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Biomedical subjects

Li Ma

Publications and source records attributed to Li Ma.

At least 37 records · Page 2Linked to original sources
PubMed2006

Growth inhibitory effects of quercetin on bladder cancer cell.

Quercetin, a flavonoid found in many fruits and vegetables, belongs to an extensive class of polyphenolic compounds. Previous studies reported that quercetin inhibits the proliferation of various cancer cells and tumor growth in animal models. We investigated the growth inhibition and colony formation of quercetin on three bladder cancer cells (EJ, J82 and T24). The expression of tumor suppressor genes and oncogenes such as P53, Survivin, PTEN, as well as the methylation status of these genes was also evaluated. We observed that quercetin induced apoptosis in bladder cancer cells in a time- and dose-dependent manner. Quercetin (100 micromolars) significantly inhibited EJ, T24 and J82 cell growth accompanied by an increase in the G0/G1 phase. In all cell lines, quercetin decreased the expression of mutant P53 and Survivin proteins. However, there was no change in the level of PTEN protein. Moreover, the DNA methylation levels of the estrogen receptor (Er-beta), P16INK4a and RASSF1A were strongly decreased (from 35 to 70%) in the quercetin-treated group compared to the control. In conclusion, our study suggested that quercetin inhibits growth, colony formation and hypermethylation of bladder cancer cell lines. Quercetin-induced apoptosis might be associated with a decrease in mutant P53 and Survivin proteins.

Apoptosis↗
PubMed2006

Detection of SNP epistasis effects of quantitative traits using an extended Kempthorne model.

Epistasis effects (gene interactions) have been increasingly recognized as important genetic factors underlying complex traits. The existence of a large number of single nucleotide polymorphisms (SNPs) provides opportunities and challenges to screen DNA variations affecting complex traits using a candidate gene analysis. In this article, four types of epistasis effects of two candidate gene SNPs with Hardy-Weinberg disequilibrium (HWD) and linkage disequilibrium (LD) are considered: additive x additive, additive x dominance, dominance x additive, and dominance x dominance. The Kempthorne genetic model was chosen for its appealing genetic interpretations of the epistasis effects. The method in this study consists of extension of Kempthorne's definitions of 35 individual genetic effects to allow HWD and LD, genetic contrasts of the 35 extended individual genetic effects to define the 4 epistasis effects, and a linear model method for testing epistasis effects. Formulas to predict statistical power (as a function of contrast heritability, sample size, and type I error) and sample size (as a function of contrast heritability, type I error, and type II error) for detecting each epistasis effect were derived, and the theoretical predictions agreed well with simulation studies. The accuracy in estimating each epistasis effect and rates of false positives in the absence of all or three epistasis effects were evaluated using simulations. The method for epistasis testing can be a useful tool to understand the exact mode of epistasis, to assemble genome-wide SNPs into an epistasis network, and to assemble all SNP effects affecting a phenotype using pairwise epistasis tests.

Computer Simulation↗
PubMed2006

Suppression of cyclic GMP-dependent protein kinase is essential to the Wnt/cGMP/Ca2+ pathway.

Novel downstream effectors sensing changes in intracellular concentrations of Ca2+ and cyclic GMP in response to activation of the Wnt/Frizzled-2 pathway were sought. Activation of Frizzled-2 suppressed protein kinase G activity while activating NF-AT-dependent transcription. Each of these responses was abolished by pertussis toxin and by knock-down of the expression of either Galphat2 or Galphao. Activation of NF-AT-dependent transcription in response to Wnt5a stimulation was suppressed by activation of protein kinase G and by buffering intracellular Ca2+. Elevation of intracellular cyclic GMP either by inhibition of cyclic GMP phosphodiesterase or by addition of 8-bromocyclic GMP was shown to activate protein kinase G, to block Ca2+ mobilization, as well as to markedly attenuate activation of NF-AT-dependent transcription in response to Wnt5a stimulation. Chemical inhibition of protein kinase G by Rp-8-pCPT-cGMP, conversely, was shown to provoke increased NF-AT gene transcription and Ca2+ mobilization in the absence of Wnt stimulation. Protein kinase G is shown to be a critical downstream effector of the noncanonical Wnt-Frizzled-2/cGMP/Ca2+ pathway.

