Biomedical subjects

S Shi

Publications and source records attributed to S Shi.

At least 37 records · Page 2Linked to original sources

PubMed2001

Suppression of tumor necrosis factor-mediated apoptosis by nuclear factor kappaB-independent bone morphogenetic protein/Smad signaling.

The activation of nuclear factor kappaB (NF-kappa B) plays a pivotal role in the regulation of tumor necrosis factor (TNF)-mediated apoptosis. However, little is known about the regulation of TNF-mediated apoptosis by other signaling pathways or growth factors. Here, unexpectedly, we found that bone morphogenetic protein (BMP)-2 and BMP-4 inhibited TNF-mediated apoptosis by inhibition of caspase-8 activation in C2C12 cells, a pluripotent mesenchymal cell line that has the potential to differentiate into osteoblasts depending on BMP stimulation. Utilizing both a trans-dominant IkappaBalpha inhibitor of NF-kappaB expressed in C2C12 cells and IkappaB kinase beta-deficient embryonic mouse fibroblast, we show that BMP-mediated survival was independent of NF-kappaB activation. Rather, the antiapoptotic activity of BMPs functioned through the Smad signaling pathway. Thus, these findings provide the first report of a BMP/Smad signaling pathway that can inhibit TNF-mediated apoptosis, independent of the prosurvival activity of NF-kappaB. Our results suggest that BMPs not only stimulate osteoblast differentiation but can also promote cell survival during the induction of bone formation, offering new insight into the biological functions of BMPs.

Animals↗

PubMed2001

Subunit-specific rules governing AMPA receptor trafficking to synapses in hippocampal pyramidal neurons.

AMPA-type glutamate receptors (AMPA-Rs) mediate a majority of excitatory synaptic transmission in the brain. In hippocampus, most AMPA-Rs are hetero-oligomers composed of GluR1/GluR2 or GluR2/GluR3 subunits. Here we show that these AMPA-R forms display different synaptic delivery mechanisms. GluR1/GluR2 receptors are added to synapses during plasticity; this requires interactions between GluR1 and group I PDZ domain proteins. In contrast, GluR2/GluR3 receptors replace existing synaptic receptors continuously; this occurs only at synapses that already have AMPA-Rs and requires interactions by GluR2 with NSF and group II PDZ domain proteins. The combination of regulated addition and continuous replacement of synaptic receptors can stabilize long-term changes in synaptic efficacy and may serve as a general model for how surface receptor number is established and maintained.

Amino Acid Sequence↗

PubMed2001

Study on Fas/Fas-L expression in liver tissue and hepatocyte apoptosis in patients with hepatitis gravis.

To explore the expression of Fas/Fas-L in liver tissue of hepatitis gravis patients and its implication in hepatocyte apoptosis, Fas/Fas-L expression and cell apoptosis was detected by the means of inmmunohistochemistry and terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL). It was found that in the 20 patients with clinical hepatitis gravis, Fas in hepatocytes showed strong expression and Fas-L also showed intensive expression in infiltrating lymphocytes and scattering hepatocytes. The apoptosis existed in all the samples, scattering in the areas of inflammatory, necrotic area and hepatic lobule. It was suggested that the overexpression of Fas/Fas-L could cause the death of hepatocytes and thus the occurrence of hepatitis gravis. The apoptosis caused by Fas might be one of the important pathogeneses of hepatitis gravis. Among the detected samples, apoptosis and necrosis coexisted, indicating that both two types of cellular death were closely associated with the pathogenesis of hepatitis gravis.

Adult↗

PubMed2001

Expression of inflammatory cytokines and beta-defensin 1 mRNAs in porcine epithelial rests of Malassez in vitro.

In the present study, we investigated the mRNA expression of inflammatory cytokines, including interleukin (IL)-1 alpha, IL-6, IL-8, and granulocyte macrophage colony-stimulating factor (GM-CSF), and beta defensin 1 (BD-1), an antimicrobial peptide, in the epithelial rests of Malassez in vitro. A reverse transcription-polymerase chain reaction (RT-PCR) assay was performed in order to observe the expression of these mRNAs. The effect of lipopolysaccharide (LPS) on the mRNA expression was also studied by quantitative RT-PCR assay, with a LightCycler, using the double-stranded DNA dye SYBR Green I. The mRNAs of the four kinds of inflammatory cytokines and BD-1 were detected in the epithelial cells under normal culture conditions. Immunocytochemical staining showed the expression of CD14, a receptor for LPS, on the epithelial cells. The mRNA expressions of IL-1 alpha, IL-6, IL-8, and GM-CSF were upregulated by stimulation with LPS, in a dose- and time-dependent manner. Epithelial cells incubated with 1000 ng/ml of LPS for 6 h showed the most significant upregulation of the cytokine mRNAs. On the other hand, no obvious alteration of BD-1 expression by LPS stimulation was observed. The results indicated that the epithelial rests of Malassez may actively participate in the inflammatory response to bacterial infection, and that they play an important role in the defense mechanism of the radicular cyst.

