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Biomedical subjects

M Huang

Publications and source records attributed to M Huang.

At least 127 records · Page 7Linked to original sources
PubMed2000

[Preliminary screen of anti-endotoxin activity of Chinese materia medica].

OBJECTIVE: To screen Chinese materia medica against E. coli. O111B4 endotoxin. METHOD: 70% alcohol extracts from 134 kinds of heat-clearing Chinese materia medica were demonstrated by using limulus test in vitro. The extracts which had anti-endotoxin effects were diluted to demonstrate their minimal anti-endotoxin concertnations. RESULTS: 75 kinds of Chinese materia medica possessed anti-endotoxin activity in various degrees in vitro. CONCLUSION: Most of heat-clearing Chinese materia medica possess anti-endotoxin effects in vitro.

Agglutination↗
PubMed2000

[A new generation of pulmonary function measuring system].

A system for measuring the pulmonary function was reported. The System consists of Fleisch flow transducer, a pressure transducer an amplifier, A/D converter, and a 486 computer. It can measure the indices of respiratory function under tidal breathing, the indices of tidal breathing flow volume loop and the dynamic indices of passive respiration.

Humans↗
PubMed2000

[Identification of high-lying odd energy levels of uranium by resonant ionization mass spectrometry].

Single-colour and two-colour multiphoton resonant ionization spectra of uranium atom were studied extensively with a Nd:YAG laser-pumped dye laser atomic beam apparatus time-of-flight mass spectrometer in our laboratory. The energy locations of high-lying odd-parity levels in the region 33,003-34,264 cm-1, measured by a two-colour three-step ionization technique, were reported here. The angular momentum quantum number J was uniquely assigned for these levels by using angular momentum selection rules.

Lasers↗
PubMed1999

Determination of norgestimate and its metabolites in human serum using high-performance liquid chromatography with tandem mass spectrometric detection.

A rapid and reliable analytical method is described for the simultaneous determination of a synthetic progestin norgestimate (NGM), and its metabolites, 17-deacetylnorgestimate (17-DA-NGM), 3-ketonorgestimate (3-keto-NGM) and norgestrel (NGL) in human serum using reversed phase high-performance liquid chromatography (HPLC) with tandem mass spectrometric (MS-MS) detection. The assay was linear over the concentration ranges of 0.1-5.0 ng/ml for 17-DA-NGM and NGL and 0.5-5.0 ng/ml for NGM and 3-keto-NGM. The inter-assay reproducibility was consistently less than 10%. The overall recovery of the analytes ranged from 72 to 92%. Serum profiles following oral administration of norgestimate to female volunteers are presented.

Chromatography, High Pressure Liquid↗
PubMed1999

Roles for glycosylation of cell surface receptors involved in cellular immune recognition.

The majority of cell surface receptors involved in antigen recognition by T cells and in the orchestration of the subsequent cell signalling events are glycoproteins. The length of a typical N-linked sugar is comparable with that of an immunoglobulin domain (30 A). Thus, by virtue of their size alone, oligosaccharides may be expected to play a significant role in the functions and properties of the cell surface proteins to which they are attached. A databank of oligosaccharide structures has been constructed from NMR and crystallographic data to aid in the interpretation of crystal structures of glycoproteins. As unambiguous electron density can usually only be assigned to the glycan cores, the remainder of the sugar is then modelled into the crystal lattice by superimposing the appropriate oligosaccharide from the database. This approach provides insights into the roles that glycosylation might play in cell surface receptors, by providing models that delineate potential close packing interactions on the cell surface. It has been proposed that the specific recognition of antigen by T cells results in the formation of an immunological synapse between the T cell and the antigen-presenting cell. The cell adhesion glycoproteins, such as CD2 and CD48, help to form a cell junction, providing a molecular spacer between opposing cells. The oligosaccharides located on the membrane proximal domains of CD2 and CD48 provide a scaffold to orient the binding faces, which leads to increased affinity. In the next step, recruitment of the peptide major histocompatibility complex (pMHC) by the T-cell receptors (TCRs) requires mobility on the membrane surface. The TCR sugars are located such that they could prevent non-specific aggregation. Importantly, the sugars limit the possible geometry and spacing of TCR/MHC clusters which precede cell signalling. We postulate that, in the final stage, the sugars could play a general role in controlling the assembly and stabilisation of the complexes in the synapse and in protecting them from proteolysis during prolonged T-cell engagement.

