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Biomedical subjects

Y Tan

Publications and source records attributed to Y Tan.

At least 55 records · Page 3Linked to original sources
PubMed2001

Hepatic angiomyolipoma: a clinicopathologic study of 10 cases.

OBJECTIVE: To study the clinicopathologic features of hepatic angiomyolipoma (AML) and to investigate the feasibility of a new antibody-A103 as a diagnostic aid for AML. METHODS: Ten cases of AML were retrieved from hospital records and analyzed morphologically. Immunohistochemistry was performed on paraffin-embedded tissues with a panel of antibodies, including antibody-A103. RESULTS: There were eight women and two men, with ages ranging from 38-58 years (median 45.7). Clinically, nine cases were asymptomatic and found by imaging techniques. None of the patients had associated tuberous sclerosis. All tumors were sharply demarcated from the surrounding liver parenchyma. Histologically they were composed of a heterogeneous mixture of three components: thick-walled blood vessels, spindle or epithelioid smooth muscle cells and adipose tissue. All tumors showed a strong immunoreactivity to A103, HMB-45 and smooth muscle actins. Follow-up information on all 10 cases showed a benign course with no signs of recurrence. CONCLUSIONS: Hepatic AML is a rare mesenchymal tumor of the liver. A103 is a promising marker for a pathologic diagnosis of hepatic AML.

Actins↗
PubMed2001

[The study of low dose radiation inducing hormesis effect on hematopoietic system].

OBJECTIVE: To study the hormesis effect on hematopoietic system induced by low dose radiation. METHOD: CFU-GM and BFU-E were cultured in methylcellulose semi-solid culture system, levels of GM-CSF and IL-3 were assayed by ELISA and mRNA levels of GM-CSF, G-CSF, IL-3 by in situ hybridization, narrow line hybridization and Northern blot. RESULTS: (1) The in vitro yields of CFU-GM and BFU-E from radiated mice was higher than that from the control. (2) The serum protein level of GM-CSF increased obviously than that of controls; (3) mRNA levels of GM-CSF and G-CSF were also increased. CONCLUSION: There is hormesis effect on hematopoietic system induced by low dose radiation, which may be related to the increasing of cytokines.

Animals↗
PubMed2001

[The difference of intracellular cytokines produced by different lymphocyte subsets of cord blood and adult peripheral blood].

OBJECTIVE: To explore the difference of intracellular cytokines between cord blood and adult peripheral blood and elucidate its significance for GVHD. METHOD: Different lymphocyte subsets were categorized in cord and adult peripheral blood by monoclonal antibodies with 3 color fluorescence using flow cytometry. The IL-2, TNF-alpha and IFN-gamma produced by various lymphocyte subsets were compared between the two groups. RESULT: (1) In cord blood, dominant T cells were CD(4)(+)CD(45RA)(+), while the major T cells were both CD(4)(+)CD(45RO)(+) and CD(8)(+)CD(45RO)(+) in adult peripheral blood. (2) The quantities of IL-2, TNF-alpha and IFN-gamma produced by cord blood lymphocytes were lower than that of adult peripheral blood lymphocytes. Moreover, the majority of cells that produced cytokines in the cord blood were CD(4)(+)CD(45RA)(+), but in adult peripheral blood were mainly CD(4)(+)CD(45RO)(+) and CD(8)(+)CD(45RO)(+). CONCLUSION: As compared with adult peripheral blood, the cord blood not only possessed different proportion of lymphocyte subsets, but also significant low level of cytokines. The differences of various lymphocyte subset proportions and lower level of cytokines in cord blood probably related to the lower incidence of GVHD in cord blood stem cell transplantation.

Adult↗
PubMed2001

[Low flow technique to perform static pressure-volume curve during mechanical ventilation].

