PubMed Health⌕ Search

Biomedical subjects

C S Yang

Publications and source records attributed to C S Yang.

At least 19 recordsLinked to original sources
PubMed2006

Charge-orbital ordering and Verwey transition in magnetite measured by resonant soft X-ray scattering.

We report experimental evidence for the charge-orbital ordering in magnetite below the Verwey transition temperature T(V). Measurements of O K-edge resonant x-ray scattering on magnetite reveal that the O 2p states in the vicinity of the Fermi level exhibit a charge-orbital ordering along the c axis with a spatial periodicity of the doubled lattice parameter of the undistorted cubic phase. Such a charge-orbital ordering vanishes abruptly above T(V) and exhibits a thermal hysteresis, correlating closely with the Verwey transition in magnetite.

Journal Article↗
PubMed2006

Long-term efficiency and stability of wetlands for treating wastewater of a lead/zinc mine and the concurrent ecosystem development.

A constructed wetland system in Guangdong Province, South of China has been used for treating Pb/Zn mine discharge since 1985. The performance in the purification of the mine discharge and the concurrent ecosystem development within the system during the period of 1985-2000 has been studied. The untreated wastewater contained rather high concentrations of cadmium (Cd) (0.05 mg L(-1)), lead (Pb) (11.5 mg L(-1)), and zinc (Zn) (14.5 mg L(-1)), which greatly exceed the upper limits for industrial wastewater discharge in China. The constructed wetland system effectively removed Cd by 94.00%, Pb by 99.04%, Zn by 97.30%, and total suspended solids (TSS) by 98.95% from the mine discharge over a long period (over 16 years) leading to significant improvement in water quality; it was also found that there were no significantly annual or monthly variations in pH values, As, Cd, Hg, Pb, and Zn concentrations in water collected from the outlet of the wetland. Moreover, diversity and abundance of living organisms, including protozoan, higher plants, terrestrial animals, and birds, increased gradually. The 16-year monitoring results showed a reciprocal relationship, at a certain extent, between restoration of the wetland ecosystem, in other words, the maturity of the wetland, and the long-term efficiency and stability on purifying heavy metal-contaminated wastewater.

China↗
PubMed2005

Movement of finger joints induced by synergistic wrist motion.

BACKGROUND: An experiment has recently been conducted to evaluate and compare the differences in tendon excursions between the flexor digitorum profundus and superficialis using three mobilization techniques. No previous studies deal with the total joint excursions with constant tendon length. The purpose of this study was to investigate the coordinated motion between the finger and wrist joints resulting from passive tension of the muscles while performing synergistic wrist motion. METHODS: The relative joint positions of the hand and wrist were measured using a three-dimensional motion analysis system with external retroreflective markers 2 mm in diameter placed on the dorsal surface of the hand. Fifty normal subjects, with a 1:1 gender ration, ranging in age from 20 to 40 years, and with no previous history of upper extremity injury, were recruited for the experiment. FINDINGS: The relationships of synergistic motion between the wrist and finger joints due to passive tension in the muscles were approximately linear. The ranges of wrist motion averaged 60 degrees extension and 60 degrees flexion. Moving the wrist from flexion into extension induced synergistic finger joint motion as follows: the distal interphalangeal joint angles changed from an average of 12 degrees of flexion to 31 degrees; proximal-interphalangeal joint angles changed from 19 degrees to 70 degrees; and metacarpal phalangeal joints changed from 27 degrees to 63 degrees of flexion. INTERPRETATION: The relationships of synergistic motion between the wrist and finger joints were systematically documented. Such a relationship could be considered in optimizing the design of dynamic splints used for rehabilitation in post-surgical tendon repair, as well as providing useful information about potential diagnoses of problems with the integrity of the flexor and extensor mechanisms.

Adult↗
PubMed2005

Taxonomic history and current status of Stachybotrys chartarum and related species.

