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Biomedical subjects

X Cheng

Publications and source records attributed to X Cheng.

At least 91 records · Page 5Linked to original sources
PubMed2000

[Vertical distribution and quantitative dynamics of dominant functional groups of arthropod community in rice fields and estimation of natural enemy effects].

The study showed that Lycosid (wolf spider) mainly distributed in the basal part of rice plants, not as wide as we know in past. Tetragnathid did not limited in the upper part of plants, but might translate to middle or lower part when affected by insecticide. The relationship between the vertical distributions of top and basal species was not significant. Besides the amount of natural enemies, the spatial distribution characteristics of natural enemies and brownplanthopper, and the proportion of brownplanthopper to total preys of natural enemies were the factors affecting the role of natural enemies on the population dynamics of brownplanthopper in rice fields. A model to evaluate the effect of natural enemies to brownplanthopper was put forward, which included the message of quantitative dynamics, spatial distribution and feeding characteristics of natural enemies, brownplanthopper and neutral insects.

Animals↗
PubMed2000

[Predation on Myzus persicae by Propylaea japonica adults with different extents of starvation].

The study showed that the functional response of predation on M. persicae by the female and male adults of P. japonica with different extents of starvation belonged to the type of Holling II. Female adults had a larger attacking rate than male adults, but the predacious amount of M. persicae by female and male adult predators of different extent of starvation within 24 hrs had no significant difference. The predacious amount by female adult was larger than that of male. The significant difference of predacious amount between female and male adults increased with the time of their starvation and the prey density. The predation by unstarved female and male adult predators on M. persicae in 24 hours was concentrated at 6:00-18:00 and the predation rate (V) between female and male adults had no significant difference. The predation by starved female and male adults for 48 h on the prey in 24 hours was at 0-4 hours after the experiment started, and the predation rate(V) between female and male starved adults had no significant difference either.

Animals↗
PubMed2000

[Effect of rice variety resistance on population dynamics of Nilaparvata lugens and Sogatella furcifera].

The effect of rice varieties with different insect-resistance on dynamics of Nilaparvata lugens and Sogatella furcifera population was examined, based on the investigation of their inhabiting ratio, egg amount, survival rate of egg and nymph, nymph development, and the amount of their offspring population. Four rice varieties, TN1, N22, AsD7 and Ptb33 were investigated. Ptb33 had a significantly lower inhabiting ratio, egg amount, and survival ratio of eggs and nymphs of both parasitic populations, a prolonged development time from nymphs to adults, and an inhibited offspring population, indicating an evident resistance of this host variety. N22 and AsD7 inhibited the development of offspring S. furcifera and N. lugens, respectively. The parasitic populations of S. furcifera and N. lugens developed more rapidly on TN1, compared with N. lugens population on N22 and S. furcifera on AsD7. The relationship between the quantitative dynamics of both population and rice variety replacement was discussed, and the possibility of using resistant rice varieties to control these two insect populations was also analyzed.

Animals↗
PubMed2000

[The study of a computer aided artificial teeth arrangement of complete denture].

OBJECTIVE: To develop a system of computer aided complete denture design (CACDD). METHODS: After 3 dimensional measurement, data process and making model of a edentulous model, artificial teeth and the maxillomandibular bite plate, on the position of centric relation, the artificial teeth were arranged according to the principle and demand of the complete denture's teeth arrangement. The relation of teeth and occlusion were adjusted by Affine and Projection transformation. RESULTS: (1) The maxillomandibular visual base on the position of centric relation were made, its mathematics model is B-Spline curve surface of the double third power. (2) The artificial teeth arrangement and 3 dimensional show of the complete denture were achieved. CONCLUSION: This system can provide a feasible tool for a computer aided complete denture design and teaching.

Centric Relation↗
PubMed2000

Relations of tumor suppressor gene p16 and RB to early diagnosis of lung cancer.

