Biomedical subjects

P Chen

Publications and source records attributed to P Chen.

At least 199 records · Page 11Linked to original sources

PubMed2000

[Identification and visualization of virus-like particles in peripheral blood mononuclear cells].

OBJECTIVE: PBMCs from patients with chronic hepatitis C were examined by electron microscopy (EM), immune EM (IEM) combined with immunohistochemistry to trace the infection and morphology of HCV in the PBMCs. METHODS: The PBMCs from 28 patients with chronic hepatitis C were analyzed firstly for HCV RNA and HCV antigens by RT-PCR and immunohistochemistry respectively. The PBMCs with positive HCV RNA and HCV antigens were then observed by electron microscopy. RESULTS: The positive rate of HCV RNA and HCV antigens were 77.27% (17/22) and 75.00% (21/28), respectively. Two types of polymorphic HCV-like particles with diameter of approximately 65 nm and 110 nm were observed in cytoplasmic vesicles of the PBMCs from HCV Ag positive patients. 10 patients with HCV Ag over expression were studied by electron microscopy and immune election microscopy. The budding phenomenon of the particles could be also visualized in the cytoplasmic vesicles of the PBMCs. Some ultrastructural changes showed an increased ratio of cytoplasm to nucleus and pyknosis of nucleus was also suggestive of the virus infection. CONCLUSIONS: The EM study demonstrated the infection and replication of HCV in the PBMCs of chronic hepatitis C patients by morphology and morphogenesis.

Hepacivirus↗

PubMed2000

[The regulation of apoptosis by Bcl-2, bcl-X(L), Bcl-2alpha and Bax in chronic liver disease].

OBJECTIVE: To analyse the expression of Fas and Fas ligand (FasL) in patients of chronic hepatitis, liver cirrhosis and hepatocellular carcinoma and to study the regulation of apotosis by Bax and Bcl-2 subfamilies. METHODS: The subfamily of Bcl-2 in the liver tissue was studied by immunohistochemistry. RESULTS: In 156 cases of chronic liver disease the expression levels of Fas and FasL in the chronic hepatitis group were significantly higher than that in hepatocellular carcinoma group(P < 0.01). The expression level of Bax subfamily in the chronic hepatitis group was significantly higher than that of Bcl-2 subfamily. CONCLUSION: It is suggested that Bcl-2 family is involved in the regulation of apoptosis in the chronic liver diseases.

Apoptosis↗

PubMed2000

[Molecular cytogenetics of bone tumors].

OBJECTIVE: To study alterations of molecular cytogenetics of bone tumor serially. METHODS: Chromosomal analysis, immunohistochemistry, molecular hybridization, nested-PCR/SSCP, DNA sequence analysis, and gene transfection techniques were used to investigate the common bone tumors. RESULTS: Chromosomal aberrations were found in 50 cases of aggressive bone tumors, with a chromosome number aberration rate of 86.96% and a structure aberration rate of 93.94%. However, there were differences among different kinds of bone tumors. The incidence of chromosomal instability in 53 patients with bone tumors was higher than that in normal controls. Meanwhile, the fragile sites of chromosomes of the patients were closely correlated with the high nonrandom chromosome breakpoints of tumor cells and related oncogene loci. The data on p53 and Rb from 305 cases and 89 cases, respectively, indicated that abnormalities of p53 and Rb were common events in bone tumors. The accumulation of p53 protein and loss of Rb protein were more common in aggressive bone tumors. Structures and their products of related proto-oncogenes (ras, myc, fos, bcl-2, met) were studied in 124 cases. Bone tumors presented multi-oncogenes abnormalities with differences in different pathological kinds. Exogenous wild-type p53 gene transfected into osteosarcoma cell line induced growth inhibition and apoptosis of tumor cells. CONCLUSIONS: Abnormalities of chromosomes, proto-oncogenes, and tumor suppressor genes frequently exist in bone tumor cells and are correlated with oncogenesis.

Bone Neoplasms↗

PubMed2000

[Combined phacoemulsification, foldable intraocular lens implantation and trabeculectomy for cataract patients with glaucoma].

