Biomedical subjects

S Yang

Publications and source records attributed to S Yang.

At least 163 records · Page 9Linked to original sources

PubMed2001

[Studies on the anti-tumorpromotion activities of dehydroepiandrosterone and its mechanism of action].

AIM: To investigate the anti-tumorpromoting activity of dehydroepiandrosterone (DHEA) and its mechanism of action. METHODS: Using croton oil-induced ear edema model and applying confocal laser scanning microscopy, flow cytometry, immuno-fluorescent techniques to investigate the inhibitory effect of DHEA on tumor promotion. RESULTS: DHEA 25 mg.kg-1 was shown to inhibit croton oil induced ear edema in mice by 51%. DHEA at dose of 40 mg.kg-1 and 10 mg.kg-1 exhibited inhibitory effects on croton oil-induced ornithine decarboxylase (ODC) activity by 64% and 53%, respectively. These results revealed that DHEA can block the change of cell cycle and the percentage of S phase was decreased to 17% at concentration of 10(-7) mol.L-1. The increase of[Ca2+]i and pH as well as PKC-activation induced by TPA stimulation were significantly inhibited by DHEA pretreatment. CONCLUSION: The present experiments demonstrate that DHEA appears to be an attractive candidate as an anti-tumorpromotion agent for tumor chemoprevention. The mechanism of its action might be related to its inhibitory effects on ODC activity and Ca(2+)-DG-PKC signal pathway.

Animals↗

PubMed2001

[Polycystic ovaraian syndrome and hyperinsulinemia].

OBJECTIVE: To identify the relationship between polycystic ovarian syndrome and hyperinsulinemia. METHODS: Age, body height, body weight, serum estradiol, progesterone, testosterone, follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), triiodothyronine (T3), tetraiodothyronine (T4), insulin, oral glucose tolerance test (OGTT), and cortisol were measured in 28 patients with polycystic ovarian syndrome (PCOS). RESULTS: Sxiteen patients (57.1% of total) had hyperinsulinemia. Among them one patient was found diabetic. No difference was noted in age, height, body weight, body mass index, serum estradiol, progesterone, testosterone, FSH, LH, PRL, T3, T4, cortisol, and glucose of OGTT between hyperinsulinemia and non-hyperinsulinemia patients. However the LH/FSH ratio (2.4 +/- 1.5) in hyperinsulinemia patients was significantly higher than 1.2 +/- 0.6 in non-hyperinsulinemia patients (P = 0.0125). In addition, the results showed that the fasting serum insulin, insulin after OGTT, the insulin/glucose ratio at 30, 120 minutes, 180 minutes, the area under curve of and the insulin, insulin resistant index (IRI) were higher in hyperinsulinemia pateints than in non-hyperinsulinemia patients respectively. Furthermore, the fasting insulin level, insulin/glucose ratio were found to be negatively related to insulin sensitivity index and positively related with beta-cell functioning index. CONCLUSION: Hyperinsulinemia and insulin resistance accompany with some of the PCOS patients in China. Further investigations will be necessary to clarify the relevant mechanisms.

Adult↗

PubMed2001

[Effect on proliferation and apoptosis of human lingual carcinoma cells cotransfected by bax and p53 genes].

OBJECTIVE: To investigate the effects on proliferation and apoptosis of human cancerous cells cotransfected by bax apoptosis-inducing gene and p53 tumor suppressor gene. METHODS: The chimeric gene pSV-CIP-bax-CAT was constructed in which bax gene was flanked upstream by a 217 bp fragment(+822(-)+1093) of the first intron and a 317 bp promoter fragment of human a 1(I) collagen gene. Human lingual carcinoma cell line Tca 8113 (LCC) in culture was respectively transfected with pSV-CIP-bax-CAT, and cotransfected with pSV-p53-CAT and pSV-CIP-bax-CAT by using the transfection reagent DOSPER. RESULTS: Immuno-slot blot and ELISA demonstrated that the expression of bax and p53 genes increased remarkably in the transfected and cotransfected LCC, compared with the controls (LCC transfected with pSV-CIP-CAT and LCC). MTT colorimetric assay, TUNEL fluorenscence microscopy and flow cytometry showed that foreign bax or p53 gene inhibited the LCC growth and induced apoptosis (23.9% and 26.1% of inhibitory rate by bax gene and p53 plus bax genes respectively). CONCLUSION: The ectopic expression of the bax gene in the LCC promoted by the cis-acting elements of human a1 (I)collagen gene has obviously synergistic effect on the proliferation and apoptosis of the LCC contransfected with p53 gene plus bax gene for 48 hours.

