Changes in proteoglycan synthesis of chondrocytes in articular cartilage are associated with the time-dependent changes in their mechanical environment

Explant loading experiments were conducted to investigate the effect of load duration on proteoglycan synthesis. A compressive load of 0.1 MPa applied for 10 min was found to stimulate proteoglycan synthesis, while the same load applied for 20 h suppressed synthesis. This bimodal response suggests that the cells are responding to different mechanical stimuli as time progresses. A theoretical model has therefore been developed to describe the mechanical environment perceived by cells within soft hydrated tissues (e.g. articular cartilage) while the tissue is being loaded. The cells are modeled, using the biphasic theory, as fluid-solid inclusions embedded in and attached to a biphasic extracellular matrix of distinct material properties. A method of solution is developed which is valid for any axisymmetric loading configuration, provided that the cell radius, a, is small relative to the tissue height, h (i.e. h/a 1). A closed-form analytical solution for this inclusion problem is then presented for the confined compression configuration. Results from this model show that the mechanical environment in and around the cells is time dependent and inhomogeneous, and can be significantly influenced by differences in properties between the cell and the extracellular matrix.     

畜禽保种－选择指数原理

根据系统保种理论有关保种和选择可以相互结合的观点,本文提出了保种－选择指数的概念、导出了适于各种资料条件和各种保种与选择目的的通用保种－选择指数公式、并探讨了该公式在几种特殊情况下的形式,为国内大量地方品种保种选育提供了必要的理论和方法。     

First experimental evidence of corals feeding on seagrass matter

We present the first experimental evidence of a coral (Oulastrea crispata) ingesting and assimilating seagrass material. Tropical seagrass meadows export a substantial portion of their productivity and can provide an important source of nutrients to neighbouring systems such as coral reefs; however, little is known about the mechanisms of this link. To investigate whether seagrass nutrient uptake via coral heterotrophy is possible, we conducted a feeding experiment with seagrass particulate and dissolved organic matter. Using gut extractions and stable isotope analyses, we determined that O. crispata ingested ¹⁵N-enriched seagrass particles and assimilated the nitrogen into its tissue at a rate of 0.75 μg N cm^?2 h^?1. Corals took up nitrogen from dissolved matter at a comparable rate of 0.98 μg N cm^?2 h^?1. While other ecological connections between seagrass meadows and reef ecosystems are well known, our results suggest a previously unstudied direct nutritional link between seagrasses and corals.     

Enhancement of in vitro growth of papaya multishoots by aeration

Efficient micropropagation of papaya (Carica papaya L.) has become crucial for multiplication of specific sex types of papaya or transgenic lines resistant to virus infection. In this study, aeration at different intervals with a 0.02 μm filter disc in the closure of culture flasks ensured exchange of gas components. The effect of aeration on development of multibuds to multishoots was investigated. Multibuds grown in culture flasks after one-week without aeration followed by a two-week aeration treatment caused a 41% increase in the number of shoots ≥0.5 cm, 42% increase in leaf expansion, and 17% increase in leaf numbers in comparison with unaerated materials. Ethylene and oxygen concentrations in the culture flasks were measured by gas chromatography and oxygen electrode at weekly intervals during the culture period. Oxygen concentrations were slightly different between aerated and unaerated culture flasks. Ethylene in the unaerated flask reached the highest level (0.11 ppm) 2 weeks after the treatment, while accumulation of ethylene in the aerated flasks was not detected. The multishoots grown for 3 weeks without aeration showed growth retardation on leaves and epinasty on petioles. This revised version was published online in June 2006 with corrections to the Cover Date.     

MicroPhenoDB Associates Metagenomic Datawith Pathogenic Microbes,Microbial Core Genes,and Human Disease Phenotypes

Microbes play important roles in human health and disease. The interaction between microbes and hosts is a reciprocal relationship, which remains largely under-explored. Current computational resources lack manually and consistently curated data to connect metagenomic data to pathogenic microbes, microbial core genes, and disease phenotypes. We developed the MicroPhenoDB database by manually curating and consistently integrating microbe-disease association data. MicroPhenoDB provides 5677 non-redundant associations between 1781 microbes and 542 human disease phenotypes across more than 22 human body sites. MicroPhenoDB also provides 696,934 relationships between 27,277 unique clade-specific core genes and 685 microbes. Disease phenotypes are classified and described using the Experimental Factor Ontology (EFO). A refined score model was developed to prioritize the associations based on evidential metrics. The sequence search option in MicroPhenoDB enables rapid identification of existing pathogenic microbes in samples without running the usual metagenomic data processing and assembly. MicroPhenoDB offers data browsing, searching, and visualization through user-friendly web interfaces and web service application programming interfaces. MicroPhenoDB is the first database platform to detail the relationships between pathogenic microbes, core genes, and disease phenotypes. It will accelerate metagenomic data analysis and assist studies in decoding microbes related to human diseases. MicroPhenoDB is available through http://www.liwzlab.cn/microphenodb and http://lilab2.sysu.edu.cn/microphenodb.