Animals↗

PubMed2001

Comparison of human dental pulp and bone marrow stromal stem cells by cDNA microarray analysis.

We compared the gene expression profiles of human dental pulp stem cells (DPSCs) and bone marrow stromal stem cells (BMSSCs) as representative populations of odontoprogenitor and osteoprogenitor cells, respectively. Total RNA from primary cultures was reverse-transcribed to generate cDNA probes and then hybridized with the Research Genetics human gene microarray filter GF211. The microarrays were analyzed using the PATHWAYS software package. Human DPSCs and BMSSCs were found to have a similar level of gene expression for more than 4000 known human genes. A few differentially expressed genes, including collagen type XVIII alpha1, insulin-like growth factor-2 (IGF-2), discordin domain tyrosine kinase 2, NAD(P)H menadione oxidoreductase, homolog 2 of Drosophila large disk, and cyclin-dependent kinase 6 were highly expressed in DPSCs, whereas insulin-like growth factor binding protein-7 (IGFBP-7), and collagen type I alpha2 were more highly expressed in BMSSCs. Furthermore, we confirmed the differential expression of these genes by semiquantitative polymerase chain reaction (PCR) and northern blot hybridization. The protein expression patterns for both IGF-2 and IGFBP-7 correlated with the differential mRNA levels seen between DPSCs and BMSSCs. This report describes the gene expression patterns of two distinct precursor populations associated with mineralized tissue, and provides a basis for further characterization of the functional roles for many of these genes in the development of dentin and bone.

Adult↗

PubMed2001

Regulation of endothelial cell barrier function by calcium/calmodulin-dependent protein kinase II.

Thrombin-induced endothelial cell barrier dysfunction is tightly linked to Ca(2+)-dependent cytoskeletal protein reorganization. In this study, we found that thrombin increased Ca(2+)/calmodulin-dependent protein kinase II (CaM kinase II) activities in a Ca(2+)- and time-dependent manner in bovine pulmonary endothelium with maximal activity at 5 min. Pretreatment with KN-93, a specific CaM kinase II inhibitor, attenuated both thrombin-induced increases in monolayer permeability to albumin and decreases in transendothelial electrical resistance (TER). We next explored potential thrombin-induced CaM kinase II cytoskeletal targets and found that thrombin causes translocation and significant phosphorylation of nonmuscle filamin (ABP-280), which was attenuated by KN-93, whereas thrombin-induced myosin light chain phosphorylation was unaffected. Furthermore, a cell-permeable N-myristoylated synthetic filamin peptide (containing the COOH-terminal CaM kinase II phosphorylation site) attenuated both thrombin-induced filamin phosphorylation and decreases in TER. Together, these studies indicate that CaM kinase II activation and filamin phosphorylation may participate in thrombin-induced cytoskeletal reorganization and endothelial barrier dysfunction.

Animals↗

PubMed2001

Electromagnetic analysis of axially symmetric diffractive optical elements illuminated by oblique incident plane waves.

We present an analysis of axially symmetric diffractive optical elements illuminated by off-axis or oblique incident plane waves. The analysis is performed with a finite-difference time-domain method that has been formulated to exploit axial symmetry yet accommodate off-axis illumination. This approach is compared with a full three-dimensional formulation and is found to be more efficient in both memory requirements and computational time. Validation and applications of this method are presented.

Journal Article↗

PubMed2001

A novel small molecule that directly sensitizes the insulin receptor in vitro and in vivo.

Insulin resistance, an important feature of type 2 diabetes, is manifested as attenuated insulin receptor (IR) signaling in response to insulin binding. A drug that promotes the initiation of IR signaling by enhancing IR autophosphorylation should, therefore, be useful for treating type 2 diabetes. This report describes the effect of a small molecule IR sensitizer, TLK16998, on IR signaling. This compound activated the tyrosine kinase domain of the IR beta-subunit at concentrations of 1 micromol/l or less but had no effect on insulin binding to the IR alpha-subunit even at much higher concentrations. TLK16998 alone had no effect on IR signaling in mouse 3T3-L1 adipocytes but, at concentrations as low as 3.2 micromol/l, enhanced the effects of insulin on the phosphorylation of the IR beta-subunit and IR substrate 1, and on the amount of phosphatidylinositol 3-kinase that coimmunoprecipitated with IRS-1. Phosphopeptide mapping revealed that the effect of TLK16998 on the IR was associated with increased tyrosine phosphorylation of the activation loop of the beta-subunit tyrosine kinase domain. TLK16998 also increased the potency of insulin in stimulating 2-deoxy-D-glucose uptake in 3T3-L1 adipocytes, with a detectable effect at 8 micromol/l and a 10-fold increase at 40 micromol/l. In contrast, only small effects were observed on IGF-1-stimulated 2-deoxy-D-glucose uptake. In diabetic mice, TLK16998, at a dose of 10 mg/kg, lowered blood glucose levels for up to 6 h. These results suggest, therefore, that small nonpeptide molecules that directly sensitize the IR may be useful for treating type 2 diabetes.