Apoptosis↗

PubMed2001

[Evaluation of sensorineural hearing loss in childhood].

OBJECTIVE: To explore the clinical and audiological characteristics of sensorineural hearing loss (SHL) with pathological changes both in cochlea and retrocochlear in children and evaluate the relationship between SHL and the lesions in the central nervous system (CNS). METHODS: Three hundred and ten cases (500 ears) of SHL accepted between 1998 and 2000 were studied. The age of patients was ranged from 1 month to 6 years old. According to the evaluation of function of CNS by pediatric neurologist, all cases were divided into two groups: SHL with CNS disease and SHL without CNS disease. Some same age children without hearing loss were subjected as control group. All children were tested using both auditory brainstem responses (ABR) and distortion product otoacoustic emissions (DPOAE). RESULTS: 1. The rate of SHL accompanied with CNS diseases was very high in these children. 2. Patients with kernicterus-cerebral palsy usually had serious hearing loss caused by acoustic nerve lesion at retrocochlear, but their cochlea function was injured slightly. Patients with external hydrocephalus had only slight acoustic nerve lesion at retrocochlear, and patients with other CNS diseases usually had no change for their cochlea function. 3. In the group of SHL caused by cochlea lesion, amplitudes of DPOAE decreased obviously when the threshold of wave V of ABR was up to 60 dB nHL, and amplitudes of DPOAE seriously decreased or disappeared when the threshold of wave V was up to above 70 dB nHL. CONCLUSION: The patients with SHL are usually accompanied with CNS diseases in childhood, and their hearing loss appears very difference from audiological characteristics. We suggest that it is necessary to test both ABR and DPOAE in these patients, and it is important that pediatric neurologist join in audiologist team for our clinical study.

Brain Edema↗

PubMed2001

[Neuronavigation-assisted resection of gliomas near eloquent regions].

OBJECTIVE: To evaluate the effect of the neuronavigation system in operation of gliomas near eloquent regions. METHOD: The brain LAB VV2 navigation system was used in 11 patients with gliomas near eloquent regions. The value of this system for glioma resection was assessed, and the accuracy and notice for application were discussed. RESULTS: The mean registration error was (1.5 +/- 0.7) mm in the patients. Total lesion removal was achieved in 9 patients (81.8%). The clinical status of all patients improved, and their functions of motor were not significantly affected. No complications were attributed to the use of this system. CONCLUSION: The neuronavigation system is reliable and accurate in surgical treatment of gliomas near eloquent regions. It increases the fraction of radical in glioma resection without injury to the critical functions.

Adolescent↗

PubMed2000

Failure of Ah receptor to mediate induction of cytochromes P450 in the CYP1 family in the human hepatoma line SK-Hep-1.

