Showing papers by "Sun Yat-sen University published in 2007"

The Chlamydomonas Genome Reveals the Evolution of Key Animal and Plant Functions

Abstract: Chlamydomonas reinhardtii is a unicellular green alga whose lineage diverged from land plants over 1 billion years ago. It is a model system for studying chloroplast-based photosynthesis, as well as the structure, assembly, and function of eukaryotic flagella (cilia), which were inherited from the common ancestor of plants and animals, but lost in land plants. We sequenced the approximately 120-megabase nuclear genome of Chlamydomonas and performed comparative phylogenomic analyses, identifying genes encoding uncharacterized proteins that are likely associated with the function and biogenesis of chloroplasts or eukaryotic flagella. Analyses of the Chlamydomonas genome advance our understanding of the ancestral eukaryotic cell, reveal previously unknown genes associated with photosynthetic and flagellar functions, and establish links between ciliopathy and the composition and function of flagella.

Evolutionary and biomedical insights from the rhesus macaque genome

Abstract: The rhesus macaque (Macaca mulatta) is an abundant primate species that diverged from the ancestors of Homo sapiens about 25 million years ago. Because they are genetically and physiologically similar to humans, rhesus monkeys are the most widely used nonhuman primate in basic and applied biomedical research. We determined the genome sequence of an Indian-origin Macaca mulatta female and compared the data with chimpanzees and humans to reveal the structure of ancestral primate genomes and to identify evidence for positive selection and lineage-specific expansions and contractions of gene families. A comparison of sequences from individual animals was used to investigate their underlying genetic diversity. The complete description of the macaque genome blueprint enhances the utility of this animal model for biomedical research and improves our understanding of the basic biology of the species.

Spatial and seasonal distributions of carbonaceous aerosols over China

Abstract: [1] Simultaneous measurements of atmospheric organic and elemental carbon (OC and EC) were taken during winter and summer seasons at 2003 in 14 cities in China. Daily PM2.5 samples were analyzed for OC and EC by the Interagency Monitoring of Protected Visual Environments (IMPROVE) thermal/optical reflectance protocol. Average PM2.5 OC concentrations in the 14 cities were 38.1 μg m−3 and 13.8 μg m−3 for winter and summer periods, and the corresponding EC were 9.9 μg m−3 and 3.6 μg m−3, respectively. OC and EC concentrations had summer minima and winter maxima in all the cities. Carbonaceous matter (CM), the sum of organic matter (OM = 1.6 × OC) and EC, contributed 44.2% to PM2.5 in winter and 38.8% in summer. OC was correlated with EC (R2: 0.56–0.99) in winter, but correlation coefficients were lower in summer (R2: 0.003–0.90). Using OC/EC enrichment factors, the primary OC, secondary OC and EC accounted for 47.5%, 31.7% and 20.8%, respectively, of total carbon in Chinese urban environments. More than two thirds of China's urban carbon is derived from directly emitted particles. Average OC/EC ratios ranged from 2.0 to 4.7 among 14 cities during winter and from 2.1 to 5.9 during summer. OC/EC ratios in this study were consistent with a possible cooling effect of carbonaceous aerosols over China.

Internationalization and the Performance of Born-Global SMEs: The Mediating Role of Social Networks

Abstract: This paper offers a social network explanation for the purported relationship between internationalization and firm performance in the context of born global small and medium enterprises (SMEs). We argue that home-based social networks play a mediating role in the relationship between inward and outward internationalization and firm performance. The mediating mechanism is attributed to three information benefits of social networks: (1) knowledge of foreign market opportunities; (2) advice and experiential learning; and (3) referral trust and solidarity. Using survey data from SMEs in the largest emerging economy of China, we found some support for this mediating role of social networks in the form of guanxi . The results imply that international business managers should consider social networks as an efficient means of helping internationally oriented SMEs to go international more rapidly and profitably

Solvothermal in situ metal/ligand reactions: a new bridge between coordination chemistry and organic synthetic chemistry.

Abstract: Several important solvothermal (including hydrothermal) in situ metal/ligand reactions and their mechanisms, including dehydrogenative carbon−carbon coupling, hydroxylation of aromatic rings, cycloaddition of organic nitriles with azide and ammonia, transformation of inorganic and organic sulfur, as well as the CuII to CuI reduction, are outlined in this Account. The current progress clearly demonstrates the important potential of such reactions in the crystal engineering of functional coordination compounds and one-pot synthesis of some unusual organic ligands that are inaccessible or not easily obtainable via conventional methods, thereby substantiating our expectation that a new bridge has been created between coordination chemistry and synthetic organic chemistry.

