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Biomedical subjects

Yan Feng

Publications and source records attributed to Yan Feng.

85 records · Page 5Linked to original sources
PubMed2003

Comparison of diagnostic techniques for Helicobacter cetorum infection in wild Atlantic bottlenose dolphins (Tursiops truncatus).

Helicobacter cetorum sp. nov. has been cultured from the stomach of Atlantic white-sided dolphins (Lagenorhynchus acutus) and the feces of Pacific white-sided (L. obliquidens) and Atlantic bottlenose (Tursiops truncatus) dolphins and a beluga whale (Delphinapterus leucas). H. cetorum has high homology to Helicobacter pylori as shown by 16S rRNA sequencing, and H. cetorum infection has been associated with gastritis and clinical signs in cetaceans. Because the prevalence of H. cetorum in wild populations is unknown, minimally invasive techniques for detecting H. cetorum were compared for 20 wild bottlenose dolphins sampled as part of a long-term health study. Fecal samples were tested for helicobacter by culture, Southern blotting, and PCR using genus-specific and H. cetorum-specific primers. An enzyme-linked immunosorbent assay (ELISA) was developed to measure H. cetorum immunoglobulin G (IgG). H. cetorum was cultured from 4 of 20 fecal samples, 7 samples were positive using Helicobacter sp. PCR, and 8 samples were positive for H. cetorum using species-specific primers. Two additional fecal samples were positive by Helicobacter sp. Southern blotting, suggesting infection with another helicobacter. All 20 sera contained high levels of IgG antibodies to H. cetorum that were significantly lowered by preabsorption of the sera with whole-cell suspensions of H. cetorum (P < 0.02). Until the specificity of the serum ELISA can be determined by testing sera from dolphins confirmed to be uninfected, PCR and Southern blot screenings of feces are the most sensitive techniques for detection of H. cetorum, and results indicate there is at least a 50% prevalence of H. cetorum infection in these dolphins.

Animals↗
PubMed2003

Observation of DNA damage of human hepatoma cells irradiated by heavy ions using comet assay.

AIM: Now many countries have developed cancer therapy with heavy ions, especially in GSI (Gesellschaft f r Schwerionenforschung mbH, Darmstadt, Germany), remarkable results have obtained, but due to the complexity of particle track structure, the basic theory still needs further researching. In this paper, the genotoxic effects of heavy ions irradiation on SMMC-7721 cells were measured using the single cell gel electrophoresis (comet assay). The information about the DNA damage made by other radiations such as X-ray, gamma-ray, UV and fast neutron irradiation is very plentiful, while little work have been done on the heavy ions so far. Hereby we tried to detect the reaction of liver cancer cells to heavy ion using comet assay, meanwhile to establish a database for clinic therapy of cancer with the heavy ions. METHODS: The human hepatoma cells were chosen as the test cell line irradiated by 80 Mev/u (20)Ne(10+) on HIRFL (China), the radiation-doses were 0, 0.5, 1, 2, 4 and 8 Gy, and then comet assay was used immediately to detect the DNA damages, 100-150 cells per dose-sample (30-50 cells were randomly observed at constant depth of the gel). The tail length and the quantity of the cells with the tail were put down. EXCEL was used for statistical analysis. RESULTS: We obtained clear images by comet assay and found that SMMC-7721 cells were all damaged apparently from the dose 0.5 Gy to 8 Gy (t-test: P<0.001, vs control). The tail length and tail moment increased as the doses increased, and the number of cells with tails increased with increasing doses. When doses were higher than 2 Gy, nearly 100 % cells were damaged. Furthermore, both tail length and tail moment, showed linear equation. CONCLUSION: From the clear comet assay images, our experiment proves comet assay can be used to measure DNA damages by heavy ions. Meanwhile DNA damages have a positive correlation with the dose changes of heavy ions and SMMC-7721 cells have a great radiosensitivity to (20)Ne(10+). Different reactions to the change of doses indicate that comet assay is a useful tool to detect DNA damage induced by heavy ions.

Carcinoma, Hepatocellular↗
PubMed2003

[Trabeculectomy combined with mitomycin C and removed suture in glaucoma].

PURPOSE: To study the clinical effect of trabeculectomy combined with Mitomycin C and removed suture. METHODS: Seventy-five patients (99 eyes) with glaucoma were randomized into two groups: a controlled group underwent normal trabeculectomy, an observed group with trabeculectomy. The intraocular pressure (IOP), the anterior chamber depth, the filtering blebs, the visual acuity and other ocular complications were measured and compared between the two groups. RESULTS: The incidence of postoperative low IOP, shallow anterior chamber, the visual acuity loss and other complications in the observed group were less than those in the controlled group. CONCLUSION: Trabeculectomy could effectively reduce the incidence of postoperative complication by controlling the amount of aqua oculi outflowing. It is worthy of application in glaucoma surgical operation.

