Search PubMed⌕ Search

Biomedical subjects

X Huang

Publications and source records attributed to X Huang.

At least 289 records · Page 16Linked to original sources
PubMed2000

[Cell proliferation in endolymphatic sac during the immune response of inner ear].

OBJECTIVE: To study the cell proliferation in endolymphatic sac(ES) during the secondary immune response in inner ear. METHODS: Fifteen healthy, female SD rats were employed in the experiment. Sensitized systematically with keyhole limpet hemocyanin (KLH), the animals were inoculated with the same antigen through cochlea basal turn into the labyrinth. Administrated 5-bromo-2'-deoxyuridine (BrdUrd) intraperitoneally, the rats were sacrificed and the temporal bones were harvested at 3, 7, 14 day after labyrinth vaccination respectively. The frozen sections of the decalcified samples were dealt with H-E staining and immunohistochemical methods to investigate the cellular infiltration, BrdUrd and IgG positive cells in the ES. RESULTS: While the ES lumen and perisaccular region were infiltrated with mononuclear-phagocyte at the 3rd day post-vaccination, plasmocyte and lymphatic cells become the predominant infiltrating cells in the ES at the 7th day. The KLH in the ES lumen were phagocytized at the 3-7th day post-vaccination. S-phase cells and IgG positive cells in ES increased markedly in the 3rd day and 7-14 days post-vaccination respectively with similar localization. CONCLUSION: The activity of cell proliferation in the ES enhance and local proliferated cells may differentiate in situ into immunocompetent cells during the secondary immune response against TD antigen in the inner ear. This indicates that ES plays an important role in immune response of inner ear.

Animals↗
PubMed2000

[The clinical significance of poststyloid space extension in nasopharyngeal carcinoma].

OBJECTIVE: To explore the clinical significance of poststyloid space extension in nasopharyngeal carcinoma. METHODS: One hundred and ninety-eight patients with newly treated nasopharyngeal carcinoma (stage I-IV a) were analyzed. These patients were divided into two groups depending on whether the poststyloid space was extended or normal. The 5-year survival rate, relapse and distant metastasis after the treatment were estimated using the Kaplan-Meier, Log-Rank methods. RESULTS: The rates of patients with oropharyngeal extension for these two groups were 72.1% and 16.8% respectively (P < 0.001). The rates of the cases with involvement of the 9, 10, 11, 12th cranial nerves were 20.9% and 6.2% respectively (P < 0.01). The rates of metastasis to cervical lymph node were 69.8% and 35.4% respectively (P < 0.01). The 5-year survival rates were 46.76% and 68.88% respectively (P = 0.0027). The local control rates were 63.7%, 78.7% respectively (P = 0.0862). The distant metastasis free survival rates were 71.7% and 84.2% respectively (P = 0.0468). These results showed that the survival rate, the local control rate were reduced and the distant metastasis was increased for patients with poststyloid space extension. CONCLUSIONS: The poststyloid space extension was an important prognostic factor with poorer treatment outcome. It is reasonable to classify such condition as stage T3 of nasopharyngeal carcinoma.

Adult↗
PubMed2000

[Relationship between tissue inhibitors of metalloproteinase and metastasis and prognosis in breast cancer].

OBJECTIVE: To investigate the clinical significance of tissue inhibitors of metalloproteinase (TIMP) -3 and TIMP-4 in human breast cancer. METHODS: The levels of TIMP-3 and TIMP-4 mRNA in paraffin-embedded breast carcinoma specimens from 70 patients with primary invasive breast cancer who had undergone radical mastectomy from January of 1984 to December of 1985 were assessed by in situ hybridization assay. Intratumoral microvessel density (MVD) and vascular endothelial growth factor (VEGF) expression were detected by the standard streptavidin biotin peroxides method. RESULTS: Both TIMP-3 and TIMP-4 mRNA expressions were higher in patients with axillary lymph node metastasis than in those without metastasis (P < 0.01), and patients with higher expression of any of these two genes had a better prognosis than those with lower expression (P < 0.01). We introduced lymph node status, TNM staging, MVD and VEGF expression, plus TIMP-3 and TIMP-4 to the Cox's proportional hazards regression model for significant analysis, and found that the TIMP-3, TNM staging and MVD play an important role in prognosis of this group. CONCLUSIONS: TIMP-3 and TIMP-4 are correlated with metastasis in breast cancer, and TIMP-3 demonstrates an independent prognostic factor for the patients. These results provide a valuable clue for developing new, practical prognosticators in breast cancer patients.

