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Biomedical subjects

Yong Chen

Publications and source records attributed to Yong Chen.

At least 199 records · Page 11Linked to original sources
PubMed2003

Chiral inversion of the second generation IMiD CC-4047 (ACTIMID ) in human plasma and phosphate-buffered saline.

CC-4047 is a racemic second-generation immunomodulatory drug currently in clinical development for various oncologic indications. It has potent effects on key cytokines including tumor necrosis factor-alpha, interleukin (IL-10), and interferon (IFN-gamma). The S-isomer of CC-4047 has been reported to be the more potent enantiomer of the racemate. In this article we report on the rapid racemization of the S-isomer of CC-4047 in human plasma and phosphate-buffered saline. These results support the further development of the racemate instead of the S-isomer.

Adjuvants, Immunologic↗
PubMed2003

Time-weighted average passive sampling with a solid-phase microextraction device.

A modified Solid-Phase Microextraction (SPME) device has been used as a passive sampler to determine the time-weighted average (TWA) concentration of volatile organic compounds (VOCs) in air. Unlike conventional sampling with SPME, in which the fiber is extended outside its needle housing, during TWA passive sampling, the fiber is retracted a known distance into its needle housing. The SPME passive sampler collects the VOCs by the mechanism of molecular diffusion and sorption on to a coated fiber as collection medium. This process has been shown to be described by Fick's first law of diffusion, whereby determination of the amounts of analytes accumulated over time enable measurement of the TWA concentration to which the sampler was exposed. A series of fibers, 100-microm poly(dimethylsiloxane), 65-microm poly(dimethylsiloxane)/divinylbenzene, and 75-microm Carboxen/poly(dimethylsiloxane), were tested for their "zero sink", face velocity, and response time behavior. Of the fibers tested, that coated with 75-microm Carboxen/poly(dimethylsiloxane) was found to be an excellent passive sampler for VOCs. TWA passive sampling with a SPME device was shown to be almost independent of face velocity and to be more tolerant of high and low analyte concentrations and long and short sampling times, because of the ease with which the diffusion path length could be changed. It was found that environmental conditions, e.g., temperature, pressure, relative humidity, and ozone, have little or no effect on sampling. The 75-microm Carboxen/poly(dimethylsiloxane) fiber can retain VOCs for up to two weeks without significant loss. When the SPME device was tested in the field and the results were compared with those from National Institute of Occupational Health and Safety method 1501, good agreement was obtained.

Air Pollutants, Occupational↗
PubMed2003

Ring-like pore structures of SecA: implication for bacterial protein-conducting channels.

SecA, an essential component of the general protein secretion pathway of bacteria, is present in Escherichia coli as soluble and membrane-integral forms. Here we show by electron microscopy that SecA assumes two characteristic forms in the presence of phospholipid monolayers: dumbbell-shaped elongated structures and ring-like pore structures. The ring-like pore structures with diameters of 8 nm and holes of 2 nm are found only in the presence of anionic phospholipids. These ring-like pore structures with larger 3- to 6-nm holes (without staining) were also observed by atomic force microscopic examination. They do not form in solution or in the presence of uncharged phosphatidylcholine. These ring-like phospholipid-induced pore-structures may form the core of bacterial protein-conducting channels through bacterial membranes.

Adenosine Triphosphatases↗
PubMed2003

Practical aspects of overexpressing bacterial secondary membrane transporters for structural studies.

Membrane transporter proteins play critical physiological roles in the cell and constitute 5-10% of prokaryotic and eukaryotic genomes. High-resolution structural information is essential for understanding the functional mechanism of these proteins. A prerequisite for structural study is to overexpress such proteins in large quantities. In the last few years, over 20 bacterial membrane transporters were overexpressed at a level of 1 mg/l of culture or higher, most often in Escherichia coli. In this review, we analyzed those factors that affect the quantity and quality of the protein produced, and summarized recent progress in overexpression of membrane transporters from bacterial inner membrane. Rapid progress in genome sequencing provides opportunities for expressing several homologues and orthologues of the target protein simultaneously, while the availability of various expression vectors allows flexible experimental design. Careful optimization of cell culture conditions can drastically improve the expression level and homogeneity of the target protein. New sample preparation techniques for mass spectrometry of membrane proteins have enabled one to identity the rigid protein core, which can be subsequently overexpressed. Size-exclusion chromatography on HPLC has proven to be an efficient method in screening detergent, pH an other conditions required for maintaining the stability and monodispersity of the protein. Such high-quality preparations of membrane transporter proteins will probably lead to successful crystallization and structure determination of these proteins in the next few years.

