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Biomedical subjects

S Xie

Publications and source records attributed to S Xie.

At least 73 records · Page 4Linked to original sources
PubMed1998

[Effect of the IL-6 transfected bone marrow stromal cells on the recovery of hematopoietic functions in bone marrow transplanted mice].

OBJECTIVE: To study the effect of the IL-6 transfected bone marrow stromal cell, QXMSC1 IL-6, on the hematopoietic reconstitution in bone marrow transplanted mice. METHODS: Bone marrow transplantation model was established by infusing hematopoietic cells combined with QXMSC1 IL-6 into syngeneic recipient mice through the tail vein. CFU-S, CFU-GM, CFU-E, BFU-E, and peripheral blood pictures were assayed. RESULTS: QXMSC1 IL-6 could increase the CFU-S, CFU-GM, CFU-E and BFU-E yields in BMT mice, and accelerate the recovery of peripheral blood cells. CONCLUSION: QXMSC1 IL-6 can improve the hematopoietic reconstitution in bone marrow transplanted mice.

Animals↗
PubMed1998

[Mechanism of preventing the recurrence of bladder carcinoma by intravesical instillation of BCG plus IL-2].

OBJECTIVE: To study the mechanism of preventing the recurrence of bladder carcinoma by intravesical instillation of BCG plus IL-2. METHOD: Intravesical instillation of BCG or BCG plus IL-2 were carried out in the bladder transitional cell carcinoma patients undergoing surgical operation (16, 19 cases respectively). RESULT: They were followed up for 14-22 months. The recurrence rates were 31.25% and 21.05% respectively. At 6 weeks after the instillation of IL-2 plus BCG, the peripheral blood NKCF activity was increased significantly and there was a significant positive correlation between the activities of NKCF and IL-2. CONCLUSION: The intravesical instillation of IL-2 plus BCG is clearly superior to only BCG in preventing recurrence of bladder carcinoma. There may be immuno-enhancement and immuno-synergism.

Adjuvants, Immunologic↗
PubMed1998

[Separation of human bladder cancer cells from bone marrow with a kind of immunomagnetic microspheres].

By binding a monoclonal antibody BDI-1 to polystyrene magnetic micospheres using physical and chemical methods together, a kind of immunomagnetic microspheres (IMMS), which can specifically bind target cells and give it magnetic response, was sucessfully constituted. The results of indirect immunofluorescence and cell binding suggest that IMMS can effectively bind target cells while do not have non-specific binding activity. The influence of antibody added and the ratio between IMMS and cells were also studied. After purging cancer cells from bone marrow of mice with IMMS, the cancer cells were effectively removed while most of the bone marrow cells were recovered.

Animals↗
PubMed1998

[Molecular spectra study of fabrication reaction of lead styphnate].

The entire reaction process in the fabrication of lead styphnate in situ was analyzed by using laser Raman spectrometer and FTIR spectrometer, including reaction time determination, testing of the reactants proportions, and identification of the resultants in terms of molecular structure.

English Abstract↗
PubMed1997

The diversity and evolutionary relationships of the pregnancy-associated glycoproteins, an aspartic proteinase subfamily consisting of many trophoblast-expressed genes.

The pregnancy-associated glycoproteins (PAGs) are structurally related to the pepsins, thought to be restricted to the hooved (ungulate) mammals and characterized by being expressed specifically in the outer epithelial cell layer (chorion/trophectoderm) of the placenta. At least some PAGs are catalytically inactive as proteinases, although each appears to possess a cleft capable of binding peptides. By cloning expressed genes from ovine and bovine placental cDNA libraries, by Southern genomic blotting, by screening genomic libraries, and by using PCR to amplify portions of PAG genes from genomic DNA, we estimate that cattle, sheep, and most probably all ruminant Artiodactyla possess many, possibly 100 or more, PAG genes, many of which are placentally expressed. The PAGs are highly diverse in sequence, with regions of hypervariability confined largely to surface-exposed loops. Nonsynonymous (replacement) mutations in the regions of the genes coding for these hypervariable loop segments have accumulated at a higher rate than synonymous (silent) mutations. Construction of distance phylograms, based on comparisons of PAG and related aspartic proteinase amino acid sequences, suggests that much diversification of the PAG genes occurred after the divergence of the Artiodactyla and Perissodactyla, but that at least one gene is represented outside the hooved species. The results also suggest that positive selection of duplicated genes has acted to provide considerable functional diversity among the PAGs, whose presence at the interface between the placenta and endometrium and in the maternal circulation indicates involvement in fetal-maternal interactions.

