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C H Pan

Publications and source records attributed to C H Pan.

At least 19 recordsLinked to original sources
PubMed2006

Toroidal symmetry of the geodesic acoustic mode zonal flow in a tokamak plasma.

The toroidal symmetry of the geodesic acoustic mode (GAM) zonal flows is identified with toroidally distributed three step Langmuir probes at the edge of the HuanLiuqi-2A (commonly referred to as HL-2A) tokamak plasmas for the first time. High coherence of both the GAM and the ambient turbulence for the toroidally displaced measurements along a magnetic field line is observed, in contrast with the high coherence of the GAM but low coherence of the ambient turbulence when the toroidally displaced measurements are not along the same field line. The radial and poloidal features of the flows are also simultaneously determined. The nonlinear three wave coupling between the high frequency turbulent fluctuations and the flows is demonstrated to be a plausible formation mechanism of the flows.

Journal Article↗
PubMed2005

Phylogenetic analysis of classical swine fever virus in Taiwan.

Two envelope glycoprotein (Erns and E2) regions of the classical swine fever virus (CSFV) were amplified by RT-PCR and sequenced directly from 158 specimens collected between 1989 and 2003 in Taiwan. Phylogenetic analysis of the two regions revealed a similar tree topology and the Erns region provided better discrimination than the E2 region. One hundred and fifteen isolates out of the 158 isolates were clustered within subgroup 2.1 (further classified as 2.1a and 2.1b) and 2.2, which were considered to be likely of the introduced strains, whereas the remaining 43 isolates were clustered within subgroup 3.4 and were considered to be of the endemic strains. The subgroup 2.1a viruses were first detected in 1994 and predominated from 1995 onwards. However, subgroup 3.4 viruses were prevalent in the early years, not being isolated after 1996. We have observed a dramatic switch in genotype from subgroup 3.4 to 2.1a. The subgroup 2.1a isolates are closely related to the Paderborn and Lao isolates, whereas 2.1b isolates have a close relationship to the Chinese Guangxi isolates. The phylogenetic tree of 27 CSFV sequences based on the complete envelope glycoprotein gene (Erns-E2) displayed better resolution than that based on the complete open reading frame.

Animals↗
PubMed2001

Suppression of immune response and protective immunity to a Japanese encephalitis virus DNA vaccine by coadministration of an IL-12-expressing plasmid.

IL-12 plays a central role in both innate and acquired immunity and has been demonstrated to potentiate the protective immunity in several experimental vaccines. However, in this study, we show that IL-12 can be detrimental to the immune responses elicited by a plasmid DNA vaccine. Coadministration of the IL-12-expressing plasmid (pIL-12) significantly suppressed the protective immunity elicited by a plasmid DNA vaccine (pE) encoding the envelope protein of Japanese encephalitis virus. This suppressive effect was associated with marked reduction of specific T cell proliferation and Ab responses. A single dose of pIL-12 treatment with plasmid pE in initial priming resulted in significant immune suppression to subsequent pE booster immunization. The pIL-12-mediated immune suppression was dose dependent and evident only when the IL-12 gene was injected either before or coincident with the pE DNA vaccine. Finally, using IFN-gamma gene-disrupted mice, we showed that the suppressive activity of the IL-12 plasmid was dependent upon endogenous production of IFN-gamma. These results demonstrate that coexpression of the IL-12 gene can sometimes produce untoward effects to immune responses, and thus its application as a vaccine adjuvant should be carefully evaluated.

Animals↗
PubMed2001

Protective mechanisms induced by a Japanese encephalitis virus DNA vaccine: requirement for antibody but not CD8(+) cytotoxic T-cell responses.

