PubMed Health⌕ Search

Biomedical subjects

C H Chen

Publications and source records attributed to C H Chen.

At least 145 records · Page 8Linked to original sources
PubMed2001

Sequential tonometry as a practical method to estimate truncal pulse wave velocity.

BACKGROUND: Pulse wave velocity (PWV) is a surrogate marker of arteriosclerosis. It can be measured by recording pressure or flow wave signals at two recording sites of an arterial segment simultaneously or sequentially. However, it is unknown how the values of pulse wave velocity derived from various techniques can be compared. Thus, the aims of the present study were to investigate whether different techniques result in different values of PWV. METHODS: We measured aortic PWV from 101 uremic and non-uremic patients using both applanation tonometry and Doppler velocimetry by sequential method. To evaluate whether there is a difference between the sequentially and simultaneously derived PWV, simultaneous method using 2 tonometer or 2 Doppler probes was also applied in 50 and 23 subjects, respectively. RESULTS: There was no significant difference between PWV derived from sequential and simultaneous tonometry (933+/-310 cm/s and 919+/-301 cm/s,p = 0.09). Likewise, there was no significant difference between PWV derived from sequential and simultaneous velocimetry (778+/-241 cm/s and 761+/-205 cm/s,p = 0.35). However, PWV determined by sequential tonometry was significantly greater than (949+/-315 cm/s and 735+/-208 cm/s, respectively,p < 0.001), yet also significantly correlated with that determined by sequential velocimetry (r = 0.83, p < 0.001). CONCLUSIONS: Sequential applanation tonometry is a practical approach to measure PWV in view of technical convenience and the cost of equipment and manpower. Furthermore, we should be cautious in interpreting PWV derived from different methodologies as greater PWV value might be obtained by applanation tonometry than by Doppler velocimetry.

Adult↗
PubMed2001

[Effect of melatonin on release of beta-endorphin, norepinephrine and 5-hydroxytryptamine in rat brain].

AIM: In order to explore the mechanism of action of melatonin to induce analgesia, the present study was undertaken to observe the effects of melatonin on the release of beta-endorphin (beta-Ep), norepinephrine (NE) and 5-hydroxytryptamine in rat brain. METHODS: With the measurement of pain threshold, push-pull perfusion technique and radioimmunoassay were used to determine the immunoreactive beta-Ep content in the perfusate from the third ventricle of rat brain. The contents of 3-methoxy-4-hydroxyphenyl glycol (MHPG) and 5-hydroxyindole acetic acid in the microdialysate from rat brain were measured by techniques of in vivo microdialysis and high performance liquid chromatography with electrochemical detection. RESULTS: The immunoreactive beta-Ep content in the perfusate from the third ventricle of rat brain was increased significantly (P < 0.05) following an intraperitoneal administration of 110 mg.kg-1 of melatonin, with the increase of pain threshold. The MHPG and 5-HIAA contents in the microdialysate from the periaqueductal gray (PAG) or the hypothalamus were not changed after the administration of melatonin. CONCLUSION: Melatonin may promote the release of beta-Ep in brain, which may be one of the mechanisms of the analgesic action of melatonin. The analgesic action of melatonin may not be related to the release of NE and 5-HT in the PAG or the hypothalamus.

Analgesics↗
PubMed2001

[Influences of melatonin on the growth of HELA cells].

AIM: To investigate the influence of melatonin (MT) on growth of HeLa cells in vitro. METHODS: The antiproliferation activities of MT were evaluated on HeLa cells by means of trypan blue dye exclusion and MTT vital staining. The morphological changes of MT on HeLa cells were observed under transmission electron microscope. Cell division cycle influenced by MT was assessed by a flow cytometer. RESULTS: MT produced a certain inhibition on HeLa cells at the concentration of 2 mmol.L-1 and prolonged the time of double amount (TD). The fraction of cells inhibited was 61.0%. The IC50 of HeLa cells exposed to MT for 96 h was 2.039 mmol.L-1. The flow cytometric analyses showed that exposure to MT for 72 h reduced the number of HeLa cells in phase S. Under electronic microscope, the HeLa cells exposed to MT for 72 h displayed morphological changes of necrosis, apoptosis, more heterochromosome and less somatic chromosome. CONCLUSION: MT showed certain influence on HeLa cells. Its mechanism may probably be attributable to reduction of the number of cells in phase S.