Cellular microRNAs contribute to HIV-1 latency in resting primary CD4 + T lymphocytes

Abstract: The latency of human immunodeficiency virus type 1 (HIV-1) in resting primary CD4+ T cells is the major barrier for the eradication of the virus in patients on suppressive highly active antiretroviral therapy (HAART). Even with optimal HAART treatment, replication-competent HIV-1 still exists in resting primary CD4+ T cells. Multiple restriction factors that act upon various steps of the viral life cycle could contribute to viral latency. Here we show that cellular microRNAs (miRNAs) potently inhibit HIV-1 production in resting primary CD4+ T cells. We have found that the 3' ends of HIV-1 messenger RNAs are targeted by a cluster of cellular miRNAs including miR-28, miR-125b, miR-150, miR-223 and miR-382, which are enriched in resting CD4+ T cells as compared to activated CD4+ T cells. Specific inhibitors of these miRNAs substantially counteracted their effects on the target mRNAs, measured either as HIV-1 protein translation in resting CD4+ T cells transfected with HIV-1 infectious clones, or as HIV-1 virus production from resting CD4+ T cells isolated from HIV-1-infected individuals on suppressive HAART. Our data indicate that cellular miRNAs are pivotal in HIV-1 latency and suggest that manipulation of cellular miRNAs could be a novel approach for purging the HIV-1 reservoir.

GeoChip: a comprehensive microarray for investigating biogeochemical, ecological and environmental processes

Abstract: Owing to their vast diversity and as-yet uncultivated status, detection, characterization and quantification of microorganisms in natural settings are very challenging, and linking microbial diversity to ecosystem processes and functions is even more difficult. Microarray-based genomic technology for detecting functional genes and processes has a great promise of overcoming such obstacles. Here, a novel comprehensive microarray, termed GeoChip, has been developed, containing 24 243 oligonucleotide (50 mer) probes and covering 410 000 genes in 4150 functional groups involved in nitrogen, carbon, sulfur and phosphorus cycling, metal reduction and resistance, and organic contaminant degradation. The developed GeoChip was successfully used for tracking the dynamics of metal-reducing bacteria and associated communities for an in situ bioremediation study. This is the first comprehensive microarray currently available for studying biogeochemical processes and functional activities of microbial communities important to human health, agriculture, energy, global climate change, ecosystem management, and environmental cleanup and restoration. It is particularly useful for providing direct linkages of microbial genes/populations to ecosystem processes and functions.

β-Carboline Alkaloids: Biochemical and Pharmacological Functions

Abstract: beta-Carboline alkaloids are a large group of natural and synthetic indole alkaloids with different degrees of aromaticity, some of which are widely distributed in nature, including various plants, foodstuffs, marine creatures, insects, mammalians as well as human tissues and body fluids. These compounds are of great interest due to their diverse biological activities. Particularly, these compounds have been shown to intercalate into DNA, to inhibit CDK, Topisomerase, and monoamine oxidase, and to interact with benzodiazepine receptors and 5-hydroxy serotonin receptors. Furthermore, these chemicals also demonstrated a broad spectrum of pharmacological properties including sedative, anxiolytic, hypnotic, anticonvulsant, antitumor, antiviral, antiparasitic as well as antimicrobial activities. In this review, we summerized the biochemical and pharmacological functions of beta-carboline alkaloids.

Highly Ordered Pd Nanowire Arrays as Effective Electrocatalysts for Ethanol Oxidation in Direct Alcohol Fuel Cells