Amino Acid Sequence↗
PubMed1997

Dominant-negative CREB inhibits tumor growth and metastasis of human melanoma cells.

The ATF/CREB family of eukaryotic transcription factors contain the bZIP structural motif and mediate their transcriptional activities via heterodimerization with ATF and AP-1 family members. Quenching of CREB-associated proteins by a dominant-negative CREB (KCREB) that is mutated within its DNA-binding domain decreases radiation resistance of human melanoma cells. The purpose of this study was to determine the role of CREB in tumor growth and metastasis of human melanoma using KCREB. Highly metastatic MeWo human melanoma cells were transfected with the KCREB expression vector and subsequently analysed for changes in their tumorigenic and metastatic potential. Expression of KCREB in MeWo human cells decreased their tumorigenic and metastatic potential in nude mice compared with parental and control transfected cells. The KCREB-transfected cells displayed downregulation of 72 kDa collagenase type IV (MMP-2) mRNA expression and activity and decreased invasiveness through Matrigel-coated filters. Moreover, transcriptional activities mediated by the CAT gene driven by the MMP-2 promoter were decreased by 14-45-fold in KCREB-transfected cells. In addition, the cell-surface adhesion molecule MCAM/MUC18 that is involved in metastasis of human melanoma was downregulated in the KCREB-transfected cells. These data indicate that, through their transcriptional activities, CREB and its associated proteins play an important role in the acquisition of the metastatic phenotype of human melanoma cells.

Animals↗
PubMed1997

Rigid porous polyacrylamide-based monolithic columns containing butyl methacrylate as a separation medium for the rapid hydrophobic interaction chromatography of proteins.

Macroporous poly(acrylamide-co-butyl methacrylate-co-N,N'-methylenebisacrylamide) monoliths containing up to 15% butyl methacrylate units have been prepared by direct polymerization within the confines of HPLC columns. The hydrodynamic and chromatographic properties of these 50 mm x 8 mm I.D. columns-such as back pressure at different flow-rates, effect of percentage of hydrophobic component in the polymerization mixture, effect of salt concentration on the retention of proteins, dynamic loading capacity, and recovery-were determined under conditions typical of hydrophobic interaction chromatography. Using the monolithic column, five proteins were easily separated within only 3 min.

Acrylic Resins↗
PubMed1997

Expression of MCAM/MUC18 by human melanoma cells leads to increased tumor growth and metastasis.

The cell surface adhesion molecule MCAM (MUC18) is strongly expressed by advanced primary and metastatic melanomas but is weaker and less frequent in nevus cells. Previous studies have shown that MCAM expression correlates with tumor thickness and metastatic potential of human melanoma cells in nude mice. To provide direct evidence that MCAM plays a role in tumor growth and metastasis of human melanoma, the nonmetastatic MCAM-negative primary cutaneous melanoma SB-2 cells were transfected with MCAM cDNA and analyzed subsequently for changes in their tumorigenic and metastatic potential. Enforced expression of MCAM in SB-2 cells rendered them highly tumorigenic and increased their metastatic potential in nude mice as compared with parental and control transfected cells. The transfected cells displayed increased homotypic adhesion, increased attachment to human endothelial cells, decreased ability to adhere to laminin, and increased invasiveness through Matrigel-coated filters. Anti-MCAM monoclonal antibody reversed these functions in the transfected cells but not in control cells. The above changes in function attributed to the expression of MCAM may underlie the contribution of MCAM/MUC18 to the malignant phenotype.

Animals↗
PubMed1997

Multiple pregnancy-associated glycoproteins are secreted by day 100 ovine placental tissue.

