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Biomedical subjects

L Li

Publications and source records attributed to L Li.

At least 973 records · Page 54Linked to original sources
PubMed1999

[Establishment of A + G ligation mediated polymerase chain reaction and its application in in vivo footprinting study].

OBJECTIVE: To establish a new ligation mediated PCR method for the work in in vivo footprinting study of some regions of low G-residue content or some regions of G-residue free. METHODS: The A > G chemical cleavage method of Maxam-Gilbert sequencing was modified for ligation mediated PCR after A + G chemical cleavage and separate the PCR products by sequencing PAGE. RESULTS: A new A + G ligation mediated method was established and could be used in vivo footprinting study. CONCLUSIONS: Our results indicated that the newly developed method could analyze the DNA-Protein interaction at both A-residue and G-residue, enabled us to get more information and enlarged the scope of its application.

Animals↗
PubMed1999

[Identification study on pig's hoofnail].

The identification characteristics of pig's hoofnail on properties and tissue slice was initially probed from the viewpoint of identification in this paper in order to make basis for the systematic research on replacing Squama manitis.

Animals↗
PubMed1999

[Experimental study on anti-oxygen and promoting intelligence development of Codonopsis lanceolata in old mice].

The water labyrinth test and determining lipid peroxide (LPO) contents were used to assay the effects of Codonopsis lanceolata on promoting intelligence development and lipid peroxide. The results showed that latent period of old mice in water labyrinth was statistically shorten and the number of mistake of old mice was visibly reduced by drinking extraction of Codonopsis lanceolate 4 g/kg and 8 g/kg. These indicated that mice drinking extraction of Codonopsis lanceloata learned faster that those of drinking water. The contents of LPO in red blood cell and brain of mice and rate drinking extraction of Codonopsis lanceolata were significantly reduced, the activities of superoxide dismutase (SOD) in serum of rat drinking extraction of Codonopsis lanceolata were visibly increased. These presents that the extraction of Codonopsis lanceolata has the role of promoting learning and memory of old animal, its mechanism might be increasing SOD activity and decreasing LPO level.

Animals↗
PubMed1999

[A comparison on postoperative shallow anterior chambers with different kinds of glaucoma surgery].

PURPOSE: Comparing the rate of postoperative shallow anterior chambers with three kinds of filtration surgery to find the most effective way of reducing the complication. METHODS: The 120 cases (154 eyes) with primary angle-closure glaucoma or primary open-angle glaucoma were enrolled in this study. The patients were divided into three groups, group 1 (12 cases, 14 eyes) treated by deep sclecatony and group two (66 cases, 82 eyes) treated by trobeculecotomy and group three (42 cases, 58 eyes) treated by trobeculecotomy combining with scleral flaps tightly sutured with releasable sutures. RESULTS: The rate of shallow anterior chambers was following: group one 21.4%, group two 19.5%, group three 5.1%. The rate of this complication between group 1 and group 2 was not different in statistics (P > 0.05), but group 3 was significantly reduced in comparing with that of the other two groups (P < 0.05). CONCLUSION: The results indicate that this kind of suture may decrease the occurrence of the complication of shallow anterior chamber in filtration surgery and it is simple to operate and the curative result is reliable.

Adult↗
PubMed1999

[Complete nucleotide sequence of the nonstructural gene of alphavirus YN87448 strain isolated in China and its relationship to other Sindbis viruses].

OBJECTIVE: To determine the complete nucleotide sequence of the nonstructural gene of YN87448 virus stain which was firstly isolated from a female patient with fever in Yunnan Province in 1986, and identified as a member of Alphavirus by the serological method. METHODS: The complete nucleotide sequence of the nonstructural region gene of YN87448 virus strain was determined with nine clones, which were obtained by using reverse transcription and polymerase chain reaction (RT-PCR), and by linking nine overlapping fragments into pGEM-T vector respectively. RESULTS: The complete nucleotide sequence of nonstructural gene of YN87448 virus strain was 7,613 nucleotides long exclusive of the 5' cap, encoding four nonstructural proteins, nsP1, nsP2, nsP3, nsP4, and contained one initiator(ATG) and two stop codons (TGA). In comparison with the consensus sequence of S.A.AR86, the homogeneity of the nucleotide sequence between YN87448 virus strain and sindbis-like virus isolate S.A.AR86 was 98.8%. YN87448 virus strain can not produce a fatal disease in adult mice. In comparison with the consensus sequence of S.A.AR86, there is a 54 nucleotide insertion from 5,256 bp to 5,309 bp, 3 nucleotide (AGT) deletion at 5,603 bp in nsP3 region, and an opal termination codon between the nsP3 and the nsP4 genes in YN87448. virus strain. This sequence has been put into Gene Bank and No. is AF103734. CONCLUSION: YN87448 is a new sindbis-like virus strain.

Alphavirus↗
PubMed1999

[Characterization of HA1 genes of influenza A (H1N1) viruses isolated in Shenzhen City].

