Biomedical subjects

Yan Shi

Publications and source records attributed to Yan Shi.

81 records · Page 5Linked to original sources

PubMed2002

Interferon--gamma control of EBV-transformed B cells: a role for CD8+ T cells that poorly kill EBV-infected cells.

Control of Epstein-Barr virus (EBV) infection requires CD8+ T cells. Surprisingly, many EBV-specific CD8+ T cells kill autologous EBV-transformed B lymphoblasts poorly. We investigated the effector functions used by poorly cytotoxic EBV-specific CD8+ D7 cloned T cells and by EBV-stimulated peripheral blood lymphocytes. D7 T cells did not inhibit B lymphoblast growth in long-term coculture, but prevented the outgrowth of newly infected autologous B cells. Optimally stimulated D7 T cells and EBV-stimulated peripheral blood lymphocytes produced interferon (IFN)-y at levels that inhibited EBV-transformed B cell outgrowth. Inhibitory factor activity was neutralized by anti-IFN-gamma monoclonal antibodies (mAb), but not by antibodies to several other cytokines. These data suggest an in vivo role for IFN-y secreting EBV-specific CD8+ T cells.

B-Lymphocytes↗

PubMed2002

In vitro selection and characterization of influenza A (A/N9) virus variants resistant to a novel neuraminidase inhibitor, A-315675.

With the recent introduction of neuraminidase (NA) inhibitors into clinical practice for the treatment of influenza virus infections, considerable attention has been focused on the potential for resistance development and cross-resistance between different agents from this class. A-315675 is a novel influenza virus NA inhibitor that has potent enzyme activity and is highly active in cell culture against a variety of strains of influenza A and B viruses. To further assess the therapeutic potential of this compound, in vitro resistance studies have been conducted and a comparative assessment has been made relative to oseltamivir carboxylate. The development of viral resistance to A-315675 was studied by in vitro serial passage of influenza A/N9 virus strains grown in MDCK cells in the presence of increasing concentrations of A-315675. Parallel passaging experiments were conducted with oseltamivir carboxylate, the active form of a currently marketed oral agent for the treatment of influenza virus infections. Passage experiments with A-315675 identified a variant at passage 8 that was 60-fold less susceptible to the compound. Sequencing of the viral population identified an E119D mutation in the NA gene, but no mutations were observed in the hemagglutinin (HA) gene. However, by passage 10 (2.56 microM A-315675), two mutations (R233K, S339P) in the HA gene appeared in addition to the E119D mutation in the NA gene, resulting in a 310-fold-lower susceptibility to A-315675. Further passaging at higher drug concentrations had no effect on the generation of further NA or HA mutations (20.5 microM A-315675). This P15 virus displayed 355-fold-lower susceptibility to A-315675 and >175-fold-lower susceptibility to zanamivir than did wild-type virus, but it retained a high degree of susceptibility to oseltamivir carboxylate. By comparison, virus variants recovered from passaging against oseltamivir carboxylate (passage 14) harbored an E119V mutation and displayed a 6,000-fold-lower susceptibility to oseltamivir carboxylate and a 175-fold-lower susceptibility to zanamivir than did wild-type virus. Interestingly, this mutant still retained susceptibility to A-315675 (42-fold loss). This suggests that cross-resistance between A-315675- and oseltamivir carboxylate-selected variants in vitro is minimal.

Acetamides↗

PubMed2002

DNA extraction from archival formalin-fixed, paraffin-embedded tissue sections based on the antigen retrieval principle: heating under the influence of pH.

