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Biomedical subjects

X Xiao

Publications and source records attributed to X Xiao.

At least 163 records · Page 9Linked to original sources
PubMed1997

[The study on SDS-PAGE technic classification of the whole protein of oral bacteria].

Oral flora was classificated by SDS-PAGE combined with Comassie blue staining and silver staining. The results showed that each species of the test oral bacteria expressed its specific electrophorectic protein pattern, the way of sample preparation, staining did not change the protein pattern. This indicated that SDS-PAGE could be used to classificate oral flora. The protein pattern was more obvious among the genus than that of within the genus. This showed that different relationship was among the bacteria.

Actinomyces viscosus↗
PubMed1997

[A study on the quality of various species of Dalbergia].

The content and main components of volatile oil and the content of totalflavone in various species of Dalbergia (DA) are studied by steam-distillation, gas chromatography-mas spectroscopy and spectrophotometry. The results show that the content of volatile oil in Dalbergia odorifera (DO) is 3.61-3.79%, and the content of total flavone is 2.51-5.82%. The content of volatile oil of other species of DA is less than 1.50%, their content of total flavone is markedly different from that of DO.

Chromatography, Thin Layer↗
PubMed1997

[Studies on the performance and applications of chloropropyl bonded silica. I. Separation of disubstituted benzene isomers and prostaglandin epimers].

The performance of chloropropyl bonded silica (CPS) in HPLC and its applications in separation of disubstituted benzene isomers and prostaglandin epimers were studied. The CPS column has high column efficiency and the kinetic curves illustrate it is suitable for fast analysis. The effect of composition and pH value of mobile phase (methanol/water or methanol/20 mmol/L H3PO4-NaOH buffer) on the retention of the solutes were investigated. Generally, the main retention mechanism of solutes was hydrophobic interaction, however there also exited polar adsorption interaction, ion-dipole interaction etc. When the mobile phase condition changed, the main separating mechanism may be changed with CPS column. So, with increasing pH value of mobile phase, the retention of isomers of nitrophenol exhibited a parabolic change. The chromatographic condition was optimized, and the isomers of nitrophenol, aminophenol and toluidine etc. as well as the epimers of 15-methyl-PGF2alpha were separated very well on the column. Moreover, the speed of separation was faster than that in general reversed-phase system. CPS showed to have good stability to heat and solvent and it was also a very stable intermediate to prepare bonded phase with various functional groups.

Adsorption↗
PubMed1997

[The protective role of heat shock gene expression on hydrogen peroxide induced pulmonary alveolar macrophages].

The aim of this study is to determine whether heat-induced heat shock gene expression in rat pulmonary alveolar macrophages (PAMs) would protect PAMs against hydrogen peroxide (H2O2)-mediated cell killing. In response to sublethal heat shock at 42 degrees C for 2 h, the cells synthesized heat shock protein 70 kD (HSP70) and other different molecular weight heat shock proteins, which were detected with gel electrophoresis after [35S]-methionin labeling cellular protein and Western blotting analysis in PAMs. Northern blot analysis showed the induction of HSP70 mRNA with heat shock treatment. Futhermore, with heat shock, there was a significant increment of survival cells after H2O2 (1,2,3 mmol.L-1, 45 min) exposure. This increase was blocked both by Cycloheximide and by Actinomycin D, and was associated with inhibition of synthesis of HSP70 protein and transcription of HSP70 mRNA. These results strongly suggest that expression of heat shock gene (especially HSP70 gene) plays an important role in the intracelluar mechanism of cytoprotection against H2O2 in rat PAMs.

Animals↗
PubMed1996

Fibronectin improves transduction of reconstituting hematopoietic stem cells by retroviral vectors: evidence of direct viral binding to chymotryptic carboxy-terminal fragments.