3T3 Cells↗

PubMed2001

[Cloning and sequence analysis of a pseudogene of liver regeneration augmenter in rats].

OBJECTIVE: To investigate the status of the augmenter of liver regeneration (ALR) in rat's genome. METHODS: Polymerase chain reaction (PCR) was used to amplify the genomic DNA of rat, with a set of specific primers designed according to the cDNA sequence of ALR. The products were ligated into pGEM Teasy vector. Two positive clones were sequenced separately. RESULTS: Two products were amplified from the rat's genome by PCR. After sequencing, one pseudogene was identified. The homology of the amino acid sequence between the ALR and its pseudogene was 88.8%. CONCLUSIONS: ALR pseudogene is found in rat's genome, implying that there is an ALR multigene family. This finding lays a foundation for further study of ALR molecular evolution mode.

Amino Acid Sequence↗

PubMed2001

[Cloning and sequence analysis of truncated S gene from circulation of patients with chronic hepatitis B virus infection].

OBJECTIVE: To find different mutated status of HBV DNA in circulation from chronic HBV patients. METHODS: Specially designed primers and polymerase chain reaction method were applied to amplify the whole S gene of HBV from the serum of 2 patients. After being sequenced, 4 clones were compared with HBV adr subtype (China strain) to identify the mutant sites. RESULTS: Sequencing results implied that there was a truncated large/middle S gene in the serum of the patients. Besides that, HBsAg and HBV DNA polymerase defective clones were also detected. CONCLUSIONS: Truncated middle S gene is found in the circulation of patients with chronical HBV infection, suggestive of a poor prognosis.

Cloning, Molecular↗

PubMed2001

[Biodegradation behavior of ethylenediaminetetraethylene acid].

Aerobic and anaerobic degradability of ethylenediaminetetraethylene acid(EDTA) were measured on Warburg respirometer and anaerobic batch reactors. Biodegradation of EDTA as a single substance was poor, but biodegradation of EDTA with co-substrate could be improved. The wastewater containing EDTA can be treated by activated sludge process. The EDTA removal efficiency was 80% under the circumstance HRT 16 h and EDTA removal efficiency reached to 92.5%-95.1% when HRT was 20 h. The main factor affecting the biodegradability of EDTA is sludge remained time.

Biodegradation, Environmental↗

PubMed2001

[Characteristics of N2O emissions from vegetal soils on Fildes peninsula, Antarctica].

The N2O fluxes from the vegetal soils were first measured on the Fildes peninsula, Antarctica, and the total N2O emission was also estimated in the summer 2 months. The daily variations of N2O fluxes appeared single-peak trend under the sunshine or rainy weather conditions but they were irregular under the snow weather conditions and inconsistent with the atmospheric temperatures. The seasonal variations of the N2O fluxes were affected by the temperature and rainfall. The conditions during the transitions between dry and wet seasons improved the N2O emission. The total N2O emissions from moss and lichen soils were 3.7152 kg and 2.5344 kg, respectively. It follows that the vegetal soils are the sources for the atmospheric N2O on the Fildes peninsula, Antarctica.

Antarctic Regions↗

PubMed2001

[Screening and characterization of human phage antibody to hepatitis C core antigen].

OBJECTIVE: To screen and characterize human phage antibody (ScFv) against hepatitis C core antigen. METHODS: The recombinant phages were panned by core antigen that was coated in a microtiter plate. After three rounds of biopanning, 48 clones were determined specific to core antigen. The specificity of each ScFv colone was determined by ELISA. The coding gene for HCV protein ScFv has been sequenced. RESULTS: Phage antibody for HCV core protein had a specific combination character with core antigen of hepatitis C virus. The DNA sequence data showed that the ScFv gene included 774 bp. CONCLUSIONS: Human single chain antibody to hepatitis C core antigen has been identified by means of the phage display technology.

Amino Acid Sequence↗

PubMed2001

[Screening of aberrant genes of immunocytes in severely scalded rats by inhibition of subtractive hybridization].

