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Biomedical subjects

Q Qian

Publications and source records attributed to Q Qian.

69 records · Page 4Linked to original sources
PubMed1997

Cloning and characterization of porcine enamelin mRNAs.

Dental enamel forms by matrix-mediated biomineralization. The components of the developing enamel matrix are generally specific for that matrix. The primary structures of three enamel proteins-amelogenin, tuftelin, and sheathlin (ameloblastin/amelin)-have been derived from cDNA sequences. Here we report the cloning and characterization of mRNA encoding a fourth enamel protein: enamelin. The longest porcine enamelin cDNA clone has 3907 nucleotides, exclusive of the poly(A) tail. The primary structure of the secreted protein is 1104 amino acids in length. Without post-translational modifications, the secreted protein has an isotope-averaged molecular mass of 124.3 kDa and an isoelectric point of 6.5. Polymerase chain-reaction phenotyping of enamelin cDNA suggests that porcine enamelin transcripts are not alternatively spliced and use a single polyadenylation/cleavage site. Immunohistochemical and Western blot analyses with an affinity-purified antipeptide antibody specific for the enamelin carboxyl terminus demonstrate that enamelin is synthesized and secreted by secretory-phase ameloblasts. The parent protein is a 186-kDa glycoprotein that concentrates along the secretory face of the ameloblast Tomes' process. Intact enamelin and proteolytic cleavage products containing its carboxyl terminus are limited to the most superficial layer of the developing enamel matrix, while other enamelin cleavage products are observed in deeper enamel.

Amino Acid Sequence↗
PubMed1997

[In vitro reversal of homoharringtonine resistance by the combination of tamoxifen and verapamil].

OBJECTIVE: To investigate the reversal of homoharringtonine (HHT)-resistance by tamoxifen (TAM) or verapamil (VER) alone or in combination. METHODS: The drug-sensitivity test was performed with semisolid agar culture. RESULTS: The cytotoxicity of HHT to K562/S cells was not enhanced by TAM or VER alone or in combination,but HHT resistance in HHT resistant cells (K562/H20) was reversed by VER and TAM at nontoxic doses (4micromol/L or 8micromol/L). The IC50 of K562/H20 for HHT decreased from 446.8 +/- 0.08microg/L to 45.1 +/- 0.02microg/L in the presence of 4micromol/L of VER, to 22.4 +/- 0.03microg/L in 8micromol/L of VER, to 85.1 +/- 0.03microg/L in 4micromol/L of TAM and to 26.4 +/- 0.02microg/L in 8micromol/L of TAM. In the presence of combinations of 2micromol/L VER and 4micromol/L TAM and of 2micromol/L VER and 8micromol/L TAM, IC50 of K562/H20 decreased to 30.4 +/- 0.02microg/L and 4.3 +/- 0.04microg/L, respectively. CONCLUSION: HHT-resistance could be reversed by VER or TAM alone, and the combination of the two drugs showed a synergistic effect.

Animals↗
PubMed1997

[The effect of antisense human Fas RNA on activation induced apoptosis of T cell].

OBJECTIVE: To explore an approach to the reduction of activation induced apoptosis of T cell so as to maximize the number of CTL and enhance the tumor cytotoxicity. METHODS: CD3-induced Jurkat cell line was used as the activated T cell apoptosis model,and the antisense Fas cDNA was introduced into Jurkat cells with retroviral vector. RESULTS: The expression level of Fas protein in Jurkat cells transducted with the retroviral vector was decreased. Apoptosis was reduced in antisense Fas-transfected Jurkat cells after anti-CD3 or anti-Fas treatment. CONCLUSION: Antisense blocking of Fas expression can partially inhibit Jurkat cell apoptosis induced by anti-CD3 or anti Fas.

Animals↗
PubMed1996

Fluid resuscitation attenuates early cytokine mRNA expression after peritonitis.