Bacterial Proteins↗
PubMed2003

Immunohistochemical studies of the expression of matrix metalloproteinase-2 and metalloproteinase-9 in human prostate cancer.

To study the expression of matrix metalloproteinase-2 and -9 in human prostate cancer, matrix metalloproteinase-2 and -9 were immunohistochemically detected in tissues of prostate cancer and benign prostatic hyperplasia (BPH). Our results showed that matrix metalloproteinase-2 and -9 levels in prostate cancer were much higher than those in tissues of BPH, with the cancer invasion being positively correlated with the expression of the metalloproteinases. It is concluded that matrix metalloproteinase-2 and -9 are better molecular markers, which are of help in the diagnosis and prediction of prognosis of prostate cancer.

Humans↗
PubMed2003

DnaK and DnaJ facilitated the folding process and reduced inclusion body formation of magnesium transporter CorA overexpressed in Escherichia coli.

Overexpression of CorA, the major magnesium transporter from bacterial inner membrane, in Escherichia coli resulted in the synthesis of 60mg of protein per liter of culture, most of which however was in the form of inclusion bodies. The levels of inclusion body formation were reduced by lowering the cell culture temperature. To dissect CorA inclusion body formation and the folding process involved, we co-expressed the protein with various chaperones and other folding modulators. Expression of DnaK/DnaJ (Hsp70) prevented inclusion bodies from forming and resulted in the integration of more CorA into the membrane. GroEL/GroES (Hsp60/Hsp10) were less effective at reducing CorA inclusion body formation. Co-expression with either Ffh/4.5S-RNA, the signal recognition particle, or SecA, the ATPase that drives protein insertion into the membrane, had little effect on CorA folding. These results indicate: (1) that CorA inclusion bodies form immediately after synthesis at 37 degrees C, (2) that CorA solubility in the cytosol can be increased by co-expressing a chaperone system, (3) membrane targeting is probably not a rate-limiting factor, and (4) that membrane insertion becomes a limitation only when large amounts of soluble CorA are present in the cytosol. These co-expression systems can be used for producing other membrane proteins in large quantities.

Cation Transport Proteins↗
PubMed2003

Differential induction of hepatic dysfunction after intraportal and intravenous challenge with endotoxin and Staphylococcal enterotoxin B.

We have previously shown that systemic infusion of the bacterial toxins Staphylococcal enterotoxin B (SEB) and endotoxin (LPS) induces hepatic dysfunction as measured by decreased biliary indocyanine green (ICG) excretion. In this study, we compare the effects of these bacterial toxins after infusion into the portal and systemic circulation and directly measure biliary bile acid excretion as a measure of cholestasis. We hypothesized that bacterial toxins infused into the portal vein would induce greater hepatic dysfunction than toxins infused into the systemic circulation. Using a chronically catheterized rat model, biliary bile acid excretion was directly measured after infusion of LPS at 10 and 100 microg/kg with and without 50 microg/kg SEB into the portal vein (IPV) or inferior vena cava (IV) at baseline, and at 6 and 24 h. We found that when LPS was infused alone, only IPV administration caused a significant decrease in bile acid excretion at 6 h. There was no change in bile acid excretion after IV administration of LPS. In contrast, when the combination of LPS and SEB was infused, both IV and IPV administration significantly decreased bile acid excretion at 6 and 24 h. At 6 h post-LPS and -SEB administration, the decrease in bile acid excretion was significantly greater after IPV than IV administration. There was no site-specific difference in IFN-gamma release after infusion of toxins. However, peak TNFalpha release was decreased in IPV-infused rats [10 microg/kg (P < 0.05) or 100 microg/kg (P = ns) LPS with SEB] compared with the same doses in IV-infused rats. These data question the role of systemic TNF-alpha and IFN-gamma in regulating hepatic dysfunction and suggest a differential functional response of the liver to systemic and gut-derived septic events. This study also further explains the frequent development of liver dysfunction in patients with sepsis, multisystem organ failure, and other diseases with altered intestinal permeability.