Breast Neoplasms↗
PubMed2000

[Isobutyramide activates transcription of human fetal gamma-globin gene selectively].

OBJECTIVE: To examine the effect of isobutyramide synthesized in our laboratory on expression of globin genes in MEL cells transfected with the recombinant construct mu LCRA gamma psi beta delta beta MEL. METHODS: The transformant cells were cultured in the medium containing different concentrations of isobutyramide for four days. The human gamma-, beta- and mouse alpha-globin mRNA were determined by RNase protection analysis. RESULTS: The inducible and dose-dependent expression of the human gamma-, beta- and mouse alpha- globin gene were observed. The induction of the human gamma-globin gene was significant stronger than that of the beta-globin gene. Under 2.5 mmol/L-5 mmol/L of isobutyramide, the induction of the human gamma-globin gene was even more effective than that of mouse alpha-globin gene. CONCLUSION: Isobutyramide can effectively and selectively activate transcription of the human gamma-globin gene at a certain degree. This function, together with the advantages of nontoxic and long halflife makes isobutyramide a promising application in the treatment of beta-thalassemia and sickle cell anemia.

Amides↗
PubMed1999

Isolation and mapping of rFUS6, a rice orthologue of Arabidopsis thaliana FUS6.

COP9 complex is one of the most important components that act in repressing photomorphogenesis in Arabidopsis thaliana. FUS6 has been identified as one of eight subunits of the COP9 complex in Arabidopsis. Using Arabidopsis Fus6 cDNA as a probe, we screened a rice root cDNA library and a rice genomic library. A 1730-bp cDNA was obtained, which has an open reading frame corresponding to 441-amino-acid. This 441 amino acids putative protein has 67% identity with Arabidopsis COP11/FUS6 (AtFUS6) and 40% identity with human GPS1, an AtFUS6 orthologue. So we designated this novel gene as rFUS6. The 6.2-kb genomic sequence of rFUS6 was also obtained. Sequence comparison showed that the rFUS6 gene had six exons and five introns. Sequence inspection of the 5'-flanking region revealed the presence of some potential light-regulated cis-elements such as a G-box, GT-1 binding sites, and a TGACG motif. Southern hybridization with rice total DNA showed that rFUS6 was perhaps a single copy gene. The rFUS6 locus was mapped by hybridization with a rice BAC library membrane and the results showed that rFUS6 had a locus at 16.3 cM of chromosome 1.

Amino Acid Sequence↗
PubMed1999

Cu(II) potentiation of alzheimer abeta neurotoxicity. Correlation with cell-free hydrogen peroxide production and metal reduction.

Oxidative stress markers as well as high concentrations of copper are found in the vicinity of Abeta amyloid deposits in Alzheimer's disease. The neurotoxicity of Abeta in cell culture has been linked to H(2)O(2) generation by an unknown mechanism. We now report that Cu(II) markedly potentiates the neurotoxicity exhibited by Abeta in cell culture. The potentiation of toxicity is greatest for Abeta1-42 > Abeta1-40 >> mouse/rat Abeta1-40, corresponding to their relative capacities to reduce Cu(II) to Cu(I), form H(2)O(2) in cell-free assays and to exhibit amyloid pathology. The copper complex of Abeta1-42 has a highly positive formal reduction potential ( approximately +500-550 mV versus Ag/AgCl) characteristic of strongly reducing cuproproteins. These findings suggest that certain redox active metal ions may be important in exacerbating and perhaps facilitating Abeta-mediated oxidative damage in Alzheimer's disease.

