Biomedical subjects

Q Yu

Publications and source records attributed to Q Yu.

At least 19 recordsLinked to original sources

PubMed2001

Angiopoietin-1, unlike angiopoietin-2, is incorporated into the extracellular matrix via its linker peptide region.

Angiopoietin-1 (Ang-1) and angiopoietin-2 (Ang-2) affect angiogenesis differently during embryogenesis and tumorigenesis. In an attempt to understand the molecular basis underlying the distinct roles of those two homologous molecules, we investigated the association of Ang-1 and Ang-2 with the extracellular matrix (ECM). TA3 murine mammary carcinoma (TA3) and Lewis lung carcinoma cells expressing v5 epitope-tagged Ang-1 and Ang-2 were used in our studies. The results indicated that Ang-1 is secreted and incorporated into the ECM of the tumor cells, whereas Ang-2 is not associated with the ECM. The mutagenesis study indicated the domain that is responsible for the ECM association of Ang-1 is the linker peptide region between the coiled-coil and the fibrinogen-like domains. A weak binding between the coiled-coil domain of Ang-1 and the ECM was observed. Immunocytochemistry study revealed a distinct ECM distribution pattern of Ang-1, which is quite different from that of fibronectin, laminin, and collagen types I and IV. The ECM-associated Ang-1 proteins are released, and Tie-2 receptors are phosphorylated upon the adhesion of human umbilical vein endothelial cells. Implications of the difference in the ECM association of Ang-1 and Ang-2, which are related to the regulation of angiopoietin activity and their roles in local versus distant angiogenesis during tumor metastasis, are discussed.

Angiopoietin-1↗

PubMed2001

Specific protection against breast cancers by cyclin D1 ablation.

Breast cancer is the most common malignancy among women. Most of these cancers overexpress cyclin D1, a component of the core cell-cycle machinery. We previously generated mice lacking cyclin D1 using gene targeting. Here we report that these cyclin D1-deficient mice are resistant to breast cancers induced by the neu and ras oncogenes. However, animals lacking cyclin D1 remain fully sensitive to other oncogenic pathways of the mammary epithelium, such as those driven by c-myc or Wnt-1. Our analyses revealed that, in mammary epithelial cells, the Neu-Ras pathway is connected to the cell-cycle machinery by cyclin D1, explaining the absolute dependency on cyclin D1 for malignant transformation in this tissue. Our results suggest that an anti-cyclin D1 therapy might be highly specific in treating human breast cancers with activated Neu-Ras pathways.

Animals↗

PubMed2001

Direct evidence for a geometrically constrained "entatic state" effect on copper(II/I) electron-transfer kinetics as manifested in metastable intermediates.

The absolute magnitude of an "entatic" (constrained) state effect has never been quantitatively demonstrated. In the current study, we have examined the electron-transfer kinetics for five closely related copper(II/I) complexes formed with all possible diastereomers of [14]aneS(4) (1,4,8,11-tetrathiacyclotetradecane) in which both ethylene bridges have been replaced by cis- or trans-1,2-cyclohexane. The crystal structures of all five Cu(II) complexes and a representative Cu(I) complex have been established by X-ray diffraction. For each complex, the cross-reaction rate constants have been determined with six different oxidants and reductants in aqueous solution at 25 degrees C, mu = 0.10 M. The value of the electron self-exchange rate constant (k(11)) has then been calculated from each cross reaction rate constant using the Marcus cross relation. All five Cu(II/I) systems show evidence of a dual-pathway square scheme mechanism for which the two individual k(11) values have been evaluated. In combination with similar values previously determined for the parent complex, Cu(II/I)([14]aneS(4)), and corresponding complexes with the two related monocyclohexanediyl derivatives, we now have evaluated a total of 16 self-exchange rate constants which span nearly 6 orders of magnitude for these 8 closely related Cu(II/I) systems. Application of the stability constants for the formation of the corresponding 16 metastable intermediates--as previously determined by rapid-scan cyclic voltammetry--makes it possible to calculate the specific electron self-exchange rate constants representing the reaction of each of the strained intermediate species exchanging electrons with their stable redox partners--the first time that calculations of this type have been possible. All but three of these 16 specific self-exchange rate constants fall within--or very close to--the range of 10(5)-10(6) M(-1) s(-1), values which are characteristic of the most labile Cu(II/I) systems previously reported, including the blue copper proteins. The results of the current investigation provide the first unequivocal demonstration of the efficacy of the entatic state concept as applied to Cu(II/I) systems.

