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Biomedical subjects

Z H Yuan

Publications and source records attributed to Z H Yuan.

14 recordsLinked to original sources
PubMed2006

Olaquindox and cyadox stimulate growth and decrease intestinal mucosal immunity of piglets orally inoculated with Escherichia coli.

One hundred and fifty piglets were randomly allotted to one of six treatments to determine the effects of olaquindox and cyadox on growth and intestinal immune response including the number of intraepithelial lymphocytes and immunoglobulin A secreting cells (ASCs) during the three-week period. A 2 x 3 factorial arrangement of treatments was employed with the following factors: (1) Escherichia coli (O(139):K(88), 10(10) CFU) inoculation or control and (2) no antimicrobials, 100 mg/kg olaquindox and 100 mg/kg cyadox in the basal diet respectively. The antimicrobial supplementations improved (p < 0.01) average daily gain and feed conversion ratio (FCR) during the experiment. Average daily gain and FCR in the cyadox-supplemented pigs were higher (p < 0.05) than those in the olaquindox-supplemented pigs. Intraepithelial lymphocytes and ASCs decreased (p < 0.05) when the diets were supplemented. Jejunal ASCs in the cyadox-supplemented pigs were lower (p < 0.05) than those in the olaquindox-supplemented pigs. Olaquindox and cyadox suppressed E. coli-induced intestinal immune activation, which may be involved in the observed growth promotion.

Animal Feed↗
PubMed2006

Effects of cyadox and olaquindox on intestinal mucosal immunity and on fecal shedding of Escherichia coli in piglets.

A 2 x 3 factorial arrangement of treatments was used to determine the effects of olaquindox and cyadox on the intestinal mucosal immune response and on fecal shedding of Escherichia coli in Landrace x Large White barrows that had been orally given 10(10) cfu of E. coli (O139:K88). Factors included 1) E. coli inoculation or no inoculation, and 2) no antimicrobial, 100 mg of olaquindox/kg, and 100 mg of cyadox/kg in the basal diet, respectively. The effects of cyadox and olaquindox were assessed in terms of fecal shedding of E. coli, the number of intraepithelial lymphocytes (IEL), immunoglobulin A-positive cells (APC) in the intestinal lamina propria, and ADG. There was no difference in the fecal shedding of total E. coli or the inoculated E. coli between olaquindox-supplemented pigs and cyadox-supplemented pigs during the experiment. However, fecal shedding of the inoculated E. coli in olaquindox- or cyadox-supplemented pigs was less (P < 0.05) than that in nonsupplemented pigs. Escherichia coli inoculation increased IEL and APC in the jejunum and ileum, but olaquindox or cyadox decreased IEL and APC (P < 0.05). Jejunal APC in cyadox-supplemented pigs was less (P < 0.05) than that in olaquindox-supplemented pigs. Escherichia coli inoculation reduced (P < 0.05) ADG, whereas the supplementations improved ADG (P < 0.01) during the experiment. Average daily gain in cyadox-supplemented pigs was greater (P < 0.05) than that in olaquindox-supplemented pigs. The data indicated that olaquindox and cyadox reduced the number of intestinal E. coli and suppressed E. coli-induced immune activation, which might be responsible for the enhanced growth that was observed.

Animals↗
PubMed2005

Roles of the polypyrimidine tract and 3' noncoding region of hepatitis C virus RNA in the internal ribosome entry site-mediated translation.

Hepatitis C virus (HCV) genome contains a 3'noncoding region (3'NCR) consisting of a variable region, a polypyrimidine tract (polyU/UC) and the X region. To examine the roles of 3'NCR and polyU/UC tract in the internal ribosome entry site (IRES)-mediated translation process, a variety of 3'NCRs containing different lengths of polyU/UC tract were obtained from HCV infected patients and cloned respectively to the downstream of the firefly luciferase coding gene linked to HCV 5'NCR and 30 nucleotides of core gene (containing IRES element). The results of in vitro translation in rabbit reticulocyte lysate (RRL) and cell transfection assay in mammalian cells showed that the IRES-mediated translation efficiency could be enhanced by the full-length of 3'NCR of HCV RNA. However, contradictory results were observed when the role of polyU/UC tract in the IRES-mediated translation was studied. While the IRES-mediated translation efficiency was inhibited by the presence of polyU/UC tract in in vitro translation experiments, transfection of these expression cassettes into hepatic cell line showed that polyU/UC tract enhanced IRES-mediated translation efficiency in vivo. Cellular-fraction complement experiments showed that cellular factors were required for the enhancement by the polyU/UC tract. Further antibody blocking assay and UV cross-linking assay suggested the correlation of IRES-mediated translation with host factors, including the La protein. The data above also indicated that the modulations of the IRES-mediated translation by the HCV 3'NCR and the polyU/UC tract were in a length-independent manner.

3' Untranslated Regions↗
PubMed2001

Comparing the immunogenicity of hepatitis B virus S gene variants by DNA immunization.

