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Biomedical subjects

Y M Li

Publications and source records attributed to Y M Li.

At least 37 records · Page 2Linked to original sources
PubMed2001

Erianin induces apoptosis in human leukemia HL-60 cells.

AIM: To investigate the effect of erianin on human HL-60 cell line and explore its mechanism of apoptosis in vitro. METHODS: Inhibition of proliferation was measured with colorimetric MTT assay. The morphologic changes were observed by fluorescence and electron microscopes. DNA fragmentation was visualized by agarose gel electrophoresis, and the DNA degradation was determined by flow cytometry. Immunohistochemical analysis was used to identify the expression of bcl-2 and bax genes. RESULTS: The growth of human HL-60 cells was significantly inhibited by erianin 20-81.9 nmol/L during 72 h treatment (P < 0.01). The IC50 value was 38 nmol/L after a 24-h exposure to erianin, while that of vincristine, the positive control, was 101 nmol/L. The typical morphologic changes were observed and the nuclear DNA fragmentation exhibited "ladder" pattern. The cell cycle of HL-60 cells was arrested in G2/M phase, and expression of bcl-2 gene was decreased while that of bax was increased. CONCLUSION: Erianin showed potent inhibitory activity on the proliferation of HL-60 cells. The inhibition might be relative to the apoptosis induced by erianin and the altered expression of bcl-2 and bax genes in HL-60 cells.

Antineoplastic Agents, Phytogenic↗
PubMed2001

[Diagnosis of bovine spongiform encephalopathy and scrapie by western blot].

The rabbits were immuned with bovine prion protein (BoPrPC) which was expressed in E. coli and anti-PrPC antibody (T1) was obtained. According to pathological prion protein (PrPSC) was resistant to protease treatment, extracts of brain tissue were digested with proteinase K and detected by western blot with T1 antibody. The results showed that protease-resistant pathological PrPSC was existed in golden hamster brain tissue which was inoculated with scrapie strain 263 K, but no protein existed in normal golden hamster brain homogenates which was detected with T1 antibody. Several bovines and sheep from Beijing were used for diagnosis of Bovine spongiform encephalopathy (BSE) and scrapie, their brain tissue were freshly collected and homogenated. The homogenates were separated on SDS-PAGE and detected by western blot with T1 antibody. The results indicated no protease-resistant protein(PrPSC) existed, this suggested they were not infected by BSE and scrapie. The same results were obtained with 1A8 antibody from England. These results indicated we could detect BSE and scrapie with T1 antibody.

Animals↗
PubMed2001

Prediction of bone fracture by bone mineral density in Taiwanese.

BACKGROUND AND PURPOSE: This study evaluated whether lumbar spine bone mineral density (BMDL) and the rate of change of BMDL could predict the risk of bone fracture in Taiwanese. METHODS: In 1989, a baseline survey was carried out in Lin-Kou Township. BMDL was measured using dual photon absorptiometry in 404 healthy volunteers. In 1994/95, a second survey was conducted to reexamine the BMDL and fracture history as well as the risk factors associated with fracture in these subjects. Fractures were classified according to the causes of the injury as severe or mild trauma. RESULTS: Of the 404 original examinees, 381 (79%) participated in the second survey. Twenty-six subjects had experienced a total of 32 fracture incidents during their lifetime and 10 subjects had experienced fracture during the observation period. After adjusting for the effect of body mass index, gender, and age, each standard deviation of decrease in BMDL was found to be associated with a significant 2.38-fold increase in the risk of mild trauma fracture, and a BMDL below the fracture threshold was associated with a 3.93-fold increase of fracture risk. Higher BMDL change rates were found in subjects with a history of fracture. CONCLUSION: This study indicates the importance of maintaining the BMDL above the fracture threshold (1 g/cm2). The strategy for fracture prevention should be directed at prevention of age-related bone loss.

Absorptiometry, Photon↗
PubMed2001

[Studies on chemical constituents in dried buds of Lonicera similis Hemsl].

OBJECTIVE: To study the chemical constituents in the dried buds of Lonicera similis. METHOD: Chromatography and spectral analysis were used to isolate and elucidate the constituents. RESULT: Nine compounds were isolated from the dried buds of L. similis, and identified as caffeic acid; 3,5-O-dicaffeoylquinic acid; chlorogenic acid; palmitic acid; luteolin; quercetin; beta-sitosterol; nonacosanol; nonacosane. CONCLUSION: All the compounds were isolated from the plant for the first time.

Caffeic Acids↗
PubMed2001

[Determination of thyroxine enantiomers in human plasma with normal high performance liquid chromatography-chiral complex exchange mobile phase].

