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Biomedical subjects

Yali Yang

Publications and source records attributed to Yali Yang.

8 recordsLinked to original sources
PubMed2006

Human Sgo1 is an excellent target for induction of apoptosis of transformed cells.

Aneuploidy, a frequent form of genomic instability, is a direct result of mis-segregation of sister chromatids during mitosis. Cohesion of sister chromatids in eukaryotes is primarily achieved by the cohesin complex. Since Sgo1 functions to protect centromeric cohesin and since depletion of Sgo1 results in precocious chromosomal segregation and massive mitotic arrest, we reasoned that disruption of Sgo1 functions by delivery of a competitive peptide could interfere with normal cell cycle progression. Treatment of HeLa and A549 cells with a Sgo1 fragment of 22 amino acids (corresponding to a conserved basic region at the C-terminus) linked with a cell-permeable peptide penetratin, but not with penetratin alone, resulted in concentration-dependent suppression of viability. Following 24 h treatment with Sgo1 peptide at a 40 muM final concentration, HeLa cell viability was dramatically reduced. The Sgo1 peptide induced rapid and drastic changes of cell and nuclear morphologies, which were associated with disappearance of cellular Sgo1 at kinetochores in mitotic cells. Moreover, the reduction in HeLa cell viability after treatment with Sgo1 peptide resulted from induction of apoptosis. Interestingly, WI-38 diploid fibroblasts were rather resistant to the treatment with Sgo1 peptide. These normal cells exhibited little changes of cellular and nuclear morphologies, and remained viable after exposure to 40 muM of Sgo1 peptide for 24 h. Our combined studies thus suggest that small peptides corresponding to conserved regions of Sgo1 are capable of functioning as dominant negative inhibitors in vivo and that Sgo1 is an excellent target for induction of apoptosis of cancer cells.

Amino Acid Sequence↗
PubMed2006

Differential subcellular localizations of two human Sgo1 isoforms: implications in regulation of sister chromatid cohesion and microtubule dynamics.

Sgo1 is an evolutionarily conserved protein that functions as a protector of centromeric cohesin during mitosis. Recent studies show that Sgo1 is kinetochorelocalized and required for accurate segregation of mitotic chromosomes because depletion of Sgo1 in mammalian cells results in precocious initiation of anaphase and mis-segregation of chromosomes. Through analysis of GFP fusion proteins, we observe that two major isoforms of human Sgo1 exhibit entirely different subcellular localization patterns. The short isoform of Sgo1 (sSgo1) that lacks exon 6 does not localize to kinetochores during any stages of the cell cycle. Instead, it is enriched at mitotic spindles. On the other hand, the longer isoform of Sgo1 primarily localizes to kinetochores during G(2) phase and mitotic prophase, metaphase, and anaphase. During late mitosis, Sgo1 does not appear to be associated with kinetochores. Intriguingly, the longer isoform of Sgo1 forms discrete foci during S phase, some of which are apparently in the nucleoli. However, a majority of these foci colocalize with CREST, a kinetochore antigen, indicating that Sgo1 is loaded onto kinetochores during or immediately after DNA replication. Together, our studies suggest that different isoforms of Sgo1 may play distinct roles during the cell cycle and that Sgo1 may have an interphase function as well.

Cell Cycle Proteins↗
PubMed2006

Real-time three-dimensional echocardiography in assessment of congenital double orifice mitral valve.

The application of real-time three-dimensional echocardiography (RT 3DE) in the diagnosis of double orifice mitral valve (DOMV) was explored. Five cases of DOMV were examined by using 2-dimensional echocardiography (2DE) and RT 3DE. The spatial morphology of malformed mitral valve and its change in hemodynamics were observed. DOMV associated with partial atrioventricular septal defect was found in 3 cases (in which 2 cases had cleft mitral valve) and isolated DOMV in 2 cases; and moderate to severe mitral regurgitation was detected in 3 cases, and mild mitral regurgitation in 1, and no regurgitation in 1 case; 1 case had complicated rhumatic heart disease. Three cases were preoperatively discovered by 2DE, while 2 missed (1 case was discovered postoperatively). Four cases were diagnosed by RT 3DE preoperatively, and 1 case was diagnosed postoperatively (not examined by RT 3DE preoperatively). It was suggested that RT 3DE is a reliable technique in the diagnosis of DOMV; it permitted comprehensive and noninvasive assessment of mitral valve and may supplement 2D TTE in the assessment of DOMV.

Abnormalities, Multiple↗
PubMed2006

Advances in mitotic inhibitors for cancer treatment.

Based on their mechanism of action, anti-tumor drugs that target the cell cycle can be generally divided into three categories, namely, blocking DNA synthesis, causing DNA damage, and disrupting mitotic processes. In terms of mitotic inhibitors, most compounds used in the clinic impair the normal function of mitotic spindles by targeting tubulins, basic building blocks of microtubules. In vivo, these compounds often exhibit significant side effects, thus limiting their efficacy. Mitotic processes are under tight control through surveillance mechanisms commonly termed checkpoints. Defects in the regulation of these checkpoints often result in genomic instability, which predisposes the cell to malignant transformation. As cancer is the consequence of uncontrolled cell division, great efforts have been devoted to discover drugs that target mitosis, thereby halting cell division and inducing mitotic catastrophe with minimal cytotoxicity to non-dividing or normally dividing cells. This review primarily focuses on mitotic proteins that have been explored as new targets for anti-cancer drug development during the past decade.

