Biomedical subjects

G Luo

Publications and source records attributed to G Luo.

At least 55 records · Page 3Linked to original sources

PubMed2000

Chk1 is an essential kinase that is regulated by Atr and required for the G(2)/M DNA damage checkpoint.

Chk1, an evolutionarily conserved protein kinase, has been implicated in cell cycle checkpoint control in lower eukaryotes. By gene disruption, we show that CHK1 deficiency results in a severe proliferation defect and death in embryonic stem (ES) cells, and peri-implantation embryonic lethality in mice. Through analysis of a conditional CHK1-deficient cell line, we demonstrate that ES cells lacking Chk1 have a defective G(2)/M DNA damage checkpoint in response to gamma-irradiation (IR). CHK1 heterozygosity modestly enhances the tumorigenesis phenotype of WNT-1 transgenic mice. We show that in human cells, Chk1 is phosphorylated on serine 345 (S345) in response to UV, IR, and hydroxyurea (HU). Overexpression of wild-type Atr enhances, whereas overexpression of the kinase-defective mutant Atr inhibits S345 phosphorylation of Chk1 induced by UV treatment. Taken together, these data indicate that Chk1 plays an essential role in the mammalian DNA damage checkpoint, embryonic development, and tumor suppression, and that Atr regulates Chk1.

Alleles↗

PubMed2000

HIV-2 transmembrane protein gp36 binds to the putative cellular receptor proteins P45 and P62.

Based on the findings that two cellular proteins of 45 kDa (P45) and 62 kDa (P62) serve as the putative receptor molecules for binding of HIV-1 transmembrane protein gp41 to human T, B lymphocytes and monocytes, we examined whether HIV-2 gp36 and HIV-1 gp41 share the putative receptor proteins P45 and P62. In SPR-assay (SPR: surface plasmon resonance), the recombinant soluble gp36 (rsgp36: Env aa518-678 from clone ROD) like the recombinant soluble gp41 (rsgp41: Env aa539-684 from clone BH10) was binding to P45 and P62. By affinity capillary electrophoresis (ACE)-analysis, formation of stable rsgp36-P45 and rsgp36-P62 complexes were confirmed, and the interactions of rsgp36 with P45 and P62 is quite strong with a fast association rate and a slow dissociation rate. These results indicate that HIV-2 gp36 and HIV-1 gp41 have the common putative cellular receptor proteins P45 and P62, and the binding of gp36 to human lymphocytes and monocytes could be based on the interaction between gp36 and P45 and P62.

Amino Acid Sequence↗

PubMed2000

The multifocal electroretinogram in age-related maculopathies.

To measure and compare the multifocal electroretinogram in control group and patients with age-related maculopathies, 17 eyes of control subjects, 9 eyes of wet-form ARMD, 8 eyes of dry-form ARMD and 14 eyes of idiopathic macular hole were tested with VERIS Sciences 4.0. The latencies and average response densities of 6 ring retinal regions in control eyes were compared with those in ARMD and macular hole. The amplitude depression and latency prolongation were found in age-related maculopathies. The changes of multifocal ERG were dramatic in wet-form ARMD and moderate in dry-form ARMD and IMH, which were correspondent with the pathological changes of the diseases. Our results suggest that the multifocal electroretinogram can be used to quantity the visual function in age-related maculopathies.

Aged↗

PubMed2000

Cancer predisposition caused by elevated mitotic recombination in Bloom mice.

Bloom syndrome is a disorder associated with genomic instability that causes affected people to be prone to cancer. Bloom cell lines show increased sister chromatid exchange, yet are proficient in the repair of various DNA lesions. The underlying cause of this disease are mutations in a gene encoding a RECQ DNA helicase. Using embryonic stem cell technology, we have generated viable Bloom mice that are prone to a wide variety of cancers. Cell lines from these mice show elevations in the rates of mitotic recombination. We demonstrate that the increased rate of loss of heterozygosity (LOH) resulting from mitotic recombination in vivo constitutes the underlying mechanism causing tumour susceptibility in these mice.

Adenosine Triphosphatases↗

PubMed2000

Photoelectrochemistry as a novel strategy for DNA hybridization detection.

The special properties of ssDNA and dsDNA molecules in structure and electric behavior, may offer us some new ideas for the fabrication of genosensors and DNA-chips. In this work, the photoelectrochemical method was firstly employed to characterize the photoelectric behavior of a ssDNA probe electrode, which was prepared with the self-assembly technique, and its resulting dsDNA electrode. The obvious decrease in the photocurrent of the dsDNA modified electrode at open potential or a bias voltage indicated that photoelectrochemistry was another useful method for DNA hybridization detection. Using the special design of ssDNA probes, we attempt to discuss further the relationship between the properties of DNA molecules and their photoelectric behaviors. In addition, the electrochemical impedance method was employed to verify the occurrence of some modifications over the electrode interface before and after the hybridization event.

