Biomedical subjects

G Zhang

Publications and source records attributed to G Zhang.

At least 289 records · Page 16Linked to original sources

PubMed1999

Ultrasonically guided inferior vena cava stent placement: experience in 83 cases.

PURPOSE: Traditionally, inferior vena cava (IVC) stent placement is performed with fluoroscopic guidance. The object of this study was to evaluate use of ultrasound (US) as guidance for IVC stent placement for the management of Budd-Chiari syndrome. MATERIALS AND METHODS: Eighty-three patients with IVC membranous stenosis (n = 30), membranous occlusion (n = 19), segmental stenosis (n = 21), or segmental occlusion (n = 13) underwent IVC recanalization, balloon dilation, and stent placement under US guidance. Among the 83 patients, 67 had at least one patent hepatic vein, while 16 patients had three occluded hepatic veins. RESULTS: IVC stents were successfully placed in 79 of 83 patients, with a success rate of 95%. After the procedure, the symptoms and signs of IVC obstruction disappeared or markedly improved in all patients, and the blockage of hepatic outflow was alleviated in 67 patients. Pericardial effusion, complete atrial ventricular block, and stent migration into the right atrium occurred, respectively, in one patient. During 1-46-month follow-up, stent restenosis occurred in one patient; the other stents remained open and functioned effectively. CONCLUSION: Because of the absence of nonionizing radiation and iodinated contrast material, and its low cost, US is well suited and often preferred for guidance of IVC stent placement.

Adolescent↗

PubMed1999

Subgenomic mRNA regulation by a distal RNA element in a (+)-strand RNA virus.

Subgenomic (sg) mRNAs are synthesized by (+)-strand RNA viruses to allow for efficient translation of products encoded 3' in their genomes. This strategy also provides a means for regulating the expression of such products via modulation of sg mRNA accumulation. We have studied the mechanism by which sg mRNAs levels are controlled in tomato bushy stunt virus, a small (+)-strand RNA virus which synthesizes two sg mRNAs during infections. Neither the viral capsid nor movement proteins were found to play any significant role in modulating the accumulation levels of either sg mRNA. Deletion analysis did, however, identify a 12-nt-long RNA sequence located approximately 1,000 nt upstream from the site of initiation of sg mRNA2 synthesis that was required specifically for accumulation of sg mRNA2. Further analysis revealed a potential base-pairing interaction between this sequence and a sequence located just 5' to the site of initiation for sg mRNA2 synthesis. Mutant genomes in which this interaction was either disrupted or maintained were analyzed and the results indicated a positive correlation between the predicted stability of the base-pairing interaction and the efficiency of sg mRNA2 accumulation. The functional significance of the long-distance interaction was further supported by phylogenetic sequence analysis which revealed conservation of base-pairing interactions of similar stability and relative position in the genomes of different tombusviruses. It is proposed that the upstream sequence represents a cis-acting RNA element which facilitates sg mRNA accumulation by promoting efficient synthesis of sg mRNA2 via a long-distance RNA-RNA interaction.

Amino Acid Sequence↗

PubMed1999

Production of polyhydroxyalkanoates by Pseudomonas nitroreducens.

A strain coded AS 1.2343 was isolated from oil-contaminated soil in an oil-field in North China Tianjian City and it was identified as Pseudomonas nitroreducens. The strain demonstrated some unusual ability to synthesize polyhydroxybutyrate (PHB) homopolymer from medium-chain-length (mcl) fatty acids including hexanoate and octanoate. While polyhydroxyalkanoates (PHA) consisting of mcl hydroxyalkanoate (HA) monomers such as hydroxyoctanoate (HO) and hydroxydecanoate (HD) were the major compositions when butyrate, decanoate, lauric acid and tetradecanoic acid were used as substrates for the cell growth, respectively. PHA was accumulated up to 77% of the cell dry weight when growth was conducted in lauric acid, it appeared that the HA contents in the PHA would not be much affected by the changing of the lauric acid concentration. Varying the concentration ratio of butyrate to octanoate could change the composition of PHA accumulated by the strain. Yet PHB homopolymer was always the only polyester synthesized by the strain, regardless of the octanoate concentration change. Additionally, the ratio of carbon to nitrogen (C/N) in butyrate media was found to have effects on the PHA monomer content, as C/N increased from 2 to 100, content of HB decreased from 100% to 7%. PHA polyester synthesized by cells of Pseudomonas nitroreducens AS 1.2343 was a blend polymers consisting of acetone-insoluble HB and acetone-soluble mcl HA monomers.

