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Biomedical subjects

L Nie

Publications and source records attributed to L Nie.

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

[Structure and function of sanL--a gene involved in nikkomycin biosynthesis of Streptomyces ansochromogenes].

The chromosome walking strategy has been used in this experiment and a 10 kb DNA fragment was cloned from the cosmid library of Streptomyces ansochromogenes using a partial DNA fragment involved in the nikkomycin biosynthesis as a probe. The nucleotide sequence showed that the DNA fragment contains two complete open reading frames (ORFs), they are designated as sanK and sanL respectively. The sanL is located on the upstream of sanK, it has 1281 nucleotides with ATG at 345 position as start codon and TGA at 623 position as stop codon. The deduced product is L-lysine 2-aminotransferase using Blastx program. The experiment of gene disruption indicated that this gene is closely related to nikkomycin biosynthesis of Streptomyces ansochromogenes.

Amino Acid Sequence↗
PubMed2000

Detection and analysis of Bacillus subtilis growth with piezoelectric quartz crystal impedance based on starch hydrolysis.

A piezoelectric quartz crystal (PQC) impedance method based on the alpha-amylase-catalyzed hydrolysis of starch present in a culture medium has been developed for in situ monitoring of the whole growth process of Bacillus subtilis and the variation in the activity of alpha-amylase during bacterial growth. An S-shaped response behavior was observed for Deltaf(0), and simultaneously inverse S-shaped responses were found for DeltaR(1) and DeltaL(1). The ratio of DeltaR(1) to Deltaf(0) or DeltaL(1) coincided well with that calculated from Martin's equations reflecting the solution density-viscosity effect, suggesting that the continuing change in liquid loading onto the PQC surface causes significant variation in Deltaf(0), DeltaR(1), and DeltaL(1). Bacterial growth equations were derived from the kinetics of the enzyme-catalyzed hydrolysis of starch, which fit well with the experimental responses of Deltaf(0), DeltaR(1), and DeltaL(1). Kinetic parameters of bacterial growth, including the asymptote (A), the maximum specific growth rate (microm), and the lag time (lambda), were obtained and were in good agreement with those obtained from the pour plate count method. The variation in the activity of alpha-amylase exhibited peak-type behavior with its maximum value at the later stage of the log phase. In addition, the influence of initial bacterial concentration was also investigated.

Algorithms↗
PubMed2000

Study of the Adsorption of Glutathione on a Gold Electrode by Using Electrochemical Quartz Crystal Impedance, Electrochemical Impedance Spectroscopy, and Cyclic Voltammetry.

Adsorption of a biological peptide, glutathione, on a gold electrode was studied by using electrochemical quartz crystal impedance (EQCI), electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) techniques. The time courses of responses of piezoelectric and electrochemical impedance parameters were simultaneously obtained during the adsorption processes of the two forms of peptide, oxidized and reduced glutathione. It was found that the frequency curve due to the oxidized glutathione (GSSG) adsorption exhibited a character of a sum of two exponential functions. For reduced glutathione (GSH), the frequency adsorption curve could be expressed by a first-order reaction kinetic model and the corresponding kinetic parameters at different amounts of GSH were obtained. The heterogeneous charge-transfer rate constants of ferricyanide/ferrocyanide before and after the peptide adsorption were determined by CV and EIS methods, respectively. According to the simple equivalent electric network of the electrochemical interface, the electrochemical impedance parameters were also obtained. The results showed that the proposed method should be found in wider applications in interfacial biochemistry studies since these combined techniques have advantages in real time multidimensional information including electrochemical and electrochemical impedance parameters. Copyright 2000 Academic Press.

Journal Article↗
PubMed2000

alpha-Amylase immobilized on bulk acoustic-wave sensor by UV-curing coating.

A new method for immobilization of alpha-amylase by UV-curing coating is proposed in this paper. The immobilization procedure of UV-curing coating on piezoelectric quartz crystal is simple and convenient, and causes less loss of enzymatic activity. The activity of the immobilized alpha-amylase is monitored by a technique based on bulk acoustic-wave (BAW) sensor. The frequency shift of BAW sensor can reflect the degree of hydrolysis of starch by the immobilized alpha-amylase. It is appropriate for the immobilized alpha-amylase to hydrolyze the soluble starch under pH 7.0 condition, which is similar to that of the free alpha-amylase. Kinetic parameters (the Michaelis constant, K(m), and the maximum initial rate V(max)) of the enzymatic hydrolysis of starch by the immobilized alpha-amylase are estimated by using a linear method of Lineweaver-Burk plot. K(m)=12.7mgml(-1) and V(max)=15.9Hzmin(-1). And the experimental results show that the immobilized alpha-amylase entrapped by the UV-curing coating retains adequate enzymatic activity and can be reused more than 50 times under certain experimental conditions.

