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Biomedical subjects

D Yu

Publications and source records attributed to D Yu.

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

HER-2/neu-targeting cancer therapy via adenovirus-mediated E1A delivery in an animal model.

Overexpression of HER-2/neu has been demonstrated in human ovarian cancer and correlated with poor prognosis. We previously found that the adenovirus type 5 early region 1A (E1A) gene product can repress overexpression and suppress the tumorigenic potential of the HER-2/neu-overexpressing cancer cells. To develop an efficient HER-2/neu-targeting gene therapy with E1A, a replication-deficient adenovirus containing the E1A gene, Ad.E1A(+), was used to transduce the HER-2/neu-overexpressing human ovarian cancer cell line SK-OV3.ip1. Tumor cell growth in vitro and colony formation in soft agarose were greatly inhibited by Ad.E1A(+) transduction. To test therapeutic efficacy in vivo, tumor-bearing mice were established by i.p. injection with ovarian cancer cells and treated by i.p. injection of 10(8) PFU viral solution containing either replication-deficient Ad.E1A(+); control virus Ad.E1A(-) which is the same adenovirus as Ad.E1A(+) except for E1A deletion, or just PBS. Ad.E1A(+) significantly prolonged survival in treated mice for 1 year (80%) whereas in control groups, all mice died of cancer within 4.5 months. Immunohistochemistry analysis indicated that Ad.E1A protein was expressed in tumor tissue and expression of HER-2/neu p185 protein was suppressed in vivo. As a control, another ovarian cancer cell line 2774, in which HER-2/neu is expressed at a basal level, was also inoculated i.p. following the same therapeutic procedure. Ad.E1A(+) could not prolong survival of 2774 cells, indicating that Ad.E1A(+) specifically targeted HER-2/neu-overexpressing tumor cells and functioned as an antitumor agent.

Adenoviridae↗
PubMed1995

Differentiation of Bacillus anthracis and other 'Bacillus cereus group' bacteria using IS231-derived sequences.

Sequences based on the conserved 20 bp inverted repeat of IS231 variants were used as polymerase chain reaction-based fingerprinting primers of the member species of the Bacillus cereus group (B. anthracis, B. cereus, B. thuringiensis and B. mycoides), because of their close association with transposons, principally Tn4430 in B. thuringiensis. Fingerprints of B. anthracis were simple, and specifically allowed its identification and sub-differentiation from other members of the group. Fingerprints for B. cereus were strain-specific; those for B. thuringensis gave a 1650 bp product, characteristic of IS231 variants A-F. The same reaction conditions gave one or two bands for both B. anthracis and B. cereus that differed by restriction endonuclease mapping from the B. thuringiensis PCR product and established IS231 restriction maps; this does not preclude some kind of relationship between these products and IS231.

Bacillus anthracis↗
PubMed1995

Determination of valproic acid and its metabolites using gas chromatography with mass-selective detection: application to serum and urine samples from sheep.

An improved method for the quantitative determination of valproic acid (VPA) and sixteen of its metabolites has been developed using gas chromatography-mass spectrometry with selected-ion monitoring. The method is applicable to serum or urine and all metabolites are measured in a single chromatographic run of 29.5 min. Ions selected for quantitative purposes were the characteristic [M-57]+ ions of the tert.-butyldimethylsilyl (tBDMS) derivatives. The method utilizes heptadeuterated VPA as well as six heptadeuterated metabolites as internal standards [i.e. 2-[2H7]propyl-2-pentenoic acid (2-ene[2H7]VPA), 2-[2H7]propyl-4-pentenoic acid (4-ene[2H7]VPA), 2-[2H7]propyl-3-oxopentanoic acid (3-keto[2H7]VPA), 2-[2H7]propyl-4-oxopentanoic acid (4-keto[2H7]VPA), 2-[2H7]propyl-3-hydroxypentanoic acid (3-OH[2H7]VPA), 2-[2H7]propyl-5-hydroxypentanoic acid (5-OH[2H7]VPA)]. The method demonstrates very good accuracy and precision over a large range of concentrations for VPA and all metabolites measured in both human and sheep biological fluids. The assay was applied to the analysis of VPA and metabolites in serum and urine samples collected from three non-pregnant ewes following intravenous bolus administration of a mixture of VPA and [13C4]VPA. Sheep were observed to produce measurable quantities of the majority of metabolites found in humans, with the notable exception of the di-unsaturated compounds (i.e. 2,3'-diene VPA and 2,4-diene VPA). The pharmacokinetics and metabolism of VPA and [13C4]VPA appear to be equivalent in the sheep model. The elimination half-life of VPA and [13C4]VPA in the ewe were estimated to be approximately 3.5 +/- 0.4 and 3.2 +/- 0.4 h, respectively.

