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Biomedical subjects

X Ji

Publications and source records attributed to X Ji.

At least 109 records · Page 6Linked to original sources
PubMed1998

[Resection of small primary liver cancer: clinical analysis of 82 cases].

OBJECTIVE: To determine which clinicopathologic features and surgical modalities are related to the prognosis of small primary liver cancer (SPLC). METHOD: Eighty-two patients who had under gone operations for SPLC (<or= 5.0 cm in diameter) from 1988 to 1995 were retrospectively studied. 60 patients were HBsAg positive, and 71 patients suffered from liver cirrhosis. Bisegmentectomy, segmentectomy and partial resections were performed in 13, 14 and 55 patients separately. RESULT: The overall operative mortality was 1.2%, and the 1-, 3-, 5-year survival rates were 92.7%, 72.5% and 54.3%, respectively. The 5-year survival rates of 78 patients with hepatocellular carcinoma according to histologic features were 79.6%, 49.9% and 41.1% in well-differentiated (15 patients), moderately (53), and poorly differentiated (10) groups. Recurrence and metastasis rates in 1, 3, 5 years were 12.8%, 40.7% and 71.5%, separately. CONCLUSION: SPLC has the same history of large PLC. Early diagnosis and limited hepatic resection are very important to decrease the mortality and increase the survival rate.

Adult↗
PubMed1998

[Synthesis and biological activity of 2,3-benzopyrone analogs].

Several 2, 3-benzopyrone analogs were synthesized for evaluating their K(+)-channel and anticancer activities. The Friedel-Crafts reaction was taken place with some replacement phenyl acetic acid or its methyl ester and vanillin as reactants in the condition of Ac2O/ZnCl2. All products were confirmed by means of MS and 1H, 13CNMR spectra. Compounds 2 and 3 showed obvious activities on the K(+)-channel and anticancer screening, while the activity of compound 5 was weak. Compound 4 was not yet tested. The primary result indicate that the potential activity of such compounds deserves further study.

Antineoplastic Agents↗
PubMed1997

cDNA cloning and characterization of a rat spermatogenesis-associated protein RSP29.

RSP29, a protein secreted by rat round spermatids, stimulates the secretory function of Sertoli cells in the testis. By making use of the N-terminal sequence homology of RSP29 and a human protein hDP1 that we had previously isolated, we cloned the full length cDNA sequence that encodes RSP29. The entire amino acid sequence of RSP29 showed significant homology with that of hDP1, which was later identified as glyoxalase II. Southern analysis showed that the RSP29 protein sequence is highly conserved in eukaryotes and possibly in prokaryotes. The RSP29 mRNA is expressed in many tissues but has an extremely high abundance in testis. These data suggest that RSP29 may have an important function in most tissues of enkaryotic organisms. The high expression of RSP29 in testis and its stimulatory effects on Sertoli cells suggest that RSP29 could be especially important in the regulation of spermatogenesis.

Amino Acid Sequence↗
PubMed1997

Activity of four allelic forms of glutathione S-transferase hGSTP1-1 for diol epoxides of polycyclic aromatic hydrocarbons.

Allelic forms of hGSTP1-1 which differ from each other by their catalytic properties and, structurally, by the amino acid(s) in position(s) 104 or (and) 113 are known to exist in human populations. The four possible isoforms of hGSTP1-1 with isoleucine or valine in position 104 and with alanine or valine in position 113 were produced by site-directed mutagenesis of the cDNA followed by bacterial expression and purification of the proteins. Glutathione-conjugating activity was measured with the diol epoxides of benzo(a)pyrene and chrysene, as well as with the model substrate 1-chloro-2,4-dinitrobenzene. Isoenzymes with valine in position 104 were more effective with the diol epoxides of polycyclic aromatic hydrocarbons but less effective with 1-chloro-2,4-dinitrobenzene than the isoforms with isoleucine 104. In addition, the transition A113V in the presence of V104 caused a pronounced increase in catalytic efficiency for the benzo(a)pyrene but not the chrysene diol epoxide. It is proposed that amino acid 113 functions as part of a clamp that lines the mouth of the water channel leading to the active sites of the hGSTP1-1 dimer and controls the access to substrates. Therefore, the hydrophobicity and the size of residue 113 are important in co-determining the substrate specificity of the isoenzymes. The widely different activities of the allelic isoforms toward carcinogenic diol epoxides of polycyclic aromatic hydrocarbons may help to explain the correlation between cancer susceptibility and genotype at the hGSTP1 locus that has been found by others.

