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Biomedical subjects

Y Sun

Publications and source records attributed to Y Sun.

At least 253 records · Page 14Linked to original sources
PubMed2000

Gamma-irradiation induces matrix metalloproteinase II expression in a p53-dependent manner.

Matrix metalloproteinases (MMPs) are a family of proteinases that degrade the basement membrane and have been implicated in promoting tumor metastasis. MMP-2, one member of this family, was recently found to be a p53 target and subject to p53 upregulation. In this study, we examined the correlation between the expression of MMP-2 and the increased expression of p53 after gamma-irradiation. Three human p53-positive cell lines that express wild-type p53, including U2-OS (osteosarcoma), RKO (colon carcinoma), MCF-7 (breast carcinoma), one mouse p53 positive cell line and HepG2 (liver carcinoma), and two p53-negative human cell lines, SAOS-2 (osteosarcoma) and RKO-E6 (colon carcinoma), were used in this study. The MMP-2 activity was analyzed by using gelatin zymography. The p53 level was measured by western blot analysis. Our results show that wild-type p53 induced by ionizing radiation caused a subsequent increase of MMP-2 activity in U2-OS and RKO cells but not in MCF-7, HepG2, SAOS-2, or RKO-E6 cells. These results suggest that the gamma-radiation-induced expression of MMP-2 is dependent on the cell type and presence of functional p53. Thus, ionizing radiation could activate MMP-2 activity in a subset of human cancer cells and may lead to an increase in their metastatic potential.

Animals↗
PubMed2000

Proteomic analysis of the renal effects of simulated occupational jet fuel exposure.

We analyzed protein expression in the cytosolic fraction prepared from whole kidneys in male Swiss-Webster mice exposed 1 h/day for five days to aerosolized JP-8 jet fuel at a concentration of 1000 mg/m3, simulating military occupational exposure. Kidney cytosol samples were solubilized and separated via large-scale, high-resolution two-dimensional electrophoresis (2-DE) and gel patterns scanned, digitized and processed for statistical analysis. Significant changes in soluble kidney proteins resulted from jet fuel exposure. Several of the altered proteins were identified by peptide mass finger-printing and related to ultrastructural abnormalities, altered protein processing, metabolic effects, and paradoxical stress protein/detoxification system responses. These results demonstrate a significant but comparatively moderate JP-8 effect on protein expression in the kidney and provide novel molecular evidence of JP-8 nephrotoxicity. Human risk is suggested by these data but conclusive assessment awaits a noninvasive search for biomarkers in JP-8 exposed humans.

Aerosols↗
PubMed2000

Proteomic analysis of the atrophying rat soleus muscle following denervation.

A proteomic analysis was performed comparing normal rat soleus muscle to denervated soleus muscle at 0.5, 1, 2, 4, 6, 8 and 10 days post denervation. Muscle mass measurements demonstrated that the times of major mass changes occurred between 2 and 4 days post denervation. Proteomic analysis of the denervated soleus muscle during the atrophy process demonstrated statistically significant (at the p < 0.01 level) changes in 73 soleus proteins, including coordinated changes in select groups of proteins. Sequence analysis of ten differentially regulated proteins identified metabolic proteins, chaperone and contractile apparatus proteins. Together these data indicate that coordinated temporally regulated changes in the proteome occur during denervation-induced soleus muscle atrophy, including changes in muscle metabolism and contractile apparatus proteins.

Animals↗
PubMed2000

Tandem mass spectrometry methods for definitive protein identification in proteomics research.