Pregnancy-associated glycoprotein (PAG)-1 (PAG1) and pregnancy-specific protein B are either identical or closely related antigens released by trophoblast binucleate cells of placentas of cattle. Sheep and other ruminants produce similar products. There is evidence, however, that these antigens, which are related structurally to the pepsinogens and other aspartic proteinases, are not single gene products but members of an extensive family. Here, the sequential use of ammonium sulfate precipitation and Sepharose blue, anion-exchange, and cation-exchange chromatographies, as well as isoelectric elution from a Mono P column, has allowed several PAG1-related molecules to be purified from the medium after culture of explants from Day 100 sheep placentas. Each of these PAGs cross-reacted to a varying extent with a panel of three different anti-PAG1 antisera. Four of them, all of which were major secretory products of the placenta, were subjected to amino-terminal microsequencing. Although each was related to ovine (ov) PAG1, none was identical. Reverse transcription-polymerase chain reaction was then used to amplify PAG1-related cDNA from Day 100 placental RNA. Seven novel full-length cDNA, all distinct from ovPAG1, were identified from 25 cDNA selected for sequencing. Only two of these (ovPAG3 and ovPAG7) encoded polypeptides identical in sequence at their inferred amino termini to one of the PAGs (ovPAG65) purified from explant cultures. Even so, they were only 84% identical in overall sequence. The remaining five cDNA were unique. In situ hybridization analysis revealed that expression of ovPAG3 and ovPAG7, like that of ovPAG1, is confined to trophoblast binucleate cells. The data confirm that at Day 100 of pregnancy the ovine placenta produces many different PAGs, which differ considerably in sequence and immunological cross-reactivity.

Amino Acid Sequence↗
PubMed1997

[Culture and characterization of rat lung microvascular endothelial cells].

Cultures of rat lung microvascular endothelial cells (RLMECs) were obtained from perepheral lung tissue. The lung tissue was cut into small pieces and cultured with RPMI-1640 containing 20% bovine calf serum, 90 micrograms/ml heparin, 4 mmol/L L-glutamine, 100 mu/ml penicillin and 100 micrograms/ml streptomycin. Erythrocytes and leukocytes left the tissue first, followed by RLMECs. Fibroblasts and other cells grew after 72 hours of culture. After 60 hours of culture, the lung tissue was discarded. RLMECs in flask showed regular cobblestone morphology and positive for binding of the lectin Bandeiraea simplicifolia I and indirect immunofluoresence staining with factor VIII antiserum.

Animals↗
PubMed1997

[Fluorescence lifetimes of squamous carcinoma, adenocarcinoma and normal human lung tissues in vitro by time-resolved fluorescence].

Using pulsed dye laser 632.8nm, lifetimes of adenocarcinoma, squamous carcinoma and normal human lung tissues in vitro have been measured by time-resolved fluorescence as 5.1, 5.6 and 6.3 ns respectively. Time-resolved fluorescence shows that the decay time of tumor tissues is faster than that of normal tissues. The results may offer new diagnostic method to determine cancer.

Adenocarcinoma↗
PubMed1996

lem7, a novel temperature-sensitive Arabidopsis mutation that reversibly inhibits vegetative development.

An important question in developmental biology concerns the mechanisms by which a few cells coordinate division and differentiation to yield the complex structures and organs found in multicellular organisms. During vegetative growth in plants, cells in the apical meristem must coordinate division and differentiation to yield the fully mature leaf organ. Alterations in these processes may result in an abnormal leaf. In this paper we present the isolation and characterization of an EMS-generated, cold-temperature-sensitive mutation in Arabidopsis thaliana, designated lem7 (leaf morphogenesis). lem7 is a semidominant mutation that maps to a novel locus on chromosome 2. When grown at 16 degrees C, lem7 reversibly arrests leaf development at the shoot apex. In contrast, lem7 grown at 30 degrees C appears phenotypically normal. Our data also suggest that the Lem7 locus may not be involved solely in leaf organogenesis, but may also play a role in floral development and the maintenance of patterns and structures after cellular differentiation. At an intermediate temperature of 23 degrees C, leaves on the lem7 plant emerged phenotypically normal but began to show drastic changes at about 13 days postgermination. These changes include a reduced bilateral symmetry, a rough leaf lamina, a reduced number of trichomes, and an altered vascular network. Leaves that developed at the permissive temperature (30 degrees C) and shifted to the nonpermissive temperature (16 degrees C) form tumor-like outgrowths. Histological analysis of these tumor-like outgrowths and leaves grown at the intermediate temperature reveal abnormally large mesophyll cells, a disorganized mesophyll layer, and collapsed epidermal cells. We propose that the reversible inhibition of leaf development in lem7 under nonpermissive temperatures may serve as a useful tool for identifying genes involved in Arabidopsis leaf organogenesis.

