Biomedical subjects

Yu Sun

Publications and source records attributed to Yu Sun.

At least 55 records · Page 3Linked to original sources

PubMed2005

Plasma membrane sequestration of apoptotic protease-activating factor-1 in human B-lymphoma cells: a novel mechanism of chemoresistance.

Burkitt lymphoma (BL) is a highly aggressive B-cell neoplasm harboring chromosomal rearrangements of the c-myc oncogene. BL cells frequently resist apoptosis induction by chemotherapeutic agents; however, the mechanism of unresponsiveness has not been elucidated. Here, we show that cytochrome c fails to stimulate apoptosome formation and caspase activation in cytosolic extracts of human BL-derived cell lines, due to insufficient levels of apoptotic protease-activating factor-1 (Apaf-1). Enforced expression of Apaf-1 increased its concentration in the cytosolic compartment, restored cytochrome c-dependent caspase activation, and rendered the prototypic Raji BL cell line sensitive to etoposide- and staurosporine-induced apoptosis. Surprisingly, in nontransfected BL cells, the bulk of Apaf-1 was found to associate with discrete domains in the plasma membrane. Disruption of lipid raft domains or the actin cytoskeleton of Raji cells liberated Apaf-1 and restored sensitivity to cytochrome c-dependent apoptosis, indicating that constitutive Apaf-1 retained its ability to promote caspase activation. Moreover, disruption of lipid rafts sensitized BL cells to apoptosis induced by etoposide. Together, our findings suggest that ectopic (noncytosolic) localization of Apaf-1 may constitute a novel mechanism of chemoresistance in B lymphoma.

Apoptosis↗

PubMed2005

BZR1 is a transcriptional repressor with dual roles in brassinosteroid homeostasis and growth responses.

Brassinosteroid (BR) homeostasis and signaling are crucial for normal growth and development of plants. BR signaling through cell-surface receptor kinases and intracellular components leads to dephosphorylation and accumulation of the nuclear protein BZR1. How BR signaling regulates gene expression, however, remains unknown. Here we show that BZR1 is a transcriptional repressor that has a previously unknown DNA binding domain and binds directly to the promoters of feedback-regulated BR biosynthetic genes. Microarray analyses identified additional potential targets of BZR1 and illustrated, together with physiological studies, that BZR1 coordinates BR homeostasis and signaling by playing dual roles in regulating BR biosynthesis and downstream growth responses.

Arabidopsis↗

PubMed2005

A small stress protein acts synergistically with trehalose to confer desiccation tolerance on mammalian cells.

The ability to desiccate mammalian cells while maintaining a high degree of viability would be very important in many areas of biological science, including tissue engineering, cell transplantation, and biosensor technologies. Certain proteins and sugars found in animals capable of surviving desiccation might aid this process. We report here that human embryonic kidney (293H) cells transfected with the gene for the stress protein p26 from Artemia and loaded with trehalose showed a sharp increase in survival during air-drying. Further, we find vacuum-drying greatly improved the ability of the cells to survive, and that the physical shape and structure of the cellular sample had a large influence on recovery following rehydration. Cells suspended in a rounded droplet survived desiccation markedly better than those spread as a thin film. Finally, we used alamarBlue to monitor cellular metabolism and Hema 3 to assess colony formation after vacuum-drying. AlamarBlue fluorescence indicated that the transfected 293H cells expressing p26 (E11'L) grew much better than the control 293H cells. In fact, immediate survival and colony formation in E11'L cells increased as much as 34-fold compared with control cells when the samples were dried to a water content of 0.2 g H2O/g dry weight, as measured by gravimetric analysis. These results indicate that p26 improves cell survival following drying and rehydration, and suggest that dry storage of mammalian cells is a likely possibility in the future.

Air↗

PubMed2005

Investigating chorion softening of zebrafish embryos with a microrobotic force sensing system.

The zebrafish is a model organism for addressing questions of vertebrate embryo development. In this paper, the softening phenomenon of the chorion envelope of zebrafish embryos at different developmental stages was mechanically quantitated by using a microrobotic force sensing system. The microrobotic system integrates a piezoelectric cellular force sensor to measure the required forces for penetrating the chorion envelope. Magnitude of penetration forces was found to decrease as an embryo develops. The results mechanically quantitate "chorion softening" in zebrafish embryos due to protease activities subtly modifying the chorion structure, providing an understanding of zebrafish embryo development.