Optimized procedures have been developed for the addition of sulfonic acid groups to the N-termini of low-level peptides. These procedures have been applied to peptides produced by tryptic digestion of proteins that have been separated by two-dimensional (2-D) gel electrophoresis. The derivatized peptides were sequenced using matrix-assisted laser desorption/ionization (MALDI) post-source decay (PSD) and electrospray ionization-tandem mass spectrometry methods. Reliable PSD sequencing results have been obtained starting with sub-picomole quantities of protein. We estimate that the current PSD sequencing limit is about 300 fmol of protein in the gel. The PSD mass spectra of the derivatized peptides usually allow much more specific protein sequence database searches than those obtained without derivatization. We also report initial automated electrospray ionization-tandem mass spectrometry sequencing of these novel peptide derivatives. Both types of tandem mass spectra provide predictable fragmentation patterns for arginine-terminated peptides. The spectra are easily interpreted de novo, and they facilitate error-tolerant identification of proteins whose sequences have been entered into databases.

Amino Acid Sequence↗
PubMed2000

Simultaneous measurements of temperature and pH in vivo using NMR in conjunction with TmDOTP5-.

NMR techniques for temperature and pH measurements have attracted increasing interest in recent years, motivated in part by the growing importance of medical hyperthermia for the treatment of cancer. The chemical shifts of thulium 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetrakis(methylene phosphonate) (TmDOTP5-) have been studied as a function of temperature and pH. The results demonstrate that TmDOTP5- resonance shifts are highly sensitive to temperature (approximately 1.0 ppm/degrees C) and pH (approximately 3.2 ppm/pH unit) at clinically relevant field strengths. A new method is presented which utilizes two magnetically non-equivalent protons in TmDOTP5- for simultaneous NMR measurements of both temperature and pH. The difference in the chemical shift values of pairs of 1H resonances provides a temperature sensitivity of about 1.6 ppm/ degrees C. The technique is demonstrated in live rats undergoing ultrasound-induced hyperthermia therapy.

Animals↗
PubMed2000

Study on the expression of Fas ligand on the surfaces of human cytotrophoblasts in normal pregnancy.

To further study the mechanism of maternal-fetal immune tolerance, the expression of Fas ligand (FasL) on the surfaces of human cytotrophoblasts in normal pregnancy was detected by using immunohistochemical method. High precise color-image measure system for immuno-histochemistry was used to quantitatively analyze the expression of FasL. The results showed that FasL were expressed on the surfaces of placental cytotrophoblasts throughout normal pregnancy. The variance among the first, second and term pregnant stages was also detected. It was suggested that the expression of FasL on the surfaces of placental cytotrophoblasts might play an important role both in the maintenance of pregnancy and in the normal development of fetus. The maternal specific T cell apoptosis induced by Fas/FasL is one of the significant mechanisms of maternal-fetal immune tolerance.

Adult↗
PubMed2000

Expression of the inducible nitric oxide synthase isoform in chorionic villi in the early spontaneous abortion.

To investigate the relationship between inducible nitric oxide synthase (iNOS) and the early spontaneous abortion., in situ hybridization and immunohistochemistry were used to detect the expression of iNOS in trophoblasts in the early pregnancy with and without spontaneous abortion (group I and group II). By light microscopy and computer color magic image analysis system (CMIAS), light density (D) and the positive cell number per statistic square (N/S) in situ hybridization were used to analyze the positive cell index, while total positive cells (N) and the positive unit (Pu) were used in immunohistochemistry. By in situ hybridization, D and N/S in trophoblasts were 0.35 +/- 0.028, 0.07 +/- 0.011 respectively in group I and 0.18 +/- 0.016, 0.015 +/- 0.003 in group II. In terms of immunohistochemical staining, N and Pu were 0.058 +/- 0.007, 11.94 +/- 2.01 in group I and 0.013 +/- 0.009, 1.08 +/- 0.35 in group II in trophoblasts. Significant differences existed between two groups. It is concluded that the higher nitric oxide produced by the higher expression of iNOS in trophoblasts might play an important role in the early spontaneous abortion.

Abortion, Spontaneous↗
PubMed2000

The binding of trivalent chromium to low-molecular-weight chromium-binding substance (LMWCr) and the transfer of chromium from transferrin and chromium picolinate to LMWCr.

