Biomedical subjects

D Q Liu

Publications and source records attributed to D Q Liu.

At least 19 recordsLinked to original sources

PubMed2005

Site-directed mutagenesis of gentisate 1,2-dioxygenases from Klebsiella pneumoniae M5a1 and Ralstonia sp. strain U2.

Gentisate 1,2-dioxygenase (GDO, EC 1.13.11.4) is the first enzyme in gentisate pathway that catalyses the ring fission of gentisate to form maleylpyruvate. Phylogenetic tree of amino acid sequences from 11 GDOs demonstrates that the GDOs from different genus share identities between 12.1% and 64.8%. According to the alignment result, four highly conserved histidine residues in GDO from Klebsiella pneumoniae M5a1 and Ralstonia sp. strain U2 were chosen to be substituted with aspartate residues. Enzyme analysis indicated that substitution of any of these four histidine residues had resulted in the complete loss of its catalytic activity.

Amino Acid Sequence↗

PubMed2005

Arg169 is essential for catalytic activity of 3-hydroxybenzoate 6-hydroxylase from Klebsiella pneumoniae M5a1.

3-Hydroxybenzoate 6-hydroxylase from Klebsiella pneumoniae M5a1 is an enzyme that utilizes 3-hydroxybenzoate (3-HBA) as substrate yielding gentisate. Site-directed mutagenesis was carried out to define which residues may be involved in catalytic reaction. Substitution of arginine to glutamate at position 169 of the enzyme resulted in the complete loss of catalytic activity. This indicated Arg169 may play an important role in 3-HBA 6-hydroxylase catalysis.

Amino Acid Sequence↗

PubMed2004

Effects of the silanized mica surface on protein crystallization.

A freshly cleaved mica surface silanized by 3-aminopropyl triethoxysilane is flat over a large area, displays a controlled degree of hydrophobicity and contains positive charges. In this paper, mica sheets silanized by this method have been used as crystallization surfaces for lysozyme, trichosanthin and three other proteins of unknown structure. Crystallization experiments have been carried out by the hanging-drop vapour-diffusion technique and the results indicate that the silanized mica surface can ameliorate the protein crystallization process considerably compared with a silanized glass cover slip control. For lysozyme on the silanized mica surface, the induction time required for crystal growth decreases markedly. For trichosanthin, the crystal size is obviously larger and the number of crystals grown is much lower. For the three proteins of unknown structure, the diffraction ability of the crystals is improved considerably.

Aluminum Silicates↗

PubMed2003

Identification of novel metabolites of pioglitazone in rat and dog.

1. Four new metabolites of pioglitazone were identified by liquid chromatography-mass spectrometry (LC-MS/MS) as being formed by hydroxylation (M-VII and M-VIII), opening of the thiazolidinedione ring (M-X) and by desaturation of the terminal ethyl side chain or tether ethoxy moiety (M-IX), respectively. The structure of one of the hydroxylated metabolites (M-VII) was confirmed by chemical modification using the Jones reaction. 2. Oxidative cleavage of the thiazolidinedione ring is a novel pathway not previously reported for pioglitazone. 3. The hydroxylated M-VII was detected in incubations with rat, dog and human liver and kidney microsomes, and in plasma from rats and dogs dosed orally with [(3)H]pioglitazone. 4. The carboxylic acid derivative of M-VII (M-V) and its taurine conjugate were the major radioactive components in dog bile.

Animals↗

PubMed2003

Metabolism and disposition of gemfibrozil in Wistar and multidrug resistance-associated protein 2-deficient TR- rats.

1. The roles of multidrug resistance-associated protein (Mrp) 2 deficiency and Mrp3 up-regulation were evaluated on the metabolism and disposition of gemfibrozil. 2. Results from in vitro studies in microsomes showed that the hepatic intrinsic clearance (CLint) for the oxidative metabolism of gemfibrozil was slightly higher (1.5-fold) in male TR- rats, which are deficient in Mrp2, than in wild-type Wistar rats, whereas CLint for glucuronidation was similar in both strains. 3. The biliary excretion of intravenously administered [14C]gemfibrozil was significantly impaired in TR-) rats compared with Wistar rats (22 versus 93% of the dose excreted as the acyl glucuronides over 72 h). Additionally, the extent of urinary excretion of radioactivity was much higher in TR- than in Wistar rats (78 versus 2.6% of the dose). 4. There were complex time-dependent changes in the total radioactivity levels and metabolite profiles in plasma, liver and kidney, some of which appeared to be related to the up-regulation of Mrp3. 5. Overall, it was demonstrated that alterations in the expression of the transporters Mrp2 and Mrp3 significantly affected the excretion as well as the secondary metabolism and distribution of [14C]gemfibrozil.