Antineoplastic Agents↗
PubMed2001

[The microscopic observed for cells in mesocarp of part medicinal plant in Citrus L].

OBJECTIVE: To illustrate the microscopic characters of cells in mesocap of some of medicinal plants in Citrus of Rutaceae. METHOD: Microscopic observation and photograph were carried out. RESULT: It has been found that many of pavenchymatous cells are branches. It is spongy tissue that has huge room between cells. The thickening of cell wall is not obvious. The uneven thickness of walls of cells in mesocarp which is reported in the old documents are not found.

Cell Wall↗
PubMed2000

Genomic organization and molecular characterization of the human ninein gene.

The centrosome plays a key role in the formation of the mitotic spindle, cell polarity, and cell locomotion. Previously we identified a novel centrosomal associated protein hNinein using GSK-3beta as a bait in the yeast two-hybrid assay. In this report, the hNinein genome was found to correspond to 29 exons of genomic sequence on human chromosome 14q22. Promoter analysis predicts that hNinein contains a TATA, two CCAAT, and three GC boxes. The promoter exhibits the following potential transcription factor binding sites: Sp1, p300, and AP-1. In addition, an alternatively spliced isoform, encoded a 2041-amino-acid protein of 237,900 Da, which was designated hNinein-Lm (GenBank AF302773). The hNinein-Lm genome was found to correspond to 28 exons (2'-29). Amino acid sequence comparison with hNinein showed that hNinein-Lm exhibited an EF-hand Ca2+ binding domain in the N-terminus which similar to mouse ninein. Northern blot showed that this hNinein-Lm isoform was expressed more than hNinein in tissues examined. Differential RT-PCR combining Southern blotting also showed that hNinein-Lm is much more abundant compared to hNinein. Two forms of ninein may also imply the status of ninein associated with a pair of the centrioles in the centrosome structure. Furthermore, molecular characterization shows that human ninein is oligomerized at the C-terminal end which overlapped with GSK-3beta binding site, suggesting that oligomerization of ninein may be regulated by GSK-3beta phosphorylation.

Alternative Splicing↗
PubMed2000

Monoclonal antibodies that bind to the core of fusion-active glycoprotein 41.

The heptad repeat regions HR1 and HR2 of HIV-1 gp41 can associate to form heterooligomers through helical coil-coil interactions that are believed to play a key role in virus-induced membrane fusion. The HR1/HR2 complex was proposed to be the core structure of the fusion-active conformation of gp41. Here, we show that two human monoclonal antibodies, Fab-d and 50-69, specifically recognize the putative fusion-active conformation of gp41. Fab-d binding requires the interaction between the HR1 and HR2 regions of gp41. The reactivity of human monoclonal antibody 50-69 to the C terminus of the HR1 sequence is dependent on the helical structure of HR1. It appears that HR2 is able to interact with HR1 and, subsequently, induce an epitope in HR1 that is required for 50-69 binding. Mutations that disrupt the helical structure of HR1 significantly compromise Fab-d and 50-69 binding. Although the epitopes are not identical, the ability of Fab-d to partially compete with 50-69 binding suggests a close proximity of the two epitopes. Antibodies that are able to interact with the core of the putative fusion-active gp41 may be useful in further unveiling the mechanism of HIV-induced membrane fusion.

Antibodies, Monoclonal↗
PubMed2000

Association of 5HT2A receptor gene polymorphism and alcohol abuse with behavior problems.

