Biomedical subjects

L Li

Publications and source records attributed to L Li.

At least 469 records · Page 26Linked to original sources

PubMed2001

[Study on the determination of photophysical parameters of the non-protected fluid room temperature phosphorescence by lifetime method].

The heavy atom pertuber (HAP) can promote the intersystem crossing and the rates of radiative and nonradiative processes of triplet state, thus shortens the phosphorescence lifetime. The determination of kinetic parameters for luminescence process is very importance to understand luminescence process and the mechanisms of the heavy atom effects. In this paper, 1-chloronaphthalene and 1-bromonaphthalene were selected as the modal compounds, the possibility of determination of photophysical parameters for emission of nonprotected fluid room temperature phosphorescence (NP-RTP) by RTP lifetime method was studied based on the definition on the phosphorescence lifetime and relation with the concentration of HAP. The results obtained by two ways prove that the RTP lifetime method can be used to determine photophysical parameters for RTP emission.

Fluorescent Dyes↗

PubMed2001

[Simultaneous determination of cobalt and nickel in catalyst by microwave digestion-dual wavelength equal absorption spectrophotometry].

Catalyst samples are digested in a microwave digestion system. The optimum parameters for microwave digestion are selected. Cobalt and nickel in the mixture of Co2+ and Ni2+ with 4-(2-pyridylazo) resorcinol (PAR) can be determined simultaneously by dual-wavelength equal absorption spectrophotometry. By means of the combination of two methods, Co2+ and Ni2+ in catalyst can be determined rapidly, accurately, and contamination problems avoided. The linear ranges are 0-30 micrograms.25 mL-1 for Co2+ and 0-25 micrograms.25 mL-1 for Ni2+. The recoveries of Co2+ and Ni2+ in synthetic samples are between 98.2%-103.6% and between 97.9%-103.7%, respectively. The relative standard deviations of analytical results in catalyst samples are less than 2.2% for Co2+ and less than 1.8% for Ni2+, and relative errors are less than +/- 2.5% for Co2+ and Ni2+.

Catalysis↗

PubMed2001

[Studies on non-protected fluid room temperature phosphorescence of phenanthrine].

A strong and stable room temperature phosphorescence (RTP) signal of phenanthrine aqueous solution in the absence of a protecting medium can be induced only by using Na2SO3 as deoxygenator and KI as heavy atom pertuber. The maximum phosphorescence intensity wavelengths are lambda ex/lambda em = 283/482,504 nm. It is also found that the kind and amount of organic solvent added to the luminescent system effects obviously the RTP properties. Under the present of 1% acetonitrile the RTP intensity is linear to phenanthrine concentration in the rage of 8.0 x 10(-7)-6.0 x 10(-6) mol.L-1 and 6.0 x 10(-6) mol.L(-1)-4.0 x 10(-5) mol.L-1, respectively. The detection limit is 2.6 x 10(-8) mol.L-1.

Acetonitriles↗

PubMed2001

[Determination of 10 elements in the 12 kinds of Chinese traditional medicines by AAS].

The 10 kinds of inorganic elements were determined in 12 kinds of Chinese traditional medicines. The relation showed that there were numerous inorganic elements in the traditional chinese medicines. The relation between these inorganic elements and the efficacies of these medicines was studied and the efficacies of these Chinese traditional medicines were discussed. The efficacies of these traditional medicines were greatly influenced by the content of inorganic elements. To guarantee the efficacies of these traditional medicines, the reasonable control lines concerned with the content of inorganic elements shall be established and the lines will be discussed in the future.

Calcium↗

PubMed2001

[Mössbauer spectroscopy and its application in the study of iron cation behavior in molten slags].

The principle, parameters and determination methods of Mössbauer spectroscopy are summarized. The iron cation behavior in molten slags is analyzed and Mössbauer spectra characteristics of Fe2+, Fetet3+ and Feoct3+ ions are detailed chemically and spetroscopically. The relationship between iron cation behavior and basicity, total iron, Na2O and Al2O3 addition in slags is also discussed here.

English Abstract↗

PubMed2001

[Study on the interaction between sparfloxacin and serum albumins by fluorescence].