Efficient transduction of reconstituting hematopoletic stem cells (HSC) is currently only possible by cocultivation of target cells directly on producer cell lines, a method not applicable to human gene therapy protocols. Our laboratory has previously shown adhesion of primitive hematopoletic stem and progenitor cells to the carboxy-terminal 30/35-kD fragment of the extracellular matrix molecule fibronectin (FN 30/35) (Nature 352:438, 1991) and increased transduction of human hematopoietic progenitor cells via retroviral vectors while adherent to this fragment (J Clin Invest 93:1451, 1994). Here we report that (1) transduction of reconstituting murine HSC assayed 12 months after infection with retrovirus supernatant on FN 30/35 is as effective as cocultivation directly on producer cells; (2) recombinant retrovirus particles directly adhere to FN 30/35 in a quantitative and dose-dependent fashion; and (3) increased transduction efficiency on FN 30/ 35 does not appear to be associated with increased cell proliferation or activation of protein phosphorylation typically induced by integrin-fibronectin interactions. Therefore, we speculate that supernatant infection of HSC on FN 30/35 leads to colocalization of retrovirus particles and target cells on FN 30/35 molecule with a large increase in local virus titer presented to the cell. These findings have direct and important implications for the modification of current human gene therapy protocols.

3T3 Cells↗
PubMed1996

Xenogeneic expression of human stem cell factor in transgenic mice mimics codominant c-kit mutations.

Mutations of c-kit, which encodes a transmembrane receptor tyrosine kinase, have been identified in mice by abnormal coat color, anemia, and germ cell defects. Mice heterozygous for mutations of c-kit have a white forehead blaze and a white ventral spot, leading these mutants to be termed dominant White spotting (W). We have previously demonstrated that the membrane-associated isoform of human stem cell factor (hSCF220, the ligand for c-kit) is inefficiently processed in murine stromal cell transfectants. Thus, in murine cell lines analyzed in vitro, hSCF220 transfectants present SCF as a membrane restricted protein in contrast to the murine SCF220 cDNA protein product, which is slowly cleaved and secreted. We show here that transgenic mice expressing the human SCF220 isoform in vivo display a phenotype indistinguishable from some alleles of W. Specifically, hSCF220-expressing transgenic mice display a prominent forehead blaze and a white ventral spot. Generations of doubly heterozygous animals that carry both a mutated c-kit allele and the hSCF220 transgene display a more severe coat color abnormality. This phenotype appears to be due to occupancy of murine c-kit by human SCF and diminished cell surface expression of endogenous murine SCF. Normal signaling events that lead to cell survival or proliferation appear to be disrupted in vivo in these transgenic mice.

Alleles↗
PubMed1996

Differential and persistent expression patterns of CNS gene transfer by an adeno-associated virus (AAV) vector.

Safe, long-term gene expression is a primary criteria for effective gene therapy in the brain, so studies were initiated to evaluate adeno-associated virus (AAV) vector transfer of a reporter gene into specific sites of the rat brain. In the 4 day old rat, site infusions of AAV-CMV-lacZ (1 microliter; 5 x 10(4) particles) produced neuronal beta-galactosidase gene expression 3 weeks later in the hippocampus and inferior colliculus, but not in the cerebral cortex. Seven days after infusion of AAV-CMV-lacZ viral vectors (1 microliter) in the adult rat, beta-galactosidase gene expression was found in the olfactory tubercle, caudate, hippocampus, piriform cortex and inferior colliculus. primarily in multipolar neurons close to the infusion site. Three months after vector microinfusion, similar levels of gene expression remained in the olfactory tubercle and the inferior colliculus, with some reduction found in the caudate, but substantial reductions in beta-galactosidase gene expression occurred in the hippocampus and piriform cortex. In no case were obvious signs of toxicity noted. Therefore, AAV vectors can transfer foreign genes into the adult and neonatal CNS, but the pattern and longevity of gene expression depends upon the area of brain being studied.

Animals↗
PubMed1996

Identification of the native NIT2 major nitrogen regulatory protein in nuclear extracts of Neurospora crassa.