OBJECTIVES: To study the incidence and mechanism of the tumor suppressor gene p16 and RB inactivation in lung cancer, and to investigate their relations to biological characteristics, clinical pathological diagnosis and gene classification. METHODS: Immunohistochemistry, double in situ hybridization, PCR, PCR-SSCP, and sequencing were used to study the changes in the p16 and RB genes in 106 patients with lung cancer. The specimen of normal lung tissue from the patients with lung cancer and specimens of the 23 patients with benign lung diseases were studied in contrast to those of the same patients. RESULTS: The total expression rate of the p16 and RB genes in the lung cancer tissues of the 106 patients was lower than that in normal lung tissues and tissues of benign lung diseases and was specially related to histological type, metastasis, and clinical stage of lung cancer. In stage I and II lung cancer, the obvious inactivation rate of the tumor suppressor gene p16 or RB was 32.6% or 28.3%. The p16 inactivation appeared largely in non-small cell lung cancer (50.1%), and the RB inactivation largely in small cell lung cancer (88.2%). Homozygous deletion, methylation, and mutation were three mechanisms for the p16 gene inactivation. The deletion rate of the p16 exon 1 and/or exon 2 was 25.8% in the patients with non-small cell lung cancer. Fifteen patients (16.9%) showed methylation at the SmaI sites of CpG island of the p16 gene. PCR-SSCP and sequencing revealed p16 gene mutation in 9 of the 106 patients with lung cancer. CONCLUSIONS: The p16 and RB genes may play an important role in genesis and progression of lung cancer. The inactivation of the p16 or RB gene may be an early sign of lung canceration, that is important for the early diagnosis. A new gene classification model for lung cancer diagnosis would be set up based on the research of the p16 and RB genes.

DNA Methylation↗
PubMed2000

[A cost-benefit evaluation of neonatal screening for phenylketonuria and congenital hypothyroidism].

OBJECTIVE: In order to make the best use of health care resources, to achieve the maximal social and economic benefits and to lay a foundation for popularizing neonatal screening for phenylketonuria (PKU) and congenital hypothyroidism (CH), a cost-benefit analysis of the screening program was conducted. METHODS: Cost for and benefit gained from screening were calculated according to the average incidence of two diseases recommended by the Ministry of Health, mean charge for neonatal screening, sampling extraction of medical history and data published in national economic statistics. RESULTS: The cost of neonatal screening, treatment for PKU with low phenylalanine milk powder and follow up, the total add up to 128 793 Yuan However the direct and indirect financial benefits is 481 263 Yuan, ratio of cost to benefit was 1:3.7. The cost of neonatal screening for CH is 129 175 Yuan. However the financial benefits including the money saved in treatment, nursing care, special education and the loss of income avoided is 468 470 Yuan, ratio of cost to benefit was 1:3.6. CONCLUSION: Neonatal screening for PKU and CH in this country reflects a better economic and social benefit and merits further popularization.

Congenital Hypothyroidism↗
PubMed2000

[Effects of alpha-tocopherol and beta-carotene on the oxidized low density lipoprotein induced by Cu2+].

The effects of different concentrations of alpha-tocopherol and beta-carotene on low density lipoprotein(LDL) oxidation were examined. LDL was oxidized by Cu2+ in a cell-free(10 mumol/L Cu2+ in PBS) system. The results showed that alpha-tocopherol and beta-carotene inhibited the oxidative modification of LDL in this system as evidenced by a concentration-dependent decrease in lipid peroxide(thiobarbituric-acid-reasting substances activity, TBARS) and the electrophoretic mobility of LDL. The effect of alpha-tocopherol on the generation of TBARS was stronger, while on the electrophoretic mobility was weaker than that of beta-carotene. Both alpha-tocopherol and beta-carotene slightly but not significantly reduced lipofusin. It suggested that the mechanisms were different. Thus, beta-carotene, as well as alpha-tocopherol, inhibit LDL oxidation and might play important roles in reducing the generation of oxidized LDL.

Antioxidants↗
PubMed2000

[HPLC quantitative analysis of berberine absorpted with macroporous resin in Rhizoma Coptidis and its preparation zuo jin wan].

Absorptive ability and elution program of macroporous resin to the berberine in the Rhizoma Coptidis and its preparation Zuo Jin Wan (containing Rhizoma Coptidis and Fructus Evodiae) were explored. The extract of 70% MeOH of samples were disolved in water, then alkalized to pH 12 with ammonia solution. The berberine was absorpted by the macroporous resin, the washed off water soluble impurity with alkalescent water, and eluted with 50% MeOH containing 0.5% H2SO4. The results of quantitative analysis of the berberine by HPLC were satisfied.

Adsorption↗
PubMed2000

[Studies on the stable integration and expression of IL-2R alpha gene in CHO cells and it's applications].

