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Biomedical subjects

C C Huang

Publications and source records attributed to C C Huang.

At least 55 records · Page 3Linked to original sources
PubMed2003

Prevalence and clinical implications of hepatitis B virus genotypes in southern Taiwan.

BACKGROUND: Hepatitis B virus (HBV) infection is a major health problem. HBV genotypes may be associated with progression of liver disease. The distribution and clinical implications of HBV genotypes in southern Taiwan are evaluated. METHODS: We used a polymerase chain reaction-restriction fragment length polymorphism genotyping method to determine HBV genotypes. RESULTS: The genotype distribution for 265 patients with chronic HBV infection was as follows: A, 3 (1%); B, 158 (60%); C, 90 (34%); D, 7 (2.5%); E, 0: F, 0; and unclassified, 7 (2.5%). Compared with genotype B patients, genotype C patients had a higher hepatitis B e antigen positive rate and higher fibrosis score. There was no significant difference in the mean age between genotype B and genotype C patients with hepatocellular carcinoma (HCC). However, when patients were stratified by age, the prevalence of genotype C was significantly higher in young HCC patients (<50 years of age) than in age-matched asymptomatic carriers (40% versus 10%, P < 0.001). Using multivariate analysis, the significant risk factors for advanced liver disease (cirrhosis or HCC) for patients with chronic HBV infection were old age, male gender and genotype C. CONCLUSIONS: These results suggest that genotype C is associated with more severe liver diseases than the B variant.

Adolescent↗
PubMed2002

Effect of enantiomeric excess on surface structures and phase sequences in free-standing liquid-crystal films.

We present differential optical reflectivity and null transmission ellipsometry data from several mixtures of MHPBC enantiomers. From this data, we have determined the chiral smectic phase sequence as a function of enantiomeric excess. The data suggest a change in the structure of the smectic-C(*)(alpha) phase and the surface tilt state as the enantiomeric excess is reduced. The results also show that the intermediate phases, smectic C(*)(FI2), smectic C(*)(FI1), and smectic C(*)(alpha), disappear sequentially on reducing the net chirality.

Journal Article↗
PubMed2002

Molecular orientation arrangements in the smectic-C* variant liquid-crystal phases.

Recent experiments have identified three-layer and four-layer distorted helical structures in the smectic liquid-crystal phases Sm C*(FI1) and Sm C*(FI2), respectively. However, no theories have explained the existence of all these phases. A discrete phenomenological model of the free-energy is analyzed and found to predict the stability of distorted three-layer and four-layer structures, as well as simple helical solutions in smectic liquid crystals. A simple physical picture is provided to explain the stability of the phases exhibiting distorted helical structures.

Journal Article↗
PubMed2002

Interlayer structures of the chiral smectic liquid crystal phases revealed by resonant X-ray scattering.

The structures of the liquid crystalline chiral subphases exhibited by several materials containing either a selenium or sulphur atom have been investigated using a resonant x-ray scattering technique. This technique provides a unique structural probe for the ferroelectric, ferrielectric, antiferroelectric, and SmC(*)(alpha) phases. An analysis of the scattering features allows the structural models of the different subphases to be distinguished, in addition to providing a measurement of the helical pitch. This paper reports resonant scattering features in the antiferroelectric hexatic phase, the three- and four-layer intermediate phases, the antiferroelectric and ferroelectric phases and the SmC(*)(alpha) phase. The helicoidal pitch has been measured from the scattering peaks in the four-layer intermediate phase as well as in the antiferroelectric and ferroelectric phases. In the SmC(*)(alpha) phase, an investigation into the helical structure has revealed a pitch ranging from 5 to 54 layers in different materials. Further, a strong resonant scattering signal has been observed in mixtures of a selenium containing material with as much as 90% nonresonant material.

Journal Article↗
PubMed2002

Dramatic effect of an additional CH2 group on the temperature variation of the Sm-C(*)(alpha) short helical pitch.

High-resolution differential optical reflectivity was used to study the temperature evolution of the short helical pitch in the Sm-C(*)(alpha) phase of successive members from two liquid-crystal homologous series. With the addition of one CH2 group, the magnitude and temperature evolution of the pitch change dramatically, and the molecular arrangements between consecutive surface layers found in free-standing films change from being anticlinic to synclinic.

Journal Article↗
PubMed2002

Unusual thickness-dependent heat-capacity anomalies in free-standing hexatic liquid-crystal films.

