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Biomedical subjects

Hao Wu

Publications and source records attributed to Hao Wu.

At least 73 records · Page 4Linked to original sources
PubMed2005

Crystal structure of MC159 reveals molecular mechanism of DISC assembly and FLIP inhibition.

The death-inducing signaling complex (DISC) comprising Fas, Fas-associated death domain (FADD), and caspase-8/10 is assembled via homotypic associations between death domains (DDs) of Fas and FADD and between death effector domains (DEDs) of FADD and caspase-8/10. Caspase-8/10 and FLICE/caspase-8 inhibitory proteins (FLIPs) that inhibit caspase activation at the DISC level contain tandem DEDs. Here, we report the crystal structure of a viral FLIP, MC159, at 1.2 Angstroms resolution. It reveals a noncanonical fold of DED1, a dumbbell-shaped structure with rigidly associated DEDs and a different mode of interaction in the DD superfamily. Whereas the conserved hydrophobic patch of DED1 interacts with DED2, the corresponding region of DED2 mediates caspase-8 recruitment and contributes to DISC assembly. In contrast, MC159 cooperatively assembles with Fas and FADD via an extensive surface that encompasses the conserved charge triad. This interaction apparently competes with FADD self-association and disrupts higher-order oligomerization required for caspase activation in the DISC.

Adaptor Proteins, Signal Transducing↗
PubMed2005

Enhanced cold tolerance in transgenic tobacco expressing a chloroplast omega-3 fatty acid desaturase gene under the control of a cold-inducible promoter.

A new cold-inducible genetic construct was cloned using a chloroplast-specific omega-3-fatty acid desaturase gene (FAD7) under the control of a cold-inducible promoter (cor15a) from Arabidopsis thaliana. RT-PCR confirmed a marked increase in FAD7 expression, in young Nicotiana tabacum (cv. Havana) plants harboring cor15a-FAD7, after a short-term exposure to cold. When young, cold-induced tobacco seedlings were exposed to low-temperature (0.5, 2 or 3.5 degrees C) for up to 44 days, survival within independent cor15a-FAD7 transgenic lines (40.2-96%) was far superior to the wild type (6.7-10.2%). In addition, the major trienoic fatty acid species remained stable in cold-induced cor15a-FAD7 N. tabacum plants under prolonged cold storage while the levels of hexadecatrienoic acid (16:3) and octadecatrienoic acid (18:3) declined in wild type plants under the same conditions (79 and 20.7% respectively). Electron microscopy showed that chloroplast membrane ultrastructure in cor15a-FAD7 transgenic plants was unaffected by prolonged exposure to cold temperatures. In contrast, wild type plants experienced a loss of granal stacking and disorganization of the thylakoid membrane under the same conditions. Changes in membrane integrity coincided with a precipitous decline in leaf chlorophyll concentration and low survival rates in wild type plants. Cold-induced double transgenic N. alata (cv. Domino Mix) plants, harboring both the cor15a-FAD7 cold-tolerance gene and a cor15a-IPT dark-tolerance gene, exhibited dramatically higher survival rates (89-90%) than wild type plants (2%) under prolonged cold storage under dark conditions (2 degrees C for 50 days).

Arabidopsis↗
PubMed2005

Rho GTPase regulation of exocytosis in yeast is independent of GTP hydrolysis and polarization of the exocyst complex.

Rho GTPases are important regulators of polarity in eukaryotic cells. In yeast they are involved in regulating the docking and fusion of secretory vesicles with the cell surface. Our analysis of a Rho3 mutant that is unable to interact with the Exo70 subunit of the exocyst reveals a normal polarization of the exocyst complex as well as other polarity markers. We also find that there is no redundancy between the Rho3-Exo70 and Rho1-Sec3 pathways in the localization of the exocyst. This suggests that Rho3 and Cdc42 act to polarize exocytosis by activating the exocytic machinery at the membrane without the need to first recruit it to sites of polarized growth. Consistent with this model, we find that the ability of Rho3 and Cdc42 to hydrolyze GTP is not required for their role in secretion. Moreover, our analysis of the Sec3 subunit of the exocyst suggests that polarization of the exocyst may be a consequence rather than a cause of polarized exocytosis.