ATP-Binding Cassette Transporters↗

PubMed2001

Use of on-line hydrogen/deuterium exchange to facilitate metabolite identification.

Biotransformation studies performed on an investigational compound (I, represented by R1-CH(NH(2))-CO-N(R2)-CH(2)-S-R3) led to the identification of five metabolites (M1-M5). Based on LC/MS (liquid chromatography/mass spectrometry) analysis which included the use of H(2)O and D(2)O in the mobile phases, they were identified as the sulfoxide (M1), sulfone (M2), carbamoyl glucuronide (M3), N-glucuronide (M4), and N-glucoside (M5) metabolites, respectively. The structure of M3, a less commonly seen carbamoyl glucuronide metabolite, was established using on-line H/D (hydrogen/deuterium) exchange experiments conducted by LC/MS. H/D exchange experiments were also used to distinguish the S-oxidation structures of M1 and M2 from hydroxylation. Herein, the application of deuterium oxide as the LC/MS mobile phase for structural elucidation of drug metabolites in biological matrices is demonstrated.

Amides↗

PubMed2001

Parallel extraction columns and parallel analytical columns coupled with liquid chromatography/tandem mass spectrometry for on-line simultaneous quantification of a drug candidate and its six metabolites in dog plasma.

A method with parallel extraction columns and parallel analytical columns (PEC-PAC) for on-line high-flow liquid chromatography/tandem mass spectrometry (LC/MS/MS) was developed and validated for simultaneous quantification of a drug candidate and its six metabolites in dog plasma. Two on-line extraction columns were used in parallel for sample extraction and two analytical columns were used in parallel for separation and analysis. The plasma samples, after addition of an internal standard solution, were directly injected onto the PEC-PAC system for purification and analysis. This method allowed the use of one of the extraction columns for analyte purification while the other was being equilibrated. Similarly, one of the analytical columns was employed to separate the analytes while the other was undergoing equilibration. Therefore, the time needed for re-conditioning both extraction and analytical columns was not added to the total analysis time, which resulted in a shorter run time and higher throughput. Moreover, the on-line column extraction LC/MS/MS method made it possible to extract and analyze all seven analytes simultaneously with good precision and accuracy despite their chemical class diversity that included primary, secondary and tertiary amines, an alcohol, an aldehyde and a carboxylic acid. The method was validated with the standard curve ranging from 5.00 to 5000 ng/mL. The intra- and inter-day precision was no more than 8% CV and the assay accuracy was between 95 and 107%.

Alcohols↗

PubMed2000

[Preliminary study on apoptosis of BEL-7402 cells induced by Chinese herbs for warming yang and dispersing stasis].

OBJECTIVE: To investigate the antitumor mechanism of Chinese herbs for warming yang and dispersing stasis and observe the action of these herbs in inducing apoptosis of BEL-7402 cells. METHOD: Apoptosis of BEL-7402 cells induced by the above-said herbs was detected through fast red tablet staining, flow cytometry and terminal uridine deoxynucleotidyl and labeling (TUNEL). RESULT: After treating BEL-7402 cells with the herbs typical apoptosis characteristics could be seen under light microscope and TUNEL positive cells were detectable. The apoptotic rate was 13.9% (drug concentration 0.5%) and 21.6% (drug concentration 1%) CONCLUSION: Chinese herbs for warming Yang and dispersing stasis could induce apoptosis of BEL-7402 cells and this effect depends on drug concentration. Inducing the apoptosis of tumor cells may be part of the mechanism displayed by Chinese herbs for warming Yang and dispersing stasis in treating hepatoma.

Antineoplastic Agents, Phytogenic↗

PubMed2000

[Studies on the sensitivity of Plasmodium falciparum to pyronaridine/sulfadoxine/pyrimethamine in vitro].

