Biomedical subjects

Chun Liu

Publications and source records attributed to Chun Liu.

At least 19 recordsLinked to original sources

PubMed2026

Development and identification of KASP-SNP markers correlated with Aeromonas hydrophila resistance traits in blunt snout bream (Megalobrama amblycephala).

The blunt snout bream (Megalobrama amblycephala) is an economically important freshwater fish species. However, it is highly susceptible to Aeromonas hydrophila infection, especially in intensive pond aquaculture in China. Molecular marker-assisted selection provides an efficient approach for breeding disease-resistant varieties; however, the key genes or molecular markers linked to A. hydrophila resistance remain scarce in this species. A 436 differential SNP sites with disease-resistant were screened on basis of whole-genome resequencing. Then, a high-throughput genomic KASP genotyping technique was utilized to discover favorable genes and SNP sites associated with A. hydrophila resistance. A total of 46 KASP markers were successfully developed with an accuracy of 92 %. These markers were used to genotyping 120 blunt snout bream individuals. Through trait correlation analysis and general linear models (GLM), five SNPs significantly (P < 0.05) associated with resistance to A. hydrophila were identified and mapped to five candidate genes (btnl2, cfhr2, slc47a1, neu3, nlrp1). Survival rate of individuals carrying the dominant genotype demonstrated an average survival rate of 81.39 %, which represents a 69.35 % increase in comparison with that of 48 % in total population. This effect was validated in an external population of 100 fish. These findings identify key genetic markers associated with A. hydrophila resistance and provide a direction for elucidating the underlying molecular immune mechanisms, thus establishing a genetic foundation for future breeding strategies.

Cyprinidae↗

PubMed2006

Lack of involvement of the autonomic nervous system in early ventilatory and pulmonary vascular acclimatization to hypoxia in humans.

The activity within the autonomic nervous system may be altered following sustained exposure to hypoxia, and it is possible that this increase in activity underlies the early acclimatization of both ventilation and the pulmonary vasculature to hypoxia. To test this hypothesis, seven individuals were infused with the ganglionic blocker trimetaphan before and after an 8 h exposure to hypoxia. The short half-life of trimetaphan should ensure that the initial infusion does not affect acclimatization to the 8 h hypoxia exposure, and the use of a ganglion blocking agent should inhibit activity within all branches of the autonomic nervous system. During the infusions of trimetaphan, measurements of ventilation and echocardiographic assessments of pulmonary vascular tone (DeltaPmax) were made during euoxia and during a short period of isocapnic hypoxia. Subjects were also studied on two control days, when a saline infusion was substituted for trimetaphan. Trimetaphan had no effect on either euoxic ventilation or the sensitivity of ventilation to acute hypoxia. Trimetaphan significantly reduced DeltaPmax in euoxia (P<0.05), but had no significant effect on the sensitivity of DeltaPmax to acute hypoxia once changes in cardiac output had been controlled for. The 8 h period of hypoxia elevated euoxic ventilation (P<0.001) and DeltaPmax (P<0.001) and increased their sensitivities to acute hypoxia (P<0.001 for both), indicating that significant acclimatization had occurred. Trimetaphan had no effect on the acclimatization response of any of these variables. We conclude that altered autonomic activity following 8 h of hypoxia does not underlie the acclimatization observed in ventilation or pulmonary vascular tone.

Acclimatization↗

PubMed2006

Study on the inclusion interaction of p-sulfonated calix[n]arenes with Vitamin K3 using methylene blue as a spectral probe.

The characteristics of host-guest complexation between p-sulfonated calix[n]arene (SCnA, n = 4, 6) and Vitamin K(3) (VK(3)) were investigated by fluorescence spectrometry and absorption spectrometry using methylene blue (MB) as a probe. Interaction with MB and SCnA led to an obvious decrease in fluorescence intensity of MB, accompanying with shifts of emission peaks. Absorption peaks also showed interesting changes; however, when VK(3) was added, fluorescence intensity and absorbance recovered and a slight and slow red shift was observed. The obtained results showed that the inclusion ability of p-sulphonated calix[n]arenes towards VK(3) was the order: p-sulphonated calix[6]arene (SC6A) >p-sulphonated calix[4]arene (SC4A). Relative mechanism was proposed to explain the inclusion process.