Caprylates↗

PubMed1999

Prevalence of enterotoxigenic Bacteroides fragilis in adult patients with diarrhea and healthy controls.

Enterotoxigenic strains of Bacteroides fragilis (ETBF) have been associated with diarrheal diseases in animals and humans. The enterotoxin of ETBF induces fluid changes in ligated intestinal segments and a cytotoxic response in HT29/C1 cells. An assay based on immunomagnetic-beads separation in combination with PCR was used to detect ETBF in fecal samples from patients with diarrhea and healthy Swedish adults. A total of 922 fecal samples were analyzed in this study, including 728 samples from patients with diarrhea and 194 samples from controls. ETBF was detected in 195 of 728 patients (26.8%) and 24 of 194 healthy controls (12.4%). The difference between the two groups was statistically significant (P<.01). ETBF was the only potential diarrheal agent in 91 (12.5%) of 728 patients. All ETBF-positive samples from patients and controls were also positive in the HT29/C1 assay. The data show high carriage of ETBF in Swedish adults, which might be associated with diarrheal disease.

Adolescent↗

PubMed1999

Distinct mutation patterns of breast cancer-associated alleles of the HRAS1 minisatellite locus.

DNA sequence analysis of 130 alleles of the HRAS1 minisatellite has demonstrated that breast cancer-associated variants arise as a consequence of both replication errors and gene conversions. Unlike mutations at other variable number of tandem repeats (VNTRs), high-risk variants of the HRAS1 minisatellite do not demonstrate positional polarity. Instead, most mutations occur at three hotspots, with replication errors confined to one hotspot, gene conversions to a second and a mixed pattern of mutation at the third. DNA sequence analysis of 66 low-risk a1 alleles revealed no evidence for hypermutation. Therefore, while the HRAS1 minisatellite may serve as a reporter for a broad-based group of mutational mechanisms, these results are consistent with a direct pathogenetic contribution by high-risk alleles as the biological basis underlying cancer association of this VNTR.

Alleles↗

PubMed1999

Protein threading by PROSPECT: a prediction experiment in CASP3.

We present an analysis of the protein fold recognition experiment using PROSPECT in The Third Community Wide Experiment on the Critical Assessment of Techniques for Protein Structure Prediction (CASP3). PROSPECT is a computer program we have recently developed for finding an optimal alignment between a protein sequence and a protein structural fold. Two unique features of PROSPECT are (a) that it guarantees to find the globally optimal sequence-structure alignment and does so in an efficient manner, when the alignment-scoring function consists of three additive terms: (i) a singleton fitness term, (ii) a pairwise contact preference term between residues that are spatially close (</=15 A between their beta-carbons) and (iii) an alignment gap penalty; and (b) that it guarantees to find the globally-optimal alignment under various constraints on the unknown protein specified by the user. In the CASP3 experiment, PROSPECT correctly identified the most similar folds for 11 targets and predicted closely-similar folds for five other targets among the 23 targets which can be classified into the category of fold-recognition problems and also had their experimentally-determined structures available. Among the 11 correctly identified folds, PROSPECT obtained good sequence-structure alignments for nine of them. On three of the five ab initio prediction problems, PROSPECT successfully located partial structures from our template library, which align accurately with the corresponding targets.

Amino Acid Sequence↗

PubMed1999

Molecular evolution of swine vesicular disease virus.