Animals↗
PubMed1999

Cdc42-induced actin filaments are protected from capping protein.

Each actin filament has a pointed and a barbed end, however, filament elongation occurs primarily at the barbed end. Capping proteins, by binding to the barbed end, can terminate this elongation. The rate of capping depends on the concentration of capping protein [1], and thus, if capping terminates elongation, the length of filaments should vary inversely with the concentration of capping protein. In cell extracts, such as those derived from neutrophils, new actin filaments can be nucleated by addition of GTPgammaS-activated Cdc42 (a small GTPase of the Rho family). To determine whether elongation of these filaments is terminated by capping, we manipulated the concentration of capping protein, the major calcium-independent capping protein in neutrophils, and observed the effects on filament lengths. Depletion of 70% of the capping protein from extracts increased the mean length of filaments elongated from spectrin-actin seeds (very short actin filaments with free barbed ends) but did not increase the mean length of filaments induced by Cdc42. Furthermore, doubling the concentration of capping protein in cell extracts by adding pure capping protein did not decrease the mean length of filaments induced by Cdc42. These results suggest that the barbed ends of Cdc42-induced filaments are protected from capping by capping protein.

Actin Cytoskeleton↗
PubMed1999

[HLA-DQA1 genes involved in the genetic susceptibility to duodenal ulcer in Wuhan Hans]

OBJECTIVE: To study the genetic susceptibility of HLA-DQA1 alleles to duodenal ulcer in Chinese Hans from Wuhan and its nearby regions. METHODS: Seventy patients with duodenal ulcer and fifty healthy controls were examined for HLA-DQA1 genotypes. HLA-DQA1 typing was carried out by digesting the locus specific polymerase chain reaction amplified products with alleles specific restriction enzymes (PCR-RFLP), Apal I, Basj I, Hph I, Fok I, Mbo II and Mnl I. RESULTS: The allele frequency of DQA1 0301 in patients with duodenal ulcer (64.3%) was significantly higher than that in healthy controls (36%). In contrast, the allele frequency of DQA1 0102 in patients with duodenal ulcer (8.6%) was significantly lower than that in healthy controls (26%). CONCLUSION: These findings suggest that DQA1 0301 is a susceptible gene for duodenal ulcer in Wuhan Hans while DQA1 0102 is its resistant gene, and there are immunogenetic differences in HLA-DQA1 locus between duodenal ulcer patients and healthy controls.

Journal Article↗
PubMed1999

Effects of microcystins on phosphorylase-a binding to phosphatase-2A: kinetic analysis by surface plasmon resonance biosensor.

Cyclic heptapeptide microcystins are a group of hepatoxicants which exert the cytotoxic effects by inhibiting the catalytic activities of phosphatase-2A (PP-2A) and phosphatase-1 (PP-1) and thus disrupt the normal signal transduction pathways. Microcystins interact with PP-2A and PP-1 by a two-step mechanism involving rapid binding and inactivation of protein phosphatase catalytic subunit, followed by a slower covalent interaction. It was proposed that inactivation of PP-2A/PP-1 catalytic activity by microcystins precedes covalent adduct formation. In this study, we used a biosensor based on surface plasmon resonance (SPR) to examine the effects of three microcystins, MCLR, MCRR and MCYR, on the binding between PP-2A and its substrate, phosphorylase-a (PL-a), during the first step of the interaction. The SPR biosensor provides real-time information on the association and dissociation kinetics of PL-a with immobilized PP-2A in the absence and presence of microcystins. It was found that the affinity of PL-a to microcystin-bound PP-2A was four times smaller compared to unbound PP-2A, due to 50% decreases in the association rates and two-fold increases in dissociation rates of PL-a binding to PP-2A. The results suggest that the rapid binding of microcystins to the PP-2A catalytic site leads to the formation of a noncovalent microcystin/PP-2A adduct. While the adduct formation fully inhibits the catalytic activity of PP-2A, it only results in partial inhibition of the substrate binding. The similar effects of the three microcystins on PP-2A suggest that the toxins bind to PP-2A at the same site and cause similar conformational changes. The present work also demonstrates the potential application of biosensor technology in environmental toxicological research.

