Biomedical subjects

Chi Chen

Publications and source records attributed to Chi Chen.

10 recordsLinked to original sources

PubMed2003

Epigallocatechin-3-gallate-induced stress signals in HT-29 human colon adenocarcinoma cells.

Epigallocatechin-3-gallate (EGCG), a major component in green tea polyphenols, has been proven to suppress colonic tumorigenesis in animal models and epidemiological studies. As EGCG is retained in the gastrointestinal tract after oral administration, this pharmacokinetics property gives it the potential to function as a chemopreventive agent against colon cancer. In this study, human colorectal carcinoma HT-29 cells were treated with EGCG to examine the anti-proliferative and pro-apoptotic effects of EGCG, as well as the molecular mechanism underlying these effects. Cell viability assay, nuclear staining, DNA fragmentation, caspase assay, cytochrome c release, DiOC6(3) staining, mitogen-activated protein kinases (MAPK) phosphorylation and trypan blue exclusion assays, were utilized to dissect the signaling pathways induced by EGCG. After 36 h treatment, EGCG inhibited HT-29 cell growth with an IC50 of approximately 100 microM. HT-29 cells treated with doses higher than 100 microM showed apparent nuclear condensation and fragmentation, which was confirmed by DNA laddering. Caspase-3 and -9 activation was detected after 12 h treatment, accompanied by mitochondrial transmembrane potential transition and cytochrome c release. Activation of MAPKs was detected as early signaling event elicited by EGCG. Inhibition of c-Jun N-terminal kinase (JNK) pathway showed the involvement of JNK in EGCG-induced cytochrome c release and cell death. EGCG-induced JNK activation was blocked by the antioxidants glutathione and N-acetyl-l-cysteine, suggesting that the cell death signaling was potentially triggered by oxidative stress. In summary, our results from this study suggest that in HT-29 human colon cancer cells (i) EGCG treatment causes damage to mitochondria, and (ii) JNK mediates EGCG-induced apoptotic cell death.

Adenocarcinoma↗

PubMed2003

The roles of JNK and apoptotic signaling pathways in PEITC-mediated responses in human HT-29 colon adenocarcinoma cells.

Phenethyl isothiocyanate (PEITC) is a potential chemopreventive agent that is present naturally in widely consumed vegetables, especially in watercress. It has been extensively investigated for its anticancer activities against lung, forestomach and esophageal tumorigenesis. Here we investigated the pro-apoptotic effect of PEITC in HT-29 human colorectal carcinoma cell line, and the mechanism of apoptosis induced by PEITC. PEITC-induced apoptosis was determined by DNA fragmentation assay and diamidino-2-phenylindole (DAPI) staining technique. To understand the mechanisms of apoptosis induced by PEITC, we studied the role of caspases, mitochondria-cytochrome c release, and mitogen-activated protein kinase (MAPK) signaling pathways involved in PEITC-induced apoptosis in HT-29 cells. Both the caspase-3 and -9 activities were stimulated by PEITC. The release of cytochrome c from the mitochondrial inter-space was time- and dose-dependent, with a maximal release at 50 micro M after 10 h treatment. Three MAPKs [JNK (c-Jun N-terminal kinase), extracellular signal-regulated protein kinase (ERK) and p38 kinase] were activated shortly after PEITC treatment in HT-29 cells. Importantly, the SP600125 compound, an anthrapyrazolone inhibitor of JNK, but not the ERK and p38 inhibitor, suppressed apoptosis induced by PEITC. Similarly, this JNK inhibitor attenuated both cytochrome c release and caspase-3 activation induced by PEITC. In summary, this study shows that PEITC can induce apoptosis in HT-29 cells in a time- and dose-dependent manner via the mitochondria caspase cascade, and the activation of JNK is critical for the initiation of the apoptotic processes. This mechanism of PEITC may play an important role in the killing of cancerous cells and offer a potential mechanism for its anticancer action in vivo.

Aldehyde Dehydrogenase↗

PubMed2003

Multichannel mueller matrix ellipsometry for simultaneous real-time measurement of bulk isotropic and surface anisotropic complex dielectric functions of semiconductors.