Alleles↗
PubMed1997

Mechanism of differential catalytic efficiency of two polymorphic forms of human glutathione S-transferase P1-1 in the glutathione conjugation of carcinogenic diol epoxide of chrysene.

The kinetics of the conjugation of glutathione (GSH) with anti-1, 2-dihydroxy-3,4-oxy-1,2,3,4-tetrahydrochrysene (anti-CDE), the activated form of the widespread environmental pollutant chrysene, catalyzed by two naturally occurring polymorphic forms of the pi class human GSH S-transferase (hGSTP1-1), has been investigated. The polymorphic forms of hGSTP1-1, which differ in their primary structure by a single amino acid in position 104, exhibited preference for the GSH conjugation of (+)-anti-CDE, which is a far more potent carcinogen than (-)-anti-CDE. When concentration of anti-CDE was varied (5-200 microM and the GSH concentration was kept constant at 2 mM, both hGSTP1-1(I104) and hGSTP1-1(V104) obeyed Michaelis-Menten kinetics. However, the Vmax of GSH conjugation of anti-CDE was approximately 5.3-fold higher for the V104 variant than for the I104 form. Calculation of catalytic efficiency (kcat/Km) thus resulted in a value for hGSTP1-1(V104), 28 mM-1 s-1, that was 7.0-fold higher than that for hGSTP1-1(I104), 4 mM-1 s-1. The mechanism of the differences in the kinetic properties of hGSTP1-1 isoforms toward anti-CDE was investigated by molecular modeling of the two proteins with GSH conjugation products in their active sites. These studies revealed that the enantioselectivity of hGSTP1-1 for (+)-anti-CDE and the differential catalytic efficiencies of the V104 and I104 forms of hGSTP1-1 in the GSH conjugation of (+)-anti-CDE were due to the differences in the active-site architecture of the two proteins. The results of the present study, for the first time, provide evidence for the toxicological relevance of GSTP1-1 polymorphism in humans and suggest that the population polymorphism of hGSTP1-1 variants with disparate enzyme activities may, at least in part, account for the differential susceptibility of individuals to environmental carcinogens such as anti-CDE and possibly other similar carcinogens.

Animals↗
PubMed1997

Structure and function of the xenobiotic substrate-binding site and location of a potential non-substrate-binding site in a class pi glutathione S-transferase.

Complex structures of a naturally occurring variant of human class pi glutathione S-transferase 1-1 (hGSTP1-1) with either S-hexylglutathione or (9R,10R)-9-(S-glutathionyl)-10-hydroxy-9, 10-dihydrophenanthrene [(9R,10R)-GSPhen] have been determined at resolutions of 1.8 and 1.9 A, respectively. The crystal structures reveal that the xenobiotic substrate-binding site (H-site) is located at a position similar to that observed in class mu GST 1-1 from rat liver (rGSTM1-1). In rGSTM1-1, the H-site is a hydrophobic cavity defined by the side chains of Y6, W7, V9, L12, I111, Y115, F208, and S209. In hGSTP1-1, the cavity is approximately half hydrophobic and half hydrophilic and is defined by the side chains of Y7, F8, V10, R13, V104, Y108, N204, and G205 and five water molecules. A hydrogen bond network connects the five water molecules and the side chains of R13 and N204. V104 is positioned such that the introduction of a methyl group (the result of the V104I mutation) disturbs the H-site water structure and alters the substrate-binding properties of the isozyme. The hydroxyl group of Y7 forms a hydrogen bond (3.2 A) with the sulfur atom of the product. There is a short hydrogen bond (2.5 A) between Y108 (OH) and (9R, 10R)-GSPhen (O5), indicating the hydroxyl group of Y108 as an electrophilic participant in the addition of glutathione to epoxides. An N-(2-hydroxethyl)piperazine-N'-2-ethanesulfonic acid (HEPES) molecule is found in the cavity between beta2 and alphaI. The location and properties of this HEPES-binding site fit a possible non-substrate-binding site that is involved in noncompetitive inhibition of the enzyme.