Amyloid beta-Peptides↗
PubMed1999

COP9 signalosome-directed c-Jun activation/stabilization is independent of JNK.

The basic region-leucine zipper transcription factor c-Jun regulates gene expression and cell function. It participates in the formation of homo- or heterodimeric complexes that specifically bind to DNA sequences called activating protein 1 (AP-1) sites. The stability and activity of c-Jun is regulated by phosphorylation within the N-terminal activation domain. Mitogen- and stress-activated c-Jun N-terminal kinases (JNKs) were previously the only described enzymes phosphorylating c-Jun at the N terminus in vivo. In this report we demonstrate a JNK-independent activation of c-Jun in vivo directed by the constitutive photomorphogenesis (COP9) signalosome. The overexpression of signalosome subunit 2 (Sgn2), a subunit of the COP9 signalosome, leads to de novo assembly of the complex with a partial incorporation of the overexpressed subunit. The de novo formation of COP9 signalosome parallels an increase of c-Jun protein resulting in elevated AP-1 transcriptional activity. The c-Jun activation caused by Sgn2 overexpression is independent of JNK and mitogen-activated protein kinase kinase 4. The data demonstrate the existence of a novel COP9 signalosome-directed c-Jun activation pathway.

COP9 Signalosome Complex↗
PubMed1999

The small subunit of carbamoyl phosphate synthetase: snapshots along the reaction pathway.

Carbamoyl phosphate synthetase (CPS) plays a key role in both arginine and pyrimidine biosynthesis by catalyzing the production of carbamoyl phosphate. The enzyme from Escherichi coli consists of two polypeptide chains referred to as the small and large subunits. On the basis of both amino acid sequence analyses and X-ray structural studies, it is known that the small subunit belongs to the Triad or Type I class of amidotransferases, all of which contain a cysteine-histidine (Cys269 and His353) couple required for activity. The hydrolysis of glutamine by the small subunit has been proposed to occur via two tetrahedral intermediates and a glutamyl-thioester moiety. Here, we describe the three-dimensional structures of the C269S/glutamine and CPS/glutamate gamma-semialdehyde complexes, which serve as mimics for the Michaelis complex and the tetrahedral intermediates, respectively. In conjunction with the previously solved glutamyl-thioester intermediate complex, the stereochemical course of glutamine hydrolysis in CPS has been outlined. Specifically, attack by the thiolate of Cys269 occurs at the Si face of the carboxamide group of the glutamine substrate leading to a tetrahedral intermediate with an S-configuration. Both the backbone amide groups of Gly241 and Leu270, and O(gamma) of Ser47 play key roles in stabilizing the developing oxyanion. Collapse of the tetrahedral intermediate leads to formation of the glutamyl-thioester intermediate, which is subsequently attacked at the Si face by an activated water molecule positioned near His353. The results described here serve as a paradigm for other members of the Triad class of amidotranferases.

Apoenzymes↗
PubMed1999

Deconstruction of the catalytic array within the amidotransferase subunit of carbamoyl phosphate synthetase.

Carbamoyl phosphate synthetase from Escherichia coli catalyzes the formation of carbamoyl phosphate from bicarbonate, glutamine, and two molecules of ATP. The enzyme consists of a large synthetase subunit, and a small amidotransferase subunit, which belongs to the Triad family of glutamine amidotransferases. Previous studies have established that the reaction mechanism of the small subunit proceeds through the formation of a gamma-glutamyl thioester with Cys-269. The roles in the hydrolysis of glutamine played by the conserved residues, Glu-355, Ser-47, Lys-202, and Gln-273, were determined by mutagenesis. In the X-ray crystal structure of the H353N mutant, Ser-47 and Gln-273 interact with the gamma-glutamyl thioester intermediate [Thoden, J. B., Miran, S. G., Phillips, J. C., Howard, A. J., Raushel, F. M., and Holden, H. M. (1998) Biochemistry 37, 8825-8831]. The mutants E355D and E355A have elevated values of K(m) for glutamine, but the overall carbamoyl phosphate synthesis reaction is unperturbed. E355Q does not significantly affect the bicarbonate-dependent ATPase or glutaminase partial reactions. However, this mutation almost completely uncouples the two partial reactions such that no carbamoyl phosphate is produced. The partial recovery of carbamoyl phosphate synthesis activity in the double mutant E355Q/K202M argues that the loss of activity in E355Q is at least partly due to additional interactions between Gln-355 and Lys-202 in E355Q. The mutants S47A and Q273A have elevated K(m) values for glutamine while the V(max) values are comparable to that of the wild-type enzyme. It is concluded that contrary to the original proposal for the catalytic triad, Glu-355 is not an essential residue for catalysis. The results are consistent with Ser-47 and Gln-273 playing significant roles in the binding of glutamine.