Adult↗
PubMed2003

[The human beta-defensins expression in female genital tract and pregnancy-related tissues].

OBJECTIVE: Human beta-defensins (HBDs) are small, cationic endogenous antimicrobial peptides isolated from the hemodialates of patients with chronic renal failure (HBD-1) and Psoriasic skin (HBD-2). They may play an important role in mucosal innate host defense against infections. In this study, we examined their mRNAs expression in normal and pregnant women genital tract. METHODS: Reverse transcription-polymerase chain reaction (RT-PCR) was performed in the detection of HBD-1 and HBD-2 mRNA expression in the samples from normal and pregnant women genital tract. beta-actin was taken as positive control. RESULTS: RT-PCR detection revealed that HBD-1 mRNA expressed in all samples of normal women taken from vagina, cervix, endometrium, fallopian tube, and ovary, and HBD-2 mRNA widely expressed in genital tract except vagina and ovary. In pregnant women, HBD-1 mRNA widely expressed in chorion, villus, placenta, and umbilical cord, but not in amnion, and HBD-2 mRNA were detected in chorion, villus and placenta tissues. CONCLUSION: The findings of this study on the wide expression of HBD-1 and HBD-2 in both the normal and the pregnant women genital tract suggest that HBDs may play an important role in human genital tract defense mechanisms.

Adult↗
PubMed2002

A naturally occurring rabbit model of enterohemorrhagic Escherichia coli-induced disease.

Enterohemorrhagic Escherichia coli (EHEC) causes hemorrhagic colitis and hemolytic-uremic syndrome (HUS) in humans. The exact mechanism by which EHEC induces disease remains unclear because of the lack of a natural animal model for the disease. An outbreak of bloody diarrhea and sudden death was investigated in a group of Dutch belted rabbits. Two of these rabbits harbored enteropathogenic E. coli O145:H(-), and 1 rabbit was coinfected with EHEC O153:H(-). A partial Shiga toxin 1 gene (stx1) fragment from E. coli O153:H(-) was confirmed by Southern blot and sequence analysis. Toxin production was demonstrated by a HeLa cell cytotoxicity assay. Histopathologic findings in all affected rabbits included erosive and necrotizing enterocolitis with adherent bacterial rods, proliferative glomerulonephritis, tubular necrosis, and fibrin thrombi within small vessels and capillaries. Our findings provide evidence for a naturally occurring animal model of EHEC-induced systemic disease that closely resembles human HUS.

Animals↗
PubMed2002

Crystallization and preliminary crystallographic analysis of acylamino-acid releasing enzyme from the hyperthermophilic archaeon Aeropyrum pernix.

Crystals of acylamino-acid releasing enzyme from the hyperthermophilic archaeon Aeropyrum pernix strain K1 have been grown at 291 K using ammonium phosphate as a precipitant. The diffraction pattern of the crystal extends to 2.4 A resolution at 100 K using Cu Kalpha radiation. The crystal belongs to space group P1, with unit-cell parameters a = 107.5, b = 109.9, c = 119.4 A, alpha = 108.1, beta = 109.8, gamma = 91.9 degrees. The presence of eight molecules per asymmetric unit gives a crystal volume per protein mass (V(M)) of 2.4 A(3) Da(-1) and a solvent content of 48% by volume. A full set of X-ray diffraction data was collected to 2.9 A from the native crystal.

Archaeal Proteins↗
PubMed2002

Crystallization and preliminary X-ray analysis of recombinant histone HPhA from the hyperthermophilic archaeon Pyrococcus horikoshii OT3.

Recombinant archaeal histone from the hyperthermophile Pyrococcus horikoshii OT3 (HPhA) was crystallized by the hanging-drop vapour-diffusion method. Crystals grew at 291 K in 200 mM (NH(4))(2)SO(4), 100 mM sodium acetate buffer pH 4.6, 19% PEG 4000. Diffraction data were obtained to a resolution of 2.3 A from a single frozen crystal, which belonged to space group P2(1) with unit-cell parameters a = 34.99, b = 46.89, c = 35.02 A, alpha = gamma = 90, beta = 104 degrees. The asymmetric unit contained two molecules and had a solvent content of approximately 35%.

Crystallization↗
PubMed2002

Identification of novel Helicobacter spp. from a beluga whale.

The gastric fluid and feces of three belugas from the Mystic Aquarium were assessed for the presence of Helicobacter spp. Gastric fluid and feces from the two clinically healthy belugas were negative for helicobacter, and endoscopy performed on these animals revealed no lesions. However, a helicobacter isolate and PCR product similar to helicobacter strains previously recovered from dolphins were identified, respectively, from the feces and gastric fluid of a beluga manifesting intermittent inappetence and lethargy. Esophageal and forestomach ulcers were noted on endoscopy. This is the first report of novel Helicobacter spp. being identified from whales.

Animals↗
PubMed2002

Helicobacter marmotae sp. nov. isolated from livers of woodchucks and intestines of cats.

