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Biomedical subjects

Y Feng

Publications and source records attributed to Y Feng.

At least 109 records · Page 6Linked to original sources
PubMed2000

Identification of impurities affecting commercial ethylene glycol UV transmittance.

As a raw material for making polyesters, ethylene glycol has a special specification of UV transmittance. At present, ethylene glycol produced by some plants still has low UV transmittance rendering it unsuitable for use in polyester production. In this paper, a method was developed for the identification of the impurities that cause commercial ethylene glycol to have low UV transmittance, using solid-phase extraction (SPE) and some analytical techniques such as high-performance liquid chromatography, gas chromatography-mass spectrometry and gas chromatography-Fourier transform infrared spectroscopy. The major UV-absorbing impurities were identified as some alkyl homologues of 2-hydroxycyclopent-2-en-1-one, including 2-hydroxy-3,5-dimethylcyclopent-2-en-1-one, 2-hydroxy-3-methylcyclopent-2-en-1-one, 2-hydroxy-3,4-dimethylcyclopent-2-en-1-one, 2-hydroxy-3-ethyl-4-methylcyclopent-2-en-1-one and 2-hydroxy-3-ethylcyclopent-2-en-1-one. Their concentrations were estimated to be less than 2 microg ml(-1). It is believed that with the above results, ethylene glycol-producing plants might make process improvements to remove these impurities more effectively and more easily.

Chromatography, High Pressure Liquid↗
PubMed2000

Overexpression of eotaxin and the CCR3 receptor in human atherosclerosis: using genomic technology to identify a potential novel pathway of vascular inflammation.

BACKGROUND: Unstable atherosclerotic lesions typically have an abundant inflammatory cell infiltrate, including activated T cells, macrophages, and mast cells, which may decrease plaque stability. The pathophysiology of inflammatory cell recruitment and activation in the human atheroma is incompletely described. METHODS AND RESULTS: We hypothesized that differential gene expression with DNA microarray technology would identify new genes that may participate in vascular inflammation. RNA isolated from cultured human aortic smooth muscle cells treated with tumor necrosis factor-alpha (TNF-alpha) was examined with a DNA microarray with 8600 genes. This experiment and subsequent Northern analyses demonstrated marked increases in steady-state eotaxin mRNA (>20 fold), a chemokine initially described as a chemotactic factor for eosinophils. Because eosinophils are rarely present in human atherosclerosis, we then studied tissue samples from 7 normal and 14 atherosclerotic arteries. Immunohistochemical analysis demonstrated overexpression of eotaxin protein and its receptor, CCR3, in the human atheroma, with negligible expression in normal vessels. Eotaxin was predominantly located in smooth muscle cells. The CCR3 receptor was localized primarily to macrophage-rich regions as defined by immunopositivity for CD 68; a minority of mast cells also demonstrated immunopositivity for the CCR3 receptor. CONCLUSIONS: Eotaxin and its receptor, CCR3, are overexpressed in human atherosclerosis, suggesting that eotaxin participates in vascular inflammation. These data demonstrate how genomic differential expression technology can identify novel genes that may participate in the stability of atherosclerotic lesions.

Actins↗
PubMed2000

Inhibition of CCR5-dependent HIV-1 infection by hairpin ribozyme gene therapy against CC-chemokine receptor 5.

CCR-5 is a major cellular coreceptor for R5 strains of HIV-1. Individuals carrying a homozygous 32-base-pair deletion in this gene are apparently healthy and are relatively resistant to HIV-1 infection. Since CCR5 appears to be dispensable for the host, but important for initial HIV-1 infection, CCR5 mRNA is an excellent therapeutic target for inhibiting HIV-1 replication via ribozyme knockout. We report here that hairpin ribozymes are able to reduce cellular CCR5 mRNA and cell surface CCR5 when stably introduced into PM1 cells by transduction with recombinant adenoassociated viral vector. The ribozymes effectively protect the cells from infection by R5 HIV-1 strains or non-syncytium-inducing clinical isolates commensurate with a reduction in CCR5 mRNA. These results suggest a novel gene therapy approach to preventing or slowing the disease progression of HIV-1 infection.

CCR5 Receptor Antagonists↗
PubMed2000

Destabilization and mislocalization of myelin basic protein mRNAs in quaking dysmyelination lacking the QKI RNA-binding proteins.