An HPLC method was developed with normal HPLC-chiral complex mobile phase for the separation and determination of D- and L-thyroxine enantiomers (D- and L-T4) in human plasma. The method includes extraction of thyroxine from plasma and separation of thyroxine enantiomers on HPLC silica column with chiral eluent containing L-proline, cupric acetate and triethylamine (TEA). The sensitivity of the method was 0.1 mg/L. The precisions of inter-day and intra-day, linearity, extraction recovery, and stability of T4 enantiomers in plasma and in deproteinized plasma were determined for the validation of the method. Baseline enantioseparation of the compounds containing D- and L-T4 was achieved. Meantime we determined the concentrations of D-T4 and L-T4 in plasma of 15 volunteers with euthyroid, hypothyroid and hyperthyroid symptoms. Liquid chromatographic method based on the described procedure was useful for the determination of D- and L-thyroxine in patient plasma and for pharmacokinetics investigation.

Chromatography, High Pressure Liquid↗
PubMed2001

[Mitochondrial permeability transition pore regulates the apoptosis in MGC-803 induced by the extract of glycyrrhiza uralensis Fisch].

In our previous studies, we have discovered that the extract of glycyrrhiza uralensis Fisch (EGUF) can induce obvious apoptosis in gastric cancer cell Line MGC-803. Here, further investigation was carried on about the time-lapse changes of mitochondria transmembrane potential, intracellular free calcium ions, DNA electrophoresis, plasma membrane permeability and chromatin condensation during the apoptotic process of MGC-803 induced by EGUF and the influences of MPT-specific inhibitor Cyclosporin A(CsA) on these changes. Enhancement of plasma membrane permeability with PI staining, increase of intracellular free calcium ion and decrease of mitochondria transmembrane potential are early events in apoptotic cascades, prior to the appearances of apoptotic peak, chromatin condensation and DNA ladder. CsA significantly inhibited enhancement of plasma membrane permeability, change of intracellular free calcium ions and decrease of mitochondria transmembrane potential, also greatly delayed the progress of apoptosis. Thus, our results suggest that calcium and CsA-sensitive MPT is involved in the apoptosis of MGC-803 induced by EGUF.

Apoptosis↗
PubMed2001

[Studies on metabolites of baicalin in human urine].

OBJECTIVE: We are interested in the metabolism of baicalin in human body to offer more information to clinic. METHOD: Urine of ten persons was collected during 2-18 h after taking 1.0 g of baicalin orally, and the urine was concentrated to 0.5 L, then filtered, the solution being loaded on an iron exchange column eluted with 1.0 L of H2O and 1.0 L of 50% EtOH. The EtOH fraction was concentrated and loaded on a Sephadex LH 20 column eluted with 0.5 L of H2O to obtain 15 fractions, which were detected by silica gel TLC (CHCl3-MeOH-H2O, 1:1:0.1). The fractions 8-11 showed flavonoid characteristics by spraying FeCl3 reagent, and the four fractions were combined to obtain the sample containing metabolites of baicalin for HPLC analysis and LCMS measurement. RESULTS AND CONCLUSIONS: M1, M2 and M3 was identified as baicalein-6-O-beta-glucopyranuronoside; 6-O-methyl-baicalin-7-O-beta-glucopyranuronoside and baicalin.

Adult↗
PubMed2001

Gamma-secretase: a catalyst of Alzheimer disease and signal transduction.

Gamma-secretase is a membrane-bound protease that cleaves within the transmembrane region of the amyloid precursor protein to generate the C termini of both major peptides that constitute the amyloid plaques found in Alzheimer disease (AD). Recent biochemical studies provide compelling evidence that presenilins, membrane-spanning proteins associated with early-onset familial AD, are novel aspartyl proteased that function within a macromolecular complex to mediate gamma-secretase activity. These new insights underscore the role of the presenilins in regulated intramembrane proteolysis and could possibly lead to the inhibition of gamma-secretase activity as a therapy for AD.

Alzheimer Disease↗
PubMed2000

A short and efficient transformation of rhamnose into activated daunosamine, acosamine, ristosamine and epi-daunosamine derivatives, and synthesis of an anthracycline antibiotic acosaminyl-epsilon-iso-rhodomycinone.

3-Amino-2,3,6-trideoxyhexopyranoses are essential constituents of most anthracycline antitumour antibiotics. For an investigation of structure-activity relationships, the four diastereomeric amino sugars daunosamine, acosamine, ristosamine, and epi-daunosamine were synthesised in short and efficient routes starting from commercially available rhamnose. Several glycosyl donors were provided and their use was exemplified in the synthesis of acosaminyl-epsilon-isorhodomycinone.