Phylogenetic analysis was used to examine the evolutionary relationships within a group of coxsackie B viruses that contained representatives of the major serotypes of this group and 45 isolates of swine vesicular disease virus (SVDV) from Asia and Europe. Separate analyses of sequence data from two regions of the viral genomes encoding the VP1 and 3BC genes both revealed that the SVDV belonged to a single monophyletic group which could be clearly distinguished from all other sampled coxsackieviruses. Regression analysis revealed that within the SVDV clade at least 80% of the synonymous variation in evolutionary divergence between isolates was explained by time, indicating the existence of an approximate molecular clock. Calibration of this clock according to synonymous substitutions per year indicated the date of occurrence of a common ancestor for the SVDV clade to be between 1945 and 1965.

Amino Acid Substitution↗

PubMed1999

Cathelicidin gene expression in porcine tissues: roles in ontogeny and tissue specificity.

Cathelicidins constitute a family of mammalian antimicrobial peptides that are synthesized in the bone marrow as prepropeptides, stored in neutrophil granules as propeptides, and released as active, mature peptides upon neutrophil degranulation. We investigated the developmental expression of two porcine cathelicidins, PR-39 and protegrin. Both cathelicidins were expressed constitutively in the bone marrow of all pigs at all of the ages tested. Peripheral blood neutrophils from young pigs expressed PR-39 and protegrin mRNA, which were not detectable at 42 days of age. At earlier ages, expression of PR-39 mRNA was detected in the kidney and liver and several lymphoid organs, including the thymus, spleen, and mesenteric lymph nodes, but disappeared at 4 weeks of age. These data provide the first evidence of cathelicidin gene expression in peripheral leukocytes and may indicate a role for these antimicrobial peptides in the development of host defense mechanisms.

Animals↗

PubMed1999

Porcine epithelial beta-defensin 1 is expressed in the dorsal tongue at antimicrobial concentrations.

Epithelial cells and phagocytes contain antimicrobial polypeptides that participate in innate host defense. A recently cloned porcine beta-defensin, PBD-1, was detected by Northern organ blots exclusively in the tongue epithelium. We generated recombinant PBD-1 peptide by using a baculovirus-insect cell expression system and obtained two forms (PBD-142 and PBD-138), which differed by N-terminal truncation. Only PBD-142 was found in scrapings of the surface of the dorsal tongue or the buccal mucosa. Immunohistochemical staining with antibody to PBD-142 revealed that PBD-1 was highly concentrated in an approximately 0.1-mm-thick layer in the cornified tips of the filiform (but not fungiform) papillae of the dorsal tongue and in the superficial squamous cell layers of the buccal mucosa. By scraping, extraction, and semiquantitative Western blotting, the concentration of PBD-1 in the dorsal tongue surface and the buccal mucosa was estimated at 20 to 100 micrograms/ml. PBD-1 had antibacterial activity against Escherichia coli, Salmonella typhimurium, Listeria monocytogenes, and Candida albicans in 10 mM sodium phosphate buffer (pH 7.4). Added NaCl progressively inhibited the activity of PBD-1 against E. coli and C. albicans. In 10 mM sodium phosphate with 125 mM NaCl, the combinations of sublethal concentrations of PBD-1 and the porcine neutrophil peptide PG-3, PR-39, or PR-26 showed synergistic activity against E. coli or the multidrug-resistant S. typhimurium DT104. At its physiologic concentration, PBD-1 has antimicrobial effects under both low- and high-salt conditions encountered in the oral cavity and may contribute to the antimicrobial barrier properties of the dorsal tongue and oral epithelium.

Amino Acid Sequence↗

PubMed1999

Absence of the derived allele at the DYS199 locus in 3 NE Chinese populations.

The allelic states of DYS199 locus were studied by allele-specific PCR. We found that all of the 107 samples chosen from three populations of northeast China had DYS199 C alleles. The result excluded the possibility that this mutation first identified in native American populations came from the three populations of northeast China.

Alleles↗

PubMed1999

A nuclear localization signal can enhance both the nuclear transport and expression of 1 kb DNA.