Animals↗
PubMed1997

Active site architecture of polymorphic forms of human glutathione S-transferase P1-1 accounts for their enantioselectivity and disparate activity in the glutathione conjugation of 7beta,8alpha-dihydroxy-9alpha,10alpha-ox y-7,8,9,10-tetrahydrobenzo(a)pyrene.

In this study, we demonstrate that the active site architecture of the human glutathione (GSH) S-transferase Pi (GSTP1-1) accounts for its enantioselectivity in the GSH conjugation of 7beta,8alpha-dihydroxy-9alpha,10alpha-oxy-7,8,9, 10-tetrahydrobenzo(a) pyrene (anti-BPDE), the ultimate carcinogen of benzo(a)pyrene. Furthermore, we report that the two polymorphic forms of human GSTP1-1, differing in their primary structure by a single amino acid in position 104, have disparate activity toward (+)-anti-BPDE, which can also be rationalized in terms of their active site structures. When concentration of (+)-anti-BPDE, which among four BPDE isomers is the most potent carcinogen, was varied and GSH concentration was kept constant at 2 mM (saturating concentration), both forms of hGSTP1-1 [hGSTP1-1(V104) and hGSTP1-1(I104)] obeyed Michaelis-Menten kinetics. The V(max) of GSH conjugation of (+)-anti-BPDE was approximately 3.4-fold higher for hGSTP1-1(V104) than for hGSTP1-1(I104). Adherence to Michaelis-Menten kinetics was also observed for both isoforms when (-)-anti-BPDE, which is a weak carcinogen, was used as the variable substrate. However, (-)-anti-BPDE was a relatively poor substrate for both isoforms as compared with (+)-anti-BPDE. Moreover, there were no significant differences between hGSTP1-1(V104) and hGSTP1-1(I104) in either V(max) or K(m) for (-)-anti-BPDE. The mechanism of differences in kinetic properties and enantioselectivity of hGSTP1-1 variants toward anti-BPDE was investigated by modeling of the two proteins with conjugation product molecules in their active sites. Molecular modeling studies revealed that the differences in catalytic properties of hGSTP1-1 variants as well as the enantioselectivity of hGSTP1-1 in the GSH conjugation of anti-BPDE can be rationalized in terms of the architecture of their active sites. Our results suggest that the population polymorphism of hGSTP1-1 variants with disparate enzyme activities may, at least in part, account for the differential susceptibility of individuals to carcinogens such as anti-BPDE and possibly other similar carcinogens.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1997

Ancient origin of the complement lectin pathway revealed by molecular cloning of mannan binding protein-associated serine protease from a urochordate, the Japanese ascidian, Halocynthia roretzi.

Recent identification of a C3-like gene in sea urchins revealed the presence of a complement system in invertebrates. To elucidate further the components and function of the pre-vertebrate complement system, we attempted to isolate an ascidian (urochordata) C3 convertase. After identification of C3 cDNA from Halocynthia roretzi, a Japanese ascidian, reverse transcriptase-PCR amplification of hepatopancreas RNA was performed using primers encoding highly conserved amino acid sequences of the vertebrate Bf and C2 serine protease domain. Two candidate sequences were identified, and the corresponding cDNA clones were isolated from a hepatopancreas library. Surprisingly, neither clone is related to Bf/C2 but rather share the same domain structure of mammalian C1r/C1s/MASP (mannan binding protein-associated serine protease), and are more related evolutionarily to mammalian MASP than to mammalian C1r or C1s. The identification of the tunicate MASP clones, amplified with primers designed to amplify Bf or C2, suggests that the lectin pathway antedated the classical and alternative pathways of complement activation.

Amino Acid Sequence↗
PubMed1997

Inhibition of growth of Dictyostelium discoideum amoebae by bisphosphonate drugs is dependent on cellular uptake.