OBJECTIVE: To study the hypothesis that fluid resuscitation alters cytokine gene expression after experimental murine peritonitis. MATERIALS AND METHODS: Mice underwent cecal ligation and puncture (CLP) to induce peritonitis and were randomized to receive variable amounts of normal saline (0, 0.25, 1.0 ml. subcutaneously) and serum (0 or 0.1 mL) after operation. Hepatic and small intestinal (ileal) tissue were harvested at 3 or 6 hours after CLP, and total tissue RNA was extracted. Reverse transcriptase polymerase chain reaction was used to provide relative quantitation of tumor necrosis factor-alpha and interleukin (IL)-1 beta messenger RNA (mRNA) compared with beta-actin. RESULTS: CLP without resuscitation resulted in significant increases in hepatic tumor necrosis factor-alpha mRNA (1190% at 6 hours compared with normal animals), and IL-1 beta mRNA (1475%), and intestinal IL-1 beta mRNA (1243%). Volume administration attenuated cytokine expression at both 3 and 6 hours, and saline seemed to have more potent effects than serum. The volume of resuscitation correlated with survival at 18 hours. Survival in the saline (1 mL) + serum group was 90% at 18 hours compared with 20 to 40% in the groups with little or no resuscitation. Overall, there were no survivors at 30 hours. CONCLUSIONS: Fluid resuscitation (amount, composition, timing) should be an important consideration in the utilization of experimental infection models. Furthermore, optimization of the patient's intravascular volume status during sepsis may have important effects on immune responses, in addition to improving hemodynamic variables.

Animals↗
PubMed1996

Cloning, DNA sequence, and alternative splicing of opossum amelogenin mRNAs.

The enamel layer that covers the surfaces of teeth is thickest and most highly mineralized in mammals. The durability of mammalian enamel may have allowed for selection against the lifelong replacement of teeth that is observed in other vertebrates. Variation in enamel structure among animals is thought to be the result of evolutionary changes in the constituents of the developing enamel matrix. In placental mammals, the principal component of this matrix is amelogenin. We have determined the complete primary structures of two opossum amelogenins through a combination of protein sequencing, cloning, and DNA sequencing. RNA messages were cloned that encode 202- and 57-residue amelogenins, which are presumed to be expressed from the same gene but differ due to alternative splicing of identical pre-mRNAs. Edman degradation of the larger amelogenin ran for 42 cycles and yielded the sequence: IPLPPHPGHPGYINFS YEVLTPLKWYQSMMRQQYPSYGYEPM. The derived 202-residue amelogenin, assuming that serine 16 is phosphorylated, has an isotope-averaged molecular mass of 23,023.75 Daltons and a pI of 6.2. This is the largest amelogenin yet characterized. The increase in length is due to the presence of a 30-residue tandem repeat of QP(I/M) in exon 6 in the same position as a similar, but shorter, repeat expressed from the bovine X-chromosome. The 57-residue amelogenin, which is known from other organisms as the leucine-rich amelogenin protein (LRAP), has an isotope-averaged molecular mass of 6764.75 Daltons and a pI of 5.5. The opossum enamel protein is highly homologous to those previously characterized in eutherians and demonstrates that amelogenins were refined structurally prior to the metatherian/eutherian divergence between 100 and 150 million years ago.

Alternative Splicing↗
PubMed1996

Cloning, cDNA sequence, and alternative splicing of porcine amelogenin mRNAs.

