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Biomedical subjects

G Wang

Publications and source records attributed to G Wang.

At least 217 records · Page 12Linked to original sources
PubMed2000

Reciprocal information flow between prefrontal cortex and ventral tegmental area in an animal model of schizophrenia.

The medial prefrontal cortex (PFC) is anatomically and functionally connected with the ventral tegmental area (VTA), the neuronal source of mesocorticolimbic system that is pathophysiologically related to schizophrenia-like symptoms. Methamphetamine (MAP) was applied to examine the functional relationship between PFC and VTA in an animal model of schizophrenia. Hyperactivity and stereotyped behavior were observed accompanied by a distinctive direction of information flow. In hyperactivity, information flow in the direction from PFC to VTA was dominant. Contrarily, dominant information flow from VTA to PFC was found in stereotyped behavior. These results indicate that dysfunctional interaction between PFC and VTA is the neuronal basis of MAP-induced schizophrenia-like psychosis. The information flow and its direction can be useful tool to explain the neurogenesis of these abnormal behaviors.

Animals↗
PubMed2000

Signals for a transition from surface to bulk emission in thermal multifragmentation.

Excitation-energy-gated two-fragment correlation functions have been studied between E(*)/A = (2-9)A MeV for equilibriumlike sources formed in 8-10 GeV/c pi(-) and p+197Au reactions. Comparison with an N-body Coulomb-trajectory code shows an order of magnitude decrease in the fragment emission time in the interval E(*)/A = (2-5)A MeV, followed by a nearly constant breakup time at higher excitation energy. The decrease in emission time is strongly correlated with the onset of multifragmentation and thermally induced radial expansion, consistent with a transition from surface-dominated to bulk emission expected for spinodal decomposition.

Journal Article↗
PubMed2000

A common interface on histidine-containing phosphocarrier protein for interaction with its partner proteins.

The bacterial phosphoenolpyruvate:sugar phosphotransferase system accomplishes both the transport and phosphorylation of sugars as well as the regulation of some cellular processes. An important component of this system is the histidine-containing phosphocarrier protein, HPr, which accepts a phosphoryl group from enzyme I, transfers a phosphoryl group to IIA proteins, and is an allosteric regulator of glycogen phosphorylase. Because the nature of the surface on HPr that interacts with this multiplicity of proteins from Escherichia coli was previously undefined, we investigated these interactions by nuclear magnetic resonance spectroscopy. The chemical shift changes of the backbone and side-chain amide (1)H and (15)N nuclei of uniformly (15)N-labeled HPr in the absence and presence of natural abundance glycogen phosphorylase, glucose-specific enzyme IIA, or the N-terminal domain of enzyme I have been determined. Mapping these chemical shift perturbations onto the three-dimensional structure of HPr permitted us to identify the binding surface(s) of HPr for interaction with these proteins. Here we show that the mapped interfaces on HPr are remarkably similar, indicating that HPr employs a similar surface in binding to its partners.

Bacterial Proteins↗
PubMed2000

[Toxic effect of fluoride-arsenic on the reproduction and development of rats].

To determine the effects of the fluoride-arsenic exposure on the reproductive function and the development of offspring. Two generations-one nest reproduction was studied in Wistar rats to assess the changes of reproductive function and structure of ovary and development of their offspring after rats were exposed to different doses of fluoride(NaF)-arsenic(As2O3) orally. The rates of the pregnancy, normal parturition, survival and feeding survival in high dose group were lower than that in low dose groups and control. The rates of pregnancy were 73.08% and 61.54% in high dose groups, and 92.31% and 84.62% in the control. But the contents of fluoride and arsenic in rats' offspring were increased. The weights of rats' offspring in high dose group were lighter than that in control. The average weights were 38.45 g in high dose group and 60.84 g in control one month after birth. Pathological changes could be found in each stage of oocytes with transmission electron microscope(TEM). Conclusion Fluoride-arsenic exposure has adverse effects on the reproductive system and the development of rats' offspring.

Animals↗
PubMed2000

Mitochondrial DNA damage and a hypoxic response are induced by CoCl(2) in rat neuronal PC12 cells.