During the course of diagnostic surgical pathology, pathologists have established a large collection of formalin-fixed, paraffin-embedded tissues that form invaluable resources for translational studies of cancer and a variety of other diseases. Accessibility of macromolecules in the fixed tissue specimens is a critical issue as exemplified by heat-induced antigen retrieval (AR) immunohistochemical (IHC) staining. On the basis of observations that heating may also enhance in situ hybridization (ISH) and the similarity of formalin-induced chemical modifications that occur in protein and in DNA, we designed a study to examine the efficiency of DNA extraction from archival formalin-fixed, paraffin-embedded tissues using an adaptation of the basic principles of the AR technique, i.e., heating the tissue under the influence of different pH values. Archival paraffin blocks of lymph nodes, tonsil, and colon were randomly selected. Each paraffin block was prepared in 34 microtubes. For each paraffin block, one tube was used as a control sample, using a non-heating DNA extraction protocol. The other 33 tubes were tested using a heating protocol under 11 variable pH values (pH 2 to 12) under three different heating conditions (80, 100, and 120C). Evaluation of the results of DNA extraction was carried out by measuring yields by photometry and PCR amplification, as well as kinetic thermocycling (KTC)-PCR methods. In general, lower pH (acid) solutions gave inferior results to solutions at higher pH (alkaline). Heating tissues at a higher temperature and at pH 6-9 gave higher yields of DNA. There appeared to be a peak in terms of highest efficiency of extracted DNA at around pH 9. The average ratios 260:280 of extracted DNA also showed better values for samples heated at 120C. PCR products of three primers showed satisfactory results for DNA extracted from archival paraffin-embedded tissues by heating protocols at pH 6-12, with results that were comparable to the control sample subjected to the standard non-heating, enzymatic DNA extraction method. This study is the first to document the use of heating at an alkaline pH for DNA extraction from archival formalin-fixed, paraffin-embedded tissues, a recommendation based on the principles of AR for protein IHC. These findings may lead to a more effective protocol for DNA extraction from archival paraffin-embedded tissues and may also provide enhanced understanding of changes that occur during formalin-induced modification of nucleic acids.

Antigens↗

PubMed2002

[The autotransplanted tracheas wrapped in united muscle flap of the neck: an experiment].

OBJECTIVE: To investigate the way of revascularization of donator's trachea wrapped in united muscle flap. METHODS: Using fiberoptic bronchoscopy, histopathology and microangiography, we evaluated the tracheal mucosal blood flow, the survival rate, the percentage of patency, and the graft viability of autograft tracheas with varying lengths wrapped in one-sided sternocephalic muscle flap and two-sided sternohyoid-sternothyroid muscle flap and autograft tracheas with the length of 5 rings without wrapped in muscle flap in 32 dogs. RESULTS: In the tracheal autograft wrapped in the united muscle flap group with a length less than 4 centimeters, the submucosal blood flow of graft could be detected by laser blood flowmetry one week after transplantation, and it reached 60% of the normal, which had no significant difference between the place near the site of anastomosis and the middle part of the graft. Dense vessels could be found to grow from the wrapped muscles into the autografted trachea by microangiography. Histopathological examination demonstrated that the structure of the autograft was the same as what it originally was. the inner surface of the autograft was covered with pseudostratified columnar ciliary epithelia, and no necrotic tracheal cartilages were found. Every autograft could survive over long time. However, at 1 week, most mucous membrane in the middle part of the graft with length over 4 cm was in gray or in pale; hyperemia, edema, and haemorrhage were found near the site of anastomosis. Mucosal blood flow measured by laser blood flowmetry in the middle part of the graft was significantly less than that near the site of anastomosis. Malacia, dissolution or granulation hyperplasia occurred in midportion of the major grafts shortly after transplanatation. As for those autografted trachea without wrapping in muscles flap, mucous membranes turned black one week after the transplantation and all dogs died of graft necrosis later. CONCLUSION: One-sided sternocephalic muscle flap and two-sided sternohyoid-sternothyroid muscle flap can provide blood for the graft and the grafted trachea can survive for a long time.

Animals↗

PubMed2002

Effect of emodin on proliferation and differentiation of 3T3-L1 preadipocyte and FAS activity.

OBJECTIVE: To study the effects of emodin on proliferation and differentiation of 3T3-L1 preadipocyte and the possible mechanism. METHODS: Cell proliferation was determined by MTT spectrophotometry, cell differentiation was determined by Oil Red O staining,and fatty acid synthase (FAS) activity was determined by spectrophotometry. RESULTS: Emodin promoted proliferation of 3T3-L1 preadipocyte at low concentration and inhibited the proliferation at high concentration in a dose-related manner. In contrast, it inhibited cell differentiation into adipocyte at low concentration in a dose-related manner. In vitro emodin inhibited the activity of FAS in a dose-related manner. CONCLUSIONS: The effects of emodin on 3T3-L1 cell's proliferation and differentiation are dose dependent. Emodin inhibits the activity of FAS. Our results suggest that emodin should have a potential to serve as a fat-reducing drug.

3T3 Cells↗

PubMed2002

[Participation of bonth splenic CD(5)(+) and CD(5)(-) B lymphocytes in production of platelet glycoprotein-specific autoantibodies in chronic ITP].