OBJECTIVE: To evaluate the therapeutic effects and safety of the combined phacoemulsification, foldable intraocular lens implantation and trabeculectomy (triple procedure) and compare the outcomes of the operation with two different small incisions, conventional scleral flap and scleral tunnel flap. METHODS: Triple procedure was performed through a 3.5 mm incision by means of conventional scleral flap or scleral tunnel flap on 44 eyes of 42 patients with cataract and glaucoma. RESULTS: After follow-up for 3 -- 6 months, the mean intraocular pressure (IOP) was (14.33 +/- 3.68) mm Hg (1 mm Hg = 0.133 kPa) with a mean pressure reduction of 10.35 mm Hg from that before the operation (P < 0.001). Postoperatively, the visual acuities were >or= 0.5 in 33 eyes (75.0%) at 1 week and in 37 eyes (84.1%) during 3 - 6 months. The mean postoperative astigmatism was (1.29 +/- 0.93) D at 1 week and only 0.17D more than the mean preoperative one (P > 0.05). There was also no statistical difference between the mean preoperative astigmatism and postoperative astigmatism at 3 - 6 months, which was (1.12 +/- 0.73) D. The filtering blebs of type I and II (functional) by Kronfeld's classification presented in 79.5% of the eyes and type III (non-functional) in 20.5% of the eyes. There were no statistical differences for the postoperative outcomes of IOP, visual acuity, astigmatism and filtering bleb between two different procedure groups (P > 0.05). CONCLUSIONS: The triple procedure is an effective, quick, repeatable and safe procedure for cataract patients with glaucoma. There are no differences at the surgical outcomes of two different incisions by means of the conventional scleral flap vs scleral tunnel flap.

Adult↗

PubMed2000

[Adherence of bovine lens epithelial cells to the surface of intraocular lens made of different materials].

OBJECTIVE: To compare the in vitro adherence of bovine lens epithelial cells (BLEC) onto the surface of intraocular lens (IOL) made of 4 different materials: polymethylmethacrylate (PMMA), silicone (SI), hydroxyethylmethacrylate (HEMA) and acrylic (Acrysof, ACRY). METHODS: BLEC were incubated with IOLs four 48 hours. Adherent cells were counted by flow cytometry technique. RESULTS: The amount of the adherent cells on IOLs of ACRY was the highest, that of HEMA the least, and there was no significant difference between the amount on PMMA and SI IOLs (P > 0.05). CONCLUSIONS: Adherence of lens epithelial cells to IOLs is influenced by the surface property of IOL materials, which may influence the occurrence of postoperative capsular opacification after IOL implantation.

Animals↗

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 experimental study on inside-out vein graft for repairing inferior alveolar nerve defect in the rabbit].

OBJECTIVE: This study describes a modification of the vein graft technique inside-out vein graft, creates an autogenous vein conduct with the collagen-rich and Schwann cells exposed to regenerating axons. To compare regeneration of inferior alveolar nerves through two conduits: inside-out vein graft and the standard vein graft. METHODS: 18 adult white rabbits were selected and vena facialises of both sides were harvested. Turned the right vena facialis into inside-out vein and used to bridge an 8 mm defect created in the right inferior alveolar nerve. An 8 mm defect of the left inferior alveolar nerve was bridged by the standard vein graft. After rabbits sacrificed at 8, 14 and 20 weeks, the regenerating nerve cables were harvested from the conduits and performed histologic study. At 20 weeks, performed also electrophysiologic studies and statistical analysis of conductive velocities and histological results. RESULTS: Regenerating nerves connected with proximal and distal nerve stumps on both sides postoperation 8 weeks, a number of regenerating nerve fibers and thickness of axon were gradually increasing. At 20 weeks regenerating nerve on the inside-out vein graft side showed superior function results--faster conduction velocities (P < 0.05) and distinct histological results--much more axon counts (P < 0.05) and thicker mylin sheaths (P < 0.05) compared with contralateral standard vein graft. CONCLUSION: The adventitial surface of vein promotes nerve regeneration by an environment with collagen-rich and Schwann cells. The inside-out vein graft is an original way to repair inferior alveolar nerve.

