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Biomedical subjects

X Liang

Publications and source records attributed to X Liang.

At least 235 records · Page 13Linked to original sources
PubMed1995

[An experimental study of middle ear implantable hearing device].

The partially middle ear implantable hearing device was designed and tested in 7 cats with conductive hearing loss and 5 cats with mixed hearing loss. It was composed of sound processor, connector and ossicular vibrator. The ossicular vibrator was made from piezoelectric ceramic bimorph which was constructed in the form of flat chip 6mm in length, 1mm in width and 0.5mm in thickness. The incus of cat was removed and the lip attachment of the vibrator was attached to the head of the stapes. The base of the vibrator was fixed to the bone wall of bulla with medical glue. The average values of the response threshold of ABR evoked by click via this vibrator got reduction of 37dB and 39dB respectively in conductive hearing loss group and mixed hearing loss group. The gain curve of hearing was flat in the range from 0.5 to 8kHz frequencies. The ABRs evoked by click via ossicular vibrator was similar to that recorded preoperatively in the wave shape. This result indicates that this device is a highly efficient sound conducting divice to inner ear.

Animals↗
PubMed1995

Induction of mucosal immunity in cotton rats to haemagglutinin-esterase glycoprotein of bovine coronavirus by recombinant adenovirus.

An effective vaccine against enteric bovine coronavirus (BCV) must be able to induce mucosal immunity. We recently described the construction of recombinant human adenovirus type 5 (hAd5) carrying the BCV haemagglutinin-esterase (HE) gene in the early transcription region 3 of the adenovirus genome. In this study, we examined the induction of systemic and mucosal immune responses to the hAd5 vector carrying the BCV HE gene (AdBcHE) following intranasal or enteric immunization of cotton rats. Regardless of the route of administration, mucosal immunization with AdBcHE induced significant levels of anti-HE IgG antibodies in serum. In addition, following intranasal immunization with AdBcHE, significant levels of anti-HE IgA antibodies were found in lung washes of immunized cotton rats. Furthermore, the specific anti-HE antibodies in sera and mucosal secretions efficiently neutralized BCV infectivity in vitro. T-cell proliferation and cell-mediated cytotoxic responses against the BCV HE were elicited in the spleen of intranasally immunized animals. The results demonstrate that mucosal immunization with AdBcHE is capable of inducing both systemic and mucosal immunity to the BCV HE. These immune responses may be important in protecting animals from BCV infection.

Adenoviridae↗
PubMed1995

[A controlled multi-centre clinical trial on cisapride in treatment of functional dyspepsia].

A controlled multi-centre clinical trial was conducted for evaluating the efficacy and safety of cisapride in the treatment of 414 cases of functional dyspepsia with 169 cases as control. Cisapride were given 5mg three times daily for 4 weeks. The results showed that cisapride could significantly improve the symptoms including early satiety, abdominal distention, epigastric pain and nausea. Total efficacy rate of cisapride and placebo were 92.99% and 41.42% respectively. There were statistically significant difference between the two groups. Side-effects are abdominal pain and diarrhoea but most of the patients can endure. The above results indicated that the cisapride was safe and effective in treatment of functional dyspepsia.

Abdominal Pain↗
PubMed1994

Human urokinase receptor expression is inhibited by amiloride and induced by tumor necrosis factor and phorbol ester in colon cancer cells.

The modulation of urokinase plasminogen activator receptor (uPAR) gene expression by tumor necrosis factor alpha (TNF alpha), phorbol ester (PMA) and amiloride was studied in three colon cancer cell lines. uPAR mRNA and protein were induced by TNF alpha and by PMA but were inhibited by amiloride at concentrations of 0.1 to 1 mM in the presence or absence of TNF alpha and PMA. Nuclear run-on transcription assay indicated that the effects of amiloride and TNF alpha were mediated at least in part at the transcriptional level, whereas PMA may act in part via a posttranscriptional mechanism. These results suggested that uPAR gene expression is modulated by multiple signal transduction pathways.