Animals↗

PubMed2005

Manipulation of cells using an ultrasonic pressure field.

A novel device is described that generates an ultrasonic force field in a fluid layer. The force field arises because of the acoustic radiation force, a second order effect, generated as an ultrasonic wave interacts with a suspended particle. This force field can be used to manipulate objects in the fluid layer trapped between this device and an arbitrary surface, in this case, a flat object slide. The device is shown to be capable of positioning and, in doing so, concentrating human cells to predictable locations. Mesenchymal and HeLa cells were used. Critically, the forces required to do this can be generated by ultrasonic pressure fields that do not affect the viability of the cells. The viability has been assessed using trypan blue dye. The device used consists of a 14 mm square glass plate that is excited by at least one of four piezotransducers attached to the edges. The resulting ultrasonic force field and, importantly, the location of the minima in the force potential at which the cells are collected, has been calculated analytically.

Cell Survival↗

PubMed2005

The small heat shock proteins and their role in human disease.

Small heat shock proteins (sHSPs) function as molecular chaperones, preventing stress induced aggregation of partially denatured proteins and promoting their return to native conformations when favorable conditions pertain. Sequence similarity between sHSPs resides predominately in an internal stretch of residues termed the alpha-crystallin domain, a region usually flanked by two extensions. The poorly conserved N-terminal extension influences oligomer construction and chaperone activity, whereas the flexible C-terminal extension stabilizes quaternary structure and enhances protein/substrate complex solubility. sHSP polypeptides assemble into dynamic oligomers which undergo subunit exchange and they bind a wide range of cellular substrates. As molecular chaperones, the sHSPs protect protein structure and activity, thereby preventing disease, but they may contribute to cell malfunction when perturbed. For example, sHSPs prevent cataract in the mammalian lens and guard against ischemic and reperfusion injury due to heart attack and stroke. On the other hand, mutated sHSPs are implicated in diseases such as desmin-related myopathy and they have an uncertain relationship to neurological disorders including Parkinson's and Alzheimer's disease. This review explores the involvement of sHSPs in disease and their potential for therapeutic intervention.

Animals↗

PubMed2005

Characterization of novel sequence motifs within N- and C-terminal extensions of p26, a small heat shock protein from Artemia franciscana.

The small heat shock proteins function as molecular chaperones, an activity often requiring reversible oligomerization and which protects against irreversible protein denaturation. An abundantly produced small heat shock protein termed p26 is thought to contribute to the remarkable stress resistance exhibited by encysted embryos of the crustacean, Artemia franciscana. Three novel sequence motifs termed G, R and TS were individually deleted from p26 by site-directed mutagenesis. G encompasses residues G8-G29, a glycine-enriched region, and R includes residues R36-R45, an arginine-enhanced sequence, both in the amino terminus. TS, composed of residues T169-T186, resides in the carboxy-extension and is augmented in threonine and serine. Deletion of R had more influence than removal of G on p26 oligomerization and chaperoning, the latter determined by thermotolerance induction in Escherichia coli, protection of insulin and citrate synthase from dithiothreitol- and heat-induced aggregation, respectively, and preservation of citrate synthase activity upon heating. Oligomerization of the TS and R variants was similar, but the TS deletion was slightly more effective than R as a chaperone. The extent of p26 structural perturbation introduced by internal deletions, including modification of intrinsic fluorescence, 1-anilino-8-naphthalene-sulphonate binding and secondary structure, paralleled reductions in oligomerization and chaperoning. Three-dimensional modeling of p26 based on wheat Hsp16.9 crystal structure indicated many similarities between the two proteins, including peptide loops associated with secondary structure elements. Loop 1 of p26 was deleted in the G variant with minimal effect on oligomerization and chaperoning, whereas loop 3, containing beta-strand 6 was smaller than the corresponding loop in Hsp16.9, which may influence p26 function.

Amino Acid Motifs↗

PubMed2005

Expression of foreign genes in Dunaliella by electroporation.