Arabidopsis↗
PubMed1996

P210 Bcr-Abl interacts with the interleukin 3 receptor beta(c) subunit and constitutively induces its tyrosine phosphorylation.

Chronic myelogenous leukemia is a neoplasm of pluripotent hematopoietic cells. The P210 Bcr-Abl oncoprotein is a deregulated cytoplasmic tyrosine kinase that has been shown to cause chronic myelogenous leukemia-like neoplasms in mice. Cytokines such as interleukin 3 and granulocyte/macrophage-colony-stimulating factor regulate the growth and differentiation of hematopoietic precursors. These cytokines activate two distinct signals to the nucleus. One signal is through the Ras pathway, and the second involves activation of Jak2. We demonstrated that Bcr-Abl co-immunoprecipitates with, and constitutively phosphorylates, the common beta(c) subunit of the interleukin 3 and granulocyte/macrophage-colony-stimulating factor receptors. Our data show that formation of this complex leads to the constitutive tyrosine phosphorylation of Jak2. It has been demonstrated that Bcr-Abl interacts with Grb2 and Shc, which in turn activates the Ras pathway. Our new findings raise the possibility that Bcr-Abl activates signaling through both pathways in a factor-independent fashion.

Cell Transformation, Neoplastic↗
PubMed1996

Determination of 3,4-dihydroxyphenyl glycol in plasma by gas chromatography-mass spectrometry and high-performance liquid chromatography methods.

Several modifications of GC-MS and HPLC methods for plasma level DHPG have been described. The effects of storage temperature and stabilizing agents on DHPG stability have been studied. The stabilizing agent has been found to play a more important role than low-temperature storage in preventing DHPG from decomposition during sample storage. A specific and sensitive GC-MS method (electron impact) has been established using stable isotope-labeled DHPG as an internal standard. HPLC has been improved by modifying the conditions, resulting in a good separation of DHPG and internal standard from solvent front other early eluting compounds. Comparison of the GC-MS and HPLC procedures demonstrates a strong correlation between these two methods.

Aluminum Oxide↗
PubMed1996

Comparative modelling and analysis of amino acid substitutions suggests that the family of pregnancy-associated glycoproteins includes both active and inactive aspartic proteinases.

The pregnancy-associated glycoproteins (PAGs) are secretory products synthesized by the outer epithelial cell layer (chorion) of the placentas of various ungulate species. The amino acid sequences of eight PAGs have been inferred from cloned cDNA of cattle and sheep, as well as of the non-ruminant pig and horse. We compare the PAG sequences and present results of the three-dimensional models of boPAG-1 and ovPAG-1 that were constructed on the basis of the crystal structures of homologous porcine pepsin and bovine chymosin using a rule-based comparative modelling approach. Further, we compare peptide binding subsites defined by interactions with pepstatin and a decapeptide inhibitor (CH-66) modelled on the basis of crystal structures of other aspartic proteinases. We have extended our analysis of the peptide binding subsites to the other PAG molecules of known sequence by aligning the PAG sequences to the structural template derived from the pepsin family and by making use of the three-dimensional models of the boPAG-1 and ovPAG-1. The residues that are likely to affect peptide binding in the boPAG-1, ovPAG-1 and other PAG molecules have been identified. Sequence comparisons reveal that all PAG molecules may have evolved from a pepsin-like progenitor molecule with the equine PAG most closely related to the pepsins. The presence of substitutions at the S1 and other subsites relative to pepsin make it unlikely that either bovine, ovine or the porcine PAG-1 have catalytic activity. Only two of the eight PAGs examined (porcine PAG-2 and equine PAG-1) retain features of active aspartic proteinases with pepsin-like activity. Our results indicate that in the PAGs so far characterized the peptide binding specificities differ significantly from each other and from pepsin, despite their high sequence identities. Analysis of the various peptide binding subsites demonstrates why both bovine and ovine PAG-1 are capable of binding pepstatin. The strong negative charge in the binding cleft of boPAG-1 and ovPAG-1 indicates a preference for lysine- or arginine-rich peptides. PAGs represent a family where the possible peptide binding function may be retained through their binding specificities, but where the catalytic activity may be lost in some cases, such as the boPAG-1, ovPAG-1 and the poPAG-1.

