Phytoplankton succession during a red tide of Skeletonema costatum in Jiaozhou Bay of China.
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China↗
Biomedical subjects
Jun Sun
Publications and source records attributed to Jun Sun.
CDw75 is a significant histopathological marker for gastric carcinoma.
AIM: To study the expression of CDw75 in patients with gastric carcinoma and to correlate CDw75 expression with progression of the tumor. METHODS: Immunohistochemical method was used to examine the expression of CDw75 in 72 cases of the gastric carcinoma and adjacent normal gastric mucosa, and the percentage of the cells positively stained with CDw75 was calculated using a computer-aided microscopic image analysis system. RESULTS: CDw75 was not expressed in normal gastric mucosa but detected in 37 of the 72 neoplastic gastric lesions. The expression of CDw75 was associated with the tumor progression as indicated by its close correlation with the depth of the tumor infiltration (chi(2)=18.415, P<0.01), TNM stage (chi(2)=10.419, P<0.05) and lymph node metastasis (chi(2)=6.675, P<0.01). The overall survival rate of the patients with positive CDw75 expression (32.4%) was significantly lower than that of the patients without CDw75 expression (71.4%) (P<0.01). There was no significant correlation between the expression of CDw75 and the sex and age and histological type of patients (P>0.05). CONCLUSION: These findings suggest that the expression of CDw75 is a significant histopathological marker for more advanced stage of gastric carcinoma and indicates a poor prognosis for the patients.
Adult↗
Allosteric control of ligand selectivity between estrogen receptors alpha and beta: implications for other nuclear receptors.
Allosteric communication between interacting molecules is fundamental to signal transduction and many other cellular processes. To better understand the relationship between nuclear receptor (NR) ligand positioning and the formation of the coactivator binding pocket, we investigated the determinants of ligand selectivity between the two estrogen receptor subtypes ERalpha and ERbeta. Chimeric receptors and structurally guided amino acid substitutions were used to demonstrate that distinct "hot spot" amino acids are required for ligand selectivity. Residues within the ligand binding pocket as well as distal secondary structural interactions contribute to subtype-specific positioning of the ligand and transcriptional output. Examination of other NRs suggests a mechanism of communication between the ligand and coactivator binding pockets, accounting for partial agonist and dimer-specific activity. These results demonstrate the importance of long-range interactions in the transmission of information through the ligand binding domain as well as in determining the ligand selectivity of closely related NR receptor subtypes.
Allosteric Regulation↗
Bacterial activation of beta-catenin signaling in human epithelia.
The mucosal lining of the human intestine is constantly bathed in a milieu of commensal gut flora, the vast majority of these being nonpathogenic microorganisms. Here, we demonstrate that microbial-epithelial cell interactions not only affect proinflammatory pathways but also influence beta-catenin signaling, a key component in regulating epithelial cell proliferation. The nonpathogenic Salmonella strain PhoP(c) activates the beta-catenin signaling pathway of human epithelia via a blockade of beta-catenin degradation. Normal beta-catenin ubiquitination necessary for constitutive beta-catenin degradation is abolished, allowing the accumulation and translocation of beta-catenin to the nucleus. Transcriptional activation mediated by the beta-catenin/T cell factor complex increases c-myc expression and enhances cell proliferation. We also show that the Salmonella effector protein AvrA is involved in modulating this beta-catenin activation. These data suggest that nonvirulent bacterial-epithelial interactions can influence beta-catenin signaling and cell growth control in a manner previously unsuspected.
Animals↗
Effects of a collective spin resonance mode on the scanning tunneling microscopy spectra of d-wave superconductors.
A high-energy spin resonance mode is known to exist in many high-temperature superconductors. Motivated by recent scanning tunneling microscopy experiments in superconducting Bi(2)Sr(2)CaCu(2)O(8+delta), we study the effects of this resonance mode on the local density of states (LDOS). The coupling between the electrons in a d-wave superconductor and the resonance mode produces high-energy peaks in the LDOS, which displays a two-unit-cell periodic modulation around a nonmagnetic impurity. This suggests a new means to not only detect the dynamical spin collective mode but also study its coupling to electronic excitations.
Journal Article↗
Microzooplankton grazing on phytoplankton in summer in the Jiaozhou Bay, China.