An electroporation procedure has been described for introducing plasmid DNA into Dunaliella salina cells. By this procedure, a bulk of plasmid DNA was delivered into the cells and retained for at least 3 d. Reverse transcriptase polymerase chain reaction (RT-PCR) and sequencing analyses indicated that the transcription and pre-mRNA splicing of ble gene (contributing the Zeocin resistance) were detected in the cells as early as 1 h after the electroporation. Individual colonies could retain the resistance to 10 mg/L Zeocin for at least 6 mo. Subsequent Southern blot analysis showed the existence of introduced plasmid DNA inside these colonies. However, most of the cells (approx 90%) lost the resistance in the presence of 5 mg/L Zeocin during subculturing, which was consistent with the observations of both rearranged and episomal plasmid DNA existed in the cells. Nevertheless, the electroporation procedure allows introducing a gene of interest and studying its expression and function in D. salina cells.

Bleomycin↗

PubMed2005

Effectiveness of vitamin B12 on diabetic neuropathy: systematic review of clinical controlled trials.

The clinical effectiveness of vitamin B12 and its active coenzyme form on diabetic neuropathy is uncertain. Therefore, we searched the English- and non-English-language literature on this topic by using MEDLINE (Ovid, PubMed), the Cochrane Controlled Trials Register, and related papers. We identified seven randomized controlled trials from June 1954 to July 2004 and reviewed them for the clinical effectiveness of vitamin B12 according to the following parameters: Measurement scales of somatic and autonomic symptoms or signs; vibrometer-detected thresholds of vibration perception; and, electrophysiologic measures such as nerve conduction velocities and evoked potentials. Three studies involved the use of vitamin B complex (including B12) as the active drug, and four used methylcobalamin. Two studies were of fairly good quality (Jadad score = 3/5), and five were of poor quality (Jadad score < or = 2/5). Both the vitamin B12 combination and pure methylcobalamin had beneficial effects on somatic symptoms, such as pain and paresthesia. In three studies, methylcobalamin therapy improved autonomic symptoms. Effects on vibration perception and electrophysiological measures were not consistent. With both the vitamin B12 combination and pure methylcobalamin, symptomatic relief was greater than changes in electrophysiological results. However, more high-quality, double-blind randomized controlled trials are needed to confirm the effects of vitamin B12 on diabetic neuropathy.

Diabetic Neuropathies↗

PubMed2005

[Correlation between the expression of VEGF-C mRNA, VEGFR-3, CD31 and tumor metastases in Chinese with prostate cancer].

The expressions of VEGF-C mRNA, VEGFR-3 and CD31 were studied in order to investigate the correlation between them and neoangiogenesis, hyperplasia of micro-lymphatics and tumor metastases. 34 cases of prostate cancer tissue and 12 cases of adjacent nontumorous tissue specimens were tested. They were marked by VEGFR-3 and CD31 with immunohistochemistic staining and analyzed with image, the micro-lymphatics count (MLC) and microvessel density (MVD) were counted using Weidner's highest vessel density count method; the expression of VEGF-C mRNA was inspected in situ hybridization. The expression of VEGF-C mRNA was 44.12% positive in 34 cases of prostate cancer, the MLC (8.26 +/- 2.73)mm2 and MVD (74.82 +/- 11.76)mm2 in prostate cancer were significantly higher than those in adjacent nontumorous tissue (MLC, 4.82 +/- 3.48/mm2; MVD, 32.86 +/- 5.41/mm2). In addition, there was a correlation between the expression of VEGF-C mRNA and micro-lymphatics metastases and there was a positive correlation between the expression of VEGFR-3 and CD31. The expressions of VEGF-C mRNA , MLC, MVD in stage III and IV and those who have lymph metastasis were higher than those in stage I and II and those who have no lymph metastasis; the expressions of VEGFR-3 and CD31 in VEGF-C mRNA positive groups were significantly higher than those in negative groups. The difference of histopathologic grading in prostate cancer had no statistical significance. VEGF-C could accelerate the hyperplasia of micro-lymphatics and neoangiogenesis induced by tumor and play an important role in tumor lymph metastases. There was a close correlation between the expressions of VEGFR-3, CD31 and tumor metastases. The increase of MLC and MVD on prostate cancer indicated the hyperplasia of new micro-lymphatics and neoangiogenesis in the tumor tissue, which could also be a signal to determine the tumor metastases in clinic.

Aged↗

PubMed2005

[Observe the dissection of the tunnels of augmentation rhinoplasty under endoscope].