Binding Sites↗
PubMed1999

Synthesis and biological properties of novel pyridinioalkanoyl thiolesters (PATE) as anti-HIV-1 agents that target the viral nucleocapsid protein zinc fingers.

Nucleocapsid p7 protein (NCp7) zinc finger domains of the human immunodeficiency virus type 1 (HIV-1) are being developed as antiviral targets due to their key roles in viral replication and their mutationally nonpermissive nature. On the basis of our experience with symmetrical disulfide benzamides (DIBAs; Rice et al. Science 1995, 270, 1194-1197), we synthesized and evaluated variants of these dimers, including sets of 4,4'- and 3,3'-disubstituted diphenyl sulfones and their monomeric benzisothiazolone derivatives (BITA). BITAs generally exhibited diminished antiviral potency when compared to their disulfide precursors. Novel, monomeric structures were created by linking haloalkanoyl groups to the benzamide ring through -NH-C(=O)- (amide) or -S-C(=O)- (thiolester) bridges. Amide-linked compounds generally lacked antiviral activity, while haloalkanoyl thiolesters and non-halogen-bearing analogues frequently exhibited acceptable antiviral potency, thus establishing thiolester benzamides per se as a new anti-HIV chemotype. Pyridinioalkanoyl thiolesters (PATEs) exhibited superior anti-HIV-1 activity with minimal cellular toxicity and appreciable water solubility. PATEs were shown to preferentially target the NCp7 Zn finger when tested against other molecular targets, thus identifying thiolester benzamides, and PATEs in particular, as novel NCp7 Zn finger inhibitors for in vivo studies.

Animals↗
PubMed1999

The study of innate drug resistance of human hepatocellular carcinoma Bel7402 cell line.

The innate drug resistance of human hepatocellular carcinoma (HCC) Bel7402 cell line was studied in vitro. MTT assay showed that Bel7402 cells were innately resistant to doxorubicin (Dox), and even more resistant to vincristine (VCR). This resistance could be effectively reversed by verapamil (Ver), one of the classical multidrug resistance (MDR) modulating agents. However, the differences in 5-fluorouracil (5-FU) toxicity between these two cell lines is much less and the resistance of Bel7402 cells could only be slightly reversed by Ver, which may be experimental noise. Immunocytochemical staining using anti-p-glycoprotein monoclonal antibody JSB-1 indicated that the expression of the P-glycoprotein (P-gp) in the innate Bel7402 cells was elevated compared with the sensitive KB cells. The accumulation of Dox in innate resistant Bel7402 cells was 50.7% lower than that in sensitive KB cells by using spectrofluometric analyses, and the accumulation of Dox increased 1.6 fold in Bel7402 cells in the presence of Ver. The susceptibility of Dox-induced apoptosis was also increased in the presence of Ver by using flow cytometric assay and DNA fragmentation quantitative assay as well as by Hoechst 33258 staining. It appears that the innate Bel7402 cells might be useful in screening new antitumour drugs or new chemosensitisers which could overcome the innate or acquired resistant mechanism, and the toxicity and reversal effects with 5-FU are different from those known to be P-gp substrates such as VCR, Dox, and taxol.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

Direct injection versus liquid-liquid extraction for plasma sample analysis by high performance liquid chromatography with tandem mass spectrometry.