The Ah receptor mediates the induction of cytochrome P450 1A1 (CYP1A1) and toxicities of 2,3,7,8tetrachlorodibanzo-p-dioxin (TCDD). It has been detected in tissues of many species and in murine and human hepatoma lines. We show that the human hepatoma line SK-Hep-1 has cytosolic Ah receptor detectable by specific binding of [3H]TCDD. Concentrations of Ah receptor were low (mean = 43 +/- 3 fmol/mg cytosol protein compared to 430 fmol/mg protein in Hepa-1); the estimated number of receptor sites per cell is approximately 9,000, compared to 35,000 in Hepa-1. Ah receptor in SK-Hep-1 cells was physicochemically similar to Ah receptor in C57BL/6 mouse liver and in other human hepatoma lines studied to date except that binding affinity for TCDD, the most avidly bound ligand, was lower (estimated Kd was 14 nM by Woolf plot analysis). Translocation of the Ah receptor-ligand complex to the nucleus was shown; binding of the activated Ah receptor-ligand complex to an XRE in the 5'-upstream region of the CYP1A1 gene was demonstrated by gel-shift analysis. However, after SK-Hep-1 cells were incubated with typical PAHs including 3-methylcholanthrene, benzanthracene, and dibenz(a,h)anthracene, each over a wide range of concentrations, no induction of aryl hydrocarbon hydroxylase activity was detectable. On Northern analysis, no message for human CYP1A1 was detected in mRNA prepared from noninduced SK-Hep-1 cells or from cells treated for 24 h with 13 microM dibenz(a,h)anthracene. Further analysis by RT-PCR did not detect the induction of CYP1A1, CYP1A2, or CYP1B1 message in response to 10(-7) M TCDD, 10(-5) M benzanthracene, or 10(-5) M 3-methylcholanthrene. Transient transfection of reporter constructs containing either a minimal promoter or the CYP1A1 promoter fused to a reporter gene (luciferase) did not show any expression in response to increasing concentrations of TCDD up to 10(-8) M. Estimation of the size of the transcripts for AhR and ARNT protein revealed normal sizes, 2.7 and 2.4 kb, respectively. Together, these data suggest that SK-Hep-1 cells express an Ah receptor defective at the level of trans-activation of gene expression. SK-Hep-1 is the first human hepatoma line described with a demonstrable defect in CYP1A1 or its regulation.

Aryl Hydrocarbon Hydroxylases↗

PubMed2000

A new superoxide-generating oxidase in murine osteoclasts.

Superoxide production contributes to osteoclastic bone resorption. Evidence strongly indicates that NADPH oxidase is an enzyme system responsible for superoxide generation in osteoclasts. A membrane-bound subunit, p91, is the catalytic domain of NADPH oxidase. However, osteoclasts from p91 knockout mice still produce superoxide at a rate similar to that observed in wild type mice. This unexpected phenomenon prompted us to examine the osteoclasts for an alternative to the p91-containing oxidase. In this study, the cloning of a NADPH oxidase subunit (Nox 4) with 578 amino acids is reported. Nox 4 has 58% similarity in amino acids with the known p91 subunit of NADPH oxidase. Nox 4 is present and active in osteoclasts. Antisense oligonucleotides of Nox 4 reduced osteoclastic superoxide generation as well as resorption pit formation by osteoclasts. This new oxidase complex was present and functional in osteoclasts from p91 knockout mice, explaining the normal resorptive activity seen in the osteoclasts where no p91 is present.

Amino Acid Sequence↗

PubMed2000

The multimerization of human immunodeficiency virus type I Vif protein: a requirement for Vif function in the viral life cycle.

The Vif (virion infectivity factor protein of human immunodeficiency virus type I (HIV-1) is essential for viral replication in vivo and productive infection of peripheral blood mononuclear cells, macrophages, and H9 T-cells. However, the molecular mechanism(s) of Vif remains unknown and needs to be further determined. In this report, we show that, like many other proteins encoded by HIV-1, Vif proteins possess a strong tendency toward self-association. In relatively native conditions, Vif proteins formed multimers in vitro, including dimers, trimers, or tetramers. Through in vivo binding assays such as coimmunoprecipitation and the mammalian two-hybrid system, we also demonstrated that Vif proteins could interact with each other within a cell, indicating that the multimerization of Vif proteins is not simply due to fortuitous aggregation. Further studies indicated that the domain affecting Vif self-association is located at the C terminus of this protein, especially the proline-enriched 151-164 region. Moreover, we found that a Vif mutant with deletion at amino acid 151-164 was unable to rescue the infectivity of vif-defective viruses generated from H9 T-cells, suggesting that the multimerization of Vif proteins could be important for Vif function in the viral life cycle. Our studies identified a new feature of Vif and should accelerate our understanding of its role in HIV-1 pathogenesis.

Animals↗

PubMed2000

Melioidosis research in China.

