Chemical remodelling of cell surfaces in living animals

Cell surfaces are endowed with biological functionality designed to mediate extracellular communication. The cell-surface repertoire can be expanded to include abiotic functionality through the biosynthetic introduction of unnatural sugars into cellular glycans, a process termed metabolic oligosaccharide engineering. This technique has been exploited in fundamental studies of glycan-dependent cell-cell and virus-cell interactions and also provides an avenue for the chemical remodelling of living cells. Unique chemical functional groups can be delivered to cell-surface glycans by metabolism of the corresponding unnatural precursor sugars. These functional groups can then undergo covalent reaction with exogenous agents bearing complementary functionality. The exquisite chemical selectivity required of this process is supplied by the Staudinger ligation of azides and phosphines, a reaction that has been performed on cultured cells without detriment to their physiology. Here we demonstrate that the Staudinger ligation can be executed in living animals, enabling the chemical modification of cells within their native environment. The ability to tag cell-surface glycans in vivo may enable therapeutic targeting and non-invasive imaging of changes in glycosylation during disease progression.     

江苏省常州市城市地价动态监测信息系统设计与实现

以常州市为例,介绍地价监测点的设立过程,并对城市地价动态监测信息系统的总体设计思路作具体阐述．系统运用迭代增量法,采用GIS控件MapX进行开发．该系统已在常州市国土资源局局域网上日常运行,并利用地价监测点资料自动编制常州市地价指数,用以分析、预测常州市地价变化的基本趋势,为科学管理和合理利用城市土地资源提供科学依据．     

Comparison of summer thermohaline field and circulation structure of the Bohai Sea between 1958 and 2000

TheBohaiSea(37°07′—41°N,117°35′—121°10′E)isashallowsemi-enclosedsea.SincetheBohaiSeaistheonlyinnerseaofChinaandalsoanimportantstra-tegicsea,itisoneofthemostinvestigatedseasinChina.Alargenumberofstudiesonthetideandthetidalcurrentaswellasnumericalsimulationofcirculationhavebeencarriedout,enhancingourunderstandingoftheBohaiSea.Long-termvariationsoftheseasurfacesalinity(SSS)andseasurfacetemperature(SST)oftheBohaiSeawereanalyzed.Linetal.[1]foundthatthepositivetrendsoftheannualmeanS…     

Infectious foot-and-mouth disease virus derived from a cloned full-length cDNA of OH／CHA／99

The China foot-and-mouth virus (FMDV) isolate OH/CHA/99 was isolated from swine, which was unable to infect bovine thyroid cells in vitro or to cause typical disease in bovines following intradermal inoculation in the tongue. To enhance antigenicity, replication, maturation and pathogenicity studies of OH/CHA/99, an infectious fulllength cDNA clone, designated pBIFMDV, was prepared. The in vitro and in vivo biological properties of the virus derived from pBIFMDV were studied by analyzing antigenicity, plaque morphology and virulence in pigs. The results showed that the virus derived from pBIFMDV had the same biological properties as the parent strain OH/CHA/99; the fulllength infections cDNA clone, pBIFMDV, will be very useful in studies of the antigenicity, virulence, pathogenesis, maturation and replication of FMDV.     

Isolation of human epidermal stem cells by adherence and the reconstruction of skin equivalents

The isolation of human epidermal stem cells is critical for their clinical applications. In the present study, we isolated three populations of epidermal keratinocytes according to their ability to adhere to collagen type IV: i.e., rapidly adhering (RA), slowly adhering (SA), and non-adhering (NA) cells. The aim of this study was to characterize RA cells and to investigate the possibility of using these cells for epidermis reconstruction. To identify RA cells, flow cytometric analysis was performed using anti-₆ integrin and anti-CD71 antibodies. RA cells express high levels of ₆ integrin and low levels of CD71, which are considered as markers of an epidermal stem cell nature. Furthermore, electron microscopy showed that RA cells are small and have a high nuclear to cytoplasmic ratio, whereas SA and NA cells have well-developed cellular organelles and abundant tonofilaments. Western blot analysis showed that RA cells are slow cycling and express p63, a putative epidermal stem cell marker, whereas SA and NA cells express c-Myc, which is known to regulate stem cell fate. To compare epidermal regenerative abilities, skin equivalents (SEs) were made using RA, SA, and NA cells. The epidermis constructed from RA cells was well formed compared to those formed from SA or NA cells. In addition, only SEs with RA cells expressed ₆ integrin and ₁ integrin at the basal layer. These results indicate that RA cells represent epidermal stem cells and are predominately comprised of stem cells. Therefore, the isolation of RA cells using a simple technique offers a potential route to their clinical application, because they are easily isolated and provide a high yield of epidermal stem cells.Received 2 July 2004; received after revision 20 August 2004; accepted 10 September 2004     

HAb18G/CD147-mediated calcium mobilization and hepatoma metastasis require both C-terminal and N-terminal domains