The nit-2 gene of Neurospora crassa encodes the major nitrogen regulatory protein which acts in a positive fashion to activate the expression of many different structural genes during conditions of nitrogen limitation. An E. coli-expressed NIT2/beta-Gal fusion protein binds specifically to DNA in vitro by recognizing GATA core elements. Nuclear extracts prepared from a wild-type N. crassa strain contain a protein factor which displays all of the properties expected for the native NIT2 protein. The native NIT2 protein in nuclear extracts binds with high affinity to DNA fragments which contain two GATA elements, weakly to fragments with a single GATA element, and fails to bind to DNAs which lack these sequences. The DNA binding ability of the protein factor in nuclear extracts is efficiently blocked by a polyclonal antibody developed against the zinc-finger region of NIT2 protein. Western blot analysis with the anti-NIT2 antiserum revealed a specific protein with a size of approximately 110,000 daltons, in excellent agreement with the predicted size of NIT2. Both the specific NIT2 DNA binding activity and the protein detected by Western blot are totally lacking in nuclear extracts of a nit-2 rip mutant strain. These results all support the conclusion that the native NIT2 protein in Neurospora cells has been identified. The NIT2 protein is localised in nuclei and could not be detected in the cytoplasmic fraction of cells subjected to nitrogen derepression or nitrogen repression, indicating that the nuclear import of NIT2 is not regulated.

Antibodies, Fungal↗
PubMed1996

Long-term gene transfer in porcine myocardium after coronary infusion of an adeno-associated virus vector.

BACKGROUND: Viral vector-mediated gene transfer into the heart represents a potentially powerful tool for studying both cardiac physiology as well as gene therapy of cardiac disease. We report here the use of a defective viral vector, which expresses no viral gene products, for gene transfer into the mammalian heart. Previous studies have used recombinant viral vectors, which retained viral genes and yielded mostly short-term expression, often with significant inflammation. METHODS: An adeno-associated virus vector was used that contains no viral genes and is completely free of contaminating helper viruses. The adeno-associated virus vector was applied to rat hearts by direct intramuscular injection; adeno-associated virus was also infused into pig hearts in vivo via percutaneous intraarterial infusion into the coronary vasculature using routine catheterization techniques. RESULTS: Gene transfer into rat heart yielded no apparent inflammation, and expression was observed for at least 2 months after injection. Infusion into pig circumflex coronary arteries resulted in successful transfer and expression of the reporter gene in cardiac myocytes without apparent toxicity or inflammation; gene expression was observed for at least 6 months after infusion. CONCLUSIONS: We report the use of adeno-associated virus vectors in the cardiovascular system as well as successful myocardial gene transfer after percutaneous coronary artery infusion of viral vectors in a large, clinically relevant mammalian model. These results suggest that safe and stable gene transfer can be achieved in the heart using standard outpatient cardiac catheterization techniques.

Animals↗
PubMed1996

Efficient long-term gene transfer into muscle tissue of immunocompetent mice by adeno-associated virus vector.

Muscle-directed gene transfer is being considered for the treatment of several metabolic diseases, including hemophilia and Duchene's muscular dystrophy. Previous efforts to target this tissue for somatic delivery with various vector systems have resulted in transient expression due to silencing of the transgene or to an immune response against the vector-transduced cells. We introduced recombinant adeno-associated virus vector (rAAV) carrying a lacZ reporter into muscle tissue of immunocompetent mice. The lacZ reporter gene was efficiently transduced and expressed with no evidence of a cellular immune response. Moreover, gene expression persisted for more than 1.5 years. Molecular characterization of rAAV vector DNA suggests a mechanism for persistence, since vector episomes convert to high-molecular-weight genomic DNA. These data provide the first report for establishing long-term gene transduction into mammalian muscle cells in vivo without the need for immune modulation of the organism.

Animals↗
PubMed1996

[Restricting effects of geologic background system on genuine crude drugs in Sichuan].

The distribution, growth, output and quality of genuine crude drugs are restricted by geologic background system (GBS), whose extensional vector system "rock-->soil-->medicinal plants" accomplishes the unity of geological grand cycle and biological pulmonary circulation. This article describes how genuine crude drugs in Sichuan, such as Coptis chinensis, etc. for example, are restricted by GBS.

Animals↗
PubMed1996

[Basic research and clinical applications of the human hair suture].