Research on melioidosis and its pathogen has been ongoing in China for more than two decades. It has been demonstrated that the natural foci are located predominantly in Hainan, Guangdong and Guangxi province, where there is a good correlation between soil isolation and the serum prevalence of antibodies to Burkholderia pseudomallei. The cases of melioidosis reported up to now are concentrated in the Hainan and Zhanjiang peninsula. Investigations on serotype, virulence, ecology, antibiotic susceptibility, whole cell analysis by gas chromatography, and genetics have led to a new understanding of the pathology of the disease. Immunological cross reactions between Burkholderia mallei and B. pseudomallei and the difference between melioidosis and glanders in horses is discussed.

Animals↗

PubMed2000

Sulfonation of poly(N-vinylcarbazole) studied by combined time-of-flight secondary ion mass spectrometry and X-ray photoelectron spectroscopy

A series of sulfonated poly(N-vinylcarbazole) (PVK) samples have been systematically studied by time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy (XPS). Negative TOF-SIMS results provided unambiguous evidence that sulfonate groups are chemically attached to the carbazole moiety of PVK. The positive SIMS spectrum of PVK was, however, little affected by the sulfonation reaction. The degree of sulfonation was quantitatively determined by XPS. Therefore, the combination of TOF-SIMS and XPS is useful to follow the sulfonation reaction, both qualitatively and quantitatively. The SIMS intensities of some characteristic fragments are linearly related to the degree of sulfonation, suggesting that quantitative analysis is possible from TOF-SIMS data.

Journal Article↗

PubMed2000

Hypomethylation and overexpression of c-jun and c-myc protooncogenes and increased DNA methyltransferase activity in dichloroacetic and trichloroacetic acid-promoted mouse liver tumors.

Dichloroacetic acid (DCA) and trichloroacetic acid (TCA) are mouse liver carcinogens. Methylation of the c-jun and c-myc genes, expression of both genes and DNA methyltransferase (DNA MTase) activity were determined in liver tumors initiated by N-methyl-N-nitrosourea and promoted by DCA and TCA in female B6C3F1 mice. Hypomethylated and over-expression of c-jun and c-myc genes were found in DCA- and TCA-promoted liver tumors. DNA MTase activity was increased in tumors while decreased in non-involved liver. Thus, DCA- and TCA-promoted carcinogenesis appears to include decreased methylation and increased expression of c-jun and c-myc genes in the presence of increased DNA MTase activity.

Alkylating Agents↗

PubMed2000

Application of liquid chromatography-nuclear magnetic resonance spectroscopy to the identification of natural products.

LC-NMR combines the separation power of high-performance liquid chromatography (HPLC) with the superior structural information content of nuclear magnetic resonance (NMR). These two techniques traditionally have been the primary tools used by natural products chemists to isolate and determine the structures of molecules of interest. Recent advances in NMR technology have allowed the practical application of LC-NMR, thus providing natural products chemists with a hyphenated technique which combines the two most important tools in their field. A brief review of the literature describing how LC-NMR has been applied to natural products research is followed by a specific example illustrating how this technique was used to identify the marine alkaloid aaptamine (1). Aaptamine was identified as the active component in the crude dichloromethane extract of the sponge Aaptos sp. which had been determined to possess inhibitory activity against the enzyme glutamine:fructose-6-phosphate amidotransferase (GFAT) by a high throughput screening (HTS) effort. Isolated aaptamine (1) exhibited an IC50 = 120 microM against this enzyme. The experience gained from the identification of aaptamine was used to define a strategy for the use of LC-NMR in a natural products HTS program.

Animals↗

PubMed2000

Multiple-site optical recording of mouse brainstem evoked by vestibulocochlear nerve stimulation.

We used optical imaging to investigate the mouse cochlear and vestibular nucleus in brainstem slices using a voltage-sensitive dye, RH 155. As a result, the spatiotemporal patterns of excitatory propagation were shown. These optical signals consisted of two components consisting of a spike-like fast signal and a long-lasting slow signal. All responses were abolished by tetrodotoxin. The slow signals were eliminated under a Ca(2+)-free solution. In addition, synaptic fatigue was also observed. The present study indicated the feasibility of optical recording for visually revealing the synaptic transmission in both the vestibular and cochlear nucleus.