The binding reaction between sparfloxacion (SPFX) and bovine serum albumin (BSA) or chicken egg albumin (CEA) in aqueous was studied using fluorescence and absorption spectra. Their binding constants are KCEA = 8.29 x 10(6) and KBSA = 4.41 x 10(7), and the binding sites are nCEA = 0.558, nBSA = 0.793 respectively. The action distances (RCEA = 1.99 nm, RBSA = 2.09 nm) and energy transfer efficiencies (ECEA = 0.766, EBSA = 0.714) between donor-acceptor and SPFX were obtained by Förster's nonradiative energy transfer mechanism. The experiment demonstrated that the higher the temperature is, the lower the slopes of quenching curves of BSA and CEA are in presence of different amounts of SPFX. It is confirmed that the combination for SPFX with BSA or CEA is a single static quenching process, their interaction may be interpreted with energy transfer mechanism. Through binding reaction of the two albumins with SPFX, the biological effects and action mechanism of SPFX with albumins in vivo were discussed.

Albumins↗

PubMed2001

[Determination of micro-elements in natural spirulina using FAAS].

The analytic results show that the spirulina powder have a plenty of microelements(K, Na, Ca, Mg, Fe, Zn). Compared with that of rice, wheat flour, maize and soybean, the content of K, Na, Ca, Mg, Fe and Zn of it is respectively as from 4 to 10 times, from 10 to 80 times, from 25 to 70 times, from 3 to 15 times, from 4 to 36 times and from 4 to 24 times as theirs. The content of microelements of it compared with vegetable is much higher. The spirulina has a certain inhibition from cancer, high blood pressure, sugar diabetes and hasten body to absorb Se and Mo, and is of benefit to cardiac muscle. The experimental result indicated that spirulina was good health care food with value of nourish and medicinal.

Bacterial Proteins↗

PubMed2001

[A comparison of lanthanum contained rinse on acid resistant abilities to human enamel and root surface].

OBJECTIVE: To compare the effect of different does of lanthanum-contained rinse solution on carious-resistance, and to investigate the acid-resistant abilities of dental enamel and root surface that treated with lanthanum-contained rinse solution. METHODS: Human dental root surfaces were treated in vitro with various doses (100 x 10(-6) - 2000 x 10(-6)) of lanthanum-contained rinse solution under the pH cycle environment that mimic the normal pH change curve of oral cavity. The qualitative and quantitative analysis was carried out on dental cementum according to their mineralized degrees. The best effective dose for carious-resistance was set for further investigation in vitro. Dental enamel and root surfaces were treated with the rinse for 1 hour each day, total for five days. RESULTS: The rinse solution containing 500 x 10(-6) lanthanum or more than it showed a obvious carious-resistant effect and there was no significant difference between root surfaces and dental enamel while treated with 500 x 10(-6) lanthanum-contained rinse solution. To compare demineralized degrees between enamel and root surfaces before or after treatment, enamel showed severer demineralization than root surfaces. CONCLUSION: 500 x 10(-6) lanthanum-contained rinse solution is considered to be the lowest effective dose for carious-resistance, and lanthanum-contained rinse solution is especially suitable for the treatment and prevention of dental root caries.

English Abstract↗

PubMed2001

[Clinical analysis of 149 cases of aldosterone-producing adrenal cortical neoplasms].

OBJECTIVE: To evaluate the diagnosis and treatment of aldosterone-producing adrenal cortical neoplasms. METHODS: From 1978 to February 2001, 149 patients with aldosterone-producing adrenal cortical neoplasms were diagnosed and treated. Of these patients, 148 had adrenal adenoma and 1 had adrenal cortical carcinoma. The diagnosis was all confirmed by surgery and pathological studies. RESULTS: The diagnostic specificity of retroperitoneal pneumography, B-ultrasonography and CT scan are 39%, 67% and 95.3% respectively. It was found that there were significant differences of diagnostic specificity between retroperitoneal pneumography and B-ultrasonography, CT scan (chi2 = 23.89, P < 0.05) and there were significant differences between B-ultrasonography and CT scan (chi2 = 32.10, P < 0.05). In all the patients, serum potassium level elevated to normal range within 1 month postoperatively. In 110 cases out of 149, the blood pressure dropped to normal range within two months after surgery. CONCLUSIONS: Appropriate treatment depends on correct qualitative diagnosis and localization of the causative lesion. B-ultrasonography and CT scan play an important role in diagnosis. Surgery is the major treatment, including laparoscopic adrenalectomy. Factors affecting the therapeutic outcome are aging systemic vascular sclerosis and long duration of the disease.