Quakingviable (qk(v)) is a well known dysmyelination mutation. Recently, the genetic lesion of qk(v) has been defined as a deletion 5' to the qkI gene, which results in the severe reduction of the qkI-encoded QKI RNA-binding proteins in myelin-producing cells. However, no comprehensive model has been proposed regarding how the lack of QKI leads to dysmyelination. We hypothesized that QKI binds to myelin protein mRNAs, and the lack of QKI causes posttranscriptional misregulation, which in turn leads to the loss of the corresponding myelin proteins. To test this hypothesis, we developed an RNase protection assay to directly measure the mRNA isoforms encoding the myelin basic proteins (MBPs) in the brain. Our result suggested that isoform-preferential destabilization of MBP mRNAs in the cytoplasm was responsible for the reduced MBPs in the qk(v)/qk(v) brain during early myelination. In addition, we detected markedly reduced MBP mRNAs in the qk(v)/qk(v) myelin fraction with concomitant accumulation of MBP mRNAs associated with membrane-free polyribosomes. Presumably, the impaired localization of MBP mRNAs to the myelin membrane may cause insufficient incorporation of the newly synthesized MBPs into the myelin sheath. Finally, we observed interactions between QKI and MBP mRNAs, and removing MBP 3'UTR significantly reduced QKI-binding. Taken together, these observations suggest that misregulation at multiple posttranscriptional steps is responsible for the severe reduction of MBPs in qk(v) dysmyelination, presumably because of the lack of interactions between MBP mRNAs and the QKI RNA-binding proteins.

Animals↗
PubMed2000

Unpaired terminal nucleotides and 5' monophosphorylation govern 3' polyadenylation by Escherichia coli poly(A) polymerase I.

In bacteria, most mRNAs and certain regulatory RNAs are rapidly turned over, whereas mature tRNA and ribosomal RNA are highly stable. The selective susceptibility of unstable Escherichia coli RNAs to 3' polyadenylation by the pcnB gene product, poly(A) polymerase I (PAP I), in vivo is a key factor in their rapid degradation by 3' to 5' exonucleases. Using highly purified His-tagged recombinant PAP I, we show that differential adenylation of RNA substrates by PAP I occurs in vitro and that this capability resides in PAP I itself rather than in any ancillary protein(s). Surprisingly, the efficiency of 3' polyadenylation is affected by substrate structure at both termini; single-strand segments at either the 5' or 3' end of RNA molecules and monophosphorylation at an unpaired 5' terminus dramatically increase the rate and length of 3' poly(A) tail additions by PAP I. Our results provide a mechanistic basis for the susceptibility of certain RNAs to 3' polyadenylation. They also suggest a model of "programmed" RNA decay in which endonucleolytically generated RNA fragments containing single-stranded monophosphorylated 5' termini are targeted for poly(A) addition and further degradation.

Escherichia coli↗
PubMed2000

Cell cycle-dependent phosphorylation of centrosomes: localization of phosphopeptide specific antibodies to the centrosome.

The microtubule nucleation capacity of the centrosome increases dramatically as cells progress from interphase into mitosis. The increase in nucleation capacity of the centrosome correlates with the cell cycle-dependent localization of the mitotic protein monoclonal-2 (MPM-2) phosphoepitope-specific antibody to the mitotic centrosome. Therefore, the phosphorylation state of centrosomal components may regulate the microtubule nucleation capacity of this organelle during mitosis. Neither the identity of the MPM-2 kinase(s) nor all of the MPM-2-reactive phosphoproteins associated with the centrosome have been fully elucidated. Only recently have the characteristics of the MPM-2 epitope site been defined, and we used this information to prepare polyclonal antibodies against synthetic phosphopeptides containing potential MPM-2 epitopes derived from the sequences of two MPM-2-reactive proteins, topoisomerase II, and microtubule associated protein 1B (MAP1B). We demonstrate that these phosphopeptide-specific antibodies also localize to the centrosome in a cell cycle-dependent fashion. Thus, polyclonal antibodies have been generated against defined phosphopeptides that reiterate many of the immunofluorescence staining properties exhibited by the MPM-2 antibody. These new phosphopeptide-specific antibodies will provide additional probes to examine the phosphorylation of centrosomal components and the functional consequences of their phosphorylation during mitosis.

Amino Acid Sequence↗
PubMed2000

Increased TNF-alpha and PGI(2), but not NO release from macrophages in 18-month-old rats.