Generation of reactive oxygen species (ROS) and activation of a transcriptional program that mimics the hypoxic response have been documented in cultured cells in the presence of cobalt chloride. We found that in the presence of hypoxia-mimicking concentrations of CoCl(2), mitochondrial but not nuclear DNA damage is induced in rat neuronal, PC12 cells. To our knowledge, this is the first documentation of induction of mitochondrial DNA (mtDNA) damage under these conditions. Likewise, we provide the first evidence for elevation of MYH, the mammalian homolog of the Escherichia coli MutY DNA glycosylase, in mammalian cells. Recently, the human MYH was implicated in repair of oxidative DNA damage and shown to carry a mitochondrial localization sequence. Here, an induction of mtDNA damage and a time-dependent increase in the MYH level were detected with exposure of cells to 100 microM CoCl(2). In addition, the levels of proteins involved in cellular responses to hypoxia, ROS and nuclear DNA damage; hypoxia-inducible factor 1alpha(HIF-1alpha), p53, p21 and PCNA were also modulated temporally. Earlier studies suggested that the mtDNA is a primary target for oxidative damage. Our findings extend these observations and suggest that activation of DNA repair processes is associated with the presence of mtDNA damage.

Animals↗
PubMed2000

Frequent activation of AKT2 and induction of apoptosis by inhibition of phosphoinositide-3-OH kinase/Akt pathway in human ovarian cancer.

We previously demonstrated that AKT2, a member of protein kinase B family, is activated by a number of growth factors via Ras and PI 3-kinase signaling pathways. Here, we report the frequent activation of AKT2 in human primary ovarian cancer and induction of apoptosis by inhibition of phosphoinositide-3-OH kinase (PI 3-kinase)/Akt pathway. In vitro AKT2 kinase assay analyses in 91 ovarian cancer specimens revealed elevated levels of AKT2 activity (>3-fold) in 33 cases (36.3%). The majority of tumors displaying activated AKT2 were high grade and stages III and IV. Immunostaining and Western blot analyses using a phospho-ser-473 Akt antibody that detects the activated form of AKT2 (AKT2 phosphorylated at serine-474) confirmed the frequent activation of AKT2 in ovarian cancer specimens. Phosphorylated AKT2 in tumor specimens localized to the cell membrane and cytoplasm but not the nucleus. To address the mechanism of AKT2 activation, we measured in vitro PI 3-kinase activity in 43 ovarian cancer specimens, including the 33 cases displaying elevated AKT2 activation. High levels of PI 3-kinase activity were observed in 20 cases, 15 of which also exhibited AKT2 activation. The remaining five cases displayed elevated AKT1 activation. Among the cases with elevated AKT2, but not PI 3-kinase activity (18 cases), three showed down-regulation of PTEN protein expression. Inhibition of PI 3-kinase/AKT2 by wortmannin or LY294002 induces apoptosis in ovarian cancer cells exhibiting activation of the PI 3-kinase/AKT2 pathway. These findings demonstrate for the first time that activation of AKT2 is a common occurrence in human ovarian cancer and that PI 3-kinase/Akt pathway may be an important target for ovarian cancer intervention.

Adenocarcinoma, Mucinous↗
PubMed2000

Temporal progression of kainic acid induced neuronal and myelin degeneration in the rat forebrain.

The excitatory amino acid glutamate has been implicated in the neurodegeneration associated with several different central nervous system diseases. Treatment with kainic acid (KA), a glutamate analog known to activate the AMPA/KA subtype of glutamate receptor, has been widely used as a model of epilepsy. Long term temporal studies of its neuropathological effects, however, are lacking. In this study, two techniques were used to directly visualize and characterize the neuropathology that occurred over a 2-month period following KA-induced status epilepticus in adult female Sprague-Dawley rats. Post-injection survival was 2, 4, 8 h, 2 days, 2 weeks, or 2 months. Labeling with Fluoro-Jade B (FJB), a fluorescent green dye that labels the cell body, dendrites, axons and axon terminals of degenerating neurons, was observed within the cortex, hippocampus, thalamus, basal ganglia, and amygdala by 4 h post-treatment. The highest level of labeling was seen in the piriform cortex, hippocampus, and thalamus. Myelin changes in the rat forebrain following KA treatment were also examined using the myelin-specific Black-Gold (BG) stain. Varicose myelinated fibers were observed in the same regions as FJB positive neurons, although these changes were evident by the 2-h survival time-point. Both stains showed a temporal progression of brain damage throughout the affected areas. By 2 months post-treatment, few degenerating neurons could be detected and abnormal myelin was absent in most regions. As myelin changes can be seen prior to neuronal degeneration, and oligodendrocytes express functional AMPA/kainate-type glutamate receptors, the neurodegeneration and myelin pathologies may occur as independent events. Thus, researchers should consider the temporal and multiple effects of kainic acid to optimize conditions for their endpoint of interest when designing experiments.