OBJECTIVE: To understand the molecular bases of intention of influenza virus activity and emergence of "O" phase of influenza A(H1N1) strains in human population in Shenzhen in recently years, and also the evolutionary characterization of influenza A(H1N1) HA1 gene. METHODS: Virion RNA was transcribed into cDNA by reverse transcriptase, cDNA was amplified by PCR, the products of PCR were purified. Afterward, RNA sequence analysis was performed by the dideoxynucleotide chain termination method using synthetic oligodeoxynucleotide primers. Finally, phylogenetic analysis of the sequencing data was performed with MegAlign (version 1.03) and Editseq (version 3.69) softwares. RESULTS: Since 1995, there were three different genetic lineages of influenza A(H1N1) virus HA1 gene cocirculating in men in Shenzhen city. Adding one and deleting one of potential glycosylation sites at 54 and 155 positions of amino acid sequences on HA1 protein domain of H1N1 viruses isolated recently was found as compared with those of A/Singapore/6/86(H1N1) virus. Meanwhile, there were some differences of amino acid sequences on HA1 protein molecules among H1N1 viruses tested and A/Singapore/6/86 (H1N1) virus. CONCLUSION: The intention of influenza A(H1N1) virus activity occurred since 1995 was due to emergence of substitution in amino acid sequences, especially the appearance of one addition and one deletion of potential glycosylation sites on their HA1 protein domains, and also was due to occurrence of influenza A(H1N1) virus with feature of "O" phase.

Amino Acid Sequence↗
PubMed1999

[An in vitro study of anti acidic etching effect of polypeptide-containing toothpaste on dental enamel]

OBJECTIVE:The present study was to investigate the anti-acidic etching effect of a kind of toothpaste containing biotin-polypeptide. METHODS:28 enamel slabs were treated with polypeptide-containing toothpaste in the pH-cycle environment,and then were analyzed by micro-hardness detector and polarized light microscope.RESULTS:The dental enamel treated with polypeptide-containing toothpaste was harder than the control group (P<0.0001);and the degree of demineralization in treated group was also less than the control one.CONCLUSION:There was certain acid resistant effect using the polypeptide containing toothpaste to treat the dental enamel.

Journal Article↗
PubMed1999

[Spectroscopic study of the 1pig Rydberg states of Na2].

Six highly excited 1pig states of the Na2 molecule have been investigated by optical-optical double resonance (OODR) flourescence excitation spectroscopy. Absolute vibrational numberings are determined and molecular constants and RKR potential curves are obtained. The lowest 10 1pig states have been relabeled according to the hydrogenic nllambda characters of the Rydberg orbital and classified into core-penetrating and core-nonpenetrating Rydberg states.

English Abstract↗
PubMed1999

[The application of ion detection in the study of spectroscopy of Na2].

Ion detection technique has been successfully used in the study of Rydberg states of Na2 by pulse optical-optical double resonance. High-lying Rydberg states near ionization limit have been observed and high sensitive and high gain spectra have been obtained. This technique is very useful for molecular spectroscopy.

English Abstract↗
PubMed1999

[Determination of rare-earth impurities in ultra-highly pure Er2O3 and Ho2O3 by [HEH(HEP)] extraction chromatography-atomic emission spectrometry].

This article applied [HEH(HEP)] (2-ethyhexyldrogen-2-ethylhexyl phosphonate) extraction chromatography to separate 14 rare earth impurities from ultra-highly pure Er2O3 and Ho2O3, and then the impurities were determined by atomic emission spectrometry. The average percentage recovery for each element is in the range of 70%-140%. The relative standard deviations of the determination are +/- 3.3%-2.2%. This method can be applied to the determination of the trace amounts of rare eath impurities in Er2O3 and Ho2O3 with a purity of 99.9999%-99.99999%.

English Abstract↗
PubMed1999

[The Raman spectra of monohydrate citric acid].

The Raman Spectra of monohydratecitric acid in different geometric arrangements have been reported in this paper. From the shift of some spectra, the anisotropic Raman scattering and depoearization effects, we can conclude that there exist hydrogen bonds in the crystal. Because of the effect of hydrogen bonds, electrical coupling between molecules causes the C-C, C-O bonds to possess some double bond character. On the other hand, the C=O bond possesses some single bond character.

Citric Acid↗
PubMed1999

[INDO/CI studies on the electronic spectra of tetraphenylporphyrin and its derivatives].

MNDO calculations and group theory were carried out on tetraphenylporphyrine (TPP) to obtain its optimum molecular geometry. We employed an INDO/CI method to study the electronic structures of tetraphenylporphyrine and its derivatives and identify their main electonic absorption bands. Five-orbital model was advanced to explain the typical characteristics of electronic spectra of H2TPP and its derivatives. The calculated wavelengths were in good agreement with the experimental values. The effects of the substitution of variant group were discussed and some helpful conclusions were drawn.

Models, Molecular↗
PubMed1999

[The Raman spectra of rubidium titanyl arsenate].