TNF-alpha is an important pro-inflammatory mediator that influences host defense against infection and cancer. Previous examinations of TNF-alpha release and synthesis within the context of age have provided conflicting data, as both increased and decreased TNF-alpha synthesis have been described in aged populations. The present study was designed to reevaluate TNF-alpha production and synthesis in primary cultured peritoneal macrophages of young and 18-month-old rats. We were also interested in the link between the production of this cytokine and other important mediators, such as prostaglandin I(2) (PGI(2)) and nitric oxide (NO) in these rats. Primary cultured peritoneal macrophages of rat were stimulated with 1.0 microg/ml of lipopolysaccharide (LPS) for 12 h. The level of TNF-alpha protein in culture supernatant was measured by enzyme-linked-immunosorbent-assay (ELISA), and TNF-alpha mRNA production was assessed by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). At the same time, the levels of NO and PGI(2) were measured. Macrophages from 18-month-old rats produced more TNF-alpha protein, PGI(2) and TNF-alpha mRNA than those from the young rats (2 month). There was no difference in NO production of macrophages between 18-month-old and young rats. The results demonstrate that TNF-alpha and PGI(2) production by rat macrophages increase with age. The results also suggest that NO might not contribute to the increased TNF-alpha production in 18-month-old rat macrophages.

Aging↗
PubMed2000

N-tosyl-L-phenylalanyl-chloromethylketone reduces hypoxic-ischemic brain injury in rat pups.

N-tosyl-L-phenylalanyl-chloromethylketone (TPCK) in vitro blocks apoptotic pathways leading to cell death. We wished to see if TPCK would reduce brain injury in vivo. Seven-day-old rat pups had the right carotid artery ligated and then received either vehicle or TPCK (5 to 100 mg/kg i.p.). They were then given 8% oxygen for 2.25 h. Twenty-two days later, the cerebral hemispheres were weighed to determine the reduction in size in the right hemisphere. TPCK decreased the reduction in right hemisphere weight from 15+/-3% (vehicle, n=20), to 4+/-2% (10 mg/kg, n = 19, P<0.01). TPCK reduced the number of cells staining for DNA breaks 3 days after injury from 1729+/-275 mm(-2) (vehicle, n = 8) to 550+/-236 mm(-2) (10 mg/kg TPCK, n = 9, P<0.01), decreased the amount of DNA fragmentation 3 days after injury by gel electrophoreses (20 mg/kg, n = 16, P<0.01) and eliminated the increase in nitric oxide metabolites 6 h after injury (vehicle 1.5+/-0.4, n = 10; and 20 mg/kg TPCK 0.0+/-0.1 nM/mg protein, n = 10, P<0.001). TPCK pretreatment in the newborn rat model of hypoxic-ischemic brain injury reduces DNA fragmentation, nitric oxide production and brain injury.

Animals↗
PubMed2000

Resin effects in solid phase S(n)Ar and S(n)2 macrocyclizations.

Seven different supports were compared in solid-phase S(N)Ar and S(N)2 macrocyclization reactions. Product purities were assayed for a relatively facile ring-closure process to give products 1 and 3. Some less-facile ring-closure reactions give the undesired dimeric macrocyclization by-products 2; some of these more-demanding ring closures were also examined. Finally, experiments were performed to gauge the rate of cyclizations on different resins, and some qualitative data were obtained for this.

Dimerization↗
PubMed2000

Fumarate reductase is essential for Helicobacter pylori colonization of the mouse stomach.

Fumarate reductase (FRD) is the key enzyme in fumarate respiration induced by anaerobic growth of bacteria. In Helicobacter pylori, this enzyme appears to be constitutively expressed under microaerobic conditions and is not essential for its survival in vitro. In this study, the role of FRD in the colonization of H. pylori was investigated using a mouse model. The frdA gene coding for subunit A of FRD, and two control genes, copA and copP associated with the export of copper out of H. pylori, were inactivated by insertion of the chloramphenicol acetyltransferase cassette into these individual genes. The isogenic mutants of H. pylori strain AH244 were obtained by natural transformation. Seventy-five ICR mice (15 mice/group) were orogastrically dosed with either the wild type H. pylori strain AH244, its isogenic mutants, or Brucella broth (negative control). Five mice from each group were killed at 2, 4 and 8 weeks post-inoculation (WPI), respectively. H. pylori colonization was not detected in mouse gastric mucosa infected with the frdA mutant at any time point in the study by both quantitative culture and PCR. In contrast, the mice inoculated with either wild type AH244, copA or copPH. pylori mutants became readily infected. These data indicate that FRD plays a crucial role in H. pylori survival in the gastric mucosa of mice. Given that FRD, present in all H. pylori strains, is immunogenic in H. pylori -infected patients and H. pylori growth in vitro can be inhibited by three anthelmintics (morantel, oxantel and thiabendazole), this enzyme could potentially be used both as a novel drug target as well as in the development of vaccines for H. pylori prevention and eradication.