OBJECTIVE: To explore the relationship between the postburn changes of gene expression of immunocytes and postburn immunological functional disturbance in severely scalded rats. METHODS: Immunocytes of female F344 rats with severe scalding were harvested and the mRNA was extracted for the inhibition of the expression of aberrant gene selected by subtractive hybridization in contrast to that before scalding. The aberrant genes were cloned and sequenced and compared to those in Genebank for homology. RESULTS: The harvested immunocytes were identified by LM to be monocytes and lymphocytes. Multiple strips located at 200 approximately 400 bp were obtained by inhibiting subtractive hybridization and were cloned into PGEM-T easy plasmid vector. Thus the genebank of aberrant expression was constructed. Twenty clones were sequenced randomly and partial obtained known genes were in accord with postburn systemic changes. Several novel genes were accepted and registered by Genebank. CONCLUSION: There exhibited change in the gene expression of peripheral immunocytes at early postburn stage in rats inflicted by severe burn.

Animals↗

PubMed2001

[A study on the change of caries activity of children with fixed orthodontic treatment].

OBJECTIVE: To investigate the change of caries activity in children with fixed appliance. METHODS: 30 children of permanent dentition were treated with edgewise appliance. CAT was used to test the degree of caries activity before the orthodontic treatment, at the first week, at the first month, at the third month and at the sixth month of appliance bonding respectively. RESULTS: Compared with pre-treatment, there was a significant difference of CAT at the first, third and sixth month of treatment; compared with the first week of treatment, there was also a significant difference of CAT at the third and sixth month of treatment. CONCLUSIONS: The CAT degree increases in children with fixed orthodontic appliance and these children are more sensitive to dental caries.

Adolescent↗

PubMed2001

[Screening and characterization of human phage antibody to hepatitis virus C NS5A antigen].

OBJECTIVE: To screen and characterize human phage antibody against hepatitis C virus (HCV)NS5A antigen. METHODS: The recombinant phages were panned by recombinant HCV NS5A antigen which was coated in a microtiter plate; after five rounds of biopanning, 35 clones were obtained and demonstrated specific to NS5A antigen. The specific binding capacity of the ScFv antibody to HCV NS5A antigen was determined by ELISA. RESULTS: HCV NS5A phage antibody had a specific combination capacity with hepatitis C virus NS5A antigen. The DNA sequence data showed that the ScFv gene was composed of 789 bp and codes for a peptide of 262 amino acid residues. CONCLUSIONS: Human single chain antibody to hepatitis C virus NS5A antigen has been identified by means of the phage display technology.

Antibodies, Viral↗

PubMed2001

[Coefficients between TEOAEs and DPOAEs in infants].

OBJECTIVE: To investigate the coefficients of TEOAEs and DPOAEs based on various pass/fail criteria. METHOD: Thirty-six Australia infants were tested (age range: 1-6 months) using both TEOAE and DPOAE. Cohen's Kappa (K) were used to analyze different criteria. RESULT: There is a significant low agreement in the screening outcomes between TEOAEs and DPOAEs, and different criteria for TEOAEs. CONCLUSION: The findings from the study of coefficients among commonly used screening pass/fail criteria suggested that there is no simple relationship among them. The possible reasons for weak agreement were discussed.

Cochlea↗

PubMed2001

Expression and deletion analysis of EcoRII endonuclease and methylase gene.

OBJECTIVE: To clone complete EcoRII restriction endonuclease gene (ecoRIIR) and methyltransferase gene (ecoRIIM) in one vector and to analyze the coordinating expression of this whole R-M system. METHODS: Unidirectional deletion subclones were constructed with ExoIII. ecoRIIR/ M genes were preliminarily located in the cloned fragment according to the enzyme activities of subclones. Exact deletion sites were determined by sequencing, and transcriptional start sites were determined by S1 mapping. RESULTS: The DNA fragment which was cloned into pBluescript SK + contained intact ecoRIIR gene and ecoRIIM gene, and two transcriptional start sites of ecoRIIR gene were determined. 132bp to 458bp from 3'end of ecoRIIR gene are indispensable to enzyme activities and deletion of 202bp from 3' end of ecoRIIM gene made enzyme lose the capability in DNA protection to resist specific cut with EcoRII endonuclease (EcoRII. R). Deletion of the coding and flanking sequences of one gene did not affect the expression of the other gene, and the recombinants only containing ecoRIIR gene appeared to be lethal to dcm+ host. CONCLUSION: ecoRIIM gene linking closely to ecoRIIR gene is very important for the existence of the R-M system in process of evolution, but the key to control EcoRII R-M order may not exist in transcriptional level .

Base Sequence↗