Copper↗

PubMed2001

Preliminary experiment of fluorescent X-ray computed tomography to detect dual agents for biological study.

The simultaneous observation of various information, such as blood flow, tissue metabolism and distribution of receptors, is quite important in order to understand the functional state of biomedical objects. The simultaneous detectability of contrast agents by fluorescent X-ray computed tomography (FXCT) with synchrotron radiation is examined in this study. The system consisted of a silicon (111) double-crystal monochromator, an X-ray slit system, a scanning table, a PIN diode, a highly purified germanium detector and an X-ray charge-coupled device (CCD) camera. The monochromatic X-ray beam energy was adjusted to 37.0 keV and collimated into a pencil beam of 1 x 1 mm. The fluorescent spectra of the K alpha lines for iodine and xenon were detected simultaneously. FXCT could image the distribution of both iodine and xenon agents in a phantom clearly and the contrast ratio was significantly better than that of transmission X-ray computed tomography images.

Fluorescence↗

PubMed2001

Tandem ligation of unprotected peptides through thiaprolyl and cysteinyl bonds in water.

Tandem ligation for the synthesis and modification of proteins entails forming two or more regiospecific amide bonds of multiple free peptide segments without a protecting-group scheme. We here describe a semi-orthogonal strategy for ligating three unprotected peptide segments, two of which contain N-terminal (NT) cysteine, to form in tandem two amide bonds, an Xaa-SPro (thiaproline), and then an Xaa-Cys. This strategy exploits the strong preference of an NT-cysteinyl peptide under acidic conditions to undergo selectively an SPro-imine ligation rather than a Cys-thioester ligation. Operationally, it was performed in the N --> C direction, first by an imine ligation at pH < 3 to afford an Xaa-thiazolidine ester bond between a peptide containing a carboxyl terminal (CT)-glycoaldehyde ester and a second peptide containing both an NT-Cys and a CT-thioester. The newly created O-ester-linked segment with a CT-thioester was then ligated to another NT-cysteinyl peptide through thioester ligation at pH > 7 to form an Xaa-Cys bond. Concurrently, this basic condition also catalyzed the O,N-acyl migration of an Xaa-thiazolidine ester to the Xaa-SPro bond at the first ligation site to complete the tandem three-segment ligation. Both ligation reactions were performed in aqueous buffered solvents. The effectiveness of this three-segment ligation strategy was tested in six peptides ranging from 19 to 70 amino acids, including thiaproline --> proline analogues of somatostatins and two CC-chemokines. The thiaproline replacements in these peptides and proteins did not result in altered biological activity. By eliminating the protecting-group scheme and coupling reagents, tandem ligation of multiple free peptide segments in aqueous solutions enhances the scope of protein synthesis and may provide a useful approach for combinatorial segment synthesis.

Amino Acid Sequence↗

PubMed2001

Tyrosine kinase-dependent, phosphatidylinositol 3'-kinase, and mitogen-activated protein kinase-independent signaling pathways prevent lung adenocarcinoma cells from anoikis.

Normal epithelial cells are anchorage-dependent. Detachment of normal epithelial cells from their substratum causes apoptosis, termed anoikis. Malignant tumor cells, however, can survive and proliferate independent of anchorage. To understand the molecular basis of tumor cell anchorage independence, we investigated the role of tyrosine kinases and their downstream signaling pathways in anoikis resistance of human lung adenocarcinoma cells. Four of the five lung adenocarcinoma cell lines analyzed are resistant to anoikis. Tyrosine kinase inhibitor genistein rendered three of them sensitive to anoikis. Although cell detachment induced rapid protein tyrosine dephosphorylation in Madin-Darby canine kidney cells, a nontransformed epithelial cell line, tyrosine phosphorylation of several proteins in the tumor cells is anchorage-independent. Similarly, phosphorylation of Akt and mitogen-activated protein kinase, two signaling proteins downstream of tyrosine kinases, was decreased in Madin-Darby canine kidney cells but increased in some of the tumor cells upon cell detachment. Inhibition of phosphorylation of the two proteins, however, did not induce anoikis in the tumor cells. Specific inhibitors to several known tyrosine kinases also failed to induce anoikis in these cells. These data suggest the existence of tyrosine kinase-dependent phosphatidylinositol 3'-kinase and mitogen-activated protein kinase-independent signaling pathways that function to regulate cell survival and death. Alteration in these pathways may count for the anchorage-independent survival of the lung adenocarcinoma cells and other malignant tumor cells.