Anthracyclines↗
PubMed2000

Photoactivated gamma-secretase inhibitors directed to the active site covalently label presenilin 1.

Cleavage of amyloid precursor protein (APP) by the beta- and gamma-secretases generates the amino and carboxy termini, respectively, of the A beta amyloidogenic peptides A beta40 and A beta42--the major constituents of the amyloid plaques in the brain parenchyma of Alzheimer's disease patients. There is evidence that the polytopic membrane-spanning proteins, presenilin 1 and 2 (PS1 and PS2), are important determinants of gamma-secretase activity: mutations in PS1 and PS2 that are associated with early-onset familial Alzheimer's disease increase the production of A beta42 (refs 4-6), the more amyloidogenic peptide; gamma-secretase activity is reduced in neuronal cultures derived from PS1-deficient mouse embryos; and directed mutagenesis of two conserved aspartates in transmembrane segments of PS1 inactivates the ability of gamma-secretase to catalyse processing of APP within its transmembrane domain. It is unknown, however, whether PS1 (which has little or no homology to any known aspartyl protease) is itself a transmembrane aspartyl protease or a gamma-secretase cofactor, or helps to colocalize gamma-secretase and APP. Here we report photoaffinity labelling of PS1 (and PS2) by potent gamma-secretase inhibitors that were designed to function as transition state analogue inhibitors directed to the active site of an aspartyl protease. This observation indicates that PS1 (and PS2) may contain the active site of gamma-secretase. Interestingly, the intact, single-chain form of wild-type PS1 is not labelled by an active-site-directed photoaffinity probe, suggesting that intact wild-type PS1 may be an aspartyl protease zymogen.

Alzheimer Disease↗
PubMed2000

Presenilin 1 is linked with gamma-secretase activity in the detergent solubilized state.

gamma-Secretase is a membrane-associated protease that cleaves within the transmembrane region of amyloid precursor protein to generate the C termini of the two Abeta peptide isoforms, Abeta40 and Abeta42. Here we report the detergent solubilization and partial characterization of gamma-secretase. The activity of solubilized gamma-secretase was measured with a recombinant substrate, C100Flag, consisting largely of the C-terminal fragment of amyloid precursor protein downstream of the beta-secretase cleavage site. Cleavage of C100Flag by gamma-secretase was detected by electrochemiluminescence using antibodies that specifically recognize the Abeta40 or Abeta42 termini. Incubation of C100Flag with HeLa cell membranes or detergent-solubilized HeLa cell membranes generates both the Abeta40 and Abeta42 termini. Recovery of catalytically competent, soluble gamma-secretase critically depends on the choice of detergent; CHAPSO (3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1-propanesulfonate) but not Triton X-100 is suitable. Solubilized gamma-secretase activity is inhibited by pepstatin and more potently by a novel aspartyl protease transition-state analog inhibitor that blocks formation of Abeta40 and Abeta42 in mammalian cells. Upon gel exclusion chromatography, solubilized gamma-secretase activity coelutes with presenilin 1 (PS1) at an apparent relative molecular weight of approximately 2.0 x 10(6). Anti-PS1 antibody immunoprecipitates gamma-secretase activity from the solubilized gamma-secretase preparation. These data suggest that gamma-secretase activity is catalyzed by a PS1-containing macromolecular complex.

Alzheimer Disease↗
PubMed2000

Chromatography on cells: analyses of solute interactions with the glucose transporter Glut1 in human red cells adsorbed on lectin-gel beads.

The affinities of the human red cell glucose transporter Glut1 for D-glucose and cytochalasin B (CB) and the stoichiometry of CB binding vary with the Glut1 environment. In order to study the native state of Glut1 we adsorbed human red cells to wheat germ lectin agarose gel beads for frontal affinity chromatographic analyses. Glut1 showed relatively high affinities for D-glucose (Kd 12+/-1 mM) and CB (Kd 59+/-17 nM). The number of CB-binding sites per Glut1 monomer, 0.46+/-0.16, was approximately doubled upon coating the cells with polylysine, which induced cell association.

Binding, Competitive↗
PubMed2000

Synthesis of a new chiral ligand, 6, 6'-dihydroxy-5, 5'-biquinoline (BIQOL) and its applications in the asymmetric addition of diethylzinc to aldehydes.

A new chiral ligand 6, 6'-dihydroxy-5, 5'-biquinoline (BIQOL, 2) was prepared via Cu2+ mediated coupling. The resolution was carried out by separating the corresponding ditrifluomethanesulfonate on chiral column. When applied to the enantioselective addition of diethylzinc to aromatic aldehydes, this ligand induced the reaction with enantioselectivity equivalent to that induced by BINOL. The effects of solvent and reaction temperature on enantioselectivity were also studied.