Animals↗
PubMed2003

Chronic Staphylococcal enterotoxin B and lipopolysaccharide induce a bimodal pattern of hepatic dysfunction and injury.

OBJECTIVE: To determine the effect of chronic exposure to endotoxin (lipopolysaccharide) and Staphylococcal enterotoxin B on hepatic injury and function. DESIGN: Prospective, controlled trial. SETTING: Research laboratory in a university hospital. SUBJECTS: Male Sprague-Dawley rats weighing 325-350 g with chronic vascular and bile catheters. INTERVENTIONS: Chronically catheterized rats were treated daily with saline, 50 microg/kg Staphylococcal enterotoxin B alone, 1000 microg/kg lipopolysaccharide alone, 1000 microg/kg lipopolysaccharide with 50 microg/kg Staphylococcal enterotoxin B, or 100 microg/kg lipopolysaccharide with 50 microg/kg Staphylococcal enterotoxin B for 10 days. Serum and biliary measures of hepatic injury and dysfunction were measured before and then 6 hrs and 1, 2, 3, 7, and 10 days after the start of treatment. The animals were killed at 10 days and the livers examined histologically. MEASUREMENTS AND MAIN RESULTS: Mean rates of bile flow, biliary indocyanine green excretion, and bile acid flux were significantly decreased immediately after treatment (6 hr, 1 and 2 days) and then at 10 days. Increases in biliary and serum gamma-glutamyltransferase and serum bile acids also occurred in a similar bimodal pattern. Animals treated with lipopolysaccharide or Staphylococcal enterotoxin B alone became tolerant and did not develop the bimodal pattern of hepatic dysfunction. Histologic examination of the liver at 10 days revealed periportal inflammation and fibrosis. CONCLUSIONS: The combination of lipopolysaccharide and Staphylococcal enterotoxin B leads to late liver injury, whereas either toxin alone does not. These data may explain the frequent development of liver dysfunction in patients exposed to multiple bacterial toxins such as in sepsis, multiple-system organ failure, and other diseases with altered intestinal permeability.

Alanine Transaminase↗
PubMed2003

Overexpression of monocyte chemoattractant protein 1 in the brain exacerbates ischemic brain injury and is associated with recruitment of inflammatory cells.

Brain cells produce cytokines and chemokines during the inflammatory process after stroke both in animal models and in patients. Monocyte chemoattractant protein 1 (MCP-1), one of the proinflammatory chemokines, can attract monocytes to the tissue where MCP-1 is overexpressed. However, the role of MCP-1 elevation in stroke has not been explored in detail. The authors hypothesized that elevated MCP-1 levels would lead to increased influx of monocytes and increased brain infarction size in stroke induced by middle cerebral artery occlusion with partial reperfusion. There were no differences in blood pressure, blood flow, or vascular architecture between wild-type mice and transgenic MBP-JE mice. Twenty-four to 48 hours after middle cerebral artery occlusion, brain infarction volumes after ischemia were significantly larger in MBP-JE mice than in wild-type controls and were accompanied by increased local transmigration and perivascular accumulation of macrophages and neutrophils. These results indicate that MCP-1 can contribute to inflammatory injury in stroke.

Animals↗
PubMed2003

Morphofunctional studies of the glomerular wall in mice lacking entactin-1.