Although the entry of DNA into the nucleus is a crucial step of non-viral gene delivery, fundamental features of this transport process have remained unexplored. This study analyzed the effect of linear double stranded DNA size on its passive diffusion, its active transport and its NLS-assisted transport. The size limit for passive diffusion was found to be between 200 and 310 bp. DNA of 310-1500 bp entered the nuclei of digitonin treated cells in the absence of cytosolic extract by an active transport process. Both the size limit and the intensity of DNA nuclear transport could be increased by the attachment of strong nuclear localization signals. Conjugation of a 900 bp expression cassette to nuclear localization signals increased both its nuclear entry and expression in microinjected, living cells.

Amino Acid Sequence↗

PubMed1999

The effects of tetrandrine on the contractile function and microvascular permeability in the stunned myocardium of rats.

The effects of tetrandrine (Tet) on the contractile function and microvascular permeability in stunned rat myocardium in vivo were studied. Stunned myocardium was induced by 15 (MS(15) group) or 20 (MS(20) group) min of myocardial ischemia plus 60 min of reperfusion. The following was shown. (1) FITC-BSA concentration was 166.0 +/- 7. 9 microg/g myocardium in the control group. The concentrations in ischemic myocardium increased by 35.4 and 45.6% in MS(15) and MS(20) groups respectively (p<0.05). (2) Administration of Tet (64.2 and 96. 3 micromol/kg, I.P.) 20 min before ischemia not only ameliorated the contractile function, but also reduced the FITC-BSA concentrations in ischemic myocardium. At 60 min after reperfusion, the contractile function parameters in Tet-treated groups were significantly superior to those in corresponding stunning groups. FITC-BSA concentrations in Tet-treated groups were lower than those in stunning groups. Then, there was already no significant difference in FITC-BSA concentrations between Tet-treated groups and the control group. The FITC-BSA concentrations at the end of experiments were correlated negatively with dp/dt(max) (r = -0.83, p<0.01). (3) Tet inhibited KCl-induced calcium influx in isolated cardiomyocytes. The results suggest that Tet given before ischemia may be involved in the reduction of microvascular permeability in stunned myocardium, which might be associated with its calcium channel blocking effect.

Alkaloids↗

PubMed1999

Synthesis and characterization of aromatic ring-based cationic lipids for gene delivery in vitro and in vivo.

A new series of cationic lipids has been synthesized for gene delivery using 3,5-dihydroxybenzyl alcohol as the backbone and starting material. Using CMV driven expression system and luciferase gene as a reporter, we demonstrated that the transfection activity of these new lipids when formulated with Tween 80 as co-lipid is comparable to that of DOTAP, one of the most commonly used cationic lipids for transfection. Among the four different cell lines tested including murine melanoma BL-6 cells, human embryonic kidney 293 cells, HepG2 and HeLa cells, the highest transgene expression was seen in 293 cells. Results from in vivo experiments using mice as an animal model show that these cationic lipids preferentially transfect the cells in the lung upon tail vein administration. The cationic lipid, N,N,N-trimethyl-N-[3,5-bis(tetradecyloxy)benzyl] ammonium bromide 4c(di-C14:0) with two 14-hydrocarbon chains exhibits the best transfection activity. These results suggest that these new aromatic ring-based cationic lipids are useful transfection reagents for both in vitro and in vivo gene transfer studies.

Animals↗

PubMed1999

[Angiotensin 1-converting enzyme gene insertion/deletion polymorphism in patients with coronary artery disease and essential hypertension and its nucleotide sequence].

OBJECTIVE: To determine angiotensin 1-coverting enzyme(ACE) gene insertion/deletion(I/D) polymorphism distributions in patients with coronary artery disease(CAD) and essential hypertension(EH),and to detect its nucleotide sequence. METHODS: ACE genotypes of 137 patients with CDA, 42 patients with EH and 63 healthy people were detected by PCR methods. At the same time, nucleotide sequences of D and I allele were determined by fluorescein labeling automatic sequencing method. RESULTS: the frequency of DD genotype in CAD group was significantly higher than that in control group (0.45 and 0.21,P < 0.01), but there was no significant difference of ACE geneI/D polymorphism distribution between EH and control group. The lengths of D and I alleles are 191bp and 479bp separately and their nucleotide sequences are somewhat different with the results of foreign countries. CONCLUSION: ACE gene I/D polymorphism is an independent risk factor of CAD, but it has no relationship with EH. A 288bp insertion segment results in the I/D polymorphism of ACE gene.