Binding, Competitive↗

PubMed2006

Study on the fluorescence behavior of p-sulfonated calix[4,6]arene in cationic surfactant cetyltrimethylammonium bromide solution and its analytical application.

The fluorescence properties of p-sulfonated calix[4,6]arene (SCnA, n=4, 6) in cationic surfactant cetyltrimethylammonium bromide (CTAB) solution were investigated. It was found that the fluorescence intensity of SCnA could be enhanced markedly by an appropriate amount of CTAB. The results indicate the formation of complex between CTAB and SCnA at a 1:1 complex stoichiometry and their association constants were calculated by applying a deduced equation. Based on the obtained results, a new fluorimetric method has been developed for rapid determination of SCnA with a good linearity in the concentration range of 2x10(-7) to 7x10(-6)mol L-1.

Buffers↗

PubMed2006

Identification and characterization of piggyBac-like elements in the genome of domesticated silkworm, Bombyx mori.

piggyBac is a short inverted terminal repeat (ITR) transposable element originally discovered in Trichoplusia ni. It is currently the preferred vector of choice for enhancer trapping, gene discovery and identifying gene function in insects and mammals. Many piggyBac-like sequences have been found in the genomes of phylogenetically species from fungi to mammals. We have identified 98 piggyBac-like sequences (BmPBLE1-98) from the genome data of domesticated silkworm (Bombyx mori) and 17 fragments from expressed sequence tags (ESTs). Most of the BmPBLE1-98 probably exist as fossils. A total of 21 BmPBLEs are flanked by ITRs and TTAA host dinucleotides, of which 5 contain a single ORF, implying that they may still be active. Interestingly, 16 BmPBLEs have CAC/GTG not CCC/GGG as the characteristic residues of ITRs, which is a surprising phenomenon first observed in the piggyBac families. Phylogenetic analysis indicates that many BmPBLEs have a close relation to mammals, especially to Homo sapiens, only a few being grouped with the T. ni piggyBac element. In addition, horizontal transfer was probably involved in the evolution of the piggyBac-like elements between B. mori and Daphnia pulicaria. The analysis of the BmPBLEs will contribute to our understanding of the characteristic of the piggyBac family and application of piggyBac in a wide range of insect species.

Amino Acid Sequence↗

PubMed2006

The biochemical characterization of ferret carotene-9',10'-monooxygenase catalyzing cleavage of carotenoids in vitro and in vivo.

Previous studies have shown that beta-carotene 15,15'-monooxygenase catalyzes the cleavage of beta-carotene at the central carbon 15,15'-double bond but cleaves lycopene with much lower activity. However, expressing the mouse carotene 9',10'-monooxygenase (CMO2) in beta-carotene/lycopene-synthesizing and -accumulating Escherichia coli strains leads to both a color shift and formation of apo-10'-carotenoids, suggesting the oxidative cleavage of both carotenoids at their 9',10'-double bond. Here we provide information on the biochemical characterization of CMO2 of the ferret, a model for human carotenoid metabolism, in terms of the kinetic analysis of beta-carotene/lycopene cleavage into beta-apo-10'-carotenal/apo-10'-lycopenal in vitro and the formation of apo-10'-lycopenoids in ferrets in vivo. We demonstrate that the recombinant ferret CMO2 catalyzes the excentric cleavage of both all-trans-beta-carotene and the 5-cis- and 13-cis-isomers of lycopene at the 9',10'-double bond but not all-trans-lycopene. The cleavage activity of ferret CMO2 was higher toward lycopene cis-isomers as compared with beta-carotene as substrate. Iron was an essential co-factor for the reaction. Furthermore, all-trans-lycopene supplementation in ferrets resulted in significant accumulation of cis-isomers of lycopene and the formation of apo-10'-lycopenol, as well as up-regulation of the CMO2 expression in lung tissues. In addition, in vitro incubation of apo-10'-lycopenal with the post-nuclear fraction of hepatic homogenates of ferrets resulted in the production of both apo-10'-lycopenoic acid and apo-10'-lycopenol, respectively, depending upon the presence of NAD+ or NADH as cofactors. Our finding of bioconversion of cis-isomers of lycopene into apo-10'-lycopenoids by CMO2 is significant because cis-isomers of lycopene are a predominant form of lycopene in mammalian tissues and apo-lycopenoids may have specific biological activities related to human health.