The architecture of the basement membranes is essential for proper function. This architecture is based on interactions among its components, which assemble in a complex network. Entactin-1 appears to be the mastermind of this assembling. In entactin-1-null transgenic mice, immunocytochemistry established the absence of entactin-1 in the glomerular basement membrane, and morphological thickening of this membrane was demonstrated. This prompted us to investigate the organization of other components of the glomerular basement membrane in the transgenic animals. The distribution of type IV collagen and laminin remained unchanged, whereas that of anionic charges was significantly altered. We also evaluated the impact of the absence of entactin-1 on cell relays by studying the alpha(3)- and the alpha(v)-integrins along the endothelial and epithelial glomerular cell plasma membranes. Only the density of alpha(v) was found to be increased. Finally, the filtration properties of the glomerular wall were evaluated by revealing endogenous albumin distribution across the basement membrane. This was altered in transgenic animals, suggesting changes in permselectivity properties. Entactin-1 appears to be an essential component in basement membranes because its absence appears to modify the molecular organization leading to alterations in functional properties.

Animals↗
PubMed2003

Difference of gene expression profiles between esophageal carcinoma and its pericancerous epithelium by gene chip.

AIM: To study the difference of gene expression between esophageal carcinoma and its pericancerous epithelium and to screen novel associated genes in the early stage of esophageal carcinogenesis by cDNA microarray. METHODS: Total RNA was extracted with the original single step way from esophageal carcinoma, its pericancerous epithelial tissue and normal esophageal epithelium far from the tumor. The cDNA retro-transcribed from equal quantity of mRNA was labeled with Cy5 and Cy3 fluorescence functioning as probes. The mixed probes were hybridized with two pieces of BioDoor 4 096 double dot human whole gene chip. Fluorescence signals were scanned by ScanArray 3 000 laser scanner and farther analyzed by ImaGene 3.0 software with the digital computer. RESULTS: (1) A total of 135 genes were screened out, in which 85 and 50 genes whose the gene expression levels (fluorescence intensity) in esophageal carcinoma were more than 2 times and less than 0.5 times respectively compared with the normal esophageal epithelium. (2) There were also total 31 genes, among then 27 and 4 whose expressions in pericancerous tissue were 2-fold up-regulated and 0.5-fold down-regulated respectively compared with normal esophageal epithelium. (3) There were 13 genes appeared simultaneously in both pericancerous epithelium and esophageal carcinoma, while another 18 genes existed in pericancerous epithelium only. CONCLUSION: With the parallel comparison among these three gene profiles, it was shown that (1). A total of 135 genes, Whose expression difference manifested as fluorescence intensity were more than 2 times between esophageal carcinoma and normal esophageal epithelium, were probably related to the occurrence and development of the esophageal carcinoma. (2). The 31 genes showing expression difference more than 2 times between pericancerous and normal esophageal epithelium might be relate to the promotion of esophageal pericancerosis and its progress. The present study illustrated that by using the gene chip to detect the difference of gene expression profiles might be of benefit to the gene diagnosis, treatment and prevention of esophageal carcinoma.

Carcinoma↗
PubMed2003

[The effect of insulin-like growth factor 1 on the fusion of cranial suture].

OBJECTIVE: To evaluate the effect of insulin-like growth factor 1 for the bone induction and the regulation for the fusion of the sagittal cranial sutures. METHODS: The cells, derived from cranial sutures in the newborn SD rats and the sagittal suture from the mice, were cultured with a serum-free medium and treated with and without insulin-like growth factor 1. The osteoblast phetotypes (osteocalcin, alkaline, osteoponcin and type-1 collagen) were measured with the RT-PCR and ELISA, and the explanted sagittal sutures were then evaluated under light microscopy. RESULTS: The cells, treated with the insulin-like growth factor 1, significantly produced more osteocalcin, alkaline, osteoponcin and type-1 collagen than those without insulin-like growth factor 1. The fusion of the sagittal suture explants will delay till to 30 days when it was not treated with IGF1. However, in the group with IGF1 the fusion was observed to start in 8 days, and a small amount of the sagittal suture fusion was found at the 20th day while a large amount was at the 30th day. CONCLUSION: The IGF1 has a direct effect on the fusion of cranial suture due to enhancing bone induction of cranial suture cell.

Animals↗
PubMed2003

[Cloning and sequence analysis of E1, E2/NS1 region of genotype 2a hepatitis C virus genome].