Animals↗

PubMed2000

[Studies on biosorption of Au3+ by Bacillus megaterium].

Some characteristics of Au3+ biosorption and bioreduction by Bacillus megaterium D01 biomass were reported. The optimum pH value of Au3+ biosorption by strain D01 was 3.0. The biosorption was a rapid process, reaching 95% of the maximal capacity within the first 5 min of contact. Temperature did not affect the biosorption. The biosorptive efficiency(99.1%) and capacity (302.0 mg Au3+/g dry weight biomass) were achieved under the conditions of pH 3.0 and 30 degrees C, both concentration with an initial Au3+/biomass radio of 305 mg/g dry weight for 30 min of the contact. The D01 biomass could reduce Au3+ in the solution to Au0, Au0 on the cells surface and in the contact solution could be crystallized to different forms gold crystals, Au3+ impregnated on SiO2 and alpha-Fe2O3 could be reduced to Au0 by D01 biomass. The results of electrochemical reaction indicated that the strain D01 exhibited a high selectivity for Au3+.

Adsorption↗

PubMed2000

[Isobutyramide activates transcription of human fetal gamma-globin gene selectively].

OBJECTIVE: To examine the effect of isobutyramide synthesized in our laboratory on expression of globin genes in MEL cells transfected with the recombinant construct mu LCRA gamma psi beta delta beta MEL. METHODS: The transformant cells were cultured in the medium containing different concentrations of isobutyramide for four days. The human gamma-, beta- and mouse alpha-globin mRNA were determined by RNase protection analysis. RESULTS: The inducible and dose-dependent expression of the human gamma-, beta- and mouse alpha- globin gene were observed. The induction of the human gamma-globin gene was significant stronger than that of the beta-globin gene. Under 2.5 mmol/L-5 mmol/L of isobutyramide, the induction of the human gamma-globin gene was even more effective than that of mouse alpha-globin gene. CONCLUSION: Isobutyramide can effectively and selectively activate transcription of the human gamma-globin gene at a certain degree. This function, together with the advantages of nontoxic and long halflife makes isobutyramide a promising application in the treatment of beta-thalassemia and sickle cell anemia.

Amides↗

PubMed1999

Inhibition of spinal protein kinase C reduces nerve injury-induced tactile allodynia in neuropathic rats.

We investigated the effects of inhibiting spinal protein kinases including PKC, PKA and PKG on tactile allodynia in rats with a unilateral tight ligation on L5/L6 spinal nerves (Chung model). The intrathecal (IT) delivery of GF109203X, a PKC inhibitor, produced a potent and long lasting anti-allodynic effect. The effect was dose-dependent and stereospecific. Bisindolymaleimide V, an inactive homologue of GF, had no effect. Additionally, two other PKC inhibitors, PKC19-31 and chelerythrine, displayed significant anti-allodynic action. Spinal PKA, but not PKG, is likely involved in Chung tactile allodynia, since H89 (a PKA inhibitor) showed anti-allodynic activity, while KT5823 (a PKG inhibitor) had only a minor effect. These data emphasize that spinal PKC plays an important role in nerve injury-induced tactile allodynia. Other protein kinases such as PKA may also contribute to this phenomenon.

Animals↗

PubMed1999

Localization of a portion of extranuclear ATM to peroxisomes.

The gene mutated in the human genetic disorder ataxia-telangiectasia codes for a protein, ATM, the known functions of which include response to DNA damage, cell cycle control, and meiotic recombination. Consistent with these functions, ATM is predominantly present in the nucleus of proliferating cells; however, a significant proportion of the protein has also been detected outside the nucleus in cytoplasmic vesicles. To understand the possible role of extra-nuclear ATM, we initially investigated the nature of these vesicles. In this report we demonstrate that a portion of ATM co-localizes with catalase, that ATM is present in purified mouse peroxisomes, and that there are reduced levels of ATM in the post-mitochondrial membrane fraction of cells from a patient with a peroxisome biogenesis disorder. Furthermore the use of the yeast two-hybrid system demonstrated that ATM interacts directly with a protein involved in the import of proteins into the peroxisome matrix. Because peroxisomes are major sites of oxidative metabolism, we investigated catalase activity and lipid hydroperoxide levels in normal and A-T fibroblasts. Significantly decreased catalase activity and increased lipid peroxidation was observed in several A-T cell lines. The localization of ATM to peroxisomes may contribute to the pleiotropic nature of A-T.