OBJECTIVE: To describe a fast, simple method to acquire static pressure-volume (P-V) curve of the respiratory system and to compare it with airway occlusion technique. METHODS: ARDS sheep model was induced by intravenously infusing 3-6 micrograms/kg LPS, static P-V curves were determined by low flow technique and airway occlusion technique. Static compliance (Cst), lower inflection point (Pinfd and Pinfb) and airway pressure were compared between the two methods. RESULTS: Pinf were (8.91 +/- 0.82) cm H2O and (8.59 +/- 0.78) cm H2O determined by low flow technique and airway occlusion technique respectively, the correlation between which was good (r = 0.93, P < 0.05). Cst determined by low flow technique was similar to that determined by airway occlusion technique [(19 +/- 7) L/cm H2O vs (20 +/- 7) L/cm H2O, P > 0.05]. The time needed to acquire a static P-V curve by low flow technique was 3-4 minutes versus 30-35 minutes by airway occlusion technique. CONCLUSION: Accuracy and reliability of low flow technique are sufficient for clinical use, it is much less time consuming than the airway occlusion technique.

Animals↗
PubMed2001

[Expression of HLA-I antigens in primary hepatocellular carcinoma].

OBJECTIVE: To find out whether hepatocellular carcinoma (HCC) cells express HLA-I antigens. METHODS: LSAB assay of immunohistochemistry was used to detect six frozen HCC specimens. RESULTS: All the HCC cells have strong expression of HLA-I antigens. CONCLUSION: In view of these data on the expression of HLA-I antigens, the authors deem it practical to develop HCC CTL vaccine.

Carcinoma, Hepatocellular↗
PubMed2001

[IL-1 beta mRNA and TNF-alpha mRNA expression in gingival tissues of patients with adult periodontitis].

OBJECTIVE: The aim of this study was to examine interleukin-1 beta (IL-1 beta) mRNA and tumor necrosis factor alpha (TNF-alpha) mRNA expression in gingival tissues of patients with adult periodontitis. METHODS: A total of 19 patients, including 10 patients with adult periodontitis and 9 healthy individuals as the control, were evaluated for were selected for evaluating IL-1 beta mRNA and TNF-alpha mRNA expression, using reverse transcription polymerase chain reaction (RT-PCR) technique. RESULTS: The relative amount of IL-1 beta mRNA expression of gingival samples from patients with adult periodontitis (0.819 +/- 0.045) (P < 0.01) was much higher than that from the normal control (0.306 +/- 0.087) (P < 0.01). The relative amount of TNF-alpha mRNA expression, gingival samples from AP patients (0.696 +/- 0.098) was also much higher than that from the normal control (0) (P < 0.01). CONCLUSION: As the inflammatory and bone absorption mediators, IL-1 beta and TNF-alpha might play important roles in the pathogenesis and development of adult periodontitis.

Adolescent↗
PubMed2000

Connexin43 suppresses MFG-E8 while inducing contact growth inhibition of glioma cells.

Gap junction expression has been reported to control the growth of a variety of transformed cells. We undertook parallel analysis of connexins Cx32 and Cx43 in glioma cells, which revealed potential mechanisms underlying this phenomenon and led to several novel findings. Cx43, but not Cx32, suppressed C6 glioma cell growth. Paradoxically, Cx32 transfection resulted in severalfold more dye transfer than Cx43. However, Cx43 transfectants shared endogenous metabolites more efficiently than Cx32 transfectants. Interestingly, a significant portion of Cx43 permeants were incorporated into macromolecules more readily than those that transferred via Cx32. Cx43 induced contact inhibition of cell growth but in contrast to other reports, did not affect log phase growth rates. Cell death, senescence, or suppression of growth factor signaling was not involved because no significant alterations were seen in cell viability, telomerase, or mitogen-activated protein kinase activity. However, suppression of cell growth by Cx43 entailed the secretion of growth-regulatory factors. Most notably, a major component of conditioned medium that was affected by Cx43 was found to be MFG-E8 (milk fat globule epidermal growth factor 8), which is involved in cell anchorage and integrin signaling. These results indicate that Cx43 regulates cell growth by the modulation of extracellular growth factors including MFG-E8. Furthermore, the ability of a Cx to regulate cell growth may rely on its ability to mediate the intercellular transfer of endogenous metabolites but not artificial dyes.