Biomarkers↗
PubMed2005

A novel mechanism for adenylyl cyclase inhibition from the crystal structure of its complex with catechol estrogen.

Catechol estrogens are steroid metabolites that elicit physiological responses through binding to a variety of cellular targets. We show here that catechol estrogens directly inhibit soluble adenylyl cyclases and the abundant trans-membrane adenylyl cyclases. Catechol estrogen inhibition is non-competitive with respect to the substrate ATP, and we solved the crystal structure of a catechol estrogen bound to a soluble adenylyl cyclase from Spirulina platensis in complex with a substrate analog. The catechol estrogen is bound to a newly identified, conserved hydrophobic patch near the active center but distinct from the ATP-binding cleft. Inhibitor binding leads to a chelating interaction between the catechol estrogen hydroxyl groups and the catalytic magnesium ion, distorting the active site and trapping the enzyme substrate complex in a non-productive conformation. This novel inhibition mechanism likely applies to other adenylyl cyclase inhibitors, and the identified ligand-binding site has important implications for the development of specific adenylyl cyclase inhibitors.

Adenosine Triphosphate↗
PubMed2005

Correlation between CD4, CD8 cell infiltration in gastric mucosa, Helicobacter pylori infection and symptoms in patients with chronic gastritis.

AIM: To evaluate the correlation between CD4, CD8 cell infiltration in gastric mucosa, Helicobacter pylori (H pylori) infection and symptoms or the assemblage of symptoms in cases with chronic gastritis. METHODS: Biopsy samples at the gastric antrum were obtained from 62 patients with chronic gastritis. CD4 and CD8 cell infiltration was evaluated by immunohistochemical assays on frozen sections of the biopsy samples. Fifteen symptoms referring to digestion-related activity and non-digestion related activity were observed. The correlation between lymphocyte infiltration and each symptom or symptom assemblage was analyzed by logistic regression and K-mean cluster methods. RESULTS: CD4 cell infiltrations in gastric mucosa were much more in patients with H. pylori infection, while CD8 cell infiltrations were similar in patients with or without H. pylori infection. Logistic regression analysis showed that the symptoms including heavy feeling in head or body (t = 2.563), and thirst (t = 2.478) were significantly related with CD4 cell infiltration in gastric mucosa (P<0.05), and cool limbs with aversion to cold were related with CD8 cell infiltration (t = 2.872, P<0.05). Further analysis showed that non-digestive related symptom assemblage could increase the predicted percentage of CD4 and CD8 cell infiltration in gastric mucosa, including lower CD4 infiltration by 12.5%, higher CD8 infiltration by 33.3%, and also non-H. pylori infection by 23.6%. K-means cluster analysis of all symptoms and CD4 and CD8 cell infiltration in gastric mucosa showed a similar tendency to increase the predicted percentage of CD4, CD8 cell infiltration and H. pylori infection. CONCLUSION: Based on correlation between the gastric mucosa lymphocyte infiltration, H. pylori infection and clinical symptoms, symptoms or symptomatic assemblages play an important role in making further classification of chronic gastritis, which might help find a more specific therapy for chronic gastritis.

Adolescent↗
PubMed2005

A positive autoregulatory loop of Jak-STAT signaling controls the onset of astrogliogenesis.

During development of the CNS, neurons and glia are generated in a sequential manner. The mechanism underlying the later onset of gliogenesis is poorly understood, although the cytokine-induced Jak-STAT pathway has been postulated to regulate astrogliogenesis. Here, we report that the overall activity of Jak-STAT signaling is dynamically regulated in mouse cortical germinal zone during development. As such, activated STAT1/3 and STAT-mediated transcription are negligible at early, neurogenic stages, when neurogenic factors are highly expressed. At later, gliogenic periods, decreased expression of neurogenic factors causes robust elevation of STAT activity. Our data demonstrate a positive autoregulatory loop whereby STAT1/3 directly induces the expression of various components of the Jak-STAT pathway to strengthen STAT signaling and trigger astrogliogenesis. Forced activation of Jak-STAT signaling leads to precocious astrogliogenesis, and inhibition of this pathway blocks astrocyte differentiation. These observations suggest that autoregulation of the Jak-STAT pathway controls the onset of astrogliogenesis.