With dilution method, this paper studied the microzooplankton grazing on phytoplankton inside, outside and in a harbor area of the Jiaozhou Bay during June and July 2002. The dominant phytoplankton species outside and inside the bay were Cylindrotheca closterium and Skeletonema costatum, while the samples in the harbor had Skeletonema costatum, Eucampia zodiacus, and Chaetoceros curvisetus as the dominant species. The dominant microzooplankton species outside and inside the Jiaozhou Bay were Tintinnopsis beroidea and unidentified Strombidium sp., while in the harbor, Strombidium sp. was the predominant microzooplankton species coexisted with few T. beroidea. The grazing rate of microzooplankton was 0.96 and 1.20 d(-1) outside the bay, 1.33 d(-1) inside the bay, and 0.36 d(-1) in the harbor. The grazing rates of microzooplankton and the consumption percentages of potential primary production increased in turn from harbor area, outside the bay, to inside the bay. They were 74% and 84% outside the bay, 93% inside the bay, and 53% in the harbor. The ingestion rate of phytoplankton carbon by microzooplankton was the highest in the harbor, with a value of 281 mgC x m(-3) x d(-1), the next was inside the bay, with a value of 102 mgC x m(-3) x d(-1), and the lowest was outside the bay, ranged from 31 to 49 mgC x m(-3) x d(-1). It seems that the phytoplankton community size structure and grazing behaviors of dominant microzooplankton species are the causes for these grazing differences. Compared with the similar studies in other bays around the world, the grazing pressure of microzooplankton in the Jiaozhou Bay is at the middle levels.
Animals↗
[Growth of Platymonas helgolandica var. tsingtaoensis, Cylindrotheca closterium and Karenia mikimotoi and their survival strategies under different N/P ratios].
In this study, laboratory culture experiments were carried out in a batch culture system, with the focus on the effect of different N/P ratios (1:1, 4:1, 16:1, 80:1 and 160:1) on the growth of Platymonas helgolandica var. tsingtaoensis, Cylindrotheca closterium and Karenia mikimotoi. The cell abundance, growth rate, and chlorophyll a and protein contents were measured every 24 h for one week. The results showed that N/P ratio significantly affected the growth of three kinds of algae. Cylindrotheca closterium grew fastest under 160:1 N/P ratio, while Platymonas helgolandica var. tsingtaoensis and Karenia mikimotoi grew fastest under 4:1 and 80:1 N/P ratio, respectively. The maximum cell density of the phytoplankton was mainly influenced by cell size and specific growth rate, the synthesis of chlorophyll a was mainly affected by nitrogen, and high N/P ratio benefited the increase of chlorophyll a content. The protein concentration in cells correlated significantly with N/P ratio, cell size and cell period. As for survival strategy, Cylindrotheca closterium showed obvious features of fast-reproductioned r-selective species, whereas Platymonas helgolandica var. tsingtaoensis and Karenia mikimotoi were most likely to be the more competitive K-selected species.
Adaptation, Physiological↗
Plasma membrane phospholipid scramblase 1 promotes EGF-dependent activation of c-Src through the epidermal growth factor receptor.
Phospholipid scramblase (PLSCR1) is a multiply palmitoylated, calcium-binding endofacial membrane protein proposed to mediate transbilayer movement of plasma membrane phospholipids. PLSCR1 is a component of membrane lipid rafts and has been shown to both physically and functionally interact with activated epidermal growth factor (EGF) receptors and other raft-associated cell surface receptors. Cell stimulation by EGF results in Tyr phosphorylation of PLSCR1, its association with both Shc and EGF receptors, and rapid cycling of PLSCR1 between plasma membrane and endosomal compartments. We now report evidence that upon EGF stimulation, PLSCR1 is phosphorylated by c-Src, within the tandem repeat sequence 68VYNQPVYNQP77. The in vivo interaction between PLSCR1 and Shc requires the Src-mediated phosphorylation on tyrosines 69 and 74. In in vitro pull down studies, phosphorylated PLSCR1 was found to bind directly to Shc through the phosphotyrosine binding domain. Consistent with the potential role of PLSCR1 in growth factor signaling pathways, granulocyte precursors derived from mice deficient in PLSCR1 show impaired proliferation and maturation under cytokine stimulation. Using PLSCR1-/- embryonic fibroblasts and kidney epithelial cells, we now demonstrate that deletion of PLSCR1 from the plasma membrane reduces the activation of c-Src by EGF, implying that PLSCR1 normally facilitates receptor-dependent activation of this kinase. We propose that PLSCR1, through its interaction with Shc, promotes Src kinase activation through the EGF receptor.