A recent model for the role of chromium in insulin signaling requires that the oligopeptide low-molecular-weight chromium-binding substance (LMWCr) tightly bind four chromic ions before the oligopeptide obtains a conformation required for binding to the tyrosine kinase active site of the insulin receptor. To test this model, the chromium-binding constant of LMWCr was determined, and the ability of LMWCr to remove chromium from Cr2-transferrin and the nutritional supplement chromium picolinate, Cr(pic)3, was examined. These results are consistent with the model of the mode of action of LMWCr; a Hill study indicates the four chromic ions bind to apoLMWCr in a highly cooperative fashion (n =3.47) with a binding constant of 1.54x 10(21). Chromium is readily transferred from transferrin to apoLMWCr at near neutral pH. The results also suggest that reduction of the chromic center of Cr(pic)3 may be required for the supplement to release chromium; thus, release of chromium is related to a mechanism by which Cr(pic)3 may generate hydroxyl radicals in cells.

Carrier Proteins↗
PubMed2000

Infarct scar: a dynamic tissue.

Infarct scar, a requisite to the rebuilding of necrotic myocardium following myocardial infarction (MI), has long been considered inert. Earlier morphologic studies suggested healing at the infarct site was complete within 6-8 weeks following MI and resultant scar tissue, albeit necessary, was acellular and simply fibrillar collagen. Utilizing molecular and cellular biologic technologies, recent studies indicate otherwise. Infarct scar is composed of phenotypically transformed fibroblast-like cells, termed myofibroblasts (myoFb) because they express alpha-smooth muscle actin (alpha-SMA) and these microfilaments confer contractile behavior in response to various peptides and amines. These cells are nourished by a neovasculature and are persistent at the MI site, where they are metabolically active expressing components requisite to angiotensin (Ang) peptide generation, including converting enzyme, receptors for AngII and transforming growth factor (TGF)-beta1. They continue to elaborate fibrillar type I collagen. Their generation of these peptides contribute to ongoing scar tissue collagen turnover and to fibrous tissue formation of noninfarcted myocardium. Infarct scar contraction accounts for its thinning and its tonus may contribute to abnormal ventricular chamber stiffness with diastolic dysfunction. Infarct scar is a dynamic tissue: cellular, vascularized, metabolically active and contractile. Pharmacologic interventions with angiotensin converting enzyme inhibitor or AT1 receptor antagonist has proven effective in attenuating scar tissue metabolic activity and minimizing adverse accumulation of fibrous tissue in noninfarcted myocardium.

Angiotensin II↗
PubMed2000

Phenolic glycosides of forage legume Onobrychis viciifolia.

A chemical examination of the extractives of the leaves of sainfoin was undertaken as part of a programme directed at understanding the factors which may contribute to its nutritive value as animal feed. Among the low molecular weight phenolic compounds characterized were seven cinnamic acid derivatives and nine flavonoid glycosides all of which were identified by NMR spectroscopy. Included among these compounds were two new natural hydroxycinnamic esters namely methyl 6-O-p-trans-coumaroyl-beta-D-glucopyranoside and methyl 6-O-p-cis-coumaroyl-beta-D-glucopyranoside and a novel flavonoid chrysoeriol-4'-O-(6''-O-acetyl)-beta-D-glucopyranoside.

Chromatography, High Pressure Liquid↗
PubMed2000

Sequence specific analysis of the heterogeneous glycan chain from peanut peroxidase by 1H-NMR spectroscopy.

The cationic peanut peroxidase is a complex enzyme consisting of a heme group, two calcium ions and three complex carbohydrate chains at positions Asn60, 144 and 185. Details of the heme and calcium ligation, necessary for oxidation, have recently been revealed from the three-dimensional structure of the peroxidase. However, the three glycans that may be important for the stability of the enzyme as well as its activity were not resolved. In order to determine the configuration of one of these glycans, PNGase A was used to cleave the glycan from the enzyme at Asn-144. This glycan was studied by two dimensional 1H-NMR spectroscopy to identify the sugar linkages. The results indicated a glycan structure comprising a Man alpha1-6(Xyl beta1-2)Man beta1-4GlcNAc beta1-4(Fuc alpha1-3)GlcNAc beta core but with an additional Man alpha1-3 appendage linked to Man3. The glycan also appeared to be heterogeneous as was noted from a single terminating galactose being linked to approximately 20-25% glycan.