Antimitotic Agents↗
PubMed2005

Simvastatin regulates myocardial cytokine expression and improves ventricular remodeling in rats after acute myocardial infarction.

PURPOSE: Studies have showed that inflammatory cytokines were involved in the process of left ventricular (LV) remodeling after acute myocardial infarction (AMI), anti-inflammation treatment ameliorated LV remodeling and improved cardiac performance. Hydroxymethylglutary coenzyme A reductase inhibition (statins) could affect the expression of inflammatory cytokines. We hypothesized that statins have beneficial effects on early LV remodeling and cardiac performance in rats with AMI by modulating the production of inflammatory cytokines. METHODS: Rats with AMI were treated with placebo or simvastatin (gastric gavage) for 4 weeks. The pro-inflammatory cytokines: tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6 and the anti-inflammatory cytokine: IL-10 excreted by cardiac myocytes was examined. Echocardiography, hemodynamics and collagen type I production were measured to evaluate LV remodeling and cardiac function. RESULTS: The mRNA expression and protein production of TNF-alpha, IL-1beta, IL-6 and IL-10 in AMI group were significantly elevated compared with sham rats. Simvastatin markedly attenuated the production of TNF-alpha, IL-1beta, IL-6 and increased IL-10 levels in the noninfarcted and infarcted regions, reduced collagen deposition in the noninfarcted myocardium and improved left ventricular function. However simvastatin did not alter plasma lipids. CONCLUSIONS: Simvastatin ameliorates early LV remodeling and improve cardiac function after AMI. Simultaneously, it decreased pro-inflammatory and increased anti-inflammatory cytokines, which suggests, but does not prove, a causal relationship independent of plasma lipid-lowering effects.

Animals↗
PubMed2005

Engineering polysaccharide-based polymeric micelles to enhance permeability of cyclosporin A across Caco-2 cells.

PURPOSE: To assess and compare the effectiveness of two types of polysaccharide-based micelles as delivery vehicles for poorly water soluble drugs by monitoring their permeability across Caco-2 cell monolayers. METHODS: Dextran (DEX) and hydroxypropylcellulose (HPC) were hydrophobically modified (HM) by grafting polyoxyethylene cetyl ether (POE-C16, 15 mol% and 5.4 mol%, respectively). The onset of micellization and mean diameter of polymeric micelles formed by HM-DEX and HM-HPC were determined by fluorescence spectroscopy and dynamic light scattering, respectively. Cyclosporin A (CsA)-loaded polymeric micelles were prepared by a dialysis procedure, and the amount of incorporated CsA was assayed by high performance liquid chromatography (HPLC). The stability of micelles in simulated gastric and intestinal fluids was studied as a function of contact time, and their cytotoxicity toward Caco-2 cells was evaluated using the MTT colorimetric assay. The bidirectional transport across Caco-2 cell monolayers of CsA entrapped in HM-DEX and HM-HPC micelles and of the polymers themselves was evaluated in the presence and absence of P-glycoprotein inhibitor. RESULTS: The amount of CsA incorporated in HM-HPC and HM-DEX micelles reached 5.5 and 8.5% w/w, respectively (entrapment efficiency of 22% or more). The polymeric micelles exhibited high stability in gastric and intestinal fluids and no significant cytotoxicity toward Caco-2 cells. The apical to basal permeability of CsA across Caco-2 cells increased significantly when loaded in polymeric micelles compared to free CsA. CONCLUSIONS: Polysaccharide-based polymeric micelles are promising carriers for the oral delivery of poorly water soluble drugs. In vitro tests indicate that, overall, HM-HPC micelles are more effective compared to HM-DEX micelles.

Biological Transport↗
PubMed2004

Echocardiographic diagnosis of total anomalous pulmonary venous connection.

To investigate the value of echocardiography in the diagnosis of total anomalous pulmonary venous connection (TAPVC), 16 patients in our hospital were diagnosed to have TAPVC by echocardiography from year 1994 to 2001. In 11 cases the results of echocardiography were compared to those of surgery. Each patient was examined by using a combination of precordial, suprasternal and subcostal windows to visualize all the pulmonary veins and their drainage sites, common pulmonary venous trunk, and other associated abnormalities. Of the 16 cases, the drainage sites were as follow: supracardiac in 10, via vertical vein in 9, directly to superior vena cava in 1; cardiac in 5, via coronary sinus in 2, directly to right atrium in 3. Diagnoses were correctly made in all the 11 cases as confirmed by surgery. Echocardiography can also assess pulmonary arterial pressure and detect other associated abnormalities. It is concluded that echocardiography is the preferred examination method in the diagnosis of TAPVC before surgery. With careful examination using multiple windows and sections, TAPVC can be accurately diagnosed by echocardiography.

Adolescent↗