Journal Article↗
PubMed2000

Phenylpropanoid glycosides from Scrophularia ningpoensis.

Three phenylpropanoid glycosides named ningposides A (3-O-acetyl-2-O-feruloyl-alpha-L-rhamnopyranose), B (4-O-acetyl-2-O-feruloyl-alpha-L-rhamnopyranose) and C (3-O-acetyl-2-O-p-hydroxycinnamoyl-alpha-L-rhamnopyranose) along with the known compounds sibirioside A, cistanoside D, angoroside C, acteoside, decaffeoylacteoside and cistanoside F were obtained from the roots of Scrophularia ningpoensis.

Glucosides↗
PubMed2000

Fast repairing of oxidized OH radical adducts of dAMP and dGMP by phenylpropanoid glycosides from Scrophularia ningpoensis Hemsl.

AIM: To investigate the antioxidative activity of the constituents of the roots of Scrophularia ningpoensis (Chinese name: Xuanshen). METHODS: The main compounds from the roots of Scrophularia ningpoensis were isolated and identified by chromatography and FABMS, NMR etc. Using the techniques of pulse radiolysis, the electron transfers from iridoid glycosides (IG) or phenylpropanoid glycosides (PG) to oxidized OH radical adducts of 2'-deoxyadenosine-5'-monophosphate acid (dAMP) or 2'-deoxyguanosine-5'-monophosphate acid (dGMP) were observed. RESULTS: Two IG: harpagoside and harpagide, two PG: angoroside C and acteoside were obtained as the main hydrophilic constituents of the plant. At 0.1 mmol/L concentration, angoroside C and acteoside were able to repair the oxidized OH adducts dAMP and dGMP significantly. However, harpagoside and harpagide had no such effect. The electron transfer rate constants of angoroside C with dAMP and dGMP were 4.2 x 10(8) and 10.3 x 10(8) L.mol-1.s-1; the electron transfer rate constants of acteoside with dAMP and dGMP were 5.3 x 10(8) and 20.2 x 10(8) L.mol-1.s-1. CONCLUSION: PG from Scrophularia ningpoensis have a potent antioxidative activity for reducing of the oxidized OH adducts of dAMP and dGMP.

Antioxidants↗
PubMed1999

Micellar electrokinetic capillary chromatography of macrolide antibiotics. Separation of tylosin, erythromycin and their related substances.

The separation of tylosin by micellar electrokinetic capillary chromatography with a mixed micelle system is described. Good selectivity was obtained with sodium phosphate buffer (80 mM, pH 7.5) containing 20 mM sodium cholate and 7 mM cetyltrimethylammonium bromide (CTAB). This method permits tylosin to be separated from its closely related substances within 15 min. The influences of type of buffer, buffer pH, the concentrations of sodium cholate and CTAB were investigated. The robustness of the method was examined for tylosin by means of a full-fraction factorial design. Quantitative results are presented. Using a similar buffer system (80 mM sodium phosphate, pH 6.0, 20 mM sodium cholate and 5 mM CTAB), separation of erythromycin and its main related substances was also obtained. However, detection sensitivity and resolution are not sufficient for analysis of related substances in erythromycin commercial samples.

Anti-Bacterial Agents↗
PubMed1999

Advanced glycation in D-galactose induced mouse aging model.

It was first reported in China that injection of a low dose of D-galactose into mice could induce changes which resembled accelerated aging. The aging model shows neurological impairment, decreased activity of anti-oxidant enzymes, and poor immune responses. However, the underlining mechanism remains largely unknown. D-galactose is a reducing sugar that can form advanced glycation endproducts (AGE) in vivo. To investigate the role of AGE in this aging model, a group of 5-month-old C57 mice were injected daily with D-galactose, D-galactose modified AGE-lysine (AGE-lysine), L-glucose, L-lysine, or control buffer for 8 weeks. Two additional groups were treated with the AGE formation inhibitor, aminoguanidine. The results show that D-galactose, L-glucose, and AGE-lysine treated mice had a significant increase in serum AGE levels, memory latency time and error rate, and skin hydroxyproline content. Similar to aged controls, these mice also had a significant decrease in motor activity, lymphocyte mitogenesis, interleukin-2 (IL-2) production, and superoxide dismutase (SOD) enzyme activity. The aminoguanidine treated D-galactose-injected mice, however, showed no significant changes in these parameters in comparison with young controls. These data indicate that D-galactose and L-glucose form AGEs in vivo and that elevated AGEs may accelerate the aging process. The fact that both D-galactose and AGE treated mice resemble aged mice suggests that advanced glycation, at least partially, accounts for the mechanism of this aging model.

Aging↗