We have applied a dual rotating-compensator multichannel ellipsometer to acquire spectra ( approximately 2.0-4.6 eV) in all 16 elements of the Mueller matrix associated with a specularly reflecting surface, in a minimum time of 0.25 s. In this initial study, such results have been collected for the (110) silicon surface at an incidence angle of approximately 70 degrees and have been used to derive spectra in the bulk isotropic dielectric function epsilon (b)= epsilon (1b)-i epsilon (2b) and the surface-induced dielectric function anisotropy Delta epsilon =Delta epsilon (1)-iDelta epsilon (2). Thus, this instrument shows promise for simultaneous real-time measurement of epsilon (b) and Delta epsilon spectra in oblique reflection during the fabrication of semiconductor structures having bulk isotropic components.

Journal Article↗

PubMed2003

Differential responses from seven mammalian cell lines to the treatments of detoxifying enzyme inducers.

Cell-based models have been used extensively in screening novel bioactive chemical entities. In this study, seven well-established mammalian cell lines, which have different origins, were utilized to compare their responses to the treatments of three detoxifying enzyme inducers, tert-butylhydroquinone (tBHQ), beta-naphthoflavone (beta-NF), and sulforaphane (SUL), which are potential chemopreventive compounds. The enzymatic activities of glutathione s-transferase (GST), NAD(P)H:quinone oxidoreductase (QR), aldehyde reductase (AR), and glutathione reductase (GR) were measured by kinetics methods using UV-Vis spectroscopy, and analyzed statistically by Student's t-test. Among these mammalian cell lines, the mouse hepatoma Hepa1c1c7 cells were the most robust and sensitive cells, which had higher basal as well as upregulated enzymatic activities. In human cell lines, the prostate LNCaP and hepatic HepG2 cells were also very responsive to the inducers. The results suggested that different cell lines responded differently to individual detoxifying gene inducer, and the selection of appropriate cell line is important for screening potential chemopreventive agents.

Aldehyde Reductase↗

PubMed2003

Computing oxygen-enhanced ventilation maps using correlation analysis.

Correlation maps of oxygen-enhanced ventilation were obtained in nine healthy volunteers using complete and selected image series. The complete series included all images acquired with the subjects alternately inhaling room air and 100% oxygen. The selected series were the subsets of the complete series and included only co-registered images that showed matched diaphragmatic position at maximal expiration. Cross-correlation was computed between the time response function of each pixel and the input function representing the alternation between periods of room air and 100% oxygen inhalation. The confidence level for the correlation analysis was set to 0.01. Pulmonary parenchymal anatomy was consistently reproduced throughout the lung, even in anterior slices where published data have reported correlation problems. The overall average correlation coefficient was 0.66 +/- 0.07 for the complete series and 0.75 +/- 0.08 for the selected series. It was concluded that correlation analysis could be used to reconstruct qualitative oxygen-enhanced ventilation maps.

Adult↗

PubMed2003

Linear plasmid SLP2 of Streptomyces lividans is a composite replicon.

SLP2 is a 50 kb linear plasmid in Streptomyces lividans that contains short (44 bp) terminal inverted repeats and covalently bound terminal proteins. The nucleotide sequence of SLP2 was determined. The rightmost 15.4 kb sequence is identical to that of the host chromosome, including the Tn4811 sequence at the border, which is interrupted by an insertion sequence (IS) element in SLP2. Examination of the flanking target sequences of Tn4811 suggests a previous recombinational event there. The 43 putative protein coding sequences contained many involved in replication (including two terminal protein homologues), partitioning, conjugal transfer and intramycelial spread. The terminally located helicase-like gene ttrA was necessary for conjugal transfer. The two telomeres diverge significantly in primary sequence, while preserving similar secondary structures. Mini-linear plasmids containing these telomeres replicated in S. lividans using the chromosomally encoded terminal protein. In addition, two pseudotelomere sequences are present near the left telomere. The G+C content and GC or AT skew profiles exhibit complex distributions. These, plus the inferred recombination at the right arm, indicate that SLP2 has evolved through rounds of exchanges involving at least three replicons.

Bacterial Proteins↗

PubMed2002

Hypermethylation of the P15INK4b and P16INK4a in agnogenic myeloid metaplasia (AMM) and AMM in leukaemic transformation.