Adaptor Proteins, Signal Transducing↗
Cloning of chicken anemia virus vp3 gene and apoptosis inductive effect of vp3 gene in vitro.
Using PCR technique, the vp3 gene of chicken anemia virus (CAV) was cloned into the eukaryotic expression vector pcDNA3 to construct a recombinant pcDNA-vp3. Restriction enzyme digestion and sequencing analysis revealed that CAV vp3 gene was correctly inserted into the blank vector pcDNA3. After LipofectAMINE-mediated transfection in vitro with pcDNA-vp3 and pcDNA3 respectively, the total mRNA was extracted from liver carcinoma cell lines HepG2 and diploid cell line L-02, and RT-PCR was performed afterward. The results of RT-PCR suggested that vp3 gene was expressed in these two cell lines. At the same time, using in situ apoptotic detection assay, TUNEL kits, the apoptotic cells were found in pcDNA-vp3 transfected HepG2, but not in mock transfected cell lines. VP3 could induce cell death by apoptosis in cancer cell lines, but not in diploid cell lines. All the results indicated that CAV vp3 gene, a potential therapeutic agents, has the potential of being used for cancer treatment.
Animals↗
Molecular basis for the subtype discrimination of the estrogen receptor-beta-selective ligand, diarylpropionitrile.
Although the two subtypes of the human estrogen receptor (ER), ERalpha and ERbeta, share only 56% amino acid sequence identity in their ligand binding domain (LBD), the residues that surround the ligand are nearly identical; nevertheless, subtype-selective ligands are known. To understand the molecular basis by which diarylpropionitrile (DPN), an ERbeta-selective ligand, is able to discriminate between the two ERs, we examined its activity on ER mutants and chimeric constructs generated by DNA shuffling. The N-terminal region of the ERbeta LBD (through helix 6) appears to be fully responsible for the ERbeta selectivity of DPN. In fact, a single ERalpha point mutation (L384M) was largely sufficient to switch the DPN response of this ER to that of the ERbeta type, but residues in helix 3 are also important in achieving the full ERbeta selectivity of DPN. Using molecular modeling, we found an energetically favorable fit for the S-DPN enantiomer in ERbeta, in which the proximal phenol mimics the A ring of estradiol, and the nitrile engages in stabilizing interactions with residues in the ligand-binding pocket of ERbeta. Our findings highlight that a limited number of critical interactions of DPN with the ERbeta ligand-binding pocket underlie its ER subtype-selective character.
Amino Acid Sequence↗
DNA shuffling method for generating estrogen receptor alpha and beta chimeras in yeast.
To facilitate our study of the molecular basis for the estrogen receptor (ER) subtype selectivity of novel ligands, we used DNA shuffling to construct chimeric ERs having ligand binding domains derived from both ER alpha and ER beta. The efficiency of chimera generation was low with traditional DNA shuffling protocols. Furthermore, ER ligand binding domain sequences lack convenient restriction sites for introducing chimeric ligand binding domain sequences into expression vectors. To overcome these problems, we developed a modified strategy whereby chimeric sequences were exclusively amplified from among the reassembled products from DNA shuffling using a special pair of PCR primers whose 3' ends specifically match the alpha and beta sequences, respectively, and whose 5' ends match sequences outside the ER beta ligand binding domain. When chimeric ligand binding domain DNA sequences, amplified with these primers, were co-transformed into a yeast strain with a linearized expression vector for ER beta, an active expression vector was produced by homologous recombination. Twenty-two different crossover sites were found; most occurred when there was a stretch of eight or more identical base pairs in both sequences, and many were concentrated in the regions important for studying ligand binding and transactivation. This method should prove to be useful for generating chimeric gene products from parent templates that share relatively low sequence identity.
Amino Acid Sequence↗
Spiral CT in gastric carcinoma: comparison with barium study, fiberoptic gastroscopy and histopathology.