Animals↗
PubMed2005

Engineering a selectable marker for hyperthermophiles.

Limited thermostability of antibiotic resistance markers has restricted genetic research in the field of extremely thermophilic Archaea and bacteria. In this study, we used directed evolution and selection in the thermophilic bacterium Thermus thermophilus HB27 to find thermostable variants of a bleomycin-binding protein from the mesophilic bacterium Streptoalloteichus hindustanus. In a single selection round, we identified eight clones bearing five types of double mutated genes that provided T. thermophilus transformants with bleomycin resistance at 77 degrees C, while the wild-type gene could only do so up to 65 degrees C. Only six different amino acid positions were altered, three of which were glycine residues. All variant proteins were produced in Escherichia coli and analyzed biochemically for thermal stability and functionality at high temperature. A synthetic mutant resistance gene with low GC content was designed that combined four substitutions. The encoded protein showed up to 17 degrees C increased thermostability and unfolded at 85 degrees C in the absence of bleomycin, whereas in its presence the protein unfolded at 100 degrees C. Despite these highly thermophilic properties, this mutant was still able to function normally at mesophilic temperatures in vivo. The mutant protein was co-crystallized with bleomycin, and the structure of the binary complex was determined to a resolution of 1.5 A. Detailed structural analysis revealed possible molecular mechanisms of thermostabilization and enhanced antibiotic binding, which included the introduction of an intersubunit hydrogen bond network, improved hydrophobic packing of surface indentations, reduction of loop flexibility, and alpha-helix stabilization. The potential applicability of the thermostable selection marker is discussed.

Amino Acid Sequence↗
PubMed2005

A role for CK2alpha/beta in Xenopus early embryonic development.

CK2 is expressed widely in early embryonic development in several animal models, however its developmental role is unclear. One of the substrates of CK2 that is important in embryonic development is beta-catenin, the transcriptional co-activator of the canonical Wnt signaling pathway. This pathway has been implicated in diverse aspects of embryonic development, including one of the earliest events in embryonic development, the establishment of the dorso-ventral embryonic axis. In Xenopus laevis, dorso-ventral axis formation is dependent upon stabilization of beta-catenin in the future dorsal side of the embryo. Since CK2 phosphorylation of beta-catenin stabilizes it, we hypothesized that CK2 might be critical to upregulation of beta-catenin in Xenopus embryos and to the process of axis establishment. Our results demonstrate that CK2 is required for dorsal axis formation and is for normal upregulation of Wnt signaling genes and targets. Thus, CK2 is a regulator of endogenous axis formation in vertebrates.

Animals↗
PubMed2005

Longitudinal alteration of circulating dendritic cell subsets and its correlation with steroid treatment in patients with severe acute respiratory syndrome.

In this study, we found that 74 patients with severe acute respiratory syndrome (SARS) exhibited a rapid, dramatic decrease in numbers of circulating myeloid and plasmacytoid dendritic cells (mDCs and pDCs) during the first 2 weeks of illness (5.3- and 28.4-fold reductions for mDCs and pDCs compared with 25 healthy individuals, respectively), with slow return to normal cell numbers during convalescence (weeks 5-7 of illness on average). In addition, numbers of circulating CD4 and CD8 T cells exhibited milder reductions (2.1- and 1.8-fold at week 1) and earlier return to normal at a mean of weeks 3 and 4, respectively. A significant inverse correlation was found between numbers of DC and T-cell subsets and high-dose steroid treatment. Our novel findings thus suggest that the acute SARS-coronavirus infection probably contributes to the initial reduction of DC and T-cell subsets in blood, and that high-dose steroid administration may subsequently exacerbate and prolong low expression of the cell subsets. These findings will aid the framing of further studies of the immunopathogenesis of SARS.

Adrenal Cortex Hormones↗
PubMed2005

DCCP and DICP: construction and analyses of databases for copper- and iron-chelating proteins.