PURPOSE: The aim of the study was to determine whether bisphosphonates are internalised by Dictyostelium amoebae and whether cellular uptake is required for their growth-inhibitory effects. Bisphosphonates inhibit growth of amoebae of the slime mould Dictyostelium discoideum, by mechanisms that appear to be similar to those that cause inhibition of osteoclastic bone resorption. METHODS: Cell-free extracts prepared from amoebae that had been incubated with bisphosphonates were analysed by 31P-n.m.r, spectroscopy or ion-exchange f.p.l.c., to identify the presence of bisphosphonates or bisphosphonate metabolites respectively. The growth-inhibitory effect of bisphosphonates towards Dictyostelium amoebae was also examined under conditions in which pinocytosis was inhibited. RESULTS: All of the bisphosphonates studied were internalised by Dictyostelium amoebae, probably by fluid-phase pinocytosis, and could be detected in cell-free extracts. Amoebae that were prevented from internalising bisphosphonates by pinocytosis were markedly resistant to the growth-inhibitory effects of these compounds. In addition, bisphosphonates encapsulated within liposomes were more potent growth inhibitors of Dictyostelium owing to enhanced intracellular delivery of bisphosphonates. CONCLUSIONS: All bisphosphonates inhibit Dictyostelium growth by intracellular mechanisms following internalisation of bisphosphonates by fluid-phase pinocytosis. It is therefore likely that bisphosphonates also affect osteoclasts by interacting with intracellular, rather than extracellular, processes.

Adenine Nucleotides↗
PubMed1997

[Recombinant human macrophage colony-stimulating factor expressed in silkworm accelerates hematopoietic recovery of radiolesion mice].

OBJECTIVE: To demonstrate the hematopoietic enhancement activity of recombinant human macrophage colony-stimulating factor (rhM-CSF). METHODS: Balb/c mice were sublethally irradiated with 60Co gamma-rays and then the rhM-CSF expressed in silkworm (10(3)U per individual for 7 days) was administered intraperitoneally. RESULTS: (1) The peripheral white blood cell counts of treatment group at day 15 and day 20 after irradiation were significantly higher than those of normal control group; (2) At days 10, 15, 20, 25 and 30 after irradiation, the difference between the peripheral monocyte counts of the treatment and control group were statistically significant; (3) At days 15, 20 and 25 after irradiation, the difference between the peripheral granulocyte counts of the two groups were also significant; (4) At day 9 after irradiation, the bone marrow CFU GM yield of the control group were significantly lower than those of the treatment group. CONCLUSION: rhM-CSF expressed in silkworm could accelerate hematopoietic recovery in irradiated mice.

Animals↗
PubMed1997

Transcriptional defects underlie loss of E-cadherin expression in breast cancer.

Decreased expression of E-cadherin (E-cad), a calcium-dependent cell adhesion molecule, has been seen in many different epithelial cancers. Although somatic mutations in the E-cad gene have been identified in a small subset of tumors, in the majority of cancers, the mechanisms underlying loss of E-cad expression are poorly understood. We have cloned the human E-cad promoter and defined its critical components in functional assays. In eight human breast cancer cell lines, there was a striking correlation between endogenous E-cad gene expression and E-cad promoter activity observed following the introduction of reporter gene constructs into the lines. These and other observations suggest that defects in trans-acting pathways regulation E-cad expression are the primary basis for the loss of its expression in most breast cancers. The results have significant implications for understanding the gene expression differences that underlie tumor heterogeneity and progression events in breast and other epithelial cancers.

Antimetabolites, Antineoplastic↗
PubMed1997

Clinical significance of serum 7S collagen and type VI collagen levels for the diagnosis of hepatic fibrosis.