Adenosine Diphosphate↗
PubMed1999

Capillary electrochromatography of proteins and peptides with porous-layer open-tubular columns.

Capillary electrochromatography (CEC) of basic proteins and peptides was carried out with porous-layer open-tubular (PLOT) columns which had a functionalized rugulose polymeric porous layer grafted to the innerwall of 20 microm I.D. fused-silica capillaries. The porous layer was highly crosslinked and prepared by in situ polymerization of vinylbenzyl chloride and divinylbenzene in the presence of 2-octanol as a porogen inside a pretreated fused-silica capillary. The chloromethyl functions at the surface of the porous polymeric support layer were reacted with N,N-dimethyldodecylamine to obtain a positively charged chromatographic surface with fixed C12 alkyl chains. A mixture of lysozyme, cytochrome c, ribonuclease A and alpha-chymotrypsinogen A was separated isocratically by counterdirectional CEC with hydro-organic mobile phases containing acetonitrile and phosphate buffer, pH 2.5. The overall migration behavior of the four proteins was the result of an interplay of chromatographic retention and electrophoretic migration, and was different from that observed in capillary zone electrophoresis or in reversed-phase chromatography under similar conditions. The separation of three basic peptides by CEC also exhibited the same behavior. The stability of the PLOT column was tested by measuring electroosmotic mobility during continual use.

Chromatography, Liquid↗
PubMed1999

Capillary columns with in situ formed porous monolithic packing for micro high-performance liquid chromatography and capillary electrochromatography.

Capillary columns with monolithic stationary phase were prepared from silanized fused-silica capillaries of 75 microns I.D. by in situ copolymerization of divinylbenzene either with styrene or vinylbenzyl chloride in the presence of a suitable porogen. The porous monolithic support in this study was used either directly or upon functionalization of the surface to obtain a stationary phase that was appropriate for the separation of peptides by capillary electrochromatography (CEC). The main advantages of monolithic columns are as follows. They do not need retaining frits, they do not have charged particles that can get dislodged in high electric field, and they have relatively high permeability and stability. Whereas such columns are designed especially for CEC, they find application in micro high-performance liquid chromatography (mu-HPLC) as well. Five different porogens were employed to prepare the monolithic columns that were examined for permeability and porosity. The flexibility of fused-silica capillaries was not adversely affected by the monolithic packing and the longevity of the columns was satisfactory. This may also be due to the polymerization technique, which resulted in a fluid-impervious outer layer of the monolith that precluded contact between the fused-silica surface and the liquid mobile phase. For the most promising columns, the conductivity ratios and the parameters of the simplified van Deemter equation, both in mu-HPLC and CEC, were evaluated. It was found that the efficiency of the monolithic columns in CEC was significantly higher than in mu-HPLC in the same way as observed with capillary columns having conventional particulate packing. This is attributed to the relaxation of band-broadening with electroosmotic flow (EOF) with respect to that with viscous flow. It follows then that the requirement of high packing uniformity to obtain high efficiency may also be relaxed in CEC. Angiotensin-type peptides were separated by CEC with columns packed with a monolithic stationary phase having fixed n-octyl chains and quaternary ammonium groups at the surface. Plate heights of about 8 microns were routinely obtained. The mechanism of the separation is based on the interplay between EOF, chromatographic retention and electrophoretic migration of the positively charged peptides. The results of the complex migration process, with highly nonlinear dependence of the migration times on the organic modifier and the salt concentration, cannot be interpreted within the framework of classical chromatography or electrophoresis.