Animals↗
PubMed1995

Oligoribonuclease is distinct from the other known exoribonucleases of Escherichia coli.

Oligoribonuclease, an exoribonuclease specific for small oligoribonucleotides, was initially characterized 20 years ago (S. K. Niyogi and A. K. Datta, J. Biol. Chem. 250:7307-7312, 1975) and shown to be different from RNase II and polynucleotide phosphorylase. Here we demonstrate, using mutant strains and purified enzymes, that oligoribonuclease is not a manifestation of RNases D, BN, T, PH, and R, exoribonucleases discovered subsequently. Thus, oligoribonuclease is the eighth distinct exoribonuclease discovered in Escherichia coli. We also show that oligoribonuclease copurifies with polynucleotide phosphorylase.

Escherichia coli↗
PubMed1995

Maturation of giardiavirus capsid protein involves posttranslational proteolytic processing by a cysteine protease.

The double-stranded RNA genome of giardiavirus (GLV) has only two large open reading frame (ORFs). The 100-kDa capsid polypeptide (p100) is encoded by ORF1, whereas the only other viral polypeptide, the 190-kDa GLV RNA-dependent RNA polymerase (p190), is synthesized as an ORF1-ORF2 fusion protein by a (-1) ribosomal frameshifting. Edman degradation revealed that p100 was N-terminally blocked except for 2 to 5% of it that showed free N terminus starting from amino acid residue 33 of ORF1. Studies using antiserum targeted against amino acid residues 6 to 27 indicated that this region (NT) is absent from viral p100 and p190, while pulse-labelling experiments showed that NT is present in nascent p100 synthesized in GLV-infected Giardia lamblia but removed subsequently. In contrast, this region was retained in the two viral proteins synthesized in vitro, and it was not removed upon prolonged incubation or inclusion of microsomal fraction in the in vitro translation reaction mixtures. These results suggest that endoplasmic reticulum is not involved in the protein processing and that the precursors of p100 and p190 are incapable of cleaving themselves or each other. This specific cleavage was reproduced when lysates from GLV-infected G. lamblia were added, but not those from uninfected cells. The cleavage activity was relatively insensitive to phenylmethylsulfonyl fluoride, but it was inhibitable by leupeptin or E-64, two known specific inhibitors of cysteine protease. The possible origin of this processing activity is discussed.

Amino Acid Sequence↗
PubMed1995

Association of p62, a multifunctional SH2- and SH3-domain-binding protein, with src family tyrosine kinases, Grb2, and phospholipase C gamma-1.

src family tyrosine kinases contain two noncatalytic domains termed src homology 3 (SH3) and SH2 domains. Although several other signal transduction molecules also contain tandemly occurring SH3 and SH2 domains, the function of these closely spaced domains is not well understood. To identify the role of the SH3 domains of src family tyrosine kinases, we sought to identify proteins that interacted with this domain. By using the yeast two-hybrid system, we identified p62, a tyrosine-phosphorylated protein that associates with p21ras GTPase-activating protein, as a src family kinase SH3-domain-binding protein. Reconstitution of complexes containing p62 and the src family kinase p59fyn in HeLa cells demonstrated that complex formation resulted in tyrosine phosphorylation of p62 and was mediated by both the SH3 and SH2 domains of p59fyn. The phosphorylation of p62 by p59fyn required an intact SH3 domain, demonstrating that one function of the src family kinase SH3 domains is to bind and present certain substrates to the kinase. As p62 contains at least five SH3-domain-binding motifs and multiple tyrosine phosphorylation sites, p62 may interact with other signalling molecules via SH3 and SH2 domain interactions. Here we show that the SH3 and/or SH2 domains of the signalling proteins Grb2 and phospholipase C gamma-1 can interact with p62 both in vitro and in vivo. Thus, we propose that one function of the tandemly occurring SH3 and SH2 domains of src family kinases is to bind p62, a multifunctional SH3 and SH2 domain adapter protein, linking src family kinases to downstream effector and regulatory molecules.