High-resolution heat-capacity and optical-reflectivity measurements have been conducted near the smectic-A to hexatic-B transition in thin free-standing films of the liquid-crystal compound 64COOBC. We find an unexpected dependence on film thickness of the integrated magnitude of the heat-capacity anomalies as the films undergo layer-by-layer transitions. We measure the penetration depths of the ordering from the surface and next-to-surface layers which are pertinent to the highly correlated thermal behavior.

Journal Article↗
PubMed2002

Observation of unusual surface ordering in a uniaxial Sm-A phase formed by a highly biaxial compound.

We have studied one banana-shaped compound using null-transmission ellipsometry. By studying free-standing films of various thicknesses we confirm that this compound exhibits the Sm-A phase. This is the first banana-shaped compound with a relatively small bend angle (approximately 140 degrees) in which a uniaxial phase has been observed. At the lower temperature end of the Sm-A phase we observe unusual ordering at the surface of the film.

Journal Article↗
PubMed2002

Isocupressic acid blocks progesterone production from bovine luteal cells.

The needles of ponderosa pine (Pinus ponderosa Laws.) were reported to induce abortions when fed to late-term pregnant beef cows in North America. An in vivo study of pregnant cows suggested that isocupressic acid (IA) was the main abortifacient isolated from needles and bark of the pine. However, the mechanism of abortifacient activity of IA is not clear yet. In a pregnant cow, the corpus luteum of the ovary helps the maintenance of pregnancy by its progesterone production. This study involved the IA extracted from the root of the Taiwan cypress (Juniperus formosana) and used a frozen-thawed bovine luteal cell culture system to investigate the action of IA on progesterone production. Thawed bovine luteal cells (1 x 10(5) cells/ml/well) in M199 medium were cultured in 24-well culture plates at 37 degrees C in a 5% CO2 incubator. Ten ml of tested drugs, IA at 1 to 1000 ng/ml and/or ovine luteinizing hormone (oLH) at 1 to 100 ng/microl or 8-bromo-cyclic adenosine monophosphate (8-Br-cAMP) with 0.1-10 mM, were added into each well. After 4 hours of incubation, the media were harvested and assayed for progesterone by an enzyme immunoassay. Progesterone production from cells was the indicator used to evaluate the action of IA. All tested doses of IA significantly inhibited progesterone production in both basal and oLH stimulating conditions. Also those dosages inhibited cyclic adenosine-3',5'- monophosphate (cAMP) stimulation, suggesting a post-cAMP mechanism is involved in the IA action. We concluded that IA can induce pregnant cows to abort partly through blocking luteal function and may be identified as a new abortifacient chemical.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2002

Combined bronchoalveolar lavage and polymerase chain reaction in the diagnosis of pulmonary tuberculosis in smear-negative patients.

SETTING: The polymerase chain reaction (PCR) may be sensitive and specific for the diagnosis of tuberculosis, but most reports are of studies conducted in well-controlled laboratories. A study to evaluate the clinical value of bronchoalveolar lavage (BAL) combined with PCR was necessary. OBJECTIVE: One hundred and thirty one patients were recruited into the study from March 1994 to February 1997. DESIGN: Patients with a positive acid-fast stain on sputum smear were recruited into group A as positive controls, patients with lung cancer and a negative acid-fast stain on sputum smear were put into group B as negative controls, and patients who had clinical symptoms of pulmonary TB without sputum or with negative smear results were the investigating group. PCR was performed on the sputum samples from group A and B patients and on the BAL fluid from those in group C. RESULTS: The sensitivity of PCR was 96% in group A, and the specificity was 100% in group B. The sensitivity of PCR in the BAL fluid from the group C patients was 36% and the specificity was 96%; the positive predictive value was 94% and the negative predictive value was 45%. CONCLUSION: BAL plus PCR is useful in the rapid diagnosis of pulmonary TB in non-productive or smear-negative patients.

Bronchoalveolar Lavage Fluid↗
PubMed2002

Levels of interferon-gamma and interleukin-2 receptor-alpha for bronchoalveolar lavage fluid and serum were correlated with clinical grade and treatment of pulmonary tuberculosis.