OBJECTIVES: To establish a novel bioassay method for quantitative analysis of human IL-2 based on the specific binding of Interleukin-2 receptor alpha subunit (IL-2R alpha) with IL-2. METHODS: Southern blot hybridization was first used to detect the stability of integration of recombinant secretive IL-2R alpha (rsIL-2R alpha) gene into the genome of highly expressed cell line reported elsewhere; the apparent Mr of the rsIL-2R alpha was then determined by using Western blotting; finally, a receptor-antibody sandwich ELISA method has been established for quantitative analysis of IL-2. RESULTS: (1) Stable integration of rsIL-2R alpha gene into the genome of #17 CHO cell line has been identified; (2) the apparent Mr of rsIL-2R alpha was approximately 40,000; (3) linear range of the standard curve obtained from the receptor-based ELISA fell between 31.25-500 U of IL-2 (r = 0.9995). The slop of the standard curve decreased significantly when IL-2 was pre-incubated with goat anti-IL-2 antibody IgG (P < 0.01). CONCLUSIONS: An IL-2R alpha-based IL-2 ELISA has been established for laboratory and clinical use with advantages of accuracy, specificity and simplicity over other conventional bioassays for IL-2 detection.

Animals↗
PubMed2000

[Papanicolaou test in pregnancy].

OBJECTIVE: To investigate the necessity, safety and acceptability of routine Papanicolaou (Pap) smear in pregnant women and cytological characteristics of the smears during pregnancy. METHODS: Pap smear were performed in 954 pregnant women, 1,053 normal controls and 1,908 gynecological out-patients. The cytological preparations were analyzed by using PAPNET method and following Bethesda (TBS-NCI) diagnostic criteria. Quality control was carried out by following TBS-NCI standard. RESULTS: Abnormal epithelial change was found in 89 women (89/954, 9.3%) of pregnant group, which was quite similar to normal controls group and gynecological group. Occurrence rate of cervical squamous intraepithelial lesion (SIL) was the lowest in pregnant group (0.94%, 9 in 954 cases), comparing with control group (2.75%) and gynecological group (6.23%). However, pregnant group had the highest infection rate (89.9%), as compared to gynecological group (64.5%), and normal controls group (69.1%) (P < 0.01). CONCLUSIONS: Cervical Pap smear test is necessary, safety and acceptable for routine prenatal tests. Any pregnant women with infections must be treated as nonpregnant one.

Adult↗
PubMed1999

Purification, characterization, and cDNA cloning of a new fibrinogenlytic venom protein, Agkisacutacin, from Agkistrodon acutus venom.

Agkisacutacin is a new fibrinogenlytic protein from Agkistrodon acutus venom. It consists of two heterologous subunits linked by an intersubunit disulfide bond. The cDNAs encoding the two chains of Agkisacutacin were cloned from a lambdagt11 cDNA library of the snake venom gland and sequenced, including the leader peptides (23/23 amino acid residues) and mature subunits (129/123 amino acid residues). It is structurally related to the family of IX/X-binding protein (IX/X-bp)-like proteins and shows high similarity (alpha-70%/beta-64%) to habu IX/X-bp from Trimeresurus flavoridis, but displays distinct biological activity with direct action on fibrinogen.

Agkistrodon↗
PubMed1999

Mobilization of the A-kinase N-myristate through an isoform-specific intermolecular switch.

Although the catalytic (C) subunit of cAMP-dependent protein kinase is N-myristylated, it is a soluble protein, and no physiological role has been identified for its myristyl moiety. To determine whether the interaction of the two regulatory (R) subunit isoforms (R(I) and R(II)) with the N-myristylated C subunit affects its ability to target membranes, the effect of N-myristylation and the R(I) and R(II) subunit isoforms on C subunit binding to phosphatidylcholine/phosphatidylserine liposomes was examined. Only the combination of N-myristylation and R(II) subunit interaction produced a dramatic increase in the rate of liposomal binding. To assess whether the R(II) subunit also increased the conformational flexibility of the C subunit N terminus, the effect of N-myristylation and the R(I) and R(II) subunits on the rotational freedom of the C subunit N terminus was measured. Specifically, fluorescein maleimide was conjugated to Cys-16 in the N-terminal domain of a K16C mutant of the C subunit, and the time-resolved emission anisotropy was determined. The interaction of the R(II) subunit, but not the R(I) subunit, significantly increased the backbone flexibility around the site of mutation and labeling, strongly suggesting that R(II) subunit binding to the myristylated C subunit induced a unique conformation of the C subunit that is associated with an increase in both the N-terminal flexibility and the exposure of the N-myristate. R(II) subunit thus appears to serve as an intermolecular switch that disrupts of the link between the N-terminal and core catalytic domains of the C subunit to expose the N-myristate and poise the holoenzyme for interaction with membranes.

Cyclic AMP-Dependent Protein Kinases↗
PubMed1999

[The feature of influenza virus activity and genetic characterization of HA1 gene of influenza A H3N2 viruses isolated from 1994-1997 in Shenzhen].