Adrenal Cortex Neoplasms↗

PubMed2001

[A multicenter study of efficacy and safety of oseltamivir in treatment of naturally acquired influenza].

OBJECTIVE: To evaluate the efficacy and safety of oseltamivir in the treatment of naturally acquired influenza in China. METHODS: A randomized, double-blinded, placebo controlled trial of oseltamivir was conducted in China. Individuals of 18 to 65 years were enrolled presenting within 36 hours of influenzal symptoms and elevated temperature of 37.8 or higher. They should have at least two of the following symptoms: nasal congestion, sore throat, cough, myalgia, fatigue, headache, chill and sweating) during an influenza outbreak in the community. Individuals were randomized either to oseltamivir group (75 mg twice daily for 5 days) or placebo group. RESULTS: A total of 478 individuals were recruited, 16(3.35%) failed to follow up or refused to continue the trial, 3 (0.6%) were excluded immediately before taking medication because they did not meet the entry criteria and 8 (1.7%) individuals were excluded in the blinding review meeting because of protocol violation. Altogether 451 individuals were analyzed for efficacy as intent-to-treat population (ITT) (216 oseltamivir, 235 placebo) and 273 individuals were identified as influenza-infected through laboratory test; they were defined as intent-to-treat infected population (ITTI) (134 oseltamivir, 139 placebo). For safety analysis, 459 individuals were included. In ITTI population, the cumulative alleviation proportion in oseltamivir group was significantly higher than that of placebo group (P = 0.046 6). The median duration of illness was 91.6 hours [95% confident interval (CI) 80.2 - 101.3 hours] in oseltamivir group and 95.0 hours (95% CI 84.5 - 105.3 hours) in placebo group. The median area under the curve (AUC) of decreased total score was significantly higher in oseltamivir group than in placebo group, being 1 382.9 and 1 236.7 score-hours respectively (P = 0.019 6). The median duration of fever and myalgia were 27.9 and 35.5 hours in oseltamivir group, being significantly shorter than that of 51.5 and 36.0 hours in placebo group (P = 0.000 1 and 0.036 1). The median AUC of decreased score for fever and nasal symptom was 337.9 and 108.5 in oseltamivir group, being significantly higher than that of 311.3 and 43.3 in placebo group (P = 0.011 8 and 0.040 3). The proportion of subjects reporting fever in oseltamivir group were significantly lower than that in placebo group at 36, 60, 72, 96, 120 and 132 hours after the initiation of treatment (P = 0.049, 0.001, 0.001, 0.007, 0.007 and 0.030). The amount of paracetamol taken, incidence of secondary complications and antibiotics usage associated with secondary complications were similar in the two groups (P = 0.085 1, 0.944, 1.000). For ITT population, similar results were seen. Adverse events reported were similar in oseltamivir and placebo group. The main adverse events were gastrointestinal symptoms, headache, vertigo, and rashes. CONCLUSION: Oseltamivir was effective and well tolerated in the treatment of early naturally acquired influenza.

Acetamides↗

PubMed2000

A stabilized molten globule protein.

A predominant conformational isomer of non-native alpha-lactalbumin (alpha-LA) has been purified by thermal denaturation of the native alpha-LA using the technique of disulfide scrambling. This unique isomer retains a substantial content of alpha-helical structure. It is stabilized by two native disulfide bonds within the alpha-helical domain and two scrambled non-native disulfide bonds at the beta-sheet domain. This denatured isomer of alpha-LA exhibits structural characteristics that are consistent with the well-documented molten globule state. The ability to prepare a stabilized and structurally defined molten globule provides a useful model for studying the folding and unfolding pathways of proteins.

Circular Dichroism↗

PubMed2000

Neoplastic transformation and tumorigenesis associated with sam68 protein deficiency in cultured murine fibroblasts.