This study investigated the association between T/C polymorphism, at position 102, of the 5-hydroxytryptamine 2A receptor gene and alcoholism with and without behavior problems. Eighty-five subjects (45 men, 40 women) with alcohol abuse, 75 subjects (51 men, 24 women) with alcohol dependence, and 70 normal control subjects (21 men, 49 women) participated in the study. The results show that the frequency of the homozygous T102 genotype was significantly lower in the group of male alcohol abuse with behavior problems than in the female group (chi(2) = 4.072, df = 1, P < 0.05) and the allele frequency of T102 was also lower in the male group than in the female group (chi(2) = 4.187, df = 1, P < 0.05). Of the male alcohol abuse subjects, the group with behavior problems was found to have lower frequencies of the T102 allele than the group without behavior problems (chi(2) = 4.328, df = 1, P < 0.05). In conclusion, this study demonstrates that alcoholism is heterogeneous and male alcohol abuse with behavioral problems was associated with T/C 102 polymorphism of the 5HT2A receptor gene. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:797-800, 2000.

Alcoholism↗
PubMed2000

Cyclic AMP activates p38 mitogen-activated protein kinase in Th2 cells: phosphorylation of GATA-3 and stimulation of Th2 cytokine gene expression.

cAMP is an important second messenger with immunomodulatory properties. Elevation of intracellular cAMP in T cells, induced by agents such as IL-1alpha or PGs, inhibits T cell activation. In effector T cells, an increase in the level of intracellular cAMP inhibits cytokine production in Th1 cells but stimulates cytokine production in Th2 cells. Here we report that cAMP-induced effects in Th2 cells occur independently of the protein kinase A pathway, which is the major mediator of cAMP-induced signaling events in most cell types. Instead, cAMP stimulates activation of p38 mitogen-activated protein kinase in Th2 cells. This appears to be a Th2-selective event because cAMP barely increased p38 phosphorylation in Th1 cells. We show that in Th2 cells, cAMP promotes the production of both IL-5 and IL-13, which play distinct but critical roles in asthma pathogenesis. Our data also show that cAMP causes increased phosphorylation of the transcription factor GATA-3, which we have shown is a critical regulator of Th2 cytokine gene expression and, in turn, of airway inflammation in mice. Thus, Th2-specific GATA-3 expression and p38 mitogen-activated protein kinase activation together provide a molecular basis for the differential effects of cAMP in the two T helper cell subsets.

Adjuvants, Immunologic↗
PubMed2000

Interaction of shrimp ras protein with mammalian caveolin-1.

BALB/3T3 cells were transformed by transfection with DNA encoding the mutated ras(Q(61)K) from shrimp Penaeus japonicus (Huang and Chuang. 1999. J Exp Zool 283:510-521). The caveolin-1 in the membrane fraction extractable with 2% octyl glucoside was significant reduced, compared to untransformed cells. To understand this in more detail, the interaction of S-Ras with caveolin was investigated using caveolin-1 purified from rat lungs. The purified caveolin-1 binds c-Src, suppressing its autophosphorylation. It also binds to phosphatidylserine-cholesterol liposomes. These reconstituted caveolin-phosphatidylserine-cholesterol vesicles, which act as a model of caveolae, recruit both bacterially expressed S-Ras and rat K(B)-Ras proteins, as demonstrated on western blots with antibodies against caveolin-1 and Ras. Caveolin-1 suppressed the intrinsic GTPase activity of S-Ras, sustaining it in the active GTP bound form. By contrast, caveolin-1 enhanced the intrinsic GTPase activity of K(B)-Ras, to convert it into the inactive GDP-bound form. These events suggest that caveolin may act as a docking site for Ras proteins and may be able to either maintain or alter their activity state. These events may be associated with the ability of S-ras(Q(61)K) to successfully transform cells.

3T3 Cells↗
PubMed2000

ATP's impact on the conformation and holoenzyme formation in relation to the regulation of brain glutamate decarboxylase.