Adaptor Proteins, Signal Transducing↗
PubMed1995

[Nationwide survey of the distribution of human parasites in China--infection with parasite species in human population].

The infection rate of main species of parasites and their character by first nationwide survey of human parasites was made. The overall infection rate of human intestinal parasite and the infection rate of most species of parasites were higher in females than that in males. The infection rate according to the age group, the highest infection rate was found in the group aged 5-14 years. With regard to the relation between parasitic infections and occupations of the infected persons, the highest infection rates of Ascaris lumbricoides were exhibited in school children, of hookworm and Clonorchis sinensis were in halfpeasants and halfmerchant and vegetable grower; of Trichuris trichiura were in fishers, of Giardia lamblia, Entamoeba histolytica and Taenia were in herdsmen and halfherdsmen and halfpeasants. In this survey it is also shown that each nationality has their main species of parasites. The family clustering of some main parasites were proved by some province/autonomous region/municipality.

Adolescent↗
PubMed1995

Tumor suppressor activity of the human consensus type I interferon gene.

Type I interferons have potent antiproliferative activity both in vitro and in vivo, and their tumor suppressor activity has been suggested. A series of eukaryotic vectors containing a synthetic human consensus type I interferon gene (IFN-con1) under the control of different promoters (cytomegalovirus early promoter, murine metallothionein promoter and the Rous sarcoma virus LTR) were constructed and stably transfected into type I IFN-deficient myelogenous leukemic K562 cells. Constitutive expression of IFNcon1 reverted the malignant phenotype, as indicated by loss of tumorgenicity in nude mice. When stably transformed cells were mixed with parental tumor cells, there was retardation of tumor growth. Constitutive expression of IFNcon1 reverted the malignant phenotype in vitro, as indicated by growth inhibition in culture, and reduction in colony formation on soft agar. Furthermore, IFNcon1 gene expression resulted in elevated erythroid differentiation, growth arrest in S phase and induced apoptosis. Thus the presence of an active IFNcon1 gene overcomes the oncogenic potential of K562 by coordinated modulation of cell proliferation, differentiation and programmed cell death, and it acts as a tumor suppressor in vivo.

Animals↗
PubMed1994

A 32P-postlabeling method for detecting unstable N-7-substituted deoxyguanosine adducts in DNA.

Many antitumor agents, including the mustards, form N-7 deoxyguanosine adducts in DNA that are difficult to quantitate by the 32P-postlabeling procedure because of their instability. We have developed a method that is successful for the analysis of such adducts using, as a prototype mustard, 14C-labeled bis(2-chloroethyl)sulfide. This agent forms the unstable product 7-hydroxyethylthioethyldeoxyguanosine in DNA. By performing enzymatic digestions to 3'-deoxynucleotides at 10 degrees C, including a second N-7-substituted guanine deoxynucleotide as an internal standard, removing most of the unmodified nucleotides and [32P]ATP on disposable anion columns, and measuring the labeled products after separation on a C18 column, we are able to detect 1 unstable N-7 deoxyguanosine adduct in 10(7) normal nucleotides with good precision.

Animals↗
PubMed1994

c-erbB-2/neu overexpression enhances metastatic potential of human lung cancer cells by induction of metastasis-associated properties.

Previously, we and others have reported high levels of expression of the c-erbB-2/neu gene in non-small cell lung cancer cell lines and primary tumors. We have also found that expression of c-erbB-2/neu-encoded p185neu was correlated with lymph node metastasis in lung squamous cell carcinomas. To investigate the potential role of the c-erbB-2/neu gene in lung cancer metastasis systematically, we introduced the human c-erbB-2/neu gene into very low p185neu-expressing NCI-H460 human non-small cell lung cancer cells and then examined the experimental metastatic potentials among the parental NCI-H460 cells and stable transfectants with increased expression of p185neu. Compared with the parental NCI-H460 cells, the NCI-H460 transfectants overexpressing p185neu produced significantly more pulmonary and extrapulmonary metastatic tumors in nude mice. The changes in experimental metastatic potential in vivo were accompanied by increased invasiveness in vitro. In addition, important steps in the invasion and metastasis process, such as secretion of basement membrane-degradative enzymes and migration through reconstituted basement membrane (Matrigel), were also increased in the NCI-H460 transfectants overexpressing p185neu. Moreover, scanning electron microscopy revealed that the p185neu-overexpressing NCI-H460 transfectants had significantly more microvilli and membrane protrusions than the parental cells, correlating with the increased invasive properties of these cells. The results demonstrate that overexpression of p185neu can enhance the experimental metastatic potential of NCI-H460 human lung cancer cells by promoting invasion and the other steps in the metastatic cascade.