Amino Acid Sequence↗
PubMed1996

Trophoblast-specific processing and phosphorylation of pregnancy-associated glycoprotein-1 in day 15 to 25 sheep placenta.

Bovine and ovine pregnancy-associated glycoproteins-1 (PAG-1) are products of binucleate trophoblast cells and belong to the aspartic proteinase gene family. Estimates of their relative molecular masses have varied considerably, from 47 to 90 kDa, even though the mature polypeptide has been inferred to be no more than 330 amino acids in length and that the glycosylated recombinant form synthesized in Chinese hamster ovary (CHO) or COS-1 cells had an apparent mass of 46 kDa. To establish the relationships among the various molecular forms, metabolic labeling, immunoprecipitation, and electrophoretic analysis were used to follow the biosynthesis of ovine PAG-1 (ovPAG-1) in placental explants. In time-course studies, ovPAG-1 could first be detected within 10 min as a 70-kDa form within the tissue. With time, forms of intermediate (53-61 kDa) and low (47 kDa) molecular mass began to accumulate. The latter predominated in medium after 6 h labeling. Pulse chase studies established that the 70-kDa forms were the precursors of the smaller species. Inhibition of glycosylation with tunicamycin or treatment with N-glycosidase F confirmed that ovPAG-1 contained N-linked oligosaccharide chains, but that this carbohydrate accounted for only a relatively small fraction (8-10 kDa) of the apparent mass. Consecutive treatment with neuraminidase and O-glycanase also reduced the apparent molecular mass of the precursor by approximately 11 kDa. OvPAG-1 incorporated 32P from [32P]orthophosphate into phosphoserine and phosphothreonine, but there was no incorporation of 35S from [35S]sulfate. The basis of the differences in molecular mass between the precursor and the final products remains to be elucidated, but the differences seem likely to be due to some unusual form of posttranslational modification introduced in the binucleate cell. The results of the study appear to explain the disparate size values that have been reported for these placenta-derived proteins.

Amino Acid Sequence↗
PubMed1996

Maternal recognition of pregnancy.

Maternal recognition of pregnancy reflects the various ways in which the mother responds to the presence of a conceptus within her reproductive tract. A part of the biochemical information she senses may be irrelevant to pregnancy outcome, but some reflects the attempts by the conceptus to gain some measure of control over corpus luteum function, uterine blood supply, the mother's immune system, and other aspects of maternal physiology. Most probably as a result of ongoing genetic conflict between the mother and the conceptus, a bewildering range of placental structures and trophoblast signaling mechanisms are encountered in eutherian mammals despite the fact that the uterus and conceptus share a common interest, which is the successful outcome of the pregnancy. Here we review some of the ways that such mammals maintain luteal function in early pregnancy and briefly discuss the related topics of embryonic loss and maternal monitoring of conceptus fitness. We next address the view that the conceptus is an intruder, recognized as foreign by the mother, that likely survives by using strategies analogous to those employed by successful parasites. In this context, we describe the pregnancy-associated glycoproteins, multiple isoforms of which are released at the trophoblast-endometrial interface during pregnancy of ungulate species. These molecules, which are structurally related to pepsin, are proposed to bind and sequester antigenic peptides, thereby serving an immunoprotective role.

Animals↗