Animals↗
PubMed2000

Aromatic DNA adducts in coke-oven workers, in relation to exposure, lifestyle and genetic polymorphism of metabolic enzymes.

OBJECTIVE: This study investigates the effect of multiple factors, including exposure to polycyclic aromatic hydrocarbons (PAHs), lifestyle, genetic polymorphism of cytochrome P450 (CYP)1A1, glutathione transferase (GST)M1, GSTP1, N-acetyltransferase (NAT)2 and gene p53, as well as any family history of cancer, on DNA adduct levels in coke-oven workers. METHODS: Sixty-five coke-oven workers employed at the largest iron-steel factory in China were recruited for the study. Personal data were collected at the interview. DNA adduct levels in total white blood cells (WBCs) were detected using 32P-postlabeling techniques. Genetic polymorphisms were analyzed by polymerase chain reaction (PCR) methods. RESULTS: The subjects were divided into low and high exposure groups, according to personal exposure to PAHs. The mean adduct value was 1.57 (range 0.54 to 4.35) per 10(8) nucleotides. A tendency for increased levels of DNA adducts in the high exposure group was observed, compared with the low exposure group (P = 0.07). In the low exposure group, DNA adducts were found to be positively associated with urinary cotinine (r = 0.44, P = 0.01). The rare allele homozygotes of CYP1A1 showed significantly higher DNA adduct levels than those of other CYP1A1 genotypes. Individuals with the NAT2 wild type had significantly increased DNA adduct levels than those with other NAT2 genotypes in the high exposure group. The p53 genetic polymorphism revealed a significantly positive effect on DNA adducts formation. There was a significantly higher adduct level in the subjects with a family history of cancer than those without, in the high exposure category. CONCLUSIONS: Effects of several variables, such as smoking, genetic polymorphism of 2 CYP1A1, NAT2, and gene p53, and a family history of cancer on DNA adduct levels were found, suggesting that these variables should be considered when evaluating the genotoxic effect of occupational exposure to PAHs using WBCs DNA adducts.

Arylamine N-Acetyltransferase↗
PubMed2000

Helicobacter pylori gastritis in cats with long-term natural infection as a model of human disease.

A natural infection with Helicobacter pylori (H. pylori) in domestic cats (Felis cattus) less than 2 years of age has been well described in a closed colony of animals. Six cats from this colony that were serially evaluated by culture, polymerase chain reaction, and light and electron microscopy for a period of 3 years demonstrated persistent gastric colonization with a single cag(-) vac(+) strain of H. pylori. In these cats, as well as five other 5- to 6-year-old cats that were examined, a long-term infection resulted in chronic diffuse lymphofollicular atrophic gastritis with areas of mucosal dysplasia in the antrum and predominantly midsuperficial gastritis in the body and cardia. Topographically, the distribution of lesions was similar in both young and older cats and closely resembled that found in humans, with the most severe changes occurring in the gastric antrum. Few granulocytes and no significant elevation in mast cells were seen in older H. pylori-infected cats compared with uninfected controls; however, marked increases in interepithelial globule leukocytes and numerous active mucosal lymphoid follicles were present in infected animals. Indices of gastritis were significantly greater in older infected cats when compared with uninfected controls and younger cats (P < 0.05). The antral cell proliferation index of infected older cats was significantly (P = 0.021) greater than that of uninfected controls. Apoptotic indices of the gastric antrum and body of infected cats were significantly (P = 0.01) increased versus controls. Chronic infection with H. pylori in cats shares many features of long-term H. pylori infection in humans, including the development of preneoplastic processes. This similarity provides useful, comparative insights into host-pathogen interactions.

Animals↗
PubMed2000

LIS1 regulates CNS lamination by interacting with mNudE, a central component of the centrosome.