Woodchucks (Marmota monax) have a high incidence of hepatocellular carcinoma (HCC) associated with chronic infection with woodchuck hepatitis virus (WHV) and serve as a model of hepatitis B virus-associated HCC in humans. Helicobacter hepaticus, an enterohepatic helicobacter in mice, is known to cause hepatocellular adenomas and carcinomas in susceptible mouse strains. In long-term chemical bioassays conducted with B6C3F(1) mice, H. hepaticus has been regarded as a confounding factor because of its tumor-promoting activity. In order to determine if woodchucks harbor a Helicobacter sp. that might play a role in potentiating hepatic inflammation or neoplasia, a study was undertaken to determine whether woodchucks' livers were infected with a Helicobacter sp. Frozen liver samples from 20 (17 WHV-infected and 3 noninfected) woodchucks, 10 with WHV-associated hepatic tumors and 10 without tumors, were cultured by microaerobic techniques and analyzed by using genus- and species-specific helicobacter PCR primers. A 1,200-bp Helicobacter sp.-specific sequence was amplified from 14 liver samples. Southern hybridization confirmed the specific identity of the PCR products. Nine of the 10 livers with tumors had positive Helicobacter sp. identified by PCR, whereas 5 of the 10 livers without tumors were positive. By use of 16S rRNA species-specific primers for H. marmotae, two additional liver samples from the nontumor group had positive PCR amplicons confirmed by Southern hybridization. A urease-, catalase-, and oxidase-positive bacterium was isolated from one liver sample from a liver tumor-positive woodchuck. By 16S rRNA analysis and biochemical and phenotypic characteristics, the organism was classified as a novel Helicobacter sp. Subsequently, four additional bacterial strains isolated from feces of cats and characterized by biochemical, phenotypic, and 16S rRNA analysis were determined to be identical to the woodchuck isolate. We propose the name Helicobacter marmotae sp. nov. for these organisms. Further studies are required to ascertain if this novel Helicobacter sp. plays a tumor promotion role in hepadnavirus-associated tumors in woodchucks or causes enterohepatic disease in cats.

Animals↗
PubMed2002

Insertion/deletion polymorphism of the ACE gene is associated with type 2 diabetes.

In an attempt to examine the role of an ACE gene insertion/deletion (I/D) polymorphism in type 2 diabetes, we conducted a case-control association study among 132 couple-pairs from northern China. The genotype frequencies for II, ID, and DD were 39.8, 39.8, and 20.3%, respectively, in the case group and 44.8, 44.8, and 10.4% in the control group. The DD frequency was significantly higher in the case group than in the control group (chi(2)(1) = 4.77, P = 0.03), suggesting that the DD genotype is associated with an increased susceptibility to type 2 diabetes in our study population.

Adult↗
PubMed2002

Analysis of amlodipine in human plasma by liquid chromatography-mass spectrometry.

A simple, sensitive, and specific liquid chromatographic method coupled with electrospray ionization (ESI)-mass spectrometry for the determination of amlodipine is developed. After extraction by ethyl acetate using nicardipine as the internal standard, solutes are separated on a C18 column with a mobile phase of methanol-1% HAc (65:35). Detection is performed on an air pressure ionization single quadruple mass spectrometer equipped with an ESI interface and operated in positive-ionization mode. Amlodipine quantitation is realized by computing the peak-area ratio (amlodipine-nicardipine) of the extracts analyzed in single ion monitoring mode (m/z 431 and m/z 480 for amlodipine and nicardipine, respectively) and comparing them with the calibration curve (r = 0.9991).

Amlodipine↗
PubMed1998

Gene therapy for human colorectal carcinoma using human CEA promoter contro led bacterial ADP-ribosylating toxin genes human CEA: PEA & DTA gene transfer.

AIM:To establish a tissue-specific gene therapy for colorectal carcinoma using bacterial ADP-ribosylating toxin genes. METHODS:Pseudomonas exotoxin A domain [II+III (PEA) was cloned from genomic DNA of Pseudomonas aeruginosa.PEA and diphtheria toxin A chain gene (DTA) were modified to express eukaryotically. After sequencing, the toxin genes under the control of human carcinoembryonic antigen (CEA)promoter were cloned into retroviral vectors to construct CEAPEA and CEADTA respectively. In vitro cotransfection of the constructs with luciferase vectors and in vivo gene transfer in nude mice were subsequently carried out. RESULTS:Both CEAPEA and CEADTA specifically inhibited the reporter gene expression in the CEA positive human colorectal carcinoma (CRC) cells in vitro. Direct injection of CEAPEA and CEADTA constructs into the established human tumors in BALB/c nude mice led to significant and selective reductions in CRC tumor size as compared with that in control groups.CONCLUSION:The toxin genes, working as therapeutic genes, are suitable for the tissue-specific gene therapy for colorectal carcinoma.

Journal Article↗