Amino Acid Sequence↗
PubMed2000

Fractal structure in the collision of vector solitons

We study the collision of two orthogonally polarized and equal-amplitude vector solitons in the nonintegrable coupled nonlinear Schrodinger equations. We show that the separation velocity versus collision velocity graph has a fractal structure. When we zoom into this graph, we get a structure qualitatively identical to the original one. In addition, collision dynamics in the zoomed-in windows is intimately related to that in the original graph. We explain this fractal dependence of the collision by a resonance mechanism between the translational motion of vector solitons and internal oscillations inside a vector soliton.

Journal Article↗
PubMed2000

BAD Ser-155 phosphorylation regulates BAD/Bcl-XL interaction and cell survival.

The BH3 domain of BAD mediates its death-promoting activities via heterodimerization to the Bcl-XL family of death regulators. Growth and survival factors inhibit the death-promoting activity of BAD by stimulating phosphorylation at multiple sites including Ser-112 and Ser-136. Phosphorylation at these sites promotes binding of BAD to 14-3-3 proteins, sequestering BAD away from the mitochondrial membrane where it dimerizes with Bcl-XL to exert its killing effects. We report here that the phosphorylation of BAD at Ser-155 within the BH3 domain is a second phosphorylation-dependent mechanism that inhibits the death-promoting activity of BAD. Protein kinase A, RSK1, and survival factor signaling stimulate phosphorylation of BAD at Ser-155, blocking the binding of BAD to Bcl-XL. RSK1 phosphorylates BAD at both Ser-112 and Ser-155 and rescues BAD-mediated cell death in a manner dependent upon phosphorylation at both sites.

14-3-3 Proteins↗
PubMed2000

Induction of apoptosis in glioma cell lines by TRAIL/Apo-2l.

TRAIL/Apo-2L, a novel cytokine, is a member of the tumor necrosis factor (TNF) family and serves as an extracellular signal triggering apoptosis. TRAIL/Apo-2L is capable of killing various transformed cells but not unstimulated primary T cells. In this study, five human glioma cells (U87, U118, U178, U563, and A172) were examined for their susceptibility to the apoptotic effects of TRAIL/Apo-2L. TRAIL/Apo-2L cDNA was isolated by RT-PCR, and recombinant TRAIL/Apo-2L protein was purified by the pMAL-c2 system (New England Biolabs, Beverly, MA). Exposure of A172 cells to bacterially expressed soluble TRAIL/Apo-2L fusion protein at a concentration of 1 microg/ml resulted in significant cell death over a 24-h period. Three experiments were performed to suggest that the TRAIL/Apo-2L killing was through the induction of apoptosis of A172 target cells. In addition, the expression of TRAIL/Apo-2L in different glioma cells was found to be variable, and TRAIL/Apo-2L-induced apoptosis was in a cell type-dependent manner. Some correlation between the susceptibility to TRAIL/Apo-2L and the expression level of one of its cognate receptors, DR4, was observed. In addition, cycloheximide worked synergistically with TRAIL/Apo-2L to induce apoptosis in glioma cells.

Apoptosis↗
PubMed2000

On the altered expression of tyrosine hydroxylase and calbindin-D 28kD immunoreactivities and viability of neurons in the ventral tegmental area of Tsai following injections of 6-hydroxydopamine in the medial forebrain bundle in the rat.