LIS1, a microtubule-associated protein, is required for neuronal migration, but the precise mechanism of LIS1 function is unknown. We identified a LIS1 interacting protein encoded by a mouse homolog of NUDE, a nuclear distribution gene in A. nidulans and a multicopy suppressor of the LIS1 homolog, NUDF. mNudE is located in the centrosome or microtubule organizing center (MTOC), and interacts with six different centrosomal proteins. Overexpression of mNudE dissociates gamma-tubulin from the centrosome and disrupts microtubule organization. Missense mutations that disrupt LIS1 function block LIS1-mNudE binding. Moreover, misexpression of the LIS1 binding domain of mNudE in Xenopus embryos disrupts the architecture and lamination of the CNS. Thus, LIS1-mNudE interactions may regulate neuronal migration through dynamic reorganization of the MTOC.

1-Alkyl-2-acetylglycerophosphocholine Esterase↗
PubMed2000

Inactivation of the mouse melanocortin-3 receptor results in increased fat mass and reduced lean body mass.

Genetic and pharmacological studies have defined a role for the melanocortin-4 receptor (Mc4r) in the regulation of energy homeostasis. The physiological function of Mc3r, a melanocortin receptor expressed at high levels in the hypothalamus, has remained unknown. We evaluated the potential role of Mc3r in energy homeostasis by studying Mc3r-deficient (Mc3r(-/-)) mice and compared the functions of Mc3r and Mc4r in mice deficient for both genes. The 4-6-month Mc3r-/- mice have increased fat mass, reduced lean mass and higher feed efficiency than wild-type littermates, despite being hypophagic and maintaining normal metabolic rates. (Feed efficiency is the ratio of weight gain to food intake.) Consistent with increased fat mass, Mc3r(-/-) mice are hyperleptinaemic and male Mc3r(-/-) mice develop mild hyperinsulinaemia. Mc3r(-/-) mice did not have significantly altered corticosterone or total thyroxine (T4) levels. Mice lacking both Mc3r and Mc4r become significantly heavier than Mc4r(-/-) mice. We conclude that Mc3r and Mc4r serve non-redundant roles in the regulation of energy homeostasis.

Adipose Tissue↗
PubMed2000

Identification of DNA variants in the SNAP-25 gene and linkage study of these polymorphisms and attention-deficit hyperactivity disorder.

The gene for the synaptic vesicle docking fusion protein, synaptosomal-associated protein of 25 kDa (SNAP-25), has been implicated in the etiology of attention-deficit hyperactivity disorder (ADHD) based on the mouse mutant strain coloboma. This neutron-irradiation induced mouse strain is hemizygous for the deletion of the SNAP-25 gene and displays spontaneous hyperactivity that is responsive to dextroamphetamine. Because of these characteristics, this strain has been suggested to be a mouse model for ADHD. We identified using single stranded conformational polymorphism analysis (SSCP) four DNA sequence variants in the 3' untranslated region of the human SNAP-25 gene. We searched for polymorphisms in the 3' untranslated region because the intron/exon structure of this gene has not yet been determined. We tested for linkage of this gene and ADHD using two of the identified polymorphisms that change a restriction enzyme recognition site. We examined the transmission of the alleles of each of these polymorphisms and the haplotypes of both polymorphisms using the transmission disequilibrium test in a sample of 97 small nuclear families consisting of a proband with ADHD, their parents, and affected siblings. We observed biased transmission of the haplotypes of the alleles of these two polymorphisms. Our findings are suggestive of a role of this gene in ADHD.

Adolescent↗
PubMed2000

Attention-deficit hyperactivity disorder and the gene for the dopamine D5 receptor.

A recent study has suggested a possible association of a polymorphism near the dopamine D5 receptor gene (DRD5) and attention-deficit hyperactivity disorder. The polymorphism studied was a (CA)n repeat located in the cosmid containing the D5 receptor gene2 and the allele that was reported to be associated with attention-deficit hyperactivity disorder (ADHD) was the 148-bp allele. In this study we sought to replicate this finding by testing for biased transmission of the alleles at this same polymorphism in a sample of 92 families with an ADHD proband. We did not observe significant evidence for biased transmission of the 148-bp allele, however we did observe biased transmission of two other alleles, the 136-bp allele and the 146-bp allele. For these two alleles the bias was for these two alleles not to be transmitted to the ADHD children. The number of informative transmissions for these two alleles was small, therefore it would be premature to make any conclusions from our study concerning the role of DRD5 in ADHD.

Adolescent↗