HAb18G/CD147 is a heavily glycosylated protein containing two immunoglobulin superfamily domains. Our previous studies have indicated that overexpression of HAb18G/CD147 enhances metastatic potentials in human hepatoma cells by disrupting the regulation of store-operated Ca²⁺ entry by nitric oxide (NO)/cGMP. In the present study, we investigated the structure-function of HAb18G/CD147 by transfecting truncated HAb18G/CD147 fragments into human 7721 hepatoma cells. The inhibitory effect of HAb18G/CD147 on 8-bromo-cGMP-regulated thapsigargin-induced Ca²⁺ entry was reversed by the expression of either C or N terminus truncated HAb18G/CD147 in T7721C and T7721N cells, respectively. The potential effect of HAb18G/CD147 on metastatic potentials, both adhesion and invasion capacities, of hepatoma cells was abolished in T7721C cells, but not affected in T7721N cells. Release and activation of matrix metalloproteinases (MMPs), MMP-2 and MMP-9, were found to be enhanced by the expression of HAb18G/CD147, and this effect was abolished by both truncations. Thapsigargin significantly enhanced release and activation of MMPs (MMP-2 and MMP-9) in non-transfected 7721 cells, and this effect was negatively regulated by SNAP. However, no effects of thapsigargin or SNAP were observed in T7721 cells, and expression of HAb18G/CD147 enhanced secretion and activation of MMPs at a stable and high level. Taken together, these results suggest that both ectodomain and intracellular domains of HAb18G/CD147 are required to mediate the effect of HAb18G/CD147 on the secretion and activation of MMPs and metastasis-related processes in human hepatoma cells by disrupting the regulation of NO/cGMP-sensitive intracellular Ca²⁺ mobilization although each domain may play different roles.Received 1 April 2004; received after revision 15 June 2004; accepted 22 June 2004     

Identification of swelling-activated Cl<Superscript>-</Superscript> current in rabbit cardiac Purkinje cells

The presence and functional role of the swelling-activated Cl^- current (I_Cl(swell)) in rabbit cardiac Purkinje cells was examined using patch-clamp methodology. Extracellular hypotonicity (210 or 135 mOsm) activated an outwardly rectifying, time-independent current with a reversal potential close to the calculated Cl^- equilibrium potential (E_Cl). The magnitude of this current was related to tonicity of the superfusate. The current was blocked by 0.5 mM 4,4-diisothiocyanostilbene-2,2-disulfonic acid (DIDS). These features are comparable to those of I_Cl(swell) found in sinoatrial nodal, atrial, and ventricular myocytes. I_Cl(swell) activation at 210 and 135 mOsm depolarized the resting membrane potential with 6 and 10 mV and shortened the action potential by 18 and 33%, respectively. DIDS partially reversed I_Cl(swell)-induced action potential changes. We conclude that I_Cl(swell) is present in Purkinje cells and its activation leads to action potential shortening and resting membrane potential depolarization, both of which can promote the development of reentrant arrhythmias.Received 20 January 2004; received after revision 17 February 2004; accepted 25 February 2004     

Oxygen intervention in the regulation of gene expression: the photosynthetic bacterial paradigm

The means by which oxygen intervenes in gene expression has been examined in considerable detail in the metabolically versatile bacterium Rhodobacter sphaeroides. Three regulatory systems are now known in this organism, which are used singly and in combination to modulate genes in response to changing oxygen availability. The outcome of these regulatory events is that the molecular machinery is present for the cell to obtain energy by means that are best suited to prevailing conditions, while at the same time maintaining cellular redox balance. Here, we explore the dangers associated with molecular oxygen relative to the various metabolisms used by R. sphaeroides, and then present the most recent findings regarding the features and operation of each of the three regulatory systems which collectively mediate oxygen control in this organism.Received 26 June 2003; received after revision 30 July 2003; accepted 8 August 2003     

What’s new in the renin-angiotensin system?

Activation of the type 1 angiotensin II receptor (AT(1)R) is associated with the aetiology of left ventricular hypertrophy, although the exact intracellular signalling mechanism(s) remain unclear. Transactivation of the epidermal growth factor receptor (EGFR) has emerged as a central mechanism by which the G protein-coupled AT(1)R, which lacks intrinsic tyrosine kinase activity, can stimulate the mitogen-activated protein kinase signalling pathways thought to mediate cardiac hypertrophy. Current studies support a model whereby AT(1)R-dependent transactivation of EGFRs on cardiomyocytes involves stimulation of membrane-bound metalloproteases, which in turn cleave EGFR ligands such as heparin-binding EGF from a plasma membrane-associated precursor. Numerous aspects of the 'triple membrane-passing signalling' paradigm of AT(1)R-induced EGFR transactivation remain to be characterised, including the identity of the specific metalloproteases involved, the intracellular mechanism for their activation and the exact EGFR subtypes required. Here we examine how 'hijacking' of the EGFR might explain the ability of the AT(1)R to elicit the temporally and qualitatively diverse responses characteristic of the hypertrophic phenotype, and discuss the ramifications of delineating these pathways for the development of new therapeutic strategies to combat cardiac hypertrophy.