Calbindin-D 28kD is a calcium binding protein reported to protect neurons from degeneration by buffering intracellular calcium. It is expressed in midbrain dopaminergic neurons reported to be relatively resistant to degeneration in Parkinson's disease and certain of its animal models. Lesions of the nigrostriatal pathway produced in rats following injection of 6-hydroxydopamine result in a neurochemical profile similar to that seen in patients with Parkinson's disease. In the present study, brains were processed to exhibit tyrosine hydroxylase- and calbindin-D 28kD immunoreactivities in sections through the ventral mesencephalon at 3, 7, 10, 14 and 21 days after 6-hydroxydopamine had been injected into the medial forebrain bundle. Numbers of ventral mesencephalic calbindin-D 28kD immunoreactive neurons were significantly reduced ipsilateral to the lesions at 3 days post-lesion and, following slight recovery, remained significantly depleted through post-lesion day 21. The densities of calbindin-D 28kD and tyrosine hydroxylase immunoreactive neurons were different only at the 3 day post-lesion time point, when the apparent loss of calbindin-D 28 kD immunoreactive profiles was significantly greater. A lesion-induced increase in the proportion of neurons exhibiting both calbindin-D 28kD and tyrosine hydroxylase immunoreactivities, expected if calbindin-D 28kD is neuroprotective, was observed in the substantia nigra, pars compacta, but not in the ventral tegmental area. It is concluded that, while the observed losses of tyrosine hydroxylase and calbindin-D 28kD immunoreactivities do not necessarily reflect neuronal degeneration, they are not consistent with CB confering a neuroprotective advantage in the ventral tegmental area following 6-OHDA lesions as administered in this study.

Animals↗
PubMed2000

Complex formation between Chromatium vinosum ferric cytochrome c' and bromophenol blue.

An unusual complex has been observed between the common electrophoresis tracer bromophenol blue (BPB) and the cytochrome c' from Chromatium vinosum during polyacrylamide gel electrophoresis. Complex formation results in a shift and increase in the intensity of the visible absorption band of BPB. Differential spectrophotometric titration of BPB with cytochrome c' indicates that one BPB binds to each of the two subunits of cytochrome c' with a binding constant of 4.2(0.5) x 10(5). The absence of a significant effect of ionic strength on the binding constant and the effect of Triton X-100 on the spectrum of BPB suggest that hydrophobic interactions are important to binding. An analysis of the structure of C. vinosum cytochrome c' shows the presence of a surface hydrophobic patch which may participate in the binding interaction. Many of the hydrophobic amino acids in the patch are well conserved by type among all known sequences of cytochrome c' and are found in loop elements of the 3D structure, suggesting a functional basis for conservation. It is proposed that the binding of BPB may mimic a relevant interaction involving the cytochrome c' biological function.

Amino Acid Sequence↗
PubMed2000

Methioninase gene therapy of human cancer cells is synergistic with recombinant methioninase treatment.

Results obtained over the past 40 years have demonstrated that tumor cells of all types tested have an elevated growth requirement for methioninase compared with normal cells. Recombinant methioninase (rMETase) cloned from Pseudomonas putida has been found previously to be an effective antitumor agent attributable to deprivation of the extracellular methionine source of the tumor. To degrade intracellular methioninase, we have now developed an adenoviral vector inserted with the P. putida methioninase (MET) gene (rAd-MET). The in vitro efficacy of rAd-MET was tested on the OVCAR-8 human ovarian cancer cell line, the HT1080 human fibrosarcoma cell line, and human normal fibroblasts. rAd-MET transduction of OVACAR-8 and HT1080 resulted in high levels of methioninase expression up to 10% or more of the total protein of the cells, depending on the multiplicity of infection. The IC50 of rAd-MET for OVCAR-8 cells in 96-well plates was approximately 2 x 106 plaque-forming units (pfu)/well. The IC50 of control adenovirus (control-rAd) was 4 x 10(7) pfu/well, 20 times higher than rAd-MET. In the presence of the IC50 of 2 x 10(6) pfu/well of rAd-MET, the addition of 0.025 units/ml of rMETase, which is 25% of the IC50, resulted in a 90% inhibition of tumor cell number. This indicated that rAd-MET enhanced the efficacy of rMETase. In contrast, 2 x 10(6) pfu/well of control-rAd in combination with 0.025 units/ml of rMETase had an efficacy of only 10% inhibition of cell number. The synergistic effect of the combination of rMETase and rAd-MET was quantitated by calculating the combination index (CI). The CIs for all combinations of rAd-MET and rMETase tested on OVCAR-8 were <0.7 with a mean of 0.5, indicating synergy. Similar synergy of rAd-MET and rMETase was seen on HT1080 human fibrosarcoma cells with a mean of 0.74. In contrast, the CIs of all combinations of rMETase and control adenovirus concentrations tested on both cell lines had a mean CI of approximately 1, which indicated that this combination had only an additive effect. The normal fibroblasts, on the other hand, appeared relatively resistant to the MET gene because in the presence of rMETase, 2.5 x 10(7) pfu/well of rAd-MET or control rAd had almost an identical effect on cell survival. The selectively strong synergy of rAd-MET and rMETase on cancer cells allows reduced levels of each agent to be used, thus decreasing potential side effects.