Sam68 is a multimeric 68-kDa RNA-binding nuclear protein of unknown function that interacts with, and is tyrosine-phosphorylated by, the oncogenic protein Src during mitosis. Random homozygous knock-out (RHKO) is a retroviral-based antisense RNA strategy that can identify chromosomal genes whose functional disablement leads to reversible tumorigenic capabilities. Here we report that RHKO-induced Sam68 deficiency results in neoplastic transformation of murine NIH3T3 fibroblasts. Whereas simple haploinsufficiency of Sam68 produced by insertion mutagenesis in a single chromosomal allele did not detectably affect cell growth, reduction of Sam68 protein to <25% of the wild type level was associated with anchorage-independent growth, defective contact inhibition, and the ability to form metastatic tumors in nude mice. These properties were reversed by cessation of RHKO inactivation. Our findings, which indicate that the Sam68 protein level can prominently affect cell proliferation, implicate Sam68 function in tumorigenesis. Consistent with these results is evidence that cells undergoing mitosis show a dramatic reduction in the level of Sam68 protein.

3T3 Cells↗

PubMed2000

Expression, purification and characterization of beta domain and beta domain dimer of metallothionein.

In order to examine the independent self-assembly of the beta fragment of metallothionein and the interaction between two domains with the linker sequence, Lys-Lys-Ser, the chemically synthesized genes of the beta domain and its dimer (beta-KKS-beta) were cloned into vector pGEX-4T-1 and expressed as carboxyl terminal extension of glutathione-S-transferase (GST). After the GST fusion proteins had been digested with thrombin on a glutathione-Sepharose 4B affinity chromatography column, the beta domain and its dimer were purified with gel filtration and analyzed for their biochemical and spectroscopic properties. Amino acid composition and molecular mass are determined to be consistent with the expected value. The analysis of metal content shows that the beta domain and its dimer can bind with about 3eq and 6eq divalent metals, respectively. The characteristic peak presented around 254 nm in the UV and CD spectrum indicated that both the beta domain and its dimer are able to form the cadmium-thiolate clusters without the aid of the alpha domain. Furthermore, the absorption peak of the beta domain dimer is much higher than that of the beta domain, which suggested that there is an interaction between two beta domains. Finally, the metal-binding ability was determined by DTNB competitive reaction and the value of half dissociation pH, the results reveal that the beta domain dimer has stronger metal-binding ability than the single beta domain, which provides further evidence of the interaction between the two domains.

Base Sequence↗

PubMed2000

The structure of denatured alpha-lactalbumin elucidated by the technique of disulfide scrambling: fractionation of conformational isomers of alpha-lactalbumin.

The structure of denatured alpha-lactalbumin (alpha-LA) has been characterized using the method of disulfide scrambling. Under denaturing conditions (urea, guanidine hydrochloride, guanidine thiocyanate, organic solvent or elevated temperature) and in the presence of thiol initiator, alpha-LA denatures by shuffling its four native disulfide bonds and converts to a mixture of fully oxidized scrambled structures. Analysis by reversed-phase HPLC reveals that the denatured alpha-LA comprises a minimum of 45 fractions of scrambled isomers. Among them, six well populated isomers have been isolated and structurally characterized. Their relative concentrations, which represent the fingerprinting of the denatured alpha-LA, vary substantially under different denaturing conditions. These results permit independent plotting of the denaturation and unfolding curves of alpha-LA. Most importantly, unique isomers of partially unfolded alpha-LA were shown to populate at mild and selected denaturing conditions. Organic solvent disrupts preferentially the hydrophobic alpha-helical domain, generating a predominant isomer containing two native disulfide bonds at the beta-sheet domain and two scrambled disulfide bonds at the alpha-helical region. Thermal denaturation selectively unfolds the beta-sheet domain of alpha-LA, producing a prevalent isomer that exhibits structural characteristics of the molten globule state of alpha-LA.

Acetonitriles↗

PubMed2000

kappa-Opioid receptor potentiates apoptosis via a phospholipase C pathway in the CNE2 human epithelial tumor cell line.

The mechanism by which kappa-opioid receptor (kappaor) modulated apoptosis was investigated in CNE2 human epithelial tumor cells. Induction of these cells to undergo apoptosis with staurosporine was associated with a massive increase in intracellular cAMP level. The inhibition of the increase in cAMP partially inhibited apoptosis as evidenced by a reduction of PARP and caspase-3 cleavage. Accordingly, a low but significant level of apoptosis is induced in these cells by the elevation of cAMP through the addition of forskolin and isobutylmethylxanthine. The existence of a cAMP-dependent and a cAMP-independent apoptotic pathway is therefore suggested. Receptor binding studies, RT-PCR experiments and Western blot analysis demonstrated the presence of type 1 kappaor in the CNE2 cells. Stimulation of kappaor in these cells resulted in the production of inositol (1,4,5)-trisphosphate, reduction of cAMP level and a marked enhancement of staurosporine-induced apoptosis. The potentiation of apoptosis by kappaor was prevented by inhibition of phospholipase C but was slightly enhanced by the presence of the active cAMP analogues, 8-CPT-cAMP and dibutyryl-cAMP. These data demonstrate for the first time that the phospholipase C pathway activated by type 1 kappaor expressed by cancer cells is involved in the potentiation of apoptosis.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed2000

Hrs interacts with sorting nexin 1 and regulates degradation of epidermal growth factor receptor.

Hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs) is a mammalian homologue of yeast vacuolar protein sorting (Vps) protein Vps27p; however, the role of Hrs in lysosomal trafficking is unclear. Here, we report that Hrs interacts with sorting nexin 1 (SNX1), a recently identified mammalian homologue of yeast Vps5p that recognizes the lysosomal targeting code of epidermal growth factor receptor (EGFR) and participates in lysosomal trafficking of the receptor. Biochemical analyses demonstrate that Hrs and SNX1 are ubiquitous proteins that exist in both cytosolic and membrane-associated pools, and that the association of Hrs and SNX occurs on cellular membranes but not in the cytosol. Furthermore, endogenous SNX1 and Hrs form a approximately 550-kDa complex that excludes EGFR. Immunofluorescence and subcellular fractionation studies show that Hrs and SNX1 colocalize on early endosomes. By using deletion analysis, we have mapped the binding domains of Hrs and SNX1 that mediate their association. Overexpression of Hrs or its SNX1-binding domain inhibits ligand-induced degradation of EGFR, but does not affect either constitutive or ligand-induced receptor-mediated endocytosis. These results suggest that Hrs may regulate lysosomal trafficking through its interaction with SNX1.

Amino Acid Sequence↗

PubMed2000

Differential processing of UV mimetic and interstrand crosslink damage by XPF cell extracts.

We have recently developed a mammalian cell free assay in which interstrand crosslinks induce DNA synthesis in both damaged and undamaged plasmids co-incubated in the same extract. We have also shown using hamster mutants that both ERCC1 and XPF are required for the observed incorporation. Here, we show that extracts from an XPF patient cell line differentially process UV mimetic damage and interstrand crosslinks in vitro. XPF extracts are highly defective in the stimulation of repair synthesis by N:-acetoxy-N:- acetylaminofluorene, but are proficient in the stimulation of DNA synthesis by psoralen interstrand crosslinks. In addition, we show that extracts from the hamster UV140 mutant, which has high UV sensitivity, but moderate mitomycin C sensitivity, are similar in both assays to XPF cell extracts. These findings support the hypothesis that the activities of XPF in nucleotide excision repair (NER) and crosslink repair are separable, and that mutations in XPF patients result in the abolition of NER, but not recombinational repair pathways, which are likely to be essential as has been observed in ERCC1 homozygous -/- mice.

Animals↗

PubMed2000

A major kinetic trap for the oxidative folding of human epidermal growth factor.

The folding pathway of human epidermal growth factor (EGF) has been characterized by structural and kinetic analysis of the acid-trapped folding intermediates. Oxidative folding of the fully reduced EGF proceeds through 1-disulfide intermediates and accumulates rapidly as a single stable 2-disulfide intermediate (designated as EGF-II), which represents up to more than 85% of the total protein along the folding pathway. Among the five 1-disulfide intermediates that have been structurally characterized, only one is native, and nearly all of them are bridges by neighboring cysteines. Extensive accumulation of EGF-II indicates that it accounts for the major kinetic trap of EGF folding. EGF-II contains two of the three native disulfide bonds of EGF, Cys(14)-Cys(31) and Cys(33)-Cys(42). However, formation of the third native disulfide (Cys(6)-Cys(20)) for EGF-II is slow and does not occur directly. Kinetic analysis reveals that an important route for EGF-II to reach the native structure is via rearrangement pathway through 3-disulfide scrambled isomers. The pathway of EGF-II to attain the native structure differs from that of three major 2-disulfide intermediates of bovine pancreatic trypsin inhibitor (BPTI). The dissimilarities of folding mechanism(s) between EGF, BPTI, and hirudin are discussed in this paper.

Amino Acid Sequence↗