We have previously shown that a plasmid (pE) encoding the Japanese encephalitis virus (JEV) envelope (E) protein conferred a high level of protection against a lethal viral challenge. In the present study, we used adoptive transfer experiments and gene knockout mice to demonstrate that the DNA-induced E-specific antibody alone can confer protection in the absence of cytotoxic T-lymphocyte (CTL) functions. Plasmid pE administered by either intramuscular or gene gun injection produced significant E-specific antibodies, helper T (Th)-cell proliferative responses, and CTL activities. Animals receiving suboptimal DNA vaccination produced low titers of anti-E antibodies and were only partially or not protected from viral challenge, indicating a strong correlation between anti-E antibodies and the protective capacity. This observation was confirmed by adoptive transfer experiments. Intravenous transfer of E-specific antisera but not crude or T-cell-enriched immune splenocytes to sublethally irradiated hosts conferred protection against a lethal JEV challenge. Furthermore, experiments with gene knockout mice showed that DNA vaccination did not induce anti-E titers and protective immunity in Igmu(-/-) and I-Abeta(-/-) mice, whereas in CD8alpha(-/-) mice the pE-induced antibody titers and protective rate were comparable to those produced in the wild-type mice. Taken together, these results demonstrate that the anti-E antibody is the most critical protective component in this JEV challenge model and that production of anti-E antibody by pE DNA vaccine is dependent on the presence of CD4(+) T cells but independent of CD8(+) T cells.

Adoptive Transfer↗
PubMed2000

Molecular epidemiological studies on foot-and-mouth disease type O Taiwan viruses from the 1997 epidemic.

Sequence diversity was assessed of the complete VP1 gene directly amplified from 49 clinical specimens during an explosive foot-and-mouth disease (FMD) outbreak in Taiwan. Type O Taiwan FMD viruses are genetically highly homogenous, as seen by the minute divergence of 0.2-0.9% revealed in 20 variants. The O/HCP-0314/TW/97 and O/TCP-022/TW/97 viral variants dominated FMD outbreaks and were prevalent in most affected pig-raising areas. Comparison of deduced amino acid sequences around the main neutralizable antigenic sites on the VP1 polypeptide showed no significant antigenic variation. However, the O/CHP-158/TW/97 variant had an alternative critical residue at position 43 in antigenic site 3, which may be due to selective pressure in the field. Two vaccine production strains (O1/Manisa/Turkey/69 and O1/Campos/Brazil/71) probably provide partial heterologous protection of swine against O Taiwan viruses. The type O Taiwan variants clustered in sublineage A1 of four main lineages in the phylogenetic tree. The O/Hong Kong/9/94 and O/1685/Moscow/Russia/95 viruses in sublineage A2 are closely related to the O Taiwan variants. The causative agent for the 1997 epidemic presumably originated from a single common source of type O FMD viruses prevalent in neighboring areas.

Amino Acid Sequence↗
PubMed1999

Isolation of efficient antivirals: genetic suppressor elements against HIV-1.

The development of general approaches for the isolation of efficient antivirals and the identification and validation of targets for drug screening are becoming increasingly important, due to the emergence of previously unrecognized viral diseases. The genetic suppressor element (GSE) technology is an approach based on the functional expression selection of efficient genetic inhibitors from random fragment libraries derived from a gene or genome of interest. We have applied this technology to isolate potent genetic inhibitors against HIV-1. Two strategies were used to select for GSEs that interfere with latent virus induction and productive HIV-1 infection based on the expression of intracellular and surface antigens. The selected GSEs clustered in seven narrowly defined regions of the HIV-1 genome and were found to be functionally active. These elements are potential candidates for the gene therapy of AIDS. The developed approaches can be applied to other viral pathogens, as well as for the identification of cellular genes supporting the HIV-1 life cycle.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Screening of protective antigens of Japanese encephalitis virus by DNA immunization: a comparative study with conventional viral vaccines.

In this study, we evaluated the relative role of the structural and nonstructural proteins of the Japanese encephalitis virus (JEV) in inducing protective immunities and compared the results with those induced by the inactivated JEV vaccine. Several inbred and outbred mouse strains immunized with a plasmid (pE) encoding the JEV envelope protein elicited a high level of protection against a lethal JEV challenge similar to that achieved by the inactivated vaccine, whereas all the other genes tested, including those encoding the capsid protein and the nonstructural proteins NS1-2A, NS3, and NS5, were ineffective. Moreover, plasmid pE delivered by intramuscular or gene gun injections produced much stronger and longer-lasting JEV envelope-specific antibody responses than immunization of mice with the inactivated JEV vaccine did. Interestingly, intramuscular immunization of plasmid pE generated high-avidity antienvelope antibodies predominated by the immunoglobulin G2a (IgG2a) isotype similar to a sublethal live virus immunization, while gene gun DNA immunization and inactivated JEV vaccination produced antienvelope antibodies of significantly lower avidity accompanied by a higher IgG1-to-IgG2a ratio. Taken together, these results demonstrate that the JEV envelope protein represents the most critical antigen in providing protective immunity.