OBJECTIVE: To investigate the percentage of splenic CD(5)(+) B lymphocytes in chronic idiopathic thrombocytopenic purpura (IT) and the impact of splenic CD(5)(+) and CD(5)(-) B lymphocytes on the production of platelet glycoprotein (GP)-specific autoantibodies. METHODS: Splenic CD(5)(+) B lymphocytes were identified by two-color flow cytometric analysis in eight patients. Four of the eight patients displayed plasma autoantibodies against both GPIIb/IIIa and GPIb/IX, and their splenic B lymphocytes were separated by Ficoll-Hypaque density gradient and sheep erythrocyte, and further purified by magnetic activate cell separation (MACS). Purified CD(5)(+) and CD(5)(-) B lymphocytes were cultured separately with or without staphylococcus aureus cowan I (SAC). GP specific autoantibodies in culture supernatants were measured by modified monoclonal antibody immobilization of platelet antigen assay (MAIPA). RESULTS: The percentage of splenic CD(5)(+) B lymphocytes in ITP patients was slightly higher than that in control with no statistical significance. MACS purified splenic CD(5)(+) and CD(5)(-) B lymphocytes from three out of four ITP patients produced high levels of anti-GPIIb/IIIa and anti-GPIb/IX antibodies. Culture supernatants of CD(5)(+) B lymphocytes from the other patient showed positive reaction only in GPIb/IX MAIPA. Culture supernatant of CD(5)(-)B lymphocytes from the same patient were double positive in both GPIIb/IIIa and GPIb/IX MAIPA. CONCLUSIONS: Both splenic CD(5)(+) and CD(5)(-) B lymphocytes produce platelet GP-specific autoantibodies in chronic ITP with similar antibody spectrum and titer, and may all play a role in the autoimmune pathogenesis of ITP.

Adolescent↗

PubMed2002

[Plasma thrombopoietin level and its influence on megakaryocytopoiesis in end-stage liver cirrhosis and uremia patients].

To clarify the thrombopoietin (TPO) production in patients with end-stage liver cirrhosis and uremia under hemodialysis, plasma TPO levels in patients with liver cirrhosis (n = 15), uremia under hemodialysis (n = 20) and healthy controls (n = 40) were measured by using a sandwich enzyme linked immunosorbent assay. Relationship between megakaryocytopoiesis and plasma TPO levels was analysed by linear regression. The results showed that the mean plasma TPO concentration in the uremic patients was significantly lower than that in the healthy volunteers, whereas plasma TPO level in end-stage liver cirrhosis was not significantly different from that of normal controls; plasma TPO levels in liver cirrhosis and uremic patients did not significantly influence megakaryocytopoiesis. It is concluded that end-stage liver cirrhosis patients maintained normal plasma TPO levels, but the production of TPO was significantly reduced in renal failure patients. Thrombocytopenia in liver cirrhosis appears to be not related to plasma TPO levels.

Adult↗

PubMed2002

[Study on the determination of manganese in the Polygonum multiflorum by flame atomic absorption spectrometry].

This paper presents a method for the determination of manganese in the organism of the Chinese herbal medicine of the Polygonum multiflorum. Manganese was complexes, extracted and determined by FAAS. The opimum condition of experiment was studied. The accuracy and the detection limit were 7.6 and 8.4 ng.mL-1 respectively. The Mn was determined in range of 0.00-2.00 micrograms.mL-1. The relative standard deviation was 1.77%.

Drugs, Chinese Herbal↗

PubMedDate not supplied

Rapamycin inhibits Akt-mediated oncogenic transformation and tumor growth.

Akt is a serine/threonine kinase that plays a critical role in cell survival and proliferation. Three isoforms of Akt have been identified and have been shown to be up-regulated in human malignancies. We examined the requirement of these pathways for Akt transformation. We generated NIH-3T3 cells over-expressing constitutively active Myr-Akt1 (3T3-Akt1 cells) or Myr-Akt2 (3T3-Akt2 cells). These cells are able to form colonies in soft-agar and 3T3-Akt1 cells formed tumors in SCID mice. Rapamycin efficiently inhibited the activation of the mTOR-p70S6K pathway and the anchorage-independent growth of both 3T3-Akt cells, demonstrating the importance of the mTOR-p70S6K pathway for transformation by Akt1 as well as by Akt2. Moreover, rapamycin dramatically inhibited the tumor formation by 3T3-Akt1 cells in SCID mice. Thus, we demonstrated the importance of mTOR-p70S6 kinase pathway in the transformation by Akt, both in tissue-cultured cells and in animal tumor models. In contrast, neither the MAPK pathway nor the p38 MAPK pathway is required for Akt-dependent transformation of NIH3T3 cells.

Amino Acid Sequence↗