OBJECTIVE: To develop an in vitro method for the assessment of drug response in P. falciparum to pyronaridine/sulfadoxine/pyrimethamine (PND/S/P). METHODS: The PND/S/P microtest plate was designed, Rieckmann in vitro microtest(WHO standard kit) was used to test the sensitivity of P falciparum in continuous culture (FCC1/HN strain), and the data obtained were analyzed using a computer programme. Fractional inhibitory concentration (FIC) was calculated to test the possible synergy between PND and S/P. RESULTS: The effect of the PND/S/P plates was fairly stable and the ED50 values of pyronaridine, sulfadoxine and pyrimethamine were 0.11, 215.12 and 2.9 pmol, respectively. The FIC obtained confirmed the synergism between PND and S/P. CONCLUSION: The in vitro method can be used to assess the sensitivity of P. falciparum to pyronaridine/sulfadoxine/pyrimethamine.

Animals↗

PubMed1997

In vitro sensitivity of Plasmodium falciparum to eight antimalarials in China-Myanmar and China-Lao PDR border areas.

In 1991-1995 by using the Rieckmann in vitro micro-method, susceptibilities of Plasmodium falciparum to eight antimalarials in the China-Lao PDR and China-Myanmar border areas were tested. The resistant rates of P. falciparum to chloroquinine were 95.0%-100%; IC50 114-240nmol/l. P. falciparum resistant rates to amodiaquine resistance accounted for 83.5%-100%, IC50 52-72nmol/l. All cases were sensitive to quinine, IC50 470-608nmol/l. P. falciparum isolates from the Lao PDR frontier were highly sensitive to artesunate, dihydroartemisinin, and arteether. Resistant rates from other areas were 0-11%. P. falciparum from China-Myanmar and Lao PDR border areas were also sensitive to mefloquine, IC50 68-88nmol/l. A longitudinal survey of the sensitivity of P. falciparum in vivo on the China-Lao PDR border showed that the average defervescent time of falciparum malaria was treated by pyronaridine increased from 32.7 +/- 16.0 hours during 1984-85 to 56.2 +/- 27.4 hours in 1995; the recrudescence rate rose up from 15.2% to 37.5%. The results monitored in vitro showed that all cases assessed in 1988 for response to pyronaridine were sensitive, but 36.4% of cases had emerging resistance, IC50 increased from 13nmol/l to 40 nmol/l. The above results suggested that P. falciparum in these areas has expressed resistance to chloroquine and amodiaquine. However, the parasites are still sensitive to artemisinin, pyronaridine, mefloquine, quinine, but with a declining sensitivities.

Amodiaquine↗

PubMed1996

[Effects of high salt-loading on the regulation of angiotensin II receptor mRNA expression].

In the present study, the angiotensin II receptor subtype I-a (AT1a) and I-b (AT1b) mRNA levels in aortic smooth muscle (ASM), ventricular myocardium (VM) and adrenal from 12-week-old stroke-prone spontaneously hypertensive rats (SHRsp) and age-matched Wistar-Kyoto (WKY) rats with normal diet (control) and high salt-loading were examined by reverse transcriptase-polymerase chain reaction (RT-PCR). The results showed that: (1) The AT1a and AT1b mRNA levels in ASM and VM from SHRsp were lower than those from WKY rats (in ASM, 10% and 23%, while in VM, 23% and 40% lower, respectively). In contrast, both AT1a and AT1b mRNA levels in adrenal from SHRsp were higher (176% and 157%, respectively). (2) In the WKY rats with high salt-loading, the AT1a and AT1b mRNA levels in adrenal, as well as AT1b mRNA level in VM, increased significantly, as compared with the control (in adrenal, 167% and 401%, while in VM, 62%). However, the AT1a and AT1b mRNA levels in ASM, as well as AT1a mRNA level in VM, showed no obvious change. (3) In SHRsp with high salt-loading, the AT1b mRNA level in ASM, as well as AT1a and AT1b mRNA levels in VM, increased markedly (in ASM, 90%, while in VM, 590% and 200%); whereas the AT1a mRNA level in adrenal decreased significantly (58%). There was little influence on the regulation of AT1a (in ASM) and AT1b (in adrenal) receptor gene expression after high salt-loading. The results suggest that AT1a and AT1b receptors may be involved in the pathogenesis of salt-induced hypertension. The up-regulation of AT1b receptors in ASM may induce the remodeling of arterial wall, while that of AT1a and AT1b receptors in VM might contribute to ventricular hypertrophy in hypertension. Furthermore, there are certain differences between SHRsp and WKY rats with respect to the regulation of AT1a and AT1b receptor gene expression with or without external stimulation.