Animals↗

PubMed2000

HLA-A2.1/K(b) transgenic murine dendritic cells transduced with an adenovirus encoding human gp100 process the same A2.1-restricted peptide epitopes as human antigen-presenting cells and elicit A2.1-restricted peptide-specific CTL.

HLA-A2.1/K(b) transgenic mice (A2.1/K(b) mice) were used to investigate the processing of human gp100 melanoma antigen by murine antigen presenting cells (APC). Bone marrow-derived dendritic cells (DC) from A2.1/K(b) mice were transduced with adenovirus encoding human gp100 (Ad2/hugp100v2). The Ad2/hugp100v2-transduced DC express human gp100, as documented by immunoperoxidase staining. Flow cytometric analysis demonstrates that Ad vector transduction does not downregulate expression of several markers, including MHC class I. We show that Ad2/hugp100v2-transduced DC are recognized by peptide-specific, A2.1-restricted CTL, suggesting correct processing and presentation of the hugp100 antigen by murine DC. To assess dominance among the various A2.1-restricted epitopes encoded by hugp100, A2.1/K(b) transgenic mice were immunized with Ad2/hugp100v2-transduced DC. Resulting effector cytotoxic T lymphocytes (CTL) were assayed for peptide specificity using a panel of six synthetic peptides known to encode A2.1-restricted epitopes of human gp100 (denoted G154, G177, G209, G280, G457, G476). CTL obtained from Ad2/hugp100v2-transduced DC immunized A2.1/K(b) mouse lysed target cells presenting five of the six epitopes, supporting the observation that murine cells correctly process the hugp100 antigen. The immunogenicity of individual gp100 epitopes correlates with their binding affinity to A2.1. CTL generated from A2.1/K(b) mice immunized with Ad2/hugp100v2-transduced DC also specifically recognize A2.1(+)/gp100(+) human melanoma cells. These data suggest that murine APC process and present the same set of HLA-restricted peptides, similar to human APC. HLA transgenic mice serve as a useful model system to study class I-restricted epitopes of human tumor-associated antigens.

Adenoviridae↗

PubMed2000

Thermal stable and oxidation-resistant variant of subtilisin E.

A remarkable thermal stable and oxidation-resistant mutant was obtained using the random mutagenesis PCR technique on the mutant M222A gene of subtilisin E. Sequencing analysis revealed an A was replaced by G at nucleotide 671 of the subtilisin E gene, converting the asparagine codon (AAT) to serine codon (AGT) at position 118. The half-life of M222A/N118S enzyme activity, when heated at 65 degrees C, was approximately 80 min while the half-life of M222A and wild-type subtilisin E were 13 min and 15 min, respectively. This suggested the stability of the M222A/N118S mutant was five times greater than that of the wild-type enzyme. The mutant was also as oxidation resistant as the mutant M222A of subtilisin E. These results indicated the M222A/N118S mutant is both an oxidation-resistant and a heat-stable variant of subtilisin E.

Amidohydrolases↗

PubMed2000

Genetic diversity and disease control in rice.

Crop heterogeneity is a possible solution to the vulnerability of monocultured crops to disease. Both theory and observation indicate that genetic heterogeneity provides greater disease suppression when used over large areas, though experimental data are lacking. Here we report a unique cooperation among farmers, researchers and extension personnel in Yunnan Province, China--genetically diversified rice crops were planted in all the rice fields in five townships in 1998 and ten townships in 1999. Control plots of monocultured crops allowed us to calculate the effect of diversity on the severity of rice blast, the major disease of rice. Disease-susceptible rice varieties planted in mixtures with resistant varieties had 89% greater yield and blast was 94% less severe than when they were grown in monoculture. The experiment was so successful that fungicidal sprays were no longer applied by the end of the two-year programme. Our results support the view that intraspecific crop diversification provides an ecological approach to disease control that can be highly effective over a large area and contribute to the sustainability of crop production.