OBJECTIVE: To understand the feature of influenza virus activity and genetic characterization of HA1 gene of influenza A H3N2 viruses isolated in recently years in Shenzhen. METHODS: The specimens were inoculated into amniotic and allantoic cavities of the embryonated chicken eggs for viral isolation. The isolates were typed with HI test. Virion RNA extracted from allantoic fluid by Rneasy RNA extraction kit was used for RT-PCR amplification. Afterward, the product of PCR was purified with purification kit. RNA sequence analysis was performed by Sanger dideoxy-mediated nucleotide chain termination method. RESULTS: Influenza A H3N2, H1N1 and B viruses were cocirculating in men in Shenzhen in recent years. However, the extent of their activities was not the same in a single year. The influenza B virus was the predominant strain in 1994 and 1997, but the predominant strain was H3N2 virus in 1996. The genetic analysis showed that the substitution of amino acids occured year by year and was mainly located at antigenic determinants or receptor binding site on HA1 domain of H3N2 viruses. CONCLUSION: Influenza A H3N2, H1N1 and B viruses were still co-circulating in men in Shenzhen in recent years, the predominant strain of influenza virus was different in different years. An increase of influenza A H3N2 virus activity in 1996 was due to the substitution of amino acids sequences on viral HA1 domain.

Amino Acid Sequence↗
PubMed1999

Isolation and identification of fxsA, an Escherichia coli gene that can suppress F exclusion of bacteriophage T7.

A selection for mutants of Escherichia coli that survive coexpression of bacteriophage T7 gene 10 and plasmid F pifA has allowed the identification of a newly defined genetic locus, fxsA. fxsA is located at 94.1 min on the E. coli chromosome; the gene is monocistronic and non-essential for growth. Overexpression of fxsA is necessary for resistance to the toxicity of T7 gene 10 in the presence of pifA; the original mutant strain contains a promoter-up mutation, changing a G residue to the "invariant" T in the -10 hexamer of a sigma(70)promoter. This chromosomal mutation causes a 25-fold increase in the level of fxsA mRNA. The initiation codon of fxsA is shown to be UUG, and the FxsA protein is then deduced to consist of 158 amino acid residues. A similar mutant selection that demanded cell survival to a challenge of T7 gene 1.2 and pifA also resulted in the isolation of the identical promoter-up mutation that affects expression of fxsA. The increased levels of FxsA resulting from the promoter-up mutation allow phage T7 to avoid exclusion by the F plasmid, presumably by protecting the cell from premature death due to gene 10 or to gene 1.2 expression in the presence of the PifA protein.

Amino Acid Sequence↗
PubMed1999

Crystal structure of the conserved core of the herpes simplex virus transcriptional regulatory protein VP16.

On infection, the herpes simplex virus (HSV) virion protein VP16 (Vmw65; alphaTIF) forms a transcriptional regulatory complex-the VP16-induced complex-with two cellular proteins, HCF and Oct-1, on VP16-responsive cis-regulatory elements in HSV immediate-early promoters called TAATGARAT. Comparison of different HSV VP16 sequences reveals a conserved core region that is sufficient for VP16-induced complex formation. The crystal structure of the VP16 core has been determined at 2.1 A resolution. The results reveal a novel, seat-like protein structure. Together with the activity of mutant VP16 proteins, the structure of free VP16 suggests that it contains (1) a disordered carboxy-terminal region that associates with HCF, Oct-1, and DNA in the VP16-induced complex, and (2) a structured region involved in virion assembly and possessing a novel DNA-binding surface that differentiates among TAATGARAT VP16-response elements.

Amino Acid Sequence↗
PubMed1999

[Discovery of men infected by avian influenza A (H9N2) virus].

OBJECTIVE: To understand whether the avian influenza A(H9N2) virus can infect men or not. METHODS: Seroepidemiological surveys for avian (H9N2) virus in human, chickens and pigs were conducted. The specimens for viral isolation were taken from throat of patients with influenza like disease, as well as from chickens, then the specimens were inoculated into embryonated chicken eggs. Afterward, the idsolates were identified with HI and NI tests. Meanwhile, the patients who would be studied individually were found to carry H9N2 virus. RESULTS: Approximately 19% of human had antibody to H9N2 virus with HI titers > or = 20, 5 strains of influenza A (H9N2) virus were isolated from the patients. CONCLUSION: Avian influenza A(H9N2) virus can infect men.

Antibodies, Viral↗