Amino Acid Sequence↗

PubMed1999

Mass spectrometric analysis of benzoylated sialooligosaccharides and differentiation of terminal alpha 2-->3 and alpha 2-->6 sialogalactosylated linkages at subpicomole levels.

Perbenzoylated sialooligosaccharides were found to be stable derivatives, giving intense signals during the matrix-assisted laser desorption/ionization (MALDI) mass spectrometric analysis in the positive-ion mode. Terminal Neu5NAc alpha 2-->3 and alpha 2-->6Gal units of oligosaccharides undergo characteristic structural changes during benzoylation, yielding easily recognizable mass spectral patterns. Subpicomole carbohydrate samples were successfully benzoylated and analyzed through MALDI mass spectrometry.

Benzoates↗

PubMed1999

Endothelin-1-induced interleukin-8 production in human brain-derived endothelial cells is mediated by the protein kinase C and protein tyrosine kinase pathways.

We have previously demonstrated that endothelin-1 (Et-1) induces human central nervous system-derived endothelial cells (CNS-EC) to produce and secrete the chemokine interleukin 8 (IL-8). In the present study, we use specific inhibitors and activators to elucidate the signal transduction pathways involved in this process. Et-1-induced IL-8 production was blocked by ET(A) receptor antagonist BQ610, but not by ET(B) receptor antagonist BQ788, demonstrating that CNS-EC activation is initiated by Et-1 binding to the ET(A) receptor. IL-8 mRNA expression is blocked by the protein kinase C inhibitor bisindolylmaleimide or protein tyrosine kinase inhibitors, genestein and geldanamycin, establishing the involvement of the protein kinase C and protein tyrosine kinase pathways in the activation process. The transcription factor, NF-kappaB, is involved in Et-1 activation as determined by specific inhibitors of translocation and direct analysis of DNA-binding proteins. Neither inhibition nor activation of cAMP-dependent protein kinase affected IL-8 production in the absence or presence of Et-1. Similarly, no effect was observed upon inhibition of protein phosphatases by okadaic acid. Thus, the signal transduction process induced by Et-1 in CNS-EC, leading to increased mRNA IL-8 expression, is initiated by Et-1 binding to ET(A) receptor followed by subsequent activation of protein kinase C, protein tyrosine kinase, and NF-kappaB. Because increased expression of Et-1 is associated with hypertension and stroke and IL-8 is likely to be involved in the accumulation of neutrophils causing tissue damage in ischemic/reperfusion injury, identification of the mechanism involved in the Et-1-induced increase in IL-8 production may have significant therapeutic value.

Antihypertensive Agents↗

PubMed1999

Signal transduction in the vomeronasal organ of garter snakes: ligand-receptor binding-mediated protein phosphorylation.

The vomeronasal (VN) system of garter snakes plays an important role in several species-typical behaviors, such as prey recognition and responding to courtship pheromones. We (X.C. Jiang et al., J. Biol. Chem. 265 (1990) 8736-8744 and Y. Luo et al., J. Biol. Chem. 269 (1994) 16867-16877) have demonstrated previously that in the snake VN sensory epithelium, the chemoattractant ES20, a 20-kDa glycoprotein derived from electric shock-induced earthworm secretion, binds to its receptor which is coupled to PTX-sensitive G-proteins. Such binding results in elevated levels of IP3. We now report that ES20-receptor binding regulates the phosphorylation of two membrane-bound proteins with molecular masses of 42- and 44-kDa (p42/44) in both intact and cell-free preparations of the VN sensory epithelium. ES20 and DAG regulate the phosphorylation of p42/44 in a similar manner. ES20-receptor binding-mediated phosphorylation of p42/44 is rapid and transient, reaching a peak value within 40 seconds and decaying thereafter. Phosphorylation of p42/44 appears to be regulated by the countervailing actions of a specific membrane-bound protein kinase and a protein phosphatase. The phosphorylation of these membrane-bound proteins significantly reduces the activity of G-proteins as evidenced by a decrease in GTPase activity, but has little effect on ligand-receptor binding. These findings suggest that p42/44 play a role in modulating the signal transduction induced by ES20 in the vomeronasal system.