Adenocarcinoma↗

PubMed2001

Retinal uptake of intravitreally injected Hsc/Hsp70 and its effect on susceptibility to light damage.

PURPOSE: To evaluate the uptake by the rat retina of an intravitreally injected mixture of the constitutive and inducible forms of the 70 kD heat shock protein (Hsc/Hsp70) and test its potential to protect photoreceptors from light damage. METHODS: Hsc/Hsp70 and actin (control protein) were labeled with fluorescein (referred to as fl-Hsc/Hsp70 and fl-actin). The labeled proteins were microinjected intravitreally into the normal or light damaged rat eye and each eye collected at three intervals after the injections. Retinal uptake of Hsc/Hsp70 or actin was studied in frozen sections using epifluorescence microscopy and in western blots of retinal homogenates using an anti-fluorescein antibody. Additionally, the cytoprotective effects of Hsc/Hsp70 were tested in rats that first were exposed to bright light (170 ft-c) for 24 h and then given an intravitreal injection of the protein immediately thereafter. Ten days later, photoreceptor damage was evaluated by measuring the area of the outer nuclear layer at fixed locations along the circumference of the retina. RESULTS: The fluorescein-labeled proteins were detected in the retina one h after administration and were retained there for more than 6 h. They were diffusely distributed, primarily in the nerve fiber layer, ganglion cell layer, and plexiform layers. Fl-Hsc/Hsp70 was also found in the outer nuclear layer (ONL) at 6 h after injection. At 24 h post-injection, the proteins were undetectable by epifluorescence microscopy of retinal sections, but could still be detected in western blots of retinal homogenates. The pattern of protein uptake was similar in light-damaged retinas. Ten days after light damage, the retinas in those eyes that received injections of Hsc/Hsp70 had greater ONL areas compared to either the light-damaged retinas of uninjected eyes or those that had received actin. The difference was statistically significant (p<0.05). CONCLUSIONS: Intravitreally injected Hsc/Hsp70 is taken up by retinal cells and, when administered after an acute injury like light damage, increased the number of surviving photoreceptors.

Animals↗

PubMed2001

Phenotypic correction of lipid storage and growth arrest in wolman disease fibroblasts by gene transfer of lysosomal acid lipase.

Wolman disease is a lethal lysosomal storage disease due to deficiency of lysosomal acid lipase (LAL). Wolman disease is characterized by pronounced hepatic involvement while neurological symptoms are uncommon, making Wolman disease an attractive candidate for liver-directed gene therapy. This study was performed to test the effects of gene replacement in fibroblasts lacking LAL, using a recombinant adenovirus encoding the human LAL cDNA (AdhLAL). Human fibroblasts from a Wolman disease patient were infected with AdhLAL and showed a dose-dependent increase in LAL protein and activity up to 5-fold above levels in control fibroblasts. Furthermore, 72 hr after infection with AdhLAL there was a dose-dependent correction of the severe lipid storage phenotype of Wolman disease fibroblasts. Electron microscopy confirmed significant correction of the lysosomal lipid storage in AdhLAL-infected Wolman disease fibroblasts at the ultrastructural level. Intravenous injection of AdhLAL into wild-type mice resulted in a 13.5-fold increase in hepatic LAL activity, and overexpression of LAL was not associated with toxic side effects. These data demonstrate high-level lysosomal expression of recombinant LAL in vitro and in vivo and show the feasibility of gene therapeutic strategies for the treatment of Wolman disease.

Adenoviridae↗

PubMed2001

Enantioselective syntheses of monotetrahydrofuran Annonaceous acetogenins tonkinecin and annonacin starting from carbohydrates.