Abstract: Direct alcohol fuel cells (DAFCs) based on liquid fuels have attracted enormous attention as power sources for portable electronic devices and fuel-cell vehicles owing to the much higher energy density of liquid fuels than gaseous fuels such as hydrogen (e.g., the energy densities of ethanol and methanol are 6.34 kWh L and 4.82 kWh L, respectively, as compared to 0.53 kWh L for gaseous hydrogen at 20 MPa. Among various liquid fuels, ethanol is particularly attractive because it is less toxic than methanol and can be produced in large quantities from agricultural products. Ethanol is also the major renewable biofuel from the fermentation of biomass. Pt and Pt-based catalysts such as PtRu/C have been extensively investigated as electrocatalysts for the electrooxidation of liquid fuels such as methanol and ethanol. However, the high cost and limited supply of Pt constitute a major barrier to the development of DAFCs. We studied recently Ptfree electrocatalysts for the electrooxidation reactions of ethanol and methanol, and the results revealed that Pd is a good electrocatalyst for ethanol oxidation in alkaline media. Metal nanowire arrays (NWAs) have attracted much attention and interest owing to their excellent physical and chemical properties and have been extensively investigated for applications such as high-density magnetic recording devices and sensors. Ordered nanowire or nanotube arrays have also been applied for methanol oxidation and H2O2 electrocatalytic reduction because of their high active surface area. Among various techniques to synthesize NWAs, the anodized aluminum oxide (AAO) template method is probably the simplest and most versatile approach to creating highly ordered metal NWAs with uniform and tunable porous structure and good mechanical and thermal stability. Electrodeposition has been shown to be an efficient method for the growth of uniform and continuous metallic nanowire arrays. Despite the exceptional physical, chemical, and electrical properties of metal NWAs, there is little information on the electrocatalytic properties of Pd NWAs. Here, we report the fabrication of highly ordered Pd NWA electrodes by the AAO templateelectrodeposition method, and the results show that Pd NWAs are highly active for ethanol oxidation in alkaline media, demonstrating the potential of applying Pd NWAs as effective electrocatalysts for DAFCs. Figure 1 shows typical scanning electron microscopy (SEM) images of Pd NWAs after the AAO template has been fully dissolved. The Pd nanowires (NWs) are highly ordered with uniform diameter and length. The average length and diameter of the Pd NWs are ca. 800 and ca. 80 nm, respectively. The NWs are uniform, well isolated, parallel to one another, and standing vertically to the electrode substrate surface. The hexagonal shape of the Pd NWs is due to the AAO porous structure during anodization. The X-ray diffraction (XRD) pattern (inset in Fig. 1a) indicates that the Pd NWAs exhibit a typical face-centered cubic (fcc) lattice structure. The strong diffraction peaks at 40.10°, 46.49°, and 68.08° correspond to the (111), (200), and (220) facets of Pd. This indicates that Pd NWAs have been successfully fabricated. Figure 2a shows cyclic voltammograms (CVs) of ethanol oxidation in a 1.0 M KOH + 1.0 M C2H5OH solution on a Pd film electrode (curve a, Pd loading: 1.10 mg cm), a Pd NWA electrode (curve c, Pd loading: 0.24 mg cm), and an E-TEK PtRu/C electrode (curve b, Pt loading: 0.24 mg cm). The cyclic voltammograms of the Pd film, E-TEK PtRu/C, and Pd NWA electrodes in 1.0 M KOH solution without ethanol are shown in Figure 2b. In the CVs obtained in 1.0 M KOH electrolyte solution, the anodic peaks appearing between –0.73 and –0.53 V versus Hg/HgO on Pd and –0.8 and –0.5 V versus Hg/HgO on Pt originate from the desorption of atomic hydrogen on the electrocatalysts (Fig. 2b). Thus the area of H desorption after the deduction of the double layer region on the CV curves represents the charge passed for the H desorption, QH, and is proportional to the electrochemically active area (EAA) of the electrocatalysts. The value QH = 10.6 mC cm –2 for the Pd NWA electrode is much higher than 3.4 mC cm for the Pd film electrode and 4.6 mC cm for the E-TEK PtRu/C electrode. This shows that the Pd NWA electrode has high EAA, most likely due to the well-defined and uniform porous structure of the nanowires in the arrays (Fig. 1). Such well-defined nanowire structure enhances the active sites for the electrooxidation reaction of ethanol. The high electrocatalytic activity of the Pd NWA electrode is also indicated by its superior performance for the electrooxC O M M U N IC A TI O N

Streptococcus suis: an emerging zoonotic pathogen

Abstract: Streptococcus suis is a major porcine pathogen worldwide, and can be transmitted to human beings by close contact with sick or carrier pigs. S suis causes meningitis, septicaemia, endocarditis, arthritis, and septic shock in both pigs and human beings, and mortality is high. Human infection with S suis occurs mainly among certain risk groups that have frequent exposure to pigs or pork. Outbreaks of human S suis infection are uncommon, although several outbreaks have occurred in China in recent years. In July, 2005, the largest outbreak of human S suis infection occurred in Sichuan province, China, where 204 people were infected and 38 of them died. There have been 409 cases of human S suis infection worldwide, most of which have occurred in China, Thailand, and the Netherlands, and these infections have led to 73 deaths. This review provides background information on the biology and molecular characteristics of this Gram-positive bacterium, and describes the clinical signs, pathology, epidemiology, diagnosis, and treatment of human infection with S suis.