Adrenal Glands↗

PubMed1995

Changes in the resistance of Plasmodium falciparum to chloroquine in Hainan, China.

In 1979, in view of the widespread resistance of Plasmodium falciparum to chloroquine in the island of Hainan, China, it use as an antimalarial was suspended throughout the island. A longitudinal survey of the chloroquine-sensitivity of P. falciparum was carried out over the period 1981-91 to investigate whether its resistance had changed from the 1979 level. In-vitro assays were carried out every 2-3 years, while in-vivo tests were performed annually over the period 1981-83 and also in 1991. Resistance to chloroquine declined progressively after its use had stopped. The in-vitro tests indicated that the rate of chloroquine-resistant P. falciparum was 97.9% in 1981, but dropped to 60.9% in 1991 (P < 0.001). The mean concentration of chloroquine for complete inhibition of schizont formation was 10.4 pmol/microliters in 1981, but decreased to 3.0 pmol/microliters in 1991 (P < 0.001). The proportion of samples taken from malaria cases that required high concentrations ( > 6.4 pmol/microliters) of chloroquine for complete inhibition of schizont formation was 83.3% in 1981, but only 17.4% in 1991 (P < 0.001); at low concentrations ( > 1.6 pmol/microliters), the corresponding proportions increased from 4.2% in 1981 to 60.8% in 1991 (P < 0.001). In the 4-week in-vivo test, the rate of chloroquine-resistant P. falciparum decreased from 84.2% in 1981 to 40% in 1991 (P < 0.001). RII + RIII cases represented 59.4% of the total resistant cases in 1981, but decreased to 37.5% in 1991 (0.02 > P > 0.01).

Adolescent↗

PubMed1994

[Effects of furyl-dihydropyridine I on coronary collateral circulation in myocardial infarction of dogs].

Effects of furyl-dihydropyridine I (FDP-1) on collateral circulation were observed in ischemic myocardium of dogs. FDP-1 (200 micrograms.kg-1) of intracoronary injection increased collateral flow, reduced systemic artery resistance, and coronary systolic pressure in infarcted region and the area of infarction decreased from 28.9 +/- 1.3% to 15.3 +/- 1.2% (P < 0.01, n = 6). The results indicated that FDP-1 could improve coronary collateral circulation, increase collateral flow in ischemic region, decrease collateral flow in ischemic region, decrease myocardial oxygen demand, and protect myocardial ischemia.

Animals↗

PubMed1994

[Longitudinal surveillance of chloroquine resistance of Plasmodium falciparum after cessation of medication in south Yunnan].

The resistance of P. falciparum to chloroquine was assayed by in vitro microtest in 1981 and after cessation of medication in 1984, 1988-1990 and 1992 in south Yunnan Province of China. The resistance rates were 97.4% (38/39), 100% (25/25), 96.1% (73/76) and 93.7% (59/63), respectively; ID50 were 170, 132, 125 and 110 nmol/L; ID95 were 1,000, 740, 707 and 576 nmol/L; mean dosages for complete inhibition of schizont formation were 55.4, 46.7, 45.8 and 35.4 (pmol/well). A comparison of the results in 1981, 1984, 1988-1990 and 1992, the resistance rate showed no marked change, ID50 dropped 22.3% (P < 0.05), 26.4% (P < 0.05) and 35.3% (P < 0.01); ID95 declined 26.0% (P < 0.05), 29.3% (P < 0.05) and 42.2% (P < 0.01); mean dosage of inhibition dropped 15.7% (P > 0.05), 17.3% (P < 0.05) and 36.1% (P < 0.01). The results show that the extent of resistance in chloroquine-resistant P. falciparum to chloroquine in south Yunnan has been declined markedly, indicating that coresistance was variable and dropped along with the declining of drug pressure.

Animals↗

PubMed1994

[Unusual manifestation of cerebral cysticercosis].