The total synthesis of two mono-THF acetogenins, tonkinecin (1) and annonacin (2), is reported in full detail. Terminal acetylene 3 prepared from D-glucono-delta-lactone and asymmetric dihydroxylation was employed as a common intermediate for both targets 1 and 2. Pd(0)-catalyzed coupling reaction of 3 with vinyl iodides 4 and 5, the chiral centers of which were taken from D-xylose and S-(-)-ethyl lactate, afforded enyne 26 and 27, respectively. Selective hydrogenation of 26 or 27 with diimide followed by removal of MOM ethers completed the synthesis of 1. A coupling reaction between the lithium derivative of 3 and epoxide 6 in the presence of boron trifluoride etherate gave 42. Both chiral centers in epoxide 6 were taken from L-ascorbic acid. Subsequent catalytic hydrogenation and MOM protection led to 43b. Introduction of the butenolide moiety by aldol condensation of protected S-lactal followed by cleavage of all MOM ethers completed the synthesis of 2.

Carbohydrates↗

PubMed2001

Deletion of the p27Kip1 gene restores normal development in cyclin D1-deficient mice.

D-type cyclins (cyclins D1, D2, and D3) are key components of cell cycle machinery in mammalian cells. These proteins are believed to drive cell cycle progression by associating with their kinase partners, cyclin-dependent kinases, and by directing phosphorylation of critical cellular substrates. In addition, D-cyclins play a kinase-independent role by sequestering cell cycle inhibitors p27(Kip1) and p21(Cip1). In the past, we and others generated cyclin D1-deficient mice and have shown that these mice display developmental abnormalities, hypoplastic retinas, and pregnancy-insensitive mammary glands. To test the significance of cyclin D1-p27(Kip1) interaction within a living mouse, we crossed cyclin D1-deficient mice with mice lacking p27(Kip1), and we generated double-mutant cyclin D1(-/-)p27(-/-) animals. Here we report that ablation of p27(Kip1) restores essentially normal development in cyclin D1-deficient mice. Our results provide genetic evidence that p27(Kip1) functions downstream of cyclin D1.

Animals↗

PubMed2001

Application of a progressive-difference method to identify climatic factors causing variation in the rice yield in the Yangtze Delta, China.

Time series of rice yields consist of a technology-driven trend and variations caused by climate fluctuations. To explore the relationship between yields and climate, the trend and temporal variation often have to be separated. In this study, a progressive-difference method was applied to eliminate the trend in time series. By differentiating yields and climatic factors in 2 successive years, the relationship between variations in yield and climatic factors was determined with multiple-regression analysis. The number of hours of sunshine, the temperature and the precipitation were each defined for different intervals during the growing season and used as different regression variables. Rice yields and climate data for the Yangtze Delta of China from 1961 to 1990 were used as a case study. The number of hours of sunshine during the tillering stage and the heading to milk stage particularly affected the yield. In both periods radiation was low. In the first period, the vegetative organs of the rice crop were formed while in the second period solar radiation was important for grain filling. The average temperature during the tillering to jointing stage reached its maximum, which affected rice yields negatively. Precipitation was generally low during the jointing and booting stages, which had a positive correlation with yield, while high precipitation had a negative effect during the milk stage. The results indicate that the climatic factors should be expressed as 20- to 30-day averages in the Yangtze Delta; a shorter or longer period, e.g. 10 or 40 days, is less appropriate.

China↗

PubMed2001

Angiopoietin-2 is implicated in the regulation of tumor angiogenesis.

We addressed the effect of angiopoietin expression on tumor growth and metastasis. Overexpression of angiopoietin-2 (Ang-2) in Lewis lung carcinoma and TA3 mammary carcinoma cells inhibited their ability to form metastatic tumors and prolonged the survival of mice injected with the corresponding transfectants. In contrast, angiopoietin-1 (Ang-1) overexpression had no detectable effect on the ability of either tumor type to disseminate. Tumors derived from Ang-2-overexpressing cells displayed aberrant angiogenic vessels that took the form of vascular cords or aggregated vascular endothelial cells with few associated smooth muscle cells. These vascular cords or aggregates were accompanied by endothelial and tumor cell apoptosis, suggesting that an imbalance in Ang-2 expression with respect to Ang-1 and vascular endothelial growth factor may disrupt angiogenesis and tumor survival in vivo. Our observations suggest that Ang-2 may play an important role in regulating tumor angiogenesis.