Antibodies to Toxoplasma gondii in Patients With Schizophrenia: A Meta-Analysis

Abstract: Recent studies have linked infectious agents to schizophrenia. The largest number of studies has involved the analysis of Toxoplasma gondii; these studies were subjected to a meta-analysis. Published articles and abstracts were identified by searches of MEDLINE, Ovid, and Google Scholar; by a search of Chinese publications; through letters to researchers; and by visiting China. Published and unpublished controlled studies that used serological methods for measuring T. gondii antibodies to assess inpatients and/or outpatients diagnosed with schizophrenia were selected for analysis, and source documents were translated as needed. Forty-two studies carried out in 17 countries over 5 decades were identified; 23 of these (6 unpublished) met selection criteria. The combined odds ratio (OR) was 2.73 (95% confidence interval, 2.10 to 3.60; chi-square with 1 df 263; P < .000001). Seven studies that included only patients with first-episode schizophrenia (OR 2.54) did not differ significantly from 16 studies that included patients in all clinical phases (OR 2.79). The results suggest that individuals with schizophrenia have an increased prevalence of antibodies to T. gondii. This association is consistent with other epidemiological studies as well as with animal studies. Although the OR of 2.73 is modest, it exceeds that for genetic or other environmental factors identified to date and suggests that Toxoplasma is in some way associated with a large number of cases of schizophrenia. If an etiological association can be proven, it would have implications for the design of measures for the prevention and treatment of this disease.

Partial hepatectomy with wide versus narrow resection margin for solitary hepatocellular carcinoma: a prospective randomized trial.

Abstract: Objective:To compare the efficacy and safety of partial hepatectomy aiming grossly at a narrow (1 cm) and a wide (2 cm) resection margin in patients with macroscopically solitary hepatocellular carcinoma (HCC).Summary Background Data:For HCC treated with partial hepatectomy, the extent of the margin

Identification of Cancer Stem Cell–Like Side Population Cells in Human Nasopharyngeal Carcinoma Cell Line

Abstract: Side population (SP) cells have been isolated from several solid tumors. They lack distinct molecular markers for cancer stem cells (CSC) and increasing evidence suggests that they may play an important role in tumorigenesis and cancer therapy. However, there are no reports about the existence and function of SP cells in nasopharyngeal carcinoma (NPC) cells thus far. In this study, we scanned SP cells from five NPC cell lines and investigated stem cell characteristics, such as proliferation, self-renewal, and differentiation, using SP cells from the widely-used CNE-2 NPC cell line. We observed a strong tumorigenesis ability of SP cells following in vivo transplantation into nonobese diabetic/severe combined immunodeficient mice. Immunofluorescence revealed that cytokine 19 was highly expressed on SP cells. SP cells were found to be more resistant to chemotherapy and radiotherapy and this was related to the ATP-binding cassette half transporter member 2 of G family protein and Smoothened protein expression, respectively. Our results not only showed that SP cells in human NPC cell line CNE-2 had stem cell characteristics in vitro but also showed that they had a strong ability to form tumors in vivo. Importantly, we found the cell marker, cytokine 19, may serve as a potential molecular marker for further characterization of CSC. Taken together, our data shed light on tumorigenesis and therapeutic-resistant mechanisms, which are helpful for developing novel targets for effective clinical treatment of NPC. [Cancer Res 2007;67(8):3716–24]

Telomere lengthening early in development.

Abstract: Stem cells and cancer cells maintain telomere length mostly through telomerase. Telomerase activity is high in male germ line and stem cells, but is low or absent in mature oocytes and cleavage stage embryos, and then high again in blastocysts. How early embryos reset telomere length remains poorly understood. Here, we show that oocytes actually have shorter telomeres than somatic cells, but their telomeres lengthen remarkably during early cleavage development. Moreover, parthenogenetically activated oocytes also lengthen their telomeres, thus the capacity to elongate telomeres must reside within oocytes themselves. Notably, telomeres also elongate in the early cleavage embryos of telomerase-null mice, demonstrating that telomerase is unlikely to be responsible for the abrupt lengthening of telomeres in these cells. Coincident with telomere lengthening, extensive telomere sister-chromatid exchange (T-SCE) and colocalization of the DNA recombination proteins Rad50 and TRF1 were observed in early cleavage embryos. Both T-SCE and DNA recombination proteins decrease in blastocyst stage embryos, whereas telomerase activity increases and telomeres elongate only slowly. We suggest that telomeres lengthen during the early cleavage cycles following fertilization through a recombination-based mechanism, and that from the blastocyst stage onwards, telomerase only maintains the telomere length established by this alternative mechanism.