OBJECTIVE: We investigated possible correlations for interferon-gamma (IFN-gamma) and soluble interleukin-2 receptor-alpha (sIL-2R-alpha) levels in bronchoalveolar lavage fluid (BALF), and clinical grade of pulmonary tuberculosis (TB), which is determined by factors such as extent of pulmonary involvement, fever and loss of body weight. DESIGN: In order to explore these correlations and address associated questions, BALF was collected from 45 patients presenting with active pulmonary TB and 14 healthy controls. Repetitive BALF was collected in 17 patients after 3 months of anti-tuberculosis chemotherapy. The epithelial lining fluid (ELF) levels for IFN-gamma and sIL-2R-alpha were measured using enzyme-linked immunosorbent assay (ELISA) after standardization with urea. RESULTS: Patients with higher-grade pulmonary TB (i.e., with more advanced pulmonary involvement, fever or body weight loss), revealed significantly higher ELF levels for IFN-gamma and sIL-2R-alpha compared to those with lower grade pulmonary TB. Similar results were also determined for sIL-2R-alpha serum levels, but not for IFN-gamma serum levels. After anti-tuberculosis chemotherapy the elevated cytokine levels for ELF and serum significantly decreased in accordance with radiographic improvement. CONCLUSIONS: ELF levels of IFN-gamma and sIL-2R-alpha were correlated with disease grading of pulmonary TB and decreased after anti-tuberculosis chemotherapy.

Bronchoalveolar Lavage Fluid↗
PubMed2001

Surface structures and transitions in the smectic-C* phase of one chiral liquid crystal compound.

Three optical probes have been employed on free-standing films to study surface structure and transitions of the SmC* phase of one liquid crystal compound. While the interior layers show the SmC* structure, the tilt in adjacent surface layers is found to be anticlinic. The number of anticlinic surface layers grows rapidly as the transition to the SmC*(FI2) phase is approached.

Journal Article↗
PubMed2001

Detailed optical studies of several banana-shaped compounds in liquid crystal B2 phase.

Null-transmission ellipsometry has been performed on free-standing films of one compound in the liquid crystal B2 phase. We have studied films of thickness from 1 to 121 layers. One of the compounds used has an unusually wide 59 K window for the B2 phase. The tilt angle was investigated as a function of temperature and found to be constant over this temperature range to within our resolution of 1 degrees. The one-layer films studied exhibit the same structure as the thicker films, and have helped us to refine the optical model for the B2 phase. For thin films we find that modeling a single smectic layer as two uniaxial layers is a better description of the data than a single biaxial layer, but that for thick films the model used does not effect the simulated result appreciably. Preliminary results also find that the surface layers are less tilted than the interior layers, in contrast to rodlike liquid crystals, which show an enhanced surface tilt.

Journal Article↗
PubMed2001

Characterization of the mechanism underlying the reversal of long term potentiation by low frequency stimulation at hippocampal CA1 synapses.

Reversal of long term potentiation (LTP) may function to increase the flexibility and storage capacity of neuronal circuits; however, the underlying mechanisms remain incompletely understood. We show that depotentiation induced by low frequency stimulation (LFS) (2 Hz, 10 min, 1200 pulses) was input-specific and dependent on N-methyl-d-aspartate (NMDA) receptor activation. The ability of LFS to reverse LTP was mimicked by a brief application of NMDA. This NMDA-induced depotentiation was blocked by adenosine A(1) receptor antagonist. However, the reversal of LTP by LFS was unaffected by metabotropic glutamate receptor antagonism. This LFS-induced depotentiation was specifically prevented by protein phosphatase (PP)1 inhibitors, okadaic acid, and calyculin A but not by the PP2A or PP2B inhibitors. Furthermore, by using phosphorylation site-specific antibodies, we found that LFS-induced depotentiation is associated with a persistent dephosphorylation of the GluR1 subunit of amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor at serine 831, a protein kinase C and calcium/calmodulin-dependent protein kinase II (CaMKII) substrate, but not at serine 845, a substrate of cAMP-dependent protein kinase. This effect was mimicked by bath-applied adenosine or NMDA and was specifically prevented by okadaic acid. Also, the increased phosphorylation of CaMKII at threonine 286 and the decreased PP activity seen with LTP were overcome by LFS, adenosine, or NMDA application. These results suggest that LFS erases LTP through an NMDA receptor-mediated activation of PP1 to dephosphorylate amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors and CaMKII in the CA1 region of the hippocampus.

Adenosine↗
PubMed2001

Orientational ordering in the chiral smectic-C*FI2 liquid crystal phase determined by resonant polarized x-ray diffraction.