Angiopoietin-2↗

PubMed2001

Rapid acquisition of entire DNA polymerase gene of a novel herpesvirus from green turtle fibropapilloma by a genomic walking technique.

A 4837-bp sequence of a newfound green turtle herpesvirus (GTHV), implicated in the etiology of green turtle fibropapilloma, was obtained from tumor tissues of a green turtle with fibropapilloma using a genomic walking method based on restriction enzyme digestion, self-ligation and inverse polymerase chain reaction (IPCR). The 4837-bp sequence was 56.23% G/C rich and contained three nonoverlapping open reading frames (ORF). The largest ORF (3507-bp) encoded the DNA polymerase gene (pol gene), which exhibited a high degree of homology at both amino acid and nucleotide levels with the DNA pol genes of human and animal herpesviruses, with a predicted protein of 1169 amino acids and molecular weight of 132.6 kilodaltons. The ATG at 518 to 520 was the first initiation codon in the ORF and was presumed to be the first methionine codon of the pol gene. Phylogenetic analysis, based on the amino acid sequence of the GTHV DNA pol gene and the corresponding regions of other known human and animal herpesviruses, indicated that GTHV belonged to the Alphaherpesvirinae subfamily. The upstream ORF of the pol gene encoded the N-terminal region of the GTHV homologue of the DNA-binding protein gene, whereas the downstream ORF was the C-terminal region of a gene which was homologous to ORFs conserved in human and animal herpesviruses, i.e., herpes simplex virus 1 (HSV1) gene UL31, Epstein-Barr virus (EBV) gene BFLF2, equine herpesvirus 1 (EHV1) gene 29, and alcelaphine herpesvirus 1 (AHV1) hypothetical protein 69 gene. The arrangement of these three genes in GTHV genome was identical to that seen in other alphaherpesviruses. The sequence and location of the DNA pol gene in the GTHV genome should greatly facilitate future studies of the viral life cycle.

Alphaherpesvirinae↗

PubMed2001

Cadmium(II) removal from aqueous solutions by pre-treated biomass of marine alga Padina sp.

In this study, the adsorption properties of a pre-treated biomass from marine alga Padina sp., a biomass collected from Surin Island, Thailand, for removal of cadmium(II) ions from aqueous solutions was investigated. Batch and column experiments were conducted to determine the adsorption properties of the modified biomass. At a pH of 5, the maximum removal capacity of the biomass is 0.53 mmol/g. The kinetics of cadmium(II) adsorption were fast with 90% of adsorption taking place within 35 min. This study demonstrated that the pre-treated biomass of Padina sp. could be used as an efficient biosorbent for the treatment of cadmium(II)-bearing wastewater streams.

Adsorption↗

PubMed2001

Suppressed apoptosis of pre-B cells in bone marrow of pre-leukemic p190bcr/abl transgenic mice.

Mice transgenic for a p190bcr/abl construct develop pre-B cell leukemia/lymphoma, providing a model of Ph+ ALL. To investigate events in tumorigenesis, immunofluorescence labeling, flow cytometry and a short-term culture assay were used to quantitate precursor B cells and their apoptotic rates in bone marrow of p190bcr/abl transgenic mice over a wide age range. Malignancies appeared rapidly at 8-12 weeks of age, followed by slower tumor onset. At 8-12 weeks in normal mice, the apoptotic rate fell among pro-B cells but increased steeply among pre-B cells, while the total number of B lineage cells declined. In contrast, in p190bcr/abl transgenic mice over the same time period, while pro-B cells remained normal in apoptotic rate and number, apoptosis of pre-B cells was markedly inhibited and the number of B lymphocytes increased. At later ages (14-30 weeks), B cell precursors in control mice remained constant in apoptotic activity and number, while in the few surviving transgenic mice B cell populations were expanded. The results reveal characteristic changes in apoptotic activity among B cell precursors in bone marrow during early life, severely perturbed in preleukemic p190bcr/abl transgenic mice by a preferential suppression of pre-B cell apoptosis. p190bcr/abl may thus promote leukemogenesis by permitting aberrant cells generated during early B cell development to evade a normal quality checkpoint and negative selection.