Amiloride↗
PubMed1994

Expression and purification of a truncated macrophage colony stimulating factor in Kluyveromyces lactis.

A truncated human macrophage colony stimulating factor (M-CSF) cDNA encoding amino acid residues from 3 to 149 of the native M-CSF was obtained by using polymerase chain reaction. When inserted into plasmid pCXJ1 and psPHO5 and introduced into Kluyveromyces lactis, it directs the the secretory expression of the biologically active dimeric form of M-CSF. Through a four-step purification protocol, i.e. ammonium sulfate salting out, DEAE-cellulose column chromatography, hydrophobic chromatography on phenyl-sepharose and Mono Q fast protein liquid chromatography, the recombinant truncated M-CSF was purified to homogenerity and show its apparent molecular mass at 21KDa on reduced SDS-PAGE, with a specific activity of 1.21 x 10(7) units/mg protein.

Amino Acid Sequence↗
PubMed1993

Mapping of heparin-binding structures on bovine herpesvirus 1 and pseudorabies virus gIII glycoproteins.

The gIII glycoproteins of both bovine herpesvirus 1 (BHV 1) and pseudorabies virus (PrV) mediate the initial and dominant interactions between virus and permissive host cells. By studying virus binding to wild-type and heparin-deficient CHO cells, we demonstrated that the cellular heparin-like moieties play an essential role in BHV 1 and PrV gIII-mediated virus attachment. Subsequent studies were carried out to map the gIII structures that are responsible for heparin binding. First, based on the observation that BHV 1 and PrV are differentially sensitive to heparin inhibition of gIII-mediated attachment to cells, we conducted a gIII domain shuffling experiment. This involved the construction of a set of recombinant BHV 1 expressing BHV 1 and PrV gIII chimeras and then using the sensitivity to heparin inhibition as a means of mapping the potential heparin-binding regions on the gIII molecules. Next, we synthesized panels of partially overlapping BHV 1 and PrV gIII peptides and examined their reactivity to heparin. The results from these experiments demonstrated five heparin-binding sites between amino acid 129 and 310 of BHV 1 gIII and four heparin-binding sites between amino acid 90 and 275 of PrV gIII.

Amino Acid Sequence↗
PubMed1993

Identification and deletion mutagenesis of the bovine herpesvirus 1 dUTPase gene and a gene homologous to herpes simplex virus UL49.5.

The gene encoding bovine herpesvirus 1 (BHV 1) deoxyuridine triphosphatase (dUTPase) was isolated by a PCR procedure using degenerate oligonucleotide primers whose sequences were based upon conserved motifs commonly present in dUTPase genes. This gene was found to reside between 0.059 and 0.066 map units in the BHV 1 Cooper strain. DNA sequence analysis of this region revealed an open reading frame of 975 base pairs capable of encoding 325 amino acids. The deduced amino acid sequence of the open reading frame exhibits significant homology with dUTPases of other herpesviruses (including human herpes simplex virus, varicella-zoster virus, and Epstein-Barr virus), and it contains five conserved amino acid motifs characteristics of all dUTPases identified to date. A mutant virus carrying a partial deletion of the putative dUTPase gene was made and was found to lack virus-encoded dUTPase activity. This further confirmed that we have identified the BHV 1 dUTPase gene. In addition, a further analysis of the genomic fragment which contains the dUTPase coding sequence revealed an additional 288-base-pair open reading frame which appears to be colinear with the HSV 1 UL49.5 gene. The deduced amino acid sequence of this open reading frame is significantly homologous to the HSV 1 UL49.5 gene product, and as with UL49.5, it contains a potential signal sequence and transmembrane domain characteristic of membrane-associated proteins. These results suggest that this open reading frame represents the BHV 1 homolog of the HSV 1 UL49.5 gene. Since our dUTPase negative mutant was fully viable and since the mutant was constructed such that the UL49.5 gene was also deleted, both the dUTPase and the UL49.5 gene homolog are not required for virus growth in cell culture.