AIM: To evaluate spiral computed tomography (CT) including virtual gastroscopy for diagnosis of gastric carcinoma in comparison with upper gastrointestinal series (UGI), fiberoptic gastroscopy (FG) and histopathology. METHODS: Sixty patients with histologically proven gastric carcinoma (54 advanced and 6 early) were included in this study. The results of spiral CT were compared with those of UGI and FG. Two observers blindly evaluated images of spiral CT and UGI and video recording of FG with consensus in terms of diagnostic confidence with a five-point scale. Sensitivities of lesion detection, Borrmann's classification of spiral CT, UGI and FG, as well as the accuracy of TNM staging of spiral CT were determined by comparing them to surgical and histological findings. RESULTS: The lesion detection rate was 98 % (59/60), 95 % (57/60) and 98 % (59/60) for spiral CT, UGI and FG, respectively. There were no statistical differences in the detection sensitivity among the three techniques (P>0.05). For the sensitivity in Borrmann's classification, spiral CT was higher than that of UGI (P=0.025) and similar to that of FG (P>0.05). The accuracy of spiral CT in staging the gastric carcinoma was 76.7 %. Six cases of early gastric carcinoma were all detected by spiral CT as well as FG. CONCLUSION: Spiral CT is equivalent to UGI and FG in the detection of gastric carcinoma, and superior to UGI but similar to FG in the Borrmann's classification of advanced gastric carcinoma. Spiral CT is more valuable than FG in the staging of gastric carcinoma.
Adult↗
Preventive effect of hydrotalcite on gastric mucosal injury in rats induced by taurocholate.
AIM: To study the preventive effect of hydrotalcite on gastric mucosal injury in rat induced by taurocholate, and to investigate the relationship between the protective mechanism of hydrotalcite and the expression of trefoil factor family 2 (TFF2) mRNA and c-fos protein. METHODS: Forty five male Wistar rats were randomly divided into hydrotalcite group, ranitidine group and control group. Gastric mucosal injury was induced by introgastric acidified taurocholate. OD value of TFF2 mRNA expression in gastric mucous cells was determined by hybridization and computer image analysis system. OD value of c-fos protein expression in gastric mucous cells was measured by immunohistochemistry and computer image analysis system. RESULTS: The gross mucosal injury index in hydrotalcite group was significantly lower than that in ranitidine group and control group (8.60+/-2.20 vs 16.32+/-4.27, 29.53+/-5.39; P<0.05, P<0.01). The expression level of TFF2 mRNA in hydrotalcite group was markedly higher than that in ranitidine group and control group (0.56+/-0.09 vs 0.30+/-0.05, 0.28+/-0.03, P<0.05). The OD value of c-fos protein in hydrotalcite group was higher than that in ranitidine group and control group (0.52+/-0.07 vs 0.31+/-0.04, 0.32+/-0.05, P<0.05). CONCLUSION: Hydrotalcite can protect gastric mucosal injury in rats induced by taurocholate, which may be related to the increased expression of TFF2 and c-fos protein.
Aluminum Hydroxide↗
Genetic diversity of microsatellite loci in fifty-six Chinese native pig breeds.
The genetic diversity of fifty-six indigenous pig breeds in China, and three introduced pig breeds (Duroc, Landrace and Large White) was surveyed using twenty-seven microsatellites recommended by the International Society for Animal Genetics (IS-AG) and Food and Agriculture Organization (FAO). By means of the allele frequencies, mean heterozygosity, effective number of alleles, estimator of gene differentiation, polymorphism information content, genetic distance and dendrogram analysis, the genetic variability and population structure of native pig breeds were estimated. Genetic variabilities within native pig breeds are as follows: Effective number of alleles vary from 2.12 to 9.03, from 0.44 to 0.87 for mean heterozygosity, from 0.39 to 0.86 for polymorphism information content. Nei's genetic distance and Nei's standard genetic distance were estimated and used to construct UPGMA and NJ dendrograms, which were evaluated by the bootstrap test. Fifty-six Chinese indigenous pig breeds were clustered into twelve groups based on the dendrogram. Compared with the classification in Pig Breeds in China, I, II and III groups in the study are equivalent to North-China type, IV group basically accords with Lower-Changjiang River Basin type, V, VI, VII, VIII and IX groups quite correspond with Central-China type, X and XI group largely correspond to South-China type, the last group, XII is equal to South-west type at large. Suggestions that the conservation farms together with conservation areas are appropriate methods for the preservation of native pig breeds in our country were proposed. The results could provide basic molecular data for the research on the germplasm characteristics of local breeds in our country and scientific basis for the conservation and utilization of those breeds.
Alleles↗
[Microzooplankton herbivory during red tide-frequent-occurrence period in spring in the East China Sea].