UNLABELLED: The fungus Stachybotrys chartarum is the type species of the genus Stachybotrys. It is a cellulolytic saprophyte with a worldwide distribution and is frequently recovered in water-damaged buildings. Three isolates of S. chartarum were studied morphologically from single-spore isolations. Significant differences were found with the sizes, lengths, width, and L/W ratio of conidia and phialides among the isolates. QPCR analysis on S. chartarum, S. yunnanensis, S. chlorohalonata, S. elegans, S. microspora, and S. nephrospora showed that the primers and probe for detecting S. chartarum used by commercial laboratories were not able to differentiate S. chartarum from S. chlorohalonata and S. yunnanensis. Results suggested that S. chartarum may not be well delineated even after S. chlorohalonata was recently segregated from the species complex. Further study on the taxonomic status of the epithet S. chartarum is necessary. PRACTICAL IMPLICATIONS: Six species of Stachybotrys are present indoors. Differentiation of Stachybotrys chartarum from S. chlorohalonata, and S. yunnanensis can be challenging using either morphological or QPCR methods. Caution should be taken to identify S. chartarum and closely related species and to explain their health effects implication for indoor air quality investigations.

Air Microbiology↗
PubMed2004

Leukotriene A4 hydrolase as a target for cancer prevention and therapy.

Leukotriene A4 hydrolase (LTA4H) is a bifunctional zinc enzyme with the activities of epoxide hydrolase and aminopeptidase. As an epoxide hydrolase, LTA4H catalyzes the hydrolysis of the epoxide LTA4 to the diol, leukotriene B4 (LTB4), which mainly functions as a chemoattractant and an activator of inflammatory cells. As an aminopeptidase, LTA4H may process peptides related to inflammation and host defense. In a chronic inflammation-associated animal model of esophageal adenocarcinoma, we have shown that LTA4H was overexpressed in tumor as compared to normal tissues. Bestatin, an LTA4H inhibitor, suppresses tumorigenesis in this animal model. Since LTA4H has long been regarded as an anti-inflammatory target, we propose LTA4H as a target for prevention and therapy of cancers, especially those associated with chronic inflammation. Here we review the gene structure, expression, regulation and functions of LTA4H, as well as its involvement in carcinogenesis. We believe LTA4H/LTB4 may play an important role in chronic inflammation associated carcinogenesis by at least two mechanisms: a) the inflammation-augmenting effect on inflammatory cells through positive feedback mediated by its receptors and downstream signaling molecules; and b) the autocrine growth-stimulatory effect of LTB4 produced by epithelial cells, and the paracrine growth-stimulatory effect of LTB4 produced by inflammatory cells, on precancerous and cancer cells. Based on our present knowledge, inhibitors of LTA4H or antagonists of LTB4 receptors may be used alone or in combination with other agents (e.g., cyclooxygenase 2 inhibitors) in cancer prevention and treatment trials to test their effectiveness.

Animals↗
PubMed2002

Changes of TGFbeta1 and TGFbetaRII expression in esophageal precancerous and cancerous lesions: a study of a high-risk population in Henan, northern China.

The level of transforming growth factor beta1 (TGFbeta1) and transforming growth factor betaII receptor (TGFbetaRII) was determined immunohistochemically in normal tissues and tissues with different severities of lesions (basal cell hyperplasia, BCH; dysplasia, DYS; carcinoma in situ, CIS; and squamous cell carcinoma, SCC) from surgically resected human esophagi and esophageal biopsies of symptom-free subjects. The samples were from an area with high esophageal cancer incidence in northern China (Linzhou, formerly Linxian, and nearby county Huixian in Henan Province). Peroxidase immunostain (ABC) and conventional hematoxylin and eosin stain were used. The tissue sections were incubated with antibodies of TGFbeta1 and TGFbetaRII overnight. The immunoreactivity was observed in cytoplasm of the esophageal specimen. From normal to BCH to DYS to CIS and to SCC, the positive immunostaining rates for TGFbeta1 increased significantly (P < 0.05). A linear correlation between the positive immunostaining rates of TGFbeta1 and the different lesions was observed (P < 0.05). From well- to moderately- and poorly differentiated SCC, the positive immunostaining rates for TGFbeta1 decreased gradually, but the difference was not significant (P > 0.05). In contrast, with the lesions progressing from normal to BCH to DYS to CIS and to SCC, the positive immunostaining rates for TGFbetaRII decreased significantly (P < 0.05). From well- to moderately- and poorly differentiated SCC, the positive immunostaining rates for TGFbetaRII decreased significantly (P < 0.05). There was a linear correlation between the positive rates of TGFbetaRII and different lesions and SCC differentiation (P < 0.05). The present results indicated that the alterations of TGFbeta1 and TGFbetaRII is a frequent event in esophageal multistage carcinogenesis, the absent or lower expression of TGFbetaRII may lead to the loss of cell proliferation control by TGFbeta1 and the overexpression of TGFbeta1 may be a negative feedback response caused by the lower expression of TGFbetaRII protein.