In mammals, the organic matrix of developing enamel is dominated by amelogenins. To investigate the expression of proteins secreted into the developing enamel matrix, we have constructed a porcine enamel organ epithelia-specific cDNA library. The amelogenin fraction of the cDNA library was characterized by the cloning of amelogenin-specific polymerase chain-reaction (PCR) amplification products, 5' and 3' rapid amplification of cDNA ends (RACE), and by helper phage rescue of unamplified clones. Clones were characterized that encode porcine amelogenin isoforms 173, 157, 56, 41, and 40 amino acids in length. The structure of the porcine amelogenin gene differs from that of any of those yet described. There are two homologous but distinct exons 1, 2, and 7. One of the two exon 7s can vary in length depending upon the selection of either of two polyadenylation signal/cleavage sites. As a rule, a given exon 1 always pairs with the same exon 2 but can be associated with either exon 7. Despite significant sequence divergence within these exons, no differences are observed in exons 3, 5, and 6. We interpret these findings as evidence of a single amelogenin gene expressed from two promoters; however, the results do not exclude the existence of a second amelogenin gene. The variability generated through the use of alternate promoters and exon 7s primarily affects the non-coding regions of the message. A given amelogenin isoform expressed from the two promoters displays four amino acid differences within the signal peptide, while the secreted proteins are identical. Similarly, the alternative use of exon 7 does not alter the structure of the protein products. The pattern of RNA splicing of amelogenin pre-mRNAs is different for the transcripts expressed from the two promoters. The 173- and the 56-residue amelogenins can be expressed from either promoter, while the 157-residue amelogenin is generated by only one of the two promoters.

Alternative Splicing↗
PubMed1996

[Detection of stromelysin mRNA expression in human hepatocellular carcinoma by in situ hybridization].

For the propose of detecting the significance of stromelysin (of matrix metalloproteinase family) mRNA expression in the invasion and metastasis process of liver cell carcinoma, 19 cases of human hepatocellular carcinoma (HCC) and their surrounding tissues were studied by in situ hybridization techniques. Nine cases of the HCC tissues were positive while all the tumor surrounding tissues were negative. The stromelysin expression levels were higher in those HCC complicated with portal tumor emboli or in those classified pathologically in II-IV degree. It is considered that portal cancer emboli is a characteristic event for intrahepatic and extrahepatic metastasis of HCC, and matrix metalloproteinase may be of importance for the tumor invasion and metastasis.

Adult↗
PubMed1996

[Mechanisms of resistance to melphalan in leukemia cell line and reversal by interferon alpha].

OBJECTIVES: To study the mechanisms of resistance to alkylating agent melphalan (Mel) in leukemia cell and to investigate effect of modulation of resistance to Mel by IFN alpha. METHODS: A Mel-resistant variant of the leukemic cell line (K562/Mel) was developed in vitro by continuous exposure to Mel. The level of expression of several resistance-related gene in K562/Mel and the effect of reversal of resistance to Mel by IFN alpha were observed. RESULTS: K562/Mel was 8.0-fold resistant to Mel and also cross-resistant to nitrogen mustand and thiophosphoramide, but not to carmustine and doxorubicin. This enhanced Mel resistance was associated with increased level of GST alpha gene and total GST, but not with increased level of expression of GST pi, GST mu, MDR-1 and Top-II gene. IFN alpha, at 500 IU/ml, a noncytotoxic dosage significantly increased the cytotoxicity of Mel to K562/Mel. The reversal of Mel resistance is related to the decrease of the level of expression of GST alpha gene. CONCLUSION: Resistance to Mel is associated with increased level of GST alpha gene and total GST in leukemic cell. IFN alpha can reverse Mel resistance.

Antineoplastic Agents, Alkylating↗
PubMed1994

Elimination of mouse splenic macrophages correlates with increased susceptibility to experimental disseminated candidiasis.