Arachis↗
PubMed2000

Effects of positive intrathoracic pressure on pulmonary and systemic hemodynamics.

The Frank-Starling Law accounts for many changes in cardiac performance previously attributed to changes in contractility in that changes in contractility might have been incorrectly inferred from changing ventricular function curves (i.e. systolic performance plotted against filling pressure) if diastolic compliance also changed. To apply the Frank-Starling Law in the presence of changing diastolic compliance, it is necessary to measure end-diastolic volume directly or to calculate end-diastolic transmural pressure, which requires that pericardial pressure be known. Under most normal circumstances, increased intrathoracic pressure (and other interventions, such as vasodilators or lower-body negative pressure, that decrease central blood volume) decreases the transmural end-diastolic pressures of both ventricles, their end-diastolic volumes and stroke work. However, when ventricular interaction is significant, the effects of these interventions might be quite different; this may be important in patients with heart-failure. Although these interventions decrease RV transmural pressure, they may increase LV transmural pressure, end-diastolic volume, and thus stroke work by the Frank-Starling mechanism.

Animals↗
PubMed2000

Transduction of hepatocellular carcinoma (HCC) using recombinant adeno-associated virus (rAAV): in vitro and in vivo effects of genotoxic agents.

BACKGROUND/AIMS: Adeno-associated virus (AAV) is an attractive tool for gene therapy. Here we investigated the in vitro and in vivo transduction of hepatocellular carcinoma (HCC) cells by an AAV vector and the efficacy of different strategies to enhance the transduction of the tumor. METHODS: Transduction efficiency was determined by analyzing AAV-mediated beta-galactosidase gene (rAAV/lacZ) expression. RESULTS: Adenovirus help or pretreatment of HCC cells with y-irradiation or with the topoisomerase inhibitor etoposide resulted in marked enhancement of cell transduction in vitro. In vivo studies in nude mice with subcutaneous HCC tumors showed that HCC cells were not transduced by AAV vector alone. However, co-infection of the tumor with adenovirus allowed an efficient expression of the reporter gene but only at the sites of vector injection. Previous gamma-irradiation of subcutaneous tumors with 1800 rad was able to improve transduction of HCC cells (up to 30%) using recombinant AAV. Continuous i.p. infusion of etoposide in buffalo rats harboring HCC tumors in the liver resulted in transduction of normal liver tissue and also of very small neoplastic lesions (<2 mm) but no transduction was observed in tumors bigger than 2 mm. To analyze this phenomenon we determined etoposide concentration in hepatic tissue. Our results revealed high concentrations of the drug in non-tumoral tissue but almost undetectable levels in big tumor nodules. CONCLUSIONS: Our results indicate that while both radiotherapy and etoposide enhance transduction of tumor cells by rAAV in vitro, only radiotherapy increases tumor transduction in vivo. Our data suggest the existence of a barrier which limits in vivo the diffusion of chemotherapeutic agents to well-established HCC nodules.

Animals↗
PubMed2000

atonal regulates neurite arborization but does not act as a proneural gene in the Drosophila brain.

Drosophila atonal (ato) is the proneural gene of the chordotonal organs (CHOs) in the peripheral nervous system (PNS) and the larval and adult photoreceptor organs. Here, we show that ato is expressed at multiple stages during the development of a lineage of central brain neurons that innervate the optic lobes and are required for eclosion. A novel fate mapping approach shows that ato is expressed in the embryonic precursors of these neurons and that its expression is reactivated in third instar larvae (L3). In contrast to its function in the PNS, ato does not act as a proneural gene in the embryonic brain. Instead, ato performs a novel function, regulating arborization during larval and pupal development by interacting with Notch.