Adult↗
PubMed2002

Endoscopic screening and determination of p53 and proliferating cell nuclear antigen in esophageal multistage carcinogenesis: a comparative study between high- and low-risk populations in Henan, northern China.

The objective of this study was to characterize the histologic changes from endoscopic screening for early esophageal cancer (EC) on subjects at high-incidence area (HIA) and low-incidence area (LIA) in Henan, China, and to further compare the changes in p53 and proliferating cell nuclear antigen (PCNA) in the multistage of human esophageal carcinogenesis from these two populations. The detection rate of basal cell hyperplasia (BCH) and dysplasia (DYS) was higher in the subjects from HIA than in those from LIA. Out of the 1568 symptom-free subjects examined at HIA, 10 (0.6%) cases with early squamous cell carcinoma (SCC) were identified. Immunoreactivity of p53 and PCNA was observed in cell nuclei of esophageal biopsies and surgically resected esophageal cancer specimens both in HIA and LIA. With the lesions progressed from normal epithelium to BCH to DYS to SCC, the positive-immunostaining cells expanded from basal layer to superficial layer, and the number of positive cells/mm2 for p53 and PCNA increased, and was significantly higher in HIA than in LIA among the similar morphological lesions (P < 0.01). The number of p53 positive cells/mm2 in SCC from HIA was almost fivefold higher than SCC from LIA (P < 0.01). The remarkable difference was also observed between HIA and LIA in DYS and BCH. The present results indicate that p53 protein accumulation is an important early biomarker for identifying high-risk subjects for EC.

Adult↗
PubMed2001

Serologic markers of Epstein-Barr virus infection and nasopharyngeal carcinoma in Taiwanese men.

BACKGROUND: It is probable but unproven that Epstein-Barr virus (EBV) has a role in nasopharyngeal carcinoma. We determined whether antibodies against EBV are present before the development of nasopharyngeal carcinoma. METHODS: A total of 9699 men were enrolled between 1984 and 1986. Blood samples were examined for IgA antibodies against EBV capsid antigen and neutralizing antibodies against EBV-specific DNase. During 131,981 person-years of follow-up, 22 pathologically confirmed new cases of nasopharyngeal carcinoma that were diagnosed more than one year after recruitment were ascertained through linkage with the National Cancer Registry of Taiwan. RESULTS: The cumulative risk of nasopharyngeal carcinoma per 100,000 person-years was 11.2 for subjects who tested positive for neither serologic marker, 45.0 for those who had one marker, and 371.0 for those who had both markers. After adjustment for age and the presence or absence of a family history of nasopharyngeal carcinoma, the relative risk of nasopharyngeal carcinoma was 32.8 for subjects with both markers (95 percent confidence interval, 7.3 to 147.2; P<0.001) and 4.0 for subjects with one marker (95 percent confidence interval, 1.6 to 10.2; P=0.003), as compared with subjects with neither marker. The longer the duration of follow-up, the greater the difference in the cumulative incidence of nasopharyngeal carcinoma between seropositive and seronegative subjects. CONCLUSIONS: IgA antibodies against EBV capsid antigen and neutralizing antibodies against EBV DNase are predictive of nasopharyngeal carcinoma.