Animals↗
PubMed2006

Calmodulin isoform-specific activation of a rice calmodulin-binding kinase conferred by only three amino-acids of OsCaM61.

The kinase activity of a Ca(2+)/calmodulin (CaM)-binding serine/threonine protein kinase from rice (Oryza sativa) (OsCBK) has been reported to be unaffected by OsCaM1 binding. In this study, we examined whether other rice CaMs can stimulate OsCBK. It was observed that OsCaM61 stimulated OsCBK in a Ca(2+)-dependent manner. In addition, Ala(111), Gly(123) and Ser(127) were identified as critical residues for OsCBK activation. Mutational study and fluorescent spectroscopy analysis indicated that CaM-binding affinity does not correlate with the kinase activity and that these key amino-acids in OsCaM61 play a vital role in suitable changes of OsCBK conformation for kinase activation.

Alanine↗
PubMed2006

Detection and characterization of metabolites in biological matrices using mass defect filtering of liquid chromatography/high resolution mass spectrometry data.

An improved mass defect filter (MDF) method employing both drug and core structure filter templates was applied to the processing of high resolution liquid chromatography/mass spectrometry (LC/MS) data for the detection and structural characterization of oxidative metabolites with mass defects similar to or significantly different from those of the parent drugs. The effectiveness of this approach was investigated using nefazodone as a model compound, which is known to undergo multiple common and uncommon oxidative reactions. Through the selective removal of all ions that fall outside of the preset filter windows, the MDF process facilitated the detection of all 14 nefazodone metabolites presented in human liver microsomes in the MDF-filtered chromatograms. The capability of the MDF approach to remove endogenous interferences from more complex biological matrices was examined by analyzing omeprazole metabolites in human plasma. The unprocessed mass chromatogram showed no distinct indication of metabolite peaks; however, after MDF processing, the metabolite peaks were easily identified in the chromatogram. Compared with precursor ion scan and neutral loss scan techniques, the MDF approach was shown to be more effective for the detection of metabolites in a complex matrix. The comprehensive metabolite detection capability of the MDF approach, together with accurate mass determination, makes high resolution LC/MS a useful tool for the screening and identification of both common and uncommon drug metabolites.

Biotransformation↗
PubMed2006

Truncated RIP3 (tRIP3) acts upstream of FADD to induce apoptosis in the human hepatocellular carcinoma cell line QGY-7703.

RIP3 (receptor-interacting protein 3) is a serine/threonine kinase that promotes apoptosis in various cell types. The C-terminal domain of RIP3 is critical for its apoptosis induction. In this study, we showed that a truncated form of RIP3 (tRIP3) containing only the unique C-terminal region (aa 224-518) induced significant apoptosis in human hepatocellular carcinoma cells QGY-7703. A FADD-dominant negative (FADD-DN) was shown to significantly block apoptosis induced by tRIP3. In contrast, the RIP3 dominant negative (RIP3-DN) was found unable to block FADD-induced apoptosis. Thus, we conclude that tRIP3 may function upstream of FADD to induce apoptosis in TNFR-1 signaling pathway. Additionally, sequence alignments of RIP3 with other death domain (DD)-containing proteins revealed that amino acids Leu 477 and Leu 488 in RIP3 are highly conserved, nonetheless, neither mutational change at Leu 477 nor at Leu 488 confers obvious effect on cell death, indicating that these two amino acids might not be critical for its pro-apoptotic activity as expected.

Adaptor Proteins, Signal Transducing↗
PubMed2006

Effect of distraction rates on expression of bone morphogenetic proteins in rabbit mandibular distraction osteogenesis.

BACKGROUND: The expression of bone morphogenetic proteins can be regarded as an indicator for biological interaction in distraction osteogenesis. It was hypothesized that different distraction rates may produce different patterns of BMP expression. MATERIAL AND METHODS: This study compared the expression of BMP-2, -4 and -7 at routine (0.9mm once daily) and rapid (2.7mm once daily) distraction rates using the rabbit mandibular lengthening model. Mandibular samples were harvested at days 1, 7 and 14 of consolidation. RESULTS: The expression of BMP-2 and BMP-4 was found throughout the experiment, their expression intensity and location being essentially similar, whereas BMP-7 had not been expressed. Expression of BMP-2 and -4 was more intense at the routine distraction rate than at the rapid distraction rate. CONCLUSIONS: BMP-7 had no expression during the consolidation period of mandibular distraction. The change in the mechanical environment created by different distraction rates led to different expression of BMP-2 and -4. In the early consolidation stage the biological environment for bone formation created by distraction at a routine rate was superior to that created by the rapid distraction rate.