Amygdala↗
PubMed2000

Determination of Guan-Fu Base A, a new anti-arrhythmic, in human plasma by gas chromatography and electron-capture detection.

A gas chromatographic-electron capture detection (GC-ECD) method has been developed for determining Guan-Fu Base A (GFA), an experimental anti-arrhythmic, in human plasma. The method was based on one-step liquid-liquid extraction with toluene and chemical derivatization with pentafluoropropionic anhydride followed by GC-ECD. The derivatives of GFA and metoprolol (Met, internal standard) were confirmed by gas chromatography-mass spectrometry (GC-MS) to be dipentafluoropropionyl-GFA and dipentafluoropropionyl-Met. The method was linear over the concentration ranges of 0.1-20.0 and 1.0-30.0 microg/ml with the detection limit of 0.05 microg/ml at S/N=5. The intra- and inter-assay precisions were less than 6 and 10%, and accuracy 99.70+/-3.30 and 97.60+/-5.99%, respectively. The absolute recoveries were 81.88, 77.35, 80.79 and 83.85% for GFA at concentrations of 0.5, 1.0, 5.0 and 14.0 microg/ml and 88.24% for Met at 3.0 microg/ml, respectively.

Adult↗
PubMed2000

Interaction in vivo and in vitro of the metastasis-inducing S100 protein, S100A4 (p9Ka) with S100A1.

The calcium-binding protein S100A4 (p9Ka) has been shown to cause a metastatic phenotype in rodent mammary tumor cells and in transgenic mouse model systems. mRNA for S100A4 (p9Ka) is present at a generally higher level in breast carcinoma than in benign breast tumor specimens, and the presence of immunocytochemically detected S100A4 correlates strongly with a poor prognosis for breast cancer patients. Recombinant S100A4 (p9Ka) has been reported to interact in vitro with cytoskeletal components and to form oligomers, particularly homodimers in vitro. Using the yeast two-hybrid system, a strong interaction between S100A4 (p9Ka) and another S100 protein, S100A1, was detected. Site-directed mutagenesis of conserved amino acid residues involved in the dimerization of S100 proteins abolished the interactions. The interaction between S100A4 and S100A1 was also observed in vitro using affinity column chromatography and gel overlay techniques. Both S100A1 and S100A4 can occur in the same cultured mammary cells, suggesting that in cells containing both proteins, S100A1 might modulate the metastasis-inducing capability of S100A4.

Animals↗
PubMed2000

Cloning of CCRL1, an orphan seven transmembrane receptor related to chemokine receptors, expressed abundantly in the heart.

In an attempt to identify novel chemokine receptor genes, cDNA expressed sequence tags (EST) were analyzed for a significant homology with mammalian chemokine receptors. The sequence from one of the selected EST clones was used to generate a full-length cDNA encoding a putative seven transmembrane receptor, CCRL1-CC chemokine receptor like 1. The full-length receptor encodes a polypeptide of 350 amino acids and has about 35% homology to the chemokine receptors CCR6 and CCR7. Northern blot analysis indicates predominant expression of about 5.0, 2.0 and 1.3kb mRNA forms in human heart tissue, while low-level expression of the 2.0 and 1.3kb forms was observed in lung, pancreas and spleen and in fetal tissues. In-situ hybridization confirmed the presence of CCRL1 mRNA in cardiac muscle cells. Similar to the chemokine receptor CCR6, CCRL1 maps to chromosome 6 and has one intron in the 5' untranslated region. Coupled transcription-translation of CCRL1 cDNA yielded a glycosylated polypeptide of about 45kDa.

Amino Acid Sequence↗
PubMed2000

Cloning and overexpression of a tyrosinase gene mel from Pseudomonas maltophila.

The tyrosinase gene (mel), which is responsible for melanin formation, was isolated by shotgun cloning of SalI fragments of Pseudomonas maltophila DNA. A 0.7-kb SalI fragment in the recombinant plasmid pWSY8 imparted the ability to synthesize melanin to an Escherichia coli host HB101. The nucleotide sequence of this DNA fragment revealed an open reading frame of 504 bp, encoding a protein of 169 amino acids. The fragment containing the mel gene was then cloned into an expression plasmid pPAS1 under the control of a promoter isolated from the host, P. maltophilia AT18. This strain increased the melanin production by 70.6% compared with the strain HB101/pWSY8, in which the cloned mel gene was under the control of the lac promoter from the vector pUC18.