An atraumatic suture was manufactured from human hair, which has been tested and used in 817 clinical cases with satisfactory results. The authors found that the suture has the following characteristics: smooth, thin, strong and elastic, structurally steady, histocompatible, atoxic, aseptic, atraumatic, with endurance of more than one thousand times of bending. It does not swell in water or blood nor it causes reaction after being buried in tissue for 150 days. It definitely has an advantage over the silk and nylon. The rich resources of hair favor its wide applications.

Adolescent↗
PubMed1996

[Carcinogenic mechanisms of multiple genes in cervical carcinoma].

The alterations of multiple genes and their carcinogenic mechanism in cervical carcinoma were studies by molecular hybridisation, PCR and PCR-ASO techniques. The G-T point mutation in the 12th coden of Ha-ras was detected in cervical carcinomas with mutation frequency of 18.2% (8/44), and the amplification rate of Ha-ras gene was 45% (9/20). The c-erb B2 was amplified 3-30 fold with an amplification rate of 73.3% (11/15) in cervical carcinomas and 5 cancerous samples showed gene rearrangement. The elevated copies of c-myc gene with amplification rate of 91.7% (11/12) were observed in cervical carcinomas. The study of HPV16 viral gene showed that the existence of HPV16 DNA sequence was positively associated with c-myc gene amplification in cervical cancerous samples. The p53 and Rb tumor suppressor genes absence of deletion were observed in the 12 specimens of cervical carcinoma investigated. As mentioned above, the study on alteration and carcinogenic mechanism of multiple genes indicated that 3 oncogenes and HPV16 viral gene were activated or integrated throygh different mechanisms and they played roles in co-carcinogenesis. The integration of HPV16 gene might promote the c-myc gene at the early stage in carcinogenesis of cervical carcinoma, while the alteration of Ha-ras and c-erb B2 gene might be middle-late event. As for the roles of the p53 and Rb tumor suppresor gene in cervical carcinogenesis need further researches.

Carcinoma, Squamous Cell↗
PubMed1996

[Measurement of maximal inspiratory flow and forced inspiratory capacity and its clinical application].

The methods of measuring the maximal inspiratory flow (V(imax)) and the forced inspiratory capacity (FIC) via forced inspiratory capacity-time curve (FIC-t curve) were investigated. Both V(imax) and FIC were measured in 35 normal subjects and 89 patients with chronic obstructive pulmonary disease (COPD). The maximal inspiratory pressure (MIP) was measured simultaneously at function residual capacity(FRC) level by modified Black Method. The results showed that there is a linear relationship between MIP and V(imax) or FIC in both normal subjects and patients with COPD. Normal subjects had a mean V(imax) and FIC much higher than those of patients with COPD. The values of V(imax) and FIC in patients were also, significantly correlated to the severity of COPD. So we suggest that both V(imax) and FIC be used as clinical indices to reflect inspiratory muscles strength.

Adult↗
PubMed1996

Effect of captopril on renal hemodynamics and renal prostaglandins in early type II diabetic patients with normo-or microalbuminuria.

In this study, we investigated the effect of captopril (CPT) on glomerular filtration rate (GFR), effective renal plasma flow (ERPF), filtration fraction (FF), urinary albumin excretion (UAE) and daily urinary excretion of thromboxane B2 (TXB2) and 6-keto- prostaglandin F1a (6-keto-PGF1a) in 29 normotensive non-insulin-dependent diabetes (NIDDM) patients without clinically discernible nephropathy. Before treatment, urinary excretion 6-keto-PGF1a was significantly increased (P < 0.05) in 29 NIDDM patients compared with 25 health subjects matched for age and sex. The values of GFR and FF were significantly higher (P < 0.01 and P < 0.005, respectively) in NIDDM than in normal volunters, whereas ERPF was comparable in both groups. Meanwhile we observed that UAE of early NIDDM was increased before treatment. After CPT treatment, GFR, FF, UAE and urinary excretion of 6-keto-PGF1a were significantly reduce (all P < 0.005) compared with those of NIDDM before treatment. These data indicated that CPT is effective in lowering glomerular filtration pressure and ameliorating microalbuminuria in the normotensive early NIDDM.

6-Ketoprostaglandin F1 alpha↗