Journal Article↗
PubMed2000

Bulk acoustic wave sensor for herbicide assay based on molecularly imprinted polymer.

A novel molecularly imprinted polymer (MIP) coated bulk acoustic wave (BAW) sensor was fabricated for liquid phases. It can be used as a sensitive portable implement for the assay of 2,4-dichlorophenoxyacetic acid. A logarithmic response relationship between 2.0 x 10(-7) M and 5.0 x 10(-4)M was found. The detection limit was 1.0 x 10(-7) M. Recoveries were 93.2-108.7%. Influencing factors were investigated in detail and optimized.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2000

[Suppressing effect of isoforskolin and forskolin on ocular hypertension in rabbits].

OBJECTIVE: To examine the effects of isoforskolin (isoF) and forskolin (FSK) suspensions administered topically on eyes with ocular hypertension (OHT) and observe the local irritation of the drugs. METHODS: The intraocular pressure (IOP) was measured with pneumotonometer in screened spontaneous or water-loading induced OHT rabbits for evaluation of drug effects, and the irritation indices were recorded as well. RESULTS: In screened OHT rabbits, isoF significantly lowered IOP from 0.5 to at least 4.5 h after the administration (P < 0.05, paired t-test vs. contralateral control eyes), with the maximum decreases of 0.25% and 1% isoF reaching 8.1 mm Hg and 7.0 mm Hg (1 mm Hg = 0.133 kPa) at about 1.5 h later, respectively. In water-loaded OHT rabbits, both 0.06%, 0.1%, 0.25%, 1% isoF and 1% FSK concentration-dependently suppressed the increments of IOP (P < 0.05 with the exception of 0.06% isoF) induced by water-loading, and the peak effects of the optimal concentration of 0.25% isoF and 1% FSK were 7.1 and 6.9 mm Hg (difference of IOP between bilateral eyes) respectively. The results also indicated that 0.25% isoF or FSK suspension had basically no irritation, but 1% induced slight irritating responses during the experiment. CONCLUSION: Both isoF and FSK had suppressing effects on OHT in rabbits with the optimal concentration being 0.25% and 1% respectively; at concentration of 0.25%, topically both drugs had basically no irritation, while 1% of the drugs may induce mild irritating responses.

Animals↗
PubMed2000

[Expression of IL-2 receptors on the surfaces of L1210 cells and bioactivity assay for IL-2-toxin fusion proteins].

OBJECTIVE: To confirm that L1210 cells surfaces express IL-2 receptors (IL-2R) and to establish experimental models for studying the cytotoxic effect of IL-2-toxin fusion protein in vivo and in vitro. METHODS: IL-2R on mouse leukemia L1210 cells was analyzed with immunofluorescence stain and FACS. The cytotoxic effects in vitro of these fusion proteins IL-2-PEZNM and IL-2-K-PEZNM were assayed by MTT method; mice ascitic L1210 leukemia was induced by i.p. L1210 cells and the therapeutic effect of IL-2-K-PEZNM was observed. RESULTS: 86.3% of L1210 cells expressed IL-2R on their surfaces and the relative fluorescence intensity was 51.55. Two fusion proteins IL-2-PEZNM and IL-2-K-PEZNM showed dose-related cytotoxicities to L1210 cells in vitro with the IC50 of 0.51 and 0.67 microgram/ml respectively. IL-2-K-PEZNM (5 micrograms/d) showed significantly inhibitory effect on L1210 cells and prolonged the survival time of mice by 78.6%. CONCLUSIONS: L1210 cells as a model system to measure the cytotoxic activity of IL-2-toxin fusion proteins both in vitro and in vivo is simpler, stabler, and safer model than those with other cells such as Hut102 and activated T lymphocytes.

Animals↗
PubMed1999

Role of mitogen-activated protein kinase and phosphoinositide 3-kinase in the differentiation of rat pancreatic AR42J cells induced by hepatocyte growth factor.

AIMS/HYPOTHESIS: Pancreatic AR42J cells express both exocrine and neuroendocrine properties. When exposed to activin A, approximately 50 % of the cells die within 3 days by apoptosis. Addition of hepatocyte growth factor prevents apoptosis induced by activin A and induces differentiation into insulin-producing cells. The present study was conducted to examine the role of mitogen-activated protein kinase and phosphoinositide 3-kinase in the action of hepatocyte growth factor. METHODS: The role of mitogen-activated protein kinase was assessed by using 2-(2'-amino-3 '-methoxyphenol)-oxanaphthalen-4-one (PD098059). Cells were also transfected with cDNA for mitogen-activated protein kinase phosphatase and constitutively active mutant of mitogen-activated protein kinase kinase. RESULTS: Hepatocyte growth factor induced sustained activation of the mitogen-activated protein kinase, which was inhibited by PD098059. PD098059 completely blocked the differentiation and also blocked the prevention of apoptosis. Transfection of the cells with cDNA for mitogen-activated protein kinase phosphatase reproduced the effect of PD098059. Conversely, transfection with cDNA for the constitutively active mutant of mitogen-activated protein kinase kinase reproduced the effect of hepatocyte growth factor. In contrast, addition of wortmannin or transfection of the dominantly negative form of the p85 subunit of the phosphoinositide 3-kinase did not affect differentiation induced by hepatocyte growth factor. Instead, wortmannin enhanced the increase in the insulin content of the differentiated AR42J cells. CONCLUSION/INTERPRETATION: The MAP kinase pathway is necessary and sufficient for the action of HGF on differentiation of AR42J cells.