Age Factors↗

PubMed2001

Evolution of hepatitis C virus genome in chronically infected patients receiving ribavirin monotherapy.

Recent results of clinical trials suggest that combination of interferon and ribavirin exhibits an enhanced antiviral effect in the treatment of chronic hepatitis C. To investigate the effect of ribavirin on hepatitis C virus (HCV) infection, we analysed the evolution of the genetic heterogeneity of HCV in relation to the anti-HCV humoral response in patients treated by ribavirin alone. The study population included 35 patients with liver biopsy proven chronic hepatitis C infected with HCV genotype 1. Among them, 26 were treated with ribavirin for at least 12 months and nine untreated patients served as a control group. Serum samples were analysed before and at 6 and 12 months of therapy. Three regions of the HCV genome, i.e. HVR1, a domain of NS5A including part of the interferon sensitivity determining region (ISDR), and a segment of NS5B, were amplified by RT-PCR using specific primers. The PCR products were then studied using single-strand conformation polymorphism (SSCP) analysis followed by either direct sequencing, or cloning and sequencing. In parallel, the humoral anti-E1 response was studied using an ELISA (Innotest HCV E1Ab, Innogenetics). The results of HCV genome analysis showed no significant effect on the amino acid sequence evolution of the HVR1, NS5A and NS5B regions of HCV. Analysis of a phylogenetic tree from the major quasispecies variants showed the absence of correlation with ribavirin response, and the absence of selection of viral strains during ribavirin treatment. A trend towards a decrease in the anti-E1 Ab response was also observed. Altogether these results suggest that ribavirin may not exhibit a direct antiviral effect, but may trigger a favourable response to interferon by modulating the immune response against HCV.

Amino Acid Sequence↗

PubMed2001

Direct binding of beta-arrestins to two distinct intracellular domains of the delta opioid receptor.

beta-Arrestins regulate opioid receptor-mediated signal transduction and play an important role in opiate-induced analgesia and tolerance/dependence. This study was carried out to measure the direct interaction between beta-arrestins and opioid receptor. Immunoprecipitation experiments demonstrated that beta-arrestin 1 physically interacts with delta opioid receptor (DOR) co-expressed in human embryonic kidney 293 cells in an agonist-enhanced manner and truncation of the carboxyl terminus of DOR partially impairs the interaction. In vitro data from glutathione-S-transferase pull-down assay showed that the carboxyl terminus (CT) and the third intracellular loop (I3L) of DOR are both capable of and either domain is sufficient for binding to beta-arrestin 1 and 2. Surface plasmon resonance determination further revealed that binding of CT and I3L of DOR to beta-arrestin is additive, suggesting these two domains bind at distinctly different sites on beta-arrestin without considerable spatial hindrance. This study demonstrated for the first time the direct binding of beta-arrestins to the two distinct domains, the carboxyl terminus and the third intracellular loop, of DOR.

Amino Acid Sequence↗

PubMed2001

Biosorption and desorption of cadmium(II) by biomass of Laminaria japonica.

Biosorption and desorption properties of cadmium(II) from aqueous solutions by the biomass of marine alga Laminaria japonica were investigated. Results indicated that the uptake capacities were solution pH dependent and a maximum uptake capacity of about 1.3 mmol g-1 (dry weight) was observed at pH 6. The adsorbed cadmium cannot be desorbed by distilled water, but it can be effectively recovered by using acidic or EDTA solutions. The equilibrium isotherms can be described well with the Langmuir adsorption equation. Biomass, pre-treated with calcium solution exhibited a higher (about 30%) uptake capacity and can be easily settled from aqueous solutions. Batch kinetics experiments indicated that more than 90% of the adsorption occurred within 20 minutes of agitation and equilibrium was reached within one hour. Fixed-bed experiments showed similar uptake capacities to those of batch results and sharp breakthrough curves were obtained. This study indicated that the biomass of L. japonica can be used as an efficient biosorbent for the removal and recovery of cadmium(II) from waste water streams.

Adsorption↗