Animals↗

PubMed1999

High H2 uptake by alkali-doped carbon nanotubes under ambient pressure and moderate temperatures

Lithium- or potassium-doped carbon nanotubes can absorb approximately 20 or approximately 14 weight percent of hydrogen at moderate (200 degrees to 400 degrees C) or room temperatures, respectively, under ambient pressure. These values are greater than those of metal hydride and cryoadsorption systems. The hydrogen stored in the lithium- or potassium-doped carbon nanotubes can be released at higher temperatures, and the sorption-desorption cycle can be repeated with little decrease in the sorption capacity. The high hydrogen-uptake capacity of these systems may be derived from the special open-edged, layered structure of the carbon nanotubes made from methane, as well as the catalytic effect of alkali metals.

Journal Article↗

PubMed1999

Transient exposure to HIV-1 Tat protein results in cytokine production in macrophages and astrocytes. A hit and run phenomenon.

The pathological correlates of dementia due to human immunodeficiency virus (HIV) infection are glial cell activation and cytokine dysregulation. These findings occur in the setting of small numbers of productively infected cells within the brain. We determined whether exposure of susceptible cells to Tat protein of HIV could result in the production of select proinflammatory cytokines. In a dose-responsive manner, Tat induced interleukin (IL)-1beta production in monocytic cells, while astrocytic cells showed an increase in mRNA for IL-1beta, but had a translation block for IL-1beta protein production. Conversely, IL-6 protein and mRNA productions were strongly induced in astrocytic cells and minimally in monocytic cells. IL-1beta and IL-6 production were independent of tumor necrosis factor-alpha production. An exposure to Tat for a few minutes was sufficient for sustained releases of cytokines for several hours. This prolonged cytokine production is likely maintained by a positive feed back loop of Tat-induced nuclear factor kappaB activation and cytokine production that is independent of extracellular calcium. Thus a transient exposure may be sufficient to initiate a cascade of events resulting in cerebral dysfunction and a "hit and run" approach may be in effect. Hence cross-sectional measurement of viral load in the brain may not be a useful indicator of the role of viral products in the neuropathogenesis of HIV dementia.

Astrocytes↗

PubMed1999

Transfer RNA modification: influence on translational frameshifting and metabolism.

Transfer RNA modification improves the rate of aa-tRNA selection at the A-site and the fitness in the P-site and thereby prevents frameshifting according to a new model how frameshifting occurs [Qian et al. (1998) Mol. Cell 1, 471-482]. Evidence that the presence of various modified nucleosides in tRNA also influences central metabolism, thiamine metabolism, and bacterial virulence is reviewed.

Frameshifting, Ribosomal↗

PubMed1999

Glucose transporter Glut3 is targeted to secretory vesicles in neurons and PC12 cells.

In rat brain and cultured neuroendocrine PC12 cells, Glut3 is localized at the cell surface and, also, in a distinct population of homogenous synaptic-like vesicles. Glut3-containing vesicles co-purify with "classical" synaptic vesicles, but can be separated from the latter by sucrose gradient centrifugation. Unlike classical synaptic vesicles, Glut3-containing vesicles possess a high level of aminopeptidase activity, which has been identified as aminopeptidase B. This enzyme has recently been shown to be a marker of the secretory pathway in PC12 cells (Balogh, A., Cadel, S., Foulon, T., Picart, R., Der Garabedian, A., Rousselet, A., Tougard, C., and Cohen, P. (1998) J. Cell Sci. 111, 161-169). We, therefore, conclude that Glut3 is targeted to secretory vesicles in both neurons and PC12 cells.

Animals↗