OBJECTIVE: To observe and analyse the dissection of the tunnels in traditional blind operation of augmentation rhinoplasty. METHODS: 11 Cases of augmentation rhinoplasty were collected and be observed by an endoscope as soon as the tunnels were formed during the operations. RESULTS: (1) Some of the tunnels did not go through one layer. (2) The bilateral cartilage separated in the mid-line. (3) There were two blood vessels in the surface of alar cartilage. There were perforating blood vessels in the edge of pyriform aperture. (4) In some cases whose incision were in unilateral alar margin, the tunnel were asymmetric. CONCLUSION: In some cases of traditional blind operation of augmentation rhinoplasty, tunnels were not suitable, they were asymmetric; and there were desmo and septa in the tunnels. Those might be the causes of complications post-op of augmentation rhinoplasty.

Endoscopes↗

PubMed2005

[Microclimate characters of urban forest in Shenyang].

This paper analyzed the diurnal changes of the temperature and humidity in Shenyang urban forest during its different growth stages. The results showed that air temperature was the lowest in the morning and the highest at noon. The highest peak point of air temperature lagged behind that of solar radiation about 2 hours, due to the influence of forest environment. The annual air temperature amplitude was in order of stop-growth period (dormancy stage) (DS) > prophase of growth season (PGS) > anaphase of growth season (AGS) > medium-term of growth season (MGS). Soil temperature of PGS, MGS and AGS at daytime was higher than that at night, while that of DS was in reverse. The daily soil temperature amplitude at different growth stages was in order of upper soil layer (20 cm) >medium soil layer (40 cm) >lower soil layer(80 cm),while the diurnal soil temperature amplitude in the same soil layer was in order of PGS > AGS > DS > MGS (20 cm) and PGS > DS > AGS > MGS (80 cm). The diurnal change of relative humidity was reverse to that of air- and soil temperature, which was higher at night than at daytime, and was in order of MGS > AGS > DS > PGS.

China↗

PubMed2005

[Transient expression of foreign ble gene in Dunaliella salina].

Plasmid pSP124S with ble gene was transformed into D. salina cell by electroporation. The retention and expression of foreign gene in D.salina was explored, proper parameters were established. A large amount of foreign plasmid was found to be introduced into cells. The plasmid was degraded gradually, but can be detected within 96 hours. The ble gene was efficiently transcribed from foreign promoter and transcription was maintained at least 72 hours. The ble gene can be translated correctly and so can be used as a selectable marker for the research of genetic tranformation in D. salina.

Bacterial Proteins↗

PubMed2004

Methylation of p16 CpG islands associated with malignant transformation of gastric dysplasia in a population-based study.

PURPOSE: Inactivation of p16 by aberrant methylation of CpG islands is a frequent event in carcinomas and precancerous lesions of various organs, including the stomach. The aim of this study is to investigate the relationship between p16 methylation and malignant transformation of human gastric dysplasia (DYS) based on follow-up endoscopic screening in a high-risk population. EXPERIMENTAL DESIGN: Genomic DNA samples were extracted from paraffin blocks of gastric mucosal biopsies that were histopathologically diagnosed as low-grade DYS from patients who developed gastric carcinomas [GCs (n = 21)] and those that did not do so (n = 21) during 5 years of follow-up. The methylation status of p16 CpG islands of each sample was detected by methylation-specific PCR, denatured high-performance liquid chromatography, and sequencing. RESULTS: Aberrant p16 methylation was observed in 5 of 21 samples of DYS that progressed to GC but in 0 of 21 samples that did not progress to GC (P = 0.048, two-sided). Sequencing results confirmed that all CpG sites were methylated in the analyzed sequence from these five p16-methylated cases. Furthermore, p16 methylation was also observed in the five subsequent GCs. Unmethylated p16 CpG islands were detected in all of the samples without p16 methylation. CONCLUSIONS: Our findings suggest p16 methylation is correlated with the malignant transformation of gastric DYS, and p16 methylation might be a useful biomarker for prediction of malignant potential of gastric DYS.

Adult↗

PubMed2004

Oligomerization, chaperone activity, and nuclear localization of p26, a small heat shock protein from Artemia franciscana.

