Purification, sequencing and synthesis of natriuretic and vasoactive rat atrial peptide

Mammalian atria contain potent natriuretic and diuretic substances which exist in high- and low-molecular-weight forms and which appear to be associated with atrium-specific granules. The natriuretic effect of atrial extract is largely accountable for by its renal haemodynamic effects; atrial extracts also antagonize hormone- and non-hormone-induced contraction of the isolated rabbit aorta and isolated rat kidney vasculature. We have completely purified a low-molecular-weight natriuretic and vasoactive substance from rat atria and characterized it as a 24-amino acid peptide. Synthetic peptide, produced by solid-phase synthesis, mimics biological effects of crude atrial extract and purified peptide; its activity is enhanced by slow oxidation, suggesting a disulphide (Cys 4-Cys 20) configuration for the native peptide. If secreted into blood, this atrial natriuretic peptide (' auriculin B') could be a novel peptide hormone of considerable importance to renal and cardiovascular homeostasis.     

Nonlinear grassland responses to past and future atmospheric CO(2)

Carbon sequestration in soil organic matter may moderate increases in atmospheric CO(2) concentrations (C(a)) as C(a) increases to more than 500 micromol mol(-1) this century from interglacial levels of less than 200 micromol mol(-1) (refs 1 6). However, such carbon storage depends on feedbacks between plant responses to C(a) and nutrient availability. Here we present evidence that soil carbon storage and nitrogen cycling in a grassland ecosystem are much more responsive to increases in past C(a) than to those forecast for the coming century. Along a continuous gradient of 200 to 550 micromol mol(-1) (refs 9, 10), increased C(a) promoted higher photosynthetic rates and altered plant tissue chemistry. Soil carbon was lost at subambient C(a), but was unchanged at elevated C(a) where losses of old soil carbon offset increases in new carbon. Along the experimental gradient in C(a) there was a nonlinear, threefold decrease in nitrogen availability. The differences in sensitivity of carbon storage to historical and future C(a) and increased nutrient limitation suggest that the passive sequestration of carbon in soils may have been important historically, but the ability of soils to continue as sinks is limited.     

A massive phytoplankton bloom induced by an ecosystem-scale iron fertilization experiment in the equatorial Pacific Ocean

The seeding of an expanse of surface waters in the equatorial Pacific Ocean with low concentrations of dissolved iron triggered a massive phytoplankton bloom which consumed large quantities of carbon dioxide and nitrate that these microscopic plants cannot fully utilize under natural conditions. These and other observations provide unequivocal support for the hypothesis that phytoplankton growth in this oceanic region is limited by iron bioavailability.     

Function of Rieger syndrome gene in left-right asymmetry and craniofacial development.

Rieger syndrome, an autosomal dominant disorder, includes ocular, craniofacial and umbilical abnormalities. The pitx2 homeobox gene, which is mutated in Rieger syndrome, has been proposed to be the effector molecule interpreting left-right axial information from the early embryonic trunk to each organ. Here we have used gene targeting in mice to generate a loss-of-function allele that would be predicted to result in organ randomization or isomerization. Although pitx2-/- embryos had abnormal cardiac morphogenesis, mutant hearts looped in the normal direction. Pitx2-/- embryos had correctly oriented, but arrested, embryonic rotation and right pulmonary isomerism. They also had defective development of the mandibular and maxillary facial prominences, regression of the stomodeum and arrested tooth development. Fgf8 expression was absent, and Bmp4 expression was expanded in the branchial-arch ectoderm. These data reveal a critical role for pitx2 in left-right asymmetry but indicate that pitx2 may function at an intermediate step in cardiac morphogenesis and embryonic rotation.     

High resolution imaging using scanning ion conductance microscopy with improved distance feedback control

Microscopy is an essential technique for observation on living cells. There is currently great interest in applying scanning probe microscopy to image-living biological cells in their natural environment at the nanometer scale. Scanning ion conductance microscopy is a new form of scanning probe microscopy, which enables non-contact high-resolution imaging of living biological cells. Based on a scanned nanopipette in physiological buffer, the distance feedback control uses the ion current to control the distance between the pipette tip and the sample surface. However, this feedback control has difficulties over slopes on convoluted cell surfaces, which limits its resolution. In this study, we present an improved form of feedback control that removes the contribution of up to the third-order slope from the ion current signal, hence providing a more accurate signal for controlling the distance. We show that this allows faster and lower noise topographic high-resolution imaging.     

Structure of a human common cold virus and functional relationship to other picornaviruses

We report the first atomic resolution structure of an animal virus, human rhinovirus 14. It is strikingly similar to known icosahedral plant RNA viruses. Four neutralizing immunogenic regions have been identified. These, and corresponding antigenic sequences of polio and foot-and-mouth disease viruses, reside on external protrusions. A large cleft on each icosahedral face is probably the host cell receptor binding site.     

Photosynthesis genes in marine viruses yield proteins during host infection

Cyanobacteria, and the viruses (phages) that infect them, are significant contributors to the oceanic 'gene pool'. This pool is dynamic, and the transfer of genetic material between hosts and their phages probably influences the genetic and functional diversity of both. For example, photosynthesis genes of cyanobacterial origin have been found in phages that infect Prochlorococcus and Synechococcus, the numerically dominant phototrophs in ocean ecosystems. These genes include psbA, which encodes the photosystem II core reaction centre protein D1, and high-light-inducible (hli) genes. Here we show that phage psbA and hli genes are expressed during infection of Prochlorococcus and are co-transcribed with essential phage capsid genes, and that the amount of phage D1 protein increases steadily over the infective period. We also show that the expression of host photosynthesis genes declines over the course of infection and that replication of the phage genome is a function of photosynthesis. We thus propose that the phage genes are functional in photosynthesis and that they may be increasing phage fitness by supplementing the host production of these proteins.     

小叙本体在设计信息及知识管理中的应用

 随着计算机辅助设计、加工、制造等应用的迅速发展,设计相关信息与知识管理面临信息量迅猛增长的挑战与机遇。其中,本体应用成为描述设计信息与知识的一种可行、有效及丰富的建模手段。本文通过回顾本体应用于设计工程领域的相关研究,对设计工程中基于本体的应用进行了整体分类,阐明了设计工程领域中本体应用的核心学术研究问题,并为后续相关的5项研究热点及未来发展方向提出了建议。