The Raman spectra of rubidium titanyl arsenate (RTA) single crystal with different geometric arrangements were obtained and compared with those of rubidium titanyl phosphate (RTP), potassium titanyl arsenate (KTA) and potassium titanyl phosphate (KTP) single crystals. The assignments of various vibration modes were made according to the experimental results. The strong Raman scattering intensity implies that RTA crystal possesses large nonlinear optical property and the strongest scattering is from the TiO6 octahedron. From the mode splitting of AsO4 tetrahedron, we conclude that the distortion of AsO4 in RTA is larger than that of PO4 in KTP.

English Abstract↗
PubMed1999

[Study on properties of fluorescence and room temperature phosphorescence of 2-bromomethyl naphthalene].

The properties of fluorescence and room temperature phosphorescense (RTP) of 2-Bromomethyl naphthalene (2-BrMN)were studied. The results show that the wavelength for maximum fluorescence of 2-BrMN is lambda(ex/lambda(em) = 274/334 nm. The fluorescence intersity is proportional to the concentration of 2BrMN in the range of 1.0 x 10(-6) - 1.2 x 10(-4) mol x L(-1), and the detection limit is 4.7 x 10(-8) mol x L(-1). The RTP signal of 2-BrMN was induced by beta-cyclodextrin (beta-(CD) in the presence of dibromopropane (DBP) acting as a heavy atom perturbation. The RTP intensity is linear for 2-BrMN/beta-CD/DBP systems of 2-BrMN concentration in the range of 1.0 x 10(-5) - 1.2 x 10(-4) mol x L(-1) (lambda(ex)/lambda(em) = 271/493,521 nm), and the detection limit is 2.7 x 10(-6) mol x L(-1).

English Abstract↗
PubMed1998

Interactions between beta2-adrenoreceptor agonist and NO donors in the relaxation of guinea pig trachea in vitro.

The effects of interaction between the beta2-adrenoreceptor agonist, salbutamol, and the nitric oxide donors, sodium nitroprusside and 3-morpholinosydnonimine (SIN-1), on guinea pig trachea contraction were studied. Cumulatively increased concentrations (0.1-10 nM) of salbutamol together with a single concentration of SNP (0.33 microM) or with SIN-1 (1 microM) showed significant (p < 0.001) synergy for the inhibition of 1 microM metacholine-induced contraction. Significant synergy (p < 0.05) was also found for the inhibition of this contraction by cumulatively increased concentrations (0.1-33 microM) of SNP and a single concentration (1 nM) of salbutamol. No synergistic effect was found on the 40 mM KC1-induced contraction. We suggest that the combination of NO donors with salbutamol has a synergistic effect on metacholine contraction.

Adrenergic beta-2 Receptor Agonists↗
PubMed1998

(R)-(-)- and (S)-(+)-Synadenol: synthesis, absolute configuration, and enantioselectivity of antiviral effect.

Synthesis of (R)-(-)- and (S)-(+)-synadenol (1a and 2a, 95-96% ee) is described. Racemic synadenol (1a + 2a) was deaminated with adenosine deaminase to give (R)-(-)-synadenol (1a) and (S)-(+)-hypoxanthine derivative 5. Acetylation of the latter compound gave acetate 6. Reaction with N, N-dimethylchloromethyleneammonium chloride led to 6-chloropurine derivative 7. Ammonolysis furnished (S)-(+)-synadenol (2a). Absolute configuration of 1a was established by two methods: (i) synthesis from (R)-methylenecyclopropanecarboxylic acid (8) and (ii) X-ray diffraction of a single crystal of (-)-synadenol hydrochloride. Racemic methylenecyclopropanecarboxylic acid (10) was resolved by a modification of the described procedure. The R-enantiomer 8 was converted to ethyl ester 13 which was brominated to give vicinal dibromides 14. Reduction with diisobutylaluminum hydride then furnished alcohol 15 which was acetylated to the corresponding acetate 16. Alkylation-elimination procedure of adenine with 16 yielded acetates 17 and 18. Deprotection with ammonia afforded a mixture of Z- and E-isomers 1a and 19 of the R-configuration. Comparison with products 1a and 2a by chiral HPLC established the R-configuration of (-)-synadenol (1a). These results were confirmed by X-ray diffraction of a single crystal of (-)-synadenol hydrochloride. The latter forms a pseudosymmetric dimer with adenine-adenine base pairing in the lattice with the nucleobase in an anti-like conformation. Enantiomers 1a and 2a exhibit varied enantioselectivity toward different viruses. Both enantiomers are equipotent against human cytomegalovirus (HCMV) and varicella zoster virus (VZV). The S-enantiomer 2a is somewhat more effective than R-enantiomer 1a in herpes simplex virus 1 and 2 (HSV-1 and HSV-2) assays. By contrast, enantioselectivity of antiviral effect is reversed in Epstein-Barr virus (EBV) and human immunodeficiency virus type 1 (HIV-1) assays where the R-enantiomer 1a is preferred. In these assays, the S-enantiomer 2a is less effective (EBV) or devoid of activity (HIV-1).

Adenine↗