We have surgically treated two patients with cerebral cysticercosis, which were pre-operatively unexpected due to unusual CT and MRI manifestations. A 24 year old chinese farmer with intermittent severe headache for 6 years was examined by CT and MRI. A huge cystic lesion with same density or intensities to CSF occupied retroclival posterior fossa to upper cervical spinal canal and displaced neural structures backwardly. By suboccipital craniectomy, watery clear cyst fluid of 44ml was aspirated and the shrunken cyst was pulled out with ease. It was unable to predict until an electron microscopic study, which revealed a larva with three layers of microvilli, vesicular tegmentum and infrategmental muscle bundles and vesicles. The findings were same to those of racemose cysticercus of human brain. Giant cysts of cysticercosis were infrequently present supratentorially, although infratentorial or basal cysticercosis were racemose and small. The present case may be the first case of a huge cyst of cysticercosis in posterior fossa. A 44 year old Japanese businessman with 15 years history of general convulsion underwent craniotomy due to a small, but growing cystic granulomatous mass in right inferior frontal gyrus. The CT scan examined at 3 years after his first general convulsion revealed a small round low density mass, 5mm in diameter, in right frontal lobe and its wall was weakly enhanced by contrast media. The follow-up CT scans and MRIs revealed that the enhancing cystic mass became thick and deformed, and perifocal edema came to evident and progressed stepwise by attacks of general convulsions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Protective effects of 3,6-dimethylamino-dibenzopyriodonium edetate on global ischemia reperfused isolated rat hearts.

The effects of 3,6-dimethylamino-dibenzopyriodonium edetate (IHC-72) on global ischemia reperfused rat hearts were investigated. In the isolated working rat heart, 40-min global ischemia followed by 30-min reperfusion resulted in increases of ventricular tachycardia (VT) and ventricular fibrillation (VF), increases of creatine kinase (CK) release and malondialdehyde (MDA) contents, but decreased superoxide dismutase (SOD) activity. Following ischemia and reperfusion, the accumulation of myocardial calcium increased. IHC-72 50 mumol.L-1 given 10 min before ischemia and during reperfusion decreased the cardiac CK release, VT, and VF, reduced the MDA contents, prevented the reduction of SOD activity and attenuated the accumulation of myocardial calcium and sodium vs control. These results indicated that IHC-72 protected myocardial reperfused injury.

Animals↗

PubMed1993

Effects of 3,6-dimethylamino-dibenzopyriodonium edetate on action potentials in guinea pig papillary muscles.

The effects of 3,6-dimethylamino-dibenzopyriodonium edetate (IHC-72) on action potentials (AP) and slow response action potentials of guinea pig papillary muscles were studied with intracellular microelectrodes. IHC-72 12.7, 25.4, and 50.8 mumol.L-1 decreased the maximal upstroke velocity (Vmax), amplitude of action potential (APA), over shot (OS), and resting potential (RP) while prolonged the action potential duration at 30%, 50%, 90%, and 100% repolarization (APD30, APD50, APD90, and APD100). IHC-72 25.4 and 50.8 mumol.L-1 decreased the APA, Vmax, and prolonged APD50 and APD90 under high K+ superfusion. IHC-72 25.4 and 50.8 mumol.L-1 depressed the automaticity, APA, and maximal diastolic potential (MDP) of the slow response action potentials induced by BaCl2. The results indicated that IHC-72 might nonspecifically inhibit the transmembrane movement of Ca2+, Na+, and K+.

Action Potentials↗

PubMed1993

[Effects of furyl-dihydropyridine on action potential ventricular myocardium of rabbit in vivo and isolated guinea pig left atrium in vitro].

Effects of furyl-dihydropyridine (FDP) on action potential of rabbit ventricular myocardium in vivo were observed with floating microelectrode technique. FDP 0.5 mg.kg-1 i.v. increased APD30 from 104 +/- 7 to 127 +/- 7 ms, APD90 from 146 +/- 10 to 177 +/- 9 ms (P < 0.01, n = 7), decreased the heart rate from 230 +/- 18 to 203 +/- 20 bpm (P < 0.05). Nifedipine (Nif) 0.5 mg.kg-1 i.v. reduced APD and increased the HR in rabbit. In guinea pig left atrium, FDP and Nif decreased the APD, the effects of acetylcholine to shorten the APD was antagonized by FDP 1 mumol.L-1. In rabbit's sinoatrial nodes, FDP 0.5, 1 mumol.L-1 also suppressed the APA and increased the spontaneous sinus cycle length (SCL) and APD50. These results indicate that FDP may inhibit the Ca2+ and K+ currents of myocardium.

Acetylcholine↗