To evaluate the role of macrophages in experimental disseminated candidiasis, mouse splenic macrophages were eliminated by i.v. delivery of liposome-entrapped dichloromethylene diphosphonate (L-Cl2MDP). Splenic tissue sections that were immunoperoxidase-stained with mAbs against marginal zone macrophages (MONTS-4), red pulp macrophages (SK39), and neutrophils (SK208) showed that 3 days after L-Cl2MDP treatment, macrophages but not neutrophils were depleted, and circulating neutrophils responded normally to an irritated peritoneum and showed normal phagocytic ability. That is, in response to thioglycollate in the peritoneum, neutrophils migrated in normal numbers to the peritoneal cavity and expressed the normal activation phenotype of high Mac-1 and low Mel-14 Ag levels. These neutrophils also showed normal ability to ingest Candida albicans yeast cells in both in vitro and in vivo assays. However, the spleens from L-Cl2MDP-treated mice lost their ability to bind yeast, which agrees with our previous findings that yeast cells bind specifically to marginal zone macrophages. When macrophage-depleted were systemically challenged with C. albicans, clearance of viable fungal elements from blood was slower, their kidneys had higher recoverable CFU, and both BALB/cByJ and congenitally thymic-deficient (nude) mouse strains did not survive as long as control mice. Mice given L-Cl2MDP recovered most of their macrophage function by 56 days and became normal in their resistance to C. albicans. These results indicate that macrophages play an important role in host resistance to experimental disseminated candidiasis, but the mechanism does not appear to involve T cell functions.

Animals↗
PubMed1994

Study of a low-selenium environment in China by INAA and Mössbauer spectrometry.

The neutron activation analysis, gamma coincidence spectroscopy, nondispersive hydrogen flame atomic fluorescence spectroscopy, and Mössbauer spectrometry were used to study the low-selenium environment of the Exi Autonomous Prefecture, a well-known Keshan disease region. The Se contents in the soil samples there range from 0.075-0.18 mg/kg with the average of 0.13 mg/kg, whereas in the maize from 0.001-0.018 mg/kg with the average of 0.0099 mg/kg. The 57Fe Mössbauer spectrum of the soil indicates an anoxic environment. In addition to the FE3+ species the compounds containing low-valence iron e.g., goethite, and so forth, also exist. The rare earth element (REE) pattern obtained by NAA further confirms the reductive soil environment, which causes the selenium deficiency.

China↗
PubMed1994

Total and methyl mercury levels in human scalp hairs of typical populations in China by NAA, GC(EC), and other techniques.

The contents of total and methyl mercury in scalp hair samples of 1179 fishermen living in a typical Hg-polluted region in northeast China and 27 lying-in women and their newborns in Beijing have been determined by INAA, GC(EC), and other techniques. Only 18 of all fishermen had Hg contents above 5 micrograms/g, which indicates that the Hg pollution there has been substantially alleviated. The longitudinal Hg patterns of the lying-in women showed a gradually lowering tendency during pregnant period. Further, the Hg contents of the newborn babies generally were above or close to those of their mothers, confirming the mechanism that the methyl Hg, an organic species of Hg with high toxicity, is readily able to penetrate the placental barrier and to accumulate in the fetus. Thus, the mercury poison has occurred at the early stage of pregnancy.

China↗
PubMed1994

Human cytomegalovirus elevates levels of the cellular protein p53 in infected fibroblasts.

Human cytomegalovirus (HCMV), like other DNA tumor viruses, induces morphological transformation of cells in vitro and stimulates host cell macromolecular synthesis in infected cells. Since other DNA tumor viruses, such as simian virus 40 and adenovirus, have previously been shown to interact with cellular protein p53, we investigated whether infection of cells by HCMV would modulate cellular p53 levels. Our results indicate that HCMV elevates cellular p53 levels on the order of 10- to 20-fold in infected fibroblasts. The induction of elevated p53 levels was dependent upon the presence of active virus and was prevented by neutralizing antibody. The induction of elevated p53 levels was determined not to be due to virus-receptor interactions or HCMV late events. The induction of elevated p53 levels commenced at immediate-early times of the HCMV multiplication cycle (6 h postinfection) and reached maximal levels by 24 h postinfection, before most of the HCMV DNA synthesis was initiated. HCMV immediate-early proteins were clearly shown to be responsible for elevating p53 levels in infected fibroblasts; expression of HCMV immediate-early region 1 and 2 proteins resulted in elevation of p53 levels in transfected human fibroblasts. This is the first report of increased p53 levels caused by HCMV in infected fibroblasts.

Antigens, Viral↗