Animals↗
PubMed2000

Labeling and in vivo evaluation of novel copper(II) dioxotetraazamacrocyclic complexes.

64Cu shows promise as both a positron emission tomography imaging and radiotherapeutic radionuclide due to its half-life (T(1/2) = 12. 7 h), decay characteristics (beta(+) [19%]; beta(-) [40%]), and the capability to produce it on a large-scale with high specific activity on a biomedical cyclotron. Macrocyclic chelators are generally used as bifunctional chelators to attach Cu(II) to antibodies and peptides due to their relatively high in vitro stability. To investigate neutral Cu(II) complexes, we performed labeling experiments with six tetraazamacrocyclic ligands with different chelate ring sizes. 1,4,8,11-Tetraazacyclotetradecane-3, 9-dione (1), 1,4,8,11-tetraazacyclotetradecane-5,7-dione (2), 1,4,7, 10-tetraazacyclotridecane-11,13-dione (3), 1,4,7, 10-tetraazacyclotridecane-2,9-dione (4), 1,4,7, 10-tetraazacyclododecane-2,9-dione (5), and 1,4,7, 10-tetraazacyclotridecane-3,8-dione (6) were radiolabeled with (64)Cu. Only (64)Cu-labeled 1 readily formed a complex in high purity, and therefore was evaluated in vivo. The rapid blood, liver, and kidney clearance of (64)Cu-labeled 1 suggest that ligand 1 may be useful as a macrocyclic structure to design new bifunctional chelators for copper radionuclides in diagnostic or radiotherapeutic studies and is a potential alternative to currently used macrocyclic bifunctional chelators.

Animals↗
PubMed2000

The effect of lipid environment in purple membrane on bacteriorhodopsin.

The decay rate of the Bacteriorhodopsin (BR) photocycle intermediate M412 and proton, the proton pump efficiency (H+/M412), the ratios of M412 to other intermediates and the rotational correlation time (tauc) in purple membrane (PM) fragments treated by the zwitterionic detergent 3-[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate (CHAPS) with different concentrations were studied. The results show that: (1) The largest effect of CHAPS on M412 decay rate and proton decay rate of BR, tauc of PM and the ratios of M412 to other intermediates in BR photocycle is in the range of its critical micelle concentration (CMC). This indicates that changes of the ratios of M412 to other intermediates, tauc, M412 decay and proton decay occur and are due to the variation of the lipid environment. (2) The dependency of proton yield on CHAPS concentrations is basically consistent with that of M412s%. This indicates the relation between proton pumping function and M412. These studies show the importance of maintaining a native environment.

Bacteriorhodopsins↗
PubMed2000

A fluorescence-based assay for 3' --> 5' exoribonucleases: potential applications to the study of mRNA decay.

A cell-free mRNA decay assay has been adapted to permit the kinetics of 3' --> 5' exoribonuclease activities to be monitored in real time. RNA probes containing 5' caps and 3' poly(A) tails generated by transcription in vitro are 3' labeled using fluorescein-N6-ATP and poly(A) polymerase. Release of fluorescein-conjugated adenosine residues from the 3' end of the RNA substrate is monitored by a time-dependent decrease in fluorescence anisotropy in the presence of cytosolic proteins. To demonstrate the utility of the assay, an RNA probe was constructed containing a fragment of the c-myc 3' untranslated region and an 85-base poly(A) tail. Following 3' fluorescein labeling, the rate of 3'-terminal adenosine excision was monitored in the presence of an S100 cytosolic extract prepared from K562 erythroleukemia cells. Removal of the fluorescein-tagged A residues resolved to a first-order decay function, allowing the rate constant and enzyme-specific activity to be determined in this extract. Further applications and advantages of this technology are discussed.

Adenosine Triphosphate↗