Direct injection versus liquid-liquid extraction for post-dose human plasma sample analysis by high performance liquid chromatography with tandem mass spectrometry (LC/MS/MS) have been studied using a drug candidate compound. For the direct-injection method, an Oasis(R) HLB column (1 x 50 mm, 30 micrometer) was used as the on-line extraction column and a conventional Waters symmetry C18 column (3.9 x 50 mm, 5 micrometer) was used as the analytical column. Each plasma sample (100 microL) was mixed with 100 microL of a working solution of the internal standard in aqueous 0.05 M ammonium acetate (pH 6.9), and portions (10 microL) of these samples were then injected into the LC/MS/MS system. For the liquid-liquid extraction method, a YMC Basic C18 column (2.0 x 50 mm, 5 micrometer) was used as the analytical column. Each sample (0.5 mL) was extracted with methyl tert-butyl ether and the extract was reconstituted and injected into the LC/MS/MS system. The total analysis time for both methods was 2.0 min per sample. The accuracy, inter-day precision and intra-day precision obtained from the quality control samples were within 8% for both methods. The analysis results of post-dose human plasma samples showed that the deviations of 91% of the concentrations obtained using the direct-injection method were within +/-20% from the concentrations obtained using the liquid-liquid extraction method, and the overall average percentage deviation was -1.5%. The results showed that the two methods were equivalent in terms of total chromatographic run time, accuracy and precision. However, for a batch of 100 samples, the sample preparation time for the direct-injection method was only about 25% of the time required for liquid-liquid extraction. This decrease in sample preparation time resulted in the doubling of the overall sample analysis throughput.

Chromatography, High Pressure Liquid↗
PubMed1999

Panax quinquefolium saponins protects low density lipoproteins from oxidation.

Oxidized low-density lipoprotein (Ox-LDL) is believed to be involved in the pathogenesis of atherosclerosis. Panax quinquefolium saponins (PQS) are extracted from the stems and leaves of the North American form of ginseng, Panax quinquefolium. Earlier studies have suggested that this extract improves the lipid profile of hyperlipidemic rats and has antioxidant properties in cultured rat cardiac myocytes. The aims of the present study were to investigate the potential of PQS in reducing LDL oxidation as well as limiting the ability of Ox-LDL to impair endothelium-dependent relaxation in rat aortic rings. LDL was isolated from the plasma of healthy human donors by sequential ultracentrifugation. Native LDL (0.2 or 0.3 mg/ml) was incubated with PQS (0.25-1 mg/ml) for 30 min at 20 degrees C. For comparison, vitamin C (50 microM) was added in place of PQS. Oxidative modification was initiated with 5 microM CuSO4 at 37 degrees C for 0-24 h. In our hands, PQS concentration-dependently reduced lipid peroxide levels as measured by the amount of thiobarbituric acid reactive substances formed. This range of PQS also retarded the alterations in relative electrophoretic mobility of Ox-LDL in a similar manner. Furthermore, measurement of phospholipid fractions content indicated that PQS could reduce the conversion of phosphatidylcholine to lysophosphatidylcholine in Ox-LDL. Functional studies demonstrated that PQS-pretreated Ox-LDL was less potent than untreated Ox-LDL at impairing endothelium-dependent relaxation in rat aortic rings. In conclusion, our results suggest that PQS has antioxidant properties and that reduction of LDL oxidation by PQS may provide a protective effect against the detrimental actions of Ox-LDL.

Acetylcholine↗
PubMed1999

Low concentrations of 17beta-estradiol reduce oxidative modification of low-density lipoproteins in the presence of vitamin C and vitamin E.

Micromolar concentrations of estradiol are required to inhibit the oxidation of low-density lipoproteins (LDL) in vitro. Recent evidence suggests that estradiol must be modified before it can become an effective antioxidant at physiological levels. Our aim was to determine other possible conditions under which low concentrations of 17beta-estradiol can reduce LDL oxidation. LDL susceptibility to oxidation was monitored by measurements of conjugated diene formation. High levels of 17beta-estradiol reduced oxidative modification of LDL. Vitamin C and vitamin E also increased LDL resistance to Cu2+-mediated oxidation. More importantly, 10 nM 17beta-estradiol, which on its own had no effect, exhibited significant antioxidant actions in the presence of either vitamins C or E. In conclusion, supraphysiological concentrations of 17beta-estradiol are required to exert antioxidant effects directly in vitro. However, in the presence of vitamins C and E, concentrations of 17beta-estradiol close to physiological levels can also protect LDL from oxidation.