Antibodies↗
PubMed2001

Light-induced structural changes occur in the transmembrane helices of the Natronobacterium pharaonis HtrII transducer.

The Natronobacterium pharaonis HtrII (NpHtrII) transducer interacts with its cognate photoactive sensory rhodopsin receptor, NpSRII, to mediate phototaxis responses. NpHtrII is predicted to have two transmembrane helices and a large cytoplasmic domain and to form a homodimer. Single cysteines were substituted into an engineered cysteine-less NpHtrII at 38 positions in its transmembrane domain. Oxidative disulfide cross-linking efficiencies of the monocysteine mutants were measured with or without photoactivation of NpSRII. The rapid cross-linking rates at several positions support that NpHtrII is a dimer when functionally expressed in the Halobacterium salinarum membrane. Thirteen positions in the second transmembrane segment (TM2) exhibited significant light-induced increases in cross-linking efficiency, and they define a single face traversing the length of the segment when modeled as an alpha-helix. Four positions in this helix showing light-induced decreases in efficiency are clustered on the cytoplasmic side of the protein. One of the monocysteine mutants, G83C, showed loss of phototaxis responses, and analysis of double mutants showed that the G83C mutation alters the dark structure of the TM2-TM2' region of NpHtrII. In summary, the results reveal conformationally active regions in the second transmembrane segment of NpHtrII and a face along the length of TM2 that becomes more available for TM2-TM2' cross-linking upon receptor photoactivation. The data also establish that one residue in TM2, Gly83, is critical for maintaining the proper conformation of NpHtrII for signal relay from the photoactivated receptor to the kinase-binding region of the transducer.

Amino Acid Sequence↗
PubMed2001

Effects of purified green and black tea polyphenols on cyclooxygenase- and lipoxygenase-dependent metabolism of arachidonic acid in human colon mucosa and colon tumor tissues.

The effects of green and black tea polyphenols on cyclooxygenase (COX)- and lipoxygenase (LOX)-dependent arachidonic acid metabolism in normal human colon mucosa and colon cancers were investigated. At a concentration of 30 microg/mL, (-)-epigallocatechin-3-gallate (EGCG), (-)-epigallocatechin (EGC), and (-)-epicatechin-3-gallate (ECG) from green tea and theaflavins from black tea inhibited LOX-dependent activity by 30-75%. The formation of 5-, 12-, and 15-LOX metabolites was inhibited to a similar extent. Tea polyphenols also inhibited COX-dependent arachidonic acid metabolism in microsomes from normal colon mucosa, with ECG showing the strongest inhibition. The formation of thromboxane (TBX) and 12-hydroxyheptadecatrienoic acid (HHT) was decreased to a greater extent than other metabolites. The inhibitory effects of tea polyphenols on COX activity, however, were less pronounced in tumor microsomes than in normal colon mucosal microsomes. Theaflavins strongly inhibited the formation of TBX and HHT, but increased the production of prostaglandin E(2) (PGE(2)) in tumor microsomes. The enhancing effect of theaflavins on PGE(2) production was related to the COX-2 level in the microsomes. Although theaflavin inhibited ovine COX-2, its activity in the formation of PGE(2) was stimulated by theaflavin when ovine COX-2 was mixed with microsomes, suggesting that theaflavin affects the interaction of COX-2 with other microsomal factors (e.g. PGE synthase). The present results indicate that tea polyphenols can affect arachidonic acid metabolism in human colon mucosa and colon tumors, and this action may alter the risk for colon cancer in humans.

Antioxidants↗
PubMed2001

Inhibitory mechanisms of tea polyphenols on the ultraviolet B-activated phosphatidylinositol 3-kinase-dependent pathway.