DNA↗

PubMed2000

Quantitative determination of surface concentration of human apolipoprotein H with capillary electrophoresis.

The phospholipid monolayer at an air/water interface is widely used to mimic the biological membrane. The dynamic process of the protein or peptide interacting with lipid molecules can be reflected in the change in surface pressure of the monolayer. But the conventional method used to measure the surface pressure change gives results that cannot easily be correlated with the contribution of a single protein molecule. Previously, measuring the surface concentration of the protein molecules at the air/water interface has required the protein to be labeled with radioactivity or fluorescence. Here, a new method using capillary electrophoresis is introduced to measure the surface concentration of the protein. The results show at least two advantages of the new method: The numerical results of protein concentration can be obtained in a more precise and rapid way; and there is no need to label the protein sample or to build a special monolayer setup.

Cell Membrane↗

PubMed2000

De novo initiation of RNA synthesis by the RNA-dependent RNA polymerase (NS5B) of hepatitis C virus.

Hepatitis C virus (HCV) NS5B protein possesses an RNA-dependent RNA polymerase (RdRp) activity, a major function responsible for replication of the viral RNA genome. To further characterize the RdRp activity, NS5B proteins were expressed from recombinant baculoviruses, purified to near homogeneity, and examined for their ability to synthesize RNA in vitro. As a result, a highly active NS5B RdRp (1b-42), which contains an 18-amino acid C-terminal truncation resulting from a newly created stop codon, was identified among a number of independent isolates. The RdRp activity of the truncated NS5B is comparable to the activity of the full-length protein and is 20 times higher in the presence of Mn(2+) than in the presence of Mg(2+). When a 384-nucleotide RNA was used as the template, two major RNA products were synthesized by 1b-42. One is a complementary RNA identical in size to the input RNA template (monomer), while the other is a hairpin dimer RNA synthesized by a "copy-back" mechanism. Substantial evidence derived from several experiments demonstrated that the RNA monomer was synthesized through de novo initiation by NS5B rather than by a terminal transferase activity. Synthesis of the RNA monomer requires all four ribonucleotides. The RNA monomer product was verified to be the result of de novo RNA synthesis, as two expected RNA products were generated from monomer RNA by RNase H digestion. In addition, modification of the RNA template by the addition of the chain terminator cordycepin at the 3' end did not affect synthesis of the RNA monomer but eliminated synthesis of the self-priming hairpin dimer RNA. Moreover, synthesis of RNA on poly(C) and poly(U) homopolymer templates by 1b-42 NS5B did not require the oligonucleotide primer at high concentrations (>/=50 microM) of GTP and ATP, further supporting a de novo initiation mechanism. These findings suggest that HCV NS5B is able to initiate RNA synthesis de novo.

Animals↗

PubMed2000

Stat5b inhibits NFkappaB-mediated signaling.

Signal transducers and activators of transcription (Stat) are latent transcription factors that participate in cytokine signaling by regulating the expression of early response genes. Our previous studies showed that Stat5 functions not only as a transcriptional activator but also as a transcriptional inhibitor, depending on the target promoter. This report further investigates the mechanism of Stat5b-mediated inhibition and demonstrates that PRL-inducible Stat5b inhibits nuclear factorkappaB (NFkappaB) signaling to both the interferon regulatory factor-1 promoter and to the thymidine kinase promoter containing multimerized NFkappaB elements (NFkappaB-TK). Further, PRL-inducible Stat5b inhibits tumor necrosis factor-alpha signaling presumably by inhibiting endogenous NFkappaB. This Stat5b-mediated inhibitory effect on NFkappaB signaling is independent of Stat5b-DNA interactions but requires the carboxyl terminus of Stat5b as well as Stat5b nuclear translocation and/or accumulation, suggesting that Stat5b is competing for a nuclear factor(s) necessary for NFkappaB-mediated activation of target promoters. Increasing concentrations of the coactivator p300/CBP reverses Stat5b inhibition at both the interferon-regulatory factor-1 and NFkappaB-TK promoters, suggesting that Stat5b may be squelching limiting coactivators via protein-protein interactions as one mechanism of promoter inhibition. These results further substantiate our observation that Stat factors can function as transcriptional inhibitors. Our studies reveal cross-talk between the Stat5b and NFkappaB signal transduction pathways and suggest that Stat5b-mediated inhibition of target promoters occurs at the level of protein-protein interactions and involves competition for limiting coactivators.

