Biomedical subjects

Ling Qiu

Publications and source records attributed to Ling Qiu.

23 records · Page 2Linked to original sources

PubMed2004

Inhibitory effects of 4-halobenzoic acids on the diphenolase and monophenolase activity of mushroom tyrosinase.

The effects of 4-halobenzoic acids (4-fluorobenzoic acid, 4-chlorobenzoic acid, and 4-bromobenzoic acid) on the activity of mushroom tyrosinase have been studied. The results show that 4-halobenzoic acids can strongly inhibit both monophenolase activity and diphenolase activity of the enzyme, and the inhibition displays a reversible course. The IC50 values were estimated as 0.26, 0.20, and 0.18 mM for diphenolase activity and as 1.03, 0.75, and 0.60 mM for monophenolase activity, respectively. Kinetic analyses show that the inhibition mechanism of all three 4-halobenzoic acids is noncompetitive inhibition to the diphenolase activity, and the inhibition constants (K1) were determined to be 0.25, 0.20, and 0.17 mM, respectively. The lag time of the monophenolase was obviously lengthened by these three 4-halobenzoic acids. When the concentration of inhibitors reached 1.4 mM, the lag time was lengthened from 30 s to 120, 125, and 150 s, respectively.

Agaricales↗

PubMed2004

Antibody response and viraemia during the course of severe acute respiratory syndrome (SARS)-associated coronavirus infection.

To understand the time-course of viraemia and antibody responses to severe acute respiratory syndrome-associated coronavirus (SARS-CoV), RT-PCR and ELISA were used to assay 376 blood samples from 135 SARS patients at various stages of the illness, including samples from patients who were in their early convalescent phase. The results showed that IgM antibodies decreased and became undetectable 11 weeks into the recovery phase. IgG antibodies, however, remained detectable for a period beyond 11 weeks and were found in 100 % of patients in the early convalescent phase. SARS-CoV viraemia mainly appeared 1 week after the onset of illness and then decreased over a period of 1 month, becoming undetectable in the blood samples of the convalescent patients. At the peak of viraemia, viral RNA was detectable in 75 % of blood samples from patients who were clinically diagnosed with SARS 1 or 2 weeks before the test.

Adolescent↗

PubMed2004

Discovery and mechanism of action of a novel series of apoptosis inducers with potential vascular targeting activity.

A novel series of 2-amino-4-(3-bromo-4,5-dimethoxy-phenyl)-3-cyano-4H-chromenes was identified as apoptosis-inducing agents through our cell-based apoptosis screening assay. Several analogues from this series, MX-58151, MX-58276, MX-76747, MX-116214, MX-126303, and MX-116407, were synthesized and further characterized. MX-116407, a lead compound from this series, induced apoptosis with an EC50 of 50 nmol/L and inhibited cell growth with a GI50 of 37 nmol/L in T47D breast cancer cells. Treatment of cells with these analogues led to G2-M arrest, cleavage of essential proapoptotic caspase substrates, and induction of nuclear fragmentation. We identified these compounds as tubulin destabilizers with binding site at or close to the colchicine binding site. Compounds in this series were also active in drug-resistant cancer cell lines with a GI50 value for one of the analogues (MX-58151) of 2.5 nmol/L in paclitaxel-resistant, multidrug-resistant MES-SA/DX5 tumor cells. This series of compounds displayed high selectivity against proliferating versus resting cells. Interestingly, these compounds were shown to disrupt preformed endothelial cell capillary tubules in vitro and affect functional vasculature to induce tumor necrosis in vivo and are thus likely to work as tumor vasculature targeting agents. Among these compounds, MX-116407 showed capillary tubule disruption activity in vitro at concentrations well below the cytotoxic dose. In a separate study, we further characterized the antitumor efficacy and pharmacokinetic profile of this series of compounds and identified MX-116407 as a potent apoptosis-inducing agent with apparent activity as tumor vasculature targeting agent.

Antineoplastic Agents↗

PubMed2003

Inhibitory effect of 4-cyanobenzaldehyde and 4-cyanobenzoic acid on mushroom (Agaricus bisporus) tyrosinase.

Mushroom tyrosinase (EC 1.14.18.1), a copper containing oxidase, catalyzes both the hydroxylation of tyrosine into o-diphenols and the oxidation of o-diphenols into o-quinones. In the current study, the effects of 4-cyanobenzaldehyde and 4-cyanobenzoic acid on the monophenolase and diphenolase activities of mushroom tyrosinase have been studied. The results show that 4-cyanobenzaldehyde and 4-cyanobenzoic acid can inhibit both the monophenolase activity and the diphenolase activity of mushroom tyrosinase. The lag phase of tyrosine oxidation catalyzed by the enzyme was obviously lengthened, and the steady-state activity of the enzyme decreased sharply. 1.0 mM 4-cyanobenzaldehyde and 4-cyanobenzoic acid can lengthen the lag phase from 78 s to 134 and 115 s, respectively. Both 4-cyanobenzaldehyde and 4-cyanobenzoic acid can lead to reversible inhibition of the enzyme. The IC50 values of 4-cyanobenzaldehyde and 4-cyanobenzoic acid were estimated as 0.62 and 2.45 mM for monophenolase and as 0.72 and 1.40 mM for diphenolase, respectively. A kinetic analysis shows that 4-cyanobenzaldehyde and 4-cyanobenzoic acid are mixed-type inhibitors for the diphenolase. The apparent inhibition constants for 4-cyanobenzaldehyde and 4-cyanobenzoic acid binding with both the free enzyme and the enzyme-substrate complex have been determined and compared.

Agaricales↗

PubMed2003

[Hyperhomocysteinemia and deep-vein thrombosis].

OBJECTIVE: To study the relationship between plasma homocysteine (Hcy) level and deep-vein thrombosis (DVT), and analyze the interaction of Hcy, folate and methylenetetrahydrofolate reductase (MTHFR) gene polymorphism in patients with DVT. METHODS: Totally 69 patients with DVT and 111 healthy controls were included in our case-control study. We determined the MTHFR C677T genotypes by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP), measured the serum folate and vitamin B12 by radioimmunoassay (RIA), and measured the plasma homocysteine level by fluorescence polarization immunoassay (FPIA). RESULTS: The frequency of the MTHFR C677T TT genotype had no significant difference between DVT group and control group (P > 0.05). The plasma Hcy level was significantly higher in DVT group than in control group (13.03 +/- 8.74 mumol/L vs 10.14 +/- 4.30 mumol/L, P < 0.05). Both serum folate and VitB12 of patients with DVT were not significantly different from those of controls. The odds radios (OR) of hyperhomocysteinemia for DVT was 2.53 (95% CI 1.08-5.92). The interaction of low folate level and TT genotype increased the risk of DVT (OR = 3.12, 95% CI 1.17-8.38). CONCLUSION: Hyperhomocysteinemia may be an independent risk factor for DVT in Han nationality, while serum folate level and MTHRF C677T genotype are not. An interaction between serum folate level and MTHFR genotype that affect the Hcy level is an important risk factor for DVT.

Adult↗