Amino Acid Sequence↗
PubMed2000

[Synthesis and identification of methylparathion artificial antigen].

In order to synthesize the artificial antigen methylparathion(M1605), methylparathion was reduced into amino-methylparathion by using acetic acid-zinc powder-hydrochloric acid. Artificial antigens (M1605-BSA, M1605-TTH) were synthesized by conjugating amino-methylparathion to bovine serum albumin(BSA) and tachypleus tridentatus hemocyanin (TTH) directly after diazotization. Rabbits were immunized with M1605-BSA for 10 weeks, and the high titer and high specificity antiserum from those rabbits was testified by double agar gel diffusion and indirect ELISA. The results showed that an artificial antigen was obtained successfully and this made it possible to establish the immunoassay of M1605.

Animals↗
PubMed2000

Cloning and characterization of the alpha(1,3/4) fucosyltransferase of Helicobacter pylori.

The gastric pathogen Helicobacter pylori can express the histo blood group antigens, which are on the surface of many human cells. Most H. pylori strains express the type II carbohydrates, Lewis X and Y, whereas a small population express the type I carbohydrates, Lewis A and B. The expression of Lewis A and Lewis X, as in the case of H. pylori strain UA948, requires the addition of fucose in alpha1,4 and alpha1,3 linkages to type I or type II carbohydrate backbones, respectively. This work describes the cloning and characterization of a single H. pylori fucosyltransferase (FucT) enzyme, which has the ability to transfer fucose to both of the aforementioned linkages in a manner similar to the human fucosyltransferase V (Fuc-TV). Two homologous copies of the fucT gene have been identified in each of the genomes sequenced. The characteristic adenosine and cytosine tracts in the amino terminus and repeated regions in the carboxyl terminus are present in the DNA encoding the two UA948fucT genes, but these genes also contain differences when compared with previously identified H. pylori fucTs. The UA948fucTa gene encodes an approximately 52-kDa protein containing 475 amino acids, whereas UA948fucTb does not encode a full-length FucT protein. In vitro, UA948FucTa appears to add fucose with a greater than 5-fold preference for type II chains but still retains significant activity using type I acceptors. The addition of the fucose to the type II carbohydrate acceptors, by UA948FucTa, does not appear to be affected by fucosylation at other sites on the carbohydrate acceptor, but the rate of fucose transfer is affected by terminal fucosylation of type I acceptors. Through mutational analysis we demonstrate that only FucTa is active in this H. pylori isolate and that inactivation of this enzyme eliminates expression of all Lewis antigens.

Amino Acid Sequence↗
PubMed2000

Membrane cofactor protein (MCP; CD46): isoform-specific tyrosine phosphorylation.

Membrane cofactor protein (MCP; CD46) is a widely expressed type 1 transmembrane glycoprotein that inhibits complement activation on host cells. It also is a receptor for several pathogens including measles virus, Streptococcus pyogenes, Neisseria gonorrhea, and Neisseria meningitidis. That MCP may have signaling capability was suggested by its microbial interactions. That is, binding of MCP on human monocytes by measles virus hemagglutinin or cross-linking by an anti-MCP Ab resulted in IL-12 down-regulation, while binding to MCP by Neisseria on epithelial cells produced a calcium flux. Through alternative splicing, MCP is expressed on most cells with two distinct cytoplasmic tails of 16 (CYT-1) or 23 (CYT-2) amino acids. These play pivotal roles in intracellular precursor processing and basolateral localization. We investigated the putative signal transduction pathway mediated by MCP and demonstrate that CYT-2, but not CYT-1, is phosphorylated on tyrosine. We examined MCP tail peptides and performed Ab cross-linking experiments on several human cell lines and MCP isoform transfectants. We found an MCP peptide of CYT-2 was phosphorylated by a src kinase system. Western blots of the cells lines demonstrated that cells bearing CYT-2 were also phosphorylated on tyrosine. Additionally, we provide genetic and biochemical evidence that the src family of kinases is responsible for the latter phosphorylation events. In particular, the src kinase, Lck, is required for phosphorylation of MCP in the Jurkat T cell line. Taken together, these studies suggest a src family-dependent pathway for signaling through MCP.

Amino Acid Sequence↗
PubMed2000

[Combined effects of lead and ethanol on rat sperms].