In this study, we investigated the effect of tea polyphenols, (-)-epigallocatechin-3-gallate or theaflavins, on UVB-induced phosphatidylinositol 3-kinase (PI3K) activation in mouse epidermal JB6 Cl 41 cells. Pretreatment of cells with these polyphenols inhibited UVB-induced PI3K activation. Furthermore, UVB-induced activation of Akt and ribosomal p70 S6 kinase (p70 S6-K), PI3K downstream effectors, were also attenuated by the polyphenols. In addition to LY294002, a PI3K inhibitor, pretreatment with a specific mitogen-activated protein/extracellular signal-regulated protein kinases (Erks) kinase 1 inhibitor, U0126, or a specific p38 kinase inhibitor, SB202190, blocked UVB-induced activation of both Akt and p70 S6-K. Pretreatment with LY294002 restrained UVB-induced phosphorylation of Erks, suggesting that in UVB signaling, the Erk pathway is mediated by PI3K. Moreover, pretreatment with rapamycin, an inhibitor of p70 S6-K, inhibited UVB-induced activation of p70 S6-K, but UVB-induced activation of Akt did not change. Interestingly, UVB-induced p70 S6-K activation was directly blocked by the addition of (-)-epigallocatechin-3-gallate or theaflavins, whereas these polyphenols showed only a weak inhibition on UVB-induced Akt activation. Because PI3K is an important factor in carcinogenesis, the inhibitory effect of these polyphenols on activation of PI3K and its downstream effects may further explain the anti-tumor promotion action of these tea constituents.

Animals↗
PubMed2001

The involvement of glutamate in recall of the conditioned NK cell response.

The molecular mechanisms responsible for the conditioned enhancement of natural killer (NK) cell activity were investigated. The primary goal of the study was to examine the roles of glutamate and gamma-aminobutyric acid (GABA) in recall of the conditioned NK cell response. Both neurochemical blocking assay and high performance liquid chromatography (HPLC) technique were used in the study. Results from the neurochemical blocking assay demonstrated that glutamate but not GABA was required in recall of the conditioned NK cell response. NMDA but not the kainate/AMPA receptors, are believed to be involved. The levels of glutamate that were released and/or taken up also appeared to be critical in that interruption of glutamate release and/or uptake blocked the conditioned NK cell response. Results from the HPLC analysis, however, did not show any significant difference in the glutamate content between the conditioned and control brains.

Administration, Inhalation↗
PubMed2001

Mechanisms of inhibition of the Ras-MAP kinase signaling pathway in 30.7b Ras 12 cells by tea polyphenols (-)-epigallocatechin-3-gallate and theaflavin-3,3'-digallate.

Our previous study showed that tea polyphenols inhibited MAP kinase and AP-1 activities in mouse epidermal JB6 cells and the corresponding H-ras-transformed cell line 30.7b Ras 12. The present study investigated the mechanisms of this inhibition. The cells were incubated with (-)-epigallocatechin-3-gallate (EGCG) or theaflavin-3,3'-digallate (TFdiG) (20 mM) for different times, and the cell lysate was analyzed by immunoblotting. EGCG treatment decreased the levels of phospho-Erk1/2 and -MEK1/2 time-dependently (by 60% at 60 min). TFdiG lowered their levels by 38%-50% at 15 min. TFdiG effectively decreased total Raf-1 protein levels, most likely through lysosomal degradation. EGCG did not affect protein levels or the activity of Raf-1 significantly but decreased its association with MEK1 as determined by co-immunoprecipitation. In addition, EGCG and TFdiG (10 mM) inhibited the phosphorylation of Elk-1 by isolated phospho-Erk1/2 in vitro. This inhibition of Erk1/2 activity is Elk-1 concentration-dependent and ATP concentration-independent, which suggests that EGCG and TFdiG interfere with the binding of the protein substrate to the kinase. The presently demonstrated specific mechanisms of inhibition of MAP kinases by EGCG and TFdiG may help us to understand the effects of tea consumption on cancer, inflammatory diseases, and cardiovascular diseases.

Adenosine Triphosphate↗
PubMed2001

Inhibitory effects of orally administered green tea, black tea, and caffeine on skin carcinogenesis in mice previously treated with ultraviolet B light (high-risk mice): relationship to decreased tissue fat.