Activins↗
PubMed1999

Genetic diversity of cattle in south China as revealed by blood protein electrophoresis.

Genetic variation of 31 blood protein loci in 236 cattle from eight South China populations (including mithan, Bos frontalis) and a Holstein population was investigated by means of horizontal starch gel electrophoresis. Thirteen loci (ALB, CAR, Hb-b, Np, PGM, Amy-I, PEP-B, AKP, 6PGD, Cp, Pa, EsD, and TF) were found to be polymorphic. The comparison of average heterozygosities (H) shows that all the native cattle embrace a rich genetic diversity. Our results on protein polymorphism suggest that cattle in China originated mainly from Bos indicus and Bos taurus; Xuwen, Hainan, Wenshan, and Dehong cattle and the Dehong zebu are close to zebu-type cattle, and Diqing and Zhaotong cattle are close to the taurine. The mithan was very different from other native cattle, and we suggest that its origin was complicated and may be influenced by other cattle species.

Alleles↗
PubMed1999

Construction and analytical application of ion-selective piezoelectric sensor for atropine sulfate.

The method describes the use of a piezoelectric quartz crystal (PQC) as a substitute for ion-selective electrodes. The approach is feasible when the membrane materials are electrically non-conductive and membrane potential measurements are consequently not possible. An ion-selective piezoelectric sensor sensitive to atropine sulfate was constructed by coating a PVC membrane containing activant on one the side of a PQC. On the basis of selective adsorption of atropine ions across the modified film and the sensitive mass response of PQC, the method exhibits a sensitive, rapid response and is easy to operate without pretreatment of the sample. The logarithm of the frequency shift gave a linear relationship with the logarithm of atropine sulfate concentration in the 1.0 x 10(-8)-1.0 x 10(-3) M range with a detection limit of 5.0 x 10(-9) M at pH 7.0. Recoveries were from 98.7-102.2%. Two activants, atropine tetraphenylborate and atropine dipicrylaminate, were synthesized and investigated. Influencing factors were also examined and optimized. The results for real samples obtained by the proposed method agreed with those obtained by conventional methods.

Atropine↗
PubMed1999

Study of a molecular imprinting polymer coated BAW bio-mimic sensor and its application to the determination of caffeine in human serum and urine.

A bio-mimic bulk acoustic wave (BAW) sensor was fabricated by coating the caffeine (CAF) template molecular imprinting polymer (MIP). This sensor exhibited high selectivity and a sensitive mass response to CAF. The response range of the sensor was between 5.0 x 10(-9) and 1.0 x 10(-4) M with a detection limit of 5.0 x 10(-9) M at pH 8.0. Recoveries were 96.1-105.6%. Influencing factors were investigated in detail and optimized. When employed to detect real samples, the proposed method proved to be a convenient method with the advantages of high sensitivity, good selectivity and ease of handling.

Biosensing Techniques↗
PubMed1999

Mitochondrial DNA variation in cattle of south China: origin and introgression.

Ten restriction endonucleases were used to investigate the mitochondrial DNA restriction fragment length polymorphism (mtDNA RFLP) of 11 native cattle breeds and one cultivated cattle breed in South China. Twenty-three restriction morphs were detected, which can be sorted into five haplotypes. A phylogenetic tree of the haplotypes was constructed by using the 'upgMa' method. Our study showed that haplotype I and II are identical to the zebu (Bos indicus) and taurine (Bos taurus) haplotypes, respectively. Zebu and taurine were the two major origins of cattle populations in South China, and the zebu probably had more influence on the native cattle population than taurine did. Haplotype III is identical to haplotype I of yak (Bos grunniens), which was only detected in the Diqing cattle breed. Haplotype IV was detected for the first time. This haplotype, found only in Dehong cattle, might be from an independent domestication event, probably from another Bos indicus population. Divergence of haplotypes I and IV occurred about 268,000-535,000 years ago, much earlier than the 10,000-year history of cattle husbandry. Our results also suggest a secondary introgession of mtDNA from yak to Diqing cattle.

Animal Husbandry↗
PubMed1999

Modulation of HERG potassium channels by extracellular magnesium and quinidine.