Animals↗
PubMed1999

Purification of chitinolytic protein from Rehmannia glutinosa showing N-terminal amino acid sequence similarity to thaumatin-like proteins.

We have purified a 21-kDa protein, designated as P1, from Rehmannia glutinosa to homogeneity by ammonium sulfate precipitation, anion exchange chromatography, hydrophobic interaction chromatography, and preparative native PAGE. The purified P1 had chitin degradation activity. The N-terminal amino acid sequence of P1 indicated that it is very similar to those of thaumatin and other reported thaumatin-like proteins.

Amino Acid Sequence↗
PubMed1999

Modulation of immune responses to DNA vaccines by codelivery of cytokine genes.

DNA vaccines containing genes for antigenic portions of viruses have recently been developed as a novel vaccination technology. Direct injection of plasmid DNA in vivo results in prolonged expression of viral proteins and may, thus, mimic the action of attenuated vaccines. An important advantage of this vaccination method is that in vivo-synthesized viral proteins can enter both major histocompatibility complex (MHC) class I and class II antigen-processing pathways to activate specific immunization. In many animal models for infectious diseases, DNA vaccines induced a broad range of immune responses, including antibody, CD8+ cytotoxic T lymphocytes (CTL) and CD4+ helper T (Th) lymphocyte responses, and protective immunity against challenge with the pathogen. The magnitude and nature of these immune responses to DNA vaccines can be further manipulated by codelivery of cytokine genes. Summarizing the many studies reported to date, we can draw conclusions regarding the adjuvant effects of these cytokine genes on DNA vaccines. Coadministration of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-2 genes induces higher antibody titers and T-cell proliferation responses than other cytokine genes tested to date. In contrast, the CTL activity is only modestly increased by the GM-CSF and IL-2 genes. The IL-12 gene polarizes the immune responses to DNA vaccines toward Th1 cell development and stimulates the strongest CTL activity. In contrast, co-injection of the IL-4 gene promotes the development of Th2 cells and increases production of antibodies, but suppresses CTL activity. Thus, the immune responses to DNA vaccines can be engineered by co-injection of an appropriate cytokine gene to favor the formation of either CTL or neutralization antibodies and, therefore, provide the best protection against a particular pathogen.

Cytokines↗
PubMed1997

Transforming growth factor beta stabilizes p15INK4B protein, increases p15INK4B-cdk4 complexes, and inhibits cyclin D1-cdk4 association in human mammary epithelial cells.

The effects of transforming growth factor beta (TGF-beta) were studied in closely related human mammary epithelial cells (HMEC), both finite-life-span 184 cells and immortal derivatives, 184A1S, and 184A1L5R, which differ in their cell cycle responses to TGF-beta but express type I and type II TGF-beta receptors and retain TGF-beta induction of extracellular matrix. The arrest-resistant phenotype was not due to loss of cyclin-dependent kinase (cdk) inhibitors. TGF-beta was shown to regulate p15INK4B expression at at least two levels: mRNA accumulation and protein stability. In TGF-beta-arrested HMEC, there was not only an increase in p15 mRNA but also a major increase in p5INK4B protein stability. As cdk4- and cdk6-associated p15INK4B increased during TGF-beta arrest of sensitive cells, there was a loss of cyclin D1, p21Cip1, and p27Kip1 from these kinase complexes, and cyclin E-cdk2-associated p27Kip1 increased. In HMEC, p15INK4B complexes did not contain detectable cyclin. p15INK4B from both sensitive and resistant cells could displace in vitro cyclin D1, p21Cip1, and p27Kip1 from cdk4 isolated from sensitive cells. Cyclin D1 could not be displaced from cdk4 in the resistant 184A1L5R cell lysates. Thus, in TGF-beta arrest, p15INK4B may displace already associated cyclin D1 from cdks and prevent new cyclin D1-cdk complexes from forming. Furthermore, p27Kip1 binding shifts from cdk4 to cyclin E-cdk2 during TGF-beta-mediated arrest. The importance of posttranslational regulation of p15INK4B by TGF-beta is underlined by the observation that in TGF-beta-resistant 184A1L5R, although the p15 transcript increased, p15INK4B protein was not stabilized and did not accumulate, and cyclin D1-cdk association and kinase activation were not inhibited.