Animals↗
PubMed2006

Effect of recombinant human tissue inhibitor of matrix metalloproteinase-1 in rabbit mandibular distraction osteogenesis: a histological and immunohistochemical study.

BACKGROUND: Bone matrix metalloproteinases are capable of degrading bone matrix during the remodelling, and their degradation activities can be down regulated by the tissue inhibitors of matrix metalloproteinases. This study evaluated the influence of exogenous tissue inhibitor of matrix metalloproteinase-1 on the expression of matrix metalloproteinases and endogenous tissue inhibitor of matrix metalloproteinases in mandibular distraction osteogenesis. MATERIAL AND METHODS: Fifteen New Zealand white rabbits were assigned to three groups: a negative control; a sham control group implanted with a collagen sheet; and an experimental group implanted with recombinant human tissue inhibitor of matrix metalloproteinase-1 impregnated in a collagen sheet. Rabbits were sacrificed at 6 weeks, 12 weeks and 24 weeks of consolidation. RESULTS: Major expression of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases was observed at the early stage of consolidation, only positive signals of tissue inhibitors of matrix metalloproteinases were observed at 24 weeks. The addition of recombinant human tissue inhibitor of matrix metalloproteinases-1 did not affect bone maturation and remodelling. CONCLUSIONS: An equilibrium of bone formation and resorption was reached at 24 weeks of consolidation in the rabbit mandible. No obvious influence of recombinant human tissue inhibitor of matrix metalloproteinase-1 on bone remodelling of mandibular distraction osteogenesis was noted.

Animals↗
PubMed2006

The centrosomal protein nephrocystin-6 is mutated in Joubert syndrome and activates transcription factor ATF4.

The molecular basis of nephronophthisis, the most frequent genetic cause of renal failure in children and young adults, and its association with retinal degeneration and cerebellar vermis aplasia in Joubert syndrome are poorly understood. Using positional cloning, we here identify mutations in the gene CEP290 as causing nephronophthisis. It encodes a protein with several domains also present in CENPF, a protein involved in chromosome segregation. CEP290 (also known as NPHP6) interacts with and modulates the activity of ATF4, a transcription factor implicated in cAMP-dependent renal cyst formation. NPHP6 is found at centrosomes and in the nucleus of renal epithelial cells in a cell cycle-dependent manner and in connecting cilia of photoreceptors. Abrogation of its function in zebrafish recapitulates the renal, retinal and cerebellar phenotypes of Joubert syndrome. Our findings help establish the link between centrosome function, tissue architecture and transcriptional control in the pathogenesis of cystic kidney disease, retinal degeneration, and central nervous system development.

Activating Transcription Factor 4↗
PubMed2006

Improved preparation of class I HLA tetramers and their use in detecting CMV-specific CTL.

Different methods were used to prepare HLA tetramers and the yields of each method were compared. Our results indicate that preliminary refolding of the heavy chain (Hc) and light chain (beta 2m) yields more monomer than the typical conventional method with urea-solubilized Hc and beta 2m. We then used the corresponding tetramers to detect cytomegalovirus (CMV)-specific cytotoxic T lymphocytes (CTL). Increasing data suggest that the adoptive transfer of CMV-specific CTL constitutes an effective strategy against CMV infections. We designed a method that efficiently induces CMV-specific CTL to a higher frequency in vitro than is currently achieved. This method increased the percentage of CMV-specific CTL from below 1% to 20% of PBL, accounting for more than 40% of CD8+ T cells. Successful HLA tetramer preparation provides the basis for the subsequent detection of CMV-specific CTL in clinical applications.

Cytomegalovirus↗
PubMed2006

Comparison of indirect and direct approaches using ion-trap and Fourier transform ion cyclotron resonance mass spectrometry for exploring viperid venom proteomes.