Amino Acid Sequence↗
PubMed1993

Bovine herpesvirus-1 vaccines.

Vaccination has been important in controlling a wide variety of viral and bacterial infections of man and animals. Vaccines to herpesvirus infection of cattle are no exception. The present review describes the different types of conventional vaccines that have been used to date and furthermore describes the novel approaches which are presently being implemented to develop more effective vaccines. These include subunit vaccines as well as genetically engineered modified live deletion mutants. Both these novel vaccine approaches appear to be more efficacious than conventional vaccines. Furthermore, these vaccines provide an additional dimension for control and eradication of infection by providing an opportunity to develop companion diagnostic tests to differentiate infected animals from vaccinated animals. This review summarizes these developments as well as present knowledge regarding the important host defence mechanisms required for preventing infection and aiding recovery from infection.

Animals↗
PubMed1993

Expression of glycoprotein gIII-human decay-accelerating factor chimera on the bovine herpesvirus 1 virion via a glycosyl phosphatidylinositol-based membrane anchor.

Mutants of bovine herpesvirus 1 that express a truncated envelope glycoprotein gIII or a gIII-human decay-accelerating factor (hDAF) chimeric protein (gIII.hDAF) were employed to evaluate the function of the transmembrane and cytoplasmic domains of the gIII molecule. Truncated gIII (i.e., lacking the transmembrane and cytoplasmic region) was readily released from infected cells and was not detected on mature virus particles. In contrast, replacement of the transmembrane and cytoplasmic domains with the carboxyl-terminal portion of hDAF restored the expression of gIII on the membranes of infected cells as well as on virion surfaces. The presence of the gIII.hDAF chimera on virus particles was also associated with normal gIII function, i.e., the mediation of virus attachment and penetration. The gIII-hDAF chimera, which is present on both infected cell surfaces and virions, could be cleaved by a phosphatidylinositol-specific phospholipase C, indicating that it was anchored in the membrane via glycosyl phosphatidylinositol. Our results from this study suggest that the transmembrane and cytoplasmic regions of the gIII molecule serve as a general membrane anchor, but they do not contain structural signals required for the specific assembly of envelope proteins into mature virions.

Animals↗
PubMed1993

The nucleotide sequence of the 5' flanking region of the Arabidopsis ACS2 gene.

The ACS2 gene of Arabidopsis thaliana encodes 1-aminocyclopropane-1-carboxylic acid (ACC) synthase (EC 4.1.1.14) - the key regulatory enzyme in the biosynthetic pathway of the plant hormone ethylene. The gene is unique among ACC synthase genes isolated thus far in that it is highly expressed in both reproductive (e.g. flower) and vegetative tissues (e.g. leaves and roots). In addition, the accumulation of ACS2 transcripts is greatly induced by protein synthesis inhibition (Liang et al 1992). We report here the DNA sequence of the 5' flanking region of the ACS2 gene and an analysis of the sequence with respect to the potential cis-acting regulatory elements that can be recognized by DNA-binding proteins from plants and other organisms.

Arabidopsis↗
PubMed1992

The 1-aminocyclopropane-1-carboxylate synthase gene family of Arabidopsis thaliana.

Genomic sequences encoding five divergent 1-aminocyclopropane-1-carboxylic acid (ACC) synthase polypeptides (ACC1, ACC2, ACC3, ACC4, and ACC5) have been isolated from Arabidopsis thaliana by using heterologous cDNAs and PCR fragments amplified from genomic DNA with degenerate oligonucleotide primers. Each gene is located on a different chromosome in the Arabidopsis genome. The genes are differentially expressed during development and in response to environmental stimuli. Protein-synthesis inhibition derepresses the expression of all genes but most dramatically derepresses that of ACC2, suggesting that their expression may be under negative control. The sequence of ACC2 was determined, and its transcription initiation site was defined. Authenticity of the polypeptide encoded by the gene was confirmed by expression experiments in Escherichia coli. The predicted size of the protein is 55,623 Da, and it contains the 11 invariant amino acid residues conserved between aminotransferases and ACC synthases from various plant species. Comparative analysis of structural and expression characteristics of ACC synthase genes from Arabidopsis and other plant species suggests that the sequence divergence of the ACC synthase genes and possibly the distinct regulatory networks governing the expression of ACC synthase subfamilies arose early in plant evolution and before the divergence of monocots and dicots.