Amino Acid Sequence↗

PubMed2006

Structure and function of glucose-6-phosphate dehydrogenase-deficient variants in Chinese population.

A systematic study on the structure and function of Glucose-6-phosphate dehydrogenase (G6PD) variations was carried out in China. A total of 155,879 participants were screened for G6PD deficiency by the G6PD/6PGD ratio method and 6,683 cases have been found. The prevalence of G6PD deficiency ranged from 0 to 17.4%. With informed consent, 1,004 cases from 11 ethnic-based groups were subjected to molecular analysis. Our results showed the followings: (1) The G6PD variants are consistent across traditional ethnic boundaries, but vary in frequencies across ethnic-based groups in Chinese population, (2) The G6PD variants in Chinese population are different from those in African, European, and Indian populations, (3) A novel G6PD-deficiency mutation, 274C-->T, has been found, and (4) Denaturing high performance liquid chromatography is of great advantage to detecting G6PD-deficient mutations for diagnosis and genetic counseling. Moreover, functional analysis of the human G6PD variants showed the following: (1) The charge property, polarity, pK-radical and side-chain radical of the substituting amino acid have an effect on G6PD activity, (2) The G6PDArg459 and Arg463 play important roles in anchoring NADP+ to the catalytic domain to maintain the enzymatic activity, and (3) The sequence from codon 459 to the carboxyl terminal is essential for the enzymatic function.

Amino Acid Substitution↗

PubMed2006

Induction of pulmonary neoplasia in the smoke-exposed ferret by 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK): a model for human lung cancer.

Research into dietary chemoprevention against lung carcinogenesis has been limited by the lack of appropriate animal models that closely mimic smoking-related human lung cancer. Ferrets (Mustela putorius furo) have been used to study the biologic activities of carotenoids against smoke-induced lung lesions, but this model has yet to be thoroughly established and validated. To determine the appropriateness of the ferret as a model for human lung cancer, we have performed a 6-month in vivo study in ferrets exposed to both tobacco smoke and a carcinogen (4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone, NNK) found in cigarette smoke. Results showed that six out 12 ferrets exposed to both NNK injection and cigarette smoke developed grossly identifiable lung tumors whereas none of nine ferrets from the sham treatment group developed any lung lesions. The histopathological types of these tumors (squamous cell carcinoma, adenosquamous carcinoma and adenocarcinoma) in ferret lungs are very similar to those in humans. In addition, 10 out of 12 ferrets exposed to both NNK and cigarette smoke developed preneoplastic lesions (squamous metaplasia, dysplasia, and atypical adenomatous hyperplasia) with complex growth patterns whereas the sham group did not show any of these lesions. Furthermore, the expression of proliferating cellular nuclear antigen increased markedly in both gross tumors and preneoplastic lesions in the lungs. In summary, the development of both preneoplastic lesions and gross lung tumors in ferrets provides an excellent and unique model for studying lung cancer chemoprevention with agents such as carotenoids, and for studying the molecular mechanism of carcinogenesis in the earlier stages of smoke-related lung cancer.

Adenocarcinoma↗

PubMed2006

Structures, regulatory regions, and inductive expression patterns of antimicrobial peptide genes in the silkworm Bombyx mori.

Antimicrobial peptides (AMPs) are a group of immune proteins that protect the host from infection. In Drosophila, seven groups of inducible AMPs have been identified, with activities against fungi and gram-positive and gram-negative bacteria. On the basis of the silkworm genome sequence and expressed sequence tags, we identified 35 AMP genes, mostly belonging to the cecropin, moricin, and gloverin gene families. We predicted the core promoters required for gene transcription and the cis-regulatory elements for NF-kappaB/Rel and GATA transcription factors. The expression profiles of these genes after an immune challenge with lipopolysaccharide were examined by reverse transcription PCR. Members of the cecropin B and gloverin A subfamilies were intensely expressed in the fat body after induction. In contrast, those of the moricin B subfamily were not expressed under the same conditions. Such results suggest that these regulatory elements and their positions in the upstream regions play an important role in regulating the transcription of these defense genes.