Artemia franciscana embryos undergo encystment, developmental arrest and diapause, the last characterized by profound metabolic dormancy and extreme stress resistance. Encysted embryos contain an abundant small heat shock protein termed p26, a molecular chaperone that undoubtedly has an important role in development. To understand better the role of p26 in Artemia embryos, the structural and functional characteristics of full-length and truncated p26 expressed in Escherichia coli and COS-1 cells were determined. p26 chaperone activity declined with increasing truncation of the protein, and those deletions with the greatest adverse effect on protection of citrate synthase during thermal stress had the most influence on oligomerization. When produced in either prokaryotic or eukaryotic cells the p26 alpha-crystallin domain consisting of amino acid residues 61-152 existed predominantly as monomers, and p26 variants lacking the amino-terminal domain but with intact carboxyl-terminal extensions were mainly monomers and dimers. The amino terminus was, therefore, required for efficient dimer formation. Assembly of higher order oligomers was enhanced by the carboxyl-terminal extension, although removing the 10 carboxyl-terminal residues had relatively little effect on oligomerization and chaperoning. Full-length and carboxyl-terminal truncated p26 resided in the cytoplasm of transfected COS-1 cells; however, variants missing the complete amino-terminal domain and existing predominantly as monomers/dimers entered the nuclei. A mechanism whereby oligomer disassembly assisted entry of p26 into nuclei was suggested, this of importance because p26 translocates into Artemia embryo nuclei during development and stress. However, when examined in Artemia, the p26 oligomer size was unchanged under conditions that allowed movement into nuclei, suggesting a process more complex than just oligomer dissociation.

Amino Acid Sequence↗

PubMed2004

The influence of polyelectrolyte charges of polyurethane membrane surface on the growth of human endothelial cells.

A novel technique to introduce free amino groups onto polyester scaffolds via aminolyzing the ester groups with diamine has been developed recently. The introduction of the free amino groups on these polyester surfaces provides us the possibility to modify polymer surface in a simpler manner, e.g. layer-by-layer assembly of charged species. By this technique, many negatively and positively charged biopolymers were deposited alternatively on polyurethane surface. The deposition process was monitored by fluorescence spectroscopy and advancing contact angle measurements. The result of human endothelial cells cultured in vitro showed that cells on negatively charged surface could not spread and flatten well due to the electrostatic repulsion. The lower attachment ratio induced the lower proliferation ratio. However, after the surface charge was inversed by collagen, both attachment and proliferation ratios increased to different extent. Observed under SEM, cells also presented a flat and spreading morphology.

Animals↗

PubMed2004

Endothelial cells stimulate self-renewal and expand neurogenesis of neural stem cells.

Neural stem cells are reported to lie in a vascular niche, but there is no direct evidence for a functional relationship between the stem cells and blood vessel component cells. We show that endothelial cells but not vascular smooth muscle cells release soluble factors that stimulate the self-renewal of neural stem cells, inhibit their differentiation, and enhance their neuron production. Both embryonic and adult neural stem cells respond, allowing extensive production of both projection neuron and interneuron types in vitro. Endothelial coculture stimulates neuroepithelial cell contact, activating Notch and Hes 1 to promote self-renewal. These findings identify endothelial cells as a critical component of the neural stem cell niche.

Animals↗

PubMed2004

[The application and early result of rectangle titanium cage in the anterior cervical spine fusion].

OBJECTIVE: To evaluate the value of rectangle titanium cage (SynCage-C) in the anterior cervical spine fusion. METHODS: Nineteen patients underwent anterior cervical discectomy and interbody fusion using SynCage-C with average follow-up of 9 months. RESULTS: All cases had cervical spondylosis with 13 cases of myelopathy and 6 cases of radiculopathy. One level fusion were 16 cases and two levels were 3 cases. The mean operation time was 40 minutes per level with average bleeding 60 ml. Patients were asked to wear a hard collar for average 8.5 weeks after the operation. The fusion was solid on lateral view X-ray films three months post-operation. Only 1 case had neck stiffness due to prolonged collar protection and another case had short term pain on bone dorner site. There were no other complications such as cage subsidence, displacement, milaligment and kyphosis of cervical spine. CONCLUSION: The SynCage-C can resort and maintain the intervertebral space effectively with the advantage of immediate stability, satisfactory fusion and easy to use.

Adult↗