In a sense, the field of snake venom proteomics has been under investigation since the very earliest biochemical studies where it was soon recognized that venoms are comprised of complex mixtures of bioactive molecules, most of which are proteins. Only with the re-emergence of 2D polyacrylamide gel electrophoresis (2D PAGE) and the recent developments in mass spectrometry for the identification/characterization of proteins coupled with venom gland transcriptomes has the field of snake venom proteomics began to flourish and provide exciting insights into the protein composition of venoms and subsequently their pathological activities. In this manuscript we will briefly discuss the state of snake venom proteomics followed by the presentation of several straightforward experiments designed to explore approaches to investigating venom proteomics. The first set of experiments used 1D gel electrophoresis (1D PAGE) of Crotalus atrox venom followed by slice-by-slice analysis of the proteins using liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS). In the second set of experiments, C. atrox and Bothrops jararaca venoms were subjected to in-solution digestion followed by Fourier transform ion cyclotron resonance (FTICR) LC/MS/MS. The peptide ion-maps of these venoms were compared along with the proteins identified. In addition, the results were compared to the results observed from the 1D PAGE approach. From these studies it is clear that sample de-complexation/fractionation before mass spectrometry is still the best approach for maximum proteome coverage. Furthermore, comparison of venom proteomes based on tryptic peptide identities between the proteomes is not particularly effective since there does not appear to be a sufficient number of such identical peptides, derived from related proteins, present in venoms. Finally, as has previously been recognized without either better databases of venom protein sequences or facile and rapid de novo sequencing technologies for mass spectrometry, snake venom proteome investigation will remain a laborious task.

Animals↗
PubMed2006

Analysis of the CDR3 length of TCR alphabeta T cells in the peripheral blood of patients with chronic hepatitis B.

To clarify the characteristics of TCR alphabeta T cells in the peripheral blood of patients with chronic hepatitis B (CHB), we investigated the patterns of Complementarity Determining Region3 (CDR3) length distribution for all 24 TCR BV gene families and 32 TCR AV gene family in the peripheral blood lymphocytes of two patients with CHB and two healthy controls by immunoscope spectratyping technique. We found that the profiles of CDR3 length distribution for all TCR AV and TCR BV family showed Gaussian distribution (the polyclonal TCR alphabeta T cells) in healthy controls, however, the restricted usage of TCR BV and TCR AV family (the oligoclonal TCR alphabeta T cells) has been monitored in two CHB patients, furthermore, the oligoclonal TCR alphabeta T cells showed the different CDR3 sequences and length, it might be correlated to the different epitope of hepatitis B virus (HBV) or the different HLA type of the patients. Detailed analysis of the CDR3 length of TCR alphabeta T cells might be interesting to light on the further study of the individualized immunotherapy of CHB and the further research of the new T lymphocyte epitope vaccine of HBV.

Journal Article↗
PubMed2006

Mitosin/CENP-F in mitosis, transcriptional control, and differentiation.

Mitosin/CENP-F is a large nuclear/kinetochore protein containing multiple leucine zipper motifs potentially for protein interactions. Its expression levels and subcellular localization patterns are regulated in a cell cycle-dependent manner. Recently, accumulating lines of evidence have suggested it a multifunctional protein involved in mitotic control, microtubule dynamics, transcriptional regulation, and muscle cell differentiation. Consistently, it is shown to interact directly with a variety of proteins including CENP-E, NudE/Nudel, ATF4, and Rb. Here we review the current progress and discuss possible mechanisms through which mitosin may function.

Cell Differentiation↗
PubMed2006

Inhibition of sickle red cell adhesion and vasoocclusion in the microcirculation by antioxidants.

In sickle cell anemia (SCA), inflammatory (i.e., intravascular sickling and transient vasoocclusive) events result in chronic endothelial activation. In addition to sickling behavior, sickle (SS) red blood cells exhibit abnormal interaction with the vascular endothelium, which is considered to have an important role in initiation of vasoocclusion. Upregulation of endothelial adhesion molecules caused by oxidants (and cytokines) may lead to increased SS red cell adhesion. We hypothesize that endothelial activation is indispensable in SS red cell adhesion to the endothelium and that antioxidants will have an inhibitory effect on this interaction. We examined the effect of selected antioxidants in ex vivo mesocecum vasculature, a well-established model that allows measurement of hemodynamic parameters and, by intravital microscopy, can allow quantification of adhesion. We tested antioxidant enzymes (SOD and catalase) and an intravascular SOD mimetic, polynitroxyl albumin (PNA), in the presence of platelet-activating factor (PAF); the latter causes endothelial oxidant generation and endothelial activation, which characterize SCA. In ex vivo preparations, PAF not only induced marked endothelial oxidant generation, it also enhanced SS red cell adhesion, resulting in frequent blockage of small-diameter venules. The adhesion, inversely related to venular diameter, and vasoocclusion were markedly inhibited by antioxidants, resulting in improved hemodynamics. PNA, the most effective antioxidant, also abolished SS red cell adhesion in non-PAF-activated preparations. Thus SS red cell adhesion and related vasoocclusion may be ameliorated by antioxidant therapy with a stable and long-acting molecule (e.g., PNA).

