Biomedical subjects

X Cheng

Publications and source records attributed to X Cheng.

At least 91 records · Page 5Linked to original sources

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↗

PubMed1999

Structure of a binary complex of HhaI methyltransferase with S-adenosyl-L-methionine formed in the presence of a short non-specific DNA oligonucleotide.

We have determined a structure for a complex formed between HhaI methyltransferase (M.HhaI) and S-adenosyl-L-methionine (AdoMet) in the presence of a non-specific short oligonucleotide. M.HhaI binds to the non-specific short oligonucleotides in solution. Although no DNA is incorporated in the crystal, AdoMet binds in a primed orientation, identical with that observed in the ternary complex of the enzyme, cognate DNA, and AdoMet or S-adenosyl-L-homocysteine (AdoHcy). This orientation differs from the previously observed unprimed orientation in the M.HhaI-AdoMet binary complex, where the S+-CH3 unit of AdoMet is protected by a favorable cation-pi interaction with Trp41. The structure suggests that the presence of DNA can guide AdoMet into the primed orientation. These results shed new light on the proposed ordered mechanism of binding and explains the stable association between AdoMet and M.HhaI.

Crystallization↗

PubMed1999

Epiregulin is a potent vascular smooth muscle cell-derived mitogen induced by angiotensin II, endothelin-1, and thrombin.

Vasoactive GTP-binding protein-coupled receptor agonists such as angiotensin II (AII), endothelin-1 (ET-1), and alpha-thrombin (alpha-Thr) have been reported to indirectly stimulate vascular smooth muscle cell (VSMC) proliferation by regulating the expression of one or more autocrine growth factors. Using ion-exchange, gel-filtration, and reverse-phase chromatographic purification methods, we isolated a major mitogenic protein present in AII-stimulated rat aortic smooth muscle (RASM) cell conditioned medium. Twenty N-terminal amino acids of the purified peptide were identified, and they had 75% amino acid sequence identity with mouse epiregulin, an epidermal growth factor (EGF)-related growth factor. We cloned the cDNA for rat epiregulin to determine its pattern of expression in G-protein-coupled receptor agonist-stimulated cells and confirm its activity as a mitogen. After treatment of RASM cells with AII, ET-1, or alpha-Thr for 1 h, induction of two epiregulin transcripts was observed, including a 4.8-kb transcript and a novel transcript of approximately 1.2 kb. Recombinant rat epiregulin was strongly mitogenic for RASM cells, stimulating DNA synthesis to levels similar to those induced by serum or platelet-derived growth factor and approximately 3-fold above that observed with saturating concentrations of EGF. In addition, epiregulin caused rapid EGF receptor activation in RASM cells. However, relative levels of EGF receptor tyrosine phosphorylation stimulated by epiregulin were less than those induced by EGF or betacellulin. Taken together, these results indicate that epiregulin is a potent VSMC-secreted mitogen, induced in common by AII, ET-1, and alpha-Thr, that may contribute to VSMC proliferation and vascular remodeling stimulated by vasoactive agonists.

3T3 Cells↗

PubMed1999

Mechanism of inhibition of DNA (cytosine C5)-methyltransferases by oligodeoxyribonucleotides containing 5,6-dihydro-5-azacytosine.

A key step in the predicted mechanism of enzymatic transfer of methyl groups from S-adenosyl-l-methionine (AdoMet) to cytosine residues in DNA is the transient formation of a dihydrocytosine intermediate covalently linked to cysteine in the active site of a DNA (cytosine C5)-methyltransferase (DNA C5-MTase). Crystallographic analysis of complexes formed by HhaI methyltransferase (M.HhaI), AdoMet and a target oligodeoxyribonucleotide containing 5-fluorocytosine confirmed the existence of this dihydrocytosine intermediate. Based on the premise that 5,6-dihydro-5-azacytosine (DZCyt), a cytosine analog with an sp3-hybridized carbon (CH2) at position 6 and an NH group at position 5, could mimic the non-aromatic character of the cytosine ring in this transition state, we synthesized a series of synthetic substrates for DNA C5-MTase containing DZCyt. Substitution of DZCyt for target cytosines in C-G dinucleotides of single-stranded or double-stranded oligodeoxyribonucleotide substrates led to complete inhibition of methylation by murine DNA C5-MTase. Substitution of DZCyt for the target cytosine in G-C-G-C sites in double-stranded oligodeoxyribonucleotides had a similar effect on methylation by M. HhaI. Oligodeoxyribonucleotides containing DZCyt formed a tight but reversible complex with M.HhaI, and were consistently more potent as inhibitors of DNA methylation than oligodeoxyribonucleotides identical in sequence containing 5-fluorocytosine. Crystallographic analysis of a ternary complex involving M.HhaI, S-adenosyl-l-homocysteine and a double-stranded 13-mer oligodeoxyribonucleotide containing DZCyt at the target position showed that the analog is flipped out of the DNA helix in the same manner as cytosine, 5-methylcytosine, and 5-fluorocytosine. However, no formation of a covalent bond was detected between the sulfur atom of the catalytic site nucleophile, cysteine 81, and the pyrimidine C6 carbon. These results indicate that DZCyt can occupy the active site of M.HhaI as a transition state mimic and, because of the high degree of affinity of its interaction with the enzyme, it can act as a potent inhibitor of methylation.