In order to study the combined effects of lead and ethanol on rat sperm, 54 male rats were divided into 9 groups randomly. One group was given distilled water as control, and the others (A-H) groups were given lead and ethanol at the concentrations of lead 11 mg/kgBW and lead 22 mg/kgBW, ethanol 0.9 g/kgBW, ethanol 1.8 g/kgBW, lead 11 mg/kgBW + ethanol 0.9 g/kgBW, lead 11 mg/kgBW + ethanol 1.8 g/kgBW, lead 22 mg/kgBW + ethanol 0.9 g/kgBW, lead 22 mg/kgBW + ethanol 1.8 g/kgBW in stomachs respectively for four weeks. The rats were sacrificed by the end of the fourth week. Epididymis were isolated and examined for sperm motility, counts and morphology. The results showed that the spermatozoa motility as well as spermatozoa count was lower; the spermatozoa morphological changed and blood lead level and ratio of epididymis to weight were higher in all combined experimental groups than those in groups with lead or ethanol alone. ANOVA analysis indicated that there were interaction between lead and ethanol on above indices (P < 0.05 P < 0.01). The multiple linear regression showed that there was linear correlation between blood lead and spermatozoa motility, spermatozoa morphological change. It is concluded that there were notable combined effects of lead and ethanol on semen quality in male rats.

Animals↗
PubMed2000

Activation of human gamma-globin gene expression via triplex-forming oligonucleotide (TFO)-directed mutations in the gamma-globin gene 5' flanking region.

Human beta-globin disorders, such as sickle cell anemia and beta-thalassemia, are relatively common genetic diseases cause by mutations in the beta-globin gene. Increasing gamma-globin gene expression has been found to greatly reduce the disease symptom. However, the gamma-globin gene is developmentally regulated and normally expressed at high levels only during the fetal stage of human development. We have explored the possibility of activating the gamma-globin gene expression by triplex-forming oligonucleotide (TFO)-directed targeted mutagenesis. Using a psoralen-conjugated TFO designed to bind to a site overlapping with an Oct-1 binding site at the -280 region of the gamma-globin gene, targeted mutagenesis of the Oct-1 binding site has been achieved by transfecting the in-vitro-formed plasmid-oligo complex into human normal fibroblast (NF) cells. The mutation frequency at the target site was estimated to be 20% by direct DNA sequencing analysis. In-vitro protein binding assays indicated that these mutations reduced Oct-1 binding to the target site. In-vivo gene expression assays demonstrated activation of gamma-globin gene expression from these mutations in mouse erythroleukemia (MEL) cells. The levels of the gamma-globin gene expression increased by as much as fourfold in mutants with single base changes. These results suggest that the -280 region of the Agamma-globin gene negatively regulates the gamma-globin gene expression, and mutations at the Oct-1 binding site can lead to activation of the gamma-globin gene and generate the hereditary persistence of fetal hemoglobin (HPFH) condition. This study may provide a novel approach for gene therapy of sickle cell disease. The data may also have implications in gene therapy for other diseases including genetic diseases and cancers by introducing mutations into transcription factor binding sites to alter the levels of target gene expression.

Animals↗
PubMed2000

Mimosine arrests cells in G1 by enhancing the levels of p27(Kip1).

The plant amino acid mimosine, an effective inhibitor of DNA replication, has been demonstrated to arrest cell cycle progression in late G1. To understand further the molecular mechanism by which mimosine affects the cell cycle, we treated quiescent cells with serum in the presence of 800 microM mimosine. The cells did not enter S phase and were completely arrested in G1 phase. Although neither the mitogenic induction of the G1 cyclins nor the protein levels of cdk2 or cdk4 were affected, serum-dependent activation of cdk2 was blocked. This corresponded to elevated levels of the cdk inhibitor p27(Kip1). This was not mediated through inhibition of degradation but rather involved increased synthesis of both p27(Kip1) mRNA and protein. Mimosine did not appear to affect mitogen-dependent signals that normally lead to p27(Kip1) downregulation since the inhibitor was induced to even greater levels in quiescent, unstimulated cells. In the presence of mimosine, actinomycin D treatment for 2 h prevented the increase of p27(Kip1) mRNA, but p27(Kip1) protein levels were still enhanced under these conditions. We propose that mimosine blocks the cell cycle in late G1 phase by upregulation of p27(Kip1) protein levels through transcriptional and posttranscriptional regulatory mechanisms.

3T3 Cells↗