DNA immunization was used to compare the immunogenicity of hepatitis B virus S gene variants. Four recombinant plasmid DNAs containing the full-length virus genome with different S gene inserts were used to immunize BALB/c and C57/BL/6 mice. These inserts were cloned from 129L (residue 129, glutamine to leucine), 129H (residue 129, glutamine to histidine) 145R (residue 145, glycine to arginine) variants and the wild-type virus. The titer of hepatitis B virus core antibodies (anti-HBc) in immunized mice was used as the control for the efficiency of DNA immunization. Serum hepatitis B surface antibody (anti-HBs) titer and cytokines induced in splenocytes stimulated with hepatitis B surface antigen (HBsAg) were monitored as specific immune responses induced by different plasmid DNAs. 129L DNA induced significantly lower anti-HBs antibodies (IgG, IgG1, and IgG2a) and less interferon-gamma, compared to those in mice immunized with the 129H variant and the wild-type HBV DNA (p < 0.05). Computer modeling showed that a change from glutamine to leucine at 129 residue led to higher hydrophobicity and could result in decreased immunogenicity. Results indicate that DNA immunization can be used to compare the humoral and cellular immunogenicity among different HBV S variants.

Animals↗
PubMed2001

A single amino acid in the reverse transcriptase domain of hepatitis B virus affects virus replication efficiency.

To explore functional domains in the hepatitis B virus (HBV) polymerase, two naturally occurring HBV isolates (56 and 2-18) with 98.7% nucleic acid sequence homology but different replication efficiencies were studied. After transfection into HepG2 cells, HBV DNA isolated from intracellular virus core particles was much higher in 56-transfected cells than in cells transfected with 2-18. The structural basis for the difference in replication efficiency between these two isolates was studied by functional domain gene substitution. The complete polymerase (P) gene and its gene segments coding for the terminal protein (TP), spacer (SP), reverse transcriptase (RT), and RNase H in 2-18 were separately replaced with their counterparts from 56 to construct full-length chimeric genomes. Cell transfection analysis revealed that substitution of the complete P gene of 2-18 with the P gene from 56 slightly enhanced viral replication. The only chimeric genome that regained the high replication efficiency of the original 56 isolate was the one with substitution of the RT gene of 2-18 with that from 56. Within the RT region, amino acid differences between isolates 2-18 and 56 were located at positions 617 (methionine versus leucine), 652 (serine versus proline), and 682 (valine versus leucine). Point mutation identified amino acid 652 as being responsible for the difference in replication efficiency. Homologous modeling studies of the HBV RT domain suggest that the mutation of residue 652 from proline to serine might affect the conformation of HBV RT which interacts with the template-primer, leading to impaired polymerase activity.

Amino Acids↗
PubMed2001

Cloning and Expression of Chinese Duck Interferon-gamma Gene.

The efficacy of cytokine therapy has been demonstrated in several viral diseases. Interferon-gamma is a cytokine that has potent antiviral property and immunomodulatory activity. To investigate the role of IFN-gamma in viral clearance during natural infection and to define the antiviral mechanism, DHBV-infected ducks was used as an animal model. To clone, express, and develop the method of quantifying DuIFN-gamma gene transcription and expression, DuIFN -gamma cDNA was amplified by RT-PCR from PHA stimulated duck PBMC. Recombinant plasmid expressing DuIFN-gamma was used to transfect COS-7, and the cell culture supernatant was analyzed by CPE inhibitory assay and MTT methods to determine the antiviral titer of IFN-gamma. The GST-DuIFN-gamma fusion protein was expressed in E.coli and purified using the GST sepharose 4B. Results indicated that the supernatant collected from COS-7 cells transfected with DuIFN-gamma cDNA was able to prevent duck fibroblasts from VSV induced CPE in a dose dependent manner. An anti-DuIFN-gamma antibody neutralized this antiviral activity.

Journal Article↗
PubMed2000

[Plant regeneration from protoplast culture in flax (Linum usitatissimum)].

Shoot protoplasts of four fiber flax (Linum usitatissimum) varieties (7309, 948, Belinka and Viking) were isolated and cultured. The optimal condition for higher protoplast yield 1.8 x 10(6)/gFW and activity 85.5% (c.v. 948) were from 10 day old seedings. Culture in V-KM Agroase-island medium led to first divisions after 3 days (c. v. 948), and after twenty days with an efficiency of 36% of divided cells and 5.2% in plating efficiency. Plant regeneration was obtained in 7309 and Belinka on agar media B5-2, MS3 containing 0.6 mg/L 6-BA and 0.1 mg/L NAA. Roots and leaves regeneration were observed in Viking and 948 respectively.

Cell Division↗
PubMed1998

Effect of plasmid DNA on immunogenicity of HBsAg-anti-HBs complex.