Adult↗
PubMed1999

Inhibitory effect of green and black tea on tumor growth.

The administration of green tea, black tea, or (-)-epigallocatechin gallate inhibited the growth of established nonmalignant and malignant tumors in tumor-bearing mice. In experiments with black tea, we found that its oral administration inhibited DNA synthesis and enhanced apoptosis in both nonmalignant and malignant tumors in tumor-bearing mice.

Animals↗
PubMed1999

Inhibition of Tenon's fibroblast proliferation and enhancement of filtration surgery in rabbits with cytosine arabinoside.

Our purpose was to study the antiproliferative effect of cytosine arabinoside (Ara-C) on rabbit Tenon's fibroblasts and the efficacy of Ara-C as an adjunctive antifibrosis treatment for glaucoma filtration surgery in the rabbit eye. Rabbit Tenon's fibroblasts were exposed to 1 microg/ml of Ara-C for various time intervals, then cell number and viability was assessed at different time points. Following posterior lip sclerectomy, rabbit eyes were treated with 10 mg subconjunctival Ara-C daily for 7 days, then every other day for 7 days. Rabbit fibroblasts exposed to 1 microg/ml Ara-C for 1 hour showed no significant decrease in cell number compared with control. Continuous or 24-hour incubation of fibroblasts with Ara-C was lethal to the cells. Exposure of cells to Ara-C for 3-, 6-, and 9-hour intervals caused significant reduction of cell proliferation. Pulsed treatment of cells with 6 hour exposure to 1 microg/ml Ara-C every 3 days caused prolonged suppression of cell proliferation. Following posterior lip sclerectomy in rabbits, topical instillation of Ara-C drops at varying concentrations and dosing intervals did not cause any significant lowering of intraocular pressure compared with control eyes, although bleb survival was prolonged in eyes treated with Ara-C (P < 0.01). In rabbit eyes treated postoperatively with subconjunctival injections of 10 mg Ara-C every other day for two weeks, the mean intraocular pressure was significantly decreased and the bleb survival time was significantly prolonged (P < 0.0067) compared with control eyes. In conclusion, Ara-C inhibits rabbit Tenon's fibroblast proliferation in vitro. Postoperative subconjunctival injection of Ara-C results in improved bleb function after filtration surgery in the rabbit.

Animals↗
PubMed1999

Study on genital tract Chlamydia trachomatis and gonococcal infection in Han and minority (Naxi and Dai) women in China's two provinces.

OBJECTIVES: To estimate the prevalence of lower female genital tract chlamydial (GTC) and gonococcal infection in 3 different ethnic groups in China, and to analyze the risk factors influencing these infections. METHODS: A cross-sectional survey + physical and laboratory examinations. 1,800 married women aged 18-35 Han (600, from Dujiangyan city, Sichuan), Naxi (600, from Yanyuan county, Sichuan), and Dai (600, from Jinghong Prefecture, Yunnan) were investigated between March 1996 to March 1997. Information was obtained about their personal history, socioeconomic status, medical history, STDs, sexual history, contraceptive history, results of both examinations. Tabulation, t-test, Chi-square test, multiple-logistic models were used to analyze the data. RESULTS: 3.2% of Han, 12.8% of Naxi and 4.5% of Dai women tested positive for gonococci; and 9.1% of Han, 16.7% of Naxi and 27.5% of Dai women tested positive for GTC infection. The differences of GTC and gonococcal infections between Han and Naxi, and Han and Dai women were significant. CONCLUSIONS: STDs are common in China today; both GTC and gonoccocal infections are related to non-use of condom, having sexual partners other than husband, number of abortions, and low education; and condom has a function in prevention of STDs.

Adolescent↗