Adult↗

PubMed1999

[A study on polymorphism of mitochondrial DNA D loop in the Han nationality in China].

OBJECTIVE: To investigate the polymorphism of mitochondrial DNA D loop in the Han nationality in China and the mean nucleic acid substitute frequency on each site. METHODS: A 465bp-long DNA fragment in mtDNA D loop was amplified by PCR technique and the polymorphism was analyzed by restriction fragment length polymorphism (RFLP) using 6 restriction enzymes (on 10 sites). Some samples were analyzed by direct sequencing of PCR products. RESULTS: RFLP analyses with 6 restriction enzymes on the 10 sites generated 14 restriction types. The calculated mean nucleic acid substitute frequency (based on Nei formula) on each site of mtDNA D loop in the Han nationality in China was 0.029. CONCLUSION: The mean nucleic acid substitute frequency on each site in the D loop region was 10 times as high as that in mtDNA.

Asian People↗

PubMed1999

[The relationship between apolipoprotein E gene polymorphism and coronary heart disease and arteriosclerotic cerebral infarction].

OBJECTIVE: To detect the relationship between ApoE gene polymorphism and coronary heart disease(CHD), arteriosclerotic cerebral infarction(ACI). METHODS: Exon 4 of ApoE gene was analyzed in normal group(87 cases), CHD group(78 cases) and ACI group(55 cases) by a combination of polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and direct AgNO(3) staining technique. RESULTS: Between the control group and CHD group, ACI group, chi(2) test showed no significant difference in genotype of E3/E3 (P>0.5, P>0.1, respectively); while mu test showed no significant difference in allele epsilon(2)(P>0.25, P>0.1, respectively), epsilon(4)(P>0.1, P>0.25, respectively) of ApoE. CONCLUSION: No relationship between ApoE gene polymorphism and CHD and ACI was noted in this study.

Apolipoproteins E↗

PubMed1999

[Mutation analysis of p16 gene in non-small cell lung carcinomas].

OBJECTIVE: To investigate the role of p16 gene in the tumorigenesis of non-small cell lung carcinomas (NSCLC). METHODS: Homozygous deletion and mutation of exon 2 of p16 genes in 40 NSCLC tissues were analyzed using PCR and dsDNA direct sequencing technique. RESULTS: In 2 NSCLC tissues, homozygous deletions of p16 gene were detected; in 14 NSCLC tissues, 19 point mutations and a frameshift were detected. CONCLUSION: Point mutations of p16 gene were frequent and might play a role in the initiation and progression of NSCLC. Nt380 in this gene was a hot spot of mutation.

Carcinoma, Non-Small-Cell Lung↗

PubMed1999

[A study on expression of autotaxin mRNA in hepatocellular carcinoma].

OBJECTIVE: To know if ATX is expressed in hepatocellular carcinoma. METHODS: 7721 hepatoma cell lines in culture, 5 normal liver tissues, and 32 histologically verified HCC specimens were obtained. Semiquantitative reverse transcription polymerase chain reaction was used to detect mRNA expression of ATX. RESULTS: The cDNA sequence of RT-PCR product of 7721 hepatoma cell lines was measured, it showed that nucleotides measured were 332 bp. ATX cDNA nucleotide sequence in HCC was found to share 99.7% homology with that in Melanoma. ATX was expressed in all of the 32 HCC and 5 normal liver tissues. The mean expression level of ATX gene in HCC samples was higher than that in normal liver tissues (0.68 +/- 0.1 vs 0.3 +/- 0.08, P < 0.01). CONCLUSION: ATX gene was found to be in existence in HCC and normal liver tissues. The homology of ATX cDNA sequence between HCC and human Melanoma was 99.7%, and ATX may play an important role in HCC metastatic mechanism.

Carcinoma, Hepatocellular↗