Breast↗
PubMed1996

Expression of two cDNAs encoding class I chitinases of rice in Escherichia coli.

Two cDNAs encoding class I chitinases of rice were expressed in Escherichia coli. The cDNAs were fused to the MS2-polymerase gene in an expression vector, pEx31. The fusion proteins, expressed under the control of the lambda PL-promoter, showed the chitinase activity independent of the existence of the hevein domain. The enzymatic hydrolysis of colloidal chitin by the fusion proteins showed that the proteins were endo-type enzymes.

Chitinases↗
PubMed1996

Alcaligenes xylosoxidans neonatal meningitis: a case report.

Neonatal meningitis caused by Alcaligenes xylosoxidans is associated with a high mortality rate. The causative microorganism is resistant to most antimicrobials. Generally, once the organism has been isolated from the cerebrospinal fluid of the infected neonate, initial therapy with a third-generation cephalosporin and trimethoprim-sulfamethoxazole is recommended before determining its susceptibility to antimicrobials. There present this is the first of neonatal meningitis with transient diabetes insipidus cause by A. xylosoxidans. The patient was treated with dDAVP for seven days and a combination of imipenem plus trimethoprim-sulfamethoxazole for 28 days. The patient was discharged in a stable condition and the end of that time, but with sequelae of hydrocephalus and hearing impairment.

Alcaligenes↗
PubMed1994

A novel inhibitor of cyclin-Cdk activity detected in transforming growth factor beta-arrested epithelial cells.

Transforming growth factor beta (TGF-beta) is a potent inhibitor of epithelial cell growth. Cyclins E and A in association with Cdk2 have been shown to play a role in the G1-to-S phase transition in mammalian cells. We have studied the effects of TGF-beta-mediated growth arrest on G1/S cyclins E and A. Inhibition of cyclin A-associated kinase by TGF-beta is primarily due to a decrease in cyclin A mRNA and protein. By contrast, while TGF-beta inhibits accumulation of cyclin E mRNA, the reduction in cyclin E protein is minimal. Instead, we find that the activation of cyclin E-associated kinase that normally accompanies the G1-to-S phase transition is inhibited. A novel inhibitor of cyclin-Cdk complexes was detected in TGF-beta-treated cell lysates. Inhibition is mediated by a heat-stable protein that targets both Cdk2 and Cdc2 kinases. In G0-arrested cells, a similar inhibitor of Cdk2 kinase was detected. These data suggest the existence of an inhibitor of cyclin-dependent kinases induced under different conditions to mediate antiproliferative responses.

Animals↗
PubMed1993

Blockage of EGF receptor signal transduction causes reversible arrest of normal and immortal human mammary epithelial cells with synchronous reentry into the cell cycle.

We demonstrate that blockage of EGF receptor signal transduction is sufficient by itself to cause a rapid, efficient, and reversible G0-like growth arrest of normal human mammary epithelial cells (HMEC) of finite lifespan as well as two immortally transformed cell lines derived from normal HMEC following in vitro transformation with benzo[a]pyrene. For normal HMEC, the significant level of endogenous production of TGF alpha requires utilization of blocking antibodies to the EGF receptor to achieve cessation of growth in mass culture, whereas removal of EGF is sufficient to arrest the immortal cell lines. In the growth-arrested cells, protein synthesis remains depressed; reexposure to EGF leads to a rapid increase in protein synthesis. Inhibition of DNA synthesis is not detectable until approximately 12 h after removal of EGF/TGF alpha and is pronounced by 24 h. Reexposure to EGF produces high levels of synthesis of the early response genes, c-myc, c-fos, c-jun, and MGSA, within 1 h. DNA synthesis increases only after 10 h, with a sharp peak after 15-20 h. Reexposure of the growth-arrested normal HMEC for 1 h with EGF allows a majority of the cells capable of cycling to subsequently enter the S phase. Little is currently known about cell cycle control in normal human epithelial cells. The efficient and gentle method of achieving reversible G0 growth arrest reported here may facilitate studies on the cell cycle of this cell type. Additionally, results from normal HMEC can be compared with those from syngeneic immortalized cell populations to determine possible cell cycle parameters altered as a result of immortal transformation.

