought to limit the primary productivity in as much as 40% of the global ocean. The Fe acquisition strategies that cyanobacteria have evolved to overcome Fe deficiency remain poorly characterized. We experimentally characterized the key players and the cooperative work mode of two Fe uptake pathways, including an active uptake pathway and a passive diffusion pathway in the model cyanobacterium sp. PCC 6803. Our finding proved that cyanobacteria use ferri-siderophore transporters to take up Fe', and they shed light on the adaptive mechanisms of cyanobacteria to cope with widespread Fe deficiency across aquatic environments.

A robust protocol for building subject-specific biomechanical models of the human knee joint is proposed which uses magnetic resonance imaging, motion analysis and force platform data in conjunction with detailed 3D finite element models. The proposed protocol can be used for determining stress and strain distributions and contact kinetics in different knee elements at different body postures during various physical activities. Several examples are provided to highlight the capabilities and potential applications of the proposed protocol. This includes preliminary results on the role of body weight on the stresses and strains induced in the knee articular cartilages and meniscus during single-leg stance and calculations of the induced stresses and ligament forces during the gait cycle.

Bone formation requires the coordinated activity of numerous proteins including the transcription factor core-binding factor ␣1 (Cbfa1). Deregulation of Cbfa1 results in metabolic bone diseases including osteoporosis and osteopetrosis. The retinoblastoma protein (pRb) that is required for osteogenesis binds Cbfa1. We reported earlier that the p200 family protein p204, which is known to be involved in the differentiation of skeletal muscle myotubes, cardiac myocytes, and macrophages, also serves as a cofactor of Cbfa1 and promotes osteogenesis. In this study we established that suppression of p204 expression by an adenovirus construct encoding p204 antisense RNA inhibited osteoblast-specific gene activation by Cbfa1 in an osteogenesis assay involving the pluripotent C2C12 mesenchymal cell line. Using protein-protein interaction assays we established that Cbfa1, pRb, and p204 form a ternary complex in which pRb serves as a linker connecting p204 and Cbfa1. Chromatin immunoprecipitation assays revealed the binding of such a p204-pRbCbfa1 transcription factor complex to the promoter of the osteocalcin gene. The pRb requirement of the stimulation of Cbfa1 activity by p204 was established in experiments involving p204 mutants lacking one or two pRb binding (LXCXE) motifs. Such mutants failed to enhance the Cbfa1-dependent transactivation of gene expression as well as osteogenesis. Furthermore, as revealed in reporter gene and in vitro osteogenesis assays p204 synergized with pRb in the stimulation of Cbfa1-dependent gene activation and osteoblast differentiation.

Abnormal tibiofemoral alignment can create loading conditions at the knee that may lead to the initiation and progression of knee osteoarthritis (OA). The degenerative changes of the articular cartilage may occur earlier and with greater severity in individuals with abnormal frontal plane tibiofemoral alignment who undergo a partial or total meniscectomy. In this investigation, subject specific 3D finite element knee models were created from magnetic resonance images of two female subjects to study the combined effect of frontal plane tibiofemoral alignment and total and partial meniscectomy on the stress and strain at the knee cartilage. Different amounts of medial and lateral meniscectomies were modeled and subject specific loading conditions were determined from motion analysis and force platform data during single-leg support. The results showed that the maximum stresses and strains occurred on the medial tibial cartilage after medial meniscectomy but a greater percentage change in the contact stresses and strains occurred in the lateral cartilage after lateral meniscectomy for both subjects due to the resultant greater load bearing role of the lateral meniscus. The results indicate that individual's frontal plane knee alignment and their unique local force distribution between the cartilage and meniscus play an important role in the biomechanical effects of total and partial meniscectomy.

Id proteins play important roles in osteogenic differentiation; however, the molecular mechanism remains unknown. In this study, we established that inhibitor of differentiation (Id) proteins, including Id1, Id2, and Id3, associate with core binding factor ␣-1 (Cbfa1) to cause diminished transcription of the alkaline phosphatase (ALP) and osteocalcin (OCL) gene, leading to less ALP activity and osteocalcin (OCL) production. Id acts by inhibiting the sequence-specific binding of Cbfa1 to DNA and by decreasing the expression of Cbfa1 in cells undergoing osteogenic differentiation. p204, an interferon-inducible protein that interacts with both Cbfa1 and Id2, overcame the Id2-mediated inhibition of Cbfa1-induced ALP activity and OCL production. We show that 1) p204 disturbed the binding of Id2 to Cbfa1 and enabled Cbfa1 to bind to the promoters of its target genes and 2) that p204 promoted the translocation from nucleus to the cytoplasm and accelerated the degradation of Id2 by ubiquitin-proteasome pathway during osteogenesis. Nucleus export signal (NES) of p204 is required for the p204-enhanced cytoplasmic translocation and degradation of Id2, because a p204 mutant lacking NES lost these activities. Together, Cbfa1, p204, and Id proteins form a regulatory circuit and act in concert to regulate osteoblast differentiation. INTRODUCTIONThe differentiation of uncommitted mesenchymal cells to osteoblasts is a fundamental process in embryonic development and bone repair. The bone morphogenetic proteins (BMPs) are important regulators of this process (Heldin et al., 1997;Miyazono et al., 2000). They function by binding cell surface receptors; signaling by Smad proteins; and activating bone-specific genes, including core binding factor ␣-1 (Cbfa1) (Ducy, 2000;Miyazono et al., 2001;Attisano and Wrana, 2002). This process is positively or negatively regulated by a variety of coactivators and corepressors (Ducy et al., 2000;Miyazono et al., 2001;Attisano and Wrana, 2002). Cbfa1, also known as Runx2, PeBP2␣A, Osf2, or AML3, is a member of the runt family of transcription factors. It is an essential transcription factor of osteoblast and bone formation (Ducy, 2000). During skeletal development, Cbfa1 is observed first in early mesenchymal condensations, and it is then principally expressed in osteoblasts . Cbfa1 Ϫ/Ϫ mice exhibit a complete lack of ossification, and they die immediately after birth (Komori et al., 1997). Cbfa1 maintains osteoblastic function by regulating the expression of several bone-specific genes such as osteopontin and osteocalcin and by controlling bone extracellular matrix deposition (Ducy, 2000). Mutations in Cbfa1 are found in 65-80% of individuals with cleidocranial dysplasia (CCD) (Lee et al., 1997;Mundlos and Olsen, 1997;Zhou et al., 1999). The molecular mechanisms underlying the pathogenesis of CCD are not completely defined. Some mutations of Cbfa1 abolish its DNA binding activity (Lee et al., 1997;Zhou et al., 1999) and others disturb the association of Cbfa1 to its binding partners, including Sma...