Agriculture↗

PubMed2000

Mitochondrial adaptations to obesity-related oxidant stress.

It is not known why viable hepatocytes in fatty livers are vulnerable to necrosis, but associated mitochondrial alterations suggest that reactive oxygen species (ROS) production may be increased. Although the mechanisms for ROS-mediated lethality are not well understood, increased mitochondrial ROS generation often precedes cell death, and hence, might promote hepatocyte necrosis. The aim of this study is to determine if liver mitochondria from obese mice with fatty hepatocytes actually produce increased ROS. Secondary objectives are to identify potential mechanisms for ROS increases and to evaluate whether ROS increase uncoupling protein (UCP)-2, a mitochondrial protein that promotes ATP depletion and necrosis. Compared to mitochondria from normal livers, fatty liver mitochondria have a 50% reduction in cytochrome c content and produce superoxide anion at a greater rate. They also contain 25% more GSH and demonstrate 70% greater manganese superoxide dismutase activity and a 35% reduction in glutathione peroxidase activity. Mitochondrial generation of H(2)O(2) is increased by 200% and the activities of enzymes that detoxify H(2)O(2) in other cellular compartments are abnormal. Cytosolic glutathione peroxidase and catalase activities are 42 and 153% of control values, respectively. These changes in the production and detoxification of mitochondrial ROS are associated with a 300% increase in the mitochondrial content of UCP-2, although the content of beta-1 ATP synthase, a constitutive mitochondrial membrane protein, is unaffected. Supporting the possibility that mitochondrial ROS induce UCP-2 in fatty hepatocytes, a mitochondrial redox cycling agent that increases mitochondrial ROS production upregulates UCP-2 mRNAs in primary cultures of normal rat hepatocytes by 300%. Thus, ROS production is increased in fatty liver mitochondria. This may result from chronic apoptotic stress and provoke adaptations, including increases in UCP-2, that potentiate necrosis.

Animals↗

PubMed2000

Cyclic nucleotides suppress tumor necrosis factor alpha-mediated apoptosis by inhibiting caspase activation and cytochrome c release in primary hepatocytes via a mechanism independent of Akt activation.

Cyclic nucleotides have been previously shown to modulate cell death processes in many cell types; however, the mechanisms by which cyclic nucleotides regulate apoptosis are unclear. In this study, we demonstrated that cAMP as well as cGMP analogs suppressed tumor necrosis factor alpha (TNFalpha) plus actinomycin D (ActD)-induced apoptosis in a dose-dependent manner in cultured primary hepatocytes. Furthermore, forskolin, which increases intracellular cAMP levels, also effectively suppressed TNFalpha+ActD-induced apoptosis. Activation of multiple caspases was suppressed in cells exposed to TNFalpha+ActD in the presence of cAMP or cGMP analogs. TNFalpha+ActD-induced cytochrome c release from mitochondria was also inhibited by cAMP or cGMP, reinforcing our conclusion that cyclic nucleotides interfere with the early signaling events of TNFalpha-mediated apoptosis. We evaluated the possibility that cAMP and cGMP inhibit apoptosis by activating the serine/threonine kinase Akt, which is known to promote cell survival. Both cAMP- and cGMP-elevating agents led to marked increases in Akt activation that was inhibited by the phosphatidylinositol 3'-kinase inhibitors, LY294002 and wortmannin. However, complete inhibition of cyclic nucleotide-induced Akt activation had little effect on cyclic nucleotide-mediated cell survival, indicating the existence of other survival pathways. Interestingly, the specific inhibitor of protein kinase A (PKA), KT5720, blocked cGMP-mediated protection but only partially prevented the anti-apoptotic effect of cAMP, indicating that both PKA-dependent and -independent mechanisms are involved in cAMP-mediated suppression of apoptosis signaling. Our data suggest that multiple survival signaling pathways coexist in cells and that cyclic nucleotides delay apoptosis by interfering with apoptosis signaling by both PKA-dependent and -independent mechanisms.

Amino Acid Chloromethyl Ketones↗