Amino Acid Sequence↗

PubMed2006

Combined antioxidant (beta-carotene, alpha-tocopherol and ascorbic acid) supplementation increases the levels of lung retinoic acid and inhibits the activation of mitogen-activated protein kinase in the ferret lung cancer model.

Interactions among beta-carotene (BC), alpha-tocopherol (AT) and ascorbic acid (AA) led to the hypothesis that using a combination of these antioxidants could be more beneficial than using a single antioxidant alone, particularly against smoke-related lung cancer. In this investigation, we have conducted an animal study to determine whether combined BC, AT and AA supplementation (AOX) protects against 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung carcinogenesis in smoke-exposed (SM) ferrets. Ferrets were treated for 6 months in the following four groups: (i) control, (ii) SM + NNK, (iii) AOX and (iv) SM + NNK + AOX. Results showed that the combined AOX supplementation (i) prevented the SM + NNK-decreased lung concentrations of retinoic acid (RA) and BC; (ii) inhibited the SM + NNK-induced phosphorylation of Jun N-terminal kinase (JNK), extracellular-signal-regulated protein kinase (ERK) and proliferating cellular nuclear antigen proteins in the lungs of ferrets; and (iii) blocked the SM + NNK-induced up-regulation of total p53 and Bax proteins, as well as phosphorylated p53 in the lungs of ferrets. In addition, there were no lesions observed in the lung tissue of ferrets in the control and/or the AOX groups after 6 months of intervention, but combined AOX supplementation resulted in a trend toward lower incidence of both preneoplastic lung lesions and lung tumor formation in SM + NNK + AOX group of ferrets, as compared with the SM + NNK group alone. These data indicate that combined AOX supplementation could be a useful chemopreventive strategy against lung carcinogenesis through maintaining normal tissue levels of RA and inhibiting the activation of mitogen-activated protein kinase pathways, cell proliferation and phosphorylation of p53.

Animals↗

PubMed2006

Study on the inclusion behavior of p-sulphonatocalix[4]arene with 9-amino-acridine by spectrofluorometric titrations.

Spectrofluorometric titrations have been performed to investigate the inclusion behavior of p-sulphonatocalix[4]arene (SC4A) and 9-amino-acridine (AA) in citrate buffer solution (pH 5.92). It was found that the fluorescence intensity of AA quenched regularly upon the addition of SC4A. The proposed interaction mechanism between SC4A and AA indicates that AA partially goes into the cavity of SC4A with the help of strong electrostatic interaction and hydrogen bonding, which formed by the protonated N atom and the amino groups of AA bonding with sulphonyl groups of SC4A, respectively. The inclusion ratio was 1:1 and the inclusion constant was 1.84 x 10(5) L mol(-1) at 25.0 degrees C.

Aminacrine↗

PubMed2006

Lycopene supplementation prevents smoke-induced changes in p53, p53 phosphorylation, cell proliferation, and apoptosis in the gastric mucosa of ferrets.

Cigarette smoking increases the risk for gastric cancer. Higher intakes or blood levels of lycopene are associated with a decreased risk of gastric cancer. However, the biological mechanisms by which lycopene may protect against gastric carcinogenesis are poorly understood. We evaluated the effects of lycopene supplementation on smoke-induced changes in protein levels of p53, p53 target genes (p21(Waf1/Cip1) and Bax-1), cell proliferation, and apoptosis in the gastric mucosa of ferrets. Ferrets were assigned to cigarette smoke exposure or to no exposure and to no, low-dose, or high-dose lycopene supplementation (2 x 3 factorial design) for 9 wk. Lycopene concentrations were significantly elevated in a dose-dependent manner in the gastric mucosa of ferrets supplemented with lycopene alone, but were markedly reduced in ferrets supplemented with lycopene and exposed to smoke. Although ferrets were given lycopene containing 95% all-trans isomers, cis isomers were the predominant forms in the gastric mucosa. Total p53 and phosphorylated p53 levels were greater in ferrets exposed to smoke alone than in all other groups. Levels were approximately 300 and 500% of the controls, respectively. However, smoke-elevated total p53 and phosphorylated p53 were markedly attenuated by both doses of lycopene. p21(Waf1/Cip1), Bax-1, and cleaved caspase 3 were substantially decreased, whereas cyclin D1 and proliferating cellular nuclear antigen (PCNA) were increased in ferrets exposed to smoke alone. Lycopene prevented smoke-induced changes in p21(Waf1/Cip1), Bax-1, cleaved caspase 3, cyclin D1, and PCNA in a dose-dependent fashion. These data indicate that lycopene may prevent smoke exposure-induced changes in p53, p53 phosphorylation, p53 target genes, cell proliferation, and apoptosis in the gastric mucosa of ferrets.