Amino Acid Sequence↗
PubMed1999

Expression of chromosome 21-localized genes in acute myeloid leukemia: differences between Down syndrome and non-Down syndrome blast cells and relationship to in vitro sensitivity to cytosine arabinoside and daunorubicin.

The high event-free survival rates of Down syndrome (DS) children with acute myeloid leukemia (AML) are due, in part, to increased in vitro sensitivity of DS myeloblasts to cytosine arabinoside (ara-C) and daunorubicin and the greater generation of ara-C triphosphate (ara-CTP) from ara-C compared with myeloblasts from non-DS patients (Taub et al, Blood 87:3395, 1996). This study further explores the molecular basis of chemotherapy sensitivity of DS AML patients by examining the expression of chromosome 21-localized genes in myeloblasts from newly diagnosed AML patients. Transcript levels of two chromosome 21-localized genes, cystathionine-beta-synthase (CBS) and superoxide dismutase (SOD), measured by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), were 12.0- and 3. 8-fold higher in DS compared with non-DS myeloblasts (P <.0001 and P <.0001, respectively). Conversely, there were no significant increases in transcripts for 2 other chromosome 21-localized genes, carbonyl reductase and the reduced folate carrier. CBS transcript levels correlated with both in vitro ara-C sensitivity measured by the 3-[4,5-dimethyl-thiazol-2-yl]-2,5-diphenyltetrazolium-bro mid e (MTT) assay (P =.003) and the generation of (3)H-ara-C triphosphate (ara-CTP) after in vitro incubations with 5 micromol/L (3)H-ara-C (P =.0003). Transcripts of deoxycytidine kinase were 2.6-fold higher in DS compared with non-DS cells and may be a factor in the enhanced metabolism of ara-C in DS cells. There was no significant correlation of SOD transcripts with in vitro ara-C and daunorubicin sensitivities. Increased CBS transcripts could result in elevated CBS activity, which modulates ara-C metabolism by altering reduced folate pools, deoxycytidine triphosphate pools, S-adenosylmethionine levels, and/or methylation of the deoxycytidine kinase gene. The further identification of the molecular mechanisms of chemotherapy sensitivity of DS AML patients may lead to significant improvements in the treatment and cure of AML.

Adolescent↗
PubMed1999

Aqueous dissolution of Alzheimer's disease Abeta amyloid deposits by biometal depletion.

Zn(II) and Cu(II) precipitate Abeta in vitro into insoluble aggregates that are dissolved by metal chelators. We now report evidence that these biometals also mediate the deposition of Abeta amyloid in Alzheimer's disease, since the solubilization of Abeta from post-mortem brain tissue was significantly increased by the presence of chelators, EGTA, N,N,N',N'-tetrakis(2-pyridyl-methyl) ethylene diamine, and bathocuproine. Efficient extraction of Abeta also required Mg(II) and Ca(II). The chelators were more effective in extracting Abeta from Alzheimer's disease brain tissue than age-matched controls, suggesting that metal ions differentiate the chemical architecture of amyloid in Alzheimer's disease. Agents that specifically chelate copper and zinc ions but preserve Mg(II) and Ca(II) may be of therapeutic value in Alzheimer's disease.

Alzheimer Disease↗
PubMed1999

Direct cloning of cell differential expression genes with full-length by a new strategy based on the multiple rounds of 'long distance' polymerase chain reaction and magnetic beads mediated subtraction.

The paper described a new cDNA subtractive cloning strategy. This strategy was based on the 'cap-finder' method, 'long distance' polymerase chain reaction (PCR), streptavidin magnetic beads mediated subtraction, and spin column chromatography. When PCR products were resolved on agarose gel after three rounds of subtraction, the 'single gene difference' group displayed a predominantly enriched band, but the 'multiple gene difference' group did not display any apparent difference. Of 200 clones inserted with 0.7-2 kb fragments from the 'multiple gene difference' group, 50% were identified to be new sequences and 35% were known. Of 100 new sequences, 35% contained coding regions and 75% were confirmed by dot-blotting to be differentially expressed by genes of the target cell. The results suggested that this strategy might be very efficient for full-length cloning of differentially expressed genes of the cell.