High-resolution resonant polarized x-ray diffraction experiments near the sulfur K edge have been performed on free-standing liquid crystal films exhibiting the chiral smectic-C*FI2 phase. It is widely accepted that this phase has a four-layer repeat unit, but the internal structure of the repeat unit remains controversial. We report different resolved features of the resonant x-ray diffraction peaks associated with the smectic-C*FI2 phase that unambiguously demonstrate that the four-layer repeat unit is locally biaxial about the layer normal and that the measured angle, describing the biaxiality, is in good agreement with optical measurements.

Journal Article↗
PubMed2001

Analysis of large-volume DNA markers and polymerase chain reaction products by capillary electrophoresis in the presence of electroosmotic flow.

We have demonstrated on-line concentration and separation of DNA in the presence of electroosmotic flow (EOF) using poly(ethylene oxide) (PEO) solutions. After injecting large-volumes DNA samples, PEO solutions entered a capillary filled with 400 mM Tris-borate (TB) buffers by EOF and acted as sieving matrices. DNA fragments stacked between the sample zone and PEO solutions. Because sample matrixes affected PEO adsorption on the capillary wall, leading to changes in EOF, migration time, concentration, and resolving power varied with the injection length. When injecting phiX174 RF DNA-HaeIII digest prepared in 5 mM Tris-HCl buffer, pH 7.0, at 250 V/cm, peak height increased linearly as a function of injection volume up to 0.9 microl (injection time 150 s). The sensitivity improvement was 100-fold compare to that injected at 25 V/cm for 10 s (0.006 microl). When injecting 1.54 microl of GeneScan 1000 ROX, the sensitivity improvement was 265-fold. The sensitivity improvement was 40-fold when injecting 0.17 microl DNA sample containing pBR 322/HaeIII, pBR 328/BglI, and pBR 328/HinfI digests prepared in phosphate-buffered saline. This method allows the analysis of polymerase chain reaction (PCR) products amplified after 17 cycles when injecting 0.32 microl (at 30 cm height for 300 s). The total analysis time was shorter (91.6 min) than that (119.6 min) obtained from injecting PCR products after 32 cycles for 10 s.

Base Sequence↗
PubMed2001

Molecular characterization of foot-and-mouth disease virus isolated from ruminants in Taiwan in 1999-2000.

In 1999, 10 sporadic outbreaks of cattle foot-and-mouth disease (FMD) occurred in Taiwan. By the time, infection was limited to the Chinese yellow cattle (a native species of beef cattle in Mainland China), which did not develop vesicular lesions under field conditions. Five viruses isolates obtained from individual farms were confirmed to be the serotype O FMD virus (O/Taiwan/1999). During January-February 2000, however, this virus has spread to dairy cattle and goat herds, causing severe mortality in goat kids and vesicular lesions in dairy cattle. Partial nucleotide sequence of the capsid coding gene 1D (VP1) was determined for the virus isolates obtained in this study. Phylogenetic analysis of the VP1 sequences indicated that the O/Taiwan/1999 viruses shared 95-97% similarities to the virus strains isolated from the Middle East and India. The species susceptibility of the O/Taiwan/1999 virus was experimentally studied in several species of susceptible animals, showing that the virus did cause generalized lesions in dairy cattle and pigs, however, it would not cause vesicular lesions on the Chinese yellow cattle and the adult goats. These studies suggested that the O/Taiwan/1999 virus was a novel FMD virus of Taiwan and it presented various levels of susceptibility in cattle species.

Amino Acid Sequence↗
PubMed2001

Resonant x-ray scattering study of the antiferroelectric and ferrielectric phases in liquid crystal devices.

Resonant x-ray scattering has been used to investigate the interlayer ordering of the antiferroelectric and ferrielectric smectic C* subphases in a device geometry. The liquid crystalline materials studied contain a selenium atom and the experiments were carried out at the selenium K edge allowing x-ray transmission through glass. The resonant scattering peaks associated with the antiferroelectric phase were observed in two devices containing different materials. It was observed that the electric-field-induced antiferroelectric to ferroelectric transition coincides with the chevron to bookshelf transition in one of the devices. Observation of the splitting of the antiferroelectric resonant peaks as a function of applied field also confirmed that no helical unwinding occurs at fields lower than the chevron to bookshelf threshold. Resonant features associated with the four-layer ferrielectric liquid crystal phase were observed in a device geometry. Monitoring the electric field dependence of these ferrielectric resonant peaks showed that the chevron to bookshelf transition occurs at a lower applied field than the ferrielectric to ferroelectric switching transition.

Journal Article↗