Carbon-Sulfur Lyases↗
PubMed2000

Lyophilization of cationic lipid-protamine-DNA (LPD) complexes.

Cationic lipid-based gene delivery systems have shown promise in transfecting cells both in vitro and in vivo. However, these systems tend to form aggregates in liquid formulation during storage, which has limited their clinical applications. As a result, lyophilization of these systems has recently become a subject of increasing interest. In this paper, lyophilization of LPD, a novel cationic lipid-based gene delivery system, was studied. Both particle size and transfection efficiency could be preserved in the presence of sufficient amount of appropriate lyoprotectant. A series of monosaccharides and disaccharides, including dextrose, galactose, mannose, lactose, maltose, sucrose and trehalose, were evaluated for their lyoprotective effect and disaccharides showed more superior protection to monosaccharides. The effect of different freezing protocols for lyophilization was also evaluated and no significant difference was found. However, for freeze-thawing, fast freezing caused less aggregation. Finally, nonlyophilized LPD and LPD lyophilized with 10% sucrose were stored at different temperatures and their stability was followed for eight weeks. Lyophilized LPD could be stored at room temperature without significant change in particle size or loss of transfection efficiency.

Animals↗
PubMed2000

Survival efficacy of the combination of the methioninase gene and methioninase in a lung cancer orthotopic model.

We have previously demonstrated the antitumor efficacy of recombinant methioninase (rMETase) derived from Pseudomonas putida. To enhance the efficacy of rMETase, we have constructed the pLGFP-METSN retrovirus encoding the P. putida methioninase (MET) gene fused with the green fluorescent protein (GFP) gene. pLGFP-METSN or control vector pLGFPSN was introduced into the human lung cancer cell line H460. The methionine level of H460-GFP-MET cells was reduced to 33% of that of H460-GFP cells. rMETase (0.08 U/mL) in the medium resulted in 10% survival of H460-GFP-MET cells compared with untreated cells in vitro. In contrast, rMETase-treated H460-GFP cells survived at 90% of control. Tissue fragments harvested from subcutaneous tumors of H460-GFP-MET or H460-MET were implanted by surgical orthotopic implantation into the lungs of nude mice. A suboptimal dose of rMETase was administered intraperitoneally daily to mice in each group. Overall survival of rMETase-treated animals with H460-GFP-MET tumors was significantly longer than either rMETase-treated or -untreated animals with H460-GFP tumors (P < .05 in log-rank test). In two repeat experiments, rMETase-treated animals with H460-GFP-MET tumors had a 30-day survival of 80% and 83%, respectively. Untreated animals with H460-GFP-MET tumors had a 30-day survival of 40% and 58%, respectively. rMETase-treated animals with H460-GFP tumors had a 30-day survival of 0% and 33%, respectively. Untreated animals with H460-GFP tumors had a 30-day survival of 0% and 33%, respectively. The retrovirus-mediated gene transfer of METase decreased the intracellular methionine level of tumor cells and consequently enhanced the efficacy of treatment with the rMETase protein. We have thus demonstrated a new strategy of combination tumor therapy with the gene and gene product of MET.

Animals↗