Anemia, Sickle Cell↗
PubMed2006

Expression and regulation of IL-22 in the IL-17-producing CD4+ T lymphocytes.

IL-22 is a novel cytokine in the IL-10 family that functions to promote innate immunity of tissues against infection. Although CD4+ helper T lymphocytes (TH) were found as a source of IL-22, the regulation of this cytokine has been poorly understood. Here, we show that IL-22 is expressed at both mRNA and protein levels by a novel subset of TH cells that also makes IL-17. IL-22 and IL-17 were found to be coordinately regulated by TGFbeta and IL-6 during TH differentiation by real-time PCR as well as ELISA analysis. However, IL-22 does not regulate TH differentiation; exogenous IL-22 or an IL-22 antagonist had no effect on TH differentiation. These data demonstrate a novel cytokine expressed by IL-17-producing T cells, and suggest interaction and synergy of IL-22 and IL-17 signaling pathways in tissue inflammation and autoimmune diseases.

Animals↗
PubMed2006

[Detection of the complex chromosomal aberrations in acute lymphoblastic leukemia by means of multiplex fluorescence in situ hybridization].

This study was aimed to establish the technique of multiplex fluorescence in situ hybridization (M-FISH) and to explore its usefulness in detection of complex chromosomal aberrations (CCAs) in acute lymphoblastic leukemia (ALL). Five ALL patients with CCAs were analyzed by combining the techniques of conventional cytogenetics (CC) and M-FISH. The results demonstrated that M-FISH confirmed the aberrations previously detected by CC, such as t (9;22), t (1;19) and t (y;1), and revealed new abnormalities as der (1) (1::3::7), der (6) t (6;9) (q?;p13), der (1) t (1;11), der (12) t (1;12), der (3) t (3;5), der (2) t (2;16), der (9) (9::18::7) and der (7) (9::18::7), and also corrected the wrong results in CC. Among these abnormalities, der (9) (9::18::7) and der (7) (9::18::7) were reported for the first time. In conclusion, M-FISH has proved to be useful in characterization of the CCAs in ALL, and it is an essential method to refine the karyotype analysis.

Adolescent↗
PubMed2006

[Culture condition optimization of engineered E. coli BL21/pET-11c/hIL-2-mGM-CSF].

OBJECTIVE: To optimize the culture condition of engineered E.coli to improve its expression efficiency of hIL-2-mGM-CSF protein. METHODS: According to an orthogonal Latin square experiment design, the effects of the culture medium, temperature and IPTG concentration at different levels on the efficiency of the engineered E. coli were evaluated for its expression of hIL-2-mGM-CSF protein. The results of SDS-PAGE were analyzed with software and the culture conditions derived from the experimental results were tested in independent cultures. The optimal culture condition was used in three large-scale cultures and the results were compared with that of routine cultures. RESULTS: The cultures with TH broth yielded higher relative expression quantity of the target protein than those with 2 x YT and LB medium. Compared with the induction temperature at 37 degrees C, induction at 42 degrees C significantly improved the expression efficiency of the target protein. IPTG at the concentration as low as 0.3 mmol/L produced better effect than 1.0 mmol/L IPTG. Statistical analysis suggested that the optimized culture conditions could obviously improve the expression efficiency of the target protein. Large scale cultures with the optimized culture condition resulted in a 5-fold improvement of the relative expression quantity of the protein, which accounted for over 29% of total bacterial protein. CONCLUSION: The optimized culture condition of the engineered E. coli can remarkably increase the expression efficiency of hIL-2-mGM-CSF, which may facilitate the subsequent purification and functional study of the protein.

Culture Media↗