Animals↗

PubMed2006

Mutation of von Hippel-Lindau tumour suppressor and human cardiopulmonary physiology.

BACKGROUND: The von Hippel-Lindau tumour suppressor protein-hypoxia-inducible factor (VHL-HIF) pathway has attracted widespread medical interest as a transcriptional system controlling cellular responses to hypoxia, yet insights into its role in systemic human physiology remain limited. Chuvash polycythaemia has recently been defined as a new form of VHL-associated disease, distinct from the classical VHL-associated inherited cancer syndrome, in which germline homozygosity for a hypomorphic VHL allele causes a generalised abnormality in VHL-HIF signalling. Affected individuals thus provide a unique opportunity to explore the integrative physiology of this signalling pathway. This study investigated patients with Chuvash polycythaemia in order to analyse the role of the VHL-HIF pathway in systemic human cardiopulmonary physiology. METHODS AND FINDINGS: Twelve participants, three with Chuvash polycythaemia and nine controls, were studied at baseline and during hypoxia. Participants breathed through a mouthpiece, and pulmonary ventilation was measured while pulmonary vascular tone was assessed echocardiographically. Individuals with Chuvash polycythaemia were found to have striking abnormalities in respiratory and pulmonary vascular regulation. Basal ventilation and pulmonary vascular tone were elevated, and ventilatory, pulmonary vasoconstrictive, and heart rate responses to acute hypoxia were greatly increased. CONCLUSIONS: The features observed in this small group of patients with Chuvash polycythaemia are highly characteristic of those associated with acclimatisation to the hypoxia of high altitude. More generally, the phenotype associated with Chuvash polycythaemia demonstrates that VHL plays a major role in the underlying calibration and homeostasis of the respiratory and cardiovascular systems, most likely through its central role in the regulation of HIF.

Adaptation, Physiological↗

PubMed2006

[Characteristics of atrazine-degrading genetically engineered microorganism (GEM) labeled with green fluorescent protein (GFP)].

The atrazine-degrading genetically engineered microorganism (GEM) was labeled by transforming a plasmid containing green fluorescent protein (GFP) gene. GFP gene could be expressed well in the cell of GEM after transforming. In the LB medium containing antibiotic, the expressing level of GFP was higher than in pure LB medium and in the basic medium. In the stable phase containing antibiotic, the expressing level of GFP was higher than in pure LB medium and in the basic medium. In the stable phase of cell growth, the expressing level of GFP was higher than in the lag phase and in the logarithmic phase. The transformation and expression of GFP gene wouldn't affect the degrading ability of GEM. The level of GFP expression was almost linear with the degrading activity. There exist two states of cells after inoculating GEM labeled with GFP into activated sludge: suspended state and adhered state to sludge floc, and the amount of suspended cells is higher than that adhered to sludge floc.