Animals↗

PubMed2000

Definition of tumor-associated antigens in hepatocellular carcinoma.

With an estimated annual incidence of about one million cases, hepatocellular carcinoma (HCC) is one of the most common neoplasms worldwide. Of all malignant diseases, it is the major cause of death in some regions of Africa and Asia. The pathogenic mechanisms responsible for HCC are not well defined, and therapeutic means, especially in inoperable HCCs, are still unsatisfactory and await improvement. In the quest for tumor antigens exploitable for gene therapy, we studied immune responses in the context of HCC. A cDNA library derived from a human HCC sample was screened using the SEREX approach. Nineteen distinct antigens reactive with autologous IgG were identified. Sequence analysis revealed three of the cDNA clones to code for hitherto unknown proteins and 16 known genes products. Proteins as diverse in function as LDH, albumin, and kinectin were found. Furthermore, proteins involved in the transcription/translation machinery had elicited an immune response in the autologous host. A panel of allogenic sera including sera from patients with hepatitis, liver cirrhosis, HCC, and other tumor entities, as well as sera from normal individuals, was used for frequency analysis of antibody responses. Whereas allogenic sera of HCC patients detected most antigens at a high percentage, control sera were rarely antibody-positive. The nature of the major fraction of antigens described here are linked to liver. Thus, our findings demonstrate not only the complexity of the humoral immune response against HCC, but may also offer new insight into mechanisms underlying transformation of the liver cell.

Adult↗

PubMed2000

[Gil-Vernet anti-reflux operation by united application of television laparoscopy and vesicourethral laparoscopy].

OBJECTIVE: To discuss the possibility of united application of television laparoscopy and vesicourethral laparoscopy in Gil-Vernet operation. METHODS: The animal model of vesicourethral reflux (VUR) was established using rabbits. The Gil-Vernet operation was carried out by united application of television laparoscopy and vesicourethral laparoscopy. RESULTS: The VUR model was successfully established in 13 rabbits, and the reflux was successfully cured by microsurgical methods. CONCLUSIONS: This method had the advantages of television laparoscopy, vesicourethral laparoscopy and the Gil-Vernet such as no dissection of inner part of ureter-bladder wall, small wound, less bleeding, fast recovery, less complication and possible repetitive operation. It can be used in ill children with VUR.

Animals↗

PubMed2000

[Prolonging the survival of transplanted alloskin by transferring the CTLA(4)Ig locally with recombinant adenovirus vector in mice].

OBJECTIVE: To find a simple and practical way to prolong the survival of transplanted alloskin to cover the burn and other wounds. METHODS: A recombinant CTLA(4)Ig-Adenovirus expression vector was constructed by means of homo recombination, and then transferred either into cultured murine skin grafts ex vivo or local wound surface. The expression of CTLA(4)Ig in cultured skin was immunohistochemically determined. Moreover, the survival time of transplanted alloskin from Kunming mice to Balb/c mice was evaluated. RESULTS: The CTLA(4)Ig-Adenovirus vector could be successfully transferred and expressed in the cultured murine skin, and the locally used recombinant CTLA(4)Ig-Adenovirus vector could significantly prolong the survival of the transplanted alloskin from 8 d to 21 d. CONCLUSION: Local transfection of the CTLA(4)Ig-Adenovirus vector is a simple and effective way to prolong the survival of alloskin grafts.

Abatacept↗

PubMed2000

[P15(INK4B) gene methylation in malignant hematopoietic diseases].

OBJECTIVE: To study the effect of operative region hypermethylation gene in human malignant hematopoietic tumors. METHODS: The abnormal methylation rate of P(15)(INK4B) gene 5'CpG island in 68 cases of malignant hematopoietic tumor samples were determined by methylation specific PCR using bisulfite modified DNA. RESULTS: The methylation rates of P(15)(INK4B) were 84%, 0, 50% and 75%, respectively, for 25 cases of acute myeloid leukemia (AML), 15 chronic myeloid leukemia (CML), 16 myelodysplastic syndrome (MDS) and 12 multiple myeloma (MM). P(15)(INK4B) gene was frequently methylated in patients with high risk MDS and early stage of MM. CONCLUSION: Hypermethylation of P(15)(INK4B) gene is one of the main causes of its inactivation. Hypermethylation of CpG island was closely related to the development of malignant hematopoietic diseases.

Acute Disease↗

PubMed2000

[The influence of experimental scotoma on multifocal electroretinogram].