Five typical stations in the Changjiang River estuary and adjacent waters of the East China Sea, were chosen as the sites to study phytoplankton growth and microzooplankton ingestion by on-deck-incubation dilution experiment from 25th April to 25th May 2002. The results showed that microzooplankton ingestion was a key process for controlling red tide event. Strombidium sulcatum, Noctiluca scintillans and Mesodinium robudium were dominant microzooplankton species. In this study, the ingestion rate of microzooplankton ranged from 0.28 to 1.13 d-1; ingestion pressure on percentage of phytoplankton standing crop ranged from 35.14% to 811.69%; ingestion pressure on percentage of potential production ranged from 74.04% to 203.25%; and ingestion rate of phytoplankton carbon ranged from 9.58 to 97.91 C.L-1.d-1. The microzooplankton grazing rate, ingestion pressure on percentage of phytoplankton standing crop, and ingestion rate of phytoplankton carbon were higher near coastal area, but lower at open sea, and the microzooplankton ingestion pressure on percentage of phytoplankton potential production was no the contrary. Compared with the similar studies around the world, the ingestion pressure of microzooplankton in the East China Sea was at a higher level. The primary deduction was that Strombidium was the key microzooplankton species on controlling Prorocentrum dentatum, the most important red tide species in the East China Sea.
Animals↗
[Structural characteristics of phytoplankton community during harmful algae bloom in Jiaozhou Bay].
Based on two days survey in August, 2001 in Jiaozhou Bay, the structural characteristics of phytoplankton community during harmful algae bloom was studied. The results showed that phytoplankton community was composed mainly by the coastal warm species, which were dominated by the diatom including 37 species. Only 7 Pyrrorophya and 1 Chlorophyta species were identified. The highest value of species number appeared in the central of Jiaozhou Bay, which included 37 species, but the lowest value in the edge of Jiaozhou Bay was only 10 species. The highest value of cell abundance appeared in the eastern waters of Jiaozhou Bay, being 6.96 x 10(3) cell.m-3, and the lowest value appeared in the mouth of Jiaozhou Bay, being 3.18 x 10(6) cell.m-3. The diversity and eveness of phytoplankton was the lowest in the eastern waters of Jiaozhou bay, but was higher in the mouth and the central of Jiaozhou Bay. Water mass movement and eutrophication were the main factors affecting the distribution of phytoplankton community in Jiaozhou Bay.
Conservation of Natural Resources↗
Sensitivity function-based model reduction: A bacterial gene expression case study.
Mathematical models used to predict the behavior of genetically modified organisms require 1). a (rather) large number of state variables, and 2). complicated kinetic expressions containing a large number of parameters. Since these models are hardly identifiable and of limited use in model-based optimization and control strategies, a generic methodology based on sensitivity function analysis is presented to reduce the model complexity at the level of the kinetics, while maintaining high prediction power. As a case study to illustrate the method and results obtained, the influence of the dissolved oxygen concentration on the cytN gene expression in the bacterium Azospirillum brasilense Sp7 is modeled. As a first modeling approach, available mechanistic knowledge is incorporated into a mass balance equation model with 3 states and 14 parameters. The large differences in order of magnitude of the model parameters identified on the available experimental data indicate 1). possible structural problems in the kinetic model and, associated with this, 2). a possibly too high number of model parameters. A careful sensitivity function analysis reveals that a reduced model with only seven parameters is almost as accurate as the original model.
Azospirillum brasilense↗
Cutting edge: Salmonella AvrA effector inhibits the key proinflammatory, anti-apoptotic NF-kappa B pathway.
Secreted prokaryotic effector proteins have evolved to modulate the cellular functions of specific eukaryotic hosts. Generally, these proteins are considered virulence factors that facilitate parasitism. However, in certain plant and insect eukaryotic/prokaryotic relationships, effector proteins are involved in the establishment of commensal or symbiotic interactions. In this study, we report that the AvrA protein from Salmonella typhimurium, a common enteropathogen of humans, is an effector molecule that inhibits activation of the key proinflammatory NF-kappaB transcription factor and augments apoptosis in human epithelial cells. This activity is similar but mechanistically distinct from that described for YopJ, an AvrA homolog expressed by the bacterial pathogen Yersinia. We suggest that AvrA may limit virulence in vertebrates in a manner analogous to avirulence factors in plants, and as such, is the first bacterial effector from a mammalian pathogen that has been ascribed such a function.
Apoptosis↗