Cloning, Molecular↗
PubMed1999

Heterolytic cleavage of a beta-phosphatoxyalkyl radical resulting in phosphate migration or radical cation formation as a function of solvent polarity.

[formula: see text] The 2-(diethylphosphatoxy)-2-(p-methoxyphenyl)-1,1-dimethylethyl radical (1) reacted to give the benzylic radical product from phosphate migration or a radical cation (or a mixture of the two) as a function of solvent. Smooth acceleration in rates of reactions of 1 in solvents of increasing polarity and consistent entropies of activation indicate that radical 1 reacts by common mechanism irrespective of the final products formed, specifically by initial heterolysis to a radical cation-phosphate anion pair.

Cations↗
PubMed1999

Snare protein expression and adenoviral transfection of amphicrine AR42J.

The amphicrine AR42J acinar cell line is an excellent model to study both exocrine and neuroendocrine exocytotic mechanisms. As a first step toward this goal, we determined the specific isoforms of the v- and t-SNARE and Munc18 families expressed in these cells. In addition, we show that dexamethasone-induced differentiation toward the exocrine phenotype causes an upregulation of several of these proteins. AR42J is notoriously difficult to transfect, limiting its usefulness as a model. However, we have now overcome this obstacle by acheiving high efficiency expression of a beta-galactosidase reporter gene and truncated SNAP-25 gene using adenoviral infection techniques. The AR42J cells can now be used to pursue and elucidate the distinct functions of individual SNARE isoforms used in endocrine and exocrine secretion within a single cell line.

Adenoviridae↗
PubMed1999

Alternative-splicing of serotonin receptor isoforms in the pharynx and muscle of the parasitic nematode, Ascaris suum.

Pharyngeal pumping is essential for nematode feeding and survival and is dramatically stimulated by serotonin (5-HT). In the present study, a cDNA pool was prepared from poly A + RNA isolated from pharynxes dissected from the parasitic nematode, Ascaris suum, and was used as a template for RT-PCR with degenerate primers designed from sequences conserved in 5-HT receptors from a variety of sources. A putative 5-HT receptor cDNA (AS1) was identified which exhibited most identity to the 5-HT2 family of receptors. AS1 was 1925 nucleotides, did not appear to be trans-spliced and contained a 3' untranslated region of 127 nucleotides with a polyadenylation signal (ATTAAA) and a short poly A+ tail. The coding region predicted a protein of 532 amino acids with a molecular weight of 60 176. When AS1 was transiently expressed in COS-7 cells, isolated membranes exhibited the high affinity, saturable binding of [125I]LSD. More importantly, [125I]LSD binding was inhibited by 5-HT, but not other biogenic amines, supporting the identification of AS1 as a 5-HT receptor. Additional cDNAs identical, in part, to AS1 were also identified. AS1deltaIV lacked a predicted 42 amino acids at the carboxy terminus of the third intracellular loop, while AS2 and AS3 contained different COOH-termini, regions implicated in G-protein coupling in other heptahelical receptors. A portion of the gene (5htn) encoding AS1 also was cloned and sequenced. This genomic fragment was about 10 kb, contained the entire AS1 open reading frame and included eight exons and seven introns. From this analysis, it appears that these different AS cDNAs were generated by alternative-splicing, AS1deltaIV from the deletion of exon IV, and AS2 and AS3 from the use of alternative sites within exon VII as 5' splice acceptor sites for exon VIII. Using RT-PCR and primers specific for each of the isoforms, AS1 -3 appeared to be expressed in pharynx, while only AS1 and AS2 were present in body wall muscle. More importantly, the deletion of exon IV appeared to be associated exclusively with AS1 in pharynx and AS2 in muscle.

Alternative Splicing↗