Treatment of SKH-1 hairless mice with ultraviolet B light (UVB; 30 mJ/cm(2)) twice a week for 22 weeks resulted in tumor-free animals with a high risk of developing malignant and nonmalignant skin tumors during the next several months in the absence of additional UVB treatment (high-risk mice). Oral administration of green tea or black tea (6 mg tea solids/ml) to UVB-pretreated high-risk SKH-1 mice for 23 weeks after stopping UVB treatment decreased the number of tumors/mouse, decreased the size of the parametrial fat pads, and decreased the thickness of the dermal fat layer away from tumors and directly under tumors. Administration of the decaffeinated teas had little or no effect on these parameters, and adding caffeine (equivalent to the amount in the regular teas) to the decaffeinated teas restored their inhibitory effects. Administration of caffeine alone also decreased the number of tumors/mouse, the size of the parametrial fat pads, and the thickness of the dermal fat layer away from tumors and under tumors. Using data from individual mice and linear regression and correlation analysis, we found a highly significant positive correlation between the thickness of the dermal fat layer away from tumors and the number of tumors/mouse (r = 0.34; P = 0.0001), but the correlation between average tumor size/mouse and the thickness of the dermal fat layer away from tumors was weak (r = 0.16; P = 0.034). The results suggested that p.o. administered tea or caffeine may have decreased tumor multiplicity in part by decreasing fat levels in the dermis. Additional analysis revealed that oral administration of caffeinated beverages (green tea, black tea, decaffeinated green tea plus caffeine, decaffeinated black tea plus caffeine, or caffeine alone) decreased the thickness of the dermal fat layer under large tumors to a much greater extent than under small tumors. This is the first demonstration of a close association between inhibition of carcinogenesis and the lowering of tissue fat levels by a chemopreventive agent.

Adipose Tissue↗
PubMed2001

On-line, continuous and automatic monitoring of extracellular malondialdehyde concentration in anesthetized rat brain cortex.

An assay for in vivo, continuous and automatic monitoring of extracellular malondialdehyde concentrations in anesthetized rat brain cortex was developed. This method involved the use of microdialysis perfusion, on-line derivatization and on-line high-performance liquid chromatographic analysis. Microdialysate from an implanted microdialysis probe was on-line reacted with thiobarbituric acid at 80 degrees C for 10 min prior to on-line collection and automatic injection into a HPLC system equipped with a fluorescence detector. This method gave a linear response between the concentrations of the malondialdehyde in the microdialysates and the TEP solution where the microdialysis probe was placed. This method was used to observe the increased extracellular malondialdehyde production following elevated extracellular glutamate levels, which were achieved by perfusion of L-trans-pyrrolidine-2,4-dicarboxylate, a competitive inhibitor of glutamate uptake transporter.

Animals↗
PubMed2001

Use of bacterially expressed EBNA-1 protein cloned from a nasopharyngeal carcinoma (NPC) biopsy as a screening test for NPC patients.

EBV serological tests have been used for many years as accessory diagnostic predictors of nasopharyngeal carcinoma (NPC). To increase the sensitivity and specificity of the NPC detection rate, a novel enzyme-linked immunosorbent assay (ELISA) was established using a bacterially-expressed GST-EBNA-1 protein, containing the EBNA-1 sequence cloned from an NPC patient. Serum samples were collected from age- and gender-matched patients with NPC, community control subjects and hospital control patients and tested using this ELISA. The positivity rates were 78.7% (247/314) in NPC, 11.5% (28/244) in hospital controls and 3.8% (10/263) in the community control group. These serum samples were also tested for IgA anti-VCA antibodies and their ability to neutralize EBV DNase and the sensitivities of the anti-VCA antibody and DNase-neutralization tests also were analyzed. The optimum combination is VCA plus EBNA-1, which can identify 92.5% (287/310) of NPC patients, and shows a specificity of 92.7% (242/261) for normal individuals.

Antibodies, Viral↗