Antibodies, Monoclonal↗
PubMed1993

[Clinical investigation by transcranial Doppler sonography of the effect of norepinephrine on cerebral arterial blood velocity of normotensive males].

Transcranial Doppler (TCD) sonography is a new, non-invasive method for evaluation of the hemodynamics of cerebral circulation. Using a 2-MHz probe, the intracranial middle, posterior, vertebral and basilar arteries can be isolated easily to obtain parameters of systolic, diastolic, mean velocities and pulsatility index (PI). Changes of blood velocities and PI can assist evaluation of the condition of intracranial arterial spasm, dilatation and cerebral vascular resistance. The purpose of this study is to evaluate the hemodynamic effect of norepinephrine (NE) on cerebral circulation. Eighteen normotensive male healthy volunteers (mean age 42 years) were studied with TCD before and during NE infusion (13-16 micrograms/min). Results showed that systolic, diastolic and mean arterial pressure were increased significantly during NE infusion. Blood velocities of middle, posterior, vertebral and basilar arteries also increased markedly. Increased cerebral vascular resistance with elevation of PI was also noted in all of the persons studied. These findings provide evidence that NE infusion induces intracerebral vasospasm.

Adult↗
PubMed1992

[Brainstem auditory evoked potentials in diabetes mellitus].

It is well-known that diabetic patients develop peripheral and autonomic neuropathy, and recent review has also suggested the occurrence of central pathway abnormality in diabetics. In this article, we conducted the BAEP study on 61 cases of NIDDM and 11 cases of IDDM. Peak latency, interpeak latency (IPL) and peak amplitude of BAEPs were analyzed in each case. For further correlation, the motor and sensory nerve conduction velocities of median nerve, the blood sugar, the serum HbA1c were measured. Two nondiabetic groups, age and sex matched with NIDDM and IDDM groups, were used as control. In NIDDM group, the results showed prolongation of all peak latency and IPL except peak latency of wave II and wave IV in the left side and bilateral IPL III-V. There was no statistically significant amplitude difference between NIDDM and age-matched control group. The result of IDDM group revealed prolongation of all peak latency and IPL, except the right IPL III-V. As for amplitude, waves III and V in the right side and waves I and V in the left side were reduced as compared with the age-matched young control group. There was no statistically significant difference in all peak latencies and IPLs between NIDDM and IDDM groups. In both groups of NIDDM and IDDM, the MNCV and SNCV of median nerve were significantly delayed in conduction. The prolongation of III and V peak latency had a linear correlation with their amplitude reduction. In conclusion, both peripheral and central conduction dysfunction occur in both IDDM and NIDDM patients.

Adult↗
PubMed1992

[Pattern shift visual evoked potentials in diabetes mellitus].

Functional exploration of the optic pathways with pattern shift visual evoked potentials (PSVEP) has been rapidly accepted as a non-invasive method of investigation of diabetics. For this article, we conducted the PSVEPs study on 46 cases of NIDDM and 13 cases of IDDM. The peak latency, interpeak latency and evoked amplitude of P100 were analyzed in each case. For further correlation, the motor and sensory nerve conduction velocities of the median nerve, blood sugar, serum HbA1c, and duration of DM were measured simultaneously. Two nondiabetic control groups which matched the age and sex of the NIDDM and IDDM groups were used for comparison. In the IDDM group, the results showed prolongation of all peak and interpeak latencies (IPL) except the peak latency of N75 on the right side. The P100 amplitude was reduced as compared with the age-matched young control group. The interocular P100 latency difference (ILD) was not statistically significant between the IDDM group and the age-matched control group. The results of the NIDDM group revealed prolongation of all peak latencies and IPLs. The P100 amplitude and ILD showed no statistically significant difference between NIDDM and the age-matched control group. The prolongation of N 75 peak latency exhibited a linear correlation with duration, HbA1c and median nerve SNCV.

Adult↗