SDIR1 Is a RING Finger E3 Ligase That Positively Regulates Stress-Responsive Abscisic Acid Signaling in Arabidopsis

Abstract: Ubiquitination plays important roles in plant hormone signal transduction. We show that the RING finger E3 ligase, Arabidopsis thaliana SALT- AND DROUGHT-INDUCED RING FINGER1 (SDIR1), is involved in abscisic acid (ABA)-related stress signal transduction. SDIR1 is expressed in all tissues of Arabidopsis and is upregulated by drought and salt stress, but not by ABA. Plants expressing the ProSDIR1–β-glucuronidase (GUS) reporter construct confirmed strong induction of GUS expression in stomatal guard cells and leaf mesophyll cells under drought stress. The green fluorescent protein–SDIR1 fusion protein is colocalized with intracellular membranes. We demonstrate that SDIR1 is an E3 ubiquitin ligase and that the RING finger conservation region is required for its activity. Overexpression of SDIR1 leads to ABA hypersensitivity and ABA-associated phenotypes, such as salt hypersensitivity in germination, enhanced ABA-induced stomatal closing, and enhanced drought tolerance. The expression levels of a number of key ABA and stress marker genes are altered both in SDIR1 overexpression and sdir1-1 mutant plants. Cross-complementation experiments showed that the ABA-INSENSITIVE5 (ABI5), ABRE BINDING FACTOR3 (ABF3), and ABF4 genes can rescue the ABA-insensitive phenotype of the sdir1-1 mutant, whereas SDIR1 could not rescue the abi5-1 mutant. This suggests that SDIR1 acts upstream of those basic leucine zipper family genes. Our results indicate that SDIR1 is a positive regulator of ABA signaling.

Comparison of Ultrasound Elastography, Mammography, and Sonography in the Diagnosis of Solid Breast Lesions

Abstract: Objective The purpose of this study was to evaluate the value of ultrasound elastography (UE) in differentiating benign versus malignant lesions in the breast and compare it with conventional sonography and mammography. Methods From September 2004 to May 2005, 296 solid lesions from 232 consecutive patients were diagnosed as benign or malignant by mammography and sonography and further analyzed with UE. The diagnostic results were compared with histopathologic findings. The sensitivity, specificity, accuracy, positive and negative predictive values, and false-positive and -negative rates were calculated for each modality and the combination of UE and sonography. Results Of 296 lesions, 87 were histologically malignant, and 209 were benign. Ultrasound elastography was the most specific (95.7%) and had the lowest false-positive rate (4.3%) of the 3 modalities. The accuracy (88.2%) and positive predictive value (87.1%) of UE were higher than those of sonography (72.6% and 52.5%, respectively). The sensitivity values, negative predictive values, and false negative rates of the 3 modalities had no differences. A combination of UE and sonography had the best sensitivity (89.7%) and accuracy (93.9%) and the lowest false-negative rate (9.2%). The specificity (95.7%) and positive predictive value (89.7%) of the combination were better, and the false-positive rate (4.3%) of the combination was lower than those of mammography and sonography. Conclusions In a clinical trial with Chinese women, UE was superior to sonography and equal or superior to mammography in differentiating benign and malignant lesions in the breast. A combination of UE and sonography had the best results in detecting cancer and potentially could reduce unnecessary biopsy. Ultrasound elastography is a promising technique for evaluating breast lesions.

Studies on the synthesis and antibacterial activities of polymeric quaternary ammonium salts from dimethylaminoethyl methacrylate

Abstract: Four quaternary ammonium salt monomers were synthesized from dimethylaminoethyl methacrylate (DMAEMA) by quaternization with benzyl chloride (BC), butyl bromide (BB), dodecyl bromide (DB) or hexadecyl bromide (HB), respectively. And then, the monomers were homopolymerized to obtain four polymeric quaternary ammonium materials with different lengths of alkyl chain, which were referred to as poly(DMAEMA-BC), poly(DMAEMA-BB), poly(DMAEMA-DB) and poly(DMAEMA-HB), respectively. The resultant monomers and related polymers were characterized by elemental analysis, FTIR, NMR, thermogravimetric analysis (TGA) and so on. Their bactericidal activities were evaluated by determining minimum bactericidal concentration (MBC) values and inhibitory zone diameters against Gram-positive bacteria ( S. aureus ) and Gram-negative bacteria ( E. coli ), respectively. The results showed that the MBC values of monomer DMAEMA-DB and DMAEMA-HB were 12–24 μg/mL against E. coli and S. aureus . However, the MBC values of monomer DMAEMA-BC and DMAEMA-BB were higher than 50 mg/mL against test microbe. It was very interesting that poly(DMAEMA-BC) and poly(DMAEMA-BB) exhibited greater bactericidal activities than their precursory monomers, but poly(DMAEMA-DB) and poly(DMAEMA-HB) present contrary results.