Hypermethylation of p15 and p16 genes was determined in 32 patients with agnogenic myeloid metaplasia(AMM), also known as idiopathic myelofibrosis (MF). These included 10 patients in leukaemic transformation phase. Using polymerase chain reaction-based methylation analysis assay methods, with substantiation using Southern blot analysis, the study showed no hypermethylation of p15 or p16 genes in the chronic phase of AMM, but p15 gene hypermethylation was found in four patients (40%) and p16 gene hypermethylation in two patients (20%) when they were in leukaemic transformation stage. Furthermore, two of the patients in leukaemic transformation were found to have both p15 and p16 gene hypermethylation, demonstrating possible multiple gene hypermethylation in the same patient. Thus, hypomethylation agents for treating patients with AMM in leukaemic transformation may be appropriate for future trials.

Blotting, Southern↗

PubMed2002

Plasma matrix metalloproteinase and tissue inhibitor of metalloproteinase in patients with agnogenic myeloid metaplasia or idiopathic primary myelofibrosis.

Agnogenic myeloid metaplasia (AMM) is characterized by bone marrow fibrosis with abnormal accumulation of extracellular matrix components (ECM), which is dependent on the balance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). Twenty-five patients with AMM, 30 with essential thrombocythemia (ET), 12 with polycythemia vera (PV) and 20 normal control subjects were studied. AMM patients had decreased plasma levels of MMP-3 and marked elevated levels of TIMP-1, but MMP-1, MMP-2 and MMP-9 levels were not significantly different from control subjects. Elevated levels of plasma TIMP-1, but not MMPs, were found in ET and PV. Reduced MMP activity together with increased TIMP-1 activity may be essential in fibrosis formation.

Aged↗

PubMed2002

Imaging the cerebrovascular tree in the cadaveric head for planning surgical strategy.

OBJECTIVE: The objective of the study was to identify whether an integration of cadaveric dissections with preoperative imaging information may enable a better understanding of pathological anatomy, especially vascular lesions, and thus allow for greater precision in surgical planning. METHODS: We selected a computed tomographic contrast agent and experimentally determined the proportion of it that could mix compatibly with the silicone compound. The resultant mixture was injected into the cerebrovascular systems of six fresh human cadaveric heads. The specimens underwent computed tomography for the purpose of digital virtual exposures in parallel with laboratory dissections performed on these specimens. RESULTS: The 1:8 ratio of contrast agent to silicone rubber was determined to be appropriate for both computed tomography and subsequent laboratory dissection of the specimens. The blood vessels in computed tomographic scans demonstrated a higher attenuation than surrounding soft tissues. The opacity consistency of the injected vessels was a critical parameter for a clear three-dimensional rendering of the vascular structures in the natural surroundings of the skull base. Static and dynamic three-dimensional images of the cadaveric vascular tree were obtained as viewed through surgical corridors of various skull base approaches. CONCLUSION: We demonstrated a new cadaveric preparation model for imaging and dissection. This model allows for static and dynamic three-dimensional examination of the surgical anatomy from a neurosurgeon's perspective. It may facilitate the study of cerebrovascular system morphology/pathology in relation to the skull base as a tool for surgical planning.

Brain↗

PubMed1998

Protective effect of YHI and HHI-I against experimental acute pancreatitis in rabbits.

AIM:To observe the protective effect of combined i.v. administraction of Yuanhu injection (YHI) and Huoxuehuayu injection-I (HHI-I) against acute pancreatitis (AP) in rabbits.METHODS:Sever acute pancreatitis (SAP) was induced by retrograde infusion of artificial bile juice into biliary-pancreatic duct, and treated with YHI and HHI-I intravenously. The protective effect was judged by the survival time and rate, serum amylase, serum interleukin-6, pancreatic microcirculation and pathological alteration.RESULTS:Combined use of YHI and HHI-I could markedly increase the rabbits' 5-day survival rate after AP (83.3% in the treatment group and 33.3% in control). The serum amylase value (x-± s) decreased to 1596.6U/L± 760.50U/L in the 5th day from the high level (6320.83U/L± 2614.12U/L) in the 1st day after AP in the treatment group, while in the control group the amylase activity in the 5th day was 2095.0U/L± 1081.87U/L, being significantly different from that before AP (837.17U/L± 189.12U/L). YHI and HHI-I also obviously improved the pancreatic microcirculation and lowered the serum interleukin-6 level, one of the indices of severe pancreatitis. Pathological examination indicated all the changes typical for AP in YHI and HHI-I treatment group were milder than those in the control.CONCLUSION:YHI and HHI-I used in combination might have protective effect against acute pancreatitis in rabbits.

Journal Article↗