Atrazine↗

PubMed2006

[Study on the inclusion behavior of p-sulphonatocalix[4]arene with acridine by spectrofluorometric titrations].

p-sulphonatocalix[4] arene (1) was prepared according to the literature, and spectrofluorometric titrations were performed to investigate the inclusion behavior of (1) and acridine in citrate buffer solution (pH 5.92, 0.1 mol x L(-1)) at different temperatures. It was found that in definite concentration range, the emission peak of acridine exhibited a slight red shift and th fluorescence intensity decreased when (1) was added. They form stable host-guest complex, and the stoichiometry of the inclusion complex is 1 : 1. The stability constants of the inclusion complex at 15.0 degrees C, 20.0, 25.0 and 30.0 degrees C were determined as 3.08 x 10(5), 4.45 x 10(4), 2.58 x 10(4) and 8.90 x 10(3), respectively. The thermodynamic parameters of inclusion process, deltaG, deltaH and deltaS, were determined. The experimental results indicated that the inclusion process was an exothermic and enthalpy-driven process. It was found that the stability constants descended when temperature rose. The most probable pattern of the inclusion complex between (1) and acridine was proposed as: acridine partially goes into the cavity of (1), and the protonated N atom and the negatively charged sulphonyl group bond firmly owing to strong electrostatic interaction. With the main contribution of electrostatic interaction and the assistance of Van de Waals and hydrophobic interaction, the host and the guest molecules form 1 : 1 supramolecular complex.

English Abstract↗

PubMed2005

Spectrofluorimetric study on the inclusion interaction between lomefloxacin and p-sulfonated calix[4]arene and its analytical application.

The characteristics of host-guest complexation between p-sulfonated calix[4]arene (SC4A) and lomefloxacin (LMFX) were investigated by fluorescence spectrometry. A 1:1 stoichiometry for the complexation was established and an association constant of 6.48x10(4) l mol-1 at 25 degrees C was calculated by applying a deduced equation. The interaction mechanism of the inclusion complex was discussed and the various factors affecting the inclusion process were examined in detail. It was found that an appropriate amount of cationic surfactant cetyltrimethylammonium bromide (CTAB) can remarkably enhance the fluorescence intensity of the supramolecular complex system. Based on the obtained results, a novel sensitive spectrofluorimetric method for the determination of lomefloxacin based on supramolecular complex was developed with a linear range of 0.01-3.0 microg ml-1 and a detection limit of 0.008 microg ml-1, for the first time. The method was applied for the determination of lomefloxacin in pharmaceutical preparations successfully.

Calixarenes↗

PubMed2005

Synthesis and optical properties of gallium phosphide nanotubes.

Gallium phosphide nanotubes with zinc blende structure were synthesized for the first time. The as-prepared GaP nanotubes are polycrystalline with diameters of 30-120 nm and occasionally partially filled. The growth has been reasonably proposed to follow vapor-liquid-solid (VLS) mechanism. The integration of the nanotubular structure with the unique intrinsic semiconducting properties of GaP might bring GaP nanotubes some novel optical and electronic properties and applications.

Journal Article↗

PubMed2005

New 6-butylamino-6-deoxycellulose and 6-deoxy-6-pyridiniumcellulose derivatives with highest regioselectivity and completeness of reaction.

This paper investigates the nucleophilic substitution (S(N)) reactions of tosylcellulose with butylamine and pyridine, respectively. The S(N) reactions of tosylcellulose 1 (DS(Total) 2.02; DS(C-6) 1.0) with butylamine carried out at 25, 50, 75 and 100 degrees C in both dimethyl sulfoxide (DMSO) and pure butylamine showed that the regioselectivity of substitution at C-6 of cellulose is temperature dependent: the highest regioselectivity at C-6 can be reached at 25 and 50 degrees C; substitution at C-2 also occurred at 75 and 100 degrees C. The substitution speed in pure butylamine is greater than that in the presence of DMSO. A complete and regioselective substitution at C-6 with a DS of 1.0 was obtained under the conditions of 50 degrees C, 40 h in butylamine. The substitution reactions of 1 with pyridine carried out at 25, 50, 75 and 100 degrees C for 24h in DMSO did not occur. In contrast to this the S(N) reactions done in pure pyridine showed that a temperature- and steric-dependent, regioselective substitution took place at C-6 at temperatures from 25 to 145 degrees C. The highest regioselectivity and completeness at C-6 can be obtained at 100 degrees C for 90 h, whereas at 145 degrees C substitution also occurs at C-2. The results were proved by 1H NMR and 13C NMR spectroscopy.

Butylamines↗