Copper and iron play important roles in a variety of biological processes, especially when being chelated with proteins. The proteins involved in the metal binding, transporting and metabolism have aroused much interest. To facilitate the study on this topic, we constructed two databases (DCCP and DICP) containing the known copper- and iron-chelating proteins, which are freely available from the website http://sdbi.sdut.edu.cn/en. Users can conveniently search and browse all of the entries in the databases. Based on the two databases, bioinformatic analyses were performed, which provided some novel insights into metalloproteins.

Animals↗
PubMed2005

DNA methylation controls the timing of astrogliogenesis through regulation of JAK-STAT signaling.

DNA methylation is a major epigenetic factor that has been postulated to regulate cell lineage differentiation. We report here that conditional gene deletion of the maintenance DNA methyltransferase I (Dnmt1) in neural progenitor cells (NPCs) results in DNA hypomethylation and precocious astroglial differentiation. The developmentally regulated demethylation of astrocyte marker genes as well as genes encoding the crucial components of the gliogenic JAK-STAT pathway is accelerated in Dnmt1-/- NPCs. Through a chromatin remodeling process, demethylation of genes in the JAK-STAT pathway leads to an enhanced activation of STATs, which in turn triggers astrocyte differentiation. Our study suggests that during the neurogenic period, DNA methylation inhibits not only astroglial marker genes but also genes that are essential for JAK-STAT signaling. Thus, demethylation of these two groups of genes and subsequent elevation of STAT activity are key mechanisms that control the timing and magnitude of astroglial differentiation.

Animals↗
PubMed2005

[Validity of high negative pressure drainage for chylous fistula after neck dissection: a report of eight cases].

BACKGROUND & OBJECTIVE: Chylous fistula, a severe complication after operation on neck, has close correlation with definite anatomical position and variation. Its treatment remains controversial. This study was to evaluate the validity of high negative pressure drainage for chylous fistula after neck dissection. METHODS: A treatment of high negative pressure (-30 to -50 kPa) drainage, fasting, and reasonable venous nutrition was applied to 8 patients with postoperative chylous fistula. RESULTS: Of the 8 patients, 7 recovered smoothly without severe complication, and pectoralis major muscle flap was adopted to cure the failed one. CONCLUSION: A treatment of high negative pressure drainage and reasonable diet is effective and safe for chylous fistula at early stage.

Chyle↗
PubMed2005

[A study of the progression of cirrhosis in patients with human immunodeficiency virus and hepatitis C virus coinfection].

OBJECTIVES: To study the progression of cirrhosis in patients with HIV/HCV coinfection. METHODS: The patients were divided into two groups, HIV/HCV coinfection group (n = 140) and simple HCV infection group (n = 33). A retrospective study was designed to compare the development of cirrhosis in a 15-year period between the two groups. RESULTS: The development of cirrhosis in the HIV/HCV coinfection group was higher than that in the simple HCV infection group (16.4% vs. 3.0%, P=0.045). Counts of CD4+ T and CD8+ T in the HIV/HCV group were 200.0+/-134.1 cells/microl and 880.6+/-444.2 cells/microl, respectively. The counts of CD4+ T and CD8+ T in the group of simple HCV infection were 752.3+/-251.7 cells/microl and 529.0+/-170.7 cells/microl, respectively. There were significant differences between the two groups regarding the counts of CD4+ T and CD8+ T. Comparing the cases of HCV RNA (+) and anti-HCV (+) with the cases of HCV RNA (+) and anti-HCV (-), we found that the ratio was 89 to 15 in the group of HIV/HCV coinfection, and 25 to 0 in the group of simple HCV infection. The difference between the two groups was statistically significant (P = 0.043). CONCLUSION: HIV/HCV coinfection can accelerate the progression of cirrhosis, which may be due to the effect of HIV on cellular immunity and humoral immunity.

Adult↗
PubMed2005

[Dexamethasone pharmacokinetics in perilymph of guinea pig after different topical administrations].