Torsades de pointes is a polymorphic ventricular arrhythmia resulting from congenital or drug-induced (acquired) QT prolongation. Pharmacologic suppression of repolarizing potassium currents is one mechanism causing the acquired long QT (LQT) syndrome. Recent studies have linked mutations in a gene encoding a potassium channel subunit (HERG) to the LQT syndrome. Clinical experience indicates that intravenous magnesium sulfate is effective in reversing torsades de pointes, but the molecular basis of this effect is not understood. This study was designed to investigate the effects of extracellular magnesium (Mg2+) on HERG potassium currents. HERG potassium channels were expressed in Xenopus oocytes and in a human cell line and were examined by voltage-clamp methods. Extracellular Mg2+ (0.3-10 mM) caused a concentration-dependent shift in the membrane-potential dependence of HERG channel opening, causing a reduction in K+ current. This effect was much greater than that observed in another human delayed rectifier K+ channel, hKv1.5, suggesting a specific interaction with the HERG channel. Quinidine is an antiarrhythmic drug that also causes torsades de pointes under certain conditions. Quinidine (3 microM) inhibited HERG currents expressed in oocytes by 32.1 +/- 3.2% (n = 5), whereas 1 microM quinidine inhibited HERG currents in tsA201 cells by 75.8 +/- 2.4% (n = 12). Increasing extracellular Mg2+ did not relieve the inhibition by quinidine, but caused additional suppression. These results indicate that extracellular Mg2+ exerts a direct action on HERG potassium channels, resulting in suppression of outward repolarizing potassium current. It is concluded that modulation of this important K+ current is not the mechanism by which intravenous magnesium terminates drug-induced LQT and torsades de pointes. Potent suppression of HERG channel current by quinidine, compared with that of I(Ks) and I(Na), is a likely contributor to torsades de pointes arrhythmias.

Animals↗
PubMed1999

[The phylogeny of 5 Chinese peculiar Parnassius butterflies using noninvasive sampling mtDNA sequences].

This paper employs nonivasive sampling DNA sequencing technique for estimating molecular phylogeny of 5 Chinese peculiar Parnassius Butterflies. Of 433bp mitochondrial cytochrome b DNA sequences, A% + T% was 75.4%, and 40 nucleotide sites were substituted (about 9.24%). The molecular phylogenetic tree constructed by parsimony method suggests that Parnassius acco is closely related to Parnassius baileyi; Parnassius apollo, Parnassius orlears, and Parnassius simo are independent branches respectively. Parnassius simo is divergent earlier. The result is identical with that of morphology.

Animals↗
PubMed1999

[Effect of Yiqi Zishen granule on ultrastructure of glomeruli of IgA nephropathy in mice].

OBJECTIVE: To study the effect and therapeutical mechanism of Yiqi Zishen granule (YQZSG) in treating IgA nephropathy. METHODS: One hundred and fifty mice were divided into 5 groups randomly, in every treatment group, the relevant drugs were given. Their kidney tissues were observed with light microscope and electron microscope in batches at the 3rd, 6th, 9th and 12th week. RESULTS: The glomerular mesangial cells and mesangial matrix were proliferative in the model group at the 6th, 9th and 12th week. The light density of glomeruli, the mesangial area, the numeral density of mesangial cells and the light density of mesangial matrix in the model group were obviously higher, the change of large and small dosage YQZSG group and positive Chinese drug group were similar, but milder in pathological degree. The light density of glomerulus area, the mesangial area, the numeral density of mesangial cells and the light density of mesangial matrix in large dosage YQZSG group were significantly lower than those in the model group (P < 0.05 or P < 0.01). CONCLUSION: YQZSG could inhibit the proliferation of mesangial cells and the mesangial matrix in IgA nephropathy.

Animals↗
PubMed1999

[Diagnostic and surgical experience of secondary syringohydromyelia].

OBJECTIVE: To analyse the diagnostic and surgical experience in 17 patients with secondary syringohydromyelia. METHODS: Physical examination and MRI were carried out before operation. Surgical treatments were selected according to their different original disorders. RESULTS: In three of 8 patients, intramedullary tumors were completely removed, 4 subtotally and 1 partially. Pathological examination showed mainly ependymoma. The tumor and syrinx on MRI were shown along the central axis of the spinal cord, but this was not the same on other 9 of the 17 patients with extramedullary disorders, which were treated for their original disorders. The syrinx was shrunken in all 5 patients taking MRI for countercheck. CONCLUSIONS: The diagnosis of secondary syringohydromyelia mainly depends on MRI. Surgical treatment should aim at their original disorders. Syringohydromyelia includes two pathological types: hydromyelia and syringomyelia. Those secondary to intramedullary ependymoma are mostly hydromyelia, which may be caused by expanding of tumor along the central canal of the spinal cord.

Adolescent↗