OBJECTIVE: To measure serum 7S collagen (7S-C) and type VI collagen (VI-C) levels by radioimmunoassay (RIA) in Chinese patients with various liver disorders and in CCl4-treated SD rats, and to investigate the significance of the elevated levels of serum 7S-C and VI-C. METHODS: Serum 7S-C and VI-C levels were measured in 40 healthy control subjects, 168 patients with various liver disorders and non-hepatic diseases, and 52 CCl4-treated SD rats by using RIA which was developed in our hospital. RESULTS: Serum 7S-C and VI-C were significantly elevated in patients with chronic active hepatitis (CAH), liver cirrhosis (LC), hepatic cellular carcinoma (HCC) (P < 0.01 respectively), chronic persistent hepatitis (CPH), and some with non-hepatic diseases (P < 0.05). Serum 7S-C, serum laminin and hyaluronic acid were well correlated. Serum 7S-C and VI-C were not closely correlated. Both collagens were correlated with serum albumin/globulin ratio, aminotransferase and total bilirubin, not with alkaline phosphatase. In CCl4-treated SD rats, serum 7S collagen and type VI collagen levels were correlated with the degree of hepatic fibrosis. CONCLUSIONS: Serum 7S collagen and type VI collagen are useful markers for diagnosing liver fibrosis. And the combined measurement of IV-C, VI-C and other markers of connective tissue metabolism or biochemical data seems to provide additional information to predict progressive hepatic fibrosis.

Animals↗
PubMed1997

[Synthesis and degradation of type IV collagen in rat experimental liver fibrosis].

OBJECTIVE: To investigate the synthesis and degradation of type IV collagen in CCl4-induced SD rat liver fibrosis. METHODS: Dynamic changes and relationships among the tissue alpha 1 (IV) procollagen mRNA, type IV collagen (Col IV) and serum 7S polypeptide fragment of Col IV in fibrotic livers induced by CCl4 with choline difficiency diet were studied using immunohistochemistry, Northern analysis, in situ hybridization and serum RIA techniques. RESULTS: The transcription of alpha 1 (IV) procollagen mRNA in fibrotic liver and the content of serum 7S polypeptide fragment derived from tissue Col IV degradation was enhanced promptly and obviously in earlier stage of experiment, but not synchronous afterwards. In the early stage of experiment, alpha 1 (IV) procollagen mRNA transcripts was localized in sinusoid Ito cells and endothelial cells. In the mid and late stage, alpha 1 (IV) procollagen mRNA transcripts was localized in myofibroblasts (MFs), fibroblasts (Fbs) and endothelia of small blood vessels in fibrotic septa. CONCLUSIONS: The change of serum 7S polypeptide fragment could reflect the motabolic state of Col IV and the degree of tissue injury in fibrogenesis and might have some clinical significance in identifying the activiation of the liver fibrosis. The "Ito cell-myofibroblast-fibroblast" effective cell system and sinusoid endothelia were the Col IV producing cells during fibrogenesis, in which sinusoid endothelia, as another source of Col IV production, participated in the capillization of liver sinusoids.

Animals↗
PubMed1996

Activation of A3 adenosine receptors on human eosinophils elevates intracellular calcium.

Adenosine (ADO) is a potent bronchoconstrictor in allergic patients and has been shown to increase the release of histamine from human lung tissues. Antagonists of ADO A1 and A2A receptors are not effective in attenuating these effects. Therefore, involvement of ADO A3 receptors in the bronchoconstrictor and/or inflammatory effects have to be considered. Eosinophils also play a pivotal role in allergic diseases such as asthma, thus it is natural to consider a link between the A3 receptor and eosinophils. Human peripheral blood eosinophils express the ADO A3 receptor as indicated by detection of the transcript for A3 receptors in polymerase chain reaction-amplified cDNA derived from the cells. A3 receptors on eosinophil membranes were characterized using the A3 receptor agonist radioligand 125I-labeled AB-MECA, which yielded Bmax and Kd values of 1.31 pmol/mg protein and 3.19 nmol/L, respectively. Treatment of eosinophils with the highly potent and selective A3 receptor agonist CI-IB-MECA clearly induced Ca2+ release from intracellular Ca2+ pools followed by Ca2+ influx, suggesting the presence of phospholipase C-coupled A3 receptors. In contrast, the ADO receptor agonists CPA and CGS 21680, selective for A1 and A2A receptors, respectively, at concentrations of < or = 30 mumol/ L did not elevate the intracellular Ca2+ level. These results attest to the existence of ADO A3 receptors on eosinophils and suggest that ADO stimulates these cells to release Ca2+ from intracellular stores via the activation of A3 receptors.