Animals↗

PubMed1999

Bilateral kidney ligation abolishes pressor response to N(G)-nitro-D-arginine.

We have shown that N(G)-nitro-D-arginine (D-NNA) is 50% as potent as N(G)-nitro-L-arginine (L-NNA) in causing pressor response and 2-3% as potent as L-NNA in inhibiting endothelium-dependent relaxation in vitro. These results suggest in vivo activation of D-NNA. Furthermore, the potency of D-NNA was markedly increased after it had been incubated with homogenate of the kidney, but not plasma or homogenate of the aorta, lungs or liver. This study examined if bilateral ligation of the kidneys attenuated the biological action of D-NNA. I.v. bolus of D-NNA (16 mg/kg), L-NNA (3 mg/kg) and norepinephrine (0.25-16 microg/kg) increased arterial pressure in sham-operated rats. Bilateral ligation of the kidneys abolished pressor response to D-NNA, but not L-NNA and norepinephrine. I.v. bolus D-NNA in sham-operated rats, but not kidney-ligated rats, inhibited relaxation response to acetylcholine in pre-constricted aortic rings ex vivo. These results indicate that the kidney is the primary organ which activates D-NNA.

Acetylcholine↗

PubMed1999

Effects of several drugs on the liver injury induced by delayed-type hypersensitivity to picryl chloride by regulating suppressor or helper T cells.

The effects of histamine, cimetidine, and diphenhydramine on picryl chloride (PCl)-induced ear contact sensitivity, as well as liver injury, were examined in mice. Histamine was found to produce less response in mice to PCl. In contrast, cimetidine, a selective antagonist of histamine type 2 receptor, significantly enhanced the response, while diphenhydramine, a selective antagonist of histamine type 1 receptor showed no effect. The pre-treatment of 2,4, 6-trinitrobenzene sulphonic acid (TNBS) significantly caused a tolerance to the formation of the liver injury induced by delayed-type hypersensitivity (DTH) to PCl. Against the tolerance, the single intravenous administration of 150 mg kg-1 cyclophosphamide (Cy) at 3 days before the TNBS-treatment recovered the response and induced a remarkable elevation of serum transaminases. On the other hand, cyclosporin A protected the liver injury. These observations revealed that the development of acute PCl-DTH liver injury was regulated by the functional state of suppressor and helper T cells.

Animals↗

PubMed1999

Coiling phagocytosis is the predominant mechanism for uptake of the colonic spirochetosis bacterium Serpulina pilosicoli by human monocytes.

Serpulina pilosicoli is a newly identified pathogenic spirochete that establishes persistent colonic infections in human beings and animals. Macrophages are one of the key defenses against invasion of mucosal surfaces by bacterial pathogens. Macrophages engulf many bacteria by conventional phagocytosis; however recent studies indicate coiling phagocytosis as a new and important mechanism for internalization of Legionella pneumophila and spirochetes of the genus Borrelia, Leptospira, and Treponema. In this study, THP-1 human monocytic cells were incubated with the human S. pilosicoli strain SP16 and the contribution of coiling and conventional phagocytosis to the total number of phagocytic events were determined by sequential ultrastructural examination between 5 and 45 minutes. The frequency of phagocytosis increased over time from 5.1% after 5 minutes up to 21.9% after 45 minutes with greater than 70% of the events involving coiling phagocytosis. The data indicate that coiling phagocytosis may be a universal mechanism for uptake of pathogenic spirochetes.

Brachyspira↗

PubMed1999

Molecular cloning and sequence analysis of cDNA encoding haemorrhagic toxin acutolysin A from Agkistrodon acutus.

By means of reverse transcription polymerase chain reaction, a full-length cDNA of 1632 bp is amplified from the snake venom gland total RNA of Agkistrodon acutus. Analysis of the nucleotide sequence indicates that the amplified cDNA contains a complete open reading frame encoding 413 amino acid residues including signal peptide sequence, zymogen sequence and proteinase domain. The zymogen sequence contains PKMCGVT motif which is highly conserved in almost all venom metalloproteinases. The metalloproteinase domain contains the conserved signature zinc-binding motif HEXXHXXGXXH in the catalytic region. The predicted amino acid sequence of the metalloproteinase domain is identical to the crystallographic sequence of acutolysin A and also shares high homology with other class I snake venom haemorrhagic toxins.

Agkistrodon↗