Hepatitis B surface antigen (HBsAg) complexed with anti-HBs is more immunogenic than HBsAg alone in mice. This complex is usually used with alum as an adjuvant, which can enhance humoral response but inhibits cell-mediated immune responses. To improve the immunogenicity of HBsAg-anti-HBs, we immunized mice with a combination of this immunogenic complex and pCMVHBs, a plasmid encoding HBsAg, or the vector pCMV. Both plasmids enhanced the anti-HBs response induced by the immunogenic complex. We found 20 microg of plasmid or vector enhanced the anti-HBs response in all mice, whereas 1 microg was less effective. Splenocytes from different immunized groups were stimulated with HBsAg in vitro, and the highest level of IL-2 detected in the supernatant was found in mice immunized with HBsAg-anti-HBs plus pCMVHBs. A plasmid (pcDNA3c191) encoding core protein of hepatitis C virus (HCV) was used as an adjuvant to the immunogenic complex. A preliminary result showed that pcDNA3c191 not only enhanced the immunogenicity of HBsAg-anti-HBs, but also induced anti-HCV core antibodies. Immunization using a plasmid DNA encoding one viral antigen in combination with antigen and antibody complex of another microbial origin could be a new approach to the development of multivalent vaccines.

Animals↗
PubMed1997

Expression, purification, and partial characterization of HCV RNA polymerase.

The product of the NS5B gene of Hepatitis C Virus (HCV) has been expressed in Escherichia Coli both as a fusion protein with glutathione-S-transferase (GST) of molecular weight 91 KDa and at high level as a single protein of molecular weight 65 KDa. The protein was sequestered within inclusion bodies and a variety of procedures designed to minimize inclusion body formation proved unsuccessful. The method finally adopted involved the purification of inclusion bodies followed by the solubilization, purification, and refolding of the expressed protein. A good recovery and protein purity of the order of 80-90% were achieved. The purified protein was shown to possess RNA polymerase activity in an assay using polyA/oligoU as template. The enzymatic activity is rifampicin resistant, poly A dependent, and requires Mg++. The availability of purified HCV RNA polymerase will allow the study of viral replication and constitute the basis for testing new anti-viral drugs.

Cloning, Molecular↗
PubMed1997

Pharmacokinetics of ampicillin and sulfadimidine in pigs infected experimentally with Streptococcus suum.

Twenty-three hybrid pigs (23 +/- 3 kg body wt) were assigned to three groups to investigate the pharmacokinetics of ampicillin (APC, 10 mg/kg) administered intravenously (i.v.) and intramuscularly (i.m.), and sulfadimidine (SDM, 50 mg/kg) administered intravenously as a bolus injection. In the first series of experiments the animals remained healthy. Subsequently, the pigs were infected with Streptococcus suum by subcutaneous (s.c.) inoculation and the experiments were repeated. The total apparent distribution volume of APC given intravenously was increased from 0.512 +/- 0.026 L/kg in uninfected pigs to 0.68 +/- 0.06 L/kg (P < 0.01) in infected pigs, whereas there were no significant changes in the same parameter for SDM (P > 0.05). The clearance of APC was increased markedly from 0.52 +/- 0.07 L/kg/h in uninfected pigs to 0.62 +/- 0.10 L/kg/h in infected pigs. In contrast, SDM clearance was decreased markedly from 0.023 +/- 0.003 L/kg/h to 0.017 +/- 0.003 L/kg/h (P < 0.05). As a result, the biological half-lives of the drugs were altered to varying degrees in infected pigs. The half-life of SDM was increased from 15.0 +/- 3.0 h in uninfected pigs to 20 +/- 7h in infected pigs (P < 0.05), but differences in APC half-lives between uninfected and infected animals were not observed (P > 0.05). There were no statistically significant differences in pharmacokinetic parameters of APC administered by intramuscular injection between the healthy and the diseased status, although its half-life was shortened from 0.76 +/- 0.22 h in the healthy to 0.57 +/- 0.23 h in the diseased. The results suggest that blood concentrations of APC and SDM are affected differently by the same disease due to its specific effects on their distribution and elimination.

Ampicillin↗
PubMed1990

Pharmacokinetics of sulfadimidine and its N4-acetyl metabolite in healthy and diseased rabbits infected with Pasteurella multocida.

The pharmacokinetics of sulfadimidine (SDM) and its N4-acetyl metabolite (N4SDM) were investigated after intravenous bolus injection of a single dose (200 mg/kg) of SDM in normal and diseased New Zealand white rabbits. The apparent distribution volume at steady state, total body clearance and elimination half-life of SDM in normal animals were 0.7 +/- 0.3 l/kg, 0.57 +/- 0.24 l/kg/h and 1.6 +/- 1.3 h, respectively. Of the administered dose, 62.1% was metabolized by N4-acetylation, and 12.7 +/- 1.1 and 2.8 +/- 1.8% of the dose was excreted as free drug by the kidney and gastrointestinal tract, respectively. The 'apparent' formation and elimination half-lives of N4SDM were 0.6 +/- 0.4 and 2.2 +/- 1.1 h, respectively. The metabolite was eliminated mainly by excretion through the kidney. There was no significant effect of acute pasteurellosis on the pharmacokinetics of either SDM or N4SDM in rabbits.

Absorption↗