Animals↗
PubMed1994

The pathogenesis of HLA-B27 associated arthritis: lessons from the B27 crystal.

The most remarkable association between a major histocompatibility complex antigen and disease susceptibility--HLA-B27 and seronegative spondyloarthropathies, particularly ankylosing spondylitis--was discovered 20 years ago. During the two intervening decades advances in basic immunology and molecular biology have not only revealed the biosynthesis and structure of HLA-B27 but also given clues to the basic function of this molecule, the presentation of allele-specific peptides to CD8+ cytotoxic T cells. The recently reported three-dimensional structure of HLA-B27 and the identification of self-peptides bound to this major histocompatibility complex class I antigen can be viewed as a landmark in the understanding of the pathogenic role of HLA-B27. Based on crystallographic evidence, a peptide-binding motif can be postulated that should allow identification of HLA-B27 complexed peptides which may trigger an immune reaction causing arthritis.

Amino Acid Sequence↗
PubMed1994

Stereotyped human behavior: a nonlinear dynamical analysis.

Some forms of stereotyped human behavior seem to occur randomly in time. A dynamical analysis of several topographies demonstrates that while such stereotypies have the spectral characteristics of random noise, the rate at which each subject exhibits his/her stereotypy is to some extent predictable and, unlike uncorrelated noise, prediction accuracy declines with increasing prediction interval. Rhythmic stereotypies appear to be more predictable than nonrhythmic topographies but both show a similar decline in prediction accuracy. Furthermore, the distribution of interresponse times exhibits self-similar behavior. These results point to a deterministic, rather than stochastic, origin for the variability of observed rates of stereotyped behaviors.

Adolescent↗
PubMed1994

Detection of sulfur mustard-induced DNA modifications.

Sulfur mustard is acutely toxic to the skin, eyes, and respiratory tract, and is considered carcinogenic to humans by the IARC. Since all of these toxicities are thought to be initiated by DNA alkylation, the level of DNA damage should serve as a biomarker for exposure. To develop methods of detecting this damage, DNA was modified by [14C]-labeled sulfur mustard and DNA adducts were released by mild acid hydrolysis. Radioactivity co-eluted on HPLC analysis with marker 7-(2-hydroxyethylthioethyl) guanine and 3-(2-hydroxyethylthio-ethyl) adenine synthesized from 2-chloroethyl 2-hydroxy-ethyl sulfide. Unambiguous identification of the major adduct, 7-(2-hydroxy-ethylthioethyl) guanine, was provided by gas chromatography combined with mass spectrometric detection. The most abundant adduct, 7-(2-hydroxyethyl-thioethyl) guanine, accounted for 61% of the total alkylation and could be detected as a fluorescent HPLC peak with a detection limit of 10 pmol. To demonstrate the applicability of this method to biological samples, DNA was extracted from the white blood cells of human blood exposed to 131 microM sulfur mustard in vitro and shown to contain 470 pmol of 7-(2-hydroxyethylthio-ethyl) guanine per mg of DNA.

Animals↗
PubMed1994

A simple method to improve the reliability of iontophoretic administration of tracer substances.

Microiontophoresis is a widely used technique for depositing tracer materials into the central nervous system for neuroanatomical experiments. However, the reliability of iontophoretic injection is often less than optimal. Coating the lumen of glass micropipettes with silicone to reduce surface tension reduced the incidence of failure for iontophoretic deposition of wheat germ agglutinin-horseradish peroxidase (WGA-HRP) from 40% to zero. Similar results were observed with other tracer substances. Siliconizing the internal surface of glass micropipettes can significantly improve the reliability of iontophoretic deposition.

Animals↗