PURPOSE: To detect the sensitivity and the repeatability of multifocal electroretinogram (mfERG). METHOD: The effects of experimental absolute and relative scotomas on mfERG with 103 hexagons were observed on 8 normal eyes. The scotomas were produced by simultaneous and multi located masks on the hexagons of the screen in 6 different locations with black paper, and the neutral filters of 0.3 and 0.6 log unit. The repeatability was evaluated by analysis the data from 5 unmasked hexagons in 4 successive tests. RESULTS: When the hexagons were 1/2 or wholly masked with the black paper and the two kinds of the filters, the amplitudes of N1 and P1 waves in these areas were significantly decreased as with the reduced transferability of light. When the hexagon was 1/3 masked, there were no significant differences between the different kinds of mask and the unmasked control. There were no significant changes in the datas from the selected unmasked hexagons in the 4 successive recordings. CONCLUSION: mfERG is an unique sensitive visual electrophysiological test with high sensitivity and good repeatability. When 103 hexagons stimulating pattern is used, it could detect the scotoma larger than 1/3 of each hexagon.

Adult↗

PubMed2000

[The contrast study of preoperative flash visual evoked potential test and the postoperative resumed visual acuity in senile cataract patients].

PURPOSE: To study the using value of flash visual evoked potentials (FVEP) in predicting the resumed visual acuities in senile cataract patients. METHODS: Forty-three eyes with senile cataract had been conducted extracapsular cataract extraction combined with posterior chamber intraocular lens implantation. The contrast study had been carried out in this research between preoperative FVEP, light projection and color discrimination tests with the postoperative regained visual acuities. RESULTS: There were significant correlations between the regained visual acuities and the amplitudes of FVEP (X1), the latencies of P1 wave (X2) as well as color discriminations (P < 0.01). The coefficients were 0.7277, -0.5678 and 0.4302 in sequence. There was no correlation between the resumed visual acuities and the light projection test before operation. The formula of linear regression between the visual acuities (Y) and the indexes of FVEP was Y = 0.2255 +0.047X1 -0.0026X2. CONCLUSION: FVEP is an effective method to evaluate the visual function before the cataract operation. It may predict the resumed visual acuity.

Aged↗

PubMed2000

[Spectral analysis and composition determination of blue ballpoint writing inks].

Main compositions of ballpoint inks were determined by analyzing some tropical Fourier Transform Infrared(FTIR) spectra of 108 kinds of ballpoint inks. By using this method, the blue ink samples have been divided to two groups, 18 species depend on their spectral characteristics such as peak location, peak intensity. The reaction mechanism of age changes due to aging of the ink's compositions was discussed. The study is the first step for establishing the analytical date base of ballpoint inks system and estimating the age of ballpoint in written text has been offered. The advantage of this method is fast, reliable and nondestructive.

Handwriting↗

PubMed2000

[Spectrum analysis of blue ball-point ink components by FTIR microsope].

The FT-IR microscope spectra of 108 kinds of blue ball-point writing inks have been analyzed in detail in this paper. According to the transmittance spectra, the composition in the ink such as the solvent, the pigment and the resin was identified. It is the base to determination of the age of ball-point writing inks nondestructively.

Handwriting↗

PubMed1999

Novel quinolizidine salicylamide influenza fusion inhibitors.

A novel series of quinolizidine salicylamides was synthesized as specific inhibitors of the H1 subtype of influenza A viruses. These inhibitors inhibit the pH-induced fusion process, thereby blocking viral entry into host cells. Compound 16 was the most active inhibitor in this series with an EC50 of 0.25 microg/mL in plaque reduction assay. The synthesis and the SAR of these compounds are discussed.

Animals↗

PubMed1999

Noncompetitive immunoassays using protein G affinity capillary chromatography and capillary electrophoresis with laser-induced fluorescence detection.

A new and simple approach to perform immunoassay using protein G affinity capillary chromatography and laser-induced fluorescence detection was described. A noncompetitive assay for monoclonal anti-bovine serum albumin (BSA) was used to test the performance of the system. Fluorescein isothiocyanate labeled BSA was used as a tracer to determine anti-BSA in pM level. Capillaries with inner diameter of 150 microns were packed with recombinant protein G-bound perfusive support. The packed capillary was used to capture the immunocomplexes, which were subsequently desorbed by 100 mM glycine (pH 9.0). Open tube capillary electrophoresis-based immunoassay (CEIA) for anti-BSA was also performed. Using standard samples, calibration curves for anti-BSA was established in both assays. Compared with CEIA, this system improved the concentration sensitivity for about 100-fold due to the pre-concentration of immunocomplex in the protein G column, while the mass sensitivity was similar in the two methods.

Antibodies, Monoclonal↗