OBJECTIVE: To determine pharmacokinetics profiles of dexamethasone (DEX) in perilymph of guinea pig with different intratympanic administrations, and to provide experimental evidence for clinical choice about administration. METHOD: Two different topical administrations placing a granule gelfoam soaked with DEX (10 g/L) in the niche of round window of guinea pig and infusing tympanic bulb with DEX solution (10 g/L) were conducted. Perilymph of the scala tympani was sampled 1-6 h after administration. DEX in the samples was assayed with high-performance liquid chromatography. RESULT: The concentrations of DEX in perilymph after placing a granule gel-foam soaked with DEX in the niche of round window were significantly higher than that after intratympanic infusing. The half-life time of DEX after placing a granule gelfoam was longer. CONCLUSION: DEX could effectively penetrate round window membrane into perilymph after different intratympanic administrations, and the method of placing a granule gelfoam soaked with DEX in the niche of round window is more effective than that of intratympanic infusing.

Administration, Topical↗
PubMed2005

[Exposing the rabbit cerebellopontine angle through post-sigmoid sinus approach and recording the direct compound action potential of the auditory nerve].

OBJECTIVE: To study the way of exposing the rabbit cerebellopontine angle through post-sigmoid sinus approach and recording the direct compound action potential of the auditory nerve, and to investigate the stability of DCAP N1 wave latency. METHOD: Fifteen New Zealand rabbits which had normal Preyer's auricle reflex were selected. Each one was studied in the left ear. After anaesthetized,the cerebellopontine angle of rabbits were exposed through post-sigmoid sinus approach under aseptic status,then the needle-shaped pole were inserted into the facial-acoustic nerve complex. The DCAP was recorded at the immediateness, 2 h and 5 h after the insertino sequentially. At last, DCAP N1 wave latencies of 15 rabbits were statisticed and analyzed using paired-samples t-test. RESULT: To the 15 sides, the distinct curves with well differentiated waves were induced in the all three times. No significant difference in any N1 wave latency had been found among the 3 times. CONCLUSION: The rabbit cerebellopontine angle could be exposed and the direct compound action potential of the auditory nerve could be recorded successfully by the way studied in this experiment. In normal state, the individual value of DCAP N1 wave latency is stable. During the process of surgery in which the cerebellopontine angle has been exposed, the DCAP N1 wave latency is a practical index for monitoring of hearing impairment.

Action Potentials↗
PubMed2005

[Development of transformation system of rice based on transformation-competent artificial chromosome (TAC) vector].

The TAC clone (NK15) containing a ca.50 kb DNA insert was introduced into Agrobacterium tumefaciens strain LBA4404 by electroporation. The NK15 was stable in Agrobacterium tumefaciens strain LBA4404 under kanamycin selection for many generations. The calli of mature embryo of Nongken58S were infected with the Agrobacterium tumefaciens strain LBA4404 carrying NK15. PCR and Southern analyses of transgenic plants indicated that the 50 kb of foreign DNA was transferred into the rice genome, and most of transgenic plants had one copy of the insertion. Genetic and PCR analyses of T1 progeny confirmed that the inserted forgein DNA was stably inherited.

Blotting, Southern↗
PubMed2005

[Carboplatin-induced injury patterns of inner hair cells missing in chinchilla cochlea].

OBJECTIVE: To explore carboplatin-induced injury patterns of inner hair cells (IHCs) in cochlea of chinchilla, namely, when injury of IHCs occurs, what extension injury of IHCs exists at different time after drug administration, where maximal injury of IHCs locates on basal membrane and how long most IHCs lose after drug administration. METHOD: Carboplatin of moderate concentration (100 mg/kg) was used to inject peritoneally one time and animals were decapitated on schedule, surface preparations were made and cochleograms were obtained to observe injury of IHCs in the cochleae of chinchillas. RESULT: Loss of outer hair cells was not observed on basal membrane from 24 hours to 3 months after drug administration except one ear. The characteristic of IHCs injury patterns was found to be: (1) IHCs were intact at 24 hours after drug administration. IHCs injury was firstly observed within 3 days. (2) The maximal rate of IHCs injury located around boundary of turn one and turn two on basal membrane from 24 hours to 3 months. (3) IHCs injury began from boundary of turn one and turn two and extended to basal turn and apical turn gradually. Compared to apical turn, IHCs injury on basal turn occurred earlier and more severely. (4) Most IHCs lost in 3 months. CONCLUSION: Carboplatin of 100 mg/kg unequally destroyed IHCs from different turns. Temporal variance of injury of IHCs from given turn is most likely due to their discrepant sensitivity to carboplatin.

Animals↗