To investigate ATP as a potential factor in the regulation of brain glutamate decarboxylase (GAD), the impact of ATP on the enzyme conformation and holoenzyme formation was investigated. ATP at 100 microM quenches fluorescence emission intensity of the holoenzyme of GAD (holoGAD) by 18% after a correction for the inner filter effect and enhances fluorescence steady-state polarization from 0.158 to 0. 183 when excited at 280 or 295 nm. These findings suggest that ATP moderately changes the microenvironment of one or more tryptophan or tyrosine residues in holoGAD and alters these residues from a more mobile state to a less mobile one. A moderate ATP-induced conformational change in holoGAD is also supported by the observations that ATP increases the thermal denaturation temperature of holoGAD by 2 degrees C, as derived from temperature-dependent fluorescence spectra, and decreases the alpha-helical content of holoGAD by 8-10%, as determined by circular dichroism. Moreover, ATP does not affect the keto-enol tautomerization of holoGAD and has little or no direct effect on its activity, implying that the ATP interacting domain in holoGAD is not at the active site. Kinetics studies, as demonstrated by stopped-flow fluorescence and UV/visible spectroscopy, demonstrate that formation of holoGAD involves two steps: a fast reaction forming an apoGAD-cofactor intermediate complex, followed by a slow reaction involving the conformational change in the intermediate complex. ATP reduces the rate constant of the fast step to one-third and decreases the rate of the slow step and the intermediate complex formation constant to 60% of their original values. The present data suggest that ATP may regulate the interconversion between apoGAD and holoGAD by interacting with apoGAD rather than holoGAD. By slowing down the rate of intermediate complex formation, ATP reduces the amount of holoGAD formed.

Adenosine Triphosphate↗
PubMed2000

Cloning and characterization of a novel human ninein protein that interacts with the glycogen synthase kinase 3beta.

Using human glycogen synthase kinase 3beta (GSK-3beta) as bait in the yeast two-hybrid system, we identified a novel human centrosome associated protein, hNinein. When the full length cDNA of hNinein was sequenced, it showed that an open reading frame encoded a protein consisting of 2047 amino acids with a predicted molecular mass of 239 kDa. The features of this protein include a potential GTP binding site, a large coiled-coil domain together with four leucine zipper domains and a GSK-3beta binding site. Fluorescence microscopy experiment showed that hNinein is localized in the pericentriolar matrix of the centrosome. In addition, hNinein also showed to react with centrosomal autoantibody sera. Our findings suggest that hNinein may be involved in the formation of centrosome matrix and interacts with the GSK-3beta, implying that it may also be regulated by GSK-3beta phosphorylation signaling.

Amino Acid Sequence↗
PubMed2000

Symmetric versus nonsymmetric structure of the phosphorus vacancy on InP(110).

The atomic and electronic structure of positively charged P vacancies on InP(110) surfaces is determined by combining scanning tunneling microscopy, photoelectron spectroscopy, and density-functional theory calculations. The vacancy exhibits a nonsymmetric rebonded atomic configuration with a charge transfer level 0.75+/-0.1 eV above the valence band maximum. The scanning tunneling microscopy (STM) images show only a time average of two degenerate geometries, due to a thermal flip motion between the mirror configurations. This leads to an apparently symmetric STM image, although the ground state atomic structure is nonsymmetric.

Journal Article↗
PubMed2000

Antigen-specific cancer immunotherapy using a GM-CSF secreting allogeneic tumor cell-based vaccine.

Granulocyte-macrophage colony-stimulating factor (GM-CSF)-transduced autologous tumor cell-based vaccines are currently one of the major forms of cancer vaccines. However, the preparation of GM-CSF-transduced autologous tumor vaccines is time-consuming and technically challenging. In addition, the host antigen presenting cells, rather than the tumor vaccine cells themselves, present tumor-specific antigens and prime the host T cells. Therefore, we tested the efficacy of antigen-specific allogeneic tumor vaccines. We used human papillomavirus 16 (HPV-16) E7 protein as a model tumor antigen, which is associated with the development of most cervical carcinoma. B16, a C57BL/6 (H-2(b)) derived melanoma cell line, was genetically engineered to produce GM-CSF alone (B16GM), HPV-16 E7 alone (B16E7), or both (B16GME7). These vaccine cells were injected into BALB/c (H-2(d)) mice (10(6) cells/mouse). Two weeks later, mice were challenged with 10(5) live HPV-16 E7(+) BL-1 (H-2(d)) tumor cells and monitored for tumor progression twice weekly. To determine the effective cell population in the antitumor immunity elicited by B16GME7, we carried out in vivo antibody depletion experiments using CD4 and CD8 specific antibodies. In addition, as a measure of the immune responses produced by B16GME7, we performed an in vitro cytotoxic T lymphocyte assay using a standard chromium release method. We found that all of the mice vaccinated with B16GME7 remained tumor free 49 days post-BL-1 challenge. In contrast, mice vaccinated with B16GM and B16E7 did not show any tumor protection against a similar dose of BL-1 cells. Furthermore, the antitumor immunity produced by B16GME7 was dependent on both CD4 and CD8 T cells. In addition, E7-specific cytotoxic T lymphocyte activity could be readily demonstrated in mice immunized with B16GME7. These results suggest that allogeneic tumor cells transduced with GM-CSF and the tumor antigen, HPV-16 E7, cannot only generate an E7-specific cytotoxic T lymphocytes response in vitro, but can also elicit a potent antitumor immune response against an E7 expressing tumor in vivo.