BACKGROUND: To investigate sequence of the complete E region of genotype 2a hepatitis C virus genome and to set up the basis for the further study on biological functions of envelope proteins of HCV. METHODS: Two cDNA fragments of 770bp, 1,100bp long, from serum of a patients infected HCV, were amplified by reverse transcription nested polymerase chain reaction (RT-nPCR). After being digested with two restriction endonucleases, the two fragments were cloned into JM105 respectively, then sequenced. RESULTS: The two corresponding nucleotide sequences were obtained and ligated. The complete nucleotide sequences of envelope region and corresponding deduced amino acid sequences were compared with those of HCV-1, HC-C2, HCV-BK, HC-J6 and HC-J8. The homology of nucleotide sequence of the isolated strains was 60.5%, 60.1%, 59.7%, 87.8% and 67.5% respectively; the amino acid sequence homology to the isolated strains was found to be 67?3%, 66.4%, 65.0%, 87.8%, 79.0%, respectively. CONCLUSIONS: The results indicate that the isolated strain (HCV-JS) belongs to genotype 2a, but there is heterogeneity between HCV-JS and HC-J6 strain.

Amino Acid Sequence↗
PubMed2003

[Morphological observation on fibronectin fibrils surrounding human breast carcinoma cells by atomic force microscopy].

This report aimed at investigation on the application of atomic force microscope (AFM) in research on interaction between cells and extracellular matrix, and function of extracellular matrix. Distribution and array of fibronectin fibrils surrounding human breast carcinoma MCF-7-R cells were observed by atomic force microscope, and comparison of AFM with other traditional techniques was performed. Whole and local AFM morphological images of several human breast carcinoma MCF-7-R cells and fibronectin fibrils around cells were obtained by AFM. Distribution and array of fibronectin fibrils were found to be very regular, and the regulated array coordinated with functions of fibronectin fibrils very well. Owing to advantages of simple sample preparation and very high resolution, AFM is an ideal tool to in situ observation of extracellular matrix.

Breast Neoplasms↗
PubMed2003

[Effect of Aphanizomenon flos-aquae toxins on some blood physiological parameters in mice].

In order to study the toxic effect of STX on mouse's blood with time lapse, STX from Aphanizomenon flosaquae was collected and the effect of toxins on physiological parameters of blood was measured by analyzing changes in cells and components in blood. Results showed that the blood parameters in mice changed after 0.5, 6, 12 and 24 hours respectively when mice were exposed to 0.5 Mu/ml Saxitoxin (STX). The numbers of red blood cell, Hemoglobin and platelet had little changed, while the number of white cells showed evident change, especially within 30 minutes. The more time extended, the less change of white cells had, namely, the effect of STX on some blood physiological parameters in mice became weaker with time spent. After 24 hours, almost all the blood physiological parameters in mice recovered to the normal level. Therefore, it can be concluded that both of STX and acid had toxic effects on blood of mice. When STX (0.5 Mu/ml, at pH5.3) were injected into blood, STX had the toxic effect within 12 hours, and after that, acid had.

Animals↗
PubMed2003

[Effect of pingyangmycin on the growth and cell cycle of human vascular endothelial cells].

OBJECTIVE: To study the effect of pingyangmycin (PYM, bleomycin A5) on the proliferation and cell cycle of the cultured ECV304 cells, a human umbilical vein endothelial cell (HUVEC) line. METHODS: The growth inhibition of PYM on ECV304 cells was measured by MTT assay and the changes in the cell cycle by flow cytometry. RESULTS: After 10 microg/ml PYM treatment of the cells for 24, 48, and 72 h, the inhibition rates were 44.7%, 59.7%, and 74.4% respectively, showing a dose- and time-dependent inhibitory effect, with the 50% inhibitory concentration (IC50) of PYM corresponding to treatment durations of 24, 48 and 72 h being 32.94, 2.56 and 0.75 microg/ml respectively. Flow cytometry showed that ECV304 cell cycle was arrested at G2-M phase after 24-hour treatment with 1 microg/ml PYM, with significant reduction in the cell ratio of S phase and increase of G2-M phase (P<0.01) CONCLUSION: PYM can effectively inhibit the proliferation of ECV304 cells, the mechanism of which might involve the blocking of cell cycle.

Antibiotics, Antineoplastic↗