Amino Acid Sequence↗
PubMed1992

An in vivo study of a glycoprotein gIII-negative bovine herpesvirus 1 (BHV-1) mutant expressing beta-galactosidase: evaluation of the role of gIII in virus infectivity and its use as a vector for mucosal immunization.

We constructed a recombinant BHV-1 in which the glycoprotein gIII gene was replaced by the Escherichia coli lacZ gene. The resultant virus mimics the simple gIII deletion mutant in its growth characteristics in cell culture; however, it expresses beta-galactosidase in virus-infected cells. Further characterization of its virulence and the immune responses elicited by it was conducted in cattle. The mutant virus retained the ability to establish an infection when administered intranasally. Infected animals were also capable of transmitting virus to sentinel penmates. However, the mutant virus showed a reduced replication efficiency in the respiratory tract of cattle, as manifested by significantly lower virus shedding and a shorter duration of shedding when compared to wild-type (wt) BHV-1 infections. The mutant virus induced an efficient anti-BHV-1 antibody response and convalescent cattle were fully protected from subsequent wt virus challenge. In addition, cattle infected with the lacZ-expressing virus developed antibodies to beta-galactosidase. Our results demonstrate that the presence of gIII is not a prerequisite for BHV-1 infection; however, gIII does play an important role in maintaining virus replication efficacy in its natural host. With respect to developing BHV-1 as a vaccine vector, our results indicate that deletion of the gIII gene, which partially attenuates the virus and serves as a vaccine virus marker, does not compromise immunogenicity to BHV-1. Most importantly, this vector is effective in delivering foreign antigens to mucosal surfaces of the respiratory tract.

Animals↗
PubMed1992

cis-element combinations determine phenylalanine ammonia-lyase gene tissue-specific expression patterns.

The bean phenylalanine ammonia-lyase gene 2 (PAL2) is expressed in the early stages of vascular development at the inception of xylem differentiation, associated with the synthesis of lignin precursors. This is part of a complex program of developmental expression regulating the synthesis of functionally diverse phenylpropanoid natural products. Analysis of the expression of PAL2 promoter-beta-glucuronidase gene fusions in transgenic tobacco plants showed that functionally redundant cis elements located between nucleotides -289 and -74 relative to the transcription start site were essential for xylem expression, but were not involved in expression in leaf primordia and stem nodes or in establishing tissue specificity in petals. The -135 to -119 region implicated in xylem expression contains a negative element that suppresses the activity of a cryptic cis element for phloem expression located between -480 and -289. The functional properties of each vascular element are conserved in stem, petiole, and root, even though the xylem and phloem are organized in different patterns in these organs. We conclude that the PAL2 promoter has a modular organization and that tissue-specific expression in the vascular system involves a negative combinatorial interaction, modulation of which may provide a flexible mechanism for modification of tissue specificity.

Base Sequence↗
PubMed1992

[The operation treatment for the age-related macular degeneration wet-type eyes and its complications].

Age-related macular degeneration (AMD) is one of the important causes for blindness in elderly population. The effect of the treatments by laser and vitrectomy in AMD wet-type eyes, which subretinal neovascularization is existed in or have vitreous hemorrhage, is reported and discussed. Using laser photocoagulation, 65% of the affected eyes had marked cicatrization and 31% were partially improved. Among the 4 AMD eyes with vitreous hemorrhage, three cases were successful after vitrectomy. It has a certain significance for rescuing the vision and controlling the development in AMD wet-type eyes.

Aged↗