Animals↗
PubMed2000

Boosting with recombinant vaccinia increases HPV-16 E7-specific T cell precursor frequencies of HPV-16 E7-expressing DNA vaccines.

We have previously linked the sorting signals of the lysosome-associated membrane protein-1 (LAMP-1) to HPV-16 E7 antigen, creating a chimera, Sig/E7/LAMP-1. We found that both Sig/E7/LAMP-1-containing recombinant vaccinia virus (Vac-Sig/E7/LAMP-1) and Sig/E7/LAMP-1 DNA can generate strong antitumor immunity. To determine whether combination of Sig/E7/LAMP-1 DNA and Vac-Sig/E7/LAMP-1 can further enhance immune responses, sequential vaccination with Sig/E7/LAMP-1 DNA and Vac-Sig/E7/LAMP-1 was given. We found that priming with Sig/E7/LAMP-1 DNA and boosting with Vac-Sig/E7/LAMP-1 generated the strongest E7-specific CD8(+) T cell responses. Our results encourage the use of the DNA prime/vaccinia booster regimen in future clinical trials.

Animals↗
PubMed2000

Three rat brain alternative splicing dynamin-like protein variants: interaction with the glycogen synthase kinase 3beta and action as a substrate.

Dynamin-like protein, a large GTP-binding protein, has recently been cloned, and studies have shown that it may be involved in the formation of coated vesicles. In this report, three different alternatively spliced dynamin-like protein variants (DLP1-WT, -11, and -37) from rat brain were identified by reverse transcription/polymerase chain reaction (RT-PCR). One novel rat alternatively spliced variant (DLP1-37), not described previously, was identified. We examined the interaction of these three rat brain dynamin-like protein variants with glycogen synthase kinase 3beta (Gsk-3beta) using the yeast two-hybrid screening, in vitro binding assay, and immunoprecipitation analysis. It was found that all three examined rat brain dynamin-like protein variants can bind to Gsk-3beta. Moreover, in vitro kinase (phosphorylation) assay showed that mammalian dynamin-like protein acts as a substrate for glycogen synthase kinase 3beta. These data suggest that Gsk-3beta may participate in a functional role in dynamin-like proteins in vesicle trafficking.

Alternative Splicing↗
PubMed2000

Enhancement of DNA vaccine potency by linkage of antigen gene to an HSP70 gene.

Nucleic acid vaccines represent an attractive approach to generating antigen-specific immunity because of their stability and simplicity of delivery. However, there is still a need to increase the potency of DNA vaccines. Using human papillomavirus type 16 E7 as a model antigen, we evaluated the effect of linkage to Mycobacterium tuberculosis heat shock protein 70 (HSP70) on the potency of antigen-specific immunity generated by naked DNA vaccines. We found that vaccines containing E7-HSP70 fusion genes increased the frequency of E7-specific CD8+ T cells by at least 30-fold relative to vaccines containing the wild-type E7 gene. More importantly, this fusion converted a less effective vaccine into one with significant potency against established E7-expressing tumors. Surprisingly, E7-HSP70 fusion vaccines exclusively targeted CD8+ T cells; immunological and antitumor effects were completely CD4-independent. These results indicate that fusion of HSP70 to an antigen gene may greatly enhance the potency of DNA vaccines via CD8-dependent pathways.

Animals↗