Adenosine↗
PubMed1996

Synthesis and characterization of 4-iodophenylboronic acid: a new enhancer for the horseradish peroxidase-catalyzed chemiluminescent oxidation of luminol.

4-Iodophenylboronic acid has been synthesized and shown to be a potent enhancer of the chemiluminescent horseradish peroxidase (Type VI-A)-catalyzed oxidation of luminol and isoluminol. The enhancer was effective (>100-fold enhancement) in the concentration range 10-1500 microM. Light emission in the presence of the enhancer peaked at 5-10 min after initiation of the reaction and then decayed very slowly. 4-Iodophenylboronic acid also enhanced reactions catalyzed by horseradish peroxidase Type IX. The detection limit for Type VI-A horseradish peroxidase was 509 amol, and optimum signal enhancement was obtained at 769 microM compared to 154 microM for 4-iodophenol under the same conditions.

Blotting, Western↗
PubMed1996

Location of a potential transport binding site in a sigma class glutathione transferase by x-ray crystallography.

The crystal structure of the sigma class glutathione transferase from squid digestive gland in complex with S-(3-iodobenzyl)glutathione reveals a third binding site for the glutathione conjugate besides the two in the active sites of the dimer. The additional binding site is near the crystallographic two-fold axis between the two alpha 4-turn-alpha 5 motifs. The principal binding interactions with the conjugate include specific electrostatic interactions between the peptide and the two subunits and a hydrophobic cavity found across the two-fold axis that accommodates the 3-iodobenzyl group. Thus, two identical, symmetry-related but mutually exclusive binding modes for the third conjugate are observed. The hydrophobic pocket is about 14 A from the hydroxyl group of Tyr-7 in the active site. This site is a potential transport binding site for hydrophobic molecules or their glutathione conjugates.

Animals↗
PubMed1996

First-sphere and second-sphere electrostatic effects in the active site of a class mu gluthathione transferase.

The activation of the thiol of glutathione (GSH) bound in the active site of the class mu glutathione transferase M1-1 from rat involves a hydrogen-bonding network that includes a direct (first-sphere) interaction between the hydroxyl group of Y6 and the sulfur of GSH and second-sphere interactions involving a hydrogen bond between the main-chain amide N-H of L12 and the hydroxyl group of Y6 and an on-face hydrogen bond between the hydroxyl group of T13 and the pi-electron cloud of Y6 (i.e., T13-OH---pi-Y6-OH--- -SG). The functions of these hydrogen bonds have been examined with a combination of site-specific mutagenesis and X-ray crystallography. The hydroxyl group of Y6 has a normal pKa of about 10 even though it is shielded from solvent and is in a largely hydrophobic environment. The apparent pKa of GSH in the binary Y6F.GSH complex is increased by 1.6 log units, and the reactivity of the enzyme-bound nucleophile is reduced. The catalytic properties of the Y6L mutant are identical to those of Y6F, suggesting that the weakly polar on-edge interaction between the aromatic ring and sulfur has no influence on catalysis. The refined three-dimensional structure of the Y6F mutant in complex with GSH shows no major structural perturbation of the protein other than a change in the coordination environment of the sulfur. Removal of the second-sphere influence of the on-face hydrogen bond between the hydroxyl groups T13 as in the T13V and T13A mutants elevates the pKa of enzyme-bound GSH by about 0.7 pKa units. Crystal structures of these mutants show that structural changes in the active site are minor and suggest that the changes in pKa of E.GSH are due to the presence or absence of the on-face hydrogen bond. The T13S mutant has a completely different side-chain hydrogen-bonding geometry than T13 in the native enzyme and catalytic properties similar to the T13A and T13V mutants consistent with the absence of an on-face hydrogen bond. The gamma-methyl group of T13 is essential in enforcing the on-face hydrogen bond geometry and preventing the hydroxyl group from forming more favorable conventional hydrogen bonds.

Animals↗